Evaluation of Polypyrrole Coating on Fe 3 O 4 and Its Effect on Nanocomposite Properties
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EE13.34.1
Evaluation of Polypyrrole Coating on Fe3O4 and Its Effect on Nanocomposite Properties S. Liong1; A.W. Harter3; R. L. Moore3; W.S. Rees, Jr.1,2 1
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332 School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332 3 Signatures Technology Laboratory, Georgia Tech Research Institute, Atlanta, GA 30332 2
ABSTRACT Magnetite (Fe3O4) nanoparticles were synthesized by chemical coprecipitation and were characterized using TEM, XRD, and VSM. XRD and TEM measurements indicate that the average particle size was approximately 10 nm. The nanoparticles were coated with polypyrrole using oxidative polymerization. TGA results show that the polypyrrole coating is 28.5wt%. TEM images indicate that the nanoparticles are bound in clusters by polypyrrole. Measurements show that nanoparticles may hinder curing of the polymer matrix, but they can be effective in producing composites with higher modulus and magnetic permeability at lower frequencies. INTRODUCTION Magnetic nanoparticles have been the focus of many studies due to their wide range of applications in biosensors, recording media, and EMI shielding. Below a critical size, magnetic particles become superparamagnetic [1]. This unique property allows for the material to approach the saturation magnetization at low applied field [1]. For magnetite (Fe3O4), superparamagnetism is expected at room temperature in particles less than 20nm in diameter [2,3]. Magnetite has one of the highest saturation magnetizations (92-95 emu/g) for an iron oxide [4]. However, unlike iron, Fe3O4 particles are relatively stable in air and liquid, thereby making them amenable for downstream processing and for application in many environments. The advantage of using conjugated polymers is that surface conductivity and thus interparticle contact can be adjusted from an insulating to a conducting phase [5]. Polymers such as polypyrrole are environmentally stable but are known for having poor mechanical properties. Such polymers are often synthesized with the support of a substrate [6], and in this study we used Fe3O4 nanoparticles.
Figure 1. Schematic of the hybrid material with magnetic and conductive properties. One suggested application of nanoparticles is as reinforcing materials. The nanoparticle interfacial area can increase available surface bonds 100 to 1000 times over those found in micron particles at the same volume fraction. One goal of this study is to compare the differences between Fe3O4 nanoparticles and micron-sized particles as fillers in composites.Though effective medium theories may qualitatively predict the electromagnetic constitutive properties of the composites, the addition of polypyrrole coating around the nanoparticles has an unknown impact on the mechanical properties. Thus another goal of this study was to initiate an experimental database for mechanical properties and correlate them with the electromagnetic properties. We find that the polypyrrole-coa
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