Mixture Of Fe2O3 Research Articles

Heteroaggregation of CeO2 nanoparticles in presence of alginate and iron (III) oxide

When manufactured nanoparticles are released to natural waters, heteroaggregation between nanoparticles and water compounds is expected to occur and play a key role in nanoparticle fate, transport and transformation. In this work, the heteroaggregation between CeO2 nanoparticles and Fe2O3 inorganic colloids, which represent the main inorganic fraction from Lake Geneva water, is studied. The heteroaggregation processes between CeO2, Fe2O3 and alginate in multiple water samples are investigated using zeta potential and z-average diameter measurements. The kinetics of heteroaggregation of individual components as well as mixtures of CeO2 nanoparticles and Fe2O3 colloids and alginate are studied using time resolved dynamic light scattering. The global attachment efficiency (αglobal) is calculated using data from kinetic experiments. αglobal for pristine CeO2 nanoparticles varied from 0.5 to 0.7 in lake and synthetic waters and is found around 1 for pristine Fe2O3 and mixture CeO2 and Fe2O3. Our findings demonstrate that heteroaggregation is highly dependent on environmental conditions and resulting electrostatic scenarios. No heteroaggregation at pH 8 between CeO2, Fe2O3 and alginate is observed in ultrapure water, because of electrostatic repulsions between negatively charged compounds. In synthetic and lake waters, the situation is opposite. Indeed, specific adsorption of divalent cations and presence of salt are found to promote heteroaggregation via cation bridging and screening effects. The kinetic experiments indicate that aggregation rate of pristine Fe2O3 is higher (89 nm/min in lake water) compared to pristine CeO2 nanoparticles (50 nm/min) and on the same level as mixture of CeO2 and Fe2O3 (96 nm/min). Low alginate concentration, 0.25 mg/L, has no effect on heteroaggregation in mixture of CeO2 and Fe2O3 in lake and synthetic waters. On the other hand, in natural water, the presence of higher alginate concentration, 2 mg/L, is found to reduce the heteroaggregation rate.

Optimization of mechanical alloying parameters for synthesis of nanostructure hexagonal BaFe12O19

In this study, barium hexaferrite nanostructure was synthesized by mechanical alloying method from a mixture of BaCO3 and Fe2O3. The effects of milling time and calcination temperature on synthesis of BaFe12O19 were investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM) were used to evaluation of structural, morphological, and magnetic properties of synthesized samples. The results showed that the amount of hematite phase increased by enhancing of the milling time from 5 to 25 h. However, the barium hexaferrite can be formed after 5 h milling and the calcination at 1100 °C. Also, the produced particles have almost spherical morphology and in some parts have polyhedral shape with an average size of about 100–150 nm. The saturation magnetization and the magnetic coercivity values were 56.48 emu/g and 5247.2 Oe, respectively. The area above the coercivity curve reveals that the sample has a hard magnetic behavior. In addition, the ratio of Mr/Ms was equal to 0.61 for the synthesized sample with the Fe/Ba molar ratio of 8. This amount is very close to the theoretical value for the random orientation of the single domain particles.

Double Layer Microwave Absorption Characteristics of Barium Hexaferrite/Silica Composite for X-Band Frequencies

Microwave absorption characteristics of double layer of barium hexaferrite attached on the silica to from a composite on the basis of wave propagation theory have been investigated. Barium hexaferrite, BaFe12O19, was synthesized through ceramic method from stoichiometric mixtures of BaCO3 and Fe2O3 as precursors. The mixture was pelletized under the pressure of 10 MPa and sintered at 1100 °C for 5 hours. Silica in the forms of powder was purified by using HCl. The crystal structure of the samples was characterized using X-ray diffraction (XRD), microstructure was examined using scanning electron microscope (SEM), hysteresis curves recorded by PERMAGRAPH techniques, whereas the microwave absorbing properties for X-band was recorded using a vector network analyzer (VNA). Relative complex permeability and permittivity, and reflection loss values were calculated at given thickness according to transmittance line theory within the range 8.2–12.4 GHz. Based on this study, the layer dimension and frequency that results in low reflection loss can be estimated from the material properties of the barium hexaferrite/silica composite material.

High-emissivity composite-oxide fillers for high temperature stable aluminum‑chromium phosphate coating

The production of high-performance heat-dissipating coatings on large structures has attracted significant attention owing to the ever-rising requirements of hypersonic vehicles. Mixtures of Al2O3, Cr2O3, Fe2O3, and MnO2 were sintered at various temperatures, and the composites obtained by sintering at 1323 and 1523 K were used as fillers for aluminum‑chromium phosphate based heat-dissipating coatings. The microstructures and compositions of the fillers and coatings were investigated by scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. Spectral emissivity and cyclic oxidation were performed up to 973 K for the coatings. The results showed that the aluminum‑chromium phosphate coating prepared with the filler sintered at 1323 K displayed the maximum spectral emissivity in the waveband 3–8 μm owing to the Mn1.5Cr1.5O4 phase. Further sintering the filler at 1523 K decreased the emissivity of the aluminum‑chromium phosphate coatings. The effects of the sintered fillers on emissivity were analyzed. In addition, the oxidation resistances, phase structures and morphologies of the aluminum‑chromium phosphate coatings after cyclic oxidation at 973 K for 200 h were studied, indicating that the aluminum‑chromium phosphate coatings prepared with the composite oxide fillers could improve the oxidation resistance of Ti alloys.

Combination of catalytic combustion and catalytic denitration on semi-coke with Fe2O3 and CeO2

The processes of catalytic combustion and catalytic denitration of semi-coke were conducted in the presence of catalysts Fe2O3 and CeO2, The comprehensive performance of these processes was evaluated with thermogravimetry analysis and infrared spectroscopy. The results indicate that the combustion activity improved significantly when we added Fe2O3 and CeO2 separately. Furthermore, the mixture of Fe2O3 and CeO2 has better combustion efficienty. When Fe2O3 and CeO2 were added separately, there was a decline in NO and CO emission (NO: 10.11% vs. 6.48%, CO: 7.18% vs. 5.28%). Meanwhile, the mixture of Fe2O3 and CeO2 caused a great decline in the total amounts of NO and CO emission (NO: 20.70%, CO: 16.33%). The denitration effect is ascribed to the homogeneous reduction of NO by CO, enhanced by adding the catalysts CeO2 and Fe2O3. Fe2O3 and CeO2 are catalytically active in promoting not only coke combustion but also NO reduction. Fe2O3 and CeO2 are associated, synergically catalyzing the semi-coke combustion.

Modification of Tribolayers of a Titanium Alloy Sliding against a Steel

The nonprotective tribolayers of the titanium alloy were modified into additives-containing tribolayers through an artificial addition of multilayer graphene (MLG), Fe2O3 nanomaterials, or their mixtures with various proportions on the titanium alloy/steel sliding interface. The sustainability of the modified tribolayers under a high load was evaluated by the critical sliding distance for a mild-to-severe wear transition. The modified tribolayers were found to significantly improve or deteriorate tribological performance of the titanium alloy, which was decided by their ingredients. The pure MLG- or Fe2O3-containing tribolayers, because of their lacking load-bearing or lubricant capacity, presented poor sustainability and readily lost protection to cause high wear loss or frictional coefficient. However, for the addition of various mixtures of MLG and Fe2O3, the modified tribolayers possessed a double-layer structure consisting of friction-reducing MLG- and wear-resistant Fe2O3-predominated layers. They presented a sustainable protection, thus remarkably improving the tribological performance of the titanium alloy.

Effect of Heat Treatment Condition on the Characteristics of MnO<sub>2</sub> Added-Fe<sub>2</sub>TiO<sub>5 </sub>Ceramics for NTC Thermistors Using Local Iron Oxide

A study on the effect of heat treatment condition on the characteristics of MnO2 added-Fe2TiO5 ceramics for NTC thermistor has been carried out. The ceramics were produced by pressing an homogenous mixture of Fe2O3 (local/ yarosite), TiO2 and MnO2 (2.0 mole %) powders in appropriate proportions to produce Fe2TiO5 based ceramics and sintering the pressed powder at 1050 °C for 3 hours in oxygen gas. Some sintered pellets were heat treated by heating them at 300 °C for 5, 15 and 25 minutes in Ar + 7% H2 gas. The XRD analyses showed that the Fe2TiO5 ceramics with and without heat treatment time had orthorhombic structure. No peak from second phase was observed from the XRD profiles. From the electrical characteristics data, it was known that the heat treatment could change the electrical characteristics of the Fe2TiO5 based-thermistor. The thermistor constant (B) and room temperature resistivity (ρRT) decreased with the increasing of heat treatment time. All ceramics made had thermistor characteristics namely B = 3459-7596 K and ρRT = 1.056-6936.062 MΩcm. Thermistor constant of the ceramics was relatively big, indicated that ceramics made from local iron oxide in this work fit the market requirement for NTC thermistor.

The Cross-Sectional Investigation of Oxide Scale FeCr Alloys and Commercial Ferritic Steel Implanted with Lanthanum and Titanium Dopants after Oxidation Test at 900°C

The cross-sectional examinations of oxide scales formed by oxidation on the surface of FeCr alloys and Ferritic Steel that implanted with lanthanum and titanium dopants were observed and investigated. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) has been used to study the cross-sectional oxides produced by specimens after oxidation process. X-ray diffraction (XRD) analysis was used to strengthen the analysis of the oxide scale morphology, oxide phases and oxidation products. Cross-sectional observations show the effectiveness of La implantation for improving thinner and stronger scale/substrate interface during oxidation process. The result shows that the thickness of oxide scales formed on the surface of La implanted FeCr alloy and ferritic steel was found less than 3 µm and 300 μm, respectively. The oxide scale formed on the surface of La implanted specimens consisted roughly of Cr2O3 with a small amount of FeO mixture. The oxidation resistance of FeCr alloy that implanted with Lanthanum showed better quality than that of commercial alloy. The beneficial effect of La implanted sample on the oxidation resistance was clearly visible to improve the adherence of oxide scale. Cross-sectional observations revealed the effectiveness of La implantation for improving thinner and stronger scale/substrate interface during oxidation process which presents the homogenous structure with good adherence and a uniform inter-diffusion layer between substrate and oxide layer.

The Cross-Sectional Investigation of Oxide Scale FeCr Alloys and Commercial Ferritic Steel Implanted with Lanthanum and Titanium Dopants after Oxidation Test at 900°C

The cross-sectional examinations of oxide scales formed by oxidation on the surface of FeCr alloys and Ferritic Steel that implanted with lanthanum and titanium dopants were observed and investigated. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) has been used to study the cross-sectional oxides produced by specimens after oxidation process. X-ray diffraction (XRD) analysis was used to strengthen the analysis of the oxide scale morphology, oxide phases and oxidation products. Cross-sectional observations show the effectiveness of La implantation for improving thinner and stronger scale/substrate interface during oxidation process. The result shows that the thickness of oxide scales formed on the surface of La implanted FeCr alloy and ferritic steel was found less than 3 μm and 300 μm, respectively. The oxide scale formed on the surface of La implanted specimens consisted roughly of Cr2O3 with a small amount of FeO mixture, which indicates that lanthanum implantation can improve the adherence, reduce the growth of the oxide scale as well as reduce the Cr evaporation. On the other side, the oxide scale formed on the surface of FeCr alloys and ferritic steel that implanted with titanium dopant was thicker, indicating that significant increase in oxidation mass gain. It can be noticed that titanium implantation ineffectively promotes Cr rich oxide. At the same time, the amount of Fe increased and diffused outwards, which caused the formation and rapid growth of FeO.

Stabilization of α-BiFeO3 structure by Sr2+ and its effect on multiferroic properties

We report a study on the effect of the substitution of Bi3+ by Sr2+ on the stabilization of R3c structure of Bi1−xSrxFeO3 (0 ≤ x ≤ 0.3, Δx = 0.05), and its effect in the magnetic and dielectric behavior. Stoichiometric mixtures of Bi2O3, Fe2O3 and SrO were mixed and milled for 5 h using a ball to powder weight ratio of 10:1 by high-energy ball milling. The obtained powder were pressed at 900 MPa to obtain cylindrical pellets and sintered at 800 °C for 2 h. X-ray diffraction and Rietveld refinement were used to evaluate the effect of Sr2+ on the crystal structure. In addition, vibrating sample magnetometry (VSM) and dielectric tests were used for describing the multiferroic behavior. The results show that Sr-doped BiFeO3 particles present rhombohedral structure (R3c) characteristic of α-BiFeO3 when the doping is below 0.10 mol of Sr. Additionally, a gradual decrease in the amount of secondary phases with the increase of the amount of strontium is observed. For doping concentration higher than 0.15 mol of Sr, a phase transition to an orthorhombic symmetry (β-BiFeO3, Pbnm) is detected. Besides, changes in relative intensities of reflection peaks planes (110) and (104) are associated with the phase transformations and with the magnetic and dielectric behavior. The α-BiFeO3 phase show antiferromagnetic behavior and high values of dielectric permittivity, whereas the β-BiFeO3 phase show a ferromagnetic behavior and low dielectric permittivity.

Effect of Fe2O3 and WO3 nanoparticle on steam injection recovery

ABSTRACTNanotechnology has the potential to introduce revolutionary changes in several areas of oil and gas industry. In this paper, the effect of different concentrations of Fe2O3 and WO3 nanoparticles at various temperatures was studied on viscosity of heavy oils. The effect of Fe2O3 and WO3 nanoparticles mixture on steam injection process is studied. The experimental tests show that some of these nanoparticles decrease the heavy oil viscosity to less than 40% in certain concentration at different temperatures. Our results of steam injection tests show that the injection of Fe2O3 and WO3 nanoparticles mixture increases the heavy oil recovery.

A novel fabrication strategy for highly porous FeAl/Al2O3 composite by thermal explosion in vacuum

The high porosity of FeAl/Al2O3 composites was successfully prepared via a low-energy consumption method of thermal explosion (TE) in vacuum from reactant mixtures of Fe, Al and Fe2O3. The temperature profiles, phase compositions, microstructure, porosity and pore size of the products were investigated. The TE reactions were ignited between 639 and 648 °C and maximum combustion temperatures reached to 1196–1867 °C. XRD patterns showed that FeAl, Fe2Al5 and Al2O3 were formed via TE reaction, and FeAl and Al2O3 were evolved as dominant phase after the final sintering at 1100 °C. The FeAl/Al2O3 composites exhibited an interconnected pore structure with porosities and pore size of 52–61% and 27–32 μm, respectively.

Iron Electrodeposition from Fe(II) Ions Dissolved in a Choline Chloride: Urea Eutectic Mixture

In this work, the Fe electrodeposition and nucleation and growth mechanisms onto a glassy carbon electrode from a choline chloride-based deep eutectic solvent (DES) were studied using electrochemical techniques and surface characterization techniques (SEM, EDS, and XPS). The current density transients were characterized by the strong effect of the induction-time during the Fe electrodeposition process. A model comprising 3D nucleation and diffusion-controlled growth that considers the induction-time offset was proposed and validated to analyze and explain the Fe nucleation and growth mechanism on the glassy carbon electrode. Kinetic parameters of Fe nucleation and diffusion-controlled growth such as the nucleation rate, A, the number density of active sites, N0, the diffusion coefficient, D, as well as induction-time were determined. Iron electrodeposit follows an electrochemical aggregative growth mechanism and was constituted by particles of Fe(0) and a mixture of FeO, Fe2O3 and Fe(OH)3.

Phase-pure BiFeO3 produced by reaction flash-sintering of Bi2O3 and Fe2O3

Nanostructured, highly-insulating, single-phase BiFeO3 is obtained by applying a small DC voltage to a mixture of Bi2O3 and Fe2O3 at 625 °C in seconds.

Uniform-Design-Based Optimization for Fuel Reactor of Chemical Looping Combustion

Abstract The thermo-chemical performance of fuel reactor (FR) for chemical looping combustion (CLC) changes with operating parameters. It is essential to optimize these operating variables to achieve the best reactor performance. Based on well-verified computational fluid dynamics (CFD) simulation, uniform design method is employed to study the influence of totally n operating variables each with m levels. With respect to the FR experiments by Son and Kim (2006)(in which fuel is pure methane, and oxygen carrier is the mixture of NiO and Fe2O3 supported by bentonite), the uniform design method has been adopted to optimize the yield of CH4 to CO2. Optimum operating condition (NiO percentage in the activated oxygen carrier of 100 %, reaction temperature of 1123 K, particle diameter of 100 μm, inlet gas velocity of 0.0125 m/s, and solid inventory in FR of 0.51 kg) is obtained, and the dependence of CO2 yield on five operating variables is approximated by the second-order polynomial model based on the uniform design method. The most critical parameter is identified as reaction temperature.

Synthesis and characterization of LaFeO3 powders prepared by a mixed mechanical/thermal processing route

Lanthanum ferrite, LaFeO3 (LF), has raised considerable interest since it can be used in many applications such as solid-oxide fuel cell electrode, sensor material (H2O and ethanol) and catalyst. Since the conventional ceramic route of synthesis has some disadvantages, mainly related to an exaggerated grain growth, LF has been prepared by different methods including combustion synthesis, sol–gel, hydrothermal processes, polymerizable complex method and mechanochemistry. As concerns this last method, a problem occurs due to the moisture sensitivity of La2O3. To overcome the problem, we used lanthanum acetate sesquihydrate [La(CH3COO)3·1.5H2O] and iron (II) oxalate dehydrate [FeC2O4·2H2O] as precursors. The mechanism of the solid-state reactions in the mixtures has been studied by TG–DSC and XRPD. Synthesis of LaFeO3 has been realized by annealing the mechanically activated mixtures for 3 h at temperatures between 500 and 800 °C. While LF prepared at 500 °C < T < 600 °C has an amorphous character, LF obtained at T ≥ 600 °C is free from carbonaceous impurities as it is shown by FT-IR and TG measurements. The specific area of the LaFeO3 powders obtained starting from the mechanically activated mixture is decreasing by increasing the annealing temperature. On the contrary, the annealing on samples of physical mixture at temperatures up to 800 °C only yields a mixture of LaFeO3, La2O3 and Fe2O3.

Two growth mechanisms in one-step fabrication of the oxide matrix for FeSiAl soft magnetic composites

Hydrolysis precipitation as a new method was used in the preparation of oxide insulation matrix for FeSiAl soft magnetic composites (SMCs). The growth and composition of the matrix can be tuned by the concentration of the Al(NO3)3 solution, reaction temperature and pH value during the hydrolysis. With optimized Al(NO3)3 concentration of 0.6 mol/L and hydrolysis temperature of 75 °C, two mechanisms have been revealed in the formation of the insulation coating depending on the pH of the Al(NO3)3 solution. When pH = 3, the coating layer contains a mixture of Al2O3 and Fe2O3, while Al2O3 and SiO2 form as the coating for pH = 8. Despite that the Al2O3 dominates for both conditions, it grows via different routes. The Al(OH)3 as the precursor forms through Al3+ hydrolysis and heterogeneous nucleation for pH = 3. With increased pH to 8, the Al3+ directly reacts with OH− to form Al(OH)3 colloidal particles which adsorb onto the surface of FeSiAl powders via electrostatic attraction. Both mechanisms give rise to satisfactory magnetic performance with high effective permeability (μe = 103.5 and 113.4) and low core loss (Pcv = 278.4 mW·cm−3 and 237.8 mW·cm−3) for pH = 3 and 8 measured at 100 mT, 50 kHz.

A Q-switched, 1.89 µm fiber laser using an Fe3O4-based saturable absorber

The potential of Fe3O4 nanoparticles as a base material for saturable absorbers (SAs) that can operate in the 2μm-wavelength regime, was investigated. An SA was fabricated on a sandwich-structured fiber-ferrule platform through the deposition of an Fe3O4 mixture with polyvinyl alcohol (PVA) onto the end surface of the fiber ferrule. Using the prepared Fe3O4/PVA-composite-based SA within a Tm-Ho codoped fiber laser, stable Q-switched pulses were readily produced at 1894nm. The temporal characteristics of the output pulses were investigated as a function of the pump power, and the maximum energy of the output pulses was 322nJ. The temporal width of the output pulses was measured as 2.6µs at the maximum pulse-repetition rate of 37.2kHz. The output performance of the passively Q-switched Tm-Ho-codoped fiber laser in this work was compared with those of recently demonstrated, passively Q-switched Tm-doped fiber lasers for which the other types of saturable-absorption materials.

Microstructure and Wear Behavior of FeCoCrNiMo0.2 High Entropy Coatings Prepared by Air Plasma Spray and the High Velocity Oxy-Fuel Spray Processes

In the present research, the spherical FeCoCrNiMo0.2 high entropy alloy (HEA) powders with a single FCC solid solution structure were prepared by gas atomization. Subsequently, the FeCoCrNiMo0.2 coatings with a different content of oxide inclusions were prepared by air plasma spraying (APS) and high-velocity oxy-fuel spraying (HVOF), respectively. The microstructure, phase composition, mechanical properties, and tribological behaviors of these HEA coatings were investigated. The results showed that both HEA coatings showed a typical lamellar structure with low porosity. Besides the primary FCC phase, a mixture of Fe2O3, Fe3O4, and AB2O4 (A = Fe, Co, Ni, and B = Fe, Cr) was identified as the oxide inclusions. The oxide content of the APS coating and HVOF coating was calculated to be 47.0% and 12.7%, respectively. The wear resistance of the APS coating was approximately one order of magnitude higher than that of the HVOF coating. It was mainly attributed to the self-lubricated effect caused by the oxide films. The mass loss of the APS coating was mainly ascribed to the breakaway of the oxide film, while the main wear mechanism of the HVOF coating was the abrasive wear.

Redox Paths in Heated TiO–Fe2O3 and TiO–Fe3O4 Mixtures—Implication of TiO as a Novel Reducing Compound

Redox Paths in Heated TiO–Fe₂O₃ and TiO–Fe₃O₄ Mixtures—Implication of TiO as a Novel Reducing Compound