52 research outputs found

    Optimization of Electrical Parameters for Production of Carbon Nanotubes

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    ABSTRACT For more than two decades, there had been extensive research on the production of carbon nanotubes (CNT) and optimization of its manufacture for the industrial applications. It is believed that they are the strong enough but most flexible materials known to mankind. They have potential to take part in new nanofabricated materials. It is known that, carbon nanotubes could behave as the ultimate one-dimensional material with remarkable mechanical properties. Moreover, carbon nanotubes exhibit strong electrical and thermal conducting properties. In the process of optimizing the production in line with the industrial application, the researchers have found a new material to act as an anode i.e. coal, which is inexpensive as compared to graphite. There are various methods such as arc discharge, laser ablation, chemical vapour deposition (CVD), template-directed synthesis and the use of the growth of CNTs in the presence of catalyst particles. The production of carbon nanotubes in large quantities is possible with inexpensive coal as the starting carbon source by the arc discharge technique. It is found that a large amount of carbon nanotubes of good quality can be obtained in the cathode deposits in which carbon nanotubes are present in nest-like bundles. This paper primarily concentrates on the optimising such parameters related to the mass production of the product. It has been shown through Simplex process that based on the cost of the SWNT obtained by the arc discharge technique, the voltage and the current should lie in the range of 30 -42 V and 49 -66 A respectively. Any combination above the given values will lead to a power consumption cost beyond the final product cost, in turn leading to infeasibility of the process

    Transformer Oil Nanofluids by Two Dimensional hexagonal Boron Nitride Nanofillers

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    This paper explores the fascinating properties of two-dimensional (2D) nanofillers based transformer oil (TO) nanofluids. Nanofluids of 2D hexagonal boron nitride (h-BN) nanosheets in TO demonstrate stable dispersion with improved dielectric breakdown strength and superior thermo physical properties like thermal conductivity, viscosity and stability. An appreciable augmentation in AC breakdown voltage (BDV) is observed compared to the state-of-the-art boron nitride (BN) particles. This enhancement in BDV is elucidated by the role of the greater surface area of Maxwell-Garnet ‘oil-sheet’ interfacial region of the 2D morphology in charge trapping perspective. The faster rate of heating and cooling along with noteworthy enhancement in thermal conductivity is due to the interfacial heat transfer via 2D nanoadditives prompting good phonon transport which agrees with Maxwell\u27s forecasts. Addition of 2D nanofiller at diluted concentration exhibits better stability and high thermal efficiency compared to its particle counterpart. Hence, 2D nanofillers are better choices for next generation transformer oil nanofluids, due to their high surface area, lower filler fraction and better stability

    Ultra-stable Transformer Oil nanofluids with significant AC Breakdown Voltage enhancement at ultra-low filler fraction of functionalized boron nitride nanosheets

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    This paper reports the purposeful fluorination of hexagonal boron nitride (h-BN) nanofillers and its impact on reinforcement of AC breakdown strength and stability of transformer oil (TO) nanofluid. Fluorine functionalized boron nitride nanosheets (f-BNNs) of ˜5 nm thickness was synthesized in house via wet synthetic exfoliation route of pristine h-BN utilizing Ammonium Fluoride (NH4F) as the shedding agent. This promotes attachment of some highly electro- negative fluorine atoms to boron. This tailored f-BNNs exhibit a diminished band gap and induced electrical conductivity which helps in elevating the AC breakdown Voltage to 26 %- 20% and a surge in resistivity at appreciably low nanofiller fraction of 0.005-0.01wt. %. These noteworthy improvement of electrical insulation properties compared to the state-of-the-art Boron nitride nanoparticles or nanosheets is explained by the parallel role played by fluorine in charge trapping as well as the role played 2D morphology of the nanofillers. Here, fluorine facilitated extrinsic energy bands in the oil-nanofiller interface acted as efficient charge trapping sites and helped to accumulate large quantities of streamer charges, more than h-BN nanosheets or BN nanoparticle for a longer time and improved the electric insulation properties to a large extent. The ultra-high steadiness of the nanofluid is also observed at these lower filler concentrations. 2D morphology, lipophilicity and electro-negativity induced electrostatic repulsion between the f-BNNs nanosheets are attributed to achieve this alluring property of the nanofluid. Such significant improvements at very low filler fractions justifies the fluorination of hexagonal boron nitride as a novel idea and a better alternative among all the reported BN brothers for high voltage applications of nano engineered liquid insulatio

    Electronic Spectroscopy of the AlSb Molecule:  A Theoretical Study

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    Branch Density-Controlled Synthesis of Hierarchical TiO<sub>2</sub> Nanobelt and Tunable Three-Step Electron Transfer for Enhanced Photocatalytic Property

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    The successful adjustment of phase composition and morphology of hierarchical TiO<sub>2</sub> nanobelts, which feature homoepitaxial nanobranches, has been developed via the hydrothermal method and chemical bath deposition technique. Effects of hydrothermal reaction time, titanium butoxide treatment in chemical bath deposition, and calcination temperature are systematically investigated. For the first time, three-step ultrafast electron transfers between the band edges of the engaged phases are realized through the enhanced photocatalytic activity results. Growth mechanism related to branch density control on nanobelt surface under such soft chemical process is discussed in detail on the basis of classical nucleation theory. The current work might provide new insights into the fabrication of one-dimensional homoepitaxial branched TiO<sub>2</sub> nanostructures as high performance photocatalysts and facilitate their application in environmental cleanup