Aging of cornstarch particles suspended in aqueous solvents at room temperature

Rheological Properties of Dense Particle Suspensions of Starches: Shear Thickening, Shear Jamming, and Shock Absorption Properties

Concentrated suspensions of Brownian and non-Brownian particles display distinctive rheological behavior highly dependent on shear rate and shear stress. Cornstarch suspensions, composed of starch particles from corn plants, served as a model for concentrated non-Brownian suspensions, demonstrating discontinuous shear thickening (DST) and dynamic shear jamming (SJ). However, starch particles from other plant sources have not yet been investigated, despite their different sizes and shapes. This study is focused on the evaluation of the effects of the structural parameters of starch particles by preparing concentrated suspensions of starch particles from 13 different plants at particle fractions of 25-50% and their rheological behavior through steady shear, pull-out, and ball-drop tests. Starch particles can be roughly classified as polygonal and ellipsoidal. The DST and SJ behavior typically reported for concentrated cornstarch suspensions were confirmed for other starch particles in both particle groups. The ball-drop test demonstrated excellent shock absorption properties for 11 concentrated suspensions of starch particles, except for sago palms. In the case of concentrated suspensions of starch particles, the particle fraction and shear applied were the dominant factors that significantly affected the rheological behavior, whereas the particle shape was not a primary contributor. The findings of this study drive further investigation on the effect of liquid and particle surface properties in concentrated particle suspensions on DST and SJ behaviors.

Effect of Liquid Properties on the Non-Newtonian Rheology of Concentrated Silica Suspensions: Discontinuous Shear Thickening, Shear Jamming, and Shock Absorbance

Concentrated particle suspensions exhibit rheological behavior, such as discontinuous shear thickening (DST) and dynamic shear jamming (SJ), which affect applications such as soft armors. Although the origin of this behavior in shear-activated particle-particle interactions has been identified, the effect of chemical factors, especially the role of liquids, on this behavior remains unexplored. Hydrogen bonding in suspensions has been proposed to be essential for frictional contacts between particles, and therefore, most studies on DST and SJ have focused on aqueous and protic organic media with a definite hydrogen bonding ability. To identify an alternative molecular mechanism, this study explored the effects of liquid polarity and an aprotic nature on the rheological behavior of concentrated suspensions of silica microparticles. Owing to their excellent particle dispersion, the DST behavior of polar liquids was observed, independent of protic and aprotic liquids. In contrast, nonpolar liquids formed particle agglomerates because of the particle-particle attraction and became a paste at a high particle fraction. The SJ behavior was confirmed for three aprotic organic liquids (propylene carbonate, 1,3-dimethyl-2-imidazolidinone, and 1,3-dimethylpropyleneurea), suggesting the hydrogen bonding ability of these aprotic liquids. The diverse mechanisms of shear-activated interactions between particles present material design possibilities for the non-Newtonian rheology of concentrated particle suspensions.

A shear-thickening colloidal electrolyte for aqueous zinc-ion batteries with resistance on impact

A conventional aqueous electrolyte is a crucial component of zinc-ion batteries providing an ion conductive medium. However, the monofunction of a liquid electrolyte cannot bear any external load. With regard to applications in electric vehicles and stationary energy storage devices, complicated battery packing materials are required to improve the mechanical properties, resulting in reduced energy or power densities from the perspective of the entire device. In this work, an electrolyte suspension combining both fluid-like and solid-like performances was developed for rechargeable zinc-ion batteries. Cornstarch water suspension is utilized in the electrolyte design forming a shear-thickening electrolyte with impact resistance ability. The formed electrolyte becomes rigid at a high shear rate. In other words, under a sudden impact, a battery with this shear-thickening electrolyte could offer additional load bearing avoiding short-circuiting and improving safety. Although an additional functionality, namely impact resistance, was added to the electrolyte, the as-prepared electrolyte still performs with comparable electrochemical performances for which it exhibits a superior ionic conductivity of 3.9 × 10^-3 S cm^-1 and Zn²⁺ transference number. This electrolyte even suppresses side-effects on the zinc anode, exhibiting a lower voltage gap in the symmetric cell compared to the aqueous electrolyte. The integrated full cell also delivered a specific capacity of 255 mA h g^-1 with commercial MnO₂ as the cathode at a current density of 0.1 A g^-1.