Preparation of mullite ceramics with equiaxial grains from powders synthesized by the sol-gel method |
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| Affiliation: | 1. State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, China;2. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China;3. Key Laboratory of Transparent Opto-functional Inorganic Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, China |
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| Abstract: | Four different alumina content of mullite ceramics were fabricated by powders synthesized using the sol-gel method. The synthesis process of powders, microstructure evolution, mechanical and optical properties of the mullite ceramics were studied. The XRD results showed that the precursors transformed into aluminosilicate spinel phase at 1000 °C and mullite phase at 1200 °C. Equiaxial grains were easy to form in the alumina-rich mullite ceramics while elongated grains were easy to form in the alumina-poor mullite ceramics. With the increase of alumina content, the grain size of the samples firstly increased and then decreased, the number of elongated grains decreased while equiaxed grains increased. The flexural strength, compression strength, fracture toughness, and Vickers hardness all decreased firstly and then increased. While the infrared transmittance increased firstly and then decreased. The transmittance at 4 μm (thickness of 0.75 mm) of the ceramics containing 66mol% Al2O3 reached the highest (72%) when sintered at 1780 °C because of the equiaxial grains. |
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| Keywords: | Mullite ceramics Alumina Sol-gel Mechanical and optical properties |
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