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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on AlGaBr4 by Materials Project

AlGaBr4 is Silicon tetrafluoride-derived structured and crystallizes in the orthorhombic Pnna space group. The structure is zero-dimensional and consists of four aluminium molecules and four GaBr4 clusters. In each GaBr4 cluster, Ga is bonded in a tetrahedral geometry to four Br atoms. There are two shorter (2.37 Å) and two longer (2.39 Å) Ga–Br bond lengths. There are two inequivalent Br sites. In the first Br site, Br is bonded in a single-bond geometry to one Ga atom. In the second Br site, Br is bonded in a single-bond geometry to one Ga atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AlC by Materials Project

AlC crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of twenty-four aluminium molecules and one AlC5 sheet oriented in the (0, 0, 1) direction. In the AlC5 sheet, there are six inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded in a distorted L-shaped geometry to three C3- atoms. There are a spread of Al–C bond distances ranging from 2.17–2.46 Å. In the second Al3+ site, Al3+ is bonded in a 2-coordinate geometry to two C3- atoms. There are one shorter (2.05 Å) and one longer (2.31 Å) Al–C bond lengths. In the third Al3+ site, Al3+ is bonded in a 2-coordinate geometry to two C3- atoms. There are one shorter (2.05 Å) and one longer (2.32 Å) Al–C bond lengths. In the fourth Al3+ site, Al3+ is bonded in a water-like geometry to two C3- atoms. Both Al–C bond lengths are 2.27 Å. In the fifth Al3+ site, Al3+ is bonded in a single-bond geometry to one C3- atom. The Al–C bond length is 2.07 Å. In the sixth Al3+ site, Al3+ is bonded in a single-bond geometry to one C3- atom. The Al–C bond length is 2.07 Å. There are thirty inequivalent C3- sites. In the first C3- site, C3- is bonded to one Al3+ and three C3- atoms to form distorted corner-sharing CAlC3 tetrahedra. There are a spread of C–C bond distances ranging from 1.51–1.60 Å. In the second C3- site, C3- is bonded to one Al3+ and three C3- atoms to form corner-sharing CAlC3 tetrahedra. There are a spread of C–C bond distances ranging from 1.53–1.59 Å. In the third C3- site, C3- is bonded to one Al3+ and three C3- atoms to form corner-sharing CAlC3 tetrahedra. There is one shorter (1.44 Å) and two longer (1.57 Å) C–C bond length. In the fourth C3- site, C3- is bonded in a distorted trigonal non-coplanar geometry to three C3- atoms. There are a spread of C–C bond distances ranging from 1.44–1.56 Å. In the fifth C3- site, C3- is bonded in a 5-coordinate geometry to two Al3+ and three C3- atoms. There are a spread of C–C bond distances ranging from 1.53–1.63 Å. In the sixth C3- site, C3- is bonded in a distorted pentagonal planar geometry to two Al3+ and three C3- atoms. Both C–C bond lengths are 1.63 Å. In the seventh C3- site, C3- is bonded in a distorted trigonal non-coplanar geometry to three C3- atoms. There is one shorter (1.55 Å) and one longer (1.56 Å) C–C bond length. In the eighth C3- site, C3- is bonded to one Al3+ and three C3- atoms to form corner-sharing CAlC3 tetrahedra. Both C–C bond lengths are 1.57 Å. In the ninth C3- site, C3- is bonded to one Al3+ and three C3- atoms to form corner-sharing CAlC3 tetrahedra. There is one shorter (1.58 Å) and one longer (1.59 Å) C–C bond length. In the tenth C3- site, C3- is bonded to one Al3+ and three C3- atoms to form distorted corner-sharing CAlC3 tetrahedra. There is one shorter (1.58 Å) and one longer (1.60 Å) C–C bond length. In the eleventh C3- site, C3- is bonded in a 4-coordinate geometry to one Al3+ and four C3- atoms. Both C–C bond lengths are 1.53 Å. In the twelfth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. There is one shorter (1.55 Å) and one longer (1.56 Å) C–C bond length. In the thirteenth C3- site, C3- is bonded to four C3- atoms to form corner-sharing CC4 tetrahedra. There is one shorter (1.53 Å) and one longer (1.54 Å) C–C bond length. In the fourteenth C3- site, C3- is bonded to four C3- atoms to form corner-sharing CC4 tetrahedra. There is one shorter (1.53 Å) and one longer (1.54 Å) C–C bond length. In the fifteenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. There is one shorter (1.55 Å) and one longer (1.56 Å) C–C bond length. In the sixteenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. Both C–C bond lengths are 1.52 Å. In the seventeenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. There is one shorter (1.53 Å) and one longer (1.56 Å) C–C bond length. In the eighteenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. Both C–C bond lengths are 1.54 Å. In the nineteenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. There is one shorter (1.53 Å) and one longer (1.56 Å) C–C bond length. In the twentieth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. Both C–C bond lengths are 1.52 Å. In the twenty-first C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-second C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-third C3- site, C3- is bonded in a water-like geometry to two C3- atoms. In the twenty-fourth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-fifth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-sixth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-seventh C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-eighth C3- site, C3- is bonded in a water-like geometry to two C3- atoms. In the twenty-ninth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the thirtieth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Performance Analysis and Radiation Damage Estimation of the Stopping Target Monitor Detectors in Mu2e

The Mu2e experiment aims to search for the charged lepton flavour violating (CLFV) process of a coherent, neutrinoless, conversion of a muon into an electron within the proximity of an aluminium nucleus. Mu2e seeks to measure the ratio (R μe ) of the rate of this conversion process, relative to that of ordinary muon capture. Mu2e will achieve world-leading sensitivity, improving the current limit of Rμe < 7 ×10 -13 (90% C.L.),set by the SINDRUM-II experiment, by an order of 104. This corresponds to a single-event sensitivity of Rμe < 2.87 × 10 -17 (90% C.L.). Many beyond Standard Model (BSM) theories require CLFV to occur at a rate accessible by Mu2e. Any observation of CLFV at Mu2e would have profound implications on particle physics. The Stopping Target Monitor (STM) will be comprised of both a HPGe and a LaBr3 detector which will monitor the signals of photons produced in stopped-muon processes to a required accuracy of 10%. To achieve the desired sensitivity, it is imperative that the detectors perform at their optimal level. The STM detectors are placed within a harsh radiation environment in the form of a high energy ‘flash’ of gamma radiation as well as a flux of fast neutrons. Estimations of radiation damage to HPGe in literature is limited. This thesis reports an approach which utilizes the Kinetic-Energy Released in Matter (KERMA) parameter that considers the energy dependence of the incident flux and the cross-section information for the incident particle. Resampling schemes have been adopted to give a realistic rate over the experiment run time. The results have then been normalized to the radiation damage caused by a 252 Cf source. The estimated time before annealing of the detector is necessary is found to be 75 and 78 months in the case of neutron damage and τ ~ 24 years, 11 months in the case of electron/positron induced damage. This shows significant improvement on the previous estimations.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Near-Infrared Noise in Intense Electron Beams

Requirements for the noise in electron beams (NEB) have recently approached the Shot-noise level in some new applications. The density fluctuations of intense beams in the near-infrared (NIR) region are being measured at the Fermilab Accelerator Science and Technology (FAST) facility. The main goal of the experiment is to accurately compare the Shot-noise model with the observations of optical transition radiation (OTR) generated by a relativistic electron beam ($\gamma \approx 63$), transiting an Aluminium metal surface. In addition, some evidence for longitudinal space-charge-induced microbunching for the chicane-compressed beam was obtained with coherent enhancements up to 100 in the various bandwidth-filtered NIR OTR photodiode signals. With micropulse charges up to 1 nC, the beam parameters are close to those proposed for a stage in an Electron-Ion Collider (EIC) with coherent electron cooling (CEC). In this paper we present the current progress of the NEB project and compare the low electron energy measurements with ImpactX simulations.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Study of Mechanical Grinding Effects on Niobium Surface

Mechanical grinding is commonly employed to eliminate surface defects such as scratches and pits from niobium cavity surfaces or sheets before cavity fabrication. Subsequently, chemically buffered polishing or electropolishing is often utilized to completely remove residues of the polishing media and any defects induced by mechanical grinding, ensuring a pristine surface. In this study, we conducted a systematic investigation to assess the influence of mechanical grinding using silicon carbide (SiC) and aluminium oxide (Al2O3) polishing media on niobium surfaces. Additionally, the study examines the effects of post-mechanical grinding chemical treatments on surface quality.

Chouhan, V.↗
DOE OSTI2022

Atomically Precise Ultra-High Performance 2D MicroElectronics

Zyvex Labs has created several p-n junction devices with a variety of gaps between the boron and phosphorus electrodes, from 0-7.7 nm, which are now being measured. We have developed a different contacting process based on palladium disilicide rather than aluminium to improve the reliability of the device contacts. Preliminary measurements indicate that these new contacts are successfully contacting the buried dopant layers, which are intact after the overgrowth process. Modelling of the p-n junction properties has made good progress, with the model matching previous published data, and modelling of n-p-n junction devices has begun. This now awaits experimental validation.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Resonant Extraction and Extinction Measurement for the Mu2e Experiment

The Mu2e experiment, currently under construction at Fermilab, will search for coherent neutrinoless muon to electron conversion, extending the sensitivity of searches for charged lepton flavour violation by four orders of magnitude in 3-5 years of data-taking. This improved sensitivity is made possible by using a pulsed beam structure that is optimized for reducing prompt backgrounds when muons are stopped on an aluminium target. Producing a high-rate pulsed beam is achieved using resonant extraction of a circulating proton beam, an “AC dipole” with a time-varying field to deflect out-of-time protons, and a system to measure the extinction of out-of-time beam particles incident on the muon production target. These proceedings summarize the systems that have been designed to achieve the required level of extinction and to continuously place limits on the presence of out-of-time beam hitting the production target with a sensitivity of <1e-10.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Broad Frequency Shift of Parametric Processes in Epsilon-Near-Zero Time-Varying Media

The ultrafast changes of material properties induced by short laser pulses can lead to a frequency shift of reflected and transmitted radiation. Recent reports highlight how such a frequency shift is enhanced in spectral regions where the material features a near-zero real part of the permittivity. Here, we investigate the frequency shift for fields generated by four-wave mixing. In our experiment, we observed a frequency shift of more than 60 nm (compared to the pulse width of ~40 nm) in the phase conjugated radiation generated by a 500 nm aluminium-doped zinc oxide (AZO) film pumped close to the epsilon-near-zero wavelength. Our results indicate applications of time-varying media for nonlinear optics and frequency conversion.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Preparation and Characterization of Materials for Low- to Intermediate-Temperature CO2 Adsorption

Global carbon dioxide emissions are rising and the use of fossil fuels in several sectors are the leading causes. As global population and economies continue to grow significantly, the most practical method of lowering such emissions is to capture CO2. Although other technologies are more developed, adsorption is very promising and has attracted much attention. To ensure this technology’s success, it is essential to have suitable CO2 adsorbent materials. In this work, several new hydrotalcites (HTs) with different initial concentrations of ion precursors were prepared for the first time by the co-precipitation method—it was possible to verify that the ion concentrations influence the characteristics of the materials. The prepared HTs were characterized by thermogravimetric analysis (TG), X-Ray diffraction (XRD), surface area measurements and temperature-programmed desorption of CO2 (TPD-CO2) to relate their CO2 capture capacity to their physicochemical properties; the CO2 adsorption equilibrium isotherms were determined at 35 and 300 °C for the prepared samples, as well as for some commercial materials: magnesium oxide, calcium oxide, aluminium oxide and Zeolite 13X. After determining which materials present the best CO2 adsorption capacity, these were submitted to adsorption-desorption cycles to study their stability. The main objective of the work was to prepare and study different CO2 adsorbents for processes that are carried out at low and intermediate temperatures. From the experimental results, it was possible to conclude that the Zeolite 13X showed the best capacity at 35 °C, 3.38 mmol·g−1 (@ pCO2 = 1 bar), and a prepared calcined HT (c-HT2) was the best at 300 °C, 0.97 mmol·g−1 (@ pCO2 = 1 bar). Moreover, it seems there is an optimum initial concentration of the ions’ solutions for the tested HTs, which depends on the final application—c-HT1 showed a better capacity at 35 °C and c-HT2 at 300 °C. From the adsorption-desorption cycles—performed at 35 and 300 °C with the best materials using a magnetic suspension microbalance at 1 bar of CO2 partial pressure —, a working cyclic capacity of 2.69 mmol∙g−1 was achieved by the Zeolite at 35 °C; in turn, c-HT2 showed a working cyclic capacity of 0.79 mmol∙g−1 at 300 °C.

Figueiredo, Anabela↗
DOE OSTI2021

Experimental investigation of elemental and isotopic evaporation processes by laser heating in an aerodynamic levitation furnace

In this report we carried out evaporation experiments on a B-type calcium–aluminium-rich inclusion (CAI) melt in a gas-mixing aerodynamic levitation laser furnace, at 1873 K and an oxygen partial pressure of 10 -9.1 atm, for durations ranging from 60 to 600 s. Evaporation of SiO 2 and MgO follow the same trend as those observed in vacuum furnace experiments at the same temperature and starting composition, showing that their evaporation relative to one another from the melt is independent of pressure, oxygen fugacity, and hydrodynamical regime specific to the furnace. Isotopic ratios of Mg and Si in evaporation residues are used to derive fractionation factors of α 26/24 Mg vap-liq = 0.9906± 0.0004 and α 30/28 Si vap-lip = 0.9943±0.0003, which are both significantly closer to unity than those found for evaporation in a vacuum, which translates to less isotope fractionation. The residues are also less isotopically fractionated than expected for cases in which transport of the gas species away from the melt is diffusion-controlled at 1-atm. By analysing the flow regimes in our furnace, we find that advection by the levitating gas is the primary mode of mass transport away from the melt surface, as opposed to diffusion-limited transport in a vacuum or 1-atm tube furnace. A modified Hertz–Knudsen–Langmuir formulation accounts for this process, and shows that isotopic fractionation of both Si and Mg reflect a saturation factor (ratio of the pressure of the evaporating species to vapour saturation pressure) equal to 0.75. This is in perfect accord with recent measurements of Cu isotopic fractionation using a similar furnace. The fact that three elements (Mg, Si, Cu) with varying equilibrium vapour pressures, activity coefficients in the liquid, and diffusion coefficients in the gas have the same scaling behaviour to saturation pressure is a strong indication that the mechanism controlling evaporation is driven by the hydrodynamical regime imposed in the furnace. Therefore, this class of experiments can be used to constrain processes in which advection dominates over diffusion, such as (but not limited to) planetary ejecta, tektites, giant impacts, nebular condensation in a turbulent flow, or nuclear fallout material. Finally, the possibility to reach high temperatures (in excess of 3500 K) in this furnace allows it to be used to evaluate the activity coefficients of melt components in extreme conditions relevant to molten planetary interiors (i.e., magma oceans), with a specific focus on refractory elements.

58 GEOSCIENCES↗
NASA NTRS1973

The effect of yield strength and ductility to fatigue damage

The cumulative damage of aluminium alloys with different yield strength and various ductility due to seismic loads was studied. The responses of an idealized beam with a centered mass at one end and fixed at the other end to El Centro's and Taft's earthquakes are computed by assuming that the alloys are perfectly elastoplastic materials and by using numerical technique. Consequently, the corresponding residual plastic strain can be obtained from the stress-strain relationship. The revised Palmgren-Miner cumulative damage theorem is utilized to calculate the fatigue damage. The numerical results show that in certain cases, the high ductility materials are more resistant to seismic loads than the high yield strength materials. The results also show that if a structure collapse during the earthquake, the collapse always occurs in the very early stage.

Yeh, H. Y.↗
NASA NTRS1973

Properties of the solar nebula and the origin of the moon.

The basic geochemical model of the structure of the moon proposed by Anderson, in which the moon is formed by differentiation of the calcium, aluminium, and titanium-rich inclusions in the Allende meteorite, is accepted, and the conditions for formation of this moon within the solar nebula models of Cameron and Pine are discussed. The basic material condenses while iron remains in the gaseous phase, which places the formation of the moon slightly inside the orbit of Mercury. Some condensed metallic iron is likely to enter the moon in this position, and since the moon is assembled at a very high temperature, it is likely to have been fully molten, so that the iron can remove the iridium from the silicate material and carry it down to form a small core. Interactions between the moon and Mercury lead to the present rather eccentric Mercury orbit and to a much more eccentric orbit for the moon, reaching past the orbit of the earth, establishing conditions which are necessary for capture of the moon by the earth.

Cameron, A. G. W.↗
NASA NTRS1973

Radionuclides at Descartes in the central highlands

Throium, uranium, potassium, aluminium-26, and sodium-22 were measured by nondestructive gamma ray spectrometry in six soil and two rock samples gathered by Apollo 16 in the lunar central highlands. The soil samples probably include both major geologic formations in the vicinity, the Cayley and Descartes Formations, although it is possible that the Descartes Formation is not represented. The rock samples have low concentrations of primordial radionuclides. The Al concentrations were lower than could be expected from the high abundance of alumina in the Apollo 16 soils reported earlier, but this could be due to lower concentrations of target elements in these soils, sampling depth variations, or regolithic mixing (exposure age variations).

Wrigley, R. C.↗
NASA NTRS1976

Design principles of a rotating medium speed mechanism

Design principles of a medium speed mechanism (MSM) are presented, including discussion on the relative merits of beryllium and aluminium as structural materials. Rotating at a speed of 60 rpm, the application envisaged for the MSM was as a despin bearing for the despun platform or despun antenna of a spin stabilized satellite. The MSM was built and tested to qualification level and is currently undergoing real time life testing.

Hostenkamp, R. G.↗
NASA NTRS1979

Hydrogen /Hydride/-air secondary battery

The use of metal hydrides as negative electrodes in a hydrogen-air secondary battery seems promising. However, in an unpressurized cell, more stable hydrides that LaNi5H6 must be selected. Partial substitutions of nickel by aluminium or manganese increase the stability of hydrides. Combined with an air reversible electrode, a specific energy close to 100 Wh/kg can be expected.

Sarradin, J.↗
NASA NTRS1981

Materials characterization study of conductive flexible second surface mirrors

The status of prequalification and qualification work on conductive flexible second surface mirrors is described. The basic material is FEP Teflon witn either aluminium or silver vacuum deposited reflectors. The top layer has been made conductive by deposition of layer of a indium oxide. The results of a prequalification program comprised of decontamination, humidity, thermal cycling, thermal shock and vibration tests are presented. Thermo-optical and electrical properties. The results of a prequalification program comprised of decontamination, humidity, thermal cycling, thermal shock and vibration tests are presented. Thermo-optical and electrical properties, the electrostatic behavior of the materials under simulated substorm environment and electrical conductivity at low temperatures are characterized. The effects of simulated ultra violet and particles irradiation on electrical and thermo-optical properties of the materials are also presented.

Levadou, F.↗