Post synthesis foaming of graphene-oxide/chitosan aerogel for efficient microwave absorbers via regulation of multiple reflections

Graphene-oxide (GO)/chitosan (CH) aerogels (GCA-1, GCA-2 & GCA-3) have been prepared through hydrothermal route by varying the GO:CH ratio (40:1, 50:1 & 60:1) and its microwave absorption mechanism is investigated. Owing to moderate electrical conductivity (-23 S/m) and high porosity (>99%), maximum attenuation (-16.5 dB) is observed for GCA-2, with 30% reflection and 68% absorption However, upon exposure to hydrazine hydrate vapor, absorption dominating attenuation of -16.3 dB is realized for GCHA-1 with reduction in reflection (SER = -0.42 dB, 8% reflection) and increment in absorption (SEA = -15.6 dB, 88% absorption), that can be attributed to trade-off between conductivity & porosity, leading to improved impedance matching and enhanced multiple internal reflections. This corresponds to absorbance per unit thickness per unit density value of 125 cm(2)/g and specific shielding effectiveness of --556 dBcm(3)/g in GCHA-1, which suggests its utility in making lightweight microwave absorbers for strategic applications.