Text

theses

The chemical durability of glass is a topic that, while being actively important for identifiable applications such as nuclear waste containment and bioactive glasses, is imperative to understand for predicting the long-term performance of both everyday and cutting-edge technological glass applications. Multicomponent glasses containing multiple network-forming oxides (i.e. SiO2, B2O3, Al2O3, P2O5) comprise the vast majority of technologically-relevant glasses whose behavior in surrounding chemical environments must be well-predicted. These glasses, however, typically have significant compositional and structural complexity which complicates the development of straightforward models to understand their chemical durability. Given the intricacy of this topic and its multifaceted importance for technological glass applications, it is vital to move from an understanding based upon simple composition-dependent models to those based upon composition-structure-property relationships. The necessity for a deeper knowledge of this topic has been propelled by the notion that understanding the relationships between the glass chemistry and their structure at the atomic level will help us in unearthing the fundamental mechanisms of glass corrosion. Based on this viewpoint, this research aims to elucidate the fundamental science governing the aqueous corrosion of multicomponent oxide glasses. With this goal in mind, this research focuses on understanding composition-structure-chemical durability relationships in simplified ternary and quaternary glass systems and addressing some of the remaining fundamental challenges / open questions relating to glass corrosion. Accordingly, glasses designed in the Na2O-B2O3-SiO2, Na2O-Al2O3-B2O3-SiO2, and Na2O-P2O5-B2O3-SiO2 systems have been the subject of this research.

Dissolution studies of sodium borosilicate glasses indicate that thermal history dictates the glass structure and dissolution rate, as the methodology used to quench the glass was shown to impact the dissolution rates by 1.5× to 3×, depending on the composition and molecular structure variations. Studies of the corrosion behavior of wide-ranged sodium aluminoborosilicate glass compositions in acidic environments display that stepwise B2O3 substitutions into nepheline (NaAlSiO4) glass, although causing non-linear changes in glass structure network structural features, lead to strikingly linear increases in the forward dissolution rate in acidic environments resulting from similar aqueous corrosion mechanisms. The strengths of MAS NMR and MD simulations converge to develop an in-depth understanding of the short- and intermediate-range structural features in the sodium borosilicate and sodium phospho-borosilicate glass systems. Furthermore, through careful compositional design in these systems, it is shown that the structural drivers of glass dissolution can be uncovered, which can be applied to develop novel borosilicate bioactive glasses with controlled ionic release. Studies on a sodium borosilicate glass dissolved in multiple solution environments display that buffer solution chemistry impacts dissolution behavior, where kinetics are controlled by acid/buffer composition in the solution. Future work recommended for this topic involves (i) the development of quantitative structure-property relationships (QSPR) from further exploration of the chemical durability of complex mixed network-former glasses and (ii) understanding the kinetics and fundamental mechanisms of glass corrosion from in situ studies or high-resolution examination of the reactive interface/gel layers.

ETD_10744

Ph.D.

Includes bibliographical references

doi:10.7282/t3-am92-mq08

ETD doctoral

The author owns the copyright to this work.