HYPOTHESIS The rheology of complex suspensions, such as nuclear waste slurries at the Hanford and Savannah River sites, imposes significant challenges on industrial-scale processing. Investigating the rheology and connecting it to the agglomerate morphology and underlying particle interactions in slurries will provide important fundamental knowledge, as well as prescriptive data for practical applications. Here, we use suspensions of nano-scale aluminum oxyhydroxide minerals in the form of boehmite as an analog of the radioactive waste slurry to investigate the correlation between particle interactions, agglomerate morphology, and slurry rheology. EXPERIMENTS A combination of Couette rheometry and small-angle scattering techniques (independently and simultaneously) were used to understand how agglomerate structure of slurry changes under flow and how these structural changes manifest themselves in the bulk rheology of the suspensions. FINDINGS Our experiments show that the boehmite slurries are thixotropic, with the rheology and structure of the suspensions changing with increasing exposure to flow. In the slurries, particle agglomerates begin as loose, system-spanning clusters, but exposure to moderate shear rates causes the agglomerates to irreversibly consolidate into denser clusters of finite size. The structural changes directly influence the rheological properties of the slurries such as viscosity and viscoelasticity. Our study shows that solution pH affects the amount of structural rearrangement and the kinetics of the rearrangement process, with an increase in pH leading to faster and more dramatic changes in bulk rheology, which can be understood via correlations between particle interactions and the strength of particle network. Nearly identical structural changes were also observed in Poiseuille flow geometries, implying that the observed changes are relevant in pipe flow as well.

中文翻译：

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将颗粒相互作用与勃姆石纳米晶体悬浮液的附聚物形态和流变学联系起来。

假设复杂悬浮液的流变学，例如汉福德和萨凡纳河遗址的核废料浆料，对工业规模的加工提出了重大挑战。研究流变学并将其与浆料中的附聚物形态和潜在颗粒相互作用联系起来，将为实际应用提供重要的基础知识和规范数据。在这里，我们使用勃姆石形式的纳米级羟基氧化铝矿物的悬浮液作为放射性废浆料的类似物，以研究颗粒相互作用、附聚物形态和浆料流变学之间的相关性。实验将库埃特流变仪和小角散射技术（独立和同时）相结合，用于了解浆料的团聚结构在流动下如何变化，以及这些结构变化如何在悬浮液的整体流变学中表现出来。研究结果我们的实验表明，勃姆石浆料具有触变性，悬浮液的流变性和结构随着暴露于流动的增加而变化。在浆料中，颗粒附聚物开始时是松散的、跨越系统的簇，但暴露于中等剪切速率会导致附聚物不可逆地固结成有限尺寸的更致密的簇。结构变化直接影响浆料的流变性能，例如粘度和粘弹性。我们的研究表明，溶液 pH 值会影响结构重排的量和重排过程的动力学，pH 值的增加会导致整体流变学发生更快、更剧烈的变化，这可以通过颗粒相互作用与颗粒强度之间的相关性来理解网络。在泊肃叶流动几何中也观察到几乎相同的结构变化，这意味着观察到的变化也与管道流动相关。