高温辐照下SiC纤维中纳米晶粒的结构稳定性研究

Continuous SiC fiber reinforced-SiC matrix ceramic composite (SiC/SiC) has a great potential to be used in the extreme environment in nuclear reactors. Among its properties, irradiation resistance is of particular importance. The irradiation effects in SiC fibers determine the composite’s strength and fracture behavior. At present, researches on irradiation behaviors have appeared on some foreign commercial SiC fibers, but are rarely reported on home-made fibers. SiC fibers contain massive SiC nano-crystals and surrounding amorphous phase. The high temperature irradiation effects of this special structure are unknown. This project is planned to use ion irradiation technique to introduce defects and helium in SiC fiber, in order to simulate neutron irradiation defects and helium transmutation effects; through characterization and analysis, to reveal how the micro-structure ( including component, crystalline and grain size) affects the irradiation stability of SiC fibers; to bridge the micro-structure evolution and macro-properties (hardness and dimension) changes; by comparing with the neutron irradiation data, to establish an effective method to evaluate the irradiation resistance of SiC fibers, in order to support the modification and screening of the SiC fibers.

连续碳化硅纤维增强碳化硅基体（SiC/SiC）复合材料在核能极端环境中有着巨大的应用潜力。其抗辐照性能是评价其适用性的关键因素。研究表明SiC陶瓷基体具有很好的高温辐照稳定性。SiC纤维的辐照效应决定了复合材料的强度和断裂行为，对复合材料辐照后的性能至关重要。当前国外已有一些SiC纤维的辐照研究，然而针对国内纤维的辐照研究鲜见报道。SiC纤维包含大量SiC纳米晶粒和非晶相，这种特殊结构的高温辐照效应尚不明确。本项目拟利用离子辐照技术在SiC纤维中快速引入辐照缺陷和He元素，以模拟中子辐照损伤和嬗变He核素的效应。通过表征分析，明确SiC纤维的辐照稳定性与相应微观结构（成分、结晶度、纳米晶粒尺寸等）的关系；搭建SiC纤维微观结构演化与材料硬度、尺寸等性质变化之间的桥梁；与中子辐照结果进行对比，建立纤维辐照评价的有效方法，为纤维的优化和和筛选提供依据。

碳化硅纤维增强碳化硅基体复合材料（SiC/SiC）在核能极端环境中有着巨大的应用潜力。其抗辐照性能是评价其适用性的关键因素。已知碳化硅陶瓷具有优异的高温辐照尺寸稳定性，而纤维的辐照效应决定了复合材料的强度和断裂行为。国际上已有针对一代、二代、三代纤维的辐照研究，然而针对国内纤维的辐照研究鲜见报道。本项目主要研究了上海应用物理所生产的二代SiC纤维和日本三代纤维的辐照稳定性。利用离子束在高温（600oC）和室温开展二者的对比实验。通过系统的辐照后表征，发现二代纤维中的纳米晶粒与三代纤维中的大晶粒具有相同的辐照非晶化规律：晶粒碎片化及非晶区域的不断增加。由于二代纤维中的晶粒小，所以在室温辐照下更容易出现非晶化。高温辐照考验发现，纳米晶粒与单晶SiC一样具有优异的辐照稳定性。通过纳米压痕表征发现，SiC纤维的硬度和模量与纤维中SiC的非晶化程度有直接关联。实验发现X射线小角散射是研究SiC纤维中晶粒尺寸和分布特征的一个很好的方法。通过TEM和Raman谱表征发现二代纤维中含有大量富余的碳（石墨结构），预计将对纤维的辐照尺寸稳定性造成不利影响。综合辐照实验结果和数据分析，为实现核用SiC/SiC复合材料的应用，开发结晶度高、近化学计量比的三代纤维势在必行。