核工业用低温烧结助剂RE-Si-C（RE=Ce、Eu和Yb）体系相图及界面相变研究

SiC基材料是下一代包壳及核聚变堆流道插件的重要候选材料之一。因其熔点高、脆性大，烧结和连接一直是核材料工程化应用的难点，同时是核级安全的重点。添加烧结助剂实现致密化烧结，在本质上包括对烧结助剂组分设计和界面相变的研究。本项目基于稀土元素的“双峰效应”，以RE-Si-C（RE=Ce、Eu和Yb）体系为研究对象，化合物RE3Si2C2为目标涂层材料，重点开展以下研究：1) 耦合高通量实验、第一性原理和相图计算（CALPHAD）构筑RE-Si-C体系热力学数据库；2) 基于相图计算指导表面涂层组分设计与工艺参数筛选；3) 研究烧结过程纳米颗粒的结构演化，阐明SiC/RE3Si2C2的界面相变机理和控制方法。本项目将揭示RE3Si2C2对烧结温度和致密化效果的作用规律，设计出适用于SiC低温液相烧结（<1200℃）且致密化效果好（>99.7%）的成分区间，并为其他相关工作提供可借鉴的研究思路。

SiC-based materials are one of the major categories suitable for the next generation cladding and nuclear fusion reactor runner inserts. Due to the high melting point and brittleness, sintering and joining issues are always being the obstacles that hinder their engineering applications. Incorporating sintering additives is the mainstream technology to achieve dense sintering in SiC, among which, it is particularly important to design the components of additives and study the behavior of interfacial phase transitions. This project is to investigate the RE-Si-C (RE= Ce, Eu and Yb) systems based on the bimodal effect of rare-earth elements, take the intermetallic compound RE3Si2C2 as the target coating, and focus on the following work: 1) establishing the thermodynamic database of the RE-Si-C systems by coupling high-throughput experiments, first-principles calculations and the CALPHAD (CALculation of PHAse Diagram) approach; 2) guiding the component design of auxiliary layer and the optimization of process parameters by the CALPHAD approach; 3) describing the interfacial phase transition mechanism of SiC/RE3Si2C2 by combining the theoretical calculations and the structure evolution of nano-particles. This project will clarify the temperature-based regularity and densification law between different rare-earth intermetallic compounds used as low-temperature additives, design appropriate composition range for the low-temperature liquid-phase sintering of SiC-based materials (<1200℃) with a fully dense microstructure (>99.7%), and provide research ideas for other related work as well.