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Oxidation Tests (oxidation + test)
Selected AbstractsSynthesis of benzotriazole derivatives as antioxidants for industrial lubricating oilsLUBRICATION SCIENCE, Issue 2 2006El-S.H. El-Ashry Abstract Evaluation of a number of benzotriazole derivatives as antioxidants for turbine oils was carried out by formulating different blends of turbine oil with viscosity grade ISO 46 with different dosages of the synthesized compounds. Oxidation tests were carried out according to IP 229 on each blend and the optimum dosages of these compounds were determined. Copyright © 2006 John Wiley & Sons, Ltd. [source] Redesigning alkylated diphenylamine antioxidants for modern lubricantsLUBRICATION SCIENCE, Issue 1 2007Vincent J. Gatto This paper describes a new alkylation technology that is very effective at synthesizing structurally different alkylated diphenylamine chemistries relative to those currently available to lubricant formulators. Examples are provided showing how this technology can be used in a practical way to produce a variety of chemically modified nonylated diphenylamine types. One example is also provided illustrating the preparation of a higher molecular weight dodecylated diphenylamine. Engine oil performance data utilizing pressurized differential scanning calorimetry (PDSC), the thermo-oxidation engine oil simulation test, and a bulk oil oxidation test demonstrate that subtle changes in alkylated diphenylamine chemical composition can result in significant oxidation and deposit control performance enhancements or losses. Examples of similar performance responses in industrial oils are demonstrated utilizing PDSC and the rotating pressure vessel oxidation test. These performance changes are directly related to specific structural changes in the modified products. Copyright © 2006 John Wiley & Sons, Ltd. [source] Probing the antioxidative properties of combinations of an organotellurium compound, BHT and thiol in oilLUBRICATION SCIENCE, Issue 2 2006David Shanks Abstract Differential scanning calorimetry experiments with an unsaturated polyolester oil at 190°C showed that an organotellurium compound in combination with a thiol or a sterically hindered phenol (BHT) could act in a synergistic fashion to protect the material from oxidation. Under more realistic conditions for an oil antioxidant (elevated temperature in the presence of oxygen, water and a copper coil; rotating pressure vessel oxidation test) the antioxidant protection offered by the organotellurium/thiol and organotellurium/BHT combinations could not match the protection offered by BHT itself at similar concentrations. In order for the novel antioxidant systems to become useful for protection of oils and fluids, more robust organotellurium compounds must be prepared. Copyright © 2006 John Wiley & Sons, Ltd. [source] High Performance SiC Oxidation Protective Coating with ZrO2 Particle Dispersion for Carbon/Carbon Composites,ADVANCED ENGINEERING MATERIALS, Issue 10 2008Y.-L. Zhang High performance SiC oxidation protective coating with ZrO2 particle dispersion for C/C composites was prepared by slurry and pack cementation. Isothermal oxidation tests at 1873,K in air showed that the as-prepared coating could effectively protect C/C composites from oxidation for 100,h. The excellent oxidation protective ability can be attributed to the introduction of ZrO2 particles in the SiC coating, which can baffle the enlargement of cracks and suppress the generation of the thermal stress. [source] The effect of an Ni,Cr protective layer on cyclic oxidation of Ti3AlJOURNAL OF MICROSCOPY, Issue 1 2006I. CVIJOVI Summary The effect of an 80Ni,20Cr (at.%) metallic coating on the cyclic oxidation behaviour of a Ti3Al-based alloy with the composition Ti,25Al,11Nb (at.%) was investigated in this study. Cyclic oxidation tests were carried out in air at 600 °C and 900 °C for 120 h. For one cycle test, the specimens were held for 24 h at test temperature and then furnace-cooled to room temperature. The oxidation rate was determined by plotting the mass gain per unit surface area of the specimen vs. exposure time. The morphology and composition of the oxidation products were characterized on the cross-section of the specimens by scanning electron microscopy, energy-dispersive X-ray spectroscopy and atomic force microscopy. The oxidation scale forms during exposure at both 600 °C and 900 °C. TiO2 is the main oxide component, whereas the Al2O3 layer appears only discontinuously. The remarkable improvement in oxidation resistance at 900 °C was attributed to the chemical composition and structure of the scale formed on the 80Ni,20Cr coating. [source] Oxidation behaviour of Fe-Cr-Al alloys during resistance and furnace heatingMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 2 2006H. Echsler Abstract The behaviour of thin Fe-Cr-Al heating element strips was investigated with respect to the oxidation limited life times and geometrical changes during resistance and furnace heating. For this purpose, isothermal and cyclic oxidation tests varying in their total exposure time and cycle duration were performed in the temperature range 1050,1200 °C. Specimens subjected to rapid cyclic, resistance heating revealed shorter life times than calculated for specimens subjected to isothermal exposure. The life times were found to increase with increasing cycle duration and hence decreasing number of cycles for a given time at temperature. This life time decrease is related to an "hour glass" waviness of the specimens, which develops during prolonged thermal cycling. The development of this plastic deformation also occurred during furnace heated, thermal cycling tests. A two-step mechanism is introduced combining an oxidation kinetics related time to the onset of significant waviness with an enhancement of this waviness as a result of a ratcheting effect. The latter seems to strongly depend on the number of cycles and on the plastic deformation generated during each cycle rather than on the total time at temperature. The development of an "hour glass" waviness leads to an enhanced aluminium depletion due to an increase of the specimen surface area. Additional deformation phenomena like "hot tube" or "corkscrew" behaviour occur during the resistance heating tests. These are related to a temperature gradient that develops over the specimen width due to the poor aspect ratio of the specimens. [source] Service conditions and their influence on oxide scale formation on metallic high temperature alloys for application in innovative combustion processesMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 2 2006G. Teneva-Kosseva Abstract The present paper focuses on two aspects: the service conditions of a flame tube in a low-NOx recirculation burner (maximum temperature experienced by the material: 1000 °C) and the interrelationship between service conditions and both the structure and growth of the oxide scale. The flame tube is exposed to extreme thermal and atmospheric conditions during service. Due to the short burner operation time followed by a pause, rapid changes of the temperature and gaseous environment occur. Three Ni-based alloys (alloy 602 CA, alloy 603 XL and alloy 693) were investigated in cyclic oxidation tests under typical conditions for the combustion of fuel oil. Flame tube temperature measurements in both the axial and the tangential directions are presented together with results concerning the influence of the fuel quality, duration of the air ventilation after burner shut down and temperature on the thickness and composition of the oxide scale. [source] Effects of minor additions and impurities on oxidation behaviour of FeCrAl alloys.MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2005Development of novel surface coatings compositions Abstract In the present work the effects of single or combined minor additions of Zr, Hf, Ti and C on the oxidation behaviour of Y-containing, FeCrAl alloys have been studied. For this purpose high-purity, model alloys with single or multiple minor alloying additions were used. The results of long term discontinuous oxidation tests and detailed kinetics studies using thermogravimetry were complemented with extensive microstructural characterisation of the formed alumina scales using SEM and STEM. Hence, the oxidation kinetics and scale spallation rates and failure modes were correlated with the oxide composition and microstructure. The results demonstrate that the frequently reported positive effect of Zr, Hf and Ti on the lifetime oxidation behaviour of FeCrAl alloys can only be fully exploited if the concentrations of the above elements are carefully adjusted and the interaction with typical alloy impurities, such as carbon, is considered. [source] Oxidation behaviour of particle reinforced MoSi2 composites at temperatures up to 1700°C.MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 3 2005Part II: Initial screening of the oxidation behaviour of MoSi2 composites Abstract In the first part of this paper a literature survey on the oxidation behaviour of MoSi2 and MoSi2 composites has been given. The present second part reports about the experimental results from oxidation tests with several MoSi2 composites containing 15 vol.-% Al2O3, Y2O3, ZrO2, HfO2, SiC, TiB2, ZrB2, or HfB2, respectively, from different development stages. The tests were conducted at 1600°C in air for 100 hours. It was shown that the production route of the powders has a significant influence on the performance of the materials at high temperatures. This was attributed to contaminations. Additionally, the results indicated that only the composites with SiC, ZrO2 or HfO2, respectively, are suitable for application above 1500°C. A more detailed report about the optimised material will follow in the third part of this paper. [source] | ||||||||||