Study of the effect of particle size on the specific absorption rate of cobalt ferrite nanoparticles in a radio frequency magnetic field

Mixed ferrite nanoparticles with compositions CoxMn1-xFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) were synthesized by a simple chemical co-precipitation method. The structure and morphology of the nanoparticles were obtained by X-ray diffraction (XRD), transmission electron microscope (TEM), Raman spectroscopy, and Mössbauer spectroscopy. The average crystallite sizes decreased with increasing x, starting with 34.9 ± 0.6 nm for MnFe2O4 (x = 0) and ending with 15.0 ± 0.3 nm for CoFe2O4 (x = 1.0). TEM images show an edge morphology with the majority of the particles having cubic geometry and wide size distributions. The mixed ferrite and CoFe2O4 nanoparticles have an inverse spinel structure indicated by the splitting of A1g peak at around 620 cm−1 in Raman spectra. The intensity ratios of the A1g(1) and A1g(2) peaks indicate significant redistribution of Co2+ and Fe3+ cations among tetrahedral and octahedral sites in the mixed ferrite nanoparticles. Magnetic hysterics loops show that all the particles possess significant remnant magnetization and coercivity at room temperature. The mass-normalized saturation magnetization is highest for the composition with x = 0.8 (67.63 emu/g), while CoFe2O4 has a value of 65.19 emu/g. The nanoparticles were PEG (poly ethylene glycol) coated and examined for the magneto thermic heating ability using alternating magnetic field. Heating profiles with frequencies of 333.45, 349.20, 390.15, 491.10, 634.45, and 765.95 kHz and 200, 250, 300, and 350 G field amplitudes were obtained. The composition with x = 0.2 (Co0.2Mn0.8Fe2O4) with saturation magnetization 57.41 emu/g shows the highest specific absorption rate (SAR) value of 190.61 W/g for 10 mg/mL water dispersions at a frequency of 765.95 kHz and 350 G field strength. The SAR values for the mixed ferrite and CoFe2O4 nanoparticles increase with increasing concentration of particle dispersions, whereas for MnFe2O4, nanoparticles decrease with increasing the concentration of particle dispersions. SARs obtained for Co0.2Mn0.8Fe2O4 and CoFe2O4 nanoparticles fixed in agar ferrogel dispersions at frequency of 765.95 kHz and 350 G field strength are 140.35 and 67.60 W/g, respectively. This study shows the importance of optimizing the occupancy of Co2+ among tetrahedral and octahedral sites of the spinel system, concentration of the magnetic nanoparticle dispersions, and viscosity of the surrounding medium on the magnetic properties and heating efficiencies.

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The Adverse Effect of Electromagnetic Radiation From Cellular Base Stations in Nigeria

Handbook of Research on 5G Networks and Advancements in Computing, Electronics, and Electrical Engineering - Advances in Computer and Electrical Engineering ◽

10.4018/978-1-7998-6992-4.ch010 ◽

2021 ◽

pp. 269-280

Author(s):

Ndidi Stella Arinze ◽

Patrick Uche Okafor ◽

Osondu Ignatius Onah

Keyword(s):

Field Strength ◽

Radio Frequency ◽

Electromagnetic Radiation ◽

Mobile Phones ◽

Absorption Rate ◽

Specific Absorption Rate ◽

Base Stations ◽

Telecommunication Industry ◽

Specific Absorption ◽

The People

On a global scale, the telecommunication industry is experiencing tremendous growth in mobile phones. Mobile phones communicate with base stations that are erected by the telecommunication industry. The base station produces radio frequency and exposes the people near the base stations to radiation. The effect of electromagnetic radiation from four base stations located at the residential area was studied by measuring their electric field strength and calculating their magnetic field strength and power density at different distances covering a frequency range of 900MHz to 2100MHz. The obtained values showed that the four cellular base stations are operating above the standard values of the International Commission on Non-Ionizing Radiation Protection Electromagnetic Field Radiation. The specific absorption rate was measured to determine the amount of radio frequency electromagnetic radiation absorbed by the human body. The result which is in the range of 3.22-3.70 W/kg is higher than the acceptable 2 W/kg for localized specific absorption rate.

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Uncertainties in the estimation of specific absorption rate during radiofrequency alternating magnetic field induced non-adiabatic heating of ferrofluids

Journal of Physics D Applied Physics ◽

10.1088/1361-6463/aa89de ◽

2017 ◽

Vol 50 (45) ◽

pp. 455005 ◽

Cited By ~ 15

Author(s):

B B Lahiri ◽

Surojit Ranoo ◽

John Philip

Keyword(s):

Magnetic Field ◽

Absorption Rate ◽

Specific Absorption Rate ◽

Adiabatic Heating ◽

Alternating Magnetic Field ◽

Specific Absorption

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Dynamics of superparamagnetic nanoparticle in viscous liquid in rotating magnetic field

10.3762/bxiv.2019.57.v1 ◽

2019 ◽

Author(s):

Nikolai A Usov ◽

Ruslan A Rytov ◽

Vasiliy A Bautin

Keyword(s):

Magnetic Field ◽

Viscous Liquid ◽

Absorption Rate ◽

Specific Absorption Rate ◽

Stochastic Equation ◽

Magnetization Vector ◽

Superparamagnetic Nanoparticles ◽

Rotating Magnetic Field ◽

Field Frequency ◽

Specific Absorption

The dynamics of magnetic nanoparticle in a viscous liquid in rotating magnetic field has been studied by means of numerical simulation and analytical calculations. In the magneto- dynamics approximation three different modes of motion of the unit magnetization vector and particle director are distinguished depending on the rotating magnetic field frequency and amplitude. The specific absorption rate of a dilute assembly of superparamagnetic nanoparticles in rotating magnetic field is calculated by solving the Landau – Lifshitz stochastic equation for unit magnetization vector and stochastic equation for particle director. At elevated frequencies an optimal range of particle diameters is found where the specific absorption rate of an assembly in rotating magnetic field has a maximum. It is shown that for magnetic hyperthermia in rotating magnetic field it is preferable to use rotating magnetic fields of moderate amplitude, H 0 = 100 Oe, in the frequency range 400-600 kHz.

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Quantitative Analysis of the Specific Absorption Rate Dependence on the Magnetic Field Strength in ZnxFe3−xO4 Nanoparticles

International Journal of Molecular Sciences ◽

10.3390/ijms21207775 ◽

2020 ◽

Vol 21 (20) ◽

pp. 7775

Author(s):

Mohamed Alae Ait Kerroum ◽

Cristian Iacovita ◽

Walid Baaziz ◽

Dris Ihiawakrim ◽

Guillaume Rogez ◽

...

Keyword(s):

Magnetic Field ◽

Relaxation Time ◽

Absorption Rate ◽

Specific Absorption Rate ◽

Large Diameter ◽

Precipitation Method ◽

Magnetization Relaxation ◽

Specific Absorption ◽

The Magnetic Field ◽

Néel Relaxation

Superparamagnetic ZnxFe3−xO4 magnetic nanoparticles (0 ≤ x < 0.5) with spherical shapes of 16 nm average diameter and different zinc doping level have been successfully synthesized by co-precipitation method. The homogeneous zinc substitution of iron cations into the magnetite crystalline structure has led to an increase in the saturation magnetization of nanoparticles up to 120 Am2/kg for x ~ 0.3. The specific absorption rate (SAR) values increased considerably when x is varied between 0 and 0.3 and then decreased for x ~ 0.5. The SAR values are reduced upon the immobilization of the nanoparticles in a solid matrix being significantly increased by a pre-alignment step in a uniform static magnetic field before immobilization. The SAR values displayed a quadratic dependence on the alternating magnetic field amplitude (H) up to 35 kA/m. Above this value, a clear saturation effect of SAR was observed that was successfully described qualitatively and quantitatively by considering the non-linear field’s effects and the magnetic field dependence of both Brown and Neel relaxation times. The Neel relaxation time depends more steeply on H as compared with the Brown relaxation time, and the magnetization relaxation might be dominated by the Neel mechanism, even for nanoparticles with large diameter.

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