Abstract
Bioglass 45S5 is well-known for its bioactivity, but it possesses poor sintering behaviour owing to viscous flow being inhibited by the crystallisation of sodium calcium silicate phases. Mg or Zn were partially (0, 25, 50, 75%) or fully (100%) substituted for Ca on a molar base, and thermal properties (differential scanning calorimetry, dilatometry) and sintering (heating microscopy, SEM and X-ray diffraction) were investigated. Here we show that sintering can be improved significantly by partial or complete substitution of Mg or Zn for Ca, owing to a pronounced decrease in crystallisation tendency. Glass transition temperature and dilatometric softening point went through minima for mixed compositions, with random mixing of Mg/Ca or Zn/Ca ions in the glass structure and the resulting effect on configurational entropy being a likely explanation. As the onset of crystallisation did not vary much with substitution, substituted glasses possessed a wider temperature range for sintering, resulting in up to 57% and 27% sample height reduction for Mg and Zn substituted glasses, respectively, compared to only 3% height reduction for Bioglass 45S5. Taken together, these results suggest that using a combination of modifiers, particularly alkaline earths or zinc, may be a promising approach for improving the sintering of Bioglass 45S5.
Highlights
This highly disrupted glass network leads to a pronounced tendency to crystallise and limits high temperature processing such as fibre drawing[7] or s intering[8]
Glass density decreased with Mg for Ca substitution (Fig. 1a) owing to the lower atomic weight of magnesium compared to calcium, while Zn substitution caused a density increase owing to its higher atomic weight
Z n2+ has an ionic radius (60 pm) similar to that of M g2+, Zn substitution resulted in a different trend: a huge drop in V m was observed for 25% Zn for Ca substitution (Fig. 1b), while increasing substitution seemed to cause a slight
Summary
This highly disrupted glass network leads to a pronounced tendency to crystallise and limits high temperature processing such as fibre drawing[7] or s intering[8]. The beneficial effect of magnesium incorporation on glass processing is typically explained by their higher field strength compared to calcium ions[13]. As zinc ions have a field strength similar to that of magnesium ions, a beneficial effect can be expected. Their beneficial biological action in the human body makes Mg and Zn ions of additional interest as components in bioactive glasses. Both ions are co-factors in various e nzymes[14,15] and known for their key roles in bone formation and mineralisation[16,17,18]. Special emphasis was put on characterising glass processing, crystallisation tendency and sintering, using a combination of thermal analysis, heating microscopy, X-ray diffraction and electron microscopy
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
