聚乙烯/大片层石墨烯复合材料吸波性能研究

Study on the Absorbing Properties of Polyethylene/Large Sheet Graphene Composites

高分子吸波复合材料广泛应用于航空航天吸波领域,通过将高性能吸波填料引入到聚乙烯基体可制备得到轻质、宽频和强吸收的复合吸波材料。石墨烯由于其轻质、比表面积大、电导率可调的特性常被用作高效高分子复合吸波材料的填料从而受到广泛关注。本文通过引入过硫酸铵膨胀法增加鳞片石墨的比表面积成功制备了高效大片层石墨烯吸收剂,在此基础上与聚乙烯复合制备不同性能的石墨烯/聚乙烯复合吸波材料,本论文详细研究了石墨烯热还原温度对复合材料吸波性能的影响并对其吸波机理进行了讨论。结果表明,采用适中温度(1200℃)热还原得到的复合吸波材料具有良好的吸波性能,在填料质量分数仅1.5%填充量下,该复合吸波材料匹配厚度为2 mm,吸收峰达到-40.2 dB,低于-10 dB吸收的有效带宽为2.675 GHz。其机理为:当还原温度较低时,复合吸波材料中吸波剂的导电性能差,难以感应电磁波形成电流对其进行损耗;还原温度过高,复合吸波材料中吸波剂的导电性很高,会在表面产生大电流,从而发生趋肤效应,难以使电磁波进入粉体内部进行有效损耗。通过该方法可简单方便地制备轻质、宽频和强吸收的复合材料,有望用作电磁波吸收器件。

The polymer absorbing composite material had been widely used in the field of aerospace absorption.By introducing high-performance absorbing fillers into the polyethylene matrix,a lightweight,broadband,and strongly absorbing composite absorbing material could be prepared.Graphene,due to its light weight,large specific surface area,and adjustable electrical conductivity,was often used as a filler for efficient high-performance polymer composite absorbing materials and had received widespread attention.In this study,an efficient large-layer graphene absorber was successfully prepared by introducing ammonium persulfate expansion method to increase the specific surface area of flake graphite.Based on this,graphene/polyethylene composite absorbing materials with different properties were prepared,and the effect of graphene thermal reduction temperature on the absorbing properties of composite materials was studied,and its absorbing mechanism was discussed.The research results show that the composite absorbing material obtained by moderate temperature thermal reduction(1200℃)has good absorbing performance.At the loading of only 1.5%,the matched thickness is 2 mm,the graphene/polyethylene composite absorbing materials intensity could reach as low as-40.2 dB.Besides,the effective microwave absorption bandwidth is 2.675 GHz.The reason is low reduction temperature results in weak electric conductivities of absorbent in composite materials,lacking induced current which can greatly dissipate microwave.High reduction temperature results in high electric conductivities of absorbent in composite materials,leading to skin effect which prevents the microwave from dissipating into absorber.This method can be used to conveniently prepare lightweight,broadband,and strongly absorbing composite materials,which are expected to be used as electromagnetic wave absorbers.