金属Ce-Fe间键合行为及相互作用机制

    Bond Behavior and Interaction Mechanism Between Metal Ce-Fe

    • 摘要: 利用真空蒸馏法对金属进行精炼、纯化,在此过程中,会存在部分逃逸的金属在真空腔室及管路内壁表面沉积,为了有效去除残余的金属,必须明确金属与金属之间的键合行为及作用机制,为后续的金属擦拭助剂的筛选提供重要的理论依据。本工作以金属铈(Ce)为研究对象,开展了不锈钢表面金属Ce的微观形貌、致密程度和沉积形态的分析,采用扫描电子显微镜(SEM)和能量色散X射线光谱仪(EDS)表征了金属Ce在316L不锈钢表面沉积的形貌和元素组成;基于密度泛函的第一性原理,采用VASP程序进行计算,研究了晶体结构中的多面体空隙,获得了金属Ce与金属Fe不同晶面相互掺杂量的结构,得到了不同掺杂结构的能量,探究了金属Ce层与316L不锈钢的相互作用机理,并结合理论计算得到了金属Ce与不锈钢基底的键合机制。对金属Ce的晶体结构进行了研究,分析了晶体结构中的多面体空隙,通过对相图中可能的金属互化物及不同Ce-Fe掺杂结构的计算,探讨了各种晶体结构的稳定性。通过理论计算,分析了Ce和Fe的成键机制,表明Ce和Fe之间形成金属键,Ce-Fe之间的键合形成了CeFe5、CeFe2、Ce2Fe17等多种金属互化物。

       

      Abstract: By using vacuum distillation to refine and purify metals, some escaped metals may deposit on the inner walls of vacuum chambers and pipelines. In order to effectively remove residual metals, it is necessary to clarify the bonding behavior and mechanism between metals, providing important theoretical basis for the screening of subsequent metal wiping aids. This study focuses on cerium(Ce) metal and analyzes the micro-structure, density, and deposition morphology of Ce metal on the surface of stainless steel. Scanning electron microscopy(SEM) and energy dispersive X-ray spectroscopy(EDS) were used to characterize the morphology and elemental composition of Ce metal deposition on the surface of stainless steel 316L. Based on density functional theory, first principles calculations were performed using VASP program to investigate polyhedral voids in the crystal structure. The structures with different doping levels of Ce metal and Fe metal planes were obtained, and the energy of different doping structures was obtained. The interaction mechanism between Ce metal layer and stainless steel 316L was explored, and the bonding mechanism between Ce metal and stainless steel substrate was obtained by theoretical calculations. In the initial stage, as Ce is transported to the substrate surface, these atoms form tiny, mobile atomic clusters on the substrate, also known as “islands” or “nuclei”. Temperature is a key factor in the formation of an alloy layer between Ce and stainless steel substrate, and high temperatures can easily promote the mutual diffusion between Ce elements and surface elements of stainless steel. As Ce is transported to the surface of the substrate, Ce grains begin to nucleate and grow on the surface of the stainless steel. Subsequently, under the influence of concentration gradient and thermal gradient diffusion, diffusion channels were formed on the surface of the substrate, and Ce atoms gradually diffused from the surface into the interior of the substrate. At the same time, due to the smaller atomic radius and higher diffusion rate of Fe element, it begins to diffuse outward from the matrix and react with Ce atoms at the interface, forming CeFe2 phase. The crystal structure of cerium metal was studied, and the polyhedral voids in the crystal structure were analyzed. By calculating possible metal inter-metallic compounds and different Ce-Fe doping structures in the phase diagram, the stability of various crystal structures was explored. Through theoretical calculations, the bonding mechanism between Ce and Fe is analyzed, indicating that metal bonds are formed between Ce and Fe, and the bonding between Ce and Fe forms various metal inter-metallic compounds such as CeFe5, CeFe2, Ce2Fe17.

       

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