Papers by Keyword: Oxygen

Abstract: Based on aerosol chemical deposition, a method was developed and the process of simultaneous formation of a composite with a carbon matrix and iron oxide nanoparticles incorporated therein was developed. As the source of carbon, o-xylene is proposed, source of nanoscale iron oxide - stabilized and unstabilized magnetic fluid based on benzoic acid in dimethylformamide solution, where benzoic acid is addition source of carbon. The proposed method makes it possible to obtain composite materials of various types with several directions of growth.

Abstract: By rapid pyrolysis of pulverized coal in oxygen and steam atmosphere, powder activated coke (PAC) nanostructured carbon material was derived by one step. Then, nitrogen adsorption measurement, scanning electric measurement (SEM) and Fourier transform infrared spectroscopy (FTIR) test were conducted to analyse the detail characteristic of the obtained PACs. The results showed that the one-step pulverized coal rapid pyrolysis process was an effective method for the production of PAC powders. The mixture of oxygen and steam as the activating agent was essential during the pyrolysis progress. Oxygen act as the most important fast activating agent for the pore formation, while steam activation protected the material matrix and weakly affected pore growth. The composition and concentration of oxygen and steam had a great effect on pore structure, surface micromorphology and functional groups of PACs. The mixed oxygen and steam atmosphere exhibited a tightly tailored micropore structure. By further optimizing activating oxygen and steam composition, the PAC products could have considerable pore structures, respectable surface morphology and functional groups.

Abstract: Titanium and its alloys possess high specific strength, excellent corrosion resistance and good biocompatibility [1] [2]. Since oxygen is an unavoidable impurity in such materials, it has been adopted as an alloying element in the development of low-cost titanium alloys. Therefore, it is important to investigate the role of oxygen in these alloys, especially in β-type alloys. In the present study, the effects of oxygen on the electrical resistivity, Vickers hardness and heat treatment behavior of a Ti-20mass%V alloy which is the lowest concentration for which the fully retained β phase is obtained were assessed. The electrical resistivity and Vickers hardness of solution-treated and quenched specimens increased with increasing oxygen content, due to the dissolution of oxygen into the β phase and solid solution hardening, respectively. Upon isothermal aging at 673 K, the addition of O accelerated a-phase precipitation. The addition of O was found to suppress the appearance of the athermal ω phase in the solution-treated and quenched state.

Abstract: Oxygen is considered to be an impurity in titanium and its alloys, and it enhances their brittleness. However, oxygen has also been recognized as a useful ingredient to improve the mechanical performance of titanium alloys for biomedical applications, because oxygen is a lightweight interstitial element that is non-toxic and non-allergenic. Some reports show that adding oxygen improves both the strength and the ductility of titanium alloys for biomedical applications. The effects of oxygen addition on the mechanical performance of titanium alloys for biomedical aplications are described.

Abstract: The effect of different interstitial impurities content (oxygen, carbon) on β - transus temperature and complex of properties in the heat-strengthened condition of the Ti-5Al-5V-5Mo-3Cr-1Zr (VST55531) titanium alloy has been studied. The possibility of determining alloy β - transus temperature by the differential scanning calorimetry method with accuracy comparable with the test quenching method is shown in this paper. It is shown that under identical aging regimes an increase of oxygen content from 0.176 to 0.25 wt.% and carbon content from 0.009 to 0.025 wt.% in VST55531 alloy results in higher strength, plastic characteristics and lower ductility, toughness characteristics, especially those which related to the crack propagation.

Abstract: Oxygen (O₂) enriched air combustion via adaption of polymeric membranes has been proposed to be a feasible alternative to increase combustion proficiency while minimizing the emission of greenhouse gases into the atmosphere. Nonetheless, majority of techno-economic assessment on the O₂ enriched combustion evolving membrane separation process are confined to assumption of constant membrane permeance. In reality, it is well known that membrane permeance is highly dependent upon the temperature and pressure to which it is operated. Therefore, in this work, an empirical model, which includes the effect of temperature and pressure to permeance, has been evaluated based on own experimental work using polysulfone membrane. The empirical model has been further validated with published experimental results. It is found that the model is able to provide an excellent characterization of the membrane permeance across a wide range of operating conditions for both pure and binary gas with determination coefficient of minimally 0.99.

Abstract: The actuality of the topic chosen by us lies in the fact that the effect of oxygen on the properties of semiconductors has not been studied sufficiently well, mainly because of the imperfections of methods for controlling the oxygen content in semiconductor materials. Almost in all such materials, oxygen is present either as an uncontrolled impurity or as a doping additive, or, in the case of oxide semiconductors, as in our case with a semiconductor film of vanadium dioxide, is part of the compound. The oxygen contained in the semiconductor film significantly affects the property of the material: in the first two cases, this influence is determined by the amount and state of the impurity, in the third - by the composition, or by the stoichiometry of the oxide compound. We set a goal to develop a technique for obtaining a semiconductor film of vanadium dioxide in a controlled atmosphere of oxygen. The semiconductor film thus obtained is used in holography to record and store optical information. For the production of VO₂ films by oxidation in a controlled atmosphere, an apparatus including an oxygen pump based on stabilized zirconia dioxide has been developed. The principle of operation and the main characteristics of such an oxygen pump is the unique application of the property of the superionics - to carry through itself exclusively oxygen ions under the influence of a constant current field and a high temperature. The technique developed by us for obtaining a semiconductor film of vanadium dioxide in a controlled atmosphere of oxygen has no analog.

Abstract: In this paper, a Ti-6Al-4V rectangular bar was successfully produced from a 5kg blended powder mixture using an industrial scale extrusion facility. The elemental hydride-dehydride (HDH) titanium and 60Al-40V master alloy mixture was warm pressed and vacuum sintered prior to β extrusion in air. The as-processed material was characterised for compositional homogeneity, oxygen pickup, microstructure, tensile properties and fracture behavior. Variation in microstructure and properties along the length of the extruded bar were also studied. It was found that oxygen pickup mainly occurred during vacuum sintering of the green billet and consequently the as-extruded material had an oxygen content of 0.55 wt.%. The processed material had a typical lamellar morphology with some evidence of micro-cracks at high magnification. A significant deviation in prior β grain and α colony sizes was observed along the length of the bar, due to variations in extrusion temperature and cooling rate. Both grains and colonies became finer as the location changed from the tip of the extruded bar to the back end. The as-processed material had ultimate tensile strength in the range of 1068-1268 MPa and elongation to fracture of 1.2-4.5%, mainly due to the high oxygen content and non-optimised microstructure. Fractographic analysis was consistent with the variation in mechanical performances obtained.

Abstract: In this work, powder injection molding (PIM) of Ti-6Al-4V alloy powder has been studied. Defect-free high performance Ti-6Al-4V parts with low carbon/oxygen contents have been successfully prepared by PIM. A pre-alloyed Ti-6Al-4V alloy powder and wax-polymer binder system have been mixed together to prepare the feedstock. In mixing stage, the solid loading percentage and mixing conditions have been optimized. Rheological and thermal debinding behaviors of prepared feedstock have been characterized and numerically expressed based on rheometry and thermal gravity experimental results. In addition, the injection molding process of Ti-6Al-4V parts has been numerically analyzed to optimize the injection molding conditions. Consequently, the defect-free Ti-6Al-4V parts with low carbon and oxygen contents have been successfully fabricated by PIM, which exhibits excellent physical and mechanical properties.

Abstract: The main components of polymer carboxyl group are introduced.The effects of macromolecular carboxyl groups on the limestone-gypsum wet flue gas desulfurization (FGD) system of coal-fired power plants in China were studied by test method. The results showed that the macromolecular carboxyl groups can accelerate the chemical absorption of SO₂ under the action of active agents and crystallization agents, improve the desulfurization efficiency of about 2%, and shorten the limestone ablation time of more than 40%, catalytic calcium sulfite oxidation of calcium sulfate.