arXiv subjects

N. Shahidzadeh

Publications and source records attributed to N. Shahidzadeh.

5 recordsLinked to original sources

arXiv2026

A multi-scale study to unravel the dehydration mechanism of hydrated salts

Understanding the dehydration mechanism of hydrated salts remains fundamentally important in solid state chemistry, as their behavior affect fields ranging from heat storage to heritage conservation and pharmaceutical crystallization. Combining Raman confocal microscopy, dynamic weight loss measurements, SEM, and micro CT, we show that dehydration kinetics of sodium sulfate decahydrate (mirabilite) unfold through two regimes: an initial nucleation controlled phase, where atomic rearrangement drives two dimensional lateral growth following an exponential law, and a subsequent phase boundary controlled regime, where growth advances into the crystal depth, limited by water vacancy formation at the hydrated dehydrated interface. The resulting thenardite product shows around 35 percent shrinkage and forms a porous, layered dual porosity nanocrystalline structure, with relative humidity directly governing crystal size. Extending this analysis to other sulfate hydrates reveals that crystallographic symmetry changes between hydrate and anhydrous phases dictate surface morphology, linking microstructure to mechanism. This multiscale framework uncovers dynamics hidden from bulk measurements and suggests structural indicators could predict dehydration pathways in other hydrated salt families, and opening route toward designing thermal energy storage materials without exhaustive experimental screening.

cond-mat.soft↗

arXiv2025

Self-similarity in creeping salt crystallization

The self-amplifying creeping of salts can produce striking macroscopic structures, such as desert roses in arid regions and salt pillars near saline lakes. While these formations are visually remarkable, salt crystallization, often seen as efflorescence on surfaces, also poses significant challenges for cultural heritage conservation, materials science, and soil management. In this study, we investigate the mechanisms underlying self-organized crystallization within efflorescence deposits. Our findings reveal that these porous salt deposits exhibit pronounced self-similarity, with the crystallization process recurring at multiple length scales. This results in smaller replicas of the overall structure nested within larger ones, creating fractal geometries similar to those found in cauliflower and broccoli. By performing controlled evaporation experiments and microscale analysis using advanced imaging techniques combined with fractal dimension analysis, we uncover the hierarchical and size-controlled precipitation of cubic microcrystals within the porous efflorescence. Furthermore, we develop a hierarchical growth model demonstrating that the ultimate height of the macroscopic salt deposit is primarily determined by the initial mass of salt, rather than by the interplay of capillary and viscous forces when salt solution flows within the porous salt structure.

cond-mat.soft↗

arXiv2021

Stringiness of Hyaluronic Acid Emulsions

In this work, we underline the importance of the molecular weight of hyaluronic acid on the elongational properties of concentrated emulsions. The filament formation properties, e.g. the stringiness, of an emulsion is a key determinant of a product liking and repeat purchase. Here, we find that high molecular weight hyaluronic acid and a high stretching speed are the control parameters affecting the filament formation of an emulsion.

cond-mat.soft↗

arXiv2021

Droplet Splashing on Rough Surfaces

When a droplet hits a surface fast enough, droplet splashing can occur: smaller secondary droplets detach from the main droplet during impact. While droplet splashing on smooth surfaces is by now well understood, the surface roughness also affects at which impact velocity a droplet splashes. In this study, the influence of the surface roughness on droplet splashing is investigated. By changing the root mean square roughness of the impacted surface, we show that the droplet splashing velocity is only affected when the droplet roughness is large enough to disrupt the spreading droplet lamella and change the droplet splashing mechanism from corona to prompt splashing. Finally, using Weber and Ohnesorge number scaling models, we also show that the measured splashing velocity for both water and ethanol on surfaces with different roughness and water-ethanol mixtures collapse onto a single curve, showing that the droplet splashing velocity on rough surfaces scales with the Ohnesorge number defined with the surface roughness length scale.

physics.flu-dyn↗

arXiv2020

Droplet impact of Newtonian fluids and blood on simple fabrics: effect of fabric pore size and underlying substrate

When a droplet impacts a fabric mesh at a sufficiently high impact velocity, it not only spreads over the fabric but also penetrate its pores. To determine the influence of this liquid penetration of the fabric on droplet spreading on thin fabric meshes, we measured the droplet spreading ratio on fabric with and without an underlying substrate using a high-speed camera. For fabrics without a substrate, the droplet spreading ratio is reduced as the fabric penetration by the liquid reduces the droplet volume spreading on top of the fabric. Using entropic lattice Boltzmann simulations, we find that the lower droplet spreading ratio on fabrics, both with and without a substrate, is due to an increase of viscous losses inside the droplet during spreading. Comparing droplet impact of blood with its Newtonian counterpart, we show that for spreading on fabrics, just like on smooth surfaces, blood can be approximated as a Newtonian fluid.

physics.flu-dyn↗