From wind power generation and new energy vehicles to smartphones and computer hard drives, you will find an essential new material inside these devices - rare earth permanent magnet materials. With the rapid development of China's economy and science and technology, rare earth permanent magnet materials play a crucial role in traditional and emerging fields such as electronics, computers, information and communication, healthcare, aerospace, automobiles, wind power, environmental protection and energy conservation. They have become irreplaceable key materials for promoting high-tech development and contemporary economic progress. Taking the core high-end equipment innovation project of the "Made in China 2025" five major projects as an example, each of its ten key areas has the application of rare earth permanent magnet materials. It is not an exaggeration to compare it to the ubiquitous "industrial monosodium glutamate".

A small magnet, a huge amount of energy

Magnetism is one of the most fundamental properties of matter, which was recognized and utilized by people as early as 3000 years ago. As we all know, the magnetic field lines of a single permanent magnet are closed, but what is the magnetic field line of multiple permanent magnets combined? In 1979, American scholar Klaus Halbach combined multiple permanent magnets according to special rules and discovered many special magnetic field lines, which were applied in some special ways. Since then, scientists have developed a strong interest in this and discovered more and more practical combinations of permanent magnets, which are collectively referred to as Halbach magnets in academia.

Magnetic materials are mainly divided into five categories: soft magnetic, permanent magnetic, moment magnetic, rotational magnetic, and piezoelectric magnetic, and are widely used in various fields of the national economy. Among them, permanent magnet materials, commonly known as "magnets" or "magnet stones", can maintain a constant magnetism after being magnetized by an external magnetic field. They can be seen everywhere in our lives, such as buttons on bags, compasses, and speakers made of this material.

Permanent magnet materials are further divided into rare earth permanent magnet materials and non rare earth permanent magnet materials. Rare earth permanent magnet materials are currently the most magnetic and widely used type of permanent magnet materials, and are important supporting materials for the progress and development of new energy vehicles, wind power generation, energy-saving household appliances, intelligent manufacturing and other fields. "Thanks to the development and innovation of production technology of rare earth permanent magnetic materials, the volume of magnets is getting smaller and smaller, but their magnetic properties are getting higher and higher. A piece of high-performance magnet with a weight of about 2g can absorb objects more than 64 times its own weight." Liu Youhao, secretary and senior engineer of the State Key Laboratory of Rare Earth Permanent Magnetic Materials, said that if rare earth permanent magnetic materials are used in signal transmission devices, the volume and weight of key components of devices can be greatly reduced, and the signal transmission can be more accurate. The Development Guidelines for the New Materials Industry jointly issued by the Ministry of Industry and Information Technology, the National Development and Reform Commission, the Ministry of Science and Technology, and the Ministry of Finance in 2017 clearly stated that "accelerate the industrialization of rare earth magnetic materials and application devices" and "vigorously develop the application of rare earth permanent magnet energy-saving motors and supporting rare earth permanent magnet materials". At present, the sintered neodymium iron boron magnet rare earth permanent magnet materials that have been applied have a market share of over 95% due to their advantages of high magnetic energy product and high cost-effectiveness.

According to incomplete statistics, the proportion of electric motor applications of rare earth permanent magnet materials has exceeded 60% in recent years. From electric bicycles to new energy vehicles, from oilfield motors to mining machinery, from electric tools to elevator traction machines, from robots to unmanned aerial vehicles, from air conditioning compressors to water pump fans, from large astronomical telescopes to nuclear fusion reaction devices, from wind power to hydropower, from computers to mobile phones, from vacuum cleaners to toys, rare earth permanent magnet applications are everywhere in the world, just like the Earth's magnetic field.

A wide variety of rare earth permanent magnet materials

Located in Lujiang County, Hefei City, the State Key Laboratory of Rare Earth Permanent Magnet Materials is an enterprise State Key Laboratory approved by the Ministry of Science and Technology in 2015 and built and operated by Anhui Dixiong New Materials Co., Ltd. Entering the laboratory exhibition hall, you can see various types of neodymium iron boron magnets, including square, circular, tile shaped, trapezoidal and other shapes of magnets; Magnets with different metal coatings such as zinc, copper, and nickel on the surface; There are also magnets embedded in automotive motor rotors, vibration motors, audio and other spare parts. In recent years, the laboratory has combined the preparation process and microstructure characteristics of neodymium iron boron magnets to break through high-performance/ultra-high performance rare earth permanent magnet material preparation technologies such as high coercivity, high temperature resistance, and low weight loss. A rare earth permanent magnet material preparation technology system with powder surface modification, grain boundary modification, strong texture molding and other technologies as the core has been constructed. In this field, the laboratory has formulated 7 national standards (4 have been implemented and 3 are under approval), applied for 27 patents (including 20 invention patents), and authorized 15 patents (including 8 invention patents).

In addition, the laboratory has completed the development of high-performance/ultra-high magnetic sintered neodymium iron boron permanent magnet materials, with the highest sum of intrinsic coercivity and maximum magnetic energy product value reaching 79.5; The development of high thermal stability sintered neodymium iron boron permanent magnet materials has been completed, and the maximum operating temperature of the magnet can reach 250 ℃; The development of high corrosion resistant rare earth permanent magnet materials has been completed. After 500 hours of high-pressure accelerated aging life test, the material has a corrosion weight loss of less than 2mg/c ㎡. The research and development of "33TH type ultra-high coercivity sintered neodymium iron boron permanent magnet" and "48SH type sintered neodymium iron boron permanent magnet for automotive motors" have been selected as new products in Anhui Province. The comprehensive performance of the magnet has reached the leading domestic and international level, meeting the application needs of new energy vehicle drive motors, industrial machinery, variable frequency air conditioning compressor motors, and other fields.

In order to improve the coating protection ability of rare earth permanent magnets, the laboratory has also developed a green/efficient protection technology system, formulated 3 national standards, applied for 24 patents, and granted 16 patents. Among them, the "Development of Key Technologies for Industrialization of High end Rare Earth Permanent Magnet Motor Magnets and Their Surface Green Protection" project won one first prize of Anhui Province Science and Technology Progress Award, and the "Innovation and Industrialization Application of Key Technologies for Rare Earth Permanent Magnet Material Anti corrosion" project won one third prize of Metallurgical Science and Technology Award. Through the study of the corrosion failure mechanism of sintered neodymium iron boron magnets in different usage environments, the laboratory has developed new green coatings and composite coating technologies such as low emission rare earth permanent magnet surface pre-treatment technology, vacuum evaporation Al coating technology, and spray zinc aluminum coating technology. These technologies have reduced the pollutant emissions during the pre-treatment process of the magnet surface by 90%, increased the adhesion of the coating by 30%, and the salt spray resistance test time has exceeded 1000 hours, and the high-pressure accelerated aging life test time has exceeded 600 hours.

Technology assistance enables the recycling of rare earth permanent magnet materials

Since the emergence of the third-generation rare earth permanent magnet material neodymium iron boron in the 1980s, magnetic applications have experienced explosive growth. By 2000, China had become the largest producer and application country of rare earth permanent magnet materials. The application technology of rare earth permanent magnet materials has many outstanding advantages, such as passivity (no additional power supply required), non-contact (air separation effect, no mechanical wear), simple structure, energy conservation and environmental protection, stability and reliability. In addition, rare earth permanent magnet motors have become increasingly popular in recent years due to their high efficiency, high power density, high torque, small size, low noise, low temperature rise, and good stability and reliability.

"In the current era of increasing demand for rare earth permanent magnet materials, it is very important to study the green regeneration industrialization technology of waste magnets." The laboratory leader introduced that the laboratory has led the development of China's first national standard "Regenerated Sintered Neodymium Iron Boron Permanent Magnet Materials", participated in the development of the industry standard "Chemical Analysis Methods for Neodymium Iron Boron Waste Part 1: Determination of Total Rare Earth Oxides", and is currently drafting the international standard "Classification, General Requirements, and Acceptance Conditions for Rare Earth Neodymium Iron Boron Magnetic Waste", the national standard "Neodymium Iron Boron Production and Processing Recycling Materials", and the industry standard "Technical Specification for Regenerated Utilization of Waste Sintered Neodymium Iron Boron Magnets". Two patents have been applied for, and one patent has been authorized. Among them, "42H type regenerated sintered neodymium iron boron permanent magnet" was selected as a new product in Anhui Province. "Green regeneration new technology and industrialization of rare earth permanent magnet secondary resources" won the first prize of the Ministry of Education's Technology Invention Award, and "Efficient recovery and reuse of industrial solid waste in rare earth permanent magnet" won the third prize of Anhui Province's Science and Technology Progress Award.

For many years, the laboratory has been committed to developing a short process fast and efficient regeneration technology for waste block magnets and processing oil sludge, achieving the recycling of rare earth resources. The main performance of regenerated magnets reaches or even exceeds that of the original magnets, and other properties are also comparable to the original magnets, which can replace ordinary magnets in various fields. The recycling and utilization technology of waste magnets has reached a leading domestic and international level, improving the "manufacturing consumption recycling reuse" rare earth resource circular economy chain and alleviating the excessive dependence of the rare earth industry on primary mineral resources.

(Transferred from: Shanghai Rare Earth Association)