Environmental Effects in Gel Derived Silicates

Conclusion

At present, it is still to early to generalize as to which of the many processing variables are important in controlling corrosion rates of gel-derived materials. Final density is obviously important but the concentration of bridging oxygen bonds may be even more important. Figure 9 indicates the potential difference in bond energy distributions that may be present in gel-derived silicate glasses in comparison with melt derived glasses of the same composition. Depending upon processing history, a substantially broader distribution of bond distances and bond angles, and therefore bond energies, may be present. The low energy tail of the bond distribution will be much more susceptible to attack by H2O, CO2, Cl2, etc. Thus, the various environmental interactions described above occur at a rate proportional to the breadth of the bond distribution curves shown in Fig. 9.

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Hench, L.L. Environmental Effects in Gel Derived Silicates. MRS Online Proceedings Library 32, 101 (1984). https://doi.org/10.1557/PROC-32-101

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