Home About us Contact
|
Home About us Contact | ||
|
|
||
Piezoelectric Materials (piezoelectric + material)
Selected AbstractsGrowth and Dielectric Characterization of Large Single Crystals of GaAsO4, a Novel Piezoelectric Material.CHEMINFORM, Issue 32 2003O. Cambon Abstract For Abstract see ChemInform Abstract in Full Text. [source] Synthesis of Bismuth Sodium Titanate Nanosized Powders by Solution/Sol,Gel ProcessJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2003Chang Yeoul Kim (Bi1/2Na1/2)TiO3 (BNT) is a prominent candidate for a lead-free piezoelectric material. In this study, BNT was synthesized using the solution/sol,gel method, in which a solution of Bi2O3 and Na2CO3 was dissolved in HNO3 as starting materials. The solution then was mixed with ethylene glycol and titanium tetraisopropoxide. The obtained BNT powder was analyzed using FT-IR, DTA-TG, Raman spectroscopy, and high-temperature XRD. Results showed that BNT crystallization occurred above 600°C. TEM investigation showed that 100,200 nm BNT particles were formed by heat-treating the sol,gel-derived BNT sol at 700°C for 6 h. [source] Piezoelectric and ferroelectric properties of [(K0.4725Na0.4725)Li0.055]NbO3,(Ag0.5Li0.5)TaO3 lead-free ceramicsPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 5 2007Jiagang Wu Abstract New lead-free piezoelectric (1 , x)[(K0.4725Na0.4725)Li0.055]NbO3, x (Ag0.5Li0.5)TaO3 [(1 , x)KNNL,x ALT] ceramics were prepared by conventional sintering. Piezoelectric and ferroelectric properties and Curie temperature of the ceramics were studied. The (1 , x)KNNL,x ALT (x = 0.04) ceramics exhibit good properties (d33 , 252 pC/N, kp , 41%, TC , 471 °C, To,t = 47 °C, Pr = 33.1 ,C/cm2, Ec = 10.6 kV/cm). These results show that (1 , x)KNNL,x ALT (x = 0.04) ceramic is a promising lead-free piezoelectric material for high temperature application. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Application of the X-FEM to the fracture of piezoelectric materialsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2009E. Béchet Abstract This paper presents an application of the extended finite element method (X-FEM) to the analysis of fracture in piezoelectric materials. These materials are increasingly used in actuators and sensors. New applications can be found as constituents of smart composites for adaptive electromechanical structures. Under in service loading, phenomena of crack initiation and propagation may occur due to high electromechanical field concentrations. In the past few years, the X-FEM has been applied mostly to model cracks in structural materials. The present paper focuses at first on the definition of new enrichment functions suitable for cracks in piezoelectric structures. At second, generalized domain integrals are used for the determination of crack tip parameters. The approach is based on specific asymptotic crack tip solutions, derived for piezoelectric materials. We present convergence results in the energy norm and for the stress intensity factors, in various settings. Copyright © 2008 John Wiley & Sons, Ltd. [source] Fully coupled non-linear analysis of piezoelectric solids involving domain switchingINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2003Wenjun Zeng Abstract Domain switching is the cause of significant non-linearity in the response of piezoelectric materials to mechanical and electrical effects. In this paper, the response of piezoelectric solids is formulated by coupling thermal, electrical, and mechanical effects. The constitutive equations are non-linear. Moreover, due to the domain switching phenomenon, the resulting governing equations become highly non-linear. The corresponding non-linear finite element equations are derived and solved by using an incremental technique. The developed formulation is first verified against a number of benchmark problems for which a closed-form solution exists. Next, a cantilever beam made of PZT-4 is studied to evaluate the effect of domain switching on the overall force,displacement response of the beam. A number of interesting observations are made with respect to the extent of non-linearity and its progressive spread as the load on the beam increases. Copyright © 2002 John Wiley & Sons, Ltd. [source] Microstructures and Piezoelectric Properties in the Li2O-Excess 0.95(Na0.5K0.5)NbO3,0.05LiTaO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2007Min-Soo Kim As a candidate for lead-free piezoelectric materials, Li2O-excess 0.95(Na0.5K0.5)NbO3,0.05LiTaO3 (NKN,5LT) ceramics were developed by a conventional sintering process. The sintering temperature was lowered by adding Li2O as a sintering aid. Abnormal grain growth in NKN,5LT ceramics was observed with varying Li2O content. This grain-growth behavior was explained in terms of interface reaction-controlled nucleation and growth. In the 1 mol% Li2O excess NKN,5LT samples sintered at 1000°C for 4 h in air, the electromechanical coupling factor and the piezoelectric constant of NKN,5LT ceramics were found to reach the highest values of 0.37 and 250 pC/N, respectively. [source] Cement-Based 0-3 Piezoelectric CompositesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2002Zongjin Li To meet the requirements of development for smart or intelligent structures in civil engineering, new functional materials that have good compatibility with civil engineering structural materials are needed. In this study, for the first time in the field of piezoelectric materials, cement-based 0-3 piezoelectric (PZT) composites were fabricated by the normal mixing and spreading method. The new materials have very good compatibility with portland cement concrete. The cement-based 0-3 piezoelectric composites were shown to have a slightly higher piezoelectric factor and electromechanical coefficient than those of 0-3 PZT/polymer composites with a similar content of PZT particles; thus, they are adequate for sensor application. There is potential for the application of cement-based 0-3 PZT composites in civil engineering because of their better piezoelectric properties and good compatibility with portland cement concrete. [source] Local solutions to a model of piezoelectric materialsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 14 2004Kamel Hamdache Abstract A local existence theorem is proved for a non-linear coupled system modelling the electromechanical motion of a one-dimensional piezoelectric body with domain switching. The system is composed by a heat equation describing the behaviour of the number of electric dipoles and by a wave equation governing the dynamic of the electric displacement. The main coupling in the system appears in the time-dependent velocity of the waves depending on the number of electric dipoles. The proof of the result relies on a time decay estimate satisfied by the number of electric dipoles and an uniform estimate of the solution of the regularized wave equation. Copyright © 2004 John Wiley & Sons, Ltd. [source] Effect of heat treatment on the electrical properties of lead zirconate titanate/poly (vinylidene fluoride) compositesPOLYMER INTERNATIONAL, Issue 6 2010Lijie Dong Abstract Ceramic/polymer composites are attracting increasing interest in materials research and practical applications due to the combination of excellent electric properties of piezoelectric ceramics and good flexibility of polymer matrices. In this case, the crystallization of the polymer has a significant effect on the electric properties of ceramic/polymer composites. Based on different heat treatment methods, the crystallization of poly(vinylidene fluoride) (PVDF) in composites of lead zirconate titanate (PZT) and PVDF can be controlled effectively. PZT/PVDF composites with various PVDF crystallizations exhibit distinctive dielectric and piezoelectric properties. When the crystallization of PVDF is 21%, the PZT/PVDF composites show a high dielectric constant (,) of 165 and a low dielectric loss (tan ,) of 0.03 at 103 Hz, and when the crystallization of PVDF reaches 34%, the piezoelectric coefficient (d33) of PZT/PVDF composites can be up to ca 100 pC N,1. By controlling the crystallization of PVDF, PZT/PVDF composites with excellent dielectric and piezoelectric properties were obtained, which can be employed as promising candidates in high-efficiency capacitors and as novel piezoelectric materials. Copyright © 2010 Society of Chemical Industry [source] New design of actuator using shear piezoelectricity of a chiral polymer, and prototype devicePOLYMER INTERNATIONAL, Issue 3 2010Michiya Sawano Abstract Chiral polymers have been known to exhibit small shear piezoelectricity for about fifty years. However, recently, we reported that poly(L -lactic acid) treated with supercritical carbon dioxide (sc-PLLA), which is a type of chiral polymer, exhibits much higher shear piezoelectricity than other chiral polymers. On the other hand, we found an important difference between motion due to shear piezoelectricity and that due to tensile piezoelectricity in piezoelectric materials through computer simulations. On the basis of these results, we fabricated a new type of electrically controlled tweezers constructed from a pair of sc-PLLA sheets with shear piezoelectricity. In general, when conventional tweezers open to the left and right, the trajectory of their motion becomes fanlike at the center of the connection (one end of the tweezers). In the new tweezers, the two small sheets making up the tweezers open parallel to each other, without the motion of parts near the connection. Moreover, a prototype ,finger' system using sc-PLLA sheets to realize complex motion in which the finger curled upon stretching of the sc-PLLA sheets was manufactured as a trial device. Using the prototype finger system, we demonstrated the firm grasping of a sample, but the sample could not be removed from a vessel. Thus, sc-PLLA increases the likelihood of realizing a device with highly operational pick-up in a very small region by using the shear piezoelectricity of a chiral polymer. Copyright © 2010 Society of Chemical Industry [source] An anisotropic finite 3D beam element for the analysis of piezoelectric structuresPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003A. Butz Dipl.-Ing. A finite element formulation for a 3D beam is presented to model rod like piezoelectric structures. Piezoelectricity is described by a mixed field theory that couples mechanical and electrical quantities. In this work the coupling between the mechanical stress and the electric displacement is considered. Therefore a 3D beam element formulation with nine degrees of freedom per node is introduced. Due to the poling process, the piezoelectric materials have anisotropic material properties which are taken into account in the presented beam formulation. Further more we suggest a special approximation for the electric potential through the cross-section of the beam. An excentric beam formulation is used to model the layerwise design that is often found on piezoelectic structures. [source] Study of the Different Types of Actuators and Mechanisms for Upper Limb ProsthesesARTIFICIAL ORGANS, Issue 6 2003Vanderlei O. Del Cura Abstract: Research in the area of actuators and mechanisms has shown steadily growing technological advances in externally activated upper limb prostheses. From among the actuators, advances include the use of piezoelectric materials, special metal alloys, polymers, and new motor applications, while the advances in mechanisms include mechanical designs based on the anatomy of the human hand and improvements in the way these components are combined. These efforts are aimed at meeting the need for anthropomorphic and functional prosthetic devices that enable patients to carry out basic daily tasks more easily and reduce the rejection rate of prostheses. This article technically discusses the several types of actuators and mechanisms, listing their main characteristics, applications, and advantages and disadvantages, and the current state of research in the area of rehabilitation of upper limb functions through the use of active prostheses. Comparisons of these devices are made with regard to the main criteria of construction and operation required to achieve optimal prosthetic performance. [source] | |||||||||||||