Calculation of ionic diffusion coefficients on the basis of migration test results
Calculation of ionic diffusion coefficients on the basis of migration test results
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DOI：
10.1007/bf02479554
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发表时间：
2003-04-01
影响因子：
3.8
通讯作者：
Snyder, KA
中科院分区：
文献类型：
--
作者：
Samson, E;Marchand, J;Snyder, KA
迁移试验现在通常用于估计水泥基材料的扩散系数。在过去的十年中，已经提出了各种方法来分析迁移测试结果。在许多情况下，测试数据的解释是基于一系列简化的假设。然而，对迁移实验期间发生的各种传输机制的彻底分析表明，其中一些可能是无效的。因此，一个更严格的方法来分析迁移测试结果。测试程序相对简单，包括测量通过样品的电流的演变。实验结果进行了分析，使用扩展的能斯特-普朗克-泊松方程组。一个简单的算法是用来确定每个实验的弯曲因子，允许最好地再现实验测量的电流曲线。这种方法的主要优点在于，系统中存在的所有离子种类的扩散系数可以使用单个系列的数据来计算。给出了该方法应用的典型实例。结果表明，使用这种方法计算的扩散系数是独立的所施加的电压和浓度水平仅略有依赖。以及上游电池溶液的化学组成。
Migration tests are now commonly used to estimate the diffusion coefficients of cement-based materials. Over the past decade, various approaches have been proposed to analyze migration test results. In many cases, the interpretation of test data is based on a series of simplifying assumptions. However, a thorough analysis of the various transport mechanisms that take place during a migration experiment suggests that some of them are probably not valid. Consequently, a more rigorous approach to analyze migration test results is presented. The test procedure is relatively simple and consists in measuring the evolution of the electrical current passing through the sample. Experimental results are then analyzed using the extended Nernst-Planck-Poisson set of equations. A simple algorithm is used to determine for each experiment the tortuosity factor that allows to best reproduce the current curve measured experimentally. The main advantage of this approach resides in the fact that the diffusion coefficients of all ionic species present in the system can be calculated using a single series of data. Typical examples of the application of this method are given. Results indicate that the diffusion coefficients calculated using this approach are independent of the applied voltage and depends only slightly on the concentration level. and the chemical make-up of the upstream cell solution.