School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran
چکیده
Airbrushing is a simple, cost-effective, and easy-to-use method for applying thin layer coatings. In this study, the Fabrication of a graphite-coated copper layer using airbrush spraying has been investigated, which requires stable graphite suspensions without any noticeable sedimentation before and while spraying. In order to obtain the best possible suspension, different ratios of Polyvinylpyrrolidone (PVP) in a mixture of water and graphite were prepared. Polyvinylpyrrolidone (PVP) was used as a surfactant agent that is able to disperse graphite particles in the liquid mixture, which also acts as a binder to improve the adhesion of graphite particles to the substrate. These materials were mixed, stirred for 15 minutes, and then sonicated for 1 hour. Finally, adequate amount PVP was added. In order to determine each suspension's stability, the turbidity of all samples in an 8 hours interval was measured with in-house made instrument. Because of the difference between each sample's sedimentation rate and testing conditions, the final results could be juxtaposed, and, therefore, their stability could be compared in this way. These observations demonstrated that there is an optimum PVP content that makes the suspension most stable, which is around 0.3 grams. A lower or higher amount of PVP was seen to make the stability worse. The sample with 0.3 grams PVP had the lowest sedimentation rate and thus was chosen for spraying. In the next step, the coated substrate that was a thin copper layer with a thickness of 20 micrometers was worked with sandpaper in order to increase the roughness of the surface and, by that, increase the possibility of adherence of graphite particles; then the suspension was sprayed on the copper layer via an airbrush. The coated layer was taken under a scanning electron microscope to determine the graphite coating's morphology. It was shown that the coating is dense and was applied uniformly, making it suitable for possible use in lithium-ion battery electrodes.
