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

Firlar E, Çınar S, Kashyap S, Akinc M, Prozorov T - Sci Rep (2015)

Bottom Line: Unusually high viscosities observed for suspensions of nanoparticles compared to those of micron size powders cannot be explained by current viscosity models.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.

View Article: PubMed Central - PubMed

Affiliation: Division of Materials Science and Engineering, US DOE Ames Laboratory, Ames, IA, 50011, USA.

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.

No MeSH data available.


(A) In situ Electron Energy Loss O K-edge spectra acquired from (1), hydrated alumina, (2) ethanol-modified alumina, and the reference materials reported in the literature: (3) γ-Al2O329, (4) α-Al(OH)330 and (6) AlO(OH)31.(B) Peak fitting of the acquired spectra.
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f5: (A) In situ Electron Energy Loss O K-edge spectra acquired from (1), hydrated alumina, (2) ethanol-modified alumina, and the reference materials reported in the literature: (3) γ-Al2O329, (4) α-Al(OH)330 and (6) AlO(OH)31.(B) Peak fitting of the acquired spectra.

Mentions: Figure 5 shows the EEL spectra of O K-edge peak acquired on specimens at different conditions. Figure 5 (A) presents the spectra from as-received alumina (1), hydrated alumina (2), ethanol-modified alumina (3), reference γ-Al2O329(4), reference α-Al(OH)330(5) and reference AlO(OH)31(6). Figure 5 (B) shows peak fitting analysis of the acquired data and details of peak fitting are given in Table SI 1.


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

Firlar E, Çınar S, Kashyap S, Akinc M, Prozorov T - Sci Rep (2015)

(A) In situ Electron Energy Loss O K-edge spectra acquired from (1), hydrated alumina, (2) ethanol-modified alumina, and the reference materials reported in the literature: (3) γ-Al2O329, (4) α-Al(OH)330 and (6) AlO(OH)31.(B) Peak fitting of the acquired spectra.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4440531&req=5

f5: (A) In situ Electron Energy Loss O K-edge spectra acquired from (1), hydrated alumina, (2) ethanol-modified alumina, and the reference materials reported in the literature: (3) γ-Al2O329, (4) α-Al(OH)330 and (6) AlO(OH)31.(B) Peak fitting of the acquired spectra.
Mentions: Figure 5 shows the EEL spectra of O K-edge peak acquired on specimens at different conditions. Figure 5 (A) presents the spectra from as-received alumina (1), hydrated alumina (2), ethanol-modified alumina (3), reference γ-Al2O329(4), reference α-Al(OH)330(5) and reference AlO(OH)31(6). Figure 5 (B) shows peak fitting analysis of the acquired data and details of peak fitting are given in Table SI 1.

Bottom Line: Unusually high viscosities observed for suspensions of nanoparticles compared to those of micron size powders cannot be explained by current viscosity models.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.

View Article: PubMed Central - PubMed

Affiliation: Division of Materials Science and Engineering, US DOE Ames Laboratory, Ames, IA, 50011, USA.

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.

No MeSH data available.