Microwave-constructed honeycomb architectures of h-BN/rGO nano-hybrids for efficient microwave conversion

Honeycomb architectures of h-BN/rGO nano-hybrids were built from the self-assemblies of hexagonal boron nitride (h-BN) and graphene oxide (GO) through microwave heating for a few seconds. Incorporation of h-BN nanosheets into 3D reduced graphene oxide (rGO) foams was accompanied by the removal of oxygen-containing groups during the rapid “bread baking” process. TEM and SEM images revealed the layer-stacked structure of the samples. XPS, Raman and XRD spectra showed the presence of h-BN layers that were interlaced into the honeycomb architectures of rGO frameworks. The microwave absorption properties and the complex permittivity could be adjusted by varying the microstructure and the content of h-BN. For the wax composite filled with 6.25 wt% h-BN/rGO nano-hybrid with thickness of 1.8 mm, the reflection loss value reached −35.63 dB at 17.2 GHz, and the effective frequency bandwidth reached 6.96 GHz at 2.6 mm with a low surface density. The honeycomb architecture of the hybrid provided multiple electromagnetic transmission paths and consumed significant amount of microwave energy due to the multiple interfaces. Embedding h-BN in the architecture enables excellent impedance matching, and provides highly efficient dielectric material that can be used for microwave absorption. This work demonstrates that microwave treatment is a facile approach to obtaining optimal microwave absorbing properties of h-BN/rGO nano-hybrids.