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

AM80 magnesium alloy was processed with Equal Channel Angular Press (ECAP)for grain refinement. Laser shock peening without coating (LSPwC)were executed on ECAP processed sample at 8 GW cm−2 and further grain refinement were observed at surface. SEM image expose the grain refinement at different stage of processing, and fine grains of sub-micron size were observed at surface level after ECAP + LSPwC. Residual stress were measured using X-ray diffraction, sin2(Ψ)method and compressive residual stress was found after ECAP. LSPwC intensify the compressive residual stress at surface. Increases in magnitude of residual stresses were noticed with 200 and 300% of LSPwC. Increase in surface roughness were noticed from 0.6 to 6.8 μm by increasing the percentage of LSPwC coverage. Fatigue tests were acknowledged the effect of ECAP and ECAP + LSPwC on reliability of grain refinement technique. ECAP sample showed fatigue life of 7539 cycles against as received. Highest fatigue life of 85,268 life cycles was observed with ECAP + LSPwC by 100% of coverage. Further process of LSPwC for 200 and 300%, fatigue life was significantly decreases to 22,987 and 384 cycles respectively. SEM images of fractured surface exhibits effect of ECAP and LSPwC on crack initiation and propagation for failure. © 2019 Elsevier B.V.

World University root node

School of Advanced Sciences

Vellore Campus

Surface and Coatings Technology

Influence of equal channel angular pressing and laser shock peening on fatigue behaviour of AM80 alloy

VIT Unitversity

Optics & Laser Technology

Residual stress, phase, microstructure and mechanical property studies of ultrafine bainitic steel through laser shock peening

The residual stress distribution due to laser peening without coating (LPwC) was measured by using the synchrotron radiation X-rays from BL-11 at INDUS-2, RRCAT, Indore, India. This was accomplished by using the effective and quick method of angle-dispersive X-ray diffraction (AD-XRD). LPwC was performed on the titanium TC6 and Ti-6Al-4V alloys with a laser wavelength of 1064 and 532 nm and samples were peened with three different laser power densities of 3, 6 and 9 GW cm −2 and subjected to multiple impacts (1/3/5). Followed by that, the residual stress measurements using synchrotron radiation beam energy (SRBE) of 20 and 30 keV were carried out. The results show that LPwC induces higher and deep residual stress depending upon the titanium alloy. The change of residual stress with laser power densities and impact times are calculated and discussed. Although a compressive residual stress (CRS) was observed in majority of the cases, the more detrimental tensile residual stress (TRS) was observed in few cases only, especially with the TC6 alloy. TC6 showed TRS with peening radiations of 532 nm (power density of 3 GW cm −2 ) and 1064 nm (power density of 9 GW cm −2 ). Besides, TRS was observed in multiple peened samples (5 times) at both radiations. In each of the instances the residual stress was measured at SRBE of 20 keV. It is suggested that for beneficial CRS, peening may be employed in conditions other than these. © 2019 Elsevier Ltd

Measurement

Measurement of residual stresses in titanium alloys using synchrotron radiation

Spinel ferrites at nanoscale showed quite different properties rather than the bulk counterpart. Among all the ferrites, ZnFe2O4 compound is chemically stable and showed very good properties at room temperature. In this investigation, we reported the synthesis and characterization of ZnFe2O4 single-phase crystals of diameter 11 nm by solvothermal reflux method. Temperature-dependent dielectric constant, dielectric loss, and ac-electrical conductivity of the pellet were measured up to 450 °C under different alternating electric field frequencies from 1 kHz to 1 MHz. The obtained data revealed interfacial or space charge polarization mechanism. Furthermore, the sample showed superparamagnetic nature at room temperature. In addition, the magnetic hyperthermia value and specific heat generation rate (SHGR) of 128.76 J s−1 g−1 for ZnFe2O4 compound at 1 mg mL−1 concentration were evaluated. The data were interpreted by spin-relaxation mechanism. ZnFe2O4 nanoparticles showed good photocatalytic activity under UV light irradiation. The data were interpreted by electron–hole pair and radical formation and degradation of Rhodamine B dye. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

Applied Physics A

Dielectric, magnetic hyperthermia, and photocatalytic properties of ZnFe2O4 nanoparticles synthesized by solvothermal reflux method

The increase in population, greater life expectancy, and lifestyle choices have caused a drastic increase in the number of bone diseases such as bone tumours, osteoarthritis and bone fractures. This results in the dire need for treatment options such as suitable bone grafts that can be easily fabricated, and are economical. In this study, fabricated composite scaffolds are made from polysaccharide biopolymers, namely gellan and guar gum, and hydroxyapatite by freeze drying method. The developed scaffolds of optimum concentration showed a maximum percentage degradation of 13.7% only until 21 days in phosphate buffered saline solution, and minimum swelling capacity. The mechanically stable scaffolds (compressive strength equivalent to cancellous bone region, ˜3–30 MPa) amongst them were then subjected to characterization tests—scanning electron microscopy, fourier transform infrared spectroscopy, X-ray diffraction, swelling ratio percentage determination, degradation profile study and water vapour transmission study. The cytotoxic evaluation of the optimised scaffolds was performed using MTT assay with murine fibroblast (L929) cells and osteosarcoma (MG63) cells. It was found that the scaffolds were non-cytotoxic and additionally, the cells had proliferated well within the scaffolds, which was confirmed by MTT assay at 1, 4 and 7 days after cell seeding onto the scaffolds. © 2019

School of Architecture

Carbohydrate Polymers

Gum based 3D composite scaffolds for bone tissue engineering applications

Tin (Sn)-doped zinc sulfide (Zn1−xSnxS) thin films at different tin (Sn) concentrations (= 0.00, 0.02, 0.05, and 0.08) were coated onto Corning 7059 glass substrates using the electron beam evaporation technique. The films were subjected to different characterization techniques to study the physical properties of the thin films. The structural properties of the films were studied using a powder X-ray diffractometer (XRD), and it was found that the films were cubic in structure without any impurity phases. The crystallite size increased with an increase of Sn concentration, and the mean crystallite size was 21 nm. The chemical composition and surface morphology of the films were studied using scanning electron microscopy (FE-SEM) with energy-dispersive analysis of X-rays (EDAX). Optical properties such as transmittance and absorbance were recorded using a diffuse reflectance spectroscope (UV–vis–NIR). All the films exhibited high optical transmittance of 85% in the visible region of the solar spectrum. The band gap of the films was calculated using Tauc’s relation, and it was found that it increased from 3.53 to 3.57 eV with an increase in the Sn doping concentration from x = 0.02 to x = 0.08. The room temperature photoluminescence studies of the films were recorded using a fluorescence spectrophotometer, and it was found that the films exhibited a prominent emission peak at 420 nm. The magnetic properties of the films and glass substrates at room temperature were studied using a vibrating sample magnetometer. From this, it was found that the films were weakly ferromagnetic at room temperature and the strength of magnetization increased with an increase of doping concentration from x = 0.02 to x = 0.05 and decreased at higher doping concentrations (x = 0.08). The films showed high magnetization at x = 0.05. The films at x = 0.05 exhibited the magnetization (Ms), retentivity (Mr), and coercive fields (Hc) 18 × 10− 6 emu/cm3, 1.6 × 10− 6 emu/cm3, and 91.80 Oe, respectively. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.

Journal of Superconductivity and Novel Magnetism

Evidence of Room Temperature Ferromagnetism in Zn1−xSnxS Thin Films

In the present study, we have discussed about the synthesis of Ca0.9Dy0.1MnO3 by using citric acid as a chelating agent. Structural and morphological studies were carried out by using XRD, FT-IR, FE-SEM equipped with EDX for the synthesized material. Magnetic studies are carried out by VSM and confirmed the paramagnetic behavior. The electric properties like dielectric, impedance and conductivity is carried out at the frequency range of 50 Hz to 5 MHz for different temperatures. Impedances studied for the activation energy and the investigation of grain and grain boundary effects. The conductivity studies were explained on the basis of Jonscher's power law and the activation energy is calculated. © 2019 The Authors.

Fulltext

Journal of Materials Research and Technology

Structural and electrical properties of Ca0.9Dy0.1MnO3 prepared by sol-gel technique.

In this paper, we focused on microwave sintered NiTiO3 nanoparticles synthesized via sol–gel method. The crystal structure was determined by the X-ray diffraction. Vibrational bands related to Ni–O and Ti–O bands were confirmed using the Fourier transform infrared spectrum. These NiTiO3 ceramics obeyed semiconductor behavior of Arrhenius type. The activation energy was found to be 0.04&nbsp;μeV. The M–H curve exhibited superparamagnetic behavior at room temperature. Keywords: NiTiO3, X-ray diffraction, HRSEM, Impedance analysis, M–H curve

Electrical and magnetic properties of NiTiO3 nanoparticles synthesized by the sol–gel synthesis method and microwave sintering

One-dimensional lead hexaferrite (PbFe12O19) nanofibers are produced using electrospinning technology combined with sol–gel followed by muffle furnace heating. PVP/DMF is used as reductant to form precursor solution for lead hexaferrite nanofiber. Polycrystalline nanofibers with an average diameter of 145 nm have been prepared by electrospinning method. The structural features of the sintered nanofibers are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and EDX. The obtained PbFe12O19 nanofibers showed a hexagonal structure after sintering. The SEM image clearly shows the fibrous morphology of PbFe12O19. Vibrating sample magnetometer (VSM) revealed very low coercivity and fairly high saturation magnetization. The fiber exhibited a ferromagnetic behaviour at room temperature, which is attributed to the nanometre-size of PbFe12O19 nanofibers. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

Department of Computational Intelligence

School of Computer Science and Engineering

Evidence of magnetism in electrospun PbFe12O19 nanofibers

In the present study, polymer electrolyte with poly(vinyl alcohol) (PVA) blended with cellulose acetate (CA) was chosen to prepare composite electrolyte using ammonium triflate salt and nano sized alumina (Al2O3- < 50 nm) by the solution casting method. The as prepared samples were characterized by X-ray diffraction, FT-IR, differential scanning calorimetry and AC impedance spectra. The loss tangent and dielectric studies were carried out for all the prepared samples using AC impedance analysis. Activation energy with regression values and relaxation time were calculated and found to be low for the highest conducting membranes. The presence of 0.1 mol content of nano alumina has enhanced the ionic conductivity significantly to the value of 2.012 × 10-3 S/cm from that of the filler-free electrolyte (2.93 × 10-4 S/cm). Ionic transference number was calculated by electrostatic polarization method and it was found to be 0.9684, which shows the conducting species were ions. A proton battery fabricated using the configuration Zn+ZnSO4. H2O || PVA-CA-0.5 mol NH4CF3SO3-0.1 mol Al2O3 || PbO2 + V2O5 produced a steady state open circuit voltage of 1.39 V, which proves the prepared composite electrolyte is suitable solid electrolyte for electrochemical devices.