Sedimentation equilibria in polydisperse ferrofluids: critical comparisons between experiment, theory, and computer simulation / Elfimova Ekaterina A.,Ivanov Alexey O.,Lakhtina Ekaterina V.,Pshenichnikov Alexander F.,Camp Philip J. // SOFT MATTER. - 2016. - V. 12, l. 18. - P. 4103-4112.

ISSN/EISSN:

1744-683X / 1744-6848

Type:

Article

Abstract:

The sedimentation equilibrium of dipolar particles in a ferrofluid is studied using experiment, theory, and computer simulation. A theory of the particle-concentration profile in a dipolar hard-sphere fluid is developed, based on the local-density approximation and accurate expressions from a recently introduced logarithmic free energy approach. The theory is tested critically against Monte Carlo simulation results for monodisperse and bidisperse dipolar hard-sphere fluids in homogeneous gravitational fields. In the monodisperse case, the theory is very accurate over broad ranges of gravitational field strength, volume fraction, and dipolar coupling constant. In the bidisperse case, with realistic dipolar coupling constants and compositions, the theory is excellent at low volume fraction, but is slightly inaccurate at high volume fraction in that it does not capture a maximum in the small-particle concentration profile seen in simulations. Possible reasons for this are put forward. Experimental measurements of the magnetic-susceptibility profile in a real ferrofluid are then analysed using the theory. The concentration profile is linked to the susceptibility profile using the second-order modified mean-field theory. It is shown that the experimental results are not consistent with the sample being monodisperse. By introducing polydispersity in the simplest possible way, namely by assuming the system is a binary mixture, almost perfect agreement between theory and experiment is achieved.

Author keywords:

THERMODYNAMIC PERTURBATION-THEORY; SIMPLE POLAR FLUIDS; EQUATION-OF-STATE; HARD-SPHERES; COLLOIDAL SUSPENSIONS; CRITICAL-TEMPERATURE; DENSITY PROFILES; MAGNETIC FLUIDS; ORDER; ULTRACENTRIFUGATION

DOI:

10.1039/c6sm00304d

Web of Science ID:

ISI:000375800500004

Соавторы в МНС:

Другие поля

Поле	Значение
Publisher	ROYAL SOC CHEMISTRY
Address	THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND
Language	English
EISSN	1744-6848
Keywords-Plus	THERMODYNAMIC PERTURBATION-THEORY; SIMPLE POLAR FLUIDS; EQUATION-OF-STATE; HARD-SPHERES; COLLOIDAL SUSPENSIONS; CRITICAL-TEMPERATURE; DENSITY PROFILES; MAGNETIC FLUIDS; ORDER; ULTRACENTRIFUGATION
Research-Areas	Chemistry; Materials Science; Physics; Polymer Science
Web-of-Science-Categories	Chemistry, Physical; Materials Science, Multidisciplinary; Physics, Multidisciplinary; Polymer Science
Author-Email	philip.camp@ed.ac.uk
ResearcherID-Numbers	Elfimova, Ekaterina/P-5003-2016 Pshenichnikov, Alexander/F-9511-2013 Ivanov, Alexey/E-4442-2011
ORCID-Numbers	Ivanov, Alexey/0000-0001-8239-4039 Elfimova, Ekaterian/0000-0002-8941-8184 Camp, Philip/0000-0002-7901-1364
Funding-Acknowledgement	Ministry of Education and Science of the Russian Federation {[}02.A03.21.0006, 3.12.2014/K]; Ural Branch, Russian Academy of Sciences {[}15-10-1-16]; Ural Federal University
Funding-Text	E. A. E. and A. O. I. gratefully acknowledge research funding from the Ministry of Education and Science of the Russian Federation (Contract No. 02.A03.21.0006, Project No. 3.12.2014/K). E. V. L. and A. F. P. thank the Ural Branch, Russian Academy of Sciences for supporting Project No. 15-10-1-16. E. A. E. and P. J. C. thank the Ural Federal University for supporting collaborative visits between the Edinburgh and Ekaterinburg groups.
Number-of-Cited-References	47
Usage-Count-Last-180-days	3
Usage-Count-Since-2013	9
Journal-ISO	Soft Matter
Doc-Delivery-Number	DL7DO