Multifunctional precursor material, preparation method thereof and application of multifunctional precursor material in production of rare earth transition metal compound spherical or nearly-spherical single crystal powder

Abstract

The invention discloses a multifunctional precursor material, a preparation method thereof and application of the multifunctional precursor material in production of rare earth transition metal compound spherical or nearly spherical single crystal powder. The invention relates to a multifunctional precursor material, in addition to oxygen, an auxiliary element calcium and inevitable impurity elements, the precursor material further comprises effective elements capable of forming a rare earth transition metal compound, and the effective elements are represented by atomic percent as REaTM100-a-b-cM1bVc (formula 1), rE is more than one of rare earth elements of lanthanum, cerium, praseodymium, neodymium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium and scandium; tM is more than one of transition metal elements of iron and cobalt; m1 is more than one of transition metal doped elements of nickel, manganese, aluminum, vanadium, titanium, chromium, zirconium, niobium, molybdenum, tungsten, tantalum, hafnium, copper, zinc, silver and gallium; v is interstitial addition element boron B; 7 < alt; 40, 0 < = blt; 15, 0 < = clt; 10. 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 present invention relates to the technical field of rare earth magnetic materials, and particularly relates to a multifunctional precursor material, a preparation method thereof, and an application in producing spherical or near-spherical single crystal powders of rare earth transition metal compounds. Background Art:

[0002] SmFe 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 and other rare earth transition metal compounds (RE-TM) have special magnetic properties and other properties, and play a key role in various application fields. For example, 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 are used in high-performance permanent magnetic materials and are widely applied in fields such as electric vehicle drive systems, computer hard disks, and sound equipment. SmFe 3 has potential in hydrogen storage materials; TbFe 2 、DyFe 2 are used as magnetostrictive materials; La(Fe,Si) 13 is used as a magnetic refrigeration material; Ce 2 Fe 17 is used as a soft magnetic material and an electromagnetic wave absorption material. In some application fields, rare earth transition metal compounds need to be used in the form of ultrafine single crystal powders. Methods for preparing ultrafine single crystal powders include powder metallurgy, chemical synthesis, and other methods.

[0003] The existing publicly disclosed method for directly preparing rare earth transition metal compound powders by the reduction-diffusion process mainly uses soluble salts as raw materials, and produces magnetic powders through steps such as coprecipitation, calcination, atmospheric reduction, and calcium thermal reduction-diffusion. For example, the patent CN1286602C applied by Nichia Chemical Industries, Ltd. The precursor materials after coprecipitation, calcination, and reduction are composed of ultrafine and uniform nanocrystals. During the subsequent reduction-diffusion treatment, coarser micron-sized compound crystals grow and coarsen from a large number of ultrafine compound nanocrystals. Therefore, when synthesizing rare earth transition metal compound powders from uniform nano-precursor materials, the diffusion of atoms is a random nucleation and growth process, and it is difficult to control the specific grain nucleation points; the formed by-product calcium oxide plays an isolation role. Naturally, the formation and distribution of calcium oxide are also difficult to specifically control and belong to a random process. This random process is difficult to control, so the prepared powders are prone to sintering together to form polycrystalline grains, which is not conducive to the orientation of the powders. Summary of the Invention:

[0004] The present invention solves the problems existing in the prior art, and provides a multifunctional precursor material, a preparation method thereof, and an application for producing spherical or near-spherical single crystal powders of rare earth transition metal compounds. The multifunctional precursor material and process provided by the present invention have universality 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 and other types of direct synthesis, spheroidization treatment, and shell composition regulation of rare earth transition metal compounds.

[0005] One of the purposes of the present invention is to provide a multifunctional precursor material. The precursor material is a multiphase composite containing calcium. In addition to oxygen, the auxiliary element calcium, and inevitable impurity elements, the precursor material also includes effective elements that can form rare earth transition metal compounds. The components of the effective elements expressed in atomic percentages are

[0006] RE a TM 100-a-b-c M1 b V c (Formula - 1)

[0007] Among them, RE is one or more of rare earth elements lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), yttrium (Y) and scandium (Sc); TM is one or more of transition metal elements iron (Fe) and cobalt (Co); M1 is one or more of transition metal doping elements nickel (Ni), manganese (Mn), aluminum (Al), vanadium (V), titanium (Ti), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), tantalum (Ta), hafnium (Hf), copper (Cu), zinc (Zn), silver (Ag), gallium (Ga); V is an interstitial addition element boron (B); 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.

[0008] More than 95 at% of calcium element generally exists in the precursor in the form of calcium oxide or calcium hydroxide.

[0009] The present invention proposes a new precursor structure design and supporting process. Using low-cost oxides such as iron oxide, cobalt oxide, and rare earth oxide as main raw materials and producing a precursor with a specific structure through a supporting process, and then efficiently producing high-performance spherical or near-spherical rare earth transition metal compound single crystal powder through a reduction - directional diffusion process, and conveniently controlling the diameter of magnetic powder particles within 0.5 - 10 microns. In addition, aiming at the deficiencies in performance such as the low coercivity of the single crystal powder prepared by the grinding process, the precursor in this application can also be used as an additive to convert the rare earth transition metal compound powder obtained by grinding into spherical single crystal magnetic powder through spheroidization treatment, so as to efficiently produce high-performance spherical or near-spherical rare earth transition metal compound single crystal magnetic powder; aiming at the deficiencies in the performance of some homogeneous alloy powders, the precursor in the present invention can also be used as a shell layer composition regulation additive, and through heat treatment, the effective elements in the composition regulation additive are transferred and enriched as beneficial elements in the product grain shell layer, so as to improve the performance by a smooth surface and enriched beneficial elements.

[0010] Preferably, different types of compounds are obtained by adjusting the proportion of effective elements of the precursor. The ratio d of the atomic numbers of a, b, c and the auxiliary element calcium to the atomic number of the rare earth element satisfies the conditions shown in Table 1 below:

[0011] Table 1

[0012] 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 > 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]]>

[0013] By adjusting the raw material ratio in the precursor to obtain the proportion of target effective elements, powders of single main phase compounds can be obtained, such as REFe 2 、RECo2 , 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.

[0014] The second object of the present invention is to provide a preparation method of the multifunctional precursor material, comprising the following steps:

[0015] S1. Using rare earth oxides, transition metal oxides or compounds, salts or metals that can decompose at high temperature to form effective element oxides that meet the purity and particle size requirements as the main raw materials, prepare a primary mixture. The primary mixture is a mixture composed of one or more oxides and composite oxides. The components of the effective elements except oxygen and inevitable impurity elements in atomic percentage are:

[0016] RE a1 TM 100-a1-b1-c1 M1 b1 V c1 (Formula - 2)

[0017] Wherein, RE is one or more of the rare earth elements lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), yttrium (Y) and scandium (Sc); TM is one or more of the elements iron (Fe) and cobalt (Co); M1 is one or more of the transition metals nickel (Ni), manganese (Mn), aluminum (Al), vanadium (V), titanium (Ti), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), tantalum (Ta), hafnium (Hf), copper (Cu), zinc (Zn), silver (Ag), gallium (Ga); V is the element boron (B); wherein, 7 ≤ a1 ≤ 50, 0 ≤ b1 < 15, 0 ≤ c1 < 10;

[0018] S2. Using the primary mixture that meets the particle size and phase structure requirements, transition metal oxides that meet the particle size requirements, and auxiliary materials as the main raw materials, prepare a secondary mixture;

[0019] S3. The secondary mixture is subjected to a reduction treatment to obtain a multi-functional precursor. The microstructure of the multi-functional precursor is that coarser transition metal particles are uniformly dispersed in a multi-phase matrix composed of ultra-fine particles such as rare earth oxides, rare earth-containing composite oxides, and calcium oxide. The coarser transition metal oxide particles are separated and embedded by the multi-phase matrix formed by the uniform mixing of various ultra-fine particles.

[0020] Preferably, the specific steps of step S1 are as follows: Using rare earth oxides and transition metal oxides that meet the purity and particle size requirements as the main raw materials, proportioning according to the effective element ratio specified in Formula-2, and calcining the uniformly mixed and dried mixture in air at 600°C - 1200°C for 1 - 10 hours to obtain a primary mixture. The primary mixture is a multi-phase mixture composed of various oxides and composite oxides, and the various oxides and composite oxide phases account for more than 95 wt% of the multi-phase mixture; or the specific steps of step S1 are as follows: Except for oxygen, carbon, nitrogen, and other inevitable impurity elements, alloy material powders with effective element ratios meeting the components specified in (Formula-1) or (Formula-2), and organic binder composite materials containing alloy powders. After these materials are scrapped, the organic impurities are removed, and then high-temperature calcination is carried out in air at 400°C - 1200°C to directly oxidize and decompose the organic matter, carbides, and nitrides. The calcination product forms a composite oxide that meets the effective element ratio and phase structure of the primary mixture, which is the primary mixture; existing in RETMO 3 、RE(TM,TM1)O 3 、RE 3 TM 5 O 12 、RE 3 (TM,TM1) 5 O 12 The rare earth elements in the form of composite oxides account for more than 50 at% of all rare earth elements in the primary mixture; the rare earth elements existing in RE 2 O 3 、REO 2 、REO 2 and other forms of oxides account for less than 50 at% of all rare earth elements in the primary mixture.

[0021] Further preferably, the rare earth elements existing in RETMO 3 、RE(TM,TM1)O 3 、RE 3 TM 5 O 12 or RE 3 (TM,TM1) 5 O 12 The rare earth elements in the form of composite oxides account for more than 80 at% of all rare earth elements in the primary mixture; existing in RE 2 O 3, REO 2 or REO 2 The rare earth elements in the form of oxides account for less than 20 at% of all rare earth elements in the primary mixture.

[0022] Preferably, the specific steps of step S2 are as follows: According to the proportion of active elements and auxiliary materials specified in formula -1, mix the primary mixture of one component or more than one component, re - crush and grind it into powder with a particle diameter of 50 - 10000 nm, add auxiliary materials containing auxiliary elements and mix evenly; the atomic number of the auxiliary element calcium is 0.5 - 20 times that of the RE element; or directly add transition metal oxide raw materials or salt solutions for precipitating corresponding elements that meet the requirements of the particle size of the secondary mixture on the basis of the primary mixture, so that the proportion of active elements and auxiliary materials meets the requirements of formula -1; calcine the dried secondary mixture in air at 500 °C - 1200 °C for 0.5 - 10 h, decompose calcium hydroxide or calcium carbonate in the secondary mixture into calcium oxide, and obtain a multiphase mixture composed of various oxides and composite oxides. These oxides and composite oxide phases account for more than 95 wt% of the multiphase mixture, and the active elements in the mixture except calcium, oxygen and impurity elements meet the proportion specified in formula -1.

[0023] Specifically, the preparation process of the precursor for producing spherical or near - spherical single - crystal powder of rare earth transition metal compounds can be divided into 3 steps: 1. Prepare the primary mixture with rare earth oxides and transition metal oxides that meet the requirements of purity and particle size as the main raw materials; 2. Prepare the secondary mixture with one or more primary mixtures that meet the requirements of particle size and phase structure, one primary mixture and transition metal oxides and auxiliary materials that meet the requirements of particle size as the main raw materials; 3. The secondary mixture becomes a multifunctional precursor for producing single - crystal powder of rare earth transition metal compounds after reduction treatment.

[0024] Raw material preparation. It includes 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:

[0025] 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 and hydroxides, such as ferrous oxide, magnetite, cobalt sesquioxide, cobalt spinel, iron 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 powder raw materials that are insoluble in water and can form oxides through calcination, such as carbonates, oxalates, and other water-insoluble salts. The poorly soluble transition metal raw materials are required to have a purity of 95.0 - 99.999 wt% and a particle diameter between 100 - 10,000 nm. 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. Ultra-fine transition metal or alloy powders with a particle diameter between 100 - 10,000 nm can also be used as raw materials. However, the ultra-fine metal powder itself is very expensive and has no cost advantage; in addition, the density of the metal powder is much higher than that of the oxide, and it is difficult to achieve a stable and uniform state during mixing.

[0026] The rare earth raw material can be added in the form of soluble salts with a purity of 99.0 wt% or more. The soluble salts include soluble inorganic salts such as nitrates, sulfates, and hydrochlorides of rare earth elements. Another way to add the rare earth raw material is industrial rare earth oxide with a purity of 99.0 wt% or more, and the particle diameter of the rare earth oxide is required to be between 10 - 1500 nm, preferably less than 300 nm.

[0027] Transition metal doping elements include one or more elements among (Ni), manganese (Mn), aluminum (Al), vanadium (V), titanium (Ti), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), tantalum (Ta), hafnium (Hf), copper (Cu), zinc (Zn), silver (Ag), and gallium (Ga). They can also be added in the form of oxides, and the particle diameter is required to be less than 300 nm, preferably less than 100 nm. These raw materials are required to have a purity of 99.0 wt% or more. One or more of the transition metal doping elements can also be added in the form of soluble salts, and the soluble salts include soluble inorganic salts such as nitrates, sulfates, and hydrochlorides of the above elements, and soluble organic salts such as formates and acetates.

[0028] The interstitial addition element boron can be directly added during batching in the form of boron oxide, boric acid, borate, ferroboron powder, etc. When added in a solid state, the particle diameter is required to be less than 200 nanometers. These raw materials are required to have a purity of 99.0 wt% or more.

[0029] Auxiliary materials, calcium oxide or calcium hydroxide or calcium carbonate, or a mixture of the three auxiliary materials. The particle diameter of the auxiliary materials calcium oxide or calcium hydroxide or calcium carbonate is less than 500 nm, preferably less than 300 nm; the auxiliary materials can also be other intermediate substances that can easily form calcium oxide and calcium hydroxide with a particle diameter less than 500 nm; the impurity content in the auxiliary materials is less than 3.0 wt%.

[0030] Chemical composition characteristics of the primary mixture: The primary mixture is a mixture composed of one or more oxides and complex oxides. The components of the effective elements except oxygen and impurity elements are expressed in atomic percentages as

[0031] RE a1 TM 100-a1-b1-c1 M1 b1 V c1 (Formula - 2)

[0032] where RE is one or more of the rare earth elements lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), yttrium (Y), and scandium (Sc); TM is one or more of the elements iron (Fe) and cobalt (Co); M1 is one or more of the transition metals nickel (Ni), manganese (Mn), aluminum (Al), vanadium (V), titanium (Ti), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), tantalum (Ta), hafnium (Hf), copper (Cu), zinc (Zn), silver (Ag), and gallium (Ga); V is the element boron (B); where 7 ≤ a1 ≤ 50, 0 ≤ b1 < 15, 0 ≤ c1 < 10.

[0033] S1. Preparation of the primary mixture: Using rare earth oxides and transition metal oxides that meet the purity and particle size requirements as the main raw materials, proportioning according to the ratio of effective elements specified in Formula - 2, and calcining the uniformly mixed and dried mixture in air at 600°C - 1200°C for 1 - 10 hours to obtain the primary mixture. In terms of raw material selection, when preparing the primary mixture, 90% - 100% of the transition metal elements iron and cobalt elements in the raw materials should be added in the form of water - insoluble solid powder raw materials, and the remaining part should be added in the form of soluble salts; the rare earth elements can be added in the form of water - insoluble solid powder raw materials, or part of them can be added in the form of soluble salts; the transition metal doping elements can be added in the form of water - insoluble solid powder raw materials, or part of them can be added in the form of soluble salts.

[0034] After calcination, the primary mixture becomes a multiphase mixture composed of various oxides and complex oxides. These oxide and complex oxide phases account for more than 95wt% of the multiphase mixture, and the effective elements in the mixture except oxygen and impurity elements meet the ratio specified in (Formula - 2).

[0035] The phases in the primary mixture after calcination can be divided into the following four categories:

[0036] The first category is the complex oxide phase formed by rare earth oxides and transition metal oxides, including but not limited to RETMO 3 、RE(TM,TM1)O3 , RE 3 TM 5 O 12 , RE 3 (TM, TM1) 5 O 12 , in these composite oxides, the rare earth elements account for more than 50 at% of all rare earth elements, preferably higher than 80 at%;

[0037] The second category is the incompletely reacted rare earth oxides, including but not limited to RE 2 O 3 , REO 2 , REO 2 , and these rare earth elements account for less than 50 at% of all rare earth elements, preferably lower than 20 at%;

[0038] The third category is the oxides of transition metals and transition metal doping elements, including but not limited to TMO, TM 2 O 3 , TM1 2 O 3 , (TM, TM1)O, (TM, TM1) 2 O 3 and other oxide phases of transition metals and transition metal doping elements;

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

[0040] In order to mix the raw materials evenly and facilitate full reaction, the mixing methods of each raw material in the primary mixture include the following 3 types:

[0041] Mixing method 1: When all raw materials are solid powders, the raw material powders that meet the requirements of particle diameter and purity are directly mechanically mixed evenly by using methods such as a high-intensity mixer and a ball mill.

[0042] Mixing method 2: When all raw materials are solid insoluble substances, water can also be added and mechanically mixed by using methods such as a high-intensity mixer, a ball mill, and a stirred mill. After mixing evenly, most of the water is separated by using equipment such as a filter press and a suction filter, and the mixture is dried by using a rotary kiln and a dryer; this method requires that the dissolution loss of each raw material in water is less than 1 wt%, and the total dissolution loss of all raw materials is less than 3 wt%.

[0043] Mixing method 3: When some raw materials are soluble salts, first use methods such as high-intensity mixers, ball mills, and stirred mills to mechanically mix the solid insoluble raw materials evenly in water; add the soluble raw materials into the ground and mixed slurry according to the proportions required by the formula and mix evenly. It is required that the total concentration of rare earth and transition metal elements in the soluble salts is lower than 4 mol / L, preferably lower than 2 mol / L; prepare a solution of the precipitant corresponding to the soluble salt with a concentration lower than 4 mol / L, preferably lower than 2 mol / L; use a stirrer to stir the slurry and drip in the precipitant solution, thereby precipitating the rare earth and transition metal elements in the slurry and evenly mixing them into the slurry; when there are both soluble rare earth and transition metal doping element raw materials, strong bases such as sodium hydroxide, potassium hydroxide, and calcium hydroxide can be used for precipitation; when there is only a soluble rare earth raw material, common rare earth precipitants such as oxalic acid, ammonium oxalate, ammonium bicarbonate, and urea can be used for precipitation; when using a low-solubility precipitant such as calcium hydroxide, the precipitant can be first added to the slurry, and then the soluble transition metal and rare earth salts can be prepared into a solution and dripped into the slurry; after precipitation, let it stand for 0 - 20 hours, use equipment such as filter presses and suction filters to separate most of the water, and use rotary kilns and dryers to dry the mixed material; this method requires that the total dissolution loss of all raw materials is less than 3 wt%.

[0044] Another preparation process for the primary mixed material: Obtain the primary mixed material in the form of recycled rare earth transition metal compound materials. Except for oxygen, carbon, nitrogen, and other impurity elements, alloy material powders with effective element ratios conforming to the compositions specified in (Equation - 1) or (Equation - 2), and organic binder composite materials containing alloy powders. After these materials are scrapped, most of the organic impurities are removed, and then high-temperature calcination is carried out in air at 400°C - 1200°C to directly oxidize and decompose the organic matter, carbides, and nitrides. The calcination products can form composite oxides that conform to the effective element ratio and phase structure of the primary mixed material. The composite oxides formed from these waste recyclables can also be directly used as the primary mixed material.

[0045] S2. Produce the secondary mixed material: Re-crush the primary mixed material, and form the secondary mixed material through adjusting the effective element ratio, adding auxiliary materials, and mixing evenly followed by calcination.

[0046] The preparation steps of the secondary mixed material are as follows: According to the effective element and auxiliary material ratios specified in (Equation - 1), mix one or more components of the primary mixed material, re-crush and grind it into powder with a particle diameter of 50 - 10000 nm, add auxiliary materials and mix evenly; the atomic number of calcium in the auxiliary materials is 10 - 160% of the transition metal element TM; calcine the dried secondary mixed material again in air at 500°C - 1200°C for 0.5 - 10 h to decompose calcium hydroxide or calcium carbonate in the secondary mixed material into calcium oxide.

[0047] The following methods can be used to adjust the proportion of effective elements: 1. Weigh one or more primary mixtures that meet the particle diameter requirements according to the proportion of effective elements specified in (Equation - 1), add auxiliary materials calcium oxide, calcium hydroxide, calcium carbonate, or three auxiliary materials in any proportion, and mix evenly; 2. Based on the primary mixture, directly add transition metal oxide raw materials that meet the particle size requirements of the secondary mixture according to the element proportion specified in (Equation - 1), add auxiliary materials calcium oxide, calcium hydroxide, calcium carbonate, or three auxiliary materials in any proportion, and mix evenly; 3. Based on the primary mixture, add transition metal oxide raw materials that meet the particle size requirements of the secondary mixture according to the element proportion specified in (Equation - 1), add auxiliary materials calcium oxide, calcium hydroxide, calcium carbonate, or three auxiliary materials in any proportion, mix evenly, titrate and add transition metal and rare earth element solutions, and continue to stir and mix evenly.

[0048] There are the following two methods for mixing the secondary mixture:

[0049] Mixing method 1: Directly mechanically dry - mix using methods such as a high - intensity mixer and a ball mill; Mixing method 2: Mechanically mix in water using methods such as a high - intensity mixer, a ball mill, and a stirred mill. After mixing evenly, separate most of the water and dry the mixture. The preferred method is wet - grinding and mixing in water.

[0050] The secondary mixture is a multiphase mixture composed of multiple oxides and composite oxides. These oxides and composite oxide phases account for more than 95 wt% of the multiphase mixture, and the effective elements in the mixture other than calcium, oxygen, and impurity elements meet the proportion specified in (Equation - 1).

[0051] The phases in the secondary mixture can be divided into the following five categories:

[0052] The first category: Oxides of transition metals and transition - metal - doped elements, including but not limited to oxides of TMO, TM 2 O 3 、TM1 2 O 3 、(TM,TM1)O、(TM,TM1) 2 O 3 and other forms of oxides of transition metals and transition - metal - doped elements;

[0053] The second category: Composite oxide phases formed by rare - earth oxides and oxides of transition metals and 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 , in these complex oxides, the rare earth elements account for more than 50 at% of all rare earth elements, preferably higher than 80 at%;

[0054] The third category, rare earth oxides, including but not limited to RE 2 O 3 , REO 2 , and these rare earth elements account for less than 50 at% of all rare earth elements, preferably lower than 20 at%;

[0055] The fourth category, complex oxides containing interstitial additive elements, including but not limited to REVO 3 , TMVO 3 , TM1VO 3 .

[0056] The fifth category, calcium oxide formed by the decomposition of auxiliary materials, 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 or one or more of these complex oxides, and these calcium-containing complex oxides account for less than 10 wt% of the precursor.

[0057] Microstructural characteristics of the secondary mixture: Coarser transition metal oxide particles are uniformly dispersed in a multiphase matrix composed of ultra-fine particles such as rare earth oxides, rare earth-containing complex oxides, and calcium oxide, and the coarser transition metal oxide particles are separated and embedded by the multiphase matrix formed by the uniform mixing of various ultra-fine particles. When part of the transition metal and transition metal doping elements are added in the form of solution-precipitation, or when transition metal raw materials with a particle diameter close to that of rare earth oxide particles are used in the preparation of the primary mixture, these transition metal elements will become ultra-fine metal oxide particles or form ultra-fine complex oxides with rare earths and enter the multiphase matrix.

[0058] S3. Calcination and reduction of the secondary mixture to form a multifunctional precursor for the production of rare earth transition metal compound powders.

[0059] The secondary mixture is reduced and the oxygen in the transition metal oxide is removed in a reducing gas such as hydrogen, methane, natural gas, or carbon monoxide at 500°C - 1000°C. After the reduction treatment is completed, the secondary mixed raw material is converted into a multifunctional precursor for producing rare earth transition metal compound powders. This precursor is a multiphase mixture composed of phases such as transition metals, rare earth oxides, and rare earth composite oxides. The effective elements in the mixture, excluding oxygen, calcium, and impurity elements, comply with the ratio specified in (Equation - 1).

[0060] The phases in the precursor can be classified into the following four categories:

[0061] The first category is the reduced transition metal elements, including but not limited to transition metal simple substances or alloy phases such as TM, TM1, and TM - TM1 alloys;

[0062] The second category is the unreduced rare earth oxides and composite oxide phases formed by rare earth oxides and transition metal oxides, including but not limited to RE 2 O 3 、REO 2 、RETMO 3 、RE(TM,TM1)O 3 、RE 3 TM 5 O 12 、RE 3 (TM,TM1) 5 O 12 ;

[0063] The third category is the composite oxides containing interstitial addition elements, including but not limited to REVO 3 、TMVO 3 、TM1VO 3 .

[0064] The fourth category is calcium oxide formed by the decomposition of auxiliary materials. Calcium oxide may also form one or more composite oxides such as 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 These calcium - containing composite oxides account for less than 5 wt% of the precursor. The above - mentioned metals, oxides, composite oxides, and calcium oxide phases account for more than 95 wt% of the precursor.

[0065] The microstructure of the multifunctional precursor material is inherited from the secondary mixed material and has the following characteristics: 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. The coarser transition metal oxide particles are separated and embedded by the multiphase matrix formed by the uniform mixing of various ultrafine particles. When part of the transition metal and transition metal doping elements are added in the form of solution-precipitation, or when transition metal raw materials with a diameter close to that of rare earth oxide particles are used in the preparation of the primary mixed material, these transition metal elements will become ultrafine metal particles or form ultrafine composite oxides with rare earths and enter the multiphase matrix.

[0066] When the precursor material with the above microstructure is used to prepare rare earth transition metal compound powder through reduction-diffusion treatment, the ultrafine particles of rare earth oxides and rare earth composite oxides that make up the matrix are also reduced to the metallic state by calcium, and at the same time, the reaction by-product calcium oxide is formed. However, various ultrafine metal particles in the matrix are embedded in the ultrafine calcium oxide particles and it is difficult to form a continuous or coarse-grained phase. Therefore, the metal atoms in the matrix can only diffuse directionally to the coarser transition metal particles and form the target compound with them. Since the larger transition metal grains in the precursor material are dispersed and embedded in the matrix, after the reduction-directional diffusion treatment, the finally formed is the single crystal powder of the compound and the by-product calcium oxide.

[0067] Similarly, when the precursor material with the above microstructure is used for the spheroidization treatment and the heat treatment for regulating the shell layer composition of the rare earth transition metal compound powder, the fine single crystal powder of the compound formed through the reduction-diffusion process is dispersed and embedded in the matrix and is difficult to grow. Under the action of surface energy, the Ostwald ripening process occurs, and the atoms on the fine grains diffuse to the coarse grains, thus completing the spheroidization of the powder and the regulation of the shell layer composition.

[0068] A third object of the present invention is to provide a spherical or near-spherical single-crystal powder of a rare-earth transition metal compound, which is prepared by a reduction-directional diffusion treatment. The specific steps for directly preparing the spherical or near-spherical single-crystal powder of the rare-earth transition metal compound by the reduction-directional diffusion treatment are as follows: Mix a multifunctional precursor with calcium particles, and perform a calcium thermal reduction treatment in a vacuum or inert atmosphere at 700°C - 1300°C for 0.5 - 10 hours. After the reduction-directional diffusion treatment, calcium oxide and spherical or near-spherical single-crystal particles of the rare-earth transition metal compound, i.e., RE-TM compound single-crystal particles, are obtained. The diameter of the spherical or near-spherical single-crystal particles of the rare-earth transition metal compound, i.e., RE-TM compound single-crystal particles, is 0.2 - 10 μm. The spherical or near-spherical single-crystal particles of the rare-earth transition metal compound, i.e., RE-TM compound single-crystal particles, are spherical or near-spherical, with complete grains and a smooth surface. The addition amount of calcium is determined by the oxygen content in rare-earth oxides or composite oxides and oxides of transition metal doping elements that cannot be reduced. The weight of the calcium particles should be 1.2 - 3.0 times the amount required for reducing the oxides. After the reduction-directional diffusion treatment, the product is calcium oxide and spherical or near-spherical single-crystal particles of the RE-TM compound. The inert atmosphere refers to inert gases such as Ar.

[0069] Method for controlling the particle size of spherical or near-spherical single-crystal powder of rare-earth transition metal compound: The particle diameter of the single-crystal powder of the transition metal compound can be made 0.2 - 10 μm and the microscopic morphology can be spherical or near-spherical by controlling the particle size of the raw material transition metal oxide of the prepared precursor, the temperature and time of reduction-directional diffusion.

[0070] Generally speaking, under the condition of the same 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 treatment is: (melting point of the target compound or peritectic reaction temperature in the equilibrium phase diagram) * 68% < reduction-directional diffusion treatment temperature < (melting point of the target compound or peritectic reaction temperature in the equilibrium phase diagram) * 95%. The treatment time of the reduction-directional diffusion process is 0.5 - 8 hours.

[0071] The following specifically describes the method for obtaining the target particle diameter of the single-crystal powder:

[0072] When the particle size of the target substance is < 1 μm, use a transition metal oxide raw material with an average particle diameter of 200 - 800 nm, and the reduction-directional diffusion temperature is (melting point of the target compound or peritectic reaction temperature in the equilibrium phase diagram) * 68% < reduction-directional diffusion treatment temperature < (melting point of the target compound or peritectic reaction temperature in the equilibrium phase diagram) * 75%;

[0073] When the target material 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 - oriented diffusion temperature is (the melting point of the target compound or the peritectic reaction temperature in the equilibrium phase diagram) * 75% < the reduction - oriented diffusion treatment temperature < (the melting point of the target compound or the peritectic reaction temperature in the equilibrium phase diagram) * 85%;

[0074] 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 - oriented diffusion temperature is (the melting point of the target compound or the peritectic reaction temperature in the equilibrium phase diagram) * 85% < the reduction - oriented diffusion treatment temperature < (the melting point of the target compound or the peritectic reaction temperature in the equilibrium phase diagram) * 90%;

[0075] When the target particle size is 4 - 10 μm, a transition metal oxide raw material with an average particle diameter of 800 - 7000 nm is used, and the reduction - oriented diffusion temperature is (the melting point of the target compound or the peritectic reaction temperature in the equilibrium phase diagram) * 90% < the reduction - oriented diffusion treatment temperature < (the melting point of the target compound or the peritectic reaction temperature in the equilibrium phase diagram) * 95%.

[0076] Or rather, 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.

[0077] In addition, the diameters of all raw material particles should be relatively uniform. The proportion of large particles with a diameter more 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 more than 5 times the average diameter should be less than 2% of the total volume of the raw materials, and there are no extra - large particles with a diameter more than 10 times the average diameter.

[0078] The fourth object of the present invention is to provide a spherical or near - spherical single - crystal powder of a rare - earth transition metal compound, and the target material is prepared by spheroidization treatment, which specifically includes the following steps:

[0079] S1. Mix the rare - earth transition metal compound powder with a particle diameter of 1 μm < particle diameter < 50 μm evenly with the multifunctional precursor powder as the spheroidization treatment aid. The addition amount of the spheroidization treatment aid is 5 - 50 wt% of the rare - earth transition metal compound powder, and the diameter of the transition metal particles in the spheroidization treatment aid is less than 1 / 2 of the particle diameter of the rare - earth transition metal compound powder;

[0080] S2. Heat-treat the mixture of the spheroidizing treatment aid, the corresponding rare-earth transition metal compound powder particles, and the metal calcium particles in a vacuum or an inert gas. The method for determining the heat-treatment temperature (absolute temperature) for spheroidization is: (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram) * 75% < spheroidizing heat-treatment temperature < (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram) * 95%. The spheroidizing heat-treatment time is 0.5 - 10 hours. The resulting product is spherical or near-spherical single-crystal rare-earth transition metal compound particles and by-product calcium oxide.

[0081] Preferably, the diameter of the transition metal particles is less than 1 / 5 of the diameter of the rare-earth transition metal compound powder particles.

[0082] The spheroidizing treatment process includes two steps: batching and mixing, and spheroidizing heat-treatment. Specifically:

[0083] S1. Batching and mixing: Mix the rare-earth transition metal compound powder evenly with the precursor powder of the spheroidizing treatment aid (the effective element ratio should match the compound type, specifically refer to Table 1 and Formula -1). The addition amount of the spheroidizing treatment aid is 5 - 50 wt% of the alloy powder. The spheroidizing process is applicable to rare-earth transition metal compound powders with 1 μm < particle diameter < 50 μm. Before batching, in order to facilitate uniform mixing and separate the alloy powder particles, it is necessary to match the particle sizes of various raw materials. The diameter of the transition metal particles in the spheroidizing treatment aid should be less than 1 / 5 of the diameter of the alloy powder particles.

[0084] The mixing methods include dry mixing and wet mixing. In dry mixing, directly mix the metal powder and the spheroidizing treatment aid evenly on mixing equipment such as a three-dimensional mixing tank, a high-intensity mixer, or a ball mill. In wet mixing, add a stable organic solvent that does not react with the raw materials, such as methanol, ethanol, heptane, or gasoline, to the spheroidizing treatment aid and the corresponding rare-earth transition metal compound powder particles, and then mix evenly on mixing equipment such as a three-dimensional mixing tank, a high-intensity mixer, or a ball mill. 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 being mixed evenly.

[0085] S2. Spheroidizing heat-treatment: Heat-treat the mixture of the spheroidizing treatment aid, the corresponding rare-earth transition metal compound powder particles, and the metal calcium particles in a vacuum or an inert gas. The method for determining the heat-treatment temperature (absolute temperature) for spheroidization is: (the melting point of the target compound or the peritectic reaction temperature in the equilibrium phase diagram) * 75% < spheroidizing heat-treatment temperature < (the melting point of the target compound or the peritectic reaction temperature in the equilibrium phase diagram) * 95%. The spheroidizing heat-treatment time is 0.5 - 10 hours.

[0086] Spheroidizing heat treatment effect: The product is single crystal particles of rare earth transition metal compounds in spherical or near-spherical shape and by-product calcium oxide. The single crystal particles with irregular shape, rough surface and edges are transformed into spherical or near-spherical single crystal powders with complete crystal grains and smooth surface.

[0087] The fifth object of the present invention is to provide a spherical or near-spherical single crystal powder of heterogeneous rare earth transition metal compounds, and to prepare the target substance by heat treatment with shell layer composition regulation, which specifically includes the following steps:

[0088] S1. Mix the multifunctional precursor powder as the composition regulation treatment aid evenly with the corresponding rare earth transition metal compound powder particles. The diameter of the rare earth transition metal compound powder particles meets the following conditions: 2 μm < particle diameter < 30 μm. The addition amount of the composition regulation treatment aid is 3-20 wt% of the rare earth transition metal compound powder. The diameter of the composition regulation treatment aid powder particles should be less than 1 / 10 of the alloy powder particles. Then add metal calcium particles to the evenly mixed material and mix evenly to obtain a mixture. The weight of the calcium particles is 1.2-3.0 times the amount required to reduce the oxide.

[0089] S2. Perform shell layer composition regulation heat treatment on the mixture in a vacuum or inert gas. The determination method of the shell layer composition regulation heat treatment temperature (absolute temperature) is: (melting point of the target substance or peritectic reaction temperature in the equilibrium phase diagram) * 65% < shell layer composition regulation heat treatment temperature < (melting point of the target substance or peritectic reaction temperature in the equilibrium phase diagram) * 85%. The heat treatment time is 0.5-5 hours. The product obtained is calcium oxide and spherical or near-spherical single crystal powder particles of heterogeneous rare earth transition metal compounds. The single crystal powder particles have complete crystal shape and smooth surface, and the shell layer is enriched with the effective metal elements in the composition regulation aid.

[0090] The shell layer composition regulation heat treatment process includes two steps: batching and mixing, and composition regulation heat treatment.

[0091] S1. Batching and mixing: Mix the precursor powder as the composition regulation treatment aid (the ratio of effective elements should match the compound type, specifically refer to Table 1 and Formula -1) evenly with the corresponding rare earth transition metal compound powder particles. The addition amount of the composition regulation treatment aid is 3-20 wt% of the alloy powder. The spheroidizing process is applicable to rare earth transition metal compound powders with 2 μm < particle diameter < 30 μm. Before batching, in order to facilitate uniform mixing and separate the alloy powder particles, it is necessary to match the particle sizes of the raw materials, that is, the diameter of the composition regulation treatment aid powder particles should be less than 1 / 10 of the alloy powder particles.

[0092] The mixing methods include dry mixing and wet mixing. In dry mixing, the metal powder and the composition-regulating treatment additives are directly mixed evenly on mixing equipment such as a three-dimensional mixing tank, a high-intensity mixer, and a ball mill. In wet mixing, stable organic solvents that do not react with the raw materials, such as methanol, ethanol, heptane, and gasoline, are added to the composition-regulating treatment additives and the corresponding rare-earth transition metal compound powder particles, and then they are mixed evenly on mixing equipment such as a three-dimensional mixing tank, a high-intensity mixer, and a ball mill. 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 for reducing the oxide. The wet mixture needs to be dried after being mixed evenly.

[0093] S2. Shell composition-regulating heat treatment: The mixture of the composition-regulating treatment additives, the corresponding rare-earth transition metal compound powder particles, and the metal calcium particles is subjected to shell composition-regulating heat treatment in a vacuum or an inert gas. The method for determining the temperature (absolute temperature) of the shell composition-regulating heat treatment is: (the melting point of the target compound or the peritectic reaction temperature in the equilibrium phase diagram) * 65% < the temperature of the shell composition-regulating heat treatment < (the melting point of the target compound or the peritectic reaction temperature in the equilibrium phase diagram) * 85%. The spheroidizing heat treatment time is 0.5 - 5 hours.

[0094] Application scenarios and effects of shell composition-regulating heat treatment: When the powder properties of the homogeneous composition are insufficient and the performance needs to be improved by regulating the surface composition of the powder particles. For example, for (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 results in insufficient coercivity. Through shell composition adjustment treatment, in (Sm 0.4 La 0.6 ) 2 Fe 17 N 3 , (Sm 0.4 Ce 0.6 ) 2 Fe 17 N 3Forming a samarium-rich shell on the magnetic powder can enhance the coercivity, or simultaneously form shells rich in both samarium and cobalt to enhance the coercivity as well as properties such as antioxidant and corrosion resistance. Through shell composition adjustment treatment, on high-lanthanum and cerium magnetic powders such as (Nd 0.4 Ce 0.6 ) 2 Fe 14 B, (Nd 0.4 La 0.6 ) 2 Fe 14 B, forming a Pr, Nd, Tb, Dy-rich shell can effectively enhance the coercivity of the magnetic powder. The product of the shell composition adjustment treatment is calcium oxide and single-crystal particles of spherical or near-spherical rare-earth transition metal compounds. The single-crystal particles with irregular shapes, rough surfaces, and sharp edges are transformed into near-spherical shapes, with relatively complete grains and smoother surfaces. At the same time, the effective elements in the composition control treatment aids are transferred and enriched as beneficial elements in the grain shells of the product, thereby enhancing the properties through the smooth surface and the enrichment of beneficial elements.

[0095] Atmosphere treatment of single-crystal powder: To control the performance characteristics of single-crystal powder, some compound powders need to be further subjected to atmosphere treatment to introduce interstitial atoms into the compound lattice. These compounds include but are not limited to the following types: samarium-based RE 2 (Fe,TM1) 17 compounds, praseodymium- and neodymium-based RE(Fe,TM1) 12 type compounds; these compounds need to be nitrided in an atmosphere containing nitrogen. Specifically, the material after reduction-directional diffusion treatment is nitrided in a nitrogen-containing gas such as high-purity nitrogen, nitrogen-hydrogen, nitrogen-ammonia, ammonia-hydrogen, etc. at 350 - 600 °C. After nitriding, the product consists 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 to be nitrided.

[0096] Separation of calcium oxide: The powders directly prepared by the reduction-directional diffusion process, the materials subjected to spheroidizing heat treatment, and the materials subjected to surface composition regulation treatment contain by-product calcium oxide. Deionized water or dilute acetic acid prepared with deionized water is required to remove the calcium oxide in the materials, so as to obtain spherical or near-spherical single-crystal powders of rare earth transition metal (RE-TM) compounds.

[0097] The sixth object of the present invention is to provide the application of the spherical or near-spherical single-crystal powders of rare earth transition metal compounds in the preparation of rare earth magnetic materials. The magnetic materials include permanent magnet powders, permanent magnet composite materials, soft magnetic powders, soft magnetic powder composite materials, magnetic wave absorbing materials, etc.

[0098] The present invention synthesizes single-crystal powders of rare earth transition metal compounds by a reduction diffusion process. The diffusion and 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 the metallic state in a reducing atmosphere such as hydrogen, and rare earth and other refractory oxides are reduced to metals by calciothermic reduction and form compounds with transition metals. A variety of atoms form compound grains through diffusion and migration, and the calcium oxide formed by calciothermic reduction has a certain isolation effect.

[0099] In order to produce spherical or near-spherical single-crystal powders of rare earth transition metal (RE-TM) compounds at low cost, stably, and efficiently, this application proposes a new structure-designed precursor and supporting preparation and application processes. Low-cost oxides such as iron oxide, cobalt oxide, and rare earth oxide are used as the main raw materials, and a multifunctional precursor with a complex-phase multi-level structure is produced through the supporting process, so as to be able to control the diffusion paths and directions of various atoms in the material, and at the same time form an effective isolation layer to effectively prevent the formed compound grains from sintering with each other to form polycrystalline particles. When directly synthesizing spherical or near-spherical single-crystal powders, performing spheroidizing treatment, and regulating the surface composition of single crystals through the precursor provided in this application, a reduction-directional diffusion treatment (Reduction-Directional Diffusion Process, hereinafter referred to as RDDP) is carried out, that is, the diffusion paths and directions of various elements during heat treatment are controlled through the structure design of the precursor.

[0100] The above belongs to a general process, which is not only applicable to the above-mentioned rare earth transition compounds, but also can be used to prepare transition metal single-element or alloy powders with a size of 0.2 - 10 μm; after replacing rare earth elements with elements such as Al, Si, Ti, Zr, Nb, V, Cr, etc., the corresponding 0.2 - 10 μm alloy powders or single-crystal powders can be prepared by the above method, such as alloy powder materials such as FeSiAl and FeSiCr as soft magnetic materials, Fe-Ti hydrogen storage alloy materials, RENi 5 type, RE 2 Ni 7Hydrogen storage materials, etc. Due to space limitations, this application only specifically describes typical Fe- and Co-based rare earth transition metal compounds.

[0101] Compared with the prior art, the present invention has the following advantages:

[0102] 1. In the present invention, the preparation of the precursor material mainly uses metal oxides or compounds and salts that can decompose to form metal oxides. The metal elements in the form of soluble salts are less than 30 at.% of all transition metal elements. Therefore, it can greatly reduce the salt-containing waste liquid generated by precipitation and save a large amount of precipitants; using oxides to largely replace soluble salts can also reduce the raw material cost. Therefore, using this process has the characteristics of low raw material cost and wide source, and has excellent environmental and economic benefits.

[0103] 2. In the present invention, the provided precursor material has a stable complex multi-phase structure. Therefore, the subsequent reduction and diffusion treatment process has the characteristics of simple operation, stability, and a wide process window; the directly prepared micron single crystal powder has the characteristics of a high single crystal ratio, easy control of the grain diameter, spherical or nearly spherical particles, and a smooth particle surface.

[0104] 3. In the present invention, the preparation process of the precursor material is formulated mainly by solid powder mixing and supplemented by chemical precipitation. A primary mixture of multiple components can be used to form the target formula (secondary mixture). Therefore, using this process has the advantages of low raw material cost, wide source, and strong raw material adaptability; at the same time, it has the characteristics of simple, efficient, stable, controllable, highly repeatable process operation, and easy realization of automated production.

[0105] 4. The precursor material provided by the present invention can be used as a spheroidizing treatment additive to convert the irregular rare earth transition metal compound powder obtained by grinding into regular spherical single crystal magnetic powder.

[0106] 5. Aiming at the insufficient performance of some homogeneous compound powders, the precursor material provided by the present invention can be used as a surface composition regulation treatment additive to form a specific element enrichment shell layer on the single crystal particles and improve related performance.

[0107] 6. The precursor material provided by the present invention and its application process have good universality, 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) 12Direct synthesis, spheroidization treatment and surface composition regulation of single crystal powders of such compounds.

[0108] 7. Since the single crystal powders provided by the present invention have the characteristics of high single crystal ratio, spherical or nearly spherical particles, and smooth surface, when using molding processes such as injection molding and magnetic field orientation molding to produce permanent magnetic composites, soft magnetic composites, and magnetic wave absorbing materials, they have the advantages of high compression density, easy orientation, high filling rate, good fluidity, and high magnetic properties. Description of the drawings:

[0109] Figure 1 XRD pattern of the primary mixture YCL1 in Example 1 after calcination at 900 °C for 3 hours;

[0110] Figure 2 XRD pattern of the secondary mixture ECL1-Ce0-2 in Example 1 after hydrogen reduction (precursor);

[0111] Figure 3 XRD pattern of the secondary mixture ECL1-Ce0-2 (precursor) in Example 1 after reduction diffusion and nitridation treatment;

[0112] Figure 4 Scanning electron microscope image of the sample ECL1-Ce0-2-RD in Example 1;

[0113] Figure 5 XRD pattern of the reS5 precursor in Example 3 after calcination treatment at 900 °C;

[0114] Figure 6 XRD pattern of the reS5 precursor in Example 3 after hydrogen reduction treatment;

[0115] Figure 7 Typical microscopic morphology image of the magnetic powder prepared from the precursor reS5 in Example 3;

[0116] Figure 8 XRD pattern of the secondary mixture ECL2-Ce0 in Example 4 after calcination treatment at 900 °C;

[0117] Figure 9 XRD pattern of the secondary mixture ECL2-Ce0 in Example 4 after hydrogen reduction treatment at 600 °C;

[0118] Figure 10 XRD pattern of the sample ECL2-Ce0-RD in Example 4 after reduction diffusion treatment;

[0119] Figure 11 Scanning electron microscope image of the sample ECL2-Ce0-RD in Example 4;

[0120] Figure 12 For the Sm before and after the spheroidization treatment in Example 5 2 Fe 17 Typical microscopic morphology images of the alloy powder, where: (a) Sm before the spheroidization treatment 2 Fe 17 Typical microscopic morphology images of the alloy powder, (b) Sm after the spheroidization treatment 2 Fe 17 Typical microscopic morphology images of the alloy powder;

[0121] Figure 13 For the (Sm 0.5 Ce 0.5 ) 2 Fe 17 Typical microscopic morphology images of the alloy powder shell layer before and after the composition regulation treatment in Example 6, where: (a) (Sm 0.5 Ce 0.5 ) 2 Fe 17 Typical microscopic morphology images of the alloy powder shell layer, (b) (Sm 0.5 Ce 0.5 ) 2 Fe 17 Typical microscopic morphology images of the alloy powder shell layer. Specific implementation manners:

[0122] The following examples are further illustrations of the present invention rather than limitations thereof.

[0123] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments and implementation manners of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. The following description of at least one exemplary instance is actually only illustrative and in no way serves as any limitation on the present invention or its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0124] The following describes the specific embodiments and technical effects.

[0125] Example 1: Preparation of single-crystal monodisperse powder of rare-earth transition metal compound (RE 2 Fe 17 N 3 ) using oxides as the main raw materials

[0126] Take industrial iron oxide with a purity of 99 wt%, ball-mill it into particles with a diameter between 100 - 1300 nm, d50 Powder with a wavelength of 830 nm; industrial samarium oxide and cerium oxide with a purity of 99.0 wt%, ball-milled into particles with a diameter between 100 - 600 nm, d 50 Powder with a wavelength of 320 nm. The above raw materials are proportioned into a primary mixture according to the ratio shown in Table 2 and mixed evenly using a ball mill. Then, the mixture is calcined at 900 °C for 3 hours. The calcined primary mixture is re-crushed and ground into particles with a diameter of 100 - 2000 nm, d 50 = 800 nm. The ground primary mixture and the auxiliary material calcium oxide are proportioned into a secondary mixture according to the ratio shown in Table 3. After wet-mixing evenly using a ball mill, most of the water is separated using a suction filtration device, and the mixture is dried in a dryer. The dried secondary mixture is calcined again in air at 800 °C for 2 h; the oxygen in iron oxide is removed from the calcined secondary mixture in a reducing gas hydrogen at 600 °C to form a precursor material. The precursor material is mixed with calcium particles, and the addition amount of calcium is 8.6 wt% of the precursor material, and reduction diffusion treatment is carried out in argon at 950 °C - 1180 °C for 2 hours.

[0127] Nitriding treatment, the (Sm,Ce) 2 Fe 17 The material is nitrided in a mixed gas of high-purity ammonia gas (2V) and hydrogen gas (1V) at 430 °C for 3 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 near-spherical (Sm,Ce) 2 Fe 17 N 3 Single crystal powder. Table 4 shows the magnetic properties of the powders obtained after reduction diffusion and nitriding treatment of a series of precursor material samples. After the powder samples are mixed with resin and subjected to magnetic field orientation and curing treatment at 1.5 T, and magnetization treatment at 3 T, the demagnetization curve is tested. The magnetic energy product (BH) max Refers to the maximum magnetic energy product at the theoretical density.

[0128] Comparing the ECL1-Ce0-RD, ECL1-Ce0.2-RD, ECL1-Ce0.4-RD, and ECL1-Ce0.6-RD samples, it can be seen that by matching the primary mixture, the (Sm,Ce) 2 Fe 17The samarium content in the compound was adjusted to obtain samples with different magnetic properties. Comparing the samples ECL1-Ce0-1-RD, ECL1-Ce0-2-RD, ECL1-Ce0-3-RD, and ECL1-Ce0-4-RD, it was found that appropriately increasing the auxiliary materials helped to increase the single-crystal ratio of the magnetic powder, thereby improving the remanence and squareness of the magnetic powder by increasing the orientation degree, and obtaining powders with high magnetic energy product. Comparing the samples ECL1-Ce0-5-RD, ECL1-Ce0-6-RD, ECL1-Ce0-7-RD, and ECL1-Ce0-8-RD, it was found that increasing the reduction diffusion temperature helped to obtain powders with high magnetic energy, but the coercivity decreased due to grain growth; conversely, reducing the reduction diffusion temperature decreased the grain size of the magnetic powder, which helped to increase the coercivity, but the single-crystal ratio of the powder decreased and the remanence was lower.

[0129] Table 2. Batch formula of the primary mixture

[0130]

[0131] Table 3. Batch formula of the secondary mixture

[0132]

[0133]

[0134] Table 4. Magnetic properties of the samples

[0135]

[0136] Figures 1 - 3 The phase structures of the primary mixing state, precursor state, and reduction diffusion-nitriding state of typical samples are shown. Figure 1 The XRD pattern of the YCL1 mixture after calcination at 900 °C for 3 hours is shown, indicating that the mixture is composed of Fe2O3 and SmFeO3 phases. Figure 2 The XRD pattern of the secondary mixture ECL1-Ce0-2 after hydrogen reduction (precursor) is shown, indicating that the precursor is composed of α-Fe, CaO, and SmFeO 3 phases. Figure 3 The XRD pattern of the precursor after reduction diffusion and nitriding treatments is shown, indicating that the mixture is composed of Sm 2 Fe 17 N 3 and CaO phases. Figure 4 The scanning electron microscope image of the sample ECL1-Ce0-2-RD is shown, indicating that the prepared Sm 2 Fe 17 N 3 magnetic powder is composed of single-crystal particles, the powder particles are spherical or nearly spherical, the grains are complete, and the surface is smooth.

[0137] Example 2: Preparation of Sm using oxide raw materials and insoluble rare earth salts as the main raw materials 2 Fe 17 N 3 single crystal monodisperse powder

[0138] Take 1.56 kg of industrial iron oxide with a purity of 97 wt%, and ball-mill it into a powder with a particle diameter between 100 - 1500 nm and d50 = 760 nm; take 1 kg of industrial samarium oxalate decahydrate with a purity of 99.5 wt% and ball-mill it into a powder with a particle diameter between 100 - 500 nm and d50 = 300 nm. Mix the above raw materials evenly using a ball mill, and then calcine the mixture at 900 °C for 5 hours. Crush and grind the calcined primary mixture again into particles with a diameter of 100 - 2000 nm and d 50 = 760 nm. Mix 0.65 kg of calcium hydroxide and the finely ground primary mixture into a secondary mixture. After wet-mixing evenly using a ball mill, use equipment such as a suction filter to separate most of the water, dry the mixture in a dryer, and then calcine the dried secondary mixture in air at 800 °C for 2 h to decompose the calcium hydroxide in the secondary mixture into calcium oxide; remove the oxygen in the iron oxide in the reducing gas hydrogen at 650 °C from the calcined secondary mixture. Mix the reduced secondary mixture evenly with 0.4 kg of calcium particles, and divide the mixture into 5 equal parts. The 5 parts of the mixture are subjected to calcium thermal reduction treatment in argon at 980 °C - 1150 °C for 3 hours. Nitridation treatment, after crushing the material subjected to reduction diffusion treatment, nitride it in a mixed gas of high-purity ammonia gas (2V) and hydrogen gas (1V) at 430 °C for 3 hours. After nitridation treatment, use deionized water and dilute acetic acid prepared from deionized water to wash and remove calcium oxide, thereby obtaining spherical or nearly spherical Sm 2 Fe 17 N 3 single crystal powder. Table 5 shows the magnetic properties of the samples.

[0139] Table 5. Magnetic properties of the samples

[0140]

[0141] Example 3: Preparation of Sm using transition metal oxides, soluble iron salts, and soluble rare earth salts as the main raw materials 2 Fe 17 N 3 single crystal monodisperse powder.

[0142] In order to synthesize Sm 2 Fe 17 compound, prepare the precursor materials according to Table 6. Ball-mill industrial iron oxide with a purity of 99 wt% in water into a powder with a particle diameter between 100 - 1500 nm and d50 Powder with a wavelength of 745 nm. Industrial samarium oxide with a purity of 99 wt% is ball-milled in water to a particle diameter between 100 - 1500 nm, and d 50 Powder with a wavelength of 378 nm. According to the quality specified in Table 6, the two oxides are placed together in a container filled with 5 liters of deionized water. According to the quality specified in Table 6, industrial samarium nitrate hexahydrate and iron nitrate decahydrate with a purity of 99.9 wt% are taken and added to the oxide slurry. A stirrer is used to mix the slurry containing the oxides and nitrates evenly and keep stirring. Sodium hydroxide is prepared into an aqueous solution with a concentration of 2 mol / L and is dropped into the continuously stirred slurry according to the addition amount specified in Table 6. After continuous stirring for 2 hours, the water is filtered off and deionized water is added again to wash away the by-product sodium nitrate from the precipitation reaction. The above mixture is dried and calcined in air at 900 °C for 3 hours, and the calcined mixture is broken again into a powder with an average particle diameter of 878 nanometers (primary mixture).

[0143] 3 L of water is added to the crushed powder, and then 0.56 kg of calcium hydroxide with an average particle diameter of 300 nm is added to each slurry, and then stirring is continued for more than 2 hours to mix the slurry evenly. The mixture is separated from most of the water using a suction filtration machine, and the mixture is dried in a dryer. The dried mixture is calcined again in air at 750 °C for 2 h (secondary mixture); the oxygen in iron oxide is removed from the calcined mixture in a reducing gas of hydrogen at 600 °C (precursor material for reduction diffusion treatment).

[0144] The reduced mixture is mixed evenly with 0.46 kg of calcium particles and subjected to calcium thermal reduction treatment in argon at 1085 °C for 2 hours. Nitridation treatment, the material after reduction diffusion treatment is nitrided in a mixed gas of high-purity ammonia gas (2V) and hydrogen gas (1V) at 430 °C for 6 hours. After nitridation treatment, calcium oxide is washed away using deionized water and dilute acetic acid prepared from deionized water to obtain spherical or near-spherical Sm 2 Fe 17 N 3 single crystal powder. Table 7 shows the magnetic properties of the samples.

[0145] As can be seen from Table 6, as the amount of nitrate used decreases, the precipitant sodium hydroxide and the by-product sodium nitrate also gradually decrease. As can be seen from Table 7, by reducing the amount of soluble salts, high-performance magnetic powder can still be prepared. Figure 5 The XRD pattern of the reS5 precursor material after calcination treatment at 900 °C is shown, indicating that the mixture consists of Fe 2 O 3 、SmFeO 3 phases. Figure 6Shows the XRD pattern of the reS5 precursor after hydrogen reduction treatment, indicating that the mixed material consists of α-Fe, CaO, and SmFeO 3 phases. Figure 7 Shows a typical microscopic morphology image of the magnetic powder prepared from the reS5 precursor, indicating that the prepared Sm 2 Fe 17 N 3 magnetic powder consists of single crystal particles, the powder particles are spherical or nearly spherical, the crystal grains are complete, and the surface is smooth.

[0146] Table 6. Ingredient list of raw materials and production of precipitation by-products (mass unit, kg) for synthesizing 1 kg of Sm 2 Fe 17 compound

[0147]

[0148] Table 7. Magnetic properties of the samples

[0149]

[0150] Example 4: Preparation of single crystal monodisperse powder of rare earth transition metal compound (RECo 5 )

[0151] Take industrial cobalt oxide (CoO) with a purity of 99 wt%, and ball mill it into a powder with a particle diameter between 100 - 1500 nm and d50 = 740 nm; industrial samarium oxide and cerium oxide with a purity of 99.0 wt%, and ball mill them into a powder with a particle diameter between 100 - 1000 nm and d50 = 260 nm. Mix the above raw materials into a primary mixture according to the ratio shown in Table 8, and use a ball mill to mix them evenly. Then, calcine the mixture at 900 °C for 3 hours.

[0152] Redefragment and grind the calcined primary mixture into particles with a particle diameter of 100 - 2000 nm and d 50 = 845 nm. Mix the finely ground primary mixture and the auxiliary material calcium oxide into a secondary mixture according to the ratio shown in Table 9. After wet mixing evenly with a ball mill, use equipment such as a suction filter to separate most of the water, dry the mixture in a dryer, and then calcine the dried secondary mixture in air at 800 °C for 2 h; remove the oxygen in iron oxide from the calcined secondary mixture in a reducing gas hydrogen at 600 °C (the precursor that can be directly used for reduction diffusion treatment). Mix the precursor with calcium particles, and the addition amount of metallic calcium is 7.4 wt% of the secondary mixture. Perform calcium thermal reduction treatment in argon at 1200 °C for 2 hours. Wash and remove calcium oxide using deionized water and dilute acetic acid prepared from deionized water, thereby obtaining spherical or nearly spherical (Sm,Ce)Co5 Single crystal powder. Table 10 shows the magnetic properties of a series of samples.

[0153] Figures 8 - 10 The phase structures of primary mixing state, secondary mixing-hydrogen reduction state, and reduction diffusion state of typical samples are displayed. Figure 8 The XRD pattern of the secondary mixture ECL2-Ce0 after calcination at 900℃ is shown, showing that the mixture is composed of CoO, SmCoO 3 Phase composition. Figure 9 The XRD pattern of the secondary mixture ECL2-Ce0 after hydrogen reduction at 600℃ is shown, showing that the precursor is composed of Co, CaO and Sm 2 O 3 Phase composition. Figure 10 The XRD pattern of the sample ECL2-Ce0-RD after reduction diffusion treatment is shown, showing that the sample is composed of SmCo 5 , CaO phase composition. Figure 11 The SEM image of the sample ECL2-Ce0-RD after reduction diffusion treatment is shown, showing that the prepared SmCo 5 The magnetic powder is mainly composed of single crystal particles, the powder particles are spherical or nearly spherical, the grains are complete and the surface is smooth.

[0154] Table 8. Ingredients of primary mixture

[0155]

[0156] Table 9. Secondary Mixture Ingredients

[0157]

[0158] Table 10. Magnetic properties of samples

[0159]

[0160]

[0161] Example 5: Preparation of Sm using transition metal oxides as main raw materials 2 Fe 17 The alloy powder is spheroidized and heat treated to prepare single crystal and monodisperse powder.

[0162] In order to synthesize Sm 2 Fe 17 The spheroidizing agent for alloy powder is prepared according to Table 11. Industrial iron oxide with a purity of 99 wt% is ball-milled in deionized water to form d 10 =133nm, d 50 =368nm, d 90ultrafine powder with an equivalent spherical diameter of 475 nm (obtained by laser particle size analysis). Industrial samarium oxide with a purity of 99 wt% was ball-milled in water to obtain ultrafine powders with d 10 = 96 nm, d 50 = 243 nm, d 90 = 337 nm (equivalent spherical diameter obtained by laser particle size analysis). According to the masses specified in Table 11, two oxides and calcium hydroxide were placed together in a container filled with 5 L of deionized water. Industrial samarium nitrate hexahydrate and ferric nitrate decahydrate with a purity of 99.9 wt% were taken according to the masses specified in Table 4 and made into a 2 mol / L aqueous solution. The soluble salt solution was dropped into the slurry while stirring continuously. After stirring for 2 hours, the water was filtered off, and the mixed material was dried in a dryer. The dried mixed material was calcined in air at 930 °C for 2 h to obtain a primary mixed material.

[0163] The primary mixed material was ground and crushed to obtain fine powders with d 10 = 586 nm, d 50 = 973 nm, d 90 = 1327 nm. In each portion of the material, 0.45 kg of calcium hydroxide with an average particle diameter of 300 nm and 5 L of deionized water were added. After mixing evenly, the water was filtered off and dried. The dried mixed material was calcined in air at 840 °C for 2 h to obtain a secondary mixed material. The oxygen in iron oxide was removed from the secondary mixed material in a reducing gas of hydrogen at 600 °C to obtain a spheroidizing agent. XRD testing showed that the PT1 spheroidizing agent was composed of α-Fe, CaO, and SmFeO 3 phase, and the PT6 spheroidizing agent was composed of α-Fe, CaO, and Sm 2 O 3 phase.

[0164] The Sm 2 Fe 17 alloy cast sheet was crushed into a powder with d 50 = 2840 nm using a jet mill. Six portions of the alloy powder, each weighing 1 kg, were taken. In each portion of the alloy powder, 0.35 kg of the spheroidizing agent and 0.07 kg of calcium particles with a particle diameter of 3 mm were added. The mixture was added to a ball mill tank, 1.5 kg of steel balls were added, and then the mixture was dry-mixed evenly in a ball mill. The mixture was spheroidized in argon at 900 °C for 1.0 hour. For nitriding treatment, the spheroidized material was nitrided in a mixed gas of high-purity ammonia gas (2V) and hydrogen gas (1V) at 445 °C for 6 hours. After nitriding treatment, calcium oxide was washed away using deionized water and dilute acetic acid prepared with deionized water to obtain spherical or near-spherical Sm 2 Fe 17 N 3Single crystal powder. Table 12 shows the magnetic properties of the samples before and after spheroidization. As can be seen from Table 12, through the spheroidization treatment, the remanence of the magnetic powder slightly decreases, while the coercivity significantly increases.

[0165] From the comparison in Table 12, it can be known that all 6 kinds of spheroidization treatment aids can prepare Sm 2 Fe 17 N 3 single crystal powder. Figure 12 (a) shows the typical microscopic morphology image of the Sm 2 Fe 17 alloy powder before spheroidization treatment. It can be seen that the powder shape is irregular and has a large number of sharp edges and corners, which is not conducive to obtaining high coercivity. Figure 12 (b) shows the typical microscopic morphology image of the Sm 2 Fe 17 alloy powder after spheroidization treatment. It can be seen that the powder shape is regular, the surface is smooth and complete, which is very conducive to obtaining high coercivity and facilitating good fluidity during injection molding.

[0166] Table 11. Ingredient list of raw materials used for the spheroidization treatment agent of the synthesized Sm 2 Fe 17 alloy powder (mass unit, kg)

[0167]

[0168] Table 12. Magnetic properties of the samples before and after spheroidization

[0169]

[0170] Example 6: Preparation of a shell composition regulating additive with transition metal oxides as the main raw material and preparation of (Sm, Ce) 2 Fe 17 N 3 heterogeneous single crystal powder.

[0171] In order to synthesize the shell composition regulating additive, the ingredients are prepared according to Table 13. The industrial iron oxide with a purity of 99 wt% is ball-milled in deionized water into ultrafine powders with d 10 = 124 nm, d 50 = 323 nm, d 90 = 459 nm (equivalent sphere diameter obtained by laser particle size test). The industrial samarium oxide with a purity of 99 wt% is ball-milled in water into d 10 = 98 nm, d 50 = 235 nm, d 90Ultrafine powder with an equivalent spherical diameter of 367 nm (obtained by laser particle size analysis). According to the quality specified in Table 13, put the two oxides and calcium hydroxide together into a container containing 5 liters of deionized water; take industrial samarium nitrate hexahydrate and ferric nitrate decahydrate with a purity of 99.9 wt%, and prepare an aqueous solution with a concentration of 2 mol / L. Drop the soluble salt solution into the slurry under continuous stirring. After continuously stirring for 2 hours, filter out the water and dry it. Calcinate the dried mixture in air at 930 °C for 2 h to obtain a primary mixture. Remove the oxygen in iron oxide from the calcined mixture in a reducing gas of hydrogen at 600 °C to obtain a shell composition regulating additive.

[0172] Grind and crush the primary mixture into fine powder with d 10 = 365 nm, d 50 = 759 nm, d 90 = 935 nm. Add 0.40 kg of calcium hydroxide with an average particle diameter of 300 nm and 5 L of deionized water to each portion of the material. After mixing evenly, filter out the water and dry it. Calcinate the dried mixture in air at 840 °C for 2 h to obtain a secondary mixture. Remove the oxygen in iron oxide from the secondary mixture in a reducing gas of hydrogen at 600 °C to obtain a shell composition regulating additive. XRD test shows that the shell composition regulating additives of QC1-QC6 are composed of α-Fe, CaO and SmFeO 3 phase or composed of α-Fe, CaO and Sm 2 O 3 phase, and QC7 is composed of α-Fe, CaO, SmFeO 3 and CeO 2 phase.

[0173] Take 7 portions of (Sm 50 Ce 0.4 ) 0.6 ) 2 Fe 17 alloy powder with d 2 = 2880 nm, 1 kg for each portion. Add 0.35 kg of shell composition regulating additive and 0.07 kg of calcium particles with a particle diameter of 3 mm to each portion of the alloy powder respectively. Put the mixture into a ball milling tank, add 1.5 kg of steel balls, and then mix evenly in a ball mill. Carry out spheroidization treatment on the mixture in argon at 820 °C for 1.0 hour. Carry out nitriding treatment. Nitride the material after spheroidization treatment in a mixed gas of high-purity ammonia gas (2V) and hydrogen gas (1V) at 445 °C for 6 hours. After nitriding treatment, wash and remove calcium oxide with deionized water and dilute acetic acid prepared from deionized water, so as to obtain near-spherical (Sm,Ce) 17 Fe 3 N

[0174] Table 14 shows the magnetic properties of the samples before and after the shell composition regulation treatment. As can be seen from Table 14, through the shell composition regulation treatment, the remanence of the magnetic powder slightly decreases, while the coercivity significantly increases. From the comparison in Table 14, it can be known that compared with the original powder, all 7 shell composition regulation additives can improve the coercivity of the single-crystal powder, and the coercivity of the powder treated with QC1-QC6 additives increases significantly. Figure 13 (b) shows (Sm,Ce) before the shell composition regulation treatment 2 Fe 17 The typical microscopic morphology image of the alloy powder shows that the powder shape is irregular and has a large number of sharp edges and corners, which is not conducive to obtaining high coercivity. Figure 13 (b) shows (Sm,Ce) after the shell composition regulation treatment 2 Fe 17 The typical microscopic morphology image of the alloy powder shows that the powder shape is regular, the surface is smooth and complete, which is very conducive to obtaining high coercivity and facilitating good fluidity during injection molding. Using an electron microscope combined with an energy spectrometer for testing, it can be known that the Sm content on the surface of the powder treated with QC1-QC6 additives is 14-32% higher than that at the powder center, while the sample treated with the QC7 additive with the same Sm / Ce atomic ratio as the original magnetic powder has a uniform composition, and no samarium-rich element shell can be detected. Therefore, the coercivity of the powder treated with QC1-QC6 additives is higher than that of the sample treated with the QC7 additive. The sample treated with the QC7 additive also has a near-spherical and smooth surface, so its coercivity is also improved compared with the original powder.

[0175] Table 13. Ingredient list of raw materials for synthesizing shell composition regulation additives (mass unit, kg) Table 14. Magnetic properties of the magnetic powder samples before and after the shell composition regulation treatment

[0176]

[0177]

[0178] Example 7: Preparation of single-crystal monodisperse powder of rare earth transition metal compound (RE 2 Fe 17 N 3 ).

[0179] Take industrial samarium oxide and iron oxide with a purity of 99.0 wt%, and conduct primary mixture batching according to Table 15. Use a ball mill to mix the two oxides evenly and grind them into a diameter between 100-400 nm, d 50Powder with a size of 243 nm, and then the mixture was calcined at 900 °C for 5 hours to obtain a primary mixture. XRD tests showed that all of the primary mixtures consisted of Fe 2 O 3 , SmFeO 3 phases, only with different proportions. The primary mixture was re-crushed and ground into particles with a particle diameter of 100 - 500 nm and a d50 = 436 nm. The secondary mixture was formulated according to Table 15. The ground primary mixture, iron oxide, and auxiliary material calcium oxide were formulated into the secondary mixture according to the proportions shown in Table 3. The d 50 of iron oxide was 1.56 μm, and the d 50 of the auxiliary material calcium oxide was 358 nm. After being wet-mixed evenly using a ball mill, most of the water was separated using a suction filtration device, and the mixture was dried in a dryer. The dried secondary mixture was calcined again in air at 800 °C for 2 h. XRD tests showed that the secondary mixture consisted of Fe 2 O 3 , SmFeO 3 and CaO. The oxygen in the iron oxide of the calcined secondary mixture was removed in a reducing gas hydrogen at 600 °C to form a precursor. XRD tests showed that the precursor consisted of α-Fe, CaO, and SmFeO 3 phases. The precursor was mixed with calcium particles, and the addition amount of calcium was 8.6 wt% of the precursor. Reduction diffusion treatment was carried out in argon at 1050 °C for 2 hours. The Sm 2 Fe 17 material after reduction diffusion treatment was nitrided in a mixed gas of high-purity ammonia gas (2V) and hydrogen gas (1V) at 430 °C for 3 hours. After nitriding treatment, calcium oxide was washed and removed using deionized water and dilute acetic acid prepared with deionized water, thereby obtaining spherical or nearly spherical Sm 2 Fe 17 N 3 single crystal powder. XRD tests showed that the material after nitriding consisted of CaO and Sm 2 Fe 17 N 3 phases. Table 16 shows the magnetic properties of the powders obtained from a series of precursor samples after reduction diffusion, nitriding treatment, and cleaning and separation. After the powder samples were mixed with resin and subjected to magnetic field orientation at 1.5 T and curing treatment, the demagnetization curve test was carried out after magnetization treatment in a 3 T magnetic field. The magnetic energy product (BH) max listed in Table 16 refers to the maximum magnetic energy product under the theoretical density.

[0180] Table 15. Raw material formulation table for preparing spherical Sm 2 Fe 17 single crystal magnetic powder (mass unit, g)

[0181]

[0182] Table 16. Magnetic properties of samarium-iron-nitrogen samples

[0183]

[0184]

[0185] The above embodiments illustrate that through the precursor materials described in the present application, not only can high-performance rare-earth transition metal compound permanent magnet materials be directly prepared, but these precursor materials can also be used for the spheroidization treatment of alloy powders and the regulation of shell layer composition, and near-spherical magnetic powders with good magnetic properties, complete and regular grains, and smooth surfaces can be obtained. These permanent magnet materials can be applied to the manufacture of high-performance bonded permanent magnet materials.

[0186] Since the chemical properties of rare-earth elements are similar, and the chemical properties of transition metal elements such as iron and cobalt are also similar, they can often replace each other in rare-earth transition metal compounds. Therefore, by adjusting the types of elements and the ratio of rare-earth / transition metal elements in the precursor materials, different types of compounds can be obtained. So, the method proposed in the present application belongs to a general process and can be used for the direct synthesis of 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 and other types of spherical or near-spherical single-crystal powders of rare-earth transition metal compounds. These powders can be applied to magnetic composite materials such as permanent magnets and soft magnets.

[0187] Since the single-crystal magnetic powder particles prepared through the precursor materials described in the present invention are spherical or near-spherical and have smooth surfaces, when 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 absorption materials, etc., they have the advantages of high compression density, easy orientation, high filling rate, good fluidity, and high magnetic properties during the production of bonded magnets by forming processes such as magnetic field orientation injection molding and magnetic field orientation compression molding.

Claims

1. A multifunctional precursor material, characterized in that, The precursor material is a multiphase complex containing calcium. In addition to oxygen, the auxiliary element calcium, and inevitable impurity elements, the precursor material further includes effective elements capable of forming rare earth transition metal compounds. The components of the effective elements expressed in atomic percentage are RE a TM 100-a-b-c M1 b V c (Equation - 1) wherein, 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 addition element boron; 7 < a < 40, 0 ≤ b < 15, 0 ≤ c < 10, and the atomic number of the auxiliary element calcium is 0.5 - 20 times that of the RE element.

2. The multifunctional precursor material according to claim 1, characterized in that, different types of compounds are obtained by adjusting the proportion of effective elements of the precursor material, and the ratios d of a, b, c and the atomic number of the auxiliary element calcium to the atomic number of the rare earth element satisfy the conditions shown in Table 1 below: Table 1 3. A method for preparing the multifunctional precursor material according to claim 1 or 2, characterized in that, comprises the following steps: S1. Using rare earth oxides, transition metal oxides or compounds, salts or metals that can be decomposed at high temperature to form effective element oxides that meet the purity and particle size requirements as the main raw materials, prepare a primary mixture. The primary mixture is a mixture composed of one or more oxides and composite oxides. The components of the effective elements except oxygen and inevitable impurity elements in atomic percentage are: RE a1 TM 100-a1-b1-c1 M1 b1 V c1 (Formula - 2) wherein, 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 iron and cobalt; M1 is one or more of the transition metals nickel, manganese, aluminum, vanadium, titanium, chromium, zirconium, niobium, molybdenum, tungsten, tantalum, hafnium, copper, zinc, silver, gallium; V is the boron element; wherein, 7 ≤ a1 ≤ 50, 0 ≤ b1 < 15, 0 ≤ c1 < 10; S2. Using the primary mixture that meets the particle size and phase structure requirements, transition metal oxides that meet the particle size requirements, and auxiliary materials as the main raw materials, prepare a secondary mixture; S3. The secondary mixture is subjected to a reduction treatment to obtain the multifunctional precursor material. The microstructure of the multifunctional precursor material is that coarser transition metal particles are uniformly dispersed in a multiphase matrix composed of rare earth oxides, rare earth-containing composite oxides, and ultrafine calcium oxide particles, and the coarser transition metal oxide particles are separated and embedded by a multiphase matrix formed by uniform mixing of various ultrafine particles.

4. The method for preparing the multifunctional precursor material according to claim 3, characterized in that, The specific steps of step S1 are as follows: Using rare earth oxides and transition metal oxides that meet the requirements of purity and particle size as the main raw materials, proportioning according to the effective element ratio specified in formula - 2, and calcining the uniformly mixed and dried mixture in air at 600°C - 1200°C for 1 - 10 hours to obtain a primary mixture. The primary mixture is a multiphase mixture composed of multiple oxides and composite oxides, and the multiple oxides and composite oxide phases account for more than 95 wt% of the multiphase mixture; or the specific steps of step S1 are as follows: Except for oxygen, carbon, nitrogen, and other inevitable impurity elements, alloy material powders with effective element ratios conforming to the components specified in (formula - 1) or (formula - 2), and organic binder composite materials containing alloy powders. After these materials are scrapped, organic impurities are removed, and then high-temperature calcination is carried out in air at 400°C - 1200°C to directly oxidize and decompose the organic matter, carbides, and nitrides. The calcination product forms a composite oxide that meets the effective element ratio and phase structure of the primary mixture, which is the primary mixture; existing in RETMO 3 、RE(TM,TM1)O 3 、RE 3 TM 5 O 12 or RE 3 (TM,TM1) 5 O 12 The rare earth elements in the form of composite oxides account for more than 50 at% of all rare earth elements in the primary mixture, preferably higher than 80 at%; the rare earth elements existing in RE 2 O 3 、REO 2 or REO 2 The rare earth elements in the form of oxides account for less than 50 at% of all rare earth elements in the primary mixture, preferably less than 20 at%.

5. The method for preparing the multifunctional precursor material according to claim 3, characterized in that, The specific steps of step S2 are as follows: According to the effective element and auxiliary material ratio specified in formula -1, mix the primary mixture of one or more components, re - crush and grind it into a powder with a particle diameter of 50 - 10000 nm, add auxiliary materials containing auxiliary elements and mix evenly, where the atomic number of the auxiliary element calcium is 0.5 - 20 times that of the RE element; or directly add transition metal oxide raw materials or salt solutions for precipitating corresponding elements that meet the particle size requirements of the secondary mixture on the basis of the primary mixture, so that the ratio of effective elements and auxiliary materials meets the requirements of formula -1; calcine the dried secondary mixture in air at 500 °C - 1200 °C for 0.5 - 10 h to decompose calcium hydroxide or calcium carbonate in the secondary mixture into calcium oxide, obtaining a multiphase mixture composed of various oxides and composite oxides, and these oxide and composite oxide phases account for more than 95 wt% of the multiphase mixture, and the effective elements in the mixture except calcium, oxygen and impurity elements meet the ratio specified in formula -1.

6. A spherical or near - spherical single - crystal powder of rare - earth transition metal compound, which is prepared by reduction - directional diffusion treatment, and is specifically prepared by the following steps: Mix the multifunctional precursor material described in claim 1 or 2 with calcium particles, and carry out calcium - thermal reduction treatment in a vacuum or inert atmosphere at 700 °C - 1300 °C for 0.5 - 10 hours. After the reduction - directional diffusion treatment, spherical or near - spherical RE - TM compound single - crystal particles of calcium oxide and rare - earth transition metal compound are obtained as the target substances. The diameter of the spherical or near - spherical RE - TM compound single - crystal particles of rare - earth transition metal compound is 0.2 - 10 μm, and the spherical or near - spherical RE - TM compound single - crystal particles of rare - earth transition metal compound are spherical or near - spherical.

7. The spherical or near - spherical single - crystal powder of rare - earth transition metal compound according to claim 6, characterized in that, when the particle size of the target substance is < 1 μm, use transition metal oxide raw materials with an average particle diameter of 200 - 800 nm, 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 particle size of the target substance is 1 - 2 μm, use transition metal oxide raw materials with an average particle diameter of 300 - 1500 nm, 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 particle size of the target substance is 2 - 4 μm, use transition metal oxide raw materials with an average particle diameter of 500 - 3000 nm, 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 particle size of the target substance is 4 - 10 μm, a transition metal oxide raw material with an average particle diameter of 800 - 7000 nm is used, and the reduction - oriented diffusion temperature is such that (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram) * 90% < reduction - oriented 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 near - spherical single - crystal powder of a rare - earth transition metal compound, characterized in that the target substance is prepared by spheroidization treatment, which specifically includes the following steps: S1. Mix uniformly a rare - earth transition metal compound powder with 1 μm < particle diameter < 50 μm and the multifunctional precursor powder described in claim 1 or 2 as a spheroidization treatment aid. The addition amount of the spheroidization treatment aid is 5 - 50 wt% of the rare - earth transition metal compound powder, and the transition metal particle diameter in the spheroidization treatment aid is less than 1 / 2 of the particle diameter of the rare - earth transition metal compound powder; S2. Perform spheroidization heat treatment on the mixture of the spheroidization treatment aid, the corresponding rare - earth transition metal compound powder particles, and metal calcium particles in a vacuum or inert gas. The method for determining the spheroidization heat treatment temperature (absolute temperature) is: (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram) * 75% < spheroidization heat treatment temperature < (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram) * 95%, and the spheroidization heat treatment time is 0.5 - 10 hours. The obtained product is spherical or near - spherical single - crystal particles of a rare - earth transition metal compound and by - product calcium oxide.

9. A spherical or near - spherical single - crystal powder of a heterogeneous rare - earth transition metal compound, characterized in that a spherical or near - spherical single - crystal powder of a heterogeneous rare - earth transition metal compound is prepared by shell - layer composition - regulated heat treatment, which specifically includes the following steps: S1. Mix uniformly the multifunctional precursor powder described in claim 1 or 2 as a composition - regulation treatment aid with the corresponding rare - earth transition metal compound powder particles. The particle diameter of the rare - earth transition metal compound powder satisfies the following conditions: 2 μm < particle diameter < 30 μm. The addition amount of the composition - regulation treatment aid is 3 - 20 wt% of the rare - earth transition metal compound powder, and the particle diameter of the composition - regulation treatment aid powder should be less than 1 / 10 of the alloy powder particle diameter; then add metal calcium particles to the uniformly - mixed material and mix evenly to obtain a mixture. The weight of the calcium particles is 1.2 - 3.0 times the amount required to reduce the oxide; S2. Perform shell - layer composition - regulated heat treatment on the mixture in a vacuum or inert gas. The method for determining the shell - layer composition - regulated heat treatment temperature (absolute temperature) is: (the melting point of the target substance or the peritectic reaction temperature in the equilibrium phase diagram) * 65% < shell - layer composition - regulated heat treatment temperature < (the 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. The obtained product is calcium oxide and spherical or near - spherical single - crystal powder particles of a heterogeneous rare - earth transition metal compound. The single - crystal powder particles have a complete crystal form, a smooth surface, and the shell is enriched with the effective metal element in the composition - regulation aid.

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

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