Cambridge 7th to 9th September
Presenting Author:
Doris Möncke
<doris.moencke@uni-jena.de>
article posted 20 Mar 2015
Doris Möncke
Doris Möncke joined the Otto-Schott-Institute of Glass Chemistry in 1998 where she acquired her Ph.D. on the topic of irradiation induced defect formation in glasses in 2001 under the supervision of Dr. Doris Ehrt.
After continuing her research as PostDoc in Jena, Doris Möncke joined the Theoretical and Physical Chemistry Institute (TPCI) of the National Hellenic Research Foundation (NHRF) in Athens as a Marie-Curie Fellow from 2007 to 2011, working with Dr. E.I. Kamitsos on NLO properties of thermally poled glasses. In 2011 she joined the group of Prof. Dr. Wondraczek in Erlangen moving 2012 with the group back to Jena where she is working since as lecturer and leader of a small work group on Glass-Archaeometry studying historic glasses.
The main focus of Dr. Möncke's research focuses on structure property correlations of glasses, especially using vibrational spectroscopy on borate- and borosilicate as well as (fluoride- or sulfo-) phosphate glasses. Another important subject of her research concerns the coordination, bonding, and clustering of polyvalent ions in glasses.
IR, Raman and NMR spectroscopic study
on the connectivity of borate and silicate groups
in sodium-borosilicate glasses
Doris Möncke1*, Gregory Tricot2, Efstratios I. Kamitsos3
In borosilicate glasses, the fraction of four - (B4) and three-fold (B3) coordinated boron is an important parameter in the discussion of the structure and of structure-related properties. However, the connectivity of the tetrahedral and trigonal borate groups to each other and to the silicate network is also of high interest, especially since the sodium borosilicate glass ternary does shows a significant compositional range with a metastable immiscibility.
The structure of a series of sodium borosilicate glasses was studied by NMR and vibrational spectroscopy. In order to study the different connectivities of the networking entities, quenched and annealed samples of glasses with a Na2O/B2O3 ratio R~0.2, were analysed. Two dimensional NMR experiments (11B/29Si) reveal a preference of B4 to bond to other borate groups (B4/B3) rather than to silicate units. Only in quenched NBS glasses, forms a significant fraction of B4-O-Si links which are lost upon annealing of the glasses. In quenched glasses, more boroxol rings and silicate rings form and all remaining connections between the borate and silicate sub-networks are based on B3-O-Si linkages.
Models of borosilicate glasses, which for historic rather than experimental reasons, still invoke the occurrence of reedmergnerite [B(OSi)4] like groups should be reconsidered in view of the new experimental evidence.
Institutions:
1 Otto-Schott-Institute, Friedrich-Schiller-University, Fraunhoferstr.6, 07743 Jena, Germany
2 LASIR, UMR CNRS 8516, USTL, Villeneuve d'Ascq Cedex, France
3 Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens, Greece