The Experts below are selected from a list of 120 Experts worldwide ranked by ideXlab platform
Akira Ohta - One of the best experts on this subject based on the ideXlab platform.
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effects of microstructure of carbon support in the catalyst layer on the performance of polymer electrolyte fuel cells
Journal of The Electrochemical Society, 1996Co-Authors: Makoto Uchida, Yuko Fukuoka, Yasushi Sugawara, Nobuo Eda, Akira OhtaAbstract:In the case of the Polymer-electrolyte fuel cells (PEFCs), the reaction sites exist on the platinum (Pt) surface covered with PFSI. Though PFSI membrane is used as an electrolyte of the PEFC, the membrane does not soak deeply into the electrodes as a liquid electrolyte does. Therefore, PFSI solution was impregnated into the catalyst layers to increase the contact areas between Pt and PFSI. In our previous work we proposed a new preparation method of the M&E assembly which emphasized the colloid formation of the PFSI to optimize the network of PFSIs in the catalyst layer and also to simplify the fabrication process of the M&E assembly. Following this work, we focused on the microstructure of the catalyst layer. The importance of the morphological properties of the gas-diffusion electrodes on performance has been reported in several papers. The catalyst layer was claimed to have had two distinctive Pore distributions with a boundary of ca. 0.1 {mu}m. The smaller Pore (Primary Pore) was identified with the space in and between the Primary particles in the agglomerate of the carbon support and the larger one (secondary Pore) was that between the agglomerates. In our recent work, we reported that the PFSI wasmore » distributed only in the secondary Pores, and the reaction sites were therefore limited to that location. The results indicated that the PEFC system required a particular design rather than a conventional one for the fuel cells with liquid electrolytes. We proposed that novel structure and/or preparation methods of the catalyst layer were keys to higher utilization of Pt.« less
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investigation of the microstructure in the catalyst layer and effects of both perfluorosulfonate ionomer and ptfe loaded carbon on the catalyst layer of polymer electrolyte fuel cells
Journal of The Electrochemical Society, 1995Co-Authors: Makoto Uchida, Yuko Aoyama, Akira OhtaAbstract:Effects of a perfluorosulfonate ionomer (PFSI) and of a polytetrafluoroethylene (PTFE) loaded carbon (PTFE-C) on the catalyst layer in the electrode of a polymer electrolyte fuel cell (PEFC) prepared by a new method based on the process of PFSI-colloid formation were investigated by electrochemical techniques and a mercury Pore sizer. The microstructure of the catalyst layer and its effect on the PEFC performance were affected by the contents of both PFSI and PTFE-C. The catalyst layer has two distinctive Pore distributions with a boundary of ca. 0.04 {micro}m. The volume of larger Pore (secondary Pore) decreased with an increase of the PFSI content and increased with an increase of the PTFE-C content. The volume of the smaller Pore (Primary Pore) was independent of the content of both PFSI and PTFE-C. The PFSI as well as the PTFE existed only in the secondary Pore. The content of PFSI affected the performance of PEFC in the whole current density range. On the other hand, the content of PTFE-C influenced it greatly at high current density due to its gas feeding faculty. In the PEFC, reaction sites were found to exist in the secondary Pore coated with the macromolecule PFSI. The hydrophobic PTFE-Cmore » works to supply the reaction gas to the reaction sites covered with the PFSI in the secondary Pore, and to exhaust the product water from there. The high performance of PEFC at high current density was achieved with the best mixture of the PFSI and the PTFE-C.« less
Makoto Uchida - One of the best experts on this subject based on the ideXlab platform.
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effects of microstructure of carbon support in the catalyst layer on the performance of polymer electrolyte fuel cells
Journal of The Electrochemical Society, 1996Co-Authors: Makoto Uchida, Yuko Fukuoka, Yasushi Sugawara, Nobuo Eda, Akira OhtaAbstract:In the case of the Polymer-electrolyte fuel cells (PEFCs), the reaction sites exist on the platinum (Pt) surface covered with PFSI. Though PFSI membrane is used as an electrolyte of the PEFC, the membrane does not soak deeply into the electrodes as a liquid electrolyte does. Therefore, PFSI solution was impregnated into the catalyst layers to increase the contact areas between Pt and PFSI. In our previous work we proposed a new preparation method of the M&E assembly which emphasized the colloid formation of the PFSI to optimize the network of PFSIs in the catalyst layer and also to simplify the fabrication process of the M&E assembly. Following this work, we focused on the microstructure of the catalyst layer. The importance of the morphological properties of the gas-diffusion electrodes on performance has been reported in several papers. The catalyst layer was claimed to have had two distinctive Pore distributions with a boundary of ca. 0.1 {mu}m. The smaller Pore (Primary Pore) was identified with the space in and between the Primary particles in the agglomerate of the carbon support and the larger one (secondary Pore) was that between the agglomerates. In our recent work, we reported that the PFSI wasmore » distributed only in the secondary Pores, and the reaction sites were therefore limited to that location. The results indicated that the PEFC system required a particular design rather than a conventional one for the fuel cells with liquid electrolytes. We proposed that novel structure and/or preparation methods of the catalyst layer were keys to higher utilization of Pt.« less
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investigation of the microstructure in the catalyst layer and effects of both perfluorosulfonate ionomer and ptfe loaded carbon on the catalyst layer of polymer electrolyte fuel cells
Journal of The Electrochemical Society, 1995Co-Authors: Makoto Uchida, Yuko Aoyama, Akira OhtaAbstract:Effects of a perfluorosulfonate ionomer (PFSI) and of a polytetrafluoroethylene (PTFE) loaded carbon (PTFE-C) on the catalyst layer in the electrode of a polymer electrolyte fuel cell (PEFC) prepared by a new method based on the process of PFSI-colloid formation were investigated by electrochemical techniques and a mercury Pore sizer. The microstructure of the catalyst layer and its effect on the PEFC performance were affected by the contents of both PFSI and PTFE-C. The catalyst layer has two distinctive Pore distributions with a boundary of ca. 0.04 {micro}m. The volume of larger Pore (secondary Pore) decreased with an increase of the PFSI content and increased with an increase of the PTFE-C content. The volume of the smaller Pore (Primary Pore) was independent of the content of both PFSI and PTFE-C. The PFSI as well as the PTFE existed only in the secondary Pore. The content of PFSI affected the performance of PEFC in the whole current density range. On the other hand, the content of PTFE-C influenced it greatly at high current density due to its gas feeding faculty. In the PEFC, reaction sites were found to exist in the secondary Pore coated with the macromolecule PFSI. The hydrophobic PTFE-Cmore » works to supply the reaction gas to the reaction sites covered with the PFSI in the secondary Pore, and to exhaust the product water from there. The high performance of PEFC at high current density was achieved with the best mixture of the PFSI and the PTFE-C.« less
Dirk Enke - One of the best experts on this subject based on the ideXlab platform.
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transformation of porous glasses into mcm 41 containing geometric bodies
Microporous and Mesoporous Materials, 2013Co-Authors: Hans Uhlig, Marieluise Gimpel, Alexandra Inayat, Roger Glaser, Wilhelm Schwieger, Wolfdietrich Einicke, Dirk EnkeAbstract:Abstract This contribution presents the transformation of Controlled Pore Glass (CPG) granules into MCM-41 material. Porous glasses with Pore diameters between 34 and 390 nm and varying Pore volumes were used as starting materials. In dependence on the textural properties of the starting porous glasses and the synthesis conditions a pseudomorphic transformation of porous glass granules into hierarchically structured MCM-41 granules was accomplished. Such MCM-41 granules exhibit not only the original macroscopic shape but also the Pore morphology of the starting porous glass. Based on systematic variations of alkalinity, glass Pore volume and glass Pore diameter the requirements for a pseudomorphic transformation are defined. Materials with a hierarchical Pore system (meso- or macroPores of the porous glass, ordered mesoPores inside the former glass walls) could be generated via the variation of the molar ratio between cetyltrimethylammonium hydroxide and total cetyltrimethylammonium template amount (CTAOH/CTAOH + CTAB). The transformation products were characterized by nitrogen adsorption, mercury intrusion, X-ray diffraction, scanning electron and light microscopy. During the transformation the Primary Pore walls were found to swell into the initial Pore space, which is caused by bulk density differences between the non-porous glass walls and the template containing MCM-41 material. A Pore volume above 1.0 cm3/g and Pore diameters above 60 nm were found to be prerequirements for a pseudomorphic transformation of the porous glasses into MCM-41. Furthermore, a complete transformation was only possible for glasses exhibiting sufficiently high surface area, which was not the case for very large Pore diameters of around 390 nm.
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Relations between texture and transport properties in the Primary Pore system of catalyst supports
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006Co-Authors: H. Preising, Dirk EnkeAbstract:Abstract Porous glasses in shape of beads and flat membranes with controlled mesoporosity in the range between 2 and 20 nm were used as model system to study the correlation between the texture properties and the transport characteristics in the Primary Pore system of catalyst supports. The beads and membranes were distinguished by comparable texture parameters. The tortuosity factors of the Pore structure were obtained from measurements of the permeability of nitrogen of the porous glass membranes. The tortuosity factors vary in the range between 1.5 and 40 depending on the Pore diameter and the porosity of the membranes. The hydrogenation of benzene over nickel catalysts based on the porous glass beads was used as test reaction. Here, the effective mesoPore diffusivities were obtained from the Arrhenius plots. Furthermore, the Pore diffusion coefficients of benzene were determined. The values are in the range between 1 × 10 −6 and 2 × 10 −5 cm 2 s −1 . A systematic correlation between the texture properties (mean Pore size) and transport characteristics (Pore diffusion coefficient) was observed.
Kang Bao-ping - One of the best experts on this subject based on the ideXlab platform.
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A STUDY ON CEMENT IN Primary Pore OF THE LEIKOUPO FORMATION RESERVOIR IN THE NORTHWEST OF SICHUAN BASIN
Natural Gas Geoscience, 2006Co-Authors: Kang Bao-pingAbstract:According to the macro-observation of the outcrop sections and drilling core of Leikoupo formation of Middle Triassic in northwest Sichuan basin,and the analysis of such supporting materials as thin-section,cathode luminescence,electron microprobe and mineral inclosure,the author makes a comparatively deep study of the structure,characteristics and composition forms of the cement in the sparry grain dolomite and the blue green algae agglutinate dolomite of the Leikoupo formation reservoir,and analyzes the diagenetic environment and the reservoir space.The six different types of the sparry cement in the protosomatic intergranular hole and the algae agglutinate ramework bore are the outcome of different the diagenetic environmen of four periods,and they vary greatly in the characteristics and composition form of the attitude,mineralogy,geochemistry and others,and as well,in their influence on the reservoir space.
M A Ioannidis - One of the best experts on this subject based on the ideXlab platform.
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dual porosity modelling of the Pore structure and transport properties of a contaminated soil
European Journal of Soil Science, 2008Co-Authors: C D Tsakiroglou, M A IoannidisAbstract:Summary We have developed a new method to characterize the Pore structure of mineral soils. We combined data from the analysis of back-scattered scanning electron microscope (BSEM) images of resin-impregnated Pore-casts, and mercury intrusion porosimetry (MIP) data, with analytical percolation models and inverse modeling algorithms. The Pore space is regarded as a dual-Pore network consisting of a Primary Euclidean Pore-and-throat network and a secondary, fractal, Pore system that is accessed through Primary Pores. The digitized 2-D BSEM images of resin-impregnated soil samples are employed to determine the autocorrelation function. The Fourier transform of this function provides the small-angle neutron scattering (SANS) intensity function, which is extended by using the surface fractal dimension obtained from high-pressure MIP data. Inversion of the extended scattering intensity function produces the volume-based radius distribution function of spherical Pore bodies (PBRD). The complete volume-based PBRD is fitted with a composite number-based PBRD composed of a lognormal Primary PBRD and a power (fractal) secondary PBRD with upper and lower cut-offs. Based on the concepts of invasion percolation, an analytic mathematical model that describes Hg intrusion into dual Pore networks is developed. The complete PBRD and Pore-throat radius distribution (PTRD) functions of the Primary network along with the drainage accessibility functions (DAFs) of the Primary and secondary Pore networks are estimated with inverse modelling of the Hg intrusion curve. Based on critical path analysis of percolation theory, approximate analytical relationships are developed to calculate explicitly the absolute permeability and electrical formation factor from the geometrical and topological parameters of the Primary Pore network. The method is demonstrated with application to four soil samples.