Pure Iron Oxide Research Articles

Structural, Magnetic and Dielectric Properties of Ba Doped BiFeO3 Thin Films

Multiferroic materials, exhibiting simultaneous presence of ferroelectric and ferromagnetic behavior, have attracted the researcher's attention due to promising applications. However, difficulties associated with BiFeO3 including volatile nature of Bi2O3, antiferromagnetic behavior, large leakage current etc. limit its industrial applications. In order to overcome these difficulties we here report synthesis and characterization of barium doped BiFeO3 thin films using sol-gel and spin coating method. The dopant concentration in Bi1-xBaFeO3 is varied as x= 0.1, 0.2, 0.3. The films are annealed at 300˚C in the presence of vacuum under an applied field of 500Oe. Barium has ionic radius of 1.42Å so it can replace bismuth that has an ionic radius of 1.17Å. Films show high dielectric constant and low tangent loss till dopant concentration of 0.2. Inclusion of dopant results in homogeneity on spin structure thus leading to ferromagnetic behavior of doped bismuth iron oxide thin films. Degradation in magnetic and dielectric properties is observed with dopant concentration of 0.3 due to the presence of dopant oxide (BaO) in pure bismuth iron oxide phase.

Sol-Gel Synthesis of BiFeO3 Nanoparticles

Among the various multiferroic materials bismuth iron oxide is a promising candidate due to its relatively high antiferromagnetic Neel temperature and high ferroelectric Curie temperature as compared to all other multiferroic materials. But synthesis of pure phase BiFeO3 is difficult due to the volatile nature of Bi2O3 that leads to bismuth deficient phases and if excess of bismuth is employed it give rise to bismuth rich phases. Moreover the synthesis of pure phase BiFeO3 requires high temperature annealing in the range of 400-700˚C. However, we here report sol-gel synthesis of bismuth iron oxide nanoparticles at low temperatures of 100-300˚C. These nanoparticles are characterized using XRD and VSM. The nanoparticles annealed at 100˚C results in amorphous behavior. Whereas peaks corresponding to pure phase bismuth iron oxide emerges at annealing temperatures of 200 and 300˚C. The nanoparticles show ferromagnetic behavior as opposed to antiferromagnetic behavior due to suppression of spiral spin structure.

Low Resistance, Carbon Black-free Magnetite Anode for Li-ion Batteries Obtained by One-step Attachment of Carbon Nanotubes

The paper describes a simple, one-step synthetic route for the fabrication of nanometric iron (III) oxide attached to multiwalled carbon nanotubes (MWCNT). TEM images show that magnetite nanoparticles with primary particle sizes of ca. 10 nm are preferentially located on the outer walls of carbon nanotubes. The obtained nanocomposites have been examined on reversible electrochemical insertion of lithium cations in a Li-ion cell. The presence of MWCNT brings about a substantial increase of the magnetite reversible capacities in the absence of any additional carbonaceous conductivity enhancing agent. With increasing MWCNT content in the material, reversible capacity consistently rises from 207 mAhg-1 for pure iron (III) oxide up to 763 mAhg-1 for the composite with 40 % of MWCNT. Cyclic voltammetry measurements reveal the expected large hysteresis between the reduction and oxidation peaks associated with Li+ insertion/deinsertion into magnetite crystal lattice. The reductive current peak maxima steadily rise with increasing MWCNT content from 0.15 A g-1 for pure iron (III) oxide up to 0.4 A g-1 for the composite with 40 % of MWCNT which confirms faster kinetics of electrochemical processes. EIS measurements directly proved the internal resistance decrease connected with the incorporation of MWCNT.

Synthesis of phase pure iron oxide polymorphs thin films and their enhanced magnetic properties

The α-Fe2O3 thin film was prepared on liquid–vapor interface at room temperature by a facile and cost effective method, which was converted to Fe3O4 and γ-Fe2O3 films by reduction and oxidation process. The morphological and structural characterizations reveal the average crystallites size in α-Fe2O3, Fe3O4 and γ-Fe2O3 films 12.8, 9.2 and 19 nm with rms roughness 4.35, 4.60 and 8.21 nm, respectively. From magnetic measurements, the α-Fe2O3 thin film shows a room temperature super-paramagnetic behavior with saturation magnetization 18 emu/cm3, while Fe3O4 and γ-Fe2O3 thin films exhibit ferrimagnetic behavior with saturation magnetization values 414.5 and 148 emu/cm3, respectively. A significantly higher value of saturation magnetization is observed in α-Fe2O3 film, which is trusted due to the uncompensated surface spins in the film. The converted Fe3O4 film also shows enhanced saturation magnetization due to the reduction in antiphase boundaries, whereas the magnetization in γ-Fe2O3 film decreases comparatively. The magnetic property of the γ-Fe2O3 is explained on the basis of the Fe3+ ions vacancy at the octahedral position in its structure.

Ab-initio modeling of an iron laser-induced plasma: Comparison between theoretical and experimental atomic emission spectra

We report on efforts to model the Fe emission spectrum generated from laser-induced breakdown spectroscopy (LIBS) measurements on samples of pure iron oxide (Fe2O3). Our modeling efforts consist of several components. We begin with ab-initio atomic structure calculations performed by solving the Hartree–Fock equations for the neutral and singly ionized stages of Fe. Our energy levels are then adjusted to their experimentally known values. The atomic transition probabilities and atomic collision quantities are also computed in an ab-initio manner. We perform LTE or non-LTE calculations that generate level populations and, subsequently, an emission spectrum for the iron plasma for a range of electron temperatures and electron densities. Such calculations are then compared to the experimental spectrum. We regard our work as a preliminary modeling effort that ultimately strives towards the modeling of emission spectra from even more complex samples where less atomic data are available.

A Smart Platform for Hyperthermia Application in Cancer Treatment: Cobalt-Doped Ferrite Nanoparticles Mineralized in Human Ferritin Cages

Magnetic nanoparticles, MNPs, mineralized within a human ferritin protein cage, HFt, can represent an appealing platform to realize smart therapeutic agents for cancer treatment by drug delivery and magnetic fluid hyperthermia, MFH. However, the constraint imposed by the inner diameter of the protein shell (ca. 8 nm) prevents its use as heat mediator in MFH when the MNPs comprise pure iron oxide. In this contribution, we demonstrate how this limitation can be overcome through the controlled doping of the core with small amount of Co(II). Highly monodisperse doped iron oxide NPs with average size of 7 nm are mineralized inside a genetically modified variant of HFt, carrying several copies of α-melanocyte-stimulating hormone peptide, which has already been demonstrated to have excellent targeting properties toward melanoma cells. HFt is also conjugated to poly(ethylene glycol) molecules to increase its in vivo stability. The investigation of hyperthermic properties of HFt-NPs shows that a Co doping of 5% is enough to strongly enhance the magnetic anisotropy and thus the hyperthermic efficiency with respect to the undoped sample. In vitro tests performed on B16 melanoma cell line demonstrate a strong reduction of the cell viability after treatment with Co doped HFt-NPs and exposure to the alternating magnetic field. Clear indications of an advanced stage of apoptotic process is also observed from immunocytochemistry analysis. The obtained data suggest this system represents a promising candidate for the development of a protein-based theranostic nanoplatform.

Origins of microspherules from the Permian–Triassic boundary event layers in South China

Volcanism and impact scenarios are two of the most plausible ways of interpreting the causes of the largest biological mass extinction at the end-Permian. Microspherules have previously been widely reported from tens of different Permian–Triassic boundary (PTB) sections in South China and some other regions. These microspherules have been interpreted as either the product of volcanic eruptions or an impact event. In order to test these scenarios, we collected 60 samples from 12 intensively-studied PTB sections in South China. In addition, four soil samples close to these PTB layers were also collected for comparison. Our investigation indicates that abundant microspherules with mosaic or dot shape crystals on rounded surface are present in the surface samples in the PTB layers at Meishan, Meili, and Shatian sections and most soil background samples in South China. Those microspherules consist of four different types based on their main chemical composition, surface features, and internal structure including iron, magnetite–silicate, glassy, pyrite microspherules and framboids. In contrast, microspherules have not been found in a few sections in remote areas such as the Selong Xishan section in Tibet and the Dalongkou section in Xinjiang, Northwest China, in the deeply-excavated samples at the Shangsi section and the hard tuff layers around the PTB at the Xiaochehe Section in Guiyang. Microspherules decrease in abundance with depth in PTB clay beds. All these microspherules except the pyrite microspherules and framboids are found in both the PTB layers and the nearby soil background samples. The iron microspherules are pure iron oxides such as magnetite, hematite or maghemite and contain low concentrations of nickel and chromium, and lack an Ni–Fe core and general extraterrestrial mineral wüstite. All these external and chemical characteristics suggest that most of iron microspherules previously reported from PTB sections in South China are modern industrial fly ashes. A low ratio of Fe3 +/FeTotal in crystals of magnetite–silicate microspherules and high ZnO contents can identify them as industrial contaminants. The pyrite microspherules and framboidal pyrite found from bed 24e and bed 26 at the Meishan sections are of depositional or/and diagenetic origins, and only the rounded quartz and the fragments containing extremely high SiO2 and TiO2 are possibly of volcanic origin.

Structural, stability, magnetic, and toxicity studies of nanocrystalline iron oxide and cobalt ferrites for biomedical applications

Iron oxide and cobalt ferrite magnetic nanoparticles (MNPs) of 5–15 nm range have been synthesized by the co-precipitation method, and the magnetic MNPs are functionalized by 3-aminopropyl triethoxy silane and citric acid. The crystalline quality of the MNPs was confirmed using X-ray diffraction, verifying the spinel structure. Spectroscopy study confirmed the presence of the corresponding functional groups on MNP surfaces and thermogravimetric analysis further confirmed functionalization. Coercivity and saturation magnetization exhibited superior superparamagnetic properties. Toxicity studies compared the dose dependent toxicity of both pure iron oxide and cobalt ferrite samples. The toxicity of surface functionalized MNPs showed the potential for use in biomedicine.

Isolation of technogenic magnetic particles

Technogenic magnetic particles (TMPs) emitted by various industrial sources, such as smelting plants, end up after atmospheric transfer on the soil surface. In the present study, we characterised the origin and composition of such particles emitted by a large iron smelting plant and deposited on particular substrates, namely tombstones, which act as a very interesting and appropriate matrix when compared to soil, tree bark, lichens or attic dust. The isolation and subsequent description of TMPs require a critical step of separation between different components of the sample and the magnetic particles; here, we described an efficient protocol that fulfils such a requirement: it resorts to water suspension, sonication, repeated magnetic extraction, sedimentation, sieving and organic matter destruction at 550°C in some instances. The isolated TMPs displayed a noticeable crystalline shape with variable compositions: a) pure iron oxides, b) iron+Cr, Ni or Zn, and c) a complex structure containing Ca, Si, Mg, and Mn. Using Scanning Electron Microscope Energy Dispersive X-ray (SEM–EDX), we obtained profiles of various and distinct magnetic particles, which allowed us to identify the source of the TMPs.

カルシウムフェライトの反応過程を考慮した焼結鉱ガス還元モデル(6界面未反応核モデル)

Reducible oxides containing iron in iron ore sinter are hematite, magnetite and quaternary calcium ferrite (abbreviated by CF), which is the complex crystalline mineral produced from Fe2O3, CaO, SiO2 and Al2O3. Equilibrium diagram for CF reduction with CO-CO2 gas mixture is a little but significantly different from the one for pure iron oxides. In previous analyses for reduction reaction of iron oxides in a blast furnace, however, sinter has been treated as pure iron oxides; existence of CF has been ignored. Reduction steps for CF can be written asCF (= ‘Fe2O3’) → ‘Fe3O4’ → ‘FeO’ → ‘Fe’,which are much the same as pure iron oxides, where ‘Fe2O3’, ‘Fe3O4’, ‘FeO’ and ‘Fe’ designate hematite, magnetite, wustite and iron stages of CF, respectively. However, a reported variation of gas composition with temperature measured in a blast furnace shows that the gas composition in the thermal reserve zone is a little higher than the wustite / iron equilibrium, the reduction potential of which is less than that of ‘FeO’ / ‘Fe’ equilibrium and hence ‘FeO’ cannot be reduced to ‘Fe’. In the present work, gaseous reduction model for sinter is developed in consideration of CF reaction process; unreacted-core shrinking model for six interfaces is proposed to take into account reaction process of CF as well as pure iron oxides. Trial comparison of the calculated reduction curve with our previously reported experimental data under simulated blast furnace conditions shows rather good agreement.

In vitro sustained release study of gallic acid coated with magnetite-PEG and magnetite-PVA for drug delivery system.

The efficacy of two nanocarriers polyethylene glycol and polyvinyl alcohol magnetic nanoparticles coated with gallic acid (GA) was accomplished via X-ray diffraction, infrared spectroscopy, magnetic measurements, thermal analysis, and TEM. X-ray diffraction and TEM results showed that Fe3O4 nanoparticles were pure iron oxide having spherical shape with the average diameter of 9 nm, compared with 31 nm and 35 nm after coating with polyethylene glycol-GA (FPEGG) and polyvinyl alcohol-GA (FPVAG), respectively. Thermogravimetric analyses proved that after coating the thermal stability was markedly enhanced. Magnetic measurements and Fourier transform infrared (FTIR) revealed that superparamagnetic iron oxide nanoparticles could be successfully coated with two polymers (PEG and PVA) and gallic acid as an active drug. Release behavior of gallic acid from two nanocomposites showed that FPEGG and FPVAG nanocomposites were found to be sustained and governed by pseudo-second-order kinetics. Anticancer activity of the two nanocomposites shows that the FPEGG demonstrated higher anticancer effect on the breast cancer cell lines in almost all concentrations tested compared to FPVAG.

Chemical conversion of NO and CO on catalysts based on cobalt or iron oxides.

Cobalt or iron oxides supported or not on zeolite Hbeta were prepared and evaluated in the reduction reaction of NO by CO in presence of O2, SO2 or H2O. XRD results evidenced the Hbeta structure and the formation of Co3O4 and Fe2O3. TPR-H2 analysis showed complete reduction of cobalt oxide at lower temperatures than for iron oxide. The catalysts are quite active and the activity depends on the reaction temperature. The highest conversions rates were observed for pure iron oxide, which can be a relatively low cost catalyst for reduction of NO by CO, with high selectivity towards the N2 formation.

Influences of non-stoichiometry on thermodynamics and kinetics of iron oxides reduction processes

Non-stoichiometry influences both the thermodynamic and kinetic analyses of the iron oxide redox processes. The thermochemical data of iron oxide redox reactions in various textbooks are not consistent, and the kinetic characteristics are not well understood because of the non-stoichiometry. To clarify such confusions, some famous thermodynamic data are compared, and highly precise experimental work conducted for verification. It is shown that the thermodynamic data for the pure iron oxide reduction reactions from JANAF agree well with the experimental results; the eutectoid temperature of iron oxides was proven to be 576°C; Dieckmann’s defect model of magnetite was proven in good agreement with the experimental results only at high oxygen activities but not low oxygen activities; and the dependences of iron deficiency on Δwt-% (weight loss ratio) and Fe2+% (ferrous ratio) were calculated and experimentally verified in pure iron oxides reduction processes.

Production and characterization of iron-chromium-zinc pigment based ceramic stain colour of red-brown shade

Considering the demand of ceramic stain colours in Bangladesh, an attempt has been taken to develop iron-chromium-zinc pigment based ceramic stain colour of red-brown shade which could be used as an import substitute material in the local ceramic industries. The desired shade of red-brown stain was synthesized from an equimolar mixture of pure chromium oxide (Cr2O3), iron oxide (Fe2O3) and zinc oxide (ZnO). The developed stain was characterized by X-ray diffraction (XRD) technique. The characteristic of the stain complied with the chemical durability. Moreover, chromium leaching was below the permissible exposure limit which makes it as a promising ceramic stain to be used in our ceramic industries. DOI: http://dx.doi.org/10.3329/bjsir.v48i3.17334 Bangladesh J. Sci. Ind. Res. 48(3), 213-216, 2013

A facile method for preparation of iron based catalysts for high temperature water gas shift reaction

Nanocrystalline Fe3O4 based catalysts with theoretical particle size of 31–78nm were synthesized by a facile direct pyrolysis method and employed in high temperature water gas shift reaction. XRD analysis showed that this method led to obtaining the catalysts directly in the active phase with chromium and copper incorporated into magnetite lattice. The results showed that the addition of chromium significantly increases the BET surface area of the pure iron oxide from 14.87 to 35.42m2g−1. Among the catalysts evaluated, Fe–Cr–Cu catalyst revealed higher activity compared to commercial catalyst and showed high stability during 10h time on stream.

Sustained Release of Prindopril Erbumine from Its Chitosan-Coated Magnetic Nanoparticles for Biomedical Applications

The preparation of magnetic nanoparticles coated with chitosan-prindopril erbumine was accomplished and confirmed by X-ray diffraction, TEM, magnetic measurements, thermal analysis and infrared spectroscopic studies. X-ray diffraction and TEM results demonstrated that the magnetic nanoparticles were pure iron oxide phase, having a spherical shape with a mean diameter of 6 nm, compared to 15 nm after coating with chitosan-prindopril erbumine (FCPE). Fourier transform infrared spectroscopy study shows that the coating of iron oxide nanoparticles takes place due to the presence of some bands that were emerging after the coating process, which belong to the prindopril erbumine (PE). The thermal stability of the PE in an FCPE nanocomposite was remarkably enhanced. The release study showed that around 89% of PE could be released within about 93 hours by a phosphate buffer solution at pH 7.4, which was found to be of sustained manner governed by first order kinetic. Compared to the control (untreated), cell viability study in 3T3 cells at 72 h post exposure to both the nanoparticles and the pure drug was found to be sustained above 80% using different doses.

Preparation and characterization of 6-mercaptopurine-coated magnetite nanoparticles as a drug delivery system.

BackgroundIron oxide nanoparticles are of considerable interest because of their use in magnetic recording tape, ferrofluid, magnetic resonance imaging, drug delivery, and treatment of cancer. The specific morphology of nanoparticles confers an ability to load, carry, and release different types of drugs.Methods and resultsWe synthesized superparamagnetic nanoparticles containing pure iron oxide with a cubic inverse spinal structure. Fourier transform infrared spectra confirmed that these Fe3O4 nanoparticles could be successfully coated with active drug, and thermogravimetric and differential thermogravimetric analyses showed that the thermal stability of iron oxide nanoparticles coated with chitosan and 6-mercaptopurine (FCMP) was markedly enhanced. The synthesized Fe3O4 nanoparticles and the FCMP nanocomposite were generally spherical, with an average diameter of 9 nm and 19 nm, respectively. The release of 6-mercaptopurine from the FCMP nanocomposite was found to be sustained and governed by pseudo-second order kinetics. In order to improve drug loading and release behavior, we prepared a novel nanocomposite (FCMP-D), ie, Fe3O4 nanoparticles containing the same amounts of chitosan and 6-mercaptopurine but using a different solvent for the drug. The results for FCMP-D did not demonstrate “burst release” and the maximum percentage release of 6-mercaptopurine from the FCMP-D nanocomposite reached about 97.7% and 55.4% within approximately 2,500 and 6,300 minutes when exposed to pH 4.8 and pH 7.4 solutions, respectively. By MTT assay, the FCMP nanocomposite was shown not to be toxic to a normal mouse fibroblast cell line.ConclusionIron oxide coated with chitosan containing 6-mercaptopurine prepared using a coprecipitation method has the potential to be used as a controlled-release formulation. These nanoparticles may serve as an alternative drug delivery system for the treatment of cancer, with the added advantage of sparing healthy surrounding cells and tissue.

Chemical reactivity at Fe/CuO interface studied in situ by X-ray photoelectron spectroscopy

The technique of X-ray photoelectron spectroscopy has been used to investigate the chemical reactivity at the Fe/CuO interfaces. The 2p core level regions of the metals have been studied. Thin films of iron (thicknesses ranging from 0.3 nm to 2.0 nm) were deposited on copper oxide substrates at room temperature. Earlier investigation on a 0.5 nm overlayer of iron on CuO showed considerable reactivity at the interfaces. The core level peaks of iron are observed to be shifted to the high BE energy side with the appearance of satellites. The spectral data have been compared with those of the oxidized iron and confirms the formation of the iron oxide at the interface. The satellite structure in the copper region is observed to disappear and the spectral features are found to approach those of elemental copper. The interface is found to consist of a mixture of iron oxide and elemental copper. Presence of unreacted iron near the interface has been observed for thicknesses greater than 0.7 nm of the iron overlayer. The effect of temperature on the interface has also been studied. The interface was formed by depositing 2.0 nm of iron on the copper oxide substrate under two different conditions. In one, the substrate temperature was kept constant during the deposition of the iron overlayer. In the other, post deposition annealing of the interface was performed. The iron overlayer is observed to be completely oxidized at the sample temperature of 450 °C and the oxidation is independent of the processing conditions. The amounts of elemental iron and iron oxide in the samples have been estimated by modeling the spectrum using the spectra of elemental iron and pure iron oxide. The process of annealing seems to have more effect on the oxidation of iron than the substrate temperature. The investigation shows room temperature chemical reactivity at the Fe/CuO interface and provides a new method of preparing sub-nano-oxide films of iron.

Oxidation Study of Pure Fe and Fe-36Ni Alloy at Elevated Temperature

There have been many studies on the oxidation of pure iron and steel at different temperatures and pressures. D. Caplan et al. demonstrated the effect of cold-work and metal grain size on the oxidation rate of iron. It was concluded that the oxidation rate of iron was accelerated with temperature, cold-work, and increased oxygen pressure, while the oxidation rate of iron, coarse-or fine-grained, cold-worked or annealed, was found to be the same at the FeO-forming temperature range [1-3].

Synthesis of phase pure praseodymium barium copper iron oxide

The control of crystallization of praseodymium barium copper iron oxide, an intermediate temperature solid oxide fuel cell cathode material, has been demonstrated for the first time using a biotemplated sol-gel synthesis technique. The results obtained showed significant improvement in purity, synthesis time, surface area and simplicity over that previously reported.