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

尽管在过去的二十年中，通过化学气相沉积在按比例放大碳纳米管制造方面取得了重大进展，但该工艺仍然面临关键挑战，例如由于催化剂寿命短而导致的产率低、纳米管成核密度低、生产速率慢、纳米管性质变化，导致纳米管成本高。由于生长过程对原料组成和流动特性的变化高度敏感，化学气相沉积经常受到复杂优化程序的困扰。对于利用碳纳米管固有的电和热各向异性的能源应用，例如热界面材料和电池电极，需要在几乎不支持生长的导电衬底上直接生长有组织的纳米管架构。该奖项为工业废气混合物作为原料在非传统基底上可规模化、低成本和连续制造高质量碳纳米管阵列铺平了道路。使用这种原料进行纳米管生长可以最大限度地减少炼油厂的烟道气，从而增强环境保护。该研究提供了一个平台，教育学生在许多层面，包括妇女和代表性不足的少数民族，在有关纳米科学，纳米技术和nanomanufacturing.The项目开发的主题需要耦合催化化学气相沉积费托合成（FTS）过程中的废物流的碳纳米管（CNT）阵列的可扩展和控制的增长的基本理解。该项目研究计划通过气相化学的修改，合理的催化剂基质改性，以及催化剂和CNT阵列的先进的非原位和原位表征，结合反应工程。由此产生的理解的废气混合物和催化剂-衬底的相互作用，在CNT生长增强的作用提供了一个合理的基础上优化和扩大CNT生长的非传统衬底。与需要严格工艺控制和生长速率的常规原料不同，CNT的面积密度及其质量通常对生长期间的废气分数不太敏感，因此允许容易的优化和放大。该研究有望有助于深入了解催化剂-基底相互作用，不同反应条件下的催化剂演变以及CNT生长过程中的气相化学。这项研究有可能在多种应用中产生广泛的影响，包括能量存储和热管理。

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.