Pressureless sintering of carbon nanotube–Al2O3 composites |
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| Authors: | Shi C Zhang William G Fahrenholtz Greg E Hilmas Edward J Yadlowsky |
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| Affiliation: | 1. Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO 65401, USA;2. HY-Tech Research Corporation, Radford, VA 24141, USA;1. Laboratoire de Mécanique des Sols, Structures et Matériaux, École Centrale Paris, CNRS UMR8579, Grande Voie des Vignes, 92290 Châtenay-Malabry, France;2. Department of Polymer Science and Engineering, University of Science & Technology Beijing, Beijing 100083, People’s Republic of China;3. Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong Special Administrative Region;1. Hamburg University of Technology, Hamburg, Germany;2. Universidade Federal de Santa Catarina, Joinville, Brazil;1. School of Engineering and Material Science, Queen Mary University of London, London E1 4NS, UK;2. Nanoforce Technology Limited, London E1 4NS, UK;3. Institute of Physics of Materials, ASCR, CEITEC IPM, Zizkova 22, 616 62 Brno, Czech Republic |
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| Abstract: | Alumina ceramics reinforced with 1, 3, or 5 vol.% multi-walled carbon nanotubes (CNTs) were densified by pressureless sintering. Commercial CNTs were purified by acid treatment and then dispersed in water at pH 12. The dispersed CNTs were mixed with Al2O3 powder, which was also dispersed in water at pH 12. The mixture was freeze dried to prevent segregation by differential sedimentation during solvent evaporation. Cylindrical pellets were formed by uniaxial pressing and then densified by heating in flowing argon. The resulting pellets had relative densities as high as ～99% after sintering at 1500 °C for 2 h. Higher temperatures or longer times resulted in lower densities and weight loss due to degradation of the CNTs by reaction with the Al2O3. A CNT/Al2O3 composite containing 1 vol.% CNT had a higher flexure strength (～540 MPa) than pure Al2O3 densified under similar conditions (～400 MPa). Improved fracture toughness of CNT–Al2O3 composites was attributed to CNT pullout. This study has shown, for the first time, that CNT/Al2O3 composites can be densified by pressureless sintering without damage to the CNTs. |
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