A new procedure for the determination of distillation temperature distribution of high-boiling petroleum products and fractions.

PubMed

Boczkaj, Grzegorz; Przyjazny, Andrzej; Kamiński, Marian

2011-03-01

The distribution of distillation temperatures of liquid and semi-fluid products, including petroleum fractions and products, is an important process and practical parameter. It provides information on properties of crude oil and content of particular fractions, classified on the basis of their boiling points, as well as the optimum conditions of atmospheric or vacuum distillation. At present, the distribution of distillation temperatures is often investigated by simulated distillation (SIMDIS) using capillary gas chromatography (CGC) with a short capillary column with polydimethylsiloxane as the stationary phase. This paper presents the results of investigations on the possibility of replacing currently used CGC columns for SIMDIS with a deactivated fused silica capillary tube without any stationary phase. The SIMDIS technique making use of such an empty fused silica column allows a considerable lowering of elution temperature of the analytes, which results in a decrease of the final oven temperature while ensuring a complete separation of the mixture. This eliminates the possibility of decomposition of less thermally stable mixture components and bleeding of the stationary phase which would result in an increase of the detector signal. It also improves the stability of the baseline, which is especially important in the determination of the end point of elution, which is the basis for finding the final temperature of distillation. This is the key parameter for the safety process of hydrocracking, where an excessively high final temperature of distillation of a batch can result in serious damage to an expensive catalyst bed. This paper compares the distribution of distillation temperatures of the fraction from vacuum distillation of petroleum obtained using SIMDIS with that obtained by the proposed procedure. A good agreement between the two procedures was observed. In addition, typical values of elution temperatures of n-paraffin standards obtained by the two procedures were compared. Finally, the agreement between boiling points of polar compounds determined from their retention times and actual boiling points was investigated.

High Temperature Test Facility Preliminary RELAP5-3D Input Model Description

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bayless, Paul David

A RELAP5-3D input model is being developed for the High Temperature Test Facility at Oregon State University. The current model is described in detail. Further refinements will be made to the model as final as-built drawings are released and when system characterization data are available for benchmarking the input model.

Ge quantum dot arrays grown by ultrahigh vacuum molecular-beam epitaxy on the Si(001) surface: nucleation, morphology, and CMOS compatibility.

PubMed

Yuryev, Vladimir A; Arapkina, Larisa V

2011-09-05

Issues of morphology, nucleation, and growth of Ge cluster arrays deposited by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface are considered. Difference in nucleation of quantum dots during Ge deposition at low (≲600°C) and high (≳600°C) temperatures is studied by high resolution scanning tunneling microscopy. The atomic models of growth of both species of Ge huts--pyramids and wedges-- are proposed. The growth cycle of Ge QD arrays at low temperatures is explored. A problem of lowering of the array formation temperature is discussed with the focus on CMOS compatibility of the entire process; a special attention is paid upon approaches to reduction of treatment temperature during the Si(001) surface pre-growth cleaning, which is at once a key and the highest-temperature phase of the Ge/Si(001) quantum dot dense array formation process. The temperature of the Si clean surface preparation, the final high-temperature step of which is, as a rule, carried out directly in the MBE chamber just before the structure deposition, determines the compatibility of formation process of Ge-QD-array based devices with the CMOS manufacturing cycle. Silicon surface hydrogenation at the final stage of its wet chemical etching during the preliminary cleaning is proposed as a possible way of efficient reduction of the Si wafer pre-growth annealing temperature.

Development of Ultra-Efficient Electric Motors Final Technical Report Covering work from April 2002 through September 2007

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rich Schiferl

2008-05-30

High temperature superconducting (HTS) motors offer the potential for dramatic volume and loss reduction compared to conventional, high horspower, industrial motors. This report is the final report on the results of eight research tasks that address some of the issues related to HTS motor development that affect motor efficiency, cost, and reliability.

High Temperature Falling Particle Receiver (2012 - 2016) - Final DOE Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, Clifford K.

The objective of this work was to advance falling particle receiver designs for concentrating solar power applications that will enable higher temperatures (>700 °C) and greater power-cycle efficiencies (≥50% thermal-to-electric). Modeling, design, and testing of components in Phases 1 and 2 led to the successful on-sun demonstration in Phase 3 of the world’s first continuously recirculating high-temperature 1 MW t falling particle receiver that achieved >700 °C particle outlet temperatures at mass flow rates ranging from 1 – 7 kg/s.

High-Temperature Rocket Engine

NASA Technical Reports Server (NTRS)

Schneider, Steven J.; Rosenberg, Sanders D.; Chazen, Melvin L.

1994-01-01

Two rocket engines that operate at temperature of 2,500 K designed to provide thrust for station-keeping adjustments of geosynchronous satellites, for raising and lowering orbits, and for changing orbital planes. Also useful as final propulsion stages of launch vehicles delivering small satellites to low orbits around Earth. With further development, engines used on planetary exploration missions for orbital maneuvers. High-temperature technology of engines adaptable to gas-turbine combustors, ramjets, scramjets, and hot components of many energy-conversion systems.

Elimination of Acid Cleaning of High Temperature Salt Water Heat Exchangers: Redesigned Pre-Production Full-Scale Heat Pipe Bleed Air Cooler for Shipboard Evaluation

DTIC Science & Technology

2011-11-01

Cleaning of High Temperature Salt Water Heat Exchangers ESTCP WP-200302 Subtitle: Redesigned Pre-production Full-Scale Heat Pipe Bleed Air Cooler For...FINAL 3. DATES COVERED (From - To) 1-Jan-2003 – 1-Oct-2009 4. TITLE AND SUBTITLE Elimination of Acid Cleaning of High Temperature Salt Water Heat...6-5 Figure 6- 6 HP-BAC Tube Sheet Being Immersed in Ultrasonic Cleaning Tank ..................................... 6-6 Figure 6- 7 Heat Pipe

Bilateral asymmetry of skin temperature is not related to bilateral asymmetry of crank torque during an incremental cycling exercise to exhaustion

PubMed Central

Formenti, Damiano; Ludwig, Nicola; Gargano, Marco; Bosio, Andrea; Rampinini, Ermanno; Alberti, Giampietro

2018-01-01

Although moderate relationships (|r| ∼ 0.5) were reported between skin temperature and performance-related variables (e.g., kinetic), it remains unclear whether skin temperature asymmetry reflects muscle force imbalance in cycling. Therefore, the aim of this study was to assess whether a relationship exists between kinetic and thermal asymmetry during a fatiguing exercise. Ten elite cyclists were enrolled and tested on a maximal incremental cycling test. Peak crank torques of both legs were obtained at the initial and final workload. Likewise, bilateral skin temperatures were recorded before and after exercise. Asymmetric indexes were also calculated for kinetic (AIK) and skin temperature (AIT) outcomes. The bilateral peak crank torques showed a larger difference at the final compared to the initial workload (p < 0.05) of the incremental exercise. Conversely, the bilateral skin temperature did not show any differences at both initial and final workload (p > 0.05). Additionally, trivial relationships were reported between AIK and AIT (−0.3 < r < 0.2) at the initial and final workload. The obtained results showed that changes in bilateral kinetic values did not reflect concurrent changes in bilateral skin temperatures. This finding emphasizes the difficulty of associating the asymmetry of skin temperature with those of muscle effort in elite cyclists. Lastly, our study also provided further insights on thermal skin responses during exhaustive cycling exercise in very highly-trained athletes. PMID:29507831

Oxygen interaction with hexagonal OsB 2 at high temperature

DOE PAGES

Xie, Zhilin; Blair, Richard G.; Orlovskaya, Nina; ...

2016-08-10

The stability of ReB 2-type hexagonal OsB 2 powder at high temperature with oxygen presence has been studied by thermogravimetric analysis, differential scanning calorimetry, SEM, EDS, and high-temperature scanning transmission electron microscopy and XRD. Results of the study revealed that OsB 2 ceramics interact readily with oxygen present in reducing atmosphere, especially at high temperature and produces boric acid, which decomposes on the surface of the powder resulting in the formation of boron vacancies in the hexagonal OsB 2 lattice as well as changes in the stoichiometry of the compound. It was also found that under low oxygen partial pressure,more » sintering of OsB 2 powders occurred at a relatively low temperature (900°C). Finally, hexagonal OsB 2 ceramic is prone to oxidation and it is very sensitive to oxygen partial pressures, especially at high temperatures.« less

Oxygen interaction with hexagonal OsB 2 at high temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Zhilin; Blair, Richard G.; Orlovskaya, Nina

The stability of ReB 2-type hexagonal OsB 2 powder at high temperature with oxygen presence has been studied by thermogravimetric analysis, differential scanning calorimetry, SEM, EDS, and high-temperature scanning transmission electron microscopy and XRD. Results of the study revealed that OsB 2 ceramics interact readily with oxygen present in reducing atmosphere, especially at high temperature and produces boric acid, which decomposes on the surface of the powder resulting in the formation of boron vacancies in the hexagonal OsB 2 lattice as well as changes in the stoichiometry of the compound. It was also found that under low oxygen partial pressure,more » sintering of OsB 2 powders occurred at a relatively low temperature (900°C). Finally, hexagonal OsB 2 ceramic is prone to oxidation and it is very sensitive to oxygen partial pressures, especially at high temperatures.« less

HEAT Sensor: Harsh Environment Adaptable Thermionic Sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Limb, Scott J.

2016-05-31

This document is the final report for the “HARSH ENVIRONMENT ADAPTABLE THERMIONIC SENSOR” project under NETL’s Crosscutting contract DE-FE0013062. This report addresses sensors that can be made with thermionic thin films along with the required high temperature hermetic packaging process. These sensors can be placed in harsh high temperature environments and potentially be wireless and self-powered.

High-Temperature Properties of Mold Flux Observed and Measured In Situ by Single/Double Hot-Thermocouple Technique

NASA Astrophysics Data System (ADS)

Wang, Wanlin; Lyu, Peisheng; Zhou, Lejun; Li, Huan; Zhang, Tongsheng

2018-05-01

Mold flux plays very important roles in the continuous casting process, and its high-temperature properties affect the quality of the final as-cast product greatly. Investigations on the melting, isothermal and nonisothermal crystallization, and phase evolution behaviors under a simulated temperature field for the mold flux system using the single/double hot-thermocouple technique (S/DHTT) were reviewed. Meanwhile, further in situ observations on the wetting behavior and heat transfer ability of the mold flux system were also carried out using the S/DHTT. The results summarized here provide a clear understanding of both the high-temperature properties of mold flux and the detailed application of advanced real-time visual high-temperature S/DHTT to this molten slag system.

Ge quantum dot arrays grown by ultrahigh vacuum molecular-beam epitaxy on the Si(001) surface: nucleation, morphology, and CMOS compatibility

PubMed Central

2011-01-01

Issues of morphology, nucleation, and growth of Ge cluster arrays deposited by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface are considered. Difference in nucleation of quantum dots during Ge deposition at low (≲600°C) and high (≳600°C) temperatures is studied by high resolution scanning tunneling microscopy. The atomic models of growth of both species of Ge huts--pyramids and wedges-- are proposed. The growth cycle of Ge QD arrays at low temperatures is explored. A problem of lowering of the array formation temperature is discussed with the focus on CMOS compatibility of the entire process; a special attention is paid upon approaches to reduction of treatment temperature during the Si(001) surface pre-growth cleaning, which is at once a key and the highest-temperature phase of the Ge/Si(001) quantum dot dense array formation process. The temperature of the Si clean surface preparation, the final high-temperature step of which is, as a rule, carried out directly in the MBE chamber just before the structure deposition, determines the compatibility of formation process of Ge-QD-array based devices with the CMOS manufacturing cycle. Silicon surface hydrogenation at the final stage of its wet chemical etching during the preliminary cleaning is proposed as a possible way of efficient reduction of the Si wafer pre-growth annealing temperature. PMID:21892938

Elevated temperature forming method and preheater apparatus

DOEpatents

Krajewski, Paul E; Hammar, Richard Harry; Singh, Jugraj; Cedar, Dennis; Friedman, Peter A; Luo, Yingbing

2013-06-11

An elevated temperature forming system in which a sheet metal workpiece is provided in a first stage position of a multi-stage pre-heater, is heated to a first stage temperature lower than a desired pre-heat temperature, is moved to a final stage position where it is heated to a desired final stage temperature, is transferred to a forming press, and is formed by the forming press. The preheater includes upper and lower platens that transfer heat into workpieces disposed between the platens. A shim spaces the upper platen from the lower platen by a distance greater than a thickness of the workpieces to be heated by the platens and less than a distance at which the upper platen would require an undesirably high input of energy to effectively heat the workpiece without being pressed into contact with the workpiece.

High Temperature Thermoelectric Materials for Waste Heat Regeneration

DTIC Science & Technology

2013-01-01

ADDRESS. 1. REPORT DATE (DD-MM-YYYY) January 2013 2. REPORT TYPE Final 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE High Temperature...National Aeronautics and Space Administration’s (NASA) deep space explorations, which use radioisotope thermoelectric generators (RTGs) to produce...their octahedral voids (shown in figure 10a) with large rare- earth atoms to reduce their lattice conductivity (20). Ions can also be inserted to

Optimisation of phenolics recovery from Vitex agnus-castus Linn. leaves by high-pressure and temperature extraction.

PubMed

Lataoui, Mohammed; Seffen, Mongi; Aliakbarian, Bahar; Casazza, Alessandro Alberto; Converti, Attilio; Perego, Patrizia

2014-01-01

To optimise recovery of phenolics from Vitex agnus-castus Linn., a non-conventional high-pressure (2-24 bar) and temperature (100-180°C) extraction method was used under nitrogen atmosphere with methanol as a solvent. Optimal temperature was between 100 and 140°C, and optimal extraction time was about one half that of conventional solid/liquid extraction at room temperature. Final yields of total polyphenols, total flavonoids, o-diphenols and anthocyanins extraction were 2.0, 3.0, 2.5 and 11-fold those obtained by conventional extraction.

Stability of Materials in High Temperature Water Vapor: SOFC Applications

NASA Technical Reports Server (NTRS)

Opila, E. J.; Jacobson, N. S.

2010-01-01

Solid oxide fuel cell material systems require long term stability in environments containing high-temperature water vapor. Many materials in fuel cell systems react with high-temperature water vapor to form volatile hydroxides which can degrade cell performance. In this paper, experimental methods to characterize these volatility reactions including the transpiration technique, thermogravimetric analysis, and high pressure mass spectrometry are reviewed. Experimentally determined data for chromia, silica, and alumina volatility are presented. In addition, data from the literature for the stability of other materials important in fuel cell systems are reviewed. Finally, methods for predicting material recession due to volatilization reactions are described.

Metamaterials as a Platform for the Development of Novel Materials for Energy Applications. Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Padilla, Willie

2016-02-11

Final report detailing the work performed on DESC0005240 at Boston College. Report details research into metamaterial absorber theory, thermophotovoltaics a dynamic 3 state material capable of switching between transmissive, reflective, and absorptive states. Also high temperature NIR metamaterials are explored.

Closed-form analytical solutions of high-temperature heat pipe startup and frozen startup limitation

NASA Technical Reports Server (NTRS)

Cao, Y.; Faghri, A.

1992-01-01

Previous numerical and experimental studies indicate that the high-temperature heat pipe startup process is characterized by a moving hot zone with relatively sharp fronts. Based on the above observation, a flat-front model for an approximate analytical solution is proposed. A closed-form solution related to the temperature distribution in the hot zone and the hot zone length as a function of time are obtained. The analytical results agree well with the corresponding experimental data, and provide a quick prediction method for the heat pipe startup performance. Finally, a heat pipe limitation related to the frozen startup process is identified, and an explicit criterion for the high-temperature heat pipe startup is derived. The frozen startup limit identified in this paper provides a fundamental guidance for high-temperature heat pipe design.

Final Report. IUT No. B560420 with UC Berkeley. Organic Chemistry at High Pressures &Temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Montgomery, W; Crowhurst, J C; Zaug, J M

We have successfully completed the research outlined in our proposal: Organic Chemistry at High Pressures and Temperatures. We have experimentally determined a phase diagram which documents the phases and reaction regimes of cyanuric acid , H{sub 3}C{sub 3}N{sub 3}O{sub 3} (1,3,5-triazine-2,4,6-trione), from 300 - 750 K and 0 - 8.1 GPa. We utilized a comparatively new technique to study thin samples of cyanuric acid in the diamond anvil cell in order to collect ambient temperature, high pressure FTIR and Raman data as well as the high-pressure, high-temperature data used in the phase diagram. These experiments made use of the CMLSmore » High-pressure lab's diamond anvil facilities as well as the FTIR and Raman systems.« less

Salt flux synthesis of single and bimetallic carbide nanowires

NASA Astrophysics Data System (ADS)

Leonard, Brian M.; Waetzig, Gregory R.; Clouser, Dale A.; Schmuecker, Samantha M.; Harris, Daniel P.; Stacy, John M.; Duffee, Kyle D.; Wan, Cheng

2016-07-01

Metal carbide compounds have a broad range of interesting properties and are some of the hardest and highest melting point compounds known. However, their high melting points force very high reaction temperatures and thus limit the formation of high surface area nanomaterials. To avoid the extreme synthesis temperatures commonly associated with these materials, a new salt flux technique has been employed to reduce reaction temperatures and form these materials in the nanometer regime. Additionally, the use of multiwall carbon nanotubes as a reactant further reduces the diffusion distance and provides a template for the final carbide materials. The metal carbide compounds produced through this low temperature salt flux technique maintain the nanowire morphology of the carbon nanotubes but increase in size to ˜15-20 nm diameter due to the incorporation of metal in the carbon lattice. These nano-carbides not only have nanowire like shape but also have much higher surface areas than traditionally prepared metal carbides. Finally, bimetallic carbides with composition control can be produced with this method by simply using two metal precursors in the reaction. This method provides the ability to produce nano sized metal carbide materials with size, morphology, and composition control and will allow for these compounds to be synthesized and studied in a whole new size and temperature regime.

High temperature combined with drought affect rainfed spring wheat and barley in South-Eastern Russia: I. Phenology and growth

PubMed Central

Hossain, Akbar; Teixeira da Silva, Jaime A.; Lozovskaya, Marina Viacheslavovna; Zvolinsky, Vacheslav Petrovich

2012-01-01

Heat stress, when combined with drought, is one of the major limitations to food production worldwide, especially in areas that use rainfed agriculture. As the world population continues to grow, and water resources for the crop production decline and temperature increases, so the development of heat- and drought-tolerant cultivars is an issue of global concern. In this context, four barley and two wheat genotypes were evaluated in south-eastern Russia to identify heat- and drought-tolerant genotypes for future breeding programmes by identifying suitable sowing times for specific genotypes. High temperature stress, when combined with drought during late sowing, decreased the days to visible awns, days to heading and days to ripe harvest, finally negatively affecting the growth and development of plants and resulting in a lower plant population m−2, tillers plant−1, plant height and dry matter production m−2. On the other hand, low temperature in combination with early sowing increased the number of days to germination, reduced seedling stand establishment and tillering capacity, finally affecting the growth and development of the crops. Compared to overall performance and optimum sowing date, barley genotypes ‘Zernograd.770’ and ‘Nutans’, and wheat genotype ‘Line4’ performed best in both late (high temperature with drought) and early (low temperature) stress conditions. PMID:23961209

The design of high precision temperature control system for InGaAs short-wave infrared detector

NASA Astrophysics Data System (ADS)

Wang, Zheng-yun; Hu, Yadong; Ni, Chen; Huang, Lin; Zhang, Aiwen; Sun, Xiao-bing; Hong, Jin

2018-02-01

The InGaAs Short-wave infrared detector is a temperature-sensitive device. Accurate temperature control can effectively reduce the background signal and improve detection accuracy, detection sensitivity, and the SNR of the detection system. Firstly, the relationship between temperature and detection background, NEP is analyzed, the principle of TEC and formula between cooling power, cooling current and hot-cold interface temperature difference are introduced. Then, the high precision constant current drive circuit based on triode voltage control current, and an incremental algorithm model based on deviation tracking compensation and PID control are proposed, which effectively suppresses the temperature overshoot, overcomes the temperature inertia, and has strong robustness. Finally, the detector and temperature control system are tested. Results show that: the lower of detector temperature, the smaller the temperature fluctuation, the higher the detection accuracy and the detection sensitivity. The temperature control system achieves the high temperature control with the temperature control rate is 7 8°C/min and the temperature fluctuation is better than +/-0. 04°C.

Structure and enhanced thermochromic performance of low-temperature fabricated VO 2/V 2O 3 thin film

DOE PAGES

Sun, Guangyao; Cao, Xun; Gao, Xiang; ...

2016-10-06

For VO 2-based smart window manufacture, it is a long-standing demand for high-quality thin films deposited at low temperature. In this paper, the thermochromic films of VO 2 were deposited by a magnetron sputtering method at a fairly low temperature of 250 °C without subsequent annealing by embedding a V 2O 3 interlayer. V 2O 3 acts as a seed layer to lower the depositing temperature and buffer layer to epitaxial grow VO 2 film. The VO 2/V 2O 3 films display high solar modulating ability and narrow hysteresis loop. Finally, our data can serve as a promising point formore » industrial production with high degree of crystallinity at a low temperature.« less

Method of treating intermetallic alloy hydrogenation/oxidation catalysts for improved impurity poisoning resistance, regeneration and increased activity

DOEpatents

Wright, Randy B.

1992-01-01

Alternate, successive high temperature oxidation and reduction treatments, in either order, of intermetallic alloy hydrogenation and intermetallic alloy oxidation catalysts unexpectedly improves the impurity poisoning resistance, regeneration capacity and/or activity of the catalysts. The particular alloy, and the final high temperature treatment given alloy (oxidation or reduction) will be chosen to correspond to the function of the catalyst (oxidation or hydrogenation).

Responses of Rapid Viscoanalyzer Profile and Other Rice Grain Qualities to Exogenously Applied Plant Growth Regulators under High Day and High Night Temperatures

PubMed Central

Fahad, Shah; Hussain, Saddam; Saud, Shah; Hassan, Shah; Chauhan, Bhagirath Singh; Khan, Fahad; Ihsan, Muhammad Zahid; Ullah, Abid; Wu, Chao; Bajwa, Ali Ahsan; Alharby, Hesham; Amanullah; Nasim, Wajid; Shahzad, Babar; Tanveer, Mohsin; Huang, Jianliang

2016-01-01

High-temperature stress degrades the grain quality of rice; nevertheless, the exogenous application of plant growth regulators (PGRs) might alleviate the negative effects of high temperatures. In the present study, we investigated the responses of rice grain quality to exogenously applied PGRs under high day temperatures (HDT) and high night temperatures (HNT) under controlled conditions. Four different combinations of ascorbic acid (Vc), alpha-tocopherol (Ve), brassinosteroids (Br), methyl jasmonates (MeJA) and triazoles (Tr) were exogenously applied to two rice cultivars (IR-64 and Huanghuazhan) prior to the high-temperature treatment. A Nothing applied Control (NAC) was included for comparison. The results demonstrated that high-temperature stress was detrimental for grain appearance and milling qualities and that both HDT and HNT reduced the grain length, grain width, grain area, head rice percentage and milled rice percentage but increased the chalkiness percentage and percent area of endosperm chalkiness in both cultivars compared with ambient temperature (AT). Significantly higher grain breakdown, set back, consistence viscosity and gelatinization temperature, and significantly lower peak, trough and final viscosities were observed under high-temperature stress compared with AT. Thus, HNT was more devastating for grain quality than HDT. The exogenous application of PGRs ameliorated the adverse effects of high temperature in both rice cultivars, and Vc+Ve+MejA+Br was the best combination for both cultivars under high temperature stress. PMID:27472200

Practical ultrasonic transducers for high-temperature applications using bismuth titanate and Ceramabind 830

NASA Astrophysics Data System (ADS)

Xu, Janet L.; Batista, Caio F. G.; Tittmann, Bernhard R.

2018-04-01

Structural health monitoring of large valve bodies in high-temperature environments such as power plants faces several limitations: commercial transducers are not rated for such high temperatures, gel couplants will evaporate, and measurements cannot be made in-situ. To solve this, we have furthered the work of Ledford in applying a practical transducer in liquid form which hardens and air dries directly onto the substrate. The transducer material is a piezoceramic film composed of bismuth titanate and a high-temperature binding agent, Ceramabind 830. The effects of several fabrication conditions were studied to optimize transducer performance and ensure repeatability. These fabrication conditions include humidity, binder ratio, water ratio, substrate roughness, and film thickness. The final product is stable for both reactive and non-reactive substrates, has a quick fabrication time, and has an operating temperature up to the Curie temperature of BIT, 650°C, well beyond the safe operating temperature of PZT (150°C).

Combined elevated temperature and soil waterlogging stresses inhibit cell elongation by altering osmolyte composition of the developing cotton (Gossypium hirsutum L.) fiber.

PubMed

Chen, Yinglong; Wang, Haimiao; Hu, Wei; Wang, Shanshan; Wang, Youhua; Snider, John L; Zhou, Zhiguo

2017-03-01

Soil waterlogging events and high temperature conditions occur frequently in the Yangtze River Valley, yet the effects of these co-occurring stresses on fiber elongation have received little attention. In the current study, the combined effect of elevated temperature (ET) and soil waterlogging (SW) more negatively affected final fiber length (reduced by 5.4%-11.3%) than either stress alone by altering the composition of osmotically active solutes (sucrose, malate, and K + ), where SW had the most pronounced effect. High temperature accelerated early fiber development, but limited the duration of elongation, thereby limiting final fiber length. Treatment of ET alone altered fiber sucrose content mainly through decreased source strength and the expression of the sucrose transporter gene GhSUT-1, making sucrose availability the primary determinant of final fiber length under ET. Waterlogging stress alone decreased source strength, down-regulated GhSUT-1 expression and enhanced SuSy catalytic activity for sucrose reduction. Waterlogging treatment alone also limited fiber malate production by down-regulating GhPEPC-1 & -2. However, combined elevated temperature and waterlogging limited primary cell wall synthesis by affecting GhCESAs genes and showed a negative impact on all three major osmotic solutes through the regulation of GhSUT-1, GhPEPC-1 & -2 and GhKT-1 expression and altered SuSy activity, which functioned together to produce a shorter fiber length. Copyright © 2017 Elsevier B.V. All rights reserved.

Thermo-mechanical simulation of liquid-supported stretch blow molding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zimmer, J.; Stommel, M.

2015-05-22

Stretch blow molding is the well-established plastics forming method to produce Polyehtylene therephtalate (PET) bottles. An injection molded preform is heated up above the PET glass transition temperature (Tg∼85°C) and subsequently inflated by pressurized air into a closed cavity. In the follow-up filling process, the resulting bottle is filled with the final product. A recently developed modification of the process combines the blowing and filling stages by directly using the final liquid product to inflate the preform. In a previously published paper, a mechanical simulation and successful evaluation of this liquid-driven stretch blow molding process was presented. In this way,more » a realistic process parameter dependent simulation of the preform deformation throughout the forming process was enabled, whereas the preform temperature evolution during forming was neglected. However, the formability of the preform is highly reduced when the temperature sinks below Tg during forming. Experimental investigations show temperature-induced failure cases due to the fast heat transfer between hot preform and cold liquid. Therefore, in this paper, a process dependent simulation of the temperature evolution during processing to avoid preform failure is presented. For this purpose, the previously developed mechanical model is used to extract the time dependent thickness evolution. This information serves as input for the heat transfer simulation. The required material parameters are calibrated from preform cooling experiments recorded with an infrared-camera. Furthermore, the high deformation ratios during processing lead to strain induced crystallization. This exothermal reaction is included into the simulation by extracting data from preform measurements at different stages of deformation via Differential Scanning Calorimetry (DSC). Finally, the thermal simulation model is evaluated by free forming experiments, recorded by a high-speed infrared camera.« less

Cooling by spontaneous decay of highly excited antihydrogen atoms in magnetic traps.

PubMed

Pohl, T; Sadeghpour, H R; Nagata, Y; Yamazaki, Y

2006-11-24

An efficient cooling mechanism of magnetically trapped, highly excited antihydrogen (H) atoms is presented. This cooling, in addition to the expected evaporative cooling, results in trapping of a large number of H atoms in the ground state. It is found that the final fraction of trapped atoms is insensitive to the initial distribution of H magnetic quantum numbers. Expressions are derived for the cooling efficiency, demonstrating that magnetic quadrupole (cusp) traps provide stronger cooling than higher order magnetic multipoles. The final temperature of H confined in a cusp trap is shown to depend as approximately 2.2T(n0)n(0)(-2/3) on the initial Rydberg level n0 and temperature T(n0).

Deflagration of thermite - ammonium nitrate based propellant mixture

NASA Astrophysics Data System (ADS)

Duraes, Luisa; Morgado, Joel; Portugal, Antonio; Campos, Jose

2001-06-01

Reaction between iron oxide (Fe2O3) and aluminum (Al) is the reference of the classic thermite compositions. The efficency of the reaction, for a given initial composition of Fe2O3 and Al, is evaluated by the final temperature and by the mass ratio of Al2O3 /AlO in products of combustion (in condensed phase). In order to increase pressure in products of thermite reaction, the original composition is mixed, with an original twin screw extruder, with a propellant binder composed of ammonium and sodium nitrates, initialy solved in formamide (CH3NO) and mixed with a polyurethane solution. The products of combustion and pyrolysis of this binder, reacting with thermite products, generates high pressure and high temperature conditions. These experimental conditions are also predicted using THOR code. The study presents DSC and TGA results of components and mixtures, and correlates them to the ignition phenomena and reaction properties. The regression rate of combustion and final attained temperature and pressure, in a closed confinement, as a function of composition of thermite components/propellant binder, are presented and discussed. They show the influence of gaseous combustion and pyrolysis products of binder in final reaction.

High and low temperatures have unequal reinforcing properties in Drosophila spatial learning.

PubMed

Zars, Melissa; Zars, Troy

2006-07-01

Small insects regulate their body temperature solely through behavior. Thus, sensing environmental temperature and implementing an appropriate behavioral strategy can be critical for survival. The fly Drosophila melanogaster prefers 24 degrees C, avoiding higher and lower temperatures when tested on a temperature gradient. Furthermore, temperatures above 24 degrees C have negative reinforcing properties. In contrast, we found that flies have a preference in operant learning experiments for a low-temperature-associated position rather than the 24 degrees C alternative in the heat-box. Two additional differences between high- and low-temperature reinforcement, i.e., temperatures above and below 24 degrees C, were found. Temperatures equally above and below 24 degrees C did not reinforce equally and only high temperatures supported increased memory performance with reversal conditioning. Finally, low- and high-temperature reinforced memories are similarly sensitive to two genetic mutations. Together these results indicate the qualitative meaning of temperatures below 24 degrees C depends on the dynamics of the temperatures encountered and that the reinforcing effects of these temperatures depend on at least some common genetic components. Conceptualizing these results using the Wolf-Heisenberg model of operant conditioning, we propose the maximum difference in experienced temperatures determines the magnitude of the reinforcement input to a conditioning circuit.

Helium (3) Rich Solar Flares

DOE R&D Accomplishments Database

Colgate, S. A.; Audouze, J.; Fowler, W. A.

1977-05-03

The extreme enrichment of {sup 3} He {sup 4} He greater than or equal to 1 in some solar flares as due to spallation and the subsequent confinement of the products in a high temperature, kT approx. = 200 keV, high density, n{sub e} approx. = 3 x 10{sup 15} cm {sup -3} plasma associated with the magnetic instability producing the flare is interpreted. The pinch or filament is a current of high energy protons that creates the spallation and maintains the temperature that produces the high energy x-ray spectrum and depletes other isotopes D, Li, Be, and B as observed. Finally the high temperature plasma is a uniquely efficient spallation target that is powered by the interaction of stellar convection and self generated magnetic field.

Analysis of impact melt and vapor production in CTH for planetary applications

DOE PAGES

Quintana, S. N.; Crawford, D. A.; Schultz, P. H.

2015-05-19

This study explores impact melt and vapor generation for a variety of impact speeds and materials using the shock physics code CTH. The study first compares the results of two common methods of impact melt and vapor generation to demonstrate that both the peak pressure method and final temperature method are appropriate for high-speed impact models (speeds greater than 10 km/s). However, for low-speed impact models (speeds less than 10 km/s), only the final temperature method is consistent with laboratory analyses to yield melting and vaporization. Finally, a constitutive model for material strength is important for low-speed impacts because strengthmore » can cause an increase in melting and vaporization.« less

Analysis of impact melt and vapor production in CTH for planetary applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quintana, S. N.; Crawford, D. A.; Schultz, P. H.

This study explores impact melt and vapor generation for a variety of impact speeds and materials using the shock physics code CTH. The study first compares the results of two common methods of impact melt and vapor generation to demonstrate that both the peak pressure method and final temperature method are appropriate for high-speed impact models (speeds greater than 10 km/s). However, for low-speed impact models (speeds less than 10 km/s), only the final temperature method is consistent with laboratory analyses to yield melting and vaporization. Finally, a constitutive model for material strength is important for low-speed impacts because strengthmore » can cause an increase in melting and vaporization.« less

Graphitization of Coke and Its Interaction with Slag in the Hearth of a Blast Furnace

NASA Astrophysics Data System (ADS)

Li, Kejiang; Zhang, Jianliang; Liu, Yanxiang; Barati, Mansoor; Liu, Zhengjian; Zhong, Jianbo; Su, Buxin; Wei, Mengfang; Wang, Guangwei; Yang, Tianjun

2016-04-01

Coke reaction behavior in the blast furnace hearth has yet to be fully understood due to limited access to the high temperature zone. The graphitization of coke and its interaction with slag in the hearth of blast furnace were investigated with samples obtained from the center of the deadman of a blast furnace during its overhaul period. All hearth coke samples from fines to lumps were confirmed to be highly graphitized, and the graphitization of coke in the high temperature zone was convinced to start from the coke surface and lead to the formation of coke fines. It will be essential to perform further comprehensive investigations on graphite formation and its evolution in a coke as well as its multi-effect on blast furnace performance. The porous hearth cokes were found to be filled up with final slag. Further research is required about the capability of coke to fill final slag and the attack of final slag on the hearth bottom refractories since this might be a new degradation mechanism of refractories located in the hearth bottom.

Characterization of dairy cattle manure/wallboard paper compost mixture.

PubMed

Saludes, Ronaldo B; Iwabuchi, Kazunori; Miyatake, Fumihito; Abe, Yoshiyuki; Honda, Yoshifumi

2008-10-01

The aim of this research was to evaluate the use of manufacturing wallboard paper scraps as an alternative bulking agent for dairy cattle manure composting. The characteristics of the composting process were studied based on the changes in physico-chemical parameters and final compost quality. Composting of dairy cattle manure with wallboard paper was performed in a 481-L cylindrical reactor with vacuum-type aeration. Rapid degradation of organic matter was observed during the thermophilic stage of composting due to high microbial activity. High temperature and alkaline pH conditions promoted intense ammonia emission during the early stage of composting. The number of mesophilic and thermophilic microorganisms were found to be affected by changes in temperature at different composting stages. The total nitrogen (N), phosphorus (P), potassium (K), and sodium (Na) concentrations of the mixture did not change significantly after 28days of composting. However, the presence of gypsum in the paper scraps increased the calcium content of the final compost. The wallboard paper had no phyto-inhibitory effects as shown by high germination index of final compost (GI=99%).

Electrical treeing behaviors in silicone rubber under an impulse voltage considering high temperature

NASA Astrophysics Data System (ADS)

Yunxiao, ZHANG; Yuanxiang, ZHOU; Ling, ZHANG; Zhen, LIN; Jie, LIU; Zhongliu, ZHOU

2018-05-01

In this paper, work was conducted to reveal electrical tree behaviors (initiation and propagation) of silicone rubber (SIR) under an impulse voltage with high temperature. Impulse frequencies ranging from 10 Hz to 1 kHz were applied and the temperature was controlled between 30 °C and 90 °C. Experimental results show that tree initiation voltage decreases with increasing pulse frequency, and the descending amplitude is different in different frequency bands. As the pulse frequency increases, more frequent partial discharges occur in the channel, increasing the tree growth rate and the final shape intensity. As for temperature, the initiation voltage decreases and the tree shape becomes denser as the temperature gets higher. Based on differential scanning calorimetry results, we believe that partial segment relaxation of SIR at high temperature leads to a decrease in the initiation voltage. However, the tree growth rate decreases with increasing temperature. Carbonization deposition in the channel under high temperature was observed under microscope and proven by Raman analysis. Different tree growth models considering tree channel characteristics are proposed. It is believed that increasing the conductivity in the tree channel restrains the partial discharge, holding back the tree growth at high temperature.

‘Hass’ avocado quality as influenced by temperature and ethylene prior to and during final ripening

USDA-ARS?s Scientific Manuscript database

Avocados (Persea americana Mill.) are often held for short periods after harvest at relatively high temperatures both in the field and in storage during preconditioning and prior to ripening with unknown effects on subsequent quality. To address this question, avocados were harvested at five differ...

Method of treating intermetallic alloy hydrogenation/oxidation catalysts for improved impurity poisoning resistance, regeneration and increased activity

DOEpatents

Wright, R.B.

1992-01-14

Alternate, successive high temperature oxidation and reduction treatments, in either order, of intermetallic alloy hydrogenation and intermetallic alloy oxidation catalysts unexpectedly improves the impurity poisoning resistance, regeneration capacity and/or activity of the catalysts. The particular alloy, and the final high temperature treatment given alloy (oxidation or reduction) will be chosen to correspond to the function of the catalyst (oxidation or hydrogenation). 23 figs.

High Temperature Superconducting State in Metallic Nanoclusters and Nano-Based Systems

DTIC Science & Technology

2013-12-01

pr.ac Semenova 1a Russia EOARD ISTC 09-7006/P-4084p Report Date: December 2013 Final Report from 01 October 2010 to 30 September 2013...CONTRACT NUMBER ISTC PPA 4084p 5b. GRANT NUMBER ISTC 09-7006 5c. PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S...discussed in the conventional theory. High Temperature Superconducting State in Metallic Nanoclusters and Nano-Based Systems ISTC Project No. 4084p

Development and evaluation of epoxidized soybean oil-based polymers

NASA Astrophysics Data System (ADS)

Juangvanich, Nuanpen

Epoxidized Soybean Oil (ESO) based polymers were developed using diamine curing agents and BF3:NH2C2H5 as catalyst. Reactions involved the curing process were explored and monitored by DSC and IR analysis. Amine-epoxy addition reactions governed the main curing reaction at the temperature range of 60--235°C, and the supplementary reactions at higher temperatures were either homopolymerization or etherification reaction. In the aliphatic curing reactions, the epoxy-rich system favored the supplementary reactions at high temperature, however, ESO cured with 1,6 hexanediamine (HDA) always produced the high temperature reaction products, due to some side reactions and the high volatile nature. The curing reaction with aromatic diamines produced inherent rigidity to the cured ESO network, which decreased the high temperature reactions. The system cured with a short aromatic diamine, 1,4-phenyldiamine (PDA), produced a small extent of high temperature reaction, as well. It was believed that the long length diamine with wide separation of the two amines underwent an intermolecular cross-linking reaction, and derived better properties than the shorter diamine. A post-cure process was used to improve the final polymer properties by increasing the temperature after the initial curing reaction was quenched due to gelation. Extending the time of post-curing did not significantly improve properties of the final ESO polymers. Exposing the cured samples at 180°C for longer than 12 hours decreased the properties of the cured material, due to thermal strain generating in the network structure. To increase time efficiency, short heat cycles were performed by post-curing right after gelation, and the cured ESO polymer had tensile strength of 32 MPa, modulus 750 MPa and toughness 1.3 MPa. With the introduction of EPON 828, the mechanical properties of a new ESO polymer improved; having strength above 40 MPa, modulus great than 1,000 MPa, and Tg higher than 40°C. Finally, a rice hull particleboard was developed using the cured ESO resin as adhesive, and the board had strength comparable to the National Bureau of Standards minimum requirement for particleboard. A 35 wt % of ESO resin imparted the highest strength for the rice hull board, with a value of 15.5 MPa.

Evaluation of quality of precipitation products: A case study using WRF and IMERG data over the central United States

NASA Astrophysics Data System (ADS)

Zhang, J.; Lin, L. F.; Bras, R. L.

2017-12-01

Hydrological applications rely on the availability and quality of precipitation products, specially model- and satellite-based products for use in areas without ground measurements. It is known that the quality of model- and satellite-based precipitation products are complementary—model-based products exhibiting high quality during winters while satellite-based products seem to be better during summers. To explore that behavior, this study uses 2-m air temperature as auxiliary information to evaluate high-resolution (0.1°×0.1° every hour) precipitation products from Weather Research and Forecasting (WRF) simulations and from version-4 Integrated Multi-satellite Retrievals for GPM (IMERG) early and final runs. The products are evaluated relative to the reference NCEP Stage IV precipitation estimates over the central United States in 2016. The results show that the WRF and IMERG final-run estimates are nearly unbiased while the IMERG early-run estimates positively biased. The results also show that the WRF estimates exhibit high correlations with the reference data when the temperature falls below 280°K and the IMERG estimates (i.e., both early and final runs) do so when the temperature exceeds 280°K. Moreover, the temperature threshold of 280°K, which distinguishes the quality of the WRF and the IMERG products, does not vary significantly with either season or location. This study not only adds insight into current precipitation research on the quality of precipitation products but also suggests a simple way for choosing either a model- or satellite-based product or a hybrid model/satellite product for applications.

Surface Effects and Challenges for Application of Piezoelectric Langasite Substrates in Surface Acoustic Wave Devices Caused by High Temperature Annealing under High Vacuum.

PubMed

Seifert, Marietta; Rane, Gayatri K; Kirbus, Benjamin; Menzel, Siegfried B; Gemming, Thomas

2015-12-19

Substrate materials that are high-temperature stable are essential for sensor devices which are applied at high temperatures. Although langasite is suggested as such a material, severe O and Ga diffusion into an O-affine deposited film was observed during annealing at high temperatures under vacuum conditions, leading to a damage of the metallization as well as a change of the properties of the substrate and finally to a failure of the device. Therefore, annealing of bare LGS (La 3 Ga 5 SiO 14 ) substrates at 800 ∘ C under high vacuum conditions is performed to analyze whether this pretreatment improves the suitability and stability of this material for high temperature applications in vacuum. To reveal the influence of the pretreatment on the subsequently deposited metallization, RuAl thin films are used as they are known to oxidize on LGS at high temperatures. A local study of the pretreated and metallized substrates using transmission electron microscopy reveals strong modification of the substrate surface. Micro cracks are visible. The composition of the substrate is strongly altered at those regions. Severe challenges for the application of LGS substrates under high-temperature vacuum conditions arise from these substrate damages, revealing that the pretreatment does not improve the applicability.

Development of Sintered Si3N4 for High Performance Thermomechanical Applications.

DTIC Science & Technology

1984-01-01

noted( 17) that final grain size of sintered Si3 N4 is quite sensitive to both temperature and time at temperature. The sintering of Si NI containing...Characterization of Ube-SN-E0 Si3 N4 Chemical Analysis Lot A-10 Lot A-18 N (alkali fusion) wt . % 38 38 0 (inert gas fusion) wt . % 1.2 1.4 C (inert gas fusion) wt ...temperature stutral applications except for the high creep rate, Which is of the ame order a NC-13. The sintering of -qfiN4ontaning 5 wt % LiAIq0 1and

Low Cost Cryocoolers for High Temperature Superconductor Communication Filters

NASA Technical Reports Server (NTRS)

Brown, Davina

1998-01-01

This final report describes the work performed by a consortium of Industry and Government to develop low cost cryocoolers. The specific application was for low cost commercial based high temperature superconductor communication filters. This program was initiated in January 1995 and resulted in the successful demonstration of an HTS filter dewar cooled by a low cost pulse tube cryocooler. Further development of this cryocooler technology is proceeding through various contracts underway and proposed at this time.

Nanostructured Coatings with Self-Healing and Temperature Homogenization Functions for High Temperature Sliding Interfaces

DTIC Science & Technology

2010-10-01

showing the stainless steel chamber (A), the rotatable substrate holder (B), the plasma burning between substrate holder and magnetrons (C) and three...Final Report University of Leoben, Austria 3 The sputtering system consists of a cylindrical stainless steel chamber (Ø 380 x 235mm) (A) which...are used. All coatings were deposited on three different substrates: AlSI M2 high speed steel , Si (100) wafers, and Fe foil. M2 substrates which

Forming Refractory Insulation On Copper Wire

NASA Technical Reports Server (NTRS)

Setlock, J.; Roberts, G.

1995-01-01

Alternative insulating process forms flexible coat of uncured refractory insulating material on copper wire. Coated wire formed into coil or other complex shape. Wire-coating apparatus forms "green" coat on copper wire. After wire coiled, heating converts "green" coat to refractory electrical insulator. When cured to final brittle form, insulating material withstands temperatures above melting temperature of wire. Process used to make coils for motors, solenoids, and other electrical devices to be operated at high temperatures.

Influence of warm rolling temperature on ferrite recrystallization in low C and IF steels

NASA Astrophysics Data System (ADS)

Barnett, Matthew Robert

Experiments involving single pass laboratory rolling and isothermal salt bath annealing were carried out; three steels were studied: a titanium stabilized interstitial free grade and two low carbon grades, one of which contained a particularly low level of manganese (˜0.009wt.%). The two low carbon grades were produced such that any complication from AlN precipitation was avoided. X-ray, neutron diffraction, optical metallography and mechanical testing measurements were carried out on the samples before and after annealing. The main aim of this work was to further the understanding of the metallurgy of recrystallization after ferrite rolling at temperatures between room temperature and 700sp°C. Deformation textures, recrystallization kinetics, final grain sizes and recrystallization textures were quantified for all the samples and experimental conditions. A major conclusion based on these data is that the influence of rolling temperature is far greater in the low carbon samples than in the IF grade. Indeed, the IF results alter only marginally with increasing temperature. In the low carbon grades, however, the rolling texture sharpens, recrystallization slows, the final grain size coarsens, and the recrystallization texture changes when the rolling temperature is increased. This distinct difference between the two steel types is explained in terms of their contrasting deformation behaviors. Solute carbon and nitrogen in the low carbon grades interact with dislocations causing high stored energy levels after low temperature rolling (due to dynamic strain aging) and high strain rate sensitivities during high temperature rolling (due to the solute drag of dislocations in the transition region between DSA and DRC). Nucleation during subsequent recrystallization is strongly influenced by both the stored energy and the strain rate sensitivity. The latter affects the occurrence of the flow localisations that enhance nucleation.

A simplified model for equilibrium and transient swelling of thermo-responsive gels.

PubMed

Drozdov, A D; deClaville Christiansen, J

2017-11-01

A simplified model is developed for the elastic response of thermo-responsive gels subjected to swelling under an arbitrary deformation with finite strains. The constitutive equations involve five adjustable parameters that are determined by fitting observations in equilibrium water uptake tests and T-jump transient tests on thin gel disks. Two scenarios for water release under heating are revealed by means of numerical simulation. When the final temperature in a T-jump test is below the volume-phase transition temperature, deswelling is characterized by smooth distribution of water molecules and small tensile stresses. When the final temperature exceeds the critical temperature, a gel disk is split into three regions (central part with a high concentration of water molecules and two domains near the boundaries with low water content) separated by sharp interfaces, whose propagation is accompanied by development of large (comparable with the elastic modulus) tensile stresses. Copyright © 2017 Elsevier Ltd. All rights reserved.

Heat treated 9 Cr-1 Mo steel material for high temperature application

DOEpatents

Jablonski, Paul D.; Alman, David; Dogan, Omer; Holcomb, Gordon; Cowen, Christopher

2012-08-21

The invention relates to a composition and heat treatment for a high-temperature, titanium alloyed, 9 Cr-1 Mo steel exhibiting improved creep strength and oxidation resistance at service temperatures up to 650.degree. C. The novel combination of composition and heat treatment produces a heat treated material containing both large primary titanium carbides and small secondary titanium carbides. The primary titanium carbides contribute to creep strength while the secondary titanium carbides act to maintain a higher level of chromium in the finished steel for increased oxidation resistance, and strengthen the steel by impeding the movement of dislocations through the crystal structure. The heat treated material provides improved performance at comparable cost to commonly used high-temperature steels such as ASTM P91 and ASTM P92, and requires heat treatment consisting solely of austenization, rapid cooling, tempering, and final cooling, avoiding the need for any hot-working in the austenite temperature range.

Layout and results from the initial operation of the high-resolution x-ray imaging crystal spectrometer on the Large Helical Device.

PubMed

Pablant, N A; Bitter, M; Delgado-Aparicio, L; Goto, M; Hill, K W; Lazerson, S; Morita, S; Roquemore, A L; Gates, D; Monticello, D; Nielson, H; Reiman, A; Reinke, M; Rice, J E; Yamada, H

2012-08-01

First results of ion and electron temperature profile measurements from the x-ray imaging crystal spectrometer (XICS) diagnostic on the Large Helical Device (LHD) are presented. This diagnostic system has been operational since the beginning of the 2011 LHD experimental campaign and is the first application of the XICS diagnostic technique to helical plasma geometry. The XICS diagnostic provides measurements of ion and electron temperature profiles in LHD with a spatial resolution of 2 cm and a maximum time resolution of 5 ms (typically 20 ms). Ion temperature profiles from the XICS diagnostic are possible under conditions where charge exchange recombination spectroscopy (CXRS) is not possible (high density) or is perturbative to the plasma (low density or radio frequency heated plasmas). Measurements are made by using a spherically bent crystal to provide a spectrally resolved 1D image of the plasma from line integrated emission of helium-like Ar(16 +). The final hardware design and configuration are detailed along with the calibration procedures. Line-integrated ion and electron temperature measurements are presented, and the measurement accuracy is discussed. Finally central temperature measurements from the XICS system are compared to measurements from the Thomson scattering and CXRS systems, showing excellent agreement.

The effect of temperature and drawing ratio on the mechanical properties of polypropylene monofilaments

NASA Astrophysics Data System (ADS)

Taheri, Hesam; Nóbrega, João Miguel; Samyn, Pieter; Covas, José Antonio

2014-05-01

In this work, the simultaneous effect of both temperature and drawing ratio during processing of polypropylene monofilaments has been investigated. The basis of this work specifically aims at emphasizing the conditions of temperature and drawing ratio applied in the cooling bath, in order to find out under which conditions the named parameters can be applied in a processing line under continuous extrusion. The effects of temperature are studied for a constant total drawing ratio to analyze the influences on mechanical properties and structural differences of the final polypropylene monofilament. The quenched monofilaments were drawn around an adjustable guide assembly in the quench bath and first drawing stage, imparting thermal and mechanical treatments to the filaments. In the heating stage, monofilaments are affected to high-speed draw rolls while passing through the oven. As such, the best conditions to produce a polypropylene monofilament with high tenacity strength were determined. Results of this study show that the monofilament properties are significantly affected by temperature in the cooling zone. The nature of the first drawing had a significant effect on the end properties and monofilaments with modulus of 637 MPa have finally been manufactured. We have also proposed a new hypothesis, which is termed "gap nucleation" and determine this phenomenon in the gap between die and cooling bath.

Computer program for pulsed thermocouples with corrections for radiation effects

NASA Technical Reports Server (NTRS)

Will, H. A.

1981-01-01

A pulsed thermocouple was used for measuring gas temperatures above the melting point of common thermocouples. This was done by allowing the thermocouple to heat until it approaches its melting point and then turning on the protective cooling gas. This method required a computer to extrapolate the thermocouple data to the higher gas temperatures. A method that includes the effect of radiation in the extrapolation is described. Computations of gas temperature are provided, along with the estimate of the final thermocouple wire temperature. Results from tests on high temperature combustor research rigs are presented.

Large-Scale Wireless Temperature Monitoring System for Liquefied Petroleum Gas Storage Tanks.

PubMed

Fan, Guangwen; Shen, Yu; Hao, Xiaowei; Yuan, Zongming; Zhou, Zhi

2015-09-18

Temperature distribution is a critical indicator of the health condition for Liquefied Petroleum Gas (LPG) storage tanks. In this paper, we present a large-scale wireless temperature monitoring system to evaluate the safety of LPG storage tanks. The system includes wireless sensors networks, high temperature fiber-optic sensors, and monitoring software. Finally, a case study on real-world LPG storage tanks proves the feasibility of the system. The unique features of wireless transmission, automatic data acquisition and management, local and remote access make the developed system a good alternative for temperature monitoring of LPG storage tanks in practical applications.

Shear melting and high temperature embrittlement: theory and application to machining titanium.

PubMed

Healy, Con; Koch, Sascha; Siemers, Carsten; Mukherji, Debashis; Ackland, Graeme J

2015-04-24

We describe a dynamical phase transition occurring within a shear band at high temperature and under extremely high shear rates. With increasing temperature, dislocation deformation and grain boundary sliding are supplanted by amorphization in a highly localized nanoscale band, which allows for massive strain and fracture. The mechanism is similar to shear melting and leads to liquid metal embrittlement at high temperature. From simulation, we find that the necessary conditions are lack of dislocation slip systems, low thermal conduction, and temperature near the melting point. The first two are exhibited by bcc titanium alloys, and we show that the final one can be achieved experimentally by adding low-melting-point elements: specifically, we use insoluble rare earth metals (REMs). Under high shear, the REM becomes mixed with the titanium, lowering the melting point within the shear band and triggering the shear-melting transition. This in turn generates heat which remains localized in the shear band due to poor heat conduction. The material fractures along the shear band. We show how to utilize this transition in the creation of new titanium-based alloys with improved machinability.

Optical and electronic properties of sub-surface conducting layers in diamond created by MeV B-implantation at elevated temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Willems van Beveren, L. H., E-mail: laurensw@unimelb.edu.au; Bowers, H.; Ganesan, K.

2016-06-14

Boron implantation with in-situ dynamic annealing is used to produce highly conductive sub-surface layers in type IIa (100) diamond plates for the search of a superconducting phase transition. Here, we demonstrate that high-fluence MeV ion-implantation, at elevated temperatures avoids graphitization and can be used to achieve doping densities of 6 at. %. In order to quantify the diamond crystal damage associated with implantation Raman spectroscopy was performed, demonstrating high temperature annealing recovers the lattice. Additionally, low-temperature electronic transport measurements show evidence of charge carrier densities close to the metal-insulator-transition. After electronic characterization, secondary ion mass spectrometry was performed to mapmore » out the ion profile of the implanted plates. The analysis shows close agreement with the simulated ion-profile assuming scaling factors that take into account an average change in diamond density due to device fabrication. Finally, the data show that boron diffusion is negligible during the high temperature annealing process.« less

Synthesis and characterization of laminated Si/SiC composites.

PubMed

Naga, Salma M; Kenawy, Sayed H; Awaad, Mohamed; Abd El-Wahab, Hamada S; Greil, Peter; Abadir, Magdi F

2013-01-01

Laminated Si/SiC ceramics were synthesized from porous preforms of biogenous carbon impregnated with Si slurry at a temperature of 1500 °C for 2 h. Due to the capillarity infiltration with Si, both intrinsic micro- and macrostructure in the carbon preform were retained within the final ceramics. The SEM micrographs indicate that the final material exhibits a distinguished laminar structure with successive Si/SiC layers. The produced composites show weight gain of ≈5% after heat treatment in air at 1300 °C for 50 h. The produced bodies could be used as high temperature gas filters as indicated from the permeability results.

Research on precise control of 3D print nozzle temperature in PEEK material

NASA Astrophysics Data System (ADS)

Liu, Zhichao; Wang, Gong; Huo, Yu; Zhao, Wei

2017-10-01

3D printing technology has shown more and more applicability in medication, designing and other fields for its low cost and high timeliness. PEEK (poly-ether-ether-ketone), as a typical high-performance special engineering plastic, become one of the most excellent materials to be used in 3D printing technology because of its excellent mechanical property, good lubricity, chemical resistance, and other properties. But the nozzle of 3D printer for PEEK has also a series of very high requirements. In this paper, we mainly use the nozzle temperature control as the research object, combining with the advantages and disadvantages of PID control and fuzzy control. Finally realize a kind of fuzzy PID controller to solve the problem of the inertia of the temperature system and the seriousness of the temperature control hysteresis in the temperature control of the nozzle, and to meet the requirements of the accuracy of the nozzle temperature control and rapid reaction.

High-temperature resins

NASA Technical Reports Server (NTRS)

Serafini, T. T.

1982-01-01

The basic chemistry, cure processes, properties, and applications of high temperature resins known as polyimides are surveyed. Condensation aromatic polymides are prepared by reacting aromatic diamines with aromatic dianhydrides, aromatic tetracarboxylic acids, or with dialkyl esters of aromatic tetracarboxylic acids, depending on the intended end use. The first is for coatings or films while the latter two are more suitable for polyimide matrix resins. Prepreg solutions are made by dissolving reactants in an aprotic solvent, and advances in the addition of a diamine on the double bond and radical polymerization of the double bond are noted to have yielded a final cure product with void-free characteristics. Attention is given to properties of the Skybond, Pyralin, and NR-150B polyimide prepreg materials and characteristics of aging in the NP-150 polyimides. Finally, features of the NASA-developed PMR polyimides are reviewed.

System for the growth of bulk SiC crystals by modified CVD techniques

NASA Technical Reports Server (NTRS)

Steckl, Andrew J.

1994-01-01

The goal of this program was the development of a SiC CVD growth of films thick enough to be useful as pseudo-substrates. The cold-walled CVD system was designed, assembled, and tested. Extrapolating from preliminary evaluation of SiC films grown in the system at relatively low temperatures indicates that the growth rate at the final temperatures will be high enough to make our approach practical. Modifications of the system to allow high temperature growth and cleaner growth conditions are in progress. This program was jointly funded by Wright Laboratory, Materials Directorate and NASA LeRC and monitored by NASA.

High temperature induced disruption of the cell wall integrity and structure in Pleurotus ostreatus mycelia.

PubMed

Qiu, Zhiheng; Wu, Xiangli; Gao, Wei; Zhang, Jinxia; Huang, Chenyang

2018-05-30

Fungal cells are surrounded by a tight cell wall to protect them from harmful environmental conditions and to resist lysis. The synthesis and assembly determine the shape, structure, and integrity of the cell wall during the process of mycelial growth and development. High temperature is an important abiotic stress, which affects the synthesis and assembly of cell walls. In the present study, the chitin and β-1,3-glucan concentrations in the cell wall of Pleurotus ostreatus mycelia were changed after high-temperature treatment. Significantly higher chitin and β-1,3-glucan concentrations were detected at 36 °C than those incubated at 28 °C. With the increased temperature, many aberrant chitin deposition patches occurred, and the distribution of chitin in the cell wall was uneven. Moreover, high temperature disrupts the cell wall integrity, and P. ostreatus mycelia became hypersensitive to cell wall-perturbing agents at 36 °C. The cell wall structure tended to shrink or distorted after high temperature. The cell walls were observed to be thicker and looser by using transmission electron microscopy. High temperature can decrease the mannose content in the cell wall and increase the relative cell wall porosity. According to infrared absorption spectrum, high temperature broke or decreased the glycosidic linkages. Finally, P. ostreatus mycelial cell wall was easily degraded by lysing enzymes after high-temperature treatment. In other words, the cell wall destruction caused by high temperature may be a breakthrough for P. ostreatus to be easily infected by Trichoderma.

Oxidation Behavior of GRCop-84 (Cu-8Cr-4Nb) at Intermediate and High Temperatures

NASA Technical Reports Server (NTRS)

Thomas-Ogbuji, Linus U.; Humphrey, Donald L.; Greenbauer-Seng, Leslie (Technical Monitor)

2000-01-01

The oxidation behavior of GRCop-84 (Cu-8 at %Cr-4 at %Nb) has been investigated in air and in oxygen, for durations of 0.5 to 50 hours and temperatures ranging from 500 to 900 C. For comparison, data was also obtained for the oxidation of Cu and NARloy-Z (Cu-3 wt% Ag-0.5 wt% Zr) under the same conditions. Arrhenius plots of those data showed that all three materials had similar oxidation rates at high temperatures (> 750 C). However, at intermediate temperatures (500 to 750 C) GRCop exhibited significantly higher oxidation resistance than Cu and NARloy-Z. The oxidation kinetics of GRCop-84 exhibited a sharp and discontinuous jump between the two regimes. Also, in the high temperature regime GRCop-84 oxidation rate was found to change from a high initial value to a significantly smaller terminal value at each temperature, with progress of oxidation; the two different oxidation rates were found to correlate with a porous intial oxide and a dense final oxide, respectively.

Auto Indexer Auto-Indexer for Percussive Hammers: Vane Motor Dynamometer Testing

DOE Data Explorer

Su, Jiann

2012-01-01

Objectives Options associated with geothermal drilling operations are generally limited by factors such as formation temperature and rock strength. The objective of the research is to expand the "tool box" available to the geothermal driller by furthering the development of a high-temperature drilling motor that can be used in directional drilling applications for drilling high temperature geothermal formations. The motor is specifically designed to operate in conjunction with a pneumatic down-the-hole-hammer. It provides a more compact design compared to traditional drilling motors such as PDMs (positive displacement motors). The packaging can help to enhance directional drilling capabilities. It uses no elastomeric components, which enables it to operate in higher temperatures ( >250 °F). Current work on the motor has shown that is a capable of operating under pneumatic power with a down-the-hole-hammer. Further development work will include continued testing and refining motor components and evaluating motor capabilities. Targets/Milestones Complete testing current motor - 12/31/2010 Make final material and design decisions - 01/31/2011 Build and test final prototype - 04/31/2011 Final demonstration - 07/31/2011 Impacts The development of the motor will help to achieve program technical objectives by improving well construction capabilities. This includes enabling high-temperature drilling as well as enhancing directional drilling. A key component in the auto indexer is the drive motor. It is an air-driven vane motor that converts the energy stored in the compressed air to mechanical energy. The motor is attached to hammer-like components which impart an impulsive load onto the drive shaft. The impulsive force on the drive shaft in turn creates an indexing action. A controlled test was performed to characterize the performance of the the vane motor for a given pressure. The Sandia dynamometer test station was used to determine the performance of the motor for a given input pressure.

Effects of temperature on the irradiation responses of Al 0.1 CoCrFeNi high entropy alloy

DOE PAGES

Yang, Tengfei; Xia, Songqin; Guo, Wei; ...

2017-09-29

Structural damage and chemical segregation in Al 0.1CoCrFeNi high entropy alloy irradiated at elevated temperatures are studied using transmission electron microscopy (TEM) and atom probe tomography (APT). Irradiation-induced defects include dislocation loops, long dislocations and stacking-fault tetrahedra, but no voids can be observed. Furthermore, as irradiation temperature increases, defect density is decreased but defect size is increased, which is induced by increasing defect mobility. Finally, APT characterization reveals that ion irradiation at elevated temperatures can induce an enrichment of Ni and Co as well as a depletion of Fe and Cr at defect clusters, mainly including dislocation loops and longmore » dislocations.« less

Effects of temperature on the irradiation responses of Al 0.1 CoCrFeNi high entropy alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Tengfei; Xia, Songqin; Guo, Wei

Structural damage and chemical segregation in Al 0.1CoCrFeNi high entropy alloy irradiated at elevated temperatures are studied using transmission electron microscopy (TEM) and atom probe tomography (APT). Irradiation-induced defects include dislocation loops, long dislocations and stacking-fault tetrahedra, but no voids can be observed. Furthermore, as irradiation temperature increases, defect density is decreased but defect size is increased, which is induced by increasing defect mobility. Finally, APT characterization reveals that ion irradiation at elevated temperatures can induce an enrichment of Ni and Co as well as a depletion of Fe and Cr at defect clusters, mainly including dislocation loops and longmore » dislocations.« less

Dynamic High-Temperature Tensile Characterization of an Iridium Alloy with Kolsky Tension Bar Techniques

DOE PAGES

Song, Bo; Nelson, Kevin; Lipinski, Ronald; ...

2015-05-29

In this study, conventional Kolsky tension bar techniques were modified to characterize an iridium alloy in tension at elevated strain rates and temperatures. The specimen was heated to elevated temperatures with an induction coil heater before dynamic loading; whereas, a cooling system was applied to keep the bars at room temperature during heating. A preload system was developed to generate a small pretension load in the bar system during heating in order to compensate for the effect of thermal expansion generated in the high-temperature tensile specimen. A laser system was applied to directly measure the displacements at both ends ofmore » the tensile specimen in order to calculate the strain in the specimen. A pair of high-sensitivity semiconductor strain gages was used to measure the weak transmitted force due to the low flow stress in the thin specimen at elevated temperatures. The dynamic high-temperature tensile stress–strain curves of a DOP-26 iridium alloy were experimentally obtained at two different strain rates (~1000 and 3000 s -1) and temperatures (~750 and 1030°C). The effects of strain rate and temperature on the tensile stress–strain response of the iridium alloy were determined. Finally, the iridium alloy exhibited high ductility in stress–strain response that strongly depended on strain-rate and temperature.« less

High pressure and synchrotron radiation studies of solid state electronic instabilities. Final technial report, May 1, 1984--April 1987

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pifer, J.H.; Croft, M.C.

This report discusses Eu and General Valence Instabilities; Ce Problem: L{sub 3} Spectroscopy Emphasis; Bulk Property Emphasis; Transition Metal Compound Electronic Structure; Electronic Structure-Phonon Coupling Studies; High Temperature Superconductivity and Oxide Materials; and Novel Materials Collaboration with Chemistry.

High-resolution grazing-incidence grating spectrometer for temperature measurements of low-Z ions emitting in the 100–300 Å spectral band

DOE PAGES

Widmann, K.; Beiersdorfer, P.; Magee, E. W.; ...

2014-09-19

In this paper, we have constructed a high-resolution grazing-incidence spectrometer designed for measuring the ion temperature of low-Z elements, such as Li + or Li 2 +, which radiate near 199 Å and 135 Å, respectively. Based on measurements at the Livermore Electron Beam Ion Trap we have shown that the instrumental resolution is better than 48 mÅ at the 200 Å setting and better than 40 mÅ for the 135-Å range. Such a high spectral resolution corresponds to an instrumental limit for line-width based temperature measurements of about 45 eV for the 199 Å Li+ and 65 eV formore » the 135 Å Li 2 + lines. Finally, recently obtained survey spectra from the Lithium Tokamak Experiment at the Princeton Plasma Physics Laboratory show the presence of these lithium emission lines and the expected core ion temperature of approximately 70 eV is sufficiently high to demonstrate the feasibility of utilizing our high-resolution spectrometer as an ion-temperature diagnostic.« less

Prospects for small cryocoolers. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radebaugh, R.

1982-01-01

Small cryocoolers are commonly used in the areas of infrared detection, satellite communication, and cryopumps. Some emerging application areas deal with SQUID and Josephson junction devices, which require temperatures of about 8 K or below. The need for high reliability in these small cryocoolers has dictated the use of regenerative-cycle machines, but such machines are presently limited to temperatures above about 8 K. This paper discusses some of the research being done to improve reliability, decrease noise, and reduce the low-temperature limit of small cryocoolers.

Phase transitions in samarium at high pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, W.Y.; Lin, T.H.; Dunn, K.J.

1987-01-15

The electrical behavior of Sm was studied for pressures up to 43 GPa and temperatures from 430 down to 2 K. The two Neel temperatures at ambient pressure are found to move toward each other as the pressure increases and finally merge into one at the dhcp phase. At room temperature, we found that Sm transforms to a new phase, presumably fcc, at about 12 GPa. The phase line between the dhcp and the new phase appears to tie with the cusp of the bcc phase line.

Technology development of a biowaste resistojet, volume 1

NASA Technical Reports Server (NTRS)

Phillips, D. G.

1972-01-01

The materials research effort conducted in support of a NASA-sponsored biowaste resistojet development program is summarized. The resistojet concept under development is the concentric tube design wherein the final pass of the gases through the thruster is through the resistance heated center tube. To produce high specific impulses, this center tube must operate at very high temperatures and it is this element that is most critical in the design. Because of the corrosive nature of the biowaste gases at high temperature, and because of the limited data available for many potential materials, the subject materials study was conducted.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Bo; Nelson, Kevin; Lipinski, Ronald

In this study, conventional Kolsky tension bar techniques were modified to characterize an iridium alloy in tension at elevated strain rates and temperatures. The specimen was heated to elevated temperatures with an induction coil heater before dynamic loading; whereas, a cooling system was applied to keep the bars at room temperature during heating. A preload system was developed to generate a small pretension load in the bar system during heating in order to compensate for the effect of thermal expansion generated in the high-temperature tensile specimen. A laser system was applied to directly measure the displacements at both ends ofmore » the tensile specimen in order to calculate the strain in the specimen. A pair of high-sensitivity semiconductor strain gages was used to measure the weak transmitted force due to the low flow stress in the thin specimen at elevated temperatures. The dynamic high-temperature tensile stress–strain curves of a DOP-26 iridium alloy were experimentally obtained at two different strain rates (~1000 and 3000 s -1) and temperatures (~750 and 1030°C). The effects of strain rate and temperature on the tensile stress–strain response of the iridium alloy were determined. Finally, the iridium alloy exhibited high ductility in stress–strain response that strongly depended on strain-rate and temperature.« less

Correlation between Fragility and the Arrhenius Crossover Phenomenon in Metallic, Molecular, and Network Liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jaiswal, Abhishek; Egami, Takeshi; Kelton, K. F.

2016-11-10

In this paper, we report the observation of a distinct correlation between the kinetic fragility index m and the reduced Arrhenius crossover temperature θ A = T A/T g in various glass-forming liquids, identifying three distinguishable groups. In particular, for 11 glass-forming metallic liquids, we universally observe a crossover in the mean diffusion coefficient from high-temperature Arrhenius to low-temperature super-Arrhenius behavior at approximately θ A ≈ 2 which is in the stable liquid phases. In contrast, for fragile molecular liquids, this crossover occurs at much lower θ A ≈ 1.4 and usually in their supercooled states. The θ A valuesmore » for strong network liquids spans a wide range higher than 2. Intriguingly, the high-temperature activation barrier E ∞ is universally found to be ~11k BT g and uncorrelated with the fragility or the reduced crossover temperature θ A for metallic and molecular liquids. Finally, these observations provide a way to estimate the low-temperature glassy characteristics (T g and m) from the high-temperature liquid quantities (E ∞ and θ A).« less

Low Temperature Rhombohedral Single Crystal SiGe Epitaxy on c-plane Sapphire

NASA Technical Reports Server (NTRS)

Duzik, Adam J.; Choi, Sang H.

2016-01-01

Current best practice in epitaxial growth of rhombohedral SiGe onto (0001) sapphire (Al2O3) substrate surfaces requires extreme conditions to grow a single crystal SiGe film. Previous models described the sapphire surface reconstruction as the overriding factor in rhombohedral epitaxy, requiring a high temperature Al-terminated surface for high quality films. Temperatures in the 850-1100 C range were thought to be necessary to get SiGe to form coherent atomic matching between the (111) SiGe plane and the (0001) sapphire surface. Such fabrication conditions are difficult and uneconomical, hindering widespread application. This work proposes an alternative model that considers the bulk sapphire structure and determines how the SiGe film nucleates and grows. Accounting for thermal expansion effects, calculations using this new model show that both pure Ge and SiGe can form single crystal films in the 450-550 C temperature range. Experimental results confirm these predictions, where x-ray diffraction and atomic force microscopy show the films fabricated at low temperature rival the high temperature films in crystallographic and surface quality. Finally, an explanation is provided for why films of comparable high quality can be produced in either temperature range.

Characteristics of hydrogen produced by partial oxidation and auto-thermal reforming in a small methanol reformer

NASA Astrophysics Data System (ADS)

Horng, Rong-Fang; Chou, Huann-Ming; Lee, Chiou-Hwang; Tsai, Hsien-Te

This paper investigates experimentally, the transient characteristics of a small methanol reformer using partial oxidation (POX) and auto-thermal reforming (ATR) for fuel cell applications. The parameters varied were heating temperature, methanol supply rate, steady mode shifting temperature, O 2/C (O 2/CH 3OH) and S/C (H 2O/CH 3OH) molar ratios with the main aim of promoting a rapid response and a high flow rate of hydrogen. The experiments showed that a high steady mode shifting temperature resulted in a faster temperature rise at the catalyst outlet and vice versa and that a low steady mode shifting temperature resulted in a lower final hydrogen concentration. However, when the mode shifting temperature was too high, the hydrogen production response was not necessarily improved. It was subsequently shown that the optimum steady mode shifting temperature for this experimental set-up was approximately 75 °C. Further, the hydrogen concentration produced by the auto-thermal process was as high as 49.12% and the volume flow rate up to 23.0 L min -1 compared to 40.0% and 20.5 L min -1 produced by partial oxidation.

High Temperature Mechanical Behavior of UHTC Coatings for Thermal Protection of Re-Entry Vehicles

NASA Astrophysics Data System (ADS)

Pulci, G.; Tului, M.; Tirillò, J.; Marra, F.; Lionetti, S.; Valente, T.

2011-01-01

In this work, the high temperature mechanical properties of ultra high temperature ceramics (UHTC) coatings deposited by plasma spraying have been investigated; particularly the stress-strain relationship of ZrB2-based thick films has been evaluated by means of 4-point bending tests up to 1500 °C in air. Results show that at each investigated temperature (500, 1000, and 1500 °C) modulus of rupture (MOR) values are higher than the ones obtained at room temperature (RT); moreover at 1500 °C the UHTC coatings exhibit a marked plastic behavior, maintaining a flexural strength 25% higher compared to RT tested samples. The coefficient of linear thermal expansion (CTE) has been evaluated up to 1500 °C: obtained data are of primary importance for substrate selection, interface design and to analyze the thermo-mechanical behavior of coating-substrate coupled system. Finally, SEM-EDS analyses have been carried out on as-sprayed and tested materials in order to understand the mechanisms of reinforcement activated by high temperature exposure and to identify the microstructural modifications induced by the combination of mechanical loads and temperature in an oxidizing environment.

Interactive effects of ocean acidification and warming on coral reef associated epilithic algal communities under past, present-day and future ocean conditions

NASA Astrophysics Data System (ADS)

Vogel, N.; Cantin, N. E.; Strahl, J.; Kaniewska, P.; Bay, L.; Wild, C.; Uthicke, S.

2016-06-01

Epilithic algal communities play critical ecological roles on coral reefs, but their response to individual and interactive effects of ocean warming (OW) and ocean acidification (OA) is still largely unknown. We investigated growth, photosynthesis and calcification of early epilithic algal community assemblages exposed for 6 months to four temperature profiles (-1.1, ±0.0, +0.9, +1.6 °C) that were crossed with four carbon dioxide partial pressure (pCO2) levels (360, 440, 650, 940 µatm), under flow-through conditions and natural light regimes. Additionally, we compared the cover of heavily calcified crustose coralline algae (CCA) and lightly calcified red algae of the genus Peyssonnelia among treatments. Increase in cover of epilithic communities showed optima under moderately elevated temperatures and present pCO2, while cover strongly decreased under high temperatures and high-pCO2 conditions, particularly due to decreasing cover of CCA. Similarly, community calcification rates were strongly decreased at high pCO2 under both measured temperatures. While final cover of CCA decreased under high temperature and pCO2 (additive negative effects), cover of Peyssonnelia spp. increased at high compared to annual average and moderately elevated temperatures. Thus, cover of Peyssonnelia spp. increased in treatment combinations with less CCA, which was supported by a significant negative correlation between organism groups. The different susceptibility to stressors most likely derived from a different calcification intensity and/or mineral. Notably, growth of the epilithic communities and final cover of CCA were strongly decreased under reduced-pCO2 conditions compared to the present. Thus, CCA may have acclimatized from past to present-day pCO2 conditions, and changes in carbonate chemistry, regardless in which direction, negatively affect them. However, if epilithic organisms cannot further acclimatize to OW and OA, the interacting effects of both factors may change epilithic communities in the future, thereby likely leading to reduced reef stability and recovery.

Identification and quantification of ethyl carbamate occurring in urea complexation processes commonly utilized for polyunsaturated fatty acid concentration.

PubMed

Vázquez, Luis; Prados, Isabel M; Reglero, Guillermo; Torres, Carlos F

2017-08-15

The concentration of polyunsaturated fatty acids by formation of urea adducts from three different sources was studied to elucidate the formation of ethyl carbamates in the course of these procedures. Two different methodologies were performed: with ethanol at high temperature and with hexane/ethanol mixtures at room temperature. It was proved that the amount of urethanes generated at high temperature was higher than at room temperature. Besides, subsequent washing steps of the PUFA fraction with water were efficient to remove the urethanes from the final products. The methodology at room temperature with 0.4mL ethanol and 3g urea provided good relationship between concentration and yield of the main bioactive PUFA, with the lowest formation of ethyl carbamates in the process. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fluid absorption solar energy receiver

NASA Technical Reports Server (NTRS)

Bair, Edward J.

1993-01-01

A conventional solar dynamic system transmits solar energy to the flowing fluid of a thermodynamic cycle through structures which contain the gas and thermal energy storage material. Such a heat transfer mechanism dictates that the structure operate at a higher temperature than the fluid. This investigation reports on a fluid absorption receiver where only a part of the solar energy is transmitted to the structure. The other part is absorbed directly by the fluid. By proportioning these two heat transfer paths the energy to the structure can preheat the fluid, while the energy absorbed directly by the fluid raises the fluid to its final working temperature. The surface temperatures need not exceed the output temperature of the fluid. This makes the output temperature of the gas the maximum temperature in the system. The gas can have local maximum temperatures higher than the output working temperature. However local high temperatures are quickly equilibrated, and since the gas does not emit radiation, local high temperatures do not result in a radiative heat loss. Thermal radiation, thermal conductivity, and heat exchange with the gas all help equilibrate the surface temperature.

Adaptive temperature-accelerated dynamics

NASA Astrophysics Data System (ADS)

Shim, Yunsic; Amar, Jacques G.

2011-02-01

We present three adaptive methods for optimizing the high temperature Thigh on-the-fly in temperature-accelerated dynamics (TAD) simulations. In all three methods, the high temperature is adjusted periodically in order to maximize the performance. While in the first two methods the adjustment depends on the number of observed events, the third method depends on the minimum activation barrier observed so far and requires an a priori knowledge of the optimal high temperature T^{opt}_{high}(E_a) as a function of the activation barrier Ea for each accepted event. In order to determine the functional form of T^{opt}_{high}(E_a), we have carried out extensive simulations of submonolayer annealing on the (100) surface for a variety of metals (Ag, Cu, Ni, Pd, and Au). While the results for all five metals are different, when they are scaled with the melting temperature Tm, we find that they all lie on a single scaling curve. Similar results have also been obtained for (111) surfaces although in this case the scaling function is slightly different. In order to test the performance of all three methods, we have also carried out adaptive TAD simulations of Ag/Ag(100) annealing and growth at T = 80 K and compared with fixed high-temperature TAD simulations for different values of Thigh. We find that the performance of all three adaptive methods is typically as good as or better than that obtained in fixed high-temperature TAD simulations carried out using the effective optimal fixed high temperature. In addition, we find that the final high temperatures obtained in our adaptive TAD simulations are very close to our results for T^{opt}_{high}(E_a). The applicability of the adaptive methods to a variety of TAD simulations is also briefly discussed.

Investigation of transient temperature's influence on damage of high-speed sliding electrical contact rail surface

NASA Astrophysics Data System (ADS)

Zhang, Yuyan; Sun, Shasha; Guo, Quanli; Yang, Degong; Sun, Dongtao

2016-11-01

In the high speed sliding electrical contact with large current, the temperature of contact area rises quickly under the coupling action of the friction heating, the Joule heating and electric arc heating. The rising temperature seriously affects the conductivity of the components and the yield strength of materials, as well affects the contact state and lead to damage, so as to shorten the service life of the contact elements. Therefore, there is vital significance to measure the temperature accurately and investigate the temperature effect on damage of rail surface. Aiming at the problem of components damage in high speed sliding electrical contact, the transient heat effect on the contact surface was explored and its influence and regularity on the sliding components damage was obtained. A kind of real-time temperature measurement method on rail surface of high speed sliding electrical contact is proposed. Under the condition of 2.5 kA current load, based on the principle of infrared radiation non-contact temperature sensor was used to measure the rail temperature. The dynamic distribution of temperature field was obtained through the simulation analysis, further, the connection between temperature changes and the rail surface damage morphology, the damage volume was analyzed and established. Finally, the method to reduce rail damage and improve the life of components by changing the temperature field was discussed.

Large-Scale Wireless Temperature Monitoring System for Liquefied Petroleum Gas Storage Tanks

PubMed Central

Fan, Guangwen; Shen, Yu; Hao, Xiaowei; Yuan, Zongming; Zhou, Zhi

2015-01-01

Temperature distribution is a critical indicator of the health condition for Liquefied Petroleum Gas (LPG) storage tanks. In this paper, we present a large-scale wireless temperature monitoring system to evaluate the safety of LPG storage tanks. The system includes wireless sensors networks, high temperature fiber-optic sensors, and monitoring software. Finally, a case study on real-world LPG storage tanks proves the feasibility of the system. The unique features of wireless transmission, automatic data acquisition and management, local and remote access make the developed system a good alternative for temperature monitoring of LPG storage tanks in practical applications. PMID:26393596

Millisecond laser ablation of molybdenum target in reactive gas toward MoS2 fullerene-like nanoparticles with thermally stable photoresponse.

PubMed

Song, Shu-Tao; Cui, Lan; Yang, Jing; Du, Xi-Wen

2015-01-28

As a promising material for photoelectrical application, MoS2 has attracted extensive attention on its facile synthesis and unique properties. Herein, we explored a novel strategy of laser ablation to synthesize MoS2 fullerene-like nanoparticles (FL-NPs) with stable photoresponse under high temperature. Specifically, we employed a millisecond pulsed laser to ablate the molybdenum target in dimethyl trisulfide gas, and as a result, the molybdenum nanodroplets were ejected from the target and interacted with the highly reactive ambient gas to produce MoS2 FL-NPs. In contrast, the laser ablation in liquid could only produce core-shell nanoparticles. The crucial factors for controlling final nanostructures were found to be laser intensity, cooling rate, and gas reactivity. Finally, the MoS2 FL-NPs were assembled into a simple photoresponse device which exhibited excellent thermal stability, indicating their great potentialities for high-temperature photoelectrical applications.

Buoyancy Suppression in Gases at High Temperatures

NASA Technical Reports Server (NTRS)

Kuczmarski, Maria A.; Gokoglu, Suleyman A.

2005-01-01

The computational fluid dynamics code FLUENT was used to study Rayleigh instability at large temperature differences in a sealed gas-filled enclosure with a cold top surface and a heated bottom wall (Benard problem). Both steady state and transient calculations were performed. The results define the boundaries of instability in a system depending on the geometry, temperature and pressure. It is shown that regardless of how fast the bottom-wall temperature can be ramped up to minimize the time spent in the unstable region of fluid motion, the eventual stability of the system depends on the prevailing final pressure after steady state has been reached. Calculations also show that the final state of the system can be different depending on whether the result is obtained via a steady-state solution or is reached by transient calculations. Changes in the slope of the pressure-versus-time curve are found to be a very good indicator of changes in the flow patterns in the system.

Correlation Between Pre-annealing Temperature and {110}<001> Annealing Texture in C- and Al-Free Fe-3 Pct Si-0.1 Pct Mn-0.002 Pct S Electrical Steel

NASA Astrophysics Data System (ADS)

Oh, Eun Jee; Heo, Nam Hoe; Koo, Yang Mo

2017-06-01

In C- and Al-free electrical steel, the increase in primary grain size with increasing pre-annealing temperature causes the transition in annealing texture after final annealing from {110} + {100} to {110}. The strip pre-annealed at 1073 K (800 °C) shows a low magnetic induction B8(T) of 1.784 T after final annealing. The strip pre-annealed at 1223 K (950 °C) shows a sharp {110}<001> Goss texture, producing a high magnetic induction B8(T) of 1.914 T comparable to that of the conventional electrical steels.

Synthesis and characterization of laminated Si/SiC composites

PubMed Central

Naga, Salma M.; Kenawy, Sayed H.; Awaad, Mohamed; Abd El-Wahab, Hamada S.; Greil, Peter; Abadir, Magdi F.

2012-01-01

Laminated Si/SiC ceramics were synthesized from porous preforms of biogenous carbon impregnated with Si slurry at a temperature of 1500 °C for 2 h. Due to the capillarity infiltration with Si, both intrinsic micro- and macrostructure in the carbon preform were retained within the final ceramics. The SEM micrographs indicate that the final material exhibits a distinguished laminar structure with successive Si/SiC layers. The produced composites show weight gain of ≈5% after heat treatment in air at 1300 °C for 50 h. The produced bodies could be used as high temperature gas filters as indicated from the permeability results. PMID:25685404

Economic analysis of the unified heliostat array. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1981-01-31

The Unified Heliostat Array (UHA) was investigated as to cost and optical performance. Two heliostats, the Veda Industrial Heliostat (VIH) and the Repowering Heliostat were investigated in conjunction with the UHA. The UHA was found to be a viable candidate for solar thermal central receiver applications. The UHA-VIH combination was shown to provide very high flux densities and to be suitable for high temperature applications in the 1000/sup 0/K to 2000/sup 0/K range. These temperatures were shown to be achievable even with very small (1 MWt) collector fields.

Dynamical Cooper pairing in nonequilibrium electron-phonon systems

DOE PAGES

Knap, Michael; Babadi, Mehrtash; Refael, Gil; ...

2016-12-08

In this paper, we analyze Cooper pairing instabilities in strongly driven electron-phonon systems. The light-induced nonequilibrium state of phonons results in a simultaneous increase of the superconducting coupling constant and the electron scattering. We demonstrate that the competition between these effects leads to an enhanced superconducting transition temperature in a broad range of parameters. Finally, our results may explain the observed transient enhancement of superconductivity in several classes of materials upon irradiation with high intensity pulses of terahertz light, and may pave new ways for engineering high-temperature light-induced superconducting states.

Effects of chemical composite, puffing temperature and intermediate moisture content on physical properties of potato and apple slices

NASA Astrophysics Data System (ADS)

Tabtaing, S.; Paengkanya, S.; Tanthong, P.

2017-09-01

Puffing technique is the process that can improve texture and volumetric of crisp fruit and vegetable. However, the effect of chemical composite in foods on puffing characteristics is still lack of study. Therefore, potato and apple slices were comparative study on their physical properties. Potato and apple were sliced into 2.5 mm thickness and 2.5 cm in diameter. Potato slices were treated by hot water for 2 min while apple slices were not treatment. After that, they were dried in 3 steps. First step, they were dried by hot air at temperature of 90°C until their moisture content reached to 30, 40, and 50 % dry basis. Then they were puffed by hot air at temperature of 130, 150, and 170°C for 2 min. Finally, they were dried again by hot air at temperature of 90°C until their final moisture content reached to 4% dry basis. The experimental results showed that chemical composite of food affected on physical properties of puffed product. Puffed potato had higher volume ratio than those puffed apple because potato slices contains starch. The higher starch content provided more hard texture of potato than those apples. Puffing temperature and moisture content strongly affected on the color, volume ratio, and textural properties of puffed potato slices. In addition, the high drying rate of puffed product observed at high puffing temperature and higher moisture content.

Constitutive Law and Flow Mechanism in Diamond Deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Xiaohui; Raterron, Paul; Zhang, Jianzhong

2012-11-19

Constitutive laws and crystal plasticity in diamond deformation have been the subjects of substantial interest since synthetic diamond was made in 1950's. To date, however, little is known quantitatively regarding its brittle-ductile properties and yield strength at high temperatures. In this paper, we report, for the first time, the strain-stress constitutive relations and experimental demonstration of deformation mechanisms under confined high pressure. The deformation at room temperature is essentially brittle, cataclastic, and mostly accommodated by fracturing on {111} plane with no plastic yielding at uniaxial strains up to 15%. At elevated temperatures of 1000°C and 1200°C diamond crystals exhibit significantmore » ductile flow with corresponding yield strength of 7.9 and 6.3 GPa, indicating that diamond starts to weaken when temperature is over 1000°C. Finally, at high temperature the plastic deformation and ductile flow is meditated by the <110>{111} dislocation glide and a very active {111} micro-twinning.« less

Microstructural, mechanical and tribological investigation of 30CrMnSiNi2A ultra-high strength steel under various tempering temperatures

NASA Astrophysics Data System (ADS)

Arslan Hafeez, Muhammad; Farooq, Ameeq

2018-01-01

The aim of the research was to investigate the variation in microstructural, mechanical and tribological characteristics of 30CrMnSiNi2A ultra-high strength steel as a function of tempering temperatures. Steel was quenched at 880 °C and tempered at five different tempering temperatures ranging from 250 °C to 650 °C. Optical microscopy and pin on disc tribometer was used to evaluate the microstructural and wear properties. Results show that characteristics of 30CrMnSiNi2A are highly sensitive to tempering temperatures. Lathe and plate shaped martensite obtained by quenching transform first into ε-carbide, second cementite, third coarsened and spheroidized cementite and finally into recovered ferrite and austenite. Hardness, tensile and yield strengths decreased while elongation increased with tempering temperatures. On the other hand, wear rate first markedly decreased and then increased. Optimum amalgamation of characteristics was achieved at 350 °C.

TDNiCr (ni-20Cr-2ThO2) forging studies

NASA Technical Reports Server (NTRS)

Filippi, A. M.

1974-01-01

Elevated temperature tensile and stress rupture properties were evaluated for forged TDNiCr (Ni-20Cr-2ThO2) and related to thermomechanical history and microstructure. Forging temperature and final annealed condition had pronounced influences on grain size which, in turn, was related to high temperature strength. Tensile strength improved by a factor of 8 as grain size changed from 1 to 150 microns. Stress-rupture strength was improved by a factor of 3 to 5 by a grain size increase from 10 to 1000 microns. Some contributions to the elevated temperature strength of very large grain material may also occur from the development of a strong texture and a preponderance of small twins. Other conditions promoting the improvement of high temperature strength were: an increase of total reduction, forging which continued the metal deformation inherent in the starting material, a low forging speed, and prior deformation by extrusion. The mechanical properties of optimally forged TDNiCr compared favorably to those of high strength sheet developed for space shuttle application.

Deformation and crack growth response under cyclic creep conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brust, F.W. Jr.

To increase energy efficiency, new plants must operate at higher and higher temperatures. Moreover, power generation equipment continues to age and is being used far beyond its intended original design life. Some recent failures which unfortunately occurred with serious consequences have clearly illustrated that current methods for insuring safety and reliability of high temperature equipment is inadequate. Because of these concerns, an understanding of the high-temperature crack growth process is very important and has led to the following studies of the high temperature failure process. This effort summarizes the results of some recent studies which investigate the phenomenon of highmore » temperature creep fatigue crack growth. Experimental results which detail the process of creep fatigue, analytical studies which investigate why current methods are ineffective, and finally, a new approach which is based on the T{sup *}-integral and its ability to characterize the creep-fatigue crack growth process are discussed. The potential validity of this new predictive methodology is illustrated.« less

Design and realization of temperature measurement system based on optical fiber temperature sensor for wireless power transfer

NASA Astrophysics Data System (ADS)

Chen, Xi; Zeng, Shuang; Liu, Xiulan; Jin, Yuan; Li, Xianglong; Wang, Xiaochen

2018-02-01

The electric vehicles (EV) have become accepted by increasing numbers of people for the environmental-friendly advantages. A novel way to charge the electric vehicles is through wireless power transfer (WPT). The wireless power transfer is a high power transfer system. The high currents flowing through the transmitter and receiver coils increasing temperature affects the safety of person and charging equipment. As a result, temperature measurement for wireless power transfer is needed. In this paper, a temperature measurement system based on optical fiber temperature sensors for electric vehicle wireless power transfer is proposed. Initially, the thermal characteristics of the wireless power transfer system are studied and the advantages of optical fiber sensors are analyzed. Then the temperature measurement system based on optical fiber temperature sensor is designed. The system consists of optical subsystem, data acquisition subsystem and data processing subsystem. Finally, the system is tested and the experiment result shows that the system can realize 1°C precision and can acquire real-time temperature distribution of the coils, which can meet the requirement of the temperature measuring for wireless power transfer.

Final Report Auto/Steel Partnership Phase II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cady, C.M.; Chen, S.R.; Gray, G.T. III

1999-06-09

This is the final report in which effects of strain-rate, temperature, and stress-state on the yield stress and the strain hardening behavior of many common steels used in automobile construction were investigated. The yield and flow stresses were found to exhibit very high rate sensitivities for most of the steels while the hardening rates were found to be insensitive to strain rate and temperature at lower temperatures or at higher strain rates. This behavior is consistent with the observation that overcoming the intrinsic Peierls stress is shown to be the rate-controlling mechanism in these materials at low temperatures. The dependencemore » of the yield stress on temperature and strain rate was found to decrease while the strain hardening rate increased. The Mechanical Threshold Stress (MTS) model was adopted to model the stress-strain behavior of the steels. Parameters for the constitutive relations were derived for the MTS model and also for the Johnson-Cook (JC) and the Zerilli-Armstrong (ZA) models. The results of this study substantiate the applicability of these models for describing the high strain-rate deformation of these materials. The JC and ZA models, however, due to their use of a power strain hardening law were found to yield constitutive relations for the materials which are strongly dependent on the range of strains for which the models were optimized.« less

Laser absorption of nitric oxide for thermometry in high-enthalpy air

NASA Astrophysics Data System (ADS)

Spearrin, R. M.; Schultz, I. A.; Jeffries, J. B.; Hanson, R. K.

2014-12-01

The design and demonstration of a laser absorption sensor for thermometry in high-enthalpy air is presented. The sensor exploits the highly temperature-sensitive and largely pressure-independent concentration of nitric oxide in air at chemical equilibrium. Temperature is thus inferred from an in situ measurement of nascent nitric oxide. The strategy is developed by utilizing a quantum cascade laser source for access to the strong fundamental absorption band in the mid-infrared spectrum of nitric oxide. Room temperature measurements in a high-pressure static cell validate the suitability of the Voigt lineshape model to the nitric oxide spectra at high gas densities. Shock-tube experiments enable calibration of a collision-broadening model for temperatures between 1200-3000 K. Finally, sensor performance is demonstrated in a high-pressure shock tube by measuring temperature behind reflected shock waves for both fixed-chemistry experiments where nitric oxide is seeded, and for experiments involving nitric oxide formation in shock-heated mixtures of N2 and O2. Results show excellent performance of the sensor across a wide range of operating conditions from 1100-2950 K and at pressures up to 140 atm.

Ionic Liquid Activation of Amorphous Metal-Oxide Semiconductors for Flexible Transparent Electronic Devices

DOE PAGES

Pudasaini, Pushpa Raj; Noh, Joo Hyon; Wong, Anthony T.; ...

2016-02-09

To begin this abstract, amorphous metal-oxide semiconductors offer the high carrier mobilities and excellent large-area uniformity required for high performance, transparent, flexible electronic devices; however, a critical bottleneck to their widespread implementation is the need to activate these materials at high temperatures which are not compatible with flexible polymer substrates. The highly controllable activation of amorphous indium gallium zinc oxide semiconductor channels using ionic liquid gating at room temperature is reported. Activation is controlled by electric field-induced oxygen migration across the ionic liquid-semiconductor interface. In addition to activation of unannealed devices, it is shown that threshold voltages of a transistormore » can be linearly tuned between the enhancement and depletion modes. Finally, the first ever example of transparent flexible thin film metal oxide transistor on a polyamide substrate created using this simple technique is demonstrated. Finally, this study demonstrates the potential of field-induced activation as a promising alternative to traditional postdeposition thermal annealing which opens the door to wide scale implementation into flexible electronic applications.« less

Structure evolution and thermoelectric properties of carbonized polydopamine thin films

DOE PAGES

Li, Haoqi; Aulin, Yaroslav V.; Frazer, Laszlo; ...

2017-02-13

Carbonization of nature-inspired polydopamine can yield thin films with high electrical conductivity. Understanding of the structure of carbonized PDA (cPDA) is therefore highly desired. In this study, neutron diffraction, Raman spectroscopy, and other techniques indicate that cPDA samples are mainly amorphous with some short-range ordering and graphite-like structure that emerges with increasing heat treatment temperature. The electrical conductivity and the Seebeck coefficient show different trends with heat treatment temperature, while the thermal conductivity remains insensitive. Finally, the largest room-temperature ZT of 2 × 10 –4 was obtained on samples heat-treated at 800 °C, which is higher than that of reducedmore » graphene oxide.« less

Method and apparatus for producing synthesis gas

DOEpatents

Hemmings, John William; Bonnell, Leo; Robinson, Earl T.

2010-03-03

A method and apparatus for reacting a hydrocarbon containing feed stream by steam methane reforming reactions to form a synthesis gas. The hydrocarbon containing feed is reacted within a reactor having stages in which the final stage from which a synthesis gas is discharged incorporates expensive high temperature materials such as oxide dispersed strengthened metals while upstream stages operate at a lower temperature allowing the use of more conventional high temperature alloys. Each of the reactor stages incorporate reactor elements having one or more separation zones to separate oxygen from an oxygen containing feed to support combustion of a fuel within adjacent combustion zones, thereby to generate heat to support the endothermic steam methane reforming reactions.

High Temperature Operation of Al 0.45Ga 0.55N/Al 0.30Ga 0.70 N High Electron Mobility Transistors

DOE PAGES

Baca, Albert G.; Armstrong, Andrew M.; Allerman, Andrew A.; ...

2017-08-01

AlGaN-channel high electron mobility transistors (HEMTs) are among a class of ultra wide-bandgap transistors that have a bandgap greater than ~3.4 eV, beyond that of GaN and SiC, and are promising candidates for RF and power applications. Long-channel Al xGa 1-xN HEMTs with x = 0.3 in the channel have been built and evaluated across the -50°C to +200°C temperature range. Room temperature drain current of 70 mA/mm, absent of gate leakage, and with a modest -1.3 V threshold voltage was measured. A very large I on/I off current ratio, greater than 10 8 was demonstrated over the entire temperaturemore » range, indicating that off-state leakage is below the measurement limit even at 200°C. Finally, combined with near ideal subthreshold slope factor that is just 1.3× higher than the theoretical limit across the temperature range, the excellent leakage properties are an attractive characteristic for high temperature operation.« less

High Temperature Operation of Al 0.45Ga 0.55N/Al 0.30Ga 0.70 N High Electron Mobility Transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baca, Albert G.; Armstrong, Andrew M.; Allerman, Andrew A.

AlGaN-channel high electron mobility transistors (HEMTs) are among a class of ultra wide-bandgap transistors that have a bandgap greater than ~3.4 eV, beyond that of GaN and SiC, and are promising candidates for RF and power applications. Long-channel Al xGa 1-xN HEMTs with x = 0.3 in the channel have been built and evaluated across the -50°C to +200°C temperature range. Room temperature drain current of 70 mA/mm, absent of gate leakage, and with a modest -1.3 V threshold voltage was measured. A very large I on/I off current ratio, greater than 10 8 was demonstrated over the entire temperaturemore » range, indicating that off-state leakage is below the measurement limit even at 200°C. Finally, combined with near ideal subthreshold slope factor that is just 1.3× higher than the theoretical limit across the temperature range, the excellent leakage properties are an attractive characteristic for high temperature operation.« less

Investigation of high temperature antennas for space shuttle

NASA Technical Reports Server (NTRS)

Kuhlman, E. A.

1973-01-01

The design and development of high temperature antennas for the space shuttle orbiter are discussed. The antenna designs were based on three antenna types, an annular slot (L-Band), a linear slot (C-Band), and a horn (C-Band). The design approach was based on combining an RF window, which provides thermal protection, with an off-the-shelf antenna. Available antenna window materials were reviewed and compared, and the materials most compatible with the design requirements were selected. Two antenna window design approaches were considered: one employed a high temperature dielectric material and a low density insulation material, and the other an insulation material usable for the orbiter thermal protection system. Preliminary designs were formulated and integrated into the orbiter structure. Simple electrical models, with a series of window configurations, were constructed and tested. The results of tests and analyses for the final antenna system designs are given and show that high temperature antenna systems consisting of off-the-shelf antennas thermally protected by RF windows can be designed for the Space Shuttle Orbiter.

Development of an Efficient Micro-Heat Exchanger: The Integration of Design Processing and Testing

DTIC Science & Technology

2005-11-01

together at high temperatures and cooled to room temperature. Additionally, alumina and zirconia powders have a major difference in densification...efficient heat exchanger. The main problem that needed to be resolved was the fact that the zirconia powders shrink much more than alumina powder...been measured. Our measurement in dimensions verifies that zirconia powders shrink substantially more than alumina powder except CR-15 after final

Static analysis of C-shape SMA middle ear prosthesis

NASA Astrophysics Data System (ADS)

Latalski, Jarosław; Rusinek, Rafał

2017-08-01

Shape memory alloys are a family of metals with the ability to change specimen shape depending on their temperature. This unique property is useful in many areas of mechanical and biomechanical engineering. A new half-ring middle ear prosthesis design made of a shape memory alloy, that is undergoing initial clinical tests, is investigated in this research paper. The analytical model of the studied structure made of nonlinear constitutive material is solved to identify the temperature-dependent stiffness characteristics of the proposed design on the basis of the Crotti-Engesser theorem. The final integral expression for the element deflection is highly complex, thus the solution has to be computed numerically. The final results show the proposed shape memory C-shape element to behave linearly in the analysed range of loadings and temperatures. This is an important observation that significantly simplifies the analysis of the prototype structure and opens wide perspectives for further possible applications of shape memory alloys.

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

NASA Astrophysics Data System (ADS)

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 evaluation of rock properties in high temperature condition.

Fail Safe, High Temperature Magnetic Bearings

NASA Technical Reports Server (NTRS)

Minihan, Thomas; Palazzolo, Alan; Kim, Yeonkyu; Lei, Shu-Liang; Kenny, Andrew; Na, Uhn Joo; Tucker, Randy; Preuss, Jason; Hunt, Andrew; Carter, Bart;

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

NASA Technical Reports Server (NTRS)

Barrett, Charles A.

1999-01-01

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

The temperature measurement research for high-speed flow based on tunable diode laser absorption spectroscopy

NASA Astrophysics Data System (ADS)

Di, Yue; Jin, Yi; Jiang, Hong-liang; Zhai, Chao

2013-09-01

Due to the particularity of the high-speed flow, in order to accurately obtain its' temperature, the measurement system should has some characteristics of not interfereing with the flow, non-contact measurement and high time resolution. The traditional measurement method cannot meet the above requirements, however the measurement method based on tunable diode laser absorption spectroscopy (TDLAS) technology can meet the requirements for high-speed flow temperature measurement. When the near-infared light of a specific frequency is through the media to be measured, it will be absorbed by the water vapor molecules and then the transmission light intensity is detected by the detector. The temperature of the water vapor which is also the high-speed flow temperature, can be accurately obtained by the Beer-Lambert law. This paper focused on the research of absorption spectrum method for high speed flow temperature measurement with the scope of 250K-500K. Firstly, spectral line selection method for low temperature measurement of high-speed flow is discussed. Selected absorption lines should be isolated and have a high peak absorption within the range of 250-500K, at the same time the interference of the other lines should be avoided, so that a high measurement accuracy can be obtained. According to the near-infrared absorption spectra characteristics of water vapor, four absorption lines at the near 1395 nm and 1409 nm are selected. Secondly, a system for the temperature measurement of the water vapor in the high-speed flow is established. Room temperature are measured through two methods, direct absorption spectroscopy (DAS) and wavelength modulation spectroscopy (WMS) ,the results show that this system can realize on-line measurement of the temperature and the measurement error is about 3%. Finally, the system will be used for temperature measurement of the high-speed flow in the shock tunnel, its feasibility of measurement is analyzed.

Atomic Layer Deposition of Vanadium Dioxide and a Temperature-dependent Optical Model.

PubMed

Currie, Marc; Mastro, Michael A; Wheeler, Virginia D

2018-05-23

Vanadium dioxide is a material that has a reversible metal-insulator phase change near 68 °C. To grow VO2 on a wide variety of substrates, with wafer-scale uniformity and angstrom level control of thickness, the method of atomic-layer deposition was chosen. This ALD process enables high-quality, low-temperature (≤150 °C) growth of ultrathin films (100-1000 Å) of VO2. For this demonstration, the VO2 films were grown on sapphire substrates. This low temperature growth technique produces mostly amorphous VO2 films. A subsequent anneal in an ultra-high vacuum chamber with a pressure of 7x10 -4 Pa of ultra-high purity (99.999%) oxygen produced oriented, polycrystalline VO2 films. The crystallinity, phase, and strain of the VO2 were determined by Raman spectroscopy and X-ray diffraction, while the stoichiometry and impurity levels were determined by X-ray photoelectron spectroscopy, and finally the morphology was determined by atomic force microscopy. These data demonstrate the high-quality of the films grown by this technique. A model was created to fit to the data for VO2 in its metallic and insulating phases in the near infrared spectral region. The permittivity and refractive index of the ALD VO2 agreed well with the other fabrication methods in its insulating phase, but showed a difference in its metallic state. Finally, the analysis of the films' optical properties enabled the creation of a wavelength- and temperature-dependent model of the complex optical refractive index for developing VO2 as a tunable refractive index material.

Gonad Transcriptome Analysis of High-Temperature-Treated Females and High-Temperature-Induced Sex-Reversed Neomales in Nile Tilapia

PubMed Central

Sun, Li Xue; Teng, Jian; Zhao, Yan; Li, Ning; Wang, Hui

2018-01-01

Background: Nowadays, the molecular mechanisms governing TSD (temperature-dependent sex determination) or GSD + TE (genotypic sex determination + temperature effects) remain a mystery in fish. Methods: We developed three all-female families of Nile tilapia (Oreochromis niloticus), and the family with the highest male ratio after high-temperature treatment was used for transcriptome analysis. Results: First, gonadal histology analysis indicated that the histological morphology of control females (CF) was not significantly different from that of high-temperature-treated females (TF) at various development stages. However, the high-temperature treatment caused a lag of spermatogenesis in high-temperature-induced neomales (IM). Next, we sequenced the transcriptome of CF, TF, and IM Nile tilapia. 79, 11,117, and 11,000 differentially expressed genes (DEGs) were detected in the CF–TF, CF–IM, and TF–IM comparisons, respectively, and 44 DEGs showed identical expression changes in the CF–TF and CF–IM comparisons. Principal component analysis (PCA) indicated that three individuals in CF and three individuals in TF formed a cluster, and three individuals in IM formed a distinct cluster, which confirmed that the gonad transcriptome profile of TF was similar to that of CF and different from that of IM. Finally, six sex-related genes were validated by qRT-PCR. Conclusions: This study identifies a number of genes that may be involved in GSD + TE, which will be useful for investigating the molecular mechanisms of TSD or GSD + TE in fish. PMID:29495590

Gonad Transcriptome Analysis of High-Temperature-Treated Females and High-Temperature-Induced Sex-Reversed Neomales in Nile Tilapia.

PubMed

Sun, Li Xue; Teng, Jian; Zhao, Yan; Li, Ning; Wang, Hui; Ji, Xiang Shan

2018-02-28

Nowadays, the molecular mechanisms governing TSD (temperature-dependent sex determination) or GSD + TE (genotypic sex determination + temperature effects) remain a mystery in fish. We developed three all-female families of Nile tilapia ( Oreochromis niloticus ), and the family with the highest male ratio after high-temperature treatment was used for transcriptome analysis. First, gonadal histology analysis indicated that the histological morphology of control females (CF) was not significantly different from that of high-temperature-treated females (TF) at various development stages. However, the high-temperature treatment caused a lag of spermatogenesis in high-temperature-induced neomales (IM). Next, we sequenced the transcriptome of CF, TF, and IM Nile tilapia. 79, 11,117, and 11,000 differentially expressed genes (DEGs) were detected in the CF-TF, CF-IM, and TF-IM comparisons, respectively, and 44 DEGs showed identical expression changes in the CF-TF and CF-IM comparisons. Principal component analysis (PCA) indicated that three individuals in CF and three individuals in TF formed a cluster, and three individuals in IM formed a distinct cluster, which confirmed that the gonad transcriptome profile of TF was similar to that of CF and different from that of IM. Finally, six sex-related genes were validated by qRT-PCR. This study identifies a number of genes that may be involved in GSD + TE, which will be useful for investigating the molecular mechanisms of TSD or GSD + TE in fish.

Simulation of Temperature Field Distribution for Cutting the Temperated Glass by Ultraviolet Laser

NASA Astrophysics Data System (ADS)

Yang, B. J.; He, Y. C.; Dai, F.; Lin, X. C.

2017-03-01

The finite element software ANSYS was adopted to simulate the temperature field distribution for laser cutting tempered glass, and the influence of different process parameters, including laser power, glass thickness and cutting speed, on temperature field distribution was studied in detail. The results show that the laser power has a greater influence on temperature field distribution than other paremeters, and when the laser power gets to 60W, the highest temperature reaches 749°C, which is higher than the glass softening temperature. It reflects the material near the laser spot is melted and the molten slag is removed by the high-energy water beam quickly. Finally, through the water guided laser cutting tempered glass experiment the FEM theoretical analysis was verified.

Lethal and sub-lethal responses of the biogenic reef forming polychaete Sabellaria alveolata to aqueous chlorine and temperature.

PubMed

Last, K S; Hendrick, V J; Beveridge, C M; Roberts, D A; Wilding, T A

2016-06-01

Sabellaria alveolata, a reef-forming marine polychaete, was exposed to aqueous chlorine which is routinely used as an anti-fouling agent in power station cooling water. Worms were treated to a range of chlorination levels (0, 0.02, 0.1 and 0.5 mg l(-1) Total Residual Oxidant referred to as control, low, intermediate and high TRO) at mean and maximum summer temperatures (18 and 23 °C respectively). Overall mortality was relatively low, however a combination of high temperature and intermediate and high TRO resulted in a significant increase in mortality compared to the control and low TRO treatments. In contrast the extension of dwelling tubes was reduced at high TRO, but increased at low and intermediate TRO levels relative to the controls independent of temperature. Finally, tube strength was found to decrease with increasing TRO, again independent of temperature. On the basis of these findings, S. alveolata can be considered tolerant of one month exposures to low TRO at water temperatures up to and including the summer maxima for southern UK waters. However, at higher TRO levels and during warm weather, high mortality would be predicted. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Plant tolerance to high temperature in a changing environment: scientific fundamentals and production of heat stress-tolerant crops

PubMed Central

Bita, Craita E.; Gerats, Tom

2013-01-01

Global warming is predicted to have a general negative effect on plant growth due to the damaging effect of high temperatures on plant development. The increasing threat of climatological extremes including very high temperatures might lead to catastrophic loss of crop productivity and result in wide spread famine. In this review, we assess the impact of global climate change on the agricultural crop production. There is a differential effect of climate change both in terms of geographic location and the crops that will likely show the most extreme reductions in yield as a result of expected extreme fluctuations in temperature and global warming in general. High temperature stress has a wide range of effects on plants in terms of physiology, biochemistry and gene regulation pathways. However, strategies exist to crop improvement for heat stress tolerance. In this review, we present recent advances of research on all these levels of investigation and focus on potential leads that may help to understand more fully the mechanisms that make plants tolerant or susceptible to heat stress. Finally, we review possible procedures and methods which could lead to the generation of new varieties with sustainable yield production, in a world likely to be challenged both by increasing population, higher average temperatures and larger temperature fluctuations. PMID:23914193

Plant tolerance to high temperature in a changing environment: scientific fundamentals and production of heat stress-tolerant crops.

PubMed

Bita, Craita E; Gerats, Tom

2013-01-01

Global warming is predicted to have a general negative effect on plant growth due to the damaging effect of high temperatures on plant development. The increasing threat of climatological extremes including very high temperatures might lead to catastrophic loss of crop productivity and result in wide spread famine. In this review, we assess the impact of global climate change on the agricultural crop production. There is a differential effect of climate change both in terms of geographic location and the crops that will likely show the most extreme reductions in yield as a result of expected extreme fluctuations in temperature and global warming in general. High temperature stress has a wide range of effects on plants in terms of physiology, biochemistry and gene regulation pathways. However, strategies exist to crop improvement for heat stress tolerance. In this review, we present recent advances of research on all these levels of investigation and focus on potential leads that may help to understand more fully the mechanisms that make plants tolerant or susceptible to heat stress. Finally, we review possible procedures and methods which could lead to the generation of new varieties with sustainable yield production, in a world likely to be challenged both by increasing population, higher average temperatures and larger temperature fluctuations.

Reactor and method for hydrocracking carbonaceous material

DOEpatents

Duncan, Dennis A.; Beeson, Justin L.; Oberle, R. Donald; Dirksen, Henry A.

1980-01-01

Solid, carbonaceous material is cracked in the presence of hydrogen or other reducing gas to provide aliphatic and aromatic hydrocarbons of lower molecular weight for gaseous and liquid fuels. The carbonaceous material, such as coal, is entrained as finely divided particles in a flow of reducing gas and preheated to near the decomposition temperature of the high molecular weight polymers. Within the reactor, small quantities of oxygen containing gas are injected at a plurality of discrete points to burn corresponding amounts of the hydrogen or other fuel and elevate the mixture to high temperatures sufficient to decompose the high molecular weight, carbonaceous solids. Turbulent mixing at each injection point rapidly quenches the material to a more moderate bulk temperature. Additional quenching after the final injection point can be performed by direct contact with quench gas or oil. The reactions are carried out in the presence of a hydrogen-containing reducing gas at moderate to high pressure which stabilizes the products.

Treatment of refractory powders by a novel, high enthalpy dc plasma

NASA Astrophysics Data System (ADS)

Pershin, L.; Mitrasinovic, A.; Mostaghimi, J.

2013-06-01

Thermophysical properties of CO2-CH4 mixtures at high temperatures are very attractive for materials processing. In comparison with argon, at the same temperature, such a mixture possesses much higher enthalpy and higher thermal conductivity. At high temperatures, CO2-CH4 mixture has a complex composition with strong presence of CO which, in the case of powder treatment, could reduce oxidation. In this work, a dc plasma torch with graphite cathode was used to study the effect of plasma gas composition on spheroidization of tungsten carbide and alumina powders. Two different gas compositions were used to generate the plasma while the torch current was kept at 300 A. Various techniques were employed to assess the average concentration of carbides and oxides and the final shape of the treated powders. Process parameters such as input power and plasma gas composition allow controlling the degree of powder oxidation and spheroidization of high melting point ceramic powders.

Preparation and rheological behavior of polymer-modified asphalts

NASA Astrophysics Data System (ADS)

Yousefi, Ali Akbar

1999-09-01

Different materials and methods were used to prepare and stabilize polymer-modified asphalts. Addition of thermoplastic elastomers improved some technically important properties of asphalt. Due to inherent factors like large density difference between asphalt and polyethylene, many physical methods in which the structure of asphalt is unchanged, failed to stabilize this system. The effect of addition of copolymers and a pyrolytic oil residue derived from used tire rubber were also studied and found to be ineffective on the storage stability of the polymer-asphalt emulsions while high and moderate temperature properties of the asphalt were found to be improved. Finally, the technique of catalytic grafting of polymer on the surface of high-density particles (e.g. carbon black) was used to balance the large density difference between asphalt and polymer. The resulting polymer-asphalts were stable at high temperatures and showed enhanced properties at low and high temperatures.

Measurements and Modeling of III-V Solar Cells at High Temperatures up to 400 $${}^{\\circ}$$ C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perl, Emmett E.; Simon, John; Geisz, John F.

2016-09-01

In this paper, we study the performance of 2.0 eV Al0.12Ga0.39In0.49P and 1.4 eV GaAs solar cells over a temperature range of 25-400 degrees C. The temperature-dependent J01 and J02 dark currents are extracted by fitting current-voltage measurements to a two-diode model. We find that the intrinsic carrier concentration ni dominates the temperature dependence of the dark currents, open-circuit voltage, and cell efficiency. To study the impact of temperature on the photocurrent and bandgap of the solar cells, we measure the quantum efficiency and illuminated current-voltage characteristics of the devices up to 400 degrees C. As the temperature is increased,more » we observe no degradation to the internal quantum efficiency and a decrease in the bandgap. These two factors drive an increase in the short-circuit current density at high temperatures. Finally, we measure the devices at concentrations ranging from ~30 to 1500 suns and observe n = 1 recombination characteristics across the entire temperature range. These findings should be a valuable guide to the design of any system that requires high-temperature solar cell operation.« less

Power Packaging of Spray-Cooled SiC Devices for High Temperature and High Voltage Operation: Final Report

DTIC Science & Technology

2008-07-01

the desired switching frequencies. * I Three- r1aL phase dc-ac ac-dc Vph converter # 4 convertr converter 1 # 2 # 3 * I r --- -- -- - 4I6l kV ACSIDE...J:-----------------.HWn.XEMEL ------- J WDC_ SI CEI.................... ... .. .. .............. .......... J . Fig. 4.1 Block diagram of a PCM4. Vph

75 FR 6013 - Energy Conservation Program for Consumer Products: Decision and Order Granting a Waiver to...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-05

... heating exceeds the high-stage compressor capacity for cooling. Finally, the test procedure must account... test method to cover Hallowell's three-capacity compressor. The two (of three potential) active stages... pumps for the heating mode as follows: a. Conduct one Maximum Temperature Test (H0 1 ), two High...

Coverage-dependent adsorption and desorption of oxygen on Pd(100)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dunnen, Angela den; Jacobse, Leon; Wiegman, Sandra

2016-06-28

We have studied the adsorption and desorption of O{sub 2} on Pd(100) by supersonic molecular beam techniques and thermal desorption spectroscopy. Adsorption measurements on the bare surface confirm that O{sub 2} initially dissociates for all kinetic energies between 56 and 380 meV and surface temperatures between 100 and 600 K via a direct mechanism. At and below 150 K, continued adsorption leads to a combined O/O{sub 2} overlayer. Dissociation of molecularly bound O{sub 2} during a subsequent temperature ramp leads to unexpected high atomic oxygen coverages, which are also obtained at high incident energy and high surface temperature. At intermediatemore » temperatures and energies, these high final coverages are not obtained. Our results show that kinetic energy of the gas phase reactant and reaction energy dissipated during O{sub 2} dissociation on the cold surface both enable activated nucleation of high-coverage surface structures. We suggest that excitation of local substrate phonons may play a crucial role in oxygen dissociation at any coverage.« less

Room-temperature nine-µm-wavelength photodetectors and GHz-frequency heterodyne receivers.

PubMed

Palaferri, Daniele; Todorov, Yanko; Bigioli, Azzurra; Mottaghizadeh, Alireza; Gacemi, Djamal; Calabrese, Allegra; Vasanelli, Angela; Li, Lianhe; Davies, A Giles; Linfield, Edmund H; Kapsalidis, Filippos; Beck, Mattias; Faist, Jérôme; Sirtori, Carlo

2018-04-05

Room-temperature operation is essential for any optoelectronics technology that aims to provide low-cost, compact systems for widespread applications. A recent technological advance in this direction is bolometric detection for thermal imaging, which has achieved relatively high sensitivity and video rates (about 60 hertz) at room temperature. However, owing to thermally induced dark current, room-temperature operation is still a great challenge for semiconductor photodetectors targeting the wavelength band between 8 and 12 micrometres, and all relevant applications, such as imaging, environmental remote sensing and laser-based free-space communication, have been realized at low temperatures. For these devices, high sensitivity and high speed have never been compatible with high-temperature operation. Here we show that a long-wavelength (nine micrometres) infrared quantum-well photodetector fabricated from a metamaterial made of sub-wavelength metallic resonators exhibits strongly enhanced performance with respect to the state of the art up to room temperature. This occurs because the photonic collection area of each resonator is much larger than its electrical area, thus substantially reducing the dark current of the device. Furthermore, we show that our photonic architecture overcomes intrinsic limitations of the material, such as the drop of the electronic drift velocity with temperature, which constrains conventional geometries at cryogenic operation. Finally, the reduced physical area of the device and its increased responsivity allow us to take advantage of the intrinsic high-frequency response of the quantum detector at room temperature. By mixing the frequencies of two quantum-cascade lasers on the detector, which acts as a heterodyne receiver, we have measured a high-frequency signal, above four gigahertz (GHz). Therefore, these wide-band uncooled detectors could benefit technologies such as high-speed (gigabits per second) multichannel coherent data transfer and high-precision molecular spectroscopy.

Room-temperature nine-µm-wavelength photodetectors and GHz-frequency heterodyne receivers

NASA Astrophysics Data System (ADS)

Palaferri, Daniele; Todorov, Yanko; Bigioli, Azzurra; Mottaghizadeh, Alireza; Gacemi, Djamal; Calabrese, Allegra; Vasanelli, Angela; Li, Lianhe; Davies, A. Giles; Linfield, Edmund H.; Kapsalidis, Filippos; Beck, Mattias; Faist, Jérôme; Sirtori, Carlo

2018-04-01

Room-temperature operation is essential for any optoelectronics technology that aims to provide low-cost, compact systems for widespread applications. A recent technological advance in this direction is bolometric detection for thermal imaging, which has achieved relatively high sensitivity and video rates (about 60 hertz) at room temperature. However, owing to thermally induced dark current, room-temperature operation is still a great challenge for semiconductor photodetectors targeting the wavelength band between 8 and 12 micrometres, and all relevant applications, such as imaging, environmental remote sensing and laser-based free-space communication, have been realized at low temperatures. For these devices, high sensitivity and high speed have never been compatible with high-temperature operation. Here we show that a long-wavelength (nine micrometres) infrared quantum-well photodetector fabricated from a metamaterial made of sub-wavelength metallic resonators exhibits strongly enhanced performance with respect to the state of the art up to room temperature. This occurs because the photonic collection area of each resonator is much larger than its electrical area, thus substantially reducing the dark current of the device. Furthermore, we show that our photonic architecture overcomes intrinsic limitations of the material, such as the drop of the electronic drift velocity with temperature, which constrains conventional geometries at cryogenic operation. Finally, the reduced physical area of the device and its increased responsivity allow us to take advantage of the intrinsic high-frequency response of the quantum detector at room temperature. By mixing the frequencies of two quantum-cascade lasers on the detector, which acts as a heterodyne receiver, we have measured a high-frequency signal, above four gigahertz (GHz). Therefore, these wide-band uncooled detectors could benefit technologies such as high-speed (gigabits per second) multichannel coherent data transfer and high-precision molecular spectroscopy.

Nucleation and growth control in protein crystallization

NASA Technical Reports Server (NTRS)

Rosenberger, Franz; Nyce, Thomas A.; Meehan, Edward J.; Sowers, Jennifer W.; Monaco, Lisa A.

1990-01-01

The five topics summarized in this final report are as follows: (1) a technique for the expedient, semi-automated determination of protein solubilities as a function of temperature and application of this technique to proteins other than lysozyme; (2) a small solution cell with adjustable temperature gradients for the growth of proteins at a predetermined location through temperature programming; (3) a microscopy system with image storage and processing capability for high resolution optical studies of temperature controlled protein growth and etching kinetics; (4) growth experiments with lysozyme in thermosyphon flow ; and (5) a mathematical model for the evolution of evaporation/diffusion induced concentration gradients in the hanging drop protein crystallization technique.

The low-temperature method for study of coniferous tissues in the environmental scanning electron microscope.

PubMed

Neděla, Vilém; Tihlaříková, Eva; Hřib, Jiří

2015-01-01

The use of non-standard low-temperature conditions in environmental scanning electron microscopy might be promising for the observation of coniferous tissues in their native state. This study is aimed to analyse and evaluate the method based on the principle of low-temperature sample stabilization. We demonstrate that the upper mucous layer is sublimed and a microstructure of the sample surface can be observed with higher resolution at lower gas pressure conditions, thanks to a low-temperature method. An influence of the low-temperature method on sample stability was also studied. The results indicate that high-moisture conditions are not suitable for this method and often cause the collapse of samples. The potential improvement of stability to beam damage has been demonstrated by long-time observation at different operation parameters. We finally show high applicability of the low-temperature method on different types of conifers and Oxalis acetosella. © 2014 Wiley Periodicals, Inc.

Development of Highly Ductile Spheroidized Steel from High C (0.61 wt.% C) Low-Alloy Steel

NASA Astrophysics Data System (ADS)

Monia, S.; Varshney, A.; Gouthama; Sangal, S.; Kundu, S.; Samanta, S.; Mondal, K.

2015-11-01

This research aims to develop a multiphase steel combining spheroidal cementite and bainite in ductile ferrite matrix possessing an optimal balance of reasonably high strength and excellent ductility. A high carbon (0.61 wt.%) high silicon (1.71 wt.%) EN45 spring steel was annealed to obtain ferrite pearlite microstructure. The samples were given 5 and 10% cold rolling followed by holding at temperature below Ac1 for about 3 h. The samples were then held in intercritical range at 770 °C temperature for different durations ranging from 5 to 20 min for partial re-austenitization followed by quenching in a salt bath maintained at 350 °C and holding for 10 min to get bainite. The samples were finally water quenched. Characterizations of the samples with the help of optical microscopy, x-ray diffraction, scanning electron microscopy, and atomic force microscopy were carried out. Optimal heat-treatment conditions were found out after correlating with tensile properties. The best combination of high tensile strength (~800 MPa) with very high elongation (~29%) was obtained. Effects of cold-rolled strain and holding time in the intercritical region on the mechanical properties and microstructural changes were studied. Finally, structural property correlation is established.

Extreme temperature stability of thermally insulating graphene-mesoporous-silicon nanocomposite

NASA Astrophysics Data System (ADS)

Kolhatkar, Gitanjali; Boucherif, Abderraouf; Rahim Boucherif, Abderrahim; Dupuy, Arthur; Fréchette, Luc G.; Arès, Richard; Ruediger, Andreas

2018-04-01

We demonstrate the thermal stability and thermal insulation of graphene-mesoporous-silicon nanocomposites (GPSNC). By comparing the morphology of GPSNC carbonized at 650 °C as-formed to that after annealing, we show that this nanocomposite remains stable at temperatures as high as 1050 °C due to the presence of a few monolayers of graphene coating on the pore walls. This does not only make this material compatible with most thermal processes but also suggests applications in harsh high temperature environments. The thermal conductivity of GPSNCs carbonized at temperatures in the 500 °C-800 °C range is determined through Raman spectroscopy measurements. They indicate that the thermal conductivity of the composite is lower than that of silicon, with a value of 13 ± 1 W mK-1 at room temperature, and not affected by the thin graphene layer, suggesting a role of the high concentration of carbon related-defects as indicated by the high intensity of the D-band compared to G-band of the Raman spectra. This morphological stability at high temperature combined with a high thermal insulation make GPSNC a promising candidate for a broad range of applications including microelectromechanical systems and thermal effect microsystems such as flow sensors or IR detectors. Finally, at 120 °C, the thermal conductivity remains equal to that at room temperature, attesting to the potential of using our nanocomposite in devices that operate at high temperatures such as microreactors for distributed chemical conversion, solid oxide fuel cells, thermoelectric devices or thermal micromotors.

The design of an air-cooled metallic high temperature radial turbine

NASA Technical Reports Server (NTRS)

Snyder, Philip H.; Roelke, Richard J.

1988-01-01

Recent trends in small advanced gas turbine engines call for higher turbine inlet temperatures. Advances in radial turbine technology have opened the way for a cooled metallic radial turbine capable of withstanding turbine inlet temperatures of 2500 F while meeting the challenge of high efficiency in this small flow size range. In response to this need, a small air-cooled radial turbine has been designed utilizing internal blade coolant passages. The coolant flow passage design is uniquely tailored to simultaneously meet rotor cooling needs and rotor fabrication constraints. The rotor flow-path design seeks to realize improved aerodynamic blade loading characteristics and high efficiency while satisfying rotor life requirements. An up-scaled version of the final engine rotor is currently under fabrication and, after instrumentation, will be tested in the warm turbine test facility at the NASA Lewis Research Center.

Advances in the high performance polymer electrolyte membranes for fuel cells.

PubMed

Zhang, Hongwei; Shen, Pei Kang

2012-03-21

This critical review tersely and concisely reviews the recent development of the polymer electrolyte membranes and the relationship between their properties and affecting factors like operation temperature. In the first section, the advantages and shortcomings of the corresponding polymer electrolyte membrane fuel cells are analyzed. Then, the limitations of Nafion membranes and their alternatives to large-scale commercial applications are discussed. Secondly, the concepts and approaches of the alternative proton exchange membranes for low temperature and high temperature fuel cells are described. The highlights of the current scientific achievements are given for various aspects of approaches. Thirdly, the progress of anion exchange membranes is presented. Finally, the perspectives of future trends on polymer electrolyte membranes for different applications are commented on (400 references).

A general strategy for performing temperature-programming in high performance liquid chromatography--further improvements in the accuracy of retention time predictions of segmented temperature gradients.

PubMed

Wiese, Steffen; Teutenberg, Thorsten; Schmidt, Torsten C

2012-01-27

In the present work it is shown that the linear elution strength (LES) model which was adapted from temperature-programming gas chromatography (GC) can also be employed for systematic method development in high-temperature liquid chromatography (HT-HPLC). The ability to predict isothermal retention times based on temperature-gradient as well as isothermal input data was investigated. For a small temperature interval of ΔT=40°C, both approaches result in very similar predictions. Average relative errors of predicted retention times of 2.7% and 1.9% were observed for simulations based on isothermal and temperature-gradient measurements, respectively. Concurrently, it was investigated whether the accuracy of retention time predictions of segmented temperature gradients can be further improved by temperature dependent calculation of the parameter S(T) of the LES relationship. It was found that the accuracy of retention time predictions of multi-step temperature gradients can be improved to around 1.5%, if S(T) was also calculated temperature dependent. The adjusted experimental design making use of four temperature-gradient measurements was applied for systematic method development of selected food additives by high-temperature liquid chromatography. Method development was performed within a temperature interval from 40°C to 180°C using water as mobile phase. Two separation methods were established where selected food additives were baseline separated. In addition, a good agreement between simulation and experiment was observed, because an average relative error of predicted retention times of complex segmented temperature gradients less than 5% was observed. Finally, a schedule of recommendations to assist the practitioner during systematic method development in high-temperature liquid chromatography was established. Copyright © 2011 Elsevier B.V. All rights reserved.

Forming metal-intermetallic or metal-ceramic composites by self-propagating high-temperature reactions

DOEpatents

Rawers, James C.; Alman, David E.; Petty, Jr., Arthur V.

1996-01-01

Industrial applications of composites often require that the final product have a complex shape. In this invention intermetallic or ceramic phases are formed from sheets of unreacted elemental metals. The process described in this invention allows the final product shape be formed prior to the formation of the composite. This saves energy and allows formation of shaped articles of metal-intermetallic composites composed of brittle materials that cannot be deformed without breaking.

Validity of multiple stress creep recovery (MSCR) test for DOTD asphalt binder specification : final report 564.

DOT National Transportation Integrated Search

2017-09-01

Numerous studies have shown that G*/Sin, the high temperature specification parameter for current Performance Graded (PG) asphalt binder is not adequate to reflect the rutting characteristics of polymer-modified binders. Consequently, many state De...

A CONTINUOUS-PURGE PULSED VALVE SUITABLE FOR HIGH-TEMPERATURE APPLICATIONS. (R825412)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Evaluation and analysis of Seasat-A scanning multichannel Microwave Radiometer (SMMR) Antenna Pattern Correction (APC) algorithm

NASA Technical Reports Server (NTRS)

Kitzis, J. L.; Kitzis, S. N.

1979-01-01

The brightness temperature data produced by the SMMR final Antenna Pattern Correction (APC) algorithm is discussed. The algorithm consisted of: (1) a direct comparison of the outputs of the final and interim APC algorithms; and (2) an analysis of a possible relationship between observed cross track gradients in the interim brightness temperatures and the asymmetry in the antenna temperature data. Results indicate a bias between the brightness temperature produced by the final and interim APC algorithm.

Polymer quenched prealloyed metal powder

DOEpatents

Hajaligol, Mohammad R.; Fleischhauer, Grier; German, Randall M.

2001-01-01

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3 % Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Method of manufacturing aluminide sheet by thermomechanical processing of aluminide powders

DOEpatents

Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleishhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

2003-12-09

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Thermomechanical processing of plasma sprayed intermetallic sheets

DOEpatents

Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

2001-01-01

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Method of manufacturing aluminide sheet by thermomechanical processing of aluminide powders

DOEpatents

Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

2000-01-01

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr.ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

A high temperature testing system for ceramic composites

NASA Technical Reports Server (NTRS)

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.

An objective algorithm for reconstructing the three-dimensional ocean temperature field based on Argo profiles and SST data

NASA Astrophysics Data System (ADS)

Zhou, Chaojie; Ding, Xiaohua; Zhang, Jie; Yang, Jungang; Ma, Qiang

2017-12-01

While global oceanic surface information with large-scale, real-time, high-resolution data is collected by satellite remote sensing instrumentation, three-dimensional (3D) observations are usually obtained from in situ measurements, but with minimal coverage and spatial resolution. To meet the needs of 3D ocean investigations, we have developed a new algorithm to reconstruct the 3D ocean temperature field based on the Array for Real-time Geostrophic Oceanography (Argo) profiles and sea surface temperature (SST) data. The Argo temperature profiles are first optimally fitted to generate a series of temperature functions of depth, with the vertical temperature structure represented continuously. By calculating the derivatives of the fitted functions, the calculation of the vertical temperature gradient of the Argo profiles at an arbitrary depth is accomplished. A gridded 3D temperature gradient field is then found by applying inverse distance weighting interpolation in the horizontal direction. Combined with the processed SST, the 3D temperature field reconstruction is realized below the surface using the gridded temperature gradient. Finally, to confirm the effectiveness of the algorithm, an experiment in the Pacific Ocean south of Japan is conducted, for which a 3D temperature field is generated. Compared with other similar gridded products, the reconstructed 3D temperature field derived by the proposed algorithm achieves satisfactory accuracy, with correlation coefficients of 0.99 obtained, including a higher spatial resolution (0.25° × 0.25°), resulting in the capture of smaller-scale characteristics. Finally, both the accuracy and the superiority of the algorithm are validated.

Refraction error correction for deformation measurement by digital image correlation at elevated temperature

NASA Astrophysics Data System (ADS)

Su, Yunquan; Yao, Xuefeng; Wang, Shen; Ma, Yinji

2017-03-01

An effective correction model is proposed to eliminate the refraction error effect caused by an optical window of a furnace in digital image correlation (DIC) deformation measurement under high-temperature environment. First, a theoretical correction model with the corresponding error correction factor is established to eliminate the refraction error induced by double-deck optical glass in DIC deformation measurement. Second, a high-temperature DIC experiment using a chromium-nickel austenite stainless steel specimen is performed to verify the effectiveness of the correction model by the correlation calculation results under two different conditions (with and without the optical glass). Finally, both the full-field and the divisional displacement results with refraction influence are corrected by the theoretical model and then compared to the displacement results extracted from the images without refraction influence. The experimental results demonstrate that the proposed theoretical correction model can effectively improve the measurement accuracy of DIC method by decreasing the refraction errors from measured full-field displacements under high-temperature environment.

Effect of sintering temperature on the microstructure and properties of foamed glass-ceramics prepared from high-titanium blast furnace slag and waste glass

NASA Astrophysics Data System (ADS)

Chen, Chang-hong; Feng, Ke-qin; Zhou, Yu; Zhou, Hong-ling

2017-08-01

Foamed glass-ceramics were prepared via a single-step sintering method using high-titanium blast furnace slag and waste glass as the main raw materials The influence of sintering temperature (900-1060°C) on the microstructure and properties of foamed glass-ceramics was studied. The results show that the crystal shape changed from grainy to rod-shaped and finally turned to multiple shapes as the sintering temperature was increased from 900 to 1060°C. With increasing sintering temperature, the average pore size of the foamed glass-ceramics increased and subsequently decreased. By contrast, the compressive strength and the bulk density decreased and subsequently increased. An excessively high temperature, however, induced the coalescence of pores and decreased the compressive strength. The optimal properties, including the highest compressive strength (16.64 MPa) among the investigated samples and a relatively low bulk density (0.83 g/cm3), were attained in the case of the foamed glass-ceramics sintered at 1000°C.

Shear induced structures in crystallizing cocoa butter

NASA Astrophysics Data System (ADS)

Mazzanti, Gianfranco; Guthrie, Sarah E.; Sirota, Eric B.; Marangoni, Alejandro G.; Idziak, Stefan H. J.

2004-03-01

Cocoa butter is the main structural component of chocolate and many cosmetics. It crystallizes in several polymorphs, called phases I to VI. We used Synchrotron X-ray diffraction to study the effect of shear on its crystallization. A previously unreported phase (phase X) was found and a crystallization path through phase IV under shear was observed. Samples were crystallized under shear from the melt in temperature controlled Couette cells, at final crystallization temperatures of 17.5^oC, 20^oC and 22.5^oC in Beamline X10A of NSLS. The formation of phase X was observed at low shear rates (90 s-1) and low crystallization temperature (17.5^oC), but was absent at high shear (720 s-1) and high temperature (20^oC). The d-spacing and melting point suggest that this new phase is a mixture rich on two of the three major components of cocoa butter. We also found that, contrary to previous reports, the transition from phase II to phase V can happen through the intermediate phase IV, at high shear rates and temperature.

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

NASA Astrophysics Data System (ADS)

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

2017-10-01

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

In situ strain and temperature measurement and modelling during arc welding

DOE PAGES

Chen, Jian; Yu, Xinghua; Miller, Roger G.; ...

2014-12-26

In this study, experiments and numerical models were applied to investigate the thermal and mechanical behaviours of materials adjacent to the weld pool during arc welding. In the experiment, a new high temperature strain measurement technique based on digital image correlation (DIC) was developed and applied to measure the in situ strain evolution. In contrast to the conventional DIC method that is vulnerable to the high temperature and intense arc light involved in fusion welding processes, the new technique utilised a special surface preparation method to produce high temperature sustaining speckle patterns required by the DIC algorithm as well asmore » a unique optical illumination and filtering system to suppress the influence of the intense arc light. These efforts made it possible for the first time to measure in situ the strain field 1 mm away from the fusion line. The temperature evolution in the weld and the adjacent regions was simultaneously monitored by an infrared camera. Finally and additionally, a thermal–mechanical finite element model was applied to substantiate the experimental measurement.« less

High-temperature catalytically assisted combustion. Final report, 1 August 1981-31 July 1983

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bracco, F.V.; Royce, B.S.H.; Santavicca, D.A.

1983-07-31

Results of research on a two-dimensional, transient catalytic combustion model and on a high temperature perovskite catalyst are presented. A recently developed two-dimensional, transient model was used to study the ignition of carbon monoxide/air mixtures in a platinum-coated catalytic honeycomb. Comparisons between calculated and measured steady-state substrate temperature profiles and exhaust-gas compositions show good agreement. A platinum-doped perovskite catalyst proposed will exhibit low-temperature light off and high-temperature stability. Preliminary tests using a perovskite powder with 1 wt.% platinium are encouraging, showing very little change in surface activity when used with propane fuel. Variations in catalytic activity from sample to samplemore » were also found, and after extensive testing the cause of these variations could not be identified. However, preliminary tests using Fourier-transform infrared photoacoustic spectroscopy do indicate differences in the various catalyst samples that may be related to the difference in catalytic activity. The use of bench-top-oven and differential-scanning-calorimetry techniques for screening catalysts in terms of relative activity and aging characteristics were also demonstrated.« less

Development of Isotropic, Micro-Toughened Titanium-Base Intermetallic Composites for High-Temperature Service Final Report CRADA No. TC-0497-93A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nieh, T. G.; Waltz, Z. R.

The purpose of this Cooperative Research and Development Agreement (CRADA) between LLNL and P&W is to develop advanced composites and their processing technologies, resulting in major improviements in the ductility and toughnes of high-strength, high-stiffness TiAl-base composite materials for commercial jet engines and U.S. Department of Energy (DOE) Defense Program applications.

Net shape processing of alnico magnets by additive manufacturing

DOE PAGES

White, Emma Marie Hamilton; Kassen, Aaron Gregory; Simsek, Emrah; ...

2017-06-07

Alternatives to rare earth permanent magnets, such as alnico, will reduce supply instability, increase sustainability, and could decrease the cost of permanent magnets, especially for high temperature applications, such as traction drive motors. Alnico magnets with moderate coercivity, high remanence, and relatively high energy product are conventionally processed by directional solidification and (significant) final machining, contributing to increased costs and additional material waste. Additive manufacturing (AM) is developing as a cost effective method to build net-shape three-dimensional parts with minimal final machining and properties comparable to wrought parts. This work describes initial studies of net-shape fabrication of alnico magnets bymore » AM using a laser engineered net shaping (LENS) system. High pressure gas atomized (HPGA) pre-alloyed powders of two different modified alnico “8” compositions, with high purity and sphericity, were built into cylinders using the LENS process, followed by heat treatment. The magnetic properties showed improvement over their cast and sintered counterparts. The resulting alnico permanent magnets were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and hysteresisgraph measurements. Furthermore, these results display the potential for net-shape processing of alnico permanent magnets for use in next generation traction drive motors and other applications requiring high temperatures and/or complex engineered part geometries.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, Emma Marie Hamilton; Kassen, Aaron Gregory; Simsek, Emrah

Alternatives to rare earth permanent magnets, such as alnico, will reduce supply instability, increase sustainability, and could decrease the cost of permanent magnets, especially for high temperature applications, such as traction drive motors. Alnico magnets with moderate coercivity, high remanence, and relatively high energy product are conventionally processed by directional solidification and (significant) final machining, contributing to increased costs and additional material waste. Additive manufacturing (AM) is developing as a cost effective method to build net-shape three-dimensional parts with minimal final machining and properties comparable to wrought parts. This work describes initial studies of net-shape fabrication of alnico magnets bymore » AM using a laser engineered net shaping (LENS) system. High pressure gas atomized (HPGA) pre-alloyed powders of two different modified alnico “8” compositions, with high purity and sphericity, were built into cylinders using the LENS process, followed by heat treatment. The magnetic properties showed improvement over their cast and sintered counterparts. The resulting alnico permanent magnets were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and hysteresisgraph measurements. Furthermore, these results display the potential for net-shape processing of alnico permanent magnets for use in next generation traction drive motors and other applications requiring high temperatures and/or complex engineered part geometries.« less

Simultaneous droplet impingement dynamics and heat transfer on nano-structured surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Jian; Graber, Christof; Liburdy, James

This study examines the hydrodynamics and temperature characteristics of distilled deionized water droplets impinging on smooth and nano-structured surfaces using high speed (HS) and infrared (IR) imaging at We = 23.6 and Re = 1593, both based on initial drop impingement parameters. Results for a smooth and nano-structured surface for a range of surface temperatures are compared. Droplet impact velocity, transient spreading diameter and dynamic contact angle are measured. The near surface average droplet fluid temperatures are evaluated for conditions of evaporative cooling and boiling. Also included are surface temperature results using a gold layered IR opaque surface on silicon.more » Four stages of the impingement process are identified: impact, boiling, near constant surface diameter evaporation, and final dry-out. For the boiling conditions there is initial nucleation followed by severe boiling, then near constant diameter evaporation resulting in shrinking of the droplet height. When a critical contact angle is reached during evaporation the droplet rapidly retracts to a smaller diameter reducing the contact area with the surface. This continues as a sequence of retractions until final dry out. The basic trends are the same for all surfaces, but the nano-structured surface has a lower dissipated energy during impact and enhances the heat transfer for evaporative cooling with a 20% shorter time to achieve final dry out. (author)« less

Silicon carbide, a semiconductor for space power electronics

NASA Technical Reports Server (NTRS)

Powell, J. Anthony; Matus, Lawrence G.

1991-01-01

After many years of promise as a high temperature semiconductor, silicon carbide (SiC) is finally emerging as a useful electronic material. Recent significant progress that has led to this emergence has been in the areas of crystal growth and device fabrication technology. High quality single-crystal SiC wafers, up to 25 mm in diameter, can now be produced routinely from boules grown by a high temperature (2700 K) sublimation process. Device fabrication processes, including chemical vapor deposition (CVD), in situ doping during CVD, reactive ion etching, oxidation, metallization, etc. have been used to fabricate p-n junction diodes and MOSFETs. The diode was operated to 870 K and the MOSFET to 770 K.

Room temperature, air crystallized perovskite film for high performance solar cells

DOE PAGES

Dubey, Ashish; Kantack, Nicholas; Adhikari, Nirmal; ...

2016-05-31

For the first time, room temperature heating free growth and crystallization of perovskite films in ambient air without the use of thermal annealing is reported. Highly efficient perovskite nanorod-based solar cells were made using ITO/PEDOT:PSS/CH 3NH 3PbI 3 nanorods/PC 60BM/rhodamine/Ag. All the layers except PEDOT:PSS were processed at room temperature thereby eliminating the need for thermal treatment. Perovskite films were spin coated inside a N-2 filled glovebox and immediately were taken outside in air having 40% relative humidity (RH). Exposure to humid air was observed to promote the crystallization process in perovskite films even at room temperature. Perovskite films keptmore » for 5 hours in ambient air showed nanorod-like morphology having high crystallinity, with devices exhibiting the highest PCE of 16.83%, which is much higher than the PCE of 11.94% for traditional thermally annealed perovskite film based devices. Finally, it was concluded that moisture plays an important role in room temperature crystallization of pure perovskite nanorods, showing improved optical and charge transport properties, which resulted in high performance solar cells.« less

Design and performance of an ultra-high vacuum scanning tunneling microscope operating at dilution refrigerator temperatures and high magnetic fields.

PubMed

Misra, S; Zhou, B B; Drozdov, I K; Seo, J; Urban, L; Gyenis, A; Kingsley, S C J; Jones, H; Yazdani, A

2013-10-01

We describe the construction and performance of a scanning tunneling microscope capable of taking maps of the tunneling density of states with sub-atomic spatial resolution at dilution refrigerator temperatures and high (14 T) magnetic fields. The fully ultra-high vacuum system features visual access to a two-sample microscope stage at the end of a bottom-loading dilution refrigerator, which facilitates the transfer of in situ prepared tips and samples. The two-sample stage enables location of the best area of the sample under study and extends the experiment lifetime. The successful thermal anchoring of the microscope, described in detail, is confirmed through a base temperature reading of 20 mK, along with a measured electron temperature of 250 mK. Atomically resolved images, along with complementary vibration measurements, are presented to confirm the effectiveness of the vibration isolation scheme in this instrument. Finally, we demonstrate that the microscope is capable of the same level of performance as typical machines with more modest refrigeration by measuring spectroscopic maps at base temperature both at zero field and in an applied magnetic field.

Analysis on the impact of FBG reflectance spectrum with different optical fiber connection in vacuum thermal environment

NASA Astrophysics Data System (ADS)

Zhang, Jingchuan; Zhang, Wen; Lv, Jianfeng; Liang, Shuo; Wang, Lei; Li, Xiyuan

2018-01-01

To satisfy the application of fiber grating sensor technology in high vacuum thermal environment, FBG on sleeve compactly single model fiber with two typical different kind of connection such as fiber splicing and optical fiber connector are researched. Influence of the different connection to the characteristic of FBG reflectance spectrum in high vacuum thermal environment is analyzed and verified. First, experimental program of influence on FBG reflection spectrum characteristics is designed. Then, a hardware-in-the-loop detection platform is set up. Finally, the influence of temperature and vacuum on the reflection peak power of FBG with two typical different connections under high vacuum thermal environment is studied and verified. Experimental results indicate that: when vacuum varied from normal pressure to 10-4Pa level and then return to normal pressure, temperature of two different single-mode optical fiber connection dropped to -196 °C from room temperature and then returned to room temperature, after 224 hours, the peak power of the FBG reflectance spectrum did not change. It provided the experimental basis for the application of optical fiber sensing technology in high vacuum (pressure about 10-4Pa level) and thermal environment (-196 °C temperature cycle).

Cryogenic Temperature-Dependent Refractive Index Measurements of CaF2 and Infrasil 301

NASA Technical Reports Server (NTRS)

Frey, Bradley J.; Leviton, Douglas B.; Madison, TImothy J.

2007-01-01

In order to enable high quality lens design using calcium fluoride (CaF2) and Heraeus Infrasil 30 (Infrasil) at cryogenic temperatures, we have measured the absolute refractive index of prisms of these two materials using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, as a function of both wavelength and temperature. For CaF2, we report absolute refractive index and thermo-optic coefficient (dn/dT) at temperatures ranging from 25 to 300 K at wavelengths from 0.4 to 5.6 micrometers; for Infrasil we cover temperatures ranging from 35 to 300K and wavelengths from 0.4 to 3.6 micrometers. We investigate the interspecimen variability between measurements of two unrelated samples of CaF2, and we also compare our results for Infrasil to previous measurements fo Corning 7980 fused silica. Finally, we provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures and compare those results to other data found in the literature.

Investigation of phase transitions in LiK 1- x(NH 4) xSO 4 mixed crystal

NASA Astrophysics Data System (ADS)

Freire, P. T. C.; Paraguassu, W.; Silva, A. P.; Pilla, O.; Teixeira, A. M. R.; Sasaki, J. M.; Mendes Filho, J.; Guedes, I.; Melo, F. E. A.

1999-02-01

We present Raman scattering results on LiK 1- x(NH 4) xSO 4 mixed crystal for temperatures between 100 and 300 K. We observed that in this temperature range the crystal undergoes two different phase transitions, which we call Bansal and Tomaszewski phase transitions. The introduction of ammonium ions in the potassium sites increases the C 66→C 3v4 (Bansal) phase transition temperature and decreases the Tomaszewski phase transition temperature. Finally, the most impressive effect of the presence of ammonium impurity in the LiKSO 4 structure is the decrease in the temperature hysteresis of Bansal phase transition and the almost complete destruction of hysteresis in the Tomaszewski phase transition, leading to a high temperature range of stability of the trigonal phase.

Fabrication of high aspect ratio nanopillars and micro/nano combined structures with hydrophobic surface characteristics by injection molding

NASA Astrophysics Data System (ADS)

Zhou, Mingyong; Xiong, Xiang; Jiang, Bingyan; Weng, Can

2018-01-01

Polymer products with micro/nano-structures have excellent mechanical and optical properties, chemical resistance, and other advantages. Injection molding is one of the most potential techniques to fabricate polymer products with micro/nano-structures artificially in large numbers. In this study, a surface approach to fabricate high aspect ratio nanopillars and micro/nano combined structures was presented. Mold insert with micropillar arrays and nanopillars on its surface was prepared by combing anodic aluminum oxide (AAO) template and etched plate. Anti-sticking modification was done on the template to realize a better demolding quality. The influences of mold temperature and polymer material on the final replication quality were investigated. The results showed that the final replication quality of high aspect ratio nanopillars was greatly improved as compared with the unprocessed template. Polymer with low elongation at break was not suitable to fabricate structures with high aspect ratio via injection molding. For polypropylene surface, the experimental results of static contact angles were almost consistent with Cassie-Baxter equation. When the mold temperature reached 178 °C, hair-like polycarbonate nanopillars were observed, resulting in an excellent hydrophobic characteristic.

Performance and Environmental Test Results of the High Voltage Hall Accelerator Engineering Development Unit

NASA Technical Reports Server (NTRS)

Kamhawi, Hani; Haag, Thomas; Huang, Wensheng; Shastry, Rohit; Pinero, Luis; Peterson, Todd; Mathers, Alex

2012-01-01

NASA Science Mission Directorate's In-Space Propulsion Technology Program is sponsoring the development of a 3.5 kW-class engineering development unit Hall thruster for implementation in NASA science and exploration missions. NASA Glenn and Aerojet are developing a high fidelity high voltage Hall accelerator that can achieve specific impulse magnitudes greater than 2,700 seconds and xenon throughput capability in excess of 300 kilograms. Performance, plume mappings, thermal characterization, and vibration tests of the high voltage Hall accelerator engineering development unit have been performed. Performance test results indicated that at 3.9 kW the thruster achieved a total thrust efficiency and specific impulse of 58%, and 2,700 sec, respectively. Thermal characterization tests indicated that the thruster component temperatures were within the prescribed material maximum operating temperature limits during full power thruster operation. Finally, thruster vibration tests indicated that the thruster survived the 3-axes qualification full-level random vibration test series. Pre and post-vibration test performance mappings indicated almost identical thruster performance. Finally, an update on the development progress of a power processing unit and a xenon feed system is provided.

Resonant Ultrasound Spectroscopy studies of Berea sandstone at high temperature

DOE PAGES

Davis, Eric S.; Sturtevant, Blake T.; Sinha, Dipen N.; ...

2016-09-04

Resonant Ultrasound Spectroscopy was used in this paper to determine the elastic moduli of Berea sandstone from room temperature to 478 K. Sandstone is a common component of oil reservoirs, and the temperature range was chosen to be representative of typical downhole conditions, down to about 8 km. In agreement with previous works, Berea sandstone was found to be relatively soft with a bulk modulus of approximately 6 GPa as compared to 37.5 GPa for α-quartz at room temperature and pressure. Finally, it was found that Berea sandstone undergoes a ~17% softening in bulk modulus between room temperature and 385more » K, followed by an abnormal behavior of similar stiffening between 385 K and 478 K.« less

Resonant Ultrasound Spectroscopy studies of Berea sandstone at high temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Eric S.; Sturtevant, Blake T.; Sinha, Dipen N.

Resonant Ultrasound Spectroscopy was used in this paper to determine the elastic moduli of Berea sandstone from room temperature to 478 K. Sandstone is a common component of oil reservoirs, and the temperature range was chosen to be representative of typical downhole conditions, down to about 8 km. In agreement with previous works, Berea sandstone was found to be relatively soft with a bulk modulus of approximately 6 GPa as compared to 37.5 GPa for α-quartz at room temperature and pressure. Finally, it was found that Berea sandstone undergoes a ~17% softening in bulk modulus between room temperature and 385more » K, followed by an abnormal behavior of similar stiffening between 385 K and 478 K.« less

Parsing multiple processes of high temperature impacts on corn/soybean yield using a newly developed CLM-APSIM modeling framework

NASA Astrophysics Data System (ADS)

Peng, B.; Guan, K.; Chen, M.

2016-12-01

Future agricultural production faces a grand challenge of higher temperature under climate change. There are multiple physiological or metabolic processes of how high temperature affects crop yield. Specifically, we consider the following major processes: (1) direct temperature effects on photosynthesis and respiration; (2) speed-up growth rate and the shortening of growing season; (3) heat stress during reproductive stage (flowering and grain-filling); (4) high-temperature induced increase of atmospheric water demands. In this work, we use a newly developed modeling framework (CLM-APSIM) to simulate the corn and soybean growth and explicitly parse the above four processes. By combining the strength of CLM in modeling surface biophysical (e.g., hydrology and energy balance) and biogeochemical (e.g., photosynthesis and carbon-nitrogen interactions), as well as that of APSIM in modeling crop phenology and reproductive stress, the newly developed CLM-APSIM modeling framework enables us to diagnose the impacts of high temperature stress through different processes at various crop phenology stages. Ground measurements from the advanced SoyFACE facility at University of Illinois is used here to calibrate, validate, and improve the CLM-APSIM modeling framework at the site level. We finally use the CLM-APSIM modeling framework to project crop yield for the whole US Corn Belt under different climate scenarios.

Simulative Global Warming Negatively Affects Cotton Fiber Length through Shortening Fiber Rapid Elongation Duration.

PubMed

Dai, Yanjiao; Yang, Jiashuo; Hu, Wei; Zahoor, Rizwan; Chen, Binglin; Zhao, Wenqing; Meng, Yali; Zhou, Zhiguo

2017-08-23

Global warming could possibly increase the air temperature by 1.8-4.0 °C in the coming decade. Cotton fiber is an essential raw material for the textile industry. Fiber length, which was found negatively related to the excessively high temperature, determines yarn quality to a great extent. To investigate the effects of global warming on cotton fiber length and its mechaism, cottons grown in artificially elevated temperature (34.6/30.5 °C, T day /T night ) and ambient temperature (31.6/27.3 °C) regions have been investigated. Becaused of the high sensitivities of enzymes V-ATPase, PEPC, and genes GhXTH1 and GhXTH2 during fiber elongation when responding to high temperature stress, the fiber rapid elongation duration (FRED) has been shortened, which led to a significant suppression on final fiber length. Through comprehensive analysis, T night had a great influence on fiber elongation, which means T n could be deemed as an ideal index for forecasting the degree of high temperature stress would happen to cotton fiber property in future. Therefore, we speculate the global warming would bring unfavorable effects on cotton fiber length, which needs to take actions in advance for minimizing the loss in cotton production.

Study on photoelectric parameter measurement method of high capacitance solar cell

NASA Astrophysics Data System (ADS)

Zhang, Junchao; Xiong, Limin; Meng, Haifeng; He, Yingwei; Cai, Chuan; Zhang, Bifeng; Li, Xiaohui; Wang, Changshi

2018-01-01

The high efficiency solar cells usually have high capacitance characteristic, so the measurement of their photoelectric performance usually requires long pulse width and long sweep time. The effects of irradiance non-uniformity, probe shielding and spectral mismatch on the IV curve measurement are analyzed experimentally. A compensation method for irradiance loss caused by probe shielding is proposed, and the accurate measurement of the irradiance intensity in the IV curve measurement process of solar cell is realized. Based on the characteristics that the open circuit voltage of solar cell is sensitive to the junction temperature, an accurate measurement method of the temperature of solar cell under continuous irradiation condition is proposed. Finally, a measurement method with the characteristic of high accuracy and wide application range for high capacitance solar cell is presented.

SPECTROSCOPIC EVIDENCE FOR A TEMPERATURE INVERSION IN THE DAYSIDE ATMOSPHERE OF HOT JUPITER WASP-33b

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haynes, Korey; Mandell, Avi M.; Madhusudhan, Nikku

We present observations of two occultations of the extrasolar planet WASP-33b using the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope, which allow us to constrain the temperature structure and composition of its dayside atmosphere. WASP-33b is the most highly irradiated hot Jupiter discovered to date, and the only exoplanet known to orbit a δ-Scuti star. We observed in spatial scan mode to decrease instrument systematic effects in the data, and removed fluctuations in the data due to stellar pulsations. The rms for our final, binned spectrum is 1.05 times the photon noise. We compare our final spectrum,more » along with previously published photometric data, to atmospheric models of WASP-33b spanning a wide range in temperature profiles and chemical compositions. We find that the data require models with an oxygen-rich chemical composition and a temperature profile that increases at high altitude. We find that our measured spectrum displays an excess in the measured flux toward short wavelengths that is best explained as emission from TiO. If confirmed by additional measurements at shorter wavelengths, this planet would become the first hot Jupiter with a thermal inversion that can be definitively attributed to the presence of TiO in its dayside atmosphere.« less

Selenium emission control at high temperatures with mineral sorbents. Final report, September 1, 1994--February 29, 1996

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh-Dastidar, A.; Mahuli, S.; Agnihotri, R.

1996-03-01

The focus of this project is on toxic metal removal by sorbent injection in the upper furnace and economizer sections of a coal- fired boiler. Selenium was chosen as the candidate heavy metal to be studied because of its high volatility and associated difficulties in removal. A thorough mechanistic investigation of the SeO{sub 2}-Ca(OH){sub 2} interaction at both medium and high temperatures has been conducted in this project. Experiments were performed in the two temperature ranges in the presence and absence of O{sub 2}; desorption studies were conducted to characterize the nature of interaction; and XRD/XPS and Ion Chromatography studiesmore » were performed for species identification. It was inferred from these findings that the selenium capture was significantly more in the medium temperature range (450-650{degrees}C) than in high temperature range (800-1000{degrees}C) and the captured selenium species in the medium temperature range is in the form of calcium selenite (CaSeO{sub 3}) and a reaction scheme was proposed for the CaO/SeO{sub 2} interaction: CaO (s) + SeO{sub 2} (g) = CaSeO{sub 3} (s). This reaction process does not require the participation of oxygen, as was confirmed by various analytical techniques and supported by the experimental evidence. Results of the high-temperature studies indicate much reduced capture at these temperatures with negligible selenium sorption above 900{degrees}C. This behavior was attributed to the decomposition of calcium selenite at higher temperatures.« less

Microstructure Evolution and Mechanical Response of Nanolaminate Composites Irradiated with Helium at Elevated Temperatures

DOE PAGES

Li, Nan; Demkowicz, Michael J.; Mara, Nathan A.

2017-09-12

In this paper, we summarize recent work on helium (He) interaction with various heterophase boundaries under high temperature irradiation. We categorize the ion-affected material beneath the He-implanted surface into three regions of depth, based on the He/vacancy ratio. The differing defect structures in these three regions lead to the distinct temperature sensitivity of He-induced microstructure evolution. The effect of He bubbles or voids on material mechanical performance is explored. Finally, overall design guidelines for developing materials where He-induced damage can be mitigated in materials are discussed.

Atomizing-gas temperature effect on cryogenic spray dropsize

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1993-01-01

Correlating expressions for two-phase flow breakup of liquid nitrogen, LN2, jets in sonic velocity nitrogen gasflows were obtained for an atomizing-gas temperature range of 111 to 442 K. The correlations were based on characteristic dropsize measurements obtained with a scattered-light scanner. The effect of droplet vaporization on the measurements of the volume-median dropsize was calculated by using previously determined heat and momentum transfer expressions for droplets evaporating in high-velocity gasflow. Finally, the dropsize of the originally unvaporized spray was calculated, normalized with respect to jet diameter and correlated with atomizing-gas flowrate and temperature.

Solar Arrays for Low-Irradiance Low-Temperature and High-Radiation Environments

NASA Technical Reports Server (NTRS)

Boca, Andreea (Principal Investigator); Stella, Paul; Kerestes, Christopher; Sharps, Paul

2017-01-01

This is the Base Period final report DRAFT for the JPL task 'Solar Arrays for Low-Irradiance Low-Temperature and High-Radiation Environments', under Task Plan 77-16518 TA # 21, for NASA's Extreme Environments Solar Power (EESP) project. This report covers the Base period of performance, 7/18/2016 through 5/2/2017.The goal of this project is to develop an ultra-high efficiency lightweight scalable solar array technology for low irradiance, low temperature and high-radiation (LILT/Rad) environments. The benefit this technology will bring to flight systems is a greater than 20 reduction in solar array surface area, and a six-fold reduction in solar array mass and volume. The EESP project objectives are summarized in the 'NRA Goal' column of Table 1. Throughout this report, low irradiance low temperature (LILT) refers to 5AU -125 C test conditions; beginning of life (BOL) refers to the cell state prior to radiation exposure; and end of life (EOL) refers to the test article condition after exposure to a radiation dose of 4e15 1MeV e(-)/cm(exp 2).

Process development of two high strength tantalum base alloys (ASTAR-1211C and ASTAR-1511C)

NASA Technical Reports Server (NTRS)

Ammon, R. L.

1974-01-01

Two tantalum base alloys, Ta-12W-1.0Re-0.7Hf-0.025C(ASTAR-1211C) and Ta-15W-1.0Re-0.7Hf-0.025C(ASTAR-1511C), were cast as 12.5 cm (5 inch) diameter ingots and processed to swaged rod, sheet, forged plate, and tubing. Swaged rod was evaluated with respect to low temperature ductility, elevated temperature tensile properties, and elevated temperature creep behavior. A standard swaging process and final annealing schedule were determined. Elevated temperature tensile properties, low temperature impact properties, low temperature DBTT behavior, and extended elevated temperature creep properties were determined. A process for producing ASTAR-1211C and ASTAR-1511C sheet were developed. The DBTT properties of GTA and EB weld sheet given post-weld anneal and thermal aging treatments were determined using bend and tensile specimens. High and low temperature mechanical properties of forging ASTAR-1211C and ASTAR-1511C plate were determined as well as elevated temperature creep properties. Attempts to produce ASTAR-1211C tubing were partially successful while attempts to make ASTAR-1511C tubing were completely unsuccessful.

Seawater-temperature and UV-radiation interaction modifies oxygen consumption, digestive process and growth of an intertidal fish.

PubMed

García-Huidobro, M Roberto; Aldana, Marcela; Duarte, Cristian; Galbán-Malagón, Cristóbal; Pulgar, José

2017-08-01

UV-radiation (UVR) and temperatures have increased substantially over recent decades in many regions of the world. Both stressors independently have shown to affect the metabolism and growth in fish. However, because increase of both stressors are occurring concomitantly, to better understand their influences on marine species, their combined effects were evaluated. We test the hypothesis that UVR and temperature act synergistically affecting the metabolism, digestive process and growth of an intertidal fish. Two UVR conditions (with and without UVR) and two temperature levels (20° C and 25° C) were used. UVR increase the oxygen consumption and this was associated to opaque feces production. The absorption efficiency was higher without UVR at high temperatures (25 °C) and with UVR at low temperatures (20 °C). Finally, independent of UVR treatment, fish subjected to low temperature have higher biomass than those of high temperature. The interaction between UVR and temperature may influence on the physiology and growth of animals that inhabit in extreme habitats as upper intertidal, it could pose significant functional for aquatic animal survivorship. Copyright © 2017 Elsevier Ltd. All rights reserved.

Microstructural evolution and mechanical properties of a low alloy high strength Ni-Cr-Mo-V steel during heat treatment process

NASA Astrophysics Data System (ADS)

Wu, C.; Han, S.

2018-05-01

In order to obtain an optimal heat treatment for a low alloy high strength Ni-Cr-Mo-V steel, the microstructural evolution and mechanical properties of the material were studied. For this purpose, a series of quenching and temper experiments were carried out. The results showed that the effects of tempering temperature, time, original microstructure on the microstructural evolution and final properties were significant. The martensite can be completely transformed into the tempered lath structure. The width and length of the lath became wider and shorter, respectively with increasing temperature and time. The amount and size of the precipitates increased with temperature and time. The yield strength (YS), ultimate tensile strength (UTS) and hardness decreased with temperature and time, but the reduction in area (Z), elongation (E) and impact toughness displayed an opposite trend, which was related to the morphological evolution of the lath tempered structure.

Argon–germane in situ plasma clean for reduced temperature Ge on Si epitaxy by high density plasma chemical vapor deposition

DOE PAGES

Douglas, Erica A.; Sheng, Josephine J.; Verley, Jason C.; ...

2015-06-04

We found that the demand for integration of near infrared optoelectronic functionality with silicon complementary metal oxide semiconductor (CMOS) technology has for many years motivated the investigation of low temperature germanium on silicon deposition processes. Our work describes the development of a high density plasma chemical vapor deposition process that uses a low temperature (<460 °C) in situ germane/argon plasma surface preparation step for epitaxial growth of germanium on silicon. It is shown that the germane/argon plasma treatment sufficiently removes SiO x and carbon at the surface to enable germanium epitaxy. Finally, the use of this surface preparation step demonstratesmore » an alternative way to produce germanium epitaxy at reduced temperatures, a key enabler for increased flexibility of integration with CMOS back-end-of-line fabrication.« less

Development of strain gages for use to 1311 K (1900 F)

NASA Technical Reports Server (NTRS)

Lemcoe, M. M.

1974-01-01

A high temperature electric resistance strain gage system was developed and evaluated to 1366 K (2000 F) for periods of at least one hour. Wire fabricated from a special high temperature strain gage alloy (BCL-3), was used to fabricate the gages. Various joining techniques (NASA butt welding, pulse arc, plasma needle arc, and dc parallel gap welding) were investigated for joining gage filaments to each other, gage filaments to lead-tab ribbons, and lead-tab ribbons to lead wires. The effectiveness of a clad-wire concept as a means of minimizing apparent strain of BCL-3 strain gages was investigated by sputtering platinum coatings of varying thicknesses on wire samples and establishing the optimum coating thickness--in terms of minimum resistivity changes with temperature. Finally, the moisture-proofing effectiveness of barrier coatings subjected to elevated temperatures was studied, and one commercial barrier coating (BLH Barrier H Waterproofing) was evaluated.

High temperature electrical energy storage: advances, challenges, and frontiers.

PubMed

Lin, Xinrong; Salari, Maryam; Arava, Leela Mohana Reddy; Ajayan, Pulickel M; Grinstaff, Mark W

2016-10-24

With the ongoing global effort to reduce greenhouse gas emission and dependence on oil, electrical energy storage (EES) devices such as Li-ion batteries and supercapacitors have become ubiquitous. Today, EES devices are entering the broader energy use arena and playing key roles in energy storage, transfer, and delivery within, for example, electric vehicles, large-scale grid storage, and sensors located in harsh environmental conditions, where performance at temperatures greater than 25 °C are required. The safety and high temperature durability are as critical or more so than other essential characteristics (e.g., capacity, energy and power density) for safe power output and long lifespan. Consequently, significant efforts are underway to design, fabricate, and evaluate EES devices along with characterization of device performance limitations such as thermal runaway and aging. Energy storage under extreme conditions is limited by the material properties of electrolytes, electrodes, and their synergetic interactions, and thus significant opportunities exist for chemical advancements and technological improvements. In this review, we present a comprehensive analysis of different applications associated with high temperature use (40-200 °C), recent advances in the development of reformulated or novel materials (including ionic liquids, solid polymer electrolytes, ceramics, and Si, LiFePO 4 , and LiMn 2 O 4 electrodes) with high thermal stability, and their demonstrative use in EES devices. Finally, we present a critical overview of the limitations of current high temperature systems and evaluate the future outlook of high temperature batteries with well-controlled safety, high energy/power density, and operation over a wide temperature range.

A Novel Technique for Sterilization Using a Power Self-Regulated Single-Mode Microwave Cavity.

PubMed

Reverte-Ors, Juan D; Pedreño-Molina, Juan L; Fernández, Pablo S; Lozano-Guerrero, Antonio J; Periago, Paula M; Díaz-Morcillo, Alejandro

2017-06-07

In this paper, a novel technique to achieve precise temperatures in food sterilization has been proposed. An accurate temperature profile is needed in order to reach a commitment between the total removal of pathogens inside the product and the preservation of nutritional and organoleptic characteristics. The minimal variation of the target temperature in the sample by means of a monitoring and control software platform, allowing temperature stabilization over 100 °C, is the main goal of this work. A cylindrical microwave oven, under pressure conditions and continuous control of the microwave supply power as function of the final temperature inside the sample, has been designed and developed with conditions of single-mode resonance. The uniform heating in the product is achieved by means of sample movement and the self-regulated power control using the measured temperature. Finally, for testing the sterilization of food with this technology, specific biological validation based on Bacillus cereus as a biosensor of heat inactivation has been incorporated as a distribution along the sample in the experimental process to measure the colony-forming units (CFUs) for different food samples (laboratory medium, soup, or fish-based animal by-products). The obtained results allow the validation of this new technology for food sterilization with precise control of the microwave system to ensure the uniform elimination of pathogens using high temperatures.

A Novel Technique for Sterilization Using a Power Self-Regulated Single-Mode Microwave Cavity

PubMed Central

Reverte-Ors, Juan D.; Pedreño-Molina, Juan L.; Fernández, Pablo S.; Lozano-Guerrero, Antonio J.; Periago, Paula M.; Díaz-Morcillo, Alejandro

2017-01-01

In this paper, a novel technique to achieve precise temperatures in food sterilization has been proposed. An accurate temperature profile is needed in order to reach a commitment between the total removal of pathogens inside the product and the preservation of nutritional and organoleptic characteristics. The minimal variation of the target temperature in the sample by means of a monitoring and control software platform, allowing temperature stabilization over 100 °C, is the main goal of this work. A cylindrical microwave oven, under pressure conditions and continuous control of the microwave supply power as function of the final temperature inside the sample, has been designed and developed with conditions of single-mode resonance. The uniform heating in the product is achieved by means of sample movement and the self-regulated power control using the measured temperature. Finally, for testing the sterilization of food with this technology, specific biological validation based on Bacillus cereus as a biosensor of heat inactivation has been incorporated as a distribution along the sample in the experimental process to measure the colony-forming units (CFUs) for different food samples (laboratory medium, soup, or fish-based animal by-products). The obtained results allow the validation of this new technology for food sterilization with precise control of the microwave system to ensure the uniform elimination of pathogens using high temperatures. PMID:28590423

Research on influence of different cover to the characteristic of FBG reflectance spectrum in vacuum thermal environment

NASA Astrophysics Data System (ADS)

Pei, Yifei; Zhang, Jingchuan; Zhang, Luosha; Liu, Yang; Zhang, Lina; Chen, Shiyu

2018-01-01

To satisfy the application of fiber grating sensor technology in high vacuum thermal environment, two different kinds of sleeve compactly single model fiber covered by acrylate and polyimide are researched. Influence of the cover to the characteristic of FBG reflectance spectrum in high vacuum thermal environment is analyzed and verified. First, transmission characteristic of single model fiber in high vacuum thermal environment is analyzed by solve the equation of heat conduction. Then, experimental program of influence on FBG reflection spectrum characteristics is designed and a hardware-in-the-loop detection platform is set up. Finally, the influence of temperature and vacuum on the reflection peak power of FBG in different coating single-mode transmission fiber under high vacuum thermal environment is studied and verified. Experimental results indicate that: when vacuum varied from normal pressure to 10-4Pa level and then return to normal pressure, temperature of two different coating single-mode transmission fiber dropped to -196 ° from room temperature and then returned to room temperature, after 224 hours, the peak power of the FBG reflectance spectrum did not change. It provided the theoretical and experimental basis for the application of optical fiber sensing technology in high vacuum (pressure about 10-4Pa level) and thermal environment (-196 ° 25 ° temperature cycle) .

Corrosion behavior in high-temperature pressurized water of Zircaloy-4 joints brazed with Zr-Cu-based amorphous filler alloys

NASA Astrophysics Data System (ADS)

Lee, Jung Gu; Lee, Gyoung-Ja; Park, Jin-Ju; Lee, Min-Ku

2017-05-01

The compositional effects of ternary Zr-Cu-X (X: Al, Fe) amorphous filler alloys on galvanic corrosion susceptibility in high-temperature pressurized water were investigated for Zircaloy-4 brazed joints. Through an Al-induced microgalvanic reaction that deteriorated the overall nobility of the joint, application of the Zr-Cu-Al filler alloy caused galvanic coupling to develop readily between the Al-bearing joint and the Al-free base metal, finally leading to massive localized corrosion of the joint. Contrastingly, joints prepared with a Zr-Cu-Fe filler alloy showed excellent corrosion resistance comparable to that of the Zircaloy-4 base metal, since the Cu and Fe elements forming fine intermetallic particles with Zr did not influence the electrochemical stability of the resultant joints. The present results demonstrate that Fe is a more suitable alloying element than Al for brazing filler alloys subjected to high-temperature corrosive environments.

Spontaneous emission of semiconductor quantum dots in inverse opal SiO2 photonic crystals at different temperatures.

PubMed

Yang, Peng; Yang, Yingshu; Wang, Yinghui; Gao, Jiechao; Sui, Ning; Chi, Xiaochun; Zou, Lu; Zhang, Han-Zhuang

2016-02-01

The photoluminescence (PL) characteristics of CdSe quantum dots (QDs) infiltrated into inverse opal SiO2 photonic crystals (PCs) are systemically studied. The special porous structure of inverse opal PCs enhanced the thermal exchange rate between the CdSe QDs and their surrounding environment. Finally, inverse opal SiO2 PCs suppressed the nonlinear PL enhancement of CdSe QDs in PCs excited by a continuum laser and effectively modulated the PL characteristics of CdSe QDs in PCs at high temperatures in comparison with that of CdSe QDs out of PCs. The final results are of benefit in further understanding the role of inverse opal PCs on the PL characteristics of QDs. Copyright © 2015 John Wiley & Sons, Ltd.

Current and efficiency optimization under oscillating forces in entropic barriers

NASA Astrophysics Data System (ADS)

Nutku, Ferhat; Aydıner, Ekrem

2016-09-01

The transport of externally overdriven particles confined in entropic barriers is investigated under various types of oscillating and temporal forces. Temperature, load, and amplitude dependence of the particle current and energy conversion efficiency are investigated in three dimensions. For oscillating forces, the optimized temperature-load, amplitude-temperature, and amplitude-load intervals are determined when fixing the amplitude, load, and temperature, respectively. By using three-dimensional plots rather than two-dimensional ones, it is clearly shown that oscillating forces provide more efficiency compared with a temporal one in specified optimized parameter regions. Furthermore, the dependency of efficiency to the angle between the unbiased driving force and a constant force is investigated and an asymmetric angular dependence is found for all types of forces. Finally, it is shown that oscillating forces with a high amplitude and under a moderate load lead to higher efficiencies than a temporal force at both low and high temperatures for the entire range of contact angle. Project supported by the Istanbul University, Turkey (Grant No. 55383).

Strength and deformation behaviors of veined marble specimens after vacuum heat treatment under conventional triaxial compression

NASA Astrophysics Data System (ADS)

Su, Haijian; Jing, Hongwen; Yin, Qian; Yu, Liyuan; Wang, Yingchao; Wu, Xingjie

2017-10-01

The mechanical behaviors of rocks affected by high temperature and stress are generally believed to be significant for the stability of certain projects involving rocks, such as nuclear waste storage and geothermal resource exploitation. In this paper, veined marble specimens were treated to high temperature treatment and then used in conventional triaxial compression tests to investigate the effect of temperature, confining pressure, and vein angle on strength and deformation behaviors. The results show that the strength and deformation parameters of the veined marble specimens changed with the temperature, presenting a critical temperature of 600 °C. The triaxial compression strength of a horizontal vein (β = 90°) is obviously larger than that of a vertical vein (β = 0°). The triaxial compression strength, elasticity modulus, and secant modulus have an approximately linear relation to the confining pressure. Finally, Mohr-Coulomb and Hoek-Brown criteria were respectively used to analyze the effect of confining pressure on triaxial compression strength.

High temperature in-situ observations of multi-segmented metal nanowires encapsulated within carbon nanotubes by in-situ filling technique.

PubMed

Hayashi, Yasuhiko; Tokunaga, Tomoharu; Iijima, Toru; Iwata, Takuya; Kalita, Golap; Tanemura, Masaki; Sasaki, Katsuhiro; Kuroda, Kotaro

2012-08-08

Multi-segmented one-dimensional metal nanowires were encapsulated within carbon nanotubes (CNTs) through in-situ filling technique during plasma-enhanced chemical vapor deposition process. Transmission electron microscopy (TEM) and environmental TEM were employed to characterize the as-prepared sample at room temperature and high temperature. The selected area electron diffractions revealed that the Pd4Si nanowire and face-centered-cubic Co nanowire on top of the Pd nanowire were encapsulated within the bottom and tip parts of the multiwall CNT, respectively. Although the strain-induced deformation of graphite walls was observed, the solid-state phases of Pd4Si and Co-Pd remain even at above their expected melting temperatures and up to 1,550 ± 50°C. Finally, the encapsulated metals were melted and flowed out from the tip of the CNT after 2 h at the same temperature due to the increase of internal pressure of the CNT.

MetroFission: New high-temperature references and sensors for the nuclear industry

NASA Astrophysics Data System (ADS)

Sadli, M.; del Campo, D.; de Podesta, M.; Deuzé, T.; Failleau, G.; Elliott, C. J.; Fourrez, S.; García, C.; Pearce, J. V.

2013-09-01

The European metrology research programme (EMRP) allows funding for metrology-oriented projects in the frame of targeted calls aimed at improving metrology for important contemporary and future needs in different fields such as energy, environment and industry. A joint research project (JRP), called "MetroFission", was selected for funding in the "Energy" call of 2010. This JRP, led by NPL (UK), aims to anticipate and to start addressing the metrological needs of the next generation of nuclear power plants. The need for improving the accuracy and reliability of temperature measurements at temperatures higher than those currently measured in nuclear power plants is dealt with in the first workpackage of the project. This project started in September 2010 and will last for three years. This paper summarizes the activities of the first half of the project and the expected final achievements, which will be essentially oriented towards new temperature references and new devices, adapted to the high temperature range as well as the particularly harsh working conditions.

Development of Metal Oxide Nanostructure-based Optical Sensors for Fossil Fuel Derived Gases Measurement at High Temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Kevin P.

2015-02-13

This final technical report details research works performed supported by a Department of Energy grant (DE-FE0003859), which was awarded under the University Coal Research Program administrated by National Energy Technology Laboratory. This research program studied high temperature fiber sensor for harsh environment applications. It developed two fiber optical sensor platform technology including regenerative fiber Bragg grating sensors and distributed fiber optical sensing based on Rayleigh backscattering optical frequency domain reflectometry. Through the studies of chemical and thermal regenerative techniques for fiber Bragg grating (FBG) fabrication, high-temperature stable FBG sensors were successfully developed and fabricated in air-hole microstructured fibers, high-attenuation fibers,more » rare-earth doped fibers, and standard telecommunication fibers. By optimizing the laser processing and thermal annealing procedures, fiber grating sensors with stable performance up to 1100°C have been developed. Using these temperature-stable FBG gratings as sensor platform, fiber optical flow, temperature, pressure, and chemical sensors have been developed to operate at high temperatures up to 800°C. Through the integration of on-fiber functional coating, the use of application-specific air-hole microstructural fiber, and application of active fiber sensing scheme, distributed fiber sensor for temperature, pressure, flow, liquid level, and chemical sensing have been demonstrated with high spatial resolution (1-cm or better) with wide temperature ranges. These include the demonstration of 1) liquid level sensing from 77K to the room temperature, pressure/temperature sensing from the room temperature to 800C and from the 15psi to 2000 psi, and hydrogen concentration measurement from 0.2% to 10% with temperature ranges from the room temperature to 700°C. Optical sensors developed by this program has broken several technical records including flow sensors with the highest operation temperature up to 750°C, first distributed chemical measurements at the record high temperature up to 700°C, first distributed pressure measurement at the record high temperature up to 800°C, and the fiber laser sensors with the record high operation temperature up to 700°C. The research performed by this program dramatically expand the functionality, adaptability, and applicability of distributed fiber optical sensors with potential applications in a number of high-temperature energy systems such as fossil-fuel power generation, high-temperature fuel cell applications, and potential for nuclear energy systems.« less

Kinetics of non-catalyzed hydrolysis of tannin in high temperature liquid water*

PubMed Central

Lu, Li-li; Lu, Xiu-yang; Ma, Nan

2008-01-01

High temperature liquid water (HTLW) has drawn increasing attention as an environmentally benign medium for organic chemical reactions, especially acid-/base-catalyzed reactions. Non-catalyzed hydrolyses of gallotannin and tara tannin in HTLW for the simultaneous preparation of gallic acid (GA) and pyrogallol (PY) are under investigation in our laboratory. In this study, the hydrolysis kinetics of gallotannin and tara tannin were determined. The reaction is indicated to be a typical consecutive first-order one in which GA has formed as a main intermediate and PY as the final product. Selective decomposition of tannin in HTLW was proved to be possible by adjusting reaction temperature and time. The present results provide an important basic data and reference for the green preparation of GA and PY. PMID:18500780

High time resolved electron temperature measurements by using the multi-pass Thomson scattering system in GAMMA 10/PDX.

PubMed

Yoshikawa, Masayuki; Yasuhara, Ryo; Ohta, Koichi; Chikatsu, Masayuki; Shima, Yoriko; Kohagura, Junko; Sakamoto, Mizuki; Nakashima, Yousuke; Imai, Tsuyoshi; Ichimura, Makoto; Yamada, Ichihiro; Funaba, Hisamichi; Minami, Takashi

2016-11-01

High time resolved electron temperature measurements are useful for fluctuation study. A multi-pass Thomson scattering (MPTS) system is proposed for the improvement of both increasing the TS signal intensity and time resolution. The MPTS system in GAMMA 10/PDX has been constructed for enhancing the Thomson scattered signals for the improvement of measurement accuracy. The MPTS system has a polarization-based configuration with an image relaying system. We optimized the image relaying optics for improving the multi-pass laser confinement and obtaining the stable MPTS signals over ten passing TS signals. The integrated MPTS signals increased about five times larger than that in the single pass system. Finally, time dependent electron temperatures were obtained in MHz sampling.

Final Technical Report - 300°C Capable Electronics Platform and Temperature Sensor System For Enhanced Geothermal Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Cheng-Po; Shaddock, David; Sandvik, Peter

2012-11-30

A silicon carbide (SiC) based electronic temperature sensor prototype has been demonstrated to operate at 300°C. We showed continuous operation of 1,000 hours with SiC operational amplifier and surface mounted discreet resistors and capacitors on a ceramic circuit board. This feasibility demonstration is a major milestone in the development of high temperature electronics in general and high temperature geothermal exploration and well management tools in particular. SiC technology offers technical advantages that are not found in competing technologies such as silicon-on-insulator (SOI) at high temperatures of 200°C to 300°C and beyond. The SiC integrated circuits and packaging methods can bemore » used in new product introduction by GE Oil and Gas for high temperature down-hole tools. The existing SiC fabrication facility at GE is sufficient to support the quantities currently demanded by the marketplace, and there are other entities in the United States and other countries capable of ramping up SiC technology manufacturing. The ceramic circuit boards are different from traditional organic-based electronics circuit boards, but the fabrication process is compatible with existing ceramic substrate manufacturing. This project has brought high temperature electronics forward, and brings us closer to commercializing tools that will enable and reduce the cost of enhanced geothermal technology to benefit the public in terms of providing clean renewable energy at lower costs.« less

Optical Fiber High Temperature Sensor Instrumentation for Energy Intensive Industries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cooper, Kristie L.; Wang, Anbo; Pickrell, Gary R.

2006-11-14

This report summarizes technical progress during the program “Optical Fiber High Temperature Sensor Instrumentation for Energy Intensive Industries”, performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. The objective of this program was to use technology recently invented at Virginia Tech to develop and demonstrate the application of self-calibrating optical fiber temperature and pressure sensors to several key energy-intensive industries where conventional, commercially available sensors exhibit greatly abbreviated lifetimes due primarily to environmental degradation. A number of significant technologies were developed under this program, including • a laser bonded silicamore » high temperature fiber sensor with a high temperature capability up to 700°C and a frequency response up to 150 kHz, • the world’s smallest fiber Fabry-Perot high temperature pressure sensor (125 x 20 μm) with 700°C capability, • UV-induced intrinsic Fabry-Perot interferometric sensors for distributed measurement, • a single crystal sapphire fiber-based sensor with a temperature capability up to 1600°C. These technologies have been well demonstrated and laboratory tested. Our work plan included conducting major field tests of these technologies at EPRI, Corning, Pratt & Whitney, and Global Energy; field validation of the technology is critical to ensuring its usefulness to U.S. industries. Unfortunately, due to budget cuts, DOE was unable to follow through with its funding commitment to support Energy Efficiency Science Initiative projects and this final phase was eliminated.« less

The effects of temperature on the stability of a neuronal oscillator.

PubMed

Rinberg, Anatoly; Taylor, Adam L; Marder, Eve

2013-01-01

The crab Cancer borealis undergoes large daily fluctuations in environmental temperature (8-24°C) and must maintain appropriate neural function in the face of this perturbation. In the pyloric circuit of the crab stomatogastric ganglion, we pharmacologically isolated the pacemaker kernel (the AB and PD neurons) and characterized its behavior in response to temperature ramps from 7°C to 31°C. For moderate temperatures, the pacemaker displayed a frequency-temperature curve statistically indistinguishable from that of the intact circuit, and like the intact circuit maintained a constant duty cycle. At high temperatures (above 23°C), a variety of different behaviors were seen: in some preparations the pacemaker increased in frequency, in some it slowed, and in many preparations the pacemaker stopped oscillating ("crashed"). Furthermore, these crashes seemed to fall into two qualitatively different classes. Additionally, the animal-to-animal variability in frequency increased at high temperatures. We used a series of Morris-Lecar mathematical models to gain insight into these phenomena. The biophysical components of the final model have temperature sensitivities similar to those found in nature, and can crash via two qualitatively different mechanisms that resemble those observed experimentally. The crash type is determined by the precise parameters of the model at the reference temperature, 11°C, which could explain why some preparations seem to crash in one way and some in another. Furthermore, even models with very similar behavior at the reference temperature diverge greatly at high temperatures, resembling the experimental observations.

Evaluation and ranking of candidate ceramic wafer engine seal materials

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.

1991-01-01

Modern engineered ceramics offer high temperature capabilities not found in even the best superalloy metals. The high temperature properties of several selected ceramics including aluminum oxide, silicon carbide, and silicon nitride are reviewed as they apply to hypersonic engine seal design. A ranking procedure is employed to objectively differentiate among four different monolithic ceramic materials considered, including: a cold-pressed and sintered aluminum oxide; a sintered alpha-phase silicon carbide; a hot-isostatically pressed silicon nitride; and a cold-pressed and sintered silicon nitride. This procedure is used to narrow the wide range of potential ceramics considered to an acceptable number for future detailed and costly analyses and tests. The materials are numerically scored according to their high temperature flexural strength; high temperature thermal conductivity; resistance to crack growth; resistance to high heating rates; fracture toughness; Weibull modulus; and finally according to their resistance to leakage flow, where materials having coefficients of thermal expansion closely matching the engine panel material resist leakage flow best. The cold-pressed and sintered material (Kyocera SN-251) ranked the highest in the overall ranking especially when implemented in engine panels made of low expansion rate materials being considered for the engine, including Incoloy and titanium alloys.

The NASA thermionic-conversion (TEC-ART) program

NASA Technical Reports Server (NTRS)

Morris, J. F.

1977-01-01

The current emphasis is on out-of-core thermionic conversion (TEC). The additional degrees of freedom offer new potentialities, but high-temperature material effects determine the level and lifetime of TEC performance: New electrodes not only raise power outputs but also maintain them regardless of emitter-vapor deposition on collectors. In addition, effective electrodes serve compatibly with hot-shell alloys. Space TEC withstands external and internal high-temperature vaporization problems, and terrestrial TEC tolerates hot corrosive atmospheres outside and near-vacuum inside. Finally, reduction of losses between converter electrodes is essential even though rather demanding geometries appear to be required for some modes of enhanced operation.

Fundamental studies of stress distributions and stress relaxation in oxide scales on high temperature alloys. [Final progress report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shores, D.A.; Stout, J.H.; Gerberich, W.W.

1993-06-01

This report summarizes a three-year study of stresses arising in the oxide scale and underlying metal during high temperature oxidation and of scale cracking. In-situ XRD was developed to measure strains during oxidation over 1000{degrees}C on pure metals. Acoustic emission was used to observe scale fracture during isothermal oxidation and cooling, and statistical analysis was used to infer mechanical aspects of cracking. A microscratch technique was used to measure the fracture toughness of scale/metal interface. A theoretical model was evaluated for the development and relaxation of stresses in scale and metal substrate during oxidation.

Method of making contamination-free ceramic bodies

NASA Technical Reports Server (NTRS)

Philipp, Warren H. (Inventor)

1991-01-01

Ceramic structures having high strength at temperatures above 1000 C after sintering are made by mixing ceramic powders with binder deflocculants such as guanidine salts of polymeric acids, guanidine salts of aliphatic organic carboxylic acids or guanidine alkylsulfates with the foregoing guanidine salts. The novelty of the invention appears to lie in the substitution of guanidine salts for the alkalai metal salt components or organic fatty acids of the prior art binder-deflocculant, ceramic processing aids whereby no undesirable metal contaminants are present in the final ceramic structure. Guanidine alkylsulfates also replace the Na or K alkylsulfates commonly used with binder-deflocculants in making high temperature ceramic structures.

Development of Nano-crystalline Doped-Ceramic Enabled Fiber Sensors for High Temperature In-Situ Monitoring of Fossil Fuel Gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Hai; Dong, Junhang; Lin, Jerry

2012-03-01

This is a final technical report for the first project year from July 1, 2005 to Jan 31, 2012 for DoE/NETL funded project DE-FC26-05NT42439: Development of Nanocrystalline Doped-Ceramic Enabled Fiber Sensors for High Temperature In-Situ Monitoring of Fossil Fuel Gases. This report summarizes the technical progresses and achievements towards the development of novel nanocrystalline doped ceramic material-enabled optical fiber sensors for in situ and real time monitoring the gas composition of flue or hot gas streams involved in fossil-fuel based power generation and hydrogen production.

Analysis of air temperature changes on blood pressure and heart rate and performance of undergraduate students.

PubMed

Siqueira, Joseana C F; da Silva, Luiz Bueno; Coutinho, Antônio S; Rodrigues, Rafaela M

2017-01-01

The increase in air temperature has been associated with human deaths, some of which are related to cardiovascular dysfunctions, and with the reduction of physical and cognitive performance in humans. To analyze the relationship between blood pressure (BP) and heart rate (HR) and the cognitive performance of students who were submitted to temperature changes in classrooms. The university students answered a survey that was adapted from the Battery of Reasoning Tests over 3 consecutive days at different air temperatures while their thermal state and HR were measured. During those 3 days, BP and HR were evaluated before and after the cognitive test. The average and final HR increased at high temperatures; the tests execution time was reduced at high temperatures; and the cognitive tests was related to Mean BP at the beginning of the test, the maximum HR during the test and the air temperature. The cognitive performance of undergraduate students in the field of engineering and technology will increase while performing activities in a learning environment with an air temperature of approximately 23.3°C (according to their thermal perception), if students have an initial MBP of 93.33 mmHg and a 60 bpm HRmax.

High Temperature Advanced Structural Composites. Volume 2. Ceramic Matrix Composites, Fiber Processing and Properties, and Interfaces

DTIC Science & Technology

1993-04-02

1977) 97. 3 W. Wieswieler, E. Fitzer, G . Nagel, and H. Jager, Thin Solid Film, 148 (1987) 93. 4 T. A. Chernyshova , L. I. Kobelova, J. Mater. Scl., 20...AD-A267 023 I[E[gh ’Temperature kdvanced Structural (Composites Rensselaer Polytechnic Institute , \\ G Troy, N. Y. 12180-3590 - Final Report -- Book 2...thermodynamic data (heats of forma- ,(T p, comp.) °+p, comp.) (1) tion, absolute entropies, heat capacities) of reactants where g ’ is the chemical

Colossal internal barrier layer capacitance effect in polycrystalline copper (II) oxide

NASA Astrophysics Data System (ADS)

Sarkar, Sudipta; Jana, Pradip Kumar; Chaudhuri, B. K.

2008-01-01

Dielectric spectroscopy analysis of the high permittivity (κ˜104) copper (II) oxide (CuO) ceramic shows that the grain contribution plays a major role for the giant-κ value at low temperature, whereas grain boundary (GB) contribution dominates around room temperature and above. Moreover, impedance spectroscopy analysis reveals electrically heterogeneous microstructure in CuO consisting of semiconducting grains and insulating GBs. Finally, the giant dielectric phenomenon exhibited by CuO is attributed to the internal barrier layer (due to GB) capacitance mechanism.

Poly(n-hexyl methacrylate) polymerization in three-component microemulsion stabilized by a cationic surfactant.

PubMed

Katime, Issa; Arellano, Jesús; Schulz, Pablo

2006-04-15

The polymerization of n-hexyl methacrylate (n-HMA) in three-component microemulsion stabilized with dodecyltrimethylammonium bromide (DTAB) is reported as a function of monomer and initiator concentrations and temperature. The obtained latices were bluish, transparent, and translucent. Particle sizes and molar masses were on the order of 20 nm and 3 x 10(6) g/mol, respectively. In all cases, high reaction rates and final conversions of 98% were obtained. Polymerization temperature has a strong effect on reaction rate and conversion.

Recombination of H atoms on the dust in fusion plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bakhtiyari-Ramezani, M., E-mail: mahdiyeh.bakhtiyari@gmail.com; Alinejad, N., E-mail: nalinezhad@aeoi.org.ir; Mahmoodi, J., E-mail: mahmoodi@qom.ac.ir

2015-07-15

We survey a model for theoretical study of the interaction of hydrogen and dust surface and apply our results for dusty plasmas to fusion devices. In this model, considering the mobility of ad-atoms from one physisorbed, or chemisorbed site, to other one by thermal diffusion, we describe the formation of H{sub 2} on grain surfaces. Finally, we calculate the formation rate on the high temperature dust surfaces for a range of temperature and density in typical conditions of divertor of tokamak.

Effect of thermal cycling. Final report, April 1985-January 1987

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobs, S.F.

The objective of this effort is to evaluate the stability of low expansion Zerodur, developmental Zerodur, ULE, and Cer-Vit as possible substrate materials for high energy laser mirrors. This effort will determine whether there is instability in developmental Zerodur, ULE and Cer-Vit over operating temperatures and coating temperatures (300-475K). Zerodur has already been shown to exhibit instability. Thermal cycling will be investigated as a possible approach to eliminate or reduce hysteresis. The effect of polishing on hysteresis will also be investigated.

A novel highly porous ceramic foam with efficient thermal insulation and high temperature resistance properties fabricated by gel-casting process

NASA Astrophysics Data System (ADS)

Yu, Jiahong; Wang, Guixiang; Tang, Di; Qiu, Ya; Sun, Nali; Liu, Wenqiao

2018-01-01

The design of super thermal insulation and high-temperature resistant materials for high temperature furnaces is crucial due to the energy crisis and the huge wasting. Although it is told that numerous studies have been reported about various of thermal insulation materials prepared by different methods, the applications of yttria-stabilized zirconia (YSZ) ceramic foams fabricated through tert-butyl alcohol (TBA)-based gel-casting process in bulk thermal isolators were barely to seen. In this paper, highly porous yttria-stabilized zirconia (YSZ) ceramic foams were fabricated by a novel gel-casting method using tert-butyl alcohol (TBA) as solvent and pore-forming agent. Different raw material ratio, sintering temperature and soaking time were all investigated to achieve optimal thermal insulation and mechanical properties. We can conclude that porosity drops gradually while compressive strength increases significantly with the rising temperature from 1000-1500°C. With prolonged soaking time, there is no obvious change in porosity but compressive strength increases gradually. All specimens have uniformly distributed pores with average size of 0.5-2μm and show good structural stability at high temperature. The final obtained ceramic foams displayed an outstanding ultra-low thermal conductivity property with only 200.6 °C in cold surface while the hot side was 1000 °C (hold 60 min to keep thermal balance before testing) at the thickness of 10 mm.

A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han

The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This paper aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide amore » comparative assessment of their high-temperature structural performance. The K JQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Finally, irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.« less

A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

DOE PAGES

Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han; ...

2016-12-07

The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This paper aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide amore » comparative assessment of their high-temperature structural performance. The K JQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Finally, irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.« less

Utilization of potatoes for life support in space. V. Evaluation of cultivars in response to continuous light and high temperature

NASA Technical Reports Server (NTRS)

Tibbitts, T. W.; Cao, W.; Bennett, S. M.

1992-01-01

Twenty-four potato (Solanum tuberosum L.) cultivars from different regions of the world were evaluated in terms of their responses to continuous light (24 h photoperiod) and to high temperature (30 C) in two separate experiments under controlled environments. In each experiment, a first evaluation of the cultivars was made at day 35 after transplanting, at which time 12 cultivars exhibiting best growth and tuber initiation were selected. A final evaluation of the 12 cultivars was made after an additional 21 days of growth, at which time plant height, total dry weight, tuber dry weight, and tuber number were determined. In the continuous light evaluation, the 12 selected cultivars were Alaska 114, Atlantic, Bintje, Denali, Desiree, Haig, New York 81, Ottar, Rutt, Snogg, Snowchip, and Troll. In the high temperature evaluation, the 12 selected cultivars were Alpha, Atlantic, Bake King, Denali, Desiree, Haig, Kennebec, Norland, Russet Burbank, Rutt, Superior, and Troll. Among the cultivars selected under continuous irradiation, Desiree, Ottar, Haig, Rutt, Denali and Alaska showed the best potential for high productivity whereas New York 81 and Bintje showed the least production capability. Among the cultivars selected under high temperature, Rutt, Haig, Troll and Bake King had best performance whereas Atlantic, Alpha, Kennebec and Russet Burbank exhibited the least production potential. Thus, Haig and Rutt were the two cultivars that performed well under continuous irradiation and high temperature conditions, and could have maximum potential for adaptation to varying stress environments. These two cultivars may have the best potential for use in future space farming in which continuous light and/or high temperature conditions may exist. However, cultivar responses under combined conditions of continuous light and high temperature remains for further validation.

Multi-Dimensional, Non-Pyrolyzing Ablation Test Problems

NASA Technical Reports Server (NTRS)

Risch, Tim; Kostyk, Chris

2016-01-01

Non-pyrolyzingcarbonaceous materials represent a class of candidate material for hypersonic vehicle components providing both structural and thermal protection system capabilities. Two problems relevant to this technology are presented. The first considers the one-dimensional ablation of a carbon material subject to convective heating. The second considers two-dimensional conduction in a rectangular block subject to radiative heating. Surface thermochemistry for both problems includes finite-rate surface kinetics at low temperatures, diffusion limited ablation at intermediate temperatures, and vaporization at high temperatures. The first problem requires the solution of both the steady-state thermal profile with respect to the ablating surface and the transient thermal history for a one-dimensional ablating planar slab with temperature-dependent material properties. The slab front face is convectively heated and also reradiates to a room temperature environment. The back face is adiabatic. The steady-state temperature profile and steady-state mass loss rate should be predicted. Time-dependent front and back face temperature, surface recession and recession rate along with the final temperature profile should be predicted for the time-dependent solution. The second problem requires the solution for the transient temperature history for an ablating, two-dimensional rectangular solid with anisotropic, temperature-dependent thermal properties. The front face is radiatively heated, convectively cooled, and also reradiates to a room temperature environment. The back face and sidewalls are adiabatic. The solution should include the following 9 items: final surface recession profile, time-dependent temperature history of both the front face and back face at both the centerline and sidewall, as well as the time-dependent surface recession and recession rate on the front face at both the centerline and sidewall. The results of the problems from all submitters will be collected, summarized, and presented at a later conference.

Heat suppression of the fiber coating on a cladding light stripper in high-power fiber laser.

PubMed

Yan, Ming-Jian; Wang, Zheng; Meng, Ling-Qiang; Yin, Lu; Han, Zhi-Gang; Shen, Hua; Wang, Hai-Lin; Zhu, Ri-Hong

2018-01-20

We present a theoretical model for the thermal effect of the fiber coating on a high-power cladding light stripper, which is fabricated by chemical etching. For the input and output of the fiber coating, a novel segmented corrosion method and increasing attenuation method are proposed for heat suppression, respectively. The relationship between the attenuation and temperature rise of the fiber coating at the output is experimentally demonstrated. The temperature distribution of the fiber coating at the input as well as the return light power caused by scattering are measured for the etched fiber with different surface roughness values. The results suggest that the rise in temperature is primarily caused by the scattering light propagating into the coating. Finally, an attenuation of 27 dB is achieved. At a room temperature of 23°C and input pump power of 438 W, the highest temperature of the input fiber coating decreases from 39.5°C to 27.9°C by segmented corrosion, and the temperature rise of the output fiber coating is close to 0.

Influence of initial heating during final high temperature annealing on the offset of primary and secondary recrystallization in Cu-bearing grain oriented electrical steels

NASA Astrophysics Data System (ADS)

Rodriguez-Calvillo, P.; Leunis, E.; Van De Putte, T.; Jacobs, S.; Zacek, O.; Saikaly, W.

2018-04-01

The industrial production route of Grain Oriented Electrical Steels (GOES) is complex and fine-tuned for each grade. Its metallurgical process requires in all cases the abnormal grain growth (AGG) of the Goss orientation during the final high temperature annealing (HTA). The exact mechanism of AGG is not yet fully understood, but is controlled by the different inhibition systems, namely MnS, AlN and CuxS, their size and distribution, and the initial primary recrystallized grain size. Therefore, among other parameters, the initial heating stage during the HTA is crucial for the proper development of primary and secondary recrystallized microstructures. Cold rolled 0.3 mm Cu-bearing Grain Oriented Electrical Steel has been submitted to interrupted annealing experiments in a lab tubular furnace. Two different annealing cycles were applied:• Constant heating at 30°C/h up to 1000°C. Two step cycle with initial heating at 100°C/h up to 600°C, followed by 18 h soaking at 600°C and then heating at 30°C/h up to 1050°C. The materials are analyzed in terms of their magnetic properties, grain size, texture and precipitates. The characteristic magnetic properties are analyzed for the different extraction temperatures and Cycles. As the annealing was progressing, the coercivity values (Hc 1.7T [A/m]) decreased, showing two abrupt drops, which can be associated to the on-set of primary and secondary recrystallization. The primary recrystallized grain sizes and recrystallized fractions are fitted to a model using a non-isothermal approach. This analysis shows that, although the resulting grain sizes were similar, the kinetics for the two step annealing were faster due to the lower recovery. The on-set of secondary recrystallization was also shifted to higher temperatures in the case of the continuous heating cycle, which might end in different final grain sizes and final magnetic properties. In both samples, nearly all the observed precipitates are Al-Si-Mn nitrides, ranging from pure AlN to Si4Mn-nitride.

Grafting of styrene into pre-irradiated fluoropolymer films: Influence of base material and irradiation temperature

NASA Astrophysics Data System (ADS)

Lappan, Uwe; Geißler, Uwe; Gohs, Uwe; Uhlmann, Steffi

2010-10-01

In this study, the influence of irradiation temperature on mechanical properties of three fluoropolymers and on grafting of styrene into the polymers by the pre-irradiation method was investigated. Electron paramagnetic resonance spectroscopy and infrared spectroscopy were used to characterize the irradiated polymers regarding trapped radical species and changes in the chemical structure, respectively. For poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA) the irradiation temperature was found to be an important factor for tensile strength and elongation at break of the pre-irradiated film. No strong effect of irradiation temperature on the mechanical properties was noticed for poly(tetrafluoroethylene-co-ethylene) (ETFE); however the yield of grafting drops at high irradiation temperatures. Finally, mechanical properties of poly(tetrafluoroethylene) (PTFE) were found to be dramatically altered, even if the film was irradiated at elevated temperature.

Temperature and solute-transport simulation in streamflow using a Lagrangian reference frame

USGS Publications Warehouse

Jobson, Harvey E.

1980-01-01

A computer program for simulating one-dimensional, unsteady temperature and solute transport in a river has been developed and documented for general use. The solution approach to the convective-diffusion equation uses a moving reference frame (Lagrangian) which greatly simplifies the mathematics of the solution procedure and dramatically reduces errors caused by numerical dispersion. The model documentation is presented as a series of four programs of increasing complexity. The conservative transport model can be used to route a single conservative substance. The simplified temperature model is used to predict water temperature in rivers when only temperature and windspeed data are available. The complete temperature model is highly accurate but requires rather complete meteorological data. Finally, the 10-parameter model can be used to route as many as 10 interacting constituents through a river reach. (USGS)

High frequency electromagnetism, heat transfer and fluid flow coupling in ANSYS multiphysics.

PubMed

Sabliov, Cristina M; Salvi, Deepti A; Boldor, Dorin

2007-01-01

The goal of this study was to numerically predict the temperature of a liquid product heated in a continuous-flow focused microwave system by coupling high frequency electromagnetism, heat transfer, and fluid flow in ANSYS Multiphysics. The developed model was used to determine the temperature change in water processed in a 915 MHz microwave unit, under steady-state conditions. The influence of the flow rates on the temperature distribution in the liquid was assessed. Results showed that the average temperature of water increased from 25 degrees C to 34 degrees C at 2 l/min, and to 42 degrees C at 1 l/min. The highest temperature regions were found in the liquid near the center of the tube, followed by progressively lower temperature regions as the radial distance from the center increased, and finally followed by a slightly higher temperature region near the tube's wall corresponding to the energy distribution given by the Mathieu function. The energy distribution resulted in a similar temperature pattern, with the highest temperatures close to the center of the tube and lower at the walls. The presented ANSYS Multiphysics model can be easily improved to account for complex boundary conditions, phase change, temperature dependent properties, and non-Newtonian flows, which makes for an objective of future studies.

Design of High Field Solenoids made of High Temperature Superconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartalesi, Antonio; /Pisa U.

2010-12-01

This thesis starts from the analytical mechanical analysis of a superconducting solenoid, loaded by self generated Lorentz forces. Also, a finite element model is proposed and verified with the analytical results. To study the anisotropic behavior of a coil made by layers of superconductor and insulation, a finite element meso-mechanic model is proposed and designed. The resulting material properties are then used in the main solenoid analysis. In parallel, design work is performed as well: an existing Insert Test Facility (ITF) is adapted and structurally verified to support a coil made of YBa{sub 2}Cu{sub 3}O{sub 7}, a High Temperature Superconductormore » (HTS). Finally, a technological winding process was proposed and the required tooling is designed.« less

Heat- and electron-beam-induced transport of gold particles into silicon oxide and silicon studied by in situ high-resolution transmission electron microscopy.

PubMed

Biskupek, Johannes; Kaiser, Ute; Falk, Fritz

2008-06-01

In this study, we describe the transport of gold (Au) nanoparticles from the surface into crystalline silicon (Si) covered by silicon oxide (SiO(2)) as revealed by in situ high-resolution transmission electron microscopy. Complete crystalline Au nanoparticles sink through the SiO(2) layer into the Si substrate when high-dose electron irradiation is applied and temperature is raised above 150 degrees C. Above temperatures of 250 degrees C, the Au nanoparticles finally dissolve into fragments accompanied by crystallization of the amorphized Si substrate around these fragments. The transport process is explained by a wetting process followed by Stokes motion. Modelling this process yields boundaries for the interface energies involved.

Results of the Mariner 6 and 7 Mars occultation experiments

NASA Technical Reports Server (NTRS)

Hogan, J. S.; Stewart, R. W.; Rasool, S. I.; Russell, L. H.

1972-01-01

Final profiles of temperature, pressure, and electron density on Mars were obtained for the Mariner 6 and 7 entry and exit cases, and results are presented for both the lower atmosphere and ionosphere. The results of an analysis of the systematic and formal errors introduced at each stage of the data-reduction process are also included. At all four occulation points, the lapse rate of temperature was subdadiabatic up to altitudes in excess of 20 km. A pronounced temperature inversion was present above the surface at the Mariner 6 exit point. All four profiles exhibit a sharp, superadiabatic drop in temperature at high altitudes, with temperatures falling below the frost point of CO2. These results give a strong indication of frozen CO2 in the middle atmosphere of Mars.

Temperature Dependence of Electrical Resistance of Woven Melt-Infiltrated SiCf/SiC Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Appleby, Matthew P.; Morscher, Gregory N.; Zhu, Dongming

2016-01-01

Recent studies have successfully shown the use of electrical resistance (ER)measurements to monitor room temperature damage accumulation in SiC fiber reinforced SiC matrix composites (SiCf/SiC) Ceramic Matrix Composites (CMCs). In order to determine the feasibility of resistance monitoring at elevated temperatures, the present work investigates the temperature dependent electrical response of various MI (Melt Infiltrated)-CVI (Chemical Vapor Infiltrated) SiC/SiC composites containing Hi-Nicalon Type S, Tyranno ZMI and SA reinforcing fibers. Test were conducted using a commercially available isothermal testing apparatus as well as a novel, laser-based heating approach developed to more accurately simulate thermomechanical testing of CMCs. Secondly, a post-test inspection technique is demonstrated to show the effect of high-temperature exposure on electrical properties. Analysis was performed to determine the respective contribution of the fiber and matrix to the overall composite conductivity at elevated temperatures. It was concluded that because the silicon-rich matrix material dominates the electrical response at high temperature, ER monitoring would continue to be a feasible method for monitoring stress dependent matrix cracking of melt-infiltrated SiC/SiC composites under high temperature mechanical testing conditions. Finally, the effect of thermal gradients generated during localized heating of tensile coupons on overall electrical response of the composite is determined.

Compact Ceramic Microchannel Heat Exchangers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewinsohn, Charles

The objective of the proposed work was to demonstrate the feasibility of a step change in power plant efficiency at a commercially viable cost, by obtaining performance data for prototype, compact, ceramic microchannel heat exchangers. By performing the tasks described in the initial proposal, all of the milestones were met. The work performed will advance the technology from Technology Readiness Level 3 (TRL 3) to Technology Readiness Level 4 (TRL 4) and validate the potential of using these heat exchangers for enabling high efficiency solid oxide fuel cell (SOFC) or high-temperature turbine-based power plants. The attached report will describe howmore » this objective was met. In collaboration with The Colorado School of Mines (CSM), specifications were developed for a high temperature heat exchanger for three commercial microturbines. Microturbines were selected because they are a more mature commercial technology than SOFC, they are a low-volume and high-value target for market entry of high-temperature heat exchangers, and they are essentially scaled-down versions of turbines used in utility-scale power plants. Using these specifications, microchannel dimensions were selected to meet the performance requirements. Ceramic plates were fabricated with microchannels of these dimensions. The plates were tested at room temperature and elevated temperature. Plates were joined together to make modular, heat exchanger stacks that were tested at a variety of temperatures and flow rates. Although gas flow rates equivalent to those in microturbines could not be achieved in the laboratory environment, the results showed expected efficiencies, robust operation under significant temperature gradients at high temperature, and the ability to cycle the stacks. Details of the methods and results are presented in this final report.« less

Distributed Low Temperature Combustion: Fundamental Understanding of Combustion Regime Transitions

DTIC Science & Technology

2016-09-07

AFRL-AFOSR-UK-TR-2016-0021 Distributed Low Temperature Combustion 133024 Peter Lindstedt IMPERIAL COLLEGE OF SCIENCE TECHNOLOGY & MEDICINE Final...TYPE Final 3. DATES COVERED (From - To) 01 Feb 2013 to 31 Jul 2016 4. TITLE AND SUBTITLE Distributed Low Temperature Combustion: Fundamental...identification of five separate fluid states. 15. SUBJECT TERMS EOARD, Low Temperature Combustion, Combustion Regime Transitions 16. SECURITY

Final Report from the Department of Kinetics of Chemical and Biological Processes, Institute of Chemical Physics of Russian Academy of Sciences

DTIC Science & Technology

1994-01-01

from polymer systems. Investigation of mechanisms of high-temperature pyrolysis and combustion reactions of network polymethacrylates. Rubailo V.L...are widely spread among agricultural important crops (i.e. cereals, fruits, grapevine, potato, cotton, tomato , leguminous) and ornamental plants

HIGH-TEMPERATURE INDUCIBLE CELL-FREE TRANSCRIPTION AND REPLICATION OF DOUBLE-STRANDED RNAS WITHIN THE PARASITIC PROTOZOAN CRYPTOSPORIDIUM PARVUM. (R825148)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Effect of initial moisture content on the in-vessel composting under air pressure of organic fraction of municipal solid waste in Morocco.

PubMed

Makan, Abdelhadi; Assobhei, Omar; Mountadar, Mohammed

2013-01-03

This study aimed to evaluate the effect of initial moisture content on the in-vessel composting under air pressure of organic fraction of municipal solid waste in Morocco in terms of internal temperature, produced gases quantity, organic matter conversion rate, and the quality of the final composts.For this purpose, in-vessel bioreactor was designed and used to evaluate both appropriate initial air pressure and appropriate initial moisture content for the composting process. Moreover, 5 experiments were carried out within initial moisture content of 55%, 65%, 70%, 75% and 85%. The initial air pressure and the initial moisture content of the mixture showed a significant effect on the aerobic composting. The experimental results demonstrated that for composting organic waste, relatively high moisture contents are better at achieving higher temperatures and retaining them for longer times.This study suggested that an initial moisture content of around 75%, under 0.6 bar, can be considered as being suitable for efficient composting of organic fraction of municipal solid waste. These last conditions, allowed maximum value of temperature and final composting product with good physicochemical properties as well as higher organic matter degradation and higher gas production. Moreover, final compost obtained showed good maturity levels and can be used for agricultural applications.

Temperature preference of the white perch, Morone americana, collected in the Wicomico River, Maryland

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, L.W. Jr.; Hocutt, C.H.; Stauffer, J.R. Jr.

1979-06-01

Temperature preference tests were conducted on fresh water white perch (Morone americana), collected from the Wicomico River, Maryland. Collection temperature was 27/sup 0/C and acclimation temperatures used in temperature preference tests were 6, 12, 18, 24, 30, and 33/sup 0/C. The following methods were used to determine the final temperature preference:linear regression, quadratic equation, and eyeball plots. Recorded final temperature preference values were 28.9, 29.3, and 30.6/sup 0/C using each method respectively.

The Genetic Control of Reproductive Development under High Ambient Temperature.

PubMed

Ejaz, Mahwish; von Korff, Maria

2017-01-01

Ambient temperature has a large impact on reproductive development and grain yield in temperate cereals. However, little is known about the genetic control of development under different ambient temperatures. Here, we demonstrate that in barley (Hordeum vulgare), high ambient temperatures accelerate or delay reproductive development depending on the photoperiod response gene PHOTOPERIOD1 (Ppd-H1) and its upstream regulator EARLY FLOWERING3 (HvELF3). A natural mutation in Ppd-H1 prevalent in spring barley delayed floral development and reduced the number of florets and seeds per spike, while the wild-type Ppd-H1 or a mutant Hvelf3 allele accelerated floral development and maintained the seed number under high ambient temperatures. High ambient temperature delayed the expression phase and reduced the amplitude of clock genes and repressed the floral integrator gene FLOWERING LOCUS T1 independently of the genotype. Ppd-H1-dependent variation in flowering time under different ambient temperatures correlated with relative expression levels of the BARLEY MADS-box genes VERNALIZATION1 (HvVRN1), HvBM3, and HvBM8 in the leaf. Finally, we show that Ppd-H1 interacts with regulatory variation at HvVRN1. Ppd-H1 only accelerated floral development in the background of a spring HvVRN1 allele with a deletion in the regulatory intron. The full-length winter Hvvrn1 allele was strongly down-regulated, and flowering was delayed by high temperatures irrespective of Ppd-H1 Our findings demonstrate that the photoperiodic and vernalization pathways interact to control flowering time and floret fertility in response to ambient temperature in barley. © 2017 American Society of Plant Biologists. All Rights Reserved.

The Genetic Control of Reproductive Development under High Ambient Temperature1[OPEN

PubMed Central

2017-01-01

Ambient temperature has a large impact on reproductive development and grain yield in temperate cereals. However, little is known about the genetic control of development under different ambient temperatures. Here, we demonstrate that in barley (Hordeum vulgare), high ambient temperatures accelerate or delay reproductive development depending on the photoperiod response gene PHOTOPERIOD1 (Ppd-H1) and its upstream regulator EARLY FLOWERING3 (HvELF3). A natural mutation in Ppd-H1 prevalent in spring barley delayed floral development and reduced the number of florets and seeds per spike, while the wild-type Ppd-H1 or a mutant Hvelf3 allele accelerated floral development and maintained the seed number under high ambient temperatures. High ambient temperature delayed the expression phase and reduced the amplitude of clock genes and repressed the floral integrator gene FLOWERING LOCUS T1 independently of the genotype. Ppd-H1-dependent variation in flowering time under different ambient temperatures correlated with relative expression levels of the BARLEY MADS-box genes VERNALIZATION1 (HvVRN1), HvBM3, and HvBM8 in the leaf. Finally, we show that Ppd-H1 interacts with regulatory variation at HvVRN1. Ppd-H1 only accelerated floral development in the background of a spring HvVRN1 allele with a deletion in the regulatory intron. The full-length winter Hvvrn1 allele was strongly down-regulated, and flowering was delayed by high temperatures irrespective of Ppd-H1. Our findings demonstrate that the photoperiodic and vernalization pathways interact to control flowering time and floret fertility in response to ambient temperature in barley. PMID:28049855

Impact of extreme high temperature on mortality and regional level definition of heat wave: a multi-city study in China.

PubMed

Gao, Jinghong; Sun, Yunzong; Liu, Qiyong; Zhou, Maigeng; Lu, Yaogui; Li, Liping

2015-02-01

Few multi-city studies have been conducted to explore the regional level definition of heat wave and examine the association between extreme high temperature and mortality in developing countries. The purpose of the present study was to investigate the impact of extreme high temperature on mortality and to explore the local definition of heat wave in five Chinese cities. We first used a distributed lag non-linear model to characterize the effects of daily mean temperature on non-accidental mortality. We then employed a generalized additive model to explore the city-specific definition of heat wave. Finally, we performed a comparative analysis to evaluate the effectiveness of the definition. For each city, we found a positive non-linear association between extreme high temperature and mortality, with the highest effects appearing within 3 days of extreme heat event onset. Specifically, we defined individual heat waves of Beijing and Tianjin as being two or more consecutive days with daily mean temperatures exceeding 30.2 °C and 29.5 °C, respectively, and Nanjing, Shanghai and Changsha heat waves as ≥3 consecutive days with daily mean temperatures higher than 32.9 °C, 32.3 °C and 34.5 °C, respectively. Comparative analysis generally supported the definition. We found extreme high temperatures were associated with increased mortality, after a short lag period, when temperatures exceeded obvious threshold levels. The city-specific definition of heat wave developed in our study may provide guidance for the establishment and implementation of early heat-health response systems for local government to deal with the projected negative health outcomes due to heat waves. Copyright © 2014 Elsevier B.V. All rights reserved.

Effects of gas temperature on nozzle damping experiments on cold-flow rocket motors

NASA Astrophysics Data System (ADS)

Sun, Bing-bing; Li, Shi-peng; Su, Wan-xing; Li, Jun-wei; Wang, Ning-fei

2016-09-01

In order to explore the impact of gas temperature on the nozzle damping characteristics of solid rocket motor, numerical simulations were carried out by an experimental motor in Naval Ordnance Test Station of China Lake in California. Using the pulse decay method, different cases were numerically studied via Fluent along with UDF (User Defined Functions). Firstly, mesh sensitivity analysis and monitor position-independent analysis were carried out for the computer code validation. Then, the numerical method was further validated by comparing the calculated results and experimental data. Finally, the effects of gas temperature on the nozzle damping characteristics were studied in this paper. The results indicated that the gas temperature had cooperative effects on the nozzle damping and there had great differences between cold flow and hot fire test. By discussion and analysis, it was found that the changing of mainstream velocity and the natural acoustic frequency resulted from gas temperature were the key factors that affected the nozzle damping, while the alteration of the mean pressure had little effect. Thus, the high pressure condition could be replaced by low pressure to reduce the difficulty of the test. Finally, the relation of the coefficients "alpha" between the cold flow and hot fire was got.

Crystallization of Ca-Al-Rich Inclusions: Experimental Studies on the Effects of Repeated Heating Events

NASA Technical Reports Server (NTRS)

Paque, Julie M.; Lofgren, Gary E.; Le, Loan

2000-01-01

The observed textures and chemistry of Ca-Al-rich inclusions (CAIs) are presumed to be the culmination of a series of repeated heating and cooling events in the early history of the solar nebula. We have examined the effects of these heating/cooling cycles experimentally on a bulk composition representing an average Type B Ca-Al-rich inclusion composition. We have tested the effect of the nature of the starting material. Although the most recent and/or highest temperature event prior to incorporation into the parent body dominates the texture and chemistry of the CAI, prior events also affect the phase compositions and textures. We have determined that heating precursor grains to about 1275 C prior to the final melting event increases the likelihood of anorthite crystallization in subsequent higher temperature events and a prior high temperature even that produced dendritic melilite results in melilite that shows evidence of rapid crystallization in subsequent lower temperature events. Prior low temperature pre-crystallization events produce final ran products with pyroxene compositions similar to Type B Ca-Al-rich inclusions, and the glass (residual liquid) composition is more anorthitic than any other experiments to date. The addition of Pt powder to the starting material appears to enhance the ability of anorthite to nucleate from this composition.

Spectroscopic detection and analysis of atomic emissions during industrial pulsed laser-drilling of structural aerospace alloys

NASA Astrophysics Data System (ADS)

Bright, Robin Michael

The ability to adequately cool internal gas-turbine engine components in next-generation commercial and military aircraft is of extreme importance to the aerospace industry as the demand for high-efficiency engines continues to push operating temperatures higher. Pulsed laser-drilling is rapidly becoming the preferred method of creating cooling holes in high temperature components due a variety of manufacturing advantages of laser-drilling over conventional hole-drilling techniques. As cooling requirements become more demanding, the impact of drilling conditions on material removal behavior and subsequent effects on hole quality becomes critical. In this work, the development of emission spectroscopy as a method to probe the laser-drilling process is presented and subsequently applied to the study of material behavior of various structural aerospace materials during drilling. Specifically, emitted photons associated with energy level transitions within excited neutral atoms in material ejected during drilling were detected and analyzed. Systematic spectroscopic studies indicated that electron energy level populations and calculated electron temperatures within ejected material are dependent on both laser pulse energy and duration. Local thermal conditions detected by the developed method were related to the characteristics of ejected material during drilling and to final hole quality. Finally, methods of utilizing the observed relationships for spectroscopic process monitoring and control were demonstrated.

High freezing point fuels used for aviation turbine engines

NASA Technical Reports Server (NTRS)

Friedman, R.

1979-01-01

Broadened-specification aviation fuels could be produced from a greater fraction of crude source material with improvements in fuel supply and price. These fuels, particularly those with increased final boiling temperatures, would have higher freezing temperatures than current aviation turbine fuels. For the small but significant fraction of commercial flights where low fuel temperatures make higher freezing-point fuel use unacceptable, adaptations to the fuel or fuel system may be made to accommodate this fuel. Several techniques are discussed. Fuel heating is the most promising concept. One simple design uses existing heat rejection from the fuel-lubricating oil cooler, another uses an engine-driven generator for electrical heating.

Evidence of a temperature transition for denuded zone formation in nanocrystalline Fe under He irradiation

DOE PAGES

El-Atwani, Osman; Nathaniel II, James E.; Leff, Asher C.; ...

2016-10-18

Nanocrystalline materials are radiation-tolerant materials’ candidates due to their high defect sink density. Here, nanocrystalline iron films were irradiated with 10 keV helium ions in situ in a transmission electron microscope at elevated temperatures. Grain-size-dependent bubble density changes and denuded zone occurrence were observed at 700 K, but not at 573 K. This transition, attributed to increased helium–vacancy migration at elevated temperatures, suggests that nanocrystalline microstructures are more resistant to swelling at 700 K due to decreased bubble density. Finally, denuded zone formation had no correlation with grain size and misorientation angle under the conditions studied.

Thermal Analysis of AlGaN/GaN High-Electron-Mobility Transistor and Its RF Power Efficiency Optimization with Source-Bridged Field-Plate Structure.

PubMed

Kwak, Hyeon-Tak; Chang, Seung-Bo; Jung, Hyun-Gu; Kim, Hyun-Seok

2018-09-01

In this study, we consider the relationship between the temperature in a two-dimensional electron gas (2-DEG) channel layer and the RF characteristics of an AlGaN/GaN high-electron-mobility transistor by changing the geometrical structure of the field-plate. The final goal is to achieve a high power efficiency by decreasing the channel layer temperature. First, simulations were performed to compare and contrast the experimental data of a conventional T-gate head structure. Then, a source-bridged field-plate (SBFP) structure was used to obtain the lower junction temperature in the 2-DEG channel layer. The peak electric field intensity was reduced, and a decrease in channel temperature resulted in an increase in electron mobility. Furthermore, the gate-to-source capacitance was increased by the SBFP structure. However, under the large current flow condition, the SBFP structure had a lower maximum temperature than the basic T-gate head structure, which improved the device electron mobility. Eventually, an optimum position of the SBFP was used, which led to higher frequency responses and improved the breakdown voltages. Hence, the optimized SBFP structure can be a promising candidate for high-power RF devices.

Effect of Groove Surface Texture on Tribological Characteristics and Energy Consumption under High Temperature Friction.

PubMed

Wu, Wei; Chen, Guiming; Fan, Boxuan; Liu, Jianyou

2016-01-01

Energy consumption and tribological properties could be improved by proper design of surface texture in friction. However, some literature focused on investigating their performance under high temperature. In the study, different groove surface textures were fabricated on steels by a laser machine, and their tribological behaviors were experimentally studied with the employment of the friction and wear tester under distinct high temperature and other working conditions. The friction coefficient was recorded, and wear performance were characterized by double light interference microscope, scanning electron microscope (SEM) and x-ray energy dispersive spectrometry (EDS). Then, the performances of energy consumptions were carefully estimated. Results showed that friction coefficient, wear, and energy consumption could almost all be reduced by most textures under high temperature conditions, but to a different extent which depends on the experimental conditions and texture parameters. The main improvement mechanisms were analyzed, such as the hardness change, wear debris storage, thermal stress release and friction induced temperature reduction by the textures. Finally, a scattergram of the relatively reduced ratio of the energy consumption was drawn for different surface textures under four distinctive experimental conditions to illustrate the comprehensive energy consumption improving ability of textures, which was of benefit for the application of texture design.

Effect of Groove Surface Texture on Tribological Characteristics and Energy Consumption under High Temperature Friction

PubMed Central

Wu, Wei; Chen, Guiming; Fan, Boxuan; Liu, Jianyou

2016-01-01

Energy consumption and tribological properties could be improved by proper design of surface texture in friction. However, some literature focused on investigating their performance under high temperature. In the study, different groove surface textures were fabricated on steels by a laser machine, and their tribological behaviors were experimentally studied with the employment of the friction and wear tester under distinct high temperature and other working conditions. The friction coefficient was recorded, and wear performance were characterized by double light interference microscope, scanning electron microscope (SEM) and x-ray energy dispersive spectrometry (EDS). Then, the performances of energy consumptions were carefully estimated. Results showed that friction coefficient, wear, and energy consumption could almost all be reduced by most textures under high temperature conditions, but to a different extent which depends on the experimental conditions and texture parameters. The main improvement mechanisms were analyzed, such as the hardness change, wear debris storage, thermal stress release and friction induced temperature reduction by the textures. Finally, a scattergram of the relatively reduced ratio of the energy consumption was drawn for different surface textures under four distinctive experimental conditions to illustrate the comprehensive energy consumption improving ability of textures, which was of benefit for the application of texture design. PMID:27035658

A hot tip: imaging phenomena using in situ multi-stimulus probes at high temperatures

NASA Astrophysics Data System (ADS)

Nonnenmann, Stephen S.

2016-02-01

Accurate high temperature characterization of materials remains a critical challenge to the continued advancement of various important energy, nuclear, electronic, and aerospace applications. Future experimental studies must assist these communities to progress past empiricism and derive deliberate, predictable designs of material classes functioning within active, extreme environments. Successful realization of systems ranging from fuel cells and batteries to electromechanical nanogenerators and turbines requires a dynamic understanding of the excitation, surface-mediated, and charge transfer phenomena which occur at heterophase interfaces (i.e. vapor-solid, liquid-solid, solid-solid) and impact overall performance. Advancing these frontiers therefore necessitates in situ (operando) characterization methods capable of resolving, both spatially and functionally, the coherence between these complex, collective excitations, and their respective response dynamics, through studies within the operating regime. This review highlights recent developments in scanning probe microscopy in performing in situ imaging at high elevated temperatures. The influence of and evolution from vacuum-based electron and tunneling microscopy are briefly summarized and discussed. The scope includes the use of high temperature imaging to directly observe critical phase transition, electronic, and electrochemical behavior under dynamic temperature settings, thus providing key physical parameters. Finally, both challenges and directions in combined instrumentation are proposed and discussed towards the end.

Thermal Flow Sensors for Harsh Environments.

PubMed

Balakrishnan, Vivekananthan; Phan, Hoang-Phuong; Dinh, Toan; Dao, Dzung Viet; Nguyen, Nam-Trung

2017-09-08

Flow sensing in hostile environments is of increasing interest for applications in the automotive, aerospace, and chemical and resource industries. There are thermal and non-thermal approaches for high-temperature flow measurement. Compared to their non-thermal counterparts, thermal flow sensors have recently attracted a great deal of interest due to the ease of fabrication, lack of moving parts and higher sensitivity. In recent years, various thermal flow sensors have been developed to operate at temperatures above 500 °C. Microelectronic technologies such as silicon-on-insulator (SOI), and complementary metal-oxide semiconductor (CMOS) have been used to make thermal flow sensors. Thermal sensors with various heating and sensing materials such as metals, semiconductors, polymers and ceramics can be selected according to the targeted working temperature. The performance of these thermal flow sensors is evaluated based on parameters such as thermal response time, flow sensitivity. The data from thermal flow sensors reviewed in this paper indicate that the sensing principle is suitable for the operation under harsh environments. Finally, the paper discusses the packaging of the sensor, which is the most important aspect of any high-temperature sensing application. Other than the conventional wire-bonding, various novel packaging techniques have been developed for high-temperature application.

Thermal Flow Sensors for Harsh Environments

PubMed Central

Dinh, Toan; Dao, Dzung Viet

2017-01-01

Flow sensing in hostile environments is of increasing interest for applications in the automotive, aerospace, and chemical and resource industries. There are thermal and non-thermal approaches for high-temperature flow measurement. Compared to their non-thermal counterparts, thermal flow sensors have recently attracted a great deal of interest due to the ease of fabrication, lack of moving parts and higher sensitivity. In recent years, various thermal flow sensors have been developed to operate at temperatures above 500 °C. Microelectronic technologies such as silicon-on-insulator (SOI), and complementary metal-oxide semiconductor (CMOS) have been used to make thermal flow sensors. Thermal sensors with various heating and sensing materials such as metals, semiconductors, polymers and ceramics can be selected according to the targeted working temperature. The performance of these thermal flow sensors is evaluated based on parameters such as thermal response time, flow sensitivity. The data from thermal flow sensors reviewed in this paper indicate that the sensing principle is suitable for the operation under harsh environments. Finally, the paper discusses the packaging of the sensor, which is the most important aspect of any high-temperature sensing application. Other than the conventional wire-bonding, various novel packaging techniques have been developed for high-temperature application. PMID:28885595

Recent advances in the characterization of high temperature industrial materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meadowcroft, D.B.; Tomkings, A.B.

1995-12-31

This paper reviews several techniques under development or recently commercialized which aid the characterization of high temperature plant components when carrying out lifetime predictions. Temperature measurements are frequently limited because of the limited lifetime and cost of thermocouples in aggressive environments and three alternative methods of assessing the ``average effective`` temperature of a component being evaluated by the authors are described steam side oxide thickness (specifically for ferritic superheater tubes), copper gold diffusion couples (``PETIT``), and the measurement of ferrite in duplex steels (``FEROPLUG``). Advances are described which have been made recently in the measurement techniques available for making plantmore » measurements on components to reduce the time needed for significant values of wastage rates to be established. In addition on-line high, temperature corrosion monitors are coming available which allow wastage rates to be assessed over periods of hours or days. These involve electrical resistance or electrochemical techniques. Finally the use of thin layer activation by a radioactive isotope is highlighted which enables the wastage of components to be assessed remotely without direct contact. Whilst available for a long time for laboratory and pilot plant studies, the authors are actively concerned with introducing the technique into operational boiler plant.« less

High temperature compounds for turbine vanes. [of SiC, Si3N4, and Si composites

NASA Technical Reports Server (NTRS)

Rhodes, W. H.; Cannon, R. M., Jr.

1974-01-01

Fabrication and microstructure control studies were conducted on SiC, Si3N and composites based on Si3N. Charpy mode impact testing to 2400 F established that Si3N4/Mo composites have excellent potential. Attempts to fabricate composites of Si3N4 with superalloys, both by hot pressing and infiltration were largely unsuccessful in comparison to using Mo, Re, and Ta which are less reactive. Modest improvements in impact strength were realized for monolithic Si3N4; however, SiC strengths increased by a factor of six and now equal values achieved for Si3N4. Correlations of impact strength with material properties are discussed. Reduced MgO densification aid additions to Si3N4 were found to decrease densification kinetics, increase final porosity, decrease room temperature bend strength, increase high temperature bend strength, and decrease bend stress rupture properties. The decrease in bend strength at high temperature for fine grain size SiC suggested that a slightly larger grain size material with a nearly constant strength-temperature relation may prove desirable in the creep and stress rupture mode.

Thermodynamics of gas and steam-blast eruptions

USGS Publications Warehouse

Mastin, L.G.

1995-01-01

Eruptions of gas or steam and non-juvenile debris are common in volcanic and hydrothermal areas. From reports of non-juvenile eruptions or eruptive sequences world-wide, at least three types (or end-members) can be identified: (1) those involving rock and liquid water initially at boiling-point temperatures ('boiling-point eruptions'); (2) those powered by gas (primarily water vapor) at initial temperatures approaching magmatic ('gas eruptions'); and (3) those caused by rapid mixing of hot rock and ground- or surface water ('mixing eruptions'). For these eruption types, the mechanical energy released, final temperatures, liquid water contents and maximum theoretical velocities are compared by assuming that the erupting mixtures of rock and fluid thermally equilibrate, then decompress isentropically from initial, near-surface pressure (???10 MPa) to atmospheric pressure. Maximum mechanical energy release is by far greatest for gas eruptions (??????1.3 MJ/kg of fluid-rock mixture)-about one-half that of an equivalent mass of gunpowder and one-fourth that of TNT. It is somewhat less for mixing eruptions (??????0.4 MJ/kg), and least for boiling-point eruptions (??????0.25 MJ/kg). The final water contents of crupted boiling-point mixtures are usually high, producing wet, sloppy deposits. Final erupted mixtures from gas eruptions are nearly always dry, whereas those from mixing eruptions vary from wet to dry. If all the enthalpy released in the eruptions were converted to kinetic energy, the final velocity (vmax) of these mixtures could range up to 670 m/s for boiling-point eruptions and 1820 m/s for gas eruptions (highest for high initial pressure and mass fractions of rock (mr) near zero). For mixing eruptions, vmax ranges up to 1150 m/s. All observed eruption velocities are less than 400 m/s, largely because (1) most solid material is expelled when mr is high, hence vmax is low; (2) observations are made of large blocks the velocities of which may be less than the average for the mixture; (3) heat from solid particles is not efficiently transferred to the fluid during the eruptions; and (4) maximum velocities are reduced by choked flow or friction in the conduit. ?? 1995 Springer-Verlag.

Hole-exciton interaction induced high field decay of magneto-electroluminescence in Alq3-based organic light-emitting diodes at room temperature

NASA Astrophysics Data System (ADS)

Zhang, Tingting; Holford, D. F.; Gu, Hang; Kreouzis, T.; Zhang, Sijie; Gillin, W. P.

2016-01-01

The magnetic field effects on the electroluminescence of aluminium tris-(8-hydroxyqinoline) (Alq3) based organic light emitting diodes have been investigated by varying the electron/hole ratio in the emissive layer. Experimental results reveal that a negative high field effect in the magneto-electroluminescence (MEL) can be found in devices with very low triplet exciton concentration at room temperature. This suggests triplet-triplet annihilation cannot be used to explain the negative high field MEL in the Alq3 system. Our results suggest that hole-exciton interaction may be the origin of the negative high field MEL and also, in parallel with this interaction, there is also the more common positive high field process occurring which has been tentatively attributed to electron-exciton interactions. The competition between these different processes decides the final shape of the MEL at high fields.

Status of high temperature superconductor development for accelerator magnets

NASA Technical Reports Server (NTRS)

Hirabayashi, H.

1995-01-01

High temperature superconductors are still under development for various applications. As far as conductors for magnets are concerned, the development has just been started. Small coils wound by silver sheathed Bi-2212 and Bi-2223 oxide conductors have been reported by a few authors. Essential properties of high T(sub c) superconductors like pinning force, coherent length, intergrain coupling, weak link, thermal property, AC loss and mechanical strength are still not sufficiently understandable. In this talk, a review is given with comparison between the present achievement and the final requirement for high T(sub c) superconductors, which could be particularly used in accelerator magnets. Discussions on how to develop high T(sub c) superconductors for accelerator magnets are included with key parameters of essential properties. A proposal of how to make a prototype accelerator magnet with high T(sub c) superconductors with prospect for future development is also given.

Environmental and strain rate effects on graphite/epoxy composites. Final Report; M.S. Thesis, 1987

NASA Technical Reports Server (NTRS)

Peimandis, Konstantinos

1991-01-01

The hygrothermal characterization of unidirectional graphite/epoxy composites over a range of strain rates was investigated. Special techniques developed for such hygrothermal characterization are also described. The mechanical properties of the composite material were obtained and analyzed by means of a time-temperature-moisture superposition principle. The results show the following: (1) the embedded gage technique was thoroughly examined and found to be appropriate for both hygrothermal expansion and mechanical strain measurements; (2) all transverse properties were found to decrease with increasing temperature and moisture content; and (3) ultimate transverse properties were found to increase with strain rate at low temperatures but follow an opposite trend at high temperatures compared to dry specimens.

Optimisation of the readout parameters when evaluating thermal neutron doses by TL dosimetry with LiF:Mg,Ti.

PubMed

German, U; Weinstein, M; Abraham, A; Alfassi, Z B

2007-01-01

The location of the glow peaks depends on the heating rate. It takes some time until the crystal reaches the heater temperature, and this time lag has a direct effect on the shift of peaks towards higher temperatures. Some information on the high-temperature peaks may be lost if the readout conditions (mainly length of time) are not properly chosen. Step heating profiles to a varying final temperature between 300 degrees C and 125 degrees C were used to study the time dependence of the collected information in the glow curves of (6)LiF:Mg,Ti crystals, and the minimal heating time for evaluation of thermal neutron doses was determined.

The electrical transport properties of liquid Rb using pseudopotential theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, A. B., E-mail: amit07patel@gmail.com; Bhatt, N. K., E-mail: amit07patel@gmail.com; Thakore, B. Y., E-mail: amit07patel@gmail.com

2014-04-24

Certain electric transport properties of liquid Rb are reported. The electrical resistivity is calculated by using the self-consistent approximation as suggested by Ferraz and March. The pseudopotential due to Hasegawa et al for full electron-ion interaction, which is valid for all electrons and contains the repulsive delta function due to achieve the necessary s-pseudisation was used for the calculation. Temperature dependence of structure factor is considered through temperature dependent potential parameter in the pair potential. Finally, thermo-electric power and thermal conductivity are obtained. The outcome of the present study is discussed in light of other such results, and confirms themore » applicability of pseudopotential at very high temperature via temperature dependent pair potential.« less

Cluster Tool for In Situ Processing and Comprehensive Characterization of Thin Films at High Temperatures.

PubMed

Wenisch, Robert; Lungwitz, Frank; Hanf, Daniel; Heller, René; Zscharschuch, Jens; Hübner, René; von Borany, Johannes; Abrasonis, Gintautas; Gemming, Sibylle; Escobar-Galindo, Ramon; Krause, Matthias

2018-06-13

A new cluster tool for in situ real-time processing and depth-resolved compositional, structural and optical characterization of thin films at temperatures from -100 to 800 °C is described. The implemented techniques comprise magnetron sputtering, ion irradiation, Rutherford backscattering spectrometry, Raman spectroscopy, and spectroscopic ellipsometry. The capability of the cluster tool is demonstrated for a layer stack MgO/amorphous Si (∼60 nm)/Ag (∼30 nm), deposited at room temperature and crystallized with partial layer exchange by heating up to 650 °C. Its initial and final composition, stacking order, and structure were monitored in situ in real time and a reaction progress was defined as a function of time and temperature.

Stress analysis in high-temperature superconductors under pulsed field magnetization

NASA Astrophysics Data System (ADS)

Wu, Haowei; Yong, Huadong; Zhou, Youhe

2018-04-01

Bulk high-temperature superconductors (HTSs) have a high critical current density and can trap a large magnetic field. When bulk superconductors are magnetized by the pulsed field magnetization (PFM) technique, they are also subjected to a large electromagnetic stress, and the resulting thermal stress may cause cracking of the superconductor due to the brittle nature of the sample. In this paper, based on the H-formulation and the law of heat transfer, we can obtain the distributions of electromagnetic field and temperature, which are in qualitative agreement with experiment. After that, based on the dynamic equilibrium equations, the mechanical response of the bulk superconductor is determined. During the PFM process, the change in temperature has a dramatic effect on the radial and hoop stresses, and the maximum radial and hoop stress are 24.2 {{MPa}} and 22.6 {{MPa}}, respectively. The mechanical responses of a superconductor for different cases are also studied, such as the peak value of the applied field and the size of bulk superconductors. Finally, the stresses are also presented for different magnetization methods.

High temperature alkali corrosion of ceramics in coal gas: Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pickrell, G.R.; Sun, T.; Brown, J.J. Jr.

1994-12-31

There are several ceramic materials which are currently being considered for use as structural elements in coal combustion and coal conversion systems because of their thermal and mechanical properties. These include alumina (refractories, membranes, heat engines); silicon carbide and silicon nitride (turbine engines, internal combustion engines, heat exchangers, particulate filters); zirconia (internal combustion engines, turbine engines, refractories); and mullite and cordierite (particulate filters, refractories, heat exchangers). High temperature alkali corrosion has been known to cause premature failure of ceramic components used in advanced high temperature coal combustion systems such as coal gasification and clean-up, coal fired gas turbines, and highmore » efficiency heat engines. The objective of this research is to systematically evaluate the alkali corrosion resistance of the most commonly used structural ceramics including silicon carbide, silicon nitride, cordierite, mullite, alumina, aluminum titanate, and zirconia. The study consists of identification of the alkali reaction products and determination of the kinetics of the alkali reactions as a function of temperature and time. 145 refs., 29 figs., 12 tabs.« less

Data Concentrator

NASA Technical Reports Server (NTRS)

Willett, Mike

2015-01-01

Orbital Research, Inc., developed, built, and tested three high-temperature components for use in the design of a data concentrator module in distributed turbine engine control. The concentrator receives analog and digital signals related to turbine engine control and communicates with a full authority digital engine control (FADEC) or high-level command processor. This data concentrator follows the Distributed Engine Controls Working Group (DECWG) roadmap for turbine engine distributed controls communication development that operates at temperatures at least up to 225 C. In Phase I, Orbital Research developed detailed specifications for each component needed for the system and defined the total system specifications. This entailed a combination of system design, compiling existing component specifications, laboratory testing, and simulation. The results showed the feasibility of the data concentrator. Phase II of this project focused on three key objectives. The first objective was to update the data concentrator design modifications from DECWG and prime contractors. Secondly, the project defined requirements for the three new high-temperature, application-specific integrated circuits (ASICs): one-time programmable (OTP), transient voltage suppression (TVS), and 3.3V. Finally, the project validated each design by testing over temperature and under load.

Phase behavior and dynamics of a micelle-forming triblock copolymer system

NASA Astrophysics Data System (ADS)

Mohan, P. Harsha; Bandyopadhyay, Ranjini

2008-04-01

Synperonic F-108 (generic name, “pluronic”) is a micelle forming triblock copolymer of type ABA , where A is polyethylene oxide (PEO) and B is polypropylene oxide (PPO). At high temperatures, the hydrophobicity of the PPO chains increase, and the pluronic molecules, when dissolved in an aqueous medium, self-associate into spherical micelles with dense PPO cores and hydrated PEO coronas. At appropriately high concentrations, these micelles arrange in a face centered cubic lattice to show inverse crystallization, with the samples exhibiting high-temperature crystalline and low-temperature fluidlike phases. By studying the evolution of the elastic and viscous moduli as temperature is increased at a fixed rate, we construct the concentration-temperature phase diagram of Synperonic F-108. For a certain range of temperatures and at appropriate sample concentrations, we observe a predominantly elastic response. Oscillatory strain amplitude sweep measurements on these samples show pronounced peaks in the loss moduli, a typical feature of soft solids. The soft solidlike nature of these materials is further demonstrated by measuring their frequency-dependent mechanical moduli. The storage moduli are significantly larger than the loss moduli and are almost independent of the applied angular frequency. Finally, we perform strain rate frequency superposition experiments to measure the slow relaxation dynamics of this soft solid.

Automatic 3D inspection metrology for high-temperature objects

NASA Astrophysics Data System (ADS)

Han, Liya; Li, Zhongwei; Zhong, Kai; Yi, Jie; Shi, Yusheng; Cheng, Xu; Zhan, Guomin; Chen, Ran

2017-06-01

3D Visual Inspection for high-temperature objects has attracted more and more attention in the industrial and manufacture field. Until now it is still difficult to measure the shape of high-temperature objects due to the following problems: 1) the radiation and heat transfer through the air seriously affect both human and measurement equipment, so the manual measurement is not capable in this situation. 2) Because of the difficulties to handle the surfaces of the hot objects, it is hard to use artificial markers to align different pieces of data. In order to solve these problems, an automatic 3D shape measurement system for high-temperature objects is proposed by combing an industrial robot with a structured blue light 3D scanner. In this system, the route for inspection is planned with the cooled object and then executed automatically with the same object in hot state to avoid artificial operations. The route is carefully planned to reduce the exposure time of the measurement equipment under the high-temperature situation. Then different pieces of data are premapped during the planning procedure. In the executing procedure, they can be aligned accurately thanks to the good repeatability of the industrial robot. Finally, different pieces of data are merged without artificial markers and the results are better than methods with traditional hand-eye calibration. Experiments verify that the proposed system can conduct the inspection of forging parts under the temperature of 900°C and the alignment precision is 0.0013rad and 0.28mm.

Containerless measurements on liquids at high temperatures

NASA Technical Reports Server (NTRS)

Weber, Richard

1993-01-01

The application of containerless techniques for measurements of the thermophysical properties of high temperature liquids is reviewed. Recent results obtained in the materials research laboratories at Intersonics are also presented. Work to measure high temperature liquid properties is motivated by both the need for reliable property data for modeling of industrial processes involving molten materials and generation of data form basic modeling of materials behavior. The motivation for this work and examples of variations in thermophysical property values from the literature are presented. The variations may be attributed to changes in the specimen properties caused by chemical changes in the specimen and/or to measurement errors. The two methods used to achieve containerless conditions were aeroacoustic levitation and electromagnetic levitation. Their qualities are presented. The accompanying slides show the layout of levitation equipment and present examples of levitated metallic and ceramic specimens. Containerless techniques provide a high degree of control over specimen chemistry, nucleation and allow precise control of liquid composition to be achieved. Effects of minor additions can thus be measured in a systematic way. Operation in reduced gravity enables enhanced control of liquid motion which can allow measurement of liquid transport properties. Examples of nucleation control, the thermodynamics of oxide contamination removal, and control of the chromium content of liquid aluminum oxide by high temperature containerless processes are presented. The feasibility of measuring temperature, emissivity, liquidus temperature, enthalpy, surface tension, density, viscosity, and thermal diffusivity are discussed in the final section of the paper.

Climate change and temperature-dependent biogeography: oxygen limitation of thermal tolerance in animals.

PubMed

Pörtner, H O

2001-04-01

Recent years have shown a rise in mean global temperatures and a shift in the geographical distribution of ectothermic animals. For a cause and effect analysis the present paper discusses those physiological processes limiting thermal tolerance. The lower heat tolerance in metazoa compared with unicellular eukaryotes and bacteria suggests that a complex systemic rather than molecular process is limiting in metazoa. Whole-animal aerobic scope appears as the first process limited at low and high temperatures, linked to the progressively insufficient capacity of circulation and ventilation. Oxygen levels in body fluids may decrease, reflecting excessive oxygen demand at high temperatures or insufficient aerobic capacity of mitochondria at low temperatures. Aerobic scope falls at temperatures beyond the thermal optimum and vanishes at low or high critical temperatures when transition to an anaerobic mitochondrial metabolism occurs. The adjustment of mitochondrial densities on top of parallel molecular or membrane adjustments appears crucial for maintaining aerobic scope and for shifting thermal tolerance. In conclusion, the capacity of oxygen delivery matches full aerobic scope only within the thermal optimum. At temperatures outside this range, only time-limited survival is supported by residual aerobic scope, then anaerobic metabolism and finally molecular protection by heat shock proteins and antioxidative defence. In a cause and effect hierarchy, the progressive increase in oxygen limitation at extreme temperatures may even enhance oxidative and denaturation stress. As a corollary, capacity limitations at a complex level of organisation, the oxygen delivery system, define thermal tolerance limits before molecular functions become disturbed.

A method to measure internal stray radiation of cryogenic infrared imaging systems under various ambient temperatures

NASA Astrophysics Data System (ADS)

Tian, Qijie; Chang, Songtao; Li, Zhou; He, Fengyun; Qiao, Yanfeng

2017-03-01

The suppression level of internal stray radiation is a key criterion for infrared imaging systems, especially for high-precision cryogenic infrared imaging systems. To achieve accurate measurement for internal stray radiation of cryogenic infrared imaging systems under various ambient temperatures, a measurement method, which is based on radiometric calibration, is presented in this paper. First of all, the calibration formula is deduced considering the integration time, and the effect of ambient temperature on internal stray radiation is further analyzed in detail. Then, an approach is proposed to measure the internal stray radiation of cryogenic infrared imaging systems under various ambient temperatures. By calibrating the system under two ambient temperatures, the quantitative relation between the internal stray radiation and the ambient temperature can be acquired, and then the internal stray radiation of the cryogenic infrared imaging system under various ambient temperatures can be calculated. Finally, several experiments are performed in a chamber with controllable inside temperatures to evaluate the effectiveness of the proposed method. Experimental results indicate that the proposed method can be used to measure internal stray radiation with high accuracy at various ambient temperatures and integration times. The proposed method has some advantages, such as simple implementation and the capability of high-precision measurement. The measurement results can be used to guide the stray radiation suppression and to test whether the internal stray radiation suppression performance meets the requirement or not.

European Science Notes. Volume 39, Number 10.

DTIC Science & Technology

1985-10-01

A.T. Hubbard (Santa Barbara, US), Electro- MODULEF--A MODULAR FINITE ELEMENT PRO- sorption at Well-Defined Surfaces; D.H. GRAM PACKAGE Kolb (Berlin...was described as having one sorption . of the highest theoretical energy densi- Finally, Despi6 described engineer- ties, about 2600 Wh/kg--a value 150...organic compounds , can be varied by compound these transport agents into changing the high temperature treatment organic solutions exhibiting high

Preparation of High-Quality FeV55N Using Ammonia as a Reductant and Nitrogen Source

NASA Astrophysics Data System (ADS)

Wu, Yue-Dong; Zhang, Guo-Hua; Chou, Kuo-Chih

2018-05-01

High-quality FeV55N has been prepared by using ammonia as a reductant and nitrogen source. The raw materials comprised ammonium vanadate and Fe2O3, which were first reduced and nitrided by ammonia to prepare FeV55N composite powders of VN and Fe2N. Subsequently, the composite powders were sintered at high temperature to obtain a bulk FeV55N alloy. The final products obtained by this method do not contain elemental Al, Si, or C impurities. Furthermore, the residual oxygen content of the final products can be reduced to 0.56 wt.%. After sintering, it is possible to obtain a FeV55N alloy with a density of up to 5.4 g/cm3.

Phase I Final Scientific Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Xijia; Fetvedt, Jeremy; Dimmig, Walker

This Final Scientific Report addresses the accomplishments achieved during Phase I of DE- FE0023985, Coal Syngas Combustor Development for Supercritical CO 2 Power Cycles. The primary objective of the project was to develop a coal syngas-fueled combustor design for use with high-pressure, high-temperature, oxy-fuel, supercritical CO 2 power cycles, with particular focus given to the conditions required by the Allam Cycle. The primary goals, from the Statement of Project Objectives, were to develop: (1) a conceptual design of a syngas-fueled combustor-turbine block for a 300MWe high-pressure, oxy-fuel, sCO2 power plant; (2) the preliminary design of a 5MWt test combustor; andmore » (3) the definition of a combustor test program. Accomplishments for each of these goals are discussed in this report.« less

A superhard, quenchable carbon polymorph formed by the room-temperature compression of graphite (Invited)

NASA Astrophysics Data System (ADS)

Wang, Y.; Kiefer, B.; Lee, K. K.

2010-12-01

As one of the revolutionary inventions of the 20th century, synthetic diamond has had a large impact on industry and on scientific research. However, the necessities of high pressures, high temperatures and a metal catalyst during the manufacturing of synthetic diamond make it energy consuming thus limits its availability and use. Here, we report on the synthesis of a superhard non-diamond material resulting from the compression of graphite above ~20 GPa at room temperature without the utilization of metal catalysts. The final product includes a nano-sized phase of carbon that is recoverable at ambient conditions. Furthermore, the ring cracks left on the diamond anvils suggest that the hardness of this post-graphite phase is at least comparable to that of diamond. We use high-resolution synchrotron x-ray diffraction and micro-Raman spectroscopy to monitor the structural transformation in graphite under high pressure and room temperature and find the transition to be sluggish. The possible crystal structure of the new, quenchable phase will be discussed and the time-dependent formation of this superhard post-graphite carbon will be addressed and compared to first-principle predictions.

ASME Material Challenges for Advanced Reactor Concepts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piyush Sabharwall; Ali Siahpush

2013-07-01

This study presents the material Challenges associated with Advanced Reactor Concept (ARC) such as the Advanced High Temperature Reactor (AHTR). ACR are the next generation concepts focusing on power production and providing thermal energy for industrial applications. The efficient transfer of energy for industrial applications depends on the ability to incorporate cost-effective heat exchangers between the nuclear heat transport system and industrial process heat transport system. The heat exchanger required for AHTR is subjected to a unique set of conditions that bring with them several design challenges not encountered in standard heat exchangers. The corrosive molten salts, especially at highermore » temperatures, require materials throughout the system to avoid corrosion, and adverse high-temperature effects such as creep. Given the very high steam generator pressure of the supercritical steam cycle, it is anticipated that water tube and molten salt shell steam generators heat exchanger will be used. In this paper, the ASME Section III and the American Society of Mechanical Engineers (ASME) Section VIII requirements (acceptance criteria) are discussed. Also, the ASME material acceptance criteria (ASME Section II, Part D) for high temperature environment are presented. Finally, lack of ASME acceptance criteria for thermal design and analysis are discussed.« less

Affordable, Robust Ceramic Joining Technology (ARCJoint) Developed

NASA Technical Reports Server (NTRS)

Steele, Gynelle C.

2001-01-01

Affordable, Robust Ceramic Joining Technology (ARCJoint) is a method for joining high temperature- resistant ceramic pieces together, establishing joints that are strong, and allowing joining to be done in the field. This new way of joining allows complex shapes to be formed by joining together geometrically simple shapes. The joining technology at NASA is one of the enabling technologies for the application of silicon-carbide-based ceramic and composite components in demanding and high-temperature applications. The technology is being developed and tested for high-temperature propulsion parts for aerospace use. Commercially, it can be used for joining ceramic pieces used for high temperature applications in the power-generating and chemical industries, as well as in the microelectronics industry. This innovation could yield big payoffs for not only the power-generating industry but also the Silicon Valley chipmakers. This technology, which was developed at the NASA Glenn Research Center by Dr. Mrityunjay Singh, is a two-step process involving first using a paste to join together ceramic pieces and bonding them by heating the joint to 110 to 120 C for between 10 and 20 min. This makes the joint strong enough to be handled for the final joining. Then, a silicon-based substance is applied to the joint and heated to 1400 C for 10 to 15 min. The resulting joint is as strong as the original ceramic material and can withstand the same high temperatures.

Development of Bio-Oil Commodity Fuel as a Refinery Feedstock from High Impact Algae Biomass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kastner, James; Mani, Sudhagar; Das, K. C.

A two-stage hydrothermal liquefaction (HTL) process was developed to 1) reduce nitrogen levels in algal oil, 2) generate a nitrogen rich stream with limited inhibitors for recycle and algae cultivation, and 3) improve downstream catalytic hydrodenitrogenation and hydrodeoxygenation of the algal oil to refinery intermediates. In the first stage, low temperature HTL was conducted at 125, 175, and 225°C at holding times ranging from 1 to 30 min (time at reaction temperature). A consortium of three algal strains, namely Chlorella sorokiniana, Chlorella minutissima, and Scenedesmus bijuga were used to grow and harvest biomass in a raceway system – this consortiummore » is called the UGA Raceway strain throughout the report. Subsequent analysis of the final harvested product indicated that only two strains predominated in the final harvest - Chlorella sorokiniana and Scenedesmus bijuga. Two additional strains representing a high protein (Spirulina platensis) and high lipid algae (Nannochloropsis) strains were also used in this study. These strains were purchased from suppliers. S. platensis biomass was provided by Earthrise Nutritionals LLC (Calipatria, CA) in dry powder form with defined properties, and was stored in airtight packages at 4°C prior to use. A Nannochloropsis paste from Reed Mariculture was purchased and used in the two-stage HTL/HDO experiments. The solids and liquids from this low temperature HTL pretreatment step were separated and analyzed, leading to the following conclusions. Overall, these results indicate that low temperature HTL (200-250°C) at short residence times (5-15 min) can be used to lyse algae cells and remove/separate protein and nitrogen before subsequent higher temperature HTL (for lipid and other polymer hydrolysis) and HDO. The significant reduction in nitrogen when coupled with low protein/high lipid algae cultivation methods at scale could significantly improve downstream catalytic HDO results. However, significant barriers and knowledge gaps exist that must be overcome and understood. The ability of the separated protein/nitrogen rich aqueous stream to support algae cultivation needs to be verified (and the kinetics of growth measured). The kinetics of algae hydrothermal liquefaction on a mechanistic basis needs to be measured and understood. A better understanding of Maillard reactions during algae HTL is needed. And the impact of Maillard reaction products and incompletely hydrolyzed cell wall components on catalyst deactivation during HDO needs to be understood. Finally, an inexpensive HDO process and associated catalyst capable of converting the algal oil to hydrocarbons needs to be developed.« less

A study of universal modulation techniques applied to satellite data collection

NASA Technical Reports Server (NTRS)

1980-01-01

A universal modulation and frequency control system for use with data collection platform (DCP) transmitters is examined. The final design discussed can, under software/firmwave control, generate all of the specific digital data modulation formats currently used in the NASA satellite data collection service and can simultaneously synthesize the proper RF carrier frequencies employed. A novel technique for DCP time and frequency control is presented. The emissions of NBS radio station WWV/WWVH are received, detected, and finally decoded in microcomputer software to generate a highly accurate time base for the platform; with the assistance of external hardware, the microcomputer also directs the recalibration of all DCP oscillators to achieve very high frequency accuracies and low drift rates versus temperature, supply voltage, and time. The final programmable DCP design also employs direct microcomputer control of data reduction, formatting, transmitter switching, and system power management.

High temperature chlorosilane corrosion of iron and AISI 316L stainless steel

NASA Astrophysics Data System (ADS)

Aller, Joshua Loren

Chlorosilane gas streams are used at high temperatures (>500°C) throughout the semiconductor, polycrystalline silicon, and fumed silica industries, primarily as a way to refine, deposit, and produce silicon and silicon containing materials. The presence of both chlorine and silicon in chlorosilane species creates unique corrosion environments due to the ability of many metals to form both metal-chlorides and metal-silicides, and it is further complicated by the fact that many metal-chlorides are volatile at high-temperatures while metal-silicides are generally stable. To withstand the uniquely corrosive environments, expensive alloys are often utilized, which increases the cost of final products. This work focuses on the corrosion behavior of iron, the primary component of low-cost alloys, and AISI 316L, a common low-cost stainless steel, in environments representative of industrial processes. The experiments were conducted using a customized high temperature chlorosilane corrosion system that exposed samples to an atmospheric pressure, high temperature, chlorosilane environment with variable input amounts of hydrogen, silicon tetrachloride, and hydrogen chloride plus the option of embedding samples in silicon during the exposure. Pre and post exposure sample analysis including scanning electron microscopy, x-ray diffraction, energy dispersive x-ray spectroscopy, and gravimetric analysis showed the surface corrosion products varied depending on the time, temperature, and environment that the samples were exposed to. Most commonly, a volatile chloride product formed first, followed by a stratified metal silicide layer. The chlorine and silicon activities in the corrosion environment were changed independently and were found to significantly alter the corrosion behavior; a phenomenon supported by computational thermodynamic equilibrium simulations. It was found that in comparable environments, the stainless steel corroded significantly less than the pure iron. This is likely due to the alloying elements present in stainless steel that promote formation of other stable silicides. Mechanistic models were developed to describe the formation and evolution of metal silicide and/or metal chloride surface corrosion products in chlorosilane environments. These models will help inform materials selection and/or support process development for next-generation chlorosilane-based production and deposition systems. The implementation of low cost materials of construction in these systems could lower the cost of final products in these industries.

Comparisons of Gas-phase Temperature Measurements in a Flame Using Thin-Filament Pyrometry and Thermocouples

NASA Technical Reports Server (NTRS)

Struk, Peter; Dietrich, Daniel; Valentine, Russell; Feier, Ioan

2003-01-01

Less-intrusive, fast-responding, and full-field temperature measurements have long been a desired tool for the research community. Recently, the emission of a silicon-carbide (SiC) fiber placed in a flowing hot (or reacting) gas has been used to measure the temperature profile along the length of the fiber. The relationship between the gas and fiber temperature comes from an energy balance on the fiber. In the present work, we compared single point flame temperature measurements using thin-filament pyrometry (TFP) and thermocouples. The data was from vertically traversing a thermocouple and a SiC fiber through a methanol/air diffusion flame of a porous-metal wick burner. The results showed that the gas temperature using the TFP technique agreed with the thermocouple measurements (25.4 m diameter wire) within 3.5% for temperatures above 1200 K. Additionally, we imaged the entire SiC fiber (with a spatial resolution of 0.14 mm) while it was in the flame using a high resolution CCD camera. The intensity level along the fiber length is a function of the temperature. This results in a one-dimensional temperature profiles at various heights above the burner wick. This temperature measurement technique, while having a precision of less than 1 K, showed data scatter as high as 38 K. Finally, we discuss the major sources of uncertainty in gas temperature measurement using TFP.

Integrity of nuclear genomic deoxyribonucleic acid in cooked meat: Implications for food traceability.

PubMed

Aslan, O; Hamill, R M; Sweeney, T; Reardon, W; Mullen, A M

2009-01-01

It is essential to isolate high-quality DNA from muscle tissue for PCR-based applications in traceability of animal origin. We wished to examine the impact of cooking meat to a range of core temperatures on the quality and quantity of subsequently isolated genomic (specifically, nuclear) DNA. Triplicate steak samples were cooked in a water bath (100 degrees C) until their final internal temperature was 75, 80, 85, 90, 95, or 100 degrees C, and DNA was extracted. Deoxyribonucleic acid quantity was significantly reduced in cooked meat samples compared with raw (6.5 vs. 56.6 ng/microL; P < 0.001), but there was no relationship with cooking temperature. Quality (A(260)/A(280), i.e., absorbance at 260 and 280 nm) was also affected by cooking (P < 0.001). For all 3 genes, large PCR amplicons (product size >800 bp) were observed only when using DNA from raw meat and steak cooked to lower core temperatures. Small amplicons (<200 bp) were present for all core temperatures. Cooking meat to high temperatures thus resulted in a reduced overall yield and probable fragmentation of DNA to sizes less than 800 bp. Although nuclear DNA is preferable to mitochondrial DNA for food authentication, it is less abundant, and results suggest that analyses should be designed to use small amplicon sizes for meat cooked to high core temperatures.

Evaluation, construction and endurance testing of compression sealed pyrolytic boron nitride slot insulation

NASA Technical Reports Server (NTRS)

Grant, W. L.

1969-01-01

A high-temperature statorette, consisting of an iron-27 percent cobalt magnetic lamination stack and nickel-clad silver conductors, was tested with pyrolytic boron nitride slot insulation. Temperatures were measured in each test to determine characteristics of slot linear heat conductance from statorette conductors. Testing was carried out to temperatures of approximately 1500 F in a vacuum environment of 10-8 torr. Three assemblies were built and tested, each having a different room temperature slot clearance. The final statorette assembly was subjected to a 100-hour vacuum aging test at 1400 F followed by 25 thermal cycles. Temperature data from the three assemblies showed that decreasing slot clearance and increasing compression loading did enhance heat transfer. The temperature difference between slot and lamination at 1400 F increased 4 F during the thermal aging and an additional 10 F during the 25 thermal cycles.

Estimating stellar effective temperatures and detected angular parameters using stochastic particle swarm optimization

NASA Astrophysics Data System (ADS)

Zhang, Chuan-Xin; Yuan, Yuan; Zhang, Hao-Wei; Shuai, Yong; Tan, He-Ping

2016-09-01

Considering features of stellar spectral radiation and sky surveys, we established a computational model for stellar effective temperatures, detected angular parameters and gray rates. Using known stellar flux data in some bands, we estimated stellar effective temperatures and detected angular parameters using stochastic particle swarm optimization (SPSO). We first verified the reliability of SPSO, and then determined reasonable parameters that produced highly accurate estimates under certain gray deviation levels. Finally, we calculated 177 860 stellar effective temperatures and detected angular parameters using data from the Midcourse Space Experiment (MSX) catalog. These derived stellar effective temperatures were accurate when we compared them to known values from literatures. This research makes full use of catalog data and presents an original technique for studying stellar characteristics. It proposes a novel method for calculating stellar effective temperatures and detecting angular parameters, and provides theoretical and practical data for finding information about radiation in any band.

High-resolution daily gridded datasets of air temperature and wind speed for Europe

NASA Astrophysics Data System (ADS)

Brinckmann, S.; Krähenmann, S.; Bissolli, P.

2015-08-01

New high-resolution datasets for near surface daily air temperature (minimum, maximum and mean) and daily mean wind speed for Europe (the CORDEX domain) are provided for the period 2001-2010 for the purpose of regional model validation in the framework of DecReg, a sub-project of the German MiKlip project, which aims to develop decadal climate predictions. The main input data sources are hourly SYNOP observations, partly supplemented by station data from the ECA&D dataset (http://www.ecad.eu). These data are quality tested to eliminate erroneous data and various kinds of inhomogeneities. Grids in a resolution of 0.044° (5 km) are derived by spatial interpolation of these station data into the CORDEX area. For temperature interpolation a modified version of a regression kriging method developed by Krähenmann et al. (2011) is used. At first, predictor fields of altitude, continentality and zonal mean temperature are chosen for a regression applied to monthly station data. The residuals of the monthly regression and the deviations of the daily data from the monthly averages are interpolated using simple kriging in a second and third step. For wind speed a new method based on the concept used for temperature was developed, involving predictor fields of exposure, roughness length, coastal distance and ERA Interim reanalysis wind speed at 850 hPa. Interpolation uncertainty is estimated by means of the kriging variance and regression uncertainties. Furthermore, to assess the quality of the final daily grid data, cross validation is performed. Explained variance ranges from 70 to 90 % for monthly temperature and from 50 to 60 % for monthly wind speed. The resulting RMSE for the final daily grid data amounts to 1-2 °C and 1-1.5 m s-1 (depending on season and parameter) for daily temperature parameters and daily mean wind speed, respectively. The datasets presented in this article are published at http://dx.doi.org/10.5676/DWD_CDC/DECREG0110v1.

Influence of Regenerator Material on Performance of a 6K High Frequency Pulse Tube Cryocooler

NASA Astrophysics Data System (ADS)

J, Quan; YJ, Liu; XY, Li; JT, Liang

2017-12-01

As very low temperature high frequency pulse tube cryocooler has been a hot topic in the field of pulse tube cryocooler, improving the cryocooler’s performance is a common goal of researchers. By integrating the former results, we found that regenerator material is a key factor for the improvement of pulse tube cryocooler’s efficiency. In this paper, methods of simulation and experiment were used to investigate the influence of stacking style on performance of 6K high frequency pulse tube cryocooler. Finally, the lowest temperature has dropped from 8.8K to 6.7K and more than 10mW of cooling power is achieved at 8K with a two-stage thermally coupled high frequency pulse tube cryocooler. The results make the space application of NbN terahertz detectors possible.

Wheat seed weight and quality differ temporally in sensitivity to warm or cool conditions during seed development and maturation

PubMed Central

Nasehzadeh, M

2017-01-01

Abstract Background and aims Short periods of extreme temperature may affect wheat (Triticum aestivum) seed weight, but also quality. Temporal sensitivity to extreme temperature during seed development and maturation was investigated. Methods Plants of ‘Tybalt’ grown at ambient temperature were moved to growth cabinets at 29/20°C or 34/20°C (2010), or 15/10°C or 34/20°C (2011), for successive 7-d periods from 7 DAA (days after anthesis) onwards, and also 7–65 DAA in 2011. Seed samples were harvested serially and moisture content, weight, ability to germinate, subsequent longevity in air-dry storage and bread-making quality were determined. Key Results High temperature (34/20°C) reduced final seed weight, with greatest temporal sensitivity at 7–14 or 14–21 DAA. Several aspects of bread-making quality were also most sensitive to high temperature then, but whereas protein quality decreased protein and sulphur concentrations improved. Early exposure to high temperature provided earlier development of ability to germinate and tolerate desiccation, but had little effect on maximum germination capacity. All treatments at 15/10°C resulted in ability to germinate declining between 58 and 65 DAA. Early exposure to high temperature hastened improvement in seed storage longevity, but the subsequent decline in late maturation preceded that in the control. Long (7–65 DAA) exposure to 15/10°C disrupted the development of seed longevity, with no improvement after seed filling ended. Longevity improved during maturation drying in other treatments. Early (7–14 DAA) exposure to high temperature reduced and low temperature increased subsequent longevity at harvest maturity, whereas late (35 or 42–49 DAA) exposure to high temperature increased and low temperature reduced it. Conclusions Temporal sensitivity to extreme temperature was detected. It varied considerably amongst the contrasting seed variables investigated. Subsequent seed longevity at harvest maturity responded negatively to temperature early in development, but positively later in development and throughout maturation. PMID:28637252

Characterizing the Chemical Stability of High Temperature Materials for Application in Extreme Environments

NASA Technical Reports Server (NTRS)

Opila, Elizabeth

2005-01-01

The chemical stability of high temperature materials must be known for use in the extreme environments of combustion applications. The characterization techniques available at NASA Glenn Research Center vary from fundamental thermodynamic property determination to material durability testing in actual engine environments. In this paper some of the unique techniques and facilities available at NASA Glenn will be reviewed. Multiple cell Knudsen effusion mass spectrometry is used to determine thermodynamic data by sampling gas species formed by reaction or equilibration in a Knudsen cell held in a vacuum. The transpiration technique can also be used to determine thermodynamic data of volatile species but at atmospheric pressures. Thermodynamic data in the Si-O-H(g) system were determined with this technique. Free Jet Sampling Mass Spectrometry can be used to study gas-solid interactions at a pressure of one atmosphere. Volatile Si(OH)4(g) was identified by this mass spectrometry technique. A High Pressure Burner Rig is used to expose high temperature materials in hydrocarbon-fueled combustion environments. Silicon carbide (SiC) volatility rates were measured in the burner rig as a function of total pressure, gas velocity and temperature. Finally, the Research Combustion Lab Rocket Test Cell is used to expose high temperature materials in hydrogen/oxygen rocket engine environments to assess material durability. SiC recession due to rocket engine exposures was measured as a function of oxidant/fuel ratio, temperature, and total pressure. The emphasis of the discussion for all techniques will be placed on experimental factors that must be controlled for accurate acquisition of results and reliable prediction of high temperature material chemical stability.

Raman scattering in single-crystal sapphire at elevated temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thapa, Juddha; Liu, Bo; Woodruff, Steven D.

Sapphire is a widely used high-temperature material and this work presents thorough characterization of all the measurable Raman scattering modes in sapphire and their temperature dependencies. Here, Raman scattering in bulk sapphire rods is measured from room temperature to 1081 °C and is illustrated as a method of noncontact temperature measurement. A single-line argon ion laser at 488 nm was used to excite the sapphire rods inside a cylindrical furnace. All the anti-Stokes peaks (or lines) were observable through the entire temperature range of interest, while Stokes peaks were observable until they were obscured by background thermal emission. Temperature measurementsmore » were found to be most reliable for A 1g and E g modes using the peaks at ±418, ±379, +578, +645, and, +750 cm -1 (+ and – are designated for Stokes and anti-Stokes peaks respectively). The 418 cm -1 peak was found to be the most intense peak. The temperature dependence of peak position, peak width, and peak area of the ±418 and ±379 peaks is presented. For +578, +645 and +750, the temperature dependence of peak position is presented. The peaks’ spectral positions provide the most precise temperature information within the experimental temperature range. Finally, the resultant temperature calibration curves are given, which indicate that sapphire can be used in high-temperature Raman thermometry with an accuracy of about 1.38°C average standard deviation over the entire >1000°C temperature range.« less

Raman scattering in single-crystal sapphire at elevated temperatures

DOE PAGES

Thapa, Juddha; Liu, Bo; Woodruff, Steven D.; ...

2017-10-25

Sapphire is a widely used high-temperature material and this work presents thorough characterization of all the measurable Raman scattering modes in sapphire and their temperature dependencies. Here, Raman scattering in bulk sapphire rods is measured from room temperature to 1081 °C and is illustrated as a method of noncontact temperature measurement. A single-line argon ion laser at 488 nm was used to excite the sapphire rods inside a cylindrical furnace. All the anti-Stokes peaks (or lines) were observable through the entire temperature range of interest, while Stokes peaks were observable until they were obscured by background thermal emission. Temperature measurementsmore » were found to be most reliable for A 1g and E g modes using the peaks at ±418, ±379, +578, +645, and, +750 cm -1 (+ and – are designated for Stokes and anti-Stokes peaks respectively). The 418 cm -1 peak was found to be the most intense peak. The temperature dependence of peak position, peak width, and peak area of the ±418 and ±379 peaks is presented. For +578, +645 and +750, the temperature dependence of peak position is presented. The peaks’ spectral positions provide the most precise temperature information within the experimental temperature range. Finally, the resultant temperature calibration curves are given, which indicate that sapphire can be used in high-temperature Raman thermometry with an accuracy of about 1.38°C average standard deviation over the entire >1000°C temperature range.« less

Elasticity and Anelasticity of Materials from Time-Resolved X-ray Diffraction

NASA Astrophysics Data System (ADS)

Sinogeikin, S. V.; Smith, J.; Lin, C.; Bai, L.; Rod, E.; Shen, G.

2014-12-01

Recent advances in synchrotron sources, x-ray optics, area detectors, and sample environment control have enabled many time-resolved experimental techniques for studying materials at extreme pressure and temperature conditions. The High Pressure Collaborative Access Team (HPCAT) at the Advanced Photon Source has made a sustained effort to develop and assemble a powerful collection of high-pressure apparatus for time-resolved research, and considerable time has been invested in developing techniques for collecting high-quality time-resolved x-ray scattering data. In this talk we will outline recently developed capabilities at HPCAT for studying elasticity and anelasticity of minerals using fast compression and cyclic compression-decompression. A few recent studies will be highlighted. For example, with fast x-ray area detectors having millisecond time resolution, accurate thermal equations of state of materials at temperatures up to 1000K and megabar pressures can be collected in a matter of seconds using membrane-driven diamond anvil cells (DAC), yielding unprecedented time and pressure resolution of true isotherms. Short duration of the experiments eliminates temperature variation during the experiments and in general allows volume measurements at higher pressures and temperatures. Alternatively, high-frequency (kilohertz range) radial diffraction measurements in a panoramic DAC combined with fast, precise cyclic loading/unloading by piezo drive could provide the short time scale necessary for studying rheology of minerals from the elastic response and lattice relaxation as a function of pressure, temperature and strain rate. Finally, we consider some possible future applications for time-resolved high-pressure, high-temperature research of mantle minerals.

46 CFR 112.50-1 - General.

Code of Federal Regulations, 2012 CFR

2012-10-01

... sounds on low oil pressure and high cooling water temperature. (i) If the prime mover is a gas turbine... Emergency Diesel and Gas Turbine Engine Driven Generator Sets § 112.50-1 General. (a) The prime mover of a... thermostatically-controlled electric water-jacket heater connected to the final emergency bus is permitted. (e) The...

46 CFR 112.50-1 - General.

Code of Federal Regulations, 2013 CFR

2013-10-01

... sounds on low oil pressure and high cooling water temperature. (i) If the prime mover is a gas turbine... Emergency Diesel and Gas Turbine Engine Driven Generator Sets § 112.50-1 General. (a) The prime mover of a... thermostatically-controlled electric water-jacket heater connected to the final emergency bus is permitted. (e) The...

46 CFR 112.50-1 - General.

Code of Federal Regulations, 2014 CFR

2014-10-01

... sounds on low oil pressure and high cooling water temperature. (i) If the prime mover is a gas turbine... Emergency Diesel and Gas Turbine Engine Driven Generator Sets § 112.50-1 General. (a) The prime mover of a... thermostatically-controlled electric water-jacket heater connected to the final emergency bus is permitted. (e) The...

Final Environmental Impact Statement (EIS) for the Space Nuclear Thermal Propulsion (SNTP) program

NASA Astrophysics Data System (ADS)

1991-09-01

A program has been proposed to develop the technology and demonstrate the feasibility of a high-temperature particle bed reactor (PBR) propulsion system to be used to power an advanced second stage nuclear rocket engine. The purpose of this Final Environmental Impact Statement (FEIS) is to assess the potential environmental impacts of component development and testing, construction of ground test facilities, and ground testing. Major issues and goals of the program include the achievement and control of predicted nuclear power levels; the development of materials that can withstand the extremely high operating temperatures and hydrogen flow environments; and the reliable control of cryogenic hydrogen and hot gaseous hydrogen propellant. The testing process is designed to minimize radiation exposure to the environment. Environmental impact and mitigation planning are included for the following areas of concern: (1) Population and economy; (2) Land use and infrastructure; (3) Noise; (4) Cultural resources; (5) Safety (non-nuclear); (6) Waste; (7) Topography; (8) Geology; (9) Seismic activity; (10) Water resources; (11) Meteorology/Air quality; (12) Biological resources; (13) Radiological normal operations; (14) Radiological accidents; (15) Soils; and (16) Wildlife habitats.

A high temperature superconductor notch filter for the Sardinia Radio Telescope

NASA Astrophysics Data System (ADS)

Bolli, Pietro; Cresci, Luca; Huang, Frederick; Mariotti, Sergio; Panella, Dario

2018-04-01

A High Temperature Superconductor filter operating in the C-band between 4200 and 5600 MHz has been developed for one of the radio astronomical receivers of the Sardinia Radio Telescope. The motivation was to attenuate an interference from a weather radar at 5640 MHz, whose power level exceeds the linear region of the first active stages of the receiver. A very sharp transition after the nominal maximum passband frequency is reached by combining a 6th order band-pass filter with a 6th order stop-band. This solution is competitive with an alternative layout based on a cascaded triplet filter. Three units of the filter have been measured with two different calibration approaches to investigate pros and cons of each, and data repeatability. The final performance figures of the filters are: ohmic losses of the order of 0.15-0.25 dB, matching better than -15 dB, and -30 dB attenuation at 5640 MHz. Finally, a more accurate model of the connection between external connector and microstrip shows a better agreement between simulations and experimental data.

Molecular Beam Epitaxy of lithium niobium oxide multifunctional materials

NASA Astrophysics Data System (ADS)

Tellekamp, M. Brooks; Shank, Joshua C.; Doolittle, W. Alan

2017-04-01

The role of stoichiometry and growth temperature in the preferential nucleation of material phases in the Li-Nb-O family are explored yielding an empirical growth phase diagram. It is shown that while single parameter variation often produces multi-phase films, combining substrate temperature control with the previously published lithium flux limited growth allows the repeatable growth of high quality single crystalline films of many different oxide phases. Higher temperatures (800-1050 °C) than normally used in MBE were necessary to achieve high quality materials. At these temperatures the desorption of surface species is shown to play an important role in film composition. Using this method single phase films of NbO, NbO2, LiNbO2, Li3NbO4, LiNbO3, and LiNb3O8 have been achieved in the same growth system, all on c-plane sapphire. Finally, the future of these films in functional oxide heterostructures is briefly discussed.

Effects of Vacancy Concentration and Temperature on Mechanical Properties of Single-Crystal γ-TiAl Based on Molecular Dynamics Simulation

NASA Astrophysics Data System (ADS)

Ruicheng, Feng; Hui, Cao; Haiyan, Li; Zhiyuan, Rui; Changfeng, Yan

2018-01-01

Molecular dynamics simulation is used to analyze tensile strength and elastic modulus under different temperatures and vacancy concentrations. The effects of temperature and vacancy concentration on the mechanical properties of γ-TiAl alloy are investigated. The results show that the ultimate stress, ultimate strain and elastic modulus decrease nonlinearly with increasing temperature and vacancy concentration. As the temperature increases, the plastic of material is reinforced. The influence of temperature on strength and elastic modulus is larger than that of vacancy concentration. The evolution process of vacancy could be observed clearly. Furthermore, vacancies with different concentrations develop into voids first as a function of external forces or other factors, micro cracks evolve from those voids, those micro cracks then converge to a macro crack, and fracture will finally occur. The vacancy evolution process cannot be observed clearly owing to the thermal motion of atoms at high temperature. In addition, potential energy is affected by both temperature and vacancy concentration.

High Temperature Low Cycle Fatigue Data for Three High Strength Nickel-Base Superalloys.

DTIC Science & Technology

1980-06-01

Stent , Mar-Test Inc. Cincinnati, Ohio June 1980 TECHNICAL REPORT AFWAL-TR-80-4077 Final Report for Period May 1976 - September 1978 Approved for...generally high in concentrations of calcium, silicon , aluminum, and magnesium. These inclusions were up to 100p in length and ranged from spherical to...used for this study were produced from Federal Mogal Inc. powder Heat 454. The composition of the powder is contained in Table 3. The powder was 100

Phonon quarticity induced by changes in phonon-tracked hybridization during lattice expansion and its stabilization of rutile TiO 2

DOE PAGES

Lan, Tian; Li, Chen W.; Hellman, O.; ...

2015-08-11

Although the rutile structure of TiO 2 is stable at high temperatures, the conventional quasiharmonic approximation predicts that several acoustic phonons decrease anomalously to zero frequency with thermal expansion, incorrectly predicting a structural collapse at temperatures well below 1000 K. In this paper, inelastic neutron scattering was used to measure the temperature dependence of the phonon density of states (DOS) of rutile TiO 2 from 300 to 1373 K. Surprisingly, these anomalous acoustic phonons were found to increase in frequency with temperature. First-principles calculations showed that with lattice expansion, the potentials for the anomalous acoustic phonons transform from quadratic tomore » quartic, stabilizing the rutile phase at high temperatures. In these modes, the vibrational displacements of adjacent Ti and O atoms cause variations in hybridization of 3d electrons of Ti and 2p electrons of O atoms. Finally, with thermal expansion, the energy variation in this “phonon-tracked hybridization” flattens the bottom of the interatomic potential well between Ti and O atoms, and induces a quarticity in the phonon potential.« less

Formation of highly preferred orientation of β-Sn grains in solidified Cu/SnAgCu/Cu micro interconnects under temperature gradient effect

NASA Astrophysics Data System (ADS)

Zhao, N.; Zhong, Y.; Dong, W.; Huang, M. L.; Ma, H. T.; Wong, C. P.

2017-02-01

β-Sn grain orientation and configuration are becoming crucial factors to dominate the lifetime of solder interconnects in three-dimensional integrated circuit packaging. In this paper, we found that a temperature gradient during solidification significantly dominated the orientation and configuration of the final β-Sn grains in Cu/SnAgCu/Cu micro interconnects. Being different from the random orientations and growth fronts meeting or cyclic twin boundary forming near the center after homogeneous temperature bonding, the β-Sn grains solidified under a certain temperature gradient were observed to follow a highly preferred orientation with their c-axis departing from the direction of temperature gradient by about 45°-88°. Meanwhile, these preferred oriented β-Sn grains consisted of low angle grain boundary structures with misorientation in the range of 0°-15°. The mechanism was explained in terms of the anisotropy and directional growth of β-Sn grains. The results pave the way for grain orientation control in 3D packaging technology.

Some Physical and Computational Issues in Land Surface Data Assimilation of Satellite Skin Temperatures

NASA Astrophysics Data System (ADS)

Mackaro, Scott M.; McNider, Richard T.; Biazar, Arastoo Pour

2012-03-01

Skin temperatures that reflect the radiating temperature of a surface observed by infrared radiometers are one of the most widely available products from polar orbiting and geostationary satellites and the most commonly used satellite data in land surface assimilation. Past work has indicated that a simple land surface scheme with a few key parameters constrained by observations such as skin temperatures may be preferable to complex land use schemes with many unknown parameters. However, a true radiating skin temperature is sometimes not a prognostic variable in weather forecast models. Additionally, recent research has shown that skin temperatures cannot be directly used in surface similarity forms for inferring fluxes. This paper examines issues encountered in using satellite derived skin temperatures to improve surface flux specifications in weather forecast and air quality models. Attention is given to iterations necessary when attempting to nudge the surface energy budget equation to a desired state. Finally, the issue of mathematical operator splitting is examined in which the surface energy budget calculations are split with the atmospheric vertical diffusion calculations. However, the high level of connectivity between the surface and first atmospheric level means that the operator splitting leads to high frequency oscillations. These oscillations may hinder the assimilation of skin temperature derived moisture fluxes.

Phase-Transformation Ductilization of Brittle High-Entropy Alloys via Metastability Engineering

DOE PAGES

Huang, Hailong; Wu, Yuan; He, Junyang; ...

2017-06-07

High-entropy alloys (HEAs) in which interesting physical, chemical, and structural properties are being continuously revealed have recently attracted extensive attention. Body-centered cubic (bcc) HEAs, particularly those based on refractory elements are promising for high-temperature application but generally fail by early cracking with limited plasticity at room temperature, which limits their malleability and widespread uses. In this paper, the “metastability-engineering” strategy is exploited in brittle bcc HEAs via tailoring the stability of the constituent phases, and transformation-induced ductility and work-hardening capability are successfully achieved. Finally, this not only sheds new insights on the development of HEAs with excellent combination of strengthmore » and ductility, but also has great implications on overcoming the long-standing strength–ductility tradeoff of metallic materials in general.« less

Phase-Transformation Ductilization of Brittle High-Entropy Alloys via Metastability Engineering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Hailong; Wu, Yuan; He, Junyang

High-entropy alloys (HEAs) in which interesting physical, chemical, and structural properties are being continuously revealed have recently attracted extensive attention. Body-centered cubic (bcc) HEAs, particularly those based on refractory elements are promising for high-temperature application but generally fail by early cracking with limited plasticity at room temperature, which limits their malleability and widespread uses. In this paper, the “metastability-engineering” strategy is exploited in brittle bcc HEAs via tailoring the stability of the constituent phases, and transformation-induced ductility and work-hardening capability are successfully achieved. Finally, this not only sheds new insights on the development of HEAs with excellent combination of strengthmore » and ductility, but also has great implications on overcoming the long-standing strength–ductility tradeoff of metallic materials in general.« less

Cryogenic cooling for high power laser amplifiers

NASA Astrophysics Data System (ADS)

Perin, J. P.; Millet, F.; Divoky, M.; Rus, B.

2013-11-01

Using DPSSL (Diode Pumped Solid State Lasers) as pumping technology, PW-class lasers with enhanced repetition rates are developed. Each of the Yb YAG amplifiers will be diode-pumped at a wavelength of 940 nm. This is a prerequisite for achieving high repetition rates (light amplification duration 1 millisecond and repetition rate 10 Hz). The efficiency of DPSSL is inversely proportional to the temperature, for this reason the slab amplifier have to be cooled at a temperature in the range of 100 K-170 K with a heat flux of 1 MW*m-2. This paper describes the thermo-mechanical analysis for the design of the amplification laser head, presents a preliminary proposal for the required cryogenic cooling system and finally outlines the gain of cryogenic operation for the efficiency of high pulsed laser.

DOE Office of Scientific and Technical Information (OSTI.GOV)

El-Atwani, Osman; Nathaniel II, James E.; Leff, Asher C.

Nanocrystalline materials are radiation-tolerant materials’ candidates due to their high defect sink density. Here, nanocrystalline iron films were irradiated with 10 keV helium ions in situ in a transmission electron microscope at elevated temperatures. Grain-size-dependent bubble density changes and denuded zone occurrence were observed at 700 K, but not at 573 K. This transition, attributed to increased helium–vacancy migration at elevated temperatures, suggests that nanocrystalline microstructures are more resistant to swelling at 700 K due to decreased bubble density. Finally, denuded zone formation had no correlation with grain size and misorientation angle under the conditions studied.

Earth Observing-1 Advanced Land Imager: Dark Current and Noise Characterization and Anomalous Detectors

NASA Technical Reports Server (NTRS)

Mendenhall, J. A.

2001-01-01

The dark current and noise characteristics of the Earth Observing-1 Advanced Land Imager measured during ground calibration at MIT Lincoln Laboratory are presented. Data were collected for the nominal focal plane operating temperature of 220 K as well as supplemental operating temperatures (215 and 225 K). Dark current baseline values are provided, and noise characterization includes the evaluation of white, coherent, low frequency, and high frequency components. Finally, anomalous detectors, characterized by unusual dark current, noise, gain, or cross-talk properties are investigated.

Two-step oxalate approach for the preparation of high performance LiNi0.5Mn1.5O4 cathode material with high voltage

NASA Astrophysics Data System (ADS)

Liu, Zushan; Jiang, Yangmei; Zeng, Xiaoyuan; Xiao, Guan; Song, Huiyu; Liao, Shijun

2014-02-01

A high voltage cathode material, LiNi0.5Mn1.5O4, is synthesized with a two-step approach, in which the nickel-manganese oxalate precipitate is firstly obtained by adding oxalic acid to the solution of nickel and manganese ions precursors, followed by calcining the oxalates to obtain spinel nickel-manganese oxide, incorporating lithium ions with ball milling and calcining at 900 °C for 15 h. The materials are characterized with TG, XRD, SEM, BET and FTIR; it is revealed that both nickel-manganese oxide and final LiNi0.5Mn1.5O4 have well defined spinel structure. The LiNi0.5Mn1.5O4 spinel materials exhibit high capacities and good cyclic stability, the capacity of the materials is in the range from 126 to 136 mAh -1, depending on the calcining temperatures. The sample calcined at an optimal temperature of 900 °C exhibits best performance, the capacity is high up to 136 mAh g-1 at tenth cycle and the capacity retention after 50 cycles is 93%. For the sample prepared by mixing and milling oxalate with lithium salt, the discharge capacity is only 115 mAh g-1. We suggest that the spinel oxide derived from oxalate may play an important role for the high performance and high stability of the final cathode materials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Jianfeng, E-mail: hjf@bit.edu.cn; Dai, Jin, E-mail: daijing491@gmail.com; Li, Jing, E-mail: jinglichina@139.com

The human islet amyloid polypeptide (hIAPP) co-operates with insulin to maintain glycemic balance. It also constitutes the amyloid plaques that aggregate in the pancreas of type-II diabetic patients. We have performed extensive in silico investigations to analyse the structural landscape of monomeric hIAPP, which is presumed to be intrinsically disordered. For this, we construct from first principles a highly predictive energy function that describes a monomeric hIAPP observed in a nuclear magnetic resonance experiment, as a local energy minimum. We subject our theoretical model of hIAPP to repeated heating and cooling simulations, back and forth between a high temperature regimemore » where the conformation resembles a random walker and a low temperature limit where no thermal motions prevail. We find that the final low temperature conformations display a high level of degeneracy, in a manner which is fully in line with the presumed intrinsically disordered character of hIAPP. In particular, we identify an isolated family of α-helical conformations that might cause the transition to amyloidosis, by nucleation.« less

The influence of activating agents on the performance of rice husk-based carbon for sodium lauryl sulfate and chrome (Cr) metal adsorptions

NASA Astrophysics Data System (ADS)

Arneli; Safitri, Z. F.; Pangestika, A. W.; Fauziah, F.; Wahyuningrum, V. N.; Astuti, Y.

2017-02-01

This research aims to study the influence of activating agents to produce rice husk based-carbon with high adsorption capacity and efficiency for either hazardous organic molecules or heavy metals which are unfriendly for the environment. Firstly, rice husk was burned by pyrolysis at different temperatures to produce rice husk-based carbon. To improve its ability as an adsorbent, carbon was treated with activating agents, namely, H3PO4 and KOH at room and high temperature (420 °C). The performance of carbon was then tested by contacting it with surfactant (SLS). Finally, the surfactant-modified active carbon was applied for chrome metal removal. The result shows that activation of carbon using phosphate acid (H3PO4) was more effective than potassium hydroxide (KOH) conducted at high temperature to adsorb sodium lauryl sulfate (SLS) and chrome metal with the adsorption capacity 1.50 mgg-1 and 0.375 mgg-1, respectively.

Aspects of structural landscape of human islet amyloid polypeptide

NASA Astrophysics Data System (ADS)

He, Jianfeng; Dai, Jin; Li, Jing; Peng, Xubiao; Niemi, Antti J.

2015-01-01

The human islet amyloid polypeptide (hIAPP) co-operates with insulin to maintain glycemic balance. It also constitutes the amyloid plaques that aggregate in the pancreas of type-II diabetic patients. We have performed extensive in silico investigations to analyse the structural landscape of monomeric hIAPP, which is presumed to be intrinsically disordered. For this, we construct from first principles a highly predictive energy function that describes a monomeric hIAPP observed in a nuclear magnetic resonance experiment, as a local energy minimum. We subject our theoretical model of hIAPP to repeated heating and cooling simulations, back and forth between a high temperature regime where the conformation resembles a random walker and a low temperature limit where no thermal motions prevail. We find that the final low temperature conformations display a high level of degeneracy, in a manner which is fully in line with the presumed intrinsically disordered character of hIAPP. In particular, we identify an isolated family of α-helical conformations that might cause the transition to amyloidosis, by nucleation.

Electro optical system to measure strains at high temperature

NASA Astrophysics Data System (ADS)

Sciammarella, Cesar A.

1991-01-01

The goals of this proposal were to develop a prototype of an electro-optics system for the measurement of strains in structures at high temperatures and to perform a test under field conditions. In the research task section, the topics addressed include: (1) correction of the effect of vibrations and thermal currents by means of an active compensation system; (2) reduction of the speckle noise by means of electronic filter and TV signal reconstruction circuit; (4) compensation of the rigid body motions by mounting the camera in a universal motion system; and (5) removal of phase errors left by the active compensation system by dynamic reading. In the design and construction section, the topics addressed include: (1) preliminary design; (2) final design; (3) software development; (4) signal conditioning; (5) data processing; (6) recorrelation of two holograms in the presence of rigid body motions; and (7) phase extraction using a computer generated image. Testing in the high temperature oven is also addressed.

Electrical properties of lanthanum chromite based ceramics in hydrogen and oxidizing atmospheres at high temperatures. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidt, V.H.

1981-06-01

Several results regarding the effect of hydrogen on lanthanum chromite were determined. Thermally-activated diffusion of hydrogen through La(Mg)CrO/sub 3/ was found with a high activation energy. It was found that its electrical conductivity drops drastically, especially at low temperature, after exposure to hydrogen at high temperature. Also, the curvature of most of the conductivity plots, as well as the inability to observe the Hall effect, lends support to the proposal by Karim and Aldred that the small-polaron model which predicts thermally activated mobility is applicable to doped lanthanum chromite. From differential thermal analysis an apparent absorption of hydrogen near 300/supmore » 0/C was noticed. Upon cooling the lanthanum chromite in hydrogen and subsequently reheating it in air, desorption occurred near 170/sup 0/C. The immediate purpose of this study was to determine whether hydrogen has a deleterious effect on lanthanum chromite in solid oxide fuel cells.« less

Effect of diurnal temperature difference on lipid accumulation and development in Calanus sinicus (Copepoda: Calanoida)

NASA Astrophysics Data System (ADS)

Zhou, Konglin; Sun, Song

2017-07-01

Calanus sinicus, the dominant copepod in the Yellow Sea, develops a large oil sac in late spring to prepare for over-summering in the Yellow Sea Cold Water Mass (YSCWM). The lipid accumulation mechanism for the initiation of over-summering is unknown. Here, we cultured C3 copepodites at four constant temperatures (10, 13, 16, and 19°C) and at three temperature regimes that mimicked the temperature variations experienced during diurnal vertical migration (10-13°C, 10-16°C, and 10-19°C) for 18 days to explore the effects of temperature differences on copepod development and lipid accumulation. C. sinicus stored more lipid at low than at high temperatures. A diurnal temperature difference (10-16°C and 10-19°C) promoted greater lipid accumulation (1.9-2.1 times) than a constant temperature of either 16°C or 19°C, by reducing the energy cost at colder temperatures and lengthening copepodite development. Thereafter, the lipid reserve supported gonad development after final molting. Only one male developed in these experiments. This highly female-skewed sex ratio may have been the result of the monotonous microalgae diet fed to the copepodites. This study provides the first evidence that diurnal temperature differences may promote lipid accumulation in C. sinicus, and provides a foundation for future investigations into the mechanisms involved in over-summering in the YSCWM.

High temperature deformation behavior, thermal stability and irradiation performance in Grade 92 steel

NASA Astrophysics Data System (ADS)

Alsagabi, Sultan

The 9Cr-2W ferritic-martensitic steel (i.e. Grade 92 steel) possesses excellent mechanical and thermophysical properties; therefore, it has been considered to suit more challenging applications where high temperature strength and creep-rupture properties are required. The high temperature deformation mechanism was investigated through a set of tensile testing at elevated temperatures. Hence, the threshold stress concept was applied to elucidate the operating high temperature deformation mechanism. It was identified as the high temperature climb of edge dislocations due to the particle-dislocation interactions and the appropriate constitutive equation was developed. In addition, the microstructural evolution at room and elevated temperatures was investigated. For instance, the microstructural evolution under loading was more pronounced and carbide precipitation showed more coarsening tendency. The growth of these carbide precipitates, by removing W and Mo from matrix, significantly deteriorates the solid solution strengthening. The MX type carbonitrides exhibited better coarsening resistance. To better understand the thermal microstructural stability, long tempering schedules up to 1000 hours was conducted at 560, 660 and 760°C after normalizing the steel. Still, the coarsening rate of M23C 6 carbides was higher than the MX-type particles. Moreover, the Laves phase particles were detected after tempering the steel for long periods before they dissolve back into the matrix at high temperature (i.e. 720°C). The influence of the tempering temperature and time was studied for Grade 92 steel via Hollomon-Jaffe parameter. Finally, the irradiation performance of Grade 92 steel was evaluated to examine the feasibility of its eventual reactor use. To that end, Grade 92 steel was irradiated with iron (Fe2+) ions to 10, 50 and 100 dpa at 30 and 500°C. Overall, the irradiated samples showed some irradiation-induced hardening which was more noticeable at 30°C. Additionally, irradiation-induced defect clusters and dislocation loops were observed and the irradiated samples did not show any bubble or void.

Improved Turn-On and Operating Voltages in AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Hao, Guo-Dong; Taniguchi, Manabu; Tamari, Naoki; Inoue, Shin-ichiro

2017-10-01

While good ohmic contact formation has been achieved on both p-GaN and n-AlGaN surfaces, the turn-on and operating voltages of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) remain very high. We find that this critical problem is mainly caused by the large difference between the annealing temperatures required for ohmic contact formation on the p-GaN and high Al-fraction n-AlGaN surfaces. We studied the effects of the high-temperature annealing treatments required for n-ohmic contact formation on the subsequent p-ohmic contact formation process in DUV-LEDs. The results show that post-annealing treatment at high temperature is necessary to form an ohmic contact on n-Al0.7Ga0.3N, but a treatment temperature of 900°C or more could cause severe degradation of the specific contact resistivity and the bulk resistivity of p-GaN. We conclude that 900°C is the optimum temperature to form an ohmic contact on n-Al0.7Ga0.3N in DUV-LEDs, where p-GaN and n-Al0.7Ga0.3N act as the p- and n-ohmic contact layers, respectively. We also found that the specific contact resistivity of p-GaN can be reduced by an additional low-temperature annealing treatment after the high-temperature annealing step; this effect can be attributed to the enhancement of the hole concentration in the p-GaN surface contact region. Finally, DUV-LEDs that emit at 280 nm were fabricated using four different annealing treatments during processing. A considerable reduction in the series resistance and thereby in the operating voltage was confirmed using the annealing process proposed above, consisting of a high-temperature anneal at 900°C followed by a low-temperature anneal at 500°C for 3 min.

A Physics-Based Temperature Stabilization Criterion for Thermal Testing

NASA Technical Reports Server (NTRS)

Rickman, Steven L.; Ungar, Eugene K.

2009-01-01

Spacecraft testing specifications differ greatly in the criteria they specify for stability in thermal balance tests. Some specify a required temperature stabilization rate (the change in temperature per unit time, dT/dt), some specify that the final steady-state temperature be approached to within a specified difference, delta T , and some specify a combination of the two. The particular values for temperature stabilization rate and final temperature difference also vary greatly between specification documents. A one-size-fits-all temperature stabilization rate requirement does not yield consistent results for all test configurations because of differences in thermal mass and heat transfer to the environment. Applying a steady-state temperature difference requirement is problematic because the final test temperature is not accurately known a priori, especially for powered configurations. In the present work, a simplified, lumped-mass analysis has been used to explore the applicability of these criteria. A new, user-friendly, physics-based approach is developed that allows the thermal engineer to determine when an acceptable level of temperature stabilization has been achieved. The stabilization criterion can be predicted pre-test but must be refined during test to allow verification that the defined level of temperature stabilization has been achieved.

Progress in the Fabrication and Testing of Telescope Mirrors for The James Webb Space Telescope

NASA Astrophysics Data System (ADS)

Bowers, Charles W.; Clampin, M.; Feinberg, L.; Keski-Kuha, R.; McKay, A.; Chaney, D.; Gallagher, B.; Ha, K.

2012-01-01

The telescope of the James Webb Space Telescope (JWST) is an f/20, three mirror anastigmat design, passively cooled (40K) in an L2 orbit. The design provides diffraction limited performance (Strehl ≥ 0.8) at λ=2μm. To fit within the launch vehicle envelope (Arianne V), the 6.6 meter primary mirror and the secondary mirror support structure are folded for launch, then deployed and aligned in space. The primary mirror is composed of 18 individual, 1.3 meter (flat:flat) hexagonal segments, each adjustable in seven degrees of freedom (six rigid body + radius of curvature) provided by a set of high precision actuators. The actuated secondary mirror ( 0.74m) is similarly positioned in six degrees of rigid body motion. The .70x.51m, fixed tertiary and 0.17m, flat fine steering mirror complete the telescope mirror complement. The telescope is supported by a composite structure optimized for performance at cryogenic temperatures. All telescope mirrors are made of Be with substantial lightweighting (21kg for each 1.3M primary segment). Additional Be mounting and supporting structure for the high precision ( 10nm steps) actuators are attached to the primary segments and secondary mirror. All mirrors undergo a process of thermal stabilization to reduce stress. An extensive series of interferometric measurements guide each step of the polishing process. Final polishing must account for any deformation between the ambient temperature of polishing and the cryogenic, operational temperature. This is accomplished by producing highly precise, cryo deformation target maps of each surface which are incorporated into the final polishing cycle. All flight mirrors have now completed polishing, coating with protected Au and final cryo testing, and the telescope is on track to meet all system requirements. We here review the measured performance of the component mirrors and the predicted performance of the flight telescope.

The effect of pigment matrix, temperature and amount of carrier on the yield and final color properties of spray dried purple corn (Zea mays L.) cob anthocyanin powders.

PubMed

Lao, Fei; Giusti, M Monica

2017-07-15

Spray drying is an economic technique to produce anthocyanin-based colorants. High pigments yields with minimum color degradation are desirable to maximize quality and profits. This study evaluated the impacts of purple corncob (PCC) anthocyanin extraction matrices (hot water, 40% ethanol, C18 purified), drying inlet temperature (130, 150, 170°C) and amount of carrier (2%, 5%, 10% maltodextrin) on the yields and quality of PCC anthocyanin powders. Monomeric and polymeric anthocyanins, color properties (CIELch, haze), and pigments composition before and after spray drying were determined. The yield and final color quality of spray dried PCC anthocyanins were affected (p<0.05) by all parameters evaluated. The pigment matrix, inlet temperature, and carrier amount had biggest impacts on product water solubility, pigments degradation and yield, respectively. The optimal combination of hot water extracts spray dried with 5% maltodextrin at 150°C gave the highest pigment yield (∼90%) with good solubility with the least color loss. Copyright © 2017 Elsevier Ltd. All rights reserved.

An overview of thixoforming process

NASA Astrophysics Data System (ADS)

Husain, N. H.; Ahmad, A. H.; Rashidi, M. M.

2017-10-01

Thixoforming is a forming process which exploits metal rheological behaviour during solidus and liquidus range temperature. Many research works in thixoforming are currently focusing on the raw material used to produce superior mechanical properties and excellent formability components, especially in automotive industries. Furthermore, the thixoforming process also produced less casting defect component such as macrosegration, shrinkage and porosity. These advantages are sufficient to attract more exploration works of thixoforming operation. However, the weakness of this process such as high production cost due to leftover billet which cannot be recycled, encourage researcher works to overcome thixoforming limitations by using various methods. The thixoforming methods that widely used are thixocasting, thixoforging, thixorolling, thixoextrusion and thixomoulding. Each method provides varieties of final product characteristics; hence offer the extensive possibility of component invention. On the other hand, new thixoforming method leads to exploration research such as microstructure evolution, heating and pouring temperature, die temperature, mechanical properties, viscosity and final product quality. This review paper presents findings in the rheological material behaviour of thixoforming, advantages and disadvantanges of thixoforming, parameters affecting the thixoforming operation, morphology of thixoforming and various methods which have been used in this research area.

Comparative study on the conventional and non thermal simultaneous saccharification and fermentation of Manihot glaziovii root starch

NASA Astrophysics Data System (ADS)

Hargono, Kumoro, Andri Cahyo; Jos, Bakti

2015-12-01

Inconventional ethanol production process, starch is converted into dextrins via liquefaction using α-amylase enzyme at high temperature (90-120°C). Then, dextrins are saccharified by glucoamylase to obtain to monomeric sugars (glucose). Recently, a granular starch hydrolyzing enzymes (GSHE), Stargen 002, was developed to convert starch into dextrins at low temperature (< 32°C) and hydrolyzes dextrins into glucose. The subject of this research was to compare ethanol production using a granular starch hydrolyzing enzymes and conventional enzymatic liquefaction and saccharification in cassava starch processing. Starch slurry concentrations were 20% w/v, and dosage of enzymes 0.50, 1.0 and 2%, respectively, were studied. After 48 hr process the final ethanol concentration for the respective enzyme concentration for conventional process were 34.90, 36.16 and 42.10 g/L, whereas for the non-thermal treatment, final ethanol concentration were 46.4, 57.62 and 59.65 g/L, respectively. By implementation of this non thermal process, the use of energy can be saved by carrying out saccharification step at lower temperature (30°C) could be realized.

Hydrocarbon Constituents of T-56 Combustor Exhaust

DTIC Science & Technology

1975-04-01

May 1973 to determine feasibility of exhaust cryotrapping and to establish analytical methodology for identifying individual hydrocarbon compounds (3...midtemperature setting was at about 166°C, and 33 psig, corresponding to the conditions of many moderate-pressure ratio engines (1). Finally the high -temperature...condition of 2040C and 50 psig simulates many newer high -pressure-ratio engines, like the F-101 and F-100. Table 2 lists typical military engines and

Effects of cooking method and final core-temperature on cooking loss, lipid oxidation, nucleotide-related compounds and aroma volatiles of Hanwoo brisket

PubMed Central

2018-01-01

Objective This study observed the effects of cooking method and final core temperature on cooking loss, lipid oxidation, aroma volatiles, nucleotide-related compounds and aroma volatiles of Hanwoo brisket (deep pectoralis). Methods Deep pectoralis muscles (8.65% of crude fat) were obtained from three Hanwoo steer carcasses with 1+ quality grade. Samples were either oven-roasted at 180°C (dry heat) or cooked in boiling water (moist heat) to final core temperature of 70°C (medium) or 77°C (well-done). Results Boiling method reduced more fat but retained more moisture than did the oven roasting method (p<0.001), thus no significant differences were found on cooking loss. However, samples lost more weight as final core temperature increased (p<0.01). Further, total saturated fatty acid increased (p = 0.02) while total monounsaturated fatty acid decreased (p = 0.03) as final core temperature increased. Regardless the method used for cooking, malondialdehyde (p<0.01) and free iron contents (p<0.001) were observed higher in samples cooked to 77°C. Oven roasting retained more inosinic acid, inosine and hypoxanthine in samples than did the boiling method (p<0.001), of which the concentration decreased as final core temperature increased except for hypoxanthine. Samples cooked to 77°C using oven roasting method released more intense aroma than did the others and the aroma pattern was discriminated based on the intensity. Most of aldehydes and pyrazines were more abundant in oven-roasted samples than in boiled samples. Among identified volatiles, hexanal had the highest area unit in both boiled and oven-roasted samples, of which the abundance increased as the final core temperature increased. Conclusion The boiling method extracted inosinic acid and rendered fat from beef brisket, whereas oven roasting intensified aroma derived from aldehydes and pyrazines and prevented the extreme loss of inosinic acid. PMID:28728407

Calculation of exchange integrals and Curie temperature for La-substituted barium hexaferrites.

PubMed

Wu, Chuanjian; Yu, Zhong; Sun, Ke; Nie, Jinlan; Guo, Rongdi; Liu, Hai; Jiang, Xiaona; Lan, Zhongwen

2016-10-31

As the macro behavior of the strength of exchange interaction, state of the art of Curie temperature T c , which is directly proportional to the exchange integrals, makes sense to the high-frequency and high-reliability microwave devices. Challenge remains as finding a quantitative way to reveal the relationship between the Curie temperature and the exchange integrals for doped barium hexaferrites. Here in this report, for La-substituted barium hexaferrites, the electronic structure has been determined by the density functional theory (DFT) and generalized gradient approximation (GGA). By means of the comparison between the ground and relative state, thirteen exchange integrals have been calculated as a function of the effective value U eff . Furthermore, based on the Heisenberg model, the molecular field approximation (MFA) and random phase approximation (RPA), which provide an upper and lower bound of the Curie temperature T c , have been adopted to deduce the Curie temperature T c . In addition, the Curie temperature T c derived from the MFA are coincided well with the experimental data. Finally, the strength of superexchange interaction mainly depends on 2b-4f 1 , 4f 2 -12k, 2a-4f 1 , and 4f 1 -12k interactions.

Thermal-electric coupled-field finite element modeling and experimental testing of high-temperature ion sources for the production of radioactive ion beams

NASA Astrophysics Data System (ADS)

Manzolaro, M.; Meneghetti, G.; Andrighetto, A.; Vivian, G.; D'Agostini, F.

2016-02-01

In isotope separation on line facilities the target system and the related ion source are two of the most critical components. In the context of the selective production of exotic species (SPES) project, a 40 MeV 200 μA proton beam directly impinges a uranium carbide target, generating approximately 1013 fissions per second. The radioactive isotopes produced in this way are then directed to the ion source, where they can be ionized and finally accelerated to the subsequent areas of the facility. In this work both the surface ion source and the plasma ion source adopted for the SPES facility are presented and studied by means of numerical thermal-electric models. Then, numerical results are compared with temperature and electric potential difference measurements, and finally the main advantages of the proposed simulation approach are discussed.

The silicon-glass microreactor with embedded sensors—technology and results of preliminary qualitative tests, toward intelligent microreaction plant

NASA Astrophysics Data System (ADS)

Knapkiewicz, P.

2013-03-01

The technology and preliminary qualitative tests of silicon-glass microreactors with embedded pressure and temperature sensors are presented. The concept of microreactors for leading highly exothermic reactions, e.g. nitration of hydrocarbons, and design process-included computer-aided simulations are described in detail. The silicon-glass microreactor chip consisting of two micromixers (multistream micromixer), reaction channels, cooling/heating chambers has been proposed. The microreactor chip was equipped with a set of pressure and temperature sensors and packaged. Tests of mixing quality, pressure drops in channels, heat exchange efficiency and dynamic behavior of pressure and temperature sensors were documented. Finally, two applications were described.

Design and development of NiTi-based precipitation-strengthened high-temperature shape memory alloys for actuator applications

NASA Astrophysics Data System (ADS)

Hsu, Derek Hsen Dai

As a vital constituent in the field of smart materials and structures, shape memory alloys (SMAs) are becoming ever-more important due to their wide range of commercial and industrial applications such as aircraft couplings, orthodontic wires, and eyeglasses frames. However, two major obstacles preventing SMAs from fulfilling their potential as excellent actuator materials are: 1) the lack of commercially-viable SMAs that operate at elevated temperatures, and 2) the degradation of mechanical properties and shape memory behavior due to thermal cyclic fatigue. This research utilized a thermodynamically-driven systems design approach to optimize the desired properties by controlling the microstructure and processing of high-temperature SMAs (HTSMAs). To tackle the two aforementioned problems with HTSMAs, the introduction of Ni2TiAl coherent nanoprecipitates in a Ni-Ti-Zr/Hf HTSMA matrix is hypothesized to strengthen the martensite phase while simultaneously increasing the transformation temperature. Differential scanning calorimetry (DSC) was used to determine the transformation temperatures and thermal cyclic stability of each alloy. Also, microstructural characterization was performed using X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atom probe tomography (APT). Lastly, compression testing was used to assess the mechanical behavior of the alloys. From the investigation of the first set of Ni48.5Ti31.5-X Zr20AlX (X = 0, 1, 2, 3) prototype alloys, Al addition was found to decrease the transformation temperatures, decrease the thermal cyclic stability, but also increase the strength due to the nucleation and growth of embrittling NiTi2 and NiTiZr Laves phases. However, the anticipated Heusler phase precipitation did not occur. The next study focused on Ni50Ti30-XHf20Al X (X = 0, 1, 2, 3, 4, 5) prototype alloys which replaced Zr with Hf to avoid the formation of brittle Laves phases. Heusler precipitation was successfully demonstrated in the aged 4 and 5% Al alloys, but no transformation was detected. Finally, the last investigation explored the potential of high transformation temperatures in Ni50Ti25-XHf25AlX and Ni50Ti20-XHf30AlX (X = 0, 1, 2, 3, 4, 5) prototype alloys. The final design was narrowed down to a Ni 50Ti20Hf25Al5 alloy aged at 800°C that is expected to exhibit high transformation temperatures while concurrently strengthened by Heusler nanoprecipitates.

Effect of water addition to a total mixed ration on feed temperature, feed intake, sorting behavior, and milk production of dairy cows.

PubMed

Felton, C A; DeVries, T J

2010-06-01

The objective of this study was to determine the effects of water addition to a high-moisture total mixed ration (TMR) on feed temperature, feed intake, feed sorting behavior, and milk production of dairy cows. Twelve lactating Holstein cows (155.8+/-60.1 DIM), individually fed once daily at 1000 h, were exposed to 3 diets in a Latin square design with 28-d treatment periods. Diets had the same ingredient composition [30.9% corn silage, 30.3% alfalfa haylage, 21.2% high-moisture corn, and 17.6% protein supplement; dry matter (DM) basis] and differed only in DM concentration, which was reduced by the addition of water. Treatment diets averaged 56.3, 50.8, and 44.1% DM. The study was conducted between May and August when environmental temperature was 18.2+/-3.6 degrees C and ambient temperature in the barn was 24.4+/-3.3 degrees C. Dry matter intake (DMI) was monitored for each animal for the last 14 d of each treatment period. For the final 7 d of each period, milk production was monitored, feed temperature and ambient temperature and humidity were recorded (daily at 1000, 1300, and 1600 h), and fresh feed and orts were sampled for determination of sorting. For the final 4 d of each period, milk samples were taken for composition analysis. Samples taken for determining sorting were separated using a Penn State Particle Separator that had 3 screens (19, 8, and 1.18 mm) and a bottom pan, resulting in 4 fractions (long, medium, short, and fine). Sorting was calculated as the actual intake of each particle size fraction expressed as a percentage of the predicted intake of that fraction. Greater amounts of water added to the TMR resulted in greater increases in feed temperature in the hours after feed delivery, greater sorting against long particles, and decreased DMI, reducing the overall intake of starch and neutral detergent fiber. Milk production and composition were not affected by the addition of water to the TMR. Efficiency of production of milk was, however, increased with greater amounts of water added to the TMR. The increases in feed temperature in the hours after feed delivery were enhanced by higher ambient temperatures; this may be indicative of feed spoilage and thus may have contributed to the reduced DMI observed. Overall, these results suggest that the addition of water to high-moisture TMR (less than 60% DM) containing primarily haylage and silage forage sources will not always discourage cows from sorting, but rather may increase this behavior and limit the nutrient consumption of cows, particularly when ambient temperature is high. 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Surface passivation of p-type Ge substrate with high-quality GeNx layer formed by electron-cyclotron-resonance plasma nitridation at low temperature

NASA Astrophysics Data System (ADS)

Fukuda, Yukio; Okamoto, Hiroshi; Iwasaki, Takuro; Otani, Yohei; Ono, Toshiro

2011-09-01

We have investigated the effects of the formation temperature and postmetallization annealing (PMA) on the interface properties of GeNx/p-Ge fabricated by the plasma nitridation of Ge substrates using an electron-cyclotron-resonance-generated nitrogen plasma. The nitridation temperature is found to be a critical parameter in improving the finally obtained GeNx/Ge interface properties. The GeNx/Ge formed at room temperature and treated by PMA at 400 °C exhibits the best interface properties with an interface trap density of 1 × 1011 cm-2 eV-1. The GeNx/Ge interface is unpinned and the Fermi level at the Ge surface can move from the valence band edge to the conduction band edge.

Bio-heat transfer model of electroconvulsive therapy: Effect of biological properties on induced temperature variation.

PubMed

de Oliveira, Marilia M; Wen, Paul; Ahfock, Tony

2016-08-01

A realistic human head model consisting of six tissue layers was modelled to investigate the behavior of temperature profile and magnitude when applying electroconvulsive therapy stimulation and different biological properties. The thermo-electrical model was constructed with the use of bio-heat transfer equation and Laplace equation. Three different electrode montages were analyzed as well as the influence of blood perfusion, metabolic heat and electric and thermal conductivity in the scalp. Also, the effect of including the fat layer was investigated. The results showed that temperature increase is inversely proportional to electrical and thermal conductivity increase. Furthermore, the inclusion of blood perfusion slightly drops the peak temperature. Finally, the inclusion of fat is highly recommended in order to acquire more realistic results from the thermo-electrical models.

The Momentum Distribution of Liquid ⁴He

DOE PAGES

Prisk, T. R.; Bryan, M. S.; Sokol, P. E.; ...

2017-07-24

We report a high-resolution neutron Compton scattering study of liquid ⁴He under milli-Kelvin temperature control. To interpret the scattering data, we performed Quantum Monte Carlo calculations of the atomic momentum distribution and final state effects for the conditions of temperature and density considered in the experiment. There is excellent agreement between the observed scattering and ab initio calculations of its lineshape at all temperatures. We also used model fit functions to obtain from the scattering data empirical estimates of the average atomic kinetic energy and Bose condensate fraction. These quantities are also in excellent agreement with ab initio calculations. Wemore » conclude that contemporary Quantum Monte Carlo methods can furnish accurate predictions for the properties of Bose liquids, including the condensate fraction, close to the superfluid transition temperature.« less

Integrated multispectral high-power laser platform for the defeat of heat-seeking missiles

NASA Astrophysics Data System (ADS)

Tadjikov, Boris; Tsekoun, Alexei; Lyakh, Arkadiy; Maulini, Richard; Barron, Rodolfo; Patel, C. Kumar N.

2011-06-01

Quantum cascade lasers are finding rapid acceptance in many defense and security applications. Our new multispectral laser platform providing watt-level outputs near 2.0 μm, 4.0 μm and 4.6 μm in continuous wave regime at room temperature. Individual lasers are spectrally beam combined into a single output beam with excellent quality. Our rugged, compact (11 × 10 × 6.5 inches), and highly reliable, air-cooled multispectral laser platform is already finding acceptance at system level. Our uncooled devices produce > 2W at 4.6 μm and >1.5W at 4.0 μm at room temperature, and maintain watt-level output at 67°C with real wallplug efficiencies >10%. Finally, all of our QCLs undergo 100-hour pre-delivery burn-in and pass shock, vibration, and temperature testing according to MIL-STD-810G.

Segregation of mass at the periphery of N -isopropylacrylamide-co-acrylic-acid microgels at high temperatures

DOE PAGES

Hyatt, John S.; Do, Changwoo; Hu, Xiaobo; ...

2015-09-29

Here, we investigate poly(N-isopropylacrylamide) (pNIPAM) microgels randomly copolymerized with large mol % of protonated acrylic acid (AAc), finding that above the lower critical solution temperature the presence of the acid strongly disrupts pNIPAM's collapse, leading to unexpected new behavior at high temperatures. We see a dramatic increase in the ratio between the radius of gyration and the hydrodynamic radius above the theoretical value for homogeneous spheres, and a corresponding increase of the network length scale, which we attribute to the presence of a heterogeneous polymer distribution that forms due to frustration of pNIPAM's coil-to-globule transition by the AAc. Finally, wemore » analyze this phenomenon using a Debye-Bueche-like scattering contribution as opposed to the Lorentzian term often used, interpreting the results in terms of mass segregation at the particle periphery.« less

Analysis of laser shock experiments on precompressed samples using a quartz reference and application to warm dense hydrogen and helium

DOE PAGES

Brygoo, Stephanie; Millot, Marius; Loubeyre, Paul; ...

2015-11-16

Megabar (1 Mbar = 100 GPa) laser shocks on precompressed samples allow reaching unprecedented high densities and moderately high ~10 3–10 4 K temperatures. We describe in this paper a complete analysis framework for the velocimetry (VISAR) and pyrometry (SOP) data produced in these experiments. Since the precompression increases the initial density of both the sample of interest and the quartz reference for pressure-density, reflectivity, and temperature measurements, we describe analytical corrections based on available experimental data on warm dense silica and density-functional-theory based molecular dynamics computer simulations. Finally, using our improved analysis framework, we report a re-analysis of previouslymore » published data on warm dense hydrogen and helium, compare the newly inferred pressure, density, and temperature data with most advanced equation of state models and provide updated reflectivity values.« less

Field Performance of Photovoltaic Systems in the Tucson Desert

NASA Astrophysics Data System (ADS)

Orsburn, Sean; Brooks, Adria; Cormode, Daniel; Greenberg, James; Hardesty, Garrett; Lonij, Vincent; Salhab, Anas; St. Germaine, Tyler; Torres, Gabe; Cronin, Alexander

2011-10-01

At the Tucson Electric Power (TEP) solar test yard, over 20 different grid-connected photovoltaic (PV) systems are being tested. The goal at the TEP solar test yard is to measure and model real-world performance of PV systems and to benchmark new technologies such as holographic concentrators. By studying voltage and current produced by the PV systems as a function of incident irradiance, and module temperature, we can compare our measurements of field-performance (in a harsh desert environment) to manufacturer specifications (determined under laboratory conditions). In order to measure high-voltage and high-current signals, we designed and built reliable, accurate sensors that can handle extreme desert temperatures. We will present several benchmarks of sensors in a controlled environment, including shunt resistors and Hall-effect current sensors, to determine temperature drift and accuracy. Finally we will present preliminary field measurements of PV performance for several different PV technologies.

Effect of initial moisture content on the in-vessel composting under air pressure of organic fraction of municipal solid waste in Morocco

PubMed Central

2013-01-01

This study aimed to evaluate the effect of initial moisture content on the in-vessel composting under air pressure of organic fraction of municipal solid waste in Morocco in terms of internal temperature, produced gases quantity, organic matter conversion rate, and the quality of the final composts. For this purpose, in-vessel bioreactor was designed and used to evaluate both appropriate initial air pressure and appropriate initial moisture content for the composting process. Moreover, 5 experiments were carried out within initial moisture content of 55%, 65%, 70%, 75% and 85%. The initial air pressure and the initial moisture content of the mixture showed a significant effect on the aerobic composting. The experimental results demonstrated that for composting organic waste, relatively high moisture contents are better at achieving higher temperatures and retaining them for longer times. This study suggested that an initial moisture content of around 75%, under 0.6 bar, can be considered as being suitable for efficient composting of organic fraction of municipal solid waste. These last conditions, allowed maximum value of temperature and final composting product with good physicochemical properties as well as higher organic matter degradation and higher gas production. Moreover, final compost obtained showed good maturity levels and can be used for agricultural applications. PMID:23369502

High performance and thermally stable tandem solar selective absorber coating for concentrated solar thermal power (CSP) application

NASA Astrophysics Data System (ADS)

Prasad, M. Shiva; Kumar, K. K. Phani; Atchuta, S. R.; Sobha, B.; Sakthivel, S.

2018-05-01

A novel tandem absorber system (Mn-Cu-Co-Ox-ZrO2/SiO2) developed on an austenitic stainless steel (SS-304) substrate to show an excellent optical performance (αsol: 0.96; ɛ: 0.23@500 °C). In order to achieve this durable tandem, we experimented with two antireflective layers such as ZrO2-SiO2 and nano SiO2 layer on top of Mn-Cu-Co-Ox-ZrO2 layer. We optimized the thickness of antireflective layers to get good tandem system in terms of solar absorptance and emittance. Field emission scanning electron microscopy (FESEM), UV-Vis-NIR and Fourier transform infrared spectroscopy (FTIR) were used to characterize the developed coatings. Finally, the Mn-Cu-Co-Ox-ZrO2/SiO2 exhibits high temperature resistance up to 800 °C, thus allow an increase in the operating temperature of CSP which may lead to high efficiency. We successfully developed a high temperature resistant tandem layer with easy manufacturability at low cost which is an attractive candidate for concentrated solar power generation (CSP).

Effects of temperature on the astaxanthin productivity and light harvesting characteristics of the green alga Haematococcus pluvialis.

PubMed

Giannelli, Luca; Yamada, Hiroyuki; Katsuda, Tomohisa; Yamaji, Hideki

2015-03-01

The green alga Haematococcus pluvialis, which accumulates astaxanthin at an optimal temperature of 20°C, was cultivated under temperatures of 20°C, 23.5°C, 27°C, and 30.5°C, in order to assess the effects on algal metabolism during the growth phase. The culture growth rate declined with above-optimal increases in temperature, and the final maximum cell concentration at 30.5°C reached only 35% of that attained at 20°C. On the contrary, the biomass productivity was increased under all the high-temperature conditions, probably reflecting the metabolism switch from cell duplication to energy accumulation that is typically observed in algal cultures subjected to environmental stress. Moreover, an increase in the light-harvesting capability of the alga was observed by means of the total pigment balance and the photosynthesis-intensity (PI) curve measured under the different cultivation conditions. Cultures kept at higher temperatures were able to better harvest and utilize the impinging light due to photo-acclimation. Finally, the differences in the astaxanthin metabolism were elucidated by subjecting the cultures to nitrogen starvation at 20°C and 27°C. In the culture at 27°C, a 1.4-fold increase in the astaxanthin productivity was observed when compared to that at 20°C, and the latter required almost two-fold more energy for the astaxanthin production compared with the 27°C culture. Copyright © 2014. Published by Elsevier B.V.

The Effects of Vanadium Pentoxide to Oxalic Acid Ratio and Different Atmospheres on the Formation of VO2 Nanopowders Synthesized via Sol-Gel Method

NASA Astrophysics Data System (ADS)

Vostakola, Mohsen Fallah; Yekta, Bijan Eftekhari; Mirkazemi, Seyed Mohammad

2017-11-01

Thermochromic VO2 nanopowders were synthesized via the sol-gel method through mixing oxalic acid and vanadium pentoxide in ethanol. We investigated the effect of oxalic acid to vanadium pentoxide ratio on the formation of final product and found that excessive oxalic acid reduced the final product from VO2 to V2O3. Because decreasing the oxalic acid to vanadium pentoxide ratio is a time-consuming process, oxygen was introduced by using a low-porosity alumina tube. The heat treatment was performed inside an electrical tube furnace and in a variety of atmospheres, including pure nitrogen (99.999% purity) and nitrogen containing 5 vol.%, 10 vol.%, and 15 vol.% hydrogen. According to x-ray diffraction (XRD) results, the appropriate atmosphere for synthesizing VO2 nanopowder was the one which contained 10 vol.% hydrogen. In order to decrease the transition temperature in VO2 from 63.5°C to room temperature, W6+ doping was done by adding different amounts of tungstic acid sol to vanadium sol precursor. Differential scanning calorimetry (DSC) results showed that W6+ reduced the transition temperature of VO2 approximately 23°C/wt.%. Lattice straining estimated from XRD results confirmed that VO2 was doped. XRD results at 25°C and 100°C along with DSC results indicated that VO2 was transformed from a low-temperature monoclinic phase to a high-temperature rutile one along this temperature interval.

Challenges and Progress in the Development of High-Temperature Shape Memory Alloys Based on NiTiX Compositions for High-Force Actuator Applications

NASA Technical Reports Server (NTRS)

Padula, Santo, II; Bigelow, Glen; Noebe, Ronald; Gaydosh, Darrell; Garg, Anita

2006-01-01

Interest in high-temperature shape memory alloys (HTSMA) has been growing in the aerospace, automotive, process control, and energy industries. However, actual materials development has seriously lagged component design, with current commercial NiTi alloys severely limited in their temperature capability. Additions of Pd, Pt, Au, Hf, and Zr at levels greater than 10 at.% have been shown to increase the transformation temperature of NiTi alloys, but with few exceptions, the shape memory behavior (strain recovery) of these NiTiX systems has been determined only under stress free conditions. Given the limited amount of basic mechanical test data and general lack of information regarding the work attributes of these materials, a program to investigate the mechanical behavior of potential HTSMAs, with transformation temperatures between 100 and 500 C, was initiated. This paper summarizes the results of studies, focusing on both the practical temperature limitations for ternary TiNiPd and TiNiPt systems based on the work output of these alloys and the ability of these alloys to undergo repeated thermal cycling under load without significant permanent deformation or "walking". These issues are ultimately controlled by the detwinning stress of the martensite and resistance to dislocation slip of the individual martensite and austenite phases. Finally, general rules that govern the development of useful, high work output, next-generation HTSMA materials, based on the lessons learned in this work, will be provided

A temperature-jump NMR probe setup using rf heating optimized for the analysis of temperature-induced biomacromolecular kinetic processes

NASA Astrophysics Data System (ADS)

Rinnenthal, Jörg; Wagner, Dominic; Marquardsen, Thorsten; Krahn, Alexander; Engelke, Frank; Schwalbe, Harald

2015-02-01

A novel temperature jump (T-jump) probe operational at B0 fields of 600 MHz (14.1 Tesla) with an integrated cage radio-frequency (rf) coil for rapid (<1 s) heating in high-resolution (HR) liquid-state NMR-spectroscopy is presented and its performance investigated. The probe consists of an inner 2.5 mm "heating coil" designed for generating rf-electric fields of 190-220 MHz across a lossy dielectric sample and an outer two coil assembly for 1H-, 2H- and 15N-nuclei. High B0 field homogeneities (0.7 Hz at 600 MHz) are combined with high heating rates (20-25 K/s) and only small temperature gradients (<±1.5 K, 3 s after 20 K T-jump). The heating coil is under control of a high power rf-amplifier within the NMR console and can therefore easily be accessed by the pulse programmer. Furthermore, implementation of a real-time setup including synchronization of the NMR spectrometer's air flow heater with the rf-heater used to maintain the temperature of the sample is described. Finally, the applicability of the real-time T-jump setup for the investigation of biomolecular kinetic processes in the second-to-minute timescale is demonstrated for samples of a model 14mer DNA hairpin and a 15N-selectively labeled 40nt hsp17-RNA thermometer.

A new apparatus design for high temperature (up to 950°C) quasi-elastic neutron scattering in a controlled gaseous environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

al-Wahish, Amal; Armitage, D.; al-Binni, U.

Our design for a sample cell system suitable for high temperature Quasi-Elastic Neutron Scattering (QENS) experiments is presented. The apparatus was developed at the Spallation Neutron Source in Oak Ridge National Lab where it is currently in use. The design provides a special sample cell environment under controlled humid or dry gas flow over a wide range of temperature up to 950°C. Using such a cell, chemical, dynamical, and physical changes can be studied in situ under various operating conditions. And while the cell combined with portable automated gas environment system is especially useful for in situ studies of microscopicmore » dynamics under operational conditions that are similar to those of solid oxide fuel cells, it can additionally be used to study a wide variety of materials, such as high temperature protonconductors. The cell can also be used in many different neutron experiments when a suitable sample holder material is selected. Finally, the sample cell system has recently been used to reveal fast dynamic processes in quasi-elastic neutron scattering experiments, which standard probes (such as electrochemical impedance spectroscopy) could not detect. In this work, we outline the design of the sample cell system and present results demonstrating its abilities in high temperature QENS experiments.« less

Wide range scaling laws for radiation driven shock speed, wall albedo and ablation parameters for high-Z materials

NASA Astrophysics Data System (ADS)

Mishra, Gaurav; Ghosh, Karabi; Ray, Aditi; Gupta, N. K.

2018-06-01

Radiation hydrodynamic (RHD) simulations for four different potential high-Z hohlraum materials, namely Tungsten (W), Gold (Au), Lead (Pb), and Uranium (U) are performed in order to investigate their performance with respect to x-ray absorption, re-emission and ablation properties, when irradiated by constant temperature drives. A universal functional form is derived for estimating time dependent wall albedo for high-Z materials. Among the high-Z materials studied, it is observed that for a fixed simulation time the albedo is maximum for Au below 250 eV, whereas it is maximum for U above 250 eV. New scaling laws for shock speed vs drive temperature, applicable over a wide temperature range of 100 eV to 500 eV, are proposed based on the physics of x-ray driven stationary ablation. The resulting scaling relation for a reference material Aluminium (Al), shows good agreement with that of Kauffman's power law for temperatures ranging from 100 eV to 275 eV. New scaling relations are also obtained for temperature dependent mass ablation rate and ablation pressure, through RHD simulation. Finally, our study reveals that for temperatures above 250 eV, U serves as a better hohlraum material since it offers maximum re-emission for x-rays along with comparable mass ablation rate. Nevertheless, traditional choice, Au works well for temperatures below 250 eV. Besides inertial confinement fusion (ICF), the new scaling relations may find its application in view-factor codes, which generally ignore atomic physics calculations of opacities and emissivities, details of laser-plasma interaction and hydrodynamic motions.

Synthesis of high-temperature viscosity stabilizer used in drilling fluid

NASA Astrophysics Data System (ADS)

Zhang, Yanna; Luo, Huaidong; Shi, Libao; Huang, Hongjun

2018-02-01

Abstract For a well performance drilling fluid, when it operates in deep wells under high temperature, the most important property required is the thermal stability. The drilling fluid properties under high temperature can be controlled by proper selection of viscosity stabilizer, which can capture oxygen to protect polymer agent in the drilling fluid. In this paper a viscosity stabilizer PB-854 is described, which was synthesized by 4-phenoxybutyl bromide, paraformaldehyde, and phloroglucinol using etherification method and condensation reaction. We studied the effect of catalyst dosage, temperature, time, and stirring rate on the synthetic yield. Under this condition: molar ratio of 2-tert-Butylphenol, paraformaldehyde and phloroglucinol of 2:1:2.5, reacting temperature of 100 °C, stirring rate of 100 r min-1, and mass content of catalyst of 15 %, char yield of 5-bromine-3-tert-butyl salicylaldehyde reached 86 %. Under this condition: molar ratio of 5-bromine-3-tert-butyl salicylaldehyde and phloroglucinol of 4, reacting temperature of 60 °C, reacting time of 30 min, volume content of sulphuric acid of 80 %, char yield of the target product viscosity stabilizer PB-854 is 86%. Finally, in this paper, infrared spectroscopy is adopted to analyse the structure of the synthetic product PB-854.The improvement in the stability of drilling fluid was further shown after adding the viscosity stabilizer in the common polymer drilling fluid under high temperature conditions of 120 °C ˜ 180 °C. The results show significant change in terms of fluid stability in the presence of this new stabilizer as it provides better stability.

Mechanical Properties of the TiAl IRIS Alloy

NASA Astrophysics Data System (ADS)

Voisin, Thomas; Monchoux, Jean-Philippe; Thomas, Marc; Deshayes, Christophe; Couret, Alain

2016-12-01

This paper presents a study of the mechanical properties at room and high temperature of the boron and tungsten containing IRIS alloy (Ti-48Al-2W-0.08B at. pct). This alloy was densified by Spark Plasma Sintering (SPS). The resultant microstructure consists of small lamellar colonies surrounded by γ regions containing B2 precipitates. Tensile tests are performed from room temperature to 1273 K (1000 °C). Creep properties are determined at 973 K (700 °C)/300 MPa, 1023 K (750 °C)/120 MPa, and 1023 K (750 °C)/200 MPa. The tensile strength and the creep resistance at high temperature are found to be very high compared to the data reported in the current literature while a plastic elongation of 1.6 pct is preserved at room temperature. A grain size dependence of both ductility and strength is highlighted at room temperature. The deformation mechanisms are studied by post-mortem analyses on deformed samples and by in situ straining experiments, both performed in a transmission electron microscope. In particular, a low mobility of non-screw segments of dislocations at room temperature and the activation of a mixed-climb mechanism during creep have been identified. The mechanical properties of this IRIS alloy processed by SPS are compared to those of other TiAl alloys developed for high-temperature structural applications as well as to those of similar tungsten containing alloys obtained by more conventional processing techniques. Finally, the relationships between mechanical properties and microstructural features together with the elementary deformation mechanisms are discussed.

Non-linear pressure/temperature-dependence of high pressure thermal inactivation of proteolytic Clostridium botulinum type B in foods.

PubMed

Maier, Maximilian B; Lenz, Christian A; Vogel, Rudi F

2017-01-01

The effect of high pressure thermal (HPT) processing on the inactivation of spores of proteolytic type B Clostridium botulinum TMW 2.357 in four differently composed low-acid foods (green peas with ham, steamed sole, vegetable soup, braised veal) was studied in an industrially feasible pressure range and temperatures between 100 and 120°C. Inactivation curves exhibited rapid inactivation during compression and decompression followed by strong tailing effects. The highest inactivation (approx. 6-log cycle reduction) was obtained in braised veal at 600 MPa and 110°C after 300 s pressure-holding time. In general, inactivation curves exhibited similar negative exponential shapes, but maximum achievable inactivation levels were lower in foods with higher fat contents. At high treatment temperatures, spore inactivation was more effective at lower pressure levels (300 vs. 600 MPa), which indicates a non-linear pressure/temperature-dependence of the HPT spore inactivation efficiency. A comparison of spore inactivation levels achievable using HPT treatments versus a conventional heat sterilization treatment (121.1°C, 3 min) illustrates the potential of combining high pressures and temperatures to replace conventional retorting with the possibility to reduce the process temperature or shorten the processing time. Finally, experiments using varying spore inoculation levels suggested the presence of a resistant fraction comprising approximately 0.01% of a spore population as reason for the pronounced tailing effects in survivor curves. The loss of the high resistance properties upon cultivation indicates that those differences develop during sporulation and are not linked to permanent modifications at the genetic level.

Selective Emitters for High Efficiency TPV Conversion: Materials Preparation and Characterisation

NASA Astrophysics Data System (ADS)

Diso, D.; Licciulli, A.; Bianco, A.; Leo, G.; Torsello, G.; Tundo, S.; De Risi, A.; Mazzer, M.

2003-01-01

Optimising the spectral emissivity of the IR radiation source in a TPV generator is one of the crucial steps towards high efficiency TPV conversion. In this paper we present different approaches to the preparation of selective emitters to be coupled to high efficiency photovoltaic cells. The emitters are designed to work at a temperature of about 1500K and they have been prepared to be used either as external coatings for the burner or as a structural material for the burner itself. Composite ceramics containing rare earth cations, prepared by slip-casting, with various concentration of rare earths were prepared by Slip Casting and Slurry Coating. Rare earth oxides have been incorporated into different oxide matrices, namely Silica, Alumina, Zirconia and their combination. The final aim was to find the material that exhibits the best performance in terms of both high selective power emission, good efficiency along with acceptable thermo-structural properties (high temperature thermal shock resistance, good strength, no creep). The power density emitted by samples as function of the temperature has been tested in the range 1000nm-5000nm. The high temperature emission measurements and the structural tests indicate that a good compromise between the functional and the thermo-structural properties may be reached. The results of the tests on the emitter coatings carried out in a TPV generator at the operating conditions are also presented in this paper.

Progress with High-Field Superconducting Magnets for High-Energy Colliders

NASA Astrophysics Data System (ADS)

Apollinari, Giorgio; Prestemon, Soren; Zlobin, Alexander V.

2015-10-01

One of the possible next steps for high-energy physics research relies on a high-energy hadron or muon collider. The energy of a circular collider is limited by the strength of bending dipoles, and its maximum luminosity is determined by the strength of final focus quadrupoles. For this reason, the high-energy physics and accelerator communities have shown much interest in higher-field and higher-gradient superconducting accelerator magnets. The maximum field of NbTi magnets used in all present high-energy machines, including the LHC, is limited to ˜10 T at 1.9 K. Fields above 10 T became possible with the use of Nb3Sn superconductors. Nb3Sn accelerator magnets can provide operating fields up to ˜15 T and can significantly increase the coil temperature margin. Accelerator magnets with operating fields above 15 T require high-temperature superconductors. This review discusses the status and main results of Nb3Sn accelerator magnet research and development and work toward 20-T magnets.

Progress with high-field superconducting magnets for high-energy colliders

DOE PAGES

Apollinari, Giorgio; Prestemon, Soren; Zlobin, Alexander V.

2015-10-01

One of the possible next steps for high-energy physics research relies on a high-energy hadron or muon collider. The energy of a circular collider is limited by the strength of bending dipoles, and its maximum luminosity is determined by the strength of final focus quadrupoles. For this reason, the high-energy physics and accelerator communities have shown much interest in higher-field and higher-gradient superconducting accelerator magnets. The maximum field of NbTi magnets used in all present high-energy machines, including the LHC, is limited to ~10 T at 1.9 K. Fields above 10 T became possible with the use of Nbmore » $$_3$$Sn superconductors. Nb$$_3$$Sn accelerator magnets can provide operating fields up to ~15 T and can significantly increase the coil temperature margin. Accelerator magnets with operating fields above 15 T require high-temperature superconductors. Furthermore, this review discusses the status and main results of Nb$$_3$$Sn accelerator magnet research and development and work toward 20-T magnets.« less

High Temperature Irradiation-Resistant Thermocouple Performance Improvements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joshua Daw; Joy Rempe; Darrell Knudson

2009-04-01

Traditional methods for measuring temperature in-pile degrade at temperatures above 1100 ºC. To address this instrumentation need, the Idaho National Laboratory (INL) developed and evaluated the performance of a high temperature irradiation-resistant thermocouple (HTIR-TC) that contains alloys of molybdenum and niobium. Data from high temperature (up to 1500 ºC) long duration (up to 4000 hours) tests and on-going irradiations at INL’s Advanced Test Reactor demonstrate the superiority of these sensors to commercially-available thermocouples. However, several options have been identified that could further enhance their reliability, reduce their production costs, and allow their use in a wider range of operating conditions.more » This paper presents results from on-going Idaho National Laboratory (INL)/University of Idaho (UI) efforts to investigate options to improve HTIR-TC ductility, reliability, and resolution by investigating specially-formulated alloys of molybdenum and niobium and alternate diameter thermoelements (wires). In addition, on-going efforts to evaluate alternate fabrication approaches, such as drawn and loose assembly techniques will be discussed. Efforts to reduce HTIR-TC fabrication costs, such as the use of less expensive extension cable will also be presented. Finally, customized HTIR-TC designs developed for specific customer needs will be summarized to emphasize the varied conditions under which these sensors may be used.« less

Experimental investigation of anisotropy evolution of AZ31 magnesium alloy sheets under tensile loading

NASA Astrophysics Data System (ADS)

Tari, D. Ghaffari; Worswick, M. J.

2011-05-01

Increasing demand for lighter final products has created new opportunities for the application of new light weight materials. Due to high strength to density ratio and good magnetic resistance properties, magnesium alloys are good candidates to replace steel and aluminum for same application. However, limited numbers of active slip deformation mechanisms, result in a decreased formability at room temperature. Furthermore, wrought magnesium alloys have an initial crystallographic texture, remained from the prior rolling operations, which makes them highly anisotropic. In this paper, tensile tests are performed at room temperature and 200° C at different strain rates and orientations relative to the rolling direction, including rolling, 30°, 45°, 60° and transverse orientation. The strain rates adopted for these experiments varied from 0.001 to 1.0. The testing results show the effect of temperature on the strain rate sensitivity of AZ31 sheets. The extent of deformation is continuously recorded using two separate high temperature extensometers. The results of testing show an increase in the r-values with the plastic deformation. The strain rate sensitivity of AZ31 increased as the temperature was elevated. At higher strain rates the measured r-values are larger and the slope of its evolution with the plastic strain is steeper.

Tucker RNG: Little machine, big impact

Treesearch

Maureen Essen; Caroline Morris; Nathaniel Anderson

2014-01-01

When the Tucker RNG thermal conversion unit connected to the power grid for the first time April 23 in Charlotte, N.C., Richard Tucker, president of Tucker Engineering Associates, could feel the weight of the world coming off his shoulders. After more than a decade of developing his high-temperature, fast pyrolysis system, he was finally seeing it export electricity...

Mechanochemical stabilization and sintering of nanocrystalline the (ZrO2)0.97 (Y2O3)0.03 solid solution from pure oxides

NASA Astrophysics Data System (ADS)

Rendtorff, N. M.; Suárez, G.; Sakka, Y.; Aglietti, E. F.

2011-10-01

The mechanochemical activation processing has proved to be an effective technique to enhance a solid-state reaction at relatively low temperatures. In such a process, the mechanical effects of milling, such as reduction of particle size and mixture homogenization, are accompanied by chemical effects, such as partial decomposition of salts or hydroxides resulting in very active reactants. The objective of the present work is to obtain (ZrO2)0.97(Y2O3)0.03 nanocrystalline tetragonal solid solution powders directly using a high energy milling on a mixture of the pure oxides. A second objective is to evaluate the efficiency of the processing proposed and to characterize both textural and structural evolution of the mixtures during the milling processes and throughout posterior low temperature treatments. The Textural and structural evolution were studied by XRD analysis, specific area measurements (BET) and SEM. Firstly a decrease of the crystallinity of the reactants was observed, followed by the disappearance of Y2O3 diffraction peaks and the partial appearance of the tetragonal phase at room temperature. The solid solution proportion was increased with the high energy milling time, obtaining complete stabilization of the tetragonal solid solution with long milling treatments (60 min).The obtained powders were uniaxially pressed and sintered at different temperatures (600-1400°C) the influence of the milling time was correlated with the sinterization degree and final crystalline composition of the materials. Finally, fully stabilized nanocrystalline zirconia materials were obtained satisfactorily by the proposed method.

The use of an optical method to evaluate prokaryotic oxygen consumption under high pressure condition

NASA Astrophysics Data System (ADS)

Garel, M.; Martini, S.; Lefèvre, D.; Tamburini, C.

2016-02-01

The heterotrophic prokaryotes are the main contributor to organic matter degradation in the ocean and particularly in the deep ocean. Nowadays, a classical way to evaluate the prokaryotic carbon demand (PCD) needs the estimation of both prokaryotic heterotrophic production (PHP) and prokaryotic respiration (PR). PHP measurements in deep-sea waters are relatively well documented and the importance of maintaining the in situ conditions (pressure and temperature) to avoid bias of the real deep-sea activities has been highlighted. However, no accurate methodology is available to measure directly, under in situ conditions (pressure and temperature) PR in the dark ocean. This study is presenting PR measurements under in situ conditions. High-pressure bottles have been adapted with a non-invasive sensor to measure prokaryotic oxygen consumption. The methodology is based on fluorescence quenching where molecular oxygen quenches the luminescence of planar-optode-oxygen sensor widely used in oceanography. Firstly, accuracy, detection limit, precision and response time of oxygen concentration measurements have been investigated in relation to an increase of hydrostatic pressure. Secondly, we will present experiments performed on natural prokaryotic consortium mixed with freshly collected particles to assess the O2 consumption in relation with increasing hydrostatic pressure (150 m depth per day). Finally, first results of coupled PHP and PR measurements at in situ conditions (temperature and pressure) from mesopelagic and bathypelagic samples of the Atlantic Ocean (PAP site), will be discussed. Finally, we will discuss first results of coupled PHP and PR measurements at in situ conditions (temperature and pressure) from Atlantic Ocean mesopelagic and bathypelagic samples (PAP site).

Bioleaching of arsenic from highly contaminated mine tailings using Acidithiobacillus thiooxidans.

PubMed

Lee, Eunseong; Han, Yosep; Park, Jeonghyun; Hong, Jeongsik; Silva, Rene A; Kim, Seungkon; Kim, Hyunjung

2015-01-01

The behavior of arsenic (As) bioleaching from mine tailings containing high amount of As (ca. 34,000 mg/kg) was investigated using Acidithiobacillus thiooxidans to get an insight on the optimal conditions that would be applied to practical heap and/or tank bioleaching tests. Initial pH (1.8-2.2), temperature (25-40 °C), and solid concentration (0.5-4.0%) were employed as experimental parameters. Complementary characterization experiments (e.g., XRD, SEM-EDS, electrophoretic mobility, cell density, and sulfate production) were also carried out to better understand the mechanism of As bioleaching. The results showed that final As leaching efficiency was similar regardless of initial pH. However, greater initial As leaching rate was observed at initial pH 1.8 than other conditions, which could be attributed to greater initial cell attachment to mine tailings. Unlike the trend observed when varying the initial pH, the final As leaching efficiency varied with the changes in temperature and solid concentration. Specifically, As leaching efficiency tended to decrease with increasing temperature due to the decrease in the bacterial growth rate at higher temperature. Meanwhile, As leaching efficiency tended to increase with decreasing solid concentration. The results for jarosite contents in mine tailings residue after bioleaching revealed that much greater amount of the jarosite was formed during the bioleaching reaction at higher solid concentration, suggesting that the coverage of the surface of the mine tailings by jarosite and/or the co-precipitation of the leached As with jarosite could be a dominant factor reducing As leaching efficiency. Copyright © 2014 Elsevier Ltd. All rights reserved.

Insights into the deformation behavior of the CrMnFeCoNi high-entropy alloy revealed by elevated temperature nanoindentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maier-Kiener, Verena; Schuh, Benjamin; George, Easo P.

A CrMnFeCoNi high-entropy alloy was investigated by nanoindentation from room temperature to 400 °C in the nanocrystalline state and cast plus homogenized coarse-grained state. In the latter case a < 100 >-orientated grain was selected by electron back scatter diffraction for nanoindentation. It was found that hardness decreases more strongly with increasing temperature than Young’s modulus, especially for the coarse-grained state. The modulus of the nanocrystalline state was slightly higher than that of the coarse-grained one. For the coarse-grained sample a strong thermally activated deformation behavior was found up to 100–150 °C, followed by a diminishing thermally activated contribution atmore » higher testing temperatures. For the nanocrystalline state, different temperature dependent deformation mechanisms are proposed. At low temperatures, the governing processes appear to be similar to those in the coarse-grained sample, but with increasing temperature, dislocation-grain boundary interactions likely become more dominant. Finally, at 400 °C, decomposition of the nanocrystalline alloy causes a further reduction in thermal activation. Furthermore, this is rationalized by a reduction of the deformation controlling internal length scale by precipitate formation in conjunction with a diffusional contribution.« less

Research on Influence and Prediction Model of Urban Traffic Link Tunnel curvature on Fire Temperature Based on Pyrosim--SPSS Multiple Regression Analysis

NASA Astrophysics Data System (ADS)

Li, Xiao Ju; Yao, Kun; Dai, Jun Yu; Song, Yun Long

2018-05-01

The underground space, also known as the “fourth dimension” of the city, reflects the efficient use of urban development intensive. Urban traffic link tunnel is a typical underground limited-length space. Due to the geographical location, the special structure of space and the curvature of the tunnel, high-temperature smoke can easily form the phenomenon of “smoke turning” and the fire risk is extremely high. This paper takes an urban traffic link tunnel as an example to focus on the relationship between curvature and the temperature near the fire source, and use the pyrosim built different curvature fire model to analyze the influence of curvature on the temperature of the fire, then using SPSS Multivariate regression analysis simulate curvature of the tunnel and fire temperature data. Finally, a prediction model of urban traffic link tunnel curvature on fire temperature was proposed. The regression model analysis and test show that the curvature is negatively correlated with the tunnel temperature. This model is feasible and can provide a theoretical reference for the urban traffic link tunnel fire protection design and the preparation of the evacuation plan. And also, it provides some reference for other related curved tunnel curvature design and smoke control measures.

High temperature annealing of ion irradiated tungsten

DOE PAGES

Ferroni, Francesco; Yi, Xiaoou; Arakawa, Kazuto; ...

2015-03-21

In this study, transmission electron microscopy of high temperature annealing of pure tungsten irradiated by self-ions was conducted to elucidate microstructural and defect evolution in temperature ranges relevant to fusion reactor applications (500–1200°C). Bulk isochronal and isothermal annealing of ion irradiated pure tungsten (2 MeV W + ions, 500°C, 1014 W +/cm 2) with temperatures of 800, 950, 1100 and 1400°C, from 0.5 to 8 h, was followed by ex situ characterization of defect size, number density, Burgers vector and nature. Loops with diameters larger than 2–3 nm were considered for detailed analysis, among which all loops had View themore » MathML source and were predominantly of interstitial nature. In situ annealing experiments from 300 up to 1200°C were also carried out, including dynamic temperature ramp-ups. These confirmed an acceleration of loop loss above 900°C. At different temperatures within this range, dislocations exhibited behaviour such as initial isolated loop hopping followed by large-scale rearrangements into loop chains, coalescence and finally line–loop interactions and widespread absorption by free-surfaces at increasing temperatures. An activation energy for the annealing of dislocation length was obtained, finding E a=1.34±0.2 eV for the 700–1100°C range.« less

Deformation and Phase Transformation Processes in Polycrystalline NiTi and NiTiHf High Temperature Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Benafan, Othmane

2012-01-01

The deformation and transformation mechanisms of polycrystalline Ni49.9Ti50.1 and Ni50.3Ti29.7Hf20 (in at.%) shape memory alloys were investigated by combined experimental and modeling efforts aided by an in situ neutron diffraction technique at stress and temperature. The thermomechanical response of the low temperature martensite, the high temperature austenite phases, and changes between these two states during thermomechanical cycling were probed and reported. In the cubic austenite phase, stress-induced martensite, deformation twinning and slip processes were observed which helped in constructing a deformation map that contained the limits over which each of the identified mechanisms was dominant. Deformation of the monoclinic martensitic phase was also investigated where the microstructural changes (texture, lattice strains, and phase fractions) during room-temperature deformation and subsequent thermal cycling were compared to the bulk macroscopic response. When cycling between these two phases, the evolution of inelastic strains, along with the shape setting procedures were examined and used for the optimization of the transformation properties as a function of deformation levels and temperatures. Finally, this work was extended to the development of multiaxial capabilities at elevated temperatures for the in situ neutron diffraction measurements of shape memory alloys on the VULCAN Diffractometer at Oak Ridge National Laboratory.

Prediction of Mechanical Behaviour of Low Carbon Steel at High Strain Rate Using Thermal Activation Theory and Static Data

NASA Astrophysics Data System (ADS)

Ogawa, Kinya; Kobayashi, Hidetoshi; Sugiyama, Fumiko; Horikawa, Keitaro

Thermal activation theory is well-known to be a useful theory to explain the mechanical behaviour of various metals in the wide range of temperature and strain-rate. In this study, a number of trials to obtain the lower yield stress or flow stress at high strain rates from quasi-static data were carried out using the data shown in the report titled “The final report of research group on high-speed deformation of steels for automotive use”. A relation between the thermal component of stress and the strain rate obtained from experiments for αFe and the temperature-strain rate parameter were used with thermal activation theory. The predictions were successfully performed and they showed that the stress-strain behaviour at high strain rates can be evaluated from quasi-static data with good accuracy.

Progress in high-power continuous-wave quantum cascade lasers [Invited].

PubMed

Figueiredo, Pedro; Suttinger, Matthew; Go, Rowel; Tsvid, Eugene; Patel, C Kumar N; Lyakh, Arkadiy

2017-11-01

Multi-watt continuous-wave room temperature operation with efficiency exceeding 10% has been demonstrated for quantum cascade lasers essentially in the entire mid-wave and long-wave infrared spectral regions. Along with interband cascade lasers, these devices are the only room-temperature lasers that directly convert electrical power into mid- and long-infrared optical power. In this paper, we review the progress in high-power quantum cascade lasers made over the last 10 years. Specifically, an overview of the most important active region, waveguide, and thermal design techniques is presented, and various aspects of die packaging for high-power applications are discussed. Prospects of power scaling with lateral device dimensions for reaching optical power level in the range from 10 W to 20 W are also analyzed. Finally, coherent and spectral beam-combining techniques for very high-power infrared platforms are discussed.

Vortices in high-performance high-temperature superconductors

DOE PAGES

Kwok, Wai-Kwong; Welp, Ulrich; Glatz, Andreas; ...

2016-09-21

The behavior of vortex matter in high-temperature superconductors (HTS) controls the entire electromagnetic response of the material, including its current carrying capacity. In this paper, we review the basic concepts of vortex pinning and its application to a complex mixed pinning landscape to enhance the critical current and to reduce its anisotropy. We focus on recent scientific advances that have resulted in large enhancements of the in-field critical current in state-of-the-art second generation (2G) YBCO coated conductors and on the prospect of an isotropic, high-critical current superconductor in the iron-based superconductors. Finally, we discuss an emerging new paradigm of criticalmore » current by design—a drive to achieve a quantitative correlation between the observed critical current density and mesoscale mixed pinning landscapes by using realistic input parameters in an innovative and powerful large-scale time dependent Ginzburg–Landau approach to simulating vortex dynamics.« less

THE FUEL ELEMENT GRAPHITE. Project DRAGON.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, L.W.; Price, M.S.T.

1963-01-15

The main requirements of a fuel element graphite for reactors based on the Dragon concept are low transmission coefficient for fission products, dimensional stability under service conditions, high strength, high thermal conductivity, high purity, and high resistance to oxidation. Since conclusions reached in early 1960, a considerable amount of information has accumulated concerning the likely behaviour of graphites in high temperature reactor systems, particularly data on dimensional stability under irradiation. The influence of this new knowledge on the development of fuel element graphite with the Dragon Project is discussed in detail in the final section of this paper.

Compact high-efficiency linear cryocooler in single-piston moving magnet design for HOT detectors

NASA Astrophysics Data System (ADS)

Rühlich, I.; Mai, M.; Rosenhagen, C.; Withopf, A.; Zehner, S.

2012-06-01

State of the art Mid Wave IR-technology has the potential to rise the FPA temperature from 77K to 130-150K (High Operation Temperature, HOT). Using a HOT FPA will significantly lower SWaP and keep those parameters finally dominated by the employed cryocooler. Therefore, compact high performance cryocoolers are mandatory. AIM has developed the SX040 cooler, optimized for FPA temperatures of about 95K (presented at SPIE 2010). The SX040 cooler incorporates a high efficient dual piston driving mechanism resulting in a very compact compressor of less than 100mm length. Higher compactness - especially shorter compressors - can be achieved by change from dual to single piston design. The new SX030 compressor has such a single piston Moving Magnet driving mechanism resulting in a compressor length of about 60mm. Common for SX040 and SX030 family is a Moving Magnet driving mechanism with coils placed outside the helium vessel. In combination with high performance plastics for the piston surfaces this design enables lifetimes in excess of 20,000h MTTF. Because of the higher FPA temperature and a higher operating frequency also a new displacer needs to be developed. Based on the existing 1/4" coldfinger interface AIM developed a new displacer optimized for an FPA temperature of 140K and above. This paper gives an overview on the development of this new compact single piston cryocooler. Technical details and performance data will be shown.

Research on low-temperature anodic bonding using induction heating

NASA Astrophysics Data System (ADS)

Chen, Mingxiang; Yi, Xinjian; Yuan, Liulin; Liu, Sheng

2006-04-01

This paper presents a new low temperature silicon-glass anodic bonding process using induction heating. Anodic bonding between silicon and glass (Pyrex 7740) has been achieved at temperature below 300 °C and almost bubble-free interfaces have been obtained. A 1KW 400KHz power supply is used to induce heat in graphite susceptors (simultaneously as the high-voltage electrodes of anodic bonding), which conduct heat to the bonding pair and permanently join the pair in 5 minutes. The results of pull tests indicate a bonding strength of above 5.0MPa for induction heating, which is greater than the strength for resistive heating at the same temperature. The fracture mainly occurs across the interface or inside the glass other than in the interface when the bonding temperature is over 200 °C Finally, the interfaces are examined and analyzed by scanning electron microscopy (SEM) and the bonding mechanisms are discussed.

The effect of forging history on the strength and microstructure of TDNiCr /Ni-20Cr-2ThO2/

NASA Technical Reports Server (NTRS)

Filippi, A. M.

1975-01-01

Forging variables were evaluated to determine their influence on the elevated temperature strength and microstructure of TDNiCr. Grain size was the principal microstructural feature related to elevated temperature strength and was controlled primarily by the thermomechanical variables of forging temperature and final annealing condition. Tests at 1366 K revealed a factor of eight increase in tensile strength as grain size increased from 1 to 150 microns, while stress-rupture strength improved by three to five times as grain size increased from 15 to 150 microns. Forged material of grain size greater than or equal to about 150 microns displayed a level of elevated temperature strength comparable to that of optimized TDNiCr sheet. The presence of a preponderance of small twins and a strong preferred orientation may have also been factors contributing to the excellent high temperature strength of large grain forged material.

Microplastics co-gasification with biomass: Modelling syngas characteristics at low temperatures

NASA Astrophysics Data System (ADS)

Ramos, Ana; Tavares, Raquel; Rouboa, Abel

2018-05-01

To assess the syngas produced through the gasification of microplastics at low temperatures, distinct blends of polyethylene terephthalate (PET) with biomass (vine pruning) were modelled using Aspen Plus. Critical gasification parameters such as co-fuel mixture, temperature and hydrogen production were evaluated, under two different gasifier agents (air and O2). Results have shown that higher PET ratios and higher temperatures (< 1200 °C) lead to enhanced hydrogen yields, for both atmospheres. The calorific content was also seen to increase with growing temperatures, superior LHV being achieved for the mixture with less microplastics fraction (9.2 MJ/Nm3) for both air and O2 environments. A final high-quality syngas was achieved, the dominant requirement determining which parameter to optimize: on one hand, higher H2 contents were seen for the blend with higher microplastic fraction, and on the other higher LHV was achieved for the equimolar mixture.

High-freezing-point fuels used for aviation turbine engines

NASA Technical Reports Server (NTRS)

Friedman, R.

1979-01-01

Broadened-specification aviation fuels could be produced from a greater fraction of crude source material with improvements in fuel supply and price. These fuels, particularly those with increased final boiling temperatures, would have higher freezing temperatures than current aviation turbine fuels. The higher-freezing-point fuels can be substituted in the majority of present commercial flights, since temperature data indicate that in-flight fuel temperatures are relatively mild. For the small but significant fraction of commercial flights where low fuel temperatures make higher freezing-point fuel use unacceptable, adaptations to the fuel or fuel system may be made to accommodate this fuel. Several techniques are discussed. Fuel heating is the most promising concept. One simple system design uses existing heat rejection from the fuel-lubricating oil cooler, another uses an engine-driven generator for electrical heating. Both systems offer advantages that outweigh the obvious penalties.

Characterization of Magma-Driven Hydrothermal Systems at Oceanic Spreading Centers

NASA Astrophysics Data System (ADS)

Farough, A.; Lowell, R. P.; Corrigan, R.

2012-12-01

Fluid circulation in high-temperature hydrothermal systems involves complex water-rock chemical reactions and phase separation. Numerical modeling of reactive transport in multi-component, multiphase systems is required to obtain a full understanding of the characteristics and evolution of hydrothermal vent systems. We use a single-pass parameterized model of high-temperature hydrothermal circulation at oceanic spreading centers constrained by observational parameters such as vent temperature, heat output, and vent field area, together with surface area and depth of the sub-axial magma chamber, to deduce fundamental hydrothermal parameters such as mass flow rate, bulk permeability, conductive boundary layer thickness at the base of the system, magma replenishment rate, and residence time in the discharge zone. All of these key subsurface characteristics are known for fewer than 10 sites out of 300 known hydrothermal systems. The principal limitations of this approach stem from the uncertainty in heat output and vent field area. For systems where data are available on partitioning of heat and chemical output between focused and diffuse flow, we determined the fraction of high-temperature vent fluid incorporated into diffuse flow using a two-limb single pass model. For EPR 9°50` N and ASHES, the diffuse flow temperatures calculated assuming conservative mixing are nearly equal to the observed temperatures indicating that approximately 80%-90% of the hydrothermal heat output occurs as high-temperature flow derived from magmatic heat even though most of the heat output appears as low-temperature diffuse discharge. For the Main Endeavour Field and Lucky Strike, diffuse flow fluids show significant conductive cooling and heating respectively. Finally, we calculate the transport of various geochemical constituents in focused and diffuse flow at the vent field scale and compare the results with estimates of geochemical transports from the Rainbow hydrothermal field where diffuse flow is absent.

Alumina Paste Sublimation Suppression Barrier for Thermoelectric Device

NASA Technical Reports Server (NTRS)

Caillat, Thierry (Inventor); Paik, Jong-Ah (Inventor)

2014-01-01

Alumina as a sublimation suppression barrier for a Zintl thermoelectric material in a thermoelectric power generation device operating at high temperature, e.g. at or above 1000K, is disclosed. The Zintl thermoelectric material may comprise Yb.sub.14MnSb.sub.11. The alumina may be applied as an adhesive paste dried and cured on a substantially oxide free surface of the Zintl thermoelectric material and polished to a final thickness. The sublimation suppression barrier may be finalized by baking out the alumina layer on the Zintl thermoelectric material until it becomes substantially clogged with ytterbia.

Climatic effects on mosquito abundance in Mediterranean wetlands

PubMed Central

2014-01-01

Background The impact of climate change on vector-borne diseases is highly controversial. One of the principal points of debate is whether or not climate influences mosquito abundance, a key factor in disease transmission. Methods To test this hypothesis, we analysed ten years of data (2003–2012) from biweekly surveys to assess inter-annual and seasonal relationships between the abundance of seven mosquito species known to be pathogen vectors (West Nile virus, Usutu virus, dirofilariasis and Plasmodium sp.) and several climatic variables in two wetlands in SW Spain. Results Within-season abundance patterns were related to climatic variables (i.e. temperature, rainfall, tide heights, relative humidity and photoperiod) that varied according to the mosquito species in question. Rainfall during winter months was positively related to Culex pipiens and Ochlerotatus detritus annual abundances. Annual maximum temperatures were non-linearly related to annual Cx. pipiens abundance, while annual mean temperatures were positively related to annual Ochlerotatus caspius abundance. Finally, we modelled shifts in mosquito abundances using the A2 and B2 temperature and rainfall climate change scenarios for the period 2011–2100. While Oc. caspius, an important anthropophilic species, may increase in abundance, no changes are expected for Cx. pipiens or the salt-marsh mosquito Oc. detritus. Conclusions Our results highlight that the effects of climate are species-specific, place-specific and non-linear and that linear approaches will therefore overestimate the effect of climate change on mosquito abundances at high temperatures. Climate warming does not necessarily lead to an increase in mosquito abundance in natural Mediterranean wetlands and will affect, above all, species such as Oc. caspius whose numbers are not closely linked to rainfall and are influenced, rather, by local tidal patterns and temperatures. The final impact of changes in vector abundance on disease frequency will depend on the direct and indirect effects of climate and other parameters related to pathogen amplification and spillover on humans and other vertebrates. PMID:25030527

Investigation on Two-Stage 300 HZ Pulse Tube Cryocooler

NASA Astrophysics Data System (ADS)

Cai, H. K.; Yang, L. W.; Hong, G. T.; Luo, E. C.; Zhou, Y.

2010-04-01

In the past few years, ultra-high frequency pulse tube cryocoolers are becoming a research hotspot for their portability and compactness in aerospace and aviation applications. For preliminary research, a two-stage pulse tube cryocooler working at 300 Hz driven by a thermoacoustic engine is established to investigate the problems due to ultra high frequency, and several results have been derived in our early reports. In order to study the effect of thermal penetration depth, this paper presents the cooler adopting copper mesh as the regenerator, and comparison with stainless steel mesh is given. In addition, the influence of inertance tube on the lowest possible cooler temperature is also tested. Finally, we discuss the improvement for getting a lower temperature.

An atomic beam source for fast loading of a magneto-optical trap under high vacuum

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDowall, Peter D.; Gruenzweig, Tzahi; Hilliard, Andrew

2012-05-15

We report on a directional atomic beam created using an alkali metal dispenser and a nozzle. By applying a high current (15 A) pulse to the dispenser at room temperature we can rapidly heat it to a temperature at which it starts dispensing, avoiding the need for preheating. The atomic beam produced is capable of loading 90% of a magneto-optical trap (MOT) in less than 7 s while maintaining a low vacuum pressure of <10{sup -11} Torr. The transverse velocity components of the atomic beam are measured to be within typical capture velocities of a rubidium MOT. Finally, we showmore » that the atomic beam can be turned off within 1.8 s.« less

Novel polyimide compositions based on 4,4': Isophthaloyldiphthalic anaydride (IDPA)

NASA Technical Reports Server (NTRS)

Pratt, J. Richard (Inventor); Saintclair, Terry L. (Inventor)

1989-01-01

A series of twelve high temperature, high performance polyimide compositions based on 4,4'-isophthaloyl diphthalic anhydride (IDPA) was prepared and characterized. Tough, film-forming, organic solvent-insoluble polyimides were obtained. Three materials were semicrystalline. Several gave excellent long-term thermooxidative stability by isothermal thermogravimetric analysis (ITGA) at 300 C and 350 C in air when compared to Kapton H film (duPont). One extensively studied material displayed different levels of semicrystallinity over a wide range of final cure time/temperatures. The polyimide from IDPA and 1,3-bis (4-aminophenoxy 4'-benzoyl) benzene exhibited multiple crystallization and melting behavior, implying the existence of two kinetic and two thermodynamic crystallization and melting transitions by differential scanning calorimetry (DSC).

Application of a Model for Quenching and Partitioning in Hot Stamping of High-Strength Steel

NASA Astrophysics Data System (ADS)

Zhu, Bin; Liu, Zhuang; Wang, Yanan; Rolfe, Bernard; Wang, Liang; Zhang, Yisheng

2018-04-01

Application of quenching and partitioning process in hot stamping has proven to be an effective method to improve the plasticity of advanced high-strength steels (AHSSs). In this study, the hot stamping and partitioning process of advanced high-strength steel 30CrMnSi2Nb is investigated with a hot stamping mold. Given the specific partitioning time and temperature, the influence of quenching temperature on the volume fraction of microstructure evolution and mechanical properties of the above steel are studied in detail. In addition, a model for quenching and partitioning process is applied to predict the carbon diffusion and interface migration during partitioning, which determines the retained austenite volume fraction and final properties of the part. The predicted trends of the retained austenite volume fraction agree with the experimental results. In both cases, the volume fraction of retained austenite increases first and then decreases with the increasing quenching temperature. The optimal quenching temperature is approximately 290 °C for 30CrMnSi2Nb with the partition conditions of 425 °C and 20 seconds. It is suggested that the model can be used to help determine the process parameters to obtain retained austenite as much as possible.

Facility for assessing spectral normal emittance of solid materials at high temperature.

PubMed

Mercatelli, Luca; Meucci, Marco; Sani, Elisa

2015-10-10

Spectral emittance is a key topic in the study of new compositions, depositions, and mechanical machining of materials for solar absorption and for renewable energies in general. The present work reports on the realization and testing of a new experimental facility for the measurement of directional spectral emittance in the range of 2.5-20 μm. Our setup provides emittance spectral information in a completely controlled environment at medium-high temperatures up to 1200 K. We describe the layout and first tests on the device, comparing the results obtained for hafnium carbide and tantalum diboride ultrarefractory ceramic samples to previous quasi-monochromatic measurements carried out in the PROMES-CNRS (PROcedes, Materiaux et Energie Solaire- Centre National de la Recherche Scientifique, France) solar furnace, obtaining a good agreement. Finally, to assess the reliability of the widely used approach of estimating the spectral emittance from room-temperature reflectance spectrum, we compared the calculation in the 2.5-17 μm spectral range to the experimental high-temperature spectral emittance, obtaining that the spectral trend of calculated and measured curves is similar but the calculated emittance underestimates the measured value.

Effect of Particle Morphology on Cold Spray Deposition of Chromium Carbide-Nickel Chromium Cermet Powders

NASA Astrophysics Data System (ADS)

Fernandez, Ruben; Jodoin, Bertrand

2017-08-01

Nickel chromium-chromium carbide coatings provide good corrosion and wear resistance at high temperatures, making them ideal for applications where a harsh environment and high temperatures are expected. Thermal spray processes are preferred as deposition technique of cermets, but the high process temperatures can lead to decarburization and reduction of the coatings properties. Cold spray uses lower temperatures preventing decarburization. Since the metallic phase remains solid, the feedstock powder morphology becomes crucial on the deposition behavior. Six commercially available powders were studied, varying in morphology and metal/ceramic ratios. The powders were categorized into 4 groups depending on their morphology. Spherical powders lead to substrate erosion due to their limited overall ductility. Porous agglomerated and sintered powders lead to severely cracked coatings. For dense agglomerated and sintered powders, the outcome depended on the initial metal/ceramic ratio: powders with 25 wt.% NiCr led to substrate erosion while 35 wt.% NiCr powders led to dense coatings. Finally, blended ceramic-metal mixtures also lead to dense coatings. All coatings obtained had lower ceramic content than the initial feedstock powders. Interrupted spray tests, combined with FEA, helped drawing conclusions on the deposition behavior to explain the obtained results.

Positron annihilation study of the high- Tc (Bi,Pb) 2Sr 2Ca 2Cu 3O x superconductor

NASA Astrophysics Data System (ADS)

Lim, H. J.; Byrne, J. G.

1997-03-01

Positron lifetime spectroscopy (PLS) and positron Doppler-broadening spectroscopy (PDBS) were applied to the high- Tc lead-doped Bi 2Sr 2Ca 2Cu 3O x (BPSCCO 2223) superconductor as a function of temperature. Neither positron lifetimes nor Doppler parameters ( S, W, and{S}/{W}) showed significant change through Tc. This may result from having the highest positron density in the open BiO 2 double layers and no significant positron density in the superconducting CuO 2 layers where positrons, if mainly present, are known to be sensitive to the transition in other high- Tc superconductors. Doppler parameters showed that the probability of positron annihilations with core electrons in the lattice slightly increased and that the probability of positron annihilations with conduction electrons slightly decreased as temperature decreased from ambient temperature to 20 K. The lifetime associated with positron annihilations in the perfect lattice of the sample ( τ1) was 209 ps and, due to the annihilations at internal surfaces or voids in the sample ( τ2) was about 540 ps, independent of temperature. Finally, the mean lifetime for BSCCO 2223 was about 307 ps.

Composite electrolyte with proton conductivity for low-temperature solid oxide fuel cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raza, Rizwan, E-mail: razahussaini786@gmail.com; Department of Energy Technology, Royal Institute of Technology, KTH, Stockholm 10044; Ahmed, Akhlaq

In the present work, cost-effective nanocomposite electrolyte (Ba-SDC) oxide is developed for efficient low-temperature solid oxide fuel cells (LTSOFCs). Analysis has shown that dual phase conduction of O{sup −2} (oxygen ions) and H{sup +} (protons) plays a significant role in the development of advanced LTSOFCs. Comparatively high proton ion conductivity (0.19 s/cm) for LTSOFCs was achieved at low temperature (460 °C). In this article, the ionic conduction behaviour of LTSOFCs is explained by carrying out electrochemical impedance spectroscopy measurements. Further, the phase and structure analysis are investigated by X-ray diffraction and scanning electron microscopy techniques. Finally, we achieved an ionic transport numbermore » of the composite electrolyte for LTSOFCs as high as 0.95 and energy and power density of 90% and 550 mW/cm{sup 2}, respectively, after sintering the composite electrolyte at 800 °C for 4 h, which is promising. Our current effort toward the development of an efficient, green, low-temperature solid oxide fuel cell with the incorporation of high proton conductivity composite electrolyte may open frontiers in the fields of energy and fuel cell technology.« less

Polymeric Mold For Providing A Microscale Part

DOEpatents

Boehme, Dale R.; Bankert, Michelle A.; Christenson, Todd R.

2005-01-11

The invention is a developer system for developing a PMMA photoresist having exposed patterns comprising features having both very small sizes, and very high aspect ratios. The developer system of the present invention comprises a developer tank, an intermediate rinse tank and a final rinse tank, each tank having a source of high frequency sonic agitation, temperature control, and continuous filtration. It has been found that by moving a patterned wafer, through a specific sequence of developer/rinse solutions, where an intermediate rinse solution completes development of those portions of the exposed resist left undeveloped after the development solution, by agitating the solutions with a source of high frequency sonic vibration, and by adjusting and closely controlling the temperatures and continuously filtering and recirculating these solutions, it is possible to maintain the kinetic dissolution of the exposed PMMA polymer as the rate limiting step.

FINAL REPORT. DOE Grant Award Number DE-SC0004062

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiesa, Luisa

With the support of the DOE-OFES Early Career Award and the Tufts startup support the PI has developed experimental and analytical expertise on the electromechanical characterization of Low Temperature Superconductor (LTS) and High Temperature Superconductor (HTS) for high magnetic field applications. These superconducting wires and cables are used in fusion and high-energy physics magnet applications. In a short period of time, the PI has built a laboratory and research group with unique capabilities that include both experimental and numerical modeling effort to improve the design and performance of superconducting cables and magnets. All the projects in the PI’s laboratory exploremore » the fundamental electromechanical behavior of superconductors but the types of materials, geometries and operating conditions are chosen to be directly relevant to real machines, in particular fusion machines like ITER.« less

Numerical simulation of temperature field, microstructure evolution and mechanical properties of HSS during hot stamping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Dongyong; Liu, Wenquan; Ying, Liang, E-mail: pinghu@dlut.edu.cn

The hot stamping of boron steels is widely used to produce ultra high strength automobile components without any spring back. The ultra high strength of final products is attributed to the fully martensitic microstructure that is obtained through the simultaneous forming and quenching of the hot blanks after austenization. In the present study, a mathematical model incorporating both heat transfer and the transformation of austenite is presented. A FORTRAN program based on finite element technique has been developed which permits the temperature distribution and microstructure evolution of high strength steel during hot stamping process. Two empirical diffusion-dependent transformation models undermore » isothermal conditions were employed respectively, and the prediction capability on mechanical properties of the models were compared with the hot stamping experiment of an automobile B-pillar part.« less

A high sensitivity ultralow temperature RF conductance and noise measurement setup.

PubMed

Parmentier, F D; Mahé, A; Denis, A; Berroir, J-M; Glattli, D C; Plaçais, B; Fève, G

2011-01-01

We report on the realization of a high sensitivity RF noise measurement scheme to study small current fluctuations of mesoscopic systems at milli-Kelvin temperatures. The setup relies on the combination of an interferometric amplification scheme and a quarter-wave impedance transformer, allowing the measurement of noise power spectral densities with gigahertz bandwidth up to five orders of magnitude below the amplifier noise floor. We simultaneously measure the high frequency conductance of the sample by derivating a portion of the signal to a microwave homodyne detection. We describe the principle of the setup, as well as its implementation and calibration. Finally, we show that our setup allows to fully characterize a subnanosecond on-demand single electron source. More generally, its sensitivity and bandwidth make it suitable for applications manipulating single charges at GHz frequencies.

Demonstrating antiphase domain boundary-free GaAs buffer layer on zero off-cut Si (0 0 1) substrate for interfacial misfit dislocation GaSb film by metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Ha, Minh Thien Huu; Hoang Huynh, Sa; Binh Do, Huy; Nguyen, Tuan Anh; Luc, Quang Ho; Chang, Edward Yi

2017-08-01

High quality 40 nm GaSb thin film was grown on the zero off-cut Si (0 0 1)-oriented substrate using metalorganic chemical vapor deposition with the temperature-graded GaAs buffer layer. The growth time of the GaAs nucleation layer, which was deposited at a low temperature of 490 °C, is systematically investigated in this paper. Cross-sections of the high resolution transmission electron microscopy images indicate that the GaAs compound formed 3D-islands first before to quasi-2D islands, and finally formed uniform GaAs layer. The optimum thickness of the 490 °C-GaAs layer was found to be 10 nm to suppress the formation of antiphase domain boundaries (APDs). The thin GaAs nucleation layer had a root-mean-square surface roughness of 0.483 nm. This allows the continued high temperature GaAs buffer layer to be achieved with low threading dislocation density of around 7.1  ×  106 cm-2 and almost invisible APDs. Finally, a fully relaxed GaSb film was grown on the top of the GaAs/Si heterostructure using interfacial misfit dislocation growth mode. These results indicate that the GaSb epitaxial layer can be grown on Si substrate with GaAs buffer layer for future p-channel metal-oxide-semiconductor field effect transistors (MOSFETs) applications.

High-speed mixture fraction and temperature imaging of pulsed, turbulent fuel jets auto-igniting in high-temperature, vitiated co-flows

NASA Astrophysics Data System (ADS)

Papageorge, Michael J.; Arndt, Christoph; Fuest, Frederik; Meier, Wolfgang; Sutton, Jeffrey A.

2014-07-01

In this manuscript, we describe an experimental approach to simultaneously measure high-speed image sequences of the mixture fraction and temperature fields during pulsed, turbulent fuel injection into a high-temperature, co-flowing, and vitiated oxidizer stream. The quantitative mixture fraction and temperature measurements are determined from 10-kHz-rate planar Rayleigh scattering and a robust data processing methodology which is accurate from fuel injection to the onset of auto-ignition. In addition, the data processing is shown to yield accurate temperature measurements following ignition to observe the initial evolution of the "burning" temperature field. High-speed OH* chemiluminescence (CL) was used to determine the spatial location of the initial auto-ignition kernel. In order to ensure that the ignition kernel formed inside of the Rayleigh scattering laser light sheet, OH* CL was observed in two viewing planes, one near-parallel to the laser sheet and one perpendicular to the laser sheet. The high-speed laser measurements are enabled through the use of the unique high-energy pulse burst laser system which generates long-duration bursts of ultra-high pulse energies at 532 nm (>1 J) suitable for planar Rayleigh scattering imaging. A particular focus of this study was to characterize the fidelity of the measurements both in the context of the precision and accuracy, which includes facility operating and boundary conditions and measurement of signal-to-noise ratio (SNR). The mixture fraction and temperature fields deduced from the high-speed planar Rayleigh scattering measurements exhibited SNR values greater than 100 at temperatures exceeding 1,300 K. The accuracy of the measurements was determined by comparing the current mixture fraction results to that of "cold", isothermal, non-reacting jets. All profiles, when properly normalized, exhibited self-similarity and collapsed upon one another. Finally, example mixture fraction, temperature, and OH* emission sequences are presented for a variety for fuel and vitiated oxidizer combinations. For all cases considered, auto-ignition occurred at the periphery of the fuel jet, under very "lean" conditions, where the local mixture fraction was less than the stoichiometric mixture fraction ( ξ < ξ s). Furthermore, the ignition kernel formed in regions of low scalar dissipation rate, which agrees with previous results from direct numerical simulations.

Ion and Electron Heating Characteristics of Magnetic Re- Connection in Mast Tokamak Merging Experiment

NASA Astrophysics Data System (ADS)

Tanabe, Hiroshi; Inomoto, Michiaki; Ono, Yasushi; Yamada, Takuma; Imazawa, Ryota; Cheng, Chio-Zong

2016-07-01

We present results of recent studies of high power heating of magnetic reconnection, the fundamental process of several astrophysical events such as solar flare, in the Mega Amp Spherical Tokamak (MAST) - the world largest merging experiment. In addition to the previously reported significant reconnection heating up to ˜1keV [1], detailed local profiles of electron and ion temperature have been measured using a ultra-fine 300 channel Ruby- and a 130 channel YAG-Thomson scattering and a new 32 channel ion Doppler tomography diagnostics [2]. 2D profile measurement of electron temperature revealed highly localized heating structure at the X point with the characteristic scale length of 0.02-0.05m0.3T), a thick layer of closed flux surface surrounding the current sheet sustains the temperature profile for longer time than the electron and ion energy relaxation time ˜4-10ms, finally forming triple peak structures of ion and electron temperatures at the X point and in the downstream. While the peak electron temperature at the X point increases with toroidal field, the bulk electron temperature and the ion temperature in the downstream are unaffected. [1] Y. Ono et.al., Plasma Phys. Control. Fusion 54, 124039 (2012) [2] H. Tanabe et. al., Nucl. Fusion 53, 093027 (2013). [3] H. Tanabe et.al., Phys. Rev. Lett. 115, 215004 (2015)

Controllable Growth of Perovskite Films by Room-Temperature Air Exposure for Efficient Planar Heterojunction Photovoltaic Cells

DOE PAGES

Yang, Bin; Dyck, Ondrej; Poplawsky, Jonathan; ...

2015-12-01

A two-step-solution-processing approach has been established to grow void-free perovskite films for low-cost and high-performance planar heterojunction photovoltaic devices. We generally applied a high-temperature thermal annealing treatment in order to drive the diffusion of CH 3NH 3I precursor molecules into the compact PbI 2 layer to form perovskite films. But, thermal annealing for extended periods would lead to degraded device performance due to the defects generated by decomposition of perovskite into PbI 2. In this work, we explored a controllable layer-by-layer spin-coating method to grow bilayer CH 3NH 3I/PbI 2 films, and then drive the interdiffusion between PbI 2 andmore » CH 3NH 3I layers by a simple room-temperature-air-exposure for making well-oriented, highly-crystalline perovskite films without thermal annealing. This high degree of crystallinity resulted in a carrier diffusion length of ~ 800 nm and high device efficiency of 15.6%, which is comparable to the reported values from thermally-annealed perovskite films based counterparts. Finally, the simplicity and high device performance of this processing approach is highly promising for direct integration into industrial-scale device manufacture.« less

Coherent band excitations in CePd 3: A comparison of neutron scattering and ab initio theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goremychkin, Eugene A.; Park, Hyowon; Osborn, Raymond

In common with many strongly correlated electron systems, intermediate valence compounds are believed to display a crossover from a high-temperature regime of incoherently fluctuating local moments to a low-temperature regime of coherent hybridized bands. In this work, we show that inelastic neutron scattering measurements of the dynamic magnetic susceptibility of CePd 3 provides a benchmark for ab initio calculations based on dynamical mean field theory. The magnetic response is strongly momentum dependent thanks to the formation of coherent f-electron bands at low temperature, with an amplitude that is strongly enhanced by local particle-hole interactions. Finally, the agreement between experiment andmore » theory shows that we have a robust first-principles understanding of the temperature dependence of f-electron coherence.« less

Solar energy

NASA Technical Reports Server (NTRS)

Rapp, D.

1981-01-01

The book opens with a review of the patterns of energy use and resources in the United States, and an exploration of the potential of solar energy to supply some of this energy in the future. This is followed by background material on solar geometry, solar intensities, flat plate collectors, and economics. Detailed attention is then given to a variety of solar units and systems, including domestic hot water systems, space heating systems, solar-assisted heat pumps, intermediate temperature collectors, space heating/cooling systems, concentrating collectors for high temperatures, storage systems, and solar total energy systems. Finally, rights to solar access are discussed.

A Study of Production of Miscibility Gap Alloys with Controlled Structures

NASA Technical Reports Server (NTRS)

Parr, R. A.; Johnston, M. H.; Burka, J. A.; Davis, J. H.; Lee, J. A.

1983-01-01

Composite materials were directionally solidified using a new technique to align the constituents longitudinally along the length of the specimen. In some instances a tin coating was applied and diffused into the sample to form a high transition temperature superconducting phase. The superconducting properties were measured and compared with the properties obtained for powder composites and re-directionally solidified powder compacts. The samples which were compacted and redirectionally solidified showed the highest transition temperature and wildest transition range. This indicates that both steps, powder compaction and resolidification, determine the final superconducting properties of the material.

Spalling of a Thin Si Layer by Electrodeposit-Assisted Stripping

NASA Astrophysics Data System (ADS)

Kwon, Youngim; Yang, Changyol; Yoon, Sang-Hwa; Um, Han-Don; Lee, Jung-Ho; Yoo, Bongyoung

2013-11-01

A major goal in solar cell research is to reduce the cost of the final module. Reducing the thickness of the crystalline silicon substrate to several tens of micrometers can reduce material costs. In this work, we describe the electrodeposition of a Ni-P alloy, which induces high stress in the silicon substrate at room temperature. The induced stress enables lift-off of the thin-film silicon substrate. After lift-off of the thin Si film, the mother substrate can be reused, reducing material costs. Moreover, the low-temperature process expected to be improved Si substrate quality.

Monolith catalysts for closed-cycle carbon dioxide lasers

NASA Technical Reports Server (NTRS)

Herz, Richard K.

1994-01-01

The general subject area of the project involved the development of solid catalysts that have high activity at low temperature for the oxidation of gases such as CO. The original application considered was CO oxidation in closed-cycle CO2 lasers. The scope of the project was subsequently extended to include oxidation of gases in addition to CO and applications such as air purification and exhaust gas emission control. The primary objective of the final phase grant was to develop design criteria for the formulation of new low-temperature oxidation catalysts utilizing Monte Carlo simulations of reaction over NASA-developed catalysts.

Development of chemically vapor deposited rhenium emitters of (0001) preferred crystal orientation

NASA Technical Reports Server (NTRS)

Yang, L.; Hudson, R. G.

1973-01-01

Rhenium thermionic emitters were prepared by the pyrolysis of rhenium chlorides formed by the chlorination of rhenium pellets. The impurity contents, microstructures, degrees of (0001) preferred crystal orientation, and vacuum electron work functions of these emitters were determined as a function of deposition parameters, such as substrate temperature, rhenium pellet temperature and chlorine flow rate. A correlation between vacuum electron work function and degree of (0001) preferred crystal orientation was established. Conditions for depositing porosity-free rhenium emitters of high vacuum electron work functions were defined. Finally, three cylindrical rhenium emitters were prepared under the optimum deposition conditions.

Research on early-warning index of the spatial temperature field in concrete dams.

PubMed

Yang, Guang; Gu, Chongshi; Bao, Tengfei; Cui, Zhenming; Kan, Kan

2016-01-01

Warning indicators of the dam body's temperature are required for the real-time monitoring of the service conditions of concrete dams to ensure safety and normal operations. Warnings theories are traditionally targeted at a single point which have limitations, and the scientific warning theories on global behavior of the temperature field are non-existent. In this paper, first, in 3D space, the behavior of temperature field has regional dissimilarity. Through the Ward spatial clustering method, the temperature field was divided into regions. Second, the degree of order and degree of disorder of the temperature monitoring points were defined by the probability method. Third, the weight values of monitoring points of each regions were explored via projection pursuit. Forth, a temperature entropy expression that can describe degree of order of the spatial temperature field in concrete dams was established. Fifth, the early-warning index of temperature entropy was set up according to the calculated sequential value of temperature entropy. Finally, project cases verified the feasibility of the proposed theories. The early-warning index of temperature entropy is conducive to the improvement of early-warning ability and safety management levels during the operation of high concrete dams.

The effect of temperature on the germination of Melocactus violaceus Pfeiff. (Cactaceae), a threatened species in restinga sandy coastal plain of Brazil.

PubMed

Zamith, Luiz R; Cruz, Denise D; Richers, Bárbara T T

2013-01-01

Melocactus violaceus is an endangered species due to habitat destruction and the overcollection of this species for ornamental use. The aim of this study was to test the effect of different temperatures on the germination of M. violaceus. Three treatments were conducted: a constant temperature of 25ºC, a 20-35ºC alternating temperature, both inside germination chamber, and an alternating temperature under room temperature (mean temperature ranged from 25-37ºC). The final seed germination rates at the alternating temperature treatments were not significantly different (65% in the seed germinator and 62.5% at room condition). However, both treatments with alternating temperatures had significantly higher germination rates compared to the treatment kept at the constant temperature (8%). Our study showed that alternating temperatures between 20 and 37ºC provides satisfactory conditions to induce a high percentage of seed germination of M. violaceus, without the passage of seeds through the digestive tract of its natural disperser, the lizard Tropidurus torquatus. This condition contributes to efficiently producing seedlings that can be reintroduced into conservation areas or used as ornamentals that may help reduce the overcollection of the remaining native populations.

Magnetic ordering temperatures in rare earth metal dysprosium under ultrahigh pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.

Magnetic ordering temperatures in heavy rare earth metal Dysprosium (Dy) have been studied using an ultrasensitive electrical transport measurement technique in a designer diamond anvil cell to extreme conditions of pressure to 69 GPa and temperature to 10 K. Previous studies using magnetic susceptibility measurements at high pressures were only able to track magnetic ordering temperature till 7 GPa in the hexagonal close packed ( hcp) phase of Dy. Our studies indicate that the magnetic ordering temperature shows an abrupt drop of 80 K at the hcp-Sm phase transition followed by a gradual decrease that continues till 17 GPa. Thismore » is followed by a rapid increase in the magnetic ordering temperatures in the double hexagonal close packed phase and finally leveling off in the distorted face centered cubic phase of Dy. Lastly, our studies reaffirm that 4f-shell remain localized in Dy and there is no loss of magnetic moment or 4f-shell delocalization for pressures up to 69 GPa.« less

Study of the Effects of High Temperatures on the Engineering Properties of Steel 42CrMo4

NASA Astrophysics Data System (ADS)

Brnic, Josip; Turkalj, Goran; Canadija, Marko; Lanc, Domagoj; Brcic, Marino

2015-02-01

The paper presents and analyzes the experimental results of the effect of elevated temperatures on the engineering properties of steel 42CrMo4. Experimental data relating to the mechanical properties of the material, the creep resistance as well as Charpy impact energy. Temperature dependence of the mentioned properties is also shown. Some of creep curves were simulated using rheological models and an analytical equation. Finally, an assessment of fracture toughness was made that was based on experimentally determined Charpy impact energy. Based on the obtained results it is visible that the tensile strength (617 MPa) and yield strength (415 MPa) have the highest value at the room temperature while at the temperature of 700 °C (973 K) these values significantly decrease. This steel can be considered resistant to creep at 400 °C (673 K), but at higher temperatures this steel can be subjected to low levels of stress in a shorter time.

Magnetic ordering temperatures in rare earth metal dysprosium under ultrahigh pressures

DOE PAGES

Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.; ...

2014-04-03

Magnetic ordering temperatures in heavy rare earth metal Dysprosium (Dy) have been studied using an ultrasensitive electrical transport measurement technique in a designer diamond anvil cell to extreme conditions of pressure to 69 GPa and temperature to 10 K. Previous studies using magnetic susceptibility measurements at high pressures were only able to track magnetic ordering temperature till 7 GPa in the hexagonal close packed ( hcp) phase of Dy. Our studies indicate that the magnetic ordering temperature shows an abrupt drop of 80 K at the hcp-Sm phase transition followed by a gradual decrease that continues till 17 GPa. Thismore » is followed by a rapid increase in the magnetic ordering temperatures in the double hexagonal close packed phase and finally leveling off in the distorted face centered cubic phase of Dy. Lastly, our studies reaffirm that 4f-shell remain localized in Dy and there is no loss of magnetic moment or 4f-shell delocalization for pressures up to 69 GPa.« less

Best Practices for Continuous Monitoring of Temperature and Flow in Wadeable Streams (Final Report)

EPA Science Inventory

This final report is a technical "best practices" document describing sensor deployment for and collection of continuous temperature and flow data at ungaged sites in wadeable streams. This document addresses questions related to equipment needs; configuration, placement, and ins...

Structure and magnetism in LaCoO 3

DOE PAGES

Belanger, David P.; Keiber, T.; Bridges, Frank; ...

2015-12-11

In this paper, the temperature dependence of the hexagonal lattice parameter c of single crystal LaCoO 3 (LCO) with H = 0 and 800 Oe, as well as LCO bulk powders with H = 0, was measured using high-resolution x-ray scattering near the transition temperature T o ≈ 35 K. The change of c(T ) is well characterized by a power law in T – T o for T > T o and by a temperature independent constant for T < T o when convoluted with a Gaussian function of width 8.5 K. Finally, this behavior is discussed in themore » context of the unusual magnetic behavior observed in LCO as well as recent generalized gradient approximation calculations.« less

High pressure study of molecular dynamics of protic ionic liquid lidocaine hydrochloride.

PubMed

Swiety-Pospiech, A; Wojnarowska, Z; Pionteck, J; Pawlus, S; Grzybowski, A; Hensel-Bielowka, S; Grzybowska, K; Szulc, A; Paluch, M

2012-06-14

In this paper, we investigate the effect of pressure on the molecular dynamics of protic ionic liquid lidocaine hydrochloride, a commonly used pharmaceutical, by means of dielectric spectroscopy and pressure-temperature-volume methods. We observed that near T(g) the pressure dependence of conductivity relaxation times reveals a peculiar behavior, which can be treated as a manifestation of decoupling between ion migration and structural relaxation times. Moreover, we discuss the validity of thermodynamic scaling in lidocaine HCl. We also employed the temperature-volume Avramov model to determine the value of pressure coefficient of glass transition temperature, dT(g)/dP|(P = 0.1). Finally, we investigate the role of thermal and density fluctuations in controlling of molecular dynamics of the examined compound.

Correlated phonons and the Tc-dependent dynamical phonon anomalies

NASA Astrophysics Data System (ADS)

Hakioğlu, T.; Türeci, H.

1997-11-01

Anomalously large low-temperature phonon anharmonicities can lead to static as well as dynamical changes in the low-temperature properties of the electron-phonon system. In this work, we focus our attention on the dynamically generated low-temperature correlations in an interacting electron-phonon system using a self-consistent dynamical approach in the intermediate coupling range. In the context of the model, the polaron correlations are produced by the charge-density fluctuations which are generated dynamically by the electron-phonon coupling. Conversely, the latter is influenced in the presence of the former. The purpose of this work is to examine the dynamics of this dual mechanism between the two using the illustrative Fröhlich model. In particular, the influence of the low-temperature phonon dynamics on the superconducting properties in the intermediate coupling range is investigated. The influence on the Holstein reduction factor as well as the enhancement in the zero-point fluctuations and in the electron-phonon coupling are calculated numerically. We also examine these effects in the presence of superconductivity. Within this model, the contribution of the electron-phonon interaction as one of the important elements in the mechanisms of superconductivity can reach values as high as 15-20% of the characteristic scale of the lattice vibrational energy. The second motivation of this work is to understand the nature of the Tc-dependent temperature anomalies observed in the Debye-Waller factor, dynamical pair correlations, and average atomic vibrational energies for a number of high-temperature superconductors. In our approach we do not claim nor believe that the electron-phonon interaction is the primary mechanism leading to high-temperature superconductivity. Nevertheless, our calculations suggest that the dynamically induced low-temperature phonon correlation model can account for these anomalies and illustrates their possible common origin. Finally, the relevance of incorporating these low-temperature effects into more realistic models of high-temperature superconductivity including both the charge and spin degrees and other similar ideas existing in the literature are discussed.

The influences of ambient temperature and crude protein levels on performance and serum biochemical parameters in broilers.

PubMed

Liu, Q W; Feng, J H; Chao, Z; Chen, Y; Wei, L M; Wang, F; Sun, R P; Zhang, M H

2016-04-01

This study was undertaken to investigate the effects of ambient temperature, crude protein levels and their interaction on performance and serum biochemical parameters of broiler chickens. A total of 216 Arbor Acre broiler chickens (108 males and 108 females) were used in a 2 × 3 factorial arrangement and randomly reared at two temperatures (normal temperature: 23 °C; daily cyclic high temperature: 28-32 °C) and fed on three diets with different crude protein levels (153.3, 183.3 or 213.3 g/kg, with constant essential amino acids) from 28 to 42 days of age. Daily cyclic high ambient temperature decreased final body weight, average daily weight gain, average daily feed intake and serum total protein contents (p < 0.001, p < 0.001, p < 0.001, p = 0.008 respectively), but increased feed/gain, mortality, respiratory rate, rectal temperature, serum uric acid contents and serum creatine kinase activity (p = 0.008, p = 0.003, p < 0.0001, p < 0.0001, p < 0.0001, p = 0.003 respectively), irrespective of crude protein levels. At the ambient temperature, reducing crude protein levels resulted in an increase in feed/gain (p < 0.001), but a decrease in serum total protein and uric acid contents. Only serum creatine kinase activity in broiler chickens was interacted by daily cyclic high ambient temperature and dietary crude protein levels (p = 0.003). These results indicated that daily cyclic high ambient temperature had a great effect on performance and serum biochemical parameters in broiler chickens, whereas dietary crude protein levels affected them partially. Journal of Animal Physiology and Animal Nutrition © 2015 Blackwell Verlag GmbH.

Alternative statistical methods for interpreting airborne Alder (Alnus glutimosa (L.) Gaertner) pollen concentrations.

PubMed

González Parrado, Zulima; Valencia Barrera, Rosa M; Fuertes Rodríguez, Carmen R; Vega Maray, Ana M; Pérez Romero, Rafael; Fraile, Roberto; Fernández González, Delia

2009-01-01

This paper reports on the behaviour of Alnus glutinosa (alder) pollen grains in the atmosphere of Ponferrada (León, NW Spain) from 1995 to 2006. The study, which sought to determine the effects of various weather-related parameters on Alnus pollen counts, was performed using a volumetric method. The main pollination period for this taxon is January-February. Alder pollen is one of the eight major airborne pollen allergens found in the study area. An analysis was made of the correlation between pollen counts and major weather-related parameters over each period. In general, the strongest positive correlation was with temperature, particularly maximum temperature. During each period, peak pollen counts occurred when the maximum temperature fell within the range 9 degrees C-14 degrees C. Finally, multivariate analysis showed that the parameter exerting the greatest influence was temperature, a finding confirmed by Spearman correlation tests. Principal components analysis suggested that periods with high pollen counts were characterised by high maximum temperature, low rainfall and an absolute humidity of around 6 g m(-3). Use of this type of analysis in conjunction with other methods is essential for obtaining an accurate record of pollen-count variations over a given period.

Analysis of the CO 2 Chemisorption in Li 5FeO 4, a New High Temperature CO 2 Captor Material. Effect of the CO 2 and O 2 Partial Pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lara-García, Hugo A.; Sanchez-Camacho, Pedro; Duan, Yuhua

Pentalithium ferrite (Li 5FeO 4) was tested in this paper as possible CO 2 captor, both by theoretical calculations and experimental measurements. The pristine Li 5FeO 4 compound with orthorhombic structure was synthesized via solid-state reaction and it was structural and microstructurally characterized. Later, sample was heat-treated at temperatures from room temperature to 900 °C under different CO 2 or CO 2–O 2 atmospheres. Li 5FeO 4 exhibits excellent CO 2 chemisorption abilities with a capture capacity about 12.9 mmol/g, which is outstanding in comparison to other previously reported ceramic captors. This material is able to react with CO 2more » from 200 °C to approximately 715 °C showing a high kinetic of reaction even at CO 2 partial pressure values as low as 0.2. Finally and additionally, results suggest that oxygen addition does enhance the CO 2 chemisorption on Li 5FeO 4 at temperatures below 700 °C, although oxygen addition seems to favor the desorption process at higher temperatures.« less

Flexible and High-Performance Amorphous Indium Zinc Oxide Thin-Film Transistor Using Low-Temperature Atomic Layer Deposition.

PubMed

Sheng, Jiazhen; Lee, Hwan-Jae; Oh, Saeroonter; Park, Jin-Seong

2016-12-14

Amorphous indium zinc oxide (IZO) thin films were deposited at different temperatures, by atomic layer deposition (ALD) using [1,1,1-trimethyl-N-(trimethylsilyl)silanaminato]indium (INCA-1) as the indium precursor, diethlzinc (DEZ) as the zinc precursor, and hydrogen peroxide (H 2 O 2 ) as the reactant. The ALD process of IZO deposition was carried by repeated supercycles, including one cycle of indium oxide (In 2 O 3 ) and one cycle of zinc oxide (ZnO). The IZO growth rate deviates from the sum of the respective In 2 O 3 and ZnO growth rates at ALD growth temperatures of 150, 175, and 200 °C. We propose growth temperature-dependent surface reactions during the In 2 O 3 cycle that correspond with the growth-rate results. Thin-film transistors (TFTs) were fabricated with the ALD-grown IZO thin films as the active layer. The amorphous IZO TFTs exhibited high mobility of 42.1 cm 2 V -1 s -1 and good positive bias temperature stress stability. Finally, flexible IZO TFT was successfully fabricated on a polyimide substrate without performance degradation, showing the great potential of ALD-grown TFTs for flexible display applications.

Analysis of the CO 2 Chemisorption in Li 5FeO 4, a New High Temperature CO 2 Captor Material. Effect of the CO 2 and O 2 Partial Pressures

DOE PAGES

Lara-García, Hugo A.; Sanchez-Camacho, Pedro; Duan, Yuhua; ...

2017-01-23

Pentalithium ferrite (Li 5FeO 4) was tested in this paper as possible CO 2 captor, both by theoretical calculations and experimental measurements. The pristine Li 5FeO 4 compound with orthorhombic structure was synthesized via solid-state reaction and it was structural and microstructurally characterized. Later, sample was heat-treated at temperatures from room temperature to 900 °C under different CO 2 or CO 2–O 2 atmospheres. Li 5FeO 4 exhibits excellent CO 2 chemisorption abilities with a capture capacity about 12.9 mmol/g, which is outstanding in comparison to other previously reported ceramic captors. This material is able to react with CO 2more » from 200 °C to approximately 715 °C showing a high kinetic of reaction even at CO 2 partial pressure values as low as 0.2. Finally and additionally, results suggest that oxygen addition does enhance the CO 2 chemisorption on Li 5FeO 4 at temperatures below 700 °C, although oxygen addition seems to favor the desorption process at higher temperatures.« less

Atomistic properties of γ uranium.

PubMed

Beeler, Benjamin; Deo, Chaitanya; Baskes, Michael; Okuniewski, Maria

2012-02-22

The properties of the body-centered cubic γ phase of uranium (U) are calculated using atomistic simulations. First, a modified embedded-atom method interatomic potential is developed for the high temperature body-centered cubic (γ) phase of U. This phase is stable only at high temperatures and is thus relatively inaccessible to first principles calculations and room temperature experiments. Using this potential, equilibrium volume and elastic constants are calculated at 0 K and found to be in close agreement with previous first principles calculations. Further, the melting point, heat capacity, enthalpy of fusion, thermal expansion and volume change upon melting are calculated and found to be in reasonable agreement with experiment. The low temperature mechanical instability of γ U is correctly predicted and investigated as a function of pressure. The mechanical instability is suppressed at pressures greater than 17.2 GPa. The vacancy formation energy is analyzed as a function of pressure and shows a linear trend, allowing for the calculation of the extrapolated zero pressure vacancy formation energy. Finally, the self-defect formation energy is analyzed as a function of temperature. This is the first atomistic calculation of γ U properties above 0 K with interatomic potentials.

Atomistic properties of γ uranium

NASA Astrophysics Data System (ADS)

Beeler, Benjamin; Deo, Chaitanya; Baskes, Michael; Okuniewski, Maria

2012-02-01

The properties of the body-centered cubic γ phase of uranium (U) are calculated using atomistic simulations. First, a modified embedded-atom method interatomic potential is developed for the high temperature body-centered cubic (γ) phase of U. This phase is stable only at high temperatures and is thus relatively inaccessible to first principles calculations and room temperature experiments. Using this potential, equilibrium volume and elastic constants are calculated at 0 K and found to be in close agreement with previous first principles calculations. Further, the melting point, heat capacity, enthalpy of fusion, thermal expansion and volume change upon melting are calculated and found to be in reasonable agreement with experiment. The low temperature mechanical instability of γ U is correctly predicted and investigated as a function of pressure. The mechanical instability is suppressed at pressures greater than 17.2 GPa. The vacancy formation energy is analyzed as a function of pressure and shows a linear trend, allowing for the calculation of the extrapolated zero pressure vacancy formation energy. Finally, the self-defect formation energy is analyzed as a function of temperature. This is the first atomistic calculation of γ U properties above 0 K with interatomic potentials.

Theoretical and Experimental Studies of Epidermal Heat Flux Sensors for Measurements of Core Body Temperature

PubMed Central

Zhang, Yihui; Webb, Richard Chad; Luo, Hongying; Xue, Yeguang; Kurniawan, Jonas; Cho, Nam Heon; Krishnan, Siddharth; Li, Yuhang; Huang, Yonggang

2016-01-01

Long-term, continuous measurement of core body temperature is of high interest, due to the widespread use of this parameter as a key biomedical signal for clinical judgment and patient management. Traditional approaches rely on devices or instruments in rigid and planar forms, not readily amenable to intimate or conformable integration with soft, curvilinear, time-dynamic, surfaces of the skin. Here, materials and mechanics designs for differential temperature sensors are presented which can attach softly and reversibly onto the skin surface, and also sustain high levels of deformation (e.g., bending, twisting, and stretching). A theoretical approach, together with a modeling algorithm, yields core body temperature from multiple differential measurements from temperature sensors separated by different effective distances from the skin. The sensitivity, accuracy, and response time are analyzed by finite element analyses (FEA) to provide guidelines for relationships between sensor design and performance. Four sets of experiments on multiple devices with different dimensions and under different convection conditions illustrate the key features of the technology and the analysis approach. Finally, results indicate that thermally insulating materials with cellular structures offer advantages in reducing the response time and increasing the accuracy, while improving the mechanics and breathability. PMID:25953120

Pathway-engineering for highly-aligned block copolymer arrays.

PubMed

Choo, Youngwoo; Majewski, Paweł W; Fukuto, Masafumi; Osuji, Chinedum O; Yager, Kevin G

2017-12-21

While the ultimate driving force in self-assembly is energy minimization and the corresponding evolution towards equilibrium, kinetic effects can also play a very strong role. These kinetic effects, such as trapping in metastable states, slow coarsening kinetics, and pathway-dependent assembly, are often viewed as complications to be overcome. Here, we instead exploit these effects to engineer a desired final nano-structure in a block copolymer thin film, by selecting a particular ordering pathway through the self-assembly energy landscape. In particular, we combine photothermal shearing with high-temperature annealing to yield hexagonal arrays of block copolymer cylinders that are aligned in a single prescribed direction over macroscopic sample dimensions. Photothermal shearing is first used to generate a highly-aligned horizontal cylinder state, with subsequent thermal processing used to reorient the morphology to the vertical cylinder state in a templated manner. Finally, we demonstrate the successful transfer of engineered morphologies into inorganic replicas.

Resilient Braided Rope Seal

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M. (Inventor); Kren, Lawrence A. (Inventor)

1996-01-01

A resilient braided rope seal for use in high temperature applications. The resilient braided rope seal includes a center core of fibers, a resilient 5 member overbraided by at least one layer of braided sheath fibers tightly packed together. The resilient member adds significant stiffness to the seal while maintaining resiliency. Furthermore, the seal permanent set and hysteresis are greatly reduced. Finally, improved load capabilities are provided.

Final report. Superconducting materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

John Ruvalds

1999-09-11

Our group has discovered a many body effect that explains the surprising divergence of the spin susceptibility which has been measured by neutron scattering experiments on high temperature superconductors and vanadium oxide metals. Electron interactions on nested - i.e., nearly parallel paths - have been analyzed extensively by our group, and such processes provide a physical explanation for many anomalous features that distinguish cuprate superconductors from ordinary metals.

Combustion method for assay of biological materials labeled with carbon-14 or tritium, or double-labeled

NASA Technical Reports Server (NTRS)

Huebner, L. G.; Kisieleski, W. E.

1969-01-01

Dry catalytic combustion at high temperatures is used for assaying biological materials labeled carbon-14 and tritium, or double-labeled. A modified oxygen-flask technique is combined with standard vacuum-line techniques and includes convenience of direct in-vial collection of final combustion products, giving quantitative recovery of tritium and carbon-14.

JPRS Report, Science & Technology, Japan

DTIC Science & Technology

1991-01-31

final test. Keywords: Spherical Pressure Hull, Titanium Alloy , Three-Dimensional Machining, Electron Beam Welding . 1. Introduction In bodies like... processed (the heat treatment involving high-temperature heating and rapid quenching in order to obtain finer grains of the titanium alloy ) and...given m Table 3. The test results were all satisfactory. Forged material of titanium alloy , manufactured by forging, beta processing , and billet

High-Temperature Structures, Adhesives, and Advanced Thermal Protection Materials for Next-Generation Aeroshell Design

NASA Technical Reports Server (NTRS)

Collins, Timothy J.; Congdon, William M.; Smeltzer, Stanley S.; Whitley, Karen S.

2005-01-01

The next generation of planetary exploration vehicles will rely heavily on robust aero-assist technologies, especially those that include aerocapture. This paper provides an overview of an ongoing development program, led by NASA Langley Research Center (LaRC) and aimed at introducing high-temperature structures, adhesives, and advanced thermal protection system (TPS) materials into the aeroshell design process. The purpose of this work is to demonstrate TPS materials that can withstand the higher heating rates of NASA's next generation planetary missions, and to validate high-temperature structures and adhesives that can reduce required TPS thickness and total aeroshell mass, thus allowing for larger science payloads. The effort described consists of parallel work in several advanced aeroshell technology areas. The areas of work include high-temperature adhesives, high-temperature composite materials, advanced ablator (TPS) materials, sub-scale demonstration test articles, and aeroshell modeling and analysis. The status of screening test results for a broad selection of available higher-temperature adhesives is presented. It appears that at least one (and perhaps a few) adhesives have working temperatures ranging from 315-400 C (600-750 F), and are suitable for TPS-to-structure bondline temperatures that are significantly above the traditional allowable of 250 C (482 F). The status of mechanical testing of advanced high-temperature composite materials is also summarized. To date, these tests indicate the potential for good material performance at temperatures of at least 600 F. Application of these materials and adhesives to aeroshell systems that incorporate advanced TPS materials may reduce aeroshell TPS mass by 15% - 30%. A brief outline is given of work scheduled for completion in 2006 that will include fabrication and testing of large panels and subscale aeroshell test articles at the Solar-Tower Test Facility located at Kirtland AFB and operated by Sandia National Laboratories. These tests are designed to validate aeroshell manufacturability using advanced material systems, and to demonstrate the maintenance of bondline integrity at realistically high temperatures and heating rates. Finally, a status is given of ongoing aeroshell modeling and analysis efforts which will be used to correlate with experimental testing, and to provide a reliable means of extrapolating to performance under actual flight conditions. The modeling and analysis effort includes a parallel series of experimental tests to determine TSP thermal expansion and other mechanical properties which are required for input to the analysis models.

Characterization of ceramics and intermetallics fabricated by self-propagating high-temperature synthesis

NASA Technical Reports Server (NTRS)

Hurst, Janet B.

1989-01-01

Three efforts aimed at investigating the process of self-propagating high temperature synthesis (SHS) for the fabrication of structural ceramics and intermetallics are summarized. Of special interest was the influence of processing variables such as exothermic dopants, gravity, and green state morphology in materials produced by SHS. In the first effort directed toward the fabrication of SiC, exothermic dopants of yttrium and zirconium were added to SiO2 or SiO2 + NiO plus carbon powder mix and processed by SHS. This approach was unsuccessful since it did not produce the desired product of crystalline SiC. In the second effort, the influence of gravity was investigated by examining Ni-Al microstructures which were produced by SHS combustion waves traveling with and opposite the gravity direction. Although final composition and total porosities of the combusted Ni-Al compounds were found to be gravity independent, larger pores were created in those specimens which were combusted opposite to the gravity force direction. Finally, it was found that green microstructure has a significant effect on the appearance of the combusted piece. Severe pressing laminations were observed to arrest the combustion front for TiC samples.

Study of high strain rate plastic deformation of low carbon microalloyed steels using experimental observation and computational modeling

NASA Astrophysics Data System (ADS)

Majta, J.; Zurek, A. K.; Trujillo, C. P.; Bator, A.

2003-09-01

This work presents validation of the integrated computer model to predict the impact of the microstructure evolution on the mechanical behavior of niobium-microalloyed steels under dynamic loading conditions. The microstructurally based constitutive equations describing the mechanical behavior of the mixed α and γ phases are proposed. It is shown that for a given finishing temperature and strain, the Nb steel exhibits strong influence of strain rate on the flow stress and final structure. This tendency is also observed in calculated results obtained using proposed modeling procedures. High strain rates influence the deformation mechanism and reduce the extent of recovery occurring during and after deformation and, in turn, increase the driving force for transformation. On the other hand, the ratio of nucleation rate to growth rate increases for lower strain rates (due to the higher number of nuclei that can be produced during an extended loading time) leading to the refined ferrite structure. However, as it was expected such behavior produces higher inhomogeneity in the final product. Multistage quasistatic compression tests and test using the Hopkinson Pressure Bar under different temperature, strain, and strain rate conditions, are used for verification of the proposed models.

Fatigue behavior and life prediction of a SiC/Ti-24Al-11Nb composite under isothermal conditions. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Bartolotta, Paul A.

1991-01-01

Metal Matrix Composites (MMC) and Intermetallic Matrix Composites (IMC) were identified as potential material candidates for advanced aerospace applications. They are especially attractive for high temperature applications which require a low density material that maintains its structural integrity at elevated temperatures. High temperature fatigue resistance plays an important role in determining the structural integrity of the material. This study attempts to examine the relevance of test techniques, failure criterion, and life prediction as they pertain to an IMC material, specifically, unidirectional SiC fiber reinforced titanium aluminide. A series of strain and load controlled fatigue tests were conducted on unidirectional SiC/Ti-24Al-11Nb composite at 425 and 815 C. Several damage mechanism regimes were identified by using a strain-based representation of the data, Talreja's fatigue life diagram concept. Results of these tests were then used to address issues of test control modes, definition of failure, and testing techniques. Finally, a strain-based life prediction method was proposed for an IMC under tensile cyclic loadings at elevated temperatures.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Zhixiao; Mukherjee, Partha P.

We report the cathode surface passivation caused by Li 2S precipitation adversely affects the performance of lithium-sulfur (Li-S) batteries. Li 2S precipitation is a complicated mesoscale process involving adsorption, desorption and diffusion kinetics, which are affected profoundly by the reactant concentration and operating temperature. In this work, a mesoscale interfacial model is presented to study the growth of Li 2S film on carbon cathode surface. Li 2S film growth experiences nucleation, isolated Li 2S island growth and island coalescence. The slow adsorption rate at small S 2- concentration inhibits the formation of nucleation seeds and the lateral growth of Limore » 2S islands, which deters surface passivation. An appropriate operating temperature, especially in the medium-to-high temperature range, can also defer surface passivation. Fewer Li 2S nucleation seeds form in such an operating temperature range, which facilitates heterogeneous growth and thereby inhibits the lateral growth of the Li 2S film, which may also result in reduced surface passivation. Finally, the high specific surface area of the cathode microstructure is expected to mitigate the surface passivation.« less

Synthesis of ligand-stabilized metal oxide nanocrystals and epitaxial core/shell nanocrystals via a lower-temperature esterification process.

PubMed

Ito, Daisuke; Yokoyama, Shun; Zaikova, Tatiana; Masuko, Keiichiro; Hutchison, James E

2014-01-28

The properties of metal oxide nanocrystals can be tuned by incorporating mixtures of matrix metal elements, adding metal ion dopants, or constructing core/shell structures. However, high-temperature conditions required to synthesize these nanocrystals make it difficult to achieve the desired compositions, doping levels, and structural control. We present a lower temperature synthesis of ligand-stabilized metal oxide nanocrystals that produces crystalline, monodisperse nanocrystals at temperatures well below the thermal decomposition point of the precursors. Slow injection (0.2 mL/min) of an oleic acid solution of the metal oleate complex into an oleyl alcohol solvent at 230 °C results in a rapid esterification reaction and the production of metal oxide nanocrystals. The approach produces high yields of crystalline, monodisperse metal oxide nanoparticles containing manganese, iron, cobalt, zinc, and indium within 20 min. Synthesis of tin-doped indium oxide (ITO) can be accomplished with good control of the tin doping levels. Finally, the method makes it possible to perform epitaxial growth of shells onto nanocrystal cores to produce core/shell nanocrystals.

Temperature Measurement Inside Protective Headgear: Comparison With Core Temperatures and Indicators of Physiological Strain During Exercise in a Hot Environment.

PubMed

Mitchell, Joel B; Goldston, Kelly R; Adams, Amy N; Crisp, Kelli M; Franklin, Brian B; Kreutzer, Andreas; Montalvo, Diego X; Turner, Marcell G; Phillips, Melody D

2015-01-01

Non-invasive temperature monitoring with a sensor inside protective headgear may be effective in detecting temperatures that are associated with heat illness. The purpose was to establish the relationship between in-hardhat temperatures (Tih) and core temperature (Tc) as measured by rectal (Tre) and esophageal (Tes) probes. Thirty males (age 24.57 ± 4.32 yrs.) completed two trials: continuous submaximal exercise (CSE) and a series of high intensity 30-s sprints (HIE) with a one-minute rest between each. Exercise in both conditions was in a 36(°)C environment (40% RH) while wearing a standard hardhat with sensors mounted on the forehead that were monitored remotely. Exercise continued until voluntary termination or until Tc reached 39.5(°)C. Temperatures, heart rate, cardiorespiratory, and perceptual responses were monitored throughout. A physiological strain index (PSI) was calculated from Tc and HR. The final temperatures in the CSE condition were 38.77 ± 0.41, 38.90 ± 0.49 and 39.29 ± 0.58(°)C and in the HIE condition, final temperatures were 38.76 ± 0.37, 38.91 ± 0.47, and 39.19 ± 0.57 f (o)C for Tih, Tre, and Tes, respectively. The PSI in CSE was 9.62 ± 062, 9.18 ± 1.11, and 10.04 ± 1.05, and in the HIE condition 9.67 ± 068, 9.29 ± 0.99. and 9.86 ± 1.02 based on Tih, Tre and Tes, respectively. The general agreement between the Tih and other temperature measures along with the consistency as indicated by a low coefficient of variation (approx. 1%) in the recordings of the Tih sensors at the point of termination suggest that this device, or similar devices, may have application as a warning system for impending heat-related problems.

The Processing and Mechanical Properties of High Temperature/High Performance Composites. Book 5. Processing and Miscellaneous Properties

DTIC Science & Technology

1993-04-01

tensile fiber stress of 150-300 MPa, too little compared to measured fiber strengths of 3-4 GPa. A final possibility is that of nonuniform inelastic...flow of the matrix as a result of a spatially nonuniform distribution of porosity; this leads to a nonuniform distribution of forces along the fiber...the damage with the specific mechanism being fiber bending. The effects due to nonuniform inelastic flow (i.e., fiber bending) can be thought to occur

Ceramic or metallic? - material aspects of compact heat regenerator energy efficiency

NASA Astrophysics Data System (ADS)

Wnek, M.

2012-05-01

The metal industry cannot afford the financial mismanagement in the era of rising energy prices and thus, the high efficiency devices should be used. In the metallurgical thermal processes the combustion air temperature increasing is one of the methods for obtaining the heat transfer intensification and the furnaces efficiency rising. Therefore the new and effective heating technologies in thermal processes are demanded all the time. The regenerative systems are most effective in terms of the heated air level. The individual regenerators for burners are the newest solutions where the temperature of 1100 °C is reachable for the exhaust temperature of 1200 °C. Based on research results, performed for the assumed exhaust temperature of 1100 °C, the paper presents possibilities of changeable different materials using as a regenerator filling in the aspect of its operation efficiency. Such materials as high-temperature steel, Al2O3 and SiC have been considered. The paper presents the selected data research, dealing with the air combustion temperature obtained for the same type of regenerator filling of considered materials. The fuel consumption reduction and reduction of CO2 emission, for metal regenerator filling, have been presented finally as an economic and environmental aspect accordingly to the air preheated.

Symmetries and multiferroic properties of novel room-temperature magnetoelectrics: Lead iron tantalate – lead zirconate titanate (PFT/PZT)

DOE PAGES

Sanchez, Dilsom A.; Ortega, N.; Kumar, Ashok; ...

2011-12-05

Mixing 60-70% lead zirconate titanate with 40-30% lead iron tantalate produces a single-phase, low-loss, room-temperature multiferroic with magnetoelectric coupling: (PbZr 0.53Ti 0.47O 3) (1-x)- (PbFe 0.5Ta 0.5O 3) x. Our study combines x-ray scattering, magnetic and polarization hysteresis in both phases, plus a second-order dielectric divergence (to epsilon = 6000 at 475 K for 0.4 PFT; to 4000 at 520 K for 0.3 PFT) for an unambiguous assignment as a C 2v-C 4v (Pmm2-P4mm) transition. Furthermore, the material exhibits square saturated magnetic hysteresis loops with 0.1 emu/g at 295 K and saturation polarization P r = 25 μC/cm 2, whichmore » actually increases (to 40 μC/cm 2) in the high-T tetragonal phase, representing an exciting new room temperature oxide multiferroic to compete with BiFeO 3. Additional transitions at high temperatures (cubic at T>1300 K) and low temperatures (rhombohedral or monoclinic at T<250 K) are found. Finally, these are the lowest-loss room-temperature multiferroics known, which is a great advantage for magnetoelectric devices.« less

Effects of extrusion variables on the properties of waxy hulless barley extrudates.

PubMed

Köksel, Hamit; Ryu, Gy-Hyung; Başman, Arzu; Demiralp, Hande; Ng, Perry K W

2004-02-01

The objective of this research was to investigate the extrudability of waxy hulless barley flour under various extrusion conditions. Waxy hulless barley flour was processed in a laboratory-scale corotating twin-screw extruder with different levels of feed moisture content (22.3, 26.8, and 30.7%) and die temperature (130, 150, and 170 degrees C) to develop a snack food with high beta-glucan content. The effects of extrusion condition variables (screw configuration, moisture, and temperature) on the system variables (pressure and specific mechanical energy), the extrudate physical properties (sectional expansion index, bulk density), starch gelatinization, pasting properties (cold peak viscosity, trough viscosity, and final viscosity), and beta-glucan contents were determined. Results were evaluated by using response surface methodology. Increased extrusion temperature and feed moisture content resulted in decreases in exit die pressure and specific mechanical energy values. For extrudates extruded under low shear screw configuration (LS), increased barrel temperature decreased sectional expansion index (SEI) values at both low and high moisture contents. The feed moisture seems to have an inverse relationship with SEI over the range studied. Bulk density was higher at higher moisture contents, for both low and high barrel temperatures, for samples extruded under high shear screw configuration (HS) and LS. Cold peak viscosities (CV) were observed in all samples. The CV increased with the increase in extrusion temperature and feed moisture content. Although beta-glucan contents of the LS extrudates were comparable to that of barley flour sample, HS samples had generally lower beta-glucan contents. The extrusion cooking technique seems to be promising for the production of snack foods with high beta-glucan content, especially using LS conditions.

The Effect of Saline Coolant on Temperature Levels during Decortication with a Midas Rex: An in Vitro Model Using Sheep Cervical Vertebrae.

PubMed

Livingston, Asher; Wang, Tian; Christou, Chris; Pelletier, Matthew H; Walsh, William R

2015-01-01

Decortication of bone with a high-speed burr in the absence of coolant may lead to local thermal necrosis and decreased healing ability, which may negatively impact clinical outcome. Little data are available on the impact of applying a coolant during the burring process. This study aims to establish an in vitro model to quantitatively assess peak temperatures during endplate preparation with a high-speed burr. Six sheep cervical vertebrae were dissected and mounted. Both end plates were used to give a total of 12 sites. Two thermocouples were inserted into each vertebra, 2 mm below the end plate surface and a thermal camera set up to measure surface temperature. A 3 mm high-pneumatic speed burr (Midas Rex, Medtronic, Fort Worth, TX, USA) was used to decorticate the bone in a side to side sweeping pattern, using a matchstick burr (M-8/9MH30) with light pressure. This procedure was repeated while dripping saline onto the burr and bone. Data were compared between groups using a Student's t-test. Application of coolant at the bone-burr interface during decortication resulted in a significant decrease in final temperature. Without coolant, maximum temperatures 2 mm from the surface were not sufficient to cause thermal osteonecrosis, although peak surface temperatures would cause local damage. The use of a high-speed burr provides a quick and an effective method of vertebral end plate preparation. Thermal damage to the bone can be minimized through the use of light pressure and saline coolant. This has implications for any bone preparation performed with a high-speed burr.

Quantitative PLIF Imaging in High-Pressure Combustion

NASA Technical Reports Server (NTRS)

Hanson, R. K.

1997-01-01

This is the final report for a research project aimed at developing planar laser-induced fluorescence (PLIF) techniques for quantitative 2-D species imaging in fuel-lean, high-pressure combustion gases, relevant to modem aircraft gas turbine combustors. The program involved both theory and experiment. The theoretical activity led to spectroscopic models that allow calculation of the laser-induced fluorescence produced in OH, NO and 02 for arbitrary excitation wavelength, pressure, temperature, gas mixture and laser linewidth. These spectroscopic models incorporate new information on line- broadening, energy transfer and electronic quench rates. Extensive calculations have been made with these models in order to identify optimum excitation strategies, particularly for detecting low levels (ppm) of NO in the presence of large 02 mole fractions (10% is typical for the fuel-lean combustion of interest). A promising new measurement concept has emerged from these calculations, namely that excitation at specific wavelengths, together with detection of fluorescence in multiple spectral bands, promises to enable simultaneous detection of both NO (at ppm levels) and 02 or possibly NO, 02 and temperature. Calculations have been made to evaluate the expected performance of such a diagnostic for a variety of conditions and choices of excitation and detection wavelengths. The experimental effort began with assembly of a new high-pressure combustor to provide controlled high-temperature and high-pressure combustion products. The non-premixed burner enables access to postflame gases at high temperatures (to 2000 K) and high pressures (to 13 atm), and a range of fuel-air equivalence ratios. The chamber also allowed use of a sampling probe, for chemiluminescent detection of NO/NO2, and thermocouples for measurement of gas temperature. Experiments were conducted to confirm the spectroscopic models for OH, NO and 02.

Downwell pump reliability: Geothermal experience update: Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ellis, P.F.

1988-01-01

Geothermal resources with temperatures between 250/sup 0/ and 360/sup 0/F (121/sup 0/C and 182/sup 0/C) are prime candidates for binary-cycle power generation, and constitute about 80% of the power-capable resources in the United States. The successful exploitation of these resources requires reliable high-capacity downwell brine production pumps, but earlier experience showed that high-capacity, high-temperature geothermal production pumps had many problems which resulted in a mean time-to-failure (MTTF) of less than 1000 h. However, steady progress has been made since 1981, and a large body of experience has been acquired by three geothermal binary plants. This survey of high-temperature geothermal downwellmore » pump users and manufacturers updates a prior survey (AP-3572) completed in early 1983. This survey traces the development of lineshaft pump technology from the late 1970s to the present (mid-1987), detailing the advances in design, materials selection, and operating practices. Case histories of 72 lineshaft pumps installed at three geothermal binary plants since late 1981 are documented, including some detailed cause of failure reports. In the recent past, pump lives in excess of 7000 h have become common, but a high continuing rate of premature failures resulted in a mean time-to-failure (MTTF) of about 5000 h. Based on recent advances which appear likely to eliminate most premature failures, the estimated near-term MTTF will be on the order of 8000 h. The survey found almost no development of high-temperature geothermal electric submersible pumps (ESP's) or close-coupled downwell hydraulic turbopumps, and concluded that considerable development and demonstration will be needed before these technologies are able to compete with existing high-temperature geothermal lineshaft pump technology. 36 refs., 10 figs., 25 tabs.« less

Model-based estimation of adiabatic flame temperature during coal gasification

NASA Astrophysics Data System (ADS)

Sarigul, Ihsan Mert

Coal gasification temperature distribution in the gasifier is one of the important issues. High temperature may increase the risk of corrosion of the gasifier wall or it may cause an increase in the amount of volatile compounds. At the same time, gasification temperature is a dominant factor for high conversion of products and completing the reactions during coal gasification in a short time. In the light of this information it can be said that temperature is one of key parameters of coal gasification to enhance the production of high heating value syngas and maximize refractory longevity. This study aims to predict the adiabatic flame temperatures of Australian bituminous coal and Indonesian roto coal in an entrained flow gasifier using different operating conditions with the ChemCAD simulation and design program. To achieve these objectives, two types of gasification parameters were carried out using simulation of a vertical entrained flow reactor: oxygen-to-coal feed ratio by kg/kg and pressure and steam-to-coal feed ratio by kg/kg and pressure. In the first part of study the adiabatic flame temperatures, coal gasification products and other coal characteristics of two types of coals were determined using ChemCAD software. During all simulations, coal feed rate, coal particle size, initial temperature of coal, water and oxygen were kept constant. The relationships between flame temperature, coal gasification products and operating parameters were fundamentally investigated. The second part of this study addresses the modeling of the flame temperature relation to methane production and other input parameters used previous chapter. The scope of this work was to establish a reasonable model in order to estimate flame temperature without any theoretical calculation. Finally, sensitivity analysis was performed after getting some basic correlations between temperature and input variables. According to the results, oxygen-to-coal feed ratio has the most influential effect on adiabatic flame temperature.

Petascale supercomputing to accelerate the design of high-temperature alloys

DOE PAGES

Shin, Dongwon; Lee, Sangkeun; Shyam, Amit; ...

2017-10-25

Recent progress in high-performance computing and data informatics has opened up numerous opportunities to aid the design of advanced materials. Herein, we demonstrate a computational workflow that includes rapid population of high-fidelity materials datasets via petascale computing and subsequent analyses with modern data science techniques. We use a first-principles approach based on density functional theory to derive the segregation energies of 34 microalloying elements at the coherent and semi-coherent interfaces between the aluminium matrix and the θ'-Al 2Cu precipitate, which requires several hundred supercell calculations. We also perform extensive correlation analyses to identify materials descriptors that affect the segregation behaviourmore » of solutes at the interfaces. Finally, we show an example of leveraging machine learning techniques to predict segregation energies without performing computationally expensive physics-based simulations. As a result, the approach demonstrated in the present work can be applied to any high-temperature alloy system for which key materials data can be obtained using high-performance computing.« less

Petascale supercomputing to accelerate the design of high-temperature alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, Dongwon; Lee, Sangkeun; Shyam, Amit

Recent progress in high-performance computing and data informatics has opened up numerous opportunities to aid the design of advanced materials. Herein, we demonstrate a computational workflow that includes rapid population of high-fidelity materials datasets via petascale computing and subsequent analyses with modern data science techniques. We use a first-principles approach based on density functional theory to derive the segregation energies of 34 microalloying elements at the coherent and semi-coherent interfaces between the aluminium matrix and the θ'-Al 2Cu precipitate, which requires several hundred supercell calculations. We also perform extensive correlation analyses to identify materials descriptors that affect the segregation behaviourmore » of solutes at the interfaces. Finally, we show an example of leveraging machine learning techniques to predict segregation energies without performing computationally expensive physics-based simulations. As a result, the approach demonstrated in the present work can be applied to any high-temperature alloy system for which key materials data can be obtained using high-performance computing.« less

Modeling and fabrication of 4H-SiC Schottky junction

NASA Astrophysics Data System (ADS)

Martychowiec, A.; Pedryc, A.; Kociubiński, A.

2017-08-01

The rapidly growing demand for electronic devices requires using of alternative semiconductor materials, which could replace conventional silicon. Silicon carbide has been proposed for these harsh environment applications (high temperature, high voltage, high power conditions) because of its wide bandgap, its high temperature operation ability, its excellent thermal and chemical stability, and its high breakdown electric field strength. The Schottky barrier diode (SBD) is known as one of the best refined SiC devices. This paper presents prepared model, simulations and description of technology of 4H-SiC Schottky junction as well as characterization of fabricated structures. The future aim of the application of the structures is an optical detection of an ultraviolet radiation. The model section contains a comparison of two different solutions of SBD's construction. Simulations - as a crucial process of designing electronic devices - have been performed using the ATLAS device of Silvaco TCAD software. As a final result the paper shows I-V characteristics of fabricated diodes.

Microwave conductance properties of aligned multiwall carbon nanotube textile sheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Brian L.; Martinez, Patricia; Zakhidov, Anvar A.

2015-07-06

Understanding the conductance properties of multi-walled carbon nanotube (MWNT) textile sheets in the microwave regime is essential for their potential use in high-speed and high-frequency applications. To expand current knowledge, complex high-frequency conductance measurements from 0.01 to 50 GHz and across temperatures from 4.2 K to 300 K and magnetic fields up to 2 T were made on textile sheets of highly aligned MWNTs with strand alignment oriented both parallel and perpendicular to the microwave electric field polarization. Sheets were drawn from 329 and 520 μm high MWNT forests that resulted in different DC resistance anisotropy. For all samples, themore » microwave conductance can be modeled approximately by a shunt capacitance in parallel with a frequency-independent conductance, but with no inductive contribution. Finally, this is consistent with diffusive Drude conduction as the primary transport mechanism up to 50 GHz. Further, it is found that the microwave conductance is essentially independent of both temperature and magnetic field.« less

Mechanism of Radiation Damage Reduction in Equiatomic Multicomponent Single Phase Alloys

DOE PAGES

Granberg, F.; Nordlund, K.; Ullah, Mohammad W.; ...

2016-04-01

Recently a new class of metal alloys, of single-phase multicomponent composition at roughly equal atomic concentrations (“equiatomic”), have been shown to exhibit promising mechanical, magnetic, and corrosion resistance properties, in particular, at high temperatures. These features make them potential candidates for components of next-generation nuclear reactors and other high-radiation environments that will involve high temperatures combined with corrosive environments and extreme radiation exposure. In spite of a wide range of recent studies of many important properties of these alloys, their radiation tolerance at high doses remains unexplored. In this work, a combination of experimental and modeling efforts reveals a substantialmore » reduction of damage accumulation under prolonged irradiation in single-phase NiFe and NiCoCr alloys compared to elemental Ni. This effect is explained by reduced dislocation mobility, which leads to slower growth of large dislocation structures. Finally and moreover, there is no observable phase separation, ordering, or amorphization, pointing to a high phase stability of this class of alloys.« less

Petascale supercomputing to accelerate the design of high-temperature alloys

NASA Astrophysics Data System (ADS)

Shin, Dongwon; Lee, Sangkeun; Shyam, Amit; Haynes, J. Allen

2017-12-01

Recent progress in high-performance computing and data informatics has opened up numerous opportunities to aid the design of advanced materials. Herein, we demonstrate a computational workflow that includes rapid population of high-fidelity materials datasets via petascale computing and subsequent analyses with modern data science techniques. We use a first-principles approach based on density functional theory to derive the segregation energies of 34 microalloying elements at the coherent and semi-coherent interfaces between the aluminium matrix and the θ‧-Al2Cu precipitate, which requires several hundred supercell calculations. We also perform extensive correlation analyses to identify materials descriptors that affect the segregation behaviour of solutes at the interfaces. Finally, we show an example of leveraging machine learning techniques to predict segregation energies without performing computationally expensive physics-based simulations. The approach demonstrated in the present work can be applied to any high-temperature alloy system for which key materials data can be obtained using high-performance computing.

Photochemically Synthesized Polyimides

NASA Technical Reports Server (NTRS)

Meador, Michael A.; Tyson, Daniel S.

2008-01-01

An alternative to the conventional approach to synthesis of polyimides involves the use of single monomers that are amenable to photopolymerization. Heretofore, the synthesis of polyimides has involved multiple-monomer formulations and heating to temperatures that often exceed 250 C. The present alternative approach enables synthesis under relatively mild conditions that can include room temperature. The main disadvantages of the conventional approach are the following: Elevated production temperatures can lead to high production costs and can impart thermal stresses to the final products. If the proportions of the multiple monomeric ingredients in a given batch are not exactly correct, the molecular weight and other physical properties of the final material could be reduced from their optimum or desired values. To be useful in the alternative approach, a monomer must have a molecular structure tailored to exploit Diels-Alder trapping of a photochemically generated ortho-quinodimethane. (In a Diels-Alder reaction, a diene combines with a dienophile to form molecules that contain six-membered rings.) In particular, a suitable monomer (see figure) contains ortho-methylbenzophenone connected to a dienophile (in this case, a maleimide) through a generic spacer group. Irradiation with ultraviolet light gives rise to a photochemical intermediate the aforementioned ortho-quinodimethane from the ortho-methylbenzophenone. This group may react with the dienophile on another such monomer molecule to produce an oligomer that, in turn may react in a stepgrowth manner to produce a polyimide. This approach offers several advantages in addition to those mentioned above: The monomer can be stored for a long time because it remains unreactive until exposed to light. Because the monomer is the only active starting ingredient, there is no need for mixing, no concern for ensuring correct proportions of monomers, and the purity of the final product material is inherently high. The use of solvents is optional: The synthesis can be performed using the neat monomer or the monomer mixed with one or more solvent(s) in dilute or concentrated solution. The solubility of the monomer and the physical and chemical properties of the final polymer can be tailored through selection of the spacer group.

Barley (Hordeum vulgare) circadian clock genes can respond rapidly to temperature in an EARLY FLOWERING 3-dependent manner

PubMed Central

Ford, Brett; Deng, Weiwei; Clausen, Jenni; Oliver, Sandra; Boden, Scott; Hemming, Megan; Trevaskis, Ben

2016-01-01

An increase in global temperatures will impact future crop yields. In the cereal crops wheat and barley, high temperatures accelerate reproductive development, reducing the number of grains per plant and final grain yield. Despite this relationship between temperature and cereal yield, it is not clear what genes and molecular pathways mediate the developmental response to increased temperatures. The plant circadian clock can respond to changes in temperature and is important for photoperiod-dependent flowering, and so is a potential mechanism controlling temperature responses in cereal crops. This study examines the relationship between temperature, the circadian clock, and the expression of flowering-time genes in barley (Hordeum vulgare), a crop model for temperate cereals. Transcript levels of barley core circadian clock genes were assayed over a range of temperatures. Transcript levels of core clock genes CCA1, GI, PRR59, PRR73, PRR95, and LUX are increased at higher temperatures. CCA1 and PRR73 respond rapidly to a decrease in temperature whereas GI and PRR59 respond rapidly to an increase in temperature. The response of GI and the PRR genes to changes in temperature is lost in the elf3 mutant indicating that their response to temperature may be dependent on a functional ELF3 gene. PMID:27580625

Synthesis of Hf 8O 7, a new binary hafnium oxide, at high pressures and high temperatures

DOE PAGES

Bayarjargal, L.; Morgenroth, W.; Schrodt, N.; ...

2017-01-23

In this paper, two binary phases in the system Hf-O have been synthesized at pressures between 12 and 34 GPa and at temperatures up to 3000 K by reacting Hf with HfO 2 using a laser-heated diamond anvil cell. In situ X-ray diffraction in conjunction with density functional theory calculations has been employed to characterize a previously unreported tetragonal Hf 8O 7 phase. This phase has a structure which is based on an fcc Hf packing with oxygen atoms occupying octahedral interstitial positions. Its predicted bulk modulus is 223(1) GPa. The second phase has a composition close to Hf 6O,more » where oxygen atoms occupy octahedral interstitial sites in an hcp Hf packing. Its experimentally determined bulk modulus is 128(30) GPa. Finally, the phase diagram of Hf metal was further constrained at high pressures and temperatures, where we show that α-Hf transforms to β-Hf around 2160(150) K and 18.2 GPa and β-Hf remains stable up to at least 2800 K at this pressure.« less

SQDFT: Spectral Quadrature method for large-scale parallel O(N) Kohn-Sham calculations at high temperature

NASA Astrophysics Data System (ADS)

Suryanarayana, Phanish; Pratapa, Phanisri P.; Sharma, Abhiraj; Pask, John E.

2018-03-01

We present SQDFT: a large-scale parallel implementation of the Spectral Quadrature (SQ) method for O(N) Kohn-Sham Density Functional Theory (DFT) calculations at high temperature. Specifically, we develop an efficient and scalable finite-difference implementation of the infinite-cell Clenshaw-Curtis SQ approach, in which results for the infinite crystal are obtained by expressing quantities of interest as bilinear forms or sums of bilinear forms, that are then approximated by spatially localized Clenshaw-Curtis quadrature rules. We demonstrate the accuracy of SQDFT by showing systematic convergence of energies and atomic forces with respect to SQ parameters to reference diagonalization results, and convergence with discretization to established planewave results, for both metallic and insulating systems. We further demonstrate that SQDFT achieves excellent strong and weak parallel scaling on computer systems consisting of tens of thousands of processors, with near perfect O(N) scaling with system size and wall times as low as a few seconds per self-consistent field iteration. Finally, we verify the accuracy of SQDFT in large-scale quantum molecular dynamics simulations of aluminum at high temperature.

SiC Integrated Circuits for Power Device Drivers Able to Operate in Harsh Environments

NASA Astrophysics Data System (ADS)

Godignon, P.; Alexandru, M.; Banu, V.; Montserrat, J.; Jorda, X.; Vellvehi, M.; Schmidt, B.; Michel, P.; Millan, J.

2014-08-01

The currently developed SiC electronic devices are more robust to high temperature operation and radiation exposure damage than correspondingly rated Si ones. In order to integrate the existent SiC high power and high temperature electronics into more complex systems, a SiC integrated circuit (IC) technology capable of operation at temperatures substantially above the conventional ones is required. Therefore, this paper is a step towards the development of ICs-control electronics that have to attend the harsh environment power applications. Concretely, we present the development of SiC MESFET-based digital circuitry, able to integrate gate driver for SiC power devices. Furthermore, a planar lateral power MESFET is developed with the aim of its co-integration on the same chip with the previously mentioned SiC digital ICs technology. And finally, experimental results on SiC Schottky-gated devices irradiated with protons and electrons are presented. This development is based on the Tungsten-Schottky interface technology used for the fabrication of stable SiC Schottky diodes for the European Space Agency Mission BepiColombo.

Self-Substitution and the Temperature Effects on the Electrochemical Performance in the High Voltage Cathode System LiMn 1.5+xNi 0.5-xO 4 (x = 0.1)

DOE PAGES

Xu, Yun; Zhao, Mingyang; Khalid, Syed; ...

2017-05-09

The high voltage cathode material, LiMn 1.6Ni 0.4O 4, was prepared by a polymer-assisted method. The novelty of this paper is the substitution of Ni with Mn, which already exists in the crystal structure instead of other isovalent metal ion dopants which would result in capacity loss. The electrochemical performance testing including stability and rate capability was evaluated. The temperature was found to impose a change on the valence and structure of the cathode materials. Specifically, manganese tends to be reduced at a high temperature of 800 °C and leads to structural changes. The manganese substituted LiMn 1.5Ni 0.5O 4more » (LMN) has proved to be a good candidate material for Li-ion battery cathodes displaying good rate capability and capacity retention. Finally, the cathode materials processed at 550 °C showed a stable performance with negligible capacity loss for 400 cycles.« less

Influence of the welding temperature and the welding speed on the mechanical properties of friction stir welds in EN AW-2219-T87

NASA Astrophysics Data System (ADS)

Bachmann, A.; Krutzlinger, M.; Zaeh, M. F.

2018-06-01

Friction Stir Welding (FSW) is an innovative joining technique, which has proven to produce high quality joints in high strength aluminum alloys. Consequently, it is commonly used to manufacture lightweight aerospace structures with stringent requirements. For these structures, it is necessary to ensure a high ultimate tensile strength (UTS). Various studies have reported that the UTS is significantly influenced by the welding parameters. Samples welded with different parameter sets showed a considerably different UTS, despite being free from detectable welding defects (e.g. tunnel defect, voids, or lack of penetration). Based on the observations in the literature, a hypothesis was posed. The welding temperature along with the welding speed determine the UTS of the weld. This study aims to prove this hypothesis experimentally by using temperature-controlled FSW to join plates of EN AW-2219-T87 in butt joint configuration. The welded samples were examined using visual inspection, metallography, X-ray imaging, and uniaxial tensile tests. Finally, a statistical analysis was conducted. Hereby, the hypothesis was confirmed.

Growth of High-Quality GaAs on Ge by Controlling the Thickness and Growth Temperature of Buffer Layer

NASA Astrophysics Data System (ADS)

Zhou, Xu-Liang; Pan, Jiao-Qing; Yu, Hong-Yan; Li, Shi-Yan; Wang, Bao-Jun; Bian, Jing; Wang, Wei

2014-12-01

High-quality GaAs thin films grown on miscut Ge substrates are crucial for GaAs-based devices on silicon. We investigate the effect of different thicknesses and temperatures of GaAs buffer layers on the crystal quality and surface morphology of GaAs on Ge by metal-organic chemical vapor deposition. Through high resolution x-ray diffraction measurements, it is demonstrated that the full width at half maximum for the GaAs epilayer (Ge substrate) peak could achieve 19.3 (11.0) arcsec. The value of etch pit density could be 4×104 cm-2. At the same time, GaAs surfaces with no pyramid-shaped pits are obtained when the buffer layer growth temperature is lower than 360°C, due to effective inhibition of initial nucleation at terraces of the Ge surface. In addition, it is shown that large island formation at the initial stage of epitaxial growth is a significant factor for the final rough surface and that this initial stage should be carefully controlled when a device quality GaAs surface is desired.

A 30 mK, 13.5 T scanning tunneling microscope with two independent tips.

PubMed

Roychowdhury, Anita; Gubrud, M A; Dana, R; Anderson, J R; Lobb, C J; Wellstood, F C; Dreyer, M

2014-04-01

We describe the design, construction, and performance of an ultra-low temperature, high-field scanning tunneling microscope (STM) with two independent tips. The STM is mounted on a dilution refrigerator and operates at a base temperature of 30 mK with magnetic fields of up to 13.5 T. We focus on the design of the two-tip STM head, as well as the sample transfer mechanism, which allows in situ transfer from an ultra high vacuum preparation chamber while the STM is at 1.5 K. Other design details such as the vibration isolation and rf-filtered wiring are also described. Their effectiveness is demonstrated via spectral current noise characteristics and the root mean square roughness of atomic resolution images. The high-field capability is shown by the magnetic field dependence of the superconducting gap of CuxBi2Se3. Finally, we present images and spectroscopy taken with superconducting Nb tips with the refrigerator at 35 mK that indicate that the effective temperature of our tips/sample is approximately 184 mK, corresponding to an energy resolution of 16 μeV.

Preparation of alumina-hercynite nano-spinel via one-step thermal conversion of Fe-doped metal-organic framework MIL-53(Al)

NASA Astrophysics Data System (ADS)

Chen, Shuyi; Lu, Huigong; Wu, Yi-nan; Gu, Yifan; Li, Fengting; Morlay, Catherine

2016-09-01

Alumina-hercynite nano-spinel powders were prepared via one-step pyrolysis of iron-acetylacetone-doped Al-based metal-organic framework (MOF), i.e., MIL-53(Al). Organic ferric source, iron acetylacetone, was incorporated in situ into the framework of MIL-53(Al) during the solvothermal synthesis process. Under high-temperature pyrolysis, alumina derived from the MIL-53(Al) matrix and ferric oxides originated from the decomposition of organic ferric precursor in the framework were thermally converted into hercynite (FeAl2O4). The prepared samples were characterized using transmission electron microscopy, X-ray diffraction, N2 sorption, thermogravimetry, Raman spectroscopy and X-ray photoelectron spectroscopy. The final products were identified to be composed of alumina, hercynite and trace amounts of carbon depending on pyrolysis temperature. The experimental results showed that hercynite phase can be obtained and stabilized at low temperatures between 900 and 1100 °C under inert atmosphere. The final products were composed of nano-sized particles with an average size below 100 nm of individual crystal and specific surface areas of 18-49 m2 g-1.

Effect of high-temperature on the swellable organically-modified silica (SOMS) and its application to gas-phase hydrodechlorination of trichloroethylene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sohn, Hyuntae; Celik, Gokhan; Gunduz, Seval

Pd catalysts supported on swellable organically-modified silica (SOMS) and high-temperature-treated swellable organically-modified silica (H-SOMS) were characterized and tested for gas-phase hydrodechlorination (HDC) of trichloroethylene (TCE) conditions. The high-temperature treatment on SOMS resulted in an increase in surface area and pore diameter as well as significant improvement of Pd dispersion on H-SOMS with smaller Pd particle sizes compared to the Pd/SOMS catalyst. Although the high-temperature treatment led to some alteration of the SOMS polysiloxane network, the hydrophobicity and organic vapor adsorption characteristics of SOMS were preserved. The reduction and oxidation characteristics of Pd on SOMS and HSOMS were investigated in situmore » using XANES technique. It was found that the Pd sites in the pores of SOMS was accessible to small molecules such as H 2, facilitating the reduction of PdO x, whereas oxidation of metallic Pd was limited even at higher temperatures when O 2 was used. This effect was only observed over Pd/SOMS catalyst. For Pd/H-SOMS, because the pores were more widely open than Pd/SOMS, both reduction and oxidation of Pd were observed. Finally, the catalytic activity of Pd/H-SOMS for gas-phase HDC of TCE was significantly better than Pd/SOMS. When water was added to the reactant stream (TCE + H 2O), both Pd/SOMS and Pd/H-SOMS maintained its catalytic performances due to hydrophobic property of the supports.« less

Single crystal growth, crystalline structure investigation and high-pressure behavior of impurity-free siderite (FeCO3)

NASA Astrophysics Data System (ADS)

Liang, Wen; Yin, Yuan; Li, Zeming; Li, Rui; Li, Lin; He, Yu; Dong, Haini; Li, Zengsheng; Yan, Shuai; Zhai, Shuangmeng; Li, Heping

2018-03-01

Single crystals of impurity-free siderite were grown successfully using high-temperature-pressure annealing. The size of crystals ranged up to 100 µm, and they exhibited a rhomboid shape upon cleavage along the (101) plane. The composition of Fe0.9988±0.0011CO3 was quantified using electron probe analysis. Accurate crystalline structural data were investigated by means of single crystal X-ray diffraction (XRD) and the unit cell dimensions obtained in the rhombohedral symmetry of the R\\bar {3}c space group were a = 4.6861(3) and c = 15.362(2), and the final R = 0.0499. Using in situ synchrotron XRD, the high-pressure behavior of impurity-free siderite was investigated up to 20 GPa at ambient temperature. The pressure-volume (P-V) EoS was fitted by a third-order Birch-Murnaghan equation, and the isothermal bulk modulus was K 0 = 97.5(11) GPa for K 0' = 4. High-pressure Raman spectroscopy was performed at up to 30 GPa at ambient temperature, and the Raman bands shifted as the increase of pressure ({{d/ν _i}}{{{d}P}} ) was determined. In combination with the high-pressure Raman results and the bulk modulus K 0, the mode Grüneisen parameters of each vibration were calculated. Meanwhile, high-temperature Raman spectroscopy was carried out at up to 300 °C and the Raman band shift ({{d/ν _i}}{{{d}t}} ) was also quantified.

Microstructure of Hot Rolled 1.0C-1.5Cr Bearing Steel and Subsequent Spheroidization Annealing

NASA Astrophysics Data System (ADS)

Li, Zhen-Xing; Li, Chang-Sheng; Zhang, Jian; Li, Bin-Zhou; Pang, Xue-Dong

2016-07-01

The effect of final rolling temperature and cooling process on the microstructure of 1.0C-1.5Cr bearing steel was studied, and the relationship between the microstructure parameters and subsequent spheroidization annealing was analyzed. The results indicate that the increase of water-cooling rate after hot rolling and the decrease of final cooling temperature are beneficial to reducing both the pearlite interlamellar spacing and pearlite colony size. Prior austenite grain size can be reduced by decreasing the final rolling temperature and increasing the water-cooling rate. When the final rolling temperature was controlled around 1103 K (830 °C), the subsequent cooling rate was set to 10 K/s and final cooling temperature was 953 K (680 °C), the precipitation of grain boundary cementite was suppressed effectively and lots of rod-like cementite particles were observed in the microstructure. Interrupted quenching was employed to study the dissolution behavior of cementite during the austenitizing at 1073 K (800 °C). The decrease of both pearlite interlamellar spacing and pearlite colony size could facilitate the initial dissolution and fragmentation of cementite lamellae, which could shorten the spheroidization time. The fragmentation of grain boundary cementite tends to form large-size undissolved cementite particles. With the increase of austenitizing time from 20 to 300 minutes, mean diameter of undissolved cementite particles increases, indicating the cementite particle coarsening and cementite dissolution occuring simultaneously. Mean diameter of cementite particles in the final spheroidized microstructure is proportional to the mean diameter of undissolved cementite particles formed during partial austenitizing.

Primary radiation damage characterization of α-iron under irradiation temperature for various PKA energies

NASA Astrophysics Data System (ADS)

Sahi, Qurat-ul-ain; Kim, Yong-Soo

2018-04-01

The understanding of radiation-induced microstructural defects in body-centered cubic (BCC) iron is of major interest to those using advanced steel under extreme conditions in nuclear reactors. In this study, molecular dynamics (MD) simulations were implemented to examine the primary radiation damage in BCC iron with displacement cascades of energy 1, 5, 10, 20, and 30 keV at temperatures ranging from 100 to 1000 K. Statistical analysis of eight MD simulations of collision cascades were carried out along each [110], [112], [111] and a high index [135] direction and the temperature dependence of the surviving number of point defects and the in-cascade clustering of vacancies and interstitials were studied. The peak time and the corresponding number of defects increase with increasing irradiation temperature and primary knock-on atom (PKA) energy. However, the final number of surviving point defects decreases with increasing lattice temperature. This is associated with the increase of thermal spike at high PKA energy and its long timespan at higher temperatures. Defect production efficiency (i.e., surviving MD defects, per Norgett-Robinson-Torrens displacements) also showed a continuous decrease with the increasing irradiation temperature and PKA energy. The number of interstitial clusters increases with both irradiation temperature and PKA energy. However, the increase in the number of vacancy clusters with PKA energy is minimal-to-constant and decreases as the irradiation temperature increases. Similarly, the probability and cluster size distribution for larger interstitials increase with temperature, whereas only smaller size vacancy clusters were observed at higher temperatures.

Biomarkers as Indicators of Respiration During Laboratory Incubations of Alaskan Arctic Tundra Permafrost Soils

NASA Astrophysics Data System (ADS)

Hutchings, J.; Schuur, E.; Bianchi, T. S.; Bracho, R. G.

2015-12-01

High latitude permafrost soils are estimated to store 1,330 - 1,580 Pg C, which account for ca. 40% of global soil C and nearly twice that of atmospheric C. Disproportionate heating of high latitude regions during climate warming potentially results in permafrost thaw and degradation of surficial and previously-frozen soil C. Understanding how newly-thawed soils respond to microbial degradation is essential to predicting C emissions from this region. Laboratory incubations have been a key tool in understanding potential respiration rates from high latitude soils. A recent study found that among the common soil measurements, C:N was the best predictor of C losses. Here, we analyzed Alaskan Arctic tundra soils from before and after a nearly 3-year laboratory incubation. Bulk geochemical values as well as the following biomarkers were measured: lignin, amino acids, n-alkanes, and glycerol dialkyl glycerol tetraethers (GDGT). We found that initial C:N did not predict C losses and no significant change in C:N between initial and final samples. The lignin acid to aldehyde (Ad:Al) degradation index showed the same results with a lack of C loss prediction and no significant change during the experiment. However, we did find that C:N and Ad:Al had a significant negative correlation suggesting behavior consistent with expectations. The failure to predict C losses was likely influenced by a number of factors, including the possibility that biomarkers were tracking a smaller fraction of slower cycling components of soil C. To better interpret these results, we also used a hydroxyproline-based amino acid degradation index and n-alkanes to estimate the contribution Sphagnum mosses to soil samples - known to have slower turnover times than vascular plants. Finally, we applied a GDGT soil temperature proxy to estimate the growing season soil temperatures before each incubation, as well as investigating the effects of incubation temperature on the index's temperature estimate.

High-temperature seals and lubricants for geothermal rock bits. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hendrickson, R.R.; Winzenried, R.W.; Jones A.H.

1981-04-01

High temperature seals (elastomeric and mechanical) and lubricants were developed specifically for journal-type rock bits to be used in geothermal well drilling. Results at simulated downhole conditions indicate that five selected elastomeric seals (L'Garde No. 267, Utex Nos. 227, 231 and HTCR, and Sandia Glow Discharge Coated Viton) are capable of 288/sup 0/C (500/sup 0/F) service. Two prototype mechanical seals did not achieve the life determined for the elastomeric seals. Six lubricants (Pacer PLX-024 oil, PLX-043 oil, PLX-045 oil, Geobond Oil, and Geobond Grease) demonstrated 316/sup 0/C (600/sup 0/F) capability. Recommendation is made for full-scale simulated geothermal drilling tests utilizingmore » the improved elastomeric seals and lubricants.« less

Atomistic structures of nano-engineered SiC and radiation-induced amorphization resistance

DOE PAGES

Imada, Kenta; Ishimaru, Manabu; Sato, Kazuhisa; ...

2015-06-18

In this paper, nano-engineered 3C–SiC thin films, which possess columnar structures with high-density stacking faults and twins, were irradiated with 2 MeV Si ions at cryogenic and room temperatures. From cross-sectional transmission electron microscopy observations in combination with Monte Carlo simulations based on the Stopping and Range of Ions in Matter code, it was found that their amorphization resistance is six times greater than bulk crystalline SiC at room temperature. High-angle bright-field images taken by spherical aberration corrected scanning transmission electron microscopy revealed that the distortion of atomic configurations is localized near the stacking faults. Finally, the resultant strain fieldmore » probably contributes to the enhancement of radiation tolerance of this material.« less

Self-assembly of core-shell structure PtO2@Pt nanodots and their formation evolution

NASA Astrophysics Data System (ADS)

Yang, Weijia; Liu, Junjie; Liu, Mingquan; Zhao, Zhicheng; Song, Yapeng; Tang, Xiufeng; Luo, Jianyi; Zeng, Qingguang; He, Xin

2018-05-01

Core-shell structure PtO2@Pt nanodots have been self-assembly by vacuum sputtering and high temperature annealing. First, Pt thin films with a small amount of PtO2 are grown on the sapphire substrates by vacuum sputtering. And then high temperature annealing on the thin films is carried out at 800 °C for 2 min to form Pt nanodots. During the cooling process, the atmosphere is deployed to supplant the nitrogen. Finally, even distributed core-shell structure PtO2@Pt nanodots with a diameter from 100 to 300 nm are achieved. Furthermore, the formation evolution of core-shell structure PtO2@Pt nanodots is also proposed. This work open up a new approach for fabricating core-shell structure nanodots.

Nonvacuum, maskless fabrication of a flexible metal grid transparent conductor by low-temperature selective laser sintering of nanoparticle ink.

PubMed

Hong, Sukjoon; Yeo, Junyeob; Kim, Gunho; Kim, Dongkyu; Lee, Habeom; Kwon, Jinhyeong; Lee, Hyungman; Lee, Phillip; Ko, Seung Hwan

2013-06-25

We introduce a facile approach to fabricate a metallic grid transparent conductor on a flexible substrate using selective laser sintering of metal nanoparticle ink. The metallic grid transparent conductors with high transmittance (>85%) and low sheet resistance (30 Ω/sq) are readily produced on glass and polymer substrates at large scale without any vacuum or high-temperature environment. Being a maskless direct writing method, the shape and the parameters of the grid can be easily changed by CAD data. The resultant metallic grid also showed a superior stability in terms of adhesion and bending. This transparent conductor is further applied to the touch screen panel, and it is confirmed that the final device operates firmly under continuous mechanical stress.

High pressure study of Pu(0.92)Am(0.08) binary alloy.

PubMed

Klosek, V; Griveau, J C; Faure, P; Genestier, C; Baclet, N; Wastin, F

2008-07-09

The phase transitions (by means of x-ray diffraction) and electrical resistivity of a Pu(0.92)Am(0.08) binary alloy were determined under pressure (up to 2 GPa). The evolution of atomic volume with pressure gives detailed information concerning the degree of localization of 5f electronic states and their delocalization process. A quasi-linear V = f(P) dependence reflects subtle modifications of the electronic structure when P increases. The electrical resistivity measurements reveal the very high stability of the δ phase for pressures less than 0.7 GPa, since no martensitic-like transformation occurs at low temperature. Remarkable electronic behaviours have also been observed. Finally, resistivity curves have shown the temperature dependence of the phase transformations together with unexpected kinetic effects.

High-Strength Aluminum Casting Alloy for High-Temperature Applications (MSFC Center Director's Discretionary Fund Final Project No. 97-10)

NASA Technical Reports Server (NTRS)

Lee, J. A.

1998-01-01

A new aluminum-silicon alloy has been successfully developed at Marshall Space Flight Center that has a significant improvement in tensile strength at elevated temperatures (550 to 700 F). For instance, the new alloy shows in average tensile strength of at least 90 percent higher than the current 390 aluminum piston alloy tested at 500 F. Compared to conventional aluminum alloys, automotive engines using the new piston alloy will have improved gas mileage, and may produce less air pollution in order to meet the future U.S. automotive legislative requirements for low hydrocarbon emissions. The projected cost for this alloy is less than $0.95/lb, and it readily allows the automotive components to be cast at a high production volume with a low, fully accounted cost. It is economically produced by pouring molten metal directly into conventional permanent steel molds or die casting.

Final Report: Ionization chemistry of high temperature molecular fluids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fried, L E

2007-02-26

With the advent of coupled chemical/hydrodynamic reactive flow models for high explosives, understanding detonation chemistry is of increasing importance to DNT. The accuracy of first principles detonation codes, such as CHEETAH, are dependent on an accurate representation of the species present under detonation conditions. Ionic species and non-molecular phases are not currently included coupled chemistry/hydrodynamic simulations. This LDRD will determine the prevalence of such species during high explosive detonations, by carrying out experimental and computational investigation of common detonation products under extreme conditions. We are studying the phase diagram of detonation products such as H{sub 2}O, or NH{sub 3} andmore » mixtures under conditions of extreme pressure (P > 1 GPa) and temperature (T > 1000K). Under these conditions, the neutral molecular form of matter transforms to a phase dominated by ions. The phase boundaries of such a region are unknown.« less

Dedicated nuclear facilities for electrolytic hydrogen production

NASA Technical Reports Server (NTRS)

Foh, S. E.; Escher, W. J. D.; Donakowski, T. D.

1979-01-01

An advanced technology, fully dedicated nuclear-electrolytic hydrogen production facility is presented. This plant will produce hydrogen and oxygen only and no electrical power will be generated for off-plant use. The conceptual design was based on hydrogen production to fill a pipeline at 1000 psi and a 3000 MW nuclear base, and the base-line facility nuclear-to-shaftpower and shaftpower-to-electricity subsystems, the water treatment subsystem, electricity-to-hydrogen subsystem, hydrogen compression, efficiency, and hydrogen production cost are discussed. The final conceptual design integrates a 3000 MWth high-temperature gas-cooled reactor operating at 980 C helium reactor-out temperature, direct dc electricity generation via acyclic generators, and high-current density, high-pressure electrolyzers based on the solid polymer electrolyte approach. All subsystems are close-coupled and optimally interfaced and pipeline hydrogen is produced at 1000 psi. Hydrogen costs were about half of the conventional nuclear electrolysis process.

Super-high color rendering properties of color temperature tunable white LEDs based on high quality InP/ZnS quantum dots via myristic acid passivation and Ag doping

NASA Astrophysics Data System (ADS)

Yang, Wu; Zhang, Wanlu; Zhang, Guilin; Zhu, Jiatao; He, Guoxing; Guo, Ruiqian

2018-07-01

We reported two types of tunable white LEDs (WLEDs) based on high quality the single emissive InP/ZnS quantum dots (QDs) and the dual emissive Ag:InP/ZnS QDs via myristic acid (MA) passivation and Ag doping. The WLEDs with three color InP/ZnS QDs could realize color rendering indices (CRIs) of 97-98, color quality scales (CQSs) of 94-98, and limited luminous efficacies (LLEs) of 238-246 lm/W at correlated color temperatures (CCTs) of 2700 K to 6500 K, and the WLEDs with dual emissive Ag:InP/ZnS and red emissive InP/ZnS QDs could realize CRIs of 90-93, CQSs of 90-93, and LLEs of 223-242 lm/W at CCTs of 2700 K to 4000 K. Finally, their luminous efficacies were estimated.

Neutron diffraction reveals hydrogen bonds critical for cGMP-selective activation: Insights for cGMP-dependent protein kinase agonist design

DOE PAGES

Huang, Gilbert Y.; Gerlits, Oksana O.; Blakeley, Matthew P.; ...

2014-10-01

High selectivity of cyclic-nucleotide binding (CNB) domains for cAMP and cGMP are required for segregating signaling pathways; however, the mechanism of selectivity remains unclear. To investigate the mechanism of high selectivity in cGMP-dependent protein kinase (PKG), we determined a room-temperature joint X-ray/neutron (XN) structure of PKG Iβ CNB-B, a domain 200-fold selective for cGMP over cAMP, bound to cGMP (2.2 Å), and a low-temperature X-ray structure of CNB-B with cAMP (1.3 Å). Finally, the XN structure directly describes the hydrogen bonding interactions that modulate high selectivity for cGMP, while the structure with cAMP reveals that all these contacts are disrupted,more » explaining its low affinity for cAMP.« less

Nonextensive statistics and skin depth of transverse wave in collisional plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hashemzadeh, M., E-mail: hashemzade@gmail.com

Skin depth of transverse wave in a collisional plasma is studied taking into account the nonextensive electron distribution function. Considering the kinetic theory for charge particles and using the Bhatnagar-Gross-Krook collision model, a generalized transverse dielectric permittivity is obtained. The transverse dispersion relation in different frequency ranges is investigated. Obtaining the imaginary part of the wave vector from the dispersion relation, the skin depth for these frequency ranges is also achieved. Profiles of the skin depth show that by increasing the q parameter, the penetration depth decreases. In addition, the skin depth increases by increasing the electron temperature. Finally, itmore » is found that in the high frequency range and high electron temperature, the penetration depth decreases by increasing the collision frequency. In contrast, by increasing the collision frequency in a highly collisional frequency range, the skin depth of transverse wave increases.« less

Contact Thermocouple Methodology and Evaluation for Temperature Measurement in the Laboratory

NASA Technical Reports Server (NTRS)

Brewer, Ethan J.; Pawlik, Ralph J.; Krause, David L.

2013-01-01

Laboratory testing of advanced aerospace components very often requires highly accurate temperature measurement and control devices, as well as methods to precisely analyze and predict the performance of such components. Analysis of test articles depends on accurate measurements of temperature across the specimen. Where possible, this task is accomplished using many thermocouples welded directly to the test specimen, which can produce results with great precision. However, it is known that thermocouple spot welds can initiate deleterious cracks in some materials, prohibiting the use of welded thermocouples. Such is the case for the nickel-based superalloy MarM-247, which is used in the high temperature, high pressure heater heads for the Advanced Stirling Converter component of the Advanced Stirling Radioisotope Generator space power system. To overcome this limitation, a method was developed that uses small diameter contact thermocouples to measure the temperature of heater head test articles with the same level of accuracy as welded thermocouples. This paper includes a brief introduction and a background describing the circumstances that compelled the development of the contact thermocouple measurement method. Next, the paper describes studies performed on contact thermocouple readings to determine the accuracy of results. It continues on to describe in detail the developed measurement method and the evaluation of results produced. A further study that evaluates the performance of different measurement output devices is also described. Finally, a brief conclusion and summary of results is provided.

Effects of High-Temperature Preoxidation on the Titanomagnetite Ore Structure and Reduction Behaviors in Fluidized Bed

NASA Astrophysics Data System (ADS)

Sun, Haoyan; Adetoro, Ajala Adewole; Pan, Feng; Wang, Zhen; Zhu, Qingshan

2017-06-01

The oxidation behaviors of South Africa (SA) titanomagnetite (TTM) and its effects on the gas solid reduction in the fluidized bed were investigated on the basis of the two-stage short process of direct reduction-electric arc furnace (DR-EAF) melting separation. The results showed that the oxidation phase transformations in the high-temperature range from 1073 K to 1223 K (800 °C to 950 °C) can be divided into two typical processes: with the fast generation of pseudobrookite and with the maghemite generation at the initial stage. The reduction efficiency for SA TTM was improved by the preoxidation treatment, mainly because of the dissociation of titania-ferrous oxides to the easy reducible hematite. However, at a preoxidation temperature higher than 1173 K (900 °C), the improving effect became weak, due to high-temperature sintering and the larger crystallite size of oxidation products. There is an extreme value of the preoxidation influence, and the optimum preoxidation time is different for various temperatures. The reduction metallization degree of SA TTM can be relatively improved by 14.5 and 4.5 pct for the first and second reduction steps, respectively, by 1173 K (900 °C) preoxidation with an optimum time of 30 minutes. Finally, the equilibrium relationship between the metallization degree and the gas reduction potential for TTM ore with preoxidation treatment was built.

Helping Aircraft Engines Lighten Up

NASA Technical Reports Server (NTRS)

2004-01-01

High-temperature polyimide/carbon fiber matrix composites are developed by the Polymers Branch at NASA's Glenn Research Center. These materials can withstand high temperatures and have good processing properties, which make them particularly useful for jet and rocket engines and for components such as fan blades, bushings, and duct segments. Applying polyimide composites as components for aerospace structures can lead to substantial vehicle weight reductions. A typical polyimide composite is made up of layers of carbon or glass fibers glued together by a high-temperature polymer to make the material strong, stiff, and lightweight. Organic molecules containing carbon, nitrogen, oxygen, and hydrogen within the polyimide keep the material s density low, resulting in the light weight. The strength of a component or part made from a polyimide comes mainly from the reinforcing high-strength fibers. The strength of the carbon fibers coupled with the stiffness of polyimides allows engineers to make a very rigid structure without it being massive. Another benefit of a polyimide s suitability for aerospace applications is its reduced need for machining. When polyimide parts are removed from a mold, they are nearly in their final shape. Usually, very little machining is needed before a part is ready for use.

The high temperature creep behavior of oxides and oxide fibers

NASA Technical Reports Server (NTRS)

Jones, Linda E.; Tressler, Richard E.

1991-01-01

A thorough review of the literature was conducted on the high-temperature creep behavior of single and polycrystalline oxides which potentially could serve as fiber reinforcements in ceramics or metal matrix applications. Sapphire when oriented with the basal plane perpendicular to the fiber axis (c-axis oriented) is highly creep resistant at temperatures in excess of 1600 C and applied loads of 100 MPa and higher. Pyramidal slip is preferentially activated in sapphire under these conditions and steady-state creep rates in the range of 10(exp -7) to 10 (exp -8)/s were reported. Data on the creep resistance of polycrystalline beryllia suggest that C-axiz oriented single crystal beryllia may be a viable candidate as a fiber reinforcement material; however, the issure of fabricability and moisture sensitivity must be addressed for this material. Yttrium aluminum garnet (YAG) also appears to be a fiber candidate material having a high resistance to creep which is due to it's complex crystal structure and high Peierl resistance. The high creep resistance of garnet suggests that there may be other complex ternary oxides such as single crystal mullite which may also be candidate materials for fiber reinforcements. Finally, CVD and single crystal SiC, although not oxides, do possess a high resistance to creep in the temperature range between 1550 and 1850 C and under stresses of 110 to 220 MPa. From a review of the literature, it appears that for high creep resistant applications sapphire, silicon carbide, yttrium aluminum garnet, mullite, and beryllia are desirable candidate materials which require further investigation.

Strain rate effects on the mechanical behavior of two Dual Phase steels in tension

NASA Astrophysics Data System (ADS)

Cadoni, E.; Singh, N. K.; Forni, D.; Singha, M. K.; Gupta, N. K.

2016-05-01

This paper presents an experimental investigation on the strain rate sensitivity of Dual Phase steel 1200 (DP1200) and Dual Phase steel 1400 (DP1400) under uni-axial tensile loads in the strain rate range from 0.001 s-1 to 600 s-1. These materials are advanced high strength steels (AHSS) having high strength, high capacity to dissipate crash energy and high formability. Flat sheet specimens of the materials having gauge length 10 mm, width 4 mm and thickness 2 mm (DP1200) and 1.25 mm (DP1400), are tested at room temperature (20∘C) on electromechanical universal testing machine to obtain their stress-strain relation under quasi-static condition (0.001 s-1), and on Hydro-Pneumatic machine and modified Hopkinson bar to study their mechanical behavior at medium (3 s-1, and 18 s-1) and high strain rates (200 s-1, 400 s-1, and 600 s-1) respectively. Tests under quasi-static condition are performed at high temperature (200∘C) also, and found that tensile flow stress is a increasing function of temperature. The stress-strain data has been analysed to determine the material parameters of the Cowper-Symonds and the Johnson-Cook models. A simple modification of the Johnson-Cook model has been proposed in order to obtain a better fit of tests at high temperatures. Finally, the fractographs of the broken specimens are taken by scanning electron microscope (SEM) to understand the fracture mechanism of these advanced high strength steels at different strain rates.

Plasma-assisted synthesis of MoS2

NASA Astrophysics Data System (ADS)

Campbell, Philip M.; Perini, Christopher J.; Chiu, Johannes; Gupta, Atul; Ray, Hunter S.; Chen, Hang; Wenzel, Kevin; Snyder, Eric; Wagner, Brent K.; Ready, Jud; Vogel, Eric M.

2018-03-01

There has been significant interest in transition metal dichalcogenides (TMDs), including MoS2, in recent years due to their potential application in novel electronic and optical devices. While synthesis methods have been developed for large-area films of MoS2, many of these techniques require synthesis temperatures of 800 °C or higher. As a result of the thermal budget, direct synthesis requiring high temperatures is incompatible with many integrated circuit processes as well as flexible substrates. This work explores several methods of plasma-assisted synthesis of MoS2 as a way to lower the synthesis temperature. The first approach used is conversion of a naturally oxidized molybdenum thin film to MoS2 using H2S plasma. Conversion is demonstrated at temperatures as low as 400 °C, and the conversion is enabled by hydrogen radicals which reduce the oxidized molybdenum films. The second method is a vapor phase reaction incorporating thermally evaporated MoO3 exposed to a direct H2S plasma, similar to chemical vapor deposition (CVD) synthesis of MoS2. Synthesis at 400 °C results in formation of super-stoichiometric MoS2 in a beam-interrupted growth process. A final growth method relies on a cyclical process in which a small amount of Mo is sputtered onto the substrate and is subsequently sulfurized in a H2S plasma. Similar results could be realized using an atomic layer deposition (ALD) process to deposit the Mo film. Compared to high temperature synthesis methods, the lower temperature samples are lower quality, potentially due to poor crystallinity or higher defect density in the films. Temperature-dependent conductivity measurements are consistent with hopping conduction in the plasma-assisted synthetic MoS2, suggesting a high degree of disorder in the low-temperature films. Optimization of the plasma-assisted synthesis process for slower growth rate and better stoichiometry is expected to lead to high quality films at low growth temperature.

The Importance of Biologically Relevant Microclimates in Habitat Suitability Assessments

PubMed Central

Varner, Johanna; Dearing, M. Denise

2014-01-01

Predicting habitat suitability under climate change is vital to conserving biodiversity. However, current species distribution models rely on coarse scale climate data, whereas fine scale microclimate data may be necessary to assess habitat suitability and generate predictive models. Here, we evaluate disparities between temperature data at the coarse scale from weather stations versus fine-scale data measured in microhabitats required for a climate-sensitive mammal, the American pika (Ochotona princeps). We collected two years of temperature data in occupied talus habitats predicted to be suitable (high elevation) and unsuitable (low elevation) by the bioclimatic envelope approach. At low elevations, talus surface and interstitial microclimates drastically differed from ambient temperatures measured on-site and at a nearby weather station. Interstitial talus temperatures were frequently decoupled from high ambient temperatures, resulting in instantaneous disparities of over 30°C between these two measurements. Microhabitat temperatures were also highly heterogeneous, such that temperature measurements within the same patch of talus were not more correlated than measurements at distant patches. An experimental manipulation revealed that vegetation cover may cool the talus surface by up to 10°C during the summer, which may contribute to this spatial heterogeneity. Finally, low elevation microclimates were milder and less variable than typical alpine habitat, suggesting that, counter to species distribution model predictions, these seemingly unsuitable habitats may actually be better refugia for this species under climate change. These results highlight the importance of fine-scale microhabitat data in habitat assessments and underscore the notion that some critical refugia may be counterintuitive. PMID:25115894

The importance of biologically relevant microclimates in habitat suitability assessments.

PubMed

Varner, Johanna; Dearing, M Denise

2014-01-01

Predicting habitat suitability under climate change is vital to conserving biodiversity. However, current species distribution models rely on coarse scale climate data, whereas fine scale microclimate data may be necessary to assess habitat suitability and generate predictive models. Here, we evaluate disparities between temperature data at the coarse scale from weather stations versus fine-scale data measured in microhabitats required for a climate-sensitive mammal, the American pika (Ochotona princeps). We collected two years of temperature data in occupied talus habitats predicted to be suitable (high elevation) and unsuitable (low elevation) by the bioclimatic envelope approach. At low elevations, talus surface and interstitial microclimates drastically differed from ambient temperatures measured on-site and at a nearby weather station. Interstitial talus temperatures were frequently decoupled from high ambient temperatures, resulting in instantaneous disparities of over 30 °C between these two measurements. Microhabitat temperatures were also highly heterogeneous, such that temperature measurements within the same patch of talus were not more correlated than measurements at distant patches. An experimental manipulation revealed that vegetation cover may cool the talus surface by up to 10 °C during the summer, which may contribute to this spatial heterogeneity. Finally, low elevation microclimates were milder and less variable than typical alpine habitat, suggesting that, counter to species distribution model predictions, these seemingly unsuitable habitats may actually be better refugia for this species under climate change. These results highlight the importance of fine-scale microhabitat data in habitat assessments and underscore the notion that some critical refugia may be counterintuitive.

Development of sensors for ceramic components in advanced propulsion systems: Survey and evaluation of measurement techniques for temperature, strain and heat flux for ceramic components in advanced propulsion systems

NASA Technical Reports Server (NTRS)

Atkinson, W. H.; Cyr, M. A.; Strange, R. R.

1988-01-01

The report presents the final results of Tasks 1 and 2, Development of Sensors for Ceramic Components in Advanced Propulsion Systems (NASA program NAS3-25141). During Task 1, an extensive survey was conducted of sensor concepts which have the potential for measuring surface temperature, strain and heat flux on ceramic components for advanced propulsion systems. Each sensor concept was analyzed and evaluated under Task 2; sensor concepts were then recommended for further development. For temperature measurement, both pyrometry and thermographic phosphors are recommended for measurements up to and beyond the melting point of ceramic materials. For lower temperature test programs, the thin-film techniques offer advantages in the installation of temperature sensors. Optical strain measurement techniques are recommended because they offer the possibility of being useful at very high temperature levels. Techniques for the measurement of heat flux are recommended for development based on both a surface mounted sensor and the measurement of the temperature differential across a portion of a ceramic component or metallic substrate.

Two-temperature model in molecular dynamics simulations of cascades in Ni-based alloys

DOE PAGES

Zarkadoula, Eva; Samolyuk, German; Weber, William J.

2017-01-03

In high-energy irradiation events, energy from the fast moving ion is transferred to the system via nuclear and electronic energy loss mechanisms. The nuclear energy loss results in the creation of point defects and clusters, while the energy transferred to the electrons results in the creation of high electronic temperatures, which can affect the damage evolution. In this paper, we perform molecular dynamics simulations of 30 keV and 50 keV Ni ion cascades in nickel-based alloys without and with the electronic effects taken into account. We compare the results of classical molecular dynamics (MD) simulations, where the electronic effects aremore » ignored, with results from simulations that include the electronic stopping only, as well as simulations where both the electronic stopping and the electron-phonon coupling are incorporated, as described by the two temperature model (2T-MD). Finally, our results indicate that the 2T-MD leads to a smaller amount of damage, more isolated defects and smaller defect clusters.« less

An Integrated Thermal Compensation System for MEMS Inertial Sensors

PubMed Central

Chiu, Sheng-Ren; Teng, Li-Tao; Chao, Jen-Wei; Sue, Chung-Yang; Lin, Chih-Hsiou; Chen, Hong-Ren; Su, Yan-Kuin

2014-01-01

An active thermal compensation system for a low temperature-bias-drift (TBD) MEMS-based gyroscope is proposed in this study. First, a micro-gyroscope is fabricated by a high-aspect-ratio silicon-on-glass (SOG) process and vacuum packaged by glass frit bonding. Moreover, a drive/readout ASIC, implemented by the 0.25 μm 1P5M standard CMOS process, is designed and integrated with the gyroscope by directly wire bonding. Then, since the temperature effect is one of the critical issues in the high performance gyroscope applications, the temperature-dependent characteristics of the micro-gyroscope are discussed. Furthermore, to compensate the TBD of the micro-gyroscope, a thermal compensation system is proposed and integrated in the aforementioned ASIC to actively tune the parameters in the digital trimming mechanism, which is designed in the readout ASIC. Finally, some experimental results demonstrate that the TBD of the micro-gyroscope can be compensated effectively by the proposed compensation system. PMID:24599191

Single Crystal Synthesis and STM Studies of High Temperature Superconductors

NASA Technical Reports Server (NTRS)

Barrientos, Alfonso

1997-01-01

This is a final report for the work initiated in September of 1994 under the grant NAG8-1085 - NASA/OMU, on the fabrication of bulk and single crystal synthesis, specific heat measuring and STM studies of high temperature superconductors. Efforts were made to fabricate bulk and single crystals of mercury based superconducting material. A systematic thermal analysis on the precursors for the corresponding oxides and carbonates were carried out to synthesized bulk samples. Bulk material was used as seed in an attempt to grow single crystals by a two-step self flux process. On the other hand bulk samples were characterized by x-ray diffraction, electrical resistivity and magnetic susceptibility, We studied the specific heat behavior in the range from 80 to 300 K. Some preliminary attempts were made to study the atomic morphology of our samples. As part of our efforts we built an ac susceptibility apparatus for measuring the transition temperature of our sintered samples.

Link between light-triggered Mg-banding and chamber formation in the planktic foraminifera Neogloboquadrina dutertrei

NASA Astrophysics Data System (ADS)

Fehrenbacher, Jennifer S.; Russell, Ann D.; Davis, Catherine V.; Gagnon, Alexander C.; Spero, Howard J.; Cliff, John B.; Zhu, Zihua; Martin, Pamela

2017-05-01

The relationship between seawater temperature and the average Mg/Ca ratios in planktic foraminifera is well established, providing an essential tool for reconstructing past ocean temperatures. However, many species display alternating high and low Mg-bands within their shell walls that cannot be explained by temperature alone. Recent experiments demonstrate that intrashell Mg variability in Orbulina universa, which forms a spherical terminal shell, is paced by the diurnal light/dark cycle. Whether Mg-heterogeneity is also diurnally paced in species with more complex shell morphologies is unknown. Here we show that high Mg/Ca-calcite forms at night in cultured specimens of the multi-chambered species Neogloboquadrina dutertrei. Our results demonstrate that N. dutertrei adds a significant amount of calcite, and nearly all Mg-bands, after the final chamber forms. These results have implications for interpreting patterns of calcification in N. dutertrei and suggest that diurnal Mg-banding is an intrinsic component of biomineralization in planktic foraminifera.

Silicon strain gages bonded on stainless steel using glass frit for strain sensor applications

NASA Astrophysics Data System (ADS)

Zhang, Zongyang; Cheng, Xingguo; Leng, Yi; Cao, Gang; Liu, Sheng

2014-05-01

In this paper, a steel pressure sensor using strain gages bonded on a 17-4 PH stainless steel (SS) diaphragm based on glass frit technology is proposed. The strain gages with uniform resistance are obtained by growing an epi-silicon layer on a single crystal silicon wafer using epitaxial deposition technique. The inorganic glass frits are used as the bonding material between the strain gages and the 17-4 PH SS diaphragm. Our results show that the output performances of sensors at a high temperature of 125 °C are almost equal those at room temperature, which indicates that the glass frit bonding is a good method and may lead to a significant advance in the high temperature applicability of silicon strain gage sensors. Finally, the microstructure of the cured organic adhesive and the fired glass frit are compared. It may be concluded that the defects of the cured organic adhesive deteriorate the hysteresis and repeatability errors of the sensors.

High-sensitivity and low-temperature magnetic field sensor based on tapered two-mode fiber interference.

PubMed

Sun, Bing; Fang, Fang; Zhang, Zuxing; Xu, Jing; Zhang, Lin

2018-03-15

A high-sensitivity and low-temperature fiber-optic magnetic field sensor based on a tapered two-mode fiber (TTMF) sandwiched between two single-mode fibers has been proposed and demonstrated. The section of TTMF has a specifically designed transition region as an efficient tool to filter higher-order modes, where the uniform modal interferometer just involved with LP 01 and LP 11 modes is achieved. The transmission spectral characteristics and the magnetic response of the proposed sensors have been investigated. The experimental results show that a maximum sensitivity of 98.2  pm/Oe within a linear magnetic field intensity ranging from 0 to 140 Oe can be achieved. Significantly, the temperature cross-sensitivity problem can be resolved owing to the lower thermal expansion coefficient of the TTMF. Finally, with its low insertion loss, compactness, and ease of fabrication, the proposed sensor would find potential applications in the measurement of a magnetic field.

New generation ICG-based contrast agents for ultrasound-switchable fluorescence imaging

PubMed Central

Yu, Shuai; Cheng, Bingbing; Yao, Tingfeng; Xu, Cancan; Nguyen, Kytai T.; Hong, Yi; Yuan, Baohong

2016-01-01

Recently, we developed a new technology, ultrasound-switchable fluorescence (USF), for high-resolution imaging in centimeter-deep tissues via fluorescence contrast. The success of USF imaging highly relies on excellent contrast agents. ICG-encapsulated poly(N-isopropylacrylamide) nanoparticles (ICG-NPs) are one of the families of the most successful near-infrared (NIR) USF contrast agents. However, the first-generation ICG-NPs have a short shelf life (<1 month). This work significantly increases the shelf life of the new-generation ICG-NPs (>6 months). In addition, we have conjugated hydroxyl or carboxyl function groups on the ICG-NPs for future molecular targeting. Finally, we have demonstrated the effect of temperature-switching threshold (Tth) and the background temperature (TBG) on the quality of USF images. We estimated that the Tth of the ICG-NPs should be controlled at ~38–40 °C (slightly above the body temperature of 37 °C) for future in vivo USF imaging. Addressing these challenges further reduces the application barriers of USF imaging. PMID:27775014

Direct exfoliation and dispersion of two-dimensional materials in pure water via temperature control.

PubMed

Kim, Jinseon; Kwon, Sanghyuk; Cho, Dae-Hyun; Kang, Byunggil; Kwon, Hyukjoon; Kim, Youngchan; Park, Sung O; Jung, Gwan Yeong; Shin, Eunhye; Kim, Wan-Gu; Lee, Hyungdong; Ryu, Gyeong Hee; Choi, Minseok; Kim, Tae Hyeong; Oh, Junghoon; Park, Sungjin; Kwak, Sang Kyu; Yoon, Suk Wang; Byun, Doyoung; Lee, Zonghoon; Lee, Changgu

2015-09-15

The high-volume synthesis of two-dimensional (2D) materials in the form of platelets is desirable for various applications. While water is considered an ideal dispersion medium, due to its abundance and low cost, the hydrophobicity of platelet surfaces has prohibited its widespread use. Here we exfoliate 2D materials directly in pure water without using any chemicals or surfactants. In order to exfoliate and disperse the materials in water, we elevate the temperature of the sonication bath, and introduce energy via the dissipation of sonic waves. Storage stability greater than one month is achieved through the maintenance of high temperatures, and through atomic and molecular level simulations, we further discover that good solubility in water is maintained due to the presence of platelet surface charges as a result of edge functionalization or intrinsic polarity. Finally, we demonstrate inkjet printing on hard and flexible substrates as a potential application of water-dispersed 2D materials.

Influence of Homogenization and Thermal Processing on the Gastrointestinal Fate of Bovine Milk Fat: In Vitro Digestion Study.

PubMed

Liang, Li; Qi, Ce; Wang, Xingguo; Jin, Qingzhe; McClements, David Julian

2017-12-20

Dairy lipids are an important source of energy and nutrients for infants and adults. The dimensions, aggregation state, and interfacial properties of fat globules in raw milk are changed by dairy processing operations, such as homogenization and thermal processing. These changes influence the behavior of fat globules within the human gastrointestinal tract (GIT). The gastrointestinal fate of raw milk, homogenized milk, high temperature short time (HTST) pasteurized milk, and ultrahigh temperature (UHT) pasteurized milk samples was therefore determined using a simulated GIT. The properties of particles in different regions of the GIT depended on the degree of milk processing. Homogenization increased the initial lipid digestion rate but did not influence the final digestion extent. Thermal processing of homogenized milk decreased the initial rate and final extent of lipid digestion, which was attributed to changes in interfacial structure. These results provide insights into the impact of dairy processing on the gastrointestinal fate of milk fat.

Chemical, morphological and functional properties of Brazilian jackfruit (Artocarpus heterophyllus L.) seeds starch.

PubMed

Madruga, Marta Suely; de Albuquerque, Fabíola Samara Medeiros; Silva, Izis Rafaela Alves; do Amaral, Deborah Silva; Magnani, Marciane; Queiroga Neto, Vicente

2014-01-15

Starches used in food industry are extracted from roots, tubers and cereals. Seeds of jackfruit are abundant and contain high amounts of starch. They are discarded during the fruit processing or consumption and can be an alternative source of starch. The starch was extract from the jackfruit seeds and characterised to chemical, morphological and functional properties. Soft and hard jackfruit seeds showed starch content of 92.8% and 94.5%, respectively. Starch granules showed round and bell shape and some irregular cuts on their surface with type-A crystallinity pattern, similar to cereals starches. The swelling power and solubility of jackfruit starch increased with increasing temperature, showing opaque pastes. The soft seeds starch showed initial and final gelatinisation temperature of 36°C and 56°C, respectively; while hard seeds starch presented initial gelatinisation at 40°C and final at 61°C. These results suggest that the Brazilian jackfruit seeds starches could be used in food products. Copyright © 2013 Elsevier Ltd. All rights reserved.

Multistage degradation modeling for BLDC motor based on Wiener process

NASA Astrophysics Data System (ADS)

Yuan, Qingyang; Li, Xiaogang; Gao, Yuankai

2018-05-01

Brushless DC motors are widely used, and their working temperatures, regarding as degradation processes, are nonlinear and multistage. It is necessary to establish a nonlinear degradation model. In this research, our study was based on accelerated degradation data of motors, which are their working temperatures. A multistage Wiener model was established by using the transition function to modify linear model. The normal weighted average filter (Gauss filter) was used to improve the results of estimation for the model parameters. Then, to maximize likelihood function for parameter estimation, we used numerical optimization method- the simplex method for cycle calculation. Finally, the modeling results show that the degradation mechanism changes during the degradation of the motor with high speed. The effectiveness and rationality of model are verified by comparison of the life distribution with widely used nonlinear Wiener model, as well as a comparison of QQ plots for residual. Finally, predictions for motor life are gained by life distributions in different times calculated by multistage model.

Effect of temperature- and frequency-dependent dynamic properties of rail pads on high-speed vehicle-track coupled vibrations

NASA Astrophysics Data System (ADS)

Wei, Kai; Wang, Feng; Wang, Ping; Liu, Zi-xuan; Zhang, Pan

2017-03-01

The soft under baseplate pad of WJ-8 rail fastener frequently used in China's high-speed railways was taken as the study subject, and a laboratory test was performed to measure its temperature and frequency-dependent dynamic performance at 0.3 Hz and at -60°C to 20°C with intervals of 2.5°C. Its higher frequency-dependent results at different temperatures were then further predicted based on the time-temperature superposition (TTS) and Williams-Landel-Ferry (WLF) formula. The fractional derivative Kelvin-Voigt (FDKV) model was used to represent the temperature- and frequency-dependent dynamic properties of the tested rail pad. By means of the FDKV model for rail pads and vehicle-track coupled dynamic theory, high-speed vehicle-track coupled vibrations due to temperature- and frequency-dependent dynamic properties of rail pads was investigated. Finally, further combining with the measured frequency-dependent dynamic performance of vehicle's rubber primary suspension, the high-speed vehicle-track coupled vibration responses were discussed. It is found that the storage stiffness and loss factor of the tested rail pad are sensitive to low temperatures or high frequencies. The proposed FDKV model for the frequency-dependent storage stiffness and loss factors of the tested rail pad can basically meet the fitting precision, especially at ordinary temperatures. The numerical simulation results indicate that the vertical vibration levels of high-speed vehicle-track coupled systems calculated with the FDKV model for rail pads in time domain are higher than those calculated with the ordinary Kelvin-Voigt (KV) model for rail pads. Additionally, the temperature- and frequency-dependent dynamic properties of the tested rail pads would alter the vertical vibration acceleration levels (VALs) of the car body and bogie in 1/3 octave frequencies above 31.5 Hz, especially enlarge the vertical VALs of the wheel set and rail in 1/3 octave frequencies of 31.5-100 Hz and above 315 Hz, which are the dominant frequencies of ground vibration acceleration and rolling noise (or bridge noise) caused by high-speed railways respectively. Since the fractional derivative value of the adopted rubber primary suspension, unlike the tested rail pad, is very close to 1, its frequency-dependent dynamic performance has little effect on high-speed vehicle-track coupled vibration responses.

High-temperature Strain Sensor and Mounting Development

NASA Technical Reports Server (NTRS)

Williams, W. Dan; Lei, Jih-Fen; Reardon, Lawrence F.; Krake, Keith; Lemcoe, M. M.; Holmes, Harlan K.; Moore, Thomas C., Sr.

1996-01-01

This report describes Government Work Package Task 29 (GWP29), whose purpose was to develop advanced strain gage technology in support of the National Aerospace Plane (NASP) Program. The focus was on advanced resistance strain gages with a temperature range from room temperature to 2000 F (1095 C) and on methods for reliably attaching these gages to the various materials anticipated for use in the NASP program. Because the NASP program required first-cycle data, the installed gages were not prestabilized or heat treated on the test coupons before first-cycle data were recorded. NASA Lewis Research Center, the lead center for GWP29, continued its development of the palladium-chromium gage; NASA Langley Research Center investigated a new concept gage using Kanthal A1; and the NASA Dryden Flight Research Center chose the well-known BCL-3 iron-chromium-aluminum gage. Each center then tested all three gages. The parameters investigated were apparent strain, drift strain, and gage factor as a function of temperature, plus gage size and survival rate over the test period. Although a significant effort was made to minimize the differences in test equipment between the three test sites (e.g., the same hardware and software were used for final data processing), the center employed different data acquisition systems and furnace configurations so that some inherent differences may be evident in the final results.

Effect of cold and hot ambient temperatures on plasma progesterone concentrations in ewes with intact and denervated ovaries containing experimentally maintained corpora lutea.

PubMed

Wheeler, A G; Blackshaw, A W

1986-11-01

Twenty ewes in which maintained corpora lutea had been established were subject to 1 of 3 treatments: denervation of the ovaries by freezing, denervation of the ovaries using the chemical 6-hydroxydopamine, or control. The animals were exposed sequentially to normal (24.5 degrees C), cold (10.7 degrees C), normal (23.8 degrees C), hot (39.4 degrees C) and normal (24.6 degrees C) temperatures, each for 1 week. On the final 3 days of exposure rectal temperatures and heart rates were measured, and on the final day the body weights, respiratory rates, and blood glucose concentrations were measured and a series of 5 blood samples was collected from each ewe for determination of the progesterone concentrations. The progesterone concentration was greatest during the hot period in 8 of the 12 animals, particularly in the ewes with denervated ovaries (6 of the 7 animals). This suggests that high ambient temperatures increase progesterone concentrations non-specifically, and that denervated ovaries are more sensitive to the circulating catecholamines that presumably mediate this effect. The progesterone concentrations were lower (P less than 0.001) in the groups with freezing or chemically denervated ovaries (2.86 and 2.73 ng/ml respectively) than in the control group (3.38 ng/ml), suggesting that the ovarian innervation plays a physiological role in regulating progesterone secretion.

Large scale crystallization of protein pharmaceuticals in microgravity via temperature change

NASA Technical Reports Server (NTRS)

Long, Marianna M.

1992-01-01

The major objective of this research effort is the temperature driven growth of protein crystals in large batches in the microgravity environment of space. Pharmaceutical houses are developing protein products for patient care, for example, human insulin, human growth hormone, interferons, and tissue plasminogen activator or TPA, the clot buster for heart attack victims. Except for insulin, these are very high value products; they are extremely potent in small quantities and have a great value per gram of material. It is feasible that microgravity crystallization can be a cost recoverable, economically sound final processing step in their manufacture. Large scale protein crystal growth in microgravity has significant advantages from the basic science and the applied science standpoints. Crystal growth can proceed unhindered due to lack of surface effects. Dynamic control is possible and relatively easy. The method has the potential to yield large quantities of pure crystalline product. Crystallization is a time honored procedure for purifying organic materials and microgravity crystallization could be the final step to remove trace impurities from high value protein pharmaceuticals. In addition, microgravity grown crystals could be the final formulation for those medicines that need to be administered in a timed release fashion. Long lasting insulin, insulin lente, is such a product. Also crystalline protein pharmaceuticals are more stable for long-term storage. Temperature, as the initiation step, has certain advantages. Again, dynamic control of the crystallization process is possible and easy. A temperature step is non-invasive and is the most subtle way to control protein solubility and therefore crystallization. Seeding is not necessary. Changes in protein and precipitant concentrations and pH are not necessary. Finally, this method represents a new way to crystallize proteins in space that takes advantage of the unique microgravity environment. The results from two flights showed that the hardware performed perfectly, many crystals were produced, and they were much larger than their ground grown controls. Morphometric analysis was done on over 4,000 crystals to establish crystal size, size distribution, and relative size. Space grown crystals were remarkably larger than their earth grown counterparts and crystal size was a function of PCF volume. That size distribution for the space grown crystals was a function of PCF volume may indicate that ultimate size was a function of temperature gradient. Since the insulin protein concentration was very low, 0.4 mg/ml, the size distribution could also be following the total amount of protein in each of the PCF's. X-ray analysis showed that the bigger space grown insulin crystals diffracted to higher resolution than their ground grown controls. When the data were normalized for size, they still indicated that the space crystals were better than the ground crystals.

Studies on in situ magnetic alignment of bonded anisotropic Nd-Fe-B alloy powders

DOE PAGES

Nlebedim, I. C.; Ucar, Huseyin; Hatter, Christine B.; ...

2016-08-30

We presented some considerations for achieving high degree of alignment in polymer bonded permanent magnets via the results of a study on in situ magnetic alignment of anisotropic Nd-Fe-B magnet powders. Contributions from effect of the alignment temperature, alignment magnetic field and the properties of the polymer on the hard magnetic properties of the bonded magnet were considered. Moreover, the thermo-rheological properties of the polymer and the response of the magnet powders to the applied magnetic field indicate that hard magnetic properties were optimized at an alignment temperature just above the melting temperature of the EVA co-polymer. This agrees withmore » an observed correlation between the change in magnetization due to improved magnetic alignment of the anisotropic powders and the change in viscosity of the binder. Finally, manufacturing cost can be minimized by identifying optimum alignment temperatures and magnetic field strengths.« less

Large spin accumulation and crystallographic dependence of spin transport in single crystal gallium nitride nanowires

PubMed Central

Park, Tae-Eon; Park, Youn Ho; Lee, Jong-Min; Kim, Sung Wook; Park, Hee Gyum; Min, Byoung-Chul; Kim, Hyung-jun; Koo, Hyun Cheol; Choi, Heon-Jin; Han, Suk Hee; Johnson, Mark; Chang, Joonyeon

2017-01-01

Semiconductor spintronics is an alternative to conventional electronics that offers devices with high performance, low power and multiple functionality. Although a large number of devices with mesoscopic dimensions have been successfully demonstrated at low temperatures for decades, room-temperature operation still needs to go further. Here we study spin injection in single-crystal gallium nitride nanowires and report robust spin accumulation at room temperature with enhanced spin injection polarization of 9%. A large Overhauser coupling between the electron spin accumulation and the lattice nuclei is observed. Finally, our single-crystal gallium nitride samples have a trigonal cross-section defined by the (001), () and () planes. Using the Hanle effect, we show that the spin accumulation is significantly different for injection across the (001) and () (or ()) planes. This provides a technique for increasing room temperature spin injection in mesoscopic systems. PMID:28569767

Al Speciation in Silicate Melts: AlV a new Network Former?

NASA Astrophysics Data System (ADS)

Neuville, D. R.; Florian, P.; de Ligny, D.; Montouillout, V.; Massiot, D.

2009-05-01

The first human glasses were made 3500 BC. It was essentially sodo-lime silicate glass. To improve the chemical resistance, the thermal properties and increase the viscosity it is interesting to add aluminum in these silicates. But what is the speciation of the aluminum and how it varies according to the chemical composition and to the temperature? The aluminum appears essentially in four or five fold coordination in glasses and melts melted. The proportion of [5]Al varies according to the alkaline or to the earth-alkaline content and to the temperature. We shall present in a first part the influence of the network-modifier on the proportion of [5]Al and then we shall present some new results of absorption of high-temperature using NMR and XANES spectroscopy at the Al K-edge. Finally, from glass transition temperature measurements we propose to explain that [5]Al can be a new network former.

Predicted exhaust emissions from a methanol and jet fueled gas turbine combustor

NASA Technical Reports Server (NTRS)

Adelman, H. G.; Browning, L. H.; Pefley, R. K.

1975-01-01

A computer model of a gas turbine combustor has been used to predict the kinetic combustion and pollutant formation processes for methanol and simulated jet fuel. Use of the kinetic reaction mechanisms has also allowed a study of ignition delay and flammability limit of these two fuels. The NOX emissions for methanol were predicted to be from 69 to 92% lower than those for jet fuel at the same equivalence ratio which is in agreement with experimentally observed results. The high heat of vaporization of methanol lowers both the combustor inlet mixture temperatures and the final combustion temperatures. The lower combustion temperatures lead to low NOX emissions while the lower inlet mixture temperatures increase methanol's ignition delay. This increase in ignition delay dictates the lean flammability limit of methanol to be 0.8, while jet fuel is shown to combust at 0.4.

Surface passivation of p-type Ge substrate with high-quality GeN{sub x} layer formed by electron-cyclotron-resonance plasma nitridation at low temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fukuda, Yukio; Otani, Yohei; Okamoto, Hiroshi

2011-09-26

We have investigated the effects of the formation temperature and postmetallization annealing (PMA) on the interface properties of GeN{sub x}/p-Ge fabricated by the plasma nitridation of Ge substrates using an electron-cyclotron-resonance-generated nitrogen plasma. The nitridation temperature is found to be a critical parameter in improving the finally obtained GeN{sub x}/Ge interface properties. The GeN{sub x}/Ge formed at room temperature and treated by PMA at 400 deg. C exhibits the best interface properties with an interface trap density of 1 x 10{sup 11 }cm{sup -2 }eV{sup -1}. The GeN{sub x}/Ge interface is unpinned and the Fermi level at the Ge surfacemore » can move from the valence band edge to the conduction band edge.« less

Ambient Dried Aerogels

NASA Technical Reports Server (NTRS)

Jones, Steven M.; Paik, Jong-Ah

2013-01-01

A method has been developed for creating aerogel using normal pressure and ambient temperatures. All spacecraft, satellites, and landers require the use of thermal insulation due to the extreme environments encountered in space and on extraterrestrial bodies. Ambient dried aerogels introduce the possibility of using aerogel as thermal insulation in a wide variety of instances where supercritically dried aerogels cannot be used. More specifically, thermoelectric devices can use ambient dried aerogel, where the advantages are in situ production using the cast-in ability of an aerogel. Previously, aerogels required supercritical conditions (high temperature and high pressure) to be dried. Ambient dried aerogels can be dried at room temperature and pressure. This allows many materials, such as plastics and certain metal alloys that cannot survive supercritical conditions, to be directly immersed in liquid aerogel precursor and then encapsulated in the final, dried aerogel. Additionally, the metalized Mylar films that could not survive the previous methods of making aerogels can survive the ambient drying technique, thus making multilayer insulation (MLI) materials possible. This results in lighter insulation material as well. Because this innovation does not require high-temperature or high-pressure drying, ambient dried aerogels are much less expensive to produce. The equipment needed to conduct supercritical drying costs many tens of thousands of dollars, and has associated running expenses for power, pressurized gasses, and maintenance. The ambient drying process also expands the size of the pieces of aerogel that can be made because a high-temperature, high-pressure system typically has internal dimensions of up to 30 cm in diameter and 60 cm in height. In the case of this innovation, the only limitation on the size of the aerogels produced would be in the ability of the solvent in the wet gel to escape from the gel network.

High pressure/high temperature thermogravimetric apparatus. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calo, J.M.; Suuberg, E.M.

1999-12-01

The purpose of this instrumentation grant was to acquire a state-of-the-art, high pressure, high temperature thermogravimetric apparatus (HP/HT TGA) system for the study of the interactions between gases and carbonaceous solids for the purpose of solving problems related to coal utilization and applications of carbon materials. The instrument that we identified for this purpose was manufactured by DMT (Deutsche Montan Technologies)--Institute of Cokemaking and Coal Chemistry of Essen, Germany. Particular features of note include: Two reactors: a standard TGA reactor, capable of 1100 C at 100 bar; and a high temperature (HT) reactor, capable of operation at 1600 C andmore » 100 bar; A steam generator capable of generating steam to 100 bar; Flow controllers and gas mixing system for up to three reaction gases, plus a separate circuit for steam, and another for purge gas; and An automated software system for data acquisition and control. The HP/TP DMT-TGA apparatus was purchased in 1996 and installed and commissioned during the summer of 1996. The apparatus was located in Room 128 of the Prince Engineering Building at Brown University. A hydrogen alarm and vent system were added for safety considerations. The system has been interfaced to an Ametek quadruple mass spectrometer (MA 100), pumped by a Varian V250 turbomolecular pump, as provided for in the original proposed. With this capability, a number of gas phase species of interest can be monitored in a near-simultaneous fashion. The MS can be used in a few different modes. During high pressure, steady-state gasification experiments, it is used to sample, measure, and monitor the reactant/product gases. It can also be used to monitor gas phase species during nonisothermal temperature programmed reaction (TPR) or temperature programmed desorption (TPD) experiments.« less

ELECTRON-CAPTURE AND β-DECAY RATES FOR sd-SHELL NUCLEI IN STELLAR ENVIRONMENTS RELEVANT TO HIGH-DENSITY O–NE–MG CORES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suzuki, Toshio; Toki, Hiroshi; Nomoto, Ken’ichi, E-mail: suzuki@phys.chs.nihon-u.ac.jp

Electron-capture and β-decay rates for nuclear pairs in the sd-shell are evaluated at high densities and high temperatures relevant to the final evolution of electron-degenerate O–Ne–Mg cores of stars with initial masses of 8–10 M{sub ⊙}. Electron capture induces a rapid contraction of the electron-degenerate O–Ne–Mg core. The outcome of rapid contraction depends on the evolutionary changes in the central density and temperature, which are determined by the competing processes of contraction, cooling, and heating. The fate of the stars is determined by these competitions, whether they end up with electron-capture supernovae or Fe core-collapse supernovae. Since the competing processes aremore » induced by electron capture and β-decay, the accurate weak rates are crucially important. The rates are obtained for pairs with A = 20, 23, 24, 25, and 27 by shell-model calculations in the sd-shell with the USDB Hamiltonian. Effects of Coulomb corrections on the rates are evaluated. The rates for pairs with A = 23 and 25 are important for nuclear Urca processes that determine the cooling rate of the O–Ne–Mg core, while those for pairs with A = 20 and 24 are important for the core contraction and heat generation rates in the core. We provide these nuclear rates at stellar environments in tables with fine enough meshes at various densities and temperatures for studies of astrophysical processes sensitive to the rates. In particular, the accurate rate tables are crucially important for the final fates of not only O–Ne–Mg cores but also a wider range of stars, such as C–O cores of lower-mass stars.« less

Using solute and heat tracers for aquifer characterization in a strongly heterogeneous alluvial aquifer

NASA Astrophysics Data System (ADS)

Sarris, Theo S.; Close, Murray; Abraham, Phillip

2018-03-01

A test using Rhodamine WT and heat as tracers, conducted over a 78 day period in a strongly heterogeneous alluvial aquifer, was used to evaluate the utility of the combined observation dataset for aquifer characterization. A highly parameterized model was inverted, with concentration and temperature time-series as calibration targets. Groundwater heads recorded during the experiment were boundary dependent and were ignored during the inversion process. The inverted model produced a high resolution depiction of the hydraulic conductivity and porosity fields. Statistical properties of these fields are in very good agreement with estimates from previous studies at the site. Spatially distributed sensitivity analysis suggests that both solute and heat transport were most sensitive to the hydraulic conductivity and porosity fields and less sensitive to dispersivity and thermal distribution factor, with sensitivity to porosity greatly reducing outside the monitored area. The issues of model over-parameterization and non-uniqueness are addressed through identifiability analysis. Longitudinal dispersivity and thermal distribution factor are highly identifiable, however spatially distributed parameters are only identifiable near the injection point. Temperature related density effects became observable for both heat and solute, as the temperature anomaly increased above 12 degrees centigrade, and affected down gradient propagation. Finally we demonstrate that high frequency and spatially dense temperature data cannot inform a dual porosity model in the absence of frequent solute concentration measurements.

Microstructure–property relationships in a high-strength 51Ni–29Ti–20Hf shape memory alloy

DOE PAGES

Coughlin, D. R.; Casalena, L.; Yang, F.; ...

2015-09-18

NiTiHf alloys exhibit remarkable shape memory and pseudoelastic properties that are of fundamental interest to a growing number of industries. In this study, differential scanning calorimetry and isothermal compression tests have revealed that the 51Ni–29Ti–20Hf alloy has useful shape memory properties that include a wide range of transformation temperatures as well as highly stable pseudoelastic behavior. These properties are governed by short-term aging conditions, which may be tailored to control transformation temperatures while giving rise to exceptionally high austenite yield strengths which aid transformation stability. The yield strength of the austenite phase can reach 2.1 GPa by aging for 3hrsmore » at 500°C, while aging for 3hrs at 700°C produced an alloy with an austenite finish temperature (A f ) of 146°C. High-resolution scanning transmission electron microscopy has revealed a new precipitate phase, H-phase, under the homogenized and extruded condition and the aged 3 hrs at 500°C condition, but only the previously identified H-phase precipitate was observed after aging at temperatures of 600°C and 700°C for 3 hrs. Finally, dislocation analysis indicated that plastic deformation of the austenite phase occurred by <100> type slip, similar to that observed in binary NiTi.« less

Development of Plastic Substrate Technology for Active Matrix Liquid Crystal Displays Final Report CRADA No. TC-761-93

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carey, P.; Kamath, H.

Raychem Corporation (RYC) and the Lawrence Livermore National Laboratory (LLNL) conducted a development program with the goal to make rugged, low-cost., high-resolution flat panel displays based on RYC's proprietary Nematic Curvilinear Aligned Phase (NCAP) liquid crystal and LLNL's patented processes for the formation and doping of polycrystalline silicon on low-temperature, flexible, plastic substrates.

Reactive Collisions and Final State Analysis in Hypersonic Flight Regime

DTIC Science & Technology

2016-09-13

Kelvin.[7] The gas-phase, surface reactions and energy transfer at these tempera- tures are essentially uncharacterized and the experimental methodologies...high temperatures (1000 to 20000 K) and compared with results from experimentally derived thermodynamics quantities from the NASA CEA (NASA Chemical...with a reproducing kernel Hilbert space (RKHS) method[13] combined with Legendre polynomials; (2) quasi classical trajectory (QCT) calculations to study