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On the sensitivity of the evaporative pattern deposition of particulate mass to the ionic strength in kinetically stable suspensions
The European Physical Journal Special Topics ( IF 2.6 ) Pub Date : 2020-09-14 , DOI: 10.1140/epjst/e2020-000005-6
Anna Zigelman , Ekhlas Homede , Ofer Manor

The deposition of particulate mass from a volatile suspension is a common process. Usually, the employed suspensions are designed to be kinetically stable, which is achieved by employing surface forces of molecular origin, e.g., the electrical double layer (EDL) or steric forces, to render high energy barriers to particle attachments. One may expect that a high energy barrier in the original suspension will render the deposit morphology solely connected to particle convection in the volatile liquid and, once most of the carrier liquid has evaporated, to capillary attraction between detached particles to each other and to the solid substrate. However, we show that variations in the magnitude of large energy barriers to particle attachments in our original suspensions are connected to variations in the deposit morphology following the evaporation of the carrier liquid. In our experiments, the different original EDL induced energy barriers are large and traverse tens and hundreds of KBT in magnitude. Nevertheless, the evaporation of the carrier liquid during the deposition process supports the convection of mass toward the three phase contact line between the suspension, substrate, and vapor phases. The convection of particle and ion mass dynamically increases particle concentration and ionic strength in the vicinity of the contact line. The elevated ionic strength reduces the energy barriers to particle attachments in that vicinity, which appears to locally support particle coagulation and adsorption effects and hence to alter the deposit morphology. Thus, the morphology of the deposit may show considerable sensitivity to the specific magnitude of energy barrier to particle attachments in the original, kinetically stable, suspension.



中文翻译:

关于动力学稳定悬浮液中颗粒状物质蒸发模式沉积对离子强度的敏感性

从挥发性悬浮液中沉积颗粒物质是常见的过程。通常,所采用的悬浮液被设计为动力学稳定的,这是通过利用分子起源的表面力(例如,双电层(EDL)或空间力)来实现的,以对粒子附着提供高能垒。可以预期的是,原始悬浮液中的高能垒将使沉积物形态仅与挥发性液体中的颗粒对流有关,并且一旦大多数载液蒸发,就会使分离的颗粒彼此之间以及与固体之间产生毛细管吸引基质。然而,我们表明,在原始悬浮液中,较大的能垒对颗粒附着的能级变化与载液蒸发后的沉积形态变化有关。在我们的实验中,不同的原始EDL诱导的能垒很大,并且穿越数十万个K B T的大小。然而,在沉积过程中载液的蒸发支持了物质向悬浮液,基材和气相之间的三相接触线的对流。粒子和离子质量的对流会动态增加接触线附近的粒子浓度和离子强度。升高的离子强度降低了附近颗粒附着的能垒,这似乎局部支持颗粒的凝结和吸附作用,从而改变了沉积物的形态。因此,沉积物的形态可以显示出对原始的,动力学上稳定的悬浮液中的颗粒附着的能垒特定大小的相当大的敏感性。

更新日期:2020-09-16
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