Way to prevent Cf/SiC composites from oxidation

Cf/SiC composites are easy to oxidize above 400°C in oxygen atmosphere and the oxidation is prone to be severer with increasing temperature.
Therefore, the improvement of oxidation resistance is essential for the application of Cf/SiC composites at high temperatures

Based on this,some Researchers focus on the fabrication of zirconium phosphate coatings at relatively low temperature to achieve a good oxidation resistance at high temperature.A ZrP-B2O3-SiO2 multi-phase inner layer was firstly applied on the surface of Cf/SiC composites with Al2O3 and MgO adopted as sintering additives. Then an outer SiO2 layer was deposited via sol-gel process on the surface of ZrP coatings to further promote the densification of coatings. After that, the microstructure and anti-oxidation performance of the coated Cf/SiC composites were investigated.

Experiment

Conclusions

1.The crystal form of zirconium phosphate is sensitive to the temperature and the decomposition of zirconium phosphate begins at temperature up to 1200°C.

2. Such novel double-layer coatings with an inner ZrP layer synthesized from mixed ceramic powders and an outer SiO2 layer fabricated by sol-gel process show excellent high temperature oxidation resistance and well self-sealing ability.

3.For coatings containing 60 wt. % ZrP, Cf/SiC composites show no obvious oxidation phenomenon after oxidation at 1500°C for 20 min and the mass retention percentage peaks at 98.6 %, while the highest flexural strength of the composites belongs to the 80 wt. %ZrP2O7 samples, reaching 303.9 MPa.

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