The novel effect mechanism of Al2O3 nano-powder in the pack cementation process to prepare SiC coating on C/C composites

As an additive, Al2O3 nano-powder can significantly improve the preparation of SiC coating by the pack cementation process. The three-dimensional morphology of the SiC coating and the interface between coating and substrate were analyzed by synchrotron radiation X-ray computed tomography (SR-CT). Combined SR-CT and other analysis results, an unpredicted effect mechanism of Al2O3 was analyzed in this work, which is obviously different from previous studies. The holes left by the chemical reaction between the Al2O3 and SiC can be the penetrating channels for the liquid Si into the C/C composites, which could obviously increase the thickness of SiC coating. At the same time, the density of SiC coating is also improved by adding the Al2O3 nano-powder.