Ferrite Surface Research Articles

Magnetic characteristics and optical band alignments of rare earth (Sm+3, Nd+3) doped garnet ferrite nanoparticles (NPs)

Yttrium iron garnet (YIG) nanoparticles (NPs) doped with rare earth (RE) metal ions (Y2.5Sm0.5Fe5O12, Y2.5Nd0.5Fe5O12) were successfully synthesized by sol-gel auto combustion approach. The cubic crystalline structure and morphology of the prepared garnet ferrite NPs were analyzed by X-ray diffractometer (XRD) and field emission scanning electron microscopy (FESEM). The cubic crystalline garnet phase of the synthesized YIG, Sm-YIG and Nd-YIG samples was successfully achieved at 950 °C sintering temperature. The force constant and absorption bands were estimated by using Fourier transform infrared spectroscopy (FTIR). The doping effect of RE metal ions on the chemical states of YIG were examined by x-ray photoelectron microscopy (XPS). The valence band (from 12.63 eV to 13.22 eV), conduction band (from 10.89 eV to 11.34 eV) edges and optical bandgap values of RE doped YIG samples were calculated using UV–Vis spectroscopy and ultraviolet photo electron spectroscopy (UPS). The magnetic analysis of the prepared NPs was studied using vibrating sample magnetometer (VSM). The XPS analysis of RE doped YIG samples exhibit the existence of RE (Sm+3, Nd+3) contents on the surface of YIG ferrite by decreasing the oxygen lattice in garnet structure. The optical bandgap (from 1.74 eV to 1.88 eV) explains the semiconducting nature of the synthesized NPs. The UPS results confirm the valence band position of YIG doped samples. The saturation magnetization and remanence of RE doped garnet ferrite samples increased from 13.45 to 18.83 emu/g and 4.06–6.53 emu/g, respectively.

Thin Ferrite Wafer Uniformly Polished with Magnetic Attraction Method

When a ferrite substrate is used to prepare thin-film InSb Hall element chips, one surface of the ferrite wafer needs to be polished. The traditional chemical mechanical polishing (CMP) method, often used for polishing of ferrite wafers, has several problems: a long time to install and remove wafers, a little high debris rate, and high cost. Taking advantage of the fact that ferrite wafers can be magnetically attracted, a method using independent RuFeB magnets to attract and hold ferrite wafers is proposed. The polishing head holding the ferrite wafer can perform planetary rotary motion to achieve uniform polishing. The polishing head floats up and down freely on the polishing pad, without the requirements of matching and process accuracy in machining, mechanical linkage, and control. The roughness of the ferrite surface after polishing is about 0.18 μm, which meets the requirements for the substrate of InSb Hall element chips. With no debris, the efficiency of installing and removing wafers is 30 times higher than that of traditional methods. At the same time, compared with traditional CMP machine, the cost of CMP equipment made by this method is very low.

DFT Analysis of Ethanol Electro-Oxidation on Fe(110) and Fe3C(110) and its Correlation with the Stress Corrosion Cracking of Carbon Steel

Striking mechanical and morphological similarities of the stress corrosion cracking (SCC) of carbon steel in ethanolic media with those governed by a cleavage-like mechanism in CO-CO2 aqueous solutions, prompted the investigation of the possibility of ethanol electrochemical oxidation into CO on ferrite (Fe) and cementite (Fe3C) surfaces. Density functional theory computations on (110) surfaces reveal that the catalytic activity of Fe and Fe3C through the α dehydrogenation pathway can significantly reduce the energy barrier of electro-oxidation of ethanol and production of CO to 0.575 and 0.480 eV, respectively. These first principle calculations indicate that at the anodic potentials applied during potentiostatic slow strain rate testing, ethanol electrooxidation to CO is thermodynamically viable on carbon steel, giving further credit to the involvement of cleavage type SCC of carbon steel in ethanolic environments.

Synthesis and study of perspective composite material based on mechanochemically synthesized magnesium ferrite and ultra-high molecular weight polyethylene

This work is devoted to the study of the newly mechanochemically synthesized composite consisted of industrially available ultra-high molecular weight polyethylene (UHMWPE) and Mg-ferrite particles for the design of components of functional electro-magnetic shielding materials needed in life support technologies. The produced material was characterized by means of scanning electron microscopy, x-ray diffraction, Mossbauer spectroscopy and differential scanning calorimetry. Mechanical activation leads to increased dispersion of ferrite component and transformation of UHMWPE submolecular structure without explicit interaction with ferrite particles surface.

Photoelectrochemistry of Ferrites: Theoretical Predictions vs. Experimental Results

AbstractThis paper gives an overview about recent theoretical and experimental work on electronic and optical properties of spinel ferritesMFe2O4. These compounds have come into focus of research due to their possible application as photocatalyst material for photoelectrochemical water splitting. The theoretical background of state-of-the-art quantum-chemical approaches applied for predicting electronic and optical band gaps, absolute band positions, optical absorption spectra, dielectric functions and Raman spectra, is briefly reviewed. Recent applications of first-principles methods on magnetic and electronic properties of ferrites withM= Mg and the first row of subgroup elements Sc to Zn are presented, where it is shown that the fundamental band gap is strongly dependent on the spin state and the degree of inversion of the spinel structure. The observed variation of electronic properties may serve as an explanation for the large scattering of experimental results. The exchange ofMand Fe cations has also a pronounced effect on the Raman spectra of ferrites, which is analyzed at atomic scale from first principles. Calculated optical absorption spectra of ferrites are compared to experimental spectra. The electronic nature of the first excitations and the role of oxygen vacancies are discussed. For the calculation of absolute band positions, which have a significant impact on the photoelectrochemical activity of the ferrites, models of the most stable ferrite surfaces are developed that take into account their polar nature and the interaction with the solvent. Theoretically predicted valence and conduction band edges are compared to results from electrochemical measurements. The role of cation exchange on the surface electronic structure is investigated both theoretically and experimentally.

Bacterial Disinfection by CuFe2O4 Nanoparticles Enhanced by NH2OH: A Mechanistic Study.

Many disinfection technologies have emerged recently in water treatment industry, which are designed to inactivate water pathogens with extraordinary efficiency and minimum side effects and costs. Current disinfection processes, including chlorination, ozonation, UV irradiation, and so on, have their inherent drawbacks, and have been proven ineffective under certain scenarios. Bacterial inactivation by noble metals has been traditionally used, and copper is an ideal candidate as a bactericidal agent owing to its high abundance and low cost. Building on previous findings, we explored the bactericidal efficiency of Cu(I) and attempted to develop it into a novel water disinfection platform. Nanosized copper ferrite was synthesized, and it was reduced by hydroxylamine to form surface bound Cu(I) species. Our results showed that the generated Cu(I) on copper ferrite surface could inactivate E. coli at a much higher efficiency than Cu(II) species. Elevated reactive oxygen species’ content inside the cell primarily accounted for the strong bactericidal role of Cu(I), which may eventually lead to enhanced oxidative stress towards cell membrane, DNA, and functional proteins. The developed platform in this study is promising to be integrated into current water treatment industry.

Synthesis, morphology, crystallite size and adsorption properties of nanostructured Mg–Zn ferrites with enhanced porous structure

Mg–Zn ferrites with porous cavity structure were produced by sol-gel auto-combustion method utilizing a new mixture of dl-alanine and urea as an organic fuel-reductant. The influence of non-magnetic Zn ions content on the structural, morphological and adsorption characteristics of Mg–Zn NPs has been investigated. It was found that Zn effects the porosity of Mg–Zn ferrospinels. X-ray diffraction analysis confirmed the formation of cubic spinel phase and the crystallite size was calculated by the SSP method, W-H method and modified Scherrer formula. SEM observations revealed mesh-like microstructure with the presence of 1–2 μm macropores and agglomerated nanoparticles. The EDS spectra confirmed the desired chemical composition of ferrites powders. Mössbauer spectroscopy confirmed the valence state of cations and their distribution over the spinel sublattices. The adsorption characteristics of spinel compounds were studied on Congo Red dye removal. The appropriateness of Langmuir, Freundlich, and Dubinin-Radushkevich adsorption models were investigated and the parameters of all models were determined. The observed data fitted well by Langmuir model, indicating that the Congo Red adsorption occurred on a homogeneous surface and that the active surface centers possessed similar energy values. The Dubinin-Radushkevich isotherm model was utilized to calculate the free energy of Congo Red adsorption, i.e. setting in the range 7.81–22.4 kJ/mol and indicating that the Zn content affects the mechanism of Congo Red adsorption onto ferrite surfaces and the removal efficiency is enhanced with the rise in Zn content.

Facile synthesis of CoFe2O4 nanoparticles and application in removal of malachite green dye

The adsorption capacity of the surface of cobalt ferrite (CoFe2O4) nanoparticles as an adsorbent was investigated. Malachite green dye in aqueous solution was used as the model compound. Various dosages of cobalt ferrite nanoparticles (0·01–0·07 g) were used to determine the capacity to adsorb malachite green. Characterisation of cobalt ferrite was performed using scanning electron microscopy and X-ray diffraction. An adsorbent loading value of 0·07 g, initial dye concentration of 10 parts per million and pH of 10 were used in the evaluation. The maximum amount of dye was absorbed from the solution within 60 min after the start of every experiment. The equilibrium concentration and the adsorption capacity at equilibrium were determined using three different sorption models, namely, Langmuir, Freundlich and Temkin isotherms. It was found that dye adsorption onto cobalt ferrite follows the Langmuir isotherm. The absorption kinetics were found to be of second order.

Photochemical Mechanism for the Air Inflammation Propagation

The Electronic Energy Explosion (EEE) in the air can be initiated by electrical discharge near the ferrite surface [1].

Morphological and compositional changes of MFe2O4@Co3O4 (M = Ni, Zn) core-shell nanoparticles after mild reduction

NiFe2O4@Co3O4 and ZnFe2O4@Co3O4 core-shell nanoparticles were synthesized and reduced to be used as catalysts for the Fischer-Tropsch synthesis. The as-synthesized materials were determined to have an incomplete Co3O4 shell around the ferrite core with a maximum thickness of 3 nm. Using in-situ TEM, it was shown that reduction of these core-shell nanoparticles in pure hydrogen at 230 °C and 250 °C, respectively, resulted in the formation of small cobalt islands on the ferrite surface. Catalytic testing of the core-shell materials, NiFe2O4@Co3O4 and ZnFe2O4@Co3O4, after reduction showed a cobalt-time yield of 13.64 μmolCO·gCo−1·s−1 and 4.27 μmolCO·gCo−1·s−1 and a C5+ selectivity of 47 C-% and 68 C-%, respectively. The observed difference in cobalt-time yield and selectivity between NiFe2O4@Co3O4 and ZnFe2O4@Co3O4 core-shell nanoparticles was ascribed to a combination of effects that arose from the morphological and compositional changes that occurred after reduction and under Fischer-Tropsch synthesis conditions.

Effect of Microstructure in the Vicinity of Ferrite Grain Surface on Coercivity in Ca-La-Co M-type Ferrite Magnets

Effect of Microstructure in the Vicinity of Ferrite Grain Surface on Coercivity in Ca-La-Co M-type Ferrite Magnets

Ferrites: magnetic materials as an alternate source of green electrical energy

Ferrites samples Mg1-xLixFe2O4 for x = 0.0, 0.1, 0.2, 0.3, were synthesized by solid-state sintering method. Detailed investigations were made on the structural, morphological, magnetic and electrical proprieties of these samples. A detailed investigation was performed on power generation of these samples and role of Li-doping has been discussed. The X-ray Diffraction (XRD) pattern confirms the spinel phase formation in samples without any impurity. It is observed from Scanning Electron Microscopy that average grain size of samples decreases with lithium doping in MgFe2O4. The saturation magnetization of MgFe2O4 (15.4 emu/g) is found to increase with Lithium percentage and maximum 39.3 emu/g for Mg0.7Li0.3Fe2O4 sample. Ferrites play a crucial role in magnetic recording, microwave magnetic devices and many applications in medical sciences. Recently, it was observed that ferrites can be an alternate source of green energy by inventing hydroelectric cell (HEC). The processes of water adsorption and dissociation on the metal-oxide surface, plays an important role in production of electricity in ferrites. When, water is sprayed on hydroelectric cell the thermodynamic driving force is responsible for the formation of stable metal-oxygen or metal-hydroxyl bonds. The reactivity of ferrite surface towards water is based on the interaction of these ions and the d orbital of the Fe atom. Due to this interaction, water dissociated in H3O+ and OH− ions and migrates toward silver and zinc electrodes respectively. A typical hydroelectric cell of 2 inch diameter produces 17.1 mA of peak current and 949 mV voltage with a maximum output power of 15.85 mW for Li = 0.2 doped MgFe2O4 sample.

A Pulsed, High-Intensity Source of XUV Radiation Based on Ferrite Surface Breakdown at High Current

High-current discharges along a ferrite surface have been studied on BIN pulsed power facility (270-kA current amplitude, 80-ns rise time, and 300-kV output voltage). The samples of the ferrite were placed in the vacuum diode as the main load of the pulser. It was found that the initial discharge pattern could be predefined by drawing on the surface with a graphite pencil. Each discharge generated an intense, reproducible pulse of optical and XUV radiation, with time-integrated optical and XUV images being similar to ~ 5 consecutive shots; thereafter, the discharge channel would start to follow the shortest path between the electrodes, and continue with similar characteristics for at least the next 10 pulses. The transverse size of the emitting region did not exceed $200~\mu \text{m}$ in the $150 eV spectral band, probably due to plasma pinching. No soft X-ray (>0.8 keV) radiation was registered using photoconducting detectors.

Limit Strains Analysis of Advanced High Strength Steels Sheets Based on Surface Roughness Measurements

The limit strains of dual-phase steels DP600 and 800 were evaluated in this work with a localization model formulated in plane-stress conditions using elasto-plastic constitutive equations. In this model, a geometrical imperfection parameter is defined from the sheet nominal thickness, initial ferrite grain size and average surface roughness. The proposed identification procedure provided a more physically meaning for this parameter and at best more conservative predictions in the drawing Forming Limit Curve (FLC) range of both investigated dual-phase steels. Nevertheless, the corresponding limit strains in the biaxial stretching region are underestimated with the present theoretical model. Thus, more detailed anisotropic yield function and hardening descriptions must be implemented to improve the accuracy of the FLC prediction of advanced high strength steels.

Generation of Intense UV Radiation during High-Current Breakdown over a Ferrite Surface

The dynamics and emission characteristics of pulsed breakdown over a ferrite surface at a current amplitude of 270 kA and current rise time of 80 ns were studied experimentally. It is shown that the characteristic transverse size of the discharge region in visible radiation is ~3 mm, while that in vacuum UV (VUV) radiation is ~200 μm. The duration of the VUV pulse with an average power of ≈0.275 GW is about 80 ns.

Visible-light photocatalytic activity of zinc ferrites

Zinc ferrite samples were prepared at temperatures between 75 °C and 1100 °C employing published synthetic methods Phase pure zinc ferrites were, however, only obtained through high-temperature methods (more than 800 °C) as revealed by XRD and Raman analysis. Photocatalytic experiments under UV and visible light irradiation as well as a series of detailed wavelength dependent measurements applying monochromatic light sources emitting at wavelengths of 365, 455, 505, and 660 nm were performed. Visible light-induced bleaching of methylene blue in aqueous suspensions of zinc ferrites was observed. However, no photocatalytic formation of OH radicals was detected. The results of flat band potential measurements revealed the interfacial electron transfer from an excited methylene blue molecule into the conduction band of zinc ferrite to be thermodynamically possible. The bleaching of methylene blue containing suspensions under visible light irradiation is, therefore, assumed to be initiated by an interfacial electron transfer from photo-excited methylene blue molecules adsorbed on the ferrite surface into the conduction band of the semiconducting zinc ferrite.

Local electrical properties of thermally grown oxide films formed on duplex stainless steel surfaces

The local electrical properties of thermally grown oxide films formed on ferrite and austenite surfaces of duplex stainless steel at different temperatures were investigated by Current sensing atomic force microscopy, X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). The current maps and XPS/AES analyses show that the oxide films covering austenite and ferrite surfaces formed at different temperatures exhibit different local electrical characteristics, thickness and composition. The dependence of electrical conductivity of oxide films covering austenite and ferrite surface on the formation temperature is attributed to the film thickness and semiconducting structures, which is intrinsically related to thermodynamics and kinetics process of film grown at different temperature. This is well elucidated by corresponding semiconductor band structures of oxide films formed on austenite and ferrite phases at different temperature.

Design Comparison of NdFeB and Ferrite Radial Flux Surface Permanent Magnet Coaxial Magnetic Gears

Magnetic gears promise the benefits of mechanical gears with added advantages from contactless power transfer. Although most of the literature focuses on minimizing the size of magnetic gears, their material costs must also be reduced to achieve economic feasibility. This paper compares the active material costs of NdFeB and ferrite radial flux coaxial magnetic gears with surface permanent magnets through a parametric two-dimensional (2-D) and 3-D finite element analysis study. Differences in optimal design trends such as pole counts and magnet thicknesses are illustrated for the two materials. The results demonstrate that, for most historical price rate scenarios, NdFeB gear designs are capable of achieving lower active material costs than ferrite gear designs, and they are always capable of achieving much higher torque densities. Based on the selected design constraints, relative to a nominal ferrite cost of $10/kg, NdFeB must cost more than $90/kg before ferrite is cost competitive. However, ferrite gears can achieve higher efficiencies than NdFeB gears, especially at high speeds, and generally emit less axial leakage flux. Additionally, contour plots are provided to show the impact of material price rate variation on the cost break points.

Transfer of Inflammation in the Air

Active Medium of the Electronic Energy Explosion EEE in Air initiated by Electric Discharge near Ferrite Surface results in inflammation of Air in the Electric Field with Tension about V cm This Property can be used for inflammation of any big Volume of Air and production of Laser Generation with any big Energy nbsp

Fabrication of cobalt ferrite/cobalt sulfide hybrid nanotubes with enhanced peroxidase-like activity for colorimetric detection of dopamine

The development of highly sensitive and low-cost biosensors for the detection of dopamine is of paramount importance for medical diagnostics. Herein, we report the preparation of a new peroxidase-like catalyst with a uniform heterostructure by using a technique involving electrospinning, annealing and solvothermal reaction. In this catalyst system, cobalt sulfide (CoS) nanoparticles were homogenously distributed and supported on the surface of cobalt ferrite (CoFe2O4) nanotubes. The as-prepared CoFe2O4/CoS hybrid nanotubes showed remarkably high catalytic efficiency as peroxidase mimics toward the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2. Owing to the synergistic effect between the CoFe2O4 and CoS component, the prepared CoFe2O4/CoS hybrid nanotubes exhibited enhanced peroxidase-like activity, exceeding that of either the CoS nanoparticles or CoFe2O4 nanotubes alone. Dopamine has been widely investigated due to its unique function in the nervous system. Consequently, various approaches have been developed for the sensitive determination of dopamine. In this work, a simple and sensitive colorimetric route for the detection of dopamine was established based on the ability of dopamine to induce the reduction of oxidized TMB to TMB with consequent fading of the blue color. This method shows a wide linear range (0–50μM) and a low detection limit of 0.58μM. The unique heterostructure with spinel/sulfide interfaces represents a new concept for the construction of highly efficient and multifunctional biocatalysts.