Nanogenerator for determination of acoustic power in ultrasonic reactors

This paper presents the novel use of a sonochemical reaction product as a sensing material in self-powered ultrasonic reactor devices for determination of ultrasound parameters. A piezoelectric nanogenerator was fabricated via sonochemical synthesis of SbSeI nanowires compressed into a bulk sample. The prepared device was used to develop two fast and simple evaluation methods for acoustic power in liquid. A calibration procedure was carried out for both methods using a VCX-750 ultrasonic processor. The ultrasound acoustic power was varied within a 150 W to 750 W range and the corresponding nanogenerator electrical responses were measured. The voltage signals of the first method fit the best with theoretical dependence. The second technique was based on the application of the Fast Fourier Transform (FFT) to the measured electric output. The results of these two approaches were convergent. Acoustic power values of 255(8) W and 222(7) W were determined for the Sonic-6 reactor using theoretical dependence fitting to experimental data and FFT analysis, respectively. Developed sensing technology possesses great potential for sonochemistry applications.     

压电陶瓷传感器的制作及压电效应演示综合性实验设计——介绍一个材料化学综合实验

从压电陶瓷传感器的制作出发,将合成方法、流延及丝网印刷技术、X射线衍射分析测试手段等内容有机整合在一起,设计了基于PZT基压电陶瓷传感器研究的一个综合性实验教学方案,有利于大学生在科研前沿体会无机化学、分析化学等基础学科与材料器件等应用学科的综合运用。     

Light-Responsive Oligothiophenes Incorporating Photochromic Torsional Switches

We present a quaterthiophene and sexithiophene that can reversibly change their effective π-conjugation length through photoexcitation. The reported compounds make use of light-responsive molecular actuators consisting of an azobenzene attached to a bithiophene unit by both direct and linker-assisted bonding. Upon exposure to 350 nm light, the azobenzene undergoes trans-to-cis isomerization, thus mechanically inducing the oligothiophene to assume a planar conformation (extended π-conjugation). Exposure to 254 nm wavelength promotes azobenzene cis-to-trans isomerization, forcing the thiophenic backbones to twist out of planarity (confined π-conjugation). Twisted conformations are also reached by cis-to-trans thermal relaxation at a rate that increases proportionally with the conjugation length of the oligothiophene moiety. The molecular conformations of quaterthiophene and sexithiophene were characterized by using steady-state UV-vis spectroscopy, X-ray crystallography and quantum-chemical modeling. Finally, we tested the proposed light-responsive oligothiophenes in field-effect transistors to probe the photo-induced tuning of their electronic properties.     

Double-layered piezo-thermoelastic hollow cylinder under some coupled loadings

In the present paper, a long thick-walled piezo-thermoelastic hollow cylinder with double layers is studied. The effects of temperature on the performance of the cylinder are obtained. Based on the theory of elasticity, the exact solutions of the cylinder under some coupled loadings are found. In the present paper, differences of a piezoelectric parameter between the two layers is taken into account. For comparison, numerical results have been carried out for both double-layered and graded cylinders. At the end of the present paper some discussions are addressed.     

Moving antiplane shear crack in hexagonal piezoelectric crystals

Closed-form solutions are obtained and discussed for the stress and electric displacement fields around a loaded Griffith-type antiplane shear strip crack moving in hexagonal piezoelectric crystals. Representative numerical results are presented for ZnO and PZT-4.     

Electroelastic field concentrations ahead of electrodes in multilayer piezoelectric actuators: experiment and finite element simulation

The effects of applied voltage on the electroelastic field concentrations ahead of electrodes in multilayer piezoelectric actuators were examined in a combined experimental and numerical investigation. Experiments were performed to measure the strain near internal and surface electrodes at various electrical loading conditions. The finite element method was also used to solve the coupled electro-elastic boundary value problem. The strain, stress and electric displacement concentrations were calculated and a non-linear behavior induced by localized polarization switching was discussed. A comparison of strain concentration was made between experiment and simulation.     

Fracture behaviors of piezoelectric materials

Theoretical analyses and experimental observations of the failure and fracture behaviors of piezoelectric materials are presented. The theoretical analyses are based on the Stroh formalism. A strip dielectric breakdown model is proposed to estimate the effect of electrical non-linearity on the piezoelectric fracture of electrically insulated cracks. The reviewed experiments include the indentation fracture test, the bending test on smooth samples, the fracture test on pre-notched or pre-cracked samples, the environment-assisted fracture test, etc. For electrically insulated cracks, the experimental results show a complicated fracture behavior under combined electrical and mechanical loading. Fracture data are greatly scattered when a static electric field is applied. For electrically conducting cracks, the experimental results demonstrate that static electric fields can fracture poled and depoled lead zirconate titanate (PZT) ceramics. A charge-free zone model is introduced to understand the failure behavior of conducting cracks in the depoled lead zirconate titanate ceramics under electrical and/or mechanical loading. These theoretical and experimental results indicate that fracture mechanics concepts are useful in the study of the failure behaviors of piezoelectric materials.     

Structure and packing of aminoxyl and piperidinyl acrylamide monomers

The closely related title compounds, 4‐acrylamido‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl, C₁₂H₂₁N₂O₂, (I), and N‐(2,2,6,6‐tetramethylpiperidin‐4‐yl)acrylamide monohydrate, C₁₂H₂₂N₂O·H₂O, (II), are important monomers in the preparation of redox‐active polymers. They comprise an acrylamide group of the usual s‐cis configuration appended to a 2,2,6,6‐tetramethyl‐substituted piperidine‐1‐oxyl radical or a piperidinyl chair, respectively. The adjacent amide and piperidinyl H atoms are approximately trans across the C—N bond. The packing in (I) is dominated by N—H...O hydrogen bonds; these are supported by C—H...O contacts to form an R₂¹(6) ring repeat, a motif which has been observed in other acrylamide structures. In (II), hydrogen bonds are again key to the packing arrangements. In this case, the incorporated solvent water molecule acts as an acceptor through its O atom and as a donor through both H atoms, binding three adjacent piperidinylacrylamide molecules into layers. In both structures, weak C—H...O contacts involving the piperidinyl methyl H atoms and a proximal acrylamide carbonyl O atom extend the structure in the third dimension.     

Light‐ and Humidity‐Induced Motion of an Acidochromic Film

A smart acidochromic agarose‐based film with 1,4‐bis(para‐hydroxystyryl)benzene as the pH‐responsive fluorophore was prepared. This film can simultaneously harness the chemical potential of light and aerial humidity gradients to convert them into mechanical work. The strong reversible hygroscopicity of the agarose matrix induces swift locomotion by mechanical deformation owing to exchange of water with the surroundings. Driven by humidity, a 20 mg composite film coupled to a piezoelectric bending transducer sensor generates a peak output of approximately 80 mV, which corresponds to a power density of 25 μW kg^?1. Excitation with UV light triggers isomerization of the chromophore, which appears as reshaping by spiraling, bending, or twisting of the film. The material also responds to changes in the pH value by reversible protonation of the fluorophore with rapid changes in color and fluorescence. The threefold sensing capability of this smart material could be utilized for the fabrication of multiresponsive actuating dynamic elements in biomedicine and soft robotics.     

Pulse width modulation (PWM) control of the bending displacement and force generation of ionomer‐based polymer actuators

This paper discusses results of the pulse width modulation (PWM) control of the bending displacement and force generation of ionomer‐based polymer actuators. The idea of PWM control for polymer actuators is based on the frequency dependence on relaxation processes of the bending motion of the actuator. The actuators were fabricated by electroless plating of platinum on a perfluorinated sulfonated polymer (i.e. Nafion). It was noted that the duty cycles of PWM can smoothly control both the displacement and force generated by the actuator. The performance of the actuator was evaluated under 40%RH and 90%RH conditions because of the moisture sensitivity of the actuators. Copyright © 2013 John Wiley & Sons, Ltd.