软磁金属/硅橡胶复合吸波材料失效、老化行为及其机理研究

Microwave absorbing material (MAM) plays an important role in solving the problems of electromagnetic radiation pollution and electromagnetic compatibility. The microwave power and temperature resistances of the MAMs determine whether they can work stably and reliably for a long time in high temperature and electromagnetic radiation environments. In this proposal, on the bases of preparation process and formulation optimizations, soft magnetic metal powder/silicone rubber composite microwave absorbers are prepared by using soft magnetic metal powders with excellent electromagnetic properties including carbonyl iron, FeNi and FeSiAlalloys as the microwave absorbents, high temperature vulcanized and room temperature vulcanized silicone rubbers as the matrix. By establishing the testing device for microwave radiation and aging test equipment with different atmosphere, the relationships among the microwave radiation intensity & time, type & filling content of the soft magnetic metal, temperature rises, changes of the composition, structure & property of the MAMs after microwave radiation are investigated. The changes of the composition, structure and property of the MAMs after heat aging are also studied. The failure laws and mechanisms of the soft magnetic metal powder/silicone rubber composite microwave absorbers in the high electromagnetic radiation environments for long time are researched, and the aging mechanisms of the soft magnetic metal powder/silicone rubber composite microwave absorbers are also expounded, which will provide the important scientific theoretical foundation and method for improving the microwave power and temperature resistances of the MAMs and researching the microwave absorbing material with high performance. The research achievements will possess important theory significance and practical value.

电磁波吸收材料在解决电磁污染和电磁兼容问题中具有非常重要的地位，吸波材料的耐温和耐功率性能是其能否在高温和高功率辐射环境下长期、稳定和可靠工作的决定因素。课题分别以具有优异电磁性能的羰基铁、FeNi和FeSiAl合金粉末为吸收剂，高温热硫化硅橡胶和室温硫化硅橡胶为基体，在优化制备工艺和配方的基础上制备软磁金属粉末/硅橡胶复合吸波材料。通过建立吸波材料微波辐射测试装置和吸波材料不同气氛热老化实验装置，系统研究功率密度、微波辐射时间、软磁金属的类型和含量与吸波材料微波辐射后的温升、材料组成、结构和性能之间的关系；吸波材料在不同气氛条件下热老化后的组成、结构和性能变化。研究并揭示软磁金属/硅橡胶吸波材料在大功率微波长时间辐射下的失效规律和机制，阐明吸波材料的热老化机理，为改善吸波材料的耐热和耐功率辐射性能、研究制备高性能吸波材料奠定理论基础，具有重要的理论意义和科学指导作用。

电磁波吸收材料的耐温性能是其能否在高温和高功率辐射环境下长期、稳定和可靠工作的决定因素。课题分别以高温热硫化硅橡胶、室温硫化硅橡胶和聚氨酯橡胶为基体，软磁金属羰基铁为吸收剂，对三种橡胶吸波材料的制备工艺与配方进行了研究与优化。设计并建立了吸波材料不同气氛热老化实验装置，分别以羰基铁、FeNi和FeSiAl合金粉末为吸收剂，研究了软磁金属/硅橡胶吸波材料的热空气老化行为，借助TG分析以及羰基铁/三元乙丙橡胶和羰基铁/聚氨酯橡胶吸波材料的热空气老化行为，发现并证实了热空气老化过程中羰基铁促进硅橡胶进一步交联的效应。羰基铁/高温硫化硅橡胶吸波材料表面的扫描电镜和ATR-FTIR分析揭示了热空气老化后吸波材料表面硅橡胶减少，表面结构受到破坏，阐明了这是吸波材料随热空气老化时间延长介电常数上升和磁导率下降的原因。. 研究了软磁金属羰基铁/硅橡胶吸波材料的真空和氩气气氛下的热老化行为，借助TG分析以及氧化铝/高温硫化硅橡胶的热空气老化行为，发现在无氧热老化条件下，羰基铁对硅橡胶没有催化交联效应，证实了羰基铁与氧的协同作用导致了热空气老化过程中羰基铁对橡胶的催化交联。软磁金属羰基铁/高温硫化硅橡胶吸波材料表面扫描电镜和ATR-FTIR分析揭示了其真空热老化过程以硅橡胶断链、降解为主。软磁金属羰基铁/高温硫化硅橡胶吸波材料热空气老化后的XPS和断面照片分析表明：在热空气老化过程中，羰基铁催化硅橡胶侧链发生氧化交联反应；此外硅橡胶断链、降解与羰基铁催化交联效应同时存在，外表面首先发生主链断裂、降解——羰基铁与氧协同作用的催化交联反应以及侧链基团氧化的循环反应，内部仅发生主链断裂、降解；随着老化时间的延长，氧气逐渐向材料内部扩散，继而羰基铁与氧协同作用的催化交联反应与侧链基团氧化由外向内逐渐发生。. 项目新增的两项研究表明：硅橡胶常用的Fe2O3、MB和4010等三种抗氧剂减弱羰基铁促进硅橡胶的催化交联效应、改善软磁金属羰基铁/高温硫化硅橡胶吸波材料老化性能的效果不显著。成功制备的片状FeSiAl合金和W型BaMe2Fe16O27铁氧体吸收剂具有优异的电磁性能。项目研究为阐明吸波材料老化失效机制、改善吸波材料的耐热性能、制备高性能吸波材料奠定理论基础，具有重要的理论意义和科学指导作用。