Laser-induced fragmentation of carbonyl iron as a clean method to enhance magnetorheological effect

Cvek, Martin; Torres–Mendieta, Rafael; Havelka, Ondřej; Urbánek, Michal; Plachý, Tomáš; Černík, Miroslav

doi:10.1016/j.jclepro.2020.120182

Cited by 12 publications

(6 citation statements)

References 39 publications

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“…The sigmoidal shape of the graph is attributed to the relationship of magnetic twisting actuation with magnetization, polar moment of inertia, and densification . In particular, the shape of the curve mainly implies that the magnetic actuation requires higher magnetic flux density exceeding the threshold point, as described by a typical magnetization hysteresis loop . At m F = 1 (CCW, ■) and 2 (CW, ●), the twisted F 1 pillar has a large discrepancy of ϕ with the case at m F = 3 (CCW, □) and 4 (CW, ○), respectively (Table S2).…”

Section: Resultsmentioning

confidence: 95%

“…19 In particular, the shape of the curve mainly implies that the magnetic actuation requires higher magnetic flux density exceeding the threshold point, as described by a typical magnetization hysteresis loop. 30 At m F = 1 (CCW, ■) and 2 (CW, •), the twisted F 1 pillar has a large discrepancy of ϕ with the case at m F = 3 (CCW, □) and 4 (CW, ○), respectively (Table S2). However, in the cases of m S = 1 (CCW, ■) and 2 (CW, •), ϕ values are nearly identical to those at m S = 4 (CCW, □) and 5 (CW, ○), respectively, at B ranging from 0.05 to 0.6 T (Figures 2c-iii and S7c,d).…”

Section: Design Of Flower Corolla-like Arraysmentioning

confidence: 96%

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On-Demand Dynamic Chirality Selection in Flower Corolla-like Micropillar Arrays

et al. 2022

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Chiral morphology has been intensively studied in various fields including biology, organic chemistry, pharmaceuticals, and optics. On-demand and dynamic chiral inversion not only cannot be realized in most intrinsically chiral materials but also has mostly been limited to chemical or light-induced methods. Herein, we report reversible real-time magneto-mechanical chiral inversion of a three-dimensional (3D) micropillar array between achiral, clockwise, and counterclockwise chiral arrangements. Inspired by the flower corolla, achiral arrays of five and six radially arranged semicylindrical micropillars were employed as model systems to investigate the dynamic symmetry properties of arrays consisting of odd and even numbers of micropillars, respectively. Each micropillar underwent twisting actuation with a different twisting angle depending on the angle with the magnetic field direction and magnetic flux density, thereby collectively changing the chirality from the achiral to chiral state. Importantly, the morphological handedness of the micropillars was inverted within a few seconds by manipulating the direction of the magnetic field. A chiral morphology consisting of magnetically twisted micropillars was shape-fixed by the introduction of a polymeric binder. This binder could be simply washed off to return the shape-fixed twisted micropillars to their initial straight state. Magnetically programmable and reproducible 3D flower corolla-like micropillar arrays are expected to expand the potential of shape-reconfigurable devices that require real-time chiral manipulation in ambient environments.

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Section: Resultsmentioning

confidence: 95%

Section: Design Of Flower Corolla-like Arraysmentioning

confidence: 96%

On-Demand Dynamic Chirality Selection in Flower Corolla-like Micropillar Arrays

et al. 2022

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“…This drawback has to be suppressed in order to develop MR fluids suitable for industrial applications [ 10 ]. Several approaches have been developed to enhance stability and thereby avoid gravitational settling, including: (i) encapsulating magnetic particles within organic/inorganic coatings, or even multi-shell layers, in order to reduce bulk density and heighten interactions with the liquid medium [ 11 , 12 ]; (ii) applying magnetic/non-magnetic nano-particles (NPs) that act as physical barriers to inhibit settling [ 13 , 14 , 15 ]; (iii) replacing the carrier medium with viscous liquids [ 16 ] or gel-like media [ 17 ]; and (iv) dispersing special types of particles, i.e., hollow/porous particles [ 18 ].…”

Section: Introductionmentioning

confidence: 99%

Stable Magnetorheological Fluids Containing Bidisperse Fillers with Compact/Mesoporous Silica Coatings

Cvek

Jamatia

Šuly

et al. 2022

IJMS

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A drawback of magnetorheological fluids is low kinetic stability, which severely limits their practical utilization. This paper describes the suppression of sedimentation through a combination of bidispersal and coating techniques. A magnetic, sub-micro additive was fabricated and sequentially coated with organosilanes. The first layer was represented by compact silica, while the outer layer consisted of mesoporous silica, obtained with the oil–water biphase stratification method. The success of the modification technique was evidenced with transmission electron microscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy and Fourier-transform infrared spectroscopy. The coating exceptionally increased the specific surface area, from 47 m2/g (neat particles) up to 312 m2/g, which when combined with lower density, resulted in remarkable improvement in the sedimentation profile. At this expense, the compact/mesoporous silica slightly diminished the magnetization of the particles, while the magnetorheological performance remained at an acceptable level, as evaluated with a modified version of the Cross model. Sedimentation curves were, for the first time in magnetorheology, modelled via a novel five-parameter equation (S-model) that showed a robust fitting capability. The sub-micro additive prevented the primary carbonyl iron particles from aggregation, which was projected into the improved sedimentation behavior (up to a six-fold reduction in the sedimentation rate). Detailed focus was also given to analyze the implications of the sub-micro additives and their surface texture on the overall behavior of the bidisperse magnetorheological fluids.

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“…Employing them can enhance yield stress, MR performance and the sedimentation profile. 13,14 An important factor concerns the amount of NPs applied for this purpose, since a "halo" effect occurs beyond a certain threshold (usually at above 5%), weakening the field-induced structures. 14 Various types of NPs, either magnetic or non-magnetic, in different forms, such as spherical, 13 rod-/needle-like 15 and plate-like 16 have been extensively…”

Section: Introductionmentioning

confidence: 99%