H₂V₃O₈ as a High Energy Cathode Material for Nonaqueous Magnesium-Ion Batteries

Rastgoo-Deylami, Mohadese,Chae, Munseok S.,Hong, Seung-Tae American Chemical Society 2018 Chemistry of materials Vol.30 No.21

<P>Magnesium-ion batteries (MIBs) suffer from a low energy density of cathode materials in a conventional nonaqueous electrolyte, contrary to the expectation due to the divalent Mg ion. Here, we report H<SUB>2</SUB>V<SUB>3</SUB>O<SUB>8</SUB>, or V<SUB>3</SUB>O<SUB>7</SUB>·H<SUB>2</SUB>O, as a high-energy cathode material for MIBs. It exhibits reversible magnesiation-demagnesiation behavior with an initial discharge capacity of 231 mAh g<SUP>-1</SUP> at 60 °C, and an average discharge voltage of ∼1.9 V vs Mg/Mg<SUP>2+</SUP> in an electrolyte of 0.5 M Mg(ClO<SUB>4</SUB>)<SUB>2</SUB> in acetonitrile, resulting in a high energy density of 440 Wh kg<SUP>-1</SUP>. The structural water remains stable during cycling. The crystal structure for Mg<SUB>0.97</SUB>H<SUB>2</SUB>V<SUB>3</SUB>O<SUB>8</SUB> is determined for the first time. Bond valence sum difference mapping shows facile conduction pathways for Mg ions in the structure. The high performance of this material with its distinct crystal structure employing water-metal bonding and hydrogen bonding provides insights to search for new oxide-based stable and high-energy materials for MIBs.</P> [FIG OMISSION]</BR>

Investigating the thermal environment effects on geometrically nonlinear vibration of smart functionally graded plates

Farzad Ebrahimi,Abbas Rastgoo,Mansoor Nikkhah Bahrami 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.3

An analytical solution for a sandwich circular FGM plate coupled with piezoelectric layers under one-dimensional heat conduction is presented. All materials of the device may be of any functional gradients in the direction of thickness. The solution exactly satisfies all the equilibrium conditions and continuity conditions for the stress, displacement and electric displacement as well as electric potential on the interfaces between adjacency layers. A nonlinear static problem is solved first to determine the initial stress state and pre-vibration deformations of the FG plate that is subjected to in-plane forces and applied actuator voltage in thermal environment in the case of simply supported boundary conditions. By adding an incremental dynamic state to the pre-vibration state, the differential equations that govern the nonlinear vibration behavior of pre-stressed piezoelectric coupled FGM plates are derived. The role of thermal environment as well as control effects on nonlinear static deflections and natural frequencies imposed by the piezoelectric actuators using high input voltages are investigated. Numerical examples are provided and simulation results are discussed. Numerical results for FGM plates with a mixture of metal and ceramic are presented in dimensionless forms. The good agreement between the results of this paper and those of the finite element (FE) analyses validated the presented approach. In a parametric study the emphasis is placed on investigating the effect of varying the applied actuator voltage and thermal environment as well as gradient index of FG plate on the dynamics and control characteristics of the structure.

FSDPT based study for vibration analysis of piezoelectric coupled annular FGM plate

Farzad Ebrahimi,Abbas Rastgoo 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.8

The vibration behavior of a piezoelectrically actuated thick functionally graded (FG) annular plate is studied based on first order shear deformation plate theory (FSDPT). A consistent formulation that satisfies the Maxwell static electricity equation is presented so that the full coupling effect of the piezoelectric layer on the dynamic characteristics of the annular FG plate can be estimated based on the free vibration results. The differential equations of motion are solved analytically for various boundary conditions of the plate. The analytical solutions are derived and validated by comparing the obtained resonant frequencies of the composite plate with those of an isotropic core plate. As a special case, assuming that the material composition of core plate varies continuously in the direction of the thickness according to a power law distribution, a comprehensive study is conducted to show the influence of functionally graded index on the vibration behavior of smart structure. Also, the good agreement between the results of this paper and those of the finite element (FE) analyses validates the presented approach.

Analytical investigation on axisymmetric free vibrations of moderatelythick circular functionally graded plate integrated with piezoelectric layers

F. Ebrahimi,A. Rastgoo,M.H.Kargarnovin 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.6

In this paper, a free vibration analysis of moderately thick circular functionally graded (FG) plate integrated with two thin piezoelectric (PZT4) layers is presented based on Mindlin plate theory. The material properties of the FG core plate are assumed to be graded in the thicknes direction, while the distribution of electric potential field along the thickness of piezoelectric layers is simulated by sinusoidal function. The diferential equations of motion are solved analytically for comparing the obtained resonant frequencies with those of an isotropic host plate. The emphasis is placed on investigat-ing the effect of varying the gradient index of FG plate on the free vibration characteristics of the structure. Good agree-ment between the results of this paper and those of the finite element analyses validated the presented approach.

Stress in piezoelectric hollow sphere with thermal gradient

M. Saadatfar,A. Rastgoo 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.8

The piezoelectric phenomenon has been exploited in science and engineering for decades. Recent advances in smart structures technology have led to a resurgence of interest in piezoelectricity, and in particular, in the solution of fundamental boundary value problems. In this paper, we develop an analytic solution to the axisymmetric problem of a radially polarized, spherically isotropic piezoelectric hollow sphere. The sphere is subjected to uniform internal pressure, or uniform external pressure, or both and thermal gradient. There is a constant thermal difference between its inner and outer surfaces. An analytic solution to the governing equilibrium equations (a coupled system of second-order ordinary differential equations) is obtained. On application of the boundary conditions, the problem is reduced to solving a system of linear algebraic equations. Finally, the stress distributions in the sphere are obtained numerically for two piezoceramics.

Comparison between conventional and ultrasound-assisted extractions of natural antioxidants from walnut green husk

Reza Tabaraki,Shahrbanoo Rastgoo 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.4

Agricultural industries produce substantial quantities of phenolic-rich by-products, which have gained muchattention due to their antioxidant properties. Ultrasonic technology was applied for extraction of antioxidants from thewalnut green husk using ethanol as a food grade solvent. Response surface methodology (RSM) was used to optimizeexperimental conditions. The responses were total phenolic content (TPC), ferric reducing antioxidant power (FRAP),scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and yield. TPC varied from 6.28 to 7.23mg GA g−1dry sample. FRAP and DPPH values varied from 0.33 to 0.46 mmol Fe2+ g−1 of dry sample and 33.98% to 56.31% inhibition,respectively. Extraction yields ranged from 33.04% to 38.72%. The optimal conditions were 60% ethanolwatermixture as solvent, temperature of 60 oC and extraction time of 30 min. Comparison of ultrasonic-assisted extraction(UAE) and conventional extraction was shown that TPC, FRAP, DPPH and yield obtained by UAE during30 min were significantly higher than by conventional extraction during 16 hours. The extract can be used as substituteof synthetic antioxidants for food products, color and oxidative stabilization.

Nonlinear vibration analysis of the viscoelastic composite nanoplate with three directionally imperfect porous FG core

M. Mohammadi,A. Rastgoo 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.2

In this study, the nonlinear vibration analysis of the composite nanoplate is studied. The composite nanoplate is fabricated by the functional graded (FG) core and lipid face sheets. The material properties in the FG core vary in three directions. The Kelvin-Voigt model is used to study the viscoelastic effect of the lipid layers. By using the Von-Karman assumptions, the nonlinear differential equation of the vibration analysis of the composite nanoplate is obtained. The foundation of the system is modeled by the nonlinear Pasternak foundation. The Bubnov-Galerkin method and the multiple scale method are used to solve the nonlinear differential equation of the composite nanoplate. The free and force vibration analysis of the composite nanoplate are studied. A comparison between the presented results and the reported results is done and good achievement is obtained. The reported results are verified by the results which are obtained by the Runge-Kutta method. The effects of different parameters on the nonlinear vibration frequencies, the primary, the super harmonic and subharmonic resonance cases are investigated. This work will be useful to design the nanosensors with high biocompatibility.

Fluid-solid interaction in electrostatically actuated carbon nanotubes

Mir Masoud Seyyed Fakhrabadi,Abbas Rastgoo,Mohammad Taghi Ahmadian 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.4

This paper deals with investigation of fluid flow on static and dynamic behaviors of carbon nanotubes under electrostatic actuation. The effects of various fluid parameters including fluid viscosity, velocity, pressure and mass ratio on the deflection and pull-in behaviorsof the cantilever and doubly clamped carbon nanotubes are studied. Furthermore, the effects of temperature variation on the static anddynamic pull-in voltages of the doubly clamped carbon nanotubes are reported. The results reveal that altering the fluid parameters significantlychanges the mechanical and pull-in behaviors. Hence, the proposed system can be applied properly as a nano fluidic sensor tosense the various parameters of the fluid.

Non stationary vibration and super harmonic resonances of nonlinear viscoelastic nano resonators

Mir Masoud Seyyed Fakhrabadi,Masoud Ajri,Abbas Rastgoo 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.70 No.5

This paper analyzes the non-stationary vibration and super-harmonic resonances in nonlinear dynamic motion of viscoelastic nano-resonators. For this purpose, a new coupled size-dependent model is developed for a plate-shape nano-resonator made of nonlinear viscoelastic material based on modified coupled stress theory. The virtual work induced by viscous forces obtained in the framework of the Leaderman integral for the size-independent and size-dependent stress tensors. With incorporating the size-dependent potential energy, kinetic energy, and an external excitation force work based on Hamilton’s principle, the viscous work equation is balanced. The resulting size-dependent viscoelastically coupled equations are solved using the expansion theory, Galerkin method and the fourth-order Runge–Kutta technique. The Hilbert–Huang transform is performed to examine the effects of the viscoelastic parameter and initial excitation values on the nanosystem free vibration. Furthermore, the secondary resonance due to the super-harmonic motions are examined in the form of frequency response, force response, Poincare map, phase portrait and fast Fourier transforms. The results show that the vibration of viscoelastic nanosystem is non-stationary at higher excitation values unlike the elastic ones. In addition, ignoring the small-size effects shifts the secondary resonance, significantly.

Multi-objective design optimization of composite laminates using discrete shuffled frog leaping algorithm

Mir Masoud Seyyed Fakhrabadi,Abbas Rastgoo,Mostafa Samadzadeh 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.6

This paper deals with the optimization of composite laminates using discrete shuffled frog leaping method. This approach is used to find optimal values of three design variables including fiber orientations in matrices, thickness of each ply and number of layers in order to minimize the weights and costs of the laminates under various loading cases. Three well-known failure criteria are employed to investigate the capability of the plate in bearing the applied loads. Moreover, the comparison of the obtained results with previously reported results is performed to prove the applicability of the algorithm in optimizing composite materials.