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The Origin of Anomalous Density Behavior of Silica Glass

Authors :
Shangcong Cheng
Source :
Materials, Vol 16, Iss 18, p 6218 (2023)
Publication Year :
2023
Publisher :
MDPI AG, 2023.

Abstract

The anomalous density–temperature relationship of vitreous silica with low hydroxyl content is explained by the formation of medium-range ordering structure in the glass transition process. The ordered medium-range structure has the shape of a “nanoflake” and consists of two layers of SiO4 tetrahedra, bonded by O atoms located in the middle of the structure. The nanoflakes interact with their surrounding structures through both covalent chemical bonds and van der Waals bonds. In the formation of the van der Waals bonds, the orientation of SiO4 tetrahedra can change, which results in an increase in distance between the nanoflakes and their surrounding structures. Thus, there is a slight volume enlargement associated with the formation of nanoflakes. Since the nanoflakes’ formation starts at a temperature near 1480 °C, and the population of the nanoflakes grows continuously as temperature decreases until about 950 °C, the bulk volume of silica glass increases in the temperature range from about 1480 °C to 950 °C. Therefore, the density anomaly of silica glass can be explained as a byproduct of forming of medium-range ordering structure in the silica glass transition.

Details

Language :
English
ISSN :
19961944
Volume :
16
Issue :
18
Database :
Directory of Open Access Journals
Journal :
Materials
Publication Type :
Academic Journal
Accession number :
edsdoj.1a1f6c8184e4463983294e05b4b0234b
Document Type :
article
Full Text :
https://doi.org/10.3390/ma16186218