Preparation and characterization of transparent conducting ZnS:Al films

Al-doped ZnS films were deposited using close-spaced evaporation of the powders synthesized by chemical precipitation method. The films were prepared for different Al concentrations in the range 0–10 at.% on glass substrates kept at 300 °C. The effect of Al-doping on ZnS composition, microstructure and optoelectronic properties of as-grown ZnS layers was determined using appropriate techniques. The films were polycrystalline and showed (111) preferred orientation for all the doping concentrations in spite of an additional phase of Al₂S₃ observed at higher dopant levels. The surface morphological studies indicated that the Al incorporation had a considerable effect on the surface roughness of the films. The optical measurements indicated that the optical energy band gap decreased slightly with the increase of dopant concentration without affecting the optical transmittance characteristics significantly. The electrical analysis indicated that the resistivity of the layers changed significantly with the doping concentration in the layers. The change of photoluminescence behaviour of the as-grown ZnS:Al films with dopant concentration was also studied.     

Two fluid flow and heat transfer in an inclined channel containing porous and fluid layer

Convective flow and heat transfer in an inclined channel bounded by two rigid plates held at constant different temperatures with one region filled with porous matrix saturated with a viscous fluid and another region with a clear viscous fluid different from the fluid in first region is studied analytically. The coupled nonlinear governing equations are solved using regular perturbation method. It is found that the presence of porous matrix in one of the region reduces the velocity and temperature. Results have been presented for a wide range of governing parameters such as Grashof number, porous parameter, angle of inclination, ratio of heights of the two layers and also the ratio of viscosities.     

Photonic control of surface anchoring on solid colloids dispersed in liquid crystals

The anchoring of liquid-crystal (LC) mesogens to the surfaces of colloids is an important factor in determining intercolloidal interactions and the symmetry of the ensuing colloidal assembly in nematic colloids. The dynamic control of surface anchoring could therefore provide a handle to tune the colloidal organization and resulting properties in these systems. In this article, we report our results on the study of thermotropic nematic LC (E7) dispersions of silica and glass microcolloids bearing photosensitive surface azobenzene groups. By the photoinduced modulation of the colloidal-LC interfacial properties, due to the trans-cis isomerization of azobenzene units, we tune the anchoring on silica colloids from homeotropic (trans-azobenzene) to homogeneous planar (cis-azobenzene) reversibly. In tune with the change in surface anchoring, the interparticle interactions were also dictated by dipolar and quadrupolar symmetries for homeotropic and homogeneous planar anchoring, respectively. In our experiments, we find that, in addition to the isomerization state of the surface-bound azobenzene units, the nature of the colloid plays a crucial role in determining the anchoring state obtained on applying photostimuli. We also study the LC anchoring on colloids as a function of the azobenzene surface density and find that beyond a threshold value the anchoring properties remain invariant.     

The role of median surface curvature in large amplitude flexural vibrations of thin shells

General conclusions regarding the non-linear vibration of structural components like curved beams, rings and thin shells are derived from the study of two specific examples, the circular ring and shallow spherical shell. It is shown that whereas the non-linear behaviour of flat plates and straight bars is generally of a hardening type, the behaviour of thin structural elements that have a finite curvature of the undeformed median surface in one or both principal axis directions may be of the hardening or softening type, depending on the structural parameters as well as on whether the shell is open or closed. It is seen that with careful judgment in the use of mode shapes of one or more terms, the resulting modal equations help one to appreciate much better the physics of the problem, whereas sophisticated mathematical models tend to obscure this.     

La2O3 promotional effect to Co3O4/γ-Al2O3 catalyst in the oxidative dehydrogenation of ethylbenzene with CO2 as soft oxidant

Co₃O₄/γ-Al₂O₃ catalysts with variable Co₃O₄ loadings (5–20 wt%) and deposition of 15% Co₃O₄ on La₂O₃/γ-Al₂O₃ were prepared by wet impregnation method. La₂O₃-γ-Al₂O₃ support with variable composition of La₂O₃ (2–6 wt%) were prepared by co-precipitation method. All the catalysts were tested for oxidative dehydrogenation of ethylbenzene with CO₂ as soft oxidant. Among the Co₃O₄/γ-Al₂O₃ catalysts, 15% Co₃O₄/γ-Al₂O₃ has shown good performance and hence this catalyst has been chosen to investigate the effect of La₂O₃ species. CO₂ pulse chemisorption data indicate more amount of CO₂ uptake over 15% Co₃O₄/4%La₂O₃/γ-Al₂O₃ catalyst which clearly indicates that this catalyst exhibits good performance in ethylbenzene dehydrogenation with CO₂ as soft oxidant because of reverse water gas shift reaction. Temperature programmed reduction studies indicate that the Co₃O₄ catalysts follow two step reduction mechanism from Co₃O₄ to CoO and then to Co and La₂O₃ promotional effect is visible through facile reduction of Co₃O₄ species. La₂O₃ doping has a vital influence in getting enhanced ethylbenzene conversion, styrene yield and alleviates catalyst deactivation compared to that of unpromoted Co₃O₄/γ-Al₂O₃ catalyst. TGA studies indicate the presence low amount coke deposition during time-on-stream over 15% Co₃O₄/4%La₂O₃/γ-Al₂O₃ catalyst compared to 15% Co₃O₄/γ-Al₂O₃ catalyst.     

Additive-free vapour-phase hydrogenation of benzonitrile over MgO-supported Ni catalysts

Research on Chemical Intermediates - MgO-supported Ni catalysts were selectively catalysed by the hydrogenation of benzonitrile to benzylamine in continuous flow at atmospheric pressure without any...     

Effect of balanced and unbalanced magnetron sputtering processes on the properties of SnO2 thin films

A comparative study has been carried on the role of balanced magnetron (BM) and unbalanced magnetron (UBM) sputtering processes on the properties of SnO₂ thin films. The oxygen partial pressure, substrate temperature and deposition pressure were kept 20%, 700 °C and 30 mTorr, respectively and the applied RF power varied in the range of 150–250 W. It is observed that the UBM deposition causes significant effect on the structural, electrical and optical properties of SnO₂ thin films than BM as evidenced by X-ray diffraction, C-V, Spectroscopic Ellipsometer and Photoluminescence measurements. The value of band gap (E_g) of the films deposited at 150 W in UBM is found as E_g = 3.83 eV which is much higher than the value of E_g = 3.69 eV as observed in BM sputtering indicating that UBM sputtering results in good crystalline quality. Further, the C-V measurements of SnO₂ thin films deposited using UBM at high power 250 W show hysteresis with large flat band shift indicating that these thin films can be used for the fabrication of memory device. The observed results have been attributed to different mechanisms which exist simultaneously under unbalanced magnetron sputtering due to ion bombardment of growing SnO₂ thin film by energetic Ar+ ions.     

A mannitol based phase selective supergelator offers a simple, viable and greener method to combat marine oil spills

Though phase selective organogelators (PSOGs) are thought to be useful for oil spill recovery, all known PSOGs require a water-miscible carrier solvent for their introduction. Providing a simple, cheap, green and practical solution to the problem of oil spills, we report a nontoxic super-PSOG that can be sprayed aerially in a carrier solvent destined to get co-congealed with the oil.