Non-metal diffusion coefficients for the Ta-C and Ta-N systems
- Vienna Univ. of Technology (Austria). Inst. for Chemical Technology of Inorganic Materials
The diffusivity of carbon in tantalum and tantalum carbides was investigated in the temperature range 1,700--2,200 C, and that of nitrogen in tantalum and tantalum nitrides between 1,700--1,950 C. The concentration-independent diffusion coefficients were obtained in all phases by investigating the enhanced layer growth in wedge-shaped specimens. In the nonmetal-rich phases having a broad homogeneity range, i.e., in {delta}-TaC{sub 1{minus}x}, {beta}-Ta{sub 2}C{sub 1{minus}x} and {beta}-Ta{sub 2}N{sub 1{minus}x}, also the concentration-dependent diffusion coefficients were calculated and compared with the concentration-independent diffusion coefficients. The calculation of the concentration-dependent diffusion coefficients was performed by fitting a modified error function on the measured concentration profiles assuming the nonmetal diffusivity being an exponential function of the nonmetal concentration. Strong dependence of the diffusion coefficient on the nonmetal concentration was found for the {delta}-TaC{sub 1{minus}x} phase, whereas the nonmetal diffusion coefficients were nearly concentration-independent for {beta}-Ta{sub 2}C{sub 1{minus}x} and {beta}-Ta{sub 2}N{sub 1{minus}x}.
- OSTI ID:
- 638314
- Journal Information:
- Acta Materialia, Journal Name: Acta Materialia Journal Issue: 10 Vol. 46; ISSN 1359-6454; ISSN ACMAFD
- Country of Publication:
- United States
- Language:
- English
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