Applied Mechanics and Materials Vols. 110-116

Abstract: This work describes the mixed Cu-La-Ce nanocomplexes materials were synthesized by coprecipitation approach with aqueous solutions of copper nitrate, lanthanum nitrate and cerium nitrate. The nanocomplexes materials were characterized by TEM, with a particle size around nanoscale particle sizes (~50 nm) with high dispersion phenomena. Further, cell cytotoxicity and the percentage cell survival was determined by using 3-(4,5-dimethylthiazol-2-yl)-5 (3-carboxymethoxyphenol)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay on human fetal lung tissue cell (MRC-5). The experimental results show that the Cu-La-Ce nanocomplexes materials only minor cause cytotoxicity effect in cultured human cells.

Abstract: Chemical bonding effects have been discussed for anhydrous niobates and tantalates using binding energy differences Δ_Nb = (BE O 1s – BE Nb 3d_5/2) and Δ_Ta = (BE O 1s – BE Ta 4f_7/2) as key parameters to relate structural and electronic properties of these dielectric oxides. Such known photocatalytic materials as K₄Nb₆O₁₇, Sr₂Nb₂O₇, Ta₂O₅, LiTaO₃, NaTaO₃, NaTa₂O₆ and Sr₂Ta₂O₇ are considered in particular.

Abstract: For energy harvesting, such as in dye-sensitized solar cells, thick films of nanostructured mesoporous titania are inevitably required. Although various mesoporous thin films, i.e., film thickness below 300 nm, such as those of TiO₂ and SiO₂, have been widely investigated via a supramolecular templating approach in the past decade, little progress has been made with thick films, i.e., film thickness of at least several micrometers. In order to develop the desperately wanted thick films of mesoporous nanostructure for titania, we have successfully modified the supramolecular templating approach, where the highly crystallized mesoporous titania thick films of varying thicknesses and different morphologies are realized, resulting in the formation of highly ordered body-centered orthorhombic and disordered wormlike mesostructures. The performance of these mesoporous films in dye-sensitized solar cells has been investigated, achieving a maximum efficiency of ~7% at the film thickness of ~6 μm. The highly ordered mesoporous titania film outperforms the disordered counterpart of the same thickness in both short circuit current and efficiency. The improved cell performance of the ordered mesoporous film is shown to arise from the enhanced electron transport in the regularly packed titania network due to the enhanced crystalline grain connectivity.

Abstract: ZnO nanostructures with different morphology have been successfully fabricated by a simple relative low temperature approach at 90 °C for 5 h without surfactant assistance. These structures can be easily tailed using varied concentrations of sodium hydroxide (NaOH) and different amounts of the hydrazine hydrate (N₂H₄·H₂O). X-ray diffraction (XRD) result proves the formation of ZnO with wurtzite structure. Microstructure as revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicates that the rod-like and chrysanthemum-like ZnO nanostructures contain many radial nanorods, which grow along the [0001] direction. Furthermore, the as-prepared ZnO nanomaterials exhibit high activity on the photo-catalytic degradation of typical persistent organic pollutants (POPs), indicating that they are promising as semiconductor photo-catalysts.

Abstract: The transport properties of the inhomogeneous system (1/4) Ag₂O-La_0.833Na_0.167MnO₃ (LNMO/Ag) have been systematically studied. X-ray diffraction patterns show that the LNMO/Ag sample is the two-phase composite and consists of a magnetic La_0.833Na_0.167MnO₃ (LNMO) perovskite phase and a nonmagnetic Ag metal phase. The resistivity of the sample decreases dramatically with Ag added into the pure perovskite LNMO manganites. For the LNMO/Ag sample, the Curie temperature T_C is 331 ± 2 K and slightly higher than that of the LNMO sample (323 ± 2 K). Due to the dope of Ag metal, the room temperature magnetoresistance effect is enhanced significantly (from 7% for the pure LNMO manganites to 23% for the LNMO/Ag sample under a relative lower field of 0.5 T and from 37.5% for the LNMO sample to 41 % for the LNMO/Ag sample under a high field of 6 T at the temperature of 330 K. In the low temperature regime, the magnetoresistance ratio of the LNMO/Ag sample is smaller than that of the LNMO sample, which is contrary to the magnetoresistance effect in high temperature. The effects are discussed qualitatively by use of a model which is based on the relative change among the intrinsic magnetoresistance effect and the extrinsic magnetoresistance effect.

Abstract: Cobalt modified TiO₂ nanotube was prepared by wet impregnation method from anodized nanotube. The microstructure and phase characteristic were studied by SEM, EDX and XRD analysis. The photocatalytic degradation of methylene blue under UV illumination was studied. Enhanced degradation efficiency could be obtained after sodium borohydride reducing. For the samples using low concentration of CoCl₂ in wet impregnation process, the degradation efficiency increased with the increase of CoCl₂ concentration and for high concentration, the degradation efficiency decreased. With increasing the post-treatment temperature, the degradation efficiency decreased.

Abstract: Polycrystalline ZnO thin films codoped with Cu and N have been obtained by chemical bath deposition. The effect of N incorporation and Cu-N incorporation on microstructure and optical properties of ZnO films has been investigated. X-ray diffraction patterns of the films indicated N incorporation deteriorated the crystalline quality while Cu-N incorporation improved the crystalline quality. The PL spectra showed that the relative intensity between the ultraviolet luminescence and the deep level-center luminescence of ZnO thin films was clearly correlated with the crystalline quality. Furthermore, the Raman spectra revealed the intensity of E₂ (high) increase with Cu-N incorporation.

Abstract: Microencapsulated phase change material (PCM) slurry is a kind of novel heat transfer fluid called latent functionally thermal fluid. Unlike conventional (sensible) materials, when the PCM reach the temperature at which they begin phase change (its melting point), they absorb large amounts of heat with little or no temperature change. Due to this, the heat transfer ability and energy transport ability can be obviously improved. Therefore, they have many potentially important applications in some fields such as energy storage, thermal conditioning of buildings, waste heat recovery, off peak power utilization, heat pump systems, space applications. In present study, the core materials are encapsulated with membrane of synthetic material. And the core materials are composed of several kinds of n-paraffin waxes (mainly nonadecane) and the membrane is a type of melamine resin. The range of diameter of the PCM particles is distributed from 0 μm to 4.5 μm, and its average diameter is 0.74 μm. The thickness of melamine resin is about 11nm. The melting point of the PCM is about 304K. Physical properties, such as density, diameter and its distribution of microencapsulated PCM slurry are investigated. Meanwhile, the thermal physical property, apparent specific heat, is determined by a Differential Scanning Calorimeter (DSC). Also, the influence of mass concentration has been discussed.

Abstract: An amperometric biosensor for H2O2 detection was developed with immobilization of Horseradish Peroxidase (HRP) on Ag nanowires (AgNWs). Ag nanowires (AgNWs) have been prepared by the reductive deposition method and characterized by the scanning electron microscopy (SEM) and the energy dispersive X-ray (EDX). The electrochemical performance of the HRP/AgNWs/GC electrode was investigated by cyclic voltammetry (CV) and chronoamperometry and the use of Ag nanowires led to an efficient enzyme loading, and also provided an increased surface area for sensing the reaction, showing high electrocatalytic activity towards the reduction of H2O2. Under the optimized conditions, the response of the biosensor towards H2O2 was investigated by chronoamperometry. The biosensor exhibited excellent sensitivity (the detection limit was down to 0.005 mM), fast response time (15 sec). Moreover, the biosensor had long-time stability and good reproducibility.

Abstract: The optical properties of electromagnetic (EM) waves propagating in one-dimensional plasma dielectric photonic crystal made of alternate thin layers of two materials namely micro plasma layer and dielectric material layer is studied theoretically. The dispersions both for ω < ω_p and ω > ω_p are deduced by transfer matrix method and the photonic band gap structure and the reflection spectra are computed. The results show that the band gap structure and reflection spectra are tuned correspondingly due to the dielectric constant of the microplasma layer modified differently in different frequency ranges. Parameter dependence of the effects is calculated and discussed.