Combustion Synthesis of Metal Chromite Powders

Fine-particle metal chromites (MCr₂O₄, where M = Mg, Ca, Mn, Fe, Co, Ni, Cu, and Zn) have been prepared by the combustion of aqueous solutions containing the respective metal nitrate, chromium(III) nitrate, and urea in stoichiometric amounts. The mixtures, when rapidly heated to 350°C, ignite and yield voluminous chromites with surface areas ranging from 5 to 25 m²/g. MgCr₂O₄, sintered in air at 1500°C for 5 h, has a density of 4.0 g/cm³.     

Silver doping: A potential means to grow high quality YBa2Cu3O7?x thin films on bare sapphire

High qualityAg-doped YBa₂Cu₃O_7–x (YBCO) thin films have been grown by laser ablation on ¯1012 bare sapphire. This work demonstrates thatAg-doping can be used as very convenient means to realize good quality YBCO films on highly coveted sapphire substrates for microwave applications of highT _c thin films.     

Two-Dimensional Siloxene–Graphene Heterostructure-Based High-Performance Supercapacitor for Capturing Regenerative Braking Energy in Electric Vehicles

The development of high-performance electrodes that increase the energy density of supercapacitors (SCs) (without compromising their power density) and have a wide temperature tolerance is crucial for the application of SCs in electric vehicles. Recent research has focused on the preparation of multicomponent materials to form electrodes with enhanced electrochemical properties. Herein, a siloxene–graphene (rGO) heterostructure electrode-based symmetric SC (SSC) is designed that delivers a high energy density (55.79 Wh kg⁻¹) and maximum power density of 15 000 W kg⁻¹. The fabricated siloxene–rGO SSC can operate over a wide temperature range from –15 to 80 °C, which makes them suitable for applications in automobiles. This study shows the practical applicability of siloxene–rGO SSC to drive an electric car as well as to capture the braking energy in a regenerative brake-electric vehicle prototype. This work opens new directions for evaluating the use of siloxene–rGO SSC as suitable energy devices in electric vehicles.     

Efficient hydrogen evolution catalysis triggered by electrochemically anchored platinum nano-islands on functionalized-MWCNT

We report the electrochemical deposition (ECD) of platinum nano-islands (Pt NIs) on functionalized multi-walled carbon nanotubes (ECD Pt NIs@f-MWCNT) as an efficient electrocatalyst for the hydrogen evolution reaction (HER). Pristine MWCNT was acid treated to induce the number of oxygen functional groups on the surface and enhances the wettability. Thereafter, Pt nanoparticles (Pt Nps) were deposited by a simple electrodeposition technique on the oxygen enriched MWCNT surface. The Pt NIs@f-MWCNT has been physicochemically characterized using X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy and X-ray photoelectron Spectroscopy (XPS). The TEM analysis showed the presence of Pt NIs on MWCNT wherein, the NIs were made up of small Pt nanoclusters of ～4 nm in dimension. The electrochemical HER studies were carried out using linear sweep voltammetry (LSV), Tafel polarization and electrochemical impedance spectroscopy (EIS). An overpotential (?) of ?84 mV was obtained at a current density (j) of ?10 mA/cm². The amount of Pt loading has been optimized through electrodeposition. Enhanced HER activity was observed with a Pt loading of 3.8 μg/cm². In order to ascertain the durability of the catalyst, accelerated degradation test (ADT) was carried out for 10,000 cycles at a scan rate (?) of 100 mV/s. The turnover frequency (TOF) was estimated to be 6.3 s^?1 at ? = ?70 mV.     

New approaches for modelling subgrade nonlinearity in thin surfaced flexible pavements

The primary objective of this paper is to present new methods in characterising flexible pavements that possess nonlinear subgrade behavior using deflection data from falling weight deflectometer (FWD). The two techniques to be introduced are Simplified Deflection Modeling and Deflection Ratio (DefR) approach. FWD deflection data can be modelled accurately using an exponential curve in a mathematical form of Y = K₁ exp (?r/K₂). K₁ is equal to deflection at D₀ in micron and K₂ is the structural parameter at the respective sensor location. K₂ parameter is found to have a direct relationship with the material constant, value of the subgrade and it is taken as a measurement of the nonlinearity of the pavement layer. As K₂ increases and approaches 500, the pavement structure is observed to possess linear elastic behaviour. In the second method, the DefR is defined as the ratio of the FWD deflection of a sensor divided by the deflection of the preceding sensor. For pavements that exhibit nonlinear subgrade behavior, the DefR shows an increasing trend for FWD sensors located at 300mm and beyond. The two techniques have provided alternative approaches for modelling subgrade nonlinearity.     

Implementation of Cognitive Radio Model for Agricultural Applications Using Hybrid Algorithms

Wireless Personal Communications - In recent days there the farmers who are having enormous expanses of land are facing heavy loss due to sudden changes like monsoon and presence of high amount of...     

High-performance platinized carbon electrodes for oxygen reduction in power sources with alkaline electrolytes

A high-performance, oxygen-reducing electrode, made from physically and chemically tailored coconut-shell charcoal substrate catalysed with 7 wt.% platinum, is reported. The electrode can be loaded with current densities of 2000 – 5200 A/m², with negligible deterioration, for periods of up to 1200 h. Extensive electron spectroscopic studies have been conducted to characterise the electroactive species present on the surface of the electrodes during service.     

Oxygen-reducing porous carbon electrode for electrochemical power sources with alkaline electrolytes

The performance of electrodes made from coconut-shell charcoal in alkaline fuel cells and metal/air batteries is reported. The electrode can be loaded