Diamond/silicon carbide composites sintered under high pressure-high temperature conditions / by Jiang Qian.

Abstract

In this dissertation work, novel bulk diamond composites with nano-size grain and nanocrystalline SiC bonding were sintered under high pressure-high temperature (HP-HT) conditions. While preserving the superior hardness, wear resistance of micron-composites, nano-composites have higher strength and fracture toughness due to effective blocking of microcrack propagation and dislocation movement by the nanocrystalline grains. New preparation method, wet mixing and high-energy ball milling, have been used to make starting materials to avoid the self-stop process due to pore closure in HP-HT liquid phase sintering. Key factors influencing the dynamics of the reaction between diamond and silicon, such as diamond graphitization process, phase composition and stress-strain, were thoroughly studied with Raman spectroscopy, x-ray diffraction, SEM and TEM techniques. Mechanical properties of the composites were characterized by ultrasonic interferometer and microindentation hardness measurements. Nanostructured composites represent a new field of fundamental science and manifest potential application in multiple industries.