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Polymer-based nanocomposite foams containing carbonic fillers have greatly facilitated scientific research efforts in electromagnetic interference (EMI) shielding, as well as piezoresistive sensing devices. The carbon-based fillers not only provide superior EMI shielding properties and extraordinary gauge factor but also offer critical advantages of electromagnetic wave absorption and supreme pressure sensitivity. Currently, electromagnetic signal interference has become a severe challenge for which wireless communication is responsible. Furthermore, considering the rapid development of the flexible electronics industry, demands for piezoresistive sensors comprising a wide range of responses and increased sensitivity are considerably increased. The present work reviews recent developments and breakthroughs in polymer foam composites primarily concentrating on various high-performance carbonic nanomaterials, including graphene, carbon nanotubes (CNTs), carbon black, and their hybrid fillers. Moreover, demands for further improvement in case of technical issues, compatibility, or synergic effect of type of nanofiller on the polymer host, as well as the influence on microstructure and electrical properties of foam materials, have been elucidated in the review. To be more specific, the effect of carbonic filler size and shape, as well as its electric, microstructure, and mechanical properties, in fabricating high-performance piezoresistive and EMI shielding polymeric composite foams is covered. In addition, cutting-edge developments in carbonic polymer nanocomposite foams in EMI shielding and piezoresistive sensor applications are highlighted. To be specific, available methods for tailoring appropriate microstructure and electrical and mechanical properties in EMI shielding materials and pressure sensors, current technological challenges in fabricating and developing nanocomposite foams for such mentioned applications, and future perspectives are discussed.

The recent global energy context has been recognized as evidence for the need to reduce our energy consumption, to prolong fossil fuel supplies and minimize shortage, and to decelerate greenhouse gas transpiration. Over the past few years, using an insulator and decreasing its thermal conductivity have been recognized as the most effective way to reduce energy consumption. Aerogels as superinsulating materials permit reduction of the heat exchange between two environments while producing facile sol−gel and diverse drying routes. Aerogels have intrigued scientists and engineers due to their unique nanocharacteristics, such as low density, fine internal void spaces, and openpore geometry, which originate from sol particles in a 3D random network. Noteworthy are aerogel-based materials that have a supreme potential as thermal insulation owing to their very low thermal conductivity based on trapped air in the meso-/ nanoporous structure. Indeed, aerogels have great appeal in terms of their thermal efficiency, producing simplicity and performance reliability as compared with a traditional insulator. In this work, we will review the main milestones along with the concept of aerogels and then discuss some new trends, strategies, and opportunities in employing various morphological and nanostructural control methods to improve the performance of aerogels, especially enhancing insulation efficiency or decreasing thermal conductivity. The focus will be on (I) tailoring the porous structure of a carbon-based aerogel such as graphene oxide and reduced graphene oxide to accommodate high thermal behavior and (II) designing strategies to achieve intrinsically superinsulating materials in synthesized polymer and bio-based materials, with/without embedding an additional component.

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The influence of reduction temperature on the electromechanical properties and actuation behavior of polydimethylsiloxane (PDMS) dielectric elastomer containing the thermally reduced graphene oxide (rGO) with different surface chemistry has been systematically investigated. A set of rGO nanosheets was prepared by thermal reduction of graphene oxide (GO) at four temperatures (150, 200, 300, and 400 °C). The dielectric permittivity, dielectric loss, and elastic modulus of PDMS composites were increased, while the electrical breakdown strength of composites was decreased with an increase of the reduction temperature of GO. A thermodynamic model applied for studying the electromechanical deformation and stability of PDMS/GO­(rGO-x) dielectric elastomer composites showed that the optimum value of the break-point was observed in PDMS/rGO-300. It is shown for the first time that the variation of electromechanical instability and recovery behavior are attributed to the surface chemistry of rGOs. A critical reduction temperature is observed at 300 °C which can be considered as proper rGO nanosheets for electromechanical applications. By employing an equivalent circuit on impedance spectroscopy, the interfacial polarization is recognized as the dominant mechanism rather than the intrinsic polarization of the matrix and nanosheets. Noteworthy, PDMS composites containing rGO, reduced at higher temperatures, have more interfacial polarized charges at the interface.

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