Advanced Materials Research Vol. 906

Abstract: A composite TiO₂ photoelectrode structure is explored to optimize the dye-sensitized solar cell (DSSC) properties. The composite TiO₂ photoanodes consist of two nanoparticular TiO₂ layers with different size and thickness. The impact of film thickness on the performance of DSSCs was also investigated. In the optimized composite photoelectrode structure with large sized TiO₂ nanoparticle as light scattering layer, the significantly improved performance of DSSC with 25% increase of current density and 13.1% increase of conversion efficiency was experimentally demonstrated.

Abstract: Single phase of Ba₃Y_{1 - x}Eu_xB₃O₉ (0.05 ≤ x ≤ 0.35) samples was prepared by the solid state reaction. The crystal structure, the surface, the particle size and luminescence properties were characterized by X-ray diffractometer, scanning electron microscopy and spectrophotometer. The results showed that the obtained samples with the particle size from 0.3 to 1.5 um were hexagonal structure. Monitored by 592 nm emission, the excitation spectra of Ba₃Y_{1 - x}Eu_xB₃O₉ were dominated by the charge transfer band of O^2-→Eu³⁺ peaking at about 259 nm until x = 0.15; the transition from ⁷F₀ to ⁵L₆ level of Eu³⁺ at about 395 nm was maximum after x > 0.15. The strongest emission peak due to the ⁵D₀→⁷F₁ transition of Eu³⁺ was all located at about 592 nm in the emission spectra of Ba₃Y_{1 - x}Eu_xB₃O₉, and the maximum emission was obtained at x = 0.15 and 0.3 under 254 and 395 nm excitation, respectively. The excitation process under the two excitation energies was analyzed. It indicated that only the centrosymmetric lattices could be excited under 254 nm excitation; both the centrosymmetric and noncentrosymmetric positions could be excited by 395 nm, accordingly, the ratio of the red emission (⁵D₀→⁷F₂) to the orange one (⁵D₀→⁷F₁) increased, leading to a better chromaticity of the phosphors.

Abstract: High purity ZrSiO₄ powder were synthesized using Si (C₂H₅O)₄ and ZrOCl₂·8H₂O as raw materials by the sol-gel method, LiCl was added as mineralizer to promote crystallization of zircon. The influences of molar ratio of Zr:Si, calcined time and calcined temperature on the synthesis of ZrSiO₄ powder were investigated. XRD, SEM and TEM were used to characterize the powders. It was found that when the molar ratio of Zr:Si was 1:1.2, the calcined temperature was 1600°C and the calcined time was 4h, the high purity ZrSiO₄ ultrafine powder was obtained. The ZrSiO₄ formation began at 1300°C and when the gel was calcined at 1600°Cfor 4 h, the formation rate of ZrSiO₄ was up to 95%. SEM and TEM studies reveal a homogeneous product with particle sizes on the order of 0.1-1μm. The IR emissivity of ultrafine ZrSiO₄ is 0.892 at the whole wavelength range, and that is up to 0.951 at the wavelength range of 8-14 μm.

Abstract: A newly criterion for the validity limits of the dipole approximation for a dielectric mixture was presented, based on the comparison between the dipole approximation and the numerical solutions by the finite-element method (FEM). In terms of this criterion and the dipole-enhanced model, a simple theoretical formula for the validity limits was derived. This formula includes three variables: the dielectric mismatch, the volume fraction of particles and the precision. Its calculated results have a good agreement with the limits determined by the empirical method in the range of our interest, which indicates the theoretical formula is creditable. Using this formula, we can approximate the precision of the dipole approximation for an arbitrary dielectric mixture. And we found that the dipole approximation is acceptable with the precision equal to 30% when the dielectric mismatch is less than 2.3 (ε_i / ε_e 2.3) for the almost touching spheres.

Abstract: Heavy ion irradiation on phase change memory cell was conducted using Monte Carlo simulations. Absorbed dose in the whole memory cell, as well as in its active layer was assessed. Phase change memory cell was modeled as a sandwiched structure of two TiW electrodes and ZnS-SiO₂ films as insulators surrounding the active region. The most commonly used phase change material, Ge₂Sb₂Te₅, was used as active layer of the cell. Ionization effects of heavy ion irradiation were investigated for various thicknesses of phase change layer and different ion energies.

Abstract: Radiation effects of ion beams in perovskite oxide memristors are analyzedand linked to absorbed dose values, calculated from simulations of ion transport. Several ion species were used in simulations, chosen to represent certain commonly encountered radiation environments. Results indicate that considerable formation of oxygen ion - oxygen vacancy pairs, as well as advent of displaced rare earth and alkaline atoms, is to be expected. Oxygen vacancies can lead to a decrease or increase of active layer resistance, depending on applied voltage polarity. The loss of vacancies from the device is bound to impair the performance of the memristor. Calculated absorbed dose values in the memristor for various incident ion beams are typically on the order of several kGy.

Abstract: The synthesis of a novel bispyrazole derivative 2,6-bis (5-(p-methylphenyl)-1-H-pyrazol-3-yl) pridine (BMPP) was described and its structure was conforrmed by ¹H NMR, FTIR, MS techniques and elemental analysis. The interactions of Zn²⁺ ion with BMPP were assessed by fluorescence quenching techniques. The results revealed that the quenching effect is resulting from the formation of Zn²⁺-BMPP nonfluorescent complex. The SternVolmer curves suggested that the quenching effect was the static quenching. The main action forces of these reactions was spontaneous, mainly hydrogen bonds and ΔS-driven obtained by using thermodynamic equations.

Abstract: The rapid development of biodiesel production yields large amount of glycerol as a by-product. It is a resource-utilization efficient and biological technical process to employ hydrogenolysis of glycerol aqueous solution for ethylene glycol generation. In this work, Raney Ni catalyst was prepared through conventional means and tested for hydrogenolysis of glycerol to produce ethylene glycol. The experiments were performed by varying the reaction time and rotate speed at a hydrogen pressure of 6.0-10.0MPa over a temperature range of 453-493K using a batch reactor. The effect of reaction conditions on the conversion of glycerol and the product distribution were also investigated and discussed. The results indicated that with the increase of reaction time the conversion of glycerol and the selectivity of 1,2-PDO tended to rise but the concentration of ethylene glycol decreased after reaching a peak point. The conversion of glycerol reached as much as 100% and the selectivity of ethylene glycol reached a maximum of 40%. Based on the experimental data, the reaction kinetics was studied and the parameters involved a two-site Langmuir-Hinshelwood model were acquired by the parameter estimation method. In the end, residual error distribution and statistic test showed that the obtained kinetic model was suitable and acceptable.

Abstract: Layered double hydroxide (MgAl LDH) and its composites containing different quantities of sodium alginate were synthesized. The adsorption characteristics of these materials were evaluated for the adsorption of Acid Blue 120 (AB 120). The adsorption capacity of the composites for the dye was higher than that of pristine LDH. The adsorption capacity varied with alginate concentration and was the highest when the alginate concentration was 5.9 wt%. The maximum adsorption capacity of the composite enhanced by 40%, compared to pristine MgAl LDH. The rate of adsorption of the dye on the composites was also higher than that of pristine MgAl LDH up to an alginate concentration of 11%. The results reveal that LDH composites are more efficient adsorbents compared to pure LDH. Sodium alginate, being a biopolymer can also improve the biocompatibility of the LDH for biological applications.

Abstract: Global warming has become more and more serious, which is caused by greenhouse gases. Cutting down the emission of CO₂ has already become one of the major research target in the world. This study is numerically investigating Thermal Swing Sorption Enhanced Reaction Process on water gas shift (WGS) reaction by Na₂O-promoted alumina. According to Le Chateliers law, the forward reaction rates and conversion can be increased by removing some products selected. Therefore, this concept can be used to generate product of high-purity hydrogen. The purified H₂ can be sent to gas turbine for generating electrical power or can be used for other energy source. Carbon dioxide can also be recovered and sequestrated to reduce greenhouse gas effects. The method of lines is utilized in simulation, combined with upwind differences, cubic spline approximation and LSODE of ODEPACK software to solve the problem. The concentration, temperature, and adsorption quantity in the bed are integrated with respect to time by LSODE of ODEPACK software. The simulation is stopped when the system reaches a cyclic steady state. In this study, we first simulate breakthrough curve of Na₂O-promoted alumina cited from literatures to prove the accuracy of simulation program. The optimal operating conditions of the WGS TSA (temperature swing adsorption) single-bed six-process is obtained by varying operating variables, such as feed time and rinse time. Furthermore, WGS TSA single-bed six-process could achieve 99.89% purity of H₂ (dry-basis) as the top product and 90.95% purity and 98.22% recovery of CO₂ (dry-basis) as the bottom product.