Graphite sublimation temperatures, carbon arcs and crystallite erosion

Abrahamson, John

doi:10.1016/0008-6223(74)90019-0

Cited by 78 publications

(33 citation statements)

References 20 publications

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“…While calculating the energies entering the particles from laser irradiation and leaving from thermal radiation are relatively straightforward, estimating the thermal loss due to contact with the substrate is more uncertain. At the threshold of conditioning, we assume the particle temperature is just high enough to reach the sublimation temperature of carbon, 4000 K [8]. Given steady state conditions, the power entering and leaving the particle at this temperature and irradiance are the same, allowing us to estimate the contact conductance with the substrate, see Eq.…”

Section: Discussionmentioning

confidence: 99%

Continuous-wave laser particle conditioning: Thresholds and time scales

Brown

Ogloza

Olson

et al. 2017

Optics & Laser Technology

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Section: Discussionmentioning

confidence: 99%

Continuous-wave laser particle conditioning: Thresholds and time scales

Brown

Ogloza

Olson

et al. 2017

Optics & Laser Technology

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“…Abrahamson proposed the presence near the anodic surface [12] of small crystallites (<3nm), derived from the breakup of the electrode surface during arc operation. He suggested that the observed temperature of the surface was in fact the temperature of these suspended particles, which were at their equilibrium temperature at the arc total pressure (here 1 atmosphere), considerably lower than the expected sublimation temperature of bulk graphite (3950K) because of the surface free energy.…”

Section: Discussionmentioning

confidence: 99%

Parameters affecting deposition of multiwalled carbon nanotubes on a continuously fed substrate using arc discharge

Shastry

Abrahamson

Yusoff

et al. 2006

2006 International Conference on Nanoscience and Nanotechnology

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Carbon nanotubes have been extensively studied since their discovery [1] due to their valuable structural and electronic properties. Direct growth of nanotubes on substrates is essential for their integration into various applications, as individual manipulation into position is both difficult and expensive due to their size. A unique single-step method has been developed of continuously depositing nanotubes on a carbon substrate using an arc discharge at atmosphere pressure [8]. This method differs from the conventional arc discharge method in that the nanotubes are grown at low currents on a moving substrate surface which acts as one of the electrodes.The effects of inter-electrode gap, buffer gas flow through the porous substrate and substrate speed on the yield and morphology of carbon nanotubes are investigated. It was found that an inter-electrode gap range of 2.5 -6.0mm is optimal for nanotube occurrence on the carbon substrate. Providing a flushing gas flow into the arc through the substrate reduced the mean diameter but not the number of nanotubes and markedly reduced the number of attached nanoparticles. The residence time of the substrate in the arc was varied by changing substrate velocity, and this was found to be critical for nanotube formation. From the parameters explored, it appears that the substrate temperature alone governs nanotube formation and this occurs at temperatures lower than reasonable sublimation temperatures. This latter fact together with the lack of influence of gas flush, indicate that carbon vapour is unlikely to dominate the formation of nanotubes in arcs.

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“…anode brightness temperature [15]. He argued that a cloud of these small crystallites evaporating at 3800 K or less might influence the radiance observed, thus the value of measured temperature.…”

Section: • Gravity Effect Is Negligiblementioning

confidence: 99%

Influence of anode surface temperature in a continuously-fed arc discharge depositing carbon nanotubes

Yusoff

Abrahamson

Shastry

2006

2006 International Conference on Nanoscience and Nanotechnology

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Mass production of carbon nanotubes (CNTs) by a cost effective process is still a challenge for further research and application of CNTs. Our group has focussed on the deposition of CNTs on a continuously-fed carbon substrate via arc discharge at atmospheric pressure. This process produces MWNTs using carbon from the substrate. The method differs in other respects from the conventional batch arc discharge method by using lower currents (< 20 A) and larger inter-electrode gaps. To help define the local conditions of nanotube growth, the substrate surface temperature (T s ) was measured by optical pyrometry. Here, we report the influence of inter-electrode gap, substrate velocity and arc current on this temperature. It is found that carbon nanotube growth is favourable over a certain temperature range and retention time in the arc. To further understand the effect of arc parameters, we used a computer simulation to model the arc plasma. Computational fluid dynamic (CFD) software, Comsol Multiphysics, was used to simulate the temperature distribution and flow properties of the arc plasma. It was found necessary to include dusty plasma conductivity near to the electrodes to adequately represent observed arc behaviour.

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Graphite sublimation temperatures, carbon arcs and crystallite erosion

Cited by 78 publications

References 20 publications

Continuous-wave laser particle conditioning: Thresholds and time scales

Continuous-wave laser particle conditioning: Thresholds and time scales

Parameters affecting deposition of multiwalled carbon nanotubes on a continuously fed substrate using arc discharge

Influence of anode surface temperature in a continuously-fed arc discharge depositing carbon nanotubes

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