In recent years, the high-temperature vacuum furnaces have been widely used in melting metals and alloys, sintering refractory hard metals or heat-treating various materials. One of the most critical factors in such furnaces is the properties of refractory materials used.
This report describes the properties of zirconia grain and graphite powder which are used as heat insulating material in the high temperature vacuum sintering furnace. Graphite powder (150 mesh under) shows more excellent features compared with zirconia grain in heat insulation as well as in gas evolution. Thus the temperature above 2500°C was obtained easily by using graphite powder under a vacuum of 2μHg or better. The thermal conductivty and gas evolution rate of such insulating materials are also estimated and discussed.
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