Modified samarium-iron-nitrogen powder as well as preparation method and application thereof

Abstract

The invention relates to modified samarium-iron-nitrogen powder and a preparation method and application thereof, and belongs to the technical field of magnetic material preparation, the preparation method comprises the following steps: 1, mixing soluble samarium salt, iron oxide and ammonia water, and reacting to obtain a mixed solution; 2, mixing the mixed solution with an alkali metal hydroxide solution, and reacting to obtain a precursor; 3, the precursor reacts in the ammonia atmosphere, and samarium-iron-nitrogen powder is obtained; 4, a coating layer is arranged on the surface of the samarium-iron-nitrogen powder, and the modified samarium-iron-nitrogen powder is obtained. The preparation method is simple and convenient, and the prepared modified samarium-iron-nitrogen powder is high in purity, moderate in alpha-Fe content and excellent in intrinsic coercive force and can be used for manufacturing high-performance samarium-iron-nitrogen magnetic powder.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic material preparation, and in particular to a modified samarium iron nitrogen powder and a preparation method and application thereof. Background Art

[0002] Since its introduction, SmFeN permanent magnet materials have attracted people's attention for their excellent magnetic properties and good temperature stability. It is a permanent magnet material that may surpass NdFeB in performance. In terms of physical and chemical properties, SmFeN has high corrosion resistance, oxidation resistance, high temperature resistance and other characteristics. It has important use value and broad market prospects in various extreme environmental conditions, especially in the automotive industry, consumer electronics, aerospace and other fields. In terms of price, samarium and iron raw materials are abundant and cheap, and have a good raw material cost advantage compared to neodymium iron boron. Therefore, samarium iron nitrogen has a wide range of applications in magnetic materials, electronic materials and other fields.

[0003] However, currently, the SmFeN powder obtained in the preparation method of samarium iron nitrogen has a high α-Fe content, which affects the intrinsic coercivity. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect of poor intrinsic coercivity of the samarium iron nitrogen material prepared in the prior art, thereby providing a modified samarium iron nitrogen powder and a preparation method and application thereof.

[0005] To this end, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a modified samarium iron nitrogen powder, comprising the following preparation steps:

[0007] Step 1: mixing a soluble samarium salt, iron oxide and ammonia water, reacting to obtain a mixed solution;

[0008] Step 2: mixing the mixed solution and an alkali metal hydroxide solution, reacting to obtain a precursor;

[0009] Step 3: reacting the precursor in an ammonia atmosphere to obtain samarium iron nitrogen powder;

[0010] Step 4: Arrange a coating layer on the surface of the samarium iron nitrogen powder to obtain the modified samarium iron nitrogen powder.

[0011] In an alternative embodiment, the soluble samarium salt comprises samarium chloride and the iron oxide comprises iron oxide.

[0012] In an optional embodiment, the particle size of the samarium chloride is 80-130 μm, and the particle size of the iron oxide is 30-80 μm.

[0013] In an optional embodiment, the mass ratio of the soluble samarium salt to the iron oxide is (1.35-1.6):1, preferably (1.5-1.6):1, and more preferably 1.6:1.

[0014] In an optional implementation manner, the mass concentration of the ammonia water is 22-28%.

[0015] In an optional embodiment, the reaction temperature is 200-400° C., the pressure is 1-5 MPa, and the time is 1-5 h.

[0016] After the soluble samarium salt, iron oxide and ammonia water are mixed, the iron oxide (iron oxide) acts as a carrier, and the soluble samarium salt (samarium chloride) and ammonia water undergo a chemical precipitation reaction to generate samarium hydroxide; during the reaction, the samarium hydroxide is heated to become samarium oxide, which is adsorbed on the surface of the carrier iron oxide and diffuses into the gaps in the iron oxide.

[0017] In an optional embodiment, the alkali metal hydroxide solution includes sodium hydroxide solution and / or potassium hydroxide solution.

[0018] In an optional embodiment, the concentration of the alkali metal hydroxide solution is 0.5-1.5 mol / L.

[0019] In an optional embodiment, the mass ratio of the mixed solution to the alkali metal hydroxide solution is 1:(1-3), preferably 1:2.

[0020] In an optional embodiment, the reaction temperature is 250-350° C., the pressure is 2-4 MPa, and the reaction time is 4-6 hours.

[0021] The mixed liquid is mixed with an alkali metal hydroxide solution. On the one hand, the alkali metal hydroxide can adjust the pH value. On the other hand, the addition of the alkali metal hydroxide can inhibit the occurrence of the reverse reaction to a certain extent, thereby ensuring the full progress of the reaction.

[0022] In an optional embodiment, after the reaction in step 2 is completed, the solid is filtered, and the filtered solid is washed with an alkali metal hydroxide solution with a concentration of 0.5 to 1.5 mol / L, and then dried to obtain a precursor.

[0023] In an optional embodiment, the number of washings is ≥ 2 times.

[0024] In an optional embodiment, step 3 includes: crushing the precursor to obtain particles, and grinding the particles by air flow to obtain precursor powder; reacting the precursor powder in an ammonia atmosphere to obtain samarium iron nitrogen powder.

[0025] In an optional embodiment, the particle size of the particles is 1 to 5 mm.

[0026] Preferably, the medium of the jet mill is ammonia gas, and the rotation speed is 100-600 r / min.

[0027] Preferably, the purity of the ammonia is ≥99.9%.

[0028] Preferably, the D50 of the precursor powder is 8 to 12 μm.

[0029] Furthermore, the precursor powder is reacted at 530-540° C. for 12-24 hours in an ammonia atmosphere to obtain samarium iron nitrogen powder.

[0030] The reaction process includes: placing the precursor powder in a nitriding furnace, performing a nitriding reaction in an ammonia atmosphere, reducing and diffusing the precursor powder with ammonia, reducing Sm2O3 to Sm, and reducing Fe2O3 to Fe, and then Sm and Fe atoms diffuse with each other to form Sm2Fe 17 The intermediate alloy is then decomposed into N atoms by thermal decomposition of ammonia into Sm2Fe 17 The intermediate alloy is cooled in the furnace to obtain samarium iron nitrogen powder.

[0031] In an optional embodiment, step 4 comprises: mixing the samarium iron nitrogen powder and the coating agent, and ball milling to obtain the modified samarium iron nitrogen powder.

[0032] The present invention adds a coating agent during the ball milling process to form a dense protective film, which reduces the activity of the material surface, thereby ensuring not only the performance of the material itself but also the safety of the ball milling process.

[0033] Preferably, the capping agent comprises phosphate and a conductive polymer.

[0034] Preferably, the phosphate accounts for 1% to 5% of the mass of the samarium iron nitrogen powder.

[0035] Preferably, the conductive polymer accounts for 1% to 5% of the mass of the samarium iron nitrogen powder.

[0036] In an optional embodiment, the phosphate includes sodium polymetaphosphate, and the conductive polymer includes polypyrrole.

[0037] In an optional embodiment, the medium for ball milling in step 4 is aqueous ammonia.

[0038] The present invention uses ammonia water as a medium in the ball milling process, which can prevent the oxidation of the powder. At the same time, the nitrogen element brought in by the ammonia water can ensure more complete nitridation of the powder.

[0039] Preferably, the mass concentration of the ammonia water is 22% to 28%.

[0040] Preferably, the ball milling frequency in step 4 is 0.5 to 7 Hz, preferably 0.5 to 4 Hz, and the time is 1 to 25 h, preferably 1 to 12 h.

[0041] Preferably, the mass ratio of balls to materials in the ball milling in step 4 is 8000:(100-2000), preferably 8000:(500-1000).

[0042] In an optional embodiment, solid-liquid separation and drying are sequentially performed after ball milling to obtain modified samarium iron nitrogen powder; preferably, the drying temperature is 70-80°C.

[0043] In a second aspect, the present invention provides modified samarium iron nitrogen powder obtained by the preparation method of the modified samarium iron nitrogen powder.

[0044] In the modified samarium iron nitrogen powder, the purity of samarium iron nitrogen obtained by fluorescence and SEM testing and analysis is ≥99%.

[0045] In a third aspect, the present invention provides the use of the modified samarium iron nitrogen powder in magnetic materials or electronic materials.

[0046] The technical solution of the present invention has the following advantages:

[0047] 1. The present invention provides a method for preparing a modified samarium iron nitrogen powder, comprising the following preparation steps: step 1: mixing a soluble samarium salt, iron oxide and ammonia water, reacting to obtain a mixed solution; step 2: mixing the mixed solution and an alkali metal hydroxide solution, reacting to obtain a precursor; step 3: reacting the precursor under an ammonia atmosphere to obtain a samarium iron nitrogen powder; step 4: providing a coating layer on the surface of the samarium iron nitrogen powder to obtain the modified samarium iron nitrogen powder. The present invention first adopts a chemical precipitation method to convert soluble samarium salt into a precipitate, and then uses ammonia water to reduce the precipitate part to provide small crystal nuclei, so that the intermediate product in the mixed solution is tightly combined; then an alkali metal hydroxide solution is added. On the one hand, the alkali metal hydroxide solution can play a role in adjusting pH, and on the other hand, the alkali metal hydroxide inhibits the occurrence of the reverse reaction to a certain extent, thereby ensuring the full progress of the reaction; then the precursor is reacted under ammonia, so that the precursor powder and ammonia are reduced and diffused to obtain samarium iron nitrogen powder; finally, the samarium iron nitrogen powder is mixed with a coating agent for ball milling, and the coating agent forms a dense protective film, which reduces the activity of the material surface, not only ensuring the performance of the material itself, but also ensuring the safety of the ball milling process. The preparation method of the present invention is simple, and the obtained modified samarium iron nitrogen powder has high purity, moderate α-Fe content, and excellent intrinsic coercivity, and can be used for the manufacture of high-performance samarium iron nitrogen magnetic powder.

[0048] 2. The present invention uses ammonia water as a medium in the ball milling process, which can prevent the oxidation of the powder. At the same time, the nitrogen element brought in by the ammonia water can ensure more complete nitridation of the powder. DETAILED DESCRIPTION

[0049] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0050] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0051] Example 1

[0052] This embodiment provides a method for preparing modified samarium iron nitrogen powder, comprising the following preparation steps:

[0053] Step 1. Mix 300 g of samarium chloride with a particle size of 100 μm and 187.5 g of iron oxide with a particle size of 50 μm, add ammonia water with a mass concentration of 25%, so that the ammonia water exceeds the surface of the mixture by 3 cm, and react for 3 hours at a temperature of 400° C. and a pressure of 3.5 MPa to obtain a mixed solution;

[0054] Step 2. The mixed solution and a sodium hydroxide solution with a concentration of 1 mol / L are mixed in a mass ratio of 1:2, and reacted at a temperature of 300° C. and a pressure of 3 MPa for 5 hours. After the reaction is completed, the solid is filtered, and the filtered solid is rinsed 3 times with a sodium hydroxide solution with a concentration of 1 mol / L, and then dried to obtain a precursor;

[0055] Step 3. The precursor is crushed by a crusher to obtain particles (particle size is 1 to 5 mm), and the obtained particles are subjected to air flow milling, the medium of the air flow mill is ammonia with a purity of 99.9%, and the rotation speed is 200r / min to obtain a precursor powder with a D50 of 10μm; the precursor powder is placed in a nitriding furnace, heated to 540°C in an ammonia atmosphere, and the nitriding reaction is carried out for 12 hours. After cooling with the furnace, samarium iron nitrogen powder is obtained;

[0056] Step 4. Take 100g of the samarium iron nitrogen powder prepared above, pour it into a ball mill equipped with 8kg steel balls, pour in an appropriate amount of ammonia water with a mass concentration of 25%, so that the ammonia water level is 2cm higher than the steel balls, then add 1g of polypyrrole and 1g of sodium polymetaphosphate, ball mill at a frequency of 4Hz for 12h, filter after ball milling, place the filtered slurry in a vacuum drying oven, and dry it at 75°C to obtain modified samarium iron nitrogen powder.

[0057] Example 2

[0058] This embodiment provides a method for preparing modified samarium iron nitrogen powder, comprising the following preparation steps:

[0059] Step 1. Mix 300 g of samarium chloride with a particle size of 100 μm and 200 g of iron oxide with a particle size of 50 μm, add ammonia water with a mass concentration of 25%, so that the ammonia water exceeds the surface of the mixture by 3 cm, and react for 3 hours at a temperature of 400° C. and a pressure of 3.5 MPa to obtain a mixed solution;

[0060] Step 2. The mixed solution and a sodium hydroxide solution with a concentration of 1 mol / L are mixed in a mass ratio of 1:2, and reacted at a temperature of 300° C. and a pressure of 3 MPa for 5 hours. After the reaction is completed, the solid is filtered, and the filtered solid is rinsed 3 times with a sodium hydroxide solution with a concentration of 1 mol / L, and then dried to obtain a precursor;

[0061] Step 3. The precursor is crushed by a crusher to obtain particles (particle size is 1 to 5 mm), and the obtained particles are subjected to air flow milling, the medium of the air flow mill is ammonia with a purity of 99.9%, and the rotation speed is 200r / min to obtain a precursor powder with a D50 of 10μm; the precursor powder is placed in a nitriding furnace, heated to 540°C in an ammonia atmosphere, and the nitriding reaction is carried out for 12 hours. After cooling with the furnace, samarium iron nitrogen powder is obtained;

[0062] Step 4. Take 100g of the samarium iron nitrogen powder prepared above, pour it into a ball mill equipped with 8kg steel balls, pour in an appropriate amount of ammonia water with a mass concentration of 25%, so that the ammonia water level is 2cm higher than the steel balls, then add 1g of polypyrrole and 1g of sodium polymetaphosphate, ball mill at a frequency of 4Hz for 12h, filter after ball milling, place the filtered slurry in a vacuum drying oven, and dry it at 75°C to obtain modified samarium iron nitrogen powder.

[0063] Example 3

[0064] This embodiment provides a method for preparing modified samarium iron nitrogen powder, comprising the following preparation steps:

[0065] Step 1. Mix 300 g of samarium chloride with a particle size of 100 μm and 215 g of iron oxide with a particle size of 50 μm, add ammonia water with a mass concentration of 25%, so that the ammonia water exceeds the surface of the mixture by 3 cm, and react for 3 hours at a temperature of 400° C. and a pressure of 3.5 MPa to obtain a mixed solution;

[0066] Step 2. The mixed solution and a sodium hydroxide solution with a concentration of 1 mol / L are mixed in a mass ratio of 1:2, and reacted at a temperature of 300° C. and a pressure of 3 MPa for 5 hours. After the reaction is completed, the solid is filtered, and the filtered solid is rinsed 3 times with a sodium hydroxide solution with a concentration of 1 mol / L, and then dried to obtain a precursor;

[0067] Step 3. The precursor is crushed by a crusher to obtain particles (particle size is 1 to 5 mm), and the obtained particles are subjected to jet milling, the medium of the jet mill is ammonia with a purity of 99.9%, and the rotation speed is 200r / min to obtain a precursor powder with a D50 of 10μm; the precursor powder is placed in a nitriding furnace, heated to 540°C in an ammonia atmosphere, and the nitriding reaction is carried out for 12 hours. After cooling with the furnace, samarium iron nitrogen powder is obtained;

[0068] Step 4. Take 100g of the samarium iron nitrogen powder prepared above, pour it into a ball mill equipped with 8kg steel balls, pour in an appropriate amount of ammonia water with a mass concentration of 25%, so that the ammonia water level is 2cm higher than the steel balls, then add 1g of polypyrrole and 1g of sodium polymetaphosphate, ball mill at a frequency of 4Hz for 12h, filter after ball milling, place the filtered slurry in a vacuum drying oven, and dry it at 75°C to obtain modified samarium iron nitrogen powder.

[0069] Example 4

[0070] This embodiment provides a method for preparing modified samarium iron nitrogen powder, comprising the following preparation steps:

[0071] Step 1. Mix 300 g of samarium chloride with a particle size of 100 μm and 187.5 g of iron oxide with a particle size of 50 μm, add ammonia water with a mass concentration of 25%, so that the ammonia water exceeds the surface of the mixture by 3 cm, and react for 3 hours at a temperature of 400° C. and a pressure of 3.5 MPa to obtain a mixed solution;

[0072] Step 2. The mixed solution and a sodium hydroxide solution with a concentration of 1 mol / L are mixed in a mass ratio of 1:2, and reacted at a temperature of 300° C. and a pressure of 3 MPa for 5 hours. After the reaction is completed, the solid is filtered, and the filtered solid is rinsed 3 times with a sodium hydroxide solution with a concentration of 1 mol / L, and then dried to obtain a precursor;

[0073] Step 3. The precursor is crushed by a crusher to obtain particles (particle size is 1 to 5 mm), and the obtained particles are subjected to jet milling, the medium of the jet mill is ammonia with a purity of 99.9%, and the rotation speed is 80 r / min to obtain a precursor powder with a D50 of 12.5 μm; the precursor powder is placed in a nitriding furnace, heated to 540° C. in an ammonia atmosphere, and the nitriding reaction is carried out for 12 hours. After cooling with the furnace, samarium iron nitrogen powder is obtained;

[0074] Step 4. Take 100g of the samarium iron nitrogen powder prepared above, pour it into a ball mill equipped with 8kg steel balls, pour in an appropriate amount of ammonia water with a mass concentration of 25%, so that the ammonia water level is 2cm higher than the steel balls, then add 1g of polypyrrole and 1g of sodium polymetaphosphate, ball mill at a frequency of 4Hz for 12h, filter after ball milling, place the filtered slurry in a vacuum drying oven, and dry it at 75°C to obtain modified samarium iron nitrogen powder.

[0075] Example 5

[0076] This embodiment provides a method for preparing modified samarium iron nitrogen powder, comprising the following preparation steps:

[0077] Step 1. Mix 300 g of samarium chloride with a particle size of 100 μm and 187.5 g of iron oxide with a particle size of 50 μm, add ammonia water with a mass concentration of 25%, so that the ammonia water exceeds the surface of the mixture by 3 cm, and react for 3 hours at a temperature of 400° C. and a pressure of 3.5 MPa to obtain a mixed solution;

[0078] Step 2. The mixed solution and a sodium hydroxide solution with a concentration of 1 mol / L are mixed in a mass ratio of 1:2, and reacted at a temperature of 300° C. and a pressure of 3 MPa for 5 hours. After the reaction is completed, the solid is filtered, and the filtered solid is rinsed 3 times with a sodium hydroxide solution with a concentration of 1 mol / L, and then dried to obtain a precursor;

[0079] Step 3. The precursor is crushed by a crusher to obtain particles (particle size is 1 to 5 mm), and the obtained particles are subjected to jet milling, the medium of the jet mill is ammonia with a purity of 99.9%, and the rotation speed is 600r / min, to obtain a precursor powder with a D50 of 8.1μm; the precursor powder is placed in a nitriding furnace, heated to 540°C in an ammonia atmosphere, and the nitriding reaction is carried out for 12 hours. After cooling with the furnace, samarium iron nitrogen powder is obtained;

[0080] Step 4. Take 100g of the samarium iron nitrogen powder prepared above, pour it into a ball mill equipped with 8kg steel balls, pour in an appropriate amount of ammonia water with a mass concentration of 25%, so that the ammonia water level is 2cm higher than the steel balls, then add 1g of polypyrrole and 1g of sodium polymetaphosphate, ball mill at a frequency of 4Hz for 12h, filter after ball milling, place the filtered slurry in a vacuum drying oven, and dry it at 75°C to obtain modified samarium iron nitrogen powder.

[0081] Example 6

[0082] This embodiment provides a method for preparing modified samarium iron nitrogen powder, comprising the following preparation steps:

[0083] Step 1. Mix 300 g of samarium chloride with a particle size of 100 μm and 187.5 g of iron oxide with a particle size of 50 μm, add ammonia water with a mass concentration of 25%, so that the ammonia water exceeds the surface of the mixture by 3 cm, and react for 3 hours at a temperature of 400° C. and a pressure of 3.5 MPa to obtain a mixed solution;

[0084] Step 2. The mixed solution and a sodium hydroxide solution with a concentration of 1 mol / L are mixed in a mass ratio of 1:2, and reacted at a temperature of 300° C. and a pressure of 3 MPa for 5 hours. After the reaction is completed, the solid is filtered, and the filtered solid is rinsed 3 times with a sodium hydroxide solution with a concentration of 1 mol / L, and then dried to obtain a precursor;

[0085] Step 3. The precursor is crushed by a crusher to obtain particles (particle size is 1 to 5 mm), and the obtained particles are subjected to jet milling, the medium of the jet mill is ammonia with a purity of 99.9%, and the rotation speed is 200r / min to obtain a precursor powder with a D50 of 10μm; the precursor powder is placed in a nitriding furnace, heated to 540°C in an ammonia atmosphere, and the nitriding reaction is carried out for 12 hours. After cooling with the furnace, samarium iron nitrogen powder is obtained;

[0086] Step 4. Take 100g of the samarium iron nitrogen powder prepared above, pour it into a ball mill equipped with 8kg steel balls, pour in an appropriate amount of ammonia water with a mass concentration of 25%, so that the ammonia water level is 2cm higher than the steel balls, then add 1g of polypyrrole and 1g of sodium polymetaphosphate, ball mill at a frequency of 0.5Hz for 12h, filter after ball milling, place the filtered slurry in a vacuum drying oven, and dry it at 75°C to obtain modified samarium iron nitrogen powder.

[0087] Example 7

[0088] This embodiment provides a method for preparing modified samarium iron nitrogen powder, comprising the following preparation steps:

[0089] Step 1. Mix 300 g of samarium chloride with a particle size of 100 μm and 187.5 g of iron oxide with a particle size of 50 μm, add ammonia water with a mass concentration of 25%, so that the ammonia water exceeds the surface of the mixture by 3 cm, and react for 3 hours at a temperature of 400° C. and a pressure of 3.5 MPa to obtain a mixed solution;

[0090] Step 2. The mixed solution and a sodium hydroxide solution with a concentration of 1 mol / L are mixed in a mass ratio of 1:2, and reacted at a temperature of 300° C. and a pressure of 3 MPa for 5 hours. After the reaction is completed, the solid is filtered, and the filtered solid is rinsed 3 times with a sodium hydroxide solution with a concentration of 1 mol / L, and then dried to obtain a precursor;

[0091] Step 3. The precursor is crushed by a crusher to obtain particles (particle size is 1 to 5 mm), and the obtained particles are subjected to jet milling, the medium of the jet mill is ammonia with a purity of 99.9%, and the rotation speed is 200r / min to obtain a precursor powder with a D50 of 10μm; the precursor powder is placed in a nitriding furnace, heated to 540°C in an ammonia atmosphere, and the nitriding reaction is carried out for 12 hours. After cooling with the furnace, samarium iron nitrogen powder is obtained;

[0092] Step 4. Take 100g of the samarium iron nitrogen powder prepared above, pour it into a ball mill equipped with 8kg steel balls, pour in an appropriate amount of ammonia water with a mass concentration of 25%, so that the ammonia water level is 2cm higher than the steel balls, then add 1g of polypyrrole and 1g of sodium polymetaphosphate, ball mill at a frequency of 7Hz for 12h, filter after ball milling, place the filtered slurry in a vacuum drying oven, and dry it at 75°C to obtain modified samarium iron nitrogen powder.

[0093] Example 8

[0094] This embodiment provides a method for preparing modified samarium iron nitrogen powder, comprising the following preparation steps:

[0095] Step 1. Mix 300 g of samarium chloride with a particle size of 100 μm and 187.5 g of iron oxide with a particle size of 50 μm, add ammonia water with a mass concentration of 25%, so that the ammonia water exceeds the surface of the mixture by 3 cm, and react for 3 hours at a temperature of 400° C. and a pressure of 3.5 MPa to obtain a mixed solution;

[0096] Step 2. The mixed solution and a sodium hydroxide solution with a concentration of 1 mol / L are mixed in a mass ratio of 1:2, and reacted at a temperature of 300° C. and a pressure of 3 MPa for 5 hours. After the reaction is completed, the solid is filtered, and the filtered solid is rinsed 3 times with a sodium hydroxide solution with a concentration of 1 mol / L, and then dried to obtain a precursor;

[0097] Step 3. The precursor is crushed by a crusher to obtain particles (particle size is 1 to 5 mm), and the obtained particles are subjected to jet milling, the medium of the jet mill is ammonia with a purity of 99.9%, and the rotation speed is 200r / min to obtain a precursor powder with a D50 of 10μm; the precursor powder is placed in a nitriding furnace, heated to 540°C in an ammonia atmosphere, and the nitriding reaction is carried out for 12 hours. After cooling with the furnace, samarium iron nitrogen powder is obtained;

[0098] Step 4. Take 100g of the samarium iron nitrogen powder prepared above, pour it into a ball mill equipped with 8kg steel balls, pour in an appropriate amount of ammonia water with a mass concentration of 25%, so that the ammonia water level is 2cm higher than the steel balls, then add 1g of polypyrrole and 1g of sodium polymetaphosphate, ball mill at a frequency of 4Hz for 3h, filter after ball milling, place the filtered slurry in a vacuum drying oven, and dry it at 75°C to obtain modified samarium iron nitrogen powder.

[0099] Example 9

[0100] This embodiment provides a method for preparing modified samarium iron nitrogen powder, comprising the following preparation steps:

[0101] Step 1. Mix 300 g of samarium chloride with a particle size of 100 μm and 187.5 g of iron oxide with a particle size of 50 μm, add ammonia water with a mass concentration of 25%, so that the ammonia water exceeds the surface of the mixture by 3 cm, and react for 3 hours at a temperature of 400° C. and a pressure of 3.5 MPa to obtain a mixed solution;

[0102] Step 2. The mixed solution and a sodium hydroxide solution with a concentration of 1 mol / L are mixed in a mass ratio of 1:2, and reacted at a temperature of 300° C. and a pressure of 3 MPa for 5 hours. After the reaction is completed, the solid is filtered, and the filtered solid is rinsed 3 times with a sodium hydroxide solution with a concentration of 1 mol / L, and then dried to obtain a precursor;

[0103] Step 3. The precursor is crushed by a crusher to obtain particles (particle size is 1 to 5 mm), and the obtained particles are subjected to jet milling, the medium of the jet mill is ammonia with a purity of 99.9%, and the rotation speed is 200r / min to obtain a precursor powder with a D50 of 10μm; the precursor powder is placed in a nitriding furnace, heated to 540°C in an ammonia atmosphere, and the nitriding reaction is carried out for 12 hours. After cooling with the furnace, samarium iron nitrogen powder is obtained;

[0104] Step 4. Take 100g of the samarium iron nitrogen powder prepared above, pour it into a ball mill equipped with 8kg steel balls, pour in an appropriate amount of ammonia water with a mass concentration of 25%, so that the ammonia water level is 2cm higher than the steel balls, then add 1g of polypyrrole and 1g of sodium polymetaphosphate, ball mill at a frequency of 4Hz for 25h, filter after ball milling, place the filtered slurry in a vacuum drying oven, and dry it at 75°C to obtain modified samarium iron nitrogen powder.

[0105] Example 10

[0106] This embodiment provides a method for preparing modified samarium iron nitrogen powder, comprising the following preparation steps:

[0107] Step 1. Mix 300 g of samarium chloride with a particle size of 100 μm and 187.5 g of iron oxide with a particle size of 50 μm, add ammonia water with a mass concentration of 25%, so that the ammonia water exceeds the surface of the mixture by 3 cm, and react for 3 hours at a temperature of 400° C. and a pressure of 3.5 MPa to obtain a mixed solution;

[0108] Step 2. The mixed solution and a sodium hydroxide solution with a concentration of 1 mol / L are mixed in a mass ratio of 1:2, and reacted at a temperature of 300° C. and a pressure of 3 MPa for 5 hours. After the reaction is completed, the solid is filtered, and the filtered solid is rinsed 3 times with a sodium hydroxide solution with a concentration of 1 mol / L, and then dried to obtain a precursor;

[0109] Step 3. The precursor is crushed by a crusher to obtain particles (particle size is 1 to 5 mm), and the obtained particles are subjected to air flow milling, the medium of the air flow mill is ammonia with a purity of 99.9%, and the rotation speed is 200r / min to obtain a precursor powder with a D50 of 10μm; the precursor powder is placed in a nitriding furnace, heated to 540°C in an ammonia atmosphere, and the nitriding reaction is carried out for 12 hours. After cooling with the furnace, samarium iron nitrogen powder is obtained;

[0110] Step 4. Take 100 g of the samarium iron nitrogen powder prepared above, pour it into a ball mill equipped with 8 kg of steel balls, pour in anhydrous ethanol so that the liquid level of anhydrous ethanol is 2 cm higher than the steel balls, then add 1 g of polypyrrole and 1 g of sodium polymetaphosphate, ball mill at a frequency of 4 Hz for 12 h, filter after ball milling, place the filtered slurry in a vacuum drying oven, and dry it at 75 ° C to obtain modified samarium iron nitrogen powder.

[0111] Comparative Example 1

[0112] The comparative example provides a method for preparing a modified samarium iron nitrogen powder, wherein the samarium iron nitrogen powder is prepared by a melt rapid quenching method (reference patent CN114008728A); then, 100 g of the prepared samarium iron nitrogen powder is poured into a ball mill equipped with 8 kg of steel balls, and an appropriate amount of ammonia water with a mass concentration of 25% is poured into it so that the ammonia water level is 2 cm higher than the steel balls, and then 1 g of polypyrrole and 1 g of sodium polymetaphosphate are added, and the mixture is ball-milled at a frequency of 4 Hz for 12 h. After ball-milling, the mixture is filtered, and the filtered slurry is placed in a vacuum drying oven and dried at 75° C. to obtain the modified samarium iron nitrogen powder.

[0113] Test Case

[0114] The modified samarium iron nitrogen powder prepared in the above examples and comparative examples was tested, and the results are shown in Table 1.

[0115] Among them, the oxygen content and nitrogen content are tested by ONH-2000 oxygen, nitrogen and hydrogen tester, D50 is tested by laser particle size distribution analyzer, the average thickness of the coating layer is obtained according to SEM electron microscope, α-Fe content is determined by X-ray diffractometer, and intrinsic coercive force is tested by NIM-2000 tester.

[0116] The oxygen content is used to characterize the degree of oxidation, the nitrogen content is used to characterize the nitriding effect of the modified samarium iron nitrogen powder, D50 is used to characterize the particle size of the powder after ball milling, and the intrinsic coercive force is used to characterize the performance of the magnetic powder after ball milling.

[0117] Table 1 Performance test table

[0118]

[0119] From the comparison of Examples 1 to 3, it can be seen that the dosage ratio of samarium chloride to iron oxide can affect the oxygen and nitrogen content and intrinsic coercivity of the samarium iron nitrogen powder. When the mass ratio of samarium chloride to iron oxide is 1.6:1, the intrinsic coercivity of the obtained samarium iron nitrogen powder is the best.

[0120] From the comparison of Examples 1, 4, and 5, it can be seen that the speed of the jet mill affects the particle size of the precursor powder, thereby affecting the magnetic properties of the samarium iron nitrogen powder, and also affects the nitridation efficiency of the samarium iron alloy during ammonia jet milling, and then affects the nitrogen content of the final samarium iron nitrogen powder. When the jet mill speed is 200r / min, the intrinsic coercivity of the obtained samarium iron nitrogen powder is the best.

[0121] From the comparison of Examples 1, 6 and 7, it can be seen that the ball milling frequency affects the powder particle size D50 and ultimately affects the powder properties. When the ball milling frequency is 4 Hz, the intrinsic coercivity of the obtained samarium iron nitrogen powder is the best.

[0122] From the comparison of Examples 1, 8 and 9, it can be seen that the ball milling time affects the powder particle size D50 and ultimately affects the powder properties. When the ball milling time is 12 hours, the intrinsic coercivity of the obtained samarium iron nitrogen powder is the best.

[0123] From the comparison between Examples 1 and 10, it can be seen that adding ammonia water as a medium during ball milling can increase the nitrogen content of the product, promote nitridation, and further increase the intrinsic coercivity.

[0124] From the comparison between Example 1 and Comparative Example 1, it can be seen that the intrinsic coercivity of the product obtained by this technical solution is better than that by the traditional melt quenching method.

[0125] The modified samarium iron nitrogen powder obtained by the method of Example 1 has an oxygen content of 1.46%, a nitrogen content of 3.11%, a powder particle size D50 of 0.92 μm, a low degree of powder oxidation, and no explosion occurs during the preparation process due to a certain coating. The intrinsic coercive force of the SmFeN powder is 15.86KOe; this shows that the preparation method of the present invention ensures the activity and magnetism of the product and can be used for the manufacture of high-performance samarium iron nitrogen magnetic powder.

[0126] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for preparing modified samarium iron nitrogen powder, characterized in that: The preparation steps include: Step 1: mixing a soluble samarium salt, iron oxide and ammonia water, reacting to obtain a mixed solution; Step 2: mixing the mixed solution and an alkali metal hydroxide solution, reacting to obtain a precursor; Step 3: reacting the precursor in an ammonia atmosphere to obtain samarium iron nitrogen powder; Step 4: Arrange a coating layer on the surface of the samarium iron nitrogen powder to obtain the modified samarium iron nitrogen powder.

2. The method for preparing modified samarium iron nitrogen powder according to claim 1, characterized in that: The step 1 at least meets one of the following conditions: (1) The soluble samarium salt comprises samarium chloride; (2) The iron oxide comprises iron oxide; (3) The mass ratio of the soluble samarium salt to the iron oxide is (1.35-1.6):1; (4) The mass concentration of the ammonia water is 22% to 28%; (5) The reaction temperature is 200-400°C, the pressure is 1-5 MPa, and the reaction time is 1-5 hours.

3. The method for preparing modified samarium iron nitrogen powder according to claim 1, characterized in that: Step 2 at least meets one of the following conditions: (1) The alkali metal hydroxide solution includes sodium hydroxide solution and / or potassium hydroxide solution; (2) The concentration of the alkali metal hydroxide solution is 0.5 to 1.5 mol / L; (3) The mass ratio of the mixed solution to the alkali metal hydroxide solution is 1:(1-3); (4) The reaction temperature is 250-350° C., the pressure is 2-4 MPa, and the reaction time is 4-6 h.

4. The method for preparing modified samarium iron nitrogen powder according to claim 1, characterized in that: Step 3 includes: crushing the precursor to obtain particles, and air-grinding the particles to obtain precursor powder; reacting the precursor powder in an ammonia atmosphere to obtain samarium iron nitrogen powder; Preferably, the medium of the jet mill is ammonia gas, and the rotation speed is 100-600 r / min; Preferably, the reaction temperature in an ammonia atmosphere is 530-540° C. and the reaction time is 12-24 h.

5. The method for preparing modified samarium iron nitrogen powder according to claim 1, characterized in that: Step 4 comprises: mixing the samarium iron nitrogen powder and the coating agent, and performing ball milling to obtain the modified samarium iron nitrogen powder; Preferably, the coating agent comprises phosphate and a conductive polymer; Preferably, the phosphate accounts for 1% to 5% of the mass of the samarium iron nitrogen powder; Preferably, the conductive polymer accounts for 1% to 5% of the mass of the samarium iron nitrogen powder.

6. The method for preparing modified samarium iron nitrogen powder according to claim 5, characterized in that: The phosphate includes sodium polymetaphosphate, and the conductive polymer includes polypyrrole.

7. The method for preparing modified samarium iron nitrogen powder according to claim 5, characterized in that: The medium for ball milling in step 4 is aqueous ammonia; Preferably, the mass concentration of the ammonia water is 22% to 28%; Preferably, the ball milling frequency is 0.5 to 7 Hz, and the time is 1 to 25 hours.

8. The method for preparing modified samarium iron nitrogen powder according to claim 5, characterized in that: The mass ratio of the ball to material in the ball milling in step 4 is: 8000: (100-2000).

9. The modified samarium iron nitrogen powder obtained by the method for preparing the modified samarium iron nitrogen powder according to any one of claims 1 to 8.

10. Use of the modified samarium iron nitrogen powder according to claim 9 in magnetic materials or electronic materials.

Images