Interfacial Modification of Microcellular Carbon: Influence of Ceramic and Carbon Nanotube Coatings

Microcellular carbon is an emerging ultra lightweight and efficient thermal management material, which also has great potential as a reinforcement material for selected composites. However, these porous materials exhibit relatively low mechanical properties, and are susceptible to degradation in oxidizing environment. The scope of this research is to investigate surface modification approaches that can address these issues. Two specific objectives were: (1) to develop ceramic coatings to improve the survivability of carbon foams in high temperature applications, and (2) to develop and test modifications that can improve cellular composites involving carbon foam. It was seen that a mixed layer of BN and SiC on the foam improves its oxidation resistance at high temperatures to the same extent as pure BN layer. However, the mixed layer had improved microstructure, and presence of silica phase, that maybe useful in development of selected functionally gradient coatings in the future. For modification related to future cellular composites, it was seen that attachment of carbon nanotubes (CNT) on the surface can significantly improve its bonding with other phases, and therefore the mechanical behavior of composites made from this foam. The influence of CNT attachment on mechanical performance and failure mechanics of foam-epoxy composite was investigated. Model studies were also carried out on planar graphite-epoxy interfaces using 3-point bending tests. It has been observed that the CNT attachment significantly improves the durability and toughness of the carbon-epoxy interface by preventing delamination.