Study on the Formation of Ultrafine Iron Particles with Paramagnetism (Gamma-Fe)

点击翻译按钮获取中文摘要

Production of gamma-Fe ultrafine particles was done with the use of microwave plasma heating. Alpha-Fe ultrafine particles were prepared by the gas evaporation method. The alpha-Fe ultrafine particles were drifted through a microwave plasma region to the gas downstream. Alpha-Fe ultra-fine particles were heated and then quenched rapidly. After that, gamma-Fe ultrafine particles were obtained.(1) Abundance of gamma-Fe ultrafine particlesThe abundance of gamma-Fe ultrafine particles depends on Ar gas pressure, microwave power and gas velocity in the plasma region. A maximum abundance of 40% was achieved with the gas pressure of 15Torr, the microwave power of 500W and gas velocity of 40m/s. As the microwave power increases above 500W, the abundance of gamma-Fe decreases gradually. The abundance of 30% was obtained at microwave power of 1KW. When the gas velocity was changed to 10m/s, the abundance of gamma-Fe decreased in comparison with the case of 40m/s.(2) Effect of carbon (CH_4) on the production of gamma-Fe ultrafine particlesIn an oil-free vacuum systems, a similar experiment was done with a small amount of CH_4 gas added to Ar gas. When the CH_4 content was 90ppm, the abundance of gamma-Fe was 55% at the following conditions as 15Torr in Ar pressure, 40m/s in the gas velocity and 500W in the microwave power. When the CH_4 content was 450ppm, Fe-C system (Fe-C,Fe_3C) was found in addition to alpha and gamma.In an experiment carried out in the CH_4 gas added to He gas, the abundance of gamma-Fe was less than in that of Ar. No Fe-C system was observed in this case.