非共格晶界及其偏析对3C-SiC在超临界二氧化碳中氧化影响的Reaxff-MD模拟  

Reaxff-MD Simulation of the Effect of Incoherent Grain Boundaries and Its Segregation on Oxidation of 3C-SiC in Supercritical Carbon Dioxide

作　　者：周起印 刘珠 张乐福[1] 龙家琛 郭相龙 Zhou Qiyin;Liu Zhu;Zhang Lefu;Long Jiachen;Guo Xianglong(School of Mechanical Engineering,Shanghai Jiao Tong University,Shanghai,200240,China)

机构地区：[1]上海交通大学机械与动力工程学院,上海200240

出　　处：《核动力工程》2023年第5期284-289,共6页Nuclear Power Engineering

基　　金：超临界水冷堆核能系统材料与化学研发(2018YFE0116200)。

摘　　要：为理解SiC材料在超临界二氧化碳(sCO_(2))反应堆中的腐蚀失效机理,本文通过分子动力学模拟研究了3C-SiC在sCO_(2)环境中的氧化行为,并深入探讨了非共格晶界处元素偏析对氧化的影响。结果显示,非共格晶界区域的氧化速度比单晶快,且硅元素或碳元素的偏析均会加剧非共格晶界处的氧化。非共格晶界的加速氧化归因于晶界区域内的未完全配位硅原子,这些硅原子更容易与氧原子成键。非共格晶界的元素偏析进一步加强了非共格晶界处SiC的氧化速度,其中硅元素的偏析使硅原子更难以完全配位,这导致晶界处有更多的硅原子带较低的正电荷,而碳元素的偏析则使得晶界处自由体积更大,氧原子可以与更深层的硅原子成键。本研究揭示了3C-SiC在sCO_(2)中的腐蚀机理以及非共格晶界加速腐蚀的原因,为SiC材料在sCO_(2)反应堆中的退化机制提供了理论支持。To understand the corrosion failure mechanism of silicon carbide(SiC) material in supercritical carbon dioxide(sCO_2) reactors,this study investigated the oxidation behavior of 3CSiC in supercritical CO_(2) environment through molecular dynamics simulation,and explored in depth the effect of element segregation at incoherent grain boundaries(GBs) on oxidation.The results show that the oxidation rate near the incoherent GBs is faster than that of single crystals,and the segregation of either silicon or carbon elements intensifies the oxidation at the incoherent GBs.The accelerated oxidation near incoherent GBs is attributed to the incompletely coordinated silicon atoms at GBs,and these silicon atoms are more likely to bond with oxygen atoms.Elemental segregation at incoherent GBs further enhances the oxidation rate of silicon carbide at incoherent GBs,where the segregation of silicon elements makes it more difficult to fully coordinate silicon atoms,which results in more silicon atoms at GBs with a lower positive charge,while the partial segregation of carbon leads to a larger free volume at the GBs,so the oxygen atoms can bond with the deeper silicon atoms.This study revealed the corrosion mechanism of 3C-SiC in sCO_(2) and the reasons for the accelerated corrosion at incoherent GBs,providing theoretical support for the degradation mechanism of SiC materials in sCO_(2) reactors.

关 键 词：非共格晶界 偏析 3C-SIC 超临界二氧化碳(sCO_(2)) 氧化 分子动力学 

分 类 号：TL341[核科学技术—核技术及应用]