Functionally Graded Carbon Nanotubes by Dynamic Control of Morphology during Chemical Vapor Deposition

该补助金将支持基础研究，旨在揭示为国家利益的新兴应用制造对齐碳纳米管的过程中的基本机制。 碳纳米管是一种比人类头发丝的万分之一还小的管，可以被认为是原子厚度的薄片，无缝地包裹在管中。单个纳米管的上级化学和物理性质，以及通过大量排列的碳纳米管的能量和质量传输的集体独特的方向性，支撑了它们在许多关键技术领域的潜力。 碳纳米管的商业生产每年超过数千吨，并且用于依赖于将各种长度和直径的随机分散纳米管分散到基质中以增强复合材料性能的产品中。 然而，新兴的应用，如高功率密度器件，3D纳米电子，纳米多孔膜，和结构材料需要更精确的控制的空间变化的尺寸，顺序和层次形态排列的碳纳米管系综。 这项研究着眼于通过对它们的初始成核和随后的生长的新理解，产生在宽度和长度上都相同的垂直排列的碳纳米管的大阵列。这些由相同的纳米管组成的“森林”具有优异的机械性能，可以用于纳米管随机长度会导致性能差的新应用领域。 该项目的研究将有助于建立将纳米管的新兴应用推向市场所需的工艺-结构-性能关系，从而提高美国的经济竞争力，同时推进分子规模制造的大学教育。通过继续开发YouTube频道，向普通观众解释与纳米技术相关的主题，将有助于公众宣传。垂直排列碳纳米管（VACNTs）的集体性质取决于其宏观森林状结构的空间变化形态。然而，目前缺乏对控制大CNT群体的成核动力学的机械化学因素的理解，导致无法在数十亿CNT的同时生长期间以可重复的方式控制这些变化。该项目旨在填补这一知识空白，以精确控制通过快速热化学气相沉积（RT-CVD）生长的空间工程VACNT，并预测其特性。这将通过VACNTs在周期性生长条件下的实验性生长来实现，其中原位监测高度动力学，结合基于非原位X射线的形态表征和电子显微镜，以及从基底结合的催化剂纳米颗粒成核的CNT的催化活化和失活速率的随机建模。因此，从这个项目产生的结果将使可预见的调整CVD生长的碳纳米管在一个过程中，是相关的工业CNT production.This奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的知识价值和更广泛的影响审查标准.

This grant will support basic research aimed at revealing the fundamental mechanisms underlying the process of manufacturing aligned carbon nanotubes for emerging applications of national interest. Carbon nanotubes are tubes that are smaller than one ten-thousandth of a human hair and can be thought of as atom-thick sheets that are wrapped seamlessly into tubes. The superior chemical and physical properties of individual nanotubes, as well as the collective unique directionality of energy and mass transport through large populations of aligned carbon nanotubes underpin their potential in many critical technological areas. The commercial production of carbon nanotubes exceeds several thousand tons per year and are used in products that rely on the random dispersion nanotubes of various lengths and diameters into a matrix to enhance the composite properties. However, emerging applications such as high power-density devices, 3D nanoelectronics, nanoporous membranes, and structural materials require more precise control of the spatial variation of sizes, order and hierarchical morphology of aligned carbon nanotube ensembles. This research looks to producing, through new understanding of their initial nucleation and subsequent growth, large arrays of vertically aligned carbon nanotubes which are all identical in width and length. These 'forests' of identical nanotubes have excellent mechanical properties and can be used in new application areas where the random length of the nanotubes would lead to poor performance. Research in this project will contribute knowledge towards building the process-structure-property relationship necessary for pushing emerging applications of nanotubes closer to market, leading to enhancing the American economic competitiveness, while advancing university-level education of molecular-scale manufacturing. Public outreach will be facilitated by the continued development of YouTube channel explaining nanotechnology-related topics to a general audience.The collective properties of vertically aligned carbon nanotubes (VACNTs) are dependent on the spatially varying morphology across their macroscopic forest-like structure. However, there is currently a lack of understanding of the mechanochemical factors governing the nucleation kinetics of large CNT populations, leading to an inability to control these variations in a repeatable fashion during the simultaneous growth of billions of CNTs. This project aims at filling this knowledge gap to enable precise control of spatially-engineered VACNTs grown by rapid thermal chemical vapor deposition (RT-CVD) and allow predicting their properties. This will be achieved by experimental growth of VACNTs under periodic growth conditions with in situ monitoring of height kinetics, combined with ex situ X-ray-based morphological characterization and electron microscopy, as well as stochastic modeling of the rates of catalytic activation and deactivation of CNTs nucleating from substrate-bound catalyst nanoparticles. Hence, the results generated from this project will enable predictably tuning CVD-grown CNTs in a process that is relevant to industrial CNT production.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.