Characterization of Al2O3 composites with fine Mo particulates,I. Microstructural development |
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| Affiliation: | 1. Institute of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan 106, ROC;1. Now with Team Young Advanced Ceramics Co., Ltd., Taoyuan, Taiwan;1. Department of Mechanical Engineering, KPR Institute of Engineeering and Technology, Coimbatore 641407, India;2. Department of Mechanical Engineering, SriGuru Institute of Technology, Coimbatore 641110, India;3. School of Mechanical Engineering, Vellore Institute of Technology, Vellore 632014, India;4. Department of Aeronautical Engineering, Kalaignarkarunanidhi Institute of Technology, Coimbatore-641402, India;5. Department of Mechanical Engineering, Sri Shakthi Institute of Engineering and Technology, Coimbatore 641062, India;1. Department of Neurosurgery, Clinical Hospital Center Zemun, Belgrade, Serbia;2. Neurosurgery Clinic, Clinical Center of Serbia, Belgrade, Serbia;1. School of Materials Science and Engineering, Beihang University, Beijing 100191, China;2. Welding and Plastic Forming Division, Beijing Institute of Aeronautical Materials, Beijing 100095, China |
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| Abstract: | Alumina based composites containing nano- or submicron-meter Mo grains in the amounts of 20 vol% or less were prepared through a dissolution of molybdenum oxide in ammonium solution, followed by spray-drying, hydrogen reduction and sintering with or without hot-pressing. The properties of alumina/molybdate solutions and the ζ-potential of alumina particles in the solution were measured. By using electron microscopic and quantified X-ray diffraction techniques, the microstructural features and the evolution of Mo paniculate in spray-dried powder and sintered bodies were analyzed. The time dependent exponent and activation energy of grain growth of Mo between 600 to 900 °C were determined. There is no glassy phase or reaction at the interfaces between Mo/Al2O3 of dense composites. Only one coherent interface was found, and the others are incoherent. The results reveal that submicrometric Mo grains may grow by surface diffusion in reduction stage (≤ 900 °C) and greatly retard the densification and reduce the grain size of alumina matrix in sintering stage. |
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