The advent of high modulus and strength carbon nanotubes (CNT) has sparked tremendous interest in nanotube-based materials and related new forms of carbon. We propose to develop novel carbon-nanofiber-reinforced ceramics and metals as tough, damage-tolerant coatings for contact and wear applications to replace traditional hard coatings. Nanocomposites containing new engineered carbon nanofibers will be fabricated, evaluated, and optimized to trigger nanoscale toughening. We propose to (i) synthesize a set of wholly new nanocomposite materials using discotic self-assembly routes unique to Brown, and CVD methods to control the structure/properties of the nanofibrous reinforcements and resulting nanocomposites, (ii) demonstrate toughness and damage tolerance in these composite systems, (iii) elucidate toughening mechanisms in these nanocomposites, (iv) investigate a range of fabrication routes for these materials, and (v) evaluate the new materials under realistic wear conditions for aluminum and steel alloys used in automotive components and machining. We focus on carbon-based reinforcements in nanocomposite coatings due to our recent observations of toughening mechanisms in CNT/ceramic composites and because of the myriad ways in which we can produce and control carbon structures to engineer anisotropic properties. Because conventional CNTs may not be necessary to achieve nanoscale toughening, we will develop composites containing an entirely new classes of nanoscale carbon fiberous bodies synthesized by surface-mediated, low-temperature assembly of low-cost polyaromatic mesogenic precursors, which allows molecular engineering of anisotropy in properties, and of the surfaces that control fiber/matrix bonding. The overall synthesis of carbon/ceramic nanocomposites will involve our novel directed polyaromatic assembly and several deposition approaches for forming fiberous carbon materials in nanochannel alumina array templates so as to generate an array of nanoceramic composites with varying fiberous structure (nanotubes, solid graphitic fibrils, "open" structure fibrils and tubes), fiberous dimensions, interfacial adhesion, residual stresses, anisotropic thermal/elastic/strength properties, friction coefficients, and geometric order. Fabrication of nanometal-matrix composites will be performed by metal deposition into free-standing fiberous structures formed via CVD or via etching of the template ceramic matrix. Focused mechanical testing will measure toughness and damage resistance, and analysis will determine the toughening mechanisms and identify how structural/chemical details at multiple scales control enhanced toughness and wear performance. The PIs are dedicated to enhancing the impact of the technical work through integration of research and education, industrial outreach, and human resource development. The project will enhance the infrastructure for science and education by training graduate students, by establishing a summer internship program targeted at under-represented groups, by integrating innovative research activities into the curriculum, and by providing opportunities for graduate students to work at GM R&D. We will cooperate with local chapters of the Women in Science and Engineering, National Society for Black Engineers, and New Scientist Program to broadly disseminate the science and application of nanotechnology and to recruit active researchers. We will integrate nanotechnology concepts into existing NSF MRSEC programs and our entrepreneurship program.
