Improved thermal conductivity of epoxy composites using a hybrid multi-walled carbon nanotube/micro-SiC filler

Improving the thermal conductivity of epoxy resin by the addition of a mixture of graphite nanoplatelets and silicon carbide microparticles

“…There are probably two reasons behind this observation: i) the flat surface of 2-D GNPs dramatically enhances the GNP/epoxy or GNP/GNP contact area, moreover, the rigidity of 2-D GNPs allows for better preservation of their high aspect ratio in comparison with the more flexible 1-D MWCNTs [4], thus 2-D GNPs are more efficient in forming heat conductive networks in epoxy matrix as compared with 1-D MWCNTs, and ii) in sharp contrast to 1-D MWCNTs, the flat surface of 2-D GNPs minimizes the geometric contribution to the thermal interface resistance since the contribution of phonon acoustic mismatch to the interface contact resistance increases with the decreasing radius of nanoparticles [5]. Furthermore, as shown in Figures 3-4, in comparison with 3-D micro-SiCs, GNPs also provided stronger improvement of the thermal conductivity of epoxy at identically low filler contents (< 12 wt%) despite the inherently lower thermal conductivity of individual GNP than micro-SiC (~390 W/(m·K) at room temperature [28]). The reason can be attributed to the special morphology of GNPs as well since it is easier for GNPs characterized by 2-D structure to form heat conductive networks in the epoxy matrix, and besides, the high aspect ratio (~447) of GNPs allows a efficient conduction of phonons over a long distance without transitions from particle to particle, whereas the poor contact of micro-SiCs due to their irregularly polyhedral shape along with a low aspect ratio of nearly unity makes it relatively difficult for them to form heat conductive networks.…”

“…FTIR spectrum of GNPs treated micro-SiC/epoxy composites. In this work, micro-SiCs were oxidized followed by silane treatment since it was demonstrated that the ability in improving the thermal conductivity of epoxy follows the sequence: oxidized and silane treated micro-SiC%>%silane treated micro-SiC%>%untreated micro-SiC [28]. It can be seen that below the percolation threshold (~52.1 wt%), the thermal conductivity of oxidized and silane treated micro-SiC/ epoxy composites rises slowly with the increasing micro-SiC content because of a lack of continuous micro-SiC heat conductive chains, but above the percolation threshold, the thermal conductivity increases rapidly, and when 71.7 wt% oxidized and silane treated micro-SiCs were added, the thermal conductivity reached the maximum, ~20.7 times that of epoxy.…”

“…As shown in Figure 6a, by adding 5 wt% GNPs + 55 wt% micro-SiCs, the thermal conductivity of epoxy composite reached 7.06 W/(m·K) (~25.2 times that of epoxy), exceeding that of 71.7 wt%micro-SiC/epoxy composites and also surpassing the previously reported value (24.3 times that of epoxy Figure 6. Thermal conductivity at room temperature of epoxy resin and epoxy composites (a), viscosity at room temperature of each uncured systems at 1 s -1 shear rate (b) [28]) of epoxy filled with 5 wt% COOH-MWCNTs + 55 wt% micro-SiCs. Furthermore, as shown in Figure 6b, the viscosity of epoxy filled with 5 wt% GNPs + 55 wt% micro-SiCs is 6.…”

“…Therefore, so far, by the routine fabrication method, the reported maximum thermal conductivity of epoxy filled with GNPs and other nanofillers is 4.7 W/(m·K) (obtained with 30 wt% GNPs + 10 wt% SWCNTs [4]), failing to exceed the aforementioned maximum thermal conductivity of GNP/epoxy composites. Silicon carbide microparticle (micro-SiC) is an attractive 3-D microfiller candidate for high temperature and high power applications in electronic industries due to its high thermal conductivity (~390 W/(m·K) at room temperature), low thermal expansion coefficient (~4.0 ppm/K, a value close to that of Si chip, ~3.5 ppm/K; 300-673 K), etc [28]. However, improving the thermal conductivity of epoxy by combining 2-D GNPs and 3-D micro-SiCs has not been considered yet.…”

Properties of Oil Palm Empty Fruit Bunch-Filled Recycled Acrylonitrile Butadiene Styrene Composites: Effect of Shapes and Filler Loadings with Random Orientation

“…Zhou et al (2010) found that the microfillers with very high loadings were required to reach the percolation threshold and obtain high thermal conductivity. To overcome this problem, they suggested that inorganic fillers with a nano size, which require a relatively small amount of filler loading, can be used.…”