Papers by Vibhav Saraswat
Fizika i tehnika poluprovodnikov, 2017
We have performed ab initio calculations for the structural, electronic, optical, elastic and the... more We have performed ab initio calculations for the structural, electronic, optical, elastic and thermal properties of CuGaTe 2. In this study, we used an accurate full potential linearized augmented plane wave (FP-LAPW) method to find the equilibrium structural parameters and to compute the full elastic tensors. We report electronic and optical properties with the recently developed density functional of Tran and Blaha. Furthermore, optical features such as dielectric functions, refractive indices, extinction coefficient, optical reflectivity, absorption coefficients, optical conductivities, were calculated for photon energies up to 30 eV. The thermodynamical properties such as Debye temperature, entropy and Gruneisen parameter, bulk modulus and hardness were calculated employing the quasi-harmonic Debye model at different temperatures (0−1000 K) and pressures (0−8 GPa) and the silent results were interpreted. Most of the investigated parameters are reported for the first time.
Materials Today: Proceedings, 2021
In the present work, the simple and efficient wet chemical route is presented for the preparation... more In the present work, the simple and efficient wet chemical route is presented for the preparation of bismuth telluride nanostructures (nanoparticles, nanorods, and nanotubes). The temperature parameter was controlled to see the effect on the structure and morphology of the Bismuth Telluride. The structural, morphological, and oxide formation of Bismuth Telluride nanostructures were studied using X-ray diffractometry (XRD), Transmission electron microscopy (TEM), and Micro-Raman spectroscopy respectively. The polycrystalline nature of Bismuth Telluride nanostructures was found from the X-ray diffraction studies. The XRD data reveals that Bismuth Telluride is present in two phases in these nanostructures. One corresponding to the Bi 2 Te 3 phase which consists of Rhombohedral structure and another corresponding to the BiTe phase consisting of Hexagonal structure. The XRD pattern also shows the presence of the oxide phase which was further confirmed using Raman spectroscopy. The Morphological features showed that the nanostructures compose small crystallites.
Pure and Applied Chemistry, Oct 10, 2017
In this work, we present the hydrogen selective gas separation properties of the track-etched pol... more In this work, we present the hydrogen selective gas separation properties of the track-etched poly (ethylene terephthalate) (PET) membranes, which were functionalized with a carboxylic group. Also, Palladium (Pd) nanoparticles of average diameter 5 nm were deposited for a various time on pore walls as well as on the surface of carboxylated membranes. Effect of Pd nanoparticles binding with the increase of deposition time on gas separation and selectivity was studied. For the study of surface morphology of these composite membranes and the confirmation of Pd nanoparticles binding on the surface as well as on pore walls is characterized by scanning electron microscopy (SEM). The gas permeability of carboxylated membrane with increasing Pd deposition timing for hydrogen (H 2), carbon dioxide (CO 2) and nitrogen (N 2) was examined. From the gas permeability data of H 2 , CO 2 and N 2 gasses, it was observed that these membranes have higher permeability for H 2 as compared with CO 2 and N 2. Selectivity of H 2 /CO 2 and H 2 /N 2 improves with the increased Pd nanoparticles deposition time. These membranes have effective application in the field of hydrogen based fuel cell.
Journal of Optoelectronics and Advanced Materials, 2006
The electrical conductivity of Zn50Se50 from room temperature to 180 o C has been studied. The sa... more The electrical conductivity of Zn50Se50 from room temperature to 180 o C has been studied. The sample was prepared using melt cooling technique. Then the sample was characterized in terms of its crystal structure and lattice parameter using X-ray diffraction method. The material was found to be polycrystalline in nature. The electrical conductivity of the sample with voltage at different fixed temperature ranging from room temperature to 180 o C has been determined. The variation in electrical conductivity is explained on the basis of structural changes in the sample with temperature.
Nucleation and Atmospheric Aerosols, 2011
Presented paper discusses the variation in optical band gap and volume dc conductivity of Se-Te-C... more Presented paper discusses the variation in optical band gap and volume dc conductivity of Se-Te-Cd ternary Chalcogenide glasses as a function of concentration of Cd i.e. the composition of the glasses. Also, the temperature dependence of volume conductivity has been studied. The amorphous nature of these glasses has been confirmed by XRD patterns. Keithley Electrometer/High resistance meter 6517A was used in its FVMI mode to record I_V characteristics at different temperatures. Variation in conductivity, derived from I_V curves, as a function of composition of sample could be accounted for the bonds formed in the system. Additionally, the Poole-Frenkel conduction mechanism has also been verified in order to investigate the good agreement with the established fact that most of Chalcogenide glasses obey the Poole-Frenkel conduction mechanism. Absorption spectra were recorded using Ocean Optics USB2000 spectrophotometer in visible region. Band gap calculation using Tauc relation reveals that the system under test is semi-conducting in nature. The observed results are found to be in good agreement with each other.
International Journal of Hydrogen Energy, Jul 1, 2020
h i g h l i g h t s Carboxyl-functionalized PET coated with block copolymer nanotemplates. Improv... more h i g h l i g h t s Carboxyl-functionalized PET coated with block copolymer nanotemplates. Improved selectivity for H 2 gas in block copolymer coated PET membrane. Block copolymer coating has an effective role for the selectivity.
Semiconductors, May 1, 2017
We have performed ab initio calculations for the structural, electronic, optical, elastic and the... more We have performed ab initio calculations for the structural, electronic, optical, elastic and thermal properties of CuGaTe 2 . In this study, we used an accurate full potential linearized augmented plane wave (FP-LAPW) method to find the equilibrium structural parameters and to compute the full elastic tensors. We report electronic and optical properties with the recently developed density functional of Tran and Blaha. Furthermore, optical features such as dielectric functions, refractive indices, extinction coefficient, optical reflectivity, absorption coefficients, optical conductivities, were calculated for photon energies up to 30 eV. The thermodynamical properties such as Debye temperature, entropy and Gruneisen parameter, bulk modulus and hardness were calculated employing the quasi-harmonic Debye model at different temperatures (0-1000 K) and pressures (0-8 GPa) and the silent results were interpreted. Most of the investigated parameters are reported for the first time.
Bulletin of Materials Science, Aug 1, 2005
The I-V characterization and the electrical resistivity of selenium rich Se 85 Cd 15-x Zn x (x = ... more The I-V characterization and the electrical resistivity of selenium rich Se 85 Cd 15-x Zn x (x = 0, 3, 7, 11 and 15) system at room temperature have been studied. Samples were obtained using melt cooling technique. So prepared samples were then characterized in terms of their crystal structure and lattice parameter using X-ray diffraction method. The materials were found to be polycrystalline in nature, having zinc blend structure over the whole range of zinc concentration. The measurements of I-V characteristics have been carried out at different temperatures from room to 140°C. The electrical resistivity of the samples with composition at room temperature has been found to vary between maximum 2⋅ ⋅7 × 10 8 Ω Ω m and minimum 7⋅ ⋅3 × 10 5 Ω Ω m and shows a maximum at 3 at. wt.% of Zn. The carrier activation energy of the samples with composition has also been determined and found to vary from 0⋅ ⋅026 eV to 0⋅ ⋅111 eV.
Macromolecular Symposia, Nov 1, 2015
The presented work deals with the synthesis and thermal characterization of TiO 2 filled Polycarb... more The presented work deals with the synthesis and thermal characterization of TiO 2 filled Polycarbonate/Polystyrene (PC/PS) blend nanocomposites. Nanoparticles of Titanium-dioxide have been synthesized by simple chemical method. Average grain size of as prepared nanoparticles have been determined by both TEM and XRD. Titanium-dioxide Filled Polycarbonate/Polystyrene blend nanocomposites have been prepared by solution casting method. The XRD pattern and FTIR spectrum confirm the formation of blend nanocomposites. Differential Scanning Calorimetry (DSC) has been used to study thermal properties. The DSC thermograms indicate that the glass transition temperature and hence thermal stability of nanocomposites enhances with addition of filler content.
Applied Thermal Engineering, Jun 1, 2007
ABSTRACT Measurements of thermophysical properties of ZnxTe100−x (x = 5, 10, 30 and 50) chalcogen... more ABSTRACT Measurements of thermophysical properties of ZnxTe100−x (x = 5, 10, 30 and 50) chalcogenide material in pellet form have been made in the temperature range from room temperature (15 °C) to 200 °C and in cooling cycle from 200 °C to 15 °C using transient plane source (TPS) technique. In heating mode the values of effective thermal conductivity (λe) and effective thermal diffusivity (χe) increase from 15 °C to 200 °C. During the cooling mode λe and χe decrease slightly in the temperature range from 200 °C to 160 °C below which λe and χe remain almost constant at all temperatures. Such type of behaviour shows thermal hysteresis in this sample, which can be explained on the basis of the change in structure of the material. XRD studies suggest that the material is polycrystalline in nature.
International Journal of Hydrogen Energy, Nov 1, 2018
The present study highlights the first-ever application of fastest lithium (Li) ion conducting co... more The present study highlights the first-ever application of fastest lithium (Li) ion conducting complex hydride containing cluster anions, namely lithium borohydride (LiBH 4 ) into an allsolid-state Li-ion battery having Bi 2 Te 3 as anode material. Bi 2 Te 3 nanostructures were prepared by the simple wet chemical method and characterized by their crystal structure, morphology and electronic structure using X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). SEM and TEM experiments revealed the dimensions as 20e60 nm for nanoparticles and 30e90 nm for nanosheets. The formation of Bi 2 Te 3 nanostructures along with Bi 2 O 3 as the residual phase is confirmed by XRD analysis. The crystallite size of nanoparticles and nanosheets are calculated as 19 nm and 39 nm respectively from XRD profile. The XPS study also confirms the formation of nanostructured Bi 2 Te 3 along with Bi 2 O 3 . Finally, the electrochemical performance of these nanostructures is observed using the galvanostatic charge-discharge curve at 0.1C and 0.5C.
International Journal of Hydrogen Energy, Jun 1, 2017
In this work, track-etched poly (ethylene terephthalate) (PET) membranes having different pore si... more In this work, track-etched poly (ethylene terephthalate) (PET) membranes having different pore sizes were functionalized by the carboxylic groups and the amino groups. Palladium (Pd) nanoparticles of average diameter 5 nm were synthesized chemically and deposited onto pore walls as well as on the surface of these pristine and functionalized membranes. Effect of Pd nanoparticles binding on these membranes were explored and aminated membrane were found to bind more Pd nanoparticles due to its affinity. The morphology of these composite membranes is characterized by Scanning Electron Microscope (SEM) for confirmation of Pd nanoparticle deposition on pore wall as well as on the surface. Gas permeability of functionalized and non-functionalized membranes for hydrogen and carbon dioxide has been examined. From the gas permeability data of hydrogen (H 2 ) and carbon dioxide (CO 2 ) gases, it was observed that these membranes have higher permeability for H 2 as compared with CO 2 . Due to absorption of hydrogen by Pd nanoparticles selectivity of H 2 over CO 2 was found higher as compared to without Pd embedded membranes. Such type of membranes can be used to develop hydrogen selective nanofilters for purification/separation technology.
Open physics journal, Aug 26, 2016
Present research work deals with the optical study of Zinc Oxide (ZnO) dispersed Polycarbonate/Po... more Present research work deals with the optical study of Zinc Oxide (ZnO) dispersed Polycarbonate/Polymethylmethacrylate (PC/PMMA) blend nanocomposites. ZnO nanoparticles have been prepared by simple chemical route and their average size has been confirmed by Transmission Electron Microscopy (TEM). The average particle size of the nanoparticles has been found to be ~11 nm. Formation of PC/PMMA blend nanocomposites has been confirmed by means of X-ray Diffraction (XRD). Absorption spectra, recorded using UV-Visible spectrophotometer, have been used to determine optical constants such as band gap, extinction coefficient, refractive index and real & imaginary part of dielectric constant. It has been found that band gap decreases as ZnO wt% increases in the blend nanocomposites. Lowest band gap has been found for PC25%/PMMA75% with ZnO 3 wt% blend nanocomposite. Increase in refractive index has also been found with increasing ZnO content. These types of blend nanocomposites have applications in UV-shielding and wave guide technologies.
Advanced Science Letters, Nov 1, 2016
International Journal of Hydrogen Energy, Aug 1, 2017
An efficient way is suggested to reduce the cost of block copolymer (BC) membranes while still ta... more An efficient way is suggested to reduce the cost of block copolymer (BC) membranes while still taking advantage of their unique properties. It is demonstrated that selectivity can be kept almost the same whereas permeability is varied by using thin copolymer films on robust porous PET polymer membranes which acts as a mechanical support. So, a nanoscopic thin selective layer of the block copolymer (PS-b-P4VP) with additive is casted on the PET porous support. Selective extraction of the additive from the block copolymer thin films leads to the formation of a layer with monodispersed pores on the PET support. Measurements of the gas permeability of PET membranes of different pore size with and without block copolymer coating reveal that permeabilities of BC coated membranes decrease whereas selectivities slightly increase in comparison to the porous PET support. Coating of the membranes with BC plays a valuable role for the selectivity against gases like H 2 over CO 2 . The surface morphology of the composite membranes has been determined by atomic force microscopy (AFM) showing the nanoscopic pores. Due to excellent mechanical stability and easy scale up, such membranes may be used in the gas separation technology.
Ferroelectrics, Oct 26, 2017
ABSTRACT Kinetics of glass transition of GeySe94-yIn6 (y = 10, 15 & 20) glassy alloys has bee... more ABSTRACT Kinetics of glass transition of GeySe94-yIn6 (y = 10, 15 & 20) glassy alloys has been studied under non-isothermal condition using Differential Scanning Calorimetery (DSC). The glassy alloys have been prepared by rapid quenching of melt technique. For structure characterization, XRD and EDAX techniques have been used. DSC thermograms have been recorded at heating rates 5, 10, 15 and 20 K/min. from room temperature to 823 K. Lasocka's empirical relation has been used to study the heating rate dependence of glass transition temperature. Activation energy of glass transition, evaluated from Kissinger Peak shift method, increases with increase of Ge content in GeySe94-yIn6 (y = 10, 15 & 20) glassy series.
Journal of Physics D, Jun 2, 2006
... View the table of contents for this issue, or go to the journal homepage for more Home Search... more ... View the table of contents for this issue, or go to the journal homepage for more Home Search Collections Journals About Contact us My IOPscience Page 2. ... V Kishore, NS Saxena1, Vibhav K Saraswat, Rakesh Sharma, Kananbala Sharma and TP Sharma ...
Non-metallic material science, Jul 2, 2021
The presented work deals with the structural and optical properties of chemically synthesized TiO... more The presented work deals with the structural and optical properties of chemically synthesized TiO 2 nanoparticles filled PC/PS blend nanocomposites. A series of PC/PS (100/0, 50/50, 0/100 wt%/wt %)-TiO 2 (1, 2, 3 wt %) blend nanocomposites have been prepared by solution casting method. Prepared blend nanocomposites have been subjected to XRD, SEM and FTIR for structural analysis. Optical constants have been analyzed using UV-Vis spectroscopy. The XRD, SEM and FTIR spectrum confirms the formation of PC/PS-TiO 2 blend nanocomposites. Results reveal the decrease in band gap and enhancement in optical constants like, extinction coefficient, refractive index and dielectric constants of blend nanocomposites with nanofiller TiO 2 content.
Research and reviews: journal of material sciences, 2016
The aim of this study is to investigate the effect of Tin (Sn) addition on Band gap (Eg) and Dc c... more The aim of this study is to investigate the effect of Tin (Sn) addition on Band gap (Eg) and Dc conductivity of Se-Te-Sn semi-conducting glasses. This is an effort towards the understanding of physics of temperature dependence of dc electrical volume conductivity of Se75Te25-xSnx (X= 2, 4, 6 & 8) glasses in bulk form. These Chalcogenide glasses were prepared by melt quenching (rapid cooling of melt) technique. The amorphous nature of as prepared glass was confirmed by XRD. Using Keithley Electrometer / High resistance Meter 6517 A, the I-V characteristics of these glasses have been recorded in a temperature range from room temperature to 100˚C. Additionally, the Poole-Frenkel conduction mechanism has also been verified in order to investigate the good agreement with the established fact that most of Chalcogenide glasses obey Poole-Frenkel conduction mechanism. To calculate the Band gap, with the help of Ocean Optics Spectrophotometer, absorption spectra has been recorded. Analysis of these absorption spectra using Tauc relation reveals that these glasses are semiconducting and direct band gap material.
Macromolecular Symposia, Dec 1, 2017
In the present paper crystallization kinetics of Ge 25-x Se 75 Sb x (x ¼ 12, 15, 18) chalcogenide... more In the present paper crystallization kinetics of Ge 25-x Se 75 Sb x (x ¼ 12, 15, 18) chalcogenide glasses has been investigated using thermal analysis (TA) technique. Ge 25-x Se 75 Sb x (x ¼ 12, 15, 18) chalcogenide glasses have been prepared by rapid quenching of melt technique. For structure characterization XRD technique has been used. Out of various TA techniques Differential Scanning Calorimetery (DSC) has been used for present study. DSC scans have been carried at different heating rates i.e. 5, 10, 15 and 20 K/min. For evaluation of activation energy of crystallization various theoretical models Kissinger, Ozawa, Augis-Bennet and Matusita-Sakka have been used. Activation energy of crystallization increases with increase of Sb content in Ge 25- x Se 75 Sb x (x ¼ 12, 15, 18) glassy series. The value of Avrami index indicates bulk crystallization with one or two dimensional growth.
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Papers by Vibhav Saraswat