• Patzig, Christian
• Jaimes, Altair T. Contreras
• Brauer, Delia S.
• Juliana, Martins De Souza E. Silva
• Karpukhina, Natalia
• Kirste, Gloria
• Massera, Jonathan
• De Pablos Martin, Araceli
• Hill, Robert G.

Abstract

A combination of XRD, solid-state NMR and state-of-the-art imaging techniques were used to investigate how the calcium orthophosphate/calcium silicate ratio affects the crystallisation of bioactive glasses in the system SiO2-P2O5-CaO-CaF2. In the phosphate-free glass, xonotlite, wollastonite and cuspidine crystallised. From 2.4 mol% P2O5, fluorapatite also formed, while the amount of wollastonite decreased. Crystallisation tendency was low for low phosphate contents, while above 3 mol% P2O5 it increased. The phosphate-free glass showed a volume crystallisation mechanism with constant activation energy. By contrast, the glass with the largest phosphate to silicate ratio showed both volume and surface crystallisation, causing a pronounced decrease in activation energy with crystallisation degree. This work shows that by changing the phosphate/silicate ratio we can determine which crystal phases form, obtaining for example fluorapatite-free or wollastonite-free glass-ceramics, depending on the desired application and properties such as mechanical strength or activity in contact with physiological solutions.

Topics

• microstructure
• surface
• phase
• x-ray diffraction
• glass
• glass
• strength
• activation
• ceramic
• Calcium
• Nuclear Magnetic Resonance spectroscopy