Fe Microparticles Research Articles

Nitrogen-doped carbon microfibers with porous textures

Nitrogen-doped carbon microfibers (N-CMFs) with porous textures have been synthesized by means of a floating catalyst chemical vapor deposition (FCCVD) with anhydrous ferric chloride as a catalyst precursor and melamine as both the carbon and nitrogen source. X-ray photoelectron spectroscope (XPS) characterization of the as-prepared N-CNFs reveals nitrogen atoms in the N-CMFs are mainly in the form of pyridine-like nitrogen and graphitic nitrogen. The sublimation and subsequent gas phase reduction of FeCl3 in H2 produces Fe micro-particles with high catalytic activity that leads to the growth of the microfibers. The electrochemical studies have shown that N-CMFs have a larger capacitance than the pure CMFs, showing promise for use as electrode materials in supercapacitors.

Papilla-like magnetic particles with hierarchical structure for oil removal from water

Inspired by selective wettability and hierarchical structure of papillae on lotus seeds, papilla-like magnetic particles were fabricated by thermal treatment of Fe microparticles. The papilla-like magnetic particles modified by lauric acid exhibited superhydrophobicity, superoleophilicity and great oil removing capability from water.

Fabrication of a 3D active mixer based on deformable Fe-doped PDMS cones with magnetic actuation

In this paper an active 3D mixer for lab-on-chip applications is presented. The micrometer size cone shape holes are ablated on a PMMA sheet utilizing a CO2 laser. The holes are filled with Fe micro-particles and the whole structure is molded with PDMS which cause the Fe micro-particles to be trapped in a PDMS cone structure. These Fe-doped PDMS cones are placed in a PMMA micro-channel structure fabricated by CO2 laser machining. By applying an external periodic magnetic field, the cones periodically bend in the micro-channel and stir the fluid. The fabrication method and the effect of the magnetic field on the bending of the cones with different aspect ratios is also discussed utilizing computer simulation. Doping the polymers with micro- and nano-metallic particles has been carried out by different research groups before, but according to our knowledge, application of such structures for the fabrication of a 3D active mixer has not been presented before.

Chemical interferences when using high gradient magnetic separation for phosphate removal: Consequences for lake restoration

A promising method for lake restoration is the treatment of lake inlets through the specific adsorption of phosphate (P) on strongly magnetizable particles (Fe) and their subsequent removal using in-flow high gradient magnetic separation (HGMS) techniques. In this work, we report an extensive investigation on the chemical interferences affecting P removal efficiencies in natural waters from 20 Mediterranean ponds and reservoirs. A set of three treatments were considered based on different Fe particles/P concentration ratios. High P removal efficiencies (>80%) were found in freshwater lakes (conductivities < 600 μS cm −1). However, a significant reduction in P removal was observed for extremely high mineralized waters. Correlation analysis showed that major cations (Mg 2+, Na + and K +) and anions (SO 4 2− and Cl −) played an essential role in P removal efficiency. Comparison between different treatments have shown that when increasing P and Fe concentrations at the same rate or when increasing Fe concentrations for a fixed P concentration, there exist systematic reductions in the slope of the regression lines relating P removal efficiency and the concentration of different chemical variables. These results evidence a general reduction in the chemical competition between P and other ions for adsorption sites on Fe particles. Additional analyses also revealed a reduction in water color, dissolved organic carbon (DOC) and reactive silicate (Si) concentrations with the addition of Fe microparticles.

Tumour cell death induced by the bulk photovoltaic effect of LiNbO3:Fe under visible light irradiation

This work reports a pioneer application of the bulk photovoltaic effect in the biomedical field. Massive necrotic cell death was induced in human tumour cell cultures grown on a bulk photovoltaic material (iron-doped lithium niobate, LiNbO(3):Fe) after irradiation with visible light. Lethal doses (≈100% cell death) were obtained with low-intensity visible light sources (10-100 mW cm(-2) irradiances) and short exposure times of the order of minutes. The wavelength dependence to induce the lethal effect observed is consistent with that corresponding to the bulk photovoltaic effect generation in LiNbO(3):Fe. Necrosis also occurred when cultured tumour cells were exposed to LiNbO(3):Fe microparticles and visible light.

Spray-dried chitosan-metal microparticles for ciprofloxacin adsorption: Kinetic and equilibrium studies

Chitosan, a natural polysaccharide obtained from chitin deacetylation, complexes with metal ions by coordination with the free electron pairs of amine groups. Based on this complexation mechanism, cross-linked chitosan-metal microparticles were prepared by spray drying using iron (II or III) or zinc ions and characterized in terms of size distribution and capacity to specifically adsorb ciprofloxacin. Chitosan-Zn(II) and chitosan-Fe(III) microparticles appear to adsorb more ciprofloxacin than plain chitosan or chitosan-Fe(II) microparticles. Adsorption isotherms for CH and CH–Fe(II) microparticles can be fitted by a single logarithm model (slope 1) with one ciprofloxacin per adsorption site, whereas for CH–Fe(II) and CH–Zn(II) microparticles, isotherms are bilogarithmic with an initial slope of 2, suggesting that a single adsorption site can bind two molecules of ciprofloxacin. In addition, the pseudo second order kinetic model fits well experimental data, proving that adsorption is mediated by a chemical reaction. CH–Fe(II) and CH–Zn(II) appear very promising for drug elimination, either from hospital waste water or from the gastrointestinal tract to prevent the emergence of antibiotic resistance.

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 &amp; Sons, Ltd.

Microstructure of stomaflex based magnetic elastomers

Stomaflex elastomers filled with two types of magnetic particles (nano- and micro-sized) were investigated. It was observed that doping with Fe3O4 nanoparticles and applying a magnetic field during the polymerisation process led to a significant change in the local structure of the elastomer. Decreases in the quasi-crystalline phase concentration, in the average size of the crystalline blocks, and in the ordering distance were observed after doping the elastomer with magnetite nanoparticles. After filling the polymer with Fe3O4 nanoparticles, yet the elastomer fractal dimension changes. For the elastomer filled with a large amount of Fe microparticles (75% particle concentration) a texture effect is observed, and this effect is larger for the samples polymerised in a magnetic field. At all microparticle concentrations, these elastomers exhibit surface fractal structure.

The effect of iron phosphate, alumina and silica coatings on the morphology of carbonyl iron particles

AbstractCarbonyl iron powders were coated with iron phosphate using phosphating method and boehmite (γ‐AlOOH) or silicon hydroxide (Si(OH)4) nanoparticles derived from the hydrolysis of tri‐sec‐butoxide (Al(OC4H9)3) or tetramethylsilane (Si(OCH3)4) using sol–gel method. The coated powders were dried and calcined at 400 °C for 3 h in air. Cross‐section morphology of coated carbonyl iron powders were investigated by scanning electron microscopy energy dispersive X‐ray analysis. Coated Fe micro‐particles were spherical in shape with ‘shell/core’ structures. The shells consisted of an amorphous layer with varying thickness (100–800 nm) and the core represented a carbonyl iron.Gelatinous morphology of dried FePO4 coating composed from nanoparticles of iron oxyhydroxides and hydrated iron phosphate with a shell thickness of ∼100 nm around iron particles was observed. In coatings based on alumina or silica xerogels with a thickness of ∼100–150 nm or ∼200–500 nm, the coatings were composed of iron oxyhydroxides and γ‐AlOOH or Si(OH)4. The resulting XRD diffractograms revealed the hematite (α‐Fe2O3) and magnetite (Fe3O4) that were formed in phosphated and sol–gel coated iron powders. The X‐ray diffraction patterns did not verify the presence of phosphates, alumina or silica and indicate the amorphous or nanocrystalline structure of FePO4, γ‐Al2O3 and SiO2. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Silicate particles engulfed in human alveolar macrophages: An analytical electron microscopy study

The chemical composition and crystalline structure of silicate particles engulfed in human alveolar macrophages were investigated by transmission analytical electron microscopy. A crystalline ZrSiO4 and an amorphous Si2AlO4 particle were identified. Small crystalline Fe microparticles (2–4 nm), which are likely ferritin molecules, were found concentrated mainly at the amorphous particle-tissue interface.