Increased Electrical Conductivity of Carbon Nanotube Fibers by Thermal and Voltage Annealing

We report the effect of annealing, both electrical and by applied voltage, on the electrical conductivity of fibers spun from carbon nanotubes (CNTs). Commercial CNT fibers were used as part of a larger goal to better understand the factors that go into making a better electrical conductor from CNT fibers. A study of thermal annealing in a vacuum up to 800 °C was performed on smaller fiber sections along with a separate analysis of voltage annealing up to 7 VDC; both exhibited a sweet spot in the process as determined by a combination of a two-point probe measurement with a nanoprobe, resonant Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Scaled-up tests were then performed in order to translate these results into bulk samples inside a tube furnace, with similar results that indicate the potential for an optimized method of achieving a better conductor sample made from CNT fibers. The results also help to determine the surface effects that need to be overcome in order to achieve this.

Wider Potential Windows of Cellulose Multiwall Carbon Nanotube Fibers Leading to Qualitative Multifunctional Changes in an Organic Electrolyte

The trend across the whole of society is to focus on natural and/or biodegradable materials such as cellulose (Cell) over synthetic polymers. Among other usage scenarios, Cell can be combined with electroactive components such as multiwall carbon nanotubes (CNT) to form composites, such as Cell-CNT fibers, for applications in actuators, sensors, and energy storage devices. In this work, we aim to show that by changing the potential window, qualitative multifunctionality of the composites can be invoked, in both electromechanical response as well as energy storage capability. Cell-CNT fibers were investigated in different potential ranges (0.8 V to −0.3 V, 0.55 V to −0.8 V, 1 V to −0.8 V, and 1.5 V to −0.8 V), revealing the transfer from cation-active to anion-active as the potential window shifted towards more positive potentials. Moreover, increasing the driving frequency also shifts the mode from cation- to anion-active. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy were conducted to determine the ion species participating in charge compensation under different conditions.

Joining of Carbon Nanotube Fiber by the Meniscus-Confined Electrochemical Deposited Silver

To use carbon nanotube fibers (CNT) extensively in a wide range of electrical and electronic applications, an essential key step is to produce a low-resistance, high-strength and reliable connection between the CNT fibers and other live parts in the circuit. In this study, meniscus-confined electrochemical deposition (ECD) process with silver was proven to be a practical way of joining CNT fibers together head-to-head. The whole ECD process was stable. The shape of the joints was found to depend on the shape of the tips of the CNT fibers. The deposited silver exhibited a dense and uniform microstructure and it was tightly bound to the CNT fibers, with a distinct interface between them. In the ECD process, the original morphology of the CNT network was maintained. The lowest electrical resistance of the CNT fibers joints was measured to be 8.72[Formula: see text][Formula: see text], which is 45% lower than that of the original CNT fibers. The deposited joint sustained a fracture load of 7.5cN with an elongation of 0.4%.