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Mechanistic Principles of Barite Formation: From Nanoparticles to Micron-Sized Crystals

机译：重晶石形成的力学原理：从纳米粒子到微米级晶体

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This Study reports evidence for barite (BaSO4) formation from aqueous solution Via nonclassical pathways Our observations support the occurrence of a liquid-liquid separation in the absence of any additive as the initial stage of the crystallization process. The first solid (primary) particles or nuclei seem to form within the initially formed liquidlike precursor phases TEM and SEM observations of the nanostructure evolution of samples quenched at successive stages of crystallization indicate two levels of oriented aggregation of nanosized solid particles. The first is the aggregation of crystalline primary nanoparticles of ca. 2-10, nm length to give larger but still nanometer-sized particles (ca. 20-100 nm length). For the first time, clear evidence of crystallographically oriented aggregation of secondary, nanometer-sized particles to forth a barite single crystal is reported. During the second aggregation step of these secondary nanoparticles, most of the porosity in the largest, micron-sized aggregates is annealed, resulting in-perfect single crystals. Once an amount of 50 ppm of additive, in our case a maleic acid/allyl sulfonic add copolymer with phosphonate groups, is present in the solution, the dense liquid precursor phase seems to be stabilized, forming a PILP (polymer induced liquid precursor) and then sedondary nanoparticles are temporarily stabilized against recrystallization. Growth by classical monomer addition, ripening processes or nanoparticle attachment also seems to contribute to barite formation, during the latest stages of the processes.
机译：该研究报告了通过非经典途径从水溶液中形成重晶石（BaSO4）的证据。我们的观察结果支持在不存在任何添加剂的情况下进行液-液分离的情况，这是结晶过程的初始阶段。最初形成的液态前体相TEM和SEM似乎形成了第一个固体（初级）颗粒或核，在连续的结晶阶段淬灭的样品的纳米结构演变表明，纳米级固体颗粒有两个方向的聚集。第一个是约ca的结晶初级纳米粒子的聚集。长度为2-10 nm，可以得到更大但仍为纳米大小的颗粒（长度为20-100 nm）。首次报道了二级纳米尺寸颗粒重晶石单晶结晶定向聚集的明确证据。在这些次级纳米粒子的第二个聚集步骤中，将最大的微米级聚集体中的大多数孔隙率退火，从而形成了完美的单晶。一旦溶液中存在50 ppm的添加剂（在我们的情况下为带有膦酸酯基的马来酸/烯丙基磺酸加成共聚物）中，稠密的液态前驱物相似乎就稳定了，形成了PILP（聚合物诱导的液态前驱物），然后将sedondary纳米颗粒暂时稳定以防止重结晶。在该过程的最新阶段，通过经典单体添加，成熟过程或纳米颗粒附着的生长似乎也有助于重晶石的形成。

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