Iron Particle Size Research Articles

Activation Energies for Chain Growth Propagation and Termination in Fischer–Tropsch Synthesis on Iron Catalyst as a Function of Catalyst Particle Size

The influence of the catalyst particle size in determining Fischer–Tropsch synthesis (FTS) performance for nano-structured iron catalysts was investigated. The catalysts were prepared by a microemulsion method and to achieve a series of catalysts with different iron particle size, the water-to-surfactant molar ratio (W/S) in the microemulsion system varied from 4 to 12. The results demonstrate that by decreasing the levels of active phase of the iron catalyst, the termination rates for chain growth are increased compared to the propagation rates. In addition, the activation energy for chain propagation is lower than for chain termination, and this difference (Et – Ep) for the hydrocarbon product distributions which is characterised by α1, is lower than the hydrocarbon product distribution which is characterised by α2 The results indicate the H2 concentration on the catalyst surface is decreased by increasing the catalyst particle size. Thus, the dependence of α (α1, and/or α2) on H2 partial pressures is increased by decreasing of catalyst particle size and the dependence of α2 on H2 partial pressures is weaker than for α1.

Systematic variation of the sodium/sulfur promoter content on carbon-supported iron catalysts for the Fischer–Tropsch to olefins reaction

The Fischer–Tropsch to olefins (FTO) process is a method for the direct conversion of synthesis gas to lower C2–C4 olefins. Carbon-supported iron carbide nanoparticles are attractive catalysts for this reaction. The catalytic activity can be improved and undesired formation of alkanes can be suppressed by the addition of sodium and sulfur as promoters but the influence of their content and ratio remains poorly understood and the promoted catalysts often suffer from rapid deactivation due to particle growth. A series of carbon black-supported iron catalysts with similar iron content and nominal sodium/sulfur loadings of 1–30/0.5–5wt% with respect to iron are prepared and characterized under FTO conditions at 1 and 10bar syngas pressure to illuminate the influence of the promoter level on the catalytic properties. Iron particles and promoters undergo significant reorganization during FTO operation under industrially relevant conditions. Low sodium content (1–3wt%) leads to a delay in iron carbide formation. Sodium contents of 15–30wt% lead to rapid loss of catalytic activity due to the covering of the iron surface with promoters during particle growth under FTO operation. Higher activity and slower loss of activity are observed at low promoter contents (1–3wt% sodium and 0.5–1wt% sulfur) but a minimum amount of alkali is required to effectively suppress methane and C2–C4 paraffin formation. A reference catalyst support (carbide-derived carbon aerogel) shows that the optimum promoter level depends on iron particle size and support pore structure.

Relationship between the dust flame propagation velocity and the combustion mode of fuel particles

A possibility of determining the regime of combustion of individual fuel particles on the basis of the dependence of the flame velocity on the fuel and oxidizer concentrations is considered by an example of a dust flame of microsized metal particles with diameters d10 < 15 μm and particle concentrations from ≈1010 to 1011 m−3 in oxygen-containing media at atmospheric pressure. The combustion mode (kinetic or diffusion) is responsible for the qualitative difference in the character of the normal velocity of the flame as a function of the basic parameters of the gas suspension. The analysis of such experimental dependences for fuel-rich mixtures shows that combustion of zirconium particles (d10 = 4 μm) in a laminar dust flame is controlled by oxidizer diffusion toward the particle surface, whereas combustion of iron particles of a similar size is controlled by kinetics of heterogeneous reactions. For aluminum particles with d10 = 5–15 μm, there are no clearly expressed features of either kinetic or diffusion mode of combustion. To obtain more information about the processes responsible for combustion of fine aluminum particles, the flame velocity is studied as a function of the particle size and initial temperature of the gas suspension. It is demonstrated that aluminum particles under the experimental conditions considered in this study burn in the transitional mode.

Novel Fe/MnK‐CNTs nanocomposites as catalysts for direct production of lower olefins from syngas

Novel Fe/MnK‐CNTs nanocomposites are developed as catalysts for direct production of lower olefins from syngas, delivering a high iron time yield of 337.2 μmolCO· ·s−1 with 51.3%C selectivity toward C2C4 olefins under the optimal reaction conditions (270°C, 2.0 MPa, 30,000 mL h−1 ). These catalysts are optimized by varying calcination temperature from 150 to 400°C. Multiple techniques including transmission electron microscopy, Elemental mapping, X‐ray diffraction, X‐ray photoelectron spectroscopy, H2‐temperature‐programmed reduction, and Raman were employed to reveal the relationship between the catalyst nature and unique catalytic behavior. In particular, the resultant catalyst from the calcination temperature of 220°C exhibits the highest selectivity of C2C4 olefins as well as good stability, which are enabled by the trade‐off among the effects of iron particle sizes, promoters, metal‐support interaction and support surface chemistry. Moreover, influences of reaction temperature, reaction pressure and space velocity are also investigated. © 2016 American Institute of Chemical Engineers AIChE J, 63: 154–161, 2017

Microstructure Characteristic and Phase Evolution of Refractory Siderite Ore during Sodium-carbonate-added Catalyzing Carbothermic Reduction

Thermodynamic analysis of refractory siderite ore during carbothermic reduction was conducted. Microstructure characteristics and phase transformation of siderite ore during sodium-carbonate-added catalyzing carbothermic reduction were investigated. X-ray diffraction (XRD), scanning electron microscopy and energy-dispersive analysis of X-rays were used to characterize the reduced samples. Results indicate that the solid reaction between FeO and SiO2 is inevitable during carbothermic reduction and the formation of fayalite is the main hindrance to the rapid reduction of siderite. The phase transformation of present siderite ore can be described as: siderite-magnetite-metallic iron, complying with the formation of abundant fayalite. Improving the reduction temperature (≤ 1050 °C) and duration is helpful for the formation and aggregation of metallic iron. The iron particle size in the reduced ore was below 20 μm, and fayalite was abundant in the absence of sodium carbonate. With 5% Na2CO3 addition, the iron particle size in the reduced ore was generally above 50 μm, and the diffraction intensity associated with metallic iron in the XRD pattern increased. The Na2O formed from the dissociation of Na2CO3 can catalyze the carbothermic reduction of the siderite. This catalytic activity may be mainly caused by an increase in the reducing reaction activity of FeO.

Oxidation of priority and emerging pollutants with persulfate activated by iron: Effect of iron valence and particle size

Persulfate (PS) activated with iron to generate sulfate radicals was employed in the oxidation of Diuron (selected as an example of priority pollutant), Caffeine and Ibuprofen (examples of emerging pollutants whose consumption is widespread). The effect of iron valence (0, 2 and 3) and particle size of Zero-Valent Iron (ZVI) was studied in a batch isothermal reactor at 20°C. The efficiency of the process was evaluated in terms of pollutant and TOC removal, as well as oxidant and iron consumption. Moreover Microtox standard procedure was employed in ecotoxicity measurements.When Fe2+ was employed as PS activator, an undesired reaction consumed both Fe2+ and SO4-. However, in case of ZVI, the release of Fe2+ to the media occurs at the particles surface through acid corrosion and reaction with PS. This allows a controlled production rate of SO4- through a slow release of Fe2+ by selecting the proper particle size, which helps minimizing this undesirable reaction increasing the efficiency of the oxidant. Better results were obtained with ZVI than with Fe2+ especially when regeneration of Fe3+ to Fe2+ through oxidation intermediates did not occur.A kinetic model capable of describing the evolution of pollutant, oxidant, and iron concentrations (at the different oxidation stages) as well as the mineralization was proposed and validated.

Investigation of the finishing characteristics in an internal tube finishing process by magnetic abrasive finishing combined with electrolysis

In this research, the finishing characteristics in a tube's internal finishing process using the method of magnetic abrasive finishing (MAF) combined with electrolysis has been studied. Electrolysis produces an aluminium oxide film that accelerates the removal of the initial hairline morphology on the surface. Subsequently, the film is removed with MAF. This process significantly minimises the surface roughness in a reduced time. The way the finishing conditions, such as the pole–pipe gap, iron particle size and abrasiveness combinations, and processing time affected the surface morphology in the MAF machining process has been particularly examined. The surface roughness was measured and images of the finished surfaces were recorded to study the morphology changes. Prolonged electrolysis finishing was seen to deepen the oxidation film and pits, which adversely affects the surface. This evidence suggests that the pit residuals contribute to higher surface roughness values.

Effect of magnetic field on reduction of magnetite

The reduction behaviour of magnetite oxide by hydrogen below Curie temperature was investigated in the presence of external magnetic field by thermogravimetric analysis. The reduction rate of magnetite powder increased with increasing external magnetic field strength below Curie temperature of magnetite. In order to figure out the effect of external magnetic field on reduction of magnetite, two types of magnetite, powder and pellet, were studied. It was possible to enhance the reduction rate of magnetite powder, because the particles of magnetite in the presence of an external magnetic field exposed more surface to the reducing gas. The effects of reduction temperature, reducing agent, iron oxide type, particle size and specimen shape on the metallisation behaviour of magnetite were visually clarified below the Curie temperature under the influence of external magnetic field. Despite of the increase in reduction degree by applied magnetic field, the rate controlling step was not changed due to the formation of porous metallic iron layer that keeps the path for reducing agent to approach the unreduced iron oxide in the core of magnetite particle.

Characterization of solid magnetic nanoparticles by means of solid sampling high resolution continuum source electrothermal atomic absorption spectrometry

Direct determination of iron concentration and particle size of solid MNPs using HR CS GFAAS.

Aerosol synthesis of phase-controlled iron-graphene nanohybrids through FeOOH nanorod intermediates.

Iron-based nanoparticles form the basis for a host of sustainable alternative technologies based on this earth-abundant, low-toxicity element that can adopt a variety of oxidation states, crystal phases, and functions. Control of size, shape, and phase stability is a challenge for many nano-iron-based technologies, especially those involving Fe0 that is susceptible to oxidation under ambient conditions. This article presents a continuous method for hybridizing Fe-based nanoparticles with carbon in the form of graphene-encapsulated Fe-based particles with core-shell symmetry that allows flexible control of iron particle size, shape, and phase stability. The method uses FeOOH nanorods and graphene oxide as precursors, and subjects them to an aerosol-phase microdroplet drying and annealing process to yield a range of Fe/C nanohybrids whose structure can be controlled through adjustment of aerosol process temperature and post-synthesis thermal treatment conditions. We demonstrate that FeOOH nanorods can be successfully encapsulated in graphene, and transform during annealing into encapsulated Fe3O4 or Fe0 nanoparticles by reductive fragmentation, where the graphene nanosack acts as a carbothermic reductant. The hybrids are characterized by vibrating sample magnetometry and Cr(VI) reduction rates in aqueous media. The Fe0-graphene hybrids show high activity, good stability, and good recyclability in aqueous Cr(VI) removal due to the effect of graphene encapsulation. The present work suggests this rapid and continuous synthesis method can produce stable Fe-based materials, and can be extended to other metal systems, where graphene encapsulation can induce in situ reduction of metal oxide precursors into zero-valent metal-graphene hybrids.

Experimental Analysis of MR Fluid by Magneto-Rheological (MR) Damper

Magneto-rheological fluids belong to a group of non-Newtonian fluids, and represent a group of purely-viscous fluids with the controllability of their properties by means of a magnetic field. In the present work, MR damper setup has designed and fabricated. MR fluid is prepared by mixing the lubricating oil, distilled water and iron particles of size 500 meshes in the standard proportions. During the experimentation, arrangement is made for load which falls on the piston head of MR damper to determine the damping effect. For every reputation, time and displacement of piston in the MR fluid is noted. Based on these parameters, velocity of the piston and rate of acceleration with respect to time and acceleration with respect to displacement is determined. Damping effect is calculated by using acceleration with respect to time and displacement respectively.

A facile controlled in-situ synthesis of monodisperse magnetic carbon nanotubes nanocomposites using water-ethylene glycol mixed solvents

Abstract In this paper, a facile and controllable method for in-situ synthesis of the magnetic carbon nanotubes nanocomposites (Fe/CNTs) in water-ethylene glycol (EG) mixed solvents is reported by the deposition–precipitation method following annealing. The effect of water/EG ratio on the physico-chemical properties of magnetic Fe/CNTs is investigated by X-ray diffraction, transmission electron microscope, scanning electron microscopy, thermogravimetric analysis and physical property measurement system. The results indicate that the iron particle size distribution and grain size can be well-tuned by adjusting the water/EG ratio. With the variation of EG fraction in the mixed solvent, the nucleation, growth and crystallization of magnetic iron oxides with a controllable morphologies and particle sizes attached on the exterior surface of CNTs can be achieved. The as-prepared Fe/CNTs nanocomposites display superparamagnetic property at room temperature and the water/EG ratio determines the magnetization of the sample. Possible formation mechanism for magnetic Fe/CNTs is proposed based on the characterization results.

Study of Reflectance Spectroscopy in River Sediments

In the present study, Sinos River basin sediments of south Brazil were characterized using reflectance spectroscopy in 350-2500 nm range. This basin is located in an industrialized and densely populated area. The results focus on the influence of aluminum and iron content, particle size, organic matter, and mineral composition in the sediment samples. Fe and Al concentrations were determined by X-ray fluorescence. Clay minerals were determined by an X-ray diffractometer and reflectance spectral curves with a high-resolution spectroradiometer ASD Field Spec. Results of the mineralogical analyses showed that quartz, kaolinite, and smectite are scattered over the entire basin for most of the studied sites. Higher reflectance was observed for the samples after removal of the organic matter, indicating features associated with clay mineral and Fe. Likewise, higher reflectance was observed for the smaller size fraction, indicating the influence of mud in the spectral albedo. At the 2200 nm wavelength, the Al-OH bond of clay mineral was detected in the spectra. This was associated with Al content. Features due to the presence of iron oxides were observed between 470-580 nm and 650-850 nm.

Growth Enhancement by Intramuscular Injection of Elemental Iron Nano- and Microparticles

We studied the influence of highly dispersed elemental iron preparations on the productivity and metabolism of broiler chicks. Iron nanoparticles were synthesized using high-temperature condensation. No toxicity of the nanoparticles and their agglomerates was observed in an experiment utilizing a genetically engineered luminescent strain of Escherichia coli (K12 TG1). The efficiency of single intramuscular injections in 120 broiler chicks (Smena 7) of preparations containing iron particles with sizes of 80 ± 5 nm (nanoparticles), 923.7 ± 29.6 nm (nanoparticle agglomerates) or 9.8 ± 0.4 nm (microparticles) was compared. The use of these preparations increased the live weight of the chickens. The maximum difference in live weight was observed 4 days after the injection of nanoparticles (9.8%; P ≤ 0.01), 17 days after the injection of agglomerates (4.97%; P ≤ 0.01), and 17 days after the injection of microparticles (8.5%; P ≤ 0.01). Injections with iron preparations were accompanied by increased protein deposition, causing daily weight gain in chickens. This gain was higher by 1.3 - 4.3 g when nanoparticles were used, by 0.6 - 1.4 g for agglomerates, and by 0.1 - 1.4 g for microparticles. The iron preparations promoted an increase in the arginine content of the chicken liver compared with that of control animals. After the use of nanoparticles, the arginine content increase was 2.25% (P ≤ 0.05) within 1 day and 3.78% (P ≤ 0.05) 7 days after injection. The arginine content increased by 2.08% (P ≤ 0.05) 7 days after the use of agglomerates and by 3.86% (P ≤ 0.05) 21 days after the use of microparticles. Thus, similar biological effects were shown for different sizes of elemental iron particles. These effects were enhanced as the particle size decreased, although further investigation is required before the joint use of metal nanoparticles and arginine.

On the optimization of activated carbon-supported iron catalysts in catalytic wet peroxide oxidation process

Different homemade iron-activated carbon catalysts (Fe/AC) have been studied in the CWPO of phenol at mild conditions (atmospheric pressure and 50°C). Both iron content and the way to introduce iron active phase in Fe/AC catalysts were analyzed to select the most stable and efficient activated carbon-supported iron catalyst. The major differences were found on their surface properties, mainly those related to iron distribution and iron particle size. Catalysts prepared by two-consecutive steps of impregnation, regardless of iron content, always presented lower leaching phenomena of iron to the reaction medium than those prepared by one-step wetness impregnation. This higher stability could be indicating an improved metal-support interaction as a consequence of the two-step methodology used to incorporate the iron, which leads to the formation of small iron particles very homogeneous in size (≈3nm). The best performance balanced between activity and stability was obtained with 2% iron 2-steps catalyst (2sFe/CN) which gave rise to complete removal of phenol after 60min, maximal reduction of TOC content and optimal use of the stoichiometric amount of H2O2 added during batch experiments at 50°C, atmospheric pressure, 500 mgL−1 catalyst loading, 100 mgL−1 and 500 mgL−1 of phenol and hydrogen peroxide concentrations, respectively, at pH0=3.The study of H2O2 decomposition in the presence of an excess of MeOH, a well-known OH scavenger, has been an useful tool to analyze the behavior of heterogeneous catalysts in CWPO reactions. 2sFe/CN catalyst led to a better and efficient use of H2O2 with higher hydroxyl radical yield in the presence of phenol instead of methanol, as a consequence of phenol adsorption onto the catalyst surface which minimizes the inefficient decomposition of H2O2 at the same operating conditions.

Orthogonal Experiments on Direct Reduction of Carbon-bearing Pellets of Bayer Red Mud

To recycle residual iron efficiently in Bayer red mud, three-factor three-level orthogonal experiments on carbon-bearing pellets of Bayer red mud were conducted on the basis of their characteristics. The influences of CaO dosage, temperature and roasting time on total iron content and iron recovery of reduced iron powder were studied. Results showed that these factors slightly influenced iron recovery, but significantly influenced total iron content. The principal factor influencing total iron content was CaO dosage, followed by temperature and roasting time. An increase in CaO dosage could decrease total iron content, whereas an increase in temperature and an extension of roasting time could improve total iron content. The reduced iron powder with total iron content of 88.41% and iron recovery rate of 97.97% can be obtained under the optimal conditions of temperature of 1 275 °C, roasting time of 60 min and CaO dosage of 7.5%. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses of the reduced pellets showed that iron minerals in red mud were almost completely reduced to metallic iron. The principal factor influencing the total iron content of reduced iron powder was the grain size of metallic iron particles. An increase in CaO dosage hindered the growth of metallic iron particles, whereas an increase in temperature and an extension of roasting time could neutralise the effect of CaO dosage. Therefore, CaO dosage should be decreased when iron minerals in red mud can be adequately reduced into metallic iron.

Instrument study of the Lunar Dust eXplorer (LDX) for a lunar lander mission II: Laboratory model calibration

A dust trajectory detector placed on the lunar surface is exposed to extend people’s knowledge on the dust environment above the lunar surface. The new design of Lunar Dust eXplorer (LDX) is well suited for lunar or asteroid landers with a broad range of particle charges (0.1–10fC), speeds (few ms−1 to few kms−1) and sizes (0.1–10μm). The calibration of dust trajectory detector is important for the detector development. We do present experimental results to characterize the accuracy of the newly developed LDX laboratory model. Micron sized iron particles were accelerated to speed between 0.5 and 20kms−1 with primary charges larger than 1fC. The achieved accuracies of the detector are ±5% and ±7% for particle charge and speed, respectively. Dust trajectories can be determined with measurement accuracy better than ±2°. A dust sensor of this type is suited for the exploration of the surface of small bodies without an atmosphere like the Earth’s moon or asteroids in future, and the minisatellites are also suitable carriers for the study of interplanetary dust and manned debris on low Earth orbits.

Preparation and characterization of submicron hybrid magnetic latex particles

Micrometer magnetic hybrid particles are of great interest in biomedical field, and various morphologies have been prepared via encapsulation processes. Regarding submicron, only few processes have been investigated and the most recent one leading to highly magnetic submicron magnetic hybrid particles is based on oil in water magnetic emulsion (MES) transformation. The encapsulation of magnetic iron oxide nanoparticles forming oil in water MES was investigated using different styrene/cross‐linker divinylbenzene volume ratio in the presence of potassium persulfate initiator. The encapsulation performed in this work is basically conducted by using well‐defined oil in water MES as a seed in radical emulsion polymerization. The chemical composition, morphology, iron oxide content, magnetic properties, electrokinetic properties, particle size, and size distribution of the prepared magnetic hybrid particles were examined using various techniques. The desired perfect magnetic core and polymer shell morphology were successfully obtained, and the final magnetic hybrid particles are superparamagnetic in nature and exhibit high iron oxide content (64 wt %). Copyright © 2015 John Wiley &amp; Sons, Ltd.

Compressive behaviour of polypropylene filled with iron ore tailings

Purpose – This paper aims to produce iron ore tailings reinforced polypropylene composites (ITR-PPCs) from conventional compo-casting (CC) and a proposed compo-indirect squeeze casting (C-ISC) processes. It intends to quantify the compressive behaviour of ITR-PPC with respect to production process, iron ore tailings volume and particle size inclusion in polypropylene (PP) through controlled material and compressive testing. The study aims to provide useful information on possibility of the use of ITR-PP for compressive applications which will culminate to judicious use of iron ore tailings that is been piled up as waste material at the iron ore beneficiation sites. Design/methodology/approach – ITR-PPC compression specimens were produced using C-ISC and CC processes. Prior to production, the iron ore tailings was dried at room temperature according to ASTM 618, ASTM 171 and ASTM E 41. The different particle sizes were generated using standard laboratory sieves. Uniaxial compressive test procedure according to ASTM D 695 was carried out on ITR-PPC compression specimens with length/diameter ratio equal to 2.0 under standard laboratory atmosphere on an Instrom 3,369 machine. Findings – It was discovered that pure PP produced using the C-ISC process exhibited better compressive strength and Young’s modulus of about 12 and 4.5 per cent, respectively, while a reduction of 9.2 per cent in yield strength was recorded. ITR-PPCs with 150-μm fillers produced from C-ISC process have lower yield stress, compressive strength and Young’s modulus at volume contents above 10 per cent. It also exhibited lower strain at fracture at volume content above 15 per cent, while composites filled with 212- and 300-μm particle size iron ore tailings using the C-ISC process had better strain at fracture. Research limitations/implications – The present work cannot ascertain the compressive behaviour of ITR-PPC produced from other production processes, hence the need for further work in this area. Practical implications – The paper provides an avenue to address the pollutant effect of iron ore tailings by putting it to judicious use through addition as fillers in plastics. It also removes the need for expensive and repeated experimentation to determine the compressive behaviour of ITR-PPCs. Originality/value – This paper has brought to fore the need to study iron ore tailings as filler in plastics and other material matrices.

Study on Magnetization and Detection the Metal Particle in Harmonic Magnetic Field

Inductance detection methods of metal particle in hydraulic oil are generally based on the inductance change detection. With this method, when particles pass through the microchannel, ferromagnetic and non-ferromagnetic metal particle can be distinguished by monitoring inductance. In this study, it was found that not only inductance pulse but also resistance pulse was produced when detecting particle by inductance detection method. The theory of inductance or resistance change caused by particle is presented from the perspective of electromagnetism in this paper. To verify this phenomenon, the oil sample mixed with different metal particles was forced through the detection coil of microfluidic by constant flow rate. Then several sizes of iron and copper particles were measured. Experimental results showed that the resistance pulses caused by iron particles and copper particles were positive. And for copper particle, SNR (Signal Noise Ratio) of copper particles detected in improved effectively by detecting the resistance pulse.