Effect of Enhanced Thermal Stability of Alumina Support Layer on Growth of Vertically Aligned Single-Walled Carbon Nanotubes and Their Application in Nanofiltration Membranes

Jung Bin In,Costas P. Grigoropoulos,Francesco Fornasiero,Seok-Min Kim,Yinmin Wang,Tung Xuan Tran,Aleksandr Noy,Kang Rae Cho

doi:10.1186/s11671-018-2585-3

Abstract

We investigate the thermal stability of alumina supporting layers sputtered at different conditions and its effect on the growth of aligned single-walled carbon nanotube arrays. Radio frequency magnetron sputtering of alumina under oxygen–argon atmosphere produces a Si-rich alumina alloy film on a silicon substrate. Atomic force microscopy on the annealed catalysts reveals that Si-rich alumina films are more stable than alumina layers with low Si content at the elevated temperatures at which the growth of single-walled carbon nanotubes is initiated. The enhanced thermal stability of the Si-rich alumina layer results in a narrower (< 2.2 nm) diameter distribution of the single-walled carbon nanotubes. Thanks to the smaller diameters of their nanotube pores, membranes fabricated with vertically aligned nanotubes grown on the stable layers display improved ion selectivity.

Highlights

Single-walled carbon nanotubes (SWCNTs) are promising materials for high-strength composites [1–3], high-speed transistors, flexible electronics [4], and nanofiltration membranes [5–7]
We explored the influence of alumina films sputtered at two different conditions on the growth of VA-SWCNTs at a high temperature (850 °C), where alumina thermal stability becomes critical
Thermal Stability of Alumina Layer atomic force microscopy (AFM) scanning on the annealed alumina films produced by the two different sputtering methods (Fig. 2) revealed drastic differences in thermal stability

Summary

Introduction

Single-walled carbon nanotubes (SWCNTs) are promising materials for high-strength composites [1–3], high-speed transistors, flexible electronics [4], and nanofiltration membranes [5–7]. For the latter application, the atomically smooth inner walls of pristine SWNTs provide nearly frictionless channels for molecular transport at extraordinarily fast rates [5, 8]. The thermal stability of a catalyst particle and the catalyst–substrate interaction is a crucial factor that determines catalyst thermal stability [15] In this regard, various chemically inert and thermally stable oxide catalyst-support layers such as oxides of silicon [15], In et al Nanoscale Research Letters (2018) 13:173 aluminum [15, 16], magnesium [17], and zirconium have been examined. Alumina (Al2O3) thin films have been widely used as a catalyst-support layer for growth of SWCNTs and have been shown to improve the growth yield of SWCNTs (including VA-SWCNTs) by preventing the formation of unwanted metal compounds and improving the dispersion of catalyst nanoparticles [13, 16]

Methods

Results

Conclusion