Hurzhii O. Lead-free silicate enamels in art and jewelry

The thesis for the scientific degree of candidate of technical sciences on specialty 05.17.11 - Technology of Refractory Non-metallic Materials, - State Higher Educational Institution "Ukrainian State University of Chemical Technology", Dnipro, 2017. The paper has presented the results of experimental and theoretical studies on the development of lead-free matrix glass and receiving jewelry enamels of wide range colors with varying degrees of transparency on its base, which can be baked in the same temperature range. We have investigated the area of the system Na2O-BaO-B2O3-SiO2, limited by the content of the components (mol%.) Na2O 10-70; BaO 5-10; B2O3 1-60; SiO2 24-83, which is promising to produce lead-free enamels for gold, silver and copper. The influence of oxides Li2O, K2O, Al2O3, TiO2, ZnO on the properties of the base glass has been investigated. Li2O absence and the ratio Na2O: K2O = 1: 2, and Al2O3: TiO2: ZnO = 1: 6: 6 have been found to increase water resistance of the base glass by 10 times. It has been found that the addition of SnO2, Sb2O5, Na2SiF6, ZrO2 into matrix transparent enamel to produce opaque white and light colored coatings does not cause opacification. The components of TiO2 in the amount up to 15 wt% excess of 100 wt% of the base glass and MoO3 - up to 3.0 wt% cause its high enough opacification. It has been established that opacification of lead-free glass using MoO3 occurs by the mechanism of diffraction. The enamel coating on the basis of molybdenum-containing glass is white with a bluish tint and opalescence effect. Using the developed lead-free matrix glass we have obtained the individual palette of enamels including white, green, mustard, purple, blue, brown, grassy, red, yellow, orange and gray enamel glass coatings of high quality with 57-99% gloss for products from gold, silver and copper.