Spectral Emissivities of Graphite and Carbon

Thorn, R. J.; Simpson, O. C.

doi:10.1063/1.1721341

Cited by 42 publications

(16 citation statements)

References 8 publications

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“…These significant differences between the scrolls and the other two samples (graphene and CNT forest) are not surprising, given the former's significantly different structure and bulky nature, where likely a much larger volume of the material is involved in the heating and cooling. Indeed, the above c/ϵ value for the scrolls appears to be approaching that of graphite, which we estimate at 3.2 Jm −2 K −1 based on data available in the literature …”

Section: Resultssupporting

confidence: 59%

“…Indeed, the above c/ε value for the scrolls appears to be approaching that of graphite, which we estimate at 3.2 Jm À2 K À1 based on data available in the literature. [30][31][32] The aforementioned analysis leads to reasonable values for c/ε, lending further credibility to our aim for radiation to be the dominant cooling mechanism, with the contribution from conduction to surroundings being, by comparison, negligible. Nonetheless, one might argue that graphene and CNTs may both have higher thermal conductivity than the scrolls, and that the faster cooling rate for those structures is partially due to conduction.…”

Section: Resultsmentioning

confidence: 53%

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Observations of Radiation‐Dominated Rapid Cooling of Structures Based on Carbon Nanotubes and Graphene

et al. 2020

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It is often desirable to cause rapid thermal cycles in isolated systems, and it is convenient to do so by means of radiant heating and cooling. In principle, the rate of heating is arbitrarily increased simply by applying sufficient irradiance. This is not true for cooling, wherein the radiant emittance of a surface is determined by its emissivity and temperature. In an optically thin structure, the cooling rate is determined by the ratio of the material's emissivity to its specific heat, a factor that is expected to be greater in materials with a short characteristic absorption length, such as graphite. Herein, several forms of carbon‐based nanostructures, which have very short thermal radiation attenuation lengths, and are very robust and can withstand the high temperatures required for substantial Planckian thermal radiant emittance, are examined. Rapid cooling times ranging from about 100 μs to 1 ms are observed in structures cooling from a typical high temperature of 1500 K to a low of roughly half that value. Such rapid extreme thermal cycling of isolated materials provides new opportunities, for both research and potentially practical applications.

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Section: Resultssupporting

confidence: 59%

Section: Resultsmentioning

confidence: 53%

Observations of Radiation‐Dominated Rapid Cooling of Structures Based on Carbon Nanotubes and Graphene

et al. 2020

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“…Detailed measurement results are shown in Table S1 as supplemental information and a brief summary is provided here. Graphite front face temperature measurement differences at 8 cm range from 25°C to 50°C for emissivity values of 0.85, 0.90, and 0.95 for temperatures of ~1550°C to 1650°C . ZrO 2 front face temperature measurement differences at 8 cm range from 20°C to 70°C for emissivity values of 0.62 and 0.75 for temperatures of ~1800°C to 2000°C .…”

Section: Methodsmentioning

confidence: 98%

“…This set of experiments involves performing temperature measurements via optical pyrometry during oxyacetylene torch testing for graphite, ZrO 2 , and ZrB 2 + 25 vol% SiC. The pyrometer is used in the 1‐color mode and the 2‐color mode using different high temperature emissivity values as reported for graphite, ZrO 2 , and ZrB 2 + SiC in literature . This will allow us to observe how temperature measurements trend using high temperature emissivity values in 1‐color and 2‐color modes.…”

Section: Methodsmentioning

confidence: 99%

Oxidation Behavior of Aerospace Materials in High Enthalpy Flows Using an Oxyacetylene Torch Facility

et al. 2015

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The oxyacetylene torch facility is used to measure the ablation rates of graphite and the surface temperatures of different aerospace materials. The free-stream flame environment is characterized as a function of flame chemistry for heat flux, pO 2 , and flow velocity. Measured ablation rates for graphite increase as a function of increasing heat flux and pO 2 , which are validated by applying an oxygen diffusion based model. The model uses experimentally measured values for temperature, pO 2 , and gas velocity in order to confirm torch testing results are reliable and reproducible. Surface temperatures of ultra-high temperature ceramic composites are measured as a function of increasing heat flux and show an enthalpic cooling effect on the flame during oxidation testing.

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“…Considered geometry for the radiation heat transfer analysis including the area and emissivity of every surface. Emissivity of alumina has been experimentally measured, and emissivity of graphite was taken from Thorn and Simpson[43].…”

mentioning

confidence: 99%

A directly irradiated solar reactor for kinetic analysis of non-volatile metal oxides reductions

Alonso

Romero

2015

Int. J. Energy Res.

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SUMMARYA directly irradiated solar reactor was designed and built to develop kinetic analysis of metal oxides reductions present in many high-temperature thermochemical processes. The reactions were monitored by measuring the oxygen concentration in a carrier gas stream. The pattern flow in the reactor cavity was determined by applying the dispersion law. The dimensionless group D/uL was calculated for flows of 9, 12, and 15 Nl/min, and room and operation temperature. It was found to be close to an ideal plug flow behavior in every case. The solar reactor was also thermally characterized, which involved the operation temperature measurement and the thermal efficiency obtaining. For an incoming power of 530 W, temperatures higher than 1400°C were measured at the middle of the cavity (where the sample should be placed), and thermal efficiency of 41.6% was calculated. Then, a methodology for kinetic analysis was proposed and applied to a case study. It consisted of a combination of experimental results and a numerical model that reproduced the reactant sample performance. Kinetic was obtained for the layer of reactive particles that were directly heated by concentrated radiation. Kinetic data were fitted to diffusion-controlled mechanism, and obtained kinetic parameters were E a = 362 kJ/mol and A = 1.39•10 9 /s.

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Spectral Emissivities of Graphite and Carbon

Cited by 42 publications

References 8 publications

Observations of Radiation‐Dominated Rapid Cooling of Structures Based on Carbon Nanotubes and Graphene

Observations of Radiation‐Dominated Rapid Cooling of Structures Based on Carbon Nanotubes and Graphene

Oxidation Behavior of Aerospace Materials in High Enthalpy Flows Using an Oxyacetylene Torch Facility

A directly irradiated solar reactor for kinetic analysis of non-volatile metal oxides reductions

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