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

Polymer based nanocomposites are gaining attention in various fields of science and technology due to its tunable properties. In this work, we report for the first time, the preparation and study on electrical and mechanical properties of standalone poly(vinyl alcohol) (PVA) based graphite nanoplatelet (GnP) composite films using modified film casting technique. Our modified tape casting method can produce films with uniform thickness, and uniform dispersion of filler deprived of pinholes. This technique is scalable for the mass production of polymer composite films for device application. We have obtained a significant enhancement in the electrical conductivity of 9 orders of magnitude and a maximum value of 0.143 S/m using PVA–GnP composites. To the best of our knowledge, this increase is the highest among the reported values for PVA–GnP composite films. However, a reduction in crystallinity and tensile strength can be seen with the addition of GnP fillers. The maximum tensile strength obtained for PVA–GnP composite films was 15 MPa and is adequate for use in electronic applications and devices. The effect of filler addition in PVA is discussed in detail. © 2020 Wiley Periodicals LLC

World University root node

Department of Physics

School of Advanced Sciences

Vellore Campus

Department of Manufacturing Engineering

School of Mechanical Engineering

Journal of Applied Polymer Science

Enhanced electrical conductivity and structural, mechanical characterization of standalone poly(vinyl alcohol)-graphite nanoplatelets composite films

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

Cost-effective conducting polymer composite films were prepared from non-conducting polymer and black Tea. The films showed conducting and considerable magnetic properties. The measured coercive field, saturation magnetization and remnant magnetization values were found to be 80 Oe, 0.14 emu g-1 (at 8 kOe), and 9.0 ×10-3 emu g-1, respectively. In order to realize the high-frequency applications of these materials, dielectric properties were measured in the frequency range of 1 Hz-1 MHz. The measured dielectric permittivity (ϵ′) and loss tangent (tanδ) values of the composite polymer thin film were found to be 260 and 0.37 (at 1 kHz) respectively. The estimated dc conductivity (σ dc) value was around 1.60 ×10-8 S cm-1. © 2019 IOP Publishing Ltd.

Materials Research Express

Enhancement in the magnetic and electrical conductivity properties of PVA- black tea composite films

Nanocrystalline CuO-CuFe2O4 composite thin films were developed from CuFeO2 ceramic target using a radio-frequency sputtering method followed by a thermal oxidation process. This fabrication process helps to develop porous sensing layers which are highly desirable for solid-state resistive gas sensors. Their sensing properties toward ethanol and hydrogen gas in dry air were examined at the operating temperatures ranging from 250 °C to 500 °C. The electrical transients during adsorption and desorption of the test gases were fitted with the Langmuir single site gas adsorption model. A composite thin film with a total thickness of 25 nm showed highest response (79%) toward hydrogen (500 ppm) at the operating temperature of 400 °C. The shortest response time (τres) was found to be 60 and 90 s for hydrogen and ethanol, respectively. The dependence of the response of the sensor on gas concentration (10-500 ppm) was also studied. © 2001-2012 IEEE.

Fulltext

IEEE Sensors Journal

Ethanol and Hydrogen Gas-Sensing Properties of CuO-CuFe2O4 Nanostructured Thin Films

The synthesis and characterization of magnesium ferrite MgFe2O4 prepared by co-precipitation and sol gel combustion is reported. Structural characterization showed that all the samples have single spinel phase. The co-precipitated sample exhibits smaller grains and twice higher BET surface than the sol gel combustion samples. The powder was shaped to dedicated chemo-resistive home-made sensors devices. The electrical properties and sensing properties towards carbon dioxide of both MgFe2O4 powders were studied. The type of charge carriers were analysed on the basis of the change in resistance in the presence of air and argon. The sensing response towards CO2 was found to be dependent on the morphology of the powder sample and the CO2 concentration. A high response of 36% towards 5000 ppm of CO2 was reached which is good for this gas. The key role of the Mg ions modulating the electrical properties is discussed. © 2018 Elsevier Ltd and Techna Group S.r.l.

Effect of synthesis method and morphology on the enhanced CO2 sensing properties of magnesium ferrite MgFe2O4

The paper reports the synthesis and characterization of cuprite/copper ferrite nanopowder composites. The composites were synthesized using co-precipitation with oxalates precursor route. The phase and microstructure of the powder samples were characterized using X-ray diffraction, BET surface area analyzer and scanning electron microscopy. The powders were fabricated to device using a simple and efficient shaping technique. These devices were used further to carry out electrical property measurements in various atmospheres. The type of charge carriers were found by noting the sense of change in resistance when the air atmosphere on the sample was replaced with argon. CO2responses were reported for the whole series of composites. The effect of cuprite concentration on the CO2sensing performance was found to be independent of cuprite concentration up to certain limits (70%at). © 2016

Journal of Alloys and Compounds

Study on the effect of cuprite content on the electrical and CO2sensing properties of cuprite-copper ferrite nanopowder composites

Stoichiometric nano sized copper ferrite particles were synthesized by sol gel combustion technique. They were then calcined at various temperatures ranging from 300–800 °C and were either furnace cooled or quenched in liquid nitrogen. A high magnetisation value of 48.2 emu/g signifying the cubic phase of copper ferrite, was obtained for sample quenched to liquid nitrogen temperature from 800 °C. The ethanol sensing response of the samples was studied and a maximum of 86% response was obtained for 500 ppm ethanol in the case of a furnace cooled sample calcined at 800 °C. The chemical sensing is seen to be correlated with the c/a ratio and is best in the case of tetragonal copper ferrite. © 2016 Elsevier B.V.

Journal of Magnetism and Magnetic Materials

Structural, magnetic and gas sensing properties of nanosized copper ferrite powder synthesized by sol gel combustion technique

Nano-sized magnesium ferrite particles were prepared by sol gel combustion synthesis and were either furnace cooled or quenched after calcining at various temperatures ranging from 300 to 800 °C. A magnetisation value of 61 emu/g was obtained at 5 K for sample calcined at 800 °C and quenched in liquid nitrogen temperature. This is one of the highest reported values of magnetisation obtained from quenching at such a lower temperature. An estimate of the number of Fe3+ ions on A and B sites was made after applying Néel Model on the magnetisation values measured at 5 K. It was estimated that Fe3+ ions segregates out from both sites disproportionately so as to cause a net decrease in the overall moment. The resultant cation distribution is found to be consistent with the coercivity data. © 2015 Elsevier B.V. All rights reserved.

A study of nanosized magnesium ferrite particles with high magnetic moment

The phase transformation in nanosized stoichiometric magnesium ferrite is being discussed. It was shown by TGA/DSC that there exist two reactions (shown by exothermic peaks) in nano sized magnesium ferrite when synthesized by sol gel combustion synthesis. First one of these reactions resulted in the precipitation of α-Fe 2 O 3 and a resultant spinel. The second reaction resulted in stoichiometric spinel from this two phase system. © 2015 AIP Publishing LLC.

AIP Conference Proceedings

Temperature dependent phase transformation in nano sized magnesium ferrite

Stoichiometric and non stoichiometric magnesium ferrite (MgFe 2+δO4, δ=0.0, 0.1) were synthesized by the sol gel combustion method resulting in nanocrystalline powders with size ranging from 10 to 100 nm. These powders were calcined at various temperatures (300-800 °C). One part of the calcined powder was quenched in liquid nitrogen and the other part furnace cooled. α-Fe2O3 was observed in all calcined samples by XRD and this was also reflected in the magnetization data. Electrical response of MgFe2.1O4+δ spinel phase to 75 ppm ethanol was found to be greater than that for a stoichiometric magnesium ferrite. © 2014 Elsevier B.V.

Physica B: Condensed Matter

Study of magnesium ferrite nano particles with excess iron content

MgFe2O4 powders with nanosize (30-100 nm) were synthesized by the solgel auto combustion method. These powders were calcined at various temperatures (300°C, 400°C, 500°C, 600°C, 700°C, 800°C). An increase in particle size was observed as a function of calcination temperature. The appearance of α-Fe2O3 in samples calcined at intermediate temperatures was studied by XRD, Raman spectra and was confirmed using magnetization data. © 2013 American Institute of Physics.