The substitution of traditional copper power transmission cables with lightweight copper–carbon nanotube (Cu–CNT) composite fibers is critical for reducing the weight, fuel consumption, and CO2 emissions of automobiles and aircrafts. Such a replacement will also allow for lowering the transmission power loss in copper cables resulting in a decrease in coal and gas consumption, and ultimately diminishing the carbon footprint. In this work, we created a lightweight Cu–CNT composite fiber through a multistep scalable process, including spinning, densification, functionalization, and double-layer copper deposition. The characterization and testing of the fabricated fiber included surface morphology, electrical conductivity, mechanical strength, crystallinity, and ampacity (current density). The electrical conductivity of the resultant composite fiber was measured to be 0.5 × 106 S/m with an ampacity of 0.18 × 105 A/cm2. The copper-coated CNT fibers were 16 times lighter and 2.7 times stronger than copper wire, as they revealed a gravimetric density of 0.4 g/cm3 and a mechanical strength of 0.68 GPa, suggesting a great potential in future applications as lightweight power transmission cables.

Previously, we reported 3D Shaped 3D Graphene (3D2G) with controlled structural design. In this work, we introduced cold rolling as a post-processing technique to obtain compressed 3D2G, referred here as C3D2G, and investigated the relationship between its microstructure and properties. The performed comprehensive materials characterization of C3D2G revealed the micro-motion of the graphene flakes from their random orientations into a stacked and aligned structure along with the extrusion of bulk material into the structural pores which acted as stress-relief spaces. The obtained new bulk morphology significantly enhanced its properties. The achieved gravimetric density, electrical conductivity, and tensile strength of C3D2G were higher than 3D2G by 37.3, 53.4, and 24.9 times, respectively. A new process was demonstrated based on the observed extrusion enabling the welding of multiple pieces of 3D2G into one structure via cold rolling, thus showing potential for dimensional scaling up. The conducted tensile and electrical conductivity studies across the welded region revealed the presence of a mechanical bond within the joined area with a higher strength than the initial pieces involved in welding. Further, a unique application of this material was explored as a reusable, etch-resistant hard mask for patterning silicon wafers, and as a protective barrier against fluorine plasma environment. The etch rate measurements showed a higher etching resistance of C3D2G compared to Si and SiO2 when exposed to a fluorine plasma Reactive Ion Etching (RIE).

Previously, we reported 3D Shaped 3D Graphene (3D2G) with controlled structural pores. In this work, we introduce cold rolling as a post-processing technique to obtain compressed 3D2G referred to as C3D2G. The gravimetric density, electrical conductivity, and tensile strength of C3D2G were higher than 3D2G by 37.3, 53.4, and 24.9 times, respectively. The performed comprehensive materials characterization of C3D2G revealed the micro-motion of the graphene flakes from their random orientations into a stacked and aligned structure along with the extrusion of bulk material into the structural pores which acted as stress-relief spaces. Further, a new process was demonstrated enabling the welding of multiple pieces into one structure via cold rolling, thus showing potential for dimensional scaling up. The conducted tensile and electrical conductivity studies across the welded region revealed the presence of a mechanical bond within the joined area with a higher strength than the initial pieces involved in welding. Due to the enhanced properties of C3D2G, a unique application of this material was explored as a reusable, etch-resistant hard mask for patterning silicon wafers, and as a protective barrier against fluorine plasma environment. The etch rate measurements showed a higher etching resistance of C3D2G compared to Si and SiO2 when exposed to a fluorine plasma Reactive Ion Etching (RIE).

In this work, we describe a simple approach for the synthesis of three-dimensional graphene (3D-G) - carbon nanotube (CNT) hybrid fibers via Chemical Vapor Deposition (CVD). The obtained hybrid fiber was employed as a free-standing current collector in an electrochemical supercapacitor thus avoiding any conductive additives or metals. The amount of graphene synthesized on the CNT fiber and its properties have been easily tuned by different processing parameters, as described in the paper below. The fabricated fibers revealed a reasonable mechanical strength of 220.4 MPa and high electrical conductivity up to 649 Scm(-1). They also showed excellent electrochemical properties and capacitance that was important for their energy storage application. Interconnected PANI nanorods were grown on these fibers by oxidation polymerization, and the resulted fibrous hybrid structures were used as electrodes to make supercapacitors. The created devices employed an ionic liquid gel electrolyte (PVDF-EMIMBF4) which had a voltage window of 3.2 V, thus increasing significantly the energy densities of the supercapacitors. The tested devices achieved a gravimetric energy density of 12.93 Wh/kg and a power density of 1350.25 W/kg at a current density of 1 A/g. They also demonstrated an areal energy density of 14.54 mWh/cm(2) and a power density of 1.37 mW/cm(2) at a current density of 1 mA/cm(2). (C) 2019 Elsevier Ltd. All rights reserved.