A rare earth permanent magnet powder with a TbCu7 structure and its preparation method

Abstract

This invention discloses a rare-earth permanent magnet powder with a TbCu7 structure and its preparation method. The TbCu7 structured rare-earth permanent magnet powder has an Sm... 1‑a Zr a Fe 9‑y‑z‑r Co y Ti z D r M x The preparation method involves using ultrasonic spray thermal decomposition or chemical co-precipitation to prepare spherical composite oxides from soluble metal salts, followed by reduction treatment at a certain temperature, and finally, high-temperature heating to control the introduction of nitrogen or carbon elements into the unit cell. The resulting magnetic powder is predominantly composed of the SmFe9 phase, effectively controlling the Th2Zn content. 17 Sm2Fe 17 The generation of impurity phases is controlled by the process optimization of this invention, resulting in magnetic powder with controllable morphology and particle size, while reducing rare earth loss, which has significant industrial value.

Description

Technical Field

[0001] This invention relates to the field of magnetic materials technology, specifically to a rare earth permanent magnet powder with a TbCu7 structure and its preparation method. Background Technology

[0002] Rare earth permanent magnet materials are known for their high coercivity (H cj ) and maximum energy product (BH) max Rare earth permanent magnets (REEs) have become core functional materials in modern industry and new energy technologies. Among existing rare earth permanent magnet systems, samarium iron nitrogen (Sm-Fe-N) materials have attracted much attention due to their excellent temperature stability and low rare earth content. Specifically, TbCu7-type SmFe9N... x Due to its high remanence (Br) and high magnetocrystalline anisotropy (Ha), this phase has become a hot research topic. Its intrinsic magnetic properties are comparable to those of currently advanced Nd₂Fe₃. 14 Comparable to B-type magnetic materials, its theoretical magnetic energy product can reach over 30 MGOe (see: Journal of Applied Physics, 1993, Vol.73, Issue 10, pp.6488-6490), and it exhibits more stable coercivity at high temperatures. Furthermore, the production process requires less heavy rare earth elements, resulting in greater economic and resource utilization advantages.

[0003] However, TbCu7-type SmFe9 is a thermodynamically metastable phase, and under conventional preparation conditions, it readily forms Th2Zn. 17 Sm2Fe 17 The presence of thermodynamically stable phases such as the α-Fe impurity phase greatly reduces the phase purity and magnetic properties of the material.

[0004] To prepare metastable phases, traditional methods such as melting and spinning and mechanized alloying methods all employ increasing the spinning speed to obtain thermodynamically metastable TbCu7-SmFe9 phases under non-equilibrium conditions. While widely used, these methods still face several technical challenges: First, because the melting point of iron (1538 ℃) is much higher than that of samarium (1072 ℃), a large amount of samarium volatilizes during melting, making it difficult to control the composition ratio. Second, to stabilize the metastable phase, it is often unavoidable to add elements other than Sm and Fe, making it difficult for the elements to be uniformly distributed during alloy melting, and high-temperature melting easily causes component segregation and grain coarsening. Third, to achieve a non-equilibrium state, the spinning speed needs to be above 40 m / s, placing high demands on the equipment. Fourth, traditional methods all require subsequent crushing, such as ball milling, to achieve the appropriate particle size. However, crushing can cause oxidation and irregular shapes, affecting the subsequent nitrogen absorption process. If the particle size is too large, nitrogen absorption is incomplete; if the particle size is too small, it is difficult to prepare and easily oxidized, ultimately leading to a significant decrease in magnetic properties.

[0005] To address the aforementioned issues, some reported studies have proposed new processes. For example, patent CN118280713A significantly improves the difficulty of nitrogen absorption after ball milling in traditional processes by precisely controlling the rapid quenching speed and the sequence of nitrogen absorption followed by crystallization. However, problems such as high-temperature volatilization of samarium still exist, and its nitrogen absorption process requires 4-6 hours of high-pressure treatment, while the spinning belt rotation still requires high speed, which limits its application to a certain extent. Summary of the Invention

[0006] The first objective of this invention is to address the shortcomings of existing technologies by providing a rare earth permanent magnet powder with a TbCu7 structure and its preparation method.

[0007] In a first aspect, the present invention provides a rare-earth permanent magnet powder having a TbCu7 structure, wherein the chemical composition of the permanent magnet powder is Sm 1-a Zr a Fe 9-y-z-r Co y Ti z D r M x Where a is 0.05~0.2, y is 1.0~1.7, z is 0.05~0.3, r is 0.05~0.5; x is 0.5~2.7, D ​​is Ni or V, and M is N or C.

[0008] Preferably, the diameter of the permanent magnet powder is 0.2-10 μm.

[0009] Secondly, the present invention provides a method for preparing rare earth permanent magnet powder with a TbCu7 structure, the method comprising the following steps:

[0010] Soluble metal salts are classified according to Sm 1-a Zr a Fe 9-y-z-r Co y Ti z D r Dissolve in stoichiometric proportions and stir until homogeneous to form a precursor solution;

[0011] Near-spherical composite oxide precursor particles with a size of 0.2-3 μm are generated from the precursor solution by spray pyrolysis or chemical coprecipitation.

[0012] The composite oxide precursor particles are reduced by segmented temperature control and uniform diffusion between elements is achieved to generate SmFe9 alloy.

[0013] SmFe9 alloy was subjected to high-temperature infiltration treatment of interstitial atoms M to obtain reduction products in which interstitial atoms M were introduced at specific interstitial positions of the unit cell.

[0014] The reduction product was purified to obtain SmFe9N with a TbCu7 structure. x Permanent magnet powder.

[0015] Preferably, the spray pyrolysis method involves generating small droplets from the precursor solution through ultrasonic spraying, and then carrying out a thermal decomposition reaction in a tube furnace under the transport of a carrier gas to obtain spherical composite oxide precursor particles.

[0016] Preferably, the chemical coprecipitation method involves mixing the precursor solution and the precipitant to carry out a coprecipitation reaction; after precipitation, stirring is continued, and the mixture is kept warm in a water bath to promote grain maturation; after maturation, the precipitate is centrifuged and dried to obtain spherical composite oxide precursor particles.

[0017] Preferably, the ratio of the sum of the number of Fe, Co, Ti, and D atoms to the number of Sm and Zr atoms in the precursor solution is 8 to 10;

[0018] Preferably, the reduction process of the composite oxide precursor particles by segmented temperature control is divided into three temperature stages:

[0019] First stage: Dehydration and pre-reduction reaction by heating at 200-600 ℃;

[0020] Second stage: Main reduction is carried out by adding a reducing agent at 700-900 ℃;

[0021] The third stage: constant temperature annealing at 1000-1200 ℃ promotes the diffusion of Sm elements and the formation of TbCu7 phase.

[0022] Preferably, the reducing agent is a strong reducing agent.

[0023] Preferably, the strong reducing agent is an active elemental metal or an ionic metal hydride, wherein the active elemental metal is one of calcium, sodium, and potassium, and the amount added is 1.8-3.5 times the molar ratio of calcium to potassium (Sm); the ionic metal hydride is CaH2, and the amount added is 1.0-2.0 times the molar ratio of CaH2 to potassium (Sm).

[0024] Preferably, the gas source is a nitrogen source or a carbon source, and the temperature is maintained in the range of 300-400 °C for 2-5 h, with a gas flow rate of 0.2-0.4 L / min.

[0025] The beneficial effects of this invention are at least as follows:

[0026] (1) This invention employs elemental doping combined with spray pyrolysis or chemical co-precipitation, avoiding the large-scale volatilization of Sm and the uneven distribution of various metal elements during high-temperature melting. It eliminates the need for traditional high-speed spinning and supercooling non-equilibrium phase formation processes, solving the problems of traditional methods requiring ball milling, excessively large powder sizes hindering nitriding, and excessively small powder sizes leading to oxidation. This yields TbCu7 structured rare-earth permanent magnet powder with precisely controllable dimensions and a near-spherical morphology. Elemental doping involves replacing Sm with Zr and Fe atoms with Ti, Co, V, or Ni. Multi-level synergistic stabilization of the metastable TbCu7 phase is achieved through the co-doping of Zr, Ti, Co, and Ni / V elements. First, the Zr atomic radius (1.6 Å) is slightly smaller than Sm (1.8 Å), causing lattice distortion after doping, optimizing the c / a axis ratio, and suppressing isomeric Th2Zn. 17 Type Sm2Fe 17 First, the formation of the TbCu7 phase; second, the Ti element enhances the uniformity of the alloy structure by refining the grains and improving the crystal orientation distribution; third, the introduction of Co-Ni / Co-V optimizes the electronic structure and surface state, creating favorable conditions for low-temperature nitrogen absorption. This multi-element synergistic stabilization mechanism significantly improves the success rate of TbCu7 phase preparation both thermodynamically and kinetically.

[0027] (2) The present invention directly produces near-spherical precursors by spray pyrolysis or chemical coprecipitation, which effectively solves the problems of powder defects and oxidation caused by subsequent crushing in traditional processes. The particle size can be precisely controlled within the range of 0.2-3 μm, making the powder easy to absorb nitrogen under low temperature conditions.

[0028] (3) Based on the low-temperature nitrogen absorption process of ammonia / hydrogen precise adjustment, this invention achieves rapid and low-temperature nitrogen absorption at 300-400 ℃ for 2-5 hours, with nitrogen content controlled at 15-20 at%, which is twice as efficient as the nitrogen absorption process of traditional permanent magnet materials (400-500 ℃), while the Sm volatilization rate is < 5 at. Attached Figure Description

[0029] Figure 1 This is a flowchart of the experimental process of the present invention.

[0030] Figure 2 The morphology comparison of products obtained at different stages in the embodiments of the present invention is shown in (a) SEM image of the spherical oxide precursor obtained by spray thermal decomposition, and (b) morphology image of the final alloy powder with TbCu7 structure.

[0031] Figure 3The morphology comparison of products with different elemental compositions prepared in the embodiments of the present invention is shown in (a) XRD pattern of SmFe9-based alloy with TbCu7 structure, (b) XRD pattern of product with added Ti, (c) XRD pattern of product with added Ti and Ni, and (d) XRD pattern of product with added Ti and V. Detailed Implementation

[0032] As mentioned above, in view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention, the main basis of which includes at least the following:

[0033] (1) In this invention, to stabilize the TbCu7-type SmFe9-based alloy, Zr is used to replace the position of Sm, and Ti, Co, V, and Ni are used to replace the position of Fe atoms. Multi-level synergistic stabilization of the TbCu7 metastable phase is achieved through the co-doping of Zr, Ti, Co, and Ni / V elements. The atomic radius of Zr (1.6 Å) is slightly smaller than that of Sm (1.8 Å), and the doping causes lattice distortion, optimizing the c / a axis ratio and suppressing isomeric Th2Zn. 17 Type Sm2Fe 17 Phase formation; Ti element enhances the uniformity of alloy structure by refining grains and improving crystal orientation distribution; the introduction of Co-Ni / Co-V optimizes electronic structure and surface state, creating favorable conditions for low-temperature nitrogen absorption.

[0034] (2) In this invention, the combination of spray pyrolysis or chemical coprecipitation with reduction diffusion avoids the problem of large-scale volatilization of Sm and uneven distribution of various metal elements during high-temperature smelting. It does not require the traditional high-speed belt spinning undercooling non-equilibrium phase formation process, and solves the problems of ball milling required by traditional methods, powder size that is too large to be nitrided, and oxidation when the size is too small. It can prepare TbCu7 type SmFe9 based alloy with a size of 0.55 micrometers and near-spherical particles, so that the samarium iron alloy grains are complete.

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0036] At least one embodiment provides a rare-earth permanent magnet powder with a TbCu7 structure, a diameter of 0.2-10 μm, and a composition of Sm. 1-a Zr a Fe 9-y-z-r Co y Ti z D r M xWhere a is 0.05~0.2, y is 1.0~1.7, z is 0.05~0.3, r is 0.05~0.5; x is 0.5~2.7, D ​​is Ni or V, and M is N or C.

[0037] At least one embodiment provides a method for preparing the above-mentioned rare earth permanent magnet powder with a TbCu7 structure, comprising the following steps:

[0038] A method for preparing rare-earth permanent magnet powder with a TbCu7 structure is disclosed, which eliminates the need for traditional high-speed spinning and supercooling processes to obtain TbCu7 structured rare-earth permanent magnet powder with precisely controllable dimensions and near-spherical morphology. The innovative process and elemental doping synergistically optimize the powder preparation process and final performance, significantly shortening the preparation cycle while effectively suppressing samarium volatilization loss during preparation. The method includes the following steps:

[0039] Step (1): Mix the soluble metal salts of Fe, Zr, Co, Ti, Ni or V and Sm elements according to Sm 1-a Zr a Fe 9-y-z- r Co y Ti z D r The stoichiometric ratios are mixed and dissolved in water, and stirred until homogeneous to form a precursor solution. For example, the stirring time is 30-60 min, preferably 30-40 min.

[0040] In one embodiment, the ratio of the sum of Fe, Co, Ti, and D atoms to the number of Sm and Zr atoms in the precursor solution is 8 to 10, preferably 8.5 to 9.5. Within this range, the α-(Fe,Co) soft magnetic phase and Th2Zn can be most effectively reduced. 17 Sm2Fe 17 Mutually.

[0041] In one embodiment, the soluble metal salt is preferably a nitrate or an organometallic salt. The nitrate system exhibits optimal solubility and thermal decomposition characteristics under current process conditions. Its concentration is preferably 1.5–2.5 mol / L, within which the atomization effect and decomposition efficiency of the solution achieve the best balance.

[0042] Step (2): The precursor solution is subjected to spray pyrolysis or chemical coprecipitation to generate near-spherical composite oxide precursor particles with a size of 0.2-3 μm.

[0043] If the oxide precursor is prepared using ultrasonic spray pyrolysis, the precursor solution is ultrasonically sprayed to generate small droplets, which are then thermally decomposed in a tube furnace under the transport of a carrier gas to obtain spherical composite oxide precursor particles. Specifically, the prepared precursor solution is added to a container equipped with an ultrasonic atomizer, and fine droplets are formed under the action of high-frequency ultrasound at 0.5-10 MHz. Ultrasonic atomization at 1.5–2.5 MHz is preferred for spray pyrolysis, as this produces droplets with a uniform particle size distribution (CV < 15%). These atomized particles are transported into the tube furnace for pyrolysis under the transport of a carrier gas (one or more of air, nitrogen, argon, or helium) at a flow rate of 2-20 L / min. The tube furnace employs a three-stage temperature control system: the front zone is maintained at 300-400℃ to rapidly dehydrate the droplets; the central zone is heated to 800-1000℃ to promote salt decomposition and oxidation reactions; and the final zone is maintained at 800-1000℃ to ensure the complete formation of uniformly sized composite oxide particles (0.5-8μm), promoting the oxidative transformation of the precursor. The reaction products are enriched in a collector at the end of the furnace and then transferred to an oven to dry at 80℃ for 12-24 hours.

[0044] If the oxide precursor is prepared by chemical coprecipitation, the precursor solution and the precipitant are stirred and mixed to carry out the coprecipitation reaction. After precipitation, stirring is continued, and the mixture is kept warm in a water bath to promote crystal maturation. After maturation, the precipitate is centrifuged and dried to obtain spherical composite oxide precursor particles. Specifically, the prepared precursor solution is slowly added dropwise at a rate of 1-5 mL / min to a continuously stirred ammonia-oxalic acid composite precipitant (ammonia concentration 1-3 mol / L, oxalic acid to metal ion molar ratio 1.2:1), maintaining the reaction system temperature at 50±5℃ and the pH value in the range of 3.5-4.5. Alternatively, NH3·H2O with pH=9 can be used, with the stirring rate maintained at 300-600 rpm to ensure the pH value is stable in the range of 8-10. After precipitation, aging is continued for 2-4 hours to promote crystal transformation. Subsequently, the precipitate is separated using a vacuum filtration device and washed sequentially with deionized water and anhydrous ethanol until the conductivity of the filtrate is <50 μS / cm. The obtained oxide precursor was placed in a vacuum drying oven at 130℃ for 24 hours and finally ball-milled and sieved to obtain a composite oxide precursor powder with uniform particle size distribution (D50=1-3 μm) and uniform chemical composition.

[0045] Step (3): The composite oxide precursor particles are reduced by segmented temperature control and uniform diffusion between elements is achieved to generate SmFe9 alloy.

[0046] The reduction process under segmented temperature control in a hydrogen atmosphere consists of three temperature stages:

[0047] The first stage involves dehydration and pre-reduction at 200-600 °C. For example, the oxide precursor is placed in an atmosphere furnace, and the furnace is repeatedly evacuated three times at room temperature to remove all oxygen. Then, the furnace is heated to 500-600 °C, and a flowing H2 atmosphere is introduced at a flow rate of 0.3-2 L / min for reduction. Reduction is carried out for 1-5 hours to obtain the pre-reduced product. The effectiveness of hydrogen reduction depends on the hydrogen reduction temperature and time. Higher reduction temperatures and longer times result in more complete reduction of iron-based oxides such as iron oxide and samarium iron oxide. Incomplete reduction will increase the amount of metal used in subsequent active metal reduction treatments.

[0048] The second stage involves adding a reducing agent at 700-900 °C for primary reduction. For example, after the hydrogen reduction product is thoroughly mixed with the reducing agent, it is placed in a crucible. The crucible is then placed in an atmosphere furnace, and the furnace is repeatedly evacuated three times at room temperature to remove all oxygen. The temperature is then raised to 700-900 °C to allow the reduction reaction to proceed slowly.

[0049] The reducing agent is a strong reducing agent. For example, the strong reducing agent is an active elemental metal or an ionic metal hydride, wherein the active elemental metal is one of calcium, sodium, and potassium, and the amount added is 1.8-3.5 times its molar ratio to Sm; the ionic metal hydride is CaH2, and the amount added is 1.0-2.0 times its molar ratio to Sm.

[0050] The third stage: After the main reduction is completed, the atmosphere furnace is directly heated to 1000-1200 ℃ and annealed at a constant temperature for 10-30 min to promote the diffusion of Sm elements and the formation of the TbCu7 metastable phase. During this process, the reduced samarium elements migrate in gaseous form and adsorb on the surface of iron particles, and enter the iron lattice through diffusion, ultimately forming a samarium-iron based alloy with uniform composition.

[0051] Step (4): The SmFe9 alloy is subjected to high-temperature infiltration treatment of interstitial atoms M to obtain a reduction product in which interstitial atoms M are introduced at specific interstitial cell positions.

[0052] The high-temperature infiltration treatment uses a nitrogen or carbon source gas, maintained at a temperature range of 300-400 °C for 2-5 hours, with a gas flow rate of 0.2-0.4 L / min. For example, the nitrogen source is ammonia or an ammonia / hydrogen mixture. The carbon source is methane or ethane gas.

[0053] The nitrogen absorption temperature is preferably 330–380 °C. Within this range, sufficient nitrogen diffusion is ensured without causing decomposition of the SmFe9 phase. The nitrogen absorption time is preferably 3–4 h to ensure uniform distribution of nitrogen atoms within the intercellular spaces. The gas flow rate is preferably 0.25–0.35 L / min to guarantee sufficient gas exchange within the reactor.

[0054] Step (5): The reduction product is purified to obtain SmFe9N with a TbCu7 structure. x Permanent magnet powder. Specifically, the reduction product is repeatedly washed with deionized water and dilute acetic acid solution until the pH of the supernatant reaches neutral. Then, residual water is removed by 3-4 displacement washings with an organic alcohol solvent. Finally, it is dried in a vacuum environment at 20-80℃ to obtain high-purity SmFe9N with a TbCu7 structure. x Permanent magnet powder.

[0055] The above experimental procedure is as follows: Figure 1 As shown.

[0056] The present invention will be further described below with reference to specific embodiments, but the methods and technical parameters involved in the solution should not be construed as limitations on the present invention.

[0057] Examples 1-3:

[0058] (1) First, based on the atomic ratio of Ti, according to Sm 0.85 Zr 0.15 Fe 7.1 Co 1.8 Ti 0.1、 Sm 0.85 Zr 0.15 Fe 7.0 Co 1.8 Ti 0.2、 Sm 0.85 Zr 0.15 Fe 6.9 Co 1.8 Ti 0.3The stoichiometric ratios were as follows: a 0.15 mol / L nitrate solution was prepared, comprising: ① Ti content 0.1: (93.5 mL Sm(NO3)3, 15 mL Zr(NO3)4, 710 mL Fe(NO3)3, 180 mL Co(NO3)2, and 10 mL TiCl3 solution); ② Ti content 0.2: (700 mL Fe(NO3)3 solution and 20 mL TiCl3 solution, the rest being the same as ①); ③ Ti content 0.3: (690 mL Fe(NO3)3 solution and 30 mL TiCl3 solution, the rest being the same as ①). The solution was thoroughly mixed and transferred to an ultrasonic atomization system. In the spray pyrolysis device, a tubular furnace heating program was set with a heating rate of 10 °C / min, a front-end temperature of 300 °C, a middle section temperature of 800 °C, and a rear-end temperature of 800 °C. After the heating process is complete, the atomizing device is turned on, and micron-sized droplets are generated using 1.5MHz high-frequency vibration. These droplets are then transported to a tube furnace with a three-stage temperature control using air at a flow rate of 15L / min. To ensure continuous atomization, the atomizing device is equipped with automatic liquid replenishment, adding 20mL of liquid every 10 minutes. Once the solution is atomized, the ultrasonic atomizer is turned off, the heating process of the tube furnace is stopped, and the furnace is shut down after the temperature inside the furnace drops to room temperature. The sprayed product, namely the spherical oxide precursor, is then collected in the filter funnel at the rear end.

[0059] The SEM image of the spherical oxide precursor is as follows: Figure 2 As shown in (a).

[0060] (2) The collected powder was placed in a collection bottle and dried in an oven at 90°C for 12 hours. 1g of the collected oxide powder was weighed, spread evenly in a small porcelain boat, and then placed in a tube furnace. The furnace was repeatedly evacuated three times to ensure no oxygen residue remained. The reaction was carried out in a flowing H2 atmosphere at 600°C for 4 hours to obtain a pre-reduction product. 1g of the pre-reduction product was weighed, and 0.2g of metallic calcium granules were added. The two were thoroughly mixed and placed in a crucible, then placed in a tube furnace. The furnace was repeatedly evacuated three times to ensure no oxygen residue remained. The reaction was carried out in a flowing Ar atmosphere at 850°C for 3 hours, followed by annealing at 1050°C for 20 minutes. At this point, TbCu7 type SmFe9 alloy powder was prepared, and 0.2g of the sample was taken out for testing. Then, the sample was nitrided at 350°C for 3 hours. The atmosphere in the tube furnace was a mixture of ammonia and hydrogen in a 1:1 ratio, with a gas flow rate of 0.4 L / min. After the reaction, samples were taken using a glove box. The obtained powder was allowed to cool to room temperature before being placed in a mortar and mixed with deionized water. The mixture was then ground and washed until no obvious calcium particles remained. Next, it was washed three times with an acetic acid solution (pH approximately 5.5), followed by three more washes with deionized water, ensuring the washing solution pH was approximately 7. Finally, it was washed three times with anhydrous ethanol to remove water from the powder surface. The cleaned product was then placed in a vacuum drying oven, evacuated to 0.05 MPa, and heated to 60°C for 12 hours. Clean alloy powder was then collected.

[0061] (3) The composition of the alloy powder was analyzed using X-ray diffraction (XRD). The XRD pattern of the Ti-containing TbCu7-type SmFe9 alloy prepared in Example 2 is shown below. Figure 3 As shown in (a), SmFe9N obtained after nitriding treatment x XRD patterns of permanent magnet materials are as follows Figure 3 As shown in (b), the microstructure of the alloy powder was observed using a scanning electron microscope (SEM), and the results are as follows. Figure 2 As shown in (b).

[0062] Examples 4-6:

[0063] The steps listed in Example 1 were followed, wherein the optimal amount of Ti element was determined by measuring 93.5 ml of Sm(NO3)3 solution, 15 ml of Zr(NO3)2 solution, 180 ml of Co(NO3)2 solution, and 20 ml of TiCl3 solution; wherein, when preparing the precursor solution, the amount of Ti element was adjusted to Sm according to the atomic ratio of Ni element. 0.85 Zr 0.15 Fe 6.9 Co 1.8 Ti 0.2 Ni 0.1、 Sm 0.85 Zr 0.15Fe 6.8 Co 1.8 Ti 0.2 Ni 0.2、 Sm 0.85 Zr 0.15 Fe 6.7 Co 1.8 Ti 0.2 Ni 0.3 The corresponding solution addition amounts were: 690 ml Fe(NO3)3 solution and 10 ml Ni(NO3)2 solution; 680 ml Fe(NO3)3 solution and 20 ml Ni(NO3)2 solution; and 670 ml Fe(NO3)3 solution and 30 ml Ni(NO3)2 solution, with other conditions the same as in Example 1. The XRD pattern of the TbCu7-type SmFe9-based permanent magnet powder containing Ti and Ni prepared in Example 5 is shown below. Figure 3 As shown in (c).

[0064] Examples 7-9:

[0065] The steps listed in Example 1 were followed, wherein the optimal amount of Ti element was determined by measuring 93.5 ml of Sm(NO3)3 solution, 15 ml of Zr(NO3)2 solution, 180 ml of Co(NO3)2 solution, and 20 ml of TiCl3 solution; wherein, when preparing the precursor solution, the amount was adjusted to Sm according to the atomic ratio of V element. 0.85 Zr 0.15 Fe 6.9 Co 1.8 Ti 0.2 V 0.1、 Sm 0.85 Zr 0.15 Fe 6.8 Co 1.8 Ti 0.2 V 0.2、 Sm 0.85 Zr 0.15 Fe 6.7 Co 1.8 Ti 0.2 V 0.3 The corresponding solution addition amounts were: 690 ml Fe(NO3)3 solution and 10 ml NaVO3 solution; 680 ml Fe(NO3)3 solution and 20 ml NaVO3 solution; and 670 ml Fe(NO3)3 solution and 30 ml NaVO3 solution, with other conditions the same as in Example 1. The XRD pattern of the TbCu7-type SmFe9-based alloy containing Ti and V prepared in Example 8 is shown below. Figure 3 As shown in (d).

[0066] Examples 10-11:

[0067] The procedure was carried out according to the steps listed in Example 5, except that the nitriding temperature was changed to 300°C or 400°C, and other conditions were the same as in Example 5.

[0068] Example 12:

[0069] Implement according to the steps listed in Example 1, based on Sm 0.85 Zr 0.15 Fe 6.8 Co 1.8 Ti 0.2 Ni 0.2 Prepare a mixed solution with a total metal ion concentration of 0.3 mol / L by measuring 93.5 ml of Sm(NO3)3 solution, 15 ml of Zr(NO3)2 solution, 680 ml of Fe(NO3)3 solution, 180 ml of Co(NO3)2 solution, 20 ml of TiCl3 solution, and 20 ml of Ni(NO3)2 solution in a constant temperature water bath at 50°C and under continuous stirring. Slowly add the mixed salt solution dropwise at a rate of 2 mL / min to an ammonia-citric acid composite precipitant with pH=4.0 (ammonia concentration 1.5 mol / L, molar ratio of citric acid to metal ions 1.2:1). After precipitation, continue aging for 3 hours, followed by vacuum filtration, alternating washing with deionized water and anhydrous ethanol, and vacuum drying at 80°C for 24 hours. Other conditions are the same as in Example 1.

[0070] Example 13:

[0071] Implement according to the steps listed in Example 1, based on Sm 0.85 Zr 0.15 Fe 6.8 Co 1.8 Ti 0.2 V 0.2 Prepare a mixed solution with a total metal ion concentration of 0.3 mol / L by measuring 93.5 ml of Sm(NO3)3 solution, 15 ml of Zr(NO3)2 solution, 680 ml of Fe(NO3)3 solution, 180 ml of Co(NO3)2 solution, 20 ml of TiCl3 solution, and 20 ml of NaVO3 solution in a constant temperature water bath at 50°C and under continuous stirring. Add the mixed salt solution dropwise at a rate of 2 mL / min to an ammonia-citric acid composite precipitant with pH=4.0 (ammonia concentration 1.5 mol / L, molar ratio of citric acid to metal ions 1.2:1). After precipitation, continue aging for 3 hours. After vacuum filtration, washing with deionized water and anhydrous ethanol alternately, and vacuum drying at 80°C for 24 hours, other conditions are the same as in Example 1.

[0072] Example 14:

[0073] The procedure was carried out according to the steps listed in Example 5, wherein small molecule infiltration selective carburizing treatment was performed at 800°C for 2 hours, the atmosphere of the tube furnace was a mixture of methane and argon, the gas flow rate was 0.4 L / min, and other conditions were the same as in Example 5.

[0074] Compare with Example 1

[0075] Implement according to the steps listed in Example 5, based on Sm 0.85 Zr 0.15 Fe 7.2 Co 1.8 The stoichiometric ratio of 0.15 mol / L nitrate solution (93.5 mL Sm(NO3)3, 15 mL Zr(NO3)4, 720 mL Fe(NO3)3, and 180 mL Co(NO3)2) was thoroughly mixed, and other conditions were the same as in Example 5.

[0076] Compare with Example 2

[0077] The steps listed in Example 5 were carried out, and according to the stoichiometric ratio of SmFe9, a 0.15 mol / L nitrate solution (110 mL of Sm(NO3)3 and 1000 mL of Fe(NO3)3) was thoroughly mixed, with other conditions being the same as in Example 5.

[0078] Compare with Example 3

[0079] In Examples 5 and 2, nitrogen absorption treatment was omitted, while other procedures and experimental parameters remained the same, ultimately yielding a TbCu7-type SmFe9-based alloy.

[0080] The products obtained above were subjected to performance and XRD tests, and the following data were obtained (Table 1):

[0081] Table 1. Performance comparison of the final product powders of Example 114 and Comparative Examples 1-3

[0082]

[0083] As shown in Table 1, the preparation method provided by this invention prepares spherical precursor powder by spray pyrolysis or chemical coprecipitation, and then reduces it with hydrogen and active metal. At the same time, metastable TbCu7 type permanent magnet powder was successfully prepared by doping with Zr, Co and Ti elements. The best results were achieved when the addition ratios were 0.15, 1.8 and 0.2. The addition of Ni or V elements is better than nitriding and inhibits the formation of α-Fe soft magnetic phase. It also significantly increases coercivity and remanence. The addition ratio of 0.2 is the optimal one. Nitrogen absorption can be completed in 3 hours at a low temperature of 350℃.

[0084] Obviously, the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A rare-earth permanent magnet powder with a TbCu7 structure, characterized in that, The chemical composition of the permanent magnet powder is Sm 1- a Zr a Fe 9-y-z-r Co y Ti z D r M x Where a is 0.05~0.2, y is 1.0~1.7, z is 0.05~0.3, r is 0.05~0.5; x is 0.5~2.7, D ​​is Ni or V, and M is N or C; The permanent magnet powder was prepared using the following method: Soluble metal salts are classified according to Sm 1-a Zr a Fe 9-y-z-r Co y Ti z D r Dissolve in stoichiometric proportions and stir until homogeneous to form a precursor solution; Near-spherical composite oxide precursor particles with a size of 0.2-3 μm are generated from the precursor solution by spray pyrolysis or chemical coprecipitation. The composite oxide precursor particles are reduced by segmented temperature control and uniform diffusion between elements is achieved to generate SmFe9 alloy. SmFe9 alloy was subjected to high-temperature infiltration treatment of interstitial atoms M to obtain reduction products in which interstitial atoms M were introduced at specific interstitial positions of the unit cell. The reduction product was purified to obtain SmFe9N with a TbCu7 structure. x Permanent magnet powder; The reduction process of the composite oxide precursor particles by segmented temperature control is divided into three temperature stages: First stage: Dehydration and pre-reduction reaction by heating at 200-600 ℃; Second stage: Main reduction is carried out by adding a reducing agent at 700-900 ℃; The third stage: constant temperature annealing at 1000-1200 ℃ promotes the diffusion of Sm elements and the formation of TbCu7 phase.

2. The rare earth permanent magnet powder with a TbCu7 structure according to claim 1, characterized in that, The diameter of the TbCu7 type permanent magnet powder is 0.2-10 μm.

3. The rare earth permanent magnet powder with a TbCu7 structure according to claim 1, characterized in that, The spray pyrolysis method involves generating small droplets from a precursor solution through ultrasonic spraying, followed by thermal decomposition in a tube furnace under the transport of a carrier gas to obtain spherical composite oxide precursor particles.

4. The rare earth permanent magnet powder with a TbCu7 structure according to claim 1, characterized in that, The chemical coprecipitation method involves mixing the precursor solution and the precipitant to carry out a coprecipitation reaction; after precipitation, stirring is continued and the mixture is kept warm in a water bath to promote grain maturation; after maturation, the precipitate is centrifuged and dried to obtain spherical composite oxide precursor particles.

5. The rare earth permanent magnet powder with a TbCu7 structure according to claim 1, characterized in that, The ratio of the sum of Fe, Co, Ti, and D atoms to the number of Sm and Zr atoms in the precursor solution is 8 to 10.

6. The rare earth permanent magnet powder with a TbCu7 structure according to claim 1, characterized in that, The reducing agent used is a strong reducing agent.

7. A rare earth permanent magnet powder with a TbCu7 structure according to claim 6, characterized in that, The strong reducing agent is an active elemental metal or an ionic metal hydride, wherein the active elemental metal is one of calcium, sodium, or potassium, and the amount added is 1.8-3.5 times the molar ratio of calcium to potassium (Sm); the ionic metal hydride is CaH2, and the amount added is 1.0-2.0 times the molar ratio of CaH2 to potassium (Sm).

8. The rare earth permanent magnet powder with a TbCu7 structure according to claim 1, characterized in that, The high-temperature infiltration treatment uses nitrogen or carbon as the gas source, and maintains a temperature range of 300-400 ℃ for 2-5 h, with a gas flow rate of 0.2-0.4 L / min.

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