It is necessary for 319 aluminium alloy castings to be heat treated (in T6 condition) for the improvement of their mechanical properties. However, heat treatment needs not only cycle time but also energy cost. The hea...
详细信息
Plasma deposition dieless manufacturing is a rapid heating and solidification process, in which how to avoid cracks and distortions is a key problem. To explore the thermal behaviors of this process, the preheated and...
详细信息
ISBN:
(纸本)0979497701
Plasma deposition dieless manufacturing is a rapid heating and solidification process, in which how to avoid cracks and distortions is a key problem. To explore the thermal behaviors of this process, the preheated and water-cooled programs were designed and evaluated numerically by finite element method and the watercooled scheme showed lower hot crackability and better formability. Thereafter, evolutions of the temperature and stress field were simulated based on the water-cooled scheme under optimized process conditions. Computational and experimental results confirm that reasonable process-cooled conditions can reduce the temperature and stress gradients and thus ultimately improve the possibly-intended formability.
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...
详细信息
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.
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...
详细信息
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.
A kind of gradient thermal and environmental barrier coating applied in internal combustion engine is brought forward to improve its reliability, emission and efficiency. The multi-layer plate and cylinder models are ...
详细信息
A kind of gradient thermal and environmental barrier coating applied in internal combustion engine is brought forward to improve its reliability, emission and efficiency. The multi-layer plate and cylinder models are established for the simulations of heat transfer and thermal stress in the coatings. Both the theoretical and the numerical analysis with multi-layer cylinder model with coating inside are carried out and compared. The results show good agreement.
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...
详细信息
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.
Si-clathrate compounds, n-type Ba8 Ga16 Znx Si30-x (x = 0, 1, 2, 3, 4), are synthesized by using the solid-state reaction method and the melting method. The effects of the replacement of Si with Zn on the structure an...
详细信息
Si-clathrate compounds, n-type Ba8 Ga16 Znx Si30-x (x = 0, 1, 2, 3, 4), are synthesized by using the solid-state reaction method and the melting method. The effects of the replacement of Si with Zn on the structure and the electrical transmission characteristics are investigated for n-type Ba8Ga16Znx Si30-x. The results indicate that the sample with the value of x = 1 has the maximal bond angle distortion Δθ, Δθ = 4.4°. The electrical conductivity of samples with x = 0, 2, 4 is higher than that of samples with x = 1, 3. Among the samples, the electrical conductivity of Ba8 Ga16 Zn1 Si29 is the lowest. The samples with x = 0, 2, 4 exhibit a higher Seebeck coefficient than that of samples with x = 1, 3, and the value of the Seebeck coefficient decreases with the increase of the Zn composition. The power factor of Ba8Ga16Zn2Si28 compound is as large as 1.03 × 10-3 W/(m· K2) at 1000K.
High-energy ball mill method was used to fabricate the stainless steel nanocomposite powder from stainless steel powder, carbon powder and titanium powder as raw materials. The X-ray diffraction, SEM and the BET metho...
详细信息
High-energy ball mill method was used to fabricate the stainless steel nanocomposite powder from stainless steel powder, carbon powder and titanium powder as raw materials. The X-ray diffraction, SEM and the BET method were used to evaluate the microstructure of treated samples. The results showed that in vacuum condition, with ball mill time increase, stainless steel powder become more and finer, the grain size can reach nanometer level. At the same time, the nano TiC can be formed during ball milling, the stainless steel-TiC nano composite powder can be obtained.
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...
详细信息
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.
Using the microwave sintering technology, the samples of WC-10Co cemented carbide were put separately at the pure electric field, the pure magnetic field and the mixture E field and H field in a single-mode TE103 cavi...
详细信息
Using the microwave sintering technology, the samples of WC-10Co cemented carbide were put separately at the pure electric field, the pure magnetic field and the mixture E field and H field in a single-mode TE103 cavity. The sintering behaviors of WC-10Co cemented carbide were researched and the effects of these positions on their properties also were analyzed.
暂无评论