Uniform Iron Research Articles

Mild and cost-effective synthesis of iron fluoride–graphene nanocomposites for high-rate Li-ion battery cathodes

Exploring high performance cathode materials is essential to realize the adoption of Li-ion batteries for application in electric vehicles and hybrid electric vehicles. FeF3, as a typical iron-based fluoride, has been attracting considerable interest due to both the high electromotive force value of 2.7 V and the high theoretical capacity of 237 mA h g−1 (1e− transfer). In this study, we report a facile low-temperature solution phase approach for synthesis of uniform iron fluoride nanocrystals on reduced graphene sheets stably suspended in ethanol solution. The resulting hybrid of iron fluoride nanocrystals and graphene sheets showed high specific capacity and high rate performance for iron fluoride type cathode materials. High stable specific capacity of about 210 mA h g−1 at a current density of 0.2 C was achieved, which is much higher than that of LiFePO4 cathode material. Notably, these iron fluoride/nanocomposite cathode materials demonstrated superior rate capability, with discharge capacities of 176, 145 and 113 mA h g−1 at 1, 2 and 5 C, respectively.

Influence of the Rest Pulse Duration in Pulsed Electrodeposition of Fe Nanowires

Highly uniform iron nanowires were synthesized in porous anodic alumina, through a pulsed electrodeposition method. The effect of the rest pulse duration in the deposition quality was systematically investigated, being the best duration found at 0.6 s with 91.9% of pores filled. A methodology of surface response design of experiment was conducted to find the optimum predicted value for the rest pulse duration, by controlling the following experimental parameters/variables: current density, electrolyte concentration and temperature. The influence of the rest pulse in the grain size of the iron nanowires was also studied trough X-ray diffraction patterns. A numerical simulation of the concentration evolution along a nanopore was performed, allowing to achieve a deeper understanding of the importance of the rest pulse in the NW electrodeposition.

Controlled Synthesis of Cobalt-Doped Magnetic Iron Oxide Nanoparticles

Uniform sphere-like Co-doped iron oxide nanoparticles were synthesized by the thermolysis of iron oleate and cobalt oleate precursors in octadecene in the presence of oleic acid.The Co/Fe mole ratios in the final Co-doped iron oxide can be controlled by changing their ratios in the reaction precursors.With the increase of Co/Fe mole ratios from 0.024 to 0.156 in the final iron oxide nanoparticles,the magnetic saturation values of the nanoparticles slightly decreased from 39to30emu·g-1,while their coercivity values increased from 0 to 190 Oe.The sizes of the Co-doped iron oxide nanoparticles increased from 7 to 14nm when the thermolysis time was increased from 0.5to 3h with a thermolysis temperature 305℃.Generally,with increasing thermolysis time the metal elements in the final nanoparticles were partially reduced.The domain polymorph of the final nanoparticles was magnetite with a very small amount of ferrous oxide for thermolysis time less than 1 h,while the phases were a mixture of magnetite and wustite ferrous oxide for thermolysis time longer than 2 h.Further increasing thermolysis time to 3h,except Fe3O4 and FeO,CoFe alloys appear too.It indicates that the iron (cobalt) elements were reduced from trivalence to bivalence,and finally to zero valence.The sizes of the iron oxide nanoparticles increased and more ferrous oxide appeared in the final products with increasing the thermolysis temperature.

Controlled synthesis of uniform magnetite nanocrystals with high-quality properties for biomedical applications

Uniform iron oxide magnetic nanoparticles, with sizes in the range 9–22 nm, have been synthesized by thermal decomposition of an iron oleate complex in 1-octadecene, controlling reaction parameters related to the nucleation and growth processes. After transferring to water through a ligand substitution process, nanoparticles display very good magnetic and magneto-thermal properties. The relationship between these properties and the size and size distribution of the particles is discussed. The colloidal stability of the nanoparticles dispersed in common biological buffers has also been studied.

Low Temperature Synthesis of Single Crystalline Iron Hydroxide and Oxide Nanorods in Aqueous Media

An easy aqueous 'one-pot' synthesis route for the fabrication of single crystalline uniform iron hydroxide (beta-FeOOH) nanorods at low temperature is reported. beta-FeOOH nanorods with diameters of 5-37 nm and lengths up to 45-185 nm were obtained by varying the reaction parameters. Addition of ethanol was found to be crucial to control the aspect ratio. After calcination at 250 degrees C for 2 h the as-obtained beta-FeOOH nanorods was converted to alpha-Fe2O3 nanorods. To the best of our knowledge, beta-FeOOH nanorods having diameter less than 6 nm is reported for the first time.

Characterization of single cotton fibers using a laser diffraction system

The fineness and maturity of a cotton fiber is determined by its cross-sectional perimeter and area. However, measuring fiber cross-sectional perimeter and area is an extremely tedious and challenging task. This paper presents an alternative approach to measure fiber longitudinal width using Fraunhofer diffraction patterns, which can be used to estimate fiber fineness and maturity. We designed a laser diffraction system, developed a software program to denoise and process diffraction patterns, and tested the system on a uniform iron wire and individual cotton fibers from ten bales. The width of the iron wire measured by our system was 25.43 μm (0.1% different from the nominal value) with a 0.01 μm standard error of the mean. Cotton fiber width measured by the laser diffraction system could differentiate among ten cotton bales, which was in accordance with their relative differences in fineness. Linear regression analyses revealed that strong linear relationships exist between the fiber width and cross-sectional perimeter and area (r2 = 0.81 and 0.77, respectively), as well as between the fiber width and fineness and micronaire (r2 = 0.79 and 0.73, respectively) (n = 10, p = 0.01). This simple, replicable, and relatively inexpensive optical system could be used for single fiber longitudinal profile characterization and cotton fineness and maturity estimation.

Aerosol-Based Self-Assembly of Nanoparticles into Solid or Hollow Mesospheres

The ability to manipulate miniature object assemblies with well-defined structures in a controllable manner is of both fundamental and applied interests. This article presents general strategies, with nanospheres as building blocks, to engineer mesoscopic spherical architectures via a process of evaporation-driven self-assembly in aerosol droplets. Uniform magnetite iron oxide (Fe(3)O(4), approximately 2.5 nm), silica (SiO(2), approximately 15 nm), and cupric oxide (CuO, approximately 6 nm) nanoparticles were employed for the structural architecture. The method enables microstructural control of the self-assembled mesospheres by tuning the competition between solvent evaporation and solute diffusion within an aerosol droplet. Furthermore, we have demonstrated it is technically feasible to assemble surface-dissimilar binary components, i.e., charge-stabilized hydrophilic SiO(2) and hydrophobic ligand-capped Fe(3)O(4) nanoparticles, into hierarchical composite structures, which could be extended for preparation of more hierarchically textured materials with desired functionalities.

Sol−Gel-Derived Iron Oxide Thin Films on Silicon: Surface Properties and Interfacial Chemistry

Uniform high-quality iron oxide thin films can be formed from the spin coating of iron oxide/hydroxide sol-gels on a silicon substrate. Thermal processing of the films at temperatures of approximately 300 degrees C results in the transformation of films into a ternary layered structure with iron oxide, Fe(2)O(3), at the surface, characterized by Mossbauer spectroscopy, and reduced, metallic iron characterized by depth profiling of the surface by X-ray photoelectron spectroscopy as a function of Ar(+) etching. Imaging of the etched surface by scanning electron microscopy reveals two distinct regions at the interface, nanoparticles that are very iron-rich separated by an unstructured region that is somewhat less iron-rich. The results demonstrate a synthetic protocol for the spontaneous formaton of a ternary layered structure from a simple one-step preparation.

Development of Receptor Targeted Magnetic Iron Oxide Nanoparticles for Efficient Drug Delivery and Tumor Imaging.

The development of multifunctional nanoparticles that have dual capabilities of tumor imaging and delivering therapeutic agents into tumor cells holds great promises for novel approaches for tumor imaging and therapy. We have engineered urokinase plasminogen activator receptor (uPAR) targeted biodegradable nanoparticles using a size uniform and amphiphilic polymer-coated magnetic iron oxide (IO) nanoparticle conjugated with the amino-terminal fragment (ATF) of urokinase plasminogen activator (uPA), which is a high affinity natural ligand for uPAR. We further developed methods to encapsulate hydrophobic chemotherapeutic drugs into the polymer layer on the IO nanoparticles, making these targeted magnetic resonance imaging (MRI) sensitive nanoparticles drug delivery vehicles. Using a fluorescent drug doxorubicin (Dox) as a model system, we showed that this hydrophobic drug can be efficiently encapsulated into the uPAR-targeted IO nanoparticles. This class of Dox-loaded nanoparticles has a compact size and is stable in pH 7.4 buffer. However, encapsulated Doxcan be released from the nanoparticles at pH 4.0 to 5.0 within 2 hrs. In comparison with the effect of equivalent dosage of free drug or non-targeted IO-Dox nanoparticles, uPAR-targeted IO-Dox nanoparticles deliver higher levels of Dox into breast cancer cells and produce a stronger inhibitory effect on tumor cell growth. Importantly, Dox-loaded IO nanoparticles maintain their T2 MRI contrast effect after being internalized into the tumor cells due to their significant susceptibility effect in the cells, indicating that this drug delivery nanoparticle has the potential to be used as targeted therapeutic imaging probes for monitoring the drug delivery using MRI.

Biomedical microdevices synthesis of iron oxide nanoparticles using a microfluidic system

The preparation of nanoparticles is essential in the application of many nanotechnologies and various preparation methods have been explored in the previous decades. Among them, iron oxide nanoparticles have been widely investigated in applications ranging from bio-imaging to bio-sensing due to their unique magnetic properties. Recently, microfluidic systems have been utilized for synthesis of nanoparticles, which have the advantages of automation, well-controlled reactions, and a high particle uniformity. In this study, a new microfluidic system capable of mixing, transporting and reacting was developed for the synthesis of iron oxide nanoparticles. It allowed for a rapid and efficient approach to accelerate and automate the synthesis of the iron oxide nanoparticles as compared with traditional methods. The microfluidic system uses micro-electro-mechanical-system technologies to integrate a new double-loop micromixer, two micropumps, and a microvalve on a single chip. When compared with large-scale synthesis systems with commonly-observed particle aggregation issues, successful synthesis of dispersed and uniform iron oxide nanoparticles has been observed within a shorter period of time (15 min). It was found that the size distribution of these iron oxide nanoparticles is superior to that of the large-scale systems without requiring any extra additives or heating. The size distribution had a variation of 16%. This is much lower than a comparable large-scale system (34%). The development of this microfluidic system is promising for the synthesis of nanoparticles for many future biomedical applications.

Redemption of Microscale Mill Waste into Commercial Nanoscale Asset

Mill-scale is a porous, hard and brittle coating of several distinct layers of iron oxides (predominantly Fe3O4) formed during the fabrication of steel structures. It is magnetic in nature with iron content up to as high as 93%. About 1240 million metric tons of steel was produced in 2006 globally, 1.5 % of which by weight accounts for the mill-scale waste. Thus, 18.6 million metric ton of mill scale waste was produced in one year alone. Most of the steel mill-scale waste (almost 80%) end ups in a landfill; a small fraction of it is also used to make reinforced concrete in Russia and some Asian countries. A purer commercial form of this oxide in combination with nickel and zinc oxide is used in making ceramic magnets (soft ferrites) which are an integral part of all the audio-visual and telecommunication media on this planet as well those in the space. The mill-scale waste could be a valuable technological resource if properly processed and converted into nanoscale species, in particular nanoscale iron particles for hydrogen fuel cell, medical imaging and water remediation applications. In order to achieve the much-discussed and sought-after hydrogen economy via an ‘econo’ viable and ‘enviro’ friendly route, a roadmap for utilizing the mill-scale waste has been developed. The method consists of reacting heated iron with steam, also appropriately called metal-steam reforming (a route well-known to the metallurgists for centuries) generating high purity hydrogen, with a twist. The innovation lies in the conversion of the coarse oxide scale into nanoscale iron by a novel solution-based technique. This produces highly uniform zerovalent iron particles as small as 5 nm. The scope of utilizing the mill-scale waste is broadened several folds as nanoscale iron and nanomagnetite find potential applications in de-arsenification of drinking water, destruction of perchlorate and reduction of hexavalent chromium ions in water sources. In addition, nanoscale iron and magnetite are finding increasing application as the preferred contrasting agents in magnetic resonance imaging - MRI.

Gelcasting of metal powders in nontoxic cellulose ethers system

A nontoxic gel system for gelcasting complex-shape metal green body was investigated. The process was based on the heat-initiated gelation characteristic of water-soluble cellulose ether (CE) or its hydroxyalkyl derivative in hydrotropic solution. In gelcasting, a highly loaded but very fluid suspension consisting of iron powder, water, antioxidant, dispersant and gelformer, was poured into a non-porous mould and gelled at 60 °C. The apparent viscosity of the suspension and factors influencing it were analyzed. The green bodies with bending strength of about 2.5 MPa had a smooth surface and homogeneous microstructure. After sintering, dense and uniform iron parts were successfully obtained.

적층구조 촉매층(Al/Fe/Al)을 이용한 탄소나노튜브의 합성에서 최상층 알루미늄 층의 역할

적층구조 촉매층(Al/Fe/Al)을 이용하여 열 화학기상증착(thermal chemical vapor deposition ; TCVD)법을 통해 탄소 나노튜브를(carbon nanotubes ; CNTs)를 합성하였다. Raman spectroscopy, SEM 및 HR-TEM 분석결과, G/D는 22.7이며, 직경이 <TEX>$1.14\;{\sim}\;1.32\;nm$</TEX>인 금속성의 단일벽 탄소 나노튜브(single-walled CNTs ; SWCNTs)의 다발(bundle)들이 기판 전체에 network 구조로 형성되어 있는 것을 확인할 수 있었다. 이는 최상층의 Al이 촉매인 Fe의 응집현상(agglomeration)을 막아주는 역할을 하여 작고 균일한 핵 생성 사이트(nucleation site)를 통해 좁은 직경분포를 가진 단일벽 탄소 나노튜브가 합성되었음을 알 수 있다. In this study, we report the synthesis of the single-walled carbon nanotubes(SWCNTs) using laminated catalyst(Al/Fe/Al) layer deposited by sputter on Si(001). SWCNTs are grown by thermal chemical vapor deposition (TCVD) method. As the results of scanning electron microscopy(SEM), high resolution transmission electron microscopy(HR-TEM) and Raman spectroscopy, we confirmed the SWCNTs bundles with narrow diameter distribution of <TEX>$1.14{\sim}1.32\;nm$</TEX> and average G&D ratio of 22.76. Compare to the sample having Fe/Al catalyst layer, it can be proposed that the top-aluminum incorporated with iron catalyst plays an important role in growing process of CNTs as a agglomeration barrier of the Fe catalyst. Thus, we suggest that a proper quantity of aluminium metal incorporated in Fe catalyst induce small and uniform iron catalysts causing SWCNTs with narrow diameter distribution.

Preparation of iron oxide nanocrystals by surfactant-free or oleic acid-assisted thermal decomposition of a Fe(III) alkoxide

A new non-hydrolytic, alkoxide-based route was developed to synthesize iron oxide nanocrystals. Surfactant-free thermal decomposition of the iron 2-methoxy-ethoxide precursors results in the formation of uniform iron oxide nanocrystals with an average size of 5.6 nm. Transmission electron microscope study shows that the nanocrystals are protected against aggregation by a repulsive surface layer, probably originating from the alkoxy-alkoxide ligands. Addition of oleic acid resulted in monodisperse nanocrystals with an average size of 4 nm. Mössbauer analysis confirmed that the nanocrystals mainly consisted of maghemite. Analysis of the magnetic hysteresis loop measurements and the zero field and field cooled measurements displayed an excellent fit to established theories for single-domain superparamagnetic nanocrystals and the size of the magnetic domains correlated well to the crystallite size obtained from transmission electron microscope.

Removal of Arsenic(V) from Aqueous Solutions Using Iron‐Oxide‐Coated Modified Activated Carbon

Removal of arsenic(V) from aqueous solutions was evaluated with the following three different sorption materials: coal-based activated carbon 12 x 40 (activated carbon), iron(II) oxide (FeO)/activated carbon-H, and iron oxide. The apparent characteristics and physical chemistry performances of these adsorbents were investigated by X-ray diffraction, nitrogen adsorption, and scanning electronic microscope. Also, batch experiments for arsenic removal were performed, and the effects of pH value on arsenic(V) removal were studied. The results suggest that the main phases of the iron oxide surface are magnetite, maghemite, hematite, and goethite; fine and uniform iron oxide particles can cover activated carbon surfaces and affect the surface area or pore structures of activated carbon; adsorption kinetics obey a pseudo-first-order rate equation; and adsorption capacities of adsorbents are affected by the values of pH. The optimum value of pH for iron oxide lies in a narrow range between 4.0 and 5.5, and arsenic(V) removal by FeO/activated carbon-H is ideal and stable in the pH range 3 to 7, while activated carbon has the lowest adsorption capacity in the entire pH range. Also, the adsorption characteristics of FeO/activated carbon-H composites and virgin activated carbon match well the Langmuir adsorption model, while those of iron oxide fit well the Freundlich adsorption model.

Dramatic Increase in Stability and Longevity of Enzymes Attached to Monodispersive Iron Nanoparticles

Enzymes are proteins that function as biocatalysts in living systems. One of the major concerns in environmental, biomedical, and other applications of enzymes is their short lifetime (J. Kim, "Single-Enzyme Nanoparticles on Nanostructured Matrices," 2003). Enzymes lose their activity due to oxidation or other processes which results in less stability and a shorter lifetime thereby rendering them less efficient. An effective way to increase the stability, longevity, and reusability of the enzymes is to attach them to magnetic iron nanoparticles. With this aim, two different catabolic enzymes, trypsin and peroxidase, were attached to uniform magnetic core-shell iron nanoparticles (MNPs) produced in our laboratory. Our study indicates that the lifetime of enzymes increases dramatically from a few hours to weeks and that MNP-Enzyme conjugates are more stable, efficient, and economical. We predict that MNPs shield the enzymes preventing them from getting oxidized or self digested. This results in an increased lifetime of the enzymes. Since the magnetization of MNPs is high (~140 emu/g), MNP-enzyme conjugates could efficiently be reused, which makes enzymes more productive. We also found that the enzyme structure plays a major role in efficient attachment of MNPs.

Reduction mechanism of uniform iron oxide nanoparticles to metal used as recording media

Uniform and stable α-Fe nanoparticles of around 40 nm in width and axial ratios from 5 to 7 have been obtained from hematite (α-Fe 2O 3) without any additive. The precursor was synthesized by forced hydrolysis of a Fe(ClO 4) 3 solution in the presence of urea and different amounts of NaH 2PO 4. These particles have been reduced to metal α-Fe by heating under a hydrogen flow and the best conditions of temperature, hydrogen flow and time to preserve the morphology have been established. There is a minimum temperature (400 °C) and a minimum hydrogen flow (20 l/h) to reduce the hematite particles to metal in a reasonable time (4 h), preserving the size and the shape of the particles. The main change in the material is related to the crystallite size of the metal particles, which increases as the reduction proceeds. A detailed analysis of the magnetic properties of these particles during the reduction process and the influence of the particle axial ratio has been carried out.

Clinical relevance of hemochromatosis-related HFE C282Y/H63D gene mutations in patients on chronic dialysis.

The actual prevalence and the clinical relevance of gene mutations of HFE (which are linked to hemochromatosis) have not yet been established in patients on chronic dialysis. On the basis of theoretical premises, it could be hypothesized that these genetic determinants might influence the response to iron intake and the susceptibility for iron overload in patients in parenteral iron therapy. Furthermore, carriers for these mutations might be prone to develop sporadic porphyria cutanea tarda and cardiovascular events. C282Y/H63D mutations of HFE gene were evaluated in 132 patients (34 in peritoneal dialysis, 98 in HD) and correlated with biochemical parameters of iron status (ferritin (FER) concentration and transferrin saturation (TSAT)), red cell parameters (red cell size and hemoglobin content), erythropoietin (EPO) dosage, major cardiovascular events and C-reactive protein as marker of chronic inflammation, in patients without iron therapy and after i.v. iron supplementation (< or = 60 mg/week) and with the presence of biopsy-proven porphyria. C282Y heterozygous mutation was found in 8/132 (6.6%); H63D homozygous and heterozygous mutations were found in 3/132 (2.3%) and 22/132 (16%) patients, respectively. Two patients (1.5%) showed double heterozygosis. No differences in baseline serum FER and TSAT and the other biochemical and clinical parameters were found in patients bearing mutations alleles nor after continuous iron therapy at low dosages. However, the prevalence of patients capable of maintaining normal hemoglobin (Hb) level without EPO therapy is increased in the C282Y-mutated patients. Only 1 patient out of the 4 with biopsy-proven porphyria cutanea tarda was bearing gene mutations (H63D heterozygosis). C282Y/H63D HFE gene mutations do not seem to be related to major abnormalities in biochemical parameters of iron status in dialysis patients without iron therapy or after i.v. iron supplementation, granted that low dosages are employed. Obviously, as our patients were exposed to a relatively uniform iron regimen in our clinical center (< or = 60 mg/week), it is unclear if other dosing regimens will unmask clinically significant differences between the heterozygotes and normals. The fact that the C282Y-mutated patients more frequently maintain high Hb values without EPO is interesting as could suggest a better use of available iron for erythopoiesis, but needs to be confirmed in larger samples. No clear association is demonstrated with porphyria cutanea tarda and major cardiovascular events.

Structural and magnetic transformation of monodispersed iron oxide particles in a reducing atmosphere

Uniform metal iron ellipsoidal particles of around 200 nm in length were obtained by reduction and passivation of alumina-coated α–Fe2O3 (hematite) particles under different conditions of temperature and hydrogen flow rate. The monodispersed hematite particles were prepared by the controlled hydrolysis of ferric sulfate and further coated with a homogeneous thin layer of Al2O3 by careful selection of the experimental conditions, mainly pH and aluminum salt concentration. The reduction mechanism of α–Fe2O3 into α–Fe was followed by x-ray and electron diffraction, and also by the measurements of the irreversible magnetic susceptibility. The transformation was found to be topotactic with the [001] direction of hematite particles, which lies along the long axis of the particles, becoming the [111] direction of magnetite and finally the [111] direction of metal iron. Temperature and hydrogen flow rate during the reduction have been found to be important parameters, which determine not only the degree of reduction but also the crystallite size of the final particles. Magnetic characterization of the samples shows that the only parameters affected by the crystallite size are the saturation magnetization and magnetic time-dependence effect, i.e., activation volume.

Plasma-based ion implantation of oxygen in stainless steel: influence of ion energy and dose

Implantation of oxygen in stainless steel (15% Cr) via plasma-based ion implantation in a distributed ECR plasma reactor has been studied as functions of ion energy and dose. Due to the formation at the surface of dielectric films with optical index and thickness depending on the implantation time and pulse voltage (up to 44 kV), various colorations can be obtained. The experimental results demonstrate the feasibility of uniform processing, the possibility of reaching perfect control of the coloring through the dose and energy of implanted ions, and that the resulting coloration varies monotonically when increasing the dose and penetration depth of implanted oxygen. Characterization of the films by scanning electron microscopy and X-ray microanalysis shows that oxygen implantation results in strong surface oxidation, but without any significant degradation of the surface aspect. The thickness and composition profiles of the oxide layers determined using X-ray photoelectron spectroscopy combined with ellipsometry indicate that the thickness, of course, increases with ion energy and dose, but that the composition of the oxide layer resulting from the implantation process is not uniform. A uniform iron oxide layer (with a stoichiometry closed to Fe 2O 3), free from chromium, is formed in the near-surface region, while chromium segregates at the interface between the oxide layer and the bulk stainless steel to form chromium oxide Cr 2O 3.