Synthesis and properties of an aluminum nitride/polyimide nanocomposite prepared by a nonaqueous suspension process
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Synthesis and properties of an aluminum nitride/polyimide nanocomposite prepared by a nonaqueous suspension process Xiaohe Chen and Kenneth E. Gonsalvesa) Polymer Science Program at the Institute of Materials Science and Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269 (Received 12 June 1996; accepted 6 December 1996)
A nanocomposite of a chemically synthesized nanostructured aluminum nitride (AlN) and a polyimide has been studied. Using a nonaqueous polar solvent, N-methylpyrrolidinone (NMP), as the suspension media, the degree of particle agglomeration of AlN was reduced dramatically from micron to nanoscale size. Upon the addition of poly(amic acid) to the AlN/NMP suspension, a further deagglomeration of the particles was observed. The surface physicochemical interactions have been investigated by characteristic model reactions using FTIR spectroscopy. A mechanistic interpretation for the deagglomeration and stabilization behavior is discussed. The formation of the AlN/PI nanocomposite was achieved by the rapid solidification of the precursor suspension followed by compression molding. Such an approach for nanocomposites exhibits better homogeneity with ultrafine fillers and allows a tailorable composition and property at the nanoscale level. Finally, AlN/PI nanocomposites with an increased ceramic loading, up to 65% by volume, were attained and their thermal and mechanical properties, along with the compositional effects, have been investigated.
I. INTRODUCTION
Nanostructured materials can be defined as materials having an average grain or particle size of less than 100 nm.1,2 Due to the high surface-to-volume ratio, it is anticipated that they will exhibit a unique behavior compared to conventional materials with micron-scale structures.1–5 The efforts and successes in synthesizing a variety of nanostructured materials have provided a new degree of freedom for the development of advanced materials with enhanced or novel properties. Nanocomposites represent the current trend in developing novel nanostructured materials. They can be defined as a combination of two or more phases containing different compositions or structures, where at least one of the phases is in the nanoscale regime.6 Examples of inorganic-organic hybrid nanocomposites include biomimetic ceramic/polymer composites,7 nonlinear optical metal colloid polymer nanocomposites,8,9 and intercalated polymer-clay nanocomposites.10 The synthesis of nanocomposites usually involves a multistep process, which may include several basic preparation techniques, such as sol-gel/polymerization, sol-gel/thermal pyrolysis, dispersion/solidification, and intercalation/solidification. An ideal nanocomposite would be one free of agglomerates, that contains the optimum content of filler powder while still maintaining its physicochemical characteristics. Development of mixing processes for a stable, a)
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