Vaporization studies over (NiO + Ni2Te3O8) in the Ni–Te–O system by transpiration thermogravimetry and Knudsen effusion mass spectrometry

Abstract

Vaporization studies over (NiO+Ni2Te3O8) in the Ni–Te–O system were carried out by transpiration thermogravimetry (TTG) and Knudsen effusion mass spectrometry (KEMS) in the temperature ranges of 960–1085K and 850–960K, respectively. Comparison of total pressures obtained by TTG with that deduced using partial pressures of vaporizing species from KEMS showed a good agreement providing reliable vapor pressures over this phase region. From vapor pressures, enthalpies of solid–gas and gas-phase equilibria were evaluated. Subsequently, enthalpy and Gibbs free energies of formation of Ni2Te3O8(s) were deduced at 298.15K: ΔfHm°=−1543±46kJmol−1; ΔfGm°=−1294±46kJmol−1. A thermochemical assessment was made to examine the possibility of formation of the ternary Ni2Te3O8(s) phase on stainless steel clad of mixed-oxide fuelled fast breeder nuclear reactors.