Abstract
Vertically aligned carbon nanotubes (VA-CNTs) were successfully grown on silicon substrates by atmospheric pressure chemical vapor deposition at 750∘C using acetylene as a carbon source and Fe-Co nanoparticle thin films as a cocatalyst. Preparation of the cocatalyst was operated by an economical sparking process. A small amount of water vapor was introduced into the reactor by controlling diffusion by heated water in a flask. The CNTs were characterized by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The VA-CNTs were obtained only when the water vapor fraction in the introduced gas was in the range of 310–440 ppm. The length of the VA-CNTs reached 0.8 mm with a growth rate of 17 μm/min. Moreover, D/G-band ratio suggests that the optimum fraction of water vapor decreases defects in CNTs.
Highlights
Carbon nanotubes (CNTs) are regarded as one of the most promising materials for various potential applications, such as electrodes for electrochemical double-layer capacitors [1,2,3], field emitters [4, 5] in flat panel displays, electron source in X-ray tubes [6], and nanoelectronic devices [7, 8]
Nasibulin and coworkers have demonstrated the effect of CO2 and H2O vapor on the synthesis of CNT grown in situ using premade Co and Fe catalyst nanoparticles and particles deposited by a hot wire generator [21]
Water vapor plays a critical role in the length of vertically aligned CNT synthesis
Summary
Carbon nanotubes (CNTs) are regarded as one of the most promising materials for various potential applications, such as electrodes for electrochemical double-layer capacitors [1,2,3], field emitters [4, 5] in flat panel displays, electron source in X-ray tubes [6], and nanoelectronic devices [7, 8]. We believe that a simple and economical fabrication system is essential for further industrial manufacturing In this view, we aimed at eliminating the traditional costly equipment for catalyst deposition and water vapor insertion. We used an iron-cobalt cocatalyst, prepared from a sparking process [19, 20] in conjunction with a diffusion-controlled water insertion method. The amount of vapor is essential in order to achieve high-purity and long vertically aligned CNTs [21] and the diffusion-controlled insertion allows precise control of water vapor even for very low gas flows. We focused on an alternative way of preparing the catalyst in a cost-effective and simple manner, using a highvoltage sparking process that can produce evenly distributed 5–30 nm in diameter nanoparticles.
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