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

Composite Polyethylene oxide (PEO)/Cobalt oxide (CoO) electrolyte containing LiClO4 salt forms composite polymer electrolytes (CPE). The ionic conductivity of CPE is noticed to be 1 order greater than PEO-LiClO4 solid polymer electrolyte (SPE) films at room temperature. The CPE films are prepared by solution costing technique. Structural, molecular and thermal properties CPE films are investigated using XRD, FTIR and DSC characterization techniques. XRD, FTIR and DSC spectra of CPE films designates molecular level changes observed in PEO polymer host leading to increased polymer chain movement results in enhanced ionic conductivity. © 2020 Author(s).

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School of Advanced Sciences

Vellore Campus

AIP Conference Proceedings

PEO/CoO composite polymer electrolytes for lithium batteries

Structural characteristics and magnetocaloric effect of Sm2NiMnO6 double perovskite oxide nanoparticles synthesized via the solution combustion technique have been investigated. From the X-ray structural study, it is found that the Sm2NiMnO6 compound crystallizes in the monoclinic structure (P21/n space group), where Ni and Mn atoms are ordered at 2c and 2d sites, respectively. Transmission electron microscopic image reveals agglomerated nanoparticles with an average particle size of 60 nm. Two magnetic Curie transition points (TC1 = 141 K, TC2 = 67 K) observed from the isofield magnetization measurement affirmed the short-range ferromagnetic behavior of Sm2NiMnO6 creating the continuous second-order transition followed by the discontinuous first-order transition. A minor cusp at 10 K confirmed the microscopic superparamagnetic behavior at low fields apart from the dual magnetic phase transition. Adiabatic demagnetization of Sm2NiMnO6 nanoparticles was measured in terms of magnetic entropy, and the magnetic refrigerant capacity was calculated to be 0.44 J kg−1 K−1 and ~ 20 J kg−1 respectively. © 2020, Springer Nature B.V.

Fulltext

Journal of Nanoparticle Research

Multiple magnetic phase transition and short-range ferromagnetic behavior influence on magnetocaloric effect of Sm2NiMnO6 nanoparticles

In this work, we propose a D-shaped photonic crystal fiber (PCF) based surface plasmon resonance sensor with a V-groove analyte channel for the detection of analytes and numerically analyze its sensing performance for a wide range of liquid analytes. In a stand out to the usual D-shaped fiber, we design a separate V-groove for holding the analyte sample, which not only minimizes the sample quantity but also reduces the metal coating region. By using the finite element method, we find that the proposed PCF sensor has a maximum wavelength sensitivity of 31,600 nm/RIU for a sensing range of 1.33–1.43 with a resolution of 3.16 × 10−6 RIU. Besides, the numerical results corroborate that the proposed sensor is robust against the variations of structural parameters. Thus, the proposed sensor is suitable for detecting biomolecules, organic and chemical samples. As the proposed sensor exhibits promising sensing performance, we envisage that the sensor could be engaged in various fields of chemical and biosensing applications. © 2020 Elsevier GmbH

Optik

High sensitive D-shaped photonic crystal fiber sensor with V-groove analyte channel

Studies on organic scintillation single crystal 1,1,4,4-Tetraphenyl-1,3-Butadiene (TPB) grown by vertical Bridgman technique for the first time is reported. Structural analysis was carried out with Single crystal and Powder X-ray diffractometer which is confirmed the cell parameters of the grown crystal. A definite vibrational analysis was identified on the fundamental modes of vibration. The refractive index of 1.618 was recorded by Abbe refractometer. UV–Vis near IR spectrum was used to determine the absorption edge and found to be 419 nm. The bandgap energy of the crystal was found to be 2.89 eV. Fluorescence spectra of the crystal exhibit a broad emission band at 440 nm. The fluorescence lifetime of TPB measured by TCSPC method reveals a short decay time of 16 ns for prompt and 40 ns for delayed. Photoconductivity of TPB exhibits the positive photoconductivity nature. The Vickers microhardness were used to determine the hardness number (Hυ) and Meyers index of the grown crystal. Essential Mechanical properties such as stiffness constant and yield strength were calculated. Chemical etching was carried out to study the defects and growth mechanism involved in the grown crystal and the etching characteristics of the crystal surface enunciate the 2-dimensional layer growth. © 2020 Elsevier B.V.

Optical Materials

Growth and characterization of organic scintillation single crystal 1,1,4,4-Tetraphenyl-1,3-Butadiene (TPB) using vertical Bridgman technique

Cobalt-doped ZnTe (Co:ZnTe) polycrystalline powders with different Co concentrations (0%, 3%, 5% and 8%) are prepared by solid state reaction method with an aim to study their dilute magnetic semiconducting behaviour. The effect of Co doping on the structural, optical and magnetic properties of the synthesized samples are investigated. The phase and crystallinity of Co:ZnTe powders are studied through X-ray diffraction and Raman spectroscopy. The surface morphology has been analysed through scanning electron microscopy. The chemical environment of the dopant in the host lattice is analysed through X-ray photoelectron spectroscopy. The optoelectronic properties of Co:ZnTe powder samples are evaluated through diffuse reflectance spectroscopy and photoluminescence spectroscopy. The ferromagnetic behaviour of the samples has been investigated at room temperature by the vibrating sample magnetometer. The origin of magnetism in ideal Co:ZnTe bulk system has been analysed through ab initio density functional theory. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

Journal of Materials Science: Materials in Electronics

Structural, optical and magnetic properties of cobalt-doped ZnTe dilute magnetic semiconductors

Polyvinylidene fluoride (PVDF) and poly methyl methacrylate (PMMA) polymer blends were prepared by loading optimized quantity of attapulgite clay (AT) and hexagonal boron nitride (h-BN) nanopowder admixture. The crystalline phases were confirmed by X-ray diffraction patterns owing to the crystallinity of PVDF and h-BN. The shape and dimension of AT and h-BN fillers were confirmed by transmission electron microscope. The morphological changes were confirmed by scanning electron microscope, and the chemical composition of elements in the blends was confirmed by energy-dispersive spectroscopy. Frequency-dependent dielectric properties of the mixtures were explored as a function of temperature. The dielectric constant (εr) was improved (~ 6.87) when the AT and h-BN were loaded in an equal ratio (5:5 wt%). A low dissipation factor (tan δ) was obtained (~ 0.2) for the optimized loadings of AT and h-BN. Thermal stability of the blends was studied, and a delay in the degradation process at various steps was studied for AT/h-BN-incorporated PVDF/PMMA blends. The overall results suggest that the optimized loading of AT and h-BN significantly improved the dielectric and thermal properties of the PVDF/PMMA blends. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

Enhanced structure, dielectric, and thermal properties of attapulgite clay and hexagonal boron nitride admixture loaded polymer blends

Chiral interactions in magnetic systems can give rise to rich physics manifested, for example, as nontrivial spin textures. The foremost interaction responsible for chiral magnetism is the Dzyaloshinskii-Moriya interaction (DMI), resulting from inversion symmetry breaking in the presence of strong spin-orbit coupling. However, the atomistic origin of DMIs and their relationship to emergent electrodynamic phenomena, such as topological Hall effect (THE), remain unclear. Here, we investigate the role of interfacial DMIs in 3d-5d transition metal-oxide-based LaMnO3/SrIrO3 superlattices on THE from a chiral spin texture. By additively engineering the interfacial inversion symmetry with atomic-scale precision, we directly link the competition between interfacial collinear ferromagnetic interactions and DMIs to an enhanced THE. The ability to control the DMI and resulting THE points to a pathway for harnessing interfacial structures to maximize the density of chiral spin textures useful for developing high-density information storage and quantum magnets for quantum information science. © 2020 American Association for the Advancement of Science. All rights reserved.

Science Advances

Interfacial tuning of chiral magnetic interactions for large topological Hall effects in LaMnO3/SrIrO3 heterostructures

A one-step citrate-gel combustion method was employed to process (Ba0.5Sr0.5Fe12O19)1-x/(Y3Fe5O12)x nanocomposite ferrites with different compositions (x = 0.1, 0.2, 0.3, and 0.4). The morphological, structural, thermal, and magnetic properties of the as-synthesized samples were investigated with respect to their structural, thermal, and magnetic properties using field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), thermogravimetric analysis and differential scanning calorimetry (TGA/DSC), and vibration sample magnetometer (VSM), respectively. The FESEM micrographs revealed homogeneous distribution of hard and soft magnetic phases throughout the sample. The XRD results confirmed the crystallization of both BSFO and YIG as hard and soft magnetic phases, respectively, without any other secondary phases. The TGA/DSC curve confirmed the phase formation of the nanocomposite material around 1100 °C with a total weight loss of ~ 63%. The magnetic hysteresis loops of as-synthesized ferrite nanocomposites demonstrated a single-phase behavior due to the existence of strong inter-grain exchange coupling between the hard and soft magnetic phases. The single peak in switching field distribution (SFD) curves of synthesized nanocomposite ferrite were observed for all the compositions. Maximum values of coercivity (6090 Oe), saturation magnetization (54 emu/g), and energy product (19.5 kJ/m3) were achieved for the BSFO0.9/YIG0.1 composition. The results of the present study suggest that the magnetic parameters such as those derived from the nanocomposite ferrites are superior as compared with that of those obtained for the constituent YIG and BSFO phases. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

Processing and characterization of Ba0.5Sr0.5Fe12O19/Y3Fe5O12 nanocomposite ferrites towards permanent magnet applications

Aim:Total Skin Electron Therapy (TSET) is a specialised radiotherapy technique to treat cutaneous T-cell lymphomas. The purpose of this article is to review different in-vivo dosimetry techniques and to identify further research direction in TSETMaterials and methods:Studies focused on in-vivo dosimetry in TSET were included. Studies based on absolute dosimetry in TSET were excluded and no restriction was applied regarding the type of treatment technique and the type of dosimeter.Result:From the review of articles, we have found that obesity index and patient position during treatment plays a major role in underdose or overdose in TSET. Many studies favour individualised boost dose to patients. The analysis showed that thermoluminescent dosimeters are the most widely used dosimeters in TSET, and time-consuming is the only drawback in the use of dosimetry.Conclusion:Study showed that the practice of using in-vivo dosimetry would be better way to treat TSET by ensuring accuracy of dose delivery to the patients. Further, only limited studies are available for dosimetry with radiochromic films. With this observation, we have started exploring the use of radiochromic film in our TSET dosimetry, and the results can be analysed to standardise the technique in future. © The Author(s), 2020. Published by Cambridge University Press.

Journal of Radiotherapy in Practice

In-vivo dosimetry in Total Skin Electron Therapy: Literature review

Moth and butterfly ommatidial nanostructures have been extensively studied for their anti-reflective properties. Especially, from the point of view of sub-wavelength anti-reflection phenomena, the moth eye structures are the archetype example. Here, a comparative analysis of corneal nipples in moth eye (both Male and Female) and butterfly eye (both Male and Female) is given. The surface of moth(Male and Female) and butterfly(Male and Female) eye is defined with regularly arranged hexagonal facets filled with corneal nipples. A detailed analysis using high-resolution scanning electron microscopy images show the intricate hexagonal arrangement of corneal nipples within the individual hexagonal facet. Individual nipples in moth are circular with an average diameter of about 140/165 nm (Male/Female) and average internipple separation of 165 nm. The moth eye show the ordered arrangement of the corneal nipples and the butterfly eye (Male/Female) show an even more complex arrangement of the nipples. Structurally, the corneal nipples in both male and female butterflies are not circular but are polygons with 5, 6, and 7 sides. The average center-to-center separation in the butterfly(Male/Female) is about 260 nm/204 nm, respectively. We find that these corneal nipples are organized into much more dense hexagonal packing with the internipple (edge-to-edge) separation ranging from 20 to 25 nm. Each hexagonal facet is divided into multiple grains separated by boundaries spanning one or two crystallographic defects. These defects are seen in both moth and butterfly. These are typical 5-coordinated and 7-coordinated defect sites typical for a solid-state material with the hexagonal atomic arrangement. Even though the isolated defects are a rarity, interwoven (7-5) defects form a grain boundary between perfectly ordered grains. These defects introduce a low-angle dislocation, and a detailed analysis of the defects is done. The butterfly eye (Male/Female) is defined with extremely high-density corneal nipple with no apparent grains. Each corneal nipple is a polygon with "n"sides (n = 5, 6, and 7). While the 5- and 7-coordinated defects exist, they do not initiate a grain rotation as seen in the moth eyes. To find out the similarity and the difference in the reflectivity of these nanostructured surfaces, we used the effective medium theory and calculated the reflectivity in moth and butterfly eyes. From this simple analysis, we find that females have better anti-reflective properties compared to the males in both moth and butterfly. Copyright © 2020 American Chemical Society.