Mechanistic Principles of Barite Formation: From Nanoparticles to Micron-Sized Crystals
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This study reports on the early stages of barite (BaSO4) precipitation from aqueous solution. TEM observations indicate that BaSO4 is formed by two levels of oriented aggregation of nanosized solid particles (nonclassical crystallization pathways). Oriented alignment of nanoparticles within micron-sized aggregates is observed, resulting in the formation of perfect monocrystalline particles of barite formed after a recrystallization process that reduces the number of grain boundaries within the aggregates. When an organic copolymer is present in solution, a dense liquid precursor phase seems to be stabilized, forming a PILP (polymer induced liquid precursor). Additionally, secondary nanoparticles are temporarily stabilized retarding recrystallization leading to the formation of BaSO4 mesocrystals.