Multifunctional precursor material for producing rare earth transition metal compound spherical or nearly spherical single crystal powder, preparation method and application

Abstract

The invention discloses a multifunctional precursor for producing rare earth transition metal compound spherical or nearly spherical single crystal powder, a preparation method and application. A multifunctional precursor material comprises oxygen, an auxiliary element calcium and inevitable impurity elements, and further comprises effective elements forming a rare earth transition metal compound, the effective elements comprise the following components expressed by atomic percent: REaTM100-a-b-cM1bVc (formula 1), RE is more than one of lanthanum, cerium, praseodymium, neodymium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium and scandium, and Vc is more than one of lanthanum, cerium, praseodymium, neodymium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium and scandium. TM is more than one of iron and cobalt elements; m1 is more than one of nickel, manganese, aluminum, vanadium, titanium, chromium, zirconium, niobium, molybdenum, tungsten, tantalum, hafnium, copper, zinc, silver and gallium; and V is interstitial addition element boron B. The single crystal powder provided by the invention has the characteristics of high single crystal proportion, spherical or nearly spherical particles, smooth surface and the like.

Description

Technical field:

[0001] The invention relates to the technical field of rare earth magnetic materials, and in particular to a multifunctional precursor material for producing spherical or nearly spherical single crystal powder of a rare earth transition metal compound, a preparation method and application thereof. Background technology:

[0002] SmF 2 、SmFe 3 、Sm 2 Fe 17 、SmCo 5 、Sm 2 Co 17 、Nd 2 Fe 14 B. Sm(Fe,TM) 12 、Nd(Fe,TM) 12 、Pr(Fe,TM) 12 、La(Fe,Si) 13 、TbFe 2 ,DyFe 2 Rare earth transition metal compounds (RE-TM) have special magnetic and other properties and play a key role in various applications. 2 Fe 17 、SmCo 5 、Sm 2 Co 17 、Nd 2 Fe 14 B. Sm(Fe,TM) 12 、Nd(Fe,TM) 12 、Pr(Fe,TM) 12 Used for high-performance permanent magnet materials, widely used in electric vehicle drive systems, computer hard disks, sound equipment and other fields. 3 Has potential in hydrogen storage materials; TbFe 2 ,DyFe 2 Application as magnetostrictive material; La(Fe,Si) 13 Application as magnetic refrigeration material; Ce 2 Fe 17 As soft magnetic materials and wave absorbing materials. In some application fields, rare earth transition metal compounds need to be used in the form of ultrafine single crystal powder. The methods for preparing ultrafine single crystal powder include powder metallurgy, chemical synthesis and other methods.

[0003] In the chemical synthesis process disclosed in patent CN1286602C applied by Nichia Chemical Co., Ltd., soluble samarium salt and iron are coprecipitated and calcined to prepare iron oxide / samarium oxide composite oxide, and then the composite oxide is mixed with metal calcium and subjected to reduction diffusion heat treatment at 800℃-1100℃. The reaction product is nitrided, cleaned and separated from the by-product calcium oxide to form a nearly spherical high-performance magnetic powder. A similar method is also used to prepare nano magnetic powder particles, such as Sm-Co, Nd-Fe-B and other magnetic powders (Inorganic Chemistry Frontiers, DOI: 10.1039 / d0qi00777c). Sumitomo Metal Mining Co., Ltd. of Japan uses oxide rare earth and metal iron powder as raw materials to prepare coarse magnetic powder through high-temperature reduction diffusion process, and obtains single crystal permanent magnetic powder with a particle size of about 3 microns after ball milling. Patent CN1093311C discloses related technology. In patent ZL200610113209.4, Yang Yingchang proposed to use the rapid solidification casting technology to prepare a sheet with a lamellar crystal microstructure and a single Sm 2 Fe 17 The alloy castings of the phase are crushed, nitrided and ground to obtain ultrafine single crystal magnetic powder. The magnetic powder prepared by the method of first synthesizing coarse magnetic powder and then grinding and crushing is difficult to obtain high coercivity, and the powder shape is irregular and the surface is rough.

[0004] The existing disclosed method of directly preparing rare earth transition metal compound powder by reduction diffusion process mainly uses soluble salt as raw material, and produces magnetic powder through steps such as coprecipitation, calcination, atmosphere reduction, calcium thermal reduction diffusion, etc., such as patent CN1286602C applied by Nichia Chemical Co., Ltd. The precursor material after coprecipitation, calcination and reduction is composed of ultrafine and uniform nanocrystalline grains. During the subsequent reduction diffusion treatment, coarser micron-crystalline compounds are obtained from a large number of ultrafine compound nanocrystals that grow and coarsen. Therefore, when synthesizing rare earth transition metal compound powder from uniform nano precursor material, the diffusion of atoms is a random nucleation and growth process, and it is difficult to control the specific grain nucleation point; the by-product calcium oxide formed plays an isolating role, and naturally, the formation and distribution of calcium oxide are also difficult to control specifically, and belong to a random process. This random process is difficult to control, so the prepared powder is easy to sinter together to form polycrystalline grains, which is not conducive to the orientation of the powder.

[0005] In addition, in RECo 5 ,RE 2 Co 17 ,RE 2 Fe 17 N 3 ,RE 2 Fe 14 B.RE(Fe,TM) 12 N x 、RE(Fe,TM) 12In the element ratio of rare earth transition metal (RE-TM) compounds, transition metal elements such as Fe and Co account for 83-91at%. Transition metal elements usually exist in soluble salts in divalent or even trivalent forms. Therefore, this traditional process requires the use of a large amount of soluble salts and precipitants, which requires a large amount of precipitants in the coprecipitation operation during the production process and produces a large amount of salt-containing waste liquid, resulting in high environmental costs. In addition, soluble salts themselves are also high-cost raw materials. This problem needs to be solved urgently. Summary of the invention:

[0006] The present invention solves the problems existing in the prior art and provides a multifunctional precursor material, a preparation method and an application thereof for producing spherical or nearly spherical single crystal powders of rare earth transition metal compounds. The multifunctional precursor material and the preparation process provided by the present invention are universal and can be used for RECo 5 ,RE 2 Co 17 ,RE 2 Fe 17 N 3 ,RE 2 Fe 14 B.RE(Fe,TM) 12 N, RE (Fe, TM) 12 Direct synthesis, spheroidization and shell composition regulation of rare earth transition metal compounds of other types.

[0007] One of the purposes of the present invention is to provide a multifunctional precursor for producing spherical or nearly spherical single crystal powder of a rare earth transition metal compound, wherein the precursor is a multiphase composite containing calcium, and the precursor contains, in addition to oxygen, auxiliary element calcium and unavoidable impurity elements, effective elements capable of forming rare earth transition metal compounds, and the composition of the effective elements expressed in atomic percentage is:

[0008] RE a TM 100-a-b-c M1 b V c (Formula-1)

[0009] Among them, RE is one or more of the rare earth elements lanthanum, cerium, praseodymium, neodymium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium and scandium; TM is one or more of the transition metal elements iron and cobalt; M1 is one or more of the transition metal doping elements nickel, manganese, aluminum, vanadium, titanium, chromium, zirconium, niobium, molybdenum, tungsten, tantalum, hafnium, copper, zinc, silver and gallium; V is the interstitial added element boron; among them, 7<a<40, 0≤b<15, 0≤c<10, and the number of atoms of the auxiliary element calcium is 0.5-20 times that of the RE element.

[0010] The atomic number of the auxiliary element calcium is 0.5-20 times that of the RE element, and more than 95 at % of the calcium element generally exists in the precursor in the form of calcium oxide or calcium hydroxide.

[0011] The precursor material proposed by the present invention can be directly used to produce spherical or nearly spherical single crystal powder of rare earth transition metal (RE-TM) compounds; the precursor material can also be used as a spheroidization treatment additive to transform the irregular powder of rare earth transition metal compounds obtained by grinding into spherical single crystal magnetic powder; the precursor material is used as a shell composition regulation additive to transform irregularly shaped, rough-surfaced, angular single crystal particles into nearly spherical single crystal powders with relatively complete grains and smoother surfaces through heat treatment, and at the same time, the effective elements in the composition regulation treatment additive are transferred as beneficial elements and enriched in the product grain shell, thereby improving the performance through smooth surface and enrichment of beneficial elements.

[0012] The present invention proposes a new precursor structure design and supporting process, uses low-cost iron oxide, cobalt oxide, rare earth oxide and other oxides as the main raw materials and uses supporting processes to make precursors with specific structures, and then uses a reduction-directional diffusion process to efficiently produce high-performance spherical or nearly spherical rare earth transition metal compound single crystal powders, and conveniently controls the diameter of magnetic powder particles to 0.5-10 microns. In addition, in view of the shortcomings of the single crystal powder prepared by the grinding process, such as low coercivity, the precursor in the present invention can also be used as an additive, and the rare earth transition metal compound powder obtained by grinding is converted into spherical single crystal magnetic powder by spheroidization treatment, so that high-performance spherical or nearly spherical rare earth transition metal compound single crystal magnetic powder can be efficiently produced; in view of the insufficient performance of some homogeneous alloy powders, the precursor in the present invention can also be used as a shell composition regulation additive, and the surface composition of the rare earth transition metal compound single crystal is regulated by heat treatment, and the performance is improved by using the specific surface composition of the single crystal particles.

[0013] Preferably, different types of compounds are obtained by adjusting the effective element ratio of the precursor material, and the ratio d of the content of a, b, c and the auxiliary element to the content of the rare earth element a satisfies the conditions shown in Table 1 below:

[0014] Table 1

[0015] a b c d Main phase compound type Type 1 33<a<40 0≤b<10 c＝0 0.5<d<3.0 <![CDATA[RE(TM,TM1) 2 <!-- 2 -->]]> Type 2 25<a<33 0≤b<10 c＝0 0.5<d<3.0 <![CDATA[RE(TM,TM1) 3 ]]> Type 3 16<a<25 0≤b<10 c＝0 1.0<d<6.0 <![CDATA[RE(TM,TM1) 5 ]]> Type 4 9<a<16 0≤b<10 c＝0 2.0<d<15.0 <![CDATA[RE 2 (TM,TM1) 17 ]]> Type 5 7<a<9 0≤b<10 c＝0 4.0<d<20.0 <![CDATA[RE(TM,TM1) 12 ]]> Type 6 9<a<16 0≤b<10 5<c<10 2.0<d<12.0 <![CDATA[RE 2 (TM,TM1) 14 B]]>

[0016] By adjusting the raw material ratio in the precursor to obtain the target effective element ratio, a powder of a single main phase compound can be obtained, such as REFe 2 、RECo 2 、REFe 3 、RECo 3 、RECo 5 ,RE 2 Co 17,RE 2 Fe 17 N 3 ,RE 2 Fe 14 B.RE(Fe,TM) 12 Type compound single crystal powder. The specific effective element ratio and corresponding compound type are shown in the table above.

[0017] The second object of the present invention is to provide a method for preparing a multifunctional precursor, which is prepared by a direct batching and mixing process, comprising the following steps:

[0018] S1. Preparation of composite oxides: Raw materials of transition metal elements, transition metal doping elements, rare earth elements and interstitial additive elements that meet the requirements of particle diameter and purity are prepared according to the ratio of effective elements shown in Formula-1. Insoluble solid powder raw materials are first mixed evenly by wet mixing to obtain composite oxide slurry, in which the concentration of solid powder in the slurry is 20-3000 g / L; when part of the raw materials are added in the form of salt solution, the concentration of effective element ions is 0.2-10 mol / L, and the effective elements are precipitated into the slurry by stirring and titration; oxides, alkalis or inorganic salts containing calcium are added as auxiliary materials, and the number of atoms of the auxiliary material element calcium is 0.5-20 times that of the RE element, and then the slurry is dried to obtain a dry composite oxide;

[0019] S2. Calcination of composite oxides: calcining the dried composite oxides in air at 500°C-1100°C for 0.5-10h, decomposing the components of calcium hydroxide, calcium carbonate, rare earth hydroxide, rare earth carbonate, transition metal hydroxide and transition metal carbonate in the calcined composite oxides that need to be converted into oxides, and further reacting some oxides to form composite oxides. The calcined materials are called calcined composite oxides. The calcined composite oxides are multiphase mixtures composed of various oxides and composite oxides, and the various oxides and composite oxide phases account for more than 95wt% of the multiphase mixture. The effective elements in the mixture except calcium, oxygen and unavoidable impurity elements meet the ratio specified in formula-1. The microstructure of the calcined composite oxides is characterized in that coarser transition metal oxide particles are uniformly dispersed in a multiphase matrix composed of ultrafine particles such as rare earth oxides, composite oxides containing rare earths, and calcium oxide, and the coarser transition metal oxide particles are separated and embedded by the multiphase matrix formed by uniform mixing of various ultrafine particles;

[0020] S3. Calcining the composite oxide and subjecting it to reduction treatment to obtain a multifunctional precursor: removing oxygen from the transition metal oxide by placing the calcined composite oxide in a reducing gas at 500°C-980°C; after the reduction treatment is completed, the calcined composite oxide is converted into a multifunctional precursor composed of transition metals, rare earth oxides, and rare earth composite oxides. The microstructure of the multifunctional precursor is that coarser transition metal particles are uniformly dispersed in a multiphase matrix composed of ultrafine particles such as rare earth oxides, composite oxides containing rare earths, and calcium oxide, and the coarser transition metal particles are separated and embedded in the multiphase matrix formed by a uniform mixture of various ultrafine particles.

[0021] Preferably, when preparing the composite oxide slurry, 70%-100% of the transition metal elements iron and cobalt in the raw materials are added in the form of water-insoluble solid powder, and the rest are added in the form of soluble salts; the auxiliary material described in step S1 is selected from one or more of calcium oxide, calcium hydroxide and calcium carbonate, and the average particle diameter of the auxiliary material is 1 / 5-1 / 20 of the transition metal element.

[0022] The preparation method of the multifunctional precursor comprises the following steps: raw material preparation, preparation of composite oxide slurry, calcination of composite oxide slurry (calcination of composite oxide), and reduction treatment of the calcined composite oxide to obtain the multifunctional precursor.

[0023] Raw material preparation: including transition metal raw materials, rare earth raw materials, transition metal doping element raw materials, and interstitial addition element raw materials. The particle size and purity requirements of these raw materials are as follows:

[0024] Transition metal raw materials refer to iron oxide (Fe 2 O 3 ) or cobalt oxide (CoO) or a mixture of the two or other forms of oxides or hydroxides, such as ferrous oxide, ferroferric oxide, cobalt trioxide, cobalt tetraoxide, ferric hydroxide (Fe(OH) 3 ), ferrous hydroxide (Fe(OH) 2 ), cobalt hydroxide (Co(OH) 2 、Co(OH) 3 ), the transition metal raw material can also be other forms of powdered raw materials that are insoluble in water and can form oxides by calcination, such as carbonates, oxalates, and other water-insoluble salts. The insoluble transition metal raw materials require a purity of 95.0-99.999wt% and a particle diameter between 100-10000nm. The transition metal element raw material can also be added in the form of soluble salts, including soluble inorganic salts such as nitrates, sulfates, and hydrochlorides of the above elements, and soluble organic salts such as formates and acetates.

[0025] Rare earth raw materials can be added in the form of soluble salts with a purity of 99.0wt% or more, and soluble salts include soluble inorganic salts such as nitrates, sulfates, and hydrochlorides of rare earth elements. Another way to add rare earth raw materials is to use industrial rare earth oxides with a purity of 99.0wt% or more, and the particle diameter of the rare earth oxide is required to be between 10-1500nm, preferably less than 300nm.

[0026] Transition metal doping elements include one or more of Ni, Mn, Al, V, Ti, Cr, Zr, Nb, Mo, W, Ta, Hf, Cu, Zn, Ag, Ga, and can also be added in the form of oxides, with a particle diameter of less than 300 nm, preferably less than 100 nm. The raw materials are required to have a purity of 99.0 wt% or more. One or more transition metal doping elements can also be added in the form of soluble salts, including soluble inorganic salts such as nitrates, sulfates, and hydrochlorides of the above elements, and soluble organic salts such as formates and acetates.

[0027] Boron is added intermittently. Boron can be added directly in the form of boron oxide, boric acid, borate, ferroboron powder, etc. when mixing ingredients. When added in solid form, the particle diameter is required to be less than 200nm. The purity of these raw materials is required to be above 99.0wt%.

[0028] The auxiliary material is calcium oxide, calcium hydroxide or calcium carbonate, or a mixture of the three auxiliary materials. The particle diameter of the auxiliary material calcium oxide, calcium hydroxide or calcium carbonate is less than 500nm, preferably less than 300nm; the auxiliary material can also be other intermediate forms of calcium oxide and calcium hydroxide that can easily form particles with a diameter less than 500nm; the impurity content in the auxiliary material is less than 3.0wt%.

[0029] A multifunctional precursor is prepared (carried out in three steps, namely, preparing a composite oxide slurry, calcining the composite oxide slurry, and reducing the calcined composite oxide to obtain a multifunctional precursor).

[0030] S1. Preparation of composite oxide slurry: In terms of raw material selection, when making composite oxide slurry, 70%-100% of the transition metal elements iron and cobalt in the raw materials should be added in the form of solid powder insoluble in water, and the rest should be added in the form of soluble salts; rare earth elements can be added in the form of solid powder insoluble in water, or partially in the form of soluble salts; transition metal doping elements can be added in the form of solid powder insoluble in water, or partially in the form of soluble salts.

[0031] The transition metal elements, transition metal doping elements, rare earth elements and interstitial addition element raw materials that meet the particle diameter and purity requirements are mixed according to the ratio of effective elements shown in (Formula-1). The specific particle diameter requirements of each type of raw material are: when used as insoluble solid particle ingredients, the average particle diameter of the transition metal doping elements, rare earth elements and interstitial addition element raw materials is 1 / 2-1 / 20 of the transition metal element.

[0032] The batching steps are as follows: first, the insoluble solid powder raw materials are mixed evenly, and the mixing method is wet mixing. First, the insoluble solid powder raw materials are added to water for grinding or stirring; secondly, water-soluble raw materials are added, and the soluble raw materials are precipitated together by titrating the precipitant. During the titration process, the slurry needs to be continuously stirred until the soluble elements are precipitated, so that the raw materials of different components are mixed evenly. When a low-solubility precipitant such as calcium hydroxide is used, the precipitant can be added to the slurry first, and the soluble transition metal and rare earth salts are mixed into a solution and dripped into the slurry. The concentration of solid powder in the slurry is 20-3000g / L, and the concentration of effective element ions is 0.2-10mol / L. Precipitants such as oxalic acid, oxalate, carbonate, bicarbonate, sodium hydroxide, potassium hydroxide, calcium hydroxide, urea, etc. or other precipitants can be used to precipitate soluble salts of transition metal elements, rare earth elements, and transition metal doping elements and evenly mix them in the slurry. The concentration of ions in the precipitant that can form precipitates with effective elements is 0.2-4 mol / L.

[0033] After obtaining the composite oxide slurry that meets the effective element ratio specified in (Formula-1), add auxiliary materials such as calcium oxide or calcium hydroxide or calcium carbonate, or a mixture of the three auxiliary materials; the average particle diameter of the auxiliary materials is required to be 1 / 5-1 / 20 of the transition metal element; the amount of auxiliary materials added is based on the mass ratio of calcium oxide in the precursor formed by calcination and reduction, requiring that calcium oxide in the precursor accounts for 10-90% of the total mass, or the number of atoms of all forms of auxiliary element calcium is 0.5-20 times that of the RE element. When using a low-solubility precipitant such as calcium hydroxide, the precipitant can be added to the slurry at one time, and then the soluble transition metal and rare earth salt solution is dripped into the slurry to directly prepare the composite oxide slurry. The water in the composite oxide slurry is filtered out and dried to form a dry composite oxide.

[0034] S2. Calcination of composite oxides: Calcine the dried composite oxides in air at 500°C-1200°C for 0.5-10h to decompose the components in the composite oxides such as calcium hydroxide, calcium carbonate, rare earth hydroxide, rare earth carbonate, transition metal hydroxide, transition metal carbonate, etc. that need to be converted into oxides, and some oxides will further react to form composite oxides. The calcined material is called calcined composite oxide. The calcined composite oxide becomes a multiphase mixture composed of various oxides and composite oxides, and these oxides and composite oxide phases account for more than 95wt% of the multiphase mixture. The effective elements in the mixture except calcium, oxygen and impurity elements meet the ratio specified in (Formula-1).

[0035] The phases in calcined composite oxides can be divided into the following five categories:

[0036] The first category: oxides of transition metals and transition metal-doped elements, including but not limited to TMO, TM 2 O 3 、TM1 2 O 3 、(TM,TM1)O、(TM,TM1) 2 O 3 Oxide phases of transition metals and transition metal-doped elements in the form of

[0037] The second category is the composite oxide phase formed by rare earth oxides, transition metal oxides, and oxides of transition metal doped elements, including but not limited to RETMO 3 、RETM1O 3 、RE(TM,TM1)O 3 ,RE 3 TM 5 O 12 ,RE 3 (TM,TM1) 5 O 12 ;

[0038] Category III, rare earth oxides, including but not limited to RE 2 O 3 、REO 2 ;

[0039] The fourth category, composite oxides containing interstitial added elements, including but not limited to REVO 3 、TMVO 3 、TM1VO 3 .

[0040] The fifth category is calcium oxide formed by decomposition of auxiliary materials.

[0041] The precursor may also contain CaTM 2 O 4、CaTM1 2 O 4 、Ca(TM,TM1) 2 O 4 , Ca 2 TM 2 O 5 , Ca 2 (TM,TM1) 2 O 4 One or more composite oxides in the precursor, wherein these calcium-containing composite oxides account for less than 10wt% of the precursor.

[0042] Microstructural characteristics of calcined composite oxides: coarser transition metal oxide particles are uniformly dispersed in a multiphase matrix composed of ultrafine particles such as rare earth oxides, composite oxides containing rare earths, and calcium oxide. Coarser transition metal oxide particles are separated and embedded by a multiphase matrix formed by a uniform mixture of various ultrafine particles. When some transition metals and transition metal doping elements are added in the form of solution-precipitation, these elements will also enter the multiphase matrix and become ultrafine metal oxide particles or form ultrafine composite oxides with rare earths.

[0043] S3. Reduction treatment of composite oxides to become multifunctional precursors: calcining composite oxides in reducing gases such as hydrogen, methane, natural gas, carbon monoxide, etc. at 500°C-980°C to remove oxygen from transition metal oxides; after the reduction treatment is completed, the calcined composite oxides are converted into multifunctional precursors composed of transition metals, rare earth oxides, and rare earth composite oxides, and these metals, oxides, composite oxides and calcium oxide phases account for more than 95wt% of the precursors.

[0044] The phases in the precursor can be divided into the following four categories:

[0045] The first category is reduced transition metals, including but not limited to transition metal single substances or alloy phases such as TM, TM1, and TM-TM1 alloys;

[0046] The second category is unreduced rare earth oxides, transition metal doped element oxides, and composite oxide phases formed by rare earth oxides and transition metal oxides and transition metal doped elements, including but not limited to RE 2 O 3 、REO 2 、RETMO 3 、RETM1O 3 、RE(TM,TM1)O 3 ,RE 3 TM 5 O 12 ,RE 3 (TM,TM1) 5 O 12 ;

[0047] The third category, composite oxides containing interstitial added elements, including but not limited to REVO 3 、TMVO 3 、TM1VO 3 ;

[0048] The fourth category is calcium oxide formed by the decomposition of auxiliary materials. Calcium oxide may also form CaTM 2 O 4 、CaTM1 2 O 4 、Ca(TM,TM1) 2 O 4 , Ca 2 TM 2 O 5 , Ca 2 (TM,TM1) 2 O 4 One or more composite oxides in the precursor, wherein the composite oxides containing calcium account for less than 5wt% of the precursor. The above metals, oxides, composite oxides and calcium oxide phases account for more than 95wt% of the precursor.

[0049] The microstructure of the multifunctional precursor is inherited from the calcined composite oxide, and has the following characteristics: the coarser transition metal particles are evenly dispersed in a multiphase matrix composed of ultrafine particles such as rare earth oxides, composite oxides containing rare earths, and calcium oxide, and the coarser transition metal particles are separated and embedded by the multiphase matrix formed by a uniform mixture of various ultrafine particles. When some transition metals and transition metal doping elements are added in the form of solution-precipitation, these elements will also enter the multiphase matrix and become ultrafine metal particles or form ultrafine composite oxides with rare earths.

[0050] The third object of the present invention is to provide a spherical or nearly spherical single crystal powder of a rare earth transition metal compound, which is prepared by reduction-directional diffusion treatment, specifically by controlling the particle size of the raw transition metal oxide, the temperature and time of reduction-directional diffusion, so that the diameter of the target material particle rare earth transition metal compound spherical or nearly spherical single crystal powder is 0.2-10μm.

[0051] When the precursor material with the above-mentioned microstructure is subjected to reduction diffusion treatment to prepare rare earth transition metal compound powder, the ultrafine particles of rare earth oxide and rare earth composite oxide constituting the matrix are also reduced to a metallic state by calcium, and calcium oxide, a reaction byproduct, is formed at the same time. However, various ultrafine metal particles in the matrix are embedded in ultrafine calcium oxide particles, and it is difficult to form a continuous or coarse grain phase. Therefore, the metal atoms in the matrix can only diffuse directionally to the coarse grain transition metal and form the target compound with it. Since the larger transition metal grains in the precursor material are dispersed and embedded in the matrix, after the reduction-directional diffusion treatment, the final result is a compound single crystal powder and a byproduct calcium oxide. The powder directly prepared by the reduction-directional diffusion process, the material subjected to spheroidization heat treatment, and the material subjected to surface composition regulation treatment contain byproduct calcium oxide, and the calcium oxide in the material needs to be removed by deionized water or dilute acetic acid prepared by deionized water, thereby obtaining a spherical or nearly spherical rare earth transition metal (RE-TM) compound single crystal powder.

[0052] Preferably, the preparation is specifically carried out by the following steps: mixing the multifunctional precursor with calcium particles, performing calcium thermal reduction treatment in a vacuum or inert atmosphere at 700°C-1300°C for 0.5-10 hours, and after reduction-directional diffusion treatment, obtaining the products of calcium oxide and spherical or nearly spherical RE-TM compound single crystal particles, wherein the RE-TM compound single crystal particles are spherical or nearly spherical, with complete grains and smooth surfaces.

[0053] Further preferably, when the target particle size is less than 1 μm, a transition metal oxide raw material with an average particle diameter of 200-800 nm is used, and the reduction-directional diffusion temperature is (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*68%<reduction-directional diffusion treatment temperature<(the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*75%;

[0054] When the target particle size is 1-2 μm, a transition metal oxide raw material with an average particle diameter of 300-1500 nm is used, and the reduction-directional diffusion temperature is (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*75%<reduction-directional diffusion treatment temperature<(the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*85%;

[0055] When the target particle size is 2-4 μm, a transition metal oxide raw material with an average particle diameter of 500-3000 nm is used, and the reduction-directional diffusion temperature is (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*85%<reduction-directional diffusion treatment temperature<(the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*90%;

[0056] When the target particle size is 4-10μm, a transition metal oxide raw material with an average particle diameter of 800-7000nm is used, and the reduction-directional diffusion temperature is (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*90%<reduction-directional diffusion treatment temperature<(the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*95%.

[0057] The single crystal powder particles prepared by the above method are spherical or nearly spherical, with complete grains and smooth surface. The particle size of the raw material transition metal oxide used to prepare the precursor, the temperature and time of reduction-directional diffusion can be controlled so that the diameter of the single crystal powder of the transition metal compound is 0.2-10μm, and the microscopic morphology is spherical or nearly spherical. In general, under the same conditions of the precursor, as the reduction-directional diffusion temperature increases and the treatment time increases, the particle diameter of the single crystal powder also increases. The method for determining the temperature (absolute temperature) of the reduction-directional diffusion process is: (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram) * 68% < reduction-directional diffusion treatment temperature < (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram) * 95%.

[0058] In other words, the average particle diameter of the transition metal oxide raw material should be less than 80% of the target particle diameter of the single crystal powder.

[0059] In addition, the diameters of all raw material particles should be relatively uniform. The proportion of large particles with a diameter greater than 3 times the average diameter should be less than 5% of the total volume of the raw materials. The proportion of large particles with a diameter greater than 5 times the average diameter should be less than 2% of the total volume of the raw materials. There are no oversized particles with a diameter greater than 10 times the average diameter.

[0060] The present invention synthesizes rare earth transition metal compound single crystal powder by reduction diffusion process, and the diffusion migration of atoms, the formation of compound particles and the isolation between compound particles are basic technical problems. Generally speaking, transition metal oxides are reduced to a metallic state under a reducing atmosphere such as hydrogen, and hard-to-reduce oxides such as rare earth are reduced to metals by calcium thermal reduction and form compounds with transition metals. Multiple atoms form compound grains by diffusion migration, and calcium oxide formed by calcium thermal reduction has a certain isolation effect.

[0061] In order to produce spherical or nearly spherical single crystal powders of rare earth transition metal (RE-TM) compounds at low cost, stably and efficiently, the present invention proposes a new precursor material structure design and supporting process, using low-cost iron oxide, cobalt oxide, rare earth oxide and other oxides as the main raw materials and using supporting processes to produce a multifunctional precursor material with a complex phase multi-level structure, so that the diffusion path and direction of various atoms in the material can be controlled, and an effective isolation layer is formed at the same time, which effectively prevents the formed compound grains from sintering to form polycrystalline particles. When the spherical or nearly spherical single crystal powder is directly synthesized by the precursor material provided by the present invention, spheroidization treatment is performed, and the surface composition of the single crystal is regulated, a reduction-directional diffusion process (hereinafter referred to as RDDP) is performed, that is, the diffusion path and direction of various elements during heat treatment are controlled by the structural design of the precursor material.

[0062] The fourth object of the present invention is to provide a spherical or nearly spherical single crystal powder of a rare earth transition metal compound, and to prepare a target substance by spheroidization treatment, which specifically comprises the following steps:

[0063] S1. Evenly mix rare earth transition metal compound powder with a particle diameter of 1 μm < 50 μm and multifunctional precursor powder as a spheroidizing agent, wherein the amount of the spheroidizing agent added is 5-50 wt % of the rare earth transition metal compound powder, and the transition metal particle diameter in the spheroidizing agent is less than 1 / 2 of the particle diameter of the rare earth transition metal compound powder;

[0064] S2. The mixture of the spheroidizing treatment aid, the corresponding rare earth transition metal compound powder particles and the metal calcium particles is subjected to spheroidizing heat treatment in a vacuum or inert gas. The temperature (absolute temperature) of the spheroidizing heat treatment is determined as follows: (melting point of the target substance or peritectic reaction temperature in the equilibrium phase diagram)*75%<spheroidizing heat treatment temperature<(melting point of the target substance or peritectic reaction temperature in the equilibrium phase diagram)*95%. The spheroidizing heat treatment time is 0.5-10 hours. The obtained product is spherical or nearly spherical rare earth transition metal compound single crystal particles and by-product calcium oxide.

[0065] Preferably, the transition metal particle diameter is less than 1 / 5 of the diameter of the rare earth transition metal compound powder particles.

[0066] When the precursor material with the above-mentioned microstructure proposed by the present invention is used for the spheroidization treatment and shell composition regulation heat treatment of rare earth transition metal compound powder, the fine compound single crystal powder formed by the reduction diffusion process is dispersed and embedded in the matrix and is difficult to grow. Under the action of surface energy, the Oswald ripening process occurs, and the atoms on the fine grains diffuse to the coarse grains, thereby completing the spheroidization of the powder and the shell composition regulation.

[0067] As a spheroidizing additive for rare earth transition metal powder, spherical or nearly spherical single crystal powder of rare earth transition metal compound is prepared by spheroidizing treatment.

[0068] Spheroidization process, spheroidization includes two steps: batching and mixing, and spheroidization heat treatment, which specifically include the following steps:

[0069] S1. Batching and mixing: evenly mix the rare earth transition metal compound powder and the precursor powder as a spheroidizing agent (the effective element ratio should match the compound type, refer to Table 1 and Formula 1 for details), and the amount of the spheroidizing agent added is 5-50wt% of the alloy powder. The spheroidizing process is suitable for rare earth transition metal compound powders with a particle diameter of 1μm < 50μm. Before batching, in order to facilitate uniform mixing and separation of alloy powder particles, it is necessary to match the particle size of various raw materials. The diameter of the transition metal particles in the spheroidizing agent should be less than 1 / 5 of the diameter of the alloy powder particles.

[0070] The mixing methods include dry mixing and wet mixing. In dry mixing, the metal powder and the spheroidizing agent are directly mixed evenly on a three-dimensional mixing tank, a strong mixer, a ball mill and other mixing equipment. In wet mixing, a stable organic solvent such as methanol, ethanol, heptane, gasoline, etc. that does not react with the raw materials is added to the spheroidizing agent and the corresponding rare earth transition metal compound powder particles, and then mixed evenly on a three-dimensional mixing tank, a strong mixer, a ball mill and other mixing equipment. In addition, metal calcium particles need to be added to the mixture, and the weight should be 1.2-3.0 times the amount required to reduce the oxide. The wet mixture needs to be dried after mixing evenly.

[0071] S2, spheroidization heat treatment, spheroidization heat treatment of a mixture of spheroidization treatment aid, corresponding rare earth transition metal compound powder particles and metal calcium particles in vacuum or inert gas. The temperature (absolute temperature) of spheroidization heat treatment is determined as follows: (melting point of target substance or peritectic reaction temperature in equilibrium phase diagram)*75%<spheroidization heat treatment temperature<(melting point of target substance or peritectic reaction temperature in equilibrium phase diagram)*95%, and the spheroidization heat treatment time is 0.5-10 hours.

[0072] Spheroidizing heat treatment effect: The product is spherical or nearly spherical single crystal particles of rare earth transition metal compounds and by-product calcium oxide. Single crystal particles with irregular shapes, rough surfaces and edges are transformed into spherical or nearly spherical single crystal powders with complete grains and smooth surfaces.

[0073] The fifth object of the present invention is to provide a spherical or nearly spherical single crystal powder of a heterogeneous rare earth transition metal compound, and to prepare a target substance by heat treatment through shell composition regulation, which specifically comprises the following steps:

[0074] S1. Mix the multifunctional precursor powder as a component regulation treatment aid with the corresponding rare earth transition metal compound powder particles, wherein the particle diameter of the rare earth transition metal compound powder satisfies the following conditions: the addition amount of the component regulation treatment aid is 3-20wt% of the rare earth transition metal compound powder, and the particle diameter of the component regulation treatment aid powder should be less than 1 / 10 of the alloy powder particles; then add metal calcium particles to the mixed material and mix them evenly to obtain a mixture, wherein the weight of the calcium particles is 1.2-3.0 times the amount required for reducing the oxide;

[0075] S2. The mixture is subjected to shell composition regulation heat treatment in a vacuum or inert gas. The temperature (absolute temperature) of the shell composition regulation heat treatment is determined as follows: (melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*65%<shell composition regulation heat treatment temperature<(melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*85%. The heat treatment time is 0.5-5 hours. The products obtained are calcium oxide and spherical or nearly spherical single crystal particles of rare earth transition metal compounds. The single crystal powder particles have complete crystal shape and smooth surface, and the shell is enriched with effective metal elements in the composition regulation auxiliary agent.

[0076] As a shell composition regulating additive for rare earth transition metal powder, heterogeneous rare earth transition metal compound powder is prepared by shell composition regulating heat treatment. The characteristic of shell composition regulating heat treatment is that single crystal particles with irregular shape, rough surface and edges are transformed into single crystal powders with nearly spherical shape, relatively complete grains and smoother surface. At the same time, the effective elements in the composition regulating treatment additive are transferred as beneficial elements and enriched in the shell of the product grains, thereby improving the performance by smoothing the surface and enriching the beneficial elements.

[0077] The shell composition control heat treatment process includes two steps: batching and mixing, and composition control heat treatment:

[0078] S1. Batching and mixing: The precursor powder (effective element ratio should match the compound type, refer to Table 1 and Formula-1 for details) used as the component control treatment aid is evenly mixed with the corresponding rare earth transition metal compound powder particles. The amount of component control treatment aid added is 3-20wt% of the alloy powder. The spheroidization process is suitable for rare earth transition metal compound powders with a particle diameter of 2μm <30μm. Before batching, in order to facilitate uniform mixing and separation of alloy powder particles, the raw materials need to be matched in particle size, that is, the particle diameter of the component control treatment aid powder should be less than 1 / 10 of the alloy powder particles.

[0079] The mixing methods include dry mixing and wet mixing. In dry mixing, the metal powder and the component regulation and treatment aid are directly mixed evenly on a three-dimensional mixing tank, a strong mixer, a ball mill and other mixing equipment. In wet mixing, methanol, ethanol, heptane, gasoline and other stable organic solvents that do not react with the raw materials are added to the component regulation and treatment aid and the corresponding rare earth transition metal compound powder particles, and then mixed evenly on a three-dimensional mixing tank, a strong mixer, a ball mill and other mixing equipment. In addition, metal calcium particles need to be added to the mixture, and the weight should be 1.2-3.0 times the amount required to reduce the oxide. The wet mixture needs to be dried after mixing evenly.

[0080] S2. Shell composition control heat treatment: The mixture of composition control treatment aid, corresponding rare earth transition metal compound powder particles and metal calcium particles is subjected to shell composition control heat treatment in vacuum or inert gas. The temperature (absolute temperature) of the shell composition control heat treatment is determined as follows: (melting point of target substance or peritectic reaction temperature in equilibrium phase diagram)*65%<shell composition control heat treatment temperature<(melting point of target substance or peritectic reaction temperature in equilibrium phase diagram)*85%. The spheroidization heat treatment time is 0.5-5 hours.

[0081] Shell composition regulation heat treatment application scenarios and effects: When the performance of the powder with homogeneous composition is insufficient and it is necessary to improve the performance by regulating the surface composition of the powder particles. For example, high La or Ce content (Nd 0.4 Ce 0.6 ) 2 Fe 14 B、(Nd 0.4 La 0.6 ) 2 Fe 14 B、(Sm 0.4 La 0.6 ) 2 Fe 17 N 3 、(Sm 0.4 Ce 0.6 ) 2 Fe 17 N 3 Magnetic powder has the advantage of cheap raw materials, but this composition causes insufficient coercivity. Through the shell composition adjustment process, in (Nd 0.4 Ce 0.6 ) 2 Fe 14 B、(Nd 0.4 La 0.6 ) 2 Fe 14 The Pr, Nd, Tb, and Dy-rich shell layer is formed on the B magnetic powder to improve the coercivity of the magnetic powder; 0.4 La 0.6 )2 Fe 17 N 3 、(Sm 0.4 Ce 0.6 ) 2 Fe 17 N 3 A samarium-rich shell is formed on the magnetic powder to improve the coercivity, or samarium-rich and cobalt-rich shells are formed at the same time to improve the coercivity and anti-oxidation, corrosion resistance and other properties.

[0082] The products obtained by heat treatment of shell composition regulation are calcium oxide and spherical or nearly spherical single crystal particles of rare earth transition metal compounds. The single crystal particles with irregular shapes, rough surfaces and edges are transformed into nearly spherical particles with relatively complete grains and smoother surfaces.

[0083] Atmosphere treatment of single crystal powder: In order to adjust the performance characteristics of single crystal powder, some compound powders need to be further treated with atmosphere to add interstitial atoms in the compound lattice. These compounds include but are not limited to the following types: samarium-based RE 2 (Fe,TM1) 17 Compounds, praseodymium, neodymium-based RE (Fe, TM1) 12 These compounds need to be nitrided in a nitrogen-containing atmosphere. Specifically, the material after reduction-directional diffusion treatment is nitrided in a nitrogen-containing gas such as high-purity nitrogen, nitrogen and hydrogen, nitrogen and ammonia, and ammonia and hydrogen at 350-600°C. After nitridation, the product is composed of calcium oxide and RE 2 (Fe,TM1) 17 N 3 、RE(Fe,TM1) 12 N x Single crystal particles. RE(TM,TM1) 2 、RE(TM,TM1) 3 、RE(TM,TM1) 5 ,RE 2 Co 17 ,RE 2 Fe 14 B. Samarium-based RE (Fe, TM) 12 Type materials generally do not need nitriding treatment.

[0084] Separation of calcium oxide: Powders directly prepared by the reduction-directional diffusion process, materials that have undergone spheroidization heat treatment, and materials that have undergone surface composition control treatment contain by-product calcium oxide. Deionized water or dilute acetic acid prepared from deionized water is required to remove the calcium oxide from the material to obtain spherical or nearly spherical rare earth transition metal (RE-TM) compound single crystal powders.

[0085] The sixth object of the present invention is to provide the use of the spherical or nearly spherical single crystal powder of the rare earth transition metal compound in the preparation of rare earth magnetic materials. The magnetic materials include permanent magnetic powders, permanent magnetic composite materials, soft magnetic powders, soft magnetic powder composite materials, magnetic wave absorbing materials, etc.

[0086] Compared with the prior art, the present invention has the following advantages:

[0087] 1. The preparation of the precursor in the present invention uses metal oxide as the main raw material, and the metal elements in the form of soluble salts are lower than 30at.% of all metal elements, thereby significantly reducing the salt-containing waste liquid generated by precipitation and saving a large amount of precipitant; using oxides to substantially replace soluble salts can also reduce raw material costs, so the use of this process has the characteristics of low raw material cost and wide sources, and has excellent environmental protection and economic benefits.

[0088] 2. In the present invention, the precursor material provided has a stable multi-phase multi-level structure, so the subsequent reduction diffusion treatment process is simple to operate, stable, and has a wide process window; the directly prepared micron single crystal powder has the characteristics of high single crystal ratio, easy to control grain diameter, spherical or nearly spherical particles, and smooth particle surface.

[0089] 3. In the present invention, the preparation process of the precursor is mainly solid powder wet mixing, supplemented by chemical precipitation, which has the characteristics of simple process operation, high efficiency, stable controllability, high repeatability, and easy realization of automated production.

[0090] 4. The precursor provided by the present invention can be used as a spheroidization treatment additive to transform the irregular rare earth transition metal compound powder obtained by grinding into regular spherical single crystal magnetic powder.

[0091] 5. In view of the insufficient performance of some homogeneous compound powders, the precursor provided by the present invention can be used as a surface composition regulation treatment additive to form a specific element enrichment shell on the single crystal particles and improve related performance.

[0092] 6. The precursor material and its application process provided by the present invention have good universality and are applicable to but not limited to the production of RECo 5 ,RE 2 Co 17 ,RE 2 Fe 17 N 3 ,RE 2 Fe 14 B.RE(Fe,TM) 12 N x 、RE(Fe,TM) 12 Direct synthesis, spheroidization and surface composition control of single crystal powders of compounds such as .

[0093] 7. Since the single crystal powder provided by the present invention has the characteristics of high single crystal ratio, spherical or nearly spherical particles, smooth surface, etc., when using injection molding, magnetic field orientation compression molding and other molding processes to produce permanent magnetic composite materials, soft magnetic composite materials, and magnetic absorbing materials, it has the advantages of high compression density, easy orientation, high filling rate, good fluidity, and high magnetic properties. Description of the drawings:

[0094] Figure 1 The XRD pattern of the S5 mixture in Example 1 after calcination at 980°C;

[0095] Figure 2 This is the XRD spectrum of the S5 precursor after hydrogen reduction treatment in Example 1;

[0096] Figure 3 This is the XRD spectrum of the S5 material after reduction-directional diffusion treatment in Example 1;

[0097] Figure 4 This is a typical microscopic morphology image of the magnetic powder prepared from the S5 precursor in Example 1;

[0098] Figure 5 The XRD patterns of typical spheroidizing additives in Example 2, the upper pattern corresponds to PT1, and the lower pattern corresponds to PT6;

[0099] Figure 6 is Sm in Example 2 2 Fe 17 Typical microscopic morphology image of alloy powder before spheroidization treatment;

[0100] Figure 7 is Sm in Example 2 2 Fe 17 Typical microscopic morphology image of alloy powder after spheroidization treatment;

[0101] Figure 8 For Example 3 (Sm 0.5 Ce 0.5 ) 2 Fe 17 Typical microscopic morphology image of alloy powder shell layer before composition control treatment;

[0102] Fig. 9 For Example 3 (Sm 0.5 Ce 0.5 ) 2 Fe 17 Typical microscopic morphology image of the alloy powder shell layer after composition control treatment. Specific implementation method:

[0103] The following examples are provided to further illustrate the present invention, rather than to limit the present invention.

[0104] In order to make the purpose, technical solutions and advantages of the present invention clearer, the embodiments and implementation schemes of the present invention will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one example is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0105] The fuel cell membrane electrode activation method and technical effects of the present invention are described below in conjunction with specific embodiments.

[0106] Example 1: Preparation of rare earth transition metal (RE-TM) compounds Sm using transition metal oxides as main raw materials 2 Fe 17 N 3 Single crystal, monodisperse powder.

[0107] In order to synthesize Sm 2 Fe 17 Compounds were prepared according to Table 2. Industrial iron oxide with a purity of 99 wt% was ball-milled in water into particles with a diameter of 500-1500 nm and a particle size of d 50 =855nm powder. Industrial samarium oxide with a purity of 99wt% is ball-milled in water into particles with a diameter between 100-650nm and d 50 =348nm powder. According to the mass specified in Table 2, the two oxides and calcium hydroxide are placed together in a container filled with 5 liters of deionized water, and 0.56kg of calcium hydroxide with an average particle diameter of 280nm is added to each portion of the material. According to the mass specified in Table 2, industrial samarium nitrate hexahydrate and iron nitrate decahydrate with a purity of 99.9wt% are taken to prepare a 2mol / L aqueous solution. Use a stirrer to mix the slurry evenly and stir continuously. Drop the soluble salt solution into the slurry that is constantly stirring. After continuous stirring for 5 hours, filter out the water, add deionized water again, and wash 0-4 times according to the amount of precipitant used to wash and remove the by-product of the precipitation reaction, calcium nitrate. Use a suction filter to separate most of the water from the mixture, dry the mixture in a dryer, and calcine the dried mixture again in air at 980°C for 2h; remove oxygen from the iron oxide from the calcined mixture in a reducing gas hydrogen at 600°C to prepare a precipitant for preparing Sm 2 Fe 17Precursor of compound single crystal powder. Each portion of the reduced precursor is mixed with 0.46 kg of calcium particles and subjected to reduction-directional diffusion treatment in argon at 1085°C for 2 hours. Nitriding treatment: the material subjected to reduction-directional diffusion treatment is nitrided in a mixed gas of high-purity ammonia (2V) and hydrogen (1V) at 460°C for 6 hours. After nitriding treatment, calcium oxide is washed and removed using deionized water and dilute acetic acid prepared from deionized water, thereby obtaining spherical or nearly spherical Sm 2 Fe 17 N 3 Single crystal powder. Table 3 shows the magnetic properties of the samples. As can be seen from Table 2, with the reduction of the amount of nitrate, the amount of precipitant and the by-product calcium nitrate also gradually decrease. As can be seen from Table 3, by reducing the amount of soluble salt, high-performance magnetic powder can still be prepared, while greatly reducing the precipitant and precipitation by-products.

[0108] Figure 1 The XRD pattern of the S5 mixed material sample after calcination at 980℃ is shown, showing that the mixed material is composed of Fe 2 O 3 、SmFeO 3 And CaO phase. Figure 2 The XRD pattern of the S5 precursor after hydrogen reduction treatment is shown, showing that the precursor is composed of α-Fe, CaO and Sm 2 O 3 Phase composition. Figure 3 The XRD pattern of S5 material after reduction-directional diffusion treatment is shown, showing that the sample is composed of CaO and Sm 2 Fe 17 Phase composition. Figure 4 The Sm prepared from S5 precursor 2 Fe 17 Typical microscopic morphology image of magnetic powder.

[0109] Table 2. Synthesis of 1 kg Sm 2 Fe 17 Ingredients list of raw materials used in the compound and yield of precipitation by-products (mass unit, kg)

[0110]

[0111] Table 3. Magnetic properties of samples

[0112]

[0113]

[0114] Example 2: Preparation of Sm using transition metal oxides as main raw materials 2 Fe 17The alloy powder is spheroidized and heat treated to prepare single crystal and monodisperse powder.

[0115] In order to synthesize Sm 2 Fe 17 The spheroidizing agent for alloy powder is prepared according to Table 4. Industrial iron oxide with a purity of 99 wt% is ball-milled in deionized water to form d 10 =133nm, d 50 =368nm, d 90 =475nm (equivalent spherical diameter obtained by laser particle size test) ultrafine powder. Industrial samarium oxide with a purity of 99wt% was ball-milled in water to form d 10 =96nm, d 50 =243nm, d 90 =337nm (equivalent sphere diameter obtained by laser particle size test) ultrafine powder. According to the mass specified in Table 4, the two oxides and calcium hydroxide are placed in a container with 5 liters of deionized water, and 0.45kg of calcium hydroxide with an average particle diameter of 300nm is added to each portion of the material. According to the mass specified in Table 4, industrial samarium nitrate hexahydrate and iron nitrate decahydrate with a purity of 99.9wt% are taken to prepare a 2mol / L aqueous solution. The soluble salt solution is dripped into the slurry that is constantly stirred. After continuous stirring for 5 hours, the water is filtered out and deionized water is added again. The by-product of the precipitation reaction is washed 0-4 times according to the amount of precipitant used. The calcium nitrate is washed and removed. The mixture is separated from most of the water using a suction filter, the mixture is dried in a dryer, and the dried mixture is calcined in air at 930°C for 2h; the calcined mixture is removed from the oxygen in the iron oxide in a reducing gas hydrogen at 600°C to obtain a spheroidizing agent.

[0116] Sm 2 Fe 17 The alloy flakes are crushed into 50 =2840nm powder, take 6 parts of alloy powder, each part is 1kg. Add 0.35kg of spheroidizing agent and 0.07kg of calcium particles with a particle diameter of 3mm to each part of alloy powder, add the mixture to a ball mill, add 1.5kg of steel balls, and then dry mix it evenly in a ball mill. Spheroidize the mixture in argon at 900℃ for 1.0 hour. Nitriding treatment, nitriding the spheroidized material in a mixed gas of high-purity ammonia (2V) and hydrogen (1V) at 445℃ for 6 hours. After nitriding treatment, use deionized water and dilute acetic acid prepared by deionized water to wash and remove calcium oxide, thereby obtaining spherical or nearly spherical Sm 2 Fe 17 N 3 Single crystal powder.

[0117] Table 5 shows the magnetic properties of the samples before and after spheroidization. As can be seen from Table 5, after spheroidization, the remanence of the magnetic powder is slightly reduced, while the coercivity is greatly improved. Figure 5 The XRD patterns of typical spheroidizing agents are shown. The figure above (corresponding to PT1) shows that PT1 spheroidizing agent is composed of α-Fe, CaO and SmFeO 3 Phase composition, the figure below (corresponding to PT6) shows that PT6 spheroidizing agent is composed of α-Fe, CaO and Sm 2 O 3 From the comparison in Table 5, it can be seen that all six spheroidizing additives can prepare Sm 2 Fe 17 N 3 Single crystal powder. Figure 6 Shows Sm 2 Fe 17 Typical microscopic morphology image of alloy powder before spheroidization treatment. It can be seen that the powder shape is irregular and has a lot of sharp edges and corners, which is not conducive to obtaining high coercivity. Figure 7 Shows Sm 2 Fe 17 Typical microscopic morphology image of alloy powder after spheroidization treatment. It can be seen that the powder has a regular shape and a smooth and complete surface, which is very conducive to obtaining high coercive force and facilitating good fluidity during injection molding.

[0118] Table 4. Synthetic Sm 2 Fe 17 Ingredients of raw materials used in alloy powder spheroidizing agent (mass unit, kg)

[0119]

[0120]

[0121] Table 5. Magnetic properties of samples before and after spheroidization

[0122]

[0123] Example 3: Preparation of shell composition control additives using transition metal oxides as main raw materials and preparation of (Sm, Ce) by shell composition control heat treatment 2 Fe 17 N 3 Inhomogeneous single crystal powder.

[0124] In order to synthesize the shell composition control additive, the ingredients were prepared according to Table 6. Industrial iron oxide with a purity of 99 wt% was ball-milled in deionized water into d 10 =124nm, d 50 =323nm, d 90=459nm (equivalent spherical diameter obtained by laser particle size test) ultrafine powder. Industrial samarium oxide with a purity of 99wt% was ball-milled in water to form d 10 =98nm, d 50 =235nm, d 90 =367nm (equivalent sphere diameter obtained by laser particle size test) ultrafine powder. According to the mass specified in Table 6, the two oxides and calcium hydroxide are placed in a container with 5 liters of deionized water, and 0.44kg of calcium hydroxide with an average particle diameter of 300nm is added to each portion of the material. According to the mass specified in Table 6, industrial samarium nitrate hexahydrate and iron nitrate decahydrate with a purity of 99.9wt% are taken to prepare a 2mol / L aqueous solution. The soluble salt solution is dripped into the slurry that is constantly stirred. After continuous stirring for 5 hours, the water is filtered out and deionized water is added again. Depending on the amount of precipitant used, it is washed 0-4 times to wash and remove the by-product calcium nitrate of the precipitation reaction. The mixture is separated from most of the water using a suction filter, the mixture is dried in a dryer, and the dried mixture is calcined in air at 930°C for 2h; the calcined mixture is removed from the oxygen in the iron oxide in a reducing gas hydrogen at 600°C to obtain a shell composition regulating additive.

[0125] (Sm 0.5 Ce 0.5 ) 2 Fe 17 The alloy flakes are crushed into 50 = 2880nm powder, take 7 parts (Sm 0.4 Ce 0.6 ) 2 Fe 17 Alloy powder, 1 kg per portion. Add 0.35 kg of shell composition regulating additives and 0.07 kg of calcium particles with a particle diameter of 3 mm to each portion of alloy powder, add the mixture to a ball mill, add 1.5 kg of steel balls, and then dry mix evenly in a ball mill. Spheroidize the mixture in argon at 820°C for 1.0 hour. Nitriding treatment, nitriding the spheroidized material in a mixed gas of high-purity ammonia (2V) and hydrogen (1V) at 445°C for 6 hours. After nitriding, use deionized water and dilute acetic acid prepared by deionized water to wash and remove calcium oxide, thereby obtaining nearly spherical (Sm, Ce) 2 Fe 17 N 3 Inhomogeneous single crystal powder.

[0126] Table 7 shows the magnetic properties of the samples before and after the shell composition regulation treatment. As can be seen from Table 7, the remanence of the magnetic powder is slightly reduced and the coercivity is greatly improved through the shell composition regulation treatment. As can be seen from the comparison in Table 7, compared with the original powder, the seven shell composition regulation additives can all improve the coercivity of the single crystal powder, among which the coercivity of the powder treated with QC1-QC6 additives is significantly increased.

[0127] Figure 8 Shows (Sm,Ce) 2 Fe 17 Typical microscopic morphology image of alloy powder before shell composition regulation treatment. It can be seen that the powder shape is irregular and has a large number of sharp edges, which is not conducive to obtaining high coercivity. Fig. 9 Shows (Sm,Ce) 2 Fe 17 Typical microscopic morphology images of alloy powder after shell composition regulation treatment show that the powder has regular shape and smooth and complete surface, which is very conducive to obtaining high coercivity and good fluidity during injection molding. Using electron microscope and energy spectrometer test, it is known that the Sm content on the surface of the powder treated with QC1-QC6 additives is 15%-30% higher than that in the center of the powder, while the sample treated with QC7 additive with the same Sm / Ce atomic ratio as the original magnetic powder is uniform in composition and no samarium-rich shell is detected. Therefore, the coercivity of the powder treated with QC1-QC6 additives is higher than that of the sample treated with QC7 additive. The sample treated with QC7 additive also has a nearly spherical and smooth surface, so its coercivity is also improved compared with the original powder.

[0128] Table 6. Ingredients of raw materials used in synthetic shell composition control additives (mass unit, kg) Table 7. Magnetic properties of magnetic powder samples before and after shell composition adjustment treatment

[0129]

[0130] The above embodiments illustrate that the precursors described in the present invention can not only directly prepare high-performance rare earth transition metal compound permanent magnet materials, but these precursors can also be used for spheroidization of alloy powders and regulation of shell composition, and obtain nearly spherical magnetic powders with good magnetic properties, complete and regular grains, and smooth surfaces. These permanent magnet materials can be used to manufacture high-performance bonded permanent magnet materials. Since the chemical properties of rare earth elements are similar, the chemical properties of transition metal elements iron and cobalt are also similar, and they can often replace each other in rare earth transition metal compounds. Therefore, by adjusting the types of elements in the precursors and the ratio of rare earth / transition metal elements, different types of compounds can be obtained. Therefore, the method proposed in the present invention is a general process and can be used to directly synthesize RECo 5,RE 2 Co 17 ,RE 2 Fe 17 N 3 ,RE 2 Fe 14 B.RE(Fe,TM) 12 N, RE (Fe, TM) 12 Spherical or nearly spherical single crystal powders of rare earth transition metal compounds of the same type can be applied to magnetic composite materials such as permanent magnets and soft magnets. Since the single crystal magnetic powder particles prepared by the precursor described in the present invention are spherical or nearly spherical and have a smooth surface, these rare earth transition metal compound (RE-TM) single crystal powders are used as permanent magnet powders, permanent magnet composite materials, soft magnetic powders, soft magnetic powder composite materials, magnetic wave absorbing materials, etc., and have the advantages of high compression density, easy orientation, high filling rate, good fluidity, high magnetic properties, etc. when producing bonded magnets by forming processes such as magnetic field oriented injection molding and magnetic field oriented compression molding.

Claims

1. A multifunctional precursor for producing spherical or near-spherical single crystal powders of rare earth transition metal compounds, Characterized in that, The precursor is a multiphase composite containing calcium. Besides oxygen, auxiliary element calcium and inevitable impurity elements, the precursor also includes effective elements capable of forming rare earth transition metal compounds. The components of the effective elements in atomic percentage are: RE a TM 100-a-b-c M1 b V c (Formula-1) Among them, RE is one or more of rare earth elements lanthanum, cerium, praseodymium, neodymium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium and scandium; TM is one or more of transition metal elements iron and cobalt; M1 is one or more of transition metal doping elements nickel, manganese, aluminum, vanadium, titanium, chromium, zirconium, niobium, molybdenum, tungsten, tantalum, hafnium, copper, zinc, silver, gallium; V is interstitial addition element boron; where 7 < a < 40, 0 ≤ b < 15, 0 ≤ c < 10, and the atomic number of auxiliary element calcium is 0.5 - 20 times that of RE element.

2. The multifunctional precursor according to claim 1, Characterized in that, Different types of compounds are obtained by adjusting the proportion of effective elements of the precursor. The ratios d of a, b, c and the content of auxiliary elements to the content of rare earth element a satisfy the conditions shown in Table 1 below: Table 1 。 3. A preparation method of the multifunctional precursor according to claim 1 or 2, Characterized in that, It is prepared by a direct batching and mixing process, including the following steps: S1. Prepare composite oxide: Weigh the raw materials of transition metal elements, transition metal doping elements, rare earth elements and interstitial addition elements that meet the requirements of particle diameter and purity according to the proportion of effective elements shown in Formula - 1. First, mix the insoluble solid powder raw materials evenly. The mixing method is wet mixing to obtain a composite oxide slurry, and the concentration of solid powder in the slurry is 20 - 3000 g / L; when some raw materials are added in the form of salt solutions, the concentration of effective element ions is 0.2 - 10 mol / L, and the effective elements are precipitated into the slurry through stirring and titration; add oxides, alkalis or inorganic salts containing calcium element as auxiliary materials, and the atomic number of auxiliary element calcium is 0.5 - 20 times that of RE element. Then dry the slurry to obtain a dried composite oxide; S2. Calcination of composite oxides: calcining the dried composite oxides in air at 500°C-1100°C for 0.5-10h, decomposing the components of calcium hydroxide, calcium carbonate, rare earth hydroxide, rare earth carbonate, transition metal hydroxide and transition metal carbonate in the calcined composite oxides that need to be converted into oxides, and further reacting some oxides to form composite oxides. The calcined materials are called calcined composite oxides. The calcined composite oxides are multiphase mixtures composed of various oxides and composite oxides, and the various oxides and composite oxide phases account for more than 95wt% of the multiphase mixture. The effective elements in the mixture except calcium, oxygen and unavoidable impurity elements meet the ratio specified in formula-1. The microstructure of the calcined composite oxides is characterized in that coarser transition metal oxide particles are uniformly dispersed in a multiphase matrix composed of ultrafine particles such as rare earth oxides, composite oxides containing rare earths, and calcium oxide, and the coarser transition metal oxide particles are separated and embedded by the multiphase matrix formed by uniform mixing of various ultrafine particles; S3, calcining the composite oxide and performing reduction treatment to obtain a multifunctional precursor: removing oxygen from the transition metal oxide by calcining the composite oxide in a reducing gas at 500° C.-980° C.; After the reduction treatment is completed, the calcined composite oxide is converted into a multifunctional precursor composed of transition metals, rare earth oxides, and rare earth composite oxides. The microstructure of the multifunctional precursor is that the coarser transition metal particles are uniformly dispersed in a multiphase matrix composed of ultrafine particles such as rare earth oxides, rare earth-containing composite oxides, and calcium oxide, and the coarser transition metal particles are separated and embedded in the multiphase matrix formed by a uniform mixture of various ultrafine particles.

4. The method for preparing the multifunctional precursor according to claim 3, It is characterized in that When preparing the composite oxide slurry, 70%-100% of the transition metal elements iron and cobalt in the raw materials are added in the form of water-insoluble solid powder, and the rest are added in the form of soluble salts; the auxiliary material described in step S1 is selected from one or more of calcium oxide, calcium hydroxide and calcium carbonate, and the average particle diameter of the auxiliary material is 1 / 5-1 / 20 of the transition metal element.

5. A spherical or nearly spherical single crystal powder of a rare earth transition metal compound, prepared by reduction-oriented diffusion treatment, specifically by controlling the particle size of the raw transition metal oxide, the temperature and time of reduction-oriented diffusion, so that the diameter of the target particle rare earth transition metal compound spherical or nearly spherical single crystal powder is 0.2-10μm.

6. The spherical or nearly spherical single crystal powder of the rare earth transition metal compound according to claim 5, It is characterized in that The preparation is specifically carried out by the following steps: mixing the multifunctional precursor described in claim 1 or 2 with calcium particles, performing calcium thermal reduction treatment in a vacuum or inert atmosphere at 700°C-1300°C for 0.5-10 hours, and after reduction-directional diffusion treatment, obtaining products of calcium oxide and spherical or nearly spherical RE-TM compound single crystal particles, wherein the RE-TM compound single crystal particles are spherical or nearly spherical, with complete grains and smooth surfaces.

7. The spherical or nearly spherical single crystal powder of the rare earth transition metal compound according to claim 6, It is characterized in that When the target particle size is less than 1 μm, a transition metal oxide raw material with an average particle diameter of 200-800 nm is used, and the reduction-directional diffusion temperature is (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*68%<reduction-directional diffusion treatment temperature<(the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*75%; When the target particle size is 1-2 μm, a transition metal oxide raw material with an average particle diameter of 300-1500 nm is used, and the reduction-directional diffusion temperature is (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*75%<reduction-directional diffusion treatment temperature<(the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*85%; When the target particle size is 2-4 μm, a transition metal oxide raw material with an average particle diameter of 500-3000 nm is used, and the reduction-directional diffusion temperature is (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*85%<reduction-directional diffusion treatment temperature<(the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*90%; When the target particle size is 4-10μm, a transition metal oxide raw material with an average particle diameter of 800-7000nm is used, and the reduction-directional diffusion temperature is (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*90%<reduction-directional diffusion treatment temperature<(the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*95%.

8. A spherical or nearly spherical single crystal powder of a rare earth transition metal compound, It is characterized in that The target substance is prepared by spheroidization, which specifically includes the following steps: S1. Mixing the rare earth transition metal compound powder with a particle diameter of 1 μm < 50 μm and the multifunctional precursor powder according to claim 1 or 2 as a spheroidizing agent, wherein the amount of the spheroidizing agent added is 5-50 wt % of the rare earth transition metal compound powder, and the transition metal particle diameter in the spheroidizing agent is less than 1 / 2 of the particle diameter of the rare earth transition metal compound powder; S2. The mixture of the spheroidizing treatment aid, the corresponding rare earth transition metal compound powder particles and the metal calcium particles is subjected to spheroidizing heat treatment in a vacuum or inert gas. The temperature (absolute temperature) of the spheroidizing heat treatment is determined as follows: (melting point of the target substance or peritectic reaction temperature in the equilibrium phase diagram)*75%<spheroidizing heat treatment temperature<(melting point of the target substance or peritectic reaction temperature in the equilibrium phase diagram)*95%. The spheroidizing heat treatment time is 0.5-10 hours. The obtained product is spherical or nearly spherical rare earth transition metal compound single crystal particles and by-product calcium oxide.

9. A spherical or nearly spherical single crystal powder of a heterogeneous rare earth transition metal compound, It is characterized in that The target substance is prepared by heat treatment through shell composition regulation, which specifically includes the following steps: S1. The multifunctional precursor powder as claimed in claim 1 or 2 as a component regulation treatment aid is mixed evenly with the corresponding rare earth transition metal compound powder particles, wherein the particle diameter of the rare earth transition metal compound powder satisfies the following conditions: 2μm<particle diameter<30μm, the amount of the component regulation treatment aid added is 3-20wt% of the rare earth transition metal compound powder, and the particle diameter of the component regulation treatment aid powder should be less than 1 / 10 of the alloy powder particles; then, metallic calcium particles are added to the mixed material and mixed evenly to obtain a mixture, wherein the weight of the calcium particles is 1.2-3.0 times the amount required for reducing the oxide; S2. The mixture is subjected to shell composition regulation heat treatment in a vacuum or inert gas, and the temperature (absolute temperature) of the shell composition regulation heat treatment is determined as follows: (melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*65%<shell composition regulation heat treatment temperature<(melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram)*85%, and the heat treatment time is 0.5-5 hours, and the products obtained are calcium oxide and spherical or nearly spherical single crystal powder particles of rare earth transition metal compounds; the single crystal powder particles have complete crystal shape, smooth surface, and the shell is enriched with effective metal elements in the composition regulation auxiliary agent.

10. Use of the spherical or nearly spherical single crystal powder of the rare earth transition metal compound according to claim 7, 8 or 9 in the preparation of rare earth magnetic materials.

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