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    Molybdenum based mixed oxide containing Mo0.65V 0.25W0.10 was investigated for the partial oxidation of methanol. The structural property and catalytic activity of the mixed oxide catalyst was studied by surface area (BET), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infra-red spectroscopy (FTIR) and X-ray diffraction (XRD). The thermal activation of the catalyst resulted increase in the conversion of methanol and the selectivity to formaldehyde. The thermal activation of the MoVW mixed oxide in nitrogen atmospheres induces partial crystallization of a Mo5O14-type oxide at 813 K. The SEM images of the thermally activated catalyst show needle like particles. These particles were agglomerates of platelet-like crystallites of a few hundreds of nanometers in size. SEM and EDX techniques show that the mixed oxide is characterized by an inhomogeneous elemental distribution on the length scale of a few microns. XRD of the thermally activated catalyst showed a nanocrystalline material identified as a mixture of Mo5O 14, MoO3 and MoO2-type MoVW oxides. The catalytic activity of the MoVW mixed oxide show a good conversion of methanol and selectivity to formaldehyde. © 2005 Springer Science+Business Media, Inc.
    (Partial oxidation of methanol to formaldehyde on molybdenum based mixed oxide catalyst) Badekai Ramachandra, B.; Choi, J.-S.; Choo, K.-Y.; Sung, J.-S.; Song, S.-D.; Kim, T.-H.
    2005
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    Synthesis and characterization of nanocrystalline Mo-V-W-Fe-O mixed oxide catalyst and its performance in selective methanol oxidation
    (2007) Badekai Ramachandra, B.; Choi, J.-S.; Kim, T.-H.
    A mixed oxide catalyst containing Mo, V, W and Fe with the composition of 63, 23, 09 and 06 wt% respectively for the selective oxidation of the methanol to formaldehyde is in reported in this paper for the first time. The characterization of the catalyst was done using BET surface analysis, X-ray diffraction (XRD), Infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Energy dispersive X-ray (EDX). The mixed oxide after calcination at 673 K in N2 which was subjected for the thermal activation in N 2flow at 813 K was used for the methanol selective oxidation. The thermal treatment shows enhanced catalytic performance. Thermal activation of the nanocrystalline Mo0.63V23W0.09Fe 0.06O x precursor oxide in nitrogen atmospheres induces partial crystallization of a Mo5O14-type oxide only in a narrow temperature range up to 813 K. XRD showed that the thermally activated mixed oxide consists of a mixture of a majority of crystalline Mo 5O14-type oxide and of small amounts of crystalline MoO3-type and MoO2-type oxides. The structural analysis suggests that the improvement of the catalytic performance of the MoVWFe oxide catalyst in the selective oxidation of methanol is related to the formation of the catalytic active site such as Mo5O14-type mixed oxide. © 2007 Springer Science+Business Media, LLC.
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    Valley-Coherent Hot Carriers and Thermal Relaxation in Monolayer Transition Metal Dichalcogenides
    (American Chemical Society service@acs.org, 2016) Kallatt, S.; Umesh, G.; Majumdar, K.
    We show room-temperature valley coherence in MoS2, MoSe2, WS2, and WSe2 monolayers using linear polarization-resolved hot photoluminescence (PL) at energies close to the excitation, demonstrating preservation of valley coherence before sufficient scattering events. The features of the copolarized hot luminescence allow us to extract the lower bound of the binding energy of the A exciton in monolayer MoS2 as 0.42 (±0.02) eV. The broadening of the PL peak is found to be dominated by a Boltzmann-type hot luminescence tail, and using the slope of the exponential decay, the carrier temperature is extracted in situ at different stages of energy relaxation. The temperature of the emitted optical phonons during the relaxation process is probed by exploiting the corresponding broadening of the Raman peaks due to temperature-induced anharmonic effects. The findings provide a physical picture of photogeneration of valley-coherent hot carriers and their subsequent energy relaxation pathways. © 2016 American Chemical Society.
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    Photoresponse of atomically thin MoS2 layers and their planar heterojunctions
    (Royal Society of Chemistry, 2016) Kallatt, S.; Umesh, G.; Bhat, N.; Majumdar, K.
    MoS2 monolayers exhibit excellent light absorption and large thermoelectric power, which are, however, accompanied by a very strong exciton binding energy-resulting in complex photoresponse characteristics. We study the electrical response to scanning photo-excitation on MoS2 monolayer (1L) and bilayer (2L) devices, and also on monolayer/bilayer (1L/2L) planar heterojunction and monolayer/few-layer/multi-layer (1L/FL/ML) planar double heterojunction devices to unveil the intrinsic mechanisms responsible for photocurrent generation in these materials and junctions. A strong photoresponse modulation is obtained by scanning the position of the laser spot, as a consequence of controlling the relative dominance of a number of layer dependent properties, including (i) the photoelectric effect (PE), (ii) the photothermoelectric effect (PTE), (iii) the excitonic effect, (iv) hot photo-electron injection from metal, and (v) carrier recombination. The monolayer and bilayer devices show a peak photoresponse when the laser is focused at the source junction, while the peak position shifts to the monolayer/few-layer junction in the heterostructure devices. The photoresponse is found to be dependent on the incoming light polarization when the source junction is illuminated, although the polarization sensitivity drastically reduces at the monolayer/few-layer heterojunction. Finally, we investigate the laser position dependent transient response of the photocurrent to reveal that trapping of carriers in SiO2 at the source junction is a critical factor to determine the transient response in 2D photodetectors, and also show that, by a systematic device design, such trapping can be avoided in the heterojunction devices, resulting in a fast transient response. The insights obtained will play an important role in designing a fast 2D TMD based photodetector and related optoelectronic and thermoelectric devices. © 2016 The Royal Society of Chemistry.
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    Microstructure and tribological behavior of flame sprayed and microwave fused CoMoCrSi/CoMoCrSi-Cr3C2 coatings
    (Institute of Physics Publishing helen.craven@iop.org, 2019) Prasad, C.D.; Joladarashi, S.; Ramesh, M.R.; Srinath, M.S.; Channabasappa, B.H.
    This present work deals with the investigation of dry sliding wear behavior of CoMoCrSi and CoMoCrSi-Cr3C2 depositing on titanium substrate through Flame spray process, subsequently fused by the microwave hybrid heating process. Prior to the deposition of the coating, CoMoCrSi powder is milled by using high energy ball milling (HEBM) process and later 30% of Cr3C2 powder is added. Microstructural features and phase analysis of milled powders, as-coated and microwave fused coatings are inspected by using SEM with EDS and XRD process respectively. The coatings before and after fusing are tested for microhardness and bond strength by using a Vickers microhardness and universal tensile machines respectively. Dry sliding wear behavior of coatings before and after fusing is conducted against alumina counter face at ambient and elevated temperatures, also normal load is varied. The wear mechanism of both coatings is examined by employing XRD, SEM-EDS techniques. The fused coatings exhibit lower friction and better wear resistance compared with as-deposited coatings. The detailed results of each test of their coatings are discussed in this paper. © 2018 IOP Publishing Ltd.
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    Effect of isoelectronic tungsten doping on molybdenum selenide nanostructures and their graphene hybrids for supercapacitors
    (Elsevier Ltd, 2019) Bhat, K.S.; Nagaraja, H.S.
    Electrochemical supercapacitors are vital for the advancement of energy storage devices. Herein, we report the synthesis of molybdenum selenide (MoSe 2 ), tungsten-doped molybdenum selenide (W–MoSe 2 ) and their graphene (G) composites (W–MoSe 2 /G) via a facile hydrothermal method. Physiochemical properties of the as-synthesized samples are examined using X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller measurements, scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy measurements. Used as working electrodes for supercapacitors, MoSe 2 nanostructures could deliver the specific capacitance of 106 F g ?1 at 2 mV s ?1 scan rate. Further, doping with tungsten (W) demonstrates the variation of specific capacitances with 2 M % of tungsten as the optimum doping amount, delivering the maximum specific capacitance of 147 F g ?1 . Furthermore, graphene composites of these nanostructures deliver the enhanced specific capacitances of 248 F g ?1 and complimented with excellent capacitance retention capability of 102% for 20000 cycles. © 2019 Elsevier Ltd
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    SnO2 nanoparticles functionalized MoS2 nanosheets as the electrode material for supercapacitor applications
    (Institute of Physics Publishing helen.craven@iop.org, 2019) Prabukumar, C.; Mohamed, M.; Krishna Bhat, D.; Udaya Bhat, K.
    Tin oxide (SnO2) nanoparticles undergo the volume expansion during an electrochemical cycle. This volume expansion leads to discontinuities in the form of microcracks in the electrode material. The problem of charge transportation associated with this microcracking limits the application of SnO2 in the energy storage application such as supercapacitors. The present work approached to solve this problem by incorporating the MoS2 nanosheets along with the SnO2 nanoparticles. The SnO2 nanoparticles are functionalized onto the surface of the MoS2 nanosheets by the ligand exchange process. The MoS2 nanosheets act as the support material for the SnO2 nanoparticles. The electrode material prepared using SnO2 nanoparticles and nanocomposite of SnO2 functionalized MoS2 nanosheets are tested by cyclic voltammetry and galvanostatic charge-discharge measurements. The specific capacity of the MoS2-SnO2 nanocomposite is calculated to be 61.6 F g-1 which is 4.4 fold higher than that of bare SnO2 nanoparticles. The improvement in the electrochemical performance of SnO2 is attributed to the high surface area and the charge transportation provided by the MoS2 nanosheets. © 2019 IOP Publishing Ltd.
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    Performance evaluation of molybdenum dichalcogenide (MoX2; X= S, Se, Te) nanostructures for hydrogen evolution reaction
    (Elsevier Ltd, 2019) Bhat, K.S.; Nagaraja, H.S.
    Hydrogen evolution reaction (HER) using transition metal dichalcogenides (TMDs) have gained interest owing to their low-cost, abundancy and predominant conductivity. However, forthright comparisons of transition metal chalcogenides for HER are scarcely conducted. In this work, we report the synthesis of series of molybdenum chalcogenide nanostructures MoX2 (X = S, Se, Te) via a facile hydrothermal method. Used as an electrocatalyst for HER, MoS2 nanograins, MoSe2 nanoflowers and MoTe2 nanotubes could afford the benchmark current densities of 10 mA cm?2 at the overpotentials of ?173 mV, ?208 mV and ?283 mV with the measured Tafel slope values of 109.81 mV dec?1, 65.92 mV dec?1 and 102.06 mV dec?1, respectively. Besides other factors influencing HER, the role of electronic conductivity in HER of these molybdenum dichalcogenides are elucidated. In addition, the presented molybdenum dichalcogenides in this work are also complimented with robustness as determined from high-current density stability measurements. © 2019 Hydrogen Energy Publications LLC
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    Development and Sliding Wear Behavior of Co-Mo-Cr-Si Cladding through Microwave Heating
    (Springer editorial@springerplus.com, 2019) Prasad, C.D.; Joladarashi, S.; Ramesh, M.R.; Srinath, M.S.; Channabasappa, B.H.
    The aim of the present study is to improve the sliding wear resistance of pure titanium grade-2 substrate by developing CoMoCrSi (Tribaloy T400) cladding on it by using microwave hybrid heating technique. The developed cladding is characterized by microstructural features, phase analysis, measurement of microhardness by employing a scanning electron microscope (SEM), X-ray diffraction (XRD) and Vickers microhardness. The cladding and substrate are subjected to sliding wear test against alumina counterpart at elevated temperatures under dry conditions using a pin on disc tribometer. The test is performed by varying normal load and temperatures, whereas sliding speed is maintained constant. The developed clad shown partial melting of CoMoCrSi powders and obtained sound metallurgical bonding with the substrate. The high specific energy of microwave diluted the substrate atoms into cladding region which forms Cr3C2, Co3Ti, and TiC, phases confirmed by phase analysis. The cladding obtained better porosity and microhardness are 1.5 ± 0.2% ?m and 760 ± 35 Hv respectively. The substrate exhibits low microhardness of 182 ± 25 Hv. The cladding exhibits 6 times of lower volume loss and 70.14% of less wear rate with respect to the substrate. The cladding experienced least coefficient of friction is 0.55 compared with the substrate. The worn surfaces of cladding and substrate are examined. The detailed mechanism of wear is discussed in this paper. © 2019, Springer Nature B.V.
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    Fluorescent MoS2 Quantum Dot-DNA Nanocomposite Hydrogels for Organic Light-Emitting Diodes
    (American Chemical Society service@acs.org, 2020) Pandey, P.K.; Ulla, H.; Satyanarayan, M.N.; Rawat, K.; Gaur, A.; Gawali, S.; Hassan, P.A.; Bohidar, H.B.
    In this study, we report the synthesis of water-soluble MoS2 quantum dots (MoS2, QD) by a hydrothermal one-step method. These QDs were mixed in an aqueous solution of 2 kbp DNA to form fluorescent nanocomposite hydrogels at a very low concentration of the nucleic acid (1.0% (w/v), normal gelation occurs at 2% (w/v)). The melting temperature Tmelt of these gels was 50 ± 2 °C while the hydrogels melt at 40 ± 2 °C, and the low-frequency storage modulus/gel strength G0 was 40 ± 2 Pa (9 ± 2 Pa for hydrogel). This clearly implied that MoS2 acted as a pseudo-cross-linker in the nanocomposite hydrogel formation. The remarkable synergy of interaction between DNA and QDs can be gauged from the fact that the gel strength and melting temperature increased with QD content regardless of the fact that both carried negative charge. Dynamic light scattering studies showed arrested dynamics at the onset of gelation, and the gel transition time or ergodicity breaking time ?EB decreased with the increase in QD concentration. Small-angle X-ray scattering data captured the internal structure of these gels. Thus, we have a unique nanocomposite DNA-based hydrogel that is fluorescent, and in 2-D, this soft matter remarkably exhibits the behavior of an organic light-emitting diode (OLED), which imparts sufficient novelty to this work. © © 2020 American Chemical Society.