Mass Spectrometric Studies of the Vaporization of Refractory Metals in Oxygen at Low Pressures.

摘要

The kinetics of formation of the various gaseous species resulting from the interaction at high temperatures (1500 - 3000K) of refractory metals with oxygen at low pressures (.000007 - .001 torr) was studied by mass spectrometry. The metals investigated were Re, W, Ta, Nb, V and Zr. For Re and W the main process is the conversion of molecular into atomic oxygen, the gaseous metal oxides ReO3 or WO3 and WO2 being of secondary importance. For Ta and Nb, competitive processes leading to a steady state take place: oxygen enters into solid solution and gaseous oxides MO and MO2 are formed, whose relative importance is a function of temperature and pressure. For V and Zr, whose behavior is analogous to that of Ta or Nb, the rate of vaporization of the oxides is not sufficient to compete with the formation of oxides in the condensed phase. Expressions are given for the rate constants of the vaporization process. (Author)