A single target RF magnetron co-sputtered iron doped tin oxide films with pillars

The SnO₂ gas sensors and catalytic surfaces are produced by different techniques with a wide range of dopants improving their selectivity and sensitivities. The surface topology is important because the active surface area can be enlarged dramatically by employing nanostructures. Many reported techniques for the tin oxide nanostructures preparation require fine powders or liquid precursors together with high temperatures above 500 °C. But the nanostructures can be formed by the RF off-axis magnetron sputtering technique at room temperature from a bulk target. The single target co-sputtering of SnO₂ target with Fe inset was used to deposit SnO₂ film doped by iron.The 400 nm diameter pillars were successfully deposited in controllable density on polished Si substrates at low pressure 0.3 Pa of argon and oxygen gas mixture. The pillars were not formatted at the beginning of deposition process but certain SnO₂ film was required. The surface around the pillars was flat without any significant texture.The iron in form of the iron oxide was found to be the doping in deposited coatings when the stannic oxide was sub-stoichiometry with oxygen vacancies.     

Chemical constitution and microstructure of TiC x coatings chemically vapour deposited on Fe-C substrates; effects of iron and chromium

TiC _x coatings were chemically vapour deposited in an industrial reactor on Fe-C substrates with carbon contents between 0.06 and 1.20 wt % C. Electron probe microanalyses showed that significant amounts of chromium and iron were present in the coatings and that chromium was also present in the substrate region adjacent to the coatings. By comparing calculated and measured lattice parameters (corrected for the internal stresses present) it became evident that the chromium was in solid solution in TiC _x , whereas the iron was not. This was confirmed by micro Auger electron spectroscopy and X-ray diffraction phase analyses. The carbon to metal ratio,x, of the TiC _x coatings decreased with increasing distance to the coating/substrate interface. The effect of iron on the X-ray diffraction line broadening and hardness of the coatings was large (in contrast with the effect of chromium) and increased with increasing distance to the coating/substrate interface because of a decreasing iron particle size. The TiC _x crystallite size was small and constant throughout the thickness of the coatings. The chromium present in the substrate region adjacent to the TiC _x coatings influenced the microstructure of the substrate by formation of iron, chromium-carbides and reduced the growth rate of the coatings.     

Ferrocene‐Incorporated Cobalt Sulfide Nanoarchitecture for Superior Oxygen Evolution Reaction

Here, ferrocene(Fc)‐incorporated cobalt sulfide (Co_xS_y) nanostructures directly grown on carbon nanotube (CNT) or carbon fiber (CF) networks for electrochemical oxygen evolution reaction (OER) using a facile one‐step solvothermal method are reported. The strong synergistic interaction between Fc‐Co_xS_y nanostructures and electrically conductive CNTs results in the superior electrocatalytic activity with a very small overpotential of ≈304 mV at 10 mA cm^?2 and a low Tafel slope of 54.2 mV dec^?1 in 1 m KOH electrolyte. Furthermore, the Fc‐incorporated Co_xS_y (FCoS) nanostructures are directly grown on the acid pretreated carbon fiber (ACF), and the resulting fabricated electrode delivers excellent OER performance with a low overpotential of ≈315 mV at 10 mA cm^?2. Such superior OER catalytic activity can be attributed to 3D Fc‐Co_xS_y nanoarchitectures that consist of a high concentration of vertical nanosheets with uniform distribution of nanoparticles that afford a large number of active surface areas and edge sites. Besides, the tight contact interface between ACF substrate and Fc‐Co_xS_y nanostructures could effectively facilitate the electron transfer rate in the OER. This study provides valuable insights for the rational design of energy storage and conversion materials by the incorporation of other transition metal into metal sulfide/oxide nanostructures utilizing metallocene.     

Fabrication of nanostructured α-Fe2O3 electrodes using ferrocene for solar hydrogen generation

Nanostructured thin films of α-Fe₂O₃ were prepared through atmospheric chemical vapour deposition (APCVD) using ferrocene and iron pentacarbonyl as precursors. Higher optical absorption was observed for hematite films prepared using ferrocene, which was attributed to the higher packing density. Photoelectrochemical (PEC) studies of the films prepared using ferrocene showed superior performance to that of iron pentacarbonyl. Photocurrent density of 540 µA/cm² and 1.5 µA/cm² at 1.23 V_RHE was achieved for hematite films prepared using ferrocene and iron pentacarbonyl, respectively. Our findings suggest that ferrocene can be used as a promising alternative to iron pentacarbonyl to prepare hematite photoelectrodes using APCVD.     

Assessment of B4C reaction with liquid iron alloys

The degree of reaction achieved when B₄C powders are brought into contact with liquid iron alloys has been assessed by a levitation dispersion test. Reaction occurs rapidly, leading to boron carbide dissolution and iron boride formation. In carbon-free iron alloys borocarbide, Fe₂₃(C, B)₆, also forms and in low-carbon iron alloys free graphite was also formed. Highcarbon alloys reacted to form both Fe₃(C, B) and free graphite. Attempts to provide protection for the B₄C by forming a TiC coating on its surface byin situ reactions with liquid Fe-Ti and Fe-Ti-C alloys proved unsuccessful, with TiC forming as a dispersed phase throughout the iron matrix     

Bulk and surface structures of iron doped zirconium oxide systems: Influence of preparation method

Three different Fe-Zr oxide systems were prepared using firstly classical impregnation of iron nitrates on calcined ZrO₂ (Fe_x/ZrO₂, x represents Fe/Zr ratio = 0.01 and 0.11), secondly impregnation of iron nitrates on dried zirconium hydroxide ZrO(OH)₂ (Fe_x/ZrO(OH)₂) and finally hydrolysis of aqueous suspension of iron and zirconium salts to coprecipitate iron and zirconium hydroxides (Fe_x-Zr). Thermal decomposition study of dried samples evidenced a delay in the temperature crystallization of zirconia for Fe_x-Zr and Fe_x/ZrO(OH)₂, the more the iron content in the sample, the more important the delay. For these samples, the formation and the stabilization of different phases were evidenced by several characterization techniques : X-Ray Diffraction (XRD), Raman spectroscopy and Electron Paramagnetic Resonance (EPR).The interaction of iron species with zirconia was different in accordance with different preparations. A bulk dispersion of the coprecipitated sample was observed and as a consequence Zr^{3 +} defects in the solid were not produced. In the case of Fe_x/ZrO₂ sample, production of surface Zr^{3 +} ions was established at low temperature of calcination (up to 600^∘C) and explained by the reaction of NO₃⁻ with Zr^{4 +} on the zirconia surface. However such interaction did not occur for Fe_x/ZrO(OH)₂ since a low dispersion of iron species was observed by X-ray Photoelectron Spectroscopy (XPS), deposited phase (Fe₂O₃) forming preferentially blocks. Temperature Programmed Reduction (TPR) showed that the reduction of small particles of Fe₂O₃ and bulk Fe₂O₃ present in the impregnated samples was easier than that of iron species well dispersed in the bulk of the coprecipitated solid.     

Study of the corrosion layer on iron obtained in solutions of water-polyethylene glycol (PEG 400)-sodium phosphate

The iron behaviour in phosphate/water/polyethylene glycol (PEG) was studied in-situ and ex-situ by spectrometry Raman, ESCA spectroscopy, X-ray diffraction, Auger spectroscopy were used as surface analysis methods. It changes with phosphate concentration. At low phosphate concentration (5 × 10^–4 M-10^–3 M-5 × 10^–3 M), iron is corroded. The thin corrosion layer is a mixture of iron oxides (-Fe₂O₃, Fe₃O₄) and iron phosphate(Fe₃(PO₄)₂, 8H₂O). At high phosphate concentration (10^–2 M-5 × 10^–2 M), the iron is protected. The protection could be due to an heterogenous layer containing PEG 400 and phosphates.     

High-pressure behavior of the crystal structure of the fullerene molecular complex with ferrocene C60·{Fe(C5H5)2}2

Abstract

The crystal structure of the molecular complex C₆₀·{Fe(C₅H₅)₂}₂ was studied by single crystal X-ray diffraction (XRD) analysis at pressures up to 5?GPa using the diamond anvil cell (DAC) technique. The XRD data and subsequent structural analysis clearly show that there is no pressure-induced polymerization in fullerene layers in pressure range studied. The reciprocal unit cell volume V₀/V is a smooth and monotonous function of pressure and fits well to the Murnaghan equation of state (V₀/V) ^B'=?{1?+?P·(B'/B₀)}, where V₀ is the volume at ambient pressure, B₀=8.7?GPa and B'=10.5 are the bulk modulus and its derivative, respectively. Pressure dependence of the shortest distance between the C₅H₅ ring of the ferrocene molecule and the center of the nearest fullerene molecule is linear, while the slope changes at 2.2?GPa indicating on the intermolecular interactions crossover. Other relevant parameter, the Fe-C bond lengths of ferrocene, sensitive to iron charge state, gradually increases. This peculiarity can a sign of pressure-induced partial charge transfer between the donor ferrocene and acceptor fullerene molecules.     

Characterizing the effects of shaking intensity on the kinetics of metallic iron dissolution in EDTA

Despite two decades of intensive laboratory investigations, several aspects of contaminant removal from aqueous solutions by elemental iron materials (e.g., in Fe⁰/H₂O systems) are not really understood. One of the main reasons for this is the lack of a unified procedure for conducting batch removal experiments. This study gives a qualitative and semi-quantitative characterization of the effect of the mixing intensity on the oxidative dissolution of iron from two Fe⁰-materials (materials A and B) in a diluted aqueous ethylenediaminetetraacetic solution (2 mM EDTA). Material A (fillings) was a scrap iron and material B (spherical) a commercial material. The Fe⁰/H₂O/EDTA systems were shaken on a rotational shaker at shaking intensities between 0 and 250 min⁻¹ and the time dependence evolution of the iron concentration was recorded. The systems were characterized by the initial iron dissolution rate (k_EDTA). The results showed an increased rate of iron dissolution with increasing shaking intensity for both materials. The increased corrosion through shaking was also evidenced through the characterization of the effects of pre-shaking time on k_EDTA from material A. Altogether, the results disprove the popular assumption that mixing batch experiments is a tool to limit or eliminate diffusion as dominant transport process of contaminant to the Fe⁰ surface.     

Properties and structure of semiconducting sodium iron germanoborate glasses

Several properties of semiconducting Na₂B₄O₇–GeO₂–Fe₂O₃ glasses have been measured. These properties include Mössbauer, density, d.c. conductivity, thermal expansion coefficient, glass transition temperature (T _g), and softening temperature (T _s). The d.c. conductivity was found to decrease as the iron content increases while the activation energy increases with increasing iron content in the glasses. From the conductivity temperature relation, it was found that the small polaron hopping model was applicable at temperature above _D/2 (_D: the Debye temperature); and the electrical conduction at T>_D/2 was due to non-adiabatic small polaron hopping of electrons between iron ions. The parameters obtained from the fits of the experimental data to this model appear reasonable and are consistent with the glass composition. Dilatometric measurements indicated that the thermal expansion coefficient decreases with the increase of iron content whereas both of the (T _g) and the (T _s) increase with increasing iron content. Different behaviors were observed in the Fourier transform infrared (FTIR) absorption spectra as a result of the progressive replacement of GeO₂ by Fe₂O₃. In the case of 20 and 25 mol % GeO₂, simultaneous existence of [GeO₄] and [GeO₆] polyhedra can be observed in the glass network. Below 20 mol % GeO₂, all germanium participating into the glass network is tetrahedrally coordinated, that is [GeO₄]. It is also indicated that, with the increase of iron content, boron attains an enhanced state for its coordination number to increase from 3 to 4, and consequently the tetrahedral [BO₄] units increase at the expense of the trigonal [BO₃] units, indicating the increase of the bridging character. The results of the measured properties were correlated with those from the FTIR spectroscopy.     

Synthesis of magnetic nanostructures: Shape tuning by the addition of a polymer at low temperature

We report a simple method for shape-controlled synthesis of iron oxide spinels such as magnetite (Fe₃O₄) and maghemite (γ-Fe₂O₃) nanostructures using a thermoresponsive polymer poly(vinyl methyl ether) (PVME) by the alkaline hydrolysis of iron salt at low temperature (20 °C). Microscopic analysis confirmed the formation of needle- and flower-shaped iron oxide nanostructures depending on reaction conditions. High-resolution transmission electron microscopic analysis of the needle- and flower-shaped nanostructures as well as their corresponding selected area electron diffraction patterns revealed that the formed nanostructures are crystalline in nature. X-ray diffraction study reveals the formation of well-crystalline pure Fe₃O₄ and γ-Fe₂O₃ nanostructures under different reaction conditions. Fourier transform Infra-red spectroscopic analysis confirms the adsorption of PVME on the surface of iron oxide nanostructures. Finally, the magnetic properties of γ-Fe₂O₃ and Fe₃O₄ nanostructures is studied that shows the superparamagnetic behavior of the formed iron oxide nanostructures.     

Austenitisation kinetics of unalloyed and alloyed ductile iron

Abstract

Specimens with different microstructures of an unalloyed iron and a 0.75 wt-%Mn ductile iron were austenitised at 870°C to study the kinetics of austenitisation. The specimens were austenitised in a salt bath furnace for different periods. The wafer specimens were ground, polished and etched before metallography and hardness tests. The thermodynamic procedure was used to calculate the Ae ₃ phase boundary as a function of composition. The results were used to explain the effect of segregation on the kinetics of austenitisation. The results showed that the transformation rate in both the alloyed and the unalloyed pearlitic ductile iron is higher than that of the ferritic iron. As far as the ferritic structure is concerned, at the early stage of transformation the alloyed iron showed a higher austenitisation rate than the unalloyed iron, while after longer transformation the unalloyed iron showed the higher rate. This change in transformation rate is supposedly because of the effect of Mn segregation in the intercellular region. In the case of specimens with a pearlitic microstructure, unalloyed iron has a higher austenitisation rate than alloyed iron because of the effect of Mn on the stability of carbides in the pearlite. It was also shown that in all the specimens the cell boundaries are the most potent sites for nucleation of austenite. The Avrami equation was used to calculate k and n parameters as a function of microstructure. The results obtained indicate that n for specimens with different microstructures varies from 1.5 to 3.5. The results also show that the effect of the initial microstructure on the n and k values is greater than that of the chemical composition of the iron.     

A nanocrystalline hematite film prepared from iron(III) chloride precursor

This paper deals with a simple and low-cost method developed to deposit hematite (α-Fe₂O₃) layers on a fluorine-doped tin oxide (FTO/F:SnO₂) substrate by thermal decomposition of solid iron(III) chloride hexahydrate (FeCl₃⋅ 6H₂O). Deposition procedure takes place through chemical intermediate iron(III) oxide chloride (FeOCl) film. A crucial influence of atmosphere dynamics involved in the calcination process of FeOCl has been observed. As-deposited films were characterized by means of Conversion Electron Mössbauer Spectroscopy (CEMS), Grazing Angle X-Ray Diffractometry (GAXRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analysis. Final nanocrystalline hematite film with a cactus-field-like design consists of 20 nm thick porous crystal plates. A process of hematite doping by tin atoms from substrate coating is also discussed.     

Synthesis of different nanostructured flower-like iron oxides and study of their performance as adsorbent

Iron oxides with different flower-like nanostructures have been successfully synthesized by decomposition of the iron alkoxide precursor at different conditions. The effect of reaction time (reflux time) and the calcination conditions on the morphology and composition of prepared iron oxides were investigated. Characterizations of the prepared powders were performed by scanning electronic microscopy, X-ray diffraction and N₂ adsorption/desorption isotherm. The results show that the prepared nanostructured iron oxides can be used as adsorbent for rapid removal of dye pollutants from water.     

Short-term synthesis of poly- and single-crystalline iron monochalcogenides

Poly- and single-crystalline samples of the Fe(Se,Te)_{1 − δ} system have been synthesized for short times by annealing bulk iron in chalcogen vapors and by reacting powdered iron with chalcogen melts. The lattice unit cell parameters and critical temperatures (T _c) of the superconducting transition in the synthesized compounds agree with published data for the materials obtained by long-term synthesis using other methods. For Fe(Se_0.8Te_0.2)_0.82 block crystals, the temperature dependence of the second critical field in the vicinity of T _c is linear with a slope of −4.9 T/K.     

The observation of stress effects during the high temperature oxidation of iron

Electron microscopy has been used to characterize the stress effects which occur during the oxidation of iron in the temperature range 400–700° C. Spalling and de-cohesion of the outer hematite (-Fe₂O₃) layer is often observed, and analysis of the resulting scrolled oxide indicates a strong compressive stress gradient. In contrast, tensile cracks are frequently seen in the magnetite (Fe₃O₄) layer, while the underlying wustite (Fe_1–xO) and the iron substrate are apparently able to accommodate the stresses to some extent by plastic deformation. The Pilling-Bedworth model can adequately be applied at the -Fe₂O₃-Fe₃O₄ interface since anion diffusion occurs in the hematite. However, since cation diffusion is dominant in the other oxides, it is suggested that the anion volume ratio can be applied to the Fe₃O₄-Fe_1–xO interface where the anion sublattice remains unchanged, in order to predict the stress state.     

Identification and properties of ultra-fine iron particles dispersed in a glass-like carbon matrix

Various kinds of iron particles and an iron species were synthesized from acetylferrocenefurfural resins in a glass-like carbon matrix by heat-treatment. These irons were investigated in terms of magnetic susceptibility, saturation magnetization, esr, and the Mössbauer effect. Body-centred cubic (b c c) iron, expanded b c c iron, hexagonal close-packed iron, and cluster iron were present as ultra-fine iron particles. The presence of Fe⁺ was well established as an iron species. The formation of iron particles and Fe⁺ is discussed on the basis of the pyrolysis of ferrocene skeletons in the resin.     

Synthesis of gold nanoparticles of variable morphologies using aqueous leaf extracts of Cocculus hirsutus

Spherical, triangular (prismatic) and square plate shaped gold nanoparticles have been synthesised from HAuCl₄?·?3H₂O solution using the aqueous leaf extract of Cocculus hirsutus. Nanoparticles are characterised using higher resolution transmission electron microscope, X-ray diffraction and UV–Vis absorption spectroscopic study. FT-IR analysis reveals that the gold nanostructures are mostly stabilised by the carbonyl and amide groups present in the active component of C. hirsutus leaf extract. Formation of gold nanostructures of variable morphologies has been explained due to slow reduction of gold ions by the mild reducing ascorbic acid present within the extract and this controlled reduction assists the preferential deposition of Au atom on different lesser-protected faces of initially grown gold nanostructure.     

THE INFLUENCE OF SYNTHESIS PARAMETERS ON THE PRODUCTION OF MULTIWALLED CARBON NANOTUBES BY THE FERROCENE CATALYZED PYROLYSIS OF TOLUENE

ABSTRACT

A high yield (～32?wt.%) of multiwalled carbon nanotubes was obtained in an iron catalyzed reaction. This was achieved in the temperature range 800–1000°C under an atmosphere of H₂/Ar by an improved solution injection method in a horizontal reactor using toluene as carbon source and ferrocene as catalyst precursor. The pyrolysis temperature, ferrocene concentration, solution feeding rate and carrier gas flow rate all influenced the yield of carbon nanotubes and the thickness of the aligned carbon nanotube films. The carbon nanotubes was prepared in high purity using optimized pyrolysis conditions.     

Effect of zinc and iron on the (micro-)structure and copper charge excess of the YBaCuO superconductor

Samples of YBa₂(Cu_1–y Zn _y )₃O_7–y and YBa₂(Cu_1–y Fe _y )₃O_7+x , withy in the range 0.0–0.16 for zinc and 0.0–0.30 for iron were synthesized by solid-state reaction. The solubility limit has been found to be equal to 7% and 19 at % for zinc and iron, respectively. Zinc has little effect on the structure which remains orthorhombic throughout all the zinc concentration range, while iron induces an important structural modification (tweed structure formation). Both impurities induce grain-growth inhibition but densification appears to be independent of the impurity content with respect to the undoped material. However, iodometry shows that the oxygen stoichiometry decreases in zinc-doped samples while it increases in iron-doped samples. Charge balance resulting from the dopant charge and the evolution of the copper charge with doping have been invoked. In zinc-doped samples, the copper charge excess (copper charge fraction>2) decreases sharply for 0.0y<0.04, then it shows a plateau-like behaviour for 0.04y<0.06, while in iron-doped samples, it decreases almost monotonically. Confirming some of our previous results there is a correlatedT _c decrease in the case of zinc-doped samples (occurrence of aT _c plateau) and in the case of iron-doped samples (quasi monotonical decrease). This difference has been interpreted in terms of structural changes related to the different substitution behaviour of zinc and iron.