Improved mechanical properties and directional heat transfer performance of h-BN matrix multilayer composites with alternately stacked untextured/textured layers

Abstract

The h-BN matrix multilayer composites with alternately stacked untextured/textured layers were fabricated by hot-pressing from the alternately stacked “fine h-BN powders” layers and “plate-like h-BN powders + 3Y2O3–5Al2O3” layers. During the hot-pressing process, Y2O3 and Al2O3 reacted, forming Y3Al5O12, which provided a liquid phase environment for h-BN plates to be readily rotated and oriented under the action of the uniaxial pressure. The residual compressive stress in textured layers, which was caused by the mismatch of thermal expansion between textured layers and untextured layers, resulted in crack arrest at the first textured layer in the multilayer composite with 49 vol% textured layers, which improved its flexural strength and fracture toughness by 33.1% and 23.4% compared with the textured monolith, respectively. The multilayer composite with 35 vol% textured layers behaved a much better directional heat transfer performance than the textured and untextured monoliths, making it a promising candidate as thermal management devices in electronics.