Development of carbon fiber reinforced ceramic matrix composites

Ceramic materials that melt at 3000 °C or higher are called ultra-high temperature ceramics (UHTC). One of the most commonly used UHTC composition is ZrB2-SiC. ZrB2-SiC still faces many obstacles today. Carbon fibers (Cf) are used as the reinforcement phase to increase the damage tolerance of UHTCs. Cf is an attractive candidate for this role due to its thermodynamic compatibility with ZrB2-SiC below ~3000 °C, high specific strength and stiffness. This thesis is about the development of UHTCs which reinforced with different types of carbon fibers. The density of the composites produced according to Archimedes' principle; phase and microstructural analyzes were carried out using SEM, EDX and XRD techniques and mechanical properties were examined. Pure and fabric carbon fiber reinforced ZrB2-SiC composites were produced by different methods. It was determined that the best mechanical properties belonged to the material produced by the dipping method and sintered in two stages at 2100 oC. Then, different types of Cf reinforced materials were produced and the effects of reinforcements on the critical parameters were examined. Best results in terms of relative density and fracture toughness in both chopped and short carbon fiber reinforced samples belonged to the 10% fiber reinforced sample, and the best results in terms of elastic modulus and hardness belonged to the 2.5% fiber reinforced sample. In the last part, composite materials were produced using rare earth oxides as sintering aids. These oxides improve the density and some mechanical properties of the materials but reduce the oxidation resistance.