title: High chloride content calcium silicate glasses.
abstract: Chloride is known to volatilize from silicate glass melts and until now, only a limited number of studies on oxychloride silicate glasses have been reported. In this paper we have synthesized silicate glasses that retain large amounts of CaCl2. The CaCl2has been added to the calcium metasilicate composition (CaO·SiO2). Glasses were produced via a melt quench route and an average of 70% of the chloride was retained after melting. Up to 31.6 mol% CaCl2has been successfully incorporated into these silicate glasses without the occurrence of crystallization.29Si MAS-NMR spectra showed the silicon being present mainly as a Q2silicate species. This suggests that chloride formed Cl-Ca(n) species, rather than Si-Cl bonds. Upon increasing the CaCl2content, the Tgreduced markedly from 782 °C to 370 °C. Glass density and glass crystallization temperature decreased linearly with an increase in the CaCl2content. However, both linear regressions revealed a breakpoint at a CaCl2content just below 20 mol%. This might be attributed to a significant change in the structure and is also correlated with the nature of the crystallizing phases formed upon heat treatment. The glasses with less than 19.2 mol% CaCl2crystallized to wollastonite, whilst the compositions with CaCl2content equal to or greater than 19.2 mol% are thought to crystallize to CaCl2. In practice, the crystallization of CaCl2could not occur until the crystallization temperature fell below the melting point of CaCl2. The implications of the results along with the high chloride retention are discussed.
authors.affiliation: Dental Physical Sciences, Institute of Dentistry, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Mile End Road, London E1 4NS, UK. n.karpukhina@qmul.ac.uk r.hill@qmul.ac.uk xiaojing.chen@qmul.ac.uk.
authors.forename: Xiaojing
authors.identifier: http://orcid.org/0000-0003-1116-6228
authors.initials: X
authors.lastname: Chen
authors.affiliation: Dental Physical Sciences, Institute of Dentistry, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Mile End Road, London E1 4NS, UK. n.karpukhina@qmul.ac.uk r.hill@qmul.ac.uk xiaojing.chen@qmul.ac.uk.
authors.forename: Natalia
authors.initials: N
authors.lastname: Karpukhina
authors.affiliation: Otto-Schott-Institut, Friedrich-Schiller-Universität, Fraunhoferstr. 6, Jena 07743, Germany.
authors.forename: Delia S
authors.initials: DS
authors.lastname: Brauer
authors.affiliation: Dental Physical Sciences, Institute of Dentistry, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Mile End Road, London E1 4NS, UK. n.karpukhina@qmul.ac.uk r.hill@qmul.ac.uk xiaojing.chen@qmul.ac.uk.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Hill