Large Iron Oxide Particles Research Articles

Effect of Y on the corrosion behavior of Fe22Cr5Al3Mo alloy in 500 ℃ super-heated steam

Fe22Cr5Al3Mo-xY (x = 0, 0.15%, mass fraction) alloys were fabricated and corroded in 500 ℃/10.3 MPa super-heated steam using a static autoclave. The results show that the oxide films present a four-layer structure consisting of Fe oxide, Cr oxide, mixed oxide region, and Al oxide from outside to inside. There is α-(Fe, Cr) in Al2O3 layer near the oxide/metal interface. The addition of Y can delay the formation of the large iron oxide particles and increase the ratio of Cr2O3 film thickness to the thickness of the flat oxide film area, thus improving the corrosion resistance of the alloys.

Forms of Zinc Occurrence in Blast-Furnace Dust

Results are given for a study of the phase and elemental composition of EVRAZ Nizhny Tagil Metallurgical Plant blast-furnace flue dust. An estimate of particle size is performed in a laser analyzer. Dust is represented by a set of particles of calcined charge with sizes from 1.5 to 1170 μm, with a median size of 82.9 μm. The elemental composition of the blast-furnace dust in local sampling points is determined by x-ray microanalysis. The dust consists of large iron oxide particles and fine particles containing MgO, CaO, SiO2, and Al2O3 in the form of complex silicates and ferrites, as well as inclusions of mechanically entrained coke. Zinc is present in form of oxide, sulphide and sulfate compounds as a surface layer on particles with increased thermal conductivity (FeOx). The zinc and sulfur contents in the layer (1–5 μm) reach 45 and 6%, respectively. The data obtained are useful for substantiating dust treatment processes.

Catalytic decomposition of N2O over Fe-ZSM-11 catalysts prepared by different methods: Nature of active Fe species

A series of Fe-ZSM-11 catalysts were prepared by different methods and tested in N2O decomposition. First, Fe-ZSM-11 catalysts with different Si/Al ratios (15, 25, 36) were prepared by wet ion exchange. The Fe content and catalytic activity were highest for the catalyst with Si/Al ratio 15. Additional Fe-ZSM-11 catalysts with higher Fe contents were prepared by semicontinuous ion exchange or by using alkaline-treated ZSM-11 as the precursor for wet ion exchange. While the catalyst prepared by semicontinuous ion exchange showed low activity, the catalyst prepared using alkaline-treated ZSM-11 turned out to be the most active in this study. Relevant characterization was conducted using X-ray diffraction, X-ray fluorescence, inductively coupled plasma, N2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible spectroscopy, 57Fe Mössbauer spectroscopy, magnetization tests, and X-ray photoelectron spectroscopy. Our data indicate that small FeOx nanoparticles and large iron oxide particles are the predominant Fe species, and small FeOx nanoparticles with low nuclearity are the active Fe species.

ToF‐SIMS analysis of iron oxide particle oxidation by isotopic and multivariate analysis

A procedure for quantitative time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) analysis of the re‐oxidation thermally‐reduced of iron oxide particles in a ceramic matrix is discussed. Iron oxide is reacted with yttria stabilized zirconia (YSZ) to create a composite that facilitates the high‐temperature reduction of CO2 and H2O to produce CO and H2 (syngas). The reactivity of this two‐step solar‐thermochemical process is being investigated by varying the concentration of iron in YSZ up to and past its solid solubility point, thus affecting the size of iron oxide particles in the matrix, and hence their rate and extent of re‐oxidation. YSZ samples containing natural abundance iron oxide were mixed with an organic binder, isostatically pressed into a disc and calcined in air at 1450 °C. The discs (~ 10 mm diameter, 2 mm thickness) were thermally reduced in inert gas at 1400 °C and then re‐oxidized at 1100 °C in the presence of C18O2. The ratio of 18O to 16O shows the extent of oxygen exchange for each iron oxide particle. ToF‐SIMS data are acquired in a fashion that maximizes the ability to correct for detector saturation, thus providing quantitative oxygen isotopic results with little error. The data analysis method uses a combination of multivariate analysis for particle identification and conventional analysis for quantitative isotopic ratioing. The results indicate that large iron oxide particles are only poorly utilized, likely due to slow transport, as 18O penetration into the particles is limited. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.

Preparation and Characterization of Iron Oxide–Silica Composite Particles Using Mesoporous SBA-15 Silica as Template and Their Internalization Into Mesenchymal Stem Cell and Human Bone Cell Lines

A new procedure for preparing iron oxide-silica nanocomposite particles using SBA-15 mesoporous silica as a template is described. These composite materials retained the 2-D hexagonal structure of the SBA-15 template. Transmission electron micrograms of the particles depicted the formation of iron oxide nanocrystals inside the mesochannels of SBA-15 silica framework. Powder x-ray diffraction showed that the iron oxide core of the composite particles consists of a mixture of maghemite (gamma-Fe(2)O(3)) and heamatite (alpha-Fe(2)O(3)), which is the predominant component. Superconducting quantum interference device (SQUID) magnetometry studies showed that these iron oxide-silica composite materials exhibit superparamagnetic properties. On increasing the iron oxide content, the composite particles exhibited a stronger response to magnetic fields but a less homogeneous core, with some large iron oxide particles which were thought to be formed outside the mesochannels of the SBA-15 template. Internalization of these particles into human cell lines (mesenchymal stem cells and human bone cells), which indicates their potential in medicine and biotechnology, is also discussed.

Influence of iron on kaolin whiteness: An electron paramagnetic resonance study

Well characterized kaolin samples from different deposits of Brazil were studied by electron paramagnetic resonance. Three paramagnetic species attributed to iron in different chemical environments were identified in raw samples. A very intense and broad line with 0.2 mT linewidth was typical of large particles of iron oxides/hydroxides. A species at g = 2.0 with 0.04 mT line width was associated with superparamagnetic particles adsorbed to kaolinite surfaces or trapped between its lamellae. An isotropic and/or orthorhombic species in the g = 4.2 region belongs to structural Fe 3+ replacing Al 3+ in sites with different crystal-field symmetries. It was verified that large iron oxide particles were responsible for keeping the kaolin whiteness at levels below 50%. Superparamagnetic iron particles mainly affect whiteness in the range of 50%< whiteness < 86%. They may be totally removed by magnetic separation followed by chemical treatment using sodium dithionite. The kaolin high whiteness levels (whiteness > 86%) were determined by Fe 3+ iron content in the kaolinite structure. However, only a small part of this species can be removed from the kaolinite structure by traditional industrial processing techniques. These results showed that EPR is a powerful technique to assist in controlling kaolin quality in industrial processes.

Transfection Agent Induced Nanoparticle Cell Loading

Loading cells with magnetic nanoparticles, and tracking their fate in vivo by high resolution MRI, is an attractive approach for enhancing the efficacy of cell-based therapies including those utilizing hematopoietic stem cells, neuroprogenitor cells, and T cells. The transfection agent (internalization agent) assisted loading with the Feridex IV nanoparticle is an attractive method of loading because of the low cost of materials, and possible low regulatory barriers for eventual clinical use. We therefore explored the interaction between Feridex IV and three internalization agents protamine (PRO), polylysine (PLL), and lipofectamine (LFA). Feridex reacted with internalization agents to form aggregates, except when either the internalization agent or Feridex was present in large excess. When Jurkat T cells were incubated with Feridex/LFA or Feridex/PRO mixtures, and washed by centrifugation, nanoparticle aggregates co-purified with cells. With C17.2 cells large iron oxide particles adhered to the cell surface. At 30 microg/mL Feridex and 3 microg/mL LFA, internalization was largely mediated by LFA and was largely cytoplasmic. However, we found that the conditions used to label cells with Feridex and transfection agents need to be carefully selected to avoid the problems of surface adsorption and nanoparticle precipitation.

EPR study of iron-doped MFI zeolite and silicalite catalysts: effect of treatments after synthesis

The systematic study of iron-doped MFI zeolite and MFI silicalite by X- and Q-band EPR spectroscopy is reported in this paper. Both samples, which contain Fe(III) ions in the MFI lattice, underwent three sequential treatments—calcination, steaming, and washing with sodium dithionite solution—which are needed to make the catalyst active by extracting iron ions from the lattice. EPR spectra could be simulated by assuming a broad distribution of spin-spin (zero-field) coupling parameters. The simulation parameters depend on sample history and reproduce the selective intensity changes that are observed in X-band spectra after each treatment. In particular, the distribution width decreases by calcining and steaming samples and then it increases by treating with aqueous dithionite solution. This is in agreement with the view that iron ions are extracted from the framework by calcining and by steaming and may form relatively large iron oxide particles which become smaller after the chemical treatment. We have also studied the temperature dependence of the EPR spectra. The most interesting results are from the steamed samples. Their behavior has been interpreted as due to the presence of superparamagnetic single domain particles of iron oxide. This agrees with the view that iron oxide particles form during steaming.

Superparamagnetic iron oxide contrast agents: physicochemical characteristics and applications in MR imaging.

Superparamagnetic iron oxide MR imaging contrast agents have been the subjects of extensive research over the past decade. The iron oxide particle size of these contrast agents varies widely, and influences their physicochemical and pharmacokinetic properties, and thus clinical application. Superparamagnetic agents enhance both T1 and T2/T2* relaxation. In most situations it is their significant capacity to reduce the T2/T2* relaxation time to be utilized. The T1 relaxivity can be improved (and the T2/T2* effect can be reduced) using small particles and T1-weighted imaging sequences. Large iron oxide particles are used for bowel contrast [AMI-121 (i.e. Lumirem and Gastromark) and OMP (i.e. Abdoscan), mean diameter no less than 300 nm] and liver/spleen imaging [AMI-25 (i.e. Endorem and Feridex IV, diameter 80-150 nm); SHU 555A (i.e. Resovist, mean diameter 60 nm)]. Smaller iron oxide particles are selected for lymph node imaging [AMI-227 (i.e. Sinerem and Combidex, diameter 20-40 nm)], bone marrow imaging (AMI-227), perfusion imaging [NC100150 (i.e. Clariscan, mean diameter 20 nm)] and MR angiography (NC100150). Even smaller monocrystalline iron oxide nanoparticles are under research for receptor-directed MR imaging and magnetically labeled cell probe MR imaging. Iron oxide particles for bowel contrast are coated with insoluble material, and all iron oxide particles for intravenous injection are biodegradable. Superparamagnetic agents open up an important field for research in MR imaging.

Rheological and cryogenic-transmission electron microscopy probing of the structure of magnetic paints

Rheological measurements and cryogenic transmission electron microscopy are used to probe the structure of model magnetic paints which contain ferrimagnetic pigment particles of barium ferrite, a wetting resin, and a solvent. As the resin concentration c increases, the storage modulus goes through a minimum. At low c, a flocculated network is developed in the paint. Milling of the paint at insufficient resin concentration does not improve its dispersion quality, but instead results in the formation of a stronger network. Milling at higher c effectively disrupts the network into small aggregates. The resin concentration required to provide effective milling is lower for paints containing the larger iron oxide particles.

Role of supported metals in the selective reduction of nitrogen monoxide with hydrocarbons over metal/alumina catalysts

The promoting effect of supported metals on alumina catalyst was investigated for the reduction of nitrogen monoxide in oxygen-rich atmospheres. For NO reduction with propene over impregnated CoO/A1 2O 3, the first reaction step was found to be the oxidation of NO to NO 2 probably catalyzed by dispersed cobalt species. The next reaction step, which is the reaction of NO 2 with propene to form N 2, was considered to take place on the alumina surface. Although the activity of impregnated FeO/A1 2O 3 was low because of the presence of large iron oxide particles catalyzing propene oxidation with dioxygen, FeO/A1 2O 3 prepared with sol-gel method showed excellent deNO x activity.

Mineralogy of three slightly palagonitized basaltic tephra samples from the summit of Mauna Kea, Hawaii

Certain palagonites from Hawaii are considered to be among the best analogs for Martian fines, based upon similar spectral properties. For this study, three distinctly colored layers were sampled from slightly palagonitized basaltic tephra just below the summit of Mauna Kea at 4145 m elevation. The mineralogy of size fractions of these samples was examined by diffuse reflectance (visible and near‐IR) and far‐IR spectroscopy, optical microscopy, X ray diffraction, Mössbauer spectroscopy, magnetic analysis, electron microprobe analysis (EMPA), and transmission and scanning electron microscopy. For the 20–1000 μm size fraction, sample HWMK11 (red) is essentially completely oxidized and has a hematite (Ti‐hematite) pigment dispersed throughout the silicate matrix. The alteration is present throughout particle volumes, and only a trace amount of glass is present; no palagonitic rinds were detected. In addition to ferric Fe‐Ti oxides, other phases detected were plagioclase feldspar and a trace of olivine. Sample HWMK12 (black) has the lowest proportion of ferric‐bearing phases and is thus least weathered. It consists mostly of unaltered glass with embedded plagioclase and minor amounts of pyroxene, olivine, and Ti‐magnetite. In some grains, a thin palagonitic rind is visible, indicating some surface alteration. The mineralogy for sample HWMK13 (yellow) is the same as that for HWMK12, except that it has distinct, well‐developed palagonitic rinds consisting of erionite and smectite. For all samples, the amount of glass and plagioclase decreases and the amount of smectite increases with decreasing particle size for size fractions &lt;20 μm. For HWMK11, the amount of hematite is essentially constant, and mica is present only in the coarse clay‐sized fraction; smectites are low in structural Fe. For HWMK12 and HWMK13, the zeolite erionite is present along with smectites and nanophase ferric oxides (np‐Ox). Erionite abundance decreases and np‐Ox abundance increases with decreasing particle size. The smectite in both black and yellow samples contains some Fe3+ in octahedral layers. There were only two mineral phases containing iron in the fine clay fraction, namely, smectites and iron oxides. For HWMK11, relatively large iron oxide particles (0.1 to 0.4 μm) were dispersed on clay surfaces; for HWMK12 and HWMK13, much finer np‐Ox particles were present in lesser concentrations. Formation of the zeolite erionite is consistent with the arid climate zone where these samples were collected. However, transient hydrothermal processes that occurred during the eruption of Mauna Kea volcano under its permanent ice cap during the Pleistocene may have resulted in minerals such as zeolites and smectites which may persist as relicts over a long period of time. Most of the iron released during weathering of basaltic tephra precipitated as poorly crystalline iron oxides and some of the Fe has substituted for the octahedral cations in the structure of authigenic smectites. The Ti‐hematite in HWMK11, however, is the result of high‐temperature oxidation of Ti‐magnetite and exsolution from ironbearing silicate phases. Visible and near‐IR reflectivity spectra for the &lt;20 μm size fraction of HWMK11 is dominated by well‐crystalline Ti‐hematite. Corresponding spectra for HWMK12 and HWMK13, whose ferric mineralogy is dominated by np‐Ox particles, are more similar to Martian bright‐region spectra.

Magnetic aqueous two-phase separation: A new technique to increase rate of phase-separation, using dextran-ferrofluid or larger iron oxide particles

A new technique to speed up the phase separation of aqueous two-phase systems is described. The technique is based on the addition of magnetically susceptible additives (ferrofluids or iron oxide particles). In a magnetic field such additives will induce a faster phase separation. In one approach, dextran-stabilized ferrofluid was added to an aqueous two-phase system containing polyethylene glycol and dextran. The ferrofluid was totally partitioned to the dextran phase. After mixing of the two-phase system, it was possible to reduce the separation time by a factor of 35 by applying a magnetic field to the system. Another approach involved the use of 1-μm iron oxide particles instead of ferrofluid. In this case also, the phase-separation time was reduced, by a factor of about 70, when the system was placed in a magnetic field. The addition of ferrofluid and/or iron oxide particles was shown to have no influence on enzyme partitioning or on enzyme activity. The partitioning of chloroplasts, on the other hand, was influenced unless the ferrofluid used had been treated with epoxysilane. A column system comprising 15 magnetic separation stages was constructed and was used for semicontinuous separation of enzyme mixtures.