Electro stamping works by trapping composite particles in the electrolyte, forcing them to plate with the metal. With this new technique, high composite particle loadings are possible even on water sensitive objects. Unlike typical electroplating, this technique does not require submerging the object in a liquid bath.
Any conductive object, regardless of its size or shape. Can be coated with functional materials. Fluorescent metal composite coatings have far reaching applications for dim light environments including aircraft maintenance equipment location, road sign illumination and travel logical markings in mechanically machine parts.
To begin weigh nickel sulfate, nickel chloride hexahydrate and boric acid as mentioned in the text manuscript and combine them in a vial together. Grind this salt mixture thoroughly to a fine powder. Make sure to use proper protective equipment, fume hoods and a hazardous waste disposal system.
Next, Weigh 1.8 grams of europium dysprosium doped strontium aluminate, europium doped yttrium oxide or europium doped barium, magnesium aluminate and grind it into a fine powder using a porcelain mortar and pestle for approximately 10 minutes. Combine the ground composite powder with the salt mixture in a container for storage. Weigh 0.188 grams of this mixture per square centimeter of the coating area and add it to an open top container add 40 microliters of water per square centimeter of coating area to this mixture and stir to dissolve the salt and form a thick paste.
Using a scissor, cut the anode to a size and shape that matches the object to be plated in order to remove organic material from the surface of the anode foil and the cathode clean it with 10 Mueller potassium hydroxide or sodium hydroxide using a cotton swab or cloth. Rinse the surface with water to remove the excess base then activate the metal surface to receive the coating by wiping it with a selective concentrated acid using a cotton swab or cloth, following the recommendations for activating specific metal surfaces and alloys. perform this in the fume hood to avoid exposure to hydrogen chloride vapors quickly deposit the prepared coating paste onto the cathode object, covering the entire area and making sure to avoid gaps.
Activate the anode surface by wiping it with concentrated acid using a cotton swab or cloth. If calculation of current efficiency is required record the mass of the anode and cathode using an analytical balance. preset a power supply to the desired current or voltage mode.
Cut a piece of a hydrophilic membrane such as a nylon sheet and place it on top of the anode coating paste to avoid direct contact with the cathode. Add a small amount of paste or dry salt mixture onto the sheet. Next, add two drops of water to partially dissolve the salt.
This process makes the nylon sheet conductive to allow the mass transport of ions through the electrolyte which is necessary to balance charge in the coating reaction. This can also be accomplished by dipping the nylon membrane in an aqueous nickel salt mixture. Place the activated anode on top and attach both the negative and positive leads to the cathode object.
Cover the entire system with plastic to help retain water and apply moderate pressure. Turn on the power supply and continue coating for a desired duration. Turn off the power supply and expose the system.
Disconnect the leads and rinse the cathode object with water wash the other components of the system by soaking them in water and then discard this aqueous solution in the properly labeled hazardous waste container. To remove any uncoated composite particles gently rubbed the cathode object by hand wearing gloves. Record the mass of the anode and cathode using an analytical balance and calculate the difference with their original mass.
Observe fluorescent coatings with an ultraviolet lamp to verify the brightness and consistency of the metal composite. Use chronopotentiometry to monitor changes in voltage under constant current and chronoamperometry to monitor changes in current under constant voltage. Turn on the potential stud and designate the duration and the applied current or voltage.
prepare the coating as previously described. Normalize the voltage to a reference standard using a calibrated three electrode system. Place a platinum wire as a pseudo reference electrode between the anode and the nylon sheet.
And to cover it with a separate nylon sheet to avoid contact. Deposit a few drops of water and a small amount of coating paste on the anode. Finally connect the leads to the electrodes then seal press and begin coating as described in the text manuscript.
Monitor the changes in voltage or current. Fluorescent or colored particle incorporation can be observed due to a change in appearance compared to the uncoated surface. Optical microscopy was used to investigate the surface coverage and to observe the surface morphology of the coating.
Samples were observed top-down or cut to reveal the cross section the percent composite particle surface coverage as a function of time for Chronoamperometry and as a function of current density for chronopotentiometry increases during coating. Surface coverage is also correlated with thickness. Coating parameters can be monitored under constant voltage using chronoamperometry and under constant current using chronopotentiometry The brightness of the metal composite coatings was quantified with fluorescent spectroscopy and the calculation for luminescence quantum yield was done using the ratios of the peak areas.
When attempting this protocol, it is important to properly clean and activate the electrodes before coating. In addition, thoroughly grinding the precursor electrolyte mixture will help lead to a smooth even coating. The precursor composite electrolyte paste can also be deposited by spray coating or powder coating to save time and materials.
This way objects can be coated at a larger scale. This new technique may stimulate scientific exploration to incorporate other large or hygroscopic composite particles which were previously incompatible with bath, jet or brush plating.
