Wang Hsiu-Wen, Nienhuis Emily T, Graham Trent R, Pouvreau Maxime, Reynolds Jacob G, Bowden Mark, Schenter Gregory K, De Yoreo James J, Rosso Kevin M, Pearce Carolyn I
Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
Pacific Northwest National Laboratory, Richland, WA, USA.
Commun Chem. 2024 Sep 4;7(1):199. doi: 10.1038/s42004-024-01285-1.
Aluminum hydroxide polymorphs are of widespread importance yet their kinetics of nucleation and growth remain beyond the reach of current models. Here we attempt to unveil the reaction processes underlying the polymorphs formation at high chemical potential. We examine their formation in-situ from supersaturated alkaline sodium aluminate solutions using deuteration and time-resolved neutron pair distribution function analyses, which indicate the formation of individual Al(OD) layers as an intermediate particle phase. These layers ultimately stack to form gibbsite- or bayerite-like layered heterostructures. Ex-situ characterization of the recovered precipitates using Al magic angle spinning nuclear magnetic resonance spectroscopy, Raman, X-ray diffraction, and scanning electron microscopy, suggests the presence of additional intermediate states, an amorphous compound bearing both tetrahededrally- and penta-coordinated Al. These observations reveal the complex pathways to form Al(OD) monolayers via either transient pentacoordinate species or amorphous-to-ordered transitions. The subsequent crystallization of admixed gibbsite/bayerite is followed by an Al(OD) monolayer attachment process.
氢氧化铝多晶型物具有广泛的重要性，但其成核和生长动力学仍超出当前模型的范畴。在此，我们试图揭示在高化学势下多晶型物形成背后的反应过程。我们使用氘化和时间分辨中子对分布函数分析，从过饱和碱性铝酸钠溶液中原位研究它们的形成，结果表明形成了单个Al(OD)层作为中间粒子相。这些层最终堆叠形成水铝石或拜耳石状的层状异质结构。使用铝魔角旋转核磁共振光谱、拉曼光谱、X射线衍射和扫描电子显微镜对回收沉淀物进行的非原位表征表明，存在额外的中间状态，即一种同时含有四面体和五配位铝的无定形化合物。这些观察结果揭示了通过瞬态五配位物种或从无定形到有序转变形成Al(OD)单层的复杂途径。混合的水铝石/拜耳石随后的结晶过程伴随着Al(OD)单层附着过程。
