Particle agglomeration is relevant to numerous industrial applications and consumer products. The present work explores interactions between and agglomeration of gamma (γ)-alumina nanoparticles in pure water and dilute aqueous salt solutions. To characterize surface- and salt-specific effects, potential of mean force (PMF) profiles between γ-alumina surfaces ([110] and [100] facets) are extracted using classical molecular dynamics (MD) simulations. Supporting experiments are conducted using dynamic light scattering (DLS) to investigate agglomeration at the macroscale. The ion pairs considered are sodium chloride, ammonium acetate, barium nitrate, and barium acetate; sampling a broad range of the Hofmeister series. As particle surfaces approach contact, free-energy fluctuations of the PMF profiles reflect structural adjustments of the intervening aqueous phase. We extract values for the cohesive energy from the MD results, and parse the resultant effective pair interactions into van der Waals and electrostatic contributions. Molecular scale findings from simulations correlate with hydrodynamic radii of γ-alumina nanoparticles, obtained from DLS experiments. The results highlight the applicability of molecular simulations to identify the origins of macroscale observables.

颗粒团聚与众多工业应用和消费品相关。目前的工作探讨了纯水和稀盐水溶液中γ (γ)-氧化铝纳米粒子之间的相互作用和团聚。为了表征表面和盐特定效应，使用经典分子动力学 (MD) 模拟提取 γ-氧化铝表面（[110] 和 [100] 面）之间的平均力 (PMF) 剖面势。使用动态光散射（DLS）进行支持实验，以研究宏观尺度的团聚。考虑的离子对是氯化钠、醋酸铵、硝酸钡和醋酸钡；对各种 Hofmeister 系列进行采样。当颗粒表面接近接触时，PMF 分布的自由能波动反映了中间水相的结构调整。我们从 MD 结果中提取内聚能值，并将所得的有效对相互作用解析为范德华和静电贡献。模拟的分子尺度结果与 DLS 实验获得的 γ-氧化铝纳米颗粒的流体动力学半径相关。结果强调了分子模拟在识别宏观可观察到的起源方面的适用性。