Advanced Materials Research Vols. 152-153

Abstract: By applying nonequilibrium Green’s function formalism combined first-principles density functional theory, we investigate the electronic transport properties of 3,3′,5,5′-Tetra-tert-butyl-azobenzene(meta-TBA) optical molecular switch. This molecular switch comprises a meta-TBA molecule with the trans and cis forms, which can be reversed from one structure to another one upon photoexcitation. The influence of HOMO-LUMO gaps and the spatial distributions of molecular orbitals on the electronic transport through the molecular device are discussed in detail. Theoretical results show that there is a large current ratio in bias window, which suggests that this system can be one of good candidates for optical switches due to this unique advantage, and have real applications in the molecular circuit.

Abstract: Calculation of steel solidification in H2 mould of FTSC with Two-dimensional thermal- mechanical coupled method, results show that steel in mould has a wide two-phase region which grows rapidly during solidification, so columnar crystal and coarse grain were well-developed. Stress calculation results show that internal tensile stress reach to 13-17MPa in two-phase region, and the closer to shell surface, the greater of SEQV. It has the condition for microcracks generation and growth in Mould. Control heat transfer in mould can uniform temperature distribution, thereby reduce stress and enhance the plastic property of shell.

Abstract: ZnO is an important functional semiconductor in application of photoelectric devices. ZnO nano-tubes and the CuO-doped ZnO have been successfully fabricated via hydrothermal method and a solution routine. The samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transformation infrared spectroscopy and room temperature photoluminescence measurement. The results show that the lattice space (d-value) of the CuO-doped ZnO increases while introducing CuO into its structure. Due to the interaction between Cu2+ and the surface atoms of ZnO, a photoluminescence confinement were observed in the CuO-doped ZnO compared with that of nano ZnO.

Abstract: This paper discussed the variation of microstructure at different locations of heat affected zone (HAZ) of a high strength steel welded joint using an optical microscope and an electron backscattered diffraction (EBSD) system. The results revealed that the change of microstructure plays an important part in the toughness properties at different locations of the HAZ. the CGHAZ (coarsen grain HAZ) microstructure contains granular bainite with the large effective grain size and a number of rod-like M/A constituents, which provide the nucleation sites and linear propagation path for micro-crack, therefore, this location becomes a local brittle zone. However, in the FGHAZ (fine grain HAZ) due to the microstructure mainly consisting of fine quasi-polygonal ferrite with high density of high angle grain boundaries, which can act as obstacles to cleavage propagation, the FGHAZ (fine grain HAZ) toughness is more excellent than the CGHAZ toughness.

Abstract: A novel route to prepare hydrophobic mesoporous SiO2 films is reported in this paper. A two step process involving tetraethyl orthosilicate (TEOS) as a precursor and cetyltrimethyl ammonium bromide (CTAB) as a template prepared SiO2 sol catalyzed by hydrochloric acid. The films are prepared by dip-coating process. It has been found that the films have low dielectric constant and good mechanical properties. Preliminary results present a very positive prospective for intermetal dielectric applications.

Abstract: The catalytic reforming of toluene was performed to investigate the possibility for directly converting tar components from hot coke oven gas (COG) with lower steam/carbon (S/C) molar ratio to light fuel gases. The Ni0.25Me0.25/Mg2.5(Al)O (Me=Fe, Cu, Zn, Mn) bimetallic catalysts derived from hydrotalcite showed excellent catalytic activity. The effects of various reaction conditions on the catalytic performance were investigated in detail. Toluene could be completely converted into small gas molecules of CH4, CO and CO2 over the catalyst at S/C=0.7 and 650-750 oC under atmospheric pressure. Lower reaction temperature and higher H2 content in feed gas both could promote the formation of CH4, while higher S/C molar ratio benefited the CO yield.

Abstract: A novel precipitation sequence, super-saturated-solution → stacking faults → Mg3Gd, i.e. S.S.S. → SF → β1, was established for a Mg-3Zn-2Gd (wt%) alloy. Solute pre-precipitation can occur during the solidification of as-cast alloy and subsequent solution-treatment, resulting in the formation of lamella structures with …ABCABC… stacking sequence. The lamella structure will transform to the Mg3Gd phase, even that Mg3Gd is not the most stable phase in this serial alloys.

Abstract: Al doped ZnO thin films（AZO films） was prepared by sol-gel method. The influence of Parameters of different processes on the crystallization properties, micro-morphology and optical properties of this kind of films were studied, using by X-ray diffractometer, filed emission stereoscan, spectral photometer, hall admeasuring apparatus. The results indicated that the crystallization properties, micro-morphology and optical properties of Al doped ZnO films were best on the condition that the sol density was 0.5mol/L, hat treatment temperature is 600 and there is a 8-layer coating.

Abstract: Tubular cathode and plate anode were prepared by gel-casting process and coating process, which used mesocarbon microbead(MCMB) as raw materials, then cathode and anode were assembled to prepare single fuel cell. The generation performance for single tubular direct methanol fuel cell was tested under different electrolyte temperatures, methanol concentrations and oxygen flow rates, and the factors that affected the cell performance were discussed. The results showed that temperature and oxygen flow rate were the important factors of the generation performance in tubular direct methanol fuel cell (TDMFC), but the methanol concentration had a relatively smaller impact on the cell performance. The stability test of the cell after working for 100h shows that the tubular MCMB cathode had a perfect stability.

Abstract: AlGaN/GaN superlattice are the important structure of optoelectronic devices such as light-emitting diodes and laser diodes. The nanostructure of the superlattice can greatly influences the optical electrical properties of final LD and LED . It is impossible to evaluate their thickness by TEM when it’s aluminum component lower than 14%.We investigated the nanostructure of strained p-type Al0.11Ga0.89N/GaN superlattice grown on sapphire by high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).By an average filtering technique, the thickness of the AlGaN layers and GaN layers were determined to be 2.409±0.092 nm and 2.371±0.062 nm from the HAADF-STEM images, respectively.