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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Revisited reaction-diffusion model of thermal desorption spectroscopy experiments on hydrogen retention in material

Desorption phase of thermal desorption spectroscopy (TDS) experiments performed on tungsten samples exposed to flux of hydrogen isotopes in fusion relevant conditions is analyzed using a reaction-diffusion model describing hydrogen retention in material bulk. Two regimes of hydrogen desorption are identified depending on whether hydrogen trapping rate is faster than hydrogen diffusion rate in material during TDS experiments. In both regimes, a majority of hydrogen released from material defects is immediately outgassed instead of diffusing deeply in material bulk when the evolution of hydrogen concentration in material is quasi-static, which is the case during TDS experiments performed with tungsten samples exposed to flux of hydrogen isotopes in fusion related conditions. In this context, analytical expressions of the hydrogen outgassing flux as a function of the material temperature are obtained with sufficient accuracy to describe main features of thermal desorption spectra (TDSP). These expressions are then used to highlight how characteristic temperatures of TDSP depend on hydrogen retention parameters, such as trap concentration or activation energy of detrapping processes. The use of Arrhenius plots to characterize retention processes is then revisited when hydrogen trapping takes place during TDS experiments. Retention processes are also characterized using the shape of desorption peaks in TDSP, and it is shown that diffusion of hydrogen in material during TDS experiment can induce long desorption tails visible aside desorption peaks at high temperature in TDSP. These desorption tails can be used to estimate activation energy of diffusion of hydrogen in material.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Formation of Ge nanoparticles in SiO{sub x}N{sub y} by ion implantation and thermal annealing

Germanium nanoparticles embedded within dielectric matrices hold much promise for applications in optoelectronic and electronic devices. Here we investigate the formation of Ge nanoparticles in amorphous SiO{sub 1.67}N{sub 0.14} as a function of implanted atom concentration and thermal annealing temperature. Using x-ray absorption spectroscopy and other complementary techniques, we show Ge nanoparticles exhibit significant finite-size effects such that the coordination number decreases and structural disorder increases as the nanoparticle size decreases. While the composition of SiO{sub 1.67}N{sub 0.14} is close to that of SiO{sub 2}, we demonstrate that the addition of this small fraction of N yields a much reduced nanoparticle size relative to those formed in SiO{sub 2} under comparable implantation and annealing conditions. We attribute this difference to an increase in an atomic density and a much reduced diffusivity of Ge in the oxynitride matrix. These results demonstrate the potential for tailoring Ge nanoparticle sizes and structural properties in the SiO{sub x}N{sub y} matrices by controlling the oxynitride stoichiometry.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Thermal phase diagram of acetamide-benzoic acid and benzoic acid-phthalimide binary systems for solar thermal applications

Thermal properties of Acetamide (AM) – Benzoic acid (BA) and Benzoic acid (BA) – Phthalimide (PM) binary eutectic systems are theoretically calculated using thermodynamic principles. We found that the binary systems of AM-BA at 67.6 : 32.4 molar ratio, BA-PM at 89.7 : 10.3 molar ratio form eutectic mixtures with melting temperatures ~ 54.5 °C and 114.3 °C respectively. Calculated latent heat of fusion for these eutectic mixtures are 191 kJ/kg and 146.5 kJ/kg respectively. These melting temperatures and heat of fusions of these eutectic mixtures make them suitable for thermal energy storage applications in solar water heating and solar cooking systems.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Joule heating induced thermomigration failure in un-powered microbumps due to thermal crosstalk in 2.5D IC technology

Thermal-crosstalk induced thermomigration failure in un-powered microbumps has been found in 2.5D integrated circuit (IC) circuit. In 2.5D IC, a Si interposer was used between a polymer substrate and a device chip which has transistors. The interposer has no transistors. If transistors are added to the interposer chip, it becomes 3D IC. In our test structure, there are two Si chips placed horizontally on a Si interposer. The vertical connections between the interposer and the Si chips are through microbumps. We powered one daisy chain of the microbumps under one Si chip; however, the un-powered microbumps in the neighboring chip are failed with big holes in the solder layer. We find that Joule heating from the powered microbumps is transferred horizontally to the bottom of the neighboring un-powered microbumps, and creates a large temperature gradient, in the order of 1000 °C/cm, through the un-powered microbumps in the neighboring chip, so the latter failed by thermomigration. In addition, we used synchrotron radiation tomography to compare three sets of microbumps in the test structure: microbumps under electromigration, microbumps under thermomigration, and microbumps under a constant temperature thermal annealing. The results show that the microbumps under thermomigration have the largest damage. Furthermore, simulation of temperature distribution in the test structure supports the finding of thermomigration.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Mechanical and Chemical Properties of Harvested Hypalon Cable Jacket Subjected to Accelerated Thermal Aging

For nuclear power plants (NPPs) that are considering second license renewal for their operation beyond 60 years, knowledge of long-term operation, condition monitoring, and viability for the reactor components including reactor pressure vessel, concrete structures, and cable systems is essential. Such knowledge will provide NPPs with a game plan to predict performance and to estimate costs that are associated with monitoring or replacement programs for the affected systems. For cable systems that encompass a wide variety of materials, manufacturers, and in-plant location, accelerated aging of harvested cable jacket and insulation can provide insight as to remaining useful life and methods for monitoring. Accelerated thermal aging in air at temperatures between 80°C and 120°C was carried out on a multi-conductor control rod cable that had been in-service for over 30 years and was made by Boston Insulated Wire with Hypalon cable jacket and ethylene-propylene rubber insulation. From elongation at break (EAB) measurements and supporting Arrhenius analysis of the jacket material, an activation energy of 97.84 kJ/mol was estimated and the time to degradation, as represented by 50% EAB at the expected maximum operating temperature of 45°C, was estimated as consistent with 80 years. These values were slightly below previous measurements and could either be attributed to in-service degradation or variations in material properties from a given manufacturer. In addition, results from indenter modulus measurements and Fourier transform infrared spectroscopy suggest possible markers that could be beneficial to monitor cable conditions.

cable aging, cable insulation, Hypalon, second lic↗
DOE OSTI2023

A fully coupled thermal–microstructural–mechanical finite element process model for directed energy deposition additive manufacturing of Ti–6Al–4V

A fully coupled thermal–microstructural–mechanical finite element modelling framework is developed to investigate the distortion and residual stresses during directed energy deposition (DED) of multi-phase Ti–6Al–4V alloy. The Johnson–Cook constitutive model is used to predict the yield strength of each phase as a function of strain, strain rate and temperature where the flow stress is calculated by a linear mixing rule based on the volumetric phase fractions. A thin-walled rectangular sample is chosen as the reference geometry and the results are compared with experimentally measured in situ thermal history and distortion data, where a reasonable agreement is achieved. The proposed modelling framework with physics-based material constitutive model provides useful information for a better understanding of process–microstructure–property relations in additive manufacturing by DED.

Tunay, Merve↗
DOE OSTI2019

PHENIX U.S.-Japan Collaboration Investigation of Thermal and Mechanical Properties of Thermal Neutron–Shielded Irradiated Tungsten

The United States and Japan have collaborated on fusion materials research in a series of agreements reaching back to 1981. The PHENIX collaboration is the latest U.S.-Japan project which spans 2013 to 2019 and has the goal of assessing technical feasibility of tungsten-based, helium-cooled plasma-facing component concepts for a demonstration fusion power reactor (DEMO). Task 2 within the PHENIX project is focused on evaluating the neutron irradiation effects in tungsten. For tungsten, the transmutation to Re and Os is at least as important to determining its properties after irradiation as the displacement damage, and the transmutation rate depends on the energy spectrum of the reactor. A large-scale, instrumented irradiation capsule with thermal neutron shielding to better mimic fusion conditions was irradiated in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. The tungsten specimens were irradiated in different temperature zones between 500°C and 1200°C to doses of ~0.2 to 0.7 displacements per atom. More than 20 varieties of pure tungsten and tungsten alloys were included in the irradiation, and they were evaluated in the 3025E hot-cell facility and at the Low Activation Materials Development and Analysis Laboratory. The elevated temperature tensile, fracture toughness, hardness, thermal conductivity, electrical resistivity, density, elemental composition, and microstructure properties of the irradiated materials are being collected. Furthermore, this paper overviews the experimental design, specimen matrix, and the initial results of postirradiation examinations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Halo-independent tests of dark matter direct detection signals: local DM density, LHC, and thermal freeze-out

From an assumed signal in a Dark Matter (DM) direct detection experiment a lower bound on the product of the DM-nucleon scattering cross section and the local DM density is derived, which is independent of the local DM velocity distribution. This can be combined with astrophysical determinations of the local DM density. Within a given particle physics model the bound also allows a robust comparison of a direct detection signal with limits from the LHC. Furthermore, the bound can be used to formulate a condition which has to be fulfilled if the particle responsible for the direct detection signal is a thermal relic, regardless of whether it constitutes all DM or only part of it. We illustrate the arguments by adopting a simplified DM model with a Z{sup ′} mediator and assuming a signal in a future xenon direct detection experiment.

43 PARTICLE ACCELERATORS↗
DOE OSTI2026

At Extreme Strain Rates, Pure Metals Thermally Harden while Alloys Thermally Soften

When materials are deformed at extreme strain rates, >10 6 s -1 , a counterintuitive mechanical response is seen where the strength and hardness of pure metals increases with increasing temperature. This anti-thermal hardening is due to dislocations meeting resistance to their motion from phonons in the crystal lattice. However, here, using optically-driven microballistic impact testing to measure dynamic strength and hardness, we show that when the composition is systematically varied away from high purity, the mechanical response of metals transitions from phonon drag of dislocations back to thermally activated pinning of dislocations, even at the highest strain rates. This boundary from “hotter-is-stronger” to “hotter-is-softer” is observed and mapped for nickel, titanium and gold. Furthermore, the ability to tune between deformation mechanisms with very different temperature dependencies speaks to new directions for alloy design in extreme conditions.

Ballistic transport↗
DOE OSTI2013

Crystallographic, electronic, thermal, and magnetic properties of single-crystal SrCo 2 As 2

In tetragonal SrCo 2 As 2 single crystals, inelastic neutron scattering measurements demonstrated that strong stripe-type antiferromagnetic (AFM) correlations occur at a temperature T = 5 K [W. Jayasekara et al., arXiv:1306.5174] that are the same as in the isostructural AFe 2 As 2 (A = Ca, Sr, Ba) parent compounds of high-T c superconductors. This surprising discovery suggests that SrCo 2 As 2 may also be a good parent compound for high-T c superconductivity. Here, structural and thermal expansion, electrical resistivity ρ, angle-resolved photoemission spectroscopy (ARPES), heat capacity C p , magnetic susceptibility χ, 75 As NMR and neutron diffraction measurements of SrCo 2 As 2 crystals are reported together with LDA band structure calculations that shed further light on this fascinating material. The c-axis thermal expansion coefficient α c is negative from 7 to 300 K, whereas α a is positive over this T range. The ρ(T) shows metallic character. The ARPES measurements and band theory confirm the metallic character and in addition show the presence of a flat band near the Fermi energy E F . The band calculations exhibit an extremely sharp peak in the density of states D(E F ) arising from a flat d x 2 -y 2 band. A comparison of the Sommerfeld coefficient of the electronic specific heat with χ(T → 0) suggests the presence of strong ferromagnetic itinerant spin correlations which on the basis of the Stoner criterion predicts that SrCo 2 As 2 should be an itinerant ferromagnet, in conflict with the magnetization data. The χ(T) does have a large magnitude, but also exhibits a broad maximum at 115 K suggestive of dynamic short-range AFM spin correlations, in agreement with the neutron scattering data. The measurements show no evidence for any type of phase transition between 1.3 and 300 K and we propose that metallic SrCo 2 As 2 has a gapless quantum spin-liquid ground state.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Thermal effects in dislocation theory. II. Shear banding

The thermodynamic dislocation theory presented in previous papers is used in this paper to describe shear-banding instabilities. Central ingredients of the theory are a thermodynamically defined effective configurational temperature and a formula for the plastic strain rate determined by thermally activated depinning of entangled dislocations. This plastic strain rate is extremely sensitive to variations of the stress and the ordinary temperature. As a result of this sensitivity, the system undergoes rapid shear banding instabilities when ordinary thermal relaxation is slow. Finally, it also undergoes rapid changes from elastic to plastic behaviors at yielding transitions.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Electron Bulk Acceleration and Thermalization at Earth’s Quasiperpendicular Bow Shock [Electron Acceleration and Thermalization at Earth's Quasi-Perpendicular Bow Shock]

Electron heating at Earth’s quasiperpendicular bow shock has been surmised to be due to the combined effects of a quasistatic electric potential and scattering through wave-particle interaction. Here we report the observation of electron distribution functions indicating a new electron heating process occurring at the leading edge of the shock front. Incident solar wind electrons are accelerated parallel to the magnetic field toward downstream, reaching an electron-ion relative drift speed exceeding the electron thermal speed. The bulk acceleration is associated with an electric field pulse embedded in a whistler-mode wave. The high electron-ion relative drift is relaxed primarily through a nonlinear current-driven instability. Here, the relaxed distributions contain a beam traveling toward the shock as a remnant of the accelerated electrons. Similar distribution functions prevail throughout the shock transition layer, suggesting that the observed acceleration and thermalization is essential to the cross-shock electron heating.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Modified Data Collection And Analysis Codes Of Using Tcm (thermal Conductivity Microscope) To Measure Thermal Conductivity And Diffusivity

The "data collection" basically involves setting up the thermal wave frequency, laser scan distance, and other parameters related to the experimental setup. The modification of this code is minor and the details of this code can be found in the earlier patent ("thermal conductivity microscope"). The "data analysis" instead, replaces the simplified analytical model by a more complete analytical model, and used a "thermoquadruple" method to solve the analytical model. The efficiency is orders of magnitude improved and the accuracy is also better. Meanwhile, the previous model can only handle a two-layer sample structure. The new, complete model can handle materials with multiple layers (any given number), which is necessary to handle post ion irradiated materials.

Hua, Zilong [Idaho National Laboratory (INL), Idah↗
DOE OSTI2010

OH species, U ions, and CO/CO 2 in thermally annealed metamict zircon (ZrSiO 4 )

Metamict zircon crystals have been thermally annealed between 500 and 1800 K and analyzed using infrared and optical spectroscopy in the spectral region of 1400–7000 cm -1 . Recrystallization and dehydroxylation via complex proton/OH diffusion, redistribution, and incorporations of additional hydrogen-related species within the crystal structure of zircon occur at temperatures above 700 K in partially metamict zircon and above 1200 K in heavily amorphized material. Thermally induced changes in O-H stretching spectra are different between E || c and E ⊥ c in weakly metamict zircon. The O-H stretching band near 3342 cm -1 (with E ⊥ c) in an untreated sample shifts to 3277 cm -1 at 1200 K, where the frequency of O-H stretching bands with E || c increases. Conversions of hydrogen-related species were observed and extra OH bands were found at temperatures between 1200 and 1600 K. A dramatic change of OH spectra was recorded between 1600 and 1800 K in partially metamict crystals, resulting in additional absorption features (near 3098 and 2998 cm -1 along E ⊥ c). U 4+ and U 5+ related spectra are also affected by high-temperature annealing. For highly metamict zircon, the U 4+ band near 4830 cm -1 shows an increase in intensity above 1200 K. Additional IR bands at 2146 and 2344 cm -1 appear in the spectra of metamict zircon annealed at high temperatures. Their frequencies are consistent with stretching vibrations of CO and CO 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2013

THE FREE GAS THERMAL TREATMENT IN MCATK: Sampling the Thermal Motion of the Target Nucleus (U)

The free gas thermal treatment for neutron scattering, as formulated for Monte Carlo by Coveyou et al., is implemented and tested in the MCATK software library. This treatment is necessary for two reasons: 1) to handle the kinematics of a neutron colliding with a target nucleus in thermal motion and 2) to accurately use ACE scattering data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗