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

尽管在过去的二十年里，化学气相沉积法在碳纳米管制造方面取得了重大进展，但该工艺仍然面临着催化剂寿命短、成核密度低、生产速度慢、纳米管性能变化等关键挑战，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，化学气相沉积常常受到复杂的优化程序的困扰。对于利用碳纳米管固有的电和热各向异性的能源应用，如热界面材料和电池电极，需要有组织的纳米管结构直接生长在几乎不支持生长的导电衬底上。该奖项为工业废气混合物作为可扩展、低成本和连续制造高质量碳纳米管阵列的原料铺平了道路。将这种原料用于纳米管生长可最大限度地减少炼油厂的烟道气量，从而加强环境保护。这项研究提供了一个平台，可以在与纳米科学、纳米技术和纳米制造相关的主题上教育各个层次的学生，包括妇女和代表性不足的少数民族。该项目发展了将催化化学气相沉积与费托合成（FTS）工艺废液相结合的基本理解，以实现碳纳米管（CNT）阵列的可扩展和可控生长。项目研究计划结合气相化学修饰反应工程、合理的催化剂底物修饰、催化剂和碳纳米管阵列先进的非原位和原位表征。由此产生的对废气混合物和催化剂-基质相互作用在碳纳米管生长增强中的作用的理解，为在非传统基质上优化和扩大碳纳米管生长提供了合理的基础。与需要严格工艺控制和生长速率的传统原料不同，CNTs的面积密度及其质量通常对生长过程中废气的比例不太敏感，因此易于优化和放大。这项研究将有助于深入了解催化剂与底物的相互作用，催化剂在不同反应条件下的演化，以及碳纳米管生长过程中的气相化学。这项研究有明显的可能性在多种应用中具有广泛的意义，包括能量储存和热管理。

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.