Characterization and photoluminescence studies on hydrothermally synthesized Mn-doped barium titanate nano powders

Manganese doped cubic barium titanate nanocrystals with [Mn/Ti] mole percent varying from 0.1 to 3 were prepared through hydrothermal route at 150 °C. The mean crystallite diameters obtained for different Mn concentrations varied within 26 to 30 nm. TEM of a typical sample showed most of the particles as single crystallites (particle size 15-40 nm) with some weakly agglomerated particles. The photo luminescent (PL) spectra of each sample showed a sharp peak in the blue band centered approximately at 464 nm and a weaker peak in the green band centered nearly at 494 nm. The luminescent efficiency passed through maxima for the sample with 2% [Mn/Ti] molar ratio. Effect of calcination temperature in the range of 200 to 600 °C on PL spectra showed that the intensity of peak corresponding to blue region decreased with the increase in calcination temperature from 200 to 600 °C and for the sample calcined at 600 °C, only a broad peak corresponding to green luminescence region was observed.     

Crystallization behaviour and mechanical properties of rapidly solidified Al<Subscript>87.5</Subscript>Ni<Subscript>7</Subscript>Mm<Subscript>5</Subscript>Fe<Subscript>0.5</Subscript> amorphous alloy

The crystallization behaviour and the mechanical properties of rapidly solidified Al_87.5Ni₇Mm₅Fe_0.5 alloy ribbons have been examined in both as-melt-spun and heat-treated condition using differential scanning calorimetry, X-ray diffractometry (XRD), transmission electron microscopy (TEM), tensile testing and Vicker’s microhardness machine. XRD and TEM studies revealed that the as-melt-spun ribbons are fully amorphous. The amorphous ribbon undergoes three-stage crystallization process upon heating. Primary crystallization resulted in the formation of fine nanocrystalline fcc-Al particles embedded in the amorphous matrix. The second and third crystallization stages correspond to the precipitation of Al₁₁(La,Ce)₃ and Al₃Ni phases, respectively. Microhardness and tensile strength of the ribbons were examined with the variation of temperature and subsequently correlated with the evolved structure. Initially, the microhardness of the ribbon increases with temperature followed by a sharp drop in hardness owing to the decomposition of amorphous matrix that leads to formation of intermetallic compounds     

Photocatalytic degradation of dyes and organic contaminants in water using nanocrystalline anatase and rutile TiO2

Nanocrystalline TiO₂ was synthesized by controlled hydrolysis of titanium tetraisopropoxide. The anatase phase was converted to rutile phase by thermal treatment at 1023 K for 11 h. The catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fourier-transform infrared absorption spectrophotometry (FT-IR) and N₂ adsorption (BET) at 77 K. This study compare the photocatalytic activity of the anatase and rutile phases of nanocrystalline TiO₂ for the degradation of acetophenone, nitrobenzene, methylene blue and malachite green present in aqueous solutions. The initial rate of degradation was calculated to compare the photocatalytic activity of anatase and rutile nanocrystalline TiO₂ for the degradation of different substances under ultraviolet light irradiation. The higher photocatalytic activity was obtained in anatase phase TiO₂ for the degradation of all substances as compared with rutile phase. It is concluded that the higher photocatalytic activity in anatase TiO₂ is due to parameters like band-gap, number of hydroxyl groups, surface area and porosity of the catalyst.     

Neotectonic study of Ganga and Yamuna tear faults,NW Himalaya,using remote sensing and GIS

The Ganga and Yamuna rivers emerge from the Himalayas along two major faults known as the Ganga and Yamuna Tear Faults respectively. The two major strike-slip faults transverse to the Siwalik range are clearly seen in satellite imagery of the Dehradun area. Earthquake records, landslide and recent changes in geomorphological features indicate that the area between the Main Boundary Thrust and the Main Frontal Thrust is tectonically active. An effort has been made to study the tectonic evolution and neotectonism of the Ganga and Yamuna tear faults. Spectral and spatial enhancement techniques have been employed to the digital data of IRS-1B LISS-I to delineate the lineaments and major faults of the area. Based on Mohr's theory, failure criteria and statistical analysis of remotely sensed lineament data, horizontal compressive stress values (S_Hmax) have been estimated at various sites of the study area. These data are found to be consistent with the published S_Hmax orientation determined from earthquake focal mechanism solutions. Active faults and lineaments have been extracted from the remotely sensed lineament data. Past earthquake data and depth to basement contour data have been used in an integrated approach with available Geographic Information System (GIS) techniques to reconstruct a present-day regional geodynamic model. Attempts have been made to investigate the genesis of Ganga and Yamuna Tear Faults and possible causes of recent tectonic activities of the area with the help of the proposed geodynamic model.     

Solidification behaviour,microstructure and mechanical properties of high Fe-containing Al–Si–V alloys

The paper deals with effect of Fe on the solidification behaviour and mechanical properties of unmodified and modified Al–V–Si alloys. Effect of thermo-mechanical processing on the mechanical properties of these alloys was also reported. The solidification proceeds through several invariant reactions, the first one corresponds to formation of Al₃(Fe,V,Si)-type phase. Modification with Ni–Mg master alloy changes the morphology, size and distribution of the primary as well as interdendritic phases. The modified alloys show an increase in first invariant reaction temperature and decrease in final invariant reaction temperature when compared with unmodified alloy, probably due to action of phase modification. In comparison to untreatable alloy, appreciable improvement in mechanical properties occurs on modification by Ni–Mg treatment. Hot rolling further improves the mechanical properties of the alloy.     

Reservoir Release Policy for Large Irrigation System

This paper describes the formulation of a model for optimized crop and water planning decisions in an irrigation system in Thailand. It facilitates consultation in which representatives of stakeholders, officials, farmers, and researchers can contribute to the decision making. Linear programming and the analytical hierarchy process are the principal modeling tools to optimize the collective system objectives: productivity, equity, and security. The results of the model are compared with observed events of one dry season. The optimized policy generated by the model suggested a diversified cropping pattern, which would decrease the water requirement by 16.4% and enhance net benefit per cubic meter of water used by 39.9%. The erratic water availability from the reservoir and the operational procedures inside the system are reviewed, analyzing historical data in terms of reliability, resiliency, and vulnerability. These include lack of proper assessment of available water, effective farmer organization, and prompt data processing and communication. Furthermore, for the effective implementation of an optimized irrigation policy, a water release pattern of the storage reservoir has been suggested.     

CFD analysis of natural convection heat transfer augmentation from square conductive horizontal and inclined pin fin arrays

Numerical investigations on natural convection heat transfer from a vertical isothermal plate with pin fins have been made by solving the Navier–Stokes equation along with the energy equation. Average Nusselt number for the plate with different configurations of pin fins have been obtained. It was observed that the maximum increase of the average Nusselt number occurs at S_v/L?=?0.2 for θ?=?45° with fin height of 24?mm (H/t?=?8). The average Nusselt number increases with fin aspect ratio and decreases with angle of inclination. There is not much difference between the average Nusselt number for in-line and staggered arrangement of fins for the range of parameters studied in the present work. A correlation is developed to predict the average Nusselt number of the plate as a function of fin spacing in stream- and span-wise direction, aspect ratio of fins and its angle of inclination.     

Comparative delivery of Diltiazem hydrochloride through synthesized polymer: Hydrogel and hydrogel microspheres

In this study, interpenetrating polymer network (IPN) hydrogel based on polyvinyl alcohol (PVA) networking with polyacrylic acid (PAA) were prepared by a non‐conventional emulsion method without any added crosslinker, using benzoyl peroxide as initiator and sodium chloride (NaCl) as additive. The IPN hydrogel was characterized by using Fourier transformed infrared (FTIR) spectrophotometry, Thermo gravimetric analysis (TGA), and Scanning electron microscopy (SEM). (PVA‐co‐PAA)/NaCl normal IPN hydrogel (H) were fabricated into hydrogel microspheres (HM) by modified emulsion crosslinking method using glutaraldehyde‐saturated toluene as crosslinker and were loaded with Diltiazem hydrochloride (DL). The IPN hydrogel showed more swelling in simulated intestinal fluid (SIF). (PVA‐co‐PAA)/NaCl HM formulation A1 showed comparatively higher DL entrapment (79%) and better control over DL release up to 24 h. By comparing antihypertensive activity of DL loaded two formulations in normotensive rats, HM formulation A1 found more effective in reducing blood pressure to 40.1%. The experimental results demonstrated that (PVA‐co‐PAA)/NaCl HM had the greater potential than normal hydrogel to be used as a drug carrier. A single use of the prepared hydrogel microsphere system of DL can effectively control hypertension in rats. The system holds promise for clinical studies. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of thermal resistant gas barrier chitosan nanobiocomposites

Nanobiocomposites of chitosan/clay were prepared by solution method using CuSO₄/glycine chelate complex as the catalyst with variable percentage of clay loading. The chemical interaction of chitosan and clay was studied by Fourier transform infrared spectroscopy. The structure of chitosan and clay nanobiocomposites was investigated by X‐ray diffraction and high resolution transmission electron microscopy. From thermogravimetric analysis, it was found that chitosan/clay nanobiocomposites were more thermally stable as compared to pure chitosan. A substantial reduction in oxygen permeability was obtained from the gas permeameter with increase in clay concentrations by which the synthesized nanocomposites materials may be used for packaging applications. POLYM. COMPOS., 35:2324–2328, 2014. © 2014 Society of Plastics Engineers