Influence Of Oxygen Atmosphere Research Articles

Enhancing External Combustion Efficiency in Stirling Engine Combustors: Influence of Oxygen Atmosphere, Ejection Ratio, and Pressure

Enhancing External Combustion Efficiency in Stirling Engine Combustors: Influence of Oxygen Atmosphere, Ejection Ratio, and Pressure

Oxidation-influenced crystallization in (GeSe2)x(Sb2Se3)1-x chalcogenide glasses

Influence of oxygen atmosphere on crystallization of (GeSe2)x(Sb2Se3)1-x glasses (for x = 0.3, 0.4 and 0.5) was investigated by differential scanning calorimetry, X-ray diffraction analysis and infrared microscopy. Particle-size-dependent study was performed to reveal the role of mechanically induced defects. The presence of oxygen led to an early formation of a thin surface crystalline layer (smoothly structured) that significantly influenced further crystal growth. The most pronounced consequence was surprisingly found in case of the (GeSe2)0.3(Sb2Se3)0.7 composition that crystallizes in volume. The thin surface crystalline layer hindered the macroscopic viscous flow, so that the samples retained their original shape, and these quasi-stationary conditions accelerated the initial nucleation and growth rates. At the same time, however, these conditions prevented the samples from reaching full crystallinity. In case of the compositions with x = 0.4 and 0.5, the crystal growth proceeded only at the surface and presence of external interfaces and mechanically induced defects took over the major role driving the crystallization kinetics. Correlation of the calorimetric, microscopic and viscosity data is discussed in detail.

MORPHOLOGICAL AND MICROSTRUCTURAL CHARACTERISTICS OF HA COMPOSITE FILMS DEPOSITED BY PULSED LASER

The influence of oxygen atmosphere and substrate temperature on morphology and microstructure of the hydroxyapatite (HA) composite films prepared by pulsed laser deposition (PLD) was studied. According to the results of X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR), it was found that the phase compositions and the crystallinity of HA were affected by the oxygen pressure and substrate temperature. High oxygen pressure can increase the crystallinity of HA, and make random oriented HA gradually transform into [Formula: see text]-axis orientation, and decrease the Ca/P atomic ratio of the film. High substrate temperature can increase the crystallinity of films and the degree of c-axis orientation of HA, but increase the Ca/P atomic ratio slightly. Changes of oxygen pressure or substrate temperature have little influence on the surface morphology and thickness of film. Valuable HA composite film could be obtained at 600[Formula: see text]C under 5[Formula: see text]Pa O2atmosphere.

Influence of Oxygen Atmosphere on Dissolution of Platinum under Potential Cycling

The influence of oxygen atmosphere on platinum (Pt) dissolution under potentiodynamic conditions was investigated in 1.0 mol dm−3 HClO4 at 80°C over the range 0.0–0.7 MPa of oxygen partial pressure (pO2). The rate of Pt dissolution depended concavely on pO2 with the minimum at 0.091 MPa. When pO2 was below 0.091 MPa, the oxygen atmosphere suppressed the platinum dissolution from an oxide-deprived Pt surface owing to an increase in the coverage of passive oxides, resulting in a decrease in the rate of Pt dissolution with increasing values of pO2. For pO2 ≥ 0.091 MPa, the current of oxygen reduction reaction (ORR) increases with pO2. This further participated in an increase in the rate of Pt dissolution, probably through the cathodic dissolution of higher-order oxides formed as intermediates in ORR.

Influence of oxygen atmosphere on the photoluminescence properties of sol–gel derived ZrO2 thin films

Homogeneous and transparent ZrO2 thin films were prepared by sol–gel dip coating method. The prepared ZrO2 thin films were annealed in air and O2 atmosphere at 500, 700 and 900 °C for 1, 5 and 10 h. X-Ray diffraction (XRD) pattern showed the formation of tetragonal phase with a change of stress in the films. Scanning electron microscope (SEM) revealed the nucleation and particle growth on the films. An average transmittance of >80 % (in UV–Vis region) was observed for all samples. The refractive index and direct energy band gap were found to vary as functions of annealing atmosphere, temperature and time. Photoluminescence (PL) revealed an intense emission peak at 379 nm weak emission peaks at 294, 586 and 754 nm. An enhancement of PL intensity was observed in films annealed in O2 atmosphere. This is due to reconstruction of zirconium nanocrystals interfaces, which help passivate the non-radiative defects. At 900 °C, oxygen atoms react with Zr easily at the interface and destroy the interface states acting as emission centres and quench the PL intensity of the film. The enhancement of the luminescence properties of ZrO2 by the passivation of non radiative defects presents in the films make it suitable for gas sensors development, tuneable lasers and compact disc (CD) read-heads.

Influence of oxygen atmosphere on crystallization and properties of LiNbO 3 thin films

Thin films of lithium niobate were deposited on the Pt/Ti/SiO 2 (111) substrates by spin coating from the polymeric precursor method (Pechini process). Annealing in static air and oxygen atmosphere was performed at 500 °C for 3 h. The films obtained were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The dielectric constant and dissipation factor were measured in frequency region from 10 Hz to 10 MHz. Electrical characterization of the films pointed to ferroelectricity via hysteresis loop. The influence of oxygen atmosphere on crystallization, morphology and properties of LiNbO 3 thin films is discussed.

Influence of oxygen atmosphere on the crystal growth of copper(II) oxide

Single crystal growth of CuO, synthetic tenorite, was accomplished in oxygen atmosphere by the chemical vapor transport technique. We present the first systematic study of the growth of CuO in various partial pressures of oxygen. Crystals were grown using trace, 0.1, and 0.5 atm partial pressures of oxygen. The growth temperatures used were 820 and 865 °C. Typical dimensions of the crystals obtained were 1 × 2 × 0.25 mm. We have shown that the stoichiometry of single crystal CuO can be controlled during the growth process. The crystals exhibited cation deficient stoichiometry, Cu1−xO, with x increasing from less than 0.005 with no added oxygen, up to 0.05 with 0.5 atm O2 when grown at 865 °C.