Lawrence Livermore National Laboratory, Livermore, California, 94550, United States.
Sci Rep. 2017 Jun 7;7(1):2942. doi: 10.1038/s41598-017-03091-3.
Moisture uptake and outgassing can be detrimental to a system by altering the chemical and mechanical properties of materials within the system over time. In this work, we conducted isotherm experiments to investigate dynamic moisture sorption and desorption in markedly different materials, i.e., a polymeric material, Sylgard-184 and a ceramic aluminosilicate material, Zircar RS-1200, at different temperatures (30 °C-70 °C) by varying the water activity (0.0-0.90). Sylgard-184 showed a linear sorption and outgassing behavior with no-hysteresis over the entire temperature and water activity range considered here. Whereas, the sorption and outgassing of Zircar RS-1200 was highly non-linear with significant hysteresis, especially at higher water activities, at all temperatures considered here. The type of hysteresis suggested the presence of mesopores in Zircar RS-1200, whereas the lack of hysteresis in Sylgard-184 indicates that it has a nonporous structure. A diffusion model coupled with a dynamic, triple-mode sorption (Langmuir, Henry, and pooling modes) model employed in this study matched our experimental data very well and provides mechanistic insight into the processes. Our triple-mode sorption model was adaptive enough to (1) model these distinctly different materials and (2) predict sorption and outgassing under conditions that are distinctly different from the parameterization experiments.
水分吸收和释放会改变系统内材料的化学和机械性能，从而对系统造成危害。在这项工作中，我们通过改变水活度（0.0-0.90），在 30°C-70°C 的不同温度下，对明显不同的材料，即聚合物材料 Sylgard-184 和陶瓷铝硅酸盐材料 Zircar RS-1200 进行了等温实验，以研究动态吸湿和解吸情况。Sylgard-184 在整个温度和水活度范围内表现出线性的吸附和解吸行为，没有滞后现象。而 Zircar RS-1200 的吸附和解吸是非线性的，存在明显的滞后现象，尤其是在所有考虑的较高水活度下。滞后现象的类型表明 Zircar RS-1200 中存在中孔，而 Sylgard-184 中没有滞后现象表明它具有无孔结构。本研究中采用的扩散模型与动态三模式吸附（朗缪尔、亨利和汇集模式）模型相结合，很好地匹配了我们的实验数据，并为这些过程提供了机制上的见解。我们的三模式吸附模型具有足够的适应性，可以（1）模拟这些明显不同的材料，以及（2）预测参数化实验条件以外的吸附和解吸情况。
