Oxygen diffusion in titanium carbide
The diffusion coefficients of oxygen were measured in TiC0.97 single crystals by a gas exchange technique in which the amount of stable isotope taken up by the carbide was controlled by introducing a constant gas volume of oxygen-marked carbon monoxide. Diffusion was extended over depths of 1 to 150 μm. The concentration profiles were measured by secondary ion mass spectroscopy (SIMS). Interpretation was made by assuming a constant superficial concentration. The results can be described by the expression D(cm2/s)=0.48 exp [-3.97 (eV) atomkT] in the temperature range 1500−2100°C. These results are compared with carbon self-diffusion data. For the low-temperature range (1000<T<1500°C) the diffusion coefficients show a departure from the high-temperature extrapolated data, which is interpreted as an enhancement of the oxygen diffusion by dislocations.