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Changes in the gas composition during the methane chemical vapor deposition growth of single- and double-walled carbon nanotubes over metal-supported MgO catalysts were investigated in an attempt to increase the nanotube yield. Monitoring the gas composition by gas chromatography as a function of the reaction time provides information on the activity and lifetime of the catalyst. The degree of methane...
The addition of nanofeatures to carbon microelectromechanical system (C-MEMS) structures would greatly increase surface area and enhance their performance in miniature batteries, super-capacitors, electrochemical and biological sensors. Negative photoresist posts were patterned on a Au/Ti contact layer by photolithography. After pyrolyzing the photoresist patterns to carbon patterns, graphitic nanofibers...
The use of selected area electron diffraction and centered dark field imaging using a transmission electron microscope is demonstrated for studying the herringbone structure of carbon nanofibers (CNFs). The experimental method is described and illustrated with CNFs that were grown via a chemical vapor deposition method with a nickel catalyst. It is demonstrated that this method gives the angle of...
The use of graphene layer encapsulated catalytic metal particles for the growth of narrower multi-walled carbon nanotubes (MWCNTs) has been studied using plasma-enhanced chemical vapor deposition and conventional thermal CVD. Ni–C or Fe–C composite nanoclusters were fabricated using the dc arc discharge technique with metal–graphite composite electrodes carrying a current of 100–200A in a stainless-steel...
Catalytically grown carbon nanofibers, a novel mesoporous carbon material for catalysis, were synthesized by the decomposition of carbon-containing gases (CH 4 , C 2 H 4 or CO) over supported nickel-iron alloy and unsupported iron. It was shown that the structures of as-synthesized and modified CNFs, including the arrangement of the graphenes in CNF, and the crystallinity and...
An efficient procedure for the purification of single-walled carbon nanotubos (SWCNTs) based on chemical treatment and physical separation is proposed and studied step-by-step by high-resolution transmission electron microscopy, thermogravimetric analyses, and nitrogen adsorption techniques. Impure raw samples prepared by the arc-discharge method containing SWCNTs, amorphous carbon, graphitic particles,...
Carbon nanotubes are synthesized by cold wall chemical vapor deposition (CVD) using methane as the carbon source and iron thin film catalyst. The yield of thin nanotubes as determined by scanning electron microscopy (SEM) is strongly dependent on the precise CVD process and the preparation of the substrate. The effects of pressure (5–80kPa), temperature (700–950°C), substrate conditioning (air preheat)...
We have synthesized double wall carbon nanotubes (DWNTs) with few defects and little amorphous carbon by hot wall chemical vapor deposition (CVD) of alcohol. Catalysts for the DWNT growth were made from cobalt and molybdenum acetates. Scanning electron microscopy, transmission electron microscopy, multi frequency resonance Raman spectroscopy and optical absorption spectroscopy were used for characterization...
Scalable large graphene single crystals have been synthesized by using a backward faced quartz cuvette in a conventional tube furnace. The effect of the restricted chamber in controlling the graphene single crystal growth has been systematically studied by considering the influence of the flow rate and ratio of H2 and CH4 experimentally. Numerical simulations were performed to uncover the underlying...
Recently, hexagonal boron nitride (h-BN) has been shown to act as an ideal substrate to graphene by greatly improving the material transport properties thanks to its atomically flat surface, low interlayer electronic coupling and almost perfect reticular matching [1]. Chemical vapour deposition (CVD) is presently considered the most scalable approach to grow graphene directly on h-BN. However, for...
The oxidative carbon removal from Cu foils was systematically studied together with the resulting suppression of the graphene flake nucleation during subsequent chemical vapor deposition (CVD). The carbon content was determined by segregating bulk dissolved carbon during a special rapid cooling process towards the surface, where it was detected by x-ray photoelectron spectroscopy. After exposure to...
Metal catalysts supporting the growth of Single Wall Carbon Nanotubes display different carbon solubilities and chemical reactivities. In order to specifically assess the role of carbon solubility, we take advantage of the physical transparency of a tight binding model established for Ni-C alloys, to develop metal carbon models where all properties, except carbon solubility, are similar. These models...
The objective of this paper is to investigate the acoustical performance of thermoacoustic sound generating devices made of bi-layer graphene and graphene foam. Bi-layer graphene and graphene foam were synthesized using chemical vapor deposition and characterized using HR Raman, X-ray photoelectron spectra, and FE-SEM. The sounds generated by the thermoacoustic devices are measured using a microphone...
Producing graphene with minimal crystalline defects and a controllable number of layers is highly desirable for its integration in advanced technological applications. Here we show how the chemical vapor deposition (CVD) protocol can be adjusted in order to control the size, the shape and the thickness of graphene domains. More particularly, this work focuses on the correlation between the conditions...
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