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

Time dependent density functional theory is used to systematically examine the band gap variation of Li-substituted adamantanes upon fluorination. It is realized that the absorption wavelength of Li-Adamantane can be fine tuned within UV–Visible region by changing the degree of fluorination. The static and dynamic hyperpolarizabilities of fluorinated Li-Adamantane derivatives were computed using coupled perturbed Kohn Sham theory. In this article, we report Pockel, dc-Kerr, ESHG, degenerate four wave mixing coefficients and nonlinear refractive indices from the first and second order hyperpolarizability calculations. A high positive nonlinear refractive index and significant second harmonic generation efficiency at Nd:YAG Laser wavelength are observed in F3Li-Adm derivative. © 2018 Elsevier B.V.

World University root node

School of Advanced Sciences

Vellore Campus

Department of Chemistry

Chemical Physics Letters

Effect of fluorination on bandgap, first and second order hyperpolarizabilities in lithium substituted adamantane: A time dependent density functional theory

Ferromagnetic insulators (FMIs) are one of the most important components in developing dissipationless electronic and spintronic devices. However, FMIs are innately rare to find in nature as ferromagnetism generally accompanies metallicity. Here, novel room-temperature FMI films that are epitaxially synthesized by deliberate control of the ratio between two B-site cations in the double perovskite Sr2Fe1+ xRe1- xO6 (−0.2 ≤ x ≤ 0.2) are reported. In contrast to the known FM metallic phase in stoichiometric Sr2FeReO6, an FMI state with a high Curie temperature (Tc ≈ 400 K) and a large saturation magnetization (MS ≈ 1.8 µB f.u.−1) is found in highly cation-ordered Fe-rich phases. The stabilization of the FMI state is attributed to the formation of extra Fe3+Fe3+ and Fe3+Re6+ bonding states, which originate from the relatively excess Fe ions owing to the deficiency in Re ions. The emerging FMI state created by controlling cations in the oxide double perovskites opens the door to developing novel oxide quantum materials and spintronic devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Fulltext

Advanced Materials

Room-Temperature Ferromagnetic Insulating State in Cation-Ordered Double-Perovskite Sr2Fe1+ xRe1− xO6Films

We have developed a vectorial type of measurement for the spin Seebeck effect (SSE) in epitaxial NiFe2O4 thin films which have been grown by pulsed laser deposition on MgGa2O4 with (001) and (011) orientations as well as CoGa2O4 (011), thus varying the lattice mismatch and crystal orientation. We confirm that a large lattice mismatch leads to strain anisotropy in addition to the magnetocrystalline anisotropy in the thin films using vibrating sample magnetometry and ferromagnetic resonance measurements. Moreover, we show that the existence of a magnetic strain anisotropy in NiFe2O4 thin films significantly impacts the shape and magnitude of the magnetic-field-dependent SSE voltage loops. We further demonstrate that bidirectional field-dependent SSE voltage curves can be utilized to reveal the complete magnetization reversal process, which establishes a vectorial magnetometry technique based on a spin caloric effect. © 2019 Author(s).

Applied Physics Letters

Vectorial observation of the spin Seebeck effect in epitaxial NiFe2O4 thin films with various magnetic anisotropy contributions

We report the fabrication, densification and characterization of polycrystalline free-standing yttrium iron garnet Y3Fe5O12 (YIG) thick films in this paper. The thick films were fabricated using a double doctor blade technique from co-precipitated nanocrystalline YIG powders. The sintering temperature of YIG thick films was varied from 1000 to 1400°C. A volume diffusion mechanism is seen to govern the densification process. A high relative density of ~99% could be achieved in a YIG thick film, with a thickness of 80 µm, sintered at a relatively low temperature of 1300 °C. The magnetization value ~1750 Oe, near to the YIG bulk magnetization value and an acceptable low ferromagnetic resonance (FMR) linewidth (∆H) of 80 Oe resulted in these high density YIG thick films with microwave device possibilities. © 2018 Elsevier Ltd and Techna Group S.r.l.

Ceramics International

Low-loss YIG thick films for microwave applications

Contemporary research on electrochemistry revolves around fabricating cost effective catalysts using non-precious compounds for environmentally benign energy storage and production. Aiming at the engineering of such a proficient catalyst we report a novel synthesis of molybdenum disulfide (MoS2)particle decorated on reduced graphene oxide (rGO)sheets. We used low cost precursors like graphene oxide (GO), sodium dodecyl sulfate (SDS)thioacetamide (Tha)and an inexpensive Keggin compound, ammonium phosphomolybdate (APM)powder, in aqueous medium using simple hydrothermal procedures at the different stage of the synthesis. The as-prepared MoS2/rGO exhibits high catalytic ability for hydrogen evolution electrochemical reaction with ∼140 mV overpotential for a current density of 10 mA cm−2 for a catalyst loading of 0.1 mg cm−2 and a Tafel slope of 50 mV dec−1 measured in glassy carbon electrode. The low charge transfer resistance value Rct 26.56 Ω, is manifested in the enhanced HER performance due to faster electron transfer. In-house reduction of APM to MoS2 on in situ reduced rGO by Tha in aqueous medium, produced the effective 2D catalyst. This is the first report of one-pot synthesis of an in situ produced electrocatalyst i.e. MoS2 onto rGO from aqueous SDS solution using solid phase dispersion of the simplest Keggin compound. © 2019 Elsevier Ltd

Electrochimica Acta

Fabrication of MoS2 decorated reduced graphene oxide sheets from solid Mo-precursor for electrocatalytic hydrogen evolution reaction

The present study investigates the effect of laser shock peening (LSP) to enhance the metallurgical and mechanical properties of weld joints in Hastelloy C-276. The joint was fabricated by the gas tungsten arc welding (GTAW) with ERNiCrMo-3 filler wire. LSP was carried out on the top surface of the fusion zone. An optical microscope and a scanning electron microscope (SEM) were used to compare the as-welded and laser shock peened microstructure on the fusion zone. The results show that the refined microstructure was observed in the laser shock peened fusion zone compared with the as-welded microstructure. The X-ray diffraction (XRD) result shows a 50% reduction in grain size after LSP. The effect of microsegregation also reduced in the laser shock peened zone. The laser shock peened zone shows slightly higher surface roughness, and improved hardness and strength compared to as-welded zone. ©2019 Old City Publishing, Inc.

Department of Manufacturing Engineering

School of Mechanical Engineering

Department of Design and Automation

Lasers in Engineering

Laser shock peening (LSP) to improve the metallurgical and mechanical properties of gas tungsten arc welding (GTAW) joints in hastelloy C-276

Cities are getting smarter every day. Municipalities are increasingly using information and communication technologies (ICT) to enrich and enhance city life, which is paramount in planning the cities of the future. This calls for connected and automated cars in the future. This emphasizes the need for efficient and fast acting controls algorithms in Engine Management System (EMS) to achieve enhanced dynamic response of the connected mobility. Artificial Intelligence and Machine learning in development of control algorithms is of paramount need. Advancements in internal combustion engine technologies have increased a need of complex features. Effective control of these features is the need for the day. The optimum solution of these features via parameter optimization needs to be effectively derived for entire engine operating range in steady and transient operation. This is very critical in case of urban mobility where synchronized and harmonized management is the need of the hour. Today developers apply supervised learning to powertrain calibration, missing physics and signature, emission control and virtual sensor development.This paper presents the implementation of machine learning algorithms for predictive models via optimal set of parameters for various powertrain features for synchronized mobility. Predictive models amalgamated with Artificial Intelligence will accurately determine the response of a system. Machine learning techniques is used to create a predictive model when no knowledge of the system is known and difficult to determine. The paper also presents the rethinking of conventional process by introducing Machine learning in all the phases mentioned: Concept Development SOP series volume production. © 2019 IEEE.

2019 IEEE Transportation Electrification Conference, ITEC-India 2019

Application of Artificial Intelligence and Machine learning in Engine Management Systems for Gen-Next mobility

The Enhancement of surface properties of various materials by laser shock peening (LSP) to prolong the service life of the industrial components gained significant importance for the past decade. Though several investigations are made on the different aluminum alloys through LSP route, very limited studies are reported on AA 7075 T651 aluminum alloy, which is extensively used in upper wing cover and fuselages of aerospace industries. In the present investigation, a Q-switched Nd:YAG laser having different pulse energies of 200, 300 and 400 mJ with black paint and water as the ablative layer and confinement medium respectively are used to study the variations in the mechanical properties. A deformed layer thickness of about 500 μm with a peak hardness of 236 Hv at the surface is obtained with pulse energy of 400 mJ. Further, the maximum compressive residual stress induced in the said specimen is 317 MPa and a wear rate of 1.18 ×10-6 g m-1 is measured. The microstructural studies performed using HR-TEM, revealed the enhancement in the properties are attributed to the grain refinement and dislocation strengthening effected by the LSP process. © 2019 IOP Publishing Ltd.

Materials Research Express

Surface modification of AA7075 T651 by laser shock peening to improve the wear characteristics

An organic nonlinear optical single-crystal 4-nitrophenol was successfully grown by vertical Bridgman technique using single-wall ampule in size of 38 × 15 mm2. The lattice parameters and crystallinity of the title crystal were confirmed through the single crystal and powder X-ray diffraction studies, respectively. The UV–Vis–NIR spectral analysis addressed that the title crystal has a lower optical cut-off wavelength at 405 nm and exhibits transparency of 82% in entire visible and near-IR regions with a wide band gap of 2.84 eV. The hardness, Meyer’s index, stiffness constant, yield strength, fracture toughness, and brittle index of the grown specimen were systematically investigated using a Vickers microhardness tester. The low value of dielectric constant and dielectric loss for the present crystal enrolls that it is well suitable for microelectronic industry. The laser-induced damage threshold value of the grown specimen is found to be 17.66 GW/cm2. The Z-scan measurement was employed to calculate the third-order nonlinear optical parameters of the title crystal. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

Applied Physics B: Lasers and Optics

Growth and characterisation of organic nonlinear optical single-crystal 4-nitrophenol grown by vertical Bridgman technique

In Additive manufacturing, direct metal laser sintering (DMLS) is a technique for manufacturing of Metal bases 3D printing. Finely pulverized metal is melted using a high-energy fibre laser, by Island principle strategy produces mechanically and thermally stable metallic components with reduced thermal gradients, stresses &amp; at high precision. Al-Si10-Mg alloys are being used in aircraft and automobile parts. However, this component is susceptible to lack of hardness and corrosion resistance when exposed to higher load bearing operations and industrial environments. The laser shot peening of Al-Si10-Mg prepared by DMLS process was found to enhance micro hardness of aluminium alloy. The formation of closed packed and oriented micro grains of metal atoms at interstitial layers have been ascertained from SEM and TEM studies. AFM measurements revealed that formation of micro rough surfaces and also dislocation of new grains have significantly contributed to enhancement of mechanical properties of Al-Si10-Mg alloys © 2019 Elsevier Ltd.