The proton exchange membrane could be sufficiently hydrated when a proton exchange membrane fuel cell (PEMFC) operated normally. Based on Springer model, the equation of the distribution of water molecules number bond...
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The proton exchange membrane could be sufficiently hydrated when a proton exchange membrane fuel cell (PEMFC) operated normally. Based on Springer model, the equation of the distribution of water molecules number bonded with SO4 in the membrane was derived. Considering the effects of the membrane thickness, operating temperature and current density, the water transfer in the membrane was analyzed. Conclusions were drawn that the thinner the membrane can be more easily self-hydrated;the thinner the membrane was and the higher the current density was, the less the time was needed to hydrate the membrane;when the thickness was less than 15 μm and current density was higher than 0.6 A/cm2, the time was decreased drastically. The conclusions were helpful for PEMFC's design and operation.
Aluminosilicate refractory waste was used to prepare high performance ceramic ball grinding media with 75% Al2O3. The influence of milling time on the particle size of raw materials, the sintering temperature, and per...
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Aluminosilicate refractory waste was used to prepare high performance ceramic ball grinding media with 75% Al2O3. The influence of milling time on the particle size of raw materials, the sintering temperature, and performance of ceramic balls were studied. Results show that with increasing milling time the particle size of the raw materials decreased, resulting in a decrease of ceramic ball sintering temperature and an increase in wear resistance and volume density. The wear rate and volume density of balls prepared by milling the materials for 72 h were 0.01886 %/h and 3.374 g/cm 3, respectively.
A physical model for mobility degradation by interface-roughness scattering and Coulomb scattering is proposed for SiGe p-MOSFET with a high-k dielectric/SiO2 gate stack. Impacts of the two kinds of scatterings on mob...
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A physical model for mobility degradation by interface-roughness scattering and Coulomb scattering is proposed for SiGe p-MOSFET with a high-k dielectric/SiO2 gate stack. Impacts of the two kinds of scatterings on mobility degradation are investigated. Effects of interlayer （SiO2） thickness and permittivities of the high-k dielectric and interlayer on carrier mobility are also discussed. It is shown that a smooth interface between high-k dielectric and interlayer, as well as moderate permittivities of high-k dielectrics, is highly desired to improve carriers mobility while keeping alow equivalent oxide thickness. Simulated results agree reasonably with experimental data.
In this paper, the lower and upper bounds of Young's modulus and Poisson ratio are determined by the effective stress method and effective strain method from material mechanics. The effective heat flux method base...
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In this paper, the lower and upper bounds of Young's modulus and Poisson ratio are determined by the effective stress method and effective strain method from material mechanics. The effective heat flux method based on the hypothesis of equivalent temperature difference and the effective temperature difference method based on the hypothesis of equivalent heat flux are proposed, the lower and upper bounds of the thermal conductivity of ceramic/metal composite material are determined similarly. The result shows that the property values of ceramic/metal composites calculated from current theoretical property formulas are within the lower and upper bounds determined by the above methods.
A peptizing-hydrothermal method to prepare nanometer γ-AlOOH crystal powder with industrial Al(OH)3 as raw materials has been proposed in the present paper. The XRD and TEM results show the product is a pure γ type ...
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A peptizing-hydrothermal method to prepare nanometer γ-AlOOH crystal powder with industrial Al(OH)3 as raw materials has been proposed in the present paper. The XRD and TEM results show the product is a pure γ type nanometer A100H crystal powder with average grain diameter of 70nm. Laser grading analysis indicates the average grain diameters of the product in the solution are 66.52nm in water and 84.33nm in N,N-dimethylformamide, respectively without surface modification and dispersant. The experimental result indicated that polymer/inorganic nano-composite with high content of nanometer AlOOH presents inorganic characteristic of polymer. The wear rate of the alumina ceramic ball sintered at 1465°C from ceramic, which contains 98% alumina (wt), can be reduced up to 40% with addition of 3.5% nanometer AlOOH.
Four Coating schemes and two substrate materials are designed to evaluate the characteristics of the ceramic/metal gradient thermal barrier coating. The gradient coating is successfully prepared by plasma spray with s...
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Four Coating schemes and two substrate materials are designed to evaluate the characteristics of the ceramic/metal gradient thermal barrier coating. The gradient coating is successfully prepared by plasma spray with single torch and single feeder. The coating performance is evaluated by observing microstructure, measuring thermal shock resistance and thermal residual stress. The coating microstructure is observed by scanning electron microscope (SEM). Diffractive peaks for the gradient coating are got at different zone by X-ray spectroscopy (XRS). The thermal shock experiment shows that the thermal shock resistance property of the gradient coating is better than that of the non-gradient coating. The measurements of thermal residual stresses in different coating schemes are carried out by hole-drilling method, the results show that compressional stress presents on 1Cr18Ni9Ti substrate and tensile stress presents on 2Cr13 substrate.
The transient stress field analysis aims at the thermal and mechanical response of LPG vessel under pool fire surrounding environment. Finite element analysis method is used to calculate the stress field. Thermal boun...
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The transient stress field analysis aims at the thermal and mechanical response of LPG vessel under pool fire surrounding environment. Finite element analysis method is used to calculate the stress field. Thermal boundary conditions of LPG vessel are determined according to heat transfer theory and calculated by the software PLGS99. The results show that the maximum whole stress of the vessel appears near the highest surface where liquid can reach, the maximum thermal stress is much greater than the maximum mechanical stress and fluctuation of liquid surface is the main reason of high stress. The highest position of the LPG vessel which liquid can reach should be protected as it is the most dangerous place.
As one of the advanced functional inorganic power materials, nanometer ZnO has extensive application fields. The specific surface area is considered to be a big factors for its application. In this paper, the gas adso...
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As one of the advanced functional inorganic power materials, nanometer ZnO has extensive application fields. The specific surface area is considered to be a big factors for its application. In this paper, the gas adsorption method was adopted to measure ZnO specific surface area, and the influences of different testing conditions on the results were studied. It was found that optimal testing condition is that sample weight, degas temperature and degas time are 0.3-0.5g, 250°C, 2h respectively.
The method of single detector, direct contact and longitudinal wave were used in this research. Ultrasonic wave attenuation coefficient of nine WC-10 Co hardmetals samples were tested, while fracture toughness values ...
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The method of single detector, direct contact and longitudinal wave were used in this research. Ultrasonic wave attenuation coefficient of nine WC-10 Co hardmetals samples were tested, while fracture toughness values were obtained by indentation method. SEM was performed to observe the sections of the samples. Distributions of the WC grains were analyzed. Density, Vickers hardness and transverse rupture strength were also tested. The relationships among ultrasonic wave attenuation coefficient, mean grain size, fracture toughness, density, Vickers hardness and transverse rupture strength were studied. Results showed that with the decrease of the mean WC grain size, the ultrasonic wave attenuation coefficient and the fracture toughness value increased. However, ultrasonic wave attenuation coefficient had no direct relation with density, Vickers hardness and transverse rupture strength. It was concluded that ultrasonic wave attenuation coefficient could be used to evaluate the fracture toughness of WC-10 Co hardmetals, instead of destructive mechanical method.
(AgSbTe2)x(PbTe)1-x (x = 0.04-0.20) samples were prepared by slow-cool-from-melts and the influences of AgSbTes content on the microstructure and thermoelectric properties were investigated. Results indicated that pha...
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(AgSbTe2)x(PbTe)1-x (x = 0.04-0.20) samples were prepared by slow-cool-from-melts and the influences of AgSbTes content on the microstructure and thermoelectric properties were investigated. Results indicated that phase segregation occurs as x increases and the samples are characterized by a bi-phased material containing one main Pb-rich phase and another Ag-Sb-rich phase. As AgSbTe2 content increases, the thermal conductivity is depressed and the electrical properties decrease to some extent. The dimensionless of figure of merits (ZT) is greater for sample with a lower AgSbTe2 content.
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