High-speed in situ X-ray scattering of carbon nanotube film nucleation and self-organization.
High-speed in situ X-ray scattering of carbon nanotube film nucleation and self-organization.
复制标题
碳纳米管薄膜成核和自组织的高速原位X射线散射。
作者：
E. Meshot;Eric Verploegen;M. Bedewy;S. Tawfick;A. Woll;K. Green;M. Hromalik;M. Hromalik;L. Koerner;L. Koerner;H. Philipp;M. Tate;S. Gruner;A. Hart
高性能碳纳米管（CNT）材料的生产需要了解单个CNT的生长行为以及CNT之间的集体效应。我们证明了第一次使用掠入射小角度X射线散射监测真实的时间的CNT薄膜的化学气相沉积的合成。我们使用一个定制的冷壁反应器沿着与高速像素阵列探测器，导致10毫秒的时间分辨率。应用于时间分辨的X射线散射图案的定量模型表明，Fe催化剂膜在还原气氛中加热期间首先迅速dewets成定义明确的半球形颗粒，然后颗粒在继续退火后缓慢粗化。在引入碳源之后，初始CNT直径分布与催化剂颗粒的直径分布紧密匹配。然而，在随后的CNT自组织过程中，CNT直径可以迅速发生显著变化。时间分辨的取向数据的X射线散射强度和高度动力学的相关性表明，自组织的速率是由CNT的生长速率和密度，和垂直CNT生长突然开始时，CNT对齐达到临界阈值。CNT尺寸演变和自组织的动力学根据催化剂退火条件和衬底温度而变化。了解这些本质上快速的过程对于改善CNT结构的控制以及能够有效制造长直CNT的高密度阵列至关重要。
The production of high-performance carbon nanotube (CNT) materials demands understanding of the growth behavior of individual CNTs as well as collective effects among CNTs. We demonstrate the first use of grazing incidence small-angle X-ray scattering to monitor in real time the synthesis of CNT films by chemical vapor deposition. We use a custom-built cold-wall reactor along with a high-speed pixel array detector resulting in a time resolution of 10 msec. Quantitative models applied to time-resolved X-ray scattering patterns reveal that the Fe catalyst film first rapidly dewets into well-defined hemispherical particles during heating in a reducing atmosphere, and then the particles coarsen slowly upon continued annealing. After introduction of the carbon source, the initial CNT diameter distribution closely matches that of the catalyst particles. However, significant changes in CNT diameter can occur quickly during the subsequent CNT self-organization process. Correlation of time-resolved orientation data to X-ray scattering intensity and height kinetics suggests that the rate of self-organization is driven by both the CNT growth rate and density, and vertical CNT growth begins abruptly when CNT alignment reaches a critical threshold. The dynamics of CNT size evolution and self-organization vary according to the catalyst annealing conditions and substrate temperature. Knowledge of these intrinsically rapid processes is vital to improve control of CNT structure and to enable efficient manufacturing of high-density arrays of long, straight CNTs.