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.

Usefulness of a Radiofrequency Transseptal Needle in the Second Puncture of Fontan Extracardiac Conduit

We performed a second puncture of the extracardiac conduit in an 11-year-old Fontan patient to assess the patency of the stent previously deployed in the left pulmonary vein. For the first puncture, a mechanical Brockenbrough needle was selected to puncture the Gore-Tex conduit, an electrical insulator. For the second puncture, the location of that previous hole was detected as an indentation covered with atrial tissue, which is an electrical conductor. The second puncture was performed safely using a radiofrequency transseptal needle.

Revealing the growth of copper on polystyrene-block-poly(ethylene oxide) diblock copolymer thin films with in situ GISAXS

Copper (Cu) as excellent electrical conductor and the amphiphilic diblock copolymer polystyrene-block-poly(ethylene oxide) (PS b PEO) as polymer electrolyte and ionic conductor can be combined with an active material in...

Single-Step Shear-Based Deformation Processing of Electrical Conductor Wires

Commercial electrical conductor wires are currently produced from aluminum alloys by multi-step deformation processing involving rolling and drawing. These processes typically require 10 to 20 steps of deformation, since the plastic strain or reduction that can be imposed in a single step is limited by material workability and process mechanics. Here, we demonstrate a fundamentally different, single-step approach to produce flat wire aluminum products using machining-based deformation that also ensures adequate material workability in the formed product. Two process routes are proposed: (1) chip formation by free-machining (FM), with a post-machining, light drawing reduction (<20%) to achieve desired finish and (2) constrained chip formation by large strain extrusion machining (LSEM). Using commercially pure aluminum conductor alloys (Al 1100 and EC1350) as representative material systems, we demonstrate key features of the machining-based processing, including (a) single-step processing to achieve flat wire geometries, (b) surface finish (Ra = 0.2 to 1.0 μm) comparable to that of commercial wire products made by drawing/rolling, (c) deformation control independent of wire size, and (d) hardness increases of 50–150% over that of annealed wires, while retaining high electrical conductivity (>56% IACS). The wire microstructure, which can also be varied via the large-strain deformation parameters, is correlated with mechanical and electrical properties. Implications for commercial manufacture of flat wire products are discussed.