Advanced Materials Research Vols. 774-776

Abstract: Tungsten oxide is a kind of multifunctional materials with excellent properties for gas sensing, electrochromic and photocatalytic applications. In this study, Tungsten oxide nanoplate thin film was prepared by hydrothermal methods. The as-prepared thin film is composed of tungsten trioxide hydrate nanoplates, which are randomly orientate on the surface. The as-grown nanoplate thin film shows good sensitivity to H₂ gas. Dehydration and phase transition to γ-phase tungsten trioxide were found after annealing, and the sensitivity as well as the response time to H₂ were improved. We found that the nanoplate in the annealing sample bursts, which raises the surface-to-volume ratio for better hydrogen diffusion and reaction. The sensing mechanism was discussed. The findings provide a way to control the structure and surface morphology for improving the H₂ sensing properties of tungsten oxide.

Abstract: Influence of polarization effect on current across GaN/AlNresonant tunneling diode (RTD) is simulated by self-consistent calculations ofSchrödinger and Poisson equations. When taking into account polarization chargesat the heterointerface, the band diagram and electronic properties of RTD areobviously changed. As a result, the current-voltage characteristics showsasymmetrical phenomenon. As the polarization effect is enhanced, the resonancepeak is shifted accordingly and even disappears.

Abstract: Kojic acid is a metabolite from some common microbe, it is a natural preservative. The kojic acid has broad prospects in the storage and preservation of fruits and vegetables. In this study, using different concentrations of kojic acid sprayed the surface of rape and stored at room temperature, observed phenotypic changes. Then the CAT and POD activity, chlorophyll content and weight loss rate were determined in rape treated by kojic acid. From the overall trend, compared with the water, spraying 0.5% and 1% kojic acid to a certain extent reduce chlorophyll loss of rape, water evaporation and dry matter decrease was slowing down, and maintains the appropriate activity of CAT and POD. It means that the kojic acid has obviously effect on rape preservation.

Abstract: The corrosion behavior and corrosion morphology of two typical TC4 titanium alloy with equiaxed structure and widmanstatten structure in hydrochloric acid solution were studied using scanning Kelvin probe techniques and observed by scanning electron microscope, respectively. The results show that along with the ongoing of corrosion, surface potential of equiaxed structure alloy is moving to positive direction and that of widmanstatten structure alloy is moving to negative direction after positive direction movement. The surface potential of two kinds structure alloy all present cathode and anode region in the corrosion process, which shows the characteristic of selective corrosion. Surface potential difference of widmanstatten structure alloy is greater than that of equiaxed structure alloy and its corrosion resistance is inferior to that of equiaxed structure alloy. Corrosion preferentially occurs in alpha phase of the two kinds structure alloy through corrosion morphology observation analysis.

Abstract: Phase field method (PFM) offers the prospect of carrying out realistic numerical calculation on dendrite growth in metallic systems. The dendritic growth process of multiple dendrites and direcitonal solidification during isothermal solidifications in a Fe-0.5mole%C binary alloy were simulated using phase field model. Competitive growth of multiple equiaxed dendrites were simulated, and the effect of anisotropy on the solute segregation and microstructural dedritic growth pattern in directional solidification process was studied in the paper. The simulation results showed the impingement of arbitrarily oriented grains, and the grains began to impinge and coalesce the adjacent grains with time going on, which made the dendrite growth inhibited obviously. In the directional solidification, the maximum concentration gradient showed in the dendrite tip, and highest solute concentration existed at the bottom of the dendrites. With the increasing of the anisotropy, dendrite tip radius became smaller, and the crystal structure is more uniform and dense.

Abstract: Through analysis and research on the surface topography of reinforced copper matrix composite materials, taking advantage of fractal statistical method to discuss distribution law about characteristics parameter which symbolizes the asperity, combining Monte-Carlo method with fractal theory to set up mathematics model of characteristics parameter which symbolizes size of asperity , talking about the construction of iterated function system in fractal interpolated theory, a easy realizable friction materials surface topography simulation algorithm was put forward.

Abstract: This paper focuses on an applied research of automatic detection method for the viscose maturity degree in the chemical fiber production and introduces the hardware structure and software process of this automatic detection device for the maturity degree of viscose. Besides, through rigorous testing, contrasting, and analysis between this device and traditional test methods , the paper also puts forward a better way to improve the precision and result consistency in the process of the viscose maturity degree detection.

Abstract: In this paper, green ceramic tapes are joined together by adhesive based lamination technique. The effects of adhesive concentration, pressure on the lamination and sintering temperature on the laminate are mainly discussed. The parameters are also optimized. It was shown that the effect of adhesive concentration and pressure on the lamination is obvious and the effect of sintering temperature is not big. 10 layers of cordierite tapes can be laminated under 2MPa with a dwell time of 3min with PVA by adhesive based lamination. The adhesive based lamination can be used to be an alternative of thermo-compressive lamination.

Abstract: The class of R₂PdSi₃ single crystals (R= rare earth element) with hexagonal AlB₂-type crystallographic structure reveals the systematic dependence of anisotropic magnetic properties governed by the interplay of crystal-electric field effects and magnetic two-ion interactions. Here we compare the floating zone (FZ) crystal growth with radiation heating of compounds Pr₂PdSi₃ and Nd₂PdSi₃. The congruent melting behavior enabled moderate growth velocities of 3 to 5 mmh^-1. The preferred growth directions are close to the basal plane of the hexagonal unit cell. The composition of the crystals, is slightly Pd-depleted with respect to the nominal composition 16.7 at.% Pd. The Pr₂PdSi₃ compound exhibit antiferromagnetic order below the Néel temperatures T_N: 2.17 K and Nd₂PdSi₃ compound order ferromagnetically below the Curie temperature T_C = 15.1 K.

Abstract: This paper focuses on theoretical research of Co-doped Fe-based oxygen carrier for CO oxidation in chemical-looping combustion (CLC) system. Density functional theory (DFT) calculations were carried out to study of interaction between CO molecules and CoO/Fe₂O₃ cluster, it is found that dissociation of O atom through breaking of Fe-O bonds in the Fe₂O₃ system is the key step for CO oxidation reaction, and Low-fold O atoms in Fe₂O₃ system could more readily dissociate from external surface. Moreover, the presence of CoO in Fe₂O₃ could decrease activation energy and reaction energy of CO/Co-Fe₂O₃ system, hence the reaction between CO and Fe₂O₃ is promoted.