Oxygen Interaction with Hexagonal OsB₂ at High Temperature

Abstract

The stability of ReB2‐type hexagonal OsB2 powder at high temperature with oxygen presence has been studied by thermogravimetric analysis, differential scanning calorimetry, SEM, EDS, and high‐temperature scanning transmission electron microscopy and XRD. Results of the study revealed that OsB2 ceramics interact readily with oxygen present in reducing atmosphere, especially at high temperature and produces boric acid, which decomposes on the surface of the powder resulting in the formation of boron vacancies in the hexagonal OsB2 lattice as well as changes in the stoichiometry of the compound. It was also found that under low oxygen partial pressure, sintering of OsB2 powders occurred at a relatively low temperature (900°C). Hexagonal OsB2 ceramic is prone to oxidation and it is very sensitive to oxygen partial pressures, especially at high temperatures.

Aluminium magnesium boride: synthesis, sintering and microstructure

“…It was generally concluded that the presence of elemental boron and a sufficient concentration of highly volatile reactants at the reaction front were prerequisites for a successful compound formation [6], as attempts to synthesise AlMgB 14 using AlB 12 and MgB 2 compounds as reactants resulted in only 25 vol.-% yield of AlMgB 14 phase in the product mix of other phases [39]. Oxidation is a common problem during synthesis of boride compounds [44][45][46][47]. The formation of MgAl 2 O 4 spinel was always reported in all synthesis attempts as a result of contamination of reactants and inevitable presence of oxygen that facilitated and was responsible for formation of thermodynamically stable oxide.…”