超细晶碳化硅包覆层的制备及其尺寸效应研究

项目名称： 超细晶碳化硅包覆层的制备及其尺寸效应研究

项目编号： No.51302148

项目类型： 青年科学基金项目

立项/批准年度： 2014

项目学科： 一般工业技术

项目作者： 刘荣正

作者单位： 清华大学

项目金额： 25万元

中文摘要： 高温气冷核反应堆由于固有安全性被认为是能够适应未来能源市场的第四代先进核反应堆堆型之一，其安全性的第一道保障就是使用了TRISO型包覆燃料颗粒。在四层包覆结构中，SiC层是承受包覆燃料颗粒内压以及阻挡裂变产物释放的关键层。为了优化材料性能指标，本项目将超细晶结构引入包覆于微米颗粒之上的SiC层，将梯度和变化的思想引入SiC包覆层的制备过程。通过梯度或脉冲变化的温度或浓度条件，或者通过外加其它反应物来促进化学气相沉积形核过程，抑制晶粒生长，以期得到高密度均匀化的超细晶SiC包覆层。同时理论研究复杂体系中SiC的晶体形核和生长机理，探索超细晶的形成机制，研究不同尺度SiC包覆层各物理性能的变化规律，建立SiC包覆层的尺寸效应，通过对包覆层精细显微结构的分析揭示尺寸效应的物理本质。本项目所取得的成果能够为超高温气冷堆燃料元件的制备提供技术储备，并能为其它相关的超细晶材料研究提供指导和借鉴。

中文关键词： 超细晶；SiC；流化床化学气相沉积；尺寸效应；核能应用

英文摘要： High temperature gas-cooled reactor (HTGR) with inherent safety characteristics is considered as one of the attractive and competitive generation IV nuclear reactors in the future energy markets. Tristructural-isotropic (TRISO)-coated particle fuel is the most significant safety aspect in this nuclear reactor, since it relies on the properties of the coatings surrounding the kernel fuel to stop the release of harmful radioactive material. Among these layers, the silicon carbide coating is considered the most important since it not only provides the TRISO particle with structural integrity but also retains fission products at elevated temperatures. In this project, the ultra-fine grain structures are designed to optimize the comprehensive performances of the high density SiC layers coated on micrometer particles. To obtain this unique structure, the idea of gradient is proposed in the preparation system. By applying the temperature or the reactant concentration with gradient or periodic changes, or by addition of other reactants, the nucleation process can be promoted and the growth process can be restrained which is very helpful for the formation of ultra-fine grain structures. To explore the formation mechanism of ultra-fine grains, the nucleation and growth process in the complex chemical vapor deposition syst

英文关键词： Ultra-fine grains；Silicon carbide；Fluidized bed chemical vapor deposition；Size effect；Nuclear application