Formation of spherical calcium sulfate mesocrystals: orientation controlled by subunit growth

Abstract

A subunit growth controlled orientation uncovering the formation mechanism of spherical calcium sulfate mesocrystals.

Single-Crystal Regular Hexagonal Microplates of Two-Dimensional α-Calcium Sulfate Hemihydrate Preparation from Phosphogypsum in Na2SO4 Aqueous Solution

“…Similar to natural gypsum, the main component of PG is also DH. However, the difference in complex impurity components, poor water resistance, and poor particle size distribution make PG insufficient for industrial applications by comparison with natural gypsum. , Hence, the use of PG as a raw material to prepare α-HH not only realizes the recycling of resources but also protects natural gypsum resources and realizes environmental, economic, and social sustainable development. , So far, some methods have been developed to prepare α-HH from DH, and the most industrial application potential method which using PG as a raw material is undoubtedly the salt solution method. − In the conventional salt solution method, α-HH with diverse morphologies can be synthesized by the use of various soluble additives, including organics and inorganics, which can selectively alter the nucleation and growth process of α-HH, resulting in changes in the crystal habit. − A lot of research shows that α-HH rods and whiskers with different aspect ratios can be obtained by adjusting the pH, crystallization medium concentration, and the use of modifiers. , However, one potential concern for the scale-up of the process to industry is its crystallization medium. At present, the most widely used crystallization medium in salt solution methods is soluble chloride salts, − which can lead to serious equipment corrosion.…”

Simultaneous effect of Na2EDTA on the phase transformation and morphology evolution during the transformation of gypsum into α-calcium sulfate hemihydrate

“…41,42 After the addition of Na 2 EDTA, Ca 2+ in the surface of α -HH and the carboxyl groups in EDTA 2− are attracted to each other due to the electrostatic interaction, and form a stable 1 : 1 complex through coordination, which is adsorbed on specific crystal surfaces, hindering the crystal growth along the c -axis to adjust the crystal morphology. 25,43…”

Alpha-calcium sulfate hemihydrate used as a water-soluble template for the synthesis of ZnO hollow microspheres

“…In addition, the hydroxyl groups of crystal water and carboxyl groups of EDTA existing in a-HH microspheres probably provided hydrogen bonding between ZnO nanoparticles and a-HH. 49 In step III, the a-HH/ ZnO core-shell microspheres were fabricated on the seed layers by the second deposition-precipitation process. During this period, ethanol instead of water was used as the solvent for NaOH to control the nucleation and growth of ZnO shell by slowing down the reaction rate, because most of the hydroxyl ions were replaced by ethoxide ions.…”