Abstract
A new preparation method of high-purity ultrafine nitride particles was demonstrated by applying the low temperature plasma induced by 2.45GHz microwaves to the gas evaporation technique. Ultrafine Al, Fe and Si particles produced by the evaporation of these metals in a low pressure N2 gas condition were nitrided by passing them through the nitrogen plasma region. From the electron diffraction, the following nitride phases were recognized as AlN, γ-Fe (solid solution of nitrogen), γ-Fe4N, ε-FexN (2<x≤3), ζ-Fe2N, α-Si3N4 and β-Si3N4. The formation of these phases depended mainly on three factors: N2 gas pressure, the gas velocity at the plasma region and the microwave power. The preferable conditions of these factors for preparing pure nitride particles were investigated. For example, the particles formed at the condition of 7 Torr in N2 pressure, 1m/sec in gas velocity and 1.2kW in microwave power consisted completely of nitrides of the starting material evaporated. In the cases of Fe-N and Si-N system, a mixture of those nitride phases was formed generally.
Particles tended to grow in the plasma region. The particle size of nitrides ranged from 20 to 300nm, which was found to be larger by a factor of 5 to 10 than that of particles collected at the front of the plasma region.
