Evaporative Crystallization of Sodium Chlorate Droplets under Controlled Humidity in the Presence of a Static Magnetic Field.

This study investigates the effects of relative humidity and a static magnetic field on the deposition patterns of evaporating sodium chlorate droplets on silicon substrates. Experiments were conducted at three controlled humidity levels (11, 33, and 59%), under both zero-field conditions and in the presence of a static magnetic field of (290 ± 5) mT. Deposition patterns were classified as single crystals, coffee-ring structures, or irregular formations. The results show that deposition morphology strongly depends on relative humidity: irregular patterns are most frequent at low humidity, coffee-ring structures dominate at intermediate humidity, while higher humidity promotes single-crystal formation. Comparison of experiments performed with and without an applied static magnetic field indicates that, within the investigated field strength, evaporation dynamics governed by relative humidity dominate over any magnetic-field-induced effects on crystallization and deposition morphology. Powder X-ray diffraction (PXRD) revealed only minor variations in lattice constants, with no clear correlation to the applied magnetic field. These results indicate that humidity-controlled evaporation dynamics are the dominant factor governing deposition morphology, whereas no measurable effects of the applied magnetic field were observed under the investigated conditions.