Atomic Ratio Of Oxygen Research Articles

Thermally and Chemically Stable Mixed Valence Copper Oxide Cluster Ions Revealed by Post Heating

Copper oxide clusters, Cu(n)O(m)(+) (n = 5-12), were prepared in the gas phase by laser ablation of a copper metal rod in the presence of oxygen diluted in He as the carrier gas. The stoichiometry of the cluster ions was investigated using mass spectrometry. The number ratio of copper atoms and oxygen atoms in Cu(n)O(m)(+) was distributed from n:m = 1:1-3:2, which was not affected significantly by the concentration of oxygen in the carrier gas as long as it exceeded 2%. When the cluster ions were heated up to 573 K downstream of the cluster source (post heating), Cu(n)O(m)(+) (n:m ≈ 3:2) clusters were selectively and dominantly formed as a result of thermal dissociation. No further changes in the ratio were observed when the clusters were heated up to 623 K. From the stoichiometry, Cu(n)O(m)(+) is considered to comprise both Cu(I) and Cu(II). Hence, the mixed valence states are found to be thermally stable for the small clusters in the gas phase, but they are not stable in the bulk phase. In addition to the thermal stability, we observed reactivity of Cu(n)O(m)(+) with CO molecules. It was found that Cu12O8(+) hardly binds to CO and that Cu9O6(+) and Cu6O4(+) along with other clusters with n:m ≈ 3:2 bind to CO very weakly, whereas CO attaches strongly to oxygen-rich clusters with release of an oxygen molecule.

Capacitive behavior of mesoporous Co(OH)2 nanowires

Dual-template synthesis, which includes porous anodic alumina and lyotropic liquid crystalline templates, has been carried out at various electrodeposition potentials, annealing and electrodeposition temperatures for mesoporous Co(OH)2 nanowires. The maximum capacitance of 1180 F g−1 has been achieved at 4 A g−1. The chemical state and detailed structure of Co(OH)2 are examined by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) respectively. It reveals that the capacitance behavior of mesoporous Co(OH)2 nanowires depends on not only the oxygen atomic ratio of Co(OH)2 to CoO chemical state, but also the packed density of the interlaced nanostructure.

A comparative study of hepatic mitochondrial oxygen consumption in four vertebrates by using Clark-type electrode

The present study was undertaken to establish a comparative account on hepatic mitochondrial oxygen consumption of Clarias gariepinus (fish), Bufo melanostictus (amphibian), Gallus gallus (bird) and Rattus norvegicus (mammal) and to correlate it with their specific metabolic rate (SMR). Mitochondrial oxygen consumption was measured with a Clarke-type electrode with succinate and pyruvate/malate as substrates. ADP was used to start state-III respiration. The results show that rats and chickens have higher oxygen consumption rate than that of fish and toads. Similarly, a species and substrate specific difference was also noticed in P/O (phosphate utilized per oxygen atom) ratio and respiratory control index. In case of rat, a significant negative correlation was noticed between P/O ratio and SMR with succinate as substrate. It is surmised that the observed difference in the mitochondrial respiration and P/O ratio in the above vertebrates is due to the difference in their metabolic activities.

New approach to modeling of a local structure of silicate glasses and melts

Structural model of silicate melts and glasses obtained by rapid cooling of the melt is far from complete at present. Modern models suggest the existence of the five different types of silicon-oxygen tetrahedra which are distinguish by the ratio of bridging and terminal oxygen atoms per silicon atom (the so-called basic structural blocks or units) in the structure of silicate glasses and melts and also assume that the several types of such units can exist in the glass and melt structures simultaneously. The knowledge of the concentrations of these units depending on the composition and temperature (the so-called Qn distribution) is a necessary element for the development of an adequate model of silicate systems and to explaining their physical and chemical properties. Three-parameter statistical method to modeling of Qn distribution in silicate melts and glasses is present in this paper. This method allows calculating the concentration of structural units in a wide composition range at different temperatures. The method is based on a destruction of a preassigned network as a model of depolymerization of the silicon-oxygen framework in the process its interaction with the modifier oxides. Qn distribution, distribution of silicon-oxygen tetrahedra according to their next-nearest neighbours, and distribution of bridging bonds in alkali-silicate glasses and melts were obtained in frame of the developed approach.

Production of graphene by reduction using a magnesiothermic reaction

We have, for the first time, employed a magnesiothermic reaction to convert microwave-irradiated graphite oxide to pure graphene. The magnesiothermic reaction increases the carbon to oxygen atomic ratio from 22.2 to 165.7 and maintains a high surface area. The new strategy demonstrates an efficient method for obtaining highly pure graphene materials.

Water-Dependent Reaction Pathways: An Essential Factor for the Catalysis in HEPD Enzyme

The hydroxyethylphosphonate dioxygenase (HEPD) catalyzes the critical carbon-carbon bond cleavage step in the phosphinothricin (PT) biosynthetic pathway. The experimental research suggests that water molecules play an important role in the catalytic reaction process of HEPD. This work proposes a water involved reaction mechanism where water molecules serve as an oxygen source in the generation of mononuclear nonheme iron oxo complexes. These molecules can take part in the catalytic cycle before the carbon-carbon bond cleavage process. The properties of trapped water molecules are also discussed. Meanwhile, water molecules seem to be responsible for converting the reactive hydroxyl radical group ((-)OH) to the ferric hydroxide (Fe(III)-OH) in a specific way. This converting reaction may prevent the enzyme from damages caused by the hydroxyl radical groups. So, water molecules may serve as biological catalysts just like the work in the heme enzyme P450 StaP. This work could provide a better interpretation on how the intermediates interact with water molecules and a further understanding on the O(18) label experimental evidence in which only a relatively smaller ratio of oxygen atoms in water molecules (∼40%) are incorporated into the final product HMP.

Correlation between carbon–oxygen atomic ratio and field emission performance of few-layer reduced graphite oxide

We report the effect of carbon–oxygen atomic ratio (C/O ratio) on the field emission properties of the chemically reduced few-layer graphite oxide (GO). The field emission properties are found to be a non-monotonic function of the C/O ratio in a wide range of 2.06–14.80. Samples with C/O ratio of 6.98 show the lowest turn-on (1.80MV/m), threshold fields (5.15MV/m) and much higher current density (44.08mA/cm2 at 9.00MV/m). Long-time (10h) current stability test of the GO at a high current density (∼13mA/cm2) resulted in the reduction of the GO. The samples with field emission induced reduction show the same non-monotonic effect of the C/O ratio on the field emission properties as that of the chemically reduced GOs. The average current fluctuation of the GO is higher than that of the reduced GO, which is due to the oxygen desorption during the electron emission. The effect of the carbon–oxygen bonds on the surface potential barrier of the reduced GO edges is proposed in detail for interpreting the experimental observations.

The effects of polymer side-chain structure on roughness formation of ArF photoresist in plasma etching processes

Low etching resistance and roughness formation of ArF photoresist during plasma etching are serious problems. We have previously found that decisive factors affecting the plasma resistance and roughness formation in an ArF photoresist are determined by ultraviolet/vacuum ultraviolet radiation and roughness formation is dominated by chemical reactions. In this paper, on the basis of our previous findings on the interaction between radiation species from plasma and ArF photoresist polymers, we investigated the polymer structural dependence for the degradation mechanism of ArF photoresist in the plasma etching processes. The etching resistance of ArF photoresist was improved by controlling the elemental ratio of oxygen atoms and ring structures in photoresist polymer. Furthermore, lactone C=O bond is found to be a key factor for roughness formation during the etching process. We have revealed the importance of the molecular structure of ArF photoresist for improving the surface roughness and etching resistance during the plasma etching process.

Structure and Raman Investigations of Nitrogen-Doped TiO<sub>2</sub> Nanotube Arrays

The N-doped TiO2 nanotube arrays were prepared by electrochemical anodization and thermal annealing in ammonia flux. All the undoped and N-doped TiO2 nanotube arrays were pure anatase phase and the N-doped TiO2 shows obviously enhanced absorption intensity in the visible light region. The investigations on the low-frequency Eg anatase mode of Raman spectra verify that the crystallite size increases from 7.5 nm to 8.5 nm with the increase of the doped nitrogen temperature. The ratio of oxygen atoms to titanium atoms is 2.419 after titania being annealing in NH3 air stream. It could be concluded that the size effect and oxide vacancies introduced by nitrogen doping lead the great increase of UV-Vis absorption for N-doped TiO2 nanotubes.

Effect of air abrasion and dye on the surface element ratio and resin bond of zirconia ceramic**This work was presented at the 8th China–Korea Symposium on Biomaterials and Nano-Bio Technology (Pyeongchang, Korea, Dec. 13–17 2010).

The purpose of this study was to evaluate the effect of the surface element composition and roughness of dyed or non-dyed zirconia ceramic by air abrasion on the bond durability to resin luting cement. The sintered zirconia ceramic specimens were divided into four groups as follows: polished, dyed/polished, abraded, dyed/abraded. The surface roughness of each group was measured by a 3D laser scanning microscope. Energy-dispersive spectroscopy was applied for identifying and quantifying the elemental composition of the zirconia ceramic surfaces Each group had 20 shear test specimens of zirconia to Panavia F and was divided into two subgroups (n = 10) after 0 or 10 000 thermal cycles to receive the shear test. Compared with polishing, air abrasion significantly reduced the oxygen atom and weight ratio, increased the zirconium atom and weight ratio, increased Ra and Ry of zirconia ceramic surface, and also increased the bond strength of dyed and non-dyed zirconia ceramic to Panavia F after 0 and 10 000 thermal cycles. The dying procedure could affect the abraded and non-abraded zirconia ceramic surface oxygen and zirconia element ratios and surface characteristics. However, the dying procedure does not affect the resin bond strength and durability of zirconia ceramic.Corrections were made to this article on 3 November 2011. The footnote for the corresponding authors was incorrectly labelled.

Formation of titanium oxide phases in vacuum condensates produced by laser evaporation

Titanium oxide vacuum condensates are produced by laser evaporation in vacuum, which involves vapor condensation onto a polycrystalline molybdenum substrate heated between 200 and 1500°C. The phases formed in titanium oxide vacuum condensates and their microstructure are studied with x-ray and electron diffraction and transmission electron microscopy. It is established that the phases formed in titanium oxide vacuum condensates are determined by substrate temperature (T s): amorphous TiO2 forms at T s < 400°C, anatase crystallizes at higher T s and coexists with rutile at T s = 700–900°C, and rutile alone is observed at T s > 900°C. Laser evaporation at T s < 1400°C promotes oxygen-rich TiO2 phases and that at T s ≥ 1400°C leads to Magneli phases in titanium oxide vacuum condensates. Higher T s results in phases in which the titanium–oxygen atomic ratio does not correspond to the TiO2 formula. It is shown that variation in the substrate temperature and the size of crystallites in titanium oxide vacuum condensates is symbate.

Numerical investigation of spherical diffusion flames at their sooting limits

Detailed numerical simulations are presented of laminar microgravity spherical diffusion flames at their experimentally observed sooting limits. Ten normal and inverse flames fueled by ethylene are considered. Observed in a drop tower, these flames were initially sooty but reached their sooting limits 2 s after ignition (or slightly before). The flames span broad ranges of stoichiometric mixture fraction (0.065–0.692), adiabatic flame temperature (2226–2670 K), and stoichiometric scalar dissipation rate (0.013–0.384 s −1). They were modeled using a one-dimensional, transient diffusion flame code with detailed chemistry (up to toluene) and transport. Radiative losses from products were modeled using a detailed absorption/emission statistical narrow-band model coupled with a discrete-ordinates method. Flame structure at the sooting limits was examined, emphasizing the behavior of carbon to oxygen atom ratio, temperature, and scalar dissipation rate. For ethylene flames with sufficiently long flow times it was found that soot formation coincides with regions where the C/ O atom ratio and temperature exceed critical values, specifically 0.53 and 1305 K, respectively. The scatter about these critical values is small, which is noteworthy considering the wide range of flame conditions. These observations are consistent with the expected effects of H radicals on the propargyl soot pathway.

Effects of sandblasting on surface character and resin bond of zirconia ceramic

To evaluate the effect of Al2O3 particles sandblasting on the surface roughness, element composition and resin bond durability of zirconia ceramic. Sixty 2.5 mm thick computer aided design and computer aided manufacture (CAD/CAM) zirconia ceramic (Vita Inceram YZ) plates were fired, polished and cleaned. Half of polished ceramic plates was sandblasted with 50 µm alumina particles at 0.3 MPa for 20 s. The surface roughness of polished and sandblasted ceramic surface were measured by 3D-laser scanning microscope, and the surface element weight and atom ratio of the ceramic surface were measured by energy disperse spectroscopy (EDS). Then polished and sandblasted ceramic plates were randomized into six groups. In Group 1 and 2 the polished and sandblasted ceramic plates were bonded irrespectively with conventional resin cement (DUOLINK). In Group 3 and 4 the ceramic plates were bonded with resin cement containing MDP (Panavia F), In Group 5 and 6 the specimens were pretreated with silane coupler acitivated by MDP (Clearfil Ceramic Primer), then bond with Panavia F. The specimens of each test group were then divided into two subgroups, and to received shear test after 0 and 10 000 time thermal cycle. The data was analyzed by one-way ANOVA and independent t test. Comparing with polishing, sandblasting reduced the oxygen atom and weight ratio of zirconia ceramic surface (P < 0.001), and increased the zirconium atom and weight ratio (P < 0.001), meanwhile increased the surface roughness (P < 0.001). The bond strength between ceramic plates and resin cement in all test groups decreased after thermocycling (P < 0.001). All specimen in test group 1 and 2 lost bond, and the bond strength of test group 3 and 5 [(0.59 ± 0.17), (0.89 ± 0.84) MPa] were significantly lower than that of test group 4 and 6 [(14.63 ± 3.03), (16.64 ± 1.90) MPa], and the bond strength of test group 6 were significanlty higher than that of test group 4. Sandblasting improves durability of bond between zirconia ceramic and resin cement containing MDP, not only by increasing the roughness and area of ceramic surface, but also by changing its surface element composition to obtain more chemical bond.

Effect of Coal Structure on Mechanical and Thermal Properties of Coal Filled Soy Protein Composites

Using different rank coals as filler, coal-soy protein isolate (SPI) composites were prepared by compression molding processing using glycerol as plasticizer. The structure of the coals used were characterized by Fourier transform infrared (FTIR), ultimate analysis, and surface functional group analysis. The effects of coal structure on the mechanical properties, water resistance, and thermal properties were investigated. The results showed that, in different rank coals, the atomic ratio of oxygen to carbon, carboxylic acid groups, phenolic hydroxyl groups, lactone bonds, and aliphatic chains decreased with coal rank. The strength, water resistance, and glass transition temperature of coal-SPI composites decreased with coal rank. Lower ran coal filler with more reactive functional groups caused the composites strong but brittle. While, higher rank coals provide poor mechanical properties for the composites.

Disturbances in the F1 ionospheric layer in April 2005

Manifestations of ionospheric disturbances at heights from 120 km to the height h m of the F2-layer maximum are analyzed. The geomagnetic disturbances on April 5, 12, and 13, 2005, are considered. These disturbances are characterized by a pronounced synchronous decrease in the electron concentration over the entire indicated height range. Using the method proposed by the authors, the noontime changes in the relative content of atomic and molecular oxygen at a height of 120 km are estimated. There are a distinct decrease in the ratio of atomic oxygen and molecular nitrogen concentrations and an increase in the ratio of oxygen molecule and atom concentrations.

Physical and electrical characteristics of silicon oxynitride films with various refractive indices

This study explores the relationship between both the physical and the electrical characteristics of silicon oxynitride (SiON) films and the refractive index. The single wafer rapid thermal process modules were used for low pressure chemical vapour deposition of SiON films. A series of SiON films with refractive index between 1.50 and 1.83 were fabricated. Fourier transform infrared absorption spectroscopy and x-ray photoelectron spectroscopy identified the chemical bonding configurations of different SiON films: the Si–N bonds are replaced by Si–O bonds as the refractive index of the SiON films declines. Moreover, the Si atomic ratio is kept between 35% and 40% while the oxygen atomic ratio increases and the nitrogen atomic ratio decreases as the refractive index of the SiON film declines. The electrical characteristics of different SiON-based silicon–oxide–nitride–oxide–silicon (SONOS) devices suggest that (1) the dielectric constant increases with increasing refractive index of the SiON film and (2) the charge-trap density is inversely proportional to the oxygen concentration in the SiON film. Based on these results, the SiON films with various refractive indices can provide a wider application for silicon-based devices, such as SONOS and MOS devices.

Synthesis of large-area, vertically aligned α-Fe2O3 nanowire and nanobelt arrays

Large-area (10 mm×10mm), vertically aligned α-Fe2O3 one-dimensional nanostructure (nanobelts and nanowires with controllable diameters) arrays are successfully synthesized by thermally oxidizing iron foil directly, which grow in the ［110］ direction of the hexagonal crystal. The morphology and microstructure of the synthesized arrays depend strongly on the growth conditions such as the oxygen pressure, temperature and reaction time. We found that the growth of α-Fe2O3 one-dimensional nanostructures follows a top-growth mechanism, in which the ratio of iron and oxygen atoms near the point of growth plays a key role.

Sputter deposition of titanium monoxide and dioxide thin films with controlled properties using optical emission spectroscopy

TiO x thin films with various oxygen atomic ratios ( x) were deposited on Si(100) wafers without intentional heating by radio-frequency magnetron sputtering of a Ti target using Ar discharge plasma, mixed with increasing O 2 flow supply. Optical emission spectroscopy was employed to monitor the intensity of Ti emission lines via a flow-supply feedback loop. By circumventing the processing hysteresis, this set-up allowed the process windows along the metallic-poisoned curve to be found for the controlled deposition of TiO x thin films, particularly titanium monoxide ( x = 1.0) and oxides with the values of x in the vicinity of 2.0. The physical properties of these films (deposition rate, electrical resistivity, composition, phase distribution, etc.) were investigated and correlated well with each other. At the as-deposited states, the TiO 1.0 film is polycrystalline, but the films with x ranging from 1.54 to 2.2 are amorphous. Finally, the crystallization behavior of these amorphous films after annealing was examined and the impact of the initial oxygen content in the pristine films on the crystallization tendency and final crystal structure was elucidated.

Cation coordination and hydrogen bonding in potassium and magnesium based-di-amidosil hybrids

Fourier transform mid-infrared and Raman spectroscopies were employed to elucidate the cation/alkylene chains, cation/cross-link, cation/anion interactions and hydrogen bonding occurring in amorphous di-amide cross-linked alkylene/siloxane hybrid materials (di-amidosils) doped with potassium and magnesium triflates (KCF 3SO 3 and Mg(CF 3SO 3) 2, respectively). Materials with compositions ∞ > n ⩾ 5 (where n expresses the molar ratio of carbonyl oxygen atoms per guest cation) were investigated. The conformations ( gauche) of the alkylene chains of the host di-amidosil matrix are not affected by the presence of the guest salt in both doped di-amidosil families. The K + and Mg 2+ ions coordinate to the carbonyl oxygen atoms of the amide cross-links within the whole range of salt concentration considered, leading to the saturation of the cross-linkages, to a redistribution of the amide–amide hydrogen-bonded aggregates of the host matrix and, in the case of the K +-doped sample with n = 10, to the formation of a new type of aggregate, stronger and more ordered than those detected at lower salt content. In both di-amidosil systems guest salt addition leads to the increase of ionic associated species and to a concomitant decrease of the concentration of “free” anions.

Electrical Characteristics and Zirconia Film Preparation by a Zirconium-Oxygen Plasma using a Positively Biased Electrode

Plasma-based ion implantation and deposition (PBII&D) is a promising technique used to modify the surface of a three-dimensional substrate, where metallic plasma sources have been used to form alloys and compounds. In this research, a positively biased electrode was placed near a metallic plasma source to mix the metallic species with the gaseous species. This method allows the metallic species to be dispersed in a large volume. The gaseous plasma was triggered by the metallic plasma, which was generated by disconnecting a pin electrode from a zirconium plate as a cathode. Zirconia film preparation was done using a pulsed argon/oxygen plasma with a pulsed dc zirconium plasma. The voltage–current characteristics in the mixed plasma were investigated as a function of the positive bias voltage and gas pressure, and characteristics of the extracted ion current and ion density were studied. It is estimated that the ion density is on the order of 1016 m−3 at a positive bias voltage of 200 V and a gas pressure ranging from 1.9 to 2.5 Pa. Zirconia film is prepared by a reactive deposition of zirconium with oxygen. As a result, a zirconium oxide film with the atomic ratio of oxygen to zirconium of 2–2.1 is found to be prepared for a variety of positive bias voltages and pulsed negative bias voltages.