Polymer composite materials with mixed fillers are widely investigated due to potentially superior properties they provide compared to a composite with a single filler. In this work, the electrical properties of multi-walled carbon nanotubes (MWCNT)/BaTiO3/epoxy composites are investigated using impedance measurements, modeling with equivalent circuit model, determining of alternating current conductivity in the range 10 Hz–2 MHz, permittivity measurements at frequencies 1–67 GHz, and temperature dependencies (77–290 K) of direct current conductivity. Measurements were processed to define the influence of filler combination (carbon nanotubes and BaTiO3) on dielectric properties of the epoxy composites. Nyquist diagrams indicate that all investigated composites have extensive conductive clusters. Permittivity increases monotonically with carbon nanotubes content with a steeper increase of the real part at lower frequencies. Alternating current conductivity has been determined to increase significantly at frequencies over 1 GHz. Temperature dependencies of direct current conductivity in the range 77–293 K exhibit a maximum near 180–220 K, which is shifted to the higher temperatures with the increase of carbon nanotubes content. The observed enhanced values of complex permittivity and electrical conductivity of three-phase MWCNT/BaTiO3/epoxy composites lead to a comparatively high microwave attenuation constant, which may be tuned by the carbon nanotubes content in the composite. It suggests that these composites might be perspective shielding and absorbing materials used for microwave applications.

中文翻译：

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多壁碳纳米管/BaTiO3/环氧树脂复合材料的阻抗特性和微波介电常数

由于与单一填料的复合材料相比，混合填料的聚合物复合材料具有潜在的优越性能，因此得到了广泛的研究。在这项工作中，使用阻抗测量、等效电路模型建模、确定 10 Hz–2 MHz 范围内的交流电导率、介电常数测量来研究多壁碳纳米管 (MWCNT)/BaTiO3/环氧树脂复合材料的电性能频率 1–67 GHz，以及直流电导率的温度依赖性 (77–290 K)。进行测量以确定填料组合（碳纳米管和 BaTiO3）对环氧树脂复合材料介电性能的影响。奈奎斯特图表明所有研究的复合材料都具有广泛的导电簇。介电常数随碳纳米管含量单调增加，在较低频率下实部增加更陡峭。已确定交流电导率在超过 1 GHz 的频率下显着增加。直流电导率在 77-293 K 范围内的温度依赖性在 180-220 K 附近表现出最大值，随着碳纳米管含量的增加，该最大值转移到更高的温度。观察到的三相 MWCNT/BaTiO3/环氧树脂复合材料的复介电常数和电导率的增强值导致相对较高的微波衰减常数，这可以通过复合材料中的碳纳米管含量进行调整。这表明这些复合材料可能是用于微波应用的透视屏蔽和吸收材料。