Effect of boron oxide addition on fibre drawing, mechanical properties and dissolution behaviour of phosphate-based glass fibres with fixed 40, 45 and 50 mol% P2O5.
Bottom Line: The mechanical properties of the fibres were found to significantly increase with increasing B2O3 content.Initial loss of mechanical properties due to annealing was found to be recovered with degradation.Both annealed and non-annealed fibres exhibited a peeling effect of the fibre's outer layer during degradation.
Affiliation: Division of Materials, Mechanics and Structures, University of Nottingham, Nottingham, UK.Show MeSH
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Mentions: For comparison, the dissolution rate of the annealed and non-annealed fibres was calculated using diameter and density of the degraded fibres at different time points for P45B0, P45B5 and P45B10 formulations (Figure 8). It was found that the dissolution rate of the annealed degraded P45B0, P45B5 and P45B10 fibres was 42%, 38% and 47% lower than the non-annealed ones. Moreover, it was still possible to handle and test the annealed fibres for a longer period of time as compared to the non-annealed ones. Cozien-Cazuc et al.30 found that after 24 h of degradation, the dissolution rate of non-annealed fibres was 2 × 10−7 g cm−2 min−1, whereas the annealed fibres showed a much lower degradation rate, i.e. 1.1 × 10−7 g cm−2 min−1. Hayden et al.51 suggested that a surface tensile stress layer was generated in the phosphate glasses during thermal annealing due to the surface re-arrangement caused by the water vapour attack. This tensile layer could account for the initial low-tensile strength values as this layer would be prone to cracking followed by a uniform degradation.51 Thus, an increase in tensile strength for fibres during the degradation process may be explained by the progressive removal of the outer tensile layer resulting in a reduction in the fibre diameter. Parsons et al.42 also suggested that stress developed in phosphate glass fibres during the fibre-drawing process could be relieved by heat treatment, which would change the mode of degradation. Thus, although the initial strength of the annealed fibres was significantly lower than the as drawn fibres, annealing appeared to impart significant improvements in the durability of the fibres. A decrease in dissolution rate was also observed with increasing B2O3 content from 0 to 10 mol%. A similar decreasing trend of dissolution rate with increasing B2O3 content was observed for bulk glasses in a previous study.40 This decrease in dissolution rate with increasing B2O3 was attributed to the replacement of P-O-P bonds with P-O-B bonds, which also correlated well with an increase in Tg and a decrease in thermal expansion coefficient.Figure 8.
Affiliation: Division of Materials, Mechanics and Structures, University of Nottingham, Nottingham, UK.