Role of electrochemical reactions in pressure solution
Role of electrochemical reactions in pressure solution
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DOI：
10.1016/j.gca.2009.02.012
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发表时间：
2009-05-15
影响因子：
5
通讯作者：
Israelachvili, Jacob N.
中科院分区：
文献类型：
--
作者：
Greene, George W.;Kristiansen, Kai;Israelachvili, Jacob N.
使用表面力装置，我们已经测量了石英和云母表面之间的电势差的变化，当表面在25 ℃下在30 mM CaCl 2的电解质水溶液中在相对低的压力（2-3 atm）下压在一起时，石英和云母表面之间的电势差的变化与石英溶解速率的变化相关。在对称系统（例如云母-云母或石英-石英）中或在经受类似压力的干燥表面之间测得没有可检测的溶解或电压电位差，这表明溶解不能归因于简单的压力效应、缓慢老化（蠕变）或石英表面的塑性变形。在压力下或在电解质溶液中紧密接触的石英-云母系统中，石英溶解的开始以石英厚度的突然、快速减小为标志，其初始速率在1 - 4 mm/min的范围内，几小时后稳定在约0.01 nm/min的恒定速率（类似于5 μ m/yr）。同时。一旦溶解速率稳定，电位下降到恒定值。衰减速率的降低被解释为是由于封闭的水膜的饱和和/或在石英表面上的斯特恩层的积累，和恒定的速率是由于稳定状态的化学溶解和溶解的二氧化硅扩散到周围的储层。溶解是“不均匀的”：随着溶解的进行，表面变得粗糙，以类似于腐蚀的方式出现凹坑。有时，快速溶解然后逐渐过渡到稳定溶解的过程会重复，这表明坑结构和Stern层是脆弱的，并且易于坍塌和/或从差距排出。在两个白云母表面之间压缩的多面研磨的石英颗粒（类似于1.0 μ m直径）的溶解的初步实验表明，在不同的晶面溶解速率的所有不对称性。电势的起源被解释为当两个不同表面被迫靠近时，它们的双电层重叠而产生。由于未知的原因，这种电位差似乎是溶解的驱动力。而不是压力。(C)2009爱思唯尔有限公司版权所有。
Using a Surface Forces Apparatus we have measured changes in the electrical potential difference between quartz and mica surfaces that correlate with the changing quartz dissolution rate when Surfaces are pressed together at relatively low pressures (2-3 atm) in aqueous electrolyte solutions of 30 mM CaCl2 at 25 degrees C. No detectable dissolution or voltage potential difference is measured in symmetrical systems (e.g. mica-mica or quartz-quartz) or between dry surfaces subjected to similar pressures, indicating that the dissolution can not be attributed to a simple pressure effect, slow aging (creep), or plastic deformation of the quartz surface. In quartz-mica systems brought together under pressure or to close proximity in electrolyte solution, the onset of quartz dissolution is marked by a sudden, rapid decrease in the quartz thickness at initial rates in the range from I to 4 mm/min, which after several hours settles into a constant rate of approximately 0.01 nm/min (similar to 5 mu m/yr). Concomitantly. the potential drops to a constant value once the dissolution rate has stabilized. The decrease in the decay rate is interpreted as being due to saturation of the confined aqueous film and/or to the buildup of a Stern layer on the quartz surface, and the constant rate as being due to the steady-state chemical dissolution and diffusion of the dissolving silica into the surrounding reservoir. The dissolution is 'non-uniform': the surfaces become rough as dissolution proceeds, with the appearance of pits in a manner analogous to corrosion. On occasions, the process of rapid dissolution followed by a gradual transition to steady dissolution repeats itself, suggesting that the pit structure and Stern layer are fragile and subject to collapse and/or expulsion from the gap. Preliminary experiments on the dissolution of multi-faceted milled quartz particles (similar to 1.0 mu m diameter) compressed between two muscovite surfaces suggest all asymmetry in the dissolution rates at different crystallographic planes. The origin of the electrical potential is interpreted its arising from the overlapping of the electric double-layers of two dissimilar surfaces when they are forced into close proximity. This electrical potential difference, for as yet unknown reasons, appears to be the driving force for the dissolution. rather than pressure. (C) 2009 Elsevier Ltd. All rights reserved.