双损耗型吸波涂层的电磁参数调控及其吸波性能研究

The values of the complex permittivity and complex permeability of the microwave absorbing coatings with both magnetic and dielectric loss composites can be altered effectively and thus improved their microwave absorption. Most present works focus on the both magnetic and dielectric loss microwave absorbing coating by changing the values of magnetic loss and/or dielectric loss, and then investigated the dependence of the reflection loss on the electromagnetic properties of such coatings. However, the microwave absorption of the coatings with magnetic and dielectric loss cannot improve only increased the dielectric loss of such coating, when the complex permittivity showed no frequency dependence. Therefore, in order to solve this key point, well controlled complex permittivity and electromagnetic properties with both magnetic and dielectric loss of absorber is an effective way to meet the demand of low reflection over a broad frequency rang. The complex permittivity of the graphene filled composites showed visible frequency dependence by changing the arrangement of the flakely graphene. Therefore, high frequency dependence of complex permittivity of the flakely graphene and carbonyl iron particles can be obtained by carefully arrange the flakely absorber, which can enhanced the microwave absorption of such composites. Through the rational design the content and arrangement of the absorber (graphene and flakely carbonyl iron) to prepared microwave absorbing coatings with high complex permeability (magnetic loss) and controlled complex permittivity (dielectric loss). By revealing the effect of microstructure and absorption mechanism of absorber on the electromagnetic properties and microwave absorbing properties, which proposing a valid way to control the values and frequency dispersion characteristics of electromagnetic properties, which provided a reliable theoretical and experimental basis for the applications of the design of double loss mechanism absorber with higher absorption.

兼具介电损耗和磁损耗的双损耗型吸波涂层是目前吸波效果最好的吸波涂层之一。为了进一步提高该吸波涂层的吸波效果，人们在提高涂层磁导率方面进行了大量工作，但提高磁导率难度很大，进展不明显。理论分析表明，在保持双损耗型吸波涂层现有磁导率的情况下，提高涂层介电常数的频散特性，能够有效提高涂层的吸波效果。同时我们实验发现，片状石墨烯在涂层中的取向分布对吸波涂层介电常数的频散特性具有明显的影响，由此可推测，片状吸收剂（石墨烯和羰基铁）在涂层中的定向分布会产生较强的介电常数频散特性，从而提高涂层的吸波效果。因此，本申请项目提出通过研究片状吸收剂定向分布来提高涂层的介电常数频散特性、进而提高吸波效果这样一个新的研究思路，以片状的石墨烯和羰基铁作为复合吸收剂制备双损耗型吸波涂层，通过调节石墨烯和片状羰基铁的含量和定向分布状态来调控吸波涂层的电磁参数和介电常数频散特性，从而达到有效提高吸波性能的目的。

开展兼具宽频和厚度薄的吸波涂层研究，不仅能促进吸波涂层电磁参数调控和吸波机理研究的发展，也能在军事、民用和工业等领域有广泛的应用前景。增大双损耗型吸波涂层的介电常数频散特性是提高其吸波性能的有效途径。本项目研究石墨烯、片状羰基铁随机分布和定向分布的双损耗型吸波涂层的电磁参数和吸波性能，通过调节石墨烯、片状羰基铁的含量及其在涂层中的分布状态（片状吸收剂随机分布和定向分布）来调控双损耗型吸波涂层介电常数和磁导率，使吸波涂层介电常数具有强的频散特性。采用流延法实现了羰基铁粉以及纳米石墨烯在树脂基体中的定向排列。对于羰基铁粉/纳米石墨烯/环氧树脂涂层，纳米石墨烯的加入提高了涂层的介电常数，匹配厚度降低，涂层能在较薄的厚度下获得较理想的吸收带宽。羰基铁粉的定向排列提高了涂层的磁导率和磁损耗，纳米石墨烯的定向提高了涂层的电损耗。羰基铁粉和纳米石墨烯定向以后的涂层，其介电常数和磁导率进一步增加。将定向的石墨烯和片状羰基铁涂层与吸收剂随机分布涂层相比，定向的石墨烯和片状羰基铁涂层能在厚度较薄时获得较宽的吸收带宽。项目制备出的具有定向分布的片状石墨烯和羰基铁的吸波涂层，能够实现调节石墨烯和片状羰基铁的含量和定向分布状态来调控吸波涂层的电磁参数和介电常数频散特性，进而有效地提高吸波性能的目的。本项目研制的兼具宽频和厚度薄片状石墨烯和羰基铁的吸波涂层具有很好的应用前景。