Boček Žan, Petkovšek Martin, Clark Samuel J, Fezzaa Kamel, Dular Matevž
Faculty of Mechanical Engineering, University of Ljubljana, Askerceva 6, 1000 Ljubljana, Slovenia.
Advanced Photon Source, Argonne National Laboratory, 9700 S Cass Ave, Lemont, IL 6043, USA.
Ultrason Sonochem. 2023 Dec;101:106657. doi: 10.1016/j.ultsonch.2023.106657. Epub 2023 Oct 21.
A lot of effort has been dedicated in recent years towards understanding the basics of cavitation induced emulsification, mainly in the form of single cavitation bubbles. Regarding bulk acoustic emulsification, a lot less research has been done. In our here presented work we utilize advanced high-speed observation techniques in visible light and X-Rays to build upon that knowledge and advance the understanding of bulk emulsion preparation. During research we discovered that emulsion formation has an acute impact on the behavior of the interface and more importantly on its position relative to the horn, hence their interdependence must be carefully studied. We did this by observing bulk emulsification with 2 cameras simultaneously and corroborating these measurements with observation under X-Rays. Since the ultrasonic horns location also influences interface behavior, we shifted its initial position to different locations nearer to and further away from the oil-water interface in both phases. We found that a few millimeters distance between the horn and interface is not enough for fine emulsion formation, but that they must be completely adjacent to each other, with the horn being located inside the oil-water interface. We also observed some previously undiscovered phenomena, such as the splitting of the interface to preserve continuous emulsion formation, climbing of the interface up the horn and circular interface protrusions towards the horn forming vertical emulsion streams. Interestingly, no visible W/O emulsion was ever formed during our experiments, only O/W regardless of initial horn position.
近年来，人们付出了大量努力来了解空化诱导乳化的基本原理，主要是针对单个空化气泡的形式。关于体声乳化，所做的研究要少得多。在我们目前展示的工作中，我们利用可见光和X射线中的先进高速观测技术，在已有知识的基础上进一步推进对体乳液制备的理解。在研究过程中，我们发现乳液形成对界面行为有显著影响，更重要的是对其相对于变幅杆的位置有显著影响，因此必须仔细研究它们之间的相互依存关系。我们通过同时用两台摄像机观察体乳化，并通过X射线观察来证实这些测量结果。由于超声变幅杆的位置也会影响界面行为，我们将其初始位置移到两相中更靠近和更远离油水界面的不同位置。我们发现变幅杆与界面之间几毫米的距离不足以形成精细乳液，但它们必须完全相邻，变幅杆位于油水界面内。我们还观察到一些以前未被发现的现象，例如界面分裂以保持连续乳液形成、界面沿变幅杆向上爬升以及朝向变幅杆的圆形界面突出形成垂直乳液流。有趣的是，在我们的实验过程中从未形成可见的W/O乳液，无论变幅杆的初始位置如何，只形成O/W乳液。
