Polymorph Discrimination of CaCO₃ Mineral in an Ethanol/Water Solution:  Formation of Complex Vaterite Superstructures and Aragonite Rods

Abstract

Polymorph discrimination of CaCO3 mineral has been easily realized in an ethanol/water mixed solution system under mild conditions without using any organic additives. The phase transition from a mixture of calcite and aragonite to pure aragonite, and then to almost pure vaterite, can be nicely captured by the choice of a suitable ratio of ethanol to distilled water in the present reaction system. In addition, a complex self-assembly process for the formation of multilayered vaterite cakes in this binary solution system has been proposed. The cakelike vaterite crystals with multilayered structures are porous with an average pore size of 24.9 nm. The results demonstrated that such a binary reaction media could provide an alternative and versatile tool for controlling the polymorph and nanostructures of inorganic minerals through manipulating the thermodynamics and kinetics. This study provides an alternative polymorph switching route for CaCO3 mineral without using any additives and can even be scaled up as a green chemistry method for the industrial production of CaCO3 with different polymorphs.

Structural stability of a colloidal solution of Ca(OH)2 nanocrystals exposed to high relative humidity conditions

“…However, important differences could happen when particles have nanoscale dimensions and when factors such as relative humidity (RH) or exposure time affect in different grade the stability of phases. Only few works consider the influence of the type of solvent and concentration [8], RH, aging [4,9,10], or additives [11]. Today commercial companies offer alcoholic colloidal nanoparticles of calcium hydroxide at different concentrations ranging between 5 and 50g / l [12].…”

Biomimetic Polymers for Chiral Resolution and Antifreeze Applications

“…[121][122] It should be mentioned here that the solvent molecules act similarily to additives to some extent, and therefore, crystallization in different solvents or solvent mixtures normally leads to the precipitation of crystals with different growth morphologies. [123][124][125][126][127][128][129][130] Polymers often serve as additives for controled crystallization. The use of polymers as surfactants, morphology modifiers, or soft templates for crystallization is inspired exclusively by the biomineralization process.…”

Symmetry-breaking assembled porous calcite microspheres and their multiple dental applications

“…Calcite is the most attractive phase for the construction of porous CaCO3 MPs, because they are more structurally stable than their vaterite counterparts [20,21]. It is believed that the porous calcite MPs with high surface area could provide multiple new possibilities for medical and dental applications.…”