Optical Properties of Cobalt Films Electrochemically Deposited from Aqueous and Non-Aqueous Ionic Liquids

The purpose of this study is to compare the deposition of cobalt onto a copper substrate from aqueous and non-aqueous cobalt chloride solutions.  The aqueous solution had a pH of 2 and had an equal concentration of cobalt as the non-aqueous. The non-aqueous solution consisted of a 2:1 molar ratio ethylene glycol to choline chloride solution. 

 Deposition was performed for 10, 15 and 30 minute intervals with both solutions at 3 volts potential difference between the copper plate and reference. The suitable electroplating temperatures were found to be 70° C for the non-aqueous solution and 22° C for the the aqueous.  The aqueous was initially run at 70° C to keep the temperature variable constant, but was found incapable of producing consistent films and was run at a lower temperature of 22° C.  The coating deposited by the non-aqueous solution was black of color and had controllable thickness based on time.  The aqueous coating was shiny silver, and was measured to be thinner than that of the non-aqueous films, but still had controllable thickness. 

The black cobalt thin films could have applications in optical systems to reduce parasitic light. Also the non-aqueous has applications in thermal active solar cells as they are conductive and absorb a wide range of the electromagnetic spectrum emitted by the sun, converting it to applicable thermal energy.  The metallic looking cobalt thin films could be applied as mirrors in x-ray optics systems after polishing, as they may have different angles of diffraction.

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