One millimeter per minute growth rates for single wall carbon nanotube forests enabled by porous metal substrates.

Naoyuki Matsumoto,Don N Futaba,Kenji Hata,Sachiko Ishizawa,Guohai Chen,Azusa Oshima

doi:10.1039/c7ra13093g

Abstract

We report an exceptionally high-efficiency synthesis of long single-wall carbon nanotube (SWCNT) forests using porous substrates (metal meshes) in place of nonporous flat substrates. This study examined the dependence of the growth efficiency on various mesh structures, including wire diameter, aperture size, and total surface area. We demonstrated that the synthesis of SWCNT forests is highly dependent on the initial porosity as well as maintaining the open pores throughout the duration of the growth. Our results show that carbon nanotubes (CNTs) can be grown on all surfaces of the mesh in high efficiency with the optimum growth efficiency observed for a mesh porosity of ∼30%. Based on these results, we demonstrated the high efficiency synthesis of SWCNT forests (height: >3.47 mm, average growth rate: 301 μm min−1, and yield: 12.7 mg cm−2 in 10 min growth time). Furthermore, we showed that the initial growth rates exceeded 1 millimeter per minute (1000 μm min−1). Our results further indicate that metal meshes represent a viable alternative to nonporous flat substrates for the efficient synthesis of tall and high yielding SWCNTs.

Highlights

Over the past 25 years, since the discovery of the single-walled carbon nanotube (SWCNT),[1,2] the eld has taken great strides in the development of SWCNT-based and carbon nanotube (CNT)-based applications, such as composite materials, strain sensors, and bers.[3,4,5] Utilizing their unique structural characteristics, such as diameter, density, and chirality, many of these applications bene t from their high aspect ratio, i.e. long length
Unlike xed bed reactors, the substrate is set at a xed position in the reactor, and the gas ow rate can be adjusted without changes in particle uidization. This independent control of the growth time and gas ow is advantageous for determining a process for optimizing the process time and synthesizing long SWCNTs
We report the examination of metal meshes as representative porous substrates and alternatives to nonporous substrates for high efficiency SWCNT synthesis

Summary

Introduction

Over the past 25 years, since the discovery of the single-walled carbon nanotube (SWCNT),[1,2] the eld has taken great strides in the development of SWCNT-based and carbon nanotube (CNT)-based applications, such as composite materials, strain sensors, and bers.[3,4,5] Utilizing their unique structural characteristics, such as diameter, density, and chirality, many of these applications bene t from their high aspect ratio, i.e. long length. One of the most common ways to efficiently grow long CNTs is to grow them as a vertically aligned assembly, o en called a “forest”. In this way, the catalysts, which are deposited onto a substrate can grow in bulk up to the millimeter-scale,[6,7,8] and have served as the basis for mass production, which is essential for the development of the CNT industry.[9] the development of high efficiency and large throughput methods for SWCNT synthesis is important for realizing the practical use of SWCNT applications. Unique to the water-assisted approach is the exceptionally high growth rates and relatively long catalyst lifetime.[11,12]

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