Magnetochemistry

21 pages, 4587 KiB

Open AccessArticle

Surface Modifications of Superparamagnetic Iron Oxide Nanoparticles with Polyvinyl Alcohol and Activated Charcoal as Methylene Blue Adsorbents

by Linh Doan

Magnetochemistry 2023, 9(9), 211; https://doi.org/10.3390/magnetochemistry9090211 - 20 Sep 2023

Cited by 1 | Viewed by 1546

Abstract

As novel methylene blue adsorbents, polyvinyl alcohol and activated charcoal were used to modify the surface of superparamagnetic iron oxide nanoparticles. The adsorption capacity after 69 h was 26.50 ± 0.99–40.21 ± 1.30 mg/g, depending on the temperature (333.15, 310.15, and 298.15 K) [...] Read more.

As novel methylene blue adsorbents, polyvinyl alcohol and activated charcoal were used to modify the surface of superparamagnetic iron oxide nanoparticles. The adsorption capacity after 69 h was 26.50 ± 0.99–40.21 ± 1.30 mg/g, depending on the temperature (333.15, 310.15, and 298.15 K) and the initial concentration of methylene blue, which was between 0.017 and 0.020 mg/mL. Based on thermodynamics parameters, the adsorption process can be considered to be spontaneous endothermic physisorption. Kinetics studies show that the pseudo-second-order model was the best-fitted model. Adsorption isotherm studies show that the best-fitted models were the Langmuir, Langmuir, and Temkin and Pyzhev isotherm models when adsorbing MB at 333.15, 310.15, and 298.15 K, respectively. Full article

(This article belongs to the Section Applications of Magnetism and Magnetic Materials)

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11 pages, 1711 KiB

Open AccessArticle

Comparative Study of Magnetic Properties of (Mn_1−xA

_{x}^{IV}

)Bi₂Te₄ A^IV = Ge, Pb, Sn

by Dmitry A. Estyunin, Anna A. Rybkina, Konstantin A. Kokh, Oleg E. Tereshchenko, Marina V. Likholetova, Ilya I. Klimovskikh and Alexander M. Shikin

Magnetochemistry 2023, 9(9), 210; https://doi.org/10.3390/magnetochemistry9090210 - 13 Sep 2023

Cited by 3 | Viewed by 1420

Abstract

We investigated the magnetic properties of the antiferromagnetic (AFM) topological insulator MnBi

_{2}

Te

_{4}

with a partial substitution of Mn atoms by non-magnetic elements (A

^{IV}

= Ge, Pb, Sn). Samples with various element concentrations (10–80%) were studied using SQUID magnetometry. The [...] Read more.

We investigated the magnetic properties of the antiferromagnetic (AFM) topological insulator MnBi

_{2}

Te

_{4}

with a partial substitution of Mn atoms by non-magnetic elements (A

^{IV}

= Ge, Pb, Sn). Samples with various element concentrations (10–80%) were studied using SQUID magnetometry. The results demonstrate that, for all substitutes the type of magnetic ordering remains AFM, while the Néel temperature (T

_{N}

) and spin-flop transition field (H

_{SF}

) decrease with an increasing A

^{IV}

= Ge, Pb, Sn concentration. The rate of decrease varies among the elements, being highest for Pb, followed by Sn and Ge. This behavior is attributed to the combined effects of the magnetic dilution and lattice parameter increase on magnetic properties, most prominent in (Mn

_{1 - x}

Pb

_{x}

)Bi

_{2}

Te

_{4}

. Besides this, the linear approximation of the experimental data of T

_{N}

and H

_{SF}

suggests higher magnetic parameters for pure MnBi

_{2}

Te

_{4}

than observed experimentally, indicating the possibility of their non-monotonic variation at low concentrations and the potential for enhancing magnetic properties through doping MnBi

_{2}

Te

_{4}

with small amounts of nonmagnetic impurities. Notably, the (Mn

_{1 - x}

Pb

_{x}

)Bi

_{2}

Te

_{4}

sample with 10% Pb substitution indeed exhibits increased magnetic parameters, which is also validated by local-probe analyses using ARPES. Our findings shed light on tailoring the magnetic behavior of MnBi

_{2}

Te

_{4}

-based materials, offering insights into the potential applications in device technologies. Full article

(This article belongs to the Section Magnetic Materials)

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14 pages, 3303 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Influence of the Particle Size on the Electrical, Magnetic and Biological Properties of the Bioglass^® Containing Iron Oxide

by Joana Soares Regadas, Sílvia Rodrigues Gavinho, Sílvia Soreto Teixeira, Juliana Vieira de Jesus, Ana Sofia Pádua, Jorge Carvalho Silva, Susana Devesa and Manuel Pedro Fernandes Graça

Magnetochemistry 2023, 9(9), 209; https://doi.org/10.3390/magnetochemistry9090209 - 12 Sep 2023

Viewed by 1687

Abstract

Bioglasses have been used throughout the past century as a biomaterial in the bone regeneration field. However, recent studies have attempted to use them as a therapeutic material as well, mainly in the treatment of osteosarcomas. The most widely recognized bioglass is the [...] Read more.

Bioglasses have been used throughout the past century as a biomaterial in the bone regeneration field. However, recent studies have attempted to use them as a therapeutic material as well, mainly in the treatment of osteosarcomas. The most widely recognized bioglass is the 45S5 Bioglass, invented by Larry Hench et al., which presents higher bioactivity. A possible application of this bioglass in the treatment of osteosarcomas can be accomplished by adding specific ions, such as iron, that will allow the use of magnetic hyperthermia and Fenton reaction as therapeutic mechanisms. In this study, a 45S5 Bioglass containing 10%mol of Fe₂O₃ was produced using the melt-quenching method. A group of samples was prepared by changing the overall ball milling time, from 1 h up to 48 h, to analyze the effects of iron in the bioactive glass matrix and evaluate the influence of particle size on their physical and biological properties. The studied bioglasses showed no evidence of changes in the amorphous structural nature compared to the 45S5 Bioglass. The data of the impedance spectroscopy study revealed that the addition of Fe₂O₃ can increase the standard rate constant of the Electro-Fenton reaction, with the sample milled for 12 h showing the most promising results. The reduction in the particle size influenced the cytotoxicity and the bioactivity. The samples with lower particle sizes showed a higher level of cytotoxicity. Full article

(This article belongs to the Special Issue Advances in Functional Materials with Tunable Magnetic Properties)

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11 pages, 2697 KiB

Open AccessArticle

Electromagnetic Property Modulation of Flaky Ferromagnetic 304 Stainless-Steel Powders for Microwave Absorption at Elevated Temperatures

by Bolin Yang, Yifan Xu, Zhihong Chen, Hang Yang, Yuchen Hu, Haoqin Wu, Mingfeng Xing, Jianguo Guan and Wei Li

Magnetochemistry 2023, 9(9), 208; https://doi.org/10.3390/magnetochemistry9090208 - 5 Sep 2023

Viewed by 1579

Abstract

Soft magnetic metallic absorbents suffer from severe oxidation, reduction in permeability and deterioration in microwave absorption when exposed to high temperatures. In this study, we prepared flaky 304 stainless-steel powders as new microwave absorbents via deformation-induced ferromagnetism. The 304 stainless-steel powders showed significant [...] Read more.

Soft magnetic metallic absorbents suffer from severe oxidation, reduction in permeability and deterioration in microwave absorption when exposed to high temperatures. In this study, we prepared flaky 304 stainless-steel powders as new microwave absorbents via deformation-induced ferromagnetism. The 304 stainless-steel powders showed significant increases in saturation magnetization (Ms) from 1.03 to 82.46 emu/g when their shape was changed from spheroids to flakes; the Ms further increased to 92.29 emu/g after heat treatment at 500 °C in air. The permeability of 304 alloy powders also showed an obvious increase after ball milling and remained roughly stable after heat treatment at 500 °C in air. Moreover, the permittivity exhibited a sharp decrease after heat treatment, enabling the improvement of impedance matching and microwave absorption. After heat treatment at 500 °C in air for 100 h, the simulated reflection loss of 304 stainless-steel powders with wax still showed attractive levels, giving a minimum value of −22 dB and remaining below −6 dB over 8.5–16.5 GHz at a thickness of 2 mm. Our work can help to include paramagnetic alloy systems as new microwave absorbents for working in harsh environments. Full article

(This article belongs to the Special Issue Advances of Soft Magnetic Particles and Composites towards Electromagnetic Wave Applications)

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21 pages, 8924 KiB

Open AccessEditor’s ChoiceArticle

The Influence of Magnetic Fields on Electrophoretic Processes in Magnetic Colloids with Different Stabilization Mechanisms

by Yurii I. Dikansky, Andrey S. Drozdov, Inna V. Eskova and Elena S. Beketova

Magnetochemistry 2023, 9(9), 207; https://doi.org/10.3390/magnetochemistry9090207 - 30 Aug 2023

Cited by 1 | Viewed by 1628

Abstract

Electrophoretic nanostructuring is a promising approach for the creation of functional surfaces and active layers. The potency of this approach may be further enhanced by additional factors of various natures, such as magnetic fields. In this work, we have studied the process of [...] Read more.

Electrophoretic nanostructuring is a promising approach for the creation of functional surfaces and active layers. The potency of this approach may be further enhanced by additional factors of various natures, such as magnetic fields. In this work, we have studied the process of electrophoresis in thin layers of water- and kerosene-based magnetic liquids and the effect of additional magnetic fields on the occurring processes. It was found that the electrophoresis process can be significantly affected by inhomogeneous magnetic fields. The possibility of compensating electrophoresis processes in such systems by means of inhomogeneous magnetic field influence was shown. Structural changes in magnetic colloids on hydrocarbon bases under the influence of an electric field have been studied. The role of electrohydrodynamic flows arising in this process is considered, and the influence of the magnetic field on the configuration of the formed labyrinth structure is studied. The dependence of the threshold value of the electric field strength corresponding to the emergence of the structure on the temperature and additionally applied magnetic field has been established. The obtained results could contribute to the development of an original method for determining the charge and magnetic moment of a single nanoparticle. Full article

(This article belongs to the Section Magnetic Materials)

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15 pages, 2562 KiB

Open AccessFeature PaperArticle

Magnetic and Impedance Analysis of Fe₂O₃ Nanoparticles for Chemical Warfare Agent Sensing Applications

by Jennifer R. Soliz, Smriti Ranjit, Joshua J. Phillips, Richard A. Rosenberg and Adam J. Hauser

Magnetochemistry 2023, 9(9), 206; https://doi.org/10.3390/magnetochemistry9090206 - 25 Aug 2023

Viewed by 1567

Abstract

A dire need for real-time detection of toxic chemical compounds exists in both civilian and military spheres. In this paper, we demonstrate that inexpensive, commercially available Fe₂O₃ nanoparticles are capable of selective sensing of chemical warfare agents (CWAs) using frequency-dependent [...] Read more.

A dire need for real-time detection of toxic chemical compounds exists in both civilian and military spheres. In this paper, we demonstrate that inexpensive, commercially available Fe₂O₃ nanoparticles are capable of selective sensing of chemical warfare agents (CWAs) using frequency-dependent impedance spectroscopy, with additional potential as an orthogonal magnetic sensor. X-ray magnetic circular dichroism analysis shows that Fe₂O₃ nanoparticles possess moderately lowered moment upon exposure to 2-chloroethyl ethyl sulfide (2-CEES) and diisopropyl methylphosphonate (DIMP) and significantly lowered moment upon exposure to dimethyl methylphosphonate (DMMP) and dimethyl chlorophosphate (DMCP). Associated X-ray absorption spectra confirm a redox reaction in the Fe₂O₃ nanoparticles due to CWA structural analog exposure, with differentiable energy-dependent features that suggest selective sensing is possible, given the correct method. Impedance spectroscopy performed on samples dosed with DMMP, DMCP, and tabun (GA, chemical warfare nerve agent) showed strong, differentiable, frequency-dependent responses. The frequency profiles provide unique “shift fingerprints” with which high specificity can be determined, even amongst similar analytes. The results suggest that frequency-dependent impedance fingerprinting using commercially available Fe₂O₃ nanoparticles as a sensor material is a feasible route to selective detection. Full article

(This article belongs to the Section Applications of Magnetism and Magnetic Materials)

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19 pages, 11319 KiB

Open AccessArticle

Viscous Effects on Nonlinear Double Tearing Mode and Plasmoid Formation in Adjacent Harris Sheets

by Nisar Ahmad, Ping Zhu, Chao Shen, Ahmad Ali and Shiyong Zeng

Magnetochemistry 2023, 9(9), 205; https://doi.org/10.3390/magnetochemistry9090205 - 24 Aug 2023

Viewed by 1435

Abstract

In this paper, we study the effects of viscosity on the evolution of the double tearing mode (DTM) in a pair of adjacent Harris sheets based on the resistive MHD model in the NIMROD code. Similar to the tearing mode in the conventional [...] Read more.

In this paper, we study the effects of viscosity on the evolution of the double tearing mode (DTM) in a pair of adjacent Harris sheets based on the resistive MHD model in the NIMROD code. Similar to the tearing mode in the conventional single Harris sheet, a transition is observed in the generation of both normal and monster plasmoids at Prandtl number

P_{r} = 1

. In the

P_{r} < 1

regime of the DTM, normal plasmoids (small plasmoids) are generated along with monster plasmoid, whereas in the single tearing mode (STM) cases, such a generation is not observed. When

P_{r}

is above the critical value, the generation of monster plasmoid is halted. Correspondingly, in the

P_{r} < 1

regime, a quadrupolar flow advects along the poloidal direction, but in the

P_{r} > 1

regime this flow advection is inhibited. Full article

(This article belongs to the Section Magnetic Field)

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Magnetochemistry, Volume 9, Issue 9 (September 2023) – 7 articles

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