RU2795757C2 - Improved heat-resistant soft magnetic powder - Google Patents

Abstract

FIELD: magnetic powder.

SUBSTANCE: invention relates to soft magnetic powder for magnetic core components and to a method for coating soft magnetic powder. The invention further relates to the use of such soft magnetic powder and to an electronic component containing such soft magnetic powder. The soft magnetic powder is coated with a silicon-based coating. The silicon-based coating contains at least one fluorine-containing compound of formula (I) Si_1-0.75cM_cO_2-0.5cF_d (I), in which c ranges from 0.01 to 0.5, d ranges from 0.04 to 2, index c and index d are in the following radio: d = 4c, and M is B or Al.

EFFECT: group of inventions contributes to the achievement of good thermal stability, high resistivity and high permeability when used in magnetic core components.

14 cl, 8 tbl

Description

The invention relates to soft magnetic powder and to a method for coating soft magnetic powder. The invention further relates to the use of such soft magnetic powder and to an electronic component containing such soft magnetic powder.

Popular applications of soft magnetic powder include magnetic core components that serve as a piece of highly permeable magnetic material used to confine and guide magnetic fields in electrical, electromechanical, and magnetic devices such as electromagnets, transformers, electric motors, and inductors. and magnetic assemblies. These components are usually produced in various shapes and sizes by molding soft magnetic powder in a high pressure mold.

In electronic applications, particularly in alternating current (AC) applications, two key characteristics of a magnetic core component are the magnetic permeability and the core loss characteristic. In this context, the magnetic permeability of a material indicates its ability to be magnetized or its ability to carry magnetic flux. Permeability is defined as the ratio of the induced magnetic flux and the magnetizing force or field strength. When the magnetic material is subjected to a rapidly changing field, the total energy of the core decreases due to the occurrence of hysteresis losses and/or eddy current losses. The hysteresis loss is caused by the energy required to overcome the retained magnetic forces within the core component. Eddy current losses are caused by the generation of electric currents in the core component due to the change in flux caused by AC conditions, and mainly result in resistance losses.

In general, devices for high frequency applications are sensitive to core losses, and good isolation of the soft magnetic powder particles is desirable to reduce eddy current losses. The easiest way to achieve this is to thicken the insulating layer for each particle. However, the thicker the insulating layer, the lower the density of the soft magnetic particle core becomes, and the magnetic flux density decreases. Thus, in order to manufacture a soft magnetic powder core having optimal key characteristics, it is necessary to simultaneously increase the resistivity and density of the core.

Another aspect of insulation concerns the thermal performance and strength of the insulation layer. Particularly high temperatures can lead to the destruction of the insulating layer due to the formation of cracks, which contribute to eddy current losses. Thus, heat resistance is another requirement for making a soft magnetic powder core with optimum performance. Ideally, the particles would be covered with a thin insulating layer providing high resistivity and high density with stable temperature characteristics.

Known methods of forming insulating layers on magnetic particles usually stop at one of the key characteristics, that is, density or resistivity. However, if the particles covered with the insulating layer are exposed to temperatures above 120° C., preferably over 150° C., for several hours, cracks can form in the insulating layer, which leads to higher eddy currents and lower values of resistivity.

European Patent Application EP 2 871 646 A1 is a silicon-based soft magnetic powder which exhibits good properties in terms of thermal stability as well as resistivity. This is achieved by special coatings based on silicon containing certain amounts of fluorine. In addition, European patent application EP 2 871 646 A1 discloses a process for producing a coated soft magnetic powder. However, due to the increasing demands on coated soft magnetic powders, in particular with regard to heat resistance, there is still a need in the art to further improve the soft magnetic powder insulating layer in order to achieve optimal results for magnetic core components made from such powders. In addition, improvements in the method of coating the soft magnetic powder are desired.

Thus, it is an object of the invention to provide an improved coated soft magnetic powder and a corresponding method for coating soft magnetic powder which is conducive to achieving good thermal stability, high resistivity, and high permeability when used in magnetic core components. In addition, the object of the invention is to provide a method that allows you to achieve the above objects in a simple, economical and uncomplicated manner. Another object of the invention is to provide electronic components including soft magnetic powder with good temperature stability, high resistivity and high permeability.

These objectives are achieved with a soft magnetic powder coated with a silicon-based coating, the silicon-based coating containing at least one fluorine-containing composition of formula (I):

Si _1-0.75c M _c O _2-0.5c F _d (I),

wherein

c is in the range from 0.01 to 0.5,

d ranges from 0.04 to 2, and

M is boron (B) or aluminum (Al).

The invention further relates to a method for coating soft magnetic powder, in which the soft magnetic powder is mixed with a silicon-based solution containing a soluble fluorinating agent. In addition, the invention relates to a soft magnetic powder produced by this coating method or a coated soft magnetic powder according to this method. The invention also relates to the use of the coated soft magnetic powder for the manufacture of electronic components, in particular magnetic core components, and to an electronic component, in particular a magnetic core component, comprising this coated soft magnetic powder.

The following description relates to a coated soft magnetic powder as well as a method for coating a soft magnetic powder according to the invention. In particular, the embodiments for the soft magnetic powder, the fluorine-containing composition, and the soluble fluorinating agent are equally applicable to the coated soft magnetic powder, the method of coating the soft magnetic powder, and the soft magnetic formulated coated composition obtained with using this method.

The invention provides a method for coating soft magnetic powder and the corresponding coated powder, which is optimally suited for the manufacture of electronic components. In particular, the coated soft magnetic powder according to the invention achieves high temperature stability, high resistivity and high permeability when used for the production of electronic components such as magnetic core components. In addition, due to the simple and uncomplicated approach of the proposed method, high quality uniformity from batch to batch can be achieved, which also enables reliable production of electronic components. In general, the soft magnetic powder coated according to the invention facilitates the production of electronic components with unique electromagnetic properties and high temperature stability, in particular at temperatures > 120°C, and preferably > 150°C, such as > 175°C.

In the context of the present invention, the individual components, eg silicon (Si), oxygen (O), fluorine (F), of the fluorine-containing compositions can be evenly distributed throughout the silicon-based coating. In this case, fluorine-containing compositions, as described herein, indicate the composition of a homogeneous silicon-based coating. Alternatively, the silicon-based coating may be non-uniform. In such a case, the individual components of the fluorine-containing compositions, as specified herein, indicate the average value of the silicon-based coating composition over the entire coating. For example, the silicon-based coating may contain one or more layers of silicon dioxide (SiO ₂ ) and one or more layers additionally containing a fluorine component. Then fluorine-containing compositions, as specified in this document, indicate the average composition of the layered or non-uniform coating based on silicon.

In the context of the present invention, specifications in wt % (wt %) refer to a fraction of the total weight of the soft magnetic powder, unless otherwise indicated. For example, a soft magnetic powder coating solution includes a soluble fluorinating agent as described above and, if desired, additional components such as a solvent. Here, % wt. refer to the percentage of the total mass of the soft magnetic powder that must be treated with a solution, unless expressly stated otherwise. Therefore, the values in % wt. recalculated for the total mass of the soft magnetic powder, excluding other components, for example, from the solution.

The soft magnetic powder of the present invention includes a plurality of particles composed of a soft magnetic material. Such powders contain particles with an average particle size between 0.5 and 250 microns, preferably between 2 and 150 microns, more preferably between 2 and 10 microns. These particles may vary in shape. With regard to the form, there are numerous options known to the person skilled in the art. The shape of the powder particles may be, for example, acicular, cylindrical, lamellar, drop-shaped, flattened or spherical. Soft magnetic particles of various shapes are commercially available. A spherical shape is preferred because such particles are easier to coat, which actually results in more efficient electrical insulation.

The soft magnetic material may be an elemental metal, an alloy, or a mixture of one or more elemental metals with one or more alloys. Typical elemental metals include iron (Fe), cobalt (Co), and nickel (Ni). Alloys may include Fe-based alloys such as Fe-Si alloy, Fe-Si-Cr alloy, Fe-Si-Ni-Cr alloy, Fe-Al alloy, Fe-N alloy, Fe-Ni alloy, Fe-C alloy , Fe-B alloy, Fe-Co alloy, Fe-P alloy, Fe-Ni-Co alloy, Fe-Cr alloy, Fe-Mn alloy, Fe-Al-Si alloy and ferrites, or rare earth alloy, in in particular, an alloy based on rare earth and Fe, such as Nd-Fe-B alloy, Sn-Fe-N alloy, or Sm-Co-Fe-Cu-Zr alloy, or Sr-ferrite, or Sm-Co alloy. In a preferred embodiment, the soft magnetic material is Fe or Fe-based alloys such as Fe-Si-Cr, Fe-Si or Fe-Al-Si.

In a particularly preferred embodiment, Fe serves as the soft magnetic material and the soft magnetic powder is carbonyl iron powder (also referred to herein as CIP). Carbonyl iron can be obtained according to known methods by the thermal decomposition of iron pentacarbonyl in the gas phase, as described, for example, in their Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Vol. A 14, page 599, or in German patents DE 3428121 or DE 3940347, and contains high-purity metallic iron.

The carbonyl iron powder is a gray fine metallic iron powder having a low content of secondary components and consisting of essentially spherical particles having an average particle diameter of up to 10 µm. The unreduced carbonyl iron powder, which is preferred in this context, has an iron content of >97 wt % (in this case based on the total weight of the powder), a carbon content of < 1.5 wt %, a nitrogen content of < 1.5 wt % and oxygen < 1.5% mass. The reduced carbonyl iron powder, which is particularly preferred in the process of the present invention, has an iron content of >99.5 wt % (in this case based on the total weight of the powder), a carbon content of < 0.1 wt %, a nitrogen content of < 0, 01% mass and oxygen content < 0.5% mass. The average diameter of the powder particles is preferably 1 to 10 μm, and their specific surface area (BET method for powder particles) is preferably 0.1 to 2.5 m ² /g.

In one embodiment, the silicon-based coating contains a fluorine-containing composition of formula (I):

Si _1-0.75c M _c O _2-0.5c F _d (I)

In formula (I) above, M is B or Al, preferably B.

In the fluorine-containing composition of formula (I), the index c is a number in the range of 0.01 to 0.5, preferably in the range of 0.05 to 0.3, and particularly preferably 0.085 to 0.2.

The index d is a number in the range of 0.04 to 2, preferably in the range of 0.2 to 1.2, and particularly preferably 0.34 to 0.8.

Preferably, index c and index d are in the following ratio: d = 4 c.

The silicon-based coating may preferably contain from >5 to 45% by weight, more preferably from 10 to 40% by weight, and particularly preferably from 20 to 35% by weight, based on the total weight of the silicon-based coating, by at least one fluorine-containing composition of formula (I).

In addition to the silicon-based coatings mentioned above, the coating can also be based on metal oxides such as alumina (Al ₂ O ₃ ), magnesium oxide (MgO) or titanium oxide (TiO ₂ , TiO, Ti ₂ O ₃ ). Such coatings can be obtained by decomposition of metal alkoxides. Metal alkoxides are usually represented by the formula M ² (OR')(OR'')… (OR ⁿ ), where M ² is a metal and n is the valency of the metal. R', R'', R ⁿ indicate organic residues, which may be the same or different. For example, r is straight or branched alkyl or substituted or unsubstituted aryl. Here r means alkyl with 1-8 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl, n-hexyl, 2-ethylhexyl, or aryl with 6-12 carbon atoms, such as phenyl, 2-, 3- or 4-methylphenyl, 2,4,6-trimethylphenyl or naphthyl. Preferred are methyl, ethyl and isopropyl. Other details regarding the process of coating soft magnetic powder with a metal oxide, in particular SiO ₂ , are described below.

In addition, the fluorine component of the fluorine-containing composition may be incorporated into the SiO ₂ matrix and/or bonded to the surface of the SiO ₂ coating. The fluorine component of the fluorine-containing composition may be homogeneously or non-homogeneously distributed within the SiO ₂ matrix. For example, the silicon-based coating may include one or more SiO ₂ coating layers and one or more SiO ₂ coating layers containing fluorine. Alternatively or additionally, the fluorine component of the fluorine-containing composition may be bonded to the surface of the SiO ₂ coating surrounding the soft magnetic powder particles, and the SiO ₂ coating may also contain the fluorine component of the fluorine-containing composition.

In another embodiment, the silicon-based coating has an average thickness of 2 to 100 nm, preferably 5 to 70 nm, and particularly preferably 10 to 50 nm. In addition, the ratio of silicon-based coating and soft magnetic material is not more than 0.1, and preferably not more than 0.02, and preferably, the soft magnetic powder contains from 0.1 to 10% by mass, more preferably, from 0.2 to 3.0% wt., and in particular, from 0.3 to 1.8% wt. coatings based on silicon, in terms of the total weight of the soft magnetic powder. Thus, the magnetic flux density of the magnetic core obtained by molding the soft magnetic powder can be prevented from being greatly reduced.

The soluble fluorinating agent used in the soft magnetic powder coating method is a fluorinating agent having a solubility in ethanol of more than 15% by mass, preferably more than 20% by mass, and particularly preferably more than 25% by mass. at 0°C. Alternatively, this fluorinating agent can be characterized by a very high solubility in water of more than 25 wt %, preferably more than 30 wt %, and particularly preferably more than 35 wt %. at 20°C. It has been found that fluorinating agents having lower solubility tend to precipitate out of solution if the solution is prepared in advance and stored at ambient temperature. This is usually observed for BF3 ⋅ NH ₂ -CH ₂ -Ph, which has been found to have a solubility in ethanol at 0°C of about 10% wt. Fluorinating agents having sufficient solubility in ethanol are usually ionic fluorinating agents. Alternatively or in addition, it is also particularly preferred if the fluorinating agent is liquid at room temperature and/or can be obtained from components that are liquid at room temperature.

In a particularly preferred embodiment, a solution of a soluble fluorinating agent in ethanol has a pH in the range of 0 to 10, preferably 6 to 9. A pH in the range of 6 to 9, preferably 7 to 9, is preferred from a potential equipment corrosion point of view. used for cooking (eg reactor) during the coating process. In addition, the preferred pH ranges provide mild conditions for coating the soft magnetic powder.

Preferably, at least one fluorinating agent has the formula (II):

[Q][MF ₄ ] (II),

wherein

M is B or Al, and

Q is a cationic group selected from H ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , Cs ⁺ or [NR ¹ ₄ ] ⁺ , where R ¹ is independently selected from the group consisting of -H, -alkyl with 1 to 12 atoms carbon, -alkenyl with 2-12 carbon atoms and -aryl with 6-18 carbon atoms, each of which may be substituted by at least one group represented by the formula -OR ² where R ² is independently selected from -H, -alkyl with 1-12 carbon atoms, -alkenyl with 2-12 carbon atoms and -aryl with 6-18 carbon atoms.

In a preferred embodiment of the invention in formula (II), M is selected from B.

In addition, preferred embodiments include cationic Q groups selected from H ⁺ or [NR ¹ ₄ ] ⁺ , where R ¹ is defined above.

In one embodiment, at least one R ¹ substituent is selected from the group consisting of -alkyl with 1-12 carbon atoms, -alkenyl with 2-12 carbon atoms and -aryl with 6-18 carbon atoms (i.e., groups defined above, with the exception of -H), each of which may be substituted by at least one group represented by the formula -OR ² where R ² is as defined above. In an alternative embodiment, the at least two R ¹ substituents are selected from the group consisting of -alkyl with 1-12 carbon atoms, -alkenyl with 2-12 carbon atoms and -aryl with 6-18 carbon atoms (i.e., other than -H), each of which may be substituted with at least one group represented by the formula -OR ² where R ² is as defined above. In an alternative embodiment, at least three R ¹ substituents are selected from the group consisting of C 1 -C 12 -alkyl, C 2 -C 12 -alkenyl, and C 6 -C 18 -aryl (i.e., other than -H), each of which may be substituted with at least one group represented by the formula -OR ² where R ² is as defined above.

In another preferred embodiment, at least one fluorinating agent of formula (II) is selected from the group consisting of HBF ₄ , [NH ₄ ][BF ₄ ] and [(R ⁴ -OR ³ ) _x -NH _3-x ][BF ₄ ], where R ³ is a group of the formula -(C _n H _2n+p )-, where n is an integer from 1 to 6, and p is an integer selected from 0 and -2;

R ⁴ is selected from -H or -(C _m H _2m+q )-CH ₃ where m is an integer from 0 to 6 and q is an integer selected from 0 and -2, provided that when m = 0, then q = 0, and

x is an integer from 1 to 3.

In one preferred embodiment, n is an integer from 1 to 3.

In an alternative preferred embodiment, p is equal to 0.

In another alternative preferred embodiment, m is an integer selected from 0 to 2.

In another alternative preferred embodiment, q is 0.

In one embodiment, R ³ is a group selected from -(CH ₂ )-, -(C ₂ H ₄ )-, -(C ₃ H ₆ )-, -(CH ₃ -CH(CH ₃ ))-, and preferably represents -(C ₂ H ₄ )-.

In one embodiment, R ⁴ is a group selected from -H and -CH ₃ , and preferably is -H.

In a particular preferred embodiment, at least one fluorinating agent of formula (II) is represented by the formula [(R ⁴ -OR ³ ) _x -NH _3-x ][BF ₄ ], where R ³ is a group of formula -(C _n H _{2n +p} )-, where n is an integer from 1 to 3 and p is 0; and R ⁴ is -H.

In another specific preferred embodiment, at least one fluorinating agent of formula (II) is represented by the formula [(R ⁴ -OR ³ ) _x -NH _3-x ][BF ₄ ], where R ³ is a group selected from -(CH ₂ )-, -(C ₂ H ₄ )-, -(C ₃ H ₆ )-, -(CH ₃ -CH(CH ₃ ))-, and is preferably -(C ₂ H ₄ )-, and R ⁴ represents - H.

In another embodiment, x is an integer selected from 1 and 2, and in a specific preferred embodiment, x is 1.

Particularly preferably, the soluble fluorinating agent is selected from the group consisting of HBF ₄ , [NH ₄ ][BF ₄ ], [HOCH ₂ -NH ₃ ][BF ₄ ], [HOC ₂ H ₄ -NH ₃ ][BF ₄ ], [HOC ₃ H ₆ -NH ₃ ][BF ₄ ], [HOC ₄ H ₈ -NH ₃ ][BF ₄ ], [HOC ₅ H ₁₀ -NH ₃ ][BF ₄ ] and [HOC ₆ H ₁₂ -NH ₃ ][BF ₄ ]. In particular, [HOC ₂ H ₄ -NH ₃ ][BF ₄ ] is preferably used as the soluble fluorinating agent. These fluorinating agents combine excellent properties in terms of ethanol solubility, solution stability, availability and efficacy as a fluorinating agent, as well as the characteristics of the silicon-based coatings obtained with them. Moreover, these fluorinating agents are less toxic than fluorinating agents such as H ₂ SiF ₆ known from European patent application EP 2 871 646 A1.

Compounds of the formula [(R ⁴ -OR ³ ) _x -NH _3-x ][BF ₄ ] can be readily obtained by mixing HBF ₄ and R ⁴ -OR ³ -NH ₂ in a ratio of 1:0.5 to 1:4 , preferably from 1:0.8 to 1:3, more preferably from 1:0.9 to 1:2 and in particular from 1:1 to 1:1.5, in a suitable solvent (e.g. ethanol ) at room temperature. The resulting solution is usually stable at room temperature and can be stored without degradation or precipitation.

Soluble fluorinating agents according to the present invention are particularly characterized in that they are a compound having good solubility in ethanol. In one preferred embodiment, the soluble fluorinating agents are preferably liquid compounds or are obtained in situ from liquid compounds, which are therefore easy to handle. The solution thus obtained is highly compatible with corrosion sensitive materials (eg reactor surfaces).

For coating soft magnetic powder with silicon dioxide (SiO ₂ ), the silicon-based solution preferably contains silicon alkoxide, which is added to the silicon-based solution in one or more steps. Suitable silicon alkoxides are, for example, tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS), tetrapropylorthosilicate and tetraisopropylorthosilicate, or mixtures thereof. Such silicon alkoxides provide a soluble form of silicon without any water or hydroxyl groups. Thus, a controlled hydrolysable silicon product can be obtained. The preferred silicon alkoxide is TEOS. Also suitable are silanes with two or three OR ⁿ groups, where R ⁿ is a residue as above, and two or one X ¹ groups (groups) directly attached to the silane, respectively, where X ¹ is a residue such as H, methyl, ethyl, C ₃ to C ₁₈ or propylamine, or even more complex examples such as (3-glycidyloxypropyl)triethoxysilane, as well as mixtures thereof, which can be further mixed with any of the silicon alkoxides mentioned above.

The soft magnetic powder is preferably mixed with the silicon based solution, and the soluble fluorinating agent is added after the soft magnetic powder is at least partially treated with the silicon based solution. For example, the soluble fluorinating agent is added during treatment with the silicon-based solution and/or immediately after treatment with the silicon-based solution. In this case, "immediately after treatment with a silicon-based solution" refers to the stage immediately following the last stage of treatment with a silicon-based solution. The last step of the silicon solution treatment typically includes or consists of distillation and drying of the coated soft magnetic powder, resulting in a dry coated soft magnetic powder. In a step immediately after treatment with a silicon based solution, a solvent including a fluorinating agent may be added to the coated soft magnetic powder to produce a soft magnetic powder coated with a silicon based coating comprising one of the fluorine-containing compositions as described herein.

In principle, the solution can also be based on other metals and contain the appropriate metal alkoxides to coat the soft magnetic powder with the metal oxide. For example, the solution may be based on titanium, magnesium (Mg) or aluminum to form a coating of alumina (Al ₂ O ₃ ), magnesium oxide (MgO) or titanium oxide (TiO ₂ , TiO, Ti ₂ O ₃ ). In addition, the solution may be based on a mixture of metals such as Si, Al, Mg or Ti and contain an appropriate mixture of metal alkoxides to form a mixed coating. Preferably, the decomposition of the metal alkoxide is carried out by hydrolysis. For hydrolysis, the metal-based solution further contains an inert suspending agent, water, and optionally a catalyst.

The reaction mixture comprising the soft magnetic powder, the metal-based solution and, if desired, the fluorinating agent may be prepared in stages, in one or more stages, or gradually. Preferably, the reaction mixture is prepared in stages. In this context, "stepwise" refers to the addition of at least one component of the reaction mixture at one or more stages during hydrolysis, and stepwise addition may also include adding at a rate over a certain range of time. Thus, the components can be added in one step at a time. Alternatively, the components can be added at regular or irregular intervals, in at least two stages. "Incrementally" means that the components are added during hydrolysis at a fixed rate or at regular intervals, such as every minute or second. Preferably, the metal alkoxide and/or the fluorinating agent is added in stages.

In the first step of the process, the soft magnetic powder may be mixed with an inert suspending agent such as water and/or an organic solvent. Suitable organic solvents are protic solvents, preferably monohydric or dihydric alcohols such as methanol, ethanol, isopropanol, glycol, diethylene glycol or triethylene glycol, or aprotic solvents, preferably ketones such as acetone, diketone, ether, for example diethyl ether, di-n-butyl ether, glycol dimethyl ether, diethylene glycol or triethylene glycol, or nitrogen containing solvents such as pyridine, piperidine, N-methylpyrrolidine or aminoethanol. Preferably, the organic solvent is water miscible. The suspending agent may be an organic solvent or an organic solvent mixed with water. Preferred organic solvents are acetone, isopropanol and ethanol. Especially preferred is ethanol. The content of an inert suspending agent in a metal-based solution can be up to 70 wt%. Preferably, the content of the inert suspending agent is between 10 and 50% by weight.

The mixture of soft magnetic powder and suspending agent is chosen so as to obtain a miscible solution. A high proportion of solids is favorable for increasing the yield per unit volume per unit time. The optimum solids fraction is easily obtained with routine experiments that allow the optimum solids fraction to be found for the reaction mixture. In addition, mechanical agitators or pump/nozzle devices can be used to increase the solids content.

In the second step of the process, a metal alkoxide may be added to the mixture. The metal alkoxide can be added to the reaction mixture as such or dissolved in an organic solvent. If an organic solvent is used, then this organic solvent contains from 10 to 90 wt %, preferably from 50 to 80 wt %. metal alkoxide. The metal alkoxide can be added stepwise or incrementally. It is preferable to add the metal alkoxide stepwise in more than one step, preferably in two steps. For example, up to 90%, up to 50% or up to 20% of the total amount of metal alkoxide required for hydrolysis is first added to the reaction mixture, and the remaining amount is added at a later stage of the process.

The total amount of metal alkoxide added to the metal based solution depends on the desired coating thickness. Depending on the particle size distribution, the particle profile (acicular or spherical) and the amount of powder particles added, the total specific surface can be easily determined. Alternatively, known methods such as the BET method can be used to determine the specific surface area. From the desired coating thickness and metal oxide density, the required amount of metal oxide can be calculated. The required total amount of metal alkoxide can then be determined using the stoichiometric ratio in the reaction.

After the addition of the metal alkoxide, hydrolysis occurs automatically as soon as water is added to the reaction mixture in the third stage. Preferably, the total amount of water is at least twice, more preferably at least five times, the stoichiometric amount required to hydrolyze the metal alkoxide. Typically, the total amount of water is not more than one hundred times, preferably twenty times the required stoichiometric amount. In the third stage, a part of the amount of water is added, which corresponds to the part of the metal alkoxide added to the reaction mixture in the second stage of the process.

To further accelerate the hydrolysis, a catalyst such as an alkali or acid catalyst may be added to the reaction mixture. The amount of added catalyst can also be adjusted in accordance with the proportion of metal alkoxide added to the reaction mixture in the second stage of the process. Suitable acid catalysts are, for example, dilute mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, and suitable alkaline catalysts are, for example, a dilute alkaline solution such as caustic soda. It is preferable to use a dilute aqueous ammonia solution, so the catalyst and water are added simultaneously in one step.

The preferred molar ratio of catalyst and metal alkoxide, in particular ammonia and silicon alkoxide, is from 1:1 to 1:2, preferably from 1:1.1 to 1:1.8. This ratio makes it possible to form a coating having good properties.

The decomposition of the metal alkoxide, preferably silicon alkoxide, can be further promoted by thermal heating of the prepared reaction mixture in the fourth stage of the process. The reaction mixture may be heated to just below the boiling point or to the reflux temperature of the reaction mixture. In the case of ethanol, for example, the temperature is maintained below 80°C, for example, about 60°C. The reaction mixture can be kept at elevated temperature under reflux for several hours, for example 3 hours. Typically, the reaction mixture is dispersed using a mechanical stirrer. In addition, dispersing agents such as anionic or ionic surfactants, acrylic resin, pigment dispersant or higher alcohols such as hexanol, octanol, nonanol or dodecanol can be added to the reaction mixture.

If the metal alkoxide is added in more than one step, then the remaining portions of the metal alkoxide, water, and catalyst may be added in one or more steps while the reaction mixture is maintained at elevated temperature. Preferred is a two-stage addition of the metal alkoxide, in which the remaining parts of the metal alkoxide, water and catalyst are added in one stage while the reaction mixture is maintained at an elevated temperature.

After hydrolysis, the reaction mixture is distilled and dried in the fifth and sixth stages of the process. The point at which hydrolysis ends can be determined by detecting a decrease in the water content of the reflux stream. If the water content is low enough, the mixture can be distilled and dried, leaving a soft magnetic powder coated with SiO ₂ . In this context, the water content can be easily determined by routine experiments.

In one embodiment of the method, the soluble fluorinating agent is added during the treatment with the silicon-based solution. Therefore, the soluble fluorinating agent is added before the silica treatment is complete, that is, before the reaction mixture has been distilled and dried.

In another embodiment, from 1.0 x 10 ^-2 to 5.5 x 10 ^-2 mol % is added to the silicon-based solution. fluorinating agent, in terms of the total amount of soft magnetic powder. Preferably, use from 1.5 x 10 ^-2 to 3.5 x 10 ^-2 mol%. fluorinating agent, in particular, from 1.7 x 10 ^-2 to 2.7 x 10 ^-2 mol%. fluorinating agent.

In another embodiment, 0.1 to 10 mmol of fluorinating agent per kg of soft magnetic powder is added to the silicon-based solution. Preferably, 1 to 7 mmol of fluorinating agent is used per kg of soft magnetic powder, in particular 3 to 5 mmol of fluorinating agent.

In another embodiment, from 0.25 to 5 mol % is added to the silicon-based solution. fluorinating agent, based on the total amount of Si in the silicon-based solution. Preferably, use from 1 to 4.5 mol%. fluorinating agent, in particular, from 1.5 to 3.5% mol. fluorinating agent.

The fluorinating agent can be added as a solid or in solution. Preferably, the fluorinating agent solution has a concentration of from about 5 to 30% by weight, in particular from 10 to 20% by weight. Typically, the solvent is water, ethanol, or the previously mentioned inert suspending agent. In a particularly preferred embodiment, the solution contains at least one fluorinating agent and at least ethanol.

In another preferred embodiment, only a portion of the silicon alkoxide is added along with the fluorinating agent. For example, from 100% silicon alkoxide, necessary for the formation of 1 - 2% wt. SiO ₂ on iron powder, 25%, 50% or 75% is added along with the fluorinating agent.

The preferred molar ratio of added fluorine atoms in the soluble fluorinating agent and silicon in the added silicon alkoxide (molar ratio F : Si) is from 1:3 to 1:18, preferably from 1:5 to 1:15, and in particular from 1 : 8 to 1 : 13 where this molar ratio refers to the ratio throughout the coating. The molar ratio F : Si may be, for example, 1 : 9.1. With this ratio, the coating can be tailored to provide high permeability due to coating thickness and good thermal stability.

In addition, the soluble fluorinating agent may be added in stages, in one or more steps, during treatment with the silicon-based solution. Preferably, the soluble fluorinating agent is added in one step. The point at which the soluble fluorinating agent is added may be chosen somewhere after the second stage of the process, ie after the addition of the metal alkoxide, and before the fifth stage of the process, ie before distillation and drying. Preferably, a soluble fluorinating agent is added while the reaction mixture is maintained at an elevated temperature. Particularly preferably, the soluble fluorinating agent is added before adding the remaining metal alkoxide fraction while the reaction mixture is maintained at an elevated temperature. Thus, the soluble fluorinating agent may be added after at least 20%, preferably at least 50%, and particularly preferably at least 70% of hydrolysis reagents, eg metal alkoxide, have been added.

The method described above is the preferred embodiment. However, the sequence of process steps may vary. The metal alkoxide may be added to the reaction mixture, for example, including a soft magnetic powder, an inert suspending agent, water and a catalyst at the same time, or water and a metal alkoxide may be added at the same time. However, in such embodiments, the stepwise addition of the metal alkoxide in more than one step is preferred, with the soluble fluorinating agent added all at once as described above.

Alternatively or additionally, a soluble fluorinating agent is added immediately after treatment with the silica based solution. If the soluble fluorinating agent is added immediately after the treatment with the silicon-based solution, the soft magnetic powder is treated with the silicon-based solution, including or without the soluble fluorinating agent. The coated soft magnetic powder can be mixed with a solvent such as ethanol and a soluble fluorinating agent in a method step following the alkoxide coating process.

The coated soft magnetic powder according to the methods described above and the coated soft magnetic powder are said to have improved permeability coupled with unchanged or even improved thermal stability compared to the prior art materials disclosed in the European patent application. patent EP 2 871 646 A1.

The coated soft magnetic powder according to the methods described above and the coated soft magnetic powder as described above are particularly suitable for the manufacture of electronic components. Electronic components such as magnetic cores can be obtained, for example, by pressing or injection molding this coated soft magnetic powder. To make such electronic components, the coated soft magnetic powder is usually mixed with one or more types of resin, such as, for example, epoxy resin, urethane resin, polyurethane resin, phenolic resin, amino resin, silicone resin, polyamide resin, polyimide resin, acrylic resin, polyester resin, polycarbonate resin, norbornene resin, styrene resin, polyethersulfone resin, silicone resin, polysiloxane resin, fluorine resin, polybutadiene resin, vinyl ether resin, polyvinyl chloride resin or vinyl ester resin. The method of mixing these components is not limited, and mixing can be carried out using a mixer, for example, a ribbon-screw mixer, a drum type mixer, a Nauta type mixer, a Henschel type mixer or an ultra-mixer, or a kneader mixer, such as a Banbury-type mixer, a kneader-kneader, rollers, kneader, paddle mixer, planetary mixer or single or double axis extruder.

To make a molded article, the soft magnetic powder can be mixed with one or more types of resin to form a powder for molding or a powder ready for pressing. For molding powder, the mixture of coated soft magnetic powder and resin can be heated and melted at the melting temperature of the resin, preferably a thermoplastic resin, and then molded into an electronic component such as a magnetic core of the desired shape. Preferably, the mixture is pressed into a mold to form a magnetic or magnetizable molded article. This pressing results in a molded article which has high strength and good heat resistance.

Another method for making a molded article involves a ready-to-compress powder that contains a coated soft magnetic powder further coated with a resin. Such a ready-to-compress powder can be compressed into a mold under a pressure of up to 1000 MPa, preferably up to 500 MPa, with or without heating. After pressing, the molded article is left to solidify. The process of coating a soft magnetic powder with a resin includes, for example, the steps of dissolving a resin, such as an epoxy resin, in a solvent, adding the soft magnetic powder to the mixture, removing the solvent from the mixture to obtain a dry product, and pulverizing the dry product to obtain a powder. The ready-to-compress powder is used to make a magnetic or magnetizable molded article.

Powder injection molding allows you to economically and efficiently produce complex metal parts. Powder injection molding typically involves molding soft magnetic powders together with a polymer as an adhesive into the desired shape, then the adhesive is removed and the powder is pressed into a hard metal part in a sintering step. This works particularly well with carbonyl iron powder because the spherical iron particles can be packed very tightly together.

Soft magnetic powder treated according to the methods described above, or containing a silicon-based coating with fluorine-containing compositions, as described above, can be used in electronic components. In particular, molded articles of this type can be used as coil cores or coil bodies used in electrical engineering. Coils with suitable coil cores or coil bodies are used, for example, as electromagnets, in generators, in transformers, in inductors, in laptop computers, in netbooks, in mobile phones, in electric motors, in AC inverters, in electronic components in automotive industry, in toys and in magnetic field concentrators. Electronic components are, in particular, magnetic core components that are used in electrical, electromechanical and magnetic devices such as electromagnets, transformers, electric motors, inductors and magnetic assemblies. Other applications for coated soft magnetic powder include the production of radio frequency identification (RFID) tags and elements for reflecting or shielding electromagnetic radiation. In the production of RFID tags, which are labels the size of rice grains for automatic localization or object identification, soft magnetic powder can be used to print the RFID structure. Finally, electronic components made from soft magnetic powder can be used to shield electronic devices. In such applications, an alternating magnetic radiation field causes the powder particles to continuously rearrange themselves. Due to the resulting friction, the powder particles convert the energy of electromagnetic waves into heat.

Examples

Metal Powder Coating - General Procedure A (Preparation Using a Planetary Mixer)

2700 kg of carbonyl iron powder, eg available from BASF, with an iron content of 99.5 g per 100 g and an average particle size d50 between 4.5 and 5 µm is added to a heated planetary mixer. The mixer is equipped with a condenser and purged with argon to create an inert atmosphere. 480 g of ethanol are added with stirring. Then add 75% of the mass. of the total amount of TEOS (the total amount of TEOS used in each experiment is indicated in tables 1 - 6 below). Then add 80% of the mass. from the total amount of an aqueous solution of NH ₃ , having a concentration of 5% wt. NH ₃ (the total amount of aqueous NH ₃ used in each experiment is given in tables 1-6 below). The temperature is now raised to 60° C. while stirring. After stirring at this temperature for about 2 hours, the fluorinating agent is added to the reaction mixture in the form of a solution in ethanol at a concentration of about 10 to 15% by weight. The temperature is maintained while the remaining 25 wt% is added over about one hour. TEOS and the remaining 20% wt. NH ₃ solution. The mixture is stirred for an additional 45 minutes. The refrigerator is removed and the product is stirred for another hour. During this time, the flow of inert gas is increased to 600 l/h, already removing some of the solvent. After one hour, the temperature is raised to 90° C. and the product is stirred under an increased flow of inert gas until dry. The coated carbonyl iron powder is obtained as a gray powder.

Metal Powder Coating - General Procedure B (flask preparation)

355 g of ethanol is added to a flask equipped with a homogenizer (rotor/stator type homogenizer available from Polytron®) and a condenser and purged with argon to obtain an inert atmosphere. The homogenizer is set to 2000 rpm. With stirring, 500 g of carbonyl iron powder, eg available from BASF, with a purity of 99.5 g iron per 100 g and an average particle size d50 between 4.5 and 5 µm, is added. The speed of the homogenizer is increased to 6000 rpm. Then add 68% of the mass. of the total TEOS (total TEOS used in each experiment is shown in Table 7 below). Then add 100% wt. from the total amount of an aqueous solution of NH ₃ , having a concentration of 2.5% wt. NH ₃ (total NH ₃ aqueous solution used in each experiment is shown in Table 7 below). Now the temperature is raised to 45°C for 20 minutes, then to 55°C for 20 minutes and finally to 65°C for 20 minutes, with stirring. After stirring at this temperature for about 1 hour more, the fluorinating agent is added to the reaction mixture in the form of a solution in ethanol at a concentration of about 10 to 15% by weight. The temperature is maintained while the remaining 32 wt. TEOS. The mixture is stirred for 1 additional hour. The product is stirred for about 3 hours at 95° C. in an inert gas flow of 600 l/h and at 47 rpm in a planetary mixer until the solvent is removed. The dried coated carbonyl iron powder was obtained as a gray powder.

Mixing with epoxy

100 g of coated carbonyl iron powder (CIP) was mixed with an epoxy resin such as Epikote™ 1004 available from Momentive by dissolving 2.8 g of the epoxy in 15 to 20 ml of solvent (methyl ethyl ketone or acetone) and adding 0. 14 g dicyandiamide, eg Dyhard® 100SH, available from Alzchem, as hardener. In a glass beaker, the coated CIP is mixed together with the epoxy composition using a dissolution mixer at 1000 rpm. After mixing, the slurry is poured into an aluminum mold pan, which is then placed in a fume hood for 8 hours. The resulting dry epoxy CIP plate is ground in a knife mill for 10 seconds to obtain a powder ready for pressing. It contains 2.8% wt. epoxy resin.

Ring core forming and winding

6.8 g (± 0.1 g) of the ready-to-compress powder is placed in a ring-type steel mold with an outer diameter of 20.1 mm and an inner diameter of 12.5 mm, giving a height of about 5 to 6 mm. The ready-to-compress powder is molded under a pressure of 440 MPa for a few seconds. Based on the exact mass and height of the ring, the density of the ring core is calculated. This ring core is wrapped with 20 turns of 0.85 mm insulated copper wire, such as Isodraht, available as Multogan 2000MH 62, to determine permeability and resistivity.

Measurement of permeability and resistivity

An LRC multimeter was used to measure the permeability of the ring core. All measurements were carried out at 100 kHz with a DC bias of 0 V. A test alternating current of 10 mA was applied to the core of the ring.

To measure the resistivity of pressed parts, a power source was connected in series to the voltmeter and the sample. 298 volts were applied to the multimeter and the sample connected in series. The voltage readings of the multimeter were used to estimate the resistance of the sample using the following equation.

R _sample = R _meter x (V _pi - V _meter )/V _meter ,

where R _{of the sample} is the resistance of the cylinder, R _{of the multimeter} is the internal resistance of the meter, V _CPI is the applied voltage from the power supply (= 298 V), and V _{of the multimeter} is the reading of the voltmeter.

Temperature stability

Before starting the temperature stability test, the epoxy resin is cured. This is done by placing the ring cores in an oven with the temperature set to 70°C. After 2 hours, the ring cores are placed in a second oven set at 155°C. After 2 hours, the ring cores are removed to check the resistivity.

These ring cores are now placed back in the oven set at 180° C. for a while. Thermal stability, for example after 24 hours, is measured after an additional 24 hours of heat treatment at 180°C. The ring core is marked as thermally stable if the measured voltage is about 0 V after 24 hours at 180°C and ≤ 30 V, preferably ≤ 25 V, and in particular ≤ 20 V after 48 hours at 180°C. In another preferred embodiment, the measured voltage is preferably ≤ 70 V, more preferably ≤ 30 V, and in particular ≤ 10 V after 120 hours at 180°C.

Test results

After heat treatment of the densified samples, the permeability and resistivity were determined as described above. The results are shown in Tables 1 to 7. The results of the corrosion resistance tests are shown in Table 8.

Table 1 summarizes Examples E-1 to E-3 and Comparative Examples C-1 and C-2. These examples and comparative examples allow comparison of coated carbonyl iron powder (CIP) using different fluorinating agents under otherwise identical conditions. As can be seen from the results, all compounds exhibit good to excellent properties in terms of permeability as well as temperature stability over time.

As shown by Examples E-4 to E-8 in Table 2, the fluorinating agents of the present invention can significantly reduce the amounts used to achieve excellent results in resistivity. Starting from 9.6 mmol fluorinating agent per kg CIP, the amount commonly used in European patent application EP 2 871 646 A1, the amount of fluorinating agent can be reduced by about 30% to 6.70 mmol/kg without adversely affecting the thermal stability if HBF ₄ is used. In fact, this decrease results in a slight improvement in terms of resistivity after 48 hours.

Table 3 shows the different reaction conditions through different ratios of TEOS, ammonia and fluorinating agent, which allows you to influence the properties of the product. As can be seen, particularly good properties with respect to resistivity as well as permeability are achieved if the molar ratio of ammonia and TEOS is within the range of 1:1.1 to 1:1.8.

Examples E-16 to E-19 in Table 4 demonstrate that the amount of fluorinating agent can be significantly reduced if [NH ₃ EtOH][BF ₄ ] is used compared to BF ₃ ⋅ NH ₂ -CH ₂ -Ph (compare with comparative example CE-4).

Table 5 shows that the use of [NH ₃ EtOH][BF ₄ ] as the fluorinating agent can further reduce the amount of SiO ₂ and fluorinating agent used compared to BF3 ⋅ NH ₂ -CH ₂ -Ph. In particular, the amount of fluorinating agent can be reduced by about 65 mole %, the amount of TEOS can be reduced by 10 mole %, and the amount of NH ₃ solution can be reduced by 20 wt % if [NH ₃ EtOH][BF ₄ ], compared with BF ₃ ⋅ NH ₂ -CH ₂ -Ph, without significant deterioration of the product properties.

Table 6 compares the use of [NH ₃ EtOH][BF ₄ ] as a fluorinating agent with the known fluorinating agent BF ₃ ⋅ NH ₂ -CH ₂ -Ph in various combinations in terms of amounts of SiO ₂ and NH ₃ solution, while the amount fluorine atoms remains approximately constant, in pairs from examples CE-6/E25, CE-7/E26, CE-8/E-7 and CE-9/E8. As can be seen from these examples and comparative examples, comparative examples using BF ₃ ⋅ NH ₂ -CH ₂ -Ph generally result in higher voltages after exposing the fabricated ring core to elevated temperature (i.e., higher resistivity). On the other hand, samples tested using BF ₃ ⋅ NH ₂ -CH ₂ -Ph often show lower permeability. In contrast, the examples of the present invention using [NH ₃ EtOH][BF ₄ ] exhibit a unique combination of relatively high permeability and low resistivity (ie measured voltage) after exposure to elevated temperature. For example, by comparing examples that exhibit a permeability of approximately 17 (+/- 0.05) (i.e., examples E-26, CE-8, and CE-9), it becomes apparent that similar permeability is achieved according to the present invention, while the resistivity after 48 hours at 180°C (15V for E-26, 143V for CE-8 and 105V for CE-9) is noticeably lower.

Table 7 shows the test results of two examples E-29 and E-30, both of which were exposed to 180°C for 120 hours. Both examples show excellent results in terms of both permeability and resistivity.

Table 1 Examples E-1 to E-3 and Comparative Examples CE-1 and CE-2 made according to General Procedure A.

No. approx. Number of TEOS
[G] Number of TEOS
[mol] Amount of SiO ₂ in relation to the total mass of CIP
[mmol/kg] Fluorinating agent
(solution in ethanol) Amount of fluorinating agent
[G] Amount of fluorinating agent
[wt % in relation to the total mass of CIP] The amount of fluorinating agent in relation to the total mass of CIP
[mmol/kg] Permeability (Dry) Measured voltage after 24h at 180°C
[IN] Measured voltage after 48h at 180°C
[IN] E-1 96.9 0.46 172.28 HBF ₄
(solution
10 wt %) 22.68 0.084 9.57 16.63 0.00 4.34 E-2 96.9 0.46 172.28 _{NH4BF4 _}
(solution
10 wt %) 27.00 0.100 9.57 15.9 0 5.1 E-3 96.9 0.46 172.28 [BF ₄ ][H ₃ N-CH ₂ -Ph]
(solution 15% wt.) 30.30 0.167 8.63 17.70 0.02 28.28 CE-1 96.9 0.46 172.28 H ₂ SiF ₆
(solution 15% wt.) 24.80 0.138 9.57 16.10 0.00 3.50 CE-2 96.9 0.46 172.28 BF ₃ NH ₂ -CH ₂ -Ph
(solution 15% wt.) 30.30 0.167 9.57 16.4 0 19

Table 2 Examples E-4 to E-8 made according to General Procedure A.

No. approx. Number of TEOS
[G] Amount of TEOS [mol] The amount of SiO ₂ in relation to the total mass of CIP
[mmol/kg] Amount of NH ₃ solution
[G] Fluorinating agent
(solution in ethanol) Amount of fluorinating agent
[G] Amount of fluorinating agent
[wt % in relation to the total mass of CIP] The amount of fluorinating agent in relation to the total mass of CIP
[mmol/kg] Permeability (Dry) Measured voltage after 24h at 180°C
[IN] Measured voltage after 48h at 180°C
[IN] E-4 96.9 0.46 172.28 134.9 HBF ₄
(solution 10% wt.) 22.7 0.084 9.57 16 0 3.9 E-5 96.9 0.46 172.28 134.9 HBF ₄
(solution 10% wt.) 18.1 0.067 7.65 16.1 0 3.4 E-6 96.9 0.46 172.28 134.9 HBF ₄
(solution 10% wt.) 15.9 0.059 6.70 15.9 0 3.8 E-7 96.9 0.46 172.28 134.9 HBF ₄
(solution 10% wt.) 13.5 0.050 5.74 16.3 0 thirty E-8 96.9 0.46 172.28 134.9 HBF ₄
(solution 10% wt.) 11.3 0.042 4.78 17.1 0.8 83

Table 3 Examples E-9 to E-15 and Comparative Example CE-3 made according to General Procedure A.

No. approx. Number of TEOS
[G] Amount of TEOS [mol] The amount of SiO ₂ in relation to the total mass of CIP
[mmol/kg] Amount of NH ₃ solution
[G] Fluorinating agent
(solution in ethanol) Amount of fluorinating agent
[G] Amount of fluorinating agent
[wt % in relation to the total mass of CIP] The amount of fluorinating agent in relation to the total mass of CIP
[mmol/kg] Permeability (Dry) Measured voltage after 24h at 180°C
[IN] Measured voltage after 48h at 180°C
[IN] E-9 96.9 0.46 172.28 94.4 HBF ₄
(solution 10% wt.) 15.93 0.059 6.70 17.2 0.14 39 E-10 96.9 0.46 172.28 107.9 HBF ₄
(solution 10% wt.) 15.93 0.059 6.70 17.5 0 3 E-11 87.2 0.41 155.05 134.9 HBF ₄
(solution 10% wt.) 18.09 0.067 7.65 16.8 0 9 E-12 77.5 0.37 137.82 134.9 HBF ₄
(solution 10% wt.) 22.68 0.084 9.57 17.5 0.5 63 E-13 82.4 0.39 146.43 134.9 HBF ₄
(solution 10% wt.) 20.41 0.076 8.63 16.6 0.23 46 E-14 96.9 0.46 172.28 101.2 HBF ₄
(solution 10% wt.) 15.93 0.059 6.70 16.3 0 3.3 E-15 87.2 0.41 155.05 107.9 (solution 10% wt.) 18.09 0.067 7.65 16.4 0 - CE-3 96.9 0.46 172.28 134.9 BF ₃ NH ₂ -CH ₂ -Ph
(solution 15% wt.) 30.30 0.167 9.57 16.4 0 19

Table 4 Examples E-16 to E-19 and Comparative Example CE-4 made according to General Procedure A.

No. approx. Number of TEOS
[G] Amount of TEOS [mol] The amount of SiO ₂ in relation to the total mass of CIP
[mmol/kg] Amount of solution NH ₃
[G] Fluorinating agent
(solution in ethanol) Amount of fluorinating agent
[G] Amount of fluorinating agent
[wt % in relation to the total mass of CIP] The amount of fluorinating agent in relation to the total mass of CIP
[mmol/kg] Permeability (Dry) Measured voltage after 24h at 180°C
[IN] Measured voltage after 48h at 180°C
[IN] E-16 96.9 0.46 172.28 134.9 [NH ₃ EtOH] [BF ₄ ]
(solution
10 wt%; molar ratio N : B = 1.785:1) 28.08 0.104 5.30 16.55 0.00 1.6 E-17 96.9 0.46 172.28 134.9 [NH ₃ EtOH] [BF ₄ ]
(solution
10 wt%; molar ratio N : B = 1.785:1) 22.68 0.084 4.24 16.5 0 7.5 E-18 96.9 0.46 172.28 101.2 [NH ₃ EtOH] [BF ₄ ]
(solution
10 wt%;
molar ratio N : B = 1.785:1) 22.68 0.084 4.24 16.51 0 0.5 E-19 87.2 0.41 155.05 107.9 [NH ₃ EtOH] [BF ₄ ]
(solution
10 wt%;
molar ratio N : B = 1.785:1) 22.68 0.084 4.24 16.85 0 5.15 CE-4 96.9 0.46 172.28 134.9 BF ₃ NH ₂ -CH ₂ -Ph (solution 15% wt.) 30.30 0.167 9.57 16.7 0 eleven

Table 5 Examples E-20 to E-24 and Comparative Example CE-5 made according to General Procedure A.

No. approx. Number of TEOS
[G] Amount of TEOS [mol] Amount of SiO ₂ in relation to the total mass of CIP
[mmol/kg] Amount of NH ₃ solution
[G] Fluorinating agent
(solution 15% wt.) Amount of fluorinating agent
[G] The amount of fluorinating agent
[wt % in relation to the total mass of CIP] The amount of fluorinating agent in relation to the total mass of CIP
[mmol/kg] Permeability (Dry) Measured voltage after 48h at 180°C
[IN] E-20 96.9 0.46 172.28 134.9 [NH ₃ EtOH] [BF ₄ ]
(molar ratio N : B = 1.3 : 1) 14.22 0.079 4.70 16.43 0.85 E-21 87.2 0.41 155.05 107.9 [NH ₃ EtOH] [BF ₄ ]
(molar ratio N : B = 1.3:1) 17.01 0.063 3.76 17.2 4 E-22 96.9 0.46 172.28 101.2 [NH ₃ EtOH] [BF ₄ ]
(molar ratio N : B = 1.3:1) 14.85 0.055 3.29 17.8 9.5 E-23 87.2 0.41 155.05 101.2 [NH ₃ EtOH] [BF ₄ ]
(molar ratio N : B = 1.3:1) 17.01 0.063 3.76 17.7 eleven E-24 87.2 0.41 155.05 107.9 [NH ₃ EtOH] [BF ₄ ]
(molar ratio N : B = 1.3:1) 14.85 0.055 3.29 17.6 15 CE-5 96.9 0.46 172.28 134.9 BF ₃ NH ₂ -CH ₂ -Ph 30.3 0.167 9.57 17.1 16.5

Table 6 Examples E-25 to E-28 and Comparative Examples CE-6 to CE-9 made according to General Procedure A.

No. approx. Number of TEOS
[G] Amount of TEOS [mol] Amount of SiO ₂ in relation to the total mass of CIP
[mmol/kg] Amount of NH ₃ solution
[G] Fluorinating agent
(solution 15% wt.) Amount of fluorinating agent
[G]
(15 wt. % in ethanol) The amount of fluorinating agent
[wt % in relation to the total mass of CIP] The amount of fluorinating agent in relation to the total mass of CIP
[mmol/kg] Number of fluorine atoms in relation to the total mass of CIP
[mmol/kg] Permeability (Dry) Measured voltage after 24h at 180°C
[IN] Measured voltage after 48h at 180°C
[IN] CE-6 96.9 0.46 172.28 134.9 BF ₃ NH ₂ -CH ₂ -Ph 30.3 0.167 9.57 28.71 16.3 0 8 E-25 96.9 0.46 172.28 134.9 [NH ₃ EtOH] [BF ₄ ]
(molar ratio N : B = 1.3:1) 21.76 0.121 7.19 28.76 15.25 0 0.25 CE-7 87.2 0.41 155.05 101.2 BF ₃ NH ₂ -CH ₂ -Ph 15.77 0.087 4.98 14.94 16.6 0.5 77 E-26 87.2 0.41 155.05 101.2 [NH ₃ EtOH] [BF ₄ ] (molar ratio N : B = 1.3:1) 11.38 0.063 3.76 15.04 17.05 0 15 CE-8 87.2 0.41 155.05 107.9 BF ₃ NH ₂ -CH ₂ -Ph 13.94 0.077 4.4 13.2 16.95 1.4 143 E-27 87.2 0.41 155.05 107.9 [NH ₃ EtOH] [BF ₄ ] (molar ratio N : B = 1.3:1) 9.95 0.055 3.29 13.16 16.45 0 37 CE-9 89.1 0.43 160.22 101.2 BF ₃ NH ₂ -CH ₂ -Ph 19.7 0.109 6.22 18.66 17 0.2 105 E-28 89.1 0.43 160.22 101.2 [NH ₃ EtOH] [BF ₄ ] (molar ratio N : B = 1.3:1) 14.22 0.079 4.7 18.8 16.2 0 3

Table 7 Examples E-29 and E-30 made according to General Procedure B.

No. approx. Number of TEOS
[G] Amount of TEOS [mmol] The amount of SiO ₂ in relation to the total mass of CIP
[mmol/kg] Amount of NH ₃ solution
[G] Fluorinating agent Amount of fluorinating agent
[G]
(15 wt. % in ethanol) Amount of fluorinating agent
[wt % in relation to the total mass of CIP] The amount of fluorinating agent in relation to the total mass of CIP
[mmol/kg] Permeability (dry) Measured voltage after 48h at 180°C
[IN] Measured voltage after 96h at 180°C
[IN] Measured voltage after 120 h at 180°C
[IN] E-29 17 81.6 163.21 60 [NH ₃ EtOH] [BF ₄ ] 2.6 0.078 4.7 16.65 0 0 1.1 E-30 17 81.6 163.21 60 [NH ₃ EtOH] [BF ₄ ] 2.6 0.078 4.7 17.2 0 0 0.5

Corrosion testing

The corrosion of various stainless steel materials was tested by exposing specimens (with dimensions: 50x20x2 mm) of stainless steel materials (test materials included in accordance with DIN EN 10027-2: 1.4541, 1.4571, 1.4462, 1.0425) to an appropriate additive solution at temperature T = 60°C for 4 x 7 days, while the solution is replaced with a fresh solution every week. The test was carried out in an adapted PTFE vessel. The test results are summarized in Table 8.

Table 8 Corrosion test results

Additive solution pH corrosion [NH ₃ EtOH] [BF ₄ ] (15 wt % in ethanol) 6 absent BF ₃ NH ₂ -CH ₂ -Ph (15% wt. in ethanol) 4 absent/little HBF ₄ (3 wt % in ethanol) 3 small HBF ₄ (10 wt % in ethanol) 3 small/strong HBF ₄ (10 wt % in water) 0 - 1 strong

As can be seen, the HBF ₄ solution is slightly to severely corrosive to stainless steel materials, depending on the solvent used. In contrast, BF ₃ ⋅ NH ₂ -CH ₂ -Ph (15 wt % in ethanol) and [NH ₃ EtOH][BF ₄ ] (15 wt % in ethanol) show little or no corrosion. Therefore, from the point of view of product purity, [NH ₃ EtOH][BF ₄ ] and BF ₃ ⋅ NH ₂ -CH ₂ -Ph are preferred in the process of coating soft magnetic powder compared to HBF ₄ . However, the latter can be used at low concentrations (i.e. 3 wt % in ethanol).

Based on the foregoing, the advantages of the present invention can be summarized as follows. The use of a fluorinating agent according to formula (II) in a method for coating a soft magnetic powder, wherein the coating contains at least one fluorine-containing composition containing a composition of formula (I), makes it possible to provide a coated soft magnetic powder having a higher permeability with comparable resistivity compared to known fluorinating agents. On the other hand, higher resistivity can be achieved with comparable permeability. In addition, the fluorinating agent of the present invention is more stable in solution, less prone to precipitating out of solution (i.e., has higher solubility), exhibits improved material compatibility (particularly against corrosion), and improved handling.

Claims (44)

1. A method of coating a soft magnetic powder for magnetic core components, wherein the coating contains at least one fluorine-containing composition containing a compound of formula (I) Si _1-0.75c M _c O _2-0.5c F _d (I), wherein c is in the range from 0.01 to 0.5, d ranges from 0.04 to 2, and M is B or Al, where the soft magnetic powder is mixed with a silicon-based solution containing at least one soluble fluorinating agent, and this at least one fluorinating agent is a compound of formula (II) [Q][MF ₄ ] (II), wherein M is B or Al; And Q is a cationic group selected from H ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , Cs ⁺ or [NR ¹ ₄ ] ⁺ , where R ¹ is independently selected from the group consisting of -H, -alkyl with 1-12 atoms carbon, -alkenyl with 2-12 carbon atoms and -aryl with 6-18 carbon atoms, each of which may be substituted by at least one group represented by the formula -OR ² where R ² is independently selected from -H, -alkyl with 1-12 carbon atoms, -alkenyl with 2-12 carbon atoms and -aryl with 1-18 carbon atoms. 2. The method of claim 1, wherein the soft magnetic powder is mixed with the silicon based solution and at least one soluble fluorinating agent is added after at least partially treating the soft magnetic powder with the silicon based solution. 3. The method according to p. 1, where at least one soluble fluorinating agent is a compound of formula (II) [Q][MF4] (II), wherein M is selected from B; A Q is a cationic group selected from H ⁺ or [NR ¹ ₄ ] ⁺ , where R ¹ is independently selected from the group consisting of -H, -alkyl with 1-12 carbon atoms, -alkenyl with 2-12 carbon atoms and -aryl with 6-18 carbon atoms, each of which may be substituted by at least one a group represented by the formula -OR ² where R ² is independently selected from -H, -alkyl with 1-12 carbon atoms, -alkenyl with 2-12 carbon atoms and -aryl with 1-18 carbon atoms. 4. The method according to p. 1, where the soluble fluorinating agent is selected from the group consisting of HBF ₄ , [NH ₄ ][BF ₄ ] and [(R ⁴ -OR ³ ) _x -NH _3-x ][BF ₄ ], Where R ³ represents a group of formula -(C _n H _2n+p )-, n is an integer from 1 to 6, p is an integer chosen from 0 and -2, R ⁴ is selected from -H or -(C _m H _2m+q )-CH ₃ , m is an integer from 0 to 6, q is an integer chosen from 0 and -2, provided that when m = 0 then q = 0, and x is an integer chosen from 1 to 3. 5. The method according to paragraphs. 1-4, where from 0.1 to 10 mmol of a fluorinating agent per 1 kg of soft magnetic powder is added to the silicon-based solution. 6. Soft magnetic powder for the components of the magnetic core, coated with a silicon-based coating, obtained using the method according to any one of paragraphs. 1-5. 7. Soft magnetic powder for magnetic core components coated with a silicon-based coating, where this silicon-based coating contains at least one fluorine-containing compound of formula (I) Si _1-0.75c M _c O _2-0.5c F _d (I), wherein c is in the range from 0.01 to 0.5, d is in the range from 0.04 to 2, index c and index d have the following relationship: d = 4c, and M is B or Al. 8. Soft magnetic powder according to claim 6 or 7, containing at least one fluorine-containing compound of formula (I), where M is B. 9. Soft magnetic powder according to claim 6 or 7, wherein the silicon-based coating contains from > 5 to 45 wt %, preferably from 10 to 40 wt %, in particular from 20 to 35 wt %, according to at least one fluorine-containing compound of formula (I). 10. Soft magnetic powder according to claim 6 or 7, wherein the fluorine component of the fluorine-containing composition is embedded within the SiO ₂ matrix and/or bonded to the surface of the SiO ₂ coating. 11. Soft magnetic powder according to claim 6 or 7, wherein the silicon-based coating has an average thickness of 2 to 100 nm. 12. Soft magnetic powder according to claim 6 or 7, and this soft magnetic powder contains from 0.1 to 10% of the mass. coatings based on silicon, in terms of the total weight of the soft magnetic powder. 13. The use of soft magnetic powder obtained by the method according to paragraphs. 1-5, or soft magnetic powder according to paragraphs. 6-12 for the manufacture of electronic components. 14. An electronic component for a magnetic core containing a soft magnetic powder obtained by the method according to paragraphs. 1-5, or soft magnetic powder according to paragraphs. 6-12.