Enhanced Thermal Conducting Behavior of Pressurized Graphene-Silver Flake Composites

Abstract

Modern electronics continue to shrink down the sizes while becoming more and more powerful. To improve heat dissipation of electronics, fillers used in the semiconductor packaging process need to possess both high electrical and thermal conductivity. Graphene is known to improve thermal conductivity but suffers from van der Waals interactions and thus poor processibility. In this study, we wrapped silver microflakes with graphene sheets, which can enable intercoupling of phonon-and electron-based thermal transport, to improve the thermal conductivity. Using just 1.55 wt % graphene for wrapping can achieve a 2.64-times greater thermal diffusivity (equivalent to 254.196 ± 10.123 W/m•K) over pristine silver flakes. Graphenewrapped silver flakes minimize the increase of electrical resistivity, which is one-order higher (1.4 × 10 −3 Ω•cm) than the pristine flakes (5.7 × 10 −4 Ω•cm). Trace contents of wrapped graphene (<1.55 wt %) were found to be enough to bridge the void between Ag flakes, and this enhances the thermal conductivity. Graphene loading at 3.76 wt % (beyond the threshold of 1.55 wt %) results in the significant graphene aggregation that decreases thermal diffusivity to as low as 16% of the pristine Ag filler. This work recognizes that suitable amounts of graphene wrapping can enhance heat dissipation, but too much graphene results in unwanted aggregation that hinders thermal conducting performance.

Excellent Medium-Temperature Thermoelectric Performance of Monolayer BiOCl

“…It is well known that mechanical strain is a conventional and feasible method to tune the electronic and optical properties of low-dimensional materials. Meanwhile, large strain could cause the distinct deformation of the lattice structure and significantly change phonon transport properties. − Here, we study the influence of biaxial tensile strain on the TE performance of monolayer BiOCl. The TE transport coefficients with respect to the tensile strains of 0, 1, and 1.5% as a function of the carrier concentration are plotted in Figure a–e.…”

Flexible Grid Graphene Electrothermal Films for Real-Time Monitoring Applications

“…Traditional electrothermal materials such as metal alloys and ceramics have high thermal stability, but their complex manufacturing processes, stiffness, and high-quality density limit their mass production of flexible electrothermal films. − Carbon-based materials, such as carbon nanotubes, , carbon black, , and graphene materials, − have become the best choice for flexible electrothermal films due to their low-quality density, high thermal conductivity, and high-temperature resistance. Among them, graphene material, due to its lightweight, excellent conductivity, mechanical properties, and high electrical-thermal conversion efficiency, has become one of the best choices for electrothermal materials. − A lot of work has been done on the properties of graphene-based electrothermal films. Wang et al prepared a graphene superhydrophobic composite material that can reach a temperature of 65 °C at 50 V and quickly remove the surface ice after 70 s, leaving no water droplet residue .…”

A highly orientational architecture formed by covalently bonded graphene to achieve high through-plane thermal conductivity of polymer composites

“…1,2 Therefore, efficient heat dissipation via electronic packaging systems with the help of high-performance thermal management materials is key to maintaining device performances and lifetimes. [3][4][5][6] Polymer materials present comprehensive properties, such as great mechanical strength, high chemical stability, and relatively light weight, but show extremely low thermal conductivities of 0.1-0.5 W m −1 K −1 due to the amorphous arrangement of molecular chains, which seriously restricts their cooling efficiency. 7 Introducing highly thermally conductive fillers into polymer matrices is an efficient way to address this issue, [8][9][10][11][12][13] in which graphene has attracted a great deal of attention due to its ultrahigh intrinsic thermal conductivity of up to ∼5000 W m −1 K −1 along the basal plane.…”