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.

&nbsp;

&nbsp;

VIT University

Department of Physics

Laser shock peening (LSP) of 6061-T6 aluminum alloy was performed and parametric effects post LSP on mechanical aspects and microstructural evolution are meticulously studied using various means of characterization techniques such as residual stress analysis, surface roughness, Vickers microhardness, tensile testing, X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and electron back scattered diffraction (EBSD). Work hardened layer of ∼1500 μm depth is obtained with significant improvement in cross-sectional microhardness up to 33.04 %. Beneficial compressive residual stress of maximum magnitude up to -273 MPa was induced in laser peened specimens concentrating its overall effect around the depth of 100 μm along the effective depth region. Second phase Mg5Si6 (βʺ) precipitates were observed post LSP while analyzing XRD profiles along with the peak broadening and peak shifting towards higher 2θ angle justifying the results obtained in residual stress profile. Mg5Si6 (βʺ) precipitates are attributed as contributing precipitates in improving the mechanical properties of LSPed specimens along with the dense dislocation density caused by severe plastic deformation during LSP. High angle grain boundaries (HAGBs) fraction was increased in LSPed specimens and its effect is noticed in microhardness profile. The collective contribution of strain hardening, second phase precipitates, peak broadening, dislocation density and increased fraction of HAGBs is observed in mechanical and microstructural aspects of LSPed specimens. The results are discussed in detailed and are strongly correlated with each other. © 2020 Elsevier B.V.

World University root node

School of Advanced Sciences

Vellore Campus

Journal of Materials Processing Technology

Effect of laser shock peening on mechanical and microstructural aspects of 6061-T6 aluminum alloy

Spinel ferrite nanoparticles are widely studied to evaluate their suitability in many applications. Magnetic, electrical, optical, and catalytic properties of spinel ferrites nanoparticles depend on: i) intrinsic property such as cation distribution among tetrahedral (A-site) and octahedral ligand (B-site) sublattices in spinel structure and ii) extrinsic properties such as specific surface area and particle size distribution of nanoparticles. To enhance the above properties by modifying both the intrinsic and extrinsic parameters, narrow size distributed Mg0.7Zn0.3Fe2O4 mixed spinel ferrite nanoparticles are synthesized by the solvothermal reflux method using high boiling point reflux solvents. The particles are crystallized in a cubic spinel structure and are single crystallites with an average particle diameter of 12 nm, measured from an electron micrograph. The temperature-dependent dielectric constant (varepsilon{prime}) and dielectric loss (varepsilon{prime prime}) of the sample show no change below 290 °C and increase with temperature up to 450 °C. Both varepsilon{prime} and varepsilon{prime} decrease with the increase of electric field frequency and shows dominant space charge polarization at grain boundaries. The DC conductivity estimated from impedance spectra (Cole-Cole plot) shows the Arrhenius model electron hopping conductivity mechanism above 390 °C. Nanoparticles show high Ms (57.41 eμg) than that synthesized by other methods. The sample shows the magnetic hyperthermia value of 189 W/g at 1 mg/mL concentration. The sample degraded 95% of rhodamine B dye in water in 320 min under UV light illumination. Some of these properties are superior to Mg0.7Zn0.3Fe2O4 nanoparticles synthesized by other wet chemical and/or ball milling methods. © 1965-2012 IEEE.

IEEE Transactions on Magnetics

Dielectric, Magnetic Hyperthermia and Photocatalytic Properties of Mg.Zn.FeO Nanocrystals

Efficient spin injection from epitaxial ferrimagnetic NiFe2O4 thin films into a Pd layer is demonstrated via spin Seebeck effect measurements in the longitudinal geometry. The NiFe2O4 films (60 nm to 1 μm) are grown by pulsed-laser deposition on isostructural spinel MgAl2O4, MgGa2O4, and CoGa2O4 substrates with lattice mismatch varying between 3.2 and 0.2%. For the thinner films (≤330 nm), an increase in the spin Seebeck voltage is observed with decreasing lattice mismatch, which correlates well with a decrease in the Gilbert damping parameter as determined from ferromagnetic resonance measurements. High-resolution transmission electron microscopy studies indicate substantial decrease of antiphase boundary and interface defects that cause strain relaxation, i.e., misfit dislocations, in the films with decreasing lattice mismatch. This highlights the importance of reducing structural defects in spinel ferrites for efficient spin injection. It is further shown that angle-dependent spin Seebeck effect measurements provide a qualitative method to probe for in-plane magnetic anisotropies present in the films. © 2020 American Physical Society.

Fulltext

Physical Review Applied

Enhancement in Thermally Generated Spin Voltage at the Interfaces between Pd and NiFe2 O4 Films Grown on Lattice-Matched Substrates

Transition metal chalcogenides have been widely studied as a promising electrocatalyst for the hydrogen evolution reaction (HER) in acidic conditions. Among various transition metal chalcogenides, tungsten disulfide (WS2) is a distinguishable candidate due to abundant active sites and good electrical properties. Herein, we report a facile and selective synthetic method to synthesize WS2 with an intriguing two-dimensional nanostructure by using cysteine (C3H7NO2S) as a chemical agent. In addition, nitrogen can be incorporated during chemical synthesis from cysteine, which may be helpful for enhancing the HER. The electrocatalytic activity of N-doped WS2 exhibits a promising HER in acidic conditions, which are not only higher than W18O49 nanowires and hex-WO3 nanowires, but also comparable to the benchmark Pt/C. Moreover, excellent electrocatalytic stability is also demonstrated for acidic HER during long-term tests, thus highlighting its potential use of practical applications as an electrolyzer. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

Catalysts

Facile synthesis of n-doped ws2 nanosheets as an efficient and stable electrocatalyst for hydrogen evolution reaction in acidic media

To date, the second harmonic generation (SHG) has a great effect on photonic devices. However, it is a formidable challenge to achieve reconfigurable SHG. Hereby, we experimentally demonstrate the SHG response from the oriented Ge2Sb2Te5 (GST) grains induced by polarized laser pulses for the first time. The orientation of GST grains is found to be perpendicular to the polarization direction of the pump laser. Such unique ordered structures result in a periodic change of SHG intensity with the input polarization angle of the pump laser rotating every 180°. These findings may pave avenues for generating nonlinear optical sources with a simple process, scalability, and switchable functionality. © 2020 American Chemical Society.

ACS applied materials \& interfaces

Tunable grain orientation of chalcogenide film and its application for second harmonic generation

Thermal lithography is an alternative technique that can fabricate patterns beyond the diffraction limit. In thermal lithography, it is hard to obtain morphology on demand due to the difficulty in controlling thermal diffusion caused by the long laser pulses. To address this issue, enhanced thermal lithography with multiple femtosecond laser pulse exposure is proposed in this paper. C-Sb2Te3 (CST), a fine-tunable phase change material, is used as a negative heat-mode resist for the first time. The resolution and steepness of the microstructure prepared by this method are obviously enhanced compared with the conventional way. The height of the wet-etched microstructures can be preciously adjusted by tuning the exposure dose of femtosecond laser pulses. Microstructure and thermal field analysis results reveal the origin of the high resolution and fine-tuning. CST-based phase-change memory cell arrays were fabricated with this method to confirm the feasibility and advantage. This work provides an effective way to achieve enhanced thermal lithography in the manufacturing of micro/nanostructure-based electronic and photonic devices. © 2019 Elsevier B.V.

Applied Surface Science

Nanostructure patterning of C-Sb2Te3 by maskless thermal lithography using femtosecond laser pulses

Background: To study and analyze the variatons in delivered doses to rectum and bladder of carcinoma prostate patents by using kilo Voltage (kV) 'Cone Beam Computed Tomography' (CBCT) images. Materials and Methods: 2-Dimensional kilo Voltage (2D kV) Imaging and CBCT were done for seven prostate cancer patents. The deviatons among their shifts were correlated and the volumetric changes of the rectum and bladder were analyzed. Rectum and bladder contours were redrawn on every boost fractons and dose calculaton were performed on CBCT images to study the effect on dose volume histograms. Results: A correlaton coefficient for set-up variatons was within 0.78 for all directons between CBCT soft tssue matching and kV bone match. The mean deviaton of bladder and rectum volume over the boost fractons was -12% to +9% (SD 31cc to 70cc) and -10.2% to+12% (SD 3.1cc to 14.9cc), respectvely. Bladder mean dose variaton was &lt;1.5Gy for all three positons whereas it was &lt;3.65Gy for rectum. D1% dose deviaton from reference plan for bladder was 1.1Gy (CBCT matched positon), 1.4Gy (kV matched positon), and 1.7Gy (no correcton), and for rectum, the deviatons were 1.2Gy, 2.2Gy, 3.6Gy, respectvely. No significant deviaton was found statstcally significant at the low dose region. Conclusion: It is possible to achieve good dose delivery and conformity in target (prostate) with CBCT image guidance rather than kV bone match, but dose contributon to the rectum is dependent on the patent's anatomy, bladder filling, and rectum filling, pertaining to the day of examinaton. © 2020 Novin Medical Radiation Institute. All rights reserved.

International Journal of Radiation Research

Volume and dosimetric analysis of rectum and bladder for prostate carcinoma patients by using kilo voltage cone beam computed tomography (CBCT)

More effective organic charge transfer nonlinear optical material of 2-(4-methlybenzylidene) malononitrile (MBM) has been synthesized via knoevenagel condensation reaction method and single crystals of unprecedented MBM were successfully cultivated in the presence of ethanol solution by the adaption of slow evaporation solution growth method. Cell parameters and phase purity of the obtained MBM crystals were investigated with the help of Single crystal and powder X-ray diffraction analysis. The morphology of the grown crystal was generated using WinXMorph software. Linear optical characterization was carried out in order to figure out its transmittance efficiency (82%), cut-off wavelength (λ = 458 nm) and energy band gap (Eg = 3.05eV) of the title material. Electrical behavior of the MBM crystal was examined on the basis of dielectric properties. Title crystals thermal tolerance and melting point was examined through TG-DSC analysis. The grown MBM crystal was subjected to Single beam Z-scan technique in order to figure out its third order nonlinear optical nature and its susceptibility is compared with other reported centrosymmetric crystals. Considering its large transmittance range, thermal stability and effective NLO performance, MBM is a potential candidate for NLO applications. © 2020 Elsevier B.V.

Optical Materials

Investigation on the growth, optical, electrical, thermal and third order NLO properties of 2-(4-methlybenzylidene) malononitrile (MBM) single crystal

Materials Today: Proceedings

Z-scan studies on organic crystal (E)-1-(2-chlorobenzylidene) cyclododecane-1-one for photonic applications

Rhodamine B (RhB), a toxic dye is environmentally hazardous and harmful to living organisms, which is primarily used in various industries. Multiferroic BiMnO3 (BMO) with (BMO 1) and without (BMO 2) surfactant (CTAB) was synthesized using hydrothermal method, which acts as a photocatalyst for the Rhodamine B dye degradation process. BMO had tested as a photocatalyst for dye degradation of Rhodamine B dye in UV and Visible light irradiation due to its narrow bandgap. On performing various structural and optical characterizations, the structure of as-prepared BMO samples confirmed, and their crystallite size and bandgap were compared for with and without CTAB treated BMO samples. Under UV irradiation, the decomposition of RhB efficiency and decay time had been calculated as 68% and 75 min for BMO 1. In H2O2 assisted visible light irradiation, BMO 2 shows better performance (90% and 55 min). © 2020, Springer Science+Business Media, LLC, part of Springer Nature.