Natural Abundance Si-29 and O-17 NMR Methods for Measuring Silicate Glass Structure

Ohio State University, The, Columbus OH

Investigators

Abstract

With this award, the Chemical Measurement and Imaging Program in the Division of Chemistry is supporting Professor Philip Grandinetti at Ohio State University to develop high-throughput methods for characterizing the atomic level structure of glasses using nuclear magnetic resonance (NMR) spectroscopy. Glasses have been used by mankind for millennia. The first historical record of man-made glasses appears as far back as 4500 years ago and the use of glass in windows began over 2000 years ago. Today the technological and economical impact of glassy materials is both immense and diverse. Despite its technological success, glass scientists and engineers still often resort to Edisonian approaches in attempts to understand the chemical compositions of glasses with desired properties. This is because the physical and chemical processes responsible for the properties of glasses and for glass transition are incompletely understood. Professor Grandinetti and his coworkers aim to achieve significantly higher throughput NMR measurements on such samples by optimally integrating two NMR sensitivity enhancement strategies, echo train acquisition and paramagnetic relaxation enhancement. Such high throughput NMR measurements in silicate glasses would considerably expand the range of chemical compositions that could be studied and eliminate the burden and cost of preparing isotopically enriched samples. This would have benefits for scientists studying the physics, chemistry, and materials science properties of glasses. The project will also provides interdisciplinary training opportunities to undergraduate, graduate and post-graduate students. The PI's ongoing partnership with scientists at the CEMHTI-CNRS lab in Orleans, France, will provide students the opportunity to collaborate across national boundaries. A partnership between Professor Grandinetti and Berea College will provide undergraduate students with summer research opportunities. In this multi-tiered project, the Grandinetti group will bring natural abundance Si-29 and O-17 2D NMR measurements of oxide glasses into the realm of routine measurements. In an effort to lay the groundwork for this project, the group will develop a next generation dynamic-angle spinning (DAS) probe in partnership with Revolution NMR, LLC. The group will then employ the DAS probe in a suite of complementary 2D NMR measurements to explore a series of thirty binary glass compositions of fundamental interest. In these studies, the Grandinetti lab will quantify the distributions of Si-O distances, Si-O-Si angles, and network-forming anionic species distributions. They will also develop the chemical shift anisotropy of Si-29 and the quadrupolar coupling of O-17 into a qualitative and quantitative probe of network modifier cation clustering, and develop the Si-29 J coupling across a Si-O-Si linkage into a more reliable probe of Si-O-Si angles and network connectivities. Taken together, these studies aim to provide a new level of qualitative and quantitative detail about structural order and disorder in glass. The structural details of glass to be elucidated through these studies would also benefit scientists seeking to develop thermodynamic models of glasses and melts, and seeking to refine potentials used in molecular dynamics simulations of glasses. Details on modifier cation clustering behavior in glasses will be useful to scientists developing improved structural models of ionic transport, of the mixed alkali effect, and of the microscopic structure of chemically strengthened glass.