PRINCIPLES GOVERNING THE BEHAVIOR OF SOLID MATERIALS IN SEVERE HIGH TEMPERATURE ENVIRONMENTS
Quarterly progress rept. 8 Mar-30 Jun 1965
UNION CARBIDE RESEARCH INST TARRYTOWN NY
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The reaction between high-density tungsten and H2O vapor has been studied from 1900 to 2800 K in the induction-heated stagnation-flow reactor at H2O partial pressures from 25 to 155 torr. The reaction is linear with time at all pressures and temperatures studied. All isobars show apparent activation energies that decrease with temperature, indicating that gas-phase diffusion limits the reaction rates at the higher temperature. Furthermore, the rates are dependent on the gas flow rate at the higher temperatures, consistent with this interpretation. Rate data previously obtained for the W-CO2 reaction are being analyzed in terms of a model including diffusion effects, reaction of the oxygen formed by cracking of CO2, and activated sticking of CO2 on the tungsten surface this model employs certain results of the mass-spectrometric studies being conducted here. Difficulties traceable to the slow reaction of W with HF were encountered in the study of the W-HF reaction in the arcimage stagnation- flow reactor. Reactions due to impurities in the HF and small amounts of air introduced through leaks in the system tend to obscure the desired reaction. The relative rates of production of gaseous O, WO, and WO2, by the W-02 and W-CO2 reactions have been studied mass-spectrometrically.
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