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The evolution of the dark energy within the scope of a spatially homogeneous and isotropic Friedmann–Robertson–Walker model filled with barotropic fluid and dark energy is examined. We have considered the two cases of an interacting and non-interacting two-fluid (barotropic and dark energy) scenario and obtained the exact solutions to the corresponding field equations. In an interacting model, we have considered linear as well as quadratic interaction between dark sectors of the universe. We have also given the quadrature form for general interaction coupling parameter via Q = αρ m n, n ⩾ 1 and discussed the evolution of energy densities and effective equation of state with cosmic time for flat, closed, and open universes. It is also examined that the matter energy density is dominated in early phase of the universe, whereas the dark energy density is dominated in later phase of the universe for both scenarios, which is in concurrence with current observations.

The Casson fluid model, which is very significant in the biomechanics and polymer processing industries, is another term used to describe non-Newtonian fluid behavior. This study of Casson fluid model on unsteady MHD Casson fluid flow with Soret-Dufour effect past a vertical plate embedded in porous medium in the presence of radiation with heat generation/absorption and viscous dissipation is presented in this research article as a numerical investigation of non Newtonian Casson fluid with applied effects. Regulating partial differential equations have been used to explain the mathematical model of the flow field. The Crank-Nicolson implicit finite difference approach has been used to numerically solve non-dimensionalized flow field governing equations. Concentration, temperature, and velocity profile effects of non-dimensional factors have been investigated using tables and graphs as aids. Tables have also been used to observe fluctuations in factors like skin friction, the Nusselt number, and the Sherwood number in relation to other parameters.

The aim of this paper is to introduce matrix polynomials L(M,?,?) n (x) and establish some properties viz, hypergeometric representation, generating matrix relations, integral representations, recurrence relations, summation formulas, series relation, fractional integral and derivative operators.

Development and demonstration of soluble lead redox flow battery (SLRFB) is hindered due to its limited cycle life caused by the formation of lead dendrites, oxygen evolution reaction (OER), and accumulation of PbO2 sludge. OER leads to an imbalanced deposition of Pb metal at anode and PbO2 at cathode. As a result, complete oxidation of Pb is stalled during discharge of SLRFB. Besides, sluggish kinetics of cathode reaction results in accumulation of PbO2. Due to incomplete dissolution and accumulation of both active materials, concentration of Pb2+ decreases continuously in the electrolyte. Under such conditions, repeated charge–discharge cycling leads to the failure of SLRFB. In this study, we propose and demonstrate a novel route of using an auxiliary gas-diffusion electrode to obviate these problems to help in extending the cycle life of SLRFB. The auxiliary electrode is operated either as an air electrode or a hydrogen electrode. When the auxiliary electrode is an air electrode, it is used as positive electrode, and on coupling with anode of SLRFB, it forms a galvanic Pb–air flow cell that on discharge helps in oxidizing Pb metal to Pb2+ ions. When the auxiliary electrode is a hydrogen electrode, it is used as negative electrode, and on coupling with cathode of SLRFB, it forms a galvanic H2–PbO2 flow cell which on discharge reduces PbO2 to Pb2+ ions and mitigates the adverse effect of sludge accumulation in SLRFB.

The present work explains the engine performance using waste cooking oil (WCO) blended with diesel. The viscosity of WCO can be reduced to be comparable with diesel by preheating at 90°C and thus improves the engine combustion efficiency. For the purpose of preheating, a shell and tube heat exchanger were designed. The optimized tube and shell diameters of the heat exchanger were estimated as 17 and 460 mm, respectively. Pressure drops in tube and shell sides changed from 28.40 - 27.40 Pa and 0.025 - 0.1 Pa respectively. Flue gas energy contents varied from 4000 W to 16000 W at the mass flow rate of 0.03-0.08 kg/s. Useful energy gained by the heat exchanger for waste cooking oil preheating varied from 1200-5500 W at 1200-3000 rpm. Kinematic viscosity for WCO was 51.85 cSt and it changed to 7.55 - 17.5 cSt for blends of 10 - 30% with diesel at 40°C. As the blending % of WCO with diesel increased, there was a minor drop in brake power because of lower calorific value of the mixture. There was a minor increment of torque because of preheating. Preheated fuel blends injection into the cylinder facilitated better fuel efficiency. Minimum and maximum values of exhaust gas temperature were 345°C and 385°C at 1200 and 3000 rpm of engine speeds respectively.

The objective of this paper is to introduce the effect of Soret-Dufour, a higher-order chemical reaction on MHD Casson fluid with a heat source/sink over a vertical plate embedded in a porous medium. The observation reveals different parts of the flow of Casson fluid, heat, and mass transfer. Crank-Nicolson finite difference method utilized for solving Non-dimensional governing partial differential equations. Computations are executed graphically to analyze the change of velocity, temperature, and concentration as well as Skin-friction, Nusselt number, and Sherwood number for different values of parameters Dufour number Du = 0.2, Chemical reaction parameter Kr = 1.2, heat source/sink parameter Q = 2, Schmidt number Sc = 0.6, Soret number Sr = 1.5, order of chemical reaction n = 2, radiation parameter R = 2.2, magnetic parameter M = 4.8, Casson parameter β = 0.4, t = 0.2, Gr = 4, Gm = 7, K = 1.5 and P r = 0.7.

As CO2 is emerging as an environment friendly working fluid its applicationin high temperature engine’s waste heat recovery systems is found to bemore suitable than other hydrocarbons. This paper presents a performancecomparison of two systems based on transcritical Rankine cycle using CO2as working fluid. A heavy-duty truck is opted for analysis in which coolantis used to preheat CO2 and further the engine exhaust is used to transferthe heat to main heater. The System-1 and System-2 having single and dualloop based transcritical Rankine cycle are analysed. The independent param-eters taken for the investigative analysis are turbine inlet temperature (TIT),pressure ratio and effectiveness of heat exchangers. Comparison results showthat System-2 is producing 11.8 kW more power than system-1 at 12 MPapressure ratio and at 489◦C TIT. However, under same conditions, system-1 ishaving 16.88% of thermal efficiency which is higher than system-2 by around3%. Further, the Engine coolant utilization rates when compared are nearlysame in both the systems, the exhaust gas utilization rate came out higherfor System-2. In respect of exergy destruction, system-1 shows maximumdestruction in regenerator and System-2 in heater-2.

Connectivity in rural areas is a key aspect of its holistic development. Rural roads are low traffic volume roads. In this paper, study has been done on the construction methodology of rural roads using local resources i.e., local labour, local materials etc. Locally available stones, cobbles, plum etc. have been used with concrete mix. This study throws light on three types of rigid pavements which follow the evolution of Roman road construction methods. These are Cobblestone pavements (CSPs), Plum Concrete pavements (PCPs) and Unreinforced Concrete pavements (UCPs). This paper discuss about the materials used and the construction methodology of all these three types of rigid pavement. The paper also presents an outline of locally available materials which helps in reducing the overall cost of construction of pavements

Ceramic compositions of (Ba1-xCdx)(Zr0.13Ti0.87)O3 with x = 0, 0.02, 0.04 and 0.06 exhibit a layered microstructure and enhanced grain growth (~ 50 µm for x = 0.06). The XRD and Raman measurements reveal the coexistence of rhombohedral, orthorhombic and tetragonal phase, and with increase in Cd content the rhombohedral phase fraction increases significantly (10–56%) whereas the phase fraction of tetragonal decreases (62–14%). Pyroelectric coefficient (p) increases with Cd content and a large value of p ~ 1841 μCm−2 K−1 is obtained for x = 0.06. Current responsivity Fi is maximum (~ 849 pmV-1) for x = 0.02, whereas the voltage responsivity Fv (~45 ×10−3 m2 C−1), detectivity Fd (~48 μPa−1/2) and thermal energy harvesting figure of merit Fe* (~34 pJ−1 m3) are maximum for x = 0.06. Ease of polarization rotation in the polymorphic state due to the coexistence of rhombohedral, orthorhombic and tetragonal phases, and a large ceramic grain size contribute to the strong pyroelectric response.

Cadmium doped barium zirconate titanate (Ba 1−x Cd x )(Zr 0.13 Ti 0.87 )O 3 (BCDZT) ferroelectric ceramic compositions with x =0, 0.02, 0.04 and 0.06 have been prepared by solid state reaction method. X-ray diffraction studies reveal a pseudocubic structure. For increasing Cd content, the bulk ceramic micro-structure reveals an increasing grain size and density. Variations in the dielectric, piezoelectric and unipolar electric field induced strain characteristics are discussed. Increasing Cd content reduces the coercive field, increases the remnant polarization and does not affect the ferroelectric-paraelectric phase transition temperature (~60 °C). An optimum Cd content x =0.06 produces highly resistive ceramics with low dielectric loss (tan δ =0.019), and a maximum value of piezoelectric charge constant d 33 =114 pC/N and unipolar electro-strain of ~0.07%.

Nickel ferrite (NiFe 2 O 4 ) powders derived by auto-combustion synthesis using three different fuels (citric acid, glycine and dl -alanine) have been characterized. The sintering behavior of ceramics using these powders has been compared. Oxygen balance (OB) setting for the chemical reaction is found to regulate the combustion reaction rate. A rapid reaction rate and a high flame temperature are achieved with d l alanine fuel yielding single phase NiFe 2 O 4 powder in the as-burnt stage, whereas powders derived with citric acid and glycine fuels show poor crystallinity and necessitate post-annealing. The powder particles are largely agglomerated with a non-uniform distribution in shape and size, and the average particle size is estimated in the range ~ 54–71 nm. Powders derived from dl -alanine fuel show better phase purity, smaller crystallite size, larger surface area and superior sintering behavior. Additional Raman modes discerned for dl -alanine derived powder support a 1:1 ordering of Ni 2+ and Fe 3+ at the octahedral sites relating to microscopic tetragonal P 4 1 22 symmetry expected theoretically for the formation of NiFe 2 O 4 with inverse spinel structure. Microstructure of sintered ceramics depends on the precursor powders that are used and sintering at 1200 °C is found to be optimum. Citric acid and glycine derived powders yield high saturation magnetization ( M s ~47–49 emu/g), but poor dielectric properties, whereas dl -alanine derived powders yield ceramics with high resistivity (~3.4×10 8 Ω cm), low dielectric loss (tan δ ~0.003 at 1 MHz) and high magnetization (46 emu/g). Dielectric dispersion and impedance analysis show good correlation with the changes in the ceramic microstructure.

Dielectric and magnetic properties of NiFe2O4 ceramics prepared with powders using DL-alanine fuel in the sol–gel auto combustion technique are studied. DL-alanine fuel yields crystalline as-burnt powders, and when used for ceramic processing yields varying microstructure at different sintering temperatures. The dielectric properties are influenced by the resulting microstructure and the magnetic properties show slight change in saturation magnetization Ms (~44 – 46 emu/g). The coercive fields, dielectric losses and dispersion are reduced considerably at higher sintering temperatures (1200–1300 °C). The influence of changing microstructure is analyzed through dielectric response, complex impedance analysis and electrical modulus spectroscopy in the frequency range (10−2–107 Hz) to understand the interactions from the grain and grain boundary phases. Sintering at 1200 °C, is found to be optimum, yields lower losses & reduced dielectric dispersion, and high resistivity (3.4×108 Ω cm).

In this paper, we study the general class of Bianchi cosmological models with holographic dark energy component. We have discussed three types of solutions of the average scale factor for the general class of Bianchi cosmological models by using a special law for the deceleration parameter, which is linear in time with a negative slope. The exact solutions to the corresponding field equations are also obtained. All the physical parameters are calculated and discussed in each physically viable cosmological model. For large time (i.e., t → ∞) the models tend asymptotically to an isotropic Friedmann–Robertson–Walker cosmological model. Quintessence scalar field and quintessence potential are also obtained for three different scenarios of scale factor.

The present study is undertaken to develop area specific weather forecasting models based on time series data for Pantnagar, Uttarakhand. The study was carried out by using time series secondary monthly weather data of 27 years (from 1981-82 to 2007-08). The trend analysis of weather parameters was done by Mann-Kendall test statistics. The methodologies adopted to forecast weather parameters were the winter’s exponential smoothing model and Seasonal Autoregressive Integrated Moving Average (SARIMA). Comparative study has been carried out by using forecast error percentage and mean square error. The study showed that knowledge of this trend is likely to be helpful in planning and production of enterprises/crops. The study of forecast models revealed that SARIMA model is the most efficient model for forecasting of monthly maximum temperature, monthly minimum temperature and monthly humidity I. The Winter’s model was found to be the most efficient model for forecasting Monthly Humidity II but no model was found to be appropriate to forecast monthly total rainfall.

Lead-carbon hybrid ultracapacitors comprise positive lead dioxide plates of the lead-acid battery and negative plates of carbon-based electrical double-layer capacitors (EDLCs). Accordingly, a lead-carbon hybrid ultracapacitor has the features of both the battery and that of an EDLC. In this study, the development and performance comparison between the two types of lead-carbon hybrid ultracapacitors, namely those with substrate-integrated and conventional pasted positive plates, is presented as such a study is lacking in the literature. The study suggests that the faradaic efficiencies for both types of lead-carbon hybrid ultracapacitors are comparable. However, their capacitance values as well as energy and power densities differ significantly. For substrate-integrated positive plate hybrid ultracapacitor, capacitance and energy density values are lower, but power density values are higher than pasted positive plate lead-carbon hybrid ultracapacitors due to their shorter response time. Accordingly, internal resistance values are also lower for substrate-integrated lead-carbon hybrid ultracapacitors. Both types of lead-carbon hybrid ultracapacitors exhibit good cycle life of 100,000 pulse charge-discharge cycles with only a nominal loss in their capacitance values.

The present work investigated microstructural stability and its concurrent effect on mechanical and electrical properties of hot-rolled Cu–8Cr–4Nb alloy samples at high temperatures (600, 800 and 1000 °C) for holding durations up to 50 h. The hot-rolled samples were prepared from the near-theoretical-density hot-pressed alloy, which was made from gas-atomized powders. The hot-rolled alloy showed excellent retention of grain size due to pining of the grain boundaries, induced by the fine and homogeneously distributed stable Cr 2 Nb dispersoids. The yield strength and ultimate tensile strength of the samples showed no appreciable change at 600 °C and 800 °C even after 50 h, whereas, YS and UTS dropped slightly on exposure of the sample to 1000 °C for 50 h due to grain growth and coarsening of precipitates. The electrical conductivity of the samples remained almost unchanged with a slight improvement with prolonged exposure at higher temperatures.

As stakes are very high, a space programme places one of the highest priorities on the integrity of structural materials and Indian space programme is no exception to this. Starting from design of process, an exhaustive series of structural simulations, mechanical and structural tests and inspection-steps at room, elevated and cryogenic temperatures are followed during qualification and acceptance of structural materials for space applications. A continuous effort of space material-scientists is to adopt the emerging advanced destructive and non-destructive testing methods in order to enhance the reliability of structures. In the second phase of Indian space programme, high temperature materials are poised to play increasingly more important role. This in turn, calls upon the scientists to develop a variety of thermo-structural materials based on dispersion strengthened alloys, ceramic matrix composites, intermetallics, ultra high temperature ceramics etc. Keeping pace with these developments, a host of characterization techniques are being evolved and facilities are being established to ensure the thermo-structural integrity of high temperature materials. The paper presents the whole gamut of important structural and thermo-structural materials that are presently in use or under development for the future missions of ISRO. It also includes the testing methodologies being adopted at VSSC/ISRO for qualifying these materials from the structural integrity point of view.

The present study is on the effect of mechanical milling of gas-atomized powders on mechanical properties of the hot-pressed and subsequently hot-rolled Cu–8 at% Cr–4 at% Nb alloy with a microstructure consisting of pure copper matrix hardened by intermetallic Cr 2 Nb precipitates. The mechanically milled powders result in lower sintering temperature during hot pressing compared to the atomized powders. The hot-pressed samples made from the milled powder exhibit significantly higher hardness and tensile strength, but lower ductility and electrical conductivity compared to that made from the un-milled gas-atomized powders. The hot rolling results in marginal increase in strength, but significant increase in ductility compared to the hot-pressed alloy for both the milled and atomized powders and it is attributed to the decrease in size of the pores and amount of porosities after hot rolling.

The densification behavior of dispersion hardened Cu–Cr–Nb alloy powders has been studied by spark plasma sintering using varying stress and temperature. The densification has been strongly inhibited by the presence of intermetallic Cr 2 Nb precipitates. The mechanically milled powders with disk shaped nature have resulted in higher relative density as compared to spherical shaped gas atomized powders in all the experiments. The hardness and compressive yield strength of the sintered alloy samples have been found to have a linear relationship with relative density and it was independent of process parameters for both the atomized and milled powders.

Fe/Fe3O4/Graphene composite electrode material was synthesized by a thermal reduction method and then used as anode material along with Nickel cathode in rechargeable Ni/Fe alkaline batteries in hybrid electric vehicles. Reduced graphene /Fe/Fe3O4 composite electrode material was prepared using a facile three step synthesis involving synthesis of iron oxalate and subsequent reduction of exfoliated graphene oxide and iron oxalate by thermal decomposition method. The synthesis approach presents a promising route for a large-scale production of reduced graphene /Fe/Fe3O4 composite as electrode material for Ni/Fe rechargeable batteries. The particle size and structure of the samples were characterized by SEM and XRD.

Copper (Cu) matrix composites reinforced with 0.2, 5 and 10. vol% single wall carbon nanotubes (SWCNT) and 5 and 10. vol% multi-wall carbon nanotubes (MWCNT) were processed by high energy milling of pure copper powder with carbon nanotubes (CNTs) and subsequent consolidation by vacuum hot pressing. Microstructural observations of the sintered composites revealed equiaxed twinned microstructure for 0.2. vol% SWCNT composite and elongated grain structure, with CNT layers in between, in composites having higher CNTs content. The porosity in the composites was associated with CNT layers. The distribution of CNTs was found to be different in axial and transverse directions. Significant improvement in hardness of Cu-SWCNT composite was observed with increase in CNTs content. Whereas, in case of MWCNT composite, hardness reduced for 10. vol% CNT composites. Compression strength of the SWCNT samples was found to be higher than the MWCNT reinforced samples. � 2012 Elsevier B.V.

The purposes of this study were to revisit the utility of ultrasonography (USG) as a primary imaging modality in acute appendicitis (AA) and to establish the role of CT scan as a second-line/problem-solving modality. All cases of suspected AA were referred for urgent USG. USG was done with standard protocol for appendicitis. Limited computed tomographic (CT) scan [NCCT ± CECT (IV contrast only)] was done for the lower abdomen and pelvis where sonographic findings were equivocal. One hundred and twenty-one patients were referred for USG for suspected appendicitis. Eight-four patients underwent surgery for AA based on clinical as well as imaging findings, of whom 76 had appendicitis confirmed at histopathology. Three patients were misdiagnosed (3.6 %) on USG as appendicitis. Of 76 patients of appendicitis confirmed histopathologically, 63 (82.8 %) had features of appendicitis on USG and did not require any additional imaging modality. Of 121 patients, 12 (10 %) needed CT scan because of atypical features on USG. Of these 12 patients, seven had retrocecal appendicitis, and three high-up paracolic appendicitis. USG alone had sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of 81, 88, 92.6, 71.6, and 83 %, respectively. When combined with CT scan in select cases, the sensitivity, specificity, PPV, NPV, and accuracy of combined USG + CT scan were 96 % (P = 0.0014), 89 %, 93 %, 93.5 % (P = 0.0001), and 93 % (P = 0.0484), respectively. Twenty-eight (23 %) patients were given alternative diagnosis on USG. Dedicated appendiceal USG should be used as a primary imaging modality in diagnosing or excluding AA. Appendiceal CT can serve as a problem-solving modality.

Layered LiNi0.8Co0.2O2 crystallizing in R (3) over barm space group is synthesized by decomposing the constituent metal-nitrate precursors. Oxidizing nature of metal nitrates stabilizes nickel in +3 oxidation state, enabling a high degree of cation ordering in the layered LiNi0.8Co0.2O2. The powder sample characterized by XRD Rietveld refinement reveals

Synthesis and structure of new (Bi, La)(3)MSb(2)O(11) phases (M = Cr, Mn, Fe) are reported in conjunction with their magnetic and photocatalytic properties. XRD refinements reflect that Bi(3)CrSb(2)O(11), Bi(2)LaCrSb(2)O(11), Bi(2)LaMnSb(2)O(11) and Bi(2)LaFeSb(2)O(11) adopt KSbO(3)-type structure (space group, Pn (3) over bar). The structure can be described through three interpenetrating networks where the first is the (M/Sb)O(6) octahedral network and other two are the identical networks having Bi(6)O(4) composition. The magnetic measurements on Bi(2)LaCrSb(2)O(11) and Bi(2)LaMnSb(2)O(11) show paramagnetic behaviour with magnetic moments close to the expected spin only magnetic moments of Cr(+3) and Mn(+3). The UV-Visible diffuse reflectance spectra are broad and indicate that these materials possess a bandgap of similar to 2 eV. The photocatalytic activity of these materials has been investigated by degrading Malachite Green (MG) under exposure to UV light.

The dielectric properties of lead lanthanum zirconate titanate (PLZT) ceramics (Pb(Zr0·57Ti0·43)O3 + x at% of La, x = 3, 5, 6, 10 and 12) have been measured in the frequency range 1 Hz-1 MHz using the vector impedance spectroscopy (VIS) at different temperatures. All the compositions show both non-dispersive and disper- sive dielectric responses in different temperature regions. The non-dispersive region obeys the universal dielectric response. A low frequency (

The compositions of lead lanthanum zirconate titanate PLZT [Pb(Zr0.57Ti0.43)O3 + x at% of La, where x = 3, 5, 6, 10 and 12] have been synthesized using mixed oxide route. The temperature dependent electromechanical parameters have been determined using vector impedance spectroscopy (VIS). The charge constant d 31 and elastic compliance s 11 show a peak in all the samples at a temperature T mt much below the ferroelectric — paraelectric transition temperature, whereas the series resonance frequency f s shows a dip at these temperatures. The Poisson’s ratio σ E increases with temperature T showing a broad peak at a temperature higher than T mt . The voltage constant g 31 decreases and the planar coupling coefficient K p remains constant up to half of the T mt and then falls sharply with T. Half of the T mt can, therefore, be used for specifying the working temperature limit of the piezoceramics for the device applications.

2 V/40 Ah valve-regulated lead-acid (VRLA) cells have been constructed with negative plates employing carbon black as well as an admixture of carbon black fumed silica as additives in negative active material for partial-state-of-charge (PSoC) applications. Electrical performance of such cells is compared with conventional 2 V/40 Ah VRLA cells for PSoC operation. Active material utilization has been found to be higher for carbon-black fumed-silica mixed negative plates while formation is faster for cells with carbon-black mixed negative plates. Both faradaic efficiency and percentage capacity delivered have been found to be higher for cells with carbon-black + fumed-silica mixed negative plates. However, a high self-discharge rate is observed for cells with carbon-black + fumed-silica mixed negative plates.

The lead-acid battery is often the weakest link in photovoltaic (PV) installations. Accordingly, various versions of lead-acid batteries, namely flooded, gelled, absorbent glass-mat and hybrid, have been assembled and performance tested for a PV stand-alone lighting system. The study suggests the hybrid VRLA batteries, which exhibit both the high power density of absorbent glass-mat design and the improved thermal properties of the gel design, to be appropriate for such an application. Among the VRLA-type batteries studied here water loss for the hybrid VRLA batteries is minimal and charge-acceptance during the service at high temperatures is better in relation to their AGM counterparts.

Nickel-iron and iron-air batteries are attractive for large-scale-electrical-energy storage because iron is abundant, low-cost and non-toxic. However, these batteries suffer from poor charge acceptance due to hydrogen evolution during charging. In this study, we have demonstrated iron electrodes prepared from carbonyl iron powder (CIP) that are capable of delivering a specific discharge capacity of about 400 mAh g−1 at a current density of 100 mA g−1 with a faradaic efficiency of about 80%. The specific capacity of the electrodes increases gradually during formation cycles and reaches a maximum in the 180th cycle. The slow increase in the specific capacity is attributed to the low surface area and limited porosity of the pristine CIP. Evolution of charge potential profiles is investigated to understand the extent of charge acceptance during formation cycles. In situ XRD pattern for the electrodes subsequent to 300 charge/discharge cycles confirms the presence of Fe with Fe(OH)2 as dominant phase.

Harnessing solar electricity generated through photovoltaic cells with lead-acid batteries remains the most compelling option at present. But lead-acid batteries have encountered problems in photovoltaic installations, mainly due to their premature failure. To circumvent the aforesaid problem, a new technology referred to as substrate-integrated lead-carbon hybrid ultracapacitor with polymeric-silica-gel electrolyte, is developed inhouse and tested for solar-electricity storage for a lighting application. The high-throughput performance tests for the device are conducted at laboratory scale and compatibility of the device for photovoltaic application is evaluated. In doing so, the device is installed with a photovoltaic panel for field test and data are collected from August 2012 through July 2013. The year round field-test data analyzed in the light of the available global-horizontalirradiance data show attractive performance for the device. It is noteworthy that, unlike lead-acid batteries, seasonal variations in solar radiance exhibit little effect on the performance of the device.

A 28-W direct borohydride–hydrogen peroxide fuel-cell stack operating at 25 °C is reported for contemporary portable applications. The fuel cell operates with the peak power-density of ca. 50 mW cm−2 at 1 V. This performance is superior to the anticipated power-density of 9 mW cm−2 for a methanol–hydrogen peroxide fuel cell. Taking the fuel efficiency of the sodium borohydride–hydrogen peroxide fuel cell as 24.5%, its specific energy is ca. 2 kWh kg−1. High power-densities can be achieved in the sodium borohydride system because of its ability to provide a high concentration of reactants to the fuel cell.

Layered LiMn 1− x M x O 2 (M = Zn or Fe) (0 ≤ x ≤ 0.3) samples are synthesized from the corresponding sodium analogues by an ion-exchange method using LiBr in n -hexanol at 160 °C. The samples are subjected to physicochemical and electrochemical characterization. X-ray diffraction data indicate the formation of layered structures for the LiMn 1− x Zn x O 2 samples up to x = 0.3 and for LiMn 1− x Fe x O 2 samples up to x = 0.2. Among these, LiMn 0.95 Zn 0.05 O 2 and LiMn 0.95 Fe 0.05 O 2 provide the highest capacity values of 180 and 193 mAh g −1 , respectively. Both Zn- and Fe-substituted samples display good capacity retention up to 30 charge–discharge cycles. Electrochemical impedance spectroscopy and galvanostatic intermittent titration data corroborate the results obtained from cyclic volatmmetry and charge–discharge cycling.

The solution-combustion route is beneficial for fast and easy synthesis of cathode materials for Li-ion cells. LiFeO 2 synthesized by this method results in an amorphous phase that exhibits poor electrochemical activity with an initial specific capacity of only about 80 mAh g −1 and on annealing it transforms into an electrochemically inactive phase. On the other hand, α-NaFeO 2 synthesized by a solution-combustion method and subjected to Na + /Li + exchange by refluxing with LiBr solution in n -hexanol to obtain layered LiFeO 2 , exhibits an initial specific capacity of about 205 mAh g −1 with capacity fading after prolonged charge–discharge cycling. LiFe 0.9 Co 0.1 O 2 , synthesized by the same route, shows a stable specific capacity of about 190 mAh g −1 .

The effect of an alkaline surface treatment on the electrochemical behavior of CP titanium, Ti–6Al–4V and Ti–13Nb–13Zr has been investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Experiments were performed in Hank’s solution as a function of immersion time. The electrochemical behavior of untreated alloys was also studied. Potentiodynamic polarization experiments conducted after 1 and 168 h of immersion in Hank’s solution indicated minimal change in passive current density for the untreated alloys. EIS data obtained after 1, 24, 72 and 168 h for untreated alloys also indicated minimal change in passive film resistance. In the case of surface-treated alloys, EIS revealed the formation of one additional layer on CP Ti and two additional layers on Ti–6Al–4V and Ti–13Nb–13Zr alloys after surface treatment and immersion in Hank’s solution. Some ideas about the nature of these layers have been obtained by fitting the EIS data to equivalent electrical circuit models. The surfaces of the treated Ti-alloys were also characterized using X-ray diffraction and scanning electron microscopy. The first additional layer has been identified as a sodium titanate hydrogel layer and the second layer, as an apatite layer. The apatite nucleation and growth on the surface occurred after immersion in Hank’s solution. Ti–6Al–4V and Ti–13Nb–13Zr alloys exhibited higher apatite film resistance compared to CP Ti.

A carbon-supported (1:1) Pt-Ru (Pt-Ru/C) alloy catalyst has been prepared in-house by the sulfito-complex route, and has been tailored to achieve enhanced activity towards methanol electro-oxidation by annealing it at varying temperatures in air. The catalyst samples annealed between 250 and 300 degrees C in air for 30 min exhibit superior catalytic activity towards methanol electro-oxidation in a solid-polymer-electrolyte direct methanol fuel cell (SPE-DMFCs) operating at 90 degrees C. Both the as-prepared and annealed Pt-Ru/C catalysts have been characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), and cyclic voltammetry. It is conjectured that while annealing the Pt-Ru/C catalysts, both Pt-Pt and Pt-Ru bonds increase whereas the Pt-O bond shrinks. This is accompanied with a positive variation in Ru/Pt metal ratio suggesting the diffusion of Ru metal from the bulk catalyst to surface with an increase in oxidic ruthenium content. Such a treatment appears seminal for enhancing the electrochemical activity of Pt-Ru catalysts towards methanol oxidation

Positive- and negative-limited lead-acid cells with conventional and polyaniline (PANI)-coated negative plates were assembled and tested at varying discharge rates. The cells with PANI-coated negative plates exhibit lower impedance in relation to conventional cells and sustain higher discharge-rates with lesser loss in capacity during prolonged charge-discharge cycling as compared to conventional cells. It is suggested that PANI-coated negative plates are beneficial in designing lead-acid batteries operating at partial-state-of-charge.

Electroreduction of hydrogen peroxide in acidic medium is reported onto carbon-supported iron tetramethoxy phenyl porphyrin (FeTMPP/C) as well as carbon-supported lead sulphate (PbSO4/C) electrodes. Both the catalytic electrodes can sustain electroreduction of hydrogen peroxide in direct borohydride fuel cells using hydrogen peroxide as oxidant but PbSO4/C electrode shows catalytic activity.