STABILITY OF CERAMIC MATERIALS AT TEMPERATURES TO 2000°C

摘要

A study was made of the oxidation resistance of a number of commercial sample of MoSi and WSip in the temperature range l600-1700°C. A thermal conductivity technique was developed to measure oxygen pick-up by the samples continuously. From the thermal conductivity measurement and the net weight change of the samples, as estimate was made of the rates of formation of volatile and non-volatile oxides. On the basis of X-ray analysis, oxidation products are believed to be volatile XO3 (vapor) and non-volatile glass of the form Si02.nX0m where X = Mo or W; n and m are not known. Tests were conducted at a total pressure of one atmosphere in a helium stream containing about 10 mm of oxygen and flowing at 119 cc/min. The oxidation of WSip was also studied in a helium stream containing 5 mm of water vapor. The principal solid product in this case was metallic tungsten.