Advanced Materials Research Vols. 774-776

Abstract: In this paper, a micromechanical model based on Generalized Method of Cells(GMC) for predicting stress-strain behaviors of polymer-matrix composites is presented. Improved Bodner-Partom viscoplastic model is incorporated into GMC to describe nonlinear mechanical behavior of composites. On this basis, strain rate and fiber volume fraction(FVF) influence on nonlinear behaviors of composites are discussed. The results show that strain rate influences on stress-strain behaviors of composites in inelastic region can be clearly discerned. Moreover, FVF tends to clearly increase stiffness behaviors of polymer-composites.

Abstract: Microneedle, as a novel way for transdermal drug delivery, due to its painless and minimally invasive, has recently attracted much attention. The present study investigated skin deformation and failure due to insertion by a single microneedle with nonlinear finite element method. The finite element model considered multilayered, non-linear and hyperelastic properties of the skin, and tissue failure was phenomenologically described by an effective stress failure criterion. The deformation and failure of skin and the force displacement behaviour of the microneedle are discussed. The numerical results show a good agreement with the reported experimental data. The performed study provided novel insights into skin failure due to insertion of microneedle, and provided useful information with which to optimise the microneedle design.

Abstract: To meet stringent exhaust emission norms worldwide, various exhaust pre-treatment and post-treatment techniques have been employed in modern engines. Using antioxidant additives in biodiesel fuels is a promising and effective NO_x reduction technology. Non-edible jatropha oil based methyl ester was produced and blended with conventional diesel. Five fuel samples (Diesel, JB5, JB5DPPD0.15%, JB15 and JB15DPPD0.15%) were tested for their use as substitute fuel for a radiator-cooled four cylinder diesel engine. Experiment results show that DPPD antioxidant additive could be reduced NO_x emission significantly with slight penalty on engine performance as well as CO and HC emission. However, when compared to diesel combustion the emissions of HC and CO were found nearly same or below. By addition of 0.15% (m) DPPD additive in JB5 and JB15 reduction of NO_x emission were 12.68% and 13.36 % compared to biodiesel blends without additive at full throttle position. As conclusion, JB5 and JB15 with addition of 0.15% (m) can be used in four cylinder diesel engine to reduce NO_x and consequently overcome the barrier to market expansion of biodiesel fuels.

Abstract: The microstructure and mechanical properties of the as-cast Mg-Zn-Ca-Zr alloys were investigated in this study. The results showed that the alloy was mainly composed of α-Mg solid solution and the secondary phases of Ca₂Mg₆Zn₃. The grain size of alloys decreased from 82 μm to 38 μm with Zr content from 0.1% to 0.5%. The addition of Zr greatly improved the ultimate tensile strength (σb) and elongation (ε), while slightly improved the tensile yield strength (σ0.2). The σb, ε and σ0.2 of the Mg-4Zn-0.5Ca-0.5Zr were 196MPa, 85MPa and 16.1% compared with the other two alloys. The reason was that grain size refinement strengthening enhanced the mechanical properties.

Abstract: Carboxymethyl cellulose (CMC)-polyvinyl alcohol (PVA) and chitosan (CS)-polyvinyl alcohol were cross-linked by Fe³⁺ and glutaraldehyde respectively to prepare cation exchange layer and anion exchange layer, and polyvinyl alcohol-sodium alginate (SA)-metal octocarboxyphthalocyanine (MePc (COOH)₈, a kind of water splitting catalyst, here, Me stands for Fe³⁺ or Co²⁺) nanofibers were prepared by electrospinning technique and introduced into the interlayer to obtain the CMC-PVA/PVA-SA-MePc (COOH)₈/CS-PVA bipolar membrane (BPM). The experimental results showed that compared with the BPM without the PVA-SA-MePc (COOH)₈ interlayer, the water splitting efficiency at the interlayer of the CMC-PVA/PVA-SA-MePc (COOH)₈/ CS-PVA BPM was obviously increased, and its membrane impedance decreased. When the concentration of FePc (COOH)₈ in the PVA-SA-FePc (COOH)₈ nanofibers was 3.0%, the trans-membrane voltage drop (IR drop) of the CMC-PVA/PVA-SA-FePc (COOH)8/CS-PVA BPM was as low as 0.6V at a high current density of 90 mA/cm².

Abstract: In this paper, high resolution transmission electron microscopy (HRTEM) has been used to observe a Zr_41.25Ti_13.75Ni₁₀Cu_12.5Be_22.5 (at. %) bulk metallic glass (BMG) prepared from different methods, i.e. ion milling and electropolishing. The ion thinning brings out the white bulb pattern on the specimen surface and induces localized temperature increasing. The electropolishing does not influence microstructure of the amorphous phase. A new preparation technique of grinding method is introduced. For BMG, the electropolishing and grinding are the better method for TEM specimen preparation as compared with the ion thinning.

Abstract: The doping acid will obviously effect on the properties of polyaniline. In order to investigate the industrial acids influence the electrical conductivity stability of polyaniline, the hydrochloric acid (HCl), sulfuric acid (SA) and methanesulfonic acid (MSA) in industrial degree were chosen as doping acids to synthesize polyaniline. The stability of electrical conductivity was measured by in situ temperature. The mechanism of temperature dependence of electrical conductivity was discussed. The results revealed that the stability of polyaniline doped by hydrochloric acid (HCl) was better than that of polyaniline doped by other acids. The variable-range hopping (VRH) model could explain the temperature dependence of electrical conductivity of polyaniline.

Abstract: Rheological properties of rice protein-dextran composite system were studied. The formation of gel network-like structure appeared to have occurred through the interaction of rice protein and dextran at certain biopolymer concentration. An increase in the protein and/or polysaccharide concentration of the mixtures would contribute to the mechanical properties of mixed gels. The differences in fracture forces among samples as noticed in experiments also suggested the difference in microstructures.

Abstract: V³⁺ ions doped YAG crystals were grown using the Czochralski method in a highly pure argon atmosphere. The transmission spectrum of trivalent vanadium in YAG crystal has been measured at room temperature. Eight bands were observed in which two bands centered at 690nm (14493cm^-1) and 1490nm (6711cm^-1) are reported for the first time. By using the crystal-field theory and introducing the average covalent factor model, we also presented the theoretical calculations of the energy level splitting of tetrahedrally coordinated V³⁺ impurity systems in YAG crystal. These calculation results are in good agreement with the optical experiment data.

Abstract: In this paper we developed a recombination model for the steady state photoconductivity (SSP) with the assumption that the correlated dangling bond states (DB) act as the essential recombination centres and the electron recombination proceeds by tunneling from the conduction band tail states (TS) for n-type a-Si:H. The modeled temperature dependence of the SSP presents the main measured features, particularly the small activation energy and the thermal quenching.