Authors: B.S. Mitchell
Affilation: Tulane University, United States
Pages: 849 - 851
Keywords: nanocomposites, hybrid materials, mechanical attrition
Near Net-Shape Manufacturing is a two-step materials processing technique, in which nanoparticles are formed via mechanical attrition, from which nanocomposites are formed by consolidation and densification using Hot Isostatic Pressing (HIP). The technique is general to all materials classes: metals, ceramics, polymer and even biological materials.The significant new accomplishments in this area are related to the extension of Near Net-Shape Manufacturing techniques into new classes of hybrid materials, particularly those involving polymers. Polymer-polymer, and polymer-ceramic nanocomposites are but two examples, in which improved blends and improved membrane performance, respectively, have been linked to the interfacial characteristics of the component nanoparticles. In Nafion®/ceramic nanocomposite proton-exchange membranes, concurrent increases in operating temperature, reduction in water uptake, and increased proton conductivity have been linked to the interfacial formation between polymer and ceramic components at the nanoscale. Similarly, polymer-polymer blends from immiscible polymers have been formed using Near Net-Shape Manufacturing.The resulting impact to the field of nanocomposite formation is that while the energy imparted during mechanical attrition can manifest itself in different ways in different materials; e.g., molecular weight reduction in polymers vs. amorphization of metals, the production of highly interfacial regions in the nanocomposite is common to all materials classes. It is these interfacial regions that lead to bulk property control, and ultimately, to property enhancement in nanocomposites. A description of these interfacial characteristics in polymer-based nanocomposites formed by Near Net-Shape Manufacturing is given, including the effect of processing parameters on Tg in polymer blends, and ionic group structure in Nafion® composite membranes.