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Sample records for temperature oxidation behavior

  1. High Temperature Oxidation Behavior of T91 Steel in Dry and Humid Condition

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    Yonghao Leong

    2016-09-01

    Full Text Available High temperature oxidation behavior of T91 ferritic/martensitic steel was examined over the temperature range of 500 to 700°C in dry and humid environments.  The weight gain result revealed that oxidation occurs at all range of temperatures and its rate is accelerated by increasing the temperature. The weight gain of the oxidized steel at 700°C in steam condition was six times bigger than the dry oxidation.. SEM/EDX of the cross-sectional image showed that under dry condition, a protective and steady growth of the chromium oxide (Cr2O3 layer was formed on the steel with the thickness of 2.39±0.34 µm. Meanwhile for the humid environment, it is found that the iron oxide layer, which consists of the hematite (Fe2O3 and magnetite (Fe3O4 was formed as the outer scale, and spinnel as inner scale. This result indicated that the oxidation behavior of T91 steel was affected by its oxidation environment. The existence of water vapor in steam condition may prevent the formation of chromium oxide as protective layer.

  2. Long-Term Cyclic Oxidation Behavior of Wrought Commercial Alloys at High Temperatures

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    Li, Bingtao [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    The oxidation resistance of a high-temperature alloy is dependent upon sustaining the formation of a protective scale, which is strongly related to the alloying composition and the oxidation condition. The protective oxide scale only provides a finite period of oxidation resistance owing to its eventual breakdown, which is especially accelerated under thermal cycling conditions. This current study focuses on the long-term cyclic oxidation behavior of a number of commercial wrought alloys. The alloys studied were Fe- and Ni-based, containing different levels of minor elements, such as Si, Al, Mn, and Ti. Oxidation testing was conducted at 1000 and 1100 C in still air under both isothermal and thermal cycling conditions (1-day and 7-days). The specific aspects studied were the oxidation behavior of chromia-forming alloys that are used extensively in industry. The current study analyzed the effects of alloying elements, especially the effect of minor element Si, on cyclic oxidation resistance. The behavior of oxide scale growth, scale spallation, subsurface changes, and chromium interdiffusion in the alloy were analyzed in detail. A novel model was developed in the current study to predict the life-time during cyclic oxidation by simulating oxidation kinetics and chromium interdiffusion in the subsurface of chromia-forming alloys.

  3. Effects of W on microstructure and high-temperature oxidation behavior of ferritic stainless steel weldment

    Science.gov (United States)

    Ji, Yijie; Xie, Yuye; Zhu, Shuangchun; Yan, Biao

    2017-07-01

    With the promotion of fuel economy policy and automobile lightweight concept, ferritic stainless steels applied in vehicles’ exhaust hot end systems have been developed. This paper simulated the high-temperature environment at which the automobile exhaust system serviced in for high-temperature corrosion. Kinetic curves were conducted in isothermal environments at 1000∘C. X-ray diffraction, scanning electron microscope and energy dispersive spectrometer were used to study the oxidation behavior of ferritic stainless steels and the effects of tungsten (W) addition. The results show that, with increasing oxidation time, the rate of weight gains increase and the main failure is spalling of surface oxide layer. The addition of W has a complicated effect on the oxidation behavior of ferritic stainless steel weldment.

  4. High-Temperature Oxidation Behavior and Kinetics of Forged 12Cr-MoVW Steel

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    Kim Yong Hwan

    2017-06-01

    Full Text Available The oxidation kinetics of forged 12Cr-MoVW steel was investigated in an air (N2+O2 atmosphere at 873-1073 K (Δ50 K using thermogravimetric analysis. The oxidized samples were characterized using X-ray diffraction, and the surface and cross-sectional morphologies were examined using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The forged 12Cr-MoVW steel samples exhibited parabolic behavior and a low oxidation rate compared with their as-cast counterparts. A protective oxide layer was uniformly formed at relatively low temperature (≤973 K for the forged samples, which thus exhibited better oxidation resistance than the as-cast ones. These oxides are considered solid-solution compounds such as (Fe, Cr2O3.

  5. High-temperature oxidation behavior of carbon-carbon composites in the field of combustion

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    Fushitani, Kazunari; Kobayashi, Noriyuki; Arai, Norio [Nagoya Univ. (Japan)

    1996-12-31

    The effects of equivalence ratio and temperature on oxidation behavior of carbon fiber reinforced carbon composites (C/C composites) were studied experimentally. Rates of weight loss of C/C composites in the field of combustion with methane-air were measured. The experiments were conducted at equivalence ratios of 0 = 0.8 and 1.3, and at temperatures of 1200, 1300 and 1400{degrees}C. It was found that higher equivalence ratio and lower temperature of methane-air were more effective in protecting C/C composites from oxidation. Changes of chemical structure on surface of C/C composites before and after experiment were also observed by Raman spectroscopy to evaluate chemically the degree of oxidation. The two peaks of Raman spectra from C/C composites appeared strongly at 1580 cm{sup -1} and weakly at 1360 cm{sup -1}. The ratios of the peak intensities at their wave numbers, R=I{sub 1360}/I{sub 1580}, which may indicate the degree of degradation of carbonaceous materials were measured. The dependence of equivalence ratio and temperature on R-value was similar to those on behavior of weight loss. This suggested that R-value obtained by Raman spectroscopy may be useful for estimation of the degree of oxidation. 8 refs., 6 figs., 1 tab.

  6. Design, microstructure, and high-temperature behavior of silicon nitride sintered with rate-earth oxides

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    Ciniculk, M.K. (California Univ., Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering)

    1991-08-01

    The processing-microstructure-property relations of silicon nitride ceramics sintered with rare-earth oxide additives have been investigated with the aim of improving their high-temperature behavior. The additions of the oxides of Y, Sm, Gd, Dy, Er, or Yb were compositionally controlled to tailor the intergranular phase. The resulting microstructure consisted of {beta}-Si{sub 3}N{sub 4} grains and a crystalline secondary phase of RE{sub 2}Si{sub 2}O{sub 7}, with a thin residual amorphous phase present at grain boundaries. The lanthanide oxides were found to be as effective as Y{sub 2}O{sub 3} in densifying Si{sub 3}N{sub 4}, resulting in identical microstructures. The crystallization behavior of all six disilicates was similar, characterized by a limited nucleation and rapid growth mechanism resulting in large single crystals. Complete crystallization of the intergranular phase was obtained with the exception of a residual amorphous, observed at interfaces and believed to be rich in impurities, the cause of incomplete devitrification. The low resistance to oxidation of these materials was attributed to the minimization of amorphous phases via devitrification to disilicates, compatible with SiO{sub 2}, the oxidation product of Si{sub 3}N{sub 4}. The strength retention of these materials at 1300{degrees}C was found to be between 80% and 91% of room-temperature strength, due to crystallization of the secondary phase and a residual but refractory amorphous grain-boundary phase. The creep behavior was found to be strongly dependent on residual amorphous phase viscosity as well as on the oxidation behavior, as evidenced by the nonsteady-state creep rates of all materials. 122 refs., 51 figs., 12 tabs.

  7. Substrate Effects on the High Temperature Oxidation Behavior of a Gold-Based Braze Filler Metal

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    Weil, K. Scott; Rice, Joseph P.

    2005-06-01

    Oxidation testing was conducted on a commercial gold-based braze alloy, Gold ABA®, and on zirconia/stainless steel couples joined using this filler metal. Preliminary results reveal that both substrates play a significant role in determining the overall oxidation behavior of the brazed joint.

  8. Mechanistic insights into the oxidation behavior of Ni alloys in high-temperature CO2

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    Oleksak, Richard P.; Baltrus, John P.; Nakano, Jinichiro; Nakano, Anna; Holcomb, Gordon R.; Dogan, Omer N.

    2017-06-01

    We present results of a Ni superalloy oxidized for short times in high purity CO2 and similarly in Ar containing ≤ 1 ppb O2. A detailed analysis of the oxidized surfaces reveals striking similarities for the two exposure environments, suggesting O2 impurities control the oxidation process in high-temperature CO2. Selective oxidation results in Cr-rich oxide layers grown by 2 outward diffusion, while Cr vacancies left in the metal contribute to significant void formation at the oxide/metal interface. Unlike for most of the alloy surface, the oxidation behavior of secondary phase metal carbides is considerably different in the two environments.

  9. The oxidation behavior of classical thermal barrier coatings exposed to extreme temperature

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    Alina DRAGOMIRESCU

    2017-03-01

    Full Text Available Thermal barrier coatings (TBC are designed to protect metal surfaces from extreme temperatures and improve their resistance to oxidation during service. Currently, the most commonly used systems are those that have the TBC structure bond coat (BC / top coat (TC layers. The top coat layer is a ceramic layer. Oxidation tests are designed to identify the dynamics of the thermally oxide layer (TGO growth at the interface of bond coat / top coat layers, delamination mechanism and the TBC structural changes induced by thermal conditions. This paper is a short study on the evolution of aluminum oxide protective layer along with prolonged exposure to the testing temperature. There have been tested rectangular specimens of metal super alloy with four surfaces coated with a duplex thermal barrier coating system. The specimens were microscopically and EDAX analyzed before and after the tests. In order to determine the oxide type, the samples were analyzed using X-ray diffraction. The results of the investigation are encouraging for future studies. The results show a direct relationship between the development of the oxide layer and long exposure to the test temperature. Future research will focus on changing the testing temperature to compare the results.

  10. Modeling of High Temperature Oxidation Behavior of FeCrAl Alloy by using Artificial Neural Network

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae Joon; Ryu, Ho Jin [KAIST, Daejeon (Korea, Republic of)

    2016-10-15

    Refractory alloys are candidate materials for replacing current zirconium-base cladding of light water reactors and they retain significant creep resistance and mechanical strength at high temperatures up to 1500 ℃ due to their high melting temperature. Thermal neutron cross sections of refractory metals are higher than that of zirconium, however the loss of neutron can be overcome by reducing cladding thickness which can be facilitated with enhanced mechanical properties. However, most refractory metals show the poor oxidation resistance at a high temperature. Oxidation behaviors of the various compositions of FeCrAl alloys in high temperature conditions were modeled by using Bayesian neural network. The automatic relevance determination (ARD) technique represented the influence of the composition of alloying elements on the oxidation resistance of FeCrAl alloys. This model can be utilized to understand the tendency of oxidation behavior along the composition of each element and prove the applicability of neural network modeling for the development of new cladding material of light water reactors.

  11. Isothermal Oxidation Behavior of Aluminized AISI 1020 Steel at the Temperature of 700 OC

    OpenAIRE

    Badaruddin, Mohammad; Suharno, Suharno; Wijaya, Hanif Ari

    2014-01-01

    The AISI 1020 steel was coated by dipping it into the molten Al bath at 700 °C for 16s. The coating layer formed on the steel substrate is consisting of Al with a little Fe, FeAl3 and Fe2Al5 layers. The morphologies of the FeAl3 and Fe2Al5 layers are platelet and columnar structures, respectively. The oxidation test was carried out isothermally at 700 °C for a various time of 1-49 h in static air. The oxidation behaviors of both of the bare steel and the aluminized steel were studied by the o...

  12. The High-Temperature Wear and Oxidation Behavior of CrC-Based HVOF Coatings

    Science.gov (United States)

    Houdková, Šárka; Česánek, Zdeněk; Smazalová, Eva; Lukáč, František

    2018-01-01

    Three commercially available chromium carbide-based powders with different kinds of matrix (Cr3C2-25%NiCr; Cr3C2-25%CoNiCrAlY and Cr3C2-50%NiCrMoNb) were deposited by an HVOF JP-5000 spraying gun, evaluated and compared. The influence of heat treatment on the microstructure and properties, as well as the oxidation resistance in a hot steam environment ( p = 24 MPa; T = 609 °C), was evaluated by SEM and XRD with respect to their potential application in the steam power industry. The sliding wear resistance measured at room and elevated ( T = 600 °C) temperatures according to ASTM G-133. For all three kinds of chromium carbide-based coatings, the precipitation of secondary carbides from the supersaturated matrix was observed during the heat treatment. For Cr3C2-25%NiCr coating annealed in hot steam environment as well as for Cr3C2-25%CoNiCrAlY coating in both environments, the inner carbide oxidation was recorded. The sliding wear resistance was found equal at room temperature, regardless of the matrix composition and content, while at elevated temperatures, the higher wear was measured, varying in dependence on the matrix composition and content. The chromium carbide-based coating with modified matrix composition Cr3C2-50%NiCrMoNb is suitable to replace the Cr3C2-25%NiCr coating in a hot steam environment to eliminate the risk of failure caused by inner carbide oxidation.

  13. Effect of pre-oxidation on high temperature sulfidation behavior of FeCr and FeCrAl alloys

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    Pillis Marina Fuser

    2004-01-01

    Full Text Available High temperature corrosion of structural alloys in sulfur bearing environments is many orders of magnitude higher than in oxidizing environments. Efforts to increase sulfidation resistance of these alloys include addition of alloying elements. Aluminum additions to iron-chromium alloys bring about increase in sulfidation resistance. This paper reports the effect of pre-oxidation on the sulfidation behavior of Fe-20Cr and Fe-20Cr-5Al alloys in H2-2% H2S environment at 800 °C. The surfaces of sulfidized specimens were also examined. Pre-oxidation of the two alloys results in an incubation period during subsequent sulfidation. After this incubation period, the Fe-20Cr alloy showed sulfidation behavior similar to that when the alloy was not pre-oxidized. The incubation period during sulfidation of the Fe-20Cr-5Al alloy was significantly longer, over 45 h, compared to 2 h for the Al free alloy. Based on the microscopic and gravimetric data a mechanism for sulfidation of these alloys with pre-oxidation has been proposed.

  14. Creep behavior of alloy 617 in high temperature air and helium environments-effect of oxidation damage

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    Jang, Chang Heui; Kim, Sung Hwan [Dept. of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Sah, Injin; Kim, Dae Jong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    The creep behavior of a nickel-base superalloy, Alloy 617, which is considered as a candidate material for the very high temperature gas cooled reactor, was studied. Creep rupture tests were carried out at 800°C, 900°C and 1000°C in static and flowing helium environments as well as in air. Creep rupture life in static helium was longer than that in air, while it was shorter in flowing helium environments. Microstructure observation of the creep tested specimens showed that the shorter creep rupture life in flowing helium was associated with the thicker oxide layer, greater decarburization depth, and deeper internal oxidation happened during the creep tests. The degree of such oxidation damage was quantified for the creep tested specimens and correlated with the creep rupture life in different environments.

  15. Chemical Makeup and Hydrophilic Behavior of Graphene Oxide Nanoribbons after Low-Temperature Fluorination.

    Science.gov (United States)

    Romero Aburto, Rebeca; Alemany, Lawrence B; Weldeghiorghis, Thomas K; Ozden, Sehmus; Peng, Zhiwei; Lherbier, Aurélien; Botello Méndez, Andrés Rafael; Tiwary, Chandra Sekhar; Taha-Tijerina, Jaime; Yan, Zheng; Tabata, Mika; Charlier, Jean-Christophe; Tour, James M; Ajayan, Pulickel M

    2015-07-28

    Here we investigated the fluorination of graphene oxide nanoribbons (GONRs) using H2 and F2 gases at low temperature, below 200 °C, with the purpose of elucidating their structure and predicting a fluorination mechanism. The importance of this study is the understanding of how fluorine functional groups are incorporated in complex structures, such as GONRs, as a function of temperature. The insight provided herein can potentially help engineer application-oriented materials for several research and industrial sectors. Direct (13)C pulse magic angle spinning (MAS) nuclear magnetic resonance (NMR) confirmed the presence of epoxy, hydroxyl, ester and ketone carbonyl, tertiary alkyl fluorides, as well as graphitic sp(2)-hybridized carbon. Moreover, (19)F-(13)C cross-polarization MAS NMR with (1)H and (19)F decoupling confirmed the presence of secondary alkyl fluoride (CF2) groups in the fluorinated graphene oxide nanoribbon (FGONR) structures fluorinated above 50 °C. First-principles density functional theory calculations gained insight into the atomic arrangement of the most dominant chemical groups. The fluorinated GONRs present atomic fluorine percentages in the range of 6-35. Interestingly, the FGONRs synthesized up to 100 °C, with 6-19% of atomic fluorine, exhibit colloidal similar stability in aqueous environments when compared to GONRs. This colloidal stability is important because it is not common for materials with up to 19% fluorine to have a high degree of hydrophilicity.

  16. Diode behavior in ultra-thin low temperature ALD grown zinc-oxide on silicon

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    Nazek El-Atab

    2013-10-01

    Full Text Available A thin-film ZnO(n/Si(p+ heterojunction diode is demonstrated. The thin film ZnO layer is deposited by Atomic Layer Deposition (ALD at different temperatures on a p-type silicon substrate. Atomic force microscopy (AFM AC-in-Air method in addition to conductive AFM (CAFM were used for the characterization of ZnO layer and to measure the current-voltage characteristics. Forward and reverse bias n-p diode behavior with good rectification properties is achieved. The diode with ZnO grown at 80°C exhibited the highest on/off ratio with a turn-on voltage (VON ∼3.5 V. The measured breakdown voltage (VBR and electric field (EBR for this diode are 5.4 V and 3.86 MV/cm, respectively.

  17. Effects of lead on oxidation behavior of Alloy 690TT within a high temperature aqueous environment

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    Hou, Qiang; Liu, Zhiyong; Li, Chengtao; Li, Xiaogang

    2017-12-01

    The chemical compositions, phases and structures of two oxide films on Alloy 690TT following exposure for 4400 h in pure water with and without lead at 320 °C were studied by surface analysis techniques. The analysis of a lead-doped oxide film prepared by a focused ion beam (FIB) demonstrated that both Cr-rich and Ni-rich oxides were alternatively distributed within the outer layer, whereas the inner layer was porous and poorly protected, causing severe corrosion of the alloy and a thicker film was formed. A duplex film model was proposed for the effects discussion of lead on the oxidation mechanism.

  18. Substrate Effects on the High Temperature Oxidation Behavior of a Gold-Based Braze Filler Metal

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    Weil, K. Scott; Rice, Joseph P.

    2005-06-30

    Oxidation testing was conducted on a commercial gold-based braze alloy, Gold ABA, and on zirconia and stainless steel joining couples prepared using this braze filler metal. Preliminary results reveal that both substrates play a significant role in determining the overall oxidation resistance of the brazed joint.

  19. Deposition Mechanisms and Oxidation Behaviors of Ti-Ni Coatings Deposited in Low-Temperature HVOF Spraying Process

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    Lin, Q. S.; Zhou, K. S.; Deng, C. M.; Liu, M.; Xu, L. P.; Deng, C. G.

    2014-08-01

    Three kinds of Ti-Ni powders were deposited on 316L stainless steel by low-temperature high-velocity oxygen fuel (LT-HVOF) spraying process, respectively. Deposition mechanisms and oxidation behaviors of the coatings were researched in this paper. The coating deposited from TiNi intermetallic powder had obvious laminar structure and the oxygen content was the highest among the three kinds of coatings. The oxygen content of the coating deposited from small-sized Ni-clad Ti powder was still high due to the melting of parts of particles. However, most of the coarse Ni-clad Ti powder was deposited in solid states without changes of chemical compositions and phase compositions. The oxygen content of the coating deposited from coarse Ni-clad Ti powder was the lowest among the three kinds of coatings. It indicated that the deposition behavior of the coating could effectively preserve the inner titanium from oxidation. The results of the present research demonstrated that it is entirely feasible to deposit active metal materials such as titanium and titanium alloy through the optimizing selection of powder in the LT-HVOF process.

  20. High-Temperature Tribological and Self-Lubricating Behavior of Copper Oxide-Doped Y-TZP Composite Sliding Against Alumina

    NARCIS (Netherlands)

    Valefi, Mahdiar; de Rooij, Matthias B.; Schipper, Dirk J.; Winnubst, Aloysius J.A.

    2011-01-01

    The tribological behavior of 5 wt% copper oxide-doped tetragonal zirconia polycrystal composite has been investigated while it slides against an alumina counterface under high temperature conditions. The effects of load (1, 2.5, and 5 N) and velocity (0.05 and 0.1 m/s) on the wear mechanism have

  1. Investigation on the oxidation behavior of AlCrVxN thin films by means of synchrotron radiation and influence on the high temperature friction

    Science.gov (United States)

    Tillmann, Wolfgang; Kokalj, David; Stangier, Dominic; Paulus, Michael; Sternemann, Christian; Tolan, Metin

    2018-01-01

    Friction minimization is an important topic which is pursued in research and industry. In addition to the use of lubricants, friction-reducing oxide phases can be utilized which occur during. These oxides are called Magnéli phases and especially vanadium oxides exhibit good friction reducing properties. Thereby, the lubrication effect can be traced back to oxygen deficiencies. AlCrN thin films are being used as coatings for tools which have to withstand high temperatures. A further improvement of AlCrN thin films concerning their friction properties is possible by incorporation of vanadium. This study analyzes the temperature dependent oxidation behavior of magnetron sputtered AlCrVN thin films with different vanadium contents up to 13.5 at.-% by means of X-ray diffraction and X-ray absorption near-edge spectroscopy. Up to 400 °C the coatings show no oxidation. A higher temperature of 700 °C leads to an oxidation and formation of Magnéli phases of the coatings with vanadium contents above 10.7 at.-%. Friction coefficients, measured by ball-on-disk test are correlated with the oxide formation in order to figure out the effect of vanadium oxides. At 700 °C a decrease of the friction coefficient with increasing vanadium content can be observed, due to the formation of VO2, V2O3 and the Magnéli phase V4O7.

  2. A study on high temperature oxidation behavior of double glow plasma surface metallurgy Fe-Al-Cr alloyed layer on Q235 steel

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    Luo, Xi-Xi; Yao, Zheng-Jun; Zhang, Ping-Ze; Miao, Qiang; Liang, Wen-Ping; Wei, Dong-Bo; Chen, Yu

    2014-06-01

    The high-temperature oxidation behavior of Q235 steel coated with Fe-Al-Cr by using double glow plasma surface metallurgy method was studied in air at different temperatures of 500, 600 and 700 °C, respectively. The Q235 and the 304 stainless steels were produced as the control samples. Electron microscopy, energy dispersive spectroscopy and X-ray diffractometry were carried out to investigate the surface morphologies, microstructures and phases of alloyed layer before and after oxidation. It showed that the structure of the Fe-Al-Cr alloyed layer was compact without any microstructure defects. This alloyed layer connected with the substrate metal by metallurgical bonding. At the temperatures of 500 and 600 °C, the high temperature oxidation resistance of the Fe-Al-Cr alloyed layer was similar to that of the 304 steel, but 2-3 times higher than that of the Q235 steel. While at 700 °C, the Fe-Al-Cr alloyed layer exhibited much better oxidation resistance than that of the 304 steel (2.5 times) and the Q235 steel (5.5 times). And this was because the special Al distribution (approximate Gaussian distribution) in the Fe-Al-Cr alloyed layer, which displayed the self-healing ability for the oxidation film on the surface of the Fe-Al-Cr alloyed layer in the high temperature oxidation conditions.

  3. 10 000-hr Cyclic Oxidation Behavior of 68 High-Temperature Co-, Fe-, and Ni- Base Alloys Evaluated at 982 deg. C (1800 deg. F)

    Science.gov (United States)

    Barrett, Charles A.

    1999-01-01

    Power systems with operating temperatures in the range of 815 to 982 C (1500 to 1800 F) frequently require alloys that can operate for long times at these temperatures. A critical requirement is that these alloys have adequate oxidation resistance. The alloys used in these power systems require thousands of hours of operating life with intermittent shutdown to room temperature. Intermittent power plant shutdowns, however, offer the possibility that the protective scale will tend to spall (i.e., crack and flake off) upon cooling, increasing the rate of oxidative attack in subsequent heating cycles. Thus, it is critical that candidate alloys be evaluated for cyclic oxidation behavior. It was determined that exposing test alloys to ten 1000-hr cycles in static air at 982 10 000-hr Cyclic Oxidation Behavior of 68 High-Temperature Co-, Fe-, and Ni-Base Alloys Evaluated at 982 C (1800 F) could give a reasonable simulation of long-time power plant operation. Iron- (Fe-), nickel- (Ni-), and cobalt- (Co-) based high-temperature alloys with sufficient chromium (Cr) and/or aluminum (Al) content can exhibit excellent oxidation resistance. The protective oxides formed by these classes of alloys are typically Cr2O3 and/or Al2O3, and are usually influenced by their Cr, or Cr and Al, content. Sixty-eight Co-, Fe-, and Ni-base high-temperature alloys, typical of those used at this temperature or higher, were used in this study. At the NASA Lewis Research Center, the alloys were tested and compared on the basis of their weight change as a function of time, x-ray diffraction of the protective scale composition, and the physical appearance of the exposed samples. Although final appearance and x-ray diffraction of the final scale products were two factors used to evaluate the oxidation resistance of each alloy, the main criterion was the oxidation kinetics inferred from the specific weight change versus time data. These data indicated a range of oxidation behavior including parabolic

  4. Initial oxidation behavior of Ni{sub 3}Al (210) surface induced by supersonic oxygen molecular beam at room temperature

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    Xu, Ya, E-mail: XU.Ya@nims.go.jp [Hydrogen Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Sakurai, Junya [Hydrogen Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Teraoka, Yuden; Yoshigoe, Akitaka [Quantum Beam Science Center, Japan Atomic Energy Research Agency, 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148 (Japan); Demura, Masahiko; Hirano, Toshiyuki [Hydrogen Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

    2017-01-01

    Graphical abstract: - Highlights: • Initial oxidation of Ni{sub 3}Al (210) induced by O{sub 2} beam was investigated. • This was done using real-time synchrotron radiation XPS. • Both the Al and the Ni atoms on the surface were oxidized. • Oxidation of Al progressed much faster than that of Ni. - Abstract: The initial oxidation behavior of a clean Ni{sub 3}Al (210) surface was studied at 300 K using a supersonic O{sub 2} molecular beam (O{sub 2} SSMB) having an O{sub 2} translational energy of 2.3 eV, and real-time photoemission spectroscopy performed with high-brilliance synchrotron radiation. The evolution behaviors of the O 1s, Ni 2p, Al 2p, and Ni 3p spectra were examined during irradiation with the O{sub 2} SSMB. The spectral analysis revealed that both the Al atoms and the Ni atoms on the surface were oxidized; however, the oxidation of Al progressed much faster than that of Ni. The oxidation of Al began to occur and AlO{sub x} was formed at an oxygen coverage of 0.26 monolayer (ML) (1 ML was defined as the atomic density of the Ni{sub 3}Al (210) surface) and saturated at an oxygen coverage of 2.5 ML. In contrast, the oxidation of Ni commenced a little late at an oxygen coverage of 1.6 ML and slowly progressed to saturation, which occurred at an oxygen coverage of 4.89 ML.

  5. Oxidation behavior of Ti2AlC in the temperature range of 1400 °C-1600 °C in steam

    Science.gov (United States)

    Tang, Chongchong; Steinbrück, Martin; Große, Mirco; Bergfeldt, Thomas; Seifert, Hans Jürgen

    2017-07-01

    The oxidation behavior of bulk Ti2AlC ceramic in steam has been investigated in the temperature range of 1400 °C-1600 °C. The oxidation kinetics followed a sub-parabolic law at the early stage of oxidation, then tended to be a linear law beyond 18 h at 1400 °C, and obeyed a linear law during the whole exposure up to 24 h at 1500 °C. At the initial stage of oxidation at 1400 °C and 1500 °C, randomly Al2TiO5 isolated islands with large elongated grains were observed on the surface. A continuous inner α-Al2O3 layer with a thin discontinuous outer layer of Al2TiO5 formed with prolonged exposure time. Outward diffusion of Ti and C through grain boundaries of the α-Al2O3 scale during steady-state oxidation result in segregation of TiO2 at the grain boundaries of α-Al2O3 and formation of gaseous CO and CO2, respectively. The scale adhesion was reduced in steam compared to that in air due to the accumulation of stresses, and generation of voids at the scale/substrate interface. The mechanical disruption of the oxide scale to relief the stresses contribute to the breakaway oxidation of Ti2AlC at 1400 °C and to the non-protective effect at 1500 °C. The sample was rapidly and completely consumed during isothermal oxidation at 1600 °C accompanied by release of heat and hydrogen. The maximum tolerant temperature of Ti2AlC in steam was approximate 1555 °C, which can be extended via a tailored pre-oxidation process.

  6. Silicon Carbide Nanotube Oxidation at High Temperatures

    Science.gov (United States)

    Ahlborg, Nadia; Zhu, Dongming

    2012-01-01

    Silicon Carbide Nanotubes (SiCNTs) have high mechanical strength and also have many potential functional applications. In this study, SiCNTs were investigated for use in strengthening high temperature silicate and oxide materials for high performance ceramic nanocomposites and environmental barrier coating bond coats. The high · temperature oxidation behavior of the nanotubes was of particular interest. The SiCNTs were synthesized by a direct reactive conversion process of multiwall carbon nanotubes and silicon at high temperature. Thermogravimetric analysis (TGA) was used to study the oxidation kinetics of SiCNTs at temperatures ranging from 800degC to1300degC. The specific oxidation mechanisms were also investigated.

  7. Effects of temperature on stress corrosion cracking behavior of stainless steel and outer oxide distribution in cracks due to exposure to high-temperature water containing hydrogen peroxide

    Science.gov (United States)

    Nakano, Junichi; Sato, Tomonori; Kato, Chiaki; Yamamoto, Masahiro; Tsukada, Takashi; Kaji, Yoshiyuki

    2014-01-01

    Cracking growth tests were conducted in high-temperature water containing hydrogen peroxide (H2O2) at 561-423 K to evaluate the effects of H2O2 on stress corrosion cracking (SCC) of stainless steel (SS) at temperature lower than the boiling water reactor (BWR) operating temperature. Small compact tension (CT) specimens were prepared from thermally sensitized type 304 SS. Despite the observation of only a small portion intergranular SCC (IGSCC) near the side groove of the CT specimen at 561 K in high-temperature water containing 100 ppb H2O2, the IGSCC area expanded to the central region of the CT specimens at 423 and 453 K. Effects of H2O2 on SCC appeared intensely at temperature lower than the BWR operating temperature because of a reduction in the thermal decomposition of H2O2. To estimate the environment in the cracks, outer oxide distribution on the fracture surface and the fatigue pre-crack were examined by laser Raman spectroscopy and thermal equilibrium calculation was performed.

  8. Oxidation and erosion-oxidation behavior of steels

    Directory of Open Access Journals (Sweden)

    Stela Maria de Carvalho Fernandes

    2008-03-01

    Full Text Available The high temperature oxidation and erosion-oxidation (E-O behavior of steels AISI 1020, 304, 310, and 410 were determined. These steels were selected to evaluate the effect of chromium content on its E-O resistance. The oxidation behavior was determined in a thermogravimetric analyzer. A test rig in which a specimen assembly was rotated through a fluidized bed of erodent particles was used to determine the E-O behavior. Alumina powder (200 µm was used as the erodent. The E-O tests were carried out in the temperature range 25-600 °C, with average particle impact velocities of 3.5 and 15 ms-1 and impact angle of 90°. The oxidation resistance of the steels increased with chromium content. The E-O behavior of the steels was determined as wastage. The E-O wastage of the steels exposed to particle impact at low velocity was low but increased with temperature above 300 °C. The E-O wastage of the different steels exposed to particle impact at high velocity was quite similar. The wastage increased with increase in temperature above 500 °C. The increases in E-O wastage of the steels observed at temperatures above 300, 400 or 500 °C, depending on the steel, were due mainly to a transition in the dominant wastage process, from 'erosion' to 'erosion-oxidation'.

  9. High Temperature Oxidation Behavior of gamma-Ni+gamma'-Ni3Al Alloys and Coatings Modified with Pt and Reactive Elements

    Energy Technology Data Exchange (ETDEWEB)

    Mu, Nan [Iowa State Univ., Ames, IA (United States)

    2007-12-01

    Materials for high-pressure turbine blades must be able to operate in the high-temperature gases (above 1000 C) emerging from the combustion chamber. Accordingly, the development of nickel-based superalloys has been constantly motivated by the need to have improved engine efficiency, reliability and service lifetime under the harsh conditions imposed by the turbine environment. However, the melting point of nickel (1455 C) provides a natural ceiling for the temperature capability of nickel-based superalloys. Thus, surface-engineered turbine components with modified diffusion coatings and overlay coatings are used. Theses coatings are capable of forming a compact and adherent oxide scale, which greatly impedes the further transport of reactants between the high-temperature gases and the underlying metal and thus reducing attack by the atmosphere. Typically, these coatings contain β-NiAl as a principal constituent phase in order to have sufficient aluminum content to form an Al2O3 scale at elevated temperatures. The drawbacks to the currently-used {beta}-based coatings, such as phase instabilities, associated stresses induced by such phase instabilities, and extensive coating/substrate interdiffusion, are major motivations in this study to seek next-generation coatings. The high-temperature oxidation resistance of novel Pt + Hf-modified γ-Ni + γ-Ni3Al-based alloys and coatings were investigated in this study. Both early-stage and 4-days isothermal oxidation behavior of single-phase γ-Ni and γ'-Ni3Al alloys were assessed by examining the weight changes, oxide-scale structures, and elemental concentration profiles through the scales and subsurface alloy regions. It was found that Pt promotes Al2O3 formation by suppressing the NiO growth on both γ-Ni and γ'Ni3Al single-phase alloys. This effect increases with increasing Pt content. Moreover, Pt exhibits this effect even at

  10. Effect of alloy grain size on the high-temperature oxidation behavior of the austenitic steel TP 347

    Directory of Open Access Journals (Sweden)

    Vicente Braz Trindade

    2005-12-01

    Full Text Available Generally, oxide scales formed on high Cr steels are multi-layered and the kinetics are strongly influenced by the alloy grain boundaries. In the present study, the oxidation behaviour of an austenite steel TP347 with different grain sizes was studied to identify the role of grain-boundaries in the oxidation process. Heat treatment in an inert gas atmosphere at 1050 °C was applied to modify the grain size of the steel TP347. The mass gain during subsequent oxidation was measured using a microbalance with a resolution of 10-5 g. The scale morphology was examined using SEM in combination with energy-dispersive X-ray spectroscopy (EDS. Oxidation of TP347 with a grain size of 4 µm at 750 °C in air follows a parabolic rate law. For a larger grain size (65 µm, complex kinetics is observed with a fast initial oxidation followed by several different parabolic oxidation stages. SEM examinations indicated that the scale formed on specimens with smaller grain size was predominantly Cr2O3, with some FeCr2O4 at localized sites. For specimens with larger grain size the main oxide is iron oxide. It can be concluded that protective Cr2O3 formation is promoted by a high density of fast grain-boundary diffusion paths which is the case for fine-grained materials.

  11. Capacitive Behavior of Single Gallium Oxide Nanobelt.

    Science.gov (United States)

    Cai, Haitao; Liu, Hang; Zhu, Huichao; Shao, Pai; Hou, Changmin

    2015-08-17

    In this research, monocrystalline gallium oxide (Ga₂O₃) nanobelts were synthesized through oxidation of metal gallium at high temperature. An electronic device, based on an individual Ga₂O₃ nanobelt on Pt interdigital electrodes (IDEs), was fabricated to investigate the electrical characteristics of the Ga2O3 nanobelt in a dry atmosphere at room temperature. The current-voltage (I-V) and I/V-t characteristics show the capacitive behavior of the Ga₂O₃ nanobelt, indicating the existence of capacitive elements in the Pt/Ga₂O₃/Pt structure.

  12. Effect of Prior Exposure at Elevated Temperatures on Tensile Properties and Stress-Strain Behavior of Three Oxide/Oxide Ceramic Matrix Composites

    Science.gov (United States)

    2015-03-26

    Comparison of the two different fiberglass tabs used during tensile testing...10,000 B.C. and became a means for transporting water and food storage. Eventually, ceramics were used to create thermal and electrical insulators [3...The high strength, electrical insulation properties and the ability to handle relatively high temperature compared to many metallic materials have

  13. Effect of oxidation on the fatigue crack propagation behavior of Z3CN20.09M dyplex stainless steel in high temperature water

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Huan Chun; Yang, Bin [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing (China); Chen, Yue Feng; Chen, Xu Dong [Collaborative Innovation Center of Steel Technology, Beijing (China)

    2017-06-15

    The fatigue crack propagation behaviors of Z3CN20.09M duplex stainless steel (DSS) were investigated by studying oxide films of specimens tested in 290°C water and air. The results indicate that a full oxide film that consisted of oxides and hydroxides was formed in 290°C water. By contrast, only a half-baked oxide film consisting of oxides was formed in 290°C air. Both environments are able to deteriorate the elastic modulus and hardness of the oxide films, especially the 290°C water. The fatigue lives of the specimens tested in 290°C air were about twice of those tested in 290°C water at all strain amplitudes. Moreover, the crack propagation rates of the specimen tested in 290°C water were confirmed to be faster than those tested in 290°C air, which was thought to be due to the deteriorative strength of the oxide films induced by the mutual promotion of oxidation and crack propagation at the crack tip. It is noteworthy that the crack propagation can be postponed by the ferrite phase in the DSS, especially when the specimens were tested in 290°C water.

  14. Low Temperature Oxidation of Methane: The Influence of Nitrogen Oxides

    DEFF Research Database (Denmark)

    Bendtsen, Anders Broe; Glarborg, Peter; Dam-Johansen, Kim

    2000-01-01

    An experimental investigation of methane oxidation in the presence of NO and NO2 has been made in an isothermal plug-flow reactor at 750-1250K. The temperature for on-set of oxidation was lowered by 250 K in the presence of NO or NO2 at residence times of 200 ms. At shorter residence times (140 ms......) this enhancement effect is reduced for NO but maintained for NO2. Furthermore two temperature regimes of oxidation separated by an intermediate regime where only little oxidation takes place exist at residence times of 140 ms, if NO is the only nitrogen oxide initially present. The results were explained...

  15. Creep and Oxidation of Hafnium Diboride Based Ultra High Temperature Ceramics at 1500C

    Science.gov (United States)

    2015-12-01

    their structural integrity and environmental durability must be assured, which requires a thorough understanding and characterization of their creep and oxidation behavior at relevant service temperatures.

  16. Adhesion property and high-temperature oxidation behavior of Cr-coated Zircaloy-4 cladding tube prepared by 3D laser coating

    Science.gov (United States)

    Kim, Hyun-Gil; Kim, Il-Hyun; Jung, Yang-Il; Park, Dong-Jun; Park, Jeong-Yong; Koo, Yang-Hyun

    2015-10-01

    A 3D laser coating technology using Cr powder was developed for Zr-based alloys considering parameters such as: the laser beam power, inert gas flow, cooling of Zr-based alloys, and Cr powder control. This technology was then applied to Zr cladding tube samples to study the effect of Cr coating on the high-temperature oxidation of Zr-based alloys in a steam environment of 1200 °C for 2000s. It was revealed that the oxide layer thickness formed on the Cr-coated tube surface was about 25-times lower than that formed on a Zircaloy-4 tube surface. In addition, both the ring compression and the tensile tests were performed to evaluate the adhesion properties of the Cr-coated sample. Although some cracks were formed on the Cr-coated layer, the Cr-coated layer had not peeled off after the two tests.

  17. Anodic Behavior of the Aluminum Current Collector in Imide-Based Electrolytes: Influence of Solvent, Operating Temperature, and Native Oxide-Layer Thickness.

    Science.gov (United States)

    Meister, Paul; Qi, Xin; Kloepsch, Richard; Krämer, Elisabeth; Streipert, Benjamin; Winter, Martin; Placke, Tobias

    2017-02-22

    The inability of imide salts to form a sufficiently effective passivation layer on aluminum current collectors is one of the main obstacles that limit their broad application in electrochemical energy-storage systems. However, under certain circumstances, the use of electrolytes with imide electrolyte salts in combination with the aluminum current collector is possible. In this contribution, the stability of the aluminum current collector in electrolytes containing either lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) or lithium fluorosulfonyl-(trifluoromethanesulfonyl) imide (LiFTFSI) as conductive salt was investigated by electrochemical techniques, that is, cyclic voltammetry (CV) and chronocoulometry (CC) in either room-temperature ionic liquids or in ethyl methyl sulfone. In particular, the influence of the solvent, operating temperature, and thickness of the native oxide layer of aluminum on the pit formation at the aluminum current collector surface was studied by means of scanning electron microscopy. In general, a more pronounced aluminum dissolution and pit formation was found at elevated temperatures as well as in solvents with a high dielectric constant. An enhanced thickness of the native aluminum oxide layer increases the oxidative stability versus dissolution. Furthermore, we found a different reaction rate depending on dwell time at the upper cut-off potential for aluminum dissolution in TFSI- and FTFSI-based electrolytes during the CC measurements; the use of LiFTFSI facilitated the dissolution of aluminum compared to LiTFSI. Overall, the mechanism of anodic aluminum dissolution is based on: i) the attack of the Al2 O3 surface by acidic species and ii) the dissolution of bare aluminum into the electrolyte, which, in turn, is influenced by the electrolyte's dielectric constant. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Low-temperature oxidizing plasma surface modification and composite polymer thin-film fabrication techniques for tailoring the composition and behavior of polymer surfaces

    Science.gov (United States)

    Tompkins, Brendan D.

    This dissertation examines methods for modifying the composition and behavior of polymer material surfaces. This is accomplished using (1) low-temperature low-density oxidizing plasmas to etch and implant new functionality on polymers, and (2) plasma enhanced chemical vapor deposition (PECVD) techniques to fabricate composite polymer materials. Emphases are placed on the structure of modified polymer surfaces, the evolution of polymer surfaces after treatment, and the species responsible for modifying polymers during plasma processing. H2O vapor plasma modification of high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), and 75A polyurethane (PU) was examined to further our understanding of polymer surface reorganization leading to hydrophobic recovery. Water contact angles (wCA) measurements showed that PP and PS were the most susceptible to hydrophobic recovery, while PC and HDPE were the most stable. X-ray photoelectron spectroscopy (XPS) revealed a significant quantity of polar functional groups on the surface of all treated polymer samples. Shifts in the C1s binding energies (BE) with sample age were measured on PP and PS, revealing that surface reorganization was responsible for hydrophobic recovery on these materials. Differential scanning calorimetry (DSC) was used to rule out the intrinsic thermal properties as the cause of reorganization and hydrophobic recovery on HDPE, LDPE, and PP. The different contributions that polymer cross-linking and chain scission mechanisms make to polymer aging effects are considered. The H2O plasma treatment technique was extended to the modification of 0.2 microm and 3.0 microm track-etched polycarbonate (PC-TE) and track-etched polyethylene terephthalate (PET-TE) membranes with the goal of permanently increasing the hydrophilicity of the membrane surfaces. Contact angle measurements on freshly treated and aged samples confirmed the wettability of the

  19. MR scanning, tattoo inks, and risk of thermal burn: An experimental study of iron oxide and organic pigments: Effect on temperature and magnetic behavior referenced to chemical analysis.

    Science.gov (United States)

    Alsing, K K; Johannesen, H H; Hvass Hansen, R; Dirks, M; Olsen, O; Serup, J

    2017-12-17

    Tattooed persons examined with magnetic resonance imaging (MRI) can develop burning sensation suggested in the literature to be thermal burn from the procedure. MRI-induced thermal effect and magnetic behavior of known tattoo pigments were examined ex vivo. Magnetic resonance imaging effects on 3 commonly used commercial ink stock products marketed for cosmetic tattooing was studied. A main study tested 22 formulations based on 11 pigment raw materials, for example, one line of 11 called pastes and another called dispersions. Samples were spread in petri dishes and tested with a 0.97 T neodymium solid magnet to observe visual magnetic behavior. Before MRI, the surface temperature of the ink was measured using an infrared probe. Samples were placed in a clinical 3T scanner. Two scans were performed, that is, one in the isocenter and one 30 cm away from the center. After scanning, the surface temperature was measured again. Chemical analysis of samples was performed by mass spectroscopy. Mean temperature increase measured in the isocenter ranged between 0.14 and 0.26°C (P tattoo pigments after MRI. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  20. Effect of the graphene oxide reduction temperature on supercapacitor performance

    Science.gov (United States)

    Choi, Eunmi; Kim, Jaekwang; Cui, Yinhua; Choi, Kyuho; Gao, Yuan; Han, Seunghee; Pyo, Sung Gyu; Yoon, Songhun

    2017-07-01

    In this study, we investigated the influence of the reduction temperature on graphene oxide. After performing the thermal reduction at specific temperatures (200, 600, and 1000 °C), the morphological and crystallographic changes were investigated by several analysis methods. The reduced graphene oxides were used as supercapacitor electrodes and analyzed with various electrochemical techniques. The capacitance exhibited an increase up to 600 °C before decreasing abruptly at 1000 °C. This behavior was ascribed to the limited ionic accessibility into the compact graphene layer.[Figure not available: see fulltext.

  1. Molybdenum Disilicide Oxidation Kinetics in High Temperature Steam

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Elizabeth Sooby [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Parker, Stephen Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Nelson, Andrew Thomas [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-09-07

    The Fuel Cycle Research and Development program’s Advanced Fuels Campaign is currently supporting a range of experimental efforts aimed at the development and qualification of ‘accident tolerant’ nuclear fuel forms. One route to enhance the accident tolerance of nuclear fuel is to replace the zirconium alloy cladding, which is prone to rapid oxidation in steam at elevated temperatures, with a more oxidation-resistant cladding. Several cladding replacement solutions have been envisaged. The cladding can be completely replaced with a more oxidation resistant alloy, a layered approach can be used to optimize the strength, creep resistance, and oxidation tolerance of various materials, or the existing zirconium alloy cladding can be coated with a more oxidation-resistant material. Molybdenum is one candidate cladding material favored due to its high temperature creep resistance. However, it performs poorly under autoclave testing and suffers degradation under high temperature steam oxidation exposure. Development of composite cladding architectures consisting of a molybdenum core shielded by a molybdenum disilicide (MoSi2) coating is hypothesized to improve the performance of a Mo-based cladding system. MoSi2 was identified based on its high temperature oxidation resistance in O2 atmospheres (e.g. air and “wet air”). However, its behavior in H2O is less known. This report presents thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and x-ray diffraction (XRD) results for MoSi2 exposed to 670-1498 K water vapor. Synthetic air (80-20%, Ar-O2) exposures were also performed, and those results are presented here for a comparative analysis. It was determined that MoSi2 displays drastically different oxidation behavior in water vapor than in dry air. In the 670-1498 K temperature range, four distinct behaviors are observed. Parabolic oxidation is exhibited in only 670

  2. Low temperature oxidation of hydrocarbons using an electrochemical reactor

    DEFF Research Database (Denmark)

    Ippolito, Davide

    at different reaction temperatures. The study of the effect of the infiltration of different electroactive materials on the electrode behavior has been carried on by the use of electrochemical impedance spectroscopy (EIS). Both the methods have been employed to understand the relationship between the catalytic...... the catalytic activity at open circuit voltage and the effect of polarization on propene oxidation rate at low temperature. The future development of this technology will see the infiltration of an active catalyst towards propene oxidation together with a NOx storage compound for the simultaneous oxidation...... high propene conversion at open circuit voltage together high rate enhancement ratio and faradaic efficiency values at low temperatures (300-350 °C). Although some stability problems affected the performance of multiple infiltrated Ce0.9Gd0.1O1.95 on LSM/CGO backbone, the strong activation of LSM upon...

  3. Hydrocarbon oxidation at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Warnatz, J.

    1983-11-01

    In this review it is described how, by suitable separation and elimination of unimportant reactions, a mechanism is developed with the aid of the present kinetic data for the elementary reactions involved. This mechanism explains, without fitting, the currently available experimental results for laminar premixed flames of alkanes, alkenes and acetylene. These experimental results are simulated by the solution of the corresponding conservation equations with suitable models describing diffusion and heat conduction in the multicomponent mixture considered. In lean and moderately rich flames the hydrocarbon is attacked by O, H, and OH in the first step. These radicals are produced by the chain-branching steps of the oxyhydrogen reaction. The alkyl radicals formed in this way always decompose to smaller alkyl radicals by fast thermal elimination of alkenes. Only the relatively slow thermal decomposition of the smallest alkyl radicals (CH/sub 3/ and C/sub 2/H/sub 5/) competes with recombination and with oxidation reactions by O atoms and O/sub 2/. This part of the mechanism is rate-controlling in the combustion of alkanes and alkenes, and is therefore the reason for the similarity of all alkane and alkene flames.

  4. Room temperature chemical oxidation of delafossite-type oxides

    Energy Technology Data Exchange (ETDEWEB)

    Trari, M.; Toepfer, J.; Doumerc, J.P.; Pouchard, M.; Hagenmuller, P. (Laboratoire de Chimie du Solide du CNRS, Talence (France)); Ammar, A. (Universite Cadi Ayyad, Marrakech (Morocco))

    1994-07-01

    Examination of the delafossite-type structure of CuLaO[sub 2] and CuYO[sub 2] suggests that there is room enough to accommodate intercalated oxide ions and the charge compensation resulting simply from the oxidation of an equivalent amount of Cu[sup +] into Cu[sup 2+]. Reaction with hypohalites in an aqueous solution leads to color change. Evidence of the formation of Cu[sup 2+] is given by TGA, iodometric titration, and magnetic (static and EPR) measurements. The obtained La and Y compounds seem to behave in a different way: Whereas CuLaO[sub 2+x] appears as a single phase, CuYO[sub 2+x] corresponds to a two-phase mixture, with respectively low and high x values, the latter being isostructural with the thermally oxidized compound recently reported. Comparison is stressed between the oxides obtained at higher temperatures.

  5. Gas detection using low-temperature reduced graphene oxide sheets

    Science.gov (United States)

    Lu, Ganhua; Ocola, Leonidas E.; Chen, Junhong

    2009-02-01

    We demonstrate a high-performance gas sensor using partially reduced graphene oxide (GO) sheets obtained through low-temperature step annealing (300 °C at maximum) in argon flow at atmospheric pressure. The electrical conductance of GO was measured after each heating cycle to interpret the level of reduction. The thermally reduced GO showed p-type semiconducting behavior in ambient conditions and were responsive to low-concentration NO2 diluted in air at room temperature. The sensitivity is attributed to the electron transfer from the reduced GO to adsorbed NO2, which leads to enriched hole concentration and enhanced electrical conduction in the reduced GO sheet.

  6. High temperature oxidation-sulfidation behavior of Cr-Al{sub 2}O{sub 3} and Nb-Al{sub 2}O{sub 3} composites densified by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Saucedo-Acuna, R.A. [Instituto e Ingenieria y Tecnologia, Universidad Autonoma de Cd. Juarez, Av. Del Charro 450 Norte, Col. Partido Romero, C.P. 32310, Cd. Juarez, Chihuahua (Mexico); Monreal-Romero, H.; Martinez-Villafane, A. [Centro de Investigacion en Materiales Avanzados, Departamento de Fisica de Materiales, Miguel de Cervantes 120, Complejo Industrial Chihuahua, C.P. 31109, Chihuahua (Mexico); Chacon-Nava, J.G. [Centro de Investigacion en Materiales Avanzados, Departamento de Fisica de Materiales, Miguel de Cervantes 120, Complejo Industrial Chihuahua, C.P. 31109, Chihuahua (Mexico)], E-mail: jose.chacon@cimav.edu.mx; Arce-Colunga, U. [Centro de Investigacion en Materiales Avanzados, Departamento de Fisica de Materiales, Miguel de Cervantes 120, Complejo Industrial Chihuahua, C.P. 31109, Chihuahua (Mexico); Universidad Autonoma de Tamaulipas, Matamoros 8 y 9 Col. Centro C.P. 87110, Cd. Victoria, Tamaulipas (Mexico); Gaona-Tiburcio, C. [Centro de Investigacion en Materiales Avanzados, Departamento de Fisica de Materiales, Miguel de Cervantes 120, Complejo Industrial Chihuahua, C.P. 31109, Chihuahua (Mexico); De la Torre, S.D. [Centro de Investigacion e Innovacion Tecnologica (CIITEC)-IPN, D.F. Mexico (Mexico)

    2007-12-15

    The high temperature oxidation-sulfidation behavior of Cr-Al{sub 2}O{sub 3} and Nb-Al{sub 2}O{sub 3} composites prepared by mechanical alloying (MA) and spark plasma sintering (SPS) has been studied. These composite powders have a particular metal-ceramic interpenetrating network and excellent mechanical properties. Oxidation-sulfidation tests were carried out at 900 deg. C, in a 2.5%SO{sub 2} + 3.6%O{sub 2} + N{sub 2}(balance) atmosphere for 48 h. The results revealed the influence of the sintering conditions on the specimens corrosion resistance, i.e. the Cr-Al{sub 2}O{sub 3} and Nb-Al{sub 2}O{sub 3} composite sintered at 1310 deg. C/4 min showed better corrosion resistance (lower weight gains) compared with those found for the 1440 deg. C/5 min conditions. For the former composite, a protective Cr{sub 2}O{sub 3} layer immediately forms upon heating, whereas for the later pest disintegration was noted. Thus, under the same sintering conditions the Nb-Al{sub 2}O{sub 3} composites showed the highest weight gains. The oxidation products were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy.

  7. Propene oxidation at low and intermediate temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Wilk, R.D.; Cernansky, N.P. (Drexel Univ., Philadelphia, PA (USA). Dept. of Mechanical Engineering); Pitz, W.J.; Westbrook, C.K. (Lawrence Livermore National Lab., CA (USA))

    1989-08-01

    A detailed chemical kinetic mechanism for propene oxidation is developed and used to model reactions in a static reactor at temperatures of 530-740 {Kappa}, equivalence ratios of 0.8-2.0, and a pressure of 600 torr. Modeling of hydrocarbon oxidation in this temperature range is important for the validation of detailed models to be used for performing calculations related to automotive engine knock. The model predicted induction periods and species concentrations for all the species and all conditions measured experimentally in the static reactor. Overall, the calculated concentrations of carbon monoxide and acetaldehyde agreed well with those measured. The calculated concentrations of ethene are low compared to the experimental measurements, and the calculated concentrations of the formaldehyde are high. Agreement for concentrations of carbon dioxide, methane, methanol, acrolein, and propene oxide is mixed. The characteristic s-shape of the fuel concentration history is well predicted. Modeling calculations identified some of the key reaction steps at the present conditions. Addition of OH to propene and H-atom abstraction by OH from propene are important steps in determining the subsequent distributions of intermediate products, such as acetaldehyde, acrolein and formaldehyde. Allyl radicals are very abundant in propene oxidation, and the primary steps found to be responsible for their consumption are reaction with HO/sub 2/ and CH/sub 3/O/sub 2/.

  8. Effect of temperature on the oxidation of soybean biodiesel

    Directory of Open Access Journals (Sweden)

    Pereira, G. G.

    2015-06-01

    Full Text Available This paper proposes to examine the effect of temperature on the oxidation behavior of biodiesel. Soybean biodiesel was oxidized at different temperatures (room temperature, 60, and 110 °C, and the increase in primary and secondary oxidation products was determined based on the peroxide and anisidine values, respectively, during the induction period (IP. The results indicated that the evolution of hydroperoxides followed zero-order reaction kinetics during the IP at all temperatures, and their rate of formation was exponentially affected by temperature. It was also deduced that temperature influenced the ratio between primary and secondary oxidation products formation, which decreased as the temperature increased. Additionally, it was possible to predict the oxidation behavior of the soybean biodiesel at room temperature by an exponential model fitted to the IP values at different temperatures (70, 80, 90, 100, and 110 °C using the Rancimat apparatus.El propósito de este trabajo es evaluar el efecto de la temperatura en el comportamiento oxidativo del biodiesel. Biodiesel derivado de aceite de soja fue oxidado a diferentes temperaturas (temperatura ambiente, 60 y 110 °C y se evaluaron el contenido de compuestos primarios y secundarios de oxidación mediante el índice de peróxidos y de anisidina, respectivamente, a lo largo del periodo de inducción. Los resultados indicaron que el contenido de hidroperóxidos evolucionó siguiendo una cinética de orden cero a lo largo del periodo de inducción a todas las temperaturas y que su velocidad de formación cambió exponencialmente con la temperatura. También se dedujo que la temperatura influyó en la relación entre la formación de los productos de oxidación primarios y secundarios, disminuyendo a medida que aumentaba la temperatura. Además, fue posible predecir el comportamiento oxidativo del biodiesel de soja a temperatura ambiente ajustando a un modelo exponencial los valores de periodo

  9. Microstructures and oxidation behavior of some Molybdenum based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ray, Pratik Kumar [Iowa State Univ., Ames, IA (United States)

    2011-01-01

    The advent of Ni based superalloys revolutionized the high temperature alloy industry. These materials are capable of operating in extremely harsh environments, comprising of temperatures around 1050 C, under oxidative conditions. Demands for increased fuel efficiency, however, has highlighted the need for materials that can be used under oxidative conditions at temperatures in excess of 1200 C. The Ni based superalloys are restricted to lower temperatures due to the presence of a number of low melting phases that melt in the 1250 - 1450 C, resulting in softening of the alloys above 1000 C. Therefore, recent research directions have been skewed towards exploring and developing newer alloy systems. This thesis comprises a part of such an effort. Techniques for rapid thermodynamic assessments were developed and applied to two different systems - Mo-Si alloys with transition metal substitutions (and this forms the first part of the thesis) and Ni-Al alloys with added components for providing high temperature strength and ductility. A hierarchical approach towards alloy design indicated the Mo-Ni-Al system as a prospective candidate for high temperature applications. Investigations on microstructures and oxidation behavior, under both isothermal and cyclic conditions, of these alloys constitute the second part of this thesis. It was seen that refractory metal systems show a marked microstructure dependence of oxidation.

  10. Intermediate Temperature Solid Oxide Fuel Cell Development

    Energy Technology Data Exchange (ETDEWEB)

    S. Elangovan; Scott Barnett; Sossina Haile

    2008-06-30

    Solid oxide fuel cells (SOFCs) are high efficiency energy conversion devices. Present materials set, using yttria stabilized zirconia (YSZ) electrolyte, limit the cell operating temperatures to 800 C or higher. It has become increasingly evident however that lowering the operating temperature would provide a more expeditious route to commercialization. The advantages of intermediate temperature (600 to 800 C) operation are related to both economic and materials issues. Lower operating temperature allows the use of low cost materials for the balance of plant and limits degradation arising from materials interactions. When the SOFC operating temperature is in the range of 600 to 700 C, it is also possible to partially reform hydrocarbon fuels within the stack providing additional system cost savings by reducing the air preheat heat-exchanger and blower size. The promise of Sr and Mg doped lanthanum gallate (LSGM) electrolyte materials, based on their high ionic conductivity and oxygen transference number at the intermediate temperature is well recognized. The focus of the present project was two-fold: (a) Identify a cell fabrication technique to achieve the benefits of lanthanum gallate material, and (b) Investigate alternative cathode materials that demonstrate low cathode polarization losses at the intermediate temperature. A porous matrix supported, thin film cell configuration was fabricated. The electrode material precursor was infiltrated into the porous matrix and the counter electrode was screen printed. Both anode and cathode infiltration produced high performance cells. Comparison of the two approaches showed that an infiltrated cathode cells may have advantages in high fuel utilization operations. Two new cathode materials were evaluated. Northwestern University investigated LSGM-ceria composite cathode while Caltech evaluated Ba-Sr-Co-Fe (BSCF) based pervoskite cathode. Both cathode materials showed lower polarization losses at temperatures as low as 600

  11. Observation of ferromagnetic semiconductor behavior in manganese-oxide doped graphene

    Directory of Open Access Journals (Sweden)

    Chang-Soo Park

    2014-08-01

    Full Text Available We have doped manganese-oxide onto graphene by an electrochemical method. Graphene showed a clear ferromagnetic semiconductor behavior after doping of manganese-oxide. The manganese-oxide doped graphene has a coercive field (Hc of 232 Oe at 10 K, and has the Curie temperature of 270 K from the temperature-dependent resistivity using transport measurement system. The ferromagnetism of manganese-oxide doped graphene attributes to the double-exchange from the coexistence of Mn3+ and Mn4+ on the surface of graphene. In addition, the semiconducting behavior is caused by the formation of manganese-oxide on graphene.

  12. Simulation of Fatigue Behavior of High Temperature Metal Matrix Composites

    Science.gov (United States)

    Tong, Mike T.; Singhal, Suren N.; Chamis, Christos C.; Murthy, Pappu L. N.

    1996-01-01

    A generalized relatively new approach is described for the computational simulation of fatigue behavior of high temperature metal matrix composites (HT-MMCs). This theory is embedded in a specialty-purpose computer code. The effectiveness of the computer code to predict the fatigue behavior of HT-MMCs is demonstrated by applying it to a silicon-fiber/titanium-matrix HT-MMC. Comparative results are shown for mechanical fatigue, thermal fatigue, thermomechanical (in-phase and out-of-phase) fatigue, as well as the effects of oxidizing environments on fatigue life. These results show that the new approach reproduces available experimental data remarkably well.

  13. Ultrasonic Studies and Microchannel Flow Behavior of Copper Oxide Nanofluid

    Science.gov (United States)

    Rashin, M. Nabeel; Hemalatha, J.; Nalini, R. Pratibha; Ramya, A. V.

    2011-07-01

    Stable suspensions of nanosized copper oxide nanoparticles in Ethylene glycol are prepared at various concentrations through ultrasonically assisted sol gel method. The structural studies are made through X-ray diffraction technique and the nanoparticle-fluid interaction studies are made through acoustical technique. The molecular interaction is studied as a function of concentration and temperature. The flow behaviors of nanofluids of various concentrations are investigated using the circular and rectangular microchannels of various diameters.

  14. Oxidation behavior of U-Si compounds in air from 25 to 1000 C

    Science.gov (United States)

    Sooby Wood, E.; White, J. T.; Nelson, A. T.

    2017-02-01

    The air oxidation behavior of U3Si2, USi, and U3Si5 is studied from room temperature to 1000 C. The onsets of breakaway oxidation for each compound are identified during synthetic air ramps to 1000 C using thermogravimetric analysis. Isothermal air oxidation tests are performed below and above the breakaway oxidation onset to discern the oxidation kinetic behavior of these candidate accident tolerant fuel forms. Uranium metal is tested in the same manner to provide a reference for the oxidation behavior. Thermogravimetric, x-ray diffraction, and scanning electron microscopy analysis are presented here along with a discussion of the oxidation behavior of these materials and the impact of the lack of oxidation resistance to their deployment as accident tolerant nuclear fuels.

  15. Rheological behavior of oxide nanopowder suspensions

    Science.gov (United States)

    Cinar, Simge

    Ceramic nanopowders offer great potential in advanced ceramic materials and many other technologically important applications. Because a material's rheological properties are crucial for most processing routes, control of the rheological behavior has drawn significant attention in the recent past. The control of rheological behavior relies on an understanding of how different parameters affect the suspension viscosities. Even though the suspension stabilization mechanisms are relatively well understood for sub-micron and micron size particle systems, this knowledge cannot be directly transferred to nanopowder suspensions. Nanopowder suspensions exhibit unexpectedly high viscosities that cannot be explained with conventional mechanisms and are still a topic of investigation. This dissertation aims to establish the critical parameters governing the rheological behavior of concentrated oxide nanopowder suspensions, and to elucidate the mechanisms by which these parameters control the rheology of these suspensions. Aqueous alumina nanopowders were chosen as a model system, and the findings were extrapolated to other oxide nanopowder systems such as zirconia, yttria stabilized zirconia, and titania. Processing additives such as fructose, NaCl, HCl, NaOH, and ascorbic acid were used in this study. The effect of solids content and addition of fructose on the viscosity of alumina nanopowder suspensions was investigated by low temperature differential scanning calorimetry (LT-DSC), rheological, and zeta potential measurements. The analysis of bound water events observed in LT-DSC revealed useful information regarding the rheological behavior of nanopowder suspensions. Because of the significance of interparticle interactions in nanopowder suspensions, the electrostatic stabilization was investigated using indifferent and potential determining ions. Different mechanisms, e.g., the effect of the change in effective volume fraction caused by fructose addition and electrostatic

  16. Study of nitric oxide catalytic oxidation on manganese oxides-loaded activated carbon at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    You, Fu-Tian [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); University of Chinese Academy of Sciences, Beijing (China); Yu, Guang-Wei, E-mail: gwyu@iue.ac.cn [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); Wang, Yin, E-mail: yinwang@iue.ac.cn [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); Xing, Zhen-Jiao [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); Liu, Xue-Jiao; Li, Jie [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); University of Chinese Academy of Sciences, Beijing (China)

    2017-08-15

    Highlights: • Loading manganese oxides on activated carbon effectively promotes NO oxidation. • NO adsorption-desorption on activated carbon is fundamental to NO oxidation. • A high Mn{sup 4+}/Mn{sup 3+} ratio contributes to NO oxidation by promoting lattice O transfer. - Abstract: Nitric oxide (NO) is an air pollutant that is difficult to remove at low concentration and low temperature. Manganese oxides (MnO{sub x})-loaded activated carbon (MLAC) was prepared by a co-precipitation method and studied as a new catalyst for NO oxidation at low temperature. Characterization of MLAC included X-ray diffraction (XRD), scanning electron microscopy (SEM), N{sub 2} adsorption/desorption and X-ray photoelectron spectroscopy (XPS). Activity tests demonstrated the influence of the amount of MnO{sub x} and the test conditions on the reaction. MLAC with 7.5 wt.% MnO{sub x} (MLAC003) exhibits the highest NO conversion (38.7%) at 1000 ppm NO, 20 vol.% O{sub 2}, room temperature and GHSV ca. 16000 h{sup −1}. The NO conversion of MLAC003 was elevated by 26% compared with that of activated carbon. The results of the MLAC003 activity test under different test conditions demonstrated that NO conversion is also influenced by inlet NO concentration, inlet O{sub 2} concentration, reaction temperature and GHSV. The NO adsorption-desorption process in micropores of activated carbon is fundamental to NO oxidation, which can be controlled by pore structure and reaction temperature. The activity elevation caused by MnO{sub x} loading is assumed to be related to Mn{sup 4+}/Mn{sup 3+} ratio. Finally, a mechanism of NO catalytic oxidation on MLAC based on NO adsorption-desorption and MnO{sub x} lattice O transfer is proposed.

  17. Gallium Oxide Nanostructures for High Temperature Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Chintalapalle, Ramana V. [Univ. of Texas, El Paso, TX (United States)

    2015-04-30

    Gallium oxide (Ga2O3) thin films were produced by sputter deposition by varying the substrate temperature (Ts) in a wide range (Ts=25-800 °C). The structural characteristics and electronic properties of Ga2O3 films were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), Rutherford backscattering spectrometry (RBS) and spectrophotometric measurements. The effect of growth temperature is significant on the chemistry, crystal structure and morphology of Ga2O3 films. XRD and SEM analyses indicate that the Ga2O3 films grown at lower temperatures were amorphous while those grown at Ts≥500 oC were nanocrystalline. RBS measurements indicate the well-maintained stoichiometry of Ga2O3 films at Ts=300-800 °C. The electronic structure determination indicated that the nanocrystalline Ga2O3films exhibit a band gap of ~5 eV. Tungsten (W) incorporated Ga2O3 films were produced by co-sputter deposition. W-concentration was varied by the applied sputtering-power. No secondary phase formation was observed in W-incorporated Ga2O3 films. W-induced effects were significant on the structure and electronic properties of Ga2O3 films. The band gap of Ga2O3 films without W-incorporation was ~5 eV. Oxygen sensor characteristics evaluated using optical and electrical methods indicate a faster response in W-doped Ga2O3 films compared to intrinsic Ga2O3 films. The results demonstrate the applicability of both intrinsic and W-doped Ga-oxide films for oxygen sensor application at temperatures ≥700 °C.

  18. Study of nitric oxide catalytic oxidation on manganese oxides-loaded activated carbon at low temperature

    Science.gov (United States)

    You, Fu-Tian; Yu, Guang-Wei; Wang, Yin; Xing, Zhen-Jiao; Liu, Xue-Jiao; Li, Jie

    2017-08-01

    Nitric oxide (NO) is an air pollutant that is difficult to remove at low concentration and low temperature. Manganese oxides (MnOx)-loaded activated carbon (MLAC) was prepared by a co-precipitation method and studied as a new catalyst for NO oxidation at low temperature. Characterization of MLAC included X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption/desorption and X-ray photoelectron spectroscopy (XPS). Activity tests demonstrated the influence of the amount of MnOx and the test conditions on the reaction. MLAC with 7.5 wt.% MnOx (MLAC003) exhibits the highest NO conversion (38.7%) at 1000 ppm NO, 20 vol.% O2, room temperature and GHSV ca. 16000 h-1. The NO conversion of MLAC003 was elevated by 26% compared with that of activated carbon. The results of the MLAC003 activity test under different test conditions demonstrated that NO conversion is also influenced by inlet NO concentration, inlet O2 concentration, reaction temperature and GHSV. The NO adsorption-desorption process in micropores of activated carbon is fundamental to NO oxidation, which can be controlled by pore structure and reaction temperature. The activity elevation caused by MnOx loading is assumed to be related to Mn4+/Mn3+ ratio. Finally, a mechanism of NO catalytic oxidation on MLAC based on NO adsorption-desorption and MnOx lattice O transfer is proposed.

  19. Oxidation Behavior of Matrix Graphite and Its Effect on Compressive Strength

    Directory of Open Access Journals (Sweden)

    Xiangwen Zhou

    2017-01-01

    Full Text Available Matrix graphite (MG with incompletely graphitized binder used in high-temperature gas-cooled reactors (HTGRs is commonly suspected to exhibit lower oxidation resistance in air. In order to reveal the oxidation performance, the oxidation behavior of newly developed A3-3 MG at the temperature range from 500 to 950°C in air was studied and the effect of oxidation on the compressive strength of oxidized MG specimens was characterized. Results show that temperature has a significant influence on the oxidation behavior of MG. The transition temperature between Regimes I and II is ~700°C and the activation energy (Ea in Regime I is around 185 kJ/mol, a little lower than that of nuclear graphite, which indicates MG is more vulnerable to oxidation. Oxidation at 550°C causes more damage to compressive strength of MG than oxidation at 900°C. Comparing with the strength of pristine MG specimens, the rate of compressive strength loss is 77.3% after oxidation at 550°C and only 12.5% for oxidation at 900°C. Microstructure images of SEM and porosity measurement by Mercury Porosimetry indicate that the significant compressive strength loss of MG oxidized at 550°C may be attributed to both the uniform pore formation throughout the bulk and the preferential oxidation of the binder.

  20. High-temperature Oxidation of Fe-Cr Steels in Steam Condition – A Review

    Directory of Open Access Journals (Sweden)

    Tedi Kurniawan

    2016-05-01

    Full Text Available The development of supercritical (SC and ultra-supercritical (USC power plants requires materials with better corrosion properties. Deep understanding on the oxidation mechanism in the boiler environment is one of the important factors to support this development. In this work, high temperature oxidation of Fe-Cr steels in steam condition is reviewed.  Several mechanisms that explain the effect of water vapor in the oxidation behavior the steel were presented.

  1. Magnetic behavior of the oxide spinels:

    Indian Academy of Sciences (India)

    Magnetic behavior of the oxide spinels: Li0.5Fe2.5−2xAlxCrxO4. U N TRIVEDI, K B MODI and H H JOSHI. Department of Physics, Saurashtra University, Rajkot 360 005, India. Abstract. In order to study the effect of substitution of Fe3+ by Al3+ and Cr3+ in Li0.5Fe2.5O4 on its structural and magnetic properties, the spinel ...

  2. Reduced graphene oxide for room-temperature gas sensors

    Energy Technology Data Exchange (ETDEWEB)

    Lu Ganhua; Chen Junhong [Department of Mechanical Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI 53211 (United States); Ocola, Leonidas E, E-mail: jhchen@uwm.ed [Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2009-11-04

    We demonstrated high-performance gas sensors based on graphene oxide (GO) sheets partially reduced via low-temperature thermal treatments. Hydrophilic graphene oxide sheets uniformly suspended in water were first dispersed onto gold interdigitated electrodes. The partial reduction of the GO sheets was then achieved through low-temperature, multi-step annealing (100, 200, and 300 {sup 0}C) or one-step heating (200 {sup 0}C) of the device in argon flow at atmospheric pressure. The electrical conductance of GO was measured after each heating cycle to interpret the level of reduction. The thermally-reduced GO showed p-type semiconducting behavior in ambient conditions and was responsive to low-concentration NO{sub 2} and NH{sub 3} gases diluted in air at room temperature. The sensitivity can be attributed mainly to the electron transfer between the reduced GO and adsorbed gaseous molecules (NO{sub 2}/NH{sub 3}). Additionally, the contact between GO and the Au electrode is likely to contribute to the overall sensing response because of the adsorbates-induced Schottky barrier variation. A simplified model is used to explain the experimental observations.

  3. Reduced graphene oxide for room-temperature gas sensors.

    Science.gov (United States)

    Lu, Ganhua; Ocola, Leonidas E; Chen, Junhong

    2009-11-04

    We demonstrated high-performance gas sensors based on graphene oxide (GO) sheets partially reduced via low-temperature thermal treatments. Hydrophilic graphene oxide sheets uniformly suspended in water were first dispersed onto gold interdigitated electrodes. The partial reduction of the GO sheets was then achieved through low-temperature, multi-step annealing (100, 200, and 300 degrees C) or one-step heating (200 degrees C) of the device in argon flow at atmospheric pressure. The electrical conductance of GO was measured after each heating cycle to interpret the level of reduction. The thermally-reduced GO showed p-type semiconducting behavior in ambient conditions and was responsive to low-concentration NO2 and NH3 gases diluted in air at room temperature. The sensitivity can be attributed mainly to the electron transfer between the reduced GO and adsorbed gaseous molecules (NO2/NH3). Additionally, the contact between GO and the Au electrode is likely to contribute to the overall sensing response because of the adsorbates-induced Schottky barrier variation. A simplified model is used to explain the experimental observations.

  4. Reduced graphene oxide for room-temperature gas sensors

    Science.gov (United States)

    Lu, Ganhua; Ocola, Leonidas E.; Chen, Junhong

    2009-11-01

    We demonstrated high-performance gas sensors based on graphene oxide (GO) sheets partially reduced via low-temperature thermal treatments. Hydrophilic graphene oxide sheets uniformly suspended in water were first dispersed onto gold interdigitated electrodes. The partial reduction of the GO sheets was then achieved through low-temperature, multi-step annealing (100, 200, and 300 °C) or one-step heating (200 °C) of the device in argon flow at atmospheric pressure. The electrical conductance of GO was measured after each heating cycle to interpret the level of reduction. The thermally-reduced GO showed p-type semiconducting behavior in ambient conditions and was responsive to low-concentration NO2 and NH3 gases diluted in air at room temperature. The sensitivity can be attributed mainly to the electron transfer between the reduced GO and adsorbed gaseous molecules (NO2/NH3). Additionally, the contact between GO and the Au electrode is likely to contribute to the overall sensing response because of the adsorbates-induced Schottky barrier variation. A simplified model is used to explain the experimental observations.

  5. Oxidation behavior and thermal stability of a NiAl-Veutectic alloy

    Energy Technology Data Exchange (ETDEWEB)

    Milenkovic, Srdjan [IMDEA Materials Institute, Eric Kandel 2, 28906 Getafe, Madrid (Spain); Caram, Rubens [Department of Materials Science and Engineering, State University of Campinas, P.O. 6122, 13083-970 Campinas, SP (Brazil)

    2013-05-15

    Oxidation behavior and thermal stability of a NiAl-V alloy with eutectic composition processed by directional solidification technique has been investigated. The surface analysis at the elevated temperature indicated that the investigated microstructures are stable at the isothermal conditions and an inert atmosphere. The oxidation testing in the synthetic air showed that the temperature of 400 C is critical. In addition, the oxidation of the NiAl-V eutectic alloy is characterized by: (a) alteration of composition immediately below the surface substrate/oxide; (b) formation of the oxide layer rich in V, adherent to the substrate; and (c) formation of external oxide layer that presents oxide mixture formed by vanadium, nickel, and aluminum. Microstructure of the substrate/oxide interface of NiAl-V alloy oxidized at 900 C for 24 h. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Fracture behavior of C/SiC composites at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Dong Hyun; Lee, Jeong Won; Kim, Jae Hoon; Shin, Ihn Cheol; Lim, Byung Joo [Chungnam National University, Daejeon (Korea, Republic of)

    2017-08-15

    The fracture behavior of carbon fiber-reinforced silicon carbide (C/SiC) composites used in rocket nozzles has been investigated under tension, compression, and fracture conditions at room temperature, 773 K and 1173 K. The C/SiC composites used in this study were manufactured by liquid silicon infiltration process at ~1723 K. All experiments were conducted using two types of specimens, considering fiber direction and oxidation condition. Experimental results show that temperature, fiber direction, and oxidation condition affect the behavior of C/SiC composites. Oxidation was found to be the main factor that changes the strength of C/SiC composites. By applying an anti-oxidation coating, the tensile and compressive strengths of the C/SiC composites increased with temperature. The fracture toughness of the C/SiC composites also increased with increase temperature. A fractography analysis of the fractured specimens was conducted using a scanning electron microscope.

  7. Magnetocaloric effect at cryogenic temperature in gadolinium oxide nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Rima, E-mail: rima.paul@saha.ac.in [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Paramanik, Tapas; Das, Kalipada [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Sen, Pintu [Variable Energy Cyclotron Centre, 1/AF Bidhannagar, Kolkata 700064 (India); Satpati, B.; Das, I. [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)

    2016-11-01

    We have synthesized fascinating nano-structure of Gadolinium oxide (Gd{sub 2}O{sub 3}) using controlled template-assisted electrochemical deposition technique which showed interesting anisotropic magnetic behavior. The nanotubes of Gd{sub 2}O{sub 3} with average diameter 200 nm, length 10 µm and wall thickness 20 nm are constituted of nanoclusters with average diameter 7.5 nm. The tubes are aligned and are almost uniform throughout their length. Detailed magnetic measurements of aligned Gd{sub 2}O{sub 3} nanotubes have been performed for both parallel and perpendicular magnetic field orientations with respect to the axis of the Gd{sub 2}O{sub 3} nanotube array. Significant differences in magnetization values have been observed between the parallel and perpendicular orientations. Experimental results indicate the superparamagnetic nature of the nanomaterial. Large magnetocaloric effect, associated with the sharp change in magnetization of the Gd{sub 2}O{sub 3} nanotubes, has been observed in the cryogenic temperature regime that shows anisotropic behavior. - Highlights: • Gd{sub 2}O{sub 3} nanotubes of diameter ~200 nm synthesized through electrochemical technique. • The nanotubes are superparamagnetic in nature. • At cryogenic temperature, the nanotubes exhibit large magnetocaloric anisotropic effect.

  8. Observation of ferromagnetic semiconductor behavior in manganese-oxide doped graphene

    OpenAIRE

    Chang-Soo Park; Yu Zhao; Yoon Shon; Chong S. Yoon; Haigun Lee; Cheol Jin Lee

    2014-01-01

    We have doped manganese-oxide onto graphene by an electrochemical method. Graphene showed a clear ferromagnetic semiconductor behavior after doping of manganese-oxide. The manganese-oxide doped graphene has a coercive field (Hc) of 232 Oe at 10 K, and has the Curie temperature of 270 K from the temperature-dependent resistivity using transport measurement system. The ferromagnetism of manganese-oxide doped graphene attributes to the double-exchange from the coexistence of Mn3+ and Mn4+ on the...

  9. High-temperature wear and oxidation behaviors of TiNi/Ti2Ni matrix composite coatings with TaC addition prepared on Ti6Al4V by laser cladding

    Science.gov (United States)

    Lv, Y. H.; Li, J.; Tao, Y. F.; Hu, L. F.

    2017-04-01

    TiNi/Ti2Ni matrix composite coatings were produced on Ti6Al4V surfaces by laser cladding the mixed powders of Ni-based alloy and different contents of TaC (0, 5, 10, 15, 20, 30 and 40 wt.%). Microstructures of the coatings were investigated. High-temperature wear tests of the substrate and the coatings were carried out at 600 °C in air for 30 min. High-temperature oxidation tests of the substrate and the coatings were performed at 1000 °C in air for 50 h. Wear and oxidation mechanisms were revealed in detail. The results showed that TiNi/Ti2Ni as the matrix and TiC/TiB2/TiB as the reinforcements are the main phases of the coatings. The friction coefficients of the substrate and the coatings with different contents of TaC were 0.431 (the substrate), 0.554 (0 wt.%), 0.486 (5 wt.%), 0.457 (10 wt.%), 0.458 (15 wt.%), 0.507 (20 wt.%), 0.462 (30 wt.%) and 0.488 (40 wt.%). The wear rates of the coatings were decreased by almost 83%-98% than that of the substrate and presented a decreasing tendency with increasing TaC content. The wear mechanism of the substrate was a combination of serious oxidation, micro-cutting and brittle debonding. For the coatings, oxidation and slight scratching were predominant during wear, accompanied by slight brittle debonding in partial zones. With the increase in content of TaC, the oxidation film better shielded the coatings from destruction due to the effective friction-reducing role of Ta2O5. The oxidation rates of the substrate and the coatings with different contents of TaC at 1000 °C were 12.170 (the substrate), 5.886 (0 wt.%), 4.937 (5 wt.%), 4.517 (10 wt.%), 4.394 (15 wt.%), 3.951 (20 wt.%), 4.239 (30 wt.%) and 3.530 (40 wt.%) mg2 cm-4 h-1, respectively. The oxidation film formed outside the coating without adding TaC was composed of TiO2, NiO, Cr2O3, Al2O3 and SiO2. When TaC was added, Ta2O5 and TaC were also detected, which effectively improved the oxidation resistance of the coatings. The addition of TaC contributed to the

  10. Room temperature ferromagnetic and semiconducting properties of graphene adsorbed with cobalt oxide using electrochemical method

    Science.gov (United States)

    Park, Chang-Soo; Lee, Kyung Su; Chu, Dongil; Lee, Juwon; Shon, Yoon; Kim, Eun Kyu

    2017-12-01

    We report the room temperature ferromagnetic properties of graphene adsorbed by cobalt oxide using electrochemical method. The cobalt oxide doping onto graphene was carried out in 0.1 M LiCoO2/DI-water solution. The doped graphene thin film was determined to be a single layer from Raman analysis. The CoO doped graphene has a clear ferromagnetic hysteresis at room temperature and showed a remnant magnetization, 128.2 emu/cm3. The temperature dependent conductivity of the adsorbed graphene showed the semiconducting behavior and a band gap opening of 0.12 eV.

  11. Low Temperature Processed Complementary Metal Oxide Semiconductor (CMOS) Device by Oxidation Effect from Capping Layer

    KAUST Repository

    Wang, Zhenwei

    2015-04-20

    In this report, both p- and n-type tin oxide thin-film transistors (TFTs) were simultaneously achieved using single-step deposition of the tin oxide channel layer. The tuning of charge carrier polarity in the tin oxide channel is achieved by selectively depositing a copper oxide capping layer on top of tin oxide, which serves as an oxygen source, providing additional oxygen to form an n-type tin dioxide phase. The oxidation process can be realized by annealing at temperature as low as 190°C in air, which is significantly lower than the temperature generally required to form tin dioxide. Based on this approach, CMOS inverters based entirely on tin oxide TFTs were fabricated. Our method provides a solution to lower the process temperature for tin dioxide phase, which facilitates the application of this transparent oxide semiconductor in emerging electronic devices field.

  12. High-Temperature Oxide Regrowth on Mechanically-Damaged Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Blau, Peter Julian [ORNL; Lowe, Tracie M [ORNL

    2008-01-01

    Here we report the effects of mechanical damage from a sharp stylus on the regrowth of oxide layers on a Ni-based superalloy known as Pyromet 80A . It was found that the oxide that reformed on the damaged portion of a pre-oxidized surface differed from that which formed on undamaged areas after the equal exposures to elevated temperature in air. These findings have broad implications for modeling the processes of material degradation in applications such as exhaust valves in internal combustion engines because they imply that static oxidation data for candidate materials may not adequately reflect their reaction to operating environments that involve both mechanical contact and oxidation.

  13. Determination of the initial oxidation behavior of Zircaloy-4 by in-situ TEM

    Energy Technology Data Exchange (ETDEWEB)

    Harlow, Wayne; Ghassemi, Hessam; Taheri, Mitra L., E-mail: mtaheri@coe.drexel.edu

    2016-06-15

    The corrosion behavior of Zircaloy-4 (Zry-4), specifically by oxidation, is a problem of great importance as this material is critical for current nuclear reactor cladding. The early formation behavior and structure of the oxide layer during oxidation was studied using in-situ TEM techniques that allowed for Zry-4 to be monitored during corrosion. These environmental exposure experiments were coupled with precession electron diffraction to identify and quantify the phases present in the samples before and after the oxidation. Following short-term, high temperature oxidation, the dominant phase was revealed to be monoclinic ZrO{sub 2} in a columnar structure. These samples oxidized in-situ contained structures that correlated well with bulk Zry-4 subjected to autoclave treatment, which were used for comparison and validation of this technique. By using in-situ TEM the effect of microstructure features, such as grain boundaries, on oxidation behavior of an alloy can be studied. The technique presented herein holds the potential to be applied any alloy system to study these effects. - Highlights: • In-situ TEM was used to oxidize samples of Zircaloy-4. • Similar behavior was found in the in-situ oxidized and autoclave-oxidized samples. • Precession diffraction was used to characterize oxide phase and texture.

  14. Resistance to High-Temperature Oxidation and Wear of Various Ferrous Alloys Used in Rolling Mills

    Science.gov (United States)

    Delaunois, Fabienne; Stanciu, Victor Ioan; Sinnaeve, Mario

    2018-01-01

    Various materials are commonly used to manufacture work rolls for hot rolling mills, such as ICDP (Indefinite Chill Double Pour) cast irons, high-chromium white cast irons, and high speed steels (HSS). Various chemical compositions and microstructures are studied in order to optimize the in-use behavior of those grades of rolls. In this paper, six grades of ferrous alloys (an ICDP cast iron; an ICDP cast iron enriched in vanadium, niobium, and molybdenum; a HSS; a graphitic HSS; a high-chromium white cast iron (Hi-Cr); and a niobium-molybdenum-doped high-chromium white cast iron) were investigated. High-temperature oxidation tests with gravimetric means at 575 °C in water vapor atmosphere and sliding wear tests were carried out. The oxidation kinetics was followed during oxidation test. The microstructure was observed by optical and scanning electron microscopies. The oxides formed on the surface of the samples were analyzed by XRD and EDS. The thickness of the oxide scales and the mass gain were measured after oxidation test. The results showed that the behavior of all the grades differed. The oxide scale of HSS and HSS-G grades was fine and their friction coefficient was low. The weight gain after oxidation test of HSS was high. Hi-Cr and M-Hi-Cr grades presented highly porous oxide layer and an important increase of the friction coefficient during wear test. ICDP and M-ICDP had intermediate behavior.

  15. Indentation Behavior of Permanently Densified Oxide Glasses

    DEFF Research Database (Denmark)

    Bechgaard, Tobias Kjær; Januchta, Kacper; Kapoor, Saurabh

    Hot isostatic compression can be used as a post treatment method to tune the properties of glass materials as well as to obtain improved understanding of the pressure-induced structural changes and densification mechanisms, e.g., during sharp contact loading. Here, we review the pressure-induced ......Hot isostatic compression can be used as a post treatment method to tune the properties of glass materials as well as to obtain improved understanding of the pressure-induced structural changes and densification mechanisms, e.g., during sharp contact loading. Here, we review the pressure......-induced changes in density, structure, and indentation behavior of a range of oxide glasses, including silicates, borates, and phosphates. The effect of compression on the structure is analyzed through both Raman and NMR spectroscopy, while the mechanical properties are investigated using Vickers micro...... number distribution of network formers, the number of non-bridging oxygens, and the packing efficiency in the glasses....

  16. Application of hydrogen injection and oxidation to low temperature solution-processed oxide semiconductors

    Directory of Open Access Journals (Sweden)

    Masashi Miyakawa

    2016-08-01

    Full Text Available Solution-processed oxide semiconductors are promising candidates for the low cost, large scale fabrication of oxide thin-film transistors (TFTs. In this work, a method using hydrogen injection and oxidation (HIO that allows the low temperature solution processing of oxide semiconductors was demonstrated. We found that this method significantly decreases the concentration of residual species while improving the film densification. Additionally, enhanced TFT performance was confirmed following the use of processing temperatures as low as 300 °C. The proposed process is potentially applicable to the fabrication of a wide variety of solution-processed oxide semiconductors.

  17. Effect of oxidation and annealing temperature on optical and ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 37; Issue 3. Effect of oxidation and ... Keywords. SnO2 thin films; optical properties; optical bandgap; Urbach energy; surface roughness; XRD. ... The effect of oxidation temperature on the optical and structural properties of SnO2 films were investigated. Higher ...

  18. Effect of oxidation and annealing temperature on optical and ...

    Indian Academy of Sciences (India)

    Administrator

    which means that initial oxidation temperature played an important role on surface uniformity of SnO2 thin films. Keywords. SnO2 thin films; optical properties; optical bandgap; Urbach energy; surface roughness; XRD. 1. Introduction. Tin oxide belongs to a class of materials that have suitable electrical conductivity and high ...

  19. Propane Oxidation at High Pressure and Intermediate Temperatures

    DEFF Research Database (Denmark)

    Hashemi, Hamid; Christensen, Jakob Munkholt; Glarborg, Peter

    Propane oxidation at intermediate temperatures (500—900 K) and high pressure (100 bar) has been characterized by conducting experiments in a laminar flow reactor over a wide range of stoichiometries. The onset of fuel oxidation was found to be 600—725 K, depending on mixture stoichiometry...

  20. High temperature oxidation of slurry coated interconnect alloys

    DEFF Research Database (Denmark)

    Persson, Åsa Helen

    with this interaction mechanism mainly give a geometrical protection against oxidation by blocking oxygen access at the surface of the oxide scale. The protecting effect is gradually reduced as the oxide scale grows thicker than the diameter of the coating particles. Interaction mechanism B entails a chemical reaction.......85Sr0.15)CoO3 + 10% Co3O4, LSC, coatings were found to be relatively successful in decreasing the oxidation rate, the chromium content in the outermost part of ii the dense scale, and the electrical resistance in the growing oxide scales when applied onto Crofer 22APU. But, the positive effects......In this project, high temperature oxidation experiments of slurry coated ferritic alloys in atmospheres similar to the atmosphere found at the cathode in an SOFC were conducted. From the observations possible interaction mechanisms between the slurry coatings and the growing oxide scale...

  1. Transient analysis of nuclear graphite oxidation for high temperature gas cooled reactor

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Wei, E-mail: wxu12@mails.tsinghua.edu.cn; Shi, Lei; Zheng, Yanhua

    2016-09-15

    Graphite is widely used as moderator, reflector and structural materials in the high temperature gas-cooled reactor pebble-bed modular (HTR-PM). In normal operating conditions or water/air ingress accident, the nuclear graphite in the reactor may be oxidized by air or steam. Oxidation behavior of nuclear graphite IG-110 which is used as the structural materials and reflector of HTR-PM is mainly researched in this paper. To investigate the penetration depth of oxygen in IG-110, this paper developed the one dimensional spherical oxidation model. In the oxidation model, the equations considered graphite porosity variation with the graphite weight loss. The effect of weight loss on the effective diffusion coefficient and the oxidation rate was also considered in this model. Based on this theoretical model, this paper obtained the relative concentration and local weight loss ratio profile in graphite. In addition, the local effective diffusion coefficient and oxidation rate in the graphite were also investigated.

  2. Oxidation and thermal behavior of Jatropha curcas biodiesel ...

    African Journals Online (AJOL)

    Oxidation and thermal behavior of Jatropha curcas biodiesel influenced by antioxidants and metal contaminants. ... International Journal of Engineering, Science and Technology. Journal Home ... The present paper is dealing with the study of oxidation and thermal behavior of JCB with respect to different metal contents.

  3. High temperature heterogeneous reaction kinetics and mechanisms of tungsten oxidation

    Science.gov (United States)

    Sabourin, Justin L.

    Tungsten, which is a material used in many high temperature applications, is limited by its susceptibility to oxidation at elevated temperatures. Although tungsten has the highest melting temperature of any metal, at much lower temperatures volatile oxides are formed during oxidation with oxygen containing species. This differs from many heterogeneous oxidation reactions involving metals since most reactions form very stable oxides that have higher melting or boiling points than the pure metal (e.g., aluminum, iron). Understanding heterogeneous oxidation and vaporization processes may allow for the expansion and improvement of high temperature tungsten applications. In order to increase understanding of the oxidation processes of tungsten, there is a need to develop reaction mechanisms and kinetics for oxidation processes involving oxidizers and environmental conditions of interest. Tungsten oxidation was thoroughly studied in the past, and today there is a good phenomenological understanding of these processes. However, as the design of large scale systems increasingly relies on computer modeling there becomes a need for improved descriptions of chemical reactions. With the increase in computing power over the last several decades, and the development of quantum chemistry and physics theories, heterogeneous systems can be modeled in detail at the molecular level. Thermochemical parameters that may not be measured experimentally may now be determined theoretically, a tool that was previously unavailable to scientists and engineers. Additionally, chemical kinetic modeling software is now available for both homogeneous and heterogeneous reactions. This study takes advantage of these new theoretical tools, as well as a thermogravimetric (TG) flow reactor developed as part of this study to learn about mechanisms and kinetics of tungsten oxidation. Oxidizers of interest are oxygen (O2), carbon dioxide (CO 2), water (H2O), and other oxidizers present in combustion and

  4. Temperature effects on surface activity and application in oxidation ...

    Indian Academy of Sciences (India)

    Correspondingly, the CMC of CTAB-SDS decreases almost by half. The increase of surface activity of CTAB-SDS can be attributed to the relatively weak electrostatic interaction at high temperature, which is supported by the increase of solubility of CTAB-SDS with rise in temperature. Catalytic effect on oxidation of toluene ...

  5. High Temperature Strength of Oxide Dispersion Strengthened Aluminium

    DEFF Research Database (Denmark)

    Clauer, A.H.; Hansen, Niels

    1984-01-01

    The tensile flow stress of coarse-grained dispersion strengthened Al-Al2O3 materials were measured as a function of temperature (77–873 K) and volume fraction (0.19-0.92 vol.%) of aluminium oxide. For the same material, the creep strength was determined as a function of temperature in the range 573...

  6. Effect of surface deposited rare earth oxide gel characteristics on cyclic oxidation behavior of Fe20-Cr alloys

    Directory of Open Access Journals (Sweden)

    Stela Maria Cristina Fernandes

    2006-06-01

    Full Text Available Rare earths have been used to increase high temperature oxidation resistance of many chromium dioxide and alumina forming alloys. These rare earths can be added as elements (or as oxide dispersions to the alloys or applied as an oxide coating to the alloy surface. The sol-gel technique is considered to be very efficient to apply fine oxide particle coatings. Oxide gel coatings of various rare earths such as lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, dysprosium, yttrium, erbium and ytterbium have been applied to an iron-chromium alloy to determine their influence on the cyclic oxidation behavior (RT-900 °C of the alloy. The morphology and coverage of the rare earth oxide gels varied with the type of rare earth. The cyclic oxidation resistance of the alloy increased with increase in time at temperature required to reach a specific chromium dioxide layer thickness and this in turn was influenced by the rare earth ion radius and characteristics of the rare earth oxide coating such as morphology, stability, coverage, resistance to thermal stresses and consequently adhesion.

  7. Computational Chemistry of Cyclopentane Low Temperature Oxidation

    KAUST Repository

    El Rachidi, Mariam

    2015-03-30

    Cycloalkanes are significant constituents of conventional fossil fuels, but little is known concerning their combustion chemistry and kinetics, particularly at low temperatures. This study investigates the pressure dependent kinetics of several reactions occurring during low-temperature cyclopentane combustion using theoretical chemical kinetics. The reaction pathways of the cyclopentyl + O2 adduct is traced to alkylhydroperoxide, cyclic ether, β-scission and HO2 elimination products. The calculations are carried out at the UCCSD(T)-F12b/cc-pVTZ-F12//M06-2X/6-311++G(d,p) level of theory. The barrierless entrance channel is treated using variable-reaction-coordinate transition state theory (VRC-TST) at the CASPT2(7e,6o) level of theory, including basis set, geometry relaxation and ZPE corrections. 1-D time-dependent multiwell master equation analysis is used to determine pressure-and temperature-dependent rate parameters of all investigated reactions. Tunneling corrections are included using Eckart barriers. Comparison with cyclohexane is used to elucidate the effect of ring size on the low temperature reactivity of naphthenes. The rate coefficients reported herein are suitable for use in cyclopentane and methylcyclopentane combustion models, even below ~900 K, where ignition is particularly sensitive to these pressure-dependent values.

  8. Alloying effects on the high-temperature oxidation resistance of Cr-Cr{sub 2}Nb

    Energy Technology Data Exchange (ETDEWEB)

    Tortorelli, P.F.; DeVan, J.H.

    1994-09-01

    Alloying effects on the high-temperature oxidation resistance of Cr-Cr{sub 2}Nb were examined on the basis of isothermal exposures to air at 950 C. Additions of either Re and Al or Fe, Ni, and Al had relatively little effect on weight gains relative to the Cr-6% Nb binary alloy. One alloying element that improved the mechanical behavior of Cr-Cr{sub 2}Nb alloys substantially increased the oxidation rates and spallation susceptibilities of Cr-6 and -12% Nb alloys. However, the addition of another element completely offset these deleterious effects. The presence of this latter element resulted in the best overall oxidation behavior (in terms of both weight gains and spallation tendencies) of all Cr-Cr{sub 2}Nb compositions. Its beneficial effect can be attributed to improvement in the oxidation resistance of the Cr-rich phase.

  9. Oxidation behavior of metallic interconnect in solid oxide fuel cell stack

    Science.gov (United States)

    Li, Jun; Zhang, Wenying; Yang, Jiajun; Yan, Dong; Pu, Jian; Chi, Bo; Jian, Li

    2017-06-01

    Oxidation behavior of integrated interconnect with bipolar plate and corrugated sheet made by ferrite steel SUS430 is investigated and compared in simulated environment and in a realistic stack. Electrical current is found to have a direction-related impact on the thickness of the Cr2O3/MnCr2O4 composite oxide scale. Oxide scale of the interconnect aged in the stack exhibits a dual-layered structure of a complex Mn-Cr oxide layer covered by iron oxide. The oxidation rates vary greatly depending on its local environment, with different thermal, electrical density, as well as gas composition conditions. By analyzing the thickness distribution of oxide scale and comparing them with the simulated test result, the oxidation behavior of interconnect in stack is described in high definition. ASR distribution is also conducted by calculation, which could help further understanding the behavior of stack degradation.

  10. Influence of oxidation temperature on the oxide scale formation of NiCoCrAl coatings

    Science.gov (United States)

    Sugiarti, E.; Zaini, K. A.; Sundawa, R.; Wang, Y.; Ohnuki, S.; Hayashi, S.

    2017-04-01

    Intermetalic coatings of NiCoCrAl have been successfully developed on low carbon steel substrate to improve oxidation resistance in extreme environments. The influence of oxidation temperature on the oxide scale formation was studied in the temperature range of 600-1000 °C. The measurements were made in air under isothermal oxidation test for 100 h. The surface morphology showed that a cauliflower like structure developed entire the oxide scale of sample oxidized at 800 °C and 1000 °C, while partly distributed on the surface of sample oxidized at 600 °C. The XRD analysis identified Cr2O3 phase predominantly formed on the oxidized sample at 600 °C and meta-stable Al2O3 with several polymorphs crystalline structures: η, δ, θ, κ, and α-Al2O3 at relatively high temperatures, i.e. 800 °C and 1000 °C. A Cross-sectional microstructure showed that complex and porous structures formed on the top surface of 600 °C and 1000 °C samples. In contrast, a very thin oxide scale formed on 800 °C oxidized samples and it appeared to act as a diffusion barrier of oxygen to diffuse inward, hence could increase in the service life of carbon steel substrate.

  11. Effect of Nb Doping on High Temperature Oxidation Resistance of Ti-Al Alloyed Coatings

    Directory of Open Access Journals (Sweden)

    DAI Jing-jie

    2017-02-01

    Full Text Available Ti-Al alloyed coatings with different Nb doping contents were fabricated on TC4 titanium alloy by laser surface alloying to improve high temperature oxidation resistance of the alloy. Structures and high temperature oxidation behaviors of the alloyed coatings were analyzed and tested by X-ray diffraction (XRD, scanning electron microscope (SEM, energy dispersive spectrometer (EDS and box-type resistance furnace. The results show that the alloyed coatings consist of TiAl and Ti3Al, and no niobium compound are formed in Ti-Al-Nb alloyed coatings. The alloyed coatings are uniform and exhibit excellent metallurgical bonding with the substrates. A large amount of surface cracks and a few penetrating cracks are formed in Ti-Al alloyed coating without Nb doping, while no obvious cracks are formed in Ti-Al alloyed coating with Nb doping. The oxidation mass gains of all the alloyed coatings were significantly lower than those of the substrate. The alloyed coatings with Nb doping exhibit more excellent high temperature oxidation resistance due to the beneficial machanism of Nb doping. The mechanism of Nb doping on improving high temperature oxidation resistance of Ti-Al alloyed coatings includes reducing the defect concentration of TiO2, refining oxide grains and promoting the formation of Al2O3.

  12. Nanocarbon synthesis by high-temperature oxidation of nanoparticles

    Science.gov (United States)

    Nomura, Ken-Ichi; Kalia, Rajiv K.; Li, Ying; Nakano, Aiichiro; Rajak, Pankaj; Sheng, Chunyang; Shimamura, Kohei; Shimojo, Fuyuki; Vashishta, Priya

    2016-04-01

    High-temperature oxidation of silicon-carbide nanoparticles (nSiC) underlies a wide range of technologies from high-power electronic switches for efficient electrical grid and thermal protection of space vehicles to self-healing ceramic nanocomposites. Here, multimillion-atom reactive molecular dynamics simulations validated by ab initio quantum molecular dynamics simulations predict unexpected condensation of large graphene flakes during high-temperature oxidation of nSiC. Initial oxidation produces a molten silica shell that acts as an autocatalytic ‘nanoreactor’ by actively transporting oxygen reactants while protecting the nanocarbon product from harsh oxidizing environment. Percolation transition produces porous nanocarbon with fractal geometry, which consists of mostly sp2 carbons with pentagonal and heptagonal defects. This work suggests a simple synthetic pathway to high surface-area, low-density nanocarbon with numerous energy, biomedical and mechanical-metamaterial applications, including the reinforcement of self-healing composites.

  13. Ni–Ta–O mixed oxide catalysts for the low temperature oxidative dehydrogenation of ethane to ethylene

    KAUST Repository

    Zhu, Haibo

    2015-09-01

    The "wet" sol-gel and "dry" solid-state methods were used to prepare Ni-Ta-O mixed oxide catalysts. The resulting Ni-Ta oxides exhibit high activity and selectivity for the low temperature oxidative dehydrogenation of ethane to ethylene. The Ta/(Ni + Ta) atomic ratios (varying from 0 to 0.11 in "wet" sol-gel method, and from 0 to 0.20 in "dry" solid-state method) as well as the preparation methods used in the synthesis, play important roles in controlling catalyst structure, activity, selectivity and stability in the oxidative dehydrogenation of ethane. Electron microscopy characterizations (TEM, EELS mapping, and HAADF-STEM) clearly demonstrate that the Ta atoms are inserted into NiO crystal lattice, resulting in the formation of a new Ni-Ta oxide solid solution. More Ta atoms are found to be located at the lattice sites of crystal surface in sol-gel catalyst. While, a small amount of thin layer of Ta2O5 clusters are detected in solid-state catalyst. Further characterization by XRD, N2 adsorption, SEM, H2-TPR, XPS, and Raman techniques reveal different properties of these two Ni-Ta oxides. Due to the different properties of the Ni-Ta oxide catalysts prepared by two distinct approaches, they exhibit different catalytic behaviors in the ethane oxidative dehydrogenation reaction at low temperature. Thus, the catalytic performance of Ni-Ta-O mixed oxide catalysts can be systematically modified and tuned by selecting a suitable synthesis method, and then varying the Ta content. ©2015 Elsevier Inc. All rights reserved.

  14. High temperature oxidation in boiler environment of chromized steel

    Science.gov (United States)

    Alia, F. F.; Kurniawan, T.; Asmara, Y. P.; Ani, M. H. B.; Nandiyanto, A. B. D.

    2017-10-01

    The demand for increasing efficiency has led to the development and construction of higher operating temperature power plant. This condition may lead to more severe thickness losses in boiler tubes due to excessive corrosion process. Hence, the research to improve the corrosion resistance of the current operated material is needed so that it can be applied for higher temperature application. In this research, the effect of chromizing process on the oxidation behaviour of T91 steel was investigated under steam condition. In order to deposit chromium, mixture of chromium (Cr) powder as master alloy, halide salt (NH4Cl) powder as activator and alumina (Al2O3) powder as inert filler were inserted into alumina retort together with the steel sample and heated inside furnace at 1050°C for ten hours under argon gas environment. Furthermore, for the oxidation process, steels were exposed at 700°C at different oxidation time (6h-24h) under steam condition. From FESEM/EDX analysis, it was found that oxidation rate of pack cemented steel was lower than the un-packed steel. These results show that Cr from chromizing process was able to become reservoir for the formation of Cr2O3 in high temperature steam oxidation, and its existence can be used for a longer oxidation time.

  15. Low temperature ozone oxidation of solid waste surrogates

    Science.gov (United States)

    Nabity, James A.; Lee, Jeffrey M.

    2015-09-01

    Solid waste management presents a significant challenge to human spaceflight and especially, long-term missions beyond Earth orbit. A six-month mission will generate over 300 kg of solid wastes per crewmember that must be dealt with to eliminate the need for storage and prevent it from becoming a biological hazard to the crew. There are several methods for the treatment of wastes that include oxidation via ozone, incineration, microbial oxidation or pyrolysis and physical methods such as microwave drying and compaction. In recent years, a low temperature oxidation process using ozonated water has been developed for the chemical conversion of organic wastes to CO2 and H2O. Experiments were conducted to evaluate the rate and effectiveness with which ozone oxidized several different waste materials. Increasing the surface area by chopping or shredding the solids into small pieces more than doubled the rate of oxidation. A greater flow of ozone and agitation of the ozonated water system also increased processing rates. Of the materials investigated, plastics have proven the most difficult to oxidize. The processing of plastics above the glass transition temperatures caused the plastics to clump together which reduced the exposed surface area, while processing at lower temperatures reduced surface reaction kinetics.

  16. OXIDATION OF INCONEL 718 IN AIR AT TEMPERATURES FROM 973K TO 1620K.

    Energy Technology Data Exchange (ETDEWEB)

    GREENE,G.A.; FINFROCK,C.C.

    2000-10-01

    regime. At temperatures below 1173 K, the rate of oxidation of the Inconel 718 surface was found to decrease markedly with time; the parabolic oxidation rate coefficient was not a constant but decreased with time. This was taken to indicate that the oxide film on the surface was having a passivating effect on oxygen transport through the oxide to the underlying metal. For temperatures in the range 1173 K to 1573 K, the time-dependent rate of oxidation as determined once again by weight-gain measurements was found to display the classical parabolic rate behavior, indicating that the rate of transport of reactants through the oxide was controlled by diffusion through the growing oxide layer. Parabolic rate coefficients were determined by least-squares analysis of time-dependent mass-gain data at 1173 K, 1273 K, 1373 K, 1473 K and 1573 K. At temperatures above 1540 K, post test examination of the oxidized samples revealed that the Inconel 718 began to lose strength and to deform. At 1540 K, samples which were suspended from their ends during testing began to demonstrate axial curvature as they lost strength and bowed under their own weight. As the temperatures of the tests were increased, rivulets were seen to appear on the surfaces of the test specimens; damage became severe at 1560 K. Although melting was never observed in any of these tests even up to. 1620 K, it was concluded from these data that the Inconel 718 clad should not be expected to protect the underlying tungsten at temperatures above 1540 K.

  17. Platinum redispersion on metal oxides in low temperature fuel cells

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Cerri, Isotta; Nagami, Tetsuo

    2013-01-01

    We have analyzed the aptitude of several metal oxide supports (TiO2, SnO2, NbO2, ZrO2, SiO2, Ta2O5 and Nb2O5) to redisperse platinum under electrochemical conditions pertinent to the Proton Exchange Membrane Fuel Cell (PEMFC) cathode. The redispersion on oxide supports in air has been studied...... in detail; however, due to different operating conditions it is not straightforward to link the chemical and the electrochemical environment. The largest differences reflect in (1) the oxidation state of the surface (the oxygen species coverage), (2) temperature and (3) the possibility of platinum...... dissolution at high potentials and the interference of redispersion with normal working potential of the PEMFC cathode. We have calculated the PtOx (x = 0, 1, 2) adsorption energies on different metal oxides' surface terminations as well as inside the metal oxides' bulk, and we have concluded that NbO2 might...

  18. Thin Films of Reduced Hafnium Oxide with Excess Carbon for High-Temperature Oxidation Protection

    Science.gov (United States)

    2010-02-01

    contamination; thus the higher oxygen content found by XPS is partly due to organic impurities (and, possibly, water ) that are mostly concentrated in the...International Service Award, 2007. 25 REFERENCES ’C. B. Bargeron, R. C. Benson, and A. N. Jette , "High-Temperature Diffusion of Oxygen in Oxidizing Hafnium...A. N. Jette , and T. E. Phillips, "Oxidation of Hafnium Carbide in the Temperature Range 1400 ° to 2060 °C," Journal of the American Ceramic Society

  19. Study on Zinc Oxide-Based Electrolytes in Low-Temperature Solid Oxide Fuel Cells.

    Science.gov (United States)

    Xia, Chen; Qiao, Zheng; Feng, Chu; Kim, Jung-Sik; Wang, Baoyuan; Zhu, Bin

    2017-12-28

    Semiconducting-ionic conductors have been recently described as excellent electrolyte membranes for low-temperature operation solid oxide fuel cells (LT-SOFCs). In the present work, two new functional materials based on zinc oxide (ZnO)-a legacy material in semiconductors but exceptionally novel to solid state ionics-are developed as membranes in SOFCs for the first time. The proposed ZnO and ZnO-LCP (La/Pr doped CeO₂) electrolytes are respectively sandwiched between two Ni 0.8 Co 0.15 Al 0.05 Li-oxide (NCAL) electrodes to construct fuel cell devices. The assembled ZnO fuel cell demonstrates encouraging power outputs of 158-482 mW cm -2 and high open circuit voltages (OCVs) of 1-1.06 V at 450-550 °C, while the ZnO-LCP cell delivers significantly enhanced performance with maximum power density of 864 mW cm -2 and OCV of 1.07 V at 550 °C. The conductive properties of the materials are investigated. As a consequence, the ZnO electrolyte and ZnO-LCP composite exhibit extraordinary ionic conductivities of 0.09 and 0.156 S cm -1 at 550 °C, respectively, and the proton conductive behavior of ZnO is verified. Furthermore, performance enhancement of the ZnO-LCP cell is studied by electrochemical impedance spectroscopy (EIS), which is found to be as a result of the significantly reduced grain boundary and electrode polarization resistances. These findings indicate that ZnO is a highly promising alternative semiconducting-ionic membrane to replace the electrolyte materials for advanced LT-SOFCs, which in turn provides a new strategic pathway for the future development of electrolytes.

  20. Ambient temperature NO oxidation over Cr-based amorphous mixed oxide catalysts: effects from the second oxide components

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Aiyong; Lin, Bo; Zhang, Hanlei; Engelhard, Mark H.; Guo, Yanglong; Lu, Guanzhong; Peden, Charles HF; Gao, Feng

    2017-01-01

    Three series of Cr-based mixed oxides (Cr-Co, Cr-Fe, and Cr-Ni oxides) with high specific surface areas and amorphous textures were synthesized using a novel sol-gel method. These mixed oxides, in comparison to their pure metal oxide (CrOx, Co3O4, FeOx and NiO) counterparts, display enhanced performance for catalytic oxidation of low-concentration NO at room temperature. The best performing catalysts achieve 100% NO conversion for ~30 h of operation at a high space velocity of 45,000 ml g-1 h-1. The amorphous structure was found to be critical for these catalysts to maintain high activity and durability. Control of Cr/M (M=Co, Fe and Ni) molar ratio, nitrate precursor decomposition temperature and catalyst calcination temperature was key to the synthesis of these highly active catalysts.

  1. Theoretical grain size limits for single-domain, pseudo-single-domain and multi-domain behavior in titanomagnetite ( x = 0.6) as a function of low-temperature oxidation

    Science.gov (United States)

    Moskowitz, Bruce M.

    1980-04-01

    A theoretical model of grain size variation of domain transitions in titanomagnetite ( x = 0.6) as a function of oxidation ( z) is presented. The superparamagnetic (SP) to single-domain (SD) transition ds, the SD to two-domain (TD) transition d0, the TD to three-domain (3D) transition and the pseudo-single domain (PSD) to multi-domain (MD) transition are calculated as a function of z. It is shown that all the transition grain sizes increase with z, except for the PSD-MD transition for z > 0.6. The calculations predict that ds increases from 0.044 to 0.197 μm, d0 increases from 0.54 to 13 μm, the TD-3D transition increases from 1.6 to 49 μm as z varies from 0 to 0.8. The PSD-MD transition increases from 42 μm at z = 0 to 150 μm at z = 0.6, whereas between z = 0.6 to z = 0.8, the PSD-MD transition decreases to 49 μm. Qualitatively, the model explains some of the trends in magnetic properties of submarine basalts with low-temperature oxidation. Quantitatively, the model does give reasonable estimates of the PSD-MD boundary and d0, which are close to the experimental values for x = 0.6 and z = 0. Furthermore, the model predicts that psarks or two-domain grains could be the major contributors to the remanence of oxidized submarine pillow basalts.

  2. Correlation between the microstructures of graphite oxides and their catalytic behaviors in air oxidation of benzyl alcohol.

    Science.gov (United States)

    Geng, Longlong; Wu, Shujie; Zou, Yongcun; Jia, Mingjun; Zhang, Wenxiang; Yan, Wenfu; Liu, Gang

    2014-05-01

    A series of graphite oxide (GO) materials were obtained by thermal treatment of oxidized natural graphite powder at different temperatures (from 100 to 200 °C). The microstructure evolution (i.e., layer structure and surface functional groups) of the graphite oxide during the heating process is studied by various characterization means, including XRD, N2 adsorption, TG-DTA, in situ DRIFT, XPS, Raman, TEM and Boehm titration. The characterization results show that the structures of GO materials change gradually from multilayer sheets to a transparent ultrathin 2D structure of the carbon sheets. The concentration of surface COH and HOCO groups decrease significantly upon treating temperature increasing. Benzyl alcohol oxidation with air as oxidant source was carried out to detect the catalytic behaviors of different GO materials. The activities of GO materials decrease with the increase of treating temperatures. It shows that the structure properties, including ultrathin sheets and high specific surface area, are not crucial factors affecting the catalytic activity. The type and amount of surface oxygen-containing functional groups of GO materials tightly correlates with the catalytic performance. Carboxylic groups on the surface of GO should act as oxidative sites for benzyl alcohol and the reduced form could be reoxidized by molecular oxygen. Copyright © 2014 Elsevier Inc. All rights reserved.

  3. Strategies for Lowering Solid Oxide Fuel Cells Operating Temperature

    Directory of Open Access Journals (Sweden)

    Albert Tarancón

    2009-11-01

    Full Text Available Lowering the operating temperature of solid oxide fuel cells (SOFCs to the intermediate range (500–700 ºC has become one of the main SOFC research goals. High operating temperatures put numerous requirements on materials selection and on secondary units, limiting the commercial development of SOFCs. The present review first focuses on the main effects of reducing the operating temperature in terms of materials stability, thermo-mechanical mismatch, thermal management and efficiency. After a brief survey of the state-of-the-art materials for SOFCs, attention is focused on emerging oxide-ionic conductors with high conductivity in the intermediate range of temperatures with an introductory section on materials technology for reducing the electrolyte thickness. Finally, recent advances in cathode materials based on layered mixed ionic-electronic conductors are highlighted because the decreasing temperature converts the cathode into the major source of electrical losses for the whole SOFC system. It is concluded that the introduction of alternative materials that would enable solid oxide fuel cells to operate in the intermediate range of temperatures would have a major impact on the commercialization of fuel cell technology.

  4. New Oxide Materials for an Ultra High Temperature Environment

    Energy Technology Data Exchange (ETDEWEB)

    Perepezko, John H. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Materials Science and Engineering

    2017-11-13

    In this project, a new oxide material, Hf6Ta2O17 has been successfully synthesized by the controlled oxidization of Hf-Ta alloys. This oxide exhibits good oxidation resistance, high temperature phase stability up to more than 2000°C, low thermal conductivity and thus could serve as a component or a coating material in an ultrahigh temperature environment. We have examined the microstructure evolution and phase formation sequence during the oxidation exposure of Hf-Ta alloys at 1500°C and identified that the oxidation of a Hf-26.7atomic %Ta alloy leads to the formation of a single phase adherent Hf6Ta2O17 with a complex atomic structure i.e. superstructure. The overall reactive diffusion pathway is consistent with the calculated Hf-Ta-O ternary phase diagram. Besides the synthesis of Hf6Ta2O17 superstructure by oxidizing Hf-Ta alloys, we have also developed a synthesis method based upon the reactive sintering of the correct ratios of mixed powders of HfO2 and Ta2O5 and verified the low thermal conductivity of Hf6Ta2O17 superstructure on these samples. We have completed a preliminary analysis of the oxidation kinetics for Hf6Ta2O17, which shows an initial parabolic oxidation kinetics.

  5. Decomposition of nitrous oxide at medium temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Loeffler, G.; Wargadalam, V.J.; Winter, F.; Hofbauer, H.

    2000-03-01

    Flow reactor experiments were done to study the decomposition of N{sub 2}O at atmospheric pressure and in a temperature range of 600--1,000 C. Dilute mixtures of N{sub 2}O with H{sub 2}, CH{sub 4}, CO with and without oxygen with N{sub 2} as carrier gas were studied. To see directly the relative importance of the thermal decomposition versus the destruction by free radicals (i.e.: H, O, OH) iodine was added to the reactant mixture suppressing the radicals' concentrations towards their equilibrium concentrations. The experimental results were discussed using a detailed chemistry model. This work shows that there are still some uncertainties regarding the kinetics of the thermal decomposition and the reaction between N{sub 2}O and the O radical. Using the recommendations applied in this work for the reaction N{sub 2}O + M {leftrightarrow} N{sub 2} + O + M and for N{sub 2}O + O {leftrightarrow} products, a good agreement with the experimental data can be obtained over a wide range of experimental conditions. The reaction between N{sub 2}O and OH is of minor importance under present conditions as stated in latest literature. The results show that N{sub 2}O + H {leftrightarrow} N{sub 2} + OH is the most important reaction in the destruction of N{sub 2}O. In the presence of oxygen it competes with H + O{sub 2} + M {leftrightarrow} HO{sub 2} + M and H + O{sub 2} {leftrightarrow} O + OH, respectively. The importance of the thermal decomposition (N{sub 2}O + M {leftrightarrow} N{sub 2} + O + M) increases with residence time. Reducing conditions and a long residence time lead to a high potential in N{sub 2}O reduction. Especially mixtures of H{sub 2}/N{sub 2}O and CO/H{sub 2}O/N{sub 2}O in nitrogen lead to a chain reaction mechanism causing a strong N{sub 2}O reduction.

  6. High temperature oxidation resistance of rare earth chromite coated Fe-20Cr and Fe-20Cr-4Al alloys

    Directory of Open Access Journals (Sweden)

    Marina Fuser Pillis

    2007-09-01

    Full Text Available Doped lanthanum chromite has been used in solid oxide fuel cell (SOFC interconnects. The high costs involved in obtaining dense lanthanum chromite have increased efforts to find suitable metallic materials for interconnects. In this context, the oxidation behavior of lanthanum chromite coated Fe-20Cr and Fe-20Cr-4Al alloys at SOFC operation temperature was studied. Isothermal oxidation tests were carried out at 1000 °C for 20, 50 and 200 hours. Cyclic oxidation tests were also carried out and each oxidation cycle consisted of 7 hours at 1000/°C followed by cooling to room temperature. The oxidation measurements and the results of SEM/EDS as well as XRD analyses indicated that lanthanum chromite coated Fe-20Cr and Fe-20Cr-4Al alloys were significantly more resistant to oxidation compared with the uncoated alloys.

  7. High temperature cyclic oxidation and hot corrosion behaviours of ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Oxidation and hot corrosion are serious problems in aircraft, marine, industrial, and land-base gas turbines. It is because of the usage of wide range of fuels coupled with increased operating temperatures, which leads to the degradation of turbine engines. To obviate these problems, superalloys, viz. Superni 75,.

  8. Temperature dependence studies on the electro-oxidation of ...

    Indian Academy of Sciences (India)

    Cyclic voltammetry; electrochemical impedance spectroscopy; activation energy; fuel cell; alcohol. Abstract. Temperature dependence on the electro-oxidation of methanol, ethanol and 1-propanol in 0.5 M H2SO4 were investigated with Pt and PtRu electrodes. Tafel slope and apparent activation energy were evaluated ...

  9. Temperature dependence studies on the electro-oxidation of ...

    Indian Academy of Sciences (India)

    Administrator

    agreed that the electro-oxidation of methanol was improved by raising the temperature and ruthenium modification. Keywords. Cyclic voltammetry; electrochemical impedance spectroscopy; activation energy; fuel cell; alcohol. 1. Introduction. The use of hydrogen carrier like alcohol as alterna- tive fuels in the direct alcohol ...

  10. High temperature cyclic oxidation and hot corrosion behaviours of ...

    Indian Academy of Sciences (India)

    Oxidation and hot corrosion are serious problems in aircraft, marine, industrial, and land-base gas turbines. It is because of the usage of wide range of fuels coupled with increased operating temperatures, which leads to the degradation of turbine engines. To obviate these problems, superalloys, viz. Superni 75, Superni ...

  11. Oxidation resistant iron and nickel alloys for high temperature use

    Science.gov (United States)

    Hill, V. L.; Misra, S. K.; Wheaton, H. L.

    1970-01-01

    Iron-base and nickel-base alloys exhibit good oxidation resistance and improved ductility with addition of small amounts of yttrium, tantalum /or hafnium/, and thorium. They can be used in applications above the operating temperatures of the superalloys, if high strength materials are not required.

  12. Electrical characterization of low temperature deposited oxide films ...

    Indian Academy of Sciences (India)

    Unknown

    Thin films of silicon dioxide are deposited on ZnO/n-Si substrate at a low temperature using tetra- ethylorthosilicate (TEOS). The ZnO/n-Si ... oxygen plasma has been extensively investigated because of its wide ranging applications in ... rapid electrical communication with the ZnO/n-Si sub- strate, whereas the oxide trapped ...

  13. Understanding the low temperature electrical properties of nanocrystalline tin oxide for gas sensor applications

    Science.gov (United States)

    Drake, Christina Hartsell

    Nanocrystalline metal/metal oxide is an important class of transparent and electronic materials due to its potential use in many applications, including gas sensors. At the nanoscale, many of the phenomena observed that give nanocrystalline semiconducting oxide enhanced performance as a gas sensor material over other conventional engineering materials is still poorly understood. This study is aimed at understanding the low temperature electrical and chemical properties of nanocrystalline SnO2 that makes it suitable for room temperature gas detectors. Studies were carried out in order to understand how various synthesis methods affect the surfaces on the nano-oxides, interactions of a target gas (in this study hydrogen) with different surface species, and changes in the electrical properties as a function of dopants and grain size. A correlation between the surface reactions and the electrical response of doped nanocrystalline metal-oxide-semiconductors exposed to a reducing gas is established using Fourier Transform Infrared (FTIR) Spectroscopy attached to a specially built custom designed catalytic cell. First principle calculations of oxygen vacancy concentrations from absorbance spectra are presented. FTIR is used for effectively screening of these nanostructures for gas sensing applications. The effect of processing temperature on the microstructural evolution and on the electronic properties of nanocrystalline trivalent doped-SnO 2 is also presented. This study includes the effect of dopants (In and Ce) on the growth of nano-SnO2, as well as their effects on the electronic properties and gas sensor behavior of the nanomaterial at room temperature. Band bending affects are also investigated for this system and are related to enhanced low temperature gas sensing. The role and importance of oxygen vacancies in the electronic and chemical behavior of surface modified nanocrystalline SnO2 are explored in this study. A generalized explanation for the low temperature

  14. Electrochemical topotactic oxidation of nonstoichiometric perovskites at ambient temperature

    Energy Technology Data Exchange (ETDEWEB)

    Nemudry, A. [Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of Russian Academy of Science, Novosibirsk (Russian Federation); Goldberg, E.L. [Limnological Institute, Russian Academy of Science, Irkutsk (Russian Federation); Aguirre, M.; Alario-Franco, M.A. [Universidad Complytense, Lab. de Quimica del Estado Solido, Madrid (Spain)

    2002-05-01

    Different approaches to describe nonstoichiometry in perovskite-related oxides, oxygen diffusion models and kinetic data on electrochemical intercalation of oxygen in perovskite-related oxides are considered in the present study. It is demonstrated that the formation of micro-heterogeneous systems is characteristic of nonstoichiometric perovskite-related oxides. The adequate models should be considered for the proper characterization of the low temperature oxygen transport in oxides. These models should account for the high concentration of the high diffusivity paths in the sample. For micro-domain textured Ca{sub 0.5}Sr{sub 0.5}FeO{sub 2.5} perovskite as example, the kinetic analysis of electrochemical oxygen intercalation is carried out. (authors)

  15. Anodes for Solid Oxide Fuel Cells Operating at Low Temperatures

    DEFF Research Database (Denmark)

    Abdul Jabbar, Mohammed Hussain

    . On the other hand, low-temperature operation poses serious challenges to the electrode performance. Effective catalysts, redox stable electrodes with improved microstructures are the prime requisite for the development of efficient SOFC anodes. The performance of Nb-doped SrT iO3 (STN) ceramic anodes......An important issue that has limited the potential of Solid Oxide Fuel Cells (SOFCs) for portable applications is its high operating temperatures (800-1000 ºC). Lowering the operating temperature of SOFCs to 400-600 ºC enable a wider material selection, reduced degradation and increased lifetime...... at 400ºC. The potential of using WO3 ceramic as an alternative anode materials has been explored. The relatively high electrode polarization resistance obtained, 11 Ohm cm2 at 600 ºC, proved the inadequate catalytic activity of this system for hydrogen oxidation. At the end of this thesis...

  16. Electric field cycling behavior of ferroelectric hafnium oxide.

    Science.gov (United States)

    Schenk, Tony; Schroeder, Uwe; Pešić, Milan; Popovici, Mihaela; Pershin, Yuriy V; Mikolajick, Thomas

    2014-11-26

    HfO2 based ferroelectrics are lead-free, simple binary oxides with nonperovskite structure and low permittivity. They just recently started attracting attention of theoretical groups in the fields of ferroelectric memories and electrostatic supercapacitors. A modified approach of harmonic analysis is introduced for temperature-dependent studies of the field cycling behavior and the underlying defect mechanisms. Activation energies for wake-up and fatigue are extracted. Notably, all values are about 100 meV, which is 1 order of magnitude lower than for conventional ferroelectrics like lead zirconate titanate (PZT). This difference is mainly atttributed to the one to two orders of magnitude higher electric fields used for cycling and to the different surface to volume ratios between the 10 nm thin films in this study and the bulk samples of former measurements or simulations. Moreover, a new, analog-like split-up effect of switching peaks by field cycling is discovered and is explained by a network model based on memcapacitive behavior as a result of defect redistribution.

  17. Analysis of the Microstructure and Oxidation Behavior of Some Commercial Carbon Fibers

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dae Ho; Kim, Bohye; Yang, Kap Seung; Im, Hun Kook [Chonnam National Univ., Gwangju (Korea, Republic of); Bang, Yun Hyuk; Kim, Sung Ryong [Hyosung Corporation, Seoul (Korea, Republic of)

    2011-10-15

    The relationship between the microstructure, mechanical properties, and oxidation behavior of pitch-, polyacrylonitrile (PAN)-, and Rayon-based carbon fibers (CFs) has been studied in detail. Three types of carbon fiber were exposed to isothermal oxidation in air and the weight change was measured by thermogravimetric analyzer (TGA) apparatus. After activation energy was gained according to the conversion at reacting temperature, the value of specific surface area and the surface morphology was compared, and the reaction mechanism of oxidation affecting development of pores of carbon fibers was examined. This study will lead to a new insight into the relationship between the microstructure and mechanical properties of carbon fibers.

  18. High throughput thermal conductivity of high temperature solid phases: The case of oxide and fluoride perovskites

    CERN Document Server

    van Roekeghem, Ambroise; Oses, Corey; Curtarolo, Stefano; Mingo, Natalio

    2016-01-01

    Using finite-temperature phonon calculations and machine-learning methods, we calculate the mechanical stability of about 400 semiconducting oxides and fluorides with cubic perovskite structures at 0 K, 300 K and 1000 K. We find 92 mechanically stable compounds at high temperatures -- including 36 not mentioned in the literature so far -- for which we calculate the thermal conductivity. We demonstrate that the thermal conductivity is generally smaller in fluorides than in oxides, largely due to a lower ionic charge, and describe simple structural descriptors that are correlated with its magnitude. Furthermore, we show that the thermal conductivities of most cubic perovskites decrease more slowly than the usual $T^{-1}$ behavior. Within this set, we also screen for materials exhibiting negative thermal expansion. Finally, we describe a strategy to accelerate the discovery of mechanically stable compounds at high temperatures.

  19. Low temperature solid oxide electrolytes (LT-SOE): A review

    Science.gov (United States)

    Singh, B.; Ghosh, S.; Aich, S.; Roy, B.

    2017-01-01

    Low temperature solid oxide fuel cell (LT-SOFC) can be a source of power for vehicles, online grid, and at the same time reduce system cost, offer high reliability, and fast start-up. A huge amount of research work, as evident from the literature has been conducted for the enhancement of the ionic conductivity of LT electrolytes in the last few years. The basic conduction mechanisms, advantages and disadvantages of different LT oxide ion conducting electrolytes {BIMEVOX systems, bilayer systems including doped cerium oxide/stabilised bismuth oxide and YSZ/DCO}, mixed ion conducting electrolytes {doped cerium oxides/alkali metal carbonate composites}, and proton conducting electrolytes {doped and undoped BaCeO3, BaZrO3, etc.} are discussed here based on the recent research articles. Effect of various material aspects (composition, doping, layer thickness, etc.), fabrication methods (to achieve different microstructures and particle size), design related strategies (interlayer, sintering aid etc.), characterization temperature & environment on the conductivity of the electrolytes and performance of the fuel cells made from these electrolytes are shown in tabular form and discussed. The conductivity of the electrolytes and performance of the corresponding fuel cells are compared. Other applications of the electrolytes are mentioned. A few considerations regarding the future prospects are pointed.

  20. Tunable room-temperature ferromagnet using an iron-oxide and graphene oxide nanocomposite

    KAUST Repository

    Lin, Aigu L.

    2015-06-23

    Magnetic materials have found wide application ranging from electronics and memories to medicine. Essential to these advances is the control of the magnetic order. To date, most room-temperature applications have a fixed magnetic moment whose orientation is manipulated for functionality. Here we demonstrate an iron-oxide and graphene oxide nanocomposite based device that acts as a tunable ferromagnet at room temperature. Not only can we tune its transition temperature in a wide range of temperatures around room temperature, but the magnetization can also be tuned from zero to 0.011 A m2/kg through an initialization process with two readily accessible knobs (magnetic field and electric current), after which the system retains its magnetic properties semi-permanently until the next initialization process. We construct a theoretical model to illustrate that this tunability originates from an indirect exchange interaction mediated by spin-imbalanced electrons inside the nanocomposite. © 2015 Scientific Reports.

  1. Defective iron-oxide nanoparticles synthesised by high temperature plasma processing: a magnetic characterisation versus temperature.

    Science.gov (United States)

    Balasubramanian, C; Joseph, B; Orpe, P B; Saini, N L; Mukherjee, S; Dziedzic-Kocurek, K; Stanek, J; Di Gioacchino, D; Marcelli, A

    2016-11-04

    Magnetic properties and phase compositions of iron-oxide nanoparticles synthesised by a high temperature arc plasma route have been investigated by Mössbauer spectroscopy and high harmonic magnetic AC susceptibility measurements, and correlated with morphological and structural properties for different synthesis conditions. The Mössbauer spectra precisely determined the presence of different iron-oxide fractions in the investigated nanoparticles, while the high harmonic magnetic susceptibility measurements revealed the occurrence of metastable magnetic phases evolving in temperature and time. This study illustrates magnetic properties and dynamics of the magnetic configurations of iron-oxide nanoparticles grown by high temperature plasma, a process less explored so far but extremely useful for synthesising large numbers of nanoparticles for industrial applications.

  2. High temperature oxidation of iron-chromium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mikkelsen, Lars

    2003-06-15

    The high temperature oxidation of the ferritic alloy Fe78Cr22 has been investigated in the present work. The effect of small alloying additions of cerium and/or silicon was also investigated. The alloys were oxidized at 973, 1173 and 1373 K in either air or a hydrogen/argon mixture. The various reaction atmospheres contained between 0.02 and 50% water vapour. The oxide scales formed on the various alloys at 973 K consisted of thin chromia layers. The oxide scales grown on the alloys at 1173 K also consisted of a chromia layer. The microstructure of the chromia scales was found to depend on the reaction atmosphere. The chromia scales grown in hydrogen/argon atmospheres formed oxide whiskers and oxide ridges at the surface of the scales, while the chromia scales grown in air formed larger oxide grains near the surface. This difference in oxide microstructure was due to the vaporization of chromium species from the chromia scales grown in air. Two different growth mechanisms are proposed for the growth of oxide whiskers. The growth rate of the chromia scales was independent of the oxygen activity. This is explained by a growth mechanism of the chromia scales, where the growth is governed by the diffusion of interstitial chromium. The addition of silicon to the iron-chromium alloy resulted in the formation of silica particles beneath the chromia scale. The presence of silicon in the alloy was found to decrease the growth rate of the chromia scale. This is explained by a blocking mechanism, where the silica particles beneath the chromia scale partly block the outwards diffusion of chromium from the alloy to the chromia scale. The addition of cerium to the iron-chromium alloy improved the adhesion of the chromia scale to the alloy and decreased the growth rate of chromia. It was observed that the minimum concentration of cerium in the alloy should be 0.3 at.% in order to observe an effect of the cerium addition. The effect of cerium is explained by the &apos

  3. Transient deformational properties of high temperature alloys used in solid oxide fuel cell stacks

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye; Kwok, Kawai; Frandsen, Henrik Lund

    2017-01-01

    Stresses and probability of failure during operation of solid oxide fuel cells (SOFCs) is affected by the deformational properties of the different components of the SOFC stack. Though the overall stress relaxes with time during steady state operation, large stresses would normally appear through...... transients in operation including temporary shut downs. These stresses are highly affected by the transient creep behavior of metallic components in the SOFC stack. This study investigates whether a variation of the so-called Chaboche's unified power law together with isotropic hardening can represent...... to describe the high temperature inelastic deformational behaviors of Crofer 22 APU used for metallic interconnects in SOFC stacks....

  4. Behavior of Clostridium perfringens at low temperatures

    NARCIS (Netherlands)

    Jong, de A.E.I.; Rombouts, F.M.; Beumer, R.R.

    2004-01-01

    Refrigerated storage is an important step in the preparation of foods and inadequate storage is one of the main causes of food poisoning outbreaks of Clostridium perfringens. Therefore, growth and germination characteristics of C. perfringens in a temperature range of 3-42 degreesC were determined

  5. Multispectral pyrometry for surface temperature measurement of oxidized Zircaloy claddings

    Science.gov (United States)

    Bouvry, B.; Cheymol, G.; Ramiandrisoa, L.; Javaudin, B.; Gallou, C.; Maskrot, H.; Horny, N.; Duvaut, T.; Destouches, C.; Ferry, L.; Gonnier, C.

    2017-06-01

    Non-contact temperature measurement in a nuclear reactor is still a huge challenge because of the numerous constraints to consider, such as the high temperature, the steam atmosphere, and irradiation. A device is currently developed at CEA to study the nuclear fuel claddings behavior during a Loss-of-Coolant Accident. As a first step of development, we designed and tested an optical pyrometry procedure to measure the surface temperature of nuclear fuel claddings without any contact, under air, in the temperature range 700-850 °C. The temperature of Zircaloy-4 cladding samples was retrieved at various temperature levels. We used Multispectral Radiation Thermometry with the hypothesis of a constant emissivity profile in the spectral ranges 1-1.3 μm and 1.45-1.6 μm. To allow for comparisons, a reference temperature was provided by a thermocouple welded on the cladding surface. Because of thermal losses induced by the presence of the thermocouple, a heat transfer simulation was also performed to estimate the bias. We found a good agreement between the pyrometry measurement and the temperature reference, validating the constant emissivity profile hypothesis used in the MRT estimation. The expanded measurement uncertainty (k = 2) of the temperature obtained by the pyrometry method was ±4 °C, for temperatures between 700 and 850 °C. Emissivity values, between 0.86 and 0.91 were obtained.

  6. Structure of liquid oxides at very high temperatures

    CERN Document Server

    Landron, C; Thiaudiere, D; Price, D L; Greaves, G N

    2003-01-01

    The structural characterization of condensed matter by synchrotron radiation combined with neutron data constitutes a powerful structural tool in material science. In order to investigate refractory liquids at very high temperatures, we have developed a new analysis chamber for performing combined X-ray absorption and diffraction measurements by using laser heating and aerodynamic levitation. A similar system has been designed for neutron experiments. This high temperature equipment presents several advantages: the container does not physically or chemically perturb the sample, heterogeneous nucleation during cooling is suppressed and pollution by the container is removed. This cell can operate under various gas conditions from room temperature up to 3000 deg. C obtained by means of a sealed 125 W CO sub 2 laser. Experiments have been performed at LURE, ESRF and at ISIS. We have studied the local structure around the cations in several liquid and solid oxides. We have shown that high temperature synchrotron d...

  7. Melting temperature of uranium - plutonium mixed oxide fuel

    Energy Technology Data Exchange (ETDEWEB)

    Ishii, Tetsuya; Hirosawa, Takashi [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center

    1997-08-01

    Fuel melting temperature is one of the major thermodynamical properties that is used for determining the design criteria on fuel temperature during irradiation in FBR. In general, it is necessary to evaluate the correlation of fuel melting temperature to confirm that the fuel temperature must be kept below the fuel melting temperature during irradiation at any conditions. The correlations of the melting temperature of uranium-plutonium mixed oxide (MOX) fuel, typical FBR fuel, used to be estimated and formulized based on the measured values reported in 1960`s and has been applied to the design. At present, some experiments have been accumulated with improved experimental techniques. And it reveals that the recent measured melting temperatures does not agree well to the data reported in 1960`s and that some of the 1960`s data should be modified by taking into account of the recent measurements. In this study, the experience of melting temperature up to now are summarized and evaluated in order to make the fuel pin design more reliable. The effect of plutonium content, oxygen to metal ratio and burnup on MOX fuel melting was examined based on the recent data under the UO{sub 2} - PuO{sub 2} - PuO{sub 1.61} ideal solution model, and then formulized. (J.P.N.)

  8. Models for the Configuration and Integrity of Partially Oxidized Fuel Rod Cladding at High Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Siefken, L.J.

    1999-01-01

    Models were designed to resolve deficiencies in the SCDAP/RELAP5/MOD3.2 calculations of the configuration and integrity of hot, partially oxidized cladding. These models are expected to improve the calculations of several important aspects of fuel rod behavior. First, an improved mapping was established from a compilation of PIE results from severe fuel damage tests of the configuration of melted metallic cladding that is retained by an oxide layer. The improved mapping accounts for the relocation of melted cladding in the circumferential direction. Then, rules based on PIE results were established for calculating the effect of cladding that has relocated from above on the oxidation and integrity of the lower intact cladding upon which it solidifies. Next, three different methods were identified for calculating the extent of dissolution of the oxidic part of the cladding due to its contact with the metallic part. The extent of dissolution effects the stress and thus the integrity of the oxidic part of the cladding. Then, an empirical equation was presented for calculating the stress in the oxidic part of the cladding and evaluating its integrity based on this calculated stress. This empirical equation replaces the current criterion for loss of integrity which is based on temperature and extent of oxidation. Finally, a new rule based on theoretical and experimental results was established for identifying the regions of a fuel rod with oxidation of both the inside and outside surfaces of the cladding. The implementation of these models is expected to eliminate the tendency of the SCDAP/RELAP5 code to overpredict the extent of oxidation of the upper part of fuel rods and to underpredict the extent of oxidation of the lower part of fuel rods and the part with a high concentration of relocated material. This report is a revision and reissue of the report entitled, Improvements in Modeling of Cladding Oxidation and Meltdown.

  9. Kinetic features of the low-temperature oxidation of propane

    Science.gov (United States)

    Sargsyan, G. N.

    2012-11-01

    The results from recording the chemiluminescence in the infrared part of the spectrum that emerges during the oxidation of propane in air under the effect of monotonically increasing pressure within the range 2666 Pa ≤ P ≤ 16000 Pa, both under isothermal conditions and in the 593-600 K temperature range, are presented. It is established that no pulsed chemiluminescence is observed at constant values of pressure within the range 2666 Pa ≤ P ≤ 16000 Pa and temperature within the range of 593-600 K in the reaction mixture.

  10. Cast iron zinc galvanizing improved by high temperature oxidation process

    OpenAIRE

    D. Jędrzejczyk; M. Hajduga

    2010-01-01

    Purpose: To evaluate influence of the high-temperature oxidation, as the preliminary stage previous to coating with zinc on the change of surface layer structure as well as subsurface layer of cast iron with flake, vermicular and nodular graphite.Design/methodology/approach: The experiment was led in the temperature range: 850-1050ºC in ambient air. Samples have been taken out from the furnace separately after: 2-12 hours. After scale layer removal the hot dip zinc coating in industrial condi...

  11. Multiferroic iron oxide thin films at room temperature.

    Science.gov (United States)

    Gich, Martí; Fina, Ignasi; Morelli, Alessio; Sánchez, Florencio; Alexe, Marin; Gàzquez, Jaume; Fontcuberta, Josep; Roig, Anna

    2014-07-16

    Multiferroic behaviour at room temperature is demonstrated in ε-Fe2 O3 . The simple composition of this new ferromagnetic ferroelectric oxide and the discovery of a robust path for its thin film growth by using suitable seed layers may boost the exploitation of ε-Fe2 O3 in novel devices. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Thermal deoxygenation of graphite oxide at low temperature

    Science.gov (United States)

    Kampars, V.; Legzdina, M.

    2015-03-01

    Synthesis of graphene via the deoxygenation of the graphite oxide (GO) is a method for the large-scale production of this nanomaterial possessing exceptional mechanical, electrical and translucent properties. Graphite oxide sheet contains at least four different oxygen atoms connected to the Csp3 and Csp2 atoms of the sheet in the form of hydroxyl, epoxy, carboxyl or carbonyl groups. Some of these functional groups are located at the surface but others situated at the edges of the platelets. To obtain the graphene nanoplatelets or the few-layer graphene the oxygen functionalities must be removed. Exfoliation and deoxygenation can be accomplished by the use of chemical reductants or heat. Thermal deoxygenation as greener and simpler approach is more preferable over chemical reduction approach. Usually a considerable mass loss of GO observed upon heating at temperatures starting at 200 °C and is attributed to the deoxygenation process. In order to avoid the defects of the obtained graphene sheets it is very important to find the methods for lowering the deoxygenation temperature of GO. Herein, we have investigated the way treatment of the Hummer's synthesis product with acetone and methyl tert-butyl ether under ultrasonication in order to lower the thermal stability of the graphite oxide and its deoxygenation temperature. The obtained results indicate that treatment of the graphite oxide with solvents mentioned above substantially reduces the reduction and exfoliation temperature (130 °C) under ambient atmosphere. The investigation of the composition of evolved gases by hyphenated Pyr/GC/MS method at different experimental conditions under helium atmosphere shows that without the expected H2O, CO and CO2 also sulphur dioxide and acetone has been released.

  13. Oxidation Behavior of Titanium Carbonitride Coating Deposited by Atmospheric Plasma Spray Synthesis

    Science.gov (United States)

    Zhu, Lin; He, Jining; Yan, Dianran; Liao, Hanlin; Zhang, Nannan

    2017-10-01

    As a high-hardness and anti-frictional material, titanium carbonitride (TiCN) thick coatings or thin films are increasingly being used in many industrial fields. In the present study, TiCN coatings were obtained by atmospheric plasma spray synthesis or reactive plasma spray. In order to promote the reaction between the Ti particles and reactive gases, a home-made gas tunnel was mounted on a conventional plasma gun to perform the spray process. The oxidation behavior of the TiCN coatings under different temperatures in static air was carefully investigated. As a result, when the temperature was over 700 °C, the coatings suffered from serious oxidation, and finally they were entirely oxidized to the TiO2 phase at 1100 °C. The principal oxidation mechanism was clarified, indicating that the oxygen can permeate into the defects and react with TiCN at high temperatures. In addition, concerning the use of a TiCN coating in high-temperature conditions, the microhardness of the oxidized coatings at different treatment temperatures was also evaluated.

  14. Behavioral responses of Atlantic cod to sea temperature changes.

    Science.gov (United States)

    Freitas, Carla; Olsen, Esben Moland; Moland, Even; Ciannelli, Lorenzo; Knutsen, Halvor

    2015-05-01

    Understanding responses of marine species to temperature variability is essential to predict impacts of future climate change in the oceans. Most ectotherms are expected to adjust their behavior to avoid extreme temperatures and minimize acute changes in body temperature. However, measuring such behavioral plasticity in the wild is challenging. Combining 4 years of telemetry-derived behavioral data on juvenile and adult (30-80 cm) Atlantic cod (Gadus morhua), and in situ ocean temperature measurements, we found a significant effect of sea temperature on cod depth use and activity level in coastal Skagerrak. During summer, cod were found in deeper waters when sea surface temperature increased. Further, this effect of temperature was stronger on larger cod. Diel vertical migration, which consists in a nighttime rise to shallow feeding habitats, was stronger among smaller cod. As surface temperature increased beyond ∼15°C, their vertical migration was limited to deeper waters. In addition to larger diel vertical migrations, smaller cod were more active and travelled larger distances compared to larger specimens. Cold temperatures during winter tended, however, to reduce the magnitude of diel vertical migrations, as well as the activity level and distance moved by those smaller individuals. Our findings suggest that future and ongoing rises in sea surface temperature may increasingly deprive cod in this region from shallow feeding areas during summer, which may be detrimental for local populations of the species.

  15. Low-Temperature Oxidation of CO in Smoke: A Review

    Directory of Open Access Journals (Sweden)

    Dyakonov AJ

    2014-12-01

    Full Text Available The low-temperature catalytic oxidation of CO has been reviewed, targeting its possible application to cigarette smoke. The treatment of CO in smoke by using a filter-packed catalyst is extremely complicated by the presence of a variety of chemically active gaseous compounds, a particulate phase, the high velocity of pulsing smoke flow, and ambient temperature. The relevant mechanisms of catalysis and the catalyst preparation variables that could help to overcome these problems are considered. Possible contributors to the overall kinetics that must include variety of diffusion processes were briefly discussed. The chemisorption of O2, CO and CO2 on Pd, Pt and Au and on partially reducible supports, surface reactions and oscillations of the CO oxidation rate were analyzed. The effects of the surface structure and electronic properties of the catalyst support, preparation conditions and presence of a second transition metal on the projected CO oxidation activity of the catalysts in smoke are also discussed. The reviewed catalyst preparation approaches can solve the low-temperature catalyst activity problem. However, more work is required to stabilize this activity of an air-exposed catalyst to provide a necessary shelf life for a cigarette. The greatest challenge seems to be a particular phase - exclusive selectivity that would not contradict with the necessary fast diffusion of gases through the catalyst pores.

  16. Finite-temperature behavior of the Bose polaron

    DEFF Research Database (Denmark)

    Levinsen, Jesper; Parish, Meera M.; Christensen, Rasmus S.

    2017-01-01

    to the critical temperature $T_c$ for Bose-Einstein condensation. These results show that the properties of the impurity vary strongly with temperature. The energy exhibits an intriguing non-monotonic behavior close to $T_c$, and the damping rises sharply close to $T_c$. We finally discuss how these effects can......We consider a mobile impurity immersed in a Bose gas at finite temperature. Using perturbation theory valid for weak coupling between the impurity and the bosons, we derive analytical results for the energy and damping of the impurity for low and high temperatures, as well as for temperatures close...

  17. First principles study of oxidation behavior of irradiated graphite

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Juan; Dong, Limin [Beijing Key Lab of Fine Ceramics, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Wang, Chen [State Key Lab of New Ceramic and Fine Processing, Tsinghua University, Beijing 100084 (China); Liang, Tongxiang, E-mail: txliang@tsinghua.edu.cn [State Key Lab of New Ceramic and Fine Processing, Tsinghua University, Beijing 100084 (China); Lai, Wensheng [Advanced Material Laboratory, School of Materials Science & Engineering, Tsinghua University, Beijing 100084 (China)

    2015-06-01

    The relationship between nuclear graphite microstructure and its oxidation resistance underlines the importance of comprehensive oxidation characterization studies of the new grades of nuclear graphite. Periodic DFT calculations are performed to model oxidation behavior of irradiated graphite. O{sub 2} molecules adsorbed on perfect and defective graphite surfaces are calculated. The adsorptive energy of O{sub 2} on defective graphite adsorption site with one carbon atom missing is approximately 10 times as strong as that on a defect-free perfect graphite surface. Monovacancy and divacancy on graphite surface can easily chemisorb O{sub 2} molecule compared to perfect surface. Two oxidation processes including CO and CO{sub 2} formation steps are analyzed. For symmetric monovacancy defect, three dangling C atoms are unsaturated and exhibit high adsorption ability, as well as reconstructed monovacancy and divacancy defects. These vacancy defects in irradiated graphite decrease oxidation resistance of nuclear graphite.

  18. Bipolar resistive switching in room temperature grown disordered vanadium oxide thin-film devices

    Science.gov (United States)

    Wong, Franklin J.; Sriram, Tirunelveli S.; Smith, Brian R.; Ramanathan, Shriram

    2013-09-01

    We demonstrate bipolar switching with high OFF/ON resistance ratios (>104) in Pt/vanadium oxide/Cu structures deposited entirely at room temperature. The SET (RESET) process occurs when negative (positive) bias is applied to the top Cu electrode. The vanadium oxide (VOx) films are amorphous and close to the vanadium pentoxide stoichiometry. We also investigated Cu/VOx/W structures, reversing the position of the Cu electrode, and found the same polarity dependence with respect to the top and bottom electrodes, which suggests that the bipolar nature is linked to the VOx layer itself. Bipolar switching can be observed at 100 °C, indicating that it not due to a temperature-induced metal-insulator transition of a vanadium dioxide second phase. We discuss how ionic drift can lead to the bipolar electrical behavior of our junctions, similar to those observed in devices based on several other defective oxides. Such low-temperature processed oxide switches could be of relevance to back-end or package integration processing schemes.

  19. Catalytic combustion over high temperature stable metal oxides

    Energy Technology Data Exchange (ETDEWEB)

    Berg, M. [TPS Termiska Processer AB, Nykoeping (Sweden)

    1996-12-31

    This thesis presents a study of the catalytic effects of two interesting high temperature stable metal oxides - magnesium oxide and manganese substituted barium hexa-aluminate (BMA) - both of which can be used in the development of new monolithic catalysts for such applications. In the first part of the thesis, the development of catalytic combustion for gas turbine applications is reviewed, with special attention to alternative fuels such as low-BTU gas, e.g. produced in an air blown gasifier. When catalytic combustion is applied for such a fuel, the primary advantage is the possibility of decreasing the conversion of fuel nitrogen to NO{sub x}, and achieving flame stability. In the experimental work, MgO was shown to have a significant activity for the catalytic combustion of methane, lowering the temperature needed to achieve 10 percent conversion by 270 deg C compared with homogeneous combustion.The reaction kinetics for methane combustion over MgO was also studied. It was shown that the heterogeneous catalytic reactions were dominant but that the catalytically initiated homogeneous gas phase reactions were also important, specially at high temperatures. MgO and BMA were compared. The latter showed a higher catalytic activity, even when the differences in activity decreased with increasing calcination temperature. For BMA, CO{sub 2} was the only product detected, but for MgO significant amounts of CO and C{sub 2}-hydrocarbons were formed. BMA needed a much lower temperature to achieve total conversion of other fuels, e.g. CO and hydrogen, compared to the temperature for total conversion of methane. This shows that BMA-like catalysts are interesting for combustion of fuel mixtures with high CO and H{sub 2} content, e.g. gas produced from gasification of biomass. 74 refs

  20. Lowering the temperature of solid oxide fuel cells.

    Science.gov (United States)

    Wachsman, Eric D; Lee, Kang Taek

    2011-11-18

    Fuel cells are uniquely capable of overcoming combustion efficiency limitations (e.g., the Carnot cycle). However, the linking of fuel cells (an energy conversion device) and hydrogen (an energy carrier) has emphasized investment in proton-exchange membrane fuel cells as part of a larger hydrogen economy and thus relegated fuel cells to a future technology. In contrast, solid oxide fuel cells are capable of operating on conventional fuels (as well as hydrogen) today. The main issue for solid oxide fuel cells is high operating temperature (about 800°C) and the resulting materials and cost limitations and operating complexities (e.g., thermal cycling). Recent solid oxide fuel cells results have demonstrated extremely high power densities of about 2 watts per square centimeter at 650°C along with flexible fueling, thus enabling higher efficiency within the current fuel infrastructure. Newly developed, high-conductivity electrolytes and nanostructured electrode designs provide a path for further performance improvement at much lower temperatures, down to ~350°C, thus providing opportunity to transform the way we convert and store energy.

  1. Low Temperature Resistive Switching Behavior in a Manganite

    Science.gov (United States)

    Salvo, Christopher; Lopez, Melinda; Tsui, Stephen

    2012-02-01

    The development of new nonvolatile memory devices remains an important field of consumer electronics. A possible candidate is bipolar resistive switching, a method by which the resistance of a material changes when a voltage is applied. Although there is a great deal of research on this topic, not much has been done at low temperatures. In this work, we compare the room temperature and low temperature behaviors of switching in a manganite thin film. The data indicates that the switching is suppressed upon cooling to cryogenic temperatures, and the presence of crystalline charge traps is tied to the physical mechanism.

  2. High-temperature oxidation and ignition of metals

    Science.gov (United States)

    Hill, Paul R; Adamson, David; Foland, Douglas H; Bressette, Walter E

    1956-01-01

    A study of the high-temperature oxidation of several aircraft construction materials was undertaken to assess the possibility of ignition under high-temperature flight conditions.Tests have been made both in open and closed jets, and, in addition, the burning of metals has been observed under static conditions in a pressurized vessel containing either air, oxygen, or nitrogen. When heated in an atmosphere of oxygen or when heated and plunged into a supersonic airstream, titanium, iron, carbon steel, and common alloys such as 4130 were found to have spontaneous-ignition temperatures in the solid phase (below melting) and they melted rapidly while burning. Inconel, copper, 18-8 stainless steel, Monel, and aluminum could not be made to ignite spontaneously at temperatures up to melting with the equipment available. Magnesium ignited spontaneously in either type of test at temperatures just above the melting temperature.A theory for the spontaneous ignition of metals, based on the first law of thermodynamics, is presented. Good correlation was obtained between calculated spontaneous-ignition temperatures and values measured in supersonic jet tests. There appears at the present time to be no need for concern regarding the spontaneous ignition of Inconel, the stainless steels, copper, aluminum, or magnesium for ordinary supersonic airplane or missile applications where the material temperature is kept within ordinary structural limits or at least below melting. For hypersonic applications where the material is to be melted away to absorb the heat of convection, the results of the present tests do not apply sufficiently to allow a conclusion.

  3. Revisiting Oxidative Dehydrogenation of Ethane by W Doping into MoVMn Mixed Oxides at Low Temperature

    Directory of Open Access Journals (Sweden)

    Mohammed H. Al-Hazmi

    2015-01-01

    Full Text Available The catalytic performance of MoVMnW mixed oxides was investigated in the oxidative dehydrogenation of ethane at three different reaction temperatures (235, 255, and 275°C using oxygen as an oxidant. The catalysts were characterized by using X-ray diffraction, temperature-programmed reduction, and scanning electron microscopy. The MoVMnW mixed oxide catalyst showed the 70–90% of ethylene selectivity at the reaction temperatures. However, a significant decrease in the selectivity of ethylene was observed by increasing the reaction temperature from 235°C to 275°C.

  4. extract attenuates MPTP-induced oxidative stress and behavioral

    African Journals Online (AJOL)

    Purpose: To evaluate the protective effects of Cuminum cyminum Linn (Apiaceae, CCY) against 1- methyl-4 phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced oxidative stress and behavioral impairments in mouse model of Parkinson's disease (PD). Methods: MPTP-intoxicated mice model of PD was used for evaluating ...

  5. Polymerization behavior of butyl bis(hydroxymethyl)phosphine oxide ...

    Indian Academy of Sciences (India)

    lenovo

    Polymerization behavior of butyl bis(hydroxymethyl)phosphine oxide: Phosphorus containing polyethers for. Li‒ion conductivities. Heeralal Vignesh Babu, Billakanti Srinivas and Krishnamurthi Muralidharan*. School of Chemistry, University of Hyderabad, Hyderabad - 500046, India. Table of Contents. TGA plots of SPE2.

  6. Modeling high temperature materials behavior for structural analysis

    CERN Document Server

    Naumenko, Konstantin

    2016-01-01

    This monograph presents approaches to characterize inelastic behavior of materials and structures at high temperature. Starting from experimental observations, it discusses basic features of inelastic phenomena including creep, plasticity, relaxation, low cycle and thermal fatigue. The authors formulate constitutive equations to describe the inelastic response for the given states of stress and microstructure. They introduce evolution equations to capture hardening, recovery, softening, ageing and damage processes. Principles of continuum mechanics and thermodynamics are presented to provide a framework for the modeling materials behavior with the aim of structural analysis of high-temperature engineering components.

  7. Sensing temperature via downshifting emissions of lanthanide-doped metal oxides and salts. A review

    Science.gov (United States)

    Dramićanin, Miroslav D.

    2016-12-01

    Temperature is important because it has an effect on even the tiniest elements of daily life and is involved in a broad spectrum of human activities. That is why it is the most commonly measured physical quantity. Traditional temperature measurements encounter difficulties when used in some emerging technologies and environments, such as nanotechnology and biomedicine. The problem may be alleviated using optical techniques, one of which is luminescence thermometry. This paper reviews the state of luminescence thermometry and presents different temperature read-out schemes with an emphasis on those utilizing the downshifting emission of lanthanide-doped metal oxides and salts. The read-out schemes for temperature include those based on measurements of spectral characteristics of luminescence (band positions and shapes, emission intensity and ratio of emission intensities), and those based on measurements of the temporal behavior of luminescence (lifetimes and rise times). This review (with 140 references) gives the basics of the fundamental principles and theory that underlie the methods presented, and describes the methodology for the estimation of their performance. The major part of the text is devoted to those lanthanide-doped metal oxides and salts that are used as temperature probes, and to the comparison of their performance and characteristics.

  8. Film collapse behavior on high temperature particle surface

    Energy Technology Data Exchange (ETDEWEB)

    Tochio, Daisuke; Abe, Yutaka [Department of Mechanical Systems Engineering, Yamagata University, Yonezawa, Yamagata (Japan)

    1999-07-01

    It is pointed out that large-scale vapor explosion may occurred during a severe accident of a nuclear power plant. It is important to predict the possibility of the vapor explosion for the accident management of the nuclear power plant during a severe accident. The thermal detonation model is proposed to predict the vapor explosion. In the thermal detonation model, vapor explosion is started by a trigger. The trigger is vapor film collapse around high temperature material droplets coarsely pre-mixed in low temperature liquid. In the premixing stage, high temperature material droplets are insulated from low temperature liquid by the vapor film. Once the vapor film is collapsed, very quick and large heat transfer starts followed by the atomization. In order to clarify the trigger condition of the vapor explosion, it is necessary to identify the mechanism of the film collapse on the high temperature droplet surface in low temperature particle surface. Since the steam film on a high temperature droplet is unstable in high subcooling condition of low temperature liquid, the possibility of the self-collapse of the steam film is high. On the other hand, the possibility of the film collapse is not high in low subcooling or saturated condition since the steam film is tough. There are many experimental studies on the vapor film collapse behavior on the high temperature material surface. Most of those studies, vapor film collapse follows by the atomization , since melted droplets are used in those experiments. And the experiments used solid material is limited for the cylindrical or flat plate geometry. At present, there is no experimental database on the microscopic mechanism of steam film collapse behavior in spherical geometry for wide range of subcooling conditions. In the present study, steam film collapse behavior on a stainless steel particle surface is experimentally investigated. The stainless steel particle heated up by a burner is immersed into water in a stainless

  9. Green synthesis of Ni-Nb oxide catalysts for low-temperature oxidative dehydrogenation of ethane

    KAUST Repository

    Zhu, Haibo

    2015-03-05

    The straightforward solid-state grinding of a mixture of Ni nitrate and Nb oxalate crystals led to, after mild calcination (T<400°C), nanostructured Ni-Nb oxide composites. These new materials efficiently catalyzed the oxidative dehydrogenation (ODH) of ethane to ethylene at a relatively low temperature (T<300°C). These catalysts appear to be much more stable than the corresponding composites prepared by other chemical methods; more than 90% of their original intrinsic activity was retained after 50h with time on-stream. Furthermore, the stability was much less affected by the Nb content than in composites prepared by classical "wet" syntheses. These materials, obtained in a solvent-free way, are thus promising green and sustainable alternatives to the current Ni-Nb candidates for the low-temperature ODH of ethane.

  10. Oxidation Behavior of Carbon Fiber-Reinforced Composites

    Science.gov (United States)

    Sullivan, Roy M.

    2008-01-01

    OXIMAP is a numerical (FEA-based) solution tool capable of calculating the carbon fiber and fiber coating oxidation patterns within any arbitrarily shaped carbon silicon carbide composite structure as a function of time, temperature, and the environmental oxygen partial pressure. The mathematical formulation is derived from the mechanics of the flow of ideal gases through a chemically reacting, porous solid. The result of the formulation is a set of two coupled, non-linear differential equations written in terms of the oxidant and oxide partial pressures. The differential equations are solved simultaneously to obtain the partial vapor pressures of the oxidant and oxides as a function of the spatial location and time. The local rate of carbon oxidation is determined at each time step using the map of the local oxidant partial vapor pressure along with the Arrhenius rate equation. The non-linear differential equations are cast into matrix equations by applying the Bubnov-Galerkin weighted residual finite element method, allowing for the solution of the differential equations numerically.

  11. Low temperature oxidation of benzene and toluene in mixture withn-decane.

    Science.gov (United States)

    Herbinet, Olivier; Husson, Benoit; Ferrari, Maude; Glaude, Pierre-Alexandre; Battin-Leclerc, Frédérique

    2013-01-01

    The oxidation of two blends, benzene/ n -decane and toluene/ n -decane, was studied in a jet-stirred reactor with gas chromatography analysis (temperatures from 500 to 1100 K, atmospheric pressure, stoichiometric mixtures). The studied hydrocarbon mixtures contained 75% of aromatics in order to highlight the chemistry of the low-temperature oxidation of these two aromatic compounds which have a very low reactivity compared to large alkanes. The difference of behavior between the two aromatic reactants is highly pronounced concerning the formation of derived aromatic products below 800 K. In the case of benzene, only phenol could be quantified. In the case of toluene, significant amounts of benzaldehyde, benzene, and cresols were also formed, as well as several heavy aromatic products such as bibenzyl, phenylbenzylether, methylphenylbenzylether, and ethylphenylphenol. A comparison with results obtained with neat n -decane showed that the reactivity of the alkane is inhibited by the presence of benzene and, to a larger extent, toluene. An improved model for the oxidation of toluene was developed based on recent theoretical studies of the elementary steps involved in the low-temperature chemistry of this molecule. Simulations using this model were successfully compared with the obtained experimental results.

  12. The tensile behavior of GH3535 superalloy at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Han, F.F.; Zhou, B.M.; Huang, H.F.; Leng, B.; Lu, Y.L. [Thorium Molten Salts Reactor Center, Shanghai Institute of Applied Physics, Chinese Academy of Sciences (China); Dong, J.S. [Superalloy Division, Institute of Metal Research, Chinese Academy of Sciences (China); Li, Z.J., E-mail: lizhijun@sinap.ac.cn [Thorium Molten Salts Reactor Center, Shanghai Institute of Applied Physics, Chinese Academy of Sciences (China); Zhou, X.T. [Thorium Molten Salts Reactor Center, Shanghai Institute of Applied Physics, Chinese Academy of Sciences (China)

    2016-10-01

    The tensile behavior of GH3535 alloy has been investigated at strain rates of 8.33 × 10{sup −5}/s{sup −1}–8.33 × 10{sup −3}/s{sup −1}, in the temperature range of 25–800 °C. The results showed that the ultimate tensile strength was decreased with increasing temperature and increased with rising strain rate, whereas the yield strength kept almost a constant value at the temperature range from 550 to 800 °C in all strain rates test. The formation of M{sub 12}C carbides at the grain boundary during the tension process played an important role in increasing the yield strength of the alloy at elevated temperatures. But inhomogeneous deformation at 650 °C resulted in the minimum ductility of the alloy. Additionally, various types of serrations were noticed on the stress-strain curves for the alloy tested in the temperature range of 500–800 °C. Normal Portevin-Le Chatelier (PLC) effect and positive strain rate sensitivity were observed in this alloy. Type A and A + B serrations were presented to stress-strain curves at temperatures below 650 °C, whereas type C serration was noticed when the temperature rose above 650 °C. The analysis suggested that the interactions between substitutional solutes migration and mobile dislocations were the main reason for the serrated flow behavior in this alloy. - Highlights: • The tensile behavior of GH3535 alloy at elevated temperature was studied. • The yield strength anomaly was observed in the temperature range from 550 to 800 °C. • The formation of M{sub 12}C improves the grain boundary strength to a certain extent. • Inhomogeneous deformation at 650 °C results in the ductility loss of the alloy. • The interaction between solute atoms and dislocations results in the PLC effect.

  13. Thermal sensor based zinc oxide diode for low temperature applications

    Energy Technology Data Exchange (ETDEWEB)

    Ocaya, R.O. [Department of Physics, University of the Free State (South Africa); Al-Ghamdi, Ahmed [Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah, 21589 (Saudi Arabia); El-Tantawy, F. [Department of Physics, Faculty of Science, Suez Canal University, Ismailia (Egypt); Center of Nanotechnology, King Abdulaziz University, Jeddah (Saudi Arabia); Farooq, W.A. [Department of Physics and Astronomy, College of Science, King Saud University, Riyadh (Saudi Arabia); Yakuphanoglu, F., E-mail: fyhan@hotmail.com [Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah, 21589 (Saudi Arabia); Department of Physics, Faculty of Science, Firat University, Elazig, 23169 (Turkey)

    2016-07-25

    The device parameters of Al/p-Si/Zn{sub 1-x}Al{sub x}O-NiO/Al Schottky diode for x = 0.005 were investigated over the 50 K–400 K temperature range using direct current–voltage (I–V) and impedance spectroscopy. The films were prepared using the sol–gel method followed by spin-coating on p-Si substrate. The ideality factor, barrier height, resistance and capacitance of the diode were found to depend on temperature. The calculated barrier height has a mean. Capacitance–voltage (C–V) measurements show that the capacitance decreases with increasing frequency, suggesting a continuous distribution of interface states over the surveyed 100 kHz to 1 MHz frequency range. The interface state densities, N{sub ss}, of the diode were calculated and found to peak as functions of bias and temperature in two temperature regions of 50 K–300 K and 300 K–400 K. A peak value of approximately 10{sup 12}/eV cm{sup 2} was observed around 0.7 V bias for 350 K and at 3 × 10{sup 12}/eVcm{sup 2} around 2.2 V bias for 300 K. The relaxation time was found to average 4.7 μs over all the temperatures, but showing its lowest value of 1.58 μs at 300 K. It is seen that the interface states of the diode is controlled by the temperature. This suggests that Al/p-Si/Zn1-xAlxO-NiO/Al diode can be used as a thermal sensors for low temperature applications. - Highlights: • Al/pSi/Zn1-xAlxO-NiO/Al Schottky diode was fabricated by sol gel method. • The interface state density of the diode is controlled by the temperature. • Zinc oxide based diode can be used as a thermal sensor for low temperature applications.

  14. Oxidation behavior of Ni powder and Ni powder compact; Ni fun oyobi Ni fun atsufuntai no sanka kyodo

    Energy Technology Data Exchange (ETDEWEB)

    Yamazaki, M.; Ochiai, S.; Watanabe, Y. [Teikyo Univ., Tokyo (Japan)

    1997-09-15

    With an objective to investigate reactions of metal powder and metal powder compact having open pores with gases, their oxidation behavior was elucidated by taking Ni powder and Ni powder compact as examples. Oxidation rate of the Ni powder can be expressed by the Jander equation, and activation energy for the oxidation was 0.948 times 10 {sup 5} J/mol. Oxidation rate of the Ni powder compact is equal to that of powder not made into compact in the initial stage of the oxidation, but it decreases as time elapses because of occurrence of packing of oxide. Difference in oxidation rate inside and outside the powder compact is very little. The oxidation rate of the powder compact was analyzed by using an improved Jander model. More specifically, a model was used, in which concentration difference of diffused components in the oxides decreases with progress of the oxidation, whereas 1.113 times 10 {sup 5} J/mol was derived as the activation energy of the oxidation. The cause for the activation energy for the oxidation of the powder and powder compact being about half of that for bulk Ni is because of low temperature oxidation of the powder, and tensile stress generated between metal particles and spherical shell shaped oxides, which make production of Ni {sup 2+} more difficult. 5 refs., 4 figs., 1 tab.

  15. Detailed product analysis during low- and intermediate-temperature oxidation of ethylcyclohexane.

    Science.gov (United States)

    Husson, B; Herbinet, O; Glaude, P A; Ahmed, S S; Battin-Leclerc, F

    2012-05-31

    An experimental study of the oxidation of ethylcyclohexane has been performed in a jet-stirred reactor with online gas chromatography, under quasi-atmospheric pressure (800 Torr), at temperatures ranging from 500 to 1100 K (low- and intermediate-temperature zone including the negative temperature coefficient area), at a residence time of 2 s, and for three equivalence ratios (0.25, 1, and 2). Ethylcyclohexane displays important low-temperature reactivity with a well-marked negative temperature coefficient behavior. In addition to 47 products with a mass lower than ethylcyclohexane which have been quantified, many species with a C(8)H(14)O formula (molecular weight of 126) were detected by GC-MS and 7 of them were quantified. These molecules are cyclic ethers, ketones, and aldehydes with the same carbon skeleton as the reactant. Experiments were also carried on under the same conditions for two other C(8) hydrocarbons, n-octane and 1-octene, showing that the reactivity of ethylcyclohexane is close to that of the alkene and lower than that of the alkane. Simulations using a detailed kinetic model of the literature allow a good prediction of the global reactivity and of the main hydrocarbon products for temperatures above 800 K. The main reaction channels leading to the observed reaction products at both low (below 800 K) and intermediate temperature (above 800 K) are discussed.

  16. A High Temperature Experimental Characterization Procedure for Oxide-Based Thermoelectric Generator Modules under Transient Conditions

    Directory of Open Access Journals (Sweden)

    Elena Anamaria Man

    2015-11-01

    Full Text Available The purpose of this study is to analyze the steady-state and transient behavior of the electrical and thermal parameters of thermoelectric generators (TEGs. The focus is on the required wait-time between measurements in order to reduce measurement errors which may appear until the system reaches steady-state. By knowing this waiting time, the total characterization time can also be reduced. The experimental characterization process is performed on a test rig known as TEGeta, which can be used to assess the output characteristics of TEG modules under different load values and temperature conditions. The setup offers the possibility to control the hot side temperature up to 1000 °C with a load variation range value between 0.22–8.13 Ω. A total of ten thermocouples are placed in the setup with the purpose of measuring the temperature in specific points between the heater and the heat sink. Based on the readings, the temperature on the hot and cold side of the modules can be extrapolated. This study provides quantitative data on the minimum waiting time of the temperatures in the surrounding system to reach equilibrium. Laboratory tests are performed on a calcium-manganese oxide module at temperatures between 400 and 800 °C to explore the high temperatures features of the setup.

  17. Investigation of the oxidation behavior of diesel particulate matter

    Energy Technology Data Exchange (ETDEWEB)

    Yezerets, Aleksey; Currier, Neal W.; Eadler, Heather A.; Suresh, Arvind; Madden, Paula F.; Branigin, Mark A. [Cummins Inc., 1900 McKinley Avenue, Columbus, IN 47201 (United States)

    2003-12-01

    In this work, an attempt was made to identify and decouple several effects contributing to the complexity of kinetics of diesel particulate matter oxidation by oxygen. Adsorbed hydrocarbons provided limited contribution to the overall reactivity of the un-pretreated particulate matter. Even upon their thermal desorption, the first few percents of carbon in particulate matter were oxidized at an anomalously high rate. Further oxidation occurred at a lower rate with rather uniform kinetic characteristics. The high initial reactivity can be restored repeatedly by exposure of particulate matter to the ambient air for the prolonged periods of time (weeks) at room temperature. The experimental results suggest that these changes in reactivity of carbon are chemical, not morphological, in nature. The results are consistent with the hypothesis that prolonged ambient aging leads to formation of some highly reactive groups on the carbon surface, responsible for the subsequent relatively facile initial oxidation. A high density of these surface groups presumably cannot be obtained during the more vigorous oxidation process at higher temperatures.

  18. Oxidation behavior of Ru–Al multilayer coatings

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yung-I, E-mail: yichen@mail.ntou.edu.tw; Zheng, Zhi-Ting; Kai, Wu; Huang, Yu-Ren

    2017-06-01

    Highlights: • Ru{sub 0.63}Al{sub 0.37} multilayer coatings were fabricated using cosputtering. • Oxidation behavior of Ru{sub 0.63}Al{sub 0.37} coatings in 1% O{sub 2}–99% Ar was studied. • Internal oxidation of Ru{sub 0.63}Al{sub 0.37} coatings at 400–600 °C was multi stage parabolic. • External oxidation of Ru{sub 0.63}Al{sub 0.37} was conducted after annealing at 700–800 °C. - Abstract: Ru{sub 0.63}Al{sub 0.37} coatings were deposited through a cyclical gradient concentration deposition at 400 °C with a substrate-holder rotation speed of 1 rpm by direct current magnetron cosputtering. Scanning electron microscopy revealed that the as-deposited coatings exhibited a multilayer structure along with the columnar structure. The oxidation behavior of the Ru{sub 0.63}Al{sub 0.37} coatings was examined through X-ray diffraction, Auger electron spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Oxidation kinetics was measured using a thermogravimetric analyzer. Internal oxidation was observed for Ru{sub 0.63}Al{sub 0.37} coatings annealed in a 1% O{sub 2}–99% Ar atmosphere at 400–600 °C accompanied with activation energies of 72–84 kJ/mol. By contrast, external oxidation was observed after annealing at 700–800 °C, resulting in the formation of a continuous alumina scale consisting of crystalline δ-Al{sub 2}O{sub 3} domains, which can be attributable to the outward diffusion of Al.

  19. Crystalline-like temperature dependence of the electrical characteristics in amorphous Indium-Gallium-Zinc-Oxide thin film transistors

    Science.gov (United States)

    Estrada, M.; Hernandez-Barrios, Y.; Cerdeira, A.; Ávila-Herrera, F.; Tinoco, J.; Moldovan, O.; Lime, F.; Iñiguez, B.

    2017-09-01

    A crystalline-like temperature dependence of the electrical characteristics of amorphous Indium-Gallium-Zinc-Oxide (a-IGZO) thin film transistors (TFTs) is reported, in which the drain current reduces as the temperature is increased. This behavior appears for values of drain and gate voltages above which a change in the predominant conduction mechanism occurs. After studying the possible conduction mechanisms, it was determined that, for gate and drain voltages below these values, hopping is the predominant mechanism with the current increasing with temperature, while for values above, the predominant conduction mechanism becomes percolation in the conduction band or band conduction and IDS reduces as the temperature increases. It was determined that this behavior appears, when the effect of trapping is reduced, either by varying the density of states, their characteristic energy or both. Simulations were used to further confirm the causes of the observed behavior.

  20. Temperature Dependent Variations of Phonon Interactions in Nanocrystalline Cerium Oxide

    Directory of Open Access Journals (Sweden)

    Sugandha Dogra Pandey

    2015-01-01

    Full Text Available The temperature dependent anharmonic behavior of the phonon modes of nanocrystalline CeO2 was investigated in the temperature range of 80–440 K. The anharmonic constants have been derived from the shift in phonon modes fitted to account for the anharmonic contributions as well as the thermal expansion contribution using the high pressure parameters derived from our own high pressure experimental data reported previously. The total anharmonicity has also been estimated from the true anharmonicity as well as quasiharmonic component. In the line-width variation analysis, the cubic anharmonic term was found to dominate the quartic term. Finally, the phonon lifetime also reflected the trend so observed.

  1. The oxidation behavior of SiC sintered with Al-B-C and improved oxidation resistance via heat treatments

    Energy Technology Data Exchange (ETDEWEB)

    Sixta, Mark [Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering

    1997-12-01

    The oxidation behavior of high strength and high toughness SiC, sintered with Al, B, and C (ABC-SiC), was examined. Kinetic data were acquired and the parabolic rate constant for oxidation was determined and compared with literature data on various SiC materials. The role of secondary phases on the oxide morphology was explored. ABC-SiC was compared to commercially available SiC, Hexoloy, and SiC sintered with 10% yttrium aluminum garnet (YAG). Two-step sintering (pre-coarsening) was employed with holds for 48 hours at 600-1,600°C, prior to the typical hot-pressing conditions of 1,900°C for 1 hour, to change the chemistry and reduce the number of bubbles in the silica scale. The effects on the oxide thickness and integrity was examined as a function of the precoarsening heat treatment temperature. Additionally, the hot-pressed ABC-SiC was subjected to heat treatments (anneals) at 1,800°C for 1 hour in nitrogen, Ar, and vacuum environments, and the effects on subsequent oxidation were evaluated. The Ar and vacuum heat treatments dramatically improved the oxidation resistance of ABC-SiC. Finally, reoxidation experiments were performed to try to alter the surface chemistry of the SiC to improve the oxidation resistance. The four-point bend strengths and two-parameter Weibull plots of the most successful heat treatments were compared with the standard ABC-SiC to ensure that significant degradation did not result from altering the processing of the material.

  2. Thermal Behavior of Cylindrical Buckling Restrained Braces at Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Elnaz Talebi

    2014-01-01

    Full Text Available The primary focus of this investigation was to analyze sequentially coupled nonlinear thermal stress, using a three-dimensional model. It was meant to shed light on the behavior of Buckling Restraint Brace (BRB elements with circular cross section, at elevated temperature. Such bracing systems were comprised of a cylindrical steel core encased in a strong concrete-filled steel hollow casing. A debonding agent was rubbed on the core’s surface to avoid shear stress transition to the restraining system. The numerical model was verified by the analytical solutions developed by the other researchers. Performance of BRB system under seismic loading at ambient temperature has been well documented. However, its performance in case of fire has yet to be explored. This study showed that the failure of brace may be attributed to material strength reduction and high compressive forces, both due to temperature rise. Furthermore, limiting temperatures in the linear behavior of steel casing and concrete in BRB element for both numerical and analytical simulations were about 196°C and 225°C, respectively. Finally it is concluded that the performance of BRB at elevated temperatures was the same as that seen at room temperature; that is, the steel core yields prior to the restraining system.

  3. Polarization-coupled tunable resistive behavior in oxide ferroelectric heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Gruverman, Alexei [Univ. of Nebraska, Lincoln, NE (United States); Tsymbal, Evgeny Y. [Univ. of Nebraska, Lincoln, NE (United States); Eom, Chang-Beom [Univ. of Wisconsin, Madison, WI (United States)

    2017-05-03

    This research focuses on investigation of the physical mechanism of the electrically and mechanically tunable resistive behavior in oxide ferroelectric heterostructures with engineered interfaces realized via a strong coupling of ferroelectric polarization with tunneling electroresistance and metal-insulator (M-I) transitions. This report describes observation of electrically conductive domain walls in semiconducting ferroelectrics, voltage-free control of resistive switching and demonstration of a new mechanism of electrical control of 2D electron gas (2DEG) at oxide interfaces. The research goals are achieved by creating strong synergy between cutting-edge fabrication of epitaxial single-crystalline complex oxides, nanoscale electrical characterization by scanning probe microscopy and theoretical modeling of the observed phenomena. The concept of the ferroelectric devices with electrically and mechanically tunable nonvolatile resistance represents a new paradigm shift in realization of the next-generation of non-volatile memory devices and low-power logic switches.

  4. Deflagration Behavior of PBX 9501 at Elevated Temperature and Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Maienschein, J L; Koerner, J G

    2008-04-15

    We report the deflagration behavior of PBX 9501 at pressures up to 300 MPa and temperatures of 150-180 C where the sample has been held at the test temperature for several hours before ignition. The purpose is to determine the effect on the deflagration behavior of material damage caused by prolonged exposure to high temperature. This conditioning is similar to that experienced by an explosive while it being heated to eventual explosion. The results are made more complicated by the presence of a significant thermal gradient along the sample during the temperature ramp and soak. Three major conclusions are: the presence of nitroplasticizer makes PBX 9501 more thermally sensitive than LX-04 with an inert Viton binder; the deflagration behavior of PBX 9501 is more extreme and more inconsistent than that of LX-04; and something in PBX 9501 causes thermal damage to 'heal' as the deflagration proceeds, resulting in a decelerating deflagration front as it travels along the sample.

  5. Effects of mine strata thermal behavior and mine initial temperatures on mobile refuge alternative temperature.

    Science.gov (United States)

    Yantek, D S; Yan, L; Bissert, P T; Klein, M D

    2017-04-01

    Federal regulations require the installation of refuge alternatives (RAs) in underground coal mines. Mobile RAs have a limited ability to dissipate heat, and heat buildup can lead to a life-threatening condition as the RA internal air temperature and relative humidity increase. The U.S. National Institute for Occupational Safety and Health (NIOSH) performed heat testing on a 10-person tent-type training RA and contracted ThermoAnalytics Inc. to develop a validated thermal simulation model of the tested RA. The model was used to examine the effects of the constant mine strata temperature assumption, initial mine air temperature, initial mine strata surface temperature (MSST), initial mine strata temperature at depth (MSTD) and mine strata thermal behavior on RA internal air temperature using 117 W (400 Btu/h) of sensible heat input per simulated miner. For the studied RA, when the mine strata temperature was treated as a constant, the final predicted RA internal air temperature was 7.1°C (12.8°F) lower than it was when the mine strata thermal behavior was included in the model. A 5.6°C (10.0°F) increase in the initial MSST resulted in a 3.9°C (7.1°F) increase in the final RA internal air temperature, whereas a 5.6°C (10°F) increase in the initial MSTD yielded a 1.4°C (2.5°F) increase in the final RA internal air temperature. The results indicate that mine strata temperature increases and mine strata initial temperatures must be accounted for in the physical testing or thermal simulations of RAs.

  6. Hydrogen reduction of molybdenum oxide at room temperature

    Science.gov (United States)

    Borgschulte, Andreas; Sambalova, Olga; Delmelle, Renaud; Jenatsch, Sandra; Hany, Roland; Nüesch, Frank

    2017-01-01

    The color changes in chemo- and photochromic MoO3 used in sensors and in organic photovoltaic (OPV) cells can be traced back to intercalated hydrogen atoms stemming either from gaseous hydrogen dissociated at catalytic surfaces or from photocatalytically split water. In applications, the reversibility of the process is of utmost importance, and deterioration of the layer functionality due to side reactions is a critical challenge. Using the membrane approach for high-pressure XPS, we are able to follow the hydrogen reduction of MoO3 thin films using atomic hydrogen in a water free environment. Hydrogen intercalates into MoO3 forming HxMoO3, which slowly decomposes into MoO2 +1/2 H2O as evidenced by the fast reduction of Mo6+ into Mo5+ states and slow but simultaneous formation of Mo4+ states. We measure the decrease in oxygen/metal ratio in the thin film explaining the limited reversibility of hydrogen sensors based on transition metal oxides. The results also enlighten the recent debate on the mechanism of the high temperature hydrogen reduction of bulk molybdenum oxide. The specific mechanism is a result of the balance between the reduction by hydrogen and water formation, desorption of water as well as nucleation and growth of new phases.

  7. The air oxidation behavior of lanthanum ion implanted zirconium at 500 deg. C

    CERN Document Server

    Peng, D Q; Chen, X W; Zhou, Q G

    2003-01-01

    The beneficial effect of lanthanum ion implantation on the oxidation behavior of zirconium at 500 deg. C has been studied. Zirconium specimens were implanted by lanthanum ions using a MEVVA source at energy of 40 keV with a fluence range from 1x10 sup 1 sup 6 to 1x10 sup 1 sup 7 ions/cm sup 2 at maximum temperature of 130 deg. C, The weight gain curves were measured after being oxidized in air at 500 deg. C for 100 min, which showed that a significant improvement was achieved in the oxidation behavior of zirconium ion implanted with lanthanum compared with that of the as-received zirconium. The valence of the oxides in the scale was analyzed by X-ray photoemission spectroscopy; and then the depth distributions of the elements in the surface of the samples were obtained by Auger electron spectroscopy. Glancing angle X-ray diffraction at 0.3 deg. incident angles was employed to examine the modification of its phase transformation because of the lanthanum ion implantation in the oxide films. It was obviously fou...

  8. Inhibited phase behavior of gas hydrates in graphene oxide: influences of surface and geometric constraints.

    Science.gov (United States)

    Kim, Daeok; Kim, Dae Woo; Lim, Hyung-Kyu; Jeon, Jiwon; Kim, Hyungjun; Jung, Hee-Tae; Lee, Huen

    2014-11-07

    Porous materials have provided us unprecedented opportunities to develop emerging technologies such as molecular storage systems and separation mechanisms. Pores have also been used as supports to contain gas hydrates for the application in gas treatments. Necessarily, an exact understanding of the properties of gas hydrates in confining pores is important. Here, we investigated the formation of CO2, CH4 and N2 hydrates in non-interlamellar voids in graphene oxide (GO), and their thermodynamic behaviors. For that, low temperature XRD and P-T traces were conducted to analyze the water structure and confirm hydrate formation, respectively, in GO after its exposure to gaseous molecules. Confinement and strong interaction of water with the hydrophilic surface of graphene oxide reduce water activity, which leads to the inhibited phase behavior of gas hydrates.

  9. Influence of temperature on oxidation behaviour of ZE41 magnesium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, M.D., E-mail: mariadolores.lopez@urjc.e [Dpto. de Ciencia e Ingenieria de Materiales, Universidad Rey Juan Carlos, 28933 Mostoles (Spain); Munez, C.J. [Dpto. de Ciencia e Ingenieria de Materiales, Universidad Rey Juan Carlos, 28933 Mostoles (Spain); Carboneras, M. [Dpto. de Ciencia e Ingenieria de Materiales, Universidad Rey Juan Carlos, 28933 Mostoles (Spain); Centro Nacional de Investigaciones Metalurgicas (CENIM), CSIC, 28040 Madrid (Spain); Rodrigo, P.; Escalera, M.D.; Otero, E. [Dpto. de Ciencia e Ingenieria de Materiales, Universidad Rey Juan Carlos, 28933 Mostoles (Spain)

    2010-02-18

    The influence of temperature on the oxidation behaviour of commercial ZE41 magnesium alloy has been studied. Thermogravimetric tests were carried out to determine the oxidation kinetics in the 350-500 {sup o}C range. Morphology and growth of the oxidation films were analysed by Scanning Electronic Microscopy (SEM), Energy Dispersive X-Ray Spectrometry (EDS) and X-Ray Diffraction (XRD). It was found that the oxidation kinetics initially follow a parabolic law, following a linear law for higher exposure times. Results also showed that the protective nature of the oxide layer depends on the oxidation temperature. At temperatures in the range of 350-450 {sup o}C the ZE41 alloy is covered by a protective oxide layer, very thin and compact, whereas the oxide layer formed at 500 {sup o}C exhibits a non-protective nature, showing an 'oxide sponges' morphology.

  10. Conductivity of SrTiO3 based oxides in the reducing atmosphere at high temperature

    DEFF Research Database (Denmark)

    Hashimoto, Shin-Ichi; Poulsen, Finn Willy; Mogensen, Mogens Bjerg

    2007-01-01

    The conductivities of several donor-doped SrTiO3 based oxides, which were prepared in air, were studied in a reducing atmosphere at high temperature. The conductivities of all specimens increased slowly with time at 1000 degrees C in 9% H-2/N-2, even after 100 h. Nb-doped SrTiO3 showed relatively...... at 500-800 degrees C, while that of La-doped SrTiO3 dropped immediately on exposure to air. The conduction behavior of Nb-doped SrTiO3 was explained by reduction of Ti4+ and/or Nb5+ and the relatively slow oxygen diffusibility. (c) 2006 Elsevier B.V. All rights reserved.......The conductivities of several donor-doped SrTiO3 based oxides, which were prepared in air, were studied in a reducing atmosphere at high temperature. The conductivities of all specimens increased slowly with time at 1000 degrees C in 9% H-2/N-2, even after 100 h. Nb-doped SrTiO3 showed relatively...... fast reduction and high conductivity compared with the other SrTiO3 based oxides. The conductivity of Nb-doped SrTiO3 was ca. 50 S cm(-1) at 500 degrees C after reduction at 1200 degrees C. After strong reduction, the conductivity of Nb-doped SrTiO3 was almost independent of the oxygen partial pressure...

  11. Bipolar Switching Properties of Neodymium Oxide RRAM Devices Using by a Low Temperature Improvement Method

    Directory of Open Access Journals (Sweden)

    Kai-Huang Chen

    2017-12-01

    Full Text Available Bipolar resistive switching properties and endurance switching behavior of the neodymium oxide (Nd2O3 thin films resistive random access memory (RRAM devices for a high resistive status/low resistive status (HRS/LRS using a low temperature supercritical carbon dioxide fluid (SCF improvement post-treatment process were investigated. Electrical and physical properties improvement of Nd2O3 thin films were measured by X-ray diffraction (XRD, scanning electron microscopy (SEM, X-ray photoelectron spectroscopy (XPS, and current versus voltage (I-V measurement. The metal-like behavior of ohmic conduction mechanism and metallic cluster reaction of hopping conduction mechanism in initial metallic filament path forming process of the SCF-treated thin films RRAM devices was assumed and discussed. Finally, the electrical conduction mechanism of the thin films RRAM derives for set/reset was also discussed and verified in filament path physical model.

  12. Study on the Hydrogen Generation Rules of Coal Oxidation at Low Temperature

    OpenAIRE

    Shao He; Zhou Fubao; Chen Kaiyan; Cheng Jianwei; Melogh, Palu H.

    2014-01-01

    Based on a hydrogen desorption experiment and a comparative experiment of low-temperature coal oxidation performed prior to and after hydrogen desorption, this paper demonstrates the occurrence of hydrogen adsorption in coal at room temperature and reveals that the hydrogen generated in the process of coal oxidation originates from coal oxidation and desorption. The results show that the hydrogen accumulation generated only by coal oxidation and the hydrogen accumulation generated...

  13. Low Temperature Constrained Sintering of Cerium Gadolinium OxideFilms for Solid Oxide Fuel Cell Applications

    Energy Technology Data Exchange (ETDEWEB)

    Nicholas, Jason Dale [Univ. of California, Berkeley, CA (United States)

    2007-01-01

    Cerium gadolinium oxide (CGO) has been identified as an acceptable solid oxide fuel cell (SOFC) electrolyte at temperatures (500-700 C) where cheap, rigid, stainless steel interconnect substrates can be used. Unfortunately, both the high sintering temperature of pure CGO, >1200 C, and the fact that constraint during sintering often results in cracked, low density ceramic films, have complicated development of metal supported CGO SOFCs. The aim of this work was to find new sintering aids for Ce0.9Gd0.1O1.95, and to evaluate whether they could be used to produce dense, constrained Ce0.9Gd0.1O1.95 films at temperatures below 1000 C. To find the optimal sintering aid, Ce0.9Gd0.1O1.95 was doped with a variety of elements, of which lithium was found to be the most effective. Dilatometric studies indicated that by doping CGO with 3mol% lithium nitrate, it was possible to sinter pellets to a relative density of 98.5% at 800 C--a full one hundred degrees below the previous low temperature sintering record for CGO. Further, it was also found that a sintering aid's effectiveness could be explained in terms of its size, charge and high temperature mobility. A closer examination of lithium doped Ce0.9Gd0.1O1.95 indicated that lithium affects sintering by producing a Li2O-Gd2O3-CeO2 liquid at the CGO grain boundaries. Due to this liquid phase sintering, it was possible to produce dense, crack-free constrained films of CGO at the record low temperature of 950 C using cheap, colloidal spray deposition processes. This is the first time dense constrained CGO films have been produced below 1000 C and could help commercialize metal supported ceria based solid oxide fuel cells.

  14. Tributylphosphate extraction behavior of bismuthate-oxidized americium.

    Science.gov (United States)

    Mincher, Bruce J; Martin, Leigh R; Schmitt, Nicholas C

    2008-08-04

    Higher oxidation states of americium have long been known; however, options for their preparation in acidic solution are limited. The conventional choice, silver-catalyzed peroxydisulfate, is not useful at nitric acid concentrations above about 0.3 M. We investigated the use of sodium bismuthate as an oxidant for Am (3+) in acidic solution. Room-temperature oxidation produced AmO 2 (2+) quantitatively, whereas oxidation at 80 degrees C produced AmO 2 (+) quantitatively. The efficacy of the method for the production of oxidized americium was verified by fluoride precipitation and by spectroscopic absorbance measurements. We performed absorbance measurements using a conventional 1 cm cell for high americium concentrations and a 100 cm liquid waveguide capillary cell for low americium concentrations. Extinction coefficients for the absorbance of Am (3+) at 503 nm, AmO 2 (+) at 514 nm, and AmO 2 (2+) at 666 nm in 0.1 M nitric acid are reported. We also performed solvent extraction experiments with the hexavalent americium using the common actinide extraction ligand tributyl phosphate (TBP) for comparison to the other hexavalent actinides. Contact with 30% tributyl phosphate in dodecane reduced americium; it was nevertheless extracted using short contact times. The TBP extraction of AmO 2 (2+) over a range of nitric acid concentrations is shown for the first time and was found to be analogous to that of uranyl, neptunyl, and plutonyl ions.

  15. Thermogravimetric study of oxidation of a PdCr alloy used for high-temperature sensors

    Science.gov (United States)

    Boyd, Darwin L.; Zeller, Mary V.

    1994-01-01

    In this study, the oxidation of Pd-13 weight percent Cr, a candidate alloy for high-temperature strain gages, was investigated by thermogravimetry. Although the bulk alloy exhibits linear electrical resistivity versus temperature and stable resistivity at elevated temperatures, problems attributed to oxidation occur when this material is fabricated into strain gages. In this work, isothermal thermogravimetry (TG) was used to study the oxidation kinetics. Results indicate that the oxidation of Pd-13 weight percent Cr was approximately parabolic in time at 600 C but exhibited greater passivation from 700 to 900 C. At 1100 C, the oxidation rate again increased.

  16. Irradiation temperature dependence of production efficiency of lattice defects in some neutron-irradiated oxides

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Moritami [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka 5900494 (Japan)]. E-mail: okada@rri.kyoto-u.ac.jp; Atobe, Kozo [Faculty of Science, Naruto University of Education, Naruto, Tokushima 7728502 (Japan); Nakagawa, Masuo [Faculty of Education, Kagawa University, Takamatsu, Kagawa 7608522 (Japan)

    2004-11-01

    Temperature dependence of production efficiency of irradiation-induced defects in neutron-irradiated oxides has been investigated. Some oxide single crystals, MgO, {alpha}-Al{sub 2}O{sub 3} (sapphire) and TiO{sub 2} (rutile), were irradiated at several controlled temperatures, 10, 20, 50, 100, 150 and 200 K, using the low-temperature irradiation facility of Kyoto University Reactor (KUR-LTL), and at ambient temperature ({approx}370 K) in the same facility. Irradiation temperature dependence of production efficiency of a 1 {mu}m band in TiO{sub 2} differs greatly from that of anion vacancy (F-type centers) in MgO and {alpha}-Al{sub 2}O{sub 3}. Results for MgO and {alpha}-Al{sub 2}O{sub 3} show steep negative gradients from 10 to 370 K, whereas that for TiO{sub 2} includes a valley between 40 and 60 K and a hump at about 130 K, and then disappear at about 200 K. In MgO and {alpha}-Al{sub 2}O{sub 3}, this behavior can be explained by the recombination of Frenkel pairs, which is activated at higher temperature. In TiO{sub 2}, in addition to the recombination mechanism, a covalent bonding property is thought to be exerted strong influence, and it is suggested that a disappearance of the 1 {mu}m band at above 200 K is due to the recombination process of Frenkel pairs which is caused by the irradiation-induced crystallization.

  17. The “Puzzle” of Water Behavior at Low Temperature

    Directory of Open Access Journals (Sweden)

    José Teixeira

    2010-09-01

    Full Text Available Thermodynamic and transport properties of liquid water are not fully understood despite a large amount of research work both experimental and theoretical. The maximum of density and the enhanced anomalies observed at low temperatures are at the origin of several models that, in some cases, predict specific and unique behavior such as spinodal lines or critical points. We show that a careful analysis of the neutron quasi-elastic scattering data, both the incoherent spectra and the dynamic of the partials, is compatible with a polymer-like model, where the hydrogen bond dynamics explains the behavior of water in the non-accessible temperature region extending from −30° C to the glass transition.

  18. Nb effect in the nickel oxide-catalyzed low-temperature oxidative dehydrogenation of ethane

    KAUST Repository

    Zhu, Haibo

    2012-01-01

    A method for the preparation of NiO and Nb-NiO nanocomposites is developed, based on the slow oxidation of a nickel-rich Nb-Ni gel obtained in citric acid. The resulting materials have higher surface areas than those obtained by the classical evaporation method from nickel nitrate and ammonium niobium oxalate. These consist in NiO nanocrystallites (7-13 nm) associated, at Nb contents >3 at.%., with an amorphous thin layer (1-2 nm) of a niobium-rich mixed oxide with a structure similar to that of NiNb 2O 6. Unlike bulk nickel oxides, the activity of these nanooxides for low-temperature ethane oxidative dehydrogenation (ODH) has been related to their redox properties. In addition to limiting the size of NiO crystallites, the presence of the Nb-rich phase also inhibits NiO reducibility. At Nb content >5 at.%, Nb-NiO composites are thus less active for ethane ODH but more selective, indicating that the Nb-rich phase probably covers part of the unselective, non-stoichiometric, active oxygen species of NiO. This geometric effect is supported by high-resolution transmission electron microscopy observations. The close interaction between NiO and the thin Nb-rich mixed oxide layer, combined with possible restructuration of the nanocomposite under ODH conditions, leads to significant catalyst deactivation at high Nb loadings. Hence, the most efficient ODH catalysts obtained by this method are those containing 3-4 at.% Nb, which combine high activity, selectivity, and stability. The impact of the preparation method on the structural and catalytic properties of Nb-NiO nanocomposites suggests that further improvement in NiO-catalyzed ethane ODH can be expected upon optimization of the catalyst. © 2011 Elsevier Inc. All rights reserved.

  19. Oxidation behavior and area specific resistance of La, Cu and B alloyed Fe-22Cr ferritic steels for solid oxide fuel cell interconnects

    Science.gov (United States)

    Swaminathan, Srinivasan; Ko, Yoon Seok; Lee, Young-Su; Kim, Dong-Ik

    2017-11-01

    Two Fe-22 wt% Cr ferritic stainless steels containing varying concentrations of La (0.14 or 0.52 wt%), Cu (0.17 or 1.74 wt%) and B (48 or 109 ppm) are investigated with respect to oxidation behavior and high temperature area specific resistance (ASR) of the surface oxide scales. To determine the oxidation resistance of developed steels, continuous isothermal oxidation is carried out at 800 °C in air, for 2000 h, and their thermally grown oxide scale is characterized using dynamic SIMS, SEM/EDX, XRD and GI-XRD techniques. To assess their electrical performance, the ASR measurement by four-point probe method is conducted at 800 °C in air, for 400 h. In higher La content steel, the La-oxides at the scale/alloy interface promotes the oxygen transport which resulted in sub-surface oxidation of Mn, Cr, Ti and Al. Moreover, the inward growth of oxides contributes to increase of Fe-Cr alloy protrusions within the scale, which reduced the ASR. In contrast, sub-surface oxidation is reduced in high Cu-alloyed steel by segregated Cu at the scale/alloy interface. Thus, addition of Cu is effective to oxidation resistance and also to better electrical performance. However, no obvious impact of B on the scale sequence and/or ASR is observed.

  20. High-temperature corrosion behavior of coatings and ODS alloys based on Fe{sub 3}Al

    Energy Technology Data Exchange (ETDEWEB)

    Tortorelli, P.F.; Pint, B.A.; Wright, I.G.

    1996-06-01

    Iron aluminides containing greater than about 20-25 @ % Al have oxidation/sulfidation resistance at temperatures well above those at which these alloys have adequate mechanical strength. In addition to alloying modifications for improved creep resistance of wrought material, this strength limitation is being addressed by development of oxide-dispersion- strengthened (ODS) iron aluminides and by evaluation of Fe{sub 3}Al alloy compositions as coatings or claddings on higher-strength, less corrosion-resistant materials. As part of these efforts, the high-temperature corrosion behavior of iron-aluminide weld overlays and ODS alloys is being characterized and compared to previous results for ingot-processed material.

  1. Next-Generation Electrochemical Energy Materials for Intermediate Temperature Molten Oxide Fuel Cells and Ion Transport Molten Oxide Membranes.

    Science.gov (United States)

    Belousov, Valery V

    2017-02-21

    High temperature electrochemical devices such as solid oxide fuel cells (SOFCs) and oxygen separators based on ceramic materials are used for efficient energy conversion. These devices generally operate in the temperature range of 800-1000 °C. The high operating temperatures lead to accelerated degradation of the SOFC and oxygen separator materials. To solve this problem, the operating temperatures of these electrochemical devices must be lowered. However, lowering the temperature is accompanied by decreasing the ionic conductivity of fuel cell electrolyte and oxygen separator membrane. Therefore, there is a need to search for alternative electrolyte and membrane materials that have high ionic conductivity at lower temperatures. A great many opportunities exist for molten oxides as electrochemical energy materials. Because of their unique electrochemical properties, the molten oxide innovations can offer significant benefits for improving energy efficiency. In particular, the newly developed electrochemical molten oxide materials show high ionic conductivities at intermediate temperatures (600-800 °C) and could be used in molten oxide fuel cells (MOFCs) and molten oxide membranes (MOMs). The molten oxide materials containing both solid grains and liquid channels at the grain boundaries have advantages compared to the ceramic materials. For example, the molten oxide materials are ductile, which solves a problem of thermal incompatibility (difference in coefficient of thermal expansion, CTE). Besides, the outstanding oxygen selectivity of MOM materials allows us to separate ultrahigh purity oxygen from air. For their part, the MOFC electrolytes show the highest ionic conductivity at intermediate temperatures. To evaluate the potential of molten oxide materials for technological applications, the relationship between the microstructure of these materials and their transport and mechanical properties must be revealed. This Account summarizes the latest results on

  2. Effect of sodium deficiency on the critical behavior near the paramagnetic to ferromagnetic phase transition temperature in La0.8Na0.2-x□xMnO3 oxides

    Science.gov (United States)

    Wali, M.; Khlifi, M.; Dhahri, E.; Hlil, E. K.

    2017-11-01

    The critical behavior associated with the magnetic phase transition has been investigated by in La0.8Na0.2-x□xMnO3 (0.00 ≤ x ≤ 0.15) (□ is the sodium deficiency). The critical exponents are estimated by various techniques such as the modified Arrott plot, Kouvel-Fisher plot and critical isotherm technique. Compared to standard models, the critical exponent values determined in our work are close to those expected by the tricritical model (β = 0.25, γ = 1, and δ = 5) for x = 0.00 and 0.05 samples and by mean field theory (β = 0.5, γ = 1, and δ = 3) for x = 0.10 and 0.15 samples. We conclude that the Na deficiency rate affect the critical exponents.

  3. High temperature silver-palladium-copper oxide air braze filler metal

    Science.gov (United States)

    Darsell, Jens Tommy

    The Ag-CuO system is currently being investigated as the basis for an air braze filler metal alloy to be used in SOFC components. The system is of interest because unlike most braze alloys, it is capable of wetting a variety of ceramic materials while being applied in an air. This thesis work examined modification of Ag-CuO filler metal system by alloying with palladium to increase the use temperature of the resulting air braze alloy. Thermal analysis was performed to track changes in the solidus and liquidus temperatures for these alloys and determine equilibrium phase present as a function of temperature and composition. Sessile drop experiments were performed to investigate the effect of palladium addition on braze wetability. The influence of copper-oxide and palladium contents on brazed joint strength was characterized by a combination of four-point bend testing and fractography. From combined thermal analysis and quenched data it was found that both the liquidus and solidus increase with increasing palladium content, and the silver-rich miscibility gap boundary could be shifted by the addition of palladium. This was employed as a tool to study the effects of two-liquid phase formation on wetting behavior. In addition, a mass loss likely attributable to silver volatilization is observed in the Pd-modified filler metals when heated over ˜1100°C. As volatilization should be avoided, the ternary alloys should be limited to 15mol% Pd. It was found by sessile drop wetting experiments that there is a definitive change in wetting behavior that corresponds directly to the miscibility gap boundary for the Pd-Ag-CuO system. The first order transition tracks with changes in the miscibility gap boundary that can be induced by increasing palladium content. This is the first experimental evidence of critical point wetting behavior reported for a metal-oxide system and further confirms that critical point wetting theory is universal. Four-point bend testing and

  4. Interfacial crack behavior in the stationary temperature field conditions

    Directory of Open Access Journals (Sweden)

    Đoković Jelena M.

    2014-01-01

    Full Text Available The brittle coatings, made of different materials, when subjected to elevated temperatures and in the heat exchange conditions, are susceptible to delamination. Those coatings, as well as thin films, can be used for various thermo insulating deposits, e.g. in turbines of thermal power plants., In layers made of different materials, due to the environmental temperature change, thermal stresses appear as a consequence of a difference in their thermal expansion coefficients. In this paper driving forces were analyzed causing delamination of one layer from the other, i.e. the interfacial fracture in the two-layered, bimaterial sample. This analysis was limited to considering the sample behavior when exposed to the stationary temperature field. The energy release rate G, which is the driving force for this interfacial fracture, is changing with temperature and that variation is increasing with increase of the temperature difference between the environment and the sample. Analysis of this relation can be used to predict the maximal temperature difference, which the two-layered sample can be subjected to, without appearance of delamination between layers.

  5. Oxidation Behavior of GRCop-84 Copper Alloy Assessed

    Science.gov (United States)

    Thomas-Ogbuji, Linus U.

    2002-01-01

    NASA's goal of safe, affordable space transportation calls for increased reliability and lifetimes of launch vehicles, and significant reductions of launch costs. The areas targeted for enhanced performance in the next generation of reusable launch vehicles include combustion chambers and nozzle ramps; therefore, the search is on for suitable liner materials for these components. GRCop-84 (Cu-8Cr-4Nb), an advanced copper alloy developed at the NASA Glenn Research Center in conjunction with Case Western Reserve University, is a candidate. The current liner of the Space Shuttle Main Engine is another copper alloy, NARloy-Z (Cu-3Ag-0.1Zr). It provides a benchmark against which to compare the properties of candidate successors. The thermomechanical properties of GRCop-84 have been shown to be superior, and its physical properties comparable, to those of NARloy-Z. However, environmental durability issues control longevity in this application: because copper oxide scales are not highly protective, most copper alloys are quickly consumed in oxygen environments at elevated temperatures. In consequence, NARloy-Z and most other copper alloys are prone to blanching, a degradation process that occurs through cycles of oxidation-reduction as the oxide is repeatedly formed and removed because of microscale fluctuations in the oxygen-hydrogen fuel systems of rocket engines. The Space Shuttle Main Engine lining typically degraded by blanching-induced hot spots that lead to surface roughening, pore formation, and coolant leakage. Therefore, resistance to oxidation and blanching are key requirements for second-generation reusable launch vehicle liners. The rocket engine ambient includes H2 (fuel) and H2O (combustion product) and is, hence, under reduced oxygen partial pressures. Accordingly, our studies were expanded to include oxygen partial pressures as low as 322 parts per million (ppm) at the temperatures likely to be experienced in service. A comparison of 10-hr weight gains of

  6. Temperature as a proximate factor in orientation behavior

    Energy Technology Data Exchange (ETDEWEB)

    Reynolds, W.W.

    1977-05-01

    Temperature serves as a proximate factor (cue, guidepost, sign stimulus, or directive factor) affecting locomotor responses of fishes. Although temperature can also serve as an ultimate ecological factor, as in behavioral thermoregulation, nonthermal factors may in some cases provide the ultimate adaptive or ecological value of a temperature response; some examples are habitat selection, intraspecific size segregation, interspecific niche differentiation, isolating mechanisms, predator avoidance, prey location, escape reactions, and migrations (thermoperiodic, diel, seasonal, spawning). Conversely, nonthermal variables such as light intensity or water depth may act as accessory proximate factors in thermoregulation. In spawning migrations, thermal requirements of eggs and larvae may take precedence over the (often different) preferenda or optima of adults. Although thermal responses of fishes are largely innate and species specific, ontogenetic and other changes can occur. Since temperature can serve as an unconditioned reinforcer in operant conditioning, thermal responses are not limited to simple kineses or taxes. Nonthermal factors such as photoperiod, circadian rhythms, currents, social and biotic interactions, stresses, infections, or chemicals can affect thermal responses, and may account for some lack of conformity between laboratory preferenda and field distributions and behaviors.

  7. Analytic behavior of the QED polarizability function at finite temperature

    Energy Technology Data Exchange (ETDEWEB)

    Bernal, A. [Dept. de Matematica Aplicada i Analisi, Universitat de Barcelona. Av Joan XXIII s/n Edifici A, Escala A, Tercer pis, Matematiques 08028, Barcelona (Spain); Perez, A. [Departament de Fisica Teorica and IFIC, Universitat de Valencia-CSIC, Dr. Moliner 50, 46100-Burjassot (Spain)

    2012-03-15

    We revisit the analytical properties of the static quasi-photon polarizability function for an electron gas at finite temperature, in connection with the existence of Friedel oscillations in the potential created by an impurity. In contrast with the zero temperature case, where the polarizability is an analytical function, except for the two branch cuts which are responsible for Friedel oscillations, at finite temperature the corresponding function is non analytical, in spite of becoming continuous everywhere on the complex plane. This effect produces, as a result, the survival of the oscillatory behavior of the potential. We calculate the potential at large distances, and relate the calculation to the non-analytical properties of the polarizability.

  8. Mechanical behavior of tungsten–vanadium–lanthana alloys as function of temperature

    Energy Technology Data Exchange (ETDEWEB)

    Palacios, T., E-mail: teresa.palacios@mater.upm.es [Departamento de Ciencia de Materiales-CISDEM, Universidad Politécnica de Madrid, E.T.S.I. Caminos, Canales y Puertos, C/Professor Aranguren s/n, 28040 Madrid (Spain); Pastor, J.Y. [Departamento de Ciencia de Materiales-CISDEM, Universidad Politécnica de Madrid, E.T.S.I. Caminos, Canales y Puertos, C/Professor Aranguren s/n, 28040 Madrid (Spain); Aguirre, M.V. [Departamento de Tecnologías Especiales Aplicadas a la Aeronáutica, Universidad Politécnica de Madrid, E.I. Aeronáutica y del Espacio, 28040 Madrid (Spain); Martín, A. [Departamento de Ciencia de Materiales-CISDEM, Universidad Politécnica de Madrid, E.T.S.I. Caminos, Canales y Puertos, C/Professor Aranguren s/n, 28040 Madrid (Spain); Monge, M.A.; Muñóz, A.; Pareja, R. [Departamento de Física, Universidad Carlos III de Madrid, Leganés (Spain)

    2013-11-15

    The mechanical behavior of three tungsten (W) alloys with vanadium (V) and lanthana (La{sub 2}O{sub 3}) additions (W–4%V, W–1%La{sub 2}O{sub 3}, W–4%V–1%La{sub 2}O{sub 3}) processed by hot isostatic pressing (HIP) have been compared with pure-W to analyze the influence of the dopants. Mechanical characterization was performed by three point bending (TPB) tests in an oxidizing air atmosphere and temperature range between 77 (immersion tests in liquid nitrogen) and 1273 K, through which the fracture toughness, flexural strength, and yield strength as function of temperature were obtained. Results show that the V and La{sub 2}O{sub 3} additions improve the mechanical properties and oxidation behavior, respectively. Furthermore, a synergistic effect of both dopants results in an extraordinary increase of the flexure strength, fracture toughness and resistance to oxidation compared to pure-W, especially at higher temperatures. In addition, a new experimental method was developed to obtain a very small notch tip radius (around 5–7 μm) and much more similar to a crack through the use of a new machined notch. The fracture toughness results were lower than those obtained with traditional machining of the notch, which can be explained with electron microscopy, observations of deformation in the rear part of the notch tip. Finally, scanning electron microscopy (SEM) examination of the microstructure and fracture surfaces was used to determine and analyze the relationship between the macroscopic mechanical properties and the micromechanisms of failure involved, depending on the temperature and the dispersion of the alloy.

  9. Electrochemical investigation of mixed metal oxide nanocomposite electrode for low temperature solid oxide fuel cell

    Science.gov (United States)

    Abbas, Ghazanfar; Raza, Rizwan; Ashfaq Ahmad, M.; Ajmal Khan, M.; Jafar Hussain, M.; Ahmad, Mukhtar; Aziz, Hammad; Ahmad, Imran; Batool, Rida; Altaf, Faizah; Zhu, Bin

    2017-10-01

    Zinc-based nanostructured nickel (Ni) free metal oxide electrode material Zn0.60/Cu0.20Mn0.20 oxide (CMZO) was synthesized by solid state reaction and investigated for low temperature solid oxide fuel cell (LTSOFC) applications. The crystal structure and surface morphology of the synthesized electrode material were examined by XRD and SEM techniques respectively. The particle size of ZnO phase estimated by Scherer’s equation was 31.50 nm. The maximum electrical conductivity was found to be 12.567 S/cm and 5.846 S/cm in hydrogen and air atmosphere, respectively at 600∘C. The activation energy of the CMZO material was also calculated from the DC conductivity data using Arrhenius plots and it was found to be 0.060 and 0.075 eV in hydrogen and air atmosphere, respectively. The CMZO electrode-based fuel cell was tested using carbonated samarium doped ceria composite (NSDC) electrolyte. The three layers 13 mm in diameter and 1 mm thickness of the symmetric fuel cell were fabricated by dry pressing. The maximum power density of 728.86 mW/cm2 was measured at 550∘C.

  10. Temperature Programmed Reduction/Oxidation (TPR/TPO) Methods

    Science.gov (United States)

    Gervasini, Antonella

    The redox properties of the metal oxides impart them peculiar catalytic activity which is exploited in reactions of oxidation and reduction of high applicative importance. It is possible to measure the extent of oxidation/reduction of given metal oxide by thermal methods which are become very popular: TPR and TPO analyses. By successive experiments of reduction and oxidation (TPR-TPO cycles) it is possible to control the reversible redox ability of a given oxide in view of its use as catalyst. The two methods are here presented with explanation on some possibility of exploitation of kinetic study to derive quantitative information on the reduction/oxidation of the oxide. Examples of selected metal oxides with well-established redox properties which have been used in catalytic processes are shown.

  11. Oxidation of X20 in Water Vapour: The Effect of Temperature and Oxygen Partial Pressure

    DEFF Research Database (Denmark)

    Hansson, Anette Nørgaard; Montgomery, Melanie; Somers, Marcel A. J.

    2009-01-01

    The oxidation behaviour of X20 in various mixtures of water, oxygen and hydrogen was investigated at temperatures between 500 C and 700 C (time: 336 h). The samples were characterised using reflected light microscopy and scanning electron microscopy equipped with energy dispersive spectroscopy....... Double-layered oxides developed during oxidation under all conditions. The morphology of the oxide layers was strongly influenced by temperature, whereas the influence of the oxidising environment appeared to be less pronounced, as long as it contained water vapour. The inner layer consisted of converted...... M23C6 embedded in Fe–Cr spinel after oxidation at 500 and 600 C, while alternating layers of Cr-rich and Cr-poor oxide were observed after oxidation at 700 C. An internal oxidation zone developed during oxidation at 500 and 600 C, with its depth influenced by the oxidising environments. The results...

  12. Gold-TiO{sub 2}-Nickel catalysts for low temperature-driven CO oxidation reaction

    Energy Technology Data Exchange (ETDEWEB)

    Hinojosa-Reyes, Mariana, E-mail: kittyhinojosa@hotmail.com [División de Materiales Avanzados, IPICYT, Instituto Potosino de Investigación Científica y Tecnológica, Camino a la Presa San José 2055 Col. Lomas 4a. sección C.P. 78216, San Luis Potosí, S.L.P., México (Mexico); Zanella, Rodolfo, E-mail: rodolfo.zanella@ccadet.unam.mx [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior S/N, Ciudad Universitaria, A. P. 70-186, Delegación Coyoacán, C.P. 04510, México D. F., México (Mexico); Maturano-Rojas, Viridiana [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior S/N, Ciudad Universitaria, A. P. 70-186, Delegación Coyoacán, C.P. 04510, México D. F., México (Mexico); and others

    2016-04-15

    Graphical abstract: - Highlights: • Nickel-doped TiO{sub 2} catalysts (1 wt. %) drive the CO oxidation at low temperature. • DRIFTS reveals the participation of nickel during the CO oxidation. • Ni(CO){sub 2} bridged species are detected by DRIFTS. • Au/TiO{sub 2}-Ni 1 is the most active and stable catalyst with respect to undoped TiO{sub 2}. • Ti{sup 3+} species corroborate Ni doped TiO{sub 2} and surface oxygen vacancies. - Abstract: Nickel-doped-TiO{sub 2} catalysts were prepared by the sol–gel method and surface modified with gold nanoparticles (AuNPs) by the urea-deposition-precipitation technique. The as-synthesized catalysts were characterized by X-ray diffraction, Raman and XPS spectroscopies, N{sub 2} physisorption, STEM-HAADF microscopy and TPR hydrogen consumption. The Au/TiO{sub 2}-Ni catalysts were evaluated catalytically performing CO oxidation reactions. The catalyst with nickel content of 1 wt. % (Au/TiO{sub 2}-Ni 1) showed the highest CO conversion with respect to the high-nickel-content or bare/commercial TiO{sub 2} at 0 °C. In situ DRIFTS showed a strong participation of both nickel due to the presence of surface-nickel-metallic nanoparticles formed during the CO adsorption process at reaction temperatures above 200 °C, and surface-bridged-nickel-CO species. A minor deactivation rate was observed for the Au/TiO{sub 2}-Ni 1 catalyst in comparison with the Au/TiO{sub 2} one. The oxygen vacancies that were created on the sol–gel-doped TiO{sub 2} improved the catalytic behavior during the performance of CO oxidation reactions, and inhibited the AuNP sintering.

  13. Additional chain-branching pathways in the low-temperature oxidation of branched alkanes

    KAUST Repository

    Wang, Zhandong

    2015-12-31

    Chain-branching reactions represent a general motif in chemistry, encountered in atmospheric chemistry, combustion, polymerization, and photochemistry; the nature and amount of radicals generated by chain-branching are decisive for the reaction progress, its energy signature, and the time towards its completion. In this study, experimental evidence for two new types of chain-branching reactions is presented, based upon detection of highly oxidized multifunctional molecules (HOM) formed during the gas-phase low-temperature oxidation of a branched alkane under conditions relevant to combustion. The oxidation of 2,5-dimethylhexane (DMH) in a jet-stirred reactor (JSR) was studied using synchrotron vacuum ultra-violet photoionization molecular beam mass spectrometry (SVUV-PI-MBMS). Specifically, species with four and five oxygen atoms were probed, having molecular formulas of C8H14O4 (e.g., diketo-hydroperoxide/keto-hydroperoxy cyclic ether) and C8H16O5 (e.g., keto-dihydroperoxide/dihydroperoxy cyclic ether), respectively. The formation of C8H16O5 species involves alternative isomerization of OOQOOH radicals via intramolecular H-atom migration, followed by third O2 addition, intramolecular isomerization, and OH release; C8H14O4 species are proposed to result from subsequent reactions of C8H16O5 species. The mechanistic pathways involving these species are related to those proposed as a source of low-volatility highly oxygenated species in Earth\\'s troposphere. At the higher temperatures relevant to auto-ignition, they can result in a net increase of hydroxyl radical production, so these are additional radical chain-branching pathways for ignition. The results presented herein extend the conceptual basis of reaction mechanisms used to predict the reaction behavior of ignition, and have implications on atmospheric gas-phase chemistry and the oxidative stability of organic substances. © 2015 The Combustion Institute.

  14. Phthalocyanines with eight oligo(ethylene oxide) alkoxy units: thermotropic phase behavior, aggregate formation and ion complexation with redox-active ions

    NARCIS (Netherlands)

    Piet, D.P.; Verheij, H.J.; Zuilhof, H.

    2003-01-01

    The thermotropic phase behavior of phthalocyanines (Pc's) with eight oligo(ethylene oxide) alkoxy side chains has been investigated. An increase in the number of ethylene oxide units results in a decrease in the solid-to-mesophase and isotropization temperatures. The investigated compounds display a

  15. Microstructural Evolution and Mechanical Behavior of High Temperature Solders: Effects of High Temperature Aging

    Science.gov (United States)

    Hasnine, M.; Tolla, B.; Vahora, N.

    2017-12-01

    This paper explores the effects of aging on the mechanical behavior, microstructure evolution and IMC formation on different surface finishes of two high temperature solders, Sn-5 wt.% Ag and Sn-5 wt.% Sb. High temperature aging showed significant degradation of Sn-5 wt.% Ag solder hardness (34%) while aging has little effect on Sn-5 wt.% Sb solder. Sn-5 wt.% Ag experienced rapid grain growth as well as the coarsening of particles during aging. Sn-5 wt.% Sb showed a stable microstructure due to solid solution strengthening and the stable nature of SnSb precipitates. The increase of intermetallic compound (IMC) thickness during aging follows a parabolic relationship with time. Regression analysis (time exponent, n) indicated that IMC growth kinetics is controlled by a diffusion mechanism. The results have important implications in the selection of high temperature solders used in high temperature applications.

  16. Efficient room temperature oxidation of cyclohexane over highly active hetero-mixed WO3/V2O5 oxide catalyst

    CSIR Research Space (South Africa)

    Makgwane, PR

    2014-09-01

    Full Text Available An efficient room temperature catalyzed oxidation of cyclohexane to cyclohexanone (K) and cyclohexanol (A) was achieved over hetero-mixed tungsten–vanadia (WO(sub3)/V(sub2)O(sub5)) using H(sub2)O(sub2) oxidant. WO(sub3)/V(sub2)O(sub5) exhibited high...

  17. Effect of temperature and time on zinc borate species formed from zinc oxide and boric acid in aqueous medium

    OpenAIRE

    Eltepe, H. Emre; Balköse, Devrim; Ülkü, Semra

    2007-01-01

    The effect of temperature and time of heating of zinc oxide and boric acid in aqueous medium on product type, dehydration behavior, crystal morphology, and structure was investigated for the production of flame retardant and smoke suppressant zinc borate. Two different products dehydrated at 140 and 350°C were obtained and characterized by thermal gravimetric analysis, X-ray diffraction, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy.

  18. Reaction mechanism and kinetics of sulfide copper concentrate oxidation at elevated temperatures

    Directory of Open Access Journals (Sweden)

    Aleksandra Mitovski

    2017-09-01

    Full Text Available Sulfide copper concentrate from domestic ore deposit (Bor, Serbia was subjected to oxidation in the air atmosphere due to a better understanding of reaction mechanism and oxidation of various sulfides present in the copper concentrate at elevated temperatures. Results of the initial sample characterization showed that concentrate is chalcopyrite–enargite-tennantite type, with an increased arsenic content. Characterization of the oxidation products showed the presence of sulfates, oxysulfates, and oxides. Based on predominance area diagrams for Me-S-O systems (Me = Cu, Fe, As combined with thermal analysis results, the reaction mechanism of the oxidation process was proposed. The reactions which occur in the temperature range 25 – 1000 °C indicate that sulfides are unstable in the oxidative conditions. Sulfides from the initial sample decomposed into binary copper and iron sulfides and volatile arsenic oxides at lower temperatures. Further heating led to oxidation of sulfides into iron oxides and copper sulfates and oxysulfates. At higher temperatures sulfates and oxysulfates decomposed into oxides. Kinetic analysis of the oxidation process was done using Ozawa’s method in the non-isothermal conditions. The values for activation energies showed that the reactions are chemically controlled and the temperature is the most influential parameter on the reaction rates.

  19. Thermal aging effects on the microstructure, oxidation behavior, and mechanical properties of as-cast nickel aluminide alloys

    Science.gov (United States)

    Lee, Dongyun

    The thermal aging effects on the microstructure, oxidation behavior at 900° and 1100°C, and mechanical properties of IC221M (Ni3Al based intermetallic alloy, ASTM A1002-99) were investigated. The microstructure consists of dendritic arms of the gamma (nickel solid solution) phase containing cube-shape gamma' (Ni3Al precipitates. The interdendritic regions are mostly gamma' (Ni3Al with up to 8 vol.% gamma + Ni5Zr eutectic constituents. Thermal aging effects on the microstructures and how microsegregation affects the oxidation behavior were examined. Four primary changes in the microstructures were observed: (1) there is considerable homogenization of the cast microstructures with aging, (2) the volume fraction of gamma' increases with aging time and temperature, (3) the gamma' phase coarsens, and (4) the volume fraction of the gamma + Ni5Zr eutectic constituents decreases. During the initial stages of oxidation at 900°C, surface oxides form along the microsegregation patterns, revealing the cast microstructures. The first oxide to form is mostly NiO with small amounts of Cr2O 3, ZrO2, NiCr2O4, and theta-Al 2O3. Initial oxidation occurs primarily in the interdendritic regions due to microsegregation of alloying elements during casting. With further aging, the predominant surface oxides become NiO and NiAl2O 4 spinel, with a continuous film of alpha-Al2O3 forming immediately beneath them. Although these oxides are constrained to the near surface region, other oxides penetrate to greater depths, facilitated by oxidation of the gamma + Ni5Zr eutectic constituents. These oxides appear in the microstructure as long, thin spikes of ZrO2 surrounded by a sheath of Al2O3. They can penetrate to depths greater than 10 times that of the continuous surface oxide. The oxidation behavior at 1100°C is similar to that at 900°C, but the oxidation kinetics are faster, NiO dominates at all aging periods, and the surface oxides do not adhere to the matrix meaning that a protective

  20. Study of the oxidation of Fe-Cr alloys at high temperatures; Estudo da oxidacao de ligas Fe-Cr a altas temperaturas

    Energy Technology Data Exchange (ETDEWEB)

    Carneiro, J.F.; Sabioni, A.C.S. [Universidade Federal de Ouro Preto (LDM/DF/UFOP), MG (Brazil). Dept. de Fisica. Lab. de Difusao em Materiais; Trindade, V.B. [Universidade Federal de Ouro Preto (DEMM/UFOP), MG (Brazil). Dept. de Engenharia Metalurgica e de Materiais; Ji, V. [Laboratoire d' Etude des Materiaux Hors-Equilibre (LEMHE), Orsay (France)

    2010-07-01

    The high temperature oxidation behavior of Fe-1.5%Cr, Fe-5.0%Cr, Fe-10%Cr and Fe- 15%Cr model alloys were investigated from 700 to 850 deg C, in air atmosphere. The oxidation treatments were performed in a thermobalance with a sensitivity of 1{mu}g. The oxide films grown by oxidation of the alloys were characterized by scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The oxide films are Fe-Cr spinels with variable composition depending on the alloy composition. For all conditions studied, the oxidation kinetics of these alloys follow a parabolic law. The comparison of the oxidation rates of the four alloys, at 700 deg C, shows that the parabolic oxidation constants decrease from 1.96x10{sup -9}g{sup 2}.cm{sup -4}.s{sup -1}, for the alloy Fe-1.5% Cr, to 1.18 x 10-14g{sup 2}.cm{sup -4}.s{sup -1} for the alloy Fe-15% Cr. Comparative analysis of the oxidation behavior of the Fe-10%Cr and Fe-15%Cr alloys, between 700 and 850 deg C, shows that the oxidation rates of these alloys are comparable to 800 deg C, above this temperature the Fe-10%Cr alloy shows lower resistance to oxidation. (author)

  1. Hydrogen permeation behavior through F82H at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Matsuda, S.; Katayama, K.; Shimozori, M.; Fukada, S. [Interdisciplinary Graduate School of Engineering Science, Kyushu University, Kyushu (Japan); Ushida, H. [Energy Science and Engineering, Faculty of Engineering, Kyushu University, Kyushu (Japan); Nishikawa, M. [Malaysia-Japan International Institute of Technology, UTM, Kuala Lumpur (Malaysia)

    2015-03-15

    F82H is a primary candidate of structural material and coolant pipe material in a blanket of a fusion reactor. Understanding tritium permeation behavior through F82H is important. In a normal operation of a fusion reactor, the temperature of F82H will be controlled below 550 C. degrees because it is considered that F82H can be used up to 30,000 hours at 550 C. degrees. However, it is necessary to assume the situation where F82H is heated over 550 C. degrees in a severe accident. In this study, hydrogen permeation behavior through F82H was investigated in the temperature range from 500 to 800 C. degrees. In some cases, water vapor was added in a sample gas to investigate an effect of water vapor on hydrogen permeation. The permeability of hydrogen in the temperature range from 500 to 700 C. degrees agreed well with the permeability reported by E. Serra et al. The degradation of the permeability by water vapor was not observed. After the hydrogen permeation reached in a steady state at 700 C. degrees, the F82H sample was heated to 800 C. degrees. The permeability of hydrogen through F82H sample which was once heated up to 800 C. degrees was lower than that of the original one. (authors)

  2. Use of Distributed Temperature Sensing Technology to Characterize Fire Behavior

    Directory of Open Access Journals (Sweden)

    Douglas Cram

    2016-10-01

    Full Text Available We evaluated the potential of a fiber optic cable connected to distributed temperature sensing (DTS technology to withstand wildland fire conditions and quantify fire behavior parameters. We used a custom-made ‘fire cable’ consisting of three optical fibers coated with three different materials—acrylate, copper and polyimide. The 150-m cable was deployed in grasslands and burned in three prescribed fires. The DTS system recorded fire cable output every three seconds and integrated temperatures every 50.6 cm. Results indicated the fire cable was physically capable of withstanding repeated rugged use. Fiber coating materials withstood temperatures up to 422 °C. Changes in fiber attenuation following fire were near zero (−0.81 to 0.12 dB/km indicating essentially no change in light gain or loss as a function of distance or fire intensity over the length of the fire cable. Results indicated fire cable and DTS technology have potential to quantify fire environment parameters such as heat duration and rate of spread but additional experimentation and analysis are required to determine efficacy and response times. This study adds understanding of DTS and fire cable technology as a potential new method for characterizing fire behavior parameters at greater temporal and spatial scales.

  3. Disordered Manganese Oxide Nano-powder Prepared by Low-temperature Synthesis Followed by Acid Treatment

    OpenAIRE

    Koyanaka, Hideki; Hata, Toshihiro; IMAMURA, Yuji

    2005-01-01

    Disordered manganese oxide, prepared by low-temperature synthesis followed by acid treatment is introduced. Aggregated nano-powder of disordered manganese oxide was obtained in this method. The disordered manganese oxide is suitable starting material for the preparation of efficient adsorbents for the removal of harmful metals from the environment.

  4. Ca-Sr-Ga-Nb mixed oxide system for high temperature superconductor substrate applications

    Energy Technology Data Exchange (ETDEWEB)

    Erdei, S.; Cross, L.E.; Ainger, F.W.; Bhalla, A. (Materials Research Lab., The Pennsylvania State Univ., Univ. Park, Pennsylvania (United States))

    1994-05-01

    Twin-free crystals with relatively low melting temperatures are desirable as substrates for high temperature superconductor (HTSC) oxide substrate materials. In the selection of new oxide substrate compositions, special requirements (e.g. suitable dielectric properties for microwave application and perovskite structure with good lattice matching with YBa[sub 2]Cu[sub 3]O[sub 7-[delta

  5. Low Temperature Synthesis and Properties of Gadolinium-Doped Cerium Oxide Nanoparticles

    DEFF Research Database (Denmark)

    Machado, M. F. S.; Moraes, L. P. R.; Monteiro, N. K.

    2017-01-01

    Gadolinium-doped cerium oxide (GDC) is an attractive ceramic material for solid oxide fuel cells (SOFCs) both as the electrolyte and in composite electrodes operating at low and intermediate temperatures. GDC exhibits high oxygen ion conductivity at a wide range of temperatures and displays a hig...

  6. The oxidation of aluminum at high temperature studied by Thermogravimetric Analysis and Differential Scanning Calorimetry.

    Energy Technology Data Exchange (ETDEWEB)

    Coker, Eric Nicholas

    2013-10-01

    The oxidation in air of high-purity Al foil was studied as a function of temperature using Thermogravimetric Analysis with Differential Scanning Calorimetry (TGA/DSC). The rate and/or extent of oxidation was found to be a non-linear function of the temperature. Between 650 and 750 ÀC very little oxidation took place; at 850 ÀC oxidation occurred after an induction period, while at 950 ÀC oxidation occurred without an induction period. At oxidation temperatures between 1050 and 1150 ÀC rapid passivation of the surface of the aluminum foil occurred, while at 1250 ÀC and above, an initial rapid mass increase was observed, followed by a more gradual increase in mass. The initial rapid increase was accompanied by a significant exotherm. Cross-sections of oxidized specimens were characterized by scanning electron microscopy (SEM); the observed alumina skin thicknesses correlated qualitatively with the observed mass increases.

  7. New Cathode Materials for Intermediate Temperature Solid Oxide Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Allan J. Jacobson

    2006-09-30

    Operation of SOFCs at intermediate temperatures (500-800 C) requires new combinations of electrolyte and electrode materials that will provide both rapid ion transport across the electrolyte and electrode-electrolyte interfaces and efficient electrocatalysis of the oxygen reduction and fuel oxidation reactions. This project concentrates on materials and issues associated with cathode performance that are known to become limiting factors as the operating temperature is reduced. The specific objectives of the proposed research are to develop cathode materials that meet the electrode performance targets of 1.0 W/cm{sup 2} at 0.7 V in combination with YSZ at 700 C and with GDC, LSGM or bismuth oxide based electrolytes at 600 C. The performance targets imply an area specific resistance of {approx}0.5 {Omega}cm{sup 2} for the total cell. The research strategy is to investigate both established classes of materials and new candidates as cathodes, to determine fundamental performance parameters such as bulk diffusion, surface reactivity and interfacial transfer, and to couple these parameters to performance in single cell tests. The initial choices for study were perovskite oxides based on substituted LaFeO{sub 3} (P1 compositions), where significant data in single cell tests exist at PNNL for example, for La{sub 0.8}Sr{sub 0.2}FeO{sub 3} cathodes on both YSZ and CSO/YSZ. The materials selection was then extended to La{sub 2}NiO{sub 4} compositions (K1 compositions), and then in a longer range task we evaluated the possibility of completely unexplored group of materials that are also perovskite related, the ABM{sub 2}O{sub 5+{delta}}. A key component of the research strategy was to evaluate for each cathode material composition, the key performance parameters, including ionic and electronic conductivity, surface exchange rates, stability with respect to the specific electrolyte choice, and thermal expansion coefficients. In the initial phase, we did this in parallel with

  8. Creep Behavior of ABS Polymer in Temperature-Humidity Conditions

    Science.gov (United States)

    An, Teagen; Selvaraj, Ramya; Hong, Seokmoo; Kim, Naksoo

    2017-04-01

    Acrylonitrile-Butadiene-Styrene (ABS), also known as a thermoplastic polymer, is extensively utilized for manufacturing home appliances products as it possess impressive mechanical properties, such as, resistance and toughness. However, the aforementioned properties are affected by operating temperature and atmosphere humidity due to the viscoelasticity property of an ABS polymer material. Moreover, the prediction of optimum working conditions are the little challenging task as it influences the final properties of product. This present study aims to develop the finite element (FE) models for predicting the creep behavior of an ABS polymeric material. In addition, the material constants, which represent the creep properties of an ABS polymer material, were predicted with the help of an interpolation function. Furthermore, a comparative study has been made with experiment and simulation results to verify the accuracy of developed FE model. The results showed that the predicted value from FE model could agree well with experimental data as well it can replicate the actual creep behavior flawlessly.

  9. Room temperature oxidation kinetics of Si nanoparticles in air, determined by x-ray photoelectron spectroscopy

    Science.gov (United States)

    Yang, D.-Q.; Gillet, Jean-Numa; Meunier, M.; Sacher, E.

    2005-01-01

    The air oxidation kinetics of low coverages of ˜5nm Si nanoparticles, deposited by pulsed excimer laser ablation (KrF, 248 nm) in He, have been characterized by x-ray photoelectron spectroscopy. A simple model, based on the evolution of the Si 2p spectral components during oxidation, has been developed to determine the nanoparticle oxide thickness. It is found that the short-term oxide thickness is greater, and the long-term room-temperature air oxidization rate of these nanoparticles is less, than those reported for bulk a-Si and c-Si. The results are also consistent with an earlier transmission electron microscope observation of the oxidation of larger Si particles at higher temperatures. The greater short-term oxide thickness may be attributed to surface defects on the prepared Si nanoparticles, and lower long-term oxidation rate is due to the nonlinear decrease of oxygen diffusion in spherical systems.

  10. Processing, Microstructure, and Oxidation Behavior of Iron Foams

    Science.gov (United States)

    Park, Hyeji; Noh, Yoonsook; Choi, Hyelim; Hong, Kicheol; Kwon, Kyungjung; Choe, Heeman

    2016-09-01

    With its historically long popularity in major structural applications, the use of iron (Fe) has also recently begun to be explored as an advanced functional material. For this purpose, it is more advantageous to use Fe as a porous structure, simply because it can provide a greater surface area and a higher reaction rate. This study uses a freeze-casting method, which consists of simple and low-cost processing steps, to produce Fe foam with a mean pore size of 10 μm. We examine the influences of various parameters ( i.e., mold bottom temperature, powder content, and sintering time) on the processing of Fe foam, along with its oxidation kinetics at 823 K (550 °C) with various heat-treatment times. We confirm that Fe2O3 and Fe3O4 oxide layers are successfully formed on the surface of Fe foam. With the Fe oxide layers as an active anode material, the Fe foam can potentially be used as a three-dimensional anode current collector for an advanced lithium-ion battery.

  11. Low-temperature solution-processed metal oxide buffer layers fulfilling large area production requirements

    Science.gov (United States)

    Stubhan, T.; Litzov, I.; Li, Ning; Wang, H. Q.; Krantz, J.; Machui, F.; Steidl, M.; Oh, H.; Matt, G. J.; Brabec, C. J.

    2012-09-01

    This paper is a review of our previous work on the field of low temperature, solution processed metal oxide buffer layers published in various journals. Our work focuses on zinc oxide (ZnO) and aluminum-doped zinc oxide (AZO) as n-type and molybdenum oxide (MoO3) as p-type solution processed buffer layer. In addition to that, we investigate the surface modification of AZO using phosphonic acid-anchored aliphatic and fullerene self assembled monolayers (SAMs).

  12. Electrode Design for Low Temperature Direct-Hydrocarbon Solid Oxide Fuel Cells

    Science.gov (United States)

    Chen, Fanglin (Inventor); Zhao, Fei (Inventor); Liu, Qiang (Inventor)

    2015-01-01

    In certain embodiments of the present disclosure, a solid oxide fuel cell is described. The solid oxide fuel cell includes a hierarchically porous cathode support having an impregnated cobaltite cathode deposited thereon, an electrolyte, and an anode support. The anode support includes hydrocarbon oxidation catalyst deposited thereon, wherein the cathode support, electrolyte, and anode support are joined together and wherein the solid oxide fuel cell operates a temperature of 600.degree. C. or less.

  13. Temperature dependence of the deformation behavior of 316 stainless steel after low temperature neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Pawel-Robertson, J.E.; Rowcliffe, A.F.; Grossbeck, M.L. [Oak Ridge National Lab., TN (United States)] [and others

    1996-10-01

    The effects of low temperature neutron irradiation on the tensile behavior of 316 stainless steel have been investigated. A single heat of solution annealed 316 was irradiated to 7 and 18 dpa at 60, 200, 330, and 400{degrees}C. The tensile properties as a function of dose and as a function of temperature were examined. Large changes in yield strength, deformation mode, strain to necking, and strain hardening capacity were seen in this irradiation experiment. The magnitudes of the changes are dependent on both irradiation temperature and neutron dose. Irradiation can more than triple the yield strength over the unirradiated value and decrease the strain to necking (STN) to less than 0.5% under certain conditions. A maximum increase in yield strength and a minimum in the STN occur after irradiation at 330{degrees}C but the failure mode remains ductile.

  14. Facile synthesis of iron oxides/reduced graphene oxide composites: application for electromagnetic wave absorption at high temperature.

    Science.gov (United States)

    Zhang, Lili; Yu, Xinxin; Hu, Hongrui; Li, Yang; Wu, Mingzai; Wang, Zhongzhu; Li, Guang; Sun, Zhaoqi; Chen, Changle

    2015-03-19

    Iron oxides/reduced graphene oxide composites were synthesized by facile thermochemical reactions of graphite oxide and FeSO4 · 7H2O. By adjusting reaction temperature, α-Fe2O3/reduced graphene oxide and Fe3O4/reduced graphene oxide composites can be obtained conveniently. Graphene oxide and reduced graphene oxide sheets were demonstrated to regulate the phase transition from α-Fe2O3 to Fe3O4 via γ-Fe2O3, which was reported for the first time. The hydroxyl groups attached on the graphene oxide sheets and H2 gas generated during the annealing of graphene oxide are believed to play an important role during these phase transformations. These samples showed good electromagnetic wave absorption performance due to their electromagnetic complementary effect. These samples possess much better electromagnetic wave absorption properties than the mixture of separately prepared Fe3O4 with rGO, suggesting the crucial role of synthetic method in determining the product properties. Also, these samples perform much better than commercial absorbers. Most importantly, the great stability of these composites is highly advantageous for applications as electromagnetic wave absorption materials at high temperatures.

  15. Oxide-Nanoparticle Containing Coatings for High Temperature Alloys

    Energy Technology Data Exchange (ETDEWEB)

    None

    2009-04-01

    This factsheet describes a study whose objective is to examine the feasibility of using Electromagnetic Stirring (EMS) techniques in dispersing the oxide nanoparticles uniformly within the liquid steel.

  16. Low temperature magnetic transition and high temperature oxidation in INCONEL alloy 718

    Energy Technology Data Exchange (ETDEWEB)

    Seehra, M.S.; Babu, V.S. [Physics Department, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)

    1996-05-01

    X-ray diffraction and temperature dependent (5 K{endash}380 K) magnetic measurements have been carried out in INCONEL 718 superalloy before and after high temperature aging treatments (INCONEL is a trademark of the INCO family of companies). The nominal composition of this alloy is Ni (52.5{percent}), Cr (19.0{percent}), Fe (18.5{percent}), Nb (5.1{percent}), Mo (3.0{percent}), Ti (0.9{percent}), Al (0.5{percent}), Cu (0.15{percent}) and C (0.08{percent}) and it yields an x-ray diffraction pattern consisting of a fcc phase with {ital a}=3.5987 (3) A and an orthorhombic phase associated with {delta}{minus}Ni{sub 3}Nb. It is concluded that the fcc pattern is due to both the {gamma} austenitic phase and {gamma}{prime} Ni{sub 3}(Al,Ti) phase of alloy 718. The standard annealing and aging treatment carried out in air at temperatures between 621 and 982{degree}C produces surface oxides (Cr,Fe){sub 2}O{sub 3} and FeNbO{sub 4} (which are easily removed by etching and polishing) and contracts the lattice. Magnetic measurements show a distinct phase transition at {ital T}{sub {ital c}}=14 K, which has been attributed to the {gamma}{prime}{minus}Ni{sub 3}(Al,Ti) phase by the process of elimination and by observing that it has most of the characteristics of the weak itinerant ferromagnet Ni{sub 74.5}Al{sub 25.5}. This transition may have some effects on the cryogenic applications of this alloy. {copyright} {ital 1996 Materials Research Society.}

  17. Effect of temperature on the electro-oxidation of ethanol on platinum

    OpenAIRE

    Ana Paula M. Camargo; Bruno A. F. Previdello; Hamilton Varela; Ernesto R. Gonzalez

    2010-01-01

    We present in this work an experimental investigation of the effect of temperature (from 25 to 180 ºC) in the electro-oxidation of ethanol on platinum in two different phosphoric acid concentrations. We observed that the onset potential for ethanol electro-oxidation shifts to lower values and the reaction rates increase as temperature is increased for both electrolytes. The results were rationalized in terms of the effect of temperature on the adsorption of reaction intermediates, poisons, an...

  18. Erosion-oxidation behavior of thermal sprayed Ni20Cr alloy and WC and Cr3C2 cermet coatings

    Directory of Open Access Journals (Sweden)

    Clarice Terui Kunioshi

    2005-06-01

    Full Text Available An apparatus to conduct high temperature erosion-oxidation studies up to 850 °C and with particle impact velocities up to 15 m.s-1 was designed and constructed in the Corrosion Laboratories of IPEN. The erosion-oxidation behavior of high velocity oxy fuel (HVOF sprayed alloy and cermet coatings of Ni20Cr, WC 20Cr7Ni and Cr3C2 Ni20Cr on a steel substrate has been studied. Details of this apparatus and the erosion-oxidation behavior of these coatings are presented and discussed. The erosion-oxidation behavior of HVOF coated Cr3C2 25(Ni20Cr was better than that of WC 20Cr7Ni, and the erosion-oxidation regimes have been identified for these coatings at particle impact velocity of 3.5 m.s-1, impact angle of 90° and temperatures in the range 500 to 850 °C.

  19. Temperature effect on the binder-free nickel copper oxide nanowires with superior supercapacitor performance

    Science.gov (United States)

    Zhang, Liuyang; Tang, Chunhua; Gong, Hao

    2014-10-01

    Although the use of nickel oxide in supercapacitor electrodes has been reported extensively, the effect of incorporating copper in the binary compound is not known. Arrays of nickel copper oxide nanowires on the current collector via a simple and industrially compatible route have been successfully synthesized. A systematic study on the effect of temperature is also presented. Strikingly, through conductivity modification and binder-free growth, the as-grown nanowires show high specific capacitance (2.24 F cm2 at 10 mA; 1955 F g-1 at 1 mV s-1), good rate capability (still 2.18 F cm2 at 50 mA, 1542 F g-1 at 50 mV s-1), and excellent cycle life (90% after 1000 cycles at a high charging-discharging rate 10 A g-1). An asymmetric full cell is then prepared and tested, and very high energy density (30 Wh kg-1) is achieved. Ideal capacitive behavior (rectangular shape of cyclic voltammetry) is shown with this tailored architecture of the full cell.Although the use of nickel oxide in supercapacitor electrodes has been reported extensively, the effect of incorporating copper in the binary compound is not known. Arrays of nickel copper oxide nanowires on the current collector via a simple and industrially compatible route have been successfully synthesized. A systematic study on the effect of temperature is also presented. Strikingly, through conductivity modification and binder-free growth, the as-grown nanowires show high specific capacitance (2.24 F cm2 at 10 mA; 1955 F g-1 at 1 mV s-1), good rate capability (still 2.18 F cm2 at 50 mA, 1542 F g-1 at 50 mV s-1), and excellent cycle life (90% after 1000 cycles at a high charging-discharging rate 10 A g-1). An asymmetric full cell is then prepared and tested, and very high energy density (30 Wh kg-1) is achieved. Ideal capacitive behavior (rectangular shape of cyclic voltammetry) is shown with this tailored architecture of the full cell. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04192e

  20. Modeling of the viscoelastic behavior of a polyimide matrix at elevated temperature

    Science.gov (United States)

    Crochon, Thibaut

    Use of Polymer Matrix Composite Materials (PMCMs) in aircraft engines requires materials able to withstand extreme service conditions, such as elevated temperatures, high mechanical loadings and an oxidative environment. In such an environment, the polymer matrix is likely to exhibit a viscoelastic behavior dependent on the mechanical loading and temperature. In addition, the combined effects of elevated temperature and the environment near the engines are likely to increase physical as well as chemical aging. These various parameters need to be taken into consideration for the designer to be able to predict the material behavior over the service life of the components. The main objective of this thesis was to study the viscoelastic behavior of a high temperature polyimide matrix and develop a constitutive theory able to predict the material behavior for every of service condition. Then, the model had to have to be implemented into commercially available finite-element software such as ABAQUS or ANSYS. Firstly, chemical aging of the material at service temperature was studied. To that end, a thermogravimetric analysis of the matrix was conducted on powder samples in air atmosphere. Two kinds of tests were performed: i) kinetic tests in which powder samples were heated at a constant rate until complete sublimation; ii) isothermal tests in which the samples were maintained at a constant temperature for 24 hours. The first tests were used to develop a degradation model, leading to an excellent fit of the experimental data. Then, the model was used to predict the isothermal data but which much less success, particularly for the lowest temperatures. At those temperatures, the chemical degradation was preceded by an oxidation phase which the model was not designed to predict. Other isothermal degradation tests were also performed on tensile tests samples instead of powders. Those tests were conducted at service temperature for a much longer period of time. The samples

  1. Degradation in Solid Oxide Cells During High Temperature Electrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Manohar Sohal

    2009-05-01

    Idaho National Laboratory has an ongoing project to generate hydrogen from steam using solid oxide electrolysis cells. One goal of that project is to address the technical and degradation issues associated with solid oxide electrolysis cells. This report covers a variety of these degradation issues, which were discussed during a workshop on “Degradation in Solid Oxide Electrolysis Cells and Strategies for its Mitigation,” held in Phoenix, AZ on October 27, 2008. Three major degradation issues related to solid oxide electrolysis cells discussed at the workshop are: • Delamination of O2-electrode and bond layer on steam/O2-electrode side • Contaminants (Ni, Cr, Si, etc.) on reaction sites (triple-phase boundary) • Loss of electrical/ionic conductivity of electrolyte. This list is not all inclusive, but the workshop summary can be useful in providing a direction for future research related to the degradation of solid oxide electrolysis cells.

  2. Moisture and temperature controls on nitrification differ among ammonia oxidizer communities from three alpine soil habitats

    Science.gov (United States)

    Osborne, Brooke B; Baron, Jill S.; Wallenstein, Matthew D.

    2016-01-01

    Climate change is altering the timing and magnitude of biogeochemical fluxes in many high elevation ecosystems. The consequent changes in alpine nitrification rates have the potential to influence ecosystem scale responses. In order to better understand how changing temperature and moisture conditions may influence ammonia oxidizers and nitrification activity, we conducted laboratory incubations on soils collected in a Colorado watershed from three alpine habitats (glacial outwash, talus, and meadow). We found that bacteria, not archaea, dominated all ammonia oxidizer communities. Nitrification increased with moisture in all soils and under all temperature treatments. However, temperature was not correlated with nitrification rates in all soils. Site-specific temperature trends suggest the development of generalist ammonia oxidizer communities in soils with greater in situ temperature fluctuations and specialists in soils with more steady temperature regimes. Rapidly increasing temperatures and changing soil moisture conditions could explain recent observations of increased nitrate production in some alpine soils.

  3. Effects of graphene oxides on the cure behaviors of a tetrafunctional epoxy resin

    Directory of Open Access Journals (Sweden)

    2011-09-01

    Full Text Available The influence of graphene oxides (GOs on the cure behavior and thermal stability of a tetrafunctional tetraglycidyl-4,4’-diaminodiphenylmethane cured with 4,4’-diaminodiphenylsulfone was investigated by using dynamic differential scanning calorimetry (DSC and thermogravimetric analysis (TGA. The dynamic DSC results showed that the initial reaction temperature and exothermal peak temperature decreased with the increase of GO contents. Furthermore, the addition of GO increased the enthalpy of epoxy cure reaction. Results from activation energy method showed that activation energies of GO/epoxy nanocomposites greatly decreased with the GO content in the latter stage, indicating that GOs significantly hindered the occurrence of vitrification. The oxygen functionalities, such as hydroxyl and carboxyl groups, on the surface of GOs acted as catalysts and facilitated the curing reaction and the catalytic effect increased with the GO contents. TGA results revealed that the addition of GOs decreased the thermal stability of epoxy.

  4. Magnetic structures synthesized by controlled oxidative etching: Structural characterization and magnetic behavior

    Directory of Open Access Journals (Sweden)

    Álvaro de Jesús Ruíz-Baltazar

    Full Text Available A facile strategy for the fabrication Fe3O4 nanostructures at room temperature and with well-defined morphology is proposed. In this methodology, the iron precursors were reduced by sodium borohydride. Subsequently an oxidative etching process promotes the formation of Fe2O3 nanostructures. Magnetic measurements revealed a well-defined superparamagnetic behavior for the material. The Zero-Field-Cooled (ZFC and Field-Cooled (FC magnetization curves reveals that critical and blocking temperature were 24 and 350 °C respectively. The Fe3O4 nanostructures were characterized using aberration-corrected (Cs scanning transmission electron microscopy (STEM and energy dispersive spectroscopy (EDS. Additionally, Raman spectra support the Fe3O4 presence and corroborate the efficiency of the synthesis process to obtain magnetite. Keywords: Chemical synthesis, Fe3O4 nanoparticles, Structural characterization, Magnetic properties

  5. Characterization and corrosion behavior of F6NM stainless steel treated in high temperature water

    Science.gov (United States)

    Li, Zheng-yang; Cai, Zhen-bing; Yang, Wen-jin; Shen, Xiao-yao; Xue, Guo-hong; Zhu, Min-hao

    2018-03-01

    F6NM martensitic stainless steel was exposed to 350 °C water condition for 500, 1500, and 2500 h to simulate pressurized water reactor (PWR) condition. The characterization and corrosion behavior of the oxide film were investigated. Results indicate that the exposed steel surface formed a double-layer oxide film. The outer oxide film is Fe-rich and contains two type oxide particles. However, the inner oxide film is Cr-rich, and two oxide films, whose thicknesses increase with increasing exposure time. The oxide film reduces the corrosion behavior because the outer oxide film has many crack and pores. Finally, the mechanism and factors affecting the formation of the oxide film were investigated.

  6. Advanced Catalysts for the Ambient Temperature Oxidation of Carbon Monoxide and Formaldehyde

    Science.gov (United States)

    Nalette, Tim; Eldridge, Christopher; Yu, Ping; Alpetkin, Gokhan; Graf, John

    2010-01-01

    The primary applications for ambient temperature carbon monoxide (CO) oxidation catalysts include emergency breathing masks and confined volume life support systems, such as those employed on the Shuttle. While Hopcalite is typically used in emergency breathing masks for terrestrial applications, in the 1970s, NASA selected a 2% platinum (Pt) on carbon for use on the Shuttle since it is more active and also more tolerant to water vapor. In the last 10-15 years there have been significant advances in ambient temperature CO oxidation catalysts. Langley Research Center developed a monolithic catalyst for ambient temperature CO oxidation operating under stoichiometric conditions for closed loop carbon dioxide (CO2) laser applications which is also advertised as having the potential to oxidize formaldehyde (HCHO) at ambient temperatures. In the last decade it has been discovered that appropriate sized nano-particles of gold are highly active for CO oxidation, even at sub-ambient temperatures, and as a result there has been a wealth of data reported in the literature relating to ambient/low temperature CO oxidation. In the shorter term missions where CO concentrations are typically controlled via ambient temperature oxidation catalysts, formaldehyde is also a contaminant of concern, and requires specially treated carbons such as Calgon Formasorb as untreated activated carbon has effectively no HCHO capacity. This paper examines the activity of some of the newer ambient temperature CO and formaldehyde (HCHO) oxidation catalysts, and measures the performance of the catalysts relative to the NASA baseline Ambient Temperature Catalytic Oxidizer (ATCO) catalyst at conditions of interest for closed loop trace contaminant control systems.

  7. Effect of temperature on the electro-oxidation of ethanol on platinum

    Directory of Open Access Journals (Sweden)

    Ana Paula M. Camargo

    2010-01-01

    Full Text Available We present in this work an experimental investigation of the effect of temperature (from 25 to 180 ºC in the electro-oxidation of ethanol on platinum in two different phosphoric acid concentrations. We observed that the onset potential for ethanol electro-oxidation shifts to lower values and the reaction rates increase as temperature is increased for both electrolytes. The results were rationalized in terms of the effect of temperature on the adsorption of reaction intermediates, poisons, and anions. The formation of oxygenated species at high potentials, mainly in the more diluted electrolyte, also contributes to increase the electro-oxidation reaction rate.

  8. Comparison of oxidation behaviors of Cr7C3 at 1173 K and 1273 K

    Science.gov (United States)

    Zhang, Lei; Huang, Zhifu; Chang, Li; Zheng, Qiaoling

    2017-10-01

    Cr7C3 has properties of high strength, low density, good chemical stability, and resistance against corrosion and oxidation at high temperature. With these excellent properties, Cr7C3 is considered especially suitable as a high temperature material. However, little attention has been paid to the oxidation behavior of Cr7C3. In this work, the oxidation behavior of Cr7C3 at 1173 K and 1273 K, with seven durations from 10 h to 70 h, was investigated. After testing, oxide morphology and phase composition were observed, and identified by SEM and XRD respectively. The results indicate that the anti-oxidation levels of Cr7C3 at the oxidation times of 1173 K and 1273 K both belong to the total anti-oxidation grade; the oxidation rate constant and oxidation rate of Cr7C3 at 1273 K show improvement over those at 1173 K by about one order of magnitude and more than two-fold respectively. The result also indicates that Cr2O3 does not peel off from the surface of Cr7C3 at 1173 K however, at 1273 K it does peel off. Furthermore, the calculation result indicates that the critical compressive stress value for Cr2O3 peeling from the surface of Cr7C3 lies between 1.14 GPa and 1.27 GPa.

  9. Ammonia oxidation at high pressure and intermediate temperatures

    DEFF Research Database (Denmark)

    Song, Yu; Hashemi, Hamid; Christensen, Jakob Munkholt

    2016-01-01

    was satisfactory. The main oxidation path for NH3 at high pressure under oxidizing conditions is NH3⟶+OH NH2⟶+HO2,NO2 H2NO⟶+O2 HNO⟶+O2 NO ⟶+NH2 N2. The modeling predictions are most sensitive to the reactions NH2 + NO = NNH + OH and NH2 + HO2 = H2NO + OH, which promote the ammonia consumption by forming OH...

  10. Mechanism study on the sulfidation of ZnO with sulfur and iron oxide at high temperature

    Science.gov (United States)

    Han, Junwei; Liu, Wei; Zhang, Tianfu; Xue, Kai; Li, Wenhua; Jiao, Fen; Qin, Wenqing

    2017-02-01

    The mechanism of ZnO sulfidation with sulfur and iron oxide at high temperatures was studied. The thermodynamic analysis, sulfidation behavior of zinc, phase transformations, morphology changes, and surface properties were investigated by HSC 5.0 combined with FactSage 7.0, ICP, XRD, optical microscopy coupled with SEM-EDS, and XPS. The results indicate that increasing temperature and adding iron oxide can not only improve the sulfidation of ZnO but also promote the formation and growth of ZnS crystals. Fe2O3 captured the sulfur in the initial sulfidation process as iron sulfides, which then acted as the sulfurizing agent in the late period, thus reducing sulfur escape at high temperatures. The addition of carbon can not only enhance the sulfidation but increase sulfur utilization rate and eliminate the generation of SO2. The surfaces of marmatite and synthetic zinc sulfides contain high oxygen due to oxidation and oxygen adsorption. Hydroxyl easily absorbs on the surface of iron-bearing zinc sulfide (Zn1-xFexS). The oxidation of synthetic Zn1-xFexS is easier than marmatite in air.

  11. Temperature-time dependent transmittance, sheet resistance and bonding energy of reduced graphene oxide on soda lime glass

    Science.gov (United States)

    Kumar, Raj; Kumar, R. Manoj; Bera, Parthasarathi; Ariharan, S.; Lahiri, Debrupa; Lahiri, Indranil

    2017-12-01

    Reduced graphene oxide coated soda lime glass can act as an alternative transparent/conducting electrode for many opto-electronic applications. However, bonding between the deposited reduced graphene oxide film and the glass substrate is important for achieving better stability of the coating and an extended device lifetime. In the present study, delamination energy of reduced graphene oxide on soda lime glass was quantified by using nanoscratch technique. Graphene oxide was deposited on soda lime glass by dip coating technique and was thermally reduced at different temperatures (100 °C, 200 °C, 300 °C, 400 °C and 500 °C) and treatment time (2 h, 3 h, 4 h, 5 h and 10 h) in Ar (95%) with H2 (5%) atmosphere. An inverse behavior of delamination energy with temperature and treatment time was observed, which could be correlated with the removal of oxygen functional groups. Sheet resistance of the film demonstrated a steady decay with increasing temperature and treatment time. Functional groups attached to the graphene planes have more influence on conductivity than groups attached to the edges. Removal of functional groups could also be related to optical transmittance of the samples. Knowledge generated in this study with respect to delamination energy, sheet resistance and optical transmittance could be extensively used for various opto-electronic applications.

  12. Growth kinetics of thin oxide layers; oxidation of Fe and Fe-N phases at room temperature

    NARCIS (Netherlands)

    Kooi, Bart J.; Somers, Marcel A.J.; Mittemeijer, Eric J.

    1996-01-01

    The evolution of iron-oxide layers at room temperature on pure polycrystalline α-Fe and on the Fe-N phases γ-Fe[N], γ'-Fe4N1-x and ε-Fe2N1-z was followed in situ with Auger-Electron Spectroscopy. The observed oxidation kinetics of the Fe and Fe-N phases were interpreted using a model considering

  13. Oxidation behavior of NiCoCrAlY coatings deposited by double-Glow plasma alloying

    Science.gov (United States)

    Cui, Shiyu; Miao, Qiang; Liang, Wenping; Li, Baiqiang

    2018-01-01

    The NiCoCrAlY coatings were deposited on the Inconel 718 alloy substrates by a novel method called double-glow plasma alloying (DG). The phases and microstructure of the coatings were investigated by X-ray diffraction analysis while their chemical composition was analyzed using scanning electron microscopy. The morphology of the NiCoCrAlY coatings was typical of coatings formed by DG, with their structure consisting of uniform submicron-sized grains. Further, the coatings showed high adhesion strength (critical load >46 N). In addition, the oxidation characteristics of the coatings and the substrate were examined at three different temperatures (850, 950, and 1050 °C) using a muffle furnace. The coatings showed a lower oxidation rate, which was approximately one-tenth of that of the substrate. Even after oxidation for 100 h, the Al2O3 phase was the primary phase in the surface coating (850 °C), with the thickness of the oxide film increasing to 0.65 μm at 950 °C. When the temperature was increased beyond 1050 °C, the elemental Al and Ni were consumed in the formation of the oxide scale, which underwent spallation at several locations. The oxidation products of Cr, which were produced in large amounts and had a prism-like structure, controlled the subsequent oxidation behavior at the surface.

  14. Comparative study of high temperature oxidation behaviour in AISI 304 and AISI 439 stainless steels

    Directory of Open Access Journals (Sweden)

    Antônio Claret Soares Sabioni

    2003-06-01

    Full Text Available This work deals with a comparison of high temperature oxidation behaviour in AISI 304 austenitic and AISI 439 ferritic stainless steels. The oxidation experiments were performed between 850 and 950 °C, in oxygen and Ar (100 vpm H2. In most cases, it was formed a Cr2O3 protective scale, whose growth kinetics follows a parabolic law. The exception was for the the AISI 304 steel, at 950 °C, in oxygen atmosphere, which forms an iron oxide external layer. The oxidation resistance of the AISI 439 does not depend on the atmosphere. The AISI 304 has the same oxidation resistance in both atmospheres, at 850 °C, but at higher temperatures, its oxidation rate strongly increases in oxygen atmosphere. Concerning the performance of these steels under oxidation, our results show that the AISI 439 steel has higher oxidation resistance in oxidizing atmosphere, above 850 °C, while, in low pO2 atmosphere, the AISI 304 steel has higher oxidation resistance than the AISI 439, in all the temperature range investigated.

  15. Light-off temperature determination of oxidation catalyst using FTIR technique

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, C.C. (Army Chemical Research, Development and Engineering Center, Aberdeen Proving Ground, MD (USA))

    1988-09-01

    There are various techniques to evaluate the performance of oxidation catalysts. Measurements of surface composition, surface structure, surface area, porosity, acidity, and dispersion of active metals of oxidation catalysts, etc., can be related to the catalyst performance. Other methods such as the decoloration of the indigo carmine solution to correlate the catalytic activity with the flash point and the recorder-equipped calorimeter technique to determine the ignition time, maximum temperature and maximum combustion temperature were used. For an oxidation catalyst, however, one direct measurement of its performance is to determine its light-off temperature, the temperature at which significant oxidation reactions occur. In generation, it is true that the lower the light-off temperature, the more effective will be the catalyst performance. Indeed, this correlation was used in the past to select the optimum reduction temperature and the duration of reduction for the preparation of the best Ni-containing catalyst. The authors have developed an in-situ FTIR technique for simultaneously determining the light-off temperatures and identifying catalytic oxidation products of oxidation catalysts. Using this newly developed technique, three three-way automatic catalysts were evaluated. The details of the subject technique and the results of catalyst performance evaluation are described in this paper.

  16. Room temperature transparent conducting oxides based on zinc oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Clatot, J. [Laboratoire de Reactivite et de Chimie des Solides, UMR CNRS 6007, 33, rue Saint-Leu, 80039 Amiens (France); Campet, G. [Institut de Chimie de la Matiere Condensee de Bordeaux (ICMCB), CNRS, 87 Avenue du Docteur A. Schweitzer, 33608 Pessac Cedex (France); Zeinert, A. [Laboratoire de Physique de la Matiere Condensee, Universite de Picardie Jules Verne, 33 rue St. Leu, 80039, Amiens (France); Labrugere, C. [Institut de Chimie de la Matiere Condensee de Bordeaux (ICMCB), CNRS, 87 Avenue du Docteur A. Schweitzer, 33608 Pessac Cedex (France); Rougier, A., E-mail: aline.rougier@u-picardie.fr [Laboratoire de Reactivite et de Chimie des Solides, UMR CNRS 6007, 33, rue Saint-Leu, 80039 Amiens (France)

    2011-04-01

    Doped zinc oxide thin films are grown on glass substrate at room temperature under oxygen atmosphere, using pulsed laser deposition (PLD). O{sub 2} pressure below 1 Pa leads to conductive films. A careful characterization of the film stoichiometry and microstructure using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) concludes on a decrease in crystallinity with Al and Ga additions ({<=}3%). The progressive loss of the (0 0 2) orientation is associated with a variation of the c parameter value as a function of the film thickness and substrate nature. ZnO:Al and ZnO:Ga thin films show a high optical transmittance (>80%) with an increase in band gap from 3.27 eV (pure ZnO) to 3.88 eV and 3.61 eV for Al and Ga doping, respectively. Optical carrier concentration, optical mobility and optical resistivity are deduced from simulation of the optical data.

  17. Interaction mechanisms between slurry coatings and solid oxide fuel cell interconnect alloys during high temperature oxidation

    DEFF Research Database (Denmark)

    Persson, Åsa Helen; Mikkelsen, L.; Hendriksen, P.V.

    2012-01-01

    oxidation rate constant was reduced with 50–90% of that for uncoated alloy. One coating consisting of MnCo2O4 did not significantly affect the oxidation rate of the alloy, and just as for uncoated samples break-away oxidation occurred for MnCo2O4 coated samples. The interaction mechanisms between...

  18. Determination the mechanism and kinetic parameters of copper sulfide minerals oxidation at elevated temperatures

    Directory of Open Access Journals (Sweden)

    Štrbac Nada D.

    2015-01-01

    Full Text Available The paper presents DTA/TG results of polymetallic sulphide copper concentrate from the mine 'Veliki Krivelj' (Serbia at 25-1000 °C. The reaction mechanism at elevated temperatures was proposed. As confirmation to the proposed mechanism, the results of EDXRF and, XRD analysis of the initial sample and the oxidation products at 550 and 950 °C, and the results of SEM/EDS analysis of the initial sample and the oxidation products at 675 ° C were presented. It can be concluded that the oxidation process goes through sulfide oxidation with characteristic exothermic effects, followed by sulfates and oxy- sulfates formation and their. Kinetic analysis of the oxidation process concentrates the test was performed according to the methods of Kissinger and Ozawa in non-isothermal conditions. The results of kinetic studies have shown that the oxidation process in the whole investigated temperature range is located in the kinetic field.

  19. High-Temperature Oxidation of Plutonium Surrogate Metals and Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sparks, Joshua C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Krantz, Kelsie E. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Christian, Jonathan H. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Washington, II, Aaron L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-07-27

    The Plutonium Management and Disposition Agreement (PMDA) is a nuclear non-proliferation agreement designed to remove 34 tons of weapons-grade plutonium from Russia and the United States. While several removal options have been proposed since the agreement was first signed in 2000, processing the weapons-grade plutonium to mixed-oxide (MOX) fuel has remained the leading candidate for achieving the goals of the PMDA. However, the MOX program has received its share of criticisms, which causes its future to be uncertain. One alternative pathway for plutonium disposition would involve oxidizing the metal followed by impurity down blending and burial in the Waste Isolation Pilot Plant (WIPP) in Carlsbad, New Mexico. This pathway was investigated by use of a hybrid microwave and a muffle furnace with Fe and Al as surrogate materials. Oxidation occurred similarly in the microwave and muffle furnace; however, the microwave process time was significantly faster.

  20. Autotrophic Growth of Bacterial and Archaeal Ammonia Oxidizers in Freshwater Sediment Microcosms Incubated at Different Temperatures

    OpenAIRE

    Wu, Yucheng; Ke, Xiubin; Hernández, Marcela; Wang, Baozhan; Dumont, Marc G.; Jia, Zhongjun; Conrad, Ralf

    2013-01-01

    Both bacteria and archaea potentially contribute to ammonia oxidation, but their roles in freshwater sediments are still poorly understood. Seasonal differences in the relative activities of these groups might exist, since cultivated archaeal ammonia oxidizers have higher temperature optima than their bacterial counterparts. In this study, sediment collected from eutrophic freshwater Lake Taihu (China) was incubated at different temperatures (4°C, 15°C, 25°C, and 37°C) for up to 8 weeks. We e...

  1. Some major aspects of the chemical behavior of rare earth oxides: An overview

    Energy Technology Data Exchange (ETDEWEB)

    Bernal, S. [Departamento de Ciencia de los Materiales, Ingenieria Metalurgica y Quimica Inorganica, Facultad de Ciencias, Universidad de Cadiz, Apartado 40, E-11510 Puerto Real, Cadiz (Spain)]. E-mail: serafin.bernal@uca.es; Blanco, G. [Departamento de Ciencia de los Materiales, Ingenieria Metalurgica y Quimica Inorganica, Facultad de Ciencias, Universidad de Cadiz, Apartado 40, E-11510 Puerto Real, Cadiz (Spain); Calvino, J.J. [Departamento de Ciencia de los Materiales, Ingenieria Metalurgica y Quimica Inorganica, Facultad de Ciencias, Universidad de Cadiz, Apartado 40, E-11510 Puerto Real, Cadiz (Spain); Omil, J.A. Perez [Departamento de Ciencia de los Materiales, Ingenieria Metalurgica y Quimica Inorganica, Facultad de Ciencias, Universidad de Cadiz, Apartado 40, E-11510 Puerto Real, Cadiz (Spain); Pintado, J.M. [Departamento de Ciencia de los Materiales, Ingenieria Metalurgica y Quimica Inorganica, Facultad de Ciencias, Universidad de Cadiz, Apartado 40, E-11510 Puerto Real, Cadiz (Spain)

    2006-02-09

    The chemical behavior of sesquioxides and higher rare earth oxides is briefly reviewed. In the first case processes implying no change in the lanthanoid oxidation state are considered, whereas in the second one the analysis is focused on their redox behavior.

  2. High-temperature oxidation behaviour of Ti3 Alx C2 in air

    Indian Academy of Sciences (India)

    Administrator

    than that of silicon at high temperature. The compound can be described by the formula, Ti3Si(1–x)AlxC2 (0 < x. < 0⋅16) (Zhu and Mei 2009). In the following ... phases of oxide using a rotating anode X-ray diffracto- meter (Model D/MAX-RB, RIGAKU Corporation,. Japan). The microstructures of oxide scales were investi-.

  3. Gold-Catalyzed Aerobic Oxidation of 5-Hydroxymethylfurfural in Water at Ambient Temperature

    DEFF Research Database (Denmark)

    Gorbanev, Yury; Kegnæs, Søren; Woodley, John

    2009-01-01

    The aerobic oxidation of 5-hydroxymethylfurfural, a versatile biomass-derived chemical, is examined in water with a titania-supported gold-nanoparticle catalyst at ambient temperature (30 degrees C). The selectivity of the reaction towords 2,5-furandicarboxylic acid and the intermediate oxidation...

  4. Hydrogen oxidation at high pressure and intermediate temperatures: experiments and kinetic modeling

    DEFF Research Database (Denmark)

    Hashemi, Hamid; Christensen, Jakob Munkholt; Gersen, Sander

    2015-01-01

    Hydrogen oxidation at 50 bar and temperatures of 700–900 K was investigated in a high pressure laminar flow reactor under highly diluted conditions. The experiments provided information about H 2 oxidation at pressures above the third explosion limit. The fuel–air equivalence ratio of the reactants...

  5. Processing and Fabrication of High Temperature Oxide Superconductors

    Science.gov (United States)

    1992-11-30

    XRD analysis of this calcined powder showed that metallic Cu, Y203, and BaCO3 formed, suggesting that NH3 is too strongly reducing and not suitable for...December 4, 1990). 10. S. M. Johnson and M. I. Gusman, "Microstructure and Critical Current Density in High-Tc Metal Oxide Superconductors," EPRI Final...superconducting closed. ceramic oxides indicate that only crude methods of D. W. Johnson et a., in the CeramicA Bulletin, VoL 53, powder preparation are

  6. High Temperature Reactions of Uranium Dioxide with Various Metal Oxides

    Science.gov (United States)

    1956-02-20

    difficulties described in (2) and (3). However, sagging of the helix, blocking the line of sight, was a troublesome problem . REFRACTORY METAL HEATER...Jr., Uranium oxide phase equilibrium systems: IV, UOr- ThOg , J. Am. Ceram. Soc. 36, 397 (1953). [20] H. von Wartenberg and E. Prophet, Melting diagrams

  7. Partial oxidation of methane in a temperature-controlled dielectric barrier discharge reactor

    KAUST Repository

    Zhang, Xuming

    2015-01-01

    We studied the relative importance of the reduced field intensity and the background reaction temperature in the partial oxidation of methane in a temperature-controlled dielectric barrier discharge reactor. We obtained important mechanistic insight from studying high-temperature and low-pressure conditions with similar reduced field intensities. In the tested range of background temperatures (297 < T < 773 K), we found that the conversion of methane and oxygen depended on both the electron-induced chemistry and the thermo-chemistry, whereas the chemical pathways to the products were overall controlled by the thermo-chemistry at a given temperature. We also found that the thermo-chemistry enhanced the plasma-assisted partial oxidation process. Our findings expand our understanding of the plasma-assisted partial oxidation process and may be helpful in the design of cost-effective plasma reformers. © 2014 The Combustion Institute.

  8. Study of oxide and α-Zr(O) growth kinetics from high temperature steam oxidation of Zircaloy-4 cladding

    Energy Technology Data Exchange (ETDEWEB)

    Sawarn, Tapan K., E-mail: sawarn@barc.gov.in; Banerjee, Suparna, E-mail: sup@barc.gov.in; Samanta, Akanksha, E-mail: akanksha@barc.gov.in; Rath, B.N., E-mail: bibhur@barc.gov.in; Kumar, Sunil, E-mail: sunilkmr@barc.gov.in

    2015-12-15

    Oxidation kinetics of Zircaloy-4 cladding of fuel pins of Indian pressurized heavy water reactors (IPHWRs) under a simulated loss of coolant accident (LOCA) condition was investigated. The kinetic rate constants for the oxide and oxygen stabilized α-Zr phase growth were established from the isothermal metal-steam reaction at high temperatures (900–1200 °C) with soaking periods in the range of 60–900 s. Oxide and α-Zr(O) layer thickness were measured to derive the respective growth rates. The observed rates obeyed a parabolic law and Arrhenius expressions of rate constants were established. Percentage equivalent clad reacted (%ECR) was calculated using Baker-Just equation. Hydrogen estimation was carried out on the oxidized samples using inert gas fusion technique. The hydrogen pick up was found to be in the range 10–30 ppm. The measured values of oxide and α-Zr(O) layer thickness were compared with the results obtained using OXYCON, an indigenously developed model. The model predicts the oxide growth reasonably well but under predicts the α-Zr(O) growth significantly at thickness values higher than 80 μm. - Highlights: • Steam oxidation kinetics of IPHWR fuel cladding material, Zircaloy-4 in the temperature range 900–1200 °C has been studied. • The growth kinetics of the oxide and α-Zr(O) were established from the microstructural analysis. • An indigenously developed model, OXYCON has been validated against the experimental data. • The hydrogen pick up in the cladding during oxidation was observed to be in the range 10–30 ppm.

  9. Atomistic study of ternary oxides as high-temperature solid lubricants

    Science.gov (United States)

    Gao, Hongyu

    Friction and wear are important tribological phenomena tightly associated with the performance of tribological components/systems such as bearings and cutting machines. In the process of contact and sliding, friction and wear lead to energy loss, and high friction and wear typically result in shortened service lifetime. To reduce friction and wear, solid lubricants are generally used under conditions where traditional liquid lubricants cannot be applied. However, it is challenging to maintain the functionality of those materials when the working environment becomes severe. For instance, at elevated temperatures (i.e., above 400 °C), most traditional solid lubricants, such as MoS2 and graphite, will easily oxidize or lose lubricity due to irreversible chemical changes. For such conditions, it is necessary to identify materials that can remain thermally stable as well as lubricious over a wide range of temperatures. Among the currently available high-temperature solid lubricants, Ag-based ternary metal oxides have recently drawn attention due to their low friction and ability to resist oxidation. A recent experimental study showed that the Ag-Ta-O ternary exhibited an extremely low coefficient of friction (0.06) at 750 °C. To fully uncover the lubricious nature of this material as a high-temperature solid lubricant, a series of tribological investigations were carried out based on one promising candidate - silver tantalate (AgTaO3). The study was then extended to alternative materials, Cu-Ta-O ternaries, to accommodate a variety of application requirements. We aimed to understand, at an atomic level, the effects of physical and chemical properties on the thermal, mechanical and tribological behavior of these materials at high temperatures. Furthermore, we investigated potassium chloride films on a clean iron surface as a representative boundary lubricating system in a nonextreme environment. This investigation complemented the study of Ag/Cu-Ta-O and enhanced the

  10. Effect of calcination temperature on formaldehyde oxidation performance of Pt/TiO2 nanofiber composite at room temperature

    Science.gov (United States)

    Xu, Feiyan; Le, Yao; Cheng, Bei; Jiang, Chuanjia

    2017-12-01

    Catalytic oxidation at room temperature over well-designed catalysts is an environmentally friendly method for the abatement of indoor formaldehyde (HCHO) pollution. Herein, nanocomposites of platinum (Pt) and titanium dioxide (TiO2) nanofibers with various phase compositions were prepared by calcining the electrospun TiO2 precursors at different temperatures and subsequently depositing Pt nanoparticles (NPs) on the TiO2 through a NaBH4-reduction process. The phase compositions and structures of Pt/TiO2 can be easily controlled by varying the calcination temperature. The Pt/TiO2 nanocomposites showed a phase-dependent activity towards the catalytic HCHO oxidation. Pt/TiO2 containing pure rutile phase showed enhanced activity with a turnover frequency (TOF) of 16.6 min-1 (for a calcination temperature of 800 °C) as compared to those containing the anatase phase or mixed phases. Density functional theory calculation shows that TiO2 nanofibers with pure rutile phase have stronger adsorption ability to Pt atoms than anatase phase, which favors the reduction of Pt over rutile phase TiO2, leading to higher contents of metallic Pt in the nanocomposite. In addition, the Pt/TiO2 with rutile phase possesses more abundant oxygen vacancies, which is conducive to the activation of adsorbed oxygen. Consequently, the Pt/rutile-TiO2 nanocomposite exhibited better catalytic activity towards HCHO oxidation at room temperature.

  11. TEMPERATURE TRENDS OF THE PERMITTIVITY IN COMPLEX OXIDES OF RARE-EARTH ELEMENTS WITH PEROVSKITE-TYPE STRUCTURE

    Directory of Open Access Journals (Sweden)

    A.G.Belous

    2003-01-01

    Full Text Available Ceramic materials based on complex oxides with both the perovskite structure (Ln2/3Nb2O6 and the structure of tetragonal tungsten bronze (Ba6-xLn8+2x/3Ti18O54 have been investigated over a wide frequency and temperature ranges. The results obtained for certain structures denote the presence of the temperature anomalies of dielectric parameters (ε, tanδ. These anomalies occur over the wide frequency range including submilimeter (SMM wavelength range, and are related neither with the processing peculiarities nor with the presence of the phase transitions. Temperature behavior of the permittivity has been considered in terms of the polarization mechanism based on the elastic-strain lattice oscillations. It has been assumed that the observed anomalies could be ascribed to a superposition of harmonic and anharmonic contribution to lattice oscillations that determines τε sign and magnitude.

  12. High temperature oxidation of stainless steel AISI316L in air plasma

    Energy Technology Data Exchange (ETDEWEB)

    Vesel, Alenka [EURATOM-MHEST, Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia)], E-mail: alenka.vesel@guest.arnes.si; Mozetic, Miran; Drenik, Aleksander [EURATOM-MHEST, Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Hauptman, Nina [National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana (Slovenia); Balat-Pichelin, Marianne [CNRS-PROMES, Laboratoire Procedes, Materiaux and Energie Solaire, UPR 8521, 7 rue du four solaire, F-66120 Font Romeu, Odeillo (France)

    2008-12-30

    A study on surface oxidation of AISI316L stainless steel surface was performed. Stainless steel was oxidized in air plasma with a high degree of dissociation of oxygen molecules of about 70%. The resultant flux of oxygen atoms to the surface was about 1 x 10{sup 24} m{sup -2} s{sup -1}. The oxidation was performed at high temperatures ranging up to 1250 K. The oxidation time was 5 min. After oxidation the surface of the samples was analyzed by different methods including Auger electron depth profiling (AES), X-ray photoelectron spectroscopy (XPS), scanning electron spectroscopy (SEM) and X-ray diffraction (XRD). The microstructure and composition of the surface were temperature dependent. In all cases high Cr concentration was observed on the surface after oxidation at a temperature above 600 K. With increasing temperature Mn concentration at the surface increased as well. Below 1000 K the oxide film was uniform, while above 1000 K islands with large spinel particles were observed to appear.

  13. Low temperature self-assembled growth of rutile TiO2/manganese oxide nanocrystalline films

    Science.gov (United States)

    Sun, Zhenya; Zhou, Daokun; Du, Jianhua; Xie, Yuxing

    2017-10-01

    We report formation of rutile TiO2 nanocrystal at low temperature range in the presence of α-MnO2 which self-assembled onto sulfanyl radical activated silicon oxide substrate. SEM, HRTEM, XPS and Raman spectroscopy were used to study the morphology and oxidation state of synthesised crystals. The results showed that when the α-MnO2 was reduced to Mn3O4, it induced the formation of rutile instead of anatase phase in the TiCl4-HCl aqueous system. The finding will promote the understanding of phase transformation mechanism when manganese oxide and titanium oxide co-exist in soil and water environment.

  14. The effect of temperature on the properties of grapheme oxide langmuir films

    Science.gov (United States)

    Seliverstova, E.; Ibrayev, N.; Dzhanabekova, R.; Gladkova, V.

    2017-01-01

    The effect of temperature on the optical properties and structure of graphene oxide langmuir films was studied. It is shown that the decrease of optical density of the films in the absorption band of graphene oxide take place when the film was heated above 100 °C. Increasing the temperature of the films over 200 °C leads to the growth of its optical density. As it was shown with the scanning electron microscopy the structure of grapheme oxide films annealed at different temperatures is practically unchanged. Measured the Raman spectra show that in the films there are a partial reducing of disordered and high-defective graphene oxide LB films occurs under heat treatment. This process accompanied by ordering of amorphous sp3 clusters and its transition in sp2-bonded carbon clusters.

  15. Recent Progress in Nanostructured Oxide TE Materials for Power Generation at High Temperatures

    DEFF Research Database (Denmark)

    Van Nong, Ngo; Pryds, Nini; Linderoth, Søren

    Thermoelectric (TE) materials, which can convert waste heat into electricity, could play an important role in a global sustainable energy solution and environmental problems. Metal oxides have been considered as potential TE materials for power generation that can operate at high temperatures......σT/κ , where S, σ, T and κ are the Seebeck coefficient, electrical conductivity, absolute temperature and thermal conductivity, respectively). We have fabricated high-quality oxide TE materials based on Ca3Co4O9 by optimizing the method for synthesis, modifying the compositions...... and by nanostructuring. This report will focus on the high temperature TE properties of heavy ions doping nanostrcutred Ca3Co4O9 oxides, which exhibit promising ZT, implying suitable polycrystalline oxide TE materials for power generation from waste heat....

  16. Comparison of zircaloy-4 and zirlo by high-temperature oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, J. R.; Jeong, H.; Park, G. H. [Kyunghee Univ., Yongin (Korea, Republic of); Ryu, T. G. [FNC Technology, Seoul (Korea, Republic of)

    2003-10-01

    An experiment on the oxidation of Zirlo was performed in steam between 850 .deg. C and 1150 .deg. C. Zirlo cladding of the reactor fuel was used for the specimen. Temperature was the range appropriate for LOCA analyses of PWR. Tube-type Zirlo was manufactured as specimens by cutting, grinding, polishing and chemical polishing (etching). After the oxidation experiments, the mass increase of each specimen was measured, and the oxidation layer was observed by an optical microscope. Oxidation layer, and those of {alpha}-phase, {beta}-phase were also observed at the specimens oxidized at high temperatures. The hardness with respect to depth also was measured. It can be compared and verified safty of Zircaloy and Zirlo in LOCA according to the data of experiment.

  17. Low-temperature oxidation effects on the morphological and structural properties of hexagonal Zn nano disks

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, R.; Villa S, G.; Rosales D, J. [Tecnologico de Estudios Superiores de Jocotitlan, Carretera Toluca-Atlacomulco Km 44.8, Jocotitlan, Estado de Mexico (Mexico); Vigueras S, E.; Hernandez L, S. [Universidad Autonoma del Estado de Mexico, Laboratorio de Investigacion y Desarrollo de Materiales Avanzados, Paseo Colon esquina Paseo Tollocan, Toluca, Estado de Mexico (Mexico); Acuna, P. [Universidad Autonoma del Estado de Mexico, Programa de Doctorado en Ciencia de Materiales, Paseo Colon esquina Paseo Tollocan, Toluca, Estado de Mexico (Mexico); Argueta V, A.; Colin B, N., E-mail: lorr810813@gmail.com [Tecnologico de Estudios Superiores de Jocotitlan, Programa de Ingenieria Mecatronica, Carretera Toluca-Atlacomulco Km 44.8, Jocotitlan, Estado de Mexico (Mexico)

    2017-11-01

    Ambient-atmosphere oxidation in the temperature range of 90-450 degrees Celsius was performed over Zn films composed by well-faceted hexagonal nano disks, which were deposited by thermal evaporation. Morphological and structural properties of oxidized Zn nano disks were studied by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction and Raman scattering measurements. It was found that Zn nano disks keep its original shape only when they are annealed at 90 or 150 degrees Celsius. Smooth oxidation occurred only on the rectangular faces of Zn nano disks heated at 150 degrees Celsius. Thermal oxidation at 250 degrees Celsius favored growth of Zn O nano needles over the surface of the Zn nano disks. Hexagonal-shape of Zn nano disks was transformed completely into a complex morphology composed by different shaped particles, with further increase in oxidation temperature to 450 degrees Celsius. (Author)

  18. Optimization of Oxidation Temperature for Commercially Pure Titanium to Achieve Improved Corrosion Resistance

    Science.gov (United States)

    Bansal, Rajesh; Singh, J. K.; Singh, Vakil; Singh, D. D. N.; Das, Parimal

    2017-03-01

    Thermal oxidation of commercially pure titanium (cp-Ti) was carried out at different temperatures, ranging from 200 to 900 °C to achieve optimum corrosion resistance of the thermally treated surface in simulated body fluid. Scanning electron microscopy, x-ray diffraction, Raman spectroscopy and electrochemical impedance spectroscopy techniques were used to characterize the oxides and assess their protective properties exposed in the test electrolyte. Maximum resistance toward corrosion was observed for samples oxidized at 500 °C. This was attributed to the formation of a composite layer of oxides at this temperature comprising Ti2O3 (titanium sesquioxide), anatase and rutile phases of TiO2 on the surface of cp-Ti. Formation of an intact and pore-free oxide-substrate interface also improved its corrosion resistance.

  19. Low-temperature glass bonding for sensor application using boron oxide thin films

    NARCIS (Netherlands)

    Legtenberg, Rob; Legtenberg, R.; Bouwstra, S.; Bouwstra, Siebe; Elwenspoek, Michael Curt

    Low-temperature glass bonding of silicon, silicon dioxide and silicon nitride is described. Boron oxide was used as the intermediate glass layer at a bonding temperature of 450°C. First experiments indicate that due to reflow and deformation of the molten glass layer, bonding over metal patterns is

  20. Investigation of NOx Reduction by Low Temperature Oxidation Using Ozone Produced by Dielectric Barrier Discharge

    DEFF Research Database (Denmark)

    Stamate, Eugen; Irimiea, Cornelia; Salewski, Mirko

    2013-01-01

    NOx reduction by low temperature oxidation using ozone produced by a dielectric barrier discharge generator is investigated for different process parameters in a 6m long reactor in serpentine arrangement using synthetic dry flue gas with NOx levels below 500 ppm, flows up to 50 slm and temperatures...

  1. Temperatures In Compost Landfill Covers As Result Of Methane Oxidation And Compost Respiration

    DEFF Research Database (Denmark)

    Scheutz, Charlotte; Merono, A. R.; Pedersen, Rasmus Broen

    2011-01-01

    This study investigated the influence of the temperature on methane (CH4) oxidation and respiration in compost sampled at a full scale biocover implemented at Klintholm landfill exhibiting high temperatures. Compost material was collected at Klintholm landfill and incubated with and without CH4...

  2. Comparison Of Different Noble Metal Catalysts For The Low Temperature Catalytic Partial Oxidation Of Methane

    Energy Technology Data Exchange (ETDEWEB)

    Rabe, S.; Truong, T.-B.; Vogel, F.

    2005-03-01

    The generation of synthesis gas at low temperatures can contribute to a more economic production of clean transportation fuels (Fischer-Tropsch liquids) from natural gas. In this report, the performance of different noble metal catalysts in a low temperature catalytic partial oxidation process is presented. (author)

  3. The Low Temperature Oxidation of 2,7-Dimethyloctane in a Pressurized Flow Reactor

    Science.gov (United States)

    Farid, Farinaz

    The complexity of real fuels has fostered the use of simple mixtures of hydrocarbons whose combustion behavior approximates that of real fuels in both experimental and computational studies to develop models of the combustion of the real fuel. These simple mixtures have been called surrogates. Lightly branched paraffins are an important class of constituents in gasoline, diesel and aviation turbine fuels and therefore are primary candidates for use as a component in a surrogate. Unfortunately, fundamental studies on combustion characteristics of high molecular weight mono- and di-methylated iso-paraffins are scarce. Therefore, this study was designed to investigate the low-temperature oxidation of 2,7-dimethyloctane (2,7-DMO) (C10H22), a lightly branched isomer of decane. Replicate 2,7-DMO oxidation experiments were conducted in a pressurized flow reactor (PFR) over the temperature range of 550 -- 850 K, at a pressure of 8 atm and an equivalence ratio of 0.3 in 4.21% oxygen / nitrogen. The reactivity was mapped by continuous monitoring of CO, CO 2, and O2 using a non-dispersive infrared (NDIR) carbon monoxide / carbon dioxide analyzer and an electrochemical oxygen sensor. For examining the underlying reaction chemistry, detailed speciation of samples was performed at selected temperatures using a gas chromatograph with a flame ionization detector coupled to a mass spectrometer. Comparable oxidation experiments for n-decane were carried out to examine the unique effects of branching on fuel reactivity and distribution of major stable intermediates. For both isomers, the onset of negative temperature coefficient (NTC) region was observed near 700 K, with the reactivity decreasing with increasing the temperature. The flow reactor study of n-decane oxidation confirmed that the isomerization reduces the amount of CO produced at peak reactivity. In addition to reaction inhibition, branching affected the distribution of C2-C 4 olefin intermediates. While the oxidation of

  4. Low-Temperature UV-Assisted Fabrication of Metal Oxide Thin Film Transistor

    Science.gov (United States)

    Zhu, Shuanglin

    Solution processed metal oxide semiconductors have attracted intensive attention in the last several decades and have emerged as a promising candidate for the application of thin film transistor (TFT) due to their nature of transparency, flexibility, high mobility, simple processing technique and potential low manufacturing cost. However, metal oxide thin film fabricated by solution process usually requires a high temperature (over 300 °C), which is above the glass transition temperature of some conventional polymer substrates. In order to fabricate the flexible electronic device on polymer substrates, it is necessary to find a facile approach to lower the fabrication temperature and minimize defects in metal oxide thin film. In this thesis, the electrical properties dependency on temperature is discussed and an UV-assisted annealing method incorporating Deep ultraviolet (DUV)-decomposable additives is demonstrated, which can effectively improve electrical properties solution processed metal oxide semiconductors processed at temperature as low as 220 °C. By studying a widely used indium oxide (In2O3) TFT as a model system, it is worth noted that compared with the sample without UV treatment, the linear mobility and saturation mobility of UV-annealing sample are improved by 56% and 40% respectively. Meanwhile, the subthreshold swing is decreased by 32%, indicating UV-treated device could turn on and off more efficiently. In addition to pure In2O3 film, the similar phenomena have also been observed in indium oxide based Indium-Gallium-Zinc Oxide (IGZO) system. These finding presented in this thesis suggest that the UV assisted annealing process open a new route to fabricate high performance metal oxide semiconductors under low temperatures.

  5. 9% Cr steel high temperature oxidation. Solutions investigated for improving corrosion resistance of the steel

    Energy Technology Data Exchange (ETDEWEB)

    Evin, Harold Nicolas; Heintz, Olivier; Chevalier, Sebastien [UMR 5209 CNRS-Bourgogne Univ. (France). Lab. Interdisciplinaire Carnot de Bourgogne; Foejer, Cecilia; Jakani, Saad; Dhont, Annick; Claessens, Serge [OCAS N.V. ArcelorMittal Global R and D, Gent (Belgium)

    2010-07-01

    The improvement of high temperature oxidation resistance of low chromium content steels, such as T/P91, is of great interest in regards with their application in thermal power generating plants. Indeed, they possess good creep properties, but are facing their limits of use at temperature higher than 600 C, due to accelerated corrosion phenomena. Good knowledge of the mechanisms involved during their oxidation process is needed to prevent the degradation of the materials and to extend life time of the power plants components. Oxide layers thermally grown, on 9% Cr steels (provided by OCAS N.V), during isothermal tests between 600 C and 750 C in laboratory air under atmospheric pressure were investigated, by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The oxidation behaviour appeared very limited at 750 C, due to the presence of a breakaway, which can be linked to iron porous oxide grown over the surface of the samples. ''In situ'' X-ray Photoelectron spectroscopy (XPS) analyses were performed in air at 600 C after short exposures (between 5 min and 25 h). A complex mixture of iron oxide, Cr{sub 2}O{sub 3} and Cr (VI) species were characterized in the scales. The in-situ analyses were compared and related to XPS analyses performed on thick oxide scales formed on samples oxidized in air at 600 C for 100h. An oxidation mechanism is then proposed to understand the oxide scale growth in the temperature range 600 - 750 C. The second step of this study consists in improving the high temperature corrosion resistance of these steels without modifying their mechanical properties. Thus several solutions were investigated such as MOCVD coatings, pack cementation coatings, and tested in cycle conditions prior. (orig.)

  6. Low-temperature CO oxidation on Co(0 0 0 1)

    Science.gov (United States)

    Wu, Jiawei; Chen, Jun; Guo, Qing; Dai, Dongxu; Yang, Xueming

    2017-09-01

    Low-temperature oxidation of CO, perhaps the most extensively studied reaction in the history of heterogeneous catalysis, is becoming increasingly important in the context of cleaning air and lowering automotive emissions. Here, we have studied low-temperature CO oxidation on Co(0 0 0 1) using temperature programed desorption method. We show that chemisorbed O adlayer on Co(0 0 0 1) does not promote CO2 formation. However, when a Co3O4-like surface is formed at 90 K, large amount of CO2 is produced at 90 K in the presence of weakly bound oxygen species, demonstrating that low-temperature CO oxidation can be rationalized on O2-saturated Co3O4-like oxide surfaces. However, the formation of carbonate species via the CO2 product and weakly bound oxygen species reduces the yield of low temperature CO2. Thus, how to block the formation of carbonate plays a key role in enhancing the low-temperature CO2 production on the Co3O4-like oxide surfaces.

  7. The evolution of titanium oxidation at elevated temperature and its oxide scale morphology

    Science.gov (United States)

    Imbrie, Peter Kenneth

    The purpose of this study was to experimentally quantify the multi-dimensional growth characteristics of the oxide scale formed on commercially pure titanium at 700°C in a flowing air environment. The geometries considered herein had characteristic dimensions that were appropriately sized to match the thickness of the oxide scale and were fabricated into shapes of solid and hollow cylinders and external and internal wedges. Scanning electron microscopy (SEM) image analysis was used to measure the oxide layer thickness and the Pilling-Bedworth ratio (PBR) as a function of time. An effective diffusion coefficient was determined from one-dimensional planar oxide thickness data and experimentally obtained PBR values served as the necessary input to a solid state diffusion model, which was modified to account for the volumetric expansion of the oxide. Oxidation of the solid cylinder and external wedge geometries were shown to develop a scale morphology similar to that observed on a flat specimen. The oxide had two notable features: (1) at the air-oxide interface, the oxide appeared to be compact and its thickness grew with time and (2) from the metal-oxide interface up to the compact scale, the oxide was found to have a porous-layered arrangement with the pore size being a function of distance from the metal-oxide interface. Conversely, the oxide scale growth on the hollow cylinders and external wedges, while still layered, appeared to be much less porous and had considerably less cracking and spalling damage. The modified solid-state diffusion model and experimentally obtained values of the diffusion coefficient and PBR were used to demonstrate the competing influences of oxide expansion and curvature effects. In addition, the predictive capability of the model, for the case of a solid cylinder, was shown to under predict experimental results, whereas scale growth on the inner surface of a hollow cylinder was over predicted. The differences are primarily attributed to

  8. Rheological behavior of Brazilian Cherry (Eugenia uniflora L. pulp at pasteurization temperatures

    Directory of Open Access Journals (Sweden)

    Alessandra Santos Lopes

    2013-03-01

    Full Text Available The rheological behavior of Brazilian Cherry (Eugenia uniflora L. pulp in the range of temperatures used for pasteurization (83 to 97 °C was studied. The results indicated that Brazilian Cherry pulp presented pseudoplastic behavior, and the Herschel-Bulkley model was considered more adequate to represent the rheological behavior of this pulp in the range of temperatures studied. The fluid behavior index (n varied in the range from 0.448 to 0.627. The effect of temperature on the apparent viscosity was described by an equation analogous to Arrhenius equation, and a decrease in apparent viscosity with an increase in temperature was observed.

  9. High-temperature oxidation of advanced FeCrNi alloy in steam environments

    Science.gov (United States)

    Elbakhshwan, Mohamed S.; Gill, Simerjeet K.; Rumaiz, Abdul K.; Bai, Jianming; Ghose, Sanjit; Rebak, Raul B.; Ecker, Lynne E.

    2017-12-01

    Alloys of iron-chromium-nickel are being explored as alternative cladding materials to improve safety margins under severe accident conditions. Our research focuses on non-destructively investigating the oxidation behavior of the FeCrNi alloy ;Alloy 33; using synchrotron-based methods. The evolution and structure of oxide layer formed in steam environments were characterized using X-ray diffraction, hard X-ray photoelectron spectroscopy, X-ray fluorescence methods and scanning electron microscopy. Our results demonstrate that a compact and continuous oxide scale was formed consisting of two layers, chromium oxide and spinel phase (FeCr2O4) oxides, wherein the concentration of the FeCr2O4 phase decreased from the surface to the bulk-oxide interface.

  10. Effect of hydrogen on the integrity of aluminium–oxide interface at elevated temperatures

    KAUST Repository

    Li, Meng

    2017-02-20

    Hydrogen can facilitate the detachment of protective oxide layer off metals and alloys. The degradation is usually exacerbated at elevated temperatures in many industrial applications; however, its origin remains poorly understood. Here by heating hydrogenated aluminium inside an environmental transmission electron microscope, we show that hydrogen exposure of just a few minutes can greatly degrade the high temperature integrity of metal–oxide interface. Moreover, there exists a critical temperature of ∼150 °C, above which the growth of cavities at the metal–oxide interface reverses to shrinkage, followed by the formation of a few giant cavities. Vacancy supersaturation, activation of a long-range diffusion pathway along the detached interface and the dissociation of hydrogen-vacancy complexes are critical factors affecting this behaviour. These results enrich the understanding of hydrogen-induced interfacial failure at elevated temperatures.

  11. Behavior of an improved Zr fuel cladding with oxidation resistant coating under loss-of-coolant accident conditions

    Energy Technology Data Exchange (ETDEWEB)

    Park, Dong Jun, E-mail: pdj@kaeri.re.kr; Kim, Hyun Gil; Jung, Yang Il; Park, Jung Hwan; Yang, Jae Ho; Koo, Yang Hyun

    2016-12-15

    This study investigates protective coatings for improving the high temperature oxidation resistance of Zr fuel claddings for light water nuclear reactors. FeCrAl alloy and Cr layers were deposited onto Zr plates and tubes using cold spraying. For the FeCrAl/Zr system, a Mo layer was introduced between the FeCrAl coating and the Zr matrix to prevent inter-diffusion at high temperatures. Both the FeCrAl and Cr coatings improved the oxidation resistance compared to that of the uncoated Zr alloy when exposed to a steam environment at 1200 °C. The ballooning behavior and mechanical properties of the coated cladding samples were studied under simulated loss-of-coolant accident conditions. The coated samples showed higher burst temperatures, lower circumferential strain, and smaller rupture openings compared to the uncoated Zr. Although 4-point bend tests of the coated samples showed a small increase in the maximum load, ring compression tests of a sectioned sample showed increased ductility. - Highlights: • Cr and FeCrAl were coated onto Zr fuel cladding for light water nuclear reactors. • Mo layer between FeCrAl and Zr prevented inter-diffusion at high temperatures. • Coated claddings were tested under loss-of-cooling accident conditions. • Coating improved high-temperature oxidation resistance and mechanical properties.

  12. Species and temperature measurements of methane oxidation in a nanosecond repetitively pulsed discharge

    OpenAIRE

    Lefkowitz, Joseph K; Guo, Peng; Rousso, Aric; Ju, Yiguang

    2015-01-01

    Speciation and temperature measurements of methane oxidation during a nanosecond repetitively pulsed discharge in a low-temperature flow reactor have been performed. Measurements of temperature and formaldehyde during a burst of pulses were made on a time-dependent basis using tunable diode laser absorption spectroscopy, and measurements of all other major stable species were made downstream of a continuously pulsed discharge using gas chromatography. The major species for a stoichiometric me...

  13. SSZ-13-supported manganese oxide catalysts for low temperature ...

    Indian Academy of Sciences (India)

    YONGZHOU YE

    demonstrated that the loading of SSZ-13 type molecular sieves with Mn compounds can be expected to extend the low temperature threshold of SCR activity. In the present study, a family of Mn/SSZ-13 cat- alysts with varying Mn loading was prepared by the co-precipitation method. The SCR activities were eval- uated, and ...

  14. SSZ-13-supported manganese oxide catalysts for low temperature ...

    Indian Academy of Sciences (India)

    A series of Mn/SSZ-13 catalysts of varying Mn content were synthesized by hydrothermal and co-precipitation methods. Their performances for the selective catalytic reduction (SCR) of NOx with NH₃ were evaluated. The results indicate that over 95% NOx conversion was achieved at a low temperature of 150◦C with an Mn ...

  15. Oxidation behavior of arc melted AlCoCrFeNi multi-component high-entropy alloys

    Energy Technology Data Exchange (ETDEWEB)

    Butler, Todd M., E-mail: tmbutler@crimson.ua.edu; Weaver, Mark L.

    2016-07-25

    Multi-component, high-entropy alloys (HEAs) are being investigated as potential alternatives for high temperature structural materials due to their reported high symmetry crystal structures, favorable mechanical properties, high temperature phase stabilities, and resistances to degradation in oxidizing/corrosive environments. However, their high temperature oxidation behaviors are poorly understood. In this work, the as-cast microstructures and 1050 °C oxidation behaviors of a series of arc-melted Al{sub x}(NiCoCrFe){sub 100-x} HEAs where x = 8, 10, 12, 15, 20, and 30 (at.%) were investigated. The dominant structure of the low Al concentration HEAs was determined to be FCC, while the high Al concentration HEAs were BCC dominant. A structural transition point at ∼15 at. % Al exists where a large fraction of both FCC and BCC are present. Each HEA exhibited initial transient oxidation followed by various degrees of parabolic oxide growth. All of the HEAs formed a combination of Al{sub 2}O{sub 3} and AlN beneath an external Cr{sub 2}O{sub 3} scale. Increased Al content improved the continuity and internal position of the Al{sub 2}O{sub 3} scale, resulting in enhanced oxidation resistances. These results are discussed relative to chemically similar conventional alloys and existing Ni–Cr–Al oxide formation models. The resulting phase equilibria has been compared to thermodynamic predictions made using the CALPHAD method. - Highlights: • The as-cast HEAs formed FCC, BCC, and/or B2 (i.e. ordered BCC) crystal structures. • Thermodynamic CALPHAD based models were fairly consistent with experimental results. • All of the HEAs selectively oxidized to form predominantly Al{sub 2}O{sub 3} and Cr{sub 2}O{sub 3} scales. • The HEAs exhibited some parabolic oxide growth comparable to model NiCrAl alloys. • The oxidation performance was heavily influenced by the relative Al concentrations.

  16. High temperature induces apoptosis and oxidative stress in pufferfish (Takifugu obscurus) blood cells.

    Science.gov (United States)

    Cheng, Chang-Hong; Yang, Fang-Fang; Liao, Shao-An; Miao, Yu-Tao; Ye, Chao-Xia; Wang, An-Li; Tan, Jia-Wen; Chen, Xiao-Yan

    2015-10-01

    Water temperature is an important environmental factor in aquaculture farming that affects the survival and growth of organisms. The change in culture water temperature may not only modify various chemical and biological processes but also affect the status of fish populations. In previous studies, high temperature induced apoptosis and oxidative stress. However, the precise mechanism and the pathways that are activated in fish are still unclear. In the present study, we investigated the effects of high temperature (34°C) on the induction of apoptosis and oxidative stress in pufferfish (Takifugu obscurus) blood cells. The data showed that high temperature exposure increased oxygen species (ROS), cytoplasmic free-Ca(2+) concentration and cell apoptosis. To test the apoptotic pathway, the expression pattern of some key apoptotic related genes including P53, Bax, caspase 9 and caspase 3 were examined. The results showed that acute high temperature stress induced up-regulation of these genes, suggesting that the p53-Bax pathway and the caspase-dependent apoptotic pathway could be involved in apoptosis induced by high temperature stress. Furthermore, the gene expression of antioxidant enzymes (Cu/Zn-SOD, Mn-SOD, CAT, GPx, and GR) and heat shock proteins (HSP90 and HSP70) in the blood cells were induced by high temperature stress. Taken together, our results showed that high temperature-induced oxidative stress may cause pufferfish blood cells apoptosis, and cooperatively activated p53-Bax and caspase-dependent apoptotic pathway. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Temperature-Independent Switching Rates for a Random Telegraph Signal in a Silicon Metal-Oxide-Semiconductor Field-Effect Transistor at Low Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Borland, Nick; Fleetwood, D.M.; Scofield, John H.

    1999-07-19

    We have observed discrete random telegraph signals (RTS'S) in the drain voltages of three, observed above 30 K were thermally activated. The switching rate for the only RTS observed below 30 K was thermally activated above 30 K but temperature-independent below 10 K. To our knowledge, this cross-over from thermal activation to tunneling behavior has not been previously observed for RTS's Metal-oxide-semiconductor field-effect transistors (MCEWETS) often exhibit relatively large levels of low-frequency (1/fl noise) [1,2]. Much evidence suggests that this noise is related to the capture all cases, switching rates have been thermally activated, often with different activation energies for capture and/or emission is accompanied by lattice relaxation. Though thermally activated behavior has sufficiently low temperatures [7,9]. While not observed in MOSFETS, cross-over from thermal activation to configurational tunneling has been observed for RTS's in junctions [13]. drain voltage was observed to randomly switch between two discrete levels, designated as Vup and Vdn, similar to RTS's reported by others [2,7'- 11 ]. We have characterized six RTS `S for temperatures above 30 K where thermally activated switching rates are observed. The properties of five of these have been the trap, i.e., the mean time a captured charge carrier spends in the trap before it is emitted. Similarly, we identify the mean time in the low resistance state ( trup in state Vup) as the capture time rc. F@ure 1 shows a typical time trace of the drain-voltage fluctuation &d(t)= Vd(t)+Vd>. This indicate that both the mean capture and emission times become independent of Tat low temperatures and where a= capture or emission, is temperature independent. The solid curve in Figure 3(a) (mean capture time) was obtained using a weighted nonlinear charge carriers are not in thermal equilibrium with the lattice, i.e., that while the lattice is being cooled Instead, we believe that the

  18. Effect of temperature on the adsorption of sulfanilamide onto aluminum oxide and its molecular dynamics simulations

    Science.gov (United States)

    Ji, Ying-xue; Wang, Feng-he; Duan, Lun-chao; Zhang, Fan; Gong, Xue-dong

    2013-11-01

    The effect of temperature on the adsorption of sulfanilamide (SA) onto aluminum oxide was researched through batch adsorption experiments, and was then simulated using the molecular dynamics (MD) method. The results show that SA can be adsorbed effectively by the adsorbent of aluminum oxide due to their interactions between SA molecule and the surface of aluminum oxide crystal, and temperature is a key factor which influences the adsorption efficiency obviously. The removal ratio of SA at 298 K is the highest among the selected temperatures (293 K, 298 K, 303 K). MD simulations revealed the interactions between SA molecules and (0 1 2) surface of aluminum oxide crystal at molecular level. The SA molecule has clung to the (0 1 2) face of aluminum oxide crystal, and its structure is deformed during its combining process with the surface. Both binding energies (Eb) and deformation energies (ΔEdeform) in the SA-aluminum oxide system follow the same order as: SA-Al2O3 (298 K) > SA-Al2O3 (293 K) > SA-Al2O3 (303 K). Their deformation energies are far less than their non-bonding energies. Analysis of radial distribution functions (RDFs) indicates that SA can be adsorbed effectively by aluminum oxide crystal mainly through non-bond interactions. The simulation results agree well with the experimental results, which verify the rationality and reliability of the MD simulation. The further MD simulations provide theoretically optimal temperature (301 K) for the adsorption of SA onto aluminum oxide. The molecular dynamics simulation will be useful for better understanding the adsorption mechanism of antibiotics onto metal oxides, which will also be helpful for optimizing experimental conditions to improve the adsorptive removal efficiency of antibiotics.

  19. Effects of temperature on the heterogeneous oxidation of sulfur dioxide by ozone on calcium carbonate

    Directory of Open Access Journals (Sweden)

    L. Y. Wu

    2011-07-01

    Full Text Available The heterogeneous oxidation of sulfur dioxide by ozone on CaCO3 was studied as a function of temperature (230 to 298 K at ambient pressure. Oxidation reactions were followed in real time using diffuse reflectance infrared Fourier transform spectrometry (DRIFTS to obtain kinetic and mechanistic data. From the analysis of the spectral features, the formation of sulfate was identified on the surface in the presence of O3 and SO2 at different temperatures from 230 to 298 K. The results showed that the heterogeneous oxidation and the rate of sulfate formation were sensitive to temperature. An interesting stage-transition region was observed at temperatures ranging from 230 to 257 K, but it became ambiguous gradually above 257 K. The reactive uptake coefficients at different temperatures from 230 to 298 K were acquired for the first time, which can be used directly in atmospheric chemistry modeling studies to predict the formation of secondary sulfate aerosol in the troposphere. Furthermore, the rate of sulfate formation had a turning point at about 250 K. The sulfate concentration at 250 K was about twice as large as that at 298 K. The rate of sulfate formation increased with decreasing temperature at temperatures above 250 K, while there is a contrary temperature effect at temperatures below 250 K. The activation energy for heterogeneous oxidation at temperatures from 245 K to 230 K was determined to be 14.63 ± 0.20 kJ mol−1. A mechanism for the temperature dependence was proposed and the atmospheric implications were discussed.

  20. Autotrophic growth of bacterial and archaeal ammonia oxidizers in freshwater sediment microcosms incubated at different temperatures.

    Science.gov (United States)

    Wu, Yucheng; Ke, Xiubin; Hernández, Marcela; Wang, Baozhan; Dumont, Marc G; Jia, Zhongjun; Conrad, Ralf

    2013-05-01

    Both bacteria and archaea potentially contribute to ammonia oxidation, but their roles in freshwater sediments are still poorly understood. Seasonal differences in the relative activities of these groups might exist, since cultivated archaeal ammonia oxidizers have higher temperature optima than their bacterial counterparts. In this study, sediment collected from eutrophic freshwater Lake Taihu (China) was incubated at different temperatures (4°C, 15°C, 25°C, and 37°C) for up to 8 weeks. We examined the active bacterial and archaeal ammonia oxidizers in these sediment microcosms by using combined stable isotope probing (SIP) and molecular community analysis. The results showed that accumulation of nitrate in microcosms correlated negatively with temperature, although ammonium depletion was the same, which might have been related to enhanced activity of other nitrogen transformation processes. Incubation at different temperatures significantly changed the microbial community composition, as revealed by 454 pyrosequencing targeting bacterial 16S rRNA genes. After 8 weeks of incubation, [(13)C]bicarbonate labeling of bacterial amoA genes, which encode the ammonia monooxygenase subunit A, and an observed increase in copy numbers indicated the activity of ammonia-oxidizing bacteria in all microcosms. Nitrosomonas sp. strain Is79A3 and Nitrosomonas communis lineages dominated the heavy fraction of CsCl gradients at low and high temperatures, respectively, indicating a niche differentiation of active bacterial ammonia oxidizers along the temperature gradient. The (13)C labeling of ammonia-oxidizing archaea in microcosms incubated at 4 to 25°C was minor. In contrast, significant (13)C labeling of Nitrososphaera-like archaea and changes in the abundance and composition of archaeal amoA genes were observed at 37°C, implicating autotrophic growth of ammonia-oxidizing archaea under warmer conditions.

  1. Low-temperature capacitive sensor based on perovskite oxides

    Science.gov (United States)

    Zaza, F.; Orio, G.; Serra, E.; Caprioli, F.; Pasquali, M.

    2015-06-01

    Energy, environmental and social issues drive towards the green political economy and the development of advanced technologies, promoting renewable energy sources, improving energy conversion efficiency and reducing exhaust gas emissions. The development of sustainable technologies requires strategic research in the area of gas sensors for monitoring air quality, controlling gas emissions and optimizing combustion processes. Solid state sensors are the most attractive one because of their simplicity in function, small size and low cost. The aim of this work is to synthetize and characterize strontium titanate and test its sensing performance. The prepared sensor device shows significant sensitivity and response rate at room-temperature. However, because of the low recovery rate, the regeneration of the sensor has to be made at high temperature for promoting the decomposition of the carbonates formed on the perovkite surface.

  2. Crystallization and unusual rheological behavior in poly(ethylene oxide)–clay nanocomposites

    KAUST Repository

    Kelarakis, Antonios

    2011-05-01

    We report a systematic study of the crystallization and rheological behavior of poly(ethylene oxide) (PEO)-clay nanocomposites. To that end a series of nanocomposites based on PEOs of different molecular weight (103 < MW < 105 g/mol) and clay surface modifier was synthesized and characterized. Incorporation of organoclays with polar (MMT-OH) or aromatic groups (MMT-Ar) suppresses the crystallization of polymer chains in low MW PEO, but does not significantly affect the crystallization of high MW matrices. In addition, the relative complex viscosity of the nanocomposites based on low MW PEO increases significantly, but the effect is less pronounced at higher MWs. The viscosity increases in the series MMT-Alk < MMT-OH < MMT-Ar. In contrast to the neat PEO which exhibits a monotonic decrease of viscosity with temperature, all nanocomposites show an increase after a certain temperature. This is the first report of such dramatic enhancements in the viscoelasticity of nanocomposites, which are reversible, are based on a simple polymer matrix and are true in a wide temperature range. © 2011 Elsevier Ltd. All rights reserved.

  3. Influence of low concentration V and Co oxide doping on the dissolution behaviors of simplified nuclear waste glasses

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Xiaonan; Neeway, James J.; Ryan, Joseph V.; Du, Jincheng

    2016-11-01

    Transition metal oxides are commonly present in nuclear waste and they can alter the structure, property and especially dissolution behaviors of the glasses used for waste immobilization. In this paper, we investigated vanadium and cobalt oxide induced structural and properties changes, especially dissolution behaviors, of International Simple Glass (ISG), a model nuclear waste glass system. Static chemical durability tests were performed at 90 °C with a pH value of 7 and a surface-area-to-solution-volume of 200 m-1 for 112 days on three glasses: ISG, ISG doped with 0.5 mol% Co2O3, and ISG doped with 2.0 mol% V2O5. ICP-MS was used to analyze the dissolved ion concentrations. It was found that doping with vanadium and cobalt oxide, even at the low doping concentration, significantly reduced the extent of the ISG glass dissolution. Differential Scanning Calorimetry (DSC) analysis showed that vanadium oxide doping reduced the glass transition temperature (Tg) while cobalt oxide did not significantly change the Tg of ISG. X-ray diffraction (XRD), Raman spectrometry and scanning electron microscopy (SEM) were used to analyze the glass samples before and after corrosion to understand the phase and microstructure changes.

  4. Effect of cerium ion implantation on the oxidation behavior of zircaloy-4 at 500 degree sign C

    CERN Document Server

    Chen, X W; Yu, H R; Zhou, Q G; Chen, B S

    2002-01-01

    In order to investigate the oxidation behavior changes of zircaloy-4 induced by cerium ion implantation using a MEVVA source at an energy of 40 keV with a dose range from 1x10 sup 1 sup 6 to 1x10 sup 1 sup 7 ions/cm sup 2 at the maximum temperature of 130 degree sign C, weight gain curves of the different specimens including as-received zircaloy-4 and cerium-implanted zircaloy-4 were measured after oxidation in air at 500 degree sign C for 100 min. It was obviously found that a significant improvement was achieved in the oxidation behavior of cerium ion implanted zircaloy-4 compared with that of the as-received zircaloy-4. The depth profile of the element composition in the surface region of the samples was obtained by Auger electron spectroscopy, and the valence of the oxides in the scale was analyzed by X-ray photoemission spectroscopy. Glancing angle X-ray diffraction employed to examine the phase transformation in the oxide films showed that the addition of cerium transformed the phase from monoclinic zir...

  5. Destructive behavior of iron oxide in projectile impact

    Science.gov (United States)

    Shang, Wang; Xiaochen, Wang; Quan, Yang; Zhongde, Shan

    2017-12-01

    The damage strain values of Q235-A surface oxide scale were obtained by scanning electron microscopy (SEM/EDS) and universal tensile testing machine. The finite element simulation was carried out to study the destruction effects of oxidation at different impact rates. The results show that the damage value of the oxide strain is 0.08%. With the increase of the projectile velocity, the damage area of the oxide scale is increased, and the damage area is composed of the direct destruction area and the indirect failure area. The indirect damage area is caused by the stress/strain to the surrounding expansion after the impact of the steel body.

  6. The effects of aging and oxidative stress on learning behavior in C. elegans.

    Science.gov (United States)

    Murakami, Shin; Murakami, Hana

    2005-06-01

    Oxidative stress is associated with age-related declines of biological functions. However, the nervous system is preserved during aging in Caenorhabditis elegans and, thus, it is not well explored whether aging and oxidative stress affect nervous functions. Here we report that age-related decline can be observed in a type of associative-learning behavior, referred to as isothermal tracking. We also report the effects of mutants with altered sensitivity to oxidative stress on learning behavior and motor activity in young adults. The isp-1 and clk-1 mutants are members of the Clk class of mutants and have deficits in the function of the mitochondrial respiratory chain, leading to reduced levels of oxidative stress, increased longevity, delayed rhythmic behaviors and other phenotypes. Both the Clk mutations and pretreatment with a metabolic antioxidant, alpha-lipoic acid (LA), increased the ability to show isothermal tracking and modestly reduced motor activity. Mutants with increased oxidative stress showed severely impaired learning behavior and modestly reduced motor activity. Therefore, physiological levels of oxidative stress may be too high for learning behavior but, perhaps, not for motor activity. We discuss the relevance of oxidative stress to the aging and evolution of behaviors.

  7. Temperature and Oxidative Stress as Triggers for Virulence Gene Expression in Pathogenic Leptospira spp.

    Directory of Open Access Journals (Sweden)

    Tricia Fraser

    2017-05-01

    Full Text Available Leptospirosis is a zooanthroponosis aetiologically caused by pathogenic bacteria belonging to the genus, Leptospira. Environmental signals such as increases in temperatures or oxidative stress can trigger response regulatory modes of virulence genes during infection. This study sought to determine the effect of temperature and oxidative stress on virulence associated genes in highly passaged Leptospira borgpeterseneii Jules and L. interrogans Portlandvere. Bacteria were grown in EMJH at 30°C, 37°C, or at 30°C before being transferred to 37°C. A total of 14 virulence-associated genes (fliY, invA, lenA, ligB, lipL32, lipL36, lipL41, lipL45, loa22, lsa21, mce, ompL1, sph2, and tlyC were assessed using endpoint PCR. Transcriptional analyses of lenA, lipL32, lipL41, loa22, sph2 were assessed by quantitative real-time RT-PCR at the temperature conditions. To assess oxidative stress, bacteria were exposed to H2O2 for 30 and 60 min with or without the temperature stress. All genes except ligB (for Portlandvere and ligB and mce (for Jules were detectable in the strains. Quantitatively, temperature stress resulted in significant changes in gene expression within species or between species. Temperature changes were more influential in gene expression for Jules, particularly at 30°C and upshift conditions; at 37°C, expression levels were higher for Portlandvere. However, compared to Jules, where temperature was influential in two of five genes, temperature was an essential element in four of five genes in Portlandvere exposed to oxidative stress. At both low and high oxidative stress levels, the interplay between genetic predisposition (larger genome size and temperature was biased towards Portlandvere particularly at 30°C and upshift conditions. While it is clear that expression of many virulence genes in highly passaged strains of Leptospira are attenuated or lost, genetic predisposition, changes in growth temperature and/or oxidative intensity and

  8. Temperature and Oxidative Stress as Triggers for Virulence Gene Expression in Pathogenic Leptospira spp.

    Science.gov (United States)

    Fraser, Tricia; Brown, Paul D

    2017-01-01

    Leptospirosis is a zooanthroponosis aetiologically caused by pathogenic bacteria belonging to the genus, Leptospira. Environmental signals such as increases in temperatures or oxidative stress can trigger response regulatory modes of virulence genes during infection. This study sought to determine the effect of temperature and oxidative stress on virulence associated genes in highly passaged Leptospira borgpeterseneii Jules and L. interrogans Portlandvere. Bacteria were grown in EMJH at 30°C, 37°C, or at 30°C before being transferred to 37°C. A total of 14 virulence-associated genes (fliY, invA, lenA, ligB, lipL32, lipL36, lipL41, lipL45, loa22, lsa21, mce, ompL1, sph2, and tlyC) were assessed using endpoint PCR. Transcriptional analyses of lenA, lipL32, lipL41, loa22, sph2 were assessed by quantitative real-time RT-PCR at the temperature conditions. To assess oxidative stress, bacteria were exposed to H2O2 for 30 and 60 min with or without the temperature stress. All genes except ligB (for Portlandvere) and ligB and mce (for Jules) were detectable in the strains. Quantitatively, temperature stress resulted in significant changes in gene expression within species or between species. Temperature changes were more influential in gene expression for Jules, particularly at 30°C and upshift conditions; at 37°C, expression levels were higher for Portlandvere. However, compared to Jules, where temperature was influential in two of five genes, temperature was an essential element in four of five genes in Portlandvere exposed to oxidative stress. At both low and high oxidative stress levels, the interplay between genetic predisposition (larger genome size) and temperature was biased towards Portlandvere particularly at 30°C and upshift conditions. While it is clear that expression of many virulence genes in highly passaged strains of Leptospira are attenuated or lost, genetic predisposition, changes in growth temperature and/or oxidative intensity and/or duration

  9. Temperature and high pressure effects on the structural features of catalytic nanocomposites oxides by Raman spectroscopy

    Science.gov (United States)

    da Silva, Antonio N.; Pinto, Raffael C. F.; Freire, Paulo T. C.; Junior, Jose Alves L.; Oliveira, Alcineia C.; Filho, Josué M.

    2015-03-01

    Structural characterizations of nanostructured oxides were studied by X-ray diffraction (XRD), Raman and infrared spectroscopy. The oxides catalysts namely, SnO2, ZrO2, CeO2, MnOx, Al2O3 and TiO2 were prepared by a nanocasting route and the effect of the temperature and pressure on the stability of the solids was evaluated. Raman spectra showed that ZrO2 and TiO2 exhibited phase transitions at moderate temperatures whereas CeO2, SnO2 and MnOx had an effective creation of defects in their structures upon annealing at elevated temperatures. The results suggested also that the effect of the temperature on the particles growth is related to the type of oxide. In this regard, phase transition by up to 600 °C accelerated the sintering of ZrO2 and CeO2 grains compared to TiO2, SnO2 and MnOx counterparts. Under hydrostatic pressures lower than 10 GPa, rutile TiO2 and tetragonal ZrO2 exhibited pressure induced phase transition whereas CeO2 and SnO2 were stable at pressures close to 15 GPa. The experiments revealed that the nanostructured SnO2 oxide exhibited stable performance at relatively high temperatures without phase transition or sintering, being suitable to be used as catalysts in the range of temperature and pressure studied.

  10. Effects of cryomilling on the microstructures and high temperature mechanical properties of oxide dispersion strengthened steel

    Science.gov (United States)

    Gwon, Jin-Han; Kim, Jeoung-Han; Lee, Kee-Ahn

    2015-04-01

    The effects of cryomilling on the microstructures and high temperature mechanical properties of oxide dispersion-strengthened (ODS) steel were examined. Cryomilling was newly tried on this ODS steel to control oxides, grains, and dislocation microstructures. Fe-14Cr-3W-0.4Ti (wt.%) alloy powder and 0.3 wt.%Y2O3 powder were mixed and were mechanically alloyed (MA) through ball milling at each of room temperature (RT) and -150 °C and then hot isostatic pressing (HIP), hot rolling, and annealing processes were implemented to manufacture two types of ODS ferritic steel, K1 (RT) and K4 (-150 °C). Oxide particles were shown to be finer and more uniformly distributed in K4 (5-10 nm size distribution) than in K1 (average size 30 nm). The two alloys were subjected to high temperature compression (RT ∼ 900 °C) tests. K4 represented higher yield strength under all temperature conditions. However, K4 showed rapid strength decreases at high temperatures exceeding 700 °C and showed similar levels of strengths to K1 at 900 °C. This is considered attributable to the fact that although cryomilling increased the number density of oxide particles, it simultaneously reduced grain sizes too much, so that grain boundary weakening at high temperatures could not be sufficiently prevented.

  11. Effects of cryomilling on the microstructures and high temperature mechanical properties of oxide dispersion strengthened steel

    Energy Technology Data Exchange (ETDEWEB)

    Gwon, Jin-Han [Dept. of Advanced Mat. Eng., Andong National University, Andong 760-749 (Korea, Republic of); Kim, Jeoung-Han [Dept. of Advanced Mat. Eng., Hanbat National University, Daejeon 305-719 (Korea, Republic of); Lee, Kee-Ahn, E-mail: keeahn@andong.ac.kr [Dept. of Advanced Mat. Eng., Andong National University, Andong 760-749 (Korea, Republic of)

    2015-04-15

    The effects of cryomilling on the microstructures and high temperature mechanical properties of oxide dispersion-strengthened (ODS) steel were examined. Cryomilling was newly tried on this ODS steel to control oxides, grains, and dislocation microstructures. Fe–14Cr–3W–0.4Ti (wt.%) alloy powder and 0.3 wt.%Y{sub 2}O{sub 3} powder were mixed and were mechanically alloyed (MA) through ball milling at each of room temperature (RT) and −150 °C and then hot isostatic pressing (HIP), hot rolling, and annealing processes were implemented to manufacture two types of ODS ferritic steel, K1 (RT) and K4 (−150 °C). Oxide particles were shown to be finer and more uniformly distributed in K4 (5–10 nm size distribution) than in K1 (average size 30 nm). The two alloys were subjected to high temperature compression (RT ∼ 900 °C) tests. K4 represented higher yield strength under all temperature conditions. However, K4 showed rapid strength decreases at high temperatures exceeding 700 °C and showed similar levels of strengths to K1 at 900 °C. This is considered attributable to the fact that although cryomilling increased the number density of oxide particles, it simultaneously reduced grain sizes too much, so that grain boundary weakening at high temperatures could not be sufficiently prevented.

  12. Two temperature approach to femtosecond laser oxidation of molybdenum and morphological study

    Science.gov (United States)

    Kotsedi, L.; Kaviyarasu, K.; Fuku, X. G.; Eaton, S. M.; Amara, E. H.; Bireche, F.; Ramponi, R.; Maaza, M.

    2017-11-01

    The two-temperature model was used to gain insight into the thermal evolution of the hot electrons and the crystal lattice of the molybdenum thin coating during femtosecond laser treatment. The heat from the laser raised the bulk temperature of the sample through heat transfer from the hot electron to the crystal lattice of the material, which then led to the melting of the top layer of the film. This process resulted in the hot melt reacting ambient oxygen, which in turn oxidized the surface of molybdenum coating. The topological study and morphology of the oxidized film was conducted using high-resolution scanning electron microscope, with micrographs taken in both the cross-sectional geometry and normal incidence to the electron beam. The molybdenum oxide nanorods were clearly observed and the x-ray diffraction patterns showed the diffraction peaks due to molybdenum oxide.

  13. Page 1 Oxide dielectrics 177 given temperature or to higher ...

    Indian Academy of Sciences (India)

    -mºw-wºw-º-º-º-. 0. 909 1110 1428K 909 1 #10 1428K. 0.2 3.2 x 10'9 5.6 2.0 ().71 31.7 11.3 4.0. 1.0 1.6 x 10°0 2.8 1.3 0.54 35.3 16.4 6.8. 2.0 3.2 x 1030 2.0 1.0 0.45 35.8 17.9 8.1. Table 3. Room temperature resistivity of specimens heated in H, ...

  14. Revealing a room temperature ferromagnetism in cadmium oxide nanoparticles: An experimental and first-principles study

    KAUST Repository

    Bououdina, Mohamed

    2015-03-26

    We obtain a single cadmium oxide phase from powder synthesized by a thermal decomposition method of cadmium acetate dehydrate. The yielded powder is annealed in air, vacuum, and H2 gas in order to create point defects. Magnetization-field curves reveal the appearance of diamagnetic behavior with a ferromagnetic component for all the powders. Powder annealing under vacuum and H2 atmosphere leads to a saturation magnetization 1.15 memu g-1 and 1.2 memu g-1 respectively with an increase by 45% and 16% compared to the one annealed in air. We show that annealing in vacuum produces mainly oxygen vacancies while annealing in H2 gas creates mainly Cd vacancy leading to room temperature ferromagnetic (RTFM) component together with known diamagnetic properties. Ab initio calculations performed on the CdO nanoparticles show that the magnetism is governed by polarized hybrid states of the Cd d and O p orbitals together with the vacancy. © The Royal Society of Chemistry 2015.

  15. Electron transport and low-temperature electrical and galvanomagnetic properties of zinc oxide and indium oxide films

    Science.gov (United States)

    Kulbachinskii, V. A.; Kytin, V. G.; Reukova, O. V.; Burova, L. I.; Kaul, A. R.; Ulyashin, A. G.

    2015-02-01

    The electrical and galvanomagnetic properties of zinc oxide films with and without gallium, aluminum, and cobalt doping and of tin-doped indium oxide films are studied over a wide range of temperatures and magnetic fields. It is shown that the mechanism for electron transport in these films changes from band to hopping transport as the degree of crystallinity of the films is reduced because of the methods and conditions for their synthesis. The change in the dimensionality of the films with band electron transport at low temperatures is studied in terms of the weak localization induced by a magnetic field. The localization radius and density of electron states in the Fermi level are estimated for the films with a hopping electron transport.

  16. New insights in the low-temperature oxidation of acetylene

    DEFF Research Database (Denmark)

    Wang, Bing-Yin; Liu, Yue-Xi; Weng, Jun-Jie

    2017-01-01

    and the reaction with O are the two major channels governing C2H2 consumption. At temperatures below 1000K, benzene is mainly formed through the C2+C4 channels:C2H2+iC4H5→fulvene→C5H5CH2 isomers→C6H6.The C1+C5 pathway: CH3+C5H5→C5H5CH3→(fulvene and C5H5CH2 radicals)→C6H6 tends to be the dominant route for benzene...... to reactions of the vinyl radical and to steps involved in the sequence C2H2→iC4H5→fulvene→C5H5CH2→C6H6. In general, the peak concentrations of intermediates gradually increase and peak locations tend to shift toward high temperatures with Φ increasing. Flux analysis indicates that the addition of H...

  17. Chloride promoted room temperature preparation of silver nanoparticles on two dimensional tungsten oxide nanoarchitectures for the catalytic oxidation of tertiary N-compounds to N-oxides

    Science.gov (United States)

    Ghosh, Shilpi; Acharyya, Shankha S.; Kumar, Malika; Bal, Rajaram

    2015-09-01

    A halide ion promoted two dimensional silver tungsten-based nanomaterial was synthesized by a facile one-pot synthesis protocol at room temperature. The 2D morphology features high activity and selectivity for the oxidation of a wide range of tertiary N-compounds to their corresponding N-oxides. The morphology of Ag/WO3 materials can be varied by changing the synthesis parameters. The unique 2D plate like morphology of tungsten oxide increases adsorption sites of the support, leading to less sintering and higher dispersion of silver nanoparticles, resulting in significantly enhanced activity for the reaction. The influence of reaction parameters such as temperature, substrate to oxidant molar ratio, reaction time, etc. was investigated in detail. The catalyst was characterized by XRD, XPS, ICP-AES, TGA, FT-IR, UV-vis, Raman, SEM, TEM and STEM. Raman studies further provide mechanistic insight which proves that the formation of peroxo tungsten species is responsible for the N-oxidation reaction. High stability and recyclability of the 2D Ag/WO3 nanoplates are also observed under the investigated conditions.A halide ion promoted two dimensional silver tungsten-based nanomaterial was synthesized by a facile one-pot synthesis protocol at room temperature. The 2D morphology features high activity and selectivity for the oxidation of a wide range of tertiary N-compounds to their corresponding N-oxides. The morphology of Ag/WO3 materials can be varied by changing the synthesis parameters. The unique 2D plate like morphology of tungsten oxide increases adsorption sites of the support, leading to less sintering and higher dispersion of silver nanoparticles, resulting in significantly enhanced activity for the reaction. The influence of reaction parameters such as temperature, substrate to oxidant molar ratio, reaction time, etc. was investigated in detail. The catalyst was characterized by XRD, XPS, ICP-AES, TGA, FT-IR, UV-vis, Raman, SEM, TEM and STEM. Raman studies

  18. Codeposition of deuterium ions with beryllium oxide at elevated temperatures

    CERN Document Server

    Markin, A V; Gorodetsky, A E; Negodaev, M A; Rozhanskii, N V; Scaffidi-Argentina, F; Werle, H; Wu, C H; Zalavutdinov, R K; Zakharov, A P

    2000-01-01

    Deuterium-loaded BeO films were produced by sputtering the beryllium target with 10 keV Ne ions in D sub 2 gas at a pressure of approximately 1 Pa. The sputtered beryllium reacts - on the substrate surface - with the residual oxygen, thus forming a beryllium oxide layer. Biasing the substrate negatively with respect to the target provides the simultaneous bombardment of the growing film surface with D ions formed by Ne-D sub 2 collisions. Substrate potential governs the maximum energy of ions striking the growing film surface while its size governs the flux density. According to X-ray photoelectron spectroscopy (XPS), electron probe microanalysis (EPMA) and reflection high energy electron diffraction (RHEED) data, the beryllium is deposited in the form of polycrystalline hcp-BeO layers with negligible (about 1 at.%) carbon and neon retention. Thermal desorption spectroscopy (TDS) data shows a strong deuterium bonding, with a desorption peak at 950 K, in the films deposited at -50 and -400 V substrate potentia...

  19. HIGH-TEMPERATURE TUBULAR SOLID OXIDE FUEL CELL GENERATOR DEVELOPMENT

    Energy Technology Data Exchange (ETDEWEB)

    S.E. Veyo

    1998-09-01

    During the Westinghouse/USDOE Cooperative Agreement period of November 1, 1990 through November 30, 1997, the Westinghouse solid oxide fuel cell has evolved from a 16 mm diameter, 50 cm length cell with a peak power of 1.27 watts/cm to the 22 mm diameter, 150 cm length dimensions of today's commercial prototype cell with a peak power of 1.40 watts/cm. Accompanying the increase in size and power density was the elimination of an expensive EVD step in the manufacturing process. Demonstrated performance of Westinghouse's tubular SOFC includes a lifetime cell test which ran for a period in excess of 69,000 hours, and a fully integrated 25 kWe-class system field test which operated for over 13,000 hours at 90% availability with less than 2% performance degradation over the entire period. Concluding the agreement period, a 100 kW SOFC system successfully passed its factory acceptance test in October 1997 and was delivered in November to its demonstration site in Westervoort, The Netherlands.

  20. Electrochemical and Oxidation Behavior of Yttria Stabilized Zirconia Coating on Zircaloy-4 Synthesized via Sol-Gel Process

    Directory of Open Access Journals (Sweden)

    S. Rezaee

    2013-01-01

    Full Text Available Sol-gel 8 wt.% Yttria Stabilized Zirconia (YSZ thin films were prepared on zirconium (zircaloy-4 alloy by dip-coating technique followed by heat treating at various temperatures (200°C, 400°C, and 700°C in order to improve both electrochemical corrosion and high temperature oxidation properties of the substrate. Differential thermal analysis and thermogravimetric analysis (DTA-TG revealed the coating formation process. X-ray diffraction (XRD was used to determine the crystalline phase structure transformation. The morphological characterization of the coatings was carried out using scanning electron microscopy (SEM. The electrochemical behavior of the coated and uncoated samples was investigated by means of open circuit potential, Tafel, and electrochemical impedance spectroscopy (EIS in a 3.5 wt.% NaCl solution. The homogeneity and surface appearance of coatings produced was affected by the heat treatment temperature. According to the corrosion parameters, the YSZ coatings showed a considerable increase in the corrosion resistance, especially at higher heat treatment temperatures. The coating with the best quality, from the surface and corrosion point of view, was subjected to oxidation test in air at 800°C. The coated sample presented a 25% reduction in oxidation rate in comparison with bare substrate.

  1. High-Temperature Oxidation and Decarburization of 14.55 wt pct Cr-Cast Iron in Dry Air Atmosphere

    Science.gov (United States)

    Efremenko, V. G.; Chabak, Yu. G.; Lekatou, A.; Karantzalis, A. E.; Efremenko, A. V.

    2016-04-01

    The oxidation and decarburization behavior of 14.55 wt pct Cr-cast iron at 1273 K to 1423 K (1000 °C to 1150 °C) in a dry air atmosphere was studied. A gravimetric investigation showed that intensive oxidation of cast iron takes place at temperatures above 1273 K (1000 °C). It is found that oxidizing heating is accompanied by decarburization, which manifests itself in secondary and eutectic carbide dissolution. The volume fraction of carbides decreases with temperature and holding duration increasing. Decarburization results in the formation of a decarburized layer up to 4 mm in depth. A carbide-free layer in depth up to 100 μm appears in the free surface after 6 to 8 hours holding at 1373 K to 1423 K (1100 °C to 1150 °C). Preliminary activation energy calculations suggested that the eutectic carbide dissolution at the depths of 50 to 400 μm is controlled by carbon diffusion in austenite. The dissolution of eutectic carbides involves a capillarity-induced mechanism, which consists of formation and growth of capillary cavities inside carbides.

  2. Magnetic properties of NiO (nickel oxide) nanoparticles : Blocking temperature and Neel temperature

    NARCIS (Netherlands)

    Tadic, Marin; Nikolic, Dobrica; Panjan, Matjaz; Blake, Graeme R.

    2015-01-01

    Crystalline nickel oxide (NiO) nanoparticles dispersed in an amorphous silica matrix have been prepared by a sol-gel combustion synthesis method. The sample was characterized using X-ray powder diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron

  3. When the Heat Is On: The Effect of Temperature on Voter Behavior in Presidential Elections

    Directory of Open Access Journals (Sweden)

    Jasper Van Assche

    2017-06-01

    Full Text Available Hot temperatures lead to heightened arousal. According to excitation transfer theory, arousal can increase both antisocial and prosocial behavior, depending on the context. Although many studies have shown that hot temperatures can increase antisocial behavior, very few studies have investigated the relationship between temperature and prosocial behavior. One important prosocial behavior is voting. We analyzed state-level data from the United States presidential elections (N = 761. Consistent with excitation transfer theory, which proposes that heat-induced arousal can transfer to other activities and strengthen those activities, changes in temperature and voter turnout were positively related. Moreover, a positive change in temperature was related to a positive change in votes for the incumbent party. These findings add to the literature on the importance of non-ideological and non-rational factors that influence voting behavior.

  4. Effect of Sintering Temperature on the Properties of Aluminium-Aluminium Oxide Composite Materials

    Directory of Open Access Journals (Sweden)

    Dewan Muhammad Nuruzzaman

    2016-12-01

    Full Text Available In this study, aluminium-aluminium oxide (Al-Al2O3 metal matrix composites of different weight percentage reinforcements of aluminium oxide were processed at different sintering temperatures. In order to prepare these composite specimens, conventional powder metallurgy (PM method was used. Three types specimens of different compositions such as 95%Al+5%Al2O3, 90%Al+10%Al2O3 and 85%Al+15%Al2O3 were prepared under 20 Ton compaction load. Then, all the specimens were sintered in a furnace at two different temperatures 550oC and 580oC. In each sintering process, two different heating cycles were used. After the sintering process, it was observed that undistorted flat specimens were successfully prepared for all the compositions. The effects of sintering temperature and weight fraction of aluminium oxide particulates on the density, hardness and microstructure of Al-Al2O3 composites were observed. It was found that density and hardness of the composite specimens were significantly influenced by sintering temperature and percentage aluminium oxide reinforcement. Furthermore, optical microscopy revealed that almost uniform distribution of aluminium oxide reinforcement within the aluminium matrix was achieved.

  5. Oxide particle coarsening at temperature over 1473K in 9CrODS steel

    Directory of Open Access Journals (Sweden)

    N. Oono

    2016-12-01

    Full Text Available The oxide particle coarsening was evaluated at temperature over 1473K by means of transmission electron microscopy (TEM. After annealing of the 9CrODS extruded bar, the size of oxide particles increases while the number density decreases, indicating that the oxide particles coarsen through Ostwald ripening. The growth rate of the oxide particles follows the fifth-power law, which is in the region of dislocation ‘pipe’ diffusion. The activation energy for pipe diffusion, however, was remarkably high, derived as 891KJ/mole. The stability of oxide particles and the difference of the diffusion velocity in between bcc-δ phase and fcc-γ phase should be considered as the contributions to the activation energy.

  6. A liquid metal reaction environment for the room-temperature synthesis of atomically thin metal oxides

    Science.gov (United States)

    Zavabeti, Ali; Ou, Jian Zhen; Carey, Benjamin J.; Syed, Nitu; Orrell-Trigg, Rebecca; Mayes, Edwin L. H.; Xu, Chenglong; Kavehei, Omid; O’Mullane, Anthony P.; Kaner, Richard B.; Kalantar-zadeh, Kourosh; Daeneke, Torben

    2017-10-01

    Two-dimensional (2D) oxides have a wide variety of applications in electronics and other technologies. However, many oxides are not easy to synthesize as 2D materials through conventional methods. We used nontoxic eutectic gallium-based alloys as a reaction solvent and co-alloyed desired metals into the melt. On the basis of thermodynamic considerations, we predicted the composition of the self-limiting interfacial oxide. We isolated the surface oxide as a 2D layer, either on substrates or in suspension. This enabled us to produce extremely thin subnanometer layers of HfO2, Al2O3, and Gd2O3. The liquid metal–based reaction route can be used to create 2D materials that were previously inaccessible with preexisting methods. The work introduces room-temperature liquid metals as a reaction environment for the synthesis of oxide nanomaterials with low dimensionality.

  7. High-temperature oxidation/corrosion of iron-based superalloys

    Science.gov (United States)

    Lemkey, F. D.; Smeggil, J. G.; Bailey, R. S.; Schuster, J. C.; Nowotny, H.

    1987-01-01

    The oxidation and sulfidation of several novel iron-base superalloys were evaluated in high-temperature cyclic tests. The experimental austenitic alloys examined were modifications of NASAUT-4GA which were developed for Stirling-engine application. The weight gains and resulting surface scales were measured and analyzed. Mixed oxide scales were found to form on all specimens exposed above 871 C. The build-up of these scales led to a depletion of Mn and Cr in a zone adjacent to the oxides. In addition, the initial oxidation of the Fe-rich alloy was inhibited by a thin but tenacious Si layer which formed at the interface between oxides and the parent layer. Sulfidation tests using Na2SO4 coatings resulted in the formation of a protective spinel and alpha-Fe2O3 phases. Preferential attack of the carbide phase by hydrogen was not observed after 350 h at 871 C.

  8. Homogenization Pressure and Temperature Affect Protein Partitioning and Oxidative Stability of Emulsions

    DEFF Research Database (Denmark)

    Horn, Anna Frisenfeldt; Barouh, Nathalie; Nielsen, Nina Skall

    2013-01-01

    it decreased the oxidative stability of emulsions with α-lactalbumin and β-lactoglobulin. For both types of emulsions the partitioning of proteins between the interface and the aqueous phase appeared to be important for the oxidative stability. The effect of pre-heating the aqueous phase with the milk proteins......The oxidative stability of 10 % fish oil-in-water emulsions was investigated for emulsions prepared under different homogenization conditions. Homogenization was conducted at two different pressures (5 or 22.5 MPa), and at two different temperatures (22 and 72 °C). Milk proteins were used...

  9. Low temperature methane oxidation on differently supported 2 nm Au nanoparticles

    DEFF Research Database (Denmark)

    Walther, Guido; Gontard, Lionel Cervera; Quaade, Ulrich

    2009-01-01

    Low temperature CH4 oxidation was studied on 2 nm gold nanoparticles supported on various metaloxides. The differences in reaction rates for the different systems suggest that the support material has an effect on the activity. From TEM analysis, we found that the gold particles were stable in size...... during the reaction. In addition to full oxidation to CO2, traces of C2H6 were detected when Au/TiO2 was used, indicating limited partial CH4 oxidation. TiO2 was found to be the best support for gold nanoparticles both in terms of activity and gold particle stability....

  10. Thermodynamic Studies of the Phase Relationships of Nonstoichiometric Cerium Oxides at Higher Temperatures

    DEFF Research Database (Denmark)

    Sørensen, Ole Toft

    1976-01-01

    Partial molar thermodynamic quantities for oxygen in nonstoichiometric cerium oxides were determined by thermogravimetric analysis in CO/CO2 mixtures in the temperature range 900–1400°C. Under these conditions compositions within the range 2.00 greater-or-equal, slanted O/M greater-or-equal, slan......Partial molar thermodynamic quantities for oxygen in nonstoichiometric cerium oxides were determined by thermogravimetric analysis in CO/CO2 mixtures in the temperature range 900–1400°C. Under these conditions compositions within the range 2.00 greater-or-equal, slanted O/M greater...

  11. Note: A method for minimizing oxide formation during elevated temperature nanoindentation

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, I. C.; Hodge, A. M., E-mail: ahodge@usc.edu [Department of Aerospace and Mechanical Engineering, University of Southern California, 3650 McClintock Avenue OHE430, Los Angeles, California 90089 (United States); Garcia-Sanchez, E. [Department of Aerospace and Mechanical Engineering, University of Southern California, 3650 McClintock Avenue OHE430, Los Angeles, California 90089 (United States); Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, Av. Universidad S/N, San Nicolás de los Garza, NL 66450 (Mexico)

    2014-09-15

    A standardized method to protect metallic samples and minimize oxide formation during elevated-temperature nanoindentation was adapted to a commercial instrument. Nanoindentation was performed on Al (100), Cu (100), and W (100) single crystals submerged in vacuum oil at 200 °C, while the surface morphology and oxidation was carefully monitored using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The results were compared to room temperature and 200 °C nanoindentation tests performed without oil, in order to evaluate the feasibility of using the oil as a protective medium. Extensive surface characterization demonstrated that this methodology is effective for nanoscale testing.

  12. Modeling selenate adsorption behavior on oxides, clay minerals, and soils using the triple layer model

    Science.gov (United States)

    Selenate adsorption behavior was investigated on amorphous aluminum oxide, amorphous iron oxide, goethite, clay minerals: kaolinites, montmorillonites, illite, and 18 soil samples from Hawaii, and the Southwestern and the Midwestern regions of the US as a function of solution pH. Selenate adsorpti...

  13. CO2 as an Oxidant for High Temperature Reactions

    Directory of Open Access Journals (Sweden)

    Sibudjing eKawi

    2015-03-01

    Full Text Available This paper presents a review on the developments in catalyst technology for the reactions utilizing CO2 for high temperature applications. These include dehydrogenation of alkanes to olefins, the dehydrogenation of ethylbenzene to styrene and finally CO2 reforming of hydrocarbon feedstock (i.e. methane and alcohols. Aspects on the various reaction pathways are also highlighted. The literature on the role of promoters and catalyst development is critically evaluated. Most of the reactions discussed in this review are exploited in industries and related to on-going processes, thus providing extensive data from literature. However some reactions, such as CO2 reforming of ethanol and glycerol which have not reached industrial scale are also reviewed owing to their great potential in terms of sustainability which are essential as energy for the future. This review further illustrates the building-up of knowledge which shows the role of support and catalysts for each reaction and the underlying linkage between certain catalysts which can be adapted for the multiple CO2-related reactions.

  14. High-temperature thermoelectric behavior of lead telluride

    Indian Academy of Sciences (India)

    Usefulness of a material in thermoelectric devices is temperature specific. The central problem in thermoelectric material research is the selection of materials with high figure-of-merit in the given temperature range of operation. It is of considerable interest to know the utility range of the material, which is decided by the ...

  15. Shape-Dependent Activity of Ceria for Hydrogen Electro-Oxidation in Reduced-Temperature Solid Oxide Fuel Cells.

    Science.gov (United States)

    Tong, Xiaofeng; Luo, Ting; Meng, Xie; Wu, Hao; Li, Junliang; Liu, Xuejiao; Ji, Xiaona; Wang, Jianqiang; Chen, Chusheng; Zhan, Zhongliang

    2015-11-04

    Single crystalline ceria nanooctahedra, nanocubes, and nanorods are hydrothermally synthesized, colloidally impregnated into the porous La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) scaffolds, and electrochemically evaluated as the anode catalysts for reduced temperature solid oxide fuel cells (SOFCs). Well-defined surface terminations are confirmed by the high-resolution transmission electron microscopy--(111) for nanooctahedra, (100) for nanocubes, and both (110) and (100) for nanorods. Temperature-programmed reduction in H2 shows the highest reducibility for nanorods, followed sequentially by nanocubes and nanooctahedra. Measurements of the anode polarization resistances and the fuel cell power densities reveal different orders of activity of ceria nanocrystals at high and low temperatures for hydrogen electro-oxidation, i.e., nanorods > nanocubes > nanooctahedra at T ≤ 450 °C and nanooctahedra > nanorods > nanocubes at T ≥ 500 °C. Such shape-dependent activities of these ceria nanocrystals have been correlated to their difference in the local structure distortions and thus in the reducibility. These findings will open up a new strategy for design of advanced catalysts for reduced-temperature SOFCs by elaborately engineering the shape of nanocrystals and thus selectively exposing the crystal facets. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Influence of oxidation temperature on the interfacial properties of n-type 4H-SiC MOS capacitors

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Yifan; Lv, Hongliang [School of Microelectronics, Xidian University, Key Laboratory of Wide Band Gap Semiconductor Materials and Devices, Xi’an 710071 (China); Song, Qingwen, E-mail: qwsong@xidian.edu.cn [School of Microelectronics, Xidian University, Key Laboratory of Wide Band Gap Semiconductor Materials and Devices, Xi’an 710071 (China); School of Advanced Materials and Nanotechnology, Xidian University, Xi’an 710071 (China); Tang, Xiaoyan, E-mail: xytang@xidian.edu.cn [School of Microelectronics, Xidian University, Key Laboratory of Wide Band Gap Semiconductor Materials and Devices, Xi’an 710071 (China); Xiao, Li; Wang, Liangyong; Tang, Guangming [Zhongxing Telecommunication Equipment Corporation, Shenzhen 518057 (China); Zhang, Yimen; Zhang, Yuming [School of Microelectronics, Xidian University, Key Laboratory of Wide Band Gap Semiconductor Materials and Devices, Xi’an 710071 (China)

    2017-03-01

    Highlights: • Effect of oxidation temperature on interfacial properties of SiO{sub 2}/SiC is investigated. • Raising the oxidation temperature effectively decreases the density of NITs and N{sub eff}. • The higher oxidation temperature reduces the surface RMS roughness of the grow SiO{sub 2}. • SIMS and XPS results reveal the improvement mechanism of high temperature oxidation. - Abstract: The effect of oxidation temperature on interfacial properties of n-type 4H-SiC metal-oxide-semiconductor capacitors has been systematically investigated. Thermal dry oxidation process with three different oxidation temperatures 1200 °C, 1300 °C and 1350 °C were employed to grow SiO{sub 2} dielectric, following by the standard post-oxidation annealing (POA) in NO ambience at 1175 °C for 2 h. The root mean square (RMS) roughness measured by Atomic Force Microscopy for the thermally grown SiO{sub 2} before POA process is reduced with increasing the oxidation temperature, obtaining an atomically flat surface with a RMS of 0.157 nm from the sample oxidized at 1350 °C. Several kinds of electrical measurements were used to evaluate the densities of near interface traps and effective fixed dielectric charge for the samples, exhibiting a trend reduced with increasing the oxidation temperature. The interface state density of 3 × 10{sup 11} cm{sup −2}eV{sup −1} at 0.2 eV from the conduction band edge was achieved from conductance method measurement for the sample oxidized at 1350 °C. The results from Secondary Ion Mass Spectroscopy and X-ray Photoelectron Spectroscopy demonstrate that high oxidation temperature can reduce the width of transition layer, the excess Si and silicon suboxide compositions near the interface, leading to effective improvement of the interfacial properties.

  17. Tribological behavior and self-healing functionality of TiNbCN-Ag coatings in wide temperature range

    Science.gov (United States)

    Bondarev, A. V.; Kiryukhantsev-Korneev, Ph. V.; Levashov, E. A.; Shtansky, D. V.

    2017-02-01

    Ag- and Nb-doped TiCN coatings with about 2 at.% of Nb and Ag contents varied between 4.0 and 15.1 at.% were designed as promising materials for tribological applications in a wide temperature range. We report on the structure, mechanical, and tribological properties of TiNbCN-Ag coatings fabricated by simultaneous co-sputtering of TiC0.5 + 10%Nb2C and Ag targets in comparison with those of Ag-free coating. The tribological characteristics were evaluated during constant-temperature tests both at room temperature and 300 °C, as well as during dynamic temperature ramp tests in the range of 25-700 °C. The coating structure and elemental composition were studied by means of X-ray diffraction, scanning and transmission electron microscopy, and glow discharge optical emission spectroscopy. The coating microstructures and elemental compositions inside wear tracks, as well as the wear products, were examined by scanning electron microscopy, energy-dispersive spectroscopy, and Raman spectroscopy. We demonstrate that simultaneous alloying with Nb and Ag permits to overcome the main drawbacks of TiCN coatings such as their relatively high values of friction coefficient at elevated temperatures and low oxidation resistance. It is shown that a relatively high amount of Ag (15 at.%) is required to provide enhanced tribological behavior in a wide temperature range of 25-700 °C. In addition, the prepared Ag-doped coatings demonstrated active oxidation protection and self-healing functionality due to the segregation of Ag metallic particles in damage areas such as cracks, pin-holes, or oxidation sites.

  18. On High-Temperature Materials: A Case on Creep and Oxidation of a Fully Austenitic Heat-Resistant Superalloy Stainless Steel Sheet

    Directory of Open Access Journals (Sweden)

    A. Kanni Raj

    2013-01-01

    Full Text Available The creep behavior of AISI 310S stainless steel taken from SAIL’s Salem stainless steel plant has been investigated by constant load tensile creep test at the temperatures of 973, 1023, and 1073 K and loads of 66.6, 74.8, 86.6, and 94.8 MPa. It exhibits steady-state creep behavior in most test conditions. The double logarithm plot of rupture life and applied stress yielded straight lines at all the three test temperatures indicating that power-law creep due to dislocation climb is the operating mechanism of creep deformation. Linear relationship was obtained for plots of logarithm of rupture life against inverse temperature obeying Arrhenius type of temperature dependence with activation energy of 340 kJ/mol. The stress-rupture data yielded a master curve of Larson-Miller parameter. The plot of Monkman-Grant relationship is typical indicating that rupture is controlled by growth of grain boundary cavities. The metallographic examination of crept samples revealed formation of grain boundary voids and cracks leading to intergranular creep fracture. Deformation twins and carbide precipitates were also observed. Oxidation tests were also carried out isothermally at 973 K, 1023 K, and 1073 K in dry air. The plots of mass gain versus square root time were linear at all the three test temperatures obeying parabolic kinetics of oxidation. It was found that scales are well adherent to the substrate. The plot of parabolic rate constant and inverse temperature was linear giving an activation energy value of 210 kJ/mol. The metallographic examination of an oxidized sample reveals duplex types of scales. Finally, rupture properties are compared with that of AISI 600 iron-based superalloy and oxidation weight gain analysis with surface nanocrystalline AISI 310S stainless steel to analyze quantitatively its behavior.

  19. As-cast microstructures and behavior at high temperature of chromium-rich cobalt-based alloys containing hafnium carbides

    Energy Technology Data Exchange (ETDEWEB)

    Berthod, Patrice, E-mail: Patrice.Berthod@univ-lorraine.fr; Conrath, Elodie

    2014-02-14

    Hafnium is often used to improve the high temperature oxidation resistance of superalloys but not to form carbides for strengthen them against creep. In this work hafnium was added in cobalt-based alloys for verifying that HfC can be obtained in cobalt-based alloys and for characterizing their behavior at a very temperature. Three Co–25Cr–0.25 and 0.50C alloys containing 3.7 and 7.4 Hf to promote HfC carbides, and four Co–25Cr– 0 to 1C alloys for comparison (all contents in wt.%), were cast and exposed at 1200 °C for 50 h in synthetic air. The HfC carbides formed instead chromium carbides during solidification, in eutectic with matrix and as dispersed compact particles. During the stage at 1200 °C the HfC carbides did not significantly evolve, even near the oxidation front despite oxidation early become very fast and generalized. At the same time the chromium carbides present in the Co–Cr–C alloys totally disappeared in the same conditions. Such HfC-alloys potentially bring efficient and sustainable mechanical strengthening at high temperature, but their hot oxidation resistance must be significantly improved. - Highlights: • Co-based alloys containing HfC carbides were successfully obtained by foundry. • HfC are pro-eutectic or form an interdendritic eutectic compound with matrix. • The HfC carbides appear very stable on long time at 1200 °C. • The hot oxidation of the alloys is fast and they require higher Cr contents. • The high stability of HfC may allow Cr-enrichment by pack-cementation.

  20. The temperature dependence on the electrical properties of dysprosium oxide deposited on n-porous GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Saghrouni, H., E-mail: hayet_sagrouni@yahoo.fr [Université de Sousse, LabEM-LR11ES34 Energie-Matériaux, Ecole Supérieure des Sciences et de la Technologie, Rue Lamine Abessi 4011, Hammam Sousse (Tunisia); Université de Sousse, Equipe de recherche caractérisations optoélectronique et spectroscopique des matériaux et nanomatériaux pour les télécommunications et capteurs, ISITCOM 4011, Hammam Sousse (Tunisia); Jomni, S. [Université de Tunis El Manar, LR: LAB MA03 Matériaux, Organisation et Propriétés, Faculté des Sciences de Tunis, 2092 (Tunisia); Cherif, A. [Université de Sousse, LabEM-LR11ES34 Energie-Matériaux, Ecole Supérieure des Sciences et de la Technologie, Rue Lamine Abessi 4011, Hammam Sousse (Tunisia); Université de Sousse, Equipe de recherche caractérisations optoélectronique et spectroscopique des matériaux et nanomatériaux pour les télécommunications et capteurs, ISITCOM 4011, Hammam Sousse (Tunisia); Belgacem, W. [Université de Tunis El Manar, LR: LAB MA03 Matériaux, Organisation et Propriétés, Faculté des Sciences de Tunis, 2092 (Tunisia); and others

    2016-08-15

    This paper describes the electrical and dielectric characteristics for the first time of the high-k Dy{sub 2}O{sub 3} oxide film deposited on the porous GaAs substrate by electron beam deposition under ultra vacuum. Morphological characterization is investigated by atomic force microscopy (AFM). The electrical and dielectric properties of Co/Au/Dy{sub 2}O{sub 3}/n-porous GaAs structure were studied in the temperature range of 80–500 K. The conductance and capacitance measurements were performed as a function of bias voltage and frequency. The dielectric constant (ε′), dielectric loss (ε″) and dielectric loss tangent (tanδ) of the structure are obtained from capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. These parameters are found to be strong functions of temperature and bias voltage. In the forward bias region, C–V plots show a negative capacitance (NC) behavior, ε′–V plots for each temperature value take negative values as well. Such negative values of C correspond to the maximum of the conductance (G/ω). The negative capacitance values appear abnormal when compared to the conventional behavior of ideal Schottky barrier diode (SBD) and metal–oxide–semiconductor (MOS) structures. The following behavior of the C and ε′ in the forward bias region has been explained with the minority-carrier injection and relaxation theory. From DC conductance study, electronic conduction is found to be dominated by thermally activated hopping at high temperature. Activation energy is deduced from the variation of conductance with temperature. The Nyquist plots exhibited single semi-circular arcs which were well fitted to an equivalent circuit. - Highlights: • The high-k Dy{sub 2}O{sub 3} oxide film is deposited on n-porous GaAs by means of electron beam deposition. • The electrical and dielectric properties of MOS structure were studied. • A strong negative capacitance (NC) phenomenon has been observed in the C-V and C

  1. Simulation study of temperature-dependent diffusion behaviors of Ag/Ag(001) at low substrate temperature

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Danyun; Mo, Yunjie [State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou, 510275 (China); Feng, Xiaofang [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-sen University, Guangzhou, 510275 (China); He, Yingyou [State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou, 510275 (China); Jiang, Shaoji, E-mail: stsjsj@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-sen University, Guangzhou, 510275 (China)

    2017-06-01

    Highlights: • The model of combinations of nearest-neighbor atoms of adatom was built to calculate the diffusion barrier of every configuration for Ag/Ag(001). • The complete potential energy curve of a specific diffusion path on the surface was worked out with the help of elementary diffusion behaviors. • The non-monotonic relation between the surface roughness and the substrate temperature (decreasing from 300 K to 100 K) was demonstrated. • A theoretical explanation of diffusion mechanism for the non-monotonic variation of roughness at low substrate temperature was presented. - Abstract: In this study, a model based on the First Principles calculations and Kinetic Monte Carlo simulation were established to study the growth characteristic of Ag thin film at low substrate temperature. On the basis of the interaction between the adatom and nearest-neighbor atoms, some simplifications and assumptions were made to categorize the diffusion behaviors of Ag adatoms on Ag(001). Then the barriers of all possible diffusion behaviors were calculated using the Climbing Image Nudged Elastic Band method (CI-NEB). Based on the Arrhenius formula, the morphology variation, which is attributed to the surface diffusion behaviors during the growth, was simulated with a temperature-dependent KMC model. With this model, a non-monotonic relation between the surface roughness and the substrate temperature (decreasing from 300 K to 100 K) were discovered. The analysis of the temperature dependence on diffusion behaviors presents a theoretical explanation of diffusion mechanism for the non-monotonic variation of roughness at low substrate temperature.

  2. Application of Flexible Micro Temperature Sensor in Oxidative Steam Reforming by a Methanol Micro Reformer

    Directory of Open Access Journals (Sweden)

    Yi-Man Lo

    2011-02-01

    Full Text Available Advances in fuel cell applications reflect the ability of reformers to produce hydrogen. This work presents a flexible micro temperature sensor that is fabricated based on micro-electro-mechanical systems (MEMS technology and integrated into a flat micro methanol reformer to observe the conditions inside that reformer. The micro temperature sensor has higher accuracy and sensitivity than a conventionally adopted thermocouple. Despite various micro temperature sensor applications, integrated micro reformers are still relatively new. This work proposes a novel method for integrating micro methanol reformers and micro temperature sensors, subsequently increasing the methanol conversion rate and the hydrogen production rate by varying the fuel supply rate and the water/methanol ratio. Importantly, the proposed micro temperature sensor adequately controls the interior temperature during oxidative steam reforming of methanol (OSRM, with the relevant parameters optimized as well.

  3. Application of Flexible Micro Temperature Sensor in Oxidative Steam Reforming by a Methanol Micro Reformer

    Science.gov (United States)

    Lee, Chi-Yuan; Lee, Shuo-Jen; Shen, Chia-Chieh; Yeh, Chuin-Tih; Chang, Chi-Chung; Lo, Yi-Man

    2011-01-01

    Advances in fuel cell applications reflect the ability of reformers to produce hydrogen. This work presents a flexible micro temperature sensor that is fabricated based on micro-electro-mechanical systems (MEMS) technology and integrated into a flat micro methanol reformer to observe the conditions inside that reformer. The micro temperature sensor has higher accuracy and sensitivity than a conventionally adopted thermocouple. Despite various micro temperature sensor applications, integrated micro reformers are still relatively new. This work proposes a novel method for integrating micro methanol reformers and micro temperature sensors, subsequently increasing the methanol conversion rate and the hydrogen production rate by varying the fuel supply rate and the water/methanol ratio. Importantly, the proposed micro temperature sensor adequately controls the interior temperature during oxidative steam reforming of methanol (OSRM), with the relevant parameters optimized as well. PMID:22319407

  4. Application of flexible micro temperature sensor in oxidative steam reforming by a methanol micro reformer.

    Science.gov (United States)

    Lee, Chi-Yuan; Lee, Shuo-Jen; Shen, Chia-Chieh; Yeh, Chuin-Tih; Chang, Chi-Chung; Lo, Yi-Man

    2011-01-01

    Advances in fuel cell applications reflect the ability of reformers to produce hydrogen. This work presents a flexible micro temperature sensor that is fabricated based on micro-electro-mechanical systems (MEMS) technology and integrated into a flat micro methanol reformer to observe the conditions inside that reformer. The micro temperature sensor has higher accuracy and sensitivity than a conventionally adopted thermocouple. Despite various micro temperature sensor applications, integrated micro reformers are still relatively new. This work proposes a novel method for integrating micro methanol reformers and micro temperature sensors, subsequently increasing the methanol conversion rate and the hydrogen production rate by varying the fuel supply rate and the water/methanol ratio. Importantly, the proposed micro temperature sensor adequately controls the interior temperature during oxidative steam reforming of methanol (OSRM), with the relevant parameters optimized as well.

  5. Metabolic rate and oxidative stress in insects exposed to low temperature thermal fluctuations.

    Science.gov (United States)

    Lalouette, L; Williams, C M; Hervant, F; Sinclair, B J; Renault, D

    2011-02-01

    Fluctuating temperatures are a predominant feature of the natural environment but their effects on ectotherm physiology are not well-understood. The warm periods of fluctuating thermal regimes (FTRs) provide opportunities for repair leading to increased survival, but there are also indications of negative effects of warm exposure. In this study, we examined respiration and oxidative stress in adult Alphitobius diaperinus exposed to FTRs and to constant low temperatures. We hypothesized that cold exposure will cause oxidative stress and that FTRs would reduce the amount of chill injuries, via activation of the antioxidant system. We measured V˙CO2, activities of super oxide dismutase (SOD), amounts of total (GSHt) and oxidized glutathione (GSSG) during cold and warm periods of FTRs. Increased severity of cold exposure caused a decrease in the glutathione pool. SOD levels increased during the recovery period in the more severe FTR. The antioxidant response was sufficient to counter the reactive oxygen species production, as the GSH:GSSG ratio increased. We conclude that cold stress causes oxidative damage in these beetles, and that a warm recovery period activates the antioxidant system allowing repair of cold-induced damage, leading to the increased survival previously noted in beetles exposed to fluctuating versus constant temperatures. Copyright © 2010 Elsevier Inc. All rights reserved.

  6. Tribological behavior and self-healing functionality of TiNbCN-Ag coatings in wide temperature range

    Energy Technology Data Exchange (ETDEWEB)

    Bondarev, A.V., E-mail: abondarev88@gmail.com; Kiryukhantsev-Korneev, Ph.V.; Levashov, E.A.; Shtansky, D.V., E-mail: shtansky@shs.misis.ru

    2017-02-28

    Highlights: • TiNbCN–Ag coatings for wide temperature range tribological applications. • Alloying with Nb and Ag improve tribological properties and oxidation resistance. • Ag-rich TiNbCN coatings show friction coefficient below 0.45 in range of 25–700 °C. • Ag-doped coatings show active oxidation protection and self-healing functionality. - Abstract: Ag- and Nb-doped TiCN coatings with about 2 at.% of Nb and Ag contents varied between 4.0 and 15.1 at.% were designed as promising materials for tribological applications in a wide temperature range. We report on the structure, mechanical, and tribological properties of TiNbCN-Ag coatings fabricated by simultaneous co-sputtering of TiC{sub 0.5} + 10%Nb{sub 2}C and Ag targets in comparison with those of Ag-free coating. The tribological characteristics were evaluated during constant-temperature tests both at room temperature and 300 °C, as well as during dynamic temperature ramp tests in the range of 25–700 °C. The coating structure and elemental composition were studied by means of X-ray diffraction, scanning and transmission electron microscopy, and glow discharge optical emission spectroscopy. The coating microstructures and elemental compositions inside wear tracks, as well as the wear products, were examined by scanning electron microscopy, energy-dispersive spectroscopy, and Raman spectroscopy. We demonstrate that simultaneous alloying with Nb and Ag permits to overcome the main drawbacks of TiCN coatings such as their relatively high values of friction coefficient at elevated temperatures and low oxidation resistance. It is shown that a relatively high amount of Ag (15 at.%) is required to provide enhanced tribological behavior in a wide temperature range of 25–700 °C. In addition, the prepared Ag-doped coatings demonstrated active oxidation protection and self-healing functionality due to the segregation of Ag metallic particles in damage areas such as cracks, pin-holes, or oxidation sites.

  7. Effects of thermal aging on thermo-mechanical behavior of a glass sealant for solid oxide cell applications

    DEFF Research Database (Denmark)

    Abdoli, Hamid; Alizadeh, Parvin; Boccaccini, Dino

    2014-01-01

    Thermo-mechanical properties of a silicate based glass and its potential use for sealing application in intermediate temperature solid oxide cell (SOC) are presented in this paper. Effects of thermal aging are discussed on structural and microstructural evolution, thermal expansion, viscosity......, modulus of elasticity, and high-temperature deformation of the glass. The balance between the viscosity and viscous flowing behavior was explored for the non-aged and aged glasses as it is essential to have a successful sealing for a SOC stack. The results reveal a temperature dependence of Young......'s modulus in which a transition between a slow softening (elastic) regime and a rapid softening one was observed. Crystallization induced by thermal aging led to higher creep resistance, but lower capability of crack healing when inspected by electron microscopy. However, potential of stress relaxation...

  8. Manganese oxide phases and morphologies: A study on calcination temperature and atmospheric dependence.

    Science.gov (United States)

    Augustin, Matthias; Fenske, Daniela; Bardenhagen, Ingo; Westphal, Anne; Knipper, Martin; Plaggenborg, Thorsten; Kolny-Olesiak, Joanna; Parisi, Jürgen

    2015-01-01

    Manganese oxides are one of the most important groups of materials in energy storage science. In order to fully leverage their application potential, precise control of their properties such as particle size, surface area and Mn (x) (+) oxidation state is required. Here, Mn3O4 and Mn5O8 nanoparticles as well as mesoporous α-Mn2O3 particles were synthesized by calcination of Mn(II) glycolate nanoparticles obtained through an economical route based on a polyol synthesis. The preparation of the different manganese oxides via one route facilitates assigning actual structure-property relationships. The oxidation process related to the different MnO x species was observed by in situ X-ray diffraction (XRD) measurements showing time- and temperature-dependent phase transformations occurring during oxidation of the Mn(II) glycolate precursor to α-Mn2O3 via Mn3O4 and Mn5O8 in O2 atmosphere. Detailed structural and morphological investigations using transmission electron microscopy (TEM) and powder XRD revealed the dependence of the lattice constants and particle sizes of the MnO x species on the calcination temperature and the presence of an oxidizing or neutral atmosphere. Furthermore, to demonstrate the application potential of the synthesized MnO x species, we studied their catalytic activity for the oxygen reduction reaction in aprotic media. Linear sweep voltammetry revealed the best performance for the mesoporous α-Mn2O3 species.

  9. Manganese oxide phases and morphologies: A study on calcination temperature and atmospheric dependence

    Directory of Open Access Journals (Sweden)

    Matthias Augustin

    2015-01-01

    Full Text Available Manganese oxides are one of the most important groups of materials in energy storage science. In order to fully leverage their application potential, precise control of their properties such as particle size, surface area and Mnx+ oxidation state is required. Here, Mn3O4 and Mn5O8 nanoparticles as well as mesoporous α-Mn2O3 particles were synthesized by calcination of Mn(II glycolate nanoparticles obtained through an economical route based on a polyol synthesis. The preparation of the different manganese oxides via one route facilitates assigning actual structure–property relationships. The oxidation process related to the different MnOx species was observed by in situ X-ray diffraction (XRD measurements showing time- and temperature-dependent phase transformations occurring during oxidation of the Mn(II glycolate precursor to α-Mn2O3 via Mn3O4 and Mn5O8 in O2 atmosphere. Detailed structural and morphological investigations using transmission electron microscopy (TEM and powder XRD revealed the dependence of the lattice constants and particle sizes of the MnOx species on the calcination temperature and the presence of an oxidizing or neutral atmosphere. Furthermore, to demonstrate the application potential of the synthesized MnOx species, we studied their catalytic activity for the oxygen reduction reaction in aprotic media. Linear sweep voltammetry revealed the best performance for the mesoporous α-Mn2O3 species.

  10. Ammonia oxidizer populations vary with nitrogen cycling across a tropical montane mean annual temperature gradient

    Science.gov (United States)

    S. Pierre; I. Hewson; J. P. Sparks; C. M. Litton; C. Giardina; P. M. Groffman; T. J. Fahey

    2017-01-01

    Functional gene approaches have been used to better understand the roles of microbes in driving forest soil nitrogen (N) cycling rates and bioavailability. Ammonia oxidation is a rate limiting step in nitrification, and is a key area for understanding environmental constraints on N availability in forests. We studied how increasing temperature affects the role of...

  11. Mechanical degradation of coating systems in high-temperature cyclic oxidation

    CSIR Research Space (South Africa)

    Pennefather, RC

    1995-01-01

    Full Text Available temperature, an extensive testing programme was undertaken. During testing an observation was made that in addition to the usual oxidation of the coating, another degradation mechanism was pragmatic; a mechanical effect caused by the instability of the coating...

  12. Body temperature reduction of graphene oxide through chitosan functionalisation and its application in drug delivery.

    Science.gov (United States)

    Justin, Richard; Chen, Biqiong

    2014-01-01

    The reduction of graphene oxide at body temperature by using a biopolymer, chitosan, was proven to be successful. This biocompatible reduction approach will provide a versatile platform for applying graphene in biomedical fields including tissue engineering and therapeutic delivery. The use of this approach for therapeutic delivery is demonstrated. © 2013.

  13. Experimental Consequences of Mottness in High-Temperature Copper-Oxide Superconductors

    Science.gov (United States)

    Chakraborty, Shiladitya

    2009-01-01

    It has been more than two decades since the copper-oxide high temperature superconductors were discovered. However, building a satisfactory theoretical framework to study these compounds still remains one of the major challenges in condensed matter physics. In addition to the mechanism of superconductivity, understanding the properties of the…

  14. Reliability of ^1^H NMR analysis for assessment of lipid oxidation at frying temperatures

    Science.gov (United States)

    The reliability of a method using ^1^H NMR analysis for assessment of oil oxidation at a frying temperature was examined. During heating and frying at 180 °C, changes of soybean oil signals in the ^1^H NMR spectrum including olefinic (5.16-5.30 ppm), bisallylic (2.70-2.88 ppm), and allylic (1.94-2.1...

  15. Ultrafast room temperature NH3 sensing with positively gated reduced graphene oxide field-effect transistors.

    Science.gov (United States)

    Lu, Ganhua; Yu, Kehan; Ocola, Leonidas E; Chen, Junhong

    2011-07-21

    Reduced graphene oxide (R-GO) under a positive gate potential (n-type conductance) exhibits an instantaneous response and fast recovery for NH(3) sensing, far superior to the performance in p-mode at zero/negative gate potential. Our findings have important implications for fast, repeatable, room temperature gas detection using graphene/R-GO.

  16. Influence of oxidation on the high-temperature mechanical properties of zirconia/nickel cermets

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Rodriguez, A. [Departamento de Fisica de la Materia Condensada, Universidad de Sevilla, Av. Reina Mercedes s/n, Facultad de Fisica, 41012 Seville (Spain)]. E-mail: amr@us.es; Bravo-Leon, A. [Departamento de Fisica de la Materia Condensada, Universidad de Sevilla, Av. Reina Mercedes s/n, Facultad de Fisica, 41012 Seville (Spain); Richter, G. [Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany); Ruehle, M. [Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany); Dominguez-Rodriguez, A. [Departamento de Fisica de la Materia Condensada, Universidad de Sevilla, Av. Reina Mercedes s/n, Facultad de Fisica, 41012 Seville (Spain); Jimenez-Melendo, M. [Departamento de Fisica de la Materia Condensada, Universidad de Sevilla, Av. Reina Mercedes s/n, Facultad de Fisica, 41012 Seville (Spain)

    2006-06-15

    influence of an oxidizing atmosphere on the high-temperature plasticity of zirconia/nickel cermets has been studied by conducting creep tests in air. The resulting microstructure has been characterized by scanning, conventional and high-resolution electron microscopy. Despite the large microstructural changes, the composites do not exhibit mechanical degradation.

  17. Temperature dependent thermoelectric property of reduced graphene oxide-polyaniline composite

    Energy Technology Data Exchange (ETDEWEB)

    Mitra, Mousumi, E-mail: mousumimitrabesu@gmail.com; Banerjee, Dipali, E-mail: dipalibanerjeebesu@gmail.com [Department of Physics, Indian Institute of Engineering Science and Technology (IIEST), Howrah-711103 (India); Kargupta, Kajari, E-mail: karguptakajari2010@gmail.com [Department of Chemical Engineering, Jadavpur University, Kolkata (India); Ganguly, Saibal, E-mail: gangulysaibal2011@gmail.com [Chemical Engineering department, Universiti Teknologi Petronas, Perak, Tronoh (Malaysia)

    2016-05-06

    A composite material of reduced graphene oxide (rG) nanosheets with polyaniline (PANI) protonated by 5-sulfosalicylic acid has been synthesized via in situ oxidative polymerization method. The morphological and spectral characterizations have been done using FESEM and XRD measurements. The thermoelectric (TE) properties of the reduced graphene oxide-polyaniline composite (rG-P) has been studied in the temperature range from 300-400 K. The electrical conductivity and the Seebeck coefficient of rG-P is higher than the of pure PANI, while the thermal conductivity of the composite still keeps much low value ensuing an increase in the dimensionless figure of merit (ZT) in the whole temperature range.

  18. Temperature dependent thermoelectric property of reduced graphene oxide-polyaniline composite

    Science.gov (United States)

    Mitra, Mousumi; Banerjee, Dipali; Kargupta, Kajari; Ganguly, Saibal

    2016-05-01

    A composite material of reduced graphene oxide (rG) nanosheets with polyaniline (PANI) protonated by 5-sulfosalicylic acid has been synthesized via in situ oxidative polymerization method. The morphological and spectral characterizations have been done using FESEM and XRD measurements. The thermoelectric (TE) properties of the reduced graphene oxide-polyaniline composite (rG-P) has been studied in the temperature range from 300-400 K. The electrical conductivity and the Seebeck coefficient of rG-P is higher than the of pure PANI, while the thermal conductivity of the composite still keeps much low value ensuing an increase in the dimensionless figure of merit (ZT) in the whole temperature range.

  19. Modified ferritic iron alloys with improved high-temperature mechanical properties and oxidation resistance

    Science.gov (United States)

    Oldrieve, R. E.

    1975-01-01

    An alloy modification program was conducted in which the compositions of two existing Fe-Cr-Al alloys (Armco 18SR and GE-1541) were changed to achieve either improved high-temperature strength or improved fabricability. Only modifications of Armco 18SR were successful in achieving increased strength without loss of fabricability or oxidation resistance. The best modified alloy, designated NASA-18T, had twice the rupture strength of Armco 18SR at 800 and 1000 C. The NASA-18T alloy also had better oxidation resistance than Armco 18SR and comparable fabricability. The nominal composition of NASA-18T is Fe-18Cr-2Al-1Si-1.25Ta. All attempted modifications of the GE-1541 alloy were unsuccessful in terms of achieving better fabricability without sacrificing high-temperature strength and oxidation resistance.

  20. Nanostructured oxide materials and modules for high temperature power generation from waste heat

    DEFF Research Database (Denmark)

    Van Nong, Ngo; Pryds, Nini

    2013-01-01

    are not easily satisfied by conventional thermoelectric materials. Not only they must possess a sufficient thermoelectric performance, they should also be stable at high temperatures, nontoxic and low-cost comprising elements, and must be also able to be processed and shaped cheaply. Oxides are among......A large amount of thermal energy that emitted from many industrial processes is available as waste heat. Thermoelectric power generators that convert heat directly into electricity can offer a very promising way for waste heat recovery. However, the requirements for this task place in the materials...... the strongest candidate materials for this purpose. In this review, the progress in the development of two representative p- and n-type novel oxide materials based on Ca3Co4O9 and doped-ZnO is presented. Thermoelectric modules built up from these oxides were fabricated, tested at high temperatures, and compared...

  1. The Effect of Cr Content on the Oxidation Behavior of Ti-Cr-N Films

    Directory of Open Access Journals (Sweden)

    James E. Krzanowski

    2014-04-01

    Full Text Available Ti1−xCrxN thin-film samples were sputter-deposited with lateral composition gradients x = 0.1–0.9 across each sample. In order to determine the effect of Cr content on oxidation, samples were air-oxidized at temperatures ranging from 650 to 950 °C. The extent and type of oxide formed was characterized using X-ray diffraction. Only minor oxidation was observed for the 650–750 °C temperature range. At 850 °C, films below x = 0.7 showed poor oxidation resistance, with the formation of TiO2 and Cr2O3 oxides, but little oxidation occurred above x = 0.7. At 950 °C, films above x = 0.7 again exhibited the best oxidation resistance. Chromium nitride films, which deposited as Cr2N, were found to begin oxidizing at 750 °C, indicating that the increased oxidation resistance of the higher-Cr Ti-Cr-N films can be attributed to the Ti-induced stabilization of the B1-structured phase. A compositionally-uniform film (x = 0.79 was also deposited and analyzed by XPS before and after oxidation. Oxidation resulted in primarily Cr2O3 at the surface, with some TiO2 also present, with the oxide richer in Cr than the starting film composition. These results suggested that at higher Cr compositions in the film, the oxidation mechanism was controlled by Cr diffusion to the surface.

  2. Deuterium permeation behavior of HTUPS4 steel with thermal oxidation layer

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yu-Ping [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Science Island Branch of Graduate School, University of Science & Technology of China, Hefei, 230031 (China); Liu, Feng; Zhao, Si-Xiang; Li, Xiao-Chun [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Wang, Jing [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Science Island Branch of Graduate School, University of Science & Technology of China, Hefei, 230031 (China); An, Zhong-Qing; Lu, Tao [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Liu, Hao-Dong [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Science Island Branch of Graduate School, University of Science & Technology of China, Hefei, 230031 (China); Ding, Fang [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Zhou, Hai-Shan, E-mail: haishanzhou@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Luo, Guang-Nan [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Science Island Branch of Graduate School, University of Science & Technology of China, Hefei, 230031 (China); Hefei Center for Physical Science and Technology, Hefei, 230031 (China); Hefei Science Center of Chinese Academy of Science, Hefei, 230027 (China)

    2016-12-15

    The permeation behavior of creep-resistant, Al{sub 2}O{sub 3}-forming HTUPS austenitic stainless steels was studied using a gas driven permeation (GDP) device. The steel samples were first thermal oxidized at air condition, followed by GDP experiments. The permeability and diffusion coefficients of oxidized samples and bare 316L steels were derived and compared. In order to characterize the oxide layer, X-ray photoelectron spectroscopy was performed. An oxide layer with a thickness of 200 nm which mainly consists of Al{sub 2}O{sub 3} was detected.

  3. Investigation of NOx Reduction by Low Temperature Oxidation Using Ozone Produced by Dielectric Barrier Discharge

    Science.gov (United States)

    Stamate, Eugen; Irimiea, Cornelia; Salewski, Mirko

    2013-05-01

    NOx reduction by low temperature oxidation using ozone produced by a dielectric barrier discharge generator is investigated for different process parameters in a 6 m long reactor in serpentine arrangement using synthetic dry flue gas with NOx levels below 500 ppm, flows up to 50 slm and temperatures up to 80 °C. The role of different mixing schemes and the impact of a steep temperature gradient are also taken into consideration. The process chemistry is monitored by Fourier transform infrared spectroscopy, chemiluminescence and absorption spectroscopy. The kinetic mechanism during the mixing in a cross flow configuration is investigated using three-dimensional simulations.

  4. Parametric Investigation of Rate Enhancement during fast Temperature Cycling of CO Oxidation in Microreactors

    DEFF Research Database (Denmark)

    Jensen, Søren; Thorsteinsson, Sune; Hansen, Ole

    2008-01-01

    and confirm earlier findings of reaction rate enhancements. The enhancement is shown to increase at high frequencies. Varying the conversion and temperature oscillation amplitude is shown to have a large effect on the rate enhancement, and a large interaction between the two parameters is detected......A new microreactor that allows investigation of the effects of temperature oscillations at frequencies 10 times higher than in previous systems is presented. As an example, we investigate CO oxidation over a supported Pt catalyst subjected to a fast forced oscillation of the reactor temperature....... For the best parameter setting, reaction rates 70% higher than during slow steady-state-like oscillations are observed....

  5. Corrosion Behavior of L80Steel in Different Temperature and Sulfur Content

    Science.gov (United States)

    Qiu, Zhichao; Xiong, Chunming; Yi, Ran; Ye, Zhengrong

    2017-10-01

    To understand the corrosion behavior of L80 steel in different temperature and sulfur content, the experiment which simulated the downhole corrosive environment was conducted. From the experiment result, when other factors were constant, the lowest corrosion rate was appeared when the temperature was 90°C. The influence of sulfur was complex. When temperature was low, the corrosion rate was decreased with the increase of sulfur content and the experimental result was opposite when temperature was high.

  6. Influence of Mn-Co Spinel Coating on Oxidation Behavior of Ferritic SS Alloys for SOFC Interconnect Applications

    DEFF Research Database (Denmark)

    Venkatachalam, Vinothini; Molin, Sebastian; Kiebach, Wolff-Ragnar

    2014-01-01

    ). The oxidation behavior of both the coated and bare alloy was evaluated at 800°C in air for 1000 h. The oxidation kinetics were investigated using weight gain and scale thickness measurements. The weight gain per unit surface area of the bare alloy exhibited parabolic oxidation behavior. The influence of Mn...

  7. Raman and XPS characterization of vanadium oxide thin films with temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ureña-Begara, Ferran, E-mail: ferran.urena@uclouvain.be [Université catholique de Louvain, Institute of Information and Communication Technologies, Electronics and Applied Mathematics (ICTEAM), Louvain-la-Neuve (Belgium); Crunteanu, Aurelian [XLIM Research Institute, UMR 7252, CNRS/Université de Limoges, Limoges (France); Raskin, Jean-Pierre [Université catholique de Louvain, Institute of Information and Communication Technologies, Electronics and Applied Mathematics (ICTEAM), Louvain-la-Neuve (Belgium)

    2017-05-01

    Highlights: • Comprehensive study of the oxidation of VO{sub 2} thin films from R.T. up to 550 °C. • Phase changes and mixed-valence vanadium oxides formed during the oxidation process. • Reported Raman and XPS signatures for each vanadium oxide. • Monitoring of the current and resistance evolution at the surface of the films. • Oxidation model describing the evolution of the vanadium oxides and phase changes. - Abstract: The oxidation mechanisms and the numerous phase transitions undergone by VO{sub 2} thin films deposited on SiO{sub 2}/Si and Al{sub 2}O{sub 3} substrates when heated from room temperature (R.T.) up to 550 °C in air are investigated by Raman and X-ray photoelectron spectroscopy. The results show that the films undergo several intermediate phase transitions between the initial VO{sub 2} monoclinic phase at R.T. and the final V{sub 2}O{sub 5} phase at 550 °C. The information about these intermediate phase transitions is scarce and their identification is important since they are often found during the synthesis of vanadium dioxide films. Significant changes in the film conductivity have also been observed to occur associated to the phase transitions. In this work, current and resistance measurements performed on the surface of the films are implemented in parallel with the Raman measurements to correlate the different phases with the conductivity of the films. A model to explain the oxidation mechanisms and phenomena occurring during the oxidation of the films is proposed. Peak frequencies, full-width half-maxima, binding energies and oxidation states from the Raman and X-ray photoelectron spectroscopy experiments are reported and analyzed for all the phases encountered in VO{sub 2} films prepared on SiO{sub 2}/Si and Al{sub 2}O{sub 3} substrates.

  8. High-temperature Corrosion Resistance of Composite Coating Prepared by Micro-arc Oxidation Combined with Pack Cementation Aluminizing

    Directory of Open Access Journals (Sweden)

    HUANG Zu-jiang

    2018-01-01

    Full Text Available Al2O3 ceramic film was obtained by micro-arc oxidation (MAO process on Al/C103 specimen, which was prepared by pack cementation aluminizing technology on C103 niobium alloy. With the aid of XRD and SEM equipped with EDS, chemical compositions and microstructures of the composite coatings before and after high-temperature corrosion were analyzed. The behavior and mechanism of the composite coatings in high-temperature oxidation and hot corrosion were also investigated. The results indicate that oxidation mass gain at 1000℃ for 10h of the Al/C103 specimen is 6.98mg/cm2, and it is 2.89mg/cm2 of the MAO/Al/C103 specimen. However, the mass gain of MAO/Al/C103 specimen (57.52mg/cm2 is higher than that of Al/C103 specimen (28.08mg/cm2 after oxidation 20h. After hot corrosion in 75%Na2SO4 and 25%NaCl at 900℃ for 50h, the mass gain of Al/C103 and MAO/Al/C103 specimens are 70.54mg/cm2 and 55.71mg/cm2 respectively, Al2O3 and perovskite NaNbO3 phases are formed on the surface; the diffusion of molten salt is suppressed, due to part of NaNbO3 accumulated in the MAO micropores. Therefore, MAO/Al/C103 specimen exhibits better hot corrosion resistance.

  9. Oxidation and creep behavior of Mo*5*Si*3* based materials

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Mitch [Iowa State Univ., Ames, IA (United States)

    1995-06-19

    Mo5Si3 shows promise as a high temperature creep resistant material. The high temperature oxidation resistance of Mo5Si3 has been found to be poor, however, limiting its use in oxidizing atmospheres. Undoped Mo5Si3 exhibits mass loss in the temperature range 800°-1200°C due to volatilization of molybdenum oxide, indicating that the silica scale does not provide a passivating layer. The addition of boron results in protective scale formation and parabolic oxidation kinetics in the temperature range of 1050{degrees}-1300°C. The oxidation rate of Mo5Si3 was decreased by 5 orders of magnitude at 1200°C by doping with less than two weight percent boron. Boron doping eliminates catastrophic "pest" oxidation at 800°C. The mechanism for improved oxidation resistance of boron doped Mo5Si3 is due to scale modification by boron.

  10. Effect of surface oxidation on thermomechanical behavior of NiTi shape memory alloy wire

    Science.gov (United States)

    Ng, Ching Wei; Mahmud, Abdus Samad

    2017-12-01

    Nickel titanium (NiTi) alloy is a unique alloy that exhibits special behavior that recovers fully its shape after being deformed to beyond elastic region. However, this alloy is sensitive to any changes of its composition and introduction of inclusion in its matrix. Heat treatment of NiTi shape memory alloy to above 600 °C leads to the formation of the titanium oxide (TiO2) layer. Titanium oxide is a ceramic material that does not exhibit shape memory behaviors and possess different mechanical properties than that of NiTi alloy, thus disturbs the shape memory behavior of the alloy. In this work, the effect of formation of TiO2 surface oxide layer towards the thermal phase transformation and stress-induced deformation behaviors of the NiTi alloy were studied. The NiTi wire with composition of Ti-50.6 at% Ni was subjected to thermal oxidation at 600 °C to 900 °C for 30 and 60 minutes. The formation of the surface oxide layers was characterized by using the Scanning Electron Microscope (SEM). The effect of surface oxide layers with different thickness towards the thermal phase transformation behavior was studied by using the Differential Scanning Calorimeter (DSC). The effect of surface oxidation towards the stress-induced deformation behavior was studied through the tensile deformation test. The stress-induced deformation behavior and the shape memory recovery of the NiTi wire under tensile deformation were found to be affected marginally by the formation of thick TiO2 layer.

  11. Characterization and Oxidation Behavior of Rayon-Derived Carbon Fibers

    Science.gov (United States)

    Jacobson, Nathan; Hull, David

    2010-01-01

    Rayon-derived fibers are the central constituent of reinforced carbon/ carbon (RCC) composites. Optical, scanning electron, and transmission electron microscopy were used to characterize the as-fabricated fibers and the fibers after oxidation. Oxidation rates were measured with weight loss techniques in air and oxygen. The as-received fibers are approximately 10 micron in diameter and characterized by grooves or crenulations around the edges. Below 800 C, in the reaction-controlled region, preferential attack began in the crenulations and appeared to occur down fissures in the fibers.

  12. High temperature oxidation and electrochemical studies on novel co-base superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Leonhard

    2013-02-27

    Isothermal oxidation in air was carried out on novel γ'-strengthened Cobalt-base superalloys of the system Co-Al-W-B. After fast initial oxide formation, a multi-layered structure establishes, consisting of an outer cobalt oxide layer, a middle spinel-containing layer, and an inner Al{sub 2}O{sub 3}-rich region. Ion diffusion in outward direction is hindered by the development of Al{sub 2}O{sub 3}, that can be either present as a continuous and protective layer or as a discontinuous Al{sub 2}O{sub 3}-rich area without comparable protective effect. Furthermore, high temperature oxidation leads to phase transformation (from γ/γ' into γ/Co{sub 3}W) at the alloy/oxide layer interface due to aluminium depletion. Pure cobalt and ternary Co-Al-W alloys exhibit parabolic oxide growth due to the lack or insufficient amounts of protective oxides, whereas quaternary Co-Al-W-B alloys possess sub-parabolic oxidation behaviour (at 900 C). At lower temperatures (800 C), even a blockage of further oxidation can be observed. High amounts of B (0.12 at%) significantly improve oxidation resistance mainly due to its beneficial effect on inner Al{sub 2}O{sub 3}-formation at the alloy/oxide interface. Furthermore, B prevents decohesion of high temperature scales due to the formation of B-rich phases (presumably tungsten borides) in the middle oxide layer. Appropriate amounts of chromium (8 at%) as additional alloying element to Co-Al-W-B alloys lead to the formation of an inner duplex layer composed of protective Cr{sub 2}O{sub 3} and Al{sub 2}O{sub 3} phases. In this respect, chromium also benefits selective oxidation of aluminium, which results in higher Al{sub 2}O{sub 3}-contents compared to chromium-free alloys. Major drawbacks of chromium additions are, on the one hand, the formation of volatile chromium-containing species at temperatures exceeding 1000 C and on the other hand, the instability of the γ/γ'-microstructure. Titanium and silicon additions lead to

  13. Oxidation of UC: An in situ high temperature environmental scanning electron microscopy study

    Science.gov (United States)

    Gasparrini, Claudia; Podor, Renaud; Horlait, Denis; Rushton, Michael J. D.; Fiquet, Olivier; Lee, William Edward

    2017-10-01

    In situ HT-ESEM oxidation of sintered UC fragments revealed the morphological changes occurring during the transformation between UC to UO2 and UO2 to U3O8 at 723-848 K and in an atmosphere of 10-100 Pa O2. Two main oxidation pathways were revealed. Oxidation at 723 K in atmospheres ≤25 Pa O2 showed the transformation from UC to UO2+x, as confirmed by post mortem HRTEM analysis. This oxidation pathway was comprised of three steps: (i) an induction period, where only surface UC particles oxidised, (ii) a sample area expansion accompanied by crack formation and propagation, (iii) a stabilisation of the total crack length inferring that crack propagation had stopped. Samples oxidised under 50 Pa O2 at 723 K and at 773-848 K for 10-100 Pa O2 showed an ;explosive; oxidation pathway: (i) sample area expansion occurred as soon as oxygen was inserted into the chamber and crack propagation and crack length followed an exponential law; (ii) cracks propagated as a network and the oxide layer fragmented, (iii) an ;explosion; occurred causing a popcorn-like transformation, typical for oxidation from UO2 to U3O8. HRTEM characterisation revealed U3O8 preferentially grow in the [001] direction. The explosive growth, triggered by ignition of UC, proceeded as a self-propagating high-temperature synthesis reaction, with a propagation speed of 150-500 ± 50 μm/s.

  14. Temporal stability of solid oxidizers at high temperature and humidity. Memorandum report

    Energy Technology Data Exchange (ETDEWEB)

    Pellenbarg, R.E.; Dotson, D.A.

    1985-09-30

    Chemical Warfare/Biological Warfare (CW/BW) decontamination operations may rely on aqueous solutions prepared from stored solid oxidizers. Needed are data defining the shipboard storage stability of candidate oxidizers. Therefore, the stability of a series of potential decontaminants has been examined at high temperature (90 + C) and humidity (95 + % R.H.). The loss of oxidizing capacity in aliquots of the oxidizers was followed with time by iodometric titration. Calcium hypochlorite lost over 99% of its oxidizing capacity in less than two days, whereas lithium hypochlorite retained one-third oxidizing capacity for approximately twenty days. Sodium perborate, and sodium persulfate were very hygroscopic and unstable with time. H-48 decomposed in approximately two days, while sodium isocyanurate lost about 80% of its oxidizing capacity in two weeks. The data presented documents severe stability problems of one sort or another with all the materials tested, although overall the sodium isocyanurate appeared to be the more stable candidate undr extreme conditions. In any case, packaging and storage considerations are shown to be important for any potential decontaminant to be stored under environmentally severe conditions.

  15. Two-color laser absorption near 5 μm for temperature and nitric oxide sensing in high-temperature gases

    Science.gov (United States)

    Almodovar, Christopher A.; Spearrin, R. Mitchell; Hanson, Ronald K.

    2017-12-01

    An infrared laser-absorption technique for in situ temperature and nitric oxide species sensing in high-temperature gases is presented. A pair of quantum cascade lasers in the mid-infrared near 5 μm were utilized to probe rovibrational transitions in nitric oxide's fundamental band. The line parameters of the selected transitions, including line strengths and collision broadening coefficients of nitric oxide with argon and nitrogen, were evaluated during controlled room-temperature static cell experiments and high-temperature shock tube experiments at temperatures between 1000 and 3000 K, and pressures between 1 and 5 atm. These studies provided new insights into the temperature dependence of nitric oxide collision broadening, highlighting the inadequacies of the power law over a broad temperature range. With an accurate spectroscopic model over a broad temperature range, the quantitative two-color temperature sensing strategy was demonstrated in non-reactive shock tube experiments from 1000 to 3000 K to validate thermometry and during a nitric oxide formation experiment near 1700 K and 4 atm to highlight capability for temporally-resolved species measurements at MHz rates. The technique has applicability for sensing in a broad range of flow fields that involve high-temperature air.

  16. Correlation between Low Temperature Adaptation and Oxidative Stress in Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    Estéfani García-Rios

    2016-08-01

    Full Text Available Many factors, such as must composition, juice clarification, fermentation temperature or inoculated yeast strain, strongly affect the alcoholic fermentation and aromatic profile of wine. As fermentation temperature is effectively controlled by the wine industry, low-temperature fermentation (10-15 ºC is becoming more prevalent in order to produce white and rosé wines with more pronounced aromatic profiles. Elucidating the response to cold in Saccharomyces cerevisiae is of paramount importance for the selection or genetic improvement of wine strains. Previous research has shown the strong implication of oxidative stress response in adaptation to low temperature during the fermentation process. Here we aimed first to quantify the correlation between recovery after shock with different oxidants and cold, and then to detect the key genes involved in cold adaptation that belong to sulfur assimilation, peroxiredoxins, glutathione-glutaredoxins and thioredoxins pathways. To do so, we analyzed the growth of knockouts from the EUROSCARF collection S. cerevisiae BY4743 strain at low and optimal temperatures. The growth rate of these knockouts, compared with the control, enabled us to identify the genes involved, which were also deleted and validated as key genes in the background of two commercial wine strains with a divergent phenotype in their low-temperature growth. We identified three genes, AHP1, MUP1 and URM1, whose deletion strongly impaired low-temperature growth.

  17. Influence of Oxidation Behavior of Feedstock on Microstructure and Ablation Resistance of Plasma-Sprayed Zirconium Carbide Coating

    Science.gov (United States)

    Hu, Cui; Ge, Xuelian; Niu, Yaran; Li, Hong; Huang, Liping; Zheng, Xuebin; Sun, Jinliang

    2015-10-01

    Plasma spray is one of the suitable technologies to deposit carbide coatings with high melting point, such as ZrC. However, in the spray processes performed under atmosphere, oxidation of the carbide powder is inevitable. To investigate the influence of the oxidation behavior of feedstock on microstructure and ablation resistance of the deposited coating, ZrC coatings were prepared by atmospheric and vacuum plasma spray (APS and VPS) technologies, respectively. SiC-coated graphite was applied as the substrate. The obtained results showed that the oxidation of ZrC powder in APS process resulted in the formation of ZrO and Zr2O phases. Pores and cracks were more likely to be formed in the as-sprayed APS-ZrC coating. The VPS-ZrC coating without oxides possessed denser microstructure, higher thermal diffusivity, and lower coefficients of thermal expansion as compared with the APS-ZrC coating. A dense ZrO2 layer would be formed on the surface of the VPS-ZrC-coated sample during the ablation process and the substrate can be protected sufficiently after being ablated in high temperature plasma jet. However, the ZrO2 layer, formed by oxidation of the APS-ZrC coating having loose structure, was easy to be washed away by the shearing action of the plasma jet.

  18. Oxidation behavior of FeCr and FeCrY alloys coated with an aluminium based paint

    Directory of Open Access Journals (Sweden)

    Marina Fuser Pillis

    2008-09-01

    Full Text Available A variety of metallic components rely on properties that are specific to the alloy and its surface. Coatings have been extensively used to protect metallic surfaces from the aggressive effects of the environment to which it is exposed. In this investigation, the high temperature oxidation behavior of a FeCr and a FeCrY alloy coated with an aluminium based paint has been studied. The objective was to form the more resistant alumina surface layer on an aluminium free alloy. Aluminium based paint coated and uncoated specimens of the two alloys were oxidized for up to 200 hours at 1000 °C in air. The oxidized specimens were examined in a scanning electron microscope coupled to an energy dispersive system and the surfaces were analyzed by X ray diffraction analysis. The aluminium based paint coating increased the oxidation resistance of the alloys, mainly over extended periods. The FeCrY alloy coated with the Al based paint exhibited the highest oxidation resistance.

  19. Effect of oxygen and oxidation on tensile behavior of V-5Cr-5Ti

    Energy Technology Data Exchange (ETDEWEB)

    Natesan, K.; Soppet, W.K. [Argonne National Laboratory, Chicago, IL (United States)

    1996-04-01

    Oxidation studies were conducted on V-5Cr-5Ti alloy specimens in an air environment to evaluate the oxygen uptake of the alloy as a function of temperature and exposure time. The oxidation rates calculated from parabolic kinetic measurements of thermogravimetric testing and confirmed by microscopic analyses of cross sections of exposed specimens were 5, 17, and 27 {mu}m per year after exposure at 300, 400, and 500{degrees}C, respectively. Uniaxial tensile tests were conducted at room temperature and at 500{degrees}C on preoxidized specimens of the alloy to examine the effects of oxidation and oxygen migration on tensile strength and ductility. Microstructural characteristics of several of the tested specimens were determined by electron optics techniques. Correlations were developed between tensile strength and ductility of the oxidized alloy and microstructural characteristics such as oxide thickness, depth of hardened layer, depth on intergranular fracture zone, and transverse crack length.

  20. Tribological Behavior of Mg97Zn1Y2 Alloy at Elevated Temperatures of 50-200 °C

    Science.gov (United States)

    An, J.; Feng, J. H.; Yan, X. H.; Li, R. G.

    2017-10-01

    The tribological behavior of Mg97Zn1Y2 alloy was investigated using a pin-on-disk wear machine at wear temperatures of 50-200 °C. Morphologies and chemical compositions of worn surfaces were analyzed using scanning electron microscope and energy-dispersive x-ray spectrometer. The microstructural evolution and hardness change in subsurfaces were examined by optical microscopy and hardness tester. The results showed that the wear temperature had significant influence on the coefficient of friction and wear rate. At wear temperatures of 50-200 °C, with increasing applied load, the coefficient of friction went down rapidly then turned to decrease slowly in the mild wear regime, and continuously decreased modestly until the largest applied load in the severe wear regime. Increasing wear temperature from 50 to 200 °C decreased the mild to severe wear transition load linearly from 120 to 60 N. In the mild wear regime, the main wear mechanisms were identified as abrasion + oxidation and delamination + surface oxidation at 50-150 °C, and delamination at 200 °C, while in the severe wear regime, the main wear mechanisms were identified as severe plastic deformation + spallation of oxide layer and surface melting at 50-150 °C, and severe plastic deformation and surface melting at 200 °C. The microstructural transformation from the deformed to the dynamically recrystallized (DRX), and hardness change from the strain hardening to softening were found in the subsurfaces before and after mild to severe transition. The DRX softening mechanism was determined for mild to severe wear transition at 50-200 °C. A wear transition map was constructed for Mg97Zn1Y2 alloy on applied load versus wear temperature.

  1. Methyl Chloride from Direct Methane Partial Oxidation: A High-Temperature Shilov-Like Catalytic System

    Energy Technology Data Exchange (ETDEWEB)

    Yongchun Tang; John (Qisheng) Ma

    2012-03-23

    The intention of this study is to demonstrate and evaluate the scientific and economic feasibility of using special solvents to improve the thermal stability of Pt-catalyst in the Shilov system, such that a high reaction temperature could be achieved. The higher conversion rate (near 100%) of methyl chloride from partial oxidation of methane under the high temperature ({approx} 200 C) without significant Pt0 precipitation has been achieved. High concentration of the Cl- ion has been identified as the key for the stabilization of the Pt-catalysts. H/D exchange measurements indicated that the over oxidation will occur at the elevated temperature, developments of the effective product separation processes will be necessary in order to rationalize the industry-visible CH4 to CH3Cl conversion.

  2. Effect of intense pulsed ion beams irradiation on the oxidation behavior of gamma sup ' -based superalloy

    CERN Document Server

    Zhang Hong Tao; Han Bao Xi; Yan Sha; Zhao Wei Jiang; Han Ya Fan

    2002-01-01

    Intense pulsed ion beams (IPIB) with three different power densities (25, 37.5 and 50 MW/cm sup 2) are employed for the surface treatment of gamma sup ' -based superalloy IC6. The influence of IPIB irradiation on the oxidation behavior of IC6 at 1100 degree sign C for up to 100 h is investigated. It is found that the phase states of IC6 are dramatically changed after IPIB irradiation and the oxidation behavior of the irradiated coupons depends greatly on the power density of IPIB. IPIB irradiation with a power density of 25 or 37.5 MW/cm sup 2 significantly reduces the oxidation rate with respect to the unirradiated coupon. The improvement of the oxidation resistance can be attributed to a change in the oxidation products from a three-layered scale of Ni-rich oxides for the unirradiated coupon to a two-layered scale of Mo- and Al-rich oxides. In contrast, IPIB irradiation with a power density of 50 MW/cm sup 2 proves to be detrimental, causing a higher oxidation rate. The oxidation mechanism for IPIB irradiat...

  3. Isothermal oxidation behavior and mechanism of a nickel-based superalloy at 1000°C

    Science.gov (United States)

    Zhu, Zhi-yuan; Cai, Yuan-fei; Gong, You-jun; Shen, Guo-ping; Tu, Yu-guo; Zhang, Guo-fu

    2017-07-01

    The oxidation behavior of a nickel-based superalloy at 1000°C in air was investigated through X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy analysis. A series of oxides, including external oxide scales (Cr2O3, (TiO2 + MnCr2O4)) and internal oxides (Al2O3,TiN), were formed on the surface or sub-surface of the substrate at 1000°C in experimental still air. The oxidation resistance of the alloy was dependent on the stability of the surface oxide layer. The continuity and density of the protective Cr2O3 scale were affected by minor alloying elements such as Ti and Mn. The outermost oxide scale was composed of TiO2 rutile and MnCr2O4 spinel, and the growth of TiO2 particles was controlled by the outer diffusion of Ti ions through the pre-existing oxide layer. Severe internal oxidation occurred beneath the external oxide scale, consuming Al and Ti of the strength phase γ' (Ni3(Al,Ti)) and thereby severely deteriorating the surface mechanical properties. The depth of the internal oxidation region was approximately 35 μm after exposure to experimental air at 1000°C for 80 h.

  4. Low-Temperature Oxidation-Free Selective Laser Sintering of Cu Nanoparticle Paste on a Polymer Substrate for the Flexible Touch Panel Applications.

    Science.gov (United States)

    Kwon, Jinhyeong; Cho, Hyunmin; Eom, Hyeonjin; Lee, Habeom; Suh, Young Duk; Moon, Hyunjin; Shin, Jaeho; Hong, Sukjoon; Ko, Seung Hwan

    2016-05-11

    Copper nanomaterials suffer from severe oxidation problem despite the huge cost effectiveness. The effect of two different processes for conventional tube furnace heating and selective laser sintering on copper nanoparticle paste is compared in the aspects of chemical, electrical and surface morphology. The thermal behavior of the copper thin films by furnace and laser is compared by SEM, XRD, FT-IR, and XPS analysis. The selective laser sintering process ensures low annealing temperature, fast processing speed with remarkable oxidation suppression even in air environment while conventional tube furnace heating experiences moderate oxidation even in Ar environment. Moreover, the laser-sintered copper nanoparticle thin film shows good electrical property and reduced oxidation than conventional thermal heating process. Consequently, the proposed selective laser sintering process can be compatible with plastic substrate for copper based flexible electronics applications.

  5. Effects of copper, hypoxia and acute temperature shifts on mitochondrial oxidation in rainbow trout (Oncorhynchus mykiss) acclimated to warm temperature

    Energy Technology Data Exchange (ETDEWEB)

    Sappal, Ravinder [Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Fast, Mark [Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Stevens, Don [Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Kibenge, Fred [Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Siah, Ahmed [British Columbia Centre for Aquatic Health Sciences, 871A Island Highway, Campbell River, British Columbia V9W 2C2 (Canada); Kamunde, Collins, E-mail: ckamunde@upei.ca [Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada)

    2015-12-15

    Highlights: • Warm acclimation reduced the electron transport system (ETS) efficiency. • Warm acclimation altered the effects of acute temperature shift, hypoxia and Cu on ETS. • Warm acclimation increased thermal sensitivity of state 3 and reduced that of state 4. • Cu stimulated while hypoxia inhibited ETS respiratory activity. • Interactions of Cu and hypoxia on the ETS and plasma metabolites were antagonistic. - Abstract: Temperature fluctuations, hypoxia and metals pollution frequently occur simultaneously or sequentially in aquatic systems and their interactions may confound interpretation of their biological impacts. With a focus on energy homeostasis, the present study examined how warm acclimation influences the responses and interactions of acute temperature shift, hypoxia and copper (Cu) exposure in fish. Rainbow trout (Oncorhynchus mykiss) were acclimated to cold (11 °C; control) and warm (20 °C) temperature for 3 weeks followed by exposure to environmentally realistic levels of Cu and hypoxia for 24 h. Subsequently, mitochondrial electron transport system (ETS) respiratory activity supported by complexes I–IV (CI–IV), plasma metabolites and condition indices were measured. Warm acclimation reduced fish condition, induced aerobic metabolism and altered the responses of fish to acute temperature shift, hypoxia and Cu. Whereas warm acclimation decelerated the ETS and increased the sensitivity of maximal oxidation rates of the proximal (CI and II) complexes to acute temperature shift, it reduced the thermal sensitivity of state 4 (proton leak). Effects of Cu with and without hypoxia were variable depending on the acclimation status and functional index. Notably, Cu stimulated respiratory activity in the proximal ETS segments, while hypoxia was mostly inhibitory and minimized the stimulatory effect of Cu. The effects of Cu and hypoxia were modified by temperature and showed reciprocal antagonistic interaction on the ETS and plasma

  6. Elevated Temperature Behavior of Metal-Matrix Composites.

    Science.gov (United States)

    1981-11-01

    in the absence of axial shear. The one dimensional stress- strain relation may be written in the Ramberg - Osgood form PT PT m-l T T =G l( + ( -T) (3...relations in terms of the initial yield stresses TTo and TAo’ the Ramberg - Osgood parameters sT’ m, sA and n and the elastic shear moduli GT and GA. We... Ramberg - Osgood parameters for that temperature. Thus, if the shear stress-strain relations at temperature are ex- pressed as 23 + 2 ( - -23 - 2GT (W

  7. Temperature and high pressure effects on the structural features of catalytic nanocomposites oxides by Raman spectroscopy.

    Science.gov (United States)

    da Silva, Antonio N; Pinto, Raffael C F; Freire, Paulo T C; Junior, Jose Alves L; Oliveira, Alcineia C; Filho, Josué M

    2015-03-05

    Structural characterizations of nanostructured oxides were studied by X-ray diffraction (XRD), Raman and infrared spectroscopy. The oxides catalysts namely, SnO2, ZrO2, CeO2, MnOx, Al2O3 and TiO2 were prepared by a nanocasting route and the effect of the temperature and pressure on the stability of the solids was evaluated. Raman spectra showed that ZrO2 and TiO2 exhibited phase transitions at moderate temperatures whereas CeO2, SnO2 and MnOx had an effective creation of defects in their structures upon annealing at elevated temperatures. The results suggested also that the effect of the temperature on the particles growth is related to the type of oxide. In this regard, phase transition by up to 600°C accelerated the sintering of ZrO2 and CeO2 grains compared to TiO2, SnO2 and MnOx counterparts. Under hydrostatic pressures lower than 10GPa, rutile TiO2 and tetragonal ZrO2 exhibited pressure induced phase transition whereas CeO2 and SnO2 were stable at pressures close to 15GPa. The experiments revealed that the nanostructured SnO2 oxide exhibited stable performance at relatively high temperatures without phase transition or sintering, being suitable to be used as catalysts in the range of temperature and pressure studied. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. extract attenuates MPTP-induced oxidative stress and behavioral

    African Journals Online (AJOL)

    Received: 9 November 2015. Revised accepted: 17 March 2016. Abstract. Purpose: To evaluate ... ability to induce oxidative damage and mitochondrial dysfunction in the nigrostriatal dopaminergic system in ... On day 22, all the brain tissues were rinsed in ice-cold isotonic saline, homogenized with 1 mL of ice-cold 0.1 M ...

  9. Relative Effects of Temperature, Light, and Humidity on Clinging Behavior of Metacercariae-Infected Ants.

    Science.gov (United States)

    Botnevik, C F; Malagocka, J; Jensen, A B; Fredensborg, B L

    2016-10-01

    The lancet fluke, Dicrocoelium dendriticum, is perhaps the best-known example of parasite manipulation of host behavior, which is manifested by a radically changed behavior that leaves infected ants attached to vegetation at times when transmission to an herbivore host is optimal. Despite the publicity surrounding this parasite, curiously little is known about factors inducing and maintaining behavioral changes in its ant intermediate host. This study examined the importance of 3 environmental factors on the clinging behavior of red wood ants, Formica polyctena , infected with D. dendriticum . This behavior, hypothesized to involve cramping of the mandibular muscles in a state of tetany, was observed in naturally infected F. polyctena under controlled temperature, light, and humidity conditions. We found that low temperature significantly stimulated and maintained tetany in infected ants while light, humidity, ant size, and infection intensity had no influence on this behavior. Under none of the experimental conditions did uninfected ants attach to vegetation, demonstrating that tetany was induced by D. dendriticum . Temperature likely has a direct impact on the initiation of clinging behavior, but it may also serve as a simple but reliable indicator of the encounter rate between infected ants and ruminant definitive hosts. In addition, temperature-sensitive behavior manipulation may protect infected ants from exposure to temperatures in the upper thermal range of the host.

  10. Elevated temperature dependent transport properties of phosphorus and arsenic doped zinc oxide thin films

    Science.gov (United States)

    Cai, B.; Nakarmi, M. L.; Oder, T. N.; McMaster, M.; Velpukonda, N.; Smith, A.

    2013-12-01

    Elevated temperature dependent Hall effect measurements were performed in a wide temperature range from 80 to 800 K to study transport properties of zinc oxide (ZnO) thin films heavily doped with phosphorus (P) and arsenic (As), and grown on sapphire substrates by RF magnetron sputtering. Double thermal activation processes in both P- and As-doped ZnO thin films with small activation energy of ˜0.04 eV and large activation energy of ˜0.8 eV were observed from variable temperature Hall effect measurements. The samples exhibited n-type conductivities throughout the temperature range. Based on photoluminescence measurements at 11 K and theoretical results, the large activation energy observed in the temperature dependent Hall effect measurement has been assigned to a deep donor level, which could be related to oxygen vacancy (VO) in the doped ZnO thin films.

  11. Low temperature diffusion of hydrogenic species in oxide crystals: Radiation induced diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y. [Oak Ridge National Lab., TN (United States); Gonzalez, R. [Universidad `Carlos III` de Madrid (Spain). Dept. de Ingenieria

    1993-10-01

    Normally stable configurations of substitutional protons or deuterons in oxide crystal become highly unstable during ionizing radiation at room temperature, resulting in the displacements of these species. The cross section for radiation-induced-displacements of protons is exceedingly large and is a strong function of temperature. The displacement cross section of protons from cation sites is twice that of deuterons. Diffusion of these species can be induced at temperatures not otherwise possible by thermal means. For example, using electron irradiation near room temperature the O-H bond is readily broken and the hydrogenic species can be channeled along the c-axis in TiO{sub 2} by an applied electric field. Radiation induced displacements of protons from anion sites (hydride ions) at room temperature are also discussed.

  12. Pressure and temperature effects on oxide melt structure: progress and prognoses (Bunsen Medal Lecture)

    Science.gov (United States)

    Stebbins, J. F.

    2009-04-01

    Thanks to decades of study by diffraction and spectroscopy, many aspects of the short-range structure of oxide glasses, and the effects of composition on them, are relatively well known. In most cases, these results represent (at best) the structure of the liquid at the glass transition, which is often far below the magmatic conditions of greatest interest for geological processes. At the same time, detailed thermodynamic and calorimetric studies at ambient pressure, and a few pioneering in-situ, high-pressure melt property measurements, have documented the fact that melt structure must change considerably as temperature and pressure are increased. Closing the gap between magma properties and our atomic-scale view thus requires much better information about temperature and pressure effects on melt structure. Recent progress on temperature effects has been made both by in-situ studies, and by work at ambient conditions on glass samples prepared with different cooling rates and thus capturing the melt structure at different fictive temperatures. The former type has the advantage of a greater accessible range of temperatures but can be limited by the inherent difficulties of high temperature experiments; for the latter, any structural tool may be applied but changes over the accessible range (typically Tg to Tg+200 K or less) can be subtle. We now know, for example, that in some systems local structural changes can be detected for network cations such as B, Al, and even Si, but that these can lead to either coordination decreases with T (e.g. B), correlated with thermal expansion, or to increases with T (e.g. Al in Ca aluminosilicates), correlated with entropic effects. In some systems, increases in the disorder of the network with T can be measured and correlated with heats of reaction among various bridging oxygen species. In a few cases, network modifier environments (e.g. Ni, Mg, Na) can be seen to change with T as well. But in general, extrapolating results from

  13. Influence of Heterogeneous OH Oxidation on the Evaporation Behavior and Composition of a Model Organic Aerosol

    Science.gov (United States)

    Kolesar, K. R.; Cappa, C. D.; Wilson, K. R.

    2011-12-01

    Heterogeneously oxidized squalane particles are used here as a model system to investigate the interplay between chemical composition and particle volatility. Reaction of squalane particles by OH radicals leads to the production of oxygenated products. Here we use the vacuum ultra-violet Aerosol Mass Spectrometer (VUV-AMS) at beamline 9.0.2 at the Advanced Light Source to monitor the evolution of specific oxidation products that result from increasing OH exposures, and how the composition changes as the oxidized particles evaporate. The soft ionization in the VUV-AMS allows us to uniquely track the parent squalane molecule and the various oxidation products over multiple generations of oxidation. Compositional changes of the oxidized particles resulting from evaporation have been measured in three sets of laboratory experiments. In the first set, a thermodenuder at varying temperatures was used to induce evaporation of particles at a fixed OH exposure. Second, the OH exposure was varied along with temperature to create a cross-sectional observation of particle composition at 50% mass fraction remaining for ten different oxidation levels. The combination of these two experiments provides information as to the compositional changes that occur during evaporation due to heating. In the third set of experiments, VUV-AMS spectra of oxidized squalane particles following dilution-induced evaporation were measured for comparison with the thermodenuder experiments. These experiments provide insights into the relationships between particle oxidation, composition and evaporation kinetics.

  14. The effect of irradiation, annealing temperature, and artificial aging on the oxidation, mechanical properties, and fracture mechanisms of UHMWPE.

    Science.gov (United States)

    Luisetto, Yannick; Wesslen, Bengt; Maurer, Frans; Lidgren, Lars

    2003-12-01

    UHMWPE crosslinked using Gamma radiation is believed to have improved wear properties, and this has been extensively studied during the past 10 years. Mechanical properties, oxidation, and wear properties of UHMWPE materials subjected to various thermal treatments have been investigated immediately after irradiation as well as after several years of aging. Nevertheless, the relationship between all these parameters is not yet fully understood. The aim of this study was to investigate the relationship between the thermal treatments that could be applied to irradiated UHMWPE [lower (gamma 60) or higher (gamma 150) than 140 degrees C, the melting temperature of the polymer] and the mechanical properties, the oxidation and the fracture behavior of the material. The effect of artificial aging on these properties was also investigated. This study concludes that immediately after the annealing, the mechanical properties (UTS and epsilon) of the irradiated and annealed material are improved compared with those of nonirradiated material. Although nonirradiated material has higher fracture toughness than irradiated and annealed materials, the materials break according to the same mechanism of fracture. After aging, no changes could be observed in any of the measured properties for nonirradiated material. On the other hand, important changes could be seen in both irradiated and annealed material after aging. Both UTS and epsilon decreased, much more so in the case of gamma 60. Furthermore, the aging induced a subsurface peak of oxidation in both irradiated and annealed materials, twice as intense for gamma 60 than for gamma 150. The mechanism of fracture of these materials changed drastically after aging, probably due to the presence of the oxidation peak, which seems to occur at a location where cracks initiate easily compared with the nonoxidized bulk of the material. In the case of gamma 60, it seems clear that a correlation between mechanical property, oxidation, and

  15. Temperature-related Intraspecific Variability in the Behavioral Manipulation of Acanthocephalan Parasites on Their Gammarid Hosts.

    Science.gov (United States)

    Labaude, Sophie; Cézilly, Frank; Rigaud, Thierry

    2017-04-01

    Understanding the effect of temperature on ecologically important species has become a major challenge in the context of global warming. However, the consequences of climate change cannot be accurately predicted without taking into consideration biotic interactions. Parasitic infection, in particular, constitutes a widespread biotic interaction, and parasites impact their hosts in multiple ways, eventually leading to consequences for communities and ecosystems. We explored the effect of temperature on the anti-predator behavior of a keystone freshwater invertebrate, the amphipod Gammarus fossarum. Gammarids regularly harbor manipulative acanthocephalan parasites that modify their anti-predator behavior in ways that potentially increase the probability of trophic transmission to their definitive hosts. We investigated the impact of temperature on gammarids infected by two acanthocephalan parasites, Pomphorhynchus tereticollis and Polymorphus minutus. Uninfected and naturally infected gammarids were acclimatized to different temperatures, and their behavior was measured. Our results showed that the effect of infection on the phototaxis of gammarids increased with increasing temperature, with a stronger effect induced by P. tereticollis. In contrast, temperature had no effect on the alteration of refuge use or geotaxis observed in infected gammarids. Our results provide the first direct evidence that temperature can affect the extent of behavioral alteration brought about by certain parasite species. However, the consequences of increased trophic transmission remain elusive; the supposedly key anti-predatory behavior was not significantly affected by exposure of gammarids to different temperatures.

  16. High Temperature Steam Oxidation Testing of Candidate Accident Tolerant Fuel Cladding Materials

    Energy Technology Data Exchange (ETDEWEB)

    Pint, Bruce A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Terrani, Kurt A [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Nelson, Andrew [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Parker, Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Parkison, Adam [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2013-12-23

    > formation, which reacted with the specimen to form a liquid reaction product. This behavior was not observed at lower temperatures where gas velocity and H2O content showed typical effects on the reaction rate. For LANL, the capabilities for oxidation testing as well as exploration of a methodology for measurement of hydrogen production of samples during oxidation under water vapor atmospheres is discussed. Results obtained for available commercial alloys are summarized, and data highlighting the performance of molybdenum, a recently proposed cladding material, are presented. Finally, leveraging of these techniques in conjunction with current and companion FCRD programs is discussed with respect to work in FY14.

  17. Corrosion behavior of construction materials for intermediate temperature steam electrolysers

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey; Petrushina, Irina; Jensen, Jens Oluf

    2013-01-01

    Different corrosion resistant stainless steels, nickel-based alloys, pure nickel, Ta-coated stainless steel (AISI 316L), niobium, platinum and gold rods were evaluated as possible materials for use in the intermediate temperature (200-400 °C) acidic water electrolysers. The corrosion resistance w...

  18. High-temperature thermoelectric behavior of lead telluride

    Indian Academy of Sciences (India)

    Applicability of a thermoelectric device (generator or refrigerator) is temperature specific. ... A parabolic band model usually provides a good description of electron (hole) energy bands. This simplification arises from the inclusion of only first term of a ... pends upon the mean free path lengths between successive collisions.

  19. Improving superconducting properties of YBCO high temperature superconductor by Graphene Oxide doping

    Energy Technology Data Exchange (ETDEWEB)

    Dadras, S., E-mail: dadras@alzahra.ac.ir; Dehghani, S.; Davoudiniya, M.; Falahati, S.

    2017-06-01

    In this research, we report the synthesis and characterization of YBa{sub 2}Cu{sub 3}O{sub 7-δ} (YBCO) high temperature superconductor prepared by sol-gel method and doped with Graphene Oxide (GO) in different weight percentages, 0, 0.1, 0.7 and 1 % wt. The x-ray diffraction (XRD) analysis confirms the formation of orthorhombic phase of superconductivity for all the prepared samples. We found that GO doping reduces the crystalline size of the samples. We evaluated the effects of GO doping on the normal state resistivity (ρ), superconducting transition temperature (T{sub c}) and critical current density (J{sub c}). The results show that the GO doping has a positive effect on these properties. Also, the highest J{sub c} is obtained for the 0.7 %wt GO doped YBCO compound that its critical current density is about 15 times more than the J{sub c} of pure one in 0.4 T magnetic field. The scanning electron microscope (SEM) analysis shows that there are better connections between the grains of GO doped samples. - Highlights: • Graphene Oxide doping increased the YBCO critical current density. • Graphene Oxide creates a better connection between the YBCO grains. • The normal resistivity of samples were decreased by GO doping to YBCO compounds. • Graphene Oxide doping has a positive effect on the critical transition temperature.

  20. Effect of temperature and illumination on pyrite oxidation between pH 2 and 6

    Directory of Open Access Journals (Sweden)

    Schoonen Martin

    2000-07-01

    Full Text Available The effect of heat and illumination with visible light on the oxidation of pyrite with dissolved molecular oxygen in solutions between pH 2 and 6 has been investigated using a combination of surface science experiments and batch oxidation experiments. The rate of the oxidation of pyrite is strongly dependent on temperature. It is, however, not possible to cast the temperature dependence in a simple Arrhenius equation because the magnitude of the activation energy depends on the progress variable chosen. Activation energies based on proton release rate, sulfate release rate, and total iron release rate vary by as much as 40 kJ mol-1, suggesting that the oxidation mechanism of the sulfur and iron component of pyrite are largely independent of each other. This difference in mechanism can also explain why the reaction rates on the basis of these three different progress variables do not show the same pH dependence. Exposed to visible light, the rate of pyrite oxidation is under most conditions accelerated by less than a factor of two. Some of this acceleration may be accounted for by a light-induced heating of the pyrite surface. Surface science experiments employing photoelectron spectroscopy show no evidence for significant changes in the chemical composition of the surface as a function of exposure to visible light. The batch sorption experiments show, however, that the reaction stoichiometry changes somewhat, which indicates that there might be a change in reaction mechanism as a result of exposure to visible light.

  1. Creep Behavior of High Temperature Alloys for Generation IV Nuclear Energy Systems

    Science.gov (United States)

    Wen, Xingshuo

    The Very High Temperature Reactor (VHTR) is one of the leading concepts of the Generation IV nuclear reactor development, which is the core component of Next Generation Nuclear Plant (NGNP). The major challenge in the research and development of NGNP is the performance and reliability of structure materials at high temperature. Alloy 617, with an exceptional combination of high temperature strength and oxidation resistance, has been selected as a primary candidate material for structural use, particularly in Intermediate Heat Exchanger (IHX) which has an outlet temperature in the range of 850 to 950°C and an inner pressure from 5 to 20MPa. In order to qualify the material to be used at the operation condition for a designed service life of 60 years, a comprehensive scientific understanding of creep behavior at high temperature and low stress regime is necessary. In addition, the creep mechanism and the impact factors such as precipitates, grain size, and grain boundary characters need to be evaluated for the purpose of alloy design and development. In this study, thermomechanically processed specimens of alloy 617 with different grain sizes were fabricated, and creep tests with a systematic test matrix covering the temperatures of 850 to 1050°C and stress levels from 5 to 100MPa were conducted. Creep data was analyzed, and the creep curves were found to be unconventional without a well-defined steady-state creep. Very good linear relationships were determined for minimum creep rate versus stress levels with the stress exponents determined around 3-5 depending on the grain size and test condition. Activation energies were also calculated for different stress levels, and the values are close to 400kJ/mol, which is higher than that for self-diffusion in nickel. Power law dislocation climb-glide mechanism was proposed as the dominant creep mechanism in the test condition regime. Dynamic recrystallization happening at high strain range enhanced dislocation climb and

  2. Investigation of Comfort Temperature and Occupant Behavior in Japanese Houses during the Hot and Humid Season

    Directory of Open Access Journals (Sweden)

    Hom B. Rijal

    2014-08-01

    Full Text Available In order to clarify the comfort temperature and to investigate the behavioral adaptation in Japanese houses, we have conducted a thermal comfort survey and occupant behavior survey in 30 living rooms during the hot and humid season in the Kanto region of Japan. We collected 3991 votes from 52 subjects. The comfort temperature was predicted by Griffiths’ method. They are analyzed according to humidity levels and compared with the adaptive model. The logistic regression analysis was conducted in order to understand occupant behavior. The mean comfort temperature in naturally ventilated mode is 27.6 °C which is within the acceptable zone of the adaptive model. The comfort temperature is related with skin moisture sensation. The results showed that the residents adapt to the hot and humid environments by increasing the air movement using behavioral adaptation such as window opening and fan use.

  3. Refeeding signal in fasting-incubating king penguins: changes in behavior and egg temperature

    National Research Council Canada - National Science Library

    R. Groscolas; F. Decrock; M.-A. Thil; C. Fayolle; C. Boissery; J.-P. Robin

    2000-01-01

    .... Behavior and egg temperature (Tegg) were continuously monitored by video monitoring and biotelemetry, respectively, in fasting-incubating king penguins kept in a pen to prevent relief by the partner until spontaneous egg abandonment...

  4. High temperature oxidation of alumina forming cast austenitic stainless steels within an environment of pure steam

    Science.gov (United States)

    Prenzlow, Elmer A.

    Steam cracking of hydrocarbons in the petrochemical industry is a multibillion dollar industry. The processes performed in these plants create byproducts that negatively affect the integrity of stainless steel piping through high temperature corrosion. Alloys used presently in industry rely on the formation of chromium oxide (chromia) as a protective layer between the bulk metal pipe and chemical byproducts. However, chromia can become susceptible to attack from aggressive species such as carbon, water vapor, and sulfur compounds, thus creating a need for a better protection method. A new series of austenitic stainless steels have been developed in recent years that, rather than forming chromia, create a protective layer of aluminum oxide (alumina) under oxidative conditions. These alloys have high nickel content for the stabilization of the austenitic phase, and a more thermodynamically stable oxide layer relative to the traditional chromia formers. Consequently, alumina forming alloys have been proposed as replacements for chromia forming alloys in the petrochemical industry. General oxidation testing has been performed on alumina forming alloys under dry and 10% water vapor conditions. However, oxidation conditions in industry resemble a 100% steam environment. Therefore, test methods to mimic such conditions are needed so that alloys can be tested and developed further for these applications. Four alloys with aluminum contents ranging from 2.6 to 3.9 wt% were cut from centrifugally cast pipes and subjected to oxidation in an environment of pure steam for up to 30 hours, at temperatures of 800 °C and 950 °C. Samples were analyzed using Raman, SEM, and EDS and showed a continuous alumina layer free of cracks. The alumina layer thickness increased with time. Additionally, larger thicknesses were observed in samples oxidized at 950 °C from those of 800 °C. Thickness measurements were used to calculate parabolic and non-parabolic oxidation rate constants

  5. CHALLENGES IN GENERATING HYDROGEN BY HIGH TEMPERATURE ELECTROLYSIS USING SOLID OXIDE CELLS

    Energy Technology Data Exchange (ETDEWEB)

    M. S. Sohal; J. E. O' Brien; C. M. Stoots; M. G. McKellar; J. S. Herring; E. A. Harvego

    2008-03-01

    Idaho National Laboratory’s (INL) high temperature electrolysis research to generate hydrogen using solid oxide electrolysis cells is presented in this paper. The research results reported here have been obtained in a laboratory-scale apparatus. These results and common scale-up issues also indicate that for the technology to be successful in a large industrial setting, several technical, economical, and manufacturing issues have to be resolved. Some of the issues related to solid oxide cells are stack design and performance optimization, identification and evaluation of cell performance degradation parameters and processes, integrity and reliability of the solid oxide electrolysis (SOEC) stacks, life-time prediction and extension of the SOEC stack, and cost reduction and economic manufacturing of the SOEC stacks. Besides the solid oxide cells, balance of the hydrogen generating plant also needs significant development. These issues are process and ohmic heat source needed for maintaining the reaction temperature (~830°C), high temperature heat exchangers and recuperators, equal distribution of the reactants into each cell, system analysis of hydrogen and associated energy generating plant, and cost optimization. An economic analysis of this plant was performed using the standardized H2A Analysis Methodology developed by the Department of Energy (DOE) Hydrogen Program, and using realistic financial and cost estimating assumptions. The results of the economic analysis demonstrated that the HTE hydrogen production plant driven by a high-temperature helium-cooled nuclear power plant can deliver hydrogen at a cost of $3.23/kg of hydrogen assuming an internal rate of return of 10%. These issues need interdisciplinary research effort of federal laboratories, solid oxide cell manufacturers, hydrogen consumers, and other such stakeholders. This paper discusses research and development accomplished by INL on such issues and highlights associated challenges that need to

  6. Oscillatory Behavior during the Catalytic Partial Oxidation of Methane: Following Dynamic Structural Changes of Palladium Using the QEXAFS Technique

    DEFF Research Database (Denmark)

    Stoetzel, Jan; Frahm, Ronald; Kimmerle, Bertram

    2012-01-01

    Pd/Al2O3 catalysts oscillate between ignition and extinction of the catalytic partial oxidation of methane when they are exposed to a 2:1 reaction mixture of methane and oxygen. The oscillations of the catalytic performance and the structure of Pd/Al2O3 catalysts in a fixed-bed reactor were...... investigated using spatially and time-resolved in situ quick scanning X-ray absorption spectroscopy with online mass spectrometry. The dynamic methane conversion oscillated between an inactive state, where only combustion occurred, and an active state, after ignition, where partial oxidation of methane...... of the Pd particles at increasing age of the catalyst was observed, which leads to a lower oscillation frequency. Effects of particle size, oven temperature, and oxygen/methane ratio on the oscillation behavior were studied in detail. The deactivation period (reoxidation of Pd) was much less influenced...

  7. Crack growth behavior of warm-rolled 316L austenitic stainless steel in high-temperature hydrogenated water

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Kyoung Joon; Yoo, Seung Chang [Department of Nuclear Science and Engineering, School of Mechanical and Nuclear Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Eonyang-eup, Ulju-gun, Ulsan 44919 (Korea, Republic of); Jin, Hyung-Ha; Kwon, Junhyun; Choi, Min-Jae; Hwang, Seong Sik [Nuclear Materials Safety Research Division, Korea Atomic Energy Research Institute (KAERI), 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057 (Korea, Republic of); Kim, Ji Hyun, E-mail: kimjh@unist.ac.kr [Department of Nuclear Science and Engineering, School of Mechanical and Nuclear Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Eonyang-eup, Ulju-gun, Ulsan 44919 (Korea, Republic of)

    2016-08-01

    To investigate the effects of warm rolling on the crack growth of 316L austenitic stainless steel, the crack growth rate was measured and the oxide structure was characterized in high-temperature hydrogenated water. The warm-rolled specimens showed a higher crack growth rate compared to the as-received specimens because the slip bands and dislocations produced during warm rolling served as paths for corrosion and cracking. The crack growth rate increased with the dissolved hydrogen concentration. This may be attributed to the decrease in performance and stability of the protective oxide layer formed on the surface of stainless steel in high-temperature water. - Highlights: • 316L Stainless steels were used for the study of crack growth behavior in PWR water. • Warm rolling was applied to simulate the irradiation hardening of stainless steels. • DH concentration was changed to see the effect on crack growth and oxide structure. • Warm-rolled stainless steels showed higher rates of corrosion and crack growth. • Higher DH concentration also promoted the rates of corrosion and crack growth.

  8. A Self-Validation Method for High-Temperature Thermocouples Under Oxidizing Atmospheres

    Science.gov (United States)

    Mokdad, S.; Failleau, G.; Deuzé, T.; Briaudeau, S.; Kozlova, O.; Sadli, M.

    2015-08-01

    Thermocouples are prone to significant drift in use particularly when they are exposed to high temperatures. Indeed, high-temperature exposure can affect the response of a thermocouple progressively by changing the structure of the thermoelements and inducing inhomogeneities. Moreover, an oxidizing atmosphere contributes to thermocouple drift by changing the chemical nature of the metallic wires by the effect of oxidation. In general, severe uncontrolled drift of thermocouples results from these combined influences. A periodic recalibration of the thermocouple can be performed, but sometimes it is not possible to remove the sensor out of the process. Self-validation methods for thermocouples provide a solution to avoid this drawback, but there are currently no high-temperature contact thermometers with self-validation capability at temperatures up to . LNE-Cnam has developed fixed-point devices integrated to the thermocouples consisting of machined alumina-based devices for operation under oxidizing atmospheres. These devices require small amounts of pure metals (typically less than 2 g). They are suitable for self-validation of high-temperature thermocouples up to . In this paper the construction and the characterization of these integrated fixed-point devices are described. The phase-transition plateaus of gold, nickel, and palladium, which enable coverage of the temperature range between and , are assessed with this self-validation technique. Results of measurements performed at LNE-Cnam with the integrated self-validation module at several levels of temperature will be presented. The performance of the devices are assessed and discussed, in terms of robustness and metrological characteristics. Uncertainty budgets are also proposed and detailed.

  9. Analysis of the temperature dependence of the thermal conductivity of insulating single crystal oxides

    Directory of Open Access Journals (Sweden)

    E. Langenberg

    2016-10-01

    Full Text Available The temperature dependence of the thermal conductivity of 27 different single crystal oxides is reported from ≈20 K to 350 K. These crystals have been selected among the most common substrates for growing epitaxial thin-film oxides, spanning over a range of lattice parameters from ≈3.7 Å to ≈12.5 Å. Different contributions to the phonon relaxation time are discussed on the basis of the Debye model. This work provides a database for the selection of appropriate substrates for thin-film growth according to their desired thermal properties, for applications in which heat management is important.

  10. Interplay between quantum phase transitions and the behavior of quantum correlations at finite temperatures

    OpenAIRE

    Werlang, T.; Ribeiro, G. A. P.; Rigolin, Gustavo

    2012-01-01

    We review the main results and ideas showing that quantum correlations at finite temperatures (T), in particular quantum discord, are useful tools in characterizing quantum phase transitions that only occur, in principle, at the unattainable absolute zero temperature. We first review some interesting results about the behavior of thermal quantum discord for small spin-1/2 chains and show that they already give us important hints of the infinite chain behavior. We then study in detail and in t...

  11. Identification of the Products of Oxidation of Quercetin by Air Oxygenat Ambient Temperature

    Directory of Open Access Journals (Sweden)

    Viktor A Utsal

    2007-03-01

    Full Text Available Oxidation of quercetin by air oxygen takes place in water and aqueous ethanol solutions under mild conditions, namely in moderately-basic media (pH ∼ 8-10 at ambient temperature and in the absence of any radical initiators, without enzymatic catalysis or irradiation of the reaction media by light. The principal reaction products are typical of other oxidative degradation processes of quercetin, namely 3,4-dihydroxy-benzoic (proto-catechuic and 2,4,6-trihydroxybenzoic (phloroglucinic acids, as well as the decarboxylation product of the latter – 1,3,5-trihydroxybenzene (phloroglucinol. In accordance with the literature data, this process involves the cleavage of the γ-pyrone fragment (ring C of the quercetin molecule by oxygen, with primary formation of 4,6-dihydroxy-2-(3,4-dihydroxybenzoyloxybenzoic acid (depside. However under such mild conditions the accepted mechanism of this reaction (oxidative decarbonylation with formation of carbon monoxide, CO should be reconsidered as preferably an oxidative decarboxylation with formation of carbon dioxide, CO2. Direct head-space analysis of the gaseous components formed during quercetin oxidation in aqueous solution at ambient temperature indicates that the ratio of carbon dioxide/carbon monoxide in the gas phase after acidification of the reaction media is ca. 96:4 %. Oxidation under these mild conditions is typical for other flavonols having OH groups at C3 (e.g., kaempferol, but it is completely suppressed if this hydroxyl group is substituted by a glycoside fragment (as in rutin, or a methyl substituent. An alternative oxidation mechanism involving the direct cleavage of the C2-C3 bond in the diketo-tautomer of quercetin is proposed.

  12. A fundamental study of the oxidation behavior of SI primary reference fuels with propionaldehyde and DTBP as an additive

    Science.gov (United States)

    Johnson, Rodney

    In an effort to combine the benefits of SI and CI engines, Homogeneous Charge Compression Ignition (HCCI) engines are being developed. HCCI combustion is achieved by controlling the temperature, pressure, and composition of the fuel and air mixture so that autoignition occurs in proper phasing with the piston motion. This control system is fundamentally more challenging than using a spark plug or fuel injector to determine ignition timing as in SI and CI engines, respectively. As a result, this is a technical barrier that must be overcome to make HCCI engines applicable to a wide range of vehicles and viable for high volume production. One way to tailor the autoignition timing is to use small amounts of ignition enhancing additives. In this study, the effect of the addition of DTBP and propionaldehyde on the autoignition behavior of SI primary reference fuels was investigated. The present work was conducted in a new research facility built around a single cylinder Cooperative Fuels Research (CFR) octane rating engine but modified to run in HCCI mode. It focused on the effect of select oxygenated hydrocarbons on hydrocarbon fuel oxidation, specifically, the primary reference fuels n-heptane and iso-octane. This work was conducted under HCCI operating conditions. Previously, the operating parameters for this engine were validated for stable combustion under a wide range of operating parameters such as engine speeds, equivalence ratios, compression ratios and inlet manifold temperature. The stable operating range under these conditions was recorded and used for the present study. The major focus of this study was to examine the effect of the addition of DTBP or propionaldehyde on the oxidation behavior of SI primary reference fuels. Under every test condition the addition of the additives DTBP and propionaldehyde caused a change in fuel oxidation. DTBP always promoted fuel oxidation while propionaldehyde promoted oxidation for lower octane number fuels and delayed

  13. Oxidized trilinoleate and tridocosahexaenoate induce pica behavior and change locomotor activity.

    Science.gov (United States)

    Kitamura, Fuki; Watanabe, Hiroyuki; Umeno, Aya; Yoshida, Yasukazu; Kurata, Kenji; Gotoh, Naohiro

    2013-01-01

    Pica behavior, a behavior that is characterized by eating a nonfood material such as kaolin and relates to the degree of discomfort in animals, and the variations of locomotor activity of rats after eating deteriorated fat and oil extracted from instant noodles were examined in our previous study. The result shows that oxidized fat and oil with at least 100 meq/kg in peroxide value (PV) increase pica behavior and decrease locomotor activity. In the present study, the same two behaviors were measured using autoxidized trilinoleate (tri-LA) and tridocosahexaenoate (tri-DHA) as a model of vegetable and fish oil, respectively, to compare fatty acid differences against the induction of two behaviors. The oxidized levels of tri-LA and tri-DHA were analyzed with PV and p-anisidine value (AnV), the method to analyze secondary oxidized products. The oxidation levels of respective triacylglycerol (TAG) samples were carefully adjusted to make them having almost the same PV and AnV. As the results, 600 or more meq/kg in PV of both TAGs significantly increased the consumption of kaolin pellets compared to the control group. Furthermore, 300 or more meq/kg in PV of tri-LA and 200 or more meq/kg in PV of tri-DHA demonstrated significant decrease in locomotor activity compared to control group. These results would indicate that the oxidized TAG having the same PV and/or AnV would induce the same type of pica behavior and locomotor activity. Furthermore, that the structure of oxidized products might not be important and the amount of hydroperoxide group and/or aldehyde group in deteriorated fats and oils might affect the pica behavior and locomotor activity were thought.

  14. Understanding Organic Film Behavior on Alloy and Metal Oxides

    Science.gov (United States)

    Raman, Aparna; Quiñones, Rosalynn; Barriger, Lisa; Eastman, Rachel; Parsi, Arash

    2010-01-01

    Native oxide surfaces of stainless steel 316L and Nitinol alloys and their constituent metal oxides namely, nickel, chromium, molybdenum, manganese, iron and titanium were modified with long chain organic acids to better understand organic film formation. The adhesion and stability of films of octadecylphosphonic acid, octadecylhydroxamic acid, octadecylcarboxylic acid and octadecylsulfonic acid on these substrates was examined in this study. The films formed on these surfaces were analyzed by diffuse reflectance infrared Fourier transform spectroscopy, contact angle goniometry, atomic force microscopy and matrix assisted laser desorption ionization mass spectrometry. The effect of the acidity of the organic moiety and substrate composition on the film characteristics and stability is discussed. Interestingly, on the alloy surfaces, the presence of less reactive metal sites does not inhibit film formation. PMID:20039608

  15. Effect of pyrolysis temperature on the chemical oxidation stability of bamboo biochar.

    Science.gov (United States)

    Chen, Dengyu; Yu, Xinzhi; Song, Chao; Pang, Xiaoli; Huang, Jing; Li, Yanjun

    2016-10-01

    Biochar produced by biomass pyrolysis has the advantage of carbon sequestration. However, some of the carbon atoms in biochar are not very stable. In this study, the effect of pyrolysis temperature on the chemical oxidation stability of bamboo biochar was investigated using the atomic ratios of H/C and O/C, Fourier transform infrared spectroscopy, and potassium dichromate (K2Cr2O7) oxidation spectrophotometric method. The results show that the carbon yield and ratios of H/C and O/C decreased from 71.72%, 0.71, and 0.32 to 38.48%, 0.22, and 0.06, respectively, as the temperature was increased from 300°C to 700°C. Moreover, the main oxygen-containing functional groups gradually decreased, while the degree of aromatization increased accordingly. The biochar showed a better stability at a higher pyrolysis temperature. The proportion of carbon loss, i.e., the amount of oxidized carbon with respect to the total carbon of the biochar, decreased from 16.52% to 6.69% with increasing temperature. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. New insights into the low-temperature oxidation of 2-methylhexane

    KAUST Repository

    Wang, Zhandong

    2016-09-24

    In this work, we studied the low-temperature oxidation of a stoichiometric 2-methylhexane/O2/Ar mixture in a jet-stirred reactor coupled with synchrotron vacuum ultraviolet photoionization molecular-beam mass spectrometry. The initial gas mixture was composed of 2% 2-methyhexane, 22% O2 and 76% Ar and the pressure of the reactor was kept at 780Torr. Low-temperature oxidation intermediates with two to five oxygen atoms were observed. The detection of C7H14O5 and C7H12O4 species suggests that a third O2 addition process occurs in 2-methylhexane low-temperature oxidation. A detailed kinetic model was developed that describes the third O2 addition and subsequent reactions leading to C7H14O5 (keto-dihydroperoxide and dihydroperoxy cyclic ether) and C7H12O4 (diketo-hydroperoxide and keto-hydroperoxy cyclic ether) species. The kinetics of the third O2 addition reactions are discussed and model calculations were performed that reveal that third O2 addition reactions promote 2-methylhexane auto-ignition at low temperatures. © 2016 The Combustion Institute.

  17. A Mechanism for the Oxidation-Related Influence on the Thermoelectric Behavior of Palladium

    Science.gov (United States)

    Ohm, W.-S.; Hill, K. D.

    2010-09-01

    Oxidation of thermocouple elements can degrade the accuracy of thermocouple-based temperature measurements. As a particular example of such effects, oxidation of the Pd element of a platinum/palladium thermocouple is known to increase the thermoelectric emf by an amount equivalent to a temperature change of the order of 100 mK to 200 mK at 420 °C (G. W. Burns, D. C. Ripple, Proceedings of TEMPMEKO `96, 6th International Symposium on Temperature and Thermal Measurements in Industry and Science. Levrotto and Bella, Torino, 1997, 171-176). A possible physical mechanism to explain how oxidation affects the thermoelectric output of a Pt/Pd thermocouple is proposed. The analysis hinges on the hypothesis that the oxide-induced strain within the Pd thermoelement leads to a change in the Seebeck coefficient, and therefore to the thermoelectric emf. A theoretical model relating deformation of the palladium lattice to the change in the Seebeck coefficient is presented. The level of agreement between the calculation and the experimental observations suggests that oxide-induced strain in the Pd thermoelement is a likely explanation for the change in thermoelectric output of a Pt/Pd thermocouple within the temperature range where oxidation is active.

  18. Creep Behavior of UFG CP Ti at Room Temperature

    Science.gov (United States)

    Luo, Lei; Zhao, Xicheng; Liu, XiaoYan; Yang, Xirong

    2017-10-01

    Ultra-fine grained commercial purity titanium (UFG CP Ti) is processed by Composite refining process (Equal channel angular pressing (ECAP), cold rolling and rotary swaging) at room temperature. The grain size is refined from 19 μm to 180 nm, and the ultimate tensile strength increase to 870 MPa. Creep tests were carried out on Ultra-fine grained commercial purity titanium with the stresses of 640, 660, 680, 700, 720, 740, 760 MPa at room temperature. Steady state creep rate and stress exponent n at various stresses were calculated for Ultra-fine grained commercial purity titanium, and creep deformation mechanism was also investigated. (With the rise of stress, the steady creep rate increases while the creep time decrease). The steady state creep rate reached maximum 1.416×10-6 s-1 (under) stress of 760 MPa. The stress exponent is 17.3 when the stress was 640 ∼ 700MPa, while the stress exponent is 55.7 when the stress was 700 ∼ 760MPa, UFG CP Ti shows good creep property at room temperature. The creep deformation mechanism of UFG CP Ti is the dislocation creep.

  19. Characterization and catalytic behavior of CuO rate at SiO{sub 2} nanocomposites towards NO oxidation and N{sub 2}O decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Tohidi, Seyed H.; Derhambakhsh, Maryam [Materials Research School, Karaj (Iran, Islamic Republic of). Nuclear Science and Technology Inst.; Grigoryan, Garnik L. [Yerevan State Univ. (Armenia). Inorganic Faculty

    2012-08-15

    A distinct concentration of copper was embedded into silica matrix to form xerogel using Cu(NO{sub 3}){sub 2} . 3H{sub 2}O as the copper source. The xerogel samples were prepared by hydrolysis and condensation of tetraethyl orthosilicate (TEOS) by the sol-gel method. The new molar ratio of H{sub 2}O/TEOS was determined to be 11.67. Also the necessary amount of trihydrated copper nitrate was added into the solution such that the concentration of the copper oxide in the final solution reached 10 wt.%. After ambient drying, the xerogel samples were heated to 100, 400, 600, 800, and 1 000 C at a slow heating rate (50 K h{sup -1}). The structural properties were characterized by means of transmission electron microscopy, surface analysis and thermal program reduction methods at different temperatures. Finally, the catalytic behavior of nanocomposites was studied for nitrogen oxide (NO) oxidation and di-nitrogen oxide (N{sub 2}O) decomposition reactions. The results present a systematic reactivity study of NO oxidation and N{sub 2}O decomposition on the dispersed copper oxide nanocatalysts over silica supports in order to determine the ability of these materials to convert nitrogen oxide and di-nitrogen oxide into harmless species at different temperatures. (orig.)

  20. Vacuum-arc chromium-based coatings for protection of zirconium alloys from the high-temperature oxidation in air

    Energy Technology Data Exchange (ETDEWEB)

    Kuprin, A.S.; Belous, V.A.; Voyevodin, V.N., E-mail: voyev@kipt.kharkov.ua; Bryk, V.V.; Vasilenko, R.L.; Ovcharenko, V.D.; Reshetnyak, E.N.; Tolmachova, G.N.; V' yugov, P.N.

    2015-10-15

    Multilayer Cr–Zr/Cr/Cr–N coatings for protection of zirconium alloys from the high-temperature oxidation in air have been obtained by the vacuum-arc evaporation technique with application of filters for plasma cleaning from macroparticles. The effect of the coatings on the corrosion resistance of zirconium alloys at test temperatures between 660 and 1100 °C for 3600 s has been investigated. The thickness, structure, phase composition, mechanical properties of the coatings and oxide layers before and after oxidation tests were examined by scanning electron microscopy, X-ray diffraction analysis and nanoindentation technique. It is shown that the hard multilayer coating effectively protects zirconium from the oxidation in air for 1 h at test temperatures. As a result of the oxidation in the coating the CrO and Cr{sub 2}O{sub 3} oxides are formed which reduce the oxygen penetration through the coating. At maximum test temperature of 1100 °C the oxide layer thickness in the coating is about 5 μm. The tube shape remains unchanged independent of alloy type. It has been found that uncoated zirconium oxidizes rapidly throughout the temperature range under study. At 1100 °C a porous monoclinic ZrO{sub 2} oxide layer of ≥120 μm is formed that leads to the deformation of the samples, cracking and spalling of the oxide layer.

  1. Mechanical behavior of a triaxially braided textile composite at high temperature

    Science.gov (United States)

    El Mourid, Amine

    The work presented in this thesis aimed at understanding the influence of viscoelasticity, temperature and aging on the mechanical behaviour of a textile composite using experimental, analytical and numerical tools. The studied material was a triaxially braided composite with fibres in the 0°/+/-60° directions. The yarns were made of carbon fibres, embedded in an MVK10 temperature resistant polyimide matrix. The first step consisted in developing analytical and numerical frameworks to predict viscoelastic behaviour in textile composites. Simulations were performed for both braided and woven textile architectures, at different stiffness contrasts and yarns volume fractions. The analytical framework accuracy was verified with the help of the numerical simulations. An important finding of this study was that the analytical framework, combined with the Mori-Tanaka model, leads to relatively accurate predictions for both the permanent and transient parts. Therefore, the authors believe that the Mori-Tanaka model with an adjusted aspect ratio to take into account yarn curvature is reliable for predicting viscoelastic behaviour in textile composites. The textile composite that was studied in this project did not display viscoelastic behaviour, due to the high yarn volume fraction. However, the framework remains relevant for higher temperature applications or lower yarn volume fractions. The second step was to investigate the temperature effect on the tensile behavior of the carbon/MVK10 triaxially braided composite material studied in this project. To achieve this goal, a series of room and high temperature tensile tests on both matrix and composite samples were performed. The tests on composite samples were performed along two different material directions at the maximum service temperature allowed by the Federal Aviation Administration for aircraft components, and a dedicated replication technique was developed in order to track crack densities as a function of

  2. A micro-nano porous oxide hybrid for efficient oxygen reduction in reduced-temperature solid oxide fuel cells

    Science.gov (United States)

    Da Han; Liu, Xuejiao; Zeng, Fanrong; Qian, Jiqin; Wu, Tianzhi; Zhan, Zhongliang

    2012-01-01

    Tremendous efforts to develop high-efficiency reduced-temperature (≤ 600°C) solid oxide fuel cells are motivated by their potentials for reduced materials cost, less engineering challenge, and better performance durability. A key obstacle to such fuel cells arises from sluggish oxygen reduction reaction kinetics on the cathodes. Here we reported that an oxide hybrid, featuring a nanoporous Sm0.5Sr0.5CoO3−δ (SSC) catalyst coating bonded onto the internal surface of a high-porosity La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) backbone, exhibited superior catalytic activity for oxygen reduction reactions and thereby yielded low interfacial resistances in air, e.g., 0.021 Ω cm2 at 650°C and 0.043 Ω cm2 at 600°C. We further demonstrated that such a micro-nano porous hybrid, adopted as the cathode in a thin LSGM electrolyte fuel cell, produced impressive power densities of 2.02 W cm−2 at 650°C and 1.46 W cm−2 at 600°C when operated on humidified hydrogen fuel and air oxidant. PMID:22708057

  3. PHASE CHANGES ON 4H AND 6H SIC AT HIGH TEMPERATURE OXIDATION

    Directory of Open Access Journals (Sweden)

    Jan Setiawan

    2016-10-01

    Full Text Available ABSTRACT PHASE CHANGES ON 4H AND 6H SIC AT HIGH TEMPERATURE OXIDATION. The oxidation on two silicon carbide contain 6H phase and contains 6H and 4H phases has been done.  Silicon carbide is ceramic non-oxide with excellent properties that potentially used in industry.  Silicon carbide is used in nuclear industry as structure material that developed as light water reactor (LWR fuel cladding and as a coating layer in the high temperature gas-cooled reactor (HTGR fuel.  In this study silicon carbide oxidation simulation take place in case the accident in primary cooling pipe is ruptured.  Sample silicon carbide made of powder that pressed into pellet with diameter 12.7 mm and thickness 1.0 mm, then oxidized at temperature 1000 oC, 1200 oC dan 1400 oC for 1 hour.  The samples were weighted before and after oxidized.  X-ray diffraction con-ducted to the samples using Panalytical Empyrean diffractometer with Cu as X-ray source.  Diffraction pattern analysis has been done using General Structure Analysis System (GSAS software. This software was resulting the lattice parameter changes and content of SiC phases.  The result showed all of the oxidation samples undergoes weight gain.  The 6S samples showed the highest weight change at oxidation temperature 1200 oC, for the 46S samples showed increasing tendency with the oxidation temperature.  X-ray diffraction pattern analysis showed the 6S samples contain dominan phase 6H-SiC that matched to ICSD 98-001-5325 card.  Diffraction pattern on 6S showed lattice parameter, composition and crystallite size changes.  Lattice parameters changes had smaller tendency from the model and before oxidation.  However, the lowest silicon carbide composition or the highest converted into other phases up to 66.85 %, occurred at oxidation temperature 1200 oC.  The 46S samples contains two polytypes silicon car-bide.  The 6H-SiC phases matched by ICSD 98-016-4972 card and 4H-SiC phase matched by ICSD 98

  4. Influence of heat treatment on the high temperature oxidation mechanisms of an Fe-TiCN cermet

    OpenAIRE

    Alvaredo Olmos, Paula; Abajo Clemente, Carolina; Tsipas, Sophia Alexandra; Gordo Odériz, Elena

    2014-01-01

    In this study, the oxidation behaviour of an iron matrix cermet containing 50 % vol. Ti(C,N) was investigated before and after heat treatment by oxidation tests performed in static air at temperatures between 500 °C and 1000 °C. The oxidation mechanism for this type of composite materials was established and it was found that the heat treated material presents lower mass gain than the as-sintered material at the early stages of the oxidation, due to the volatilization of oxides. The oxidation...

  5. Room temperature fatigue behavior of OFHC copper and CuAl25 specimens of two sizes

    DEFF Research Database (Denmark)

    Singhal, A.; Stubbins, J.F.; Singh, B.N.

    1994-01-01

    requiring an understanding of their fatigue behavior.This paper describes the room temperature fatigue behavior of unirradiated OFHC (oxygen-free high-conductivity) copper and CuAl25 (copper strengthened with a 0.25% atom fraction dispersion of alumina). The response of two fatigue specimen sizes to strain...... controlled fatigue loading is examined, and differences in behavior are discussed. Specimens with the smaller size are now being irradiated in several reactors...

  6. Relative effects of temperature, light, and humidity on clinging behavior of metacercariae-infected ants

    DEFF Research Database (Denmark)

    Botnevik, C.F.; Malagocka, Joanna; Jensen, Annette Bruun

    2016-01-01

    . This behavior, hypothesized to involve cramping of the mandibular muscles in a state of tetany, was observed in naturally infected F. polyctena under controlled temperature, light, and humidity conditions. We found that low temperature significantly stimulated and maintained tetany in infected ants while light...

  7. Geomechaical Behavior of Shale Rocks Under High Pressure and Temperature

    Science.gov (United States)

    Villamor Lora, R.; Ghazanfari, E.

    2014-12-01

    The mechanical properties of shale are demanding parameters for a number of engineering and geomechanical purposes. Borehole stability modeling, geophysics, shale oil and shale gas reservoirs, and underground storage of CO2 in shale formations are some of these potential applications to name a few. The growing interest in these reservoirs, as a source for hydrocarbons production, has resulted in an increasing demand for fundamental rock property data. These rocks are known to be non-linear materials. There are many factors, including induced cracks and their orientation, partial saturation, material heterogeneity and anisotropy, plasticity, strain rate, and temperature that may have an impact on the geomechanical behaviour of these shales.Experimental results and theoretical considerations have shown that the elastic moduli are not single-value, well-defined parameters for a given rock. Finding suitable values for these parameters is of vital importance in many geomechanical applications. In this study, shale heterogeneity and its geomechanical properties are explored through an extensive laboratory experimental program. A series of hydrostatic and triaxial tests were performed in order to evaluate the elasticity, viscoplasticity, yielding and failure response of Marcellus shale samples as a function of pressure and temperature. Additional characterization includes mineralogy, porosity, and permeability measurements. The shale samples were taken from a Marcellus outcrop at State Game Lands 252, located in Lycoming and Union counties, Allenwood, Pennsylvania. Laboratory experiments have shown that creep behaviour is highly sensitive to temperature. Furthermore, the non-linear nature of these rocks reveals interesting behaviour of the elastic moduli highly dependent on stress history of the rock. Results from cyclic triaxial tests point out the different behaviour between 1st-loading and unloading-reloading cycles. Experimental results of these Marcellus shales are

  8. Room temperature transparent conducting magnetic oxide (TCMO properties in heavy ion doped oxide semiconductor

    Directory of Open Access Journals (Sweden)

    Juwon Lee

    2017-08-01

    Full Text Available Bismuth doped ZnO (ZnBi0.03O0.97 thin films are grown using pulsed laser deposition. The existence of positively charged Bi, absence of metallic zinc and the Zn-O bond formation in Bi doped ZnO are confirmed using X-ray Photoelectron Spectroscopy (XPS. Temperature dependent resistivity and UV-visible absorption spectra show lowest resistivity with 8.44 × 10-4 Ω cm at 300 K and average transmittance of 93 % in the visible region respectively. The robust ferromagnetic signature is observed at 350 K (7.156 × 10-4 emu/g. This study suggests that Bi doped ZnO films should be a potential candidate for spin based optoelectronic applications.

  9. The Oxidation of a Gasoline Surrogate in the Negative Temperature Coefficient Region

    Science.gov (United States)

    2009-02-12

    During the oxidation of the surrogate, three major species were quantified that could only be produced from toluene , specifically, benzaldehyde ...were attributable to toluene decomposition, specifi- cally, benzaldehyde , benzene, phenol, and ethyl-benzene. Two new pathways have been suggested to...Surrogate n-Heptane Iso-octane Toluene 1-Pentene Flow reactor This experimental study investigated the preignition reactivity behavior of a gasoline

  10. Temperature-dependent optical resonance in a thin-walled tubular oxide microcavity

    Directory of Open Access Journals (Sweden)

    Yangfu Fang

    2017-08-01

    Full Text Available This work proposes a temperature-response capability of optical resonance in tubular optical oxide microcavities. The thin wall thickness with a subwavelength scale enables these microcavities to interact with the environment effectively. By optimization of the geometries and materials, the tubular microcavities can be tuned into temperature-inert in vacuum, and the experiments support this design. The experiments prove the idea of utilizing them as temperature-inert microcavities. Contrary wavelength shifts from previous studies were observed, which can be explained with the theoretical model. Furthermore, the theoretical results of the present work suggest that novel rolled-up microtubes could act as an exceptional optical microcavity for the application in temperature response.

  11. Method of Hydrogenous Fuel Usage to Increase the Efficiency in Tandem Diverse Temperature Oxidation System

    Directory of Open Access Journals (Sweden)

    Zubkova Marina

    2016-01-01

    Full Text Available This paper presents the results of estimation energy efficiency, the collation data of thermodynamic calculations and data on material balance for an assessment of electric and thermal components in considered ways to use convention products, performance enhancement in the tandem system containing the high-temperature fuel cell and the low-temperature fuel cell with full heat regeneration for hydrogenous fuel (CH4. The overall effective efficiency (ηΣef. making full use of the recovered heat considered tandem system depends on the efficiency of its constituent fuel cells. The overall effective efficiency of the tandem installation including the fuel converter, separating system, high-temperature oxidation system, and hydrogen disposal system in case of fuel use in the low-temperature fuel cell, is higher than for each of the fuel cell elements separately.

  12. Oxidative stress and antioxidant defense responses of Etroplus suratensis to acute temperature fluctuations.

    Science.gov (United States)

    Joy, Susan; Alikunju, Aneesa Painadath; Jose, Jisha; Sudha, Hari Sankar Haridasanpillai; Parambath, Prabhakaran Meethal; Puthiyedathu, Sajeevan Thavarool; Philip, Babu

    2017-12-01

    Fishes are always exposed to various environmental stresses and the chances of succumbing to such stresses are of great physiological concern. Any change in temperature from the ambient condition can induce various metabolic and physiological changes in the body. The present study evaluates the effects of temperature induced stress on the antioxidant profile of Etroplus suratensis such as superoxide dismutase, catalase, glutathione peroxidase and lipid peroxidation. Fishes of same size were kept in a thermostatized bath at three different temperature regimes viz 16°C, 27°C (ambient temperature) and 38°C for 72h. These temperatures were selected based on the CT Max (Critical Thermal Maximum) and CT Min (Critical Thermal Minimum) exhibited by E. suratensis. Superoxide dismutase and catalase activity was found maximum in brain and muscle respectively during the 48th hour of exposure in fishes kept at 38°C. At 16°C the antioxidant response of glutathione peroxidase was maximum in muscles, whereas the lipid peroxidation rate was found to be high in gills compared to other tissues. The profound increase in the levels of oxidative stress related biomarkers indicate that the thermal stressors severely affected oxidative state of E. suratensis by the second day of experiment. Such down-regulation of redox state accompanied with the induction of oxidative stress cascade may lead to physiological damage in various tissues in fishes, in vivo. However current data indicate that a transition to low and high temperature environment from ambient condition severely affected the levels and profile of the antioxidant markers overtime in E. suratensis. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. In vitro corrosion behavior and cellular response of thermally oxidized Zr-3Sn alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, F.Y.; Wang, B.L.; Qiu, K.J. [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); Li, H.F. [Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Li, L. [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); Zheng, Y.F., E-mail: yfzheng@pku.edu.cn [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Han, Y. [State Key Laboratory for Mechanical Behavior of Materials, Xian Jiaotong University, Xian 710049 (China)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer A main monoclinic ZrO{sub 2} layer formed on ZrSn alloy after thermal oxidation. Black-Right-Pointing-Pointer Corrosion resistance of ZrSn alloy was improved with thermal oxidation. Black-Right-Pointing-Pointer The oxide layer inhibited the release of the ions into the mediums. Black-Right-Pointing-Pointer Oxidized ZrSn alloy exhibited an excellent in vitro biocompatibility. - Abstract: In this study, ZrSn alloy was thermally oxidized at 600 Degree-Sign C for 3 h and its morphological and structural characteristics, corrosion behavior, ion release and in vitro cytocompatibility were studied to evaluate the feasibility of applying it as dental implant. After oxidation, a dense black oxide layer formed on ZrSn alloy surface, which consisted of predominant monoclinic zirconia and a few non-stoichiometric oxides. The scratching and water contact angle test results demonstrated that the oxide layer exhibited good adhesion strength and similar hydrophilicity to zirconia. The oxidized ZrSn alloy showed higher corrosion resistance, as indicated by far lower corrosion current density and passive current density compared to pure Ti and untreated ZrSn alloy in artificial saliva with and without H{sub 2}O{sub 2}. The amount of ions released from the oxidized ZrSn alloy was much lower than that dissolved from pure Ti in simulated corrosive oral mediums. Moreover, the oxidized ZrSn alloy did not present any significant toxic effect to both osteoblast-like cells and fibroblast cells, and osteoblast-like cells could adhere well onto the surface and exhibited a good proliferative pattern. The combination of improved surface properties, superior corrosion resistance and good biocompatibility made the oxidized ZrSn alloy promising for oral implantology application.

  14. Modifications of operant thermoregulatory behavior of the young pig by environmental temperature and food availability.

    Science.gov (United States)

    Swiergiel, A H

    1997-12-31

    Piglets (Sus scrofa domesticus) were weaned at 14 days and acclimated to 10 ("cold animals") or 35 degrees C ("warm animals"). Cold animals were either fed ad lib. (10HH) or maintained on a high (10H) or low (10L) nutrition plane. Warm animals were maintained on a high (35H), low (35L), or a very low (35LL) nutrition plane. After 3 weeks of acclimation, operant thermoregulatory behavior (animals pressed a lever to turn on a heater) at 15 degrees C was assessed immediately following or 22 h after a meal. It was found that cold piglets or those on low nutrition planes produced more heat reinforcements than warm piglets and those on high nutrition planes. All animals tested 22 h after a meal produced more reinforcements than when tested immediately after a meal. Rectal temperature before the sessions of operant heating was lower in cold animals and those on low nutrition planes than in warm animals and those on high nutrition planes, but the difference dissipated after 90 min of access to heat. Piglets were then "deacclimated" for 24 h at 25 degrees C and their behavior observed once again. Deacclimation eliminated the effect of acclimation temperature on body temperature and behavior but it did not eliminate the effect due to nutrition. There was no interaction between temperature of acclimation and nutrition. The experiments demonstrate that the body temperature of the pig is independently affected by environmental temperature, the quantity of food eaten by the animal, and a possibility to use behavior. The behavioral drive is to reach body temperature which can be defined as a thermal set-point (temperature at which there is no need for a thermoregulatory response to occur) for behavioral thermoregulatory responses. Adaptation to different environmental conditions does not affect this behavioral set-point, but it can involve a temporary shift in the set points for specific autonomic thermoregulatory responses.

  15. Effects of temperature on nitrous oxide (N2O) emission from intensive aquaculture system.

    Science.gov (United States)

    Paudel, Shukra Raj; Choi, Ohkyung; Khanal, Samir Kumar; Chandran, Kartik; Kim, Sungpyo; Lee, Jae Woo

    2015-06-15

    This study examines the effects of temperature on nitrous oxide (N2O) emissions in a bench-scale intensive aquaculture system rearing Koi fish. The water temperature varied from 15 to 24 °C at interval of 3 °C. Both volumetric and specific rate for nitrification and denitrification declined as the temperature decreased. The concentrations of ammonia and nitrite, however, were lower than the inhibitory level for Koi fish regardless of temperature. The effects of temperature on N2O emissions were significant, with the emission rate and emission factor increasing from 1.11 to 1.82 mg N2O-N/d and 0.49 to 0.94 mg N2O-N/kg fish as the temperature decreased from 24 to 15 °C. A global map of N2O emission from aquaculture was established by using the N2O emission factor depending on temperature. This study demonstrates that N2O emission from aquaculture is strongly dependent on regional water temperatures as well as on fish production. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Relations of Counterface Hardness with Wear Behavior and Tribo-Oxide Layer of AISI H13 Steel

    Science.gov (United States)

    Zhang, Q. Y.; Wang, S. Q.; Li, X. X.; Zhou, Y.; Chen, K. M.; Cui, X. H.

    2016-12-01

    Dry sliding wear tests of AISI H13 steel (50 HRC) against AISI D2 steel counterface with three hardness levels (55, 50, and 42 HRC) were performed at 298 K to 873 K (25 °C to 600 °C). The relations of counterface hardness with the wear behavior and tribo-oxide layer of AISI H13 steel were explored. When sliding against the different-hardness counterface, H13 steel presents appreciably changed wear behavior as a function of temperature. For H d/ H p (the hardness ratio of disk to pin) > 1, the wear rate increases with the increase of temperature, but the wear rate variation is roughly inversed for H d/ H p 1, at 474 K (200 °C) for H d/ H p = 1, and at 673 K (400 °C) for H d/ H p 1 and at 673 K to 873 K (400 °C to 600 °C) for H d/ H p = 1. These findings suggest that the tribo-oxide layers are liable to exist stably for H d/ H p ≤ 1 but to readily delaminate for H d/ H p > 1.

  17. Enhancement of room temperature ferromagnetism in tin oxide nanocrystal using organic solvents

    Science.gov (United States)

    Sakthiraj, K.; Hema, M.; Balachandra Kumar, K.

    2017-10-01

    The effect of organic solvents (ethanol & ethylene glycol) on the room temperature ferromagnetism in nanocrystalline tin oxide has been studied. The samples were synthesized using sol-gel method with the mixture of water & organic liquid as solvent. It is found that pristine SnO2 nanocrystal contain two different types of paramagnetic centres over their surface:(i) surface chemisorbed oxygen species and (ii) Sn interstitial & oxygen vacancy defect pair. The magnetic moment induced in the as-prepared samples is mainly contributed by the alignment of local spin moments resulting from these defects. These surface defect states are highly activated by the usage of ethylene glycol solvent rather than ethylene in tin oxide nanostructure synthesis. Powder X-ray diffraction, transmission electron microscope imaging, energy dispersive spectrometry, Fourier transformed infrared spectroscopy, UV-vis absorption spectroscopy, photoluminescence spectroscopy, vibrating sample magnetometer measurement and electron spin resonance spectroscopy were employed to characterize the nanostructured tin oxide materials.

  18. Low-Energy, Low-Cost Production of Ethylene by Low- Temperature Oxidative Coupling of Methane

    Energy Technology Data Exchange (ETDEWEB)

    Radaelli, Guido [Siluria Technologies, Inc., San Francisco, CA (United States); Chachra, Gaurav [Siluria Technologies, Inc., San Francisco, CA (United States); Jonnavittula, Divya [Siluria Technologies, Inc., San Francisco, CA (United States)

    2017-12-30

    In this project, we develop a catalytic process technology for distributed small-scale production of ethylene by oxidative coupling of methane at low temperatures using an advanced catalyst. The Low Temperature Oxidative Coupling of Methane (LT-OCM) catalyst system is enabled by a novel chemical catalyst and process pioneered by Siluria, at private expense, over the last six years. Herein, we develop the LT-OCM catalyst system for distributed small-scale production of ethylene by identifying and addressing necessary process schemes, unit operations and process parameters that limit the economic viability and mass penetration of this technology to manufacture ethylene at small-scales. The output of this program is process concepts for small-scale LT-OCM catalyst based ethylene production, lab-scale verification of the novel unit operations adopted in the proposed concept, and an analysis to validate the feasibility of the proposed concepts.

  19. Effect of electrolyte temperature on the thickness of anodic aluminium oxide (AAO layer

    Directory of Open Access Journals (Sweden)

    P. Michal

    2016-07-01

    Full Text Available Effect of electrolyte temperature on the thickness of resulting oxide layer has been studied. Unlike previous published studies this article was aimed to monitor the relationship between electrolyte temperature and resulting AAO layer thickness in interaction with other input factors affecting during anodizing process under special process condition, i.e. lower concentration of sulphuric acid, oxalic acid, boric acid and sodium chloride. According to Design of Experiments (DOE 80 individual test runs of experiment were carried out. Using statistical analysis and artificial intelligence for evaluation, the computational model predicting the thickness of oxide layer in the range from 5 / μm to 15 / μm with tolerance ± 0,5 / μm was developed.

  20. Low-temperature atomic layer deposition of copper(II) oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Iivonen, Tomi, E-mail: tomi.iivonen@helsinki.fi; Hämäläinen, Jani; Mattinen, Miika; Popov, Georgi; Leskelä, Markku [Laboratory of Inorganic Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki (Finland); Marchand, Benoît; Mizohata, Kenichiro [Division of Materials Physics, Department of Physics, University of Helsinki, P.O. Box 43, FI-00014 Helsinki (Finland); Kim, Jiyeon; Fischer, Roland A. [Chair of Inorganic Chemistry II, Ruhr-University Bochum, Universitätsstrasse 150, 44780 Bochum (Germany)

    2016-01-15

    Copper(II) oxide thin films were grown by atomic layer deposition (ALD) using bis-(dimethylamino-2-propoxide)copper [Cu(dmap){sub 2}] and ozone in a temperature window of 80–140 °C. A thorough characterization of the films was performed using x-ray diffraction, x-ray reflectivity, UV‐Vis spectrophotometry, atomic force microscopy, field emission scanning electron microscopy, x-ray photoelectron spectroscopy, and time-of-flight elastic recoil detection analysis techniques. The process was found to produce polycrystalline copper(II) oxide films with a growth rate of 0.2–0.3 Å per cycle. Impurity content in the films was relatively small for a low temperature ALD process.

  1. A High Temperature Cyclic Oxidation Data Base for Selected Materials Tested at NASA Glenn Research Center

    Science.gov (United States)

    Barrett, Charles A.

    2003-01-01

    The cyclic oxidation test results for some 1000 high temperature commercial and experimental alloys have been collected in an EXCEL database. This database represents over thirty years of research at NASA Glenn Research Center in Cleveland, Ohio. The data is in the form of a series of runs of specific weight change versus time values for a set of samples tested at a given temperature, cycle time, and exposure time. Included on each run is a set of embedded plots of the critical data. The nature of the data is discussed along with analysis of the cyclic oxidation process. In addition examples are given as to how a set of results can be analyzed. The data is assembled on a read-only compact disk which is available on request from Materials Durability Branch, NASA Glenn Research Center, Cleveland, Ohio.

  2. Preparation, characterization and electrocatalytic behavior of zinc oxide/zinchexacyanoferrate and ruthenium oxide hexacyanoferrate hybrid film-modified electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Chu, H.-W.; Thangamuthu, R. [Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, No. 1, Section 3, Chung-Hsiao East Road, Taipei 106, Taiwan (China); Chen, S.-M. [Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, No. 1, Section 3, Chung-Hsiao East Road, Taipei 106, Taiwan (China)], E-mail: smchen78@ms15.hinet.net

    2008-02-15

    Polynuclear mixed-valent hybrid films of zinc oxide/zinchexacyanoferrate and ruthenium oxide hexacyanoferrate (ZnO/ZnHCF-RuOHCF) have been deposited on electrode surfaces from H{sub 2}SO{sub 4} solution containing Zn(NO{sub 3}){sub 2}, RuCl{sub 3} and K{sub 3}[Fe(CN){sub 6}] by potentiodynamic cycling method. Simultaneous cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM) measurements demonstrate the steady growth of hybrid film. Surface morphology of hybrid film was investigated using scanning electron microscopy (SEM). Energy dispersive spectrometer (EDS) data confirm existence of zinc oxide and ruthenium oxide hexacyanoferrate (RuOHCF) in the hybrid film. The effect of type of monovalent cations on the redox behavior of hybrid film was investigated. In pure supporting electrolyte, electrochemical responses of Ru{sup II/III} redox transition occurring at negative potential region resemble with that of a surface immobilized redox couple. The electrocatalytic activity of ZnO/ZnHCF-RuOHCF hybrid film was investigated towards oxidation of epinephrine, dopamine and L-cysteine, and reduction of S{sub 2}O{sub 8}{sup 2-} and SO{sub 5}{sup 2-} as well as IO{sub 3}{sup -} using cyclic voltammetry and rotating ring disc electrode (RRDE) techniques.

  3. THE INFLUENCE OF OBESITY AND AMBIENT TEMPERATURE ON PHYSIOLOGICAL AND OXIDATIVE RESPONSES TO SUBMAXIMAL EXERCISE

    OpenAIRE

    Ahn, N.; Kim, K.

    2014-01-01

    This study investigated the effects of obesity and ambient temperature on physiological responses and markers of oxidative stress to submaximal exercise in obese and lean people. Sixteen healthy males were divided into an obese group (n=8, %fat: 27.00±3.00%) and a lean group (n=8, %fat: 13.85±2.45%). Study variables were measured during a 60 min submaximal exercise test at 60% VO2max in a neutral (21±1°C) and a cold (4±1°C) environment. Heart rate, blood lactate, rectal temperature, serum lev...

  4. Optimizing headspace sampling temperature and time for analysis of volatile oxidation products in fish oil

    DEFF Research Database (Denmark)

    Rørbæk, Karen; Jensen, Benny

    1997-01-01

    Headspace-gas chromatography (HS-GC), based on adsorption to Tenax GR(R), thermal desorption and GC, has been used for analysis of volatiles in fish oil. To optimize sam sampling conditions, the effect of heating the fish oil at various temperatures and times was evaluated from anisidine values (......) and HS-CC. AV indicated sample degradations at 90 degrees C but only small alterations between 60 and 75 degrees C. HS-GC showed increasing response with temperature and rime. Purging at 75 degrees C for 45 min was selected as the preferred sampling condition for oxidized fish oil....

  5. Room-temperature fabrication of light-emitting thin films based on amorphous oxide semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Junghwan, E-mail: JH.KIM@lucid.msl.titech.ac.jp; Miyokawa, Norihiko; Ide, Keisuke [Materials and Structures Laboratory, Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Toda, Yoshitake [Materials Research Center for Element Strategy, Tokyo Institute of Technology, Mailbox SE-6, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio [Materials and Structures Laboratory, Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, Mailbox SE-6, 4259 Nagatsuta, Midori-ku, Yokohama (Japan)

    2016-01-15

    We propose a light-emitting thin film using an amorphous oxide semiconductor (AOS) because AOS has low defect density even fabricated at room temperature. Eu-doped amorphous In-Ga-Zn-O thin films fabricated at room temperature emitted intense red emission at 614 nm. It is achieved by precise control of oxygen pressure so as to suppress oxygen-deficiency/excess-related defects and free carriers. An electronic structure model is proposed, suggesting that non-radiative process is enhanced mainly by defects near the excited states. AOS would be a promising host for a thin film phosphor applicable to flexible displays as well as to light-emitting transistors.

  6. Sorption characteristics of fluoride on to magnesium oxide-rich phases calcined at different temperatures.

    Science.gov (United States)

    Sasaki, Keiko; Fukumoto, Naoyuki; Moriyama, Sayo; Hirajima, Tsuyoshi

    2011-07-15

    The effect of calcination temperature during production of magnesium oxide-rich phases from MgCO(3) on the sorption of F(-) ions in the aqueous phase has been investigated. Magnesium oxide-rich phases were formed by calcination at over 873 K for 1h. Higher calcination temperatures produced more crystalline MgO with smaller specific surface area and provided larger values of the total basicity per unit surface area. The higher calcination temperatures lead to slower F(-) removal rate, and lower equilibrium F(-) concentrations, when the equilibrium F(-) concentrations are less than 1 mmol dm(-3). Larger total basicity per unit surface area made the reactivity with F(-) ions in aqueous phase more feasible, resulting in a greater degree of F(-) sorption. For equilibrium F(-) concentrations more than 1 mmol dm(-3), lower calcination temperatures favored the co-precipitation of F(-) with Mg(OH)(2), probably leading to the formation of Mg(OH)(2-x)F(x), and the achievement of larger sorption density. This is the first paper which describes the relationship between the solid base characteristics obtained by CO(2)-TPD for MgO with different calcination temperatures as a function of the reactivity of F(-) sorption in the aqueous phase. Copyright © 2011 Elsevier B.V. All rights reserved.

  7. Oxidative Stress, Motor Abilities, and Behavioral Adjustment in Children Treated for Acute Lymphoblastic Leukemia.

    Science.gov (United States)

    Hockenberry, Marilyn J; Krull, Kevin R; Insel, Kathleen C; Harris, Lynnette L; Gundy, Patricia M; Adkins, Kristin B; Pasvogel, Alice E; Taylor, Olga A; Koerner, Kari M; Montgomery, David W; Ross, Adam K; Hill, Adam; Moore, Ida M

    2015-09-01

    To examine associations among oxidative stress, fine and visual-motor abilities, and behavioral adjustment in children receiving chemotherapy for acute lymphoblastic leukemia (ALL)
. A prospective, repeated-measures design
. Two pediatric oncology settings in the southwestern United States. 89 children with ALL were followed from diagnosis to the end of chemotherapy. Serial cerebrospinal fluid samples were collected during scheduled lumbar punctures and analyzed for oxidative stress biomarkers. Children completed fine motor dexterity, visual processing speed, and visual-motor integration measures at three time points. Parents completed child behavior ratings at the same times. Oxidative stress, fine motor dexterity, visual processing, visual-motor integration, and behavioral adjustment
. Children with ALL had below-average fine motor dexterity, visual processing speed, and visual-motor integration following the induction phase of ALL therapy. By end of therapy, visual processing speed normalized, and fine motor dexterity and visual-motor integration remained below average. Oxidative stress measures correlated with fine motor dexterity and visual-motor integration. Decreased motor functioning was associated with increased hyperactivity and anxiety
. Oxidative stress occurs following chemo-therapy for childhood ALL and is related to impaired fine motor skills and visual symptoms
. Early intervention should be considered to prevent fine motor and visual-spatial deficits, as well as behavioral problems.

  8. Adsorption behavior and mechanism of methyl blue on zinc oxide nanoparticles

    Science.gov (United States)

    Zhang, Fan; Lan, Jing; Yang, Ye; Wei, Tiefeng; Tan, Ruiqin; Song, Weijie

    2013-11-01

    The adsorption behavior and mechanism of methyl blue (MB) on zinc oxide (ZnO) nanoparticles were investigated in this work. The adsorption capacity of MB on the ZnO nanoparticles reached 10.70 ± 0.80 mmol/g, which was the highest among today's adsorbents for removing MB. The adsorption process was independent of pH and temperature in the experimental range. The adsorption kinetics was elucidated by the pseudo-second-order model and exhibited 2-stage intra-particle diffusion model. The adsorption isotherm fitted well with the Temkin model. The calculated parameter from Temkin model indicated the adsorption process was spontaneous with a uniform distribution of binding energies. The mechanism studies by XPS analysis confirmed that ionic bonding between Zn2+ in Zn(OH)+ and sulfonic groups of MB was the major interaction between MB and ZnO nanoparticles. The adsorption for MB by ZnO nanoparticles was selective. This work indicates that ZnO nanoparticles are promising adsorbents for removal of MB from waste water.

  9. Adsorption behavior and mechanism of methyl blue on zinc oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Fan [Chinese Academy of Sciences, Ningbo Institute of Material Technology and Engineering (China); Lan, Jing [Qingdao Agricultural University, College of Chemistry and Pharmaceutical Sciences (China); Yang, Ye; Wei, Tiefeng [Chinese Academy of Sciences, Ningbo Institute of Material Technology and Engineering (China); Tan, Ruiqin [Ningbo University, Faculty of Information Science and Engineering (China); Song, Weijie, E-mail: weijiesong@nimte.ac.cn [Chinese Academy of Sciences, Ningbo Institute of Material Technology and Engineering (China)

    2013-11-15

    The adsorption behavior and mechanism of methyl blue (MB) on zinc oxide (ZnO) nanoparticles were investigated in this work. The adsorption capacity of MB on the ZnO nanoparticles reached 10.70 ± 0.80 mmol/g, which was the highest among today’s adsorbents for removing MB. The adsorption process was independent of pH and temperature in the experimental range. The adsorption kinetics was elucidated by the pseudo-second-order model and exhibited 2-stage intra-particle diffusion model. The adsorption isotherm fitted well with the Temkin model. The calculated parameter from Temkin model indicated the adsorption process was spontaneous with a uniform distribution of binding energies. The mechanism studies by XPS analysis confirmed that ionic bonding between Zn{sup 2+} in Zn(OH){sup +} and sulfonic groups of MB was the major interaction between MB and ZnO nanoparticles. The adsorption for MB by ZnO nanoparticles was selective. This work indicates that ZnO nanoparticles are promising adsorbents for removal of MB from waste water.

  10. Low Temperature Synthesis of Metal Oxides by a Supercritical Seed Enhanced Crystallization (SSEC) Process

    DEFF Research Database (Denmark)

    Jensen, Henrik; Brummerstedt Iversen, Steen; Joensen, Karsten Dan

    2006-01-01

    A novel method for producing crystalline nanosized metal oxides by a Supercritical Seed Enhanced Crystallization (SSEC) Process has been developed. The process is a modified sol-gel process taking place at temperatures as low as 95 ºC with supercritical CO2 as solvent and polypropylene as seeding....... The crystallinity can be controlled by changing the heating rate of the initial formation of the nanoparticles and the morphology can be altered by changing the process time....

  11. Temperature dependence of Hall mobility in indium--tin oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Morris, J.E.; Ridge, M.I.; Bishop, C.A.; Howson, R.P.

    1980-03-01

    Carrier concentrations and mobilities of vacuum-prepared indium--tin oxide films have been measured to determine the effects of annealing. The apparent variation of electron mobility with temperature in these films is interpreted in terms of a grain-boundary barrier model. No grain growth was observed in the films studied; all changes in electron density and mobility may be explained by oxygen diffusion in the grain boundaries and, from them, into the grains themselves.

  12. Facile reduction of graphene oxide at room temperature by ammonia borane via salting out effect.

    Science.gov (United States)

    Zhuo, Qiqi; Zhang, Yiping; Du, Qingchuan; Yan, Chao

    2015-11-01

    Nascent hydrogen as a strong reducing and environmentally benign agent can be used as the efficient reductant of graphene oxide. The common method is to dissolve metal in acid graphene oxide (GO) solution to generate nascent hydrogen and reduce graphene oxide. However, hydrophobic metal particles cannot contact well with hydrophilic GO. Lots of nascent hydrogen atoms generated surrounding metal particles would quickly form hydrogen instead of reducing GO, which results in low reduction efficiency. In this work, based on the salting effect of GO, we report a facile approach to synthesize graphene by mild reducing of GO using NH3BH3 as the reducing agent and Co3O4 as the catalyst at room temperature. This method exhibited higher nascent hydrogen reduction efficiency and higher C/O atomic ratio of reduced graphene oxide than using Fe, Zn, and Al among others. Also the reaction is conducted under mild conditions (room temperature), resulting in fewer defects. Crown Copyright © 2015. Published by Elsevier Inc. All rights reserved.

  13. Effect of the temperature on structural and optical properties of zinc oxide nanoparticles.

    Science.gov (United States)

    Hadia, N M A; García-Granda, Santiago; García, José R

    2014-07-01

    Zinc nitrate hexahydrate, Zn(NO3)2 x 6H2O was used as a precursor with urea NH2CONH2 to prepare hydrozincite Zn5(CO3)2(OH)6 powder using hydrothermal method for 8 h at 90 degrees C. Zinc oxide (ZnO) nanoparticles (NPs) were prepared by thermal annealing of hydrozincite powder at different annealing temperatures, i.e., 350, 550 750 and 950 degrees C in air for 2 h. The resulting materials were characterized by X-ray diffraction, scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). The optical properties of the products were characterized by Fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy and photoluminescence (PL) spectra. It was found that the particle size increased from - 33 to 250 nm with increasing in the annealing temperatures. FTIR results showed that the standard peaks of zinc oxide were presented at 428.17 and 532.32 cm(-1). Thermal analysis study showed that the primary weight loss starts at - 93 degrees C is due to solvent evaporation. The secondary weight loss, observed at - 378 degrees C, is due to phase transition from hydrated zinc oxide to zinc oxide. The band gaps of the products were in the range - 3.26-3.30 eV. The PL spectrum showed that the as-synthesized ZnO nanoparticles had UV (381 nm) and green (537 nm) emissions.

  14. Propene oxidation at low and intermediate temperatures: A detailed chemical kinetic study

    Energy Technology Data Exchange (ETDEWEB)

    Wilk, R.D.; Gernansky, N.P.; Pitz, W.J.; Westbrook, C.K.

    1987-01-01

    A detailed chemical kinetic mechanism for propene oxidation is developed and used to model reactions in a static reactor at temperatures of 575-715 K, equivalence ratios of 0.8 - 2.0, and a pressure of 600 torr. Modeling of hydrocarbon oxidation in this temperature range is important for the validation of detailed models to be used for performing calculations related to automotive engine knock. The model predicted induction periods and species concentrations for all the species and all conditions measured experimentally in the static reactor. Overall, the calculated concentrations of carbon monoxide, acetaldehyde, acrolein, and propene oxide agreed well with those measured. The calculated concentrations of ethene are low compared to the experimental measurements, and the calculated concentrations of formaldehyde are high. Agreement for concentrations of carbon dioxide, methane, and methanol is mixed. The characteristic s-shape of the fuel concentration history is well predicted. Modeling calculations identified some of the key reaction steps at the present conditions. Addition of OH to propene and H atom abstraction by OH from propene are important steps in determining the subsequent distributions of intermediate products, such as acetaldehyde, acrolein and formaldehyde. Allyl radicals are very abundant in propene oxidation, and the primary steps found to be responsible for their consumption are reaction with CH/sub 3/O/sub 2/ and HO/sub 2/.

  15. Propene oxidation at low and intermediate temperatures: A detailed chemical kinetic study

    Energy Technology Data Exchange (ETDEWEB)

    Wilk, R.D.; Cernansky, N.P.; Pitz, W.J.; Westbrook, C.K.

    1987-03-24

    A detailed chemical kinetic mechanism for propene oxidation is developed and used to model reactions in a static reactor at temperatures of 575-715 K, equivalence ratios of 0.8 - 2.0, and a pressure of 600 torr. Modeling of hydrocarbon oxidation in this temperature range is important for the validation of detailed models to be used for performing calculations related to automotive engine knock. The model predicted induction periods and species concentrations for all the species and all conditions measured experimentally in the static reactor. Overall, the calculated concentrations of carbon monoxide, acetaldehyde, acrolein, and propane oxide agreed well with those measured. The calculated concentrations of ethane are low compared to the experimental measurements, and the calculated concentrations of formaldehyde are high. Agreement for concentrations of carbon dioxide, methane, and methanol is mixed. The characteristic s-shape of the fuel concentration history is well predicted. Modeling calculations identified some of the key reaction steps at the present conditions. Addition of OH to propene and H atom abstraction by OH from propene are important steps in determining the subsequent distributions of intermediate products, such as acetaldehyde, acrolein and formaldehyde. Allyl radicals are very abundant in propene oxidation, and the primary steps found to be responsible for their consumption are reaction with CH/sub 3/O/sub 2/ and HO/sub 2/. 37 refs., 5 figs., 1 tab.

  16. Auger electron spectroscopy study of oxidation of a PdCr alloy used for high-temperature sensors

    Science.gov (United States)

    Boyd, Darwin L.; Zeller, Mary V.; Vargas-Aburto, Carlos

    1993-01-01

    A Pd-13 wt. percent Cr solid solution is a promising high-temperature strain gage alloy. In bulk form it has a number of properties that are desirable in a resistance strain gage material, such as a linear electrical resistance versus temperature curve to 1000 C and stable electrical resistance in air at 1000 C. However, unprotected fine wire gages fabricated from this alloy perform well only to 600 C. At higher temperatures severe oxidation degrades their electrical performance. In this work Auger electron spectroscopy was used to study the oxidation chemistry of the alloy wires and ribbons. Results indicate that the oxidation is caused by a complex mechanism that is not yet fully understood. As expected, during oxidation, a layer of chromium oxide is formed. This layer, however, forms beneath a layer of metallic palladium. The results of this study have increased the understanding of the oxidation mechanism of Pd-13 wt. percent Cr.

  17. Measuring the complex behavior of the SO2 oxidation reaction

    Directory of Open Access Journals (Sweden)

    Muhammad Shahzad

    2015-09-01

    Full Text Available The two step reversible chemical reaction involving five chemical species is investigated. The quasi equilibrium manifold (QEM and spectral quasi equilibrium manifold (SQEM are used for initial approximation to simplify the mechanisms, which we want to utilize in order to investigate the behavior of the desired species. They show a meaningful picture, but for maximum clarity, the investigation method of invariant grid (MIG is employed. These methods simplify the complex chemical kinetics and deduce low dimensional manifold (LDM from the high dimensional mechanism. The coverage of the species near equilibrium point is investigated and then we shall discuss moving along the equilibrium of ODEs. The steady state behavior is observed and the Lyapunov function is utilized to study the stability of ODEs. Graphical results are used to describe the physical aspects of measurements.

  18. Temperature dependence of electron magnetic resonance spectra of iron oxide nanoparticles mineralized in Listeria innocua protein cages

    Science.gov (United States)

    Usselman, Robert J.; Russek, Stephen E.; Klem, Michael T.; Allen, Mark A.; Douglas, Trevor; Young, Mark; Idzerda, Yves U.; Singel, David J.

    2012-10-01

    Electron magnetic resonance (EMR) spectroscopy was used to determine the magnetic properties of maghemite (γ-Fe2O3) nanoparticles formed within size-constraining Listeria innocua (LDps)-(DNA-binding protein from starved cells) protein cages that have an inner diameter of 5 nm. Variable-temperature X-band EMR spectra exhibited broad asymmetric resonances with a superimposed narrow peak at a gyromagnetic factor of g ≈ 2. The resonance structure, which depends on both superparamagnetic fluctuations and inhomogeneous broadening, changes dramatically as a function of temperature, and the overall linewidth becomes narrower with increasing temperature. Here, we compare two different models to simulate temperature-dependent lineshape trends. The temperature dependence for both models is derived from a Langevin behavior of the linewidth resulting from "anisotropy melting." The first uses either a truncated log-normal distribution of particle sizes or a bi-modal distribution and then a Landau-Liftshitz lineshape to describe the nanoparticle resonances. The essential feature of this model is that small particles have narrow linewidths and account for the g ≈ 2 feature with a constant resonance field, whereas larger particles have broad linewidths and undergo a shift in resonance field. The second model assumes uniform particles with a diameter around 4 nm and a random distribution of uniaxial anisotropy axes. This model uses a more precise calculation of the linewidth due to superparamagnetic fluctuations and a random distribution of anisotropies. Sharp features in the spectrum near g ≈ 2 are qualitatively predicted at high temperatures. Both models can account for many features of the observed spectra, although each has deficiencies. The first model leads to a nonphysical increase in magnetic moment as the temperature is increased if a log normal distribution of particles sizes is used. Introducing a bi-modal distribution of particle sizes resolves the unphysical

  19. Composite electrolyte with proton conductivity for low-temperature solid oxide fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Raza, Rizwan, E-mail: razahussaini786@gmail.com [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Department of Energy Technology, Royal Institute of Technology, KTH, Stockholm 10044 (Sweden); Ahmed, Akhlaq; Akram, Nadeem; Saleem, Muhammad; Niaz Akhtar, Majid; Ajmal Khan, M.; Abbas, Ghazanfar; Alvi, Farah; Yasir Rafique, M. [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Sherazi, Tauqir A. [Department of Chemistry, COMSATS Institute of Information Technology, Abbotabad 22060 (Pakistan); Shakir, Imran [Sustainable Energy Technologies (SET) center, College of Engineering, King Saud University, PO-BOX 800, Riyadh 11421 (Saudi Arabia); Mohsin, Munazza [Department of Physics, Lahore College for Women University, Lahore, 54000 (Pakistan); Javed, Muhammad Sufyan [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Department of Applied Physics, Chongqing University, Chongqing 400044 (China); Zhu, Bin, E-mail: binzhu@kth.se, E-mail: zhubin@hubu.edu.cn [Department of Energy Technology, Royal Institute of Technology, KTH, Stockholm 10044 (Sweden); Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Faculty of Physics and Electronic Science/Faculty of Computer and Information, Hubei University, Wuhan, Hubei 430062 (China)

    2015-11-02

    In the present work, cost-effective nanocomposite electrolyte (Ba-SDC) oxide is developed for efficient low-temperature solid oxide fuel cells (LTSOFCs). Analysis has shown that dual phase conduction of O{sup −2} (oxygen ions) and H{sup +} (protons) plays a significant role in the development of advanced LTSOFCs. Comparatively high proton ion conductivity (0.19 s/cm) for LTSOFCs was achieved at low temperature (460 °C). In this article, the ionic conduction behaviour of LTSOFCs is explained by carrying out electrochemical impedance spectroscopy measurements. Further, the phase and structure analysis are investigated by X-ray diffraction and scanning electron microscopy techniques. Finally, we achieved an ionic transport number of the composite electrolyte for LTSOFCs as high as 0.95 and energy and power density of 90% and 550 mW/cm{sup 2}, respectively, after sintering the composite electrolyte at 800 °C for 4 h, which is promising. Our current effort toward the development of an efficient, green, low-temperature solid oxide fuel cell with the incorporation of high proton conductivity composite electrolyte may open frontiers in the fields of energy and fuel cell technology.

  20. Temperature effects on the nitric acid oxidation of industrial grade multiwalled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, Nadia F., E-mail: nadia@fisica.ufc.br [Universidade Federal do Ceara, Departamento de Fisica (Brazil); Martinez, Diego Stefani T., E-mail: diegostefani.br@gmail.com; Paula, Amauri J., E-mail: amaurijp@gmail.com [Universidade Estadual de Campinas (UNICAMP), Laboratorio de Quimica do Estado Solido (LQES), Instituto de Quimica (Brazil); Silveira, Jose V. [Universidade Federal do Ceara, Departamento de Fisica (Brazil); Alves, Oswaldo L., E-mail: oalves@iqm.unicamp.br [Universidade Estadual de Campinas (UNICAMP), Laboratorio de Quimica do Estado Solido (LQES), Instituto de Quimica (Brazil); Souza Filho, Antonio G., E-mail: agsf@fisica.ufc.br [Universidade Federal do Ceara, Departamento de Fisica (Brazil)

    2013-07-15

    In this study, we report an oxidative treatment of multiwalled carbon nanotubes (MWCNTs) by using nitric acid at different temperatures (25-175 Degree-Sign C). The analyzed materials have diameters varying from 10 to 40 nm and majority lengths between 3 and 6 {mu}m. The characterization results obtained by different techniques (e.g., field emission scanning electron microscopy, thermogravimetric analysis, energy-filtered transmission electron microscopy, Braunauer, Emmet and Teller method, {zeta}-potential and confocal Raman spectroscopy) allowed us to access the effects of temperature treatment on the relevant physico-chemical properties of the MWCNTs samples studied in view of an integrated perspective to use these samples in a bio-toxicological context. Analytical microbalance measurements were used to access the purity of samples (metallic residue) after thermogravimetric analysis. Confocal Raman spectroscopy measurements were used to evaluate the density of structural defects created on the surface of the tubes due to the oxidation process by using 2D Raman image. Finally, we have demonstrated that temperature is an important parameter in the generation of oxidation debris (a byproduct which has not been properly taken into account in the literature) in the industrial grade MWCNTs studied after nitric acid purification and functionalization.

  1. Influence of temperature and chemical composition on phase transformations of selected oxide melts

    Directory of Open Access Journals (Sweden)

    J. Dobrovská

    2013-07-01

    Full Text Available The paper deals with structural changes of solid phase of selected oxide systems during their transition into liquid state. Analyses concerned poly-component systems forming basis of casting powders for CCM mould. Industrially used oxide system with prevailing contents of CaO–Al2O3–SiO2 components and with numerous accompanying admixtures was tested. Investigation was focused on temperatures, during which individual phases disappear and precipitate, as well as on influence of CaO content on phase composition at selected temperatures. The experiments were realised with use of original methodology consisting of shock cooling of the tested melt in liquid nitrogen. Thus obtained samples were further investigated by X-ray diffraction phase analyses at ambient temperatures. The obtained results provide additional data on physical-chemical properties of oxide systems, such as surface tension, viscosity, sintering intervals, etc., which can be used in technological practice for appropriate lubrication effect of casting powders in the mould.

  2. Low Temperature Flux Growth of 2H-SiC and Beta-Gallium Oxide

    Science.gov (United States)

    Singh, N. B.; Choa, Fow-Sen; Su, Ching-Hua; Arnold, Bradley; Kelly, Lisa

    2016-01-01

    We present brief overview of our study on the low temperature flux growth of two very important novel wide bandgap materials 2H-SiC and Beta-gallium oxide (Beta-Ga2O3). We have synthesized and grown 5 millimeter to 1 centimeter size single crystals of Beta-gallium oxide (Beta-Ga2O3). We used a flux and semi wet method to grow transparent good quality crystals. In the semi-wet method Ga2O3 was synthesized with starting gallium nitrate solution and urea as a nucleation agent. In the flux method we used tin and other metallic flux. This crystal was placed in an alumina crucible and temperature was raised above 1050 degrees Centigrade. After a time period of thirty hours, we observed prismatic and needle shaped crystals of gallium oxide. Scanning electron microscopic studies showed step growth morphology. Crystal was polished to measure the properties. Bandgap was measured 4.7electronvolts using the optical absorption curve. Another wide bandgap hexagonal 2H-SiC was grown by using Si-Al eutectic flux in the graphite crucible. We used slight AlN also as the impurity in the flux. The temperature was raised up to 1050 degrees Centigrade and slowly cooled to 850 degrees Centigrade. Preliminary characterization results of this material are also reported.

  3. Linear topology in amorphous metal oxide electrochromic networks obtained via low-temperature solution processing

    Science.gov (United States)

    Llordés, Anna; Wang, Yang; Fernandez-Martinez, Alejandro; Xiao, Penghao; Lee, Tom; Poulain, Agnieszka; Zandi, Omid; Saez Cabezas, Camila A.; Henkelman, Graeme; Milliron, Delia J.

    2016-12-01

    Amorphous transition metal oxides are recognized as leading candidates for electrochromic window coatings that can dynamically modulate solar irradiation and improve building energy efficiency. However, their thin films are normally prepared by energy-intensive sputtering techniques or high-temperature solution methods, which increase manufacturing cost and complexity. Here, we report on a room-temperature solution process to fabricate electrochromic films of niobium oxide glass (NbOx) and `nanocrystal-in-glass’ composites (that is, tin-doped indium oxide (ITO) nanocrystals embedded in NbOx glass) via acid-catalysed condensation of polyniobate clusters. A combination of X-ray scattering and spectroscopic characterization with complementary simulations reveals that this strategy leads to a unique one-dimensional chain-like NbOx structure, which significantly enhances the electrochromic performance, compared to a typical three-dimensional NbOx network obtained from conventional high-temperature thermal processing. In addition, we show how self-assembled ITO-in-NbOx composite films can be successfully integrated into high-performance flexible electrochromic devices.

  4. Peak Temperature Reduction by Physical Information Driven Behavioral Synthesis with Resource Usage Allocation

    Science.gov (United States)

    Yu, Junbo; Zhou, Qiang; Qu, Gang; Bian, Jinian

    High temperature adversely impacts on circuit's reliability, performance, and leakage power. During behavioral synthesis, both resource usage allocation and resource binding influence thermal profile. Current thermal-aware behavioral syntheses do not utilize location information of resources from floorplan and in addition only focus on binding, ignoring allocation. This paper proposes thermal-aware behavioral synthesis with resource usage allocation. Based on a hybrid metric of physical location information and temperature, we rebind operations and reallocate the number of resources under area constraint. Our approach effectively controls peak temperature and creates even power densities among resources of different types and within resources of the same type. Experimental results show an average of 8.6°C drop in peak temperature and 5.3% saving of total power consumption with little latency overhead.

  5. Thulium oxide fuel characterization study: Part 2, Environmental behavior and mechanical, thermal and chemical stability enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, C.A.

    1970-12-01

    A study was performed of the correlation between fuel form stability and exposure environment of (temperature and atmosphere). 100% Tm/sub 2/O/sub 3/, 80% Tm/sub 2/O/sub 3//20% Yb/sub 2/O/sub 3/ and 100% Yb/sub 2/O/sub 3/ wafers were subjected to air, dynamic vacuum and static vacuum at temperatures to 2000/sup 0/C for times to 100 hours. Results showed the Tm/sub 2/O/sub 3//Yb/sub 2/O/sub 3/ cubic structure to be unaffected by elemental levels of iron, aluminum, magnesium and silicon and unaffected by the environmental conditions imposed on the wafers. A second task emphasized the optimization of the thermal, mechanical and chemical stability of Tm/sub 2/O/sub 3/ fuel forms. Enhancement was sought through process variable optimization and the addition of metal oxides to Tm/sub 2/O/sub 3/. CaO, TiO/sub 2/ and Al/sub 2/O/sub 3/ were added to form a grain boundary precipitate to control fines generation. The presence of 1% additive was inadequate to depress the melting point of Tm/sub 2/O/sub 3/ or to change the cubic crystalline structure of Tm/sub 2/O/sub 3//Yb/sub 2/O/sub 3/. Tm/sub 2/O/sub 3//Yb/sub 2/O/sub 3/ wafers containing CaO developed a grain boundary phase that improved the resistance to fines generation. The presence of Yb/sub 2/O/sub 3/ did not appear to measurably influence behavior.

  6. Effect of minor alloying elements La, C and B on the cyclic oxidation behavior of Ni-Cr-W-Mo superalloys

    Science.gov (United States)

    Yun, Dae Won; Seo, Seong Moon; Jeong, Hi Won; Yoo, Young Soo

    2017-09-01

    The cyclic oxidation behavior of Ni-Cr-W-Mo base alloys with various La, C and B contents is investigated at 1150 °C in ambient air with 15 min of high-temperature exposure and 5 min of air cooling. Oxidation resistance is evaluated by the weight change during cyclic oxidation. The cross-section of the oxide scale is observed by scanning electron microscopy after the cyclic oxidation test. The oxide scale mainly consists with spinels and a chromia layer. NiWO4 oxide particles and NiO are also observed in some areas. The addition of La improves the cyclic oxidation resistance significantly. However, the addition of 0.03 wt% B reduces the beneficial effect of La. The additions of B and C increase the spallation at the initial stage such that severe weight loss is observed. However, the spallation is reduced at the later stage. The addition of a proper amounts of B and C can be beneficial to improve the cyclic oxidation resistance of Ni-Cr-W-Mo alloys.

  7. Low-temperature oxidative degradation of PBX 9501 and its components determined via molecular weight analysis of the poly [ester urethane] binder

    Energy Technology Data Exchange (ETDEWEB)

    Kress, Joel D [Los Alamos National Laboratory

    2008-01-01

    The results of following the oxidative degradation of a plastic-bonded explosive (PBX 9501) are reported. Into over 1100 sealed containers were placed samples of PBX 9501 and combinations of its components and aged at relatively low temperatures to induce oxidative degradation of the samples. One of the components of the explosive is a poly(ester urethane) polymer and the oxidative degradation of the samples were following by measuring the molecular weight change of the polymer by gel permeation chromatography (coupled with both differential refractive index and multiangle laser light scattering detectors). Multiple temperatures between 40 and 64 {sup o}C were used to accelerate the aging of the samples. Interesting induction period behavior, along with both molecular weight increasing (crosslinking) and decreasing (chain scissioning) processes, were found at these relatively mild conditions. The molecular weight growth rates were fit to a random crosslinking model for all the combinations of components. The fit rate coefficients show Arrhenius behavior and activation energies and frequency factors were obtained. The kinetics of molecular weight growth shows a compensatory effect between the Arrhenius prefactors and activation energies, suggesting a common degradation process between PBX 9501 and the various combinations of its constituents. An oxidative chemical mechanism of the polymer is postulated, consistent with previous experimental results, that involves a competition between urethane radical crosslinking and carbonyl formation.

  8. The Pre-Onset, Transitional, and Foot Regions in Resistance Versus Temperature Behavior in High-T sub 2 Cuprates: Inferences Regarding Maximum T sub 2

    Science.gov (United States)

    1992-09-01

    linearity region, the transitional regime, and the foot region in the resistance versus temperature behavior of high-Tc oxide superconductors ... superconductor Tl1Ca 1Ba2 Cu207.6 to show commonality of pyramidal building blocks, and also to the well known A2 BX4 related archetype. The structure...The material shows strong levitation , high density, very low porosity, large grain size, and very high electrical conductivity in the normal state. In

  9. Nitric Oxide Contributes to Behavioral, Cellular, and Developmental Responses to Low Oxygen in Drosophila

    OpenAIRE

    Wingrove, James A.; O’Farrell, Patrick H.

    1999-01-01

    A nitric oxide (NO)/cyclic GMP (cGMP) signaling pathway is thought to play an important role in mammalian vasodilation during hypoxia. We show that Drosophila utilizes components of this pathway to respond to hypoxia. Hypoxic exposure rapidly induced exploratory behavior in larvae and arrested the cell cycle. These behavioral and cellular responses were diminished by an inhibitor of NO synthase and by a polymorphism affecting a form of cGMP-dependent protein kinase. Conversely, these response...

  10. Aloe vera gel improves behavioral deficits and oxidative status in streptozotocin-induced diabetic rats.

    Science.gov (United States)

    Tabatabaei, Seyed Reza Fatemi; Ghaderi, Shahab; Bahrami-Tapehebur, Mohammad; Farbood, Yaghoob; Rashno, Masome

    2017-12-01

    Oxidative stress has a major role in progression of diabetes-related behavioral deficits. It has been suggested that Aloe vera has anti-diabetic, antioxidative, and neuroprotective effects. The present study was designed to determine the effects of Aloe vera gel on behavioral functions, oxidative status, and neuronal viability in the hippocampus of streptozotocin (STZ)-induced diabetic rats. Fifty five adult male Wistar rats were randomly divided into five groups, including: control (normal saline 8ml/kg/day; P.O.), diabetic (normal saline 8ml/kg/day; P.O.), Aloe vera gel (100mg/kg/day; P.O.), diabetic+Aloe vera gel (100mg/kg/day; P.O.) and diabetic+NPH insulin (10 IU/kg/day; S.C.). All treatments were started immediately following confirmation of diabetes in diabetic groups and were continued for eight weeks. Behavioral functions were evaluated by employing standard behavioral paradigms. Additionally, oxidative status and neuronal viability were assessed in the hippocampus. The results of behavioral tests showed that diabetes enhanced anxiety/depression-like behaviors, reduced exploratory and locomotor activities, decreased memory performance, and increased stress related behaviors. These changes in diabetic rats were accompanied by increasing oxidative stress and neuronal loss in the hippocampus. Interestingly, eight weeks of treatment with Aloe vera gel not only alleviated all the mentioned deficits related to diabetes, but in some aspects, it was even more effective than insulin. In conclusion, the results suggest that both interrelated hypoglycemic and antioxidative properties of Aloe vera gel are possible mechanisms that improve behavioral deficits and protect hippocampal neurons in diabetic animals. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  11. Low-temperature activation of hematite nanowires for photoelectrochemical water oxidation.

    Science.gov (United States)

    Ling, Yichuan; Wang, Gongming; Wang, Hanyu; Yang, Yi; Li, Yat

    2014-03-01

    Hematite (α-Fe2 O3 ) nanostructures have been extensively studied as photoanode materials for photoelectrochemical (PEC) water oxidation. However, the photoactivity of pristine hematite nanostructures is fairly low and typically requires thermal activation at temperature of 650 °C or above. Here, we report a new method for enhancing the photocurrent of hematite nanowires at a substantially lower temperature of 350 °C by means of a two-step annealing process (activation process). Hydrothermally grown β-FeOOH nanowires were first annealed in a pure N2 environment at 350 °C to form magnetite, followed by partial oxidation in air to convert magnetite to hematite. During this process, Fe(2+) sites (oxygen vacancies) were intentionally created to increase the donor density and therefore the electrical conductivity of hematite. The oxygen-deficient hematite nanowire photoanode created at low temperature (350 °C) show considerably enhanced photoactivity compared to pristine hematite sample that prepared by thermal annealing of β-FeOOH nanowires at 550 °C in air. Moreover, this low-temperature annealing method can be coupled with an element doping method to further increase the photoactivity of hematite nanowire. Sn-doped hematite nanowires prepared by the same low-temperature annealing method show at least three fold enhanced photocurrent compared to the undoped sample. Significantly, the highest temperature in the entire annealing process was 350 °C, which is the lowest activation temperature ever reported for hematite nanowire photoanodes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Fundamental study of FC-72 pool boiling surface temperature fluctuations and bubble behavior

    Science.gov (United States)

    Griffin, Alison R.

    A heater designed to monitor surface temperature fluctuations during pool boiling experiments while the bubbles were simultaneously being observed has been fabricated and tested. The heat source was a transparent indium tin oxide (ITO) layer commercially deposited on a fused quartz substrate. Four copper-nickel thin film thermocouples (TFTCs) on the heater surface measured the surface temperature, while a thin layer of sapphire or fused silica provided electrical insulation between the TFTCs and the ITO. The TFTCs were micro-fabricated using the liftoff process to deposit the nickel and copper metal films. The TFTC elements were 50 mum wide and overlapped to form a 25 mum by 25 mum junction. TFTC voltages were recorded by a DAQ at a sampling rate of 50 kHz. A high-speed CCD camera recorded bubble images from below the heater at 2000 frames/second. A trigger sent to the camera by the DAQ synchronized the bubble images and the surface temperature data. As the bubbles and their contact rings grew over the TFTC junction, correlations between bubble behavior and surface temperature changes were demonstrated. On the heaters with fused silica insulation layers, 1--2°C temperature drops on the order of 1 ms occurred as the contact ring moved over the TFTC junction during bubble growth and as the contact ring moved back over the TFTC junction during bubble departure. These temperature drops during bubble growth and departure were due to microlayer evaporation and liquid rewetting the heated surface, respectively. Microlayer evaporation was not distinguished as the primary method of heat removal from the surface. Heaters with sapphire insulation layers did not display the measurable temperature drops observed with the fused silica heaters. The large thermal diffusivity of the sapphire compared to the fused silica was determined as the reason for the absence of these temperature drops. These findings were confirmed by a comparison of temperature drops in a 2-D simulation of

  13. Correlations between preparation methods, structural features and electrochemical Li-storage behavior of reduced graphene oxide.

    Science.gov (United States)

    Sonia, Farjana J; Kalita, Hemen; Aslam, M; Mukhopadhyay, Amartya

    2017-08-10

    Wide differences in the structural features of graphenic carbon, especially in the case of reduced graphene oxides (rGO), are expected to have considerable impacts on the properties, thus leading to significant scatter and poor understanding/prediction of their performances for various applications, including as electrode materials for electrochemical Li-storage. In this context, the present work develops a comprehensive understanding (via thorough experimentation, including in situ X-ray diffraction studies, and analysis) on the effects of graphene oxide (GO) reduction methods/conditions on the structural features (mainly 'graphenic' ordering) and concomitant influences of the same on electrochemical Li-storage behavior. 'Moderately oxidized' GO (O/C ∼0.41) was reduced via three different methods, viz., (i) using hydrazine hydrate vapor at room temperature (rGO-H; O/C ∼0.23), (ii) thermal reduction by annealing at just 500 °C (rGO-A; O/C ∼0.20) and (iii) hydrazine treatment, followed by the same annealing treatment (rGO-HA; O/C ∼0.17). Raman spectroscopy, in situ X-ray diffraction recorded during annealing and high resolution TEM imaging indicate that while GO and rGO-H had considerable defect contents [I(D)/I(G) ∼1.4 for rGO-H], including a very non-uniform interlayer spacing (varying between 3.1 and 3.6 Å), the 500 °C annealed rGO-A and rGO-HA had significantly reduced defect contents [I(D)/I(G) ∼0.6] and near-perfect 'graphenic' ordering with a uniform interlayer spacing of ∼3.35 Å. Despite the nanoscaled dimensions, defect structures, especially the non-uniform interlayer spacing, resulted in relatively poor reversible Li-capacity and rate capability for the non-annealed rGO-H, even in comparison to the bulk graphitic carbon. By contrast, the annealed rGOs, especially the rGO-HA, not only possessed a superior reversible Li-capacity of ∼450 mA h g -1 (at C/20), but also exhibited a significantly improved rate capability (even compared to

  14. Study of Solid Particle Behavior in High Temperature Gas Flows

    Science.gov (United States)

    Majid, A.; Bauder, U.; Stindl, T.; Fertig, M.; Herdrich, G.; Röser, H.-P.

    2009-01-01

    The Euler-Lagrangian approach is used for the simulation of solid particles in hypersonic entry flows. For flow field simulation, the program SINA (Sequential Iterative Non-equilibrium Algorithm) developed at the Institut für Raumfahrtsysteme is used. The model for the effect of the carrier gas on a particle includes drag force and particle heating only. Other parameters like lift Magnus force or damping torque are not taken into account so far. The reverse effect of the particle phase on the gaseous phase is currently neglected. Parametric analysis is done regarding the impact of variation in the physical input conditions like position, velocity, size and material of the particle. Convective heat fluxes onto the surface of the particle and its radiative cooling are discussed. The variation of particle temperature under different conditions is presented. The influence of various input conditions on the trajectory is explained. A semi empirical model for the particle wall interaction is also discussed and the influence of the wall on the particle trajectory with different particle conditions is presented. The heat fluxes onto the wall due to impingement of particles are also computed and compared with the heat fluxes from the gas.

  15. The Effect of Central Amygdala Nitric Oxide in Expression Of Drug Seeking Behaviors

    Directory of Open Access Journals (Sweden)

    Mahnaz Rahimpour

    2011-11-01

    Full Text Available Introduction: Previous studies shows L-arginin (nitric oxide precursor increases conditioned place preference and drug seeking behaviors whereas LG-nitro-arginine methyl ester L-NAME( as nitric oxide synthase inhibitor decreases this process. In this project, effects of intra-central amygdale bilateral injection of nitric oxide agents on drug-seeking behaviors including rearing, sniffing and compartment entrance were investigated. Method: animals were wistar male rats (200-250 g which allowed to be recovered after they’re being suffered from a surgery by strereotaxis apparatus to be cannulated in coordination of central amygdale nucleus (CeA. CPP was conducted using a five-day schedule of unbiased procedure. Findings: morphine (2.5-10 mg/kg s.c induced significant drug-seeking behaviors. Naloxone (0.1-0.4 mg/kg i.p injection pretesting (after conditioning by morphine 7.5 mg/kg decreased the expression of behaviors. When L-arginine (0.3-3 µgr/rat injected intra–CeA prior to naloxone (0.4 mg/kg, increased behaviors but L-NAME (0.3-3 µgr/rat intra–CeA injections prior to L-arginine (0.3 µgr/rat pretesting, caused significant decreasement of L-arginine response. Conclusion: NO in the CeA may play an important role in the drug seeking behaviors induced of morphine.

  16. Effects of Surface Roughness, Oxidation, and Temperature on the Emissivity of Reactor Pressure Vessel Alloys

    Energy Technology Data Exchange (ETDEWEB)

    King, J. L. [University of Wisconsin–Madison, Department of Engineering Physics, Madison, Wisconsin; Jo, H. [University of Wisconsin–Madison, Department of Engineering Physics, Madison, Wisconsin; Tirawat, R. [National Renewable Energy Laboratory, Concentrating Solar Power Group, Golden, Colorado; Blomstrand, K. [University of Wisconsin–Madison, Department of Engineering Physics, Madison, Wisconsin; Sridharan, K. [University of Wisconsin–Madison, Department of Engineering Physics, Madison, Wisconsin

    2017-08-31

    Thermal radiation will be an important mode of heat transfer in future high-temperature reactors and in off-normal high-temperature scenarios in present reactors. In this work, spectral directional emissivities of two reactor pressure vessel (RPV) candidate materials were measured at room temperature after exposure to high-temperature air. In the case of SA508 steel, significant increases in emissivity were observed due to oxidation. In the case of Grade 91 steel, only very small increases were observed under the tested conditions. Effects of roughness were also investigated. To study the effects of roughening, unexposed samples of SA508 and Grade 91 steel were roughened via one of either grinding or shot-peening before being measured. Significant increases were observed only in samples having roughness exceeding the roughness expected of RPV surfaces. While the emissivity increases for SA508 from oxidation were indeed significant, the measured emissivity coefficients were below that of values commonly used in heat transfer models. Based on the observed experimental data, recommendations for emissivity inputs for heat transfer simulations are provided.

  17. Species and temperature measurements of methane oxidation in a nanosecond repetitively pulsed discharge.

    Science.gov (United States)

    Lefkowitz, Joseph K; Guo, Peng; Rousso, Aric; Ju, Yiguang

    2015-08-13

    Speciation and temperature measurements of methane oxidation during a nanosecond repetitively pulsed discharge in a low-temperature flow reactor have been performed. Measurements of temperature and formaldehyde during a burst of pulses were made on a time-dependent basis using tunable diode laser absorption spectroscopy, and measurements of all other major stable species were made downstream of a continuously pulsed discharge using gas chromatography. The major species for a stoichiometric methane/oxygen/helium mixture with 75% dilution are H(2)O, CO, CO(2), H(2), CH(2)O, CH(3)OH, C(2)H(6), C(2)H(4) and C(2)H(2). A modelling tool to simulate homogeneous plasma combustion kinetics is assembled by combining the ZDPlasKin and CHEMKIN codes. In addition, a kinetic model for plasma-assisted combustion (HP-Mech/plasma) of methane, oxygen and helium mixtures has been assembled to simulate the measurements. Predictions can accurately capture reactant consumption as well as production of the major product species. However, significant disagreement is found for minor species, particularly CH(2)O and CH(3)OH. Further analysis revealed that the plasma-activated low-temperature oxidation pathways, particularly those involving CH(3)O(2) radical reactions and methane reactions with O((1)D), are responsible for this disagreement. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  18. Dynamic chemical expansion of thin-film non-stoichiometric oxides at extreme temperatures.

    Science.gov (United States)

    Swallow, Jessica G; Kim, Jae Jin; Maloney, John M; Chen, Di; Smith, James F; Bishop, Sean R; Tuller, Harry L; Van Vliet, Krystyn J

    2017-07-01

    Actuator operation in increasingly extreme and remote conditions requires materials that reliably sense and actuate at elevated temperatures, and over a range of gas environments. Design of such materials will rely on high-temperature, high-resolution approaches for characterizing material actuation in situ. Here, we demonstrate a novel type of high-temperature, low-voltage electromechanical oxide actuator based on the model material PrxCe1-xO2-δ (PCO). Chemical strain and interfacial stress resulted from electrochemically pumping oxygen into or out of PCO films, leading to measurable film volume changes due to chemical expansion. At 650 °C, nanometre-scale displacement and strain of >0.1% were achieved with electrical bias values <0.1 V, low compared to piezoelectrically driven actuators, with strain amplified fivefold by stress-induced structural deflection. This operando measurement of films 'breathing' at second-scale temporal resolution also enabled detailed identification of the controlling kinetics of this response, and can be extended to other electrochemomechanically coupled oxide films at extreme temperatures.

  19. Dynamic chemical expansion of thin-film non-stoichiometric oxides at extreme temperatures

    Science.gov (United States)

    Swallow, Jessica G.; Kim, Jae Jin; Maloney, John M.; Chen, Di; Smith, James F.; Bishop, Sean R.; Tuller, Harry L.; van Vliet, Krystyn J.

    2017-07-01

    Actuator operation in increasingly extreme and remote conditions requires materials that reliably sense and actuate at elevated temperatures, and over a range of gas environments. Design of such materials will rely on high-temperature, high-resolution approaches for characterizing material actuation in situ. Here, we demonstrate a novel type of high-temperature, low-voltage electromechanical oxide actuator based on the model material PrxCe1-xO2-δ (PCO). Chemical strain and interfacial stress resulted from electrochemically pumping oxygen into or out of PCO films, leading to measurable film volume changes due to chemical expansion. At 650 °C, nanometre-scale displacement and strain of >0.1% were achieved with electrical bias values <0.1 V, low compared to piezoelectrically driven actuators, with strain amplified fivefold by stress-induced structural deflection. This operando measurement of films `breathing’ at second-scale temporal resolution also enabled detailed identification of the controlling kinetics of this response, and can be extended to other electrochemomechanically coupled oxide films at extreme temperatures.

  20. The Wear behavior of UHMWPE against Surface Modified CP-Titanium by Thermal Oxidation

    Directory of Open Access Journals (Sweden)

    B.T. Prayoga

    2016-12-01

    Full Text Available The effects of thermal oxidation duration on hardness, roughness, and wettability of the CP-titanium surfaces were investigated in this paper. The thermal oxidation treatment was done at 700 oC for 12-36 hours in an air atmosphere. The wear behavior of the UHMWPE sliding against treated thermal oxidation of the CP-titanium was tested by a pin-on-plate tribometer under lubrication of the solution of 75 % distilled water and 25 % bovine serum. The results showed that the layer of the oxide titanium was formed on the surface after being treated by the thermal oxidation for 12-36 hours. The oxide titanium layer was dominated by rutile form of TiO2, that offers an improvement of hardness and wettability of the CP-titanium surfaces. The average wear factor of the UHMWPE reduced significantly when the sliding against of the CP-titanium was modified by the thermal oxidation, and the lowest average wear factor was reached when the sliding against the 12 hour oxidized CP-titanium counterfaces.

  1. Low temperature high density plasma nitriding of stainless steel molds for stamping of oxide glasses

    Directory of Open Access Journals (Sweden)

    Aizawa Tatsuhiko

    2016-01-01

    Full Text Available Various kinds of stainless steels have been widely utilized as a die for mold- and direct-stamping processes of optical oxide glasses. Since they suffered from high temperature transients and thermal cycles in practice, they must be surface-treated by dry and wet coatings, or, by plasma nitriding. Martensitic stainless steel mold was first wet plated by the nickel phosphate (NiP, which was unstable at the high temperature stamping condition; and, was easy to crystalize or to fracture by itself. This issue of nuisance significantly lowered the productivity in fabrication of optical oxide-glass elements. In the present paper, the stainless steel mold was surface-treated by the low-temperature plasma nitriding. The nitrided layer by this surface modification had higher nitrogen solute content than 4 mass%; the maximum solid-solubility of nitrogen is usually 0.1 mass% in the equilibrium phase diagram. Owing to this solid-solution with high nitrogen concentration, the nitrided layer had high hardness over 1400 HV within its thickness of 50 μm without any formation of nitrides after plasma nitriding at 693 K for 14.4 ks. This plasma-nitrided mold was utilized for mold-stamping of two colored oxide glass plates at 833 K; these plates were successfully deformed and joined into a single glass plate by this stamping without adhesion or galling of oxide glasses onto the nitrided mold surface.

  2. Effect of high ambient temperature on behavior of sheep under semi-arid tropical environment

    Science.gov (United States)

    De, Kalyan; Kumar, Davendra; Saxena, Vijay Kumar; Thirumurugan, Palanisamy; Naqvi, Syed Mohammed Khursheed

    2017-07-01

    High environmental temperature is a major constraint in sheep production under semi-arid tropical environment. Behavior is the earliest indicator of animal's adaptation and responses to the environmental alteration. Therefore, the objective of this study was to assess the effects of high ambient temperature on the behavior of sheep under a semi-arid tropical environment. The experiment was conducted for 6 weeks on 16 Malpura cross (Garole × Malpura × Malpura (GMM)) rams. The rams were divided equally into two groups, designated as C and T. The rams of C were kept in comfortable environmental conditions served as control. The rams of T were exposed to a different temperature at different hours of the day in a climatic chamber, to simulate a high environmental temperature of summer in semi-arid tropic. The behavioral observations were taken by direct instantaneous observation at 15-min intervals for each animal individually. The feeding, ruminating, standing, and lying behaviors were recorded twice a week from morning (0800 hours) to afternoon (1700 hours) for 6 weeks. Exposure of rams to high temperature (T) significantly ( P animals of T spent significantly ( P behavior of sheep which is directed to circumvent the effect of the stressor.

  3. Metallic interconnects for proton ceramic fuel cells : oxidation behavior under simulated fuel cell conditions

    OpenAIRE

    Skilbred, Anders Werner Bredvei

    2012-01-01

    Fuel cells are expected to serve as a contribution to meet the demand for clean energy. High temperature fuel cells such as solid oxide fuel cells (SOFC) and proton ceramic fuel cells (PCFC) are developed for use as environment friendly energy conversion devices. However, the successful implementation of such devices in practical applications relies on series connections of multiple cells by so-called interconnects. During operation at high temperatures (600 – 850 °C) facing both air and fuel...

  4. Modulatory effects of caffeine on oxidative stress and anxiety-like behavior in ovariectomized rats.

    Science.gov (United States)

    Caravan, Ionut; Sevastre Berghian, Alexandra; Moldovan, Remus; Decea, Nicoleta; Orasan, Remus; Filip, Gabriela Adriana

    2016-09-01

    Menopause is accompanied by enhanced oxidative stress and behavioral changes, effects attenuated by antioxidants. The aim of this study was to evaluate the effects of caffeine on behavior and oxidative stress in an experimental model of menopause. Female rats were divided into the following groups: sham-operated (CON), sham-operated and caffeine-treated (CAF), ovariectomized (OVX), ovariectomized and caffeine-treated (OVX+CAF). Caffeine (6 mg/kg) and vehicle were administered for 21 days (subchronic) and 42 days (chronic), using 2 experimental subsets. Behavioral tests and oxidative stress parameters in the blood, whole brain, and hippocampus were assessed. The subchronic administration of caffeine decreased the lipid peroxidation and improved the antioxidant defense in the blood and brain. The GSH/GGSG ratio in the brain was improved by chronic administration, with reduced activities of antioxidant enzymes and enhanced nitric oxide and malondialdehyde levels. In particular, the lipid peroxidation in the hippocampus decreased in both experiments. The rats became hyperactive after 21 days of treatment, but no effect was observed after chronic administration. In both experimental subsets, caffeine had anxiolytic effects as tested in elevated plus maze. The administration of low doses of caffeine, for a short period of time, may be a new therapeutic approach to modulating the oxidative stress and anxiety in menopause.

  5. Electrochemical performance for the electro-oxidation of ethylene glycol on a carbon-supported platinum catalyst at intermediate temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kosaka, Fumihiko; Oshima, Yoshito [Department of Environment Systems, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563 (Japan); Otomo, Junichiro, E-mail: otomo@k.u-tokyo.ac.jp [Department of Environment Systems, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563 (Japan)

    2011-11-30

    Highlights: > High oxidation current in ethylene glycol electro-oxidation at intermediate temperature. > High C-C bond dissociation ratio of ethylene glycol at intermediate temperature. > Low selectivity for CH{sub 4} in ethylene glycol electro-oxidation. > High selectivity for CO{sub 2} according to an increase in steam to carbon ratios. - Abstract: To determine the kinetic performance of the electro-oxidation of a polyalcohol operating at relatively high temperatures, direct electrochemical oxidation of ethylene glycol on a carbon supported platinum catalyst (Pt/C) was investigated at intermediate temperatures (235-255 {sup o}C) using a single cell fabricated with a proton-conducting solid electrolyte, CsH{sub 2}PO{sub 4}, which has high proton conductivity (>10{sup -2} S cm{sup -1}) in the intermediate temperature region. A high oxidation current density was observed, comparable to that for methanol electro-oxidation and also higher than that for ethanol electro-oxidation. The main products of ethylene glycol electro-oxidation were H{sub 2}, CO{sub 2}, CO and a small amount of CH{sub 4} formation was also observed. On the other hand, the amounts of C{sub 2} products such as acetaldehyde, acetic acid and glycolaldehyde were quite small and were lower by about two orders of magnitude than the gaseous reaction products. This clearly shows that C-C bond dissociation proceeds almost to completion at intermediate temperatures and the dissociation ratio reached a value above 95%. The present observations and kinetic analysis suggest the effective application of direct alcohol fuel cells operating at intermediate temperatures and indicate the possibility of total oxidation of alcohol fuels.

  6. Effects of prior surface damage on high-temperature oxidation of Fe-, Ni-, and Co-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Blau, Peter Julian [ORNL; Lowe, Tracie M [ORNL; Pint, Bruce A [ORNL

    2009-01-01

    Multi-component metallic alloys have been developed to withstand high-temperature service in corrosive environments. Some of these applications, like exhaust valve seats in internal combustion engines, must also resist sliding, impact, and abrasion. The conjoint effects of temperature, oxidation, and mechanical contact can result in accelerated wear and the formation of complex surface layers whose properties differ from those of the base metal and the oxide scale that forms in the absence of mechanical contact. The authors have investigated the effects of prior surface damage, produced by scratch tests, on the localized reformation of oxide layers. Three high-performance commercial alloys, based on iron, nickel, and cobalt, were used as model materials. Thermogravimetric analysis (TGA) was used to determine their static oxidation rates at elevated temperature (850o C). A micro-abrasion, ball-cratering technique was used to measure oxide layer thickness and to compare it with TGA results. By using taper-sectioning techniques and energy-dispersive elemental mapping, a comparison was made between oxide compositions grown on non-damaged surfaces and oxides that formed on grooves produced by a diamond stylus. Microindentation and scratch hardness data revealed the effects of high temperature exposure on both the substrate hardness and the nature of oxide scale disruption. There were significant differences in elemental distribution between statically-formed oxides and those that formed on scratched regions

  7. Materials and Components for Low Temperature Solid Oxide Fuel Cells – an Overview

    Directory of Open Access Journals (Sweden)

    D. Radhika

    2013-06-01

    Full Text Available This article summarizes the recent advancements made in the area of materials and components for low temperature solid oxide fuel cells (LT-SOFCs. LT-SOFC is a new trend in SOFCtechnology since high temperature SOFC puts very high demands on the materials and too expensive to match marketability. The current status of the electrolyte and electrode materials used in SOFCs, their specific features and the need for utilizing them for LT-SOFC are presented precisely in this review article. The section on electrolytes gives an overview of zirconia, lanthanum gallate and ceria based materials. Also, this review article explains the application of different anode, cathode and interconnect materials used for SOFC systems. SOFC can result in better performance with the application of liquid fuels such methanol and ethanol. As a whole, this review article discusses the novel materials suitable for operation of SOFC systems especially for low temperature operation.

  8. Nanofiber-based composite cathodes for intermediate temperature solid oxide fuel cells

    Science.gov (United States)

    Ahn, Minwoo; Lee, Jongseo; Lee, Wonyoung

    2017-06-01

    We demonstrate the Sm0.5Sr0.5CoO3-δ (SSC) nanofiber-based composite cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs), showing a cathode area-specific resistance (ASR) value of 0.024 Ωcm2 at 650 °C. The hollow and porous SSC nanofiber layer, fabricated by electrospinning, is sintered at low temperatures to preserve the high specific surface area for facile oxygen surface exchange reactions. The low sintering temperature is enabled by additional SSC powder layer, providing sufficient adhesion between the electrolyte and the nanofiber layer. Our results can provide a design guideline to fully utilize the nanostructured electrodes by engineering the structural properties of the surface and the interface, and hence high-performance IT-SOFCs can be achieved by structural modification with conventional materials.

  9. Role of Oxides and Porosity on High-Temperature Oxidation of Liquid-Fueled HVOF Thermal-Sprayed Ni50Cr Coatings

    Science.gov (United States)

    Song, B.; Bai, M.; Voisey, K. T.; Hussain, T.

    2017-02-01

    High chromium content in Ni50Cr thermally sprayed coatings can generate a dense and protective scale at the surface of coating. Thus, the Ni50Cr coating is widely used in high-temperature oxidation and corrosion applications. A commercially available gas atomized Ni50Cr powder was sprayed onto a power plant steel (ASME P92) using a liquid-fueled high velocity oxy-fuel thermal spray with three processing parameters in this study. Microstructure of as-sprayed coatings was examined using oxygen content analysis, mercury intrusion porosimetry, scanning electron microscope (SEM), energy-dispersive x-ray spectroscopy (EDX) and x-ray diffraction (XRD). Short-term air oxidation tests (4 h) of freestanding coatings (without boiler steel substrate) in a thermogravimetric analyzer at 700 °C were performed to obtain the kinetics of oxidation of the as-sprayed coating. Long-term air oxidation tests (100 h) of the coated substrates were performed at same temperature to obtain the oxidation products for further characterization in detail using SEM/EDX and XRD. In all samples, oxides of various morphologies developed on top of the Ni50Cr coatings. Cr2O3 was the main oxidation product on the surface of all three coatings. The coating with medium porosity and medium oxygen content has the best high-temperature oxidation performance in this study.

  10. Behavior of metal oxide nanoparticles in natural aqueous matrices

    Science.gov (United States)

    Keller, A. A.; Zhou, D.; Wang, H.

    2009-12-01

    The increasing use of nanomaterials in consumer products that are exposed to environmental media has led to a need to understand their fate and transport. In particular, metal oxide (MeO) nanoparticles, such as TiO2, ZnO and CeO2, are increasingly incorporated into a wide range of products, from sunscreens to paints and other coatings, and catalysts. With regard to their transport, it is important to determine how far these nanoparticles will travel in different ambient waters, such as rivers, lakes and seawater. There have been a number of studies that have addressed the aggregation of different nanoparticles in simpler aqueous solutions. However, it is important to understand the combined effect of pH, ionic strength, ionic composition, NOM and other characteristics of the aqueous media in which the nanoparticles will be dispersed, which may result in either aggregation and settling, or stabilization and transport. This also affects the bioavailability of the nanomaterials, and the phase (water column or sediments) in which the bulk of the particles are likely to reside. For this study we considered several natural aqueous matrices, including seawater, freshwater, groundwater, rainwater and treated wastewater, as well as two different water matrices used in micro- and mesocosm studies of nanoparticle toxicity. We determined that the two most important water quality characteristics controlling the rate of aggregation, relatively independent of particle composition, are [NOM] and ionic strength.

  11. Potential behavioral and pro-oxidant effects of Petiveria alliacea L. extract in adult rats.

    Science.gov (United States)

    de Andrade, Thaís Montenegro; de Melo, Ademar Soares; Dias, Rui Guilherme Cardoso; Varela, Everton Luís Pompeu; de Oliveira, Fábio Rodrigues; Vieira, José Luís Fernandes; de Andrade, Marcieni Ataíde; Baetas, Ana Cristina; Monteiro, Marta Chagas; Maia, Cristiane do Socorro Ferraz

    2012-09-28

    Petiveria alliacea (Phytolaccaceae) is a perennial shrub indigenous to the Amazon Rainforest and tropical areas of Central and South America, the Caribbean, and sub-Saharan Africa. In folk medicine, Petiveria alliacea has a broad range of therapeutic properties; however, it is also associated with toxic effects. The present study evaluated the putative effects of Petiveria alliacea on the central nervous system, including locomotor activity, anxiety, depression-like behavior, and memory, and oxidative stress. Two-month-old male and female Wistar rats (n=7-10 rats/group) were administered with 900 mg/kg of hydroalcoholic extracts of Petiveria alliacea L. The behavioral assays included open-field, forced swimming, and elevated T-maze tests. The oxidative stress levels were measured in rat blood samples after behavioral assays and methemoglobin levels were measured in vitro. Consistent with previous reports, Petiveria alliacea increased locomotor activity. It also exerted previously unreported anxiolytic and antidepressant effects in behavioral tests. In the oxidative stress assays, the Petiveria alliacea extract decreased Trolox equivalent antioxidant capacity levels and increased methemoglobin levels, which was related to the toxic effects. The Petiveria alliacea extract exerted motor stimulatory and anxiolytic effects in the OF test, antidepressant effects in the FS test, and elicited memory improvement in ETM. Furthermore, the Petiveria alliacea extract also exerted pro-oxidant effects in vitro and in vivo, inhibiting the antioxidant status and increasing MetHb levels in human plasma, respectively. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  12. Low-temperature behavior of graphite-tin composite anodes for Li-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Nobili, F.; Mancini, M.; Dsoke, S.; Tossici, R.; Marassi, R. [Scuola di Scienze e Tecnologie, Sezione Chimica, Universita di Camerino, Via S. Agostino, 1, I-62032 Camerino (MC) (Italy)

    2010-10-15

    The challenge of increasing low-temperature performances of anodes for Li-ion batteries is faced by preparing graphite-tin composite electrodes. The anodes are prepared by mixing partially oxidized graphite with nanometric Sn powder or by coating the oxidized graphite electrode with a thin Sn layer. Long-term cycling stability and intercalation/deintercalation performances of the composite anodes in the temperature range 20 C to -30 C are evaluated. Kinetics is investigated by cyclic voltammetry and electrochemical impedance spectroscopy, in the attempt to explain the role of Sn in reducing the overall electrode polarization at low temperature. Two possible mechanisms of action for bulk metal powder and surface metal layer are proposed. (author)

  13. Microwave assisted sintering of gadolinium doped barium cerate electrolyte for intermediate temperature solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Arumugam Senthil, E-mail: senthu.ramp@gmail.com [Department of Physics, PSG College of Technology, Coimbatore, 641 004, Tamilnadu (India); Balaji, Ramamoorthy [Department of Physics, PSG College of Technology, Coimbatore, 641 004, Tamilnadu (India); Jayakumar, Srinivasalu [Department of Physics, PSG Institute of Technology and Applied Research, Coimbatore, 641 062, Tamilnadu (India); Pradeep, Chandran [Department of Physics, Indian Institute of Technology, Madras, 600 036, Tamilnadu (India)

    2016-10-01

    In Solid Oxide Fuel Cell (SOFC), electrolyte plays a vital role to increase the energy conversion efficiency. The main hurdle of such electrolyte in fuel cell is its higher operating temperature (1000 °C) which results in design limitation and higher fabrication cost. In order to reduce the operating temperature of SOFC, a suitable electrolyte has been prepared through co-precipitation method followed by microwave sintering of solid ceramic. The calcination temperature for the as-prepared powder was identified using Differential Scanning Calorimetry. The crystal structure of the sample was found to exhibit its orthorhombic perovskite structure. The particle size was determined using High-Resolution Transmission Electron Microscope with uniform in shape and size, match with XRD results and confirmed from structural analysis. Thus, the sample prepared via co-precipitation method and the solid ceramic sintered through microwave can be a promising electrolyte for fuel cells operated at intermediate temperature. - Highlights: • To synthesis the composite electrolyte by chemical method and sinter using microwave. • To reduce the operating temperature of electrolyte for high ionic conductivity in SOFC's. • To study the phase purity and to develop nanocomposite at reduced temperature.

  14. Adsorption behavior of oxidized galactomannans onto amino terminated surfaces and their interaction with bovine serum albumin

    Energy Technology Data Exchange (ETDEWEB)

    Sierakowski, M.-R; Silva, Maria R.V. da [Universidade Federal do Parana, Curitiba, PR (Brazil). Dept. de Quimica. Lab. de Biopolimeros]. E-mail: mrbiopol@quimica.ufpr.br; Freitas, R.A.; Moreira, Jose S.R. [Universidade Federal do Parana, Curitiba, PR (Brazil). Dept. de Bioquimica; Fujimoto, J.; Petri, D.F.S.; Cordeiro, Paulo R.D. [Sao Paulo Univ., SP (Brazil). Inst. de Quimica]. E-mail: dfsp@quim.iq.usp.br; Andrade, Fabiana D

    2001-07-01

    A galactomannan (CF) extracted from Cassia fastuosa seeds was purified and oxidized with (2,2,6,6- tetramethylpiperidine-1-oxyl) to form a uronic acid-containing polysaccharide (CFOX) with a degree of oxidation (DO) of 0.22. The chemical structures of CF and CFOX were characterized. The adsorption behavior of CF and CFOX onto amino-terminated surfaces was studied by means of ellipsometric measurements. The influence of p H and ionic strength on the adsorption was also investigated. At p H 4, there was a maximum in the adsorbed amount caused by strong electrostatic attraction between the substrate and the oxidized galactomannans. There was no ionic strength effect on the adsorption behavior. The immobilization of bovine serum albumin onto CF and CFOX was studied as a function of p H. At the isoelectric point a maximum in the adsorbed amount was found. (author)

  15. Effect of Temperature on the Corrosion Behavior of API X120 Pipeline Steel in H2S Environment

    Science.gov (United States)

    Okonkwo, Paul C.; Sliem, Mostafa H.; Shakoor, R. A.; Mohamed, A. M. A.; Abdullah, Aboubakr M.

    2017-08-01

    The corrosion behavior of newly developed API X120 C-steel that is commenced to be used for oil pipelines was studied in a H2S saturated 3.5 wt.% NaCl solution between 20 and 60 °C using potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The corrosion products formed on the surface of the alloy were characterized using x-ray diffraction and scanning electron microscopy. It has been noticed that the formation of corrosion product layer takes place at both lower and higher temperatures which is mainly comprised of iron oxides and sulfides. The electrochemical results confirmed that the corrosion rate decreases with increasing temperature up to 60 °C. This decrease in corrosion rate with increasing temperature can be attributed to the formation of a protective layer of mackinawite layer. However, cracking in the formed mackinawite layer may not be responsible for the increase in the corrosion rate. More specifically, developed pourbaix diagrams at different temperatures showed that the formed protective layer belongs to mackinawite (FeS), a group of classified polymorphous iron sulfide, which is in good agreement with the experimental results. It is also noticed that the thickness of corrosion products layer increases significantly with decrease in the corrosion rate of API X120 steel exposed to H2S environment. These findings indicate that API X120 C-steel is susceptible to sour corrosion under the above stated experimental conditions.

  16. The effect of the impactor diameter and temperature on low velocity impact behavior of CFRP laminates

    Science.gov (United States)

    Evci, C.; Uyandıran, I.

    2017-02-01

    Impact damage is one of the major concerns that should be taken into account with the new aircraft and spacecraft structures which employ ever-growing use of composite materials. Considering the thermal loads encountered at different altitudes, both low and high temperatures can affect the properties and impact behavior of composite materials. This study aims to investigate the effect of temperature and impactor diameter on the impact behavior and damage development in balanced and symmetrical CFRP laminates which were manufactured by employing vacuum bagging process with autoclave cure. Instrumented drop-weight impact testing system is used to perform the low velocity impact tests in a range of temperatures ranged from 60 down to -50 °C. Impact tests for each temperature level were conducted using three different hemispherical impactor diameters varying from 10 to 20 mm. Energy profile method is employed to determine the impact threshold energies for damage evolution. The level of impact damage is determined from the dent depth on the impacted face and delamination damage detected using ultrasonic C-Scan technique. Test results reveal that the threshold of penetration energy, main failure force and delamination area increase with impactor diameter at all temperature levels. No clear influence of temperature on the critical force thresholds could be derived. However, penetration threshold energy decreased as the temperature was lowered. Drop in the penetration threshold was more obvious with quite low temperatures. Delamination damage area increased while the temperature decreased from +60 °C to -50 °C.

  17. Characteristics of oxide scale formed on Cu-bearing austenitic stainless steel during early stages of high temperature oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Swaminathan, Srinivasan, E-mail: swaminathan@kist.re.kr [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 136 791 (Korea, Republic of); Krishna, Nanda Gopala [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Kim, Dong-Ik, E-mail: dongikkim@kist.re.kr [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 136 791 (Korea, Republic of)

    2015-10-30

    Highlights: • Initial oxidation characteristics of Cu-bearing austenitic stainless steel at 650 °C were studied. • Strong segregation and oxidation of Mn and Nb were found in the entire oxide scale. • Surface coverage by metallic Cu-rich precipitates increases with exposure time. • Chemical heterogeneity of oxide scale revealed initial oxidation to be non-selective. • Fe-Cr and Mn-Cr mixed oxides were realized along with binary oxides of Fe, Cr and Mn. - Abstract: Oxide scale evolution on Cu-bearing austenitic stainless steel 304H at 650 °C, in ambient air, for exposure times 100, 300, 500 and 1000 h, has been investigated. Surface morphology and chemistry of the oxide scale grown were examined using SEM/EDX and XPS. The oxidation kinetics was determined by measuring the weight change using an electronic balance. At the initial stage, up to 500 h of exposure time, the oxidation rate was rapid due to surface reactions governed primarily by oxygen ingress, and then, dropped to a low rate after prolonged oxidation for 1000 h. The diffusion of reactants through the initially formed oxide scale limits the oxidation rate at longer times, thus, the progress of reaction followed the parabolic kinetics. The formed oxide scale was enriched significantly with segregation and subsequent oxidation of Nb, and finely dispersed metallic Cu particles. Within the time frame of oxidation, the oxide scale was mainly composed of mixed oxides such as FeCr{sub 2}O{sub 4} and MnCr{sub 2}O{sub 4} along with the binary oxides of Fe, Cr and Mn. Moreover, the precipitation fraction of Cu-rich particles on the oxide scale increased markedly with increase of exposure times. The chemical heterogeneity of oxide scale suggests that the oxidation occurred in a non-selective manner.

  18. Oxidation/Corrosion Behaviour of ODS Ferritic/Martensitic Steels in Pb Melt at Elevated Temperature

    Directory of Open Access Journals (Sweden)

    O. I. Yaskiv

    2014-01-01

    Full Text Available Lead-based melts (Pb, Pb-Bi are considered as candidate coolants and spallation neutron targets due to their excellent thermophysical and nuclear properties. However, the corrosion of structural materials remains a major issue. Oxide dispersion strengthened (ODS ferritic/martensitic steels are considered for high temperature application for both fission and fusion reactor concepts. The oxidation/corrosion kinetics in a static oxygen-saturated Pb melt at temperature of 550°C as well as the morphology and composition of scales formed on ferritic/martensitic Fe-9Cr-1.5W and ferritic Fe-14Cr-1.5W ODS steels have been investigated. Both materials showed homogeneous multiple, dense scales that consisted of typical combination of Fe3O4 as outer sublayer and (Fe,Cr3O4 as inner sublayer. A nonuniform growth of inner oxide sublayers into the metal matrix as well as a good adhesion to the metal substrate is observed. With the prolongation of exposure from 240 to 1000 h, observed scales grow from 35 µm to 45 µm for ODS Fe-9Cr steel and from 40 µm to 60 µm for ODS Fe-14Cr steel with the thinning rates of 0,22 and 0,31 mm/year correspondingly. The mechanism of scales formation is discussed.

  19. Temperature Dependence of the Seebeck Coefficient in Zinc Oxide Thin Films

    Science.gov (United States)

    Noori, Amirreza; Masoumi, Saeed; Hashemi, Najmeh

    2017-12-01

    Thermoelectric devices are reliable tools for converting waste heat into electricity as they last long, produce no noise or vibration, have no moving elements, and their light weight makes them suitable for the outer space usage. Materials with high thermoelectric figure of merit (zT) have the most important role in the fabrication of efficient thermoelectric devices. Metal oxide semiconductors, specially zinc oxide has recently received attention as a material suitable for sensor, optoelectronic and thermoelectric device applications because of their wide direct bandgap, chemical stability, high-energy radiation endurance, transparency and acceptable zT. Understanding the thermoelectric properties of the undoped ZnO thin films can help design better ZnO-based devices. Here, we report the results of our experimental work on the thermoelectric properties of the undoped polycrystalline ZnO thin films. These films are deposited on alumina substrates by thermal evaporation of zinc in vacuum followed by a controlled oxidation process in air carried out at the 350-500 °C temperature range. The experimental setup including gradient heaters, thermometry system and Seebeck voltage measurement equipment for high resistance samples is described. Seebeck voltage and electrical resistivity of the samples are measured at different conditions. The observed temperature dependence of the Seebeck coefficient is discussed.

  20. High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors.

    Science.gov (United States)

    Banger, Kulbinder K; Peterson, Rebecca L; Mori, Kiyotaka; Yamashita, Yoshihisa; Leedham, Timothy; Sirringhaus, Henning

    2014-01-28

    Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm(2) V(-1) s(-1). We show that it is possible to solution-process these materials at low process temperature (225-200 °C yielding mobilities up to 4.4 cm(2) V(-1) s(-1)) and demonstrate a facile "ink-on-demand" process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium.

  1. Low temperature synthesis of lamellar transition metal oxides containing surfactant ions

    Energy Technology Data Exchange (ETDEWEB)

    Janauer, G.G.; Chen, R.; Dobley, A.D.; Zavalij, P.Y.; Whittingham, M.S. [State Univ. of New York, Binghamton, NY (United States)

    1997-09-01

    Recently there has been much interest in reacting vanadium oxides hydrothermally with cationic surfactants to form novel layered compounds. A series of new transition metal oxides, however, has also been formed at or near room temperature in open containers. Synthesis, characterization, and proposed mechanisms of formation are the focus of this work. Low temperature reactions of vanadium pentoxide and ammonium (DTA) transition metal oxides with long chain amine surfactants, such as dodecyltrimethylammonium bromide yielded interesting new products many of which are layered phases. DTA{sub 4}H{sub 2}V{sub 10}O{sub 28}{center_dot}8H{sub 2}O, a layered highly crystalline phase, is the first such phase for which a single crystal X-ray structure has been determined. The unit cell for this material was found to be triclinic with space group P {bar 1} and dimensions a = 9.895(1){angstrom}, b = 11.596(1){angstrom}, c = 21.924(1){angstrom}, {alpha} = 95.153(2){degree}, {beta} = 93.778(1){degree}, and {gamma} = 101.360(1){degree}. Additionally, the authors synthesized a dichromate phase and a manganese chloride layered phase, with interlayer spacings of 26.8{angstrom}, and 28.7{angstrom} respectively. The structure, composition, and synthesis of the vanadium compound are described, as well as the synthesis and preliminary characterization of the new chromium and manganese materials.

  2. Protective effect of alprazolam against sleep deprivation-induced behavior alterations and oxidative damage in mice.

    Science.gov (United States)

    Singh, Anant; Kumar, Anil

    2008-04-01

    Sleep deprivation is considered as a risk factor for various diseases. Sleep deprivation leads to behavioral, hormonal, neurochemical and biochemical alterations in the animals. The present study was designed to explore the possible involvement of GABAergic mechanism in protective effect of alprazolam against 72h sleep deprivation-induced behavior alterations and oxidative damage in mice. In the present study, sleep deprivation caused anxiety-like behavior, weight loss, impaired ambulatory movements and oxidative damage as indicated by increase in lipid peroxidation, nitrite level and depletion of reduced glutathione and catalase activity in sleep-deprived mice brain. Treatment with alprazolam (0.25 and 0.5 mg/kg, ip) significantly improved behavioral alterations. Biochemically, alprazolam treatment significantly restored depleted reduced glutathione, catalase activity, reversed raised lipid peroxidation and nitrite level. Combination of flumazenil (0.5 mg/kg) and picrotoxin (0.5 mg/kg) with lower dose of alprazolam (0.25mg/kg) significantly antagonized protective effect of alprazolam. However, combination of muscimol (0.05 mg/kg) with alprazolam (0.25 mg/kg, ip) potentiated protective effect of alprazolam. On the basis of these results, it might be suggested that alprazolam might produce protective effect by involving GABAergic system against sleep deprivation-induced behavior alterations and related oxidative damage.

  3. On the behavior of Bronsted-Evans-Polanyi Relations for Transition Metal Oxides

    Energy Technology Data Exchange (ETDEWEB)

    Vojvodic, Aleksandra

    2011-08-22

    Versatile Broensted-Evans-Polanyi (BEP) relations are found from density functional theory for a wide range of transition metal oxides including rutiles and perovskites. For oxides, the relation depends on the type of oxide, the active site and the dissociating molecule. The slope of the BEP relation is strongly coupled to the adsorbate geometry in the transition state. If it is final state-like the dissociative chemisorption energy can be considered as a descriptor for the dissociation. If it is initial state-like, on the other hand, the dissociative chemisorption energy is not suitable as descriptor for the dissociation. Dissociation of molecules with strong intramolecular bonds belong to the former and molecules with weak intramolecular bonds to the latter group. We show, for the prototype system La-perovskites, that there is a 'cyclic' behavior in the transition state characteristics upon change of the active transition metal of the oxide.

  4. Device performances of organic light-emitting diodes with indium tin oxide, gallium zinc oxide, and indium zinc tin oxide anodes deposited at room temperature.

    Science.gov (United States)

    Lee, Changhun; Ko, Yoonduk; Kim, Youngsung

    2013-12-01

    Thin films of Indium tin oxide (ITO), Gallium zinc oxide (GZO), and Indium zinc tin oxide (IZTO) were deposited on glass substrates by pulsed direct current magnetron sputtering at room temperature. The structural, optical, and electrical properties of the films were investigated towards evaluating their applications as flexible anodes. IZTO films exhibited the lowest resistivity (6.3 x 10(-4) Omega cm). Organic light-emitting diodes (OLEDs) were fabricated using the ITO, GZO, and IZTO films as anode layers. The turn-on voltages at a current density of 4.5 mA/cm2, 5.5 mA/cm2, 6.5 mA/cm2 were 5.5 V, 13.7 V, and 4.7 V for the devices with ITO, GZO, and IZTO anodes, respectively. The best performance was observed with the IZTO film, indicating its suitability as an alternative material for conventional ITO anodes used in OLEDs and flexible displays.

  5. Measuring hydroperoxide chain-branching agents during n-pentane low-temperature oxidation

    KAUST Repository

    Rodriguez, Anne

    2016-06-23

    The reactions of chain-branching agents, such as HO and hydroperoxides, have a decisive role in the occurrence of autoignition. The formation of these agents has been investigated in an atmospheric-pressure jet-stirred reactor during the low-temperature oxidation of n-pentane (initial fuel mole fraction of 0.01, residence time of 2s) using three different diagnostics: time-of-flight mass spectrometry combined with tunable synchrotron photoionization, time-of-flight mass spectrometry combined with laser photoionization, and cw-cavity ring-down spectroscopy. These three diagnostics enable a combined analysis of HO, C-C, and C alkylhydroperoxides, C-C alkenylhydroperoxides, and C alkylhydroperoxides including a carbonyl function (ketohydroperoxides). Results using both types of mass spectrometry are compared for the stoichiometric mixture. Formation data are presented at equivalence ratios from 0.5 to 2 for these peroxides and of two oxygenated products, ketene and pentanediones, which are not usually analyzed during jet-stirred reactor oxidation. The formation of alkenylhydroperoxides during alkane oxidation is followed for the first time. A recently developed model of n-pentane oxidation aids discussion of the kinetics of these products and of proposed pathways for C-C alkenylhydroperoxides and the pentanediones.

  6. UV-Mediated Photochemical Treatment for Low-Temperature Oxide-Based Thin-Film Transistors.

    Science.gov (United States)

    Carlos, Emanuel; Branquinho, Rita; Kiazadeh, Asal; Barquinha, Pedro; Martins, Rodrigo; Fortunato, Elvira

    2016-11-16

    Solution processing of amorphous metal oxides has lately been used as an option to implement in flexible electronics, allowing a reduction of the associated costs and high performance. However, the research has focused more on the semiconductor layer rather than on the insulator layer, which is related to the stability and performance of the devices. This work aims to evaluate amorphous aluminum oxide thin films produced by combustion synthesis and the influence of far-ultraviolet (FUV) irradiation on the properties of the insulator on thin-film transistors (TFTs) using different semiconductors, in order to have compatibility with flexible substrates. An optimized dielectric layer was obtained for an annealing of 30 min assisted by FUV exposure. These thin films were applied in gallium-indium-zinc oxide TFTs as dielectrics showing the best results for TFTs annealed at 180 °C with FUV irradiation: good reproducibility with a subthreshold slope of 0.11 ± 0.01 V dec (-1) and a turn-on voltage of -0.12 ± 0.05 V, low operating voltage, and good stability over time. Finally, the dielectric layer was applied in solution-processed indium oxide (In2O3) TFTs at low temperature, 180 °C, with a short processing time being compatible with flexible electronic applications.

  7. Mechanical behavior of intragranular, nano-porous electrodeposited zinc oxide

    Energy Technology Data Exchange (ETDEWEB)

    Raghavan, Rejin, E-mail: r.raghavan@mpie.de [Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures, Feuerwerkstrasse 39, 3602 Thun (Switzerland); Elias, Jamil [Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures, Feuerwerkstrasse 39, 3602 Thun (Switzerland); Erni, Rolf; Parlinska, Magdalena [Empa, Swiss Federal Laboratories for Materials Science and Technology, Electron Microscopy Center, Ueberlandstrasse 129, 8600 Duebendorf (Switzerland); Philippe, Laetitia; Michler, Johann [Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures, Feuerwerkstrasse 39, 3602 Thun (Switzerland)

    2015-03-02

    The mechanical properties and deformation mechanisms of nano-porous ZnO thin films electrodeposited on glass substrates were determined by nanoindentation and in situ scanning electron microscope (SEM) micropillar compression. The intragranular nature of the nanoscale porosity within the individual mono-crystals of the films was probed at nano- and micro-scales for determining their mechanical response. The hardness (3.5 GPa) and reduced elastic modulus (65 GPa) of the compact thin film were found to decrease by increasing the intragranular porosity controlled by the electrochemical deposition potential of ZnO. Focused ion beam (FIB) cross-sections of residual imprints reveal that the decrease in hardness and elastic modulus observed is primarily due to compaction of the nano-porous structure. In situ SEM compression of FIB machined micropillars reveals brittle fracture and near theoretical strengths in the compact film (~ 2 GPa), and a higher flaw tolerant response despite lower failure stress in the most porous film. - Highlights: • Micromechanical behavior of intragranular, nanoporous electrodeposited ZnO thin films • Densification by closure of porosity during indentation • Resistance to fracture by crack deflection and blunting in porous films during microcompression.

  8. Anamolous reduction of magnetic coercivity of graphene oxide and reduced graphene oxide upon cooling

    OpenAIRE

    Bagani, K.; Bhattacharya, A; Kaur, J.; Chowdhury, A. Rai; Ghosh, B.; Sardar, M.; Banerjee, S.

    2013-01-01

    In this report we present the temperature evolution of magnetic coercivity of graphene oxide (GO) and reduced graphene oxide (RGO). We report an anamolous decrease in coercivity of GO and RGO with decreasing temperature. We could explain this anamolous behavior invoking the inherent presence of ripple in graphene. We observe antiferromagnetic and ferromagnetic behavior at room temperature for GO and RGO respectively, but at low temperatures both shows paramagnetic behavior.

  9. Temperature-driven growth of reduced graphene oxide/copper nanocomposites for glucose sensing

    Science.gov (United States)

    Zhang, Qi; Wu, Zhong; Xu, Chen; Liu, Lei; Hu, Wenbin

    2016-12-01

    A one-spot method was developed for the synthesis of graphene sheet decorated with copper nanoparticles using different reduction temperatures via a molecular level mixing process. Here, we demonstrate that the reduction temperature is a crucial determinant of the properties of reduced graphene oxide (RGO)/metal composite and its electrocatalytic application in glucose sensing. To show this, we prepared a series of RGO/Cu composites at different reduction temperatures and examined the change rules of size, loading and dispersion of Cu particles, and the reduction extent of the RGO. Results showed that the Cu particle size increased with increasing reduction temperatures due to the Ostwald ripening process. Meanwhile, the Cu loading decreased with increasing reduction temperatures and the aggregation had not appeared in the high Cu loading situation. Additionally, the increasing reduction temperatures led to the decreasing concentrations of various oxygen-containing functional group of RGO with various degrees. The cyclic voltammogram showed that the RGO/metal composites fabricated under lower reduction temperatures exhibited higher electrocatalytic activity for glucose sensing, which was attributed to the higher surface area from larger loading of RGO/metal composites with smaller particle size. It can be concluded that the above factors play more significant roles in electrocatalytic efficiency than the decreased electron transfer rate between RGO and Cu within a certain range. These results highlight the importance of the reduction temperature influencing the properties of the RGO/metal composite and its application. We believe that these findings can be of great value in the further developing RGO/metal-based sensors for electrochemical detection of different analytes in emerging fields.

  10. Sodium-promoted Pd/TiO2 for catalytic oxidation of formaldehyde at ambient temperature.

    Science.gov (United States)

    Zhang, Changbin; Li, Yaobin; Wang, Yafei; He, Hong

    2014-05-20

    Catalytic oxidation of formaldehyde (HCHO) to CO2 at ambient conditions is of great interest for indoor HCHO purification. Here, we report that sodium-doped Pd/TiO2 is a highly effective catalyst for the catalytic oxidation of HCHO at room temperature. It was observed that Na doping has a dramatic promotion effect on the Pd/TiO2 catalyst and that nearly 100% HCHO conversion could be achieved over the 2Na-Pd/TiO2 catalyst at a GHSV of 95000 h(-1) and HCHO inlet concentration of 140 ppm at 25 °C. The mechanism of the Na-promotion effect was investigated by using Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), CO chemisorption, Temperature-programmed reduction by H2 (H2-TPR), X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption of O2 (O2-TPD) methods. The results showed that Na species addition can induce and further stabilize a negatively charged and well-dispersed Pd species, which then facilitates the activation of H2O and chemisorbed oxygen, therefore resulting in the high performance of the 2Na-Pd/TiO2 catalyst for the ambient HCHO destruction.

  11. Effects of Oxygen Partial Pressure on Oxidation Behavior of CMnSi TRIP Steel in an Oxidation-Reduction Scheme

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seong-Hwan; Huh, Joo-Youl [Korea University, Seoul (Korea, Republic of); Kim, Myung-Soo; Kim, Jong-Sang [POSCO Technical Research Laboratories, Gwangyang (Korea, Republic of)

    2017-02-15

    An oxidation-reduction scheme is an alternative approach for improving the galvanizability of advanced high-strength steel in the continuous hot-dip galvanizing process. Here, we investigated the effect of oxygen partial pressure (Po{sub 2}) on the oxidation behavior of a transformation-induced plasticity steel containing 1.5 wt% Si and 1.6 wt% Mn during heating to and holding for 60 s at 700 ℃ under atmospheres with various Po{sub 2} values. Irrespective of Po{sub 2}, a thin amorphous Si-rich layer of Si-Mn-O was formed underneath the Fe