Control of the Nano-Particle Weight Ratio in Stainless Steel Micro and Nano Powders by Radio Frequency Plasma Treatment

This study describes how to make stainless steel hybrid micro-nano-powders (a mixture of micro-powder and nano-powder) using an in situ one-step process via radio frequency (RF) thermal plasma treatment. Nano-particles attached to micro-powders were successfully prepared by RF thermal plasma treatment of stainless steel powder with an average size of 35 μm. The ratio of nano-powders is estimated with a two-dimensional fluid simulation that calculates the temperature profile influencing the rate of surface evaporation. The simulation is conducted to determine the variation of the input power and the distance from the plasma torch to the feeding nozzle. It was demonstrated experimentally that the nano-powder ratio in the micro-nano-powder mixture can be controlled by adjusting the feeding rate, plasma power, feeding position and quenching effect during plasma treatment. The ratio of nano-particles in the micro-nano-powder mixture was controlled in a range from 0.1 (wt. %) to 30.7 (wt. %). © 2015 by the authors; licensee MDPI, Basel, Switzerland.