A magnetic composite material, its preparation method, and magnetic devices prepared therefrom.

Abstract

This invention discloses a magnetic composite material, its preparation method, and magnetic devices prepared using the same, belonging to the technical field of bonded magnetic composite materials. The invention provides a magnetic powder comprising 0.5-4.5 wt.% lanthanum, 5.0-9.0 wt.% cerium, 2.5-4.0 wt.% praseodymium, 9.0-16.0 wt.% neodymium, 1.0-4.0 wt.% zirconium, 0.1-1.0 wt.% aluminum, 0.5-1.5 wt.% boron, with the remainder being iron (Fe). It also provides a magnetic composite material comprising 83-93 parts of the magnetic powder, 0.2-2 parts of a coupling agent, 7-17 parts of a resin polymer, 0.5-3 parts of a polymeric elastomer, and 0.1-0.5 parts of a lubricant. The magnetic composite material disclosed in this invention, when applied to magnetic devices, possesses characteristics such as low cost, low thermal demagnetization, high magnetic properties, and excellent mechanical and processability, meeting the requirements for magnetic devices in thermal management systems.

Description

Technical Field

[0001] This application belongs to the field of rare earth element bonded magnetic composite materials technology, specifically relating to a magnetic composite material prepared using rare earth elements, a preparation method thereof, and magnetic devices prepared using the same. Background Technology

[0002] The thermal management system for new energy vehicles includes battery thermal management systems and automotive air conditioning systems, involving control components, heat exchange components, and drive components. Neodymium iron boron (NdFeB) composite materials have higher magnetic properties than ferrite composite materials, better aligning with the development trends of miniaturization, lightweighting, and precision, and are widely used in the manufacture of magnetic components in thermal management systems. With the rapid development of the new energy vehicle industry, the demand for NdFeB composite materials has increased significantly. However, NdFeB uses a large amount of low-abundance rare earth elements, resulting in large price fluctuations and heavy resource dependence, which affects its widespread application. Furthermore, the thermal management system places high demands on the performance of magnetic components, requiring them to maintain magnetic stability as temperature rises.

[0003] Lanthanum and cerium, rare earth elements, are abundant and inexpensive. Rare earth magnetic composite materials containing lanthanum and cerium have a broad market prospect, avoiding the excessive consumption of high-value rare earth elements such as neodymium and dysprosium, and aligning with the concept of resource recycling. While existing technologies have addressed this issue extensively, shortcomings remain, including high cost, limited resources, high thermal demagnetization rates, inability to operate stably at high temperatures, and failure to meet the requirements of magnetic devices in thermal management systems. For example, patent application CN 118918200A discloses a lanthanum-cerium-yttrium-iron-boron magnetic powder with a maximum magnetic energy product (BH). max With a flux density of only 4-8 MGOe, the thermal demagnetization rate reaches as high as 3.88% under 100℃ and 24-hour conditions, which cannot meet the requirements of thermal management systems for new energy vehicles. Patent CN113674945 B discloses a low-cost, high-coercivity LaCe-rich NdFeB permanent magnet, but it adds 0.1-1 wt.% of heavy rare earth elements Dy, Tb, and Ho, and 0.1-3 wt.% of Co, significantly increasing the magnet's cost and limiting resource availability. Patent CN 111593261 A discloses a lanthanum-cerium co-doped isotropic bonded magnetic powder, which reduces irreversible flux loss by adding Nb. Patent CN 108133797 A discloses the preparation of a mixed rare earth iron boron magnet that suppresses the CeFe2 phase. This is an anisotropic sintered magnet with extremely low Hcj (around 4 kOe), resulting in extremely high thermal demagnetization, thus failing to meet the requirements of thermal management systems for new energy vehicles. Summary of the Invention

[0004] To address the shortcomings of existing technologies and to solve the problems of high cost of praseodymium and neodymium rare earth elements, and high thermal demagnetization after partial substitution with other elements, which does not meet the requirements of thermal management systems for new energy vehicles, this invention aims to design and provide a magnetic composite material, a preparation method, and magnetic devices prepared using the same. This invention reduces the use of praseodymium and neodymium rare earth elements by introducing high-abundance rare earth elements lanthanum (La) and cerium (Ce) into the magnetic composite material to replace part of praseodymium (Pr) and neodymium (Nd), and by controlling the proportions of each component. The invention prepares isotropic magnetic powder, which is simple to prepare and low in cost. Furthermore, the magnetic devices prepared based on this method exhibit thermal stability and anti-demagnetization capabilities, making them suitable for thermal management systems in industries such as new energy vehicles.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] On one hand, the present invention provides a magnetic powder, which is an isotropic magnetic powder, comprising the following raw materials in weight percentage:

[0007] Lanthanum 0.5–4.5 wt.%, cerium 5.0–9.0 wt.%, praseodymium 2.5–4.0 wt.%, neodymium 9.0–16.0 wt.%, zirconium 1.0–4.0 wt.%, aluminum 0.1–1.0 wt.%, boron 0.5–1.5 wt.%, the remainder being iron (Fe);

[0008] The total mass percentage of lanthanum and cerium is greater than or equal to 6.0 wt.%.

[0009] Secondly, the present invention provides a method for preparing the aforementioned magnetic powder, comprising the following steps:

[0010] Weigh the raw materials of the magnetic powder, melt them to obtain a molten alloy, rapidly cool and solidify it to form a solid, anneal it, and crush it to obtain the magnetic powder.

[0011] The method for preparing magnetic powder, wherein the melting conditions are: temperature 1300~1500℃;

[0012] The rapid solidification method is as follows: molten alloy is sprayed onto a rapid quenching roller with a linear velocity of 30~50 m / s;

[0013] The annealing temperature is 500~900℃;

[0014] The magnetic powder has an average particle size of 40~100 μm.

[0015] Thirdly, the present invention provides a magnetic composite material comprising the following parts by weight of raw materials:

[0016] The composition includes 83-93 parts magnetic powder, 0.2-2 parts coupling agent, 7-17 parts resin polymer, 0.5-3 parts polymer elastomer, and 0.1-0.5 parts lubricant.

[0017] The magnetic composite material is wherein the resin polymer is polyphenylene sulfide or polyamide;

[0018] The polymer elastomer is at least one of thermoplastic polyurethane (TPU) or styrene-butadiene-styrene block copolymer (SBS); it is uniformly dispersed in the resin polymer to improve the mechanical properties of the magnetic composite material, so that it can meet the usage requirements of magnetic devices involved in the thermal management system, especially the thermal management system of new energy vehicles.

[0019] The lubricant is at least one of calcium stearate or stearamide, used to improve the processing performance of magnetic composite materials.

[0020] Fourthly, the present invention provides a method for preparing the aforementioned magnetic composite material, comprising the following steps:

[0021] Weigh the magnetic powder and add it to an ethanol solution containing a coupling agent, stir, and dry to obtain pretreated magnetic powder;

[0022] Weigh out the resin polymer, high molecular elastomer and lubricant, mix them evenly with the pretreated magnetic powder to form a mixture, and then knead and granulate to obtain a magnetic composite material.

[0023] The method for preparing a magnetic composite material, wherein the mixing conditions are as follows: mixing is carried out in a screw extruder at a temperature of 200~350℃.

[0024] Furthermore, when the resin polymer is polyphenylene sulfide, the mixing temperature is 280~350℃, specifically selected from 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, or other values ​​within the range, which can be selected according to actual needs and are not limited here; when the resin polymer is polyamide, the mixing temperature is 200~250℃, specifically selected from 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, or other values ​​within the range, which can be selected according to actual needs and are not limited here.

[0025] Fifthly, the present invention provides the use of the magnetic powder and the magnetic composite material in the preparation of magnetic devices with high thermal stability and resistance to demagnetization.

[0026] In a sixth aspect, the present invention provides a magnetic device prepared using the aforementioned magnetic composite material.

[0027] In a seventh aspect, the present invention provides the use of the magnetic device in a thermal management system.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] First, the magnetic powder of the present invention, through formulation improvement and optimization, introduces high-abundance rare earth elements lanthanum (La) and cerium (Ce) to replace part of praseodymium (Pr) and neodymium (Nd), significantly reducing costs and alleviating resource dependence, and achieving the maximum magnetic energy product (BH). max The maximum magnetic energy product (BH) of the magnetic composite material prepared based on this method reaches 11~15 MGOe. max It reaches 4~6 MGOe.

[0030] Secondly, this invention, by adding an appropriate proportion of high-melting-point metallic zirconium (Zr) and non-rare-earth element aluminum (Al), achieves a synergistic effect between zirconium and aluminum. The Zr-Fe / Nd intermetallic compound formed by zirconium can be more uniformly dispersed within the refined grain boundaries of aluminum, further optimizing grain size, grain boundary structure, and magnetic domain distribution. This further enhances the Hcj of the powder, forming a stable precipitate phase, inhibiting grain growth, and improving coercivity. Consequently, it improves the thermal stability and demagnetization resistance of the magnetic powder, achieving a coercivity of 9745 Oe. Under environmental conditions of 150℃ and 24 hours, the magnetic moment decay can be as low as 7.4%. The powder particle size is controlled within 40~100 μm, which is beneficial for improving the processing performance of the composite material. The magnetic composite material prepared based on this method exhibits a magnetic moment decay value of less than 5% after being placed at 150℃ for 100 hours, meeting the performance requirements of magnetic composite materials in thermal management systems.

[0031] Third, the magnetic composite material and magnetic device obtained by combining the magnetic powder of the present invention with polymer has the characteristics of low cost, high magnetic performance, low thermal demagnetization, and excellent mechanical and processability. It can meet the usage requirements of magnetic devices in thermal management system and has broad market and application prospects. Attached Figure Description

[0032] Figure 1 The image shows the actual magnetic powder prepared in Example 1;

[0033] Figure 2 The composite material prepared in Example 1;

[0034] Figure 3 This is a diagram illustrating the process of pressing magnetic powder into shape within a copper mold in Example 7.

[0035] Figure 4 These are the injection molding mechanical test specimens and standard blocks used in Example 8. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, not all of them. Based on the technical solutions and embodiments provided by this invention, all other technical solutions obtained by those skilled in the art without creative effort are within the scope of protection of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used in this invention whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0037] It should be noted that this invention is designed for magnetic devices in thermal management systems, particularly for rotors in water pumps, oil pumps, throttle valves, water valves, and cooling devices. The performance requirements for magnetic composite materials in thermal management systems are: (1) The maximum magnetic energy product (BH) is tested according to GB / T 3217-2013. max ≥4 MGOe; (2) After the high-temperature environmental test of φ10×10mm cylinder (150℃, 100h), the magnetic moment attenuation is ≤5%; (3) According to the test method of GB / T 3682-2000, when the resin polymer is polyphenylene sulfide, under the test conditions of 310 ℃ and 10 kg, the melt flow index MFR is ≥100 g / 10min; when the resin polymer is polyamide, under the test conditions of 270 ℃ and 10 kg, the melt flow index MFR is ≥100 g / 10min; (4) According to GB / T 1040.2-2006, the tensile strength is ≥40 MPa; (5) GB / T 9341-2008, the flexural strength is ≥50 MPa; (6) GB / T 1843-2008, the impact strength is ≥5.0 kJ / m 2 (7) No cracking was observed during the high and low temperature impact test.

[0038] The magnetic devices in this application can be manufactured using magnetic composite materials through processes such as compression molding, injection molding, extrusion molding, and calendering. The magnetic devices in this application can be used in rotors involved in thermal management systems, such as magnetic rotors in control components (electronic expansion valves, water valves, etc.), heat exchange components (cooling plates, coolers, oil coolers, etc.), and drive components (electronic water pumps and oil pumps, etc.), and can meet the performance requirements of magnets in thermal management systems, such as magnetic properties, thermal stability, processing performance, and mechanical properties.

[0039] The present application will be further described below through embodiments.

[0040] Example 1:

[0041] Step 1, Preparation of magnetic powder

[0042] The raw materials for the magnetic powder were melted in a rapid quenching furnace at 1460℃. The molten alloy was sprayed onto a rapid quenching roller with a linear velocity of 42 m / s and rapidly cooled into a thin strip. The strip was annealed at 780℃ and then crushed to obtain the magnetic powder. The raw materials and their mass percentages for the magnetic powder are as follows: Lanthanum (La) 4.1 wt.%, Cerium (Ce) 7.8 wt.%, Praseodymium (Pr) 3.0 wt.%, Neodymium (Nd) 12.0 wt.%, Zirconium (Zr) 2.3 wt.%, Aluminum (Al) 0.4 wt.%, Boron (B) 1.0 wt.%, with the remainder being Iron (Fe). The powder particle size is 70 μm. A picture of the actual product is shown below. Figure 1 As shown.

[0043] Step 2, Pretreatment of magnetic powder

[0044] Ninety parts of the magnetic powder obtained in step 1 were immersed in an ethanol solution containing 0.6 parts of γ-aminopropyltriethoxysilane coupling agent, stirred at 50°C for 3 hours, and then vacuum dried at 110°C to obtain the pretreated magnetic powder.

[0045] Step 3, magnetic composite material mixing and granulation

[0046] The pretreated magnetic powder obtained in step 2, 10 parts of polyphenylene sulfide, 0.9 parts of thermoplastic polyurethane (TPU), and 0.2 parts of calcium stearate were mixed evenly in a mixer to form a mixture. The mixture was then added to a twin-screw extruder and kneaded and granulated at 310℃ to obtain the magnetic composite material. A picture of the actual product is shown below. Figure 2 As shown.

[0047] Example 2:

[0048] Step 1, Preparation of magnetic powder

[0049] The raw materials for the magnetic powder were melted in a rapid quenching furnace at 1460℃. The molten alloy was sprayed onto a rapid quenching roller with a linear velocity of 42 m / s and rapidly cooled into a thin strip. The strip was annealed at 780℃ and then crushed to obtain the magnetic powder. The raw materials and mass percentages of the magnetic powder were as follows: lanthanum (La) 3.9 wt.%, cerium (Ce) 6.7 wt.%, praseodymium (Pr) 3.0 wt.%, neodymium (Nd) 13.5 wt.%, zirconium (Zr) 2.1 wt.%, aluminum (Al) 0.4 wt.%, boron (B) 1.0 wt.%, with the remainder being iron (Fe); the particle size of the powder was 70 μm.

[0050] Step 2, Pretreatment of magnetic powder

[0051] Ninety parts of the magnetic powder obtained in step 1 were immersed in an ethanol solution containing 0.6 parts of γ-aminopropyltriethoxysilane coupling agent, stirred at 50°C for 3 hours, and then vacuum dried at 110°C to obtain the pretreated magnetic powder.

[0052] Step 3, magnetic composite material mixing and granulation

[0053] The pretreated magnetic powder obtained in step 2, 10 parts of polyphenylene sulfide, 0.9 parts of thermoplastic polyurethane (TPU), and 0.2 parts of calcium stearate are placed in a mixer and mixed evenly to form a mixture. The mixture is then added to a twin-screw extruder and kneaded and granulated at 310°C to obtain a magnetic composite material.

[0054] Example 3:

[0055] Step 1, Preparation of magnetic powder

[0056] The raw materials for the magnetic powder were melted in a rapid quenching furnace at 1460℃. The molten alloy was sprayed onto a rapid quenching roller with a linear velocity of 42 m / s and rapidly cooled into a thin strip. The strip was annealed at 780℃ and then crushed to obtain the magnetic powder. The raw materials and mass percentages of the magnetic powder were as follows: lanthanum (La) 1.6 wt.%, cerium (Ce) 5.0 wt.%, praseodymium (Pr) 3.9 wt.%, neodymium (Nd) 15.9 wt.%, zirconium (Zr) 1.0 wt.%, aluminum (Al) 0.8 wt.%, boron (B) 1.0 wt.%, and the remainder was iron (Fe); the particle size of the powder was 70 μm.

[0057] Step 2, Pretreatment of magnetic powder

[0058] Ninety parts of the magnetic powder obtained in step 1 were immersed in an ethanol solution containing 0.6 parts of γ-aminopropyltriethoxysilane coupling agent, stirred at 50°C for 3 hours, and then vacuum dried at 110°C to obtain the pretreated magnetic powder.

[0059] Step 3, magnetic composite material mixing and granulation

[0060] The pretreated magnetic powder obtained in step 2, 10 parts of polyphenylene sulfide, 0.9 parts of thermoplastic polyurethane (TPU), and 0.2 parts of calcium stearate are placed in a mixer and mixed evenly to form a mixture. The mixture is then added to a twin-screw extruder and kneaded and granulated at 310°C to obtain a lanthanum-cerium-neodymium iron boron composite material.

[0061] Example 4:

[0062] Step 1, Preparation of magnetic powder

[0063] The raw materials for the magnetic powder were melted in a rapid quenching furnace at 1460℃. The molten alloy was sprayed onto a rapid quenching roller with a linear velocity of 42 m / s and rapidly cooled into a thin strip. The strip was annealed at 780℃ and then crushed to obtain the magnetic powder. The raw materials and mass percentages of the magnetic powder were as follows: lanthanum (La) 1.6 wt.%, cerium (Ce) 5.0 wt.%, praseodymium (Pr) 3.9 wt.%, neodymium (Nd) 15.9 wt.%, zirconium (Zr) 1.6 wt.%, aluminum (Al) 0.8 wt.%, boron (B) 1.0 wt.%, and the remainder was iron (Fe); the particle size was 70 μm.

[0064] Step 2, Pretreatment of magnetic powder

[0065] Ninety parts of the magnetic powder obtained in step 1 were immersed in an ethanol solution containing 0.6 parts of γ-aminopropyltriethoxysilane coupling agent, stirred at 50°C for 3 hours, and then vacuum dried at 110°C to obtain the pretreated magnetic powder.

[0066] Step 3, magnetic composite material mixing and granulation

[0067] The pretreated magnetic powder obtained in step 2, 10 parts of polyphenylene sulfide, 0.9 parts of thermoplastic polyurethane (TPU), and 0.2 parts of calcium stearate are placed in a mixer and mixed evenly to form a mixture. The mixture is then added to a twin-screw extruder and kneaded and granulated at 310°C to obtain a magnetic composite material.

[0068] Example 5:

[0069] Step 1, Preparation of magnetic powder

[0070] The raw materials for the magnetic powder were melted in a rapid quenching furnace at 1300℃. The molten alloy was sprayed onto a rapid quenching roller with a linear speed of 30 m / s and rapidly cooled into a thin strip. The strip was annealed at 900℃ and then crushed to obtain the magnetic powder. The raw materials and mass percentages of the magnetic powder were as follows: lanthanum (La) 0.5 wt.%, cerium (Ce) 9.0 wt.%, praseodymium (Pr) 2.5 wt.%, neodymium (Nd) 9 wt.%, zirconium (Zr) 4.0 wt.%, aluminum (Al) 0.1 wt.%, boron (B) 1.5 wt.%, and the remainder was iron (Fe). The average particle size of the powder was 40 μm.

[0071] Step 2, Pretreatment of magnetic powder

[0072] 87.5 parts of the magnetic powder obtained in step 1 were immersed in an ethanol solution containing 2 parts of γ-aminopropyltriethoxysilane coupling agent, stirred at 50°C for 3 hours, and then vacuum dried at 110°C to obtain the pretreated magnetic powder.

[0073] Step 3, magnetic composite material mixing and granulation

[0074] The pretreated magnetic powder obtained in step 2, 12.5 parts of polyamide, 0.5 parts of styrene-butadiene-styrene block copolymer (SBS), and 0.5 parts of stearamide are placed in a mixer and mixed evenly to form a mixture. The mixture is then added to a twin-screw extruder and kneaded and granulated at 200°C to obtain a magnetic composite material.

[0075] Example 6:

[0076] Step 1, Preparation of magnetic powder

[0077] The raw materials for the magnetic powder were melted in a rapid quenching furnace at 1500℃. The molten alloy was sprayed onto a rapid quenching roller with a linear speed of 50 m / s and rapidly cooled into a thin strip. The strip was annealed at 500℃ and then crushed to obtain the magnetic powder. The raw materials and mass percentages of the magnetic powder were as follows: lanthanum (La) 4.5 wt.%, cerium (Ce) 9.0 wt.%, praseodymium (Pr) 2.5 wt.%, neodymium (Nd) 9 wt.%, zirconium (Zr) 4.0 wt.%, aluminum (Al) 1.0 wt.%, boron (B) 0.5 wt.%, and the remainder was iron (Fe). The average particle size of the powder was 100 μm.

[0078] Step 2, Pretreatment of magnetic powder

[0079] 93 parts of the magnetic powder obtained in step 1 were immersed in an ethanol solution containing 2 parts of γ-aminopropyltriethoxysilane coupling agent, stirred at 50°C for 3 hours, and then vacuum dried at 110°C to obtain the pretreated magnetic powder.

[0080] Step 3, magnetic composite material mixing and granulation

[0081] The pretreated magnetic powder obtained in step 2, 7 parts of polyamide, 3 parts of styrene-butadiene-styrene block copolymer (SBS), and 0.1 parts of stearamide are placed in a mixer and mixed evenly to form a mixture. The mixture is then added to a twin-screw extruder and kneaded and granulated at 200°C to obtain a magnetic composite material.

[0082] Comparative Example 1:

[0083] Step 1, Preparation of magnetic powder

[0084] The raw materials for the magnetic powder were melted in a rapid quenching furnace at 1460℃. The molten alloy was sprayed onto a rapid quenching roller with a linear velocity of 42 m / s and rapidly cooled into a thin strip. The strip was annealed at 780℃ and then crushed to obtain the magnetic powder. The raw materials and mass percentages of the magnetic powder were as follows: lanthanum (La) 1.6 wt.%, cerium (Ce) 5.0 wt.%, praseodymium (Pr) 5.2 wt.%, neodymium (Nd) 18.2 wt.%, boron (B) 1.0 wt.%, and the remainder was iron (Fe); the particle size was 70 μm.

[0085] Step 2, Pretreatment of magnetic powder

[0086] Ninety parts of the magnetic powder obtained in step 1 were immersed in an ethanol solution containing 0.6 parts of γ-aminopropyltriethoxysilane coupling agent, stirred at 50°C for 3 hours, and then vacuum dried at 110°C to obtain the pretreated magnetic powder.

[0087] Step 3, magnetic composite material mixing and granulation

[0088] The pretreated magnetic powder obtained in step 2, 10 parts of polyphenylene sulfide, 0.9 parts of thermoplastic polyurethane (TPU), and 0.2 parts of calcium stearate are placed in a mixer and mixed evenly to form a mixture. The mixture is then added to a twin-screw extruder and kneaded and granulated at 310°C to obtain a magnetic composite material.

[0089] Comparative Example 2:

[0090] Step 1, Preparation of magnetic powder

[0091] The raw materials for the magnetic powder were melted in a rapid quenching furnace at 1460℃. The molten alloy was sprayed onto a rapid quenching roller with a linear velocity of 42 m / s and rapidly cooled into a thin strip. The strip was annealed at 780℃ and then crushed to obtain the magnetic powder. The raw materials and mass percentages of the magnetic powder were as follows: lanthanum (La) 1.6 wt.%, cerium (Ce) 5.0 wt.%, praseodymium (Pr) 5.2 wt.%, neodymium (Nd) 18.2 wt.%, aluminum (Al) 0.8 wt.%, boron (B) 1.0 wt.%, and the remainder was iron (Fe); the particle size was 70 μm.

[0092] Step 2, Pretreatment of magnetic powder

[0093] Ninety parts of the magnetic powder obtained in step 1 were immersed in an ethanol solution containing 0.6 parts of γ-aminopropyltriethoxysilane coupling agent, stirred at 50°C for 3 hours, and then vacuum dried at 110°C to obtain the pretreated magnetic powder.

[0094] Step 3, magnetic composite material mixing and granulation

[0095] The pretreated magnetic powder obtained in step 2, 10 parts of polyphenylene sulfide, 0.9 parts of thermoplastic polyurethane (TPU), and 0.2 parts of calcium stearate are placed in a mixer and mixed evenly to form a mixture. The mixture is then added to a twin-screw extruder and kneaded and granulated at 310°C to obtain a magnetic composite material.

[0096] Comparative Example 3:

[0097] Step 1, Preparation of magnetic powder

[0098] The raw materials for the magnetic powder were melted in a rapid quenching furnace at 1460℃. The molten alloy was sprayed onto a rapid quenching roller with a linear velocity of 42 m / s and rapidly cooled into a thin strip. The strip was annealed at 780℃ and then crushed to obtain the magnetic powder. The raw materials and mass percentages of the magnetic powder were as follows: lanthanum (La) 1.6 wt.%, cerium (Ce) 5.0 wt.%, praseodymium (Pr) 5.2 wt.%, neodymium (Nd) 18.2 wt.%, zirconium (Zr) 1.6 wt.%, boron (B) 1.0 wt.%, with the remainder being iron (Fe); the particle size was 70 μm.

[0099] Step 2, Pretreatment of magnetic powder

[0100] Ninety parts of the magnetic powder obtained in step 1 were immersed in an ethanol solution containing 0.6 parts of γ-aminopropyltriethoxysilane coupling agent, stirred at 50°C for 3 hours, and then vacuum dried at 110°C to obtain the pretreated magnetic powder.

[0101] Step 3, magnetic composite material mixing and granulation

[0102] The pretreated magnetic powder obtained in step 2, 10 parts of polyphenylene sulfide, 0.9 parts of thermoplastic polyurethane (TPU), and 0.2 parts of calcium stearate are placed in a mixer and mixed evenly to form a mixture. The mixture is then added to a twin-screw extruder and kneaded and granulated at 310°C to obtain a magnetic composite material.

[0103] Comparative Example 4:

[0104] Step 1, Preparation of magnetic powder

[0105] The raw materials for the magnetic powder were melted in a rapid quenching furnace at 1460℃. The molten alloy was sprayed onto a rapid quenching roller with a linear velocity of 42 m / s and rapidly cooled into a thin strip. The strip was annealed at 780℃ and then crushed to obtain the magnetic powder. The raw materials and mass percentages of the magnetic powder were as follows: lanthanum (La) 27.9 wt.%, cerium (Ce) 18.4 wt.%, praseodymium (Pr) 1.5 wt.%, neodymium (Nd) 6.1 wt.%, zirconium (Zr) 0.2 wt.%, aluminum (Al) 0.1 wt.%, boron (B) 0.1 wt.%, and the remainder was iron (Fe); the particle size was 70 μm. This is the same elemental composition as in Example 2 of patent application CN 108133797 A.

[0106] Step 2, Pretreatment of magnetic powder

[0107] Ninety parts of the magnetic powder obtained in step 1 were immersed in an ethanol solution containing 0.6 parts of γ-aminopropyltriethoxysilane coupling agent, stirred at 50°C for 3 hours, and then vacuum dried at 110°C to obtain the pretreated magnetic powder.

[0108] Step 3, magnetic composite material mixing and granulation

[0109] The pretreated magnetic powder obtained in step 2, 10 parts of polyphenylene sulfide, 0.9 parts of thermoplastic polyurethane (TPU), and 0.2 parts of calcium stearate are placed in a mixer and mixed evenly to form a mixture. The mixture is then added to a twin-screw extruder and kneaded and granulated at 310°C to obtain a magnetic composite material.

[0110] Example 7: Magnetic Powder Performance Testing

[0111] The magnetic powders with different component ratios obtained in step 1 of Examples 1-6 and Comparative Examples 1-4 were subjected to remanence Br, coercivity Hcj, and maximum energy product (BH). max The testing standard is in accordance with GB / T 43750-2024; for example... Figure 3 As shown in Table 1 below, the magnetic powder was pressed into shape in a copper mold with a diameter of φ10×10mm. The magnetic moment decay performance of the magnetic powder was tested by measuring the magnetic moment value of the sample column after magnetization saturation and the magnetic moment decay value after it was placed in an environment of 150℃ for 24 hours.

[0112] Table 1. Test results of remanence, coercivity, maximum energy product, and magnetic moment decay.

[0113]

[0114] As can be seen from Table 1, by comparing Examples 1-6 with Comparative Examples 1-3, it can be seen that as the proportion of Nd decreases and the proportions of La and Ce increase, the cost of the magnetic powder decreases significantly, and its remanence Br, coercivity Hcj, and maximum energy product (BH) also increase. max All showed a decreasing trend. This is because lanthanum (La) and cerium (Ce) replaced neodymium (Nd) in Nd₂Fe. 14 In B lattice, the difference in atomic radius leads to an increase in lattice constant, which disrupts the consistency of magnetocrystalline anisotropy. Lanthanum (La) has no magnetic moment, and cerium (Ce) has a lower magnetic moment than neodymium (Nd). After substitution, the overall magnetic moment of the alloy decreases, resulting in a decrease in remanence. The addition of lanthanum (La) and cerium (Ce) also reduces the sintering driving force, leading to non-uniform grain size, weakened domain wall pinning effect, and decreased coercivity.

[0115] Comparing Example 4 with Comparative Examples 1-3, it can be seen that when an appropriate amount of zirconium (Zr) is added, it preferentially forms Zr-Fe / Nd intermetallic compounds with Fe and Nd, and disperses as fine precipitates at the grain boundaries or within the main phase. This hinders the long-distance diffusion of Fe atoms, reduces the softening and loss of the Nd-rich phase, inhibits grain growth, and stabilizes the main phase grain size within the optimal range of 2-5 μm. Furthermore, Zr atoms can partially replace Nd₂Fe. 14Nd atoms in the B lattice enhance the coercivity Hcj of the powder. When an appropriate amount of aluminum (Al) is added, it forms an Al-Nd-Fe ternary compound with Nd and Fe, which is uniformly distributed in the form of fine particles at the grain boundaries, replacing the continuous network-rich Nd phase, refining the grain boundary phase, enhancing the pinning effect on the main phase grains, and thus improving the coercivity. When an appropriate amount of zirconium (Zr) and aluminum (Al) are added, zirconium and aluminum have a synergistic effect. The Zr-Fe / Nd intermetallic compound formed by zirconium can be more uniformly dispersed in the aluminum-refined grain boundaries, further optimizing the grain size, grain boundary structure, and magnetic domain distribution, thereby further improving the Hcj of the powder and reducing the high-temperature magnetic moment decay.

[0116] The magnetic powders prepared in Examples 1-6 through innovative formulation optimization significantly reduced costs while maintaining high magnetic properties. In contrast, the powder prepared in Comparative Example 4, due to its excessively high La and Ce ratios, resulted in excessive lanthanum and cerium entering the main phase cell of the magnet. This led to the absence of a dual-phase structure or core-shell structure, hindering the formation of favorable grain boundary phases. Consequently, grain boundary discontinuities or enrichment occurred, and stress or non-magnetic phases were generated at the phase interfaces, affecting remanence (Br), coercivity (Hcj), and maximum energy product (BH). max They are all very low, and the magnetic moment decay is extremely high, resulting in poor thermal stability.

[0117] Compared to Comparative Example 4 (the ratio of Example 2 in patent application CN 108133797 A), the appropriate La-Ce ratios in Examples 1-6 and Comparative Examples 1-3 all showed better results in remanence, coercivity, maximum energy product, and magnetic moment decay performance tests than Comparative Example 4, which had an excessively high La-Ce ratio. Combined with the above mechanism explanation, it can be concluded that the La-Ce ratio and other raw material selections of this invention result in technical effects far exceeding the expectations of existing technical solutions.

[0118] Example 8: Performance Testing of Magnetic Composite Materials

[0119] The magnetic composite materials obtained in step 3 of Examples 1-6 and Comparative Examples 1-4 were tested and characterized. The corresponding test methods and sample preparation conditions are shown in Table 2 and 3. Figure 4As shown in Table 2, the test methods for maximum magnetic energy product (BH), melt flow index (MFR), tensile strength, flexural strength, and impact strength are respectively referred to in the corresponding national standards. Magnetic moment decay was measured by examining the magnetic moment value of a φ10×10mm cylinder (same as the maximum magnetic energy product test sample) after magnetization saturation and the magnetic moment decay value after being placed at 150℃ for 100 hours. The high and low temperature impact cracking rate test involved rapidly switching between -40℃ and 150℃ for temperature impact on 10 ring rotors with an outer diameter of 20mm and an inner diameter of 18mm. Each temperature was maintained for 0.5 hours to fully reach the corresponding temperature, and then rapidly transferred to another temperature and maintained for 0.5 hours. This cycle was repeated 500 times, and the number of cracks in the 10 samples was observed. The test results are shown in Table 3.

[0120] Table 2 Test methods and sample preparation conditions

[0121]

[0122] Table 3 Test Results

[0123]

[0124] As can be seen from Table 3, compared with Examples 1-6, Comparative Examples 1-4 show that the cost of the magnetic composite material of the present invention is significantly reduced while still possessing a high maximum energy product (BH). max The magnetic moment decay is low and the mechanical properties are excellent. No cracking was observed in the high and low temperature shock cycle test after the rotor magnetic device was fabricated, meeting the usage requirements of magnetic devices involved in the thermal management system. Furthermore, the magnetic moment decay increases with the decrease of the Nd ratio and the increase of the lanthanum (La) and cerium (Ce) ratios. Specifically, comparing Example 4 with Comparative Examples 1-3 shows that by appropriately adding zirconium (Zr) and aluminum (Al), the thermal stability and demagnetization resistance of the magnetic composite material can be improved, and the magnetic moment decay is reduced. However, Comparative Example 4, due to the poor thermal stability of the powder used, is prone to oxidation during granulation, resulting in a magnetic composite material with low magnetic properties, extremely high thermal demagnetization, and low mechanical properties. The circular rotor with the metal shaft showed 20% cracking in the high and low temperature shock test, failing to meet the usage requirements of the thermal management system for new energy vehicles.

[0125] The above embodiments are only used to illustrate this application and are not intended to limit the technical solutions described in this application. The understanding of this application should be based on those skilled in the art. Although this specification has described this application in detail with reference to the above embodiments, those skilled in the art should understand that they can still make modifications or equivalent substitutions to this application. All technical solutions and improvements that do not depart from the spirit and scope of this application should be covered within the scope of the claims of this application.

Claims

1. A magnetic powder, characterized in that, It comprises the following raw materials by weight percentage: Lanthanum 0.5–4.5 wt.%, cerium 5.0–9.0 wt.%, praseodymium 2.5–4.0 wt.%, neodymium 9.0–16.0 wt.%, zirconium 1.0–4.0 wt.%, aluminum 0.1–1.0 wt.%, boron 0.5–1.5 wt.%, the remainder being iron (Fe); The total mass percentage of lanthanum and cerium is greater than or equal to 6.0 wt.%; The magnetic powder has an average particle size of 40~100 μm; The method for preparing the magnetic powder includes: weighing the raw materials of the magnetic powder, melting them to obtain a molten alloy, rapidly cooling and solidifying it to form a solid, annealing it, and crushing it to obtain the magnetic powder. The annealing temperature is 500~900℃; The zirconium-formed Zr-Fe / Nd intermetallic compound is uniformly dispersed within the refined grain boundaries of aluminum; The rapid cooling and solidification method is as follows: the molten alloy is sprayed onto a rapid quenching roller with a linear velocity of 30~50 m / s.

2. The magnetic powder as described in claim 1, characterized in that, The smelting conditions are: temperature 1300~1500℃.

3. A magnetic composite material, characterized in that, Contains the following raw materials by weight: The composition as described in claim 1 includes 83-93 parts of magnetic powder, 0.2-2 parts of coupling agent, 7-17 parts of resin polymer, 0.5-3 parts of polymer elastomer, and 0.1-0.5 parts of lubricant. The resin polymer is polyphenylene sulfide or polyamide; The polymeric elastomer is at least one of thermoplastic polyurethane or styrene-butadiene-styrene block copolymer.

4. The magnetic composite material as described in claim 3, characterized in that, The lubricant is at least one of calcium stearate or stearamide.

5. The method for preparing a magnetic composite material as described in claim 3, characterized in that, Includes the following steps: Weigh the magnetic powder and add it to an ethanol solution containing a coupling agent, stir, and dry to obtain pretreated magnetic powder; Weigh out the resin polymer, high molecular elastomer and lubricant, mix them evenly with the pretreated magnetic powder to form a mixture, and then knead and granulate to obtain a magnetic composite material.

6. The method for preparing a magnetic composite material as described in claim 5, characterized in that, The mixing conditions are as follows: mixing is carried out in a screw extruder at a temperature of 200~350℃.

7. A magnetic device, characterized in that, It is prepared using the magnetic composite material as described in claim 3.

Images