Valorization of Ricinus communis outer shell biomass to biochar: Impact of thermal decomposition temperature on physicochemical properties and EMI shielding performance

The rising awareness of electromagnetic pollution has increased interest in renewable and ecologically sustainable materials for shielding electromagnetic waves. Research on carbon-based electromagnetic wave absorption materials derived from agro waste is widely explored due to their advantageous characteristics, including low density and consistent physicochemical properties. The research aims to produce biochar with maximum carbon content from Ricinus communis outer shell (RCOS) and to examine the characteristics of biochar/epoxy composites for their application in electromagnetic (EM) shielding. In this study, the composite made from RCOS-based biochar was effectively developed using slow pyrolysis at 400°C to 700°C. The characterisations of enhanced properties of biochar were conducted by using yield analysis and proximate analysis, elemental analysis, field emission scanning electron microscope (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), electrical conductivity. The biochar pyrolysis results revealed that the biochar yield, fixed carbon and maximum carbon content were 30 wt%, 50.49 wt% and 79.2 wt%, respectively, at 700°C. Fourier transform infrared (FTIR) spectroscopy revealed that for the biochar at 700°C, C=C and C-H functional groups were present, and the others were eliminated as volatile gases during biochar production. TG analysis demonstrated higher biochar stability with residues of 75% for 700°C. The biochar produced at 700°C possesses the maximum electrical conductivity of 95 S/m due to the presence of graphitic carbon. The vector network analyser (VNA) measured a maximum shielding efficiency of 26.5 dB in the X-band frequency when adding 40 wt% biochar prepared at 700°C to the epoxy matrix. The results suggest that the RCOS biochar/epoxy composites have promise as a novel type of absorbent materials because of their low density, lightweight structure, and extensive absorption capacities. These biochar-based lightweight composites can be used as a shielding material for electronic enclosures, telecommunication equipment, and aerospace applications. • The novel RCOS was successfully converted into a valuable product by the slow pyrolysis process. • Pyrolysis temperature influences biochar yield, functional group, pore size and carbon wt%. • Biochar prepared at 700°C had a superior electrical conductivity of 95 S/m. • The 40 wt% RCOS-700 in the epoxy composite possesses SE T of 26.5 dB in the 8–12 GHz.