Modification of Structure and Physico-Mechanical Properties of Al–Cu–Fe Quasicrystal Alloy at Plasma Spraying

The structure and physico-mechanical properties of coatings of the quasicrystal alloy Al₆₃Cu₂₅Fe₁₂ produced by plasma spraying are investigated. Modification of structure of the sprayed alloys depends on spraying modes, in particular, on substrate temperature. The optimum temperature range of substrate (600 °C < T < 700 °C) which provides the maximum content (up to 80%) of quasicrystal phase is determined. The correlation between level of mechanical properties and content of icosahedral phase in the coating is established. It is revealed that allocation of nanostructural grains (d < 100 nm) resulted in additional increase of mechanical characteristics.     

Synthesis,crystal structure,and magnetic characteristics of chiral cyanide-bridged Fe–Cu complex

Based on the building blocks, trans-dicyanide Fe(III) precursor and chiral amine Cu(II) compound, the chiral cyanide-bridged heterometallic Fe(III)–Cu(II) complex with the formula {[Cu(R/R-Chxn)₂Fe(bpmb)·(CN)₂][Fe(bpmb)(CN)₂]}·CH₃OH·H₂O (1) [bpmb^2– = 1,2-bis(pyridine-2-carboxamido)-4-methylbenzenate, R,R-Chxn = R,R-1,2-diaminocyclohexane] has been synthesized and characterized by elemental analysis, IR spectra and X-ray analysis. The latter revealed that the complex contained the cyanide-bridged cationic binuclear entity and free anionic cyanide building block. The complex demonstrated weak ferromagnetic coupling between neighboring Fe(III) and Cu(II) ions via the bridging cyanide group.     

Thermokinetic study of Fischer–Tropsch synthesis on Fe2Cu1 and FeCu surfaces with comparison to Fe(110) and Cu(111) catalysts by the UBI-QEP method

The purpose of this study is to predict the activation barriers and enthalpy for elementary steps in the process of Fischer–Tropsch (F-T) on the surfaces of Fe(110), Cu(111) and Fe/Cu alloys catalyst using “Unity Bond Index-Quadratic Exponential Potential” method aimed at predicting the activity and selectivity on the basis of energy criteria. The elementary steps, such as dissociation of CO, hydrogenation of carbidic carbon, C–C chain growth by insertion of CH₂ versus CO into the metal-alkyl bonds, and chain termination, which lead to hydrocarbons (alkanes versus α-olefins) or oxygenates are discussed in detail. The results show that metallic Fe(110) is necessary to produce the carbidic carbon from CO dissociation, but the synthesis of hydrocarbons and oxygenates can effectively proceed on Cu(111) surface. For optimum performance of F-T synthesis catalyst, these conflicting properties must be optimized. In this regard, we studied Fe/Cu alloy catalyst. On all the catalyst surfaces, the energetically preferred path to initiate the alkyl chain growth is via insertion of a CH_2,s group into the carbon–metal bond of a CH_3,s group. On FeCu catalyst surface, the activation barrier for termination of alkyl chain growth by β-elimination of hydrogen is found to be lower than that for α-addition of hydrogen and consequently for this catalyst, olefins are expected to form more readily than paraffins. The results of the model for a single metal surface are in agreement with the experimental data.     

Study on the Growth and Photorefractive Properties of In：Fe：Cu：LiNbO3 Crystals

Fe(0.2 mol%):Cu(0.04 mol%):LiNbO3 crystals with different doping concentration of In3+ (0, 1.0, 2.0, 3.0mol%) were grown by Czochralski method, and then oxidized and reduced. The infrared transmittance spectra of crystals were measured to investigate the location of doping ion and its threshold concentration. The photorefractive properties of the crystals were tested by two beam coupling experiment. The results showed that the threshold concentration of In ions is 2.0～ 3.0 mol% and In ions take the place of NbL 4i+ to form ( In L2i+) before reaching its threshold concentration, and then the location of normal Nb ions. In the (2.0 mol%):Fe:Cu:LiNbO3 crystal with the oxidation treatment having the highest diffraction efficiency (η = 45.8%), the photo-damage resistance threshold value R of In(3.0 mol%):Fe:Cu:LiNbO3 was 3.67×104 W/cm2 which was two orders of magnitude higher than that of Fe:Cu:LiNbO3 crystal (4.30×102 W/cm2). And the photo-damage resistance ability was enhanced by oxidized treatment. The In(2.0～3.0 mol%):Fe:Cu:LiNbO3 crystals with oxidized treatment have the best photorefractive properties.     

Adsorption and Vibration of O Atoms on Fe Low-index and Fe （211） High-index Surfaces

IntroductionThe interaction of oxygen with iron in lowcoverageregimes is considered to be an important step in the for-mation of oxides in corrosion science and in Fisher-Tro-psch process for the synthesis of ammonia over the het-erogeneous catalysts[1]. …     

Iodo Derivatives of Bimetallic Fe—Pd and Fe—Pt Complexes. Crystal Structures of

Summary.  Iodo derivatives of diphosphine-bridged heterobimetallic Fe—Pd and Fe—Pt complexeshave been prepared in which an alkoxysilyl ligand bridges the two metals in a μ₂−η²-SiO manner. In the course of their synthesis by halide exchange from (dppx = dppm (Ph₂ PCH₂ PPh₂) or dppa (Ph₂PNHPPh₂); M = Pd or Pt), loss of the alkoxysilyl ligand occurred resulting in the formation of complexes in which a bridging iodide has replaced, as a 3e⁻-donor, the bridging alkoxysilyl ligand. These complexes of formula (M = Pd, Pt are better prepared by reaction of with [MI₂(cod)]. The crystal structures of (2a), (2b), and  · CH₂Cl₂ (3b · CH₂Cl₂) have been determined by X-ray diffraction. Received January 24, 2001. Accepted February 12, 2001     

Electronic structure and bonding of transition metal complexes MCO (MCu,Fe, Ti)

SCF-CI calculations with pseudopotentials using the CIPSI iterative algorithm have been carried out for various properties of CuCO, FeCO and TiCO complexes such as geometries, dissociation energies, dipole moments, force constants and vibration frequencies. These observables are compared to experimental data available for corresponding triatomic systems and, possibly, for chemisorbed CO. Their variations from Cu to Fe and Ti are rationalized in terms of σ donation and π back-donation effects computed from the molecular charge distribution.     

Mössbauer study and magnetic properties of Fe–Si–B–Cu amorphous systems with minor substitution of carbon

Journal of Radioanalytical and Nuclear Chemistry - The effect of minor substitution of carbon on the structure and magnetic properties of Fe–Si–B–Cu-type metallic glasses was...     

Decomposition of methane over alumina supported Fe and Ni–Fe bimetallic catalyst: Effect of preparation procedure and calcination temperature

Catalytic decomposition of methane has been studied extensively as the production of hydrogen and formation of carbon nanotube is proven crucial from the scientific and technological point of view. In that context, variation of catalyst preparation procedure, calcination temperature and use of promoters could significantly alter the methane conversion, hydrogen yield and morphology of carbon nanotubes formed after the reaction. In this work, Ni promoted and unpromoted Fe/Al₂O₃ catalysts have been prepared by impregnation, sol–gel and co-precipitation method with calcination at two different temperatures. The catalysts were characterized by X-ray diffraction (XRD), N₂ physisorption, temperature programmed reduction (TPR) and thermogravimetric analysis (TGA) techniques. The catalytic activity was tested for methane decomposition reaction. The catalytic activity was high when calcined at 500 °C temperature irrespective of the preparation method. However while calcined at high temperature the catalyst prepared by impregnation method showed a high activity. It is found from XRD and TPR characterization that disordered iron oxides supported on alumina play an important role for dissociative chemisorptions of methane generating molecular hydrogen. The transmission electron microscope technique results of the spent catalysts showed the formation of carbon nanotube which is having length of 32–34 nm. The Fe nanoparticles are present on the tip of the carbon nanotube and nanotube grows by contraction–elongation mechanism. Among three different methodologies impregnation method was more effective to generate adequate active sites in the catalyst surface. The Ni promotion enhances the reducibility of Fe/Al₂O₃ oxides showing a higher catalytic activity. The catalyst is stable up to six hours on stream as observed in the activity results.     

The removal and kinetic study of Mn,Fe, Ni and Cu ions from wastewater onto activated carbon from coconut shells

Activated carbon from coconut shells (ACCS) was synthesised and used for the removal of metal ions (manganese, iron, nickel and copper) from aqueous solutions. Two different adsorption models were used for analysing the data. Adsorption capacities were determined: copper ions exhibited the greatest adsorption on activated carbon obtained from coconut shells because of their size and pH conditions. Adsorption capacity varied as a function of the pH. Adsorption isotherms from aqueous solutions of heavy metals on ACCS were determined and were found to be consistent with Langmuir’s adsorption model. Adsorbent quantity and immersion enthalpy were studied. The results were compared with other adsorbents used in a prior study.     

Kinetics and Mechanism of Dechlorination of o-Chlorophenol by Nanoscale Pd／Fe

IntroductionTherehasbeenagrowinginterestintheuseofzero valentironforthetreatmentofchlorinatedor ganiccompounds(COCs)inwaterandgroundwater .Thestudieshavebeenfocusedonsuchcompoundsascarbontetrachloride ,trichloroethene ,pesticidesandtherelatedcompounds[1— 7] .Whenironisincontactwithalessreductivemetalsuchaspalladiumwhosecomplexhasbeenusedtohydrogenatenitroben zene[8] ,themetalcouplecanformgalvaniccells .ThisledtothediscoveryofaPd/Febimetalliccomplexofwhichpalladiumservesasacatalystandironasa…     

Ce-promoted Fe–Cu–ZSM-5 catalyst: SCR-NO activity and hydrothermal stability

Research on Chemical Intermediates - Fe–Cu–ZSM-5 and Ce–Fe–Cu–ZSM-5 solids prepared using solid-state ion exchange method (SSIE) were tested in the NH3–SCR of NO...     

Syntheses and Structures of Heterometallic Fe–Ta Chalcogenido Clusters

Two Fe–Ta containing sulfido complexes were prepared by the reaction of the metal halide salts with bis-trimethylsilylsulfide in the presence of PMe₃. The complexes demonstrate that coordination chemistry with iron sulfides can give access to a range of heterometallic complexes. In [Cl(Me₃P)Ta( ₂-S)₂( ₃-S)Fe(PMe₃)₂]₂ the two [Cl(Me₃P)Ta] units are arranged around one central Fe₂( ₂-S)₂ unit. In [(Me₃P)₄(MeCN)₂Fe^II]²⁺[(Me₃P)₂Ta^IVFe^II ₃( ₃-S)₄Br₄]^2– a [TaFe₃S₄]²⁺ cuboidal arrangement was observed. The complex salt forms a polymeric structure in the solid-state with weak H-bonds between the ions. The [(Me₃P)₂Ta^IVFe^II ₃( ₃-S)₄Br₄]^2– ion was characterised by magnetic measurements showing strong antiferromagnetic interactions between the metal centres.     

Electrical properties and initial permeability of Cu–Mg ferrites

A series of polycrystalline spinel ferrites with composition Cu_1−xMg_xFe₂O₄ where 0.0 ≤ x ≤ 1 are prepared by the standard ceramic method. The single-phase cubic spinel structure of all the samples has been confirmed from X-ray diffraction analysis. The lattice constant increases linearly with increasing magnesium content obeying Vegard's law. The electrical properties (ɛ′, and σ) of the prepared samples are measured at different temperatures as a function of applied frequency ranging from 100 kHz up to 5 MHz. The general trend of ɛ′, and σ is decreased with increasing Mg²⁺ and increases with increasing temperature. The observed variation of dielectric properties is explained on the basis of Cu²⁺/Cu¹⁺ ionic concentration as well as the electronic hopping frequency between Fe²⁺ and Fe³⁺ ions in the present samples. The data of initial permeability is also discussed.     

Synthesis and Re—refinement of Cu3PSe4

1 INTRODUCTION The chemistry of mixed 15/16 main group compounds has attracted great attentions over the last years[1]. The metal chalcogenophosphides synthesized by solid state reactions[2] are the potential candidates for a wide range of applications such as semiconducting properties, two-dimensional magnetic behavior, anisotropy of conductivity and charge density waves. Some of these compounds are of lamellar structure, which are good materials for the investigation of intercalatio…     

Evaluation of stability of silica-supported Fe–Pd and Fe–Pt nanoparticles in aerobic conditions using thermal analysis

The applications of zerovalent iron nanoparticles (nZVI) exploit their high reactivity which decreases due to oxidation in aerobic conditions during manufacture, application, and storage. In this study, we present the new procedure for estimation of the nZVI stability to oxidation in air. The procedure is suitable for characterization of the novel materials based on the supported nZVI. Nanoscale particles were synthesized inside porous silica supports by incipient wetness impregnation with the metal precursor solutions followed by thermal treatment. The TG–DTA studies revealed the decomposition temperature of the supported precursors, as well as the interaction of Fe and precious metal precursors, which resulted in the formation of alloy nanoparticles. Characterization of the samples by XRD confirmed the formation of the nanoparticles of the metallic Pd, Pt, and Fe phases supported on SiO₂ carriers, as well as the formation of solid solutions based on the structure of precious metals. The new procedure for estimation of the nZVI stability included (1) TPR with hydrogen up to 400–425 °C followed by isothermal reduction at these temperatures; (2) in situ reoxidation with oxygen at room temperature. The samples were reduced “as obtained” and after in situ reoxidation. The results of the TPR studies exhibited that introduction of both Pd and Pt protected the Fe nanoparticles from oxidation with oxygen and air at ambient conditions.     

Synthesis of quasi-crystalline phases in the Al–Cu–Fe–Cr system

Phase equilibria in the Al–Cu–Fe system alloyed with 5% Cr were studied. Based on the data of X-ray powder diffraction analysis, electron microscopy, and differential thermal analysis, the effect of temperature on i ? d phase transitions in alloys Al₆₅Cu₂₅Fe₅Cr₅ and Al₇₀Cu₂₀Fe₅Cr₅. In the Al–Cu–Fe–Cr system, multiphase structures were detected; these structures are mixtures of quasi-crystalline and approximant phases, the contents and morphologies of which depend on the composition of the initial mixture and the crystallization rate.     

The polythermal section of the Cu–Fe–Ni–S phase diagram constructed using directional crystallization and thermal analysis

The polythermal section of the Cu–Fe–Ni–S liquid–solid diagram in a field of equilibrium between sulfide melt L and monosulfide solid solution has been constructed using the quazi-equilibrium directional crystallization of melt Cu = 10.0, Fe = 38.5, Ni = 2.5, S = 49.0 mol% and DTA. The curves of distribution of Ni, Fe, Cu, and S in the sample were constructed. These data were used for determining the crystallization path in concentration tetrahedron and for calculating the distribution coefficients of components between solid and liquid solutions. To plot the liquidus line with the help of the DTA method, we determined the melting points of specially synthesized samples.