skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Synthesis of high yield single helical carbon microsprings by catalytic chemical vapor deposition and an experimental investigation of their growth mechanism

Abstract

A type of single helical carbon microsprings (SHCMSs) was synthesized by catalytic chemical vapor deposition. The as-prepared SHCMSs were characterized by a number of techniques such as scanning and transmission electron microscopy, x-ray powder diffraction, and x-ray photoelectron spectroscopy. Experimental results indicate that during the synthesis both morphology change and crystalline phase transformation occur for cobalt catalytic particles and certain chemical bonding form between cobalt and sulfur atoms. Based on the data from this study, a possible growth mechanism of SHCMSs was discussed.

Authors:
;  [1]
  1. Nanomaterials and nanotubes Research Laboratory, Center of Excellence for Nano-, Micro-, and Neuro-Electronics, Sensors and Systems, College of Engineering, University of Arkansas, 700 Research Center Boulevard, Fayetteville, Arkansas 72701 (United States)
Publication Date:
OSTI Identifier:
20979424
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 11; Other Information: DOI: 10.1063/1.2737381; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CARBON; CATALYSTS; CHEMICAL BONDS; CHEMICAL VAPOR DEPOSITION; COBALT; CRYSTAL GROWTH; MORPHOLOGY; NANOSTRUCTURES; PARTICLES; PHASE TRANSFORMATIONS; SCANNING ELECTRON MICROSCOPY; SULFUR; SYNTHESIS; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION; X-RAY PHOTOELECTRON SPECTROSCOPY

Citation Formats

Xie Jining, and Varadan, V. K. Synthesis of high yield single helical carbon microsprings by catalytic chemical vapor deposition and an experimental investigation of their growth mechanism. United States: N. p., 2007. Web. doi:10.1063/1.2737381.
Xie Jining, & Varadan, V. K. Synthesis of high yield single helical carbon microsprings by catalytic chemical vapor deposition and an experimental investigation of their growth mechanism. United States. doi:10.1063/1.2737381.
Xie Jining, and Varadan, V. K. Fri . "Synthesis of high yield single helical carbon microsprings by catalytic chemical vapor deposition and an experimental investigation of their growth mechanism". United States. doi:10.1063/1.2737381.
@article{osti_20979424,
title = {Synthesis of high yield single helical carbon microsprings by catalytic chemical vapor deposition and an experimental investigation of their growth mechanism},
author = {Xie Jining and Varadan, V. K.},
abstractNote = {A type of single helical carbon microsprings (SHCMSs) was synthesized by catalytic chemical vapor deposition. The as-prepared SHCMSs were characterized by a number of techniques such as scanning and transmission electron microscopy, x-ray powder diffraction, and x-ray photoelectron spectroscopy. Experimental results indicate that during the synthesis both morphology change and crystalline phase transformation occur for cobalt catalytic particles and certain chemical bonding form between cobalt and sulfur atoms. Based on the data from this study, a possible growth mechanism of SHCMSs was discussed.},
doi = {10.1063/1.2737381},
journal = {Journal of Applied Physics},
number = 11,
volume = 101,
place = {United States},
year = {Fri Jun 01 00:00:00 EDT 2007},
month = {Fri Jun 01 00:00:00 EDT 2007}
}
  • Nonequilibrium quantum chemical molecular dynamics (QM/MD) simulation of early stages in the nucleation process of carbon nanotubes from acetylene feedstock on an Fe38 cluster was performed based on the density-functional tight-binding (DFTB) potential. Representative chemical reactions were studied by complimentary static DFTB and density functional theory (DFT) calculations. Oligomerization and cross-linking reactions between carbon chains were found as the main reaction pathways similar to that suggested in previous experimental work. The calculations highlight the inhibiting effect of hydrogen for the condensation of carbon ring networks, and a propensity for hydrogen disproportionation, thus enriching the hydrogen content in already hydrogen-rich speciesmore » and abstracting hydrogen content in already hydrogen-deficient clusters. The ethynyl radical C2H was found as a reactive, yet continually regenerated species, facilitating hydrogen transfer reactions across the hydrocarbon clusters. The nonequilibrium QM/MD simulations show the prevalence of a pentagon-first nucleation mechanism where hydrogen may take the role of one arm of an sp2 carbon Y-junction. The results challenge the importance of the metal carbide formation for SWCNT cap nucleation in the VLS model and suggest possible alternative routes following hydrogen-abstraction acetylene addition (HACA)-like mechanisms commonly discussed in combustion synthesis.« less
  • The influence of temperature on synthesizing single-walled carbon nanotubes (SWCNTs) by catalytic chemical vapor deposition of methane over Mo-Co-MgO catalyst was studied by Transmission Electron Microscope (TEM) and Raman scattering. The Mo-Co-MgO bimetallic catalyst was prepared by decomposing the mixture of magnesium nitrate, ammonium molybdate, citric acid, and cobalt nitrate. The results show that Mo-Co-MgO bimetallic catalyst is effective to synthesize SWCNTs. By using Mo-Co-MgO bimetallic catalyst, generation of SWCNTs even at 940 K was demonstrated. The optimum temperature of synthesizing SWCNTs over Mo-Co-MgO bimetallic catalyst may be about 1123 K. At 1123 K, the diameters of SWCNTs are inmore » the range of 0.75-1.65 nm. The content of SWCNTs is increased with the increase of temperature below 1123 K and the carbon yield rate is also increased with the increase of synthesis temperature. Therefore, the amount of SWCNTs increases with the increase of temperature below 1123 K. However, above 1123 K, the content of SWCNTs is decreased with the increase of temperature; therefore, it is not effective to increase the amount of SWCNTs through increasing synthesis temperature above 1123 K.« less
  • Abstract not provided.
  • Highlights: ► The well crystalline and structurally uniform SnO{sub 2} nanobelts were prepared. ► Au-modified small Sn particle was used as source material to ensure the high yield. ► The SnO{sub 2} nanobelt exhibited better gas sensing property to NO{sub 2} than nanoparticle. ► The SnO{sub 2} nanobelt showed obvious sensing selectivity towards NO{sub 2} over CO and CH{sub 4}. -- Abstract: Well-crystallized one-dimensional (1D) SnO{sub 2} nanobelts were in situ prepared using a simple water-assisted chemical vapor deposition (CVD) method. The small Sn particles with Au-modifications were used as source materials instead of big size Sn grains to ensuremore » the high yield of SnO{sub 2} belts. The Au layer was modified on the small Sn particles by treating Sn powders in HAuCl{sub 4} solution combined with the UV irradiation. The as-prepared SnO{sub 2} nanobelts were characterized by SEM, HRTEM, XRD, EDS and XPS. These results indicate that the growth temperature plays an important role in controlling the length-to-width ratio of nanobelts. The length-to-width ratio decreases with the growth temperature from 850 °C to 1000 °C. The nanobelts prepared at 850 °C shows a single-crystalline tetragonal rutile phase with a high length-to-width ratio (approximately tens of microns in length and 40–70 nm in width). However, below 850 °C, nanobelts cannot be formed. The as-prepared nanobelts exhibited excellent sensing properties compared with SnO{sub 2} nanoparticles and high sensing selectivity towards NO{sub 2}. The high sensing selectivity to NO{sub 2} is attributed to the oxygen vacancies presenting in the as-prepared nanobelts.« less