The three-dimensional computing models of the cathode of PEM fuel cell within serpentine flow field and pin flow field are developed. By coupling computation the continuity equation, momentum equation, Darcy equation ...
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The three-dimensional computing models of the cathode of PEM fuel cell within serpentine flow field and pin flow field are developed. By coupling computation the continuity equation, momentum equation, Darcy equation and Stefan-Maxwell equation, the gas velocity distribution in the middle of GDL and concentration distribution of O2 and H2O at the catalyst GDL interface of two different flow fields are displayed. The performance of PEMFC within serpentine flow field and pin flow field are compared experimentally.
Activation process has important impact on the performance of proton exchange membrane fuel cells (PEMFCs). In this paper, an activation procedure was designed and used to primarily investigate the activation process ...
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Activation process has important impact on the performance of proton exchange membrane fuel cells (PEMFCs). In this paper, an activation procedure was designed and used to primarily investigate the activation process of a 25 kW PEMFC stack. The performance of the stack during and after the activation process was examined. The investigation indicates that the forced activation at varied current can finish the activation process quickly. More effective procedure and method should be investigated to quicken the activation process of a PEMFC stack.
Water management is the key for PEMFC to operate efficiently. To maintain a suitable hydrated state for PEM but without flooding in the porous medium polarity is an ideal case which is difficult to achieve. PEMFC is a...
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Water management is the key for PEMFC to operate efficiently. To maintain a suitable hydrated state for PEM but without flooding in the porous medium polarity is an ideal case which is difficult to achieve. PEMFC is a complex system with the characteristics of multi-phases, multi-dimensions, multi-physics fields and dynamics. The flow, heat and mass transfer, phase change, multi-phase flow and electrochemical process inside PEMFC have influences on each other, the mechanism is sophisticated and hard to measure or observe directly. This paper summaries the achievement in respects of water transfer mechanism, humidification methods, measurement and diagnostic of liquid water in PEMFC, methods of discharge liquid water and modeling of the water behaviors inside PEMFC. The water management, heat management, gas management and electricity management are associated each other, therefore the flow, heat and mass transfer, phase change, multi-phase flow and electrochemical process inside PEMFC should be considered systematically, relevant researches are to be carried out continuously.
In this research, we developed a three-dimensional finite-difference-time-domain algorithm that incorporated the Lorentz-Drude model through the use of Z-transform technique. This algorithm was used to compute the spe...
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In this research, we developed a three-dimensional finite-difference-time-domain algorithm that incorporated the Lorentz-Drude model through the use of Z-transform technique. This algorithm was used to compute the spectral response of infrared bandpass filters which consisted of the openings of cross-shaped structures in a thin gold film. In creating structures, a graphical user interface was built using Matlab development environment. The created structures were then simulated by running the simulation code written in Fortran. It was observed that cross-shaped structures with large center-broadening effect yielded the highest transmission intensity among the structures that were simulated with a transmittance of approximately 80% at the wavelength of 1.2 μm.
Water management is critical for high performance of proton exchanges membrane fuel cell (PEMFC). The liquid water transport model for gradient structure gas diffusion layer of PEMFC was established based on the capil...
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Water management is critical for high performance of proton exchanges membrane fuel cell (PEMFC). The liquid water transport model for gradient structure gas diffusion layer of PEMFC was established based on the capillary pressure theory, and then the liquid water flux through GDL was calculated based on the assumption that a fixed liquid saturation difference exists between the interfaces of catalyst layer/GDL and GDL/gas channel, the results were analyzed. Results showed that under steady condition the liquid water flux through GDL increasing with the increasing of porosity, GDL with gradient porosity was more favorable for liquid water to be discharged from MEA to gas channel;the larger the gradient was, the more easily the liquid water was to be discharged out.
This research is that cellulose/poly-silicate hybrid material was prepared with viscose and poly-silicate by sol-gel method. The influence of aluminum salt and poly-silicate on hybrid material thermal property was stu...
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This research is that cellulose/poly-silicate hybrid material was prepared with viscose and poly-silicate by sol-gel method. The influence of aluminum salt and poly-silicate on hybrid material thermal property was studied. Based on the analysis of the DSC and TG curve of hybrid material, we have found that the hybrid material has splendid heat-resistance and fire retardancy.
TiB_2 ceramics powder was synthesized from B_2O_3-TiO_2-Mg system. The effects of TiB_2 addition as diluent on the combustion synthesis process were investigated. The results of thermodynamic calculation and experimen...
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TiB_2 ceramics powder was synthesized from B_2O_3-TiO_2-Mg system. The effects of TiB_2 addition as diluent on the combustion synthesis process were investigated. The results of thermodynamic calculation and experiments show that the increase of TiB_2 content ranging from 0 to 20wt% can reduce the adiabatic temperature T_(ad) from 3100 K to 2896 K and combustion temperature T_c from 2139 K to 1621 K respectively. The particle size and half width of the particle distribution are also increased with the addition of TiB_2 increasing from 0 to 20wt%. The combustion product is a mixture of TiB_2, MgO, and other intermediate phases. The leached product contains mainly TiB_2, TiO_2 and TiN, and its oxygen content is 7.77wt%.
Patterned ZnO nanorods have been first grown on patterned silicon nanocrystallite (SiNC) films that were fabricated on (100) orientation p-type boron-doped silicon wafer by hydrogen ion implantation technique and the ...
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Patterned ZnO nanorods have been first grown on patterned silicon nanocrystallite (SiNC) films that were fabricated on (100) orientation p-type boron-doped silicon wafer by hydrogen ion implantation technique and the anodic etching method, and their field emission properties were obtained. Field emission measurements demonstrated that the synthesized ZnO nanorods have excellent field emission properties, namely low turn-on field, low threshold field, and high emission spot density. The patterned ZnO nanorods have great potential in the application of flat panel displays.
In order to unclose the dynamics of SPS densification, a special sintering sample (Cu/Ti wires compact) was designed. Characters of the shrinkage rates during sintering process and microstructures of products fabricat...
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In order to unclose the dynamics of SPS densification, a special sintering sample (Cu/Ti wires compact) was designed. Characters of the shrinkage rates during sintering process and microstructures of products fabricated by the spark plasma sintering(SPS) and hot-press sintering were investigated. The experimental results reveal that a higher temperature field is formed at the connected area and conductive net of the compact. These high-temperature parts deformed more easily than other parts, which is believed to be the main cause of SPS fast densification, according to a hard-core and soft-hell material model.
Polymer-protected monodisperse nickel nanoparticles were synthesized by a modified polyol reduction method in the presence of poly（N-vinyl-2-Pyrrolidone）.These nanoparticles were characterized by transmission electr...
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Polymer-protected monodisperse nickel nanoparticles were synthesized by a modified polyol reduction method in the presence of poly（N-vinyl-2-Pyrrolidone）.These nanoparticles were characterized by transmission electron microscopy（TEM）,X-ray diffraction（XRD）,selected area electron diffraction（SAED）,as well as vibrating sample magnetometer（VSM）.The experimental results show that the addition of PVP and the concentration of NaOh have strong influences on the *** and uniformity of *** the presence of PVP and NaoH with low *** nickel nanoparticles with average diameters about 42 nm were obtained and characterized to the pure nickel crystalline with foc *** structures such as *** strings resulted from magnetic interactions between particles were *** chemical interaction between the PVP and nickel nanoparticles was found by *** saturation magnetization（Ms）.remanent magnetization（Mr）and coercivity（Hc）of these nickel nanoparticles are lower than those of bulk nickel.
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