Permanent magnets, also known as permanent magnets or hard magnetic materials, refer to materials that can maintain constant magnetism once magnetized. It can be a natural product (such as magnetite) or artificially manufactured (such as neodymium iron boron magnets). Permanent magnets have characteristics such as wide hysteresis loop, high coercivity, and high remanence, which can maintain their magnetism for a long time without easily losing or magnetizing. According to material composition, modern permanent magnet materials are mainly divided into three categories: metal alloy permanent magnets (such as aluminum nickel cobalt), ferrite permanent magnets, and rare earth permanent magnet materials (such as neodymium iron boron, samarium cobalt). Among them, neodymium iron boron magnets are known as the "king of permanent magnets" due to their excellent magnetic properties and are currently the most widely used permanent magnet materials.
The development history of permanent magnets
The development history of permanent magnet materials can be traced back to the discovery of natural magnetite by humans 5000 years ago. 2300 years ago, the Chinese made the world's first guider by grinding the natural magnet into a spoon shape; The compass was invented 1000 years ago; Around 1100, a magnetic compass for navigation was developed. The major breakthrough in modern permanent magnet materials occurred in the 20th century: in the 1930s, Japan discovered nickel aluminum cobalt alloy magnets; In 1967, high-performance samarium cobalt permanent magnet materials were introduced; In 1982, Japanese scientist Shinto Sagawa invented neodymium iron boron magnets, which had a magnetic energy product surpassing all known magnets at the time, becoming a milestone in the development history of permanent magnet materials.
In terms of manufacturing technology, modern permanent magnets are mainly produced through powder metallurgy, including complex processes such as batching, melting (high temperature above 1600 ℃), casting, hydrogen treatment, sintering, etc. With the advancement of technology, the performance of permanent magnet materials continues to improve, and their application fields are also constantly expanding.
The main application areas of permanent magnets
Permanent magnets have extremely wide applications in modern technology and industry, almost penetrating into various fields:
Electronic devices such as hard drives, mobile phones, headphones, speakers, and other consumer electronics all rely on permanent magnets. For example, permanent magnets and current carrying coils in hard drives work together to achieve data storage; The permanent magnet in the speaker converts electrical energy into mechanical energy to produce sound.
Electric motors and generators: Permanent magnet motors are widely used in fields such as new energy vehicles, industrial equipment, and household appliances due to their high efficiency, high power density, and miniaturization advantages. Neodymium iron boron permanent magnets greatly improve the performance of modern motors and significantly reduce their volume.
In the field of new energy, high-performance permanent magnet materials are widely used in wind turbines, electric vehicle drive systems, and other applications. For example, Goldwind Technology's wind turbines use permanent magnet technology to reduce weight by 18% and extend maintenance cycles.
Medical equipment: MRI machines, dental correction devices, and other medical devices rely on permanent magnets to generate a stable magnetic field. The 3.0T MRI equipment of Lianying Medical can improve the resolution to 0.2mm by using new permanent magnet materials
Industrial applications: Permanent magnet technology is widely used in industrial equipment such as magnetic separators, magnetic pumps, and magnetic bearings. For example, in the production of lithium battery materials, neodymium iron boron iron remover can capture magnetic impurities at the 0.5 micron level, greatly improving the purity of battery materials.
Latest research progress and future trends
The current research on permanent magnet materials mainly focuses on the following directions:
High performance rare earth permanent magnets: Neodymium iron boron is still a research and development focus, achieving heavy rare earth reduction through grain boundary diffusion technology while maintaining high coercivity. The maximum magnetic energy product of nanocomposite magnetic materials in the laboratory has exceeded 60 MGOe.
New type of rare earth free permanent magnet: Inspired by iron nickel alloy meteorites, scientists are developing low-cost and high-performance rare earth free permanent magnets. Iron nitride permanent magnets exhibit high coercivity of 35kOe and excellent high-temperature stability, and are known as the "holy grail of magnetic materials".
Manufacturing process innovation: 3D printing magnet technology can achieve integrated molding of complex magnetic circuits; Plasma assisted sintering technology compresses the grain boundary diffusion time from 72 hours to 8 hours, significantly improving production efficiency.
Future development trends include:
The proportion of high-end applications has increased, such as new energy vehicle drive motors, precision medical equipment, etc
Diversified material system to meet the needs of different scenarios
Global industrial chain layout, Asia, especially China, will continue to maintain manufacturing advantages
Intelligent production and system integration, evolving from a single component to a holistic solution
Conclusion
The development of permanent magnets, from ancient compasses to modern high-tech devices, has witnessed humanity's exploration and innovation of magnetic materials. As a key functional material, permanent magnets play an irreplaceable role in fields such as energy conversion, information storage, and medical diagnosis. With the development of new materials and technological advancements, permanent magnets will continue to drive technological progress and make greater contributions to the sustainable development of human society. In the future, high-performance, low-cost, and environmentally friendly permanent magnet materials will become a research and development focus to meet the needs of emerging fields such as new energy and intelligent manufacturing.
