Volume Fraction Of Iron Research Articles

Structural, Optical, Charge-Transport, and Dielectric Properties of Double-Perovskite La2Co1-zFezMnO6 (z = 0, 0.2-1.0).

A series of double-perovskite La2Co1−zFezMnO6 (z = 0, 0.2–1.0) ceramics were synthesized using a well-established sol–gel method. The series of samples with a monoclinic phase and a P21/n symmetry were characterized by XRD, FTIR, conductivity, and capacitance measurement to extract charge-transport and dielectric characteristics at room temperature. The obtained IR spectra fitted well with the Lorentz oscillator model to calculate the damping factor, optical frequency, and oscillator strength and compared with the theory, which gave better agreement. The calculated activation energies from the Arrhenius plot supported the semiconducting nature of all samples. The temperature and frequency-dependent dielectric parameters, such as the real part (), imaginary part () of the dielectric constant, dielectric loss (tanδ), and ac-conductivity (σac) were extracted. The dielectric constant () and dielectric loss (tanδ) were enhanced at a low frequency, while the ac-conductivity (σac) displayed higher values at higher frequencies. The enhancement in the dielectric parameters with increasing iron concentrations arose due to the higher surface volume fraction of iron (Fe3+) ions than the cobalt (Co3+) ions. The radius of the Fe3+ (0.645 Å) was relatively higher than the Co3+ ions (0.61 Å), significantly influenced by the grains and grain boundaries, and enhanced the barrier for charge mobility at the grain boundaries that play a vital role in space charge polarization.

Improved properties of soft magnetic composites with hollow microstructures

Soft magnetic composites (SMCs) possess promising electromagnetic characteristics and attract intense research and application interest in the engineering community. Fabrication of composites with customized architecture is feasible due to the recent advances in additive manufacturing (AM) techniques. The systematic progress of computational optimization has opened up the possibility of devising such structures. This article presents newly structured SMCs which can recently be possible by AM. The effective permeability and eddy current losses are studied in comparison to those properties of traditionally fabricated SMCs. With this hollow inclusion arrangement, for the same iron volume fraction, the effective permeability can be greatly enhanced (more than tenfold) while the eddy current losses decrease considerably. For the same magnetic property, we save iron material, make the composite lighter, and benefit from a lower level of eddy current losses with the hollow configuration.

Characterization of Aluminium Iron Intermetallic Produced by Stir Casting

Iron is the most common impurity found in aluminium. It has a high solubility in molten aluminium and is therefore easily dissolved in the liquid state of aluminium, however its solubility in the solid state is very low. The low solubility of iron in the solid state is accompanied by decreased ductility as a result of the formation of intermetallic phases like AlFe and/or AlFe3. These intermetallic phases increase the strength of the aluminium alloy. They also enhance corrosion resistance. Intermetallic phases based on the high activity of aluminium have very attractive properties such as low density, high melting point, high thermal conductivity, excellent oxidation, hot corrosion resistance and good mechanical properties. In the present work, the formation of intermetallic of Aluminium and Iron is obtained by preparing the intermetallic by stir casting route. The tensile properties, hardness and topography are explored. The ultimate tensile strength was found to be enhanced by around 30% when the volume fraction of Iron in the intermetallic increases from zero to 6%. The average hardness was found to be increased from 62VHN to 69 VHN.

Electrical Interconnects Fabricated From Biodegradable Conductive Polymer Composites.

This study presents the development and characterization of biodegradable electrical interconnects for transient implantable medical devices. The interconnects comprised micropatterned biodegradable conductive polymer composites, which were developed using iron (Fe) microparticles as the conductive filler and polycaprolactone (PCL) as the insulating matrix. The electrical properties of the composites were investigated under various degradation conditions. Electrical percolation was observed at 17% iron volume fraction, but higher volume fractions exhibited more stable electrical resistivity throughout the time course of physiological degradation. The electrical resistivity of 40%vf Fe-PCL composites increased tenfold in an emulated packaged environment under degradation. Biodegradable electrical interconnects based on 40%vf Fe-PCL composites were successfully micropatterned in daisy chain structures, illustrating the process compatibility of Fe-PCL composites for interconnect applications. The electrical resistance of the packaged daisy chain structures exhibited a reasonable increase under degradation. An electrical lifetime of over 5 days was also achieved. System integration with a commercial humidity sensor and analytical calculations supporting other application scenarios confirmed the feasibility of micropatterned Fe-PCL interconnects for use in implantable electrical systems.

Nanofluids Application in the Drilling Process

A high performance of heat transfer fluid has a great influence on the size, weight and cost of heat transfer systems, therefore a high-performance heat transfer fluid is very important in many industries. Over the last decades nanofluids have been developed. According to many researchers and publications on nanofluids its evident that nanofluids are found to exhibit enhance thermal conductivity. The aim of this experiment was to investigate the change of workpiece temperature during drilling using Jatropha oil with nanoparticle and water with iron nanoparticle as lubricating and cooling fluids. These experiments were carried out with samples of nanofluid with different volume ratio. Samples JN1, JN5 and JN10 of iron nanoparticles in the base Jatropha oil with iron volume fraction 1%, 5% and 10% respectively. Samples WN1, WN5 and WN10 of iron nanoparticles in the base water with iron volume fraction 1%, 5% and 10% respectively. The work arises from the projects which were realized at University J. E. Purkyně, Faculty of Mechanical Engineering, in cooperation with Namibia University of Science and technology, department of Mechanical Engineering.

Correlation of rheological properties of ferrofluid-based magnetorheological fluids using the concentration-magnetization superposition

In this work, the yield stress previously measured for some ferrofluid-based magnetorheological fluids (FF-MRFs) with various volume fractions of nanosize magnetite ( φ) and micrometer size iron particle ( Φ F e), for a wide range of magnetic fields (B), is further investigated from a new point of view. The mean magnetization (MM) approximation developed for conventional magnetorheological (MR) suspensions is extended to FF-MRFs and a characteristic magnetic stress is defined and determined by using the average iron particles magnetization in FF-MRF suspensions. We thus generate a rheological master curve of static yield stress vs characteristic magnetic stress, for different values of φ, Φ F e, and B by using a single variable, the characteristic magnetic stress, which contains only data that can be determined experimentally. This indicates, for the first time in literature, a concentration-magnetization superposition in the case of FF-MRFs. This master curve is useful to determine an optimal composition that allows one to obtain FF-MRFs with the best possible MR properties for a particular application. We also find that, regardless of the magnetite nanoparticles' volume fraction in the carrier ferrofluid, when the iron volume fraction is close to Φ F e * = 30 % a change in magnetorheological behavior appears; this is most probably due to the structural transition from chainlike structures of iron particles to more complex ones. In addition, in order to show that the MM approximation may be used even for the FF-MRFs, we employ the finite element method (FEM) to compute a characteristic force and a characteristic magnetic stress by considering a very simple model of a FF-MRF. We find that the FEM model developed for FF-MRFs on the basis of the MM approximation gives reasonably good results especially for low and saturation magnetic field regimes.In this work, the yield stress previously measured for some ferrofluid-based magnetorheological fluids (FF-MRFs) with various volume fractions of nanosize magnetite ( φ) and micrometer size iron particle ( Φ F e), for a wide range of magnetic fields (B), is further investigated from a new point of view. The mean magnetization (MM) approximation developed for conventional magnetorheological (MR) suspensions is extended to FF-MRFs and a characteristic magnetic stress is defined and determined by using the average iron particles magnetization in FF-MRF suspensions. We thus generate a rheological master curve of static yield stress vs characteristic magnetic stress, for different values of φ, Φ F e, and B by using a single variable, the characteristic magnetic stress, which contains only data that can be determined experimentally. This indicates, for the first time in literature, a concentration-magnetization superposition in the case of FF-MRFs. This master curve is useful to determine an optimal...

Metallographic Examination of Forming Improved Mechanical Properties via Surfacing of Steel HARDOX 450 with Flux Cored Wire

Phase composition, defect substructure, and mechanical and tribological properties of the steel Hardox 450 surfaced with С-V-Cr-Nb-W wire are analyzed relying on procedures of transmission diffraction microscopy, mechanical and tribological methods. As a result of surfacing, wear resistance of the material is 138 – 153 times higher than that of the steel Hardox 450, and the friction factor diminishes 2 – 2.5 times. The changing dislocation substructure and phase composition of the deposited metal are analyzed in the paper. The authors have come to the conclusion that the change in analyzed properties is caused by initiation of a multiphase nanostructure. It has been revealed that its strengthening is possible due to the developing of the α-matrix martensitic pattern and a high inclusion of the volume fraction of iron-, chromium-, tungsten,- and niobium-based carbide phase. It has been ascertained in the paper that the iterative surfacing results in attenuation of the oxide phase and in the significant growth of the volume fraction inclusion of the carbide phase.

Remote sensing of soot carbon – Part 1: Distinguishing different absorbing aerosol species

Abstract. We describe a method of using the Aerosol Robotic Network (AERONET) size distributions and complex refractive indices to retrieve the relative proportion of carbonaceous aerosols and free iron minerals (hematite and goethite). We assume that soot carbon has a spectrally flat refractive index and enhanced imaginary indices at the 440 nm wavelength are caused by brown carbon or hematite. Carbonaceous aerosols can be separated from dust in imaginary refractive index space because 95 % of biomass burning aerosols have imaginary indices greater than 0.0042 at the 675–1020 nm wavelengths, and 95 % of dust has imaginary refractive indices of less than 0.0042 at those wavelengths. However, mixtures of these two types of particles can not be unambiguously partitioned on the basis of optical properties alone, so we also separate these particles by size. Regional and seasonal results are consistent with expectations. Monthly climatologies of fine mode soot carbon are less than 1.0 % by volume for West Africa and the Middle East, but the southern African and South American biomass burning sites have peak values of 3.0 and 1.7 %. Monthly averaged fine mode brown carbon volume fractions have a peak value of 5.8 % for West Africa, 2.1 % for the Middle East, 3.7 % for southern Africa, and 5.7 % for South America. Monthly climatologies of free iron volume fractions show little seasonal variability, and range from about 1.1 to 1.7 % for coarse mode aerosols in all four study regions. Finally, our sensitivity study indicates that the soot carbon retrieval is not sensitive to the component refractive indices or densities assumed for carbonaceous and free iron aerosols, and the retrieval differs by only 15.4 % when these parameters are altered from our chosen baseline values. The total uncertainty of retrieving soot carbon mass is ∼ 50 % (when uncertainty in the AERONET product and mixing state is included in the analysis).

Thermal characterization of composites made up of magnetically aligned carbonyl iron particles in a polyester resin matrix

The thermal characterization of composites made up by magnetically aligned carbonyl iron micro-sized particles embedded in a polyester resin matrix is performed using photothermal radiometry technique. The measured experimental data show that the thermal conductivity and thermal diffusivity of the composite, in the direction of the applied magnetic field, increase with the concentration of the particles and are enhanced with respect to their corresponding values for a random distribution of the particles. This thermal enhancement has a maximum at a concentration of particles of 10% and is very low at small and high iron volume fractions, such that for particles concentrations of about 40%, the composite thermal conductivity reduces to its values for random particles. This behavior indicates that for high volume fractions, the effect of the microparticles concentration plays a dominant role over the effect of their alignment. It is shown that the thermal conductivity of the composite can be modeled in terms of the Nielsen model, under an appropriate parameterization of the form factor of the particles. The results of this work could be highly useful for improving the thermal performance of mechanical and electronic devices involving composite materials.

Microwave absorption properties of the carbonyl iron/EPDM radar absorbing materials

Employing carbonyl iron powder and Ethylene-Propylene-Diene Monomer (EPDM) as the absorbent and matrix, rubber radar absorbing materials (RAM) were prepared. Effects of the carbonyl iron volume fraction and the thickness of the RAM on the microwave absorption properties in the frequency range of 2.6–18GHz were studied, and a mathematical analysis was made using the electromagnetic theory. The experimental results indicate that the minimum reflectivity of the radar absorbing materials continuously decreases with the increase of the carbonyl iron volume fraction, and the absorption peak also moves towards the low frequency for the same thickness of the RAM. The minimum reflectivity of the 3.0 mm RAM is −21.7dB at 3.5 GHz when the volume fraction of carbonyl iron is 45%. The reflectivity of the RAM is not in direct proportional to the thickness of the RAM, when the RAM has the same volume fraction of the carbonyl iron. The reflectivity of the RAM presents a regular trend at a given carbonyl iron volume fraction in the frequency range of 2.6–18 GHz. With the increase of the thickness, the maximum absorption peak moves towards low frequency band, the minimum reflectivity firstly decreases and then increases, and the absorption bandwidth for reflectivity<−10 dB firstly increases and then decreases. The microwave absorption properties of the RAM are determined by the thickness and the composition of the radar absorbing materials. Theoretical analysis indicates that the reflectivity of the RAM is determined by the matching degree of the air’s characteristic impedance and the input impedance.

Electromagnetic and absorption properties of carbonyl iron/rubber radar absorbing materials

We measured the effective complex magnetic permeability /spl mu//sub eff//sup */ and dielectric permittivity /spl epsiv//sub eff//sup */ spectra in rubber radar absorbing material (RAM) with various carbonyl iron volume fractions by using the transmission/reflection method with a vector network analyzer. We studied the effects of carbonyl iron content and rubber thickness on the microwave absorption properties in the frequency range of 2.6 to 18 GHz. Our mathematical analysis is based on electromagnetic theory. The results indicate that the effective complex magnetic permeability and dielectric permittivity values of the RAM increase as the carbonyl iron volume fraction increases. For sample thickness of 3.0 mm, an increase in carbonyl iron content reduces the minimum reflection loss from -1.3 to -23.9 dB and shifts the frequency of the minimum reflection loss from 15.5 to 3.5 GHz. For an equal volume fraction of carbonyl iron, the frequency of the minimum reflection loss decreases as the thickness is increased. However, the dip in the reflection loss plot (in decibels) initially decreases to a minimum value before it increases with a further increase in thickness. We determined the value of the reflection loss for the samples by the impedance matching degree (reflection coefficient), which depends on the thickness and composition of the RAM.

Polyaniline/iron nanocomposites prepared by cryomilling

The polyaniline/iron nanocomposites with both conducting and magnetic properties have been prepared by cryomilling (high-energy ball milling under cryogenic temperature), in which the average size of iron grains attains 20 nm. Enhanced coercivity of 206 Oe and decreased conductivity of 0.1 S cm−1 at room temperature have been obtained for the nanocomposites containing 10% volume fraction of iron in polyaniline after cryomilling for 20 h. The high value of the coercivity could be considered due to the presence of a fraction of single-domain particles in the nanocomposites. The low value of the conductivity could be considered due to the dedoping of conducting polyaniline with the cryomilling time. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3157–3164, 2006

Interior structure of terrestrial planets: Modeling Mars' mantle and its electromagnetic, geodetic, and seismic properties

We present a new procedure to describe the one‐dimensional thermodynamical state and mineralogy of any Earth‐like planetary mantle, with Mars as an example. The model parameters are directly related to expected results from a geophysical network mission, in this case electromagnetic, geodetic, and seismological processed observations supplemented with laboratory measurements. We describe the internal structure of the planet in terms of a one‐dimensional model depending on a set of eight parameters: for the crust, the thickness and the mean density, for the mantle, the bulk volume fraction of iron, the olivine volume fraction, the pressure gradient, and the temperature profile, and for the core, its mass and radius. Currently, available geophysical and geochemical knowledge constrains the range of the parameter values. In the present paper, we develop the forward problem and present the governing equations from which synthetic data are computed using a set of parameter values. Among all Martian models fitting the currently available knowledge, we select eight candidate models for which we compute synthetic network science data sets. The synergy between the three geophysical experiments of electromagnetic sounding, geodesy, and seismology is emphasized. The stochastic inversion of the synthetic data sets will be presented in a companion paper.

Rheological study of the stabilization of magnetizable colloidal suspensions by addition of silica nanoparticles

An experimental investigation is described on the stability of magnetorheological fluids (MRFs) consisting of iron suspensions in silicone oil with a thixotropic agent (silica nanoparticles) as stabilizer. The rheological properties were investigated using a commercial rheometer with a parallel-plate measuring cell. Several kinds of experiments were performed in steady-state, oscillatory, and transient regimes. The effects of the volume fraction of magnetic particles, the concentration of silica, magnetic flux density, B, and waiting time after preshear on the rheology of the MRFs were considered. Steady-state measurements demonstrated that our systems only display plastic behavior, for which a yield stress, σy, is appreciable, for the highest iron concentrations and/or magnetic fields. The yield stress was found to be independent of the magnetic flux density when the concentration of silica particles was large enough (> ∼20 g/L). This is a manifestation of the entrapment of iron particles in the silica gel. The adhesion of silica on iron particles by acid-base (proton donation) reactions between both colloids in apolar media is also investigated as another mechanism that hinders the aggregation among iron particles under the external field action. For the same reasons, σy ceased to scale as B2, or to increase with iron volume fraction, for such a threshold silica concentration. Oscillometric determinations were performed at a frequency of 1 Hz, and the complex viscosity was found to increase with B due to structure formation as a result of magnetic particle–particle interactions. In agreement with steady-state results, if the concentration of silica is sufficiently large, the complex viscosity reaches high values, but independent of magnetic flux density. Creep-recovery experiments are particularly sensitive to MRF stability, because the interplay between iron and silica concentrations, magnetic flux density, and waiting time after preshear, led to a broad range of behaviors, ranging from liquid-like to almost elastic solid.

Self-propagating high-temperature synthesis and magnetic features of Fe-Al2O3 granulated films

The classical solid-phase reaction between Fe2O3 and Al layers in thin films is initiated. It is shown that, in the reaction products, Fe granulated films are formed in the Al2O3 nonconducting matrix. Analysis of the reaction equation demonstrates that the volume fraction of iron in the granulated films is less than the percolation threshold. This determines the magnetic properties of iron clusters in a superparamagnetic state. It is assumed that the nanocrystalline microstructure exists in thin films after solid-phase reactions proceeding under conditions of self-propagating high-temperature synthesis.

Magnetic properties of iron-polyethylene nanocomposites prepared by high energy ball milling

Metal-polymer nanocomposites in the system iron-polyethylene have been prepared by high energy ball milling. Minimum average grain size obtained is of the order of 9 nm. Enhanced coercivity of 230 Oe at room temperature and 510 Oe at 5 K have been obtained for the sample containing 0.1 volume fraction of iron in polyethylene after milling for 200 h. This high value of the coercivity could be ascribed to the presence of a fraction of single-domain particles in the sample as evidenced from the thermal dependence of the magnetization and ac susceptibility measurements.

Magnetic properties and grain growth stability of nanocomposite Fe–ZrO2 granular solids prepared by mechanical milling

Correlations between the grain size [or the diffracting particle size (DPS)] and the magnetic properties of mechanically milled Fe–ZrO2 nanocomposite powders are reported. Nanocomposite powders with iron volume fractions below, near, and above the percolation value were annealed at temperatures between 573 and 1083 K and investigated. The composite as-milled powders exhibited enhanced coercivities (≳300 Oe) compared to similar mechanically milled iron powders. The iron diffracting particle size (grain size) as a function of annealing temperature showed two regimes. The first regime, corresponding to temperatures at and below 773 K, consisted of enhanced coercivities and remanence ratios with a relatively stable iron diffracting particle size of ∼25 nm. In the second temperature regime, above 773 K, the DPS increased, but remained well below the value for pure iron. Concomitant with this increase, large reductions in the coercivities were observed in the second regime.

Ferromagnetic resonance study on Fe-SiO2 granular films

Ferromagnetic resonance (FMR) measurement was performed at the frequency of 9.8 GHz and at the room temperature on a series of Fe-SiO2 granular films fabricated by the Ar+-beam sputtering technique. Our results indicated that when the iron volume fraction (fv) of the films exceeds 0.28, the FMR spectra are superpositions of volume modes and surface modes. The analysis on the effective anisotropy field suggests that the intrinsic anisotropy (including the volume and interface one) becomes maximal when fv near the percolation threshold (fp). In particular, it was found for the films with fv=0.42 that the spin wave resonance modes satisfy the relation Hres∝n with a separation field of about 174 Gs between the successive modes. Our study reveals that Fe particles are coupled by a yet unknown interparticle interaction when fv is just below fp.

Lunar magnetic fields: Implications for utilization and resource extraction

Although the Moon possesses no large‐scale intrinsic magnetic field, locally strong crustal fields exist which must be considered in assessing lunar utilization scenarios. On the basis of available data, orbital anomalies most probably imply the presence of subsurface concentrations of metallic iron in the single‐domain size range. Such concentrations may indicate larger iron volume fractions than are characteristic of sampled materials, allowing more efficient extraction of metal than is now considered likely using nominal regolith compositions. Most other implications relate to the deflection of interplanetary and magnetospheric ions by crustal fields. Numerical simulations are employed to show that solar wind ion deflection by strong lunar magnetic anomalies can produce local increases, as well as decreases, in the implantation rate of solar wind hydrogen. The largest concentrations of implanted solar wind volatiles may therefore be found in local areas near strong anomalies. If water ice exists in permanently shadowed regions of the lunar poles, locally strong magnetic fields can shield these volatiles from sputter erosion losses by interplanetary and magnetospheric ion fluxes. Model simulations indicate that the ability of magnetic anomalies to shield the surface from incident ions increases with the angle of incidence and hence for most particle sources, with selenographic latitude. Finally, the possibility that relatively strong anomalies can provide significant protection of men and materials against major solar flare particle events is examined and found to be unlikely.

Experimental investigation of Fe-(SiO2) granular films

Fe-(SiO2) granular films were fabricated by sputtering with a mosaic target. The fractional area of iron on the target was varied from 0.29 to 0.42. The volume fraction of iron was found from the saturation magnetization to be within 0.03 of that predicted by the target composition. The sample coercivities ranged from Hc = 130 to 950 Oe at room temperature and 690 to 2390 Oe at 77 K. Characteristics relevant for recording media were investigated for the highest-coercivity sample. The squareness values for hysteresis loops measured in and out of the plane of the film, Mr/Ms = 0.54 and 0.43, respectively, indicate that the granules have a uniaxial anisotropy and the easy axes tend to lie more in the plane of the film. The rotational hysteresis was measured at room temperature; the rotational hysteresis integral was calculated to be Ir = 1.56. Because the magnetization reversal is assisted by thermal fluctuation, the low temperature value of Ir was estimated by scaling the measured value by the ratio of the coercivities measured at 77 K and at room temperature. The value of Ir ≊ 0.6 is closest to the theoretical value for the coherent rotation mechanism. The relative decay of magnetization between 30 and 3600 s had a maximum value of ΔM/Ms = 0.10 for a reversal field near Hc. This value falls within the range of the values reported for conventional particulate media, which suggests that a stable transition can be recorded in this material.