Nano-sized particles formed by pulsed discharge of powders sealed in heat-shrinkable tubes

Abstract

Pulsed wire discharge has been developed as a method to form nano-sized particles, wherein a large electrical current pulse is passed through a thin metal wire. Various wire materials have been used to form nano-sized particles by this method so far. However, materials which are not sufficiently ductile to form thin wires are unsuitable for this method. We have developed a new method for powders to be discharged to form nano-scale particles instead of wires. The powders were placed in heat-shrinkable tubes and sealed by heating. Short metal wires were set at both the ends of each tube for electrical connection to the electrodes of the discharge equipment. These tubes were set in a chamber whose atmosphere could be controlled. A large current pulse was then applied to the powders in the tubes. SiC particles with a cubic crystalline structure were synthesized in N2 gas from mixed powders of Si and C with a C/Si molar ratio of unity. However, mostly the Si phase remained in the particles. Then, mixed powders with a C/Si ratio of 2 were discharged. The obtained particles were mainly composed of the SiC phase, although Si and graphite phases remained mingled.