Direct Visualization of the Hydration Layer on Alumina Nanoparticles with the Fluid Cell STEM in situ

Abstract

Rheological behavior of aqueous suspensions containing nanometer-sized powders is of relevance to many branches of industry. Unusually high viscosities observed for suspensions of nanoparticles compared to those of micron size powders cannot be explained by current viscosity models. Formation of so-called hydration layer on alumina nanoparticles in water was hypothesized, but never observed experimentally. We report here on the direct visualization of aqueous suspensions of alumina with the fluid cell in situ. We observe the hydration layer formed over the particle aggregates and show that such hydrated aggregates constitute new particle assemblies and affect the flow behavior of the suspensions. We discuss how these hydrated nanoclusters alter the effective solid content and the viscosity of nanostructured suspensions. Our findings elucidate the source of high viscosity observed for nanoparticle suspensions and are of direct relevance to many industrial sectors including materials, food, cosmetics, pharmaceutical among others employing colloidal slurries with nanometer-scale particles.

A thermodynamic model of nanofluid viscosity based on a generalized Maxwell-type constitutive equation

“…Our thermodynamics modelling of the size effect on the viscosity in the mixture Li-Ar is in agreement with the results obtained by Ruydak and Krassnolutskii [42] based on molecular dynamics simulation and experiments. Our approach is also in accord with the data reported for the more classical nanofluids, involving alumina particles dispersed in water [48,51].…”

“…Argon is found in the literature, we have assumed that h=0.2 nm, which is of the order of magnitude of the Van der Waals radius of Ar, which, by the way, lies within the range of values proposed for other fluids [44][45][46][47][48][49].…”

Mussel‐Glue Inspired Adhesives: A Study on the Relevance of l‐Dopa and the Function of the Sequence at Nanomaterial‐Peptide Interfaces

“…Nonetheless, the results from submotif 2D NMR analysis were set as restraints in molecular dynamics simulations to gain insights into the Pep 3 OX structure at the Al 2 O 3 (Table S5 and S6, Supporting Information). Considering the heterogeneity of the Al 2 O 3 surfaces and the existence of a tightly bound hydration layer at the surface, the peptide‐inorganic contact interface was approximated in the model as a dynamic surface water layer (Figure S23, Supporting Information). The assumption to investigate a flexible water layer instead of an Al 2 O 3 crystal surface allows for incorporation of H‐bond donors and counter ions that are relevant for peptide adsorption.…”

In-situ realtime monitoring of nanoscale gold electroplating using micro-electro-mechanical systems liquid cell operating in transmission electron microscopy

“…There are trials to replace the membrane with graphene to improve the imaging resolution. [14][15][16] Commercially available LCTEM increases the interest for in-liquid nanoscale electrochemical researches, 17,18 especially to reveal the mechanisms of nanoparticle growth from ligand/metal self-assembly, 19 the role of a hydration layer in the formation of aggregates 20 or also the nucleation of conjugated polymer such as the organic poly(3,4-ethylenedioxythiophene) (PEDOT) by electrochemical process. 21 However, LCTEM suffers from the vibration, dose limitation of electron beam irradiation, which prevent nanoscale observation of electroplating without other electrodeposition effects for a long duration.…”