Thermal Stability and Environmental Degradation of YB 2 C 2 Ceramics

This study investigates the melting, oxidation, and ambient moisture‐induced corrosion behaviors of high‐purity yttrium borocarbide (YB 2 C 2 ) ceramics. The YB 2 C 2 ceramic exhibited decomposition and melting behaviors at approximately 2100°C under low‐vacuum conditions (below 20 Pa). Thermogravimetric (TG) analysis performed between 40°C and 1400°C in air, combined with x‐ray diffraction (XRD) analysis, confirmed that the significant oxidation of sintered YB 2 C 2 initiates above 810°C. This process leads to the extensive phase transformation into YBO 3 , B 2 O 3 , and Y 2 O 3 after the thermal cycle. Furthermore, the sintered YB 2 C 2 was observed to react with atmospheric moisture under ambient conditions, disintegrating into a fine powder while forming amorphous yttrium and boron hydroxide species. The resulting morphology and crystalline structure of these hydro‐corroded products differed significantly from those of the oxidation products. The underlying mechanisms for the oxidation and ambient moisture corrosion were systematically analyzed. These findings indicate that YB 2 C 2 ceramics may require robust environmental barrier coatings (EBCs) or other protective strategies for practical applications in oxygen‐ or moisture‐containing environments.