Department of Chemistry and Institute for Nanotechnology, Bar-Ilan University, Ramat Gan, 52900, Israel.
Nanoscale. 2014;6(3):1545-51. doi: 10.1039/c3nr05240k.
Here we demonstrate an approach to enhance the growth of vertically aligned carbon nanotubes (CNTs) by including a catalyst reservoir underneath the thin-film alumina catalyst underlayer. This reservoir led to enhanced CNT growth due to the migration of catalytic material from below the underlayer up to the surface through alumina pinholes during processing. This led to the formation of large Fe particles, which in turn influenced the morphology evolution of the catalytic iron surface layer through Ostwald ripening. With inclusion of this catalyst reservoir, we observed CNT growth up to 100% taller than that observed without the catalyst reservoir consistently across a wide range of annealing and growth durations. Imaging studies of catalyst layers both for different annealing times and for different alumina support layer thicknesses demonstrate that the surface exposure of metal from the reservoir leads to an active population of smaller catalyst particles upon annealing as opposed to a bimodal catalyst size distribution that appears without inclusion of a reservoir. Overall, the mechanism for growth enhancement we present here demonstrates a new route to engineering efficient catalyst structures to overcome the limitations of CNT growth processes.
在这里，我们展示了一种通过在薄膜氧化铝催化剂底层下方包含催化剂储层来增强垂直排列碳纳米管 (CNT) 生长的方法。由于在处理过程中，催化材料通过氧化铝针孔从底层下方迁移到表面，因此储层导致 CNT 生长增强。这导致形成了大的 Fe 颗粒，这些颗粒通过奥斯特瓦尔德熟化反过来影响催化铁表面层的形态演变。通过包含这个催化剂储层，我们观察到 CNT 的生长比没有催化剂储层的情况下高 100%，这在广泛的退火和生长时间范围内都是一致的。对不同退火时间和不同氧化铝支撑层厚度的催化剂层的成像研究表明，储层中金属的表面暴露导致退火时出现更小的催化剂颗粒的活性群体，而不是没有储层时出现的双峰催化剂尺寸分布。总的来说，我们在这里提出的生长增强机制展示了一种新的工程有效催化剂结构的途径，以克服 CNT 生长过程的限制。
