Permanent magnet ferrite is a functional material made of SrO or BaO and Fe2O3 as raw materials, through ceramic process (pre-sintering, crushing, milling, pressing molding, sintering and grinding), with wide hysteresis loop, high coercivity, high residual magnetism, and can maintain constant magnetic properties once magnetized. According to different production processes, permanent magnet ferrites are divided into two types: sintering and bonding, of which sintering is divided into dry press molding and wet press molding, and bonding is divided into extrusion molding, compression molding and injection molding. Magnets made of bonded ferrite powder compounded with synthetic rubber with flexibility, elasticity and twistability are also called rubber magnets. According to whether the magnetic field is applied during molding, it is divided into isotropic permanent magnets and anisotropic permanent magnets.
The current era is the electronic age, without permanent magnet ferrite there is no electronic industry, permanent magnet ferrite as a basic functional material of the electronic industry, has penetrated into all fields of human production and life. It has been widely used in automobiles, motorcycles, televisions, audio, computers, communication terminals, medical instruments, etc., and it is an important aspect of energy development. Whether from the perspective of resources, energy and application, the development prospects of permanent magnet ferrites are very broad, and their demand is increasing day by day. China's demand for permanent magnet ferrite in 1995 was 45,000 tons (about 50,000 tons of pre-burned material), 6-70,000 tons in 1997 (7-80,000 tons of pre-burned material), and 150,000 tons (180,000 tons of pre-burned material) in 2000 During the "Eighth Five-Year Plan" period, China's total permanent magnet ferrite production has gradually replaced the "permanent magnet kingdom" Japan, ranking first.
Preparation method of permanent magnet ferrite powder
At present, there are various preparation methods of permanent magnet ferrite, but there are mainly the following methods: (1) chemical co-precipitation method, (2) molten salt method, (3) glass crystallization method, (4) hydrothermal synthesis method, (5) sol-gel method, (6) spray pyrolysis method, (7) organic resin method, (8) self-propagating high temperature synthesis method.
New technology and new process of permanent magnet ferrite
Ways to improve the performance of permanent magnet ferrites: (1) Improve orientation. (2) Improve sintering density. (3) Increase the Mn Kl of the ferrite M phase. (4) Refine the grains and improve the existence rate of single-domain particles (5) Control the uniform size of ferrite sintered particles.
Permanent magnet ferrite is currently the largest permanent magnet material. Since the advent of permanent magnet ferrite materials, the technical performance has been continuously improved, the variety of products has been increasing, the manufacturing process has been continuously improved, the equipment used has been continuously updated, and the application range has been expanding, so the social and economic benefits have continued to grow. Due to the limitations of raw materials, labor shortages and the environment, foreign countries have no longer produced raw materials for such products, so they have moved to the third world. At present, in some large and medium-sized factories in China, taking advantage of their abundant funds and technical advantages, they purchase key production equipment and domestic replica equipment from abroad and domestic auxiliary equipment to form advanced production lines. Some township enterprises and individual enterprises have taken advantage of the technical strength and scientific and technological personnel of large and medium-sized enterprises, the use of traditional equipment and cheap human resources, and the diversification and flexibility of operation and management, so that the output has increased sharply, and it is expected that there will be a further upward trend in the next few years.
