Influence of primary particle size distribution on nanoparticles aggregation and suspension yield stress: A theoretical study

The influence of primary particle size distribution (PPSD) on aggregation behaviour and the resulting effect on yield stress of a concentrated colloidal suspension was investigated theoretically. The discrete element model (DEM) combined with the well-known DLVO theory was employed to obtain an insight into the aggregation process of nanoparticles with different PPSDs, where a modified version of the Flatt and Brown model [J. Am. Ceram. Soc. 89 (2006) 1244–1256] [9] was employed to calculate the corresponding suspension yield stress from the simulation results. Specifically, the aggregate growth and structure in terms of fractal dimension, coordination number and the longest dimension were examined.It was shown that at small PPSD variances, a netlike structure was formed with aggregate branches interconnected in multiple locations, whereas at large variances aggregates with more compact structure and smaller longest dimension were generated. The rate of aggregation and particle assemblage was found to be faster at broader PPSDs, in turn generating aggregates with narrower size distributions and more compact structures. The influence of PPSD on coordination number (CN) was found to be minor while a decrease in PPSD variances led to an increase in both the mass-equivalent size and the longest dimension of aggregates. Further, suspension yield stress decreased as PPSD became broader. The simulation results agreed well with the experimental measurements and the published data.

DEM combined with the DLVO theory was applied to simulate the aggregation of nano-sized particles under different primary particle size distributions (PPSD), with the aim of obtaining an insight into the effect of PPSD on nanoparticle aggregation in terms of aggregate growth and structure, and the resulting effect on the yield stress of concentrated colloidal suspensions.Figure optionsDownload as PowerPoint slideHighlights
► The effect of particle size distribution on nanoparticle aggregation was studied.
► A suspension yield stress model was developed based on the aggregate structure.
► DEM coupled with DLVO theory was applied to model nanoparticle aggregation.