Nanocrystalline C-BN synthesized by mechanical alloying

Nanocrystalline carbon-boron nitride (C-BN) compounds have been synthesized by solid phase mechanical alloying of C_x(BN)_1-x powder with various carbon fractions x. Ternary mixing within the structures was found to occur after ball milling and hot-pressing. High temperature recrystallization led to a change in structural configuration, specifically, into alternating layers of graphite and BN. The hardness of the C-BN plates increased when the carbon fraction x increased from 0 to 0.5, and then decreased when x increased thereafter. The composite C_0.5(BN)_0.5 possessed the highest hardness equalling twice that of nanocrystalline graphite and three times that of nanocrystalline BN. The lattice parameters c and a were larger and smaller, respectively, than those of graphite and hBN. The property differences between the initial and resultant materials were attributed to the structural transformation of the original substances into heterogeneously layered C_x(BN)_1-x compounds. New additional peaks were also observed and matched those of shock-wave compressed BN.