Papers by Keyword: Al2O3

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Authors: Zhong Chun Chen, Sri Nugroho, Akira Kawasaki
Abstract: Al2O3 matrix composites reinforced with Ba-b-Al2O3 phase were synthesized through reactive sintering using Al2O3 and BaCO3 as starting powders. Dense Al2O3/Ba-b-Al2O3 composites can be obtained by spark plasma sintering from Al2O3/BaO•Al2O3 powder, which was prepared by calcining Al2O3/BaCO3 powder mixture. The Ba-b-Al2O3 reinforcing phase exhibited an elongated morphology due to preferred diffusion of Ba cations. The existence of Ba-b-Al2O3 phase as well as low sintering temperature and short holding time during reactive sintering inhibit grain growth and thus result in small grain sizes of the Al2O3 matrix.
Authors: Agus Sukarto Wismogroho, Wahyu Bambang Widayatno
Abstract: In this study a new technique for producing an Al/Al2O3 composite coating on a steel substrate by an in situ process was examined. The pre-treating of the steel substrate with Al was carried out by MA at room temperature, followed by MA using a low-energy ball mill at 200-500°C. An Al/Al2O3 coating layer with a homogenous distribution of Al2O3 particles were achieved. The coating layer has not only high hardness but also high fracture toughness.
Authors: Bing Qiang Liu, Chang Chun Wang, Ai Ling Sun, Chuan Zhen Huang
Abstract: A TiC whisker toughening Al2O3 composite ceramic tool material was developed by an in situ carbothermal reduction synthesis technology. The influence of different synthesis temperatures (1480°C and 1700°C) and holding times (90min, 60min and 30min) on the mechanical properties of the composite was investigated. The results showed that either the lower synthesis temperature (1480°C) or the higher synthesis temperature (1700°C) was necessary to the improvement on the fracture toughness of the composite. However, when an Al2O3-TiO2 eutectic system was formed during the higher temperature synthesis process, grain coarsening of the Al2O3 matrix became much serious, which resulted in obvious decrease in the flexure strength of the composite. Therefore, the carbothermal reduction synthesis process should be divided into two parts including the lower temperature synthesis process for increasing the yield of the TiC whisker and the subsequent higher temperature synthesis process for increasing the carbon content in the TiC whisker, and and the lower temperature synthesis process should be held for enough time (e.g. 60min) to avoid an incomplete carbothermal reduction of TiO2.
Authors: Helio R. Simoni, Eduardo Saito, Claudinei dos Santos, Felipe Antunes Santos, Alfeu Saraiva Ramos, Olivério Moreira Macedo Silva
Abstract: In this work, the effect of the milling time on the densification of the alumina ceramics with or without 5wt.%Y2O3, is evaluated, using high-energy ball milling. The milling was performed with different times of 0, 2, 5 or 10 hours. All powders, milled at different times, were characterized by X-Ray Diffraction presenting a reduction of the crystalline degree and crystallite size as function of the milling time increasing. The powders were compacted by cold uniaxial pressing and sintered at 1550°C-60min. Green density of the compacts presented an increasing as function of the milling time and sintered samples presented evolution on the densification as function of the reduction of the crystallite size of the milled powders.
Authors: Svetlana Beljakowa, Thomas Frank, Gerhard Pensl, Kun Yuan Gao, Florian Speck, Thomas Seyller
Abstract: An alternative oxidation technique is developed and built up, which provides monatomic oxygen during the whole oxidation process. The set-up consists of a tungsten lamp furnace and a microwave-plasma. A number of different gases can be introduced into the oxidation quartz tube. In addition, an Al2O3-layer is deposited on a part of the oxide layers by atomic layer chemical vapor deposition (ALCVD). First oxidation runs result in encouraging low values of the density of interface states Dit and in the flatband voltage UFB. It turns out that with the present experimental conditions, the comparison of MOS capacitors fabricated with different dielectric layers favors gate dielectrics grown in O2/N2-ambient.
Authors: Tian Xiang Dai, Z. Mohammadi, Stephen A.O. Russell, Craig A. Fisher, Michael R. Jennings, Philip A. Mawby
Abstract: Trench structure etching is one of the most important processes for the fabrication of 4H-SiC Trench MOSFETs. This paper introduced Al2O3 as an etching mask for the fabrication of trench structures. The effect of dry etching parameters to the shape of trench structures were studied systematically. Micro trenches were successfully eliminated from trench structure etching process and preliminary trench MOSFET test structures were fabricated and characterized.
Authors: Hai Bo Wang, Xi Bao Wang, Hui Li
Abstract: In this paper, metal reduction preparation of TiB2 powder via magnesium reduction and aluminothermic reduction were studied. The carbon rod arc heating generated from the spread of the reaction of TiB2,and then the examinations were performed after pickling, crushing and grinding such as SEM and XRD. The results showed that the aluminothermic reduction occurred into the powder impurity phase less, but the need for better technology separation of Al2O3. Magnesium reduction reaction products with more impurities, pickling process removes only the reactants of MgO and other impurities not removed in the air and impurities were analyzed and compared.
Authors: Yi Lin, Chiung Fang Huang, Hsin Chung Cheng, Yung Kang Shen
Abstract: Hydroxyapatite (HA) coating of hard tissue implants is widely employed for its biocompatible and osteoconductive properties as well as its improved mechanical properties. In this study, a novel micro-blasting process has been used to successfully modify a titanium alloy substrate with a HA treatment using a dopant/abrasive regime. The impact of a series of apatite abrasives, was investigated to determine the effect of abrasive particle size on the surface properties of both micro-blasting (abrasive only) and continuous (HA/abrasive) treatments. The resultant HA treated substrates were compared to substrates treated with abrasive only (micro-blasted) and an untreated Ti. The HA powder, apatite abrasives and the treated substrates were characterized for chemical composition, coating coverage, crystalline and topography. The results show that the surface roughness of the HA blasted modification was affected by the particle size of the apatite abrasives used. This study demonstrates the ability of the continuous process to deposit HA coatings with a range of surface properties onto Ti alloy substrates. The ability of the continuous technology to offer diversity in modifying surface topography offers exciting new prospects in tailoring the properties of medical devices for applications ranging from dental to orthopedic settings.
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