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首页> 外文期刊>Materials Characterization >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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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

机译：电子显微镜研究催化镍粒子颗粒形成机制及羰基硫化物在20Cr-25ni钢碳沉积中的作用

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摘要

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 degrees C, the formation of filamentary carbon was suppressed by the addition 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 gas mixtures 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.
机译：奥氏体不锈钢用作晚期气冷核反应堆（AGR）中的燃料包层。在升高的温度下，当钢暴露于基于CO2的环境时，在钢的表面上形成丝状碳沉积物。已知该丝碳沉积被金属镍的颗粒催化。将痕量的羰基硫化物（COS）加入气体混合物中抑制碳沉积。在本前的工作中，已经表明，在600摄氏度下，通过将215ppb col加入沉积的气体混合物（含有约1000Vppm C 2 H 4/1％CO / BAL），抑制丝状碳的形成已知提供适合碳沉积的环境。使用电子显微镜技术将其暴露于气体混合物的样品，以了解富含镍的颗粒的形成机制和由于添加COS。电子衍射研究表明富含镍的颗粒在氧化物层中，无论COS添加，均像下面的奥氏体金属的结晶术相同。目前的观察结果还表明，金属氧化物界面是富含镍的，并且已经提出了一种简单的模型来解释富含氧化镍的镍颗粒。此外，发现当加入氧化物层中的富含镍颗粒的氧化镍颗粒时，在扫描透射电子显微镜（茎）上被发现富含氧化物层的表面。据信，表面硫吸附到富镍的颗粒上，而不是大量硫化物形成，导致钢上的碳变形抑制。

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