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Dissolution Kinetics of Titanium Pyrochlore Ceramics at 90°C by Single-Pass Flow-Through Experiments

  • J. P. Icenhower (a1), B. P. Mcgrail (a2), H. T. Schaef (a2) and E. A. Rodriguez (a2)

Abstract

Corrosion resistances of titanium-based ceramics are quantified using single-pass flow-through (SPFT) experiments. The materials tested include simple pyrochlore group (B2Ti2O7, where B=Lu3+ or Gd 3+) and compositionally complex pure phase pyrochlore (PY12) or zirconolite- and brannerite-bearing pyrochlore-dominated (BSL3) ceramics. Experiments are conducted at 90°C over a range of pH-buffered conditions with typical duration of experiments in excess of 120 days. Apparent steady-state dissolution rates at pH=2 determined on the Gd2Ti2O7 and Lu2Ti2O7 samples indicate congruent dissolution, with rates of the former (1.3×10-3to 4.3×10-3) slightly faster than the latter (4.4×10−4 to 7.0×10−4g m−2d−1). Rates for PY12 materials into pH=2 solutions are 5.9×10−5 to 8.6×10−5 g m−2 d−1. In contrast, experiments with BSL3 material do not reach steady-state conditions, and appear to undergo rapid physical and chemical corrosion into solution. Dissolution rates of PY12 display a shallow amphoteric behavior, with a minimum (2.7×10−5 g m−2 d−1) near pH values of 7. Dissolution rates display a measurable increase (∼10X) with increasing flow-through rate indicating the strong influence that chemical affinity exerts on the system. These results step towards an evaluation of the corrosion mechanism and an evaluation of the long-term performance of Pu-bearing titanate engineered materials in the subsurface.

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References

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1 Begg, B.D., Weber, W.J., Devanathan, R., Icenhower, J.P., Thevuthasan, S., and McGrail, B.P., Am. Ceram. Soc. Trans. (in press).
2 Boucier, W.L., unpublished LLNL report, 1999.
3 Dove, P.M. and Crerar, D.A., Geochim. Cosmochim. Acta, 54, 955969 (1990).
4 Aagaard, P. and Helgeson, H.C., Amer. J. Sci., 282, 237285 (1982).

Dissolution Kinetics of Titanium Pyrochlore Ceramics at 90°C by Single-Pass Flow-Through Experiments

  • J. P. Icenhower (a1), B. P. Mcgrail (a2), H. T. Schaef (a2) and E. A. Rodriguez (a2)

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