Performance of conventional CSZP-based ceramic coating on oxidation of carbon–carbon composites

Low-expansion compositions of Ca1−xSrxZr4(PO4)6 [CSZP] system, synthesized by solid-state reaction method were characterized for axial and bulk thermal expansion by high-temperature XRD and dilatometry to obtain a suitable composition with matching expansion behaviour with carbon–carbon composite. Sinterability of the powders was promoted by the addition of 3 and 5 wt.% ZnO and the corresponding effects on the bulk thermal properties were determined. Coating of the most suitable composition with x = 0.25 was applied on the composite by normal spraying technique. The coating was matured at 1100 °C to obtain a continuous protective layer with low porosity and almost no visible reaction at the interface. Oxidation studies of coated and uncoated composites carried out at 600–900 °C temperature range up to 6 h established that the coating helped to improve the oxidation resistance of the composite at elevated temperature.