An Axially Continuous Graphene–Copper Wire for High‐Power Transmission: Thermoelectrical Characterization and Mechanisms

Abstract

The demand for high‐power electrical transmission continues to increase with technical advances in electric vehicles, unmanned drones, portable devices, and deployable military applications. In this study, significantly enhanced electrical properties (i.e., a 450% increase in the current density breakdown limit) are demonstrated by synthesizing axially continuous graphene layers on microscale‐diameter wires. To elucidate the underlying mechanisms of the observed enhancements, the electrical properties of pure copper wires and axially continuous graphene–copper (ACGC) wires with three different diameters are characterized while controlling the experimental conditions, including ambient temperature, gases, and pressure. The study reveals that the main mechanism that allows the application of extremely large current densities (>400 000 A cm−2) through the ACGC wires is threefold: the continuous graphene layers considerably improve: 1) surface heat dissipation (224% higher), 2) electrical conductivity (41% higher), and 3) thermal stability (41.2% lower resistivity after thermal cycles up to 450 °C), compared with pure copper wires. In addition, it is observed, through the use of high‐speed camera images, that the ACGC wires exhibit very different failure behavior near the current density limit, compared with the pure copper wires.

Synthesis of Vertical Graphene Nanowalls on Substrates by PECVD as Effective EMI Shielding Materials

“…33−35 By contrast, metals such as Cu have a high charge-carrier density (8.491 × 10 28 m −3 ) but low carrier mobility (32 cm 2 •V −1 • s −1 ). 36,37 By combining the complementary properties of VGNs and Cu foam, the improved electrical performance of VGN−metal composites are guaranteed.…”

“…The porous structure will greatly increase the reflecting probability of the incident EM waves in VGNs, making the elimination of the internal EM waves promising to be preferable. On the other hand, graphene has extremely high carrier mobility (>10 4 cm 2 ·V –1 ·s –1 ) but a low intrinsic carrier density of 10 11 –10 12 cm –2 . − By contrast, metals such as Cu have a high charge-carrier density (8.491 × 10 28 m –3 ) but low carrier mobility (32 cm 2 ·V –1 ·s –1 ). , By combining the complementary properties of VGNs and Cu foam, the improved electrical performance of VGN–metal composites are guaranteed.…”

Energy Relaxation and Cooling in Impure Bilayer Graphene at Low Temperatures

“…This leads to the observation of hot electron phenomena, one of the most vibrant areas in graphene research that has been intensively explored experimentally and theoretically. [3][4][5][6][7][8][9][10][11][12] Its significance springs from the fact that the thermal link between electrons and phonons in graphene is relatively weak, and this makes graphene an improved potential candidate for use in high-speed devices, [6] calorimetry, and bolometry. [1,2,9] For equilibration, the hot electrons begin to lose their energy through some cooling pathways of which the electronphonon (el-ph) interaction forms the principal channel of relaxation, as shown in Figure 1a.…”

“…[1,2,9] For equilibration, the hot electrons begin to lose their energy through some cooling pathways of which the electronphonon (el-ph) interaction forms the principal channel of relaxation, as shown in Figure 1a. [5][6][7][8][9] The energy loss can occur through the emission of several types of phonons depending on the temperature range. Longitudinal and transverse types of acoustic, [8,13] optic, [14][15][16] substrate surface, [17,18] piezoelectric, [19,20] and flexural phononic modes can appear as modes of el-ph scattering [12] under different environments (suspended, substrated, etc.)…”

“…Recent studies indicate a growing interest in engineering and scientific communities in the thermal transport properties of graphene and its bilayer, arising from the perspective of the enormous possibilities of applications that rely on thermal transport. [ 1–6 ] Growing integration densities, speed, and power of electronic and optoelectronic devices require efficient management of waste heat. The charge carriers in graphene, when exposed to incident radiation and/or to the electric field, get heated, and therefore the electronic temperature () becomes greater than the temperature of the lattice ().…”