Optimization of sintering temperature in CdZnS films using reflection spectroscopy

In the present investigation, the polycrystalline films of Cd _X Zn_1–X S were prepared using a sintering technique. We coated slurry consisting of CdS, ZnS in the desired proportion—CdCl₂ (as adhesive) and ethylene glycol (as binder)—onto the glass substrates. The films were sintered at a range of temperatures in air atmosphere for the optimization of sintering temperatures using reflection spectroscopy. It was noticed that below 500°C, CdS-dominated films were obtained, and above 500°C, ZnS-dominated films were obtained. The films of desired composition giving appropriate results are obtained at 500°C. The reason is easily understood through reflection spectroscopic studies. Thus, we found 500°C to be the optimum sintering temperature and 10 min was the proper sintering time.     

Calculation of Channel Capacity Considering the Effect of Different Seasons for Higher Altitude Platform System

This paper presents effect of the weather impairments on a high altitude platform (HAP) broadband wireless communication system. It is shown that attenuation due to oxygen, water vapor, fog, cloud, and rain has significant effect on a radio link which is operating in a millimeter frequency range. Channel capacity is calculated for different seasons using Shannon’s channel capacity theorem. The location of HAP is taken to be Delhi (India). Further, it is considered that a user and the HAP platform are stationary.     

Interaction of lanthanide and actinide with BaHfO3 perovskite: A case study with cerium and uranium

Speciation of actinide (An) and lanthanide (Ln) in technologically important ceramics is very important from both fundamental as well as technological aspects. The intrinsic structural flexibility of perovskite containing AO₆ and BO₁₂ polyhedra makes them suitable and rich hosts for An and Ln. In this work, emphasis was given to deciphering information such as oxidation state, local dopant site, charge compensating defects, excited state kinetics, and so forth in BaHfO₃ (BHO) related to dopant uranium (BHO-U) and cerium (BHO-Ce). Several spectroscopic techniques namely, time-resolved photoluminescence (TRPL), positron annihilation lifetime spectra (PALS), and thermoluminescence (TL) spectroscopy coupled with density functional theory (DFT) were employed to probe the same. Ce and U though are distributed at both Ba and Hf sites, Ce prefers the former, while U prefers the latter site. Uranium on the other hand stabilizes as U⁶⁺ in the form of octahedral uranate ion giving green emission. PALS suggested the formation of defects in BHO-Ce and BHO-U with oxygen vacancies predominating in the former whereas BHO-U perovskites are loaded with cation vacancies and vacancy clusters. These cation vacancies are responsible for lower TL output in BHO-U. TL measurements also suggested cerium doping leads to a higher density of deeper traps in BHO-Ce compared to uranium doping in BHO-U which is in concurrence with DFT results and may have implications in designing afterglow phosphors based on perovskite. We believe this work would have a long-term impact on exploring the potential of perovskite for nuclear waste host and afterglow phosphors applications.     

Predicting and optimizing the heat transfer performance of radiator with functionalized graphene nanofluids

Accurately predicting the heat transfer characteristics of coolants used in thermal management of energy systems like heat exchangers, power electronics, and heating, ventilation, and air conditioning is indispensable in maintaining its operating conditions within safety limits. Apart from safety, factors such as power consumption and operating cost are the most important constraints to be considered in designing an energy-efficient and cost-effective cooling solution. In this study, the experimental data available from previous research on the use of functionalized graphene-based nanofluids in compact heat exchangers such as the automotive radiator is used to optimize the heat transfer performance parameters like Nusselt number of the nanofluid, the friction factor, and effectiveness of the heat exchanger. A supervised machine learning technique like the artificial neural network is used to obtain the objective functions of the response variables in terms of input features such as Reynolds number, Prandtl number, the volume concentration of nanoparticles in the base fluid, number of transfer units, heat capacity, the density of nanofluid, pressure drop and velocity. On the current dataset, it is found that by using the Bayesian regularization training algorithm and tangent sigmoidal activation function in the neural network, the best accuracies in the prediction can be achieved. Well-known nature-inspired optimization algorithms like genetic algorithms and simulated annealing are used in optimizing the above-mentioned response variables. Both algorithms converged to the same values of the objective functions. The optimum values of Nusselt number, effectiveness, and friction factor are 105.65, 0.506, and 0.0038, respectively, for the given composition of the nanofluid and radiator configuration.     

Exploration of radiative heat on magnetohydrodynamic rotating fluid flow through a vertical sheet

An analysis is built up for the exploration of radiative heat transport on the magnetohydrodynamic flow of rotating fluid over a vertical sheet. The inclusion of thermal radiation in conjunction with the reacting species enhances the energy as well as the solutal profiles respectively. In an advance, external heat source and applied magnetic field effects are considered for further improvement. As the magnetic Reynolds number is low, the influence of the induced magnetic field is neglected. The transformation of governing nonlinear partial differential equations into coupled nonlinear ordinary differential equations is attained with a proper supposition of similarity variables. Moreover, the solution of these transformed equations is scheduled using the “Runge–Kutta fourth-order” method numerically in association with the “shooting technique.” The simulation or various illustrating parameters affecting the flow phenomena are obtained and displayed through graphs and for numerical validation with earlier published work shows the convergence process of the methodology applied. The main findings of the study are; the Dufour number is favorable to enhance the fluid temperature throughout the domain and the destructive chemical reaction also encourages the solutal profile significantly.     

Estimation of vapour pressure and partial pressure of subliming compounds by low-pressure thermogravimetry

A method for the estimation of vapour pressure and partial pressure of subliming compounds under reduced pressure, using rising temperature thermogravimetry, is described in this paper. The method is based on our recently developed procedure to estimate the vapour pressure from ambient pressure thermogravimetric data using Langmuir equation. Using benzoic acid as the calibration standard, vapour pressure-temperature curves are calculated at 80, 160 and 1000 mbar for salicylic acid and vanadyl bis-2,4-pentanedionate, a precursor used for chemical vapour deposition of vanadium oxides. Using a modification of the Langmuir equation, the partial pressure of these materials at different total pressures is also determined as a function of temperature. Such data can be useful for the deposition of multi-metal oxide thin films or doped thin films by chemical vapour deposition (CVD).     

Hybrid polymer networks of unsaturated polyester–urethane as composite matrices for jute reinforcement

Reactions of unsaturated polyester resin and 4,4′ diphenyl methane diisocyanate were carried out at different NCO/OH ratios in presence of catalysts to form the hybrid polymer networks. Chain extender (1,4 butanediol) added in the hybrid network (NCO/OH ratio: 0.76) was optimized at a level of ～ 3 wt % only of the polyester resin. The curing of these networks was studied by a rigid body pendulum type (RPT) method in terms of reduced damping ratio and increased frequency. Lack of multiple glass transition temperatures, sharp Tan delta peak, and particulate composite type morphology clearly demonstrated the formation of phase mixed domains in the hybrid networks. The storage modulus and loss modulus master curves obtained by dynamic mechanical analysis indicate that hybrid polymer networks retained higher modulus at lower and intermediate frequencies over the polyester resin showing their superior time‐dependent response. Efficacy of these hybrid network resins was examined as matrices in the jute composites and compared with those of polyester resin and unsaturated polyester–polyurethane interpenetrating network matrices. It is found that the hybrid polymer network matrix composites exhibited superior physicomechanical properties under both dry and boiling water age test. Fractographic evidences such as fiber–matrix adhesion, hackle markings, and fiber breakage also supported their superior behavior over other composite matrices. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

SPECTROSCOPIC CHARACTERIZATION OF SOLVENT SOLUBLE FRACTIONS OF PETROLEUM VACUUM RESIDUES

ABSTRACT

NMR and FTIR spectroscopic techniques were used to investigate the effect of different solvent extraction schemes on the composition and chemical nature of species of vacuum residues of two Indian crude oils (namely Jodhpur and Heera) extractable into polar (ethyl acetate) and non-polar (n-pentane and n-heptane) solvents. The obtained soluble fractions were found to consist of mainly simple aliphatic and naphthenic ring structures, while insoluble fractions consisted primarily aromatic compounds. The results were used to draw inferences on the relative utility of different extraction schemes to upgrade vacuum residues as feedstocks for secondary conversion processes in petroleum industry.     

Pressure dependent phase transitions in (Pb,Ca)TiO3: Determination of structure using high pressure synchrotron X-ray and Raman studies

Pressure dependent studies on technologically important ferroelectric material Pb_0.70Ca_0.30TiO₃ show the occurrence of a new hitherto unreported pressure dependent phase transition around 4 GPa. In the pressure range 4–14 GPa, the parent tetragonal (P4mm) phase of Pb_0.70Ca_0.30TiO₃ transforms in to a monoclinic (Cm) phase before attaining its paraelectric cubic (Pm3m) phase around 15 GPa. High pressure Raman studies reveal the presence of a critical pressure above which the ferroelectric phase starts to reappear in the paraelectric phase. This critical pressure is found to be much lower than the critical pressure observed in pure PbTiO₃. Possible reasons for this lowering of the critical pressure are presented.