Formation of perovskite-related structures CaMO3 (M = Sn, Ti) by mechanical milling

Nanoparticle calcium stannate (CaSnO₃) and calcium titanate (CaTiO₃) have been prepared by the mechanical milling of mixtures of calcium(II) oxide with tin(IV) oxide or titanium(IV) oxide. The formation of calcium titanate (CaTiO₃) is more easily achieved by milling calcium(II) oxide with the rutile modification of titanium (IV) oxide than with the anatase form.     

Synergistic effect of transition metal oxides and ozone on PCDD/F destruction

Catalytic oxidations of PCDD/Fs (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans) with ozone on the transition metal oxides (iron oxide or manganese oxide) at the temperature range of 120-180 degrees C were investigated. These two catalysts were prepared by precipitation methods. Iron oxide has a higher surface area (330 m(2)/g) than manganese oxide (53 m(2)/g). In the absence of ozone, the removal efficiencies of PCDD/Fs achieved with iron oxide or manganese oxide were between 83% and 85%, while the destruction efficiencies were only between 20% and 25% at 180 degrees C. It indicates that adsorption was the main removal mechanism of PCDD/Fs over these two catalysts. On the other hand, ozone addition greatly enhanced the catalytic activity of iron oxide or manganese oxide catalysts on the oxidation of gaseous PCDD/Fs. At 180 degrees C, the destruction efficiencies of gaseous PCDD/Fs achieved with iron oxide or manganese oxide with 100 ppm O(3) exceeded 90%. It indicates that catalytic ozonation achieved with iron oxide or manganese oxide is effective in decomposing PCDD/Fs and the application of ozone lowers the reaction temperature of PCDD/F oxidation below 200 degrees C. Furthermore, the synergistic effect of iron oxide and ozone is superior to that of manganese oxide due to the fact that the surface of iron oxide has more hydroxyl groups, which easily form hydrogen bonds with ozone and decompose to form atomic oxygen for the further reaction with dioxin molecules.     

聚苯乙烯/氧化石墨纳米复合材料的制备与性能

利用十六烷基三甲基溴化铵对氧化石墨进行插层改性。以原住插层聚合的方式合成了聚苯乙烯／氧化石墨（PS／GO）纳米复合材料。用XRD和TEM进行的形态研究表明,氧化石墨被剥离成10nm-30nm厚的层片而分散在聚合物基体中。热重分析证明PS／GO复合材料比PS材料和普通石墨粉填充的PS材料表现出更好的热稳定性。     

Immobilization of calcium phosphate nano-clusters into alkoxy-derived porous TiO2 coatings

Alkoxy-derived porous coatings of titanium oxide were fabricated on commercially pure titanium substrates by an electrochemical method in methanolic electrolytes. Nano-clusters of brushite (CaHPO4 · 2H2O) were immobilized into the pores of the oxide network by reacting these coatings in acidic calcium phosphate solutions at 50°C. The acid-base reaction between calcium phosphate solutions and the hydroxyl groups of the oxide network resulted in the formation of nano-clusters of brushite crystals immobilized inside the oxide pores. This treatment resulted in the conversion of the porous oxide network into a coherent mass with improved physical integrity. Nano-clusters of brushite crystals immobilized in the oxide matrix were converted into amorphous calcium phosphate (ACP) and poorly crystallized hydroxyapatite (HA) by further treatment of the oxide in alkaline solutions. The porous oxide coating also reacted strongly with concentrated phosphoric acid. The phosphate-modified oxide resulting from this reaction was further treated in calcium hydroxide solution to form nano-clusters of poorly crystallized HA within the oxide network.     

Transition Metal and Rare-Earth Metal Doping in SnO2 Nanoparticles

Journal of Superconductivity and Novel Magnetism - Nanoparticles of tin oxide (SnO2) doped with iron oxide (α-Fe2O3) and Europium oxide (Eu2O3) were synthesized through the solid-state...     

Interstitial oxide ion conductivity in the layered tetrahedral network melilite structure

High-conductivity oxide ion electrolytes are needed to reduce the operating temperature of solid-oxide fuel cells. Oxide mobility in solids is associated with defects. Although anion vacancies are the charge carriers in most cases, excess (interstitial) oxide anions give high conductivities in isolated polyhedral anion structures such as the apatites. The development of new families of interstitial oxide conductors with less restrictive structural constraints requires an understanding of the mechanisms enabling both incorporation and mobility of the excess oxide. Here, we show how the two-dimensionally connected tetrahedral gallium oxide network in the melilite structure La(1.54)Sr(0.46)Ga(3)O(7.27) stabilizes oxygen interstitials by local relaxation around them, affording an oxide ion conductivity of 0.02-0.1 S cm(-1) over the 600-900 degrees C temperature range. Polyhedral frameworks with central elements exhibiting variable coordination number can have the flexibility needed to accommodate mobile interstitial oxide ions if non-bridging oxides are present to favour cooperative network distortions.     

Role of iron oxide impurities in electrocatalysis by multiwall carbon nanotubes: An investigation using a novel magnetically modified ITO electrodes

The role of iron oxide impurities in the electrocatalytic properties of multiwall carbon nanotubes (MWCNTs) prepared by catalytic chemical vapour decomposition method (CCVD) is studied in detail. A novel magnetically modified electrodes have been developed by which MWCNTs were immobilized on indium-tin oxide (ITO) electrodes, without any chemical binders. The electro-catalytic oxidation of dopamine, and reduction of hydrogen peroxide have been studied by cyclic voltammetry on magnetically modified electrodes with (i) MWCNTs with occluded iron oxide impurities (Fe-MWCNTs), (ii) MWCNTs grown on iron oxide nanoparticle particulate films (Io-MWCNTs) and (iii) pristine iron oxide nanoparticle particulate film (Io-NPs). A shift towards less positive potentials for the oxidation of dopamine was observed which is in the order of Fe-MWCNTs < Io-MWCNTs < Io-NPs. Similarly, trend towards less negative potentials for the reduction of hydrogen peroxide was observed. Thus, the electrocatalytic activities displayed by MWCNTs have been attributed to the iron oxide impurities associated with it. The systematic variation was related to the nature of interaction of iron oxide nanoparticles with MWCNT surface.     

Improved electrical and reliability characteristics in metal/oxide/nitride/oxide/silicon capacitors with blocking oxide layers formed under the radical oxidation process

We propose a Metal-Oxide-Nitride-Oxide-Silicon (MONOS) structure whose blocking oxide is formed by radical oxidation on the silicon nitride (Si3N4) layer to improve the electrical and reliability characteristics. We directly compare the electrical and reliability properties of the MONOS capacitors with two different blocking oxide (SiO2) layers, which are called a "radical oxide" grown by the radical oxidation and a "CVD oxide" deposited by chemical vapor deposition (CVD) respectively. The MONOS capacitor with a radical oxide shows a larger C-V memory window of 3.6 V at sweep voltages from 9 V to -9 V, faster program/erase speeds of 1 micros/1 ms at bias voltages of -6 V and 8 V, a lower leakage current of 7 pA and a longer data retention, compared to those of the MONOS capacitor with a CVD oxide. These improvements have been attributed to both high densification of blocking oxide film and increased nitride-related memory traps at the interface between the blocking oxide and Si3N4 layer by radical oxidation.     

Effect of chitosan-incorporated Fe3O4 nanocomposites on the photocatalytic removal of organic molecules

Journal of Materials Science: Materials in Electronics - The bare iron oxide (IO) and iron oxide/chitosan (IOC) nanocomposites were prepared by co-precipitation method. The iron oxide and iron...     

Chlorobenzene oxidation using ozone over iron oxide and manganese oxide catalysts

A low-temperature catalytic oxidation of chlorobenzene (CB) has been performed at temperatures of 60-210°C using ozone (O(3)) over iron oxide and manganese oxide, respectively. In the absence of ozone, CB conversion achieved with these two catalysts at 200°C was below 10%. However, addition of 1200 ppm ozone results in a remarkable increase in CB conversion and the conversion reaches 91.7% at 150°C for iron oxide, while 81.5% conversion is achieved with manganese oxide at 90°C. The activation energy of manganese oxide (48 kJ mol(-1)) is higher than that of iron oxide (43 kJ mol(-1)) without ozone. However, as ozone is added, the activation energy is significantly reduced to 20.0 kJ mol(-1) for iron oxide. CO and CO(2) are the only carbon-containing products detected in the effluent gas stream. For the long-term test, no obvious deactivation was found in iron oxide and ozone. However, in the case of manganese oxide and ozone, 3% reduction of CB conversion was observed. Slight deactivation might be attributed to a small amount of reaction byproducts (carboxylic acid species) and residual chloride (MnCl(2)) being deposited on the active sites of the catalysts.     

Influence of concentration and annealing temperature on spin-coated metal oxide thin films for optoelectronic devices

Journal of Materials Science: Materials in Electronics - The metal oxide thin films, such as cadmium oxide (CdO) and zinc oxide (ZnO) thin films, were deposited by sol–gel-derived spin...     

ESEM observations of SCC initiation for 4340 high strength steel in distilled water

The stress corrosion cracking (SCC) initiation process for 4340 high strength steel in distilled water at room temperature was studied using a new kind of instrument: an environmental scanning electron microscope (ESEM). It was found that the applied stress accelerated oxide film formation which has an important influence on the subsequent SCC initiation. SCC was observed to initiate in the following circumstances: (1) cracking of a thick oxide film leading to SCC initiation along metal grain boundaries, (2) the initiation of pits initiating SCC in the metal and (3) SCC initiating from the edge of the specimen.All these three SCC initiation circumstances are consistent with the following model which couples SCC initiation with cracking of a surface protective oxide. There is a dynamic interaction between oxide formation, the applied stress, oxide cracking, pitting and the initiation of SCC. An aspect of the dynamic interaction is cracks forming in a protective surface oxide because of the applied stress, exposing to the water bare metal at the oxide crack tip, and oxidation of the bare metal causing crack healing. Oxide crack healing would be competing with the initiation of intergranular SCC if an oxide crack meets the metal surface at a grain boundary. If the intergranular SCC penetration is sufficiently fast along the metal grain boundary, then the crack yaws open preventing healing of the oxide crack. If intergranular SCC penetration is not sufficiently fast, then the oxidation process could produce sufficient oxide to fill both the stress corrosion crack and the oxide crack; in this case there would be initiation of SCC but only limited propagation of SCC. Stress-induced cracks in very thin oxide can induce pits which initiate SCC, and under some conditions such stress induced cracks in a thin oxide can directly initiate SCC.     

Preparation of gold nanosheets using poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) block copolymers via photoreduction

Gold nanosheets having single crystalline structure were successfully synthesized using the bulk phase mixture of HAuCl₄ and poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) block copolymers through the irradiation of a glow lamp for 5 days. When the molar ratio of propylene oxide to ethylene oxide block units in the block copolymer is about 1.75, mostly gold nanosheets were obtained. Gold nanosheets with an average width of 8 and 5 μm were obtained from the when the molar ratio of gold salt to the ethylene oxide units in the block copolymer were 1/80 and 1/160, respectively.     

The reactivity of ethylene oxide in contact with iron oxide fines as measured by adiabatic calorimetry

Samples of various iron oxides suspended above ethylene oxide in an adiabatic calorimeter exhibit exothermic activity at temperatures as low as room temperature. A gamma-Fe(2)O(3) sample was found to show the highest reactivity with ethylene oxide. Ethylene oxide in combination with most of the iron oxide fines tested displayed exothermic activity below 100 degrees C. Self-heat rates near 2000 degrees C/min were observed for the gamma-Fe(2)O(3) fines while rates in excess of 100 degrees C/min were found for other fines (alpha-Fe(2)O(3) and hydrated alpha-Fe(2)O(3)). In two cases (alpha-Fe(3)O(4) and alpha-Fe(2)O(3)), pressurization rates above 1000 psi/min took place. No reactivity was observed for ethylene oxide with the FeO. Thermal inertia effects in commercial operation, such as heat uptake by the equipment to which fines are attached, are presumed to be a factor in limiting the occurrence of related exotherms in ethylene oxide manufacturing facilities.     

Metal oxide mesocrystals and mesoporous single crystals: synthesis,properties and applications in solar energy conversion

Metal oxide mesocrystals (MCs) and mesoporous single crystals (MSCs) exhibit superior carrier transport ability,high specific surface area,shortened photo-carrier diffusion lengths to interfaces and enhanced absorbance of the incident sunlight.These advanced features make metal oxide MCs and MSCs be a promising candidate material in photocatalysis,photoelectrocatalysis,dye sensitized solar cells (DSSCs) and perovskite solar cells (PSCs).Recently,remarkable advances of applying metal oxide MCs and MSCs in these areas have been achieved.Therefore,it is extremely important to deeply understand the influence of the unique properties of metal oxide MCs and MSCs on solar energy conversion systems.Herein,we presented a brief introduction on the synthesis and carrier transfer behavior of metal oxide MCs and MSCs.Then,the rational structure design and modification of metal oxide MCs and MSCs for photocatalysis,photoelectrocatalysis,DSSCs and PSCs are systematically discussed.Finally,the perspectives on extending the application of metal oxide MCs and MSCs are addressed.     

氧化钒纳米管的自组装合成机理

以V₂O₅和十六胺为原料在水热条件下合成了氧化钒纳米管, 采用XRD、SEM、TEM、FTIR、ESR等手段分析研究了氧化钒纳米管的形成机理. 结果表明, 氧化钒纳米管的形成主要基于“卷曲机理”, 其形成过程包括: 表面活性剂分子嵌入到钒氧化物层间, 形成新层状化合物前驱体; 水热驱动下层状化合物边缘松动, 并开始卷曲, 降低体系能量; 合适的水热反应时间下最终形成钒氧化物纳米管. 模板剂嵌入到钒氧化物层间形成一定大小的层间距以及V⁴⁺的存在对从层状化合物卷曲成纳米管起到了积极的作用.     

A reflection electron diffraction study on some metal oxide solar collector coatings: Part I

The capability of reflection electron diffraction (RED) in the structural analysis of thin films is shown with studies made on copper oxide, zinc oxide, black chrome and cobalt oxide solar-selective coatings. The growth of copper oxide layers could be observed as changing from an initial epitaxial growth to random orientation followed by growth of oxide needles. The resulting copper oxide coating was found to consist of a needle structure of cupric oxide formed on a smooth cuprous oxide layer. In the zinc oxide overgrowths, epitaxial growth could not be observed, and the coating consisted of relatively small zinc oxide crystallites throughout the film. No crystalline zinc inclusions could be found in this layer.Black chrome deposited onto nickel showed an increase in chromium oxide with distance from the substrate, although no change in the orientation of the microcrystalline chrome could be observed. The formation of black cobalt was also investigated using scanning electron microscopy (SEM) and reflection diffraction analysis. The plated cobalt overgrowths were found to change from an initially smooth nodular coating to a plate-like oxide layer with heat treatment time. This latter layer could be indexed to cobalt(II, III) oxide.The study conclusively shows that RED, combined with SEM and ion milling procedures, can indeed lead to structural characterization of thin films without the need for their removal from their substrates and the concominant introduction of artifacts.     

Appropriate conditions for preparing few-layered graphene oxide and reduced graphene oxide

Oxidation time and exfoliated conditions of graphite oxides (GOs) were investigated to prepare few–layer graphene oxide and reduced graphene oxide via a modified Hummers approach. Different oxidative degree of GOs was prepared by changing oxidation time, and the effects of oxidative degree of GOs in different oxidation time were studied by XRD, FT-IR. Afterwards, highly oxidized GOs were used as precursor to prepare graphene oxide and reduced graphene oxide by ultrasonic dispersion method and thermal expansion method. The exfoliated conditions (ultrasonic power and ultrasonic time, thermal exfoliated temperature) were investigated to prepare few-layered graphene oxide and reduced graphene oxide.     

Field effect in a graphene oxide transistor for proton and electron–hole conductivities

Proton (wet atmosphere) and electron (reduced graphene oxide) conductivities can be observed in graphene oxide films. The field effect in a graphene oxide transistor for different conductivity types has been discovered and investigated.     

Temperature programmed desorption study of the oxide layer formed by the interaction of polycrystalline nickel with oxygen

In a 100 l exposure of oxygen, an oxide layer was formed on a nickel surface, this surface was heated and maintained at 623 K to dissociate the oxide, then by exposure to 5 l oxygen, a small amount of oxygen was adsorbed again. From the Temperature Programmed Desorption spectrum of this O₂/Ni surface it can be concluded that the original oxide layer on the nickel surface was not a stoichiometric nickel (II) oxide, but may be a compound of a variety of oxides such as nickel (II) oxide, nickel (III) species and excess oxygen.