In Situ Raman Monitoring of the Formation and Growth of Carbon Nanotubes via Chemical Vapor Deposition

Abstract

An in situ measurement technique based on Raman spectroscopy is established to simultaneously monitor the parameters of interest of the solid and gas phases during the formation and growth of carbon nanotubes (CNT) in a cold wall reactor for catalytic chemical vapor deposition (CCVD). Iron nanoparticles were used as a catalyst and acetylene as a carbon source. This new developed technique makes possible the simultaneous in situ measurement of the gas phase composition, the gas phase temperature and the micro structure of the deposited CNTs, such that finally the decomposition of the carbon source and its effect on the gas temperature and on the CNTs formation and growth can be followed as a function of the reaction time. Comprehensive qualitative and quantitative analyses have been performed to assess the catalyst performance with respect to the growing carbon nanostructures. On the basis of the real-time in situ Raman spectra of the emerging solid phase, the moment of nucleation or first signal detection, the time-range of the CNT growth and the end of the deposition is monitored via the characteristic D and G Raman bands for carbon materials. Information about catalytic activity is qualitatively provided and the estimated in situ D/G ratio reveals the defect and disorder content of the growing nanostructures. The Raman spectroscopy setup for the gas phase analysis exhibits high detection sensitivity as well as high accuracy and precision. Correlation could be found between the catalyst activity, acetylene conversion and micro structure of the resulting CNTs.

Diamond Deposition on Graphite in Hydrogen Microwave Plasma

“…(after the 3h process) to 11.2 cm -1 (13h), confirming a better quality of the diamond particles produced for longer etching/growth time (the smaller Δν value indicates a higher crystalline quality and purity [29,30]). The growth process of the diamond particles prepared by hydrogen plasma etching graphite as the carbon source is schematically shown in Figure 5.…”

Characterization and Catalytic Activity of Different Carbon Supported Pd Nanocomposites

“…The N-CNT samples shows relatively great I D /I G ratio (1.4), compared to the non-doped counterparts (SWCNT, MWCNT). I D /I G ration of nitrogen free, multiwall carbon nanotubes from acetylene were 1.05, [27] In the case of highly oriented pyrolytic graphite, the D band not visible on the Raman spectra, the I D /I G of the high graphitized single wall carbon nanotube was obtained 0.09 [28,29].…”

Advanced polymer processing technologies for micro‐ and nanostructured surfaces: A review

“…In general, the use of CVD processes in fabrication of superhydrophobic surfaces have served the two purposes: to create unique surface roughness and/or to deposit a low surface energy hydrophobic monolayer. [51][52][53][54][55][56][57][58][59][60][61][62][63] Crick et al [64] employed an aerosolassisted CVD (AACVD) technique to fabricate a superhydrophobic and photocatalytic surface. PDMS and functionalized titania nanoparticles were mixed in a chloroform solvent to fabricate films with surface projections of around 3-5 μm.…”