Post synthesis foaming of graphene-oxide/chitosan aerogel for efficient microwave absorbers via regulation of multiple reflections. (November 2021)

• Record Type: Journal Article
• Authors: Chadha, Neakanshika; Saini, Parveen
• Is Part Of: Materials research bulletin. Volume 143(2021)
• Publication Date: 2021-11
• Subjects: Aerogels -- Foaming -- Electrical conductivity -- Microwave absorption -- EMI shielding -- Multiple internal reflections (MIRs); Materials -- Periodicals; Crystal growth -- Periodicals; Matériaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Crystal growth; Materials; Periodicals; 620.11
• DOI: 10.1016/j.materresbull.2021.111458
• Languages: English
• ISSNs: 0025-5408

Abstract

Highlights: GO/CH aerogels have been synthesized by sequential hydrothermal & freeze drying route. Effect of CH proportion & hydrazine vapor on morphology & EMI shielding is examined. Role of aerogel foaming on regulating absorption & reflection is highlighted. Improvement in multiple internal reflections due to foaming is demonstrated. Foamed aerogel displays dominance of absorbance with SSE of ~−556 dBcm 3 /g. Abstract: 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. Graphical abstract: Image, graphical abstract