Decreasing nanofluid droplet heating time with alternating magnetic fields

Fachini, Fernando F.; Bakuzis, Andris F.

doi:10.1063/1.3489983

Cited by 7 publications

(9 citation statements)

References 27 publications

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“…In addition, several other novel potential applications have been proposed over the past few decades concerning, in particular, cancer treatment through the delivery of drugs, genes, peptides or heat. [8][9][10][11][12][13][14][15][16][17] The heating of tumorous cells is based upon the magnetic hyperthermia phenomenon, which consists of an increase in the temperature of magnetic nanoparticles due to the interaction of their magnetic moments with an alternating magnetic field. Recently, there has been a considerable effort from the community to develop more efficient heating centers.…”

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confidence: 99%

Field dependent transition to the non-linear regime in magnetic hyperthermia experiments: Comparison between maghemite, copper, zinc, nickel and cobalt ferrite nanoparticles of similar sizes

et al. 2012

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Further advances in magnetic hyperthermia might be limited by biological constraints, such as using sufficiently low frequencies and low field amplitudes to inhibit harmful eddy currents inside the patient's body. These incite the need to optimize the heating efficiency of the nanoparticles, referred to as the specific absorption rate (SAR). Among the several properties currently under research, one of particular importance is the transition from the linear to the non-linear regime that takes place as the field amplitude is increased, an aspect where the magnetic anisotropy is expected to play a fundamental role. In this paper we investigate the heating properties of cobalt ferrite and maghemite nanoparticles under the influence of a 500 kHz sinusoidal magnetic field with varying amplitude, up to 134 Oe. The particles were characterized by TEM, XRD, FMR and VSM, from which most relevant morphological, structural and magnetic properties were inferred. Both materials have similar size distributions and saturation magnetization, but strikingly different magnetic anisotropies. From magnetic hyperthermia experiments we found that, while at low fields maghemite is the best nanomaterial for hyperthermia applications, above a critical field, close to the transition from the linear to the non-linear regime, cobalt ferrite becomes more efficient. The results were also analyzed with respect to the energy conversion efficiency and compared with dynamic hysteresis simulations. Additional analysis with nickel, zinc and copper-ferrite nanoparticles of similar sizes confirmed the importance of the magnetic anisotropy and the damping factor. Further, the analysis of the characterization parameters suggested core-shell nanostructures, probably due to a surface passivation process during the nanoparticle synthesis. Finally, we discussed the effect of particle-particle interactions and its consequences, in particular regarding discrepancies between estimated parameters and expected theoretical predictions.

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confidence: 99%

Field dependent transition to the non-linear regime in magnetic hyperthermia experiments: Comparison between maghemite, copper, zinc, nickel and cobalt ferrite nanoparticles of similar sizes

et al. 2012

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“…For a high magnetic heat source compared with that one provided by the heat flux from the gasphase, the temperature inside the droplet is uniform. 27 In the region close to the droplet surface, both heat sources, magnetic heating and heat conduction from gas phase, have the same intensity. Consequently, a thermal boundary layer is established in that region during the droplet heating process.…”

Section: Physical Modelmentioning

confidence: 99%

Ferrofluid droplet heating and vaporization under very large magnetic power: A thermal boundary layer model

Cristaldo

Fachini

2013

Physics of Fluids

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In this work, heating and vaporization of a liquid droplet with dispersed magnetic nanoparticles (ferrofluid) are analyzed. The ferrofluid droplet is in a quiescent inert gas phase with a temperature which is set down equal to, higher and lower than the liquid boiling temperature. Under these conditions, an alternating magnetic field is applied and, as a result, the magnetic nanoparticles generate heat by the Brownian relaxation mechanism. In this mechanism, the magnetic dipoles present a random orientation due to collisions between the fluid molecules and nanoparticles. The magnetic dipoles tend to align to the magnetic field causing rotation of the nanoparticles. Consequently the temperature increases due to the energy dissipated by the friction between the resting fluid and the rotating nanoparticles. Assuming a very large magnetic power and a uniform distribution of nanoparticles, the droplet core is uniformly heated. A thermal boundary layer is established in the liquid-phase adjacent to the droplet surface due to heat flux from the ambient atmosphere. The temperature profile inside the thermal boundary layer is obtained in appropriate time and length scales. In the present model, the ferrofluid droplet is heated up to its boiling temperature in a very short time. In addition, the combination of the heat generated by magnetic nanoparticles and heat conduction from gas phase results in a higher vaporization rate. Under specific conditions, the boiling temperature is achieved not at the surface but inside the thermal boundary layer. Moreover, the results point out that the thermal boundary layer depends directly on the vapor Lewis number but the vaporization rate reciprocally on it.

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“…When magnetic nanoparticles are embedded in these droplets, it is possible to accelerate those processes allowing the construction of more compact chambers. [12][13][14] Ferrofluids contain magnetic particles whose mobility can be controlled by a magnetic field. Regarding the applications in MH, the interest is the absorption of large amounts of energy when the magnetization of the particles is reversed.…”

Section: Introductionmentioning

confidence: 99%

“…Several research studies have been done in the sense of achieving higher heating rates but considering a regime where both relaxation processes are operating at the same time. 12,25 However, in situations where the size of the particles is very reduced or the particles are immobilized, the Néel mechanism rules the thermal relaxation. In fact, the Néel relaxation time is reduced exponentially with the volume of the particle, while the Brownian mechanism is reduced linearly with volume.…”

Section: Introductionmentioning

confidence: 99%

A microscopic approach to heating rate of ferrofluid droplets by a magnetic field

Siqueira

Jurelo

et al. 2019

Journal of Applied Physics

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In this work, we study the heating process of colloidal ferrofluids by a magnetic field. The heating of the fluid occurs by the magnetic relaxation of the nanoparticles which provide thermal energy for the host liquid. In the limit of small volumes, the relaxation process occurs through the Néel mechanism since the magnetic nanoparticles present superparamagnetic behavior. Within this limit, we have used a microscopic model for the coupling to phonons and external magnetic field in order to model the relaxation mechanism and to obtain an expression for the heating rate of the fluid as a function of microscopic parameters. The analysis allows determining appropriate conditions for an optimal heating rate for ferrofluids based on superparamagnetic nanoparticles.

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Decreasing nanofluid droplet heating time with alternating magnetic fields

Cited by 7 publications

References 27 publications

Field dependent transition to the non-linear regime in magnetic hyperthermia experiments: Comparison between maghemite, copper, zinc, nickel and cobalt ferrite nanoparticles of similar sizes

Field dependent transition to the non-linear regime in magnetic hyperthermia experiments: Comparison between maghemite, copper, zinc, nickel and cobalt ferrite nanoparticles of similar sizes

Ferrofluid droplet heating and vaporization under very large magnetic power: A thermal boundary layer model

A microscopic approach to heating rate of ferrofluid droplets by a magnetic field

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