Exfoliated and reassembled graphite (ERG): a nanostructured material with multiple applications at the macroscopic scale L, P. Santos and F, Galembeck GG & FG Ltda and IQ - Unicamp

Reference Presenter Authors
(Institution)
Abstract
05-005
Fernando Galembeck Galembeck, F.(University of Campinas); Santos, L.P.(GG & FG Ltda.); The GG & FG company is exploring a platform of new conductive soft materials, based on exfoliated and reassembled graphite (ERG). This novel material is obtained in various forms, from coatings with a high aspect ratio (1 : >100000) to monoliths with volumes up to 1 dm3. The coatings are highly conductive and adherent to many substrates. The coating precursor is an aqueous dispersion of graphite that exfoliates spontaneously within alkaline cellulose solutions, forming stable dispersions. Their application to the substrates is made using different coating techniques, including those used in painting and lithography, followed by suitable finishing techniques. Coated paper sheets are flexible and they perform as the leads in electric circuitry and as electrodes in electrodeposition, supercapacitors, hygroelectricity cells and other electrochemical devices suitable for flexible and wearable electronics. These unique properties of ERG derive from the amphiphilic character of cellulose that allows it to play the roles of exfoliant, dispersant, stabilizer, adhesive and plasticizer while transforming graphite powder in a laminated nanocomposite. ERG can be modified by adding other functional materials, e.g. activated charcoal is used to make supercapacitor electrodes. This material shows relatively low capacitance per unit weight, but its capacitance per unit area compares favorably to competitor supercapacitor electrode materials. The following ERG-based products are now in advanced development stages: 1) Electric circuit boards designed for experimenter kits. Two kits have been produced in development lots as large as 500 hundred units, one for distinguishing conductive from insulating solids and liquids, the other for performing 12 experiments on basic electricity and electrostatics. The first has already been tested with ca. 500 students in high-schools, vocational courses, and engineering junior colleges and it was found highly effective as a teaching tool. The second was produced in a small 20-units series that was sent to expert teachers, for assessment. A 500-unit series followed, for broader distribution and assessment. In January 2019 it will be used by up to 180 high-school students, in the “Ciência e Arte nas Férias” program in Unicamp. 2) Low power-density heaters, where the heating elements occupy a large area, allowing extensive contact with the target objects. This allows the operation of the heater at lower temperatures while keeping the heating power at a lower-than-usual level. Decreasing the temperature gradient across the system decreases the entropy production in the heating operation, thus increasing its efficiency. Various other products of this platform are in earlier development stages, for energy production through hygroelectricity, electrical devices, and sensors, as well as functional paints for non-electrical applications.
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