Determination of55Fe/58Fe and59Fe/58Fe isotopic ratios in irradiated Na2/FeNO/CN/5/.2H2O by SSMS

A procedure for the measurement of the isotopic composition of Fe in rradiated Na₂/FeNO/CN/₅/.2H₂O samples by SSMS is described. Decomposition with K₂S₂O₇, followed by extraction of Fe was necessary to eliminate interferences in the mass spectra. A study of the remaining interferences showed that they were of organic origin from the residual MIBK used for the extraction. The order of magnitude of the⁵⁵Fe/⁵⁸Fe and⁵⁹Fe/⁵⁸Fe ratios was calculated.SSMS: spark source mass spectrometry.     

Electronic behavior of three oxygen non-stoichiometric Fe/Fe oxoperovskites

For comparison with the Mn⁴⁺/Mn³⁺ oxoperovskites at the crossover from localized to itinerant behavior of the σ-bonding e electrons, the electronic properties of three oxygen non-stoichiometric, mixed-valent Fe⁴⁺/Fe³⁺ oxoperovskites were explored by measuring their resistivity ρ(T), thermoelectric power α(T), and magnetic susceptibility χ(T). Oxidation of Ca₂Fe₂O₅ by annealing in ozone progresses by oxygen insertion to give conductive CaFeO₃ perovskite clusters in a localized-electron, weakly oxidized brownmillerite Ca₂Fe₂O_5+δ matrix. Removal of 0.12 oxygen per formula unit from La_1/3Sr_2/3FeO₃ lowers somewhat its cooperative disproportionation reaction, and fivefold-coordinated ions neighboring oxygen vacancies in the more ionically bonded slabs act as donors to the covalently bonded Fe(V)O₆ planes. Single-crystal SrFeO_2.83 exhibited bad-metal behavior with superparamagnetic, electron-rich fluctuations below 240 K that, on cooling below 190 K, become progressively trapped by the oxide-ion vacancies as an immobile second phase; long-range antiferromagnetic order is stabilized below a T_N≈60 K.     

Influence of mechanical activation time,annealing, and Fe/O ratio on Fe3O4/Fe composites formation from Fe2O3 and Fe powders mixture

Commercially, iron (α-Fe) and hematite (α-Fe₂O₃) powders were used for the synthesis of composite powders of Fe₂O₃/Fe type by mechanical milling. Several ratios of Fe₂O₃/Fe were chosen for the composite synthesis; the atomic percent of oxygen in the starting mixtures ranged from 21 to 46 %. The Fe₂O₃/Fe composite samples with various Fe/O ratios were milled for different milling times. The milled composite samples were subjected to the heat treatments in argon up to 900 °C. During the heat treatment at temperatures that do not exceed 550 °C, Fe₃O₄/Fe composite particles are formed by the reaction between the Fe₂O₃ and Fe. Further increase of the heat treatment up to 700 °C leads to the reaction of the Fe₃O₄/Fe composite component phases, resulting thus in the formation of FeO/Fe composite. The heat treatment up to 900 °C of the Fe₂O₃/Fe leads to the formation of a composite of FeO/Fe₃O₄/Fe independent of the milling time and Fe₂O₃/Fe ratios. The onset temperatures of the Fe₃O₄ and FeO formations decrease upon increasing the milling time. Another important aspect is that, in the case of the same milling time but with a large amount of iron into the composite powder the formations temperatures of Fe₃O₄ and FeO are also decreasing. The influence of the mechanical activation time, heat treatment temperature, and Fe/O ratio on the formation of the (Fe₃O₄, FeO)/Fe composite from Fe₂O₃+Fe precursor mixtures was studied by differential scanning calorimetry and X-ray diffraction techniques.     

Synthesis of Fe3O4, Fe2O3, Ag/Fe3O4 and Ag/Fe2O3 nanoparticles and their electrocatalytic properties

Two important iron oxides:Fe3O4 and Fe2O3,as well as Fe3O4 and Fe2O3 nanoparticles mingling with Ag were successfully synthesized via a hydrothermal procedure.The samples were confirmed and characterized by X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).The morphology of the samples was observed by transmission electron microscopy(TEM).The results indicated Fe3O4,Fe2O3,Ag/Fe3O4 and Ag/Fe2O3 samples all were nanoparticles with smaller sizes.The samples were modified on a glassy carbon electrode and their elctrocatalytic properties for p-nitrophenol in a basic solution were investigated.The results revealed all the samples showed enhanced catalytic performances by comparison with a bare glassy carbon electrode.Furthermore,p-nitrophenol could be reduced at a lower peak potential or a higher peak current on a glassy carbon electrode modified with Ag/Fe3O4 or Ag/Fe2O3 composite nanoparticles.     

Systematic synthesis of heterometallic Ni/Fe/S and Cu/Fe/S clusters with a pentlandite-like M8S6 core

The systematic synthesis of heterometallic Ni/Fe/S and Cu/Fe/S clusters with a M8S6 core structure that resembles that of pentlandite minerals is described. The chemical properties and electronic structures of the new clusters have been investigated and are reported in this communication.     

Effect of the presence of iron vapors on the volumetric emission of Ar/Fe and Ar/Fe/HZ plasmas

The net volumetric emission coefficient was calculated using the escape factor method for Ar/Fe and Ar/H₂/Fe plasmas, at atmospheric pressure, over the temperature range from 3000 K to 30,000 K. The calculation involved 712 lines for Ar I, Ar II, and Ar III, 3481 lines for Fe I, Fe II, and Fe III, and 230 lines for H in the Ar/H₂/Fe case. A semiempirical method was used for the determination of line profiles and line broadening. The results show a strong influence of the presence of even traces of iron vapors at low temperatures where the volumetric emission increases by several orders of magnitude. Special attention is given to self-absorption of the argon resonance lines which prevents the radiation from escaping within a few millimeters from the emission source.     

Synthesis and characterization of magnetic poly(divinyl benzene)/Fe3O4, C/Fe3O4/Fe, and C/Fe onionlike fullerene micrometer-sized particles with a narrow size distribution

Magnetic poly(divinyl benzene)/Fe(3)O(4) microspheres with a narrow size distribution were produced by entrapping the iron pentacarbonyl precursor within the pores of uniform porous poly(divinyl benzene) microspheres prepared in our laboratory, followed by the decomposition in a sealed cell of the entrapped Fe(CO)(5) particles at 300 °C under an inert atmosphere. Magnetic onionlike fullerene microspheres with a narrow size distribution were produced by annealing the obtained PDVB/Fe(3)O(4) particles at 500, 600, 800, and 1100 °C, respectively, under an inert atmosphere. The formation of carbon graphitic layers at low temperatures such as 500 °C is unique and probably obtained because of the presence of the magnetic iron nanoparticles. The annealing temperature allowed control of the composition, size, size distribution, crystallinity, porosity, and magnetic properties of the produced magnetic microspheres.     

Reductive carbonylation of nitrobenzene over Pd/Fe/I2/Py and Pd/C/Fe/I2/Py catalytic systems

A simple catalytic system containing metallic palladium, iron and iodine has been shown to be very active in the carbonylation of nitrobenzene to carbamate. The influence of the components of the catalytic system studied on its selectivity and activity has been established. It has been found that the catalytic activity of palladium supported on carbon (using both lignite coal and bituminous coal) was not lower than the activity of metallic palladium. This revised version was published online in August 2006 with corrections to the Cover Date.     

Carbon-supported Fe/Co-N electrocatalysts synthesized through heat treatment of Fe/Co-doped polypyrrole-polyaniline composites for oxygen reduction reaction

In this paper,we synthesized cathode catalysts(PANI-PPYR,Fe/PANI-PPYR,Co/PANI-PPYR and Fe-Co/PANI-PPYR)with high performance oxygen reduction by using a simple heat treatment process.These catalysts were fabricated by directly calcining the Fe and/or Co doped polyaniline(PANI)-polypyrrole(PPYR)composites.Their electrocatalytic activity for ORR both in acidic and in alkaline media was investigated by voltammetric techniques.Among the prepared catalysts,Co/PANI-PPYR presents the most positive ORR onset potential of 0.62 V(vs.SCE)in 0.5 mol/L H2SO4 solution or?0.09 V(vs.SCE)in 1 mol/L NaOH solution.In addition,the Co/PANI-PPYR catalyst shows the largest limiting-diffusion current density for ORR,which is 4.3 mA/cm2@0.2 V(vs.SCE)in acidic and 2.3 mA/cm2@?0.3 V(vs.SCE)in alkaline media.In acidic media,a four-electron reaction of ORR on the Co/PANI-PPYR and Fe/PANI-PPYR catalysts is more dominant than a two-electron reaction.In alkaline media,however,a four-electron and a two-electron mechanisms are co-present for the ORR on all the prepared catalysts.Co/PANI-PPYR catalyst also presents good electrocatalytic activity stability for ORR both in acidic and in alkaline media.     

High rate capability of Fe/FeO/Fe3O4 composite as anode material for lithium-ion batteries

Fe/FeO/Fe₃O₄ composite was synthesized by a simple solid method using ferric citrate and phenolic resin as raw materials. The reaction processes of raw materials mixture were characterized by thermogravimetric analysis (TGA) under nitrogen. X-Ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the structure and morphology of the products. The results showed that the obtained material was octahedral Fe/FeO/Fe₃O₄ composite with a size of 2-4 μm. The electrochemical performances of Fe/FeO/Fe₃O₄ composite as anode material were also evaluated, which exhibited a stable specific capacity of 260.3 mAh g^-1 and an ideal initial coulombic efficiency of 90.8% in the range of 0.05~3 V at the 5C rate. A good rate capacity of Fe/FeO/Fe₃O₄ composite electrode was also shown by the charge-discharge testing even at the rate of 60C. The better rate capability of Fe/FeO/Fe₃O₄ electrode could be measured in higher temperature.     

Reduction of Azide to Amine Using Fe/AlCl3 or Fe/BiCl3 System in Aqueous EtOH

Azides were reduced to the corresponding amines by two new metal/Lewis acid systems in aqueous EtOH with yields ranging from 80% to 95%. The new reduction systems were Fe/AlCl3·6H2O or Fe/BiCl3 system in H2O/ethanol （2 ： 1, Ⅴ ：Ⅴ） at room temperature. Fifteen azides with different functional groups were well reduced to the corresponding amines in excellent yields.     

ZrO_2、TiO_2担载氧化铁催化剂上二氧化碳加氢制低碳烃(英文)

采用创新方法制备的ZrO2、TiO2担载氧化铁催化剂在二氧化碳加氢制低碳烃反应中显示出良好的催化活性和产物选择性,由15wt?/ZrO2给出的最佳结果为：CO2转化率为20%,除甲烷以外的低碳烃的选择性接近70%。还考察了金属Fe担载量及催化剂的预还原温度对催化活性的影响,发现催化活性随金属Fe担载量的增加而呈现“双峰”现象,这种现象可能与活性物种(零价铁及配位不饱和的三价或二价铁)在催化剂表面的几何排布有关,而两种催化剂的最佳还原温度分别为723 K(5wt?/ZrO2)和773 K(5wt?/TiO2)。     

热力学基本原理在Fe/Fe_3O_4纳米磁性材料合成中的应用

探讨了热力学基本原理及判据,以及如何利用吉布斯自由能判断变化的方向和限度;并对Fe/Fe_3O_4纳米磁性材料合成过程中的热力学行为进行了较详细的研究。通过热力学分析,认为可以利用歧化反应及以Fe~(2+)离子作为起始物合成Fe/Fe_3O_4磁性材料。     

Active Sites in Fe/ZSM-5 Zeolite

Fe/ZSM-5 zeolite has shown great potential in the selective oxidations of hydrocarbons such as methane and benzene. The various competing active sites of Fe/ZSM-5 zeolite are reviewed, including the mono-iron, oxygen-bridged [Fe, X] (X = Fe, Al) and peroxide species; in addition, the influences of H₂ pretreatment are considered. For the mono-iron species, the H₂ molecules are chemisorbed on the Fe(III) sites via the η²-binding mode. Both high- and low-spin Fe(III) ions play an important role during the H₂ reduction process whereas the former predominates in the N₂O decomposition process. As the calculated energy barriers indicate, the Fe(III) ions are facile to be reduced by H₂ pretreatment and therefore the active site of the mono-iron species should be in the FeO(OH) form. Instead, the oxygen-bridged [Fe, X] and peroxide species remain stable by H₂ pretreatment. The suitable oxygen-bridged [Fe, X] structures are screened out by comparisons with the experimental data and energy considerations from computational aspects. The geometries are in good agreement with the experimental data; meanwhile, it provides sound explanations to the distribution of the iron valence states, the thermodynamic facilitation of the “alfa-oxygen” generation by the introduction of extra-lattice Al ions as well as the shift of the Fe–Fe distances from ca. 3.06 to 2.53 Å. The superoxide species exists in Fe/ZSM-5 zeolite but not with the presence of extra-lattice Al ions. As the temperature increases, it gradually converts into the peroxide species and probably is the precursor of the peroxide species, one of the competing active sites in Fe/ZSM-5 zeolite. The clarification of active sites lays a solid foundation on the understanding of the catalytic processes and improvement of the Fe/ZSM-5 catalyst, one of the promising candidates to meet the industry challenges.     

The phosphorescence of Fe ions in oxide host lattices. Zero-phonon transitions in Fe/LiAl5O8

Phosphorescence and excitation spectra have been measured of Fe³⁺-doped LiAl₅O₈, β-NaAlO₂, Na-silicate glass and crystalline alumino-silicates. All excitation spectra fit quite well the Tanabe-Sugano diagram for a high spin d⁵ configuration. The expected tetrahedral site symmetry of Fe³⁺ in the host lattices and the value of the crystalline field parameter are strong evidence for phosphorescence of Fe³⁺ ions in tetrahedral oxygen coordination.     

聚集态的Fe氧化物在Fe/ZSM-5催化N_2O直接分解中的作用(英文)

研究了以离子交换法制备的Fe/ZSM-5上聚合态的Fe氧化物(FeOx)在催化N2O直接分解中的作用.Fe/ZSM-5催化剂利用600–900 ℃的高纯Ar处理,使催化剂中的FeOx发生聚合.利用一系列的表征手段(XRD,BET,DRIFTS,UV/vis-DRS,XAFS,N2O脉冲和O2-TPD)对催化剂进行了表征.结果发现,分子筛骨架外的FeOx在Fe/ZSM-5催化N2O分解中起重要作用;通过研究高温处理的Fe/ZSM-5催化剂中不同FeOx的比例与催化剂活性的关系,得到多核的FeOx是催化N2O分解的主要活性物种;并且,无定形态的FeOx中键长较长的Fe–O键((Fe–O)2)是参与反应的重要物种.     

Mössbauer study of Fe/III/-reducing sugar complexes

Iron/III/ complexes with glucose, galactose, mannose and lactose have been prepared. The Mössbauer and magnetic susceptibility data demonstrate the polymeric structure of the complexes. The thermal behaviour of the Fe/III/-glucose complex has been monitored by Mössbauer spectroscopy.     

Hydrogenation of CO2 on Fe/carbon catalysts

The hydrogenation of CO₂ on activated carbon-supported iron catalysts has been carried out at atmospheric pressure and using a H₂/CO₂ ratio of 4. The specific activities for this reaction are lower than those obtained for the Fischer-Tropsch synthesis using the same catalysts. CO and CH₄ are the only products obtained in the hydrogenation of CO₂ under the experimental conditions used. The apparent activation energies determined for the production of CO are lower than those for the production of CH₄.

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CO₂ , , H₂/CO₂=4. , - . CO CH₄ , CO₂ . - CO , CH₄.