压电/磁致伸缩/环氧树脂层合复合材料的磁电效应及其频响特性

磁电复合材料在磁-电能量转换等领域具有重要的潜在应用价值, 研究磁电复合材料在较高频率下的磁电耦合特性对于实际应用具有重要意义。本文中以0-3型的Terfenol-D(Tb_0.30Dy_0.70Fe₂)/环氧树脂复合材料为磁致伸缩层, 以PZT 压电陶瓷为压电层, 制备了三明治结构的层合磁电复合材料。研究了Terfenol-D/环氧树脂复合材料层的磁致伸缩性质, 并对所制备的层合磁电复合材料磁通密度、 介电常数以及磁电电压系数等随频率和偏磁场的变化规律进行了系统研究。结果表明, 由于Terfenol-D/环氧树脂复合材料的引入, 层合磁电复合材料呈现出良好的频率响应特性, 可靠工作范围大大拓宽。层合磁电复合材料具有优良的动态磁电耦合性能, 在优化偏磁场630 Oe和共振频率69.6kHz下的磁电效应高达21.2 V/cmOe。此外, 层合磁电复合材料的磁电效应随偏磁场的变化发生明显变化, 并存在优化偏磁场。对上述现象和结果进行了详细讨论, 并给出了层合磁电复合材料的磁电耦合机制。      

夹持效应对层状磁电复合材料磁电效应的影响

设计了Terfenol-D/PZT/Terfenol-D(T/P/T)、Terfenol-D/PZT(T/P)、Terfenol-D/PZT/Glass(T/P/G)3种不同结构的层状磁电复合材料,研究了夹持效应对其振动模式的调控作用及其磁电效应的影响。结果表明,对称结构只有长度振动模式,而非对称结构同时具有弯曲振动和长度振动模式;夹持效应使两种共振模式的共振频率均向高频方向移动;夹持效应提高了低共振频率下的一阶弯曲振动强度;在准静态频率下,T/P/G结构的磁电耦合系数有最大值0.89V/(cm·Oe)。在低频下,弯曲振动模式占主导地位,同时夹持效应显著抑制了长度振动模式,该两种振动模式引起的磁电效应相反,从而使得总磁电耦合系数得到提高,所以夹持效应提高了器件在低频应用的可能性。     

Fe3O4-PDMS纳米复合材料磁电阻特性及变化模型的研究

主要研究了复合材料磁电阻特性,提出了复合材料的制备方法,并测量了材料形貌、磁化特性、磁电阻随磁场的变化特性。结果表明,复合材料在环境磁场中能够产生磁电阻效应,其磁电阻特性受材料中分散的纳米颗粒的磁化特性所影响,并且复合材料磁电阻随着材料中纳米颗粒的分散浓度的增大而增大。根据磁场环境下复合材料中纳米颗粒之间沿磁场方向的相互作用以及聚合物材料的粘弹性,重点分析了该复合材料的磁电阻变化机理并提出了复合材料的磁电阻变化模型。随后,利用纳米颗粒的磁化数据以及PDMS的动力学参数进行了复合材料磁电阻变化特性的数值仿真,并将仿真数据与实测数据进行对比,对比结果显示该模型能够准确描述复合材料的磁电阻变化特性。     

功能梯度铁电铁磁复合材料弯曲模态下的磁电效应

基于磁致伸缩相与压电相的本构方程,应用弹性力学的方法,建立了功能梯度铁电铁磁复合材料弯曲模态下的磁电耦合静态力学模型。假设铁电和铁磁材料的物理参数均为沿厚度方向的线性或指数函数,分析计算了由PZT作为铁电材料和CoFe2O4作为铁磁材料的双层复合材料的磁电效应。结果表明,在弯曲模态下,磁电电压系数出现两个峰值。负梯度的铁电(或铁磁)材料提高磁电效应,正梯度的铁电(或铁磁)材料降低磁电效应。同号梯度的铁电铁磁材料对磁电效应的影响更大。     

基于微驱动材料的智能摩擦阻尼器试验研究

摩擦阻尼器结构简单、安装容易、性能稳定,具有广泛的应用领域.传统摩擦阻尼器,因阻尼力不具备调节能力,而只能对结构的振动产生有限的控制效果.压电材料和磁致伸缩材料分别具有在电场或磁场激励作用下的快速变形能力,是两类重要的智能材料.利用以上两类智能材料制成的驱动器,调节摩擦阻尼器摩擦面的正压力,进而达到调节摩擦力的目的,是实现摩擦阻尼器智能化的重要途径.利用三个形状基本相同,材质分别为Terfenol-D金属、树脂基磁致伸缩复合材料以及压电陶瓷制成的驱动器,与同一参数的摩擦阻尼器复合,制成了三个阻尼力可调的智能摩擦阻尼器,并完成了它们的阻尼力及响应时间测试.结果表明,利用Terfenol-D驱动器复合的阻尼器(GMM摩擦阻尼器)具有最大的绝对出力和可调范围,利用树脂基磁致伸缩驱动器复合的阻尼器(GMPC摩擦阻尼器)次之,利用压电陶瓷驱动器复合的阻尼器(PZT摩擦阻尼器)最弱.GMM阻尼器和PZT阻尼器的响应时间分别在60 ms-80 ms以及30 ms左右.     

磁电复合材料PMN-PT/Terfenol-D/PMN-PT磁电耦合性能的有限元分析

由铁电相和铁磁相组成的磁电复合材料被证明有非常显著的磁电耦合效应,近年来受到越来越多的关注。利用有限元PDE的方法对磁电复合材料PMN-PT/Terfenol-D/PMN-PT的磁电耦合性能进行了分析,主要研究了边界条件、结构尺寸对磁电耦合性能的影响。研究发现,当上下表面y方向固定,其它表面自由时,磁电复合材料长度方向伸缩更加明显,具有更大的磁电耦合系数;铁电相和铁磁相厚度比与磁电耦合系数程非线性关系,当铁电相厚度为1.1mm,铁磁相厚度为1.9mm时,磁电耦合系数具有最大值3.354((V/m)/A/m));当铁电层尺寸保持不变,铁磁层长度超过10mm后,铁磁层长度对磁电耦合系数影响不明显。该理论结果可以用于提高磁电耦合性能同时达到节省材料的目的。     

压电-磁致伸缩双层磁电复合材料的机电谐振

基于压电相和磁致伸缩相的本构方程以及弹性体的运动方程,简要推导了一维机电谐振模式下压电-磁致伸缩双层磁电复合材料横向磁电电压系数的表达式。采用相应的材料参数计算分析了Tb_1-x Dy_x Fe_2-y (TDF)-Pb(Zr,Ti)O₃(PZT)双层磁电复合材料的横向磁电电压系数与交流磁场频率的关系,以及复合材料的长度和压电相体积分数对机电谐振频率的影响。计算与分析结果表明,双层磁电复合材料在机电谐振频率处具有明显的磁电 响应特性。当有效机械品质因数为50,在谐振频率55.2 kHz处横向磁电电压系数达到峰值11.2 V·cm^-1·Oe^-1,是低频下峰值(281.9 mV·cm^-1·Oe^-1)的40倍。机电谐振频率随复合材料长度的减小和压电相体积分数的增加而上升。实验结果说明TDF-PZT双层磁电复合材料在机电谐振频率处具有显著增强的磁电效应,实际有效机械品质因数约为48。     

Terfenol-D颗粒取向对树脂基磁致伸缩复合材料性能的影响

已有的研究表明,在树脂基磁致伸缩复合材料固化过程中,施加一定的磁场使Terfenol-D颗粒沿磁场方向取向排列可以形成伪1-3型复合结构,其静态磁致伸缩性能较颗粒随机取向的0～3型复合材料有一定程度的提高。本文旨在研究颗粒取向对磁致伸缩复合材料其它性能的影响。以Terfenol—D颗粒体积含量为50％的0-3型和1-3型环氧基磁致伸缩复合材料为研究对象,通过实验和计算对比两种材料的动静态磁致伸缩性能、增量磁导率、弹性模量、磁机械耦合系数。结果表明．颗粒取向不仅可以提高树脂基磁致伸缩复合材料的静态磁致伸缩性能和动态磁致伸缩性能,还能略微提高其弹性模量,但会适度降低其磁机械耦合系数。     

高介电常数PVDF/PZT/Terfenol-D复合材料的介电性能研究

以聚偏氟乙烯(PVDF)为聚合物基体,PZT为陶瓷相,稀土铁合金粒子Tedenol-D为添加组分,运用聚合物熔融压片法制备了聚合物体积含量为30%的0.3PVDF/(0.7-f)PZT/fTerfenol-D三相复合材料.研究了Tedenob-D的体积含量、频率对复合材料介电性能的影响.结果显示:Tedenol-D粒子的加入,可以提高0.3PVDF/0.7PZT复合材料的介电常数,PVDF/PZT/Terfenol-D复合材料具有介电常数高、介电损耗小的特点.     

FeGa/BTO/FeGa层状复合结构中的磁电效应

采用区域熔炼法制备了FeGa磁致伸缩材料并测量了其磁致伸缩性能.利用该材料制备了FeGa/BTO/FeGa层状复合结构,并对该样品的磁电性能进行了系统研究.结果表明,该材料在共振频率95kHz下,磁电性能高于低频下性能7～10倍.磁电电压随直流偏磁场的变化发生明显变化,出现5.97×104A/m的优化偏置场,这主要是由FeGa层的压磁系数q随偏磁场的变化所致.3层复合材料的磁电系数与交流驱动场变化呈线性关系.另外,较薄的BTO压电层可以提高压应力,从而获得较高的磁电性能.     

Post-curing effect on magnetoelectric performance of single PZT rod/continuous Terfenol-D fiber/epoxy 1-1-3 composites

A magnetoelectric (ME) composite consisting of a single PZT rod embedded in a matrix of continuous Terfenol-D fiber and epoxy medium has been fabricated and characterized. With an optimized aspect ratio of the composite rods, a large ME effect has been observed. The magnetostrictive effect of the continuous Terfenol-D fiber/epoxy medium can be enhanced by imposing an optimal pre-loading stress on the material and this pre-loading stress can be induced by suitable heat treatment. Experimental results show that the ME effect of the single PZT rod/continuous Terfenol-D fiber/epoxy composites can be enhanced significantly by a post-curing process. A thermal stress-mediated continuous fiber composite model has been used to explain the ME enhancement of the post-cured composites.     

Effect of Electric Field on the Response of Clamped-FreeMagnetostrictive/Piezoelectric/Magnetostrictive Laminates

This work deals with the response of clamped-free magnetostrictive/piezoelectric/magnetostrictive laminates under electric field both numerically and experimentally. The laminate is fabricated using two magnetostrictive Terfenol-D layers and a soft piezoelectric PZT layer. Easy axis of Terfenol-D layers is length direction, while the polarization of PZT layer is the thickness direction. The magnetostriction of the Terfenol-D layers bonded to the upper and lower surfaces of the PZT layer is first measured. Next, a nonlinear finite element analysis is employed to evaluate the second-order magnetoelastic constants in the Terfenol-D layers bonded to the PZT layer using measured data. The induced magnetic field and internal stresses for the laminates under electric field parallel to the poling are then calculated and discussed in detail. In addition, the induced magnetic field is measured, and test results are presented to validate the predictions.     

Magnetoelectric properties of Ni/PZT/Ni layered composite for low field applications

A composite material when placed under the external magnetic/electric fields exhibits voltage/induced magnetization is known as magnetoelectric (ME) composite. Such composite materials should have ferroelectric and ferro/ferri magnetic phases as constituents. The magnetoelectric output is exhibited as a product property. Magnetoelectric composites are being used for variety of applications including resonators, filters, phase shifters, optical isolators, actuators and magnetic field sensors. Metal/ferroelectric/metal magnetoelectric composite using Ni and PZT as constituent phases has been fabricated in 2-2 composite pattern to study its product property. The paper presents magnetoelectric studies of Ni/PZT/Ni composite using low dc magnetic field magnetoelectric set-up. Using this ME set-up ME output of Ni/PZT/Ni composite is studied as a function of dc magnetic field. The results were analyzed to identify the useful magnetic field (dc and ac) range in which Ni/PZT/Ni sensor can be utilized for applications.     

Magnetoelectricity in polyurethane films loaded with different magnetic particles

Particulate polymer composites consisting of Terfenol-D/Polyurethane, Fe₃O₄/Polyurethane, Nickel/Polyurethane and particulate composite layers were prepared by using a simple solution cast method. Magnetoelectric (ME) effect is characterized by measuring the amplitude of the magnetoelectric current versus different input parameters that appear in the theoretical current expression. The results yield two conclusions: 1.Whatever the filler type (Terfenol-D, Fe₃O₄ or Nickel), the microcomposites show a magnetoelectric effect. 2. The magnetostrictive property of the material does not have a direct influence on the ME effect since ME sensitivity is dc field independent and the magnetoelectric coefficient α_p has close values in ac field for all types of polymer fillers.     

Design of magnetostrictive/piezoelectric laminate composite for coil-less magnetic force control

We propose a magnetic force control device consisting of laminate composites of magnetostrictive material and piezoelectric material. The magnetic force control is based on energy conversion in the composite, such that the variation of magnetization of the magnetostrictive material induced by the piezoelectric material is converted to the variation of magnetic force by magnetic circuits. Because of the capacitive property of the piezoelectric material, the device requires little current in order to maintain control of a constant force. The laminate composite can be fabricated easily and in small sizes. In this paper, we report the magnetic force control properties of a composite of Terfenol-D and piezoelectric material plates (PZTs) and discuss the design of the laminate composite. Our theoretical magnetic force formulation derived by an equivalent magnetic analysis and finite-element analysis of strain distribution in the Terfenol-D, and measurements with various thicknesses of PZT demonstrated that there are appropriate thicknesses to provide large variation of the magnetic force and energy conversion efficiency. Stacking the composites was found effective for increasing the effective area of the Terfenol-D.     

Longitudinal and transverse magnetoelectric voltage coefficients of magnetostrictive/piezoelectric laminate composite: theory

This paper presents a novel, long-type of magnetostrictive and piezoelectric laminate composite design in which the layers are, respectively, magnetized/poled along their length axes, and a theory for modeling its behavior. Using piezoelectric and magnetostrictive constitutive equations, and an equation of motion, a magneto-elasto-electric bieffect equivalent circuit is developed. The circuit is used to predict the longitudinal and transverse magnetoelectric (ME) voltage coefficients of our Terfenol-D/Pb(Zr/sub 1-x/Ti/sub x/)O/sub 3/ laminate design. It is found that the longitudinal ME voltage coefficient is significantly higher (/spl sim/5x) than the transverse one, and that our new laminate design has significantly higher ME voltage coefficients under small applied direct current (DC) magnetic bias fields than designs reported previously by other groups. Experimental values were found to be coincidental with predicted ones.     

Magnetoelectric properties of CoFe2O4–Pb(Zr0.52Ti0.48)O3 multilayered composite film via sol–gel method

CoFe₂O₄–Pb(Zr_0.52Ti_0.48)O₃ (CFO–PZT) multilayered composite film was prepared on Pt/Ti/SiO₂/Si substrate via a sol–gel method and spin-coating technique. Results show that PZT and CFO phases exist in the composite film, calcined at 700 °C, besides substrate phase, and no obvious impurity phases can be detected. The composite film exhibits layered structure with obvious boundary between CFO and PZT films. Ferroelectric and ferromagnetic properties were simultaneously observed in the composite film, evidencing the ferroelectric and ferromagnetic properties in the composite film. The composite film exhibits both good magnetic and electric properties, as well as, magnetoelectric (ME) effect. The saturation magnetization value of the composite film is lower than that of the pure CFO film derived by the same processing as a result of the effect of the nonferromagnetic PZT layers. Ferroelectric hysteresis loops reveal that saturated polarization and remanent polarization of the composite film are lower than those of the pure PZT films. The composite film exhibits a very large ME effect, which makes the composite film attractive for technological applications as devices.     

Magnetic force control with composite of giant magnetostrictive and piezoelectric materials

We propose a new magnetic force control device, composed of a giant magnetostrictive material (Terfenol-D) and a piezoelectric material (PZT), for coilless magnetic force control. The device uses the inverse magnetostrictive effect, whereby the variation of magnetization of a Terfenol-D rod controlled by PZT is converted to the variation of magnetic force by a magnetic circuit. Because PZT is electrically capacitive, the method has the advantage of low power consumption and low heat generation in static operation. We have fabricated several devices with different geometrical shapes of the rods and magnetic yokes, and we describe their characteristics such as power consumption, heat generation, and response. We discuss a magnetic circuit design strategy that uses the /spl Delta/E effect in magnetostrictive materials to increase the energy conversion efficiency.