Effects of air oxidation on the evolution of surface area within nuclear graphite and the contribution of macropores

Kane, Joshua J.; Matthews, Austin C.; Swank, W.D.; Windes, William E.

doi:10.1016/j.carbon.2020.05.018

Cited by 24 publications

(5 citation statements)

References 48 publications

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“…The mechanical and thermal properties of graphite are deteriorated by its oxidation [9][10][11][12]. Therefore, many studies have been carried out to investigate the oxidation behavior of different graphite [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. The American Society for Testing and Materials (ASTM) issued the ASTM D7542 standard to measure oxidation performances of carbon and graphite materials in 2009 (updated in 2015) [28].…”

Section: Introductionmentioning

confidence: 99%

Oxidation Experiments and Kinetics Analysis of Nuclear Graphite ET-10 by Gas Analysis and Microstructure Observation

et al. 2021

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Nuclear graphite can be used in fission and fusion systems due to its excellent nuclear performance and mechanical properties where the ability of oxidation resistance is usually concerned. Although the excellent performance of new graphite ET-10 was revealed by previous experiments regarding the accident conditions of a fission reactor, further studies are needed to oxidize the graphite under the conditions recommended by the ASTM D7542 standard. A test facility was designed and developed to oxidize the cylindrical specimen with a 10 L/min airflow. According to oxidation rates and microstructures of specimens, the chemical kinetics-controlled regime was determined as 675–750 °C, where the activation energy was obtained as 172.52 kJ/mol. The experiment results revealed the excellent ability of graphite ET-10 for oxidation resistance with lower oxidation rates and longer oxidation times compared with some mainstream graphite. The main reasons are the low contents of some impurities and the binder and the low active surface area due to the non-impregnation baking process undertaken to produce graphite with coal tar pitch coke. It should be noted that the evolution of oxidation behavior at the bottom part of the specimen (facing the airflow) was quicker than that at the upper part of the specimen. We also suggest that the abundance of oxygen supply and the good linearity of the Arrhenius plot are prerequisites of the chemical kinetics-controlled regime rather than sufficient conditions.

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Section: Introductionmentioning

confidence: 99%

Oxidation Experiments and Kinetics Analysis of Nuclear Graphite ET-10 by Gas Analysis and Microstructure Observation

et al. 2021

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“…The gas-escape pores and micro-cracks show various shapes, orientations and sizes in nuclear graphite. Direct observation and statistical analysis of graphite gas-escape pores have been achieved for pristine graphite [1][2][3], oxidized graphite [4,5] and irradiated graphite [6]. The X-ray tomography is a powerful technique to make a nondestructive analysis of large graphite pores (with the best resolution of around 1 μm) [3,5,6].…”

Section: Introductionmentioning

confidence: 99%

“…Direct observation and statistical analysis of graphite gas-escape pores have been achieved for pristine graphite [1][2][3], oxidized graphite [4,5] and irradiated graphite [6]. The X-ray tomography is a powerful technique to make a nondestructive analysis of large graphite pores (with the best resolution of around 1 μm) [3,5,6]. Digital image processing combined with optical microscopy has also been used to analyze the pore structures of various graphite grades [1,2,4].…”

Section: Introductionmentioning

confidence: 99%

“…nuclear graphite. Direct observation and statistical analysis of graphite gas-escape pores have been achieved for pristine graphite, [1][2][3] oxidized graphite, 4,5 and irradiated graphite. 6 X-ray tomography has been used to compare pore structures of several graphite grades 3 and to investigate porosity changes induced by oxidation.…”

mentioning

confidence: 99%

“…6 X-ray tomography has been used to compare pore structures of several graphite grades 3 and to investigate porosity changes induced by oxidation. 5 The best resolution of X-ray tomography is around 1 μm. A technique combining optical microscopy and digital image processing has also been adopted to analyze pore structures of various graphite grades.…”

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confidence: 99%

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A statistical analysis of pores and microcracks in nuclear graphite

Huang

Tang

2021

Surface & Interface Analysis

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Microstructure characterization is of great value to understanding nuclear graphite's properties and irradiation behavior. However, graphite is soft and could be easily damaged during sample preparation. A three-step polishing method involving mechanical polishing, ion milling, and rapid oxidation is proposed for graphite. Ion milling is adopted to remove the broken graphite pieces produced by mechanical polishing. Rapid oxidation is then adopted to remove irradiation-induced damage layer during ion milling. The Raman spectra show very small G peak width and very low I D /I G ratio after rapid oxidation. The microcracks that were conventionally observed via a transmission electron microscope can be observed on rapid-oxidized surface in a scanning electron microscope. By digital image processing, the microcracks along with the gas-escape pores in nuclear graphite IG-110 are statistically analyzed. Porosity's distributions on crack (pore) size (spanning from 10 nm to 100 μm) are given, which could help to understand and simulate graphite's performances in reactors.

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Depth profile analysis of oxidized nuclear graphite microstructures using micro-focused synchrotron X-ray diffraction

Huang

et al. 2022

J Mater Sci

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Effects of air oxidation on the evolution of surface area within nuclear graphite and the contribution of macropores

Cited by 24 publications

References 48 publications

Oxidation Experiments and Kinetics Analysis of Nuclear Graphite ET-10 by Gas Analysis and Microstructure Observation

Oxidation Experiments and Kinetics Analysis of Nuclear Graphite ET-10 by Gas Analysis and Microstructure Observation

A statistical analysis of pores and microcracks in nuclear graphite

Depth profile analysis of oxidized nuclear graphite microstructures using micro-focused synchrotron X-ray diffraction

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