Nanocomposites of polymer gel electrolyte based on poly(ethylene glycol diacrylate) and Mg–Al layered double hydroxides

The present paper describes the synthesis and characterization of nanocomposite materials composed of the polymer gel electrolyte and a layered double hydroxide (LDH) inorganic filler. Mg–Al LDHs were prepared with various ratios of Mg/Al. It was observed that the layered structure of Mg–Al LDH was totally exfoliated by the PEGDA. The ionic conductivity and mechanical strength were highly improved in the nanocomposite systems. In the case of the composite films having 4.5 wt% of the Mg–Al LDH, the ionic conductivity reached 1.6 × 10^?3 S cm^?1 at room temperature. The incorporation of nanoparticles into the gel resulted in a two‐ or threefold increase in the tensile modulus. Copyright © 2004 Society of Chemical Industry     

Excitation of local field enhancement on silicon nanowires

The interaction between light and reduced-dimensionality silicon attracts significant interest due to the possibilities of designing nanoscaled optical devices, highly cost-efficient solar cells, and ultracompact optoelectronic systems that are integrated with standard microelectronic technology. We demonstrate that Si nanowires (SiNWs) possessing metal-nanocluster coatings support a multiplicatively enhanced near-field light-matter interaction. Raman scattering from chemisorbed probing molecules provides a quantitative measure of the strength of this enhanced coupling. An enhancement factor of 2 orders of magnitude larger than that for the surface plasmon resonance alone (without the SiNWs) along with the attractive properties of SiNWs, including synthetic controllability of shape, indicates that these nanostructures may be an attractive and versatile material platform for the design of nanoscaled optical and optoelectronic circuits.     

Computation of Thermal Fracture Parameters for Inclined Cracks in Functionally Graded Materials Using J k -Integral

This article describes the formulation and implementation of the J _k -integral for the analysis of inclined cracks located in functionally graded materials (FGMs) that are subjected to thermal stresses. The generalized definition of the J _k -integral over a vanishingly small curve at the tip of an inclined crack is converted to a domain independent form that consists of area and line integrals defined over finite domains. A numerical procedure based on the finite element method is then developed, which allows the evaluation of the components of the J _k -integral, the modes I and II stress intensity factors and the T-stresses at the crack tips. The developed procedure is validated and the domain independence is demonstrated by providing comparisons to the results obtained by means of the displacement correlation technique (DCT). Detailed parametric analyses are conducted by considering an inclined crack in an FGM layer that is subjected to steady-state thermal stresses. Numerical results show the influences of the thermal conductivity and thermal expansion coefficient variation profiles and the crack inclination angle on the mixed-mode fracture parameters.     

Frictional Hertzian contact between a laterally graded elastic medium and a rigid circular stamp

This study investigates the problem of sliding frictional contact between a laterally graded elastic medium and a rigid circular stamp. Analytical and computational methods are developed to evaluate the contact stresses. In the analytical formulation, spatial variation in the shear modulus of the graded medium is represented by an exponential function, and Poisson’s ratio is taken as a constant. Coulomb’s dry friction law is assumed to hold within the contact area. The two-dimensional plane elasticity problem is formulated utilizing Fourier transforms, and the resulting Cauchy-type singular integral equation of the second type is solved by applying an expansion–collocation technique. The finite element method is used in the computational analysis of the contact problem. In the finite element model, continuous variation of the shear modulus is taken into account by specifying this property at the centroid of each finite element. The finite element-based solution procedure is verified by making comparisons to the results obtained through the analytical method. Numerical results generated for the laterally graded medium with an exponential variation in the shear modulus illustrate the influences of lateral gradation and coefficient of friction upon the contact stress distributions. The capability of the proposed finite element method is further demonstrated by providing numerical results for a laterally graded medium whose shear modulus is represented by a power function.     

Numerical modeling and analysis of ECC structures

The objective of this paper is to develop a tool for the numerical analysis of full-scale ECC structures. For this purpose, a macroscopic cyclic constitutive model for engineered cementitious composite (ECC) materials is developed based on the response of the material at the stress–strain level under different loading regimes. Various features specific to ECC material such as the unloading and reloading characteristics, different backbone curves in tension and compression, and residual strains are taken into account in the model development. The input parameters are limited to those that can be obtained from conventional monotonic compression and tension tests, thus facilitating its use with minimum information. The model is first validated at the stress–strain level and then implemented into fiber-based finite element analysis software for structural level simulation. The results from simulation of ECC members under cyclic and static time history loading are compared to experimental data for model validation at the structural level. Finally, a parametric study is conducted at the member level to investigate the effect of ECC tensile strength and ductility on the structural level response metrics: stiffness, strength, ductility, and energy dissipation capacity. It is observed that the structural level response metrics change considerably depending on the material properties. With its sensitivity to the main behavioral features of ECC, its simplicity, and its sufficient accuracy, the model is suited for use in predicting the behavior of ECC structures under monotonic, cyclic, and dynamic loading scenarios.     

Synthesis and characterization of multi‐hollow opaque polymer pigments

A new generation multihollow opaque polymer pigment was synthesized by suspension polymerization of “water‐in‐oil‐in‐water” emulsion method, where methyl methacrylate and ethylene glycol dimethacrylate monomer mixture was used as oil phase. The effects of surfactant and cosurfactant composition in terms of “hydrophilic/lipophilic balance” on the stability of the “water‐in‐oil” emulsion and the size of water droplets were studied. Low droplet sizes and the optimum stability were obtained with “Span 80&Tween 80” surfactant mixture at an HLB value of 8. The desired size distribution was obtained at “monomer/surfactant/water” ratio of 75.5/9.4/15.1 at an ultrasonic mixing power of 80 W lasting for 30 s. The surface morphology and hollow structure of polymer pigments were analyzed by scanning and transmission electron microscopy techniques. L*a*b color and gloss properties of polymer pigments were examined. The opacity values were assessed by contrast ratio measurements, and the pigments provided up to 97.3% opacity with 50% v/v solid content in resin. In addition, the pigments exhibited low gloss values and yielded matte films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43696.     

Preparation of polyester resin/graphene oxide nanocomposite with improved mechanical strength

Graphene oxide (GO) has attracted huge scientific interest due to its unique physical and chemical properties as well as its wide‐scale applicability including facile synthesis and high yield. Here, we report preparation of nanocomposites based on GO and unsaturated polyester resin (PE). The synthesized samples were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, and tensile strength measurements. A good dispersion of the GO sheets within the resin matrix was observed from the morphological analysis. A significant enhancement in mechanical properties of the PE/GO composites is obtained at low graphene loading. Around 76% improvement of tensile strength and 41% increase of Young's modulus of the composites are achieved at 3 wt % loading of GO. Thermal analysis of the composite showed a noticeable improvement in thermal stability in comparison to neat PE. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Approximate Controllability of Impulsive Neutral Stochastic Differential Equations Driven by Poisson Jumps

This work studies the approximate controllability of a class of impulsive neutral stochastic differential equations with infinite delay and Poisson jumps involving generalized Caputo fractional derivative under the condition that the corresponding linear system is approximately controllable. Utilizing the fixed point theory and sectorial operator theory, the existence of the mild solution of the impulsive neutral stochastic equation is established imposing weaker regularity on nonlinear terms. A set of sufficient conditions establishing controllability results is derived with the help of stochastic analysis and fractional calculus. Finally, an example is provided to illustrate the obtained abstract result.     

Antheraea assama Silk Fibroin‐Based Functional Scaffold with Enhanced Blood Compatibility for Tissue Engineering Applications

The architecture and surface chemistry of a scaffold determine its utility in tissue engineering (TE). Conventional techniques have limitations in fabricating a scaffold with control over both architecture and surface chemistry. To ameliorate this, in this report, we demonstrate the fabrication of an Antheraea assama silk fibroin (AASF)‐based functional scaffold. AASF is a non‐mulberry variety having superior qualities to mulberry SF and is largely unexplored in the context of TE. First, a 3D scaffold with biomimetic architecture is fabricated. The scaffold is subsequently made blood compatible by modifying the surface chemistry through a simple sulfation reaction. EDX and FTIR analysis demonstrate the successful sulfation of the scaffold. SEM observations reveal that sulfation has no any effect on the scaffold architecture. TGA reveals that it has increased thermal stability. The sulfation reaction significantly improves the overall hydrophilicity of the scaffold, as is evident from the increase in water holding capacity; this possibly enhances the blood compatibility. The enhancement in blood compatibility of the sulfated scaffold is determined from in vitro haemolysis, protein adsorption and platelet adhesion studies. The sulfated scaffold is non‐toxic and supports cell adhesion and growth, as revealed by indirect and direct contact‐based in vitro cytotoxicity assays. This study reveals that the AASF‐based functional scaffold, which has biomimetic architecture and blood‐compatible surface chemistry, could be suitable for TE applications.