The objective of this research is to synthesize and characterize microstructures and some elastic properties of bioactive glasses subject to relaxation and/or devitrification treatments. We synthesize two kinds of bioglasses, i.e. P-richer 45S5 and P-poorer 55S4.3. After tempering, the as-prepared bioactive glasses are transparent, 55S4.3 being colorless while 45S5 pale pink in color. The thermal events in DTA analysis indicated that the crystallization of 45S5 and 55S4.3 starts at 620oC and 680oC, respectively. The two bioactive glasses became ivory upon heating at 715oC, and the degree of being opaque increases with dwelling time.
The crystalline phase for 45S5 is Na2CaSiO4 -derived Na2Ca2Si3O9 or Na4CaSi3O9. By XRD traces and polarizing optical micrographs, we conclude that the crystal is based on simple cubic structure with a=7.5054Å and space group P213 (198). Due to poor crystallization rate, the crystal in P-poor 55S4.3 glass was not investigated in detail. However, according to the similarity of Raman spectra for devitrified 45S5 and 55S4.3, we suggest that the crystal is similar for the two devitrified glasses.
Raman spectra indicated that the relaxed 45S5 has predominant Q2 and Q3 species and the Q3/Q2 ratio decreases with firing time at 715oC. As for relaxed 55S4.3, the major structural unit is Q3, and the intensity of Q3 is higher for 55S4.3 than 45S5. As the Na+/Si4+ ratio increases, the intensity of 946 (or 947) cm-1 increases while bands near 1100 cm-1 decrease. Based on the Raman spectra of devitrified 45S5 and 55S4.3, the crystals in the two glasses have a common structural unit of SiO32- (Q2).
The elasticity measurement by Brillouin scattering indicated that the moduli for devitrified glass 45S5 are greater than undevitrified 45S5 and 55S4.3 glass. The elasticity of the present bioactive glasses is lower than hydroxyapatite and fluorapatite.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0709104-225627 |
| Date | 09 July 2004 |
| Creators | Huang, Li-jen |
| Contributors | Pou-yan Shen, Der-shin Gan, Ker-chang Hsieh |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0709104-225627 |
| Rights | not_available, Copyright information available at source archive |
Page generated in 0.0025 seconds