Phase sepd. glass articles with silicon di:oxide rich surface layer - by leaching an alkali-boron-silicate or alkali-germanium oxide-silicate glass after phase sepn., washing out leaching prods. and heating

摘要

Glass articles are made by (a) melting and forming a preformed glass article in the phase separatable range of the alkali-boron-silicate or alkali-gemermanium oxide-silicate system; (b) phase separating the article; (c) leaching out a low SiO2 phase from the surface regions only to form a structure with porous surface layers surrounding a solid region of the original glass compsn.; (d) washing this structure for 5 mins.-24 hrs. with an organic medium contg. 50%, pref. 25% water, which dissolves the oxides of boron and other leaching out products; and (e) drying and heating to collapse the porous surface layer to form a glass with a SiO2 rich surface region surrounding a solid region of the original glass compsn. The washing stage with the organic medium overcomes the tendency to breaking of the prods. during dehydration and consolidation. The prods. are useful as cooking utensils, radar couplers, aircraft and space vehicle windscreens, windows for structural building, containers, etc..