Abstract

Changes in the pressure of hydrogen, helium and neon due to diffusion through the wall of silica crystal growth ampoules at elevated temperatures were determined experimentally. We show that, while both He- and Ne-losses closely follow the conventional model of diffusive gas permeation through the wall, hydrogen losses, particularly at low fill pressures, can be much larger. This is interpreted in terms of the high solubility of hydrogen in silica glasses.

Article Outline

1. Introduction

2. Theoretical calculations

3. Experimental procedure

4. Results and discussion

5. Conclusions

Acknowledgements

References

(6K)
Fig. 1. Relative pressures, P/P(init.) of neon, hydrogen, and helium as a function of annealing time. T_a=1000°C, P(init.)=1 atm, GE214 glass. Solid lines are exponential best-fit curves.

(7K)
Fig. 2. Relative pressures, P/P(init.) of hydrogen as a function of annealing time. P(init.)0.015 atm, GE214 glass. Solid lines – calculated ignoring chemical solubility of hydrogen; dashed lines – calculated including chemical solubility (Eq. 7); dotted line – calculated including `tarnishing' reactions (Eq. 11).

(9K)
Fig. 3. Permeation constants of helium, hydrogen, and neon in fused silica glass as a function of temperature. Experimental data: solid symbols – P(init.)=1 atm; open symbols – P(init.)=0.01 atm (the data were derived ignoring the initial unusual pressure drop). The curves are based on literature data and extrapolated for higher temperatures.

(19K)
Fig. 4. Dependence of the half-time, _1/2, on temperature for different ampoule geometrical factors A/(Vd). (a) helium; (b) hydrogen and (c) neon.

References

1. M.M. Faktor and I. Garrett. Growth of Crystals from the Vapour Chapman and Hall, London (1974).

2. B. Andrews, private communication.

3. D.I. Popov, L.L. Regel, W.R. Wilcox, ACCG-10/ICVGE-9 meeting, 4–9 August, 1996, Vail, CO, USA.

4. D.J. Larson, in: Microgravity Materials Science Conf., 10–11 June 1996, Huntsville, Alabama, USA.

5. R. Wilcox and L.L. Regel. Int. J. Microgravity Sci. Technol. 8 1 (1995), p. 56.

6. T. Duffar, P. Boiton, P. Dusserre and J. Abadie. J. Crystal Growth 179 (1998), p. 397.

7. J.E. Shelby. J. Am. Cer. Soc. 55 (1972), p. 61. Abstract-INSPEC  

8. J.E. Shelby. Phys. Chem. Glasses 13 (1972), p. 167. Abstract-Compendex | Abstract-INSPEC  

9. J.E. Shelby. J. Appl. Phys. 51 (1980), p. 2589. Abstract-Compendex | Abstract-INSPEC   | Full Text via CrossRef

10. J. Crank. The Mathematics of Diffusion Oxford University Press, Oxford (1967).

11. J.M. Wiesenfeld, J. Stone, D. Marcase, C.A. Burrus and S. Yang. J. Appl. Phys. 61 (1987), p. 5447. Abstract-INSPEC   | Full Text via CrossRef

12. R.W. Lee. J. Chem. Phys. 38 (1963), p. 448.

13. W. Palosz, in: Materials research in low gravity, N. Ramachandran (Ed.), Proc. 42nd SPIE Meeting, vol. 3123, 1997, p. 34.

14. J.E. Shelby. J. Appl. Phys. 48 (1977), p. 3387. Abstract-Compendex | Abstract-INSPEC   | Full Text via CrossRef

15. O.V. Mazurin, M.V. Streltsina and T.P. Shvaiko-Shvaikovskaya Editors, Handbook of Glass Data Elsevier, New York (1983).

16. R.K. Iler. The Chemistry of Silica Wiley and Sons, New York (1974).

17. G.H.A.M. Van der Steen. Philips Res. Rep. 30 (1975), p. 309. Abstract-Compendex  

18. G.H.A.M. Van der Steen and E. Papanikolau. Philips Res. Rep. 30 (1975), p. 103. Abstract-Compendex  

19. W. Palosz, in preparation.

20. R. Bruckner. J. Non-Cryst. Solids 5 (1970), p. 123. Abstract

^*Fax: +1 205 5448765; e-mail: witold.palosz@msfc.nasa.gov.