Oxidation Protection Coatings for Carbon Materials by Interfacial Control

概要

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Porous carbon substrates have been sealed completely with a molten silicate glass, where the wettability of the carbon to the molten glass was improved by infiltration and pyrolysis of perhydropolysilazane. The interfacial structure between the carbon and glass depended on the N2 partial pressures during sealing. Coating of the glass at a higher N2 partial pressure was not followed by formation of cristobalite due to oxidation of the products pyrolyzed on the carbon substrate. The molten glass easily infiltrated into the substrate. Under lower N2 partial pressures such as in Ar, the glass covered only the carbon substrate and seldom penetrated into the substrate. In this case, cristobalite was produced at the interface, with many pores also forming at the interface. The pores are due to the large amount of SiO produced by oxidation of the pyrolyzed species, leading to suppression of molten glass infiltration into the carbon. The structural changes occurring as a result of variation in N2 partial pressures are described in terms of thermodynamic calculations.
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