CN113801632B - Dispersing agent for permanent magnetic ferrite material and preparation method and application thereof - Google Patents

Dispersing agent for permanent magnetic ferrite material and preparation method and application thereof Download PDF

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CN113801632B
CN113801632B CN202111191028.4A CN202111191028A CN113801632B CN 113801632 B CN113801632 B CN 113801632B CN 202111191028 A CN202111191028 A CN 202111191028A CN 113801632 B CN113801632 B CN 113801632B
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dispersant
permanent magnetic
dispersing agent
water
magnetic ferrite
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CN113801632A (en
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杨武国
申屠金昂
何震宇
蒋有福
厉一俊
陆荐良
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Hengdian Group DMEGC Magnetics Co Ltd
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/26—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on ferrites
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    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
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    • C04B35/6261—Milling

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Abstract

The invention belongs to the technical field of permanent magnetic ferrite materials, and discloses a dispersing agent for a permanent magnetic ferrite material, and a preparation method and application thereof. The dispersing agent for the permanent magnetic ferrite material is prepared by mixing citric acid, ammonia water, sodium hydroxide and water, wherein the mass concentration of the ammonia water is 20-30%, and the mass ratio of the citric acid to the water to the ammonia water is 1: 0.7-1.3: 0.5-1.5, and the pH value of the dispersant is 4-7. The dispersant is a water-based dispersant which is independently synthesized by cheap industrial raw materials, can be applied to the preparation process of the permanent magnetic ferrite material, can effectively improve the comprehensive magnetic property of the material, and basically does not influence the yield of final products.

Description

Dispersing agent for permanent magnetic ferrite material and preparation method and application thereof
Technical Field
The invention relates to the technical field of permanent magnetic ferrite materials, in particular to a dispersing agent for a permanent magnetic ferrite material, and a preparation method and application thereof.
Background
The permanent magnetic ferrite magnet is one of basic functional materials of a permanent magnetic direct current motor, can meet the use requirements of the motor under various environments, has high sensitivity and stability, and can be widely applied to various motors with high power, high rotating speed and high torque, such as high-grade automobile motors (ABS motors, starting motors and the like), motorcycle starting motors, household appliances, electric tool motors and the like. With the development of miniaturization and light weight of motors and generators, the market requires further improvement of the magnetic performance of ferrite permanent magnets.
The magnetic performance of the permanent magnetic material mainly comprises three parameters, namely residual magnetic flux density (Br), intrinsic coercive force (Hcj) and maximum magnetic energy product (BH) max. Wherein the remanent flux density (Br) mainly depends on the density of the magnet, the degree of crystal orientation, the saturation magnetization (Ms) of the material, and the like. Generally, there are two methods for improving the magnetic performance of sintered ferrite permanent magnet materials, one is to optimize the material components and improve the saturation magnetization and magnetocrystalline anisotropy constant of the magnetic phase (M phase); the other method is to improve the preparation process, optimize the microstructure of the magnet and improve the remanence and the coercive force of the magnet.
In order to obtain a high-performance permanent magnetic ferrite product, it is important to ensure that the powder particles after ball milling have uniform size, are in a single-domain state as much as possible and are not easy to agglomerate, so that the application of the high-performance dispersing agent in the magnetic field forming process is indispensable. The addition of a proper amount of dispersing agent can reduce agglomeration among material particles, change the size and uniformity of magnetic particles and improve the degree of orientation, thereby effectively improving the crystal structure and the product performance of the magnetic powder. At present, the most used dispersant in ferrite manufacturers in China is mainly calcium gluconate (the molecular formula is Ca (C))6H11O7)2) Mainly, it has the advantages of relatively low price, good dispersibility, Ca contained in the alloy being beneficial to improving the residual magnetic flux density (Br), and the like. In the ball milling process, calcium gluconate containing high hydrophilic groups is adsorbed to the surfaces of the oxide particles to play a role of steric hindrance, and meanwhile, a plurality of high hydrophilic groups contained in the calcium gluconate can improve the wettability of the oxide particles and water, so that the dispersibility of the oxide particles is improved. However, since a plurality of hydrophilic groups of calcium gluconate have strong water retention, if excessive addition is performed, water removal is difficult in the forming process, and residual calcium gluconate is decomposed in the sintering process to cause cracking of the magnet, thereby affecting production efficiency and yield. If too little calcium gluconate is added, the slurry is difficult to fully disperse, and the product performance is influenced, which is an important problem troubling ferrite manufacturers.
Disclosure of Invention
The invention aims to overcome the defects of the background technology and provides a dispersing agent for a permanent magnetic ferrite material, and a preparation method and application thereof. The dispersant is a water-based dispersant which is synthesized by cheap industrial raw materials, can be applied to the preparation process of the permanent magnetic ferrite material, can effectively improve the comprehensive magnetic property of the material, and basically does not influence the yield of final products.
In order to achieve the purpose of the invention, the dispersant for the permanent magnetic ferrite material is prepared by mixing citric acid, ammonia water, sodium hydroxide and water, wherein the mass concentration of the ammonia water is 20-30%, and the mass ratio of the citric acid to the water to the ammonia water is 1: 0.7-1.3: 0.5-1.5, and the pH value of the dispersant is 4-7.
Further, in some embodiments of the present invention, the mass concentration of the ammonia water is 23 to 27%.
Further, in some embodiments of the present invention, the mass ratio of the citric acid to the water to the ammonia water is 1: 0.9-1.2: 0.6-1.5.
Further, in some embodiments of the invention, the dispersant has a pH of 5 to 6.
In another aspect, the present invention also provides a preparation method of the foregoing dispersant, the method comprising the steps of:
(1) mixing the citric acid solid with water, and stirring uniformly until the citric acid is completely dissolved;
(2) adding ammonia water into the solution obtained in the step (1);
(3) adding solid sodium hydroxide into the solution obtained in the step (1), uniformly stirring, and adjusting the pH value of the solution to be between 4 and 7 to obtain the liquid dispersing agent.
In a further aspect, the invention also provides an application of the dispersing agent, wherein the dispersing agent is applied to a permanent magnetic ferrite material ball milling procedure. The dispersing agent can generate a particularly outstanding dispersing effect on ferrite powder in the magnetic field forming process, can realize uniform dispersion of the ferrite powder particularly in the process of ball milling of the ferrite powder, and improves the magnetic performance of the prepared ferrite magnetic material on the premise of not reducing the qualification rate of the ferrite magnetic material product.
Further, in some embodiments of the present invention, the step of applying the dispersant to the permanent ferrite material ball milling process comprises:
(1) ball milling: adding corresponding additives into the permanent magnetic ferrite pre-sintered material powder, adding water with the mass of 1.0-1.5 times of that of the pre-sintered material powder, then adding the dispersing agent, stirring uniformly, and transferring into a ball mill for wet ball milling to obtain slurry with the average particle size of 0.75-0.85 mu m;
(2) a molding procedure: adjusting the solid content of the slurry obtained in the step to 65-75wt%, and then performing magnetic field forming by adopting a mold to obtain a formed blank;
(3) and (3) sintering: firstly, preserving the temperature of the formed blank in the step at 200-300 ℃ to remove the moisture and residual dispersant in the formed blank, then heating to a reasonable sintering temperature in an air atmosphere and preserving the temperature to obtain a permanent ferrite magnet semi-finished product;
(4) and grinding the permanent magnetic ferrite magnet semi-finished product according to requirements to obtain a finished magnet.
In the wet ball milling process of the permanent magnetic ferrite wet ball milling, slurry is generally alkalescent due to the hydrolysis effect of a small amount of Sr and Ca ions in the pre-sintering material and the additive, and the pH value of normal ball milling slurry is approximately between 9 and 12 according to different pre-sintering material formulas and preparation processes. When the pH value of the slurry is too high, the slurry is stuck to a mold and is not dehydrated smoothly in the magnetic field forming process, so that the yield of the final product is influenced; on the other hand, the rotation of ferrite particles in a magnetic field is not facilitated, so that the orientation degree is not high, and the comprehensive magnetic performance of the final magnet is lower. In the invention, the dispersing agent is added in a ball milling process, so that alkalescence in slurry can be effectively neutralized, the pH value of the slurry is properly reduced, on one hand, the fluidity of the slurry is improved, the ball milling efficiency is improved, the particle size uniformity of the slurry is improved, and meanwhile, in a magnetic field forming process, the improvement of the orientation degree of ferrite particles is facilitated, so that the comprehensive magnetic performance of the material is finally improved.
Further, in some embodiments of the present invention, a dispersant is added in the step (1) in an amount of 0.5 to 5% by weight of the pre-sinter powder; preferably, a dispersant accounting for 1-4% of the weight of the pre-sintering powder is added in the step (1). If the addition amount of the dispersing agent is too small, the influence on the pH value of ferrite slurry is limited, and the grinding aid effect in the ball milling process and the dispersing effect in the magnetic field forming process are small, so that the comprehensive magnetic property of the product is not obviously improved; if the addition amount of the dispersing agent is too large, on one hand, the cost is too high, and on the other hand, the pH value is also obviously reduced, so that the stability of ferrite particles in slurry is influenced, and the improvement of the magnetic performance of the product is not facilitated.
In the permanent magnetic ferrite magnetic field forming procedure, ferrite magnetic powder particles in slurry are orderly arranged through a magnetic field, and the addition of the dispersing agent can effectively improve the orientation degree. At the same time, the forming process also requires that the slurry with the solid content of about 70 wt% is pressed by suction filtration to become a formed blank with the solid content of about 90%, so that about 20 wt% of water containing the dispersing agent is removed by suction filtration. Compared with the conventional slightly water-soluble calcium gluconate dispersing agent, the dispersing agent prepared by the invention is water-soluble, and part of the dispersing agent is removed along with the suction filtration water in the forming process, so that the residual organic components in the actual formed blank are relatively less, and the final influence on the finished product rate is limited even if the adding amount of the dispersing agent is relatively large.
In the permanent magnetic ferrite sintering step, the molded blank is first subjected to moderate heat preservation at about 300 ℃ to remove moisture and residual dispersant from the molded blank. The boiling point of the main components of the conventional calcium gluconate dispersing agent is 674 ℃, the flash point is 375 ℃, so that the calcium gluconate remained in the blank is difficult to completely decompose at the heat preservation section at about 300 ℃ in the sintering process, the product is easy to crack in the subsequent rapid heating process, and the yield of the product is greatly reduced particularly when the addition amount is too much. The main component of the dispersant in the formed blank is ammonium citrate which begins to decompose at about 185 ℃, and the dispersant remaining in the blank of the heat preservation section at about 300 ℃ can be completely decomposed and removed, so that the finished product rate of the final product is not influenced.
Further, in some embodiments of the present invention, the formed blank in the step (3) is kept at 200 ℃ and 300 ℃ for 0.5-2h, which is favorable for removing the residual dispersant in the formed blank.
Further, in some embodiments of the present invention, the sintering temperature in step (3) is 1180-.
Compared with the prior art, the invention has the following advantages:
(1) according to the invention, common cheap raw materials such as industrial citric acid, ammonia water and sodium hydroxide are adopted, are subjected to simple mixing reaction to synthesize the water system dispersing agent, and are directly added in the ball milling process, so that on one hand, the ball milling efficiency is improved by reducing the pH value of slurry; on the other hand, the magnetic powder can be used as a dispersing agent in the magnetic field forming process to improve the fluidity of slurry and the orientation degree of magnetic powder particles in the forming process, so that the aim of improving the comprehensive magnetic performance of the material is fulfilled.
(2) The dispersant is a water-based dispersant, when slurry is filtered and pressed into a formed blank with solid content of about 90%, about 20 wt% of water containing the dispersant is removed through the filtering process, the dispersant has less residue in the formed blank and is easy to decompose and remove in the sintering process, so that the finished product rate of the final product is not influenced basically even if the addition amount of the dispersant is large, the residual magnetism and the coercive force of the ferrite magnet are improved by more than 100 on the basis of ensuring that the finished product rate reaches 96%, and the ferrite material field is remarkably improved.
(3) The independently synthesized water system dispersant adopts common industrial raw materials, can be prepared on site by simple mixing, and has low cost.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. It is to be understood that the following description is only illustrative of the present invention and is not to be construed as limiting the present invention.
The terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.
When an amount, concentration, or other value or parameter is expressed as a range, preferred range, or as a range of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted to include the ranges "1 to 4", "1 to 3", "1 to 2 and 4 to 5", "1 to 3 and 5", and the like. When a range of values is described herein, unless otherwise stated, the range is intended to include the endpoints thereof and all integers and fractions within the range.
The indefinite articles "a" and "an" preceding an element or component of the invention are not intended to limit the number requirement (i.e., the number of occurrences) of the element or component. Thus, "a" or "an" should be read to include one or at least one, and the singular form of an element or component also includes the plural unless the number clearly indicates the singular.
Furthermore, the description below of the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily for the same embodiment or example. Further, the technical features of the embodiments of the present invention may be combined with each other as long as they do not conflict with each other.
Example 1
Synthesis of a dispersing agent: putting 10kg of commercially available citric acid solid into a plastic barrel, adding 10kg of tap water, fully stirring and uniformly mixing until the citric acid is completely dissolved; (2) 6kg of ammonia water with the mass concentration of 25% is added into the solution and stirred uniformly; (3) about 10kg of solid sodium hydroxide was further added to the above solution and uniformly stirred to test the pH of the solution to 6, to obtain a liquid dispersant of the present invention, No. FS 1.
Example 2
Synthesis of a dispersing agent: putting 10kg of commercially available citric acid solid into a plastic barrel, adding 10kg of tap water, fully stirring and uniformly mixing until the citric acid is completely dissolved; (2) adding 10kg of 25% ammonia water into the solution, and stirring uniformly; (3) about 5kg of solid sodium hydroxide was further added to the above solution and uniformly stirred to test the pH of the solution to 5, to obtain a liquid dispersant of the present invention, No. FS 2.
Example 3
Synthesis of a dispersing agent: putting 10kg of commercially available citric acid solid into a plastic barrel, adding 10kg of tap water, fully stirring and uniformly mixing until the citric acid is completely dissolved; (2) adding 12kg of 25% ammonia water into the solution, and stirring uniformly; (3) about 8kg of sodium hydroxide solid was further added to the above solution and uniformly stirred to test the pH of the solution to 6, to obtain a liquid dispersant of the present invention, No. FS 3.
Example 4
Synthesis of a dispersing agent: putting 10kg of commercially available citric acid solid into a plastic barrel, adding 10kg of tap water, fully stirring and uniformly mixing until the citric acid is completely dissolved; (2) adding 15kg of 25% ammonia water into the solution, and uniformly stirring; (3) about 10kg of solid sodium hydroxide was further added to the above solution and uniformly stirred to test the pH of the solution to be 7, to obtain a liquid dispersant of the present invention, No. FS 4.
Example 5
Application of the dispersant:
the prepared dispersant is applied to the batch production of the permanent magnetic ferrite:
(1) taking 3.0 tons of conventional permanent magnetic ferrite pre-sintering material powder, adding corresponding additives, adding 3.6 tons of tap water, then adding the FS1# dispersing agent accounting for 3.5 wt% of the weight of the pre-sintering material powder, stirring uniformly, transferring into a ball mill, carrying out wet ball milling for 16 hours to obtain ferrite molding slurry, wherein the tested average particle size is 0.78 mu m;
(2) adjusting the water content of the slurry obtained in the step, adjusting the solid content of the slurry to about 70 wt%, and then performing magnetic field forming by adopting a special die to obtain a formed blank;
(3) preserving the temperature of the formed blank in the step for 1.0 hour at 300 ℃, then heating to 1230 ℃ in the air atmosphere and preserving the temperature for 1.0 hour to obtain a permanent magnetic ferrite magnet semi-finished product;
(4) and grinding and processing the semi-finished sintered magnet into a standard shape for magnetic property testing, grinding and processing all semi-finished sintered magnets according to the requirements of a customer drawing to obtain finished magnets, and calculating the finished product rate of the final products.
Through magnetic performance tests, the obtained ferrite magnet has the remanence Br of 4365Gs, the coercive force Hcj of 4052Oe, the maximum magnetic energy product (BH) max of 4.59MGOe and the yield of 97.8 percent.
Example 6
Application of the dispersant:
the prepared dispersant is applied to the batch production of the permanent magnetic ferrite:
(1) taking 2.0 tons of conventional permanent magnetic ferrite pre-sintering material powder, adding corresponding additives, adding 2.5 tons of tap water, then adding the FS2# dispersing agent accounting for 2.5 wt% of the weight of the pre-sintering material powder, stirring uniformly, transferring into a ball mill, carrying out wet ball milling for 16 hours to obtain ferrite molding slurry, wherein the tested average particle size is 0.78 mu m;
(2) adjusting the water content of the slurry obtained in the step, adjusting the solid content of the slurry to about 70 wt%, and then performing magnetic field forming by adopting a special die to obtain a formed blank;
(3) preserving the temperature of the formed blank in the step for 1.5 hours at 280 ℃, then heating to 1220 ℃ in the air atmosphere and preserving the temperature for 1.0 hour to obtain a permanent magnetic ferrite magnet semi-finished product;
(4) and grinding and processing the semi-finished sintered magnet into a standard shape for magnetic property testing, grinding and processing all semi-finished sintered magnets according to the requirements of a customer drawing to obtain finished magnets, and calculating the finished product rate of the final products.
Through magnetic performance tests, the obtained ferrite magnet has the remanence Br of 4325Gs, the coercive force Hcj of 4064Oe, the maximum magnetic energy product (BH) max of 4.48MGOe and the yield of 96.8 percent.
Example 7
Application of the dispersant:
the prepared dispersant is applied to the batch production of the permanent magnetic ferrite:
(1) taking 3.0 tons of conventional permanent magnetic ferrite pre-sintering material powder, adding corresponding additives, adding 3.3 tons of tap water, then adding the FS3# dispersing agent accounting for 1.5 wt% of the weight of the pre-sintering material powder, stirring uniformly, transferring into a ball mill, performing wet ball milling for 16 hours to obtain ferrite molding slurry, wherein the tested average particle size is 0.79 mu m;
(2) adjusting the water content of the slurry obtained in the step, adjusting the solid content of the slurry to about 70 wt%, and then performing magnetic field forming by adopting a special die to obtain a formed blank;
(3) preserving the temperature of the formed blank in the step for 1.0 hour at 320 ℃, then heating to 1200 ℃ in the air atmosphere and preserving the temperature for 1.5 hours to obtain a permanent magnetic ferrite magnet semi-finished product;
(4) and grinding and processing the semi-finished sintered magnet into a standard shape for magnetic property testing, grinding and processing all semi-finished sintered magnets according to the requirements of a customer drawing to obtain finished magnets, and calculating the finished product rate of the final products.
Through magnetic property test, the obtained ferrite magnet has remanence Br4310Gs, coercive force Hcj4096Oe maximum magnetic energy product (BH)max4.42MGOe, and the yield reached 97.5%.
Example 8
Application of the dispersant:
the prepared dispersant is applied to the batch production of the permanent magnetic ferrite:
(1) taking 2.0 tons of conventional permanent magnetic ferrite pre-sintering material powder, adding corresponding additives, adding 2.8 tons of tap water, then adding the FS4# dispersing agent accounting for 4.0 wt% of the weight of the pre-sintering material powder, stirring uniformly, transferring into a ball mill, performing wet ball milling for 16 hours to obtain ferrite molding slurry, wherein the tested average particle size is 0.77 mu m;
(2) adjusting the water content of the slurry obtained in the step, adjusting the solid content of the slurry to about 70 wt%, and then performing magnetic field forming by adopting a special die to obtain a formed blank;
(3) preserving the temperature of the formed blank in the step for 2.0 hours at 300 ℃, then heating to 1230 ℃ in the air atmosphere and preserving the temperature for 1.5 hours to obtain a permanent magnetic ferrite magnet semi-finished product;
(4) and grinding and processing the semi-finished sintered magnet into a standard shape for magnetic property testing, grinding and processing all semi-finished sintered magnets according to the requirements of a customer drawing to obtain finished magnets, and calculating the finished product rate of the final products.
Through magnetic property test, the obtained ferrite magnet has remanence Br4380Gs, coercive force Hcj4095Oe maximum magnetic energy product (BH)max4.61MGOe and the yield reaches 96.5%.
Comparative example 1
Compared to example 5, except that no dispersant was added:
(1) taking 3.0 tons of conventional permanent magnetic ferrite pre-sintered material powder, adding corresponding additives, adding 3.6 tons of tap water, stirring uniformly, transferring into a ball mill, and carrying out wet ball milling for 16 hours to obtain ferrite molding slurry, wherein the average particle size is 0.84 mu m;
(2) adjusting the water content of the slurry obtained in the step, adjusting the solid content of the slurry to about 70 wt%, and then performing magnetic field forming by adopting a special die to obtain a formed blank;
(3) preserving the temperature of the formed blank in the step for 1.0 hour at 300 ℃, then heating to 1230 ℃ in the air atmosphere and preserving the temperature for 1.0 hour to obtain a permanent magnetic ferrite magnet semi-finished product;
(4) and grinding and processing the semi-finished sintered magnet into a standard shape for magnetic property testing, grinding and processing all semi-finished sintered magnets according to the requirements of a customer drawing to obtain finished magnets, and calculating the finished product rate of the final products.
Through magnetic property test, the obtained ferrite magnet has remanence Br4205Gs, coercive force Hcj3966Oe, maximum magnetic energy product (BH)max4.28MGOe and the yield reaches 95.4%.
Comparative example 2
Compared with the embodiment 6, the difference is that the additive of the invention is not added, but 0.5 wt% of calcium gluconate is added:
(1) taking 2.0 tons of conventional permanent magnetic ferrite pre-sintering material powder, adding corresponding additives, adding 2.5 tons of tap water, then adding the calcium gluconate dispersing agent accounting for 0.5 wt% of the weight of the pre-sintering material powder, stirring uniformly, transferring into a ball mill, performing wet ball milling for 16 hours to obtain ferrite molding slurry, and testing the average particle size to be 0.78 mu m;
(2) adjusting the water content of the slurry obtained in the step, adjusting the solid content of the slurry to about 70 wt%, and then performing magnetic field forming by adopting a special die to obtain a formed blank;
(3) preserving the temperature of the formed blank in the step for 1.5 hours at 280 ℃, then heating to 1220 ℃ in the air atmosphere and preserving the temperature for 1.0 hour to obtain a permanent magnetic ferrite magnet semi-finished product;
(4) and grinding and processing the semi-finished sintered magnet into a standard shape for magnetic property testing, grinding and processing all semi-finished sintered magnets according to the requirements of a customer drawing to obtain finished magnets, and calculating the finished product rate of the final products.
Through magnetic property test, the obtained ferrite magnet has remanence Br4320Gs, coercive force Hcj4029Oe, maximum magnetic energy product (BH)max4.45MGOe and the yield reaches 85.6%.
Comparative example 3
Compared with the embodiment 7, the difference is that the additive of the invention is not added, but 1.5 wt% of calcium gluconate is added:
(1) taking 3.0 tons of conventional permanent magnetic ferrite pre-sintering material powder, adding corresponding additives, adding 3.3 tons of tap water, then adding the calcium gluconate dispersing agent accounting for 1.5 wt% of the weight of the pre-sintering material powder, stirring uniformly, transferring into a ball mill, performing wet ball milling for 16 hours to obtain ferrite molding slurry, and testing the average particle size to be 0.79 mu m;
(2) adjusting the water content of the slurry obtained in the step, adjusting the solid content of the slurry to about 70 wt%, and then performing magnetic field forming by adopting a special die to obtain a formed blank;
(3) preserving the temperature of the formed blank in the step for 1.0 hour at 320 ℃, then heating to 1200 ℃ in the air atmosphere and preserving the temperature for 1.5 hours to obtain a permanent magnetic ferrite magnet semi-finished product;
(4) and grinding the semi-finished sintered magnet into a standard shape for magnetic performance test, grinding all the semi-finished sintered magnets according to the requirements of a customer drawing to obtain finished magnets, and calculating the finished product rate of the final products.
Through magnetic property test, the obtained ferrite magnet has remanence Br4360Gs, coercive force Hcj4067Oe, maximum magnetic energy product (BH)max4.55MGOe and the yield reaches 48.6%.
The particle size, magnetic properties and yield obtained by combining the above examples 5 to 8 and comparative examples 1 to 3 are shown in Table 1 below.
TABLE 1 magnetic properties and yields of ferrites obtained in examples 5 to 8 and comparative examples 1 to 3
Figure BDA0003301197850000121
From the above results, it is obvious that the dispersant prepared by the invention can properly reduce the average particle size of the molding slurry when used for preparing the permanent magnetic ferrite material, can effectively improve the magnetic performance, and can ensure that the yield is not reduced basically when the dispersant is added in a large amount, thereby having excellent technical effects.
It will be understood by those skilled in the art that the foregoing is only exemplary of the present invention, and is not intended to limit the invention, which is intended to cover any variations, equivalents, or improvements therein, which fall within the spirit and scope of the invention.

Claims (10)

1. The dispersing agent for the permanent magnetic ferrite material is characterized by being prepared by mixing citric acid, ammonia water, sodium hydroxide and water, wherein the mass concentration of the ammonia water is 20-30%, and the mass ratio of the citric acid to the ammonia water is 1: 0.7-1.3: 0.5-1.5, and the pH value of the dispersant is 4-7.
2. The dispersant for a permanent magnetic ferrite material according to claim 1, wherein the mass concentration of said aqueous ammonia is 23 to 27%.
3. The dispersant for a permanent magnetic ferrite material according to claim 1, wherein the mass ratio of the citric acid to the water to the ammonia water is 1: 0.9-1.2: 0.6-1.5.
4. The dispersant for a permanent magnetic ferrite material according to claim 1, wherein the pH value of said dispersant is 5 to 6.
5. A process for the preparation of the dispersant of any of claims 1 to 4, characterized in that said process comprises the steps of:
(1) mixing the citric acid solid with water, and stirring uniformly until the citric acid is completely dissolved;
(2) adding ammonia water into the solution obtained in the step (1);
(3) adding solid sodium hydroxide into the solution obtained in the step (1), uniformly stirring, and adjusting the pH value of the solution to be between 4 and 7 to obtain the liquid dispersing agent.
6. The use of the dispersing agent according to any of claims 1 to 4, wherein the use is to apply the dispersing agent in a permanent ferrite material ball milling process.
7. The application of claim 6, wherein the step of applying the dispersing agent in the ball milling process of the permanent magnetic ferrite material comprises the following steps:
(1) ball milling: adding a corresponding additive into the permanent magnetic ferrite pre-sintered material powder, adding water in an amount which is 1.0 to 1.5 times the mass of the pre-sintered material powder, then adding the dispersing agent, stirring uniformly, and then transferring into a ball mill for wet ball milling to obtain slurry with the average particle size of 0.75 to 0.85 mu m;
(2) a molding procedure: adjusting the solid content of the slurry obtained in the step to 65-75wt%, and then performing magnetic field forming by adopting a mold to obtain a formed blank;
(3) and (3) sintering: firstly, preserving the temperature of the formed blank in the step at 200-300 ℃ to remove the moisture and residual dispersant in the formed blank, then heating to a reasonable sintering temperature in an air atmosphere and preserving the temperature to obtain a permanent ferrite magnet semi-finished product;
(4) and grinding the permanent magnetic ferrite magnet semi-finished product according to requirements to obtain a finished magnet.
8. The use of claim 7, wherein in step (1) a dispersant is added in an amount of 0.5-5% by weight of the pre-sinter powder.
9. The use as claimed in claim 7, wherein the shaped blank in step (3) is incubated at 200 ℃ and 300 ℃ for 0.5-2 h.
10. The use as claimed in claim 7, wherein the sintering temperature in step (3) is 1180-1250 ℃ and the holding time is 0.5-2 h.
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Denomination of invention: A dispersant for permanent magnet ferrite material and its preparation method and application

Effective date of registration: 20230913

Granted publication date: 20220315

Pledgee: Dongyang Branch of China Construction Bank Co.,Ltd.

Pledgor: HENGDIAN GROUP DMEGC MAGNETICS Co.,Ltd.

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