Evolution of the crystal growth mechanism of zeolite W (MER) with temperature

Abstract

The morphology of zeolite W (MER topology) synthesized from Hydrated Silicate Ionic Liquids (HSILs) shows a distinct temperature dependence, reflected in a fundamental difference in the underlying crystal growth mechanism as revealed by Atomic Force Microscopy (AFM). Zeolite W crystals obtained at 90 °C develop in a highly supersaturated solution through birth and spread growth, whereas synthesis at 175 °C results in elongated, spiral grown zeolite W particles. Supersaturation was measured through the concentration of dissolved aluminate, being the limiting species. The evolution of the aluminum concentration during crystallization at different temperatures was monitored with 27 Al Nuclear Magnetic Resonance (NMR) spectroscopy. Supersaturation conditions determine the nucleation rate, the prevailing crystal growth mechanism, and resulting crystal morphology.

Adsorption of Aqueous As (III) in Presence of Coexisting Ions by a Green Fe-Modified W Zeolite

“…According to the SEM analysis (Figure 2a,b) the W zeolite has a morphology of pseudo-spherical aggregated of long needle-like crystals. The W zeolite has been obtained as long needle-like crystallites and elongated crystals [58,59]. In the EDS spectra of Fe-modified W zeolite ( Figure 2d) was noticed that signal corresponding to potassium was decreased while the iron signal increased in comparison to those observed in pristine W zeolite ( Figure 2c).…”

On the key role of aluminium and other heteroatoms during interzeolite conversion synthesis

“…137,138 As such, dissolved Al plays a crucial role in building condensed structures. 139 Computational efforts at relevant synthesis conditions indicate that cyclization of condensation products is thermodynamically favoured and SDAs such as Na + or Ca 2+ further increase condensation tendency. 138 Of course, the kinetics of oligomerization should also be considered.…”

Reversible magnetic spiral domain

“…Warm sea level temperatures and strong rising air currents are known to be important causes of tropical cyclones, and the direction of spiral rotation is determined by the Coriolis effect 1 , 4 , 5 . Apart from these giant spirals, spirals also exist on the atomic scale in crystalline growth 1 , 6 , 7 . In living things, gastropod shells have spiral shapes because it is the most convenient way to keep growing in size while maintaining the same shape 1 .…”