EFFECT OF METALLIC NANOCOATINGS DEPOSITED ON SILICON OXIDE ON WETTING BY FILLER MELTS
І. WETTING OF Ti, Nb, Cr, V, AND Mo NANOCOATINGS DEPOSITED ON SiO₂ WITH FILLER MELTS

Abstract

The effect of metallic nanocoatings on the wetting of silicon oxide with lead-based filler melts (Pb–15 wt.% In and Pb–2.5 wt.% Ag) was studied by the sessile drop method with capillary cleaning of the melt in 1 · 10^–3 Pa vacuum at 500 °С. The dependence of the contact angle formed by the filler melt on single coatings (Ti, Nb, Cr, V, Mo) on their thickness δ is shown: the contact angle decreases linearly (from the angle for silicon oxide to the angle for ‘threshold’ coating thickness) with increasing coating thickness. The ‘threshold’ coating thickness for different metals depends on the chemical affinity of the coating metal to oxygen. The higher the chemical affinity, the greater the ‘threshold’ thickness coating. The immobilization (adhesive bonding) of metal coatings on the substrate surface is determined by the contact interaction of SiO₂ and the coating metal. The selection of metal pairs for Mo–Cu, Nb–Cu, V–Cu, Cr–Cu, and Ti–Cu double coatings deposited on SiO₂ is due to various metal interactions. The dependences of contact angle on thickness at a constant thickness of the second layer—the Cu coating (δ_Сu = 100 nm)—are similar in nature to that for a single coating. In these systems, wetting improves linearly with increasing coating thickness in the region of small δ. The wetting of the metallic coating deposited on the oxide surface by metallic melt is determined by the coating thickness (amount of metal deposited), coating structure, affinity of the coating metal to oxygen (coating–substrate adhesive attraction) promoting the shape of ‘islands’ and the ease of dispersion, dissolution of the coating in the filler melt, and wetting of the oxide coating of the adhesion-active metal.