Fabrication and characterization of flexible piezoelectric composites with natural rubber matrix

Abstract

This work aims to fabricate and characterize flexible piezoelectric composites with natural rubber (NR) matrix. Different amounts of Pb(Mg_1/3Nb_2/3)_0.65Ti_0.35O₃ (PMNT) powders were added in NR matrices. Porosity, tensile strength and percent elongation at break of composites tended to decrease with increasing PMNT content. The dielectric constant of the NR materials was found to be 3.5. It was raised up to 4.2, 5.0, 4.5, 4.8 and 5.1 when 60, 80, 100, 120 and 150 phr PMNT powders were added. However, dielectric loss of NR materials did not change with PMNT additions. Among this composite system, the NR/100PMNT composite showed the best piezoelectric properties, which its output voltage, piezoelectric coefficient (d₃₃) and piezoelectric voltage coefficient (g₃₃) values were equal to 1.61 V, 2.1?×?10^?4 pC/N and 5.4?×?10^?6 V?m/N, respectively. This composition composite is a promising material suitable for further improvement to be used as piezoelectric generators in energy harvesting applications.     

Development and application of a diagnostic system for electrically driven valves

We briefly describe the system for diagnosing electrically driven valves that was developed jointly at the All-Russia Institute for Nuclear Power Plant Research and ZAO Diaprom, and which is being put in operation at many Russian nuclear power stations for revealing a wide spectrum of malfunctions that may occur in valves and their drives.     

柔性机械臂振动控制中的压电传感器故障诊断

压电传感器常被应用于结构的振动控制中,为了解决压电传感器故障给控制系统的带来的不稳定问题,根据压电柔性臂振动用压电传感片故障的特点,提出运用小波包变换和RBF神经网络的故障诊断方法。首先运用小波包分解和重构原理将传感器输出信号分解到不同频段中,提取每个频段的能量作为状态监测的特征向量,作为RBF网络的输入,然后利用最佳的RBF神经网络进行压电传感器故障分类。实验结果表明该方法具有良好的非以此线性跟踪能力,置信度达到90%,为后续振动容错控制研究奠定良好的基础。     

Optimal design and application of a piezoelectric energy harvesting system using multiple piezoelectric modules

To enhance the output power of piezoelectric energy harvesting system up to the watt level, we designed a multi-piezoelectric array (MPA) energy harvesting system that can overcome the limitations of a single-piezoelectric harvesting systems. The MPA energy harvesting system was designed using an impact-type harvester utilizing a hitting stick, as such systems can generate higher output power than vibration-type methods using a cantilever in a single-piezoelectric energy harvesting system. We investigated the effects that various connection and rectification methods had on the output power of a piezoelectric energy harvesting system consisting of four 35?×45?×?0.2 mm³ piezoelectric modules. We found that the output power was highest when each module was rectified before the modules were connected in parallel and that the optimal load resistance was inversely proportional to the number of modules if they were connected in parallel. To obtain watt-level power from the proposed MPA energy harvesting system, we designed a system consisting of 102 piezoelectric modules based on the derived optimized experimental conditions, from which we were able to obtain an output power of 1.99 W at 1800 hpm (hits per minute) and 500 Ω.     

Fabrication and characterization of PZT (lead zirconate titanate) bridge-shaped resonator for mass sensing application

Our research, based on executing theoretical modeling depending on the dimensions of PZT (lead zirconate titanate) thin film, was applied to two different bridge-shaped resonators. The critical point of having two different types of resonators is that it is a way of releasing the bridge. The first type of bridge-shaped resonator is released through use of an isotropic etching method using XeF₂ gas, while the second type of bridge-shaped resonator is released by a wet etching method that uses a KOH solution. The bridge-shaped resonators are anticipated to have accurate mass detecting sensors based on high mass sensitivity compared to the other shapes, such as diaphragms and cantilevers. The feasibility of a bridge-shaped PZT resonator as a mass sensor has been researched through studying the resonant frequency shift of a bridge-shaped resonator. The actual resonant properties of bridge-shaped resonators were determined by measuring resonant frequency and Q-factor measurements using an LDV (Laser Doppler Vibrometer). The resonant frequency appears in the ranges of 378.4?C419.8, 144.0?C180.3, and 107.8?C123.4?kHz for dimensions of 50???m?×?250???m, 100???m?×?500???m, and 150???m?×?750???m, respectively. Finally, four different thicknesses of Titanium (Ti) were loaded on the bridge-shaped resonator to confirm its variation and mass sensitivity. Significantly, mass sensitivities with dimensions of 50???m?×?250???m, 100???m?×?500???m, and 150???m?×?750???m were 2.02?Hz/pg, 330.42?Hz/ng, and 43.67?Hz/ng, respectively. Thus, the bridge-shaped resonator with dimensions of 50???m?×?250???m was able to detect the picogram-level of a mass.     

Fabrication and characteristics of piezoelectric PZT cantilever for high speed atomic force microscopy

Abstract

A PZT actuator integrated onto cantilever structure was fabricated for high speed atomic force microscopy (AFM). Five different electrodes were used to investigate the effect of top electrodes on the adhesion and the electrical properties in the PZT capacitors. The PZT capacitors with RuO₂ top electrodes exhibited the best characteristics of five electrodes. The tip deflection and the resonant frequency of the PZT actuator were 11 μim at 10 V and 79 kHz, respectively. The PZT actuator provided much better AFM image quality and imaging speed than those done by using the conventional bulk PZT tube scanner. The creep distortion in the AFM image was greatly improved by using the high speed PZT film actuator.     

压电传感器低频动态补偿数字滤波器设计

弹载压电传感器调理电路因测试环境的特殊性,难以采用精密的高输入阻抗电荷放大器.本文针对该问题设计了小体积的调理电路,并针对该测量电路因低频特性不足而导致的低频信号测量误差较大的问题,提出了动态实时补偿数字滤波器方法.运用CPLD器件实现了基于数字滤波器的实时动态误差校正,经实验验证,该补偿滤波器有效地延伸了压电传感器的低频测量范围,提高了弹载传感器的测量精度.     

机载压电传感器调理电路的设计

在某些测试系统中,压电类传感器作为非电量采集设备,采集设备具有较高内阻且受感到的电荷信号很小,电荷容易被后端二次设备的阻抗耗散掉,导致采集精度较差。本文针对上述问题,设计了一款高精度、高稳定性、抗干扰性能强的电荷信号调理器。与传统的电荷转换设备相比,本文设计的电荷信号调理器具有精度高、误差小、体积小等优点,适宜在复杂的机载环境中使用。通过搭建实验环境测试可知本文方法的有效可行,此方法可以推广应用在其它非电量压电传感器数据采集场合。     

压电式四维力传感器的有限元分析

选用石英作为敏感元,研究一种压电式四维力传感器,根据不同切型石英的特点按特定方式排列组合,构成一个"晶组"式的传感器,实现无耦合测量空间多方向的力和力矩。通过有限元分析,对所提出的压电式四维力传感器进行仿真,得到影响该传感器原型开发的输出电压与输入力之间关系曲线、电压灵敏度、维间干扰等重要性能指标,并证明了该传感器能够有效地实现空间四维力的测量,为研制新型传感器原型奠定了重要基础。     

KPFM导电探针的制备及应用

开尔文探针力显微镜(KPFM)可以测量样品与探针之间的接触电势差(CPD),从而可以测得样品表面电势.为了更好地测量样品表面电势的微小变化,需要制备新型导电探针.金属铱稳定的化学性质与高导电率等特性能够稳定地测量尖端样品之间的电势差.实验使用物理气相沉积(PVD)的方法修饰硅探针,使针尖镀上一层厚度为纳米级的金属铱薄膜...     

Nanoscale characterization of polycrystalline ferroelectric materials for piezoelectric applications

In this work, the nanoscale electromechanical properties of several important piezoelectric materials [as exemplified by PbZr _x Ti_1−x O₃ (PZT)] suitable for both bulk actuator and microelectromechanical system (MEMS) applications are reported. The investigations are performed by the piezoresponse force microscopy (PFM) that is currently the most suitable tool for both ferroelectric domain imaging and local piezoelectric studies. The local piezoresponse of individual grains is measured in PZT films and compared with average piezoelectric behavior. Frequency dependencies of local piezoelectric coefficients are presented and analyzed. The results on local piezoelectric nonlinearity, as well as on nanoscale fatigue and aging are briefly discussed. These measurements demonstrate that PFM is promising for studying local piezoelectric phenomena in polycrystalline ferroelectrics where defects and other inhomogeneities are essential for the interpretation of macroscopic piezoelectric properties. Finally, local electromechanical properties of polycrystalline relaxors (PMN-PT, PLZT, doped BaTiO₃) are briefly outlined.     

Analysis and phase control of a piezoelectric traveling-wave ultrasonic motor for haptic stick application

An original modeling of a traveling-wave ultrasonic motor is established in order to provide a new torque control law for this category of actuators. In particular, self-driving is implemented, avoiding the classical drawbacks of frequency control, i.e., pull-out phenomenon. With such a robust control, force feedback application is available. Experimental results are obtained on an active haptic stick.     

Modelling and characterization of piezoelectric and polarization gradients

A gradient of the piezoelectric properties in monolithic ceramics can be useful to minimize mechanical stresses inside piezoelectric bending actuators or at interfaces between layers with different electromechanical properties, and increase the bandwidth of ultrasonic transducers. Piezoelectric gradients can be prepared by different techniques. We use a powder pressing technique to prepare a gradient of the chemical composition, which is transformed to the piezoelectric gradient by the poling process. Conventional mixed-oxide powders of BaTiO₃ with different amount of Sn from 7.5 up to 15 mol% and Mn-doped BaTiO₃ were used to produce lead-free ceramic samples. We describe the poling process using a equivalent circuit approach. The ferroelectric behavior of the different layers are described by the Preisach model. In the Ba(Ti,Sn)O₃ system the properties can be changed from ferroelectric to paraelectric depending on the Sn content. A gradient of polarization and piezoelectric properties can be observed in monolithic ceramics with a tin gradient. The profile of the polarization distribution was measured by the thermal wave method. A gradient of polarization where the sign of polarization changes can be induced in a system consisting of piezoelectric hard and soft materials. We describe a special poling process using our poling model. The principle is demonstrated in a two layer model system.     

超声传感器调制特性及收发电路研究

本文分析了广泛应用于无线通信中的频率键控调制(FSK)及幅值键控调制(ASK)技术的基本概念及调制原理,针对收发分体式超声波传感器T40-16及R40-16,设计并实现了超声波调制发射与解调接收电路,在此基础上进行了超声波FSK及ASK调制特性的实验研究.实验结果表明:可以对超声波信号进行FSK调制发射,调制、解调电路易于实现且调制与解调效果好;对超声波信号进行ASK调制发射时存在"余振"现象,可以通过调整加在超声波发射传感器两端的激励信号的占空比而进行改善.     

Fabrication process of pzt piezoelectric cantilever unimorphs using surface micromachining

Abstract

This paper discusses the fabrication process and challenges for fabrication of piezoelectric cantilever beam microaccelerometers by using surface micromachining techniques. PZT thin films were used as the piezoelectric material to detect the acceleration of the cantilever beam. In this paper, we discuss in detail the process challenges encountered in piezoelectric microaccelerometers. These major challenges include PZT thin film deposition and encapsulation during final micromachining membrane release.     

十字叠层压电定子双面驱动的平面电机

旨在提升电机性能及推动电机微型化发展,提出了一种新型十字叠层压电定子双面驱动的平面电机,利用面外、面内弯振耦合形成的椭圆轨迹推动动子精密移动;首先探讨了质点椭圆运动轨迹的形成条件并论述了电机的运行机理;然后基于灵敏度分析确定结构参数优化变量并对定子进行优化,简并了工作模态频率且使其分别为43252Hz、43258Hz、43289Hz;最后利用Ansys对定子进行仿真计算,验证了定子设计的合理性和可行性,且仿真表明在激励电压为250V、频率43300Hz时,定子驱动足各向最大振动位移均达到了1.5μm,动子的运动速度达到了46mm/s。     

Fabrication and properties of 1-3-2 multi-element piezoelectric composite

A design method is presented for 1-3-2 type multi-element piezoelectric composite so as to provide basis for the development and study of transducer and transducer array. The composite samples have been fabricated by a twice dice-filling process from lead zirconate titanate (PZT-4), epoxy resin and silicone, the properties of the composites have been measured and investigated physically. The results show that the piezoelectric, dielectric and electromechanical coupling properties of the composite exhibit a good consistency, while it has a high thickness electromechanical coupling factor K _t and a wide bandwidth of pulse-echo signal. The impedance plot of every element indicates good behavior that all elements show excellent frequency consistency, and on the other hand the chance of coupling of lateral resonance and thickness resonance is very small, and with a clear thickness resonance mode at around 100?kHz. Silicon has extremely decoupling properties which can efficiently block the transmission of the acoustic vibrations and eliminate coupling effect among elements. And the farther the distance between the incentive element and receiving element is, the smaller the response signal become, while the response signal decay rate exhibits the trend of increase, the largest up to 95%.     

Fabrication and evaluation of PZT/Ag composites and functionally graded piezoelectric actuators

Metallic Ag as the second phase was added into PZT ceramic matrix to fabricate piezoelectric composites and functionally graded actuators by gradually altering Ag concentration, aimed to improve mechanical properties and to solve possible interfacial debonding usually observed in conventional bimorph-type piezoelectric actuator. The PZT/Ag composites were obtained by directly co-firing PZT and Ag powders at 1200^∘C for 1 h. The fracture strength σ _f and fracture toughness K _IC , as well as the corresponding piezoelectric properties, were firstly evaluated upon the PZT/Ag composites for Ag concentrations of 0–30 vol%. The mechanical properties for the PZT/Ag composites were found to be greatly enhanced compared with pure PZT ceramics: from 69 to 129 MPa for σ _f and from 1.0 to 3.7 MPa.m^1/2 for K _IC . With increasing Ag concentration, the piezoelectric constant d ₃₃ of PZT/Ag composites was found to decrease from 419 to 86 pC/N. Then, a functionally graded actuator was fabricated and evaluated in terms of electric-induced curvature k. The PZT/Ag FGM actuator with size of 12 mm × 3 mm × 1 mm has a curvature k of 0.03–0.17 m⁻¹ that corresponds to applied voltages of 100–500 V. A comprehensive comparison was made on the mechanical property enhancements by the metal particles dispersion, and the bending displacements produced by the FGM actuators between the PZT/Ag and previously fabricated PZT/Pt systems.     

Fabrication and characteristics of PZT thick films on Pt/Ti foil substrates for piezoelectric vibrators

Crack free perovskite PbZr_0.53Ti_0.47O₃ (PZT (53/47)) thick films up to 30 μm were prepared on flexible platinum-coated titanium foil substrates (Pt/Ti) by a metal organic decomposition (MOD) process. The dielectric, ferroelectric and piezoelectric properties of the films were examined and discussed. A well-saturated hysteresis loop of the thick film was present in almost rectangular shape (Pr?=?35 μC/cm²; Ec?=?32 kV/cm). The efficient piezoelectric coefficient d _{33, f} of the thick film is about 448 (1 kHz). PZT piezoelectric vibrators were made in bimorph mode. The displacements of the vibrators were investigated as the functions of the applied electric field and the substrate thickness. Under the same condition, the vibrator made from the thinnest Pt/Ti substrate gives the largest displacement.     

Preparation and characterization of novel piezoelectric andpyroelectric polymer electrets

The preparation and characterization of novel piezoelectric and pyroelectric electrets is discussed with respect to their electret properties. Charged heterogeneous electrets, like closed-cell microporous polypropylene (pp) foams and `soft-hard' fluoropolymer hybrids are shown to yield large quasi-static and dynamic piezoelectric responses, indistinguishable from true piezoelectricity. Piezoelectric coefficients comparable to that of ceramic counterparts have been achieved. For the investigation of the piezoelectric and pyroelectric properties of the electret materials, the thermal-pulse technique has been extended towards temperature-dependent investigations and measurements on planar, cylindrical or spherical samples. The potential of the thermal-pulse technique not only for the measurement of electric-field and polarization distributions, but also for acoustical, electromechanical and pyroelectric properties is outlined