The diffusion and solubility of T were measured in vapor-deposited -phase material. The solubility measurements were performed at temperatures ranging from 1000 to 1600C, and pressures ranging from 0.01 to 1atm. The diffusivity was determined at temperatures ranging from 1100 to 1500C. It was found that the diffusivity was much lower than that for metals, and that the activation energy was much higher. The measured solubility indicated a negative heat of solution and, when corrected for surface absorption, it varied linearly with the square root of the pressure. The low diffusivity, together with the apparent negative heat of solution, were suggested to reflect trap-controlled migration of T in the carbide.

R.A.Causey, W.R.Wampler, J.R.Retelle, J.L.Kaae: Journal of Nuclear Materials, 1993, 203[3], 196-205