Yang Ning, Li Meng, Patscheider Jörg, Youn Seul Ki, Park Hyung Gyu
Nanoscience for Energy Technology and Sustainability, Department of Mechanical and Process Engineering, Eidgennössische Technische Hochschule (ETH) Zürich, Tannenstrasse 3, Zürich CH-8092, Switzerland.
Laboratory for Nanoscale Material Science, Empa (Swiss Federal Laboratories for Materials Science and Technology), Überlandstrasse 129, Dübendorf CH-8600, Switzerland.
Sci Rep. 2017 Apr 21;7:46725. doi: 10.1038/srep46725.
A precise control of the dimension of carbon nanotubes (CNTs) in their vertical array could enable many promising applications in various fields. Here, we demonstrate the growth of vertically aligned, single-walled CNTs (VA-SWCNTs) with diameters in the sub-1.5-nm range (0.98 ± 0.24 nm), by engineering a catalyst support layer of alumina via thermal annealing followed by ion beam treatment. We find out that the ion beam bombardment on the alumina allows the growth of ultra-narrow nanotubes, whereas the thermal annealing promotes the vertical alignment at the expense of enlarged diameters; in an optimal combination, these two effects can cooperate to produce the ultra-narrow VA-SWCNTs. According to micro- and spectroscopic characterizations, ion beam bombardment amorphizes the alumina surface to increase the porosity, defects, and oxygen-laden functional groups on it to inhibit Ostwald ripening of catalytic Fe nanoparticles effectively, while thermal annealing can densify bulk alumina to prevent subsurface diffusion of the catalyst particles. Our findings contribute to the current efforts of precise diameter control of VA-SWCNTs, essential for applications such as membranes and energy storage devices.
精确控制垂直排列的碳纳米管（CNT）的尺寸能够在各个领域实现许多有前景的应用。在此，我们通过对氧化铝催化剂支撑层进行热退火，随后进行离子束处理，展示了直径在亚1.5纳米范围内（0.98 ± 0.24纳米）的垂直排列单壁碳纳米管（VA-SWCNT）的生长。我们发现，对氧化铝进行离子束轰击可实现超窄纳米管的生长，而热退火则以增大直径为代价促进垂直排列；在最佳组合下，这两种效应可协同产生超窄VA-SWCNT。根据微观和光谱表征，离子束轰击使氧化铝表面非晶化，从而增加其孔隙率、缺陷和含氧官能团，有效抑制催化铁纳米颗粒的奥斯特瓦尔德熟化，而热退火可使块状氧化铝致密化，防止催化剂颗粒的亚表面扩散。我们的研究结果有助于当前对VA-SWCNT进行精确直径控制的工作，这对于诸如膜和储能装置等应用至关重要。
