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RISS 인기검색어
- 검색키워드
- 저자 : Yoshiba, Masayuki (검색결과 4 건)
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Processing and mechanical property evaluation of maize fiber reinforced green composites
Dauda, Mohammed,Yoshiba, Masayuki,Miura, Kazuhiro,Takahashi, Satoru The Korean Society for Composite Materials 2007 Advanced composite materials Vol.16 No.4
Green composites composed of long maize fibers and poly $\varepsilon$-caprolactone (PCL) biodegradable polyester matrix were manufactured by the thermo-mechanical processing termed as 'Sequential Molding and Forming Process' that was developed previously by the authors' research group. A variety of processing parameters such as fiber area fraction, molding temperature and forming pressure were systematically controlled and their influence on the tensile properties was investigated. It was revealed that both tensile strength and elastic modulus of the composites increase steadily depending on the increase in fiber area fraction, suggesting a general conformity to the rule of mixtures (ROM), particularly up to 55% fiber area fraction. The improvement in tensile properties was found to be closely related to the good interfacial adhesion between the fiber and polymer matrix, and was observed to be more pronounced under the optimum processing condition of $130^{\circ}C$ molding temperature and 10 MPa forming pressure. However, processing out of the optimum condition results in a deterioration in properties, mostly fiber and/or matrix degradation together with their interfacial defect as a consequence of the thermal or mechanical damages. On the basis of microstructural observation, the cause of strength degradation and its countermeasure to provide a feasible composite design are discussed in relation to the optimized process conditions.
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Minsung Jeon,Shuhei Yoshiba,Koichi Kamisako 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1
The hydrogenated amorphous silicon (a-Si:H) films used as intrinsic passivation layers were pre- pared using the radio-frequency remote-plasma chemical vapor deposition method under various deposition conditions for application to heterojunction solar cells. Their characteristics, such as their structural properties and carrier lifetimes, were investigated. When the substrate tempera- ture was set to 250℃, the optimal deposition gas ratio (rH = SiH4/H2) and the RF power were 1/15 and 80 W, respectively. Furthermore, to improve the passivation effect, we performed an annealing treatment. The highest improvement was displayed at an annealing temperature of 250℃. In the FT-IR analysis, the Si-H2 stretching mode, which means defects in the films, was shifted to Si-H stretching mode, which means a good quality film, after annealing treatment. Moreover, the highest carrier lifetime was 1.5 ms, which is higher value than the bulk lifetime of 900 us. From these results, we conclude that a combination of optimal deposition conditions and annealing treatment is essential to improve the surface and bulk passivation. The hydrogenated amorphous silicon (a-Si:H) films used as intrinsic passivation layers were pre- pared using the radio-frequency remote-plasma chemical vapor deposition method under various deposition conditions for application to heterojunction solar cells. Their characteristics, such as their structural properties and carrier lifetimes, were investigated. When the substrate tempera- ture was set to 250℃, the optimal deposition gas ratio (rH = SiH4/H2) and the RF power were 1/15 and 80 W, respectively. Furthermore, to improve the passivation effect, we performed an annealing treatment. The highest improvement was displayed at an annealing temperature of 250℃. In the FT-IR analysis, the Si-H2 stretching mode, which means defects in the films, was shifted to Si-H stretching mode, which means a good quality film, after annealing treatment. Moreover, the highest carrier lifetime was 1.5 ms, which is higher value than the bulk lifetime of 900 us. From these results, we conclude that a combination of optimal deposition conditions and annealing treatment is essential to improve the surface and bulk passivation.
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Minsung Jeon,Shuhei Yoshiba,Koichi Kamisako 한국물리학회 2010 Current Applied Physics Vol.10 No.2
Hydrogenated amorphous silicon (a-Si:H) thin films as passivation layer are deposited at various substrate temperatures using the remote-plasma-enhanced chemical vapor deposition method. Their properties are investigated and a method for further improvement is explored. The highest effective carrier lifetime as 850 μs is obtained at optimal deposition temperature of 250 ℃. Moreover, the further improvement is found after thermal annealing treatment at 250 ℃ for 20 s. A combination of the optimal deposition conditions for a-Si:H film and annealing treatment provides excellent surface and bulk passivation.
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