Bamboriya Om Prakash, Tirumkudulu Mahesh S
Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
Soft Matter. 2023 Apr 5;19(14):2605-2611. doi: 10.1039/d2sm01688e.
Fast evaporation of particle-suspension drops results in complex morphologies of the final dried granules. Understanding the morphological transformations is important to industrial processes such as spray drying where droplets of particulate suspensions are dried at a fast rate to produce granules of thermally sensitive materials. The transformation of an initial spherical shell to complex morphologies of the final dried granule has been attributed to the buckling of particle-packed shells. Here, we demonstrate a universal scaling law for buckling that depends on the particle size, hardness, particle packing and size of drying drop. The critical transition for buckling is set by a dimensionless number that measures the competition between the compressive stress generated by capillary forces and the elastic strength of the packing. The same dimensionless number is also responsible for cracking of drying colloidal films, suggesting a universality in the mechanical behaviour of particle packings saturated with a solvent. These results should enable design of hierarchically structured, buckle-free granules with varying porosity, surface composition and internal structure.
颗粒悬浮液滴的快速蒸发会导致最终干燥颗粒呈现复杂的形态。理解形态转变对于诸如喷雾干燥等工业过程至关重要，在喷雾干燥中，颗粒悬浮液滴会快速干燥以生产热敏材料颗粒。初始球形壳向最终干燥颗粒复杂形态的转变归因于颗粒填充壳的屈曲。在此，我们展示了一种关于屈曲的通用标度律，它取决于颗粒大小、硬度、颗粒堆积以及干燥液滴的大小。屈曲的临界转变由一个无量纲数设定，该无量纲数衡量了毛细力产生的压缩应力与堆积的弹性强度之间的竞争。同一个无量纲数也导致干燥胶体薄膜的开裂，这表明在被溶剂饱和的颗粒堆积的力学行为中存在普遍性。这些结果应能实现具有不同孔隙率、表面组成和内部结构的分级结构、无屈曲颗粒的设计。
