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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Discrimination and quantification of Fe and Ni abundances in Genesis solar wind implanted collectors using X-ray standing wave fluorescence yield depth profiling with internal referencing

In this paper, X-ray standing wave fluorescence yield depth profiling was used to determine the solar wind implanted Fe and Ni fluences in a silicon-on-sapphire (SoS) Genesis collector (60326). An internal reference standardization method was developed based on fluorescence from Si and Al in the collector materials. Measured Fe fluence agreed well with that measured previously by us on a sapphire collector (50722) as well as SIMS results by Jurewicz et al. Measured Ni fluence was higher than expected by a factor of two; neither instrumental errors nor solar wind fractionation effects are considered significant perturbations to this value. Impurity Ni within the epitaxial Si layer, if present, could explain the high Ni fluences and therefore needs further investigation. As they stand, these results are consistent with minor temporally-variable Fe and Ni fractionation on the timescale of a year.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effective moisture penetration depth model for residential buildings: Sensitivity analysis and guidance on model inputs

Moisture buffering of building materials has a significant impact on the building's indoor humidity, and building energy simulations need to model this buffering to accurately predict the humidity. Researchers requiring a simple moisture-buffering approach typically rely on the effective-capacitance model, which has been shown to be a poor predictor of actual indoor humidity. This paper describes an alternative two-layer effective moisture penetration depth (EMPD) model and its inputs. While this model has been used previously, there is a need to understand the sensitivity of this model to uncertain inputs. In this paper, we use the moisture-adsorbent materials exposed to the interior air: drywall, wood, and carpet. We use a global sensitivity analysis to determine which inputs are most influential and how the model's prediction capability degrades due to uncertainty in these inputs. We then compare the model's humidity prediction with measured data from five houses, which shows that this model, and a set of simple inputs, can give reasonable prediction of the indoor humidity.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2017

Faulting of natural serpentinite: Implications for intermediate-depth seismicity

The seismic potential of serpentinites at high pressure was investigated via deformation experiments on cored natural serpentinite samples, during which micro-seismicity was monitored by recording Acoustic Emissions (AEs). Deformation was performed at pressures of 3–5 GPa, using a Deformation-DIA device, and over a wide range of temperatures, both within and outside antigorite's stability field. Below 400 °C, serpentinite deformation involves “silent” semi-brittle mechanisms, even in cases where strain localization is observed. At high temperature (i.e., above 600 °C), despite conditions propitious to dehydration embrittlement (i.e., fast strain rates and reaction kinetics), joint deformation and dehydration lead to ductile shear, without generation of AEs. Brittle behavior was observed in a narrow temperature window ca. 500 °C. In this latter case, AEs are consistently observed upon faulting and extremely sharp strain localization is observed in recovered samples. The resulting microstructures are consistent with the inverse ductile-to-brittle transition proposed by Proctor and Hirth (2016) in antigorite. This may therefore be a source of seismicity in subducting slabs at mantle pressures and temperatures from 500 to 600 °C. However, the acoustic signal observed here is orders of magnitude weaker than what is obtained at low PT conditions with brittle failure, consistently with low radiation efficiency of serpentinite faulting (Prieto et al., 2013) and suggests that other mechanisms are responsible for large intermediate-depth earthquakes. In fact, the present results are in line with a recent study (Ferrand et al., 2017), that suggests that intermediate earthquakes are likely induced by mechanical instabilities due to dehydration in partly hydrated peridotites.

58 GEOSCIENCES↗
DOE OSTI2018

Integrating quantitative defense-in-depth metrics into new reactor designs

Risk-informed, performance-based (RIPB) methods have progressed to the point where high-level guidance can be used to augment traditional, deterministic, nuclear safety design practices in areas important to nuclear reactor safety. This paper describes an approach for augmenting the traditional defense-in-depth (DID) qualitative approach with quantitative risk information from a plant-specific probabilistic risk assessment (PRA) in a way that is structured, can be applied on a consistent basis, and allows for clear acceptance criteria. Adding performance-based targets that should be achieved is expected to result in safer and more economical plant designs. Evaluations of DID can be conducted throughout the design process as well as in support of design certification and operating license applications to identify where defense protections could be enhanced or relaxed. Consistent with the United States Nuclear Regulatory Commission's policy statement encouraging greater use of PRA to improve safety decision making and regulatory efficiency, this scenario-based DID method can be used to evaluate changes and overall plant design as part of the normal design control process. Although the RIPB method presented in this paper was developed for application to advanced passive light water reactor designs, the metrics could be tailored to other reactor designs. This risk-informed approach to DID helps to ensure that public and worker risk insights are integrated into the design process holistically.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2021

Periodicity Analysis of Earthquake Occurrence and Hypocenter Depth Near Parkfield, California, 1994–2002 Versus 2006–2014

In central California, periodic earthquake occurrence suggests a relationship with annual hydrological, atmospheric, thermal, and tidal loadings. Here, in catalogs of declustered earthquakes within 100 km from Parkfield, CA, we study a semiannual periodicity for the monthly number of ≤7.2-km-deep earthquakes and the monthly median hypocenter depth over 1994–2002 and 2006–2014. Peak-trough months in fitted periodic components differ between time spans and event populations. Deeper earthquakes present no semiannual and a weak annual periodicity. Although modeled pore pressure shows a Spring peak, when added to the elastic Coulomb stress from surface hydrospheric loads, it fails to predict a 6-month periodicity for 2006–2014. In 1994–2002, the pore-pressure amplitude appears to be of same order as the elastic stress and may have had a stronger effect. In 2006–2014, we did not find load model parameters explaining the observed pattern or apparent changes following the 2003 San Simeon and 2004 Parkfield earthquakes.

58 GEOSCIENCES↗
DOE OSTI2020

Nanoscale depth and lithiation dependence of V 2 O 5 band structure by cathodoluminescence spectroscopy

Vanadium pentoxide (V 2 O 5 ) is a very well-known cathode material that has attracted considerable interest for its potential use in solid-state lithium-ion batteries. We pioneer the use of depth-resolved cathodoluminescence spectroscopy (DRCLS) to monitor the changes in the electronic structure of lithiated V 2 O 5 from the free surface to the thin film bulk several hundred nm below as a function of lithiation. DRCLS measurements of V 2 O 5 interband transitions are in excellent agreement with density functional theory (DFT) calculations. The direct measure of V 2 O 5 's electronic band structure as a function of lithiation level provided by DRCLS can help inform solid-state battery designs to further withstand degradation and increase efficiency. In particular, these unique electrode measurements may reveal physical mechanisms of lithiation that change V 2 O 5 irreversibly, as well as methods to mitigate them in solid-state batteries.

25 ENERGY STORAGE↗
DOE OSTI2026

Effect of externally applied pressure on rechargeable alkaline zinc batteries at limited depth of discharge

Rechargeable alkaline zinc batteries (AZBs) are being actively researched for grid-scale energy storage due to their safety, low toxicity, abundance, low cost, and ease-of-production. However, numerous studies on alkaline Zn–MnO 2 batteries have shown that issues such as heterogeneous Zn deposition, passivation, dendrite formation, hydrogen evolution, and formation of chemically irreversible byproducts on the electrode surfaces still limit their rechargeability. Several mitigating strategies have been proposed to improve the rechargeability of alkaline Zn–MnO 2 batteries, but the effect of pressure on electrochemical behavior has not been systematically investigated. In this paper, we demonstrate that an externally applied pressure at 20% MnO 2 depth-of-discharge (DOD MnO 2 ) has a profound effect on impedance, electrochemical cycling behavior, and materials morphology of alkaline Zn–MnO 2 batteries. Better electrochemical performance and improved morphology were achieved at 2.12 MPa pressure compared to 0.05 MPa pressure. Moreover, we examined the effect of externally applied pressure from 0 to 5.05 MPa before cycling and found that charge transfer resistance decreases significantly with pressure. Furthermore, we reported stable electrochemical cycling of MnO 2 ‖MnO 2 symmetric cells for 500 hours at 20% DOD under 2.12 MPa pressure. In conclusion, our efforts in understanding the effect of pressure could help design high performance and durable rechargeable alkaline Zn–MnO 2 batteries for grid-scale energy storage.

Rechargeable alkaline batteries↗
DOE OSTI2013

The change of microstructure and thermal properties in ion irradiated carbon nanotube mats as a function of ion penetration depth

A stack of three carbon nanotube (CNT) mats was irradiated with 3 MeV He ions. The change in structural and thermal properties of individual mats as a function of ion penetration depth was characterized using electron microscopy and laser flash techniques. Ion irradiation can enhance thermal conductivity of the mats by introducing inter-tube displacements, which improve phonon transport across adjacent nanotubes. The enhancement, however, is reduced at higher damage levels due to the increasing phonon-defect scattering within the tubes. This study demonstrates the feasibility of using ion irradiation to manipulate thermal transport in carbon nanotubes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Tsunami and acoustic-gravity waves in water of constant depth

A study of wave radiation by a rather general bottom displacement, in a compressible ocean of otherwise constant depth, is carried out within the framework of a three-dimensional linear theory. Simple analytic expressions for the flow field, at large distance from the disturbance, are derived. Realistic numerical examples indicate that the Acoustic-Gravity waves, which significantly precede the Tsunami, are expected to leave a measurable signature on bottom-pressure records that should be considered for early detection of Tsunami.

58 GEOSCIENCES↗
DOE OSTI2014

Multiscale modeling and experimental validation for nanochannel depth control in atomic force microscopy-based nanofabrication

Nanochannels are essential features of many microelectronic and biomedical devices. To date, the most commonly employed method to fabricate these nanochannels is atomic force microscopy (AFM). However, there is presently a very poor understanding on the fundamental principles underlying this process, which limits its reliability and controllability. In this study, we present a comprehensive multiscale model by incorporating strain gradient plasticity and strain gradient elasticity theories, which can predict nanochannel depths during AFM-based nanofabrication. The modeling results are directly verified with experiments performed on Cu and Pt substrates. As this model can also be extended to include many additional conditions, it has broad applicability in a wide range of AFM-based nanofabrication applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Probing depth dependent structure and magnetic properties of thin films using polarized neutron reflectivity

Novel properties of materials produced using nanoscale manufacturing processes often arise from interactions across interfaces between dissimilar materials. In order to understand the physical and magnetic properties of such nanostructures, a thorough and detailed structural and magnetic characterization with interface specificity is required. X-ray reflectivity and polarized neutron reflectivity (PNR) are two nondestructive techniques that provide quantitative measures of the chemical and magnetic depth profiles of the films with less than nanometer resolution averaged over the lateral dimensions of the entire sample (typically 100 mm{sup 2}). PNR specifically gives simultaneous structure and magnetic information of the interfaces. Unquestionably, neutron reflectivity has played a decisive role in the development and study of new emergent phenomena at interfaces.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Depth-dependent phase change in Gd{sub 2}O{sub 3} epitaxial layers under ion irradiation

Epitaxial Gd{sub 2}O{sub 3} thin layers with the cubic structure were irradiated with 4-MeV Au{sup 2+} ions in the 10{sup 13}–10{sup 15} cm{sup −2} fluence range. X-ray diffraction indicates that ion irradiation induces a cubic to monoclinic phase change. Strikingly, although the energy-deposition profile of the Au{sup 2+} ions is constant over the layer thickness, this phase transformation is depth-dependent, as revealed by a combined X-ray diffraction and ion channeling analysis. In fact, the transition initiates very close to the surface and propagates inwards, which can be explained by an assisted migration process of irradiation-induced defects. This result is promising for developing a method to control the thickness of the rare-earth oxide crystalline phases.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Earthquakes clustering based on the magnitude and the depths in Molluca Province

In this paper, we present a model to classify the earthquakes occurred in Molluca Province. We use K-Means clustering method to classify the earthquake based on the magnitude and the depth of the earthquake. The result can be used for disaster mitigation and for designing evacuation route in Molluca Province.

58 GEOSCIENCES↗
DOE OSTI2018

Universal doping evolution of the superconducting gap anisotropy in single crystals of electron-doped Ba(Fe 1– x Rh x ) 2 As 2 from London penetration depth measurements

Doping evolution of the superconducting gap anisotropy was studied in single crystals of 4d-electron doped Ba(Fe 1–x Rh x ) 2 As 2 using tunnel diode resonator measurements of the temperature variation of the London penetration depth Δλ( T ). Single crystals with doping levels representative of an underdoped regime x = 0.039 ( T c = 15.5 K), close to optimal doping x = 0.057 ( T c = 24.4 K) and overdoped x = 0.079 ( T c = 21.5 K) and x = 0.131( T c = 4.9 K) were studied. Superconducting energy gap anisotropy was characterized by the exponent, n, by fitting the data to the power-law, Δλ = AT n . The exponent n varies non-monotonically with x, increasing to a maximum n = 2.5 for x = 0.079 and rapidly decreasing towards overdoped compositions to 1.6 for x = 0.131. This behavior is qualitatively similar to the doping evolution of the superconducting gap anisotropy in other iron pnictides, including hole-doped (Ba,K)Fe 2 As 2 and 3d-electron-doped Ba(Fe,Co) 2 As 2 superconductors, finding a full gap near optimal doping and strong anisotropy toward the ends of the superconducting dome in the T-x phase diagram. The normalized superfluid density in an optimally Rh-doped sample is almost identical to the temperature-dependence in the optimally doped Ba(Fe,Co) 2 As 2 samples. In conclusion, our study supports the universal superconducting gap variation with doping and pairing at least in iron based superconductors of the BaFe 2 As 2 family.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Quasiparticle spectroscopy in technologically relevant niobium using London penetration depth measurements: experiment and theory

Abstract The London penetration depth, λ ( T ) , was measured in various forms of niobium, including foils, thin films, single crystals, and samples from superconducting radio-frequency (SRF) cavities. We observed a significant difference in λ ( T ) at low temperatures, T < T c / 3 , due to low-energy quasiparticles. In particular, an unusual downturn of λ ( T ) on cooling in the SRF cavity samples required to take into account deep in-gap bound states. Theoretical modeling using the generalized Dynes density of states shows that such in-gap states lead to a downturn or a peak in λ ( T ) upon cooling. Combined, experimental and theoretical findings provide a method for detecting two-level systems or states related to magnetic impurities in the bulk of niobium. This result is particularly relevant for the quantum informatics sciences technologies used in qubits and circuit quantum electrodynamics architecture based on SRF cavities.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

London penetration depth at zero temperature and near the superconducting transition

Herein, a simple relation is established between the zero- T penetration depth λ ( 0 ) and the slope of λ – 2 ( T ) near T c , similar to Helfand-Werthamer's relation for H c 2 ( 0 ) and the slope of H c 2 ( T ) at T c for the isotropic s -wave case with nonmagnetic scattering. When the scattering parameter ρ = ℏ v / 2 π T c ℓ ( v is the Fermi velocity and ℓ is the mean free path) varies from 1 to 10, the coefficient of proportionality between λ – 2 ( 0 ) and T c ( d λ – 2 / d T ) T c changes from 0.43 to 0.38. Combining this relation with the Rutgers thermodynamic identity, one can express λ ( 0 ) in terms of the slope ( d H c 2 / d T ) T c and the density of states.

Condensed Matter & Materials Physics↗
DOE OSTI2020

Universal temperature dependence of the London penetration depth in κ - ( ET ) 2 X superconductors

High-precision radio-frequency magnetic susceptibility measurements were performed on single crystals of fully deuterated $κ-(ET)_2Cu[N(CN)_2]\,Br$, hereafter designated as $κ-(ET)_2Cu[N(CN)_2]\,Br$. This material phase separates into superconducting and antiferromagnetic regions, the degree of which depends strongly upon the cooling rate. Here, we show that the screening fraction $η_{sc}$ varies logarithmically with the cooling rate over nearly five decades. The average size of superconducting regions is estimated to vary from 5 to $40μm$, depending upon cooling rate, consistent with previous infrared microscopy measurements. In the region $T≲T_c/3$, the effective magnetic penetration depth exhibits power-law behavior $λ(T)-λ(0)~T^n$ with $n=1.6$, independent of the cooling rate. Changes in cooling rate and the consequent phase separation evidently do not introduce the kind of disorder that would alter the exponent $n$ in a $d$-wave superconductor. The exponent remains close to $n=$ 1.5, reported in single crystals of $κ-(ET)_2Cu[N(CN)_2]\,Br$ and $κ-(ET)_2Cu(NCS)_2$ [A. Carrington et al., Phys. Rev. Lett 83, 4172 (1999)]. The transition temperature fell linearly with $1-η_{sc}$. Measurements were also made on $κ-(ET)_2Cu[N(CN)_2]\,Cl$ of normal isotopic abundance in which a very small amount of superconducting phase $η_{sc}≈10^{-4}$ developed, presumably through the strain-induced sample mounting. This material showed a power-law exponent of $n=1.64$, independent of the cooling rate.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Superconducting penetration depth through a Van Hove singularity: Sr 2 ⁢RuO 4 under uniaxial stress

A plethora of experiments in Sr 2 RuO 4 have reached conflicting conclusions about the symmetry of the superconducting gap. To probe the gap’s structure in k-space, we use strain to continuously tune the band structure through a Van Hove singularity (VHS) while imaging the superconductivity with scanning SQUID microscopy. We find that the superfluid density peaks at the VHS and that the temperature dependence of the penetration depth is T 2 -quadratic over the entire measured range of strain ε. These results are consistent with a gap structure that has vertical line nodes, experimentally confirming that non-local effects in the Meissner screening can lead to T 2 behavior and clarifying the nature of the low-energy excitations in Sr 2 RuO 4 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗