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Phase evolution and mechanical properties of novel nanocrystalline Y_(2)(TiZrHfMoV)_(2)O_(7) high entropy pyrochlore

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Journal of Materials science & Technology 2021年第23期82卷 214-226页

作者： g.Karthick Lavanya Raman b.s.Murty Department of Metallurgical and Materials Engineering Indian Institute of Technology MadrasChennai600036India Indian Institute of Technology Hyderabad Kandi502285India

High entropy pyrochlores(HEP)are potential candidates as dispersoids in the oxide dispersed strengthened steels or alloys,which can be used in nuclear reactors and supercritical *** the first time,HEP oxides Y_(2)(TiZrHfMoV)_(2)O_(7) were synthesized with Y_(2)Ti_(2)O_(7) as a base structure with the b site(Ti)substituted with five cations through reverse co-precipitation technique in the nanocrystalline form at lowest synthesis *** synthesis parameters for Y_(2)(TiZrHfMoV)_(2)O_(7)(5C)and other derived compositions(five compositions of four cationic systems with each cation eliminated at b site from 5 C)are optimised to obtain lower crystallite and particle sizes.5C has a smaller crystallite size(27 nm)than other single-phase *** cation’s influence,oxidation state,and oxygen vacancy in the phase formation were analysed through *** single-phase HEPs are consolidated through spark plasma sintering.Y_(2)(TiZrHfMo)_(2)O_(7)(4 C-V)shows the highest hardness among the compositions reported so far due to its finer grain size,and Y_(2)(TiHfMoV)_(2)O_(7)(4 C-Zr)has a higher Young’s modulus compared to other single-phase composition due to its higher degree of order in the structure.

关键词： High entropy pyrochlores Reverse co-precipitation b site substitution Hardness Young’s modulus

study of hybrid nanofluid flow in a stationary cone-disk system with temperature-dependent fluid properties

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Applied Mathematics and Mechanics(English Edition) 2024年第4期45卷 677-694页

作者： A.s.JOHn b.MAHAnTHEsH g.LOREnZInI Center for Mathematical needs Department of MathematicsCHRIST(Deemed to be University)Karnataka 560029India school of Mathematical and statistical sciences The University of Texas Rio Grande ValleyTexas 78539U.S.A. Department of Engineering and Architecture University of ParmaParma 43124Italy

Cone-disk systems find frequent use such as conical diffusers,medical devices,various rheometric,and viscosimetry *** this study,we investigate the three-dimensional flow of a water-based Ag-Mg O hybrid nanofluid in a static cone-disk system while considering temperature-dependent fluid *** the variable fluid properties affect the dynamics and heat transfer features is studied by Reynolds's linearized model for variable viscosity and Chiam's model for variable thermal *** single-phase nanofluid model is utilized to describe convective heat transfer in hybrid nanofluids,incorporating the experimental *** model is developed as a coupled system of convective-diffusion equations,encompassing the conservation of momentum and the conservation of thermal energy,in conjunction with an incompressibility condition.A self-similar model is developed by the Lie-group scaling transformations,and the subsequent self-similar equations are then solved *** influence of variable fluid parameters on both swirling and non-swirling flow cases is ***,the nusselt number for the disk surface is *** is found that an increase in the temperature-dependent viscosity parameter enhances heat transfer characteristics in the static cone-disk system,while the thermal conductivity parameter has the opposite effect.

关键词： hybrid nanofluid cone-disk system laminar flow variable fluid property nusselt number

Optoelectronic Response of geZn_(2)O_(4) through the Modified becke-Johnson Potential

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Chinese Physics Letters 2012年第9期29卷 142-146页

作者： Iftikhar Ahmad b.Amin M.Maqbool s.Muhammad g.Murtaza s.Ali n.A.noor Department of Physics University of MalakandPakistan Materials Modeling Lab Department of PhysicsHazara University21300Pakistan Department of Physics and Astronomy Ball State UniversityIndiana47306-0505USA Department of Physics Islamia College UniversityPeshawarPakistan Department of Physics University of the PunjabQuaid-e-Azam Campus54590Pakistan

A first-principles technique capable of describing the nearly excited states of semiconductors and insulators,namely the modified becke–Johnson(mbJ)potential approximation,is used to investigate the electronic band structure and optical properties of spinel oxides:geZn_(2)O_(4).The predicted band gaps using the mbJ approximation are significantly more accurate than the proposed previous theoretical work using the common LDA and *** gap dependent optical parameters,like the dielectric constant,index of refraction,reflectivity and optical conductivity are calculated and *** results from the dielectric constant shows that the numerical value of the static dielectric,after dropping constantly,becomes less than zero and the material exhibits metallic *** refractive index also drops below unity for photons higher than 18 eV,which indicates that the velocities of incident photons are greater than the velocity of ***,these phenomena can be explained by the fact that a signal must be transmitted as a wave packet rather than a monochromatic *** comprehensive theoretical study of the optoelectronic properties predicts that these materials can effectively be used in optical devices.

关键词： wave. dielectric approximation

Thermodynamic properties of 3C-siC

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Chinese Physics b 2013年第10期22卷 429-435页

作者： b.Y.Thakore s.g.Khambholja A.Y.Vahora n.K.bhatt A.R.Jani Department of Physics Sardar Patel UniversityVallabh Vidyanagar388120GujaratIndia Indus University Ahmedabad 380001GujaratIndia

In the present paper, we report on the results of various thermodynamic properties of 3C-siC at high pressure and temperature using first principles calculations. We use the plane-wave pseudopotential density functional theory as im- plemented in Quantum EsPREssO code for calculating various cohesive properties in ambient condition. Further, ionic motion at a finite temperature is taken into account using the quasiharmonic Debye model. The calculated thermody- namic properties, phonon dispersion curves, and phonon densities of states at different temperatures and structural phase transitions at high pressures are found to be in good agreement with experimental and other theoretical results.

关键词： phase transition phonon dispersion curve Debye model thermodynamic property

CFD simulation of helicopter rotor flow based on unsteady actuator disk model

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Chinese Journal of Aeronautics 2020年第9期33卷 2313-2328页

作者： g.n.bARAKOs T.FITZgIbbOn A.n.KUsYUMOV s.A.KUsYUMOV s.A.MIKHAILOV James Watt school of Engineering Glasgow UniversityGlasgow G128QQUnited Kingdom Department of Aerohydrodynamics Kazan National Research Technical University named after A.N.TupolevKazan 420111Russia

Actuator Disks(AD)can provide characterizations of rotor wakes while reducing computational expense associated with modeling the fully resolved *** work presents an unsteady actuator disk method based on surface circulation distribution combined with empirical data,blade element theory and rotor momentum *** nonuniform circulation distribution accounts for 3 D blade load effects,and in particular,tip *** simulations were conducted for the isolated pressure sensitive paint model rotor blade in hover and forward flight using the HMb3 CFD solver of glasgow *** of CFD results in comparison with published numerical data was performed in hover,for a range of blade pitch angles using fully turbulent flow and the k-x ssT *** forward flight,the vortex structures predicted using the unsteady actuator disk model showed configurations similar to the ones obtained using fully resolved rotor *** the reduced grid cells number,the CFD results for AD models captured well the main vortical structures around the rotor disk in comparison to the fully resolved cases.

关键词： CFD Fully resolved blades rotor PsP rotor surface circulation distribution Unsteady actuator disk model

Investigation into machining performance of microstructurally engineered in-situ particle reinforced magnesium matrix composite

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Journal of Magnesium and Alloys 2023年第3期11卷 916-935页

作者： s.K.sahoo b.n.sahoo s.K.Panigrahi Department of Mechanical Engineering Indian Institute of Technology MadrasChennai 600036India Applied Magnesium Research group Center of Excellence in Materials and Manufacturing for Futuristic MobilityIndian Institute of Technology MadrasChennai 600036India Department of Mechanical Engineering Sardar Vallabhbhai National Institute of TechnologySurat 395007India

Magnesium and magnesium in-situ composites have significant potential in the application of design and manufacturing for automotive and aerospace industries because of their high specific strength and reduced fuel *** there are many challenges for machining of Mg based alloys and composites because of the high tendency of fire and *** challenges can be minimized through microstructural *** this present study,the machining performances of AZ91 Mg alloy and in-situ hybrid TiC+Tib_(2)reinforced AZ91 metal matrix composite was *** effectβ-Mg_(17)Al_(12)phases and grain refinement with and without in-situ particles on machinability were studied through microstructural engineering via aging and friction stir *** end milling operation was carried out at different cutting speeds ranging from 25 mm/min to 90 mm/min under dry environment by using an AlTin-coated tungsten carbide *** optimum cutting speed for machining was found to be 75 mm/min based on the surface roughness values of all conditioned *** base material with dendritic microstructure was found to have poor machinability in terms of inadequate surface finish and edge-burrs *** combined effect of in-situ TiC+Tib_(2)particles addition and grain refinement enhanced the machining performance of the material with superior surface finish,negligible edge-burr formation and better tool wear *** influence of in-situ TiC+Tib_(2)particles,β-Mg_(17)Al_(12)phases and grain refinement on machining characteristics are explained based on the tool wear mechanisms,chip behavior and machining induced affected zone.

关键词： Magnesium In-situ composite End-milling Tool wear Chip morphology

Compact analytical model for single gate AlInsb/Insb high electron mobility transistors

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Journal of semiconductors 2014年第11期35卷 46-50页

作者： s.Theodore Chandra n.b.balamurugan g.subalakshmi T.shalini g.Lakshmi Priya national Instruments Electronics Laboratory Department of ECEThiagarajar College of Engineering

We have developed a 2D analytical model for the single gate Allnsb/lnsb HEMT device by solving the Poisson equation using the parabolic approximation method. The developed model analyses the device perfomance by calculating the parameters such as surface potential, electric field distribution and drain current. The high mobility of the AlInsb/Insb quantum makes this HEMT ideal for high frequency, high power applications. The working of the single gate Allnsb/Insb HEMT device is studied by considering the variation of gate source voltage, drain source voltage, and channel length under the gate region and temperature. The carrier transport efficiency is improved by uniform electric field along the channel and the peak values near the source and drain regions. The results from the analytical model are compared with that of numerical simulations （TCAD） and a good agreement between them is achieved.

关键词： high electron mobility transistor AlInsb/Insb quantum well 2D analytical model Poisson's equation surface potential electric field

Investigation of Ti6Al4V and AA7075 alloy embedded nanofluid flow over longitudinal porous fin in the presence of internal heat generation and convective condition

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Communications in Theoretical Physics 2020年第2期72卷 23-29页

作者： g sowmya b J gireesha s sindhu b C Prasannakumara Department of Pg studies and Research in Mathematics Kuvempu UniversityShankaraghatta-577451KarnatakaIndia Department of Mathematics Davangere UniversityDavangere-577002KarnatakaIndia

The thermal attributes of porous fin due to radiation and natural convection have been carried out in the presence of nanofluid *** geometry of the fin taken for the analysis is rectangular profiled longitudinal *** temperature-dependent internal heat generation condition is also considered along with Darcy’s *** two types of nanofluid containing titanium alloy(Ti6Al4V)and aluminium alloy(AA7075)immersed in water is considered for the *** modelled nonlinear ordinary differential equation is numerically solved by the Runge–Kutta–Fehlberg *** impact of geometric parameter on the heat transfer analysis of the fin due to the flow of both nanofluids is plotted and consequences are physically *** is observed that the presence of the water-based titanium alloy better enhances the fin heat transfer rate.

关键词： alloys nanofluid porous fin heat transfer analysis convective condition internal heat generation

Coefficient of restitution for particles impacting on wet surfaces： An improved experimental approach

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Particuology 2016年第2期14卷 1-9页

作者： b. Cunger V. salikov s. Heinrich s. Antonyuk V.s. sutkar n.g. Deen J.A.M. Kuipers Institute of solids Process Engineering and Particle Technology Hamburg University of Technology Denickestrasse 15 21073 Hamburg Germany Particle Process Engineering Department of Mechanical and Process Engineering University ofKaiserslautern Cottlieb-Daimler-Strasse 67663 Kaiserslautern Germany Multiphase Reactors group Department of Chemical Engineering and Chemistry Eindhoven University of Technology P.O. Box 513 5600 MB EindhovenThe Netherlands

The coefficient of restitution is widely used to characterize the energy dissipation rate in numerical simulations involving particle collisions. The challenge in measuring the coefficient of restitution is the strong scatter seen in experimental data that results from varying particle properties, i.e. shape and surface roughness, and from imperfections in the experimental technique. To minimize this scattering, a novel experimental setup was developed based on two synchronized high-speed cameras capturing the collision behaviour of a particle in three dimensions. To measure the wet restitution coefficient, which describes particle impact in the presence of a liquid layer in the contact region, additional accuracy can be achieved by measuring the liquid layer thickness by a high-precision optical confocal sensor. The coefficient of restitution was measured for glass particles with two different diameters, at different relative velocities and liquid layer thicknesses, with a focus on small collision velocities and thin liquid layers, using both the improved （three dimensional） and the conventional （two dimensional） approaches to quantify the improvement of the new method＇s accuracy.

关键词： Particle impact Coefficient of restitution Liquid layer Improved experimental setup