3D Porous Graphene Based Aerogel for Electromagnetic Applications

Abstract

Lightweight multifunctional electromagnetic (EM) absorbing materials with outstanding thermal properties, chemical resistance and mechanical stability are crucial for space, aerospace and electronic devices and packaging. Therefore, 3D porous graphene aerogels are attracting ever growing interest. In this paper we present a cost effective lightweight 3D porous graphene-based aerogel for EM wave absorption, constituted by a poly vinylidene fluoride (PVDF) polymer matrix filled with graphene nanoplatelets (GNPs) and we show that the thermal, electrical, mechanical properties of the aerogel can be tuned through the proper selection of the processing temperature, controlled either at 65 °C or 85 °C. The produced GNP-filled aerogels are characterized by exceptional EM properties, allowing the production of absorbers with 9.2 GHz and 6.4 GHz qualified bandwidths with reflection coefficients below -10 dB and -20 dB, respectively. Moreover, such aerogels show exceptional thermal conductivities without any appreciable volume change after temperature variations. Finally, depending on the process parameters, it is shown the possibility to obtain water repellent aerogel composites, thus preventing their EM and thermal properties from being affected by environmental humidity and allowing the realization of EM absorber with a stable response.

Figure 1

(a) Schematic procedure for the production of PVDF-GNP nanocomposite aerogel samples. Lightweight aerogel samples made of neat PVDF (b) and GNP-loaded PVDF (c) over flower petals. Water drop over the hydrophilic of (d) or hydrophobic (e) surfaces of aerogel samples, made of PVDF or GNP-loaded PVDF, respectively. (f) List of the produced graphene-based aerogel samples with their GNP concentrations, density and porosity values.

Figure 2

SEM images at different magnifications of the produced aerogel samples with different content of GNPs, as reported in Fig. 1(f). (a,b) G0A; (c,d) G0B; (e,f) G7A; (g,h) G7B; (i,l) G11A; (m,n) G11B; (o,p) G15A; (q,r) G15B.

Figure 3

Results of characterization tests performed on the produced aerogel samples loaded with different GNP content, as reported in Fig. 1(f). (a) FTIR; (b) XRD; (c) Thermal conductivity vs. mid-height sample temperature. (d) Percent volume reduction after thermal conductivity test; (e,f) compression test vs. deformation. The inset of (b) highlights the peak shift due to β phase transition.

Figure 4

(a) Measured compression elastic modulus and (b) DC electrical conductivity of the produced samples as a function of the GNP weight content. (c) Real part and (d) imaginary part of the measured effective complex permittivity, and (e) AC electrical conductivity extracted from the imaginary part of the permittivity. (f) Reflection coefficient of absorbing panels made of materials G11A, G11B, G15A and G15B backed on a perfect electrically conducting surface.