Ziemecka I, Brau F, De Wit A
Nonlinear Physical Chemistry Unit, Université Libre de Bruxelles (ULB), Brussels 1050, Belgium.
Chaos. 2020 Jan;30(1):013140. doi: 10.1063/1.5128107.
Various cobalt silicate precipitation patterns can be observed when an aqueous solution of cobalt ions gets into contact with a solution of silicate ions upon injection of one solution into the other in the confined geometry of a Hele-Shaw cell. The properties of these precipitation patterns are studied here as a function of the injection flow rate, densities and viscosities of the solutions, and the choice of which solution is injected into the other one. Our results show that the structure of the precipitation pattern depends on the local velocity as well as on the difference in viscosities between the injected and the displaced solutions. Specifically, decreasing the injection flow rate and/or decreasing the density jump while increasing the difference in viscosities between the reactant solutions results in more circular patterns. Moreover, we show that some structures are robustly observed in given ranges of the local flow velocity in the cell. Locally, precipitation can then transition from one type of pattern to another during injection, according to that preferred structure at the given local velocity. We also show that injection of the cobalt solution into the silicate solution results in the so-called direct patterns that are different from the reverse patterns obtained when the silicate solution is injected in the solution of cobalt ions. Our results help in understanding the production of precipitate structures under nonequilibrium flow conditions.
当在Hele-Shaw盒的受限几何结构中，将一种溶液注入另一种溶液时，钴离子水溶液与硅酸根离子溶液接触，会观察到各种硅酸钴沉淀模式。在此研究这些沉淀模式的特性，作为注入流速、溶液密度和粘度以及选择哪种溶液注入另一种溶液的函数。我们的结果表明，沉淀模式的结构取决于局部速度以及注入溶液和被置换溶液之间的粘度差异。具体而言，降低注入流速和/或降低密度跃变，同时增加反应物溶液之间的粘度差异，会产生更圆形的模式。此外，我们表明在盒内局部流速的给定范围内可以稳定地观察到一些结构。在局部，根据给定局部速度下的优选结构，沉淀在注入过程中可以从一种模式转变为另一种模式。我们还表明，将钴溶液注入硅酸盐溶液会产生所谓的直接模式，这与将硅酸盐溶液注入钴离子溶液时获得的反向模式不同。我们的结果有助于理解非平衡流动条件下沉淀结构的产生。
