In order to investigate the peculiarities of the aggregation processes in ferrofluids in a quasi-2D geometry, a combination of density functional theory (DFT) and molecular dynamics (MD) simulations is presented. The microstructure formation in monodisperse ferrofluid monolayers is studied thoroughly through a comparison of the theoretical and computational results. Theoretical and simulation results show similar trends which renders the theoretical approach a useful tool for getting insight into the microstructure formation in monolayers.
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http://dx.doi.org/10.1088/0953-8984/20/20/204125 | DOI Listing |
Langmuir
April 2021
Department for Physics and Astronomy, Uppsala University, Uppsala, Sweden.
We study the assembly of magnetite nanoparticles in water-based ferrofluids in wetting layers close to silicon substrates with different functionalization without and with an out-of-plane magnetic field. For particles of nominal sizes 5, 15, and 25 nm, we extract density profiles from neutron reflectivity measurements. We show that self-assembly is only promoted by a magnetic field if a seed layer is formed at the silicon substrate.
View Article and Find Full Text PDFScience
July 2019
Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
Solid ferromagnetic materials are rigid in shape and cannot be reconfigured. Ferrofluids, although reconfigurable, are paramagnetic at room temperature and lose their magnetization when the applied magnetic field is removed. Here, we show a reversible paramagnetic-to-ferromagnetic transformation of ferrofluid droplets by the jamming of a monolayer of magnetic nanoparticles assembled at the water-oil interface.
View Article and Find Full Text PDFSoft Matter
October 2016
Department of Mechanical Engineering and Materials Science, Duke University, Box 90300 Hudson Hall, Durham, NC 27708, USA.
Experiments and simulations are used to study the kinetics of crystal growth in a mixture of magnetic and nonmagnetic particles suspended in ferrofluid. The growth process is quantified using both a bond order parameter and a mean domain size parameter. The largest single crystals obtained in experiments consist of approximately 1000 particles and form if the area fraction is held between 65-70% and the field strength is kept in the range of 8.
View Article and Find Full Text PDFSoft Matter
March 2015
Duke University, Department of Mechanical Engineering and Materials Science, Box 90300 Hudson Hall, Durham, NC 27708, USA.
Phase transformations can be difficult to characterize at the microscopic level due to the inability to directly observe individual atomic motions. Model colloidal systems, by contrast, permit the direct observation of individual particle dynamics and of collective rearrangements, which allows for real-space characterization of phase transitions. Here, we study a quasi-two-dimensional, binary colloidal alloy that exhibits liquid-solid and solid-solid phase transitions, focusing on the kinetics of a diffusionless transformation between two crystal phases.
View Article and Find Full Text PDFSci Rep
July 2014
Department of Electrical and Computer Engineering, University of Maryland, College Park, MD 20742, USA.
We demonstrate a novel artificial optical material, the "photonic hyper-crystal", which combines the most interesting features of hyperbolic metamaterials and photonic crystals. Similar to hyperbolic metamaterials, photonic hyper-crystals exhibit broadband divergence in their photonic density of states due to the lack of usual diffraction limit on the photon wave vector. On the other hand, similar to photonic crystals, hyperbolic dispersion law of extraordinary photons is modulated by forbidden gaps near the boundaries of photonic Brillouin zones.
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