WO2020252551A1 - Particulate material for obtaining a soft magnetic composite and particulate material production process for obtaining a soft magnetic composite - Google Patents

Particulate material for obtaining a soft magnetic composite and particulate material production process for obtaining a soft magnetic composite Download PDF

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WO2020252551A1
WO2020252551A1 PCT/BR2020/050218 BR2020050218W WO2020252551A1 WO 2020252551 A1 WO2020252551 A1 WO 2020252551A1 BR 2020050218 W BR2020050218 W BR 2020050218W WO 2020252551 A1 WO2020252551 A1 WO 2020252551A1
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soft magnetic
particles
layer
ferromagnetic particles
particulate material
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PCT/BR2020/050218
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French (fr)
Portuguese (pt)
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Leandro Lima EVANGELISTA
Antonio Itamar Filho RAMOS
Letícia Espíndola MACHADO
Gustavo TONTINI
Aloisio Nelmo Klein
Valderes DRAGO
Gisele Hammes
Cristiano Binder
Nelson Jhoe Batistela
Roberto Binder
Felipe Darabas RZATKI
Bernardo Sena da SILVA
Indiara Pitta Corrêa da SILVA
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Universidade Federal De Santa Catarina
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60Q—ARRANGEMENT OF SIGNALLING OR LIGHTING DEVICES, THE MOUNTING OR SUPPORTING THEREOF OR CIRCUITS THEREFOR, FOR VEHICLES IN GENERAL
    • B60Q1/00—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor
    • B60Q1/26—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic
    • B60Q1/34—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic for indicating change of drive direction
    • B60Q1/38—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic for indicating change of drive direction using immovably-mounted light sources, e.g. fixed flashing lamps
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
    • H01F1/33—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials mixtures of metallic and non-metallic particles; metallic particles having oxide skin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/16—Metallic particles coated with a non-metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60Q—ARRANGEMENT OF SIGNALLING OR LIGHTING DEVICES, THE MOUNTING OR SUPPORTING THEREOF OR CIRCUITS THEREFOR, FOR VEHICLES IN GENERAL
    • B60Q1/00—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor
    • B60Q1/26—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic
    • B60Q1/34—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic for indicating change of drive direction
    • B60Q1/346—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic for indicating change of drive direction with automatic actuation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60Q—ARRANGEMENT OF SIGNALLING OR LIGHTING DEVICES, THE MOUNTING OR SUPPORTING THEREOF OR CIRCUITS THEREFOR, FOR VEHICLES IN GENERAL
    • B60Q1/00—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor
    • B60Q1/26—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic
    • B60Q1/34—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic for indicating change of drive direction
    • B60Q1/40—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic for indicating change of drive direction having mechanical, electric or electronic automatic return to inoperative position

Definitions

  • the present invention describes a particulate material for obtaining a soft magnetic composite (SMC), this material comprising ferromagnetic particles coated by at least two layers of coating, at least one layer of oxide nanoparticles and at least one layer glassy, said covering layers promoting greater continuity, homogeneity and adhesion of insulating coatings on ferromagnetic particles.
  • SMC soft magnetic composite
  • the present invention also relates to a process of producing particulate material to obtain soft magnetic composite (SMC).
  • the present invention is located in the field of Mechanical Engineering, Electrical Engineering, Chemical Engineering and Materials Engineering. Fundamentals of the Invention
  • Soft Magnetic Composite - SMC Soft Magnetic Composite - SMC
  • this material is composed of ferromagnetic particles covered with an electrical insulating material, thus preventing the passage of electrical current between particles. This fact allows the SMC to considerably eliminate the difficulty related to eddy currents and thereby maintain the efficiency of machines and electrical devices at medium and high frequency.
  • the SMC presents another important characteristic, which is its three-dimensional isotropic ferromagnetic behavior, which offers the electrical equipment design possibilities for improvement in relation to thermal characteristics, design flexibility, processing and assembly , in addition to the contribution in reducing the costs of scale production.
  • SMCs with organic coating present themselves as advantageous in terms of cost and simplicity of the production process in relation to inorganic coatings.
  • the temperature limitation for heat treatment of SMCs with organic coating makes the losses of this type of SMC relatively high, especially due to the static loss component.
  • this type of SMC also suffers from the degradation of polymers over time, leading to deterioration of mechanical resistance and electrical resistivity.
  • SMCs that have inorganic coatings allow heat treatments at higher temperatures, providing greater stress relief and lower losses, which would lead to the possibility of more efficient electrical machines.
  • This patented material was designed focusing on high frequency applications and, according to the invention, its good characteristics for working in these conditions are due to the fact that (a) the metal particle with average diameters of 20 to 70nm easily form magnetic domains, (b) the the metallic particle is covered with a stable first insulating layer such as Si02 and (c) that the first insulating layer is covered by a eutectic crystal produced by the reaction between the first and the second insulating layer.
  • the material can be processed in order to produce a component through (1) lamination (sheet-molding), being able to rely on magnetic alignment, followed by heating to form the eutectic between the oxides that make up the insulating coating to form the composite matrix or by (2) grinding the particles coated with a double layer in a ball mill, followed by washing, drying, dispersion in acetone, centrifugation, organization of the particles in acetone in order to achieve high density, separation of acetone maintaining the ordering carried out, drying of residual acetone, compaction using a pressure close to 10OMPa in a body with a thickness close to 400pm, and heat treatment in an argon atmosphere at 500 ° C.
  • the material is dedicated to the production of small devices, such as antennas, making it difficult to use for electrical machine projects with larger volume cores, for example.
  • the material of the patent US2008 / 0029300A1 is especially used in applications above 100MHz, that is, in frequencies where eddy currents represent the dominant fraction over the losses of a ferromagnetic core.
  • the high density of the SMC is vital to achieve high permeability and low losses through hysteresis, which have an appreciable weight on the total magnetic losses at frequencies up to 1kHz.
  • the density of composites obtained by the methods described in US2008 / 0029300A1 hardly reach those obtained by the conventional compaction process and heat treatment of SMCs using micrometric particles.
  • FeSiAl or FeSi powder mixed with ethanol, a silane coupling agent and deionized water, and to that mixture is added a silicon precursor, such as tetraethyl orthosilicate (TEOS), and a certain amount of ammonia.
  • TEOS tetraethyl orthosilicate
  • Such mixture is stirred for 2-8 hours at a temperature of 40-100 ° C and pH adjusted between 7-8, followed by magnetic separation, washing with anhydrous ethanol and deionized water and drying at 40-100 ° C to obtain the particles coated with SiO2.
  • these particles are mixed with n-butyl borate, absolute ethanol, polyethylene glycol and deionized water, with a pH adjusted between 5-6 using acetic acid.
  • the mixture is kept under stirring at 40-80 ° C for 1-5 hours to complete the reaction and finally, the coated and dry powder undergoes calcination carried out between 400 - 500 ° C.
  • the patent WO2018035595 also claims the production of SMCs using alkali metal silicates containing submicrometric particles dispersed inside.
  • the submicrometric particles dispersed in the silicate act (a) as thermal masses, absorbing the heat provided during the heat treatment and increasing the time necessary for the coating to undergo the glass transition; (b) as a thickening agent, keeping the coating adhered to the surface of the particles even after their glass transition; (c) as a nucleating agent, encouraging the silicate crystallization process at lower temperatures; (d) dissolving and partially or totally altering the composition of the silicate itself.
  • a particulate material for obtaining a soft magnetic composite comprising ferromagnetic particles coated by at least two layers of coating, at least one layer of oxide nanoparticles and at least one glassy layer, said layers of coating promoting greater continuity , homogeneity and adhesion of insulating coatings on ferromagnetic particles.
  • the objective of the present invention to provide a particulate material for obtaining a soft magnetic composite (SMC) in which the first layer of the coating, called oxide layer, contributes to increase the electrical resistivity due to its insulating nature and improves the conditions of wetting of the second insulating layer of the coating, called the vitreous layer, on the ferromagnetic particles during the heat treatment to produce the soft magnetic composites.
  • SMC soft magnetic composite
  • SMC soft magnetic composite
  • a particulate material to obtain a soft magnetic composite comprising ferromagnetic particles covered by at least one oxide layer and at least one glassy layer; said particulate material in which said ferromagnetic particles comprise pure metals or ferromagnetic alloys containing at least one of the elements selected from Fe, Ni and Co and comprises particles of average size between 10pm and 500pm;
  • the oxide layer comprises nanometric particles of oxides selected from ZnO, T1O2, MgO, AI2O3, M h 3 ⁇ 04, MnO, M h 2q3, MnCh, MnCb and M h 2q7 with an average size between 0.005pm and lpm;
  • the vitreous layer comprises vitreous phase or precursor to vitreous phase based on compounds selected from alkali metal silicates such as liquid glass like Na20-nSiC> 2 and BbO-mSiCh or boron oxide or boron oxide precursors such as boric acid, metabolic acid, t
  • the objectives are achieved through a process of producing particulate material for obtaining a soft magnetic composite in which the coating of ferromagnetic particles by the oxide layer is characterized by a liquid mixing of the ferromagnetic particles with a suspension of nanoparticles of at least one of the oxides selected from ZnO, T1O2, MgO, AI2O3, Mn3C> 4, MnO, Mn2C> 3, MnC> 2, MnC> 3, Mn2C> 7.
  • nanoparticles of at least one of the oxides ZnO, THIO2, MgO, AI2O3, M h 3q4, MnO, M3 ⁇ 4q3, M h q2, M h q3, M h 2q7 are preferably synthesized from of metallic hydroxides of Zn, Ti, Mg, Ai or Mn simultaneously to the said mixing stage with ferromagnetic particles by the reaction between water-soluble hydroxides and precursors of metallic hydroxides.
  • the process of producing particulate material to obtain soft magnetic composite provides that water-soluble hydroxides are selected from NaOH, KOH, NH 4 OH and metal salts precursors of the hydroxides Metals are selected from Zn, Ti, Mg, Ai or Mn salts.
  • the production process provides that the coating of the ferromagnetic particles with the oxide layer is carried out in a liquid medium; the process comprising the steps of: (I) mixing, under agitation, the ferromagnetic particles, in a mass proportion of 30% to 60%, with a suspension containing oxide nanoparticles or metallic hydroxides precursors of nanoparticles synthesized simultaneously with the mixing step of this suspension with ferromagnetic particles, containing a molar concentration of nanoparticles between 1 and 500mM; (II) removal of excess nanoparticles suspension and subsequent drying of the mixture obtained in step (I) at temperatures between room temperature and 150 ° C.
  • the ferromagnetic particles previously covered by the oxide layer are covered with the insulating material of the vitreous layer, the process comprising the steps: (I ) coating of ferromagnetic particles by immersion or incipient wetting with a suspension of alkali metal silicates of the type liquid glass or boron oxide or glass phase precursor based on boron oxide precursors selected from boric acid, metabolic acid, tetraboric acid, ammonium tetraborate, pentaborate, peroxyborate, in the proportion by weight of 65% to 95% of coated ferromagnetic particles and 5% to 35% of glass phase suspension or glass phase precursor; and (II) drying the coated composite at a temperature between room temperature and 150 ° C.
  • the solution of boron oxide precursors is composed of the dilution of one or more precursors selected from boric acid, metabolic acid, tetraboric acid, ammonium tetraborate, pentaborate, peroxyborate; the solution of said precursors being prepared in a concentration between 0.001g / mL and lg / mL and containing a mass of precursors between 0.01% to 10.00% in relation to the mass of ferromagnetic particles of the soft magnetic composite.
  • the alkali metal silicate solution is composed of the dilution of one or more silicates, and the molar ratio between the silica molecules and alkali metal oxides must be between 0.5 and 8; the alkali metal silicate solution or mixture of silicates should contain a solids concentration between 0.001mg / ml and 15mg / ml.
  • Figure 1 illustrates ferromagnetic particles with double insulating coating
  • Figure 2 illustrates the behavior of the oxide and vitreous layers during the stages of compaction and heat treatment at the interface between the coated ferromagnetic particles
  • Figure 3 illustrates the advantages in magnetic behavior in terms of reducing magnetic losses of the patented material with double insulating layer in relation to solutions containing only one insulating layer;
  • a particulate material for obtaining a soft magnetic composite (here also called SMC) comprising ferromagnetic particles coated by at least one oxide layer and at least one vitreous layer ;
  • the oxide layer comprises nanometric particles of oxides selected from ZnO, T1O2, MgO, AI2O3, MnsCq, MnO, Mh2q3, Mhq2, MnCb and Mh2q7, "where the glassy layer comprises an oxide phase with low glass transition temperature or glass phase precursor based on compounds selected from alkali metal silicates such as liquid glass like Na20-nSiC> 2 and BbO-mSiCh or boron oxide or boron oxide precursors like boric acid, metabolic acid, tetraboric acid, ammonium tetraborate, pentaborate, peroxyborate; the soft magnetic composite in which the nanoparticles comprising the oxide layer have an average size between 0.005pm and
  • the particulate material for obtaining a soft magnetic composite consists of more than one insulating layer, being a first layer of inorganic insulation based on nanometric oxide particles, referred to in this invention as the oxide layer.
  • This layer includes nanoparticles of zinc oxide, magnesium oxide, aluminum oxide, titanium oxide or manganese oxide, or a mixture of these oxides.
  • These nanometric particles cover the ferromagnetic particles preferentially in a liquid medium by contact under agitation with a dispersion of nanometric particles of these oxides or with sol-gel suspensions of hydroxides of these elements, which are converted to oxide form in the course of processing.
  • the aforementioned nanometric particles in the oxide layer penetrate, even if minimally, the surface of the ferromagnetic particles. This effect leads to an increase in oxide layer on the ferromagnetic particles.
  • This layer named in this invention as the vitreous layer, has high electrical resistivity and good wetting in relation to the compounds of the oxide layer, in order to allow the mechanism of self-healing of cracks during heat treatment. Adding to the crack regeneration effect and the adhesion of the first layer on the ferromagnetic particles, there is a complete coating of the ferromagnetic particles, promoting the high electrical resistivity and low magnetic losses of the SMC.
  • the selection of the particle size defines an effective way of adjusting the optimal properties for application at different frequencies, using the same insulating system and the same covering method.
  • the first layer of the coating contributes to increase the electrical resistivity due to its insulating nature and improves the wetting conditions of the second insulating layer of the coating, called the glassy layer, on the ferromagnetic particles during the heat treatment for production of soft magnetic composites.
  • the oxides formed have great chemical affinity in relation to the vitreous layer, reducing the interface energy between the compounds and resulting in a good wettability between them, that is, they form a low contact angle of the vitreous layer on the oxide nanoparticles layer. Because of this good wettability, it is possible to obtain a complete coating of the ferromagnetic particle and promote a synergistic effect between the two layers that results in an insulating film of high resistivity and good adhesion on the ferromagnetic particles.
  • the oxide layer can also act as a nucleating agent for the crystallization process of the vitreous phase, which increases the viscosity of the vitreous layer and assists in maintaining the high electrical resistivity of the insulating film. .
  • the present invention proposes a process for the production of a particulate material to obtain a soft magnetic composite in which the coating of the ferromagnetic particles by the oxide layer is characterized by occurring through liquid mixing of the ferromagnetic particles with a suspension of nanoparticles of at least one of the oxides selected from ZnO, T1O2, MgO, AI2O3, Mn3C> 4, MnO, Mn2C> 3, MnCó, MnCq, Mn2C> 7.
  • nanoparticles of at least one of the oxides ZnO, T1O2, MgO, AI2O3, Mh3q4, MnO, M3 ⁇ 4q3, Mhq2, Mhq3, Mh2q7 are preferably synthesized from metallic hydroxides of Zn, Ti, Mg, Ai or Mn simultaneously to said mixing stage with ferromagnetic particles by the reaction between water-soluble hydroxides and precursors of metal hydroxides; the water-soluble hydroxides being selected from NaOH, KOH, NH4OH or similar and metal salts precursor to the metal hydroxides are selected from Zn, Ti, Mg, Ai or Mn salts.
  • the ferromagnetic particles are coated with the oxide layer in a liquid medium; the process comprises the steps of: mixing, under agitation, the ferromagnetic particles, in a mass proportion of 30% to 60%, with a suspension containing oxide nanoparticles or metallic hydroxides precursors of nanoparticles synthesized simultaneously with the mixing step of this suspension with the particles ferromagnetic, containing a molar concentration of nanoparticles between 1 and 500mM, and removal of excess nanoparticles suspension and subsequent drying of the mixture obtained in step (I) at temperatures between room temperature and 150 ° C.
  • the coating with insulating material of the vitreous layer occurs, in a process comprising the steps of: coating of the ferromagnetic particles by immersion or incipient wetting with a suspension of alkali metal silicates such as liquid glass or boron oxide or glass phase precursor based on boron oxide precursors selected from boric acid, metabolic acid, tetraboric acid, ammonium tetraborate, pentaborate, peroxyborate or similar, na mass proportion of 65% to 95% of coated ferromagnetic particles and 5% to 35% of glass phase suspension or glass phase precursor; and drying the coated composite with temperature between room temperature and 150 ° C.
  • alkali metal silicates such as liquid glass or boron oxide or glass phase precursor based on boron oxide precursors selected from boric acid, metabolic acid, tetraboric acid, ammonium tetraborate, pentaborate, peroxyborate or similar, na mass proportion of 65% to 95% of coated ferromagnetic particles
  • the solution of boron oxide precursors is composed of the dilution of one or more precursors selected from boric acid, metabolic acid, tetraboric acid, ammonium tetraborate, pentaborate, peroxyborate or the like; the solution of said precursors being prepared at a concentration between 0.001g / mL and lg / mL and more preferably between 0.002g / mL and 0.02g / mL, and containing a mass of precursors between 0.01% to 10.00% and more preferably between 0.05% and 5.00% in relation to the mass of ferromagnetic particles of the soft magnetic composite.
  • the alkali metal silicate solution is composed of the dilution of one or more silicates, with the molar ratio between the silica molecules and alkali metal oxides being between 0.5 and 8 and more preferably between 1.5 and 4; the alkali metal silicate solution or mixture of silicates must contain a solids concentration between 0.001mg / ml and 15mg / ml and more preferably between 0.005mg / ml and 5mg / ml.
  • incipient wetting arises from the English translation of the expression Inc ⁇ p ⁇ ent wetness, which can also be translated by "capillary impregnation” or “dry impregnation” and refers to cyclic processes of partial and drying a solution on a substrate; in the case of that patent, on ferromagnetic particles. During this process, a layer of precipitates forms on the particles homogeneously and with a layer thickness that can be controlled.
  • a route to the production process of a particulate material for obtaining generalized soft magnetic composite for the production of powders containing double coating for the manufacture of soft magnetic composite materials follows the steps: 1 - Preparation of a suspension containing oxide or hydroxide nanoparticles, which can be prepared directly by dispersing commercial nanoparticles in liquid medium or by mixing appropriate chemical solutions for the synthesis of these nanoparticles simultaneously with the subsequent step. 2 - Mixing of ferromagnetic particles, under agitation, with the suspension prepared in step 1 promoting the adhesion of the oxide or hydroxide nanoparticles, synthesized simultaneously or not, to the surface of the ferromagnetic particles, thus forming the oxide layer.
  • 3 Magnetic separation of ferromagnetic powder, coated with the oxide layer, from the rest of the suspension and drying. 4 - Addition of the vitreous layer, by immersion or incipient wetting, to the ferromagnetic powder previously coated with the oxide layer, using a solution containing glassy compounds or precursors that will form the vitreous layer. 5 - Magnetic separation of ferromagnetic powder coated with double layer of insulators from the rest of the suspension and drying.
  • the double-coated ferromagnetic particles are obtained as schematically shown in Figure 1. Next, these particles are mixed with a compaction lubricant, followed by the uniaxial compaction and heat treatment steps, resulting in the dimensions and microstructure suitable for use of the SMC material.
  • the nanoparticles that make up the oxide layer slightly penetrate the surface of the ferromagnetic particles due to the difference in hardness. This leads to a better anchoring of the oxide layer on the ferromagnetic powder, despite generating some discontinuity of the insulating film due to the high pressures of the compaction step.
  • some precursors of the vitreous layer such as boric acid (H 3 BO 3 ), for example, can add a lubricating effect, helping to process the material in this compacting stage.
  • SMC compacted parts are usually heat treated to relieve stress and increase mechanical strength.
  • the formation of the vitreous phase is also sought, when only precursors of that phase are added, and the process of self-healing of the cracks.
  • Self-regeneration comes from good wettability between the compounds used in the oxide layer and the compounds that make up the glassy layer at the end of the heat treatment.
  • the vitreous layer ends up covering the entire ferromagnetic particle, allowing to regenerate the cracks of coating generated during the compaction stage during the subsequent heat treatment.
  • the oxide layer also acts as a nucleating agent for the crystallization process of the vitreous phase, and may even be partially dissolved during this process.
  • the behavior of the oxide and vitreous layers during the stages of compaction and heat treatment at the interface between two coated ferromagnetic particles are shown schematically in Figure 2.
  • the iron particles covered with the insulating nanoparticles are separated from the rest of the suspension, washed with a mixture of ethanol and water, and finally dried in a vacuum oven at 80 ° C for 30 minutes. After drying, the iron particles are coated with a layer of zinc oxide (ZnO) nanoparticles. This layer comes from the transformation of Zn (OH) 2 into ZnO, which started in the mixing stage and ended in the drying stage.
  • ZnO zinc oxide
  • a heated solution of isopropanol containing a mass concentration of 0.5% boric acid (H 3 BO 3 ) dissolved is prepared.
  • the iron powder, coated with ZnO as an oxide layer, is then immersed in this solution so that the mass concentration of the ferromagnetic powder in this solution is 83.5%.
  • the powder is kept in contact with the solution until complete drying by evaporation of isopropanol.
  • iron particles have a double coating of insulators, that is, containing the oxide layer and precursor to the glassy layer.
  • the iron particles covered with the insulating nanoparticles are separated from the rest of the suspension, washed with a mixture of ethanol and water, and finally dried in a vacuum oven at 80 ° C for 30 minutes. After drying, the iron particles are coated with a layer of zinc oxide (ZnO) nanoparticles. This layer comes from the transformation of Zn (OH) 2 into ZnO, which started in the mixing stage and ended in drying step.
  • ZnO zinc oxide
  • a level of lubricant extraction temperature in this example, a temperature of 320 ° C is used for 30 minutes, and a second level at a higher temperature for stress relief and increased mechanical strength, where for the sample in question, the temperature of 500 ° is used C at a 30-minute level.
  • Iron particles with an average particle size of 180pm, are immersed in a heated isopropanol solution containing a mass concentration of 0.5% dissolved boric acid (H3BO3).
  • the iron powder without previous coating, is then immersed in this solution so that the mass concentration of the ferromagnetic powder is 83.5%.
  • the powder is kept in contact with the solution until complete drying by evaporation of isopropanol. After the isopropanol has dried, the iron particles have only the precursor coating of the vitreous layer.
  • the iron particles covered with the insulating nanoparticles are separated from the rest of the suspension, washed with a mixture of ethanol and water, and finally dried in a vacuum oven at 80 ° C for 30 minutes. After drying, the iron particles are coated with a layer of zinc oxide (ZnO) nanoparticles. This layer comes from the transformation of Zn (OH) 2 into ZnO, mixing stage and finalized in the drying stage.
  • ZnO zinc oxide
  • an aqueous solution containing manganese acetate tetrahydrate (Mn (CH3COO) 2 ⁇ 4H2O) with a mass concentration of 0.97% and the same volume as the previous NaOH solution is added, under strong stirring, to the NaOH solution containing the iron particles in order to synthesize manganese hydroxide (Mn (OH) 2) nanoparticles concomitantly with the adhesion of these nanoparticles to the surface of the iron particles.
  • Mn (OH) 2 manganese hydroxide
  • the iron particles covered with the insulating nanoparticles are separated from the rest of the suspension, washed with a mixture of ethanol and water, and finally dried in a vacuum oven at 80 ° C for 30 minutes. After drying, the iron particles are coated with a layer of manganese oxide nanoparticles (MnsCh). This layer comes from the transformation of Mn (OH) 2 into (MnsCh), which started in the mixing stage and ended in the drying stage.
  • H3B03 a heated isopropanol solution containing a mass concentration of 0.5% dissolved boric acid
  • an aqueous solution containing magnesium chloride hexahydrate (MgCl2 ⁇ 6H2O) with a mass concentration of 0.81% and the same volume as the previous NaOH solution is added, under strong stirring, to the NaOH solution containing the iron particles, in order to synthesize magnesium hydroxide (Mg (OH) 2) nanoparticles concomitantly with the adhesion of these nanoparticles to the surface of the iron particles.
  • Mg (OH) 2 magnesium hydroxide
  • the iron particles covered with the insulating nanoparticles are separated from the rest of the suspension, washed with a mixture of ethanol and water, and finally dried in a vacuum oven at 80 ° C for 30 minutes. After drying, the iron particles are coated with a layer of magnesium oxide (MgO) nanoparticles. This layer comes from the transformation of Mg (OH) 2 into MgO, which started in the mixing stage and ended in the drying stage.
  • MgO magnesium oxide
  • (b) Vitre Layer Formation - B2O3 Precursor After adding the first coating layer, a heated isopropanol solution containing 0.5% mass concentration of dissolved boric acid (H 3 BO 3 ) is prepared . The iron powder, coated with MgO as an oxide layer, is then immersed in this solution so that the mass concentration of the ferromagnetic powder in this solution is 83.5%. The powder is kept in contact with the solution until complete drying by evaporation of isopropanol. After the isopropanol has dried, iron particles have a double coating of insulators, that is, containing the oxide layer and precursor to the glassy layer.
  • H 3 BO 3 dissolved boric acid
  • (a) Formation of the Oxide Layer - TIO 2 Iron particles, with an average particle size of 180pm, are immersed in an aqueous suspension containing commercial titanium oxide (T1O2) nanoparticles with a dispersion mass concentration of 0.16 % and average particle size equal to 20nm. Iron powder is added to this suspension in such a way that the concentration of ferromagnetic particles in the suspension is equal to 28.5%, equivalent to a molar concentration of 20mM. The mixture is kept under stirring, strong enough to keep the iron particles suspended, for the period of 1 hour.
  • T1O2 commercial titanium oxide
  • the iron particles covered with the insulating nanoparticles are separated from the rest of the suspension, washed with a mixture of ethanol and water, and finally dried in a vacuum oven at 80 ° C for 30 minutes. After drying, the iron particles are coated with a layer of titanium oxide nanoparticles.
  • a heated solution of isopropanol containing a mass concentration of 0.5% of dissolved boric acid (H3BO3) is prepared.
  • the iron powder, coated with T1O2 as an oxide layer, is then immersed in this solution so that the mass concentration of the ferromagnetic powder in this solution is 83.5%.
  • the powder is kept in contact with the solution until complete drying by evaporation of isopropanol.
  • the iron particles with double insulating coating that is, containing the oxide layer and precursor to the vitreous layer.
  • AI2O3 commercial aluminum oxide
  • the iron particles covered with the insulating nanoparticles are separated from the rest of the suspension, washed with a mixture of ethanol and water, and finally dried in an oven vacuum at 80 ° C for 30 minutes. After drying, the iron particles are coated with a layer of aluminum oxide nanoparticles.
  • a heated solution of isopropanol containing a mass concentration of 0.5% of dissolved boric acid (H3BO3) is prepared.
  • the iron powder, coated with AI2O3 as an oxide layer, is then immersed in this solution so that the mass concentration of the ferromagnetic powder in this solution is 83.5%.
  • the powder is kept in contact with the solution until complete drying by evaporation of isopropanol.
  • iron particles have a double coating of insulators, that is, containing the oxide layer and precursor to the glassy layer.
  • Samples in the form of toroid produced in examples 1 to 6 and comparative examples 1 and 2 have approximate dimensions of outside diameter, inside diameter and height respectively equal to 65, 55 and 5mm. These samples were measured on a bench for measuring magnetic properties MPG 200D manufactured by Brockhaus Messtechn ⁇ k and their results are shown in Table 1 and Table 2.
  • Table 1 Losses in maximum magnetic induction of 1T and maximum relative permeability at different frequencies of samples containing respectively double layer of insulators, only oxide layer (ZnO) and only vitreous layer (B2O3).
  • Table 2 Losses in maximum magnetic induction of 1T and maximum relative permeability at different frequencies of samples containing different combinations of oxide layer and vitreous layer.
  • the oxide layer it allows a significant improvement in the wetting of the vitreous layer on the ferromagnetic particle, in addition to this synergy between the layers leading to the self-healing mechanism of the cracks generated in the compaction stage, with the possibility of increasing the electrical resistivity during the heat treatment. It is important to note that for this phenomenon to occur as shown in the examples of this invention, both layers must be present and added in two stages as a way to ensure that from the surface of the ferromagnetic powder, the oxide layer is found first and then the layer glassy.
  • the properties achieved and demonstrated in the examples of this invention present the possibility of immediate use for several applications, especially with a focus on medium frequency.
  • optimizations for different conditions of use, especially in relation to the frequency of operation can be carried out through modifications of process parameters keeping the same molds claimed by the invention, such as example: size of ferromagnetic particles, control of particle size, composition and concentration of nanoparticles in suspension, composition of the liquid medium of the suspension, mixing time with the suspension, pH of the suspension, stirring speed, composition and glass phase concentration or precursors, in addition to process parameters such as lubricant quantity, compaction pressure, compaction temperature, as well as temperature and heat treatment time.

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Abstract

The present invention describes a particulate material for obtaining a soft magnetic composite (SMC), this material comprising ferromagnetic particles coated by at least two coating layers (at least one layer of oxide nanoparticles and at least one vitreous layer), wherein said coating layers promote greater continuity, homogeneity, and adhesion of insulating coatings on ferromagnetic particles. The present invention also relates to a particulate material production process for obtaining a soft magnetic composite (SMC).

Description

"MATERIAL PARTICULADO PARA OBTENÇÃO DE COMPOSITO MAGNÉTICO MOLE E PROCESSO DE PRODUÇÃO DE MATERIAL PARTICULADO PARA A OBTENÇÃO DE COMPÓSITO MAGNÉTICO MOLE" "PARTICULATED MATERIAL FOR OBTAINING MOLE MAGNETIC COMPOSITES AND PARTICULATED MATERIAL PRODUCTION PROCESS FOR OBTAINING MOLE MAGNETIC COMPOSITES"
Campo da Invenção Field of the Invention
[0001] A presente invenção descreve um material particulado para obtenção de um compósito magnético mole (SMC) , este material que compreende partículas ferromagnéticas revestidas por, ao menos, duas camadas de recobrimento sendo ao menos uma camada de nanopartícuias óxidas e ao menos uma camada vítrea, ditas camadas de recobrimento promovendo uma maior continuidade, homogeneidade e adesão dos revestimentos isolantes sobre as partículas ferromagnéticas. A presente invenção refere-se ainda a um processo de produção de material particulado para obtenção de compósito magnético mole (SMC) . A presente invenção se situa no campo da Engenharia Mecânica, Engenharia Elétrica, Engenharia Química e Engenharia de Materiais. Fundamentos da Invenção [0001] The present invention describes a particulate material for obtaining a soft magnetic composite (SMC), this material comprising ferromagnetic particles coated by at least two layers of coating, at least one layer of oxide nanoparticles and at least one layer glassy, said covering layers promoting greater continuity, homogeneity and adhesion of insulating coatings on ferromagnetic particles. The present invention also relates to a process of producing particulate material to obtain soft magnetic composite (SMC). The present invention is located in the field of Mechanical Engineering, Electrical Engineering, Chemical Engineering and Materials Engineering. Fundamentals of the Invention
[0002] A miniaturização e diminuição de peso de máquinas elétricas e dispositivos eletromagnéticos, muito em parte impulsionado pelos mercados automotivo e aeroespacial, estão rapidamente se configurando como projetos desses equipamentos para operações em frequências elétricas superiores àquelas outrora utilizadas para as mesmas aplicações. Esse impulso, no entanto, frequentemente esbarra, especialmente para as tradicionais chapas de aço elétrico, na problemática causada pela queda da eficiência atribuída à intensa aparição de correntes parasitas em médias e altas frequências. [0002] The miniaturization and weight reduction of electrical machines and electromagnetic devices, much in part driven by the automotive and aerospace markets, are rapidly becoming projects for such equipment for operations at electrical frequencies higher than those used for the same applications. This impulse, however, often comes up against, especially for traditional electric steel sheets, in the problem caused by the drop in efficiency attributed to the intense appearance of eddy currents in medium and high frequencies.
[0003] Como um material capaz de manter um alto nível de magnetização de saturação combinada com uma alta resistividade elétrica, os compósitos magnéticos moles (Soft Magnetic Composite - SMC) se apresentam como uma excelente solução técnica para continuidade da tendência de miniaturização . Isso ocorre pelo fato desse material ser composto por partículas ferromagnéticas recobertas com um material isolante elétrico, evitando assim a passagem de corrente elétrica entre partículas. Esse fato permite que o SMC consiga suprimir consideravelmente a dificuldade relacionada às correntes parasitas e com isso manter a eficiência das máquinas e dispositivos elétricos em média e alta frequência. [0003] As a material capable of maintaining a high level of saturation magnetization combined with a high electrical resistivity, soft magnetic composites (Soft Magnetic Composite - SMC) present themselves as an excellent technical solution for the continuity of the miniaturization trend. This is due to the fact that this material is composed of ferromagnetic particles covered with an electrical insulating material, thus preventing the passage of electrical current between particles. This fact allows the SMC to considerably eliminate the difficulty related to eddy currents and thereby maintain the efficiency of machines and electrical devices at medium and high frequency.
[0004] Contribuindo para a questão da miniaturização, o SMC apresenta uma outra característica importante que é o seu comportamento ferromagnético isotrópico tridimensional, o que oferece ao projeto de equipamentos elétricos possibilidades de melhoria em relação as características térmicas, flexibilidade de projeto, processamento e montagem, além da contribuição na redução de custos de uma produção em escala. [0004] Contributing to the issue of miniaturization, the SMC presents another important characteristic, which is its three-dimensional isotropic ferromagnetic behavior, which offers the electrical equipment design possibilities for improvement in relation to thermal characteristics, design flexibility, processing and assembly , in addition to the contribution in reducing the costs of scale production.
[0005] Existe uma extensa quantidade de trabalhos acadêmicos no desenvolvimento de SMCs, assim como uma série de patentes depositadas considerando diferentes processos produtivos e composições de materiais como, por exemplo, pós de ferro e suas ligas revestidos com materiais orgânicos como resinas (US2012/0229245A1 ) ou inorgânicos como fosfatos (US8187394B2 ) , compostos de boro (US2010/0224822A1 ) e silicatos (US2013/ 0181802A1 ) . [0005] There is an extensive amount of academic work in the development of SMCs, as well as a series of patents filed considering different production processes and material compositions such as, for example, iron powders and their alloys coated with organic materials such as resins (US2012 / 0229245A1) or inorganic as phosphates (US8187394B2), boron compounds (US2010 / 0224822A1) and silicates (US2013 / 0181802A1).
[0006] Os SMCs com revestimento orgânico se apresentam como vantajosos quanto ao custo e à simplicidade do processo produtivo em relação aos revestimentos inorgânicos. No entanto, a limitação de temperatura para tratamento térmico dos SMCs com revestimento orgânico torna as perdas desse tipo de SMC relativamente altas, em especial devido à componente de perdas estática. Além disso, esse tipo de SMC também sofre com a degradação dos polímeros ao longo do tempo, levando a deterioração da resistência mecânica e da resistividade elétrica. Os SMCs que contam com revestimentos inorgânicos, por sua vez, permitem tratamentos térmicos em temperaturas mais elevadas, proporcionando um maior alívio de tensões e menores perdas, o que levaria à possibilidade de máquinas elétricas mais eficientes. [0006] SMCs with organic coating present themselves as advantageous in terms of cost and simplicity of the production process in relation to inorganic coatings. However, the temperature limitation for heat treatment of SMCs with organic coating makes the losses of this type of SMC relatively high, especially due to the static loss component. In addition, this type of SMC also suffers from the degradation of polymers over time, leading to deterioration of mechanical resistance and electrical resistivity. SMCs that have inorganic coatings, in turn, allow heat treatments at higher temperatures, providing greater stress relief and lower losses, which would lead to the possibility of more efficient electrical machines.
[0007] Dentre as patentes que exploram os potenciais de revestimentos inorgânicos pode-se citar a patente US2008/0029300A1, em que são reivindicados SMCs produzidos a partir de partículas ferromagnéticas nanométricas , de 5 a 500nm, revestidas com dupla camada de óxidos isolantes capazes de formar um eutético entre si. Esse material patenteado foi projetado focando em aplicações de alta frequência e, segundo a invenção, suas boas características para trabalho nessas condições são devidas ao fato (a) da partícula metálica com diâmetros médios de 20 a 70nm formarem facilmente monodomínios magnéticos, (b) da partícula metálica estar recoberta com uma primeira camada isolante estável como Si02 e (c) que a primeira camada de isolante está recoberta por um cristal eutético produzido pela reação entre a primeira e a segunda camada de isolantes. Na patente US2008/0029300A1 são previstos alguns pares de óxidos que satisfazem a condição de formação de eutético, tais como: B2O3 — AI2O3, B2O3 — GeCh, B2O3 — S1O2, B2O3 — WO3, B2O3 — Cr2C>3, B2O3 — M0O3, B2O3 — Nb2C>5, B2O3 — L12O3, B2O3 — BaO, B2O3 — ZnO, B2O3 — La2C>3, B2O3 — CoO, B2O3 — CS2O, B2O3 — K2O, K2O — GeCh, K20 -Si02, K20 - W03. K20 - M0O3, K20 - Nb205, Na20 - Ge02, Na20 - S1O2, Na20 - W03, Na20 - MoO, Na20 - Nb205, M0O3 - Cs20, M0O3 - Li20, M0O3 - WO3, Cs20 - Si02 e Cs20 - Nb2Os. O material, tal como expressado na descrição detalhada da patente descrita em US2008/0029300A1, pode ser processado de maneira a produzir um componente através de (1) laminação (sheet- moulding) , podendo contar com alinhamento magnético, seguida de aquecimento para formação do eutético entre os óxidos que compõem o revestimento isolante para formação da matriz do compósito ou ainda por (2) moagem das partículas revestidas com dupla camada em moinho de bolas, seguida de lavagem, secagem, dispersão em acetona, centrifugação, organização das partículas em acetona de forma a alcançar alta densidade, separação da acetona mantendo o ordenamento realizado, secagem da acetona residual, compactação utilizando uma pressão próxima de lOOMPa em um corpo de espessura próxima de 400pm, e tratamento térmico em uma atmosfera de argônio em 500°C. Independentemente do método utilizado, o material é dedicado à produção de dispositivos de pequenas dimensões, como antenas, dificultando seu uso para projetos de máquinas elétricas com núcleos de maior volume, por exemplo. [0007] Among the patents that exploit the potentials of inorganic coatings can be cited the patent US2008 / 0029300A1, in which SMCs are claimed made from nanometric ferromagnetic particles, from 5 to 500nm, coated with a double layer of insulating oxides capable of form a eutectic with each other. This patented material was designed focusing on high frequency applications and, according to the invention, its good characteristics for working in these conditions are due to the fact that (a) the metal particle with average diameters of 20 to 70nm easily form magnetic domains, (b) the the metallic particle is covered with a stable first insulating layer such as Si02 and (c) that the first insulating layer is covered by a eutectic crystal produced by the reaction between the first and the second insulating layer. In the US2008 / 0029300A1 patent there are some oxide pairs that satisfy the eutectic formation condition, such as: B2O3 - AI2O3, B2O3 - GeCh, B2O3 - S1O2, B2O3 - WO3, B2O3 - Cr2C> 3, B2O3 - M0O3, B2O3 - Nb2C> 5, B2O3 - L12O3, B2O3 - BaO, B2O3 - ZnO, B2O3 - La2C> 3, B2O3 - CoO, B2O3 - CS2O, B2O3 - K2O, K2O - GeCh, K 2 0 -Si02, K 2 0 - W03 . K 2 0 - M0O3, K 2 0 - Nb 2 0 5 , Na 2 0 - Ge0 2 , Na20 - S1O2, Na 2 0 - W0 3 , Na 2 0 - MoO, Na 2 0 - Nb 2 0 5 , M0O3 - Cs 2 0, M0O3 - Li 2 0, M0O3 - WO3, Cs 2 0 - Si0 2 and Cs 2 0 - Nb 2 Os. The material, as expressed in the detailed patent description described in US2008 / 0029300A1, can be processed in order to produce a component through (1) lamination (sheet-molding), being able to rely on magnetic alignment, followed by heating to form the eutectic between the oxides that make up the insulating coating to form the composite matrix or by (2) grinding the particles coated with a double layer in a ball mill, followed by washing, drying, dispersion in acetone, centrifugation, organization of the particles in acetone in order to achieve high density, separation of acetone maintaining the ordering carried out, drying of residual acetone, compaction using a pressure close to 10OMPa in a body with a thickness close to 400pm, and heat treatment in an argon atmosphere at 500 ° C. Regardless of the method used, the material is dedicated to the production of small devices, such as antennas, making it difficult to use for electrical machine projects with larger volume cores, for example.
[0008] O material da patente US2008/0029300A1 é especialmente empregado em aplicações acima de 100MHz, isto é, em frequências em que as correntes parasitas representam a fração dominante sobre as perdas de um núcleo ferromagnético. Para aplicações que focam principalmente em operação em média frequência, a alta densidade do SMC é vital para se alcançar alta permeabilidade e baixas perdas por histerese, as quais possuem um peso apreciável sobre as perdas magnéticas totais em frequências de até 1kHz. De fato, a densidade dos compósitos obtidos pelos métodos descritos em US2008/0029300A1 dificilmente alcançam aquelas obtidas pelo processo de compactação e tratamento térmico convencionais de SMCs que utilizam partículas micrométricas . Por outro lado, alcançar altas densidades, ainda que utilizando partículas micrométricas, demanda a aplicação de pressões de compactação elevadas, tipicamente na ordem de até lGPa. Essa necessidade de cargas elevadas leva frequentemente ao problema de quebra do revestimento isolante durante essa etapa do processamento, levando à formação de contatos entre as partículas metálicas e, consequente, redução da resistividade elétrica do compósito. Como forma de superar esse desafio tecnológico, grupos de desenvolvimento de SMCs têm buscado dois diferentes caminhos: 1) Formação ín-sítu do revestimento isolante (WO2018035595) e 2) Autorregeneração do filme isolante durante tratamento térmico. [0008] The material of the patent US2008 / 0029300A1 is especially used in applications above 100MHz, that is, in frequencies where eddy currents represent the dominant fraction over the losses of a ferromagnetic core. For applications that focus mainly on medium frequency operation, the high density of the SMC is vital to achieve high permeability and low losses through hysteresis, which have an appreciable weight on the total magnetic losses at frequencies up to 1kHz. In fact, the density of composites obtained by the methods described in US2008 / 0029300A1 hardly reach those obtained by the conventional compaction process and heat treatment of SMCs using micrometric particles. On the other hand, reaching high densities, even using micrometric particles, demands the application of high compaction pressures, typically in the order of up to 1GPa. This need for high loads often leads to the problem of breaking the insulating coating during this processing step, leading to the formation of contacts between metallic particles and, consequently, a reduction in the electrical resistivity of the composite. As a way of overcoming this technological challenge, SMC development groups have sought two different paths: 1) In-situ formation of the insulating coating (WO2018035595) and 2) Self-regeneration of the insulating film during heat treatment.
[0009] Dentro dessa segunda estratégia, encontra-se a patente CN103177838B em que são utilizadas partículas de FeSi ou FeSiAl revestidas primeiramente com S1O2 e na sequência com borato de n-butilo, precursor de B2O3. Dessa maneira, configura-se um SMC com partículas de FeSi ou FeSiAl revestidas com uma dupla camada de óxido especificamente S1O2 - B2O3, em que se observa a capacidade de autorregeneração de trincas no filme isolante durante o tratamento térmico. Como resultado dessa habilidade de autorregeneração, é obtido um aumento da resistividade elétrica do material e, consequentemente, diminuição da contribuição de correntes parasitas para as perdas magnéticas. Para tanto, parte-se de pó de FeSiAl ou FeSi misturados com etanol, um agente acoplador de silanos e água deionizada, sendo que a essa mistura é posteriormente adicionado um precursor de silício, como tetraetil ortosilicato (TEOS), e uma determinada quantia de amónia. Tal mistura é agitada por 2-8 horas em uma temperatura de 40-100°C e pH ajustado entre 7-8, seguido de separação magnética, lavagem com etanol anidro e água deionizada e secagem em 40-100°C para obtenção das partículas revestidas com SÍO2. Na sequência, essas partículas são misturadas com borato de n-butilo, etanol absoluto, polietileno glicol e água deionizada, com pH ajustado entre 5-6 utilizando ácido acético. A mistura é mantida sob agitação em 40-80°C por 1-5 horas para completar a reação e por fim, o pó revestido e seco passa por uma calcinação realizada entre 400 - 500°C. [0009] Within this second strategy, there is the patent CN103177838B in which FeSi or FeSiAl particles are first coated with S1O2 and then with n-butyl borate, a precursor of B2O3. In this way, an SMC is configured with FeSi or FeSiAl particles coated with a double layer of oxide specifically S1O2 - B2O3, in which the capacity for self-healing of cracks in the insulating film is observed during the heat treatment. As a result of this self-healing ability, an increase in the electrical resistivity of the material is obtained and, consequently, a decrease in the contribution of eddy currents to the magnetic losses. For that, it starts with FeSiAl or FeSi powder mixed with ethanol, a silane coupling agent and deionized water, and to that mixture is added a silicon precursor, such as tetraethyl orthosilicate (TEOS), and a certain amount of ammonia. Such mixture is stirred for 2-8 hours at a temperature of 40-100 ° C and pH adjusted between 7-8, followed by magnetic separation, washing with anhydrous ethanol and deionized water and drying at 40-100 ° C to obtain the particles coated with SiO2. Then, these particles are mixed with n-butyl borate, absolute ethanol, polyethylene glycol and deionized water, with a pH adjusted between 5-6 using acetic acid. The mixture is kept under stirring at 40-80 ° C for 1-5 hours to complete the reaction and finally, the coated and dry powder undergoes calcination carried out between 400 - 500 ° C.
[0010] A patente WO2018035595 também reivindica a produção de SMCs utilizando silicatos de metais alcalinos contendo partículas submicrométricas dispersas no seu interior. Apesar de não haver efeito de autorregeneração de trincas causadas na etapa de compactação de forma eficiente por não haver ordenamento entre camadas, as partículas submicrométricas dispersas no silicato atuam (a) como massas térmicas, absorvendo o calor fornecido durante o tratamento térmico e aumentando o tempo necessário para que o revestimento sofra a transição vítrea; (b) como agente espessante, mantendo o revestimento aderido à superfície das partículas mesmo após a sua transição vítrea; (c) como agente nucleador incentivando o processo de cristalização do silicato em temperaturas mais baixas; (d) dissolvendo e alterando parcial ou totalmente a composição do próprio silicato . [0010] The patent WO2018035595 also claims the production of SMCs using alkali metal silicates containing submicrometric particles dispersed inside. Although there is no effect of self-healing of cracks caused in the compaction step efficiently because there is no ordering between layers, the submicrometric particles dispersed in the silicate act (a) as thermal masses, absorbing the heat provided during the heat treatment and increasing the time necessary for the coating to undergo the glass transition; (b) as a thickening agent, keeping the coating adhered to the surface of the particles even after their glass transition; (c) as a nucleating agent, encouraging the silicate crystallization process at lower temperatures; (d) dissolving and partially or totally altering the composition of the silicate itself.
[0011] É com base neste cenário que surge a presente invenção . [0011] It is based on this scenario that the present invention arises.
Objetivos da invenção Objectives of the invention
[0012] Assim, é o objetivo fundamental da invenção em revelar um material particulado para obtenção de compósito magnético mole (SMC) que compreende partículas ferromagnéticas revestidas por, ao menos, duas camadas de recobrimento sendo ao menos uma camada de nanopartícuias óxidas e ao menos uma camada vítrea, ditas camadas de recobrimento promovendo uma maior continuidade, homogeneidade e adesão dos revestimentos isolantes sobre as partículas ferromagnéticas. [0012] Thus, it is the fundamental objective of the invention in reveal a particulate material for obtaining a soft magnetic composite (SMC) comprising ferromagnetic particles coated by at least two layers of coating, at least one layer of oxide nanoparticles and at least one glassy layer, said layers of coating promoting greater continuity , homogeneity and adhesion of insulating coatings on ferromagnetic particles.
[0013] Ademais, é objetivo da presente invenção prover um material particulado para obtenção de compósito magnético mole (SMC) em que a primeira camada do revestimento, denominada camada óxida, contribui para aumento da resistividade elétrica pela sua natureza isolante e melhora as condições de molhamento da segunda camada isolante do revestimento, denominada camada vítrea, sobre as partículas ferromagnéticas durante o tratamento térmico para produção dos compósitos magnéticos moles. [0013] Furthermore, it is the objective of the present invention to provide a particulate material for obtaining a soft magnetic composite (SMC) in which the first layer of the coating, called oxide layer, contributes to increase the electrical resistivity due to its insulating nature and improves the conditions of wetting of the second insulating layer of the coating, called the vitreous layer, on the ferromagnetic particles during the heat treatment to produce the soft magnetic composites.
[0014] É um objetivo adicional da presente invenção prover um material particulado para obtenção de compósito magnético mole (SMC) em que os óxidos que formam a camada óxida apresentam boa molhabilidade em relação a camada vítrea, sendo capazes de promover efeito sinérgico entre as duas camadas e resultando em um filme isolante de alta resistividade e boa adesão sobre as partículas ferromagnéticas . [0014] It is an additional objective of the present invention to provide a particulate material for obtaining a soft magnetic composite (SMC) in which the oxides that form the oxide layer have good wettability in relation to the vitreous layer, being able to promote a synergistic effect between the two. layers and resulting in an insulating film of high resistivity and good adhesion on ferromagnetic particles.
[0015] Adicionalmente, é objetivo da presente invenção revelar um material particulado para obtenção de compósito magnético mole em que durante a etapa de compactação, as partículas nanométricas que compõem a camada óxida ligeiramente penetram na superfície das partículas ferromagnéticas devido à diferença de dureza, levando a um melhor ancoramento da camada óxida sobre as partículas ferromagnéticas . [0015] Additionally, it is the objective of the present invention to reveal a particulate material for obtaining a soft magnetic composite in which, during the compaction stage, the nanometric particles that make up the oxide layer slightly penetrate the surface of the ferromagnetic particles due to the difference in hardness, leading to a better anchoring of the oxide layer on ferromagnetic particles.
[0016] É, também, objetivo da presente invenção prover um processo de produção de um material particulado para obtenção de compósito magnético mole em que a camada óxida permita uma melhoria significativa do molhamento da camada vítrea sobre a partícula ferromagnética com possibilidade de aumento da resistividade elétrica durante o tratamento térmico por efeito da autorregeneração do filme isolante exercida pela camada vítrea ancorada pela camada óxida. Sumário da invenção [0016] It is also the objective of the present invention to provide a process for the production of a particulate material to obtain a soft magnetic composite in which the oxide layer allows a significant improvement in the wetting of the vitreous layer on the ferromagnetic particle with the possibility of increasing resistivity. during the heat treatment due to the self-regeneration of the insulating film exerted by the vitreous layer anchored by the oxide layer. Summary of the invention
[0017] Todos os objetivos acima citados são atingidos por meio de um material particulado para obtenção de compósito magnético mole compreendendo partículas ferromagnéticas recobertas por ao menos uma camada óxida e ao menos uma camada vítrea; o dito material particulado em que as ditas partículas ferromagnéticas compreendem metais puros ou ligas ferromagnéticas contendo ao menos um dos elementos selecionado entre Fe, Ni e Co e compreende partículas de tamanho médio entre lOpm e 500pm; a camada óxida compreende partículas nanométricas de óxidos selecionados a partir de ZnO, T1O2, MgO, AI2O3, Mh3<04, MnO, Mh2q3, MnCh, MnCb e Mh2q7 com tamanho médio entre 0,005pm e lpm; a camada vítrea compreende fase vítrea ou precursor de fase vítrea baseado em compostos selecionados a partir de silicatos de metais alcalinos do tipo vidro líquido como Na20-nSiC>2 e BbO-mSiCh ou óxido de boro ou precursores de óxido de boro como ácido bórico, ácido metabórico, ácido tetrabórico, tetraborato de amónia, pentaborato, peroxiborato . [0017] All the objectives mentioned above are achieved by means of a particulate material to obtain a soft magnetic composite comprising ferromagnetic particles covered by at least one oxide layer and at least one glassy layer; said particulate material in which said ferromagnetic particles comprise pure metals or ferromagnetic alloys containing at least one of the elements selected from Fe, Ni and Co and comprises particles of average size between 10pm and 500pm; the oxide layer comprises nanometric particles of oxides selected from ZnO, T1O2, MgO, AI2O3, M h 3 <04, MnO, M h 2q3, MnCh, MnCb and M h 2q7 with an average size between 0.005pm and lpm; the vitreous layer comprises vitreous phase or precursor to vitreous phase based on compounds selected from alkali metal silicates such as liquid glass like Na20-nSiC> 2 and BbO-mSiCh or boron oxide or boron oxide precursors such as boric acid, metabolic acid, tetraboric acid, ammonium tetraborate, pentaborate, peroxyborate.
[0018] Ademais, os objetivos são alcançados por meio de uma processo de produção de material particulado para obtenção de compósito magnético mole em que o recobrimento das partículas ferromagnéticas pela camada óxida se caracteriza por ocorrer através de mistura via líquida das partículas ferromagnéticas com uma suspensão de nanopartícuias de ao menos um dos óxidos selecionados dentre ZnO, T1O2, MgO, AI2O3, Mn3C>4, MnO, Mn2C>3, MnC>2, MnC>3, Mn2C>7. [0018] In addition, the objectives are achieved through a process of producing particulate material for obtaining a soft magnetic composite in which the coating of ferromagnetic particles by the oxide layer is characterized by a liquid mixing of the ferromagnetic particles with a suspension of nanoparticles of at least one of the oxides selected from ZnO, T1O2, MgO, AI2O3, Mn3C> 4, MnO, Mn2C> 3, MnC> 2, MnC> 3, Mn2C> 7.
[0019] Adicionalmente, no processo ora proposto, as nanopartícuias de ao menos um dos óxidos ZnO, TÍO2, MgO, AI2O3, Mh3q4, MnO, M¾q3, Mhq2, Mhq3, Mh2q7 são preferencialmente sintetizadas a partir de hidróxidos metálicos de Zn, Ti, Mg, Ai ou Mn simultaneamente à dita etapa de mistura com as partículas ferromagnéticas pela reação entre hidróxidos solúveis em água e precursores de hidróxidos metálicos. [0019] Additionally, in the process now proposed, nanoparticles of at least one of the oxides ZnO, THIO2, MgO, AI2O3, M h 3q4, MnO, M¾q3, M h q2, M h q3, M h 2q7 are preferably synthesized from of metallic hydroxides of Zn, Ti, Mg, Ai or Mn simultaneously to the said mixing stage with ferromagnetic particles by the reaction between water-soluble hydroxides and precursors of metallic hydroxides.
[0020] Ainda, de acordo com a invenção, o processo de produção de material particulado para obtenção de compósito magnético mole, prevê que os hidróxidos solúveis em água são selecionados a partir de NaOH, KOH, NH4OH e sais metálicos precursores dos hidróxidos metálicos são selecionados a partir de sais de Zn, Ti, Mg, Ai ou Mn. [0020] Also, according to the invention, the process of producing particulate material to obtain soft magnetic composite, provides that water-soluble hydroxides are selected from NaOH, KOH, NH 4 OH and metal salts precursors of the hydroxides Metals are selected from Zn, Ti, Mg, Ai or Mn salts.
[0021] Também, para atingir os objetivos propostos, o processo de produção prevê que o recobrimento das partículas ferromagnéticas com a camada óxida é realizado em meio líquido; o processo compreendendo as etapas de: (I) mistura, sob agitação, das partículas ferromagnéticas, na proporção em massa de 30% a 60%, com uma suspensão contendo nanopartícuias óxidas ou hidróxidos metálicos precursores de nanopartícuias sintetizados simultaneamente à etapa de mistura dessa suspensão com as partículas ferromagnéticas, contendo uma concentração molar de nanopartícuias entre 1 e 500mM; (II) remoção do excesso da suspensão de nanopartícuias e subsequente secagem da mistura obtida na etapa (I) em temperaturas entre temperatura ambiente e 150 °C. [0021] Also, to achieve the proposed objectives, the production process provides that the coating of the ferromagnetic particles with the oxide layer is carried out in a liquid medium; the process comprising the steps of: (I) mixing, under agitation, the ferromagnetic particles, in a mass proportion of 30% to 60%, with a suspension containing oxide nanoparticles or metallic hydroxides precursors of nanoparticles synthesized simultaneously with the mixing step of this suspension with ferromagnetic particles, containing a molar concentration of nanoparticles between 1 and 500mM; (II) removal of excess nanoparticles suspension and subsequent drying of the mixture obtained in step (I) at temperatures between room temperature and 150 ° C.
[0022] Além disso, no processo de produção de material particulado para obtenção de compósito magnético mole da presente invenção, as partículas ferromagnéticas previamente recobertas pela camada óxida, são recobertas com o material isolante da camada vítrea, o processo compreendendo as etapas: (I) recobrimento das partículas ferromagnéticas por meio de imersão ou molhamento incipiente com uma suspensão de silicatos de metal alcalino do tipo vidro líquido ou óxido de boro ou precursor de fase vítrea baseado em precursores de óxido de boro selecionados a partir de ácido bórico, ácido metabórico, ácido tetrabórico, tetraborato de amónia, pentaborato, peroxiborato, na proporção em massa de 65% a 95% de partículas ferromagnéticas revestidas e 5% a 35% de suspensão de fase vítrea ou precursor de fase vítrea; e (II) secagem do compósito revestido com temperatura entre temperatura ambiente e 150 °C. [0022] Furthermore, in the process of producing particulate material to obtain the soft magnetic composite of the present invention, the ferromagnetic particles previously covered by the oxide layer, are covered with the insulating material of the vitreous layer, the process comprising the steps: (I ) coating of ferromagnetic particles by immersion or incipient wetting with a suspension of alkali metal silicates of the type liquid glass or boron oxide or glass phase precursor based on boron oxide precursors selected from boric acid, metabolic acid, tetraboric acid, ammonium tetraborate, pentaborate, peroxyborate, in the proportion by weight of 65% to 95% of coated ferromagnetic particles and 5% to 35% of glass phase suspension or glass phase precursor; and (II) drying the coated composite at a temperature between room temperature and 150 ° C.
[0023] Ademais, no processo em questão a solução de precursores de óxido de boro é composta pela diluição de um ou mais precursores selecionados a partir de ácido bórico, ácido metabórico, ácido tetrabórico, tetraborato de amónia, pentaborato, peroxiborato; a solução dos ditos precursores sendo preparada em uma concentração entre 0,001g/mL e lg/mL e contendo uma massa de precursores entre 0,01% a 10,00% em relação à massa de partículas ferromagnéticas do compósito magnético mole. [0023] Furthermore, in the process in question the solution of boron oxide precursors is composed of the dilution of one or more precursors selected from boric acid, metabolic acid, tetraboric acid, ammonium tetraborate, pentaborate, peroxyborate; the solution of said precursors being prepared in a concentration between 0.001g / mL and lg / mL and containing a mass of precursors between 0.01% to 10.00% in relation to the mass of ferromagnetic particles of the soft magnetic composite.
[0024] Por fim, no processo de produção ora proposto, a solução de silicato de metal alcalino é composta pela diluição de um ou mais silicatos, sendo que a razão molar entre as moléculas de sílica e óxidos de metal alcalino deve estar entre 0,5 e 8; a solução de silicato de metal alcalino ou mistura de silicatos deve conter uma concentração de sólidos entre 0,001mg/ml e 15mg/ml. [0024] Finally, in the production process now proposed, the alkali metal silicate solution is composed of the dilution of one or more silicates, and the molar ratio between the silica molecules and alkali metal oxides must be between 0.5 and 8; the alkali metal silicate solution or mixture of silicates should contain a solids concentration between 0.001mg / ml and 15mg / ml.
Breve descrição das figuras Brief description of the figures
[0025] Apresente invenção é pormenorizadamente detalhada com base nas figuras abaixo listadas, as quais: [0025] Present invention is detailed in detail based on the figures listed below, which:
[0026] A figura 1 ilustra as partículas ferromagnéticas com duplo revestimento isolante; [0026] Figure 1 illustrates ferromagnetic particles with double insulating coating;
[0027] A figura 2 ilustra o comportamento das camadas óxida e vítrea durante as etapas de compactação e tratamento térmico na interface entre as partículas ferromagnéticas recobertas ; [0027] Figure 2 illustrates the behavior of the oxide and vitreous layers during the stages of compaction and heat treatment at the interface between the coated ferromagnetic particles;
[0028] A figura 3 ilustra as vantagens no comportamento magnético em termos de redução de perdas magnéticas do material patenteado com dupla camada de isolantes em relação as soluções contendo apenas uma camada de isolante; [0028] Figure 3 illustrates the advantages in magnetic behavior in terms of reducing magnetic losses of the patented material with double insulating layer in relation to solutions containing only one insulating layer;
Descrição Detalhada da Invenção Detailed Description of the Invention
[0029] As descrições e discussões que se seguem são apresentadas a título de aprofundamento, não limitativas ao escopo da invenção, e farão compreender de forma mais clara o objeto da presente invenção. Também são apresentados exemplos específicos de aplicação da invenção com vantagens atingidas . [0029] The descriptions and discussions that follow are presented for the sake of depth, not limiting the scope of the invention, and will make the object of the present invention more clearly understood. Specific examples of application of the invention with advantages achieved are also presented.
[0030] De acordo com os objetivos centrais da invenção em questão, é revelado um material particulado para obtenção de compósito magnético mole (aqui, também, denominado de SMC) compreendendo partículas ferromagnéticas revestidas por ao menos uma camada óxida e ao menos uma camada vítrea; em que a camada óxida compreende partículas nanométricas de óxidos selecionados a partir de ZnO, T1O2, MgO, AI2O3, MnsCq, MnO, Mh2q3, Mhq2, MnCb e Mh2q7," em que a camada vítrea compreende uma fase óxida com baixa temperatura de transição vítrea ou precursor de fase vítrea baseado em compostos selecionados a partir de silicatos de metais alcalinos do tipo vidro líquido como Na20-nSiC>2 e BbO-mSiCh ou óxido de boro ou precursores de óxido de boro como ácido bórico, ácido metabórico, ácido tetrabórico, tetraborato de amónia, pentaborato, peroxiborato ; o compósito magnético mole no qual as nanopartícuias que compreendem a camada óxida possuem tamanho médio entre 0,005pm e lpm e mais preferencialmente entre 0,01 pm e 0,5 pm; as partículas ferromagnéticas compreendendo metais puros ou ligas ferromagnéticas contendo ao menos um dos elementos selecionado entre Fe, Ni e Co e compreende partículas de tamanho médio entre 10pm e 500pm e mais preferencialmente entre 100 pm e 300 pm. [0030] In accordance with the central objectives of the invention in question, a particulate material is disclosed for obtaining a soft magnetic composite (here also called SMC) comprising ferromagnetic particles coated by at least one oxide layer and at least one vitreous layer ; where the oxide layer comprises nanometric particles of oxides selected from ZnO, T1O2, MgO, AI2O3, MnsCq, MnO, Mh2q3, Mhq2, MnCb and Mh2q7, "where the glassy layer comprises an oxide phase with low glass transition temperature or glass phase precursor based on compounds selected from alkali metal silicates such as liquid glass like Na20-nSiC> 2 and BbO-mSiCh or boron oxide or boron oxide precursors like boric acid, metabolic acid, tetraboric acid, ammonium tetraborate, pentaborate, peroxyborate; the soft magnetic composite in which the nanoparticles comprising the oxide layer have an average size between 0.005pm and lpm and more preferably between 0.01 pm and 0.5 pm; ferromagnetic particles comprising pure metals or ferromagnetic alloys containing at least one of the elements selected from Fe, Ni and Co and comprising particles of average size between 10pm and 500pm and more preferably between 100 pm and 300 pm.
[0031] Como acima relatado, o material particulado para obtenção de compósito magnético mole é constituído por mais de uma camada de isolante, sendo uma primeira camada de isolante inorgânico baseado em partículas nanométricas de óxidos, denominada nessa invenção como camada óxida. Essa camada inclui nanopartícuias de óxido de zinco, óxido de magnésio, óxido de alumínio, óxido de titânio ou óxido de manganês, ou ainda mistura desses óxidos. Essas partículas nanométricas recobrem as partículas ferromagnéticas preferencialmente em meio líquido por contato sob agitação com uma dispersão de partículas nanométricas desses óxidos ou com suspensões sol-gel de hidróxidos desses elementos, os quais são convertidos para forma de óxidos no decorrer do processamento. Durante a etapa de compactação, as mencionadas partículas nanométricas da camada óxida penetram, ainda que minimamente, a superfície das partículas ferromagnéticas. Esse efeito leva a um aumento da adesão da camada óxida sobre as partículas ferromagnéticas. [0031] As reported above, the particulate material for obtaining a soft magnetic composite consists of more than one insulating layer, being a first layer of inorganic insulation based on nanometric oxide particles, referred to in this invention as the oxide layer. This layer includes nanoparticles of zinc oxide, magnesium oxide, aluminum oxide, titanium oxide or manganese oxide, or a mixture of these oxides. These nanometric particles cover the ferromagnetic particles preferentially in a liquid medium by contact under agitation with a dispersion of nanometric particles of these oxides or with sol-gel suspensions of hydroxides of these elements, which are converted to oxide form in the course of processing. During the compaction stage, the aforementioned nanometric particles in the oxide layer penetrate, even if minimally, the surface of the ferromagnetic particles. This effect leads to an increase in oxide layer on the ferromagnetic particles.
[0032] Uma segunda camada de isolante inorgânico contendo uma fase óxida com baixa temperatura de transição vítrea ou um precursor da mesma, tal como silicatos de metais alcalinos do tipo vidro líquido (Na20 · nSiCb e K2O · mSiCb ) , óxido de boro B2O3 ou seus precursores como ácido bórico, ácido metabórico, ácido tetrabórico, tetraborato de amónia, pentaborato, peroxiborato ou similares. Essa camada, nomeada nessa invenção como camada vítrea, possui alta resistividade elétrica e bom molhamento em relação aos compostos da camada óxida, de forma a permitir o mecanismo de autorregeneração de trincas durante tratamento térmico. Somando-se o efeito de regeneração de trincas e a adesão da primeira camada sobre as partículas ferromagnéticas, tem-se um revestimento completo das partículas ferromagnéticas, promovendo a alta resistividade elétrica e baixas perdas magnéticas do SMC . [0032] A second layer of inorganic insulator containing an oxide phase with a low glass transition temperature or a precursor thereof, such as alkali metal silicates such as liquid glass (Na20 · nSiCb and K2O · mSiCb), boron oxide B2O3 or its precursors such as boric acid, metabolic acid, tetraboric acid, ammonium tetraborate, pentaborate, peroxyborate or similar. This layer, named in this invention as the vitreous layer, has high electrical resistivity and good wetting in relation to the compounds of the oxide layer, in order to allow the mechanism of self-healing of cracks during heat treatment. Adding to the crack regeneration effect and the adhesion of the first layer on the ferromagnetic particles, there is a complete coating of the ferromagnetic particles, promoting the high electrical resistivity and low magnetic losses of the SMC.
[0033] Referente as partículas ferromagnéticas, a seleção do tamanho de partícula define uma forma eficaz de ajustar as propriedades ótimas para aplicação em diferentes frequências, utilizando o mesmo sistema de isolantes e mesmo método de recobrimento . [0033] Regarding ferromagnetic particles, the selection of the particle size defines an effective way of adjusting the optimal properties for application at different frequencies, using the same insulating system and the same covering method.
[0034] A primeira camada do revestimento, denominada camada óxida, contribui para aumento da resistividade elétrica pela sua natureza isolante e melhora as condições de molhamento da segunda camada isolante do revestimento, denominada camada vítrea, sobre as partículas ferromagnéticas durante o tratamento térmico para produção dos compósitos magnéticos moles. [0034] The first layer of the coating, called the oxide layer, contributes to increase the electrical resistivity due to its insulating nature and improves the wetting conditions of the second insulating layer of the coating, called the glassy layer, on the ferromagnetic particles during the heat treatment for production of soft magnetic composites.
[0035] Os óxidos formados apresentam grande afinidade química em relação a camada vítrea, reduzindo a energia de interface entre os compostos e resultando em uma boa molhabilidade entre eles, ou seja, formam um baixo ângulo de contato da camada vítrea sobre a camada de nanopartícuias óxidas . Por conta dessa boa molhabilidade, pode-se obter um recobrimento completo da partícula ferromagnética e promover um efeito sinérgico entre as duas camadas que resulta em um filme isolante de alta resistividade e boa adesão sobre as partículas ferromagnéticas. [0035] The oxides formed have great chemical affinity in relation to the vitreous layer, reducing the interface energy between the compounds and resulting in a good wettability between them, that is, they form a low contact angle of the vitreous layer on the oxide nanoparticles layer. Because of this good wettability, it is possible to obtain a complete coating of the ferromagnetic particle and promote a synergistic effect between the two layers that results in an insulating film of high resistivity and good adhesion on the ferromagnetic particles.
[0036] Outra importante vantagem que essa sinergia entre as camadas isolantes produz, é a possibilidade de utilizar a capacidade de autorregeneração do revestimento vítreo durante o tratamento térmico sem passar pelos problemas de escoamento dessa camada para fora da interface entre as partículas ferromagnéticas. Esse efeito somente é possível graças ao ancoramento dessa camada vítrea pelas nanopartícuias da camada óxida. Dessa forma, evita-se a redução drástica da resistividade elétrica observado em compósitos magnéticos moles que se utilizam apenas de um recobrimento vítreo. Por conta desse ancoramento pode-se também utilizar temperaturas de tratamento térmicos mais elevadas que as usuais ( aproximadamente 500 °C) sem que ocorra grande prejuízo da resistividade elétrica do compósito, resultando assim em um material com menores perdas estáticas, especialmente interessante para aplicações em baixas frequências (50-60 Hz) . Além de agir como ancorador da camada vítrea durante o tratamento térmico, a camada óxida também pode atuar como agente nucleador para o processo de cristalização da fase vítrea, o que aumenta a viscosidade da camada vítrea e auxilia na manutenção da alta resistividade elétrica do filme isolante. [0036] Another important advantage that this synergy between the insulating layers produces, is the possibility of using the self-healing capacity of the vitreous coating during the thermal treatment without going through the problems of flowing that layer out of the interface between the ferromagnetic particles. This effect is only possible thanks to the anchoring of this vitreous layer by the nanoparticles of the oxide layer. In this way, the drastic reduction in electrical resistivity observed in soft magnetic composites that use only a glassy coating is avoided. Because of this anchoring, it is also possible to use heat treatment temperatures higher than the usual ones (approximately 500 ° C) without causing great damage to the electrical resistivity of the composite, thus resulting in a material with lower static losses, especially interesting for applications in low frequencies (50-60 Hz). In addition to acting as an anchor for the vitreous layer during heat treatment, the oxide layer can also act as a nucleating agent for the crystallization process of the vitreous phase, which increases the viscosity of the vitreous layer and assists in maintaining the high electrical resistivity of the insulating film. .
[0037] É importante ressaltar que, ao longo do texto, são definidas faixas específicas para tamanho das partículas ferromagnéticas, tamanho das nanoparticulas que compõem a camada óxida, concentração molar da suspensão de nanoparticulas, concentração da solução e massa de precursores de fase vítrea, razão molar entre moléculas de sílica e óxidos de metal alcalino, além da concentração de sólidos na suspensão de silicato de metal alcalino. Essas faixas específicas foram definidas no processo de desenvolvimento visando aplicações em média e baixa frequência. No entanto, o compósito magnético mole ora proposto encontra aplicações voltadas para alta frequência, onde tamanhos menores de partículas ferromagnéticas e condições de processamento que levem a formação de filmes mais espessos são tecnicamente benéficos. Esses benefícios são facilmente alcançados utilizando as técnicas mencionadas nessa patente com ajustes de parâmetros técnicos, mas sem prejuízo da rota ou da caracterização do produto final. [0037] It is important to note that, throughout the text, specific ranges for particle size are defined ferromagnetic, size of the nanoparticles that make up the oxide layer, molar concentration of the nanoparticle suspension, solution concentration and mass of glass phase precursors, molar ratio between silica molecules and alkali metal oxides, in addition to the concentration of solids in the silicate suspension of alkali metal. These specific bands were defined in the development process aiming at medium and low frequency applications. However, the proposed soft magnetic composite now finds applications aimed at high frequency, where smaller sizes of ferromagnetic particles and processing conditions that lead to the formation of thicker films are technically beneficial. These benefits are easily achieved using the techniques mentioned in this patent with adjustments to technical parameters, but without prejudice to the route or characterization of the final product.
[0038] Ainda, e como acima relatado, a presente invenção propõe um processo de produção de um material particulado para obtenção de compósito magnético mole em que o recobrimento das partículas ferromagnéticas pela camada óxida se caracteriza por ocorrer através de mistura via líquida das partículas ferromagnéticas com uma suspensão de nanoparticulas de ao menos um dos óxidos selecionados dentre ZnO, T1O2, MgO, AI2O3, Mn3C>4, MnO, Mn2C>3, MnCó, MnCq, Mn2C>7. [0038] Also, and as reported above, the present invention proposes a process for the production of a particulate material to obtain a soft magnetic composite in which the coating of the ferromagnetic particles by the oxide layer is characterized by occurring through liquid mixing of the ferromagnetic particles with a suspension of nanoparticles of at least one of the oxides selected from ZnO, T1O2, MgO, AI2O3, Mn3C> 4, MnO, Mn2C> 3, MnCó, MnCq, Mn2C> 7.
[0039] Ademais, no processo ora proposto, as nanoparticulas de ao menos um dos óxidos ZnO, T1O2, MgO, AI2O3, Mh3q4, MnO, M¾q3, Mhq2, Mhq3, Mh2q7 são preferencialmente sintetizadas a partir de hidróxidos metálicos de Zn, Ti, Mg, Ai ou Mn simultaneamente à dita etapa de mistura com as partículas ferromagnéticas pela reação entre hidróxidos solúveis em água e precursores de hidróxidos metálicos; sendo que os hidróxidos solúveis em água são selecionados a partir de NaOH, KOH, NH4OH ou similares e sais metálicos precursores dos hidróxidos metálicos são selecionados a partir de sais de Zn, Ti, Mg, Ai ou Mn . [0039] Furthermore, in the process now proposed, nanoparticles of at least one of the oxides ZnO, T1O2, MgO, AI2O3, Mh3q4, MnO, M¾q3, Mhq2, Mhq3, Mh2q7 are preferably synthesized from metallic hydroxides of Zn, Ti, Mg, Ai or Mn simultaneously to said mixing stage with ferromagnetic particles by the reaction between water-soluble hydroxides and precursors of metal hydroxides; the water-soluble hydroxides being selected from NaOH, KOH, NH4OH or similar and metal salts precursor to the metal hydroxides are selected from Zn, Ti, Mg, Ai or Mn salts.
[0040] Preferencialmente, o recobrimento das partículas ferromagnéticas com a camada óxida é realizado em meio líquido; o processo compreende as etapas de: mistura, sob agitação, das partículas ferromagnéticas, na proporção em massa de 30% a 60%, com uma suspensão contendo nanopartícuias óxidas ou hidróxidos metálicos precursores de nanopartícuias sintetizados simultaneamente à etapa de mistura dessa suspensão com as partículas ferromagnéticas, contendo uma concentração molar de nanopartícuias entre 1 e 500mM, e remoção do excesso da suspensão de nanopartícuias e subsequente secagem da mistura obtida na etapa (I) em temperaturas entre temperatura ambiente e 150 °C. [0040] Preferably, the ferromagnetic particles are coated with the oxide layer in a liquid medium; the process comprises the steps of: mixing, under agitation, the ferromagnetic particles, in a mass proportion of 30% to 60%, with a suspension containing oxide nanoparticles or metallic hydroxides precursors of nanoparticles synthesized simultaneously with the mixing step of this suspension with the particles ferromagnetic, containing a molar concentration of nanoparticles between 1 and 500mM, and removal of excess nanoparticles suspension and subsequent drying of the mixture obtained in step (I) at temperatures between room temperature and 150 ° C.
[0041] Posteriormente ao recobrimento das partículas ferromagnéticas, que previamente foram recobertas pela camada óxida, ocorre o recobrimento com material isolante da camada vítrea, em um processo que compreende as etapas de: recobrimento das partículas ferromagnéticas por meio de imersão ou molhamento incipiente com uma suspensão de silicatos de metal alcalino do tipo vidro líquido ou óxido de boro ou precursor de fase vítrea baseado em precursores de óxido de boro selecionados a partir de ácido bórico, ácido metabórico, ácido tetrabórico, tetraborato de amónia, pentaborato, peroxiborato ou similares, na proporção em massa de 65% a 95% de partículas ferromagnéticas revestidas e 5% a 35% de suspensão de fase vítrea ou precursor de fase vítrea; e secagem do compósito revestido com temperatura entre temperatura ambiente e 150 °C. [0041] Subsequent to the coating of the ferromagnetic particles, which were previously covered by the oxide layer, the coating with insulating material of the vitreous layer occurs, in a process comprising the steps of: coating of the ferromagnetic particles by immersion or incipient wetting with a suspension of alkali metal silicates such as liquid glass or boron oxide or glass phase precursor based on boron oxide precursors selected from boric acid, metabolic acid, tetraboric acid, ammonium tetraborate, pentaborate, peroxyborate or similar, na mass proportion of 65% to 95% of coated ferromagnetic particles and 5% to 35% of glass phase suspension or glass phase precursor; and drying the coated composite with temperature between room temperature and 150 ° C.
[0042] No processo de recobrimento das partículas com material isolante da camada vítrea, a solução de precursores de óxido de boro é composta pela diluição de um ou mais precursores selecionados a partir de ácido bórico, ácido metabórico, ácido tetrabórico, tetraborato de amónia, pentaborato, peroxiborato ou similares; a solução dos ditos precursores sendo preparada em uma concentração entre 0,001g/mL e lg/mL e mais preferencialmente entre 0,002g/mL e 0,02g/mL, e contendo uma massa de precursores entre 0,01% a 10,00% e mais preferencialmente entre 0,05% e 5,00% em relação à massa de partículas ferromagnéticas do compósito magnético mole. [0042] In the process of covering the particles with insulating material of the vitreous layer, the solution of boron oxide precursors is composed of the dilution of one or more precursors selected from boric acid, metabolic acid, tetraboric acid, ammonium tetraborate, pentaborate, peroxyborate or the like; the solution of said precursors being prepared at a concentration between 0.001g / mL and lg / mL and more preferably between 0.002g / mL and 0.02g / mL, and containing a mass of precursors between 0.01% to 10.00% and more preferably between 0.05% and 5.00% in relation to the mass of ferromagnetic particles of the soft magnetic composite.
[0043] Preferencialmente no processo ora proposto, a solução de silicato de metal alcalino é composta pela diluição de um ou mais silicatos, sendo que a razão molar entre as moléculas de sílica e óxidos de metal alcalino deve estar entre 0,5 e 8 e mais preferencialmente entre 1,5 e 4; a solução de silicato de metal alcalino ou mistura de silicatos deve conter uma concentração de sólidos entre 0,001mg/ml e 15mg/ml e mais preferencialmente entre 0,005mg/mL e 5mg/mL. [0043] Preferably in the process now proposed, the alkali metal silicate solution is composed of the dilution of one or more silicates, with the molar ratio between the silica molecules and alkali metal oxides being between 0.5 and 8 and more preferably between 1.5 and 4; the alkali metal silicate solution or mixture of silicates must contain a solids concentration between 0.001mg / ml and 15mg / ml and more preferably between 0.005mg / ml and 5mg / ml.
[0044] Aqui é essencial destacar que a expressão "molhamento incipiente" surge da tradução do inglês da expressão Incípíent wetness, que também pode ser traduzido por "impregnação capilar" ou "impregnação seca" e refere-se a processos cíclicos de molhamento parcial e secagem de uma solução sobre um substrato; no caso dessa patente, sobre as partículas ferromagnéticas. Durante esse processo, uma camada de precipitados se forma sobre as partículas de forma homogénea e com uma espessura de camada que pode ser controlada . [0044] Here it is essential to highlight that the expression "incipient wetting" arises from the English translation of the expression Incípíent wetness, which can also be translated by "capillary impregnation" or "dry impregnation" and refers to cyclic processes of partial and drying a solution on a substrate; in the case of that patent, on ferromagnetic particles. During this process, a layer of precipitates forms on the particles homogeneously and with a layer thickness that can be controlled.
[0045] Como uma realização preferencial da presente invenção, uma rota para o processo de produção de um material particulado para obtenção de compósito magnético mole generalizada para produção dos pós contendo duplo revestimento com vista a fabricação de materiais compósitos magnéticos moles segue os passos: 1 - Preparação de uma suspensão contendo nanoparticulas de óxidos ou hidróxidos, a qual pode ser preparada diretamente pela dispersão de nanoparticulas comerciais em meio liquido ou ainda pela mistura de soluções químicas apropriadas para síntese dessas nanoparticulas de forma simultânea à etapa subsequente. 2 - Mistura de partículas ferromagnéticas, sob agitação, com a suspensão preparada na etapa 1 promovendo a adesão das nanoparticulas de óxidos ou hidróxidos, sintetizados simultaneamente ou não, à superfície das partículas ferromagnéticas, formando assim a camada óxida. 3 - Separação magnética do pó ferromagnético, revestido com a camada óxida, do restante da suspensão e secagem. 4 - Adição da camada vítrea, por imersão ou ainda por molhamento incipiente, ao pó ferromagnético recoberto previamente com a camada óxida, usando uma solução contendo compostos vítreos ou precursores que formarão a camada vítrea. 5 - Separação magnética do pó ferromagnético revestido com dupla camada de isolantes do restante da suspensão e secagem. [0045] As a preferred embodiment of the present invention, a route to the production process of a particulate material for obtaining generalized soft magnetic composite for the production of powders containing double coating for the manufacture of soft magnetic composite materials follows the steps: 1 - Preparation of a suspension containing oxide or hydroxide nanoparticles, which can be prepared directly by dispersing commercial nanoparticles in liquid medium or by mixing appropriate chemical solutions for the synthesis of these nanoparticles simultaneously with the subsequent step. 2 - Mixing of ferromagnetic particles, under agitation, with the suspension prepared in step 1 promoting the adhesion of the oxide or hydroxide nanoparticles, synthesized simultaneously or not, to the surface of the ferromagnetic particles, thus forming the oxide layer. 3 - Magnetic separation of ferromagnetic powder, coated with the oxide layer, from the rest of the suspension and drying. 4 - Addition of the vitreous layer, by immersion or incipient wetting, to the ferromagnetic powder previously coated with the oxide layer, using a solution containing glassy compounds or precursors that will form the vitreous layer. 5 - Magnetic separation of ferromagnetic powder coated with double layer of insulators from the rest of the suspension and drying.
[0046] Após as etapas de revestimento e secagem, são obtidas as partículas ferromagnéticas com duplo revestimento tal qual esquematicamente apresentadas na Figura 1. Na sequência, essas partículas são misturadas a um lubrificante de compactação, seguida pelas etapas de compactação uniaxial e tratamento térmico, resultando nas dimensões e microestrutura adequadas para uso do material SMC . [0046] After the coating and drying steps, the double-coated ferromagnetic particles are obtained as schematically shown in Figure 1. Next, these particles are mixed with a compaction lubricant, followed by the uniaxial compaction and heat treatment steps, resulting in the dimensions and microstructure suitable for use of the SMC material.
[0047] Durante a etapa de compactação as nanoparticulas que compõem a camada óxida penetram ligeiramente na superfície das partículas ferromagnéticas devido à diferença de dureza. Isso leva a um melhor ancoramento da camada óxida sobre o pó ferromagnético, apesar de gerar alguma descontinuidade do filme isolante devido às altas pressões da etapa de compactação. Adicionalmente, alguns precursores da camada vítrea, como ácido bórico (H3BO3) por exemplo, podem adicionar um efeito lubrificante, auxiliando o processamento do material nessa etapa de compactação. Após a compactação, as peças compactadas de SMC são normalmente levadas a um tratamento térmico para alívio de tensões e aumento de resistência mecânica. Para o material da presente invenção, além dos objetivos anteriores também se busca a formação da fase vítrea, quando adicionados apenas precursores dessa fase, e o processo de autorregeneração das trincas. A autorregeneração advém da boa molhabilidade entre os compostos utilizados na camada óxida e os compostos que compõem a camada vítrea ao final do tratamento térmico. Desses pares de óxidos da camada óxida e da camada vítrea com boa molhabilidade entre si, pode-se citar: ZnO - B2O3, MgO — B2O3, AI2O3 — B2O3, T1O2 — B2O3, Mh3q4 — B2O3, ZnO — K20-mSi02, MgO - K20-mSi02, AI2O3 - K20-mSi02, T1O2 - K20-mSi02, Mh3q4 - K20-mSi02, ZnO - Na20-nSi02, MgO - Na20-nSi02, AI2O3 - Na20-nSi02, T1O2 - Na20-nSi02, M¾q4 - Na20-nSi02; onde se lê Mh3q4 também pode-se utilizar outros óxidos de manganês como MnO, M¾q3, Mhq2, Mhq3 e M¾q7. Uma vez que a camada óxida encontra-se bem aderida à superfície da partícula ferromagnética, a camada vítrea acaba por recobrir toda a partícula ferromagnética, permitindo regenerar as trincas de revestimento geradas na etapa de compactação durante o tratamento térmico posterior. Além de agir como ancorador da camada vítrea durante o tratamento térmico, a camada óxida também atua como agente nucleador para o processo de cristalização da fase vítrea, podendo inclusive ser parcialmente dissolvida durante esse processo. O comportamento das camadas óxida e vítrea durante as etapas de compactação e tratamento térmico na interface entre duas partículas ferromagnéticas revestidas são esquematicamente apresentadas na Figura 2. [0047] During the compaction stage, the nanoparticles that make up the oxide layer slightly penetrate the surface of the ferromagnetic particles due to the difference in hardness. This leads to a better anchoring of the oxide layer on the ferromagnetic powder, despite generating some discontinuity of the insulating film due to the high pressures of the compaction step. In addition, some precursors of the vitreous layer, such as boric acid (H 3 BO 3 ), for example, can add a lubricating effect, helping to process the material in this compacting stage. After compacting, SMC compacted parts are usually heat treated to relieve stress and increase mechanical strength. For the material of the present invention, in addition to the previous objectives, the formation of the vitreous phase is also sought, when only precursors of that phase are added, and the process of self-healing of the cracks. Self-regeneration comes from good wettability between the compounds used in the oxide layer and the compounds that make up the glassy layer at the end of the heat treatment. Of these oxide pairs of the oxide layer and the vitreous layer with good wettability, we can mention: ZnO - B 2 O 3 , MgO - B2O3, AI2O3 - B2O3, T1O2 - B2O3, M h 3q4 - B2O3, ZnO - K 2 0-mSi0 2 , MgO - K 2 0-mSi0 2 , AI2O3 - K 2 0-mSi0 2 , T1O2 - K 2 0-mSi0 2 , M h 3q4 - K20-mSi02, ZnO - Na20-nSi02, MgO - Na20 -nSi02, AI2O3 - Na20-nSi02, T1O2 - Na20-nSi02, M¾q4 - Na20-nSi02; where Mh 3 q 4 is read, other manganese oxides such as MnO, M¾q3, Mhq2, Mhq3 and M¾q7 can also be used. Once the oxide layer is well adhered to the surface of the ferromagnetic particle, the vitreous layer ends up covering the entire ferromagnetic particle, allowing to regenerate the cracks of coating generated during the compaction stage during the subsequent heat treatment. In addition to acting as an anchor for the vitreous layer during heat treatment, the oxide layer also acts as a nucleating agent for the crystallization process of the vitreous phase, and may even be partially dissolved during this process. The behavior of the oxide and vitreous layers during the stages of compaction and heat treatment at the interface between two coated ferromagnetic particles are shown schematically in Figure 2.
Realizações Preferenciais Preferred Achievements
[0048] Na sequência são apresentados alguns exemplos não limitativos ao escopo da invenção e de aplicação do processo de produção e do material particulado reivindicados nessa invenção . [0048] Following are some examples not limited to the scope of the invention and application of the production process and particulate material claimed in that invention.
Exemplo 1 : ZnO - B2O3 Example 1: ZnO - B2O3
[0049] (a) Formação da Camada Óxida - ZnO: Partículas de ferro, com tamanho médio de partícula de 180pm, são imersas em uma solução aquosa contendo hidróxido de sódio (NaOH) de concentração 0,32%, de tal maneira que a concentração mássica de partículas ferromagnéticas na solução seja igual a 44%. Na sequência, uma solução aquosa contendo acetato de zinco dihidratado ( Zn (CH3COO) 2 · 2H2O) com concentração mássica de 0,87% e mesmo volume que a solução de NaOH anterior é adicionada, sob forte agitação, à solução de NaOH contendo as partículas de ferro, a fim de sintetizar nanopartícuias de hidróxido de zinco (Zn (OH) 2), em um pH controlado próximo de 8, concomitantemente à adesão dessas nanopartícuias à superfície das partículas de ferro. Como resultado da mistura de reagentes, obtém-se uma suspensão de Zn (OH) 2 de concentração molar igual a 20mM, a qual é mantida em contato com as partículas de ferro sob agitação forte o suficiente para manter as partículas de ferro suspensas, durante o período de 1 hora. Após o tempo de mistura, as partículas de ferro recobertas com as nanopartícuias isolantes são separadas do restante da suspensão, lavadas com uma mistura de etanol e água, e por fim secas em estufa a vácuo em 80°C por 30 minutos. Após a secagem, obtém-se as partículas de ferro revestidas com uma camada de nanopartícuias de óxido de zinco (ZnO) . Essa camada advém da transformação do Zn (OH) 2 em ZnO, iniciada ainda na etapa de mistura e finalizada na etapa de secagem. [0049] (a) Formation of the Oxide Layer - ZnO: Iron particles, with an average particle size of 180pm, are immersed in an aqueous solution containing sodium hydroxide (NaOH) with a concentration of 0.32%, in such a way that the mass concentration of ferromagnetic particles in the solution is equal to 44%. Then, an aqueous solution containing zinc acetate dihydrate (Zn (CH3COO) 2 · 2H2O) with a mass concentration of 0.87% and the same volume as the previous NaOH solution is added, under strong stirring, to the NaOH solution containing the iron particles, in order to synthesize zinc hydroxide (Zn (OH) 2) nanoparticles, at a controlled pH close to 8, concomitantly with the adhesion of these nanoparticles to the surface of the iron particles. As a result of mixing reagents, a suspension of Zn (OH) 2 of 20 mM molar concentration is obtained, which is kept in contact with the iron particles under agitation strong enough to keep the iron particles suspended for the period of 1 hour. After the mixing time, the iron particles covered with the insulating nanoparticles are separated from the rest of the suspension, washed with a mixture of ethanol and water, and finally dried in a vacuum oven at 80 ° C for 30 minutes. After drying, the iron particles are coated with a layer of zinc oxide (ZnO) nanoparticles. This layer comes from the transformation of Zn (OH) 2 into ZnO, which started in the mixing stage and ended in the drying stage.
[0050] (b) Formação da Camada Vítrea - Precursor de B2O3: [0050] (b) Formation of the Vitreous Layer - B2O3 Precursor:
Após a adição da primeira camada de revestimento, prepara- se uma solução aquecida de isopropanol contendo concentração mássica de 0,5% de ácido bórico (H3BO3) dissolvido. O pó de ferro, revestido com ZnO como camada óxida, é então imerso nessa solução de forma que a concentração mássica do pó ferromagnético nessa solução seja de 83,5%. O pó é mantido em contato com a solução até a secagem completa por evaporação do isopropanol. Após a secagem do isopropanol, têm-se as partículas de ferro com duplo revestimento de isolantes, isto é, contendo a camada óxida e precursor da camada vítrea. After adding the first coating layer, a heated solution of isopropanol containing a mass concentration of 0.5% boric acid (H 3 BO 3 ) dissolved is prepared. The iron powder, coated with ZnO as an oxide layer, is then immersed in this solution so that the mass concentration of the ferromagnetic powder in this solution is 83.5%. The powder is kept in contact with the solution until complete drying by evaporation of isopropanol. After the isopropanol has dried, iron particles have a double coating of insulators, that is, containing the oxide layer and precursor to the glassy layer.
[0051] (c) Processamento por Metalurgia do Pó: Uma vez que o pó ferromagnético tenha passado pelas duas etapas de revestimento, este é misturado com 0,3% em peso de lubrificante, compactado em prensa uniaxial de duplo efeito com uma pressão de 800 MPa no formato de um toróide e tratado termicamente . O tratamento térmico é realizado sob uma atmosfera de ar sintético com um patamar de temperatura de extração de lubrificante; nesse exemplo é utilizada uma temperatura de 320°C por 30 minutos, e um segundo patamar em uma temperatura mais alta para alivio de tensões e aumento da resistência mecânica, em que para a amostra do exemplo em questão, é utilizada a temperatura de 500°C em um patamar de 30 minutos. [0051] (c) Powder Metallurgy Processing: Once the ferromagnetic powder has passed through the two coating steps, it is mixed with 0.3% by weight of lubricant, compacted in a double-acting uniaxial press with a pressure of 800 MPa in the shape of a toroid and heat treated. The heat treatment is carried out under an atmosphere of synthetic air with a level of lubricant extraction temperature; in this example, a temperature of 320 ° C for 30 minutes, and a second level at a higher temperature for stress relief and increased mechanical strength, where for the sample in question, the temperature of 500 ° C is used at a level of 30 minutes.
Exemplo Comparativo 1 : Somente ZnO Comparative Example 1: ZnO only
[0052] (a) Formação da Camada Óxida - ZnO: Partículas de ferro, com tamanho médio de partícula de 180pm, são imersas em uma solução aquosa contendo hidróxido de sódio (NaOH) de concentração 0,32%, de tal maneira que a concentração mássica de partículas ferromagnéticas na solução seja igual a 44%. Na sequência, uma solução aquosa contendo acetato de zinco dihidratado ( Zn (CH3COO) 2 · 2H2O) com concentração mássica de 0,87% e mesmo volume que a solução de NaOH anterior é adicionada, sob forte agitação, à solução de NaOH contendo as partículas de ferro, a fim de sintetizar nanopartícuias de hidróxido de zinco (Zn (OH) 2), em um pH controlado próximo de 8, concomitantemente à adesão dessas nanopartícuias à superfície das partículas de ferro. Como resultado da mistura de reagentes, obtém-se uma suspensão de Zn (OH) 2 de concentração molar igual a 20mM, a qual é mantida em contato com as partículas de ferro sob agitação forte o suficiente para manter as partículas de ferro suspensas, durante o período de 1 hora. Após o tempo de mistura, as partículas de ferro recobertas com as nanopartícuias isolantes são separadas do restante da suspensão, lavadas com uma mistura de etanol e água, e por fim secas em estufa a vácuo em 80°C por 30 minutos. Após a secagem, obtém-se as partículas de ferro revestidas com uma camada de nanopartícuias de óxido de zinco (ZnO) . Essa camada advém da transformação do Zn (OH) 2 em ZnO, iniciada ainda na etapa de mistura e finalizada na etapa de secagem. [0052] (a) Formation of the Oxide Layer - ZnO: Iron particles, with an average particle size of 180pm, are immersed in an aqueous solution containing sodium hydroxide (NaOH) with a concentration of 0.32%, in such a way that the mass concentration of ferromagnetic particles in the solution is equal to 44%. Then, an aqueous solution containing zinc acetate dihydrate (Zn (CH3COO) 2 · 2H2O) with a mass concentration of 0.87% and the same volume as the previous NaOH solution is added, under strong stirring, to the NaOH solution containing the iron particles, in order to synthesize zinc hydroxide (Zn (OH) 2) nanoparticles, at a controlled pH close to 8, concomitantly with the adhesion of these nanoparticles to the surface of the iron particles. As a result of mixing reagents, a suspension of Zn (OH) 2 of 20 mM molar concentration is obtained, which is kept in contact with the iron particles under agitation strong enough to keep the iron particles suspended, during the 1 hour period. After the mixing time, the iron particles covered with the insulating nanoparticles are separated from the rest of the suspension, washed with a mixture of ethanol and water, and finally dried in a vacuum oven at 80 ° C for 30 minutes. After drying, the iron particles are coated with a layer of zinc oxide (ZnO) nanoparticles. This layer comes from the transformation of Zn (OH) 2 into ZnO, which started in the mixing stage and ended in drying step.
[0053] (b) Processamento por Metalurgia do Pó: Após a adição da primeira camada de revestimento, o pó é misturado com 0,3% em peso de lubrificante, compactado em prensa uniaxial de duplo efeito com uma pressão de 800 MPa no formato de um toróide e tratado termicamente . O tratamento térmico é realizado sob uma atmosfera de ar sintético com um patamar de temperatura de extração de lubrificante; nesse exemplo é utilizada uma temperatura de 320°C por 30 minutos, e um segundo patamar em uma temperatura mais alta para alivio de tensões e aumento da resistência mecânica, em que para a amostra do exemplo em questão, é utilizada a temperatura de 500°C em um patamar de 30 minutos. [0053] (b) Powder Metallurgy Processing: After adding the first coating layer, the powder is mixed with 0.3% by weight of lubricant, compacted in a double-acting uniaxial press with a pressure of 800 MPa in the format of a toroid and heat treated. The heat treatment is carried out under an atmosphere of synthetic air with a level of lubricant extraction temperature; in this example, a temperature of 320 ° C is used for 30 minutes, and a second level at a higher temperature for stress relief and increased mechanical strength, where for the sample in question, the temperature of 500 ° is used C at a 30-minute level.
Exemplo Comparativo 2 : Somente B2O3 Comparative Example 2: B2O3 only
[0054] (a) Formação da Camada Vítrea - Precursor de B2O3: [0054] (a) Formation of the Vitreous Layer - B2O3 Precursor:
Partículas de ferro, com tamanho médio de partícula de 180pm, são imersas em uma solução aquecida de isopropanol contendo concentração mássica de 0,5% de ácido bórico dissolvido (H3BO3) . O pó de ferro, sem revestimento prévio, é então imerso nessa solução de forma que a concentração mássica do pó ferromagnético seja de 83,5%. O pó é mantido em contato com a solução até a secagem completa por evaporação do isopropanol. Após a secagem do isopropanol, tem-se as partículas de ferro contendo apenas o revestimento de precursor da camada vítrea. Iron particles, with an average particle size of 180pm, are immersed in a heated isopropanol solution containing a mass concentration of 0.5% dissolved boric acid (H3BO3). The iron powder, without previous coating, is then immersed in this solution so that the mass concentration of the ferromagnetic powder is 83.5%. The powder is kept in contact with the solution until complete drying by evaporation of isopropanol. After the isopropanol has dried, the iron particles have only the precursor coating of the vitreous layer.
[0055] (b) Processamento por Metalurgia do Pó: Após a adição do precursor da camada vítrea, o pó ferromagnético é misturado com 0,3% em peso de lubrificante, compactado em prensa uniaxial de duplo efeito com uma pressão de 800 MPa no formato de um toróide e tratado termicamente. O tratamento térmico é realizado sob uma atmosfera de ar sintético com um patamar de temperatura de extração de lubrificante; nesse exemplo é utilizada uma temperatura de 320°C por 30 minuto, e um segundo patamar em uma temperatura mais alta para alivio de tensões e aumento da resistência mecânica, em que para a amostra do exemplo em questão, é utilizada a temperatura de 500°C em um patamar de 30 minutos. [0055] (b) Powder Metallurgy Processing: After adding the precursor to the vitreous layer, the ferromagnetic powder is mixed with 0.3% by weight of lubricant, compacted in a double-acting uniaxial press with a pressure of 800 MPa in the toroid shaped and heat treated. The heat treatment is carried out under an atmosphere of synthetic air with a level of lubricant extraction temperature; in this example, a temperature of 320 ° C is used for 30 minutes, and a second level at a higher temperature for stress relief and increased mechanical strength, where for the sample in question, the temperature of 500 ° is used C at a 30-minute level.
Exemplo 2: ZnO - mSiCh Example 2: ZnO - mSiCh
Figure imgf000026_0001
Figure imgf000026_0001
[0056] (a) Formação da Camada Óxida - ZnO: Partículas de ferro, com tamanho médio de partícula de 180pm, são imersas em uma solução aquosa contendo hidróxido de sódio (NaOH) de concentração 0,32%, de tal maneira que a concentração mássica de partículas ferromagnéticas na solução seja igual a 44%. Na sequência, uma solução aquosa contendo acetato de zinco dihidratado ( Zn (CH3COO) 2 · 2H2O) com concentração mássica de 0,87% e mesmo volume que a solução de NaOH anterior é adicionada, sob forte agitação, à solução de NaOH contendo as partículas de ferro, a fim de sintetizar nanopartícuias de hidróxido de zinco (Zn (OH) 2) concomitantemente à adesão dessas nanopartícuias à superfície das partículas de ferro. Como resultado da mistura de reagentes, obtém-se uma suspensão de Zn (OH) 2 de concentração molar igual a 20mM, a qual é mantida em contato com as partículas de ferro sob agitação forte o suficiente para manter as partículas de ferro suspensas, durante o período de 1 hora. Após o tempo de mistura, as partículas de ferro recobertas com as nanopartícuias isolantes são separadas do restante da suspensão, lavadas com uma mistura de etanol e água, e por fim secas em estufa a vácuo em 80°C por 30 minutos. Após a secagem, obtém-se as partículas de ferro revestidas com uma camada de nanopartícuias de óxido de zinco (ZnO) . Essa camada advém da transformação do Zn (OH) 2 em ZnO, iniciada ainda na etapa de mistura e finalizada na etapa de secagem. [0056] (a) Formation of the Oxide Layer - ZnO: Iron particles, with an average particle size of 180pm, are immersed in an aqueous solution containing sodium hydroxide (NaOH) of 0.32% concentration, in such a way that the mass concentration of ferromagnetic particles in the solution is equal to 44%. Then, an aqueous solution containing zinc acetate dihydrate (Zn (CH3COO) 2 · 2H2O) with a mass concentration of 0.87% and the same volume as the previous NaOH solution is added, under strong stirring, to the NaOH solution containing the iron particles in order to synthesize zinc hydroxide (Zn (OH) 2) nanoparticles concomitantly with the adhesion of these nanoparticles to the surface of the iron particles. As a result of mixing reagents, a suspension of Zn (OH) 2 of 20 mM molar concentration is obtained, which is kept in contact with the iron particles under agitation strong enough to keep the iron particles suspended, during the 1 hour period. After the mixing time, the iron particles covered with the insulating nanoparticles are separated from the rest of the suspension, washed with a mixture of ethanol and water, and finally dried in a vacuum oven at 80 ° C for 30 minutes. After drying, the iron particles are coated with a layer of zinc oxide (ZnO) nanoparticles. This layer comes from the transformation of Zn (OH) 2 into ZnO, mixing stage and finalized in the drying stage.
[0057] (b) Formação da Camada Vitrea - K20-mSiC>2: Após a adição da primeira camada de revestimento, prepara-se uma solução aquosa contendo silicato de potássio (K20-mSi02, com m= 3,0 - 3,5) com uma concentração mássica de sólidos de 2,7%. O pó de ferro, revestido com ZnO como camada óxida, é então imerso na solução aquosa de silicato de potássio de forma que a concentração mássica do pó ferromagnético nessa solução seja igual a 49,5%. Após a imersão, o pó de ferro é agitado no interior da solução com auxilio de imãs durante 5 minutos. Passado esse tempo, o restante da solução e descartada e o pó é levado para secagem em estufa a vácuo em 80°C por 2 horas. [0057] (b) Vitrea Layer Formation - K 2 0-mSiC> 2 : After adding the first coating layer, an aqueous solution containing potassium silicate (K20-mSi02, with m = 3.0 - 3.5) with a solids mass concentration of 2.7%. The iron powder, coated with ZnO as an oxide layer, is then immersed in the aqueous potassium silicate solution so that the mass concentration of the ferromagnetic powder in this solution is equal to 49.5%. After immersion, the iron powder is stirred inside the solution with the aid of magnets for 5 minutes. After that time, the rest of the solution is discarded and the powder is dried in a vacuum oven at 80 ° C for 2 hours.
[0058] (c) Processamento por Metalurgia do Pó: Uma vez que o pó ferromagnético tenha passado pelas duas etapas de revestimento, este é misturado com 0,3% em peso de lubrificante, compactado em prensa uniaxial de duplo efeito com uma pressão de 800 MPa no formato de um toróide e tratado termicamente . O tratamento térmico é realizado sob uma atmosfera de ar sintético com um patamar de temperatura de extração de lubrificante; nesse exemplo é utilizada uma temperatura de 350°C por 30 minutos, e um segundo patamar em uma temperatura mais alta para alivio de tensões e aumento da resistência mecânica, em que para a amostra do exemplo em questão é utilizada a temperatura de 500°C em um patamar de 30 minutos. [0058] (c) Powder Metallurgy Processing: Once the ferromagnetic powder has passed through the two coating stages, it is mixed with 0.3% by weight of lubricant, compacted in a double-acting uniaxial press with a pressure of 800 MPa in the shape of a toroid and heat treated. The heat treatment is carried out under an atmosphere of synthetic air with a level of lubricant extraction temperature; in this example, a temperature of 350 ° C is used for 30 minutes, and a second level at a higher temperature for stress relief and increased mechanical strength, where for the sample in question the temperature of 500 ° C is used at a 30-minute level.
Exemplo 3 : Mh3q4 - B2O3 Example 3: Mh3q4 - B2O3
[0059] (a) Formação da Camada Óxida - MnO: Partículas de ferro, com tamanho médio de partícula de 180pm, são imersas em uma solução aquosa contendo hidróxido de sódio (NaOH) de concentração 0,32%, de tal maneira que a concentração mássica de partículas ferromagnéticas na solução seja igual a 44%. Na sequência, uma solução aquosa contendo acetato de manganês tetrahidratado (Mn (CH3COO) 2 · 4H2O) com concentração mássica de 0,97% e mesmo volume que a solução de NaOH anterior é adicionada, sob forte agitação, à solução de NaOH contendo as partículas de ferro, a fim de sintetizar nanopartícuias de hidróxido de manganês (Mn (OH) 2) concomitantemente à adesão dessas nanopartícuias à superfície das partículas de ferro. Como resultado da mistura de reagentes, obtém-se uma suspensão de Mn (OH) 2 de concentração molar igual a 20mM, a qual é mantida em contato com as partículas de ferro sob agitação forte o suficiente para manter as partículas de ferro suspensas, durante o período de 1 hora. Após o tempo de mistura, as partículas de ferro recobertas com as nanopartícuias isolantes são separadas do restante da suspensão, lavadas com uma mistura de etanol e água, e por fim secas em estufa a vácuo em 80°C por 30 minutos. Após a secagem, obtém-se as partículas de ferro revestidas com uma camada de nanopartícuias de óxido de manganês (MnsCh) . Essa camada advém da transformação do Mn (OH) 2 em (MnsCh) , iniciada ainda na etapa de mistura e finalizada na etapa de secagem. [0059] (a) Formation of the Oxide Layer - MnO: Iron particles, with an average particle size of 180pm, are immersed in an aqueous solution containing sodium hydroxide (NaOH) with a concentration of 0.32%, in such a way that the mass concentration of ferromagnetic particles in the solution is equal to 44%. Then, an aqueous solution containing manganese acetate tetrahydrate (Mn (CH3COO) 2 · 4H2O) with a mass concentration of 0.97% and the same volume as the previous NaOH solution is added, under strong stirring, to the NaOH solution containing the iron particles in order to synthesize manganese hydroxide (Mn (OH) 2) nanoparticles concomitantly with the adhesion of these nanoparticles to the surface of the iron particles. As a result of mixing reagents, a suspension of Mn (OH) 2 of 20 mM molar concentration is obtained, which is kept in contact with the iron particles under agitation strong enough to keep the iron particles suspended during the 1 hour period. After the mixing time, the iron particles covered with the insulating nanoparticles are separated from the rest of the suspension, washed with a mixture of ethanol and water, and finally dried in a vacuum oven at 80 ° C for 30 minutes. After drying, the iron particles are coated with a layer of manganese oxide nanoparticles (MnsCh). This layer comes from the transformation of Mn (OH) 2 into (MnsCh), which started in the mixing stage and ended in the drying stage.
[0060] (b) Formação da Camada Vítrea - Precursor de B2O3: Após a adição da primeira camada de revestimento, prepara- se uma solução aquecida de isopropanol contendo concentração mássica de 0,5% de ácido bórico (H3B03) dissolvido. O pó de ferro, revestido com Mh3q4 como camada óxida, é então imerso nessa solução de forma que a concentração mássica do pó ferromagnético nessa solução seja de 83,5%. O pó é mantido em contato com a solução até a secagem completa por evaporação do isopropanol. Após a secagem do isopropanol, têm-se as partículas de ferro com duplo revestimento de isolantes, isto é, contendo a camada óxida e precursor da camada vítrea. [0060] (b) Formation of the Vitreous Layer - B2O3 Precursor: After adding the first coating layer, a heated isopropanol solution containing a mass concentration of 0.5% dissolved boric acid (H3B03) is prepared. The iron powder, coated with Mh3q4 as an oxide layer, is then immersed in this solution so that the mass concentration of the ferromagnetic powder in this solution is 83.5%. The powder is kept in contact with the solution until complete drying by evaporation of isopropanol. After the drying of the isopropanol, the iron particles have a double coating of insulators, that is, containing the oxide layer and precursor to the vitreous layer.
[0061] (c) Processamento por Metalurgia do Pó: Uma vez que o pó ferromagnético tenha passado pelas duas etapas de revestimento, este é misturado com 0,3% em peso de lubrificante, compactado em prensa uniaxial de duplo efeito com uma pressão de 800 MPa no formato de um toróide e tratado termicamente . O tratamento térmico é realizado sob uma atmosfera de ar sintético com um patamar de temperatura de extração de lubrificante; nesse exemplo é utilizada uma temperatura de 320°C por 30 minutos, e um segundo patamar em uma temperatura mais alta para alívio de tensões e aumento da resistência mecânica, em que para a amostra do exemplo em questão, é utilizada a temperatura de 500°C em um patamar de 30 minutos. [0061] (c) Powder Metallurgy Processing: Once the ferromagnetic powder has passed through the two coating stages, it is mixed with 0.3% by weight of lubricant, compacted in a double-acting uniaxial press with a pressure of 800 MPa in the shape of a toroid and heat treated. The heat treatment is carried out under an atmosphere of synthetic air with a level of lubricant extraction temperature; in this example, a temperature of 320 ° C is used for 30 minutes, and a second level at a higher temperature for stress relief and increased mechanical strength, where for the sample in question, the temperature of 500 ° is used C at a 30-minute level.
Exemplo 4 : MgO - B2O3 Example 4: MgO - B2O3
[0062] (a) Formação da Camada Óxida - MgO: Partículas de ferro, com tamanho médio de partícula de 180pm, são imersas em uma solução aquosa contendo hidróxido de sódio (NaOH) de concentração 0,32%, de tal maneira que a concentração mássica de partículas ferromagnéticas na solução seja igual a 44%. Na sequência, uma solução aquosa contendo cloreto de magnésio hexahidratado (MgCl2 · 6H2O) com concentração mássica de 0,81% e mesmo volume que a solução de NaOH anterior é adicionada, sob forte agitação, à solução de NaOH contendo as partículas de ferro, a fim de sintetizar nanopartícuias de hidróxido de magnésio (Mg (OH) 2) concomitantemente à adesão dessas nanopartícuias à superfície das partículas de ferro. Como resultado da mistura de reagentes, obtém-se uma suspensão de Mg (OH) 2 de concentração molar igual a 20mM, a qual é mantida em contato com as partículas de ferro sob agitação forte o suficiente para manter as partículas de ferro suspensas, durante o período de 1 hora. Após o tempo de mistura, as partículas de ferro recobertas com as nanopartícuias isolantes são separadas do restante da suspensão, lavadas com uma mistura de etanol e água, e por fim secas em estufa a vácuo em 80°C por 30 minutos. Após a secagem, obtém-se as partículas de ferro revestidas com uma camada de nanopartícuias de óxido de magnésio (MgO) . Essa camada advém da transformação do Mg (OH) 2 em MgO, iniciada ainda na etapa de mistura e finalizada na etapa de secagem. [0062] (a) Formation of the Oxide Layer - MgO: Iron particles, with an average particle size of 180pm, are immersed in an aqueous solution containing sodium hydroxide (NaOH) with a concentration of 0.32%, in such a way that the mass concentration of ferromagnetic particles in the solution is equal to 44%. Then, an aqueous solution containing magnesium chloride hexahydrate (MgCl2 · 6H2O) with a mass concentration of 0.81% and the same volume as the previous NaOH solution is added, under strong stirring, to the NaOH solution containing the iron particles, in order to synthesize magnesium hydroxide (Mg (OH) 2) nanoparticles concomitantly with the adhesion of these nanoparticles to the surface of the iron particles. As a result of the mixture of reagents, a suspension of Mg (OH) 2 of molar concentration equal to 20mM is obtained, which is kept in contact with the iron particles under strong agitation or enough to keep the iron particles suspended for a period of 1 hour. After the mixing time, the iron particles covered with the insulating nanoparticles are separated from the rest of the suspension, washed with a mixture of ethanol and water, and finally dried in a vacuum oven at 80 ° C for 30 minutes. After drying, the iron particles are coated with a layer of magnesium oxide (MgO) nanoparticles. This layer comes from the transformation of Mg (OH) 2 into MgO, which started in the mixing stage and ended in the drying stage.
[0063] (b) Formação da Camada Vitrea - Precursor de B2O3: Após a adição da primeira camada de revestimento, prepara- se uma solução aquecida de isopropanol contendo concentração mássica de 0,5% de ácido bórico (H3BO3) dissolvido. O pó de ferro, revestido com MgO como camada óxida, é então imerso nessa solução de forma que a concentração mássica do pó ferromagnético nessa solução seja de 83,5%. O pó é mantido em contato com a solução até a secagem completa por evaporação do isopropanol. Após a secagem do isopropanol, têm-se as partículas de ferro com duplo revestimento de isolantes, isto é, contendo a camada óxida e precursor da camada vítrea. [0063] (b) Vitre Layer Formation - B2O3 Precursor: After adding the first coating layer, a heated isopropanol solution containing 0.5% mass concentration of dissolved boric acid (H 3 BO 3 ) is prepared . The iron powder, coated with MgO as an oxide layer, is then immersed in this solution so that the mass concentration of the ferromagnetic powder in this solution is 83.5%. The powder is kept in contact with the solution until complete drying by evaporation of isopropanol. After the isopropanol has dried, iron particles have a double coating of insulators, that is, containing the oxide layer and precursor to the glassy layer.
[0064] (c) Processamento por Metalurgia do Pó: Uma vez que o pó ferromagnético tenha passado pelas duas etapas de revestimento, este é misturado com 0,3% em peso de lubrificante, compactado em prensa uniaxial de duplo efeito com uma pressão de 800 MPa no formato de um toróide e tratado termicamente . O tratamento térmico é realizado sob uma atmosfera de ar sintético com um patamar de temperatura de extração de lubrificante; nesse exemplo é utilizada uma temperatura de 320°C por 30 minutos, e um segundo patamar em uma temperatura mais alta para alivio de tensões e aumento da resistência mecânica, em que para a amostra do exemplo em questão, é utilizada a temperatura de 500°C em um patamar de 30 minutos. [0064] (c) Powder Metallurgy Processing: Once the ferromagnetic powder has passed through the two coating steps, it is mixed with 0.3% by weight of lubricant, compacted in a double-acting uniaxial press with a pressure of 800 MPa in the shape of a toroid and heat treated. The heat treatment is carried out under an atmosphere of synthetic air with a level of lubricant extraction temperature; in this example a temperature of 320 ° C is used for 30 minutes, and a second level in a higher temperature for stress relief and increased mechanical strength, where for the sample in question, the temperature of 500 ° C is used at a 30-minute level.
Exemplo 5: Ti02 - B2O3 Example 5: Ti02 - B2O3
[0065] (a) Formação da Camada Óxida - TÍO2 : Partículas de ferro, com tamanho médio de partícula de 180pm, são imersas em uma suspensão aquosa contendo nanopartículas de óxido de titânio (T1O2) comercial com concentração mássica da dispersão de 0,16% e tamanho médio de partícula igual a 20nm. O pó de ferro é adicionado a essa suspensão de tal maneira que a concentração de partículas ferromagnéticas na suspensão seja igual a 28,5%, equivalente a uma concentração molar de 20mM. A mistura é mantida sob agitação, forte o suficiente para manter as partículas de ferro suspensas, durante o período de 1 hora. Após o tempo de mistura, as partículas de ferro recobertas com as nanopartículas isolantes são separadas do restante da suspensão, lavadas com uma mistura de etanol e água, e por fim secas em estufa a vácuo em 80°C por 30 minutos. Após a secagem, obtém-se as partículas de ferro revestidas com uma camada de nanopartículas de óxido de titânio. [0065] (a) Formation of the Oxide Layer - TIO 2: Iron particles, with an average particle size of 180pm, are immersed in an aqueous suspension containing commercial titanium oxide (T1O2) nanoparticles with a dispersion mass concentration of 0.16 % and average particle size equal to 20nm. Iron powder is added to this suspension in such a way that the concentration of ferromagnetic particles in the suspension is equal to 28.5%, equivalent to a molar concentration of 20mM. The mixture is kept under stirring, strong enough to keep the iron particles suspended, for the period of 1 hour. After the mixing time, the iron particles covered with the insulating nanoparticles are separated from the rest of the suspension, washed with a mixture of ethanol and water, and finally dried in a vacuum oven at 80 ° C for 30 minutes. After drying, the iron particles are coated with a layer of titanium oxide nanoparticles.
[0066] (b) Formação da Camada Vitrea - Precursor de B2O3: [0066] (b) Formation of the Vitre Layer - B2O3 Precursor:
Após a adição da primeira camada de revestimento, prepara- se uma solução aquecida de isopropanol contendo concentração mássica de 0,5% de ácido bórico (H3BO3) dissolvido. O pó de ferro, revestido com T1O2 como camada óxida, é então imerso nessa solução de forma que a concentração mássica do pó ferromagnético nessa solução seja de 83,5%. O pó é mantido em contato com a solução até a secagem completa por evaporação do isopropanol. Após a secagem do isopropanol, têm-se as partículas de ferro com duplo revestimento de isolantes, isto é, contendo a camada óxida e precursor da camada vítrea. After adding the first coating layer, a heated solution of isopropanol containing a mass concentration of 0.5% of dissolved boric acid (H3BO3) is prepared. The iron powder, coated with T1O2 as an oxide layer, is then immersed in this solution so that the mass concentration of the ferromagnetic powder in this solution is 83.5%. The powder is kept in contact with the solution until complete drying by evaporation of isopropanol. After the isopropanol has dried, there are the iron particles with double insulating coating, that is, containing the oxide layer and precursor to the vitreous layer.
[0067] (c) Processamento por Metalurgia do Pó: Uma vez que o pó ferromagnético tenha passado pelas duas etapas de revestimento, este é misturado com 0,3% em peso de lubrificante, compactado em prensa uniaxial de duplo efeito com uma pressão de 800 MPa no formato de um toróide e tratado termicamente . O tratamento térmico é realizado sob uma atmosfera de ar sintético com um patamar de temperatura de extração de lubrificante; nesse exemplo é utilizada uma temperatura de 320°C por 30 minutos, e um segundo patamar em uma temperatura mais alta para alívio de tensões e aumento da resistência mecânica, em que para a amostra do exemplo em questão é utilizada a temperatura de 500°C em um patamar de 30 minutos. [0067] (c) Powder Metallurgy Processing: Once the ferromagnetic powder has passed through the two coating stages, it is mixed with 0.3% by weight of lubricant, compacted in a double-acting uniaxial press with a pressure of 800 MPa in the shape of a toroid and heat treated. The heat treatment is carried out under an atmosphere of synthetic air with a level of lubricant extraction temperature; in this example, a temperature of 320 ° C is used for 30 minutes, and a second level at a higher temperature for stress relief and increased mechanical strength, in which for the sample in question the temperature of 500 ° C is used at a 30-minute level.
Exemplo 6: A1203 - B2O3 Example 6: A1203 - B2O3
[0068] (a) Formação da Camada Óxida - AI2O3: Partículas de ferro, com tamanho médio de partícula de 180pm, são imersas em uma suspensão aquosa contendo nanopartícuias de óxido de alumínio (AI2O3) comercial com concentração mássica da dispersão de 0,20% e tamanho médio de partícula igual a 20nm. O pó de ferro é adicionado a essa suspensão de tal maneira que a concentração de partículas ferromagnéticas na suspensão seja igual a 28,5%, equivalente a uma concentração molar de 20mM. A mistura é mantida sob agitação, forte o suficiente para manter as partículas de ferro suspensas, durante o período de 1 hora. Após o tempo de mistura, as partículas de ferro recobertas com as nanopartícuias isolantes são separadas do restante da suspensão, lavadas com uma mistura de etanol e água, e por fim secas em estufa a vácuo em 80°C por 30 minutos. Após a secagem, obtém-se as partículas de ferro revestidas com uma camada de nanopartícuias de óxido de alumínio. [0068] (a) Formation of the Oxide Layer - AI2O3: Iron particles, with an average particle size of 180pm, are immersed in an aqueous suspension containing commercial aluminum oxide (AI2O3) nanoparticles with a mass concentration of 0.20 dispersion % and average particle size equal to 20nm. Iron powder is added to this suspension in such a way that the concentration of ferromagnetic particles in the suspension is equal to 28.5%, equivalent to a molar concentration of 20mM. The mixture is kept under stirring, strong enough to keep the iron particles suspended, for the period of 1 hour. After the mixing time, the iron particles covered with the insulating nanoparticles are separated from the rest of the suspension, washed with a mixture of ethanol and water, and finally dried in an oven vacuum at 80 ° C for 30 minutes. After drying, the iron particles are coated with a layer of aluminum oxide nanoparticles.
[0069] (b) Formação da Camada Vítrea - Precursor de B2O3: [0069] (b) Formation of the Vitreous Layer - B2O3 Precursor:
Após a adição da primeira camada de revestimento, prepara- se uma solução aquecida de isopropanol contendo concentração mássica de 0,5% de ácido bórico (H3BO3) dissolvido. O pó de ferro, revestido com AI2O3 como camada óxida, é então imerso nessa solução de forma que a concentração mássica do pó ferromagnético nessa solução seja de 83,5%. O pó é mantido em contato com a solução até a secagem completa por evaporação do isopropanol. Após a secagem do isopropanol, têm-se as partículas de ferro com duplo revestimento de isolantes, isto é, contendo a camada óxida e precursor da camada vítrea. After adding the first coating layer, a heated solution of isopropanol containing a mass concentration of 0.5% of dissolved boric acid (H3BO3) is prepared. The iron powder, coated with AI2O3 as an oxide layer, is then immersed in this solution so that the mass concentration of the ferromagnetic powder in this solution is 83.5%. The powder is kept in contact with the solution until complete drying by evaporation of isopropanol. After the isopropanol has dried, iron particles have a double coating of insulators, that is, containing the oxide layer and precursor to the glassy layer.
[0070] (c) Processamento por Metalurgia do Pó: Uma vez que o pó ferromagnético tenha passado pelas duas etapas de revestimentos, este é misturado com 0,3% em peso de lubrificante, compactado em prensa uniaxial de duplo efeito com uma pressão de 800 MPa no formato de um toróide e tratado termicamente . O tratamento térmico é realizado sob uma atmosfera de ar sintético com um patamar de temperatura de extração de lubrificante; nesse exemplo é utilizada uma temperatura de 320°C por 30 minutos, e um segundo patamar em uma temperatura mais alta para alívio de tensões e aumento da resistência mecânica, em que para a amostra do exemplo em questão, é utilizada a temperatura de 500°C em um patamar de 30 minutos. [0070] (c) Powder Metallurgy Processing: Once the ferromagnetic powder has passed through the two coatings stages, it is mixed with 0.3% by weight of lubricant, compacted in a double-acting uniaxial press with a pressure of 800 MPa in the shape of a toroid and heat treated. The heat treatment is carried out under an atmosphere of synthetic air with a level of lubricant extraction temperature; in this example, a temperature of 320 ° C is used for 30 minutes, and a second level at a higher temperature for stress relief and increased mechanical strength, where for the sample in question, the temperature of 500 ° is used C at a 30-minute level.
[0071] As amostras no formato de toróide produzidas nos exemplos 1 a 6 e exemplos comparativos 1 e 2 possuem dimensões aproximadas de diâmetro externo, diâmetro interno e altura respectivamente iguais a 65, 55 e 5mm. Essas amostras foram medidas em uma bancada para medição de propriedades magnéticas MPG 200D fabricada pela Brockhaus Messtechník e seus resultados são apresentados na Tabela 1 e Tabela 2. [0071] Samples in the form of toroid produced in examples 1 to 6 and comparative examples 1 and 2 have approximate dimensions of outside diameter, inside diameter and height respectively equal to 65, 55 and 5mm. These samples were measured on a bench for measuring magnetic properties MPG 200D manufactured by Brockhaus Messtechník and their results are shown in Table 1 and Table 2.
[0072] Tabela 1 - Perdas em indução magnética máxima de 1T e permeabilidade relativa máxima em diferentes frequências de amostras contendo respectivamente dupla camada de isolantes, somente camada óxida (ZnO) e somente camada vítrea ( B2O3) . [0072] Table 1 - Losses in maximum magnetic induction of 1T and maximum relative permeability at different frequencies of samples containing respectively double layer of insulators, only oxide layer (ZnO) and only vitreous layer (B2O3).
Figure imgf000034_0001
Figure imgf000034_0001
Tabela 1 Table 1
[0073] Tabela 2 - Perdas em indução magnética máxima de 1T e permeabilidade relativa máxima em diferentes frequências de amostras contendo distintas combinações de camada óxida e camada vítrea. [0073] Table 2 - Losses in maximum magnetic induction of 1T and maximum relative permeability at different frequencies of samples containing different combinations of oxide layer and vitreous layer.
Figure imgf000035_0001
Figure imgf000035_0001
Tabela 2 Table 2
[0074] Pelos resultados apresentados na Tabela 1 e Figura 3, percebe-se a vantagem de se utilizar o SMC contendo a dupla camada - camada óxida e camada vítrea - em relação aos SMCs que contenham apenas uma dessas camadas. A amostra do Exemplo Comparativo 1, que contém apenas a camada óxida, apresenta valores de perdas maiores que a amostra do Exemplo 1, o que pode ser explicado pela quebra da camada isolante durante a compactação, levando à redução da resistividade elétrica do SMC e consequentemente ao aumento das perdas dinâmicas. Por outro lado, os resultados do Exemplo Comparativo 2 demonstram a baixa molhabilidade das partículas metálicas pela fase vítrea quando a camada óxida não está presente, levando a permeabilidade em frequências menores mais elevadas dado o maior contato entre as partículas ferromagnéticas, mas com considerável diminuição da permeabilidade com o aumento da frequência. Esse mesmo fenômeno de baixa molhabilidade do revestimento explica também as elevadas perdas observadas, em especial para altas frequências, condição em que as perdas dinâmicas influenciam fortemente as perdas totais mensuradas. [0074] The results presented in Table 1 and Figure 3 show the advantage of using SMC containing the double layer - oxide layer and vitreous layer - in relation to SMCs that contain only one of these layers. The sample of Comparative Example 1, which contains only the oxide layer, presents higher loss values than the sample of Example 1, which can be explained by the breakdown of the insulating layer during compaction, leading to a reduction in the electrical resistivity of the SMC and consequently the increase in dynamic losses. On the other hand, the results of Comparative Example 2 demonstrate the low wettability of the metallic particles by the glass phase when the oxide layer is not present, leading to permeability at lower higher frequencies given the greater contact between the ferromagnetic particles, but with considerable decrease in the permeability with increasing frequency. This same phenomenon of low wettability of the coating also explains the high losses observed, especially for high frequencies, a condition in which dynamic losses strongly influence the total measured losses.
[0075] Como mencionado anteriormente, a camada óxida permite uma melhoria significativa do molhamento da camada vítrea sobre a partícula ferromagnética, além dessa sinergia entre as camadas levar ao mecanismo de autorregeneração das trincas geradas na etapa de compactação, com possibilidade de aumento da resistividade elétrica durante o tratamento térmico. É importante salientar que para que esse fenômeno ocorra como apresentado nos exemplos dessa invenção, ambas as camadas devem estar presentes e serem adicionadas em duas etapas como forma de garantir que a partir da superfície do pó ferromagnético primeiro se encontre a camada óxida e depois a camada vítrea. [0075] As mentioned earlier, the oxide layer it allows a significant improvement in the wetting of the vitreous layer on the ferromagnetic particle, in addition to this synergy between the layers leading to the self-healing mechanism of the cracks generated in the compaction stage, with the possibility of increasing the electrical resistivity during the heat treatment. It is important to note that for this phenomenon to occur as shown in the examples of this invention, both layers must be present and added in two stages as a way to ensure that from the surface of the ferromagnetic powder, the oxide layer is found first and then the layer glassy.
[0076] Os resultados apresentados na Tabela 2 demonstram que é possível atingir excelentes resultados com diferentes composições na camada óxida e na camada vítrea. Dentre os exemplos, no entanto, observa-se que ao sintetizar as nanopartícuias simultaneamente com a formação da camada óxida sobre o pó ferromagnético são obtidos resultados magnéticos mais interessantes em relação àqueles obtidos com nanopartícuias comerciais. Esse resultado pode ser interpretado como interessante também do ponto de vista financeiro, uma vez que os reagentes utilizados para produção dessas nanopartícuias são relativamente baratos quando comparadas ao custo das nanopartícuias comerciais. [0076] The results presented in Table 2 demonstrate that it is possible to achieve excellent results with different compositions in the oxide layer and in the vitreous layer. Among the examples, however, it is observed that by synthesizing the nanoparticles simultaneously with the formation of the oxide layer on the ferromagnetic powder, more interesting magnetic results are obtained in relation to those obtained with commercial nanoparticles. This result can be interpreted as interesting also from a financial point of view, since the reagents used to produce these nanoparticles are relatively inexpensive when compared to the cost of commercial nanoparticles.
[0077] De forma geral, as propriedades alcançadas e demonstradas nos exemplos dessa invenção apresentam possibilidade de uso imediato para diversas aplicações, especialmente com foco em média frequência. No entanto, otimizações para diferentes condições de uso, em especial em relação à frequência de operação, podem ser realizadas através de modificações de parâmetros de processo mantendo os mesmos moldes reivindicados pela invenção, como por exemplo: tamanho das partículas ferromagnéticas, controle de tamanho de partícula, composição e concentração de nanopartícuias em suspensão, composição do meio líquido da suspensão, tempo de mistura com a suspensão, pH da suspensão, velocidade de agitação, composição e concentração de fase vítrea ou precursores, além de parâmetros de processo como quantidade de lubrificante, pressão de compactação, temperatura de compactação, bem como temperatura e tempo de tratamento térmico. [0077] In general, the properties achieved and demonstrated in the examples of this invention present the possibility of immediate use for several applications, especially with a focus on medium frequency. However, optimizations for different conditions of use, especially in relation to the frequency of operation, can be carried out through modifications of process parameters keeping the same molds claimed by the invention, such as example: size of ferromagnetic particles, control of particle size, composition and concentration of nanoparticles in suspension, composition of the liquid medium of the suspension, mixing time with the suspension, pH of the suspension, stirring speed, composition and glass phase concentration or precursors, in addition to process parameters such as lubricant quantity, compaction pressure, compaction temperature, as well as temperature and heat treatment time.
[0078] É importante ressaltar que a descrição acima tem como único objetivo descrever de forma exemplificativa a concretização particular da invenção em questão. Portanto, torna-se claro que modificações, variações e combinações construtivas dos elementos que exercem a mesma função substancialmente da mesma forma para alcançar os mesmos resultados, continuam dentro do escopo de proteção delimitado pelas reivindicações anexas. [0078] It is important to note that the above description has the sole purpose of describing in an exemplary way the particular embodiment of the invention in question. Therefore, it is clear that modifications, variations and constructive combinations of the elements that perform the same function in substantially the same way to achieve the same results, remain within the scope of protection defined by the attached claims.

Claims

RE IVINDICAÇÕES RE IVICATIONS
1. Material particulado para obtenção de compósito magnético mole compreendendo partículas ferromagnéticas recobertas por ao menos uma camada óxida e ao menos uma camada vítrea; 1. Particulate material for obtaining a soft magnetic composite comprising ferromagnetic particles covered by at least one oxide layer and at least one glassy layer;
o dito material particulado caracterizado pelo fato de que: said particulate material characterized by the fact that:
as ditas partículas ferromagnéticas compreendem metais puros ou ligas ferromagnéticas contendo ao menos um dos elementos selecionado entre Fe, Ni e Co e compreende partículas de tamanho médio entre lOpm e 500pm; said ferromagnetic particles comprise pure metals or ferromagnetic alloys containing at least one of the elements selected from Fe, Ni and Co and comprise particles of average size between 10pm and 500pm;
a camada óxida compreende partículas nanométricas de óxidos selecionados a partir de ZnO, T1O2, MgO, AI2O3, Mh3<04, MnO, Mh2q3, MnCb, MnCb e Mh2q7 com tamanho médio entre 0,005pm e lpm; the oxide layer comprises nanometric particles of oxides selected from ZnO, T1O2, MgO, AI2O3, M h 3 <04, MnO, M h 2q3, MnCb, MnCb and M h 2q7 with an average size between 0.005pm and lpm;
a camada vítrea compreende fase vítrea ou precursor de fase vítrea baseado em compostos selecionados a partir de silicatos de metais alcalinos do tipo vidro líquido como Na20-nSiC>2 e K2OT1SÍO2 ou óxido de boro ou precursores de óxido de boro como ácido bórico, ácido metabórico, ácido tetrabórico, tetraborato de amónia, pentaborato, peroxiborato . the vitreous layer comprises vitreous phase or vitreous phase precursor based on compounds selected from alkali metal silicates such as liquid glass like Na20-nSiC> 2 and K2OT1SÍO2 or boron oxide or boron oxide precursors such as boric acid, metabolic acid , tetraboric acid, ammonium tetraborate, pentaborate, peroxyborate.
2. Processo de produção de material particulado para obtenção de compósito magnético mole, conforme definido na reivindicação 1, caracterizado pelo fato de que o recobrimento das partículas ferromagnéticas pela camada óxida se caracteriza por ocorrer através de mistura via líquida das partículas ferromagnéticas com uma suspensão de nanopartícuias de ao menos um dos óxidos selecionados dentre ZnO, T1O2, MgO, AI2O3, Mh3q4, MnO, M¾q3, Mhq2, Mhq3, Mh2q7. 2. Production process of particulate material for obtaining a soft magnetic composite, as defined in claim 1, characterized by the fact that the coating of ferromagnetic particles by the oxide layer is characterized by occurring through liquid mixing of ferromagnetic particles with a suspension of nanoparticles of at least one of the oxides selected from ZnO, T1O2, MgO, AI2O3, M h 3q4, MnO, M¾q3, M h q2, M h q3, M h 2q7.
3. Processo de produção de material particulado para obtenção de compósito magnético mole, de acordo com a reivindicação 2, caracterizado pelo fato das nanoparticulas de ao menos um dos óxidos ZnO, TÍO2, MgO, AI2O3, Mn3C>4, MnO, Mh2<03, Mhq2, Mhq3, Mh2<07 serem sintetizadas a partir de hidróxidos metálicos de Zn, Ti, Mg, Ai ou Mn simultaneamente à dita etapa de mistura com as partículas ferromagnéticas pela reação entre hidróxidos solúveis em água e precursores de hidróxidos metálicos. 3. Production process of particulate material to obtain a soft magnetic composite, according to claim 2, characterized by the fact that the nanoparticles of at least one of the oxides ZnO, THIO2, MgO, AI2O3, Mn3C> 4, MnO, Mh2 <03, Mhq2, Mhq3, Mh2 <07 be synthesized from metallic hydroxides of Zn, Ti, Mg, Ai or Mn simultaneously to the said mixing stage with ferromagnetic particles by the reaction between water-soluble hydroxides and precursors of metal hydroxides.
4. Processo de produção de material particulado para obtenção de compósito magnético mole, de acordo com a reivindicação 3, caracterizado pelo fato de que os hidróxidos solúveis em água são selecionados a partir de NaOH, KOH, NH4OH e sais metálicos precursores dos hidróxidos metálicos são selecionados a partir de sais de Zn, Ti, Mg, Ai ou Mn. 4. Process for the production of particulate material to obtain a soft magnetic composite, according to claim 3, characterized by the fact that water-soluble hydroxides are selected from NaOH, KOH, NH 4 OH and metal salts preceding the hydroxides Metals are selected from Zn, Ti, Mg, Ai or Mn salts.
5. Processo de produção de material particulado para obtenção de compósito magnético mole, de acordo com a reivindicação 2, caracterizado pelo fato de que o recobrimento das partículas ferromagnéticas com a camada óxida ser realizado em meio líquido; o processo compreendendo as etapas de: 5. Production process of particulate material to obtain a soft magnetic composite, according to claim 2, characterized by the fact that the coating of ferromagnetic particles with the oxide layer is carried out in a liquid medium; the process comprising the steps of:
I. mistura, sob agitação, das partículas ferromagnéticas, na proporção em massa de 30% a 60%, com uma suspensão contendo nanoparticulas óxidas ou hidróxidos metálicos precursores de nanoparticulas sintetizados simultaneamente à etapa de mistura dessa suspensão com as partículas ferromagnéticas, contendo uma concentração molar de nanoparticulas entre 1 e 500mM; I. mixing, under agitation, the ferromagnetic particles, in a mass ratio of 30% to 60%, with a suspension containing oxide nanoparticles or metallic hydroxides precursors of nanoparticles synthesized simultaneously with the mixing step of this suspension with the ferromagnetic particles, containing a concentration molar nanoparticles between 1 and 500mM;
II. remoção do excesso da suspensão de nanoparticulas e subsequente secagem da mistura obtida na etapa (I) em temperaturas entre temperatura ambiente e 150 °C. II. removing excess nanoparticles suspension and subsequently drying the mixture obtained in step (I) at temperatures between room temperature and 150 ° C.
6. Processo de produção de material particulado para obtenção de compósito magnético mole, conforme definido na reivindicação 1, caracterizado pelo fato das partículas ferromagnéticas previamente recobertas pela camada óxida, serem recobertas com o material isolante da camada vítrea, o processo compreendendo as etapas: 6. Production process of particulate material to obtain a soft magnetic composite, as defined in claim 1, characterized by the fact that the ferromagnetic particles previously covered by the oxide layer, are covered with the insulating material of the glassy layer, the process comprising the steps:
I . recobrimento das partículas ferromagnéticas por meio de imersão ou molhamento incipiente com uma suspensão de silicatos de metal alcalino do tipo vidro líquido ou óxido de boro ou precursor de fase vítrea baseado em precursores de óxido de boro selecionados a partir de ácido bórico, ácido metabórico, ácido tetrabórico, tetraborato de amónia, pentaborato, peroxiborato, na proporção em massa de 65% a 95% de partículas ferromagnéticas revestidas e 5% a 35% de suspensão de fase vítrea ou precursor de fase vítrea; e I. coating of ferromagnetic particles by immersion or incipient wetting with a suspension of alkali metal silicates like liquid glass or boron oxide or glass phase precursor based on boron oxide precursors selected from boric acid, metabolic acid, acid tetraboric, ammonium tetraborate, pentaborate, peroxyborate, in a proportion of 65% to 95% by weight of coated ferromagnetic particles and 5% to 35% of glass phase suspension or glass phase precursor; and
II. secagem do compósito revestido com temperatura entre temperatura ambiente e 150 °C. II. drying of the coated composite at a temperature between room temperature and 150 ° C.
7. Processo de produção de material particulado para obtenção de compósito magnético mole, de acordo com a reivindicação 6, caracterizado pelo fato da solução de precursores de óxido de boro ser composta pela diluição de um ou mais precursores selecionados a partir de ácido bórico, ácido metabórico, ácido tetrabórico, tetraborato de amónia, pentaborato, peroxiborato; a solução dos ditos precursores sendo preparada em uma concentração entre 0,001g/mL e lg/mL e contendo uma massa de precursores entre 0,01% a 10,00% em relação à massa de partículas ferromagnéticas do compósito magnético mole. 7. Process for the production of particulate material to obtain a soft magnetic composite, according to claim 6, characterized by the fact that the boron oxide precursor solution is composed by the dilution of one or more precursors selected from boric acid, acid metabolic, tetraboric acid, ammonia tetraborate, pentaborate, peroxyborate; the solution of said precursors being prepared in a concentration between 0.001g / mL and lg / mL and containing a mass of precursors between 0.01% to 10.00% in relation to the mass of ferromagnetic particles of the soft magnetic composite.
8. Processo de produção de material particulado para obtenção de compósito magnético mole, de acordo com a reivindicação 6, caracterizado pelo fato da solução de silicato de metal alcalino ser composta pela diluição de um ou mais silicatos, sendo que a razão molar entre as moléculas de sílica e óxidos de metal alcalino deve estar entre 0,5 e 8; a solução de silicato de metal alcalino ou mistura de silicatos deve conter uma concentração de sólidos entre 0,001mg/ml e 15mg/ml. 8. Production process of particulate material to obtain soft magnetic composite, according to claim 6, characterized by the fact that the alkali metal silicate solution is composed of the dilution of one or more silicates, with the molar ratio between the silica molecules and alkali metal oxides being between 0.5 and 8; the alkali metal silicate solution or mixture of silicates should contain a solids concentration between 0.001mg / ml and 15mg / ml.
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