Combustion synthesis of β-SnWO4-rGO: Anode material for Li-ion battery and photocatalytic dye degradation

This article reports the synthesis β-SnWO₄–rGO nanocomposite (NC) by a simple solution combustion method followed by low temperature hydrothermal method. The β-SnWO₄–rGO NC has been characterized using various analytical tools such as X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HR-TEM), Ultraviolet-Differential reflectance spectroscopy (UV-DRS). X-ray diffraction pattern shows the formation of cubic structured β-SnWO₄ nanoparticles (NPs) and Raman spectrum shows the presence of rGO in the composite. Transmission Electron Microscopy image shows that SnWO₄ NPs were embedded on the surface of rGO. β-SnWO₄ NPs and β-SnWO₄-rGO NC has been examined as an electrode material for Li-ion battery (LIB). β-SnWO₄ NPs and β-SnWO₄-rGO NC displays an initial discharge capacity of 1351 mAhg^?1 and 1662 mAhg^?1 which is about 23% increase in capacity. Electrochemical performance of β-SnWO₄-rGO NC at different current densities proves that it is one of the good candidates as an electrode material for LIB. β-SnWO₄-rGO NC shows enhanced photocatalytic activity against rose bengal (RB) and methylene blue (MB) compared to pure β-SnWO₄ NPs.     

Novel poly(3,4‐dialkoxythiophene)s carrying 1,3,4‐oxadiazolyl‐biphenyl moieties: synthesis and nonlinear optical studies

Two new donor–acceptor types of polymer, poly{2‐(biphenyl‐4‐yl)‐5‐[3,4‐dialkoxy‐5‐(1,3,4‐oxadiazol‐2‐yl)thiophen‐2‐yl]‐1,3,4‐oxadiazole}s, were synthesized starting from 2,2′‐sulfanediyldiacetic acid and diethyl ethanedioate through multi‐step reactions. The polymerization was carried out via the polyhydrazide precursor route. The optical and charge‐transporting properties of the polymers were investigated using UV‐visible and fluorescence emission spectroscopic and cyclic voltammetric studies. The polymers showed bluish‐green fluorescence in solutions. The electrochemical band gaps of the polymers were determined to be 2.16 and 2.22 eV. The nonlinear optical properties of the polymers were investigated at 532 nm using the single‐beam Z‐scan technique with nanosecond laser pulses. The polymers showed strong optical limiting behaviour due to effective three‐photon absorption. The values of the three‐photon absorption coefficients for the polymers were found to be 9 × 10^?24 and 17 × 10^?24 m³ W^?2, which are comparable to those of good optical limiting materials. Copyright © 2010 Society of Chemical Industry     

Generic Molding Platform for Simple,Low‐Cost Fabrication of Polymeric Microneedles

Micromolding technology is widely used for the fabrication of polymer microneedles for transdermal and intradermal drug delivery applications. Geometric features of microneedles in molding are solely determined by geometry of the master mold template. Fabrication of master mold template usually involves costly and cumbersome technologies due to small feature sizes typical of microneedles. In this research, a novel molding platform is designed that is fabricated using low‐cost and simple techniques with flexibility of producing large number of microneedle geometries. The proposed molding platform eliminates need for developing multiple mold templates for fabrication of various geometries of polymer microneedles. Utility of this molding platform is demonstrated in polylactic acid‐based solid thermoplastic microneedles and polyacrylic acid‐based dissolvable microneedles with various aspect ratio settings. Various microneedles fabricated at heights differing with resolution of as low as 100 µm are successfully achieved using specified settings in the molding platform. The suitability of fabricated microneedles for drug delivery applications is evaluated by in vitro and in vivo testing.     

Evaluation of Progressive Failure of Composite T-Joint Using Mixed Mode Cohesive Zone Model

T shaped stiffeners are the most commonly used structures in aerospace components. De-lamination/de-bond initiation followed by its growth is one of the most common reasons for failure in a fiber reinforced composite structure. It is caused by the interlaminar normal and shear stresses between different structural constituents. In a typical structural T-joint, the failure mechanism and location may differ based on the structural design parameters like fillet radius, thickness, layup sequence, filler stiffness, etc. In this study, finite element analysis has been performed using cohesive zone model (CZM) on a composite T-joint to simulate the pull out test conditions. A simplified plane strain model coupled with CZM is proposed, which can evaluate the failure initiation and progression accurately with lesser computational efforts. The final failure occurs at a displacement of 8.04 mm and the computed failure load is 2240 N. The results obtained by the proposed numerical model are validated by experimental results and it is observed that predicted regions of failure, failure displacements and failure load calculated are correlating reasonably well with the experiment.     

The tensile fatigue behaviour of a silica nanoparticle-modified glass fibre reinforced epoxy composite

An anhydride-cured thermosetting epoxy polymer was modified by incorporating 10 wt.% of well-dispersed silica nanoparticles. The stress-controlled tensile fatigue behaviour at a stress ratio of R = 0.1 was investigated for bulk specimens of the neat and the nanoparticle-modified epoxy. The addition of the silica nanoparticles increased the fatigue life by about three to four times. The neat and the nanoparticle-modified epoxy resins were used to fabricate glass fibre reinforced plastic (GFRP) composite laminates by resin infusion under flexible tooling (RIFT) technique. Tensile fatigue tests were performed on these composites, during which the matrix cracking and stiffness degradation was monitored. The fatigue life of the GFRP composite was increased by about three to four times due to the silica nanoparticles. Suppressed matrix cracking and reduced crack propagation rate in the nanoparticle-modified matrix were observed to contribute towards the enhanced fatigue life of the GFRP composite employing silica nanoparticle-modified epoxy matrix.     

Perceptual thresholds and electrode impedance in three retinal prosthesis subjects.

Three test subjects blind from retinitis pigmentosa were implanted with retinal prostheses as part of a FDA-approved clinical trial. The implant consisted of an extraocular unit that contained electronics for wireless data, power, and generation of stimulus current, and an intraocular unit that consisted of 16 platinum stimulating electrodes arranged in a 4 x 4 pattern within a silicone rubber substrate. The array was held to the retina by a small tack. The stimulator was connected to the array by a multiwire cable and was controlled by a computer based external system that allowed precise control over each electrode. Perception thresholds and electrode impedance were obtained on each electrode from the subjects over several months of testing. The electrode distance from the retina was determined from optical coherence tomography imaging of the array and retina. Across all subjects, average thresholds ranged from 24-702 microA (1-ms pulse). The data show that proximity to the retina played a role in determining the threshold and impedance, but only for electrodes that were greater than 0.5 mm from the retina.     

Effect of Retrogression Heat Treatment Time on Microstructure and Mechanical Properties of AA7010

The effect of retrogression time during retrogression and re-aging (RRA) treatment of AA7010 is evaluated by performing tensile tests and characterizing the microchemistry of the grain boundary precipitates (GBPs) using transmission electron microscope coupled with the energy-dispersive spectroscopy. Retrogression time is evaluated so that the ultimate tensile strength of the RRA-treated sample is equal to that of the T6-treated sample and the grain boundary microstructure similar to that of the over-aged (T7451) condition. The investigation reveals that the sample retrogressed at 200 °C for 20 min has UTS of 586 MPa which is equivalent to that of the T6 sample and 11.5% higher than that of the T7451 condition. The fracture toughness of the RRA-treated sample was 41 MPa√m. Microstructure of the RRA-treated sample is similar to T7451, along the grain boundaries and in the grain interior similar to that of the T6-treated sample. Energy-dispersive spectroscopy confirmed the increment of Cu content on the GBP’s with increase in the retrogression time, which is expected to improve the stress corrosion cracking resistance of the alloy.     

Electron irradiation effects on the Schottky diode characteristics of p-Si

Particle irradiation can induce transient and permanent changes in the electrical properties of semiconductor devices in radiation environments. The effects of electron irradiation on the device properties of Al/p-Si Schottky diodes are reported here. Schottky diodes were exposed to a maximum cumulative dose of 100 kGy at room temperature. Their forward and reverse current-voltage (I-V) characteristics were studied at room temperature. The diode parameters such as ideality factor, reverse saturation current, barrier height and series resistance were calculated from the forward I-V characteristics. An increase in the values of the ideality factor and a decrease in the barrier height values were observed over this dose range. Also, the reverse current was found to increase with increasing dose.