非晶SiOC陶瓷的辐照损伤机理研究

Radiation damage is a major problem for materials used in nuclear reactor environment. Aiming at the problem that amorphization and swelling of traditional crystalline materials after ion irradiation cause changes of material shape and property, this project proposes to select amorphous SiOC polymer-derived ceramics, to explore the possibility of reducing or eliminating radiation structural damage by intrinsic defects (vacancies, interfaces, etc.) in amorphous structures, thus providing theoretical guidance and experimental evidence for the research and development of new radiation resistant materials. The chemical compositions and amorphous structure of the SiOC ceramics can be controlled by adjusting the compositions, structures of precursors, and precursor pyrolysis and sintering process. The changes of microstructures, thermodynamics, and macroscopic properties of the amorphous SiOC before and after irradiation were systematically studied, and a series of key scientific questions, such as the mechanisms of radiation damage, thermodynamic nature of the structure damage, and the dependence of radiation resistance on microstructures, were clarified. It provides kinetics and thermodynamics basis for the design and control of radiation resistant amorphous microstructures, and provides scientific and reasonable evaluation of potential applications and prospects of amorphous materials in the fields of nuclear radiation protection. Of course, under the guidance of this concept, the studies of anti-radiation process and mechanism will face many problems. It is believed the proposition and solution of these problems can, to a certain extent, induce innovative sources for the design and development of new materials “immune” to ion irradiations.

辐照损伤是材料在核反应堆环境下面临的重大难题。本项目针对传统晶体材料受到离子辐照后发生非晶化并肿胀，造成材料外形及性能改变的问题，提出选用非晶SiOC前驱体陶瓷为研究对象，探讨非晶结构中的本征缺陷（空位、界面等）对于减少或消除辐照结构损伤的可能性，为新型抗辐照材料的研发提供理论指导和实验依据。通过调整前驱体的成分、结构及裂解烧结工艺，实现非晶SiOC化学组分及非晶结构的控制。系统研究辐照前后非晶SiOC微观结构、热力学性质及宏观性能的变化，阐明其辐照损伤机理、结构损伤的热力学本质及抗辐照性能对微观结构的依赖性等一系列关键科学问题。为抗辐照非晶结构的设计调控提供动力学、热力学依据，为非晶材料在核辐射防护领域的潜在应用和前景给出科学合理的评估。当然，在这种理念指导下的抗辐照过程及机理研究将面临许多问题。请相信，这些问题的提出和解决一定能够在一定程度上诱发“辐照免疫”新材料设计和研发的创新源头。

辐照结构损伤是材料在核反应堆环境下面临的重大难题。对于晶体材料来说，辐照会导致晶体结构完整性破坏，发生非晶化，进而引发肿胀及材料性能下降。被激发原子的随机迁移性与晶体结构有序性之间的矛盾，是制约晶态材料耐辐照性能的主要原因。而非晶材料原子排列长程无序，由辐照引起的原子排列的混乱变化极易湮没在本身的无序结构中，非晶材料有可能是一种潜在的抗辐照材料。. 本项目以自制的具有高结晶温度（＞1200ºC）的非晶SiOC前驱体陶瓷为研究对象，系统研究具有不同成分的纯非晶SiOC陶瓷、非晶纳米晶SiOC陶瓷在离子辐照前后的微观结构演变、热力学性能以及宏观性能变化，结合分子动力学模拟研究，阐明非晶SiOC陶瓷的辐照损伤过程及机理、辐照损伤热力学及其与微观结构变化关联性等科学问题。结果表明，对于纯非晶结构SiOC陶瓷，1.47GeV Au快重离子辐照后，非晶Si-O-C网络结构中的含Si四面体单元的交联度略微降低，自由碳被破坏，材料的热力学稳定性有所下降，仍然维持非晶结构。对于含β-SiC纳米晶和石墨微区的非晶纳米晶SiOC陶瓷，4MeV Si离子辐照后，非晶Si-O-C网络结构发生重排但依然维持非晶，β-SiC纳米晶维持晶态，石墨发生非晶化；材料的形貌和力学性能基本不变。随着非晶相含量增加，辐照引发非晶Si-O-C网络结构重排和石墨的非晶化程度减小。非晶结构在湮灭辐照缺陷、抑制气泡形成等方面的作用可能大于其本身非晶结构变化的影响。此外，项目研究了非晶SiOC陶瓷在有氧环境下的高温稳定性，揭示了其表面氧化膜的动态演变规律，为其在高温服役环境下的可用性提供支撑。同时，制备出轻质、可回弹SiOC/SiC陶瓷，并对多其多功能性（隔热、吸波等）开展了探索性研究。. 非晶SiOC陶瓷是一种潜在的抗辐照材料，有望应用于核材料领域。项目的研究成果，对设计和制备抗辐照新材料具有重要的指导意义，对进一步丰富和发展抗辐照损伤机理具有重要的科学意义。