1H MAS NMR and IR studies on powdered alkali-lime-silica glasses

Abstract

Powdered samples of glasses with the composition 16 R2O ∙ 10 CaO ∙ 74 SiO2 (R = Na, K, Cs) and a concentration of water in glass of about 0.03 mol ∙ l^-1 were studied by solid state 1H MAS NMR (magic angle spinning nuclear magnetic resonance). Three superimposed NMR signals at about 6.3, 12.5 and 15.6 ppm were recorded, which were assigned to three different proton sites involved in weak, strong and very strong hydrogen bonds, respectively. The relative intensity of the NMR signals depends on the type of alkali in the glass. The amount of OH groups with strong and very strong hydrogen bonding increases in relation to the weakly bonded hydroxyl groups upon substitution of Na2O, K2O or Cs2O, respectively. The result is in good agreement with the earlier IR findings for these glasses. Thus, Scholze's interpretation [1 to 3] of the region of the OH stretching vibrations in the IR spectra could be verified firstly by NMR spectroscopy as an independent analytical method.