Ibrahim, Sukaina (2010)
M.Res. thesis, University of Birmingham.
There is ongoing research into calcium phosphate glasses as possible candidates for use in dental restoration and in the field of bone implants. This is due to the fact that calcium phosphate glasses have many useful properties such as bioactivity, biocompatibility, bioresorbability and non toxicity. However, on the other hand they are also known to fail catastrophically and therefore cannot be used in load bearing applications and are limited as coatings to metallic substrates. Calcium phosphate glasses with different types of oxides such as magnesium, [27-28, 30-34] sodium, [14, 36-40] fluorine [41-42] in the presence of titania have been used in research to investigate whether addition of these oxides can help improve the properties of the glasses. It has been shown that calcium phosphate glasses containing fluorine have shown to produce fluoroapatite which is beneficial as it is known to be one of the ways in order to improve chemical durability of calcium phosphate glass-ceramics. [41-42] In the present study, type A glass and glass-ceramics demonstrated the effect of TiO2 addition with reduction of calcium to phosphorus ratio and type B glass and glass-ceramics demonstrated the effect of TiO2 addition with constant calcium to phosphorus ratio on the structure of fluorine containing calcium phosphate glasses and glass-ceramics. The TiO2 addition in type A took place in 5 %, 15 % and 20 % molar content of TiO2 and in type B, TiO2 was added to glasses in 4.76 %, 11.11 %, 16.66 % and 20 % molar content of TiO2. FTIR, DSC, XRD, ESEM and TGA (performed only on amorphous glasses) were used to characterise the glasses and glass-ceramics produced. DSC and density measurements showed that when 15 mol % TiO2 was added in type A; it caused disruption in the glass network which was confirmed by a reduction in the Tg. When TiO2 was added into the glass in type B, there was a general increase in Tg observed which confirmed that TiO2 might strengthen the glass network. XRD results showed that in both type A and type B glass-ceramics, crystal phases corresponding to calcium metaphosphate, calcium pyrophosphate and titanium pyrophosphate were present. No phase however corresponding to fluorine was found. FTIR results of type A and type B glasses showed peaks corresponding to metaphosphate, pyrophosphate and orthophosphate groups. In the FTIR spectra of both the glass-ceramics however, peaks corresponding to the metaphosphate and pyrophosphate groups were decomposed into several narrow peaks. ESEM images demonstrated the presence of different crystal phases in the glass-ceramics. Titanium pyrophosphate was seen mainly at the surface of the glass-ceramics but in the bulk of the glass-ceramics, crystals corresponding to metaphosphate and pyrophosphate were observed. TGA and EDX analysis confirmed that unfortunately only some fluorine was retained in the amorphous glass and there was no crystalline phase that contained fluorine.
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