| Popis: |
This paper investigated the oxidation behavior of LaB6 in the temperature range of 700–1185 °C. The results obtained by thermogravimetric analysis (TGA) showed that the initial oxidation has parabolic kinetics in the temperatures between 800–945 °C. The oxidation process exhibited temperature dependence with an activation energy of 195±15 kJ/mol in air and in pure oxygen atmosphere. Two possible reactions, either the evaporation of B2O3 species (occurring ⩾945 °C) or the oxidation of surface LaB6 (⩽800 °C), influence the oxidation mechanism to be interfacial reaction control, which results in mass loss deviating from parabolic behavior. The details of the microstructure evolution of the formation of glass and crystalline La(BO2)3 grains are investigated. The effects of porosity, the melting of La(BO2)3, coarsening of La(BO2)3 grains are reported and discussed. |
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