Oxidation behavior of TiB₂ from 600 to 1400 ℃ considering microstructure evolution, oxidation kinetics, and mechanisms

Titanium diboride (TiB₂) is a candidate material in thermal protection systems (TPS) as fillers in multi-phase ultra-high temperature ceramics due to its excellent oxidation resistance. However, the research on its oxidation process and mechanism is modest as compared with ZrB₂. Here, static oxidation tests on TiB₂ ceramics at various temperatures were conducted using laser heating to systematically and comprehensively explore the dynamic evolution of oxidation behavior with oxidation time under different working conditions. It was found that the oxidation product (TiO₂) undergoes a microstructural change at increased temperatures. Additionally, the oxidation products (TiO₂ and B₂O₃) were observed to exhibit a mosaic arrangement characterized by regular aggregations. The oxidation model extends existing ones and its oxidation mechanism is systematically explained based on the evolution of oxidation products and oxide layer microstructure. Through isothermal oxidation experiments, it is found that the oxidation kinetics of TiB₂ follows a parabolic law, and combined with theoretical models, it is shown that the oxidation process is governed by oxygen diffusion through the oxide layer. Based on the in-situ measurement method, the oxidation activation energy of TiB₂ ceramics in air was determined to be 9.30×10⁴ J/mol.