TY - GEN
T1 - The role of fluorine in glass formation in the Ca-Si-Al-O-N system
AU - Hanifi, Amir Reza
AU - Genson, Annaik
AU - Pomeroy, Michael J.
AU - Hampshire, Stuart
PY - 2008
Y1 - 2008
N2 - Oxynitride glasses are found as grain boundary phases in silicon nitride ceramics. They are effectively alumino-silicate glasses in which nitrogen substitutes for oxygen in the glass network, and this causes increases in glass transition and softening temperatures, viscosities (by two to three orders of magnitude), elastic moduli and microhardness. Calcium silicate-based 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 glasses with enhanced mechanical stability for use in biomedical applications. This paper reports glass formation and evaluation of glass properties in the Ca-Si-Al-O-N-F system. Within the previously defined Ca-Si-Al-O-N glass forming region at 20 eq.% N, 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, and also nitrogen loss. As these gases evolve, bubbles are formed in the glass. The compositional limits for both dense and porous glass formation at 5 eq.% F have been mapped. At high fluorine contents under conditions when Ca-F bonding is favoured, CaF2 crystals precipitate in the glass. The maximum fluorine content found in this system is 7 eq% at a composition Ca 28Si51Al21O73N20F 7. The role of the different cations in these oxyfluoro-nitride glasses is discussed.
AB - Oxynitride glasses are found as grain boundary phases in silicon nitride ceramics. They are effectively alumino-silicate glasses in which nitrogen substitutes for oxygen in the glass network, and this causes increases in glass transition and softening temperatures, viscosities (by two to three orders of magnitude), elastic moduli and microhardness. Calcium silicate-based 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 glasses with enhanced mechanical stability for use in biomedical applications. This paper reports glass formation and evaluation of glass properties in the Ca-Si-Al-O-N-F system. Within the previously defined Ca-Si-Al-O-N glass forming region at 20 eq.% N, 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, and also nitrogen loss. As these gases evolve, bubbles are formed in the glass. The compositional limits for both dense and porous glass formation at 5 eq.% F have been mapped. At high fluorine contents under conditions when Ca-F bonding is favoured, CaF2 crystals precipitate in the glass. The maximum fluorine content found in this system is 7 eq% at a composition Ca 28Si51Al21O73N20F 7. The role of the different cations in these oxyfluoro-nitride glasses is discussed.
UR - http://www.scopus.com/inward/record.url?scp=57649231285&partnerID=8YFLogxK
M3 - Conference contribution
AN - SCOPUS:57649231285
SN - 9780470196335
T3 - Ceramic Engineering and Science Proceedings
SP - 337
EP - 346
BT - Mechanical Properties and Performance of Engineering Ceramics and Composites III - A Collection of Papers Presented at the 31st International Conference on Advanced Ceramics and Composites
T2 - 31st International Conference on Advanced Ceramics and Composites
Y2 - 21 January 2007 through 26 January 2007
ER -