Authors: M. Yusop, De Liang Zhang, M. Wilson
Abstract: Alumina-iron nanocomposite powders containing 5vol.% of iron were fabricated by
high-energy ball milling with different ball-to-powder weight ratios (BPRs) as part of the study of
ceramic-metal nanocomposite magnetic materials. The microstructure and morphology of the
composite powders were characterized using the X-ray diffraction, optical microscopy and scanning
electron microscopy. XRD analysis and SEM examination in combination with energy dispersive
X-ray spectrometry confirmed that the nanocomposite structure of the powder particles formed only
after 8 hours milling for both BPRs used. With a higher BPR of 16:1, Fe-Cr alloy material was
broken from the stainless steel balls and incorporated into the nanocomposite powder. However,
such a problem did not occur with a lower BPR of 5:1. The mechanism for formation of the alumina
matrix nanocomposite powder is found to be dependent on BPR and milling time.
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Authors: Jian Feng Zhu, Guo Quan Qi, Fen Wang, Hai Bo Yang
Abstract: Ti2AlC powders with high purity were successfully synthesized via high energy milling and heat treatment of Ti, C and Al powders. The effects of composition and thermal treatment on the formation and purity of Ti2AlC were examined in detail. The results shown a mechanically induced self-propagating reaction (MSR) was triggered to form Ti3AlC2, TiC and TiAlx during the high energy milling. When the as-milled powders were heat treated, Ti2AlC was initially formed by the reaction between TiAl and TiC. With continuously increasing temperature, Ti2AlC was also produced by the reaction between TiAl and Ti3AlC2.
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Authors: Hai Jiang, Chun Yan Tian
Abstract: Silicon nitride nanoceramics were fabricated by hot press sintering two kinds of Si3N4 nano-sized powders. The effect of starting powders on microstructure, mechanical properties and thermal shock resistance were investigated. The microstructure of sintered materials consists of spherical grains and the addition of α–Si3N4 to starting powders does not affect the grain morphology. The flexural strength, fracture toughness and thermal shock resistance increase with the increase in amount of α–Si3N4 starting powders, and the maximum mechanical properties are obtained when the amount of α–Si3N4 powders is 40wt.%. The hardness values decrease with the increase of α–Si3N4 amount.
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Authors: Xue Tan Ren, Yan Chun Liu, Shui Hui Chen, Lai Guang Hou, Guo Long Wang, Yuan Cheng Teng
Abstract: The TiC powders were synthesized by carbothermal reduction of TiO2 in vacuum using the titania and carbon black as raw materials. The molar ratio of C to TiO2 was 3:1. The crystalline phase, microstructure and morphology of the obtained samples were investigated by XRD and SEM. The results show that single-phase and well-crystallized TiC powders were obtained at 1300°C for 1h when the system pressure was 20 Pa. The particle morphologies are composed of fine grains about 200 nm.
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Authors: Yu Hua Zhen, Kai Li Jia, Lin Ling Li, Yu Xi Qiao, Fu Hua Sun, Min Zhang
Abstract: This study is aimed at obtaining (K,Na)NbO3 powders with wide grain size distribution methods. (K,Na)NbO3 powders were successfully synthesized by different ways, including hydrothermal method, sol-gel method, and molten-salt method. The experiment results showed that the hydrothermal and sol-gel methods could not control the grain size of the (K,Na)NbO3 powders effectively . The grain size of (K,Na)NbO3 powders can be only tailored by the molten-salt method through controlling the starting oxide powder morphology, as well as crystallization temperature. The grain size was not affected by the experimental parameters whether or not the initial powders were milled. Furthermore, it has been found that the crystallization temperature could change the grain size of the powders monotonously. The (K,Na)NbO3 powders synthesized by molten salt method distributed from nanoscale to micron level, which can lay the foundation for further research on the grain size effect of (K,Na)NbO3 lead free piezoelectric ceramics.
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