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Iron oxides are frequently found in natural and industrial glass compositions and can affect various physical and chemical properties of the glasses and their melts. Thus, a fundamental understanding of iron-bearing silicate melts and glasses is of both scientific and technological importance. This study investigates the structures of sodium iron silicate glasses with compositions of NaFeSiO4, NaFeSi2O6, NaFeSi3O8, and Na5FeSi4O12 using molecular dynamics simulations in combination with Extended X-ray Absorption Fine Structure (EXAFS) characterizations. Short and medium range structural features of these glasses support that ferrous (Fe2+) and ferric (Fe3+) ions play the roles of network modifier and network former, respectively, with the Fe oxidation states playing an important role in the polymerization of the glass network. These simulation results agree well with newly measured room temperature EXAFS spectra. The simulated glass structures were also compared to the melts structures with the same composition but different redox ratios. The average coordination numbers of the cations were found to be affected both by the melt temperature and iron redox ratio.
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Water as a Modifier in a Hybrid Coordination Network Glass
Abstract Chemical diversification of hybrid organic–inorganic glasses remains limited, especially compared to traditional oxide glasses, for which property tuning is possible through addition of weakly bonded modifier cations. In this work, it is shown that water can depolymerize polyhedra with labile metal–ligand bonds in a cobalt‐based coordination network, yielding a series of nonstoichiometric glasses. Calorimetric, spectroscopic, and simulation studies demonstrate that the added water molecules promote the breakage of network bonds and coordination number changes, leading to lower melting and glass transition temperatures. These structural changes modify the physical and chemical properties of the melt‐quenched glass, with strong parallels to the “modifier” concept in oxides. It is shown that this approach also applies to other transition metal‐based coordination networks, and it will thus enable diversification of hybrid glass chemistry, including nonstoichiometric glass compositions, tuning of properties, and a significant rise in the number of glass‐forming hybrid systems by allowing them to melt before thermal decomposition.
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- PAR ID:
- 10405640
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Small
- Volume:
- 19
- Issue:
- 14
- ISSN:
- 1613-6810
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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