Iron Ferrites Research Articles

Tuning the physical properties of ternary alloys (NiCuCo) for in vitro magnetic hyperthermia: experimental and theoretical investigation

Most of published research on magnetic hyperthermia focused on iron oxides, ferrites, and binary alloy nanostructures, while the ternary alloys attracted much limited interest. Herein, we prepared NiCuCo ternary alloy nanocomposites with variable compositions by mechanical alloying. Physical properties were fully characterized by XRD, Rietveld analysis, XPS, SEM/EDX, TEM, ZFC/FC and H-M loops. DFT calculations were used to confirm the experimental results in terms of structure and magnetism. The results showed that the fabricated nanoalloys are face centered cubic (FCC) with average core sizes of 9–40 nm and behave as superparamagnetic with saturation in the range 4.67–42.63 emu/g. Langevin fitting corroborated the superparamagnetic behavior, while law of approach to saturation (LAS) was used to calculate the magnetic anisotropy constants. Heating effciencies were performed under an alternating magnetic field (AMF, H0 = 170 Oe and f = 332.5 kHz), and specific absorption rate (SAR) values were determined. The highest magnetic saturation (Ms), heating potentials, and SAR values were attained for Ni35Cu30Co35 containing the lowest Cu but highest Ni and Co percentages, and the least for Ni15Cu70Co15. Importantly, the nanoalloys reached the required temperatures for magnetic hyperthermia (42 °C) in relatively short times. We also showed that heat dissipiation can be simply tuned by changing many parameters such as concentration, field amplitude, and frequency. Finally, cytotoxicity viability assays against two different breast cancer cell lines treated with Ni25Cu50Co25 nanoalloy in the presence and absence of AMF were investigated. No significant decrease in cancer cell viability was observed in the absence of AMF. When tested against tumorigenic KAIMRC2 breast cancer cells under AMF, the NiCuCo nanoalloy was found to be highly potent to the cells (~ 2-fold enhancement), killing almost all the cells in short times (20 min) and clinically-safe AC magnetic fields. These findings strongly suggest that the as-prepared ternary NiCuCo nanoalloys hold great promise for potential magnetically-triggered cancer hyperthermia.

Exploring novel magnetic behaviors in cobalt-doped magnetite synthesized by plasma arc discharge method

Magnetite, a naturally occurring iron oxide, has been widely studied due to its potential applications in various fields. Doping magnetite with foreign ions can significantly alter its structural and magnetic properties. This study aimed to investigate the effects of Co2+ ion doping on the structural and magnetic properties of magnetite. The work introduces cobalt-substituted iron ferrites synthesized using a novel plasma arc discharge (PAD) method and systematically explores how cobalt content affects magnetic properties, aiming to optimize the material for enhanced performance. A series of CoxFe1-xFe2O4 (x=0, 0.1, 0.2, 0.3, and 0.5) ferrites with varying Co2+ concentrations (x=0, 0.1, 0.2, 0.3, and 0.5) were synthesized using a PAD method. The synthesized materials were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Magnetic properties were evaluated through magnetic hysteresis loops and permeability spectra. XRD analysis confirmed the formation of a nanostructured spinel-type oxide in all samples. FESEM images revealed ultra-fine particles with a homogeneous composition and narrow size distribution. The optimal combination of magnetic properties was achieved at a Co2+ concentration of x=0.1, which exhibited a high saturation magnetization, low coercivity, moderate effective anisotropy constant, and a relatively high magnetic permeability at 5 MHz. The results demonstrate that Co2+ ion doping can effectively tailor the structural and magnetic properties of magnetite. The optimized composition (x=0.1) offers promising potential for applications requiring a balance of high magnetization and low coercivity.

Comparative Mössbauer and first principles calculations for selected iron oxides and ferrites nanoparticles

Magnetic ferrites and related iron oxides, such as Fe3O4 and γ -Fe2O3, are widely explored due to their commercial and scientific importance. While typical ferrites exhibit cubic structures, maghemite (γ-Fe2O3) has two probable phases at room temperature, namely cubic (C) and the lately discovered tetragonal (T) structures. Here, we explore the structural and electronic properties of these two distinct maghemite phases using density functional theory (DFT). To assure the reliability of our DFT calculations, we perform comparative calculations on the most stable inverse spinal structure, namely NiFe2O4, and the cubic magnetite (Fe3O4). We also explore the systematic oxidation of Fe3O4 into γ-Fe2O3 when a portion of Fe+2 ions, at octahedral sites, are oxidized into Fe+3 by controlling the vacancies ratio from one to three vacancies per cell. The obtained calculations are supported by X-ray diffraction (XRD), UV–visible, and Mössbauer spectroscopies measured for partially-oxidized magnetite, maghemite, and NiFe2O4 nanoparticle samples of different size, prepared by the conventional chemical methods. Comparative DFT calculations for C γ-Fe2O3 phase and Fe3O4, with tunable vacancies, showed that the smooth conversion of Fe3O4 into γ-Fe2O3 involves a slight reduction in the lattice parameters with increasing maghemite vacancy ratio, in agreement with the experimental XRD results for the prepared samples. Likewise, a clear signature of the successful fabrication of partially-oxidized Fe3O4 and γ-Fe2O3 phases was confirmed from Mössbauer results. The energy gap obtained from the calculated band structures for γ-Fe2O3 and NiFe2O4 were consistent with the values obtained from UV–visible spectroscopy. The present work demonstrates the effectiveness of DFT methods to predict and explain fine structural and physical properties of magnetic materials and iron oxides of different structures and complexity.

Metal and Metal Oxides Nanoparticles and Nanosystems in Anticancer and Antiviral Theragnostic Agents.

The development of antiviral treatment and anticancer theragnostic agents in recent decades has been associated with nanotechnologies, and primarily with inorganic nanoparticles (INPs) of metal and metal oxides. The large specific surface area and its high activity make it easy to functionalize INPs with various coatings (to increase their stability and reduce toxicity), specific agents (allowing retention of INPs in the affected organ or tissue), and drug molecules (for antitumor and antiviral therapy). The ability of magnetic nanoparticles (MNPs) of iron oxides and ferrites to enhance proton relaxation in specific tissues and serve as magnetic resonance imaging contrast agents is one of the most promising applications of nanomedicine. Activation of MNPs during hyperthermia by an external alternating magnetic field is a promising method for targeted cancer therapy. As therapeutic tools, INPs are promising carriers for targeted delivery of pharmaceuticals (either anticancer or antiviral) via magnetic drug targeting (in case of MNPs), passive or active (by attaching high affinity ligands) targeting. The plasmonic properties of Au nanoparticles (NPs) and their application for plasmonic photothermal and photodynamic therapies have been extensively explored recently in tumor treatment. The Ag NPs alone and in combination with antiviral medicines reveal new possibilities in antiviral therapy. The prospects and possibilities of INPs in relation to magnetic hyperthermia, plasmonic photothermal and photodynamic therapies, magnetic resonance imaging, targeted delivery in the framework of antitumor theragnostic and antiviral therapy are presented in this review.

Synthesis and Characterization of an Fe/Co Ferrite Spinel Oxide Film Produced by Using N2/Steam Heat Treatment on Two Maraging Steels

An experimental procedure was developed to obtain an oxide layer formed mainly by spinel on maraging steels. It consists of different stages with specific conditions, such as atmospheres rich in nitrogen and water vapor, and different steps of temperatures and times. Tests were performed on grade 300 and 350 maraging steels. Oxide layer characterization was done using optical and electron microscopy, spectroscopy, X-ray diffraction, and nanoscratch tests in order to determine the adhesion force as well as to observe the main deformation mechanism induced under sliding tests. In both steels, oxide layers are formed by the spinel’s Fe3O4 and CoFe2O4 in amounts close to ca. 85 pct, whereas TiO2 and MoO3 represent the other 15 pct. No hematite was found. The low oxygen availability during the heat treatment was fundamental for avoiding hematite formation. A nickel-rich austenitic phase formed at the metal-oxide interface due the kinetics of the oxidation process of the cobalt, iron, and molybdenum. The particular conditions of the heat treatments induced the formation of a mixture of iron, nickel, and cobalt spinel ferrites, thereby contradicting previous studies that said that only magnetite would be formed. The sliding tests at the nanometric length scale highlight that the layer formed on maraging 300 grade presents a better adhesion than the other investigated material due to the fact that it requires more load in order to induce cracks located at the edge of the sliding track and, subsequently, the chipping of the formed layer.

Synthesis, structure, and visible-light-driven activity of o-YbFeO3/h-YbFeO3/CeO2 photocatalysts

Photo-Fenton-like oxidation of organic substances is one of the key advanced oxidation processes based on the reversible Fe2+↔Fe3+ transition and the generation of a strong oxidant ·OH in the presence of H2O2 and is currently considered as a promising method for the purification of polluted aqueous media. However, the absence of effective and stable photocatalysts of this process, operating under the action of visible light, necessitates the exploratory studies, mainly among iron oxides and ferrites of various compositions and structures. In this work, using the method of solution combustion followed by heat treatment in air the heterojunction nanocomposites based on ytterbium orthoferrite and cerium dioxide of the composition o-YbFeO3/h-YbFeO3/CeO2 (0–20 mol.%) with high absorption in the visible region and advanced photo-Fenton-like activity were obtained. The nanocomposites were studied by EDS, SEM, XRD, BET, and DRS methods. The photo-Fenton-like activity of the nanocomposites was investigated during the degradation of methyl violet under the action of visible (λmax = 410 nm) radiation. As a result, the formation of I-type heterojunction based on stable rhombic (55.4–79.0 nm) and metastable hexagonal (19.5–24.0 nm) modifications of ytterbium orthoferrite (o-YbFeO3 and h-YbFeO3, respectively) and cubic cerium dioxide CeO2 (13.2–19.2 nm) nanocrystals was established. It was shown that the obtained nanocomposites had foamy morphology and were characterized by a specific surface in the range of 9.1–25.0 m2/g, depending on the CeO2 content. It was found that nanocrystalline components were chemically and phase-pure, uniformly spatially distributed over the nanocomposite, and had multiple contacts with each other. Based on this fact and the established electronic structure of the nanocomposite components, the formation of I-type heterojunction with the participation of o-YbFeO3 (Eg = 2.15 eV), h-YbFeO3 (Eg = 2.08 eV), and CeO2 (Eg = 2.38 eV) was shown, the presence of which increased photocatalytic activity of the resulting nanocomposite. The optimal content of CeO2 in the nanocomposite was 5%, and the o-YbFeO3/h-YbFeO3/CeO2–5% sample was characterized by the highest rate constant of photo-Fenton-like degradation of methyl violet under the action of visible light equal to k = 0.138 min–1, which was 2.5 to 5 times higher than for nanocomposites based on ytterbium orthoferrite. The obtained results obtained indicate that the developed nanocomposites can be considered as a promising basis for the advanced oxidation processes for the purification of aqueous media from organic pollutants.

Extremely Stable and Durable Mixed Fe–Mn Oxides Supported on ZrO2 for Practical Utilization in CLOU and CLC Processes

This paper contains the results of research on a promising combustion technology known as chemical looping combustion (CLC) and chemical looping with oxygen uncoupling (CLOU). The remarkable advantages of CLC are, among others, that concentrated CO2 stream can be obtained after water condensation without any energy penalty for its separation or significant decrease of NOx emissions. The objective of this work was to prepare a novel bi-metallic Fe–Mn supported on ZrO2 oxygen carriers. Performance of these carriers for the CLOU and CLC process with nitrogen/air and hard coal/air was evaluated. One-cycle CLC tests were conducted with supported Fe–Mn oxygen carriers in thermogravimetric analyzer utilizing hard coal as a fuel. The effects of the oxygen carrier chemical composition and process temperature on the reaction rates were determined. Our study proved that for CLOU, properties formation of bixbyite and spinel forms are responsible. Among iron ferrites, we concluded that iron-rich compounds such as Fe2MnO4 over FeMn2O4 spinel type oxides are more effective for CLOU applications.

Oxidation Behavior of Maraging 300 Alloy Exposed to Nitrogen/Water Vapor Atmosphere at 500 °C

Aging heat treatments in maraging steels are fundamental to achieve the excellent mechanical properties required in several industries, i.e., nuclear, automotive, etc. In this research, samples of maraging 300 alloy were aged using a novel procedure that combines different steps with two atmospheres (nitrogen and water vapor) for several hours. The oxidized surface layer was chemical, microstructural and micromechanically characterized. Due to the thermodynamic and kinetic conditions, these gases reacted and change the surface chemistry of this steel producing a thin iron-based oxide layer of a homogeneous thickness of around 500 nm. Within the aforementioned information, porosity and other microstructural defects showed a non-homogeneous oxide, mainly constituted by magnetite, nickel ferrite, cobalt ferrite, and a small amount of hematite in the more external parts of the oxide layer. In this sense, from a chemical point of view, the heat treatment under specific atmosphere allows to induce a thin magnetic layer in a mixture of iron, nickel, and cobalt spinel ferrites. On the other hand, the oxide layer presents an adhesive force 99 mN value that shows the capability for being used for tribological applications under sliding contact tests.

Aqueous Sol-Gel Synthesis of Different Iron Ferrites: From 3D to 2D.

In this study, an aqueous sol-gel synthesis method and subsequent dip-coating technique were applied for the preparation of yttrium iron garnet (YIG), yttrium iron perovskite (YIP), and terbium iron perovskite (TIP) bulk and thin films. The monophasic highly crystalline different iron ferrite powders have been synthesized using this simple aqueous sol-gel process displaying the suitability of the method. In the next step, the same sol-gel solution was used for the fabrication of coatings on monocrystalline silicon (100) using a dip-coating procedure. This resulted, likely due to substrate surface influence, in all coatings having mixed phases of both garnet and perovskite. Thermogravimetric (TG) analysis of the precursor gels was carried out. All the samples were investigated by X-ray powder diffraction (XRD) analysis. The coatings were also investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Mössbauer spectroscopy. Magnetic measurements were also carried out.

Influence of the preparation method and aluminum ion substitution on the structure and electrical properties of lithium–iron ferrites

In this study, we report the synthesis of nanosized Al-substituted lithium–iron ferrites Li0.5AlxFe2.5-xO4(0 ≤ x ≤ 1) by sol–gel auto-combustion method and by ceramic method with double sintering. Synthesized materials were studied using X-ray diffraction and impedance spectroscopy. The samples obtained by chemical methods have a higher homogeneity of the distribution of elements by volume, good repeatability of the result, high crystallinity, small crystallite size and perfect stoichiometry. Based on Koop's theory, the basic regularities of the behavior of the dielectric constant and the loss tangent are explained. The jump mechanism of conductivity has been realized by the transition of an electron between iron ions in different valence states. Samples synthesized by the sol–gel auto-combustion show technological characteristics, compared with systems obtained by solid-phase method.

Magnetic properties, 57Fe Mössbauer spectroscopy and 1H NMR relaxometry of ε-Fe2−xGaxO3 nanoparticles: The effect of gallium doping on magnetic and MRI performance

Magnetic nanoparticles of ε-Fe1.76Ga0.24O3 were prepared by thermal treatment of a mesoporous silica matrix impregnated with nitrates. The chosen Ga-doping enhanced magnetization and suppressed the low-temperature spin-reorientation transition typical for ε-Fe2O3. Despite the small mean size of 11 nm, the nanoparticles were in the blocked state over the whole temperature range under study, unlike standard superparamagnetic contrast agents based on other iron oxides or ferrites. The role of Ga-doping in local magnetic properties of the epsilon polymorph of ferric oxide was probed by 57Fe Mössbauer spectroscopy. The particles were further coated with silica and their performance in MRI was tested both in relaxometry and ultra-high-field imaging. The obtained dependences of relaxivity on temperature and thickness of the coating were placed in the context of relevant theoretical models of particle-induced relaxation – motional averaging and static dephasing regimes.

Novel hollow α-Fe2O3 nanofibers via electrospinning for dye adsorption.

Nanomaterials such as iron oxides and ferrites have been intensively investigated for water treatment and environmental remediation applications. In this work, hollow α-Fe2O3 nanofibers made of rice-like nanorods were successfully synthesized via a simple hydrothermal reaction on polyvinyl alcohol (PVA) nanofiber template followed by calcination. The crystallographic structure and the morphology of the as-prepared α-Fe2O3 nanofibers were characterized by X-ray diffraction, energy dispersive X-ray spectrometer, and scanning electron microscope. Batch adsorption experiments were conducted, and ultraviolet-visible spectra were recorded before and after the adsorption to investigate the dye adsorption performance. The results showed that hollow α-Fe2O3 fiber assembles exhibited good magnetic responsive performance, as well as efficient adsorption for methyl orange in water. This work provided a versatile strategy for further design and development of functional nanofiber-nanoparticle composites towards various applications.

Nanoparticles in magnetic resonance imaging: from simple to dual contrast agents.

Magnetic resonance imaging (MRI) has become one of the most widely used and powerful tools for noninvasive clinical diagnosis owing to its high degree of soft tissue contrast, spatial resolution, and depth of penetration. MRI signal intensity is related to the relaxation times (T1, spin–lattice relaxation and T2, spin–spin relaxation) of in vivo water protons. To increase contrast, various inorganic nanoparticles and complexes (the so-called contrast agents) are administered prior to the scanning. Shortening T1 and T2 increases the corresponding relaxation rates, 1/T1 and 1/T2, producing hyperintense and hypointense signals respectively in shorter times. Moreover, the signal-to-noise ratio can be improved with the acquisition of a large number of measurements. The contrast agents used are generally based on either iron oxide nanoparticles or ferrites, providing negative contrast in T2-weighted images; or complexes of lanthanide metals (mostly containing gadolinium ions), providing positive contrast in T1-weighted images. Recently, lanthanide complexes have been immobilized in nanostructured materials in order to develop a new class of contrast agents with functions including blood-pool and organ (or tumor) targeting. Meanwhile, to overcome the limitations of individual imaging modalities, multimodal imaging techniques have been developed. An important challenge is to design all-in-one contrast agents that can be detected by multimodal techniques. Magnetoliposomes are efficient multimodal contrast agents. They can simultaneously bear both kinds of contrast and can, furthermore, incorporate targeting ligands and chains of polyethylene glycol to enhance the accumulation of nanoparticles at the site of interest and the bioavailability, respectively. Here, we review the most important characteristics of the nanoparticles or complexes used as MRI contrast agents.

Organic synthesis via magnetic attraction: benign and sustainable protocols using magnetic nanoferrites

Magnetic nano-catalysts have been prepared using simple modification of iron ferrites. The nm size range of these particles facilitates the catalysis process, as an increased surface area is available for the reaction; the easy separation of the catalysts by an external magnet and their recovery and reuse are additional beneficial attributes. Glutathione bearing nano-ferrites have been used as organocatalysts for the Paal–Knorr reaction and homocoupling of boronic acids. Nanoferrites, post-synthetically modified by ligands, were used to immobilize nanometals (Cu, Pd, Ru, etc.) which enabled the development of efficient, sustainable and green procedures for azide–alkynes-cycloaddition (AAC) reactions, C–S coupling, O-allylation of phenol, Heck-type reactions and hydration of nitriles.

State of adsorption layers of fatty acids on the surfaces of iron, manganese, and copper ferrites

States of adsorbed substances in surface layers arising during the adsorption of oleic, linoleic, and linolenic acids from carbon tetrachloride, heptane, and cyclohexane solutions on the surfaces of iron, manganese, and copper ferrites, are investigated. Adsorption isotherms and two-dimensional state diagrams of surface layers of iron, manganese, and copper ferrites are obtained experimentally. It is shown that the adsorption of fatty acids from solutions in organic solvents proceeds via filling the volume of the ferrites’ porous space with adsorption solutions, while the state of ferrite surface layers changes due to the structural rearrangement of adsorption solutions upon an increase in solute concentration.

Synthesis of α-Fe2O3 nanofibers for applications in removal and recovery of Cr(VI) from wastewater

Nanomaterials such as iron oxides and ferrites have been intensively investigated for water treatment and environmental remediation applications. The purpose of this work is to synthesize α-Fe(2)O(3) nanofibers for potential applications in removal and recovery of noxious Cr(VI) from wastewater. α-Fe(2)O(3) nanofibers were synthesized via a simple hydrothermal route followed by calcination. The crystallographic structure and the morphology of the as-prepared α-Fe(2)O(3) nanofibers were characterized by X-ray diffraction, scanning electron microscope, and transmission electron microscope. Batch adsorption experiments were conducted, and Fourier transform infrared spectra were recorded before and after adsorption to investigate the Cr(VI) removal performance and adsorption mechanism. Langmuir and Freundlich modes were employed to analyze the adsorption behavior of Cr(VI) on the α-Fe(2)O(3) nanofibers. Very thin and porous α-Fe(2)O(3) nanofibers have been successfully synthesized for investigation of Cr(VI) removal capability from synthetic wastewater. Batch experiments revealed that the as-prepared α-Fe(2)O(3) nanofibers exhibited excellent Cr(VI) removal performance with a maximum adsorption capacity of 16.17 mg g(-1). Furthermore, the adsorption capacity almost kept unchanged after recycling and reusing. The Cr(VI) adsorption process was found to follow the pseudo-second-order kinetics model, and the corresponding thermodynamic parameters ΔG°, ΔH°, and ΔS° at 298 K were calculated to be -26.60 kJ mol(-1), -3.32 kJ mol(-1), and 78.12 J mol(-1) K(-1), respectively. The as-prepared α-Fe(2)O(3) nanofibers can be utilized as efficient low-cost nano-absorbents for removal and recovery of Cr(VI) from wastewater.

Nano- and microparticles of iron with a modified surface and prospects for their application. Part III: Ferroparticles within magnetically controlled sorbents

The sorption characteristics of magnetoplastic grains composed of fine-grained particles of iron and hard magnetic ferrites in polyvinyl alcohol have been investigated. The possibility of controlling the time characteristics of the sorption and desorption using magnetic fields is shown. A field with a variable strength gradient decreases the characteristic times of the sorption/desorption by a factor of 7–10, while a constant field increases them by a factor of 1.322.5. It is also shown that the use of sorbents in the composition of hard magnetic grains to treat suppurative wounds based on the magnetic fluidization in variable fields increases the treating efficiency by a factor of about 9.

Preparation of Cu-doped γ-Fe2O3 nanowires with high coercivity by chemical vapor deposition

Abstract

Decomposition of Carbon Dioxide at 500 °C over Reduced Iron, Cobalt, Nickel, and Zinc Ferrites: A Combined XANES−XRD Study

A series of ferrite spinels [AFe2O4, where A = Fe(II), Co(II), Ni(II), or Zn(II)] synthesized by coprecipitation were reduced in hydrogen and subsequently studied in the decomposition of carbon dioxide at 500 °C by a combination of in situ XANES, XRD, and mass spectrometry methods. The reducibilities of the ferrites in hydrogen depend on the A metal. In the reduction to the metallic states, XANES data reveal that iron(II) oxide is formed as an intermediate product with A(II) being expelled to form A(II) oxides as the spinel structure breaks down. Carbon monoxide is produced in the decomposition of carbon dioxide through the oxidation of iron(II) or metallic iron. The highest activities in the reaction were observed for nickel and zinc ferrite. However, as opposed to cobalt ferrite and magnetite, the regeneration to the original ferrite structure in carbon dioxide was not complete for these two materials. For nickel ferrite, which exhibits high reducibility and carbon dioxide reactivity, magnetite is forme...

In situX-ray diffraction analysis of iron ore sinter phases

Owing to the depletion of world lump iron ore stocks, pre-treated agglomerates of fine ores are making up a growing proportion of blast-furnace feedstock (∼80%). These agglomerations, or `sinters', are generally composed of iron oxides, ferrites (most of which are silicoferrites of calcium and aluminium, SFCAs), glasses and dicalcium silicates (C2S). SFCA is the most important bonding phase in iron ore sinter, and its composition, structural type and texture greatly affect its physical properties. Despite its prevalence and importance, the mechanism of SFCA formation is not fully understood.In situpowder X-ray diffraction investigations have been conducted into the formation of SFCA, allowing the study of the mechanism of its formation and the observation of intermediate phases with respect to time and temperature. Studies have been carried out to investigate the effects of changing the substitution levels of aluminium for iron. The use of the Rietveld method for phase quantification gives an indication of the order and comparative rates of phase formation throughout the experiments.