Home About us Contact
|
Home About us Contact | ||
|
|
||
Mass Transport Processes (mass + transport_process)
Selected AbstractsIntelligent structure design of membrane cathode assembly for direct methanol fuel cellINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2005K. Furukawa Abstract The performance and the structural model of membrane electrode assembly (MEA) have been developed and experimentally verified with fundamental calculations of the direct methanol fuel cell (DMFC). The model provides information concerning the influence of the operating and structural parameters. The composition and performance optimization of MEA structure in DMFC has been investigated by including both electrochemical reaction and mass transport process. In the experimentation, the effect of Nafion content and loading method in the catalyst layer of cathode for DMFC was investigated. For the spray method electrode (SME), the cell performance and cathode performance using a dynamic hydrogen electrode (DHE) as a reference electrode was improved in comparison with those of the PME electrode by decreasing cathode potential. From ac impedance measurements of the cathode, the adsorption resistance of the SME electrode was decreased compared with that of the PME electrode. The higher cell performance was mostly dependent on the adsorption resistance. In the modelling, the cathode overpotential was decreased with increasing ionomer content, due to increasing ionic conductivity for proton transfer and the larger reaction site. The resistance to oxygen transport was increased at the same time, and became dominant at higher ionomer loadings, leading to an increase in the voltage loss. The ratio of ionomer to void space in the cathode affected the cathode polarization, which had the lowest resistance of oxygen diffusion at the ratio of 0.1,0.2. Copyright © 2005 John Wiley & Sons, Ltd. [source] Treatment of Fenton-refractory olive oil mill wastes by electrochemical oxidation with boron-doped diamond anodesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2006Pablo Cañizares Abstract In this work, the electrochemical oxidation of an actual industrial waste with conductive diamond anodes has been studied. The wastewater is the effluent of a wastewater treatment plant consisting of a Fenton reactor followed by a settler and a sand filter, in which the wastes generated in an olive oil mill are treated. These wastes contain a residual chemical oxygen demand of nearly 700 mg dm,3 which cannot be further oxidized with the Fenton process. The electrolyses were carried out under galvanostatic conditions, using a bench-scale plant equipped with a single-compartment electrochemical flow cell. Boron-doped diamond (BDD) and stainless steel (AISI 304) were use as anode and cathode of the cell, respectively. The complete mineralization of the waste was obtained with high current efficiencies limited only by mass transport processes. This confirms that besides the hydroxyl radical-mediated oxidation that occurs in the Fenton process, the electrochemical oxidation with conductive diamond electrodes combines other important oxidation processes such as direct electro-oxidation on the BDD surface and oxidation mediated by other electrochemically formed compounds generated in this electrode. Copyright © 2006 Society of Chemical Industry [source] Prediction of gas sorption kinetics for porous media using MRIAICHE JOURNAL, Issue 9 2006Matthew J. Watt-Smith Abstract Diffusion and reaction within porous media involving condensable vapors are important processes in catalysis, fuel cells, and membrane separations. In this work, 3-D maps of the spatial variation of porosity, pore size and network tortuosity within a porous solid, derived from magnetic resonance images, have been used to construct a structural model for a mesoporous catalyst pellet. Simulations of the kinetic uptake, adsorption and capillary condensation of butane vapor within the porous solid, conducted on the structural model, have successfully predicted experimental measurements of the effects of the onset of capillary condensation on mass transfer rates without the need of the various adjustable parameters prevalent in other models. These findings suggest that accurate mathematical models for both the complex void space of the porous medium, and the mass transport processes taking place within it, have been successfully developed. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Effect of growth interruption on In-rich InGaN/GaN single quantum well structuresPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003Soon-Yong Kwon Abstract We successfully grew In-rich InGaN/GaN single quantum well structures by metal-organic chemical vapor deposition and confirmed their formation by optical and structural measurements. Relatively high growth temperature (730 °C) for InGaN layer facilitated the formation of 2-dimensional quantum well structures, presumably due to high adatom mobility. As the growth interruption time increased, the PL emission efficiency from InGaN layer improved with peak position blue-shifted and the dislocation density decreased by one order of magnitude. The high resolution cross-sectional TEM images clearly showed that the In-rich InGaN layer thickness reduced from 2.5 nm (without GI) to about 1 nm (with 10 s GI) and the InGaN/GaN interface became very flat with 10 s GI. We suggest that decomposition and mass transport processes on InGaN during GI is responsible for these phenomena. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||