Successive melting and crystallization of poly(3-hexylthiophene) in the melt-memory domain versus isotropic melt domain

Journal of Materials Science - We studied the influence of self-nuclei of poly(3-hexylthiophene), present at different temperatures in the melt-memory domain, and thermal polymer degradation during...     

A Long‐Cycle‐Life Lithium–CO2 Battery with Carbon Neutrality

Lithium–CO₂ batteries are attractive energy‐storage systems for fulfilling the demand of future large‐scale applications such as electric vehicles due to their high specific energy density. However, a major challenge with Li–CO₂ batteries is to attain reversible formation and decomposition of the Li₂CO₃ and carbon discharge products. A fully reversible Li–CO₂ battery is developed with overall carbon neutrality using MoS₂ nanoflakes as a cathode catalyst combined with an ionic liquid/dimethyl sulfoxide electrolyte. This combination of materials produces a multicomponent composite (Li₂CO₃/C) product. The battery shows a superior long cycle life of 500 for a fixed 500 mAh g^?1 capacity per cycle, far exceeding the best cycling stability reported in Li–CO₂ batteries. The long cycle life demonstrates that chemical transformations, making and breaking covalent C? O bonds can be used in energy‐storage systems. Theoretical calculations are used to deduce a mechanism for the reversible discharge/charge processes and explain how the carbon interface with Li₂CO₃ provides the electronic conduction needed for the oxidation of Li₂CO₃ and carbon to generate the CO₂ on charge. This achievement paves the way for the use of CO₂ in advanced energy‐storage systems.     

Simulation of CNT based mass resonator sensor and investigation on the effect of vacancy defect on sensing performances

Microsystem Technologies - In this paper carbon nanotube (CNT) as a mass resonator sensor has been modelled by molecular structural mechanics approach. Then the effect of a single vacancy defect...     

Comparison of viscoelastic properties of polydimethylsiloxane/poly(2‐hydroxyethyl methacrylate) IPNs with their physical blends

Interpenetrating polymer networks (IPNs) of polydimethylsiloxane (PDMS) and poly(2‐hydroxyethyl methacrylate) (PHEMA) were prepared by sequential method. The dynamic mechanical parameters of obtained IPNs and their variations with the structural composition were evaluated. The results for the IPNs were compared with corresponding physically blended systems. The tensile properties and damping factor (tan δ) were assessed by stress–strain measurement and dynamic mechanical thermal analysis (DMTA), respectively. The glass–rubber transition temperature (T_g) was assessed by DMTA and differential scanning calorimetry (DSC). The results showed higher tensile strength and elongation at break for IPNs than those for physical blends. The shifts of T_g for that two components that make up the IPNs were greater than those for corresponding blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3480–3485, 2002     

Modified stable Euler-number algorithm implementation for real-time image binarization

The stable Euler-number-based image binarization has been shown to give excellent visual results for images containing high amount of image noise. Being computationally expensive, its applications are limited mostly to general-purpose processors and in application specific integrated circuits. In this paper a modified stable Euler-number-based algorithm for image binarization is proposed and its real-time hardware implementation in a Field Programmable Gate Array with a pipelined architecture is presented. The proposed modifications to the algorithm facilitate hardware implementation. The end result is a design that out-performs known software implementations. The amount of noisy pixels introduced during the binarization process is also minimized. Despite the stable Euler-number-based image binarization being computationally expensive, our simulations show that the proposed architecture gives accurate results and this in real time and without consuming all chip resources.     

High-blocking-voltage UMOSFETs with reformed electric field distribution

A high-performance vertical GaN metal–oxide–semiconductor field-effect transistor (MOSFET) with a U-shaped gate (UMOSFET) and high blocking voltage is proposed. The main concept behind this work is to reform the electric field distribution to achieve high blocking voltage. The proposed structure includes p-regions in the drift region, which we call reformed electric field (REF) regions. Simulations using the two-dimensional SILVACO simulator reveal the optimum doping concentration, and width and height of the REF regions to achieve the maximum depletion region at the breakdown voltage in the drift region. Also, the electric field distribution in the REF-UMOSFET is reformed by producing additional peaks, which decreases the common peaks under the gate trench. We discuss herein the impact of the height, width, and doping concentration of the REF regions on the ON-resistance (R_ON) and blocking voltage. The blocking voltage, specific ON-resistance, and figure of merit \( \left( {{\text{FOM}} = \frac{{V_{{{\text{BR}}}}^{2} }}{{R_{{{\text{ON}}}} }}} \right) \) are 1140 V, 0.587 mΩ cm² (V_GS = 15 V, V_DS = 1 V), and 2.214 GW/cm², respectively. The blocking voltage and FOM are increased by about 72 % and 171 % in comparison with a conventional UMOSFET (C-UMOSFET).     

Microstructures and mechanical properties of friction stir welded dissimilar steel-copper joints

Welding dissimilar metals by fusion welding is challenging. It results in welding defects. Friction stir welding (FSW) as a solid-state joining method can overcome these problems. In this study, 304L stainless steel was joined to copper by FSW. The optimal values of the welding parameters traverse speed, rotational speed, and tilt angle were obtained through Response surface methodology (RSM). Under optimal welding conditions, the effects of welding pass number on the microstructures and mechanical properties of the welded joints were investigated. Results indicated that appropriate values of FSW parameters could be obtained by RSM and grain size refinement during FSW mainly affected the hardness in the weld regions. Furthermore, the heat from the FSW tool increased the grain size in the Heat-affected zones (HAZs), especially on the copper side. Therefore, the strength and ductility decreased as the welding pass number increased because of grain size enhancement in the HAZs as the welding pass number increased.     

Prediction of a highly sensitive molecule sensor for SOx detection based on TiO2/MoS2 nanocomposites: a DFT study

First principles calculations within density functional theory have been carried out to investigate the adsorptions of SO_x (x?=?1, 2) molecules on TiO₂/MoS₂ nanocomposites in order to fully discover the gas sensing capabilities of TiO₂/MoS₂ composite systems. The van der Waals interactions were included to obtain the most stable geometrical structures of TiO₂/MoS₂ nanocomposites with adsorbed SO_x molecules. SO_x molecules preferentially interact with the doped nitrogen and fivefold coordinated titanium sites of the TiO₂ anatase nanoparticles because of their higher activities in comparison with the other sites. The results presented include structural parameters such as bond lengths and bond angles and energetics of the systems such as adsorption energies. The variation of electronic structures are discussed in view of the density of states and molecular orbitals of the SO_x molecules adsorbed on the nanocomposites. The results show that the adsorption of the SO_x molecule on the N-doped TiO₂/MoS₂ nanocomposite is energetically more favorable than the adsorption on the undoped one, implying that the nitrogen doping helps to strengthen the interaction of SO_x molecules with TiO₂/MoS₂ nanocomposites. These calculated results thus provide a theoretical basis for the potential applications of TiO₂/MoS₂ nanocomposites in the removal and sensing of harmful SO_x molecules.     

Selecting model for treatment of oily wastewater by MF-PAC hybrid process using mullite-alumina ceramic membranes

Hermia’s models for cross flow filtration were used to investigate the fouling mechanisms of mullite-alumina ceramic membranes in treatment of oily wastewaters in a hybrid microfiltration-powdered activated carbon process (MF-PAC). Results show that cake filtration model can be applied for prediction of permeation flux decline for MF and MF-PAC process up to 400 ppm PAC. The complete pore blocking model and the intermediate pore blocking model can predict permeation flux decline with time for MF-PAC with 800 and 1200 ppm PAC respectively. Average error for prediction of permeation flux with cake filtration model is 2.19% for MF process and 2.16, 2.06 and 1.31% for MF-PAC process with 100, 200 and 400 ppm PAC respectively. Also for MF-PAC process with 800 and 1200 ppm PAC, average error for prediction of permeation flux with complete pore blocking model and intermediate pore blocking model was 6.11 and 6% respectively.     

Sonochemical degradation of Basic Blue 41 dye assisted by nanoTiO2 and H2O2

The sonolysis of Basic Blue 41 dye in aqueous solution was performed at 35 kHz using ultrasonic power of 160 W and aqueous temperature of 25+1 degrees C within 180 min. The TiO2 nanoparticles were used as a catalyst to assist the sonication process. The effect of experimental parameters such as pH, H2O2 concentration and initial dye concentration on the reaction were investigated. It was recognized that in lower pH values the dye removal rate decreased. However, dye removal increased via increase in H2O2 concentration and lowering the initial dye concentration. All intermediate compounds were detected by integrated gas chromatography-mass spectrometry (GC/MS) and also ion chromatograph (IC). During the decolorization, all nitrogen atoms and aromatic groups of Basic Blue 41 were converted to urea, nitrate, formic acid, acetic acid and oxalic acid, etc. Kinetic studies revealed that the degradation process followed pseudo-first order mechanism with the correlation coefficient (R2) of 0.9918 under experimental conditions. The results showed that power ultrasound can be regarded as an appropriate tool for degradation of azo dyes to non-toxic end products.