Fe Stoichiometry Research Articles

Understanding Variations in Ferrate Detection through the ABTS Method in the Presence of Electron-Rich Organic Compounds.

The chromogenic reaction between 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and ferrate [Fe(VI)] has long been utilized for Fe(VI) content measurement. However, the presence of electron-rich organic compounds has been found to significantly impact Fe(VI) detection using the ABTS method, leading to relative errors ranging from ∼88 to 100%. Reducing substances consumed ABTS•+ and resulted in underestimated Fe(VI) levels. Moreover, the oxidation of electron-rich organics containing hydroxyl groups by Fe(VI) could generate a phenoxyl radical (Ph•), promoting the transformation of Fe(VI) → Fe(V) → Fe(IV). The in situ formation of Fe(IV) can then contribute to ABTS oxidation, altering the ABTS•+:Fe(VI) stoichiometry from 1:1 to 2:1. To overcome these challenges, we introduced Mn(II) as an activator and 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic agent for Fe(VI) detection. This Mn(II)/TMB method enables rapid completion of the chromogenic reaction within 2 s, with a low detection limit of approximately 4 nM and a wide detection range (0.01-10 μM). Importantly, the Mn(II)/TMB method exhibits superior resistance to reductive interference and effectively eliminates the impact of phenoxyl-radical-mediated intermediate valence iron transfer processes associated with electron-rich organic compounds. Furthermore, this method is resilient to particle interference and demonstrates practical applicability in authentic waters.

Effects of addition of nitrogen-enriched biochar on bacteria and fungi community structure and C, N, P, and Fe stoichiometry in subtropical paddy soils

Biochar can be a soil amendment that increases nutrient retention and carbon (C) sequestration in rice paddy systems. However, biochar can lose nutrient during its production processes so modifications such as coating with the nitrogen (N) that can slowly release nutrients to soil following application are necessary. Dynamic changes in paddy soil microbial communities affect the biogeochemical cycling of soil nutrients; however, the effects of addition of N-enriched biochar on paddy soil microorganisms and nutrient stoichiometry are unclear. Here, we investigated the effects of N-enriched biochar on soil bacteria and fungi community structure and on carbon (C), N, phosphorous (P), and iron (Fe) stoichiometry in subtropical paddy soils. The soil concentrations of TC, TN and TP increased by 0.27–18.55%, 1.31–18.15% and 10.35–54.24% respectively under the nitrogen rich biochar treatment. Under N-enriched biochar application, ratios of N/P and C/P decreased, while P-fixation capacity increased; the decrease in N/P ratio indicated that rice productivity was N-limited. The quantity of soil fungi increased by 42.07% and 10.89% in early and late rice, respectively in the treatment group applying 4t ha−1 of N-enriched biochar. Relative abundance of the bacteria Bacillus, Geobacter, and Sideroxydans decreased with N-enriched biochar, whereas that of Thiobacillus and Thermomonas increased; relative abundance of the fungi Spicellomyces and Crustoderma increased with biochar. Relative abundance of the bacteria Bacteroides was negatively correlated with TC and Fe3+ (P < 0.05) and Sideroxydans and Geoyhrx was negatively correlated with soil TP (P < 0.05). Relative abundance of the fungi genera Westerdykella, Synchytrium, Russula, and Orbilia was positively correlated with soil TC (P < 0.05), Trapelia, Leptosphaerulina, and Tremella was positively correlated with soil TN (P < 0.05), and relative abundance of Leucanium, Monoblepharis was positively correlated with soil TP (P < 0.05). Overall, application of N-enriched biochar to paddy soils affected the microbial community composition through changes in soil physicochemical properties that led to shifts in microbial community function and associated improvements in soil nutrient enrichment.

High‐pressure hydrogen storage properties of Ti x Cr 1 − y Fe y Mn 1.0 alloys

TixCr1 − yFeyMn1.0 (x = 1.02, 1.05, 1.1, 0.05 ≤ y ≤ 0.25) alloys were prepared by plasma arc melting and annealing at 1273 K for 2 hours. The XRD results show that the main phase of all alloys is the C14 type Laves phase, and a little secondary phase exists in a mixture of the binary alloy phase. The lattice parameters increase with Ti super-stoichiometry ratio increasing, whereas smaller lattice parameters emerge with increasing Fe stoichiometry content. Additionally, as the Ti super-stoichiometry ratio decreases, the pressure-composition-temperature measurements indicated that hydrogen absorption and desorption plateau pressures of TixCr0.9Fe0.1Mn1.0 (x = 1.1, 1.05, 1.02) alloys increase from 3.15, 0.67, to 5.94, 1.13 MPa at 233 K, respectively. On the other hand, with the Fe content increasing in Ti1.05Cr1 − yFeyMn1.0 (0.1 ≤ y ≤ 0.25) alloys from 0.1 to 0.25, the hydrogen desorption plateau pressures increased from 1.41 to 2.46 MPa at 243 K. The hydrogen desorption plateau slopes reduce to 0.2 with Ti super-stoichiometry ratio decreasing to 1.02, but the alloys are very difficult to activate for hydrogen absorption and cannot activate when the Fe substituting for Cr exceeds 0.2. The maximum hydrogen storage capacities were more than 1.85 wt% at 201 K. The reversible hydrogen storage capacities can remain more than 1.55 wt% at 271 K. The enthalpy and entropy for all hydride dehydrogenation are in the range of 21.0 to 25.5 kJ/mol H2 and 116 to 122 J mol−1 K−1, respectively. Our results suggest that Ti1.05Cr0.75Fe0.25Mn1.0 alloy with low enthalpy holds great promise for a high hydrogen pressure hybrid tank in a hydrogen refueling station (45 MPa at 333 K), and the other alloys of low cost may be used for a potable hybrid tank due to high dissociation pressure at 243 K and high volumetric density exceeding 40 kg/m3.

Design of D022 superlattice with superior strengthening effect in high entropy alloys

Precipitation strengthening is one of the most promising mechanisms to develop high-performance high entropy alloys (HEAs). However, the design of a reinforcing phase with an excellent strengthening effect is still one of the most pivotal challenges. In the present study, a design strategy based on overall valence electron concentration (OVEC) is developed, and a coherent D022 superlattice (noted as γ″ phase) with superior strengthening effect is designed. The newly developed γ″ phase is systematically characterized using transmission electron microscope and atom probe tomography. Differentiating from the traditional Ni3Nb γ″ phase, the present high-entropy γ″ phase contains ∼7.7% Co and follows the (Ni,Co,Cr,Fe)3(Nb,Fe) stoichiometry. Three γ″ phase variants are observed with crystallographic orientation relationships of [001]γ″//<001>γ and (001)γ″//{100}γ. The lenticular γ″ particles with small volume fraction (7%) causes a significant yield strength increase (670 MPa) and ductility retention (40%), resulting in excellent yield strength-ductility combination. The excellent strengthening effect of the γ″ phase is attributed to both ordering strengthening and coherency strengthening. The present study proposes a new design strategy of precipitates and develops a superior reinforcing phase for HEAs. These findings will not only promote the development of precipitation-hardened HEAs but deepen the fundamentals of precipitates design for other complex concentrated alloys as well.

Reductive Dissolution Mechanisms at the Hematite-Electrolyte Interface Probed by in Situ X-ray Scattering

The electron-catalyzed dissolution and reprecipitation of iron (oxyhydr)oxides constitute critical steps in natural geochemical iron cycling. However, the atomic-scale mechanisms of reductive dissolution and oxidative precipitation of Fe2+ remain poorly understood because they are difficult to directly experimentally probe. Using in situ synchrotron X-ray scattering and a novel electrochemical cell, we interrogate the interfacial structure between the hematite (α-Fe2O3) (1102) surface and acidic aqueous solution (5 mM Na2SO4, pH 4.0) under controlled electrochemical potential from the open circuit condition to cathodic bias as the reductive dissolution potential is approached and then exceeded. The crystalline order of the surface improves under mild reducing conditions, and the surface Fe stoichiometry changes with cathodic bias. After significant reductive dissolution occurs and cathodic bias is removed, dissolved Fe is redeposited, forming a disordered interface. Unlike at circumneutral pH, water laye...

Optimization of lithium content in LiFePO4 for superior electrochemical performance: the role of impurities.

Carbon coated LixFePO4 samples with systematically varying Li-content (x = 1, 1.02, 1.05, 1.10) have been synthesized via a sol–gel route. The Li : Fe ratios for the as-synthesized samples is found to vary from ∼0.96 : 1 to 1.16 : 1 as determined by the proton induced gamma emission (PIGE) technique (for Li) and ICP-OES (for Fe). According to Mössbauer spectroscopy, sample Li1.05FePO4 has the highest content (i.e., ∼91.5%) of the actual electroactive phase (viz., crystalline LiFePO4), followed by samples Li1.02FePO4, Li1.1FePO4 and LiFePO4; with the remaining content being primarily Fe-containing impurities, including a conducting FeP phase in samples Li1.02FePO4 and Li1.05FePO4. Electrodes based on sample Li1.05FePO4 show the best electrochemical performance in all aspects, retaining ∼150 mA h g−1 after 100 charge/discharge cycles at C/2, followed by sample Li1.02FePO4 (∼140 mA h g−1), LiFePO4 (∼120 mA h g−1) and Li1.10FePO4 (∼115 mA h g−1). Furthermore, the electrodes based on sample Li1.05FePO4 retain ∼107 mA h g−1 even at a high current density of 5C. Impedance spectra indicate that electrodes based on sample Li1.05FePO4 possess the least charge transfer resistance, plausibly having influence from the compositional aspects. This low charge transfer resistance is partially responsible for the superior electrochemical behavior of that specific composition.

Design of D0 &lt;sub&gt;22&lt;/sub&gt; Superlattice with Superior Strengthening Effect in High Entropy Alloys

Precipitation strengthening is one of the most promising mechanisms to develop high-performance high entropy alloys (HEAs). However, the design of a reinforcing phase with an excellent strengthening effect is still one of the most pivotal challenges. In the present study, a design strategy based on overall valence electron concentration (OVEC) is developed, and a coherent γ″ phase with superior strengthening effect is designed. The newly developed γ″ phase is systematically characterized using transmission electron microscope and atom probe tomography. Differentiating from the traditional Ni3Nb γ″ phase, the present high-entropy γ″ phase contains ~7.7% Co and follows the (Ni,Co,Cr,Fe)3(Nb,Fe) stoichiometry. Three γ″ phase variants are observed with crystallographic orientation relationships of [001]γ″// γ and (001)γ″//{100}γ. The lenticular γ″ particles with small volume fraction (7%) causes a significant yield strength increase (670 MPa) and ductility retention (40%), resulting in excellent yield strength-ductility combination. The excellent strengthening effect of the γ″ phase is attributed to both ordering strengthening and coherency strengthening. The present study proposes a new design strategy of precipitates and develops a superior reinforcing phase for HEAs. These findings not only promote the development of precipitation-strengthened HEAs but deepen the understanding of precipitates design in HEAs as well.

Interactions between magnetite and humic substances: redox reactions and dissolution processes

Humic substances (HS) are redox-active compounds that are ubiquitous in the environment and can serve as electron shuttles during microbial Fe(III) reduction thus reducing a variety of Fe(III) minerals. However, not much is known about redox reactions between HS and the mixed-valent mineral magnetite (Fe3O4) that can potentially lead to changes in Fe(II)/Fe(III) stoichiometry and even dissolve the magnetite. To address this knowledge gap, we incubated non-reduced (native) and reduced HS with four types of magnetite that varied in particle size and solid-phase Fe(II)/Fe(III) stoichiometry. We followed dissolved and solid-phase Fe(II) and Fe(III) concentrations over time to quantify redox reactions between HS and magnetite. Magnetite redox reactions and dissolution processes with HS varied depending on the initial magnetite and HS properties. The interaction between biogenic magnetite and reduced HS resulted in dissolution of the solid magnetite mineral, as well as an overall reduction of the magnetite. In contrast, a slight oxidation and no dissolution was observed when native and reduced HS interacted with 500 nm magnetite. This variability in the solubility and electron accepting and donating capacity of the different types of magnetite is likely an effect of differences in their reduction potential that is correlated to the magnetite Fe(II)/Fe(III) stoichiometry, particle size, and crystallinity. Our study suggests that redox-active HS play an important role for Fe redox speciation within minerals such as magnetite and thereby influence the reactivity of these Fe minerals and their role in biogeochemical Fe cycling. Furthermore, such processes are also likely to have an effect on the fate of other elements bound to the surface of Fe minerals.

(Invited) Effect of Ni:Fe Stoichiometry and Architectural Expression on the Bifunctional Activity of Nanoscale Ni y Fe1–Y ox

The efficient electrocatalysis of reactions involving molecular oxygen determines the performance of many electrochemical energy-storage and -conversion systems. Electrocatalysis of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) was assessed for a series of Ni-substituted ferrites (Ni y Fe1–y Ox, where y=0.1–0.9) prepared as high surface area nanoarchitectures using epoxide-based sol–gel chemistry. Wet gels were processed using either ambient-pressure or supercritical-fluid drying to render ambigel or aerogel nanoarchitectures, respectively. For this series of Ni y Fe1–y Ox materials, we correlate electrocatalytic activity with Ni:Fe stoichiometry and nanoarchitecture. In order to ensure in-series comparisons, calcining at 350°C in air was necessary to crystallize the respective Ni y Fe1–y Ox nanoarchitectures, which index to the inverse spinel structure for Fe-rich materials (y ≤ 0.33), biphasic for intermediate stoichiometries (0.5 ≤ y ≤ 0.67), and rock-salt for the most Ni-rich material (y = 0.9). For the OER, Ni-rich nanoarchitectures (y > 0.5) exhibit high activity (low overpotential, η), while both the ambigel and aerogel series in the intermediate Ni:Fe stoichiometry range (0.33 ≤ y ≤ 0.67) exhibit a monotonic increase in current density with progressively higher specific surface area. The commensurate OER activity obtained for ambigel and aerogel expressions across a given Ni:Fe stoichiometry highlights the fact that competitive electrocatalytic performance can be achieved without the additional complexity of supercritical-fluid extraction. We also find improved OER performance (η decreases from 390 to 373 mV) for Ni0.67Fe0.33Ox aerogel when heated at 300°C under flowing Ar, owing to an increase in crystallite size (2.7 to 4.1 nm). For the ORR, electrocatalytic activity favors Fe-rich Ni y Fe1–y Ox (y < 0.5) materials. As the Ni-content increases beyond y = 0.5, a two-electron reduction pathway is still exhibited, demonstrating that bifunctional OER and ORR activity may be possible by choosing a Ni y Fe1–y Ox nanoarchitecture that provides high OER activity with decent ORR activity. We find that assessing catalytic activity requires an appreciation of the multivariate interplay between Ni:Fe stoichiometry, surface area, crystallographic phase, and crystallite size rather than basing electrocatalyst selection on Ni:Fe stoichiometry alone.

Electroanalytical Assessment of the Effect of Ni:Fe Stoichiometry and Architectural Expression on the Bifunctional Activity of Nanoscale NiyFe1-yOx.

Electrocatalysis of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) was assessed for a series of Ni-substituted ferrites (NiyFe1-yOx, where y = 0.1 to 0.9) as expressed in porous, high-surface-area forms (ambigel and aerogel nanoarchitectures). We then correlate electrocatalytic activity with Ni:Fe stoichiometry as a function of surface area, crystallite size, and free volume. In order to ensure in-series comparisons, calcination at 350 °C/air was necessary to crystallize the respective NiyFe1-yOx nanoarchitectures, which index to the inverse spinel structure for Fe-rich materials (y ≤ 0.33), rock salt for the most Ni-rich material (y = 0.9), and biphasic for intermediate stoichiometry (0.5 ≤ y ≤ 0.67). In the intermediate Ni:Fe stoichiometric range (0.33 ≤ y ≤ 0.67), the OER current density at 390 mV increases monotonically with increasing Ni content and increasing surface area, but with different working curves for ambigels versus aerogels. At a common stoichiometry within this range, ambigels and aerogels yield comparable OER performance, but do so by expressing larger crystallite size (ambigel) versus higher surface area (aerogel). Effective OER activity can be achieved without requiring supercritical-fluid extraction as long as moderately high surface area, porous materials can be prepared. We find improved OER performance (η decreases from 390 to 373 mV) for Ni0.67Fe0.33Ox aerogel heat-treated at 300 °C/Ar, owing to an increase in crystallite size (2.7 to 4.1 nm). For the ORR, electrocatalytic activity favors Fe-rich NiyFe1-yOx materials; however, as the Ni-content increases beyond y = 0.5, a two-electron reduction pathway is still exhibited, demonstrating that bifunctional OER and ORR activity may be possible by choosing a nickel ferrite nanoarchitecture that provides high OER activity with sufficient ORR activity. Assessing the catalytic activity requires an appreciation of the multivariate interplay among Ni:Fe stoichiometry, surface area, crystallographic phase, and crystallite size.

Low temperature synthesis by spray pyrolysis of La0.9Sr0.1Co0.2Fe0.8O3 thin films using ethanol and water as a solvent and their microstructural characterization

The synthesis via spray pyrolysis was investigated of lanthanum ferrite films doped with strontium and cobalt (LSCF) on silicon substrates for application as cathodes in solid oxide fuel cells (SOFCs). The following precursors were utilized: La(NO3)3·6H2O, SrCl2·6H2O, CO(NO3)2·6H2O, and Fe(NO3)3·9H2O, with La:Sr:Co:Fe (9:1:2:8) stoichiometry. A solution of water and ethanol (1:3 proportion) was used. The relation among the morphology of the films, i) the temperature of the substrate and ii) the distance of deposition was investigated. The results indicate that it is possible to obtain the LSCF film with a porous morphology at 200°C and at a distance of deposition of 120mm. This morphology is adequate for applications of LSCF as a cathode for use in solid oxide fuel cells.

The Effect of Stoichiometry on Hydrogen Embrittlement of Ordered Ni3Fe Intermetallics

The effects of Fe stoichiometry on hydrogen embrittlement and hydrogen diffusion in ordered Ni3Fe intermetallics were investigated. The experimental results show that the ordered Ni3Fe alloy with the normal stoichiometry has the lowest mechanical property, the highest susceptibility to hydrogen, and the highest ability of catalytic reaction. The mechanical properties, the susceptibility to hydrogen embrittlement, and the amount of adsorbed hydrogen of the ordered Ni3Fe alloy are dependent of degree of order of the alloy. The apparent hydrogen diffusion coefficient of the ordered Ni3Fe alloy is independent on degree of order of the alloy but depends on Fe stoichiometry. The activation energy of hydrogen diffusion decreased linearly with Fe stoichiometry for the ordered Ni3Fe alloy.

The Effect of Stoichiometry and Degree of Order on Mechanical Properties of Ni&lt;sub&gt;3&lt;/sub&gt;Fe Intermetallics

The effects of Fe stoichiometry and degree of order on mechanical properties of intermetallics Ni3Fe were investigated. The experimental results showed that the phase composition and the grain size of Ni3Fe alloy was independent on Fe stoichiometry. The Ni3Fe alloy with the normal stoichiometry had the lowest elongation in the ordered and disordered alloys. The tensile strength of Ni3Fe alloy depended on Fe stoichiometry of alloy. The effect of Fe stoichiometry on the mechanical properties of the ordered alloy was larger than that of disordered alloy. There were more point defects in lattice when the alloy stoichiometry deviating from the normal stoichiometry in the Ni3Fe alloy. The changes of the concentration of the point defects and degree of order altered the deformation behavior of the Ni3Fe alloy.

Fluctuations and the ferromagnetic instability in YFe2Al10: The role of Fe stoichiometry

AbstractYFe2Al10 forms in a well‐ordered crystal structure, with a unique site for the magnetic atom Fe. At elevated temperatures YFe2Al10 behaves electronically as a good metal. At low temperatures on the other hand, signatures of correlated behavior develop and eventually non‐Fermi‐liquid scaling dominates all of the physical properties: the electrical resistivity develops a negative temperature coefficient below 20 K, and the specific heat Cp(T)/T and χ(T) both assume a power‐law increase upon lowering the temperature below ≃3 K. Lowest temperature studies have failed to find magnetic ordering in YFe2Al10 in spite of compelling evidence that there is impending order in this compound and that it is indeed of ferromagnetic character. Here we report on measurements of thermal and electronic transport as well as heat capacity studies on the series of compounds YFe2 + δAl10 with δ ≤ |0.1|, with the purpose of testing the stability of the low‐temperature divergences in physical properties against off‐stoichiometric Fe.

High capacity nanostructured Li2FexSiO4/C with Fe hyperstoichiometry for Li-ion batteries

Li2FeSiO4-based materials have attracted a great deal of interest as cathodes for lithium ion batteries for its excellent thermal stability and good cycling ability. Nanoporous Li2FeSiO4/C composites with varying Fe stoichiometry were synthesized by a PVA-assisted sol–gel method. Different gel formation processes were used to control morphology and pore size distribution. The pore size distribution was controlled by adjusting the parameters of the gel ageing process, the carbon content and phase purity was controlled by adjusting the starch content, and the amount of secondary phases was controlled by adjusting the Fe stoichiometry. The electrochemical properties of the Li2FeSiO4/C composite were assessed using coin cells at 24 °C, and the optimized material showed an initial discharge capacity of 163 mAh g−1 at a discharge rate of C/16 (C = 160 mA g−1) and a high capacity retention of 96% after 200 cycles at a discharge rate of 1 C.

Phase Diagram ofKxFe2−ySe2−zSzand the Suppression of its Superconducting State by anFe2−Se/STetrahedron Distortion

We report structurally tuned superconductivity in a K(x)Fe(2-y)Se(2-z)S(z) (0 ≤ z ≤ 2) phase diagram. Superconducting T(c) is suppressed as S is incorporated into the lattice, eventually vanishing at 80% of S. The magnetic and conductivity properties can be related to stoichiometry on a poorly occupied Fe1 site and the local environment of a nearly fully occupied Fe2 site. The decreasing T(c) coincides with the increasing Fe1 occupancy and the overall increase in Fe stoichiometry from z = 0 to z = 2. Our results indicate that the irregularity of the Fe2-Se/S tetrahedron is an important controlling parameter that can be used to tune the ground state in the new superconductor family.

Vapor growth and characterization of pyrite (FeS 2) doped with Co, Ni, and As: Variations in semiconducting properties

Pyrite (FeS 2) crystals doped with As, Ni and Co were synthesized with chemical vapor transport over an 18 cm horizontal gradient of 700–600 °C in evacuated quartz tubes, from a mixture of FeS and S, with FeBr 3 as a transport agent. Sulfur fugacity and thus S:Fe stoichiometry was constrained by the Fe 1− x S/FeS 2− y buffer. As, Ni and Co concentrations were ∼3–800 ppm, ∼200–1500 ppm and ∼ 450–3700 ppm, respectively. Semiconducting properties were measured at room temperature using a van der Pauw and Hall measurement system. Ni and Co-doped pyrite are n-type while As-doped pyrite tends to be p-type. Resistivity for Co-doped pyrite ranged from 0.009 to 0.02 Ω cm while for Ni- and As-doped pyrite, resistivity ranged from 2 to 17 Ω cm. Undoped pyrite resistivity ranged from 15 to 85 Ω cm. Carrier concentration was similar for undoped and Ni-doped pyrite, ranging from 10 15 to 10 16.6 cm −3, while for Co-doped pyrite it ranged from 10 18.7 to 10 19.3 cm −3 and for As-doped pyrite it ranged from 10 14 to 10 18 cm −3. Hall mobility was similar for Co and Ni-doped pyrite ranging from 60 to 270 cm 2 v −1 s −1 while for undoped pyrite it ranged from 8 to 70 cm 2 v −1 s −1. Hall mobility for As-doped pyrite ranged from 55.0 to 0.2 cm 2 v −1 s −1 for electrons and from 0.1 to 11.3 cm 2 v −1 s −1 for holes with the exception of one sample (of 22). These values should be viewed more as trends than as definitive. The results obtained for Ni, Co, and undoped pyrite are similar to those reported in the literature while results for As-doped synthetic pyrite have not previously been reported.

Cementation-induced recovery of self-assembled ultrafine copper powders from spent etching solutions of printed circuit boards

Ultrafine copper powders have been recovered from spent etching solutions of printed circuit boards by cementation on helical-form iron scrap chips. The tested solution is an ammoniacal copper solution containing 135 g/l copper with minor impurities. The influences of contact time, temperature, pH, initial copper concentration and Fe stoichiometry on the yield, purity and grain size and shape of the precipitated copper powders were studied. Ultrafine self-assembled copper nanocubes with high purity of about > 99% was obtained at temperature 25 °C, time 20 min, pH 2, Fe stoichiometry 1 X and initial copper concentration 20 g/l Cu. It was proposed that the precipitation of copper from the solution involved two main processes: (1) adsorption of copper ions on the surface of the iron chips due to the iron oxides present on it and (2) cementation of copper ions onto the metallic iron contained in the chips. Scrap iron chips is seen to be an effective material for copper powder recovery from spent etching solutions in a pure and fine form.

Approach for defect suppression and preparation of high quality semi-insulating InP

Semi-insulating (SI) InP materials have been prepared via Fe-doping in liquid encapsulated Czochraski growth and high temperature annealing undoped InP, respectively. The SI-InP materials exhibit different electrical properties and thermal stability. Deep level defects in the material have been studied in order to understand the mechanism. It is found that the quality of SI-InP depends on the concentration of deep level defects with energy levels in the range of 0.1–0.4 eV within the band gap. SI-InP with negligible low concentration of the defects exhibits high mobility and good thermal stability. Fe-diffused SI-InP which is obtained by annealing in iron phosphide ambient contains very low concentration of the defects. The origin of the defects has been studied by comparing the influence of the Fe incorporation method and stoichiometry on the defects formation in the SI-InP materials. The results suggest an approach for an improvement of the growth of high quality SI-InP material.

Strength of Terfenol-D

The strength of the magnetostrictive material, Terfenol-D, Tb0.27Dy0.73Fe2.0, has been evaluated by measuring the modulus of rupture as a function of the Fe stoichiometry of the compound. It is shown that the strength improves markedly as the Fe concentration decreases from the stoichiometric value of 2.0 in the compound. The increased strength results from the increasing volume fraction of the rare-earth metal phase produced in the Terfenol-D matrix by the solidification process at lower Fe concentrations.