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Sample records for high-temperature pyrolysis mechanisms

  1. Fast pyrolysis of biomass at high temperatures

    DEFF Research Database (Denmark)

    Trubetskaya, Anna

    This Ph.D. thesis describes experimental and modeling investigations of fast high temperature pyrolysis of biomass. Suspension firing of biomass is widely used for power generation and has been considered as an important step in reduction of greenhouse gas emissions by using less fossil fuels. Fast...... to investigate the effects of operating parameters and biomass types on yields of char and soot, their chemistry and morphology as well as their reactivity using thermogravimetric analysis. The experimental study was focused on the influence of a wide range of operating parameters including heat treatment...... alkali metals. In this study, potassium lean pinewood (0.06 wt. %) produced the highest soot yield (9 and 7 wt. %) at 1250 and 1400°C, whereas leached wheat straw with the higher potassium content (0.3 wt. %) generated the lowest soot yield (2 and 1 wt. %). Soot yields of wheat and alfalfa straw at both...

  2. High temperature materials and mechanisms

    CERN Document Server

    2014-01-01

    The use of high-temperature materials in current and future applications, including silicone materials for handling hot foods and metal alloys for developing high-speed aircraft and spacecraft systems, has generated a growing interest in high-temperature technologies. High Temperature Materials and Mechanisms explores a broad range of issues related to high-temperature materials and mechanisms that operate in harsh conditions. While some applications involve the use of materials at high temperatures, others require materials processed at high temperatures for use at room temperature. High-temperature materials must also be resistant to related causes of damage, such as oxidation and corrosion, which are accelerated with increased temperatures. This book examines high-temperature materials and mechanisms from many angles. It covers the topics of processes, materials characterization methods, and the nondestructive evaluation and health monitoring of high-temperature materials and structures. It describes the ...

  3. Experimental study of rapid brown coal pyrolysis at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Lin; Sun, Shaozeng; Meng, Shun; Meng, Xianyu; Guo, Yangzhou [Harbin Institute of Technology, Harbin (China). Combustion Engineering Research Inst.

    2013-07-01

    Rapid coal pyrolysis is a very important step in the early stage of combustion. Rapid pyrolysis experiments of a brown coal at high temperature have been studied on a laminar drop tube furnace. The volatile mass release measured in this study is high for low rank coal. The activation energy and pre-exponential factor of pyrolysis are 19901.22 kJ/mol and 102.71, respectively. The nitrogen distribution between volatile and char is 0.54. With the increase of temperature, the yields of NH{sub 3} decreases, while those of HCN increases, leading the value of HCN/NH{sub 3} to become larger. At high temperature, the main nitrogen- containing species of pyrolysis in volatile is HCN.

  4. High temperature SU-8 pyrolysis for fabrication of carbon electrodes

    DEFF Research Database (Denmark)

    Hassan, Yasmin Mohamed; Caviglia, Claudia; Hemanth, Suhith

    2017-01-01

    In this work, we present the investigation of the pyrolysis parameters at high temperature (1100 °C) for the fabrication of two-dimensional pyrolytic carbon electrodes. The electrodes were fabricated by pyrolysis of lithographically patterned negative epoxy based photoresist SU-8. A central...... composite experimental design was used to identify the influence of dwell time at the highest pyrolysis temperature and heating rate on electrical, electrochemical and structural properties of the pyrolytic carbon: Van der Pauw sheet resistance measurements, cyclic voltammetry, electrochemical impedance...... spectroscopy and Raman spectroscopy were used to characterize the pyrolytic carbon. The results show that the temperature increase from 900 °C to 1100 °C improves the electrical and electrochemical properties. At 1100 °C, longer dwell time leads to lower resistivity, while the variation of the pyrolysis...

  5. High temperature mechanical properties of iron aluminides

    International Nuclear Information System (INIS)

    Morris, D. G.; Munoz-Morris, M. A.

    2001-01-01

    Considerable attention has been given to the iron aluminide family of intermetallics over the past years since they offer considerable potential as engineering materials for intermediate to high temperature applications, particularly in cases where extreme oxidation or corrosion resistance is required. Despite efforts at alloy development, however, high temperature strength remains low and creep resistance poor. Reasons for the poor high-temperature strength of iron aluminides will be discussed, based on the ordered crystal structure, the dislocation structure found in the materials, and the mechanisms of dislocation pinning operating. Alternative ways of improving high temperature strength by microstructural modification and the inclusion of second phase particles will also be considered. (Author)

  6. Multi-species time-history measurements during high-temperature acetone and 2-butanone pyrolysis

    KAUST Repository

    Lam, Kingyiu; Ren, Wei; Pyun, Sunghyun; Farooq, Aamir; Davidson, David Frank; Hanson, Ronald Kenneth

    2013-01-01

    High-temperature acetone and 2-butanone pyrolysis studies were conducted behind reflected shock waves using five species time-history measurements (ketone, CO, CH3, CH4 and C2H4). Experimental conditions covered temperatures of 1100-1600 Kat 1.6 atm

  7. Multi-species time-history measurements during high-temperature acetone and 2-butanone pyrolysis

    KAUST Repository

    Lam, Kingyiu

    2013-01-01

    High-temperature acetone and 2-butanone pyrolysis studies were conducted behind reflected shock waves using five species time-history measurements (ketone, CO, CH3, CH4 and C2H4). Experimental conditions covered temperatures of 1100-1600 Kat 1.6 atm, for mixtures of 0.25-1.5% ketone in argon. During acetone pyrolysis, the CO concentration time-history was found to be strongly sensitive to the acetone dissociation rate constant κ1 (CH3COCH3 → CH3 + CH3CO), and this could be directly determined from the CO time-histories, yielding κ1(1.6 atm) = 2.46 × 1014 exp(-69.3 [kcal/mol]/RT) s-1 with an uncertainty of ±25%. This rate constant is in good agreement with previous shock tube studies from Sato and Hidaka (2000) [3] and Saxena et al. (2009) [4] (within 30%) at temperatures above 1450 K, but is at least three times faster than the evaluation from Sato and Hidaka at temperatures below 1250 K. Using this revised κ1 value with the recent mechanism of Pichon et al. (2009) [5], the simulated profiles during acetone pyrolysis show excellent agreement with all five species time-history measurements. Similarly, the overall 2-butanone decomposition rate constant κtot was inferred from measured 2-butanone time-histories, yielding κ tot(1.5 atm) = 6.08 × 1013 exp(-63.1 [kcal/mol]/RT) s -1 with an uncertainty of ±35%. This rate constant is approximately 30% faster than that proposed by Serinyel et al. (2010) [11] at 1119 K, and approximately 100% faster at 1412 K. Using the measured 2-butanone and CO time-histories and an O-atom balance analysis, a missing removal pathway for methyl ketene was identified. The rate constant for the decomposition of methyl ketene was assumed to be the same as the value for the ketene decomposition reaction. Using the revised κtot value and adding the methyl ketene decomposition reaction to the Serinyel et al. mechanism, the simulated profiles during 2-butanone pyrolysis show good agreement with the measurements for all five species.

  8. Toluene pyrolysis studies and high temperature reactions of propargyl chloride

    Energy Technology Data Exchange (ETDEWEB)

    Kern, R.D.; Chen, H.; Qin, Z. [Univ. of New Orleans, LA (United States)

    1993-12-01

    The main focus of this program is to investigate the thermal decompositions of fuels that play an important role in the pre-particle soot formation process. It has been demonstrated that the condition of maximum soot yield is established when the reaction conditions of temperature and pressure are sufficient to establish a radical pool to support the production of polyaromatic hydrocarbon species and the subsequent formation of soot particles. However, elevated temperatures result in lower soot yields which are attributed to thermolyses of aromatic ring structures and result in the bell-shaped dependence of soot yield on temperature. The authors have selected several acyclic hydrocarbons to evaluate the chemical thermodynamic and kinetic effects attendant to benzene formation. To assess the thermal stability of the aromatic ring, the authors have studied the pyrolyses of benzene, toluene, ethylbenzene, chlorobenzene and pyridine. Time-of-flight mass spectrometry (TOF) is employed to analyze the reaction zone behind reflected shock waves. Reaction time histories of the reactants, products, and intermediates are constructed and mechanisms are formulated to model the experimental data. The TOF work is often performed with use of laser schlieren densitometry (LS) to measure density gradients resulting from the heats of various reactions involved in a particular pyrolytic system. The two techniques, TOF and LS, provide independent and complementary information about ring formation and ring rupture reactions.

  9. Potassium and soot interaction in fast biomass pyrolysis at high temperatures

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Hofmann Larsen, Flemming; Shchukarev, Andrey

    2018-01-01

    2 reactivity was studied by thermogravimetric analysis. The XPS results showed that potassium incorporation with oxygen-containing surface groups in the soot matrix did not occur during high temperature pyrolysis. The potassium was mostly found as water-soluble salts such as KCl, KOH, KHCO3 and K2CO...... potassium amount was incorporated in the soot matrix during pyrolysis. Raman spectroscopy results showed that the carbon chemistry of biomass soot also affected the CO2 reactivity. The less reactive pinewood soot was more graphitic than herbaceous biomass soot samples with the disordered carbon structure...

  10. Hydrogen production from biomass pyrolysis gas via high temperature steam reforming process

    International Nuclear Information System (INIS)

    Wongchang, Thawatchai; Patumsawad, Suthum

    2010-01-01

    Full text: The aim of this work has been undertaken as part of the design of continuous hydrogen production using the high temperature steam reforming process. The steady-state test condition was carried out using syngas from biomass pyrolysis, whilst operating at high temperatures between 600 and 1200 degree Celsius. The main reformer operating parameters (e.g. temperature, resident time and steam to biomass ratio (S/B)) have been examined in order to optimize the performance of the reformer. The operating temperature is a key factor in determining the extent to which hydrogen production is increased at higher temperatures (900 -1200 degree Celsius) whilst maintaining the same as resident time and S/B ratio. The effects of exhaust gas composition on heating value were also investigated. The steam reforming process produced methane (CH 4 ) and ethylene (C 2 H 4 ) between 600 to 800 degree Celsius and enhanced production ethane (C 2 H 6 ) at 700 degree Celsius. However carbon monoxide (CO) emission was slightly increased for higher temperatures all conditions. The results show that the use of biomass pyrolysis gas can produce higher hydrogen production from high temperature steam reforming. In addition the increasing reformer efficiency needs to be optimized for different operating conditions. (author)

  11. Mechanical properties of concrete for power reactor at high temperatures

    International Nuclear Information System (INIS)

    Kawase, Kiyotaka; Tanaka, Hitoshi; Nakano, Masayuki

    1985-01-01

    The purpose of this study is to investigate the mechanical properties of concrete for power reactor at high temperature. This paper presents the creep behavior of concrete at high temperature and the cause by which a specified aggregate is broken at a specified high temperature. The creep coefficient at high temperature is smaller than that at ordinary temperature. (author)

  12. High temperature shock tube experiments and kinetic modeling study of diisopropyl ketone ignition and pyrolysis

    KAUST Repository

    Barari, Ghazal

    2017-03-10

    Diisopropyl ketone (DIPK) is a promising biofuel candidate, which is produced using endophytic fungal conversion. In this work, a high temperature detailed combustion kinetic model for DIPK was developed using the reaction class approach. DIPK ignition and pyrolysis experiments were performed using the UCF shock tube. The shock tube oxidation experiments were conducted between 1093K and 1630K for different reactant compositions, equivalence ratios (φ=0.5–2.0), and pressures (1–6atm). In addition, methane concentration time-histories were measured during 2% DIPK pyrolysis in argon using cw laser absorption near 3400nm at temperatures between 1300 and 1400K near 1atm. To the best of our knowledge, current ignition delay times (above 1050K) and methane time histories are the first such experiments performed in DIPK at high temperatures. Present data were used as validation targets for the new kinetic model and simulation results showed fair agreement compared to the experiments. The reaction rates corresponding to the main consumption pathways of DIPK were found to have high sensitivity in controlling the reactivity, so these were adjusted to attain better agreement between the simulation and experimental data. A correlation was developed based on the experimental data to predict the ignition delay times using the temperature, pressure, fuel concentration and oxygen concentration.

  13. High temperature shock tube experiments and kinetic modeling study of diisopropyl ketone ignition and pyrolysis

    KAUST Repository

    Barari, Ghazal; Pryor, Owen; Koroglu, Batikan; Sarathy, Mani; Masunov, Artë m E.; Vasu, Subith S.

    2017-01-01

    Diisopropyl ketone (DIPK) is a promising biofuel candidate, which is produced using endophytic fungal conversion. In this work, a high temperature detailed combustion kinetic model for DIPK was developed using the reaction class approach. DIPK ignition and pyrolysis experiments were performed using the UCF shock tube. The shock tube oxidation experiments were conducted between 1093K and 1630K for different reactant compositions, equivalence ratios (φ=0.5–2.0), and pressures (1–6atm). In addition, methane concentration time-histories were measured during 2% DIPK pyrolysis in argon using cw laser absorption near 3400nm at temperatures between 1300 and 1400K near 1atm. To the best of our knowledge, current ignition delay times (above 1050K) and methane time histories are the first such experiments performed in DIPK at high temperatures. Present data were used as validation targets for the new kinetic model and simulation results showed fair agreement compared to the experiments. The reaction rates corresponding to the main consumption pathways of DIPK were found to have high sensitivity in controlling the reactivity, so these were adjusted to attain better agreement between the simulation and experimental data. A correlation was developed based on the experimental data to predict the ignition delay times using the temperature, pressure, fuel concentration and oxygen concentration.

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

    Science.gov (United States)

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

    2018-04-01

    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.

  15. Mechanical properties of rock at high temperatures

    International Nuclear Information System (INIS)

    Kinoshita, Naoto; Abe, Tohru; Wakabayashi, Naruki; Ishida, Tsuyoshi.

    1997-01-01

    The laboratory tests have been performed in order to investigate the effects of temperature up to 300degC and pressure up to 30 MPa on the mechanical properties of three types of rocks, Inada granite, Sanjoume andesite and Oya tuff. The experimental results indicated that the significant differences in temperature dependence of mechanical properties exist between the three rocks, because of the difference of the factors which determine the mechanical properties of the rocks. The effect of temperature on the mechanical properties for the rocks is lower than that of pressure and water content. Temperature dependence of the mechanical properties is reduced by increase in pressure in the range of pressure and temperature investigated in this paper. (author)

  16. Mechanism of high-temperature resistant water-base mud

    Energy Technology Data Exchange (ETDEWEB)

    Luo, P

    1981-01-01

    Based on experiments, the causes and laws governing the changes in the performance of water-base mud under high temperature are analyzed, and the requisites and mechanism of treating agents resisting high temperature are discussed. Ways and means are sought for inhibiting, delaying and making use of the effect of high temperature on the performance of mud, while new ideas and systematic views have been expressed on the preparation of treating agents and set-up of a high temperature resistant water-base mud system. High temperature dispersion and high temperature surface inactivation of clay in the mud, as well as their effect and method of utilization are reviewed. Subjects also touched upon include degradation and cross-linking of the high-temperature resistant treating agents, their use and effect. Based on the above, the preparation of a water-base and system capable of resisting 180 to 250/sup 0/C is recommended.

  17. High temperature mechanical forming of Mg alloys

    International Nuclear Information System (INIS)

    Mwembela, A.; McQueen, H.J.; Myshlyaev, M.

    2002-01-01

    Mg alloys are hot worked in the range 180-450 o C and 0.0-10 s -1 ; the present project data are compared with a wide selection of published results. The flow stresses and their dependence on temperature and strain rate are fairly similar to simple Al alloys: however, the hot ductility is much lower (≤3 in torsion). Twinning plays a significant role in Mg alloys almost independently of temperature; the twins initiate at low strains in grains poorly oriented for basal slip and in consequence become well disposed for such slip. As T rises, there is increasing formation of subgrains that spread toward the grain centers from grain and twin boundaries: this is indicative of stress concentrations inducing non-basal sup which helps provide the geometrically necessary dislocations. Above about 240 o C, dynamic (DRX) nucleates at grain and twin boundaries, preferentially at intersections; this again is evidence of non-basal slip that provides the highly misoriented cells. The boundaries in which further strain concentrates producing further DRX. The microstructure remains very heterogeneous compared to the uniform dynamically recovered substructure in Al alloys, thus giving rise to the reduced ductility. These results are employed to interpret the mechanical and microstructural behavior of Mg alloys in extrusion, rolling and forging. (author)

  18. Techno-economic evaluation of high temperature pyrolysis processes for mixed plastic waste.

    NARCIS (Netherlands)

    Westerhout, R.W.J.; Westerhout, R.W.J.; van Koningsbruggen, M.P.; van der Ham, Aloysius G.J.; Kuipers, J.A.M.; van Swaaij, Willibrordus Petrus Maria

    1998-01-01

    Three pyrolysis processes for Mixed Plastic Waste (MPW) with different reactors (Bubbling Fluidized Bed, Circulating Fluidized Bed and Rotating Cone Reactor, respectively BFB, CFB and RCR) were designed and evaluated. The estimated fixed capital investment for a 50 kton/year MPW pyrolysis plant

  19. New diffusion mechanism for high temperature diffusion in solids

    International Nuclear Information System (INIS)

    Doan, N.V.; Adda, Y.

    1986-09-01

    A new atomic transport mechanism in solids at high temperatures has been discovered by Molecular Dynamics computer simulation. It can be described as a ring sequence of atomic replacements induced by unstable Frenkel pairs. This transport process takes place without stable defects, the atomic migration occurring indeed by simultaneous creation and migration of unstable defects. Starting from the analysis of this mechanism in different solids at high temperature (CaF 2 , Na, Ar) and in irradiated copper by subthreshold collisions, we discuss the role of this mechanism on various diffusion controlled phenomena and also on the atomic processes of defect creation

  20. Failure mechanisms in high temperature gas cooled reactor fuel particles

    International Nuclear Information System (INIS)

    Soo, P.; Uneberg, G.; Sabatini, R.L.; Schweitzer, D.G.

    1979-01-01

    BISO coated UO 2 and ThO 2 particles were heated to high temperatures to determine failure mechanisms during hypothetical loss of coolant scenarios. Rapid failure begins when the oxides are reduced to liquid carbides. Several failure mechanisms are applicable, ranging from hole and crack formation in the coatings to catastrophic particle disintegration

  1. Effect of fast pyrolysis conditions on biomass solid residues at high temperatures

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Jensen, Peter Arendt; Jensen, Anker Degn

    2016-01-01

    Fast pyrolysis of wood and straw was conducted in a drop tube furnace (DTF) and compared with corresponding data from a wire mesh reactor (WMR) to study the influence of temperature (1000-1400)°C, biomass origin (pinewood, beechwood, wheat straw, alfalfa straw), and heating rate (103 °C/s, 104 °C...... in its half-width with respect to the parental fuel, whereas the alfalfa straw char particle size remained unaltered at higher temperatures. Soot particles in a range from 60 to 300 nm were obtained during fast pyrolysis. The soot yield from herbaceous fuels was lower than from wood samples, possibly due...

  2. Effect of Fast Pyrolysis Conditions on Structural Transformation and Reactivity of Herbaceous Biomasses at High Temperatures

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Jensen, Anker D.; Jensen, Peter Arendt

    of organic and inorganic matter on the char structural transformations. The results indicate no influence of the free radicals on char reactivity and burnout. The formation of free radicals in fast pyrolysis is related to the differences in the ash composition, namely presence of K+ ions in the wheat straw...

  3. Effects of Lignocellulosic Compounds on the Yield, Nanostructure and Reactivity of Soot from Fast Pyrolysis at High Temperatures

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Broström, Markus; Kling, Jens

    reactor. The specific objectives of this study were to: (1) obtain knowledge about lignocellulosic compounds and monolignols influence on the yield, nanostructure, composition, and reactivity of soot during high-temperature gasification, (2) understand the influence of Soxhlet extraction on the soot......Gasification offers the utilization of biomass to a wide variety of applications such as heat, electricity, chemicals and transport fuels in an efficient and sustainable manner. High soot yields in the high-temperature entrained flow gasification lead to intensive gas cleaning and can cause...... primary, secondary and teriary pyrolysis products such as organic acids, aldehydes and phenolics [1]. In this study, therefore, the impacts of lignocellulosic compounds and monolignols (syringol, guaiacol, p-hydroxyphenol) on the yield and characteristics of soot were investigated at 1250°C in a drop tube...

  4. High Temperature Electro-Mechanical Devices For Nuclear Applications

    International Nuclear Information System (INIS)

    Robertson, D.

    2010-01-01

    Nuclear power plants require a number of electro-mechanical devices, for example, Control Rod Drive Mechanisms (CRDM's) to control the raising and lowering of control rods and Reactor Coolant Pumps (RCP's) to circulate the primary coolant. There are potential benefits in locating electro-mechanical components in areas of the plant with high ambient temperatures. One such benefit is the reduced need to make penetrations in pressure vessels leading to simplified plant design and improved inherent safety. The feature that limits the ambient temperature at which most electrical machines may operate is the material used for the electrical insulation of the machine windings. Conventional electrical machines generally use polymer-based insulation that limits the ambient temperature they can operate in to below 200 degrees Celsius. This means that when a conventional electrical machine is required to operate in a hot area it must be actively cooled necessitating additional systems. This paper presents data gathered during investigations undertaken by Rolls-Royce into the design of high temperature electrical machines. The research was undertaken at Rolls-Royce's University Technology Centre in Advanced Electrical Machines and Drives at Sheffield University. Rolls- Royce has also been investigating high temperature wire and encapsulants and latterly techniques to provide high temperature insulation to terminations. Rolls-Royce used the experience gained from these tests to produce a high temperature electrical linear actuator at sizes representative of those used in reactor systems. This machine was tested successfully at temperatures equivalent to those found inside the reactor vessel of a pressurised water reactor through a full series of operations that replicated in service duty. The paper will conclude by discussing the impact of the findings and potential electro-mechanical designs that may utilise such high temperature technologies. (authors)

  5. Mechanical properties of LMR structural materials at high temperature

    International Nuclear Information System (INIS)

    Kim, D. W.; Kuk, I. H.; Ryu, W. S. and others

    1999-03-01

    Austenitic stainless is used for the structural material of liquid metal reactor (LMR) because of good mechanical properties at high temperature. Stainless steel having more resistant to temperature by adding minor element has been developing for operating the LMR at higher temperature. Of many elements, nitrogen is a prospective element to modify type 316L(N) stainless steel because nitrogen is the most effective element for solid solution and because nitrogen retards the precipitation of carbide at grain boundary. Ti, Nb, and V are added to improve creep properties by stabilizing the carbides through forming MC carbide. Testing techniques of tensile, fatigue, creep, and creep-fatigue at high temperature are difficult. Moreover, testing times for creep and creep-fatigue tests are very long up to several tens of thousands hours because creep and creep-fatigue phenomena are time-dependent damage mechanism. So, it is hard to acquire the material data for designing LMR systems during a limited time. In addition, the integrity of LMR structural materials at the end of LMR life has to be predicted from the laboratory data tested during the short term because there is no data tested during 40 years. Therefore, the effect of elements on mechanical properties at high temperature was reviewed in this study and many methods to predict the long-term behaviors of structural materials by simulated modelling equation is shown in this report. (author). 32 refs., 9 tabs., 38 figs

  6. The catalytic cracking mechanism of lignite pyrolysis char on tar

    International Nuclear Information System (INIS)

    Lei, Z.; Huibin, H.; Xiangling, S.; Zhenhua, M.; Lei, Z.

    2017-01-01

    The influence of different pyrolysis conditions for tar catalytic cracking will be analyzed according to the lignite pyrolysis char as catalyst on pyrolytic tar in this paper. The pyrolysis char what is the by-product of the cracking of coal has an abundant of pore structure and it has good catalytic activity. On this basis, making the modified catalyst when the pyrolysis char is activation and loads Fe by impregnation method. The cracking mechanism of lignite pyrolytic tar is explored by applying gas chromatograph to analyze splitting products of tar. The experimental results showed that: (1) The effect of tar cracking as the pyrolysis temperature, the heating rate, the volatilization of pyrolysis char and particle size increasing is better and better. The effect of the catalytic and cracking of lignite pyrolysis char in tar is best when the heating rate, the pyrolysis temperature, the volatiles of pyrolysis char, particle size is in specific conditions.(2) The activation of pyrolysis char can improve the catalytic effect of pyrolysis char on the tar cracking. But it reduces the effect of the tar cracking when the pyrolysis char is activation loading Fe. (author)

  7. Reaction mechanisms in cellulose pyrolysis: a literature review

    Energy Technology Data Exchange (ETDEWEB)

    Molton, P.M.; Demmitt, T.F.

    1977-08-01

    A bibliographic review of 195 references is presented outlining the history of the research into the mechanisms of cellulose pyrolysis. Topics discussed are: initial product identification, mechanism of initial formation of levoglucosan, from cellulose and from related compounds, decomposition of cellulose to other compounds, formation of aromatics, pyrolysis of levoglucosan, crosslinking of cellulose, pyrolytic reactions of cellulose derivatives, and the effects of inorganic salts on the pyrolysis mechanism. (JSR)

  8. Mechanical behavior of high strength ceramic fibers at high temperatures

    Science.gov (United States)

    Tressler, R. E.; Pysher, D. J.

    1991-01-01

    The mechanical behavior of commercially available and developmental ceramic fibers, both oxide and nonoxide, has been experimentally studied at expected use temperatures. In addition, these properties have been compared to results from the literature. Tensile strengths were measured for three SiC-based and three oxide ceramic fibers for temperatures from 25 C to 1400 C. The SiC-based fibers were stronger but less stiff than the oxide fibers at room temperature and retained more of both strength and stiffness to high temperatures. Extensive creep and creep-rupture experiments have been performed on those fibers from this group which had the best strengths above 1200 C in both single filament tests and tests of fiber bundles. The creep rates for the oxides are on the order of two orders of magnitude faster than the polymer derived nonoxide fibers. The most creep resistant filaments available are single crystal c-axis sapphire filaments. Large diameter CVD fabricated SiC fibers are the most creep and rupture resistant nonoxide polycrystalline fibers tested to date.

  9. Thermal-mechanical fatigue of high temperature structural materials

    Science.gov (United States)

    Renauld, Mark Leo

    Experimental and analytical methods were developed to address the effect of thermal-mechanical strain cycling on high temperature structural materials under uniaxial and biaxial stress states. Two materials were used in the investigation, a nickel-base superalloy of low ductility, IN-738LC and a high ductility material, 316 stainless steel. A uniaxial life prediction model for the IN-738LC material was based on tensile hysteresis energy measured in stabilized, mid-life hysteresis loops. Hold-time effects and temperature cycling were incorporated in the hysteresis energy approach. Crack growth analysis was also included in the model to predict the number of TMF cycles to initiate and grow a fatigue crack through the coating. The nickel-base superalloy, IN-738LC, was primarily tested in out-of-phase (OP) TMF with a temperature range from 482-871sp°C (900-1600sp°F) under continuous and compressive hold-time cycling. IN-738LC fatigue specimens were coated either with an aluminide, NiCoCrAlHfSi overlay or CoNiCrAlY overlay coating on the outer surface of the specimen. Metallurgical failure analysis via optical and scanning electron microscopy, was used to characterize failure behavior of both substrate and coating materials. Type 316 SS was subjected to continuous biaxial strain cycling with an in-phase (IP) TMF loading and a temperature range from 399-621sp°C (750-1150sp°F). As a result, a biaxial TMF life prediction model was proposed on the basis of an extended isothermal fatigue model. The model incorporates a frequency effect and phase factors to assess the different damage mechanisms observed during TMF loading. The model was also applied to biaxial TMF data generated on uncoated IN-738LC.

  10. High temperature mechanical tests performed on doped fuels

    International Nuclear Information System (INIS)

    Dugay, C.; Mocellin, A.; Dehaudt, P.; Sladkoff, M.

    1998-01-01

    The high-temperature compressive deformation of large-grained UO 2 doped with metallic oxides has been investigated and compared with that of pure UO 2 with a standard microstructure. All the specimens are made from a single batch of UO 2 powder. Tests with constant applied strain rate of 20μm.min -1 show that Cr 2 O 3 additions cause a decrease in the flow stress of about 15 MPa compared with the reference material. When reduced in hydrogen at 1500 deg. C the specimens present a peak stress close to the flow stress of the pure UO 2 . Measurements of creep rates are made at 1500 deg. C at applied stresses varying from 20 to 70 MPa. Cr 2 O 3 additions increase the creep-rate, up to several orders of magnitude-change from the pure material to a doped one. All the doped materials exhibit power-law creep with exponents in the range of 4.9 to 6.3. The activation energy varies from 466 to 451 kJ/mol depending on the dopant concentration. The creep of the undoped material is divided into three regimes of deformation depending on stress. At low stresses the strain rate shows a second power dependence on stress. At high stress levels a higher stress dependence is observed. The creep power-law breaks down and an exponential law holds true at higher stresses. The activation energies are found to be 410 and 560 kJ/mol in the low- and high-stress regions respectively. The former value is in good agreement with the grain boundary diffusion energy in stoichiometric polycrystalline uranium dioxide and the latter corresponds to that found for self-diffusion energy of uranium. Creep behaviours are discussed in terms of deformation mechanisms. (author)

  11. Investigation on the bisoliton mechanism of high-temperature superconductors

    International Nuclear Information System (INIS)

    Zhang Lingyun; Li Bozang; Pu Fucho; Lin Jiatih

    1996-01-01

    Microscopic parameters in the Davydov model are calculated on the basis of the bisoliton idea. The energy gap is obtained from combining the condition for the solution of Davydov's equation with the condensation energy of the superconductive state in zero field, and some characteristic parameters of high-temperature superconductors such as coherence length, penetration depth, and density of critical current for a thin film in weak magnetic field are given. It is also proved that lattice displacement in Davydov's equation satisfies the φ 4 field form. The critical temperature and the coefficient of linear specific heat of high-temperature superconductors are studied from the statistics of lattice kinks. The agreement between theoretical and experimental values for YBaCuO oxide ceramics suggests that the bisoliton model gives a reasonable explanation of high-temperature superconductivity. (orig.)

  12. Analyses of residual iron in carbon nanotubes produced by camphor/ferrocene pyrolysis and purified by high temperature annealing

    Energy Technology Data Exchange (ETDEWEB)

    Antunes, E.F., E-mail: ericafa@las.inpe.br [Instituto Tecnologico de Aeronautica (ITA), Praca Marechal Eduardo Gomes, 50, CEP 12.228-900, Sao Jose dos Campos, SP (Brazil); Instituto Nacional de Pesquisas Espaciais (INPE), Av. dos Astronautas, 1758, CEP 12.227-010, Sao Jose dos Campos, SP (Brazil); Resende, V.G. de; Mengui, U.A. [Instituto Nacional de Pesquisas Espaciais (INPE), Av. dos Astronautas, 1758, CEP 12.227-010, Sao Jose dos Campos, SP (Brazil); Cunha, J.B.M. [Universidade Federal do Rio Grande do Sul (UFRGS), Av. Bento Goncalves, 9500, CEP 91.501-970, Porto Alegre, RS (Brazil); Corat, E.J.; Massi, M. [Instituto Nacional de Pesquisas Espaciais (INPE), Av. dos Astronautas, 1758, CEP 12.227-010, Sao Jose dos Campos, SP (Brazil)

    2011-07-01

    A detailed analysis of iron-containing phases in multiwall carbon nanotube (MWCNT) powder was carried out. The MWCNTs were produced by camphor/ferrocene and purified by high temperature annealing in an oxygen-free atmosphere (N{sub 2} or VC). Thermogravimetric analysis, Moessbauer spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy enabled the evaluation of the residual iron in MWCNTs after purification. The VC treatments provided MWCNTs with a purity degree higher than 99%. Moreover, Raman spectroscopy revealed a significant improvement in graphitic ordering after thermal annealing. A brief description of the mechanism of iron removal was included. We highlight the mobility of iron atoms through graphitic sheets and the large contact angle of iron clusters formed on MWCNT surfaces at high temperatures.

  13. High temperature mechanical properties of unirradiated dispersion strengthened copper

    International Nuclear Information System (INIS)

    Gentzbittel, J.M.; Rigollet, C.; Robert, G.

    1994-01-01

    Oxide Dispersion Strengthened (ODS) copper material, due to its excellent thermal conductivity associated with a high temperature strength is a candidate material for structural applications as divertor plasma facing components of thermonuclear fusion reactor. Tensile and creep results of oxide dispersion strengthened copper are presented. The most important features of ODS copper high temperature behaviour are the high strength corresponding to low creep rates, high stress creep rate dependence, a poor ductility and a brittleness which result in a premature creep fracture at high applied stress. (R.P.) 2 refs.; 6 figs

  14. Mechanism of death at high temperatures in Helix and Patella

    Energy Technology Data Exchange (ETDEWEB)

    Grainger, J N.R.

    1975-10-01

    In Patella vulgata and Helix aspersa which had been killed by exposure to high temperatures, the rates of oxygen consumption of gill, foot muscle and hepatopancreas are remarkably steady when measured at lower temperatures, although the absolute levels are in some cases different from normal animals. These tissues are thus substantially metabolically intact in heat dead individuals. In Helix there is a fall in blood sodium and a rise in blood potassium during heat death. In Patella there is a marked rise in blood Na/sup +/ and a consequent disturbance of the Na/sup +//K/sup +/ ratio. These ionic disturbances are thought to be a prime cause of heat death. The significance of the results is discussed.

  15. Flash pyrolysis at high temperature of ligno-cellulosic biomass and its components - production of synthesis gas

    International Nuclear Information System (INIS)

    Couhert, C.

    2007-11-01

    Pyrolysis is the first stage of any thermal treatment of biomass and governs the formation of synthesis gas for the production of electricity, hydrogen or liquid fuels. The objective of this work is to establish a link between the composition of a biomass and its pyrolysis gas. We study experimental flash pyrolysis and fix the conditions in which quantities of gas are maximal, while aiming at a regime without heat and mass transfer limitations (particles about 100 μm): temperature of 950 C and residence time of about 2 s. Then we try to predict gas yields of any biomass according to its composition, applicable in this situation where thermodynamic equilibrium is not reached. We show that an additivity law does not allow correlating gas yields of a biomass with fractions of cellulose, hemi-cellulose and lignin contained in this biomass. Several explanations are suggested and examined: difference of pyrolytic behaviour of the same compound according to the biomass from which it is extracted, interactions between compounds and influence of mineral matter. With the aim of industrial application, we study pyrolysis of millimetric and centimetric size particles, and make a numerical simulation of the reactions of pyrolysis gases reforming. This simulation shows that the choice of biomass affects the quantities of synthesis gas obtained. (author)

  16. Kinetics and mechanism of dimethylzinc pyrolysis

    International Nuclear Information System (INIS)

    Lambert-Pacht, I.

    1964-05-01

    We have studied the pyrolysis of dimethyl-zinc in sealed bulbs between 250 and 400 Celsius degrees with and without cyclohexane, one or other of the reactants being completely deuterated. We have thus shown that the following mechanism occurs: -1) CH 3 Zn CH 3 → CH 3 + Zn CH 3 , -2) CH 3 + C 6 H 12 → CH 4 + C 6 H 11 , -3) 2 CH 3 Zn → (CH 3 Zn) 2 which decomposes to give methane. We have calculated the activation energy for step I: E I = 45.5 ± 3.3 kCal/mole. The study of the reaction in the absence of cyclohexane has made it possible to show that it is not a chain reaction; also the lower limit of the activation energy for the reaction: -4) CH 3 + CH 3 Zn CH 3 → CH 4 + CH 2 Zn CH 3 , has been calculated. It has been found that E 4 ≥ 15 kCal/mole. (author) [fr

  17. Direct Synthesis of Fe3C-Functionalized Graphene by High Temperature Autoclave Pyrolysis for Oxygen Reduction

    DEFF Research Database (Denmark)

    Hu, Yang; Jensen, Jens Oluf; Zhang, Wei

    2014-01-01

    We present a novel approach to direct fabrication of few-layer graphene sheets with encapsulated Fe3C nanoparticles from pyrolysis of volatile non-graphitic precursors without any substrate. This one-step autoclave approach is facile and potentially scalable for production. Tested as an electroca...

  18. Characterization of free radicals by electron spin resonance spectroscopy in biochars from pyrolysis at high heating rates and at high temperatures

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Jensen, Peter Arendt; Jensen, Anker Degn

    2016-01-01

    The concentration and type of free radicals from the decay (termination stage) of pyrolysis at slow and fast heating rates and at high temperatures (above 1000°C) in biomass char have been studied. A room temperature electron spin resonance spectroscopy study was conducted on original wood...... because the free radicals were trapped in a char consisting of a molten amorphous silica at heating rates of 103-104 K s-1. The experimental electron spin resonance spectroscopy spectra were analyzed by fitting to simulated data in order to identify radical types, based on g-values and line widths......, herbaceous biomass, holocelluloses, lignin and their chars, prepared at high temperatures in a wire mesh reactor, an entrained flow reactor, and a tubular reactor. The radical concentrations in the chars from the decay stage range up between 7·1016 and 1.5·1018 spins g -1. The results indicated...

  19. Statistical mechanics of flux lines in high-temperature superconductors

    International Nuclear Information System (INIS)

    Dasgupta, C.

    1992-01-01

    The shortness of the low temperature coherence lengths of high T c materials leads to new mechanisms of pinning of flux lines. Lattice periodic modulations of the order parameters itself acts to pin vortex lines in regions of the unit cell were the order parameter is small. A presentation of flux creep and flux noise at low temperature and magnetic fields in terms of motion of simple metastable defects on flux lines is made, with a calculation of flux lattice melting. 12 refs

  20. High Temperature Degradation Mechanisms in Polymer Matrix Composites

    Science.gov (United States)

    Cunningham, Ronan A.

    1996-01-01

    Polymer matrix composites are increasingly used in demanding structural applications in which they may be exposed to harsh environments. The durability of such materials is a major concern, potentially limiting both the integrity of the structures and their useful lifetimes. The goal of the current investigation is to develop a mechanism-based model of the chemical degradation which occurs, such that given the external chemical environment and temperatures throughout the laminate, laminate geometry, and ply and/or constituent material properties, we can calculate the concentration of diffusing substances and extent of chemical degradation as functions of time and position throughout the laminate. This objective is met through the development and use of analytical models, coupled to an analysis-driven experimental program which offers both quantitative and qualitative information on the degradation mechanism. Preliminary analyses using a coupled diffusion/reaction model are used to gain insight into the physics of the degradation mechanisms and to identify crucial material parameters. An experimental program is defined based on the results of the preliminary analysis which allows the determination of the necessary material coefficients. Thermogravimetric analyses are carried out in nitrogen, air, and oxygen to provide quantitative information on thermal and oxidative reactions. Powdered samples are used to eliminate diffusion effects. Tests in both inert and oxidative environments allow the separation of thermal and oxidative contributions to specimen mass loss. The concentration dependency of the oxidative reactions is determined from the tests in pure oxygen. Short term isothermal tests at different temperatures are carried out on neat resin and unidirectional macroscopic specimens to identify diffusion effects. Mass loss, specimen shrinkage, the formation of degraded surface layers and surface cracking are recorded as functions of exposure time. Geometry effects

  1. High Temperature Deformation Mechanisms in a DLD Nickel Superalloy

    Directory of Open Access Journals (Sweden)

    Sean Davies

    2017-04-01

    Full Text Available The realisation of employing Additive Layer Manufacturing (ALM technologies to produce components in the aerospace industry is significantly increasing. This can be attributed to their ability to offer the near-net shape fabrication of fully dense components with a high potential for geometrical optimisation, all of which contribute to subsequent reductions in material wastage and component weight. However, the influence of this manufacturing route on the properties of aerospace alloys must first be fully understood before being actively applied in-service. Specimens from the nickel superalloy C263 have been manufactured using Powder Bed Direct Laser Deposition (PB-DLD, each with unique post-processing conditions. These variables include two build orientations, vertical and horizontal, and two different heat treatments. The effects of build orientation and post-process heat treatments on the materials’ mechanical properties have been assessed with the Small Punch Tensile (SPT test technique, a practical test method given the limited availability of PB-DLD consolidated material. SPT testing was also conducted on a cast C263 variant to compare with PB-DLD derivatives. At both room and elevated temperature conditions, differences in mechanical performances arose between each material variant. This was found to be instigated by microstructural variations exposed through microscopic and Energy Dispersive X-ray Spectroscopy (EDS analysis. SPT results were also compared with available uniaxial tensile data in terms of SPT peak and yield load against uniaxial ultimate tensile and yield strength.

  2. Possible antipolar pairing mechanism in high-temperature superconductors

    International Nuclear Information System (INIS)

    Cardwell, D.A.; Shorrocks, N.M.

    1989-01-01

    An antipolar pairing mechanism for free charge carriers in high-T c superconducting compounds is proposed qualitatively. This involves the establishment of a two-dimensional (2D) array of effective charge-coupling centers within the superconducting lattice via a specific phonon distortion of cation species along a nonmajor crystallographic direction. A fundamental requirement of this model is that the density of such coupling centers decreases with decreasing temperature. In the case of Y-Ba-Cu-O, it is asserted that charge carriers in a 2D oxygen band adjacent to the phonon-containing plane become localized by the resulting (local) field distortion. Cooper pairs may then form when the charge-coupling-center density falls below the charge-carrier density. Such a mechanism could be mediated by a longitudinal phonon which softens at low temperatures to produce an antipolar state, such as that incipient to an antiferroelectric distortion of the lattice (i.e., in the zero-frequency limiting case). This model, which may be investigated experimentally by low-temperature Raman spectroscopy, isotopic substitution, and x-ray diffractometry at 4.2 K, can be applied to all p-type high-T c systems. In addition, it may account for the observed lattice anisotropy and short coherence length characteristic of these materials

  3. Auto shredder residue recycling: Mechanical separation and pyrolysis

    International Nuclear Information System (INIS)

    Santini, Alessandro; Passarini, Fabrizio; Vassura, Ivano; Serrano, David; Dufour, Javier; Morselli, Luciano

    2012-01-01

    Highlights: ► In this work, we exploited mechanical separation and pyrolysis to recycle ASR. ► Pyrolysis of the floating organic fraction is promising in reaching ELV Directive targets. ► Zeolite catalyst improve pyrolysis oil and gas yield. - Abstract: sets a goal of 85% material recycling from end-of-life vehicles (ELVs) by the end of 2015. The current ELV recycling rate is around 80%, while the remaining waste is called automotive shredder residue (ASR), or car fluff. In Europe, this is mainly landfilled because it is extremely heterogeneous and often polluted with car fluids. Despite technical difficulties, in the coming years it will be necessary to recover materials from car fluff in order to meet the ELV Directive requirement. This study deals with ASR pretreatment and pyrolysis, and aims to determine whether the ELV material recycling target may be achieved by car fluff mechanical separation followed by pyrolysis with a bench scale reactor. Results show that flotation followed by pyrolysis of the light, organic fraction may be a suitable ASR recycling technique if the oil can be further refined and used as a chemical. Moreover, metals are liberated during thermal cracking and can be easily separated from the pyrolysis char, amounting to roughly 5% in mass. Lastly, pyrolysis can be a good starting point from a “waste-to-chemicals” perspective, but further research should be done with a focus on oil and gas refining, in order both to make products suitable for the chemical industry and to render the whole recycling process economically feasible.

  4. Offgas Analysis and Pyrolysis Mechanism of Activated Carbon from Bamboo Sawdust by Chemical Activation With KOH

    Institute of Scientific and Technical Information of China (English)

    TIAN Yong; LIU Ping; WANG Xiufang; ZHONG Guoying; CHEN Guanke

    2011-01-01

    Bamboo sawdust was used as the precursor for the multipurpose use of waste.Offgases released during the activation process of bamboo by KOH were investigated quantitatively and qualitatively by a gas analyzer. TG/DTG curves during the pyrolysis process with different impregnation weight ratios (KOH to bamboo) were obtained by a thermogravimetric analyzer. Pyrolysis mechanism of bamboo was proposed. The results showed that the offgases were composed of CO, NO,SO2 and hydrocarbon with the concentration of 1 372, 37, 86, 215 mg/L, respectively. Thermogravimetric analysis indicated that the pyrolytic process mainly experienced two steps. The first was the low temperature activation step (lower than 300 ℃), which was the pre-activation and induction period.The second was the high temperature activation step(higher than 550 ℃), which was a radial activation followed by pore production. The second process was the key to control the pore distribution of the final product.

  5. Direct synthesis of Fe3 C-functionalized graphene by high temperature autoclave pyrolysis for oxygen reduction.

    Science.gov (United States)

    Hu, Yang; Jensen, Jens Oluf; Zhang, Wei; Huang, Yunjie; Cleemann, Lars N; Xing, Wei; Bjerrum, Niels J; Li, Qingfeng

    2014-08-01

    We present a novel approach to direct fabrication of few-layer graphene sheets with encapsulated Fe3 C nanoparticles from pyrolysis of volatile non-graphitic precursors without any substrate. This one-step autoclave approach is facile and potentially scalable for production. Tested as an electrocatalyst, the graphene-based composite exhibited excellent catalytic activity towards the oxygen reduction reaction in alkaline solution with an onset potential of ca. 1.05 V (vs. the reversible hydrogen electrode) and a half-wave potential of 0.83 V, which is comparable to the commercial Pt/C catalyst. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Influence of niobium addition on the high temperature mechanical properties of a centrifugally cast HP alloy

    International Nuclear Information System (INIS)

    Andrade, A.R.; Bolfarini, C.; Ferreira, L.A.M.; Vilar, A.A.A.; Souza Filho, C.D.; Bonazzi, L.H.C.

    2015-01-01

    The influence of niobium addition on the mechanical properties at high temperature of HP alloy has been investigated. Two HP alloys were centrifugally cast with a similar chemical composition differing only in the niobium content. Low strain rate high temperature tensile tests and creep-rupture tests were performed in the range of 900–1100 °C, and the results compared between the alloys. According to the results, the high temperature mechanical behavior of both alloys is controlled by several factors like solid solution, network of eutectic carbides, intradendritic precipitation and dendrite spacing. A significant increase in the mechanical properties for the HP alloy with niobium addition was found within the temperature range of 900–1050 °C. Beyond this temperature the mechanical behavior of both alloys is basically the same

  7. Investigation of mechanical and structural characteristics of platinum and palladium at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Trumie, B. T.; Gomidzelovie, L.; Marjanovic, S. R.; Krstic, V. R.

    2015-03-30

    In order to broaden future application of products based on platinum and palladium a comparative analysis of their high-temperature mechanical properties was performed. Platinum and palladium are of great importance and are widely used in chemical industry, electronics, for making laboratory dishes, to name a few. Mechanical properties of pure metals, such as: tensile strength, creep rate and rupture time were investigated using universal testing machine for tensile testing of materials. Microstructure of samples was investigated by optical microscopy. Based on obtained results it can be concluded that the platinum, compared to palladium, is superior for high-temperature applications. (Author)

  8. Investigation of mechanical and structural characteristics of platinum and palladium at high temperatures

    International Nuclear Information System (INIS)

    Trumie, B. T.; Gomidzelovie, L.; Marjanovic, S. R.; Krstic, V. R.

    2015-01-01

    In order to broaden future application of products based on platinum and palladium a comparative analysis of their high-temperature mechanical properties was performed. Platinum and palladium are of great importance and are widely used in chemical industry, electronics, for making laboratory dishes, to name a few. Mechanical properties of pure metals, such as: tensile strength, creep rate and rupture time were investigated using universal testing machine for tensile testing of materials. Microstructure of samples was investigated by optical microscopy. Based on obtained results it can be concluded that the platinum, compared to palladium, is superior for high-temperature applications. (Author)

  9. Fracture mechanical evaluation of high temperature structure and creep-fatigue defect assessment

    Energy Technology Data Exchange (ETDEWEB)

    Park, Chang Gyu; Kim, Jong Bum; Lee, Jae Han

    2004-02-01

    This study proposed the evaluation procedure of high temperature structures from the viewpoint of fracture mechanics on the cylindrical structure applicable to the KALIMER, which is developed by KAERI. For the evaluation of structural integrity, linear and non-linear fracture mechanics parameters were analyzed. Parameters used in creep defect growth applicable to high temperature structure of liquid metal reactor and the evaluation codes with these parameters were analyzed. The evaluation methods of defect initiation and defect growth which were established in R5/R6 code(UK), JNC method (Japan) and RCC-MR A16(France) code were analyzed respectively. The evaluation procedure of leak before break applicable to KALIMER was preliminarily developed and proposed. As an application example of defect growth, the creep-fatigue defect growth on circumferential throughwall defect in high temperature cylindrical structure was evaluated by RCC-MR A16 and this application technology was established.

  10. Artificial neural networks in prediction of mechanical behavior of concrete at high temperature

    International Nuclear Information System (INIS)

    Mukherjee, A.; Nag Biswas, S.

    1997-01-01

    The behavior of concrete structures that are exposed to extreme thermo-mechanical loading is an issue of great importance in nuclear engineering. The mechanical behavior of concrete at high temperature is non-linear. The properties that regulate its response are highly temperature dependent and extremely complex. In addition, the constituent materials, e.g. aggregates, influence the response significantly. Attempts have been made to trace the stress-strain curve through mathematical models and rheological models. However, it has been difficult to include all the contributing factors in the mathematical model. This paper examines a new programming paradigm, artificial neural networks, for the problem. Implementing a feedforward network and backpropagation algorithm the stress-strain relationship of the material is captured. The neural networks for the prediction of uniaxial behavior of concrete at high temperature has been presented here. The results of the present investigation are very encouraging. (orig.)

  11. Influence of High Temperature Treatment on Mechanical Behavior of a Coarse-grained Marble

    Science.gov (United States)

    Rong, G.; Peng, J.; Jiang, M.

    2017-12-01

    High temperature has a significant influence on the physical and mechanical behavior of rocks. With increasing geotechnical engineering structures concerning with high temperature problems such as boreholes for oil or gas production, underground caverns for storage of radioactive waste, and deep wells for injection of carbon dioxides, etc., it is important to study the influence of temperature on the physical and mechanical properties of rocks. This paper experimentally investigates the triaxial compressive properties of a coarse-grained marble after exposure to different high temperatures. The rock specimens were first heated to a predetermined temperature (200, 400, and 600 oC) and then cooled down to room temperature. Triaxial compression tests on these heat-treated specimens subjected to different confining pressures (i.e., 0, 5, 10, 15, 20, 25, 30, 35, and 40 MPa) were then conducted. Triaxial compression tests on rock specimens with no heat treatment were also conducted for comparison. The results show that the high temperature treatment has a significant influence on the microstructure, porosity, P-wave velocity, stress-strain relation, strength and deformation parameters, and failure mode of the tested rock. As the treatment temperature gradually increases, the porosity slightly increases and the P-wave velocity dramatically decreases. Microscopic observation on thin sections reveals that many micro-cracks will be generated inside the rock specimen after high temperature treatment. The rock strength and Young's modulus show a decreasing trend with increase of the treatment temperature. The ductility of the rock is generally enhanced as the treatment temperature increases. In general, the high temperature treatment weakens the performance of the tested rock. Finally, a degradation parameter is defined and a strength degradation model is proposed to characterize the strength behavior of heat-treated rocks. The results in this study provide useful data for

  12. High-Temperature Performance and Multiscale Damage Mechanisms of Hollow Cellulose Fiber-Reinforced Concrete

    Directory of Open Access Journals (Sweden)

    Liping Guo

    2016-01-01

    Full Text Available Spalling resistance properties and their damage mechanisms under high temperatures are studied in hollow cellulose fiber-reinforced concrete (CFRC used in tunnel structures. Measurements of mass loss, relative dynamic elastic modulus, compressive strength, and splitting tensile strength of CFRC held under high temperatures (300, 600, 800, and 1050°C for periods of 2.5, 4, and 5.5 h were carried out. The damage mechanism was analyzed using scanning electron microscopy, mercury intrusion porosimetry, thermal analysis, and X-ray diffraction phase analysis. The results demonstrate that cellulose fiber can reduce the performance loss of concrete at high temperatures; the effect of holding time on the performance is more noticeable below 600°C. After exposure to high temperatures, the performance of ordinary concrete deteriorates faster and spalls at 700–800°C; in contrast, cellulose fiber melts at a higher temperature, leaving a series of channels in the matrix that facilitate the release of the steam pressure inside the CFRC. Hollow cellulose fibers can thereby slow the damage caused by internal stress and improve the spalling resistance of concrete under high temperatures.

  13. Decarburization behavior and mechanical properties of Inconel 617 during high temperature oxidation in He environment

    International Nuclear Information System (INIS)

    Kim, Young Do; Kim, Dae Gun; Jo, Tae Sun; Kim, Hoon Sup; Lim, Jeong Hun

    2010-04-01

    Among Generation IV reactor concepts, high temperature gas-cooled reactors (HTGRs) are high-efficiency systems designed for the economical production of hydrogen and electricity. Inconel 617 is a solid-solution strengthening Ni-based superalloy that shows excellent strength, creep-rupture strength, and oxidation resistance at high temperatures. Thus, it is a desirable candidate for tube material of IHX and HGD in HTGRs. In spite of these excellent properties, aging degradation by long time exposure at high temperature induced to deterioration of mechanical properties and furthermore alloys' lifetime because of Cr-depleted zone and carbide free zone below external scale. Also, machinability of Inconel 617 is a important property for system design. In this study, oxidation and decarbrization behavior were evaluated at various aging temperature and environment. Also, cold rolling was carried out for the machinability evaluation of Inconel 617 and then microstructure change was evaluated

  14. High temperature mechanical performance of a hot isostatically pressed silicon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Wereszczak, A.A.; Ferber, M.K.; Jenkins, M.G.; Lin, C.K.J. [and others

    1996-01-01

    Silicon nitride ceramics are an attractive material of choice for designers and manufacturers of advanced gas turbine engine components for many reasons. These materials typically have potentially high temperatures of usefulness (up to 1400{degrees}C), are chemically inert, have a relatively low specific gravity (important for inertial effects), and are good thermal conductors (i.e., resistant to thermal shock). In order for manufacturers to take advantage of these inherent properties of silicon nitride, the high-temperature mechanical performance of the material must first be characterized. The mechanical response of silicon nitride to static, dynamic, and cyclic conditions at elevated temperatures, along with reliable and representative data, is critical information that gas turbine engine designers and manufacturers require for the confident insertion of silicon nitride components into gas turbine engines. This final report describes the high-temperature mechanical characterization and analyses that were conducted on a candidate structural silicon nitride ceramic. The high-temperature strength, static fatigue (creep rupture), and dynamic and cyclic fatigue performance were characterized. The efforts put forth were part of Work Breakdown Structure Subelement 3.2.1, {open_quotes}Rotor Data Base Generation.{close_quotes} PY6 is comparable to other hot isostatically pressed (HIPed) silicon nitrides currently being considered for advanced gas turbine engine applications.

  15. Mechanical Property and Its Comparison of Superalloys for High Temperature Gas Cooled Reactor

    International Nuclear Information System (INIS)

    Kim, Woo Gon; Kim, D. W.; Ryu, W. S.; Han, C. H.; Yoon, J. H.; Chang, J.

    2005-01-01

    Since structural materials for high temperature gas cooled reactor are used during long period in nuclear environment up to 1000 .deg. C, it is important to have good properties at elevated temperature such as mechanical properties (tensile, creep, fatigue, creep-fatigue), microstructural stability, interaction between metal and gas, friction and wear, hydrogen and tritium permeation, irradiation behavior, corrosion by impurity in He. Thus, in order to select excellent materials for the high temperature gas cooled reactor, it is necessary to understand the material properties and to gather the data for them. In this report, the items related to material properties which are needed for designing the high temperature gas cooled reactor were presented. Mechanical properties; tensile, creep, and fatigue etc. were investigated for Haynes 230, Hastelloy-X, In 617 and Alloy 800H, which can be used as the major structural components, such as intermediate heat exchanger (IHX), hot duct and piping and internals. Effect of He and irradiation on these structural materials was investigated. Also, mechanical properties; physical properties, tensile properties, creep and creep crack growth rate were compared for them, respectively. These results of this report can be used as important data to select superior materials for high temperature gas reactor

  16. Microstructural control and high temperature mechanical property of ferritic/martensitic steels for nuclear reactor application

    International Nuclear Information System (INIS)

    Adetunji, G.J.

    1991-04-01

    The materials under study are 9-12% Cr ferritic/martensitic steels, alternative candidate materials for application in core components of nuclear power reactors. This work involves (1) Investigation of high temperature fracture mechanism during slow tensile and limited creep testing at 600 o C (2) Extensive study of solute element segregation both theoretically and experimentally (3) Investigation of effects by thermal ageing and irradiation on microstructural developments in relation to high temperature mechanical behaviour. From (1) the results obtained indicate that the important microstructural characteristics controlling the fracture of 9-12% Cr ferritic/martensitic steels at high temperature are (a) solute segregation to inclusion-matrix interfaces (b) hardness of the martensitic matrix and (c) carbide particle size distribution. From (2) the results indicate a strong concentration gradient of silicon and molybdenum near lath packet boundaries for certain quenching rates from the austenitizing temperature. From (3) high temperature tensile data were obtained for irradiated samples with thermally aged ones as control. (author)

  17. High-temperature mechanical relaxation in glass-like B2O3

    International Nuclear Information System (INIS)

    Lomovskoj, V.A.

    1987-01-01

    The study of high-temperature mechanical relaxation in glass-like B 2 O 3 was carried out at the temperatures from 470 to 620 K using the method of internal friction at freely damped tortional vibrations (frequency range is 0.05 - 10 Hz) and forced torsional vibrations (frequency range is 0.1 -0.00001 Hz). Possible mechanisms of high-temperature mechanical relaxation are considered. It is shown that several possible mechanisms of high-temperature mechanical relaxation in glass-like B 2 O 3 can be singled out. Switching of B-O bridge bond between two boroxol cycles of boroxol grouping for oxygen vacancy in spatial structure of glass-like B 2 O 3 , formed as a result of thermal breaking of one out of three B-O bonds, according to diffusion theory of glass viscosity. The slip of one layer boroxol groupings as to another one in the presence of only tricoordinated boron atoms in the structure of glass-like B 2 O 3

  18. High temperature mechanical properties and surface fatigue behavior improving of steel alloy via laser shock peening

    International Nuclear Information System (INIS)

    Ren, N.F.; Yang, H.M.; Yuan, S.Q.; Wang, Y.; Tang, S.X.; Zheng, L.M.; Ren, X.D.; Dai, F.Z.

    2014-01-01

    Highlights: • The properties of 00C r 12 were improved by laser shock processing. • A deep layer of residual compressive stresses was introduced. • Fatigue life was enhanced about 58% at elevated temperature up to 600 °C. • The pinning effect is the reason of prolonging fatigue life at high temperature. - Abstract: Laser shock peening was carried out to reveal the effects on ASTM: 410L 00C r 12 microstructures and fatigue resistance in the temperature range 25–600 °C. The new conception of pinning effect was proposed to explain the improvements at the high temperature. Residual stress was measured by X-ray diffraction with sin 2 ψ method, a high temperature extensometer was utilized to measure the strain and control the strain signal. The grain and precipitated phase evolutionary process were observed by scanning electron microscopy. These results show that a deep layer of compressive residual stress is developed by laser shock peening, and ultimately the isothermal stress-controlled fatigue behavior is enhanced significantly. The formation of high density dislocation structure and the pinning effect at the high temperature, which induces a stronger surface, lower residual stress relaxation and more stable dislocation arrangement. The results have profound guiding significance for fatigue strengthening mechanism of components at the elevated temperature

  19. High Cycle Fatigue Damage Mechanisms of MAR-M 247 Superalloy at High Temperatures

    Czech Academy of Sciences Publication Activity Database

    Šmíd, Miroslav; Horník, Vít; Hutař, Pavel; Hrbáček, K.; Kunz, Ludvík

    2016-01-01

    Roč. 69, č. 2 (2016), s. 393-397 ISSN 0972-2815 R&D Projects: GA TA ČR(CZ) TA04011525; GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : High cycle fatigue * S-N curves * Fractography * High temperature * EBSD analysis Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.533, year: 2016

  20. Pyrolysis mechanism of microalgae Nannochloropsis sp. based on model compounds and their interaction

    International Nuclear Information System (INIS)

    Wang, Xin; Tang, Xiaohan; Yang, Xiaoyi

    2017-01-01

    Highlights: • Pyrolysis experiments were conducted by model compounds of algal components. • Interaction affected little bio-crude yield of model compounds co-pyrolysis. • Some interaction pathways between microalgae components were recommended. • N-heterocyclic compounds were further pyrolysis products of Maillard reaction products. • Surfactant synthesis (lipid-amino acids and lipid-glucose) between algal components. - Abstract: Pyrolysis is one of important pathways to convert microalgae to liquid biofuels and key components of microalgae have different chemical composition and structure, which provides a barrier for large-scale microalgae-based liquid biofuel application. Microalgae component pyrolysis mechanism should be researched to optimal pyrolysis process parameters. In this study, single pyrolysis and co-pyrolysis of microalgal components (model compounds castor oil, soybean protein and glucose) were conducted to reveal interaction between them by thermogrametric analysis and bio-crude evaluation. Castor oil (model compound of lipid) has higher pyrolysis temperature than other model compounds and has the maximum contribution to bio-crude formation. Bio-crude from soybean protein has higher N-heterocyclic compounds as well as phenols, which could be important aromatic hydrocarbon source during biorefineries and alternative aviation biofuel production. Potential interaction pathways based on model compounds are recommended including further decomposition of Maillard reaction products (MRPs) and surfactant synthesis, which indicate that glucose played an important role on pyrolysis of microalgal protein and lipid components. The results should provide necessary information for microalgae pyrolysis process optimization and large-scale pyrolysis reactor design.

  1. High temperature deformation mechanisms of L12-containing Co-based superalloys

    Science.gov (United States)

    Titus, Michael Shaw

    Ni-based superalloys have been used as the structural material of choice for high temperature applications in gas turbine engines since the 1940s, but their operating temperature is becoming limited by their melting temperature (Tm =1300degrees C). Despite decades of research, no viable alternatives to Ni-based superalloys have been discovered and developed. However, in 2006, a ternary gamma' phase was discovered in the Co-Al-W system that enabled a new class of Co-based superalloys to be developed. These new Co-based superalloys possess a gamma-gamma' microstructure that is nearly identical to Ni-based superalloys, which enables these superalloys to achieve extraordinary high temperature mechanical properties. Furthermore, Co-based alloys possess the added benefit of exhibiting a melting temperature of at least 100degrees C higher than commercial Ni-based superalloys. Superalloys used as the structural materials in high pressure turbine blades must withstand large thermomechanical stresses imparted from the rotating disk and hot, corrosive gases present. These stresses induce time-dependent plastic deformation, which is commonly known as creep, and new superalloys must possess adequate creep resistance over a broad range of temperature in order to be used as the structural materials for high pressure turbine blades. For these reasons, this research focuses on quantifying high temperature creep properties of new gamma'-containing Co-based superalloys and identifying the high temperature creep deformation mechanisms. The high temperature creep properties of new Co- and CoNi-based alloys were found to be comparable to Ni-based superalloys with respect to minimum creep rates and creep-rupture lives at 900degrees C up to the solvus temperature of the gamma' phase. Co-based alloys exhibited a propensity for extended superlattice stacking fault formation in the gamma' precipitates resulting from dislocation shearing events. When Ni was added to the Co-based compositions

  2. Characteristics of liquid product from the pyrolysis of waste plastic mixture at low and high temperatures: influence of lapse time of reaction.

    Science.gov (United States)

    Lee, Kyong-Hwan; Shin, Dae-Hyun

    2007-01-01

    Pyrolysis of a waste plastic mixture (high-density polyethylene: low-density polyethylene: polypropylene: polystyrene = 3:2:3:1) into a liquid product was carried out in a stirred semi-batch reactor at low (350 degrees C) and high (400 degrees C) temperatures. The effect of lapse time of reaction in the reactor and also degradation temperature on the characteristics of the liquid product from pyrolysis of the mixture was investigated. Liquid products were described by cumulative amount distribution, paraffin, olefin, naphthene and aromatic (PONA) distribution and molecular weight distribution. Their characteristic was quite differed with a lapse time of reaction and also at a low and high degradation temperatures, because of the different physicochemical properties of the plastic types in the mixture. With increase of lapse time of reaction, the order for the main products in PONA components obtained at 350 degrees C was firstly aromatic products and then olefin products, while at 400 degrees C the order was firstly aromatic products, then olefin products and finally paraffin products. The experiments also showed from the molecular weight distribution of liquid PONA components that the paraffin and olefin products had a wide distribution by mainly random scission of polymer, but in the case of olefin products were produced by an end-chain scission mechanism as well as random scission mechanism, as evidenced by much more light olefin products. This phenomenon was evident at a higher degradation temperature. Also, both the light olefin and naphthene products with a molecular weight of around 120, as a main product, showed a similar trend as a function of lapse time, which had a maximum fraction at 343 min (at 350 degrees C) and 83 min (at 400 degrees C). Among PONA components, the highest concentrations of aromatic products were obtained with a molecular weight of around 100 at the fastest lapse time of reaction, regardless of degradation temperature. It was

  3. Characteristics of liquid product from the pyrolysis of waste plastic mixture at low and high temperatures: Influence of lapse time of reaction

    International Nuclear Information System (INIS)

    Lee, Kyong-Hwan; Shin, Dae-Hyun

    2007-01-01

    Pyrolysis of a waste plastic mixture (high-density polyethylene: low-density polyethylene: polypropylene: polystyrene = 3:2:3:1) into a liquid product was carried out in a stirred semi-batch reactor at low (350 deg. C) and high (400 deg. C) temperatures. The effect of lapse time of reaction in the reactor and also degradation temperature on the characteristics of the liquid product from pyrolysis of the mixture was investigated. Liquid products were described by cumulative amount distribution, paraffin, olefin, naphthene and aromatic (PONA) distribution and molecular weight distribution. Their characteristic was quite differed with a lapse time of reaction and also at a low and high degradation temperatures, because of the different physicochemical properties of the plastic types in the mixture. With increase of lapse time of reaction, the order for the main products in PONA components obtained at 350 deg. C was firstly aromatic products and then olefin products, while at 400 deg. C the order was firstly aromatic products, then olefin products and finally paraffin products. The experiments also showed from the molecular weight distribution of liquid PONA components that the paraffin and olefin products had a wide distribution by mainly random scission of polymer, but in the case of olefin products were produced by an end-chain scission mechanism as well as random scission mechanism, as evidenced by much more light olefin products. This phenomenon was evident at a higher degradation temperature. Also, both the light olefin and naphthene products with a molecular weight of around 120, as a main product, showed a similar trend as a function of lapse time, which had a maximum fraction at 343 min (at 350 deg. C) and 83 min (at 400 deg. C). Among PONA components, the highest concentrations of aromatic products were obtained with a molecular weight of around 100 at the fastest lapse time of reaction, regardless of degradation temperature. It was concluded that the

  4. Characterisation of high-temperature damage mechanisms of oxide dispersion strengthened (ODS) ferritic steels

    International Nuclear Information System (INIS)

    Salmon-Legagneur, Hubert

    2017-01-01

    The development of the fourth generation of nuclear power plants relies on the improvement of cladding materials, in order to achieve resistance to high temperature, stress and irradiation dose levels. Strengthening of ferritic steels through nano-oxide dispersion allows obtaining good mechanical strength at high temperature and good resistance to irradiation induced swelling. Nonetheless, studies available from open literature evidenced an unusual creep behavior of these materials: high anisotropy in time to rupture and flow behavior, low ductility and quasi-inexistent tertiary creep stage. These phenomena, and their still unclear origin are addressed in this study. Three 14Cr ODS steels rods have been studied. Their mechanical behavior is similar to those of other ODS steels from open literature. During creep tests, the specimens fractured by through crack nucleation and propagation from the lateral surfaces, followed by ductile tearing once the critical stress intensity factor was reached at the crack tip. Tensile and creep properties did not depend on the chemical environment of specimens. Crack propagation tests performed at 650 C showed a low value of the stress intensity factor necessary to start crack propagation. The cracks followed an intergranular path through the smaller-grained regions, which partly explains the anisotropy of high temperature strength. Notched specimens have been used to study the impact of the main loading parameters (deformation rate, temperature, stress triaxiality) on macroscopic crack initiation and stable propagation, from the central part of the specimens. These tests allowed revealing cavities created during high temperature loading, but unexposed to the external environment. These cavities showed a high chemical reactivity of the free surfaces in this material. The performed tests also evidenced different types of grain boundaries, which presented different damage development behaviors, probably due to differences in local

  5. Influence of phase transformations on the mechanical behaviour of refractory ceramics at high temperature

    International Nuclear Information System (INIS)

    Schmitt, N.; Poirier, J.

    2009-01-01

    Refractories used at high temperature are subjected to high chemical and mechanical stresses. The mastery of their microstructure as well as the phase changes occurring in service is essential to ensure resistance to wear and failure of refractory linings. Great progress has been made: combining efficient techniques for the investigation of the microstructure with powerful numerical tools (thermochemical and thermo-mechanical computations) provides information (e.g., degradation mechanisms) that cannot be obtained directly. Also multi-physical and multi-scale models developing materials with high-performance for higher temperature and with longer lifetime. In this paper, through several examples we show some interactions between the mechanical behavior and the microstructure transformations of refractory ceramics. The tools developed to characterize their microstructure change in situ (e.g., at high temperature) and to identify their kinetics are described. Some methodologies and tools developed in recent years, today, provide a better understanding of in-service behavior of refractories while identifying the critical material and process parameters likely to increase life-time. (authors)

  6. Microstructure and mechanical properties of metallic high-temperature materials. Research report

    International Nuclear Information System (INIS)

    Mughrabi, H.; Gottstein, G.; Mecking, H.; Riedel, H.; Toboloski, J.

    1999-01-01

    This volume contains 38 lectures of research studies performed in the course of the Priority Programme 'Microstructure and Mechanical Properties of Metallic High-Temperature Materials' supported by the Deutsche Forschungsgemeinschaft (DFG) over a period of six years from 1991 to 1997. The four materials selected were: 1. light metal PM-aluminium and titanium base alloys; 2. ferritic chromium and austenitic alloy 800 steels; 3. (monocrystalline) nickel-base superalloys; and 4. nickel- and iron-base oxide-dispersion-strengthened superalloys. All papers have been abstracted separately for the ENERGY database

  7. Mechanisms Governing the Creep Behavior of High Temperature Alloys for Generation IV Nuclear Energy Systems

    International Nuclear Information System (INIS)

    Vasudevan, Vijay; Carroll, Laura; Sham, Sam

    2015-01-01

    This research project, which includes collaborators from INL and ORNL, focuses on the study of alloy 617 and alloy 800H that are candidates for applications as intermediate heat exchangers in GEN IV nuclear reactors, with an emphasis on the effects of grain size, grain boundaries and second phases on the creep properties; the mechanisms of dislocation creep, diffusional creep and cavitation; the onset of tertiary creep; and theoretical modeling for long-term predictions of materials behavior and for high temperature alloy design.

  8. Mechanisms Governing the Creep Behavior of High Temperature Alloys for Generation IV Nuclear Energy Systems

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, Vijay [Univ. of Cincinnati, OH (United States); Carroll, Laura [Idaho National Lab. (INL), Idaho Falls, ID (United States); Sham, Sam [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-04-06

    This research project, which includes collaborators from INL and ORNL, focuses on the study of alloy 617 and alloy 800H that are candidates for applications as intermediate heat exchangers in GEN IV nuclear reactors, with an emphasis on the effects of grain size, grain boundaries and second phases on the creep properties; the mechanisms of dislocation creep, diffusional creep and cavitation; the onset of tertiary creep; and theoretical modeling for long-term predictions of materials behavior and for high temperature alloy design.

  9. The mechanism behind redox instability of anodes in high-temperature SOFCs

    DEFF Research Database (Denmark)

    Klemensø, Trine; Chung, Charissa; Larsen, Peter Halvor

    2005-01-01

    Bulk expansion of the anode upon oxidation is considered to be responsible for the lack of redox stability in high-temperature solid oxide fuel cells (SOFCs). The bulk expansion of nickel-yttria stabilized zirconia (YSZ) anode materials was measured by dilatometry as a function of sample geometry......, ceramic component, temperature, and temperature cycling. The strength of the ceramic network and the degree of Ni redistribution appeared to be key parameters of the redox behavior. A model of the redox mechanism in nickel-YSZ anodes was developed based on the dilatometry data and macro...

  10. Sodium effects on mechanical performance and consideration in high temperature structural design for advanced reactors

    Science.gov (United States)

    Natesan, K.; Li, Meimei; Chopra, O. K.; Majumdar, S.

    2009-07-01

    Sodium environmental effects are key limiting factors in the high temperature structural design of advanced sodium-cooled reactors. A guideline is needed to incorporate environmental effects in the ASME design rules to improve the performance reliability over long operating times. This paper summarizes the influence of sodium exposure on mechanical performance of selected austenitic stainless and ferritic/martensitic steels. Focus is on Type 316SS and mod.9Cr-1Mo. The sodium effects were evaluated by comparing the mechanical properties data in air and sodium. Carburization and decarburization were found to be the key factors that determine the tensile and creep properties of the steels. A beneficial effect of sodium exposure on fatigue life was observed under fully reversed cyclic loading in both austenitic stainless steels and ferritic/martensitic steels. However, when hold time was applied during cyclic loading, the fatigue life was significantly reduced. Based on the mechanical performance of the steels in sodium, consideration of sodium effects in high temperature structural design of advanced fast reactors is discussed.

  11. Microstructural evolutions and mechanical behaviour of the nickel based alloys 617 and 230 at high temperature

    International Nuclear Information System (INIS)

    Chomette, S.

    2009-11-01

    High Temperature Reactors (HTR), is one of the innovative nuclear reactor designed to be inherently safer than previous generation and to produce minimal waste. The most critical metallic component in that type of reactor is the Intermediate Heat exchanger (IHX). The constraints imposed by the conception and the severe operational conditions (high temperature of 850 C to 950 C, lifetime of 20,000 h) have guided the IHX material selection toward two solid solution nickel base alloys, the Inconel 617 and the Haynes 230. Inconel 617 is the primary candidate alloy thanks to its good high temperature mechanical and corrosion properties and the large data base developed in previous programs. However, its high cobalt content has to be considered as an issue (nuclear activation). The more recent alloy Haynes 230, in which most of the cobalt has been replaced by tungsten, present characteristics similar to the 617 alloy. The objective of this thesis is to study the high temperature mechanical behaviour of both alloys in relation with their microstructural evolutions. The as received microstructural observations have revealed primary carbides (M 6 C). Most of this precipitates are evenly distributed in the materials. Few M 23 C 6 secondary carbides are observed in both alloys in the as received state. Thermal ageing treatments at 850 C lead to an important M 23 C 6 precipitation on slip lines and at grain boundaries. The size of this carbides increases and their number decreases with increasing ageing duration. The intragranular precipitation of secondary carbides at 950 C is more limited and the intergranular evolution more important than at 850 C. The microstructural observations and the hardness evolution of both alloys show that the main microstructural evolutions occur before 1,000 h at both studied temperatures. The mechanical properties of the Inconel 617 and the Haynes 230 have been studied using tensile, creep, fatigue and relaxation-fatigue tests. Particularly, the

  12. Investigation of deterioration mechanism of electrical ceramic insulating materials under high temperature

    International Nuclear Information System (INIS)

    Mizutani, Yoshinobu; Ito, Tetsuo; Okamoto, Tatsuki; Kumazawa, Ryoji; Aizawa, Rie; Moriyama, Hideshige

    2000-01-01

    It is thought that ceramic insulator can be applied to electric power equipments that are under high temperature not to be able use organic materials. Our research has suggested components of mica-alumina combined insulation. As the results of and carried out temperature accelerating test, combined insulation life is expected long term over 40 years at over 500-Celsius degrees. However to construct high reliable insulating system, it is clarified deterioration mechanism on combined insulation and evaluates life of that. Therefore we carried out metal behavior test and voltage aging test using mica-sheet and alumina-cloth that are components of combined insulation under high temperature in nitrogen gas atmosphere. It is cleared two metal behavior mechanisms: One is that the opening of insulator are filled up with copper that is oxidized, the other is the metal diffuses in alumina-cloth through surface. And distance of metal behavior is able to be estimated at modulate temperature and in modulate time. It is also cleared that alumina-cloth is deteriorated by metal behavior into alumina-cloth. These results indicate that combined insulation is deteriorated from electrode side by metal behavior and is finally broken down through alumina-cloth. (author)

  13. The strengthening mechanism of a nickel-based alloy after laser shock processing at high temperatures

    International Nuclear Information System (INIS)

    Li, Yinghong; Zhou, Liucheng; He, Weifeng; He, Guangyu; Wang, Xuede; Nie, Xiangfan; Wang, Bo; Luo, Sihai; Li, Yuqin

    2013-01-01

    We investigated the strengthening mechanism of laser shock processing (LSP) at high temperatures in the K417 nickel-based alloy. Using a laser-induced shock wave, residual compressive stresses and nanocrystals with a length of 30–200 nm and a thickness of 1 μm are produced on the surface of the nickel-based alloy K417. When the K417 alloy is subjected to heat treatment at 900 °C after LSP, most of the residual compressive stress relaxes while the microhardness retains good thermal stability; the nanocrystalline surface has not obviously grown after the 900 °C per 10 h heat treatment, which shows a comparatively good thermal stability. There are several reasons for the good thermal stability of the nanocrystalline surface, such as the low value of cold hardening of LSP, extreme high-density defects and the grain boundary pinning of an impure element. The results of the vibration fatigue experiments show that the fatigue strength of K417 alloy is enhanced and improved from 110 to 285 MPa after LSP. After the 900 °C per 10 h heat treatment, the fatigue strength is 225 MPa; the heat treatment has not significantly reduced the reinforcement effect. The feature of the LSP strengthening mechanism of nickel-based alloy at a high temperature is the co-working effect of the nanocrystalline surface and the residual compressive stress after thermal relaxation. (paper)

  14. Characterization of Free Radicals By Electron Spin Resonance Spectroscopy in Biochars from Pyrolysis at High Heating Rates and at High Temperatures

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Jensen, Anker Degn; Larsen Andresen, Mogens

    of mathematical models that can predict yields, composition and rates of product (char, tar, light gases) formation from fast pyrolysis. The modeling of cross-linking and polymerization reactions in biomass pyrolysis includes the formation of free radicals and their disappearance. Knowledge about these radical...... reactions is important in order to achieve the high fuel conversion at short residence times. However, little is known about the extent of free radical reactions in pulverized biomass at fast pyrolysis conditions.The concentration and type of free radicals from the decay (termination stage) of pyrolysis...... to the less efficient catalytic effects of potassium on the bond-breaking and radical re-attachments. The high Si levels in the rice husk caused an increase in the char radical concentration compared to the wheat straw because the free radicals were trapped in a char consisting of a molten amorphous silica...

  15. Mechanical properties, reliability assessment and design of ceramic components used in high temperature assemblies

    International Nuclear Information System (INIS)

    Bendeich, P.J.

    2002-01-01

    The use of ceramic materials in high temperature structural components holds may advantages over conventional materials such as metals. These include high temperature strength, creep resistance, wear resistance, corrosion resistance, and stiffness. The tradeoff for these improved properties is the brittle nature of ceramics and their tendency for catastrophic failure and lack of damage tolerance. In this work some the various strategies available to overcome these limitations are reviewed. These include stochastic design strategies using the Weibull and Batdorf methods of failure probability prediction rather than the more familiar deterministic methods. Fracture mechanics analysis is also used extensively in this work to predict damage tolerance and failure conditions. A range of testing methods was utilised to provide material information for the methods outlined above. These included: flexural strength measurement for the determination of failure probability parameters; fracture toughness measurement using indentation methods and crack growth measurement; thermal expansion measurement; temperature dependant dynamic Young's modulus measurement; and thermal shock testing using a central heating laser. A new inverse method for measuring specific heat was developed and critically examined for practical use. This is particularly valuable in modelling transient thermal conditions for use in thermal shock analysis. A shape optimisation technique utilising a biological growth law was adapted for use with ceramic components utilising failure probability as the objective function. These methods were utilised in the design and subsequent failure analysis of a high temperature hotpress ram. The results of the failure probability analysis showed that the design had a very low probability of failure under normal operating conditions. Fracture mechanics analysis indicated that damage tolerance in the critical retaining bolt mechanism was high with damage likely to cause

  16. Effects of thermal - mechanical treatment in the creep - and tensile properties of niobium at high temperature

    International Nuclear Information System (INIS)

    Botta Filho, W.J.; Pinatti, Dyonisio G.

    1981-01-01

    Mechanical behavior of Nb at high temperature was studied based upon the samples morfology. The samples were obtainned after thermal mechanical treatment of 50mm diameter and 250mm length ingot produced by electron beam vacuum. A lot of the samples was tensile tested as a function of temperature showing small interstitials solute effect and a matrix hardened probably by substitutionals. Other lot was creep tested at homologous temperature of 0,34 and stress between 80 and 120 MPa. The results of these tests were analysed as a function of the sample morfology and showed a dependence of the percentage of recrystalization and of the grain size on the minimum creep rate. The fracture analysis showed significant effect of the oxygen content although it didn't contribute to the creep results. (Author) [pt

  17. Effect of grain size on the high temperature mechanical properties of type 316LN stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D. W.; Lee, Y. S.; Ryu, W. S.; Jang, J. S.; Kim, S. H.; Kim, W. G.; Cho, H. D.; Han, C. H

    2001-02-01

    Nitrogen increases the high temeprature mechanical properties and decreases grain size. The effect of nitrogen on the high temperature mechanical properties was investigated in the viewpoint of grain size. Tensile strength increases with the decrease of grain size and agrees with the Hall-Petch relationship. Effect of grain size on the low cycle fatigue life properties were investigated as measuring the fatigue life from the results which had been obtained by the constant strain rate and various strain range. There was no effect on the low cycle fatigue properties by the grain size. The time to rupture decreased with the increase of grain size. The steady state creep rate decreased to a minimum and then increased as the grain size increased. This result agrees with the result predicted from Garofalo equation. The rupture elongation at the intermediate grain size showed a minimum due to the cavity formed easily by carbide precipitates in the grain boundaries.

  18. Tensile properties and fracture mechanism of IN-100 superalloy in high temperature range

    Directory of Open Access Journals (Sweden)

    Milan T. Jovanović

    2017-06-01

    Full Text Available Tensile properties and fracture mechanism of a polycrystalline IN-100 superalloy have been investigated in the range from room temperature to 900°C. Optical microscopy (OM and transmission electron microscopy (TEM applying replica technique were used for microstructural investigation, whereas scanning electron microscopy (SEM was utilized for fracture study. High temperature tensile tests were carried out in vacuumed chamber. Results show that strength increases up to 700°C, and then sharply decreases with further increase in temperature. Elongation increases very slowly (6-7.5% till 500°C, then decreases to 4.5% at 900°C. Change in elongation may be ascribed to a change of fracture mechanism. Appearance of a great number of microvoids prevails up to 500°C resulting in a slow increase of elongation, whereas above this temperature elongation decrease is correlated with intergranular crystallographic fracture and fracture of carbides.

  19. Grain boundary sliding mechanism during high temperature deformation of AZ31 Magnesium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Roodposhti, Peiman Shahbeigi, E-mail: pshahbe@ncsu.edu [North Carolina State University (United States); University of Connecticut (United States); Sarkar, Apu; Murty, Korukonda Linga [North Carolina State University (United States); Brody, Harold [University of Connecticut (United States); Scattergood, Ronald [North Carolina State University (United States)

    2016-07-04

    High temperature tensile creep tests were conducted on AZ31 Magnesium alloy at low stress range of 1–13 MPa to clarify the existence of grain boundary sliding (GBS) mechanism during creep deformation. Experimental data within the GBS regime shows the stress exponent is ~2 and the activation energy value is close to that for grain boundary diffusion. Analyses of the fracture surface of the sample revealed that the GBS provides many stress concentrated sites for diffusional cavities formation and leads to premature failure. Scanning electron microscopy images show the appearances of both ductile and brittle type fracture mechanism. X-ray diffraction line profile analysis (based on Williamson-Hall technique) shows a reduction in dislocation density due to dynamic recovery (DRV). A correlation between experimental data and Langdon's model for GBS was also demonstrated.

  20. ASM Inaugural Lecture 2009: High temperature superconductors: Materials, mechanisms and applications

    International Nuclear Information System (INIS)

    Roslan Abdul Shukor

    2009-01-01

    A surprising variety of new superconducting materials has been discovered in recent years. Many compounds with light elements such as fullerenes, oxides, borides, nitrides, some organic materials and also heavy fermions have been found to superconductor at various temperatures. Hitherto, superconductors have proven to be highly varied in composition but elusive and mysterious. The juxtaposition of superconductivity and magnetism at the nano scale in some of these new materials has paved the way to a rich and exciting new field in condensed matter and materials research. An overview of superconductor research in Malaysian institutions is presented in this paper. Some of the new superconducting materials and their possible mechanisms, conventional and exotic, are presented. The possible role of lattice vibrations in the mechanisms of high temperature superconductivity and the study of this via acoustic methods are discussed. Frozen flux superconductors in a nano magnet-superconductor hybrid system are also discussed. (author)

  1. Experimental study and modelling of the high temperature mechanical behavior of oxide dispersion strengthened ferritic steels

    International Nuclear Information System (INIS)

    Steckmeyer, A.

    2012-01-01

    The strength of metals, and therefore their maximum operating temperature, can be improved by oxide dispersion strengthening (ODS). Numerous research studies are carried out at the French Atomic Energy Commission (CEA) in order to develop a cladding tube material for Gen IV nuclear power reactors. Oxide dispersion strengthened steels appear to be the most promising candidates for such application, which demands a minimum operating temperature of 650 C. The present dissertation intends to improve the understanding of the mechanical properties of ODS steels, in terms of creep lifetime and mechanical anisotropy. The methodology of this work includes mechanical tests between room temperature and 900 C as well as macroscopic and polycrystalline modelling. These tests are carried out on a Fe-14Cr1W0,26Ti + 0,3 Y 2 O 3 ODS ferritic steel processed at CEA by mechanical alloying and hot extrusion. The as-received material is a bar with a circular section. The mechanical tests reveal the high mechanical strength of this steel at high temperature. A strong influence of the strain rate on the ductility and the mechanical strength is also observed. A macroscopic mechanical model has been developed on the basis of some experimental statements such as the high kinematic contribution to the flow stress. This model has a strong ability to reproduce the mechanical behaviour of the studied material. Two different polycrystalline models have also been developed in order to reproduce the mechanical anisotropy of the material. They are based on its specific grain morphology and crystallographic texture. The discrepancy between the predictions of both models and experimental results reveal the necessity to formulate alternate assumptions on the deformation mechanisms of ODS ferritic steels. (author) [fr

  2. Application of CCG Sensors to a High-Temperature Structure Subjected to Thermo-Mechanical Load

    Directory of Open Access Journals (Sweden)

    Weihua Xie

    2016-10-01

    Full Text Available This paper presents a simple methodology to perform a high temperature coupled thermo-mechanical test using ultra-high temperature ceramic material specimens (UHTCs, which are equipped with chemical composition gratings sensors (CCGs. The methodology also considers the presence of coupled loading within the response provided by the CCG sensors. The theoretical strain of the UHTCs specimens calculated with this technique shows a maximum relative error of 2.15% between the analytical and experimental data. To further verify the validity of the results from the tests, a Finite Element (FE model has been developed to simulate the temperature, stress and strain fields within the UHTC structure equipped with the CCG. The results show that the compressive stress exceeds the material strength at the bonding area, and this originates a failure by fracture of the supporting structure in the hot environment. The results related to the strain fields show that the relative error with the experimental data decrease with an increase of temperature. The relative error is less than 15% when the temperature is higher than 200 °C, and only 6.71% at 695 °C.

  3. Fracture Mechanisms of Zirconium Diboride Ultra-High Temperature Ceramics under Pulse Loading

    Science.gov (United States)

    Skripnyak, Vladimir V.; Bragov, Anatolii M.; Skripnyak, Vladimir A.; Lomunov, Andrei K.; Skripnyak, Evgeniya G.; Vaganova, Irina K.

    2015-06-01

    Mechanisms of failure in ultra-high temperature ceramics (UHTC) based on zirconium diboride under pulse loading were studied experimentally by the method of SHPB and theoretically using the multiscale simulation method. The obtained experimental and numerical data are evidence of the quasi-brittle fracture character of nanostructured zirconium diboride ceramics under compression and tension at high strain rates and the room temperatures. Damage of nanostructured porous zirconium diboride -based UHTC can be formed under stress pulse amplitude below the Hugoniot elastic limit. Fracture of nanostructured ultra-high temperature ceramics under pulse and shock-wave loadings is provided by fast processes of intercrystalline brittle fracture and relatively slow processes of quasi-brittle failure via growth and coalescence of microcracks. A decrease of the shear strength can be caused by nano-voids clusters in vicinity of triple junctions between ceramic matrix grains and ultrafine-grained ceramics. This research was supported by grants from ``The Tomsk State University Academic D.I. Mendeleev Fund Program'' and also N. I. Lobachevski State University of Nizhny Novgorod (Grant of post graduate mobility).

  4. Effect of high temperature and type of cooling on some mechanical properties of cement mortar

    Directory of Open Access Journals (Sweden)

    Abdulhussei Faisal

    2018-01-01

    Full Text Available Mortar of cement as construction materials subjected sometimes to high temperature. Some of properties of this mortar being studied after this effect. The effect of high temperature 100, 200, 400 and 700°C (exposed for two hrs. on some mechanical properties (compressive and flexural strength of two groups of cement mortar samples (with and without the addition of crushed bricks and superplasticizer as modifying materials has been studied. Two methods of cooling samples by air and by water for 1/2 hr. was used, then tested after 3, 7 and 28 days. The results showed that the compressive and flexural strength for reference mix exposed to 700°C and water cooling decreased by 65.3 % and 64.7%, respectively, compared with their reference mix tested at 20°C in 28 days. While mixes containing 100% of crushed brick as an additive and air cooling decreases by 12.3% and 9% of their compressive and flexural strength, respectively compared with the mixes tested at 20°C in 28 days. Also showed that the decreases in flexural strength for no sand mixes containing 100% of crushed brick and 4% of superplasticizer exposed to 700°C and then water cooling was 28.2% compared to those for reference mixes tested at 20°C.

  5. Morphology and formation mechanism of ceria nanoparticles by spray pyrolysis

    International Nuclear Information System (INIS)

    Shih, Shao-Ju; Wu, Ying-Ying; Chen, Chin-Yi; Yu, Chin-Yang

    2012-01-01

    Ceria-based materials are used in industrial applications such as catalyst supports, carbon monoxide reduction catalysts, and solid oxide fuel cell electrolytes. Various applications require different morphological particles. The ceria particles with various morphologies from the precursors of cerium(III) acetate hydrate, cerium(IV) nitrate hydrate, and cerium(IV) ammonium nitrate were prepared by spray pyrolysis (SP) because SP has the potential for simple and continuous process. The precursor behaviors and the particle morphologies were characterized by thermogravimetric analysis and by transmission electron microscopy. Four main morphologies of solid spherical, hollow spherical with a single pore, hollow concave, and hollow spherical with multiple pores were observed. The experimental results suggest that the morphological formation mechanism is highly correlated with the factors of precursor solubilities, solvent evaporation rates (droplet diameters), and precursor melting temperatures. In addition, total concentrations of cerium(III) in the ceria particles from various precursors were examined using X-ray photoelectron spectroscopy.

  6. Pyrolysis of superfine pulverized coal. Part 3. Mechanisms of nitrogen-containing species formation

    International Nuclear Information System (INIS)

    Liu, Jiaxun; Jiang, Xiumin; Shen, Jun; Zhang, Hai

    2015-01-01

    Highlights: • NH 3 and NO formation mechanisms during superfine pulverized coal pyrolysis are investigated. • Influences of temperature, heating rate, particle size, atmosphere, and acid wash on the NH 3 and NO formation are analyzed. • Transformations of nitrogen-containing structures in coal/char during pyrolysis are recognized through XPS observation. • Relationships among nitrogen-containing gaseous species during pyrolysis are discussed. - Abstract: With more stringent regulations being implemented, elucidating the formation mechanisms of nitrogen-containing species during the initial pyrolysis step becomes important for developing new NO x control strategies. However, there is a lack of agreement on the origins of NO x precursors during coal pyrolysis, in spite of extensive investigations. Hence, it is important to achieve a more precise knowledge of the formation mechanisms of nitrogen-contain species during coal pyrolysis. In this paper, pyrolysis experiments of superfine pulverized coal were performed in a fixed bed at low heating rates. The influences of temperature, coal type, particle size and atmosphere on the NH 3 and NO evolution were discussed. There is a central theme to develop knowledge of the relationship between particle sizes and evolving behaviors of nitrogen-containing species. Furthermore, the catalytic role of inherent minerals in coal was proved to be effective on the partitioning of nitrogen during coal pyrolysis. In addition, the conversion pathways of heteroaromatic nitrogen structures in coal/char during pyrolysis were recognized through the X-ray photoelectron spectroscopy (XPS) analysis. Large quantities of pyridinic and quanternary nitrogen functionalities were formed during the thermal degradation. Finally, the relationships among the nitrogen-containing gaseous species during coal pyrolysis were discussed. In brief, a comprehensive picture of the volatile-nitrogen partitioning during coal pyrolysis is obtained in this

  7. Charge exchange as a recombination mechanism in high-temperature plasmas

    International Nuclear Information System (INIS)

    Hulse, R.A.; Post, D.E.; Mikkelsen, D.R.

    1980-03-01

    Charge exchange with neutral hydrogen is examined as a recombination mechanism for multi-charged impurity ions present in high-temperature fusion plasmas. At sufficiently low electron densities, fluxes of atomic hydrogen produced by either the injection of neutral heating beams or the background of thermal neutrals can yield an important or even dominant recombination process for such ions. Equilibrium results are given for selected impurity elements showing the altered ionization balance and radiative cooling rate produced by the presence of various neutral populations. A notable result is that the stripping of impurities to relatively non-radiative ionization states with increasing electron temperature can be postponed or entirely prevented by the application of intense neutral beam heating power. A time dependent calculation modelling the behavior of iron in recent PLT tokamak high power neutral beam heating experiments is also presented

  8. Mechanism of Corrosion by Naphthenic Acids and Organosulfur Compounds at High Temperatures

    Science.gov (United States)

    Jin, Peng

    Due to the law of supply and demand, the last decade has witnessed a skyrocketing in the price of light sweet crude oil. Therefore, refineries are increasingly interested in "opportunity crudes", characterized by their discounted price and relative ease of procurement. However, the attractive economics of opportunity crudes come with the disadvantage of high acid/organosulfur compound content, which could lead to corrosion and even failure of facilities in refineries. However, it is generally accepted that organosulfur compounds may form protective iron sulfide layers on the metal surface and decrease the corrosion rate. Therefore, it is necessary to investigate the corrosive property of crudes at high temperatures, the mechanism of corrosion by acids (naphthenic acids) in the presence of organosulfur compounds, and methods to mitigate its corrosive effect. In 2004, an industrial project was initiated at the Institute for Corrosion and Multiphase Technology to investigate the corrosion by naphthenic acids and organosulfur compounds. In this project, for each experiment there were two experimentation phases: pretreatment and challenge. In the first pretreatment phase, a stirred autoclave was filled with a real crude oil fraction or model oil of different acidity and organosulfur compound concentration. Then, the stirred autoclave was heated to high temperatures to examine the corrosivity of the oil to different materials (specimens made from CS and 5% Cr containing steel were used). During the pretreatment, corrosion product layers were formed on the metal surface. In the second challenge phase, the steel specimens pretreated in the first phase were inserted into a rotating cylinder autoclave, called High Velocity Rig (HVR). The HVR was fed with a high-temperature oil solution of naphthenic acids to attack the iron sulfide layers. Based on the difference of specimen weight loss between the two steps, the net corrosion rate could be calculated and the protectiveness

  9. Thermal and irradiation effects on high-temperature mechanical properties of materials for SCWR fuel cladding

    International Nuclear Information System (INIS)

    Kano, F.; Tsuchiya, Y.; Oka, K.

    2009-01-01

    The thermal and irradiation effects on high-temperature mechanical properties are examined for candidate alloys for fuel cladding of supercritical water-cooled reactors (SCRWs). JMTR (Japan Materials Testing Reactor) and Experimental Fast Reactor JOYO were utilized for neutron irradiation tests, considering their fluence and temperature. Irradiation was performed with JMTR at 600degC up to 4x10 24 n/m 2 and with JOYO at 600degC and 700degC up to 6x10 25 n/m 2 . Tensile test, creep test and hardness measurement were carried out for high-temperature mechanical properties. Based on the uniaxial creep test, the extrapolation curves were drawn with time-temperature relationships utilizing the Larson and Miller Parameter. Several candidate alloys are expected to satisfy the design requirement from the estimation of the creep rupture stress for 50000 hours. Comparing the creep strengths under irradiated and unirradiated conditions, it was inferred that creep deformation was dominated by the thermal effect rather than the irradiation at SCWR core condition. The microstructure was examined using transmission electron microscope (TEM) analysis, focusing on void swelling and helium (He) bubble formation. Void formation was observed in the materials irradiated with JOYO at 600degC but not at 700degC. However, its effect on the deformation of components was estimated to be tolerable since their size and density were negligibly small. The manufacturability of the thin-wall, small-diameter tube was confirmed for the potential candidate alloys through the trial tests in the factory where the fuel cladding tube is manufactured. (author)

  10. Evaluation of the mechanical performance of silicon carbide in TRISO fuel at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rohbeck, Nadia, E-mail: nadia.rohbeck@manchester.ac.uk; Xiao, Ping, E-mail: p.xiao@manchester.ac.uk

    2016-09-15

    The HTR design envisions fuel operating temperatures of up to 1000 °C and in case of an accident even 1600 °C are conceivable. To ensure safety in all conditions a thorough understanding of the impact of an extreme temperature environment is necessary. This work assesses the high temperature mechanical performance of the silicon carbide (SiC) layer within the tristructural-isotropic (TRISO) fuel particle as it poses the main barrier against fission product release into the primary circuit. Therefore, simulated fuel was fabricated by fluidized bed chemical vapour deposition; varying the deposition conditions resulted in strongly differing SiC microstructures for the various samples. Subsequently the TRISO particles were annealed in inert atmosphere at temperatures ranging from 1600 °C up to 2200 °C. Scanning electron microscopy and Raman spectroscopy showed that strong disintegration of the SiC layer occurred from 2100 °C onwards, but initial signs of porosity formation were visible already at 1800 °C. Still, the elastic modulus and hardness as measured by nanoindentation were hardly impaired. After annealing stoichiometric SiC coatings showed a reduction in fracture strength as determined by a modified crush test, however the actual annealing temperature from 1600 °C to 2000 °C had no measureable effect. Furthermore, a technique was developed to measure the elastic modulus and hardness in situ up to 500 °C using a high temperature nanoindentation facility. This approach allows conducting tests while the specimen and indenter tip are heated to a specific measurement temperature, thus obtaining reliable values for the temperature dependent mechanical properties of the material. For the SiC layer in TRISO particles it was found that the elastic modulus decreased slightly from room temperature up to 500 °C, whereas the hardness was reduced more severely to approximately half of its ambient temperature value.

  11. Evaluation of the Mechanical Performance of Silicon Carbide in TRISO Fuel at High Temperatures

    International Nuclear Information System (INIS)

    Rohbeck, N.; Xiao, P.

    2014-01-01

    The HTR design envisions fuel operating temperatures of up to 1000°C and in case of an accident even 1600°C are conceivable. To ensure safety in all conditions a thorough understanding of the impact of an extreme temperature environment is necessary. This work assesses the high temperature mechanical performance of the silicon carbide (SiC) layer within the tristructural-isotropic (TRISO) fuel particle as it poses the main barrier against fission product release into the primary circuit. Therefore simulated fuel was fabricated by fluidized bed chemical vapour deposition; varying the deposition conditions resulted in strongly differing SiC microstructures for the various samples. Subsequently the TRISO particles were annealed in inert atmosphere at temperatures ranging from 1600°C up to 2200°C. Scanning electron microscopy and Raman spectroscopy showed that strong disintegration of the SiC layer occurred from 2100°C onwards, but initial signs of porosity formation were visible already at 1800°C. Still, the elastic modulus and hardness as measured by nanoindentation were hardly impaired. After annealing stoichiometric SiC coatings showed a reduction in fracture strength as determined by a modified crush test, however the actual annealing temperature from 1600°C to 2000°C had no measureable effect. Furthermore, a technique was developed to measure the elastic modulus and hardness in-situ up to 500°C using a high temperature nanoindentation facility. This approach allows conducting numerous tests on small sample volumes and thus promises to improve our knowledge of irradiation effects on the mechanical properties. For the SiC layer in TRISO particles it was found that the elastic modulus decreased slightly from room temperature up to 500°C, whereas the hardness was reduced more severely to approximately half of its ambient temperature value. (author)

  12. Evaluation of the mechanical performance of silicon carbide in TRISO fuel at high temperatures

    International Nuclear Information System (INIS)

    Rohbeck, Nadia; Xiao, Ping

    2016-01-01

    The HTR design envisions fuel operating temperatures of up to 1000 °C and in case of an accident even 1600 °C are conceivable. To ensure safety in all conditions a thorough understanding of the impact of an extreme temperature environment is necessary. This work assesses the high temperature mechanical performance of the silicon carbide (SiC) layer within the tristructural-isotropic (TRISO) fuel particle as it poses the main barrier against fission product release into the primary circuit. Therefore, simulated fuel was fabricated by fluidized bed chemical vapour deposition; varying the deposition conditions resulted in strongly differing SiC microstructures for the various samples. Subsequently the TRISO particles were annealed in inert atmosphere at temperatures ranging from 1600 °C up to 2200 °C. Scanning electron microscopy and Raman spectroscopy showed that strong disintegration of the SiC layer occurred from 2100 °C onwards, but initial signs of porosity formation were visible already at 1800 °C. Still, the elastic modulus and hardness as measured by nanoindentation were hardly impaired. After annealing stoichiometric SiC coatings showed a reduction in fracture strength as determined by a modified crush test, however the actual annealing temperature from 1600 °C to 2000 °C had no measureable effect. Furthermore, a technique was developed to measure the elastic modulus and hardness in situ up to 500 °C using a high temperature nanoindentation facility. This approach allows conducting tests while the specimen and indenter tip are heated to a specific measurement temperature, thus obtaining reliable values for the temperature dependent mechanical properties of the material. For the SiC layer in TRISO particles it was found that the elastic modulus decreased slightly from room temperature up to 500 °C, whereas the hardness was reduced more severely to approximately half of its ambient temperature value.

  13. Mechanical alloying and self-propagating high-temperature synthesis of stable icosahedral quasicrystals

    International Nuclear Information System (INIS)

    Bokhonov, B.B.

    2008-01-01

    The phase evolution of the mechanically alloyed ternary 63%Al + 25%Cu + 12%Fe and 65%Al + 20%Cu + 15%Fe powder mixtures with milling time has been studied by X-ray diffraction method. It was found that an icosahedral quasicrystalline phase was formed directly during high-energy ball milling of the Al-Cu-Fe mixtures. The X-ray and scanning electron microscopic investigations demonstrated the possibility to use self-propagating high-temperature synthesis (SHS) in combination with preliminary mechanical activation for the synthesis of stable icosahedral quasicrystals. The typical morphology of the Al 63 Cu 25 Fe 12 icosahedral quasicrystals formed in the SHS process is a pentagonal dodecahedron with a size of 3-5 mm. The phase composition of the SHS products depends on the time of preliminary mechanical activation. The content of cubic intermetallic phase in SHS products increases with the time of preliminary mechanical activation of the 63%Al + 25%Cu + 12%Fe powder mixtures

  14. Stress Corrosion Cracking of alloy 600 in high temperature water: a study of mechanisms

    International Nuclear Information System (INIS)

    Boursier, J.M.; Bouvier, O. de; Gras, J.M.; Noel, D.; Vaillant, F.; Rios, R.

    1992-12-01

    Investigations of the stress corrosion cracking behaviour of Alloy 600 tubing in high temperature water were performed in order to get a precise knowledge of the different stages of the cracking and their dependence on various parameters. The compatibility of the results with the main mechanisms to be considered was examined. Results showed three stages in the cracking: a true incubation time, a slow-rate propagation period followed by a rapid-propagation stage. Tests separating stress and strain rate contributions show that the strain rate is the main parameter which controls the crack propagation. The hydrogen overpressure was found to increase the crack growth rate up to 1-4 bar, but a strong decrease is observed from 4 to 20 bar. Analysis of the hydrogen ingress in the metal showed that it is neither correlated to the hydrogen overpressure nor to the severity of cracking; so cracking resulting from an hydrogen-model is unlikely. No detrimental effect of oxygen (4 bar) was noticed both in the mill-annealed and the sensitized conditions. Finally, none of the classical mechanisms, neither hydrogen-assisted cracking nor slip-step dissolution, can correctly describe the observed behaviour. Some fractographic examinations, and an influence of primary water on the creep rate of Alloy 600, lead to consider that other recent mechanisms, involving an interaction between dissolution and plasticity, have to be considered

  15. High temperature fatigue behaviour of TZM molybdenum alloy under mechanical and thermomechanical cyclic loads

    International Nuclear Information System (INIS)

    Shi, H.J.; Niu, L.S.; Korn, C.; Pluvinage, G.

    2000-01-01

    High temperature isothermal mechanical fatigue and in-phase thermomechanical fatigue (TMF) tests in load control were carried out on a molybdenum-based alloy, one of the best known of the refractory alloys, TZM. The stress-strain response and the cyclic life of the material were measured during the tests. The fatigue lives obtained in the in-phase TMF tests are lower than those obtained in the isothermal mechanical tests at the same load amplitude. It appears that an additional damage is produced by the reaction of mechanical stress cycles and temperature cycles in TMF situation. Ratcheting phenomenon occurred during the tests with an increasing creep rate and it was dependent on temperature and load amplitude. A model of lifetime prediction, based on the Woehler-Miner law, was discussed. Damage coefficients that are functions of the maximum temperature and the variation of temperature are introduced in the model so as to evaluate TMF lives in load control. With this method the lifetime prediction gives results corresponding well to experimental data

  16. Investigation on multilayer failure mechanism of RPV with a high temperature gradient from core meltdown scenario

    Energy Technology Data Exchange (ETDEWEB)

    Jianfeng, Mao, E-mail: jianfeng-mao@163.com [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Engineering Research Center of Process Equipment and Remanufacturing, Ministry of Education (China); Xiangqing, Li [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Shiyi, Bao, E-mail: bsy@zjut.edu.cn [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Engineering Research Center of Process Equipment and Remanufacturing, Ministry of Education (China); Lijia, Luo [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Zengliang, Gao [Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); Engineering Research Center of Process Equipment and Remanufacturing, Ministry of Education (China)

    2016-12-15

    Highlights: • The multilayer failure mechanism is investigated for RPV under CHF. • Failure time and location of RPV are predicted under various SA scenarios. • The structural behaviors are analyzed in depth for creep and plasticity. • The effect of internal pressure and temperature gradient is considered. • The structural integrity of RPV is secured within the required 72 creep hours. - Abstract: The Fukushima accident shows that in-vessel retention (IVR) of molten core debris has not been appropriately assessed, and a certain pressure (up to 8.0 MPa) still exists inside the reactor pressure vessel (RPV). In the traditional concept of IVR, the pressure is supposed to successfully be released, and the temperature distributed among the wall thickness is assumed to be uniform. However, this concept is seriously challenged by reality of Fukushima accident with regard to the existence of both internal pressure and high temperature gradient. Therefore, in order to make the IVR mitigation strategy succeed, the numerical investigation of the lower head behavior and its failure has been performed for several internal pressures under high temperature gradient. According to some requirements in severe accident (SA) management of RPV, it should be ensured that the IVR mitigation takes effect in preventing the failure of the structure within a period of 72 h. Subsequently, the failure time and location have to be predicted under the critical heat flux (CHF) loading condition for lower head, since the CHF is limit thermal boundary before the melt-through of RPV. In illustrating the so called ‘multilayer failure mechanism’, the structural behaviors of RPV are analyzed in terms of the stress, creep strain, deformation, damage on selected paths.

  17. Investigation on multilayer failure mechanism of RPV with a high temperature gradient from core meltdown scenario

    International Nuclear Information System (INIS)

    Jianfeng, Mao; Xiangqing, Li; Shiyi, Bao; Lijia, Luo; Zengliang, Gao

    2016-01-01

    Highlights: • The multilayer failure mechanism is investigated for RPV under CHF. • Failure time and location of RPV are predicted under various SA scenarios. • The structural behaviors are analyzed in depth for creep and plasticity. • The effect of internal pressure and temperature gradient is considered. • The structural integrity of RPV is secured within the required 72 creep hours. - Abstract: The Fukushima accident shows that in-vessel retention (IVR) of molten core debris has not been appropriately assessed, and a certain pressure (up to 8.0 MPa) still exists inside the reactor pressure vessel (RPV). In the traditional concept of IVR, the pressure is supposed to successfully be released, and the temperature distributed among the wall thickness is assumed to be uniform. However, this concept is seriously challenged by reality of Fukushima accident with regard to the existence of both internal pressure and high temperature gradient. Therefore, in order to make the IVR mitigation strategy succeed, the numerical investigation of the lower head behavior and its failure has been performed for several internal pressures under high temperature gradient. According to some requirements in severe accident (SA) management of RPV, it should be ensured that the IVR mitigation takes effect in preventing the failure of the structure within a period of 72 h. Subsequently, the failure time and location have to be predicted under the critical heat flux (CHF) loading condition for lower head, since the CHF is limit thermal boundary before the melt-through of RPV. In illustrating the so called ‘multilayer failure mechanism’, the structural behaviors of RPV are analyzed in terms of the stress, creep strain, deformation, damage on selected paths.

  18. Effects of several types of biomass fuels on the yield, nanostructure and reactivity of soot from fast pyrolysis at high temperatures

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Jensen, Peter Arendt; Jensen, Anker Degn

    2016-01-01

    This study presents the effect of biomass origin on the yield, nanostructure and reactivity of soot. Soot was produced from wood and herbaceous biomass pyrolysis at high heating rates and at temperatures of 1250 and 1400 °C in a drop tube furnace. The structure of solid residues was characterized...

  19. Examination and evaluation of the use of screen heaters for the measurement of the high temperature pyrolysis kinetics of polyethene and polypropene.

    NARCIS (Netherlands)

    Westerhout, R.W.J.; Westerhout, R.W.J.; Balk, R.H.P.; Balk, R.H.P.; Meijer, R.; Kuipers, J.A.M.; van Swaaij, Willibrordus Petrus Maria

    1997-01-01

    A screen heater with a gas sweep was developed and applied to study the pyrolysis kinetics of low density polyethene (LDPE) and polypropene (PP) at temperatures ranging from 450 to 530 C. The aim of this study was to examine the applicability of screen heaters to measure these kinetics. On-line

  20. Mechanical twinning and texture evolution in severely deformed Ti-6Al-4V at high temperatures

    International Nuclear Information System (INIS)

    Yapici, Guney Guven; Karaman, Ibrahim; Luo Zhiping

    2006-01-01

    We have investigated the deformation behavior and texture evolution of two-phase Ti-6Al-4V subjected to severe plastic deformation using equal channel angular extrusion (ECAE) at a high temperature (∼0.55T m ). Significant deformation twinning activity was observed after one and two ECAE passes in a 90 deg, die at 800 deg. C. Twinning activity at such a high temperature is a first-time observation in this material and is attributed to the high strain and stress levels imposed during ECAE. High stress levels and the stress state can affect the separation of twinning partials considerably. Resolved shear stress magnitudes on twin partials were found to be high during the ECAE process that helps the nucleation of mechanical twinning. The twinning mode was identified as the {101-bar 1} type using electron diffraction patterns which is one of the twinning modes observed in Ti at temperatures above 350 deg. C. Although only one twinning variant was mainly evident after one pass, multiple twin variants of the same mode were observed after the second pass with a significant increase in twin volume fraction. ECAE processing aligned the basal planes of the hexagonal close-packed α phase, initially having a random texture, with the ECAE shear plane. Texture evolution during ECAE was successfully predicted using a viscoplastic self-consistent crystal plasticity framework capturing the effect of the observed twinning mode on texture. Mechanical twins formed during ECAE and grain refinement led to a noteworthy improvement in flow stresses under tension and compression at room temperature. A strong directional anisotropy in yield strengths was also evident which cannot be explained only by crystallographic texture. It was speculated that the asymmetry of critical resolved shear stresses of deformation modes and the processing-induced deformation structure should play a role. With the supporting evidence from our previous works on the severe plastic deformation of other

  1. Mechanical characterization of alloys in extreme conditions of high strain rates and high temperature

    Science.gov (United States)

    Cadoni, Ezio

    2018-03-01

    The aim of this paper is the description of the mechanical characterization of alloys under extreme conditions of temperature and loading. In fact, in the frame of the Cost Action CA15102 “Solutions for Critical Raw Materials Under Extreme Conditions (CRM-EXTREME)” this aspect is crucial and many industrial applications have to consider the dynamic response of materials. Indeed, for a reduction and substitution of CRMs in alloys is necessary to design the materials and understand if the new materials behave better or if the substitution or reduction badly affect their performance. For this reason, a deep knowledge of the mechanical behaviour at high strain-rates of considered materials is required. In general, machinery manufacturing industry or transport industry as well as energy industry have important dynamic phenomena that are simultaneously affected by extended strain, high strain-rate, damage and pressure, as well as conspicuous temperature gradients. The experimental results in extreme conditions of high strain rate and high temperature of an austenitic stainless steel as well as a high-chromium tempered martensitic reduced activation steel Eurofer97 are presented.

  2. Mathematical modelling of NO emissions from high-temperature air combustion with nitrous oxide mechanism

    International Nuclear Information System (INIS)

    Yang, Weihong; Blasiak, Wlodzimierz

    2005-01-01

    A study of the mathematical modelling of NO formation and emissions in a gas-fired regenerative furnace with high-preheated air was performed. The model of NO formation via N 2 O-intermediate mechanism was proposed because of the lower flame temperature in this case. The reaction rates of this new model were calculated basing on the eddy-dissipation-concept. This model accompanied with thermal-NO, prompt-NO and NO reburning models were used to predict NO emissions and formations. The sensitivity of the furnace temperature and the oxygen availability on NO generation rate has been investigated. The predicted results were compared with experimental values. The results show that NO emission formed by N 2 O-intermediate mechanism is of outstanding importance during the high-temperature air combustion (HiTAC) condition. Furthermore, it shows that NO models with N 2 O-route model can give more reasonable profile of NO formation. Additionally, increasing excess air ratio leads to increasing of NO emission in the regenerative furnace. (author)

  3. Analysis of high temperature deformation mechanism in ODS EUROFER97 alloy

    Science.gov (United States)

    Ramar, A.; Spätig, P.; Schäublin, R.

    2008-12-01

    Oxide dispersion in tempered martensitic EUROFER97 steel is an efficient approach to improve its strength. The oxide dispersion strengthened (ODS) EUROFER97 steel shows a good strength up to 600 °C, but degrades rapidly beyond that temperature. To understand the origin in the microstructure of this drop in strength in situ heating experiment in TEM was performed from room temperature to 1000 °C. Upon heating neither microstructure changes nor dislocation movement are observed up to 600 °C. Movement of dislocations are observed above 680 °C. Phase transformation to austenite starts at 840 °C. Yttria particles remain stable up to 1000 °C. Changes in mechanical properties thus do not relate to changes in yttria dispersion. It is attempted to relate these observations to the thermal activation parameters measured by the technique of conventional strain rate experiment, which allow to identify at a mesoscopic scale the microstructural mechanisms responsible for the degradation of ODS steel at high temperatures.

  4. Development of a High Temperature Antenna Pointing Mechanism for BepiColombo Planetary Orbiter

    Science.gov (United States)

    Campo, Pablo; Barrio, Aingeru; Puente, Nicolas; Kyle, Robert

    2013-09-01

    BepiColombo is an ESA mission to Mercury its planetary orbiter (MPO) has two antenna pointing mechanism, High gain antenna pointing mechanism steers and points a large reflector which is integrated at system level by TAS-I Rome. Medium gain antenna (MGA) APM points a 1.5 m boom with a horn antenna. Both radiating elements exposed to sun fluxes as high as 10 solar constants without protections.The pointing mechanism is a major challenge as high performances are required in a harsh environment. It has required the development of new technologies, and components specially dedicated for the mission needs. Some of the state of the art required for the mission was achieved during the preparatory technology development activities [1]. However the number of critical elements involved, and the difficulties of some areas have required the continuation of the developments, and new research activities had to be launched in CD phase. Some of the major concerns and related areas of development are:- High temperature and long life requirements for the gearhead motors (up to 15500 equivalent APM revolutions, 19 million motor revolution)- Low thermal distortion of the mechanical chain, being at the same time insulating from external environment and interfaces (55 arcsec pointing error)- Low heat leak to the spacecraft (in the order of 50W per APM)- High precision position control, low microvibration noise and error stability in motion (16 arcsec/s)- High power radio frequency (18W in band Ka, 30 in X band) with phase stability for use in radio-science (3mm in Ka band, 5o in X band).- Wide range of motion (full 360o with end-stops)Currently HGA APM EQM azimuth and elevation stages are assembled and ready for test at actuator level.

  5. Experimental characterization and modelling of UO2 mechanical behaviour at high temperatures and high strain rates

    International Nuclear Information System (INIS)

    Salvo, Maxime

    2014-01-01

    The aim of this work is to characterize and model the mechanical behavior of uranium dioxide (UO 2 ) during a Reactivity Initiated Accident (RIA). The fuel loading during a RIA is characterized by high strain rates (up to 1/s) and high temperatures (1000 C - 2500 C). Two types of UO 2 pellets (commercial and high density) were therefore tested in compression with prescribed displacement rates (0.1 to 100 mm/min corresponding to strain rates of 10 -4 - 10 -1 /s) and temperatures (1100 C - 1350 C - 1550 C et 1700 C). Experimental results (geometry, yield stress and microstructure) allowed us to define a hyperbolic sine creep law and a Drucker-Prager criterion with associated plasticity, in order to model grain boundaries fragmentation at the macroscopic scale. Finite Element Simulations of these tests and of more than 200 creep tests were used to assess the model response to a wide range of temperatures (1100 C - 1700 C) and strain rates (10 -9 /s - 10 -1 /s). Finally, a constitutive law called L3F was developed for UO 2 by adding to the previous model irradiation creep and tensile macroscopic cracking. The L3F law was then introduced in the 1.5D scheme of the fuel performance code ALCYONE-RIA to simulate the REP-Na tests performed in the experimental reactor CABRI. Simulation results are in good agreement with post tests examinations. (author) [fr

  6. Study on Collapse Mechanism of Steel Frame Structure under High Temperature and Blast Loading

    Science.gov (United States)

    Baoxin, Qi; Yan, Shi; Bi, Jialiang

    2018-03-01

    Numerical simulation analysis for collapsing process and mechanism of steel frame structures under the combined effects of fire and explosion is performed in this paper. First of all, a new steel constitutive model considering fire (high temperature softening effect) and blast (strain rate effect) is established. On the basis of the traditional Johnson-Cook model and the Perzyna model, the relationship between strain and scaled distance as well as the EOUROCODE3 standard heating curve taking into account the temperature effect parameters is introduced, and a modified Johnson-Cook constitutive model is established. Then, the influence of considering the scaled distance is introduced in order to more effectively describe the destruction and collapse phenomena of steel frame structures. Some conclusions are obtained based on the numerical analysis that the destruction will be serious and even progressively collapse with decreasing of the temperature of the steel column for the same scaled distance under the combined effects of fire and blast; the damage will be serious with decreasing of the scaled distance of the steel column under the same temperature under the combined effects of fire and blast; in the case of the combined effects of fire and blast happening in the side-spans, the partial progressive collapse occurs as the scaled distance is less than or equal to 1.28; six kinds of damages which are no damage, minor damage, moderate damage, severe damage, critical collapse, and progressive collapse.

  7. Enhancing the Accuracy of Advanced High Temperature Mechanical Testing through Thermography

    Directory of Open Access Journals (Sweden)

    Jonathan Jones

    2018-03-01

    Full Text Available This paper describes the advantages and enhanced accuracy thermography provides to high temperature mechanical testing. This technique is not only used to monitor, but also to control test specimen temperatures where the infra-red technique enables accurate non-invasive control of rapid thermal cycling for non-metallic materials. Isothermal and dynamic waveforms are employed over a 200–800 °C temperature range to pre-oxidised and coated specimens to assess the capability of the technique. This application shows thermography to be accurate to within ±2 °C of thermocouples, a standardised measurement technique. This work demonstrates the superior visibility of test temperatures previously unobtainable by conventional thermocouples or even more modern pyrometers that thermography can deliver. As a result, the speed and accuracy of thermal profiling, thermal gradient measurements and cold/hot spot identification using the technique has increased significantly to the point where temperature can now be controlled by averaging over a specified area. The increased visibility of specimen temperatures has revealed additional unknown effects such as thermocouple shadowing, preferential crack tip heating within an induction coil, and, fundamental response time of individual measurement techniques which are investigated further.

  8. Texture of high temperature superconductor thick films TI-1223 and TI-2223/LaAlO3 deposited by spray pyrolysis

    International Nuclear Information System (INIS)

    Nguyen Xuan, H.; Beauquis, S.; Galez, Ph.; Jorda, J.L.; Phok, S.; De-Barros, D.

    2004-01-01

    Superconducting TI-1223 and TI-2223 films have been prepared in a two steps process: deposition of Ba:Ca:Cu = 2:2:3 precursor by spray pyrolysis and ex-situ thallination. Pure textured TI-1223 films with good superconducting properties (T c =113 K and J c =0.7 MA/cm 2 at 77 K, 0T) have been obtained. Almost pure TI-2223 films have been obtained when precursor films have been thallinated with fluorinated sources. (orig.)

  9. High temperature oxidation of metals: vacancy injection and consequences on the mechanical properties

    International Nuclear Information System (INIS)

    Perusin, S.

    2004-11-01

    The aim of this work is to account for the effects of the high temperature oxidation of metals on their microstructure and their mechanical properties. 'Model' materials like pure nickel, pure iron and the Ni-20Cr alloy are studied. Nickel foils have been oxidised at 1000 C on one side only in laboratory air, the other side being protected from oxidation by a reducing atmosphere. After the oxidation treatment, the unoxidized face was carefully examined by using an Atomic Force Microscope (AFM). Grain boundaries grooves were characterised and their depth were compared to the ones obtained on the same sample heat treated in the reducing atmosphere during the same time. They are found to be much deeper in the case of the single side oxidised samples. It is shown that this additional grooving is directly linked to the growth of the oxide scale on the opposite side and that it can be explained by the diffusion of the vacancies produced at the oxide scale - metal interface, across the entire sample through grain boundaries. Moreover, the comparison between single side oxidised samples and samples oxidised on both sides points out that voids in grain boundaries are only observed in this latter case proving the vacancies condensation in the metal when the two faces are oxidised. The role of the carbon content and the sample's geometry on this phenomenon is examined in detail. The diffusion of vacancies is coupled with the transport of oxygen so that a mechanism of oxygen transport by vacancies is suggested. The tensile tests realised at room temperature on nickel foils (bamboo microstructure) show that the oxide scale can constitute a barrier to the emergence of dislocations at the metal surface. Finally, the Ni-20Cr alloy is tested in tensile and creep tests between 25 and 825 C in oxidising or reducing atmospheres. (author)

  10. The high temperature mechanical characteristics of superplastic 3 mol% yttria stabilized zirconia

    International Nuclear Information System (INIS)

    Owen, D.M.; Chokshi, A.H.

    1998-01-01

    A detailed study was undertaken to characterize the deformation behavior of a superplastic 3 mol% yttria-stabilized tetragonal zirconia (3YTZ) over a wide range of strain rates, temperatures and grain sizes. The experimental data were analyzed in terms of the following equation for high temperature deformation: SR ∝ FS n d -p exp(-Q/RT), where SR is the strain rate, FS is the flow stress, d is the grain size, Q is the activation energy, R is the gas constant, T is the absolute temperature, and n and p are constants termed the stress exponent and the inverse grain size exponent, respectively. The experimental data over a wide range of stresses revealed a transition in stress exponent. Deformation in the low and high stress regions was associated with n about 3 and p about 1, and n about 2 and p about 3, respectively. The transition stress between the two regions decreased with increasing grain size. The activation energy was similar for both regions with a value of about 550 kJ/mol. Microstructural measurements revealed that grains remained essentially equiaxed after the accumulation of large strains, and very limited concurrent grain growths occurred in most experiments. Assessment of possible rate controlling creep mechanisms and comparison with previous studied indicate that in the n=2 region, deformation occurs by a grain boundary sliding process whose rate is independent of impurity content. Deformation in the n=3 region is controlled by an interface reaction that is highly sensitive to impurity content. It is concluded that an increase in impurity content increases yttrium segregation to grain boundaries, which enhances the rate of the interface reaction, thereby decreasing the apparent transition stress between the n=2 and n=3 regions. This unified approach incorporating two sequential mechanisms can rationalize many of the apparently dissimilar results that have been reported previously for deformation of 3YTZ

  11. Microstructure and mechanical properties of a novel rapidly solidified, high-temperature Al-alloy

    Energy Technology Data Exchange (ETDEWEB)

    Overman, N.R., E-mail: Nicole.Overman@pnnl.gov [Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (United States); Mathaudhu, S.N. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (United States); University of California, Riverside, 3401 Watkins Dr., Riverside, CA 92521 (United States); Choi, J.P.; Roosendaal, T.J.; Pitman, S. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (United States)

    2016-02-15

    Rapid solidification (RS) processing, as a production method, offers a variety of unique properties based on far-from-equilibrium microstructures obtained through rapid cooling rates. In this study, we seek to investigate the microstructures and properties of a novel Al-alloy specifically designed for high temperature mechanical stability. Synthesis of, AlFe{sub 11.4}Si{sub 1.8}V{sub 1.6}Mn{sub 0.9} (wt.%), was performed by two approaches: rotating cup atomization (“shot”) and melt spinning (“flake”). These methods were chosen because of their ability to produce alloys with tailored microstructures due to their inherent differences in cooling rate. The as-solidified precursor materials were microstructurally characterized with electron microscopy. The results show that the higher cooling rate flake material exhibited the formation of nanocrystalline regions as well additional phase morphologies not seen in the shot material. Secondary dendritic branching in the flake material was on the order of 0.1–0.25 μm whereas branching in the shot material was 0.5–1.0 μm. Consolidated and extruded material from both precursor materials was mechanically evaluated at both ambient and high (300 °C) temperature. The consolidated RS flake material is shown to exhibit higher strengths than the shot material. The ultimate tensile strength of the melt spun flake was reported as 544.2 MPa at room temperature and 298.0 MPa at 300 °C. These results forecast the ability to design alloys and processing approaches with unique non-equilibrium microstructures with robust mechanical properties at elevated temperatures. - Highlights: • A novel alloy, AlFe{sub 11.4}Si{sub 1.8}V{sub 1.6}Mn{sub 0.9} was fabricated by rapid solidification. • Room temperature yield strength exceeded 500 MPa. • Elevated temperature (300 °C) yield strength exceeded 275 MPa. • Forging, after extrusion of the alloy resulted in microstructural coarsening. • Decreased strength and ductility was

  12. Prediction study on mechanical and thermodynamic properties of orthorhombic Mg2SiO4 under high temperature

    International Nuclear Information System (INIS)

    Zhou, Jianting; Zhang, Hong; Chen, Yue; Shong, Jun; Chen, Zhuo; Yang, Juan; Zheng, Zhou; Wang, Feng

    2014-01-01

    In this work, based on density functional theory and quasi-harmonic Debye model, mechanical and thermodynamic properties of orthorhombic Mg 2 SiO 4 under high temperature are predicted. We found out that α-Mg 2 SiO 4 is mechanically stable under the condition from about 0 to 74 GPa. Results indicate that the main cause of mechanical instability is high pressure, and the effect caused by high temperature is small. C 11 , C 22 , C 33 , B and v p reduce with temperature just a little and increase with pressure obviously. Mg 2 SiO 4 has excellent resistance to strong compression; however the resistance to shear is unsatisfactory. The C v tends to the Petit and Dulong limit at high temperature under any pressure, and it is proportional to T 3 at extremely low temperature. Pressure has an opposite effect on C v than temperature. The suppressed effect on C v caused by pressure is not obvious under low and very high temperature. Mg 2 SiO 4 has three different thermal expansion coefficients (α) along a-, b- and c-axes, and α a <α c <α b . α increases rapidly at low temperature (about <300 K), and slows down at high temperature. High pressure would greatly suppress expansion caused by temperature. Nevertheless, increasing tendency of α b and α c is still obvious under high pressure, especially α b . All the properties are mainly due to Si–O covalent bonds and their directions

  13. Understanding the mechanism of catalytic fast pyrolysis by unveiling reactive intermediates in heterogeneous catalysis

    Science.gov (United States)

    Hemberger, Patrick; Custodis, Victoria B. F.; Bodi, Andras; Gerber, Thomas; van Bokhoven, Jeroen A.

    2017-06-01

    Catalytic fast pyrolysis is a promising way to convert lignin into fine chemicals and fuels, but current approaches lack selectivity and yield unsatisfactory conversion. Understanding the pyrolysis reaction mechanism at the molecular level may help to make this sustainable process more economic. Reactive intermediates are responsible for product branching and hold the key to unveiling these mechanisms, but are notoriously difficult to detect isomer-selectively. Here, we investigate the catalytic pyrolysis of guaiacol, a lignin model compound, using photoelectron photoion coincidence spectroscopy with synchrotron radiation, which allows for isomer-selective detection of reactive intermediates. In combination with ambient pressure pyrolysis, we identify fulvenone as the central reactive intermediate, generated by catalytic demethylation to catechol and subsequent dehydration. The fulvenone ketene is responsible for the phenol formation. This technique may open unique opportunities for isomer-resolved probing in catalysis, and holds the potential for achieving a mechanistic understanding of complex, real-life catalytic processes.

  14. Hydrogen desorption from mechanically milled carbon micro coils hydrogenated at high temperature

    International Nuclear Information System (INIS)

    Yoshio Furuya; Shuichi Izumi; Seiji Motojima; Yukio Hishikawa

    2005-01-01

    Carbon micro coils (CMC) have been prepared by the catalytic pyrolysis of acetylene at 750-800 C. The as grown coils have an almost amorphous structure and contain about 1 mass% hydrogen. They have 0.1 - 10 mm coil length, 1-5 μm coil diameter, 0.1-0.5 μm coil pitch and about 100 m 2 /g specific surface area. They were graphitized, as maintaining the morphology of the coils, by heat-treating at a higher temperature than 2500 C in Ar atmosphere. The layer space (d) of graphitized CMC was determined to be 0.341 nm, forming a 'herringbone' structure with an inclination of 10-40 degree versus the coiled fiber axis, having a specific surface area of about 8 m 2 /g. The hydrogen absorption behaviors of CMC were investigated from RT to 1200 C by a thermal desorption spectrometry (TDS) using a quadrupole mass analyzer. In TDS measurements, pre-existing hydrogen, which was due to the residual acetylene incorporated into CMC on its growing, desorbed from 700 C and peaked at about 900 C. The increment in the main peak of desorbed hydrogen in the as-grown CMC heat-treated at 500 C for 1 h under high pressure of hydrogen gas (1.9 or 8.9 MPa) was not remarkable as is shown in Fig.1. While, in the CMC samples milled mechanically for 1 h at RT using a planetary ball mill, the increase of desorbed hydrogen became to be great with the hydrogen pressure (up to 8.9 MPa) on heat-treating at 500 C, as is shown in Fig.2. In these CMC samples, the building up temperature of the hydrogen desorption was shifted to a lower one and the temperature range of desorption became to be wider than those in the as-grown CMC because of the appearance of another desorption peak at about 600 C in addition to the peak ranging from 850 C to 900 C. The same kind of peak was also slightly observed in as-grown CMC (Fig.1). It is clear that this desorption at about 600 C has contributed to the remarkable increase of desorbed hydrogen in the milled CMC. In this work, values of more than 2 mass% were obtained

  15. Failure Mechanical Behavior of Australian Strathbogie Granite at High Temperatures: Insights from Particle Flow Modeling

    Directory of Open Access Journals (Sweden)

    Sheng-Qi Yang

    2017-05-01

    Full Text Available Thermally induced damage has an important influence on rock mechanics and engineering, especially for high-level radioactive waste repositories, geological carbon storage, underground coal gasification, and hydrothermal systems. Additionally, the wide application of geothermal heat requires knowledge of the geothermal conditions of reservoir rocks at elevated temperature. However, few methods to date have been reported for investigating the micro-mechanics of specimens at elevated temperatures. Therefore, this paper uses a cluster model in particle flow code in two dimensions (PFC2D to simulate the uniaxial compressive testing of Australian Strathbogie granite at various elevated temperatures. The peak strength and ultimate failure mode of the granite specimens at different elevated temperatures obtained by the numerical methods are consistent with those obtained by experimentation. Since the tensile force is always concentrated around the boundary of the crystal, cracks easily occur at the intergranular contacts, especially between the b-b and b-k boundaries where less intragranular contact is observed. The intergranular and intragranular cracking of the specimens is almost constant with increasing temperature at low temperature, and then it rapidly and linearly increases. However, the inflection point of intergranular micro-cracking is less than that of intragranular cracking. Intergranular cracking is more easily induced by a high temperature than intragranular cracking. At an elevated temperature, the cumulative micro-crack counts curve propagates in a stable way during the active period, and it has no unstable crack propagation stage. The micro-cracks and parallel bond forces in the specimens with elevated temperature evolution and axial strain have different characteristics than those at lower temperature. More branch fractures and isolated wider micro-cracks are generated with increasing temperature when the temperature is over 400

  16. Thermo-mechanical modelling of high temperature crack growth in electron beam welding of a CuCrZr alloy

    International Nuclear Information System (INIS)

    Wisniewski, J.

    2009-03-01

    The aim of this research thesis is to find out which crack initiation criteria can be applied in the case of electron beam welding of CuCrZr alloy components. After a literature survey on the high temperature cracking phenomenon, the author describes its microscopic origins and presents the main high temperature crack growth criteria. He reports metallurgical, thermal and mechanical characterizations of the studied alloy performed by optical, scanning electronic and transmission electronic microscopy, crystallographic analysis, residual stress determination using the hole method, mechanical testing at room and high temperature (from room temperature to 1000 C), determination of solidification route and of thermal conductivity, and thermal expansion measurements. He describes electron beam weldability tests performed on the alloy. As these tests are performed on simple geometry samples, they allow the high temperature crack growth to be observed. These experiments are then modelled using two finite element codes, Castem and Calcosoft. Then, after a presentation of the main hypotheses used in these numerical models, the author applies the high temperature crack growth criteria. Results obtained for theses criteria are then analysed and discussed

  17. Mechanical Performance of Asphalt Mortar Containing Hydrated Lime and EAFSS at Low and High Temperatures.

    Science.gov (United States)

    Moon, Ki Hoon; Falchetto, Augusto Cannone; Wang, Di; Riccardi, Chiara; Wistuba, Michael P

    2017-07-03

    In this paper, the possibility of improving the global response of asphalt materials for pavement applications through the use of hydrated lime and Electric Arc-Furnace Steel Slag (EAFSS) was investigated. For this purpose, a set of asphalt mortars was prepared by mixing two different asphalt binders with fine granite aggregate together with hydrated lime or EAFSS at three different percentages. Bending Beam Rheometer (BBR) creep tests and Dynamic Shear Rheometer (DSR) complex modulus tests were performed to evaluate the material response both at low and high temperature. Then, the rheological Huet model was fitted to the BBR creep results for estimating the impact of filler content on the model parameters. It was found that an addition of hydrated lime and EAFSS up to 10% and 5%, respectively, results in satisfactory low-temperature performance with a substantial improvement of the high-temperature behavior.

  18. Mechanical Performance of Asphalt Mortar Containing Hydrated Lime and EAFSS at Low and High Temperatures

    Directory of Open Access Journals (Sweden)

    Ki Hoon Moon

    2017-07-01

    Full Text Available In this paper, the possibility of improving the global response of asphalt materials for pavement applications through the use of hydrated lime and Electric Arc-Furnace Steel Slag (EAFSS was investigated. For this purpose, a set of asphalt mortars was prepared by mixing two different asphalt binders with fine granite aggregate together with hydrated lime or EAFSS at three different percentages. Bending Beam Rheometer (BBR creep tests and Dynamic Shear Rheometer (DSR complex modulus tests were performed to evaluate the material response both at low and high temperature. Then, the rheological Huet model was fitted to the BBR creep results for estimating the impact of filler content on the model parameters. It was found that an addition of hydrated lime and EAFSS up to 10% and 5%, respectively, results in satisfactory low-temperature performance with a substantial improvement of the high-temperature behavior.

  19. The effect of microalloying B on the High temperature mechanical properties of Ti3Al

    International Nuclear Information System (INIS)

    Newkirk, J.W.; Feldewerth, G.B.

    1989-01-01

    This paper presents a study of the effect of adding boron to Ti 3 Al on the microstructure and high temperature tensile properties. Boron caused a large grain refinement that dominated the tensile properties at all temperatures. Particles of Ti 2 B were found in all of the boron containing alloys. TiB was found only at concentrations of 0.1% B or more

  20. Development of high temperature mechanical rig for characterizing the viscoplastic properties of alloys used in solid oxide cells

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye; Greco, Fabio; Kwok, Kawai

    2018-01-01

    Analyzing the thermo-mechanical reliability of solid oxide cell (SOC) stack requires precise measurement of the mechanical properties of the different components in the stack at operating conditions of the SOC. It is challenging to precisely characterize the time dependent deformational properties...... temperature and in controlled atmosphere. The methodology uses a mechanical loading rig designed to apply variable as well as constant loads on samples within a gas-tight high temperature furnace. In addition, a unique remotely installed length measuring setup involving laser micrometer is used to monitor...... deformations in the sample. Application of the methodology is exemplified by measurement of stress relaxation, creep and constant strain rate behaviors of a high temperature alloy used in the construction of SOC metallic interconnects at different temperatures. Furthermore, measurements using the proposed...

  1. High temperature strengthening mechanism of hafnium carbide in a tungsten-rhenium matrix

    International Nuclear Information System (INIS)

    Luo, A.; Shin, K.S.; Jacobson, D.L.

    1991-01-01

    The interrelationship between the testing temperature and HfC strength increment of an arc-melted W-3.6Re-0.4HfC was determined from 1950 K to 2980 K in a vacuum of better than 1.3x10 -5 Pa (10 -7 torr). The present research was focused on the characteristic temperature at which the rapid coarsening of HfC particles occurred and the effect of the second-phase particle size on the high temperature strength properties of this material. It was found that the HfC particle strengthening was effective in a W-Re matrix up to a characteristic temperature of 2450 K in the short-term tensile test. Carbon was found to be the rate-limiting solute in the HfC particle growth. The strength of HfC strengthened alloy at temperature above 0.5 T m is proportional to the square root of particle volume fraction. The yield strengths of W-3.6Re-0.26HfC calculated based on the particle statistical distribution had good agreement with the experimental values from 1950 K to 2980 K. Besides, an addition of 0.26 percent HfC in tungsten resulted in about 28 percent increase in the activation energy of plastic deformation at high temperatures

  2. Density functional theory study of the concerted pyrolysis mechanism for lignin models

    Science.gov (United States)

    Thomas Elder; Ariana Beste

    2014-01-01

    ABSTRACT: Studies on the pyrolysis mechanisms of lignin model compounds have largely focused on initial homolytic cleavage reactions. It has been noted, however, that concerted mechanisms may also account for observed product formation. In the current work, the latter processes are examined and compared to the former, by the application of density functional theory...

  3. Probabilistic Material Strength Degradation Model for Inconel 718 Components Subjected to High Temperature, Mechanical Fatigue, Creep and Thermal Fatigue Effects

    Science.gov (United States)

    Bast, Callie Corinne Scheidt

    1994-01-01

    This thesis presents the on-going development of methodology for a probabilistic material strength degradation model. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes four effects that typically reduce lifetime strength: high temperature, mechanical fatigue, creep, and thermal fatigue. Statistical analysis was conducted on experimental Inconel 718 data obtained from the open literature. This analysis provided regression parameters for use as the model's empirical material constants, thus calibrating the model specifically for Inconel 718. Model calibration was carried out for four variables, namely, high temperature, mechanical fatigue, creep, and thermal fatigue. Methodology to estimate standard deviations of these material constants for input into the probabilistic material strength model was developed. Using the current version of PROMISS, entitled PROMISS93, a sensitivity study for the combined effects of mechanical fatigue, creep, and thermal fatigue was performed. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing a combination of mechanical fatigue and high temperature effects by model to the combination by experiment were conducted. Thus, for Inconel 718, the basic model assumption of independence between effects was evaluated. Results from this limited verification study strongly supported this assumption.

  4. Mechanically activated self-propagated high-temperature synthesis of nanometer-structured MgB2

    International Nuclear Information System (INIS)

    Radev, D.D.; Marinov, M.; Tumbalev, V.; Radev, I.; Konstantinov, L.

    2005-01-01

    Nanometer-sized MgB 2 was prepared via a two-step modification of the mechanically activated self-propagated high-temperature synthesis. The experimental conditions and some structural and phase characteristics of the synthesized product are reported. It is shown that a single-phase material can be prepared after 2 h of intense mechanical treatment of the starting magnesium and boron powders and a synthesis induced at a current-pulse density of 30 A cm -2 . The average size of MgB 2 particles synthesized in this way is 70-80 nm. It is also shown that using the same reagents and the 'classic' high-temperature interaction at 850 deg C with a protective atmosphere of pure Ar, mean particle size of the MgB 2 obtained is 50 μm

  5. Nanoscale strain-induced pair suppression as a vortex-pinning mechanism in high-temperature superconductors

    International Nuclear Information System (INIS)

    Llordes, Anna; Palau, A.; Gazquez, J.; Coll, M.; Vlad, R.; Pomar, A.; Arbiol, Jordi; Guzman, Roger; Ye, S.; Rouco, V.; Sandiumenge, Felip; Ricart, Susagna; Puig, Teresa; Varela del Arco, Maria; Chataigner, D.; Vanacken, J.; Gutierrez, J.; Moschalkov, V.; Deutscher, G.; Magen Dominguez, Cesar; Obradors, Xavier

    2012-01-01

    Boosting large-scale superconductor applications require nanostructured conductors with artificial pinning centres immobilizing quantized vortices at high temperature and magnetic fields. Here we demonstrate a highly effective mechanism of artificial pinning centers in solution-derived high-temperature superconductor nanocomposites through generation of nanostrained regions where Cooper pair formation is suppressed. The nanostrained regions identified from transmission electron microscopy devise a very high concentration of partial dislocations associated with intergrowths generated between the randomly oriented nanodots and the epitaxial YBa 2 Cu 3 O 7 matrix. Consequently, an outstanding vortex-pinning enhancement correlated to the nanostrain is demonstrated for four types of randomly oriented nanodot, and a unique evolution towards an isotropic vortex-pinning behaviour, even in the effective anisotropy, is achieved as the nanostrain turns isotropic. We suggest a new vortex-pinning mechanism based on the bond-contraction pairing model, where pair formation is quenched under tensile strain, forming new and effective core-pinning regions.

  6. Mechanism of high-temperature background of internal friction in metals

    International Nuclear Information System (INIS)

    Shapoval, B.I.; Arzhavitin, V.M.

    1988-01-01

    Data of theoretical and experimental studies on energy dissipation in vibrating metal at small amplitudes and elevated temperatures (high temperature background of internal friction) are generalized and systematized. Evolution of knowledge of the background as a phenomenon influenced mainly by crystal structure defects - their form, quantity, mobility and interaction is followed. Considered is a wide range of investigated metal states and measurement conditions, and interrelations with other characteristics, for instance, strength ones. On the basis of the data obtained by authors and other investigations a concept of an additional third stage of the background increase with the temperature - the stage of deviation from exponential dependence at premelting point, is introduced. 107 refs.; 32 figs.; 3 tabs

  7. Mechanisms of High Temperature Resistance of Synechocystis sp. PCC 6803: An Impact of Histidine Kinase 34

    Directory of Open Access Journals (Sweden)

    Jan Červený

    2015-03-01

    Full Text Available Synechocystis sp. PCC 6803 is a widely used model cyanobacterium for studying responses and acclimation to different abiotic stresses. Changes in transcriptome, proteome, lipidome, and photosynthesis in response to short term heat stress are well studied in this organism, and histidine kinase 34 (Hik34 is shown to play an important role in mediating such response. Corresponding data on long term responses, however, are fragmentary and vary depending on parameters of experiments and methods of data collection, and thus are hard to compare. In order to elucidate how the early stress responses help cells to sustain long-term heat stress, as well as the role of Hik34 in prolonged acclimation, we examined the resistance to long-term heat stress of wild-type and ΔHik34 mutant of Synechocystis. In this work, we were able to precisely control the long term experimental conditions by cultivating Synechocystis in automated photobioreactors, measuring selected physiological parameters within a time range of minutes. In addition, morphological and ultrastructural changes in cells were analyzed and western blotting of individual proteins was used to study the heat stress-affected protein expression. We have shown that the majority of wild type cell population was able to recover after 24 h of cultivation at 44 °C. In contrast, while ΔHik34 mutant cells were resistant to heat stress within its first hours, they could not recover after 24 h long high temperature treatment. We demonstrated that the early induction of HspA expression and maintenance of high amount of other HSPs throughout the heat incubation is critical for successful adaptation to long-term stress. In addition, it appears that histidine kinase Hik34 is an essential component for the long term high temperature resistance.

  8. Mechanisms of High Temperature Resistance of Synechocystis sp. PCC 6803: An Impact of Histidine Kinase 34.

    Science.gov (United States)

    Červený, Jan; Sinetova, Maria A; Zavřel, Tomáš; Los, Dmitry A

    2015-03-02

    Synechocystis sp. PCC 6803 is a widely used model cyanobacterium for studying responses and acclimation to different abiotic stresses. Changes in transcriptome, proteome, lipidome, and photosynthesis in response to short term heat stress are well studied in this organism, and histidine kinase 34 (Hik34) is shown to play an important role in mediating such response. Corresponding data on long term responses, however, are fragmentary and vary depending on parameters of experiments and methods of data collection, and thus are hard to compare. In order to elucidate how the early stress responses help cells to sustain long-term heat stress, as well as the role of Hik34 in prolonged acclimation, we examined the resistance to long-term heat stress of wild-type and ΔHik34 mutant of Synechocystis. In this work, we were able to precisely control the long term experimental conditions by cultivating Synechocystis in automated photobioreactors, measuring selected physiological parameters within a time range of minutes. In addition, morphological and ultrastructural changes in cells were analyzed and western blotting of individual proteins was used to study the heat stress-affected protein expression. We have shown that the majority of wild type cell population was able to recover after 24 h of cultivation at 44 °C. In contrast, while ΔHik34 mutant cells were resistant to heat stress within its first hours, they could not recover after 24 h long high temperature treatment. We demonstrated that the early induction of HspA expression and maintenance of high amount of other HSPs throughout the heat incubation is critical for successful adaptation to long-term stress. In addition, it appears that histidine kinase Hik34 is an essential component for the long term high temperature resistance.

  9. Microstructure and Mechanical Property of ODS Ferritic Steels Using Commercial Alloy Powders for High Temperature Service Applications

    Energy Technology Data Exchange (ETDEWEB)

    Noh, Sanghoon; Choi, Byoung-Kwon; Kang, Suk Hoon; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    Oxide dispersion strengthening (ODS) is one of the promising ways to improve the mechanical property at high temperatures. This is mainly attributed to uniformly distributed nano-oxide particle with a high density, which is extremely stable at the high temperature and acts as effective obstacles when the dislocations are moving. In this study, as a preliminary examination to develop the advanced structural materials for high temperature service applications, ODS ferritic steels were fabricated using commercial alloy powders and their microstructural and mechanical properties were investigated. In this study, ODS ferritic steels were fabricated using commercial stainless steel 430L powder and their microstructures and mechanical properties were investigated. Morphology of micro-grains and oxide particles were significantly changed by the addition of minor alloying elements such as Ti, Zr, and Hf. The ODS ferritic steel with Zr and Hf additions showed ultra-fine grains with fine complex oxide particles. The oxide particles were uniformly located in grains and on the grain boundaries. This led to higher hardness than ODS ferritic steel with Ti addition.

  10. Development of a high-performance, coal-fired power generating system with a pyrolysis gas and char-fired high-temperature furnace

    International Nuclear Information System (INIS)

    Shenker, J.

    1995-01-01

    A high-performance power system (HIPPS) is being developed. This system is a coal-fired, combined-cycle plant that will have an efficiency of at least 47 percent, based on the higher heating value of the fuel. The original emissions goal of the project was for NOx and SOx to each be below 0.15 lb/MMBtu. In the Phase 2 RFP this emissions goal was reduced to 0.06 lb/MMBtu. The ultimate goal of HIPPS is to have an all-coal-fueled system, but initial versions of the system are allowed up to 35 percent heat input from natural gas. Foster Wheeler Development Corporation is currently leading a team effort with AlliedSignal, Bechtel, Foster Wheeler Energy Corporation, Research-Cottrell, TRW and Westinghouse. Previous work on the project was also done by General Electric. The HIPPS plant will use a high-Temperature Advanced Furnace (HITAF) to achieve combined-cycle operation with coal as the primary fuel. The HITAF is an atmospheric-pressure, pulverized-fuel-fired boiler/air heater. The HITAF is used to heat air for the gas turbine and also to transfer heat to the steam cycle. its design and functions are very similar to conventional PC boilers. Some important differences, however, arise from the requirements of the combined cycle operation

  11. Development of a high-performance, coal-fired power generating system with a pyrolysis gas and char-fired high-temperature furnace

    Energy Technology Data Exchange (ETDEWEB)

    Shenker, J.

    1995-11-01

    A high-performance power system (HIPPS) is being developed. This system is a coal-fired, combined-cycle plant that will have an efficiency of at least 47 percent, based on the higher heating value of the fuel. The original emissions goal of the project was for NOx and SOx to each be below 0.15 lb/MMBtu. In the Phase 2 RFP this emissions goal was reduced to 0.06 lb/MMBtu. The ultimate goal of HIPPS is to have an all-coal-fueled system, but initial versions of the system are allowed up to 35 percent heat input from natural gas. Foster Wheeler Development Corporation is currently leading a team effort with AlliedSignal, Bechtel, Foster Wheeler Energy Corporation, Research-Cottrell, TRW and Westinghouse. Previous work on the project was also done by General Electric. The HIPPS plant will use a high-Temperature Advanced Furnace (HITAF) to achieve combined-cycle operation with coal as the primary fuel. The HITAF is an atmospheric-pressure, pulverized-fuel-fired boiler/air heater. The HITAF is used to heat air for the gas turbine and also to transfer heat to the steam cycle. its design and functions are very similar to conventional PC boilers. Some important differences, however, arise from the requirements of the combined cycle operation.

  12. High-temperature mechanical properties of high-purity 70 mass% Cr-Fe alloy

    Energy Technology Data Exchange (ETDEWEB)

    Asahina, M.; Harima, N.; Takaki, S.; Abiko, K. [Tohoku Univ., Sendai (Japan). Inst. for Materials Research

    2002-01-16

    An ingot of high-purity 70 mass% Cr-Fe alloy was prepared by high-frequency induction melting in a high-purity argon atmosphere using a cold copper crucible. Its tensile properties such as hot-ductility and tensile strength were measured, and compared with the results for a high-purity 50 mass% Cr-Fe alloy, a high-purity 60 mass% Cr-Fe alloy and a Ni-based super-alloy. The formation of {sigma}-phase was also examined. The purity of a 70Cr-Fe alloy (70 mass% Cr-Fe alloy) ingot is more than 99.98 mass% and the total amount of gaseous impurities (C, N, O, S, H) in the 70Cr-Fe alloy is 69.9 mass ppm. The strength of the 70Cr-Fe alloy is higher than those of the 60Cr-Fe alloy and the 50Cr-Fe alloy at the temperatures between 293 and 1573 K, without decrease in ductility with increasing Cr content. The 70Cr-Fe alloy also possesses excellent high-temperature ductility. The {sigma}-phase was not observed after aging of 3.6 Ms at 873 K. Consequently, the 70Cr-Fe alloy is an excellent alloy as the base of super heat-resistant alloys. (orig.)

  13. Mechanism for microstructural evolution induced by high temperature deformation in Zr-based bulk metallic glasses

    International Nuclear Information System (INIS)

    Cheng, Sirui; Wang, Chunju; Ma, Mingzhen; Shan, Debin; Guo, Bin

    2016-01-01

    In the Zr_4_1_._2Ti_1_3_._8Cu_1_2_._5Ni_1_0Be_2_2_._5 (Vit1) alloy undergoing high temperature deformation, its thermal properties and microstructure are quite different from those in the annealing alloy. In order to research the coupled effect of temperature and plastic strain on microstructural evolution of Zr-based amorphous, uniaxial compression test of Vit1 alloy with good amorphous nature has been performed, and then the structural state and thermal properties of Vit1 alloy after thermal deformation and isothermal annealing in the supercooled liquid region were investigated. It is revealed that the deformed specimens possess higher characteristic temperature and lower enthalpy change of microstructural relaxation. In addition, the smaller inter-atomic distance and higher order degree of atomic arrangement can be observed in those deformed Vit1 alloy. That can be deduced that thermal deformation is in favor of the microstructural evolution from a metastable amorphous state to stable crystallization state, because plastic strain promotes the annihilation of free volume and provide excess driving force of atomic diffusion. However, upon increasing the ambient temperature, the influence of plastic deformation on microstructure gradually decreased owing to the decreasing proportion of the plastic deformation-induced annihilation of free volume during the whole thermal deformation process. - Highlights: • The deformed specimens possess closer microstructure and higher characteristic temperatures. • The order degree of microstructures in deformed specimens is higher than that in annealed specimens. • Thermal deformation accelerates the microstructural evolution of Zr-based BMGs. • The influence of thermal deformation on microstructure decreases with the temperature increasing.

  14. Mechanism for microstructural evolution induced by high temperature deformation in Zr-based bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Sirui [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wang, Chunju [Key Laboratory of Micro-Systems and Micro-Structures Manufacturing, Ministry of Education, Harbin Institute of Technology, Harbin 150080 (China); School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Ma, Mingzhen [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Shan, Debin, E-mail: shandebin@hit.edu.cn [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Key Laboratory of Micro-Systems and Micro-Structures Manufacturing, Ministry of Education, Harbin Institute of Technology, Harbin 150080 (China); School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Guo, Bin [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2016-08-15

    In the Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10}Be{sub 22.5} (Vit1) alloy undergoing high temperature deformation, its thermal properties and microstructure are quite different from those in the annealing alloy. In order to research the coupled effect of temperature and plastic strain on microstructural evolution of Zr-based amorphous, uniaxial compression test of Vit1 alloy with good amorphous nature has been performed, and then the structural state and thermal properties of Vit1 alloy after thermal deformation and isothermal annealing in the supercooled liquid region were investigated. It is revealed that the deformed specimens possess higher characteristic temperature and lower enthalpy change of microstructural relaxation. In addition, the smaller inter-atomic distance and higher order degree of atomic arrangement can be observed in those deformed Vit1 alloy. That can be deduced that thermal deformation is in favor of the microstructural evolution from a metastable amorphous state to stable crystallization state, because plastic strain promotes the annihilation of free volume and provide excess driving force of atomic diffusion. However, upon increasing the ambient temperature, the influence of plastic deformation on microstructure gradually decreased owing to the decreasing proportion of the plastic deformation-induced annihilation of free volume during the whole thermal deformation process. - Highlights: • The deformed specimens possess closer microstructure and higher characteristic temperatures. • The order degree of microstructures in deformed specimens is higher than that in annealed specimens. • Thermal deformation accelerates the microstructural evolution of Zr-based BMGs. • The influence of thermal deformation on microstructure decreases with the temperature increasing.

  15. High temperature microplasticity of fine-grained Y-TZP zirconia studied by mechanical spectroscopy

    International Nuclear Information System (INIS)

    Donzel, L.; Schaller, R.

    1997-01-01

    Mechanical spectroscopy has been used to study the early stage of the plastic deformation, i.e. the microplasticity of Y-TZP ceramics. Measurements on samples with different grain sizes have shown that the mechanical loss is proportional to the inverse of the square root of the grain size. The existence of a threshold stress has been observed. (orig.)

  16. Study of alloy 600'S stress corrosion cracking mechanisms in high temperature water

    International Nuclear Information System (INIS)

    Rios, R.

    1994-06-01

    In order to better understand the mechanisms involved in Alloy 600's stress corrosion cracking in PWR environment, laboratory tests were performed. The influence of parameters pertinent to the mechanisms was studies : hydrogen and oxygen overpressures, local chemical composition, microstructure. The results show that neither hydrogen nor dissolution/oxidation, despite their respective roles in the process, are sufficient to account for experimental facts. SEM observation of micro-cleavage facets on specimens' fracture surfaces leads to pay attention to a new mechanism of corrosion/plasticity interactions. (author). 113 refs., 73 figs., 15 tabs., 4 annexes

  17. Study of alloy 600 (NC15Fe) stress corrosion cracking mechanisms in high temperature water

    International Nuclear Information System (INIS)

    Rios, Richard

    1993-01-01

    In order to better understand the mechanisms involved in Alloy 600's stress corrosion cracking in PWR environment, laboratory tests were performed. The influence of parameters pertinent to the mechanisms was studies: hydrogen and oxygen overpressures, local chemical composition, microstructure. The results show that neither hydrogen nor dissolution/oxidation, despite their respective roles in the process, are sufficient to account for experimental facts. SEM observation of micro-cleavage facets on specimens' fracture surfaces leads to pay attention to a new mechanism of corrosion/plasticity interactions. (author) [fr

  18. Mechanical and microstructural stability of P92 steel under uniaxial tension at high temperature

    International Nuclear Information System (INIS)

    Giroux, P.F.; Dalle, F.; Sauzay, M.; Malaplate, J.; Fournier, B.; Gourgues-Lorenzon, A.F.

    2010-01-01

    9-12%Cr creep-resistant ferritic-martensitic steels are candidates for structural components of Generation IV nuclear power plants. However, they are sensitive to softening during low-cycle fatigue, creep and creep-fatigue tests, due to the destabilisation of the tempered martensite microstructure, possibly inducing a decrease in further creep resistance. To better identify the softening mechanisms in P92 steel during uniaxial deformation, tensile tests were carried out at 823 K, showing an extended and stable softening stage on true stress-strain curves after some work-hardening. Three phenomena were studied in order to understand this behaviour: mechanical instability (necking), damage and grain size evolution. Examination of fractured and non-fractured tensile specimens (light optical and electron microscopy, macrohardness) suggested that the physical mechanisms responsible for softening are mainly (sub)grain size evolution and diffuse necking. Models were proposed to predict grain growth and beginning of the mechanical instability during homogeneous deformation.

  19. Mechanical behaviour of aluminium matrix composites with particles in high temperature

    International Nuclear Information System (INIS)

    Amigo, V.; Salvador, M. D.; Ferrer, C.; Costa d, C. E.; Busquets, D.

    2001-01-01

    The aluminium matrix composites materials reinforced by ceramic particles can be elaborated by powder metallurgy techniques, with extrusion processes. These can provide new materials, with a better mechanical behaviour and moreover when we need those properties at higher temperatures. Aluminium alloy reinforced composites with silicon nitride particles by powder extrusion process was done. Their mechanical properties were characterised at room and elevated temperatures. (Author) 28 refs

  20. Analysis of mechanical characteristics of superconducting field coil for 17 MW class high temperature superconducting synchronous motor

    International Nuclear Information System (INIS)

    Kim, J. H.; Park, S. I.; Im, S. H.; Kim, H. M.

    2013-01-01

    Superconducting field coils using a high-temperature superconducting (HTS) wires with high current density generate high magnetic field of 2 to 5 [T] and electromagnetic force (Lorentz force) acting on the superconducting field coils also become a very strong from the point of view of a mechanical characteristics. Because mechanical stress caused by these powerful electromagnetic force is one of the factors which worsens the critical current performance and structural characteristics of HTS wire, the mechanical stress analysis should be performed when designing the superconducting field coils. In this paper, as part of structural design of superconducting field coils for 17 MW class superconducting ship propulsion motor, mechanical stress acting on the superconducting field coils was analyzed and structural safety was also determined by the coupling analysis system that is consists of commercial electromagnetic field analysis program and structural analysis program.

  1. Mechanisms for neutron damage in graphite from low to high temperatures from first principles - 15308

    International Nuclear Information System (INIS)

    Heggie, M.I.; Latham, C.D.; McKenna, A.J.; Trevethan, T.P.; Vuong, A.B.; Young, P.J.L.

    2015-01-01

    Mechanism is key to understanding the reliability and applicability of materials test reactor data to in-service behaviour. Here we review the historic understanding of dimensional change, drawing out the prima facie inadequacies of the standard model, and describing additional mechanisms (buckle, ruck and tuck) based on basal shear during radiation. Finally, we summarise new findings that vacancy aggregation into lines which heal and contract the basal layers is more credible now than appeared to be the case 10 years ago and that it can also give rise to ramps connecting graphite layers. (authors)

  2. Mechanical response of novel SiOC glasses to high temperature exposition

    Czech Academy of Sciences Publication Activity Database

    Halasová, Martina; Chlup, Zdeněk; Strachota, Adam; Černý, Martin; Dlouhý, Ivo

    2012-01-01

    Roč. 32, č. 16 (2012), s. 4489-4495 ISSN 0955-2219 R&D Projects: GA ČR GA106/09/1101 Institutional research plan: CEZ:AV0Z30460519; CEZ:AV0Z40500505 Institutional support: RVO:68081723 ; RVO:61389013 Keywords : Glass * Hardness * Mechanical properties Subject RIV: JL - Materials Fatigue, Friction Mechanics; CD - Macromolecular Chemistry (UMCH-V); JH - Ceramic s, Fire-Resistant Materials and Glass (USMH-B) Impact factor: 2.360, year: 2012

  3. Mechanical and structural characteristics in high temperature of stainless steel welded joint

    International Nuclear Information System (INIS)

    Monteiro, S.N.; Carvalho Mota, A.F. de

    1980-01-01

    The mechanical behavior at 600 0 C of weldments made of type 304 stainless as base metal and niobium containing type 347 stainless as weld metal has been investigated. This was done through tensile and creep tests. Heat treatments at 600 0 C and up to 6000 hours permited a simultaneous follow up of the mechanical and microstructural changes. It was observed that the exposure at 600 0 C under load contributes, from the begining, to the strengthening of the weld. This is due to the acceleration of the second phase precipitation hardening. (Author) [pt

  4. In situ high temperature MAS NMR study of the mechanisms of catalysis. Ethane aromatization on Zn-modified zeolite BEA.

    Science.gov (United States)

    Arzumanov, Sergei S; Gabrienko, Anton A; Freude, Dieter; Stepanov, Alexander G

    2009-04-01

    Ethane conversion into aromatic hydrocarbons over Zn-modified zeolite BEA has been analyzed by high-temperature MAS NMR spectroscopy. Information about intermediates (Zn-ethyl species) and reaction products (mainly toluene and methane), which were formed under the conditions of a batch reactor, was obtained by (13)C MAS NMR. Kinetics of the reaction, which was monitored by (1)H MAS NMR in situ at the temperature of 573K, provided information about the reaction mechanism. Simulation of the experimental kinetics within the frames of the possible kinetic schemes of the reaction demonstrates that a large amount of methane evolved under ethane aromatization arises from the stage of direct ethane hydrogenolysis.

  5. Investigation into mechanical properties of joints of heterogeneous materials brazed with high-temperature solders

    International Nuclear Information System (INIS)

    Lomenko, V.I.; Merkushev, V.P.; Borodina, L.M.; Sycheva, T.S.; Tokhtina, O.A.; Frolov, N.N.

    1988-01-01

    Mechanical properties of copper joints with copper, 12Kh18M10T steel and KhD50 composite obtained by vacuum brazing by copper-titanium solder as compared with properties of joints brazed by PSr 72 and PMFOTsr 6-4-0.03 solders in hydrogen are studied. Dependences of joints strength on temperature of contact - reactive vacuum brazing are obtained. Possible applications of joints of dissimilar materials in electrovacuum devices subjected to the effect of dynamic loadings are established

  6. Compensation mechanisms at high temperature in Y-doped BaTiO3

    International Nuclear Information System (INIS)

    Paredes-Olguín, M.; Lira-Hernández, I.A.; Gómez-Yáñez, C.; Espino-Cortés, F.P.

    2013-01-01

    Samples of BaTiO 3 with different concentrations of Y were synthesized from powders. The mixtures of powders were pressed and sintered at 1500 °C for 1 h. Two groups of samples were processed, one satisfying Ba/(Ti+Y) 3+ occupies the Ti 4+ lattice sites. The conductivity behavior as a function of Y concentration suggests that the compensation mechanisms are hole and oxygen vacancies. Due to the presence of charge carriers in the material, high values for the dielectric constant and dielectric loss were observed. Analysis of the microstructure showed that the average grain size decreases as the Y concentration is increased.

  7. Mechanical properties of Mo and TZM alloy neutron-irradiated at high temperatures

    International Nuclear Information System (INIS)

    Ueda, Kazukiyo; Satou, Manabu; Hasegawa, Akira; Abe, Katsunori

    1997-01-01

    This work reports the mechanical properties of irradiated molybdenum (Mo) and its alloy, TZM. Recrystallized and stress-relieved specimens were irradiated at five temperatures between 373 and 800degC in FFTF/MOTA to fluence levels of 6.8 to 34 dpa. Irradiation embrittlement and hardening were evaluated by three-point bend test and Vickers hardness test, respectively. Stress-relieved materials showed the enough ductility even after high fluence irradiation. The role of layered structure of stress-relieved specimen was discussed. (author)

  8. High temperature treatment effect on physical and mechanical properties of titanium alloys

    International Nuclear Information System (INIS)

    Shinyaev, A.Ya.; Illarionov, Eh.I.

    2000-01-01

    The kinetics of variations in electric conductivity, hardness, strength and plastic properties is studied for Ti - 0.75 % W, Ti - 3.5 % W, Ti - 3.5 % W - 2.8 % Zr, Ti - 3.7 % W - 5.4 % Al, Ti - 6.4 % Al - 3.5 % W - 3 % Zr alloys on quench ageing at 400 - 700 Deg C. In the temperature dependences of electric conductivity and mechanical properties the extreme values are observed which may be interpreted as evidence of β-solid solution binodal decomposition [ru

  9. Metallurgical and Mechanical Characterization of High Temperature Titanium Alloys Joined by Friction Stir Welding

    Science.gov (United States)

    Gangwar, Kapil Dev

    In the world of joining, riveting and additive manufacturing, weight reduction, and omission of defects (at both macro and micro level) remain of paramount. Therefore, in the wake of ubiquitous fusion welding (FW) and widely accepted approach of riveting using Inconel bolts to resist corrosion at higher temperature, friction stir welding (FSW) has emerged as a novice jewel in friction based additive manufacturing industry. With advancements in automation of welding process and tool material, FSW of materials with higher work hardening such as steel and titanium has also become probable. Process and property relations associated with FSW are inevitable in case of dissimilar titanium alloys, due to presence of heterogeneity (whether atrocious or advantageous) in and around the weld nugget. These process property relationships are needed to be studied and addressed properly in order to optimize the processing window for improved mechanical and metallurgical properties. In this study FSWed similar and dissimilar butt joints of α+β, and near α titanium, alloys have been produced for varying processing conditions in order to study the effect of rotation speed (rpm) and traverse speed (TS; mm-min-1). The aim of this study is to assess the effect of tool geometry, tool rpm, TS on microstructure and mechanical properties of most widely used α+β titanium alloy, Ti-6Al-4V (Ti-64), standard grain and fine grain in addition to α+β,Ti-5Al-4V (T-54M), standard grain, and near α, Ti-6Al-2Mo-4Zr-2Sn (Ti-6242), standard grain (SG) and fine grain (FG). During FSW, a unique α+β fine-grained microstructure has been formed depending on whether or not the peak temperature in the weld nugget (WN) reached above or below β transus temperature. The resulting microstructure consists of acicular α+β, emanating from the prior β grain boundary as the weld cools off. The changes in the microstructure are observed by optical microscopy (OM). Later, a detailed analysis of material

  10. High-temperature mechanical and material design for SiC composites

    International Nuclear Information System (INIS)

    Ghoniem, N.M.

    1992-01-01

    Silicon Carbide (SiC) fiber reinforced composites (FRC's) are strong potential candidate structural and high heat flux materials for fusion reactors. During this past decade, they have been vigorously developed for use in aerospace and transportation applications. Recent fusion reactor systems studies, such as ARIES, have concluded that further development of SiC composites will result in significant safety, operational, and waste disposal advantages for fusion systems. A concise discussion of the main material and design issues related to the use of SiC FRC's as structural materials in future fusion systems is given in this paper. The status of material processing of SiC/SiC composites is first reviewed. The advantages and shortcomings of the leading processing technology, known as Chemical Vapor Infiltration are particularly highlighted. A brief outline of the design-relevant physical, mechanical, and radiation data base is then presented. SiC/SiC FRC's possess the advantage of increased apparent toughness under mechanical loading conditions. This increased toughness, however, is associated with the nucleation and propagation of small crack patterns in the structure. Design approaches and failure criteria under these conditions are discussed

  11. Effects of high-temperature gas dealkalization on surface mechanical properties of float glass

    Science.gov (United States)

    Senturk, Ufuk

    The surface topography, and the near-surface structure and mechanical property changes on float glass, that was treated in atmospheres containing SOsb2, HCl, and 1,1 difluoroethane (DFE) gases, at temperatures in the glass transition region, were studied. Structure was investigated using surface sensitive infrared spectroscopy techniques (attenuated total reflectance (ATR) and diffuse reflectance (DRIFT)) and the topography was evaluated using atomic force microscopy (AFM). The results obtained from the two FTIR methods were in agreement with each other. Mechanical property characteristics of the surface were determined by measuring microhardness using a recording microindentation set-up. A simple analysis performed on the three hardness calculation methods-LVH, LVHsb2, and Lsb2VH-indicated that LVH and LVHsb2 are less effected by measurement errors and are better suited for the calculation of hardness. Contact damage characteristics of the treated glass was also studied by monitoring the crack initiation behavior during indentation, using acoustic emission. The results of the studies, aiming for the understanding of the structure, topography, and hardness property changes indicate that the treatment parameters-temperature, time, and treatment atmosphere conditions-are significant factors influencing these properties. The analysis of these results suggest a relation to exist between the three properties. This relation is used in understanding the surface mechanical properties of the treated float glasses. The difference in the thermal expansion coefficients between the dealkalized surface and bulk, the nature of surface structure changes, structural relaxation, surface water content, and glass transformation temperature are identified as the major factors having an influence on the properties. A model connecting these features is suggested. A difference in the structure, hardness, and topography on the air and tin sides of float glass is also shown to exist. The

  12. Short-time, high temperature mechanical testing of electrically conductive materials

    International Nuclear Information System (INIS)

    Marion, R.H.; Karnes, C.H.

    1975-10-01

    Design and performance details are given for a facility which was developed to obtain the mechanical properties of materials under high heating rate or transient temperature conditions and medium strain rates. The system is shown to be applicable to materials possessing electrical resistivities ranging from that of aluminum to that of graphite without taxing the heating capability. Heating rates as high as 2000 0 K/s in graphite are attained under controlled conditions. Methods of measuring temperature and the effects of expected temperature distributions are discussed. A method for measuring strain valid for transient temperature conditions to 3000 0 K is described. Results are presented for the stress-strain behavior of 316 stainless steel and ATJ(S) graphite obtained for heating times of a few seconds. (auth)

  13. Compensation mechanisms at high temperature in Y-doped BaTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Paredes-Olguin, M., E-mail: myriampaol@gmail.com [Department of Metallurgical and Materials Engineering, ESIQIE National Polytechnic Institute, U.P.A. Lopez Mateos, Zacatenco, Mexico City 07738 (Mexico); Lira-Hernandez, I.A.; Gomez-Yanez, C. [Department of Metallurgical and Materials Engineering, ESIQIE National Polytechnic Institute, U.P.A. Lopez Mateos, Zacatenco, Mexico City 07738 (Mexico); Espino-Cortes, F.P. [Department of Electrical Engineering, SEPI-ESIME National Polytechnic Institute, U.P.A. Lopez Mateos, Zacatenco, Mexico City 07738 (Mexico)

    2013-02-01

    Samples of BaTiO{sub 3} with different concentrations of Y were synthesized from powders. The mixtures of powders were pressed and sintered at 1500 Degree-Sign C for 1 h. Two groups of samples were processed, one satisfying Ba/(Ti+Y)<1 and the other satisfying Ba/(Ti+Y)=1. X-ray diffraction patterns were analyzed by Rietveld refinement and it was concluded that Y{sup 3+} occupies the Ti{sup 4+} lattice sites. The conductivity behavior as a function of Y concentration suggests that the compensation mechanisms are hole and oxygen vacancies. Due to the presence of charge carriers in the material, high values for the dielectric constant and dielectric loss were observed. Analysis of the microstructure showed that the average grain size decreases as the Y concentration is increased.

  14. High-temperature deformation of a mechanically alloyed niobium-yttria alloy

    International Nuclear Information System (INIS)

    Chou, I.; Koss, D.A.; Howell, P.R.; Ramani, A.S.

    1997-01-01

    Mechanical alloying (MA) and hot isostatic pressing have been used to process two Nb alloys containing yttria particles, Nb-2 vol.%Y 2 O 3 and Nb-10 vol.%Y 2 O 3 . Similar to some thermomechanically processed nickel-based alloys, both alloys exhibit partially recrystallized microstructures, consisting of a 'necklace' of small recrystallized grains surrounding much larger but isolated, unrecrystallized, cold-worked grains. Hot compression tests from 1049 to 1347 C (0.5-0.6T MP ) of the 10% Y 2 O 3 alloy show that MA material possesses a much higher yield and creep strength than its powder-blended, fully recrystallized counterpart. In fact, the density-compensated specific yield strength of the MA Nb-10Y 2 O 3 exceeds that of currently available commercial Nb alloys. (orig.)

  15. High-temperature mechanical properties of a uniaxially reinforced zircon-silicon carbide composite

    International Nuclear Information System (INIS)

    Singh, R.N.

    1990-01-01

    This paper reports that mechanical properties of a monolithic zircon ceramic and zircon-matrix composites uniaxially reinforced with either uncoated or BN-coated silicon carbide monofilaments were measured in flexure between 25 degrees and 1477 degrees C. Monolithic zircon ceramics were weak and exhibited a brittle failure up to abut 1300 degrees C. An increasing amount of the plastic deformation was observed before failure above about 1300 degrees C. In contrast, composites reinforced with either uncoated or BN-coated Sic filaments were stronger and tougher than the monolithic zircon at all test temperatures between 25 degrees and 1477 degrees. The ultimate strength and work-of-fracture of composite samples decreased with increasing temperature. A transgranular matrix fracture was shown by the monolithic and composite samples tested up to about 1200 degrees C, whereas an increasing amount of the intergranular matrix fracture was displayed above 1200 degrees C

  16. Mechanism of magnetite formation in high temperature corrosion by model naphthenic acids

    International Nuclear Information System (INIS)

    Jin, Peng; Robbins, Winston; Bota, Gheorghe

    2016-01-01

    Highlights: • Magnetite scales were found in naphthenic acid (NAP) corrosion. • Magnetite scales were formed due to thermal decomposition of iron naphthenates. • Formation and protectiveness of magnetite scales depended on structure of NAP. • Carboxylic acids confirm corrosion observations for commercial NAP. - Abstract: Naphthenic acid (NAP) corrosion is a major concern for refineries. The complexity of NAP in crude oil and the sulfidation process hinder a fundamental knowledge of their corrosive behavior. Studies with model acids were performed to explore the corrosion mechanism and magnetite scales were found on carbon steel. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and X-ray diffraction methods detected differences in the quantity and quality of magnetite formed by model acids. These scales exhibited different resistance to higher severity NAP corrosion in a flow through apparatus. Magnetite is proposed to be formed by thermal decomposition of iron naphthenates.

  17. Relation between the mechanical properties and SCC behavior of the alloys used in high temperature water

    International Nuclear Information System (INIS)

    Tsubota, M.; Katayama, Y.; Kanazawa, Y.

    2007-01-01

    It was shown in the previous reports that carbon and low alloy steels, martensitic stainless steels and cold worked austenitic stainless steels have shown high SCC susceptibility in the highly hardened condition. Those steels had similar critical hardness for SCC (HV300-340), over which the materials showed SCC susceptibility, even though the hardening process was different. Hardening processes applied for the alloys were as follows: (1) Martensitic transformation: Carbon and low alloy steels and martensitic stainless steels. (2) Alpha-prime decomposition (precipitation hardening): martensitic stainless steels. (3) Cold work: austenitic stainless steels. The relationship between the mechanical properties and SCC susceptibility of the alloys is discussed and summarized in the present paper. (author)

  18. New WC-Cu thermal barriers for fusion applications: High temperature mechanical behaviour

    Science.gov (United States)

    Tejado, E.; Dias, M.; Correia, J. B.; Palacios, T.; Carvalho, P. A.; Alves, E.; Pastor, J. Y.

    2018-01-01

    The combination of tungsten carbide and copper as a thermal barrier could effectively reduce the thermal mismatch between tungsten and copper alloy, which are proposed as base armour and heat sink, respectively, in the divertor of future fusion reactors. Furthermore, since the optimum operating temperature windows for these divertor materials do not overlap, a compatible thermal barrier interlayer between them is required to guarantee a smooth thermal transition, which in addition may mitigate radiation damage. The aim of this work is to study the thermo-mechanical properties of WC-Cu cermets fabricated by hot pressing. Focus is placed on the temperature effect and composition dependence, as the volume fraction of copper varies from 25 to 50 and 75 vol%. To explore this behaviour, fracture experiments are performed within a temperature range from room temperature to 800 °C under vacuum. In addition, elastic modulus and thermal expansion coefficient are estimated from these tests. Results reveal a strong dependence of the performance on temperature and on the volume fraction of copper and, surprisingly, a slight percent of Cu (25 vol%) can effectively reduce the large difference in thermal expansion between tungsten and copper alloy, which is a critical point for in service applications. The thermal performance of these materials, together with their mechanical properties could indeed reduce the heat transfer from the PFM to the underlying element while supporting the high thermal stresses of the joint. Thus, the presence of these cermets could allow the reactor to operate above the ductile to brittle transition temperature of tungsten, without compromising the underlying materials.

  19. Biomass pyrolysis: Thermal decomposition mechanisms of furfural and benzaldehyde

    Science.gov (United States)

    Vasiliou, AnGayle K.; Kim, Jong Hyun; Ormond, Thomas K.; Piech, Krzysztof M.; Urness, Kimberly N.; Scheer, Adam M.; Robichaud, David J.; Mukarakate, Calvin; Nimlos, Mark R.; Daily, John W.; Guan, Qi; Carstensen, Hans-Heinrich; Ellison, G. Barney

    2013-09-01

    The thermal decompositions of furfural and benzaldehyde have been studied in a heated microtubular flow reactor. The pyrolysis experiments were carried out by passing a dilute mixture of the aromatic aldehydes (roughly 0.1%-1%) entrained in a stream of buffer gas (either He or Ar) through a pulsed, heated SiC reactor that is 2-3 cm long and 1 mm in diameter. Typical pressures in the reactor are 75-150 Torr with the SiC tube wall temperature in the range of 1200-1800 K. Characteristic residence times in the reactor are 100-200 μsec after which the gas mixture emerges as a skimmed molecular beam at a pressure of approximately 10 μTorr. Products were detected using matrix infrared absorption spectroscopy, 118.2 nm (10.487 eV) photoionization mass spectroscopy and resonance enhanced multiphoton ionization. The initial steps in the thermal decomposition of furfural and benzaldehyde have been identified. Furfural undergoes unimolecular decomposition to furan + CO: C4H3O-CHO (+ M) → CO + C4H4O. Sequential decomposition of furan leads to the production of HC≡CH, CH2CO, CH3C≡CH, CO, HCCCH2, and H atoms. In contrast, benzaldehyde resists decomposition until higher temperatures when it fragments to phenyl radical plus H atoms and CO: C6H5CHO (+ M) → C6H5CO + H → C6H5 + CO + H. The H atoms trigger a chain reaction by attacking C6H5CHO: H + C6H5CHO → [C6H6CHO]* → C6H6 + CO + H. The net result is the decomposition of benzaldehyde to produce benzene and CO.

  20. High temperature mechanical properties of zirconia tapes used for electrolyte supported solid oxide fuel cells

    Science.gov (United States)

    Fleischhauer, Felix; Bermejo, Raul; Danzer, Robert; Mai, Andreas; Graule, Thomas; Kuebler, Jakob

    2015-01-01

    Solid-Oxide-Fuel-Cell systems are efficient devices to convert the chemical energy stored in fuels into electricity. The functionality of the cell is related to the structural integrity of the ceramic electrolyte, since its failure can lead to drastic performance losses. The mechanical property which is of most interest is the strength distribution at all relevant temperatures and how it is affected with time due to the environment. This study investigates the impact of the temperature on the strength and the fracture toughness of different zirconia electrolytes as well as the change of the elastic constants. 3YSZ and 6ScSZ materials are characterised regarding the influence of sub critical crack growth (SCCG) as one of the main lifetime limiting effects for ceramics at elevated temperatures. In addition, the reliability of different zirconia tapes is assessed with respect to temperature and SCCG. It was found that the strength is only influenced by temperature through the change in fracture toughness. SCCG has a large influence on the strength and the lifetime for intermediate temperature, while its impact becomes limited at temperatures higher than 650 °C. In this context the tetragonal 3YSZ and 6ScSZ behave quite different than the cubic 10Sc1CeSZ, so that at 850 °C it can be regarded as competitive compared to the tetragonal compounds.

  1. High Temperature Mechanical Constitutive Modeling of a High-Nb TiAl Alloy

    Directory of Open Access Journals (Sweden)

    DONG Chengli

    2018-02-01

    Full Text Available Uniaxial tensile, low cycle fatigue, fatigue-creep interaction and creep experiments of a novel high-Nb TiAl alloy (i.e. Ti-45Al-8Nb-0.2W-0.2B-0.02Y (atom fraction/% were conducted at 750℃ to obtain its tested data and curves. Based on Chaboche visco-plasticity unified constitutive model, Ohno-Wang modified non-linear kinematic hardening was introduced in Chaboche constitutive model to describe the cyclic hardening/softening, and Kachanov damage was coupled in Chaboche constitutive model to characterize the accelerated creep stage. The differential equations of the constitutive model discretized by explicit Euler method were compiled in to ABAQUS/UMAT to simulate the mechanical behavior of high-Nb TiAl alloy at different test conditions. The results show that Chaboche visco-plasticity unified constitutive model considering both Ohno-Wang modified non-linear kinematic hardening and Kachanov damage is able to simulate the uniaxial tensile, low cycle fatigue, fatigue-creep interaction and creep behavior of high-Nb TiAl alloy and has high accuracy.

  2. Relationship of electrical, magnetic, and mechanical properties to processing in high-temperature superconductors

    International Nuclear Information System (INIS)

    Blendell, J.E.; Chiang, C.K.; Cranmer, D.C.

    1987-01-01

    The interrelation between processing, microstructure, and properties is an important factor in understanding the behavior of ceramic materials. This type of understanding will be particularly important in the development of the new high T/sub c/ superconducting ceramic oxides of the type Ba/sub 2/YCu/sub 3/O/sub 7-x/. As an initial effort in understanding these relations, a number of properties have been measured for these superconducting ceramics and related to their microstructure and processing sequence. The Ba/sub 2/YCu/sub 3/O/sub 7-x/ ceramics were prepared by powder processing techniques, followed by dry pressing and sintering in both air and flowing oxygen at various temperatures. The sintered bodies were annealed at various temperatures and environments. Superconducting properties, such as the transition temperature and the width of the transition, were measured by both electrical conductivity and AC magnetic susceptibility; both of these properties show a strong sensitivity to annealing temperature and atmosphere. The microstructure and density were also strongly dependent on processing conditions. In this regard, compositional mapping proved to be an important technique for quantifying microstructural variations. Mechanical properties, such as elastic modulus, hardness, and fracture toughness, which will be important for the reliable use of these materials in large scale structures, were also determined

  3. Mechanical properties of Ni-base superalloys in high temperature steam environments

    International Nuclear Information System (INIS)

    Jang, Changheui; Kim, Donghoon; Sah, Injin; Lee, Ho Jung

    2015-01-01

    The effects of environmental damages on the mechanical properties of Ni-base superalloys, Alloy 617 and Haynes 230, were evaluated for VHTR-HTSE applications. Tensile tests were carried out at room temperature after ageing at 900 deg. C in vacuum, steam, and steam + 20 vol.% H2 environments up to 3 000 h. Also, creep rupture test were performed in air, steam, and steam + 20 vol.% H2 environments. The degradations such as oxidation, decarburization, and redistribution of carbides were studied in view of the interaction of materials with the environment. During the long-term ageing at 900 deg. C in vacuum, secondary phases such as M23C6 and M6C were precipitated and coarsened, which caused increase in tensile strength and decrease in ductility. For the specimens aged in steam environments, surface and internal oxides acted as preferential sites for crack initiation and consequently, decreased the tensile and creep strength. Also, the formation of decarburization region resulted in glide plane failure during tensile test and reduction in creep rupture life due to grain boundary migration and recrystallisation. During creep tests, tensile stress caused the crack and void formation in oxide layer. Consequently, fast diffusion of oxidant occurred and environmental damage were accelerated. Among the test conditions, such environmental damage was much severe in steam environments. (authors)

  4. Reconstruction mechanisms of tantalum oxide coatings with low concentrations of silver for high temperature tribological applications

    Energy Technology Data Exchange (ETDEWEB)

    Stone, D. S.; Bischof, M.; Aouadi, S. M., E-mail: samir.aouadi@unt.edu [Department of Material Science and Engineering, University of North Texas, Denton, Texas 76207 (United States); Gao, H.; Martini, A. [School of Engineering, University of California Merced, Merced, California 95343 (United States); Chantharangsi, C.; Paksunchai, C. [Department of Physics, King Mongkut' s University of Technology Thonburi, Bangkok 10140 (Thailand)

    2014-11-10

    Silver tantalate (AgTaO{sub 3}) coatings have been found to exhibit outstanding tribological properties at elevated temperatures. To understand the mechanisms involved in the tribological behavior of the Ag-Ta-O system, tantalum oxide coatings with a small content of silver were produced to investigate the metastable nature of this self-lubricating material. The coatings were produced by unbalanced magnetron sputtering, ball-on-disk wear tested at 750 °C, and subsequently characterized by X-ray diffraction, Scanning Auger Nanoprobe, cross-sectional Scanning Electron Microscopy, and Transmission Electron Microscopy. Complementary molecular dynamic simulations were carried out to investigate changes in the chemical and structural properties at the interface due to sliding for films with varying silver content. Both the experimental characterization and the theoretical modeling showed that silver content affects friction and wear, through the role of silver in film reconstruction during sliding. The results suggest that the relative amount of silver may be used to tune film performance for a given application.

  5. Reconstruction mechanisms of tantalum oxide coatings with low concentrations of silver for high temperature tribological applications

    International Nuclear Information System (INIS)

    Stone, D. S.; Bischof, M.; Aouadi, S. M.; Gao, H.; Martini, A.; Chantharangsi, C.; Paksunchai, C.

    2014-01-01

    Silver tantalate (AgTaO 3 ) coatings have been found to exhibit outstanding tribological properties at elevated temperatures. To understand the mechanisms involved in the tribological behavior of the Ag-Ta-O system, tantalum oxide coatings with a small content of silver were produced to investigate the metastable nature of this self-lubricating material. The coatings were produced by unbalanced magnetron sputtering, ball-on-disk wear tested at 750 °C, and subsequently characterized by X-ray diffraction, Scanning Auger Nanoprobe, cross-sectional Scanning Electron Microscopy, and Transmission Electron Microscopy. Complementary molecular dynamic simulations were carried out to investigate changes in the chemical and structural properties at the interface due to sliding for films with varying silver content. Both the experimental characterization and the theoretical modeling showed that silver content affects friction and wear, through the role of silver in film reconstruction during sliding. The results suggest that the relative amount of silver may be used to tune film performance for a given application

  6. Contribution to the explanation of the spalling of small specimen without any mechanical restraint exposed to high temperature

    International Nuclear Information System (INIS)

    Morais, Marcus V.G. de; Pliya, Prosper; Noumowe, Albert; Beaucour, Anne-Lise; Ortola, Sophie

    2010-01-01

    The behaviour of concrete subjected to high temperature is studied. The aim of the study is to explain the spalling or bursting phenomenon observed during experimental studies in the laboratory. Mechanical computations are carried out with the finite element code CAST3M developed at the French Atomic Energy Agency (CEA). Heat gradient and water vapour pressure inside the concrete element are determined by using a thermo-hydrous model. Then, the mechanical stresses generated in the studied concrete element are calculated according to two behaviour assumptions: the linear isotropic elastic law and an elastoplastic model. Numerical simulations show that, during the heating cycles, tension stresses are developed in the central part and compression stresses at the surface of the cylindrical concrete element. The highest stresses appear when the surface temperature of the concrete element is about 300 o C. The tension stresses in the specimens then exceed the concrete tensile strength.

  7. Contribution to the explanation of the spalling of small specimen without any mechanical restraint exposed to high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Morais, Marcus V.G. de, E-mail: mvmorais@unb.b [Cergy-Pontoise University - L2MGC, 5 mail Gay-Lussac Neuville sur Oise, 95031 Cergy-Pontoise Cedex (France); Pliya, Prosper [Cergy-Pontoise University - L2MGC, 5 mail Gay-Lussac Neuville sur Oise, 95031 Cergy-Pontoise Cedex (France); Noumowe, Albert, E-mail: Albert.Noumowe@u-cergy.f [Cergy-Pontoise University - L2MGC, 5 mail Gay-Lussac Neuville sur Oise, 95031 Cergy-Pontoise Cedex (France); Beaucour, Anne-Lise; Ortola, Sophie [Cergy-Pontoise University - L2MGC, 5 mail Gay-Lussac Neuville sur Oise, 95031 Cergy-Pontoise Cedex (France)

    2010-10-15

    The behaviour of concrete subjected to high temperature is studied. The aim of the study is to explain the spalling or bursting phenomenon observed during experimental studies in the laboratory. Mechanical computations are carried out with the finite element code CAST3M developed at the French Atomic Energy Agency (CEA). Heat gradient and water vapour pressure inside the concrete element are determined by using a thermo-hydrous model. Then, the mechanical stresses generated in the studied concrete element are calculated according to two behaviour assumptions: the linear isotropic elastic law and an elastoplastic model. Numerical simulations show that, during the heating cycles, tension stresses are developed in the central part and compression stresses at the surface of the cylindrical concrete element. The highest stresses appear when the surface temperature of the concrete element is about 300 {sup o}C. The tension stresses in the specimens then exceed the concrete tensile strength.

  8. Optical Method for Detecting Displacements and Strains at Ultra-High Temperatures During Thermo-Mechanical Testing

    Science.gov (United States)

    Smith, Russell W. (Inventor); Rivers, H. Kevin (Inventor); Sikora, Joseph G. (Inventor); Roth, Mark C. (Inventor); Johnston, William M. (Inventor)

    2016-01-01

    An ultra-high temperature optical method incorporates speckle optics for sensing displacement and strain measurements well above conventional measurement techniques. High temperature pattern materials are used which can endure experimental high temperature environments while simultaneously having a minimum optical aberration. A purge medium is used to reduce or eliminate optical distortions and to reduce, and/or eliminate oxidation of the target specimen.

  9. Novel technique for coal pyrolysis and hydrogenation product analysis

    Energy Technology Data Exchange (ETDEWEB)

    Pfefferle, L.D.; Boyle, J.

    1993-03-15

    A microjet reactor coupled to a VUV photoionization time-of-flight mass spectrometer has been used to obtain species measurements during high temperature pyrolysis and oxidation of a wide range of hydrocarbon compounds ranging from allene and acetylene to cyclohexane, benzene and toluene. Initial work focused on calibration of the technique, optimization of ion collection and detection and characterization of limitations. Using the optimized technique with 118 nm photoionization, intermediate species profiles were obtained for analysis of the hydrocarbon pyrolysis and oxidation mechanisms. The soft'' ionization, yielding predominantly molecular ions, allowed the study of reaction pathways in these high temperature systems where both sampling and detection challenges are severe. Work has focused on the pyrolysis and oxidative pyrolysis of aliphatic and aromatic hydrocarbon mixtures representative of coal pyrolysis and hydropyrolysis products. The detailed mass spectra obtained during pyrolysis and oxidation of hydrocarbon mixtures is especially important because of the complex nature of the product mixture even at short residence times and low primary reactant conversions. The combustion community has advanced detailed modeling of pyrolysis and oxidation to the C4 hydrocarbon level but in general above that size uncertainties in rate constant and thermodynamic data do not allow us to a priori predict products from mixed hydrocarbon pyrolyses using a detailed chemistry model. For pyrolysis of mixtures of coal-derived liquid fractions with a large range of compound structures and molecular weights in the hundreds of amu the modeling challenge is severe. Lumped models are possible from stable product data.

  10. Mechanical characterization of metallic materials for high-temperature gas-cooled reactors in air and in helium environments

    International Nuclear Information System (INIS)

    Sainfort, G.; Cappelaere, M.; Gregoire, J.; Sannier, J.

    1984-01-01

    In the French R and D program for high-temperature gas-cooled reactors (HTGRs), three metallic alloys were studied: steel Chromesco-3 with 2.25% chromium, alloy 800H, and Hastelloy-X. The Chromesco-3 and alloy 800H creep behavior is the same in air and in HTGR atmosphere (helium). The tensile tests of Hastelloy-X specimens reveal that aging has embrittlement and hardening effects up to 700 0 C, but the creep tests at 800 0 C show opposite effects. This particular behavior could be due to induced precipitation by aging and the depletion of hardening elements from the matrix. Tests show a low influence of cobalt content on mechanical properties of Hastelloy-X

  11. Effect of high temperature tempering on the mechanical properties and microstructure of the modified 410 martensitic stainless steel

    Science.gov (United States)

    Mabruri, Efendi; Pasaribu, Rahmat Ramadhan; Sugandi, Moh. Tri; Sunardi

    2018-05-01

    This paper reports the influence of high tempering temperature and holding time on the mechanical properties and microstructure of the recently modified 410 martensitic stainless steel. The modified steel was prepared by induction melting followed by hot forging, quenching and tempering. The hardness and tensile strength of the steels decreased with increasing tempering temperature from 600 to 700 °C and with increasing holding time from 1 to 6 h. Based on microstructural images, it was observed the coarsening of lath martensite and of the metal carbides as well. However, a relatively high hardness and strength were still exibited by this steel after tempering at a such high temperature of 600-700 °C. The partition of Mo into the carbides identified by EDS analysis may correlate with this situation.

  12. Effects of Electromagnetic Stirring on the Microstructure and High-Temperature Mechanical Properties of a Hyper-eutectic Al-Si-Cu-Ni Alloy

    Science.gov (United States)

    Jang, Youngsoo; Choi, Byounghee; Kang, Byungkeun; Hong, Chun Pyo

    2015-02-01

    A liquid treatment method by electromagnetic stirring was applied to a hyper-eutectic Al-15wt pctSi-4wt pctCu-3wt pctNi alloy for the piston manufacturing with diecasting process in order to improve high-temperature mechanical properties of the piston heads. The mechanical properties, such as hardness, high-temperature tensile stress, thermal expansion, and high-temperature relative wear resistance, were estimated using the specimens taken from the liquid-treated diecast products, and the results were compared with those of a conventional metal-mold-cast piston.

  13. Wood Modification at High Temperature and Pressurized Steam: a Relational Model of Mechanical Properties Based on a Neural Network

    Directory of Open Access Journals (Sweden)

    Hong Yang

    2015-07-01

    Full Text Available Thermally modified wood has high dimensional stability and biological durability.But if the process parameters of thermal modification are not appropriate, then there will be a decline in the physical properties of wood.A neural network algorithm was employed in this study to establish the relationship between the process parameters of high-temperature and high-pressure thermal modification and the mechanical properties of the wood. Three important parameters: temperature, relative humidity, and treatment time, were considered as the inputs to the neural network. Back propagation (BP neural network and radial basis function (RBF neural network models for prediction were built and compared. The comparison showed that the RBF neural network model had advantages in network structure, convergence speed, and generalization capacity. On this basis, the inverse model, reflecting the relationship between the process parameters and the mechanical properties of wood, was established. Given the desired mechanical properties of the wood, the thermal modification process parameters could be inversely optimized and predicted. The results indicated that the model has good learning ability and generalization capacity. This is of great importance for the theoretical and applicational studies of the thermal modification of wood.

  14. High Temperature Deformation Mechanism in Hierarchical and Single Precipitate Strengthened Ferritic Alloys by In Situ Neutron Diffraction Studies.

    Science.gov (United States)

    Song, Gian; Sun, Zhiqian; Li, Lin; Clausen, Bjørn; Zhang, Shu Yan; Gao, Yanfei; Liaw, Peter K

    2017-04-07

    The ferritic Fe-Cr-Ni-Al-Ti alloys strengthened by hierarchical-Ni 2 TiAl/NiAl or single-Ni 2 TiAl precipitates have been developed and received great attentions due to their superior creep resistance, as compared to conventional ferritic steels. Although the significant improvement of the creep resistance is achieved in the hierarchical-precipitate-strengthened ferritic alloy, the in-depth understanding of its high-temperature deformation mechanisms is essential to further optimize the microstructure and mechanical properties, and advance the development of the creep resistant materials. In the present study, in-situ neutron diffraction has been used to investigate the evolution of elastic strain of constitutive phases and their interactions, such as load-transfer/load-relaxation behavior between the precipitate and matrix, during tensile deformation and stress relaxation at 973 K, which provide the key features in understanding the governing deformation mechanisms. Crystal-plasticity finite-element simulations were employed to qualitatively compare the experimental evolution of the elastic strain during tensile deformation at 973 K. It was found that the coherent elastic strain field in the matrix, created by the lattice misfit between the matrix and precipitate phases for the hierarchical-precipitate-strengthened ferritic alloy, is effective in reducing the diffusional relaxation along the interface between the precipitate and matrix phases, which leads to the strong load-transfer capability from the matrix to precipitate.

  15. Effects of carbon content on high-temperature mechanical and thermal fatigue properties of high-boron austenitic steels

    Directory of Open Access Journals (Sweden)

    Xiang Chen

    2016-01-01

    Full Text Available High-temperature mechanical properties of high-boron austenitic steels (HBASs were studied at 850 °C using a dynamic thermal-mechanical simulation testing machine. In addition, the thermal fatigue properties of the alloys were investigated using the self-restraint Uddeholm thermal fatigue test, during which the alloy specimens were cycled between room temperature and 800°C. Stereomicroscopy and scanning electron microscopy were used to study the surface cracks and cross-sectional microstructure of the alloy specimens after the thermal fatigue tests. The effects of carbon content on the mechanical properties at room temperature and high-temperature as well as thermal fatigue properties of the HBASs were also studied. The experimental results show that increasing carbon content induces changes in the microstructure and mechanical properties of the HBASs. The boride phase within the HBAS matrix exhibits a round and smooth morphology, and they are distributed in a discrete manner. The hardness of the alloys increases from 239 (0.19wt.% C to 302 (0.29wt.% C and 312 HV (0.37wt.% C; the tensile yield strength at 850 °C increases from 165.1 to 190.3 and 197.1 MPa; and the compressive yield strength increases from 166.1 to 167.9 and 184.4 MPa. The results of the thermal fatigue tests (performed for 300 cycles from room temperature to 800 °C indicate that the degree of thermal fatigue of the HBAS with 0.29wt.% C (rating of 2–3 is superior to those of the alloys with 0.19wt.% (rating of 4–5 and 0.37wt.% (rating of 3–4 carbon. The main cause of this difference is the ready precipitation of M23(C,B6-type borocarbides in the alloys with high carbon content during thermal fatigue testing. The precipitation and aggregation of borocarbide particles at the grain boundaries result in the deterioration of the thermal fatigue properties of the alloys.

  16. Modeling of mechanical behavior of quenched zirconium-based nuclear fuel claddings after a high temperature oxidation

    International Nuclear Information System (INIS)

    Cabrera-Salcedo, A.

    2012-01-01

    During the second stage of Loss Of Coolant Accident (LOCA) in Pressurized Water Reactors (PWR) zirconium-based fuel claddings undergo a high temperature oxidation (up to 1200 C), then a water quench. After a single-side steam oxidation followed by a direct quench, the cladding is composed of three layers: an oxide (Zirconia) outer layer (formed at HT), always brittle at Room Temperature (RT), an intermediate oxygen stabilized alpha layer, always brittle at RT, called alpha(O), and an inner 'prior-beta' layer, which is the only layer able to keep some significant Post Quench (PQ) ductility at RT. However, hydrogen absorbed because of service exposure or during the LOCA transient, concentrates in this layer and may leads to its embrittlement. To estimate the PQ mechanical properties of these materials, Ring Compression Tests (RCT) are widely used because of their simplicity. Small sample size makes RCTs advantageous when a comparison with irradiated samples is required. Despite their good reproducibility, these tests are difficult to interpret as they often present two or more load drops on the engineering load-displacement curve. Laboratories disagree about their interpretation. This study proposes an original fracture scenario for a stratified PQ cladding tested by RCT, and its associated FE model. Strong oxygen content gradient effect on layers mechanical properties is taken into account in the model. PQ thermal stresses resulting from water quench of HT oxidized cladding are investigated, as well as progressive damage of three layers during an RCT. The proposed scenario is based on interrupted RCT analysis, post- RCT sample's outer layers observation for damage evaluation, RCTs of prior-beta single-layer rings, and mechanical behavior of especially chemically adjusted samples. The force displacement curves appearance is correctly reproduced using the obtained FE model. The proposed fracture scenario elucidates RCTs of quenched zirconium-based nuclear fuel

  17. Mechanical properties of steel fiber reinforced reactive powder concrete following exposure to high temperature reaching 800 deg. C

    Energy Technology Data Exchange (ETDEWEB)

    Tai, Yuh-Shiou, E-mail: ystai@cc.cma.edu.tw [Department of Civil Engineering, ROC Military Academy, Kaohsiung, Taiwan (China); Pan, Huang-Hsing; Kung, Ying-Nien [Department of Civil Engineering, Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan (China)

    2011-07-15

    Highlights: > The stress-strain relation of reactive powder concrete after exposure to high temperatures are tested by using displacement control. > Develops regression formulae to estimate the mechanical properties of RPC. > Valuable experimental data have been obtained about RPC with various fiber contents. These data include compressive strength, peak strain and modulus of elasticity. - Abstract: This study investigates the stress-strain relation of RPC in quasi-static loading after an elevated temperature. The cylinder specimens of RPC with {phi} 50 mm x 100 mm are examined at the room temperature and after 200-800 deg. C. Experimental results indicate that the residual compressive strength of RPC after heating from 200-300 deg. C increases more than that at room temperature, but, significantly decreases when the temperature exceeds 300 deg. C. The residual peak strains of RPC also initially increase up to 400-500 deg. C, then decrease gradually beyond 500 deg. C. Meanwhile, Young's modulus diminishes with an increasing temperature. Based on the regression analysis results, this study also develops regression formulae to estimate the mechanical properties of RPC after an elevated temperature, thus providing a valuable reference for industrial applications and design.

  18. Corrosion mechanism of 13Cr stainless steel in completion fluid of high temperature and high concentration bromine salt

    International Nuclear Information System (INIS)

    Liu, Yan; Xu, Lining; Lu, Minxu; Meng, Yao; Zhu, Jinyang; Zhang, Lei

    2014-01-01

    Highlights: • The corrosion behavior of 13Cr steel exposed to bromine salt completion fluid containing high concentration bromine ions was investigated. • There are passive circles around pits on the 13Cr steel surface after 7 d of exposure. • Macroscopic galvanic corrosion formed between the passive halo and the pit. • The mechanism of pitting corrosion on 13Cr stainless steel exposed to heavy bromine brine was established. - Abstract: A series of corrosion tests of 13Cr stainless steel were conducted in a simulated completion fluid environment of high temperature and high concentration bromine salt. Corrosion behavior of specimens and the component of corrosion products were investigated by means of scanning electron microscope (SEM), confocal laser scanning microscopy (CLSM) and X-ray photoelectron spectroscopy (XPS). The results indicate that 13Cr steel suffers from severe local corrosion and there is always a passive halo around every pit. The formation mechanism of the passive halo is established. OH − ligand generates and adsorbs in a certain scale because of abundant OH − on the surface around the pits. Passive film forms around each pit, which leads to the occurrence of passivation in a certain region. Finally, the dissimilarities in properties and morphologies of regions, namely the pit and its corresponding passive halo, can result in different corrosion sensitivities and may promote the formation of macroscopic galvanic pairs

  19. Effect of microstructure on high-temperature mechanical behavior of nickel-base superalloys for turbine disc applications

    Science.gov (United States)

    Sharpe, Heather Joan

    2007-05-01

    Engineers constantly seek advancements in the performance of aircraft and power generation engines, including, lower costs and emissions, and improved fuel efficiency. Nickel-base superalloys are the material of choice for turbine discs, which experience some of the highest temperatures and stresses in the engine. Engine performance is proportional to operating temperatures. Consequently, the high-temperature capabilities of disc materials limit the performance of gas-turbine engines. Therefore, any improvements to engine performance necessitate improved alloy performance. In order to take advantage of improvements in high-temperature capabilities through tailoring of alloy microstructure, the overall objectives of this work were to establish relationships between alloy processing and microstructure, and between microstructure and mechanical properties. In addition, the projected aimed to demonstrate the applicability of neural network modeling to the field of Ni-base disc alloy development and behavior. The first phase of this work addressed the issue of how microstructure varies with heat treatment and by what mechanisms these structures are formed. Further it considered how superalloy composition could account for microstructural variations from the same heat treatment. To study this, four next-generation Ni-base disc alloys were subjected to various controlled heat-treatments and the resulting microstructures were then quantified. These quantitative results were correlated to chemistry and processing, including solution temperature, cooling rate, and intermediate hold temperature. A complex interaction of processing steps and chemistry was found to contribute to all features measured; grain size, precipitate distribution, grain boundary serrations. Solution temperature, above a certain threshold, and cooling rate controlled grain size, while cooling rate and intermediate hold temperature controlled precipitate formation and grain boundary serrations. Diffusion

  20. High Temperature Degradation Behavior and its Mechanical Properties of Inconel 617 alloy for Intermediate Heat Exchanger of VHTR

    International Nuclear Information System (INIS)

    Jo, Tae Sun; Kim, Se Hoon; Kim, Young Do; Park, Ji Yeon

    2008-01-01

    Inconel 617 alloy is a candidate material of intermediate heat exchanger (IHX) and hot gas duct (HGD) for very high temperature reactor (VHTR) because of its excellent strength, creep-rupture strength, stability and oxidation resistance at high temperature. Among the alloying elements in Inconel 617, chromium (Cr) and aluminum (Al) can form dense oxide that act as a protective surface layer against degradation. This alloy supports severe operating conditions of pressure over 8 MPa and 950 .deg. C in He gas with some impurities. Thus, high temperature stability of Inconel 617 is very important. In this work, the oxidation behavior of Inconel 617 alloy was studied by exposure at high temperature and was discussed the high temperature degradation behavior with microstructural changes during the surface oxidation

  1. The Processing and Mechanical Properties of High Temperature/ High Performance Composites. Mechanism-Based Constitutive Laws and Design. Book 1

    Science.gov (United States)

    1994-03-01

    NTIS CRA&I IDT!C TAB TABLE OF CONTENTS U.11 nulce Distf ib,.tion, I Availab~iity Cojes EXECUTIVE SUMMARY Dist spc :BOOKh1 MECHANISM-BASED...unit cylinders (H=D), but rather by slightly squat cylinders. This is in contrast to the results of Bao et al. [1] in which unit cylinders resulted in

  2. A visualization instrument to investigate the mechanical-electro properties of high temperature superconducting tapes under multi-fields

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wei; Zhang, Xingyi, E-mail: zhangxingyi@lzu.edu.cn; Liu, Cong; Zhang, Wentao; Zhou, Jun; Zhou, YouHe [Key Laboratory of Mechanics on Disaster and Environment in Western China Attached to the Ministry of Education of China, Lanzhou University, Lanzhou, Gansu 730000, People’s Republic of China and Department of Mechanics and Engineering Sciences, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China)

    2016-07-15

    We construct a visible instrument to study the mechanical-electro behaviors of high temperature superconducting tape as a function of magnetic field, strain, and temperature. This apparatus is directly cooled by a commercial Gifford-McMahon cryocooler. The minimum temperature of sample can be 8.75 K. A proportion integration differentiation temperature control is used, which is capable of producing continuous variation of specimen temperature from 8.75 K to 300 K with an optional temperature sweep rate. We use an external loading device to stretch the superconducting tape quasi-statically with the maximum tension strain of 20%. A superconducting magnet manufactured by the NbTi strand is applied to provide magnetic field up to 5 T with a homogeneous range of 110 mm. The maximum fluctuation of the magnetic field is less than 1%. We design a kind of superconducting lead composed of YBa2Cu3O7-x coated conductor and beryllium copper alloy (BeCu) to transfer DC to the superconducting sample with the maximum value of 600 A. Most notably, this apparatus allows in situ observation of the electromagnetic property of superconducting tape using the classical magnetic-optical imaging.

  3. 3D characterization and modeling of low cycle fatigue damage mechanisms at high temperature in a cast aluminum alloy

    International Nuclear Information System (INIS)

    Dezecot, Sebastien; Maurel, Vincent; Buffiere, Jean-Yves; Szmytka, Fabien; Koster, Alain

    2017-01-01

    Synchrotron X-ray tomography was used to monitor damage evolution in three dimensions during in situ Low Cycle Fatigue (LCF) tests at high temperature (250 °C) for an industrial material. The studied material is an AlSi7Cu3Mg aluminum alloy (close to ASTM A319) produced by Lost Foam Casting (LFC), a process which generates coarse microstructures but is nevertheless used for engine parts by the automotive industry. The volume analysis (3D images) has shown that cracks are extremely sensitive to microstructural features: coarse pores and hard particles of the eutectic regions are critical regarding respectively the main crack initiation and the crack growth. Finite Elements (FE) simulations, performed on meshes directly generated from 3D volumes and containing only pores, have revealed that mechanical fields also play a major role on the crack behavior. Initiation sites corresponded to areas of maximum inelastic strain while the crack path was globally correlated to high stress triaxiality and inelastic strain fields.

  4. A new disordering mechanism in A15 type compounds submitted to low temperature irradiation or to quenching from high temperatures

    International Nuclear Information System (INIS)

    Fluekiger, R.

    1984-05-01

    A new diffusion mechanism describing the changes of the long range order parameter in A15 type compounds after both quenching from high temperatures or low temperature irradiation with high energy particles is presented. It is based on the occupation of nonequilibrium or 'virtual' sites centered halfway between two neighbouring A atoms on 6c sites, arising from the instability of a single 6c vacancy recently found by Welch and coworkers by pair potential calculations. After low temperature irradiation, the occupation of this interstitial site creates the necessary conditions for A B site exchanges over several interatomic distances by focused replacement collision sequences. Due to the occupation of a certain concentration of virtual sites, atomic 'overlapping' is not only possible between A atoms on the chains or between A and B atoms (due to deviations from perfect ordering),but also between B atoms on BBB sequences. The latter are retained after low temperature irradiation only and are responsible for the observed lattice expansion and static displacement. (orig.) [de

  5. Structural mechanisms of high-temperature shape changes in titanium-nickel alloys after low-temperature thermomechanical treatment

    International Nuclear Information System (INIS)

    Prokoshkin, S.D.; Turenne, S.; Khmelevskaya, I.Yu.; Brailovski, V.; Trochu, F.

    2000-01-01

    High-Temperature Shape Memory Effect (HTSME) in Ti-Ni alloys and corresponding structural and internal stress changes were studied using dilatometry, in situ electron microscope and X-ray diffractometry. The HTSME induced by the Low Temperature Thermomechanical Treatment (LTMT) consists of two stages. The temperature range of the first stage is limited to 250 o C, while the second stage extends to 400-500 o C. The first stage is caused by the oriented reverse martensite transformation. The heterogeneous residual stress field causes a different thermal stability for the different martensite orientations. During the reverse transformation an anisotropic shift of martensite and austenite X-ray lines is observed that can be due to a relaxation of the orientated stresses and to changes in the martensite lattice. The second stage of HTSME is caused by internal stress relaxation during recovery and polygonization of austenite that are not typical shape memory mechanisms. The possible reasons for the martensite stabilization induced by LTMT will be discussed. (author)

  6. Using vacuum pyrolysis and mechanical processing for recycling waste printed circuit boards

    International Nuclear Information System (INIS)

    Long Laishou; Sun Shuiyu; Zhong Sheng; Dai Wencan; Liu Jingyong; Song Weifeng

    2010-01-01

    The constant growth in generation of waste printed circuit boards (WPCB) poses a huge disposal problem because they consist of a heterogeneous mixture of organic and metallic chemicals as well as glass fiber. Also the presence of heavy metals, such as Pb and Cd turns this scrap into hazardous waste. Therefore, recycling of WPCB is an important subject not only from the recovery of valuable materials but also from the treatment of waste. The aim of this study was to present a recycling process without negative impact to the environment as an alternative for recycling WPCB. In this work, a process technology containing vacuum pyrolysis and mechanical processing was employed to recycle WPCB. At the first stage of this work, the WPCB was pyrolyzed under vacuum in a self-made batch pilot-scale fixed bed reactor to recycle organic resins contained in the WPCB. By vacuum pyrolysis the organic matter was decomposed to gases and liquids which could be used as fuels or chemical material resources, however, the inorganic WPCB matter was left unaltered as solid residues. At the second stage, the residues obtained at the first stage were investigated to separate and recover the copper through mechanical processing such as crushing, screening, and gravity separation. The copper grade of 99.50% with recovery of 99.86% based on the whole WPCB was obtained. And the glass fiber could be obtained by calcinations in a muffle furnace at 600 deg. C for 10 min. This study had demonstrated the feasibility of vacuum pyrolysis and mechanical processing for recycling WPCB.

  7. Mechanical Stability of H3PO4-Doped PBI/Hydrophilic-Pretreated PTFE Membranes for High Temperature PEMFCs

    International Nuclear Information System (INIS)

    Park, Jaehyung; Wang, Liang; Advani, Suresh G.; Prasad, Ajay K.

    2014-01-01

    Graphical abstract: - Highlights: • PBI/PTFE membrane was prepared by porous PTFE with hydrophilic surface pretreatment. • The durability of the prepared PBI/PTFE membrane was compared with pure PBI, PBI with untreated PTFE, and PBI-Nafion with untreated PTFE membranes. • Accelerated durability tests and SEM showed improved durability based the PBI/PTFE membrane with pretreated PTFE. - Abstract: A novel polybenzimidazole (PBI)/poly(tetrafluoroethylene) (PTFE) composite membrane doped with phosphoric acid was fabricated for high temperature operation in a polymer electrolyte membrane (PEM) fuel cell. A hydrophilic surface pretreatment was applied to the porous PTFE matrix film to improve its interfacial adhesion to the PBI polymer, thereby avoiding the introduction of Nafion ionomer which is traditionally used as a coupling agent. The pretreated PTFE film was embedded within the composite membrane during solution-casting using 5wt% PBI/DMAc solution. The mechanical stability and durability of three types of MEAs assembled with PBI only, PBI with pretreated PTFE, and PBI-Nafion with untreated PTFE membranes were evaluated under an accelerated degradation testing protocol employing extreme temperature cycling. Degradation was characterized by recording polarization curves, hydrogen crossover, and proton resistance. Cross-sections of the membranes were examined before and after thermal cycling by scanning electron microscope. Energy-dispersive X-ray spectroscopy verified that the PBI is dispersed homogeneously in the porous PTFE matrix. Results show that the PBI composite membrane with pretreated PTFE has a lower degradation rate than the Nafion/PBI membrane with untreated PTFE. Thus, the hydrophilic pretreatment employed here greatly improved the mechanical stability of the composite membrane, which resulted in improved durability under an extreme thermal cycling regime

  8. The Effect of Increasing Sn Content on High-Temperature Mechanical Deformation of an Mg-3%Cu-1%Ca Alloy

    Directory of Open Access Journals (Sweden)

    Georgios S.E. Antipas

    2013-11-01

    Full Text Available Chill casting of magnesium alloy samples with secondary alloying elements of Cu, Ca and Sn at % w.t. concentrations in the range 1–5, 0.1–5 and 0.1–3 respectively, gave rise to appreciably enhanced resistance to high-temperature creep, while maintaining good heat conductivity. The latter was considered to be driven by Cu and Mg-Cu intermetallics while it was clear that Sn mediated the high-temperature performance, mainly via networks of Mg2Sn and MgCaSn precipitates along the Mg matrix grain boundaries. It was postulated that Sn formed intermetallics by preferential substitution of Ca atoms and, thus, did not degrade the heat conductivity by retaining Cu. The % w.t. stoichiometry with the optimum combination of heat conductivity and resistance to high-temperature creep was found to be Mg-3Cu-1Ca-0.1Sn.

  9. Flash pyrolysis at high temperature of ligno-cellulosic biomass and its components - production of synthesis gas; Pyrolyse flash a haute temperature de la biomasse ligno-cellulosique et de ses composes - production de gaz de synthese

    Energy Technology Data Exchange (ETDEWEB)

    Couhert, C

    2007-11-15

    Pyrolysis is the first stage of any thermal treatment of biomass and governs the formation of synthesis gas for the production of electricity, hydrogen or liquid fuels. The objective of this work is to establish a link between the composition of a biomass and its pyrolysis gas. We study experimental flash pyrolysis and fix the conditions in which quantities of gas are maximal, while aiming at a regime without heat and mass transfer limitations (particles about 100 {mu}m): temperature of 950 C and residence time of about 2 s. Then we try to predict gas yields of any biomass according to its composition, applicable in this situation where thermodynamic equilibrium is not reached. We show that an additivity law does not allow correlating gas yields of a biomass with fractions of cellulose, hemi-cellulose and lignin contained in this biomass. Several explanations are suggested and examined: difference of pyrolytic behaviour of the same compound according to the biomass from which it is extracted, interactions between compounds and influence of mineral matter. With the aim of industrial application, we study pyrolysis of millimetric and centimetric size particles, and make a numerical simulation of the reactions of pyrolysis gases reforming. This simulation shows that the choice of biomass affects the quantities of synthesis gas obtained. (author)

  10. High-temperature superconductivity

    International Nuclear Information System (INIS)

    Ginzburg, V.L.

    1987-07-01

    After a short account of the history of experimental studies on superconductivity, the microscopic theory of superconductivity, the calculation of the control temperature and its possible maximum value are presented. An explanation of the mechanism of superconductivity in recently discovered superconducting metal oxide ceramics and the perspectives for the realization of new high-temperature superconducting materials are discussed. 56 refs, 2 figs, 3 tabs

  11. RELATION BETWEEN MECHANICAL PROPERTIES AND PYROLYSIS TEMPERATURE OF PHENOL FORMALDEHYDE RESIN FOR GAS SEPARATION MEMBRANES

    Directory of Open Access Journals (Sweden)

    MONIKA ŠUPOVÁ

    2012-03-01

    Full Text Available The aim of this paper has been to characterize the relation between the pyrolysis temperature of phenol-formaldehyde resin, the development of a porous structure, and the mechanical properties for the application of semipermeable membranes for gas separation. No previous study has dealt with this problem in its entirety. Phenol-formaldehyde resin showed an increasing trend toward micropore porosity in the temperature range from 500 till 1000°C, together with closure of mesopores and macropores. Samples cured and pyrolyzed at 1000°C pronounced hysteresis of desorption branch. The ultimate bending strength was measured using a four-point arrangement that is more suitable for measuring of brittle materials. The chevron notch technique was used for determination the fracture toughness. The results for mechanical properties indicated that phenol-formaldehyde resin pyrolyzates behaved similarly to ceramic materials. The data obtained for the material can be used for calculating the technical design of gas separation membranes.

  12. High-temperature mechanical properties and fracture mechanisms of Al–Si piston alloy reinforced with in situ TiB{sub 2} particles

    Energy Technology Data Exchange (ETDEWEB)

    Han, Gang [School of Mechanical Engineering, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081 (China); Zhang, Weizheng, E-mail: zhangwz@bit.edu.cn [School of Mechanical Engineering, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081 (China); Zhang, Guohua; Feng, Zengjian; Wang, Yanjun [Shandong Binzhou Bohai Piston Co., Ltd., Binzhou 256602 (China)

    2015-05-01

    In order to assess the high-temperature performance of aluminum–silicon alloy reinforced with titanium diboride particles as potential piston material, the tensile behaviors and fracture mechanisms of in situ 4 wt% TiB{sub 2}/Al–Si composite were investigated in the temperature range 25–350 °C. The tensile results revealed that the composite exhibited higher modulus than the matrix alloy at all testing temperatures, but both the matrix alloy and the composite presented similar strength levels above 200 °C. The ductility of the composite was found to be lower than that of the unreinforced matrix alloy at 25 and 200 °C, but no obvious distinction was observed at 350 °C. The effects of temperature and the presence of TiB{sub 2} particles on tensile properties of the composite had been evaluated. Fractographic morphology studies were done using scanning electron microscope, which indicated that the fracture of the composite altered from brittle to ductile mode with temperature increasing. At 25 and 200 °C, fracture was dominated by cracked silicon particles and separated TiB{sub 2} particles, while decohesion at particle–matrix interface was prevalent at 350 °C. Analysis of the fracture surfaces also showed that regions of clustered TiB{sub 2} particles were found to be the locations prone to damage in the composite at both room and high temperatures.

  13. High temperature mechanical properties on multi stage blazed fin body with ultra fine off-set fin for compact heat exchanger

    International Nuclear Information System (INIS)

    Ishiyama, Shintaro; Muto, Yasushi

    2003-01-01

    Three stage blazed plate fin body with ultra fine off-set fin (thickness x height x pitch x off-set pitch = 0.22 mm x 1.2 mm x 1.6 mm x 5 mm) for 600 MWt High Temperature Gas Cooled Reactor Gas Turbin (HTGR-GT) system was fabricated and tested on its high temperature mechanical properties and the following results were derived. (1) tested body shows almost the same strength an fatigue behavior of SUS 304 as main structural material at elevated temperatures up to 873 K, (2) static and fatigue fracture mainly occurred at ultra fine off-set and (3) high temperature strength and fatigue life are improved by blazing technique to double side walls of the fin by Ni blaze material. (author)

  14. Mechanical properties data of 2-1/4Cr-1Mo steel for the experimental very high temperature gas-cooled reactor

    International Nuclear Information System (INIS)

    Oku, Tatsuo; Kikuyama, Toshihiko; Fukaya, Kiyoshi; Kodaira, Tsuneo

    1978-11-01

    This is a collection of mechanical properties data of 2-1/4Cr-1Mo steel necessary for structural design and safety analysis of the pressure vessel of the Experimental Very High Temperature Gas-Cooled Reactor (VHTR). These include physical properties, mechanical properties, temper embrittlement, creep with fatigue, fracture toughness and irradiation effects. A review of the data shows the research areas to be carried out particularly in the future for more data. (author)

  15. High temperature materials

    International Nuclear Information System (INIS)

    2003-01-01

    The aim of this workshop is to share the needs of high temperature and nuclear fuel materials for future nuclear systems, to take stock of the status of researches in this domain and to propose some cooperation works between the different research organisations. The future nuclear systems are the very high temperature (850 to 1200 deg. C) gas cooled reactors (GCR) and the molten salt reactors (MSR). These systems include not only the reactor but also the fabrication and reprocessing of the spent fuel. This document brings together the transparencies of 13 communications among the 25 given at the workshop: 1) characteristics and needs of future systems: specifications, materials and fuel needs for fast spectrum GCR and very high temperature GCR; 2) high temperature materials out of neutron flux: thermal barriers: materials, resistance, lifetimes; nickel-base metal alloys: status of knowledge, mechanical behaviour, possible applications; corrosion linked with the gas coolant: knowledge and problems to be solved; super-alloys for turbines: alloys for blades and discs; corrosion linked with MSR: knowledge and problems to be solved; 3) materials for reactor core structure: nuclear graphite and carbon; fuel assembly structure materials of the GCR with fast neutron spectrum: status of knowledge and ceramics and cermets needs; silicon carbide as fuel confinement material, study of irradiation induced defects; migration of fission products, I and Cs in SiC; 4) materials for hydrogen production: status of the knowledge and needs for the thermochemical cycle; 5) technologies: GCR components and the associated material needs: compact exchangers, pumps, turbines; MSR components: valves, exchangers, pumps. (J.S.)

  16. Mechanical response of local rapid cooling by spray water on constrained steel frame structure at high temperature in fire

    Directory of Open Access Journals (Sweden)

    Xia Yunchun

    2015-01-01

    Full Text Available Locally rapid cooling of spray water had strong impact on high temperature steel structure. When temperature of beam reached 600°C and cooling rate was more than 20°C/s, the maximum axial tension could reach more than 5 times of the originally compressive force. The compressive bending moment at joint of beam-to-column changed to tensile bending moment, and the maximum bending moment could reach above 4 times as that when heated. After rapid cooling by spray water, deflection at mid-span increased slightly.

  17. Novel technique for coal pyrolysis and hydrogenation product analysis. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    Pfefferle, L.D.; Boyle, J.

    1993-03-15

    A microjet reactor coupled to a VUV photoionization time-of-flight mass spectrometer has been used to obtain species measurements during high temperature pyrolysis and oxidation of a wide range of hydrocarbon compounds ranging from allene and acetylene to cyclohexane, benzene and toluene. Initial work focused on calibration of the technique, optimization of ion collection and detection and characterization of limitations. Using the optimized technique with 118 nm photoionization, intermediate species profiles were obtained for analysis of the hydrocarbon pyrolysis and oxidation mechanisms. The ``soft`` ionization, yielding predominantly molecular ions, allowed the study of reaction pathways in these high temperature systems where both sampling and detection challenges are severe. Work has focused on the pyrolysis and oxidative pyrolysis of aliphatic and aromatic hydrocarbon mixtures representative of coal pyrolysis and hydropyrolysis products. The detailed mass spectra obtained during pyrolysis and oxidation of hydrocarbon mixtures is especially important because of the complex nature of the product mixture even at short residence times and low primary reactant conversions. The combustion community has advanced detailed modeling of pyrolysis and oxidation to the C4 hydrocarbon level but in general above that size uncertainties in rate constant and thermodynamic data do not allow us to a priori predict products from mixed hydrocarbon pyrolyses using a detailed chemistry model. For pyrolysis of mixtures of coal-derived liquid fractions with a large range of compound structures and molecular weights in the hundreds of amu the modeling challenge is severe. Lumped models are possible from stable product data.

  18. Thermophysical and Mechanical Properties of Granite and Its Effects on Borehole Stability in High Temperature and Three-Dimensional Stress

    Directory of Open Access Journals (Sweden)

    Wang Yu

    2014-01-01

    Full Text Available When exploiting the deep resources, the surrounding rock readily undergoes the hole shrinkage, borehole collapse, and loss of circulation under high temperature and high pressure. A series of experiments were conducted to discuss the compressional wave velocity, triaxial strength, and permeability of granite cored from 3500 meters borehole under high temperature and three-dimensional stress. In light of the coupling of temperature, fluid, and stress, we get the thermo-fluid-solid model and governing equation. ANSYS-APDL was also used to stimulate the temperature influence on elastic modulus, Poisson ratio, uniaxial compressive strength, and permeability. In light of the results, we establish a temperature-fluid-stress model to illustrate the granite’s stability. The compressional wave velocity and elastic modulus, decrease as the temperature rises, while poisson ratio and permeability of granite increase. The threshold pressure and temperature are 15 MPa and 200°C, respectively. The temperature affects the fracture pressure more than the collapse pressure, but both parameters rise with the increase of temperature. The coupling of thermo-fluid-solid, greatly impacting the borehole stability, proves to be a good method to analyze similar problems of other formations.

  19. Correlation between Mechanical Behavior and Actuator-type Performance of Ni-Ti-Pd High-temperature Shape Memory Alloys

    Science.gov (United States)

    Bigelow, Glen S.; Padula, Santo A., II; Garg, Anita; Noebe, Ronald D.

    2007-01-01

    High-temperature shape memory alloys in the NiTiPd system are being investigated as lower cost alternatives to NiTiPt alloys for use in compact solid-state actuators for the aerospace, automotive, and power generation industries. A range of ternary NiTiPd alloys containing 15 to 46 at.% Pd has been processed and actuator mimicking tests (thermal cycling under load) were used to measure transformation temperatures, work behavior, and dimensional stability. With increasing Pd content, the work output of the material decreased, while the amount of permanent strain resulting from each load-biased thermal cycle increased. Monotonic isothermal tension testing of the high-temperature austenite and low temperature martensite phases was used to partially explain these behaviors, where a mismatch in yield strength between the austenite and martensite phases was observed at high Pd levels. Moreover, to further understand the source of the permanent strain at lower Pd levels, strain recovery tests were conducted to determine the onset of plastic deformation in the martensite phase. Consequently, the work behavior and dimensional stability during thermal cycling under load of the various NiTiPd alloys is discussed in relation to the deformation behavior of the materials as revealed by the strain recovery and monotonic tension tests.

  20. Oxidation kinetics and mechanisms of carbon/carbon composites and their components in water vapour at high temperatures

    International Nuclear Information System (INIS)

    Qin, Fei; Peng, Li-na; He, Guo-qiang; Li, Jiang; Yan, Yong

    2015-01-01

    Highlights: • 4D-C/C composite was fabricated using carbon fibre and coal tar pitch. • The rate of mass loss and oxidation kinetics parameters of fibres-H 2 O and matrix-H 2 O are obtained. • The rate of mass loss and oxidation kinetics parameters of C/C–H 2 O are obtained. • Oxidation rate of the fibre bundle is greater than the oxidation rate of the matrix. - Abstract: Thermogravimetric analysis and scanning electron microscopy were used to study the oxidation kinetics of four-direction carbon/carbon composites and their components (fibres and matrices) in a H 2 O–Ar atmosphere at high temperatures. The oxidation processes were restricted to reaction-limited oxidation. The rate of mass loss was estimated for the four-direction carbon/carbon composites and their components at high temperature. The pressure exponent for the reaction of the carbon/carbon composites with H 2 O was 0.59, and the pre-exponential factor and activation energy for the reactions of H 2 O with the carbon/carbon composites, carbon fibres and matrices were determined

  1. Thermophysical and mechanical properties of granite and its effects on borehole stability in high temperature and three-dimensional stress.

    Science.gov (United States)

    Wang, Yu; Liu, Bao-lin; Zhu, Hai-yan; Yan, Chuan-liang; Li, Zhi-jun; Wang, Zhi-qiao

    2014-01-01

    When exploiting the deep resources, the surrounding rock readily undergoes the hole shrinkage, borehole collapse, and loss of circulation under high temperature and high pressure. A series of experiments were conducted to discuss the compressional wave velocity, triaxial strength, and permeability of granite cored from 3500 meters borehole under high temperature and three-dimensional stress. In light of the coupling of temperature, fluid, and stress, we get the thermo-fluid-solid model and governing equation. ANSYS-APDL was also used to stimulate the temperature influence on elastic modulus, Poisson ratio, uniaxial compressive strength, and permeability. In light of the results, we establish a temperature-fluid-stress model to illustrate the granite's stability. The compressional wave velocity and elastic modulus, decrease as the temperature rises, while poisson ratio and permeability of granite increase. The threshold pressure and temperature are 15 MPa and 200 °C, respectively. The temperature affects the fracture pressure more than the collapse pressure, but both parameters rise with the increase of temperature. The coupling of thermo-fluid-solid, greatly impacting the borehole stability, proves to be a good method to analyze similar problems of other formations.

  2. High temperature mechanical behavior of tube stackings – Part I: Microstructural and mechanical characterization of Inconel® 600 constitutive material

    Energy Technology Data Exchange (ETDEWEB)

    Marcadon, V., E-mail: Vincent.Marcadon@onera.fr [Onera – The French Aerospace Lab, F-92322 Châtillon (France); Davoine, C.; Lévêque, D.; Rafray, A.; Popoff, F.; Horezan, N.; Boivin, D. [Onera – The French Aerospace Lab, F-92322 Châtillon (France)

    2016-11-20

    This paper is the first part of a set of two papers dedicated to the mechanical behavior of cellular materials at high temperatures. For that purpose, cellular materials made of brazed tube stacking cores have been considered here. This paper addresses the characterization of the elasto-viscoplastic properties of the constitutive material of the tubes, Inconel®600, by means of tensile tests. Various temperatures and strain rates were investigated, from room temperature to 800 °C, in order to study the influence of both the brazing heat treatment and the test temperature on the mechanical properties of Inconel®600. Whereas the heat treatment drastically decreases the strength of the tubes, a significant viscous effect is revealed at 800 °C. Electron backscattered diffraction analyses carried out post-mortem on samples showed that both dynamic recrystallization and recovery occurred during tensile tests performed at 800 °C, especially at lower strain rates. In contrast, a highly deformed and textured microstructure was observed for the tubes loaded at lower temperatures.

  3. Effect of cold deformation on latent energy value and high-temperature mechanical properties of 12Cr18Ni10Ti steel

    International Nuclear Information System (INIS)

    Maksimkin, O.P.; Shiganakov, Sh.B.; Gusev, M.N.

    1997-01-01

    Energetic and magnetic characteristics and also the high-temperature mechanical properties depending on the preliminary cold deformation of 12Cr18Ni10Ti steel are presented. It is shown that the value of storage energy in the steel has being grown with increase of the deformation. The rate of its growth has been increased after beginning of martensitic γ→α'- transformation when value of comparative storage energy at first decreased and then has been stay practically constant. Level of mechanical properties of the steel at 1073 K has been determined not only by value of cold deformation but and structural reconstruction corresponding to deformations 35-45% and accompanying with α'-phase martensite formation and change of energy accumulating rate. Preliminary cold deformation (40-60 %) does not improve high- temperature plasticity of steel samples implanted by helium. refs. 7, figs. 2

  4. Mechanical strength and thermophysical properties of PM212: A high temperature self-lubricating powder metallurgy composite

    Science.gov (United States)

    Edwards, Phillip M.; Sliney, Harold E.; Dellacorte, Christopher; Whittenberger, J. Daniel; Martineau, Robert R.

    1990-01-01

    A powder metallurgy composite, PM212, composed of metal bonded chromium carbide and solid lubricants is shown to be self-lubricating to a maximum application temperature of 900 C. The high temperature compressive strength, tensile strength, thermal expansion and thermal conductivity data needed to design PM212 sliding contact bearings and seals are reported for sintered and isostatically pressed (HIPed) versions of PM212. Other properties presented are room temperature density, hardness, and elastic modulus. In general, both versions appear to have adequate strength to be considered as sliding contact bearing materials, but the HIPed version, which is fully dense, is much stronger than the sintered version which contains about 20 percent pore volume. The sintered material is less costly to make, but the HIPed version is better where high compressive strength is important.

  5. Effects of high temperature neutron irradiation on the physical, chemical and mechanical properties of fine-grained isotropic graphite

    International Nuclear Information System (INIS)

    Matsuo, H.; Nomura, S.; Imai, H.; Oku, T.; Eto, M.

    1987-01-01

    Effects of neutron irradiation on the dimensional change, coefficient of thermal expansion(CTE), thermal conductivity, corrosion rate, Young's modulus and strengths were studied for the candidate graphite material IG-110 of the experimental very high temperature gas-cooled reactor(VHTR) after irradiation at 585 - 1273 deg C to neutron fluences of up to about 3 x 10 25 n/m 2 (E > 29 fJ) in the JMTR and JRR-2, and to about 7 x 10 25 n/m 2 (E > 29 fJ) in the HFR. The results were compared with the irradiation behaviors of other graphites. Dimensional shrinkage was observed in the whole irradiation temperature range, showing lower value than 2 %. The shrinkage rate showed the minimum in the irradiation temperature of around 850 deg C, followed by the increase for the samples irradiated at higher temperatures. The dimensional stability of the material was clarified to be almost the same with that of H451 graphite. The CTE, thermal resistivity and Young's modulus increased in the early stage of irradiation and then only the CTE decreased while the thermal resistivity and Young's modulus levelled off with further irradiation. The neutron fluence showing the maximum CTE shifted to the lower fluence with increasing irradiation temperature. The increases of both thermal resistivity and Young's modulus were remarkable for the samples irradiated at lower temperatures. Compressive and bending strengths measured at room temperature increased after irradiation as well. The corrosion rate with water-vapor of 0.65 % in helium at high temperatures decreased owing to irradiation and the reduction was independent of irradiation temperature and neutron fluence. The activation energy for the reaction was estimated to be the same before and after irradiation. (author)

  6. Supersymmetry at high temperatures

    International Nuclear Information System (INIS)

    Das, A.; Kaku, M.

    1978-01-01

    We investigate the properties of Green's functions in a spontaneously broken supersymmetric model at high temperatures. We show that, even at high temperatures, we do not get restoration of supersymmetry, at least in the one-loop approximation

  7. High-temperature oxidation behavior of dense SiBCN monoliths: Carbon-content dependent oxidation structure, kinetics and mechanisms

    International Nuclear Information System (INIS)

    Li, Daxin; Yang, Zhihua; Jia, Dechang; Wang, Shengjin; Duan, Xiaoming; Zhu, Qishuai; Miao, Yang; Rao, Jiancun; Zhou, Yu

    2017-01-01

    Highlights: •The scale growth for all investigated monoliths at 1500 °C cannot be depicted by a linear or parabolic rate law. •The carbon-rich monoliths oxidize at 1500 °C according to a approximately linear weight loss equation. •The excessive carbon in SiBCN monoliths deteriorates the oxidation resistance. •The oxidation resistance stems from the characteristic oxide structures and increased oxidation resistance of BN(C). -- Abstract: The high temperature oxidation behavior of three SiBCN monoliths: carbon-lean SiBCN with substantial Si metal, carbon-moderate SiBCN and carbon-rich SiBCN with excessive carbon, was investigated at 1500 °C for times up to15 h. Scale growth for carbon-lean and −moderate monoliths at 1500 °C cannot be described by a linear or parabolic rate law, while the carbon-rich monoliths oxidize according to a approximately linear weight loss equation. The microstructures of the oxide scale compose of three distinct layers. The passivating layer of carbon and boron containing amorphous SiO 2 and increased oxidation resistance of BN(C) both benefit the oxidation resistance.

  8. Strength and rupture-life transitions caused by secondary carbide precipitation in HT-9 during high-temperature low-rate mechanical testing

    International Nuclear Information System (INIS)

    DiMelfi, R.J.; Gruber, E.E.; Kramer, J.M.; Hughes, T.H.

    1992-01-01

    The martensitic-ferritic alloy HT-9 is slated for long-term use as a fuel-cladding material in the Integral Fast Reactor. Analysis of published high-temperature mechanical property data suggests that secondary carbide precipitation would occur during service life causing substantial strengthening of the as-heat-treated material. Aspects of the kinetics of this precipitation process are extracted from calculations of the back stress necessary to produce the observed strengthening effect under various creep loading conditions. The resulting Arrhenius factor is shown to agree quantitatively with shifts to higher strength of crept material in reference to the intrinsic strength of HT-9. The results of very low constant strain-rate high-temperature tensile tests on as-heat-treated HT-9 that focus on the transition in strength with precipitation will be presented and related to rupture-life

  9. Implementation of constitutive equations for creep damage mechanics into the ABAQUS finite element code - some practical cases in high temperature component design and life assessment

    International Nuclear Information System (INIS)

    Segle, P.; Samuelson, L.Aa.; Andersson, Peder; Moberg, F.

    1996-01-01

    Constitutive equations for creep damage mechanics are implemented into the finite element program ABAQUS using a user supplied subroutine, UMAT. A modified Kachanov-Rabotnov constitutive equation which accounts for inhomogeneity in creep damage is used. With a user defined material a number of bench mark tests are analyzed for verification. In the cases where analytical solutions exist, the numerical results agree very well. In other cases, the creep damage evolution response appear to be realistic in comparison with laboratory creep tests. The appropriateness of using the creep damage mechanics concept in design and life assessment of high temperature components is demonstrated. 18 refs

  10. Chapter 8: Pyrolysis Mechanisms of Lignin Model Compounds Using a Heated Micro-Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Robichaud, David J.; Nimlos, Mark R.; Ellison, G. Barney

    2015-10-03

    Lignin is an important component of biomass, and the decomposition of its thermal deconstruction products is important in pyrolysis and gasification. In this chapter, we investigate the unimolecular pyrolysis chemistry through the use of singly and doubly substituted benzene molecules that are model compounds representative of lignin and its primary pyrolysis products. These model compounds are decomposed in a heated micro-reactor, and the products, including radicals and unstable intermediates, are measured using photoionization mass spectrometry and matrix isolation infrared spectroscopy. We show that the unimolecular chemistry can yield insight into the initial decomposition of these species. At pyrolysis and gasification severities, singly substituted benzenes typically undergo bond scission and elimination reactions to form radicals. Some require radical-driven chain reactions. For doubly substituted benzenes, proximity effects of the substituents can change the reaction pathways.

  11. Stress corrosion cracking of alloy 600 in water at high temperature: contribution to a phenomenological approach to the understanding of mechanisms

    International Nuclear Information System (INIS)

    Abadie, Pascale

    1998-01-01

    This research thesis aims at being a contribution to the understanding of mechanisms of stress corrosion cracking of an alloy 600 in water at high temperature. More precisely, it aimed at determining, by using quantitative data characterizing cracking phenomenology, which mechanism(s) is (are) able to explain crack initiation and crack growth. These data concern quantitative characterization of crack initiation, of crack growth and of the influence of two cracking parameters (strain rate, medium hydrogen content). They have been obtained by quantifying cracking through the application of a morphological model. More precisely, these data are: evolution of crack density during a tensile test at slow rate, value of initial crack width with respect to grain boundary length, and relationship between crack density and medium hydrogen content. It appears that hydrogen absorption seems to be involved in the crack initiation mechanism. Crack growth mechanisms and crack growth rates are also discussed [fr

  12. Effect of C particle size on the mechanism of self-propagation high-temperature synthesis in the Ni-Ti-C system

    International Nuclear Information System (INIS)

    Yang, Y.F.; Wang, H.Y.; Wang, J.G.; Jiang, Q.C.

    2011-01-01

    Highlights: → We investigated the effect of C particle size on the self-propagating high temperature reaction mechanism. → Coarse C particle size (>38 μm) resulted in the formation of prior TiC x layer between Ti and C. → Prior TiC x layer control the whole reaction of Ni-Ti-C and domain the reaction kinetics. → The selection of C particle size is the most important factor to fabricate TiC/Ni composite using Ti, C and Ni mixtures. - Abstract: Effect of C particle size on the mechanism of self-propagation high-temperature synthesis (SHS) in the Ni-Ti-C system was investigated. Fine C particle resulted in a traditional mechanism of dissolution-precipitation while coarse C particle made the reaction be controlled by a mechanism of the diffusion of C through the TiC x layer. The whole process can be described: C atoms diffusing through the TiC x layer dissolved into the Ni-Ti liquid and TiC were formed once the liquid became supersaturated. Simultaneously, the heat generated from the TiC formation made the unstable TiC x layer break up. However, with the spread of Ti-Ni liquid, a new TiC x layer was formed again at the interface between spreading liquid and C particle. This process cannot stop until all the C particles are consumed completely.

  13. Fundamental Processes of Coupled Radiation Damage and Mechanical Behavior in Nuclear Fuel Materials for High Temperature Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Phillpot, Simon; Tulenko, James

    2011-09-08

    The objective of this work has been to elucidate the relationship among microstructure, radiation damage and mechanical properties for nuclear fuel materials. As representative nuclear materials, we have taken an hcp metal (Mg as a generic metal, and Ti alloys for fast reactors) and UO2 (representing fuel). The degradation of the thermo-mechanical behavior of nuclear fuels under irradiation, both the fissionable material itself and its cladding, is a longstanding issue of critical importance to the nuclear industry. There are experimental indications that nanocrystalline metals and ceramics may be more resistant to radiation damage than their coarse-grained counterparts. The objective of this project look at the effect of microstructure on radiation damage and mechanical behavior in these materials. The approach to be taken was state-of-the-art, large-scale atomic-level simulation. This systematic simulation program of the effects of irradiation on the structure and mechanical properties of polycrystalline Ti and UO2 identified radiation damage mechanisms. Moreover, it will provided important insights into behavior that can be expected in nanocrystalline microstructures and, by extension, nanocomposites. The fundamental insights from this work can be expected to help in the design microstructures that are less susceptible to radiation damage and thermomechanical degradation.

  14. Fundamental Processes of Coupled Radiation Damage and Mechanical Behavior in Nuclear Fuel Materials for High Temperature Reactors

    International Nuclear Information System (INIS)

    Phillpot, Simon; Tulenko, James

    2011-01-01

    The objective of this work has been to elucidate the relationship among microstructure, radiation damage and mechanical properties for nuclear fuel materials. As representative nuclear materials, we have taken an hcp metal (Mg as a generic metal, and Ti alloys for fast reactors) and UO2 (representing fuel). The degradation of the thermo-mechanical behavior of nuclear fuels under irradiation, both the fissionable material itself and its cladding, is a longstanding issue of critical importance to the nuclear industry. There are experimental indications that nanocrystalline metals and ceramics may be more resistant to radiation damage than their coarse-grained counterparts. The objective of this project look at the effect of microstructure on radiation damage and mechanical behavior in these materials. The approach to be taken was state-of-the-art, large-scale atomic-level simulation. This systematic simulation program of the effects of irradiation on the structure and mechanical properties of polycrystalline Ti and UO2 identified radiation damage mechanisms. Moreover, it will provided important insights into behavior that can be expected in nanocrystalline microstructures and, by extension, nanocomposites. The fundamental insights from this work can be expected to help in the design microstructures that are less susceptible to radiation damage and thermomechanical degradation.

  15. Multi-scale modelling of the physicochemical-mechanical coupling of fuel behaviour at high temperature in pressurized water reactors

    International Nuclear Information System (INIS)

    Julien, Jerome

    2008-01-01

    Within the frame of the problematic of pellet-sheath interaction in a nuclear fuel rod, a good description of the fuel thermo-mechanical behaviour is required. This research thesis reports the coupling of physics-chemistry (simulation of gas transfers between different cavities) and mechanics (assessment of fuel viscoplastic strains). A new micromechanical model is developed which uses a multi-scale approach to describe the evolution of the double population of cavities (cavities with two different scales) while taking internal pressures as well as the fuel macroscopic viscoplastic behaviour into account. The author finally describes how to couple this micromechanical mode to physics-chemistry models [fr

  16. Development of ball bearing in high temperature water for in-vessel type control rod drive mechanism of advanced marine reactor

    Energy Technology Data Exchange (ETDEWEB)

    Nunokawa, Hiroshi [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan); Yoritsune, Tsutomu; Imayoshi, Shou; Ochiai, Masa-aki; Ishida, Toshihisa [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Kasahara, Yoshiyuki [Advanced Reactor Technology Co., Ltd., Tokyo (Japan)

    2001-06-01

    An advanced marine reactor MRX designed by Japan Atomic Energy Research Institute (JAERI) adopts an in-vessel type control rod drive mechanism, which is installed inside the reactor vessel. Since the in-vessel type control rod drive mechanism should work at a severe condition of a high temperature and high pressure water - 310degC and 12 MPa -, the JAERI has developed the components, a ball bearing of which especially is one of key technologies for realization of this type mechanism. The present report describes the development of the ball bearing containing a survey of materials, material screening tests on oxidation in an autoclave and rolling wear by a small facility, a trial fabrication of the full size ball bearing, and endurance test of it in the high temperature water. As a result, it was found from the development that the materials of cobalt alloy for both of the inner and outer races, cermet for the ball, and graphite for the retainer can satisfy the design condition of the ball bearing. (author)

  17. Natural Catalysts for Molten Cellulose Pyrolysis to Targeted Bio-Oils

    Energy Technology Data Exchange (ETDEWEB)

    Dauenhauer, Paul J. [Univ. of Minnesota, Minneapolis, MN (United States)

    2017-06-02

    Catalysis of biomass biopolymer cellulose by alkaline earth metals is a fundamental chemistry relevant to energy processes including combustion, pyrolysis and gasification. In this work, the catalytic decomposition of cellulose by calcium ions was evaluated at high temperature (400-500°C) to elucidate the chemical mechanisms leading to the formation of volatile organic compounds.

  18. Physical and Mechanical Properties of Composites Made with Aluminous Cement and Basalt Fibers Developed for High Temperature Application

    Directory of Open Access Journals (Sweden)

    Pavel Reiterman

    2015-01-01

    Full Text Available Present paper deals with the experimental study of the composition of refractory fiber-reinforced aluminous cement based composites and its response to gradual thermal loading. Basalt fibers were applied in doses of 0.25, 0.5, 1.0, 2.0, and 4.0% in volume. Simultaneously, binder system based on the aluminous cement was modified by fine ground ceramic powder originated from the accurate ceramic blocks production. Ceramic powder was dosed as partial replacement of used cement of 5, 10, 15, 20, and 25%. Influence of composition changes was evaluated by the results of physical and mechanical testing; compressive strength, flexural strength, bulk density, and fracture energy were determined on the different levels of temperature loading. Increased dose of basalt fibers allows reaching expected higher values of fracture energy, but with respect to results of compressive and flexural strength determination as an optimal rate of basalt fibers dose was considered 0.25% in volume. Fine ground ceramic powder application led to extensive increase of residual mechanical parameters just up to replacement of 10%. Higher replacement of aluminous cement reduced final values of bulk density but kept mechanical properties on the level of mixtures without aluminous cement replacement.

  19. High temperature mechanisms and kinetics of SiC oxidation under low partial pressures of oxygen: application to the fuel cladding of gas fast reactors

    International Nuclear Information System (INIS)

    Hun, N.

    2011-01-01

    Gas Fast Reactor (GFR) is one of the different Generation IV concepts under investigation for energy production. SiC/SiC composites are candidates of primary interest for a GFR fuel cladding use, thanks to good corrosion resistance among other properties. The mechanisms and kinetics of SiC oxidation under operating conditions have to be identified and quantified as the corrosion can decrease the mechanical properties of the composite. An experimental device has been developed to study the oxidation of silicon carbide under high temperature and low oxygen partial pressure. The results pointed out that not only parabolic oxidation, but also interfacial reactions and volatilization occur under such conditions. After determining the kinetics of each mechanism, as functions of oxygen partial pressure and temperature, the data are used for the modeling of the composites oxidation. The model will be used to predict the lifetime of the composite in operating conditions. (author) [fr

  20. RCC-MRx: Design and construction rules for mechanical components in high-temperature structures, experimental reactors and fusion reactors

    International Nuclear Information System (INIS)

    2015-01-01

    The RCC-MRx code was developed for sodium-cooled fast reactors (SFR), research reactors (RR) and fusion reactors (FR-ITER). It provides the rules for designing and building mechanical components involved in areas subject to significant creep and/or significant irradiation. In particular, it incorporates an extensive range of materials (aluminum and zirconium alloys in response to the need for transparency to neutrons), sizing rules for thin shells and box structures, and new modern welding processes: electron beam, laser beam, diffusion and brazing. The RCC-MR code was used to design and build the prototype Fast Breeder Reactor (PFBR) developed by IGCAR in India and the ITER Vacuum Vessel. The RCC-Mx code is being used in the current construction of the RJH experimental reactor (Jules Horowitz reactor). The RCC-MRx code is serving as a reference for the design of the ASTRID project (Advanced Sodium Technological Reactor for Industrial Demonstration), for the design of the primary circuit in MYRRHA (Multi-purpose hybrid Research Reactor for High-tech Applications) and the design of the target station of the ESS project (European Spallation Source). Contents of the 2015 edition of the RCC-MRx code: Section I General provisions; Section II Additional requirements and special provisions; Section III Rules for nuclear installation mechanical components: Volume I: Design and construction rules: Volume A (RA): General provisions and entrance keys, Volume B (RB): Class 1 components and supports, Volume C (RC): Class 2 components and supports, Volume D (RD): Class 3 components and supports, Volume K (RK): Examination, handling or drive mechanisms, Volume L (RL): Irradiation devices, Volume Z (Ai): Technical appendices; Volume II: Materials; Volume III: Examinations methods; Volume IV: Welding; Volume V: Manufacturing operations; Volume VI: Probationary phase rules

  1. Microstructure evolution and its influence on deformation mechanisms during high temperature creep of a nickel base superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Safari, Javad [Materials Science and Engineering Department, Shahid Chamran University, Ahwaz (Iran, Islamic Republic of)], E-mail: javadsafari@yahoo.com; Nategh, Saeed [Materials Science and Engineering Department, Sharif University of Technology, P.O. Box 11365-9466, Tehran (Iran, Islamic Republic of)], E-mail: nategh@sharif.edu

    2009-01-15

    The interaction of dislocation with strengthening particles, including primary and secondary {gamma}', during different stages of creep of Rene-80 was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). During creep of the alloy at 871 deg. C under stress of 290 MPa, the dislocation network was formed during the early stages of creep, and the dislocation glide and climb process were the predominant mechanism of deformation. The density of dislocation network became more populated during the later stages of the creep, and at the latest stage of the creep, primary particles shearing were observed alongside with the dislocation glide and climb. Shearing of {gamma}' particles in creep at 871 deg. C under stress of 475 MPa was commenced at the earlier creep times and governed the creep deformation mechanism. In two levels of examined stresses, as far as the creep deformation was controlled by glide and climb, creep curves were found to be at the second stage of creep and commence of the tertiary creep, with increasing creep rate, were found to be in coincidence with the particles shearing. Microstructure evolution, with regard to {gamma}' strengthening particles, led to particles growth and promoted activation of other deformation mechanisms such as dislocation bypassing by orowan loop formation. Dislocation-secondary {gamma}' particles interaction was detected to be the glide and climb at the early stages of creep, while at the later stages, the dislocation bypassed the secondary precipitation by means of orowan loops formation, as the secondary particle were grown and the mean inter-particle distance increased.

  2. Generalized corrosion of nickel base alloys in high temperature aqueous media: a contribution to the comprehension of the mechanisms

    International Nuclear Information System (INIS)

    Marchetti-Sillans, L.

    2007-11-01

    In France, nickel base alloys, such as alloy 600 and alloy 690, are the materials constituting steam generators (SG) tubes of pressurized water reactors (PWR). The generalized corrosion resulting from the interaction between these alloys and the PWR primary media leads, on the one hand, to the formation of a thin protective oxide scale (∼ 10 nm), and on the other hand, to the release of cations in the primary circuit, which entails an increase of the global radioactivity of this circuit. The goal of this work is to supply some new comprehension elements about nickel base alloys corrosion phenomena in PWR primary media, taking up with underlining the effects of metallurgical and physico-chemical parameters on the nature and the growth mechanisms of the protective oxide scale. In this context, the passive film formed during the exposition of alloys 600, 690 and Ni-30Cr, in conditions simulating the PWR primary media, has been analyzed by a set of characterization techniques (SEM, TEM, PEC and MPEC, XPS). The coupling of these methods leads to a fine description, in terms of nature and structure, of the multilayered oxide forming during the exposition of nickel base alloys in primary media. Thus, the protective part of the oxide scale is composed of a continuous layer of iron and nickel mixed chromite, and Cr 2 O 3 nodules dispersed at the alloy / mixed chromite interface. The study of protective scale growth mechanisms by tracers and markers experiments reveals that the formation of the mixed chromite is the consequence of an anionic mechanism, resulting from short circuits like grain boundaries diffusion. Besides, the impact of alloy surface defects has also been studied, underlining a double effect of this parameter, which influences the short circuits diffusion density in oxide and the formation rate of Cr 2 O 3 nodules. The sum of these results leads to suggest a description of the nickel base alloys corrosion mechanisms in PWR primary media and to tackle some

  3. 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...

  4. Failure Mechanisms and Color Stability in Light-Emitting Diodes during Operation in High- Temperature Environments in Presence of Contamination

    Energy Technology Data Exchange (ETDEWEB)

    Lall, Pradeep; Zhang, Hao; Davis, J Lynn

    2015-05-26

    The energy efficiency of light-emitting diode (LED) technology compared to incandescent light bulbs has triggered an increased focus on solid state luminaries for a variety of lighting applications. Solid-state lighting (SSL) utilizes LEDs, for illumination through the process of electroluminescence instead of heating a wire filament as seen with traditional lighting. The fundamental differences in the construction of LED and the incandescent lamp results in different failure modes including lumen degradation, chromaticity shift and drift in the correlated color temperature. The use of LED-based products for safety-critical and harsh environment applications necessitates the characterization of the failure mechanisms and modes. In this paper, failure mechanisms and color stability has been studied for commercially available vertical structured thin film LED (VLED) under harsh environment conditions with and without the presence of contaminants. The VLED used for the study was mounted on a ceramic starboard in order to connect it to the current source. Contamination sources studied include operation in the vicinity of vulcanized rubber and adhesive epoxies in the presence of temperature and humidity. Performance of the VLEDs has been quantified using the measured luminous flux and color shift of the VLEDs subjected to both thermal and humidity stresses under a forward current bias of 350 mA. Results indicate that contamination can result in pre-mature luminous flux degradation and color shift in LEDs.

  5. Experimental and numerical study of the high temperature mechanical behaviour of the MoTiC cermets

    International Nuclear Information System (INIS)

    Cedat, Denis

    2006-01-01

    In this work, in order to study the mechanical behaviour of Mo-TiC cermets, compression tests have been carried out on different compositions as well as on different temperatures on the composition (MoTiC 25at% ) which will be extruded. The main results show that: 1)the increase of the (TiC) ceramic rate in the cermet increases the rupture stress but decreases the rupture resistance of this material. Moreover, a transition of behaviour seems to be observed for a critical TiC rate (MoTiC 25at% ), this transition seems to be due to the percolation of the ceramic particles. 2)the behaviour of the MoTiC 25at% cermet is brittle at ambient temperature and begins to have a plastic deformation at 300 C. Thus, the rupture stress decreases proportionally to the increase of the temperature whereas the rupture deformation increases. (O.M.)

  6. Effect of a high temperature cycle on the mechanical properties of silicon carbide/titanium metal matrix composites

    Science.gov (United States)

    Naik, R. A.; Johnson, W. S.; Pollock, W. D.

    1989-01-01

    An investigation is conducted of the effects of the SPF/DB cycle on continuous SiC fiber-reinforced Ti-15V-3Cr-3Al-3Sn composite's matrix, fiber, and matrix-fiber interface. The fibers in question, designated SCS-6, have a carbon core and thin, carbon-rich surface. The fatigue endurance limit at 50,000 cycles for the SPF/DB specimens was 50 percent lower than for the as-fabricated material. The substantial changes in tensile strength, fatigue life, and fracture-surface appearance due to the SPF-DB cycle are explained by a difference in the failure mechanisms due to SPF/DB-induced changes in the fiber/matrix interface strength.

  7. Synthesis of TiC/Ni cermets via mechanically activated self-propagating high-temperature synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Dubois, S.; Heian, E.; Karnatak, N.; Beaufort, M.F. [Lab. de Metallurgie Physique, Futuroscope (France); Vrel, D. [Lab. d' Ingenierie des Materiaux et des Hautes Pressions, Villetaneuse (France)

    2003-07-01

    Stoichiometric mixtures of Ti and C were milled in a high-energy vibratory mill for varying times and the results carefully characterized via X-ray diffraction and TEM. Cermets of stoichiometric TiC and 20 w% Ni were combustion synthesized from non-milled and milled reactant powders, resulting in porous solids composed of roughly spherical TiC particles surrounded by a layer of Ni. Time resolved infrared analysis shows that the kinetics of the reaction performed with milled reactant powders are drastically enhanced over non-milled reactants. This result may be attributed to the microstructure and uniformity of the milled reactant mixtures. It is also demonstrated that mechanical milling of Ti and C powders strongly affects the TiC grain size in the products, most likely due to a reduction in TiC crystal growth as a consequence of the increase in the reaction kinetics. (orig.)

  8. Oxygen-induced intergranular fracture of the nickel-base alloy IN718 during mechanical loading at high temperatures

    Directory of Open Access Journals (Sweden)

    Krupp Ulrich

    2004-01-01

    Full Text Available There is a transition in the mechanical-failure behavior of nickel-base superalloys from ductile transgranular crack propagation to time-dependent intergranular fracture when the temperature exceeds about 600 °C. This transition is due to oxygen diffusion into the stress field ahead of the crack tip sufficient to cause brittle decohesion of the grain boundaries. Since very high cracking rates were observed during fixed-displacement loading of IN718, it is not very likely that grain boundary oxidation governs the grain-boundary-separation process, as has been proposed in several studies on the fatigue-damage behavior of the nickel-base superalloy IN718. Further studies on bicrystal and thermomechanically processed specimens of IN718 have shown that this kind of brittle fracture, which has been termed "dynamic embrittlement", depends strongly on the structure of the grain boundaries.

  9. Friction Stir Welding of Low-Carbon AISI 1006 Steel: Room and High-Temperature Mechanical Properties

    Science.gov (United States)

    Shunmugasamy, Vasanth C.; Mansoor, Bilal; Ayoub, Georges; Hamade, Ramsey

    2018-03-01

    Friction stir welding (FSW) is an ecologically benign solid-state joining process. In this work, FSW of low-carbon AISI 1006 steel was carried out to study the microstructure and mechanical properties of the resulting joints at both room temperature (RT) and 200 °C. In the parameter space investigated here, a rotational tool speed and translation feed combination of 1200 rpm and 60 mm/min produced a defect-free weld with balanced mechanical properties and a superior Vickers microhardness profile compared to all other conditions and to base metal (BM). At faster translation feeds (100 and 150 mm/min), wormhole defects were observed in the weld microstructure and were attributed to higher strain rate experienced by the weld zone. Under tensile loading, welded material exhibited yield strength that was up to 86 and 91% of the BM at RT and 200 °C, respectively. On the other hand, tensile strength of welded material was nearly similar to that of the base metal at both RT and 200 °C. However, at both temperatures the tensile ductility of the welded joints was observed to be significantly lower than the BM. Annealing of the 1200 rpm and 60 mm/min FSW specimen resulted in tensile strength of 102% compared to base material and 47% increase in the strain at failure compared to the as-welded specimen. The Charpy impact values revealed up to 62 and 53% increase in the specific impact energy for the 1200 rpm and 60 mm/min welded joints as compared with the BM.

  10. Influence of radiative heat and mass transfer mechanism in system “water droplet-high-temperature gases” on integral characteristics of liquid evaporation

    Directory of Open Access Journals (Sweden)

    Glushkov Dmitrii O.

    2015-01-01

    Full Text Available Physical and mathematical (system of differential equations in private derivatives models of heat and mass transfer were developed to investigate the evaporation processes of water droplets and emulsions on its base moving in high-temperature (more than 1000 K gas flow. The model takes into account a conductive and radiative heat transfer in water droplet and also a convective, conductive and radiative heat exchange with high-temperature gas area. Water vapors characteristic temperature and concentration in small wall-adjacent area and trace of the droplet, numerical values of evaporation velocities at different surface temperature, the characteristic time of complete droplet evaporation were determined. Experiments for confidence estimation of calculated integral characteristics of processes under investigation - mass liquid evaporation velocities were conducted with use of cross-correlation recording video equipment. Their satisfactory fit (deviations of experimental and theoretical velocities were less than 15% was obtained. The influence of radiative heat and mass transfer mechanism on characteristics of endothermal phase transformations in a wide temperature variation range was established by comparison of obtained results of numerical simulation with known theoretical data for “diffusion” mechanisms of water droplets and other liquids evaporation in gas.

  11. Rates and Mechanisms of Oil Shale Pyrolysis: A Chemical Structure Approach

    Energy Technology Data Exchange (ETDEWEB)

    Fletcher, Thomas; Pugmire, Ronald

    2015-01-01

    Three pristine Utah Green River oil shale samples were obtained and used for analysis by the combined research groups at the University of Utah and Brigham Young University. Oil shale samples were first demineralized and the separated kerogen and extracted bitumen samples were then studied by a host of techniques including high resolution liquid-state carbon-13 NMR, solid-state magic angle sample spinning 13C NMR, GC/MS, FTIR, and pyrolysis. Bitumen was extracted from the shale using methanol/dichloromethane and analyzed using high resolution 13C NMR liquid state spectroscopy, showing carbon aromaticities of 7 to 11%. The three parent shales and the demineralized kerogens were each analyzed with solid-state 13C NMR spectroscopy. Carbon aromaticity of the kerogen was 23-24%, with 10-12 aromatic carbons per cluster. Crushed samples of Green River oil shale and its kerogen extract were pyrolyzed at heating rates from 1 to 10 K/min at pressures of 1 and 40 bar and temperatures up to 1000°C. The transient pyrolysis data were fit with a first-order model and a Distributed Activation Energy Model (DAEM). The demineralized kerogen was pyrolyzed at 10 K/min in nitrogen at atmospheric pressure at temperatures up to 525°C, and the pyrolysis products (light gas, tar, and char) were analyzed using 13C NMR, GC/MS, and FTIR. Details of the kerogen pyrolysis have been modeled by a modified version of the chemical percolation devolatilization (CPD) model that has been widely used to model coal combustion/pyrolysis. This refined CPD model has been successful in predicting the char, tar, and gas yields of the three shale samples during pyrolysis. This set of experiments and associated modeling represents the most sophisticated and complete analysis available for a given set of oil shale samples.

  12. High temperature corrosion of metals

    International Nuclear Information System (INIS)

    Quadakkers, W.J.; Schuster, H.; Ennis, P.J.

    1988-08-01

    This paper covers three main topics: 1. high temperature oxidation of metals and alloys, 2. corrosion in sulfur containing environments and 3. structural changes caused by corrosion. The following 21 subjects are discussed: Influence of implanted yttrium and lanthanum on the oxidation behaviour of beta-NiA1; influence of reactive elements on the adherence and protective properties of alumina scales; problems related to the application of very fine markers in studying the mechanism of thin scale formation; oxidation behaviour of chromia forming Co-Cr-Al alloys with or without reactive element additions; growth and properties of chromia-scales on high-temperature alloys; quantification of the depletion zone in high temperature alloys after oxidation in process gas; effects of HC1 and of N2 in the oxidation of Fe-20Cr; investigation under nuclear safety aspects of Zircaloy-4 oxidation kinetics at high temperatures in air; on the sulfide corrosion of metallic materials; high temperature sulfide corrosion of Mn, Nb and Nb-Si alloys; corrosion behaviour or NiCrAl-based alloys in air and air-SO2 gas mixtures; sulfidation of cobalt at high temperatures; preoxidation for sulfidation protection; fireside corrosion and application of additives in electric utility boilers; transport properties of scales with complex defect structures; observations of whiskers and pyramids during high temperature corrosion of iron in SO2; corrosion and creep of alloy 800H under simulated coal gasification conditions; microstructural changes of HK 40 cast alloy caused by exploitation in tubes in steam reformer installation; microstructural changes during exposure in corrosive environments and their effect on mechanical properties; coatings against carburization; mathematical modeling of carbon diffusion and carbide precipitation in Ni-Cr-based alloys. (MM)

  13. Pyrolyzed feather fibers for adsorbent and high temperature applications

    Science.gov (United States)

    Senoz, Erman

    Chicken feather fibers (CFF) are problematic and costly for the poultry industry in terms of managing maintenance and disposal. Considering their great availability, low cost, and unique protein structure, CFF can be an environmentally friendly and bio-renewable candidate to replace petroleum products. CFF's low degradation and melting temperature render them useless at high temperatures. Pyrolysis methods were developed for CFF by using two temperature steps to convert them into high temperature resistant and adsorbent fibers while retaining their original physical appearance and affine dimensions. An intermolecular crosslinking mechanism in the first step of pyrolysis at 215 ºC for 24 h provided an intact fibrous structure with no subsequent melting. The evidence obtained from the thermal, bulk, and surface analysis techniques was indication of the simultaneous side chain degradation, polypeptide backbone scission, disulfide bond cleavage, and isopeptide crosslinking. The variation in the reaction kinetics of disulfide bond cleavage and isopeptide crosslinking played an important role in the melting transition. Consequently, long-lasting heat treatments below the melting point provided sufficient crosslinks in the protein matrix to keep the fibrous structure intact. Water-insoluble and crosslinked CFF reinforced the triglyceride-fatty acid based composites by providing a 15 fold increase in storage and tensile modulus at room temperature. These thermally stable fibers can be used instead of CFF in composites which may require high temperature compounding and molding processes. The second step of pyrolysis at 400--450 ºC for 1 h resulted in microporous fibers with a micropore volume of ˜0.18 cm3/g STP and with a narrower pore size distribution than commercial activated carbons through thermal degradation. Nearly all accessible pores in the microporous pyrolyzed chicken feather fibers (PCFF) had diameters less than 1 nm and therefore, showed a potential to be

  14. High-temperature uncertainty

    International Nuclear Information System (INIS)

    Timusk, T.

    2005-01-01

    Recent experiments reveal that the mechanism responsible for the superconducting properties of cuprate materials is even more mysterious than we thought. Two decades ago, Georg Bednorz and Alex Mueller of IBM's research laboratory in Zurich rocked the world of physics when they discovered a material that lost all resistance to electrical current at the record temperature of 36 K. Until then, superconductivity was thought to be a strictly low-temperature phenomenon that required costly refrigeration. Moreover, the IBM discovery - for which Bednorz and Mueller were awarded the 1987 Nobel Prize for Physics - was made in a ceramic copper-oxide material that nobody expected to be particularly special. Proposed applications for these 'cuprates' abounded. High-temperature superconductivity, particularly if it could be extended to room temperature, offered the promise of levitating trains, ultra-efficient power cables, and even supercomputers based on superconducting quantum interference devices. But these applications have been slow to materialize. Moreover, almost 20 years on, the physics behind this strange state of matter remains a mystery. (U.K.)

  15. Mechanical analysis of ferritic stainless steel applied in radiation tubes in high temperature; Analise mecanica de acos inoxidaveis ferriticos aplicados em tubos de radiacao em altas temperaturas

    Energy Technology Data Exchange (ETDEWEB)

    Moreto, J.A.; Ponte, H.A.; Oliveira, V.L.; Silva, C.A. [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil)

    2008-07-01

    Nowadays Brazilian oil refineries face an important challenge: to adjust their units to the processing of more aggressive crudes. The use of this kind of oil has caused an increase on corrosion on process streams in high temperatures. This study's objective is to evaluate the changes in mechanic properties and phases processing occurred in tubes from de radiation furnaces type A268/446 Tp ferritic stainless steel tubes used in conditions of high temperatures. For comparison samples of the APM/Kanthal alloy tube were examined. Hot tensile tests were performed in the studied materials evidence bodies. The evidence bodies for the hot tensile tests were extracted from the longitudinal position of the tubes and were machined with cylindrical shape with threads. There was a series of trials for each tube (at different traction speeds) at temperature of 600 deg C. With the traction test it was possible to evaluate resistance and ductility characteristics and was used to establish criteria for quality control to ensure satisfactory performance in certain applications. Data testing creep were performed in the evidence bodies taken from the longitudinal position of the tubes in constant charge form. Data testing creep were executed in the constant stress mode at various levels of temperature. Through data testing creep it was possible to predict for how long the material is good for use. Data from testing creep were treated by the method of Larson and Miller. (author)

  16. High temperature corrosion in gasifiers

    Directory of Open Access Journals (Sweden)

    Bakker Wate

    2004-01-01

    Full Text Available Several commercial scale coal gasification combined cycle power plants have been built and successfully operated during the last 5-10 years. Supporting research on materials of construction has been carried out for the last 20 years by EPRI and others. Emphasis was on metallic alloys for heat exchangers and other components in contact with hot corrosive gases at high temperatures. In this paper major high temperature corrosion mechanisms, materials performance in presently operating gasifiers and future research needs will be discussed.

  17. Effect of high hydrogen content on metallurgical and mechanical properties of zirconium alloy claddings after heat-treatment at high temperature

    International Nuclear Information System (INIS)

    Turque, Isabelle

    2016-01-01

    Under hypothetical loss-of-coolant accident conditions, fuel cladding tubes made of zirconium alloys can be exposed to steam at high temperature (HT, up 1200 C) before being cooled and then quenched in water. In some conditions, after burst occurrence the cladding can rapidly absorb a significant amount of hydrogen (secondary hydriding), up to 3000 wt.ppm locally, during steam exposition at HT. The study deals with the effect, poorly studied up to date, of high contents of hydrogen on the metallurgical and mechanical properties of two zirconium alloys, Zircaloy-4 and M5, during and after cooling from high temperatures, at which zirconium is in its β phase. A specific facility was developed to homogeneously charge in hydrogen up to ∼ 3000 wt.ppm cladding tube samples of several centimeters in length. Phase transformations, chemical element partitioning and hydrogen precipitation during cooling from the β temperature domain of zirconium were studied by using several techniques, for the materials containing up to ∼ 3000 wt.ppm of hydrogen in average: in-situ neutron diffraction upon cooling from 700 C, X-ray diffraction, μ-ERDA, EPMA and electron microscopy in particular. The results were compared to thermodynamic predictions. In order to study the effect of high hydrogen contents on the mechanical behavior of the (prior-)μ phase of zirconium, axial tensile tests were performed at various temperatures between 20 and 700 C upon cooling from the β temperature domain, on samples with mean hydrogen contents up to ∼ 3000 wt.ppm. The results show that metallurgical and mechanical properties of the (prior-)β phase of zirconium alloys strongly depend on temperature and hydrogen content. (author) [fr

  18. High temperature battery. Hochtemperaturbatterie

    Energy Technology Data Exchange (ETDEWEB)

    Bulling, M.

    1992-06-04

    To prevent heat losses of a high temperature battery, it is proposed to make the incoming current leads in the area of their penetration through the double-walled insulating housing as thermal throttle, particularly spiral ones.

  19. High temperature refrigerator

    International Nuclear Information System (INIS)

    Steyert, W.A. Jr.

    1978-01-01

    A high temperature magnetic refrigerator is described which uses a Stirling-like cycle in which rotating magnetic working material is heated in zero field and adiabatically magnetized, cooled in high field, then adiabatically demagnetized. During this cycle the working material is in heat exchange with a pumped fluid which absorbs heat from a low temperature heat source and deposits heat in a high temperature reservoir. The magnetic refrigeration cycle operates at an efficiency 70% of Carnot

  20. Mechanical characteristics of heterogeneous structures obtained by high-temperature brazing of corrosion-resistant steels with rapidly quenched non-boron nickel-based alloys

    Science.gov (United States)

    Kalin, B.; Penyaz, M.; Ivannikov, A.; Sevryukov, O.; Bachurina, D.; Fedotov, I.; Voennov, A.; Abramov, E.

    2018-01-01

    Recently, the use rapidly quenched boron-containing nickel filler metals for high temperature brazing corrosion resistance steels different classes is perspective. The use of these alloys leads to the formation of a complex heterogeneous structure in the diffusion zone that contains separations of intermediate phases such as silicides and borides. This structure negatively affects the strength characteristics of the joint, especially under dynamic loads and in corrosive environment. The use of non-boron filler metals based on the Ni-Si-Be system is proposed to eliminate this structure in the brazed seam. Widely used austenitic 12Cr18Ni10Ti and ferrite-martensitic 16Cr12MoSiWNiVNb reactor steels were selected for research and brazing was carried out. The mechanical characteristics of brazed joints were determined using uniaxial tensile and impact toughness tests, and fractography was investigated by electron microscopy.

  1. The effect of heat treatment on the micro-structure and the mechanical properties of high-temperature nickel-base-superalloys

    International Nuclear Information System (INIS)

    Schubert, R.; Horn, E.

    1974-01-01

    General review of heat treatment applied to high-temperature nickel-base-superalloys as a function of the volume percent of the γ'-phase. Heat treatment schedule. γ'-morphology and γ'-distribution as well as their effect on mechanical properties. Values obtained from tensile tests up to 1,000 0 C. Results obtained from creep tests. Limitation for the heat treatment of alloys having an unstable γ'-phase. Alloys X 5 NiCrTi 26 15, ATS 270 (approximately INCO 718), NiCr 20 TiAl, NiCr 20 Co 18 Ti, ATS 342 (approximately Waspaloy), ATS 354 (approximately Udimet 520), NiCo 20 Cr 15 MoAlTi, ATS 382 (approximately Udimet 710), ATS 381-G (approximately Mar M 246), FIS 145 and ATS 391-G (aproximately IN 100). (orig.) [de

  2. Development of the novel ferrous-based stainless steel for biomedical applications, part I: high-temperature microstructure, mechanical properties and damping behavior.

    Science.gov (United States)

    Wu, Ching-Zong; Chen, Shih-Chung; Shih, Yung-Hsun; Hung, Jing-Ming; Lin, Chia-Cheng; Lin, Li-Hsiang; Ou, Keng-Liang

    2011-10-01

    This research investigated the high-temperature microstructure, mechanical properties, and damping behavior of Fe-9 Al-30 Mn-1C-5 Co (wt.%) alloy by means of electron microscopy, experimental model analysis, and hardness and tensile testing. Subsequent microstructural transformation occurred when the alloy under consideration was subjected to heat treatment in the temperature range of 1000-1150 °C: γ → (γ+κ). The κ-phase carbides had an ordered L'1(2)-type structure with lattice parameter a = 0.385 nm. The maximum yield strength (σ(y)), hardness, elongation, and damping coefficient of this alloy are 645 MPa, Hv 292, ~54%, and 178.5 × 10(-4), respectively. These features could be useful in further understanding the relationship between the biocompatibility and the wear and corrosion resistance of the alloy, so as to allow the development of a promising biomedical material. Copyright © 2011 Elsevier Ltd. All rights reserved.

  3. Ceramics for high temperature applications

    International Nuclear Information System (INIS)

    Mocellin, A.

    1977-01-01

    Problems related to materials, their fabrication, properties, handling, improvements are examined. Silicium nitride and silicium carbide are obtained by vacuum hot-pressing, reaction sintering and chemical vapour deposition. Micrographs are shown. Mechanical properties i.e. room and high temperature strength, creep resistance fracture mechanics and fatigue resistance. Recent developments of pressureless sintered Si C and the Si-Al-O-N quaternary system are mentioned

  4. Effects of electron beam irradiation on mechanical properties at low and high temperature of fiber reinforced composites using PEEK as matrix material

    International Nuclear Information System (INIS)

    Sasuga, Tsuneo; Seguchi, Tadao; Sakai, Hideo; Odajima, Toshikazu; Nakakura, Toshiyuki; Masutani, Masahiro.

    1987-11-01

    Carbon fiber reinforced composite (PEEK-CF) using polyarylether-ether-ketone (PEEK) as a matrix material was prepared and the electron beam radiation effects on the mechanical properties at low and high temperature and the effects of annealing after irradiation were studied. Cooling down to 77 K, the flexural strength of PEEK-CF increased to about 20 % than that at room temperature. The data of flexural strength for the irradiated specimens showed some scattering, but the strength and modulus at 77 K were changed scarcely up to 120 MGy. The flexural strength and modulus in the unirradiated specimen decreased with increasing of measurement temperature, and the strength at 140 deg C, which is the just below temperature of the glass transition of PEEK, was to 70 % of the value at room temperature. For the irradiated specimens, the strength and modulus increased with dose and the values at 140 deg C for the specimen irradiated with 120 MGy were nearly the same with the unirradiated specimen measured at room temperature. The improvement of mechanical properties at high temperature by irradiation was supported by a viscoelastic measurement in which the glass transition shifted to the higher temperature by the radiation-induced crosslinking. A glass fiber reinforced PEEK composite (PEEK-GF) was prepared and its irradiation effects by electron beam was studied. Unirradiated PEEK-GF showed the same performance with that for GFRP of epoxide resin as matrix material, but by irradiation the flexual strength and modulus decreased with dose. It was revealed that this composite was destroyed by delamination because inter laminar shear strength (ILSS) decreased with dose and analysis of the profile of S-S curve showed typical delamination. Fractoglaphy by electron microscopy supported the delamination which is caused by the lowering of adhesion on interface between the fiber and matrix with increase of dose. (author)

  5. Indirect improvement of high temperature mechanical properties of a Mg-based alloy Elektron21 by addition of AlN nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Daudin, R. [Univ. Grenoble Alpes, CNRS, SIMaP, F-38000 Grenoble (France); Terzi, S. [European Space Agency, ESTEC, TEC-TS, EPN Campus, CS20156, 38042 Grenoble Cedex 9 (France); Mallmann, C. [Univ. Grenoble Alpes, CNRS, SIMaP, F-38000 Grenoble (France); Martín, R. Sánchez [IMDEA Materials Institute, Tecnogetafe C/ Eric Kandel, 2, 28906 Getafe, Madrid (Spain); Lhuissier, P. [Univ. Grenoble Alpes, CNRS, SIMaP, F-38000 Grenoble (France); Boller, E.; Pacureanu, A. [European Synchrotron Radiation Facility, 71 Avenue des Martyrs, 38000 Grenoble (France); Katsarou, L.; Dieringa, H. [Helmholtz-Zentrum Geesthacht, Magnesium Innovation Centre – MagIC, Max-Planck-Str. 1, 21502 Geesthacht (Germany); Salvo, L. [Univ. Grenoble Alpes, CNRS, SIMaP, F-38000 Grenoble (France)

    2017-03-14

    Magnesium being the lightest metal on earth used as a structural material, the design of the chemistry and the microstructures of Mg-based alloys has been developed over the years to always further ameliorate their mechanical properties. A supplementary option consists in adding ceramic nanoparticles to such alloys to design Mg-based metal matrix nanocomposites (MMNCs) displaying improvement of both strength and ductility. In practice however, careful attention is required to understand the fundamental mechanisms at the heart of the enhancement of these properties as they still remain quite uncertain and subjected to misleading interpretations. Here, high temperature (350 °C) strain rate jump tests in compression reveal an enhancement of 20–60% of the mechanical properties when AlN nano-particles are added to the Elektron21 alloy (Mg-2.8Nd-1.2Gd-0.4Zr-0.3Zn, in wt%). At the same time, nano-indentation investigations suppose that forest or Orowan strengthening, due to particles-dislocations interactions, is unlikely to occur. Instead, using complementary microstructural characterization techniques (scanning electron macroscopy, energy dispersive spectroscopy as well as micro- and nano-tomography), we show that AlN nano-particles physically and chemically interact with the alloy and modify the overall microstructure, in particular the intermetallic phase, at the origin of the improvement of the mechanical properties.

  6. Kinetics and mechanism of dimethylzinc pyrolysis; Cinetique et mecanisme de la pyrolyse du dimethylzinc

    Energy Technology Data Exchange (ETDEWEB)

    Lambert-Pacht, I [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-05-01

    We have studied the pyrolysis of dimethyl-zinc in sealed bulbs between 250 and 400 Celsius degrees with and without cyclohexane, one or other of the reactants being completely deuterated. We have thus shown that the following mechanism occurs: -1) CH{sub 3}Zn CH{sub 3} {yields} CH{sub 3} + Zn CH{sub 3}, -2) CH{sub 3} + C{sub 6}H{sub 12} {yields} CH{sub 4} + C{sub 6}H{sub 11}, -3) 2 CH{sub 3}Zn {yields} (CH{sub 3}Zn){sub 2} which decomposes to give methane. We have calculated the activation energy for step I: E{sub I} = 45.5 {+-} 3.3 kCal/mole. The study of the reaction in the absence of cyclohexane has made it possible to show that it is not a chain reaction; also the lower limit of the activation energy for the reaction: -4) CH{sub 3} + CH{sub 3}Zn CH{sub 3} {yields} CH{sub 4} + CH{sub 2}Zn CH{sub 3}, has been calculated. It has been found that E{sub 4} {>=} 15 kCal/mole. (author) [French] Nous avons etudie la pyrolyse du dimethylzinc en ampoule scellee, entre 250 et 400 degres Celsius, en presence et en l'absence de cyclohexane, l'un ou l'autre des reactifs etant completement deutere. Nous avons ainsi mis en evidence le mecanisme suivant: -1) CH{sub 3}Zn CH{sub 3} {yields} CH{sub 3} + Zn CH{sub 3}, -2) CH{sub 3} + C{sub 6}H{sub 12} {yields} CH{sub 4} + C{sub 6}H{sub 11}, -3) 2 CH{sub 3}Zn {yields} (CH{sub 3}Zn){sub 2} qui se decompose avec formation de methane. Nous avons calcule pour l'etape 1 l'energie d'activation: E{sub 1} s 45,5 kCal/mole {+-} 3,3. L'etude de la reaction en l'absence de cyclohexane a permis de montrer que celle-ci n'etait pas une reaction en chaine et de calculer une limite inferieure pour l'energie d'activation de la reaction: -4) CH{sub 3} + CH{sub 3}Zn CH{sub 3} {yields} CH{sub 4} + CH{sub 2}Zn CH{sub 3}. Nous avons trouve E{sub 4} > 15 kCal/mole.

  7. Thermal degradation behaviors of polyethylene and polypropylene. Part I: Pyrolysis kinetics and mechanisms

    International Nuclear Information System (INIS)

    Aboulkas, A.; El harfi, K.; El Bouadili, A.

    2010-01-01

    Study of the decomposition kinetics is an important tool for the development of polymer recycling in industrial scale. In this work, the activation energy and the reaction model of the pyrolysis of high density polyethylene (HDPE), low density polyethylene (LDPE) and polypropylene (PP) have been estimated from non-isothermal kinetic results. Firstly, the activation energy values obtained by Friedman, Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa isoconversional methods, are 238-247 kJ/mol for HDPE, 215-221 kJ/mol for LDPE and 179-188 kJ/mol for PP. Secondly, the appropriate conversion model of the process was determined by Coats-Redfern and Criado methods. The pyrolysis reaction models of HDPE and LDPE are accounted for by 'Contracting Sphere' model, whereas that of PP by 'Contracting Cylinder' model.

  8. Mechanism study on cellulose pyrolysis using thermogravimetric analysis coupled with infrared spectroscopy

    Institute of Scientific and Technical Information of China (English)

    WANG Shurong; LIU Qian; LUO Zhongyang; WEN Lihua; CEN Kefa

    2007-01-01

    Based on the investigation of the polysaccharide structure of cellulose by using Fourier transform spectrum analysis,the pyrolysis behaviour of cellulose was studied at a heating rate of 20 K/min by thermogravimetric (TG) analysis coupled with Fourier transform infrared (FTIR) spectroscopy.Experimental results show that the decomposition of cellulose mainly occurs at the temperature range of 550-670 K.The weight loss becomes quite slow when the temperature increases further up to 680 K and the amount of residue reaches a mass percent of 14.7%.The FTIR analysis shows that free water is released first during cellulose pyrolysis,followed by depolymerization and dehydration.Glucosidic bond and carbon-carbon bond break into a series of hydrocarbons,alcohols,aldehydes,acids,etc.Subsequently these large-molecule compounds decompose further into gases,such as methane and carbon monoxide.

  9. Metallurgical and mechanical behaviours of PWR fuel cladding tube oxidised at high temperature; Comportements metallurqigue et mecanique des materiaux de gainage du combustible REP oxydes a haute temperature

    Energy Technology Data Exchange (ETDEWEB)

    Stern, A

    2007-12-15

    Zirconium alloys are used as cladding materials in Pressurized Water Reactors (PWR). As they are submitted to very extreme conditions, it is necessary to check their behaviour and especially to make sure they meet the safety criteria. They are therefore studied under typical in service-loadings but also under accidental loadings. In one of these accidental scenarios, called Loss of Coolant Accident (LOCA) the cladding temperature may increase above 800 C, in a steam environment, and decrease before a final quench of the cladding. During this temperature transient, the cladding is heavily oxidised, and the metallurgical changes lead to a decrease of the post quench mechanical properties. It is then necessary to correlate this drop in residual ductility to the metallurgical evolutions. This is the problem we want to address in this study: the oxidation of PWR cladding materials at high temperature in a steam environment and its consequences on post quench mechanical properties. As oxygen goes massively into the metallic part - a zirconia layer grows at the same time - during the high temperature oxidation, the claddings tubes microstructure shows three different phases that are the outer oxide layer (zirconia) and the inner metallic phases ({alpha}(O) and 'ex {beta}') - with various mechanical properties. In order to reproduce the behaviour of this multilayered material, the first part of this study consisted in creating samples with different - but homogeneous in thickness - oxygen contents, similar to those observed in the different phases of the real cladding. The study was especially focused on the {beta}-->{alpha} phase transformation upon cooling and on the resulting microstructures. A mechanism was proposed to describe this phase transformation. For instance, we conclude that for our oxygen enriched samples, the phase transformation kinetics upon cooling are ruled by the oxygen partitioning between the two allotropic phases. Then, these materials

  10. High temperature niobium alloys

    International Nuclear Information System (INIS)

    Wojcik, C.C.

    1991-01-01

    Niobium alloys are currently being used in various high temperature applications such as rocket propulsion, turbine engines and lighting systems. This paper presents an overview of the various commercial niobium alloys, including basic manufacturing processes, properties and applications. Current activities for new applications include powder metallurgy, coating development and fabrication of advanced porous structures for lithium cooled heat pipes

  11. High temperature storage loop :

    Energy Technology Data Exchange (ETDEWEB)

    Gill, David Dennis; Kolb, William J.

    2013-07-01

    A three year plan for thermal energy storage (TES) research was created at Sandia National Laboratories in the spring of 2012. This plan included a strategic goal of providing test capability for Sandia and for the nation in which to evaluate high temperature storage (>650ÀC) technology. The plan was to scope, design, and build a flow loop that would be compatible with a multitude of high temperature heat transfer/storage fluids. The High Temperature Storage Loop (HTSL) would be reconfigurable so that it was useful for not only storage testing, but also for high temperature receiver testing and high efficiency power cycle testing as well. In that way, HTSL was part of a much larger strategy for Sandia to provide a research and testing platform that would be integral for the evaluation of individual technologies funded under the SunShot program. DOEs SunShot program seeks to reduce the price of solar technologies to 6/kWhr to be cost competitive with carbon-based fuels. The HTSL project sought to provide evaluation capability for these SunShot supported technologies. This report includes the scoping, design, and budgetary costing aspects of this effort

  12. High Temperature Electrolysis

    DEFF Research Database (Denmark)

    Elder, Rachael; Cumming, Denis; Mogensen, Mogens Bjerg

    2015-01-01

    High temperature electrolysis of carbon dioxide, or co-electrolysis of carbon dioxide and steam, has a great potential for carbon dioxide utilisation. A solid oxide electrolysis cell (SOEC), operating between 500 and 900. °C, is used to reduce carbon dioxide to carbon monoxide. If steam is also i...

  13. Hydrocracking mechanisms in molten zinc chloride. Isotope scrambling and pyrolysis studies

    International Nuclear Information System (INIS)

    Larsen, J.W.; Earnest, S.

    1979-01-01

    Bruceton coal was hydrocracked in molten zinc chloride using H 2 -D 2 mixtures. No H-D was observed. The pyrolysis of Bruceton coal and a lignite in molten zinc chloride and an inert salt was carried out and the tetrahydrofuran and pyridine extractability of the products determined. In the absence of H 2 , zinc chloride is not an effective cracking catalyst. It is tentatively concluded that the catalytically active species is formed from zinc chloride and something in the coal and H 2 . The interactions between zinc chloride and the lignite appear to be significantly different than the interactions between zinc chloride and the bituminous coal. (Auth.)

  14. Molecular mechanisms in the pyrolysis of unsaturated chlorinated hydrocarbons: formation of benzene rings. 1. Quantum chemical studies.

    Science.gov (United States)

    McIntosh, Grant J; Russell, Douglas K

    2013-05-23

    Analogues of important aromatic growth mechanisms in hydrocarbon pyrolysis and combustion systems are extended to chlorinated systems. We consider the addition of C2Cl2 to both C4Cl3 and C4Cl5 radicals at the M06-2X/6-311+G(3df,3p)//B3LYP/6-31G(d) level of theory, and we demonstrate that these reaction systems have much in common with those of nonchlorinated species. In particular, we find that these radicals appear to lead preferentially to fulvenes, and not to the observed aromatic products, as is found in nonchlorinated systems. We have therefore also considered nonradical C4/C2 channels by way of Diels-Alder cyclization of C4Cl4/C2Cl2 and C4H2Cl2/C2HCl pairs to describe aromatic formation. While the latter pair readily leads to the formation of partially chlorinated benzenes, the fully chlorinated congeners are sterically prohibited from ring closing directly; this leads to a series of novel rearrangement processes which predict the formation of hexachloro-1,5-diene-3-yne, in addition to hexachlorobenzene, in good agreement with experiment. This suggests, for the first time, that facile nonradical routes to aromatic formation are operative in partially and fully chlorinated pyrolysis and combustion systems.

  15. Mechanism of Microwave-Assisted Pyrolysis of Glucose to Furfural Revealed by Isotopic Tracer and Quantum Chemical Calculations.

    Science.gov (United States)

    Bao, Liwei; Shi, Lei; Luo, Hu; Kong, Lingzhao; Li, Shenggang; Wei, Wei; Sun, Yuhan

    2017-08-10

    Glucose labeled with 13 C or 18 O was used to investigate the mechanism of its conversion into furfural by microwaveassisted pyrolysis. The isotopic content and location in furfural were determined from GC-MS and 13 C NMR spectroscopic measurements and data analysis. The results suggest that the carbon skeleton in furfural is mainly derived from C1 to C5 of glucose, whereas the C of the aldehyde group and the O of the furan ring in furfural primarily originate from C1 and O5 of glucose, respectively. For the first time, the source of O in the furan ring of furfural was elucidated directly by experiment, providing results that are consistent with predictions from recent quantum chemical calculations. Moreover, further theoretical calculations indicate substantially lower energy barriers than previous predictions by considering the potential catalytic effect of formic acid, which is one of the pyrolysis products. The catalytic role of formic acid is further confirmed by experimental evidence. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Electric Response and Conductivity Mechanism in H3PO4‑Doped Polybenzimidazole-4N−HfO2 Nanocomposite Membranes for High Temperature Fuel Cells

    International Nuclear Information System (INIS)

    Nawn, Graeme; Vezzù, Keti; Bertasi, Federico; Pagot, Gioele; Pace, Giuseppe; Conti, Fosca; Negro, Enrico

    2017-01-01

    Relaxation and polarization phenomena of phosphoric acid-doped [PBI4N(HfO 2 ) x ](H 3 PO 4 ) y nanocomposite membranes for high-temperature proton-exchange membrane fuel cells are studied using Dynamic Mechanical Analysis (DMA) and Broadband Electrical Spectroscopy (BES). The membranes are obtained by casting combinations of a polybenzimidazole polymer (PBI4N) with increasing amounts of hafnium oxide nanofiller, resulting in [PBI4N(HfO 2 ) x ] hybrid systems with 0 ≤ x ≤ 0.32. Phosphoric acid at varying content levels (0 ÷ 18 wt%) is used as a doping agent, giving rise to [PBI4N(HfO 2 ) x ](H 3 PO 4 ) y membranes. DMA and BES studies lead us to determine that the electric response of the membranes is modulated by polarization phenomena and by α and β dielectric relaxation events of the polymer matrix. Additionally, the experimental results suggest that in [PBI4N(HfO 2 ) x ](H 3 PO 4 ) y membranes the conductivity occurs owing to three conductivity pathways: two mechanisms involving inter-domain proton migration phenomena by “hopping” events; and one mechanism in which proton exchange occurs between delocalization bodies. These results highlight the significant effect of the hafnium oxide nanofiller content on the conductivity of [PBI4N(HfO 2 ) x ](H 3 PO 4 ) y where, at x ≥ 0.04, demonstrates conductivity higher (9.0 × 10 −2 S/cm) than that of pristine H 3 PO 4 -doped PBI4N (4.8 × 10 −2 S/cm) at T ≥ 155 °C.

  17. High-temperature deformation behavior and mechanical properties of rapidly solidified Al-Li-Co and Al-Li-Zr alloys

    International Nuclear Information System (INIS)

    Sastry, S.M.L.; Oneal, J.E.

    1984-01-01

    The deformation behavior at 25-300 C of rapidly solidified Al-3Li-0.6Co and Al-3Li-0.3Zr alloys was studied by tensile property measurements and transmission electron microscopic examination of dislocation substructures. In binary Al-3Li and Al-3Li-Co alloys, the modulus normalized yield stress increases with an increase in temperature up to 150 C and then decreases. The yield stress at 25 C of Al-3Li-0.3Zr alloys is 180-200 MPa higher than that of Al-3Li alloys. However, the yield stress of the Zr-containing alloy decreases drastically with increasing temperatures above 75 C. The short-term yield stresses at 100-200 C of the Al-3Li-based alloys are higher than that of the conventional high-temperature Al alloys. The temperature dependences of the flow stresses of the alloys were analyzed in terms of the magnitudes and temperature dependences of the various strengthening contributions in the two alloys. The dislocation substructures at 25-300 C were correlated with mechanical properties. 19 references

  18. Mechanical and functional properties of two-phase Ni53Mn22Co6Ga19 high-temperature shape memory alloy with the addition of Dy

    International Nuclear Information System (INIS)

    Yang, S Y; Wang, C P; Liu, X J

    2013-01-01

    The effects of Dy addition on microstructure, martensitic transformation, mechanical and shape memory properties of the two-phase Ni 53 Mn 22 Co 6 Ga 19 high-temperature shape memory alloy were investigated. It is found that a small Dy addition results in the refinement of grain size, which can effectively improve the tensile ductility and strength of the two-phase Ni 53 Mn 22 Co 6 Ga 19 alloy. However, a Dy(Ni,Mn) 4 Ga precipitate forms in the alloys with the Dy addition, and its amount increases with an increase in the Dy addition. This change causes the ductility of the alloys to decrease when the Dy addition is further increased to 0.3 at.%. The results further show that the changes in the martensitic transformation temperature of the studied alloys can be attributed to the combined effects of the tetragonality (c/a) and electron concentration (e/a) of martensite. Additionally, the shape memory effects of the alloys are closely related to the refinement of grain size and the alloy strength. In this study, the (Ni 53 Mn 22 Co 6 Ga 19 ) 99.8 Dy 0.2 alloy exhibits a variety of good properties, including a high martensitic transformation starting temperature of 385.7 °C, a tensile ductility of 10.3% and a shape memory effect of 2.8%. (paper)

  19. Influence of molybdenum on the high-temperature mechanical resistance especially creep resistance around 7000C of 18-14 type stainless steels

    International Nuclear Information System (INIS)

    Ben Marzouk, M.T.

    1977-06-01

    The influence of molybdenum on the mechanical properties under traction, the creep parameters, sub-structure and diffusion parameters of iron in stainless steels was investigated. Between 20 0 C and 800 0 C molybdenum has no significant effect on the elastic limit, breaking load or consolidation coefficient but increases the distributed elongation between 500 0 C and 800 0 C; its influence is greatest at 700 0 C. Addition of molybdenum reduces the creep rate at high temperature from the start of the test up to breaking point. In the temperature range studied, 600 0 C to 900 0 C, its influence is greatest at 600 0 C, decreases as the temperature rises and disappears at 900 0 C. Addition of 2% molybdenum increases the activation energy from 72 kcal/mole to 88 kcal/mole. At 700 0 C molybdenum hardly affects the precipitation and structure of dislocations but delays healing processes. Between 1000 0 C and 1300 0 C molybdenum has no effect on the iron diffusion coefficient: Q=68.7kcal/mole, D 0 =1.3cm 2 /s. The influence of Mo on the creep resistance of austenitic steels between 600 0 C and 900 0 C does not seem to be due to precipitation but to a solid solution effect, which could be a decrease in the diffusion coefficient of iron below 900 0 C [fr

  20. Microstructure, martensitic transformation, mechanical and shape memory properties of Ni–Co–Mn–In high-temperature shape memory alloys under different heat treatments

    International Nuclear Information System (INIS)

    Yang, Shuiyuan; Wang, Cuiping; Shi, Zhan; Wang, Jinming; Zhang, Jinbin; Huang, Yixiong; Liu, Xingjun

    2016-01-01

    The microstructure, martensitic transformation behavior, mechanical and shape memory properties of Ni 40 Co 10 Mn 41+x In 9−x (x=0, 2 and 4) high-temperature shape memory alloys annealed at 900 °C for 24 h or at 800 °C for 2 h were investigated, respectively. The tetragonal martensite phase and fcc γ phase are observed in all the studied alloys. The reversible martensitic transformation temperatures of the alloys increase with the increases of the electron concentration and the tetragonality of martensite phase. The amount of γ phase gradually increases with the decrease of In content, and much more γ phase in the alloys annealed at 900 °C results in slightly larger compressive fracture strain. Although the alloys with x=0 and 2 have a mass of γ phase, they still exhibit good shape memory properties. The amount of γ phase reaches about 20% in the alloy with x=0 after annealed at 900 °C, but a full recovery strain of 3.6% and a two-way shape memory effect of 0.8% can be obtained after two thermomechanical cycles.

  1. Microstructure and High Temperature Mechanical Property of Fe-Cr-B Based Metal/Ceramic Composite Manufactured by Metal Injection Molding Process

    Science.gov (United States)

    Lee, Kee-Ahn; Gwon, Jin-Han; Yoon, Tae-Sik

    2018-03-01

    This study investigated the microstructure and the room and high temperature mechanical properties of Fe-Cr-B alloy manufactured by metal injection molding. In addition, hot isostatic pressing was performed to increase the density of the material, and a comparison of properties was made. Microstructural observation confirmed a bi-continuous structure composed of a three-dimensional network of α-Fe phase and (Cr,Fe)2B phase. The HIPed specimen featured a well-formed adhesion between the α-Fe phase and boride, and the number of fine pores was significantly reduced. The tensile results confirmed that the HIPed specimen (RT to 900 °C) had higher strengths compared to the as-sintered specimen, and the change of elongation starting from 700 °C was significantly greater in the HIPed specimen. Fractography suggested that cracks propagated mostly along the interface between the α-Fe matrix and boride in the as-sintered specimen, while direct fracture of boride was observed in addition to interface separation in the HIPed specimen.

  2. Effects of Heat Treatment on the Microstructures and High Temperature Mechanical Properties of Hypereutectic Al-14Si-Cu-Mg Alloy Manufactured by Liquid Phase Sintering Process

    Science.gov (United States)

    Heo, Joon-Young; Gwon, Jin-Han; Park, Jong-Kwan; Lee, Kee-Ahn

    2018-05-01

    Hypereutectic Al-Si alloy is an aluminum alloy containing at least 12.6 wt.% Si. It is necessary to evenly control the primary Si particle size and distribution in hypereutectic Al-Si alloy. In order to achieve this, there have been attempts to manufacture hypereutectic Al-Si alloy through a liquid phase sintering. This study investigated the microstructures and high temperature mechanical properties of hypereutectic Al-14Si-Cu-Mg alloy manufactured by liquid phase sintering process and changes in them after T6 heat treatment. Microstructural observation identified large amounts of small primary Si particles evenly distributed in the matrix, and small amounts of various precipitation phases were found in grain interiors and grain boundaries. After T6 heat treatment, the primary Si particle size and shape did not change significantly, but the size and distribution of CuAl2 ( θ) and AlCuMgSi ( Q) changed. Hardness tests measured 97.36 HV after sintering and 142.5 HV after heat treatment. Compression tests were performed from room temperature to 300 °C. The results represented that yield strength was greater after heat treatment (RT 300 °C: 351 93 MPa) than after sintering (RT 300 °C: 210 89 MPa). Fracture surface analysis identified cracks developing mostly along the interface between the primary Si particles and the matrix with some differences among temperature conditions. In addition, brittle fracture mode was found after T6 heat treatment.

  3. Advances in high temperature chemistry 1

    CERN Document Server

    Eyring, Leroy

    2013-01-01

    Advances in High Temperature Chemistry, Volume 1 describes the complexities and special and changing characteristics of high temperature chemistry. After providing a brief definition of high temperature chemistry, this nine-chapter book goes on describing the experiments and calculations of diatomic transition metal molecules, as well as the advances in applied wave mechanics that may contribute to an understanding of the bonding, structure, and spectra of the molecules of high temperature interest. The next chapter provides a summary of gaseous ternary compounds of the alkali metals used in

  4. Effluent Gas Flux Characterization During Pyrolysis of Chicken Manure

    Science.gov (United States)

    Clark, S. C.; Ryals, R.; Miller, D. J.; Mullen, C. A.; Pan, D.; Zondlo, M. A.; Boateng, A. A.; Hastings, M. G.

    2017-12-01

    Pyrolysis is a viable option for the production of agricultural resources from diverted organic waste streams and renewable bioenergy. This high temperature thermochemical process yields material with beneficial reuses, including bio-oil and biochar. Gaseous forms of carbon (C) and nitrogen (N) are also emitted during pyrolysis. The effluent mass emission rates from pyrolysis are not well characterized, thus limiting proper evaluation of the environmental benefits or costs of pyrolysis products. We present the first comprehensive suite of C and N mass emission rate measurements of a biomass pyrolysis process using chicken manure as feedstock to produce biochar and bio-oil. Two chicken manure fast pyrolysis experiments were conducted at controlled temperature ranges of 450 - 485 °C and 550 - 585 °C. Mass emission rates of N2O, NO, CO, CO2, CH4 and NH3 were measured using trace gas analyzers. Based on the system mass balance, 23-25% of the total mass of the manure feedstock was emitted as gas, while 52-55% and 23% were converted to bio-oil and biochar, respectively. CO2 and NH3 were the dominant gaseous species by mass, accounting for 58 - 65% of total C mass emitted and 99% of total reactive N mass emitted, respectively. Our gas flux measurements suggest that 1.4 to 2.7 g NH3 -N would be produced from the pyrolysis of one kg of manure. Conservatively scaling up these NH3 pyrolysis emissions in the Chesapeake Bay Watershed, where an estimated 8.64 billion kg of poultry manure is applied to agricultural soils every year, as much as 1.2 x 107 kg of NH3 could be emitted into the atmosphere annually, increasing the potential impact of atmospheric N deposition without a mechanism to capture the gas exhaust during pyrolysis. However, this is considerably less than the potential emissions from NH3 volatilization of raw chicken manure applications, which can be 20-60% of total N applied, and amount to 3.4 x 107 - 1.0 x 108 kg NH3-N yr-1. Pyrolysis has the potential to

  5. Theoretical Study on Vibrational Spectra, Detonation Properties and Pyrolysis Mechanism for Cyclic 2-Diazo-4,6-dinitrophenol

    Science.gov (United States)

    Li, Xiao-hong; Yin, Geng-xin; Zhang, Xian-zhou

    2012-10-01

    Based on the full optimized molecular geometrical structures at the DFT-B3LYP/6-311+G** level, there exists intramolecular hydrogen bond interaction for cyclic 2-diazo-4,6-dinitrophenol. The assigned infrared spectrum is obtained and used to compute the thermodynamic properties. The results show that there are four main characteristic regions in the calculated IR spectra of the title compound. The detonation velocities and pressures are also evaluated by using Kamlet-Jacobs equations based on the calculated density and condensed phase heat of formation. Thermal stability and the pyrolysis mechanism of 2-diazo-4,6-dinitrophenol are investigated by calculating the bond dissociation energies at the B3LYP/6-311+G** level.

  6. High temperature superconductors

    CERN Document Server

    Paranthaman, Parans

    2010-01-01

    This essential reference provides the most comprehensive presentation of the state of the art in the field of high temperature superconductors. This growing field of research and applications is currently being supported by numerous governmental and industrial initiatives in the United States, Asia and Europe to overcome grid energy distribution issues. The technology is particularly intended for densely populated areas. It is now being commercialized for power-delivery devices, such as power transmission lines and cables, motors and generators. Applications in electric utilities include current limiters, long transmission lines and energy-storage devices that will help industries avoid dips in electric power.

  7. High temperature radioisotope capsule

    International Nuclear Information System (INIS)

    Bradshaw, G.B.

    1976-01-01

    A high temperature radioisotope capsule made up of three concentric cylinders, with the isotope fuel located within the innermost cylinder is described. The innermost cylinder has hemispherical ends and is constructed of a tantalum alloy. The intermediate cylinder is made of a molybdenum alloy and is capable of withstanding the pressure generated by the alpha particle decay of the fuel. The outer cylinder is made of a platinum alloy of high resistance to corrosion. A gas separates the innermost cylinder from the intermediate cylinder and the intermediate cylinder from the outer cylinder

  8. High temperature reaction kinetics

    International Nuclear Information System (INIS)

    Jonah, C.D.; Beno, M.F.; Mulac, W.A.; Bartels, D.

    1985-01-01

    During the last year the dependence of the apparent rate of OD + CO on water pressure was measured at 305, 570, 865 and 1223 K. An explanation was found and tested for the H 2 O dependence of the apparent rate of OH(OD) + CO at high temperatures. The isotope effect for OH(D) with CO was determined over the temperature range 330 K to 1225 K. The reason for the water dependence of the rate of OH(OD) + CO near room temperatures has been investigated but no clear explanation has been found. 1 figure

  9. Summary: High Temperature Downhole Motor

    Energy Technology Data Exchange (ETDEWEB)

    Raymond, David W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-10-01

    Directional drilling can be used to enable multi-lateral completions from a single well pad to improve well productivity and decrease environmental impact. Downhole rotation is typically developed with a motor in the Bottom Hole Assembly (BHA) that develops drilling power (speed and torque) necessary to drive rock reduction mechanisms (i.e., the bit) apart from the rotation developed by the surface rig. Historically, wellbore deviation has been introduced by a “bent-sub,” located in the BHA, that introduces a small angular deviation, typically less than 3 degrees, to allow the bit to drill off-axis with orientation of the BHA controlled at the surface. The development of a high temperature downhole motor would allow reliable use of bent subs for geothermal directional drilling. Sandia National Laboratories is pursuing the development of a high temperature motor that will operate on either drilling fluid (water-based mud) or compressed air to enable drilling high temperature, high strength, fractured rock. The project consists of designing a power section based upon geothermal drilling requirements; modeling and analysis of potential solutions; and design, development and testing of prototype hardware to validate the concept. Drilling costs contribute substantially to geothermal electricity production costs. The present development will result in more reliable access to deep, hot geothermal resources and allow preferential wellbore trajectories to be achieved. This will enable development of geothermal wells with multi-lateral completions resulting in improved geothermal resource recovery, decreased environmental impact and enhanced well construction economics.

  10. High temperature thermometric phosphors

    Science.gov (United States)

    Allison, Stephen W.; Cates, Michael R.; Boatner, Lynn A.; Gillies, George T.

    1999-03-23

    A high temperature phosphor consists essentially of a material having the general formula LuPO.sub.4 :Dy.sub.(x),Eu.sub.y) wherein: 0.1 wt %.ltoreq.x.ltoreq.20 wt % and 0.1 wt %.ltoreq.y.ltoreq.20 wt %. The high temperature phosphor is in contact with an article whose temperature is to be determined. The article having the phosphor in contact with it is placed in the environment for which the temperature of the article is to be determined. The phosphor is excited by a laser causing the phosphor to fluoresce. The emission from the phosphor is optically focused into a beam-splitting mirror which separates the emission into two separate emissions, the emission caused by the dysprosium dopant and the emission caused by the europium dopent. The separated emissions are optically filtered and the intensities of the emission are detected and measured. The ratio of the intensity of each emission is determined and the temperature of the article is calculated from the ratio of the intensities of the separate emissions.

  11. Some theories of high temperature superconductivity

    International Nuclear Information System (INIS)

    Cohen, M.L.

    1990-01-01

    In this paper a brief review is given of some historical aspects of theoretical research on superconductivity including a discussion of BCS theory and some theoretical proposals for mechanisms which can cause superconductivity at high temperatures

  12. A coupled model between mechanical deformation and chemical diffusion: An explanation for the preservation of chemical zonation in plagioclase at high temperatures

    Science.gov (United States)

    Zhong, Xin; Vrijmoed, Johannes; Moulas, Evangelos; Tajcmanová, Lucie

    2016-04-01

    Compositional zoning in metamorphic minerals have been generally recognized as an important geological feature to decipher the metamorphic history of rocks. The observed chemical zoning of, e.g. garnet, is commonly interpreted as disequilibrium between the fractionated inner core and the surrounding matrix. However, chemically zoned minerals were also observed in high grade rocks (T>800 degree C) where the duration of metamorphic processes was independently dated to take several Ma. This implies that temperature may not be the only factor that controls diffusion timescales, and grain scale pressure variation was proposed to be a complementary factor that may significantly contribute to the formation and preservation of chemical zoning in high temperature metamorphic minerals [Tajcmanová 2013, 2015]. Here, a coupled model is developed to simulate viscous deformation and chemical diffusion. The numerical approach considers the conservation of mass, momentum, and a constitutive relation developed from equilibrium thermodynamics. A compressible viscoelastic rheology is applied, which associates the volumetric change triggered by deformation and diffusion to a change of pressure. The numerical model is applied to the chemically zoned plagioclase rim described by [Tajcmanová 2014]. The diffusion process operating during the plagioclase rim formation can lead to a development of a pressure gradient. Such a pressure gradient, if maintained during ongoing viscous relaxation, can lead to the preservation of the observed chemical zonation in minerals. An important dimensionless number, the Deborah number, is defined as the ratio between the Maxwell viscoelastic relaxation time and the characteristic diffusion time. It characterizes the relative influence between the maintenance of grain scale pressure variation and chemical diffusion. Two extreme regimes are shown: the mechanically-controlled regime (high Deborah number) and diffusion-controlled regime (low Deborah number

  13. High temperature structural silicides

    International Nuclear Information System (INIS)

    Petrovic, J.J.

    1997-01-01

    Structural silicides have important high temperature applications in oxidizing and aggressive environments. Most prominent are MoSi 2 -based materials, which are borderline ceramic-intermetallic compounds. MoSi 2 single crystals exhibit macroscopic compressive ductility at temperatures below room temperature in some orientations. Polycrystalline MoSi 2 possesses elevated temperature creep behavior which is highly sensitive to grain size. MoSi 2 -Si 3 N 4 composites show an important combination of oxidation resistance, creep resistance, and low temperature fracture toughness. Current potential applications of MoSi 2 -based materials include furnace heating elements, molten metal lances, industrial gas burners, aerospace turbine engine components, diesel engine glow plugs, and materials for glass processing

  14. High temperature materials characterization

    Science.gov (United States)

    Workman, Gary L.

    1990-01-01

    A lab facility for measuring elastic moduli up to 1700 C was constructed and delivered. It was shown that the ultrasonic method can be used to determine elastic constants of materials from room temperature to their melting points. The ease in coupling high frequency acoustic energy is still a difficult task. Even now, new coupling materials and higher power ultrasonic pulsers are being suggested. The surface was only scratched in terms of showing the full capabilities of either technique used, especially since there is such a large learning curve in developing proper methodologies to take measurements into the high temperature region. The laser acoustic system does not seem to have sufficient precision at this time to replace the normal buffer rod methodology.

  15. High temperature metallic recuperator

    Science.gov (United States)

    Ward, M. E.; Solmon, N. G.; Smeltzer, C. E.

    1981-06-01

    An industrial 4.5 MM Btu/hr axial counterflow recuperator, fabricated to deliver 1600 F combustion air, was designed to handle rapid cyclic loading, a long life, acceptable costs, and a low maintenance requirement. A cost benefit anlysis of a high temperature waste heat recovery system utilizing the recurperator and components capable of 1600 F combustion air preheat shows that this system would have a payback period of less than two years. Fifteen companies and industrial associations were interviewed and expressed great interest in recuperation in large energy consuming industries. Determination of long term environmental effects on candidate recuperator tubing alloys was completed. Alloys found to be acceptable in the 2200 F flue gas environment of a steel billet reheat furnace, were identified.

  16. Investigations in the mechanism of carbothermal reduction of yttria stabilized zirconia for ultra-high temperature ceramics application and its influence on yttria contained in it

    Science.gov (United States)

    Sondhi, Anchal

    Zirconium carbide (ZrC) is a high modulus ceramic with an ultra-high melting temperature and, consequently, is capable of withstanding extreme environments. Carbon-carbon composites (CCCs) are important structural materials in current commercial and future hypersonic aircraft; however, these materials may be susceptible to degradation when exposed to elevated temperatures during extreme velocities. At speeds of exceeding Mach 5, intense heating of leading edges of the aircraft triggers rapid oxidation of carbon in CCCs resulting in degradation of the structure and probable failure. Environmental/thermal barrier coatings (EBC/TBC) are employed to protect airfoil structures from extreme conditions. Yttria stabilized zirconia (YSZ) is a well-known EBC/TBC material currently used to protect metallic turbine blades and other aerospace structures. In this work, 3 mol% YSZ has been studied as a potential EBC/TBC on CCCs. However, YSZ is an oxygen conductor and may not sufficiently slow the oxidation of the underlying CCC. Under appropriate conditions, ZrC can form at the interface between CCC and YSZ. Because ZrC is a poor oxygen ion conductor in addition to its stability at high temperatures, it can reduce the oxygen transport to the CCC and thus increase the service lifetime of the structure. This dissertation investigates the thermodynamics and kinetics of the YSZ/ZrC/CCC system and the resulting structural changes across multiple size scales. A series of experiments were conducted to understand the mechanisms and species involved in the carbothermal reduction of ZrO2 to form ZrC. 3 mol% YSZ and graphite powders were uniaxially pressed into pellets and reacted in a graphite (C) furnace. Rietveld x-ray diffraction phase quantification determined that greater fractions of ZrC were formed when carbon was the majority mobile species. These results were validated by modeling the process thermochemically and were confirmed with additional experiments. Measurements were

  17. High temperature mechanical behaviour of glass-ceramics in the YSiAlON and ErSiAlON systems

    Energy Technology Data Exchange (ETDEWEB)

    Bondanini, A.; Massouras, G.; Besson, J.L. [ENSCI, Limoges (France). SPCTS

    2002-07-01

    The high temperature mechanical behaviour of oxynitride glass-ceramics in the YSiAlON and ErSiAlON systems was studied in the 950-1150 C temperature range under compressive stresses ranging from 20 to 100 MPa. The parent glass had a composition of 35 Y(or Er)-45 Si-20 Al-83 O-17 N in equivalent percent. Starting from these glasses, glass-ceramics were prepared using a two stage heat treatment: nucleation at the optimum nucleation temperature followed by crystal growth at 1050, 1150 or 1250 C. The two parent glasses had similar viscosities, with that of the Er-glass being slightly less than that of the Y-glass. After the devitrification treatment at 1050 C, B-phase (M{sub 2}SiAlO{sub 5}N) was the only crystalline phase formed in both systems. The creep behaviour was similar for the yttrium and the erbium materials. It was characterised by a long transient stage, due to the viscoelastic response of the residual glass, with recovered strain after unloading decreasing as loading time increased. The creep resistance was compared to that of the parent glasses in terms of apparent viscosity. The crystallisation of 75% of the glass resulted in an increase in viscosity such that a temperature some 100 C higher showed the same viscosity value. After heat treatment at 1150 C, the phase assemblage in the yttrium material changed with the formation of wollastonite and partial conversion of B-phase into Iw-phase. The apparent viscosity was 2 orders of magnitude higher than that of the samples heat treated at 1050 C and no strain recovery was observed upon unloading. In contrast, the erbium materials retained the same microstructure as after the heat treatment at 1050{sup b}C and there was no difference in the creep behaviour of the samples heat treated at 1050 or 1150 C. After a crystallisation treatment at 1250 C of the yttrium parent glass, the glass-ceramic consisted of yttrium aluminium garnet, N-apatite and {beta}-Y{sub 2}Si{sub 2}O{sub 7} and showed excellent creep

  18. High temperature interface superconductivity

    International Nuclear Information System (INIS)

    Gozar, A.; Bozovic, I.

    2016-01-01

    Highlight: • This review article covers the topic of high temperature interface superconductivity. • New materials and techniques used for achieving interface superconductivity are discussed. • We emphasize the role played by the differences in structure and electronic properties at the interface with respect to the bulk of the constituents. - Abstract: High-T_c superconductivity at interfaces has a history of more than a couple of decades. In this review we focus our attention on copper-oxide based heterostructures and multi-layers. We first discuss the technique, atomic layer-by-layer molecular beam epitaxy (ALL-MBE) engineering, that enabled High-T_c Interface Superconductivity (HT-IS), and the challenges associated with the realization of high quality interfaces. Then we turn our attention to the experiments which shed light on the structure and properties of interfacial layers, allowing comparison to those of single-phase films and bulk crystals. Both ‘passive’ hetero-structures as well as surface-induced effects by external gating are discussed. We conclude by comparing HT-IS in cuprates and in other classes of materials, especially Fe-based superconductors, and by examining the grand challenges currently laying ahead for the field.

  19. Materials corrosion and protection at high temperatures

    International Nuclear Information System (INIS)

    Balbaud, F.; Desgranges, Clara; Martinelli, Laure; Rouillard, Fabien; Duhamel, Cecile; Marchetti, Loic; Perrin, Stephane; Molins, Regine; Chevalier, S.; Heintz, O.; David, N.; Fiorani, J.M.; Vilasi, M.; Wouters, Y.; Galerie, A.; Mangelinck, D.; Viguier, B.; Monceau, D.; Soustelle, M.; Pijolat, M.; Favergeon, J.; Brancherie, D.; Moulin, G.; Dawi, K.; Wolski, K.; Barnier, V.; Rebillat, F.; Lavigne, O.; Brossard, J.M.; Ropital, F.; Mougin, J.

    2011-01-01

    This book was made from the lectures given in 2010 at the thematic school on 'materials corrosion and protection at high temperatures'. It gathers the contributions from scientists and engineers coming from various communities and presents a state-of-the-art of the scientific and technological developments concerning the behaviour of materials at high temperature, in aggressive environments and in various domains (aerospace, nuclear, energy valorization, and chemical industries). It supplies pedagogical tools to grasp high temperature corrosion thanks to the understanding of oxidation mechanisms. It proposes some protection solutions for materials and structures. Content: 1 - corrosion costs; macro-economical and metallurgical approach; 2 - basic concepts of thermo-chemistry; 3 - introduction to the Calphad (calculation of phase diagrams) method; 4 - use of the thermodynamic tool: application to pack-cementation; 5 - elements of crystallography and of real solids description; 6 - diffusion in solids; 7 - notions of mechanics inside crystals; 8 - high temperature corrosion: phenomena, models, simulations; 9 - pseudo-stationary regime in heterogeneous kinetics; 10 - nucleation, growth and kinetic models; 11 - test experiments in heterogeneous kinetics; 12 - mechanical aspects of metal/oxide systems; 13 - coupling phenomena in high temperature oxidation; 14 - other corrosion types; 15 - methods of oxidized surfaces analysis at micro- and nano-scales; 16 - use of SIMS in the study of high temperature corrosion of metals and alloys; 17 - oxidation of ceramics and of ceramic matrix composite materials; 18 - protective coatings against corrosion and oxidation; 19 - high temperature corrosion in the 4. generation of nuclear reactor systems; 20 - heat exchangers corrosion in municipal waste energy valorization facilities; 21 - high temperature corrosion in oil refining and petrochemistry; 22 - high temperature corrosion in new energies industry. (J.S.)

  20. Pyrolysis of Pine Wood

    DEFF Research Database (Denmark)

    Fjellerup, Jan Søren; Ahrenfeldt, Jesper; Henriksen, Ulrik Birk

    2005-01-01

    In this study, pinewood has been pyrolyzed using a fixed heating rate with a variable end-temperature. The pyrolysis process has been simulated using a mechanism with three parallel reactions for the formation of char, gas and tar. First order irreversible kinetics is assumed. This kind of model ...

  1. High temperature pipeline design

    Energy Technology Data Exchange (ETDEWEB)

    Greenslade, J.G. [Colt Engineering, Calgary, AB (Canada). Pipelines Dept.; Nixon, J.F. [Nixon Geotech Ltd., Calgary, AB (Canada); Dyck, D.W. [Stress Tech Engineering Inc., Calgary, AB (Canada)

    2004-07-01

    It is impractical to transport bitumen and heavy oil by pipelines at ambient temperature unless diluents are added to reduce the viscosity. A diluted bitumen pipeline is commonly referred to as a dilbit pipeline. The diluent routinely used is natural gas condensate. Since natural gas condensate is limited in supply, it must be recovered and reused at high cost. This paper presented an alternative to the use of diluent to reduce the viscosity of heavy oil or bitumen. The following two basic design issues for a hot bitumen (hotbit) pipeline were presented: (1) modelling the restart problem, and, (2) establishing the maximum practical operating temperature. The transient behaviour during restart of a high temperature pipeline carrying viscous fluids was modelled using the concept of flow capacity. Although the design conditions were hypothetical, they could be encountered in the Athabasca oilsands. It was shown that environmental disturbances occur when the fluid is cooled during shut down because the ground temperature near the pipeline rises. This can change growing conditions, even near deeply buried insulated pipelines. Axial thermal loads also constrain the design and operation of a buried pipeline as higher operating temperatures are considered. As such, strain based design provides the opportunity to design for higher operating temperature than allowable stress based design methods. Expansion loops can partially relieve the thermal stress at a given temperature. As the design temperature increase, there is a point at which above grade pipelines become attractive options, although the materials and welding procedures must be suitable for low temperature service. 3 refs., 1 tab., 10 figs.

  2. Advances in high temperature chemistry

    CERN Document Server

    Eyring, Leroy

    1969-01-01

    Advances in High Temperature Chemistry, Volume 2 covers the advances in the knowledge of the high temperature behavior of materials and the complex and unfamiliar characteristics of matter at high temperature. The book discusses the dissociation energies and free energy functions of gaseous monoxides; the matrix-isolation technique applied to high temperature molecules; and the main features, the techniques for the production, detection, and diagnosis, and the applications of molecular beams in high temperatures. The text also describes the chemical research in streaming thermal plasmas, as w

  3. Catalytic pyrolysis of hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Vail' eva, N A; Buyanov, R A

    1979-01-01

    Catalytic pyrolysis of petroleum fractions (undecane) was performed with the object of clarifying such questions as the mechanism of action of the catalyst, the concepts of activity and selectivity of the catalyst, the role of transport processes, the temperature ranges and limitations of the catalytic process, the effect of the catalyst on secondary processes, and others. Catalysts such as quartz, MgO, Al/sub 2/O/sub 3/, were used. Analysis of the experimental findings and the fact that the distribution of products is independent of the nature of the surface, demonstrate that the pyrolysis of hydrocarbons in the presence of catalysts is based on the heterogeneous-homogeneous radical-chain mechanism of action, and that the role of the catalysts reduces to increasing the concentration of free radicals. The concept of selectivity cannot be applied to catalysts here, since they do not affect the mechanism of the unfolding of the process of pyrolysis and their role consists solely in initiating the process. In catalytic pyrolysis the concepts of kinetic and diffusive domains of unfolding of the catalytic reaction do not apply, and only the outer surface of the catalyst is engaged, whereas the inner surface merely promotes deletorious secondary processes reducing the selectivity of the process and the activity of the catalyst. 6 references, 2 figures.

  4. Environmental performance, mechanical and microstructure analysis of concrete containing oil-based drilling cuttings pyrolysis residues of shale gas.

    Science.gov (United States)

    Wang, Chao-Qiang; Lin, Xiao-Yan; He, Ming; Wang, Dan; Zhang, Si-Lan

    2017-09-15

    The overall objective of this research project is to investigate the feasibility of incorporating oil-based drilling cuttings pyrolysis residues (ODPR) and fly ash serve as replacements for fine aggregates and cementitious materials in concrete. Mechanical and physical properties, detailed environmental performances, and microstructure analysis were carried out. Meanwhile, the early hydration process and hydrated products of ODPR concrete were analyzed with X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The results indicated that ODPR could not be categorize into hazardous wastes. ODPR had specific pozzolanic characteristic and the use of ODPR had certain influence on slump and compressive strength of concrete. The best workability and optimal compressive strength were achieved with the help of 35% ODPR. Environmental performance tests came to conclusion that ODPR as recycled aggregates and admixture for the preparation of concrete, from the technique perspective, were the substance of mere environmental contamination. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Probing the doping mechanisms and electrical properties of Al, Ga and In doped ZnO prepared by spray pyrolysis

    KAUST Repository

    Maller, Robert

    2016-05-24

    The measured structural, optical and electrical properties of Al, Ga and In doped ZnO films deposited using spray pyrolysis are reported over the doping range 0.1 - 3 atomic percent (at. %). Over the entire doping series highly transparent, polycrystalline thin films are prepared. Using the AC Hall effect we probe the electronic properties of our doped films separating the impact of doping on the measured charge carrier concentrations and Hall mobility, with an emphasis on the low doping, < 1 at. %, range. In this doping range highly resistive films are formed and we highlight AC Hall as a reliable and highly reproducible technique for analysing the doping mechanism. The implementation of a simple, post-deposition heat treatment of our AZO films creates typical films with charge carrier concentrations exceeding > 1019 cm-3 and electron mobilities over 10 cm2/Vs. We describe in detail the nature of the defect chemistry and the role of intrinsic defects, particularly traps, and show that despite significant variations in dopant species and grain boundary concentrations that the defect chemistry dominates the electrical characteristics.

  6. Probing the doping mechanisms and electrical properties of Al, Ga and In doped ZnO prepared by spray pyrolysis

    KAUST Repository

    Maller, Robert; Porte, Yoann; Alshareef, Husam N.; McLachlan, Martyn

    2016-01-01

    The measured structural, optical and electrical properties of Al, Ga and In doped ZnO films deposited using spray pyrolysis are reported over the doping range 0.1 - 3 atomic percent (at. %). Over the entire doping series highly transparent, polycrystalline thin films are prepared. Using the AC Hall effect we probe the electronic properties of our doped films separating the impact of doping on the measured charge carrier concentrations and Hall mobility, with an emphasis on the low doping, < 1 at. %, range. In this doping range highly resistive films are formed and we highlight AC Hall as a reliable and highly reproducible technique for analysing the doping mechanism. The implementation of a simple, post-deposition heat treatment of our AZO films creates typical films with charge carrier concentrations exceeding > 1019 cm-3 and electron mobilities over 10 cm2/Vs. We describe in detail the nature of the defect chemistry and the role of intrinsic defects, particularly traps, and show that despite significant variations in dopant species and grain boundary concentrations that the defect chemistry dominates the electrical characteristics.

  7. HIgh Temperature Photocatalysis over Semiconductors

    Science.gov (United States)

    Westrich, Thomas A.

    Due in large part to in prevalence of solar energy, increasing demand of energy production (from all sources), and the uncertain future of petroleum energy feedstocks, solar energy harvesting and other photochemical systems will play a major role in the developing energy market. This dissertation focuses on a novel photochemical reaction process: high temperature photocatalysis (i.e., photocatalysis conducted above ambient temperatures, T ≥ 100°C). The overarching hypothesis of this process is that photo-generated charge carriers are able to constructively participate in thermo-catalytic chemical reactions, thereby increasing catalytic rates at one temperature, or maintaining catalytic rates at lower temperatures. The photocatalytic oxidation of carbon deposits in an operational hydrocarbon reformer is one envisioned application of high temperature photocatalysis. Carbon build-up during hydrocarbon reforming results in catalyst deactivation, in the worst cases, this was shown to happen in a period of minutes with a liquid hydrocarbon. In the presence of steam, oxygen, and above-ambient temperatures, carbonaceous deposits were photocatalytically oxidized over very long periods (t ≥ 24 hours). This initial experiment exemplified the necessity of a fundamental assessment of high temperature photocatalytic activity. Fundamental understanding of the mechanisms that affect photocatalytic activity as a function of temperatures was achieved using an ethylene photocatalytic oxidation probe reaction. Maximum ethylene photocatalytic oxidation rates were observed between 100 °C and 200 °C; the maximum photocatalytic rates were approximately a factor of 2 larger than photocatalytic rates at ambient temperatures. The loss of photocatalytic activity at temperatures above 200 °C is due to a non-radiative multi-phonon recombination mechanism. Further, it was shown that the fundamental rate of recombination (as a function of temperature) can be effectively modeled as a

  8. High Temperature Piezoelectric Drill

    Science.gov (United States)

    Bao, Xiaoqi; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Shrout, Tom

    2012-01-01

    Venus is one of the planets in the solar systems that are considered for potential future exploration missions. It has extreme environment where the average temperature is 460 deg C and its ambient pressure is about 90 atm. Since the existing actuation technology cannot maintain functionality under the harsh conditions of Venus, it is a challenge to perform sampling and other tasks that require the use of moving parts. Specifically, the currently available electromagnetic actuators are limited in their ability to produce sufficiently high stroke, torque, or force. In contrast, advances in developing electro-mechanical materials (such as piezoelectric and electrostrictive) have enabled potential actuation capabilities that can be used to support such missions. Taking advantage of these materials, we developed a piezoelectric actuated drill that operates at the temperature range up to 500 deg C and the mechanism is based on the Ultrasonic/Sonic Drill/Corer (USDC) configuration. The detailed results of our study are presented in this paper

  9. Thermal and kinetic behaviors of biomass and plastic wastes in co-pyrolysis

    International Nuclear Information System (INIS)

    Çepelioğullar, Özge; Pütün, Ayşe E.

    2013-01-01

    Graphical abstract: - Highlights: • Co-pyrolysis of biomass together with the plastic wastes in thermogravimetric analyzer. • Investigations into thermal and kinetic behaviors at high temperature regions. • Determination of the kinetic parameters. - Abstract: In this study, co-pyrolysis characteristics and kinetics of biomass-plastic blends were investigated. Cotton stalk, hazelnut shell, sunflower residue, and arid land plant Euphorbia rigida, were blended in definite ratio (1:1, w/w) with polyvinyl chloride (PVC) and polyethylene terephthalate (PET). Experiments were conducted with a heating rate of 10 °C min −1 from room temperature to 800 °C in the presence of N 2 atmosphere with a flow rate of 100 cm 3 min −1 . After thermal decomposition in TGA, a kinetic analysis was performed to fit thermogravimetric data and a detailed discussion of co-pyrolysis mechanism was achieved. Experimental results demonstrated that the structural differences between biomass and plastics directly affect their thermal decomposition behaviors. Biomass pyrolysis generally based on three main steps while plastic material’s pyrolysis mechanism resulted in two steps for PET and three steps for PVC. Also, the required activation energies needed to achieve the thermal degradation for plastic were found higher than the biomass materials. In addition, it can be concluded that the evaluation of plastic materials together with biomass created significant changes not only for the thermal behaviors but also for the kinetic behaviors

  10. High-Temperature Piezoelectric Sensing

    Directory of Open Access Journals (Sweden)

    Xiaoning Jiang

    2013-12-01

    Full Text Available Piezoelectric sensing is of increasing interest for high-temperature applications in aerospace, automotive, power plants and material processing due to its low cost, compact sensor size and simple signal conditioning, in comparison with other high-temperature sensing techniques. This paper presented an overview of high-temperature piezoelectric sensing techniques. Firstly, different types of high-temperature piezoelectric single crystals, electrode materials, and their pros and cons are discussed. Secondly, recent work on high-temperature piezoelectric sensors including accelerometer, surface acoustic wave sensor, ultrasound transducer, acoustic emission sensor, gas sensor, and pressure sensor for temperatures up to 1,250 °C were reviewed. Finally, discussions of existing challenges and future work for high-temperature piezoelectric sensing are presented.

  11. High Temperature Superconductor Resonator Detectors

    Data.gov (United States)

    National Aeronautics and Space Administration — High Temperature Superconductor (HTS) infrared detectors were studied for years but never matured sufficiently for infusion into instruments. Several recent...

  12. A study on heat resistance of high temperature resistant coating

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Liping; Wang, Xueying; Zhang, Qibin; Qin, Yanlong; Lin, Zhu [Research Institute of Engineering Technology of CNPC, Tianjin (China)

    2005-04-15

    A high temperature resistant coating has been developed, which is mainly for heavy oil production pipes deserved the serious corrosion. The coating has excellent physical and mechanical performance and corrosion resistance at room and high temperature. In order to simulate the underground working condition of heavy oil pipes,the heat resistance of the high temperature resistant coating has been studied. The development and a study on the heat resistance of the DHT high temperature resistance coating have been introduced in this paper

  13. A study on heat resistance of high temperature resistant coating

    International Nuclear Information System (INIS)

    Zhang, Liping; Wang, Xueying; Zhang, Qibin; Qin, Yanlong; Lin, Zhu

    2005-01-01

    A high temperature resistant coating has been developed, which is mainly for heavy oil production pipes deserved the serious corrosion. The coating has excellent physical and mechanical performance and corrosion resistance at room and high temperature. In order to simulate the underground working condition of heavy oil pipes,the heat resistance of the high temperature resistant coating has been studied. The development and a study on the heat resistance of the DHT high temperature resistance coating have been introduced in this paper

  14. Relation between Mechanical Properties and Pyrolysis Temperature of Phenol Formaldehyde Resin for Gas Separation Membranes

    Czech Academy of Sciences Publication Activity Database

    Šupová, Monika; Svítilová, Jaroslava; Chlup, Zdeněk; Černý, Martin; Weishauptová, Zuzana; Suchý, Tomáš; Machovič, Vladimír; Sucharda, Zbyněk; Žaloudková, Margit

    2012-01-01

    Roč. 56, č. 1 (2012), s. 40-49 ISSN 0862-5468 R&D Projects: GA ČR GA203/09/1327 Institutional research plan: CEZ:AV0Z30460519; CEZ:AV0Z20410507 Keywords : glassy carbon * membranes * mechanical properties Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.418, year: 2012 http://www.ceramics-silikaty.cz/2012/pdf/2012_01_40.pdf

  15. Oxidation kinetics and mechanisms of four-direction carbon/carbon composites and their components in carbon dioxide at high temperature

    International Nuclear Information System (INIS)

    Qin, Fei; Peng, Li-na; He, Guo-qiang; Li, Jiang

    2013-01-01

    Highlights: •Four-direction C/C composite was fabricated using carbon fibres and coal tar pitches. •Large-sized bulk matrix was prepared using same process as matrix of C/C composites. •A and E a of C/C, bulk matrix and fibres in CO 2 were determined, respectively. •Pressure exponent n was 0.62 in C/C–CO 2 . -- Abstract: Thermogravimetric analysis and scanning electron microscopy were used to study the oxidation kinetics of four-direction carbon/carbon composites and their components (fibres and matrix) in a CO 2 atmosphere at high temperature. The ablation processes were restricted to reaction-limited oxidation. The mass loss rate was estimated for the four-direction carbon/carbon composites and their components within the temperature of range of 600–1400 °C. The pressure exponent for the reaction of carbon/carbon composites and CO 2 was 0.62, and the pre-exponential factor and activation energy for the reactions of CO 2 and the carbon/carbon composites, carbon fibres and matrix were determined, respectively

  16. High temperature superconducting devices for SQUIDs, HF- and FIR-applications. Subproject: Thin-film heterostructures for devices and loss mechanisms in HTS. Final report

    International Nuclear Information System (INIS)

    Froehlich, O.

    1994-06-01

    The successful use of electronic devices fabricated from the High Temperature Superconductors (HTS) in SQUID systems as well as HF- and FIR-applications requires the development of a suitable thin-film and device technology. Within the present research project we successfully established the technological base for the deposition and patterning of epitaxial HTS thin-films (YBaCuO, NdCeCuO) and heterostructures of HTS and insulating materials (e.g. NdGaO 3 ). YBaCuO/NdCeCuO superlattices could be successfully fabricated such that both components of the hterostructure were in a superconducting state. This allows for the fabrication and study of superconducting p-n structures. With respect to the fabrication of single grain boundary Josephson junctions based on the bicrystal technique we could establish an international leadership. The small spread of the junction parameters (∝20%) allowed the controllable fabrication of simple devices such as SQUIDs or flux-flow transistors. By the development of a new measuring technique the homogeneity of the critical current density distribution in grain-boundary junctions could be investigated on a sub-μm-scale. Within this project we also could establish a good understanding of the physical background of the transport phenomena in the mixed state of HTS in the presence of a temperature gradient. (orig./MM) [de

  17. Characterization of thick and thin film SiCN for pressure sensing at high temperatures.

    Science.gov (United States)

    Leo, Alfin; Andronenko, Sergey; Stiharu, Ion; Bhat, Rama B

    2010-01-01

    Pressure measurement in high temperature environments is important in many applications to provide valuable information for performance studies. Information on pressure patterns is highly desirable for improving performance, condition monitoring and accurate prediction of the remaining life of systems that operate in extremely high temperature environments, such as gas turbine engines. A number of technologies have been recently investigated, however these technologies target specific applications and they are limited by the maximum operating temperature. Thick and thin films of SiCN can withstand high temperatures. SiCN is a polymer-derived ceramic with liquid phase polymer as its starting material. This provides the advantage that it can be molded to any shape. CERASET™ also yields itself for photolithography, with the addition of photo initiator 2, 2-Dimethoxy-2-phenyl-acetophenone (DMPA), thereby enabling photolithographical patterning of the pre-ceramic polymer using UV lithography. SiCN fabrication includes thermosetting, crosslinking and pyrolysis. The technology is still under investigation for stability and improved performance. This work presents the preparation of SiCN films to be used as the body of a sensor for pressure measurements in high temperature environments. The sensor employs the phenomenon of drag effect. The pressure sensor consists of a slender sensitive element and a thick blocking element. The dimensions and thickness of the films depend on the intended application of the sensors. Fabrication methods of SiCN ceramics both as thin (about 40-60 μm) and thick (about 2-3 mm) films for high temperature applications are discussed. In addition, the influence of thermosetting and annealing processes on mechanical properties is investigated.

  18. Characterization of Thick and Thin Film SiCN for Pressure Sensing at High Temperatures

    Directory of Open Access Journals (Sweden)

    Rama B. Bhat

    2010-02-01

    Full Text Available Pressure measurement in high temperature environments is important in many applications to provide valuable information for performance studies. Information on pressure patterns is highly desirable for improving performance, condition monitoring and accurate prediction of the remaining life of systems that operate in extremely high temperature environments, such as gas turbine engines. A number of technologies have been recently investigated, however these technologies target specific applications and they are limited by the maximum operating temperature. Thick and thin films of SiCN can withstand high temperatures. SiCN is a polymer-derived ceramic with liquid phase polymer as its starting material. This provides the advantage that it can be molded to any shape. CERASET™ also yields itself for photolithography, with the addition of photo initiator 2, 2-Dimethoxy-2-phenyl-acetophenone (DMPA, thereby enabling photolithographical patterning of the pre-ceramic polymer using UV lithography. SiCN fabrication includes thermosetting, crosslinking and pyrolysis. The technology is still under investigation for stability and improved performance. This work presents the preparation of SiCN films to be used as the body of a sensor for pressure measurements in high temperature environments. The sensor employs the phenomenon of drag effect. The pressure sensor consists of a slender sensitive element and a thick blocking element. The dimensions and thickness of the films depend on the intended application of the sensors. Fabrication methods of SiCN ceramics both as thin (about 40–60 µm and thick (about 2–3 mm films for high temperature applications are discussed. In addition, the influence of thermosetting and annealing processes on mechanical properties is investigated.

  19. A detailed kinetic mechanism including methanol and nitrogen pollutants relevant to the gas-phase combustion and pyrolysis of biomass-derived fuels

    Energy Technology Data Exchange (ETDEWEB)

    Coda Zabetta, Edgardo; Hupa, Mikko [Aabo Akademi Process Chemistry Centre, Piispankatu 8, FI-20500 Turku (Finland)

    2008-01-15

    A detailed chemical kinetic mechanism for the simulation of the gas-phase combustion and pyrolysis of biomass-derived fuels was compiled by assembling selected reaction subsets from existing mechanisms (parents). The mechanism, here referred to as ''AaA,'' includes reaction subsets for the oxidation of hydrogen (H{sub 2}), carbon monoxide (CO), light hydrocarbons (C{sub 1} and C{sub 2}), and methanol (CH{sub 3}OH). The mechanism also takes into account reaction subsets of nitrogen pollutants, including the reactions relevant to staged combustion, reburning, and selective noncatalytic reduction (SNCR). The AaA mechanism was validated against suitable experimental data from the literature. Overall, the AaA mechanism gave more accurate predictions than three other mechanisms of reference, although the reference mechanisms performed better occasionally. The predictions from AaA were also found to be consistent with the predictions of its parent mechanisms within most of their range of validity, thus transferring the validity of the parents to the inheriting mechanism (AaA). In parametric studies the AaA mechanism predicted that the effect of methanol on combustion and pollutants is often similar to that of light hydrocarbons, but it also showed that there are important exceptions, thus suggesting that methanol should be taken into account when simulating biomass combustion. To our knowledge, the AaA mechanism is currently the only mechanism that accounts for the chemistry of methanol and nitrogen relevant to the gas-phase combustion and pyrolysis of biomass-derived fuels. (author)

  20. Mechanism of waste biomass pyrolysis: Effect of physical and chemical pre-treatments

    International Nuclear Information System (INIS)

    Das, Oisik; Sarmah, Ajit K.

    2015-01-01

    To impart usability in waste based biomass through thermo-chemical reactions, several physical and chemical pre-treatments were conducted to gain an insight on their mode of action, effect on the chemistry and the change in thermal degradation profiles. Two different waste biomasses (Douglas fir, a softwood and hybrid poplar, a hardwood) were subjected to four different pre-treatments, namely, hot water pre-treatment, torrefaction, acid (sulphuric acid) and salt (ammonium phosphate) doping. Post pre-treatments, the changes in the biomass structure, chemistry, and thermal makeup were studied through electron microscopy, atomic absorption/ultra violet spectroscopy, ion exchange chromatography, and thermogravimetry. The pre-treatments significantly reduced the amounts of inorganic ash, extractives, metals, and hemicellulose from both the biomass samples. Furthermore, hot water and torrefaction pre-treatment caused mechanical disruption in biomass fibres leading to smaller particle sizes. Torrefaction of Douglas fir wood yielded more solid product than hybrid poplar. Finally, the salt pre-treatment increased the activation energies of the biomass samples (especially Douglas fir) to a great extent. Thus, salt pre-treatment was found to bestow thermal stability in the biomass. - Highlights: • Pre-treatments reduce ash, extractives, alkalines and hemicellulose from biomass. • Torrefaction of Douglas fir yields more solid product than hybrid poplar. • Salt pretreatment significantly increases the activation energy of biomass. • Acid and salt pretreatment bestows thermal stability in biomass.

  1. Mechanism of waste biomass pyrolysis: Effect of physical and chemical pre-treatments

    Energy Technology Data Exchange (ETDEWEB)

    Das, Oisik [Department of Biological Systems Engineering, Washington State University, Pullman 99164-6120, WA (United States); Department of Civil and Environmental Engineering, University of Auckland, Auckland 1142 (New Zealand); Sarmah, Ajit K., E-mail: a.sarmah@auckland.ac.nz [Department of Civil and Environmental Engineering, University of Auckland, Auckland 1142 (New Zealand)

    2015-12-15

    To impart usability in waste based biomass through thermo-chemical reactions, several physical and chemical pre-treatments were conducted to gain an insight on their mode of action, effect on the chemistry and the change in thermal degradation profiles. Two different waste biomasses (Douglas fir, a softwood and hybrid poplar, a hardwood) were subjected to four different pre-treatments, namely, hot water pre-treatment, torrefaction, acid (sulphuric acid) and salt (ammonium phosphate) doping. Post pre-treatments, the changes in the biomass structure, chemistry, and thermal makeup were studied through electron microscopy, atomic absorption/ultra violet spectroscopy, ion exchange chromatography, and thermogravimetry. The pre-treatments significantly reduced the amounts of inorganic ash, extractives, metals, and hemicellulose from both the biomass samples. Furthermore, hot water and torrefaction pre-treatment caused mechanical disruption in biomass fibres leading to smaller particle sizes. Torrefaction of Douglas fir wood yielded more solid product than hybrid poplar. Finally, the salt pre-treatment increased the activation energies of the biomass samples (especially Douglas fir) to a great extent. Thus, salt pre-treatment was found to bestow thermal stability in the biomass. - Highlights: • Pre-treatments reduce ash, extractives, alkalines and hemicellulose from biomass. • Torrefaction of Douglas fir yields more solid product than hybrid poplar. • Salt pretreatment significantly increases the activation energy of biomass. • Acid and salt pretreatment bestows thermal stability in biomass.

  2. Study of mechanical properties and high temperature oxidation behavior of a novel cold-spray Ni-20Cr coating on boiler steels

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Narinder [Semiconductor Materials and Device Laboratory, Department of Semiconductor Science, Dongguk University-Seoul, Seoul 100715 (Korea, Republic of); Kumar, Manoj [School of Mechanical, Materials & Energy Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab (India); Sharma, Sanjeev K.; Kim, Deuk Young [Semiconductor Materials and Device Laboratory, Department of Semiconductor Science, Dongguk University-Seoul, Seoul 100715 (Korea, Republic of); Kumar, S.; Chavan, N.M.; Joshi, S.V. [International Advanced Research Centre for Powder Metallurgy & New Materials (ARCI), Hyderabad 500005 (India); Singh, Narinder [Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar, Punjab (India); Singh, Harpreet, E-mail: harpreetsingh@iitrpr.ac.in [School of Mechanical, Materials & Energy Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab (India)

    2015-02-15

    Highlights: • A presynthesized Ni-20Cr nanocrystalline powder was successfully deposited on T22 and SA 516 boilers steels using cold spray process. • The coatings are observed to have more than 2-folds microhardness in comparison with the base steels. • The coating was successful in reducing the weight gain of T22 and SA 516 steel by 71% and 94%. - Abstract: In the current investigation, high temperature oxidation behavior of a novel cold-spray Ni-20Cr nanostructured coating was studied. The nanocrystalline Ni-20Cr powder was synthesized by the investigators using ball milling, which was deposited on T22 and SA 516 steels by cold spraying. The crystallite size based upon Scherrer's formula for the developed coatings was found to be in nano-range for both the substrates. The accelerated oxidation testing was performed in a laboratory tube furnace at a temperature 900 °C under thermal cyclic conditions. Each cycle comprised heating for one hour at 900 °C followed by cooling for 20 min in ambient air. The kinetics of oxidation was established using weight change measurements for the bare and the coated steels. The oxidation products were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) and X-ray mapping techniques. It was found from the results that the coating was successful in reducing the weight gain of SA213-T22 and SA 516-Grade 70 steel by 71% and 94%, respectively. This may be attributed to relatively denser structure, lower porosity and lower oxide content of the coating. Moreover, the developed nano-structured Ni-20Cr powder coating was found to perform better than its counterpart micron-sized Ni-20Cr powder coating, in terms of offering higher oxidation resistance and hardness.

  3. Advanced High Temperature Structural Seals

    Science.gov (United States)

    Newquist, Charles W.; Verzemnieks, Juris; Keller, Peter C.; Rorabaugh, Michael; Shorey, Mark

    2002-10-01

    This program addresses the development of high temperature structural seals for control surfaces for a new generation of small reusable launch vehicles. Successful development will contribute significantly to the mission goal of reducing launch cost for small, 200 to 300 pound payloads. Development of high temperature seals is mission enabling. For instance, ineffective control surface seals can result in high temperature (3100 F) flows in the elevon area exceeding structural material limits. Longer sealing life will allow use for many missions before replacement, contributing to the reduction of hardware, operation and launch costs.

  4. Creep of high temperature composites

    International Nuclear Information System (INIS)

    Sadananda, K.; Feng, C.R.

    1993-01-01

    High temperature creep deformation of composites is examined. Creep of composites depends on the interplay of many factors. One of the basic issues in the design of the creep resistant composites is the ability to predict their creep behavior from the knowledge of the creep behavior of the individual components. In this report, the existing theoretical models based on continuum mechanics principles are reviewed. These models are evaluated using extensive experimental data on molydisilicide-silicon carbide composites obtained by the authors. The analysis shows that the rule of mixture based on isostrain and isostress provides two limiting bounds wherein all other theoretical predictions fall. For molydisilicide composites, the creep is predominantly governed by the creep of the majority phase, i.e. the matrix with fibers deforming elastically. The role of back stresses both on creep rates and activation energies are shown to be minimum. Kinetics of creep in MoSi 2 is shown to be controlled by the process of dislocation glide with climb involving the diffusion of Mo atoms

  5. High temperature superconductor accelerator magnets

    NARCIS (Netherlands)

    van Nugteren, J.

    2016-01-01

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding 20T. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and

  6. High Temperature Materials Laboratory (HTML)

    Data.gov (United States)

    Federal Laboratory Consortium — The six user centers in the High Temperature Materials Laboratory (HTML), a DOE User Facility, are dedicated to solving materials problems that limit the efficiency...

  7. Application of High Temperature Superconductors to Accelerators

    CERN Document Server

    Ballarino, A

    2000-01-01

    Since the discovery of high temperature superconductivity, a large effort has been made by the scientific community to investigate this field towards a possible application of the new oxide superconductors to different devices like SMES, magnetic bearings, flywheels energy storage, magnetic shielding, transmission cables, fault current limiters, etc. However, all present day large scale applications using superconductivity in accelerator technology are based on conventional materials operating at liquid helium temperatures. Poor mechanical properties, low critical current density and sensitivity to the magnetic field at high temperature are the key parameters whose improvement is essential for a large scale application of high temperature superconductors to such devices. Current leads, used for transferring currents from the power converters, working at room temperature, into the liquid helium environment, where the magnets are operating, represent an immediate application of the emerging technology of high t...

  8. Influence of phase transformations on the mechanical behaviour of refractory ceramics at high temperature;Effets des transformations de phase sur la tenue mecanique a haute temperature des ceramiques refractaires

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, N. [LMT-Cachan, ENS de Cachan, UMR 8535 CNRS, Universite Paris 6, 94 - Cachan (France); IUFM de Creteil, Universite Paris-Est Creteil, 93 - Saint-Denis (France); Poirier, J. [CNRS-CEMHTI, 45 - Orleans (France); Polytech, Universite d' Orleans, 45 - Orleans (France)

    2009-07-01

    Refractories used at high temperature are subjected to high chemical and mechanical stresses. The mastery of their microstructure as well as the phase changes occurring in service is essential to ensure resistance to wear and failure of refractory linings. Great progress has been made: combining efficient techniques for the investigation of the microstructure with powerful numerical tools (thermochemical and thermo-mechanical computations) provides information (e.g., degradation mechanisms) that cannot be obtained directly. Also multi-physical and multi-scale models developing materials with high-performance for higher temperature and with longer lifetime. In this paper, through several examples we show some interactions between the mechanical behavior and the microstructure transformations of refractory ceramics. The tools developed to characterize their microstructure change in situ (e.g., at high temperature) and to identify their kinetics are described. Some methodologies and tools developed in recent years, today, provide a better understanding of in-service behavior of refractories while identifying the critical material and process parameters likely to increase life-time. (authors)

  9. Development of Semi-Stochastic Algorithm for Optimizing Alloy Composition of High-Temperature Austenitic Stainless Steels (H-Series) for Desired Mechanical and Corrosion Properties.

    Energy Technology Data Exchange (ETDEWEB)

    Dulikravich, George S.; Sikka, Vinod K.; Muralidharan, G.

    2006-06-01

    The goal of this project was to adapt and use an advanced semi-stochastic algorithm for constrained multiobjective optimization and combine it with experimental testing and verification to determine optimum concentrations of alloying elements in heat-resistant and corrosion-resistant H-series stainless steel alloys that will simultaneously maximize a number of alloy's mechanical and corrosion properties.

  10. In situ 3D characterization of high temperature fatigue damage mechanisms in a cast aluminum alloy using synchrotron X-ray tomography

    International Nuclear Information System (INIS)

    Dezecot, Sebastien; Buffiere, Jean-Yves; Koster, Alain; Maurel, Vincent; Szmytka, Fabien; Charkaluk, Eric; Dahdah, Nora; El Bartali, Ahmed; Limodin, Nathalie; Witz, Jean-Francois

    2016-01-01

    Fatigue tests were performed at 250 °C on a cast AlSi7Cu3Mg aluminum alloy and monitored with Synchrotron in situ X-ray tomography in order to understand the micro-mechanisms of crack initiation and propagation. The analysis of the 3D images reveals that internal shrinkage pores are responsible for the main crack initiation. Crack propagation is mainly due to the complex and highly interconnected network of hard particles of the eutectic regions.

  11. Effect of high-temperature exposure on the mechanical properties of 18Cr–8Ni–W–Nb–V–N stainless steel

    International Nuclear Information System (INIS)

    Nikulin, I.; Kipelova, A.; Kaibyshev, R.

    2012-01-01

    Highlights: ► Niobium stabilized 18Cr–8Ni austenitic steel was subjected to long-time aging. ► The main phases precipitated during aging are Z-phase and Laves-phase. ► Intragranular phases and solid solution are responsible for tensile strength. ► Intergranular particles affect impact toughness. - Abstract: The change in the mechanical properties of 18Cr–8Ni–W–Nb–V–N austenitic stainless steel due to aging was investigated at room temperature and 650 °C. It was shown that long-term aging decreases strength characteristics despite increasing hardness. The impact toughness decreases from 255 J/cm 2 for an un-aged steel to 135 J/cm 2 for the steel aged for 3000 h. However, evidence of ductile fracture was found even after long-term aging. This study suggests that the reduction in impact toughness occurs due to the precipitation of Z-phase and Laves-phase particles at the grain boundaries. The degradation of impact toughness and mechanical properties with aging is discussed in terms of microstructure evolution, secondary phase precipitations and fracture mechanisms.

  12. Diffusion processes in Cu-Al-Ni shape memory alloys studied by mechanical spectroscopy and in situ transmission electron microscopy at high temperatures

    International Nuclear Information System (INIS)

    No, M.L.; Ibarra, A.; Lopez-Echarri, A.; Bocanegra, E.H.; San Juan, J.

    2006-01-01

    We have studied the mobility of defects in the frozen β phase of the Cu-Al-Ni shape memory alloys by mechanical spectroscopy as a function of temperature. In parallel, we have characterized the microstructure and their evolution with over-heating treatments. Thermal treatments have been performed in situ in a transmission electron microscope by using a heating stage. Internal friction and modulus defect measurements have been correlated with the microstructural observations by transmission electron microscopy. We discuss the behavior of the internal friction spectra, corresponding to over-heating in the β-phase, and propose microscopic mechanisms responsible for the evolution when the material is not in thermal equilibrium. In particular, the dislocations became mobile in the temperature range between 750 and 800 K where the L2 1 atomic order changes to the B2 order. A relaxation peak has been observed in the equilibrium β phase domain, which has been examined in detail by isothermal measurements as a function of frequency. The activation enthalpy of the peak has been determined to be 3.05 ± 0.1 eV, and possible microscopic mechanisms responsible for the peak are discussed

  13. Bitumen pyrolysis

    International Nuclear Information System (INIS)

    Braehler, G.; Noll, T.

    2014-01-01

    In the past bitumen was a preferred matrix for the embedding of low and intermediate level radioactive waste: its geological history promised long term stability in final repositories. A great variety of waste has been embedded: technological waste, spent ion exchange resins, concrete, rubble, etc. Liquid waste like evaporator concentrates can be dried and embedded simultaneously in extruders, allowing simple processes and equipment. Unfortunately, during long term intermediate storage the bituminized waste drums proved out being not as stable as expected: a significant number turned out to be no longer acceptable for final disposal, and some of them even needed repacking to enable further intermediate storage. A method to rework such drums with bituminized radioactive waste seems to be urgently needed. Pyrolysis and pyro-hydrolysis (= pyrolysis with water steam added) have a long history for the treatment of organic waste: spent solvent (TBP), spent ion exchange resins, alpha waste (predominantly PVC), etc. Due to its low process temperature and the endothermic character, such processes offer significant safety advantages, as compared to incineration or dissolving in organic solvents. Results of lab-scale investigations and concepts for facilities are presented. (authors)

  14. Highly efficient high temperature electrolysis

    DEFF Research Database (Denmark)

    Hauch, Anne; Ebbesen, Sune; Jensen, Søren Højgaard

    2008-01-01

    High temperature electrolysis of water and steam may provide an efficient, cost effective and environmentally friendly production of H-2 Using electricity produced from sustainable, non-fossil energy sources. To achieve cost competitive electrolysis cells that are both high performing i.e. minimum...... internal resistance of the cell, and long-term stable, it is critical to develop electrode materials that are optimal for steam electrolysis. In this article electrolysis cells for electrolysis of water or steam at temperatures above 200 degrees C for production of H-2 are reviewed. High temperature...... electrolysis is favourable from a thermodynamic point of view, because a part of the required energy can be supplied as thermal heat, and the activation barrier is lowered increasing the H-2 production rate. Only two types of cells operating at high temperature (above 200 degrees C) have been described...

  15. High-temperature metallography setup

    International Nuclear Information System (INIS)

    Blumenfeld, M.; Shmarjahu, D.; Elfassy, S.

    1979-06-01

    A high-temperature metallography setup is presented. In this setup the observation of processes such as that of copper recrystallization was made possible, and the structure of metals such as uranium could be revealed. A brief historical review of part of the research works that have been done with the help of high temperature metallographical observation technique since the beginning of this century is included. Detailed description of metallographical specimen preparation technique and theoretical criteria based on the rate of evaporation of materials present on the polished surface of the specimens are given

  16. Effects of exposure to high-temperature helium containing oxygen on the mechanical properties of molybdenum and TZM-Mo alloy at room temperature

    International Nuclear Information System (INIS)

    Noda, T.; Okada, M.; Watanabe, R.

    1980-01-01

    The effects of exposure to helium containing oxygen of 0.1-115 vpm at 1000 0 C on the mechanical properties of molybdenum and TZM-Mo alloy at room temperature were studied. The stress-relieved molybdenum specimen which was not recrystallized at test temperature showed the ductility after exposure to helium containing oxygen. The recrystallized molybdenum and TZM lost ductility after exposure to helium containing oxygen of 0.1-13 vpm in a few hours. The embrittlement of molybdenum was considered to be due to the grain boundary weakening. Molybdenum to which carbon was added seemed to hinder the grain boundary weakening by the oxygen contamination. Both stress-relieved and recrystallized TZM specimens picked up oxygen linearly with time of exposure to helium. The increase in oxygen content of TZM, which was considered to be caused by the internal oxidation of titanium and zirconium, results in the embrittlement of TZM. (orig.)

  17. High temperature (900-1300 C) mechanical behaviour of dendritic web grown silicon ribbons - Strain rate and temperature dependence of the yield stress

    Science.gov (United States)

    Mathews, V. K.; Gross, T. S.

    1987-01-01

    The mechanical behavior of dendritic web Si ribbons close the melting point was studied experimentally. The goal of the study was to generate data for modeling the generation of stresses and dislocation structures during growth of dendritic web Si ribbons, thereby permitting modifications to the production process, i.e., the temperature profile, to lower production costs for the photovoltaic ribbons. A laser was used to cut specimens in the direction of growth of sample ribbons, which were then subjected to tensile tests at temperatures up to 1300 C in an Ar atmosphere. The tensile strengths of the samples increased when the temperature rose above 1200 C, a phenomena which was attributed to the diffusion of oxygen atoms to the quasi-dislocation sites. The migration to the potential dislocations sites effectively locked the dislocations.

  18. Effect of Ni-Co Ternary Molten Salt Catalysts on Coal Catalytic Pyrolysis Process

    Science.gov (United States)

    Cui, Xin; Qi, Cong; Li, Liang; Li, Yimin; Li, Song

    2017-08-01

    In order to facilitate efficient and clean utilization of coal, a series of Ni-Co ternary molten salt crystals are explored and the catalytic pyrolysis mechanism of Datong coal is investigated. The reaction mechanisms of coal are achieved by thermal gravimetric analyzer (TGA), and a reactive kinetic model is constructed. The microcosmic structure and macerals are observed by scanning electron microscope (SEM). The catalytic effects of ternary molten salt crystals at different stages of pyrolysis are analyzed. The experimental results show that Ni-Co ternary molten salt catalysts have the capability to bring down activation energy required by pyrolytic reactions at its initial phase. Also, the catalysts exert a preferable catalytic action on macromolecular structure decomposition and free radical polycondensation reactions. Furthermore, the high-temperature condensation polymerization is driven to decompose further with a faster reaction rate by the additions of Ni-Co ternary molten salt crystal catalysts. According to pyrolysis kinetic research, the addition of catalysts can effectively decrease the activation energy needed in each phase of pyrolysis reaction.

  19. Understanding the fast pyrolysis of lignin.

    Science.gov (United States)

    Patwardhan, Pushkaraj R; Brown, Robert C; Shanks, Brent H

    2011-11-18

    In the present study, pyrolysis of corn stover lignin was investigated by using a micro-pyrolyzer coupled with a GC-MS/FID (FID=flame ionization detector). The system has pyrolysis-vapor residence times of 15-20 ms, thus providing a regime of minimal secondary reactions. The primary pyrolysis product distribution obtained from lignin is reported. Over 84 % mass balance and almost complete closure on carbon balance is achieved. In another set of experiments, the pyrolysis vapors emerging from the micro-pyrolyzer are condensed to obtain lignin-derived bio-oil. The chemical composition of the bio-oil is analyzed by using GC-MS and gel permeation chromatography techniques. The comparison between results of two sets of experiments indicates that monomeric compounds are the primary pyrolysis products of lignin, which recombine after primary pyrolysis to produce oligomeric compounds. Further, the effect of minerals (NaCl, KCl, MgCl(2), and CaCl(2)) and temperature on the primary pyrolysis product distribution is investigated. The study provides insights into the fundamental mechanisms of lignin pyrolysis and a basis for developing more descriptive models of biomass pyrolysis. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Effects of high temperature treatment on microstructure and mechanical properties of laser-clad NiCrBSi/WC coatings on titanium alloy substrate

    International Nuclear Information System (INIS)

    Li, Guang Jie; Li, Jun; Luo, Xing

    2014-01-01

    Laser-clad composite coatings on the Ti6Al4V substrate were heat-treated at 700, 800, and 900 °C for 1 h. The effects of post-heat treatment on the microstructure, microhardness, and fracture toughness of the coatings were investigated by scanning electron microscopy, X-ray diffractometry, energy dispersive spectroscopy, and optical microscopy. The wear resistance of the coatings was evaluated under dry reciprocating sliding friction at room temperature. The coatings mainly comprised some coarse gray blocky (W,Ti)C particles accompanied by the fine white WC particles, a large number of black TiC cellular/dendrites, and the matrix composed of NiTi and Ni 3 Ti; some unknown rich Ni- and Ti-rich particles with sizes ranging from 10 nm to 50 nm were precipitated and uniformly distributed in the Ni 3 Ti phase to form a thin granular layer after heat treatment at 700 °C. The granular layer spread from the edge toward the center of the Ni 3 Ti phase with increasing temperature. A large number of fine equiaxed Cr 23 C 6 particles with 0.2–0.5 μm sizes were observed around the edges of the NiTi supersaturated solid solution when the temperature was further increased to 900 °C. The microhardness and fracture toughness of the coatings were improved with increased temperature due to the dispersion-strengthening effect of the precipitates. Dominant wear mechanisms for all the coatings included abrasive and delamination wear. The post-heat treatment not only reduced wear volume and friction coefficient, but also decreased cracking susceptibility during sliding friction. Comparatively speaking, the heat-treated coating at 900 °C presented the most excellent wear resistance. - Highlights: • TiC + WC reinforced intermetallic compound matrix composite coatings were produced. • The formation mechanism of the reinforcements was analyzed. • Two precipitates were generated at elevated temperature. • Cracking susceptibility and microhardness of the coatings were improved

  1. High-temperature plasma physics

    International Nuclear Information System (INIS)

    Furth, H.P.

    1988-03-01

    Both magnetic and inertial confinement research are entering the plasma parameter range of fusion reactor interest. This paper reviews the individual and common technical problems of these two approaches to the generation of thermonuclear plasmas, and describes some related applications of high-temperature plasma physics

  2. High Temperature Superconductor Machine Prototype

    DEFF Research Database (Denmark)

    Mijatovic, Nenad; Jensen, Bogi Bech; Træholt, Chresten

    2011-01-01

    A versatile testing platform for a High Temperature Superconductor (HTS) machine has been constructed. The stationary HTS field winding can carry up to 10 coils and it is operated at a temperature of 77K. The rotating armature is at room temperature. Test results and performance for the HTS field...

  3. High Temperature Transparent Furnace Development

    Science.gov (United States)

    Bates, Stephen C.

    1997-01-01

    This report describes the use of novel techniques for heat containment that could be used to build a high temperature transparent furnace. The primary objective of the work was to experimentally demonstrate transparent furnace operation at 1200 C. Secondary objectives were to understand furnace operation and furnace component specification to enable the design and construction of a low power prototype furnace for delivery to NASA in a follow-up project. The basic approach of the research was to couple high temperature component design with simple concept demonstration experiments that modify a commercially available transparent furnace rated at lower temperature. A detailed energy balance of the operating transparent furnace was performed, calculating heat losses through the furnace components as a result of conduction, radiation, and convection. The transparent furnace shells and furnace components were redesigned to permit furnace operation at at least 1200 C. Techniques were developed that are expected to lead to significantly improved heat containment compared with current transparent furnaces. The design of a thermal profile in a multizone high temperature transparent furnace design was also addressed. Experiments were performed to verify the energy balance analysis, to demonstrate some of the major furnace improvement techniques developed, and to demonstrate the overall feasibility of a high temperature transparent furnace. The important objective of the research was achieved: to demonstrate the feasibility of operating a transparent furnace at 1200 C.

  4. High temperature electronic gain device

    International Nuclear Information System (INIS)

    McCormick, J.B.; Depp, S.W.; Hamilton, D.J.; Kerwin, W.J.

    1979-01-01

    An integrated thermionic device suitable for use in high temperature, high radiation environments is described. Cathode and control electrodes are deposited on a first substrate facing an anode on a second substrate. The substrates are sealed to a refractory wall and evacuated to form an integrated triode vacuum tube

  5. Containment of high temperature plasmas

    International Nuclear Information System (INIS)

    Bass, R.W.; Ferguson, H.R.P.; Fletcher, H. Jr.; Gardner, J.; Harrison, B.K.; Larsen, K.M.

    1973-01-01

    Apparatus is described for confining a high temperature plasma which comprises: 1) envelope means shaped to form a toroidal hollow chamber containing a plasma, 2) magnetic field line generating means for confining the plasma in a smooth toroidal shape without cusps. (R.L.)

  6. Chemistry of high temperature superconductors

    CERN Document Server

    1991-01-01

    This review volume contains the most up-to-date articles on the chemical aspects of high temperature oxide superconductors. These articles are written by some of the leading scientists in the field and includes a comprehensive list of references. This is an essential volume for researchers working in the fields of ceramics, materials science and chemistry.

  7. Properties of high temperature SQUIDS

    International Nuclear Information System (INIS)

    Falco, C.M.; Wu, C.T.

    1978-01-01

    A review is given of the present status of weak links and dc and rf biased SQUIDs made with high temperature superconductors. A method for producing reliable, reproducible devices using Nb 3 Sn is outlined, and comments are made on directions future work should take

  8. High temperature component life assessment

    CERN Document Server

    Webster, G A

    1994-01-01

    The aim of this book is to investigate and explain the rapid advances in the characterization of high temperature crack growth behaviour which have been made in recent years, with reference to industrial applications. Complicated mathematics has been minimized with the emphasis placed instead on finding solutions using simplified procedures without the need for complex numerical analysis.

  9. Intermetallic-Based High-Temperature Materials

    Energy Technology Data Exchange (ETDEWEB)

    Sikka, V.K.

    1999-04-25

    The intermetallic-based alloys for high-temperature applications are introduced. General characteristics of intermetallics are followed by identification of nickel and iron aluminides as the most practical alloys for commercial applications. An overview of the alloy compositions, melting processes, and mechanical properties for nickel and iron aluminizes are presented. The current applications and commercial producers of nickel and iron aluminizes are given. A brief description of the future prospects of intermetallic-based alloys is also given.

  10. Applications of high-temperature superconductivity

    International Nuclear Information System (INIS)

    Malozemoff, A.P.; Gallagher, W.J.; Schwall, R.E.

    1987-01-01

    The new high temperature superconductors open up possibilities for applications in magnets, power transmission, computer interconnections, Josephson devices and instrumentation, among many others. The success of these applications hinges on many interlocking factors, including critical current density, critical fields, allowable processing temperatures, mechanical properties and chemical stability. An analysis of some of these factors suggests which applications may be the easiest to realize and which may have the greatest potential

  11. Modeling of concrete response at high temperature

    International Nuclear Information System (INIS)

    Pfeiffer, P.; Marchertas, A.

    1984-01-01

    A rate-type creep law is implemented into the computer code TEMP-STRESS for high temperature concrete analysis. The disposition of temperature, pore pressure and moisture for the particular structure in question is provided as input for the thermo-mechanical code. The loss of moisture from concrete also induces material shrinkage which is accounted for in the analytical model. Examples are given to illustrate the numerical results

  12. 1982 Annual status report: high-temperature materials

    International Nuclear Information System (INIS)

    Van de Voorde, M.

    1983-01-01

    The High Temperature Materials Programme is executed at the JRC, Petten Establishment and has for the 1980/83 programme period the objective to promote within the European Community the development of high temperature materials required for future energy technologies. Materials and engineering studies include: corrosion with or without load, mechanical properties under static or dynamic loads, surface protection creep of tubular components in corrosive environments and high temperature materials data bank

  13. High Temperature, High Power Piezoelectric Composite Transducers

    Science.gov (United States)

    Lee, Hyeong Jae; Zhang, Shujun; Bar-Cohen, Yoseph; Sherrit, StewarT.

    2014-01-01

    Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined. PMID:25111242

  14. Comparison of microstructural and mechanical properties of joints developed by high temperature brazing, GTAW and laser welding methods on AISI 316 L stainless steel for specific applications in nuclear components

    International Nuclear Information System (INIS)

    Venkatesu, Sadu; Saxena, Rajesh; Ravi Kumar, R.; Chaurasia, P.K; Murugan, S.; Venugopal, S.

    2016-01-01

    Fabrication of instrumented irradiation capsule for evaluating the irradiation performance of fuel and structural materials in a nuclear reactor requires development of thin wall joints capable of withstanding high temperature and/or internal pressure. Thin wall joints for high temperature (∼550℃) applications can be made by laser beam welding (LBW), gas tungsten Arc welding (GTAW) and High Temperature Brazing (HLT) method

  15. Comparison of carrier transport mechanism under UV/Vis illumination in an AZO photodetector and an AZO/p-Si heterojunction photodiode produced by spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Shasti, M.; Mortezaali, A., E-mail: mortezaali@alzahra.ac.ir; Dariani, R. S. [Department of Physics, Alzahra University, Tehran 1993893973 (Iran, Islamic Republic of)

    2015-01-14

    In this study, Aluminum doped Zinc Oxide (AZO) layer is deposited on p-type silicon (p-Si) by spray pyrolysis method to fabricate ultraviolet-visible (UV/Vis) photodetector as Al doping process can have positive effect on the photodetector performance. Morphology, crystalline structure, and Al concentration of AZO layer are investigated by SEM, XRD, and EDX. The goal of this study is to analyze the mechanism of carrier transport by means of current-voltage characteristics under UV/Vis illumination in two cases: (a) electrodes connected to the surface of AZO layer and (b) electrodes connected to cross section of heterojunction (AZO/p-Si). Measurements indicate that the AZO/p-Si photodiode exhibits a higher photocurrent and lower photoresponse time under visible illumination with respect to AZO photodetector; while under UV illumination, the above result is inversed. Besides, the internal junction field of AZO/p-Si heterojunction plays an important role on this mechanism.

  16. Comparison of carrier transport mechanism under UV/Vis illumination in an AZO photodetector and an AZO/p-Si heterojunction photodiode produced by spray pyrolysis

    International Nuclear Information System (INIS)

    Shasti, M.; Mortezaali, A.; Dariani, R. S.

    2015-01-01

    In this study, Aluminum doped Zinc Oxide (AZO) layer is deposited on p-type silicon (p-Si) by spray pyrolysis method to fabricate ultraviolet-visible (UV/Vis) photodetector as Al doping process can have positive effect on the photodetector performance. Morphology, crystalline structure, and Al concentration of AZO layer are investigated by SEM, XRD, and EDX. The goal of this study is to analyze the mechanism of carrier transport by means of current-voltage characteristics under UV/Vis illumination in two cases: (a) electrodes connected to the surface of AZO layer and (b) electrodes connected to cross section of heterojunction (AZO/p-Si). Measurements indicate that the AZO/p-Si photodiode exhibits a higher photocurrent and lower photoresponse time under visible illumination with respect to AZO photodetector; while under UV illumination, the above result is inversed. Besides, the internal junction field of AZO/p-Si heterojunction plays an important role on this mechanism

  17. High-temperature geothermal cableheads

    Science.gov (United States)

    Coquat, J. A.; Eifert, R. W.

    1981-11-01

    Two high temperature, corrosion resistant logging cable heads which use metal seals and a stable fluid to achieve proper electrical terminations and cable sonde interfacings are described. A tensile bar provides a calibrated yield point, and a cone assembly anchors the cable armor to the head. Electrical problems of the sort generally ascribable to the cable sonde interface were absent during demonstration hostile environment loggings in which these cable heads were used.

  18. High temperature fusion reactor design

    International Nuclear Information System (INIS)

    Harkness, S.D.; dePaz, J.F.; Gohar, M.Y.; Stevens, H.C.

    1979-01-01

    Fusion energy may have unique advantages over other systems as a source for high temperature process heat. A conceptual design of a blanket for a 7 m tokamak reactor has been developed that is capable of producing 1100 0 C process heat at a pressure of approximately 10 atmospheres. The design is based on the use of a falling bed of MgO spheres as the high temperature heat transfer system. By preheating the spheres with energy taken from the low temperature tritium breeding part of the blanket, 1086 MW of energy can be generated at 1100 0 C from a system that produces 3000 MW of total energy while sustaining a tritium breeding ratio of 1.07. The tritium breeding is accomplished using Li 2 O modules both in front of (6 cm thick) and behind (50 cm thick) the high temperature ducts. Steam is used as the first wall and front tritium breeding module coolant while helium is used in the rear tritium breeding region. The system produces 600 MW of net electricity for use on the grid

  19. High temperature oxidation behavior of TiAl-based intermetallics

    International Nuclear Information System (INIS)

    Stroosnijder, M.F.; Sunderkoetter, J.D.; Haanappel, V.A.C.

    1996-01-01

    TiAl-based intermetallic compounds have attracted considerable interest as structural materials for high-temperature applications due to their low density and substantial mechanical strength at high temperatures. However, one major drawback hindering industrial application arises from the insufficient oxidation resistance at temperatures beyond 700 C. In the present contribution some general aspects of high temperature oxidation of TiAl-based intermetallics will be presented. This will be followed by a discussion of the influence of alloying elements, in particular niobium, and of the effect of nitrogen in the oxidizing environment on the high temperature oxidation behavior of such materials

  20. High-temperature bulk acoustic wave sensors

    International Nuclear Information System (INIS)

    Fritze, Holger

    2011-01-01

    Piezoelectric crystals like langasite (La 3 Ga 5 SiO 14 , LGS) and gallium orthophosphate (GaPO 4 ) exhibit piezoelectrically excited bulk acoustic waves at temperatures of up to at least 1450 °C and 900 °C, respectively. Consequently, resonant sensors based on those materials enable new sensing approaches. Thereby, resonant high-temperature microbalances are of particular interest. They correlate very small mass changes during film deposition onto resonators or gas composition-dependent stoichiometry changes of thin films already deposited onto the resonators with the resonance frequency shift of such devices. Consequently, the objective of the work is to review the high-temperature properties, the operation limits and the measurement principles of such resonators. The electromechanical properties of high-temperature bulk acoustic wave resonators such as mechanical stiffness, piezoelectric and dielectric constant, effective viscosity and electrical conductivity are described using a one-dimensional physical model and determined accurately up to temperatures as close as possible to their ultimate limit. Insights from defect chemical models are correlated with the electromechanical properties of the resonators. Thereby, crucial properties for stable operation as a sensor under harsh conditions are identified to be the formation of oxygen vacancies and the bulk conductivity. Operation limits concerning temperature, oxygen partial pressure and water vapor pressure are given. Further, application-relevant aspects such as temperature coefficients, temperature compensation and mass sensitivity are evaluated. In addition, approximations are introduced which make the exact model handy for routine data evaluation. An equivalent electrical circuit for high-temperature resonator devices is derived based on the one-dimensional physical model. Low- and high-temperature approximations are introduced. Thereby, the structure of the equivalent circuit corresponds to the

  1. High-temperature bulk acoustic wave sensors

    Science.gov (United States)

    Fritze, Holger

    2011-01-01

    Piezoelectric crystals like langasite (La3Ga5SiO14, LGS) and gallium orthophosphate (GaPO4) exhibit piezoelectrically excited bulk acoustic waves at temperatures of up to at least 1450 °C and 900 °C, respectively. Consequently, resonant sensors based on those materials enable new sensing approaches. Thereby, resonant high-temperature microbalances are of particular interest. They correlate very small mass changes during film deposition onto resonators or gas composition-dependent stoichiometry changes of thin films already deposited onto the resonators with the resonance frequency shift of such devices. Consequently, the objective of the work is to review the high-temperature properties, the operation limits and the measurement principles of such resonators. The electromechanical properties of high-temperature bulk acoustic wave resonators such as mechanical stiffness, piezoelectric and dielectric constant, effective viscosity and electrical conductivity are described using a one-dimensional physical model and determined accurately up to temperatures as close as possible to their ultimate limit. Insights from defect chemical models are correlated with the electromechanical properties of the resonators. Thereby, crucial properties for stable operation as a sensor under harsh conditions are identified to be the formation of oxygen vacancies and the bulk conductivity. Operation limits concerning temperature, oxygen partial pressure and water vapor pressure are given. Further, application-relevant aspects such as temperature coefficients, temperature compensation and mass sensitivity are evaluated. In addition, approximations are introduced which make the exact model handy for routine data evaluation. An equivalent electrical circuit for high-temperature resonator devices is derived based on the one-dimensional physical model. Low- and high-temperature approximations are introduced. Thereby, the structure of the equivalent circuit corresponds to the Butterworth

  2. High Temperature Phenomena in Shock Waves

    CERN Document Server

    2012-01-01

    The high temperatures generated in gases by shock waves give rise to physical and chemical phenomena such as molecular vibrational excitation, dissociation, ionization, chemical reactions and inherently related radiation. In continuum regime, these processes start from the wave front, so that generally the gaseous media behind shock waves may be in a thermodynamic and chemical non-equilibrium state. This book presents the state of knowledge of these phenomena. Thus, the thermodynamic properties of high temperature gases, including the plasma state are described, as well as the kinetics of the various chemical phenomena cited above. Numerous results of measurement and computation of vibrational relaxation times, dissociation and reaction rate constants are given, and various ionization and radiative mechanisms and processes are presented. The coupling between these different phenomena is taken into account as well as their interaction with the flow-field. Particular points such as the case of rarefied flows an...

  3. The metallurgy of high temperature alloys

    Science.gov (United States)

    Tien, J. K.; Purushothaman, S.

    1976-01-01

    Nickel-base, cobalt-base, and high nickel and chromium iron-base alloys are dissected, and their microstructural and chemical components are assessed with respect to the various functions expected of high temperature structural materials. These functions include the maintenance of mechanical integrity over the strain-rate spectrum from creep resistance through fatigue crack growth resistance, and such alloy stability expectations as microstructural coarsening resistance, phase instability resistance and oxidation and corrosion resistance. Special attention will be given to the perennial conflict and trade-off between strength, ductility and corrosion and oxidation resistance. The newest developments in the constitution of high temperature alloys will also be discussed, including aspects relating to materials conservation.

  4. High-temperature LDV seed particle development

    Science.gov (United States)

    Frish, Michael B.; Pierce, Vicky G.

    1989-05-01

    The feasibility of developing a method for making monodisperse, unagglomerated spherical particles greater than 50 nm in diameter was demonstrated. Carbonaceous particles were made by pyrolyzing ethylene with a pulsed CO2 laser, thereby creating a non-equilibrium mixture of carbon, hydrogen, hydrocarbon vapors, and unpyrolyzed ethylene. Via a complex series of reactions, the carbon and hydrocarbon vapors quickly condensed into the spherical particles. By cooling and dispersing them in a supersonic expansion immediately after their creation, the hot newly-formed spheres were prevented from colliding and coalescing, thus preventing the problem of agglomeration which as plagued other investigators studying laser-simulated particle formation. The cold particles could be left suspended in the residual gases indefinitely without agglomerating. Their uniform sizes and unagglomerated nature were visualized by collecting the particles on filters that were subsequently examined using electron microscopy. It was found the mean particle size can be coarsely controlled by varying the initial ethylene pressure, and can be finely controlled by varying the fluence (energy/unit area) with which the laser irradiates the gas. The motivating application for this research was to manufacture particles that could be used as laser Doppler velocimetry (LDV) seeds in high-temperature high-speed flows. Though the particles made in this program will not evaporate until heated to about 3000 K, and thus could serve as LDV seeds in some applications, they are not ideal when the hot atmosphere is also oxidizing. In that situation, ceramic materials would be preferable. Research performed elsewhere has demonstrated that selected ceramic materials can be manufactured by laser pyrolysis of appropriate supply gases. It is anticipated that, when the same gases are used in conjunction with the rapid cooling technique, unagglomerated spherical ceramic particles can be made with little difficulty. Such

  5. Study on the decomposition mechanism of alkyl carbonate on lithium metal by pyrolysis-gas chromatography-mass spectroscopy

    Science.gov (United States)

    Mogi, Ryo; Inaba, Minoru; Iriyama, Yasutoshi; Abe, Takeshi; Ogumi, Zempachi

    The surface films formed on deposited lithium in electrolyte solutions based on ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) were analyzed by pyrolysis-gas chromatography-mass spectroscopy (Py-GC-MS). In 1 M LiClO 4/EC, the main component of the surface film was easily hydrolyzed to give ethylene glycol after exposure to air, and hence was considered to have a chemical structure of ROCH 2CH 2OR', of which OR and OR' are OLi or OCO 2Li. Ethylene oxide, acetaldehyde, and 1,4-dioxane were detected in decomposition products, and they were considered to have been formed by pyrolysis of ROCH 2CH 2OR' in the pyrolyzer. The presence of ethanol in decomposition products confirmed that ring cleavage at the CH 2O bonds of EC occurs by one electron reduction. In addition, the presence of methanol implied the cleavage of the CC bond of EC upon reduction. From the surface films formed in 1 M LiClO 4/DEC and /DMC, ethanol and methanol, respectively, were detected, which suggested that corresponding lithium alkoxides and/or lithium alkyl carbonates were the main components. In 1 M LiClO 4/EC+DEC (1:1), EC dominantly decomposed to form the surface film. The surface film formed in 1 M LiPF 6/EC+DEC (1:1) contained a much smaller amount of organic compounds.

  6. Laser induced pyrolysis techniques

    International Nuclear Information System (INIS)

    Vanderborgh, N.E.

    1976-01-01

    The application of laser pyrolysis techniques to the problems of chemical analysis is discussed. The processes occurring during laser pyrolysis are first briefly reviewed. The problems encountered in laser pyrolysis gas chromatography are discussed using the analysis of phenanthrene and binary hydrocarbons. The application of this technique to the characterization of naturally occurring carbonaceous material such as oil shales and coal is illustrated

  7. Passivation of high temperature superconductors

    Science.gov (United States)

    Vasquez, Richard P. (Inventor)

    1991-01-01

    The surface of high temperature superconductors such as YBa2Cu3O(7-x) are passivated by reacting the native Y, Ba and Cu metal ions with an anion such as sulfate or oxalate to form a surface film that is impervious to water and has a solubility in water of no more than 10(exp -3) M. The passivating treatment is preferably conducted by immersing the surface in dilute aqueous acid solution since more soluble species dissolve into the solution. The treatment does not degrade the superconducting properties of the bulk material.

  8. High temperature structural sandwich panels

    Science.gov (United States)

    Papakonstantinou, Christos G.

    High strength composites are being used for making lightweight structural panels that are being employed in aerospace, naval and automotive structures. Recently, there is renewed interest in use of these panels. The major problem of most commercial available sandwich panels is the fire resistance. A recently developed inorganic matrix is investigated for use in cases where fire and high temperature resistance are necessary. The focus of this dissertation is the development of a fireproof composite structural system. Sandwich panels made with polysialate matrices have an excellent potential for use in applications where exposure to high temperatures or fire is a concern. Commercial available sandwich panels will soften and lose nearly all of their compressive strength temperatures lower than 400°C. This dissertation consists of the state of the art, the experimental investigation and the analytical modeling. The state of the art covers the performance of existing high temperature composites, sandwich panels and reinforced concrete beams strengthened with Fiber Reinforced Polymers (FRP). The experimental part consists of four major components: (i) Development of a fireproof syntactic foam with maximum specific strength, (ii) Development of a lightweight syntactic foam based on polystyrene spheres, (iii) Development of the composite system for the skins. The variables are the skin thickness, modulus of elasticity of skin and high temperature resistance, and (iv) Experimental evaluation of the flexural behavior of sandwich panels. Analytical modeling consists of a model for the flexural behavior of lightweight sandwich panels, and a model for deflection calculations of reinforced concrete beams strengthened with FRP subjected to fatigue loading. The experimental and analytical results show that sandwich panels made with polysialate matrices and ceramic spheres do not lose their load bearing capability during severe fire exposure, where temperatures reach several

  9. "Green" High-Temperature Polymers

    Science.gov (United States)

    Meador, Michael A.

    1998-01-01

    PMR-15 is a processable, high-temperature polymer developed at the NASA Lewis Research Center in the 1970's principally for aeropropulsion applications. Use of fiber-reinforced polymer matrix composites in these applications can lead to substantial weight savings, thereby leading to improved fuel economy, increased passenger and payload capacity, and better maneuverability. PMR-15 is used fairly extensively in military and commercial aircraft engines components seeing service temperatures as high as 500 F (260 C), such as the outer bypass duct for the F-404 engine. The current world-wide market for PMR-15 materials (resins, adhesives, and composites) is on the order of $6 to 10 million annually.

  10. CONFINEMENT OF HIGH TEMPERATURE PLASMA

    Science.gov (United States)

    Koenig, H.R.

    1963-05-01

    The confinement of a high temperature plasma in a stellarator in which the magnetic confinement has tended to shift the plasma from the center of the curved, U-shaped end loops is described. Magnetic means are provided for counteracting this tendency of the plasma to be shifted away from the center of the end loops, and in one embodiment this magnetic means is a longitudinally extending magnetic field such as is provided by two sets of parallel conductors bent to follow the U-shaped curvature of the end loops and energized oppositely on the inside and outside of this curvature. (AEC)

  11. High temperature divertor plasma operation

    International Nuclear Information System (INIS)

    Ohyabu, Nobuyoshi.

    1991-02-01

    High temperature divertor plasma operation has been proposed, which is expected to enhance the core energy confinement and eliminates the heat removal problem. In this approach, the heat flux is guided through divertor channel to a remote area with a large target surface, resulting in low heat load on the target plate. This allows pumping of the particles escaping from the core and hence maintaining of the high divertor temperature, which is comparable to the core temperature. The energy confinement is then determined by the diffusion coefficient of the core plasma, which has been observed to be much lower than the thermal diffusivity. (author)

  12. High temperature superconductors and method

    International Nuclear Information System (INIS)

    Ruvalds, J.J.

    1977-01-01

    This invention comprises a superconductive compound having the formula: Ni/sub 1-x/M/sub x/Z/sub y/ wherein M is a metal which will destroy the magnetic character of nickel (preferably copper, silver or gold); Z is hydrogen or deuterium; x is 0.1 to 0.9; and y, correspondingly, 0.9 to 0.1, and method of conducting electric current with no resistance at relatively high temperature of T>1 0 K comprising a conductor consisting essentially of the superconducting compound noted above

  13. High temperature thermoelectric energy conversion

    International Nuclear Information System (INIS)

    Wood, C.

    1986-01-01

    Considerable advances were made in the late '50's and early early '60's in the theory and development of materials for high-temperature thermoelectric energy conversion. This early work culminated in a variety of materials, spanning a range of temperatures, with the product of the figure of merit, Z, and temperature, T, i.e., the dimensionless figure of merit, ZT, of the order of one. This experimental limitation appeared to be universal and led a number of investigators to explore the possibility that a ZT - also represents a theoretical limitation. It was found not to be so

  14. Ecotoxicological characterization of biochars: role of feedstock and pyrolysis temperature.

    Science.gov (United States)

    Domene, X; Enders, A; Hanley, K; Lehmann, J

    2015-04-15

    Seven contrasting feedstocks were subjected to slow pyrolysis at low (300 or 350°C) and high temperature (550 or 600°C), and both biochars and the corresponding feedstocks tested for short-term ecotoxicity using basal soil respiration and collembolan reproduction tests. After a 28-d incubation, soil basal respiration was not inhibited but stimulated by additions of feedstocks and biochars. However, variation in soil respiration was dependent on both feedstock and pyrolysis temperature. In the last case, respiration decreased with pyrolysis temperature (r=-0.78; pmanagement recommendations. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. High-temperature flaw assessment procedure

    International Nuclear Information System (INIS)

    Ruggles, M.B.; Takahashi, Y.; Ainsworth, R.A.

    1989-08-01

    The current program represents a joint effort between the Electric Power Research Institute (EPRI) in the USA, the Central Research Institute of Electric Power Industry (CRIEPI) in Japan, and the Central Electricity Generating Board (CEGB) in the UK. The goal is to develop an interim high-temperature flaw assessment procedure for high-temperature reactor components. This is to be accomplished through exploratory experimental and analytical studies of high-temperature crack growth. The state-of-the-art assessment and the fracture mechanics database for both types 304 and 316 stainless steels, completed in 1988, serve as a foundation for the present work. Work in the three participating organizations is progressing roughly on schedule. Results to-date are presented in this document. Fundamental tests results are discussed in Section 2. Section 3 focuses on results of exploratory subcritical crack growth tests. Progress in subcritical crack growth modeling is reported in Section 4. Exploratory failure tests are outlined in Section 5. 21 refs., 70 figs., 7 tabs

  16. Deformation of high-temperature superconductors

    International Nuclear Information System (INIS)

    Goretta, K.C.; Routbort, J.L.; Miller, D.J.; Chen, N.; Dominguez-Rodriguez, A.; Jimenez-Melendo, M.; De Arellano-Lopez, A.R.

    1994-08-01

    Of the many families of high-temperature superconductors, only the properties of those discovered prior to 1989 - Y-Ba-Cu-O, Tl-Ba(Sr)-Ca-Cu-O, and Bi(Pb)-Sr-Ca-Cu-O - have been studied extensively. Deformation tests have been performed on YBa 2 Cu 3 O x (Y-123), YBa 2 Cu 4 O x (Y-124), TlBa 2 Ca 2 Cu 3 O x (Bi-2223). The tests have revealed that plasticity is generally limited in these compounds and that the rate-controlling diffusional kinetics for creep are very slow. Nevertheless, hot forming has proved to be quite successful for fabrication of bulk high-temperature superconductors, so long as deformation rates are low or large hydrostatic stresses are applied. Steady-state creep data have proved to be useful in designing optimal heat treatments for superconductors and in support of more-fundamental diffusion experiments. The high-temperature superconductors are highly complex oxides, and it is a challenge to understand their deformation responses. In this paper, results of interest and operant creep mechanisms will be reviewed

  17. Pyrolysis of D-Glucose to Acrolein

    Science.gov (United States)

    Shen, Chong; Zhang, Igor Ying; Fu, Gang; Xu, Xin

    2011-06-01

    Despite of its great importance, the detailed molecular mechanism for carbohydrate pyrolysis remains poorly understood. We perform a density functional study with a newly developed XYG3 functional on the processes for D-glucose pyrolysis to acrolein. The most feasible reaction pathway starts from an isomerization from D-glucose to D-fructose, which then undergoes a cyclic Grob fragmentation, followed by a concerted electrocyclic dehydration to yield acrolein. This mechanism can account for the known experimental results.

  18. High temperature materials; Materiaux a hautes temperatures

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2003-07-01

    The aim of this workshop is to share the needs of high temperature and nuclear fuel materials for future nuclear systems, to take stock of the status of researches in this domain and to propose some cooperation works between the different research organisations. The future nuclear systems are the very high temperature (850 to 1200 deg. C) gas cooled reactors (GCR) and the molten salt reactors (MSR). These systems include not only the reactor but also the fabrication and reprocessing of the spent fuel. This document brings together the transparencies of 13 communications among the 25 given at the workshop: 1) characteristics and needs of future systems: specifications, materials and fuel needs for fast spectrum GCR and very high temperature GCR; 2) high temperature materials out of neutron flux: thermal barriers: materials, resistance, lifetimes; nickel-base metal alloys: status of knowledge, mechanical behaviour, possible applications; corrosion linked with the gas coolant: knowledge and problems to be solved; super-alloys for turbines: alloys for blades and discs; corrosion linked with MSR: knowledge and problems to be solved; 3) materials for reactor core structure: nuclear graphite and carbon; fuel assembly structure materials of the GCR with fast neutron spectrum: status of knowledge and ceramics and cermets needs; silicon carbide as fuel confinement material, study of irradiation induced defects; migration of fission products, I and Cs in SiC; 4) materials for hydrogen production: status of the knowledge and needs for the thermochemical cycle; 5) technologies: GCR components and the associated material needs: compact exchangers, pumps, turbines; MSR components: valves, exchangers, pumps. (J.S.)

  19. Studies of high temperature superconductors

    International Nuclear Information System (INIS)

    Narlikar, A.

    1989-01-01

    The high temperature superconductors (HTSCs) discovered are from the family of ceramic oxides. Their large scale utilization in electrical utilities and in microelectronic devices are the frontal challenges which can perhaps be effectively met only through consolidated efforts and expertise of a multidisciplinary nature. During the last two years the growth of the new field has occurred on an international scale and perhaps has been more rapid than in most other fields. There has been an extraordinary rush of data and results which are continually being published as short texts dispersed in many excellent journals, some of which were started to ensure rapid publication exclusively in this field. As a result, the literature on HTSCs has indeed become so massive and so diffuse that it is becoming increasingly difficult to keep abreast with the important and reliable facets of this fast-growing field. This provided the motivation to evolve a process whereby both professional investigators and students can have ready access to up-to- date in-depth accounts of major technical advances happening in this field. The present series Studies of High Temperature Superconductors has been launched to, at least in part, fulfill this need

  20. High temperature PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jianlu; Xie, Zhong; Zhang, Jiujun; Tang, Yanghua; Song, Chaojie; Navessin, Titichai; Shi, Zhiqing; Song, Datong; Wang, Haijiang; Wilkinson, David P.; Liu, Zhong-Sheng; Holdcroft, Steven [Institute for Fuel Cell Innovation, National Research Council Canada, Vancouver, BC (Canada V6T 1W5)

    2006-10-06

    There are several compelling technological and commercial reasons for operating H{sub 2}/air PEM fuel cells at temperatures above 100{sup o}C. Rates of electrochemical kinetics are enhanced, water management and cooling is simplified, useful waste heat can be recovered, and lower quality reformed hydrogen may be used as the fuel. This review paper provides a concise review of high temperature PEM fuel cells (HT-PEMFCs) from the perspective of HT-specific materials, designs, and testing/diagnostics. The review describes the motivation for HT-PEMFC development, the technology gaps, and recent advances. HT-membrane development accounts for {approx}90% of the published research in the field of HT-PEMFCs. Despite this, the status of membrane development for high temperature/low humidity operation is less than satisfactory. A weakness in the development of HT-PEMFC technology is the deficiency in HT-specific fuel cell architectures, test station designs, and testing protocols, and an understanding of the underlying fundamental principles behind these areas. The development of HT-specific PEMFC designs is of key importance that may help mitigate issues of membrane dehydration and MEA degradation. (author)

  1. NSTX High Temperature Sensor Systems

    International Nuclear Information System (INIS)

    McCormack, B.; Kugel, H.W.; Goranson, P.; Kaita, R.

    1999-01-01

    The design of the more than 300 in-vessel sensor systems for the National Spherical Torus Experiment (NSTX) has encountered several challenging fusion reactor diagnostic issues involving high temperatures and space constraints. This has resulted in unique miniature, high temperature in-vessel sensor systems mounted in small spaces behind plasma facing armor tiles, and they are prototypical of possible high power reactor first-wall applications. In the Center Stack, Divertor, Passive Plate, and vessel wall regions, the small magnetic sensors, large magnetic sensors, flux loops, Rogowski Coils, thermocouples, and Langmuir Probes are qualified for 600 degrees C operation. This rating will accommodate both peak rear-face graphite tile temperatures during operations and the 350 degrees C bake-out conditions. Similar sensor systems including flux loops, on other vacuum vessel regions are qualified for 350 degrees C operation. Cabling from the sensors embedded in the graphite tiles follows narrow routes to exit the vessel. The detailed sensor design and installation methods of these diagnostic systems developed for high-powered ST operation are discussed

  2. Experimental and Chemical Kinetic Modeling Study of Dimethylcyclohexane Oxidation and Pyrolysis

    KAUST Repository

    Eldeeb, Mazen A.; Jouzdani, Shirin; Wang, Zhandong; Sarathy, Mani; Akih-Kumgeh, Benjamin

    2016-01-01

    A combined experimental and chemical kinetic modeling study of the high-temperature ignition and pyrolysis of 1,3-dimethylcyclohexane (13DMCH) is presented. Ignition delay times are measured behind reflected shock waves over a temperature range

  3. Theoretical study of the pyrolysis of vanillin as a model of secondary lignin pyrolysis

    Science.gov (United States)

    Wang, Meng; Liu, Chao; Xu, Xiaoxiao; Li, Qibin

    2016-06-01

    The unimolecular and bimolecular decomposition reactions in processes of vanillin pyrolysis were theoretically investigated by employing density functional theory (DFT) method at M06-2X/6-31 G+(d,p) level. The result shows that the homolytic cleavage of O-CH3 bond could be the dominant initial step in the pyrolysis of vanillin. The hydrogen abstractions from functional groups of vanillin by the formed radicals play important roles in the formation of main products. Both formyl, hydroxyl and methoxyl group contribute to the formation of CO. Benzene is formed from the hydrogen addition reaction between hydrogen radical and phenol at high temperature.

  4. Chemical and structural effects on the high-temperature mechanical behavior of (1−x)(Na{sub 1/2}Bi{sub 1/2})TiO{sub 3}-xBaTiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Deluca, Marco [Materials Center Leoben Forschung GmbH, Roseggerstraße 12, 8700 Leoben (Austria); Institut für Struktur- und Funktionskeramik, Montanuniversitaet Leoben, Peter Tunner Straße 5, 8700 Leoben (Austria); Picht, Gunnar [Institute of Applied Materials, Ceramics in Mechanical Engineering, Karlsruhe Institute of Technology, 76131 Karlsruhe (Germany); Robert Bosch GmbH, Corporate Sector Research and Advance Engineering Applied Research 1, Robert Bosch Platz 1, 70839 Gerlingen (Germany); Hoffmann, Michael J. [Institute of Applied Materials, Ceramics in Mechanical Engineering, Karlsruhe Institute of Technology, 76131 Karlsruhe (Germany); Rechtenbach, Annett; Töpfer, Jörg [Department of SciTec, University of Applied Sciences Jena, Carl-Zeiß-Promenade 2, 07745 Jena (Germany); Schader, Florian H.; Webber, Kyle G., E-mail: webber@ceramics.tu-darmstadt.de [Institute of Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany)

    2015-04-07

    Bismuth sodium titanate–barium titanate [(1−x)(Na{sub 1/2}Bi{sub 1/2})TiO{sub 3}-xBaTiO{sub 3}, NBT-100xBT] is one of the most well studied lead-free piezoelectric materials due in large part to the high field-induced strain attainable in compositions near the morphotropic phase boundary (x = 0.06). The BaTiO{sub 3}-rich side of the phase diagram, however, has not yet been as comprehensively studied, although it might be important for piezoelectric and positive temperature coefficient ceramic applications. In this work, we present a thorough study of BaTiO{sub 3}-rich NBT-100xBT by ferroelastic measurements, dielectric permittivity, X-ray diffraction, and Raman spectroscopy. We show that the high-temperature mechanical behavior, i.e., above the Curie temperature, T{sub C}, is influenced by local disorder, which appears also in pure BT. On the other hand, in NBT-100xBT (x < 1.0), lattice distortion, i.e., tetragonality, increases, and this impacts both the mechanical and dielectric properties. This increase in lattice distortion upon chemical substitution is counterintuitive by merely reasoning on the ionic size, and is due to the change in the A-O bond character induced by the Bi{sup 3+} electron lone pair, as indicated by Raman spectroscopy.

  5. The high-temperature reactor

    International Nuclear Information System (INIS)

    Kirchner, U.

    1991-01-01

    The book deals with the development of the German high-temperature reactor (pebble-bed), the design of a prototype plant and its (at least provisional) shut-down in 1989. While there is a lot of material on the HTR's competitor, the fast breeder, literature is very incomplete on HTRs. The author describes HTR's history as a development which was characterised by structural divergencies but not effectively steered and monitored. There was no project-oriented 'community' such as there was for the fast breeder. Also, the new technology was difficult to control there were situations where no one quite knew what was going on. The technical conditions however were not taken as facts but as a basis for interpretation, wishes and reservations. The HTR gives an opportunity to consider the conditions under which large technical projects can be carried out today. (orig.) [de

  6. High temperature creep of vanadium

    International Nuclear Information System (INIS)

    Juhasz, A.; Kovacs, I.

    1978-01-01

    The creep behaviour of polycrystalline vanadium of 99.7% purity has been investigated in the temperature range 790-880 0 C in a high temperature microscope. It was found that the creep properties depend strongly on the history of the sample. To take this fact into account some additional properties such as the dependence of the yield stress and the microhardness on the pre-annealing treatment have also been studied. Samples used in creep measurements were selected on the basis of their microhardness. The activation energy of creep depends on the microhardness and on the creep temperature. In samples annealed at 1250 0 C for one hour (HV=160 kgf mm -2 ) the rate of creep is controlled by vacancy diffusion in the temperature range 820-880 0 C with an activation energy of 78+-8 kcal mol -1 . (Auth.)

  7. High temperature industrial heat pumps

    Energy Technology Data Exchange (ETDEWEB)

    Berghmans, J. (Louvain Univ., Heverlee (Belgium). Inst. Mechanica)

    1990-01-01

    The present report intends to describe the state of the art of high temperature industrial heat pumps. A description is given of present systems on the market. In addition the research and development efforts on this subject are described. Compression (open as well as closed cycle) systems, as well as absorption heat pumps (including transformers), are considered. This state of the art description is based upon literature studies performed by a team of researchers from the Katholieke Universiteit Leuven, Belgium. The research team also analysed the economics of heat pumps of different types under the present economic conditions. The heat pumps are compared with conventional heating systems. This analysis was performed in order to evaluate the present condition of the heat pump in the European industry.

  8. Faraday imaging at high temperatures

    Science.gov (United States)

    Hackel, Lloyd A.; Reichert, Patrick

    1997-01-01

    A Faraday filter rejects background light from self-luminous thermal objects, but transmits laser light at the passband wavelength, thus providing an ultra-narrow optical bandpass filter. The filter preserves images so a camera looking through a Faraday filter at a hot target illuminated by a laser will not see the thermal radiation but will see the laser radiation. Faraday filters are useful for monitoring or inspecting the uranium separator chamber in an atomic vapor laser isotope separation process. Other uses include viewing welds, furnaces, plasma jets, combustion chambers, and other high temperature objects. These filters are can be produced at many discrete wavelengths. A Faraday filter consists of a pair of crossed polarizers on either side of a heated vapor cell mounted inside a solenoid.

  9. Faraday imaging at high temperatures

    International Nuclear Information System (INIS)

    Hackel, L.A.; Reichert, P.

    1997-01-01

    A Faraday filter rejects background light from self-luminous thermal objects, but transmits laser light at the passband wavelength, thus providing an ultra-narrow optical bandpass filter. The filter preserves images so a camera looking through a Faraday filter at a hot target illuminated by a laser will not see the thermal radiation but will see the laser radiation. Faraday filters are useful for monitoring or inspecting the uranium separator chamber in an atomic vapor laser isotope separation process. Other uses include viewing welds, furnaces, plasma jets, combustion chambers, and other high temperature objects. These filters are can be produced at many discrete wavelengths. A Faraday filter consists of a pair of crossed polarizers on either side of a heated vapor cell mounted inside a solenoid. 3 figs

  10. Mechanical and microstructural behaviour of alumina-zirconia ceramic filaments for high temperature applications; Comportement mecanique et microstructure de filaments ceramiques alumine-zircone pour applications a haute temperature

    Energy Technology Data Exchange (ETDEWEB)

    Poulon-Quintin, A

    2002-04-01

    This thesis is a contribution to the development and to the study of two-phase alumina-zirconia ceramic filaments resistant to creep and chemical and microstructural degradation. The materials studied are experimental two-phase filaments (diameter of few millimeters) with a fibrillary structure obtained by coextrusion of sol-gels or of powder pastes and a nanocrystalline fiber of thin diameter (11{mu}m) with a homogeneous structure. They have been respectively perfected and chosen for their very promising microstructures and compositions concerning the creep resistance. This study is concentrated on the mechanical characterization at high temperature of these materials and especially on the understanding of the deformation and rupture mechanisms in relation with the microstructural evolution. The commercial fiber (Nextel 650) is a {alpha} alumina (grain size {>=}0.1{mu}m) in which the grains of the second phase zirconia are dispersed in a homogeneous way in intra (5-10 nm) as in inter-granular (20-30 nm). After a heat treatment at temperatures superior to 1200 C, it can be noted a strong grains growth preferentially to the axis of the fiber. The tensile properties decrease to a considerable extent with high temperatures ({>=}1000 C). The creep behaviour has been determined between 1000 and 1300 C (value of 2.5 for the stress exponent and of 850 kJ/mol for the activation energy). The evolution of the microstructure to a long grains microstructure is favourable for the creep resistance. A comparison with other fibers of compositions near the Nextel 650 fiber show that the Nextel 650 fiber has interesting properties for being used at high temperatures (until 1200 C). The study of co-extruded alumina-zirconia filaments with a fibrillary structure has at first required those of filaments which composition are each of the phases obtained from pastes (powder-thermoplastics or sol-gels). The composition of each of the phases has been optimized in order to adapt the

  11. Modern high-temperature superconductivity

    International Nuclear Information System (INIS)

    Ching Wu Chu

    1988-01-01

    Ever since the discovery of superconductivity in 1911, its unusual scientific challenge and great technological potential have been recognized. For the past three-quarters of a century, superconductivity has done well on the science front. This is because sueprconductivity is interesting not only just in its own right but also in its ability to act as a probe to many exciting nonsuperconducting phenomena. For instance, it has continued to provide bases for vigorous activities in condensed matter science. Among the more recent examples are heavy-fermion systems and organic superconductors. During this same period of time, superconductivity has also performed admirably in the applied area. Many ideas have been conceived and tested, making use of the unique characteristics of superconductivity - zero resistivity, quantum interference phenomena, and the Meissner effect. In fact, it was not until late January 1987 that it became possible to achieve superconductivity with the mere use of liquid nitrogen - which is plentiful, cheap, efficient, and easy to handle - following the discovery of supercondictivity above 90 K in Y-Ba-Cu-O, the first genuine quaternary superconductor. Superconductivity above 90 K poses scientific and technological challenges not previously encountered: no existing theories can adequately describe superconductivity above 40 K and no known techniques can economically process the materials for full-scale applications. In this paper, therefore, the author recalls a few events leading to the discovery of the new class of quaternary compounds with a superconducting transition temperature T c in the 90 K range, describes the current experimental status of high-temperature superconductivity and, finally, discusses the prospect of very-high-temperature superconductivity, i.e., with a T c substantially higher than 100 K. 97 refs., 7 figs

  12. High temperature incineration. Densification of granules from high temperature incineration

    International Nuclear Information System (INIS)

    Voorde, N. van de; Claes, J.; Taeymans, A.; Hennart, D.; Gijbels, J.; Balleux, W.; Geenen, G.; Vangeel, J.

    1982-01-01

    The incineration system of radioactive waste discussed in this report, is an ''integral'' system, which directly transforms a definite mixture of burnable and unburnable radioactive waste in a final product with a sufficient insolubility to be safely disposed of. At the same time, a significant volume reduction occurs by this treatment. The essential part of the system is a high temperature incinerator. The construction of this oven started in 1974, and while different tests with simulated inactive or very low-level active waste were carried out, the whole system was progressively and continuously extended and adapted, ending finally in an installation with completely remote control, enclosed in an alpha-tight room. In this report, a whole description of the plant and of its auxiliary installations will be given; then the already gained experimental results will be summarized. Finally, the planning for industrial operation will be briefly outlined. An extended test with radioactive waste, which was carried out in March 1981, will be discussed in the appendix

  13. Development of high temperature resistant ceramic matrix composites based on SiC- and novel SiBNC-fibres

    International Nuclear Information System (INIS)

    Daenicke, Enrico

    2014-01-01

    Novel ceramic fibres in the quaternary system Si-B-C-N exhibit excellent high temperature stability and creep resistance. In th is work it was investigated, to what extent these outstanding properties of SiBNC-fibres can be transferred into ceramic matrix composites (CMC) in comparison to commercial silicon carbide (SiC) fibres. For the CMC development the liquid silicon infiltration (LSI) as well as the polymer infiltration and pyrolysis process (PIP) was applied. Extensive correlations between fibre properties, fibre coating (without, pyrolytic carbon, lanthanum phosphate), process parameters of the CMC manufacturing method and the mechanical and microstructural properties of the CMC before and after exposure to air could be established. Hence, the potential of novel CMCs can be assessed and application fields can be derived.

  14. High Temperature Fluoride Salt Test Loop

    Energy Technology Data Exchange (ETDEWEB)

    Aaron, Adam M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cunningham, Richard Burns [Univ. of Tennessee, Knoxville, TN (United States); Fugate, David L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Holcomb, David Eugene [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Kisner, Roger A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Peretz, Fred J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Robb, Kevin R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wilson, Dane F. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Yoder, Jr, Graydon L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-12-01

    with 3 cm diameter graphite-based fuel pebbles slowly circulating up through the core. Molten salt coolant (FLiBe) at 700°C flows concurrently (at significantly higher velocity) with the pebbles and is used to remove heat generated in the reactor core (approximately 1280 W/pebble), and supply it to a power conversion system. Refueling equipment continuously sorts spent fuel pebbles and replaces spent or damaged pebbles with fresh fuel. By combining greater or fewer numbers of pebble channel assemblies, multiple reactor designs with varying power levels can be offered. The PB-AHTR design is discussed in detail in Reference [1] and is shown schematically in Fig. 1. Fig. 1. PB-AHTR concept (drawing taken from Peterson et al., Design and Development of the Modular PB-AHTR Proceedings of ICApp 08). Pebble behavior within the core is a key issue in proving the viability of this concept. This includes understanding the behavior of the pebbles thermally, hydraulically, and mechanically (quantifying pebble wear characteristics, flow channel wear, etc). The experiment being developed is an initial step in characterizing the pebble behavior under realistic PB-AHTR operating conditions. It focuses on thermal and hydraulic behavior of a static pebble bed using a convective salt loop to provide prototypic fluid conditions to the bed, and a unique inductive heating technique to provide prototypic heating in the pebbles. The facility design is sufficiently versatile to allow a variety of other experimentation to be performed in the future. The facility can accommodate testing of scaled reactor components or sub-components such as flow diodes, salt-to-salt heat exchangers, and improved pump designs as well as testing of refueling equipment, high temperature instrumentation, and other reactor core designs.

  15. Effect of microstructure on the high temperature mechanical properties of (CeO{sub 2}){sub 0.8}(GdO{sub 1.5}){sub 0.2} electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Sammes, N.M.; Zhang, Y. [Univ. of Waikato, Hamilton (New Zealand)

    1996-12-31

    CeO{sub 2}-based oxides have recently been shown to have great potential as electrolytes in medium temperature solid oxide fuel cell applications, primarily due to their high ionic conductivity. Steele et al., for example, have examined a cell of the type: O{sub 2}, La{sub 0.6}Sr{sub 0.4}Fe{sub 0.8}Co{sub 0.2}O{sub 3}{vert_bar}Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95}{vert_bar}Ni-ZrO{sub 2}, H{sub 2}/H{sub 2}O at 715{degrees}C. Gd{sub 2}O{sub 3} doped CeO{sub 2} has been reported as having one of the highest oxygen ion conductivities of the ceria-based materials. An ionic conductivity of 8.3 x 10{sup -2} s/cm has been reported for (CeO{sub 2}){sub 0.8}(GdO{sub 1.5}){sub 0.2} at 800{degrees}C, which is approximately four times that of Y{sub 2}O{sub 3}-doped ZrO{sub 2}, at the same temperature. Although the electrical properties of the material have been examined in detail, very little work has considered the microstructural/property relationships, particularly in relation to the mechanical properties. It is well know that CeO{sub 2}-based materials are difficult to density and attempts have been performed to examine this. Preliminary studies have also been undertaken to examine the effect of sintering on the mechanical properties of the material. In this paper we examine the effect of microstructure on the high temperature mechanical properties of (CeO{sub 2}){sub 0.8}(GdO{sub 1.5}){sub 0.2}.

  16. High temperature superconductor current leads

    International Nuclear Information System (INIS)

    Zeimetz, B.; Liu, H.K.; Dou, S.X.

    1996-01-01

    Full text: The use of superconductors in high electrical current applications (magnets, transformers, generators etc.) usually requires cooling with liquid Helium, which is very expensive. The superconductor itself produces no heat, and the design of Helium dewars is very advanced. Therefore most of the heat loss, i.e. Helium consumption, comes from the current lead which connects the superconductor with its power source at room temperature. The current lead usually consists of a pair of thick copper wires. The discovery of the High Temperature Superconductors makes it possible to replace a part of the copper with superconducting material. This drastically reduces the heat losses because a) the superconductor generates no resistive heat and b) it is a very poor thermal conductor compared with the copper. In this work silver-sheathed superconducting tapes are used as current lead components. The work comprises both the production of the tapes and the overall design of the leads, in order to a) maximize the current capacity ('critical current') of the superconductor, b) minimize the thermal conductivity of the silver clad, and c) optimize the cooling conditions

  17. Container floor at high temperatures

    International Nuclear Information System (INIS)

    Reutler, H.; Klapperich, H.J.; Mueller-Frank, U.

    1978-01-01

    The invention describes a floor for container which is stressed at high, changing temperatures and is intended for use in gas-cooled nuclear reactors. Due to the downward cooling gas flow in these types of reactor, the reactor floor is subjected to considerable dimensional changes during switching on and off. In the heating stage, the whole graphite structure of the reactor core and floor expands. In order to avoid arising constraining forces, sufficiently large expansion spaces must be allowed for furthermore restoring forces must be present to close the gaps again in the cooling phase. These restoring forces must be permanently present to prevent loosening of the core cuits amongst one another and thus uncontrollable relative movement. Spring elements are not suitable due to fast fatigue as a result of high temperatures and radiation exposure. It is suggested to have the floor elements supported on rollers whose rolling planes are downwards inclined to a fixed point for support. The construction is described in detail by means of drawings. (GL) [de

  18. High Temperature Superconductor Accelerator Magnets

    CERN Document Server

    AUTHOR|(CDS)2079328; de Rijk, Gijs; Dhalle, Marc

    2016-11-10

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding $20T$. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and development before they can be applied in a practical accelerator magnet. In order to study HTS in detail, a five tesla demonstrator magnet named Feather-M2 is designed and constructed. The magnet is based on ReBCO coated conductor, which is assembled into a $10kA$ class Roebel cable. A new and optimized Aligned Block layout is used, which takes advantage of the anisotropy of the conductor. This is achieved by providing local alignment of the Roebel cable in the coil windings with the magnetic field lines. A new Network Model capable of analyzing transient electro-magnetic and thermal phenomena in coated conductor cables and coils is developed. This model is necessary to solve critical issues in coated conductor ac...

  19. High Temperature Superconducting Underground Cable

    International Nuclear Information System (INIS)

    Farrell, Roger A.

    2010-01-01

    The purpose of this Project was to design, build, install and demonstrate the technical feasibility of an underground high temperature superconducting (HTS) power cable installed between two utility substations. In the first phase two HTS cables, 320 m and 30 m in length, were constructed using 1st generation BSCCO wire. The two 34.5 kV, 800 Arms, 48 MVA sections were connected together using a superconducting joint in an underground vault. In the second phase the 30 m BSCCO cable was replaced by one constructed with 2nd generation YBCO wire. 2nd generation wire is needed for commercialization because of inherent cost and performance benefits. Primary objectives of the Project were to build and operate an HTS cable system which demonstrates significant progress towards commercial progress and addresses real world utility concerns such as installation, maintenance, reliability and compatibility with the existing grid. Four key technical areas addressed were the HTS cable and terminations (where the cable connects to the grid), cryogenic refrigeration system, underground cable-to-cable joint (needed for replacement of cable sections) and cost-effective 2nd generation HTS wire. This was the worlds first installation and operation of an HTS cable underground, between two utility substations as well as the first to demonstrate a cable-to-cable joint, remote monitoring system and 2nd generation HTS.

  20. High-temperature axion potential

    International Nuclear Information System (INIS)

    Dowrick, N.J.; McDougall, N.A.

    1989-01-01

    We investigate the possibility of new terms in the high-temperature axion potential arising from the dynamical nature of the axion field and from higher-order corrections to the θ dependence in the free energy of the quark-gluon plasma. We find that the dynamical nature of the axion field does not affect the potential but that the higher-order effects lead to new terms in the potential which are larger than the term previously considered. However, neither the magnitude nor the sign of the potential can be calculated by a perturbative expansion of the free energy since the coupling is too large. We show that a change in the magnitude of the potential does not significantly affect the bound on the axion decay constant but that the sign of the potential is of crucial importance. By investigating the formal properties of the functional integral within the instanton dilute-gas approximation, we find that the sign of the potential does not change and that the minimum remains at θ=0. We conclude that the standard calculation of the axion energy today is not significantly modified by this investigation

  1. Pressure sensor for high-temperature liquids

    International Nuclear Information System (INIS)

    Forster, G.A.

    1978-01-01

    A pressure sensor for use in measuring pressures in liquid at high temperatures, especially such as liquid sodium or liquid potassium, comprises a soft diaphragm in contact with the liquid. The soft diaphragm is coupled mechanically to a stiff diaphragm. Pressure is measured by measuring the displacement of both diaphragms, typically by measuring the capacitance between the stiff diaphragm and a fixed plate when the stiff diaphragm is deflected in response to the measured pressure through mechanical coupling from the soft diaphragm. Absolute calibration is achieved by admitting gas under pressure to the region between diaphragms and to the region between the stiff diaphragm and the fixed plate, breaking the coupling between the soft and stiff diaphragms. The apparatus can be calibrated rapidly and absolutely

  2. High temperature creep-fatigue design

    International Nuclear Information System (INIS)

    Tavassoli, A. A. F.; Fournier, B.; Sauzay, M.

    2010-01-01

    Generation IV fission and future fusion reactors envisage development of more efficient high temperature concepts where materials performances are key to their success. This paper examines different types of high temperature creep-fatigue interactions and their implications on design rules for the structural materials retained in both programmes. More precisely, the paper examines current status of design rules for the stainless steel type 316L(N), the conventional Modified 9Cr-1Mo martensitic steel and the low activation Eurofer steel. Results obtained from extensive high temperature creep, fatigue and creep-fatigue tests performed on these materials and their welded joints are presented. These include sequential creep-fatigue and relaxation creep-fatigue tests with hold times in tension, in compression or in both. Effects of larger plastic deformations on fatigue properties are studied through cyclic creep tests or fatigue tests with extended hold time in creep. In most cases, mechanical test results are accompanied with microstructural and fractographic observations. In the case of martensitic steels, the effect of oxidation is examined by performing creep-fatigue tests on identical specimens in vacuum. Results obtained are analyzed and their implications on design allowable and creep-fatigue interaction diagrams are presented. While reasonable confidence is found in predicting creep-fatigue damage through existing code procedures for austenitic stainless steels, effects of cyclic softening and coarsening of microstructure of martensitic steels throughout the fatigue life on materials properties need to be taken into account for more precise damage calculations. In the long-term, development of ferritic/martensitic steels with stable microstructure, such as ODS steels, is proposed. (authors)

  3. High temperature creep-fatigue design

    Energy Technology Data Exchange (ETDEWEB)

    Tavassoli, A. A. F.; Fournier, B.; Sauzay, M. [CEA Saclay, DEN DMN, F-91191 Gif Sur Yvette (France)

    2010-07-01

    Generation IV fission and future fusion reactors envisage development of more efficient high temperature concepts where materials performances are key to their success. This paper examines different types of high temperature creep-fatigue interactions and their implications on design rules for the structural materials retained in both programmes. More precisely, the paper examines current status of design rules for the stainless steel type 316L(N), the conventional Modified 9Cr-1Mo martensitic steel and the low activation Eurofer steel. Results obtained from extensive high temperature creep, fatigue and creep-fatigue tests performed on these materials and their welded joints are presented. These include sequential creep-fatigue and relaxation creep-fatigue tests with hold times in tension, in compression or in both. Effects of larger plastic deformations on fatigue properties are studied through cyclic creep tests or fatigue tests with extended hold time in creep. In most cases, mechanical test results are accompanied with microstructural and fractographic observations. In the case of martensitic steels, the effect of oxidation is examined by performing creep-fatigue tests on identical specimens in vacuum. Results obtained are analyzed and their implications on design allowable and creep-fatigue interaction diagrams are presented. While reasonable confidence is found in predicting creep-fatigue damage through existing code procedures for austenitic stainless steels, effects of cyclic softening and coarsening of microstructure of martensitic steels throughout the fatigue life on materials properties need to be taken into account for more precise damage calculations. In the long-term, development of ferritic/martensitic steels with stable microstructure, such as ODS steels, is proposed. (authors)

  4. Modelling of biomass pyrolysis

    International Nuclear Information System (INIS)

    Kazakova, Nadezhda; Petkov, Venko; Mihailov, Emil

    2015-01-01

    Pyrolysis is an essential preliminary step in a gasifier. The first step in modelling the pyrolysis process of biomass is creating a model for the chemical processes taking place. This model should describe the used fuel, the reactions taking place and the products created in the process. The numerous different polymers present in the organic fraction of the fuel are generally divided in three main groups. So, the multistep kinetic model of biomass pyrolysis is based on conventional multistep devolatilization models of the three main biomass components - cellulose, hemicelluloses, and lignin. Numerical simulations have been conducted in order to estimate the influence of the heating rate and the temperature of pyrolysis on the content of the virgin biomass, active biomass, liquid, solid and gaseous phases at any moment. Keywords: kinetic models, pyrolysis, biomass pyrolysis.

  5. Formation of N2 in the fixed-bed pyrolysis of low rank coals and the mechanisms; Koteisho netsubunkai ni okeru teitankatan kara no N2 no sisei

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Z.; Otsuka, Y. [Tohoku University, Sendai (Japan). Institute for Chemical Reaction Science

    1996-10-28

    In order to establish coal NOx preventive measures, discussions were given on formation of N2 in the fixed-bed pyrolysis of low rank coals and the mechanisms thereof. Chinese ZN coal and German RB coal were used for the discussions. Both coals do not produce N2 at 600{degree}C, and the main product is volatile nitrogen. Conversion into N2 does not depend on heating rates, but increases linearly with increasing temperature, and reaches 65% to 70% at 1200{degree}C. In contrast, char nitrogen decreases linearly with the temperature. More specifically, these phenomena suggest that the char nitrogen or its precursor is the major supply source of N2. When mineral substances are removed by using hydrochloric acid, their catalytic action is lost, and conversion into N2 decreases remarkably. Iron existing in ion-exchanged condition in low-rank coal is reduced and finely diffused into metallic iron particles. The particles react with heterocyclic nitrogen compounds and turn into iron nitride. A solid phase reaction mechanism may be conceived, in which N2 is produced due to decomposition of the iron nitride. 5 refs., 4 figs., 1 tab.

  6. High temperature oxidation of metals: vacancy injection and consequences on the mechanical properties; Consequences de l'oxydation haute temperature sur l'injection de defauts et le comportement mecanique des materiaux metalliques

    Energy Technology Data Exchange (ETDEWEB)

    Perusin, S

    2004-11-15

    The aim of this work is to account for the effects of the high temperature oxidation of metals on their microstructure and their mechanical properties. 'Model' materials like pure nickel, pure iron and the Ni-20Cr alloy are studied. Nickel foils have been oxidised at 1000 C on one side only in laboratory air, the other side being protected from oxidation by a reducing atmosphere. After the oxidation treatment, the unoxidized face was carefully examined by using an Atomic Force Microscope (AFM). Grain boundaries grooves were characterised and their depth were compared to the ones obtained on the same sample heat treated in the reducing atmosphere during the same time. They are found to be much deeper in the case of the single side oxidised samples. It is shown that this additional grooving is directly linked to the growth of the oxide scale on the opposite side and that it can be explained by the diffusion of the vacancies produced at the oxide scale - metal interface, across the entire sample through grain boundaries. Moreover, the comparison between single side oxidised samples and samples oxidised on both sides points out that voids in grain boundaries are only observed in this latter case proving the vacancies condensation in the metal when the two faces are oxidised. The role of the carbon content and the sample's geometry on this phenomenon is examined in detail. The diffusion of vacancies is coupled with the transport of oxygen so that a mechanism of oxygen transport by vacancies is suggested. The tensile tests realised at room temperature on nickel foils (bamboo microstructure) show that the oxide scale can constitute a barrier to the emergence of dislocations at the metal surface. Finally, the Ni-20Cr alloy is tested in tensile and creep tests between 25 and 825 C in oxidising or reducing atmospheres. (author)

  7. Secondary α-deuterium isotope effects as a probe to the relationship between structure and mechanism of pyrolysis of secondary azoalkanes

    International Nuclear Information System (INIS)

    Grizzle, P.L.

    1975-01-01

    This study was carried out to investigate the mechanism of azoalkane thermolysis and the effect of molecular structure on the potential-energy hypersurface for pyrolysis utilizing secondary α-deuterium isotope effects. Since the magnitude of the α-effect for 1,1'-diphenylazoethane is of singular importance in the interpretation of those for related compounds, it has been redetermined. To investigate the effect of molecular structure on the potential-energy hypersurface for thermolysis, α-effects have been determined for 2,2,2',2'-tetramethyl-1,1'-diphenylazoethane and (2,2-dimethyl-1-phenylpropyl)azomethane; the inability to prepare these compounds by conventional methods necessitated the development of a new method for synthesis of secondary azoalkanes. A convenient synthesis of secondary azo compounds is reported. Secondary α-deuterium isotope effects were obtained for the thermal decomposition of 1,1'-diphenylazoethane (III) and 1,1'-diphenylazoethane-1,1'-d 2 (III-d 2 ). The isotope effect is entirely consistent with a simultaneous one-step thermolysis mechanism. Secondary α-deuterium isotope effects and activation parameters were obtained in the thermolysis of 2,2,2',2'-tetramethyl-1,1'-diphenylazopropane (VIII) and (2,2-dimethyl-1-phenylpropyl)azomethane (IX). The data for VIII is considered in terms of both a one- and two-step thermolysis mechanism. The α-effect and activation energy for VIII are not obviously reconcilable with a one-step mechanism. The α-effects, activation energies, and rates of thermolysis for VIII, IX, and (1-phenylethyl)azomethane are most easily rationalized by a two-step mechanism

  8. High Temperature Chemistry at NASA: Hot Topics

    Science.gov (United States)

    Jacobson, Nathan S.

    2014-01-01

    High Temperature issues in aircraft engines Hot section: Ni and Co based Superalloys Oxidation and Corrosion (Durability) at high temperatures. Thermal protection system (TPS) and RCC (Reinforced Carbon-Carbon) on the Space Shuttle Orbiter. High temperatures in other worlds: Planets close to their stars.

  9. High temperature turbine engine structure

    Energy Technology Data Exchange (ETDEWEB)

    Carruthers, W.D.; Boyd, G.L.

    1993-07-20

    A hybrid ceramic/metallic gas turbine is described comprising; a housing defining an inlet, an outlet, and a flow path communicating the inlet with the outlet for conveying a flow of fluid through the housing, a rotor member journaled by the housing in the flow path, the rotor member including a compressor rotor portion rotatively inducting ambient air via the inlet and delivering this air pressurized to the flow path downstream of the compressor rotor, a combustor disposed in the flow path downstream of the compressor receiving the pressurized air along with a supply of fuel to maintain combustion providing a flow of high temperature pressurized combustion products in the flow path downstream thereof, the rotor member including a turbine rotor portion disposed in the flow path downstream of the combustor and rotatively expanding the combustion products toward ambient for flow from the turbine engine via the outlet, the turbine rotor portion providing shaft power driving the compressor rotor portion and an output shaft portion of the rotor member, a disk-like metallic housing portion journaling the rotor member to define a rotational axis therefore, and a disk-like annular ceramic turbine shroud member bounding the flow path downstream of the combustor and circumscribing the turbine rotor portion to define a running clearance therewith, the disk-like ceramic turbine shroud member having a reference axis coaxial with the rotational axis and being spaced axially from the metallic housing portion in mutually parallel concentric relation therewith and a plurality of spacers disposed between ceramic disk-like shroud member and the metallic disk-like housing portion and circumferentially spaced apart, each of the spacers having a first and second end portion having an end surface adjacent the shroud member and the housing portion respectively, the end surfaces having a cylindrical curvature extending transversely relative to the shroud member and the housing portion.

  10. Materials for advanced high temperature reactors

    International Nuclear Information System (INIS)

    Graham, L.W.

    1977-01-01

    Materials are studied in advanced applications of high temperature reactors: helium gas turbine and process heat. Long term creep behavior and corrosion tests are conducted in simulated HTR helium up to 1000 deg C with impurities additions in the furnace atmosphere. Corrosion studies on AISI 321 steels at 800-1000 deg C have shown that the O 2 partial pressure is as low as 10 -24+-3 atm, Ni and Fe cannot be oxidised above about 500 and 600 deg C, Cr cease to oxidise at 800 to 900 deg C and Ti at 900 to 1000 deg C depending on alloy composition γ' strengthened superalloys must depend on a protective corrosion mechanism assisted by the presence of Ti and possibly Cr. Carburisation has been identified metallographically in several high temperature materials: Hastelloy X and M21Z. Alloy TZM appears to be inert in HTR Helium at 900 and 1000 deg C. In alloy 800 and Inconel 625 surface cracks initiation is suppressed but crack propagation is accelerated but this was not apparent in AISI steels, Hastelloy X or fine grain Inconel at 750 deg C

  11. High temperature embrittlement of metals by helium

    International Nuclear Information System (INIS)

    Schroeder, H.

    1983-01-01

    The present knowledge of the influence of helium on the high temperature mechanical properties of metals to be used as structural materials in fast fission and in future fusion reactors is reviewed. A wealth of experimental data has been obtained by many different experimental techniques, on many different alloys, and on different properties. This review is mostly concentrated on the behaviour of austenitic alloys -especially austenitic stainless steels, for which the data base is by far the largest - and gives only a few examples of special bcc alloys. The effect of the helium embrittlement on the different properties - tensile, fatigue and, with special emphasis, creep - is demonstrated by representative results. A comparison between data obtained from in-pile (-beam) experiments and from post-irradiation (-implantation) experiments, respectively, is presented. Theoretical models to describe the observed phenomena are briefly outlined and some suggestions are made for future work to resolve uncertainties and differences between our experimental knowledge and theoretical understanding of high temperature helium embrittlement. (author)

  12. Recent advances in design procedures for high temperature plant

    International Nuclear Information System (INIS)

    1988-01-01

    Thirteen papers cover several aspects of design for high temperature plant. These include design codes, computerized structural analysis and mechanical properties of materials at high temperatures. Seven papers are relevant for fast reactors and these are indexed separately. These cover shakedown design, design codes for thin shells subjected to cyclic thermal loading, the inelastic behaviour of stainless steels and creep and crack propagation in reactor structures under stresses caused by thermal cycling loading. (author)

  13. High temperature vapors science and technology

    CERN Document Server

    Hastie, John

    2012-01-01

    High Temperature Vapors: Science and Technology focuses on the relationship of the basic science of high-temperature vapors to some areas of discernible practical importance in modern science and technology. The major high-temperature problem areas selected for discussion include chemical vapor transport and deposition; the vapor phase aspects of corrosion, combustion, and energy systems; and extraterrestrial high-temperature species. This book is comprised of seven chapters and begins with an introduction to the nature of the high-temperature vapor state, the scope and literature of high-temp

  14. Experimental investigation of pyrolysis process of corn straw

    OpenAIRE

    Lei Wang; Shengqiang Shen; Shuhua Yang; Xinguang Shi

    2010-01-01

    The present paper was performed to analyze the pyrolysis process of corn straw. Based on the thermogravimetric analysis, the component of pyrolysis gas of corn straw was tested using the gas chromatograph analyzer. Experimental results showed that, as the reaction temperature increases, the component of H 2 and CH 4 increases, whereas the component of CO and CO 2 decreases. Finally, the mechanism of pyrolysis process of corn straw was revealed from the point of view of the molecular structure...

  15. Some effects of gas adsorption on the high temperature volatile release behavior of a terrestrial basalt, tektite and lunar soil

    Science.gov (United States)

    Graham, D. G.; Muenow, D. W.; Gibson, E. K., Jr.

    1979-01-01

    Mass pyrograms obtained from high-temperature, mass psectrometric pyrolysis of a glassy theoleiitic submarine basalt and a tektite, ground in air to less than 64 microns, have shown N2 and SO release patterns very similar to those from the pyrolysis of mature lunar soil fines. The N2 and CO release behavior from the terrestrial samples reproduces the biomodal, high-temperature (approximately 700 and 1050 C) features from the lunar samples. Unground portions of the basalt and tektite show no release of N2 and CO during pyrolysis. Grinding also alters the release behavior and absolute amounts of H2O and CO2. It is suggested that adsorption of atmospheric gases in addition to solar wind implantation of ions may account for the wide range of values in previously reported concentrations of carbon and nitrogen from lunar fines.

  16. High temperature superconductivity space experiment (HTSSE)

    International Nuclear Information System (INIS)

    Nisenoff, M.; Gubser, D.V.; Wolf, S.A.; Ritter, J.C.; Price, G.

    1991-01-01

    The Naval Research Laboratory (NRL) is exploring the feasibility of deploying high temperature superconductivity (HTS) devices and components in space. A variety of devices, primarily passive microwave and millimeter wave components, have been procured and will be integrated with a cryogenic refrigerator system and data acquisition system to form the space package, which will be launched late in 1992. This Space Experiment will demonstrate that this technology is sufficiently robust to survive the space environment and has the potential to significantly improved space communications systems. The devices for the initial launch (HTSSE-I) have been received by NRL and evaluated electrically, thermally and mechanically and will be integrated into the final space package early in 1991. In this paper the performance of the devices are summarized and some potential applications of HTS technology in space system are outlined

  17. High Temperature Particle Filtration Technology; TOPICAL

    International Nuclear Information System (INIS)

    Besmann, T.M.

    2001-01-01

    High temperature filtration can serve to improve the economic, environmental, and energy performance of chemical processes. This project was designed to evaluate the stability of filtration materials in the environments of the production of dimethyldichlorosilane (DDS). In cooperation with Dow Corning, chemical environments for the fluidized bed reactor where silicon is converted to DDS and the incinerator where vents are cornbusted were characterized. At Oak Ridge National Laboratory (ORNL) an exposure system was developed that could simulate these two environments. Filter samples obtained from third parties were exposed to the environments for periods up to 1000 hours. Mechanical properties before and after exposure were determined by burst-testing rings of filter material. The results indicated that several types of filter materials would likely perform well in the fluid bed environment, and two materials would be good candidates for the incinerator environment

  18. Preparation of silver doped high temperature superconductors

    International Nuclear Information System (INIS)

    Stavek, Jiri; Zapletal, Vladimir

    1989-01-01

    High temperature superconductors were prepared by the controlled double-jet precipitation to manipulate the chemical composition, composition gradients, average grain size, grain size distribution, and other factors which contribute to the actual properties and performance of HTSC. The cations (Y-Ba-Cu or Bi-Pb-Ca-Sr-Cu) and oxalic anions solutions were simultaneously separately introduced to the crystallizer with a stirred solution of gelatin under conditions where the temperature, excess of oxalic anions in solution, pH, reactant addition rate, and other reaction conditions were tightly controlled to prepare the high sinterability powder. To increase the sinterability of submicron particles of produced precursor, the silver ions were introduced at the end of the controlled double-jet precipitation. This approach improves the electrical and mechanical properties of produced HTSC specimens. The controlled double jet precipitation provides a viable technique for preparation of oxide superconductors and the process is amenable for scaling up

  19. Materials for high temperature reactor vessels

    International Nuclear Information System (INIS)

    Buenaventura Pouyfaucon, A.

    2004-01-01

    Within the 5th Euraton Framework Programme, a big effort is being made to promote and consolidate the development of the High Temperature Reactor (HTR). Empresarios Agrupados is participating in this project and among others, also forms part of the HTR-M project Materials for HTRs. This paper summarises the work carried out by Empresarios Agrupados regarding the material selection of the HTR Reactor Pressure Vessel (RPV). The possible candidate materials and the most promising ones are discussed. Design aspects such as the RPV sensitive zones and material damage mechanisms are considered. Finally, the applicability of the existing design Codes and Standards for the design of the HTR RPV is also discussed. (Author)

  20. IAEA high temperature gas cooled reactor activities

    International Nuclear Information System (INIS)

    Kendall, J.M.

    2001-01-01

    IAEA activities on high temperature gas cooled reactors are conducted with the review and support of Member States, primarily through the International Working Group on Gas Cooled Reactors (IWGGCR). This paper summarises the results of the IAEA gas cooled reactor project activities in recent years along with ongoing current activities through a review of Co-ordinated Research Projects (CRPs), meetings and other international efforts. A series of three recently completed CRPs have addressed the key areas of reactor physics for LEU fuel, retention of fission products, and removal of post shutdown decay heat through passive heat transport mechanisms. These activities along with other completed and ongoing supporting CRPs and meetings are summarised with reference to detailed documentation of the results. (author)

  1. Thermomechanics of composite structures under high temperatures

    CERN Document Server

    Dimitrienko, Yu I

    2016-01-01

    This pioneering book presents new models for the thermomechanical behavior of composite materials and structures taking into account internal physico-chemical transformations such as thermodecomposition, sublimation and melting at high temperatures (up to 3000 K). It is of great importance for the design of new thermostable materials and for the investigation of reliability and fire safety of composite structures. It also supports the investigation of interaction of composites with laser irradiation and the design of heat-shield systems. Structural methods are presented for calculating the effective mechanical and thermal properties of matrices, fibres and unidirectional, reinforced by dispersed particles and textile composites, in terms of properties of their constituent phases. Useful calculation methods are developed for characteristics such as the rate of thermomechanical erosion of composites under high-speed flow and the heat deformation of composites with account of chemical shrinkage. The author expan...

  2. Probing High Temperature Superconductors with Magnetometry in Ultrahigh Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lu [Univ. of Michigan, Ann Arbor, MI (United States)

    2017-07-26

    The objective of this research is to investigate the high-field magnetic properties of high temperature superconductors, materials that conduct electricity without loss. A technique known as high-resolution torque magnetometry that was developed to directly measure the magnetization of high temperature superconductors. This technique was implemented using the 65 Tesla pulsed magnetic field facility that is part of the National High Magnetic Field Laboratory at Los Alamos National Laboratory. This research addressed unanswered questions about the interplay between magnetism and superconductivity, determine the electronic structure of high temperature superconductors, and shed light on the mechanism of high temperature superconductivity and on potential applications of these materials in areas such as energy generation and power transmission. Further applications of the technology resolve the novel physical phenomena such as correlated topological insulators, and spin liquid state in quantum magnets.

  3. High temperature gas dynamics an introduction for physicists and engineers

    CERN Document Server

    Bose, Tarit K

    2014-01-01

    High Temperature Gas Dynamics is a primer for scientists, engineers, and students who would like to have a basic understanding of the physics and the behavior of high-temperature gases. It is a valuable tool for astrophysicists as well. The first chapters treat the basic principles of quantum and statistical mechanics and how to derive thermophysical properties from them. Special topics are included that are rarely found in other textbooks, such as the thermophysical and transport properties of multi-temperature gases and a novel method to compute radiative transfer. Furthermore, collision processes between different particles are discussed. Separate chapters deal with the production of high-temperature gases and with electrical emission in plasmas, as well as related diagnostic techniques.This new edition adds over 100 pages and includes the following updates: several sections on radiative properties of high temperature gases and various radiation models, a section on shocks in magneto-gas-dynamics, a sectio...

  4. Deep Trek High Temperature Electronics Project

    Energy Technology Data Exchange (ETDEWEB)

    Bruce Ohme

    2007-07-31

    This report summarizes technical progress achieved during the cooperative research agreement between Honeywell and U.S. Department of Energy to develop high-temperature electronics. Objects of this development included Silicon-on-Insulator (SOI) wafer process development for high temperature, supporting design tools and libraries, and high temperature integrated circuit component development including FPGA, EEPROM, high-resolution A-to-D converter, and a precision amplifier.

  5. Corrosion behaviour of high temperature alloys in the cooling gas of high temperature reactors

    International Nuclear Information System (INIS)

    Quadakkers, W.J.; Schuster, H.

    1989-01-01

    The reactive impurities in the primary cooling helium of advanced high temperature gas cooled reactors (HTGR) can cause oxidation, carburization or decarburization of the heat exchanging metallic components. By studies of the fundamental aspects of the corrosion mechanisms it became possible to define operating conditions under which the metallic construction materials show, from the viewpoint of technical application, acceptable corrosion behaviour. By extensive test programmes with exposure times of up to 30,000 hours, a data base has been obtained which allows a reliable extrapolation of the corrosion effects up to the envisaged service lives of the heat exchanging components. (author). 6 refs, 7 figs

  6. High temperature phase equilibria and phase diagrams

    CERN Document Server

    Kuo, Chu-Kun; Yan, Dong-Sheng

    2013-01-01

    High temperature phase equilibria studies play an increasingly important role in materials science and engineering. It is especially significant in the research into the properties of the material and the ways in which they can be improved. This is achieved by observing equilibrium and by examining the phase relationships at high temperature. The study of high temperature phase diagrams of nonmetallic systems began in the early 1900s when silica and mineral systems containing silica were focussed upon. Since then technical ceramics emerged and more emphasis has been placed on high temperature

  7. Development of High Temperature Solid Lubricant Coatings

    National Research Council Canada - National Science Library

    Bhattacharya, Rabi

    1999-01-01

    ... environment. To test this approach, UES and Cleveland State University have conducted experiments to form cesium oxythiotungstate, a high temperature lubricant, on Inconel 718 surface from composite coatings...

  8. A review of the chemical and physical mechanisms of the storage stability of fast pyrolysis bio-oils

    Energy Technology Data Exchange (ETDEWEB)

    Diebold, J.P.

    1999-01-27

    Understanding the fundamental chemical and physical aging mechanisms is necessary to learn how to produce a bio-oil that is more stable during shipping and storage. This review provides a basis for this understanding and identifies possible future research paths to produce bio-oils with better storage stability.

  9. Modeling of biomass pyrolysis

    International Nuclear Information System (INIS)

    Samo, S.R.; Memon, A.S.; Akhund, M.A.

    1995-01-01

    The fuels used in industry and power sector for the last two decades have become expensive. As a result renewable energy source have been emerging increasingly important, of these, biomass appears to be the most applicable in the near future. The pyrolysis of biomass plays a key role amongst the three major and important process generally encountered in a gas producer, namely, pyrolysis, combustion and reduction of combustion products. Each biomass has its own pyrolysis characteristics and this important parameters must be known for the proper design and efficient operation of a gasification system. Thermogravimetric analysis has been widely used to study the devolatilization of solid fuels, such as biomass. It provides the weight loss history of a sample heated at a predetermined rate as a function of time and temperature. This paper presents the experimental results of modelling the weight loss curves of the main biomass components i.e. cellulose, hemicellulose and lignin. Thermogravimetric analysis of main components of biomass showed that pyrolysis is first order reaction. Furthermore pyrolysis of cellulose and hemicelluloe can be regarded as taking place in two stages, for while lignin pyrolysis is a single stage process. This paper also describes the Thermogravimetric Analysis (TGA) technique to predict the weight retained during pyrolysis at any temperature, for number of biomass species, such as cotton stalk, bagasse ad graoundnut shell. (author)

  10. High temperature degradation in power plants and refineries

    Directory of Open Access Journals (Sweden)

    Furtado Heloisa Cunha

    2004-01-01

    Full Text Available Thermal power plants and refineries around the world share many of the same problems, namely aging equipment, high costs of replacement, and the need to produce more efficiently while being increasingly concerned with issues of safety and reliability. For equipment operating at high temperature, there are many different mechanisms of degradation, some of which interact, and the rate of accumulation of damage is not simple to predict. The paper discusses the mechanisms of degradation at high temperature and methods of assessment of such damage and of the remaining safe life for operation.

  11. Catalytic biomass pyrolysis process

    Science.gov (United States)

    Dayton, David C.; Gupta, Raghubir P.; Turk, Brian S.; Kataria, Atish; Shen, Jian-Ping

    2018-04-17

    Described herein are processes for converting a biomass starting material (such as lignocellulosic materials) into a low oxygen containing, stable liquid intermediate that can be refined to make liquid hydrocarbon fuels. More specifically, the process can be a catalytic biomass pyrolysis process wherein an oxygen removing catalyst is employed in the reactor while the biomass is subjected to pyrolysis conditions. The stream exiting the pyrolysis reactor comprises bio-oil having a low oxygen content, and such stream may be subjected to further steps, such as separation and/or condensation to isolate the bio-oil.

  12. Effect of hydrothermal carbonization on migration and environmental risk of heavy metals in sewage sludge during pyrolysis.

    Science.gov (United States)

    Liu, Tingting; Liu, Zhengang; Zheng, Qingfu; Lang, Qianqian; Xia, Yu; Peng, Nana; Gai, Chao

    2018-01-01

    The heavy metals distribution during hydrothermal carbonization (HTC) of sewage sludge, and pyrolysis of the resultant hydrochar was investigated and compared with raw sludge pyrolysis. The results showed that HTC reduced exchangeable/acid-soluble and reducible fraction of heavy metals and lowered the potential risk of heavy metals in sewage sludge. The pyrolysis favored the transformation of extracted/mobile fraction of heavy metals to residual form especially at high temperature, immobilizing heavy metals in the chars. Compared to the chars from raw sludge pyrolysis, the chars derived from hydrochar pyrolysis was more alkaline and had lower risk and less leachable heavy metals, indicating that pyrolysis imposed more positive effect on immobilization of heavy metals for the hydrochar than for sewage sludge. The present study demonstrated that HTC is a promising pretreatment prior to pyrolysis from the perspective of immobilization of heavy metals in sewage sludge. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. High-temperature x-ray camera

    Energy Technology Data Exchange (ETDEWEB)

    Il' inskii, A G; Romanova, A V; Prikhod' ko, N P

    1974-03-25

    A high-temperature x-ray chamber for taking x-ray photographs of flat horizontally set samples in a vacuum or gas medium is described. The chamber is fitted out with a water-cooled vacuum closed hull with a window letting the x-rays pass, a centering mechanism and a device for heating the samples. To widen its functional abilities the chamber is provided with a goniometric device, fixed immovably to the body foundation by means of two stands. Bearings are mounted to the stands; one of them is equipped with a screw wheel and an endless screw with a limb in the ring; a traverse to which a counter for the x-ray radiation is installed is attached to the shafts of both the bearings. The centering mechanism has a cooled metalic rod, which is connected through a spiral screw thread with the limb fixable by a fork. The position of the shaft of rotation of the counter is adjusted with the help of a nit, extended through the plug openings, positioned on the stands. The chamber can be applied for x-ray structural analyses.

  14. Recrystallization of high temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kouzoudis, Dimitris [Iowa State Univ., Ames, IA (United States)

    1996-05-09

    Currently one of the most widely used high Tc superconductors is the Bi-based compounds Bi2Sr2CaCu2Oz and Bi2Sr2Ca2Cu3Oz (known as BSCCO 2212 and 2223 compounds) with Tc values of about 85 K and 110 K respectively. Lengths of high performance conductors ranging from 100 to 1000 m long are routinely fabricated and some test magnets have been wound. An additional difficulty here is that although Bi-2212 and Bi-2223 phases exist over a wide range of stoichiometries, neither has been prepared in phase-pure form. So far the most successful method of constructing reliable and robust wires or tapes is the so called powder-in-tube (PIT) technique [1, 2, 3, 4, 5, 6, 7] in which oxide powder of the appropriate stoichiometry and phase content is placed inside a metal tube, deformed into the desired geometry (round wire or flat tape), and annealed to produce the desired superconducting properties. Intermediate anneals are often incorporated between successive deformation steps. Silver is the metal used in this process because it is the most compatible with the reacting phase. In all of the commercial processes for BSCCO, Ag seems to play a special catalytic role promoting the growth of high performance aligned grains that grow in the first few micrometers near the Ag/BSCCO interface. Adjacent to the Ag, the grain alignment is more perfect and the current density is higher than in the center of the tape. It is known that Ag lowers the melting point of several of the phases but the detailed mechanism for growth of these high performance grains is not clearly understood. The purpose of this work is to study the nucleation and growth of the high performance material at this interface.

  15. Evaluation of high temperature pressure sensors

    International Nuclear Information System (INIS)

    Choi, In-Mook; Woo, Sam-Yong; Kim, Yong-Kyu

    2011-01-01

    It is becoming more important to measure the pressure in high temperature environments in many industrial fields. However, there is no appropriate evaluation system and compensation method for high temperature pressure sensors since most pressure standards have been established at room temperature. In order to evaluate the high temperature pressure sensors used in harsh environments, such as high temperatures above 250 deg. C, a specialized system has been constructed and evaluated in this study. The pressure standard established at room temperature is connected to a high temperature pressure sensor through a chiller. The sensor can be evaluated in conditions of changing standard pressures at constant temperatures and of changing temperatures at constant pressures. According to the evaluation conditions, two compensation methods are proposed to eliminate deviation due to sensitivity changes and nonlinear behaviors except thermal hysteresis.

  16. Heat transfer from a high temperature condensable mixture

    International Nuclear Information System (INIS)

    Chan, S.H.; Cho, D.H.; Condiff, D.W.

    1978-01-01

    A new development in heat transfer is reported. It is concerned with heat transfer from a gaseous mixture that contains a condensable vapor and is at very high temperature. In the past, heat transfer associated with either a condensable mixture at low temperature or a noncondensable mixture at high temperature has been investigated. The former reduces to the classical problem of fog formation in, say, atmosphere where the rate of condensation is diffusion controlled (molecular or conductive diffusions). In the presence of noncondensable gases, heat transfer to a cooler boundary by this mechanism is known to be drastically reduced. In the latter case, where the high temperature mixture is noncondensable, radiative transfer may become dominant and a vast amount of existing literature exists on this class of problem. A fundamentally different type of problem of relevance to recent advances in open cycle MHD power plants and breeder reactor safety is considered. In the advanced coal-fired power plant using MHD as a topping cycle, a condensable mixture is encountered at temperatures of 2000 to 3000 0 . Condensation of the vaporized slag and seed materials at such a high temperature can take place in the MHD generator channel as well as in the radiant boiler. Similarly, in breeder reactor accident analyses involving hypothetical core disruptive accidents, a UO 2 vapor mixture at 400 0 K or higher is often considered. Since the saturation temperature of UO 2 at one atmosphere is close to 4000 0 K, condensation is also likely at a very high temperature. Accordingly, an objective of the present work is to provide an understanding of heat transfer and condensation mechanics insystems containing a high temperature condensable mixture. The results of the study show that, when a high temperature mixture is in contact with a cooler surface, a thermal boundary layer develops rapidly because of intensive radiative cooling from the mixture

  17. Incineration, pyrolysis and gasification of electronic waste

    Science.gov (United States)

    Gurgul, Agnieszka; Szczepaniak, Włodzimierz; Zabłocka-Malicka, Monika

    2017-11-01

    Three high temperature processes of the electronic waste processing: smelting/incineration, pyrolysis and gasification were shortly discussed. The most distinctive feature of electronic waste is complexity of components and their integration. This type of waste consists of polymeric materials and has high content of valuable metals that could be recovered. The purpose of thermal treatment of electronic waste is elimination of plastic components (especially epoxy resins) while leaving non-volatile mineral and metallic phases in more or less original forms. Additionally, the gaseous product of the process after cleaning may be used for energy recovery or as syngas.

  18. Incineration, pyrolysis and gasification of electronic waste

    Directory of Open Access Journals (Sweden)

    Gurgul Agnieszka

    2017-01-01

    Full Text Available Three high temperature processes of the electronic waste processing: smelting/incineration, pyrolysis and gasification were shortly discussed. The most distinctive feature of electronic waste is complexity of components and their integration. This type of waste consists of polymeric materials and has high content of valuable metals that could be recovered. The purpose of thermal treatment of electronic waste is elimination of plastic components (especially epoxy resins while leaving non-volatile mineral and metallic phases in more or less original forms. Additionally, the gaseous product of the process after cleaning may be used for energy recovery or as syngas.

  19. Quantum electrodynamics at high temperature. 2

    International Nuclear Information System (INIS)

    Alvarez-Estrada, R.F.

    1988-01-01

    The photon sector of QED in d = 3 spatial dimensions is analyzed at high temperature thereby generalizing nontrivially a previous study for d = 1. The imaginary time formalism and an improved renormalized perturbation theory which incorporates second order Debye screening are used. General results are presented for the leading high temperature contributions to all renormalized connected photon Green's functions for fixed external momenta (much smaller than the temperature) to all orders in the improved perturbation theory. Those leading contributions are ultraviolet finite, infrared convergent and gauge invariant, and display an interesting form of dimensional reduction at high temperature. A new path integral representations is given for the high temperature partition function with an external photon source, which is shown to generate all leading high temperature Green's functions mentioned above, and, so, it displays neatly the kind of dimensional reduction which makes QED to become simpler at high temperature. This limiting partition function corresponds to an imaginary time dependent electron positron field interacting with an electromagnetic field at zero imaginary time, and it depends on the renormalized electron mass and electric charge, the second order contribution to the usual renormalization constant Z 3 and a new mass term, which is associated to the photon field with vanishing Lorentz index. The new mass term corresponds to a finite number of diagrams in the high temperature improved perturbation theory and carriers ultraviolet divergences which are compensated for by other contributions (so that the leading high temperature Green's functions referred to above are ultraviolet finite). The dominant high temperature contributions to the renormalized thermodynamic potential to all perturbative orders: i) are given in terms of the above leading high-temperature contributions to the photon Green's functions (except for a few diagrams of low order in the

  20. An experimental and kinetic modeling study of glycerol pyrolysis

    International Nuclear Information System (INIS)

    Fantozzi, F.; Frassoldati, A.; Bartocci, P.; Cinti, G.; Quagliarini, F.; Bidini, G.; Ranzi, E.M.

    2016-01-01

    Highlights: • Glycerol pyrolysis can produce about 44–48%v hydrogen at 750–800 °C. • A simplified 452 reactions kinetic model of glycerol pyrolysis has been developed. • The model has good agreement with experimental data. • Non condensable gas yields can reach 70%. - Abstract: Pyrolysis of glycerol, a by-product of the biodiesel industry, is an important potential source of hydrogen. The obtained high calorific value gas can be used either as a fuel for combined heat and power (CHP) generation or as a transportation fuel (for example hydrogen to be used in fuel cells). Optimal process conditions can improve glycerol pyrolysis by increasing gas yield and hydrogen concentration. A detailed kinetic mechanism of glycerol pyrolysis, which involves 137 species and more than 4500 reactions, was drastically simplified and reduced to a new skeletal kinetic scheme of 44 species, involved in 452 reactions. An experimental campaign with a batch pyrolysis reactor was properly designed to further validate the original and the skeletal mechanisms. The comparisons between model predictions and experimental data strongly suggest the presence of a catalytic process promoting steam reforming of methane. High pyrolysis temperatures (750–800 °C) improve process performances and non-condensable gas yields of 70%w can be achieved. Hydrogen mole fraction in pyrolysis gas is about 44–48%v. The skeletal mechanism developed can be easily used in Computational Fluid Dynamic software, reducing the simulation time.

  1. Kinetics of ethylcyclohexane pyrolysis and oxidation: An experimental and detailed kinetic modeling study

    KAUST Repository

    Wang, Zhandong

    2015-07-01

    Ethylcyclohexane (ECH) is a model compound for cycloalkanes with long alkyl side-chains. A preliminary investigation on ECH (Wang et al., Proc. Combust. Inst., 35, 2015, 367-375) revealed that an accurate ECH kinetic model with detailed fuel consumption mechanism and aromatic growth pathways, as well as additional ECH pyrolysis and oxidation data with detailed species concentration covering a wide pressure and temperature range are required to understand the ECH combustion kinetics. In this work, the flow reactor pyrolysis of ECH at various pressures (30, 150 and 760Torr) was studied using synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (PIMS) and gas chromatography (GC). The mole fraction profiles of numerous major and minor species were evaluated, and good agreement was observed between the PIMS and GC data sets. Furthermore, a fuel-rich burner-stabilized laminar premixed ECH/O2/Ar flame at 30Torr was studied using synchrotron VUV PIMS. A detailed kinetic model for ECH high temperature pyrolysis and oxidation was developed and validated against the pyrolysis and flame data performed in this work. Further validation of the kinetic model is presented against literature data including species concentrations in jet-stirred reactor oxidation, ignition delay times in a shock tube, and laminar flame speeds at various pressures and equivalence ratios. The model well predicts the consumption of ECH, the growth of aromatics, and the global combustion properties. Reaction flux and sensitivity analysis were utilized to elucidate chemical kinetic features of ECH combustion under various reaction conditions. © 2015 The Combustion Institute.

  2. Microstructure degradation in high temperature fatigue of TiAl

    Czech Academy of Sciences Publication Activity Database

    Kruml, Tomáš; Obrtlík, Karel

    2014-01-01

    Roč. 65, AUG (2014), s. 28-32 ISSN 0142-1123 R&D Projects: GA ČR(CZ) GAP107/11/0704 Institutional support: RVO:68081723 Keywords : Low cycle fatigue * lamellar TiAl alloy * high temperature fatigue * dislocations Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.275, year: 2014

  3. High temperature alloys and ceramic heat exchanger

    International Nuclear Information System (INIS)

    Okamoto, Masaharu

    1984-04-01

    From the standpoint of energy saving, the future operating temperatures of process heat and gas turbine plants will become higher. For this purpose, ceramics is the most promissing candidate material in strength for application to high-temperature heat exchangers. This report deals with a servey of characteristics of several high-temperature metallic materials and ceramics as temperature-resistant materials; including a servey of the state-of-the-art of ceramic heat exchanger technologies developed outside of Japan, and a study of their application to the intermediate heat exchanger of VHTR (a very-high-temperature gas-cooled reactor). (author)

  4. High-temperature peridotites - lithospheric or asthenospheric?

    International Nuclear Information System (INIS)

    Hops, J.J.; Gurney, J.J.

    1990-01-01

    High-temperature peridotites by definition yield equilibration temperatures greater than 1100 degrees C. On the basis of temperature and pressure calculations, these high-temperature peridotites are amongst the deepest samples entrained by kimberlites on route to the surface. Conflicting models proposing either a lithospheric or asthenospheric origin for the high-temperature peridotites have been suggested. A detailed study of these xenoliths from a single locality, the Jagersfontein kimberlite in the Orange Free State, has been completed as a means of resolving this controversy. 10 refs., 2 figs

  5. High temperature resistant cermet and ceramic compositions

    Science.gov (United States)

    Phillips, W. M. (Inventor)

    1978-01-01

    Cermet compositions having high temperature oxidation resistance, high hardness and high abrasion and wear resistance, and particularly adapted for production of high temperature resistant cermet insulator bodies are presented. The compositions are comprised of a sintered body of particles of a high temperature resistant metal or metal alloy, preferably molybdenum or tungsten particles, dispersed in and bonded to a solid solution formed of aluminum oxide and silicon nitride, and particularly a ternary solid solution formed of a mixture of aluminum oxide, silicon nitride and aluminum nitride. Also disclosed are novel ceramic compositions comprising a sintered solid solution of aluminum oxide, silicon nitride and aluminum nitride.

  6. High temperature oxidation behavior of ODS steels

    Science.gov (United States)

    Kaito, T.; Narita, T.; Ukai, S.; Matsuda, Y.

    2004-08-01

    Oxide dispersion strengthened (ODS) steels are being developing for application as advanced fast reactor cladding and fusion blanket materials, in order to allow increased operation temperature. Oxidation testing of ODS steel was conducted under a controlled dry air atmosphere to evaluate the high temperature oxidation behavior. This showed that 9Cr-ODS martensitic steels and 12Cr-ODS ferritic steels have superior high temperature oxidation resistance compared to 11 mass% Cr PNC-FMS and 17 mass% Cr ferritic stainless steel. This high temperature resistance is attributed to earlier formation of the protective α-Cr 2O 3 on the outer surface of ODS steels.

  7. Symposium on high temperature and materials chemistry

    International Nuclear Information System (INIS)

    1989-10-01

    This volume contains the written proceedings of the Symposium on High Temperature and Materials Chemistry held in Berkeley, California on October 24--25, 1989. The Symposium was sponsored by the Materials and Chemical Sciences Division of Lawrence Berkeley Laboratory and by the College of Chemistry of the University of California at Berkeley to discuss directions, trends, and accomplishments in the field of high temperature and materials chemistry. Its purpose was to provide a snapshot of high temperature and materials chemistry and, in so doing, to define status and directions

  8. Symposium on high temperature and materials chemistry

    Energy Technology Data Exchange (ETDEWEB)

    1989-10-01

    This volume contains the written proceedings of the Symposium on High Temperature and Materials Chemistry held in Berkeley, California on October 24--25, 1989. The Symposium was sponsored by the Materials and Chemical Sciences Division of Lawrence Berkeley Laboratory and by the College of Chemistry of the University of California at Berkeley to discuss directions, trends, and accomplishments in the field of high temperature and materials chemistry. Its purpose was to provide a snapshot of high temperature and materials chemistry and, in so doing, to define status and directions.

  9. Electronic phase separation and high temperature superconductors

    International Nuclear Information System (INIS)

    Kivelson, S.A.

    1994-01-01

    The authors review the extensive evidence from model calculations that neutral holes in an antiferromagnet separate into hole-rich and hole-poor phases. All known solvable limits of models of holes in a Heisenberg antiferromagnet exhibit this behavior. The authors show that when the phase separation is frustrated by the introduction of long-range Coulomb interactions, the typical consequence is either a modulated (charge density wave) state or a superconducting phase. The authors then review some of the strong experimental evidence supporting an electronically-driven phase separation of the holes in the cuprate superconductors and the related Ni oxides. Finally, the authors argue that frustrated phase separation in these materials can account for many of the anomalous normal state properties of the high temperature superconductors and provide the mechanism of superconductivity. In particular, it is shown that the T-linear resistivity of the normal state is a paraconductivity associated with a novel composite pairing, although the ordered superconducting state is more conventional

  10. Development of high temperature strain gage, (5)

    International Nuclear Information System (INIS)

    Yuuki, Hiroshi; Kobayashi, Yukio; Kanai, Kenji; Yamaura, Yoshio

    1976-01-01

    Development and improvement of resistance wire type strain gages usable for experimental measurement of thermal strains generated at high temperature in various structures and equipments that consist of a Fast Breeder Reactor have been carried out, and various characteristics of the strain gages have been investigated. Based on the results obtained up to now, development and research of this time mainly aim to improve strain and fatigue characteristics. As the results, characteristics of strain gages with sensing elements of nichrome V are improved, specifically mechanical hysteresis is decreased, strain limit is increased, etc. Also, improvement is recognized in thermal output, and it becomes clear that dummy gages work effectively. However, a filling method of MgO and an inserting method of active-dummy elements are selected as primary objects to improve strain characteristics, and many hours are taken for these objects, so confirmations of characteristics of platinum-tungsten strain gages, strain sensing elements of which are troublesome to produce, have not been completely done, though the performance of the gages has been improved in several points. As to nichrome V strain gages, there is a fair prospect of obtaining ones, specifications of which are quite close to the goal, though problems in manufacturing technics remain for future. As to platinum-tungsten strain gages, it is expected that similar strain gages to nichrome V are obtainable by improvement in manufacturing of sensing elements. (auth.)

  11. The moon as a high temperature condensate.

    Science.gov (United States)

    Anderson, D. L.

    1973-01-01

    The accretion during condensation mechanism, if it occurs during the early over-luminous stage of the sun, can explain the differences in composition of the terrestrial planets and the moon. An important factor is the variation of pressure and temperature with distance from the sun, and in the case of the moon and captured satellites of other planets, with distance from the median plane. Current estimates of the temperature and pressure in the solar nebula suggest that condensation will not be complete in the vicinity of the terrestrial planets, and that depending on location, iron, magnesium silicates and the volatiles will be at least partially held in the gaseous phase and subject to separation from the dust by solar wind and magnetic effects associated with the transfer of angular momentum just before the sun joins the Main Sequence. Many of the properties of the moon, including the 'enrichment' in Ca, Al, Ti, U, Th, Ba, Sr and the REE and the 'depletion' in Fe, Rb, K, Na and other volatiles can be understood if the moon represents a high temperature condensate from the solar nebula.

  12. Diffusion and plasticity at high temperature

    Science.gov (United States)

    Philibert, J.

    1991-06-01

    High temperature plastic deformation requires atomic migration whatever the mechanism of deformation. The constitutive equations contain a diffusion coefficient and the deformation rate follows an Arrhenius law. This paper will only discuss the case of viscous creep in order to elucidate the nature of the diffusion processes and the expression of the diffusion coefficient involved in alloys or compounds. La déformation plastique à haute température met en jeu des migrations atomiques, quel que soit le mécanisme de déformation. Les lois de comportement contiennent donc un coefficient de diffusion et la vitesse de déformation obéit à une loi d'Arrhenius. Dans cet article, qui ne conceme qu'un seul type de déformation, lefluage visqueux, on s'efforce de préciser la nature des processus de diffusion et du coefficient de diffusion mis en jeu dans le cas des alliages et des composés.

  13. Margins in high temperature leak-before-break assessments

    International Nuclear Information System (INIS)

    Budden, P.J.; Hooton, D.G.

    1997-01-01

    Developments in the defect assessment procedure R6 to include high-temperature mechanisms in Leak-before-Break arguments are described. In particular, the effect of creep on the time available to detect a leak and on the crack opening area, and hence leak rate, is discussed. The competing influence of these two effects is emphasized by an example. The application to Leak-before-Break of the time-dependent failure assessment diagram approach for high temperature defect assessment is then outlined. The approach is shown to be of use in assessing the erosion of margins by creep

  14. Annual report of the Division of High Temperature Engineering

    International Nuclear Information System (INIS)

    1982-10-01

    Research activities conducted in the Division of High Temperature Engineering during fiscal 1981 are described. R and D works of our division are mainly related to a multi-purpose very high-temperature gas-cooled reactor (VHTR) and a fusion reactor. This report deals with the main results obtained on material test, development of computer codes, heat transfer, fluid-dynamics, structural mechanics and the construction of an M + A (Mother and Adapter) section of a HENDEL (Helium Engineering Demonstration Loop) as well. (author)

  15. 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.

  16. High Temperature Materials Characterization and Advanced Materials Development

    International Nuclear Information System (INIS)

    Ryu, Woo Seog; Kim, D. H.; Kim, S. H.

    2007-06-01

    The project has been carried out for 2 years in stage III in order to achieve the final goals of performance verification of the developed materials, after successful development of the advanced high temperature material technologies for 3 years in Stage II. The mechanical and thermal properties of the advanced materials, which were developed during Stage II, were evaluated at high temperatures, and the modification of the advanced materials were performed. Moreover, a database management system was established using user-friendly knowledge-base scheme to complete the integrated-information material database in KAERI material division

  17. Margins in high temperature leak-before-break assessments

    Energy Technology Data Exchange (ETDEWEB)

    Budden, P.J.; Hooton, D.G.

    1997-04-01

    Developments in the defect assessment procedure R6 to include high-temperature mechanisms in Leak-before-Break arguments are described. In particular, the effect of creep on the time available to detect a leak and on the crack opening area, and hence leak rate, is discussed. The competing influence of these two effects is emphasized by an example. The application to Leak-before-Break of the time-dependent failure assessment diagram approach for high temperature defect assessment is then outlined. The approach is shown to be of use in assessing the erosion of margins by creep.

  18. Biennial report of the Department of High Temperature Engineering

    International Nuclear Information System (INIS)

    1984-10-01

    Research activities conducted in the Department of High Temperature Engineering during fiscal 1982 and 1983 are described. Research and development works of the department are mainly related to a multipurpose very high-temperature gas-cooled reactor (VHTR) and a fusion reactor. This report deals with the main results obtained on material test, heat transfer, fluid-dynamics, structural mechanics, development of computer codes and operation of an M + A (Mother and Adapter) section and a T 1 test section of the HENDEL (Helium Engineering Demonstration Loop). (author)

  19. High Temperature Integrated Thermoelectric Ststem and Materials

    Energy Technology Data Exchange (ETDEWEB)

    Mike S. H. Chu

    2011-06-06

    The final goal of this project is to produce, by the end of Phase II, an all ceramic high temperature thermoelectric module. Such a module design integrates oxide ceramic n-type, oxide ceramic p-type materials as thermoelectric legs and oxide ceramic conductive material as metalizing connection between n-type and p-type legs. The benefits of this all ceramic module are that it can function at higher temperatures (> 700 C), it is mechanically and functionally more reliable and it can be scaled up to production at lower cost. With this all ceramic module, millions of dollars in savings or in new opportunities recovering waste heat from high temperature processes could be made available. A very attractive application will be to convert exhaust heat from a vehicle to reusable electric energy by a thermoelectric generator (TEG). Phase I activities were focused on evaluating potential n-type and p-type oxide compositions as the thermoelectric legs. More than 40 oxide ceramic powder compositions were made and studied in the laboratory. The compositions were divided into 6 groups representing different material systems. Basic ceramic properties and thermoelectric properties of discs sintered from these powders were measured. Powders with different particles sizes were made to evaluate the effects of particle size reduction on thermoelectric properties. Several powders were submitted to a leading thermoelectric company for complete thermoelectric evaluation. Initial evaluation showed that when samples were sintered by conventional method, they had reasonable values of Seebeck coefficient but very low values of electrical conductivity. Therefore, their power factors (PF) and figure of merits (ZT) were too low to be useful for high temperature thermoelectric applications. An unconventional sintering method, Spark Plasma Sintering (SPS) was determined to produce better thermoelectric properties. Particle size reduction of powders also was found to have some positive benefits

  20. High Temperature Electrostrictive Ceramics, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — TRS Technologies proposes to develop high temperature electrostrictors from bismuth-based ferroelectrics. These materials will exhibit high strain and low loss in...

  1. High Temperature Superconductor Bolometers for Planetary Science

    Data.gov (United States)

    National Aeronautics and Space Administration — This work is a design study of an instrument optimized for JPL's novel high temperature superconductor bolometers. The work involves designing an imaging...

  2. Resonance integral calculations for high temperature reactors

    International Nuclear Information System (INIS)

    Blake, J.P.H.

    1960-02-01

    Methods of calculation of resonance integrals of finite dilution and temperature are given for both, homogeneous and heterogeneous geometries, together with results obtained from these methods as applied to the design of high temperature reactors. (author)

  3. Panel report on high temperature ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Nolet, T C [ed.

    1979-01-01

    Fundamental research is reported concerning high temperature ceramics for application in turbines, engines, batteries, gasifiers, MHD, fuel cells, heat exchangers, and hot wall combustors. Ceramics microstructure and behavior are included. (FS)

  4. Novel High Temperature Strain Gauge, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced high-temperature sensor technology and bonding methods are of great interests in designing and developing advanced future aircraft. Current state-of-the-art...

  5. High-Temperature Cuprate Superconductors Experiment, Theory, and Applications

    CERN Document Server

    Plakida, Nikolay Maksimilianovich

    2010-01-01

    High-Temperature Cuprate Superconductors provides an up-to-date and comprehensive review of the properties of these fascinating materials. The essential properties of high-temperature cuprate superconductors are reviewed on the background of their theoretical interpretation. The experimental results for structural, magnetic, thermal, electric, optical and lattice properties of various cuprate superconductors are presented with respect to relevant theoretical models. A critical comparison of various theoretical models involving strong electron correlations, antiferromagnetic spin fluctuations, phonons and excitons provides a background for understanding of the mechanism of high-temperature superconductivity. Recent achievements in their applications are also reviewed. A large number of illustrations and tables gives valuable information for specialists. A text-book level presentation with formulation of a general theory of strong-coupling superconductivity will help students and researches to consolidate their...

  6. High-temperature cuprate superconductors. Experiment, theory, and applications

    International Nuclear Information System (INIS)

    Plakida, Nikolay

    2010-01-01

    High-Temperature Cuprate Superconductors provides an up-to-date and comprehensive review of the properties of these fascinating materials. The essential properties of high-temperature cuprate superconductors are reviewed on the background of their theoretical interpretation. The experimental results for structural, magnetic, thermal, electric, optical and lattice properties of various cuprate superconductors are presented with respect to relevant theoretical models. A critical comparison of various theoretical models involving strong electron correlations, antiferromagnetic spin fluctuations, phonons and excitons provides a background for understanding of the mechanism of high-temperature superconductivity. Recent achievements in their applications are also reviewed. A large number of illustrations and tables gives valuable information for specialists. A text-book level presentation with formulation of a general theory of strong-coupling superconductivity will help students and researches to consolidate their knowledge of this remarkable class of materials. (orig.)

  7. Probability based high temperature engineering creep and structural fire resistance

    CERN Document Server

    Razdolsky, Leo

    2017-01-01

    This volume on structural fire resistance is for aerospace, structural, and fire prevention engineers; architects, and educators. It bridges the gap between prescriptive- and performance-based methods and simplifies very complex and comprehensive computer analyses to the point that the structural fire resistance and high temperature creep deformations will have a simple, approximate analytical expression that can be used in structural analysis and design. The book emphasizes methods of the theory of engineering creep (stress-strain diagrams) and mathematical operations quite distinct from those of solid mechanics absent high-temperature creep deformations, in particular the classical theory of elasticity and structural engineering. Dr. Razdolsky’s previous books focused on methods of computing the ultimate structural design load to the different fire scenarios. The current work is devoted to the computing of the estimated ultimate resistance of the structure taking into account the effect of high temperatur...

  8. High temperature superconductors and other superfluids

    CERN Document Server

    Alexandrov, A S

    2017-01-01

    Written by eminent researchers in the field, this text describes the theory of superconductivity and superfluidity starting from liquid helium and a charged Bose-gas. It also discusses the modern bipolaron theory of strongly coupled superconductors, which explains the basic physical properties of high-temperature superconductors. This book will be of interest to fourth year graduate and postgraduate students, specialist libraries, information centres and chemists working in high-temperature superconductivity.

  9. PLA recycling by hydrolysis at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Cristina, Annesini Maria; Rosaria, Augelletti; Sara, Frattari, E-mail: sara.frattari@uniroma1.it; Fausto, Gironi [Department of Chemical Engineering Materials Environment, University of Rome “La Sapienza”, Via Eudossiana 18– 00184 Roma (Italy)

    2016-05-18

    In this work the process of PLA hydrolysis at high temperature was studied, in order to evaluate the possibility of chemical recycling of this polymer bio-based. In particular, the possibility to obtain the monomer of lactic acid from PLA degradation was investigated. The results of some preliminary tests, performed in a laboratory batch reactor at high temperature, are presented: the experimental results show that the complete degradation of PLA can be obtained in relatively low reaction times.

  10. High-temperature materials and structural ceramics

    International Nuclear Information System (INIS)

    1990-01-01

    This report gives a survey of research work in the area of high-temperature materials and structural ceramics of the KFA (Juelich Nuclear Research Center). The following topics are treated: (1) For energy facilities: ODS materials for gas turbine blades and heat exchangers; assessment of the remaining life of main steam pipes, material characterization and material stress limits for First-Wall components; metallic and graphitic materials for high-temperature reactors. (2) For process engineering plants: composites for reformer tubes and cracking tubes; ceramic/ceramic joints and metal/ceramic and metal/metal joints; Composites and alloys for rolling bearing and sliding systems up to application temperatures of 1000deg C; high-temperature corrosion of metal and ceramic material; porous ceramic high-temperature filters and moulding coat-mix techniques; electrically conducting ceramic material (superconductors, fuel cells, solid electrolytes); high-temperature light sources (high-temperature chemistry); oil vapor engines with caramic components; ODS materials for components in diesel engines and vehicle gas turbines. (MM) [de

  11. On high temperature strength of carbon steels

    International Nuclear Information System (INIS)

    Ichinose, Hiroyuki; Tamura, Manabu; Kanero, Takahiro; Ihara, Yoshihito

    1977-01-01

    In the steels for high temperature use, the oxidation resistance is regarded as important, but carbon steels show enough oxidation resistance to be used continuously at the temperature up to 500 deg. C if the strength is left out of consideration, and up to 450 deg. C even when the strength is taken into account. Moreover, the production is easy, the workability and weldability are good, and the price is cheap in carbon steels as compared with alloy steels. In the boilers for large thermal power stations, 0.15-0.30% C steels are used for reheater tubes, main feed water tubes, steam headers, wall water tubes, economizer tubes, bypass pipings and others, and they account for 70% of all steel materials used for the boilers of 350 MW class and 30% in 1000 MW class. The JIS standard for the carbon steels for high temperature use and the related standards in foreign countries are shown. The high temperature strength of carbon steels changes according to the trace elements, melting and heat treatment as well as the main compositions of C, Si and Mn. Al and N affect the high temperature strength largely. The characteristics of carbon steels after the heating for hours, the factors controlling the microstructure and high temperature strength, and the measures to improve the high temperature strength of carbon steels are explained. (Kako, I.)

  12. High temperature, oxygen, and performance: Insights from reptiles and amphibians.

    Science.gov (United States)

    Gangloff, Eric J; Telemeco, Rory S

    2018-04-25

    Much recent theoretical and empirical work has sought to describe the physiological mechanisms underlying thermal tolerance in animals. Leading hypotheses can be broadly divided into two categories that primarily differ in organizational scale: 1) high temperature directly reduces the function of subcellular machinery, such as enzymes and cell membranes, or 2) high temperature disrupts system-level interactions, such as mismatches in the supply and demand of oxygen, prior to having any direct negative effect on the subcellular machinery. Nonetheless, a general framework describing the contexts under which either subcellular component or organ system failure limits organisms at high temperatures remains elusive. With this commentary, we leverage decades of research on the physiology of ectothermic tetrapods (amphibians and non-avian reptiles) to address these hypotheses. Available data suggest both mechanisms are important. Thus, we expand previous work and propose the Hierarchical Mechanisms of Thermal Limitation (HMTL) hypothesis, which explains how subcellular and organ system failures interact to limit performance and set tolerance limits at high temperatures. We further integrate this framework with the thermal performance curve paradigm commonly used to predict the effects of thermal environments on performance and fitness. The HMTL framework appears to successfully explain diverse observations in reptiles and amphibians and makes numerous predictions that remain untested. We hope that this framework spurs further research in diverse taxa and facilitates mechanistic forecasts of biological responses to climate change.

  13. Pyrolysis of Pine Wood, Experiments and Theory

    DEFF Research Database (Denmark)

    Fjellerup, Jan Søren; Ahrenfeldt, Jesper; Henriksen, Ulrik Birk

    In this study, pinewood has been pyrolyzed using a fixed heating rate with a variable end-temperature. The pyrolysis process has been simulated using a mechanism with three parallel reactions for the formation of char, gas and tar. First order irreversible kinetics is assumed. This kind of model...... may predict the variation of product yield with operating conditions such as temperature and heating rate. The system of coupled differential equations describing the pyrolysis process is solved using the software DYMOLA. Various literature values for kinetic parameters have been compared...

  14. NMR spectroscopy of coal pyrolysis products

    Energy Technology Data Exchange (ETDEWEB)

    Polonov, V.M.; Kalabin, G.A.; Kushnarev, D.F.; Shevchenko, G.G.

    1985-12-01

    The authors consider the scope for using H 1 and C 13 NMR spectroscopy to describe the products from coal pyrolysis and hydrogenization. The accuracy of the structural information provided by the best NMR methods is also considered. The stuctural parameters derived from H 1 and C 13 NMR spectra are presented. Results demonstrate the high accuracy and sensitivity of the structural information provided by H 1 AND C 13 NMR spectra for coal products. There are substantial structural differences between the soluble products from medium-temperature coking of Cheremkhov coal and high-speed pyrolysis of Kan-Acha coal, and also differences in behavior during hydrogenation. These differences are related to the structure of the organic matter in the initial coal and to differences in the pyrolysis mechanisms.

  15. Properties of Reinforced Concrete Steel Rebars Exposed to High Temperatures

    OpenAIRE

    Topçu, İlker Bekir; Karakurt, Cenk

    2008-01-01

    The deterioration of the mechanical properties of yield strength and modulus of elasticity is considered as the primary element affecting the performance of steel structures under fire. In this study, hot-rolled S220 and S420 reinforcement steel rebars were subjected to high temperatures to investigate the fire performance of these materials. It is aimed to determine the remaining mechanical properties of steel rebars after elevated temperatures. Steels were subjected to 20, 100, 200, 300, 5...

  16. Investigations into High Temperature Components and Packaging

    Energy Technology Data Exchange (ETDEWEB)

    Marlino, L.D.; Seiber, L.E.; Scudiere, M.B.; M.S. Chinthavali, M.S.; McCluskey, F.P.

    2007-12-31

    The purpose of this report is to document the work that was performed at the Oak Ridge National Laboratory (ORNL) in support of the development of high temperature power electronics and components with monies remaining from the Semikron High Temperature Inverter Project managed by the National Energy Technology Laboratory (NETL). High temperature electronic components are needed to allow inverters to operate in more extreme operating conditions as required in advanced traction drive applications. The trend to try to eliminate secondary cooling loops and utilize the internal combustion (IC) cooling system, which operates with approximately 105 C water/ethylene glycol coolant at the output of the radiator, is necessary to further reduce vehicle costs and weight. The activity documented in this report includes development and testing of high temperature components, activities in support of high temperature testing, an assessment of several component packaging methods, and how elevated operating temperatures would impact their reliability. This report is organized with testing of new high temperature capacitors in Section 2 and testing of new 150 C junction temperature trench insulated gate bipolar transistor (IGBTs) in Section 3. Section 4 addresses some operational OPAL-GT information, which was necessary for developing module level tests. Section 5 summarizes calibration of equipment needed for the high temperature testing. Section 6 details some additional work that was funded on silicon carbide (SiC) device testing for high temperature use, and Section 7 is the complete text of a report funded from this effort summarizing packaging methods and their reliability issues for use in high temperature power electronics. Components were tested to evaluate the performance characteristics of the component at different operating temperatures. The temperature of the component is determined by the ambient temperature (i.e., temperature surrounding the device) plus the

  17. High-Temperature Corrosion Behavior of Alloy 617 in Helium Environment of Very High Temperature Gas Reactor

    International Nuclear Information System (INIS)

    Lee, Gyeong-Geun; Jung, Sujin; Kim, Daejong; Jeong, Yong-Whan; Kim, Dong-Jin

    2012-01-01

    Alloy 617 is a Ni-base superalloy and a candidate material for the intermediate heat exchanger (IHX) of a very high temperature gas reactor (VHTR) which is one of the next generation nuclear reactors under development. The high operating temperature of VHTR enables various applications such as mass production of hydrogen with high energy efficiency. Alloy 617 has good creep resistance and phase stability at high temperatures in an air environment. However, it was reported that the mechanical properties decreased at a high temperature in an impure helium environment. In this study, high-temperature corrosion tests were carried out at 850°C-950°C in a helium environment containing the impurity gases H_2, CO, and CH_4, in order to examine the corrosion behavior of Alloy 617. Until 250 h, Alloy 617 specimens showed a parabolic oxidation behavior at all temperatures. The activation energy for oxidation in helium environment was 154 kJ/mol. The SEM and EDS results elucidated a Cr-rich surface oxide layer, Al-rich internal oxides and depletion of grain boundary carbides. The thickness and depths of degraded layers also showed a parabolic relationship with time. A normal grain growth was observed in the Cr-rich surface oxide layer. When corrosion tests were conducted in a pure helium environment, the oxidation was suppressed drastically. It was elucidated that minor impurity gases in the helium would have detrimental effects on the high temperature corrosion behavior of Alloy 617 for the VHTR application.

  18. Biofuel Production from Jatropha Bio-Oil Derived Fast Pyrolysis: Effect and Mechanism of CoMoS Supported on Al2O3

    Science.gov (United States)

    Rodseanglung, T.; Ratana, T.; Phongaksorn, M.; Tungkamani, S.

    2018-03-01

    The aims of this research was to understand the CoMo/Al2O3 sulfide catalyst effect to remove oxygen-containing and nitrogen-containing molecules from Jatropha bio-oil derived fast pyrolysis converted to biofuels via hydrotreating process. The activity and selectivity of CoMo/γ-Al2O3 sulfided catalysts in hydrodeoxygenation (HDO) of Jatropha bio-oil derived fast pyrolysis was evaluated in a Parr batch reactor under 50 bar of H2 atmosphere for 2 h at 300 320 and 340 °C. It appeared that the CoMo/Al2O3 sulfide catalyst have high performance in activity for promoting the fatty acid, fatty ester, fatty amide and fatty nitrile compounds were converted to paraffin/olefin (Diesel range), this could be the CUS site on supported Al2O3 catalyst. The difference in selectivity products allowed us to propose a reaction scheme.

  19. Optimization, Yield Studies and Morphology of WO3Nano-Wires Synthesized by Laser Pyrolysis in C2H2and O2Ambients—Validation of a New Growth Mechanism

    Directory of Open Access Journals (Sweden)

    Sideras-Haddad E

    2008-01-01

    Full Text Available Abstract Laser pyrolysis has been used to synthesize WO3nanostructures. Spherical nano-particles were obtained when acetylene was used to carry the precursor droplet, whereas thin films were obtained at high flow-rates of oxygen carrier gas. In both environments WO3nano-wires appear only after thermal annealing of the as-deposited powders and films. Samples produced under oxygen carrier gas in the laser pyrolysis system gave a higher yield of WO3nano-wires after annealing than the samples which were run under acetylene carrier gas. Alongside the targeted nano-wires, the acetylene-ran samples showed trace amounts of multi-walled carbon nano-tubes; such carbon nano-tubes are not seen in the oxygen-processed WO3nano-wires. The solid–vapour–solid (SVS mechanism [B. Mwakikunga et al., J. Nanosci. Nanotechnol., 2008] was found to be the possible mechanism that explains the manner of growth of the nano-wires. This model, based on the theory from basic statistical mechanics has herein been validated by length-diameter data for the produced WO3nano-wires.

  20. Influence of Pyrolysis Temperature and Type of Ligno-Cellulose and Cellulose Biomass on Yield, Specific Surface Area and Mechanical Resistance of Active Coal

    OpenAIRE

    Pohořelý, Michael

    2012-01-01

    In the Czech Republic, there are many contaminated agricultural soils due to anthropogenic activity and geogenic origin. The contaminated biomass of plants grown on the contaminated soils needs to be appropriately disposed of to prevent the re-releace of heavy metals into the environment. One way of processing contaminated biomass is pyrolysis, where the heavy metals are concentrated in biochar (active coal). This can be applied to soil where it improves the physical properties. The aim of ...

  1. Changes in structure and in mechanical properties during the pyrolysis conversion of crosslinked polymethylsiloxane and polymethylphenylsiloxane resins to silicon oxycarbide glass

    Czech Academy of Sciences Publication Activity Database

    Černý, Martin; Chlup, Zdeněk; Strachota, Adam; Halasová, Martina; Rýglová, Šárka; Schweigstillová, Jana; Svítilová, Jaroslava; Havelcová, Martina

    2015-01-01

    Roč. 41, č. 5 (2015), s. 6237-6247 ISSN 0272-8842 R&D Projects: GA ČR GAP107/12/2445 Institutional support: RVO:67985891 ; RVO:68081723 ; RVO:61389013 Keywords : hardness * silicon oxycarbide * pyrolysis * indentation modulus * precursor Subject RIV: JI - Composite Materials; JH - Ceramics, Fire-Resistant Materials and Glass (UFM-A) Impact factor: 2.758, year: 2015

  2. High-temperature discrete dislocation plasticity

    Science.gov (United States)

    Keralavarma, S. M.; Benzerga, A. A.

    2015-09-01

    A framework for solving problems of dislocation-mediated plasticity coupled with point-defect diffusion is presented. The dislocations are modeled as line singularities embedded in a linear elastic medium while the point defects are represented by a concentration field as in continuum diffusion theory. Plastic flow arises due to the collective motion of a large number of dislocations. Both conservative (glide) and nonconservative (diffusion-mediated climb) motions are accounted for. Time scale separation is contingent upon the existence of quasi-equilibrium dislocation configurations. A variational principle is used to derive the coupled governing equations for point-defect diffusion and dislocation climb. Superposition is used to obtain the mechanical fields in terms of the infinite-medium discrete dislocation fields and an image field that enforces the boundary conditions while the point-defect concentration is obtained by solving the stress-dependent diffusion equations on the same finite-element grid. Core-level boundary conditions for the concentration field are avoided by invoking an approximate, yet robust kinetic law. Aspects of the formulation are general but its implementation in a simple plane strain model enables the modeling of high-temperature phenomena such as creep, recovery and relaxation in crystalline materials. With emphasis laid on lattice vacancies, the creep response of planar single crystals in simple tension emerges as a natural outcome in the simulations. A large number of boundary-value problem solutions are obtained which depict transitions from diffusional to power-law creep, in keeping with long-standing phenomenological theories of creep. In addition, some unique experimental aspects of creep in small scale specimens are also reproduced in the simulations.

  3. HIGH-TEMPERATURE IONIZATION IN PROTOPLANETARY DISKS

    Energy Technology Data Exchange (ETDEWEB)

    Desch, Steven J. [School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287-1404 (United States); Turner, Neal J. [Jet Propulsion Laboratory, Mail Stop 169-506, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)

    2015-10-01

    We calculate the abundances of electrons and ions in the hot (≳500 K), dusty parts of protoplanetary disks, treating for the first time the effects of thermionic and ion emission from the dust grains. High-temperature ionization modeling has involved simply assuming that alkali elements such as potassium occur as gas-phase atoms and are collisionally ionized following the Saha equation. We show that the Saha equation often does not hold, because free charges are produced by thermionic and ion emission and destroyed when they stick to grain surfaces. This means the ionization state depends not on the first ionization potential of the alkali atoms, but rather on the grains’ work functions. The charged species’ abundances typically rise abruptly above about 800 K, with little qualitative dependence on the work function, gas density, or dust-to-gas mass ratio. Applying our results, we find that protoplanetary disks’ dead zone, where high diffusivities stifle magnetorotational turbulence, has its inner edge located where the temperature exceeds a threshold value ≈1000 K. The threshold is set by ambipolar diffusion except at the highest densities, where it is set by Ohmic resistivity. We find that the disk gas can be diffusively loaded onto the stellar magnetosphere at temperatures below a similar threshold. We investigate whether the “short-circuit” instability of current sheets can operate in disks and find that it cannot, or works only in a narrow range of conditions; it appears not to be the chondrule formation mechanism. We also suggest that thermionic emission is important for determining the rate of Ohmic heating in hot Jupiters.

  4. WC-3015 alloy (high-temperature alloy)

    International Nuclear Information System (INIS)

    Anon.

    1974-01-01

    WC-3015 Nb alloy containing 28 to 30 Hf, 1 to 2 Zr, 13 to 16 W, 0 to 4 Ta, 0 to 5 Ti, 0.07 to 0.33 C, less than or equal to 0.02 N, less than or equal to 0.03 O, less than or equal to 0.001 H was developed for use at high temperature in oxidizing environments. Its composition can be tailored to meet specific requirements. When WC-3015 is exposed to O at elevated temperature, Hf and Nb oxidized preferentially and HfO 2 dissolves in Nb 2 O 5 to form 6HfO-Nb 2 O 5 . This complex oxide has a tight cubic lattice which resists the diffusion of O into the substrate. During 24-h exposure to air at 2400 0 F, the alloy oxidizes to a depth of approximately 0.035 in. with a surface recession of 0 to 0.004 in. Oxidation resistance of WC-3015 welds and base material can be further enhanced greatly by applying silicide coatings. WC-3015 alloy can be machined by conventional and electrical-discharge methods. It can be hot worked readily by extrusion, forging or rolling. Cold working can be used at room or elevated temperature. It can be welded by the electron-beam or Tig processes. Physical constants, typical mechanical properties at 75 to 2400 0 F, and effects of composition and heat treatment on tensile and stress-rupture properties of the alloy are tabulated

  5. HIGH-TEMPERATURE IONIZATION IN PROTOPLANETARY DISKS

    International Nuclear Information System (INIS)

    Desch, Steven J.; Turner, Neal J.

    2015-01-01

    We calculate the abundances of electrons and ions in the hot (≳500 K), dusty parts of protoplanetary disks, treating for the first time the effects of thermionic and ion emission from the dust grains. High-temperature ionization modeling has involved simply assuming that alkali elements such as potassium occur as gas-phase atoms and are collisionally ionized following the Saha equation. We show that the Saha equation often does not hold, because free charges are produced by thermionic and ion emission and destroyed when they stick to grain surfaces. This means the ionization state depends not on the first ionization potential of the alkali atoms, but rather on the grains’ work functions. The charged species’ abundances typically rise abruptly above about 800 K, with little qualitative dependence on the work function, gas density, or dust-to-gas mass ratio. Applying our results, we find that protoplanetary disks’ dead zone, where high diffusivities stifle magnetorotational turbulence, has its inner edge located where the temperature exceeds a threshold value ≈1000 K. The threshold is set by ambipolar diffusion except at the highest densities, where it is set by Ohmic resistivity. We find that the disk gas can be diffusively loaded onto the stellar magnetosphere at temperatures below a similar threshold. We investigate whether the “short-circuit” instability of current sheets can operate in disks and find that it cannot, or works only in a narrow range of conditions; it appears not to be the chondrule formation mechanism. We also suggest that thermionic emission is important for determining the rate of Ohmic heating in hot Jupiters

  6. Refining fast pyrolysis of biomass

    NARCIS (Netherlands)

    Westerhof, Roel Johannes Maria

    2011-01-01

    Pyrolysis oil produced from biomass is a promising renewable alternative to crude oil. Such pyrolysis oil has transportation, storage, and processing benefits, none of which are offered by the bulky, inhomogeneous solid biomass from which it originates. However, pyrolysis oil has both a different

  7. Burst annealing of high temperature GaAs solar cells

    Science.gov (United States)

    Brothers, P. R.; Horne, W. E.

    1991-01-01

    One of the major limitations of solar cells in space power systems is their vulnerability to radiation damage. One solution to this problem is to periodically heat the cells to anneal the radiation damage. Annealing was demonstrated with silicon cells. The obstacle to annealing of GaAs cells was their susceptibility to thermal damage at the temperatures required to completely anneal the radiation damage. GaAs cells with high temperature contacts and encapsulation were developed. The cells tested are designed for concentrator use at 30 suns AMO. The circular active area is 2.5 mm in diameter for an area of 0.05 sq cm. Typical one sun AMO efficiency of these cells is over 18 percent. The cells were demonstrated to be resistant to damage after thermal excursions in excess of 600 C. This high temperature tolerance should allow these cells to survive the annealing of radiation damage. A limited set of experiments were devised to investigate the feasibility of annealing these high temperature cells. The effect of repeated cycles of electron and proton irradiation was tested. The damage mechanisms were analyzed. Limitations in annealing recovery suggested improvements in cell design for more complete recovery. These preliminary experiments also indicate the need for further study to isolate damage mechanisms. The primary objective of the experiments was to demonstrate and quantify the annealing behavior of high temperature GaAs cells. Secondary objectives were to measure the radiation degradation and to determine the effect of repeated irradiation and anneal cycles.

  8. Burst annealing of high temperature GaAs solar cells

    International Nuclear Information System (INIS)

    Brothers, P.R.; Horne, W.E.

    1991-01-01

    One of the major limitations of solar cells in space power systems is their vulnerability to radiation damage. One solution to this problem is to periodically heat the cells to anneal the radiation damage. Annealing was demonstrated with silicon cells. The obstacle to annealing of GaAs cells was their susceptibility to thermal damage at the temperatures required to completely anneal the radiation damage. GaAs cells with high temperature contacts and encapsulation were developed. The cells tested are designed for concentrator use at 30 suns AMO. The circular active area is 2.5 mm in diameter for an area of 0.05 sq cm. Typical one sun AMO efficiency of these cells is over 18 percent. The cells were demonstrated to be resistant to damage after thermal excursions in excess of 600 degree C. This high temperature tolerance should allow these cells to survive the annealing of radiation damage. A limited set of experiments were devised to investigate the feasibility of annealing these high temperature cells. The effect of repeated cycles of electron and proton irradiation was tested. The damage mechanisms were analyzed. Limitations in annealing recovery suggested improvements in cell design for more complete recovery. These preliminary experiments also indicate the need for further study to isolate damage mechanisms. The primary objective of the experiments was to demonstrate and quantify the annealing behavior of high temperature GaAs cells. Secondary objectives were to measure the radiation degradation and to determine the effect of repeated irradiation and anneal cycles

  9. Raman spectroscopy in high temperature chemistry

    International Nuclear Information System (INIS)

    Drake, M.C.; Rosenblatt, G.M.

    1979-01-01

    Raman spectroscopy (largely because of advances in laser and detector technology) is assuming a rapidly expanding role in many areas of research. This paper reviews the contribution of Raman spectroscopy in high temperature chemistry including molecular spectroscopy on static systems and gas diagnostic measurements on reactive systems. An important aspect of high temperature chemistry has been the identification and study of the new, and often unusual, gaseous molecules which form at high temperatures. Particularly important is the investigation of vibrational-rotational energy levels and electronic states which determine thermodynamic properties and describe chemical bonding. Some advantages and disadvantages of high temperature Raman spectrosocpy for molecular studies on static systems are compared: (1) Raman vs infrared; (2) gas-phase vs condensed in matries; and (3) atmospheric pressure Raman vs low pressure techniques, including mass spectroscopy, matrix isolation, and molecular beams. Raman studies on molecular properties of gases, melts, and surfaces are presented with emphasis on work not covered in previous reviews of high temperature and matrix isolation Raman spectroscopy

  10. Raman spectroscopy in high temperature chemistry

    International Nuclear Information System (INIS)

    Drake, M.C.; Rosenblatt, G.M.

    1979-01-01

    Raman spectroscopy (largely because of advances in laser and detector technology) is assuming a rapidly expanding role in many areas of research. This paper reviews the contribution of Raman spectroscopy in high temperature chemistry including molecular spectroscopy on static systems and gas diagnostic measurements on reactive systems. An important aspect of high temperature chemistry has been the identification and study of the new, and often unusual, gaseous molecules which form at high temperatures. Particularly important is the investigation of vibrational-rotational energy levels and electronic states which determine thermodynamic properties and describe chemical bonding. Some advantages and disadvantages of high temperature Raman spectrosocpy for molecular studies on static systems are compared: (1) Raman vs infrared; (2) gas-phase vs condensed in matrices; and (3) atmospheric pressure Raman vs low pressure techniques, including mass spectroscopy, matrix isolation, and molecular beams. Raman studies on molecular properties of gases, melts, and surfaces are presented with emphasis on work not covered in previous reviews of high temperature and matrix isolation Raman spectroscopy

  11. Sandia_HighTemperatureComponentEvaluation_2015

    Energy Technology Data Exchange (ETDEWEB)

    Cashion, Avery T. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-03-01

    The objective of this project is to perform independent evaluation of high temperature components to determine their suitability for use in high temperature geothermal tools. Development of high temperature components has been increasing rapidly due to demand from the high temperature oil and gas exploration and aerospace industries. Many of these new components are at the late prototype or first production stage of development and could benefit from third party evaluation of functionality and lifetime at elevated temperatures. In addition to independent testing of new components, this project recognizes that there is a paucity of commercial-off-the-shelf COTS components rated for geothermal temperatures. As such, high-temperature circuit designers often must dedicate considerable time and resources to determine if a component exists that they may be able to knead performance out of to meet their requirements. This project aids tool developers by characterization of select COTS component performances beyond published temperature specifications. The process for selecting components includes public announcements of project intent (e.g., FedBizOps), direct discussions with candidate manufacturers,and coordination with other DOE funded programs.

  12. Platform for high temperature materials (PHiTEM)

    International Nuclear Information System (INIS)

    Baluc, N.; Hoffelner, W.; Michler, J.

    2007-01-01

    Advanced energy power systems like Generation IV fission reactors, thermonuclear fusion reactors, solar thermal/solar chemical reactors, gas turbines and coal gasification systems require materials that can operate at high temperatures in extreme environments: irradiation, corrosion, unidirectional and cyclic loads. On the path to development of new and adequate high temperature materials, understanding of damage formation and evolution and of damage effects is indispensable. Damage of materials in components takes place on different time and length scales. Component failure is usually a macroscopic event. Macroscopic material properties and their changes with time (e.g., hardening, creep embrittlement, corrosion) are determined by the micro- to nano-properties of the material. The multi scale is an ambitious and challenging attempt to take these facts into consideration by developing an unified model of the material behaviour. This requires, however, dedicated tools to test and analyse materials on different scales. The platform for high temperatures materials is being set up within the framework of collaboration between the EPFL, the PSI and the EMPA. It has three main goals: 1) Establish a platform that allows the multi scale characterization of relationships between microstructure and mechanical properties of advanced, high temperature materials, with a focus on irradiated, i.e. radioactive, materials, by combining the use of a focused ion beam and a nano indentation device with multi scale modelling and simulations. 2) Use the methods developed and the results gained for existing materials for developing improved high temperature materials to be used in advanced and sustainable future energy power plants. 3) Become an attractive partner for industry by providing a wide knowledge base, flexibility in answering technical questions and skills to better understand damage in already existing plants and to support development of new products at the industrial scale

  13. High temperature microplasticity of fine-grained ceramics

    International Nuclear Information System (INIS)

    Lakki, A.; Schaller, R.

    1996-01-01

    Several fine-grained ceramics exhibit enhanced ductility or even structural superplasticity at high temperature. Grain boundaries play a dominant role in the deformation process of these materials which usually involves diffusion-accommodated grain boundary sliding. Sliding is either lubricated by an amorphous intergranular phase or takes place by glide and climb of grain boundary dislocations. At high temperature, anelastic deformation precedes plastic deformation and stems from the short range motion of lattice defects, such as dislocations and grain boundaries. The energy loss (''mechanical loss'') associated with such motion can be measured by using the technique of mechanical spectroscopy. Moreover, at the onset of plasticity (''microplasticity''), long range irrecoverable motion of defects contributes to additional mechanical loss. Mechanical loss spectra may then give an insight into mechanisms operating at the transition between anelastic and plastic deformation. As an illustration, the spectra of three fine-grained ceramics (Si 3 N 4 , ZrO 2 , Al 2 O 3 ) are presented. In all cases, anelastic relaxation phenomena (peak and background) have been observed at high temperature (> 1200 K), bearing a close relation with creep behaviour. Their analysis permits to distinguish between different types of microstructrual elements: bulk regions of amorphous intergranular phase at triple points, grain boundaries separated by a thin glassy film and ''clean'' grain boundaries. (orig.)

  14. Co-pyrolysis of coal with organic solids

    Energy Technology Data Exchange (ETDEWEB)

    Straka, P.; Buchtele, J. [Inst. of Rock Structure and Mechanics, Prague (Czechoslovakia)

    1995-12-01

    The co-pyrolysis of high volatile A bituminous coal with solid organic materials (proteins, cellulose, polyisoprene, polystyrene, polyethylene-glycolterephtalate-PEGT) at a high temperature conditions was investigated. Aim of the work was to evaluate, firstly, the changes of the texture and of the porous system of solid phase after high temperature treatment in presence of different types of macromolecular solids, secondly, properties and composition of the tar and gas. Considered organic solids are important waste components. During their co-pyrolysis the high volatile bituminous coal acts as a hydrogen donor in the temperature rank 220-480{degrees}C. In the rank 500- 1000{degrees}C the solid phase is formed. The co-pyrolysis was carried out at heating rate 3 K/min. It was found that an amount of organic solid (5-10%) affects important changes in the optical texture forms of solid phase, in the pore distribution and in the internal surface area. Transport large pores volume decreases in presence of PEGT, polystyrene and cellulose and increases in presence of proteins and polyisoprene. (image analysis measurements show that the tendency of coal to create coarse pores during co-pyrolysis is very strong and increases with increasing amount of organic solid in blend). An addition of considered materials changes the sorption ability (methylene blue test, iodine adsorption test), moreover, the reactivity of the solid phase.

  15. Nuclear fuels for very high temperature applications

    International Nuclear Information System (INIS)

    Lundberg, L.B.; Hobbins, R.R.

    1992-01-01

    The success of the development of nuclear thermal propulsion devices and thermionic space nuclear power generation systems depends on the successful utilization of nuclear fuel materials at temperatures in the range 2000 to 3500 K. Problems associated with the utilization of uranium bearing fuel materials at these very high temperatures while maintaining them in the solid state for the required operating times are addressed. The critical issues addressed include evaporation, melting, reactor neutron spectrum, high temperature chemical stability, fabrication, fission induced swelling, fission product release, high temperature creep, thermal shock resistance, and fuel density, both mass and fissile atom. Candidate fuel materials for this temperature range are based on UO 2 or uranium carbides. Evaporation suppression, such as a sealed cladding, is required for either fuel base. Nuclear performance data needed for design are sparse for all candidate fuel forms in this temperature range, especially at the higher temperatures

  16. Ultra-high temperature direct propulsion

    International Nuclear Information System (INIS)

    Araj, K.J.; Slovik, G.; Powell, J.R.; Ludewig, H.

    1987-01-01

    Potential advantages of ultra-high exhaust temperature (3000 K - 4000 K) direct propulsion nuclear rockets are explored. Modifications to the Particle Bed Reactor (PBR) to achieve these temperatures are described. Benefits of ultra-high temperature propulsion are discussed for two missions - orbit transfer (ΔV = 5546 m/s) and interplanetary exploration (ΔV = 20000 m/s). For such missions ultra-high temperatures appear to be worth the additional complexity. Thrust levels are reduced substantially for a given power level, due to the higher enthalpy caused by partial disassociation of the hydrogen propellant. Though technically challenging, it appears potentially feasible to achieve such ultra high temperatures using the PBR

  17. High temperature high vacuum creep testing facilities

    International Nuclear Information System (INIS)

    Matta, M.K.

    1985-01-01

    Creep is the term used to describe time-dependent plastic flow of metals under conditions of constant load or stress at constant high temperature. Creep has an important considerations for materials operating under stresses at high temperatures for long time such as cladding materials, pressure vessels, steam turbines, boilers,...etc. These two creep machines measures the creep of materials and alloys at high temperature under high vacuum at constant stress. By the two chart recorders attached to the system one could register time and temperature versus strain during the test . This report consists of three chapters, chapter I is the introduction, chapter II is the technical description of the creep machines while chapter III discuss some experimental data on the creep behaviour. Of helium implanted stainless steel. 13 fig., 3 tab

  18. High Temperature, Wireless Seismometer Sensor for Venus

    Science.gov (United States)

    Ponchak, George E.; Scardelletti, Maximilian C.; Taylor, Brandt; Beard, Steve; Meredith, Roger D.; Beheim, Glenn M.; Hunter Gary W.; Kiefer, Walter S.

    2012-01-01

    Space agency mission plans state the need to measure the seismic activity on Venus. Because of the high temperature on Venus (462? C average surface temperature) and the difficulty in placing and wiring multiple sensors using robots, a high temperature, wireless sensor using a wide bandgap semiconductor is an attractive option. This paper presents the description and proof of concept measurements of a high temperature, wireless seismometer sensor for Venus. A variation in inductance of a coil caused by the movement of an aluminum probe held in the coil and attached to a balanced leaf-spring seismometer causes a variation of 700 Hz in the transmitted signal from the oscillator/sensor system at 426? C. This result indicates that the concept may be used on Venus.

  19. High temperature gas cleaning for pressurized gasification. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Alden, H.; Hagstroem, P.; Hallgren, A.; Waldheim, L. [TPS Termiska Processer AB, Nykoeping (Sweden)

    2000-04-01

    The purpose of the project was to build an apparatus to study pressurized, high temperature gas cleaning of raw gasification gas generated from biomass. A flexible and easy to operate pressurized apparatus was designed and installed for the investigations in high temperature gas cleaning by means of thermal, catalytic or chemical procedures. A semi continuos fuel feeding concept, at a maximum rate of 700 g/h, allowed a very constant formation of a gas product at 700 deg C. The gas product was subsequently introduced into a fixed bed secondary reactor where the actual gas cleanup or reformation was fulfilled. The installation work was divided into four work periods and apart from a few delays the work was carried out according to the time plan. During the first work period (January - June 1994) the technical design, drawings etc. of the reactor and additional parts were completed. All material for the construction was ordered and the installation work was started. The second work period (July - December 1994) was dedicated to the construction and the installation of the different components. Initial tests with the electrical heating elements, control system and gas supply were assigned to the third work period (January - June 1995). After the commissioning and the resulting modifications, initial pyrolysis and tar decomposition experiments were performed. During the fourth and final work period, (June - December 1995) encouraging results from first tests allowed the experimental part of the project work to commence, however in a slightly reduced program. The experimental part of the project work comparatively studied tar decomposition as a function of the process conditions as well as of the choice of catalyst. Two different catalysts, dolomite and a commercial Ni-based catalyst, were evaluated in the unit. Their tar cracking ability in the pressure interval 1 - 20 bar and at cracker bed temperatures between 800 - 900 deg C was compared. Long term tests to study

  20. Fusion blanket high-temperature heat transfer

    International Nuclear Information System (INIS)

    Fillo, J.A.

    1983-01-01

    Deep penetration of 14 MeV neutrons makes two-temperature region blankets feasible. A relatively low-temperature (approx. 300 0 C) metallic structure is the vacuum/coolant pressure boundary, while the interior of the blanket, which is a simple packed bed of nonstructural material, operates at very high temperatures (>1000 0 C). The water-cooled shell structure is thermally insulated from the steam-cooled interior. High-temperature steam can dramatically increase the efficiency of electric power generation, as well as produce hydrogen and oxygen-based synthetic fuels at high-efficiency

  1. Brazing, high temperature brazing and diffusion welding

    International Nuclear Information System (INIS)

    1989-01-01

    Brazing and high temperature brazing is a major joining technology within the economically important fields of energy technology, aerospace and automotive engineering, that play a leading role for technical development everywhere in the world. Moreover diffusion welding has gained a strong position especially in advanced technologies due to its specific advantages. Topics of the conference are: 1. high-temperature brazing in application; 2. basis of brazing technology; 3. brazing of light metals; 4. nondestructive testing; 5. diffusion welding; 6. brazing of hard metals and other hard materials; and 7. ceramic-metal brazing. 28 of 20 lectures and 20 posters were recorded separately for the database ENERGY. (orig./MM) [de

  2. Materials for high-temperature fuel cells

    CERN Document Server

    Jiang, San Ping; Lu, Max

    2013-01-01

    There are a large number of books available on fuel cells; however, the majority are on specific types of fuel cells such as solid oxide fuel cells, proton exchange membrane fuel cells, or on specific technical aspects of fuel cells, e.g., the system or stack engineering. Thus, there is a need for a book focused on materials requirements in fuel cells. Key Materials in High-Temperature Fuel Cells is a concise source of the most important and key materials and catalysts in high-temperature fuel cells with emphasis on the most important solid oxide fuel cells. A related book will cover key mater

  3. Melt processed high-temperature superconductors

    CERN Document Server

    1993-01-01

    The achievement of large critical currents is critical to the applications of high-temperature superconductors. Recent developments have shown that melt processing is suitable for producing high J c oxide superconductors. Using magnetic forces between such high J c oxide superconductors and magnets, a person could be levitated.This book has grown largely out of research works on melt processing of high-temperature superconductors conducted at ISTEC Superconductivity Research Laboratory. The chapters build on melt processing, microstructural characterization, fundamentals of flux pinning, criti

  4. Close-Spaced High Temperature Knudsen Flow.

    Science.gov (United States)

    1986-07-15

    radiant heat source assembly was substituted for the brazed molybdenum one in order to achieve higher radiant heater temperatures . 2.1.4 Experimental...at very high temperature , and ground flat. The molybdenum is then chemically etched to the desired depth using an etchant which does not affect...RiB6 295 -CLSE PCED HIGH TEMPERATURE KNUDSEN FLOU(U) RASOR I AiASSOCIATES INC SUNNYVALE CA J 8 MCVEY 15 JUL 86 NSR-224 AFOSR-TR-87-1258 F49628-83-C

  5. Initial stages of high temperature metal oxidation

    International Nuclear Information System (INIS)

    Yang, C.Y.; O'Grady, W.E.

    1981-01-01

    The application of XPS and UPS to the study of the initial stages of high temperature (> 350 0 C) electrochemical oxidation of iron and nickel is discussed. In the high temperature experiments, iron and nickel electrodes were electrochemically oxidized in contact with a solid oxide electrolyte in the uhv system. The great advantages of this technique are that the oxygen activity at the interface may be precisely controlled and the ability to run the reactions in uhv allows the simultaneous observation of the reactions by XPS

  6. Carbon Isotope Measurements of Experimentally-Derived Hydrothermal Mineral-Catalyzed Organic Products by Pyrolysis-Isotope Ratio Mass Spectrometry

    Science.gov (United States)

    Socki, Richard A.; Fu, Qi; Niles, Paul B.

    2011-01-01

    We report results of experiments to measure the C isotope composition of mineral catalyzed organic compounds derived from high temperature and high pressure synthesis. These experiments make use of an innovative pyrolysis technique designed to extract and measure C isotopes. To date, our experiments have focused on the pyrolysis and C isotope ratio measurements of low-molecular weight intermediary hydrocarbons (organic acids and alcohols) and serve as a proof of concept for making C and H isotope measurements on more complicated mixtures of solid-phase hydrocarbons and intermediary products produced during high temperature and high pressure synthesis on mineral-catalyzed surfaces. The impetus for this work stems from recently reported observations of methane detected within the Martian atmosphere [1-4], coupled with evidence showing extensive water-rock interaction during Martian history [5-7]. Methane production on Mars could be the result of synthesis by mineral surface-catalyzed reduction of CO2 and/or CO by Fischer-Tropsch Type (FTT) reactions during serpentization reactions [8,9]. Others have conducted experimental studies to show that FTT reactions are plausible mechanisms for low-molecular weight hydrocarbon formation in hydrothermal systems at mid-ocean ridges [10-12]. Further, recent experiments by Fu et al. [13] focus on examining detailed C isotope measurements of hydrocarbons produced by surface-catalyzed mineral reactions. Work described in this paper details the experimental techniques used to measure intermediary organic reaction products (alcohols and organic acids).

  7. Formulation and catalytic performance of MOF-derived Fe@C/Al composites for high temperature Fischer–Tropsch synthesis

    KAUST Repository

    Oar-Arteta, Lide; Valero-Romero, Marí a José ; Wezendonk, Tim; Kapteijn, Freek; Gascon, Jorge

    2017-01-01

    High productivity towards C-2-C-4 olefins together with high catalyst stability are key for optimum operation in high temperature Fischer-Tropsch synthesis (HT-FTS). Here, we report the fabrication of Fe@C/Al composites that combine both the outstanding catalytic properties of the Fe-BTC MOF-derived Fe catalyst and the excellent mechanical resistance and textural properties provided by the inorganic AlOOH binder. The addition of AlOOH to Fe-BTC followed by pyrolysis in N-2 atmosphere at 500 degrees C results in composites with a large mesoporosity, a high Fe/Fe3O4 ratio, 10-35 nm average Fe crystallite size and coordinatively unsaturated Al3+ sites. In catalytic terms, the addition of AlOOH binder gives rise to enhanced C-2-C-4 selectivity and catalyst mechanical stability in HT-FTS, but at high Al contents the activity decreases. Altogether, the productivity of these Fe@C/Al composites is well above most known Fe catalysts for this process.

  8. Formulation and catalytic performance of MOF-derived Fe@C/Al composites for high temperature Fischer–Tropsch synthesis

    KAUST Repository

    Oar-Arteta, Lide

    2017-11-15

    High productivity towards C-2-C-4 olefins together with high catalyst stability are key for optimum operation in high temperature Fischer-Tropsch synthesis (HT-FTS). Here, we report the fabrication of Fe@C/Al composites that combine both the outstanding catalytic properties of the Fe-BTC MOF-derived Fe catalyst and the excellent mechanical resistance and textural properties provided by the inorganic AlOOH binder. The addition of AlOOH to Fe-BTC followed by pyrolysis in N-2 atmosphere at 500 degrees C results in composites with a large mesoporosity, a high Fe/Fe3O4 ratio, 10-35 nm average Fe crystallite size and coordinatively unsaturated Al3+ sites. In catalytic terms, the addition of AlOOH binder gives rise to enhanced C-2-C-4 selectivity and catalyst mechanical stability in HT-FTS, but at high Al contents the activity decreases. Altogether, the productivity of these Fe@C/Al composites is well above most known Fe catalysts for this process.

  9. A high temperature testing system for ceramic composites

    Science.gov (United States)

    Hemann, John

    1994-01-01

    Ceramic composites are presently being developed for high temperature use in heat engine and space power system applications. The operating temperature range is expected to be 1090 to 1650 C (2000 F to 3000 F). Very little material data is available at these temperatures and, therefore, it is desirable to thoroughly characterize the basic unidirectional fiber reinforced ceramic composite. This includes testing mainly for mechanical material properties at high temperatures. The proper conduct of such characterization tests requires the development of a tensile testing system includes unique gripping, heating, and strain measuring devices which require special considerations. The system also requires an optimized specimen shape. The purpose of this paper is to review various techniques for measuring displacements or strains, preferably at elevated temperatures. Due to current equipment limitations it is assumed that the specimen is to be tested at a temperature of 1430 C (2600F) in an oxidizing atmosphere. For the most part, previous high temperature material characterization tests, such as flexure and tensile tests, have been performed in inert atmospheres. Due to the harsh environment in which the ceramic specimen is to be tested, many conventional strain measuring techniques can not be applied. Initially a brief description of the more commonly used mechanical strain measuring techniques is given. Major advantages and disadvantages with their application to high temperature tensile testing of ceramic composites are discussed. Next, a general overview is given for various optical techniques. Advantages and disadvantages which are common to these techniques are noted. The optical methods for measuring strain or displacement are categorized into two sections. These include real-time techniques. Finally, an optical technique which offers optimum performance with the high temperature tensile testing of ceramic composites is recommended.

  10. Promising materials for HTGR high temperature heat exchangers

    International Nuclear Information System (INIS)

    Kuznetsov, E.V.; Tokareva, T.B.; Ryabchenkov, A.V.; Novichkova, O.V.; Starostin, Yu.D.

    1989-01-01

    The service conditions for high-temperature heat-exchangers with helium coolant of HTGRs and requirements imposed on materials for their production are discussed. The choice of nickel-base alloys with solid-solution hardening for long-term service at high temperatures is grounded. Results of study on properties and structure of types Ni-25Cr-5W-5Mo and Ni-20Cr-20W alloy in the temperature range of 900 deg. - 1,000 deg. C are given. The ageing of Ni-25Cr-5W-5Mo alloy at 900 deg. - 950 deg. C results in decreased corrosion-mechanical properties and is caused by the change of structural metal stability. Alloy with 20% tungsten retains a high stability of both structure and properties after prolonged exposure in helium at above temperatures. The alloy has also increased resistance to delayed fracture and low-cycle fatigue at high temperatures. The developed alloy of type Ni-20Cr-20W with microalloying is recommended for production of tubes for HTGR high-temperature heat-exchangers with helium coolant. (author). 3 refs, 8 figs

  11. High temperature structural ceramic materials manufactured by the CNTD process

    International Nuclear Information System (INIS)

    Stiglich, J.J. Jr.; Bhat, D.G.; Holzl, R.A.

    1980-01-01

    Controlled Nucleation Thermochemical Deposition (CNTD) has emerged from classical chemical deposition (CVD) technology. This paper describes the techniques of thermochemical grain refinement. The effects of such refinement on mechanical properties of materials at room temperature and at elevated temperatures are outlined. Emphasis is given to high temperature structural ceramic materials such as SiC, Si 3 N 4 , AlN, and TiB 2 and ZrB 2 . An example of grain refinement accompanied by improvements in mechanical properties is SiC. Grain sizes of 500 to 1000 A have been observed in CNTD SiC with room temperature MOR of 1380 to 2070 MPa (4 pt bending) and MOR of 3450 to 4140 MPa (4 pt bending) at 1350 0 C. Various applications of these materials to the solution of high temperature structural problems are described. (author)

  12. Dynamics of Gauge Fields at High Temperature

    NARCIS (Netherlands)

    Nauta, B.J.

    2000-01-01

    An effective description of dynamical Bose fields is provided by the classical (high-temperature) limit of thermal field theory. The main subject of this thesis is to improve the ensuing classical field theory, that is, to include the dominant quantum corrections and to add counter terms for the

  13. High temperature oxidation resistant cermet compositions

    Science.gov (United States)

    Phillips, W. M. (Inventor)

    1976-01-01

    Cermet compositions are designed to provide high temperature resistant refractory coatings on stainless steel or molybdenum substrates. A ceramic mixture of chromium oxide and aluminum oxide form a coating of chromium oxide as an oxidation barrier around the metal particles, to provide oxidation resistance for the metal particles.

  14. Technology development for high temperature logging tools

    Energy Technology Data Exchange (ETDEWEB)

    Veneruso, A.F.; Coquat, J.A.

    1979-01-01

    A set of prototype, high temperature logging tools (temperature, pressure and flow) were tested successfully to temperatures up to 275/sup 0/C in a Union geothermal well during November 1978 as part of the Geothermal Logging Instrumentation Development Program. This program is being conducted by Sandia Laboratories for the Department of Energy's Division of Geothermal Energy. The progress and plans of this industry based program to develop and apply the high temperature instrumentation technology needed to make reliable geothermal borehole measurements are described. Specifically, this program is upgrading existing sondes for improved high temperature performance, as well as applying new materials (elastomers, polymers, metals and ceramics) and developing component technology such as high temperature cables, cableheads and electronics to make borehole measurements such as formation temperature, flow rate, high resolution pressure and fracture mapping. In order to satisfy critical existing needs, the near term goal is for operation up to 275/sup 0/C and 7000 psi by the end of FY80. The long term goal is for operation up to 350/sup 0/C and 20,000 psi by the end of FY84.

  15. Dense high-temperature plasma transport processes

    International Nuclear Information System (INIS)

    Giniyatova, Sh.G.

    2002-01-01

    In this work the transport processes in dense high-temperature semiclassical plasma are studied on the base of the kinetic equation, where the semiclassical potential was used, in its collision integral. The coefficient of plasma electrical conductivity, viscosity and thermal conductivity were received. There were compared with the other authors' results. The Grad's method was used obtaining of viscosity and thermal coefficients. (author)

  16. Nuclear and quark matter at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Biro, Tamas S. [H.A.S. Wigner Research Centre for Physics, Budapest (Hungary); Jakovac, Antal [Roland Eotvos University, Budapest (Hungary); Schram, Zsolt [University of Debrecen, Institute for Theoretical Physics, Debrecen (Hungary)

    2017-03-15

    We review important ideas on nuclear and quark matter description on the basis of high-temperature field theory concepts, like resummation, dimensional reduction, interaction scale separation and spectral function modification in media. Statistical and thermodynamical concepts are spotted in the light of these methods concentrating on the -partially still open- problems of the hadronization process. (orig.)

  17. High temperature brazing of reactor materials

    International Nuclear Information System (INIS)

    Orlov, A.V.; Nechaev, V.A.; Rybkin, B.V.; Ponimash, I.D.

    1990-01-01

    Application of high-temperature brazing for joining products of such materials as molybdenum, tungsten, zirconium, beryllium, magnesium, nickel and aluminium alloys, graphite ceramics etc. is described. Brazing materials composition and brazed joints properties are presented. A satisfactory strength of brazed joints is detected under reactor operation temperatures and coolant and irradiation effect

  18. The discovery of high temperature superconductivity

    International Nuclear Information System (INIS)

    Muller, K. A.; Bednorz, J.G.

    1988-01-01

    This article recalls the different stages which led to the display of high temperature superconductivity for Ba, La, Cu, O and the following avalanche of discoveries for other oxides; the numerous theoretical models which tentatively explain the current experimental results are also reviewed. 30 refs

  19. The discovery of high temperature superconductivity

    International Nuclear Information System (INIS)

    Muller, K.A.; Bednorz, J.G.

    1988-01-01

    This article recalls the different stages which led to the display of high temperature superconductivity for Ba La Cu O, and the following avalanche of discoveries for other oxides; the numerous theoretical models which tentatively explain the current experimental results are also reviewed [fr

  20. High temperature applications of nuclear energy

    International Nuclear Information System (INIS)

    1994-08-01

    The meeting was organized to review industry/user needs designs, status of technology and the associated economics for high temperature applications. It was attended by approximately 100 participants from nine countries. The participants presented 17 papers. A separate abstract was prepared for each of these papers. Refs, figs and tabs