The release of trapped gases from amorphous solid water films. I. "Top-down" crystallization-induced crack propagation probed using the molecular volcano.
The release of trapped gases from amorphous solid water films. I. "Top-down" crystallization-induced crack propagation probed using the molecular volcano.
复制标题
从非晶固体水膜中释放捕获的气体。
DOI：
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发表时间：
2013
影响因子：
4.4
通讯作者：
B. D. Kay
中科院分区：
文献类型：
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作者：
R. Alan May;R. S. Smith;B. D. Kay
在本文（论文 I）和配套论文（论文 II；R. May、R. Smith 和 B. Kay, J. Chem. Phys. 138, 104502 (2013)）中，我们研究了从非晶固体水 (ASW) 膜下方释放捕获气体的机制。在之前的工作中，我们报道了与 ASW 结晶相一致的捕获气体的间歇性释放，我们将这种现象称为“分子火山”。观察到的突然解吸是由于形成了跨越薄膜的裂纹，形成了连接的释放路径。在本文中，我们利用“分子火山”解吸峰来表征结晶诱导裂纹的形成。我们发现裂纹长度分布与捕获气体（Ar、Kr、Xe、CH4、N2、O2 或 CO）无关。惰性气体层的选择性放置用于显示裂纹在薄膜顶部附近形成并向下传播到薄膜中。等温实验表明，经过一段诱导时间后，裂纹随时间线性扩展，其速度与阿伦尼乌斯相关，对应的活化能为 54 kJ/mol。该值与其他人报道的结晶生长速率一致，并在结晶生长速率和裂纹扩展速率之间建立了直接联系。两步模型中，成核和结晶发生在薄膜顶部附近的感应区，随后结晶/裂纹前沿扩展至薄膜中，这与程序升温解吸结果非常一致。
In this (Paper I) and the companion paper (Paper II; R. May, R. Smith, and B. Kay, J. Chem. Phys. 138, 104502 (2013)), we investigate the mechanisms for the release of trapped gases from underneath amorphous solid water (ASW) films. In prior work, we reported the episodic release of trapped gases in concert with the crystallization of ASW, a phenomenon that we termed the "molecular volcano." The observed abrupt desorption is due to the formation of cracks that span the film to form a connected pathway for release. In this paper, we utilize the "molecular volcano" desorption peak to characterize the formation of crystallization-induced cracks. We find that the crack length distribution is independent of the trapped gas (Ar, Kr, Xe, CH4, N2, O2, or CO). Selective placement of the inert gas layer is used to show that cracks form near the top of the film and propagate downward into the film. Isothermal experiments reveal that, after some induction time, cracks propagate linearly in time with an Arrhenius dependent velocity corresponding to an activation energy of 54 kJ∕mol. This value is consistent with the crystallization growth rates reported by others and establishes a direct connection between crystallization growth rate and the crack propagation rate. A two-step model in which nucleation and crystallization occurs in an induction zone near the top of the film followed by the propagation of a crystallization∕crack front into the film is in good agreement with the temperature programmed desorption results.