Preparation and protective surface coatings for low density C/C composite for harden insulation

Abstract

To improve the anti-erosion and anti-oxidation performances is crucial for low density carbon/carbon (LD-C/C) composites to serve as a harden insulation material in high temperature equipment. Surface sealing treatment to the LD-C/C composite is an effective method. In the present study, first, diverse LD-C/C composite samples with different densities were fabricated, and then the effects of high temperature purification process on the density and thermal conductivity of the composites were briefly investigated. Furthermore, two protective coatings (graphite and SiC coatings) were respectively processed on the selected LD-C/C composite by painting graphite or silicon powder plus following heat-treatment, and the gas sealing and oxidation tests were performed on the coated samples. The experimental results indicated that the morphology (size and shape) of graphite powder particle played an important role in the microstructures of the coatings, resulting in varying gas sealing performance. The surface sealing process by using the silicon powder can also obtain a good gas sealing effect due to the effective infiltration of liquid silicon into the porous C/C composite and the formation of SiC, and thus the SiC coated sample presented the best oxidation resistance. However, there was no consistent relationship between the gas sealing performance and the oxidation resistance in the coated composite samples, which are closely related with the microstructural and physical characteristics of the coatings.

Keywords:

• Carbon/carbon composites
• Coating
• Microstructure
• Gas sealing
• Oxidation

Acknowledgements

This work was funded by National Natural Science Foundation of China (grant no. 51172177), the National High-Tech R&D Program of China (863 Program) (grant no. SQ2011AAJY2755), the Program for New Century Excellent Talents in University (grant no. NCET-11-0425), the Natural Science Foundation of Shaanxi province (grant no. 2012JM6004), and the Fundamental Research Funds for the Central Universities.