CN119263806A - Preparation method of strontium ferrite and strontium ferrite thereof - Google Patents

Abstract

The invention discloses a preparation method of strontium ferrite and the strontium ferrite, belonging to the technical field of permanent magnet materials, and the technical scheme is characterized in that the preparation method of the strontium ferrite comprises the following preparation steps of S1, mixing 80-88 parts of ferric oxide, 6.5-8.5 parts of strontium carbonate and 0.5-0.9 part of calcium carbonate powder according to parts by weight, S2, carrying out primary wet ball milling on the mixture A to obtain a mixture A slurry, S3, drying the mixture A slurry obtained in the step S2, carrying out presintering, crushing to obtain presintering material powder, S4, mixing 0.8-1.5 parts by weight of cobaltosic oxide, 3-4 parts by weight of lanthanum oxide, 0.2-0.6 parts by weight of silicon dioxide, 2-6 parts by weight of dispersing agent and the material powder, carrying out secondary wet ball milling on the mixture B slurry to obtain a mixture B, drying the mixture B, and then carrying out sintering to obtain the strontium ferrite, wherein the sintering temperature is 1175-1205 ℃, and the magnetic performance of the strontium ferrite is improved after the presintering.

Description

Preparation method of strontium ferrite and strontium ferrite thereof

Technical Field

The invention relates to the technical field of permanent magnetic materials, in particular to a preparation method of strontium ferrite and the strontium ferrite.

Background

The permanent magnetic material is widely applied to the fields of automobiles, computers, information communication, aerospace, electric appliance manufacturing and the like, and in the age of increasingly developed global manufacturing industry, the permanent magnetic ferrite is used as one of the permanent magnetic materials, and has the advantages of abundant raw material sources, simple production conditions, controllable process, strong erosion resistance of products and the like, so that the permanent magnetic material becomes the most widely applied permanent magnetic material at present, and takes up the main place in production and application.

The strontium ferrite is used as permanent magnet, has stable hexagonal magnetoplumbite (M-shaped) structure, higher coercive force, magnetic energy and resistivity, can be used in high-frequency occasions, has low price and wide sources of raw materials, has simple manufacturing process and is suitable for mass production. The existing permanent magnetic strontium ferrite production process comprises pre-sintering material production and magnetic piece production, the pre-sintering is one of the important procedures for producing the permanent magnetic ferrite by an oxide method, plays an important role in the quality of products, the pre-sintering aims at preserving the temperature of the mixture for several hours to enable the mixture particles to generate preliminary solid-phase reaction to generate partial ferrite, the role is mainly reflected in the aspects of reducing the non-uniformity of chemical activity, reducing the shrinkage rate of sintered products, improving the sintering density and easy forming of the products and the like, and a few low-melting sintering auxiliary agents are added in the pre-sintering process to realize the sintering effect at a lower sintering temperature, but the obtained strontium ferrite has poorer magnetic performance and is difficult to meet market demands.

Disclosure of Invention

In order to improve the magnetic performance of the strontium ferrite, the invention provides a preparation method of the strontium ferrite and the strontium ferrite.

The first aspect of the present invention provides a method for preparing strontium ferrite, which adopts the following technical scheme:

a preparation method of strontium ferrite comprises the following preparation steps:

S1, preparing raw materials, namely mixing 80-88 parts of ferric oxide, 6.5-8.5 parts of strontium carbonate and 0.5-0.9 part of calcium carbonate powder according to parts by weight to obtain a mixture A;

s2, performing wet ball milling on the mixture A for the first time to obtain mixture A slurry;

S3, drying the mixture A slurry obtained in the step S2, and crushing the dried mixture A slurry after presintering to obtain presintering powder;

S4, mixing 0.8-1.5 parts by weight of cobaltosic oxide, 3-4 parts by weight of lanthanum oxide, 0.2-0.6 parts by weight of silicon dioxide, 2-6 parts by weight of dispersing agent and presintered material powder, and performing secondary wet ball milling to obtain mixture B slurry;

S5, drying the mixture B slurry, compacting, sintering to obtain the strontium ferrite, wherein the sintering temperature is 1175-1205 ℃, and preserving the heat for 4-6h.

By adopting the technical scheme, the addition of the additives of the calcium carbonate and the silicon dioxide can reduce the sintering temperature, promote the solid phase reaction, improve the residual magnetism of the ferrite, shorten the production period and achieve the aim of saving energy, and can be used as a dispersing agent in the secondary ball milling process to improve the residual magnetism and the orientation degree of the permanent magnetic ferrite during the compression molding, and the dispersing agent is distributed at a grain boundary to control the overgrowth of grains in the sintering process and improve the coercive force of the permanent magnetic ferrite.

Specifically, the calcium carbonate is in a molten state at a lower temperature, so that the liquid phase reaction for promoting the reaction rate can be realized, the density of a magnet is promoted, the production period can be shortened, the sintering cost is reduced, a small amount of calcium ions generated in the calcium carbonate sintering process can replace strontium ions, most of calcium ions can be used as a sintering aid to promote the solid phase reaction to proceed, the densification of ferrite is promoted, the remanence is further improved, and because the radii of the calcium ions and the strontium ions are similar, excessive calcium ions and strontium ions, lanthanum ions and the like in the substituted raw components can form impurities, the magnetic performance is not improved, and excessive calcium ions can cause overgrowth and non-uniformity of crystal grains.

The silica additive has the effects that the silica has a high melting point, the silica reacts with ferric oxide to generate ferric silicate with a low melting point, the sintering temperature is greatly reduced, the purpose of reducing the solid phase reaction temperature is achieved, the density of a magnet is improved, the ferric silicate can inhibit the growth of crystal grains, and therefore a higher coercive force is obtained, but excessive silica is added to reduce the density and remanence of the material.

The lanthanum ion partially replaces strontium in the strontium ferrite, so that the crystal structure can be stabilized, and meanwhile, the magnetic performance of the strontium ferrite is obviously improved, so that the magnetic performance of the ferrite can be effectively improved by matching various additives.

The increase of sintering temperature is favorable for the growth of crystal grains, the grain size is increased along with the densification of the crystal grain growth in the solid-phase sintering process, the residual magnetism of the material is improved, but the coercive force of the material is reduced, in order to simultaneously improve the residual magnetism and the coercive force, the crystal grains are ensured to be uniform and fine while the densification of the crystal grains is ensured, and additives of cobaltosic oxide, lanthanum oxide and silicon dioxide are added as sintering aids in the secondary ball milling process to realize liquid-phase sintering, so that the sintering aids form a liquid phase at high temperature, the sintering reaction process can be promoted, and the crystal grains can be adhered to the surface of the crystal grains to prevent the crystal grains from growing, namely the uniform, fine and densification growth of the crystal grains is realized, so that the coercive force and the residual magnetism of ferrite can be effectively ensured when the sintering temperature is limited within the range of 1175-1205 ℃.

Preferably, the step S4 further includes 0.1 to 0.2 parts by weight of aluminum oxide.

By adopting the technical scheme, the radii of aluminum ions and iron ions are very close, the magnetocrystalline anisotropy field of the magnet is increased by adding the aluminum oxide, and meanwhile, the aluminum oxide is dispersed among crystal boundaries to refine crystal grains, so that the additive can greatly improve the coercive force of the magnet, but the residual magnetism of the magnet can be reduced by adding excessive aluminum oxide.

Preferably, the cobaltosic oxide is 1-1.3 weight parts and the silicon dioxide is 0.35-0.5 weight parts.

Preferably, the suspended particles in the slurry of mixture A have an average particle size of 1.0-1.5 μm.

Preferably, the suspended particles in the slurry of mixture B have an average particle size of 0.65-0.75 μm.

Preferably, in the step S3, the pre-sintering process is performed at a temperature of 1260-1340 ℃ for 1-1.5h.

Through adopting above-mentioned technical scheme, the setting of presintering makes ferrite fully, reduces the deformation degree of final product, and presintering makes the crystal volume reduce simultaneously, can discharge gas in this in-process, does not need to escape gas during the secondary sintering to make the ferrite densification that finally obtains and mechanical strength promoted, and then reduce the deformation degree of product.

Preferably, the temperature rising rate in the step S5 is 2.5-4.5 ℃ per minute.

Preferably, the dispersing agent adopts one or two of isobutene-maleic anhydride copolymer and sorbitol.

Preferably, the weight ratio of the isobutene-maleic anhydride copolymer to the sorbitol is 1 (1-1.5).

By adopting the technical scheme, after the dispersing agent consists of the isobutene-maleic anhydride copolymer and the sorbitol, the dispersion of the magnetic crystal grains is effectively improved, so that the magnetic crystal grains are distributed more uniformly, and the magnetic performance of the ferrite is improved.

The second aspect of the invention provides a strontium ferrite obtained by the preparation method of the strontium ferrite.

In summary, the invention has the following beneficial effects:

1. The addition of the additives of calcium carbonate and silicon dioxide reduces the sintering temperature, promotes the solid phase reaction, and the addition of the cobaltosic oxide and the lanthanum oxide can improve the residual magnetism of ferrite, and the calcium carbonate, the silicon dioxide, the cobaltosic oxide and the lanthanum oxide are used as dispersing agents in the secondary ball milling process, so that the residual magnetism and the orientation degree of the permanent magnetic ferrite can be improved during compression molding, and the permanent magnetic ferrite is distributed at a grain boundary, so that overgrowth of crystal grains in the sintering process is controlled, the coercive force of the permanent magnetic ferrite is improved, and the magnetic property of the strontium ferrite is ensured.

2. The combination of pre-sintering and sintering in the application improves the magnetic property and mechanical strength of the finally obtained ferrite, and the improvement of mechanical strength can effectively reduce the deformation degree of the strontium ferrite product.

Detailed Description

The present invention will be described in further detail with reference to examples.

A preparation method of strontium ferrite comprises the following preparation steps:

S1, preparing raw materials, namely mixing 80-88 parts of ferric oxide, 6.5-8.5 parts of strontium carbonate and 0.5-0.9 part of calcium carbonate powder according to parts by weight to obtain a mixture A;

s2, performing wet ball milling on the mixture A for the first time to obtain mixture A slurry;

S3, drying the mixture A slurry obtained in the step S2, and crushing the dried mixture A slurry after presintering to obtain presintering powder;

S4, mixing 0.8-1.5 parts by weight of cobaltosic oxide, 3-4 parts by weight of lanthanum oxide, 0.2-0.6 parts by weight of silicon dioxide, 2-6 parts by weight of dispersing agent and presintered material powder, and performing secondary wet ball milling to obtain mixture B slurry;

S5, drying the mixture B slurry, compacting, sintering to obtain the strontium ferrite, wherein the sintering temperature is 1175-1205 ℃, and preserving the heat for 4-6h.

Preferably, the step S4 further includes 0.1 to 0.2 parts by weight of aluminum oxide.

Preferably, the cobaltosic oxide is 1-1.3 weight parts and the silicon dioxide is 0.35-0.5 weight parts.

Preferably, the suspended particles in the slurry of mixture A have an average particle size of 1.0-1.5 μm.

Preferably, the suspended particles in the slurry of mixture B have an average particle size of 0.65-0.75 μm.

Preferably, in the step S3, the pre-sintering process is performed at a temperature of 1260-1340 ℃ for 1-1.5h.

Preferably, the temperature rising rate in the step S5 is 2.5-4.5 ℃ per minute.

Preferably, the dispersing agent adopts one or two of isobutene-maleic anhydride copolymer and sorbitol.

Preferably, the weight ratio of the isobutene-maleic anhydride copolymer to the sorbitol is 1 (1-1.5).

Example 1

A preparation method of strontium ferrite comprises the following preparation steps:

S1, preparing raw materials, namely mixing 80kg of ferric oxide, 6.5kg of strontium carbonate and 0.5kg of calcium carbonate powder to obtain a mixture A;

S2, performing primary wet ball milling on the mixture A until the average particle size of suspended particles in the slurry of the mixture A is 1.0 mu m, and stopping ball milling to obtain the slurry of the mixture A;

S3, drying the mixture A slurry obtained in the step S2, and then presintering, wherein the presintering process is to keep the temperature at 1260 ℃ for 1.5 hours and then crush the mixture A slurry to obtain presintering powder;

S4, mixing 0.8kg of cobaltosic oxide, 3kg of lanthanum oxide, 0.2kg of silicon dioxide, 2kg of dispersing agent sorbitol and presintered material powder, performing secondary wet ball milling until the average particle size of suspended particles in the slurry of the mixture B is 0.65 mu m, and stopping wet milling to obtain the slurry of the mixture B;

S5, drying the mixture B slurry, compacting, sintering to obtain strontium ferrite, heating to 1175 ℃ at a rate of 2.5 ℃ per minute, and preserving heat for 6 hours.

Example 2

A preparation method of strontium ferrite comprises the following preparation steps:

S1, preparing raw materials, namely mixing 84kg of ferric oxide, 7.5kg of strontium carbonate and 0.7kg of calcium carbonate powder to obtain a mixture A;

S2, performing primary wet ball milling on the mixture A until the average particle size of suspended particles in the slurry of the mixture A is 1.0 mu m, and stopping ball milling to obtain the slurry of the mixture A;

s3, drying the mixture A slurry obtained in the step S2, and then presintering, wherein the presintering process is to keep the temperature at 1300 ℃ for 1.5 hours and then crush the mixture A slurry to obtain presintering powder;

S4, mixing 0.8kg of cobaltosic oxide, 3kg of lanthanum oxide, 0.2kg of silicon dioxide, 2kg of dispersing agent sorbitol and presintered material powder, performing secondary wet ball milling until the average particle size of suspended particles in the slurry of the mixture B is 0.65 mu m, and stopping wet milling to obtain the slurry of the mixture B;

S5, drying the mixture B slurry, compacting, sintering to obtain strontium ferrite, heating to 1175 ℃ at a rate of 2.5 ℃ per minute, and preserving heat for 6 hours.

Example 3

A preparation method of strontium ferrite comprises the following preparation steps:

S1, preparing raw materials, namely mixing 88kg of ferric oxide, 8.5kg of strontium carbonate and 0.9kg of calcium carbonate powder to obtain a mixture A;

S2, performing primary wet ball milling on the mixture A until the average particle size of suspended particles in the slurry of the mixture A is 1.0 mu m, and stopping ball milling to obtain the slurry of the mixture A;

S3, drying the slurry of the mixture A obtained in the step S2, and then presintering, wherein the presintering process is to keep the temperature at 1340 ℃ for 1h and then crush the slurry to obtain presintering powder;

S4, mixing 0.8kg of cobaltosic oxide, 3kg of lanthanum oxide, 0.2kg of silicon dioxide, 2kg of dispersing agent sorbitol and presintered material powder, performing secondary wet ball milling until the average particle size of suspended particles in the slurry of the mixture B is 0.65 mu m, and stopping wet milling to obtain the slurry of the mixture B;

S5, drying the mixture B slurry, compacting, sintering to obtain strontium ferrite, heating to 1175 ℃ at a rate of 2.5 ℃ per minute, and preserving heat for 6 hours.

Example 4

A preparation method of strontium ferrite comprises the following preparation steps:

S1, preparing raw materials, namely mixing 84kg of ferric oxide, 7.5kg of strontium carbonate and 0.7kg of calcium carbonate powder to obtain a mixture A;

S2, performing primary wet ball milling on the mixture A until the average particle size of suspended particles in the slurry of the mixture A is 1.0 mu m, and stopping ball milling to obtain the slurry of the mixture A;

s3, drying the mixture A slurry obtained in the step S2, and then presintering, wherein the presintering process is to keep the temperature at 1300 ℃ for 1.5 hours and then crush the mixture A slurry to obtain presintering powder;

S4, mixing 1kg of cobaltosic oxide, 3.5kg of lanthanum oxide, 0.35kg of silicon dioxide and 4kg of dispersant isobutene-maleic anhydride copolymer with the presintered powder, performing secondary wet ball milling until the average particle size of suspended particles in the slurry of the mixture B is 0.65 mu m, and stopping wet milling to obtain the slurry of the mixture B;

S5, drying the mixture B slurry, compacting, sintering to obtain strontium ferrite, heating to 1175 ℃ at a rate of 2.5 ℃ per minute, and preserving heat for 6 hours.

Example 5

A preparation method of strontium ferrite comprises the following preparation steps:

S1, preparing raw materials, namely mixing 84kg of ferric oxide, 7.5kg of strontium carbonate and 0.7kg of calcium carbonate powder to obtain a mixture A;

S2, performing primary wet ball milling on the mixture A until the average particle size of suspended particles in the slurry of the mixture A is 1.0 mu m, and stopping ball milling to obtain the slurry of the mixture A;

s3, drying the mixture A slurry obtained in the step S2, and then presintering, wherein the presintering process is to keep the temperature at 1300 ℃ for 1.5 hours and then crush the mixture A slurry to obtain presintering powder;

S4, mixing 1.3kg of cobaltosic oxide, 3.5kg of lanthanum oxide, 0.5kg of silicon dioxide and 5kg of dispersant isobutene-maleic anhydride copolymer with the presintered material powder, performing secondary wet ball milling until the average particle size of suspended particles in the slurry of the mixture B is 0.65 mu m, and stopping wet milling to obtain the slurry of the mixture B;

S5, drying the mixture B slurry, compacting, sintering to obtain strontium ferrite, heating to 1175 ℃ at a rate of 2.5 ℃ per minute, and preserving heat for 6 hours.

Example 6

A preparation method of strontium ferrite comprises the following preparation steps:

S1, preparing raw materials, namely mixing 84kg of ferric oxide, 7.5kg of strontium carbonate and 0.7kg of calcium carbonate powder to obtain a mixture A;

S2, performing primary wet ball milling on the mixture A until the average particle size of suspended particles in the slurry of the mixture A is 1.0 mu m, and stopping ball milling to obtain the slurry of the mixture A;

s3, drying the mixture A slurry obtained in the step S2, and then presintering, wherein the presintering process is to keep the temperature at 1300 ℃ for 1.5 hours and then crush the mixture A slurry to obtain presintering powder;

S4, mixing 1.5kg of cobaltosic oxide, 4kg of lanthanum oxide, 0.6kg of silicon dioxide and 6kg of dispersant isobutene-maleic anhydride copolymer with the presintered powder, performing secondary wet ball milling until the average particle size of suspended particles in the slurry of the mixture B is 0.65 mu m, and stopping wet milling to obtain the slurry of the mixture B;

S5, drying the mixture B slurry, compacting, sintering to obtain strontium ferrite, heating to 1175 ℃ at a rate of 2.5 ℃ per minute, and preserving heat for 6 hours.

Example 7

A preparation method of strontium ferrite is different from example 5 in that 0.1kg of aluminum oxide is further added in step S4, and all the other components are the same as in example 5.

Example 8

A preparation method of strontium ferrite is different from example 5 in that 0.2kg of aluminum oxide is further added in step S4, and all the other components are the same as in example 5.

Example 9

A preparation method of strontium ferrite is different from example 8 in that in the wet ball milling of step S2, ball milling is stopped until the average particle diameter of suspended particles in the mixture A slurry is 1.3 μm to obtain the mixture A slurry, and the other steps are the same as example 8.

Example 10

A preparation method of strontium ferrite is different from example 8 in that in the wet ball milling of step S2, ball milling is stopped until the average particle diameter of suspended particles in the mixture A slurry is 1.5 μm to obtain the mixture A slurry, and the other steps are the same as example 8.

Example 11

A preparation method of strontium ferrite is different from that of the embodiment 8 in that in the wet ball milling of the step S2, the ball milling is stopped until the average particle size of suspended particles in the slurry of the mixture A is 1.3 mu m, the slurry of the mixture A is obtained, and in the step S4, the wet ball milling is stopped until the average particle size of suspended particles in the slurry of the mixture B is 0.70 mu m, and the wet ball milling is stopped, so that the slurry of the mixture B is obtained, and the other steps are the same as the embodiment 8.

Comparative example 11

A preparation method of strontium ferrite is different from example 11 in that in step S4, wet milling is performed twice until the average particle diameter of suspended particles in slurry of mixture B is 0.60 μm, and then wet milling is stopped to obtain slurry of mixture B, and all the other steps are the same as example 11.

Example 12

A preparation method of strontium ferrite is different from that of the embodiment 8 in that in the wet ball milling of the step S2, the ball milling is stopped until the average particle size of suspended particles in the slurry of the mixture A is 1.3 mu m, the slurry of the mixture A is obtained, and in the step S4, the wet ball milling is stopped until the average particle size of suspended particles in the slurry of the mixture B is 0.75 mu m, and the wet ball milling is stopped, so that the slurry of the mixture B is obtained, and the other steps are the same as the embodiment 8.

Comparative example 12

A preparation method of strontium ferrite is different from example 12 in that in step S4, secondary wet ball milling is performed until the average particle size of suspended particles in the slurry of the mixture B is 0.80 μm, and then wet milling is stopped to obtain the slurry of the mixture B, and all the other steps are the same as in example 12.

Example 13

A preparation method of strontium ferrite is different from example 11 in that the presintering process is that after heat preservation is carried out for 1h at 680 ℃, the temperature is then increased to 950 ℃, and after heat preservation is carried out for 1.5h, presintering material powder is obtained by crushing, and the other materials are all the same as example 11.

Example 14

A method for preparing strontium ferrite is different from example 11 in that the temperature rising rate in step S5 is different, specifically, the temperature rises to 1175 ℃ at a rate of 4.5 ℃ per minute, and the temperature is kept for 6 hours.

Example 15

A method for preparing strontium ferrite is different from example 11 in that the temperature rising rate in step S5 is different, specifically, the temperature rises to 1175 ℃ at a rate of 5.5 ℃ per minute, and the temperature is kept for 6 hours.

Example 16

A method for preparing strontium ferrite, which is different from example 11 in that the sintering temperature is 1205 ℃ and the sintering time is 4 hours.

Example 17

A method for preparing strontium ferrite, which is different from example 11 in that the sintering temperature is 1220 ℃ and the sintering time is 4 hours.

Example 18

A preparation method of strontium ferrite is different from example 11 in that the dispersant comprises isobutylene-maleic anhydride copolymer and sorbitol in a weight ratio of 1:1 in the case that the total amount of the dispersant is 5 kg.

Example 19

A preparation method of strontium ferrite is different from example 11 in that the dispersant comprises isobutylene-maleic anhydride copolymer and sorbitol in a weight ratio of 1:1.5 in the case that the total amount of the dispersant is 5 kg.

Example 20

A preparation method of strontium ferrite is different from example 18 in that the dispersant comprises isobutylene-maleic anhydride copolymer and calcium gluconate in a weight ratio of 1:1 with a total amount of dispersant of 5 kg.

Comparative example 1

The preparation method of strontium ferrite is different from example 5 in that no presintering process is adopted, and specifically comprises the following steps:

S1, preparing raw materials, namely mixing 84kg of ferric oxide, 7.5kg of strontium carbonate, 0.7kg of calcium carbonate powder, 1.3kg of cobaltosic oxide, 3.5kg of lanthanum oxide, 0.5kg of silicon dioxide and 5kg of dispersant isobutene-maleic anhydride copolymer to obtain a mixture;

S2, performing wet ball milling on the mixture until the average particle size of suspended particles in the mixture slurry is 0.65 mu m, and stopping wet milling to obtain the mixture slurry;

s3, drying the mixed slurry, compacting, sintering to obtain strontium ferrite, heating to 1175 ℃ at the speed of 2.5 ℃ per minute, and preserving heat for 6 hours.

Comparative example 2

The preparation method of strontium ferrite is different from that of example 5 in that no tricobalt tetraoxide is used in step S4, and the other steps are the same as those of example 5.

Comparative example 3

The preparation method of strontium ferrite is different from example 5 in that no silica is present in step S4, and the other components are the same as in example 5.

Comparative example 4

The preparation method of strontium ferrite is different from example 5 in that lanthanum oxide is not present in step S4, and the other steps are the same as in example 5.

Comparative example 5

A method for preparing strontium ferrite was different from example 5 in that the content of calcium carbonate powder in step S1 was 1.1kg, and the other was the same as in example 5.

Comparative example 6

The difference between the preparation method of strontium ferrite and the embodiment 5 is that in the step S4, the content of cobaltosic oxide is 1.8kg, the content of lanthanum oxide is 4.3kg, the content of silicon dioxide powder is 0.8kg, and the other steps are the same as the embodiment 5.

Comparative example 7

The difference between the preparation method of strontium ferrite and the embodiment 5 is that in the step S4, the content of cobaltosic oxide is 0.6kg, the content of lanthanum oxide is 2.5kg, the content of silicon dioxide powder is 0.1kg, and the other steps are the same as the embodiment 5.

Performance detection

The strontium ferrite obtained in the above examples and comparative examples was subjected to residual magnetism (Br), intrinsic coercive force (Hcj), magnetic energy product (BH) and density detection, and the detection results are shown in table 1.

TABLE 1 magnetic properties test results table of strontium ferrite

As can be seen from the table above:

The strontium ferrite obtained in the embodiment 1-3 of the application has the residual magnetism larger than or equal to 4426Gs, the intrinsic coercivity higher than 4690Oe and the magnetic energy product higher than 4.6MGOe, and thus the strontium ferrite obtained in the embodiment 1-3 of the application has good magnetic performance.

Examples 4-6 in comparison with example 2, when the contents of the iron oxide, the strontium carbonate, and the calcium carbonate were unchanged, the residual magnetism, the intrinsic coercive force, and the magnetic energy product of the strontium ferrite obtained in examples 4-6 were higher than those in example 2 with the increase of the contents of the cobalt oxide, the lanthanum oxide, the silicon dioxide, and the calcium carbonate, and it was found that the magnetic properties of the strontium ferrite were further improved with the increase of the contents of the cobalt oxide, the lanthanum oxide, the silicon dioxide, and the silicon dioxide, but the magnetic properties of the strontium ferrite were not further improved when the contents of the cobalt oxide, the lanthanum oxide, the silicon dioxide, and the silicon dioxide were up to the limit of the contents in example 6, and it was found that the contents of the cobalt oxide, the lanthanum oxide, the silicon dioxide, and the silicon dioxide were within the ranges defined in the present application, and the magnetic properties of the strontium ferrite were effectively ensured.

Compared with the embodiment 5, the embodiment 7-8 further improves the residual magnetism, intrinsic coercive force and magnetic energy product of the strontium ferrite by adding the aluminum oxide, and can effectively improve the magnetic performance of the strontium ferrite by matching the aluminum oxide with the cobaltosic oxide, the lanthanum oxide and the silicon dioxide.

Examples 9-12 the average particle size of the suspended particles in the mixture a slurry and the average particle size of the suspended particles in the mixture B slurry also have a certain effect on the magnetic properties of the strontium ferrite, in particular the average particle size of the suspended particles in the mixture B slurry, compared with example 8, and it can be seen from comparative examples 11 and 12 that when the average particle size of the suspended particles in the mixture B slurry is lower or higher than the average particle size defined in the present application, the magnetic properties of the strontium ferrite of comparative examples 11 and 12 are lowered, and it can be seen that the particle size of the suspended particles in the mixture B slurry has a significant effect on the magnetic properties of the strontium ferrite.

Examples 14 to 15 are provided to ensure the magnetic properties of strontium ferrite when the temperature rising rate at sintering is in the range of 4.5C/min as compared with example 11, but when the temperature rising rate exceeds 4.5C/min, it can be seen from example 15 that the magnetic properties of strontium ferrite are reduced as compared with example 14.

In example 16, the magnetic properties of the strontium ferrite obtained in example 16 were increased as compared with example 11 with an increase in the sintering temperature, but the magnetic properties of the strontium ferrite obtained in example 17 were rather decreased when the sintering temperature exceeded 1205 ℃, and it was found that the magnetic properties of the strontium ferrite were effectively improved when the sintering temperature was limited to 1175 to 1205 ℃.

Examples 18-19 when the dispersant is a mixture of isobutylene-maleic anhydride copolymer and sorbitol as compared to example 11, the magnetic properties of the strontium ferrite obtained in examples 18-19 are improved as compared to example 11, and it can be seen that the use of the two dispersants in combination results in a more uniform dispersion of the magnetic particles and a more uniform particle size distribution after grinding, thereby contributing to an improvement in the magnetic properties of the strontium ferrite.

In example 20, compared with example 18, the magnetic properties of the strontium ferrite obtained in example 20 were reduced compared with example 18, and it was found that the magnetic properties of the strontium ferrite could be effectively ensured by the combination of the isobutylene-maleic anhydride copolymer and sorbitol.

Compared with the embodiment 5, the magnetic performance of the strontium ferrite obtained in the embodiment 1 is obviously reduced compared with the embodiment after grinding each raw material once after no sintering process, and the pre-sintering arrangement in the application can effectively improve the magnetic performance of the strontium ferrite.

Comparative examples 2-4 the magnetic properties of the strontium ferrite obtained in comparative examples 2-4 were all reduced when the tricobalt tetraoxide or silica or lanthanum oxide was absent in step S4 compared with example 5, and it was seen that the addition of these three additives effectively improved the magnetic properties of the strontium ferrite.

Comparative examples 5 to 7 when the content of calcium carbonate or the content of tricobalt tetraoxide, silica, lanthanum oxide is not within the range defined by the present application as compared with example 5, the magnetic properties of the strontium ferrite obtained in comparative examples 5 to 7 are reduced as compared with example 5, and it is seen that the content of calcium carbonate, tricobalt tetraoxide, silica, lanthanum oxide has a direct influence on the magnetic properties of the strontium ferrite.

The embodiments of the present invention are all preferred embodiments of the present invention, and are not limited in scope by the present invention, so that all equivalent changes according to the structure, shape and principle of the present invention are covered by the scope of the present invention.

Claims (10)

1. A method for preparing strontium ferrite, characterized in that it comprises the following preparation steps: S1. Raw material preparation: by weight, 80-88 parts of ferric oxide, 6.5-8.5 parts of strontium carbonate, and 0.5-0.9 parts of calcium carbonate powder are mixed to obtain a mixture A; S2, wet ball milling the mixture A to obtain a mixture A slurry; S3, drying the mixture A slurry obtained in step S2, pre-sintering it, and then crushing it to obtain pre-sintered powder; S4, 0.8-1.5 parts by weight of cobalt trioxide, 3-4 parts by weight of lanthanum oxide, 0.2-0.6 parts by weight of silicon dioxide, 2-6 parts by weight of a dispersant and the pre-sintered powder are mixed and then subjected to secondary wet ball milling to obtain a mixture B slurry; S5. Dry the mixture B slurry, press it into green compacts, and then sinter it to obtain strontium ferrite. The sintering temperature is 1175-1205° C. and the temperature is kept for 4-6 hours. 2. The method for preparing strontium ferrite according to claim 1, characterized in that: the step S4 further comprises 0.1-0.2 parts by weight of aluminum oxide. 3. The method for preparing strontium ferrite according to claim 1, characterized in that the cobalt tetroxide contains 1-1.3 parts by weight and the silicon dioxide contains 0.35-0.5 parts by weight. 4. The method for preparing strontium ferrite according to claim 1, characterized in that the average particle size of the suspended particles in the mixture A slurry is 1.0-1.5 μm. 5. The method for preparing strontium ferrite according to claim 1, characterized in that the average particle size of the suspended particles in the mixture B slurry is 0.65-0.75 μm. 6. The method for preparing strontium ferrite according to claim 1, characterized in that: in the step S3, the pre-sintering process is carried out at a temperature of 1260-1340°C for 1-1.5 hours. 7. The method for preparing strontium ferrite according to claim 1, characterized in that the heating rate in step S5 is 2.5-4.5°C/min. 8. The method for preparing strontium ferrite according to claim 1, characterized in that the dispersant is one or both of isobutylene-maleic anhydride copolymer and sorbitol. 9 . The method for preparing strontium ferrite according to claim 8 , wherein the weight ratio of the isobutylene-maleic anhydride copolymer to sorbitol is 1:(1-1.5). 10. Strontium ferrite obtained by the method for preparing strontium ferrite according to any one of claims 1 to 9.