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Multifunctionality in Ceramic/Metal Nanocomposites
Sekino, Tohru,Kondo, Hiroki,Niihara, Koichi The Korean Powder Metallurgy Institute 2001 한국분말재료학회지 (KPMI) Vol.8 No.3
Several fabrication processes, corresponding nanostructural features and multifunctionality as well has been investigated for oxide ceramic based nanocomposites with metal nanodispersion (i.e., ceramic/metal nanocomposites). Transition metal (Ni, Co, etc) dispersed alumina and zirconia based nanocomposites have been synthesized by reducing and hot-press sintering of ceramic and metal oxide mixtures prepared by several method. Improved fracture strength (1.1 and 1.9 GPa for $Al_2O_3/Ni$ and $ZrO_2/Ni$ nanocomposites, respectively) of these composites have been achieved according to their nanostructures. In addition, ferromagnetic characteristic has been kept. The variation of magnetization with an applied stress has found to be more sensitive as smaller as the magnetic metal dispersion is. This result thus suggests the possibility of fracture and/or stress sensing of the composites by simple magnetic measurement.
Fabrication of Nanocomposite Powders by Sonochemical Method
Hayashi, Yamato,Sekino, Tohru,Niihara, Koichi The Korean Powder Metallurgy Institute 2001 한국분말재료학회지 (KPMI) Vol.8 No.3
Nano particles have recently been a major research interest, motivated by their unusual physical and chemical properties. Such particles can be synthesized using physical and chemical methods. The physical methods need expensive installation like vacuum induction furnace, whereas in chemical methods the process in generally very simple and low cost. In this study, simple and new fabrication process by using ultrasound was investigated to prepare the nano-sized metal particles on various powders at room temperature.
Thermoelectric properties of perovskite-type rare earth cobalt oxide solid solutions Pr1−xDyx
Hideki Hashimoto,Takafumi Kusunose,Tohru Sekino 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.3
Perovskite-type rare earth cobalt oxide Pr1−xDyxCoO3 (x = 0, 0.25, 0.5, 0.75 and 1) ceramics were fabricated by reaction sintering of the corresponding metal oxide powders, and their thermoelectric properties were evaluated up to 873 K. The electrical properties of Pr1−xDyxCoO3 varied according to a variation in the x value, whereas the thermal conductivity of the solid solutions (x = 0.25 − 0.75) tends to be lower than that of both end components (x = 0 and 1). As the results,Pr0.75Dy0.25CoO3 (x = 0.25) showed the highest figure of merit, Z = 5.72 × 10−5 K−1 at 773 K in the present Pr1−xDyxCoO3 system. This is considered due mainly to the effect of decreasing thermal conductivity caused by phonon scattering of partially substituted A-site ions. These results suggest that the fabrication of solid solutions is effective in improving the thermoelectric properties of the RCoO3 system.
Hydrolysis of Biopex-R-allografts cement and the osteoblastic response to the cement
Shunro Yamaguchi,Takuya Nomoto,Tohru Sekino,코이치니하라 한양대학교 세라믹연구소 2004 Journal of Ceramic Processing Research Vol.5 No.1
A composite of clinically used Biopex-R and allografts was hydrolyzed in calf serum to obtain hydroxyapatite (HAP), while Biopex-R was hydrolyzed in calf serum to obtain octacalcium phosphate (OCP) and HAP. The products from Biopex-Rallografts composite as well as the Biopex-R exhibited rough surfaces. After the hydrolysis, MC3T3-E1 cells were cultured on the Biopex-R-allografts composite. Adherence of cells on Biopex-R-allografts composite is greater in number than on the Biopex-R. The composition of the resulting products affected the cell growth.
Residual stress determination in plasma sprayed Al₂O₃ coatings
Jia Zhang,Huang Chen,Tohru Sekino,Seung Ho Kim,Soo Wohn Lee 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.3
Residual stress is a problem which could reduce the lifetime of plasma sprayed coatings. So it is necessary to find the relationship between plasma spray parameters and residual stress. In this study, a plasma spraying technique was used to deposit Al2O3 coatings on stainless steel substrates under different spraying parameters. The residual stresses were determined by an X-ray diffraction method. Furthermore, surface roughness and porosity of the plasma sprayed Al2O3 coatings were measured. Residual stress is a problem which could reduce the lifetime of plasma sprayed coatings. So it is necessary to find the relationship between plasma spray parameters and residual stress. In this study, a plasma spraying technique was used to deposit Al2O3 coatings on stainless steel substrates under different spraying parameters. The residual stresses were determined by an X-ray diffraction method. Furthermore, surface roughness and porosity of the plasma sprayed Al2O3 coatings were measured.
Choa, Yong Ho,Nakayama, Tatachika,Sekino, Tohru,Niihara, Koichi 대한금속재료학회(대한금속학회) 1999 METALS AND MATERIALS International Vol.5 No.2
Nanocrystalline iron-oxide powder was fabricated with an inert gas condensation (IGC) method combined with evaporation, and in-situ oxidation techniques. The particle size of iron-oxide powder was controlled by varying the helium gas pressure between 0.1 and 10 Torr, with the smallest one =10 nm at 0.1 Torr. The nanostructure was characterized by TEM. Nanocrystalline iron-oxide powder was sintered with the pulse electric current sintering (PECS) method to obtain densified γ-Fe₂O₃ materials, and suitably densified nano-grained γ-Fe₂O₃ materials (◎ 40 nm) of great hardness were obtained. The correlation between the nanostructure and magnetic properties of nanocrystalline powder and densified γ-Fe₂O₃ materials was also investigated.
Youn-Gyu Han,Takafumi Kusunose,Tohru Sekino 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.2
In the present study, we report on the fabrication of hybrid composites of conductive silicone elastomer with TiO2/PANI-DBSA dispersion. The hybrid composites with conductive fillers, TiO2/PANI-DBSA, were prepared via an in-situ polymerization method with various TiO2 contents. The novel elastomer composites were prepared by dispersing TiO2/PANI-DBSA at room temperature in vulcanized silicone elastomers. The morphological, structural and electrical properties of TiO2/PANI-DBSA and their elastomer blends were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and electrical resistivity measurements. It was found that the electrical conductivity of the composite powder coated with about 20 wt.% PANI-DBSA was 46,000 (104) times higher than that of bare TiO2 powder. Also the electrical conductivity of the silicone elastomers composites of TiO2/PANI-DBSA were changed from 10−14 S/cm to 0.295S/cm (10 wt.% TiO2/PANI-DBSA). The novel elastomer composite had a percolation threshold between 1-3 wt.% PANI-DBSA. In the present study, we report on the fabrication of hybrid composites of conductive silicone elastomer with TiO2/PANI-DBSA dispersion. The hybrid composites with conductive fillers, TiO2/PANI-DBSA, were prepared via an in-situ polymerization method with various TiO2 contents. The novel elastomer composites were prepared by dispersing TiO2/PANI-DBSA at room temperature in vulcanized silicone elastomers. The morphological, structural and electrical properties of TiO2/PANI-DBSA and their elastomer blends were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and electrical resistivity measurements. It was found that the electrical conductivity of the composite powder coated with about 20 wt.% PANI-DBSA was 46,000 (104) times higher than that of bare TiO2 powder. Also the electrical conductivity of the silicone elastomers composites of TiO2/PANI-DBSA were changed from 10−14 S/cm to 0.295S/cm (10 wt.% TiO2/PANI-DBSA). The novel elastomer composite had a percolation threshold between 1-3 wt.% PANI-DBSA.
Behavior of residual stress in plasma sprayed ZrO₂ coatings with different contents of LaPO₄
Soo Wohn Lee,Jia Zhang,Huang Chen,Tohru Sekino,Seung Ho Kim 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.6
In this study, ZrO2-LaPO4 composite coatings were deposited by a plasma spraying technique. For nondestructive evaluation and easy practicability, the X-ray diffraction method was chosen to determine the residual stress in plasma sprayed ZrO2- LaPO4 composite coatings. The relationship between residual stress and content of LaPO4 was investigated. In this study, ZrO2-LaPO4 composite coatings were deposited by a plasma spraying technique. For nondestructive evaluation and easy practicability, the X-ray diffraction method was chosen to determine the residual stress in plasma sprayed ZrO2- LaPO4 composite coatings. The relationship between residual stress and content of LaPO4 was investigated.