Fabrication of HfB₂-TiC/HfB₂-TiC-CNT Bilayer Compositeand Investigation of its Oxidation Resistance

In the present study, a bilayer composite of HfB₂-TiC/HfB₂-TiC-CNT was fabricated using Spark PlasmaSintering (SPS) at a temperature of ۲۰۰۰°C for ۸ minutes under a pressure of ۳۵ MPa. To assess theoxidation resistance of this composite, three samples were subjected to temperatures of ۹۰۰°C, ۱۰۰۰°C,and ۱۲۰۰°C for ۲۰ minutes, and their properties were evaluated. The samples were examined usingScanning Electron Microscopy (SEM), X-ray Diffraction Analysis (XRD), and Thermal GravimetricAnalysis (TGA) coupled with Differential Thermal Analysis (DTA). The results indicated that the thermaloxidation process led to the oxidation of TiB₂ and HfB₂ phases and the formation of new phases,including TiO₂ and HfO₂. At ۸۰۰°C, HfB₂ decomposed, forming a liquid phase B₂O₃, which improvedoxidation resistance. However, this phase evaporated at ۱۰۰۰°C, resulting in a decrease in oxidationresistance. XRD analysis revealed that with an increase in the heat treatment temperature from ۹۰۰°C to۱۲۰۰°C, the size of crystallites and the number of oxide phases (HfO₂ and TiO₂) increased, while latticestrain decreased. Hardness also decreased from ۱۹.۴ to ۱۷.۲ GPa. Microscopic images demonstrated thatthe oxidation reactions of HfB₂ and TiC formed a protective oxide layer on the HfB₂-TiC/HfB₂-TiC-CNTcomposite.

کلیدواژه ها:

HfB₂-TiC-CNT ، SPS ، oxidation ، Thermal Gravimetric Analysis (TGA)