Roughening of hollow glass microspheres by NaF for Ni electroless plating

Roughening of non-conductive substrate ceramic materials with hydrofluoric acid (HF) is usually an essential step to enhance adhesion of the coating by electroless chemical plating. However, the violent reaction between HF and the hollow glass microspheres (HGMs) usually causes breakage and damage of the thin shells of HGMs. This paper proposes a modified roughening strategy for Ni electroless plating, i.e., eroding HGMS slowly with a mixture of sodium fluoride (NaF) and hydrochloric acid (HCl). The Na2SiF6 by-products from the reaction of NaF with SiO2 were erased by the following NaOH washing to expose the surface of HGMs without any obvious pores or breakage. Such a modified roughening and followed alkali washing strategy can thus not only reduce the surface corrosion, but also hinder the further damage of HGMs by covering Na2SiF6 sediments. The successive plating of uniform Ni nanoparticles on HGMs was conducted, and the related mechanism was discussed in detail.