Advanced Si-Based Ceramics and Composites

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Authors: Takero Fukudome, Sazo Tsuruzono, Tetsuo Tatsumi, Yoshihiro Ichikawa, Tohru Hisamatsu, Isao Yuri
Abstract: Silicon nitride is one of the most practical candidates for ceramic gas turbines. The SN282 is silicon nitride material developed by Kyocera for gas turbines. Several new technologies have been developed to achieve materialization of ceramic gas turbines, such as material, fabrication process, evaluation / analysis technology. Recent technology is focused on recession of silicon-based ceramics under combustion gas. Environmental Barrier Coatings (EBCs) are developed to suppress these recession. We have found rare-earth element silicate and yttrium stabilized zirconium oxide (YSZ) have high corrosion resistance to the combustion gas. These materials were applied to the ceramic gas turbine components. The components with EBCs were evaluated in the actual engine tests. We have confirmed that the EBCs effectively work for the recession resistance.
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Authors: Akira Kohyama
Abstract: As one of the most important breakthrough in the field of SiC/SiC composite materials, the new process called Nano-powder Infiltration and Transient Eutectoid (NITE) Process has been developed. The outstanding total properties of the NITE SiC/SiC composites are presented. Then, the current efforts to make attractive GFR based on the NITE SiC/SiC composites and the technology R & D to make reactor components with the NITE SiC/SiC composites are provided together with our efforts on innovative reactor designs.
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Authors: Chang An Wang, Ke Tang, Yong Huang
Abstract: Bulk Ti3SiC2 material with 95 wt% of purity was synthesized by hot pressing from Ti, SiC and graphite powders. This work focuses on the electric properties of Ti3SiC2 at high frequency alternating current using a specific clamp device. The result shows that Ti3SiC2 exhibits an electric property of inductance (the order of magnitude is about 10-8 H at 1 ~ 40 MHz), which indicates that Ti3SiC2 shows a stronger electric property of metal rather than that of common ceramics. In this study, the equation to calculate the external inductance of nonferromagnetic metal is also applicable to Ti3SiC2 material at high frequency.
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Authors: Jing Feng Li, Song Zhe Jin, Yong Li
Abstract: Si-based high-temperature ceramics are attractive materials for power microelectromechanical systems (power MEMS), such as microscale gas turbines, micro-combustors and micro-reactors. This presentation introduces a novel process for the microfabrication of Si3N4 ceramics, which mainly consists of pre-sintering of Si powder compacts, micromachining of pre-sintered Si preforms and reaction sintering of the micromachined Si preforms. The present process has its high potential for Si3N4 3-dimensional microfabrication because it combines the machinablity of pre-sintered Si powder compacts and near-net shaping characteristic of S3N4 reaction sintering. Si3N4 micro-components such as micro nozzle arrays and micro-rotor were fabricated by using the present process.
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Authors: Jeong Ho Chang, Jun Liu
Abstract: This work describes chemically functionalized nanoporous silica as a novel catalyst for the rapid hydrolysis of a phenyl ester. Work demonstrates a very simple and flexible approach to control surface reactivity on the nanometer scale using a self-assembled organic monolayer consisting of polar, (dihydroxyl, carboxyl, ethylene-diamine, and dihydroimidazole), and non-polar (isobutyl) groups. All five functional groups are an essential requirement in preparing an enzymelike catalyst because of the synergistic effect and hydrophobic partitioning, which has been verified by a 13C CP- MAS solid-state NMR technique. Catalytic activities were obtained from the catalytic efficiency constant and specificity constant using Michaelis-Menten kinetics. Catalytic activities were close to those of a natural enzyme when 12% of the surface was covered by hydrophobic isobutyl silane. The rate of enzyme catalyzed activity was dependent on the energy of the transition state as defined in terms of an energy barrier derived from the relationship between transfer free energy and specificity constant.
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Authors: Jeong Ho Chang, Chang Han Shim, Kyung Ja Kim
Abstract: This work describes an innovative approach to preparation of the highly controlled drug delivery materials that involves a self-assembly process at the molecular level based upon the silicified L3 phase silicates and thermoresponsive PNIPAm integrated L3 phase silicates. The materials designed by the integration of thermosensitive polymer have been prepared and demonstrated for the highly controlled drug releasing system over a longer period of time due to their high degree of continuity and contigunity in 3-D interconnected porous structure. This approach is suitable for long term drug delivery systems with constant release in hard tissue engineering due to nanodiffusion mechanism. The structural characterization was achieved by TEM, SEM, SAXD, solid-state 29Si NMR, and BET.
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Authors: Jun Suh Yu, Jae Chun Lee, Sung Park, Min Sung Hong
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Authors: Myeong Woo Cho, Won Seung Cho, Dong Sam Park, Jae Hyung Lee, Eun Sang Lee, Tae Il Seo, D.W. Kim
Abstract: In this study, micro powder blasting techniques are applied to micro-pattern making process using developed Si3N4-hBN composites. Material properties of the developed machinable ceramics according to the variation of h-BN contents, those are used to give good machinability to the ceramics, are evaluated. And, a series of required experimental works are performed to determine optimum powder blasting conditions for micro-pattern making. The experiments are performed for the prepared samples with no mask, and samples with three different mask patterns. As the results, it can be observed that the machinability of the developed Si3N4-hBN composites increases as the h-BN contents in the composites. Also, from the experimental results, it is possible to determine the optimum blasting conditions for micro-pattern making process with Si3N4-hBN composites.
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Authors: Jae Won Kim, Seong Hwan Park, H.C. Kim, Yeon Gil Jung, Je Hyun Lee, Ung Yu Paik
Abstract: In order to exploit the anti-oxidation property of graphite mould, a new type of oxidation protective coating is produced by a pack cementation diffusion coating technique. To enable this material to be used at high temperatures, graphite moulds are coated with Si/SiC slips. The anionic dispersant is added to disperse the slip uniformly, of which the optimal amount is evaluated with viscosity. The graphite mold specimens are surface-modified at 100 °C for 10 minutes in a non-polar polymer aqua-solution, considering the uniform wettability of slip. The surface-modified graphite mold specimen shows better wettability than the nonsurface- modified graphite one when coating process is performed through the slip. The interface-reaction of the specimens is performed at 1450 °C in a reduction atmosphere. The microstructure and composition before and after the pack cementation are observed by SEM and EDS, and the phase identify was performed with XRD. The layer of specimens double-coated by the pack cementation and Si/SiC slip coating method is stable, and properties of SiC coating layer formed on the graphite mould surface are dependent on particle size of starting material, Si, and open-pore size of the graphite mould surface. It is found that larger particle size of Si and smaller open-pore size of the graphite mold were the preferable conditions for the interface produces an optimal reaction which anti-oxidation coating.
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