WANG Dalei, LI Ruifeng, CHEN Han, GUO Lucun
(College of Materials Science and Engineering, Nanjing University of Technology, Nanjing, Jiangsu 210009)
Abstract: The effects of nitrogen and air atmosphere on flexural strength, fracture toughness, thermal shock resistance and oxidation properties of SiC/Al2O3 ceramics were investigated. The mechanical properties of the samples were characterized by a universal testing machine; the indexes of thermal shock resistance of the samples were determined by an automatic thermal shock resistance tester; the composition and microstructure were studied by an X-ray diffractometer (XRD) aand a scanning electron microscope (SEM); SiC oxidation degrees were analyzed by mass difference method. The experimental results showed that the samples sintered in nitrogen had higher strength than in air (the highest strengthen reached 479.86 MPa); SiC additive improved the thermal shock resistance of the material (the highest index of thermal shock resistance Г reached 32.98 while the Г of pure Al2O3 was 23.83). The results also showed that micro -sized SiC had better oxidation resistance than nano-scale SiC at low temperature, micro-sized SiC was oxidized totally in the air at 1600℃. XRD results revealed that the oxidized SiC then further reacted with alumina to form mullite, which improved its thermal shock resistance.
Key words SiC; Al2O3; sintering atmosphere; mechanical property; thermal shock resistance