Effect of proton irradiation on electrical properties of a-As₂S₃

Gautam, S.,Thakur, A.,Shukla, D.K.,Shin, H.J.,Chae, K.H.,Singh, K.P.,Goyal, N. North-Holland 2011 Journal of non-crystalline solids Vol.357 No.11

This paper reports the effect of proton irradiation on the electrical properties of a-As<SUB>2</SUB>S<SUB>3</SUB> in the temperature range of 323-418K and frequency range 0.1-100kHz. The variation of transport property is studied with proton irradiation dose (1x10<SUP>13</SUP>ions/cm<SUP>2</SUP> and 1x10<SUP>15</SUP>ions/cm<SUP>2</SUP>). It has been observed that proton irradiation changes the dc conductivity (σ<SUB>dc</SUB>), dc activation energy (ΔE<SUB>dc</SUB>) and ac conductivity (σ<SUB>ac</SUB>(ω)). The σ<SUB>dc</SUB> and σ<SUB>ac</SUB>(ω) increases with dose of proton irradiation. The value of frequency exponent (s) decreases with the temperature and irradiation dose. These results are explained in terms of change in density of defect states in these glasses.

Polyethylenimine-modified mesoporous silica adsorbent for simultaneous removal of Cd(II) and Ni(II) from aqueous solution

Thakur, A.K.,Nisola, G.M.,Limjuco, L.A.,Parohinog, K.J.,Torrejos, R.E.C.,Shahi, V.K.,Chung, W.J. Korean Society of Industrial and Engineering Chemi 2017 Journal of industrial and engineering chemistry Vol.49 No.-

<P>Nano-spherical amine-rich polyethylenimine (PEI) grafted on mesoporous silica (MCM-41) (PEI/MCM-41) was developed for Cd(II) and Ni(II) removal from water. Characterization of PEI/MCM-41 using various techniques confirms its successful fabrication. Adsorption results reveal that pH and adsorbent dosage must be controlled for maximum removal. The adsorption rate was pseudo-second-order, and fitted well with Langmuir and Freundlich isotherms at equilibrium. The adsorption was thermodynamically spontaneous, endothermic and favourable. Adsorption capacities of 156.0 mg g(-1) Cd(II) and 139.7 mg g(-1) Ni(II) were on par with other high performing reported adsorbents. The PEI/MCM-41 was successfully reused demonstrating its potential for heavy metal decontamination application. (C) 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.</P>

Orbital anisotropy in SnO₂ thin films and its modification by swift heavy ion irradiation

Thakur, H.,Kumar, R.,Thakur, P.,Brookes, N.B.,Sharma, K.K.,Singh, A.P.,Kumar, Y.,Gautam, S.,Chae, K.H. North Holland ; Elsevier Science Ltd 2011 Chemical physics letters Vol.511 No.4

We report on the observation of a strong orbital anisotropy in the orthorhombic phase of SnO<SUB>2</SUB> thin films and its modification by swift heavy ion (SHI) irradiation. Structural investigations along with the Raman spectroscopy show a significant distortion of the SnO<SUB>6</SUB> octahedra after SHI irradiation. The X-ray absorption and X-ray linear dichroism (XLD) experiments provide the direct evidences of change in orbital anisotropy/electronic structure due to orbital reconstruction in the SnO<SUB>2</SUB> lattice after irradiation. The XLD measurements at the O K edge confirm the deterioration in the SnO<SUB>6</SUB> octahedra due to controlled structural disorder induced by SHI irradiation.

Evolution of magnetic nanophases of Ni embedded in Al₂O₃ (001) matrix by X-ray magnetic circular dichroism

Thakur, P.,Kumar, R.,Cezar, J.C.,Brookes, N.B.,Sharma, A.,Arora, S.K.,Gautam, S.,Kumar, A.,Chae, K.H.,Shvets, I.V. North Holland 2011 Chemical physics letters Vol.501 No.4

We report on the element-specific magnetic characterization of Ni nanoparticles (NPs) embedded in Al<SUB>2</SUB>O<SUB>3</SUB> (001) matrix prepared by ion-implantation (Ni:5x10<SUP>16</SUP>-2x10<SUP>17</SUP>ionscm<SUP>-2</SUP>) technique. The X-ray diffraction studies reveal the coexistence of fcc Ni NPs of average size ~8-19nm along with the other NiO<SUB>x</SUB> phases. X-ray magnetic circular dichroism (XMCD) experiments demonstrate the competing nature of magnetic interactions between the Ni NPs and NiO<SUB>x</SUB> phases. The ferromagnetism at 10K (for all the Ni implants) is related to the combined contribution of both phases, while the room temperature superparamagnetism at higher fluence is dominated by Ni NPs phase as confirmed by Ni L<SUB>3,2</SUB> XMCD measurements.

Synchronization and Operation of Parallel Inverters using Droop Control

L. K. Sahoo,N. D. Thakur,K. Rai,P Sensarma,R. D. Jha,P. Mohanty,A Sharma 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

To obtain a continuous power supply Distributed Generation (DG) with a Decentralized Power System (DPS), i.e. replacing a single UPS unit with multiple, smaller units in parallel, is emerging as new paradigm. The technically challenging aspect of DPS is the synchronization of inverters and load sharing among the parallel connected inverters. In this paper, a control method is proposed and implemented for synchronization and parallel operation of inverters. Droop control method has been used for equal power sharing, and design of power control loop. The design issues for voltage control loop are analyzed with the discussion of relative stability of the system. A current control loop is designed and analyzed to provide synchronization between the inverters.

Influence of Isobutyric Acid Supplementation on Nutrient Intake, Its Utilization, Blood Metabolites and Growth Performance of Crossbred Calves Fed Wheat Straw Based Low Protein Diets

Misra, A.K.,Thakur, S.S. Asian Australasian Association of Animal Productio 2001 Animal Bioscience Vol.14 No.2

The effects of dietary supplementation with the sodium salt of isobutyric acid in a low protein (10% CP) wheat straw based diet on nutrient utilization, blood metabolites and growth performance were studied with male crossbred calves. The calves were divided into two equal groups of 6 each. The animals of the control group were fed a basal diet consisting of wheat straw, concentrate mixture and green oat fodder in 40:40:20 proportion whereas BCFA supplemented group received the basal diet+isobutyric acid at 0.75 percent of basal diet. The duration of study was 120 days. The feed intake between experimental groups did not differ significantly and the average total DMI (% BW) was 1.99 and $1.95kg\;day^{-1}$ in control and BCFA supplemented diets. The dietary supplementation of BCFA improved (p<0.01) the DM, OM, CP (p<0.05), NDF and cellulose digestibilities by 8.50, 9.01, 5.39, 17.78 and 18.44 per cent over those fed control diet. The total N retention on BCFA supplementation was improved (p<0.01) due to the decreased (p<0.05) faecal N excretion. The BCFA supplementation did not alter the blood circulatory levels of glucose, total protein, albumin, urea N and amino acids. However after 120 days of experimental feeding a significant (p<0.05) increase in the concentrations of non-esterified fatty acid was observed in control group. The DCP intake and the DCP content of experimental diets was similar in both groups. However, the TDN content of BCFA supplemented diet was significantly (p<0.01) higher (64.35%) than that of control (59.60%). The total live weight gain in BCFA supplemented diet increased by 15.94% over control. The average daily gain and efficiency of feed conversion were also improved in BCFA fed calves by 13.38 and 26.71% respectively, compared to control. It is concluded that dietary supplementation with isobutyric acid improved the digestibility of nutrients and growth performance of calves.

Effect of Dietary Supplementation of Sodium Salt of Isobutyric Acid on Ruminal Fermentation and Nutrient Utilization in a Wheat Straw Based Low Protein Diet Fed to Crossbred Cattle

Misra, A.K.,Thakur, S.S. Asian Australasian Association of Animal Productio 2001 Animal Bioscience Vol.14 No.4

The effect of dietary supplementation of sodium salt of isobutyric acid in low protein (10% CP) wheat straw based diet on nutrient utilization and rumen fermentation was studied in ruminally fistulated male crossbred cattle. The study included a 7 day metabolism and a 3 day rumen fermentation trials. The cattle were distributed into two equal groups of 4 each. The animals of control group were fed a basal diet consisting of wheat straw, concentrate mixture and green maize fodder in 40:40:20 proportion whereas branched chain volatile fatty acid (BCFA) supplemented group received a basal diet + isobutyric acid at 0.75 percent of basal diet. The duration of study was 36 days. The feed intake between experimental groups did not differ significantly and the average total DMI (% BW) was 2.01 and $2.28kg\;day^{-1}$ in control and BCFA supplemented diets. The dietary supplementation of BCFA improved (p<0.05) the DM, OM, NDF and cellulose digestibility by 4.46, 6.63, 10.57 and 11.31 per cent over those fed control diet. The total N retention on BCFA supplementation was improved (p<0.01) due to decreased (p<0.05) urinary N excretion. The concentrations of ruminal total N was 37.07 and $34.77mg\;100ml^{-1}$ in control and BCFA fed groups, respectively. Dietary supplementation BCFA significantly (p<0.01) reduced the ruminal ammonia N concentration as compared to control and the mean values ($mg\;100ml^{-1}$) were 13.18 and 9.42 in control and BCFA fed groups. The total VFA concentration was higher (p<0.01) in BCFA supplemented group (101.14 mM) than the control (93.05 mM). Among the VFAs, the molar proportion of acetate was higher (p<0.01) in BCFA supplemented group (71.07 mM) as compared to control (64.98 mM). However, the concentration of propionate and butyrate remained unchanged. Amino acids composition of bacterial hydrolysates was similar in both the groups. Ruminal outflow rate of liquid digesta was higher (p<0.01) in BCFA fed group ($67.56l\;day^{-1}$) than control ($52.73l\;day^{-1}$). It is concluded that the dietary supplementation of Na-salt of isobutyric acid in low protein diet improved the nutrient utilization and ruminal fermentation characteristics.

Universal microstructure and conductivity relaxation of polymer-conductor composites across the percolation threshold

Maheswar Panda,V. Srinivas,A.K. Thakur 한국물리학회 2014 Current Applied Physics Vol.14 No.11

Micro-structural and impedance analysis of series of insulating polymer/conductor composites (PCC) as a function of frequency and volume fractions of the conductor (fcon) have been studied. Evidences of conductivity relaxation have been noticed with a correlation with the sample micro-structure. This has been understood and explained in terms of equivalent electrical circuit model of the material established through complex impedance spectroscopy (CIS) across the percolation threshold (fc) for all the PCC. CIS analysis confirmed that PCC with fcon fc, exhibit conductivity/interfacial relaxation due to polarization of MaxwelleWagnereSillars (MWS) type at fc and the relaxation frequency increases with increase of fcon. The modulus spectroscopy analysis suggests the presence of two types of relaxations in different frequency ranges; (i) dipolar relaxation associated with the flipping of dipoles present in the pure polymer for fcon < fc and (ii) the conductivity/interfacial relaxation due to the formation of artificial MWS dipoles at the interface of the two components. A long range dc conductivity appears at fcon fc and Jonschers universal fractional power law is satisfied for both the regions of fcon < fc and fcon fc in all PCC.

Effect of design modification on efficiency enhancement in Sb2S3 absorber based solar cell

Islam M.T.,Thakur A.K. 한국물리학회 2023 Current Applied Physics Vol.49 No.-

The effect of tailored architecture and interfacial engineering on efficiency enhancement ~3.5 times vis-`a-vis experimental value in Sb2S3 absorber based solar cell is reported. It is attributed to design driven lowered interfacial recombination for identical absorber based solar cell. The design modification comprises optimal intrinsic layer insertion, carrier density control, absorber bandgap widening, Fermi level pinning and back surface field at Sb2S3/metal junction. Hole carrier density lowering and band gap engineering near Sb2S3/CdS junction and interfacial recombination lowering improved short circuit current (~90%), open circuit voltage (~67%), fill factor (~15%) and efficiency (~255%). The simulation analysis confirmed that CdS buffer layer donor defects pinned the Fermi level near conduction band edge at Sb2S3/CdS interface causing lower recombination. A high hole concentration thin layer at Sb2S3/metal interface also reduced back contact interfacial recombination. Modified solar cell architecture confirmed possibility of chalcogenide solar cell having enhanced efficiency ~16% vis-`a-vis 4.5% reported in literature.

Structural, Morphological and Optical Properties of Sprayed Nanocrystalline Thin Films of Cd1-xZnxS Solid Solution

Urvashi Verma,Vikas Thakur,Poolla Rajaram,A. K. Shrivastava 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.1

A series of nanocrystalline thin films of cadmium zinc sulphide(Cd1-xZnxS) solid solution were deposited on glass substrates usingspray pyrolysis. Cadmium chloride (CdCl2), zinc chloride (ZnCl2) andthiourea (NH2CSNH2) were used as the sources of Cd, Zn and Srespectively. The films were characterized using structural, morphologicaland optical techniques. X-ray diffraction (XRD) studies show thatthe films of Cd1-xZnxS are polycrystalline and single phase having thewurtzite structure. The crystallites in the thin films of pure CdS possesspreferred crystallographic orientation along the <002> direction. Thepreferred orientation of crystallites in the Cd1-xZnxS films changes from<002> to <101> with increase in Zn concentration. The latticeparameters of Cd1-xZnxS decrease with increase in Zn concentration. Scanning electron microscopy (SEM) and atomic force microscopy(AFM) studies show that the surfaces of the films are smooth and areuniformly covered with nanoparticles. Energy dispersive analysis of xrays(EDAX) results reveal that the grown films have goodstoichiometry. Optical transmission spectra confirm the good qualityof the Cd1-xZnxS films.