Thermal treatments for biochar and their electrical characterization in epoxy resin composites

Polymer composite based on carbon filler are used to tune the properties (electrical, mechanical and thermal) of final product. Beside the traditional carbon filler like carbon black, nanotubes and graphene, in recent years, biochar is also used. Biochar is a carbon rich material derived from pyrolysis of biomass. Scientific interest on this material is due to its low cost and its great availability. Normally, the pyrolysis thermal treatment to obtain biochar is in the range of 500-700°C (standard product). Here, starting from commercial biochar, we improve its electrical properties by thermal annealing biochar up to 1500°C. Three different treatment temperature (550, 700 and 1500) were investigated. The relevant impact of such thermal treatments on the DC and complex permittivity in the microwave frequency range of the composites is reported.