Applied Mechanics and Materials Vols. 423-426

Abstract: The band gaps and the absorption properties of In_xGa_1-xAs used as the infrared-extension negative electron affinity (NEA) photocathode are discussed based on first principle. The analysis about the band gaps of the In_xGa_1-xAs with different In component proves that the models and the computational accuracy are reliable. It is found that the absorption peak P1 moves to the high energy region and the absorption coefficient becomes smaller with the increase of the In component x when the photon energy is less than 4 eV. Absorption peak P3 moves to the high energy region and the absorption coefficient becomes bigger with the increase of the In component x when the photon energy is more than 6 eV. The analysis about the absorption property offers a theoretical foundation for the design of the NEA InxGa1-xAs photocathode according to the photoelectric emission mechanism.

Abstract: Antireflective coatings with stable hydrophobicity for solar tube were prepared via sol-gel method and hexamethyldisilazane (HMDS) treatment. The coatings have a high porosity, groove-like surface morphology and a big static water contact angle. As a result, the coatings exhibit high transmittance even in high humidity environments. The transmittance peak can reach up to 99.02% which increased by 7% compared with the substrate and the wavelength band increased by more than 5% is from 438nm to 1000nm. After prolonged exposure to strong ultraviolet (UV) irradiation, the static water contact angle of the HMDS treated antireflective coatings decreased very small from 102^o to 98^o. In addition, the low-temperature tests showed the contact angle did not decline even at-50°C. The results suggest that the coatings prepared in present paper have stable hydrophobic and antireflective performance in the environment of strong UV radiation and low temperature.

Abstract: The thermal effect arisen from absorbing inclusions is the main factor which causes the damage of optical materials or component irradiated by the longer pulse duration laser. The unsteady heat conduction depends markedly on both the thermal properties of inclusions and the parameters of laser. Based on the differential equation of heat conduction, the temperature distribution caused by single absorbing inclusion is solved by use of finite difference method. The effect of the laser intensity and the pulse duration on temperature field is analyzed in detail. The result demonstrates that the smaller size inclusion and the smaller pulse duration cause relative safe thermal effect, consequently, the less probability to be damaged by thermal effect.

Abstract: The thermal effect caused by absorbing inclusions irradiated by multi-pulse laser is different from that of single pulse laser. The temperature field induced by multi-pulse laser depends markedly on both inclusion size and pulse duration, and repetition interval of pulse. Based on the differential equation of heat conduction, the temperature field caused by single absorbing inclusion is solved by use of finite difference method. The effect of inclusion size, pulse duration and repetition interval of pulse on the evolution of temperature field at the center of inclusion and interface between inclusion and dielectric are discussed qualitatively.

Abstract: Alkali niobate lead-free piezoelectric ceramics with nominal compositions [(Na_0.52K_0.48)_{0.94+ x}Li_0.06-x](Nb_0.94Sb_0.06)O₃ ((NK)_xLNS) were prepared by normal sintering. Crystalline phase, piezoelectric properties and sintering behavior of (NK)_xLNS ceramics were investigated with a special emphasis on the influence of alkli metal content. The x-ray diffraction patterns and the corresponding calculation of lattice parameters indicated that a phase transition from tetragonal to orthorhombic symmetry occurs as x=0.01, resulting in enhanced piezoelectric constant and planar electromechanical coupling coefficient of 266 pC/N and 38.5%, respectively. With x=0.01, the ceramics sintered at 1050 C show higher density and better electrical properties. Our results indicate the importance of sintering temperature and elaborate compositional control for enhancing piezoelectric properties in niobate-based ceramics.

Abstract: A Fe/ZSM-5 catalyst was prepared by impregnation method and evaluated in the synthesis of light olefins from CO₂ hydrogenation. It is found that The conversion of CO₂, the yield of light olefins and hydrocarbons content reach 82.42%, 12.65%, 0.4885mol respectively under the conditions as follow, mass concentration of ferric nitrate 9%, silica to alumina ratio 25, calcination temperature of the catalyst 500°C. By the studies of NH₃ temperature programmed desorption, performance changes of the catalysts was analysis. A possible mechanism is proposed on the basis of mineral composition changes of Fe/ZSM-5 catalyst in the synthesis of light olefins through XRD analysis.

Abstract: Cadmium sulfide and cadmium selenide have been the subject of considerable interest because of their potentialapplications in many fields. In this paper, the synthesis of cadmium sulfide and cadmium selenide nanostructures is described. The Morphologies of as prepared cadmium sulfide and cadmium selenide nanostructures are summarized. And the applications and prospects of cadmium sulfide and cadmium selenide in this field also are analyzed.

Abstract: The variation of carbonyl compounds in diesel exhaust at four loads before and after the treatment of Direct Non-thermal Plasma (DNTP) is studied with 2,4-dinitrophenylhydrazine (DNPH) derivatization method and high performance liquid chromatography (HPLC) analysis technique. The results show that the mass concentration of carbonyl compounds decreases firstly and then increases with the growing of diesel load before the treatment of DNTP. After the treatment of DNTP, the mass concentration of carbonyl compounds reduces remarkably. Maximum removal efficiency for total carbonyl compounds can reach 93.8% at 75% load. For acrolein, acetone, butyraldehyde and 2-butanone, removal efficiency can reach 100% at 25% load, 50% load and 100% load. At the same time, total ozone formation potential decrease dramatically.

Abstract: The reactivity photoacoustic technology was used to detect the laser induced photoacoustic spectroscopy characteristics of explosives (PETN and HNS). The results showed that: the reflectivity of pure PETN and HNS under laser irradiation was large and the photoacoustic signal was weak. After doping with carbon nanotubes (CNTs) and carbon black (CB), the reflectivity decreased. The photothermal conversion and the optical absorption coefficient rate increased and the photoacoustic signal enhanced. For the same sample, the intensity of the signal was proportional to the incident laser energy. For the same explosives and under the same doping amount, the photoacoustic signal of the CNTs doped sample is greater than that of the CB doped sample. For the same sample and the same dopant, the greater the amount of doping, the stronger the photoacoustic signal. There was optimum ignition energy. By using TG-DSC technology for thermal analysis of the samples, the results from the thermal analysis could explain the reactivity photoacoustic experiment.

Abstract: According to the principle of heat transfer to set up corresponding model of lumped parameters, and calculate the heat production of proton exchange membrane fuel cell. Under the steady state condition, with the help of numerical simulation and calculation in Sinda/Fluent,heat which from the internal of battery can be diffused through the heat pipe,especially dealing with issues such as local overheating. The result of this research shows that the use of the technique of liquid phase change heat transfer in the close room can have a high heat transfer efficiency, also start quickly and isothermal performance is good, the finally , its control is simple and it is very suitable for heat removal of PEMFC battery pack.