Polymer Composites with Oriented Magnetic Nanowires as Fillers
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1058-JJ06-26
Polymer Composites with Oriented Magnetic Nanowires as Fillers Li Sun, and Kusuma Keshoju Department of Mechanical Engineering, University of Houston, Houston, TX, 77204-4006 ABSTRACT Metallic nickel nanowires with excellent physical properties have been introduced into polydimethylsiloxane (PDMS) matrix to form polymer nanocomposites. Nanowires were synthesized by template-assisted electrochemical deposition. By utilizing ferromagnetic nickel nanowires, small external magnetic field can be used to control their alignment and distribution during composite synthesis. Unlike dielectrophoresis, optical tweezers, and microfluidic flow control, magnetic manipulation provides a cost-effective, non-contact, and versatile approach to control nanostructured materials in fluids over a large area. Polydimethylsiloxane composites with nanowires arranged in longitudinal, transverse, and random orientations with respect to the applied load direction were studied. Tensile tests showed that the composites with longitudinal arrangement have higher elastic modulus and tensile strength than the other composite samples. Experimentally obtained elastic modulus values were compared with the prediction of classical Halpin-Tsai model. INTRODUCTION Polymer nanocomposites is a rapidly growing area in nano-engineered materials research. The use of nanoscale fillers to augment the properties of polymers has led to the development of nanocomposites and has provided a radical alternative to the conventional polymer composite systems. Nanocomposites can possess a combination of properties that cannot be achieved with either of the constituents acting alone [1]. In this study, we have explored the synthesis and mechanical characterization of polymer-nickel (Ni) nanowire composites. The nanowires were synthesized by template-assisted electrodeposition [2], in which a desired material is electrochemically deposited inside the nanopores of template and shaped into a nanowire with controlled dimensions and composition. Manipulation of nanomaterials is not only an engineering challenge, but can also help in understanding the nanoscale physics problems. To improve the effectiveness of manipulation, most of the experiments were performed on nanomaterials suspended in fluids. Techniques based on Langmuir-Blodgett film formation [3], microfluidic flow [4], electric [5] and magnetic [6] fields, dielectrophoresis [7], and optical tweezers [8] have been explored. Among all these methods, magnetic manipulation provides a cost-effective, non-contact, and versatile approach to control nanostructured materials in fluids over a large area. The ferromagnetic materials can be effectively manipulated with very small external magnetic field and the magnetic interaction can be three or four orders of magnitude stronger than any other interactions [9].
Based on the analysis of magnetic driving field and fluid drag force, the motion of nanowires can be well quantified [10]. The schematic of the geometry during nanowire rotation is shown in Figure 1(a). Th
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