High-Yield Synthesis of Helical Carbon Nanofibers Using Iron Oxide Fine Powder as a Catalyst

Abstract

Carbon nanocoil (CNC), which is synthesized by a catalytic chemical vapor deposition (CCVD) method, has a coil diameter of 300-900 nm and a length of several tens of μm. Although it is very small, CNC is predicted to have a high mechanical strength and hence is expected to have a use in nanodevices such as electromagnetic wave absorbers and field emitters. For nanodevice applications, it is necessary to synthesize CNC in high yield and purity. In this study, we improved the conditions of catalytic layer formation and CCVD. Using optimized CVD conditions, a CNC layer with a thickness of >40 μm was grown from a SnO2/Fe2O3/SnO2 catalyst on a substrate, and its purity increased to 81% ± 2%.

Preparation of carbon nanofibers/tubes using waste tyres pyrolysis oil and coal fly ash derived catalyst

“…In this morphology, the graphene layers are arranged in a fish-bone structure along the vertical axis of the carbon filament. [15,53] The growth mechanism of CNMs is known to be exothermic in nature, therefore, there is a temperature gradient at the catalyst particle. [46,48] With the solubility of carbon on metal catalyst dependent on temperature, precipitation occurs at the colder zones of the metal catalyst and thus allowing the carbon filament to grow at the same diameter as the metal catalyst.…”

“…This challenge has led the research community into a quest for finding cheap feedstocks to substitute the conventional way of synthesis. [13][14][15][16][17][18] There have been reports of synthesizing CNMs using raw materials such as lava, natural minerals and botanical hydrocarbons. [19] However, there is still a need to identify other low-cost feedstocks.…”

Chemical Vapor Deposition of Helical Carbon Nanofibers

“…In this section, the experimental results that increase the purity of CNC by improving the structure of the catalyst layer and CVD conditions are introduced [52]. By forming a triplelayer structure of SnO 2 /Fe 2 O 3 /SnO 2 catalyst on the substrate and optimizing the CVD conditions, a CNC layer with a thickness of 40 μm or more was grown, and the CNC purity inside this layer successfully raised to 81 ± 2%.…”

Electromagnetic wave absorption properties of carbon nanocoil composites in the millimeter waveband

“…After that, we dropped the catalyst solution (150 μl) onto a graphite substrate heated at 350°C for 5 min, and the dripped solution was dry-heated for 5 min. We synthesized CNCs on the prepared catalyst substrate using a chemical vapor deposition (CVD) equipment [1] using the synthesis conditions shown in Table 1. As a result, about 700 mg of carbon deposits were synthesized on one substrate.…”

“…1. CNC is composed of amorphous carbon and is often synthesized from Fe-Sn binary catalyst [1]. The diameter of the fiber is in the range of 100 to 200 nm, the outside diameter of the coil about the helical axis is in the range of 300 to 900 nm, and the length is in the order of micrometer.…”