Mo-doped,Cr-Doped,and Mo–Cr codoped TiO2 thin-film photocatalysts by comparative sol-gel spin coating and ion implantation

Uniformly codoped anatase TiO₂ thin films of varying (equal) Mo and Cr concentrations (≤1.00 mol% for each dopant) were fabricated using sol-gel spin coating and deposited on fused silica substrates. All films were annealed at 450 °C for 2 h to recrystallise anatase. Undoped anatase films have been subjected to dual ion implantation for the first time, using Mo, Cr, and sequential Mo + Cr at 1 × 10¹⁴ atoms/cm². The films were characterised by GAXRD, AFM, SIMS, XPS, and UV–Vis and the performance was assessed by dye degradation. Despite the volumetric doping by sol-gel and the directional doping by ion implantation, neither method resulted in homogeneous dopant distributions. Both methods caused decreasing crystallinities and associated partial amorphisation. The XPS signal of the uniformly codoped films is dominated by undissolved dopant ions, which is not the case for the ion-implanted films. Increasing Ti valences are attributed to the fully oxidised condition of the Ti⁴⁺ ions that diffuse to the surface from Ti vacancy formation compared to the Ti valence of the bulk lattice, which contains Ti³⁺. Increasing O valence is attributed to the electronegativity of O^2?, which is higher than that of Ti⁴⁺. Detailed structural mechanisms for the solubility and energetics mechanisms involve the initial formation of Mo and Cr interstitials that fill the two voids adjacent to the central Ti ion in the TiO₆ octahedron, followed by integrated solid solubility (ISS) and intervalence/multivalence charge transfer (IVCT/MVCT). The sequential order of the last two is reversed for the two different doping methods. These two effects are likely to be the source of synergy, if any, between the two dopant ions. The photocatalytic performances of the uniformly codoped films are relatively poor and correlate well with the band gap (E_g). The performances of the ion-implanted films do not correlate with the E_g, where TiO₂–Mo performs poorly but TiO₂–Cr and TiO₂–Mo–Cr outperform the undoped film. These results are interpreted in terms of the competition between the effects of Mo doping, which causes partial amorphisation and/or blockage of active sites, and Cr doping, which may cause Mo–Cr synergism, Cr-based heterojunction formation, and/or improved charge-carrier separation owing to the surface-deposition nature of ion implantation.     

Comparative study of dielectric and electro-optical properties of pure and polymer ferroelectric liquid crystal composites

The ferroelectric liquid crystals (FLCs) displays normally suffer from less contrast ratio and vision angle. To produce high optical contrast and colors in FLC displays, Guest-host mode is widely used. Addition of a small amount of polymer in the pure FLC results in considerable change in its dielectric and electro-optical properties. In the present paper we have investigated the effect of adding polymer (PMMA) on the FLC material (Felix 17/100). Polymer doped FLC composites (FLCPC) has been prepared by the dispersion of 1% wt/wt concentration of polymer in pure FLC. Planar aligned cells have been used to study dielectric and electro-optical properties in SmC* phase of both the samples i.e. pure FLC and FLCPC. Considerable change in various properties like spontaneous polarization, anchoring parameters, Goldstone mode relaxation time and relaxation strength have been noticed for both the samples. These changes have been explained by considering polymer network formed in the FLC matrix.     

Efficient Generation of Electricity from Methane using High Temperature Fuel Cells – Status,Challenges and Prospects

High temperature fuel cells (HTFCs), comprising solid oxide fuel cells and molten carbonate fuel cells, present efficient means for generating electricity from methane and natural gas. The high quality heat generated by HTFCs allows operation in the combined heat and power mode (CHP) to further enhance efficiency. The overall fuel-to-electricity conversion efficiency of an HTFC system operating in CHP mode can approach up to 80 %. Despite the high operating efficiency of HTFCs, high capital costs and durability issues have hindered their widespread commercialization. This article provides an overview of the operating principles, technical challenges, commercialization status of HTFCs, and outlines the strategies being adopted to lower capital costs and increase durability.     

Removal of mercury(II) from aqueous solutions and chlor-alkali industry wastewater using 2-mercaptobenzimidazole-clay

The 2-mercaptobenzimidazole loaded natural clay was prepared for the removal of Hg(II) from aqueous media. Adsorption of the metal ions from aqueous solution as a function of solution concentration, agitation time, pH, temperature, ionic strength, particle size of the adsorbent and adsorbent dose was studied. The adsorption process follows a pseudo-second-order kinetics. The rate constants as a function of initial concentration and temperature were given. The adsorption of Hg(II) increased with increasing pH and reached a plateau value in the pH range 4.0-8.0. The removal of Hg(II) was found to be >99% at an initial concentration of 50 mg/l. Mercury(II) uptake was found to increase with ionic strength and temperature. Further, the adsorption of Hg(II) increased with increasing adsorbent dose and decrease with adsorbent particle size. Sorption data analysis was carried out using Langmuir and modified Langmuir isotherms for the uptake of metal ion in an initial concentration range of 50-1,000 mg/l. The significance of the two linear relationships obtained by plotting the data according to the conventional Langmuir equation is discussed in terms of the binding energies of the two population sites involved which have a widely differing affinity for Hg(II) ions. Thermodynamic parameters such as changes of free energy, enthalpy, and entropy were calculated to predict the nature of adsorption. It was found that the values of isosteric heat of adsorption were varied with surface loading. The chlor-alkali industry wastewater samples were treated by MBI-clay to demonstrate its efficiency in removing Hg(II) from wastewater.     

Phase transition studies of polymer–liquid crystal composite using dielectric and optical transmittance techniques

Dielectric properties of polymer–liquid crystal composite comprised of the polymer poly(methyl methacrylate) and low‐molecular mass liquid crystal, cholesteryl palmitate are investigated in the frequency range from 1 kHz to 10 MHz and in the temperature range of 27–120°C. The dielectric permittivity and dielectric loss shows substantial changes with the addition of polymer. The significant feature is that the pure liquid crystal exhibits broad absorption, showing dielectric relaxation in the range of 10 – 100 kHz whereas the composite shows relaxation peaks at 10 MHz. The percentage optical transmittance of pure liquid crystal and composite have also been measured and compared to study its phase transition behavior. The smectic phase observed in the pure liquid crystal is suppressed on formation of polymer composites. The mass spectrometry measurement does not show any abduct formation between the pure liquid crystal and the composite. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Flow and thermal analysis of Oldroyd 8 constant fluid in a porous channel

The present research is based on the thermal and flow properties of the viscoelastic Oldroyd 8 constant fluid in an upright microchannel. The energy and momentum equations were solved with the support of temperature Jump and velocity slip boundary conditions. To measure the irreversibility rate of the flow system, the acquired results of velocity and thermal equations were used. To crack the current mathematical model problem, the numerical Runge–Kutta–Fehlberg method was used. With the aid of graphs, the effect of physical parameters such as thermal radiation, thermal-dependent heat source, Joule heating, fluid parameters, velocity slip, and temperature Jump parameters on the fluid flow, thermal energy, and system entropy generation was discussed. Fluid parameters have different effects on the velocity profile. The Grashof and Hartmann numbers demonstrate opposite effects on the momentum field. The thermal energy of the system reduces with thermal radiation and temperature Jump factor. The thermal radiation, Hartmann number, and temperature Jump parameters reduce the system's irreversibility rate. With the Brinkman number and temperature Jump parameter, the irreversibility ratio increases.     

Volume modelling for emerging manufacturing technologies

The next generation manufacturing technologies will draw on new developments in geometric modelling. Based on a comprehensive analysis of the desiderata of next generation geometric modellers, we present a critical review of the major modelling paradigms, namely, CSG, B-Rep, non-manifold, and voxel models. We present arguments to support the view that voxel-based modellers have attributes that make it the representation scheme of choice in meeting the emerging requirements of geometric modelling.     

Simultaneous Design and Control of Stiffened Laminated Composite Structures

The problem investigated here concerns the simultaneous design and control of structures. The structure considered is a laminated stiffened composite plate for which an optimum control system is designed by the minimization of an appropriate performance index with respect to both the control forces and structural design variables consisting of stiffener areas and the number of plies of a given orientation. To ensure a physically realistic structure appropriate constraints on the stiffener sizes, total weight, and structural frequencies are imposed. Nonlinear mixed‐integer programming is used to force the number of plies to take on integral values. The entire problem is posed as a three‐level optimization problem. Using the well‐known independent modal space control method, effects of plate geometry, initial disturbance conditions, and control effort penalty parameters on the optimal design are considered. The minimization process requires derivatives of eigenvalues and eigenvectors with respect to the design variables. These derivatives can be computed by an involved analytical procedure or a relatively simple finite‐difference procedure. This paper also examines the computer cost‐effectiveness of these two procedures for the sensitivity‐derivative calculations.     

Enrichment of phosphatidyl choline – alcohol fractionation of carbon dioxide de-oiled lecithin from soybean (Glycine max)

Crude soylecithin was extracted with carbon dioxide at pressures of 120, 200, 240, 280 and 320 bar (12, 20, 24, 28 and 32 MPa, respectively) and at a temperature of 40°C to obtain de-oiled lecithin. The amount of phospholipids (acetone insoluble) increased with increasing pressure. The carbon-dioxide-extracted lecithin (CDEL) was fractionated with alcohol into alcohol-soluble and alcohol-insoluble fractions. Depending on the pressure, the alcohol-soluble fraction of CDEL was found to contain up to 70.0% phosphatidyl choline as against 21.1% present in crude lecithin. The alcohol-insoluble fraction of CDEL was found to contain up to 37.1% phosphatidyl inositol as against 12.3% in crude lecithin. The chemical parameters of CDEL and the alcohol-soluble and alcohol-insoluble fractions were evaluated.     

Climate Variability Influences on Hydrological Responses of a Large Himalayan Basin

The hydrological cycle, a fundamental component of climate is likely to be altered in important ways due to climate change. In this study, the historical daily runoff has been simulated for the Chenab River basin up to Salal gauging site using a simple conceptual snowmelt model (SNOWMOD). The model has been used to study the impact of plausible hypothetical scenarios of temperature and rainfall on the melt characteristics and daily runoff of the Chenab River basin. The average value of increase in snowmelt runoff for T + 1°C, T + 2°C and T + 3°C scenarios are obtained to be 10, 28 and 43%, respectively. Whereas, the average value of increase in total streamflow runoff for T + 1°C, T + 2°C and T + 3°C are obtained to be 7, 19 and 28%, respectively. Changes in rainfall by −10 and + 10% vary the average annual snowmelt runoff over the T + 2°C scenario by −1% and + 1% only. The result shows that melt is much more sensitive to increase in temperature than to rainfall.