Gas Nanobubbles as Nucleation Acceleration in the Gas-Hydrate Memory Effect
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- 作者：Tsutomu Uchida ; Kenji Yamazaki ; Kazutoshi Gohara
- 刊名：Journal of Physical Chemistry C
- 出版年：2016
- 出版时间：December 1, 2016
- 年：2016
- 卷：120
- 期：47
- 页码：26620-26629
- 全文大小：432K
- ISSN：1932-7455
文摘
Gas-hydrate crystals have important roles in various energy and environmental issues and also have potential industrial applications. Yet their formation and dissociation mechanisms remain unclear. To accelerate their crystallization, one can use a thermal hysteresis process called the “memory effect”, which is recognized as a shortening of the induction time of gas hydrate nucleation. Although its mechanism is still under debate, submicron-sized bubbles, called “micro- and nanobubbles (MNBs)”, that are generated after the hydrate dissociation are thought to play an important role. In this study, we use a transmission electron microscope to observe freeze-fracture replicas of the ethane (C2H6)-hydrate dissociated solution to identify the existence of MNBs. We find that a significant number of MNBs remain dispersed in the dissociated solution for more than 1 day. We then measure the induction time of C2H6-hydrate formation under stirred conditions with and without such MNB solutions. Not only in the C2H6-hydrate dissociated water but also in the C2H6-bubbling solution we identify a significant and clear memory effect. We apply these findings to the mechanism of the memory effect in gas-hydrate crystallization, particularly the role of MNBs on the memory effect.