Glass - Back to the Future!



Presenting Author:
Oliver Alderman
<oalderman@gmail.com>

article posted 18 March 2016


Oliver Alderman currently works as Research Scientist at Materials Development Inc., and is a Visiting Scientist at Argonne National Laboratory. He obtained an MPhys degree in Physics in 2009, and a PhD in 2013, both at the University of Warwick. His PhD studies included the use of x-ray and neutron diffraction and nuclear magnetic resonance spectroscopy to study the structure of oxide glasses and related materials. Current topics of research include the study of highly refractory melts and the temperature dependent structure of liquids during glass formation, primarily through the use of the aerodynamic levitation and laser heating approach, combined with x-ray and neutron scattering, x-ray spectroscopy and computational modelling.






Changes in local structure about Ti and Fe
during melting and glass formation

Oliver Alderman1,2 *, Lena Lazareva3, Martin C. Wilding4,
Chris J. Benmore2, Lawrie B. Skinner3, Steve Heald2,
Charles E. Johnson5, Jacqueline A. Johnson5,6, Hien-Yoong Hah5,6,
Samuel Sendelbach1, Anthony Tamalonis1, John B. Parise3,
Richard Weber1,2


The local structure about Ti4+, Fe3+ and Fe2+ cations in oxide melts and glasses has been studied using both high-energy x-ray diffraction and x-ray absorption near edge structure (XANES) spectroscopy. In-situ measurements on melts were enabled by the use of an aerodynamic levitation system combined with CO2 laser beam heating.

Oxygen partial pressure was controlled using an environmental chamber and by varying the levitation gas composition, allowing various Fe3+/Fe2+ ratios to be accessed. The results show that both iron and titanium typically have average coordination numbers of 5 or less in the molten state.


Furthermore, changes in the XANES spectra upon melt quenching to form glasses imply that Ti4+ coordination to oxygen increases moderately during cooling, but remains smaller than the octahedral value of 6 found in most of the corresponding crystalline materials.




Changes in iron environment on glass formation are also evident, but interpretation is complicated by possible oxidation during quenching and the presence of both Fe3+ and Fe2+ which may display differential changes. Compositions were chosen from the FeO-Fe2O3-TiO2-MgO-CaO-Al2O3-SiO2 system, including various simplified endmembers, as well as the binary alkaline-earth and rare-earth titanates.















Institutions:

1. Materials Development, Inc., Arlington Heights, IL 60004, USA


2. X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA


3. Mineral Physics Institute, Stony Brook University, Stony Brook, New York, NY 11794-2100, USA


4. Department of Physics, University of Bath, Claverton Down, Bath, BA2 7AY, UK


5. Center for Laser Applications, University of Tennessee Space institute, Tullahoma, USA


6. Department of Mechanical, Aeronautical and Biomedical Engineering, University of Tennessee Space Institute, Tullahoma, TN 37388, USA