XPS and ToF‐SIMS characterization of a Finemet surface: effect of heating

X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) were used to study the surface composition and electronic structure of Finemet, Fe₇₃Si_15.8B_7.2Cu₁Nb₃, in the original amorphous state and after gradual heating in vacuum to a temperature of 400 °C and cooling back to room temperature. It was found that relaxation processes occurring during heat treatment well below the crystallization onset caused the physico‐chemical state of Finemet surface to change irreversibly. In the relaxed alloy, the surface originally covered with the native air‐formed oxide was significantly enriched with elemental iron and depleted of other alloy constituents compared with the original state. Yet in the as‐quenched state, clustering of copper atoms on the Finemet surface was detected which was enhanced by heating. The thermal treatment resulted in the selective reduction of iron oxides and caused noticeable changes in the valence band structure and the Fe L₃VV Auger spectrum associated with atomic redistribution. Copyright © 2009 John Wiley & Sons, Ltd.     

Oxidation behavior of NiAl alloy at low temperatures

Oxidation behavior of NiAl alloy at low temperatures was studied. A NiAl plate was oxidized by exposure to ambient atmosphere at room temperature, heated at 473 K in air, and heated at 773 K in air. The oxide formed on the NiAl surface was investigated by angle‐resolved X‐ray photoelectron spectroscopy (AR‐XPS). Chemical composition and atomic concentration in the oxide layer were analyzed with factor analysis of XPS spectra. Exposure of the NiAl plate to the ambient atmosphere resulted in the formation of an Al₂O₃ layer along with a small amount of NiO. Oxidation of the NiAl plate at 473 K in air formed a film of double‐layered oxide; the top layer consisted of NiAl₂O₄ and a small amount of NiO, and the second layer was Al₂O₃. Successive oxidation at 773 K only changed the oxide‐layer thickness without changing the structure. Formation of oxide observed in the present study corresponds to the thermodynamic prediction for the oxidation behavior of NiAl at 1373 K. Copyright © 2007 John Wiley & Sons, Ltd.     

AES and LEED study of well‐ordered oxide film grown on Cu–9at.%Al(111)

An alloy of Cu–9at.%Al(111) has been oxidized in a low‐energy electron diffraction (LEED)/AES and a scanning AES instrument at elevated temperatures. Dosing with 1300 L of oxygen at 995 K gives rise to well‐ordered oxide layer formation on the Cu–9at.%Al alloy. The structure of the ordered oxide confirmed by LEED is ( ) R30°. The chemical state of the oxide was Al₂O₃. The morphology of the surface observed with SEM in the scanning AES instrument revealed flat oxide growth with triangular defects of the same orientation. The possible epitaxy between the alloy substrate and alumina layer has been discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

ToF‐SIMS studies of the oxidation of Fe by D2O vapour: comparison with XPS

The oxidation of iron (Fe) by water (D₂O) vapour at low pressures and room temperature was investigated using time‐of‐flight (ToF) SIMS. The results supported those found previously using XPS and the QUASES^? program in that a duplex oxide structure was found containing a thin outer surface hydroxide (Fe(OD)₂) layer over an inner oxide (FeO) layer. The extraordinary depth resolution of the ToF‐SIMS profiles assisted in identifying the two phases; this resolution was achieved by compensation for surface roughness. A substantial concentration of deuterium was found in the subsurface oxide layer. This observation confirmed previous assessments that the formation of FeO was from the reaction of Fe(OD)₂ with outward‐diffusing Fe, leaving deuterium as a reaction product. Copyright © 2005 John Wiley & Sons, Ltd.     

Surface analysis of nitride layers formed on Fe‐based alloys through plasma nitride process

Nitriding phenomena that occur on the surfaces of pure Fe and Fe? Cr alloy (16 wt% Cr) samples were investigated. An Ar + N₂ mixture‐gas glow‐discharge plasma was used so that surface nitriding could occur on a clean surface etched by Ar⁺ ion sputtering. In addition, the metal substrates were kept at a low temperature to suppress the diffusion of nitrogen. These plasma‐nitriding conditions enabled us to characterize the surface reaction between nitrogen radicals and the metal substrates. The emission characteristics of the band heads of the nitrogen molecule ion (N₂⁺) and nitrogen molecule from the glow‐discharge plasma suggest that the active nitrogen molecule is probably the major nitriding reactant. AES and angle‐resolved XPS were used to characterize the thickness of the nitride layer and the concentration of elements and chemical species in the nitride layer. The thickness of the nitride layer did not depend on the metal substrate type. An oxide layer with a thickness of a few nanometers was formed on the top of the nitride layer during the nitriding process. The oxide layer consisted of several species of N_x‐Fe_y‐O, NO⁺, and NO₂^?. In the Fe? Cr alloy sample, these oxide species could be reduced because chromium is preferentially nitrided. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermally Stable Super Ionic Conductor from Carbon Sphere Oxide

A highly stable proton conductor has been developed from carbon sphere oxide (CSO). Carbon sphere (CS) generated from sucrose was oxidized successfully to CSO using Hummers’ graphite oxidation technique. At room temperature and 90 % relative humidity, the proton conductivity of thin layer CSO on microsized comb electrode was found to be 8.7×10^?3 S cm^?1, which is higher than that for a similar graphene oxide (GO) sample (3.4×10^?3 S cm^?1). The activation energy (E_a) of 0.258 eV suggests that the proton is conducted through the Grotthuss mechanism. The carboxyl functional groups on the CSO surface are primarily responsible for transporting protons. In contrast to conventional carbon‐based proton conductors, in which the functional groups decompose around 80 °C, CSO has a stable morphology and functional groups with reproducible proton conductivity up to 400 °C. Even once annealed at different temperatures at high relative humidity, the proton conductivity of CSO remains almost unchanged, whereas significant change is seen with a similar GO sample. After annealing at 100 and 200 °C, the respective proton conductivity of CSO was almost the same, and was about ～50 % of the proton conductivity at room temperature. Carbon‐based solid electrolyte with such high thermal stability and reproducible proton conductivity is desired for practical applications. We expect that a CSO‐based proton conductor would be applicable for fuel cells and sensing devices operating under high temperatures.     

Thin films of vanadium oxide grown on vanadium metal: oxidation conditions to produce V2O5 films for Li‐intercalation applications and characterisation by XPS,AFM, RBS/NRA

Thin films of vanadium oxide were grown on vanadium metal surfaces (i) in air at ambient conditions, (ii) in 5 mM H₂SO₄ (aq), pH 3, (iii) by thermal oxidation at low oxygen pressure (10^?5 mbar) at temperatures between 350 and 550 °C and (iv) at near‐atmospheric oxygen pressure (750 mbar) at 500 °C. The oxide films were investigated by atomic force microscopy (AFM), X‐ray photoelectron spectroscopy (XPS), X‐Ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA). The lithium intercalation properties were studied by cyclic voltammetry (CV). The results show that the oxide films formed in air at room temperature (RT), in acidic aqueous solution, and at low oxygen pressure at elevated temperatures are composed of V₂O₃. In air and in aqueous solution at RT, the oxide films are ultra‐thin and hydroxylated. At 500 °C, nearly atmospheric oxygen pressure is required to form crystalline V₂O₅ films. The oxide films grown at pO₂ = 750 mbar for 5 min are about 260‐nm thick, and consist of a 115‐nm outer layer of crystalline V₂O₅. The inner oxide is mainly composed of VO₂. For all high temperature oxidations, the oxygen diffusion from the oxide film into the metal matrix was considerable. The oxygen saturation of the metal at 450 °C was found, by XPS, to be 27 at.% at the oxide/metal interface. The well‐crystallized V₂O₅ film, formed by oxidation for 5 min at 500 °C and 750 mbar O₂, was shown to have good lithium intercalation properties and is a promising candidate as electrode material in lithium batteries. Copyright © 2005 John Wiley & Sons, Ltd.     

Electrochemical synthesis of oxide nanotubes on Ti6Al7Nb alloy and their interaction with the simulated body fluid

The aim of the present work was to investigate electrochemical behavior of the Ti6Al7Nb alloy in the simulated body fluid (SBF) containing Ca²⁺, HCO₃ ^?, and HPO₄ ^2? ions. At first, optimal conditions necessary for oxide nanotube formation were determined. The experiments were conducted in the 1 M (NH₄)₂SO₄ with 0.5 wt% NH₄F electrolyte at room temperature. Anodization of the alloy samples was carried out under variable external voltage U in the range from 10 to 40 V at room temperature. Obtained surface morphology was examined by SEM and X-ray techniques. Nanotube diameter was calculated and correlated with the imposed voltage. Having control over the size of nanotubes, samples with the obtained nanostructures of a chosen diameter were immersed into SBF solution with pH = 7.4 for a fixed period of time. Then, they were removed from the fluid and subjected to the electrochemical investigation. Corrosion current and corrosion potential were determined, and it was found that the best anticorrosion properties were obtained for heat-treated nanotube layer: i _corr = 39 nA/cm² and E _corr = ?0.236 V vs Ag/AgCl. Finally, the interaction between the oxide surface and the solution was studied using polarization and electrochemical impedance spectroscopy (EIS) techniques.     

Characterization of surface composition on Alloy 22 in neutral chloride solutions

The composition of anodically grown oxide films on Alloy 22, a Ni‐Cr‐Mo(W) alloy, has been investigated in 5 mol l^?1 NaCl at room temperature using X‐ray photoelectron spectroscopy and time‐of‐flight secondary ion mass spectrometry. For applied potentials up to 0.2 V (vs Ag/AgCl (saturated KCl solution)), a Cr(III) oxide barrier layer develops at the alloy/oxide interface accounting for the excellent passivity demonstrated to prevail in this potential region by previous electrochemical impedance spectroscopy measurements. At higher potentials, this layer is destroyed by defect injection as Cr(III) is oxidized to the more soluble Cr(VI). The overall oxide/hydroxide film thickness is, however, increased as Mo(VI)/W(VI) species accumulate at the oxide solution interface. The potential of 0.2 V at which the barrier layer switches from growth to destruction coincides with the previously demonstrated threshold potential for the initiation of crevice corrosion. Copyright © 2012 John Wiley & Sons, Ltd.     

Multirotations of (Anilinium)([18]Crown‐6) Supramolecular Cation Structure in Magnetic Salt of [Ni(dmit)2]−

A solid‐state dynamic supramolecular structure consisting of (anilinium)([18]crown‐6) was arranged as the cation in a salt of [Ni(dmit)₂]^? (dmit=2‐thioxo‐1,3‐dithiole‐4,5‐dithiolate). With the ammonium moiety of anilinium located within the cavity of [18]crown‐6, a hydrogen‐bonded supramolecular structure is formed, with an orthogonal arrangement between the π plane of anilinium and the mean O6 plane of [18]crown‐6. In this supramolecular cation, both anilinium and [18]crown‐6 act as dynamic units with different rotational modes in the solid state. The uniform stacks of cations form an antiparallel arrangement, thus producing a layer structure. Sufficient space for the 180° flip‐flop motion of the phenyl ring and the rotation of [18]crown‐6 was observed in the cation layer. Thermally activated 180° flip‐flop motions, with a frequency of 6 MHz at room temperature and an activation energy of 31 kJ mol^?1, were confirmed by temperature‐dependent ²H NMR spectra of ([D₅]anilinium)‐([18]crown‐6)[Ni(dmit)₂]. A double‐minimum potential for the molecular rotation of anilinium, with a barrier of approximately 40 kJ mol^?1, was indicated by ab initio calculations. The wide‐line ¹H NMR spectra indicated a thermally activated rotation of [18]crown‐6 at temperatures above 250 K. Therefore, multiple molecular motions of the 180° flip‐flop motion of the phenyl ring and the rotation of [18]crown‐6 occur simultaneously in the solid state. The temperature‐dependent dielectric constants revealed that the molecular motion of [18]crown‐6, other than the flip‐flop motion, dominates the dielectric response in the measured temperature and frequency range.     

Effects of gold‐induced crystallization process on the structural and electrical properties of germanium thin films

Gold‐induced (Au‐) crystallization of amorphous germanium (α‐Ge) thin films was investigated by depositing Ge on aluminum‐doped zinc oxide and glass substrates through electron beam evaporation at room temperature. The influence of the postannealing temperatures on the structural properties of the Ge thin films was investigated by employing Raman spectra, X‐ray diffraction, and scanning electron microscopy. The Raman and X‐ray diffraction results indicated that the Au‐induced crystallization of the Ge films yielded crystallization at temperature as low as 300°C for 1 hour. The amount of crystallization fraction and the film quality were improved with increasing the postannealing temperatures. The scanning electron microscopy images show that Au clusters are found on the front surface of the Ge films after the films were annealed at 500°C for 1 hour. This suggests that Au atoms move toward the surface of Ge film during annealing. The effects of annealing temperatures on the electrical conductivity of Ge films were investigated through current‐voltage measurements. The room temperature conductivity was estimated as 0.54 and 0.73 Scm⁻¹ for annealed samples grown on aluminum‐doped zinc oxide and glass substrates, respectively. These findings could be very useful to realize inexpensive Ge‐based electronic and photovoltaic applications.     

一种新型氧离子导体：La3GaMo2O12

A new oxide ion conductor,La_3GaMo_2O_(12),with a bulk conductivity of 2.7×10~(-2)S·cm~(-1) at 800 ℃ in air at-mosphere was prepared by the traditional solid-state reaction.The room temperature X-ray diffraction data could beindexed on a monoclinic cell with lattice parameters of a=0.5602(2) nm,b=0.3224(1) nm,c=1.5741(1) nm,β=102.555(0)°,V= 0.2775(2) nm~3 and space group Pc(7).Ac impedance measurements in various atmospheres furthersupport that it is an oxide ion conductor.This material was stable in various atmospheres with oxygen partial pres-sure p(O_2)ranging from 1.0×10~5 to 1.0×10~(-7) Pa at 800 ℃.A reversible polymorphic phase transition occurred atelevated temperatures as confirmed by the differential thermal analysis and dilatometric measurement.     

Synthesis,Crystal Structure,Spectroscopic and Electrochemical Properties of a Copper Coordination Polymer with Unprecedented Topology

A copper cyanide coordination polymer [Cu₈(CN)₈(bbtz)₂]_n ( 1 ) [bbtz = 1,4‐bis(1,2,4‐trizal‐1‐ylmethyl)benzene] was synthesized following a synchronous redox and self‐assembly reaction under the solvothermal condition, and characterized by elemental analysis, infrared spectroscopy, and single‐crystal X‐ray diffraction. Interestingly, complex 1 exhibits a two‐dimensional conjugated pillared double‐layer architecture and an unprecedented (3,3,4)‐connected network with the point symbol (6.7.10)₂(6.7²)₂(6².7³.10) topology. Moreover, the thermogravimetric analysis indicates complex 1 has highly thermal stability, and the solid‐state emission spectrum for its crystalline material displays a strong green luminescence band (λ_max = 565 nm) at room temperature. The electrochemical behavior of complex 1 is determined by the scan rates in the range from –0.5 to +0.3 V at room temperature, and exhibits different redox processes.     

Influence of sintering on the structural and electronic properties of TiO2 nanoporous layers prepared via a non-sol–gel approach

In this work, a nonaqueous method is used to fabricate thin TiO₂ layers. In contrast to the common aqueous sol–gel approach, our method yields layers of anatase nanocrystallites already at low temperature. Raman spectroscopy, electron microscopy and charge extraction by linearly increasing voltage are employed to study the effect of sintering temperature on the structural and electronic properties of the nanocrystalline TiO₂ layer. Raising the sintering temperature from 120 to 600?°C is found to alter the chemical composition, the layer’s porosity and its surface but not the crystal phase. The room temperature mobility increases from 2?×?10^?6 to 3?×?10^?5?cm²/Vs when the sinter temperature is increased from 400 to 600?°C, which is explained by a better interparticle connectivity. Solar cells comprising such nanoporous TiO₂ layers and a soluble derivative of cyclohexylamino-poly(p-phenylene vinylene) were fabricated and studied with regard to their structural and photovoltaic properties. We found only weak polymer infiltration into the oxide layer for sintering temperatures up to 550?°C, while the polymer penetrated deeply into titania layers that were sintered at 600?°C. Best photovoltaic performance was reached with a nanoporous TiO₂ film sintered at 550?°C, which yielded a power conversion efficiency of 0.5?%. Noticeably, samples with the TiO₂ layer dried at 120?°C displayed short-circuit currents and open circuit voltages only about 15–20?% lower than for the most efficient devices, meaning that our nonaqueous route yields titania layers with reasonable transport properties even at low sintering temperatures.     

Low‐Temperature Solid‐State Microwave Reduction of Graphene Oxide for Transparent Electrically Conductive Coatings on Flexible Polydimethylsiloxane (PDMS)

Microwaves (MWs) are applied to initialize deoxygenation of graphene oxide (GO) in the solid state and at low temperatures (～165 °C). The Fourier‐transform infrared (FTIR) spectra of MW‐reduced graphene oxide (rGO) show a significantly reduced concentration of oxygen‐containing functional groups, such as carboxyl, hydroxyl and carbonyl. X‐ray photoelectron spectra confirm that microwaves can promote deoxygenation of GO at relatively low temperatures. Raman spectra and TGA measurements indicate that the defect level of GO significantly decreases during the isothermal solid‐state MW‐reduction process at low temperatures, corresponding to an efficient recovery of the fine graphene lattice structure. Based on both deoxygenation and defect‐level reduction, the resurgence of interconnected graphene‐like domains contributes to a low sheet resistance (～7.9×10⁴ Ω per square) of the MW‐reduced GO on SiO₂‐coated Si substrates with an optical transparency of 92.7 % at ～547 nm after MW reduction, indicating the ultrahigh efficiency of MW in GO reduction. Moreover, the low‐temperature solid‐state MW reduction is also applied in preparing flexible transparent conductive coatings on polydimethylsiloxane (PDMS) substrates. UV/Vis measurements indicate that the transparency of the thus‐prepared MW‐reduced GO coatings on PDMS substrates ranges from 34 to 96 %. Correspondingly, the sheet resistance of the coating ranges from 10⁵ to 10⁹ Ω per square, indicating that MW reduction of GO is promising for the convenient low‐temperature preparation of transparent conductors on flexible polymeric substrates.     

Synthesis and characterization of a new modification of PtAl

A new PtAl phase, which is stable at room temperature under oxidizing conditions, has been synthesized at 200 °C and 5 MPa. X‐ray studies reveal it to be different from the known polymorphs of PtAl, which crystallize in the FeSi and CsCl structure types. The crystal structure of the new PtAl modification is found to be isotypical with the low‐temperature modification of PdAl. In situ high‐temperature X‐ray diffraction experiments in air were performed to study the thermal behavior of the new PtAl alloy. In the temperature range between 400 and 700 °C, Pt₅Al₃ forms as an intermediate phase. At higher temperature the alloy decomposes, resulting in the formation of platinum and Al₂O₃. The thermodynamic instability at high temperatures explains why this new modification has not been observed using contemporary metallurgic processes. Copyright © 2003 John Wiley & Sons, Ltd.     

Epitaxy‐like orientation of nanoscale Ag islands grown on air‐oxidized Si(110)‐(5 × 1) surfaces

Growth of Ag islands under ultra‐high vacuum condition on air‐oxidized Si(110)‐(5 × 1) surfaces has been investigated by in situ reflection high energy electron diffraction and ex situ scanning electron microscopy and cross‐sectional transmission electron microscopy. A thin oxide is formed on Si via exposure of the clean Si(110)‐(5 × 1) surface to air. The oxide layer has a short range order. Deposition of Ag at different thicknesses and at different substrate temperatures reveal that the crystalline qualities of the Ag film are almost independent of the thickness of the Ag layer and depend only on the substrate temperature. Ag deposition at room temperature leads to the growth of randomly oriented Ag islands while preferred orientation evolves when Ag is deposited at higher temperatures. For deposition at 550 °C sharp spots in the reflection high energy electron diffraction pattern corresponding to an epitaxial orientation with the underlying Si substrate are observed. The presence of a short range order on the oxidized surface apparently influences the crystallographic orientation of the Ag islands. Copyright © 2011 John Wiley & Sons, Ltd.     

High efficiency of Mn–Ce‐modified TiO2 catalysts for the low‐temperature oxidation of Hg0 under a reducing atmosphere

Manganese‐ and cerium oxide‐modified titania catalysts were prepared by the deposition precipitation for the removal of elemental mercury (Hg⁰) from simulated yellow phosphorus off‐gas at low temperature. In addition, these catalysts were characterized by X‐ray diffraction, Brunauer–Emmett–Teller measurements, X‐ray photoelectron spectroscopy and field‐emission scanning electron microscope to determine the surface morphology of the obtained compounds and explore their formation mechanism. The results revealed that a Mn–Ce loading and reaction temperature of 10% and 150 °C, respectively, as well as a Mn/Ce molar ratio of 2:1, led to an optimal efficiency for the oxidation of elemental mercury. Furthermore, the effects of flue gas components were investigated. The presence of O₂ clearly promoted the oxidation of Hg⁰. A CO atmosphere did not affect the Hg⁰ oxidation, when compared with N₂, whereas the presence of H₂S and water vapor inhibited the oxidation process. Furthermore, the X‐ray photoelectron spectroscopy spectra of Hg 4f revealed that the elemental mercury adsorbed by the catalyst is present as HgO. Finally, the Hg⁰ catalytic oxidation mechanism was discussed on the basis of the experimental results and characterization analysis.     

Synthesis,Crystal Structure,Bonding, and Properties of (Ba6O)(OsN3)2

The new barium nitridoosmate oxide (Ba₆O)(OsN₃)₂ was prepared by reacting elemental barium and osmium (3:1) in nitrogen at 815–830 °C. The crystal structure of (Ba₆O)(OsN₃)₂ as determined by laboratory powder X‐ray diffraction ( , No 148: a=b=8.112(1) Å, c=17.390(1) Å, V=991.0(1) ų, Z=3), consists of sheets of trigonal OsN₃ units and trigonal‐antiprismatic Ba₆O groups, and is structurally related to the “313 nitrides” AE₃MN₃ (AE=Ca, Sr, Ba, M=V–Co, Ga). Density functional calculations, using a hybrid functional, likewise indicate the existence of oxygen in the Ba₆ polyhedra. The oxidation state 4+ of osmium is confirmed, both by the calculations and by XPS measurements. The bonding properties of the OsN₃^5? units are analyzed and compared to the Raman spectrum. The compound is paramagnetic from room temperature down to T=10 K. Between room temperature and 100 K it obeys the Curie–Weiss law (μ=1.68 μ_B). (Ba₆O)(OsN₃)₂ is semiconducting with a good electronic conductivity at room temperature (8.74×10^?2 Ω^?1 cm^?1). Below 142 K the temperature dependence of the conductivity resembles that of a variable‐range hopping mechanism.     

Ruthenium(V) Oxides from Low‐Temperature Hydrothermal Synthesis

Low‐temperature (200 °C) hydrothermal synthesis of the ruthenium oxides Ca_1.5Ru₂O₇, SrRu₂O₆, and Ba₂Ru₃O₉(OH) is reported. Ca_1.5Ru₂O₇ is a defective pyrochlore containing Ru^V/VI; SrRu₂O₆ is a layered Ru^V oxide with a PbSb₂O₆ structure, whilst Ba₂Ru₃O₉(OH) has a previously unreported structure type with orthorhombic symmetry solved from synchrotron X‐ray and neutron powder diffraction. SrRu₂O₆ exhibits unusually high‐temperature magnetic order, with antiferromagnetism persisting to at least 500 K, and refinement using room temperature neutron powder diffraction data provides the magnetic structure. All three ruthenates are metastable and readily collapse to mixtures of other oxides upon heating in air at temperatures around 300–500 °C, suggesting they would be difficult, if not impossible, to isolate under conventional high‐temperature solid‐state synthesis conditions.