Iron Particle Size Research Articles

Space Weathering and Lunar OH/H2O—Insights from Ab Initio Mie Modeling of Submicroscopic Iron

Abstract Lunar OH/H2O has been confirmed and mapped by analyzing the 3 μm absorption band in spectra acquired by the Moon Mineralogy Mapper (M3) instrument. Space weathering leads to accumulation of submicroscopic iron particles in the uppermost layer of the regolith which gradually changes the spectral signature of airless planetary bodies and thus may affect the detection of lunar OH/H2O. The contribution of this paper is twofold. (1) Our new technique combines Hapke reflectance modeling and ab initio Mie scattering calculations to model the scattering behavior of submicroscopic iron which governs the optical effects due to space weathering. (2) Thermally corrected M3 spectra of mature and immature sample points in mare and highland regions are used to assess the performance of the simulation framework and are analyzed to understand maturity-related changes of the OH/H2O band depth. We find that the simulation method can convincingly reproduce the spectral changes of maturing lunar soil. It becomes clear that there is only a minor effect on the 3 μm absorption feature. This finding makes the analysis of the lunar OH/H2O mapping largely invariant with respect to space weathering. In general, the absorption features around 1 and 2 μm are more strongly obstructed than the feature around 3 μm. Further, we discuss agglutination as the main cause for slight deviations found around the 2 μm band and layering/clustering as a likely reason to explain predicted iron particle sizes that are larger than observed.

Significance of particle size on the improved performance of magnetorheological gels

Abstract Magnetorheological (MR) gels are a class of smart materials whose mechanical characteristics can be modified by the application of an external magnetic field. This paper aims at the investigation of the effect of the size of spherically shaped particles on the magnetorheological gels and the significance of its influence on the properties of the MR gels. MR gels are prepared using magnetite (Fe3O4) nanoparticles and/or carbonyl iron (CI) microparticles dispersed in a polymer gel. A free decay test apparatus built in-house is used to obtain the magnetic field dependent shear response of the gels under dynamic conditions at room temperature and the results are compared for varying sizes of particles. The results indicate a clear trend of increase in storage modulus of the magnetic gel with the decrease in the size of the particles under same conditions of magnetic field and mass fraction. For example, the increase in the shear storage moduli of the magnetic gel, prepared with a mass fraction of 20% of carbonyl iron particles of sizes 3.4 μm and 1.4 μm increase by 16.3% and 18% respectively of the zero field moduli, while the gel with the same mass fraction of magnetite nanoparticles increases to 28%.

Effects of Silicone Oil Viscosity and Carbonyl Iron Particle Weight Fraction and Size on Yield Stress for Magnetorheological Grease Based on a New Preparation Technique.

This paper investigated the effects of silicone oil viscosity (SOV) and carbonyl iron particle (CIP) weight fraction and size on dynamic yield stress for magnetorheological (MR) grease. The MR grease samples were prepared using orthogonal array L9 on the basis of a new preparation technology. The shear rheological tests were undertaken using a rotational shear rheometer and yield stress was obtained based on the Bingham fluid model. It was found that CIP fractions ranging from 65 wt% to 75 wt% and SOV varying from 50 m2·s−1 to 1000 m2·s−1 significantly affect the magnetic field-dependent yield stress of MR grease, but the CIPs with sizes of 3.2–3.9 μm hardly had any influence based on the analysis of variance (ANOVA). In addition, the yield stress of MR grease mainly depended on the CIP fraction and SOV by comparing their percent contribution (PC). It was further confirmed that there were positive effects of CIP fraction and SOV on yield stress through response surface analysis (RSA). The results showed a high dynamic yield stress. It indicated that MR grease is an intelligent material candidate which can be applied to many different areas requiring high field-induced rheological capabilities without flow for suspension. Moreover, based upon the multivariate regression equation, a constitutive model was developed to express the function of the yield stress as the SOV and fraction of CIPs under the application of magnetic fields.

Correlation Study Between Material Parameters and Mechanical Properties of Iron–Carbon Compacts Using Sensitivity Analysis and Regression Model

Changing the material parameters such as powder characteristics and additives affects the final properties of an iron–carbon alloy. This study investigated the influences of three typical material parameters, iron particle size, graphite addition, and powder lubricant addition, on the density and mechanical properties of an iron–carbon alloy formed via powder compaction and sintering. Each material parameter was designed with five levels, and all of the powder mixtures were compacted under 500 MPa and sintered at 1120 °C for 30 min. The microstructure of the samples was observed for the green part and sintered part. Through the tensile test, yield strength, ultimate tensile strength, and elongation were measured. The tensile fracture surface was also examined to understand the changes in mechanical properties according to the parameters. The correlations between mechanical properties and material parameters were characterized by the mapping functions, and a sensitivity analysis was carried out to investigate which parameter had the larger influence on the mechanical properties. The results showed that graphite addition has the greatest influence on the mechanical properties due to the microstructural changes from hypoeutectoid structure to hypereutectoid structure. Further, a regression model was developed to describe the mechanical response of the iron–carbon alloy depending on the material conditions.

The history and state-of-the-art of the studies of native iron in terrestrial and extraterrestrial rocks

A brief review on the history of studying native iron in terrestrial rocks and meteorites is presented. The synthesis and systematization of extensive data on the distribution, composition, and grain size of metal iron particles in sediments, other terrestrial rocks, and meteorites obtained by thermomagnetic analysis with heating to 800 °C combined with microprobe analysis are described. The studies show that ironparticles in all the studied sediments typically have extraterrestrial origin. Based on the statistical analysis of the thermomagnetic data, a number of indications (statistical regularities) are proposed testifying to the overwhelmingly extraterrestrial origin of iron particles in sediments. The similarity of the formation conditions of terrestrial and extraterrestrial metal iron particles makes it possible to suggest a petromagnetic scheme for the structure of planets based on the distribution of metal iron in them.

Preparation and characterization of nano magnetic fluid for automotive applications

Purpose: of this paper is to prepare a nano magnetic fluids with nano additives to have the combined characteristics of high yield stress and better magnetic properties for smart vehicles. This study focuses on increasing the sedimentation time of the fluid using suitable nano additive nickel along with graphene as fillers. Design/methodology/approach: Magnetic nano sized nickel particle based electro- magneto-rheological fluid was prepared and graphene nanoparticle with thickness less than 10nm was introduced as an additive to reduce its sedimentation. This added plate like graphene acts as filler which seals the interfaces of nickel particles and thereby it improves the resistance to sedimentation. Triton X 100 was added as the surfactant for the fluid to reduce the agglomeration of the particles. Findings: Morphology of pure nickel and graphene were examined using scanning electron microscopy (SEM) images. Research limitations/implications: The important limitations is that freely dispersed micron sized iron particles could settle over a period of time, in the form of cakes at the bottommost, and it is tedious to recuperate as dispersed phase. In this investigation, nano sized nickel particles were used as additive to reduce the sedimentation of micron sized iron particles so that, the mixture is homogeneous for extended period of time. In future, addition of different types composite additives in the magnetorheological fluid could be made for the better sedimentation control. Practical implications: The sedimentation problem is one of the major drawback in the smart fluids, which can be eliminated by adding nano particles. For conventional fluid, the complete sedimentation will occur in 2 hours while the improved nano magnetic fluid with additive has good resistance to settle the micron sized iron particle up to 10 hours. Originality/value: To prepare a low cost magnetorheological fluid with nano additives like nickel particles along with fillers as graphene nano particles. With this addition of nickel and inclusion of graphene, the sedimentation problem in magnetorheological fluids is significantly reduced. This magnetorheological fluids can be used in brakes and dampers of automobiles.

The Role of Volume Fraction and Additives on the Rheology of Suspensions of Micron Sized Iron Particles

The increase of the yield stress versus the magnetic field is the most important quantity characterizing the efficiency of a magnetorheological suspension. The theory based on the formation of columnar aggregates predicts a linear variation with the volume fraction of magnetic particles. We shall review previous models for the calculation of forces and yield stress and will introduce a new one based on rupture at zero strain. The predictions of these models are compared with the experimental data obtained for carbonyl iron particles by different authors. Whereas previous analytical prediction strongly overestimates experimental yield stress, the one calculated from Finite Element Method (FEM) used with affine trajectories well reproduce the experiments and show a linear dependence with the volume fraction and a H3/2 behavior between 50 and 200kA/m. Nevertheless, at very high volume fractions (>55%) where the suspension can only flow in the presence of specific additives, the dependence of the yield stress versus the volume fraction and the magnetic field is dramatically changed. We observe a jamming transition which is triggered by the application of a low magnetic field and which depends strongly of the volume fraction. We will discuss the new perspectives arising by the use of these very high volume fractions.

Preparation and characterization of nano magnetic fluid for automotive applications

Purpose: of this paper is to prepare a nano magnetic fluids with nano additives to have the combined characteristics of high yield stress and better magnetic properties for smart vehicles. This study focuses on increasing the sedimentation time of the fluid using suitable nano additive nickel along with graphene as fillers. Design/methodology/approach: Magnetic nano sized nickel particle based electro- magneto-rheological fluid was prepared and graphene nanoparticle with thickness less than 10nm was introduced as an additive to reduce its sedimentation. This added plate like graphene acts as filler which seals the interfaces of nickel particles and thereby it improves the resistance to sedimentation. Triton X 100 was added as the surfactant for the fluid to reduce the agglomeration of the particles. Findings: Morphology of pure nickel and graphene were examined using scanning electron microscopy (SEM) images. Research limitations/implications: The important limitations is that freely dispersed micron sized iron particles could settle over a period of time, in the form of cakes at the bottommost, and it is tedious to recuperate as dispersed phase. In this investigation, nano sized nickel particles were used as additive to reduce the sedimentation of micron sized iron particles so that, the mixture is homogeneous for extended period of time. In future, addition of different types composite additives in the magnetorheological fluid could be made for the better sedimentation control. Practical implications: The sedimentation problem is one of the major drawback in the smart fluids, which can be eliminated by adding nano particles. For conventional fluid, the complete sedimentation will occur in 2 hours while the improved nano magnetic fluid with additive has good resistance to settle the micron sized iron particle up to 10 hours. Originality/value: To prepare a low cost magnetorheological fluid with nano additives like nickel particles along with fillers as graphene nano particles. With this addition of nickel and inclusion of graphene, the sedimentation problem in magnetorheological fluids is significantly reduced. This magnetorheological fluids can be used in brakes and dampers of automobiles.

Experimental Investigations on the Effect of Relative Particle Sizes of Abrasive and Iron Powder in Polishing Fluid Composition for Ball End MR Finishing of Copper

Demand for ultra-finished copper mirrors is very high in defence and laser optics industries due to their high heat conductivity and durability. In ultra-finishing, soft materials require gentle finishing for scratch free highest degree of surface quality. Ball end magnetorheological finishing is an advanced finishing process that confirms both the requirements of optical industries, i.e., finishing of complex surfaces and up to nanometre level of surface finish. In this study it is explored that the relative particle sizes of the abrasive and the ferromagnetic substance in magnetorheological fluid affect the chain structure and in turn the quality of the finished surface. The study has been carried out over magnetorheological polishing fluids composed of different sizes of iron particles and abrasives. The results show that magnetorheological polishing fluid having iron particles of 300 mesh size and alumina powder of 1,000 mesh size is most suitable combination for best surface finishing on copper samples.

Электропроводный материал на основе порошковой меди с повышенными механическими свойствами

The methods of pressing, rolling, and sintering in hydrogen at 800°C have been applied to production of powdered materials based on copper of the Cu–Fe–Al system. The influence of single components and their blends on compaction, structure, and main functional properties of composite materials—electrical conductivity, hardness, and strength (yield stress)—has been analyzed as a function of process variables: compacting pressure of 200–700 MPa, deformation by rolling of 40–85%, dispersity of iron powders having particle sizes <50 and 63–100 μm, contents of iron powder of 5–10 wt % and Fe2Al5 intermetallic powder of 2.5–5 wt %. The best combination of physicomechanical properties has been found for composite material with the composition (wt %) 92.5 Cu + 2.5 Fe2Al5 + 5 Fe, together with iron particle sizes of 63–100 μm. It has been demonstrated that dispersion strengthening of copper by Fe2Al5 particles and filling of its structure with iron fibers formed by rolling provides high relative density of 98–99% and subsequent strength properties of the composite material: hardness HB of 980 MPa, yield stress of 150 MPa at electrical conductivity of 71% of copper conductivity.

Microchannel Plate Efficiency to Detect Low Velocity Dust Impacts

AbstractRecent space experiments suggest that electron and ion energy analyzers using microchannel plates (MCPs) as detectors are also registering direct hits by nanodust particles. To allow the analysis and interpretation of these putative dust events, the detection efficiency of MCPs has to be characterized. We report on a series of experiments to investigate the detection efficiency of MCP detectors to direct impacts for both positively and negatively charged micron and submicron sized iron particles. A double‐stack MCP detector in a chevron configuration was mounted as a target in a dust accelerator. A range of particle velocities and masses were used for a comprehensive examination. The MCP detected and produced definite signals associated with confirmed particle impacts of the MCP for both positively and negatively charged dust particles. The detection efficiency was found to be (6 ± 1)% for positively charged dust and (9 ± 3)% for negatively charged dust particles with a characteristic mass of 6.0 × 1011μ (10−15 kg) and speed of 100 m/s. The examined particle velocity range accurately replicates Rosseta's interaction with dust grains emanating from comet 67P/ Churyumov‐Gerasimenko's nucleus. Additionally, the MCP detection efficiency for low velocity particles shows a possible underestimate of higher speed nanograin signals from Cassini's electron plasma spectrometer during its flyby through Enceladus' active south pole.

Influence of manufacturing parameters on magnetic parameters of soft magnetic composites cores

Abstract The paper presents results of investigations of powder composites made of magnetically soft iron powder and dielectric - PVC - insulating and bonding molecules of this powder. The research was done on self-developed cylindrical samples. The study was aimed to determine the effect of molding pressure and the grain size of Fe on the magnetic properties of the samples. The studies have showed that an increase in core forming pressure obtaining higher induction B values at a lower H field intensity. It was also found that better parameters were obtained in the case of samples with a larger iron particle size.

The influence of large particles of iron powder on the microstructure and properties of FeAl intermetallic phase

Data from the literature indicate a significant influence of powder refinement on the kinetics and the structure of an obtained material. Decreasing the size of aluminum particles has little or no effect, whereas decreasing the size of iron particles has a significant influence. In this work, detailed results from this research on the influence of removing large particles of iron on the structure and properties of Fe40Al sinters are presented. X-ray diffraction analysis has shown that the intensity of the iron peaks has dropped significantly. Similarly, in the hardness analysis, a twofold decrease in standard deviation was observed. This decrease in the standard deviation is related not only to a decrease in the fraction of areas rich in iron but also to a decrease in aluminum-rich phases (micro-hardness tests).

Study of the influence of Carbonyl iron particulate size as an electromagnetic radiation absorbing material in 12.4 to 18 GHz (Ku) Band

This paper presents the influence of different sizes of carbonyl iron particles on the reflectivity measurements of Radar Absorbing Material (RAM). The electromagnetic characterization was performed with a vector network analyzer and a rectangular waveguide in the frequency range of 12.4 to 18GHz (Ku Band). The influence of different parameters such as thicknesses, particle sizes and concentration of carbonyl iron were evaluated. Reflectivity results showed the influence of these parameters on the performance of the RAM. The best reflectivity values (~ -18 dB) were obtained for samples with 60 wt% concentration and 5 mm thickness. We provide information about significantly reflection loss improvement by simply controlling carbonyl iron particulate size.

Electronic and magnetic properties of the adsorption of As harmful species on zero-valent Fe surfaces, clusters and nanoparticules

A systematic theoretical study of the adsorption of H3AsO3 and H3AsO4 acids on Fe nanoparticles was carried out using the Density Functional Theory (DFT). Different sizes of zero-valent iron particles and also the two most stable surfaces of Fe, (1 1 1) and (1 1 0), were studied by characterizing the type of interaction present between the substrates and the adsorbates. Arsenic acid (H3AsO4) is spontaneously reduced in both extended surfaces of iron, producing arsenious acid and oxidizing the metal surface. Arsenious acid (H3AsO3) completely decomposes into (AsOH)(OH)(OH) fragments on the smallest particles, Fe32 and Fe59, but also on the (1 1 1) surface. However, on greater particles (NP80 and NP113) and on the (1 1 0) surface, H3AsO3 retains its initial free configuration and is joined to the surface through both atoms, As and O. Large dispersion components of the adsorption energy were observed when the acids interact with the substrates without decomposition. From a Bader analysis of the atomic charges, important charge transfers were found. Both the As and the interacting Fe atom are slightly reduced on the (1 1 0) surface and NP80. However, the four nearest neighboring irons are oxidized because of the interaction with H3AsO3. In the case of the Fe32 cluster, where this acid is totally broken, all the interacting Fe atoms are oxidized. A significant decrease of the magnetic moment was found for the Fe atom that interacts with H3AsO3. This fact was confirmed with the diminution of the spin up population and the increase of the spin down population observed in the PDOS of d states after the acid was bond to the iron substrates. Besides, important changes in the PDOS have point out the central role of the iron d orbitals on the reactivity of the surface and nanoparticles, but also an important participation of the p ones in the case of the cluster Fe32.

Integrating ZVI-dehalogenation into an electrolytic soil-washing cell

Combination into a single electrochemical reactor of soil washing, ZVI dehalogenation and anodic oxidation can be used to degrade directly the clopyralid contained in spiked soil. Treatment is efficient, achieving the complete removal of chlorinated organics as well as the complete mineralization of the liquid waste produced. However, this combined process does not seem to improve the efficiency with respect to a system operated without addition of iron. Results show that the dechlorinated intermediates formed are less reactive than the parent pollutants, being particularly important the formation of oxalic acid, because its combination with iron (II) helps to explain the decrease in the overall rate of mineralization. This negative impact on the efficiency of the electrochemical process is not completely undesirable, because the toxicity of the waste decreases importantly in the very early stages with the use of iron, opening the possibility of a combination with biological treatments. Again, the accumulation of oxalate intermediates helps to explain this conclusion. Results point out the important effect of the size of iron particles used on the treatment and the complexity of the mechanisms that develop in the cell, which are explained in terms of the different parameters monitored.

Evaluation of Magnetic Separation Efficiency on a Cassiterite-Bearing Skarn Ore by Means of Integrative SEM-Based Image and XRF–XRD Data Analysis

Image analysis data obtained from scanning electron microscopy provided data for a detailed evaluation of the separation efficiency for various processes involving the beneficiation of particulate materials. A dry magnetic separation by a drum type magnetic separator served as a case study to visualize effects of processing of a skarn ore with a high content of cassiterite as ore mineral (~4 wt%). For this material, iron oxides and silicates are the main gangue mineral groups. Based on the obtained data, partition curves were generated with the help of local regression. From the partition curves, the separation efficiency was evaluated and the relevant particle properties deduced. A detailed analysis of the bias of the quantitative mineralogical data is presented. This bias was monitored and further analyzed in detail. Thorough analysis of feed and products of magnetic separation enabled identification of the most important factors that control losses of cassiterite to the magnetic product, namely the association with iron oxides and particle sizes below ~40 µm. The introduced methodology is a general approach applicable for the optimization of different separation processes and is not limited to the presented case study.

Removal of Heavy Metals and Metalloids by Amino‐Modified Biochar Supporting Nanoscale Zero‐Valent Iron

Nanoscale zero-valent iron (nZVI), an environmentally benign material, has been used to remove heavy metals and metalloids from the aqueous phase because of its high reactivity and abundant reactive sites. To improve the stability of nZVI, nanoscale zero-valent iron supported by amino-modified biochar (ZVIA-BC) was prepared and characterized. Its ability to remove heavy metals and metalloid was investigated. Fourier transform infrared spectroscopy analyses showed that the amino group was chemically bound to the functional groups of biochar. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction revealed that zero-valent iron was loaded on the biochar surface. High-resolution transmission electron microscope images showed that the particle size of iron was ∼50 nm and the particles consisted of roughly spherical cores covered with a shell that was uniformly 2- to 3-nm thick. Furthermore, measuring the zeta potentials at various pH values indicated that the iso-electric points occurred within the pH range of 7.50 to 7.56. Additionally, heavy metals and metalloids, including Cd(II), Ni(II), Cu(II), Cr(VI) and As(V) adsorption isotherms, on ZVIA-BC were significantly nonlinear, and ZVIA-BC exhibited a superior ability to remove these heavy metals and metalloids, especially for Cr(VI) and As(V). Characterization with high-resolution XPS revealed that reduction of heavy metals and metalloids occurred on the surface of ZVIA-BC. The main mechanisms for removal were reduction, complexation, co-precipitation, and electrostatic interaction.

The degradation of diethyl phthalate by reduced smectite clays and dissolved oxygen

Reduced smectite clay plays an important role in producing hydroxyl radical (OH) and degrading organic contaminants. In this study, the OH formation was examined in the suspension of reduced clay particles (Red-Na-NAu-2) with oxygen; diethyl phthalate (DEP), a widely detected plasticizer in soils, could be degraded in the reaction system. The results show the reactivity of Red-Na-NAu-2 is related to iron content, reduction extents and particle sizes; the oxidation process of Red-Na-NAu-2 may change structural Fe coordination or even destruct clay morphology. There are two stages in the oxidation process, fast oxidation and slow oxidation, which were closely related to active structural Fe(II) entities (e.g. Fe(II)Fe(II)Fe(II)-OH) and less active structural Fe(II) entities (e.g. Fe(II)Fe(II)-OH), respectively. It was hypothesized that dissolved oxygen could accept electrons from Fe(II) in outer surface layers (tetrahedral layers and at broken edges) based on spectra (FTIR, XPS and EELS) analyses, and inner lattice Fe(II) in octahedral layers could donate electrons to outer surface Fe(III) through one-electron pathway. The findings of this study provide a thorough understanding about the degradation of organic pollutants in subsurface environments, an omitted natural attenuating pathway, which should be important in soil remediation.

Applicability of fine industrial metallic iron-rich waste powders for hydrothermal production of hydrogen gas: The influence of non-ferrous contaminants

Low to negative cost fine industrial metallic iron-rich waste powders are available in large amounts all over the world and are currently often landfilled. The goal of this paper is to investigate the applicability of such waste powders as raw materials for a recently developed hydrothermal hydrogen gas production method, optimised for pure metallic iron powder and operating at a mild hydrothermal temperature of 160 °C for 16 h. The influence of several metallic, oxide and salt compounds of elements (M) that are commonly present in metallic iron-rich powder wastes was systematically investigated for two concentration levels, (M:Fe)low and (M:Fe)high. The kinetics of hydrogen gas formation was measured during reaction and the obtained solid residues were analysed. This work shows that the oxidation of metallic iron particles and the consequent H2 gas production in the investigated hydrothermal reaction system were inhibited through three main effects by the here studied contaminants, namely passivation of the reaction surface, carbonate precipitation and/or redox effects. On the other side, Ni addition promotes the reaction kinetics and acts as a catalyst. However, an excess of Ni inhibits complete iron oxidation through fast precipitation of Fe3O4 on the metallic iron particle surface, forming a passivation layer. Finally, three industrial iron waste powders were treated according to the same hydrothermal treatment. Hydrogen gas formation for an iron-rich foundry sand (IWP-A) was inhibited by the formation of a silicate deposit on the iron particles, while the hydrogen gas production from iron works’ waste powders (IWP-B and IWP-C) increased with decreasing particle size of the metallic iron particles in the powder.