Thermal Decomposition of Niobium and Tantalum Monocarbides

摘要: The thermal decomposition of polycrystalline NbC was investigated from 2000° to 3200°C, and TaC 1890° 3320°C in the presence one atmosphere helium. It found that both compounds lose carbon preferentially, final carbon/metal molar ratio obtained may be represented by an equation form C/M=A—B exp(λt), where t is maximum temperature heating for a constant time (30 min cases). Similarly resultant lattice expressed as a0=A′—B′ exp(λ′t), a0 A at 25°C. For 3000°C times 30 12 hr, a0=4.459084+0.0093071 exp(—0.18916 τ) NbC, τ hours. a0=4.414712+0.056862 (C/Nb) C/Nb range 0.885 0.981 a0=4.385779+0.070204 (C/Ta) C/Ta 0.906 0.996. By extrapolation, constants stoichiometric should 4.47157±0.00012 25°C 4.45598±0.00038 25°C, respectively.