Characterisation of crude oil for enhanced oil recovery: study with anionic surfactant

A chemically enhanced recovery technique is used where thermal recovery is not feasible. It reduces the interfacial tension by forming a microemulsion. In this paper, characterisation of crude oil in terms of chemical bonds present is investigated by Fourier transform infrared spectroscopy (FTIR). The peaks at different wave number show saturated groups such as n-alkane –CH, –CH₂, –CH₃ and short chain of n-alkane C–C bond present in the oil samples. Since the crudes are collected from an anionic reservoir, sodium dodecyl sulphate (SDS) of 0.4% critical micelle concentration is suitable. It has been seen that the particle size increases in the case of a surfactant solution with oil compared to one without oil indicating entrapment of oil components inside the surfactant micelle. The larger absorptions of SDS from UV spectroscopy are caused by electrons moving between π and π* orbitals due to the presence of more unsaturated groups in the solution.     

Adhesion release and yield enhancement of microstructures usingpulsed Lorentz forces

Adhesion of microstructures is an important failure mechanism in surface-micromachined devices. In this paper, a simple and effective method for releasing pinned microstructures is presented. The method uses the Lorentz force due to the interaction of a current with an external magnetic field to generate an upward force that frees the microstructures. The static and transient behavior of beams under the Lorentz force is examined. Critical values of current and pulse durations needed to release the microstructures are determined and verified with experimental data. Using this technique, previously pinned beams and rectangular plates have been released. The release technique is suitable for mass production environments since it is easily applied during the electrical testing of the device, thereby increasing the manufacturing yield     

Amorphous silicon films with high deposition rate prepared using argon and hydrogen diluted silane for stable solar cells

Hydrogenated amorphous silicon films with high deposition rate (4–5 Å/s) and reduced Staebler–Wronski effect are prepared using a mixture of silane (SiH₄), hydrogen and argon. The films show an improvement in short and medium range order. The structural, transport and stability studies on the films are done using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman scattering studies, electrical conductivity and diffusion length measurement. Presence of both atomic hydrogen and Ar^* in the plasma causes breaking of weak SiSi bonds and subsequent reconstruction of strong bonds resulting in improvement of short and medium range order. The improved structural order enhances the stability of these films against light soaking. High deposition rate is due to the lesser etching of growing surface compared to the case of only hydrogen diluted silane.     

Mie scattering computation of spherical particles with very large size parameters using an improved program with variable speed and accuracy

The electromagnetic radiation scattering patterns were computed using an improved C program to study variations in the patterns with changes in the size distribution, size parameters and refractive index of small particles in a volume element. The particle size distributions considered were gamma, normal and lognormal. The program is stable for computation of the theoretical values of the non-zero elements of the scattering matrix, efficiency factors, single scattering albedo, radiation pressure and asymmetry parameter for particles ranging from very small to very large size parameters. One of the significant features of the program is that it incorporates two methods for the determination of the optimal number of terms required for the computation of Mie series with the added benefit of having the option of either going for computational speed or accuracy. After a comparison of the C program with other reported benchmark results, it has been found that the program is very accurate and reliable for electromagnetic scattering computations.     

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     

Facile Development of Iron-Platinum Nanoparticles to Harness Multifunctionality in Single Entity

Engineered magnetic nanosystems exhibit attractive options for implementing unique diagnostic options and therapeutic solutions in biomedical applications. Here we report a facile, thermo-free and aqueous synthetic method to prepare ascorbic acid-stabilized iron-platinum nanoparticles. The effects of reducing agent, pH and sequence of precursor addition are investigated, and optimized reaction condition is identified to obtain a unique iron-platinum(Pt-FePt)nanosystems. The multifunctionality of the developed nanosystem has been realized by catalytic efficiency of platinum for therapeutic application and superparamagnetic property of Fe Pt for magnetic resonance imaging contrast enhancement.Moreover, the multifunctional imaging and therapeutic activities have been achieved at physiological pH. The developed multifunctional nanoparticles are monodisperse with uniform morphology as well as stable in solution and non-toxic.     

The effect of withering on fermentation of tea leaf and development of liquor characters of black teas

Depression in polyphenol oxidase (PPO) activity during the withering of tea leaf (Camellia sinensis) in black tea manufacture affected the oxidative-condensation of tea flavanols in forming theaflavins (TF) and thearubigins (TR), which are associated with brightness, briskness and ‘body’ of tea liquors. In contrast to conventionally manufactured CTC teas, unwithered fresh leaf CTC produces a higher proportion of TF and lower TR, resulting in bright, brisk and thin liquors. Hardness of wither was accompanied by a further depression in PPO activity, and formation of TF also declined with a concomitant loss in brightness and briskness. The TR content increased up to a certain degree of wither and thereby improved the ‘body’ of the liquor. Very hard wither, accompanied by a large reduction in moisture content, restricts PPO activity. It appears that in the fresh leaf, high moisture levels together with dissolved oxygen accelerate the enzymic oxidation and produce large amounts of TF. Senescence of the leaf seems to facilitate the production of TR.     

Enhanced conversion efficiency of quasi solid state dye sensitized solar cells based on functionalized multi-walled carbon nanotubes incorporated TiO<Subscript>2</Subscript> photoanode

A series of quasi solid state dye sensitized solar cells were fabricated based on the different weight% of MWCNT@TiO₂ photoanode. The MWCNT@TiO₂ nanocomposites were synthesized by simple wet impregation method. The incorporation of MWCNT into the TiO₂ was confirmed by X-ray diffraction, energy dispersive X-ray spectrum and UV–visible spectroscopy. The morphological properties of the nanocomposites were analyzed by transmission electron microscopic analysis. The performance of the quasi solid state dye sensitized solar cell depends solely on the MWCNT content of the photoanode, as the same PVA polymer gel electrolyte has been used. Compared to the conventional TiO₂ photoanode based DSSCs 0.05 wt% MWCNT containing photoanode provide the maximum short circuit current density and the photo conversion efficiency of 9.811 mA/cm^?2 and 3.59 %. The introduction of MWCNT into the TiO₂ results in the rapid electron transport in the photoanode by forming a conductive network due to which improvement in the short circuit current was observed.     

Effect of Cobalt Doping on the Structural,Microstructure and Microwave Dielectric Properties of MgTiO3 Ceramics Prepared by Semi Alkoxide Precursor Method

We report a systematic investigation on crystal structure, microstructure, and microwave dielectric properties of (Mg_1?xCo_x)TiO₃ (x = 0–0.07) ceramics prepared by semialkoxide precursor method. All the as‐made samples exhibit an ilmenite structure with an incredible reduction in sintering temperature from 1350°C to 1200°C. Lattice parameter increases with increasing Co content due to the larger ionic radius of Co²⁺ as compared to Mg²⁺. The relative density, dielectric constant, and Q × f₀ values increase with increasing Co up to 0.05 and decreases for x > 0.05. This is attributed to local lattice distortion, maximum relative density, and uniform grain growth. Q × f₀ values were enhanced from 126 THz for x = 0 to a maximum value 170 THz for x = 0.05. A best combination of microwave dielectric properties (ε_r ~ 17.03, Q × f₀ ~ 170 THz @ 9.4 GHz and τ_f of ?40 ppm/°C) was obtained for (Mg_0.95Co_0.05)TiO₃ ceramic sintered at 1200°C for 3 h. The observed results reveal (Mg_0.95Co_0.05)TiO₃ ceramic as one of the promising dielectric materials for low‐loss and millimeter‐microwave applications.