Effect of Nitrogen Dopant on Electrical Resistance of Hot Zone of SiC Heating Elements

Abstract

In the present work gaseous nitrogen is used as dopant in silicon carbide heating element to study the effect of electrical resistance in heat generation portion of heating elements. The silicon carbide heating elements are used mainly in non-ferrous alloy melting and holding furnaces in automotive and aerospace industrial applications. The gaseous nitrogen plays a major role as dopant in achieving the electrical resistance of SiC heating elements. The green silicon carbide is used to prepare the heating element by powder metallurgy process because of its high mechanical strength, resistance to corrosion, and high thermal conductivity at elevated temperature. However, the nitrogen acts as dopant in silicon carbide to achieve the electrical resistivity in the heating element to generate uniform heat in hot zone portion of SiC heating elements while sintering. The hot zone of SiC heating element is connected with cold zone at both the terminals of heating element to pass the current to hot zone to generate the heat by its higher resistivity. A range of nitrogen gas flow rate ranges from76 lt/hr to 84 lt/hr with 99.99% purity of industrial grade passed to the sintering furnace, in turn it acts as dopant and creates inert atmosphere in the sintering furnace, then the SiC heating element tubes were made and analysed. The results indicate that the quantity of gaseous nitrogen dopant influenced the electrical resistivity of the heat generating portion of SiC heating element.