Kinetics of the Oxygen—Tungsten Reaction at High Temperatures

Abstract

The rate of reaction of molecular oxygen with tungsten was measured ffOm 2000° to 3300 0 K at pressures from 0.11 to 11.5 torr. High gas-phase mass transfer coefficients were obtained by impinging a high-velocity gas jet on the sample. A maximum reaction rate was observed at each O2 ~ressure, the tempera~ure. of maximum rate increasing with pressure. Below the temperatures of the maXIma, an apparent activatIOn energy near 23 kcal mole-1 was observed. These results are well described by the empirical equations of Perkins, Price, and Crooks, except that no transition to a regime of higher activation energy at lower temperatures was observed here and the maxima were found at slightly higher rates and te:uperatures than previously reported. Appreciable diffusion effects were found only near the observed maXIma. These data and the 10-4 torr data of Schissel and Trulson were correlated in terms of the two-layer oxygen-atom adsorption model for tungsten oxidation kinetics proposed by the latter authors. Kinetic constants for a slightly modified version of this model were obtained.

Surface terraces in pure tungsten formed by high temperature oxidation

“…Although tungsten has the highest melting point, it readily oxidises above 400 °C [15][16][17]. Tungsten trioxide (WO3), along with its variants like W18O49 and WO2.9, is the main oxide formed during oxidation up to temperatures of 2000 °C [16][17][18]. Once formed, the oxide readily sublimes above 1000 °C [19,20].…”

Chemical Erosion of Refractory-Metal Nozzle Inserts in Solid-Propellant Rocket Motors

“…At sufficiently high temperatures, the metal surface is prone to chemical attack by such oxidizing species as H 2 O, CO 2 , O 2 , and O. Although the reactivity of metals with oxygen is significant [17,18], this effect can be ignored due to the fuel-rich nature of AP/ HTPB propellants, which produce negligible amounts of O 2 and O in the gas phase. The main species considered in the combustion stream are thus H 2 O, CO 2 , CO, HCl, N 2 , and H 2 .…”

Fundamentals of Spacecraft Thermal Design

“…In this instance, calculations on the wall surface degradation rate can be performed readily with the aid of the boundary-layer multicoiroonent injection correlations Eqs. (13)(14)(15)(16)(17)(18).…”

“…The most widely known result is that from Drude single electron theory. 18 The greatest attribute of the Drude theory results from an engineering standpoint is probably the simplicity of the expression for spectral emittance. The Drude theory result for spectral emittance, however, does not agree well with experimental data for metals for wavelengths less than about 5y.…”