Quasi layer by layer spray deposition of high-quality Ag coatings with excellent micro mechanical properties

In this paper, quasi layer by layer (quasi-LbL) spray deposition has been developed to produce pure and homogeneous metallic coatings on plastic surfaces. Comparing with Ag coatings by electroless deposition, the surfaces prepared by quasi-LbL show reflective and white characteristics that made of uniform nanoparticles of uneven size. By changing pH of spraying solution and spray passes, the surface morphology, roughness, composition, deposition weight and electrical properties of the Ag coatings by quasi-LbL were studies in details. The Ag coating with excellent electrical conductivity was face centered cubic (fcc) metallic state without any other phase, but with less oxides on the top surfaces than Ag coatings prepared by electroless plating. The deposition weight of Ag coatings would increase as the spray passes steps up, and Ag salts were the defining parameter for deposition weight even the spray atmosphere is air or N-2. Nanoindentation tests were used to studies the micro mechanical properties. The modulus and the hardness of Ag coatings are 2.649 GPa and 0.118 GPa respectively, which are higher than those of electroless Ag coatings. The quasi-LbL method shows the possibility of producing high-quality metallic coatings and also be exploited to produce other kinds of metallic coatings, such as Ni and Cu.