Synthesis and characterization of an azobenzene‐ and acrylamide‐based photoresponsive copolymer and gel

This article reports the synthesis and characterization of a new type of copolymer consisting of acrylamide and trans‐4‐methacroyloxyazobenzene and their gel. Free‐radical polymerization initiated with 2,2′‐azobisisobutyronitrile was used to conduct the synthesis although N,N′‐methylene bisacrylamide was used as a crosslinking agent for the gel synthesis. Despite the insolubility of the different monomers in a single solvent, a certain ratio of water/tetrahydrofuran (THF) enabled the propagating species to stay in the solution and thus to facilitate chain growth. The solubility, Fourier transform infrared spectra, and solid‐state ¹³C NMR investigations revealed that two monomers in the copolymer were chemically bonded. The compositions of the incorporated acrylamide and azobenzene in the copolymer and the gel were determined by NMR spectroscopy. Because the potential actuating behavior of such materials was due to the volume change involved in reversible solvent uptake, the sorption and evaporation of the gel were also investigated and showed that the gel could absorb about 460% water, which corresponded to a polymer content of the weight gel of 18% and was compatible with thermogravimetric analysis of a saturated gel that revealed about 83 wt % of a swollen gel was lost within 12 h. Finally, photoinduced trans–cis isomerization kinetics of the copolymer was investigated in a 30:70 mixture of water and THF against irradiation time. A photostationary state was reached within 5.5 min with a corresponding conversion of 70% of the trans isomer to the cis form. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2886–2896, 2004     

Determination of piezoelectric coefficients of ferroelectric thin films using GaAs:Cr adaptive interferometer

We report on simple interferometric technique for the measurement of piezoelectric coefficients of thin films using GaAs:Cr adaptive photodetectors in the geometry of modified Mach–Zehnder interferometer. The technique needs no special vibroinsulation and automatically adjusts and keeps the operation point of the interferometer. Strong hysteresis effects with a slightly asymmetric form of the hysteresis loop were observed at the dependence of d₃₃ coefficients of the Pb(Zr,Ti)O₃ (PZT) thin film versus DC electric field. The obtained values of d₃₃ coefficients are in agreement with known data.     

Sol-Gel Synthesis of Nanocrystalline PZT Using a Novel System

A simple system has been developed for the preparation of lead zirconate titanate, Pb(Zr _x Ti_{1 – x} )O₃ powders by sol-gel process. To achieve stable and homogeneous precursor solutions, chelating ligands such as acetic acid and acetylacetone have been used for the chemical modification of titanium and zirconium starting precursors. Phase-pure PZT powders were obtained, through a pyrochlore-free pathway, from the amorphous xerogel after heat treatment at 600°C. The formation of the crystalline phase, compositional homogeneity, sinterability, dielectric and piezoelectric characteristics of PZT are reported.     

溶剂型智能驱动材料的研究进展

智能驱动材料可对光、电、温度、溶剂、湿度等外界刺激做出可控的力学响应,并将这些能量转化为机械能而被广泛关注.溶剂型驱动材料是基于简单的湿度或溶剂气氛变化将化学能转换成机械能,并在机械发电、微型器件制备等方面具有重要的潜在应用.本文综述了溶剂型智能驱动材料的驱动类型、驱动原理,性能及其相关应用进展,并对溶剂型智能驱动材料在未来人工智能方面的应用前景进行了展望.     

Powderless processing of ceramics: Thin-layer electroceramics

A review is made of progress on the sol-gel processing of dense insulating electroceramics by polymeric condensation routes. Up until the past ten years, powders and porous coatings were principally made for optical and conductive applications. Much effort was expended on silica (SiO₂) and silicate-based systems. Recently, these approaches have been extended to non-silicate systems [1]. In this paper information is presented for the powderless processing of selected electroceramics in thin-layer form. Materials include PbTiO₃, BaTiO₃, Ba_1–x Pb _x TiO₃, PbZrO₃, Pb(Zr_1–y Ti _y )O₃ and (Pb_1–x La _x )(Zr_1–y Ti _y )O₃ which find applications in ceramic capacitors, piezoelectric transducers and electrooptic modulators. The approach is to avoid powders, and the attendent problems of powder handling, flow, packing, etc., and make use of polymerization condensation reactions to form extended networks with chemical linkage. Data are reported for the synthesis and low temperature processing routes for amorphous and polycrystalline ceramics.     

Lead Zirconate-Titanate Films Prepared from Soluble Powders

Precursor powders for Pb(Zr1 – xTix) O3 (PZT) thin films were produced by the reaction of zirconium-and titanium-n-propoxides with acetylacetone and lead acetate trihydrate. The subsequent complete removal of volatile components yielded powders that can be handled in air. The powders are indefinitely stable under ambient conditions.High molarity (>2m) coating sols were prepared by dissolution of the precursor powders in mixtures of 1,3-propanediol, triethanolamine (TEA) and water. Excess amounts of lead to compensate lead loss during firing were easily introduced into these solutions.The deposition of these sols on steel substrates and firing at 600°C yielded PZT films. Many physical parameters like film thickness, morphology and electrical performance could be influenced by choice of the solvent mixture composition and oxide content of the sols. Depending on the preparation dielectric permittivities, r of up to 840 were measured at 1 kHz. By hysteresis measurements at 50 Hz and a field amplitude of 50 V/m a remanent polarization of about 40 C/cm2 and coercivity of about 8 V/m was obtained. The films were stable against dielectric breakdown up to 70V/m.     

光响应形变液晶聚合物的结构与应用

液晶聚合物能够在外界刺激下发生形状变化,是一类重要的柔性智能材料.其中液晶有序排列的改变诱导材料的宏观形变.光响应聚合物具有可远程操作、易于控制等特点,在刺激响应性聚合物的设计中受到了广泛关注.将具有光响应性的基团引入到液晶聚合物体系中,可以得到一系列具有重要应用前景的光致形变材料.本文综述了近年来光响应形变液晶聚合物...     

带有末端集中质量的双连杆柔性机械臂主动控制

对带有末端集中质量的双连杆柔性机械臂的主动控制进行了研究,给出系统的动力学方程,采用非线性解耦反馈控制方法分别得出系统大范围运动方程和柔性臂的动力学方程,采用机械臂逆动力学方法和LQR方法分别设计大范围运动控制律和压电作动器控制律.仿真结果显示,本文控制方法能够有效地进行机械臂的轨迹跟踪,柔性臂的弹性振动可以得到有效抑制.     

悬线式物镜力矩器动态特性的仿真实验研究

悬线式物镜力矩器是目前光学头系统中使用最为广泛的力矩器,其动态特性直接决定了光学头的读写性能。基于ANSYS参数化设计语言(APDL)建立了悬线式光学头物镜力矩器的仿真设计平台。通过仿真平台进行了力矩器一阶共振频率和峰值、二阶共振频率和峰值、扭转共振频率、静态灵敏度、动态灵敏度和相位等动态特性参数的仿真实验,仿真计算的结果与实际测量的结果相比,最大相对误差为4.2%。该仿真平台对于二维乃至三维悬线式物镜力矩器的设计和评价都具有重要的指导意义。     

基于压电叠堆惯性作动器的随机振动控制研究 1)

本文主要研究了基于压电叠堆惯性作动器的随机振动控制方法并分析了控制力时滞对控制效果的影响规律。首先,对压电叠堆惯性作动器的动力学特性进行分析,建立了考虑惯性作动器动力学的主结构的随机动力学模型;接着,提出主结构随机振动 "线性"二次高斯控制(linear quadratic Gaussian,LQG)方法,并探讨了作动器惯性质量和刚度等对控制效果的影响规律;最后,研究了控制力时滞对控制效果的影响,并提出了利用时滞优化控制效果的方法。研究结果表明,压电叠堆惯性作动器对结构的随机振动具有较好的控制效果,当控制时滞时间$\tau = 0.025$s时控制效果可以得到进一步优化。