Graduation Year

2004

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Physics

Major Professor

Hariharan, Srikanth

Keywords

multifunctional devices, nanoparticles, dispersion, composites, magnetism

Abstract

Magnetic nanoparticles embedded in polymer matrices have excellent potential for electromagnetic device applications like electromagnetic interference (EMI) suppression. Using chemical precipitation methods and Nanogen , a microwave plasma method, we have synthesized various nanoparticles including iron, polystyrene-coated iron, iron oxide (both hematite and magnetite), nickel ferrite, and manganese zinc ferrite. We have synthesized polymer nanocomposites of polymethylmethacrylate (PMMA), polystyrene (PS), and polypyrrole (PPy) doped with varying concentrations of these nanoparticles. These nanocomposites were processed using melt blending and sonication techniques. The concentration of nanoparticles was varied in a controlled way. Although polymer processing conditions were optimized to achieve good uniform dispersion of the nanoparticles in the polymer matrix, surface characterization with SEM indicates areas of clustering of the nanoparticles.

This agglomeration is attributed to the particle interactions mediated by steric forces in the polymer matrix. Static magnetic properties such as susceptibility and M-H loops were studied using a Physical Property Measurement System (PPMS). The variation of the magnetic responses were consistent with the varying volume concentration of the nanoparticles, the polymers themselves contributing diamagnetic responses. Overall, the reasonable dispersion and control over magnetic properties achieved in our experiments is promising for electromagnetic applications of these materials.

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