Ca-Si-Al-O-N glasses: Effects of fluorine on glass formation and properties

Stuart Hampshire, Amir R. Hanifi, Annaik Genson, Michael J. Pomeroy

Research output: Contribution to journalArticlepeer-review

Abstract

Oxynitride glasses are effectively alumino-silicate glasses in which nitrogen substitutes for oxygen in the glass network, resulting in increases in glass transition and softening temperatures, viscosities (by two to three orders of magnitude), elastic moduli and microhardness. Calcium alumino-silicate glasses containing fluorine are known to have useful characteristics as potential bioactive materials. Therefore, the combination of both nitrogen and fluorine additions to these glasses may give useful bioglasses with enhanced mechanical stability. This paper gives a review of oxynitride glasses and reports glass formation and evaluation of glass properties in the Ca-Si-Al-O-N-F system. Within the previously defined glass forming region in the Ca-Si-Al-O-N system, homogeneous, dense glasses are formed. However, addition of fluorine affects glass formation and reactivity of the glass melts and can lead to fluorine loss as SiF4, but also nitrogen loss, and cause bubble formation. At high fluorine and high Ca contents under conditions when CaF bonding is favoured, CaF2 crystals precipitate in the glass. It was found that fluorine expands the glass forming region of Ca-Sialon system and facilitates the solution of nitrogen into the melt.

Original languageEnglish
Pages (from-to)165-172
Number of pages8
JournalKey Engineering Materials
Volume352
DOIs
Publication statusPublished - 2007

Keywords

  • Ca-Sialon glasses
  • Fluorine
  • Glass formation
  • Oxynitride glasses

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