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Microstructure studies of air-plasma-spray-deposited CoNiCrAlY coatings before and after thermal cyclic loading for high-temperature application

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International Journal of Minerals,Metallurgy and Materials 2016年第8期23卷 934-942页

作者： Dipak kumar k.N.pandey Dipak kumar Das Mechanical Engineering Department Motilal Nehru National Institute of TechnologyAllahabad-211004India Defense Metallurgical research Laboratory Hyderabad-500058India

In the present study, bond-coats for thermal barrier coatings were deposited via air plasma spraying（APS） techniques onto Inconel 800 and Hastelloy C-276 alloy substrates. Scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, X-ray diffraction（XrD）, and atomic force microscopy（AFM） were used to investigate the phases and microstructure of the as-sprayed, APS-deposited Co Ni Cr Al Y bond-coatings. The aim of this work was to study the suitability of the bond-coat materials for high temperature applications. Confirmation of nanoscale grains of the γ/γ′-phase was obtained by TEM, high-resolution TEM, and AFM. We concluded that these changes result from the plastic deformation of the bond-coat during the deposition, resulting in Co Ni Cr Al Y bond-coatings with excellent thermal cyclic resistance suitable for use in high-temperature applications. Cyclic oxidative stability was observed to also depend on the underlying metallic alloy substrate.

关键词： thermal barrier coatings coating structure plasma spraying thermal cycle high-temperature applications microstructure studies

Model development for analyzing 2DEG sheet charge density and threshold voltage considering interface DOS for AlInN/GaN MOSHEMT

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Journal of Semiconductors 2014年第10期35卷 26-29页

作者： Devashish pandey T.r.Lenka Department of Electronics and Communication Engineering National Institute of Technology Silchar

A model predicting the behavior of various parameters, such as 2DEG sheet charge density and thresh- old voltage, with the variation of barrier thickness and oxide thickness considering interface density of states is presented. The mathematical dependence of these parameters is derived in conjunction with the interface density of states. The dependence of sheet charge density with the barrier thickness and with the oxide thickness is plotted and an insight into the barrier scaling properties of AIInN based MOSHEMTs is presented. The threshold voltage is also plotted with respect to barrier thickness and oxide thickness, which reveals the possibility of the enhance- ment mode operation of the device at low values of the interface DOS. The results are in good agreement with the fabricated device available in the literature.

关键词： DOS AIlnN MOSHEMT 2DEG barrier scaling

Dynamics of Entanglement in Qubit-Qutrit with x-Component of DM Interaction

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Communications in Theoretical Physics 2016年第3期65卷 278-284页

作者： kapil k.Sharma S.N.pandey Department of Physics Motilal Nehru National Institute of Technology

In this present paper,we study the entanglement dynamics in qubit A-qutrit B pair under x component of Dzyaloshinshkii-Moriya interaction(D_x)by taking an auxiliary qubit ***,we consider an entangled qubit-qutrit pair initially prepared in two parameter qubit-qutrit states and one auxiliary qubit prepared in pure state interacts with the qutrit of the pair through DM *** trace away the auxiliary qubit and calculate the reduced dynamics in qubit A-qutrit B pair to study the influence of the state of auxiliary qubit C and D_x on *** find that the state(probability amplitude)of auxiliary qubit does not influence the entanglement,only D_x influences the *** phenomenon of entanglement sudden death(ESD)induced by D_x has also been *** also present the affected and unaffected two parameter qubit-qutrit states by D_x.

关键词： entanglement dynamics qubit-qutrit DM interaction ESD

One Step Synthesis and Growth Mechanism of Carbon Nanotubes

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Journal of Materials Science & Technology 2014年第2期30卷 112-116页

作者： Akshay kumar k.Singh O.P.pandey Sri Guru Granth Sahib World University School of Physics and Materials Science Thapar University

A simple one step, reproducible, synthesis route for carbon nanotubes was proposed. No external catalyst was used for the synthesis. These nanotubes were obtained after decomposition of acetone at 650 ℃ in a specially designed autoclave. The pressure generated due to decomposition of acetone played a vital role in the synthesis. The X-ray diffraction pattern and transmission electron microscopy of the sample showed that the diameter of nanotubes is in the range of 3-14 nm. The thermo gravimetric analysis showed 3% weight loss below 500 ℃; the content of amorphous carbon is very less. The growth mechanism of CNTs was also proposed in the present paper.

关键词： Nanostructures Chemical synthesis Electron diffraction raman spectroscopy Defects

Generation of VLF Mode Instability by Generalized Distribution Function in the Presence of Parallel AC Electric Field in Uranus

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Plasma Science and Technology 2010年第4期12卷 421-425页

作者： r.S.pandey M.SINGH Pramod kUMAr k.M.SINGH S.kUMAr Department of Applied Physics Amity School of Science and TechnologyAmity University Noida UP Department of Physics J. L. N. College Chakradharpur Ranchi University Ranch Department of Physics Veer Kunwar Singh University Department of Physics Nalanda college Biharsharif Nalanda MU Bodh Gaya Bihar

VLF （very low frequency） mode instability with parallel AC electric field was studied for generalized loss-cone distribution with an index j, which is reducible to bi-Maxwellian, loss- cone and delta function for j = 0, 1 and co. The particle trajectories and dispersion relation are obtained through a kinetic approach and method of characteristic solutions. The calculations are compared with the observations of low frequency waves of Voyager 2. The growth rate of plasma parameters suited to magnetosphere of Uranus is obtained. It is inferred that the magnitude as well as frequency of AC （alternating current） field increases the growth rate and widen the band width significantly. In addition to temperature anisotropy, particles in plasma having generalized loss-cone distribution provide an additional source of energy.

关键词： generation of VLF mode instability in Uranus

Low power digitally controlled oscillator designs with a novel 3-transistor XNOr gate

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Journal of Semiconductors 2012年第3期33卷 52-59页

作者： Manoj kumar Sandeep k.Arya Sujata pandey Department of Electronics&Communication Engineering Guru Jambheshwar University of Science&Technology Amity University

Digital controlled oscillators（DCOs） are the core of all digital phase locked loop（ADPLL） circuits. Here,DCO structures with reduced hardware and power consumption having full digital control have been proposed. Three different DCO architectures have been proposed based on ring based ***,four and five bit controlled DCO with NMOS,PMOS and NMOS PMOS transistor switching networks are presented.A three-transistor XNOr gate has been used as the inverter which is used as the delay *** has been controlled digitally with a switch network of NMOS and PMOS *** three bit DCO with one NMOS network shows frequency variations of 1.6141-1.8790 GHz with power consumption variations 251.9224-276.8591μW. The four bit DCO with one NMOS network shows frequency variation of 1.6229-1.8868 GHz with varying power consumption of 251.9225-278.0740μW.A six bit DCO with one NMOS switching network gave an output frequency of 1.7237-1.8962 GHz with power consumption of 251.928-278.998μ*** frequency and power consumption results for 4 6 bit DCO circuits with one PMOS and NMOS PMOS switching network have also been *** phase noise parameter with an offset frequency of 1 MHz has also been reported for the proposed *** with earlier reported circuits have been made and the present approach shows advantages over previous circuits.

关键词： digital control oscillator delay cell power consumption voltage controlled oscillators

An Updated review on Low-Temperature Nanocomposites with a Special Focus on Thermal Management in Buildings

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Energy Engineering 2022年第4期119卷 1299-1325页

作者： John Paul k.kadirgama M.Samykano r.Saidur A.k.pandey r.V.Mohan Faculty of Mechanical&Automotive Engineering Technology Universiti Malaysia PahangPekan26600Malaysia College of Engineering Universiti Malaysia PahangPekan26600Malaysia research Centre for Nanomaterials and Energy Technology School of Engineering and TechnologySunway UniversityPetaling Jaya47500Malaysia Joint School of Nanoscience&Nanoengineering North Carolina A&T State UniversityNorth CarolinaGreensboro27401USA

Buildings contribute to 33%of total global energy consumption,which corresponds to 38%of greenhouse gas *** building’s energy efficiency remains predominant in mitigating global ***-ments in thermal energy storage(TES)techniques using phase change material(PCM)have gained much attention among researchers,primarily to minimize energy consumption and to promote the use of renewable energy *** technology stays as the most promising technology for developing high-performance and energy-efficient *** major drawback of PCM is its poor thermal conductivity which limits its potential use which could be resolved by dispersing conductive *** acquired database on synthesis routes,properties,and performance of nano-dispersed phase change materials(NDPCMs)with various techniques presented in the paper should deliver useful information in the production of NDPCMs with desirable characteristics mainly for building construction *** outline of contemporary developments and use of NDPCMs as TES medium is ***,a brief discussion on challenges and the outlook was also ***-depth research is needed to explore the fundamental mechanisms behind the enhanced thermal conductivity of NDPCM with nanofillers dispersion and also a thorough investigation on how these mechanisms drive improvement in building performance.

关键词： Thermal conductivity latent heat building applications energy savings

Unsteady peristaltic transport of Maxwell fluid through finite length tube:application to oesophageal swallowing

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Applied Mathematics and Mechanics(English Edition) 2012年第1期33卷 15-24页

作者： S. k. pandey D. TrIPATHI Department of Applied Mathematics Institute of Technology Banaras Hindu University Department of Mathematics Indian Institute of Technology Ropar

This paper analytically investigates the unsteady peristaltic transport of the Maxwell fluid in a finite tube. The walls of the tube are subjected to the contraction waves that do not cross the stationary boundaries. The analysis is carried out by a long wavelength approximation in the non-dimensional form. The expressions for the axial and radial velocities are derived. The pressures across the wavelength and the tubelength are also estimated. The reflux phenomenon is discussed, which culminates into the determination of the reflux limit. Mathematical formulations are physically interpreted for the flow of masticated food materials such as bread and white eggs in the oesophagus. It is revealed that the Maxwell fluids are favorable to flow in the oesophagus as compared with the Newtonian fluids. This endorses the experimental finding of Takahashi et al. （Takahashi, T., Ogoshi, H., Miyamoto, k., and Yao, M. L. Viscoelastic properties of commercial plain yoghurts and trial foods for swallowing disorders. rheology, 27, 169- 172 （1999））. It is further revealed that the relaxation time does not affect the shear stress and the reflux limit. It is found that the pressure peaks are identical in the integral case while different in the non-integral case.

关键词： peristaltic transport Maxwell fluid oesophagus axisymmetric flow reflux

Fe–EBT Chelate Complex: A Novel Mean for Growth of α-FeOOH and γ-Fe_2O_3 Nanostructures

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Acta Metallurgica Sinica(English Letters) 2014年第6期27卷 1127-1133页

作者： Gajanan pandey Department of Applied Chemistry Babasaheb Bhimrao Ambedkar University

Acicular goethite（a-Fe OOH） and worm-like maghamite（γ-Fe2O3） nanostructures have been prepared adopting a novel route, using Na2[Fe（HL）2（H2O）2] chelate complex in alkaline medium. It is found that concentration of hydrated Fe（III） ions increased with increasing temperature, which later play a key role in generation of different phases of iron oxide. Phase and morphology of the products are investigated using XrD, FTIr, SEM, and TEM analysis. Using UV–Vis spectra, various electronic transitions of goethite and maghamite particles are examined. Maghamite nanostructures exhibit superparamagnetic property at room temperature. On the basis of experimental observations and analytical data, growth mechanism of the nanostructures is discussed.

关键词： Iron oxide Nanostructures Chemical synthesis Growth mechanism Magnetic properties