Formation of Salt Crystal Whiskers on Porous Nanoparticle Coatings

Abstract

Salt crystal whiskers were grown from aqueous solution on porous nanoparticle silica coatings. Coated substrates were partially immersed in an aqueous potassium chloride solution and then kept in a controlled relative humidity chamber for whisker growth. The salt solution was pulled into the porous coating, reaching a steady level about 1 h after immersion. Crystals with whisker morphologies, typically 2-50 microm in lateral dimension and up to approximately 1 cm in length, emerged from the coating surface at a position above the original liquid level. Crystallites pushed upward by attached whiskers indicated a base growth mechanism in which ions are added to the surface of a growing whisker that is in contact with the coating. Sheetlike crystals formed from the base growth of whiskers that had fallen flat onto the porous coating surface. The effects of solution concentration and relative humidity on growth were characterized and used to elaborate the transport phenomena and growth mechanisms. Salt whiskers were also grown on bare substrates immersed in salt solutions containing nanoparticles. In this case, growth occurred below the original contact line on coatings created by convective assembly.

Formation and development of salt crusts on soil surfaces

“…The saturated salt solution forms a thin film along walls [15] and sallows solution transport to the crust depending on humidity and the solution concentration [15,38]. Therefore, the solution film along the cylindrical wall sustains the crust migration.…”

“…The effect of the substrate hydrophobicity or hydrophilicity on the topological character of precipitates has been observed in other salts such as K 2 Cr 2 O 7 [34], ammonium chloride [13], potassium nitrate, potassium chloride, and ammonium chloride [13,38]. …”

“…Recent studies have addressed crystal growth in pores and ensuing damage [3,9,28,[31][32][33], the mechanisms of efflorescence and subflorescence, as well as their emergence as part of transport/evaporation processes [8,12,18,24,29,35,38]. However, the formation and physical properties of salt crusts remain poorly known, primarily due to their thin and fragile characteristics that challenge laboratory experiments [29].…”

Graphene Oxide-Assisted Growth of Ultralong and Soft Single-Crystalline NaCl Ionic Nanowires for Potential Optical Nanodevices

“…Now, we discuss the underlying physics of the growth of NaCl nanowires on the GO membrane. It has been reported that the growth of ionic nanowires is determined by solution diffusion and evaporation. − Figure a,b shows the typical morphologies of a nanowire base. The nanowire has a pyramid base and a layer of dendritic crystals, both covered by GO sheets.…”

Thermal stability of thin Au films deposited on salt whiskers

“…We utilized the technique of Zhang et al [24,25] for the growth of KCl whiskers, which in turn relies on the previous observations of Gyulai [26] and Shichiri [27]. In this technique, glass slides are cleaned in an ultrasonic bath containing detergent water, then rinsed in ethanol and distilled water, and dried at 120 o C for 1 hour.…”