Shimada Wataru, Takeya Satoshi, Kamata Yasushi, Uchida Tsutomu, Nagao Jiro, Ebinuma Takao, Narita Hideo
National Institute of Advanced Industrial Science and Technology (AIST), Tsukisamu-Higashi, Sapporo 062-8517, Japan.
J Phys Chem B. 2005 Mar 31;109(12):5802-7. doi: 10.1021/jp044624t.
We used a confocal scanning microscope to observe growth and texture change of ice due to the dissociation of methane gas clathrate hydrate (CH(4) hydrate). The experiments were done under CH(4) gas atmospheric pressure and isothermal conditions between 170 and 268 K. Above 193 K, the dissociation of CH(4) hydrate resulted in many small ice particles that covered the hydrate surface. These ice particles had roughly the same shape and density between 193 and 210 K. In contrast, above 230 K the ice particles developed into a sheet of ice that covered the hydrate surface. Moreover, the measured release of CH(4) gas decreased when the sheet of ice formed at the surface of the hydrate. These findings can explain the anomalous preservation behavior of CH(4) hydrate; that is, the known increase of storage stability of CH(4) hydrate above 240 K is likely related to the formation of the ice that we observed in the experiments.
我们使用共聚焦扫描显微镜来观察由于甲烷气体水合物（CH₄水合物）分解而导致的冰的生长和结构变化。实验在CH₄气体大气压和170至268 K的等温条件下进行。在193 K以上，CH₄水合物的分解产生了许多覆盖水合物表面的小冰粒。在193至210 K之间，这些冰粒的形状和密度大致相同。相比之下，在230 K以上，冰粒发展成覆盖水合物表面的冰层。此外，当水合物表面形成冰层时，测得的CH₄气体释放量减少。这些发现可以解释CH₄水合物的异常保存行为；也就是说，已知在240 K以上CH₄水合物储存稳定性的增加可能与我们在实验中观察到的冰的形成有关。
