Thermal conductivity from hierarchical heat sinks using carbon nanotubes and graphene nanosheets

Abstract

The in-plane (kip) and through-plane (ktp) thermal conductivities of heat sinks using carbon nanotubes (CNTs), graphene nanosheets (GNs), and CNT/GN composites are extracted from two experimental setups within the 323-373 K temperature range. Hierarchical three-dimensional CNT/GN frameworks display higher kip and ktp values, as compared to the CNT- and GN-based heat sinks. The kip and ktp values of the CNT/GN-based heat sink reach as high as 1991 and 76 W m(-1) K(-1) at 323 K, respectively. This improved thermal conductivity is attributed to the fact that the hierarchical heat sink offers a stereo thermal conductive network that combines point, line, and plane contact, leading to better heat transport. Furthermore, the compression treatment provided an efficient route to increase both kip and ktp values. This result reveals that the hierarchical carbon structures become denser, inducing more thermal conductive area and less thermal resistivity, i.e., a reduced possibility of phonon-boundary scattering. The correlation between thermal and electrical conductivity (ε) can be well described by two empirical equations: kip = 567 ln(ε) + 1120 and ktp = 20.6 ln(ε) + 36.1. The experimental results are obtained within the temperature range of 323-373 K, suitably complementing the thermal management of chips for consumer electronics.

Thermal Transport on Graphene-Based Thin Films Prepared by Chemical Exfoliations from Carbon Nanotubes and Graphite Powders

“…This finding reveals that the efficiency of thermal transport of heat sinks depends not only on the intrinsic thermal properties (e.g., intrinsic k value), but also on the physical and mechanical preparation method (e.g., compressive treatment). Using the same test platform, the GN-G2 sample was found to possess higher k value than the other designs of heat sinks such as CNT/GN hybrid (1991 W/m K at 323 K) [2] and Al 2 O 3 -coated graphite (1128 W/m K at 323 K) [3]. It can be concluded that the selection of carbon materials is the major contributor to the thermal conduction.…”

“…For accuracy, three pieces of heat sinks were used to get their average readings. One test platform system for determining the k value of the heat sinks was reported in previous studies [2,4].…”

“…Recently, one-and two-dimensional carbon nanostructures-especially carbon nanotubes (CNTs) and graphene nanosheets (GNs)-have attracted a great deal of scientific and technological attention, owing to their extraordinary electrical and thermal properties, exhibiting their applicable feasibility [1,2]. Both CNTs and GNs have been demonstrated to display high theoretical thermal conductivities (k), thus heralding beneficial applications in heat exchangers and thermal management systems.…”

“…However, an obvious gap exists between the actual k values of GN-based layers or heat sinks and the theoretical ones. As to the nano-structured carbons, the k values reported thus far include aligned functionalized multilayer GN architecture (112 W/m K at 298 K) [1], three-dimensional CNT/GN framework (1991 W/m K at 323 K) [2], graphene nanoribbons (2300 W/m K at 300 K) [7], GN-Cu-GN heterogeneous films (373 W/m K at 300 K) [10], and N-doped GN/Cu composite film (543 W/m K) [11]. The major gap can be attributed to the fact that the efficiency of thermal transport is mainly influenced by the presence of topological defects, surface roughness, surface heterogeneity, and porosity in carbon-based heat sinks [7].…”

Synergistic effect of graphene and silicon dioxide hybrids through hydrogen bonding self-assembly in elastomer composites

“…On the one hand, a certain part of evenly distributed SiO 2 is used to bridge the graphene sheet gaps in the in-plane direction that enlarge the phonon transmission channel and benet the phonon propagation, while the re-aggregation of SiO 2 induces larger interfacial thermal resistance that further decreases the thermal conductivity of GS@NR. 49 On the other hand, previous studies [50][51][52] indicated that when graphene sheets are over stacked into a paper, its thermal conductivity greatly drops one order of magnitude due to the phonons leakage across the interface and the enhanced umklapp scattering of out-plane acoustic phonons. However, graphene layers in HGS hybrid llers are intercalated by SiO 2 particles.…”