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The Neodymium magnet, also referred to as the NdFeB magnet, is a tetragonal crystal system composed of neodymium, iron, and boron (Nd2Fe14B). It was first discovered in 1982 by Mr. Sagawa of Sumitomo Special Metals. This magnet has a magnetic energy product, or BHmax, larger than that of the samarium cobalt magnets. For many years after its discovery, it had the highest BHmax rating in the world. Further to that, Sumitomo Special Metals developed the process of producing NdFeB magnets using the powder metallurgy process. Then came General Motors‘ success in developing the melt-spinning process which could mass-produce NdFeB magnets.
NdFeB ranks as the strongest permanent magnet known today, aside from holmium absolute zero magnets. Among the rare-earth magnets, these are very common in electronic devices like hard disks, cell phones, headphones, and battery-powered tools. Their magnetic properties are truly exceptional and highly wanted by industries in need of strong but compact magnets. Their wide usage suggests the significant role that NdFeB magnets have in contemporary electronic products and technological development.
According to the production process, NdFeB magnets are classified as either sintered or bonded. They have already replaced other types of magnets in many applications requiring strong and compact magnets. That requires strong permanent magnets, including but not limited to electric motors in cordless tools, hard disk drives, and magnetic fasteners.
The DOE has realized the requirement to find substitutes for permanent magnet technology’s rare earth metals and assigned funding for the required research. The Rare Earth Alternatives in Critical Technologies or REACT program, under the Advanced Research Projects Agency for Energy or ARPA-E, was specially devised to discover substitute material replacements. ARPA-E funded $31.6 million in 2011 for the Rare Earth Alternatives program.
Given the role that neodymium plays in permanent magnets for wind turbines, neodymium has been advanced as a prime target for geopolitical competition in a renewable energy world. This perspective has been criticized for overlooking the fact that most wind turbines do not use permanent magnets and for underestimating the influence of economic incentives on production expansion.
NdFeB permanent magnetic material, with its superior magnetic properties and lower cost, has rapidly become an absolute leader in the rare earth permanent magnet market since its discovery. It contributes 90% of the output value of rare earth permanent magnet materials in the world. In addition, with continuous improvement in the preparation process and production technology, its performance has been constantly improved, and its application fields are being expanded step by step. Therefore, the application extent of NdFeB permanent magnet material marks the level of modernization. NdFeB permanent magnet material has always been an up-and-coming sector in the rare earth material industry.
What is permanent magnet material?l
Permanent magnetic material is a functional material that can be magnetized to saturation under the action of an external magnetic field and retains its magnetic performance after the external magnetic field has been removed. It can also be called hard magnetic material. As early as during the Warring States period in China, the invention of “Sinan” (the prototype of a compass) was to utilize the role of the magnet to guide and identify the direction.
Although mankind has known about magnetic materials for over 2,000 years, man-made permanent magnets began with the invention of magnetized steel needles in China in the tenth century. Significant progress in the development and application of magnetic materials began in the late nineteenth and early twentieth centuries. People mainly used tungsten steel, carbon steel, chromium steel, and cobalt steel as permanent magnet materials at the beginning of the twentieth century. At the end of the 1930s, Alnico permanent magnetic materials were successfully developed,d and then permanent magnetic materials began to be applied on a large scale. In the 1950s, barium ferrite appeared. The cost of permanent magnets was reduced and, at the same time, the range of uses of permanent magnet materials expanded to high frequency. Rare earth cobalt permanent magnets were successfully developed in the sixties; permanent magnet applications entered a new era. In 1967, the United States University of Dayton successfully prepared SmCo5 permanent magnetic steel, which marked the arrival of the era for rare earth permanent magnets. Rare earth permanent magnetic materials so far have been developed from the first generation of 1:5 type SmCo5, the second generation of precipitation hardening type Sm2Co17, to the third generation Nd-Fe-B permanent magnetic material.
In addition, it has used Cu-Ni-Fe, Fe-Co-V, Fe-Co-Mo, A1MnC, and Mand nBi alloys as permanent magnet materials. All these alloys above are seldom used on most occasions owing to their poor performance and low-cost performance. Up to now, FeCrCo, AlNiCo, PtCo, and some other alloys are still used on some special occasions. Ba, Sr ferrite is still the largest quantity of permanent magnet materials in use today but is being replaced by Nd-Fe-B materials in many fields of applications. At present, the output value of rare earth permanent magnet material has far exceeded that of ferrite permanent magnet material, and the production of rare earth permanent magnet material has developed into a big industry. Nd-Fe-B has become the most widely used rare earth permanent magnet material. NdFeB is now the most widely used rare-earth permanent magnetic material in the world, and also the most powerful magnetic permanent material available today.
Introduction of NdFeB
NdFeB is a rare earth permanent magnetic compound, its elements include the rare earth metal of neodymium, the metal element of iron, the non-metal element of boron, an added amount of the element praseodymium, dysprosium, niobium, aluminum, gallium, copper, and others. NdFeB permanent magnetic materials boast superior magnetic properties and are light in weight, fairly cheap, and thus find wide applications in various fields. It is also called “king of magnets” and up to now, the cheapest magnet material.
NdFeB powerful magnets have a big magnetocrystalline anisotropy field and high intensity magnetic polarization. Its theoretical magnetic energy product is 64MGOe. Its magnetic property is over 100 times the magnet steel that people used in the 19th century and 10 times than usual ferrite and alnico. With the properties of super-high coercivity and super-high energy density, the dimensions of magnetic material components decrease substantially. This again promotes miniaturization, lightweight, thinning, and high efficiency of instrumentation, electro-acoustic motors, computers, cellular phones, etc. Because of these merits, a lot of improvements or performances for products would be promoted to make some particular special devices appear. NdFeB has fine mechanical characteristics and is readily cut or machined with processing easily. Preparation technology is comparatively mature, the Curie temperature of this magnet is about 580K, and it can serve at as high temperatures as up to 150 degrees Celsius.
NdFeB does not include strategic elements Co and Ni. The raw materials of the product are also abundant. The high-cost performance makes such a big sales volume: since the appearance of NdFeB in 1983, up to 2006, the output increased to 55,540 tons, and surged even more in 2015 to around 130,000 tons. Sintered NdFeB permanent magnetic materials have excellent magnetic properties and are widely used in electronic equipment, electric machinery, medical treatment, toys, packaging, hardware machinery, aerospace, and aviation.
