Papers by Keyword: Aluminum Borate

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Authors: H. Takano, Takafumi Kusunose, Tohru Sekino, Rajagopalan Ramaseshan, Koichi Niihara
Abstract: 6061 aluminum alloy composite reinforced with α-alumina and aluminum borate is fabricated by casting method. The above mentioned composite has been compared to a similar composite without aluminum borate reinforcement for their machinability. The aluminum borate filler was controlled up to (2.5, 5.0 and 30vol %) on the surface of α-alumina. The reaction zone between alumina and the matrix in both the systems are analyzed with the help of TEM micrographs as well as X-ray diffraction profiles. At the reaction zone between alumina and the aluminum alloys, some spinel-like compounds (MgAl2O4) are identified. Finally, machinability was analyzed with the single point tool machining.
Authors: Pat Sooksaen, Pisud Prasertcharoensuk, Jiraporn Damnernsawat, Nimit Pattamawitayanimit
Abstract: This study investigated the bulk crystallization of 54B2O3-19SiO2-17Al2O3-5BaO-5MgO (mol%) glass. Melting was carried out at 1500°C for 1 h using a bottom-load electric furnace. The glass melt was cast into a block and annealed at 500°C for 2 h. Isothermal heat treatment was carried out at 1100°C for 2, 4, 8, 16, 32 h to form bulk crystallized glass-ceramics using a heating and cooling rate of 5°C/min. Phases present in the glass-ceramic samples were studied by x-ray diffraction. Crystalline Al4B2O9 and Al18B4O33 were the main phases and the phase stability depended on the isothermal time. Microstructures were observed by a scanning electron microscope. The size of aluminum borate whiskers/rods tend to increase with longer isothermal holding period. The whisker/ rod-like crystals uniformly oriented throughout the microstructure in all heat treated samples. This led to interlocking microstructure and hence an increase in hardness and fracture toughness. Glass-ceramics synthesized at longer heat treatment times resulted in an increase in the surface hardness and shorter path length at the corner of the diamond pyramid-shaped indenter. Glass-ceramics synthesized in this study can be applied as high temperature resistant machinable materials because their microstructures can resist micro-cracking upon indentation.
Authors: Gen Sasaki, Makoto Yoshida, Osamu Yanagisawa, Nobuyuki Fuyama, Toshio Fujii
Authors: Zhao Jun Mo, Jing Lin, Ying Fan, Xing Hua Zhang, Yan Ming Xue, Chun Yong Liang, Hong Shui Wang, Xue Wen Xu, Long Hu, Zhun Ming Lu, Cheng Chun Tang
Abstract: Large quantities of BN-coated aluminum borate (Al18B4O33) nanowhiskers with typical 20 - 50 nm in diameter and 0.5 - 2 m in length have been successfully synthesized by sol-gel and post-thermal-treatment methods. The dependence of morphology and structures on the synthetic process of the coated nanowhiskers has been investigated systematically. Al4B2O9 nanowhiskers were first prepared at a relative low temperature, and then converted into Al18B4O33 nanowhiskers at higher temperatures in the air due to their high-temperature instability. Besides Al18B4O33phase, Al5BO9 and B2O3 could also be generated in the process of transition. However, if a flow of NH3 gas was introduced during the post-thermal-treatment of Al4B2O9 nanowhiskers, the Al5BO9 and B2O3 phases disappeared and BN-coated Al18B4O33 nanowhiskers were finally obtained. Uniform BN layers were coated on the surface of the nanowhiskers by the interfacial reaction between NH3 and B2O3 vapor which was in-situ generated from the nanowhiskers. The NH3-introducing temperature has a significant effect on the morphology and composition of the nanowhiskers. The BN-coated Al18B4O33nanowhiskers are envisaged to become prime candidates as reinforcement in light metal matrix composites.
Authors: Pat Sooksaen
Abstract: Aluminium borate nanowhiskers with varying aspect ratio were synthesized via sol–gel synthesis. The morphology of aluminum borate (Al4B2O9 and Al18B4O33) nanowhiskers could be controlled by varying the aluminum to boron (Al:B) molar ratio in the sol–gel derived precursors. Sintering temperatures (850 and 1100°C) and sintering times (4 and 32 hours) also affected the phase composition and size of the nanowhiskers. Citric acid was also added in the sol–gel derived precursors as a surface stabilizer for obtaining uniform finely dispersed nanostructures. Fine nanowhiskers were obtained by the calcination at 850°C, whereas higher temperature of 1100°C led to thicker and longer nanowhiskers and became rod-like crystals. The morphology and phase composition were investigated by field emission scanning electron microscope and X-ray diffraction. Chemical bond vibrations in the synthesized nanowhiskers were investigated by Fourier-transform infrared spectroscopy.
Authors: Guo Sheng Wang, Kang Jun Wang, Jia Hou, Yu Feng Xu
Abstract: Aluminum borate (Al4B2O9) nanomaterials were synthesized via a sol-gel process using Na2B4O7·10H2O and Al (NO3)3·9H2O. The effect of reaction volume concentration, calcination temperature and feeding modes on the morphology of Aluminum borate was investigated. The material was characterized with SEM and XRD. Results reveal that Al4B2O9 nanowires, nanorods could be synthesized, and its morphology also can be tailored by controlling calcination temperature and feeding modes.
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