Similarity solutions for laminar free convection flow of a thermomicropolar fluid past a non-isothermal vertical flat plate

Laminar free convection boundary layer flow of a thermomicropolar fluid past a non-isothermal vertical flat plate has been studied in detail. It has been established that the flow problem has similarity solutions when the variation in the temperature of the plate is a linear function of the distance from the leading edge measured along the plate. The resulting system of the nonlinear ordinary differential equations has been solved numerically by “Shooting Method” for various values of the material parameters. The effects of these parameters has been studied on the velocity and microrotation fields graphically. Also “Tables” have been given for the values of temperature, skin-friction parameter, microrotation gradient on the wall and Nusselt number. Two types of boundary conditions are prescribed for the microrotation on the wall.     

Kinetics of the thermal dissociation of Co4S3 under reduced pressure

Kinetics of the thermal dissociation of Co₄S₃ were investigated under reduced pressures of 5 × 10^-2 and 1.5 × 10^-4 mm Hg in the temperature range 1120° to 1405°C. The initial 10 pct dissociation was found to take place in accordance with a linear rate law, with activation energies of 20 and 17 kcal per mole under low and high vacuums, respectively. Subsequent dissociation up to about 35 pct was observed to be parabolic in nature, with activation energies of 38 and 40 kcal per mole under the respective vacuums. Further dissociation up to about 90 pct was found to fit into another linear rate law, with activation energies of 47 and 49 kcal per mole under the reduced pressures of 5 × 10^-2 and 1.5 × 10^-4 mm Hg, respectively. Beyond 90 pct, the dissociation was found to be very sluggish. These results have been interpreted with the help of the Co-S phase diagram. It has also been possible to achieve more than 99 pct dissociation of Co₄S₃ in 2 hr at 1405°C under low vacuum or 1355°C under high vacuum.     

Thermal and thermomechanical properties of hyperbranched polyurethane‐urea/cenosphere hybrids

Hyperbranched polyurethane (HBPU)‐urea/cenosphere hybrid coatings were synthesized by incorporating various concentrations of cenosphere into HB polyester matrix by ultrasonication technique, and this polyester was further used for the preparation of isocyanate terminated HBPU prepolymers by reacting with excess isophorone diisocyanate (IPDI) in a NCO/OH ratio of 1.6 : 1. The desired hybrid coating is obtained by moisture curing the excess NCO present in the prepolymer through film casting. The structure of the hyperbranched polyester (HBPE) was conformed by ¹H, ¹³C NMR and FTIR spectroscopy and the degree of branching (DB) was calculated using Frechet and Frey equations. These hybrid films were characterized by powder XRD, FTIR, SEM, DMTA, and TGA. The structure property correlation, intermolecular/intramolecular hydrogen bonding, the surface morphology, and viscoelastic properties were studied. These results showed an increase in T_g and thermal stability of the hybrid coatings than the base polymer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polarization-sensitive nanowire photodetectors based on solution-synthesized CdSe quantum-wire solids

Polarization-sensitive photodetectors are demonstrated using solution-synthesized CdSe nanowire (NW) solids. Photocurrent action spectra taken with a tunable white light source match the solution linear absorption spectra of the NWs, showing that the NW network is responsible for the device photoconductivity. Temperature-dependent transport measurements reveal that carriers responsible for the dark current through the nanowire solids are thermally excited across CdSe band gap. The NWs are aligned using dielectrophoresis between prepatterned electrodes using conventional optical photolithography. The photocurrent through the NW solid is found to be polarization-sensitive, consistent with complementary absorption (emission) measurements of both single wires and their ensembles. The range of solution-processed semiconducting NW materials, their facile synthesis, ease of device fabrication, and compatibility with a variety of substrates make them attractive for potential nanoscale polarization-sensitive photodetectors.     

Dissipative heat for the Casson fluid flow past an expanding cylindrical surface

A non-Newtonian model is developed by considering the flow of non-Newtonian Casson fluid past an expanding cylinder embedded in a porous medium. The novelty arises because of the conjunction of dissipative heat, and the additional heat source that enriches the heat transport phenomenon significantly. The application of the study is vital due to the flow of blood through the artery, a physiological study. Therefore, the study of Casson fluid plays an important role. The nonlinear partial differential equations that appeared in the formulation are now renovated to the coupled nonlinear ordinary differential equations. However, a numerical technique associated with shooting-based followed by Runge–Kutta fourth-order is employed for the solution of these transformed equations. The uniqueness of diverse pertinent parameters on the flow phenomena is scrutinized through graphs and numerically simulated results presented in tables. The important observations are as follows; the magnetic parameter and permeability augment the shear rate coefficients, whereas the Casson parameter rendered the opposite impact. Furthermore, the non-Newtonian Casson parameter retards the fluid temperature, and the curvature parameter significantly enhances it.     

Graphene-induced Pd nanodendrites: A high performance hybrid nanoelectrocatalyst

A facile and green approach has been developed for the in situ synthesis of hybrid nanomaterials based on dendrite-shaped Pd nanostructures supported on graphene （RG）. The as-synthesized hybrid nanomaterials （RG-PdnDs） have been thoroughly characterized by high resolution transmission electron microscopy, X-ray photoelectron spectroscop）~ atomic force microscop）~ Raman spectroscopy and electrochemical techniques. The mechanism of formation of such dendrite- shaped Pd nanostructures on the graphene support has been elucidated using transmission electron microscopy （TEM） measurements. The RG induces the formation of, and plays a decisive role in shaping, the dendrite morphology of Pd nanostructures on its surface. Cyclic voltammetry and chronoamperometry techniques have been employed to evaluate the electrochemical performance of RG-PdnDs towards oxidation of methanol. The electrochemical （EC） activities of RG-PdnDs are compared with graphene-supported spherical-shaped Pd nanostructures, Pd nanodendrites alone and a commercial available Pd/C counterpart. The combined effect of the graphene support and the dendrite morphology of RG-PdnDs triggers the high electrocatalytic activity and results in robust tolerance to CO poisoning.