Influence of Heat Treatment Temperature on Bonding and Oxidation Resistance of Diamond Coated TiO2 Film

TiO2 films were prepared on the surface of diamond through a sol-gel method. The effect of heat treatment temperature on morphology, phase composition, phase transition, bonding with diamond, and oxidation resistance of diamond coated with TiO2 films were characterized through SEM, FTIR, Raman spectroscopy, X-ray diffraction analysis, XPS, TG-DSC and fracturing strength tests. The results show that when the heat treatment temperature rises to 600 degrees C, TiO2 film on the diamond surface changes from amorphous state to a dense anatase film and Ti-O-C chemical bond is formed between TiO2 and diamond substrate. When the heat treatment temperature increases to 800 degrees C, TiO2 film is still anatase phase, graphitization of diamond substrate occurs, graphitized C forms Ti-O-C chemical bond with TiO2 film; however, TiO2 film begins to crack. Meanwhile, the heat treatment temperature of TiO2 films has a greater impact on the oxidation resistance of diamond in air. When the heat treatment temperature is 600 degrees C, the initial oxidation temperature of the diamond reaches a maximum value of 754 degrees C. After oxidation at 800 degrees C for 0.5 h in air, the mass loss rate and compressive strength is 6.7 wt% and 15.7 N, respectively.