Pereira Luiz, Vasseur Jérémie, Wadsworth Fabian B, Trixler Frank, Dingwell Donald B
Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München, 80333, Munich, Germany.
Department of Earth Sciences, Durham University, Durham, DH1 3LE, UK.
Sci Rep. 2022 Jun 2;12(1):9226. doi: 10.1038/s41598-022-12948-1.
We study the rheology of silicate melts containing platinum-group element (PGE) particles. They exhibit a shear-thinning behaviour, an intense aggregation tendency, and an anomalously high apparent viscosity in the low shear rate limit, even at very low particle volume fraction. Using a compilation of published experimental data, we analyse these effects in three steps. Firstly, we observe that the viscosities of these suspensions are much higher than those of natural silicate crystal-bearing melts for low shear rate regimes. Secondly, we demonstrate that the viscosities at low shear rate limit cannot be estimated by classical rheological models but rather may be understood as the result of particle aggregation, trapping dead fluid, and thereby increasing the effective particle volume fraction. Finally, we scale the critical shear rates for shear-thinning using a Peclet number analysis-invoking a competition between random thermal particle motion and hydrodynamic shearing motion-and, using an empirical extension, we additionally account for the particle-particle interaction energetics. We propose a framework in which the rheology of this family of particle-bearing melts can be predicted, and demonstrate that at low Peclet numbers, PGE-bearing particle aggregation is driven by interparticle forces and Brownian motion.
我们研究了含有铂族元素（PGE）颗粒的硅酸盐熔体的流变学。它们表现出剪切变稀行为、强烈的聚集趋势，并且在低剪切速率极限下具有异常高的表观粘度，即使在颗粒体积分数非常低的情况下也是如此。利用已发表的实验数据汇编，我们分三步分析这些效应。首先，我们观察到在低剪切速率范围内，这些悬浮液的粘度远高于天然含硅酸盐晶体熔体的粘度。其次，我们证明低剪切速率极限下的粘度不能用经典流变模型估计，而可以理解为颗粒聚集、截留死流体从而增加有效颗粒体积分数的结果。最后，我们使用佩克莱数分析来确定剪切变稀的临界剪切速率——考虑随机热颗粒运动和流体动力剪切运动之间的竞争——并且通过经验扩展，我们还考虑了颗粒间相互作用能。我们提出了一个可以预测这类含颗粒熔体流变学的框架，并证明在低佩克莱数下，含PGE颗粒的聚集是由颗粒间力和布朗运动驱动的。
