Electron microscopy study of the formation mechanism of catalytic nickel rich particles and the role of carbonyl sulphide in the suppression of carbon deposition on 20Cr-25Ni steel

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@article{a8bee3c3135c458e94d12d1915bb32f2,
title = "Electron microscopy study of the formation mechanism of catalytic nickel rich particles and the role of carbonyl sulphide in the suppression of carbon deposition on 20Cr-25Ni steel",
abstract = "Austenitic stainless steel is used as fuel cladding in advanced gas-cooled nuclear reactors (AGR). At elevated temperatures, when the steel is exposed to CO2 based environments filamentary carbon deposits form on the surface of the steel. This filamentary carbon deposition is known to be catalysed by metallic nickel-rich particles. Adding trace amount of carbonyl sulphide (COS) into the gas mixtures suppresses the carbon deposition. In this current work, it has been shown that at 600 °C, the formation of filamentary carbon was suppressed by theaddition of 215 ppb COS to a depositing gas mixture (containing approximately 1000 vppm C2H4/1% CO/bal. CO2) which was known to provide the environment suitable for carbon deposition. Samples exposed to the gasmixtures with and without 215 ppb COS were characterised using electron microscopy techniques to understand the formation mechanism of the nickel-rich particles and the inhibition mechanism due to the addition of COS.Electron diffraction study shows that the nickel-rich particles in the oxide layers assume the same crystallography as that of the austenitic metal underneath, regardless of the COS addition. The current observations also show that the metal-oxide interfaces was nickel-rich and a simple model has been proposed to explain the formation of nickel-rich particles within the subsurface oxide. Furthermore, it was found that when COS was added the surface of the nickel-rich particles in the oxide layer was found to be sulphur-rich by energy dispersive spectroscopy (EDS) on a scanning transmission electron microscope (STEM). It is believed that the surface sulphur adsorption onto the nickel-rich particles, rather than bulk sulphide formation, resulted in the inhibition of carbon deformation on the steel.",
author = "Subash Rai and Mary Taylor and Yu-Lung Chiu and Hugh Evans and Brian Connolly and Neal Smith and Clive Mowforth",
year = "2018",
month = oct,
doi = "10.1016/j.matchar.2018.07.039",
language = "English",
volume = "144",
pages = "505--515",
journal = "Materials Characterization",
issn = "1044-5803",
publisher = "Elsevier",

}

RIS

TY - JOUR

T1 - Electron microscopy study of the formation mechanism of catalytic nickel rich particles and the role of carbonyl sulphide in the suppression of carbon deposition on 20Cr-25Ni steel

AU - Rai, Subash

AU - Taylor, Mary

AU - Chiu, Yu-Lung

AU - Evans, Hugh

AU - Connolly, Brian

AU - Smith, Neal

AU - Mowforth, Clive

PY - 2018/10

Y1 - 2018/10

N2 - Austenitic stainless steel is used as fuel cladding in advanced gas-cooled nuclear reactors (AGR). At elevated temperatures, when the steel is exposed to CO2 based environments filamentary carbon deposits form on the surface of the steel. This filamentary carbon deposition is known to be catalysed by metallic nickel-rich particles. Adding trace amount of carbonyl sulphide (COS) into the gas mixtures suppresses the carbon deposition. In this current work, it has been shown that at 600 °C, the formation of filamentary carbon was suppressed by theaddition of 215 ppb COS to a depositing gas mixture (containing approximately 1000 vppm C2H4/1% CO/bal. CO2) which was known to provide the environment suitable for carbon deposition. Samples exposed to the gasmixtures with and without 215 ppb COS were characterised using electron microscopy techniques to understand the formation mechanism of the nickel-rich particles and the inhibition mechanism due to the addition of COS.Electron diffraction study shows that the nickel-rich particles in the oxide layers assume the same crystallography as that of the austenitic metal underneath, regardless of the COS addition. The current observations also show that the metal-oxide interfaces was nickel-rich and a simple model has been proposed to explain the formation of nickel-rich particles within the subsurface oxide. Furthermore, it was found that when COS was added the surface of the nickel-rich particles in the oxide layer was found to be sulphur-rich by energy dispersive spectroscopy (EDS) on a scanning transmission electron microscope (STEM). It is believed that the surface sulphur adsorption onto the nickel-rich particles, rather than bulk sulphide formation, resulted in the inhibition of carbon deformation on the steel.

AB - Austenitic stainless steel is used as fuel cladding in advanced gas-cooled nuclear reactors (AGR). At elevated temperatures, when the steel is exposed to CO2 based environments filamentary carbon deposits form on the surface of the steel. This filamentary carbon deposition is known to be catalysed by metallic nickel-rich particles. Adding trace amount of carbonyl sulphide (COS) into the gas mixtures suppresses the carbon deposition. In this current work, it has been shown that at 600 °C, the formation of filamentary carbon was suppressed by theaddition of 215 ppb COS to a depositing gas mixture (containing approximately 1000 vppm C2H4/1% CO/bal. CO2) which was known to provide the environment suitable for carbon deposition. Samples exposed to the gasmixtures with and without 215 ppb COS were characterised using electron microscopy techniques to understand the formation mechanism of the nickel-rich particles and the inhibition mechanism due to the addition of COS.Electron diffraction study shows that the nickel-rich particles in the oxide layers assume the same crystallography as that of the austenitic metal underneath, regardless of the COS addition. The current observations also show that the metal-oxide interfaces was nickel-rich and a simple model has been proposed to explain the formation of nickel-rich particles within the subsurface oxide. Furthermore, it was found that when COS was added the surface of the nickel-rich particles in the oxide layer was found to be sulphur-rich by energy dispersive spectroscopy (EDS) on a scanning transmission electron microscope (STEM). It is believed that the surface sulphur adsorption onto the nickel-rich particles, rather than bulk sulphide formation, resulted in the inhibition of carbon deformation on the steel.

U2 - 10.1016/j.matchar.2018.07.039

DO - 10.1016/j.matchar.2018.07.039

M3 - Article

VL - 144

SP - 505

EP - 515

JO - Materials Characterization

JF - Materials Characterization

SN - 1044-5803

ER -