Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Department of Physics

Tin doped ZnS powders (Zn1−xSnxS, x = 0.00, 0.02, 0.05&amp;0.08) were synthesized by a simple Solid state reaction and were characterized by Powder X-ray diffractometer (XRD), UV–Vis–NIR diffuse reflectance spectrophotometer, fluorescence spectrophotometer, scanning electron microscope (SEM) and vibrating sample magnetometer (VSM). The XRD studies revealed that no change in crystal structure was observed by the substitution of Sn into ZnS lattice. The crystallite size was calculated by Scherrer's formula and found that the crystallize size of Sn doped ZnS powders were in the range of 35–45 nm. From the diffused reflectance spectra, the band gap values of Zn1−xSnxS powders were estimated, and they were found to be in the range of 3.53–3.58 eV. The pure ZnS particles showed higher optical absorption in visible region than that of Sn doped ZnS nano particles. The Photoluminescence (PL) spectra of Zn1−xSnxS powders were recorded in the range of 400–700 nm with an excitation wavelength of 360 nm. The Zn1−xSnxS powders exhibited ferromagnetism at low temperature (100 K) and super paramagnetism at room temperature (300 K). The strength of magnetization increased with increase of Sn doping concentration from 0.015 emu/g to 0.18 emu/g, when x increased from 0.00–0.05. © 2017 Elsevier B.V.

VIT Unitversity

School of Advanced Sciences

Vellore Campus

World University root node

Physica B: Condensed Matter

Structural, optical and magnetic properties of Sn doped ZnS nano powders prepared by solid state reaction

The present study aimed at verifying the water equivalency of the PAGAT gel and metal nano particle (different concentration of gold and silver) PAGAT (MPAGAT) gel in terms of effective atomic number (Zeff). In addition to Zeff, energy absorption buildup factor (EABF) and exposure buildup factor (EBF) have been calculated for MPAGAT. Auto-Zeff computer program was used to calculate the effective atomic number for MPAGAT in the energy region 10 keV to 1 GeV. EABF and EBF were calculated by using geometric progression (GP) fitting formula in the energy region from 0.015 to 15 MeV up to penetration depths of 40 mean free path. Mass attenuation coefficient of MPAGAT gel was obtained by the XCOM program and the results were compared with Monte Carlo simulation. It has been found that Au and Ag doped PAGAT gels show excellent water equivalency than undoped PAGAT gel at dopant concentrations of 0.1, 0.5 and 1 mM. From the results, it was noted that the EABF and EBF were significantly varied with respect to photon energy and chemical composition of given PAGAT gel with different concentration of metal nano particle. Since mass attenuation coefficients were used to obtain Zeff and EABF, the reliability of the mass attenuation coefficient data were cross checked with Monte Carlo simulation, and a good agreement was obtained between XCOM and Monte Carlo simulation.

Vacuum

Effective atomic number and buildup factor calculations for metal nano particle doped polymer gel

The titanium alloy TC6 was laser peened without coating (LPwC) with a pulsed Nd:YAG laser (1064 nm) at power densities of 3, 6 and 9 GW cm− 2. Microhardness data revealed that hardness does not linearly scale with power density. Residual stress analysis indicated that the profile has two distinct regions, one near surface (&lt; 100 μm) showing thermal effects due to laser beam-material interaction and a far-surface region (&gt; 100 μm) with decreasing compressive residual stresses with increasing power density. Transmission electron microscopy (TEM) showed high dislocation density with dislocation tangles and dislocation walls without dislocation cell or nanocrystals in the near surface region. Synchrotron radiation showed the increase in volume fraction of β phase with increase in power density in the far-surface region. Fatigue performance of the samples (number of cycles to failure) subjected to LPwC at a power density of 6 GW cm− 2 was found to have increased by a factor of 2–4, in the load range of 12.5–15 kN. Further, it was observed that in addition to the normally observed sub-surface crack nucleation of LPwC samples, additional formation of β phase in the far-surface region improves fatigue performance. © 2017 Elsevier Inc.

Materials Characterization

Phase gradient in a laser peened TC6 titanium alloy analyzed using synchrotron radiation

An organic quinolinium derivative crystal 1-ethyl-2-[2-(3,4,5-trimethoxy-phenyl) vinyl]-quinolinium iodide has been synthesized by knoevenagel condensation reaction and the crystals were grown by solution growth method for the first time. The grown crystal structure was confirmed by single crystal X-ray diffraction analysis and it showed that TMQI crystal belong to the triclinic space group P-1. The molecular structure and composition of the crystal was further confirmed by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (FT-NMR) spectroscopic techniques. The thermal stability of the title crystal has been investigated by TG/DSC curves. The linear optical response of the grown crystal has been examined by using UV–Vis-NIR spectral analysis, and the photoluminescence spectrum exhibits strong emission radiation at 558 nm. The chemical etching analysis was carried to reveal the growth pattern of TMQI crystal. Laser induced damage threshold of the title crystal was found to be 1.15 GW/cm2. The third order nonlinear optical property of grown crystal was studied using Z-scan technique and the magnitude of third order nonlinear susceptibility has found to be in the order of 10−3 esu, which is higher than the reported quinolinium derivative crystals. © 2017, Springer Science+Business Media New York.

Journal of Materials Science: Materials in Electronics

Synthesis, growth, structural, optical and third order nonlinear optical properties of new quinolinium derivative single crystal: 1-ethyl-2-[2-(3,4,5-trimethoxy-phenyl) vinyl]-quinolinium iodide

Transition metal cations distribution among tetrahedral and octahedral sites in Fe3O4 has profound influence on it properties. The cations distribution among these sites were influenced by crystal field stabilization energy (CFSE) of a substituent ion. It was reported that Cu2+ substitutes both Fe3+ in tetrahedral and Fe2+ in octahedral sites of magnetite though it has high CFSE for octahedral sites. Thus it promotes mixed (normal &amp; inverse) spinel structure and hence the properties deviate from the prediction. Here we show that selective octahedral site substitution of Fe2+ by Cu2+ in single crystal Fe3O4 nanoparticles was possible by solvothermal reflux method at moderate temperatures (≈300 °C). It was attributed to reduced energy barrier for crystallization and high diffusion coefficient of the metal cations at moderate temperature in low viscous organic solvents mixture, at ambient pressure, compared to coprecipitation and solid state reaction protocols. In addition, effective removal of exothermic crystal lattice energy, released during nucleation and growth process, by natural gas bubbles formed in the reflux organic solvent mixture. This promotes effective diffusion of cations during the growth process and easy octahedral occupation by Cu2+ in Fe1−xCuxFe2O4 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5 &amp; 0.6) single crystal nanospheres. The octahedral substitution was confirmed by reduction of crystal lattice parameter as well as ferromagnetic strength of octahedral sublattice with enhanced Cu2+ concentration. In addition, morphology, lattice vibrational frequency and electron excitation spectra of the nanospheres were studied. The Langevin function fit analysis reveals that superparamagnetic domain diameter were slightly less than the particle diameter obtained from TEM micrograph. © 2017 Elsevier B.V.

Journal of Crystal Growth

Site selective Cu 2+ substitution in single crystal Fe 3 O 4 biocompatible nanospheres by solvothermal reflux method

The present article deals with the preparation and characterization of pure and lead oxide (PbO) nanoparticles embedded polyvinyl alcohol (PVA) films by using a colloidal processing technique. PbO nanoparticles were successfully synthesized using the simple precipitation method. Polymer/ceramic-based flexible and self-standing films were obtained and further characterized using various analytical techniques. The mechanical and dielectric properties were also investigated. The Fourier Transform Infrared Spectroscopy (FTIR) results indicate that the structural characterization of PVA is strongly affected by the incorporation of PbO. Thermal analysis results indicate that the thermal stability of the PbO-doped PVA film has improved as compared with the neat PVA film. The mechanical property of nanocomposites has improved significantly due to an increase in filler loadings, indicating that a good interaction exists between PbO nanoparticles and PVA matrix. The dielectric constant of PVA/PbO nanocomposites has significantly improved with comparatively low dielectric loss values, indicating that the nanocomposites can be considered as an attractive material for embedded capacitor applications. © 2015 Wiley Periodicals, Inc.

Advances in Polymer Technology

Investigation of Microstructure, Morphology, Mechanical, and Dielectric Properties of PVA/PbO Nanocomposites

Polymer Composites

Coir pith/nylon/epoxy hybrid composites: Dynamic mechanical, ageing, and dielectric properties

Biocompatible Mg1− xZnxFe2O4 (x = 0.2, 0.4, 0.5, 0.6 &amp; 0.8) nanoparticles were synthesized by solvothermal reflux method. All compounds were crystallized in cubic spinel structure with slightly enhance of lattice parameter with biocompatible substituent Zn2+ concentration. All compounds were shown spherical geometry with average particle diameter is around 12 nm (colloidal size). The spinel structure formation was confirmed by X-ray diffraction,electron diffraction, infrared, Raman shift measurements. Infrared analysis shows oleic acid coating on the surface of nanoparticles and TGA analysis shows that oleic acid desorbs from nanoparticle by decomposition at around 400 °C. UV-Vis-NIR spectra show all the compounds show energy band gap in the semiconductor range (≈ 1.9 eV). All compounds show superparamagnetic characteristics at room temperature with enhanced saturated mass magnetization (Ms) with Zn2+ concentration up to x = 0.5 and then reduces with further enhance of x up to 0.8. The Ms changes were ascribed to occupation of Zn2 + at tetrahedral sites and proportional enhance of Fe3+ at octahedral sites. The enhanced Fe3+ concentration at octahedral sublattice leads to formation Fe3+-O2−-Fe3+ networks which favor antiferromagnetic interactions due to superexchange phenomenon. Photocatalytic activity of all compounds were studied through methylene blue (MB) degradation analysis. All compounds show ≈ 96% degradation of MB upon 70 min irradiation of light on photoreactor vessel. In addition, photocatalytic activity (degradation efficiency) enhances with Zn2 + concentration in MgFe2O4. The Zn2+ substitution enhances both Ms and photocatalytic activity biocompatible of MgFe2O4 nanoparticles. © 2017

Journal of Photochemistry and Photobiology B: Biology

Photocatalytic study and superparamagnetic nature of Zn-doped MgFe 2 O 4 colloidal size nanocrystals prepared by solvothermal reflux method

Department of Biotechnology

School of Bio Sciences and Technology

Materials Technology

Laser induced optical and microscopic studies of salicylic acid influenced KH2PO4crystal for photonic device applications

Poly(vinyl chloride) (PVC)—poly(butyl methacrylate) (PBMA) blended polymer electrolytes with lithium perchlorate (LiClO4) as the complexing salts are prepared by solution casting technique. The addition of PBMA into PVC matrix is found to induce considerable changes in physical and electrical properties of the polymer electrolytes. Addition of PBMA into PVC matrix is found to increase the conductivity by two orders of magnitude (1.108 × 10−5 S cm−1) when compared with that of the pristine PVC polymer electrolyte (10−7 S cm−1). Structural, thermal, mechanical, morphological, and polymer–salt interactions are ascertained from X-ray diffraction (XRD), thermogravimetry/differential thermal analysis (TG/DTA), mechanical analysis, scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) respectively. A thermal stability upto 250 °C is asserted from the TG/DTA analysis. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44939. © 2017 Wiley Periodicals, Inc.