- Boron Nitride Dispersed Nanocomposites with High Thermal Shock Resistance
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T. Kusunose, T. Sekino, Y.H. Choa, T. Nakayama, K. Niihara
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J Korean Powder Metall Inst. 2001;8(3):174-178.
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- The microstructure and mechanical properties of Si_3N_4/BN nanocomposites synthesized by chemical processing were investigated. The nanocomposites containing 15 vol% hexagonal BN (h-BN) were fabricated by hot-pressing alpha-Si_3N_4powders covered with turbostratic BN (t-BN). The t-BN coating on alpha-Si_3N_4particles was prepared by heating alpha-Si_3N_4 particles covered with a mixture of boric acid and urea in hydrogen gas. TEM observations of this nanocomposite revealed that nano-sized h-BN particles were homogeneously dispersed within Si_3N_4grains as well as at grain boundaries. The strength and thermal shock resistance were significantly improved in comparison with the Si_3N_4/BN microcomposites.
- Fabrication of Metallic Particle Dispersed Ceramic Based Nanocomposite Powders by the Spray Pyrolysis Process Using Ultrasonic Atomizer and Reduction Process
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Y.H. Choa, B.H. Kim, Y.K. Jeong, K.W. Chae, T.Nakayama, Kusunose T., T.Sekino, Niibara K.
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J Korean Powder Metall Inst. 2001;8(3):151-156.
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- MgO based nanocomposite powder including ferromagnetic iron particle dispersions, which can be available for the magnetic and catalytic applications, was fabricated by the spray pyrolysis process using ultra-sonic atomizer and reduction processes. Liquid source was prepared from iron (Fe)-nitrate, as a source of Fe nano-dispersion, and magnesium (Mg)-nitrate, as a source of MgO materials, with pure water solvent. After the chamber were heated to given temperatures (500~800°C), the mist of liquid droplets generated by ultrasonic atomizer carried into the chamber by a carrier gas of air, and the ist was decomposed into Fe-oxide and MgO nano-powder. The obtained powders were reduced by hydrogen atmosphere at 600~800°C. The reduction behavior was investigated by thermal gravity and hygrometry. After reduction, the aggregated sub-micron Fe/MgO powders were obtained, and each aggregated powder composed of nano-sized Fe/MgO materials. By the difference of the chamber temperature, the particle size of Fe and MgO was changed in a few 10 nm levels. Also, the nano-porous Fe-MgO sub-micron powders were obtained. Through this preparation process and the evaluation of phase and microstructure, it was concluded that the Fe/MgO nanocomposite powders with high surface area and the higher coercive force were successfully fabricated.
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