Those polishing silver have always known that averting the tarnish seems impossible. Even the procedure of polishing is believed to rub away some of the precious metal. Well, it now appears that nanotechnology has come to the rescue for protecting the surface of silver. With a highly innovative approach, scientists have now crafted a protective coating which is so thin that it can’t be seen with the naked eye.
The method used to apply this coating may be termed as atomic layer deposition. With the help of this method, experts can seemingly govern over the thickness of the film at a sub-nanometer level itself. Nanometer thick films of aluminum oxide can be supposedly applied to a sample silver wafer through a special reactor inside a clean room. The films apparently conform to the recesses and protrusions of the silver, creating a protective barrier. However, those into art conservation presume that atomic layer deposition or ALD will undergo rigorous testing before they use it to protect irreplaceable treasures.
“Part of the challenge is to determine what the optimal thickness is that keeps sulfur off the silver surface. Eventually, thermodynamics tells us that the sulfur will diffuse through any layer we put down. The denser the layer, the slower the diffusion. So we’ll start with films that may be a few nanometers thick and investigate the efficacy of these films all the way out to maybe a few hundred nanometers. If we can increase the lifetime of these films to a century, you may not need to do this very often,” stated materials scientist Ray Phaneuf.
In the lab, the coating was subjected to a series of tests. Researchers employed a spectrometer to measure how light reflects off the surface of a test wafer and the way the ALD coating affects the wafer’s color. During the second test, the speed at which sulfur penetrates the coated wafer was gauged. It helped ascertain how many layers of coating will be needed to keep the silver shiny. In another controlled chamber, a coated wafer was heated to speed up the tarnishing.
The ALD not only protects silver, but also seemingly vaporizes the need for polishing.