Sodium weakening of heavitree quartzite: Preliminary results
Sodium weakening of heavitree quartzite: Preliminary results
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DOI：
10.1029/jb089ib06p04271
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发表时间：
1984-06
影响因子：
--
通讯作者：
O. Jaoul
中科院分区：
文献类型：
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作者：
O. Jaoul
少量杂质（如铝、过渡金属、碱金属或H₂O）的存在会改变石英的电子能带结构。由于HOH作为浅电子受体，电离缺陷（如带电氧空位或硅间隙）浓度增加，硅和氧的自扩散得到增强。相比之下，钠是一种浅电子供体，会阻碍这些物质的扩散。为了评估钠掺杂剂对强度的影响，我们对含有350ppm原子钠的赫维特里石英岩（粒径0.2毫米）进行了一个简单的蠕变实验（两次实验，P = 1.5 GPa，T = 1073、1163°K，σ = 0.2到1 GPa）。这些掺杂样品的变形速度比相同条件下未掺杂的样品快10倍（在相同应力和温度下）。因此，蠕变速率不太可能由简单的扩散控制，但赫希提出的一种替代理论似乎与数据相符。根据赫希的模型，这种弱化可解释为由于带电扭折数量增加导致位错滑移速度增加。这意味着电子转移受杂质（包括羟基）的性质和含量的强烈影响。钠可能有利于带负电扭折的形核。虽然这只是初步研究，且是使用含有晶界和其他杂质（铝）的样品进行的，但由于其对地质学的重要性，我们决定迅速报告这一结果：岩石（如本例中的石英岩）不仅含有水，还含有许多不同的杂质，这些杂质肯定会影响它们的强度。
The electronic band structure of quartz is altered by the presence of small amounts of impurities such as aluminum, transition metals, alkalies or H2O. Silicon and oxygen selfdiffusion are enhanced by an increase in the concentration of ionized defects such as charged oxygen vacancies or silicon interstitials due to HOH acting as a shallow electronic acceptor. Sodium, by contrast, is a shallow electronic donor and retards the diffusion of these species. To evaluate the effect of the sodium dopant on strength we performed a simple creep experiment (two runs, P = 1.5 GPa, T = 1073, 1163°K, σ = 0.2 to 1 GPa) on, Heavitree quartzite (.2 mm grain size) containing 350 ppm at. Na. These doped samples deformed 10 times faster than equivalent undoped ones (at the same stress and temperature). Simple diffusion-control of the creep rate is therefore unlikely but an alternative proposed by Hirsch seems consistent with the data. Using Hirsch's model, the weakening could be interpreted as due to an increase in the dislocation glide velocity through an increase of the charged kink population. This implies electronic transfers are strongly influenced by the nature and the abundance of the impurities (including hydroxyls). Sodium could favour the nucleation of negatively Charged kinks. Although this is preliminary and was performed using specimens containing grain boundaries and other impurities (Al), we decided to report it rapidly because of its importance to geology: rocks (like quartzites in this example) not only carry water, but also many different impurities which certainly affect their strengths.