科研之友
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摘要
Under pressure and temperature conditions like those found in deep geological repositories (DGRs), rare-earth cations may react with silicates to form rare-earth disilicates. This study establishes the stability range of yttrium disilicates in response to changes in pH. The alpha, beta, gamma, and delta polymorphs of Y(2)Si(2)O(7) were synthesized by the sol-gel process at temperatures between 1100 and 1650 degrees C and subjected to pH(stat) leaching tests. By measuring the Y and Si leaching rates and monitoring the transformation of the crystalline and amorphous phases, we showed that yttrium disilicates were stable at pH > 5. At pH < 5, the pH stability sequence was consistent with the temperature-dependent stabilities of Y(2)Si(2)O(7) phases, with the delta polymorph showing the lowest leaching rates. Because rare-earth compounds can be used as a proxy for analogous actinide hosts, the results of this study can be used to predict the performance of engineered barriers in DGR.
- 出版日期2011-10
