High temperature oxidation of multilayered SiC processed by tape casting and sintering
The oxidation behaviour of a multilayer SiC ceramic was investigated at high temperatures. The ceramic samples were processed by tape casting of a slurry containing α-SiC powders, forming of green tubular components and sintering without pressure. The oxidation resistance of this ceramic material was investigated by temperature programmed oxidation (TPO): the gaseous oxidation products were analysed by mass spectrometry. Thermal gravimetric analyses (TGA) were also performed. Buckles, machined from the multilayer ceramic tubes, were submitted to long-term oxidation treatments carried out at 1200, 1400 and 1600 °C in air. The microstructure and the radial compressive strength of these specimens were compared before and after oxidation. Microstructure was investigated by SEM-EDS and X-ray diffraction. The multilayered SiC showed increased toughness with respect to conventional ceramics, owing to delamination phenomena occurring before failure. Oxidation mainly affected the material surface, where a thin layer of silica grew. Oxidation treatments did not suppress the energy adsorbing mechanism occurring during the fracture process.