Surface Of Iron Particles Research Articles

Ferrite Coating on Iron Particles in Aqueous Solution: Effect of Surface Functionalization

Ferrite coating of acid treated iron particles with have been optimized using electroless process. The effect of the functionalization was monitored by XPS and SEM analysis whereas adhesion behavior of ferrite thin films was characterized using a non-conventional ultrasonic test. It is shown that acidic treatments increase the amount of hydroxyl groups on the surface of iron particles, allowing the creation of chemical bonds between the iron core and its ferrite shell. It leads to an increase of the adhesion between both materials. It is shown that the reactivity of iron particles improves the ferrite deposition process. A homogeneous adhesive ferrite coating of around 2 μm with a deposition process of 90 min has been obtained.

Effective Composite Preparation between Graphite and Iron Particles by the Interfacial Mediation of Force-Activated Oxygen Atoms

Mechanochemically activated graphite (Gp) and iron particle surfaces were prepared, and the Gp/iron composite interfaces were elucidated to utilize new functions. Activated iron particles with the oxygen atoms prepared by a milling under oxygen atmosphere were shown. Alternately, the Gp particles activated by the milling under argon atmosphere easily agglomerated because of the dangling bonds on the edge surfaces. In the composites, the interfacial bonds (e.g., Fe–O–C) between the Gp and iron oxides on the iron were clearly induced while preserving the carbon atom six-ring structures. Furthermore, the molecular orbital calculations suggested that the activated oxygen atoms in the iron oxides effectively abstract hydrogen atoms from the C–H groups of the Gp edge, resulting in the active bare carbon atoms which can form the interfacial bonds; therefore, the interfacial Fe–O–C bonds for a higher adhesive strength were successfully prepared.

Preparation and Characterization of Fe/SiO_{2} Powder Composites Using Impregnation Method

Fe/SiO2 powder composite materials based on irregularly and/or spherically shaped iron powder particles with an addition of SiO2 nanopowder were prepared in two ways, (i) by mixing the Fe/SiO2 powder with 1.0 wt.% of Shellac dissolved in ethanol and (ii) by vacuum/pressure impregnation of low-temperature sintered Fe/SiO2 components with shellac dissolved in ethanol and with thermoplast SL450. SiO2 was implemented either as nanopowder or by sol-gel coating. Vacuum/pressure impregnation (VPI) of pre-sintered samples was performed in a steel container. The in uence of iron particle shape and processing conditions on the electro-insulating layer was microscopically evaluated and correlated with the values of the electrical resistivity and coercivity. It has been found that the continuity, distribution and thickness of insulating phase is strongly controlled by the shape of iron particles. Using the VPI procedure, the irregular surface of iron particles may cause discontinuities of insulating layer, while the spherical iron particles are well covered with continuous evenly distributed insulating layer.

Surface modification of iron particles with polystyrene and surfactants under high-energy ball milling

Metal–polymer composites are widely used in many applications including efficient microwave absorbing materials. Interface makes up a great fraction in the composite bulk and may significantly affect the functional properties of the composite. In this work, we have modified the surface of iron particles with polystyrene and fluorine-substituted/alkyl carbon acids by wet mechanochemical treatment. The study was performed by means of Fourier-Transform Infrared (FT-IR) spectroscopy, Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy and X-ray Photoelectron Spectroscopy (XPS). It is shown that wet mechanochemical treatment is accompanied by chemisorption of the surfactant molecules on the iron particle surface through the formation of the carboxylate derivatives and catalytic dehydrogenation resulting in the formation of condensed polyaromatic structures. Surface modification of particles with polystyrene is observed in all cases regardless of the presence and type of surfactant in the milling environment. Stable binding of polystyrene with the particle surface is achieved by different ways, including binding through the oxygen-containing groups, covalent bonding with the polyaromatic structures and/or tails of the chemisorbed fluorine-substituted acid. As-formed organic layers stabilize the metal particles preventing them from oxidation and agglomeration and increase their chemical compatibility with polymer matrices in subsequent fabrication of the metal–polymer composites.

Efficient Methane Conversion to Hydrogen by the Force-Activated Oxides on Iron Particle Surfaces

Mechanochemically activated iron oxide formation on α-iron (Fe) microparticles for the efficient reaction with methane (CH4) was investigated using a simple milling process to successfully clarify the efficient CH4 adsorption as well as the C–H bonding dissociation. First, the oxides with different oxidation degrees (i.e., disordered or ordered iron oxides) were formed on the Fe by mechanochemical milling under an oxygen atmosphere. The surface analyses by X-ray diffraction, Raman, and X-ray photoelectron spectroscopy (XPS) revealed that the surface iron oxides consisted of two phases (α-Fe2O3 and Fe3O4), and the Fe2O3-like structure was dominantly grown on the near-surface of the disordered iron oxides during the initial oxidation time (0.08 and 0.80 h). Furthermore, the signals from an electron spin resonance analysis suggested dangling bondings on the disordered oxides, indicating the successful formation of the active O sites. Second, the mechanochemical reaction of the resultant iron oxide surfaces with CH4 was investigated. As a result, the efficient CH4 adsorption as well H2 generation were prominently observed on the disordered oxides, indicating an effectively dissociative adsorption. XPS analysis of the resultant particles revealed that the C–H bonding dissociation dominantly occurred on the near-surface oxygen atoms. Furthermore, using a molecular orbital calculation analysis, the activated O atoms with dangling bondings in the disordered iron oxides were found to affect the C–H dissociation of the adsorbate molecules (e.g., CH4 and CH3•) and exhibit an efficient H2 generation. On the other hand, the O atoms in the ordered lattice could not induce the C–H dissociation of CH3• to produce the equilibrium adsorption/desorption states and lower H2 generation amount, suggesting the importance of both the force-induced activated O atoms and closest interatomic distances. Therefore, we first achieved the efficient mechanochemical decomposition of CH4 and CH3• to generate H2 by the disordered iron oxide surfaces on α-Fe particles.

Effective Functionalization of Disordered Oxide Lattices on Iron Particle Surfaces Using Mechanochemical Reactions

The mechanochemical surface functionalization of iron oxides with disordered lattices on bare iron (Fe) particles was investigated using simple milling processes to clarify the formation mechanism of the oxide layer and investigate the near-surface models with different states. The homogeneous α-Fe particles at the milling equilibrium were first prepared under an argon atmosphere. After the subsequent milling reaction of the particles with oxygen molecules, the surface analyses by X-ray diffraction and Raman and X-ray photoelectron spectroscopies revealed that the near-surface layers consisted of two iron oxide phases (α-Fe2O3 and Fe3O4) through oxygen atom diffusion, and the α-Fe2O3 was dominantly grown on the near surface. During the initial reaction, the signals from an electron spin resonance suggested the dangling bond formation on α-Fe2O3. The oxygen atoms effectively induce disordered lattices in the local area to form oxidized Fe3+ clusters, and the geometric distortion formed the dangling bonds, ...

The role of polyaniline in the formation of iron-containing nanocomposites

Polyaniline (PANI)-coated iron-based nanocomposites with a range of magnetisation and coercivity values were produced by in situ polymerisation of aniline and chemical reduction of Fe3+ by BH4 −. We have varied the ratio of aniline to iron, keeping the amount of BH4 − added constant, and vice versa. Room-temperature magnetisation loops, X-ray diffraction patterns, Mossbauer spectra and transmission electron microscopy images show that PANI plays two distinct roles: on the one hand, it coats the iron particle surface, preventing oxidation of the Fe cores and, on the other, it enhances the formation of an Fe100−x B x alloy. The incorporation of boron in the alloy is facilitated by the polymer entrapment of small Fe nuclei. The mean particle size determined for composites obtained with low PANI content is (50 ± 20) nm, while for PANI-rich composites (30 ± 10) nm particles are formed.

Study on Preparation Process of Magnetic Abrasive Particles

Abstract: With the industrial development and improvement of mechanical product quality, the demand of part surface quality and accuracy gets more and more high. As some parts of complex shape, can’t be machined by the traditional processing technology, therefore, the magnetic abrasive technique was proposed. The magnetic abrasive particles play an important role in the magnetic abrasive finishing, it use strong magnetic iron particles and abrasive particles mixed together (called magnetic abrasive). The prepared method of magnetic abrasive one of is sintering method, the aim is to change the internal structure of abrasive particles, make the abrasive particles is distributed on the surface of magnetic iron particles, get a kind of magnetic abrasive, which can be magnetized in a magnetic field and improve processing efficiency and surface quality in magnetic abrasive finishing. In this paper, sintering method is used to make iron particles, abrasive particles mixed with some binder, after suppression, drying, sintering, cooling, break up and sieving, analysis surface morphology and composition of the magnetic abrasive particles by scanning electron microscopy, discusses the effect of the abrasive particles size ratio, sintering time, sintering temperature for the finishing performs, the preparation process of the magnetic abrasive has been optimized, work out the standard of preparation of the magnetic abrasive process

Magnetorheology of carbonyl iron particles coated with polypyrrole ribbons: The steady shear study

The aim of this study is a preparation and application of polymer coating on the surface of carbonyl iron particles. Oxidative polymerization of the pyrrole provides ribbon-like morphology. Compact coating of particles has a slightly negative impact on their magnetic properties (measured for magnetic field strength in the range from 0 to 300 mT); however, there is a significant increase in sedimentation stability. The effect of the particle concentration and temperature on the toughness of the internal structures was also investigated.

Surface modification of iron particles with a polyfluorinated disulfude: Effect of solvent and temperature

Adsorption of bis(2-chloro-3-oxaperfluorobutyl) disulfide from nonaqueous solutions onto the surface of carbonyl iron particles was studied with the aim of modification of these particles. The adsorption parameters were calculated using the Langmuir equation from the adsorption isotherms obtained in the interval 20-60°C. With an increase in temperature and in the solvent affinity for the modifying agent, the limiting amounts of the reagent that has interacted with the iron particle surface increase. This fact suggests the chemisorption nature of the process. The products of the reaction of iron with the disulfide can be desorbed from the particle surface.

Strain induced martensite formation in PM nickel steels

Powder metallurgy (PM) nickel steels are often selected because they have high strength, high impact resistance and good abrasion resistance. The microstructure of slowly cooled PM nickel steels typically contains pearlite, bainite, martensite and a fair volume fraction of retained austenite. Since volume diffusion is really low at conventional sintering temperatures [1120–1150°C (≈2050–2100°F)], nickel rich areas are usually found where prior admixed nickel particles were located, i.e. at the surface of iron particles and in sintering necks. Therefore, there is a discrepancy between the rather low mechanical properties of austenite and the high strength of PM nickel steel. Hence, the hypotheses that stress induced or strain induced martensite formation takes place during mechanical testing have been investigated. Results show that martensite forms during mechanical testing, and its final volume fraction is proportional to nickel content.

Iron-based soft magnetic composites with Mn–Zn ferrite nanoparticles coating obtained by sol–gel method

This paper focuses on iron-based soft magnetic composites which were synthesized by utilizing Mn–Zn ferrite nanoparticles to coat iron powder. The nanocrystalline iron powders, with an average particle diameter of 20nm, were obtained via the sol–gel method. Scanning electron microscopy, energy dispersive X-ray spectroscopy and distribution maps show that the iron particle surface is covered with a thin layer of Mn–Zn ferrites. Mn–Zn ferrite uniformly coated the surface of the powder particles, resulting in a reduced imaginary permeability, increased electrical resistivity and a higher operating frequency of the synthesized magnets. Mn–Zn ferrite coated samples have higher permeability and lower magnetic loss when compared with the non-magnetic epoxy resin coated compacts. The real part of permeability increases by 33.5% when compared with the epoxy resin coated samples at 10kHz. The effects of heat treatment temperature on crystalline phase formation and on the magnetic properties of the Mn–Zn ferrite were investigated via X-ray diffraction and a vibrating sample magnetometer. Ferrites decomposed to FeO and MnO after annealing above 400°C in nitrogen; thus it is the optimum annealing temperature to attain the desired permeability.

Thin Organic Layers Grown on the Surface of Iron Particles under High-Energy Ball Milling in the Presence of Polystyrene and Various Surfactants: X-ray Absorption and Photoelectron Spectroscopy Studies

High-energy mechanical milling is conventionally and successfully used for fabrication of magnetic filler particles for metal–polymer composites applied in different microwave absorption devices. Chemical modification of the metal surface by wet mechanochemical synthesis allows one to improve chemical compatibility between a metal particle and a host polymer matrix in the composites. In this paper, we have studied the structure of an as-modified thin organic layer depending on different surfactants used under mechanical milling of iron powder in the polystyrene solution. The study was performed with high-resolution X-ray spectroscopic techniques, using synchrotron radiation from the BESSY II storage ring. It has been shown that stearic acid, added as a surfactant into the milling environment, forms a close-packed thin layer, but chemical inertness of its alkyl groups does not provide strong anchoring of the polystyrene fragments to the iron surface. The perfluorononanoic acid molecules form a thin layer w...

Surface structure analysis of stabilized iron particles by XPS with chemical derivatization

The surface structure of iron particles stabilized by oleic acid and unsaturated alcohol, isophytol, was studied by XPS and chemical derivatization. It was shown that there are hydroxyl groups, iron carboxylate complexes, and iron complexes coordinated with alcohol groups in the proportion one part metal to one part ligand on the outer surface of the stabilizing coating. The formation of stabilizing layers based on unsaturated compounds leads to the conversion of double bonds, resulting in the polymerization of oleic acid and isophytol in condensed close-packed self-organizing stabilizing layers on the surface of iron particles.

Study on Sintering Process of Magnetic Abrasive Particles

The magnetic abrasive prepared by sintering method, the aim is to change the internal structure of abrasive particles by sintering method, make the abrasive particles parceled on the surface of magnetic iron particles, and compared with the abrasive particles phase to get a kind of magnetic abrasive particles with high durability, strong magnetic, which can be magnetized in a magnetic field and improve processing efficiency and surface quality in magnetic abrasive machining. Sintering is used to prepare magnetic abrasive in this paper, to make iron particles, abrasive particles mixed with some binder, after suppression, drying, sintering, cooling, crushing and screening. This paper makes analysis for surface morphology and composition of the magnetic abrasive particles by scanning electron microscopy and discusses the effect that the abrasive particles size ratio, sintering time, sintering temperature on the magnetic abrasive, and the preparation of the magnetic abrasive process has been optimized.

Degradation of aqueous carbamazepine in ultrasonic/Fe 0/H 2O 2 systems

This study investigated the suitability of carbamazepine (CBZ) oxidation by an improved Fenton's process. CBZ (42 μM) is used as probe for non-halogenated pharmaceuticals. The experiments were performed at room temperature (21 ± 2 °C) and different pHs (3, 5, 7 and 9). Powerful oxidative hydroxyl radicals for CBZ oxidation are produced by H 2O 2 (12.5–100 mM) and Fe 0 (0.44–3.57 mM) additives under low frequency ultrasonication (40 kHz). Results showed no CBZ oxidation in the presence of an OH scavenger (MeOH), confirming the Fenton's nature of the process. Acid-washed Fe 0 feeding showed increased CBZ oxidative degradation up to 85%. Recycling experiments demonstrated also the ability of Fe 0 to maintain its capability of releasing Fe 2+ into the media to promote OH generation for CBZ degradation (>80% after 4 cycles). This was ascribed to the cracking effect on the surface of iron particles preventing thereby the formation of passive oxide. The process was also efficient in natural waters containing different species (e.g. Na +, Ca 2+, Mg 2+, Cl −, SO 4 2−, HCO 3 −, NO 3 −, etc.). Intermediate oxidation products (by-products) were identified by LC/MS. However, by-products disappeared with longer experimental durations. The Fe 0/H 2O 2 ultrasonic process is a promising technique for oxidative removal of non-halogenated pharmaceuticals under mild conditions.

영가철과 활성슬러지를 이용한 독립영양방식의 퍼클로레이트 제거: 회분배양연구

Perchlorate () is a contaminant found in surface water and soil/ground water. Autotrophic perchlorate-reducing bacteria (PRB) use hydrogen gas () as an electron donor to remove perchlorate. Since iron corrosion can produce , feasibility of autotrophic perchlorate-removal using zero-valent iron (ZVI) was examined in this study using activated sludge that is easily available from a wastewater treatment plant. Batch test showed that activated sludge microorganisms could successfully degrade perchlorate in the presence of ZVI. The perchlorate biodegradation was confirmed by molar yield of as perchlorate was degraded. Scanning electron microscope revealed that rod-shaped microorganisms on the surface of iron particles used for the autotrophic perchlorate-removal, suggesting that iron particles could serve as supporting media for the formation of biofilm as well. DGGE analyses revealed that microbial profile of the inoculum (activated sludge) was different from that of biofilm sample obtained from the ZVI-added enrichment culture used for -degradation. A major band of the biofilm sample was most closely related to the class Clostridia.

Synthesis of polypyrrole coatings on surface of iron particles

AbstractA simple oxidative polymerization of pyrrole (Py) directly onto the surface of Fe microparticles was applied to enhance its mechanical properties and to increase the content of carbon in resulting material. The study is focused on investigation of the chemical synthesis of polypyrrole (PPy) coatings on the surface of iron particles, and their effect on the internal and surface structure. Moreover, the effect of PPy coating on the compressibility of coated Fe powder is analyzed. Namely, a set of specimens was uniaxially pressed in a steel die. Compaction pressures ranged from 100 up to 600 MPa. To quantify the compressibility of powders, the compressibility equation proposed by Panelli and Ambrosio Filho has been. It was found that PPy coating has a positive effect on the compaction behavior of iron powders.Detection and quantification of the PPy coatings obtained were performed by means of pyrolysis gas chromatography (Py‐GC). Both the light optical and scanning electron microscopy (LOM, SEM) were used to characterize the morphology and surface appearance of samples coated with PPy. It was found that the content of PPy in final powder material can be controlled by conditions of chemical oxidative polymerization process. The surface morphology of powder particles coated with PPy layers was changed in compliance with PPy content. Copyright © 2010 John Wiley & Sons, Ltd.

Microstructure evolution in Fe–Mn–C during step sintering

Mn was introduced, with graphite, as fine ferromanganese particles to form compacts of Fe–3%Mn–0·5%C. Each was sintered in dry 25%H2 + 75%N2 for 3 min at 770, 1040, 1080, 1170 and 1220°C respectively, held for 3 min and quenched. The surface of a successively heated specimen was similarly examined. Specimens were sectioned and, especially the reacting ferromanganese particles and adjoining regions, investigated using light and scanning electron microscopy and EDX. Development of microstructure and microcompositions during sintering was related, from 740°C, to diffusion and condensation of Mn vapour on iron particle surfaces and subsequent chemical reactions. Above 1080°C microstructures included features resulting from a transient liquid phase, in accord with a ∼45 wt%Mn ternary eutectic calculated by ThermoCalc. The thicknesses of the highly Mn enriched regions were substantially higher than those resulting from bulk Mn diffusion in the Fe lattice; our interpretation invokes predominant operation of another type of mechanism: diffusion induced grain boundary migration.

Preparation and Compaction Behaviour of Poly(methyl methacrylate) Coated Iron Microparticles

The p oly(methyl methacrylate) (PMMA) coatings onto surface of iron particles were electrochemically prepared and the efiect on both surface structure and internal structure of the resulted material after compaction was carried out. The electrochemical polymerization treatment was performed in a ∞uidized bed electrolyzer using sulphuric acid solution containing potassium persulphate and methyl methacrylate (MMA). The surface topography and the microstructure of the samples were observed by scanning electron microscopy (SEM) and optical microscopy (OM). It was found that the PMMA layer coated onto iron particles results in improvement of their compressibility compared with uncoated powders, and classical lubricants are not necessary for compacting particles coated.