TY - BOOK

T1 - Interaction of water with oxide glass structures

AU - Balzer, Robert

PY - 2019

Y1 - 2019

N2 - The aim of this thesis is to investigate the influence of different network converters on different glass structures. A special focus lies hereby on the incorporation of water regarding its corrosive behavior on the glass network. This in turn improves the understanding of water-related material fatigue and subcritical crack growth in technical glasses. For this purpose, two lithium-magnesium aluminophosphate glasses (30Li2O 20-xMgO xAl2O3 50P2O5 with x = 0 and 5), 4 silicoborate glasses (15- xNa2O xCaO 15SiO2 70B2O3 with x = 0; 7.5 and 10, as well as 10Na2O 15SiO2 and 75B2O3) and three aluminosilicate glasses (22.5-xNa2O xK2O 22.5 Al2O3 55SiO2 with x = 0; 7.5; 11.25) were prepared. Water bearing glasses between 0-8 wt% H2O were synthesized at 500 MPa using an Internally Heated Pressure Vessel (IHPV) at temperatures between 1473 – 1873 K. With respect to the structure and water speciation in the glasses, anhydrous and hydrous glasses have been analyzed using MAS-NMR (Magic Angle Spinning Nuclear Magnetic Resonance) and infrared-spectroscopy (IR). The glass transition temperature (Tg) was determined by Differential Thermal Analysis (DTA). IR spectroscopy on phosphate glasses reveal that OH groups are the dominating water species. A similar trend was observed in silicoborates. The incorporation of water results in a dominance of hydroxyl groups, here too. A dominance of OH groups was also observed in aluminum-containing phosphates. However, the proportion of molecular water is higher compared to aluminum-free phosphates. In aluminosilicates, on the other hand, the incorporated water is present in molecular form at water contents above 3 % wt%. The decrease in Tg upon hydration is similarly continuous for phosphates and silica borates, while a dramatic decrease has been observed for aluminosilicates. This indicates that the incorporation of OH groups has a significantly weaker effect on structural relaxation in phosphate and borate systems than in silicate dominated glasses. The depolymerization of the glass network during hydration varies depending on the glass system. The incorporation of water has a very strong depolymerizing effect on the phosphate structure, as more and more Q1 and even Q0 species are formed at the expense of Q3 and Q2 species as the water content increases. 11B MAS NMR in silicoborates reveals that the BO4 species depends mainly on the alkali and alkaline earth content and that water plays only a minor role in the formation of the BO4 species. However, the efficiency for the formation of BO4 units in silicoborates is higher than in pure borate glasses. 27Al MAS NMR spectra of aluminosilicates reveal that aluminum is exclusively present in the form of AlO4 tetrahedra in both dry and hydrous glasses. The incorporation of water causes the relaxation of highly distorted Q4 species by forming slightly depolymerized Q3 species.

AB - The aim of this thesis is to investigate the influence of different network converters on different glass structures. A special focus lies hereby on the incorporation of water regarding its corrosive behavior on the glass network. This in turn improves the understanding of water-related material fatigue and subcritical crack growth in technical glasses. For this purpose, two lithium-magnesium aluminophosphate glasses (30Li2O 20-xMgO xAl2O3 50P2O5 with x = 0 and 5), 4 silicoborate glasses (15- xNa2O xCaO 15SiO2 70B2O3 with x = 0; 7.5 and 10, as well as 10Na2O 15SiO2 and 75B2O3) and three aluminosilicate glasses (22.5-xNa2O xK2O 22.5 Al2O3 55SiO2 with x = 0; 7.5; 11.25) were prepared. Water bearing glasses between 0-8 wt% H2O were synthesized at 500 MPa using an Internally Heated Pressure Vessel (IHPV) at temperatures between 1473 – 1873 K. With respect to the structure and water speciation in the glasses, anhydrous and hydrous glasses have been analyzed using MAS-NMR (Magic Angle Spinning Nuclear Magnetic Resonance) and infrared-spectroscopy (IR). The glass transition temperature (Tg) was determined by Differential Thermal Analysis (DTA). IR spectroscopy on phosphate glasses reveal that OH groups are the dominating water species. A similar trend was observed in silicoborates. The incorporation of water results in a dominance of hydroxyl groups, here too. A dominance of OH groups was also observed in aluminum-containing phosphates. However, the proportion of molecular water is higher compared to aluminum-free phosphates. In aluminosilicates, on the other hand, the incorporated water is present in molecular form at water contents above 3 % wt%. The decrease in Tg upon hydration is similarly continuous for phosphates and silica borates, while a dramatic decrease has been observed for aluminosilicates. This indicates that the incorporation of OH groups has a significantly weaker effect on structural relaxation in phosphate and borate systems than in silicate dominated glasses. The depolymerization of the glass network during hydration varies depending on the glass system. The incorporation of water has a very strong depolymerizing effect on the phosphate structure, as more and more Q1 and even Q0 species are formed at the expense of Q3 and Q2 species as the water content increases. 11B MAS NMR in silicoborates reveals that the BO4 species depends mainly on the alkali and alkaline earth content and that water plays only a minor role in the formation of the BO4 species. However, the efficiency for the formation of BO4 units in silicoborates is higher than in pure borate glasses. 27Al MAS NMR spectra of aluminosilicates reveal that aluminum is exclusively present in the form of AlO4 tetrahedra in both dry and hydrous glasses. The incorporation of water causes the relaxation of highly distorted Q4 species by forming slightly depolymerized Q3 species.

U2 - 10.15488/5554

DO - 10.15488/5554

M3 - Doctoral thesis

CY - Hannover

ER -