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.
Highly ordered CoFe2O4 nanowire arrays were prepared in anodic aluminum oxide (AAO) templates with two diameters (50 nm and 200 nm) by Sol-gel method. The scanning electron microscope (SEM), transmission electron micr...
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Highly ordered CoFe2O4 nanowire arrays were prepared in anodic aluminum oxide (AAO) templates with two diameters (50 nm and 200 nm) by Sol-gel method. The scanning electron microscope (SEM), transmission electron microscope (TEM) and high-resolution transmission electron microscope (HRTEM) were used to characterize the structures of the nanowire arrays. The hysteresis loops of the CoFe2O4 nanowire arrays reveal that there was no preferential magnetic orientation in both of the nanowire arrays with different diameters. The measured coercivity of CoFe2O4 nanowire arrays with smaller diameter (50 nm) was larger than that of the nanowire arrays with bigger diameter (200 nm). The possible explanation for this behavior was given.
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%.
X-ray diffraction (XRD) analysis on different polished surfaces normal to the hot pressing direction reveals that the phase compositions of the polished surfaces from the outside to the inside are pure TiC, Ti_3AlC_2+...
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X-ray diffraction (XRD) analysis on different polished surfaces normal to the hot pressing direction reveals that the phase compositions of the polished surfaces from the outside to the inside are pure TiC, Ti_3AlC_2+TiC, pure Ti_3AlC_2 and Ti_2AlC+Ti_3AlC_2, no matter elemental powder or TiC is used as raw materials. It is found that ternary-layered carbide Ti_2AlC samples synthesized at 1500 ℃ by hot-pressing sintering are inhomogeneous and have a gradient *** probe X-ray micro-analysis (EPMA) indicates that the Al content along the hot pressing axis is parabolic, it is the highest in the center and the lowest at the both ends, while the Ti content is constant along the axis. The experimental result reveals that the evaporation of Al in samples in an open system during hot pressing sintering results in a gradient structure.
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.
ZrB2 ceramics were prepared by self-propagating high-temperature synthesis（SHS） and were sintered by hot pressing（HP）.The effects of the granularities and doses of raw materials in Zr-B2O3-Mgon SHS process and pro...
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ZrB2 ceramics were prepared by self-propagating high-temperature synthesis（SHS） and were sintered by hot pressing（HP）.The effects of the granularities and doses of raw materials in Zr-B2O3-Mgon SHS process and product were *** and combustion temperature curves prove that the ideal SHS reactants of Zr-B2O3-Mg are 50μm Zr powder,75μm B2O3 powder and 400μm Mg powder with 45% *** particle sizes of SHS product,acid-leached product,sintered product are 2-5μm,0.5-2μm,2-10μm *** analysis indicates that the acid-leached product consists of ZrB2（94.59%）,ZrO2（3.87%）,and H3BO3（1.54%）,The sintered product has a relative density of 95.4%.
When boiler runs under certain pressure and temperature, the disfigurement and crack will propagate, resulting in failure of the boiler drum. According to the Assess criterion of Pressure Container's Disfigurement...
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When boiler runs under certain pressure and temperature, the disfigurement and crack will propagate, resulting in failure of the boiler drum. According to the Assess criterion of Pressure Container's Disfigurement, the maximal stress value in the dangerous area for 125MW boiler drum and its change within certain time frame under different working conditions are found out by means of finite element method. The allowable length of crack is calculated with COD mode and the yearly crack-propagating value is predicted and analyzed.
Based on the boundary conditions of the running parameters and test data of 125 MW boiler drum, the transient thermal stress, mechanical stress and whole stresses of the boiler drum under four different working condit...
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Based on the boundary conditions of the running parameters and test data of 125 MW boiler drum, the transient thermal stress, mechanical stress and whole stresses of the boiler drum under four different working conditions were computed by finite element methods under 3-dimension model. The relationship among the three kinds of stresses was discussed as well as the spot of maximum stress and its varying tendency with the time was obtained.
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