Conformal Carbon Nanotube Coatings for Ceramic Composite Structures
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Conformal Carbon Nanotube Coatings for Ceramic Composite Structures Ken Bosnick1, Pouyan Motamedi1, Tim Patrie1, Kenneth Cadien2 1
National Institute for Nanotechnology, National Research Council Canada, Edmonton, AB, Canada. 2
Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada. ABSTRACT Catalytic chemical vapor deposition enables the synthesis and deposition of carbon nanotubes (CNT) directly on substrates, thereby immobilizing them and potentially preventing them from bundling after synthesis. In this work, we investigate the use of this strategy to prepare ceramic hybrids with unbundled CNTs on aluminum oxide (AO) powder and fabric substrates, which are commonly used in the fabrication of ceramic laminate composites. CNT – AO powder hybrids are produced in 250 g batches with up to about 3 wt% CNT content, which is a sufficient amount for sintering into composite plates for mechanical and ballistic characterization. CNT – AO fabric hybrids are produced and it is found that the polymer coating that comes on the as-purchased fabric aids with CNT deposition. Conformal nickel and nickel oxide films deposited by an atomic layer deposition process are found to be excellent catalysts for CNT deposition. These conformal metal films are being used to create better CNT – ceramic hybrids for processing into better composite materials. INTRODUCTION Carbon nanotubes (CNTs) have been widely studied for the last couple of decades and it has been recognized for nearly as long that they should have a profound impact on the mechanical properties of composite materials [1]. The extreme aspect ratios, strong sp2 carbon bonds, and high chemical stability all contribute to making CNTs ideal reinforcement fillers. However, the problems associated with dispersing these materials in the composite's matrix has hindered the realization of this impact, as the CNTs tend to aggregate into bundles making them effectively much larger particles [2]. Various strategies, such as chemical functionalization, have been attempted to aid with the dispersion of bulk CNTs in a composite matrix during processing with some success [2]. Catalytic chemical vapor deposition (CVD) differs from other CNT synthesis methods in that the CNTs can be synthesized directly on a substrate, thereby immobilizing them and potentially preventing them from bundling after synthesis [3]. In this work, we investigate the use of this strategy to prepare ceramic composite structures with unbundled CNTs. CNTs are synthesized as conformal coatings on various ceramic materials, including aluminum oxide (AO) powder and fabric mats following a conformal catalyst deposition. The CNT deposition is carried out in a large volume CVD reactor [4,5]. The conformal catalyst is deposited by atomic layer deposition (ALD) of ultra-thin nickel or nickel oxide films, or via deposition from an iron nitrate solution. The resulting hybrid materials are characterized and the processing optimized to improve the CNT coatings. The optimized CNTceramic hybrids
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