Studies of Electroless Silver Plating on Cenospheres

Silver coated cenospheres used as wave absorbing materials have been successfully prepared by electroless silver plating on cenospheres with diameter in 3～ 10μm . Formaldehyde-silver ammonia solution was applied as silver-plating solution. The influences of the pH value, stabilizing agent and bath loading on silver plating have been investigated by measurement of the silver content in plated powders and scanning electronic microscope (SEM). The results indicate that the amount of deposited silver increases with increasing the concentration of NaOH in plating bath, which results in the compactness of silver coating layer. Adding stabilizing agent in bath prevents the plating from decomposition, but brings about the discontinuous silver coating layer. By adjustment of bath loading, the thickness of silver coating can be controlled in the range 50～ 200nm , meanwhile the decomposition of plating bath decreased.