Nanostructured boron nitride fiber/matrix interphase in carbon-carbon composites

A boron nitride (BN) coating, prepared by the nitridation of carbon fibers dip-coated in an ethanoic boric acid and urea precursor, presented decorations of nanosphere colonies on the carbon fiber surface and nanodiscs overlying the nanospheres in the microfurrows of fibers. The presence of residual boron impurity points to the formation of the nanostructures. Oxidation and ablation resistance studies of up to about 2500°C showed that the subsequently prepared Cf/BN/C composite's ablation rate and shrinkage was three times better than that for the Cf/C composite (without BN fiber coating). The interaction of the B2O3 with the pores that formed on the fiber surface revealed the stages of protection from partial sealing to complete denudation of the B2O3 phase. The overall protection of the BN and/or B2O3 coating on the carbon fibers is dependent on the integrity of the carbon matrix.