Influence of microscopic precipitate structures on macroscopic pattern formation in reactive flows in a confined geometry

Abstract

Thanks to the coupling between chemical precipitation reactions and hydrodynamics, new dynamic phenomena may be obtained and new types of materials can be synthesized.

Polymorph Selection of ROY by Flow-Driven Crystallization

“…It has recently been shown that the interaction between precipitation reactions and such hydrodynamic instabilities produces a wealth of precipitation patterns and crystalline structures that can be significantly different from those obtained in well-mixed homogeneous reactors [5,6,[18][19][20][21][22][23][24][25]. It is even possible to favor the product of thermodynamically unstable composition, as has been shown in the calcium-oxalate [5,23] and the calcium-carbonate [24] systems.…”

Magnetic‐Field‐Manipulated Growth of Flow‐Driven Precipitate Membrane Tubes

“…This is caused by the better mixing between the reactants in the vicinity of the reaction zone and thus a larger number of precipitate nuclei is produced. Those colloid nuclei are linked through van der Waals interactions and are able to form coherent precipitate membranes . If Q is sufficiently low, the slowly growing membrane partially follows the stream line but also forces it to tilt towards the magnet in a smoother manner, thus h becomes larger than it would have been without the precipitate.…”

“…Those colloidn uclei are linked through van der Waals interactions and are able to form coherentp recipitate membranes. [15] If Q is sufficiently low,t he slowly growingm embrane partially follows the stream line but also forcesittotilt towards the magnet in as moother manner,t hus h becomes larger than it would have been without the precipitate. This effect, therefore, depends also on the flexibility of the membrane;m ore rigid membrane leads to larger h. If Q increases, the precipitate nuclei composing the membrane are formed earlier and in a larger number thus the upward shifto ft he stream line is restricted.…”

“…If the host liquid layer is sufficiently deep, buoyancy plays an important role in determining product properties, for example, the thermodynamically unstable polymorph of a given chemical compound can be synthesized . As an alternative possibility, confining the system helps in reducing buoyancy contribution, which gives rise to more pronounced manifestation of chemical character dependent product properties …”

“…[10] As an alternative possibility,c onfining the system helps in reducing buoyancy contribution,w hich gives rise to more pronouncedm anifestation of chemical character dependent product properties. [11][12][13][14][15] To go one step further on the way of controlled synthesis of complex precipitationp atterns,t he application of an external drivingf orce is at empting possibility.O ptical control, for example, hasb een utilized by Cooper et al [16] to develop the desired polyoxometalate-based microtubes for which the major drivingf orce is the local convection arising from the laser as a local heat source. In this context,m anipulating with am agnetic field may provide the advantageso fa ne asily adjustable field strength and direction, whereas it is noninvasive, but sensitive to composition-dependent magnetic susceptibility.A lso, magnetic field may affect chemical equilibria and crystallization steps.…”