Papers by Keyword: Oxygen

Abstract: The phase equilibrium in the Fe-Ge-O system is investigated by measuring EMF of galvanic elements with solid oxygen-conductive electrolytes. The samples for investigation were prepared by the solid phase reaction at 900 °C. The samples were analyzed to determine the total and phase composition. The gross composition of the samples was refined by chemical analysis. The iron content was determined by the standard method of bichromatometric titration, while that of germanium was determined by the photometric method, which is based on measuring the optical density of the colored colloid solution of germanium phenyl fluoronate, which is formed upon the interaction of germanium dioxide with phenylfluorone in the acidic medium. The phase composition was established using X-ray diffractometry and electron probe microanalysis using a DRON-3 diffractometer and a JEOL JSM-6460LV computer controlled scanning (raster) microscope. The experimental function of EMF galvanic elements of temperature is formulated. After processing the obtained data, the equilibrium oxygen pressures over the samples were calculated, the solubility of germanium in iron monoxide (wustite) was determined, the phase composition of the regions bordering the wustite region was established, the isothermal sections of the state diagram of the system were constructed at 1173 and 1273 K in the equilibrium region of the wustite solution with metallic and spinel phases

Abstract: In anaerobic environment, dominant sulfate reducing bacteria (SRB) consortia are found to cause many serious problems to the oil such as sour oil, hydrogen sulfide (H₂S), and metal corrosion. They are obligatory anaerobes using sulfate, thiosulfate and sulfites as final electron acceptors and use organic acids or alcohols as a carbon source. In the aerobic system, other dominant niches are sulfur-oxidizing bacteria (SOB) playing role in biological oxidation of hydrogen sulfide. These SOB convert H₂S into elemental sulfur (S⁰) by partial oxidation. Since the levels of reduction and oxidation are dependent on the oxygen concentration. In the condition of limited oxygen, sulfate generated by SOB can also be contributed to the reduction of oxygen which encourages SRB proliferation in anaerobic environment. In this research, we were interested to manage the conditions to control the dominant niches by management of oxygen levels. In the experiment, the concentration of sulfate concentration, acidity, sulfide were determined to understand the microbial activity. The results showed after cocultures of SRB and SOB niches in the present of oxygen, the activity of SRB was prevented since a decrease in H₂S product but an increase in sulfate concentration were observed. This revealed a promising niches of SOB isolates in the presence of oxygen and active in high sulfide removal. These data indicated the situation suitable for either SOB or SRB community is dependent on oxygen concentration. The management of SOB community can be used as an alternative method to remove contaminating H₂S from the system.

Abstract: The oxygen absorption and diffusion properties are studied in γ-TiAl and TiAl₃ alloys within density functional theory using projector augmented wave method in the plane-wave basis. It is shown that the octahedral site inside the Ti-rich octahedron is preferable for oxygen in case of γ-TiAl alloy whereas the Al-rich octahedron is more favorable environment for oxygen in TiAl₃. It is shown that the energy barriers for oxygen jumps between different sites in bulk alloys depend significantly on the local environments of oxygen and increase for its jump from Ti-rich sites. The trajectories with minimum energy barriers are determined for both Ti-Al alloys. It is shown that the increase of Al content in alloy leads to the decrease of barriers for oxygen jumps.

Abstract: The effect of the grain size on the high-temperature oxidation resistance of unalloyed titanium was experimentally investigated using titanium samples with two different grain sizes of 219 μm and 118 μm. The weight gain during oxidation and the penetration depth of oxygen from a metal surface were larger in the small-grain-size sample compared with the large-grain-size sample. In addition, oxygen diffusion was faster in the substrate of the small-grain-size sample. These results were attributed to the grain-boundary diffusion of oxygen. A steep change in the oxygen concentration was observed at a grain boundary. Our simulation results suggested that slower oxygen diffusion into the inner grain from the surface through the grain boundary with high diffusivity can cause the observed steep change in the oxygen concentration.

Abstract: We present a novel structure to supply gases to microchambers in microfluidic chips. An exemplary application is the continuous feeding of oxygen and CO₂ for on-chip cell cultivation of mammalian cells. In our device, the surrounding air diffuses into the culture medium inside the chip through a porous wall of agarose hydrogel resulting in an easy and robust design. One common method is the usage of gas permeable PDMS chips. However, liquid medium in which the cells grow is absorbed by PDMS causing unknown concentrations and memory effects. Another possibility is a complex setup where medium with already dissolved gas is pumped constantly through the chip. We designed and realized a silicon and borosilicate glass chip containing a gas permeable wall of agarose preventing leakage of medium. In order to precisely position the walls in the chip, we made use of surficial phaseguides (50nm high). The blue-bottle-experiment makes the effective dissipation of oxygen visible when the colorless leucomethylen-blue reacts to methylene-blue. Successful results were achieved when applying 0.5 g/l methylene blue, 10 g/l glucose and a pH of 12.6 set by a buffer solution. As a result a continuous color gradient through the chip was obtained, which reflects the oxygen gradient and confirms the oxygen diffusion.

Abstract: The paper presents the results of the experimental investigation of the pulsed electron beam propagation propagated in a drift tube filled with oxygen. The pressure was 50, 300, and 760 Torr in the drift tube. The experiments were carried out using a TEA-500 pulsed electron accelerator (450 kV accelerating voltage; 10 kA electron beam current; 80±1 ns pulse duration to the base; up to 200 J pulse energy; and 5 cm diameter beam). The electron beam was propagated in the drift tube (40 cm long), 14 cm in diameter composed of two sections equipped with two reverse current shunts. The experiments were carried out which fixed the absorbed dose registered on the walls of the drift chamber.

Abstract: The results of the study of the spectral characteristics and photo cathodoluminescence zinc tungstate crystals subjected to heat treatment in an oxygen atmosphere, or flows of high-energy irradiation of oxygen ions. It was observed that additional introduction of oxygen leads to decline in luminescence’s effectiveness. It was discovered, that introduction of oxygen by thermal processing leads to changes in excitation spectrum. Decline of excitation effectiveness proportional to increase of excitation quanta energy from 4.5 to 6.5 eV was observed; in the meantime, in the unprocessed crystals it declined by only 25-30%. The effect can be explained by destruction of complex defects with luminescence centers during introduction of additional oxygen. It was demonstrated, that characteristic oxygen’s depth of entry during thermal processing is 20 nm.

Abstract: Tetramethylammonium hydroxide (TMAH) is a common etchant for Sigma shape formation in IC manufacturing. The impact of oxygen dissolved in TMAH solution on process was studied in this paper. A novel O2 gas injector was developed to improve the process stabilization by control of the oxygen concentration in TMAH solution

Abstract: One of the challenges in PM Ti alloys is to control the impurities level. Oxygen affects the microstructure and the mechanical properties of titanium alloys. Ti-6Al-7Nb is a promising alloy to use in PM due to its outstanding biocompatibility and mechanical properties required for load bearing medical implants. In this work, the influence of the impurities content on the ductility, fatigue resistance and microstructure of Ti-6Al-7Nb alloy processed by metal injection moulding was examined. Tensile and fatigue specimens were manufactured using Ti-6Al-7Nb gas atomized powder. Depending on the thermal treatment time, various oxygen contents were introduced into the specimens. The resulting oxygen content was determined by melt extraction technique. Tensile tests and high cycle four-point bending fatigue tests at room temperature were performed. First studies about the effect of oxygen content on crack initiation and propagation were done by the observation of microstructures and fractured surfaces using light and electron microscopy (SEM).

Abstract: The oxygen air production are generally be achieved by pressure swing adsorption (PSA) and cryogenic distillation. Both of the techniques are able to produce high purity oxygen level which is more than 95% with a production volume of 20 – 300 tons per day. These techniques however required high energy consumption and with the rising cost of energy, membrane separation is a good option as it require relatively low energy requirement. Membrane separation technique is an emerging technique which garners the interest from academia and industry from last decade as an alternative method to produce oxygen enriched air. To date, the commercially available and research institution self-fabricated polymeric membrane are unable to produce an economically viable membrane with high permeability and selectivity in a large scale production relative to the conventional method. In this works, the progress of the application of polymeric in O₂/N₂ separation which including the recent developed of self fabricated polymeric membrane and the aspect of operation parameter is discussed. Finally, the paper also intends to present a brief overview of the development of membrane separation technique in O2/N2 separation in addressing the strategies and improvement in the fulfillment of industrial application interest.