Facile Synthesis, Static, and Dynamic Magnetic Characteristics of Varying Size Double-Surfactant-Coated MesoscopicMagnetic Nanoparticles Dispersed Stable Aqueous Magnetic Fluids

The present work reports the synthesis of a stable aqueous magnetic fluid (AMF) by dispersing double-surfactant-coated Fe3O4 magnetic nanoparticles (MNPs) in water using a facile ambient scalable wet chemical route. MNPs do not disperse well in water, resulting in low stability. This was improved by dispersing double-surfactant (oleic acid and sodium oleate)-coated MNPs in water, where cross-linking between the surfactants improves the stability of the AMFs. The stability was probed by rheological measurements and all the AMF samples showed a good long-term stability and stability against a gradient magnetic field. Further, the microwave spin resonance behavior of AMFs was studied in detail by corroborating the experimental results obtained from the ferromagnetic resonance (FMR) technique to theoretical predictions by appropriate fittings. A broad spectrum was perceived for AMFs which indicates strong ferromagnetic characteristics. The resonance field shifted to higher magnetic field values with the decrease in particle size as larger-size MNPs magnetize and demagnetize more easily since their magnetic spins can align in the field direction more definitely. The FMR spectra was fitted to obtain various spin resonance parameters. The asymmetric shapes of the FMR spectra were observed with a decrease in particle sizes, which indicates an increase in relaxation time. The relaxation time increased with a decrease in particle sizes (sample A to D) from 37.2779 ps to 42.8301 ps. Further, a detailed investigation of the structural, morphological, and dc magnetic properties of the AMF samples was performed. Room temperature dc magnetic measurements confirmed the superparamagnetic (SPM) characteristics of the AMF and the M-H plot for each sample was fitted with a Langevin function to obtain the domain magnetization, permeability, and hydrodynamic diameter of the MNPs. The saturation magnetization and coercivity of the AMF samples increased with the increase in dispersed MNPs’ size of the samples. The improvement in the stability and magnetic characteristics makes AMFs suitable candidates for various biomedical applications such as drug delivery, magnetic fluid hyperthermia, and biomedicines.

Download Full-text

Effects of Magnetic Fluid on Machining Characteristics in Magnetic Field Assisted Polishing Process

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.797.396 ◽

2013 ◽

Vol 797 ◽

pp. 396-400

Author(s):

Shao Hui Yin ◽

Zhi Qiang Xu ◽

Hong Jie Duan ◽

Feng Jun Chen

Keyword(s):

Magnetic Field ◽

Surface Roughness ◽

Magnetic Fluid ◽

Material Removal ◽

Magnetorheological Fluid ◽

Magnetic Fluids ◽

Magnetic Characteristics ◽

Polishing Process ◽

Magnetic Cluster ◽

Machining Characteristics

Magnetic characteristics of three magnetic polishing fluids such as magnetic fluid (MF), magnetorheological fluid (MRF), and magnetic compound fluid (MCF) under magnetic field are experimentally investigated and analyzed. Their magnetic cluster structures under action of magnet field are observed, and their magnetic cluster models are established. Magnetic flied assisted polishing experiments for tungsten carbide are developed used these three kinds of magnetic fluids, material removal and surface roughness are respectively measured. At last, the machining characteristic of three magnetic fluids are contrasted and discussed according to experimental results.

Download Full-text

Magnetic domains characterization of crystalline Fe3O4 under DC and AC magnetic field

Microscopy ◽

10.1093/jmicro/dfz018 ◽

2019 ◽

Vol 68 (4) ◽

pp. 310-315

Author(s):

Xiang Li ◽

Xiaojuan Zhu ◽

Dong Pan ◽

Yan Xue ◽

Qingqing Jia ◽

...

Keyword(s):

Magnetic Field ◽

Magnetic Measurements ◽

Magnetic Domain ◽

Sample Surface ◽

Magnetic Characteristics ◽

Magnetic Domains ◽

Force Microscopy ◽

Phase Images ◽

Crystallite Sizes ◽

Physical Features

Abstract Fe3O4 nanoparticles with crystallite sizes around 10 nm were synthesized by an emulsion method. X-ray diffractometer (XRD) shows that nanocrystalline Fe3O4 possesses face center cubic structure. The magnetic characteristics are investigated by magnetic force microscopy (MFM). Magnetic field directions were applied parallel and perpendicular to the Fe3O4 sample surface for magnetic measurements. Under the perpendicular magnetic field, the phase images of most magnetic nanoparticles exhibit bright or dark MFM contrast. In comparison, the parallel field phase images display a bright–dark dipole MFM contrast, with in-plane magnetic domain configurations. Furthermore, the investigation of strip domains inside Fe3O4 particles under altering magnetic fields indicates the existence of magnetic anisotropy energies, dipole energies as well as inter-grain coupling energies inside the clusters. This approach for probing magnetic responses on nanoscale magnetic domains can be further extended to the analysis of local physical features.

Download Full-text

The impact of prepolarization on Earth’s field laboratory nuclear-magnetic-resonance relaxation experiments

Geophysics ◽

10.1190/geo2013-0272.1 ◽

2014 ◽

Vol 79 (3) ◽

pp. EN39-EN48 ◽

Cited By ~ 2

Author(s):

Jan O. Walbrecker ◽

Rosemary Knight ◽

Elliot Grunewald

Keyword(s):

Magnetic Field ◽

Nuclear Magnetic Resonance ◽

Relaxation Time ◽

Magnetic Resonance ◽

Remanent Magnetization ◽

Solid Phase ◽

Magnetic Measurements ◽

High Plains ◽

The Impact ◽

Nuclear Magnetic

To advance our understanding, and the application of surface nuclear magnetic resonance (NMR), we need to conduct Earth’s magnetic field (EF) laboratory NMR measurements of the acquired relaxation times. In EF laboratory NMR, prepolarization is used to achieve detectable signal levels. This involves exposing the sample to a static magnetic field to increase the equilibrium magnetization associated with the nuclear spins of protons in the pore fluid. We found that prepolarization can also have a significant impact on the commonly measured relaxation time [Formula: see text]. We studied this impact on [Formula: see text] using a set of sand samples taken from boreholes in the U.S. High Plains aquifer. Using rock-magnetic measurements, we found that prepolarization at 25 mT increased the magnetization of the solid phase of the samples up to a factor of 10. For these samples, we observed [Formula: see text] that decreased from 30 to 3 ms with increasing magnetization. Surface NMR data collected at the borehole site indicate significantly longer [Formula: see text] (50–80 ms) at the depths from which the samples were taken. We attributed our observations to prepolarization inducing remanent magnetization in the solid phase of the sample, which results in elevated internal magnetic fields that reduce [Formula: see text]. In contrast, we found good agreement between EF laboratory and surface NMR measurements of the relaxation time [Formula: see text]. Because [Formula: see text] is unaffected by internal fields, this supports our conclusion that prepolarization is significantly impacting the laboratory measurement of [Formula: see text]. To mitigate these undesired effects, we have developed the inclusion of a demagnetization pulse after prepolarization in EF laboratory experiments. By applying the demagnetization pulse along the same direction of the static field only the remanent magnetization of the solid phase of the sample would be removed, whereas the prepolarized state of the nuclear spin magnetization of the liquid phase would be retained.

Download Full-text

RESEARCH OF PROPERTIES OF MAGNETIC LUBRICANTS BASED ON ORGANOSILICON LIQUID

Vestnik of Ulyanovsk state agricultural academy ◽

10.18286/1816-4501-2020-4-26-32 ◽

2020 ◽

pp. 26-32

Author(s):

V.V. Terentyev ◽

◽

А. М. Bausov ◽

М. V. Toropov ◽

◽

...

Keyword(s):

Magnetic Field ◽

Mathematical Model ◽

Oleic Acid ◽

Magnetic Fluid ◽

Magnetic Fluids ◽

Ferromagnetic Phase ◽

Magnetic Liquid ◽

Metal Base ◽

Adhesion Coefficient ◽

The Stability

The results of research on lubricants which are magnetic fluids are presented. The positive effect on the characteristics of the lubricant of pondemotor force that occurs when an external magnetic field is applied is noted. The purpose of this work is to study the properties of magnetic lubricants based on polyethylsiloxane liquids and confirm the previously stated theoretical assumptions. The main objectives of the research are to develop the composition of a lubricant based on a polyethylsiloxane magnetic fluid, to determine the characteristics of adhesion of this material to a metal base, to obtain an adequate mathematical model describing the characteristics of adhesion of the lubricant to the surface, and to determine its stability during operation. Experimental installations and methods for determining the characteristics of the coupling of magnetic fluids with the friction surface, as well as the stability of magnetic fluid itself during operation, have been developed. The prospects of introducing oleic acid into the organosilicon base of the magnetic liquid are noted. A decrease in the adhesion coefficient with an increase in the rotational speed of the samples at loads from 160 N to 320 N was revealed by an average of 1.6...2.7 times. It is proved that the magnetic lubricant adheres to the metal base more strongly than Litol-24 by an average of 6 times, which prevents the rolling elements from slipping during the operation of the samples. Different patterns of changes in adhesion to metal surfaces of Litol-24 and magnetic fluids are noted. An increase in the adhesion coefficient of magnetic fluids under the conditions of applying a constant magnetic field at loads on samples from 480 N to 800 N due to the magnetorheological effect by 20...30% is established. A mathematical model is obtained that adequately describes the change in the adhesion coefficient of the obtained magnetic lubricant. The composition of the magnetic liquid is recommended, consisting of a polyethylene siloxane carrier liquid, a surfactant-oleic acid, and a ferromagnetic phase-magnetite with a particle size of 7.5 nm. High stability of the developed magnetic fluids during longterm operation has been experimentally established. The stability coefficient of the magnetic fluid decreased by 2.51 times in 366 hours.

Download Full-text

The stability of a rigidly rotating magnetic fluid column effect of a periodic azimuthal magnetic field

Journal of Physics A General Physics ◽

10.1088/0305-4470/30/10/031 ◽

1997 ◽

Vol 30 (10) ◽

pp. 3585-3602 ◽

Cited By ~ 12

Author(s):

Yusry O El-Dib

Keyword(s):

Magnetic Field ◽

Magnetic Fluid ◽

Azimuthal Magnetic Field ◽

The Stability

Download Full-text

The effect of a periodic tangential magnetic field on the stability of a horizontal magnetic fluid sheet

Heat Transfer-Asian Research ◽

10.1002/htj.21583 ◽

2019 ◽

Vol 48 (8) ◽

pp. 4074-4104 ◽

Cited By ~ 2

Author(s):

Galal M. Moatimid ◽

Nabil T. Eldabe ◽

Aya Sayed

Keyword(s):

Magnetic Field ◽

Magnetic Fluid ◽

The Stability

Download Full-text

Analysis of Wide Lorentzian-Shaped Electron Spin Resonance Lines

Canadian Journal of Physics ◽

10.1139/p72-079 ◽

1972 ◽

Vol 50 (6) ◽

pp. 579-582 ◽

Cited By ~ 6

Author(s):

F. T. Hedgcock ◽

T. W. Raudorf

Keyword(s):

Magnetic Field ◽

Line Width ◽

Resonance Field ◽

Lorentzian Line ◽

Line Shapes ◽

At Resonance ◽

Spin Resonance ◽

Half Power ◽

Mn Doped ◽

The Magnetic Field

Significant distortion of ESR line shapes can result when the half-power line width is comparable to the magnetic field at resonance. Unless adequate compensation is made, this distortion leads to errors in measuring the resonance field and the line width. These corrections are derived explicitly for a Lorentzian line shape and illustrated by experimental data for Mn-doped GeTe.

Download Full-text