Faculty Publications

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Author: search.filters.author.Bhat, D.K.

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    Synthesis of different phases of nano manganese oxides and their dielectric behaviour in chitosan composites
    (2011) Harshita, B.A.; Bhat, D.K.; Bhatt, A.S.
    Nanoscale oxides of transition metals, particularly manganese, are desirable for many applications in designing electric, magnetic and heterogeneous catalytic materials. Manganese oxides exist in different phases, viz. MnO, MnO2, Mn2O3, Mn2O 7 and Mn3O4. Using different synthetic routes it is possible to synthesize different phases of manganese oxides. Moreover, composites of these oxides with polymer have the potential to address the needs of emerging dielectric technologies. In the present work, using manganese chloride and hydrazine hydrate, Mn3O4 and Mn 2O3 nanoparticles were successfully synthesized by conventional and hydrothermal method respectively. The variation in the formation of the different phases has been discussed. The nanoparticles were well characterized by X-ray Diffraction and using the Debye Scherrer formula, the average size of Mn3O4 and Mn2O3 nanoparticles were calculated to be 35 nm and 25 nm respectively. Using solution casting method, nanocomposites of chitosan/Mn3O4 were prepared and their electrochemical properties were studied using electrochemical impedance spectroscopy. It was observed that with increase in the content of nano oxides, the conductivity of the films increased. Also, the variation in the permittivity of these samples with respect to frequency was studied. The results suggest that the composites have a fair chance to be used in energy storage devices. © 2011 American Institute of Physics.
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    Effect of solvent on the morphology of MoS2 nanosheets prepared by ultrasonication-assisted exfoliation
    (American Institute of Physics Inc. subs@aip.org, 2018) Prabukumar, C.; Mohamed, M.M.J.; Bhat, D.K.; Bhat, K.U.
    The MoS2 nanosheets are prepared via liquid-phase exfoliation route. Bulk MoS2 powder is exfoliated by ultrasonication-assisted method with the aid of different solvents. The effect of solvents used on the morphology of the MoS2 nanosheets is investigated. The exfoliated material is analysed by using scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy and X-ray diffractometry. The MoS2 nanosheets exfoliated by using NMP-water mixture showed the better morphology than that exfoliated with the other solvent mixtures. © 2018 Author(s).
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    NiO nanoplates for energy storage application: Role of electrolyte concentration on the energy storage property
    (Elsevier Ltd, 2020) Sethi, M.; Bhat, D.K.
    Here in, synthesis of NiO nanoplates by employing a mixed solvent system under solvothermal method followed by calcining the obtained product nickel hydroxide in air is reported. Diffraction, microscopic, and spectroscopic results confirmed the formation of NiO phase. The as synthesized NiO nanoplates are tested as a robust material for energy storage applications. The effect of electrolyte concentration on the capacitive behavior of NiO is studied thoroughly. The outcome from the electrochemical analysis reveals that NiO nanoplates have a high specific capacity value of 108.4 C g-1 (270 F g-1) in 6 M KOH electrolyte and the value decreases to 85.0 C g-1 (212.5 F g-1) and 78.2 C g-1 (195.5 F g-1) for 4 M, and 2 M KOH electrolyte, respectively. The resistance values also decreased with increase in the KOH concentration. The better electrochemical performance depicted by the 6 M KOH electrolyte is mainly ascribed to the availability of plenty of OH- ions in the electrolyte solution, which helped in the proper wettability of the sample so that the OH- ions can participate to higher extent during the electrochemical redox reactions, due to which the observed charge storage capacity is more in higher electrolyte concentration and vice-versa. Thus, the results suggest the usefulness of this material for energy storage applications. © 2019 Elsevier Ltd. All rights reserved.
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    Novel porous graphene synthesized through solvothermal approach as high performance electrode material for supercapacitors
    (American Institute of Physics Inc. subs@aip.org, 2020) Sethi, M.; Bhat, D.K.
    A facile solvent mediated chemical route is employed for the fruitful synthesis of porous graphene (PG). The formation of PG is thoroughly characterized by microscopic and spectroscopic techniques. Elemental analysis showed the presence of carbon and oxygen only as elements in the PG sample, indicating the purity of the product. The as synthesized sample is utilized as an energetic electrode material for supercapacitor in 2M KOH aqueous electrolyte. The fabricated symmetrical supercapacitor exhibited a capacitance value of 248.0 F g-1 at an applied current density of 1 Ag-1, and 220.0 F g-1 at a scan rate of 5 mV s-1. The supercapacitor provided an energy density value of 7.3 Wh kg-1 while maintaining a power density of 6405.0 W kg-1 at an applied current density of 8 A g-1. Apart from these values, the supercapacitor device can sustain up to 5000 charge-discharge cycles at a higher applied current density of 8 A g-1, with 96% of initial capacitance retention demonstrating the good rate profile. Hence, considering the above facts, it can be suggested that this material can have high practical utility in supercapacitor application. © 2020 Author(s).
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    BaTiO3-graphene nanocomposite as a photocatalyst for the degradation of methylene blue
    (American Institute of Physics Inc. subs@aip.org, 2020) Bantawal, H.; Bhat, D.K.
    BaTiO3-graphene composite (BG) was synthesized by a facile two step solvothermal approach. The synthesized materials were thoroughly characterized by X-ray diffraction technique, field emission scanning electron microscopy, energy-dispersive X-ray analysis, Raman analysis, diffuse reflectance spectroscopy and photoluminescence spectroscopic techniques. The photocatalytic activity of 7.5 BG composite was found to be higher as compared to bare BaTiO3, which can be attributed to the enhanced visible light response., excellent adsorption of methylene blue dye via π-πinteraction and low recombination rate of photoinduced charges. © 2020 Author(s).
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    Engineered porous nanopillars of Co3O4: Hydrothermal synthesis and energy storage application
    (American Institute of Physics Inc. subs@aip.org, 2020) Sethi, M.; Bhat, D.K.
    The ever increasing demand of energy for daily needs is knocking globally and in this scenario the energy storage devices were paid more attention as they store more charge and release it efficiently which can be used in many applications. Nanopillars like porous Co3O4 nanostructures were synthesized by using a facile hydrothermal method which could be a potential candidate for energy storage applications. The as synthesized Co3O4 nanostructures are thoroughly analyzed by diffraction and microscopic tools which corroborated its successful synthesis. The porous Co3O4 nanostructures when utilized as an electrode material for supercapacitor application, a high capacitance value of 495.5 F g-1 is obtained at a scan rate of 5 mV s-1 from cyclic voltammetry (CV) data and 275 F g-1 (110 C g-1) at a current density of 1 A g-1 from charge-discharge (CD) data in 6 M KOH electrolyte. The charge bearing capacity of porous Co3O4 in other electrolytes like 4 M and 2 M KOH electrolyte is also studied and a capacitance value of 361.7 and 349.5 F g-1 is obtained in 4 M, and 2 M KOH electrolyte, respectively at a scan rate of 5 mV s-1. From the experiment it is found that the charge storage capacity is decreasing as the electrolyte concentration decreases and the value is 220 F g-1 (88 C g-1), and 214 F g-1 (86 C g-1) at a current density of 1 A g-1 for 4 M and 2 M KOH, respectively. Similarly the resistance value also decreases as the electrolyte concentration is increasing and vice-versa. The exciting result produced by this novel material suggests its suitable utility for energy storage applications. © 2020 Author(s).
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    Biodegradability of PMMA blends with some cellulose derivatives
    (2006) Bhat, D.K.; Muthu, M.S.
    High polymer blends of Polymethyl methacrylate (PMMA) with cellulose acetate (CA) and Cellulose acetate phthalate (CAP) of varying blend compositions have been prepared to study their biodegradation behavior and blend miscibility. Films of PMMA-CA, and PMMA-CAP blends have been prepared by solution casting using Acetone and Dimethyl formamide(DMF) as solvents respectively. Biodegradability of these blends has been studied by four different methods namely, soil burial test, enzymatic degradation, and degradation in phosphate buffer and activated sludge degradation followed by water absorption tests to support the degradation studies. Degradation analysis was done by weight loss method. The results of all the tests showed sufficient biodegradability of these blends. Degradability increased with the increase in CA and CAP content in the blend compositions. The miscibility of PMMA-CA and PMMA-CAP blends have been studied by solution viscometric and ultrasonic methods. The results obtained reveal that PMMA forms miscible blends with either CA or CAP in the entire composition range. Miscibility of the blends may be due to the formation of hydrogen bond between the carbonyl group of PMMA and the free hydroxyl group of CA and CAP. © Springer Science+Business Media, Inc. 2006.
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    N and p doped poly(3,4-ethylenedioxythiophene) electrode materials for symmetric redox supercapacitors
    (2007) Bhat, D.K.; Muthu, M.S.
    A symmetric redox supercapacitor has been fabricated based on n and p doped Poly(3,4-ethylenedioxythiophene)(PEDOT) coated on stainless steel (SS) electrodes. The characterization and performance of the supercapacitor has been studied by FTIR, Cyclic Voltammetry and AC Impedance spectroscopy. The supercapacitor showed a maximum specific capacitance of 121 F g-1 at a scan rate of 10 mV s-1. The time constant calculated for the supercapacitor through the active-reactive power behavior measurement was 12 milliseconds indicating the suitability of the system for efficient use at low frequency range. © 2007 Springer Science+Business Media, LLC.
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    Preparation and characterization of an all solid supercapacitor based on polyaniline-Al2O3 layer on aluminium alloy-Al-2024
    (2007) Muthu, M.S.; Bhat, D.K.
    The characteristics of an all solid state supercapacitor based on polyaniline (Pani)-Al2O3 coating on aluminium alloy 2024 (Al-2024) surface prepared by the constant current method have been investigated. Three stages are observed in the potential- electrolysis time relation for the simultaneous preparation of the dielectric layer and the conducting polymer on the aluminium foil. The deposition of polyaniline film has been confirmed by cyclic voltammetry. The solid state capacitor has been studied by AC impedance spectroscopy and the capacitive behaviour of the cell is discussed in terms of Nyquist plots, complex capacitance and complex power. The study revealed that the capacitor has comparatively good capacitance, ranging from 450 to 600nF/cm2, a low time constant and also very low resistance. The normalized reactive power, |Q|/|S| and active power |P|/|S| versus frequency plot for the solid state capacitor allow an overview of the whole frequency behaviour of the supercapcitors, ranging from a pure resistance at high frequency to a pure capacitance at low frequency. When a capacitor is used as a source stiffening capacitor and is buffering the supply by delivering initial current, a lower RC time constant allows delivering significantly more current. So this type of solid-state capacitor can be used for the DC-DC converter modules.
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    Facile synthesis of ZnO nanorods by microwave irradiation of zinc-hydrazine hydrate complex
    (2008) Bhat, D.K.
    ZnO nanorods have been successfully synthesized by a simple microwave-assisted solution phase approach. Hydrazine hydrate has been used as a mineralizer instead of sodium hydroxide. XRD and FESEM have been used to characterize the product. The FESEM images show that the diameter of the nanorods fall in the range of about 25-75 nm and length in the range of 500-1,500 nm with an aspect ratio of about 20-50. UV-VIS and photoluminescence spectra of the nanorods in solution have been taken to study their optical properties. A mechanism for microwave synthesis of the ZnO nanorods using hydrazine hydrate precursor has also been proposed.