A cerium valence regulator for high-abundance cerium magnet and a preparation method of high-abundance cerium magnet

Abstract

This invention provides a cerium valence regulator for high-abundance cerium magnets and a method for preparing high-abundance cerium magnets, belonging to the field of rare earth permanent magnet technology. The cerium valence regulator for high-abundance cerium magnets provided by this invention comprises the following components by volume percentage: hydroxylamine hydrochloride 1-10%; tributyl phosphate 5-8%; and the balance being hydrocarbon solvent. In this invention, hydroxylamine hydrochloride facilitates the regulation of cerium valence, while tributyl phosphate plays a stabilizing role in the cerium valence regulator. Using the cerium valence regulator provided by this invention, it is possible to prepare high-abundance, high-performance cerium magnets with a 50% cerium-to-praseodymium / neodymium weight percentage, remanence Br ≥ 12 kGs, and intrinsic coercivity Hcj ≥ 12 kOe. Compared with current technologies, the high-abundance cerium permanent magnets obtained by this invention have approximately 30% higher trivalent cerium content, approximately 1.5% higher remanence Br, and approximately 8% higher coercivity.

Description

Technical Field

[0001] This invention relates to the field of rare earth permanent magnet technology, specifically to a cerium valence modifier for high-abundance cerium magnets and a method for preparing high-abundance cerium magnets. Background Technology

[0002] Cerium-rich permanent magnets are a new type of rare-earth permanent magnet material, characterized by the use of cerium (Ce) as the main rare-earth element, partially or completely replacing traditional neodymium (Nd) and praseodymium (Pr). Cerium is a rare-earth element with high abundance and low cost, therefore cerium-rich permanent magnets are of great significance in reducing material costs and resource dependence.

[0003] Developing high-abundance cerium-containing permanent magnets is a crucial approach to addressing the problem of large-scale stockpiling of inexpensive cerium resources. However, the mixed valence states of cerium are a significant obstacle to achieving high-performance, high-abundance cerium-containing permanent magnets. Current research on controlling the mixed valence states of cerium in high-cerium magnets is still in its early stages, primarily focusing on employing dual-phase methods and element substitution to minimize the presence of +4 valence Ce, which is detrimental to magnetic properties, while maximizing the presence of +3 valence Ce, which is beneficial to magnetic properties. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a cerium valence modifier for high-abundance cerium magnets and a method for preparing high-abundance cerium magnets. The cerium valence modifier provided by this invention can significantly increase the weight of trivalent cerium and improve remanence (Br) and coercivity (Hcj).

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a cerium valence modifier for high-abundance cerium magnets, comprising the following components by volume percentage: Hydroxylamine hydrochloride 1~10%; Tributyl phosphate 5-8%; Remaining amount of hydrocarbon solvent.

[0006] Preferably, the hydrocarbon solvent includes aviation gasoline and / or kerosene.

[0007] Preferably, the density of the cerium valence modifier used in the high-abundance cerium magnet is 0.75~0.85 g / cm³. 3 .

[0008] This invention provides a method for preparing the above-mentioned cerium valence modifier for high-abundance cerium magnets, comprising the following steps: Hydroxylamine hydrochloride powder, tributyl phosphate, and hydrocarbon solvent were ultrasonically mixed to obtain a cerium valence modifier for high-abundance cerium magnets.

[0009] Preferably, the particle size of the hydroxylamine hydrochloride powder is 0.6~0.8 mm; The frequency of the ultrasound is 0.15~0.3Hz, and the duration is 20~30min.

[0010] This invention provides the application of the above-mentioned cerium valence modifier for high-abundance cerium magnets in promoting the conversion of +4 valence Ce to +3 valence Ce in cerium magnets.

[0011] This invention provides a method for preparing a high-abundance cerium magnet, comprising the following steps: The cerium magnet raw material was subjected to hydrogen crushing coarse powder stirring, air jet milling fine powder stirring, green body forming, green body sintering, aging treatment and grain boundary diffusion in sequence to obtain a high-abundance cerium magnet. During the processes of hydrogen crushing coarse powder stirring, air jet milling fine powder stirring, and green body forming, the aforementioned high-abundance cerium valence modifier for cerium magnets is added to the cerium magnet material.

[0012] Preferably, during the stirring process of the hydrogen crushing coarse powder, the volume ratio of the added cerium valence regulator to the mass ratio of the cerium magnet is 0.8~2mL:1kg; During the airflow milling process, the volume ratio of the added cerium valence regulator to the mass ratio of the cerium magnet is 0.5~1.5mL:1kg. During the green body forming process, the volume ratio of the added cerium valence regulator to the mass ratio of the cerium magnet is 0.2~2.3mL:1kg.

[0013] Preferably, the green body sintering process includes: The first heat preservation stage is carried out at 130~160℃ for 120~150 minutes. The second heat preservation stage is carried out at 280~330℃ for 150~180 minutes. The high-temperature sintering stage is carried out at 1030~1060℃, and the temperature is held for 4~6 hours. The timeliness processing procedure includes: The first heat preservation stage is carried out at 130~160℃ for 60~90 minutes. The aging treatment is carried out at 400~600℃ for 6~8 hours.

[0014] Preferably, after the aging treatment, grain boundary diffusion is also performed; The diffusion element for the grain boundary diffusion is Dy, the weight gain ratio for the grain boundary diffusion is 0.4~0.5%, the diffusion temperature is 900~920℃, and the holding time is 10~15h.

[0015] This invention provides a cerium valence regulator for high-abundance cerium magnets, comprising the following components by volume percentage: hydroxylamine hydrochloride 1-10%; tributyl phosphate 5-8%; and the balance being hydrocarbon solvent. In this invention, hydroxylamine hydrochloride is an essential component of the cerium valence regulator, facilitating the regulation of cerium valence, while tributyl phosphate plays a stabilizing role in the cerium valence regulator. Using the cerium valence regulator provided by this invention, it is possible to prepare high-abundance, high-performance cerium magnets with a 50% cerium-to-praseodymium / neodymium weight percentage, remanence Br ≥ 12 kGs, and intrinsic coercivity Hcj ≥ 12 kOe. Compared with current technologies, the high-abundance cerium permanent magnets obtained using the cerium valence regulator provided by this invention show an approximately 30% increase in the weight percentage of trivalent cerium, an approximately 1.5% increase in remanence Br, and an approximately 8% increase in coercivity. Using the cerium valence modifier provided in this invention, it is possible to prepare high-abundance, high-performance magnets with a cerium substitution rate of 20% for praseodymium and neodymium, exhibiting a remanence of Br ≥ 13.3 kGs and an intrinsic coercivity Hcj ≥ 20 kOe after a trace amount of Dy diffused at grain boundaries. This invention significantly improves the cost-effectiveness of high-abundance rare-earth permanent magnets and saves production costs, laying a solid foundation for the sustainable and high-value utilization of inexpensive cerium resources and the upgrading of the high-abundance permanent magnet industry.

[0016] This invention provides a method for preparing a high-abundance cerium magnet, comprising the following steps: sequentially subjecting cerium magnet raw materials to hydrogen crushing and coarse powder stirring, air jet milling and fine powder stirring, green body forming, green body sintering, and aging treatment to obtain a high-abundance cerium magnet; during the hydrogen crushing and coarse powder stirring, air jet milling and fine powder stirring, and green body forming processes, the aforementioned cerium valence regulator for high-abundance cerium magnets is added to the cerium magnet material. This invention, by adding the cerium valence regulator during the hydrogen crushing and coarse powder stirring, air jet milling and fine powder stirring, and green body forming processes, can significantly increase the weight of trivalent cerium and improve remanence (Br) and coercivity (Hcj). Furthermore, the preparation method provided by this invention is simple to operate, low in cost, and easy to implement for industrial mass production. Attached Figure Description

[0017] Figure 1 This represents the typical valence state distribution of the high-abundance cerium magnet obtained in Example 1; Figure 2 This is a typical valence state distribution of the high-abundance cerium magnet obtained in Comparative Example 1. Detailed Implementation

[0018] This invention provides a cerium valence modifier for high-abundance cerium magnets, comprising the following components by volume percentage: Hydroxylamine hydrochloride 1~10%; Tributyl phosphate 5-8%; Remaining amount of hydrocarbon solvent.

[0019] The cerium valence regulator provided by this invention, by volume percentage, comprises 1-10% hydroxylamine hydrochloride, preferably 2-8%, specifically 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. In this invention, the hydroxylamine hydrochloride is preferably added in powder form, and the particle size of the hydroxylamine hydrochloride powder is preferably 0.4-1 mm, more preferably 0.6-0.8 mm, and even more preferably 0.7 mm. This invention preferably passes the hydroxylamine hydrochloride powder through a 16-30 mesh sieve, more preferably a 20 mesh sieve, to remove impurities introduced from the raw materials. In this invention, the hydroxylamine hydrochloride is an essential component of the cerium valence regulator, which is beneficial for controlling the cerium valence.

[0020] The cerium valence regulator provided by this invention comprises 5-8% tributyl phosphate, preferably 6-7%, by volume percentage. In this invention, the tributyl phosphate plays a stabilizing role in the cerium valence regulator.

[0021] The cerium valence modifier provided by this invention, by volume percentage, comprises the balance being a hydrocarbon solvent. In this invention, the hydrocarbon solvent preferably comprises aviation gasoline and / or kerosene.

[0022] In this invention, the density of the cerium valence modifier for the high-abundance cerium magnet is preferably 0.75~0.85 g / cm³. 3 More preferably, it is 0.78~0.82 g / cm³. 3 Further preferred is 0.8 g / cm³ 3 .

[0023] This invention provides a method for preparing the above-mentioned cerium valence modifier for high-abundance cerium magnets, comprising the following steps: Hydroxylamine hydrochloride powder, tributyl phosphate, and hydrocarbon solvent were ultrasonically mixed to obtain a cerium valence modifier for high-abundance cerium magnets.

[0024] In this invention, hydroxylamine hydrochloride powder is preferably sieved through a 16-30 mesh sieve to remove impurities introduced from the raw materials, and more preferably through a 20 mesh sieve. In this invention, the particle size of the hydroxylamine hydrochloride powder is preferably 0.4-1 mm, more preferably 0.6-0.8 mm, and even more preferably 0.7 mm.

[0025] In this invention, the frequency of ultrasonic mixing is preferably 0.15~0.3Hz, more preferably 0.2~0.25Hz, and the time is preferably 20~30min, more preferably 25min. By controlling the ultrasonic mixing conditions, this invention can ensure the rapid dissolution of solid powder raw materials.

[0026] After ultrasonic mixing, the resulting liquid is preferably subjected to settling and filtration. In this invention, the settling time is preferably 30-60 minutes, more preferably 45 minutes. In this invention, the filtration is preferably through a 16-30 mesh sieve, more preferably through a 20 mesh sieve. This invention, through secondary filtration, thoroughly removes impurities introduced from the raw materials.

[0027] In this invention, the storage and use temperature of the cerium valence regulator for high-abundance cerium magnets is preferably -15~35℃, more preferably 15~25℃.

[0028] This invention provides the application of the aforementioned cerium valence modifier for high-abundance cerium magnets in promoting the conversion of +4 valence Ce to +3 valence Ce in cerium magnets. In this invention, the total volume of the cerium valence modifier added to the mass ratio of the cerium magnet is preferably 1.5~4 mL:1 kg, more preferably 2~3 mL:1 kg.

[0029] This invention provides a method for preparing a high-abundance cerium magnet, comprising the following steps: The cerium magnet raw material was subjected to hydrogen crushing coarse powder stirring, air jet milling fine powder stirring, green body forming, green body sintering and aging treatment in sequence to obtain high-abundance cerium magnets; During the processes of hydrogen crushing coarse powder stirring, air jet milling fine powder stirring, and green body forming, the aforementioned high-abundance cerium valence regulator for cerium magnets is added to the cerium magnet material.

[0030] In this invention, the cerium magnet raw material preferably comprises a cerium magnet in which cerium replaces 50% of praseodymium and neodymium by weight, or a cerium magnet in which cerium replaces 20% of praseodymium and neodymium by weight. In this invention, the cerium magnet in which cerium replaces 50% of praseodymium and neodymium by weight, by mass percentage, preferably comprises the following components: PrNd 31.5~32%; Ce 15.75~16%; B 0.88~0.92%; Co 0.3~0.4%; Ga 0.2~0.3%; Al 0.15~0.3%; Cu 0.1~0.25%; one or both of Zr or Ti, totaling 0.25~0.5%; the remainder being Fe. More preferably, the cerium magnet, which replaces praseodymium and neodymium by 50% by weight, comprises the following components: PrNd 31.8%; Ce 15.9%; B 0.91%; Co 0.35%; Ga 0.25%; Al 0.25%; Cu 0.2%; one or two of Zr or Ti, with a content of 0.4%; and the remainder being Fe.

[0031] The cerium magnet, with a cerium-to-praseodymium / neodymium weight percentage of 20%, preferably comprises the following components: PrNd 30.8-31.5%; Ce 6.16-6.3%; Co 0.4-0.6%; B 0.88-0.92%; Ga 0.05-0.2%; Al 0.05-0.15%; Cu 0.1-0.25%; one or both of Zr and Ti, totaling 0.25-0.5%; with the remainder being Fe. More preferably, the cerium magnet, with a cerium-to-praseodymium / neodymium weight percentage of 20%, comprises the following components: PrNd 31%; Ce 6.2%; Co 0.5%; B 0.9%; Ga 0.15%; Al 0.1%; Cu 0.2%; one or both of Zr and Ti, with a content of 0.35%; with the remainder being Fe.

[0032] In this invention, the method for preparing the hydrogen-crushed coarse powder preferably includes the following steps: hydrogen-crushing the cerium magnet raw material to obtain hydrogen-crushed coarse powder. This invention does not impose any special requirements on the hydrogen crushing method; any hydrogen crushing process well-known to those skilled in the art can be used. In this invention, the particle size of the hydrogen-crushed coarse powder is preferably 200-400 mm, more preferably 300-350 mm.

[0033] In this invention, during the stirring of the hydrogen-crushed coarse powder, the volume ratio of the added cerium valence regulator to the mass of the cerium magnet is preferably 0.8~2 mL:1 kg, more preferably 1~1.5 mL:1 kg. In this invention, the stirring frequency of the hydrogen-crushed coarse powder is preferably ≤40 Hz, more preferably 20~40 Hz. In this invention, the stirring of the hydrogen-crushed coarse powder is preferably discontinuous, i.e., sequentially performing a first stirring, a first settling period, a second stirring, and a second settling period. In this invention, the first stirring time is preferably 30 min, the first settling period is preferably 15 min, the second stirring time is preferably 30 min, and the second settling period is preferably 45 min. This invention ensures uniform mixing of the coarse powder and the cerium valence regulator by controlling the above stirring process.

[0034] In this invention, the method for preparing the air-jet milled powder preferably includes the following steps: grinding the hydrogen-crushed coarse powder using an air-jet mill to obtain the air-jet milled powder. In this invention, the air-jet milling is preferably performed without oxygen supplementation. This invention does not have special requirements for the specific operation process of the air-jet milling; air-jet milling processes well-known to those skilled in the art can be used. In this invention, the particle size of the air-jet milled powder is preferably 2.7~3.0 μm.

[0035] In this invention, during the air-jet milling process, the volume ratio of the added cerium valence regulator to the mass of the cerium magnet is preferably 0.5~1.5 mL:1 kg, more preferably 0.8~1.2 mL:1 kg. In this invention, the stirring frequency of the air-jet milling process is preferably ≤35 Hz, more preferably 25~35 Hz. In this invention, the air-jet milling process is preferably discontinuous, i.e., sequentially performing a first stirring, a first settling period, a second stirring, and a second settling period. In this invention, the first stirring time is preferably 30 min, the first settling period is preferably 30 min, the second stirring time is preferably 30 min, and the second settling period is preferably 90 min. This invention ensures uniform mixing of the fine powder and the cerium valence regulator by controlling the above stirring process.

[0036] In this invention, during the green body forming process, the cerium valence regulator is preferably added via spraying. The spraying time is preferably 0.1~0.3s, more preferably 0.2s; the nozzle diameter is preferably 0.3~0.5mm, more preferably 0.4mm; and the spraying pressure is preferably 0.15~0.25MPa, more preferably 0.2MPa. During the green body forming process, the volume ratio of the added cerium valence regulator to the mass of the cerium magnet is preferably 0.2~2.3mL:1kg, more preferably 0.5~2mL:1kg, and even more preferably 1mL:1kg.

[0037] In this invention, the initial vacuum degree of the green body sintering is preferably <0.05 Pa. In this invention, the green body sintering process preferably includes: The first heat preservation stage is carried out at 130~160℃ for 120~150 minutes. The second heat preservation stage is carried out at 280~330℃ for 150~180 minutes. The high-temperature sintering stage is carried out at 1030~1060℃, and the temperature is maintained for 4~6 hours.

[0038] In this invention, the temperature of the first heat preservation stage is preferably 130~160℃, more preferably 140~150℃; the heating rate to the first heat preservation stage is preferably 2℃ / min; and the heat preservation time of the first heat preservation stage is preferably 120~150min, more preferably 130~140min. This invention, through the first heat preservation stage, facilitates the increase of the weight of trivalent cerium.

[0039] In this invention, the temperature of the second heat preservation stage is preferably 280~330℃, more preferably 300~320℃; the heating rate to the temperature of the second heat preservation stage is preferably 2℃ / min; and the heat preservation time of the second heat preservation stage is preferably 150~180min, more preferably 160~170min. Through the second heat preservation stage, this invention enables the cerium valence regulator to volatilize and form a green body.

[0040] In this invention, the temperature of the high-temperature sintering stage is preferably 1030~1060℃, more preferably 1040~1050℃, the heating rate to the high-temperature sintering stage temperature is preferably 2℃ / min, and the time of the high-temperature sintering stage is preferably 4~6h, more preferably 5h. Through the high-temperature sintering stage, this invention obtains a dense, high-abundance cerium permanent magnet sintered blank.

[0041] In this invention, the initial vacuum degree of the aging treatment is preferably <5 Pa. In this invention, the aging treatment procedure preferably includes: The first heat preservation stage is carried out at 130~160℃ for 60~90 minutes. The aging treatment is carried out at 400~600℃ for 6~8 hours.

[0042] In this invention, the temperature of the first heat preservation stage is preferably 130~160℃, more preferably 150℃, and the heat preservation time is preferably 60~90min, more preferably 80min. In this invention, the heating rate to the temperature of the first heat preservation stage is preferably 3℃ / min. In this invention, the temperature of the aging treatment stage is preferably 400~600℃, more preferably 500℃, and the heat preservation time is preferably 6~8h, more preferably 6~7h. In this invention, the heating rate to the aging treatment stage is preferably 3℃ / min.

[0043] In this invention, when the cerium magnet raw material is a cerium magnet in which cerium replaces 20% of praseodymium and neodymium by weight, the invention also preferably performs grain boundary diffusion on the resulting aging-treated blank. In this invention, the grain boundary diffusion preferably includes the following steps: The aged blank is sliced ​​to obtain a grain boundary diffusion substrate; Dy elements diffuse along the grain boundary along the orientation direction.

[0044] In this invention, the weight gain ratio of the grain boundary diffusion is preferably 0.4~0.5%, more preferably 0.4%, the diffusion temperature is preferably 900~920℃, more preferably 900℃, and the holding time is preferably 10~15h, more preferably 12h.

[0045] The following detailed description, in conjunction with embodiments, of the cerium valence modifier for high-abundance cerium magnets and the preparation method of high-abundance cerium magnets provided by the present invention, should not be construed as limiting the scope of protection of the present invention.

[0046] Example 1 Hydroxylamine hydrochloride powder is sieved through a 20-mesh sieve to remove impurities introduced from the raw materials, with a particle size requirement of 0.6~0.8mm. Then, an initial solution is prepared according to the following volume fractions: 8% hydroxylamine hydrochloride, 6% tributyl phosphate, and the remainder aviation gasoline. The initial solution is ultrasonically stirred at 0.2 Hz for 25 minutes to ensure rapid dissolution of the solid powder particles, and then allowed to stand for 45 minutes. A second filtration is then performed to thoroughly remove impurities introduced from the raw materials, yielding the cerium valence regulator. The storage and usage temperature is 15~25℃.

[0047] The weight percentage composition of the cerium permanent magnet casting is PrNd 31.8%; Ce 15.9%; B 0.91%; Co 0.35%; Ga 0.25%; Al 0.25%; Cu 0.2%; one or two of Zr or Ti, with a content of 0.4%; and the remainder is Fe.

[0048] Cerium permanent magnet castings were subjected to hydrogen crushing to obtain coarse hydrogen-crushed powder with a particle size of 200-400 mm. Specifically, a cerium valence modifier was added during the stirring process. The addition ratio was 1.25 mL of cerium valence modifier per kilogram of cerium permanent magnet powder. The stirring frequency was less than 40 Hz, and the stirring process was non-continuous, consisting of 30 minutes of stirring followed by 15 minutes of resting, then a second stirring for 30 minutes followed by 45 minutes of resting, to ensure uniform mixing of the coarse powder and the cerium valence modifier.

[0049] The above-mentioned hydrogen-crushed coarse powder was subjected to air jet milling without oxygen supplementation to obtain air jet milled fine powder with a particle size of 2.7~3.0μm. Specifically, during the air jet milling process, 1.0mL of cerium valence regulator was added to 1kg of cerium permanent magnet air jet milled fine powder. The stirring frequency was less than 35Hz, and the stirring process was non-continuous, i.e., stirring for 30 minutes and then letting it stand for 30 minutes, followed by stirring again for 30 minutes and then letting it stand for 90 minutes, to ensure that the air jet milled fine powder and cerium valence regulator were mixed evenly.

[0050] The above-mentioned air-jet milled powder was used to form green bodies. Specifically, during the green body forming process, 1.0 mL of cerium valence modifier was added to 1 kg of cerium permanent magnet green body via automatic spraying. The spraying volume was controlled by spraying time, nozzle diameter, and spraying pressure. The spraying time was 0.2 seconds, the nozzle diameter was 0.4 mm, and the spraying pressure was 0.2 MPa. During the green body sintering process, the initial vacuum degree was less than 0.05 Pa, and the temperature was increased to 150℃ at a rate of 2℃ / min and held for 130 min. Then, the temperature was increased to 300℃ at a rate of 2℃ / min and held for 160 min to allow the cerium valence modifier to volatilize into the green body. Subsequently, the temperature was increased to 1050℃ at a rate of 2℃ / min and held for 5 h to obtain a dense, high-abundance cerium permanent magnet sintered green body.

[0051] The high-abundance cerium permanent magnet sintered blanks were subjected to aging treatment. Specifically, during the aging process, the initial vacuum degree was less than 5 Pa, and the temperature was increased to 150℃ at a rate of 3℃ / min and held for 80 min. Subsequently, the temperature was increased to 500℃ at a rate of 2℃ / min and held for 7 h to obtain the aged blanks.

[0052] The goal was to obtain a high-abundance cerium magnet with remanence Br≥12kGs and intrinsic coercivity Hcj≥12kOe.

[0053] Comparative Example 1 The high-abundance cerium magnet obtained according to the method of Example 1 differs only in that the cerium valence modifier is replaced with an antioxidant and lubricant containing zinc stearate, wherein the zinc stearate content is 0.3% by mass.

[0054] Figure 1 This represents the typical valence state distribution of the high-abundance cerium magnet obtained in Example 1; Figure 2 Table 1 shows the typical valence state distribution of the high-abundance cerium magnets obtained in Comparative Example 1. It also compares the weighting of typical cerium valence states in the high-abundance cerium magnets obtained in Example 1 and Comparative Example 1.

[0055] Table 1. Comparison of the weighting of typical cerium valence states in the high-abundance cerium magnets obtained in Example 1 and Comparative Example 1.

[0056] Combination Figure 1 and Figure 2 As can be seen from Table 1, compared with the current technology, the high-abundance cerium permanent magnet obtained by using the cerium valence regulator provided by the present invention has an increased weight ratio of trivalent cerium by about 30%.

[0057] Table 2 shows a comparison of the magnetic properties of the high-abundance cerium magnets obtained in Example 1 and Comparative Example 1 at 20°C.

[0058] Table 2. Magnetic property data of high-abundance cerium permanent magnet samples with the same composition obtained in Example 1 and Comparative Example 1.

[0059] Example 2 Hydroxylamine hydrochloride powder is sieved through a 20-mesh sieve to remove impurities introduced from the raw materials, with a particle size requirement of 0.6~0.8mm. Then, an initial solution is prepared according to the following volume fractions: 8% hydroxylamine hydrochloride, 6% tributyl phosphate, and the remainder aviation gasoline. The initial solution is ultrasonically stirred at 0.2 Hz for 25 minutes to ensure rapid dissolution of the solid powder particles, and then allowed to stand for 45 minutes. A second filtration is then performed to thoroughly remove impurities introduced from the raw materials, yielding the cerium valence regulator. The storage and usage temperature is 15~25℃.

[0060] The cerium permanent magnet casting has the following composition by weight percentage: PrNd 31%; Ce 6.2%; Co 0.5%; B 0.9%; Ga 0.15%; Al 0.1%; Cu 0.2%; one or two of Zr or Ti, with a content of 0.35%; and the remainder is Fe.

[0061] Cerium permanent magnet castings were subjected to hydrogen crushing to obtain coarse hydrogen-crushed powder with a particle size of 300-350 mm. Specifically, a cerium valence modifier was added during the stirring process. The addition ratio was 1.25 mL of cerium valence modifier per kilogram of cerium permanent magnet powder. The stirring frequency was less than 40 Hz, and the stirring process was non-continuous, consisting of stirring for 30 minutes, letting it stand for 15 minutes, then stirring again for 30 minutes and letting it stand for 45 minutes to ensure uniform mixing of the coarse powder and the cerium valence modifier.

[0062] The above-mentioned hydrogen-crushed coarse powder was subjected to air jet milling without oxygen supplementation to obtain air jet milled fine powder with a particle size of 2.7~3.0μm. Specifically, during the air jet milling process, 1.0mL of cerium valence regulator was added to 1kg of cerium permanent magnet air jet milled fine powder. The stirring frequency was less than 35Hz, and the stirring process was non-continuous, i.e., stirring for 30 minutes and then letting it stand for 30 minutes, followed by stirring again for 30 minutes and then letting it stand for 90 minutes, to ensure that the air jet milled fine powder and cerium valence regulator were mixed evenly.

[0063] The above-mentioned air-jet milled powder is then used for green body forming. Specifically, the green body forming process involves automatically spraying 1.0 mL of cerium valence modifier into 1 kg of cerium permanent magnet green body. The spray volume is controlled by the spray time, nozzle diameter, and spray pressure. The spray time is 0.2 seconds, the nozzle diameter is 0.4 mm, and the spray pressure is 0.2 MPa.

[0064] The sintered blank is obtained according to the industry's conventional sintering process. Specifically, in the sintering process of the green blank of the high-abundance cerium magnet, the initial vacuum degree is less than 0.05 Pa, and the temperature is increased to 150℃ at a rate of 2℃ / min and held for 130 min. Then, the temperature is increased to 300℃ at a rate of 2℃ / min and held for 160 min to allow the cerium valence modifier to volatilize into the green blank. Subsequently, the temperature is increased to 1050℃ at a rate of 2℃ / min and held for 5 h to obtain a dense sintered blank of the high-abundance cerium permanent magnet.

[0065] The sintered blanks of the high-abundance cerium permanent magnets were subjected to aging treatment. Specifically, in the aging process of the high-abundance cerium magnets, the initial vacuum degree was less than 5 Pa, and the temperature was increased to 150°C at a rate of 3°C / min and held for 80 min. Then, the temperature was increased to 500°C at a rate of 2°C / min and held for 7 h to obtain the aged blanks.

[0066] A 4mm×4mm×3mm grain boundary diffusion substrate was obtained by slicing the aged blank. A trace amount of Dy was diffused along the grain boundaries in the three orientation directions with a weight gain ratio of 0.4%. The diffusion temperature was 900℃ and the holding time was 12 hours. Finally, a high-abundance cerium magnet with remanence Br≥13.3kGs and intrinsic coercivity Hcj≥20kOe was obtained.

[0067] Comparative Example 2 The high-abundance cerium magnet obtained according to the method of Example 2 differs only in that the cerium valence modifier is replaced with an antioxidant and lubricant containing zinc stearate, wherein the zinc stearate content is 0.3% by mass.

[0068] The magnetic properties of the grain boundary diffused Dy high-abundance cerium magnets obtained in Example 2 and Comparative Example 2 are shown in Table 3.

[0069] Table 3 Magnetic property data of high-abundance cerium magnets with grain boundary diffusion Dy

[0070] As demonstrated in Example 1 and Comparative Example 1 above, the cerium valence modifier provided by this invention enables the preparation of high-abundance, cost-effective magnets with a cerium weight percentage replacing praseodymium and neodymium (50%), remanence Br ≥ 12 kGs, and intrinsic coercivity Hcj ≥ 12 kOe. Compared with current technologies, the high-abundance cerium permanent magnets obtained using the cerium valence modifier provided by this invention increase the weight percentage of trivalent cerium, increase remanence Br by approximately 1.5%, and increase coercivity by approximately 8%. This invention can save production costs and enhance product competitiveness.

[0071] As can be seen from Example 2 and Comparative Example 2 above, by using the cerium valence regulator provided by the present invention, it is also possible to achieve a high abundance and high performance magnet with a remanence of Br≥13.3kGs and intrinsic coercivity Hcj≥20kOe after a trace amount of Dy is diffused at the grain boundaries when cerium replaces 20% of the substrate. This broadens the application range of high abundance cerium permanent magnets in the field of high thermal stability.

[0072] Comparative Example 3 The difference from Example 1 is that the volume fraction of hydroxylamine hydrochloride is 15%, the volume fraction of tributyl phosphate is 6%, and the remainder is aviation gasoline. High-abundance cerium magnets were prepared according to the method of Example 1, with the same weight percentage of cerium permanent magnet casting composition as in Example 1.

[0073] The magnetic properties of the high-abundance cerium magnets obtained in Comparative Example 3 and Example 1 at 20°C are compared in Table 4.

[0074] Table 4. Magnetic property data of high-abundance cerium permanent magnet samples with the same composition obtained in Comparative Example 3 and Example 1.

[0075] Comparative Example 4 The difference from Example 2 is that the volume fraction of hydroxylamine hydrochloride is 15%, the volume fraction of tributyl phosphate is 6%, and the remainder is aviation gasoline. High-abundance cerium magnets were prepared according to the method of Example 2, with the same weight percentage of cerium permanent magnet casting composition as in Example 2.

[0076] The magnetic properties of the grain boundary diffused Dy high-abundance cerium magnets obtained in Comparative Example 4 and Example 2 are shown in Table 5.

[0077] Table 5 Magnetic property data of high-abundance Dy cerium magnets with grain boundary diffusion

[0078] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A cerium valence modifier for high-abundance cerium magnets, characterized in that, Components including the following volume percentages: Hydroxylamine hydrochloride 1~10%; Tributyl phosphate 5-8%; Remaining amount of hydrocarbon solvent.

2. The cerium valence modifier for high-abundance cerium magnets according to claim 1, characterized in that, The hydrocarbon solvents include aviation gasoline or kerosene.

3. The cerium valence modifier for high-abundance cerium magnets according to claim 1, characterized in that, The density of the cerium valence modifier used in the high-abundance cerium magnet is 0.75~0.85 g / cm³. 3 .

4. The method for preparing the cerium valence modifier for high-abundance cerium magnets according to any one of claims 1 to 3, characterized in that, Includes the following steps: Hydroxylamine hydrochloride powder, tributyl phosphate, and hydrocarbon solvent were ultrasonically mixed to obtain a cerium valence modifier for high-abundance cerium magnets.

5. The preparation method according to claim 4, characterized in that, The particle size of the hydroxylamine hydrochloride powder is 0.4~1mm; The frequency of the ultrasound is 0.15~0.3Hz, and the duration is 20~30min.

6. The cerium valence modifier for high-abundance cerium magnets according to any one of claims 1 to 3, or the cerium valence modifier for high-abundance cerium magnets according to any one of claims 4 to 5, is used to promote the conversion of +4 valence Ce to +3 valence Ce in cerium magnets.

7. A method for preparing a high-abundance cerium magnet, characterized in that, Includes the following steps: The cerium magnet raw material was subjected to hydrogen crushing coarse powder stirring, air jet milling fine powder stirring, green body forming, green body sintering and aging treatment in sequence to obtain high-abundance cerium magnets; During the processes of hydrogen crushing coarse powder stirring, air jet milling fine powder stirring, and green body forming, the cerium valence regulator for high-abundance cerium magnets as described in any one of claims 1 to 3 or the cerium valence regulator for high-abundance cerium magnets as described in any one of claims 4 to 5 is added to the cerium magnet material.

8. The preparation method according to claim 7, characterized in that, During the stirring process of the hydrogen crushing coarse powder, the volume ratio of the added cerium valence regulator to the mass ratio of the cerium magnet is 0.8~2mL:1kg; During the airflow milling process, the volume ratio of the added cerium valence regulator to the mass ratio of the cerium magnet is 0.5~1.5mL:1kg. During the green body forming process, the volume ratio of the added cerium valence regulator to the mass ratio of the cerium magnet is 0.2~2.3mL:1kg.

9. The preparation method according to claim 7, characterized in that, The green body sintering process includes: The first heat preservation stage is carried out at 130~160℃ for 120~150 minutes. The second heat preservation stage is carried out at 280~330℃ for 150~180 minutes. The high-temperature sintering stage is carried out at 1030~1060℃, and the temperature is held for 4~6 hours. The timeliness processing procedure includes: The first heat preservation stage is carried out at 130~160℃ for 60~90 minutes. The aging treatment is carried out at 400~600℃ for 6~8 hours.

10. The preparation method according to claim 7, characterized in that, The aging process also includes grain boundary diffusion. The diffusion element for the grain boundary diffusion is Dy, the weight gain ratio for the grain boundary diffusion is 0.4~0.5%, the diffusion temperature is 900~920℃, and the holding time is 10~15h.

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