Kinetic Study on Reaction of Titanium with Low Pressure of Oxygen at High Temperature

Abstract

The reaction kinetics of titanium foil with oxygen at the very low pressures of 8 ×10-6 to 6×10-5 Torr has been studied in the temperature range of 4750 to 890°C, by means of an ultra-high vacuum microbalance. The rate of reaction was separable in two types, i. e., the linear rate law in the initial and the parabolic rate law in the latter period. The linear rate law was obeyed for longer times as the reaction temperature increased, . the rate being almost unchanged within the temperature range of 475° to 890°C. In the initial linear part, the reaction rate was proportional to the oxygen pressure at each temperature which showed the linear oxidation to be controlled by the rate of arrival. The sticking probability and pumping speed per unit area (cm2) for oxygen were constant with the change of oxygen pressure, e. g., 0.023 for the sticking probability and 0.45 liters/sec for pumping speed at 700°C.On the bases of kinetic data including isothermal reaction rates with rapid change of oxygen pressure and vacuum annealing, discussion was made on the process of transformation in the reaction rate law.