What are the functions of magnet powder in NdFeB magnets

What are the functions of magnet powder in NdFeB magnets? Magnetic powder is the abbreviation of magnetic powder, which is an aggregate composed of a large number of basic material particles and gaps between particles. Powders are substances between solids and colloids. Solids below 0.1 μm are called colloids, while solids above 0.1 μm are called compacts or solids. There are many small holes between the particles in the neodymium magnetic powder, and the bonding surface is very small.

The atoms on the surface cannot form strong bonds. Therefore, the powder body does not have a fixed shape like a dense body, but exhibits a fluidity similar to that of a liquid. There are no macroscopic pores in dense bodies, they are connected by the bonding force of atoms. Powder metallurgy is commonly used in the preparation of rare earth magnet alloys. Alloy ingots are produced by this method.

Neodymium magnet powder is divided into three processes: coarse, medium and fine, and the powder size is required to be 3-5μm. Rare earth magnet metals are easily oxidized, for example, producing SMZ03 and ND203. These oxide fine powders will spontaneously ignite in air at higher temperatures, and through magnetic interaction, the powders will become secondary powder particles, i.e. aggregated together by van der Waals forces, London forces and the magnetic interaction between the powders a group of small particles.

Therefore, the above-mentioned rare earth permanent magnet alloy powder has poor fluidity in the main air, which leads to certain difficulties in the directional forming in the magnetic field in the next step.