In contrast to pure silica, SiO2, liquid alumina Al2O3 does not form a glass. This is in accordance with Zachiariasen's rules, since a significant fraction of aluminium atoms exhibit a coordination number of more than four and share edges. However, the introduction of CaO increases the O:Al ratio, allowing the formation of corner-shared AlO4 tetrahedra that facilitate glass formation. Liquid calcium aluminates are important components of natural magmas and their glasses have important applications for infrared-transmitting optics. A detailed and accurate description of the structural role of Al and Ca in high temperature CaO-Al2O3 liquids is important for understanding glass-forming mechanisms. Furthermore, pressure-induced structural transformations in calcium-aluminosilicate melts, and associated changes in physical properties (e.g. compressibility and viscosity), have a profound impact for the rheology of natural magmas and geophysical processes, from planetary formation to present-day volcanism.
In this communication, I will summarise recent progress in using the containerless high-temperature technique of aerodynamic levitation with CO2 laser heating, in combination with synchrotron x-ray diffraction, neutron diffraction with isotope substitution, and state-of-the-art molecular dynamics computer simulations, to reveal unique insight into dramatic and unexpected structural transformations on local and intermediate-range length-scales which take place during vitrification of these non-traditional glass-forming liquids [1,2,3]. I will also discuss the results of in situ laser-heated diamond anvil cell experiments with synchrotron x-ray diffraction of calcium-aluminate liquids and glasses, which reveal pressure-induced Al-coordination change and the development of short-range topological ordering [4].
[1] Drewitt, J.W.E., Jahn, S., Cristiglio, V., Bytchkov, A., Leydier, M., Brassamin, S., Fischer H.E., and Hennet, L. 2011 J. Phys.: Condens. Mat. 23 155101
[2] Drewitt, J.W.E., Hennet, L., Zeidler, A., Jahn, S., Salmon, P.S., Neuville, D.R., Fischer, H.E., 2012 Phys Rev. Lett. 109 235501
[3] Drewitt, J.W.E., Barnes, A.C., Jahn, S., Kohn, S.C., Walter, M.J., Novikov, A.N., Neuville, D.R., Fischer, H.E., and Hennet, L. 2017 Phys. Rev. B 95 064203
[4] Drewitt, J.W.E., Jahn, S., Sanloup, C., de Grouchy, C., Garbarino, G., and Hennet, L. 2015 J. Phys. Condens. Mat. 27 105103
| Subject : | : | Invited Talk (By invitation only) |
| Topics | : | STRUCTURE 6 |
| Keywords | : | aluminate glass ; extreme conditions ; high temperature ; high pressure ; liquid structure ; neutron diffraction ; synchrotron Xray diffraction |
| PDF version | : |  PDF version |
