Novel Processing of 1-3 Piezoelectric Ceramic/Polymer Composites for Transducer Applications

Piezoelectric ceramic/polymer composites with 1-3 connectivity were made by weaving sized lead zirconate titanate (PZT) fiber bundles through a honeycomb support. Bundles comprised of fine-scale, 20-50 μm green fibers, made using the viscous suspension spinning process, were sized to increase their manageability. The sizing step comprised of soaking the green PZT fiber bundles in an aqueous solution of poly(vinyl alcohol), then pulling the wet fibers through a steel sizing die. Sizing resulted in dense and flexible fiber bundles, which facilitated composite construction and led to composites with increased volume fractons. Sintering, polymer embedding, and machining produced a composite exhibiting 1-3 connectivity. Composites with 10 vol% PZT yilded d ₃₃ values of 230 pC/N and a dielectric constant of 130.     

Moisture in Epoxy Resin Composites

The effect of external loading on the rate of water uptake by unidirectional composites is examined as a function of the loading angle (0) with respect to the fibre direction in glass and graphite-reinforced epoxies. The moisture uptake under the effect of the external load increases with 0, suggesting a dependence on the matrix volume increase, itself a function of the strain and of the Poisson's ratio.     

Moisture in Epoxy Resin Composites

The effect of external loading on the rate of water uptake by unidirectional composites is examined as a function of the loading angle (0) with respect to the fibre direction in glass and graphite-reinforced epoxies. The moisture uptake under the effect of the external load increases with 0, suggesting a dependence on the matrix volume increase, itself a function of the strain and of the Poisson's ratio.     

大功率铅基压电陶瓷材料的研究进展

本文综述了大功率压电陶瓷材料的研究进展,介绍了其体系结构、应用和制备方法,最后指出掺杂改性、探索新的材料体系和制备工艺是改进其制备的有效途径。     

微波技术在环氧树脂及其复合材料中的应用

论述了近年来微波固化技术在环氧树脂及其复合材料固化中的应用,重点比较了微波固化与传统热固化后环氧树脂及其复合材料的力学性能、热性能和粘结强度的变化,并对环氧树脂复合材料微波固化的研究进行了展望。     

环氧树脂复合材料的固化动力学

将环氧树脂与适量的玻璃纤维混合加工到一起,形成一种含有玻璃纤维特性的环氧树脂复合材料。而且玻璃纤维的加入可以加强环氧树脂复合材料的固化动力学特性,为此提出环氧树脂复合材料的固化动力学特性分析,并对弹性效果以及伸缩抗压的特性变化进行分析。结果表明:当加入玻璃纤维时,环氧树脂复合材料固化动力学特性增强,当玻璃纤维比例达到50%时,其固化动力学特性达到最佳状态。     

Adhesion Tests Using Epoxy Quasicrystal Composites

Abstract

Quasicrystals (QC) are usually complex metal alloys with atypical structures. Due to their physical, mechanical and surface properties, quasicrystals have been widely studied. Although methods to manufacture quasicrystalline materials are well known, much effort has been expended in obtaining suitable quasicrystalline materials for use in industry. As quasicrystalline materials are very brittle, they are usually used in powder form as a reinforcement for additives in composites as well as in coating technology. In this work, Al–Cu–Fe quasicrystalline powder was used as a reinforcement in epoxy resin and the influence of the quasicrystal particles incorporation on the adhesive properties of the epoxy was investigated. Single lap joints (SLJ) adhesion tests were performed in order to assess the shear mode bond strength. Results show that the effect of QC reinforcement is not linear with respect to the adherence of the composites.     

环氧鱼油的性质及其应用研究

采用一步环氧化工艺制得环氧值为4．5％的环氧鱼油,研究环氧鱼油的性质及其在氯乙烯中的作用。研究结果表明：环氧鱼油耐热性高,用于聚氯乙烯中,与金属皂并用有良好的协同稳定作用,作用效果与环氧大豆油相当甚至更好些,可作为聚氯乙烯优良的增塑剂兼稳定剂。     

Novel Self-Crosslinking Epoxy Oligomers for Cationic-Cure Coatings Applications

ABSTRACT

Novel epoxy functional oligomers containing phosphate-esters, carboxylate-ester, and urethane linkages with varying molecular weight and functionality have been synthesized from commercially available epoxy compounds. These oligomers are characterized for the parameters relevant to the study by physical, spectroscopic, and chemical methods. Two series of cationic thermal-cure coating compositions have been formulated using these oligomers as principal film-forming components. The cured films of these self-crosslinked oligomers have been studied and compared. A correlation between structure of these oligomers and their film properties has been established.     

香蕉纤维的表面改性及其增强环氧树脂复合材料的性能研究

采用硅烷偶联剂(A-174)偶联、高锰酸钾接枝和乙酰化包覆等3种方法对香蕉纤维进行表面改性,制备了改性香蕉纤维增强环氧树脂复合材料,测试其拉伸、弯曲、压缩、冲击等力学性能。结果表明,偶联、接枝、包覆等表面改性均能明显改善香蕉纤维与基体树脂的相容性,提高复合材料的力学性能,其中偶联改性的效果最好。当改性香蕉纤维含量为10wt%时,与未改性的香蕉纤维比较,复合材料的拉伸强度、弯曲强度、压缩强度分别提高了1.8、1.0、2.6倍;随着纤维含量的增加,复合材料的力学性能明显提高。     

Piezoelectric Properties of a Pioneering 3‐1 Type PZT/Epoxy Composites Based on Freeze‐Casting Processing

Lead zirconate titanate (PbZr_1 ? xTi_xO₃, PZT)/epoxy composites with one‐ dimensional epoxy in PZT matrix (called 3‐1 type piezocomposites) have been fabricated by tert‐butyl alcohol (TBA)‐based directional freeze casting of PZT matrix and afterward infiltration of epoxy. The composites with PZT volume fraction ranging from 0.36 to 0.69 were obtained by adjusting initial solid loading in freeze‐casting slurry. The effect of poling voltage on piezoelectric properties of the composites was studied for various volume fraction of PZT phase. With the increasing of PZT volume fraction, relative permittivity (ε_r) increased linearly and piezoelectric coefficient (d₃₃ and d₃₁) increased step by step. The resultant composites with 0.57 PZT volume fraction possessed the highest hydrostatic piezoelectric strain coefficient (d_h) value (184 pC/N), voltage coefficient (g_h) value (13.6 × 10^?3 V/m Pa), and hydrostatic figure of merit (HFOM) value (2168 × 10^?15 Pa^?1).     

Fabrication and Characterization of PZT/Thermoplastic Polymer Composites for High-Frequency Phased Linear Arrays

A new method of fabricating PZT/potymer composites with 2-2 connectivity is described. This fabrication technique offers significant advantages over conventional dice-and-fill fabrication methods, and the composites exhibit the high electromechanical coupling expected from conventional PZT/polymer composites. In this method, thin (≤20μm) sintered PZT plates and sheets of a thermoplastic polymer film (≤6 μm) are bonded together via thermal processing. A technique for sintering thin, flat PZT plates from tape cast materials was developed to provide the necessary PZT plates. The resulting composite blocks were cut to required dimensions, electroded, and poled. Electromechanical properties were measured to evaluate the composites.     

新型光稳定剂应用于水性环氧涂料的研究

水性环氧涂料已发展成为解决一般常用传统高VOC溶剂型涂料的高污染问题,它具有有效减少或不使用溶剂的优点,而环保型涂料所遭遇的挑战之一是需要光稳定剂来保护涂料预防光降解产生。针对水性环氧涂料开发了一种新型复配型光稳定剂EVERSORB EP5,应用实验设计(DOE)研究结果表明:3种不同类型光稳定剂添加至2种不同类型溶液-水和水性环氧涂料中进行分散过滤试验,EVERSORB EP5分散效果最好,人工加速老化试验结果显示:增加EVERSORB EP5在水性涂料中的有效浓度,可以增强相对的保护效果,增加涂料的膜厚无法得到某种程度的保护效果。     

Physicomechanical Properties of Carbon Fiber Reinforced Epoxy Composites

Fabrication of carbon fiber reinforced epoxy composites from the matrix resins diglycidyl ether of bisphenol-A (DGEBA) and tetraglycidyl bis(aminotolyl) cyclohexane (TGBATC) using 4,4′-diaminodiphenyl methane (DDM) as curing agent. The composites were evaluated for their physical and mechanical properties. A significant improvement in the properties was observed on addition of 20 phr of an epoxy fortifier.     

T-ZnO晶须增强环氧树脂复合材料的抗静电性

研究了T—ZnO晶须增强环氧树脂复合材料的抗静电性。结果表明：具有半导体性的T—ZnO晶须在复合材料中,相互搭接形成导电通路,以价带传导方式传导电荷,而起抗静电作用,使环氧树脂材料的体积电阻率降低了8个数量级,用比表面因子修正了网络形成临界体积分数模型。T—ZnO晶须的网络形成临界体积分数(0．057)是球形粒子的网络形成临界体积分数(0．38)的1／10。     

玻璃纤维／环氧树脂复合材料的热性能

本文采用E-玻璃纤维作为增强材料、双酚A环氧树脂和芳胺类固化剂作为基体制成复合材料试样,利用动态与静态热分析方法测定玻璃纤维／环氧树脂基复合材料的热性能,研究了玻璃纤维含量对复合材料动态热机械性能、玻璃化温度等热性能的影响。     

Joining of Carbon-Carbon Composites for Thermonuclear Fusion Applications

Carbon-fiber-reinforced carbon (CfC) composites have been joined by using different joining agents: metals (silicon, aluminum, and titanium), an intermetallic compound (magnesium silicide, Mg₂Si), and glasses (borosilicates and zinc borates). These joining agents have been chosen by considering their possible use in a thermonuclear fusion reactor, as suggested by their low-activation properties, reasonably high working temperature, industrial feasibility, and potential scale-up of the joined carboncarbon structures using pressureless-processing techniques. Each joined structure (CfC composite–joining material-CfC composite) has been first morphologically characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffractometry. Then, single-lap shear tests have been performed on the most-promising joined structures, i.e., silicon- and aluminum-joined CfC-composite samples, which have shown an average shear strength of 22 and 10 MPa, respectively.     

有机累托石/环氧树脂复合材料的结构及性能

以热稳定性较高的离子液体1-十六烷基-3-甲基咪唑溴盐(1-hexadecy1-3-methylimidazolium bromide,C16mimBr)为改性剂,制备了有机累托石(organic-rectorite,OREC).以环氧树脂(epoxy resin,EP)为基体,分别用2-乙基-4-甲基咪唑(2-eth...     

Porous PZT Ceramics with Aligned Pore Channels for Energy Harvesting Applications

In this study, aligned porous lead zirconate titanate (PZT) ceramics with high pyroelectric figures‐of‐merit were successfully manufactured by freeze casting using water‐based suspensions. The introduction of aligned pores was demonstrated to have a strong influence on the resultant porous ceramics, in terms of mechanical, dielectric, and pyroelectric properties. As the level of porosity was increased, the relative permittivity decreased, whereas the Curie temperature and dielectric loss increased. The aligned porous structure exhibited improvement in the compressive strength ranging from 19 to 35 MPa, leading to easier handling, better processability and wider applications for such type of porous material. Both types of pyroelectric harvesting figures‐of‐merit (F_E and F′_E) of the PZT ceramics with a porosity level of 25–45 vol% increased in all porous ceramics, for example, from 11.41 to 12.43 pJ/m³/K² and 1.94 to 6.57 pm³/J, respectively, at 25°C, which were shown to be higher than the dense PZT counterpart.