Characterization of silica-functionalized carbon nanotubes dispersed in water
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RESEARCH PAPER
Characterization of silica-functionalized carbon nanotubes dispersed in water Peter Stynoski • Paramita Mondal Erik Wotring • Charles Marsh
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Received: 21 September 2012 / Accepted: 21 December 2012 Ó Springer Science+Business Media Dordrecht 2013
Abstract Carbon nanotubes (CNTs) have the potential to enhance the strength, toughness, and multifunctional ability of composite materials. However, suitable dispersion and interfacial bonding remain as key challenges. Composites that are formed by reactions with water, like Portland cement concrete and mortar, pose a special challenge for dispersing the inherently hydrophobic nanotubes. The hydration of Portland cement also offers a specific chemical framework for interfacial bonding. In this study, nanoscale silica
Electronic supplementary material The online version of this article (doi:10.1007/s11051-012-1396-1) contains supplementary material, which is available to authorized users. P. Stynoski (&) P. Mondal Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, 205 N Mathews Avenue, Urbana, IL 61801, USA e-mail: [email protected] P. Mondal e-mail: [email protected] P. Stynoski E. Wotring C. Marsh US Army Construction Engineering Research Laboratory, 2902 Newmark Drive, Champaign, IL 61822, USA e-mail: [email protected] C. Marsh e-mail: [email protected] C. Marsh Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, 104 S Wright Street, Urbana, IL 61801, USA
functional groups are covalently bonded to CNTs to improve their dispersion in water while providing interfacial bond sites for the proposed matrix material. The bond signatures of treated nanotubes are characterized using Fourier transform infrared spectroscopy. In situ dispersion is characterized using cryogenic transmission electron microscopy and point of zero charge (PZC) measurements. At the nanoscale, interparticle spacing was greatly increased. A slight increase in the PZC after treatment indicates the importance of steric effects in the dispersion mechanism. Overall, results indicate successful functionalization and dramatically improved dispersion stability in water. Keywords Carbon nanotube (CNT) Functionalization Tetraethyl orthosilicate (TEOS) Dispersion Point of zero charge Portland cement Introduction Carbon nanotubes (CNTs) have gained popularity in several fields of study. Researchers have taken interest in harnessing the high specific strength, tunable electrical properties, and variable high-aspect ratio geometry of this material (Barreiro et al. 2006; Tombler 2000; Wong et al. 1997). The discovery of CNTs is usually attributed to Iijima (1991), who formed them by arc discharge and observed the cylindrical graphitic structure in an electron microscope. However, other studies reported as early as 1952 provide evidence of the synthesis and identification of CNTs (Monthioux and
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Kuznetsov 2006; Radushkevich and Lukyanovich
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