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In this article, we report the results of a study of the effects of high-temperature stress annealing in nitrogen on the index of refraction of SiO[sub 2] layers in metal/oxide/semiconductor (MOS) devices. In this study, we have experimentally characterized the dependence of mechanical stress in the Si-SiO[sub 2] system on the oxidation and annealing conditions and correlated such properties with the dependence of the index of refraction on processing conditions and oxide thickness. We consider the contributions of the thermal-relaxation and nitrogen-incorporation processes in determining changes in the index of refraction with annealing time. This description is consistent with other annealing studies carried out in argon where only the thermal-relaxation process is present. Correlations of these experimental observations with the electrical properties of the same MOS devices are presented in a companion article. [ABSTRACT FROM AUTHOR]

In this article, we report the results of a study of the effects of high-temperature stress annealing in nitrogen on the electrical properties of metal/oxide/semiconductor devices. In this study, we have experimentally characterized the dependence of the reduced effective contact-potential difference, the effective oxide charge (N[sub eff]), and the midgap interface trap density (D[sub it]) on the annealing conditions in nitrogen. We have correlated such properties with the dependence of the index of refraction and oxide stress on the annealing conditions and oxide thickness in a companion article. We consider the contributions of the thermal-relaxation and nitrogen-incorporation processes in determining changes in the electrical properties with annealing time. This model description is consistent with other annealing studies carried out in argon where only the thermal-relaxation process is present. [ABSTRACT FROM AUTHOR]

Explosion hazards involving mixtures of different states of aggregation continue to occur in facilities where dusts, gases or solvents are handled or processed. In order to prevent or mitigate the risk associated with these mixtures, more knowledge of the explosion behavior of hybrid mixtures is required. An experimental investigation of the minimum ignition temperature (MIT) and the lower explosion limit/minimum explosion concentration (LEL/MEC) of three component hybrid mixtures of combustible dusts, gases and vapors in air were performed in a modified Godbert-Greenwald (GG) furnace. The study comprised three dusts, two gases and two solvents vapors. For the dusts alone, the experimental protocol was in accordance with the European standard EN 50281-2-1, whereas for the gases, solvent vapors and mixtures of these with dusts, this protocol had to be modified slightly. It was found that the MITs of the gases and solvent vapors decreased significantly when a combustible dust at a concentration below the MEC of the dust alone, was added. A significant decrease in the MIT was also found if the gas/vapor atmosphere was mixed with a dispersed combustible dust that could not be ignited alone at the given temperature in the GG furnace. For example, the MIT of methane decrease from 600 °C to 585 °C when a small amount of starch was added. This hybrid MIT further decreased to 490 °C when a non-explosible third component, ethanol, was added. It was also found that a hybrid cloud of a combustible dust at a concentration less than the MEC and a combustible gas at a concentration less than the LEL could be ignited in the GG furnace. For example, the MEC of starch decreased from about 145 g/m3 to 40 g/m3 when methane at a concentration below the LEL was added. This explosible concentration of starch– methane mixture further decreased to 25 g/m3 when a small fraction of a third component, hexane, was added. [ABSTRACT FROM AUTHOR]

Taking raw coal as object， by using self-made “thermal-hydro-mechanical coupled with triaxial servo-controlled seepage apparatus for containing-gas coal”， the effect of temperature on the mechanical properties of containing-gas raw coal was studied under constant confining pressure and unloading confining pressure. The results showed that: 1) Under the same initial confining pressure， gas pressure and temperature， compared with the constant confining pressure， the yield stage of the coal under unloading confining pressure is shortened. Besides， its peak stress and associated axial strain decrease， the transverse strain rate increases， and the evolution processes of its lateral expansion ratio and deformation modulus are accelerated. 2) Under the same initial confining pressure and gas pressure， with the increase of temperature， the strength of coal under unloading confining pressure decreases， the axial strain at peak stress， the absolute value of the transverse strain and volumetric strain decrease， and the lateral expansion ratio and the deformation modulus increase. 3) The risk of coal unstable failure and coal and gas outburst becomes higher under high temperature environment， leading to more strict requirements for the support of coal face roadway and the control of coal and gas outburst. [ABSTRACT FROM AUTHOR]

A series of polybenzimidazoles containing sulfonyl groups were synthesized in Eaton's reagent for high temperature H 2 /CO 2 separation membranes. The key monomer, 3,3′,4,4′-tetraaminodiphenylsulfone, was prepared via a novel and economical synthetic route starting from 4,4′-dichlorodiphenylsulfone. These polybenzimidazoles with sulfonyl moieties had enhanced solubilities in dipolar aprotic solvents relative to the commercial Celazole ® that is prepared from diaminobenzidine. Thermal gravimetric analysis showed that the materials were stable at elevated temperatures with 5% weight loss values of at least 485 °C in either air or N 2 . Glass transition temperatures of three polybenzimidazoles in this series were ascertained by dynamic mechanical analysis to be 438–480 °C. These sulfonyl-containing polybenzimidazoles exhibited excellent gas separation properties for H 2 /CO 2 . Polymers from tetraaminodiphenylsulfone and either terephthalic or isophthalic acid crossed Robeson's upper bound for H 2 /CO 2. [ABSTRACT FROM AUTHOR]

An analysis of data agreement as the main method for estimation of the reliability is performed for the thermophysical properties of matter using three examples: (1) the density of liquid mercury at 20°C, (2) the transport properties and the second virial coefficient of rarefied gases, and (3) the compressibility of alkali metal vapors at high temperatures and pressures. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, the effect of the hydrogen and the air temperature values on the temperature distribution in a Planar Solid Oxide Fuel Cell is studied by the aid of a two-dimensional mathematical model. Two different configurations of the Solid Oxide Fuel Cells are examined: i) the Anode Supported Planar Solid Oxide Fuel Cell (ASP_SOFC) and ii) the Electrolyte Supported Planar Solid Oxide Fuel Cell (ESP_SOFC). In order to describe the temperature distribution within the SOFC, the coupling of the mass and energy transport phenomena along with the electrochemistry is required. The studied parameters are: a) the hydrogen and the air temperature values and b) the geometry configurations. The complex system of the governing equations is numerically solved with the finite differences method and the calculation of the temperature distribution within each domain of the SOFCs is calculated via the 2-D mathematical model processed by FORTRAN language. Finally, the mathematical model predictions for the temperature distribution under the influence of the studied parameters are thoroughly discussed. [Copyright &y& Elsevier]

Abstract: For HTR fuel irradiation tests in the HFR Petten a specific installation was designed and installed, dubbed the “Sweep Loop Facility” (SLF). The SLF is tasked with three functions, namely temperature control by gas mixture technique, surveillance of safety parameters (temperature, pressure, radioactivity etc.) and analysis of fission gas release for three individual capsules in two separate experiments. The SLF enables continuous and independent surveillance of all gas circuits. The release of volatile fission products of the in-pile experiments is monitored by continuous gas purging. The fractional release of these fission products, defined as the ratio between release rate of a gaseous fission isotope (measured) to its instantaneous birth rate (calculated), is a licensing-relevant test for HTR fuel. The newly developed gamma spectrometry station allows for higher measurement frequencies, thus enabling follow-up of rapid and massive release transients. The designed stand-alone system was tested and fully used through the final irradiation period of the HFR-EU1 experiment which was terminated on 18 February 2010. Its robustness allowed us to use it as extra safety instrumentation. This paper describes the gas activity measurement technique based on HPGe gamma spectrometry and illustrates how qualitative and quantitative analysis of volatile fission products can be performed on-line. [Copyright &y& Elsevier]

Abstract: Recent high temperature reactor (HTR) concepts for nuclear co-generation foresee hot gas temperatures up to 850°C. While suitable materials for the high temperature exposed components well-known from conventional technologies are taken into consideration, extended material qualification tests must still be performed for reactor design and licensing to guarantee safe and economic operation. For this purpose data management tools are required. For administration of materials data coming from European R&D projects the Joint Research Centre – Institute for Energy (JRC-IE) offers the web-enabled MAterials DataBase (MatDB Online) free of charge to the European research community. It represents a comprehensive tool for storing, retrieving and evaluating materials test data together with related documentation in a linked document management database (DoMa). MatDB Online hosts materials data from the former German high temperature reactor programme and was, respectively is involved in several GENeration IV (GEN IV) reactor systems related European R&D projects such as HTR-M/M1 (high temperature reactor materials) and RAPHAEL (reactor for process heat, hydrogen and electricity generation) and the cross-cutting project GETMAT (GEN IV and transmutation materials). The paper gives an overview of MatDB Online and DoMa as a central storage system for European R&D materials data and documents, describes the HTR materials and the data content within MatDB Online, and gives evaluation examples of HTR materials data. Noting the data transfer obligations within GIF (GEN IV International Forum), the paper concludes with recommendations for further materials testing. [Copyright &y& Elsevier]

Abstract: The special feature of high-temperature gas-cooled reactors (HTGRs) is stressed operating conditions for equipment due to high temperature of the primary circuit helium, up to 950°C, as well as acoustic and hydrodynamic loads upon the gas path elements. Therefore, great significance is given to reproduction of real operation conditions in tests. Experimental investigation of full-size nuclear power plant (NPP) primary circuit components is not practically feasible because costly test facilities will have to be developed for the power of up to hundreds of megawatts. Under such conditions, the only possible process to validate designs under development is representative tests of smaller scale models and fragmentary models. At the same time, in order to take in to validated account the effect of various physical factors, it is necessary to ensure reproduction of both individual processes and integrated tests incorporating needed integrated investigations. Presented are approaches to experimental validation of thermohydraulic and vibroacoustic characteristics for main equipment components and primary circuit path elements under standard loading conditions, which take account of their operation in the HTGR. Within the framework of the of modular helium reactor project, including a turbo machine in the primary circuit, a new and difficult problem is creation of multiple-bearing flexible vertical rotor. Presented are approaches to analytical and experimental validation of the rotor electromagnetic bearings, catcher bearings, flexible rotor electromagnetic bearings system operability. [Copyright &y& Elsevier]

The LaF surface-modified LiCrMnO samples were synthesized by co-precipitation method and characterized by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray detector (EDX). HAADF-STEM and EDX observations showed that LaF deposited on the surface of LiCrMnO particles. When tested as the cathode materials for lithium-ion battery, the LaF-modified LiCrMnO exhibited significantly improved cyclic and rate performances at high temperature (55 °C). Electrochemical impedance spectrum analyses demonstrated that the surface of LiCrMnO modified by LaF was much more stable during the electrochemical process and could greatly facilitate the charge-transfer reaction, which may be attributed to the protection of active material by LaF from the HF attack. [ABSTRACT FROM AUTHOR]

Abstract: In order to understand the behaviour of ruthenium oxides in the reactor coolant system during an air ingress accident, new tests were performed in the frame of the RUSET (RUthenium Separate Effect Test) experimental program. These aimed to ascertain the effects of different surfaces (quartz, stainless steel (SS), zirconium alloy, alumina, oxidised metal, and surfaces with Mo or Cs deposits) on the transport and decomposition of ruthenium oxides in air stream along the temperature gradient zone (1100–100°C). The results demonstrated that the heterogeneous phase decomposition of RuO3 and RuO4 to RuO2 is catalysed more efficiently by the quartz surface than by the SS or alumina surfaces. The presence of MoO3 layers decreased the RuO x precipitation extent on all investigated surfaces. The trapping effect of Cs deposit on Ru in the temperature gradient zone was proved in the case of the SS surface. On the contrary, presence of Cs precipitate on alumina and especially on quartz surfaces was found to decrease their catalytic effect on the decomposition of ruthenium oxides, and thus increased the RuO4 concentration in the outlet air. Similarly to the effect observed for Cs deposition, the presence of other fission products in the evaporation area (at 1100°C) decreased the partial pressure of RuO4 in the outlet air at the SS surface and increased it at quartz and alumina surfaces. When zirconium (E110) cladding material was placed in the temperature gradient zone, no Ru transmittance occurred until the high temperature end of the zirconium tube was completely oxidised. After the intense oxidation of E110, Ru release occurred only in the presence of other fission product species. Pre-oxidation of SS surfaces in steam had no significant effect on the Ru passage. [Copyright &y& Elsevier]

Mathematical and physical modeling of thermochemical destruction of a heat-shielding material under the action of a high-temperature pulsating gas flow has been considered. [ABSTRACT FROM AUTHOR]

Abstract: In this paper the technology of the “Linn” type Si fluxless solder bonding oven and the thermal and gas flow characterization of the oven are discussed. This oven is used for fixing silicon chips on metal substrates with high temperature solder bonding process. The solder is applied in a foil form which is placed between the Si chip and the metal substrate. This does not contain any flux, therefore a reducing agent has to be applied to avoid the oxidation of the joints during the soldering process. In this technology the reducing agent is the forming gas which is a mixture of 10vol.% H2 and 90vol.% N2. The key factors of this soldering process was studied; the suitable temperature (350–370°C for 13–15min) and the adequate H2 concentration (8–10vol.%). A detailed 3D gas flow model of the Linn oven was prepared which is based on the finite volume model (FVM) method. The gas flow circumstances using the basic and a hypothetic oven setting were compared by simulations applied the ANSYS–FLUENT system. The gas flow model was verified by the measurements of the temperature, the H2 concentration and the pressure inside the oven. Furthermore the heating ability of the oven under full load was characterized by the change of the heating temperature and the time coefficient of the heating. [ABSTRACT FROM AUTHOR]

The resurgence of high temperature reactor (HTR) technology has prompted the development and application of modern calculation methodologies, many of which are already utilized in the existing power reactor industry, to HTR designs. To this end, the use of nodal diffusion methods for full core neutronic analysis is once again considered for both their performance and accuracy advantages. Recently a number of different approaches to two-dimensional and 3D multigroup cylindrical nodal diffusion methods were proposed by various institutions for use in HTR and, specifically, pebble-bed modular reactor (PBMR) calculations. In this regard, we may mention the NEM code from the Pennsylvania State University based on the nodal expansion method and the OSCAR-4 code from NECSA, utilizing a conformal mapping approach to the analytic nodal method. In this work we will compare these two approaches in terms of accuracy and performance. Representative problems, selected tQ test the methods thoroughly, were devised and based on both a modified version of the PBMR 400 MW benchmark problem and a "cylindrisized" version of the IAEA two-group problem. The comparative results between OSCAR-4 and NEM are given, focusing on global reactivity estimation, as well as power and flux errors as compared with reference finite-difference solutions. These results indicate that both OSCAR-4 and NEM recover the global reference solution for the IAEA problem and show power errors, which are generally acceptable for nodal methods. For the PBMR problem the accuracy is similar but some convergence difficulties are experienced at the outer boundaries of the system due to the very large dimensions of the reflector (when compared with typical water-moderated reactors). For both codes a significant performance increase was found, as compared with finite-difference calculations, which is the method currently employed by the PBMR (Pty) Ltd. In conclusion it seems that nodal methods have potential for use in the HTR analysis and, specifically, the PBMR calculational arena, although cylindrical geometry based nodal methods will have to develop toward maturity before becoming the industry standard. [ABSTRACT FROM AUTHOR]

Abstract: Gases from gasification processes contain H2S which is highly harmful for almost all catalyst materials and metal constructions such as in IGCC plants. Metal oxides and/or their admixtures are widely used for the removal of H2S from gases at high temperatures. These sorbents, however, suffer from several problems which adversely affect their performances. In this study, a new method was explored to prepare sorbents from nano-size (sub-micron) CuO supported on SiO2 materials. Three sorbents with 38.5 wt.%, 41.5 wt.% and 49.6 wt.% Cu contents were prepared and characterized. Results indicated that, the produced materials are mesoporous composite type materials of nano-size CuO and amorphous SiO2. The H2S adsorption characteristics of the prepared sorbents were studied in a laboratory scale fixed-bed reactor through sulfidation–regeneration cycles in the temperature range of 788–838 K at atmospheric pressure. The average sulfur uptake capacities of the sorbents, based on the breakthrough point H2S concentration of 20 ppm, were determined to be in the range of 2.38–2.91 g S/100 g sorbent after 3 cycles. Although the process at high temperatures appeared to disturb the structure of the sorbents to some extent, the drop in their sulfur adsorption capacities remained limited. [Copyright &y& Elsevier]

Energy and exergy assessments are reported of integrated power generation using solid oxide fuel cells (SOFCs) with internal reforming and a gas turbine cycle. The gas turbine inlet temperature is fixed at 1573 K and the high-temperature turbine exhaust heats the natural gas and air inputs, and generates pressurized steam. The steam mixes at the SOFC stack inlet with natural gas to facilitate the reformation process. The integration of solid oxide fuel cells with gas turbines increases significantly the power generation efficiency relative to separate processes and reduces greatly the exergy loss due to combustion, which is the most irreversible process in the system. The other main exergy destruction is attributable to electrochemical fuel oxidation in the SOFC. The energy and exergy efficiencies of the integrated system reach 70-80%, which compares well to the efficiencies of approximately 55% typical of conventional combined-cycle power generation systems. Variations in the energy and exergy efficiencies of the integrated system with operating conditions are provided, showing, for example, that SOFC efficiency is enhanced if the fuel cell active area is augmented. The SOFC stack efficiency can be maximized by reducing the steam generation while increasing the stack size, although such measures imply a significant and nonproportional cost rise. Such measures must be implemented cautiously, as a reduction in steam generation decreases the steam/methane ratio at the anode inlet, which may increase the risk of catalyst coking. A detailed assessment of an illustrative example highlights the main results. [ABSTRACT FROM AUTHOR]

Abstract: The behaviour of composite steel–concrete beams at elevated temperatures is an important problem. A three-dimensional push test model is developed herein with a two-dimensional temperature distribution field based on the finite element method (FEM) and which may be applied to steel–concrete composite beams. The motivation for this paper is to increase the awareness of the structural engineering community to the concepts behind composite steel–concrete structural design for fire exposure. The behaviour of reinforced concrete slabs under fire conditions strongly depends on the interaction of the slabs with the surrounding elements which include the structural steel beam, steel reinforcing and shear connectors. This study was carried out to consider the effects of elevated temperatures on the behaviour of composite steel–concrete beams for both solid and profiled steel sheeting slabs. This investigation considers the load–slip relationship and ultimate load behaviour for push tests with a three-dimensional non-linear finite element program ABAQUS. As a result of elevated temperatures, the material properties change with temperature. The studies were compared with experimental tests under both ambient and elevated temperatures. Furthermore, for the elevated temperature study, the models were loaded progressively up to the ultimate load to illustrate the capability of the structure to withstand load during a fire. It is concluded that finite element analysis showed that the shear connector strength under fire exposure was very sensitive. It is also shown that profiled steel sheeting slabs exhibit greater fire resistance when compared with that of a solid slab as a function of their ambient temperature strength. [Copyright &y& Elsevier]

In this work we discuss how and to what extent the thermodynamic concepts and the thermodynamic formalism can be extended to the description of high temperature states of the plasma not necessarily associated with a Boltzmann distribution and with thermal equilibrium. The discussion is based on the "magnetic or electrostatic entropy concept", an interpretative and predictive tool based on probability and information, defined in a suitably coarse-grained possibility space of all current density or of all electric charge density distributions under testable constraints, and whose variation properties are proven to be related under certain conditions to the equilibrium and the stability of the system. In the case of magnetic equilibrium the potentiality of the magnetic entropy concept is illustrated by comparing the predictions of the current density and pressure profiles with the observations in different tokamak machines and different tokamak regimes, as well as by showing how the equilibrium and the stability in devices as different as the reversed field pinch or the magnetic well are described by the variation properties of the same entropy functional applied to the different situations. In fact it emerges that the maximum of the entropy can be seen in these different cases as an optimization constraint for the minimum of the magnetic energy. The application of the entropy concept to the electrostatic processes shows in particular that the so-called reactive instabilities (non-dissipative, non-resonant instabilities with a marginal point) admit a neighboring state with higher entropy and are therefore of special relevance from the point of view of the physical evolution of the system. In this case the thermodynamic formalism allows the introduction of the concept of "thermodynamic fluctuations" of the macroscopic charge density and provides a method for the calculation of the "thermodynamic" fluctuation levels both on the stable as well as on the linearly unstable side of the marginal point. The paper discusses the relation between the variations of the entropy functional defined on statistical grounds and the motion of the underlying system of particles. It is found that the vanishing of the first variation of the entropy is connected, under certain assumptions, with the Hamilton's principle, while the second variation is not directly related to the dynamics but is an expression of the fact that the entropy is a predictive tool based on probability and information. [ABSTRACT FROM AUTHOR]

The initiation of a reactive material by an inert particle at a high initial temperature and with a limited heat reserve is studied numerically. The possibility of using known ignition criteria to study the process are analyzed. The effect of burnout on high-temperature ignition by a particle with a limited heat reserve is studied. Four regimes of the process and the critical parameters separating these regimes are determined. [ABSTRACT FROM AUTHOR]

A stationary model of filtration combustion of a gas with allowance for conditions at the entrance to the porous body and conditions of heat exchange with the gas phase surrounding the burner and with the heat exchanger is proposed and numerically analyzed. Ranges of parameters where the regime of gas combustion with a narrow reaction zone near the outer surface of the porous body are determined. Mechanical stresses arising in the porous body owing to high temperature gradients and gas pressure in the pores are estimated. The rate of gas combustion and the radiative heat flux from the burner surface are plotted as functions of process-dependent parameters. [ABSTRACT FROM AUTHOR]

Abstract: High temperature compliance testing in four-point bending geometry were performed at various temperatures in air to understand visco-elastic behaviour of SiC ceramics sintered with R2O3–AlN (R=Y, Lu) and YAG–AlN additives. The stiffness, calculated from the slope of the loading–unloading curve, essentially characterises the elastic and fast recoverable anelastic components of the material''s behaviour. The slow anelastic and plastic behaviour can be determined from the loop area. Excellent visco-elastic behaviour were observed for SiC sintered with Lu2O3–AlN additives as compared to that of with Y2O3–AlN or commercial SiC (Eka-SiC T). Substitution of Y3+ by Lu3+ modifies the grain boundary composition and thickness which governs the high temperature mechanical behaviour. HRTEM investigation on grain-boundary elucidate the property-microstructure correlation. [Copyright &y& Elsevier]

Phosphosilicate molecular precursor for the synthesis of NASICON, natrium super ionic conductor, Na 1+ xZr 2Si xP 3− xO 12( x= 1 and 2) has been devised and prepared by the hydrolysis of tetraethoxysilane (TEOS) employing sodium phosphate solution. The molecular precursor was reacted with Zr(OC 3H 7) 4in ethanol under solvolytic condition to yield nano precursor material of NASICON. This material was annealed at high temperature to yield phase-pure NASICON. The molecular precursor was characterized using 31P NMR, FTIR spectral data, powder XRD pattern and TG/DTA studies. The structure of the molecular precursor was deduced from the powder XRD data, which indicates the presence of edge sharing tetrahedral arrangement of −O−Si−O−P−O−Si− chain. The NASICON precursor material was characterized using TG/DTA, FTIR, TEM, SEM, MAS 31P NMR and XRD. The conductivity of the synthesized NASICON material was measured using the pellet annealed at 900 °C and was found to be 5.5 x10 −3S cm −1. The details on the preliminary investigation are presented in this paper. [ABSTRACT FROM AUTHOR]

Abstract: A description of lifetime shock tests on tantalum and tungsten is given and of modelling studies as part of the research into solid targets for a Neutrino Factory. A fast high current pulse is applied to a thin wire of the sample material and the number of pulses measured before the wire visibly deteriorates. These measurements are made at temperatures up to ∼2000K. The stress on the wire is calculated and compared to the stress expected in the target using the computer code LS-DYNA. It has been found that tantalum is too weak to sustain prolonged stress at these temperatures but a tungsten wire has reached over 13 million pulses (equivalent to 10 years of operation) at the stress expected in the target. Further work is in progress to study graphite and other materials. Measurement of the surface acceleration of the wire using a VISAR are to be made, which, combined with LS-DYNA modelling, will allow the evaluation of the constitutive equations of state of the materials at high temperature and provide a more accurate model of the stresses in a number of target geometries. [Copyright &y& Elsevier]

Abstract: The warm formability of AZ31 sheet has affected with strain rate as well as temperature because elongations are changed by the temperature and strain rate at an elevated temperature. Therefore, the formability must be investigated with the effects of both strain rate and temperature. In this study, the effects of temperature and strain rate were investigated on square cup drawing by the experimental and FE analysis. And, the uni-axial tensile test and stretching test by the hemi-spherical punch were performed to analyze causes of forming limits for various forming conditions. AZ31 alloy sheet shows increased total elongation by increasing the deformation temperature from 200 to 400°C on uni-axial tensile test. The uniform elongation decreased by increasing the temperature and increased by the increasing the strain rate. On the other hand, the post-uniform elongation increased with higher temperature and lower strain rate. Forming limit by FLD test was worse on higher strain rate. Also, the failures were occurred frequently at high forming speed on square cup deep drawing. After all, the forming limit was dependent with the post-uniform elongation more than uniform elongation. Finally, the effect of strain rate must be considered on the FEM analysis. Therefore, the viscoplastic material model and strain rate-dependent FLD curve were used to simulate forming process and predict the failure. The simulated results show good agreement with the experimental results. [Copyright &y& Elsevier]

Abstract: Colored products have been obtained by thermal treatment of erionite mixed with elemental sulfur and alkalis (Na2CO3 or K2CO3). Synthesis at lower temperature (500°C) resulted in forming colored materials with preserved ERI structure (particularly with potassium cations), whereas the treatment of highly alkaline mixtures at high temperature (800°C) caused re-crystallization to SOD (when Na was used) or to unknown structures (with K). The ESR spectra of the products with preserved original ERI structure recorded at room temperature show two signals, one with g =2.030 and another with g tensor value either 2.045 (for sodium containing samples) or 2.005 (for the potassium bearing products). The latter signal could be considered as a reflection of radicals immobilized in small ε-cages, but it is more likely that it presents anisotropic component of the radical spectrum. The spectra measured at 77K show anisotropy indicating three values of orthorhombic g-tensor, which is typical of radical, although the values vary for particular samples. [Copyright &y& Elsevier]

In this paper the relaxation times and heat propagation velocity for ultra-high temperature region are investigated. The universal bounds for relaxation times are obtained. The Proca thermal equation for ultra-high temperature electron and nucleon gases are obtained [ABSTRACT FROM AUTHOR]

Abstract: The aim of the present study was the investigation of the effects of macroscopic stress triaxiality on the presence and evolution of damage in particulate MMC. Two Al6061/Al2O3/10p and 20p particulate reinforced composites were investigated on smooth and differently notched specimens pulled in tension at 20 and 250°C. Fractographic analyses and microstructural observations were carried out in order to identify and to map damage mechanisms. Particle fracture was the prominent form of material damage at 20°C, while debonding was the main damage mechanism at 250°C. The distribution of the two damage forms within the specimen volume was interpreted on the basis of the results of finite element analyses. At a given level of triaxiality (considered as the hydrostatic to Von Mises stress ratio), particle fracture localized in regions of high maximum principal stress, generally associated to the high hydrostatic stress. It was further observed that matrix/interface debonding concentrated in the same regions, but developed on other particles at higher/lower load level depending on test temperature. [Copyright &y& Elsevier]

Numerical calculations are becoming more and more efficient in estimating the lifetime of structures under thermomechanical loading. However, these life estimations cannot be reliable if the necessary parameters have not been correctly identified and measured and if all the causes of damage have not been considered. Disk testing under gas pressure is similar to oil bulging testing. However, disk testing can easily be used for the mechanical characterization of materials subject to more varied solicitations: monotone loading (biaxial rupture tests at strain rates from 10−6 to 100 s−1), constant loading under high stresses (sustained load) at elevated temperature (creep tests), cyclic loading (mechanical slow fatigue tests); the temperature may be chosen between 20 and 900 °C and the environment may be studied by comparing the results obtained with either an inert gas or reactive gas. Moreover, disk testing reveals light damage since crossing cracks through the thin membrane create leakages detected by a mass spectrometer. In this paper, we present an original method of calculation developed to determine the true mechanical properties of the pressurized disk; the method of calculation is validated because its numerical results are identical to the measured tensile properties. In addition, the range of uniform deformation is correctly determined; this property is needed to establish sheet formability which is not clearly determined by oil bulging. Of course, the mechanical behaviour can be determined within the whole ranges of temperature and strain rates; such wide ranges cannot be tested by other techniques such as tensile testing or oil bulging. As disk edges are not stressed during testing, the results are very reproducible at any temperature and at any strain rate while the machining or cutting defects initiate very scattered ruptures of tensile specimens tested at high temperature or at high strain rate. The disk and its loading simulate real applications with thin walls embedded by thick parts such as thermal exchangers or spatial engines. The analytical method of calculation may be used for identifying the needed parameters of thermomechanical modelling; it will be optimized by finite elements methods and it would allow a rational quantification of hydrogen embrittlement. [ABSTRACT FROM AUTHOR]

The fatigue of single thermoplastic fibres has been well documented to occur in a reproducible manner when they are subjected to certain cyclic loading conditions. The fatigue fracture morphologies of these fibres are very distinctive and differ markedly from other types of failure. This type of behaviour, which is clearly seen with the unambiguous tests on single fibres, must reflect behaviour of fibres in more complex structures which are subjected to cyclic loading. Only limited numbers of reports have, however, shown similar fracture morphologies with fibres extracted from fibre bundles embedded in a matrix material such as rubber. Usually the fractured ends of fibres taken from structures are seen to be shorter than those obtained in single fibre tests and also they show more complex and confused crack growth. The present study reveals that the low thermal conductivity of the fibres, exacerbated when they are embedded in a rubber matrix, leads to very high temperature rises, which is not the case in single fibre tests and under these conditions, crack initiation occurs across the fibre section instead of being restricted to the near surface region. Tests on single fibres at temperatures up to and beyond the glass transition temperature have shown how the fracture morphologies become modified. The fatigue process has been seen to become generalised throughout the fibre and failure occurs due to the coalescence of several cracks, some of which are initiated in the core of the fibre. In all cases, the cracks can be seen to have been initiated by solid inclusions in the fibres. [ABSTRACT FROM AUTHOR]

Abstract: Albany HTS cable project is going on with the support of US Federal and New York States. The HTS cables included the Bi2223 tapes sintered by CT-OP (controlled over-pressure) process has 34.5kV and 800A capacity. The cable system was manufactured in Japan, and shipped to Albany. A 320m cable and a 30m cable were installed into the conduits under the ground. Subsequently, a splice box was assembled in the vault, and two terminations were connected to the HTS cable on the ground. Cryogenic refrigeration system was also mounted at the site by BOC. Initial cooling process was conducted as measuring distributed temperatures along the cable. The results of off-grid test, i.e. measuring heat loss, pressure loss, critical current, and DC withstand test, were carried out successfully. HTS cable system was connected to the real grid on 20 July 2006. The cable has been operated stably for 3months as monitored by Remote Operation Center of BOC. This report outlines the installation and test results on Albany HTS cable project. [Copyright &y& Elsevier]

Abstract: Ac loss behavior in HTS bulk materials is studied by developing an analytic method. The self-heating effect on the distributions of temperature in HTS bulks has been calculated. A critical frequency which sets the upper limit for driving frequency of the external field in sustaining a superconducting state is obtained. Our model provides useful information of understanding the experimental phenomena, including an anomalous ac loss behavior, a retardation of the inner field respect to the external ac field, etc., in HTS bulk materials. [Copyright &y& Elsevier]

Al2O3–ZrO2 composites were sintered using low cost extended arc thermal plasma reactor and conventional heating. Composites prepared in a wide range of composition were studied in terms of their density, shrinkage, hardness, structure, microstructure and dielectric response. Experimental parameter such as sintering time, sintering temperature and plasma power were optimized to achieve higher sintered end product. Highly dense sintered products were obtained by plasma heating route within short sintering time compared with conventional sintered method. Interesting development pertaining to structure and phase evolution, structure and dielectric response are analyzed. It is found that compositional variation in this composite produces structural phase separation at different sintering conditions, which is more in plasma heating product than conventional heated product. Plasma sintered product always shows less dielectric constant as compared to conventional sintered sample. [ABSTRACT FROM AUTHOR]

Abstract: The carbon monoxide (CO) poisoning effect on carbon supported catalysts (Pt–Ru/C and Pt/C) in polymer electrolyte membrane (PEM) fuel cells has been investigated at higher temperatures (T >100°C) under different relative humidity (RH) conditions. To reduce the IR losses in higher temperature/lower relative humidity, Nafion®–Teflon®–Zr(HPO4)2 composite membranes were applied as the cell electrolytes. Fuel cell polarization investigation as well as CO stripping voltammetry measurements was carried out at three cell temperatures (80, 105 and 120°C), with various inlet anode relative humidity (35%, 58% and 100%). CO concentrations in hydrogen varied from 10ppm to 2%. The fuel cell performance loss due to CO poisoning was significantly alleviated at higher temperature/lower RH due to the lower CO adsorption coverage on the catalytic sites, in spite that the anode catalyst utilization was lower at such conditions due to higher ionic resistance in the electrode. Increasing the anode inlet relative humidity at the higher temperature also alleviated the fuel cell performance losses, which could be attributed to the combination effects of suppressing CO adsorption, increasing anode catalyst utilization and favoring OHads group generation for easier CO oxidation. [Copyright &y& Elsevier]

Various methods of gas compression are reviewed, which are intended for heating the gas. Special attention is given to units of nonisentropic compression of the mechanical heat-engineering type, in which the gas is transferred from chamber to chamber in order to increase the temperature. The units are subdivided into classes or systems, namely, those of impulse, pulse-periodic, and continuous operation. Methods are discussed of mathematical description of processes occurring in units of this type, including analytical investigation of simplified qualitative models and numerical simulation in more complex cases close to reality. [ABSTRACT FROM AUTHOR]

Discrete auroras have (1) narrow size s<=30 km in at least one dimension (e.g., north-south) and (2) often rapid variation of forms, especially where the size is extremely small, s<=1 km. These points mesh with spatial and temporal features observed at several Earth radii in earthward flows (bursts) of hot plasma along high-latitude geomagnetic field lines. The flows (include PSBL) usually have some filamentary structure with transverse widths of a few local gyroradii of the hot protons (kT∼1–30 keV), i.e., widths that encompass auroral-arc size when scaled by magnetic field-line separation. At these widths, modest density gradients (δn∼0.01–0.1 cm-3) lead to charge separation by differential mirroring of hot protons and electrons and large perpendicular electric fields. Thermal escape of ionspheric electrons into positive charge layer builds up magnetic field-aligned potential difference that accelerates hot electrons from negative charge layer into the ionosphere within auroral arc thickness. As a corollary, the model delineates a mechanism for charge-driven plasma instabilities. [ABSTRACT FROM AUTHOR]

Abstract: A product analysis study of γ-irradiated benzophenone aqueous solutions from room temperature to 400°C has been carried out by the combination of a flow irradiation system and a liquid chromatographic method. At room temperature, the main decomposition products are phenol and hydroxybenzophenone isomers. In high temperature and supercritical water solutions, 9-fluorenone appears as an important product and the G-value of benzophenone consumption depends significantly on the water density under supercritical conditions. [Copyright &y& Elsevier]

Abstract: The silicon-on-insulator (SOI) wafer fabrication technique has been developed by using ion-cut process, based on proton implantation and wafer bonding techniques. Proton implantation has been done at energies ranging from 70keV to 466keV for thick SOI wafers (200–5000nm SOI) fabrication. A preliminary experiments showed that effective doses were in the 6–9×1016 H+/cm2 range, and the annealing at 450–550°C for 30min was found to be optimum for wafer splitting. Direct wafer bonding was performed by joining two wafers together after creating hydrophilic surfaces by a modified RCA cleaning, and an IR inspection was followed to ensure a void free bonding. The wafer splitting was accomplished by annealing at the predetermined optimum condition, and high temperature annealing was then performed at 1100°C for 60min to stabilize the bonding interface. TEM observation revealed no detectable defect at the SOI structure, and the interface trap charge density at the upper interface of the BOX was measured to be low enough to keep ‘thermal’ quality. [Copyright &y& Elsevier]

Ge and Ta ion implantation of silicon and carbon substrates has been obtained at PALS Research Laboratory in Prague by using laser pulses of 400 ps duration, 438 nm wavelength, 10 14-16 W/cm 2 intensity. Substrates were exposed in vacuum at different distances from the target and at different angles with respect to the normal to the target surface. ‘On line’ measurements of ion energy were obtained with time-of-flight techniques by using an electrostatic deflector as ion energy analyzer. ‘Off line’ measurements of ion energy were obtained by Rutherford backscattering spectrometry (RBS) of 2.25 MeV He 2+ beam at CEDAD Laboratory of Lecce University. The RBS spectra have given the depth profiles of the ion-implanted species and the implanted doses as a function of the laser intensity, angular position and target distance. A spectra deconvolution method based on the ion stopping power in the substrate matrix was applied in order to evidence the energy of the implanted ions. Measurements indicate that ions with energy ranging between 100 keV and 10 MeV and dose of the order of 10 14-16 /cm 2 are implanted and that the process of ion implantation occurs mainly in substrates placed at little angles with respect to the normal to the target surface. Only a thin film deposition occurs for substrates placed at large angles with respect to the normal direction. Results indicate that the ion energies measured with the ‘on line’ and the ‘off line’ techniques are in good agreement. [ABSTRACT FROM AUTHOR]

The transient internal probe (TIP) is a diagnostic for local internal field measurements in high temperature plasmas. A verdet material, which rotates the polarization angle of the laser light under magnetic fields, is launched into a plasma at about 1.8 km/s. A linearly polarized Ar+ laser illuminates the probe in transit and the light retroreflected from the probe is analyzed to determine the local magnetic field profiles. The TIP has been used for magnetic field measurements on the helicity injected torus where electron temperature Te<=80 eV. In order to apply the TIP in higher temperature plasmas, refractory clad probes have been developed utilizing a sapphire tube, rear disc, and a MgO window on the front. The high melting points of these refractory materials should allow probe operation at plasma electron temperatures up to Te∼300 eV. A retroreflecting probe has also been developed using “catseye” optics. The front window is replaced with a plano-convex MgO lens, and the back surface of the probe is aluminized. This approach reduces spurious polarization effects and provides refractory cladding for the probe entrance face. In-flight measurements of a static magnetic field demonstrate the ability of the clad probes to withstand gun-launch acceleration, and provide high accuracy measurements of magnetic field. [ABSTRACT FROM AUTHOR]

Abstract: The interaction of hot plasma with material in fusion devices can result in material erosion and irreversible damage. Carbon based materials are proposed for ITER divertor armour. To simulate carbon erosion under high heat fluxes, electron beam heating in the JUDITH facility has been used. In this paper, carbon erosion under energetic electron impact is modeled by the 3D thermomechanics code ‘PEGASUS-3D’. The code is based on a crack generation induced by thermal stress. The particle emission observed in thermal shock experiments is a result of breaking bonds between grains caused by thermal stress. The comparison of calculations with experimental data from JUDITH shows good agreement for various incident power densities and pulse durations. A realistic mean failure stress has been found. Pre-heating of test specimens results in earlier onset of brittle destruction and enhanced particle loss in agreement with experiments. [Copyright &y& Elsevier]

The mass spectra of gases liberated from single-walled carbon nanotubes saturated with deuterium under a pressure of 5 GPa at temperatures up to 500°C (10.8 wt % D) have been measured at different steps of heating to 550°C in a vacuum. Hydrocarbons were found to dominate in the spectra at temperatures up to 400°C, whereas the D2 and HD molecules became the main components of the spectra at 500–550°C. Changes in the spectra with temperature are consistent with the hypothesis that the major portion of hydrogen in the single-walled carbon nanotubes hydrogenated under pressure and reverted to normal conditions was present in the molecular form. The low temperatures of the hydrocarbon liberation are indicative of lower kinetic barriers in the reaction paths of the hydrocarbon liberation as compared with the liberation of D2 molecules. Spectral-peak-shape analysis demonstrates the high hydrophilicity of hydrogenated single-walled carbon nanotubes, whereas the sorption of atmospheric oxygen is insignificant as compared with the sorption of water. © 2004 MAIK “Nauka/Interperiodica”. [ABSTRACT FROM AUTHOR]

We report on the design and performance of a combined heating/cooling stage for the thermalization of clusters in a gas phase time-of-flight mass spectrometer. With this setup the cluster temperature can sensitively be adjusted within the range from 100 up to 800 K and higher. The unique combination of a heating stage with a subsequent cooling stage allows us to perform thermodynamic investigations on clusters at very high temperatures without quality losses in the spectra due to delayed fragmentation in the drift tube of the mass spectrometer. The performance of the setup is demonstrated by the example of (C[sub 60])[sub n] clusters. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]