Interaction of silica glass with molten mixtures of lead and potassium nitrates

The formation of lead–silicate coatings onto the surface of silica glass after its treatment in molten mixtures of Pb(NO3)2–KNO3 and Pb(NO3)2–Cu(NO3)2–KNO3 at 420–520 °C was investigated. The coating formation was supported by the appearance and adsorption/sedimentation of lead–oxide cations and nano-particles, from the salt melt, onto the treated glass surface. These particles, deposited onto the substrate, interacted with the structure of silica glass and formed an amorphous lead–silicate coating exhibiting a chemical composition gradient from PbO to SiO2. The admixture of Cu(NO3)2 in the abovementioned salt mixture favored higher rates of lead oxide sedimentation (co-sedimentation with copper oxide). The external potion of this coating was progressively crystallized during treatment in the molten mixture of Pb(NO3)2–Cu(NO3)2–KNO3 due to the nucleation of Cu2O crystals supporting the formation of Pb8Cu(Si2O7)3, Pb3O4 and 2PbO · SiO2.