TEM analysis of nanocrystalline SiC ceramics sintered by SPS using Al2O3–TiO2 additive

AbstractNanocrystalline SiC ceramics was fabricated by spark plasma sintering (SPS) using Al2O3 and TiO2 additives with the composition of 5, 10 and 20mass% (Al2O3–TiO2). XRD analysis revealed formation of TiC phase. And also mullite phase with preferred orientation was detected in SiC with 20mass% addition. From TEM observation and EDS analysis, TiC, aluminosilicate glass and mullite crystal phases were identified. Segregation of titanium atoms in addition to aluminum and oxygen atoms was observed at intergranular glassy phase with the thickness of 1–2nm. The electrical conductivity was the same level as the Al2O3 single addition to SiC ceramics

Health Risk Assessment as Educational Tools for Health Promotion

Abstract: Health risk Assessment (HRA) was developed to have patients modify their lifestyle from a viewpoint of primary prevention of lifestyle-related diseases. HRA has the following functions; 1) to estimate the risk of occurrence of lifestylerelated diseases, 2) to specify lifestyles which deteriorate these diseases, and 3) to evaluate health age and life expectancy after these lifestyles are modified. This paper discusses the criteria for selecting risk factors in developing HRA. The selected risk factors are predictable enough to alter the natural course of the diseases. HRA provides appropriate information to detect unsound lifestyles and offers life skills to recognize suitable approach to change the lifestyle. This paper also reviews effectiveness of HRA as the health educational tools. There have not been enough researches which show capabilities of HRA in primary prevention. Combination of health check-ups and HRA in Japan is expected to be a useful tool for individual health. Efficacy of HRA in modifying unsound lifestyles should be elucidated

An Online Database of Illustrative Sentences for Supporting German Writing

This article delineates the general idea of an online German-Japanese sentence database, which is now being developed by the authors at Hiroshima University. The database will serve Japanese learners of German - in their German writing in- and outside the class as a kind of online dictionary with abundant illustrative sentences. The most-likely users are freshmen and sophomores who begin German newly after entering university. On the Internet, there are already plenty of German learning materials for improving passive skills, such as listening, reading, and some kinds of grammar exercises, but it is not the case with writing. For the training of the productive skills like writing, still very important is the role of a human teacher who can care for learners individually, particularly through giving feedback on learners' compositions or free writing assignments. But in reality, it is very difficult to realize under the present institutional frameworks of foreign language learning in Japanese universities: too little learning time (only 90 required hours for absolute beginners), and too big class size (with more than 40 students in a class), to name just a couple of factors. In order to compensate for such disadvantages, writing help devices on Internet have been developed at Hiroshima University (see Iwasaki 2004, Lauer 2003). The database project to be described here is a part of the general project for that purpose. The concerned database has the following characteristics: 1. It will consist of at least 100,000 German illustrated sentences, i.e., approximately 600,000 words by the end of academic year 2004. 2. It makes use of not only a plain exact word search but also some advanced searches, such as wildcard search, phrasesearch, AND/OR- search, and capitalization sensitive/insensitive search. 3. It is not only a German monolingual but also German-Japanese bilingual database that has the same number of Japanese counterparts together with a search function with Japanese key words in it. 4. It provides representative sentences with their sounds, which users can hear via Internet (in MP3 format). 5. It allows users to make a worksheet from the search result by virtue of functions such as sorting, making quizzes by replacing key words with blank spaces, printing, and so on. 6. It will be edited by remote control on Internet, so the collaboration of teachers in its maintenance and expansion is possible. Acknowledgement Our sincere gratitude goes to Dr. Fumiyoshi SHOJI (Assistant Researcher of the Distance Communication Section, Information Media Center, Hiroshima University) for his generous support in implementing sentence data and making the technical devices for our database on Internet

Effective Stress Analysis by Shear Strain Controllable Model and its Application to Centrifuge Shaking Model Test

Effective stress FEM which is able to control the growth of shear strains is proposed. Its validity is firstly confirmed through the simulation of undrained cyclic torsional shear tests. Then, it is applied to simulation of centrifuge shaking model tests; the experimental model consists of a caisson type quay wall and reclamation laid on the sand layer. Development of shear strain is shown to be controlled arbitrary keeping the excess porewater pressure generation unchanged through the simulation of undrained cyclic torsional shear test, which indicates that proposed model can be applicable to variety of soils with different density and fines contents. Displacement is shown to be controlled keeping excess porewater pressure generation constant in the centrifugal model, too, and good agreement is obtained between test and analysis by controlling the parameter for shear strain development

FORMATION OF CARBON INTERPHASE ON POLYCRYSTALLINE AND AMORPHOUS SiC FIBERS IN SiC/SiC COMPOSITES BY ELECTROPHORETIC DEPOSITION

Continuous silicon carbide fiber-reinforced silicon carbide matrix (SiC/SiC) composites have been recognized as key materials for aerospace industries, high-temperature gas turbines and future nuclear and fusion applications because they show a pseudo-ductile fracture behavior and excellent fracture tolerance. Fiber/matrix interfaces act as an important role for toughening and strengthening SiC/SiC composites. Currently, carbon or hexagonal-boron nitride has been formed on SiC fibers as the interphases, and these interphases have been generally formed by chemical vapor infiltration (CVI), chemical vapor deposition (CVD) or solution-coating/pyrolysis process. However, these processes generally require long manufactuiring time and complicated apparatuses, and they use toxic, flammable or combustible reactant gases, resulting in much higher production cost and an increase in environmental load. Present authors paid attention to EPD process to form interphases on SiC fibers in SiC/SiC composites and demonstrated that EPD process was effective to form homogeneous C-interphase on SiC fibers [1-5]. In this study, EPD was applied for carbon interphase formation on polycrystalline (electric conductive) and amorphous (low electric conductive) SiC fibers in SiC/SiC composites, and microstructure and mechanical properties of the SiC/SiC composites were evaluated. From TEM micrograph of carbon interphase on the polycrystalline SiC fiber in the SiC/SiC composite formed by EPD, it was observed that flaky carbon particles were deposited parallel to the SiC fiber. Carbon has a layered structure and the layers bonded by weak van der Waals forces enable a low friction coefficient. As a result, the SiC/SiC composites with carbon interphases showed excellent mechanical properties with a pseudo-ductile fracture behavior. For amorphous SiC fibers, thin electric conductive polymer was coated on the amorphous SiC fibers, and carbon interphase formation was successfully achieved by EPD. The SiC/SiC composites reinforced with the carbon-coated amorphous SiC fibers also showed pseudo-ductile fracture behavior. References [1] K. Yoshida et al., Key Eng. Mater., 352 (2007) 133. [2] K. Yoshida et al., J. Nucl. Mater., 386-388 (2009) 643. [3] K. Yoshida et al., Mater. Sci. Eng. B, 161 (2009) 188. [4] K. Yoshida, J. Ceram. Soc. Japan, 118 (2010) 82. [5] K. Yoshida et al., Compos. Sci. Technol., 72 (2012) 1665. [6] K. Yoshida et al., Key Eng. Mater., 617 (2014) 213. [7] K. Yoshida, Chapter 18, in “MAX Phases and Ultra-High Temperature Ceramics for Extreme Environments” (2013)