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.     

Charge‐Generating Mode Control in High‐Performance Transparent Flexible Piezoelectric Nanogenerators

In this work, we demonstrate the mode transition of charge generation between direct‐current (DC) and alternating‐current (AC) from transparent flexible (TF) piezoelectric nanogenerators (NGs), which is dependent solely on the morphology of zinc oxide (ZnO) nanorods without any use of an AC/DC converter. Tilted ZnO nanorods grown on a relatively low‐density seed layer generate DC‐type piezoelectric charges under a pushing load, whereas vertically aligned ZnO nanorods on a relatively high‐density seed layer create AC‐type charge generation. The mechanism for the geometry‐induced mode transition is proposed and characterized. We also examine the output performance of TF‐NGs which employ an indium zinc tin oxide (IZTO) film as a TF electrode. It is demonstrated that an IZTO film has improved electrical, optical, and mechanical properties, in comparison with an indium tin oxide (ITO) film. Enhanced output charge generation is observed from IZTO‐based TF‐NGs when TF‐NGs composed of only ITO electrodes are compared. This is attributed to the higher Schottky barrier and the lower series resistance of the IZTO‐based TF‐NGs. Thus, by using IZTO, we can expect TF‐NGs with superior mechanical durability and power generating performance.     

基于压电式新型三维力传感器的设计

从生物压电效应和人体“皮肤效应”原理出发，提出了一种基于压电式的新型三向力检测方法，阐述了三向力传感器的设计思想和基本组成结构，并从理论上对传感器工作原理进行了检测，推导了计算空间三向力大小和方向的公式。该三向力传感器不但可以用于机械空间力的测量，且还可用于机器人表皮的传感，为实现新型的智能机器人触觉力传感器系统提供了一种新的方法。     

偏氰乙烯—醋酸乙烯共聚物的压电特性

偏氰乙烯与醋酸乙烯的交替共聚物是一种能显示出压电特性的无定形聚合物。共聚物试样在Tg((?)170—180℃)温度和电场(20—60MV/m)作用下,沿电场方向排列的偶极子可通过降低温度而被冻结起来,获得很强的压电性。其压电应力常数e_(33)和机电耦合系数K_(33)分别为70mC/m~2和0.25。 ·     

A Modal Multifield Approach for an Extended Flexible Body Description in Multibody Dynamics

This paper presents a new methodology to simulate the behaviour of flexible bodies influenced by multiple physical field quantities in addition to the classical mechanical terms. The theoretical framework is based on the extended Hamilton Principle and an adapted modal multifield approach. Furthermore, the use of finite element analysis for the necessary data preprocessing is explained. Numerical solution strategies for the coupled system of differential equations with different time scale properties are mentioned. The method is applied to simulate a structure with distributed piezo-ceramic devices inducing an additional electrostatic field. Two thermoelastic problems, which have to consider the influence of spatial temperature distribution, also demonstrate the benefits of the presented approach.     

PVDF的特性及其生产现状

在氟塑料中，聚偏氟乙烯（ＰＶＤＦ）具有独特的性能（压电性、耐射线性、ＰＶＴ相关性、成型性）。本文综述了它的特性及生产现状。     

压电石英亚表面损伤层分析

压电石英基片在加工过程中会带来表面/亚表面损伤,这种损伤会直接影响电子器件的性能、稳定性及寿命。该文采用扫描电镜(SEM)观测与X-射线双晶回摆曲线检测化学腐蚀逐层剥离深度相结合的方法,定量分析了36°AT切压电石英基片亚表面损伤层厚度,并探讨了亚表面损伤层的形成原因及对器件性能的影响。     

Detection of void and metallic inclusion in 2D piezoelectric cantilever beam using impedance measurements

The aim of current work is to improve the existing inverse methodology of void-detection based on a target impedance curve, leading to quick-prediction of the parameters of single circular void. In this work, mode-shape dependent shifting phenomenon of peaks of impedance curve with change in void location has been analyzed. A number of initial guesses followed by an iterative optimization algorithm based on univariate method has been used to solve the problem. In each iteration starting from each initial guess, the difference between the computationally obtained impedance curve and the target impedance curve has been reduced. This methodology has been extended to detect single circular metallic inclusion in 2D piezoelectric cantilever beam. A good accuracy level was observed for detection of flaw radius and flaw-location along beam-length, but not the precise location along beam-width.     

Piezoelectricity in Monolayer Hexagonal Boron Nitride

2D hexagonal boron nitride (hBN) is a wide-bandgap van der Waals crystal with a unique combination of properties, including exceptional strength, large oxidation resistance at high temperatures, and optical functionalities. Furthermore, in recent years hBN crystals have become the material of choice for encapsulating other 2D crystals in a variety of technological applications, from optoelectronic and tunneling devices to composites. Monolayer hBN, which has no center of symmetry, is predicted to exhibit piezoelectric properties, yet experimental evidence is lacking. Here, by using electrostatic force microscopy, this effect is observed as a strain-induced change in the local electric field around bubbles and creases, in agreement with theoretical calculations. No piezoelectricity is found in bilayer and bulk hBN, where the center of symmetry is restored. These results add piezoelectricity to the known properties of monolayer hBN, which makes it a desirable candidate for novel electromechanical and stretchable optoelectronic devices, and pave a way to control the local electric field and carrier concentration in van der Waals heterostructures via strain. The experimental approach used here also shows a way to investigate the piezoelectric properties of other materials on the nanoscale by using electrostatic scanning probe techniques.