Liquid phase sintering and characterization of siliconcarbide ceramics which have different cations

Silicon carbide (SiC) based ceramics have wide application areas because of long term properties due to their high mechanical strengths, thermal and chemical stabilities, high melting points, oxidation and wear resistances. Hot pressing is widely used in production of SiC based ceramics. In this thesis, liquid phase sintering was used to decrease sintering temperature, pressure and to reduce the cost. SiC based ceramics were sintered by Gas Pressure Sintering (GPS) and Spark Plasma Sintering (SPS) techniques at different sintering temperatures, time and at a set pressure in Argon atmosphere in order to enhance the physical and mechanical properties, to reduce the porosity and to obtain high density ceramics. In this study, SiC ceramics were sintered at 1950°C via GPS and SPS methods with sintering additives as Al2O3, Y2O3, MgAl2O4, Kaolen, Sc2O3 and HfO2. Relative density of SiC based ceramics was measured by Archiemede's method. The chemical composition was characterized by X-Ray Diffraction (XRD), and the microstructure of the samples was examined by using Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray (EDX). The hardness and the fracture toughness of SiC ceramics were evaluated by the vickers indentation technique. As a result of this study, it has been concluded that the physical and mechanical properties of the SiC based ceramics were increased positively with addition of 15 weight % various oxide additives via SPS technique. Keywords: Silicon Carbide, SPS, Sintering Additives, Rare-Earth Oxides, Physical and Mechanical Properties