Abstract:Driven by the surface activity of graphene, electrically conductive elastomeric foams have been synthesized by the controlled reassembly of graphene sheets; from their initial stacked morphology, as found in graphite, to a percolating network of exfoliated sheets, defining hollow spheres. This network creates a template for the formation of composite foams, whose swelling behavior is sensitive to the composition of the solvent, and whose electrical resistance is sensitive to physical deformation. The self-asse… Show more
“…Consequently, the localization of BNNSs in the matrix results in a higher probability of filler networking, and thus enhances the TC owing to the reduced phonon scaterring at the filler-filler interfaces. 32,35,[47][48][49][50][51][52]…”
A composite foam consisting of foamed cross-linking polystyrene (c-PS) and boron nitride nanosheets (BNNSs) was synthesized, which shows a higher thermal conductivity (TC) than the corresponding solid counterparts. The BNNSs fillers are found to be aligned along the cell wall as a result of the biaxial stress field from cell expansion during the formation of 3-dimensional interconnectivity in the foams, resulting in an enhanced TC of 1.28 W/m K, near 2 and 4 times those of its solid counterpart and pure c-PS, respectively. It is found that the foaming-assisted formation of the filler network is an efficient strategy to improve the TC at low filler loadings in the composites. Furthermore, the composite foams exhibit low-density, rather low dielectric constants and dissipation factors at wide frequency and temperature ranges. The present work provides a novel approach to designing and preparing lightweight heat conductive polymers with low filler loadings as low-density heat management materials for potential applications in aeronautics and aerospace components.
“…Consequently, the localization of BNNSs in the matrix results in a higher probability of filler networking, and thus enhances the TC owing to the reduced phonon scaterring at the filler-filler interfaces. 32,35,[47][48][49][50][51][52]…”
A composite foam consisting of foamed cross-linking polystyrene (c-PS) and boron nitride nanosheets (BNNSs) was synthesized, which shows a higher thermal conductivity (TC) than the corresponding solid counterparts. The BNNSs fillers are found to be aligned along the cell wall as a result of the biaxial stress field from cell expansion during the formation of 3-dimensional interconnectivity in the foams, resulting in an enhanced TC of 1.28 W/m K, near 2 and 4 times those of its solid counterpart and pure c-PS, respectively. It is found that the foaming-assisted formation of the filler network is an efficient strategy to improve the TC at low filler loadings in the composites. Furthermore, the composite foams exhibit low-density, rather low dielectric constants and dissipation factors at wide frequency and temperature ranges. The present work provides a novel approach to designing and preparing lightweight heat conductive polymers with low filler loadings as low-density heat management materials for potential applications in aeronautics and aerospace components.
“…1 b) it exfoliates, with the individual graphene sheets spreading to cover the interface as depicted in Fig. 1 c 36 , 40 – 43 . Figure 1 ( a ) Vial containing hexadecane (top), water (bottom), and graphite.…”
Section: Resultsmentioning
confidence: 99%
“…1b) it exfoliates, with the individual graphene sheets spreading to cover the interface as depicted in Fig. 1c 36,[40][41][42][43] .…”
Paper diagnostics are of growing interest due to their low cost and easy accessibility. Conductive inks, necessary for manufacturing the next generation diagnostic devices, currently face challenges such as high cost, high sintering temperatures, or harsh conditions required to remove stabilizers. Here we report an effective, inexpensive, and environmentally friendly approach to graphene ink that is suitable for screen printing onto paper substrates. The ink formulation contains only pristine graphite, water, and non-toxic alkanes formed by an interfacial trapping method in which graphite spontaneously exfoliates to graphene. The result is a viscous graphene stabilized water-in-oil emulsion-based ink. This ink does not require sintering, but drying at 90 °C or brief microwaving can improve the conductivity. The production requires only 40 s of shaking to form the emulsion. The sheet resistance of the ink is approximately 600 Ω/sq at a thickness of less than 6 µm, and the ink can be stabilized by as little as 1 wt% graphite.
“…For nanocomposites filled with heavy fillers such as Ag, Fe, and Cu, the effective mass density can be reduced by ∼70% by using graphene-wrapped hollow nanoparticles rather than solid nanoparticles, while still preserving the same κ eff of 1 Wm −1 K −1 . This is not only beneficial to the reduction of the weight and materials costs, but also beneficial to the preservation of the flexibility performances of the polymers which can easily be damaged by a high loading level [46][47][48][49][50] . As shown in Figure 6b, the V f of the nanocomposites filled with graphenewrapped hollow nanoparticles is universally reduced, compared with the counterpart in the nanocomposites filled with solid nanoparticles.…”
Section: Figures 1a-d Show the Microstructures Ofmentioning
Heat removal has become an increasingly crucial issue for microelectronic chips due to increasingly high speed and high performance. One solution is to increase the thermal conductivity of the corresponding dielectrics. However, traditional approach to adding solid heat conductive nanoparticles to polymer dielectrics led to a significant weight increase. Here we propose a dielectric polymer filled with heat conductive hollow nanoparticles to mitigate the weight gain. Our mesoscale simulation of heat conduction through this dielectric polymer composite microstructure using the phase-field spectral iterative perturbation method demonstrates the simultaneous achievement of enhanced effective thermal conductivity and the low density. It is shown that additional heat conductivity enhancement can be achieved by wrapping the hollow nanoparticles with graphene layers. The underlying mesoscale mechanism of such a microstructure design and the quantitative effect of interfacial thermal resistance will be discussed. This work is expected to stimulate future efforts to develop light-weight thermal conductive polymer nanocomposites.
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