Anomalous Diffusion of 14C in TiC0.67

The self-diffusion of ¹⁴C in TiC_0.67 was studied in the temperature range 1745°–2720°C. The diffusivity, which exhibits a discontinuity at 2080°C, can be represented by two expressions: $D_{\text{0.67}}^{*}{\text{=(2.85±0.20)×10}}^{\text{−4}}\exp \text{[−(49\hspace{0.17em}600±300)/RT]\hspace{0.17em}}{\mathrm{cm}}^2\mathrm{/sec}$ above 2080°C and $D_{\text{0.67}}^{*}{\text{=(1.14±0.66)×10}}^2\exp \text{[−(109,900±2000)/RT]\hspace{0.17em}}{\mathrm{cm}}^2\mathrm{/sec}$ below this temperature. No discontinuity was found in carbon saturated TiC_0.97 and the self-diffusion coefficient for this composition can be described to a temperature of 2720°C by the single expression D^*_0.97=(6.98±1.24) exp[−(95 300±700) / RT] cm²/sec.