Gas Evaporating
Copper evaporates in inert gas atmosphere, then a conflict with an inert gas and the particles, cooling, condensation forming nano copper particles. The forming powder process including 3 stages: one is metal evaporates and produces vapor, another one is metal vapor diffuses in inert gas and nucleation and crystal nucleus growth. The powder particle size is mainly determined by the growth process from the evaporation surface to this temperature region, and this process is affected by evaporation temperature and the pressure and the type of inert gas, the influence of temperature gradients within the device and convection conditions. Metal ultra micro powder with 10nm-1μm can be fabricated by the process parameters controlling. This method is the most direct and effective in metal ultra micro powder fabricating, a company from France uses induction heating to improve the gas evaporating and succeed in fabricating copper ultra micro powder.
Plasma
Plasma has high temperature and high reaction speed, you can get a uniform, nano-powder of small particles, easily to achieve mass production, can be prepared almost any nanomaterials. It can be specifically divided into direct current arc (DC), high frequency (RF) and mixture (HP). DC has many advantages, such as simple equipment and operation, high efficiency and wide application, but it will easily melt and evaporate at high temperature, which will pollute the product; RF has no pollution of electrode, high speed of reaction, but its energy utilization rate is lower and instability. HP is combined with DC and RF, which has large space of plasma, high purity, high efficiency and good stability.
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