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Magnetic Phase Separation in Diluted Magnetic System:Zn1-xFexO

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Acta Metallurgica Sinica(English Letters) 2017年第6期30卷 521-527页

作者： Archita Mondal Sanchari Sarkar Neepamala Giri Souvik Chatterjee Ruma Ray Department of Physics Jadavpur UniversityKolkata 700 032India ugc-dae consortium for scientific research Kolkata CentreSector IIILB-8Salt LakeKolkata 700098India

Single-phase diluted magnetic systems Zn1-xFexO have been prepared by chemical route. Structural and spectroscopic （UV-Vis and Mossbauer） studies indicate the incorporation of Fe^3＋ ions in the lattice sites. The UV-Vis results point to a systematic increase in the band gap with increasing Fe doping. The room temperature magnetization of Zni-xFexO indicates a paramagnetic behavior which is in accordance with the Mossbauer results, illustrating quadrupolar doublet. At low temperature, the zero-field-cooled （ZFC） magnetization shows a cusp and this temperature increases systematically with decreasing particle size. The weak exchange bias effect manifested by a M-H loop shift is observed for x = 0.03. This shift is accompanied by the enhancement of coercivity. The dc magnetization results suggest the coexis tence of ferromagnetic and antiferromagnetic exchange interactions for low doping of Fe, i.e., for x = 0.03.

关键词： Diluted magnetic system Optical band gap Moissbauer Exchange bias effect

Optical and electrical properties and phonon drag effect in low temperature TEP measurements of AgSbSe_2 thin films

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Journal of Semiconductors 2014年第5期35卷 1-6页

作者： T Namitha Asokan K S Urmila Rajani Jacob Rachel Reena Philip G S Okram V Ganesan B Pradeep Solid State Physics Laboratory Department of Physics Cochin University of Science and Technology Thin Film research Lab Department of Physics Union Christian College ugc-dae consortium for scientific research

Polycrystalline thin films of silver antimony selenide have been deposited using a reactive evaporation technique onto an ultrasonically cleaned glass substrate at a vacuum of 10-5 torr. The preparative parameters, like substrate temperature and incident fluxes, have been properly controlled in order to get stoichiometric, good quality and reproducible thin film samples. The samples are characterized by XRD, SEM, AFM and a UV-vis-NIR spectrophotometer. The prepared sample is found to be polycrystalline in nature. From the XRD pattern, the average particle size and lattice constant are calculated. The dislocation density, strain and number of crystallites per unit area are evaluated using the average particle size. The dependence of the electrical conductivity on the temperature has also been studied and the prepared AgSbSe2 samples are semiconducting in nature. The AgSbSe2 thin films exhibited an indirect allowed optical transition with a band gap of 0.64 eV. The compound exhibits promising thermoelectric properties, a large Seebeck coefficient of 30 mV/K at 48 K due to strong phonon electron interaction. It shows a strong temperature dependence on thermoelectric properties, including the inversion of a dominant carrier type from p to n over a low temperature range 9-300 K, which is explained on the basis of a phonon drag effect.

关键词： silver antimony selenide reactive evaporation thermoelectric power phonon drag effect

A Novel Synthesis of Malic Acid Capped Silver Nanoparticles using Solanum lycopersicums Fruit Extract

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Journal of Materials Science & Technology 2013年第4期29卷 317-322页

作者： M.Umadevi M.R.Bindhu V.Sathe Department of Physics Mother Teresa Women's UniversityKodaikanal 624 102Tamil NaduIndia ugc-dae consortium for scientific research University CampusKhandwa RoadIndore 452 017India

Integration of green chemistry principles to nanotechnology is one of the key issues in nanoscience research. The development of the concept of green nanoparticle preparation has been growingly needed for environmentally benign metal nanoparticle synthesis protocols to avoid adverse effects in medical applications. Keep this in mind, in the present study, silver nanoparticles were synthesized using Solanum lycopersicums fruit extract. The prepared silver nanoparticles were characterized by UV-visible spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy techniques. The surface plasmon resonance peak was found at 445 nm. The synthesized silver nanoparticles were spherical in shape with the average size of 10 nm. The citric acid present in S. lycopersicums fruit extract acted as reducing agent and malic acid was responsible for capping of the bioreduced silver nanoparticles.

关键词： Silver nanoparticles Solanum lycopersicums UV--visible spectroscopy Fourier transform infrared spectroscopy Ramanspectroscopy

Electrochemical Synthesis of Novel Zn-Doped TiO_2 Nanotube/ZnO Nanoflake Heterostructure with Enhanced DSSC Efficiency

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Nano-Micro Letters 2016年第4期8卷 381-387页

作者： Aijo John K Johns Naduvath Sudhanshu Mallick Jacob W.Pledger S.K.Remillard P.A.De Young Manju Thankamoniamma T.Shripathi Rachel Reena Philip Department of Physics Union Christian College Department of Metallurgical Engineering and Material Science Indian Institute of Technology Present Address Department of Physics St.Thomas College Department of Physics Hope College Department of Physics Sree Sankara College ugc-dae consortium for scientific research Indore

The paper reports the fabrication of Zn-doped TiO_2 nanotubes(Zn-TONT)/ZnO nanoflakes heterostructure for the first time,which shows improved performance as a photoanode in dye-sensitized solar cell(DSSC).The layered structure of this novel nanoporous structure has been analyzed unambiguously by Rutherford backscattering spectroscopy,scanning electron microscopy,and X-ray *** cell using the heterostructure as photoanode manifests an enhancement of about an order in the magnitude of the short circuit current and a seven-fold increase in efficiency,over pure TiO_2 *** further reveal that the Zn-TONT is preferentially oriented in [001] direction and there is a Ti metal-depleted interface layer which leads to better band alignment in DSSC.

关键词： Zn-doped TiO2 nanotubes ZnO nanoflakes Heterostructures DSSC

Effect of metal fluorides on chromium ions doped bismuth borate glasses for optical applications

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Chinese Physics B 2019年第3期28卷 366-372页

作者： L Haritha K Chandra Sekhar R Nagaraju G Ramadevudu Vasanth G Sathe Md.Shareefuddin Department of Physics Telangana University Department of Physics Osmania University Department of Physics Vasavi College of Engineering ugc-dae consortium of scientific research

Fluoride based glasses with composition CaF_2-ZnF_2-Bi_2 O_3-B_2 O_3 doped with chromium ions have been investigated using physical, optical, electron paramagnetic resonance(EPR), Fourier-transform infrared spectroscopy(FTIR), and Raman studies. The amorphous nature of samples was confirmed from x-ray diffraction spectra. The density is evaluated from the Archimedes principle and the values of optical band gap and Urbach energy values were evaluated from the optical absorption spectra. Thus, molar volume, refractive index, etc., were also evaluated. The observed decrease in density and the optical band gap with CaF2 is explained using the crystalline density of metal fluorides and the ionicity of fluorine ions,respectively. The three peaks near 450 nm, 606 nm, and 720 nm, which are shown in the absorption spectra, are accredited to ~4 A)(2 g) → ~4 T_(1 g), ~4 A_(2 g)→ ~4 T_(2 g), ~4 A_(2 g)→~2 E transitions, respectively. Resonance signals at g≈ 4.82 and g≈ 1.99 were observed in EPR spectra which are assigned. FTIR and Raman analysis were carried out to examine the impact of metal fluorides on the structure of bismuth borate glasses.

关键词： glasses x-ray diffraction electron paramagnetic resonance Fourier-transform infrared spectroscopy(FTIR) Raman spectra

Enhancing the efficiency of nitrogen removing bacterial population to a wide range of C:N ratio(1.5:1 to 14:1)for simultaneous C&N removal

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Frontiers of Environmental Science & Engineering 2022年第8期16卷 149-163页

作者： Shaswati Saha Rohan Gupta Shradhanjali Sethi Rima Biswas Academy of scientific and Innovative research(AcSIR) CSIR-Human Resource Development Centre(CSIR-HRDC)Ghaziabad Uttar Pradesh-201002India Wastewater Technology Division CSIR-National Environmental Engineering Research InstituteNagpur Maharashtra-440020India

High C:N ratio in the wastewater limits biological nitrogen removal(BNR),especially in anammox based *** present study attempts to improve the COD tolerance of the BNR process by associating methanogens with nitrogen removing bacterial(NRB)*** new microbial system coined as‘Methammox’,was investigated for simultaneous removal of COD(C)and ammonia(N)at C:N ratio 1.5:1 to 14:*** ammonia removal rate(11.5 mg N/g VSS/d)and the COD removal rates(70.6 mg O/g VSS/d)of Methammox was close to that of the NRB(11.1 mg N/g VSS/d)and the methanogenic populations(77.9 mg O/g VSS/d),*** activities established that these two populations existed simultaneously and independently in‘Methammox’.Further studies in biofilm reactor fetched a balanced COD and ammonia removal(55%–60%)at a low C:N ratio(£2:1)and high C:N ratio(≥9:1).The population abundance of methanogens was reasonably constant,but the nitrogen removal shifted from mixotrophy to heterotrophy as the C:N ratio shifted from low(C:N£2:1)to high(C:N≥9:1).The reduced autotrophic NRB(ammonia-and nitrite-oxidizing bacteria and Anammox)population at a high C:N ratio was compensated by the fermentative group that could carry out denitrification *** functional plasticity of the Methammox system to adjust to a broad C:N ratio opens new frontiers in biological nitrogen removal of high COD containing wastewaters.

关键词： Methanogens Biological Nitrogen Removal(BNR) Simultaneous Methammox C:N ratio

Analysis of Activation Energies &Experimental Evidence for Energetic Phase Separation in Ge<sub>x</sub>Se<sub>1-x</sub>Glassy System

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New Journal of Glass and Ceramics 2014年第2期4卷 38-41页

作者： Deepak Sharma Anand Mohan Awasthi Applied Science Department SCRIET CCS University Meerut India ugc-dae consortium for scientific research Indore India

Glass science reveals peculiar properties due to the lack of long range order and presence of heterogeneity in Chalcogenide glasses. In thermal studies, structural relaxation at the glass transition region is governed by the activation energy of the cooperative unit (zU). In the cooperative molecular dynamics, we are considering the analysis of three activation energies, namely activation energy per BMS (U), activation energy of the cooperative unit (zU) and the apparent activation energy (z2U). From the energetic dynamics of activation energy analysis across the GexSe1-x glass series, data represent three-phase segregation. From our data, we also observed that the value of UCRR/RTg across the GexSe1-x glass series is nominally changed from 34.343 to 36.19.

关键词： Activation Energies Chalcogenide Glasses Glass Transition Heterogeneity Molecular Dynamics Structural Relaxation

Sb_(2)Te_(3)/graphite nanocomposite: A comprehensive study of thermal conductivity

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Journal of Materiomics 2021年第3期7卷 545-555页

作者： Subarna Das P.Singha V.A.Kulbachinskii V.G.Kytin Gangadhar Das S.Janaky A.K.Deb Sudip Mukherjee A.Maignan S.Hebert R.Daou Chandrabhas Narayana S.Bandyopadhyay Aritra Banerjee Department of Physics University of Calcutta92 A P C RoadKolkata700009India Laboratoire de Cristallographie et Sciences des Materiaux(CRISMAT) Normandie UniversiteUMR6508 CNRSENSICAENUNICAEN14000CaenFrance Department of Low Temperature Physics and Superconductivity Physics FacultyM.V.Lomonosov Moscow State University119991MoscowRussia Moscow Institute of Physics and Technology 141700DolgoprudnyMoscow RegionRussia Chemistry and Physics of Materials Unit Jawaharlal Nehru Centre for Advanced Scientific ResearchJakkur P.OBangalore560064India Department of Physics Raiganj UniversityUttar DinajpurWest Bengal733134India ugc-dae consortium for scientific research Mumbai CentreR-5 ShedBARC CampusTrombayMumbai400008India Center for research in Nanoscience and Nanotechnology University of CalcuttaJD-2Sector-IIISaltlakeKolkata700106India

Thermoelectric performance largely depends on the reduction of lattice thermal conductivity(kL).The study of the thermal conductivity(k)of a Sb_(2)Te_(3)/graphite nanocomposite system demonstrates-40%reduction in kL with graphite incorporation.A plausible explanation of intrinsic low kL observed in Sb_(2)Te_(3) based system is presented by modeling experimental specific heat(Cp)*** spectroscopy measurement combined to X-Ray diffraction data confirms the presence of graphite as separate phase in the composite *** is found that phonon scattering dominates heat transport mechanism in the nanostructured Sb_(2)Te_(3)/graphite *** reduction in kL is accomplished by intensifying scattering rate of phonons via various *** introduces effective scattering sources,i.e.,defects of different dimensionalities in synthesized nanocomposite ***,graphite mediates phonon-phonon coupling and enhances lattice anharmonicity,which causes an intrinsic scattering of phonons with all frequencies in the Sb_(2)Te_(3)/graphite nanocomposite *** density and phonon anharmonicity of the synthesized samples are estimated from in depth analysis of temperature dependent synchrotron powder diffraction and Raman spectroscopic *** value as low as 0.8 W m1 K1 at 300 K,achieved with graphite dispersion in Sb_(2)Te_(3) based composite system makes the present comprehensive study an interesting concept to be developed in thermoelectric materials.

关键词： Thermoelectric systems Thermal conductivity Phonons X-ray powder diffraction Raman spectroscopy Specific heat measurements

Climatology, trend of aerosol-cloud parameters and their correlation over the Northern Indian Ocean

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Geoscience Frontiers 2023年第4期14卷 173-186页

作者： Harshbardhan Kumar Shani Tiwari Academy of scientific and Innovative research(AcSIR) Ghaziabad201002India Aerosol and Cloud research Lab Geological Oceanography DivisionCSIR–National Institute of OceanographyGoa403004India

Aerosols are one of the important atmospheric constituents and exert indirect impact on climate through the modification of microphysical and radiative properties of clouds that in turn perturb the precipitation ***,the long term quantification of changes in aerosol and cloud characteristics and their interactions on both temporal as well as spatial scale will provide a crucial information for the better assessment of future climate *** present study,18 years(2003-2020)MODerate Resolution Imaging Spectro-radiometer(MODIS)derived aerosol-cloud dataset over the Northern Indian Ocean(NIO)were analysed to assess climatology and trend of aerosol,cloud characteristics and their *** found a strong heterogeneity in spatio-temporal variation of aerosol and cloud parameters over the NIO that are more prominent for the coastal *** climatological mean of aerosol loading is found high(AOD≥0.5)over the outflow region along the Indian sub-continent and low(AOD≤0.2)over the northern equatorial open *** climatological mean of cloud properties shows dominance of optically thicker deep convective(CTP700 hPa and CTT>273 K)over the northwestern Arabian Sea(AS).Similarly,bigger effective radii(>17µm)observed along the equatorial open ocean whereas smaller CER(0.

关键词： Aerosol Cloud properties Northern Indian Ocean Climatology Trend Correlation