•Faraday rotation data is reported in oleic acid and oleyl amine capped Fe3O4 nanoparticles prepared using wet chemical method.•Faraday rotation data is found to be independent of the concentration ...of the nanoparticles and the rotation saturates at moderate magnetic fields.•Faraday rotation data fits to a single scattering model compared to the well-known chain model.
Magnetite (Fe3O4) nanoparticles capped with oleic acid and oleylamine were prepared by wet-chemical method. Faraday rotation on the synthesized Fe3O4 nanoparticles were measured as a function of magnetic field strength and concentration. The magnitude of the three components of the dielectric tensor of the Fe3O4 nanoparticle were obtained based on single-scattering model. These are Im∊xy=5.2×10-4,Im∊xx/yy=-0.07, and Im∊zz=-0.32. Besides, we found that Faraday rotation data obtained show two distinct features when compared to the data reported in the literature. The distinct features are 1) saturation in Faraday rotation with magnetic field strength, and 2) negligible concentration dependence. More importantly, our samples did not follow chain formation like other samples reported in the literature. These observations can be attributed to a stable colloid without any aggregation in our samples as a result of sample preparation method. In samples reported in the literature although they are stable these suffer from aggregation which can lead to the formation of chains easily than in our samples.
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•CNTs facilitate formation of chains in MNF and result in higher TC in compare with Fe3O4 ferrofluid.•CNTs aligned through their axis in thinner chains and at border of thicker ...ones.•TC of the MNF under MF increases and the thermal behavior is anisotropic.•TC is higher when the heat current and MF are parallel.
Nanofluids are new generation of heat transfer fluids with enhanced thermal properties. When using nanofluids, one of the major problems is aggregation of nanoparticles. In this study, in order to benefit from controlled aggregation of nanoparticles by application of magnetic field, we used magnetic nanoparticles (MNPs) as one of the most useful nanoparticles in recent energy and biomedical researches. To achieve a more precise insight about behavior of MNPs under magnetic field, a water-based nanofluid of Fe3O4/MWNTs was studied. Due to the importance of thermal conductivity (TC) of nanofluids, it was investigated for the mentioned nanofluid. Taking advantage of magnetic properties of magnetite nanoparticles besides high thermal conductivity of multi-wall carbon nanotubes, a water-based nanofluid of 0.1 wt% Fe3O4/MWNT was prepared and its thermal conductivity was measured for the situations in which temperature gradient and magnetic field were either parallel or perpendicular. The findings suggested that TC was increased by 52% and 11.9% at H = 0.14 T for the two situations, respectively. This finding proved the anisotropic behavior of magnetic nanofluid. Formation of chain-like structures of MNPs was demonstrated through a novel approach. This phenomenon was found to be the reason of thermal conductivity enhancement. Our findings show that employing Fe3O4/MWNT is a promising approach for improving heat transfer efficiency of heat carriers.
In this article a boundary layer analysis has been carried out to examine the Darcy–Forchheimer flow of Carreau ferrofluid through a sensor duct between two parallel plates. The top plate is assumed ...to be squeezed whereas the lower plate is at rest. Inspection has been accomplished in the occupancy of thermal radiation and magnetic dipole. Thermal conductivity is also considered, which is determined by temperature. After incorporating these speculations, dimensional equations supervising the flow and heat transfer distinctions are transfigured into a dimensionless system of differential equations by implementing similarity transformations. The result of squeezed flow index b, ferrohydrodynamic interaction β
∗
, porous medium permeability parameter S
1
, local inertia coefficient S
2
, Eckert number λ, Prandtl number Pr, Curie temperature g, and Weissenberg number W
e
on velocity and temperature curves are observed. The numerical solution for boundary layer momentum and energy equations is obtained. The present analysis demonstrates that velocity profile significantly drops owing to a rise in Weissenberg number.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Fluids responding to magnetic fields (ferrofluids) offer a scene with no equivalent in nature to explore long-range magnetic dipole interactions. Here, we studied the very original class of binary ...ferrofluids, embedding soft and hard ferrimagnetic nanoparticles. We used a combination of X-ray magnetic spectroscopy measurements supported by multi-scale experimental techniques and Monte-Carlo simulations to unveil the origin of the emergent macroscopic magnetic properties of the binary mixture. We found that the association of soft and hard magnetic nanoparticles in the fluid has a considerable influence on their inherent magnetic properties. While the ferrofluid remains in a single phase, magnetic interactions at the nanoscale between both types of particles induce a modification of their respective coercive fields. By connecting the microscopic properties of binary ferrofluids containing small particles, our findings lay the groundwork for the manipulation of magnetic interactions between particles at the nanometer scale in magnetic liquids.
Hard ferrimagnetic CoFe
2
O
4
nanoparticles become softer in the presence of neighbouring soft ferrimagnetic MnFe
2
O
4
nanoparticles.
•Thermal conductivity, diffusivity and specific heat of a ferrofluid were measured.•All these thermal parameters can be externally controlled with a magnetic field.•The magnetic control is due to ...particle agglomerations induced by field.•The measured thermal conductivity is compared with some theoretical models.•Experimental results are well explained by Maxwell and Hamilton-Crosser models.
The effective thermal conductivity, keff, for a kerosene-based ferrofluid with magnetite particles was determined, both in absence and presence of a static magnetic field, H over the range (0–90) kA/m. In zero polarizing field, keff of the ferrofluid is greater than the thermal conductivity of the carrier liquid (kerosene) kF, and increases greatly by applied of the static magnetic field. The obtained experimental results for keff of the ferrofluid sample, were compared with the computed values of keff using four theoretical models of the thermal conductivity. The effective specific heat (Ceff) and the effective thermal diffusivity (Deff) were also computed, both in the absence and presence of the static magnetic field. The obtained results show that all the investigated thermal parameters of the ferrofluid can be externally controlled by means of the magnetic field. These results are of particular practical importance and suggest that the investigated ferrofluid may be a potential candidate for incorporation into heat transfer devices and other thermal applications.
In this work, we have developed novel multifunctional magnetic-polymeric nanoparticles (MMPNs) based ferrofluids by encapsulating oleylamine (OM)-coated hydrophobic superparamagnetic iron oxide ...nanoparticles (SPIONs) inside the poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) individually, and along with two drugs such as curcumin (Cur, a chemotherapeutic drug (CHD)), and/or verapamil (Ver, a calcium channel blocker (CCB)). Herein, several parameters such as weighed amount (wt%) of PLGA polymer (i.e., Resomer), stabilizer (i.e., polyvinyl alcohol (PVA)), organic solvents, amount of the SPIONs (in liquid suspension and powder forms), and amount of the drugs (i.e., Cur or/and Ver) are varied during the encapsulation process to optimize the formulation of PLGA NPs. The resulting polymeric NPs including empty PLGA NPs (i.e., without SPIONs/drugs), and MMPNs such as SPIONs-loaded PLGA NPs, Cur-SPIONs-loaded PLGA NPs, Ver-SPIONs-loaded PLGA NPs, and Cur-Ver-SPIONs-loaded PLGA NPs have displayed (i) hydrodynamic diameters and zeta potentials in the range of 280.8–287.3 nm, and −21 to – 26 mV, respectively, and (ii) better encapsulation efficiency for the SPIONs/Cur/Ver. In addition, the MMPNs have exhibited (i) magnetization values in the range of 7.6–9.5 emu/g with superparamagnetic behaviour, (ii) concentration based time-dependent temperature raise up-to 42 °C (minimum therapeutic temperature in magnetic fluid hyperthermia (MFH)/thermotherapy) with heating efficacies i.e., specific absorption rate (SAR) and intrinsic loss power (ILP) values ranging from 7 to 36 W/gFe and 0.1–0.4 nHm2/kg, respectively and (iii) better cytocompatibility. Finally, the SPIONs and dual-drugs (Cur &Ver) co-loaded PLGA NPs have shown enhanced therapeutic efficacy in HepG2 cancer cells via combined therapies (i.e., thermotherapy and chemotherapy), as compared to the individual therapy (i.e., thermotherapy or chemotherapy) using the SPIONs/Cur/Ver loaded PLGA NPs. Thus, the as-prepared SPIONs/dual-drugs co-loaded PLGA NPs (i.e., MMPNs based ferrofluids) are potential therapeutic candidates for multi-modal treatment of cancer in vitro using thermotherapy and chemotherapy.
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•Direct synthesis of oleylamine coated hydrophobic SPIONs via thermal decomposition•Co-encapsulation of SPIONs and/or single/dual drugs (curcumin & verapamil) in PLGA•Development of novel multifunctional magnetic-polymeric nanoparticles (MMPNs)•Better encapsulation efficiency and better cytocompatibility are achieved for MMPNs.•High therapeutic efficacy in HepG2 cancer cells is attained via combined therapies.
A stable oil-in-water (O/W) magnetic emulsion was prepared by the emulsification of organic ferrofluid in an aqueous media, and its theranostic applications were investigated. The synthesis and ...characterization of the organic ferrofluid were carried out comprising of superparamagnetic maghemite nanoparticles with oleic acid coating stabilized in octane. Both exhibit spherical morphology with a mean size of 6 nm and 200 nm, respectively, as determined by TEM. Thermogravimetric analysis was carried out to determine the chemical composition of the emulsion. The research work described here is novel and elaborates the fabrication of thin-film gradients with 5, 10, 15, and 20 bilayers by layer-by-layer technique using polydimethyl diallyl ammonium chloride (PDAC) and prepared magnetic colloidal particles. The thin-film gradients were characterized for their roughness, morphology, and wettability. The developed gradient films and colloids were explored in magnetic resonance imaging (MRI) and hyperthermia. T1- and T2-weighted images and their corresponding signal intensities were obtained at 1.5 T. A decreasing trend in signal intensities with an increase in nanoparticle concentration in colloids and along the gradient was observed in T2-weighted images. The hyperthermia capability was also evaluated by measuring temperature rise and calculating specific absorption rates (SAR). The SAR of the colloids at 259 kHz, 327 kHz, and 518 kHz were found to be 156 W/g, 255 W/g, and 336 W/g, respectively. The developed magnetic combinatorial thin-film gradients present a significant potential for the future efficient simultaneous diagnostic and therapeutic bioapplications.
This article is focused on Maxwell ferromagnetic fluid and heat transport characteristics under the impact of magnetic field generated due to dipole field. The viscous dissipation and heat ...generation/absorption are also taken into account. Flow here is instigated by linearly stretchable surface, which is assumed to be permeable. Also description of magneto-thermo-mechanical (ferrohydrodynamic) interaction elaborates the fluid motion as compared to hydrodynamic case. Problem is modeled using continuity, momentum and heat transport equation. To implement the numerical procedure, firstly we transform the partial differential equations (PDEs) into ordinary differential equations (ODEs) by applying similarity approach, secondly resulting boundary value problem (BVP) is transformed into an initial value problem (IVP). Then resulting set of non-linear differentials equations is solved computationally with the aid of Runge–Kutta scheme with shooting algorithm using MATLAB. The flow situation is carried out by considering the influence of pertinent parameters namely ferro-hydrodynamic interaction parameter, Maxwell parameter, suction/injection and viscous dissipation on flow velocity field, temperature field, friction factor and heat transfer rate are deliberated via graphs. The present numerical values are associated with those available previously in the open literature for Newtonian fluid case (γ 1 = 0) to check the validity of the solution. It is inferred that interaction of magneto-thermo-mechanical is to slow down the fluid motion. We also witnessed that by considering the Maxwell and ferrohydrodynamic parameter there is decrement in velocity field whereas opposite behavior is noted for temperature field.
MgO/Mg(OH)2-based materials have been intensively explored for CO2 adsorption due to their high theoretical but low practical CO2 capture efficiency. Our previous study on the effect of H2O wetting ...on CO2 adsorption in MgO/Mg(OH)2 nanostructures found that the presence of H2O molecules significantly increases (decreases) CO2 adsorption on the MgO (Mg(OH)2) surface. Furthermore, the magneto-water-wetting technique is used to improve the CO2 capture efficiency of various nanofluids by increasing the mass transfer efficiency of nanobeads. However, the influence of magneto-wetting to the CO2 adsorption at nanobead surfaces remains unknown. The effect of magneto-water-wetting on CO2 adsorption on MgO/Mg(OH)2 nanocomposites was investigated experimentally in this study. Contrary to popular belief, magneto-water-wetting does not always increase CO2 adsorption; in fact, if Mg(OH)2 dominates in the nanocomposite, it can actually decrease CO2 adsorption. As a result of our structural research, we hypothesized that the creation of a thin H2O layer between nanograins prevents CO2 from flowing through, hence slowing down CO2 adsorption during the carbon-hydration aging process. Finally, the magneto-water-wetting technique can be used to control the carbon-hydration process and uncover both novel insights and discoveries of CO2 capture from air at room temperature to guide the design and development of ferrofluid devices for biomedical and energy applications.
This paper addresses the operation in microgravity of the surface reconstruction device whose design is detailed in the first part of the manuscript. The system, employed during the drop tower ...campaign of the UNOOSA DropTES 2019 StELIUM experiment, studies the axisymmetric and lateral oscillations of a ferrofluid solution in microgravity. The free liquid surface is reconstructed in a cylindrical tank and relevant metrics of the magnetic sloshing problem, such as contact angles, hysteresis parameters, natural oscillation frequencies, or damping ratios, are derived. The result is a rich and unique database where several phenomena of scientific and technological interest are reported for the first time. The dependence of the fundamental axisymmetric and lateral modal frequencies with the applied magnetic field is consistent with the literature and past experiments. Although the detection system was designed and built using low-cost hardware, high-quality results are obtained.
•Microgravity measurements from a novel surface reconstruction device are presented.•The system successfully reconstructs the movement of a free ferrofluid surface.•Relevant metrics of the magnetic sloshing problem are measured for the first time.•Modal shapes and frequencies are identified as a function of the magnetic environment.
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