Showing papers by "Shanyi Du published in 2010"

Synergistic effect of carbon nanofiber and carbon nanopaper on shape memory polymer composite

Abstract: The present work studies the synergistic effect of carbon nanofiber (CNF) and carbon nanopaper on the shape recovery of shape memory polymer (SMP) composite. The combination of CNF and carbon nanopaper was used to improve the thermal and electrical conductivities of the SMP composite. The carbon nanopaper was coated on the surface of the SMP composite in order to achieve the actuation by electrical resistive heating. CNFs were blended with the SMP resin to improve the thermal conductivity to facilitate the heat transfer from the nanopaper to the underlying SMP composite to accelerate the electroactive responses.

Shape-Memory Polymers and Multifunctional Composites

Abstract: Overview of Shape-Memory Polymers, M Behl and A Lendlein The Structural Variety of Shape-Memory Polymers, H-Y Jiang and AM Schmidt Thermomechanical Behavior and Modeling Approaches, HJ Qi and ML Dunn Thermomechanical Characterizations of Shape-Memory Polymers (Dual/Triple-Shape) and Modeling Approaches, K Kratz, W Wagermaier, M Heuchel, and A Lendlein Electrical, Thermomechanical and Shape-Memory Properties of the PU Shape-Memory Polymer, WM Huang and B Yang Multifunctional Shape Memory Polymers and Actuation Methods, J Leng, H Lu and S Du Shape Memory Polymer Composites, J Leng, X Lan and S Du Applications of Shape Memory Polymers in Aerospace, Y Liu and J Leng Shape Memory Polymer Foam and Applications, WM Sokolowski Shape Memory Polymer Textile, J Hu Applications of Shape Memory Polymers in Biomedicine, WM Sokolowski and J Leng Novel Applications and Future of Shape Memory Polymers, WM Huang Index

Electrical properties and shape-memory behavior of self-assembled carbon nanofiber nanopaper incorporated with shape-memory polymer

Abstract: The present paper studies the electrical and shape-memory behavior of self-assembled carbon nanofiber (CNF) nanopaper incorporated with shape-memory polymer (SMP). The morphology and structure of the self-assembled nanopapers were characterized with scanning electron microscopy (SEM). A continuous and compact network was observed from the SEM images, which indicates that the CNF nanopaper could have highly conductive properties. The electrical conductivity of the CNF nanopaper was measured by the four-point probe method and its temperature coefficient effect was studied. Finally, the actuation of SMP was demonstrated by the electrical resistive heating of the CNF nanopaper.

Electroactive shape-memory polymer nanocomposites incorporating carbon nanofiber paper

Abstract: A conductive carbon nanofiber (CNF) paper is described for the actuation of shape recovery of a shape-memory polymer (SMP) by electrically resistive Joule heating. The CNF paper was manufactured using a traditional physical vapor deposition process and the microscale morphology and structure of the CNF paper were observed using a scanning electron microscope. The CNF paper was found to be porous, with the pore size determined by the weight concentration of CNF. The excellent electrical properties of pure CNF papers and their SMP composites were characterized by the four-point probe method. Shape recovery actuation of this type of SMP composite induced by electrically resistive heating was achieved with a 12 V voltage. Additionally, the thermomechanical properties of the SMP composite were studied with respect to the volume fraction of CNF paper.

Device and method for preparing particle-reinforced gradient composite materials by using ultrasonic waves

Abstract: The invention relates to a device and a method for preparing particle-reinforced gradient composite materials by using ultrasonic waves, and solves the problems that only a composite material system with a relatively large magnetic permeability of second-phase particles and a metal matrix can be prepared by the conventional method for preparing the gradient composite materials by using electromagnetism, the surface of the second-phase particles and liquid metal have poor wetting and bonding performance, and the prepared gradient composite materials have poor strength, plasticity, toughness, compactness and the like in the conventional method for preparing the gradient composite materials. In the device, an ultrasonic generation device is arranged below a preparation container, and a heating element is 10 to 30mm away from the preparation container. The method comprises the following steps: heating metal materials until the metal materials are completely molten; adding second-phase reinforced particles into the molten metal materials, applying ultrasonic vibration to the mixture for 2 to 120s, and then stopping heating; and continuing applying the ultrasonic waves to the mixture and cooling the mixture until the mixture is solidified to obtain the particle-reinforced gradient composite materials. The device and the method are used for preparing the particle-reinforced gradient composite materials.

X-ray diffraction stress analysis of ferroelectric thin films with ideal (h k l) textures considering the piezoelectric coupling effect

Abstract: Ferroelectric thin films present large residual stress and strong texture during preparation, which affect the mechanical, dielectric and piezoelectric properties of the thin films. The determination of residual stresses in ferroelectric thin films with different textures is therefore very important. In this paper, an extended crystallite group model to evaluate the residual stresses of ferroelectric thin films using X-ray diffraction is proposed by considering the constitutive equation of orthogonally anisotropic ferroelectric medium. The effects of anisotropy and piezoelectric coupling on residual stresses of ferroelectric thin films are analyzed. X-ray stress factors for ideal ( h k l )-textured ferroelectric thin films are obtained. An example of calculating the residual stresses of tetragonal perovskite ferroelectric thin films with (1 1 1) and (1 0 0) textures using the extended model is provided to validate the model.

Shape Memory Polymers: A Potential Material for Future’s Changing Shape

Abstract: Shape memory polymers (SMPs) undergo significant macroscopic deformation upon the application of an external stimulus. As a novel and promising kind of smart materials, they have been widely researched since the 1980s. SMPs present many potential technical advantages that surpass those of shape memory alloys and shape memory ceramics such as good shape recoverability, low density, ease in processing and in tailoring of properties (e.g., transition temperature, stiffness, bio-degradability, and ease of functionally grading), programmability and controllability of recovery behavior, and most importantly, low cost. This paper aims to provide a comprehensive review of SMPs, encompassing a fundamental understanding of the shape memory of SMPs. The synthesis of SMPs is presented firstly. In order to realize the actuation of SMPs for a special application, the investigation of actuations in multi ways are performed, namely electroactive SMPs, light-responsive SMPs, magnetism-induced SMPs, and chemo-responsive SMPs. These novel actuation approaches play a critical role in the development of multifunctional materials that not only exhibit the shape memory effect but also perform particular functions. Based on the unique properties of such materials, primary applications are also listed, and the potential directions and applications of SMPs are proposed to be developed in future research.Copyright © 2010 by ASME