Advanced Materials Research Vols. 591-593

Abstract: As a kind of wide band-gap material focused on in recent years, SnO₂ thin Film with μm level has been widely applied in many fields such as solar cells, electric heating devices, transparent electrodes, and gas sensors, ect. This paper develops a real-time system to measure thermal expansion coefficients of SnO₂ thin film, which can obtain directly surface morphology information of the samples. Micro-imaging and digital image correlation method is adopted to investigate the correlation by comparing the object surface image before deformation with that after deformation. Because of the lower demand for measurement environment and no damage to object, it’s easy to acquire on-line images, calculate synchronously and display real-time results. In the paper, thermal expansion coefficients of SnO₂ thin film are determined in situ with change of the temperature. Both of ceramic and SnO₂ thin film have shown anisotropy thermal expansion, thermal and residual stress appears between the ceramic substrate and SnO₂ thin film as a result of thermal expansion coefficients mismatch. According to experimental results, the maximum stress values can be calculated between film and substrate and inside the substrate.

Abstract: In this paper, two different layers of Huadian oil shale were selected. In the basic of oil shale density, moisture and oil yeild, and electrical physical properties of oil shale are researched by theoretical, experimental and comparative analysis. The experiments showed that under room temperature, the oil shale does not have a conductivity, but when the temperature increases, the ions are activated, so the ions has a higher energy to break through to the energy dam limits. Therefore, with the temperature increases, the conductivity of oil shale is getting better. And it has another three factors impact the conductivity: the higher temperature, the greater moisture content, and the less oil content.

Abstract: The ground state geometrical of cyclic sulfur molecules S8 has been studied with RHF/6-311G* of ab initio methods. Gibbs free energy of CO, SO2, S8 and CO2 from 300 to 1673K has been calculated using ab initio method. Besides, the reaction free enthalpies were calculated. The results show that resultants of reaction of CO and SO2 are S8 and CO2 below 1451K and the reaction is spontaneous.Fe2O3 in glass can is reduced into FeO whose redox number is negative. The Gibbs free energy of FeO is smaller than that of FeS while chemical stability of FeO is higher than that of FeS. Structures of cycle sulfur are versatile. Bond energy of S8, S12 and S18 is broken, which need high energy. When small sulfur ring molecules be formed, the chemical and heat stability of S8 are improved.

Abstract: The responses of saturated soft soil foundation under dynamic loading are analyzed using numerical method. The distributions of pore pressure in space are given, and the variations of pore pressure with time are also discussed. Besides, the distributions of vertical stresses and vertical displacement are also given. Studies show that during the period of dynamic loading, the pore pressure and stress in soil layer grows very fast, and also decreases rapidly in the unloading phase. With the increase of dynamic compaction time, the locations of the maximum values gradually move down. Moreover, the pore pressure and stress gradually decreases with the increase of the distance away from hammer point. On the other hand, the tamping pit in ground surface under dynamic loading has a larger settlement, and furthermore decreases with the increase of depth.

Abstract: The preparation of scaffolds consisted of a polymer composites with inorganic materials has received extensive attention in the field of tissue engineering recently.Electrospinning is a good method to obtain nano-scaled fibers from polymer solutions. In this paper ,we successfully prepared nanofibers of poly(lactide-co-glycolde) (PLGA)/hydroxyapatite(HA)by electrospinning.Their structure morphology and degradation behaviors were studied.The in vitro degradation of PLGA/ HA composite membranes was examined for up to 16 weeks in phosphate-buffered saline (PBS, pH 7.4) at 37°C. The results indicated that the surface of hybrid fibers was much coarser because of the introduction of HA nano-particles. The alkaline HA nano-particles inhibited the self-catalysis of PLGA during the degradation and slowed down the degradation rates of hybrid fibers.The introduction of hydroxyapatite component changed the hydrophilic/hydrophobic balance and, thus, influenced degradation behavior and mechanical properties of the composite membranes during degradation. The preliminary results show that comprehensive properties are well better on the hybrid scaffolds than pure scaffolds and PLGA/ HA bionanocomposites have the potential in tissue regeneration applications.

Abstract: The purpose of this work is to study the effect of testing method on the tensile properties index of p-Phenylene terephthalamid (PPTA) fibers. Three different brand fibers were employed, namely Kevlar 129, Twaron and Heracon. The results indicate that tensile strength index is strongly affected by gauge and twist coefficient, while the influence of loading rate is minor. The ballistic performance is also evaluated according to a proposed ballistic performance index U*. The results indicated that ballistic performance is strongly affected by twist coefficient

Abstract: In this paper, the microstructure and properties of AZ91D-xCa-ySr were studied by adding alloying elements. The mechanical properties were investigated by WDT-10 micro-electric universal testing machine and WD-T low cycle fatigue testing machine. The OLYMPUS-GX71 Optical electronic microscope, XRD and SEM were employed to investigate the microstructure of AZ91D. The results showed that the grains were refined by adding Ca,Sr,Gd and Y. Low cycle fatigue (LCF) behavior of AZ91D-0.4Ca-0.3Sr was improved obviously by adding 3.0%Gd and 3.0%Y into material, the tensile strengthen was up to 299Mpa, the elongation was 0.78%.

Abstract: This paper demonstrates the comparisons of molding with micro molds made of different elastomeric polymers. Micro molds made of pure polydimethylsiloxane (PDMS), 0.3% carbon nanotube (CNT) enforced polydimethylsiloxane (PDMS), 2% carbon nanotube (CNT) enforced polydimethylsiloxane (PDMS) and commercial available high temperature silicon rubber sheet (Avon Group) were studied. Micro moldings using different molding pressures were performed. By comparing the dimensions of micro features produced with different molding pressures, molding accuracies of using micro molds made of different elastomeric polymers are obtained. Results of this study provide valuable information for the development of elastomer micro mold insert for micro injection molding.

Abstract: The Ni-Nd₂O₃ nanocomposite coatings were prepared by electrodeposition under dual-frequency ultrasound(DU). The Nd₂O₃ content and surface morphology of Ni-Nd₂O₃ nanocomposite coatings were analyzed by scanning electron microscopy (SEM). The results showed that the Nd₂O₃ content of the nanocomposite coating prepared by electrodeposition using DU was high at 3.48% and the surface morphologies of DU nanocomposite coating showed better smooth surface, finer grain and more compact microstructure. A kind of method to prepare high quality Ni-Nd₂O₃ nanocomposite coating was obtained, which was: 40 g/L Nd₂O₃ nanoparticles, 45°C the temperature of electrolyte, 4A/dm² cathode current density, 240W the power of bath-type ultrasound(BU), 100kHz the frequency of BU, 30W the power of probe-type ultrasound(PU), 20kHz the frequency of PU, and 1000r/min the stirring speed.

Abstract: Tear propagation is the typical fracture mode of fabric laminates, which is affected by stress and damage shape (size). In this paper, envelope material which is mainly composed of fabric laminates used in stratospheric airship is the objective of the study. The tear propagation and tear strength of Cross-shaped specimens with initial damage which were in different situations (size, angle and shape) were studied through biaxial tensile test which was conducted in a tailor-made testing machine, and the strength is noted simultaneously to gain the mechanical properties of the specimens. A finite element model was also built in ABAQUS, simulating the biaxial tensile condition, and the simulation results were compared with the test results and observed to have good agreement between them.