Dual‐Functional Graphene Composites for Electromagnetic Shielding and Thermal Management

Abstract

and environment. [12][13][14] The current industrial and safety standards require blocking of more than 99% of the EM radiation from any electronic devices. [1,[15][16][17] From the other side, the operation of the electronic devices can be disrupted by the outside EM waves. The heat and EM radiation have an inherent connection-absorption of EM waves by any material results in its heating. The energy from EM wave transfers to electrons and then to phonons-quanta of crystal lattice vibrations. The conventional approach for handling the heat and EM radiation problems is based on utilization of the thermal interface materials (TIM), which can spread the heat, and electromagnetic interference (EMI) shielding materials, which can protect from EM waves. These two types of materials have different, and, often, opposite characteristics, e.g., excellent EMI material can be a poor heat conductor, while efficient TIM can utilize electrically nonconductive fillers, resulting in its transparency for EM waves. Here, we propose a concept of the "dual-functional" EMI shielding-TIM materials, and demonstrate it on the example of graphene composites.It is well known that EMI shielding requires interaction of the EM waves with the charge carriers inside the material so that EM radiation is reflected or absorbed. For this reason, the EMI shielding material must be electrically conductive or contain electrically conductive fillers, although a high electrical conductivity is not required. The bulk electrical resistivity on the order of 1 Ω cm is sufficient for most of EMI shielding applications. [1,3,15] Most of the polymer-based materials widely used as TIMs in electronic packaging are electrically insulating and, therefore, transmit EM waves. Conventionally, metal particles are added as fillers in high volume fractions to the base polymer matrix in order to increase the electrical conductivity and prevent EM wave propagation from the device to the environment and vice versa. [1,[18][19][20][21] However, the polymer-metal composites suffer from high weight, cost, and corrosion, which make them an undesirable choice for the state-of-the-art downscaled electronics. Several studies reported the use of carbon fibers, [22][23][24][25][26][27][28][29] carbon black, [30,31] bulk graphite, [32][33][34] carbon nanotubes (CNT), [16,17,[35][36][37][38][39] reduced graphene oxide (rGO), [2,6,[40][41][42][43][44][45][46][47][48][49][50] graphene, [51][52][53][54] and combination of carbon allotropes with orThe synthesis and characterization of epoxy-based composites with few-layer graphene fillers, which are capable of dual-functional applications, are reported. It is found that composites with certain types of few-layer graphene fillers reveal an efficient total electromagnetic interference shielding, SE tot ≈ 45 dB, in the important X-band frequency range, f = 8.2 −12.4 GHz, while simultaneously providing high thermal conductivity, K ≈ 8 W m −1 K −1 , which is a factor of ×35 larger than that of the base matrix material. The efficiency of the d...

Thermal Properties of the Binary‐Filler Hybrid Composites with Graphene and Copper Nanoparticles

“…The intrinsic thermal conductivity of a large sheet of single‐layer graphene (SLG) can exceed than that of the basal planes of high‐quality graphite, which by itself is high: ≈ 2000 Wm −1 K −1 at RT . Although the few‐layer graphene (FLG) sheets have lower intrinsic thermal conductivity than SLG, they are more technologically feasible for practical applications . The FLG fillers preserve the high thermal conductivity, close to that of graphite, and possess mechanical flexibility, facilitating coupling to the matrix material.…”

“…The FLG fillers preserve the high thermal conductivity, close to that of graphite, and possess mechanical flexibility, facilitating coupling to the matrix material. It is known that FLG can be mass produced at low cost, which is an important factor for any fillers in TIMs, composites, and coatings . The sheets of FLG are also less vulnerable to defects induced by processing, mechanical stresses, rolling, and folding, which happens often during the mixing of fillers with the polymer matrix .…”

“…[10,14,[21][22][23] Although the few-layer graphene (FLG) sheets have lower intrinsic thermal conductivity than SLG, they are more technologically feasible for practical applications. [10,24,25] The FLG fillers preserve the high thermal conductivity, close to that of graphite, and possess mechanical flexibility, facilitating coupling to the matrix material. It is known that FLG can be mass produced at low cost, which is an important factor for any fillers in TIMs, composites, and coatings.…”

“…It is known that FLG can be mass produced at low cost, which is an important factor for any fillers in TIMs, composites, and coatings. [2,5,7,10,20,[24][25][26][27][28] The sheets of FLG are also less vulnerable to defects induced by processing, mechanical stresses, rolling, and folding, which happens often during the mixing of fillers with the polymer matrix. [10,20,24] The first study of graphene composites reported an enhancement of the thermal conductivity of epoxy from 0.2 to ≈ 5 Wm −1 K −1 at the low graphene loading of ≈ 10 vol%.…”

A General Approach for Buckled Bulk Composites by Combined Biaxial Stretch and Layer‐by‐Layer Deposition and Their Electrical and Electromagnetic Applications

“…[5,6] These elastic conductors have been used to construct different types of devices, such as interconnects, electromagnetic interference (EMI) shielding materials, antennas, and so on. [7][8][9][10][11][12][13][14][15][16][17][18][19] The ideal stretchable conductors present high conductivity and stable conductance during large deformation, and a uniform bulk structure. It should be noted that the uniform bulk structure is the premise of making ideal stretchable Fabrication of high quality stretchable conductors that show bulk structure, high electrical conductivity, and stable conductance under large deformations is crucial for wearable electronics and soft robots.…”