Coulson And Richardson Volume 1 Pdf 163
In addition to the wideband EM properties, the samples produced in this study show exceptional thermal conductivities and stability, i.e. a negligible volume change after temperature variations. All these characteristics make the proposed aerogels good candidates for EM absorption in aerospace, space and electronic applications. Moreover, depending on the process parameters, the PVDF/GNP aerogels can be rendered water repellent. This quality is particularly relevant for electronic packaging, since the EM and thermal performances of these materials will not be affected by environmental humidity.
coulson and richardson volume 1 pdf 163
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.
The measured results of volume reduction due to sample heating after the thermal conductivity tests are displayed in (Fig. 3d). Only neat PVDF aerogel samples and the ones filled with 7% wt. of GNP exhibit a reduction of volume size, due to polymer shrinkage. This effect becomes negligible when a higher amount of GNP is added. In fact, the samples filled with GNPs at 11% and 15% wt. are not affected by any relevant volume reduction. This can be attributed to the fact that for higher GNP concentration, the aerogel is supported mechanically by a skeleton made of a 3D network of GNPs, which prevents the thermally induced shrinkage of the aerogel39. On the contrary, for lower GNP concentration, the polymeric nature of the aerogel is predominant over the observed volume reduction. 350c69d7ab