Fluidized Bed Sputtering for Particle and Powder Metallization

A system for sputter deposition of thin (10 1000 nm) metal and ceramic coatings onto vibro-fluidized beds of microparticles has been fabricated. Coatings are sputtered onto microparticles of various sizes, shapes, and materials. Experiments show that the coating deposition rate onto particles decreases with decreasing particle size for the case of a fixed total bed mass. Factors affecting particle coating thickness also include sputter power and fluidized bed container size. Coating surface morphology is evaluated using scanning electron microscopy. Lower sputter deposition powers create smoother, less porous coatings. Fluidizing parameters such as driving amplitude and frequency are also shown to affect coating morphology. Barrier coatings on salt microparticles are produced and shown to slow the dissolution of the coated salt particles in water. Dual-layer memetal-ceramicoatings are also demonstrated using the sputter deposition technique. A dual-layer aluminum/tin-oxide coating is produced on glass microspheres, which are then shown to have distinct reflectance characteristics and colors. A model is developed to estimate coating thickness based on size, shape, and number of particles.
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