Thermodynamics of the Al_2O_3-Al_4C_3 system I. Thermochemical functions of Al oxide, carbide and oxycarbides between 298 and 2100 K

摘要

A consistent set of thermochemical functions are proposed for aluminium oxide (Al_2O_3), carbide (Al_4C_3) and oxycarbides (Al_4O_4C, Al_2OC), including Gibbs free energies, enthalpies and entropies of formation as well as heat capacities, between 298 and 2100 K. Heat capacities of the base components of the Al-O-C system are also given. All equations are compared with existing functions in terms of relative errors, pointing important discrepancies for aluminium carbide and aluminium oxycarbide Al_2OC. When some are used to determine equilibrium partial pressures of carbon monoxide in classical high temperature solid-gas reactions, these discrepancies are confirmed or amplified. As a consequence, the present equations are suggested to describe the thermodynamic behaviour of aluminium carbide and aluminium oxycarbide Al_2OC.