Schubert S, Klumbies H, Müller-Meskamp L, Leo K
Dresdener Innovationszentrum für Energieeffizienz, Institut für Angewandte Photophysik, Technische Universität Dresden, George-Bähr Strasse 1, 01062 Dresden, Germany.
Rev Sci Instrum. 2011 Sep;82(9):094101. doi: 10.1063/1.3633956.
We discuss the electrical calcium test--a method to measure very small rates of water vapor permeation through barrier films with high throughput. The sensitivity range for our design is found to be 10(-5) to 15 g/(m(2) d). Moreover, a closer look at the importance of electrodes series resistance is taken: We show that permeation rates are underestimated if it is neglected. Taking this series resistance and Fickian diffusion into account not only the steady, but also the transient state of the permeation curve can be fitted. Using this approach, permeation barriers with different permeabilities are evaluated leading to water vapor transmission rates well comparable to coulometric measurements. The calcium layer morphology is investigated by atomic force microscopy measurements indicating microscopical inhomogeneities during degradation. Variations of electrode material and calcium layer thickness are carried out to examine their influence on the measured permeation. Additionally, optical and electrical calcium tests are compared. Small differences in the time dependence are observed and discussed.
我们讨论了电钙测试——一种以高通量测量水蒸气透过阻隔膜的极低速率的方法。我们发现我们设计的灵敏度范围为10(-5)至15 g/(m(2) d)。此外，我们更深入地探讨了电极串联电阻的重要性：我们表明，如果忽略它，渗透速率会被低估。考虑到这种串联电阻和菲克扩散，不仅可以拟合渗透曲线的稳态，还可以拟合瞬态。使用这种方法，对具有不同渗透率的渗透阻隔层进行了评估，得出的水蒸气透过率与库仑法测量结果具有良好的可比性。通过原子力显微镜测量研究了钙层形态，结果表明在降解过程中存在微观不均匀性。进行了电极材料和钙层厚度的变化实验，以研究它们对测量渗透率的影响。此外，还比较了光学钙测试和电钙测试。观察并讨论了时间依赖性方面的微小差异。
