Oxidation Behavior of HfB۲-SiC-Nd۲O۳ Ultra-High Temperature Composite Sintered through SPS Process

The current study aims to fabricate HfB۲-۳۰ vol. % SiC and HfB۲-۳۰ vol. % SiC-۲ vol. % Nd۲O۳ composites through Spark Plasma Sintering (SPS) method at ۱۹۵۰ °C for ۱۰ min. The oxidation behavior of the prepared composites was investigated at ۱۴۰۰ °C and different times namely ۴, ۸, ۱۲, and ۱۶ hours. The relative density, hardness, toughness, and strength of the HfB۲-۳۰ vol. % SiC composite increased from ۹۸.۵ %, ۲۰.۱۹ GPa, ۴۱۴.۹ MPa, and ۴.۳۶ MPa.m۰.۵ up to ۹۹.۱ % , ۲۴.۴۷ GPa, ۴۸۵ .۵ MPa, and ۴.۹۳MPa.m۰.۵ for HfB۲-۳۰ vol. % SiC-۲ vol. % Nd۲O۳ composite, respectively. After ۱۶ hours of oxidation, SiO۲ layer, which was extremely thick, was produced locally on the oxidized HfB۲-۳۰ vol. % SiC composite surface. The thinckness of the SiO۲ layer was calculated to be around ۲۵ μm. The thickness measurement revealed the SiO۲ produced layer on the surface of the HfB۲-۳۰ vol. % SiC-۲ vol. % Nd۲O۳ composite to be ۵ μm. The oxidation kinetic results of the composite exhibited linear-parabolic behavior. The chemical reaction during the oxidation process controlled the oxidation rate after eight hours. After ۱۶ hours of performing the oxidation procedure at ۱۴۰۰ °C, HfB۲-۳۰ vol. % SiC-۲ vol. % Nd۲O۳ composite exhibited parabolic behavior, while HfB۲-۳۰ SiC exhibited linear behavior. This composite's improved oxidation resistance was attributed to Nd(Hf,Si)OxCy phases and decreased porosity, resulting in the generation of thin, dense, adherent, and protective layers. Therefore, it was concluded that the oxygen diffusion rate could control the oxidation process in HfB۲-۳۰ vol. % SiC-۲ vol. % Nd۲O۳ composite.

Keywords:

HfB۲-SiC-Nd۲O۳ Composite , Oxidation behavior , Spark Plasma Sintering , Rare earth element