Effect of Zr/Ce molar ratio on the structure of powders and Zr1-xCexO2 coatings on quartz fiber reinforced polyimide matrix composites via sol-gel process

In this investigation, Zr1-xCexO2 coatings were fabricated on quartz fiber reinforced polyimide matrix composites via sol-gel process at 400 degrees C. The phase evolution, structural and morphological characteristic of specimens were investigated by differential scanning calorimetric, Fourier transform infrared spectroscopy, powder X-ray diffraction and scanning electron microscopy. The significant phase evolution of final powders with the decreasing Zr/Ce molar ratio could be observed as follows: tetragonal (t') -> cubic + tetragonal (t') -> tetragonal (t ''). BET specific surface areas of powders exhibited a decreased tendency with the increasing calcination temperature as well as the decreasing Zr/Ce molar ratio. The average crystallite size and the mean particle size increased with the elevated calcination temperature, while the particle size also increased with the increase in Ce content. The progressive addition of Ce could promote the sintering process and the densification of coating. Morphologies of coatings changed with the variation of the Zr/Ce molar ratio. The results indicate that Zr0.75Ce0.25O2 coating with the Zr/Ce molar ratio of 3 is a stable uniform coating with excellent adhesion.