Ferrite Surface Research Articles

Influence of DC Bias on the Electrical Characteristics of SMD Inductors

As the dc bias flows through a ferrite chip surface mount device (SMD) inductor, it tends to premagnetize the core and reduce its inductance and impedance. It is observed that this drop is especially emphasized when the dc current exceeds the safety limit given by the manufacturer. Therefore, it is necessary to investigate and predict the degree of electrical characteristics degradation as well as the dependence of the core losses on core temperature. In this paper, a measurement technique for the investigation of the influence of dc bias on the electrical characteristics of SMD inductors (i.e., inductance, resistance, Q factor, and real and imaginary part of impedance) for printed circuit board applications is presented. Analysis is based on the model of the SMD inductor, which can be presented as a two-port equivalent circuit with intrinsic and extrinsic parameters. For calculation of the parameters of the SMD inductor, extracted from measured S-parameters using vector network analyzer, the in-house software tool IndCalc was used.

Evaluation of Composite Structures by Light Microscopy and Image Analysis

A composite is a material which is made up of two or more distinct materials. Composite materials are generally used for buildings, bridges and structures such as boat hulls, swimming pool panels, race car bodies, shower stalls, bathtubs, storage tanks, imitation granite and cultured marble sinks and counter tops. As a result of absorption of liquids usually occurs a change in volume, which is referred to as swelling. This process can give rise to physical and chemical properties of polymers.NIS - Elements 3.0 was used to evaluate the microstructure of composite materials with different contents of ferrite powder filler. Using NIS - Elements 3.0 assessed the number of particles Sr ferrite surface area and perimeter Sr ferrite particles and the volume fraction of Sr ferrite in the microstructure.

Measurement and Evaluation of Ferrite Surface Crack

An acquisition of ferrite surface images has been taken with a LY-WN-YH Hyper-depth measurement system, from which the crack condition was analyzed with MATLAB. Based on the contradistinction between experimental data from ferrite work pieces of different quality, a preliminary conclusion has been drawn that the surface quality of ferrite materials has a direct link to the quantity and length of the crack on them. By measuring the quantity and length of the crack, an initial criterion was obtained for judging the surface quality of ferrite.

Calculated Stability and Structure of Nickel Ferrite Crystal Surfaces in Hydrothermal Environments

A comprehensive theoretical investigation of nickel ferrite (NiFe2O4) surfaces is undertaken to understand the structure and stability of nanocrystallites that would be present under conditions of hydrothermal synthesis (HTS). In particular, the focus is on conditions characteristic to an operating pressurized water nuclear reactor (PWR). Solid–liquid equilibrium is assumed between bulk nickel ferrite and the aqueous environment saturated with respect to nickel ferrite. A theoretical framework is developed in which the surface energies are evaluated in terms of concentrations of aqueous metal cations, pH, temperature, and pressure. The energies of the bare and water terminated surfaces are calculated and discussed. Surfaces that have more metal cations exposed are found to be more stable. Water adsorption on the nickel ferrite surfaces is an exothermic process, with the magnitude of exothermicity decreasing as a function of temperature. At temperatures relevant to operating PWRs, the energy gain due to wa...

Preparation and properties of La-doped barium ferrite/poly (3-methylthiophene) composites

La-doped barium ferrite/poly(3-methylthiophene)(LB/P3MTH) composites have been successfully synthesized by in suit chemical polymerization with ferrite chloride (FeCl3) as an initiator. The composites structure is investigated by X-ray diffraction analysis (XRD) and Fourier transform infrared spectroscopy, and the morphology of samples is observed by transmission electron microscopy (TEM). Magnetic properties of the composites are tested by vibrating sample magnetometer. XRD analysis shows that La3+ has got into the lattice of Ba-ferrite and replaces the Ba2+ and that the best La3+ amount of La-doped Ba-ferrite is not more than 0.08. La-doped Ba-ferrite particles are coated with poly (3-methylthiophene). TEM image reveals that La-doped Ba-ferrite particles have spherical morphology and are agglomerated due to the coated polymer. P3MTH covers the ferrite surface and has crystallite boundaries, which influences the composites’ physical and chemical properties.

Functionalization of Cobalt Ferrite Nanoparticles by a Vitamin C-Assisted Covering with Gold

We report the design and methodology for functionalization of the surface of small Co-ferrite nanoparticles with a mean size of up to 5.0 nm through the attachment of vitamin C molecules initiating [AuCl4]− reduction and the subsequent deposition of gold. By this method, Co-ferrite-Au nanoparticles have been fabricated for the first time in a simple and controllable manner, consisting of the determination of the consumed ascorbic acid content. The sequential addition of vitamin C and HAuCl4 to the ferrofluid at low concentrations leads to the formation of a gold shell on the ferrite core. This approach avoids the additional stabilization of ferrite nanoparticles before gold deposition, and is of great importance in view of the preparation of biodegradable superparamagnetic particles for nanomedicine applications. The deposition of gold onto the ferrite surface was proved herein by UV-vis absorption and energy-dispersive X-ray (EDX) spectroscopy, inductively coupled plasma mass spectrometry analysis, atomic force microscopy (AFM), high resolution transmission electron microscopy (HRTEM) and Mössbauer spectroscopy.

Electromagnetic properties of BaZn2Fe16O27/antimony-doped tin oxide composite absorbing materials by co-precipitation method

W-type barium ferrite (BaZn2Fe16O27)/antimony-doped tin oxide (ATO) composite absorbing materials were synthesized by co-precipitation method, using BaZn2Fe16O27 prepared by traditional solid method and SnCl4·5H2O, SbCl3 as main raw materials. The structure and morphology of the composites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM). The result shows that BaZn2Fe16O27/ATO composites were obtained by co-precipitation method, and ATO nano-particles were coated on the surface of BaZn2Fe16O27 ferrite. The complex permittivity and complex permeability of BaZn2Fe16O27/ATO composite absorbing materials at the frequency range from 2 to 18 GHz were analyzed by vector network analyzer. It is indicated that ATO has strong dielectric property and ferrite shows superior magnetic performance. The result shows that the complex permittivity and dielectric loss of the BaZn2Fe16O27/ATO composite absorbing materials are higher than the pure ferrite, and the complex permeability and magnetic loss are higher than the pure ferrite and the pure ATO. When the mole ratio of BaZn2Fe16O27/ATO is 1:2, the minimum reflection loss is about −31.14 dB at 12.4 GHz, moreover, the absorption bandwidth reaches 9.6 GHz when RL is −10 dB in the measured frequency range of Ku-band.

Establishment of the Prediction Model for Ferrite Surface Roughness in Ultrasonic Vibration Grinding

In this paper, the author performed orthogonal tests of ultrasonic vibration grinding on ferrite in the DMG machining center, and established a prediction model of ferrite surface roughness in ultrasonic vibration grinding with multiple linear regression analysis method based on the test results, and carried out significance tests on regression equation and regression coefficient, showing that the prediction model had high credibility, the effect of spindle speed and amplitude of ultrasonic vibration on surface roughness was significant, but of grinding depth and feed rate was not obvious.

Measurement and Evaluation of Ferrite Materials Surface Quality

A measurement on the topography and 3D roughness parameters of the ferrite surface has been taken by using a 3D optical profiler. Based on the analysis of the experimental data and the contradistinction between the ferrite devices with different quality and service performance, one preliminary conclusion has been obtained that the surface quality of ferrite materials can be evaluated by using the 3D roughness parameters, and this method is applicable and stable. With qualitative and quantitative analysis, it could be predicted that the surface quality has a direct influence on the service performance of ferrite devices.

Chemisorption of Cyanogen Chloride by Spinel Ferrite Magnetic Nanoparticles

Spinel ferrite magnetic nanoparticles, MnFe2O4, NiFe2O4, and CoFe2O4, were synthesized and used as gas-phase adsorbents for the removal of cyanogen chloride from dry air. Fixed-bed adsorption breakthrough experiments show adsorption wave behavior at the leading edge of the breakthrough curve that is not typical of physically adsorbed species. Fourier transform infrared spectroscopy (FTIR) results indicate that CK is reacting with the spinel ferrite surface and forming a carbamate species. The reaction is shown to be a function of the hydroxyl groups and adsorbed water on the surface of the particles as well as the metallic composition of the particles. The surface reaction decreases the remnant and saturation magnetism of the MnFe2O4 and CoFe2O4 particles by approximately 25%.

Preparation and characterization of spinel-type MeFe2O4 (Me = Cu, Cd, Ni and Zn) for catalyst applications

Four kinds of spinel ferrites, MeFe2O4 (Me = Cu, Ni, Zn and Cd), were prepared by so called “selfcombustion method” using nitrates as precursors. The morphological and structural characterization of the ferrite powders have been performed with various techniques: X-ray diffraction (XRD), to determine the phase composition, SEM observations to evaluate nanostructure characteristics, EDAX spectroscopy to evaluate the chemical composition and BET analysis to determine the specific surface area. The ferrite powders have been tested catalytically in combustion reaction of three diluted gases: acetone/air, ethanol/air and methanol/air. The results revealed a pronounced decrease in the combustion temperature when Cu- and Ni-ferrites are used as catalysts. A probable cause was ascribed to multiple valences of Cu and Ni ions which favor a rapid increase in the oxygen ion species adsorbed on ferrite surface.

Humidity sensing exclusively by physisorption of water vapors on magnesium ferrite

Abstract Water vapor adsorption phenomenon on magnesium ferrite surface has been analyzed by determining binding energy involved in adsorption of water vapor. Activation energy for charge conduction has been calculated by fitting Arrhenius equation using temperature dependent (25–45 °C) conductivity data in the range for 0–90%RH. Nominal change in activation energy observed with increasing humidity. Clausius–Clapeyron heat equation has been used to calculate the isosteric heats of adsorption utilizing the equilibrium data of the isotherms measured for 25–45 °C. The results have exhibited a decrease in heat of adsorption from 0.14 eV at 10%RH to 0.02 eV for 90%RH. While binding energy computed has been found less than 0.2 eV supporting prominent physisorption of water vapors on porous magnesium ferrite. Also, complete recovery of conductivity values in adsorption–desorption curve confirms the physisorption of water vapors. The electrical conduction mechanism in magnesium ferrite with changing humidity has been analyzed by impedance spectroscopy.

Production, electrical conductivity, and gas-sensing properties of thin nickel ferrite films

83 Oxide materials based on nickel ferrite are well known owing to their magnetic properties. However, in recent years, their electrical properties have also been intensely studied. In particular, NiFe2O4�based ferrites are promising as sensing materials for gas sen� sors (1). The mechanism of the sensing of oxide mate� rials is based on the change in the electrical conductiv� ity of a thin film of a material in the course of the adsorption of molecules of a gas being sensed (meth� ane, propane-butane mixtures, etc.). At the same time, there are a number of difficulties in creating a gassensing module that would include a ferritebased sensing element. First of all, this is because of the instability and ambiguity of the physical properties while producing thin nanostructured layers of oxide materials. Ferrites are of the spinel structure type, and their physical properties are significantly dependent on the lattice parameters and also on the type and nature of the ion distribution in the lattice (2, 3). By the present time, certain results have been achieved and methods have been developed for obtain� ing ferrite films by laser deposition, aerosol pyrolysis, sol-gel processes, and ion beam sputtering (4). Investi� gation of the properties of thin ferrite films and the improvement of their production methods will allow one to relate the structural and physical characteristics with the parameters determining the gas sensing of a given material. In the context of solving this problem, in this work, we studied the possibility of producing a NiFe2O4�based material with predictable properties and stable composition by ion beam sputtering of a fer� rite powder of a given composition. This method allows one to apply thin films of oxide materials to substrates made of either conductive or nonconductive materials. The main advantage of the method is the possibility of forming layers ~1 μm thick within a single stage. In gas sensors, oxide layers consisting of nanosized particles are mainly used. A most important factor determining the gas sensing of a layer is its specific sur� face area because the main mechanism of the sensing of the sensing layer is the change in the electrical con� ductivity during the adsorption of molecules of a gas being sensed (5). Therefore, since the adsorption occurs in the nearsurface zone and the sensing layer is usually applied to a nonconductive substrate with recording electrodes, it is necessary to produce the thinnest possible layer with a highly developed ferrite surface for using as a sensing material. In view of the above, in this work, we studied the electrical conduction characteristics of films applied to glass or silicon substrates and the effect of the gas concentration on the behavior of the electrical resis� tance of a thin ferrite film.

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.

Magnetoactive feature of in-situ polymerised polyaniline film developed on the surface of manganese–zinc ferrite

A polyaniline film exhibits magnetoactive properties when deposited on the surface of multidomain particles of manganese–zinc ferrite during in-situ polymerisation of aniline. This is reflected in the increased coercivity and thermomagnetic stability of an in-situ prepared composite compared with bare ferrite and its mixed composite with polyaniline. In addition, the deposition of a polyaniline film results in a shift of the complex-permeability dispersion region towards ultrahigh frequency band. These changes in the magnetic properties of polyaniline-coated ferrite are attributed to the increased value of the inner demagnetisation factor, which results from stress-induced magnetic anisotropy due to the pinning of domain walls appearing on the surface of ferrite. This study is focused on the mechanism of pinning of domain walls and its influence on the magnetic properties of in-situ prepared composites in terms of the molecular mechanism of oxidative polymerisation of aniline. Ferrite stimulates the propagation of polyaniline chains, which start to grow on the domain walls on the ferrite surface. It leads to the pinning of domain walls and restricts their mobility in a magnetic field. The further increase in the coercivity and the resonance frequency of polyaniline-coated ferrite due to film shrinkage after deprotonation of polyaniline makes it obvious that polyaniline coating induces elastic stresses in a ferrite particle that stimulate the growth of the effective magnetic anisotropy. Stress-induced magnetic anisotropy contributes to the reorientation of the magnetisation vectors in domains with respect to the new directions of easy magnetisation, given by magnetoelastic stresses, which leads to complex changes in the magnetic properties of in-situ prepared composites.

Adsorption isotherms of linoleic and linolenic acids from solutions in carbon tetrachloride on surfaces of highly dispersed manganese and copper ferrites

A comparative study of adsorption-desorption isotherms of linoleic and linolenic acids from solutions in carbon tetrachloride on surfaces of manganese and copper ferrites is performed by means of equilibrium adsorption. Adsorption isotherms of fatty acids are described in terms of the theory of volume filling of micropores, and the values of the limiting adsorption, the characteristic adsorption energy, and the pore space volume are calculated. It is established that the limiting adsorption values of linoleic and linolenic acids from solutions in carbon tetrachloride on a copper ferrite surface are higher than on a manganese ferrite surface. It is shown that the adsorption-desorption isotherms have a hysteresis loop.

Variant selection of bainite on the surface of allotriomorphic ferrite in a low carbon steel

Abstract The crystallographic orientations of bainitic plates on the surface of allotriomorphic ferrite were analyzed in a low carbon Fe-0.05C-2.9Mn-1.8Si alloy which after austenitization was isothermally held successively at 725 and 340 °C. Nearly 80% of ferrite allotriomorphs had a Kurdjumov–Sachs orientation relationship with one of the austenite grains. In the grain that had an almost exact Kurdjumov–Sachs relationship with the ferrite allotriomorph bainitic plates nucleated with the same variant as that of ferrite. In the grain deviated slightly from the Kurdjumov–Sachs relationship bainitic plates chose the variant proximate to that of ferrite. No variant selection appeared to occur at irrational ferrite/austenite boundaries. The nucleation potency of Kurdjumov–Sachs related and irrational boundaries is discussed in terms of the ability of the variant of bainite nuclei to form a low energy boundary with the ferrite and the possible difference in the amount of carbon build-up which arises out of the difference in boundary mobility.

Salt-assisted solution combustion synthesis of ZnFe<sub>2</sub>O<sub>4</sub> nanoparticles and photocatalytic activity with TiO<sub>2</sub> (P25) as nanocomposite

Well-dispersed zinc ferrite (ZnFe2O4) nanoparticles were successfully prepared by a novel salt-assisted solution combustion process. The effects of types and amounts of the added salt on the properties of the products were investigated by XRD, SEM, and BET nitrogen adsorption techniques. The results indicated that the introduction of salt into reaction system facilitate the formation of well-dispersed spinel zinc ferrite and increase specific surface area of the resultants from 7.14 to 88.34 m2·g−1 when KCl/M ratio is 2/3. A visible-light-active ZnFe2O4/TiO2 photocatalyst was prepared by physically grinding the ZnFe2O4 nanoparticles with TiO2 (P25) at ambient temperature, and it exhibited excellent photocatalytic activity for the mineralization of rhodamine B. With increasing of ZnFe2O4 amount from 0 to 3wt %, the activity of ZnFe2O4/TiO2 composite increased. The maximum photoactivity is observed when the amount of ZnFe2O4 is 3 wt % and more than 97% of rhodamine B disappears after 4 h visible-light irradiation.

Synthesis, characterization, magnetic and electrical properties of the novel conductive and magnetic Polyaniline/MgFe 2O 4 nanocomposite having the core–shell structure

Conductive and magnetic Polyaniline/MgFe 2O 4 nanocomposite was successfully synthesized in the form of core–shell via in situ chemical polymerization of aniline in the presence of MgFe 2O 4 nano-particles. X-ray powder diffraction of ferrites indicated that the structure of the core material is having the spinel structure, and demonstrated the formation of PAni/MgFe 2O 4 nanocomposite. XRD and TEM photographs showed that the particle's size of the MgFe 2O 4 core-material were around 30–35 nm before coating with Polyaniline, and grown up to 45 nm in the core–shell nanocomposite after coating. Although PAni has a relatively smaller electrical field coefficient than the core–shell nanocomposite, the resistivity of the core–shell material decreased, and hence its conductivity increased after a certain threshold voltage of 0.98 V equivalent to threshold electric field value equals 5.5 V cm −1. The magnetic hysteresis loops investigated with VSM indicated that coating MgFe 2O 4 with Polyaniline has an healing effect which covers the ferrite surface defects, thus decreasing the magnetic surface anisotropy of ferrite particles leading to a decrease of the saturated magnetization (Ms) from 21.33 emu/g to 5.905 emu/g and a decrease of the coercivity (Hc) from 88.66 Oe to 81.6 Oe for MgFe 2O 4 and the core–shell nanocomposite respectively due to the amount of Polyaniline added. TGA and DTA revealed improved thermal stability of the core–shell nanocomposite with respect to that of Polyaniline due to the incorporation of ferrites. Raman spectroscopy confirmed TGA, DTA and XRD studies, and revealed that pure PAni is less stable than the corresponding core–shell nanocomposite with respect to molecular changes which might occur during heating at elevated temperatures. Moreover, Raman study confirmed the interfacial interaction between the core and the shell materials, and lead to an assumption about the presence of different conjugation chain lengths and types, such as the presence of the semi-quinones aside the quinone rings in the polymer chain, which showed different response upon heating the sample.

Effects of titanate coupling agent on the dielectric properties of NiZn ferrite powders–epoxy resin coatings

During ferrite powder–polymer resin slurry preparation, the ferrite particles tend to hold together, forming agglomerates, which lead to the formation of micro-structural defects in the ferrite powder–polymer coatings. These defects affect the quality of magnetic devices. In this study, the titanate coupling agent effects on the NiZn ferrites powder dispersion in an epoxy resin and solvent system and the electromagnetic properties of NiZn ferrite powders–epoxy resin composite coatings are investigated. It was observed that the dispersion of NiZn ferrite powders and the affinity of NiZn ferrites and epoxy resin can be substantially enhanced by coating a titanate coupling agent onto the ferrite powder surfaces. This coating promotes mixing homogeneity and increases the dielectric constants at low frequencies (below 100 Hz) due to the increase in phase boundary between the NiZn ferrite powders and epoxy resin.