Experimental investigation of the morphology of salt deposits from drying sessile droplets by white‐light interferometry

Abstract

This study presents a new approach to investigate the drying behavior and the structure of deposit resulting from drying of solid containing micro droplets. It is shown that deposit structure (porosity and "footprint") depends on drying conditions. This dependency may contribute to better understanding of particle-forming processes, such as fluidized bed coating. In the framework of this study, sessile droplets containing sodium benzoate dissolved in water were dried on thin glass plates in a small drying chamber. The drying conditions (temperature, moisture content and flow rate of drying gas) and material parameters (solid content of solution) were systematically varied. The drying rate of droplets was determined from the moisture balance of the drying gas. The final three-dimensional shape of dried sessile droplets was measured using white-light interferometry and transformed into a two-dimensional profile using a Monte Carlo method. Moreover the mean porosity of dried droplets was calculated. By comparison of structural information and process conditions it is shown that the drying process may have a large influence on deposit structure. T g,in , gas inlet temperature; _ V air , gas volume flow rate; Y in , inlet air moisture content; c s , initial solid mass fraction.

Analysis of profile and morphology of colloidal deposits obtained from evaporating sessile droplets

“…Note that the evaporating water droplets in ambient temperature do not exhibit Marangoni effect [37]. The second issue in this arena is that the quantitative measurements of ring profile or dimensions as a function of particle size and concentration have not been reported to the best of our knowledge, with an exception of the work of Sondej et al [30]. In this study, quantitative measurements of the ring profiles were reported at different particles concentration [30].…”

“…The second issue in this arena is that the quantitative measurements of ring profile or dimensions as a function of particle size and concentration have not been reported to the best of our knowledge, with an exception of the work of Sondej et al [30]. In this study, quantitative measurements of the ring profiles were reported at different particles concentration [30]. The present work investigates the cross-sectional profile of the ring as a function of particle size and concentration.…”

“…Sondej et al [30] used white light interferometry to measure the ring profiles obtained after evaporation of a sessile water droplet containing sodium benzoate particles and reported an increase in ring height and reduction of drying rate with an increase in the particles concentration.…”

In‐depth investigation of incremental layer build‐up from dried deposited droplets

“…Msambwa et al 12 studied structural alterations that can be attained by various additives, while Sliz et al 13 investigated the control of structure formation via substrate heating. Sondej et al 14 presented a study on the influence of drying conditions on the resulting deposits. Especially this last aspect is of great importance, as it can be directly and easily controlled in most coating processes.…”

Influence of Thermal Conditions on Particle Properties in Fluidized Bed Layering Granulation

“…The influence of selected process conditions on product porosity as a key property was investigated by Rieck et al [9] and Hoffmann et al [10] for the formation of sodium benzoate granules. The underlying solidification process was studied in great detail by Sondej et al [11]. Therein, the influence of different operation parameters on the structure of the deposits from drying a sessile sodium benzoate droplet was studied.…”