Thermodynamic properties over (Ni2Te3O8 + NiTe2O5) in the Ni–Te–O system: Transpiration thermogravimetric and Knudsen effusion mass spectrometric studies

Abstract

Abstract Vaporisation studies over (Ni2Te3O8 + NiTe2O5) in the Ni–Te–O system were carried out by means of transpiration thermogravimetry (TTG) and Knudsen effusion mass spectrometry (KEMS) in the temperature ranges of 950 – 1 060 K and 850 – 950 K respectively. The transpiration measurements were performed for the first time. Comparison of total pressures obtained by TTG with that deduced using partial pressures of vaporising species from KEMS showed a good agreement providing reliable vapour pressures over this phase region. From vapour pressures, enthalpies of solid–gas and gas-phase equilibria and subsequently enthalpy and Gibbs free energies of formation of NiTe2O5(s) were derived. A thermochemical calculation was performed to assess the possibility of formation of the ternary NiTe2O5(s) phase on stainless steel clad of mixed-oxide fuelled fast breeder nuclear reactors.