Magnetic-field-induced nematic–nematic phase separation and droplet formation in colloidal goethite

Pol, E. van den; Verhoeff, A. A.; Lupascu, A.; Diaconeasa, M. A.; Dozov, I.; Kuipers, Martijn; Thies‐Weesie, Dominique M. E.; Vroege, G. J.

doi:10.1088/0953-8984/23/19/194108

Cited by 15 publications

(9 citation statements)

References 30 publications

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“…In applications to manufacturing of high density recording films and discs, spin alignment is required to carry the recorded information when spins in magnetic nanorods are prone to align parallel to the nanorod axis . In optical applications, magnetic liquid crystals are attractive candidates for making reconfigurable magnetooptical devices with the fast time response measured in milliseconds …”

Section: Introductionmentioning

confidence: 99%

Ferromagnetic Nanorods in Applications to Control of the In‐Plane Anisotropy of Composite Films and for In Situ Characterization of the Film Rheology

Kornev

2016

Adv Funct Materials

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3796 wileyonlinelibrary.com nanorods as the fi llers are believed to be the best candidates for materials working in extreme environment and hence they are on demand in aerospace and space exploration applications. [39][40][41][42][43] In composite fi lms needed for inductor and antennae applications, the alignment of magnetic particles is required to increase the high frequency permeability and to lower the hysteresis losses. [44][45][46][47] In applications to manufacturing of high density recording fi lms and discs, spin alignment is required to carry the recorded information when spins in magnetic nanorods are prone to align parallel to the nanorod axis. [ 37,[48][49][50] In optical applications, magnetic liquid crystals are attractive candidates for making reconfi gurable magnetooptical devices with the fast time response measured in milliseconds. [11][12][13][14][15][16][17][18][51][52][53] In all these applications, one needs to control the alignment of magnetic nanorods in liquid medium. Therefore, this problem is actively discussed in the literature; however, the general strategy for making macroscopic samples with ordered nanorods has not been developed yet and it remains the main challenge of materials engineering [32][33][34][35][39][40][41][42]54 ] Processing of multifunctional coatings and thin fi lms require many steps and hence one needs to control the fi lm properties at each step.Rheological properties of the fi lms at each stage of their processing play the most important role in nanorod ordering and keeping nanorods in place. Characterization of thin coating fi lms during composite manufacturing remains challenging. Different experimental methods have been proposed and developed for in situ characterization of rheological properties of thin fi lms and coatings. [ 20,[25][26][27][55][56][57][58][59][60] It appears that unique features of rotation of ferromagnetic nanorods can be used for characterization of very thin fi lms when other methods fall short. Recently introduced magnetic rotational spectroscopy (MRS) with nanoparticles and nanorods allows one to probe fl uid rheology in very thin fi lms and nanoliter droplets. [ 12,20,22,25,60,61 ] MRS takes advantage of a distinguishable behavior of rotating magnetic tracers as the frequency of applied rotating fi eld changes. Unlike many methods based on the analysis of small oscillations, which are diffi cult to interpret when the fi lm is very thin, MRS with magnetic nanorods enjoys analysis of full revolutions of magnetic tracers. [ 20,22,24,25,60,62,63 ] Understanding of the characteristic features of rotation of a single nanorod in complex fl uids and alignment of an assembly

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Section: Introductionmentioning

confidence: 99%

Ferromagnetic Nanorods in Applications to Control of the In‐Plane Anisotropy of Composite Films and for In Situ Characterization of the Film Rheology

Kornev

2016

Adv Funct Materials

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“…Studies involving mineral liquid crystals, like boehmite or goethite are also based on many-particle effects such as birefringence and scattering. [7][8][9][10] The first real-space data on 3D systems of rods on the single-particle level were reported by Maeda et al in 2003. 11 They showed the process of self-ordering for several aspect ratios of inorganic rods.…”

Section: Introductionmentioning

confidence: 99%

Phase behavior of colloidal silica rods

et al. 2012

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“…1b). Magnetic field orients the nanorods in the vertical direction, but the nanorods are free to move presumably forming a paranematic-type liquid crystal [2] where the crystal elasticity is mostly caused by the long range dipole-dipole interactions between nanorods [21][22][23][24][25][26]. As the magnet moves closer to the droplet, the nanorods form long chains from the droplet bottom to the top free surface.…”

Section: Introductionmentioning

confidence: 99%

Sharpening the surface of magnetic paranematic droplets

et al. 2014

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In a non-uniform magnetic field, the droplets of colloids of nickel nanorods and nanobeads aggregate to form a cusp at the droplet surface not deforming the entire droplet shape. When the field is removed, nanorods diffuse away and the cusp disappears. Spherical particles can form cusps in a similar way, but they stay aggregated after the release of the field; finally, the aggregates settle down to the bottom of the drop. The X-ray phase contrast imaging reveals that nanorods in the cusps stay parallel to each other without visible spatial order of their centers of mass. The formation of cusps can be explained with a model that includes magnetostatic and surface tension forces. The discovered possibility of controlled assembly and quenching of nanorod orientation under the cusped liquid surface offers vast opportunities for alignment of carbon nanotubes, nanowires and nanoscrolls, prior to spinning them into superstrong and multifunctional fibers. Magnetostatic and electrostatic analogies suggest that a similar ideal alignment can be achieved with the rod-like dipoles subject to a strong electric field.

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Magnetic-field-induced nematic–nematic phase separation and droplet formation in colloidal goethite

Cited by 15 publications

References 30 publications

Ferromagnetic Nanorods in Applications to Control of the In‐Plane Anisotropy of Composite Films and for In Situ Characterization of the Film Rheology

Ferromagnetic Nanorods in Applications to Control of the In‐Plane Anisotropy of Composite Films and for In Situ Characterization of the Film Rheology

Phase behavior of colloidal silica rods

Sharpening the surface of magnetic paranematic droplets

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