Cryogenic characteristics of graphene composites—evolution from thermal conductors to thermal insulators

Abstract

The development of cryogenic semiconductor electronics and superconducting quantum computing requires composite materials that can provide both thermal conduction and thermal insulation. We demonstrated that at cryogenic temperatures, the thermal conductivity of graphene composites can be both higher and lower than that of the reference pristine epoxy, depending on the graphene filler loading and temperature. There exists a well-defined cross-over temperature—above it, the thermal conductivity of composites increases with the addition of graphene; below it, the thermal conductivity decreases with the addition of graphene. The counter-intuitive trend was explained by the specificity of heat conduction at low temperatures: graphene fillers can serve as, both, the scattering centers for phonons in the matrix material and as the conduits of heat. We offer a physical model that explains the experimental trends by the increasing effect of the thermal boundary resistance at cryogenic temperatures and the anomalous thermal percolation threshold, which becomes temperature dependent. The obtained results suggest the possibility of using graphene composites for, both, removing the heat and thermally insulating components at cryogenic temperatures—a capability important for quantum computing and cryogenically cooled conventional electronics.

A Highly‐Flexible and Breathable Photo‐Thermo‐Electric Membrane for Energy Harvesting

“…For carbon‐based nanofiber films, phonons are dominant in the heat transfer process. [ 47,48 ] However, the nanostructure amplifies the scattering effect on phonons, thereby impeding the ordered transfer of heat between fibers, [ 49 ] as shown in Figure 4a. Consequently, this temperature difference extended to the TE layer as well.…”

Role of four-phonon processes in thermal conductivity of two-dimensional materials and thermal-transport enhancement arising from interconnected nanofiller networks in polymer/nanofiller composites

“…Percolation at high concentrations was also explored in recent work by Nataj et al , 121 who measured the thermal conductivities of graphene/epoxy composites over a wide range of temperatures, from 2 K to room temperature, and for a range of graphene volume fractions. They showed that at low graphene concentrations, a cross-over temperature existed, below which, the thermal conductivity of the composite decreased with an increase in graphene concentration, and above the cross-over temperature, the thermal conductivity increased with increasing filler loading.…”

Transition metal-substituted polyoxometalate-ionic liquids with remarkable flame retardancy performance

“…6,7 Owing to these outstanding characteristics, epoxy resins have been applied in a diverse range of fields including transportation, construction, electronics and renewable energy. 8,9 The flammability of epoxy resins, however, limits their application range so as to comply with fire-safety regulations and prevent the release of toxic combustion products. 10,11 Generally, flame-retardant additives have been developed to improve the flame retardancy of epoxy resins.…”