Microstructure, Rheology and Tribology of Dense Colloidal Suspensions

The shear thickening of dense colloidal suspensions is an active area of research aimed to understand the non-linear flow response under various processing conditions. Efforts in theoretical models and simulations seek to examine the underlying physics thought to be controlled by nanometric inter-particle forces, including lubrication hydrodynamics [1,2] and frictional contact forces [3-5], whereas experimental tests of these latest theories are lacking. My research focusing on experimental validation, showing comparisons between rheological measurements and frictional contact model for a variety of colloidal dispersions varying from model systems to industrially commercial dispersions where both shear and first normal stress differences are available [6]. Particle-scale measurements of friction coefficients are provided through a survey of the literature. Secondly, microstructures on model suspensions under shear with known levels of friction is measured via small angle neutron scattering, revealing how structures evolve with increase shear rate. Further research of this work studies the relationship between rheology and topology of particles by measuring surface roughness via AFM. Investigation of rheology, microstructure, friction and topology provide quantitative information valuable for those modeling suspensions to understand the mechanistic role of lubrication hydrodynamics and frictional contact in shear thickening. The comparisons presented in this work provide quantitative suggestions for further model improvement.

References

[1] N. J. Wagner and J. F. Brady, Physics Today 62, 27 (2009).
[2] C. D. Cwalina and N. J. Wagner, Journal of Rheology 58, 949 (2014).
[3] R. Mari, R. Seto, J. F. Morris, and M. M. Denn, Journal of Rheology 58, 1693 (2014).
[4] J. F. Morris, Annual Review of Fluid Mechanics 52, null (2020).
[5] R. Seto, R. Mari, J. F. Morris, and M. M. Denn, Phys Rev Lett 111, 218301 (2013).
[6] Y.-F. Lee, Y. Luo, S. C. Brown, and N. J. Wagner, Journal of Rheology (2020)

Publications

1. Lee, Y. F., Luo, Y., Bai, T., Velez, C., Brown, S. C., & Wagner, N. J. (2021). Microstructure and rheology of shear-thickening colloidal suspensions with varying interparticle friction: Comparison of experiment with theory and simulation models. Physics of Fluids, 33(3), 033316.

2. Lee, Y. F., Luo, Y., Brown, S. C., & Wagner, N. J. (2020). Experimental test of a frictional contact model for shear thickening in concentrated colloidal suspensions. Journal of Rheology, 64(2), 267-282.

3.Luo, Y., Lee, Y. F., Dennis, K. A., Velez, C., Brown, S. C., Furst, E. M., & Wagner, N. J. (2020). One-step, in situ jamming point measurements by immobilization cell rheometry. Rheologica Acta, 1-17.