Effect of pore size distribution on the mechanical performance of carbon foams reinforced by in situ grown Si₃N₄ whiskers

In the present study, Si₃N₄-whisker reinforced carbon foam composites were fabricated by in situ growth of Si₃N₄ whiskers via catalyst-assisted nitridation of Si and the effects of whisker content on the composites' pore size distribution and compressive strength were investigated. It was found that pore size decreased and its size range became narrower with increasing whisker content whereas compressive strength experienced an upward trend and reached the maximum value of 52.4MPa, a 300% improvement over net carbon foam, at a Si concentration of 80wt%. Microstructural observations of fractured composite surfaces indicated randomly oriented, in situ grown Si₃N₄ whiskers were uniformly dispersed across the cell walls of carbon foams while composites became more compact with increasing whiskers content.