Ultrafine powder preparation technology

Ultrafine powder usually refers to fine powder with a particle size of 10 to 100 nm, and sometimes fine particles with a particle size of less than 100 nm are called nano fine powder. Nano-powder has obvious volume and surface effects. Therefore, it has significantly different physical, chemical, and mechanical properties than conventional fine powders. As a potential functional material and structural material, the development of ultra-fine powder has been received by industrial countries in the world. Pay attention. Nano-powder manufacturing methods are: sol-gel method, spray heat conversion method, precipitation method, electrolytic method, mercury law, carbonyl method, freeze-drying method, ultrasonic grinding method, evaporation-coagulation method, explosion method, plasma method and the like.

The greatest difficulty encountered in making ultrafine powders is the collection and storage of powders. In addition, the ultrafine powders produced by the wet process require heat treatment, which may cause the specific surface area of ​​the particles to decrease, the activity is reduced, the characteristics of the ultrafine powders are lost, and it is difficult to avoid binding to the carbonyl groups on the surface. Therefore, it is generally preferred to adopt them now. Dry milling.

Nano-powder is a new type of powder metallurgy material and raw material. It is mainly used in high-density magnetic recording materials, conductive materials for thin film integrated circuits, microporous filters, chemical catalysts, automotive reduction catalysts, ultra-fine particle film sensors, and carbon fiber. Vapor-phase nucleation materials, etc.

The nano-powder has high activity, is easy to agglomerate and moisture oxidize, and has poor formability. Therefore, there are still some technical problems to be solved as powder metallurgy raw materials. In addition, nanopowders must have economical manufacturing methods and stable quality as raw materials for powder products. The nano-powder sintering temperature is particularly low (the sintering temperature of the silver powder with a particle size of 20 nm is 60 to 80° C., and the 20-nm nickel powder starts to be welded at 200° C.), once the powdered metallurgical products can be produced industrially using the nano-powders. Breakthrough changes will be made to powder metallurgy technology.