Tribological Properties and Thermal Conductivity of Si3 N4 / Si3N4-BN Alternate Layered Composites
Alternate layered composites of Si3N4 layers and layers of Si3N4 with 20 vol% of hBN (Si3N4-BN layers) were fabricated and their tribological properties and thermal conductivities were evaluated. The layered composites were fabricated by alternate stacking of a monolithic Si3N4 layer and a Si3N4-BN layer in the form of a green sheet, followed by hot-pressing or annealing. For comparison, Si3N4 and Si3N4 with 10% hBN were fabricated by hot-pressing powder mixtures. Tribological properties were evaluated on the side plane of the composites by a block-on-ring test method under a dry sliding condition and thermal conductivities were evaluated. The layered composites were found to have lower friction coefficients and higher wear resistance than to simple composites. Moreover, for the layered composite with an aligned β-Si3N4, the friction coefficient on the plane composed of faceted hexagonal grains was lower. The layered composite with an aligned β-Si3N4 in the Si3N4 layer, fabricated by annealing for 72 h indicated both a low friction coefficient (0.28) and high thermal conductivity (130 W/mK).
T. Ohji, T. Sekino and K. Niihara
T. Hirao, K. Hirao, Y. Yamauchi, "Tribological Properties and Thermal Conductivity of Si3 N4 / Si3N4-BN Alternate Layered Composites", Key Engineering Materials, Vols. 317-318, pp. 363-368, 2006