Nanomanufacturing of Vertically Aligned Carbon Nanotube Arrays from Industrial Waste Gas Mixture

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Although significant progress has been made in the past two decades in scaling up carbon nanotube manufacture via chemical vapor deposition, the process still faces key challenges such as poor yield due to short catalyst lifetime, low nanotube nucleation density, slow production rate, variations in nanotube properties, resulting in high cost of the nanotubes. Chemical vapor deposition is often plagued by complicated optimization procedures due to the high sensitivity of the growth process to variations in the feedstock composition and flow characteristics. For energy applications that exploit the intrinsic electrical and thermal anisotropy of carbon nanotubes, such as thermal interface materials and battery electrodes, organized nanotube architectures are required to be grown directly on conductive substrates that hardly support growth. This award paves the way for an industrial waste-gas mixture to be used as a feedstock for scalable, low-cost, and continuous manufacture of high-quality carbon nanotube arrays on nontraditional substrates. The use of this feedstock for nanotube growth minimizes the amount of flue gases in oil refineries, thus enhancing environmental protection. The study provides a platform for educating students at many levels, including women and under-represented minorities, on topics related to nanoscience, nanotechnology and nanomanufacturing.The project develops the fundamental understanding required to couple catalytic chemical vapor deposition to the waste stream of Fischer-Tropsch synthesis (FTS) process for scalable and controlled growth of carbon nanotube (CNT) arrays. The project research plan combines reaction engineering through modification of gas-phase chemistry, rational catalyst substrate modification, and advanced ex situ and in situ characterization of catalysts and CNT arrays. The resulting understanding of the roles of the waste-gas mixture and catalyst-substrate interactions in CNT growth enhancement provides a rational basis for optimization and scale-up of CNT growth on nontraditional substrates. Unlike conventional feedstocks that require strict process control and growth rate, area density of CNTs and their quality are generally less sensitive to the fraction of the waste gas during growth, and thus allow for easy optimization and scale-up. The research is expected to contribute in-depth understanding of catalyst-substrate interactions, catalyst evolution under different reaction conditions, and gas-phase chemistries during CNT growth. This study has the distinct possibility of having broad implications in multiple applications, including energy storage and thermal management.