Carbon composite foams with improved strength and electromagnetic absorption from sucrose and multi-walled carbon nanotube

• Carbon composite foams were prepared from molten sucrose and MWCNT.
• The highest compressive strength of 4.9 MPa is achieved at 0.5 wt% MWCNT.
• EMI shielding effectiveness of 39 dB is achieved at 2.5 wt% MWCNT.
• Local shrinkage of sucrose polymer within the MWCNT agglomerates creates mesopores.
• Mechanism of EMI shielding due to dielectric loss within mesopores is established.

Multi-walled carbon nanotube (MWCNT) reinforced carbon composite foams with interconnected cellular structure were prepared by thermo-foaming of MWCNT dispersions in molten sucrose followed by carbonization. The foaming and foam setting time decreases with an increase in the MWCNT concentration. The carbonization shrinkage, foam density and compressive strength showed a decreasing trend after reaching a maximum at a MWCNT concentration of 0.5 wt% indicating MWCNT agglomeration beyond 0.5 wt%. The maximum compressive strength (4.9 MPa) and specific compressive strength (21 MPa/g/cm3) obtained at 0.5 wt% MWCNT concentration corresponded to an increase of 189 and 133%, respectively. The cell walls and struts of the carbon composite foams contained micropores produced by an in situ activation and large mesopores produced by local shrinkage of sucrose polymer within the MWCNT agglomerates. The carbon composite foam showed the highest EMI shielding effectiveness and specific shielding effectiveness of 39 dB and 166 dB/g/cm3, respectively, at a MWCNT concentration of 2.5 wt%. The dielectric loss due to the interaction of electromagnetic waves with walls of the mesopores created by the local shrinkage of sucrose polymer within the MWCNT agglomerates contributed to the electromagnetic absorption.