Moduli carbon nitrides

Motivated by the reports of the S5mthesis of die IV-V nitrides, P principles calculations were performed on a hypothetical carbon nitride phase, C3N4, patterned on the P-SijN stmcture t) e [28]. A semi-empirical formula for bulk modulus developed out of this work, predicted the latter nitride would be of hardness comparable to diamond [28]. Inspection of... 

Nonoxide fibers, such as carbides, nitrides, and carbons, are produced by high temperature chemical processes that often result in fiber lengths shorter than those of oxide fibers. Mechanical properties such as high elastic modulus and tensile strength of these materials make them excellent as reinforcements for plastics, glass, metals, and ceramics. Because these products oxidize at high temperatures, they are primarily suited for use in vacuum or inert atmospheres, but may also be used for relatively short exposures in oxidizing atmospheres above 1000°C. 

Boron nitride derived from the borazine oligomer has been successfully used to replace the carbonaceous matrix in carbon fiber/carbon matrix composites (C/C) [15,18]. The carbon fiber/boron nitride matrix composites (C/BN) exhibit improved oxidation resistance over the C/C. Excellent mechanical strength and toughness have also been observed in the C/BN. As shown in Figure 2.16, both the flexural strength and modulus of pitch carbon fiber/BN specimens actually increase with extended heat treatment [18]. 

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