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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

In situ synchrotron diffraction of pressure-induced phase transition in DyPO 4 under variable hydrostaticity

In situ synchrotron x-ray diffraction was conducted on polycrystalline DyPO 4 to elucidate the details of the pressure-induced transition from the xenotime polymorph to the monazite polymorph. We used three different pressure-transmitting media (neon, a 16:3:1 methanol-ethanol-water mixture, and potassium chloride) to investigate the effect of hydrostaticity on the phase behavior. Specifically, our data clearly show a hydrostatic onset pressure of the xenotime-monazite transition of 9.1 GPa, considerably lower than the 15.3 GPa previously determined by Raman spectroscopy. Based on (quasi)hydrostatic data taken in a neon environment, third-order Birch-Murnaghan equation-of-state fits give a xenotime bulk modulus of 144 GPa and a monazite bulk modulus of 180 GPa (both with pressure derivatives of 4.0). Structural data and axial compressibilities show that DyPO 4 is sensitive to shear and has an anisotropic response to pressure. More highly deviatoric conditions cause the onset of the transition to shift to pressures at least as low as 7.0 GPa. We attribute early transition to shear-induced distortion of the PO4 tetrahedra. Finally, our characterization of the high-pressure behavior of DyPO 4 under variable hydrostaticity is critical for advancing rare earth orthophosphate fiber coating applications in ceramic matrix composites and may inform future tailoring of phase composition for controlled shear and pressure applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Piezothermal effect in a spinning gas

A spinning gas, heated adiabatically through axial compression, is known to exhibit a rotation-dependent heat capacity. However, as equilibrium is approached, an effect is identified here wherein the temperature does not grow homogeneously in the radial direction, but develops a temperature differential with the hottest region on axis, at the maximum of the centrifugal potential energy. This phenomenon, which we call a piezothermal effect , is shown to grow bilinearly with the compression rate and the amplitude of the potential. As a result, numerical simulations confirm a simple model of this effect, which can be generalized to other forms of potential energy and methods of heating.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Structural inheritance and difference between Ti 2 AlC, Ti 3 AlC 2 and Ti 5 Al 2 C 3 under pressure from first principles

The structural inheritance and difference between Ti 2 AlC, Ti 3 AlC 2 and Ti 5 Al 2 C 3 under pressure from first principles are studied. The results indicate that the lattice parameter a are almost the same within Ti 2 AlC, Ti 3 AlC 2 and Ti 5 Al 2 C 3 , and the value of c in Ti 5 Al 2 C 3 is the sum of Ti 2 AlC and Ti 3 AlC 2 which is revealed by the covalently bonded chain in the electron density difference: Al–Ti–C–Ti–Al for Ti 2 AlC, Al–Ti 2 –C–Ti 1 –C–Ti 2 –Al for Ti 3 AlC 2 and Al–Ti 3 –C 2 –Ti 3 –Al–Ti 2 –C 1 –Ti 1 –C 1 –Ti 2 –Al for Ti 5 Al 2 C 3 . The calculated axial compressibilities, volumetric shrinkage, elastic constant c 11 , c 33 /c 11 ratio, bulk modulus, shear modulus, and Young’s modulus of Ti 5 Al 2 C 3 are within the range of the end members (Ti 2 AlC and Ti 3 AlC 2 ) in a wide pressure range of 0–100 GPa. Only Ti 2 AlC is isotropic crystal at about 50 GPa within the Ti–Al–C compounds. All of the Ti 3 d density of states curves of the three compounds move from lower energy to higher energy level with pressure increasing. The similarities of respective bond length, bond overlap population (Ti–C, Ti–Al and Ti–Ti), atom Mulliken charges under pressure as well as the electron density difference for the three compounds are discovered. Among the Ti–Al–C ternary compounds, Ti–Ti bond behaves least compressibility, whereas the Ti–Al bond is softer than that of Ti–C bonds, which can also been confirmed by the density of states and electron density difference. Bond overlap populations of Ti–Ti, Ti–C and Ti–Al indicate that the ionicity interaction becomes more and more stronger in the three structures as the pressure increasing. Lastly, Mulliken charges of Ti 1 , Ti 2 , Ti 3 , C and Al are 0.65, 0.42, 0.39, –0.73, –0.04 at 0 GPa, respectively, which are consistent with the Pauling scale.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Compressional behavior and spin state of δ-(Al,Fe)OOH at high pressures

Hydrogen transport from the surface to the deep interior and distribution in the mantle are important in the evolution and dynamics of the Earth. An aluminum oxy-hydroxide, δ-AlOOH, might influence hydrogen transport in the deep mantle because of its high stability extending to lower mantle conditions. The compressional behavior and spin states of δ-(Al,Fe 3+ )OOH phases were investigated with synchrotron X-ray diffraction and Mössbauer spectroscopy under high pressure and room temperature. Pressure-volume (P-V) profiles of the δ-(Al 0.908(9) 57 Fe 0.045(1) )OOH 1.14(3) [Fe/(Al+Fe) = 0.047(10), δ-Fe5] and the δ-(Al 0.832(5) 57 Fe 0.117(1) )OOH 1.15(3) [Fe/(Al+Fe) = 0.123(2), δ-Fe12] show that these hydrous phases undergo two distinct structural transitions involving changes in hydrogen bonding environments and a high- to low-spin crossover in Fe 3+ . A change of axial compressibility accompanied by a transition from an ordered ( P 2 1 nm ) to disordered hydrogen bond ( Pnnm ) occurs near 10 GPa for both δ-Fe5 and δ-Fe12 samples. Through this transition, the crystallographic a and b axes become stiffer, whereas the c axis does not show such a change, as observed in pure δ-AlOOH. A volume collapse due to a transition from high- to low-spin states in the Fe 3+ ions is complete below 32–40 GPa in δ-Fe5 and δ-Fe12, which i ~10 GPa lower than that reported for pure ε-FeOOH. Evaluation of the Mössbauer spectra of δ-(Al 0.824(10) 57 Fe 0.126(4) )OOH 1.15(4) [Fe/(Al+Fe) = 0.133(3), δ-Fe13] also indicate a spin transition between 32–45 GPa. Phases in the δ-(Al,Fe)OOH solid solution with similar iron concentrations as those studied here could cause an anomalously high ρ/ν Φ ratio (bulk sound velocity, defined as √K/ρ at depths corresponding to the spin crossover region (~900 to ~1000 km depth), whereas outside the spin crossover region a low ρ/ν Φ anomaly would be expected. Here, these results suggest that the δ-(Al,Fe)OOH solid solution may play an important role in understanding the heterogeneous structure of the deep Earth.

58 GEOSCIENCES↗
DOE OSTI2021

Deformation and strength of mantle relevant garnets: Implications for the subduction of basaltic-rich crust

Garnet is an important mineral phase in the upper mantle as it is both a key component in bulk mantle rocks, and a primary phase at high pressure within subducted basalt. In this work, we focus on the strength of garnet and the texture that develops within garnet during accommodation of differential deformational strain. We use X-ray diffraction in a radial geometry to analyze texture development in situ in three garnet compositions under pressure at 300 K: a natural garnet (Prp 60 Alm 37 ) to 30 GPa, and two synthetic majorite-bearing compositions (Prp 59 Maj 41 and Prp 42 Maj 58 ) to 44 GPa. All three garnets develop a modest (100) texture at elevated pressure under axial compression. Elasto-viscoplastic self-consistent (EVPSC) modeling suggests that two slip systems are active in the three garnet compositions at all pressures studied: {110}<$1\bar{1}1$> and {001}<110>. We determine a flow strength of ~5 GPa at pressures between 10 to 15 GPa for all three garnets; these values are higher than previously reported yield strengths measured on natural and majoritic garnets. Strengths calculated using the experimental lattice strain differ from the strength generated from those calculated using EVPSC. Prp 67 Alm 33 , Prp 59 Maj 41 , and Prp 42 Maj 58 are of comparable strength to each other at room temperature, which indicates that majorite substitution does not greatly affect the strength of garnets. Additionally, all three garnets are of similar strength as lower mantle phases such as bridgmanite and ferropericlase, suggesting that garnet may not be notably stronger than the surrounding lower mantle/deep upper mantle phases at the base of the upper mantle.

58 GEOSCIENCES↗
DOE OSTI2018

Deformation and Fracture in Complex-Shaped Energetic Particles

A new technical basis on the mechanics of energetic materials at the individual particle scale has been developed. Despite these particles being in most of our Sandia non-nuclear explosive components, we have historically lacked any understanding of particle behavior. Through the novel application of nanoidentation methods to single crystal films and single particles of energetic materials with complex shapes, discovery data has been collected elucidating phenomena of particle strength, elastic and plastic deformation, and fracture. This work specifically developed the experimental techniques and analysis methodologies to distill data into relationships suitable for future integration into particle level simulations of particle reassembly. This project utilized experimental facilities at CINT and the Explosive Components Facility to perform ex-situ and in-situ nanoidentation experiments with simultaneous scanning electron microscope (SEM) imaging. Data collected by an applied axial compressive load in either force-control or displacement-control was well represented by Hertzian contact theory for linear elastic materials. Particle fracture phenomenology was effectively modeled by an empirical damage model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Mechanical Characterization of Loblolly Pine

Biorefineries are faced with various material flow challenges during feeding and handling, due to inherent variability and inhomogeneity of biomass feedstocks. This impacts the efficiency of refinery processes and unit operations. Proper characterization of bulk properties allows for optimal process design and reduction of overall costs. This work is aimed at evaluating the physical and mechanical properties that impact bulk flow of loblolly pine. Cyclic axial compression tests are performed to elucidate consolidation behavior under different stress conditions. The results are then used to develop correlations between material parameters (particle size, tissue type, moisture content) and Elastic Modulus of bulk samples.

09 BIOMASS FUELS↗
DOE OSTI2022

Ultrasonic rivet joining of dissimilar materials

A method for joining dissimilar materials is provided. The method includes a solid-state joining process in which a rivet is plunged into a predrilled hole in a top workpiece. When the rivet contacts the bottom workpiece, ultrasonic vibration by oscillatory motion of a sonotrode, such as horizontal, vertical, or rotational motion, creates frictional heat at the interface between the rivet and the lower workpiece. With the aid of frictional heat and axial compression, metallurgical bonding is achieved at the interface between the rivet and the bottom sheet, while being below the melting temperature of the bottom workpiece. The sonotrode is retracted while the rivet remains.

Lim, Yong Chae↗
DOE OSTI2016

In-pile investigation results of re-sintering for uranium dioxide fuel with large grain size at temperature 650-700 C

When determining the radiation creep of nuclear fuel, apart from deformation caused by axial compressive stress, there is a shrinkage process induced by radiation re-sintering, which may contribute in total value of in-pile deformation. The aim of this work was to study re-sintering for large grain size fuel of uranium dioxide. WWER fuel pellets with grain size greater than 25 μm have been piled up in a special device and irradiated in the channel number 7 of the RBT-6 pool-type reactor. The height of the fuel column was continuously measured during the irradiation. The average temperature value in the fuel column center was 682 Celsius degrees and the total time of irradiation reached 1800 hours which corresponds to a specific burnup of 2.5 MWd/KgU, taking into account fission density and initial fuel stoichiometry. The results show that re-sintering throughout the height equals to 0.08% which correlates well with thermal re-sintering test and does not have an impact on the steady-state creep rate.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Wire rivet

A rivet assembly for securing a wire in electrical communication with a substrate having a hollow cylindrical body with a first opening at a proximal end and a second opening at a distal end. The rivet assembly further includes a wire with a portion in electrical communication with the cylindrical body. The rivet assembly yet further includes a compression mechanism configured for use selectively compressing the cylindrical body along an axial direction. Compression of the cylindrical body can cause diametric expansion of an outer diameter of the cylindrical body to retain the cylindrical body within a substrate. The rivet assembly additionally includes wire retention structure configured for holding the wire in electrical contact with the compressed cylindrical body.

Briggs, Timothy↗
DOE OSTI2025

Hybrid Simulations of FRC Merging and Compression

An improved understanding of field-reversed configuration (FRC) merging and stability in high acceleration and compression magnetic fields is needed to speed up the development of the pulsed fusion concept developed at Helion Energy. All previous theoretical and simulation work on FRC merging and compression was performed using two-dimensional (2D) magnetohydrodynamic (MHD) models. The results of novel 2D hybrid simulations (fluid electrons and full-orbit kinetic ions) of FRC merging and compression are presented. Results of kinetic and MHD simulations, computed using the HYM code, are compared and analyzed. In cases without axial magnetic compression, both the MHD and hybrid simulations show a high sensitivity to the initial parameters (i.e. FRC separation, velocity, normalized separatrix radius, and plasma viscosity), showing that FRCs with large elongation and separatrix radius either do not merge or merge partially, forming a doublet FRC. In conclusion, application of a mirror coil field at the FRC ends with increasing strength is shown to lead to fast and complete merging of the FRCs in MHD and kinetic simulations.

FRC↗
DOE OSTI2020

Z-pinch fusion

The Z-pinch configuration offers the promise of a compact fusion device owing to its simple geometry, unity beta, and absence of external magnetic field coils. Increasing the axial current compresses the plasma, resulting in a rapid rise of the fusion reaction rate. Historically, the Z pinch has been plagued by fast growing instabilities that limit plasma lifetimes. Recent progress has resulted from investigating approaches that provide stability. One approach exploits sheared-flow stabilization to produce an equilibrium Z pinch, which sustains the compressed plasma state for durations much longer than other plasma timescales. Recent experimental and simulation results encourage pursuit of the stabilized Z pinch to explore its fusion performance limits.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Axial magnetic flux amplification in Hall-magnetohydrodynamic simulations of externally magnetized z-pinches

It is shown that externally magnetized gas-puff z-pinches under compression can exhibit robust axial flux amplification under suitable axial boundary conditions. This effect relies upon the Hall term in the generalized Ohm's law to generate azimuthal currents in the presence of a driving axial electric field. Under dynamic compression, the total current tends to flow in a mostly force-free boundary layer, separating the predominately azimuthal field outside the layer and the predominately axial field inside the layer. The effect only appears to occur if the axial boundaries allow for outflow or absorption of electromagnetic energy. The effect is mitigated by imposing either periodic or conducting axial boundary conditions. A semi-analytic equilibrium analysis agrees with steady-state solutions of the time-dependent electron-magnetohydrodynamic equations and provides an estimate of the scaling of the boundary layer as well as suggesting a scenario for the formation of the boundary layer. When operative, the effect can significantly impede plasma compression due to the increase in axial flux that diffuses into the pre-compressed plasma or through the presence of conductors that inhibit movement of the generated axial flux. Several facilities have noted unusual implosion behavior in z-pinch experiments with applied axial fields that does not appear to be explainable within the standard magnetohydrodynamic model. In conclusion, it is suggested that these experiments can be explained by the axial flux amplification and concentration effect

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Applied axial magnetic field effects on laboratory plasma jets: Density hollowing, field compression, and azimuthal rotation

We experimentally measure the effects of an applied axial magnetic field (B z ) on laboratory plasma jets and compare experimental results with numerical simulations using an extended magnetohydrodynamics code. A 1 MA peak current, 100 ns rise time pulse power machine is used to generate the plasma jet. On application of the axial field, we observe on-axis density hollowing and a conical formation of the jet using interferometry, compression of the applied B z using magnetic B-dot probes, and azimuthal rotation of the jet using Thomson scattering. Experimentally, we find densities ≤ 5×10 17 cm -3 on-axis relative to jet densities of ≥ 3×10 18 cm -3 . For aluminum jets, 6.5 ± 0.5 mm above the foil, we find on-axis compression of the applied 1.0 ± 0.1 T B z to a total 2.4 ± 0.3 T, while simulations predict a peak compression to a total 3.4 T at the same location. On the aluminum jet boundary, we find ion azimuthal rotation velocities of 15-20 km/s, while simulations predict 14 km/s at the density peak. We discuss possible sources of discrepancy between the experiments and simulations, including: surface plasma on B-dot probes, optical fiber spatial resolution, simulation density floors, and 2D vs. 3D simulation effects. Lastly, this quantitative comparison between experiments and numerical simulations helps elucidate the underlying physics that determine the plasma dynamics of magnetized plasma jets.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Investigating the Electromechanical Sensitivity of Carbon-Nanotube-Coated Microfibers

The piezoresistance of carbon nanotube (CNT)-coated microfibers is examined using diametric compression. Diverse CNT forest morphologies were studied by changing the CNT length, diameter, and areal density via synthesis time and fiber surface treatment prior to CNT synthesis. Large-diameter (30–60 nm) and relatively low-density CNTs were synthesized on as-received glass fibers. Small-diameter (5–30 nm) and-high density CNTs were synthesized on glass fibers coated with 10 nm of alumina. The CNT length was controlled by adjusting synthesis time. Electromechanical compression was performed by measuring the electrical resistance in the axial direction during diametric compression. Gauge factors exceeding three were measured for small-diameter (<25 μm) coated fibers, corresponding to as much as 35% resistance change per micrometer of compression. The gauge factor for high-density, small-diameter CNT forests was generally greater than those for low-density, large-diameter forests. A finite element simulation shows that the piezoresistive response originates from both the contact resistance and intrinsic resistance of the forest itself. The change in contact and intrinsic resistance are balanced for relatively short CNT forests, while the response is dominated by CNT electrode contact resistance for taller CNT forests. These results are expected to guide the design of piezoresistive flow and tactile sensors.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Fuel cladding post-quench LOCA embrittlement: mechanical test relevance

During a loss-of-coolant-accident (LOCA), the fuel cladding is submitted to a high temperature increase in a steam environment, along with an internal pressure increase which would eventually lead to ballooning and burst of the cladding. Steam could then penetrate through the burst opening and lead to inner surface oxidation and secondary-hydriding of the cladding. Post-quench cladding rupture can then occur either in two-sided oxidized area with wall thinning due to ballooning, or in single-sided oxidized area with large hydrogen content. Common tests involved in the evaluation of the post-quench ductility are Ring Compression Tests (RCT), Expansion Due to Compression Test (EDC) or Axial Tensile Tests (AT). Questions arise about these mechanical tests, as for instance, the influence on sample failure of the oxide layer thickness partitioning between inner and outer diameter. A systematic study was carried out to compare several mechanical tests on both single-sided and two-sided Zircaloy-4 oxidized samples. Five different mechanical tests were compared, including RCT: C-shaped ring Compression Test (CCT), Axial Tensile test (AT), Ring Tensile Test with well-defined machined gage section (RTT) and plain Ring Tensile Test (pRTT). All samples were taken from cladding tubes which had been oxidized in steam at 1200 Celsius degrees and then water-quenched. Mechanical tests were performed at room temperature and two to three samples were tested for each oxidation conditions and for every sample geometry to assess the reproducibility. Metallographic examinations were carried out to measure the ZrO{sub 2} and αZr(O) layer thicknesses and the ex-β/α(O) phase fraction. Mean hydrogen content measurements were also performed systematically on each sample. Results indicate that the different mechanical tests have not the same sensitivity to the oxide layer partitioning: RTT and pRTT load at failure seems to depend mainly on the cumulated oxide layer thickness rather than on its partitioning, whereas this parameter has an impact on CCT and AT test results. For all tensile tests, stresses at failure were derived from load-displacement curves. The failure of brittle samples was assumed to be governed by linear elastic fracture mechanics. Using conventional stress intensity factor solution, a value of the material fracture toughness controlling the sample failure was determined from experimental results and discussed. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗