Extensive studies have been conducted to manipulate the morphology of sodium chloride salt crystals to tailor their physical and chemical properties. Among the myriad factors considered, the effects of the substrate and additives have profound impacts on the types of salt depositions. Surface charge effects and various ionic surfactants influence ion movement, resulting in diverse crystal morphologies. This manuscript aims to provide a consolidated summary by concurrently studying multiple effects to uncover the salt crystal morphology under the influence of two oppositely charged ionic surfactants on charged and neutral surfaces. The cationic surfactant cetyltrimethylammonium bromide induces skeletal crystal growth by retarding salt precipitation until supersaturation is reached. Conversely, the anionic surfactant sodium dodecyl sulfate hinders ion diffusion at the three-phase contact line. Each surfactant effect is dominant at higher molar concentrations. Surface charge affects the amount of surface adsorption and free-moving ions within the saline surfactant droplets, greatly influencing the number of salt crystals formed on the neutral substrate. However, charge neutralization at the highest concentrations of both surfactants nullifies the surface charge effect, resulting in practically indistinguishable salt crystals with similar sizes and numbers, leading to only a small area difference of 1461 μm². This study provides insights into the kinetics of crystallization under the combined influence of anionic, cationic, and surface charge interactions. The findings can serve as a future reference for predicting and controlling ionic interactions and crystal morphology.

中文翻译：

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混合表面活性剂对无柄液滴蒸发驱动盐结晶形态的影响


已经进行了广泛的研究来操纵氯化钠盐晶体的形态以调整其物理和化学性质。在考虑的众多因素中，基材和添加剂的影响对盐沉积的类型有深远的影响。表面电荷效应和各种离子表面活性剂会影响离子运动，从而导致不同的晶体形态。本手稿旨在通过同时研究多种效应来提供综合总结，以揭示在两种带相反电荷的离子表面活性剂对带电和中性表面的影响下盐晶体形态。阳离子表面活性剂十六烷基三甲基溴化铵通过延缓盐沉淀直至达到过饱和度来诱导骨架晶体生长。相反，阴离子表面活性剂十二烷基硫酸钠阻碍了三相接触线处的离子扩散。每种表面活性剂效应在较高摩尔浓度下占主导地位。表面电荷会影响盐水表面活性剂液滴内的表面吸附量和自由移动的离子量，从而极大地影响在中性基材上形成的盐晶体的数量。然而，两种表面活性剂最高浓度的电荷中和抵消了表面电荷效应，导致几乎无法区分的大小和数量相似的盐晶体，导致只有 1461 μm² 的小面积差异。本研究为在阴离子、阳离子和表面电荷相互作用的共同影响下的结晶动力学提供了见解。这些发现可以作为预测和控制离子相互作用和晶体形态的未来参考。