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Nakamura S.,University of Shiga Prefecture | Nakamura S.,Hitachi Ltd. | Tokumitsu K.,University of Shiga Prefecture | Yamaguchi T.,Japan Electronic Beam Irradiation Service Ltd
Journal of Applied Polymer Science | Year: 2013

This article investigates the effects of electron beam irradiation on the mechanical and thermal properties of polypropylene/polyamide6 blends (45/55) with talc 20% (w/w) as filler, SEBS-g-MAH 5% (w/w) as compatibilizer, and 10 phr triallyl isocyanurate (TAIC). TAIC is a polyfunctional monomer and acts as a crosslinking agent. Although the tensile and flexural moduli and strengths of the PP/PA6 blends with talc, SEBS-g-MAH, and TAIC were increased by the application of electron beam irradiation, the impact strength was decreased. Differential scanning calorimetry measurements showed that the melting temperatures and the degree of crystallinity decreased for all PP/PA6 blends as the electron beam irradiation dose increased, because of the number of structural defects in each crystalline phase. From dynamic mechanical analyzer results, a storage modulus curve in the plateau region was observed only in the PP/PA6 blends with talc, SEBS-g-MAH, and TAIC. The modulus increased with increasing electron beam irradiation dose, indicating that the three-dimensional network developed gradually in the more amorphous PA6. Consequently, the most significant improvement to heat distortion under high load (1.8 MPa) was observed at 200 kGy. Copyright © 2013 Wiley Periodicals, Inc. Source


Kageyama S.,Osaka University | Seino S.,Osaka University | Nakagawa T.,Osaka University | Nitani H.,High Energy Accelerator Research Organization | And 4 more authors.
Journal of Nanoparticle Research | Year: 2011

PtRu nanoparticle catalysts with 2-nm size supported on carbon were synthesized by a radiolytic process, assisted with the addition of dl-tartaric acid. Gradual alloying with the addition was confirmed by structural analyses with techniques of the X-ray diffraction and the X-ray absorption fine structure. Their methanol oxidation activities evaluated by the linear sweep voltammetry were higher than that of the commercial one, and found to be enhanced in accordance with the gradual change in the bimetallic structure from the Pt-core/Ru-shell to the random alloy. A good correlation was found between the catalytic activity and the indicators, which stands for the occurring frequency of the Pt-Ru bonds, calculated from the coordination numbers determined by the extended X-ray absorption fine structure analysis. It was confirmed that the addition of dl-tartaric acid in the radiolytic process certainly promoted the random alloy formation of PtRu bimetallic nanoparticles and enhanced their methanol oxidation activity. © 2011 Springer Science+Business Media B.V. Source


Yamamoto T.A.,Osaka University | Kageyama S.,Osaka University | Seino S.,Osaka University | Nitani H.,High Energy Accelerator Research Organization | And 5 more authors.
Applied Catalysis A: General | Year: 2011

Nanoparticle catalysts of PtRu/C for the direct methanol fuel cell anode were synthesized by a radiolytic process. Bimetallic substructures were controlled by varying irradiation dose rate and by addition of NH4OH or NaH2PO2. Material characterization was performed with the transmission electron microscopy, the X-ray diffraction, the X-ray fluorescence spectroscopy and the X-ray absorption fine structure techniques. Methanol oxidation activity was evaluated by the linear sweep voltammetry. We concluded that the structure of the radiolytically synthesized catalysts has a Pt-rich core/Ru-rich shell structure or incomplete alloy structure. A correlation between the substructures and catalytic activities was found by using a pairing factor defined from coordination numbers determined by the extend X-ray absorption fine structure analysis, which indicates the validity of the bifunctional mechanism in the PtRu nanoparticle system. This radiolytic process is promising for synthesizing advanced PtRu/C catalysts with well-mixed bimetallic substructures enhancing methanol oxidation. © 2011 Elsevier B.V. All rights reserved. Source


Ohkubo Y.,Osaka University | Kageyama S.,Osaka University | Seino S.,Osaka University | Nakagawa T.,Osaka University | And 4 more authors.
Journal of Nanoparticle Research | Year: 2013

Electrode catalysts composed of carbon-supported PtRu nanoparticles (PtRu/C) for use as a direct methanol fuel cell anode were synthesized by the reduction of precursor ions in an aqueous solution via irradiation with a high-energy electron beam. The effect of pH control in the precursor solution on the PtRu mixing state and the methanol oxidation activity was studied in order to enhance the catalytic activity for methanol oxidation. The PtRu/C structures were characterized by transmission electron microscopy, inductively coupled plasma atomic emission spectrometry, X-ray fluorescence spectrometry, and X-ray diffraction and X-ray absorption fine structure techniques. The methanol oxidation activity was evaluated by linear sweep voltammetry. The initial pH of the precursor solution has little influence on the average grain size for the metal particles (approximately 3.5 nm) on the carbon particle supports, but the dispersibility of the metal particles, PtRu mixing state, and methanol oxidation activity differed. The maintenance of a low pH in the precursor solution gave the best dispersibility of the PtRu nanoparticles supported on the surface of the carbon particles, whereas, a high pH gave the best PtRu mixing state and the highest oxidation current although a low dispersibility of the PtRu nanoparticles supported on the surface of the carbon particles was obtained. The PtRu mixing state strongly correlated with the methanol oxidation current. In addition, a high pH was more effective for PtRu mixing when using an electron beam irradiation reduction method, because the complexation reaction of the chelating agents was improved, which resulted in an enhancement of the catalytic activity for methanol oxidation. © 2013 Springer Science+Business Media Dordrecht. Source


Kugai J.,Osaka University | Moriya T.,Osaka University | Seino S.,Osaka University | Nakagawa T.,Osaka University | And 4 more authors.
Journal of Physical Chemistry C | Year: 2013

The structure of bimetallic nanoparticles has a great impact on catalytic performance. By radiation-induced reduction of metal ions in the aqueous phase, supported bimetallic Pt-Cu catalysts were synthesized with various Cu loadings, support materials, and copper sources. These parameters had a great impact on the structural properties of Pt-Cu nanoparticles. On carbon black, Pt-Cu alloy nanoparticles were readily formed with little oxide phase. On CeO2 support, Pt-Cu was highly oxidized for the low-Cu region (Cu/Pt < 1), and Pt-Cu alloy nanoparticles were formed together with CuOx for the high-Cu region (Cu/Pt > 1). The structure of CeO2-supported catalysts obtained from two different copper sources (CuSO4 and CuCl2) suggested that such a drastic change in oxidation state is the result of two competing effects, CeO2 to oxygenate metals and the sulfate ion to stabilize them in the metallic state. The reaction characteristics in preferential CO oxidation reflected the Pt-Cu structure (oxidation state) determined by those parameters in the synthesis stage. The low-Cu oxidic samples showed excellent light-off performance, which was attributed to high oxygen transport from CeO2 to metals through the metal-CeO2 interface. The high-Cu samples comprising a Pt-Cu alloy and CuOx showed excellent selectivity, which was attributed to the metal-CuOx interface predominating over metal-CeO2. The latter exhibited 100% CO conversion in a wide temperature range in excess O 2 conditions. © 2013 American Chemical Society. Source

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