Advanced Materials Research Vols. 343-344

Abstract: A Eu³⁺ activated strontium silicate phosphor was synthesized by solid-state reaction and Li⁺ ion was added to balance the charge valence. X-ray powder diffraction analysis confirmed the formation of pure Sr₂SiO₄ phase without second phase or phases of starting materials irrespective of the adding amount of Li⁺. Scanning electron microscopy showed large particle size and necking shape were obtained as the concentrations of Li⁺ ions increase. In the PL studies, the excitation spectrum of Sr₂SiO₄:Eu³⁺,Li⁺ phosphors exhibited a broad band in the UV region centered at about 270 nm attributed to charge transfer state (CTS) band. As the Li⁺ ion concentration increased, the photoluminescence intensity of the red emission at 617 nm of Eu³⁺ ions was enhanced. The results showed that Li⁺ ion is a effective charge compensators used in Sr₂SiO₄:Eu³⁺ phosphor.

Abstract: Based on the partial differential equations on the carbonation of porous materials, this paper develops the natural and super-critical carbonation model by the multi-physics field coupling software to simulate and predict the relation between carbonation degree and the period of carbonation. It is shown that the carbonation degree after 1 day under super-critical condition is equivalent to that after 1 year under natural condition. The bidirectional carbonation makes the concrete porous brick carbonated faster than the concrete block, thus it is suitable for commercial production.

Abstract: In this paper, the indium tin oxide (ITO) thin films were prepared by a sol-gel spin coating method and then annealed under different temperatures (400, 500 and 550°C) in a mixture atmosphere of 3.75% H₂ with 96.25% N₂ gases. The microstructure, optical and electrical properties of the prepared films were investigated and discussed. The XRD patterns of the ITO thin films indicated the main peak of the (222) plane and showed a high degree of crystallinity with an increase of the annealing temperature. In addition, due to the pores existing in the prepared films, the optical and electrical properties of the prepared films are degraded through the sol-gel process. Thus, the best transmittance of 70.0 %in the visible wavelength region and the lowest resistivity of about 1.1×10^-2 Ω-cm were obtained when the prepared film was annealed at 550°C.

Abstract: A series of single-shot detonation experiments was performed to understand the matching characteristics of wave and flame in DDT for H₂/air mixures in a 60mm square tube that was 2m in length. The ion-probes and pressure transducers were respectively utilized to get the signal of flame and wave, and high-speed digital imaging was used to track flame propagation of DDT area. The matching rule of shock-flame was achieved by analyzing the intensity、velocity and position characteristics of wave and flame in different time along the tube. The results indicate that intensity of wave and flame is positive feedback characteristic and the velocity of wave and flame is alternant change process. The speed amplitude of flame is rapid than that of wave in deflagration phase. This result in the overdrivern detonation wave form and flame is temporarily in front of flame when flame catch up wave. Shock is in front of flame in phase which the overdrivern detonation evolve into steady detonation wave.

Abstract: The progress in the use of templating method for the controlled synthesis of nano, meso and macro porous materials opens many new application areas, one of which is the water treatment membrane. This paper presents a critical review on the fabrication of water treatment membrane using the templating method. Three templating methods are investigated including the block copolymer templating method, the polystyrene beads templating method, and the particles templating method. The future research directions are also discussed.

Abstract: The objective of the present study is to investigate the effect of pyrolysis time and temperature on the mechanical properties of recycled carbon fiber, based on tensile strength measurements, determining the optimum decomposition conditions for carbon fiber-reinforced polymers (CFRPs) by superheated steam. In this research, CFRPs were efficiently depolymerized and reinforced fibers were separated from resin by superheated steam. Tensile strength of fibrous recyclates was measured and compared to that of virgin fiber. Although tensile strength of recycled fibers were litter lower than that of virgin fiber, under some conditions tensile strength of recycled fibers were close to that of virgin fiber. With pyrolysis, some char residue from the polymer remains on the fibers and degrees of char on the recycled fibers were closely examined by scanning electron microscopy.

Abstract: The time delay between the changed quantity of the injected fuel and the detection of the resulting change of the air-fuel ratio determines the dynamic nature of the closed-loop control for air-fuel ratio, and the response delay of oxygen sensor itself is a main effect factor. The response characteristics of switching zirconia oxygen sensor will change and even deteriorate with the increasing service time of oxygen sensor. In this paper, the response characteristics of switching zirconia oxygen sensor and the impact of response slowing on air-fuel ratio and emissions are studied through engine bench test, the impact of response delay of switching zirconia oxygen sensor on air-fuel ratio control is analysed, and a new controller of air-fuel ratio based on discrete PI controller is proposed.

Abstract: The complex chemical reactions in the Si-Cl-H system with relation to modified Siemens process have been studied in this paper based on the thermodynamic data of related substance. The influence of the temperature, pressure and initial feed ratio (n_Si / n_SiHCl3) on the silicon yield have been studied. Furthermore, the diagram of Kinetic constant k as a function of temperature for the rate controlled reaction has also been fitted in the SiHCl3 hydrogen system. Finally 1425K, 1.5atm and the initial feed ratio of 15 is the best conditions. Under these conditions, the silicon yield is 34.815%.

Abstract: The doping effects of Cu on the microstructure and non-ohmic electrical properties of ZnO varistors were studied. Addition of Cu₂O can enhance the ZnO grain growth during sintering. The SEM and EDS results revealed that the added Cu mainly distributed in the grain boundary and spinel phases of ZnO varistors. The Cu₂O addition increased the both of grain and grain boundary resistances. However it decreased the non-ohmic electrical characteristics of ZnO varistors, which is a good agreement with similar findings on Ag₂O additions, but contrasts to the reports of good non-ohmic electrical property which found on binary Cu doped ZnO varistors.

Abstract: A computational study of the bandgap structure in one-dimensional photonic crystals (PhCs) built with an elementary cell consisting of two sub-layers or four sub-layers is presented. The computational approach uses a finite element method to solve the differential systems with the continuous jump conditions. It is well known that the band structure and its features are strongly influenced by the number of periods, the lattice constant and the material dispersion. By choosing the geometrical parameters of the elementary cell optimally and controlling the band structure, we study the relationship between the gap and the number of periods, the lattice constant and the material dispersion. Then the optimal design of one-dimensional photonic crystals can be obtained by the numerical simulation. The numerical results show our finite element algorithm is efficient.