Method and system for uniformly distributing additive magnetic domains in magnet grain boundaries

Abstract

A method of incorporating additive domains in a rare earth magnet, a system for incorporating additive domains in a rare earth magnet, and a traction motor including a rare earth magnet. An inert gas and a plurality of coarse neodymium iron boron (NdFeB) particles are introduced into a chamber of a jet mill. The plurality of coarse NdFeB particles collide with each other to produce a plurality of refined NdFeB particles. The plurality of refined NdFeB particles are also impinged on a target comprising a target material, and a portion of the target material is transferred onto a surface of the refined NdFeB particles. The plurality of refined NdFeB particles including the target are separated from the plurality of coarse NdFeB particles and collected to form the rare earth magnet.

Description

Technical Field

[0001] The present invention belongs to the automotive field, and more particularly relates to a method and a system for uniformly distributing additive magnetic domains in magnet grain boundaries. Background Art

[0002] Traction motors are used in electric vehicles and hybrid electric vehicles to provide propulsion. Traction motors are powered by electricity stored in the vehicle's batteries and convert that power into motion. Traction motors are ideal in applications that require relatively high power density. To achieve the ideal power-to-volume ratio, traction motors use magnets that typically contain rare earth metals, such as neodymium iron boron (NdFeB) magnets. For example, NdFeB magnets are chosen for traction motor applications because they exhibit remanence (Br). Magnets may lose their magnetic properties when exposed to external magnetic forces, especially at the corners of the magnets and at high temperatures.

[0003] The coercivity, intrinsic coercivity (Hci, also called Hcj or iHc) of a magnetic material (a measure of the magnetic field strength required to reduce the material's magnetization to zero) and normal coercivity (Hcb, also called Hc) (a measure of the magnetic field required to reduce the magnetic flux to zero) are measures of a material's ability to retain its magnetic properties (i.e., magnetism) when exposed to an external magnetic field. An increase in the (normal or intrinsic) coercivity indicates that the material is less likely to lose its magnetic properties at a selected temperature. When magnetism is lost, the loss usually begins at the grain boundaries. The intrinsic coercivity and normal coercivity are mathematically related and are not independent of each other.

[0004] It has been found that adding additional elements, such as heavy rare earth elements, including, for example, dysprosium and terbium, within the grain boundaries of a rare earth magnet increases the coercivity of the magnet, particularly at the operating temperature of the motor, taking into account the effect of temperature on coercivity. The increase in coercivity reduces magnetic losses at the operating temperature of the motor. The additional elements can be incorporated into the grain boundaries, which can result in the use of less heavy rare earth elements.

[0005] However, conventional methods of including heavy rare earth elements in grain boundaries use processes such as grain boundary diffusion. In grain boundary diffusion, the target heavy rare earth element is applied to the surface of a magnet close to the finished product by any of a variety of processes, for example, lithography or sputtering, and then diffused by exposure to high temperatures for several hours and up to 24 hours. These processes result in the concentration of heavy rare earth elements being mainly concentrated at and near the surface of the magnet. In addition, due to the increase in surface roughness, it is necessary to remove the heavy rare earth element layer at the outermost surface of the magnet, which inevitably removes a relatively significant portion of the applied heavy rare earth element.

[0006] Thus, while rare earth magnets used in traction motors and methods of forming rare earth magnets are adequate for their current purposes, there is room for improvement. The present disclosure relates to systems and methods for uniformly distributing heavy rare earth elements or additional elements in grain boundaries in a relatively uniform manner throughout the volume of a rare earth magnet. Summary of the invention

[0007] Therefore, according to various aspects, the present disclosure relates to a method for incorporating additive magnetic domains in a rare earth magnet. The method includes introducing an inert gas into a chamber of a jet mill and forming an inert gas flow, introducing a plurality of coarse neodymium iron boron (NdFeB) particles into the chamber, agitating the plurality of coarse NdFeB particles with the inert gas flow, and causing the plurality of coarse NdFeB particles to collide with each other to produce a plurality of refined NdFeB particles. The method also includes causing the plurality of refined NdFeB particles to collide with a target including a target material, causing a portion of the target material to be transferred to the surface of the refined NdFeB particles. The target is at least partially formed of at least one of a metal, a metal alloy, an intermetallic compound, and a ceramic. The method also includes separating the plurality of refined NdFeB particles including the target material from the plurality of coarse NdFeB particles, separating the plurality of refined NdFeB particles including the target material from the inert gas flow, and collecting the plurality of refined NdFeB particles including the target material. The plurality of refined NdFeB particles including the target material form a plurality of grains in the magnet, and the target material forms additive magnetic domains in the magnet.

[0008] In the above-mentioned embodiment, the target further comprises a core and a coating disposed on the core, wherein the coating is formed of a target material. Further, transferring a portion of the target material comprises transferring a portion of the coating to the surface of a refined NdFeB particle. In another embodiment, transferring a portion of the target material comprises transferring a portion of the core to the surface of a refined NdFeB particle, and the core is formed of a target material different from the target material forming the coating.

[0009] In any of the above embodiments, the target includes target particles, and causing the refined NdFeB particles to impact the target includes causing the refined NdFeB particles and the coarse NdFeB particles to impact the target particles. In further embodiments, the target particles exhibit one or more particle sizes in the range of 10 microns to 100 microns. And, in yet other embodiments, the target particles are larger than the coarse NdFeB particles.

[0010] In alternative or additional embodiments, the target includes a baffle connected to the chamber of the jet mill, and causing the refined NdFeB particles to impact the target includes causing the refined NdFeB particles and the coarse NdFeB particles to impact the baffle.

[0011] In further alternative or additional embodiments, the target comprises a mesh screen connected to a cyclone separator, and causing the refined NdFeB particles to impact the target comprises causing the refined NdFeB particles to impact the mesh screen. In addition, separating a plurality of refined NdFeB particles comprising target material from the inert gas stream, and collecting a plurality of refined NdFeB particles comprising target material is performed in a cyclone separator.

[0012] In any of the above embodiments, the target is at least partially formed of at least one heavy rare earth element. In further embodiments, the target is formed of at least one of terbium and dysprosium. In additional or alternative embodiments, the target is at least partially formed of at least one of copper and aluminum.

[0013] In any of the above embodiments, the coarse NdFeB particles have one or more particle sizes ranging from 10 microns up to 100 microns, and the refined NdFeB particles have one or more particle sizes ranging from 0.1 microns to 10 microns.

[0014] In any of the above embodiments, the method further includes pressing refined NdFeB particles including the target material into a rare earth magnet and applying a magnetic field. The method further includes sintering the rare earth magnet and magnetizing the rare earth magnet. The refined NdFeB particles form a plurality of grains, the plurality of grains define a plurality of grain boundaries, and the target material forms additive magnetic domains between the grain boundaries.

[0015] In the above embodiments, the plurality of grains exhibit one or more grain sizes in the range of 1 micron to at most 10 microns, and the additive magnetic domains exhibit one or more magnetic domain sizes in the range of 0.1 microns to at most 10 microns.

[0016] In further embodiments of the foregoing, the additive domains comprise 0.1 wt % to 10 wt % of the total weight of the rare earth magnet.

[0017] In any of the above embodiments, in any given cubic millimeter, the weight percentage of the additive domains deviates by less than 10 weight percent from the average weight of the additive domains per cubic millimeter of the rare earth magnet.

[0018] According to several other aspects, the present disclosure relates to a system for incorporating additive magnetic domains into rare earth magnets. The system includes a jet mill including a chamber, a particle inlet for introducing a plurality of coarse neodymium iron boron (NdFeB) particles into the chamber, and a gas inlet for introducing an inert gas flow into the chamber. The inert gas flow agitates the plurality of coarse NdFeB particles to produce a plurality of refined NdFeB particles. The system also includes a cyclone collector for removing a plurality of refined NdFeB particles from the inert gas flow and a gas filter included in a gas filtration unit for removing NdFeB fine particles from the inert gas flow. The system also includes a gas flow path defined between the gas inlet and the gas filter for conveying refined NdFeB particles and NdFeB fine particles, and a target including a target material located in the gas flow path, wherein the target is at least partially formed of an additive magnetic domain material, and the refined NdFeB particles impact the target located in one of the chamber and the cyclone collector to transfer at least a portion of the target material to the surface of the refined NdFeB particles.

[0019] According to various other aspects, the present disclosure relates to a traction motor for a vehicle. The traction motor includes a stator and a rotor. The rotor includes a rare earth magnet, which includes: a plurality of grains, a plurality of grain boundaries defined by the grains, and a plurality of additive magnetic domains dispersed between the grain boundaries. The plurality of grains include a mixture of neodymium, iron, and boron, and the additive magnetic domains account for 0.1 weight percent to 10 weight percent of the total weight of the rare earth magnet. In addition, in any given cubic millimeter, the weight percentage of the additive magnetic domains deviates from the average weight of the additive magnetic domains per cubic millimeter of the rare earth magnet by less than 10 weight percent.

[0020] In the above embodiments, the additive magnetic domain includes at least one of terbium and dysprosium.

[0021] In additional or alternative embodiments, the additive magnetic domains include at least one of copper and aluminum. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

[0023] Figure 1 Embodiments of a vehicle including a traction motor utilizing rare earth element magnets are shown according to embodiments of the present disclosure.

[0024] Figure 2A Embodiments of traction motor rotors including rare earth magnets are shown according to embodiments of the present disclosure.

[0025] Figure 2B According to the embodiment of the present disclosure, Figure 2A Embodiment of a cross section of a traction motor rotor.

[0026] Figure 3A Embodiments of rare earth magnets are shown according to embodiments of the present disclosure.

[0027] Figure 3B According to the embodiment of the present disclosure, there is Figure 3A Illustration of the grains and additives in a section of a rare earth magnet, where the scale is 10 micrometers.

[0028] Figure 4 Embodiments of methods of forming a rare earth magnet including additives incorporated into grain boundaries are shown in accordance with embodiments of the present disclosure.

[0029] Figure 5A Embodiments of a jet mill system including target particles are shown according to embodiments of the present disclosure.

[0030] Figure 5B Embodiments of a jet mill system including a target plate are shown according to embodiments of the present disclosure.

[0031] Figure 5C Embodiments of a jet mill system including a target screen are shown according to embodiments of the present disclosure.

[0032] Figure 6 Embodiments of a target, in this case a baffle, comprising multiple layers of material are shown in accordance with embodiments of the present disclosure. DETAILED DESCRIPTION

[0033] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application or use. Furthermore, no intention is made to be bound by any express or implied theory presented in the preceding background, summary of the invention or the following detailed description. It should be understood that throughout the drawings, corresponding reference numerals indicate similar or corresponding parts and features.

[0034] Reference will now be made in detail to several embodiments of the present disclosure as shown in the accompanying drawings. Whenever possible, the same or similar reference numerals are used in the drawings and the specification to refer to the same or similar components or steps. The drawings are in simplified form and are not drawn to exact scale.

[0035] The present disclosure relates to methods and systems for uniformly distributing additives in the grain boundaries of magnets, particularly rare earth magnets. The additives may change the magnetic properties. For example, the additives may be used to change the coercivity of the rare earth magnets, and in embodiments, to improve the coercivity of the rare earth magnets. Rare earth magnets include neodymium iron boron (NdFeB) magnets, including additives. The rare earth magnets described herein can be used for a variety of applications within vehicles. For example, rare earth magnets can be used for traction motors, heating, ventilation and air conditioning systems (HVAC systems), transmissions, steering, brakes, window controls and door controls, and sensors.

[0036] As used in this disclosure, the term "vehicle" is not limited to automobiles. Although the present technology is primarily described with respect to electric vehicles, the technology is not limited to electric vehicles. These concepts can be used in a variety of applications, such as those related to components used in hybrid electric vehicles, motorcycles, mopeds, locomotives, aircraft, ships, and other vehicles, as well as for other applications utilizing rare earth magnets.

[0037] Figure 1 A vehicle 100 is shown that includes rare earth magnets, as further described herein, for various applications within the vehicle 100. These applications include, but are not limited to, a propulsion system 120. The propulsion system 120 typically includes an electric motor 124 and a battery 126 for powering the electric motor 124. Additionally, in many embodiments of the propulsion system 120, the propulsion system 120 includes an inverter 128 for changing power from DC (direct current) provided by the battery 126 to AC (alternating current) when used by the electric motor 124. The inverter 128 may be included in a power electronics module that includes, for example, transistors and diodes for switching power from DC to AC and vice versa.

[0038] The controller 130 is connected to the inverter 128 and is programmed to control and manage the operation of the motor 124 and related hardware (including the inverter 128). The motor 124 is connected to a transmission (drive unit) 136 and drive lines 138, which transmit mechanical power and rotation to wheels 141 of the vehicle 100. The controller 130 includes one or more processors 132 and tangible non-transitory memory 134.

[0039] Referring again to the motor 124, the motor 124 includes a stator 140 and a rotor 142 arranged together with the stator 140. The stator 140 is the fixed portion of the motor 124. The stator 140 provides a rotating magnetic field, and the stationary magnetic field of the rotor 142 attempts to align with the rotating magnetic field, causing the rotor 142 to rotate in a so-called motoring mode. In other applications, the rotating field of the rotor 142 (caused by the physical rotation) generates a current in the stator 140, and this mode of operation is called power generation, and the motor 124 used in this manner is called a generator. In traction motor vehicle applications, the driving mode provides movement to the vehicle. The power generation mode absorbs some of the energy recovered by braking during vehicle stopping and stores it back into the vehicle battery. The rotor 142 is arranged on a rotor shaft 144. Reference Figure 2A and Figure 2B, which shows a front view and a cross-sectional view of an embodiment of the rotor 142. The rotor 142 defines a central hole 150 that receives a rotor shaft 144. The rotor shaft 144 is connected to the rotor 142 and the transmission 136. The core 148 of the rotor 142 is formed by a series of plates 154 stacked together. The plates 154 may define the outer periphery of the rotor 142, or the sleeves 156 may be disposed on the outer periphery of the plates 154. A channel 160 is defined in the plate 154 and extends along at least a portion of the length 162 of the stacked plates 154, and a rare earth magnet 164 is inserted into the channel 160. As shown, the channel 160 is arranged on a circumference around the stacked plates 154.

[0040] Rare earth magnets include neodymium iron boron (NdFeB) magnets. Figure 3A and Figure 3B , which shows an embodiment of a cross-section 310 of a rare earth magnet 300 and a diagram of the material composition of the rare earth magnet 300. Although a rectangular, cuboid magnet 300 is shown, the rare earth magnet 300 can take on any shape. The rare earth magnet 300 includes a plurality of grains 302, wherein the grains 302 include a mixture of neodymium, iron, and boron. In an embodiment, the composition of neodymium, iron, and boron is Nd2Fe 14 B. In addition, other elements such as cobalt, aluminum and praseodymium may be present in the NdFeB structure to modify the properties of the NdFeB magnet. It should be understood that the chemical formula Nd2Fe 14 B is used to refer to the crystalline material without the addition of elements, while reference to NdFeB means the addition of Nd2Fe 14 Other elements may be present in the B structure. Grains are understood herein as distinct crystal structures, also referred to as crystallites, wherein each grain includes a combination of neodymium, iron, and boron, as well as other elements such as praseodymium, cobalt, aluminum, dysprosium, and terbium. In an embodiment, the grains 302 exhibit one or more grain sizes in the range of 0.1 microns to at most 10 microns, including all values ​​and ranges therein.

[0041] There is a generally amorphous, neodymium-rich phase between the grain boundaries 304 of the neodymium-iron-boron grains 302. In an embodiment, the additive magnetic domain 306 includes at least one of terbium and dysprosium in the grain boundary phase. Alternatively or additionally, the additive magnetic domain 306 includes at least one of another heavy rare earth element, transition metal element, alkali metal element and metalloid. Other heavy rare earth elements include at least one of lanthanum, cerium, praseodymium, samarium, europium, scandium, yttrium, gadolinium, holmium, erbium, thulium, ytterbium and lutetium. Transition metal elements include one or more of the elements of the 4th to 12th groups and the 4th to 7th periods of the periodic table. Alkaline metal elements (also referred to as post-transition metals) include one or more of aluminum, copper, gallium, indium, tin, thallium, lead and bismuth. Metalloids include one or more of boron, silicon, germanium, arsenic, antimony, tellurium and polonium. In addition, alloys of the above-mentioned reference materials can be incorporated into the additive magnetic domain 306. In further or alternative embodiments, the additive domains 306 increase the coercivity of the rare earth magnet to a value relatively higher than the coercivity of a rare earth magnet without the additive domains 306 at temperatures up to 200 degrees Celsius. With the addition of terbium and dysprosium to NdFeB magnets, it has been observed that the coercivity can be increased by up to 20%.

[0042] As described above, the NdFeB grains 302 individually exhibit a size (measured along the longest linear dimension) of 0.1 microns to at most 10 microns, including all values ​​and ranges therein. The additive magnetic domains 306 present in the grain boundary amorphous phase exhibit a size range of 0.5 nm to 10 microns in magnetic domain size (maximum linear dimension), including all values ​​and increments therein. The additive magnetic domains 306 account for 0.1 wt % to 10 wt % of the total weight of the magnet 300, including all values ​​and ranges therein, such as 0.2 wt % to 0.7 wt %. In addition, the additive magnetic domains 306 are present in a relatively uniform amount throughout the volume of the magnet, wherein, in any given cubic millimeter, the weight percentage of the additive magnetic domains 306 deviates from the average weight of the additive magnetic domains 306 per cubic millimeter in the magnet by less than 10 wt %.

[0043] Now turn to Figure 4 , and refer to Figure 3A , 3B , 5A, 5B, and 5C illustrate a method 400 for uniformly distributing additive magnetic domains 306 between grain boundaries 304 in a rare earth magnet 300 throughout the volume of the magnet. Figure 5A , 5B , 5C shows a reference Figure 4 An embodiment of a jet milling system 500 in the method described. The material used to create the additive magnetic domains 306 described above is added to the coarse NdFeB particles 502 and the refined NdFeB particles 512 using one or more targets 550, 550', 550" provided in an inert gas stream 508 of the jet milling system 500.

[0044] As described above, the targets 550, 550', 550" are at least partially formed of a material that forms the additive magnetic domains 306. For example, the material that forms the additive magnetic domains 306 (also referred to as the target material) can coat the targets 550, 550', 550", or the targets 550, 550', 550" can be completely formed of the material that forms the additive magnetic domains 306. In addition, multiple targets 550, 550', 550" can be provided, each target including a different material for forming the additive magnetic domains 306.

[0045] As described above, each target 550, 550', 550" includes a target material including at least one of a metal, a metal alloy, an intermetallic compound, and a ceramic. In an embodiment, the target 550, 550', 550" includes at least one of terbium and dysprosium. Alternatively or additionally, the targets 550, 550', 550" include at least one of another heavy rare earth element, a transition metal element, an alkali metal element, and a metalloid. Other heavy rare earth elements include at least one of lanthanum, cerium, praseodymium, samarium, europium, scandium, yttrium, gadolinium, holmium, erbium, thulium, ytterbium, and lutetium. Transition metal elements include one or more of elements from Groups 4 to 12 and Periods 4 to 7 of the periodic table. Alkaline metal elements (also called post-transition metals) include one or more of aluminum, gallium, indium, tin, thallium, lead, and bismuth. Metalloids include one or more of boron, silicon, germanium, arsenic, antimony, tellurium, and polonium. In addition, alloys of the above-mentioned reference materials may be included in the target.

[0046] In a further embodiment, Figure 6 As shown and mentioned earlier, Figure 5B The baffle target 550', for example, may also include a coating 560 disposed on a core 562 of the target 550'. The coating 560 is formed of one of the target materials described above, and the core 562 is formed of one of the target materials described above or another material. It should be understood that there may be more than one layer of coating 560, wherein the coatings 560 are layered on top of each other or on different portions of the target 550'. Although shown Figure 5B baffle target 550', but it should be understood that Figure 5A and Figure 5C Any other configuration of the target 550, 550" may also include a core and one or more coatings.

[0047] The method 400 generally includes introducing coarse NdFeB particles 502 of neodymium, iron, and boron into a chamber 505 of a jet mill 504 through a particle inlet 506 at block 402. The coarse NdFeB particles 502 are reduced in size in the chamber 505 of the jet mill 504. The coarse NdFeB particles 502 are introduced into the chamber 505 exhibiting one or more particle sizes greater than 10.0 microns and up to 100 microns, including all values ​​and ranges therein.

[0048] The flow of inert gas (inert gas flow) 508 is also introduced under pressure by one or more gas inlets 510. Inert gas includes, for example, one of argon, xenon and nitrogen. In an embodiment, gas inlet 510 includes a gas injector, which is configured to introduce inert gas flow 508 from a gas source under pressure, and the pressure range is 0.34 MPa (MPa) (50 pounds per square inch (psi)) to 1.37 MPa (200 psi), including all values ​​and ranges therein, such as 0.68 MPa (100 psi) to 0.86 MPa (125 psi). The gas source may include a pump for pressurizing the gas, or the gas may be stored in the gas source under pressure. In addition, in an embodiment, a flow regulator or a flow meter may be used to deliver gas at a constant feed rate. Inert gas flow 508 flows between gas inlet 510 and gas filter unit 524, defining the flow path of various particles through jet milling system 500. During jet milling, the inert gas stream 508 entrains and agitates the coarse NdFeB particles 502, causing the coarse NdFeB particles 502 to impact and collide with each other, reducing the size of the coarse NdFeB particles 502 to produce refined NdFeB particles 512 and fine particles 516. The refined NdFeB particles exhibit a relatively smaller particle size than the coarse NdFeB particles, and the fine particles exhibit a relatively smaller particle size than the refined NdFeB particles.

[0049] exist Figure 5A and Figure 5B In the illustrated embodiment, targets 550, 550' are positioned in an inert gas stream 508 within a jet milling chamber 505 and are impacted by coarse NdFeB particles 502, refined NdFeB particles 512, and fines 516. A portion of the target material is transferred to the surface of the refined NdFeB particles 512 and the surface of the coarse NdFeB particles 502 that impact the targets 550, 550'.

[0050] In such Figure 5AIn the above further embodiment shown, the target 550 is formed of a plurality of target particles 552 that are circulated in the jet mill 504 by the inert gas stream 508 and can be entrained in the inert gas stream 508. In an embodiment, the target particles 552 exhibit one or more particle sizes (measured by the largest linear dimension of each particle) in the range of 10 microns to 100 microns (including all values ​​and ranges therein). In a further embodiment, the target particles 552 exhibit one or more particle sizes that are relatively larger than the coarse NdFeB particles 502. The target particles 552 are introduced into the inert gas stream 508 together with the coarse NdFeB particles 502 through the coarse NdFeB particle inlet 506 (as shown) or through a second inlet (not shown).

[0051] In alternative or additional embodiments, Figure 5B As shown, the target 550' is arranged to be fixed to one or more baffles 554 in the chamber 505 of the jet mill 504 in the inert gas flow 508. Figure 5B In the jet mill 504, although two baffles 554 are shown as being fixed on either side of the milling chamber 505, near the top of the milling chamber 505, it should be understood that one or more baffles 554 providing the target 550' can be fixed at any location of the milling chamber 505 located in the inert gas flow 508, including the center of the milling chamber 505. In addition, the baffles 554, although shown as having a rectangular parallelepiped shape with a rectangular cross-section, can also be in the shape of a truncated cone or one or more rods or arcuate geometries. The coarse NdFeB particles 502 and the refined NdFeB particles 512 and the fine particles 516 impact the baffles 554 while circulating in the jet mill 504, transferring the target 550' material to the coarse NdFeB particles 502 and the refined NdFeB particles 512.

[0052] At box 404, refined NdFeB particles 512 and fines 516, including target material that may be present, are separated from the coarse NdFeB particles 502 in the inert gas stream 508 using a size separator 514. In an embodiment, the size separator 514 includes a classifying rotor positioned at the top of the jet mill 504 to separate the refined NdFeB particles 512 and fines 516 from the coarse NdFeB particles 502. The refined NdFeB particles 512 exhibit one or more particle sizes (determined by the largest linear dimension) in the range of 1 micron to 10 microns (including all values ​​and ranges therein), and the fines 516 exhibit one or more particle sizes (determined by the largest linear dimension) in the range of 1 nanometer to less than 1 micron. The target material (if present) transferred to the refined NdFeB particles 512 exhibits one or more particle sizes (determined by the largest linear dimension) in the range of 1 nanometer to 1 micron (including all values ​​and ranges therein). The coarse NdFeB particles 502 and target particles 550 , 552 that exhibit one or more particle sizes greater than 5 microns remain in the jet mill 504 or are transferred back into the jet mill 504 and milled again in block 402 .

[0053] In block 406, the refined NdFeB particles 512 and fines 516 are transferred to a cyclone separator 518 via an inert gas stream 508. Figure 5C In an additional or alternative embodiment in which the targets 550, 550' are added to the jet mill 504, the target 550" may be added to the inert gas stream 508 in the cyclone separator 518, as further described below. The target 550" is impacted by the refined NdFeB particles 512 and the fines 516, breaking the material from the target 550" and transferring the material to the surface of the refined NdFeB particles 512. The refined NdFeB particles 512 are separated from the inert gas stream 508 and fall to the bottom of the cyclone separator 518 and into the collection container 520.

[0054] Now turn to Figure 5C , the target 550" is set as one or more mesh screens 556 in the inert gas flow 508 in the cyclone collector 518. It should be noted that three mesh screens 556 are shown. The refined NdFeB particles 512 and fine particles 516 impact the target 550" while circulating in the cyclone collector 518. Upon impact, a portion of the target material is transferred to the surface of the refined NdFeB particles 512 or fine particles 516 before separating the refined NdFeB particles 512 from the inert gas flow 508.

[0055] At box 408, the fines 516 are conveyed to a gas filtration unit 524, which removes the fines 516 from the inert gas stream 508 using one or more filters 526. Cleaned inert gas 530 from the inert gas stream 508 is recycled to a compressor 532, and the fines 516 are collected in the filters 526 and a fines collection vessel 534. The fines 516 may be remelted and formed into coarse particles 502 again.

[0056] At box 410, the refined NdFeB particles 512 including the target material are then pressed into the rare earth magnet 300. The refined NdFeB particles 112 form the grains 302 of the magnet 300, and the target material transferred to the surface of the refined NdFeB particles 112 forms the additive magnetic domains 306 located between the grain boundaries 304 of the grains 302. Pressing includes applying pressure to the refined NdFeB particles 512 with the additive 306 along one or more axes. While applying the pressure, a magnetic field is applied that orients the magnetic field direction of each particle in the magnet 300. The pressure can be applied in one of the following directions: aligned along the magnetization direction, transverse to the magnetization direction, and balanced in all directions regardless of the magnetization direction. In addition, in an embodiment, the magnet can be pressed multiple times, each time in any one or more of the directions indicated above. Then, at box 412, the magnet 300 is sintered and optionally machined and coated. At block 414 , the magnet 300 is magnetized by applying a voltage in a magnetizing coil in which the magnet 300 is disposed to align the magnetic domains in the same direction.

[0057] In the above embodiment, before the jet mill 504 is introduced at frame 402, the coarse NdFeB particles 502 can be formed by melting neodymium, iron and boron together in a furnace. In alternative embodiments, the melt can be formed by the reaction product of neodymium, boron, iron, iron oxide (Fe2O3), neodymium oxide (Nd2O3) and calcium (Ca) provided to the furnace. The furnace can be a vacuum furnace heated by, for example, induction heating. The molten metal is then solidified into particles using a solidification process, such as strip casting (also known as melt spinning) or atomization. The particles are in the form of flakes. Alternatively, the particles can be spherical. However, it should be understood that the coarse NdFeB particles 502 can be derived from a supplier.

[0058] The methods and systems herein provide numerous advantages. These advantages include, for example, relatively uniform incorporation of additive magnetic domains throughout the volume of the magnet. Other advantages include elimination of post-processing steps, such as diffusion and screen printing to form additional domains. Additionally, when utilizing materials such as terbium and dysprosium, the resulting coercivity can be greater than the coercivity exhibited by the magnet 300 formed using the diffusion and screen printing processes described above. Additionally, the amount of heavy rare earth elements (e.g., terbium and dysprosium) used to form the additive magnetic domains 306 can be reduced, particularly compared to diffusion processes and processes for incorporating heavy rare earth elements into neodymium, iron, and boron grains. Additionally, the methods and systems described herein allow for convenient incorporation of a variety of non-rare earth elements for experimental purposes to determine which affects the magnetic properties in a desired manner.

[0059] As used herein, the term "controller" and related terms such as microcontroller, control module, module, controller, control unit, processor and similar terms refer to one or more combinations of application specific integrated circuits (ASICs), programmable gate arrays (FPGAs), electronic circuits, central processing units such as microprocessors, and related non-transitory memory components in the form of memory and storage devices (read-only, programmable read-only, random access, hard drives, etc.). The vehicle controller 130 may also be composed of multiple controllers that are in electrical communication with each other. The vehicle controller 130 may be interconnected with additional systems and / or controllers of the vehicle 100, thereby allowing the vehicle controller 130 to access data such as the speed, acceleration, braking, and steering angle of the vehicle 100.

[0060] The processor can be a custom or commercially available processor, a central processing unit (CPU), a graphics processing unit (GPU), an auxiliary processor of multiple processors associated with the controller 130, a semiconductor-based microprocessor (in the form of a microchip or chipset), a macroprocessor, a combination thereof, or generally a device for executing instructions.

[0061] The tangible non-transitory memory 134 may include volatile and non-volatile storage devices such as read-only memory (ROM), random access memory (RAM), and keep-alive memory (KAM). KAM is a persistent or non-volatile memory that can be used to store various operating variables when the processor 132 is powered off. The tangible non-transitory memory 134 may be implemented using a plurality of storage devices such as a PROM (programmable read-only memory), an EPROM (electrical PROM), an EEPROM (electrically erasable PROM), flash memory, or other electrical, magnetic, optical, or combination storage devices capable of storing data, some of which represent executable instructions used by the controller 130 to control various systems of the vehicle 100.

[0062] The description of the present disclosure is merely exemplary in nature, and variations that do not depart from the gist of the present disclosure are intended to fall within the scope of the present disclosure. These variations should not be regarded as departing from the spirit and scope of the present disclosure.

Claims

1. A method for doping additive magnetic domains into a rare earth magnet, comprising: Introducing an inert gas into the chamber of the jet mill to form an inert gas flow; introducing a plurality of coarse neodymium iron boron (NdFeB) particles into the chamber; agitating the plurality of coarse NdFeB particles with the inert gas flow; causing the plurality of coarse NdFeB particles to collide with each other to produce a plurality of refined NdFeB particles; causing the plurality of refined NdFeB particles to impact a target comprising a target material; transferring a portion of the target material onto a surface of the refined NdFeB particles, wherein the target is at least partially formed of at least one of a metal, a metal alloy, an intermetallic compound, and a ceramic; separating the plurality of refined NdFeB particles including the target material from the plurality of coarse NdFeB particles; separating the plurality of refined NdFeB particles including the target material from the inert gas stream; and The plurality of refined NdFeB particles including the target material are collected, wherein the plurality of refined NdFeB particles including the target material form a plurality of grains in a magnet and the target material forms additive magnetic domains in the magnet.

2. The method according to claim 1, wherein: The target includes target particles, and causing the refined NdFeB particles to impact the target includes causing the refined NdFeB particles and the coarse NdFeB particles to impact the target particles.

3. The method according to claim 2, wherein: The target particles are larger than the coarse NdFeB particles.

4. The method according to claim 1, wherein: The target includes a baffle connected to the chamber of the jet mill, and causing the refined NdFeB particles to impact the target includes causing the refined NdFeB particles and the coarse NdFeB particles to impact the baffle.

5. The method according to claim 1, wherein: The target includes a mesh screen connected in a cyclone separator, and causing the refined NdFeB particles to impact the target includes causing the refined NdFeB particles to impact the mesh screen, wherein separating the plurality of refined NdFeB particles including the target material from the inert gas flow and collecting the plurality of refined NdFeB particles including the target material are performed in the cyclone separator.

6. The method according to claim 1, wherein: The target is formed of at least one of terbium and dysprosium.

7. The method according to claim 1, wherein: The coarse NdFeB particles have one or more particle sizes ranging from 10 microns to at most 100 microns, and the refined NdFeB particles have one or more particle sizes ranging from 0.1 microns to 10 microns.

8. The method according to claim 1, further comprising: pressing the refined NdFeB particles including the target material into a rare earth magnet and applying a magnetic field, wherein the refined NdFeB particles form a plurality of grains defining a plurality of grain boundaries and the target material forms additive magnetic domains between the grain boundaries; sintering the rare earth magnet; and magnetizing the rare earth magnet.

9. The method according to claim 8, wherein: The additive magnetic domains account for 0.1 wt % to 10 wt % of the total weight of the rare earth magnet.

10. The method according to claim 9, wherein: In any given cubic millimeter, the weight percentage of the additive domains deviates by less than 10 weight percent from the average weight of the additive domains per cubic millimeter of the rare earth magnet.

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