Carbon nanotube/epoxy composites with low percolation threshold and negative dielectric constant

The tunability of negative dielectric constant value and its frequency dispersion determines the performance design and specific use of the functional devices. However, how to precisely tune the negative permittivity to match electronic applications remains an unsolved problem. For carbon nanotubes/epoxy resin (CNTs/Epoxy) composites, people often pay attention to their positive dielectric properties, but ignore their negative dielectric properties. In this paper, CNTs/epoxy composites with negative dielectric constant use carbon nanotubes as the functional phase and epoxy resin as the matrix. By adjusting the content and distribution of carbon nanotubes in the composite, the conduction mechanism of the conductor–insulator composite was explored, found the conductivity of the two conduction mechanisms, jump conduction and metalloid conduction, plays an equally important role, and the effective regulation of negative permittivity was achieved. When the content of CNTs was 20.1 vol%, the phenomenon of near-zero dielectric and negative dielectric constant appeared. When the content of CNTs is 24.6 vol%, the dielectric constants are all negative in the test frequency band, showing Drude-type dispersion. Through further impedance analysis, it was found that inductance is necessary to achieve negative dielectric constant. Constructing negative dielectric materials under low percolation threshold provides a method to realize negative dielectric constant. These findings may pave the way for simple and efficient control of negative permittivity and facilitate its application in electronic components and electromagnetic shielding.