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Time-dependence of the electromechanical bending actuation observed in ionic-electroactive polymers

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Journal of Advanced Dielectrics 2017年第2期7卷 1-6页

作者： Patrick S.Bass Lin z.ang z.-y.cheng Materials Research and Education Center Auburn UniversityAuburnAL 36849USA

The characteristics of the electromechanical response observed in an ionic-electroactive polymer(i-EAP)are represented by the time(t)dependence of its bending actuation(y).The electromechanical response of a typical i-EAP—poly(ethylene oxide)(PEO)doped with lithium perchlorate(LP)—is *** shortcomings of all existing models describing the electromechanical response obtained in i-EAPs are discussed.A more reasonable model:y=y_(max)^(e-T/t)is introduced to characteriz. this time dependence for all *** advantages and correctness of this model are confirmed using results obtained in PEO-LP actuators with different LP contents and at different *** applicability and universality of this model are validated using the reported results obtained from two different i-EAPs:one is Flemion and the other is polypyrrole actuators.

关键词： i-EAP PEO electromechanical response model

Electrocaloric devices part Ⅱ:All-solid heat pump without moving parts

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Journal of Advanced Dielectrics 2020年第6期10卷 29-44页

作者： Farrukh Najmi Jianping He Lorenz. Cremaschi z.-y.cheng Materials Research and Education Center Auburn University AuburnAL 36849USA School of Materials Engineering Shanghai University of Engineering Science Shanghai 201620 P.R.China Department of Mechanical Enginering Auburn University AuburnAL 36849US

Various designs have been introduced to build heat pumps using the electrocaloric effect (ECE). Each of all the curent designs usesat least one moving part, which significantly reduces the reliability of the pump and adds complexities. In this work, a new all-soliddesign is introduced, in which two layers of an electrocaloric material (ECM) are permanently sandwiched in the source and sink,which would significantly increase the device's reliability since nothing moves and all are permanently bound together. Moreimportantly, the electric fields applied on two ECM layers are independently controlled. A special sequence for the electric fields on .two ECM layers is introduced. Numerical calculation was used to simlulate the device's performance by using the newly introducedanalytical solutions for the heat conduction in the system. It is concluded that a continuous heat transformation from the source tosink at the same temperature can be achieved when the contacting cofficient, K_(ε)=√(k^(c)p^(c)c^(c)_(p))/(k^(o)p^(o)c^(o)_(p)), is very small, where k,ρ, and Cp are thermal conductivity, density, and heat capacity, respectively, while the superscript c and 0 represent the ECM andsource/sink, respectively.

关键词： Electrocaloric based heat pump electrocaloric effect numerical calculation

Electrocaloric devices part Ⅰ:Analytical solution of one-dimensional transient heat conduction in a multilayer electrocaloric system

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Journal of Advanced Dielectrics 2020年第6期10卷 19-28页

作者： Farrukh Najmi Wenxian Shen Lorenz. Cremaschi z.-y.cheng Materials Research and Education Center Auburn University AuburnAL 36849USA Department of Mathematics and Statistics Auburn UniversityAuburnAL 36849USA Department of Mechanical Engineering Auburn University AuburnAL 36849USA

The analytical solution is reported for one-dimensional(1D)dynamic conduction heat transfer within a mulilayer system that is the typical structure of electrocaloric ***,the multilayer structure of typical electrocaloric devices is simplified as four layers in which two layers of electrocaloric materials(ECMs)are sandwiched between two semi infinite bodies representing the thermal sink and *** temperature of electrocaloric layers can be instantaneously changed by extemal electic field to establish the initial temperature *** analytical solution includes the temperatures in four bodies as a function of both time and location and heat flux through each of the three interfaces as a function of *** of these analytical solutions includes five infinite *** is proved that each of these series is convergent so that the sum of each series can be calculated using the first N terms of the *** formula for calculating the value of N is presented so that the simulation of an electrocaloric device,such as the temperature distribution and heat transferred from one body to another can be *** value of N is dependent on the thickness of electrocaloric material layers,the time of heat conduction,and thermal properties of the materials *** on a case study,it is concluded that the N is mostly less than 20 and barely reaches more than *** application of the analytical solutions for the simulation of real electrocaloric devices is discussed.

关键词： Thermal conduction multilayer structure electrocaloric effect heat pump

Enhanced thermal and pyroelectric properties in 0-3 TGS:PVDF composites doped with graphene for infrared application

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Journal of Advanced Dielectrics 2017年第1期7卷 39-44页

作者： Xiaodong Feng Minqiang Wang Le Li z.i yang Minghui Cao z.-y.cheng Electronic Materials Research Laboratory(EMRL)Key Laboratory of Education Ministry International Center for Dielectric Research(ICDR)Xi'an Jiaotong University Xi'an 710049P.R.China Materials Research and Education Center Auburn University AuburnAL 36849USA

Pyroelectric composites of triglycine sulfate(TGS)-polyvinylidene difluoride(PVDF)doped with graphene are *** is found that the graphene can effectively improve the polling efficiency and thermal property of the composites so that the infrared detective performance can be significantly *** example,by adding about 0.83 wt.%of graphene,the infrared detective property can be improved by more than 30%.It is also found that the siz. of the graphene plays a critical role on the property *** example,the small-siz.d graphene prepared by ultrasonic exfoliation(UE)method is more effective than the big-siz.d graphene prepared by electrochemical exfoliation(EE)method.

关键词： Composites polling thermal pyroelectric graphene doping

DEVELOPMENT OF POLyMER-BASED 0-3 COMPOSITES WITH HIGH DIELECTRIC CONSTANT

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Journal of Advanced Dielectrics 2011年第4期1卷 389-406页

作者： LIN z.ANG z.-y.cheng Materials Research and Education Center Auburn University AuburnAL 36849USA

Composites have been extensively studied for dielectric and related *** is a reviewof polymer based 0-3 composites that exhibit a high dielectric *** composites areclassified into two ***-dielectric composite and conductor-dielectric *** physical principles and related models are presented with associated assumptions and *** general,a dielectric-dielectric composite needs a higher concentration of thefillers to reach a high dielectric constant than a conductor-dielectric *** high dielectric constant observed in the conductor-dielectric composites is usually associated with ahigh dielectric loss and a low electric breakdown *** experimental results are summariz.d toillustrate the principles for,and the achievements in,the development of these *** challenges facing the fundamental understanding and the further development of these compo-sites for diferent applications are discussed.

关键词： Dielectric property dielectric constant composite 0-3 composite percolation

Characteriz.tion of percolation behavior in conductor-dielectric 0-3 composites

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Journal of Advanced Dielectrics 2014年第4期4卷 65-71页

作者： Lin z.ang Patrick Bass z.i-Min Dang z.-y.cheng Materials Research and Education Center Auburn University Auburn AL 36849 USA Laboratory of Dielectric Polymer Materials and Devices School of Chemistry and Biological Engineering University of Science and Technology Beijing Beijing 100083 P.R.China

The equationε_(eff)■/φ_(c)φ)^(s)which shows the relationship between effective dielectric constant(ε_(eff))and the filler concentration(φ),is widely used to determine the percolation behavior and obtain parameters,such as percolation thresholdφc and the power constant s in conductor-dielectric composites(CDCs).Six different systems of CDCs were used to check the expression by fitting experimental *** is found that the equation can fit the experimental results at any ***,it is found that the fitting constants do not reflect the real percolation behavior of the *** is found that the dielectric constant is strongly dependent on the frequency,which is mainly due to the fact that the frequency dependence of the dielectric constant for the composites close toφ_(c)is almost independent of the matrix.

关键词： Composite dielectric constant percolation threshold conductivity

Influence of silane coupling agent on microstructure and properties of CCTO-P(VDF-CTFE)composites

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Journal of Advanced Dielectrics 2018年第2期8卷 22-30页

作者： yang Tong Lin z.ang Patrick Bass Terry D.Rolin z.-y.cheng Materials Research and Education Center Auburn University AuburnAL 36849USA Marshall Space Flight Center Huntsville AL 35812USA

Influence of the coupling agent on microstructure and dielectric properties of ceramic-polymer composites is systematically studied using CaCu_(3)Ti_(4)O_(12)(CCTO)as the filler,trichloro-(1H,1H,2H,2H-perfluorooctyl)-silane(Cl_(3)-silane)as coupling agent,and P(VDF-CTFE)88/12 mol.%copolymer as the *** is demonstrated that Cl_(3)-silane molecules can be attached onto CCTO surface using a simple *** experimental results show that coating CCTO with Cl_(3)-silane can improve the microstructure uniformity of the composites due to the good wettability between Cl_(3)-silane and P(VDF-CTFE),which also significantly improves the electric breakdown field of the *** is found that the composites using CCTO coated with 1.0 wt.%Cl_(3)-silane exhibit a higher dielectric constant with a higher electric breakdown *** the composites with 15 vol.%CCTO that is coated with 1.0 wt.%Cl_(3)-silane,an electric breakdown field of more than 240 MV/m is obtained with an energy density of more than 4.5 J/cm^(3).It is also experimentally found that the dielectric constant can be used to easily identify the optimiz.d content of coupling agent.

关键词： Ceramic-polymer energy density CCTO coupling agent breakdown strength

Dielectric composites with a high and temperature-independent dielectric constant

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Journal of Advanced Ceramics 2012年第4期1卷 310-316页

作者： Xiaobing SHAN Lin z.ANG Xiqiao yANG z.y.cheng Materials Research and Education Center Auburn UniversityAuburnAL 36849USA

Dielectric composites made using P(VDF-CTFE)88/12 mol%as polymer matrix and both micro-siz.d and nano-siz.d CaCu3Ti4O12(CCTO)particles as filler are *** composites exhibit high dielectric constant with a small dielectric *** importantly,it is found that the dielectric constant of these composites is almost independent of temperature from 25℃to 125℃.Comparing the composites made using micro-siz.d CCTO particles,the composites made using nano-siz.d CCTO particles exhibit a smaller dielectric *** dielectric properties of these composites indicate that the nano-siz.d CCTO particles have a smaller dielectric constant than the micro-siz.d CCTO particles.

关键词： dielectric constant composite CCTO P(VDF-CTFE) temperature dependence

Optimal placement of dampers and actuators based on stochastic approach

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Earthquake Engineering and Engineering Vibration 2002年第2期1卷 237-249页

作者： Franklin y.cheng Hongping Jiang Xiaoz.e z.ang Department of Civil Engineering University of Missouri-RollaRollaMissouri 65409USA Technical Development Department Magnatrax Corporation124 Kirby DrivePortlandTN 37148USA

A general method is developed for optimal application of dampers and actuators by installing them at optimal location on seismic-resistant *** study includes development of a statistical criterion,formulation of a general optimiz.tion problem and establishment of a solution *** analysis of the seismic response in time-history of controlled structures is used to verify the proposed method for optimal device application and to demonstrate the effectiveness of seismic response control with optimal device *** study shows that the proposed method for the optimal device application is simple and general,and that the optimally applied dampers and actuators are very efficient for seismic response reduction.

关键词： optimal device placement dampers actuators seismic response control stochastic seismic response seismic-resistant structures equivalent modal analysis