Hybrid coatings from novel silane-modified glycidyl carbamate resins and amine crosslinkers

Organic–inorganic hybrid coatings were prepared using silane-modified glycidyl carbamate resins and different amine crosslinkers via the sol–gel process. Two different silane-modified glycidyl carbamate resins with 33% and 20% silane modification were prepared. The synthesized resins were crosslinked with amine crosslinkers such as Amicure PACM, Ancamide 805, Ancamide 2050, Ancamide 2353, Epicure 3164, Jeffamine D-400, etc., at different epoxy to amine equivalent ratios. The formulated hybrid coatings were cured at laboratory temperature and humidity for more than 20 days and subjected to different tests. The hybrid coatings were analyzed using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) during network maturation. Post-cured coatings were also analyzed to understand the effect of structural variables on the coatings thermal properties. Mechanical testing of the post-cured coatings such as König pendulum hardness, crosshatch adhesion and impact resistance were also evaluated. Solvent resistance of the coatings was evaluated by of testing the methyl ethyl ketone (MEK) double rub resistance. Atomic force microscopy (AFM) was used to characterize the surface topography of the hybrid coatings. Finally, structure–property correlations were given based on the observed results.     

Preparation of platinum-doped hollow spheres and their electrocatalytic activity in water electrolysis

Pure TiO₂ hollow spheres were prepared by using poly(styrene-methacrylic acid) latex particles as template; thereafter, titania hollow spheres were coated by platinum with an appropriate amount of choloroplatinic acid solution to obtain Pt/TiO₂ catalysts. The morphology and structure of nonstructural Pt/TiO₂ hollow spheres were characterized by BET, XRD, TGA, SEM and TEM analysis. In the samples, a remarkably uniform layer of Pt consisting of particles from 5 to 70 nm in size was formed over TiO₂ hollow spheres. We found the electrocatalytic nature of the samples by cyclic voltammetric experiment in acidic solution. The anodic peak current density of 20 wt% Pt-loaded TiO₂ hollow particles was observed 2.5 times higher than that of 5 wt% Pt/TiO₂ in the same experimental condition. Also, the anodic current density of 20 wt% Pt/TiO₂ hollow spheres calcined at various temperatures followed the order: 400 °C≈500 °C>600 °C. The electrocatalytic activity of the Pt-loaded TiO₂ hollow spheres depends on the amount of atomic platinum present in the sample; a higher concentration of platinum results in a larger current density value in anodic sweep, resulting in more oxygen production during electrolysis. Pt/TiO₂ hollow sphere catalysts have also shown long term electrocatalytic stability in acidic media.     

Augmenting the performance of acrylonitrile–butadiene–styrene plastics for low‐noise dynamic applications

The main objective of this study was to enhance the performance of acrylonitrile–butadiene–styrene (ABS) plastics for dynamic structural applications, including those of automobile relevance. First, ABS was modified by blending with maleic anhydride grafted styrene–ethylene–butadiene–styrene block copolymer (MA‐g‐SEBS) in various proportions. Squeaking noise characteristics were evaluated by measurement of the frictional behavior in an in‐house fabricated friction testing apparatus, and the results are explained on the basis of the change in surface energy upon modification. Detailed dynamic mechanical analyses (strain, frequency, and temperature sweep) revealed significant improvements in the damping characteristics of the modified ABS, especially that modified with 10 wt % MA‐g‐SEBS, without much sacrifice in its mechanical strength. The modulus values predicted with Kerner's model of the blends were well correlated with the morphological changes upon modification. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Dielectric properties of EVA/LDPE TPE system: Effect of nanosilica and controlled irradiation

The pristine nanosilica particles were melt‐blended with a model low‐density polyethylene–ethylene vinyl acetate thermoplastic elastomers (TPE) system by varying the sequence of addition and nanosilica contents. Bis‐[3‐(triethoxysilyl)propyl] tetrasulfide (Si‐69) was used to improve the state of dispersion of nanosilica particles in one of the compositions. The dielectric properties of the TPE systems are influenced remarkably by loadings of silica, variation of sequence of addition of ingredients during mixing, addition of Si‐69, and controlled electron beam irradiation. The effects of interfacial and orientation polarization on the permittivity and the loss tangent were studied by dielectric analyses. These were correlated with the structures of various nanocomposites. An attempt has also been made to support the dielectric results by volume resistivity measurements, measurements of breakdown voltage, and swelling–deswelling kinetic results. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Optimal location of three heat sources on the wall of a square cavity using genetic algorithms integrated with artificial neural networks

In this work, optimization of location of heat sources in a square enclosure with natural convection is performed to maximize the global conductance in the enclosure. For this study we have taken a square enclosure with three adiabatic walls, one isothermal wall opposing the wall having three heat sources. Numerical simulations are done by changing positions of heat sources for different Rayleigh numbers using Fluent 6.3(2d, double precision). And for some configurations maximum temperature inside the enclosure is noted. Optimization is done using genetic algorithms (GA) combined with artificial neural networks (ANN). An ANN is trained using the above data obtained from numerical solutions. The trained ANN will be the simulation tool, whenever required by the GA for optimization. It is shown that at high Rayleigh number the spacing between the heat sources should be zero for optimum heat transfer. Variation in optimum solution for unequal heat fluxes are also studied.     

Analysis of parallel-operated self excited induction generators

The paper presents an iterative solution for the problems related to steady state performance of self-excited induction generators operating in parallel. The analysis is based on voltage and current balance equations derived from an inverse-model for the steady state equivalent circuit of induction machines. The nonlinearity in the magnetization characteristics has been taken into account by piecewise linearisation. The proposed method is general and can be applied for analysis of any number of parallel connected machines. Theoretical predictions and experimental results are presented to study different performance characteristics of the system     

A Comparative Study of Submicron Phonon Transport Using the Boltzmann Transport Equation and the Lattice Boltzmann Method

The subcontinuum energy transport mechanism in solids can be explained by the Lattice Boltzmann Method (LBM), a discrete representation of the Boltzmann Transport Equation (BTE). The present study focuses on a detailed comparison of the LBM and BTE. Results reveal that at continuum scale, the LBM follows the BTE almost precisely. However, as the device dimensions are reduced, approaching the ballistic limit, the LBM deviates from the BTE results in terms of thermal property estimation. The inherent nonisotropic lattice configuration has a dominant contribution to the performance of the LBM. A threshold length scale is also proposed for successful implementation of the LBM solver.     

Influence of martensite morphology on the work-hardening behavior of high strength ferrite–martensite dual-phase steel

This study concerns influence of martensite morphology on the work-hardening behavior of high-strength ferrite–martensite dual-phase (DP) steel. A low-carbon microalloyed steel was subjected to intermediate quenching (IQ), step quenching (SQ), and intercritical annealing (IA) to develop different martensite morphologies, i.e., fine and fibrous, blocky and banded, and island types, respectively. Analyses of work-hardening behavior of the DP microstructures by differential Crussard–Jaoul technique have demonstrated three stages of work-hardening for IQ and IA samples, whereas the SQ sample revealed only two stages. Similar analyses by modified Crussard–Jaoul technique showed only two stages of work-hardening for all the samples. Among different treatments, IQ route has yielded the best combination of strength and ductility due to its superior work-hardening behavior. The influence of martensite morphology on nucleation and growth of microvoids/microcracks has been correlated with the observed tensile ductility.     

Plastic collapse moment equations of throughwall axially cracked elbows subjected to combined internal pressure and in-plane bending moment

Plastic collapse moment (PCM) equations of throughwall axially cracked (TAC) elbow subjected to in-plane closing/opening bending moment were previously proposed by the present authors. However, in actual situation, an elbow may often be subjected to combined internal pressure and bending moment loading. The present work investigates the effect of internal pressure on the in-plane plastic collapse moment of throughwall axially cracked elbows through 3-D elastic-plastic finite element analysis. Equations of un-pressurized cases are recommended where it is conservative and in other cases new equations are proposed.