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RISS 인기검색어
- 검색키워드
- 저자 : Matsushita Jun-Ichi (검색결과 4 건)
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Sintering and Mechanical Properties of Chromium Boride-chromium Carbide Composites
Matsushita Jun-Ichi,Shimao Kenji,Machida Yoshiyuki,Takao Takumi,Iizumi Kiyokata,Sawada Yutaka,Shim Kwang-Bo 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Several boride sintered bodies such as , , and were previously reported. In the present study, the sinterability and physical properties of chromium boride containing chromium carbide sintered bodies were investigated in order to determine its new advanced material. The samples were sintered at desired temperature for 1 hour in vacuum under a pressure by hot pressing. The relative density of sintered bodies was measured by Archimedes' method. The relative densities of addition of 0, 5, 10, 15 and 20 mass% composites were 92 to 95%. The Vickers hardness of the with 10 and 15 mass% composites were about 14 and 15 GPa at room temperature, respectively. The Vickers hardness at high temperature of the addition of 10 mass% composite decreased with increasing measurement temperature. The Vickers hardness at 1273 K of the sample was 6 GPa. The Vickers hardness of addition of composites was higher than monolithic sintered body. The powder X-ray diffraction analysis detected CrB and phases in containing composites.
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Oxidation behavior of a silicon boride composite
Jun-ichi Matsushita,심광보,Koichi Niihara,Akiko Kitajima,Satoshi Okuhata,Keun Ho Auh 한양대학교 세라믹연구소 2004 Journal of Ceramic Processing Research Vol.5 No.2
The oxidation resistance of a silicon hexaboride (SiB6) composite at high temperature was investigated in order to determine the possibility of its use as an advanced high temperature structural material. Fortunately, monolithic SiB6 and its composites were known to be chemically stable up to high temperatures. To date, there have been few reports regarding the properties of SiB6 ceramics. In this study, the oxidation resistance at high temperature of a dense SiB6 composite prepared from SiB6 with the addition of 10 mass% C as starting powders has been studied. The samples were oxidized at room temperature up to 1173 K for 25 h in air. The weight changes were measured to estimate the oxidation resistance. The oxidation of samples oxidized for a short oxidation time of 5 minutes started at 973 K, and the weight gain increased with increasing oxidation temperature. On the other hand, at oxidation times of above 1 h, a maximum weight gain value at 973 K was observed. After that a SiB6 composite oxidized at 973 to 1073 K for 25 h exhibited increased weight gain with increasing oxidation temperature; the oxidation changed in accordance with the parabolic law during the initial oxidation stage. However, even if the oxidation temperature was increased only a slight additional weight change occurred. The weight gain of the sample oxidized at 1173 K for 25 h was approximately 2.5%. Finally, the SiB6 composite showed a good oxidation resistance at high temperature, because the surface oxide film formed by oxidation acted as an oxidation-resistant layer.
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Mechanochemical Synthesis of Zinc Ferrite, ZnFe2O4
Sawada Yutaka,Iizumi Kiyokata,Kuramochi Tomokazu,Wang Mei-Han,Sun Li-Xian,Okada Shigeru,Kudou Kunio,Shishido Toetsu,Matsushita Jun-Ichi 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Mechanochemical synthesis of zinc ferrite, ZnFe2O4, was attempted from a powder mixture of iron (III) oxide, alpha-Fe2O3 and zinc (II) oxide, ZnO. Nanocrystalline zinc ferrite, ZnFe2O4 powders were successfully synthesized only bymilling for 30 hours. Evidence of the ZnFe2O4 formation was absent for the powders milled for 10 and 20 hours; the milling lowered the crystallinity of the starting materials. Heating after milling enhanced the formation of ZnFe2O4, crystal growth of ZnFe2O4 and the unreacted starting materials. The unreacted starting materials decreased their amounts by heating at higher temperatures.
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방전 플라즈마 소결법으로 제조된 silicon boride 세라믹스의 열전 특성
심승환,이대웅,채재홍,심광보,Shim, Seung-Hwan,Lee, Dae-Woong,Chae, Jae-Hong,Matsushita, Jun-Ichi,Shim, Kwang-Bo 한국결정성장학회 2005 한국결정성장학회지 Vol.15 No.2
본 연구에서는 고온 융점과 높은 Seebeck 계수로 인해 고온 열전 재료로서 매우 우수한 silicon boride ($SiB_6$)의 고밀도 소결체를 방전 플라즈마 소결법(spark plasma sintering, SPS)을 도입하여 제조하였으며, 소결된 시편의 미세구조 및 열전 특성을 평가하였다. $1500^{\circ}C$의 비교적 저온에서 이론 밀도의 약 99%의 소결밀도로 SPS법을 통해 효과적으로 $SiB_6$를 치밀화 할 수 있었으며 이들 시편들의 열전특성 평가로부터, hot-press법으로 제조된 시편과 비교하여 매우 향상된 Seebeck 계수를 얻을 수 있었으며 상대적으로 높은 출력인자 값을 나타냈다. Silicon boride ($SiB_6$) is very promising for use as thermoelectric materials at high temperature because of its high melting point and relatively large Seebeck coefficient. In the present work, spark plasma sintering (SPS) was applied for preparing dense $SiB_6$ ceramics, and their thermoelectric properties were investigated, together with their microstructural evaluation. The SPS process was found to be effective in densifying a $SiB_6$ ceramic, typically 99 % of the theoretical density at low temperature of $1500^{\circ}C$. In comparison with $SiB_6$ specimen prepared by hot-pressing, the SPS-processed specimen exhibited the significantly improved Seebeck coefficient, resulting in the higher power factor.
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