Metallic Iron Powder Research Articles

The oxidation kinetics study of ultrafine iron powders by thermogravimetric analysis

The oxidation kinetics of ultrafine metallic iron powder to hematite (α-Fe2O3) up to temperatures 800 °C were studied in air using non-isothermal and isothermal thermogravimetric (TG) analysis. The powders with average particles size of 90, 200, and 350 nm were made by the electric explosion of wire. It was observed that the reactivity of the iron powder is increased with the decreasing particle size of powder. The experimental TG curves clearly suggest a multi-step process for the oxidation, and therefore a model-fitting kinetic analysis based on multivariate non-linear regressions was conducted. The complex reaction can be best described with a three-step reaction scheme consisting of two concurrent and one parallel reaction step. In one reaction pathway Fe is oxidized to α-Fe2O3. The other pathway is described by the oxidation of Fe to magnetite (Fe3O4). At higher temperatures the formed Fe3O4 is further oxidized in a α-Fe2O3. It is established that the best fitting three-step mechanism employed a branching set of n-order equations for each step.

New direct method for evaluating recoilless f-factors of two iron-sites in Fe-bearing compounds using Mössbauer spectrometry

We propose a new direct method for calculating simultaneously two recoilless f-factors of any iron-bearing compound relative to that of a reference material by collecting only a single-temperature Mössbauer spectrum. This methodology is comparatively much simpler than the usual one which requires taking Mössbauer spectra of the compound at several temperatures and subsequently fitting the temperature dependence of the subspectral area or the isomer shift data with a lattice vibrational model. We demonstrate the applicability of this new methodology in the case of three common iron-bearing compounds: magnetite, akaganeite and goethite, but of course this type of study can be extended to other materials. The two f-factors for each compound were related to iron ions located in sites of different origin: for magnetite, these were related to irons with two different oxidation states; for akaganeite to irons in two different crystallographic sites; and for goethite to irons in similar crystal sites but located in grains of different sizes. In the case of magnetite, we found that the f-factors for the Fe(3+) and Fe(2.5+) sites relative to that of metallic iron powder were of fFe (3+)∕fFe = 0.97 ± 0.05 and fFe (2.5+)∕fFe = 0.92 ± 0.05, respectively. Interestingly, the quotient of these two f-factors, i.e., fFe (2.5+)∕fFe (3+), is equal to 0.95 ± 0.05, which compares fairly well with a value reported in literature obtained using the complex methodology based on the temperature dependence of the absolute subspectral area and the Debye approximation. For akaganeite, the f-factors of the doublet 1, D1, and doublet 2, D2, sites relative to that of metallic iron powder were of fD 1∕fFe = 0.95 ± 0.08 and fD 2∕fFe = 0.98 ± 0.15, respectively. And for goethite we found that the f-factors of the sextet 1, G1, and sextet 2, G2, sites relative to that of metallic iron powder were of fG 1∕fFe = 0.80 ± 0.02 and fG 2∕fFe = 0.80 ± 0.02, respectively. The similarity of these last two factors is perhaps due to a sharp distribution of large grains.

Study on Phosphorus Removal of High-Phosphorus Oolitic Hematite by Coal-Based Direct Reduction and Magnetic Separation

In this article, mineralogical phase changes and structural changes of iron oxides and phosphorus-bearing minerals during the direct reduction roasting process were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). It has been found that the reduction of hematite follows the following general pathway: Fe2O3 → Fe3O4 → FeO → Fe. The last step of the reduction process contains two side reactions: either FeO → Fe2SiO4 → Fe or FeO → FeAl2O4 → Fe depending on the micro mineralogical makeup of the ore. In the reduction process of FeO → Fe, oolitic structure was destroyed completely and fluorapatite was diffused into gangue while metallic phase is coarsening at temperatures below 1200°C. Therefore, the separation of phosphorus-bearing gangue and metallic iron can be achieved by wet grinding and magnetic separation, and low phosphorus content metallic iron powder can be obtained. However, when the temperature reached 1250°C and beyond, some of the fluorapatite was reduced to elemental P and diffused into the metallic iron phase, making the P content higher in the metallic iron powder.

Upgrading and dephosphorization of Western Australian iron ore using reduction roasting by adding sodium carbonate

The technology of direct reduction by adding sodium carbonate (Na2CO3) and magnetic separation was developed to treat Western Australian high phosphorus iron ore. The iron ore and reduced product were investigated by optical microscopy and scanning electron microscopy. It is found that phosphorus exists within limonite in the form of solid solution, which cannot be removed through traditional ways. During reduction roasting, Na2CO3 reacts with gangue minerals (SiO2 and Al2O3), forming aluminum silicate-containing phosphorus and damaging the ore structure, which promotes the separation between iron and phosphorus during magnetic separation. Meanwhile, Na2CO3 also improves the growth of iron grains, increasing the iron grade and iron recovery. The iron concentrate, assaying 94.12wt% Fe and 0.07wt% P at the iron recovery of 96.83% and the dephosphorization rate of 74.08%, is obtained under the optimum conditions. The final product (metal iron powder) after briquetting can be used as the burden for steelmaking by an electric arc furnace to replace scrap steel.

Synthesis of magnetite nanoparticles by high energy ball milling

We report on the preparation of magnetite nanoparticles, with size ranging from 12nm to 20nm, by high energy ball milling. The synthesis is made using stoichiometric amounts of distilled water and metallic iron powder. The milled powder samples were analyzed by Mossbauer spectroscopy (MS), X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). Our results indicate that the milling time is a key parameter of the synthesis. By increasing the milling time one achieves high purity magnetite samples. Also, the particle size decreases with the milling time. The sample milled during 10h contained a fraction of 56nm metallic Fe particles and 20nm magnetite particles. By increasing the milling time to 96h we have obtained a sample that is mainly composed of 12nm magnetite particles. MS performed at room temperature showed a spectrum consisting of two sextets with hyperfine parameters related to iron ions occupying octahedral (A) and tetrahedral (B) sites. We have used a self-consistent method to investigate the impact of the dipolar interaction to drive the system to a magnetically blocked regime.

The influence of reactive milling on the structure and magnetic properties of nanocrystalline MnFe2O4

Abstract Nanocrystalline manganese ferrites (MnFe2O4) have been synthesized by direct milling of metallic manganese (Mn) and iron (Fe) powders in distilled water (H2O). In order to overcome the limitation of wet milling, dry milling procedure has also been utilized to reduce crystallite size. The effects of milling time on the formation and crystallite size of wet milled MnFe2O4 nanoparticles have been investigated. It has been observed that single phase 18.4 nm nanocrystalline MnFe2O4 is obtained after 24 h milling at 400 rpm. Further milling caused deformation of the structure as well as increased crystallite size. With the aim of reducing the crystallite size of 18.4 nm, MnFe2O4 sample dry milling has been implemented for 2 and 4 h at 300 rpm. As a result, the crystallite size has been reduced to 12.4 and 8.7 nm, respectively. Effects of the crystalline sizes on magnetic properties were also investigated. Magnetization results clearly demonstrated that crystallite size has much more effect on the magnetic properties than average particle size.

Interparticle interaction effects on magnetic behaviors of hematite (α-Fe2O3) nanoparticles

The interparticle magnetic interactions of hematite (α-Fe2O3) nanoparticles were investigated by temperature and magnetic field dependent magnetization curves. The synthesis were done in two steps; milling metallic iron (Fe) powders in pure water (H2O), known as mechanical milling technique, and annealing at 600°C. The crystal and molecular structure of prepared samples were determined by X-ray powder diffraction (XRD) spectra and Fourier transform infrared (FTIR) spectra results. The average particle sizes and the size distributions were figured out using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The magnetic behaviors of α-Fe2O3 nanoparticles were analyzed with a vibrating sample magnetometer (VSM). As a result of the analysis, it was observed that the prepared α-Fe2O3 nanoparticles did not perform a sharp Morin transition (the characteristic transition of α-Fe2O3) due to lack of unique particle size distribution. However, the transition can be observed in the wide temperature range as “a continuously transition”. Additionally, the effect of interparticle interaction on magnetic behavior was determined from the magnetization versus applied field (σ(M)) curves for 26±2nm particles, dispersed in sodium oxalate matrix under ratios of 200:1, 300:1, 500:1 and 1000:1. The interparticle interaction fields, recorded at 5K to avoid the thermal interactions, were found as ∼1082Oe for 26±2nm particles.

Effect of milling time on the synthesis of magnetite nanoparticles by wet milling

Abstract In this study, nanosize magnetite (Fe3O4) particles have been prepared directly from metallic iron (Fe) powder within distilled water (H2O) by using a planetary ball mill, and the effect of milling time has been investigated. According to Rietveld refinement result obtained from X-ray diffraction (XRD) analyses, the amount of Fe decreases from 98.2% to 0.0%, and it is transformed into Fe3O4, from 1.8% to 100.0%, with the increasing milling time from 1 to 48 h. Due to similar crystal structure of the magnetite and maghemite (γ-Fe2O3), FTIR and Raman spectroscopies as well as a chemical analysis method was used to verify the magnetite structure. FTIR spectra have clearly revealed absorption peaks around 628, 581 and 443 cm−1, which are in good agreement with the characteristic absorption peaks of Fe3O4. In addition Raman analysis verified the formation of magnetite phase with a clear main band peak at 671 cm−1. Chemical analyses have shown that the total amount of Fe in the milled sample for 48 h is 73.04%, which contains 24.10% Fe2+ and 49.34% Fe3+. These results are consistent with the theoretically estimated values of the magnetite. It has been observed that the saturation magnetization decreased from 146.02 to 63.68 emu/g with increasing milling time due to the formation of the ferrimagnetic magnetite phase.

Kinetic modeling based on the non-linear regression analysis for the degradation of Alizarin Red S by advanced photo Fenton process using zero valent metallic iron as the catalyst

The degradation of Alizarin Red S (ARS), an anthraquinone dye was investigated by advanced photo Fenton process using zero valent metallic iron (ZVMI) powder as the catalyst with symmetrical peroxides like hydrogen peroxide (HP)/ammonium persulfate (APS) as the oxidants. APS is proved to be a better oxidant compared to HP as it provides efficient acidic medium which is critical for Fenton process. A kinetic/mathematical model was developed based on the non-linear regression analysis and the validity of the model was tested by comparing the observed experimental values with the theoretically calculated data. The rate equation obtained was found to be a function of iron dosage, oxidant and dye concentration at pH 3. k = 0.2456 [ Fe ] 0.21 [ APS ] 0.15 [ ARS ] − 0.76 k = 0.58 [ Fe ] 0.12 [ HP ] 0.10 [ ARS ] − 0.86 The degradation pathway was followed by UV–vis spectroscopy and GC–MS techniques. Based on the intermediates analyzed, a probable degradation mechanism has been proposed.

Solvothermal Synthesis of Si3N4 Nanomaterials at a Low Temperature

Silicon nitride nanowires or nanorods have been synthesized from SiCl4, NaN3, and metallic Mg at temperatures ranging from 200° to 300°C. X‐ray powder diffraction patterns indicated that the as‐obtained products were mainly β‐Si3N4. Scanning electron microscope and high‐resolution transmission electronic microscopy showed that the samples mostly consisted of Si3N4 nanowires or nanorods. As metallic iron powder was used, α‐Si3N4 was mainly formed at 250°C.

Synthesis of Fe 3O 4 nanoparticles by wet milling iron powder in a planetary ball mill

Fe 3O 4 nanoparticles with sizes ranging from 30 to 80 nm were synthesized by wet milling iron powders in a planetary ball mill. The phase composition and the morphologies of the as-synthesized products were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Nanosized Fe 3O 4 particles were prepared by wet milling metallic iron powder (−200 mesh, 99%) in a planetary ball mill equipped with stainless steel vials using iron balls under distilled water with a ball-to-powder mass ratio of 50:1 and at a rotation speed of 300 rpm. The use of the iron balls in this method played a key role in Fe 3O 4 formation. The present technique is simple and the process is easy to carry out.

Facile Synthesis of Bibenzyl by Reductive Homocoupling of Benzyl Halides in Aqueous Media

A facile synthesis of bibenzyl derivatives by reductive homocoupling reaction is described. Treatment of benzyl halides with metallic iron powder in the presence of a catalytic amount of cuprous salt in aqueous media gives bibenzyls in good yields.

Bentonite–iron interactions under alkaline condition: An experimental approach

The clay–iron interactions in presence of an alkaline (Ca, Na) fluid were experimentally investigated at three temperatures (80, 150 and 300 °C) for three durations of 3, 6 and 9 months. The starting product, a bentonite (MX-80), was mixed with iron powder (metallic iron and magnetite) and placed in contact with a metallic iron plate. Mineralogical changes have been characterised by XRD and SEM imaging, and the crystal chemistry of clay particles and by-products has been determined by EELS- and EDS-TEM. The rate and nature of the clay transformations depend on two critical parameters: temperature and distance to metallic iron plate. At 300 °C, run products are dominated by zeolite (mordenite-type zeolite) and Fe-rich vermiculite, the iron/magnesium ratio of vermiculite increasing at proximity of the iron plate. At 80 and 150 °C, di-octahedral smectite remains the predominant clay, but is progressively enriched in Fe, especially at proximity of the iron plate. Besides the clay transformation, the progressive dissolution of feldspars and of the metallic iron powder is observed. Thus, the dissolution of metallic iron results in the formation of magnetite and Fe-rich clays (Fe-rich smectite, Fe-vermiculite), which are different from those (Fe-saponite, chlorite) produced in experiments carried out with neutral pH solutions.

Direct reduction of mechanically activated specular iron oxide

Specular hematite is the most stable form of hematite, which resists reduction even at high temperatures in a reducing gaseous atmosphere. Therefore, the mechanical activated reduction of specular (micaceous) hematite concentrates has been investigated. The specular hematite particles were milled in a high-energy attritor mill with varying milling time to obtain lamellar-free particles and fine iron oxide. The oxide powder was converted into redundant metallic iron powder by heat treatment at various temperatures (700–1100°C) in a 40% H2+Ar atmosphere. The influence of processing variables on powder characteristics has been evaluated. The reduced iron powders were characterised by using inductive couple plasma analysis, X-ray diffraction and scanning electron microscopy. In this manner, fine (15 μm in size) reduced iron powders with low carbon (0·01% C) and sulphur (0·05% S) content were successfully produced at low temperature (950°C).

Olivary Particles: Unique Carbon Microstructure Synthesized by Catalytic Pyrolysis of Acetone

Olivary (olive-shaped) carbon particles (OCPs) with a diameter of approximately 1.5-2 mum at the middle and a length of approximately 3-4 mum were synthesized by pyrolysis of acetone with metallic zinc as the catalyst at 600 degrees C. The content of the OCPs in the product is related to the catalyst, the pyrolysis temperature, and the time of ultrasonic dispersion before pyrolysis. The content of the OCPs was over 90% of the product under the optimum condition. Mg, Ni, Fe, Cu, Zn, and Cd powder were used as catalysts in the experiments, respectively, in which the metallic zinc powder was outstanding in the pyrolyzing process; the metallic iron and cadmium powder also improved the formation of the olivary carbon particles; however, magnesium, nickel, and copper could not operate the catalysis. Through Fourier transform infrared spectroscopy analysis, the mechanism of the formation of the olivary carbon particles was suggested to be an indirectly catalytic and self-assemble process. By high-resolution transmission electron microscope observation, an interesting arrangement of crystal planes of carbon was found that (002) planes of graphite near the surface are vertical to the surface of the OCPs and not parallel as usual.

Synthesis of ZnFe 2O 4 from metallic zinc and iron by wet-milling process

Nanosized zinc ferrite (ZnFe 2O 4) has been prepared directly from metallic iron (Fe) and zinc (Zn) powders by using wet-milling technique. Structural and magnetic properties of the samples were investigated by X-ray diffraction (XRD), thermo gravimetric analysis (TGA) and vibrating sample magnetometer (VSM). It is found that the particle size varied from 38.2 to 19.4 nm as the milling time was increased from 2 to 20 h. Magnetic measurements at room temperature revealed that the magnetization of the samples increased as the particle size decreased.

Kinetics of trichloroethene dechlorination with iron powder

The dechlorination of trichloroethene (TCE) with metallic iron is an advantageous method for the remediation of contaminated groundwater and soil. The toxic reaction intermediates such as dichloroethenes (DCEs) and vinyl chloride (VC), however, occasionally accumulate in the pathway of the reaction. We have been trying to suppress these intermediates by using metallic iron powder containing impurities. In order to investigate the reaction pathways, we measured the production rates of the intermediates and the final products of the dechlorination of TCE such as DCEs, VC, ethyne or ethene. Ethyne, ethene, ethane and cis-DCE were observed as the major products, and trans-DCE, 1,1-DCE, VC, C3-hydrocarbons (such as propane, propylene), C4-hydrocarbons (such as n-butane) and methane were observed as the minors. Also the rate constants of TCE to ethyne and ethyne to ethene were larger than any other constants. These fact show the production of ethene/ethane via ethyne is the main pathway of the dechlorination of TCE using the metallic iron powder.

Structural and Mössbauer characterization of the ball-milledFex(Al2O3)100−x system

Metal-oxide composites were synthesized by high-energy ball milling of metallic iron (α-Fe) and alumina (α-Al2O3) powders, varying the starting relative concentration and the milling time. The samples were characterized by scanning electron microscopy, x-ray diffraction, and Mössbauer spectroscopy. The results revealed the formation of a FeAl2O3+W spinel phase (hercynite) and of iron (super)paramagnetic nanoprecipitates, in addition to residual magnetic iron and alumina. We also observed that the relative amounts of nanoprecipitates and hercynite for isochronally milled samples were correlated with the sample nominal concentration x, with the precursor iron being relatively more converted in those phases for low x values. Particularly for x=10 milled sample, the relative amounts of the (super)paramagnetic and spinel phases were observed to increase linearly with the milling time. An x=20∕24h milled sample was annealed in H2 atmosphere and revealed the reduction of hercynite, with iron phase separation.

Reduction of Nitroarenes to Aromatic Amines with Nanosized Activated Metallic Iron Powder in Water.

A practical reduction of nitroarenes with nanosized activated metallic iron powder in water at 210 °C (near-critical water) has been developed. The reduction generates the corresponding aromatic amines in excellent yields.

A Novel Synthesis Route for LiFePO[sub 4]/C Cathode Materials for Lithium-Ion Batteries

A novel synthesis route for cathode materials was developed based on a ballmilling technique. In the new synthesis route metallic iron powder and iron(III) phosphate were used as the iron source instead of iron(II). A composite precursor was prepared by a mechanical/chemical reaction of a stoichiometric mixture of metal iron powder, and together with the proper amount of sucrose as conductive additive precursor. The resulting product was heat-treated at 600°C for 30 min to obtain the cathode material. X-ray diffraction analysis indicated olivine type product with a pure orthorhombic phase indexed to the Pnmb space group. The material shows excellent cycle performance with a high capacity of 164 mAh/g at the 0.1C discharge rate and 137 mAh/g at the 1C discharge rate, respectively. No obviously capacity fade was observed after 60 cycles. © 2004 The Electrochemical Society. All rights reserved.