Formation of Laves phases in buoyancy matched hard sphere suspensions

Abstract

Colloidal Laves phases (LPs) are promising precursors for photonic materials. Laves phases have not yet been observed to form in experiments on colloidal suspensions of hard spheres (HS), even though they have been reported in computer simulations. LP formation so far has been achieved only for binary mixtures of colloidal charged spheres or ligand-stabilized nano-particles after drying. Using static light scattering, we monitored LP formation and annealing in a binary mixture of buoyant hard sphere approximants (size ratio Γ = 0.77, number or molar fraction of small spheres xS = 0.76) for volume fractions in the fluid-crystal coexistence regions. All samples spontaneously formed MgZn2 type LPs on the time scale of weeks to months via bulk nucleation and growth. Irrespective of the initial suspension volume fractions, the LP volume fraction at coexistence is ΦCOEX = 0.59 which is significantly below the close packing limit ΦMAX = 0.615 and remarkably close to the expectation from simulation. At low volume fractions, crystals anneal to high quality during coarsening which is in line with recent theoretical expectations for the thermodynamic stability of different LP types. At large volume fractions, however, the diffractograms evolve towards a more MgCu2-like appearance which we attribute to the formation of randomly stacked LPs. Such structures are not known from atomic systems.

Addresses

Institut für Makromolekulare Chemie, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany. eckhard.bartsch@physchem.uni-freiburg.de.

Autoren

N Schaertl
D Botin
T Palberg
E Bartsch

DOI

10.1039/c7sm02348k

eISSN

1744-6848

Externe Identifier

PubMed Identifier: 29881859

Funding acknowledgements

Graduate School of Excellence Materials Science In Mainz: GSC 266
Deutsche Forschungsgemeinschaft: Ba1619/2
Deutsche Forschungsgemeinschaft: Pa459/13

Open access

false

ISSN

1744-683X

Ausgabe der Veröffentlichung

24

Zeitschrift

Soft matter

Sprache

eng

Medium

Print

Paginierung

5130 - 5139

Datum der Veröffentlichung

2018

Status

Published

Datum der Datenerfassung

2018

Titel

Formation of Laves phases in buoyancy matched hard sphere suspensions.

Sub types

Journal Article

Ausgabe der Zeitschrift

14

Datenquelle: Europe PubMed Central

Abstract

Colloidal Laves phases (LPs) are promising precursors for photonic materials. Laves phases have not yet been observed to form in experiments on colloidal suspensions of hard spheres (HS), even though they have been reported in computer simulations. LP formation so far has been achieved only for binary mixtures of colloidal charged spheres or ligand-stabilized nano-particles after drying. Using static light scattering, we monitored LP formation and annealing in a binary mixture of buoyant hard sphere approximants (size ratio Γ = 0.77, number or molar fraction of small spheres xS = 0.76) for volume fractions in the fluid-crystal coexistence regions. All samples spontaneously formed MgZn2 type LPs on the time scale of weeks to months via bulk nucleation and growth. Irrespective of the initial suspension volume fractions, the LP volume fraction at coexistence is ΦCOEX = 0.59 which is significantly below the close packing limit ΦMAX = 0.615 and remarkably close to the expectation from simulation. At low volume fractions, crystals anneal to high quality during coarsening which is in line with recent theoretical expectations for the thermodynamic stability of different LP types. At large volume fractions, however, the diffractograms evolve towards a more MgCu2-like appearance which we attribute to the formation of randomly stacked LPs. Such structures are not known from atomic systems.

Autoren

N Schaertl
D Botin
T Palberg
E Bartsch

Autoren-URL

https://www.ncbi.nlm.nih.gov/pubmed/29881859

DOI

10.1039/c7sm02348k

eISSN

1744-6848

Ausgabe der Veröffentlichung

24

Zeitschrift

Soft Matter

Sprache

eng

Country

England

Paginierung

5130 - 5139

Datum der Veröffentlichung

2018

Status

Published

Datum, an dem der Datensatz öffentlich gemacht wurde

2018

Titel

Formation of Laves phases in buoyancy matched hard sphere suspensions.

Sub types

Journal Article

Ausgabe der Zeitschrift

14

Datenquelle: PubMed

Abstract

Colloidal Laves phases (LPs) are promising precursors for photonic materials. Laves phases have not yet been observed to form in experiments on colloidal suspensions of hard spheres (HS), even though they have been reported in computer simulations. LP formation so far has been achieved only for binary mixtures of colloidal charged spheres or ligand-stabilized nano-particles after drying. Using static light scattering, we monitored LP formation and annealing in a binary mixture of buoyant hard sphere approximants (size ratio \textgreekG = 0.77, number or molar fraction of small spheres xS = 0.76) for volume fractions in the fluid-crystal coexistence regions. All samples spontaneously formed MgZn2 type LPs on the time scale of weeks to months via bulk nucleation and growth. Irrespective of the initial suspension volume fractions, the LP volume fraction at coexistence is \textgreekFCOEX = 0.59 which is significantly below the close packing limit \textgreekFMAX = 0.615 and remarkably close to the expectation from simulation. At low volume fractions, crystals anneal to high quality during coarsening which is in line with recent theoretical expectations for the thermodynamic stability of different LP types. At large volume fractions, however, the diffractograms evolve towards a more MgCu2-like appearance which we attribute to the formation of randomly stacked LPs. Such structures are not known from atomic systems.

Autoren

N Schaertl
D Botin
T Palberg
E Bartsch

DOI

10.1039/c7sm02348k

Zeitschrift

Soft matter

Notes

file: http://www.ncbi.nlm.nih.gov/pubmed/29881859

Artikelnummer

24

Paginierung

5130 - 5139

Datum der Veröffentlichung

2018

Datum der Datenerfassung

2020

Titel

Formation of Laves phases in buoyancy matched hard sphere suspensions

Sub types

article

Ausgabe der Zeitschrift

14

Datenquelle: Manual

Formation of Laves phases in buoyancy matched hard sphere suspensions

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