Papers by Keyword: Oxygen Partial Pressure

Abstract: The effects of heat treatment in different ambient pressures or oxygen concentration on the wettability of the titanium (Ti) surface were examined. Polished titanium plates were heat-treated at various temperatures and periods in the pressure-controlled or oxygen concentration-controlled atmospheres. The wettability was evaluated by water contact angle measurement. The X-ray photoelectron spectroscopy was performed on the heat-treated and stored Ti surface to analyze adsorbates and surface products. The heat-treated Ti in the atmospheric air became hydrophilic due to the desorption of hydrocarbons on the surface. Then, the adsorption of hydrocarbons during storage in the atmospheric air returned its wettability to that before heating. On the other hand, the heat-treated Ti in a vacuum (low ambient pressures) or low oxygen concentration became hydrophobic due to an increase in the CH/OH (hydrocarbon/hydroxyl group) ratio on the surface. The wettability of hydrophobized Ti retained its wettability during storage in the atmospheric air.

Abstract: Magnesium Oxide (MgO) thin films were deposited on SiO₂/Si substrate by electron beam evaporation. The properties of MgO thin film with and without oxygen partial pressure have been investigated by X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and Ultra-Violet Photoemission Spectroscopy (UPS). The XPS was used to investigate the chemical state of the film. REELS spectra revealed that MgO thin films deposited under oxygen partial pressure had band gaps of 6.07 eV. Meanwhile, the band gap for MgO thin films grown without oxygen partial pressure was 7.17 eV. The UPS results showed that the work functions of MgO thin film with and without oxygen partial pressure are 4.75 and 4.84 eV, respectively. In the MgO thin film with oxygen partial pressure, the intensity for the valence band peak at 12.16 eV decreased, but the work function remained relatively the same. Our results demonstrated that the oxygen partial pressure played a crucial role in improving the electronic properties of MgO thin films.

Abstract: It is shown that the value of the equilibrium oxygen partial pressure, Po₂ as a value available for measurements is possible to be taken as a measure of slag redox potential of, taking into account its electronic system performance. Application of the electromotive force method (EMF) allowed establishing the character of a change in the average oxidation state of iron ν_Fe depending on Po₂, the temperature and slag composition. The study of Mössbauer absorption spectra of quenched slag samples confirmed the possibility of simultaneous presence of iron in the flux in oxidation states from 0 to +3.

Abstract: Two kinds of TRIP steel with different Al and Si content were researched in this article. Different annealing atmosphere in the trial was achieved by the Hot Dip Galvanized Simulator by Iwatani. The segregation of alloying elements after annealing under different atmosphere were investigated and the compounds on the surface were shown. Furhermore, the distribution of oxides was abserved on the surface and the reactive wetting was assessed and the results after galvanizing was provided. We found out the increasing wettability was abserved under more reducing atmosphere with less Si because of a decrease oxide amount and an increase internal oxidation.

Abstract: Ferroelectric BiFeO₃ (BFO) thin films were prepared on Pt (111)/Ti/SiO₂/Si substrates by pulsed-laser deposition under various oxygen partial pressures (P_O2). The effects of P_O2 on the phase, orientation, surface morphology, and ferroelectric properties of the films were investigated, particularly in regard to relationships between structure and properties. It was found that the crystallographic orientation and surface morphology of the BFO thin films strongly depended on P_O2. Films prepared at P_O2=10 Pa had a high degree of (111) orientation and densely packed grains. A maximum of twice the remanent polarization for the BFO thin film was 68 μC/cm².

Abstract: Titania (TiO₂) thin films have been deposited using d.c. reactive unbalance magnetron sputtering on unheated substrate by various different oxygen partial pressures while working pressure and sputtering power were kept constant. A pure metallic titanium disk was used for sputtering target in atmospheric of the mixture gases between argon and oxygen. The X-ray diffraction (XRD) and atomic force microscopy (AFM) were used for characterization of characteristics structure and surface morphologies of the films, respectively. The optical transmission of the films were measured by spectrophotometer. The photocatalytic activities of the films were investigated from measurement of methylene blue degradation by using absorbance value after UV irradiation for 6 hr. The results show that the crystalline structures of the films showed the presence of single-anatase phase and mixed-anatase/rutile phase of TiO₂ thin films. The surface morphology and photocatalytic activities of the films depend on oxygen partial pressure that grains size, surface roughness and thickness of the films were deceased when increasing oxygen partial pressure due to poisoning phenomenon and the high reactive gases. In addition, it was found that all TiO₂ thin films were deposited by different oxygen partial pressure exhibit a good transparentness. Moreover, it was found that the TiO₂ thin films deposited by used low oxygen partial pressure and single-anatase phase exhibited the best photocatalytic activity.

Abstract: In this paper, effect of oxygen partial pressure on formation of Fe₂O₃ nanostructure during Thermal Oxidation was studied. Fe₂O₃ nanostructure was formed by controlling oxidation conditions (Po₂) and using the method of thermal oxidation. To begin with, a piece of pure iron in a ceramic crucible was put in the tube furnace (SYS-G-Z-13). Next the metallic Fe was oxidized at 500°C for 4 hours, under different oxygen partial pressure including pure argon (Po₂ = 0atm), air Po₂ = 0.21atm) and pure oxygen (Po₂ = 1atm) to produce nanostructure, respectively. The surface morphology of the oxidized specimens was observed by SEM. The crystalline structure of the nanostructure was determined by transmission electron microscope. The experimental results show that the density of nanosheets increases with increasing oxygen partial pressure.

Abstract: The Bi3.25La0.75O12 films were prepared on the Pt/TiO2/SiO2/Si substrate using RF-magnetron sputtering method. The effects of sputtering conditions, including sputtering pressure, oxygen partial pressure and substrate temperature on microstructure, ferroelectric properties were investigated. When deposited at low substrate temperature (room temperature), the BLT thin film exhibits preferentially c-axis oriented. With the increasing of substrate temperature, the (117) diffraction peak become stronger, indicating the changing of the microstructure in the BLT films. The BLT film samples deposited at 4.5-6Pa exhibit desired bismuth-layered structure, with no any preferred orientation. However, when BLT films were deposited above 5 Pa, some weak pyrochlore diffraction peaks appear in the X-ray diffraction pattern. The Pr is a maximum for the BLT film deposited at 5 Pa with O2/Ar ratio 1/5 and decreases with both decreasing and increasing deposition pressure.

Abstract: Titanium dioxide thin films were deposited by DC reactive magnetron sputtering on silicon wafer and glass slide at sputtering power of 210 watt under total pressure of 5.0×10^-3 mbar at different oxygen partial pressure. A pure metallic titanium target was sputtered in a mixture of argon and oxygen gases. The crystal structure and surface morphology were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. The optical transmission was measured by spectrophotometer. The results show that the crystalline was pure anatase structure titanium dioxide thin films. The surface morphology of the films is strongly the oxygen partial pressure. It was found that surface roughness of the thin films was around 2.42 to 4.82 nm and the thickness was around 72 to130 nm. In addition, it was found that all the titanium dioxide thin films were deposited by reactive sputtering with the different oxygen pressure exhibit the transparency property.

Abstract: Highly c-axis oriented ZnO thin films were deposited on n-Si (111) substrate at various oxygen partial pressures by pulsed laser deposition (PLD). X-ray diffraction (XRD), Atomic force microscopy (AFM) were used to analyze the influence of the oxygen partial pressure on the crystallization and morphology of the ZnO thin films. X-ray photoelectron spectroscopy (XPS) was used to analyze relationships between chemical shifts of XPS energy spectra and stoichiometric ratios of ZnO thin films, and quantitative relationships between content of Zn, O and oxygen partial pressures. An optimal crystallized and stoichiometric ZnO thin film was observed at the oxygen partial pressure of 6.5Pa.