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

Novel complex ceramic oxides, Ln 2 TiO 5 (Ln = La, Sm, Gd, Tb, Dy, Ho, Er, and Yb), for polyphase nuclear waste‐forms

Abstract As part of a broader study of ceramic nuclear waste‐forms, four different lanthanide titanates were fabricated; La 0.1 Sm 0.1 Gd 0.1 Tb 0.1 Dy 0.3 Ho 0.1 Er 0.2 YbTiO 5 , Sm 0.3 Gd 0.3 Dy 0.3 Yb 1.1 TiO 5 , Sm 0.1 Gd 0.4 Dy 0.4 Yb 1.1 TiO 5 , and Sm 0.2 Gd 0.2 Dy 0.2 Yb 1.4 TiO 5 . The aim was to produce single‐phase novel materials with cubic symmetry, capable of incorporating a wide variety of cations and with acceptable radiation tolerance. The chemistry flexibility and radiation tolerance are some of the major desirable properties for nuclear waste‐form materials. By using multiple lanthanides the average lanthanide radius can be controlled and consequently the structure, along with properties such as radiation tolerance. The radiation tolerance was assessed using in situ 1 MeV krypton irradiation and transmission electron microscopy characterization. Those materials for which cubic symmetry was achieved displayed better radiation tolerance; a greater critical fluence of ions ( F c ) was required for the crystalline to amorphous transition, and a lower temperature was required to maintain crystallinity ( T c ) during irradiation.

Aughterson, Robert D.↗
NASA NTRS1971

Neutron capture on Sm-149 in lunar samples.

High precision isotopic composition measurements of Sm have been carried out for two terrestrial and seven lunar samples from three Apollo sites. The lunar samples, selected to show a wide variation in cosmic ray exposure ages, have a wide range of enrichments in Sm-150/Sm-154 (up to 0.8%) and depletions in Sm-149/Sm-154 which are due to neutron capture. The ratio of the number of neutrons captured per atom by Sm-149 to Gd-157 is 0.9 and reflects a hardened lunar neutron spectrum. This ratio is in reasonable but not exact agreement with that obtained from the theoretical lunar neutron energy spectrum of Lingenfelter, Canfield and Hampel. The average composition for terrestrial samarium is given.

Russ, G. P., III↗
NASA NTRS1991

Sm-Nd and Rb-Sr isotopic systematics of ureilites

The present evaluation of Sm-Nd and Rb-Sr isotopic data for seven ureilites establishes their divisions into three groups on the bases of Sm-Nd isotopic systematics. The first group of ureilites is made up of whole-rock samples whose highly depleted assemblages indicate Sm-Nd model ages consistent with 4.55 Ga. The second group of whole-rock samples of Kenna, Novo Urei, and ALHA77257 are heterogeneous mixtures of an unidentified light REE-enriched component and a light REE-depleted olivine-pyroxene assemblage. In the third group, LEW85440 neither has a model Sm-Nd age of 4.55 Ga nor plots of the 3.74 Ga isochron of the Kenna group; it might have had an evolution similar to the Kenna group, but involving different times and/or isotopic compositions.

Goodrich, Cyrena Anne↗
NASA NTRS1992

Rb-Sr and Sm-Nd chronology of an Apollo 17 KREEP basalt

The paper determines Sm-Nd and Rb-Sr mineral isochrons for an Apollo 17 KREEP (pigeonite) basalt clast from breccia 72275 collected from Boulder 1, Station 2 in the Valley of Taurus-Littrow. Sm-Nd analyses of the basalt yield a precise mineral isochron age of 4.08 +/-0.07 Ga for lambda(Sm-147) = 0.00654/Ga. The concordancy of Sm-Nd and Rb-Sr ages for the basalt suggests that it crystallized about 4.08 Ga ago. Distinct ages and initial Sr isotopic ratios for Apollo 17 KREEP basalts and Apollo 14 and 15 KREEP suggest that these two types of KREEP basalts were not derived from the same source. Apollo 17 KREEP basalts are contemporaneous with some Apollo 14 aluminous mare basalts. The ages and Sr and Nd isotopic data suggest that these two different types of basalts were produced from sources having similar Rb/Sr ratios but different Sm/Nd ratios.

Shih, C.-Y.↗
NASA NTRS1993

The Sm-Nd systematics of silicate inclusions in iron meteorites: Results from Caddo (IAB)

The timing of events leading to the formation of silicate-rich and metal-rich regions in planetesimals remains an important problem in the study of planetary formation and differentiation in the early solar system. The IAB irons are especially important as they are considered to represent a magmatic differentiation series. Iron meteorites present a particular challenge for chronological studies, due to the relative paucity of phases serving as hosts for radioactive parent-daughter nuclides. Recent work using the Re-Os system, following on the pioneering work by Herr et al. and Luck and Allegre, appears promising, but investigators up to now have concentrated on whole rock isochrons. Silicate clasts enclosed within iron meteorites can provide information about the chronology and thermal history of irons. Extensive work on Rb-Sr, K-Ar, and I-Xe has been reported on silicate inclusions in iron meteorites. We report the initial results from our Sm-Nd study of an inclusion with the Caddo IAB iron, the first Sm-Nd isotopic study of a silicate clast embedded within an iron meteorite. Our results include measurements of the standard long-lived Sm-147/Nd-143 (tau = 152 AE) system, as well as the shorter-lived SM-146/Nd-142 (tau = 0.149 AE) system, which has been shown to be very useful in deciphering the history of the early solar system. The Caddo silicate clast was described by Palme et al., who kindly provided us with a major part of the inclusion. The inclusion is coarse-grained consisting predominantly of olivine, clinopyroxene, and plagioclase, with lesser amounts of orthopyroxene, Fe-Ni metal, sulfide, and phosphate. The relatively large grain size (up to 3 mm) and 120 degree grain boundaries suggest extensive metamorphism at high temperatures. Based on study of a thin section, there is evidence for metal invading along grain boundaries in some regions of the inclusion, suggesting that the Fe-Ni metal was molten when the silicate clast was incorporated. Metamorphic recrystallization may have occurred during this event.

Stewart, Brian W.↗
NASA NTRS2008

Assessment of the LC-2 Prelaunch Fatigue Spectra of the CM-to-SM Flange Weld

The pad stay and rollout components of the Ares I-X life cycle can generate cyclic stress oscillations to the vehicle that could initiate and grow fatigue cracks from weld defects. The Ares I-X Project requested that a study be performed to determine if stabilization of the vehicle is required to reduce the stresses that could initiate and grow fatigue cracks at the flange-to-skin weld of the Command Module (CM) and Service Module (SM) interface. A fatigue crack growth analysis was conducted that used loads (LC-2) and stress analyses developed by the Ares I-X Project and utilized material data and analysis methods developed by a critical initial flaw size (CIFS) analysis conducted by NASA Engineering and Safety Center (NESC) for the Upper Stage Simulator (USS) of the Ares I-X vehicle. A full CIFS analysis for the CM-to-SM flange-to-skin weld was not performed because the full flight spectrum was not provided and was not necessary to answer the question posed by the Ares I-X Project. Instead, an approach was developed to determine if the crack growth due to the pad stay and rollout components of the flight spectrum would adversely influence the CIFS. The approach taken used a number of conservative assumptions that eliminated the need for high-fidelity analyses and additional material testing, but still provided a bounding solution for the uncertainties of the problem. The results from this analysis indicate that the LC-2 pad stay and rollout spectrum components would not produce significant fatigue crack growth on the CM-to-SM flange-to-skin weld. Thus, from a fatigue crack growth standpoint, no stabilization is required to reduce the LC-2 pad stay and rollout cyclic stresses on the CM-to-SM flange-to-skin weld.

Dawicke, David S.↗
NASA NTRS2010

The SMAP Level 4 Surface and Root-zone Soil Moisture (L4_SM) Product

The Soil Moisture Active and Passive (SMAP) mission is being developed by NASA for launch in 2013 as one of four first-tier missions recommended by the U.S. National Research Council Committee on Earth Science and Applications from Space in 2007. The primary science objectives of SMAP are to enhance understanding of land surface controls on the water, energy and carbon cycles, and to determine their linkages. Moreover, the high resolution soil moisture mapping provided by SMAP has practical applications in weather and seasonal climate prediction, agriculture, human health, drought and flood decision support. In this paper we describe the assimilation of SMAP observations for the generation of the planned SMAP Level 4 Surface and Root-zone Soil Moisture (L4_SM) product. The SMAP mission makes simultaneous active (radar) and passive (radiometer) measurements in the 1.26-1.43 GHz range (L-band) from a sun-synchronous low-earth orbit. Measurements will be obtained across a 1000 km wide swath using conical scanning at a constant incidence angle (40 deg). The radar resolution varies from 1-3 km over the outer 70% of the swath to about 30 km near the center of the swath. The radiometer resolution is 40 km across the entire swath. The radiometer measurements will allow high-accuracy but coarse resolution (40 km) measurements. The radar measurements will add significantly higher resolution information. The radar is however very sensitive to surface roughness and vegetation structure. The combination of the two measurements allows optimal blending of the advantages of each instrument. SMAP directly observes only surface soil moisture (in the top 5 cm of the soil column). Several of the key applications targeted by SMAP, however, require knowledge of root zone soil moisture (approximately top 1 m of the soil column), which is not directly measured by SMAP. The foremost objective of the SMAP L4_SM product is to fill this gap and provide estimates of root zone soil moisture that are informed by and consistent with SMAP observations. Such estimates are obtained by merging SMAP observations with estimates from a land surface model in a soil moisture data assimilation system. The land surface model component of the assimilation system is driven with observations-based surface meteorological forcing data, including precipitation, which is the most important driver for soil moisture. The model also encapsulates knowledge of key land surface processes, including the vertical transfer of soil moisture between the surface and root zone reservoirs. Finally, the model interpolates and extrapolates SMAP observations in time and in space. The L4_SM product thus provides a comprehensive and consistent picture of land surface hydrological conditions based on SMAP observations and complementary information from a variety of sources. The assimilation algorithm considers the respective uncertainties of each component and yields a product that is superior to satellite or model data alone. Error estimates for the L4_SM product are generated as a by-product of the data assimilation system.

Reichle, Rolf↗
NASA NTRS2011

Rb-Sr And Sm-Nd Ages, and Petrogenesis of Depleted Shergottite Northwest Africa 5990

Northwest Africa (NWA) 5990 is a very fresh Martian meteorite recently found on Hamada du Draa, Morocco and was classified as an olivine-bearing diabasic igneous rock related to depleted shergottites [1]. The study of [1] also showed that NWA 5990 resembles QUE 94201 in chemical, textural and isotopic aspects, except QUE 94201 contains no olivine. The depleted shergottites are characterized by REE patterns that are highly depleted in LREE, older Sm-Nd ages of 327-575 Ma and highly LREE-depleted sources with Nd= +35~+48 [2-7]. Age-dating these samples by Sm-Nd and Rb-Sr methods is very challenging because they have been strongly shocked and contain very low abundances of light rare earth elements (Sm and Nd), Rb and Sr. In addition, terrestrial contaminants which are commonly present in desert meteorites will compromise the equilibrium of isotopic systems. Since NWA 5990 is a very fresh meteorite, it probably has not been subject to significant desert weathering and thus is a good sample for isotopic studies. In this report, we present Rb-Sr and Sm-Nd isotopic results for NWA 5990, discuss the correlation of the determined ages with those of other depleted shergottites, especially QUE 94201, and discuss the petrogenesis of depleted shergottites.

Shih, C. Y.↗
NASA NTRS2013

Peering Through a Martian Veil: ALHA84001 Sm-Nd Age Revisited

The ancient Martian orthopyroxenite ALH84001experienced a complex history of impact and aqueous alteration events. Here we summarize Sm-147-Nd-143 and Sm-146-Nd-142 analyses performed at JSC. Further, using REE data, we model the REE abundance pattern of the basaltic magma parental to ALH84001 cumulus orthopyroxene. We find the Sm-146-Nd-142 isotopic data to be consistent with isotopic evolution in material having the modeled Sm/Nd ratio from a time very close to the planet's formation to igneous crystallization of ALH84001 as inferred from the Sm-Nd studies.

Nyquist, Laurence E.↗
DOE OSTI2020

Materials Data on Sm(MnGe)2 by Materials Project

SmMn2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Sm is bonded in a 8-coordinate geometry to eight equivalent Ge atoms. All Sm–Ge bond lengths are 3.13 Å. Mn is bonded to four equivalent Ge atoms to form a mixture of corner and edge-sharing MnGe4 tetrahedra. All Mn–Ge bond lengths are 2.45 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Sm, four equivalent Mn, and one Ge atom. The Ge–Ge bond length is 2.68 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm(AlCl4)2 by Materials Project

Sm(AlCl4)2 crystallizes in the monoclinic P2/c space group. The structure is two-dimensional and consists of one Sm(AlCl4)2 sheet oriented in the (1, 0, 0) direction. Sm2+ is bonded in a 8-coordinate geometry to eight Cl1- atoms. There are a spread of Sm–Cl bond distances ranging from 2.96–2.99 Å. Al3+ is bonded in a tetrahedral geometry to four Cl1- atoms. There are three shorter (2.17 Å) and one longer (2.18 Å) Al–Cl bond lengths. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a distorted bent 120 degrees geometry to one Sm2+ and one Al3+ atom. In the second Cl1- site, Cl1- is bonded in a distorted L-shaped geometry to one Sm2+ and one Al3+ atom. In the third Cl1- site, Cl1- is bonded in a distorted L-shaped geometry to one Sm2+ and one Al3+ atom. In the fourth Cl1- site, Cl1- is bonded in a 2-coordinate geometry to one Sm2+ and one Al3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm(AsO)2 by Materials Project

Sm(AsO)2 crystallizes in the tetragonal I4_1/amd space group. The structure is zero-dimensional and consists of eight Sm(AsO)2 clusters. Sm2+ is bonded in a linear geometry to two equivalent O2- atoms. Both Sm–O bond lengths are 2.23 Å. As1+ is bonded in a single-bond geometry to one O2- atom. The As–O bond length is 1.77 Å. O2- is bonded in a water-like geometry to one Sm2+ and one As1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm(AlBr4)3 by Materials Project

Sm(AlBr4)3 crystallizes in the trigonal P3_121 space group. The structure is one-dimensional and consists of one Sm(AlBr4)3 ribbon oriented in the (0, 0, 1) direction. Sm3+ is bonded in a 8-coordinate geometry to eight Br1- atoms. There are a spread of Sm–Br bond distances ranging from 2.95–3.14 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded in a tetrahedral geometry to four Br1- atoms. There are a spread of Al–Br bond distances ranging from 2.27–2.41 Å. In the second Al3+ site, Al3+ is bonded in a tetrahedral geometry to four Br1- atoms. All Al–Br bond lengths are 2.34 Å. There are six inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a distorted L-shaped geometry to one Sm3+ and one Al3+ atom. In the second Br1- site, Br1- is bonded in a single-bond geometry to one Al3+ atom. In the third Br1- site, Br1- is bonded in a distorted L-shaped geometry to one Sm3+ and one Al3+ atom. In the fourth Br1- site, Br1- is bonded in an L-shaped geometry to one Sm3+ and one Al3+ atom. In the fifth Br1- site, Br1- is bonded in a single-bond geometry to one Al3+ atom. In the sixth Br1- site, Br1- is bonded in a distorted L-shaped geometry to one Sm3+ and one Al3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm(MgBi)2 by Materials Project

SmMg2Bi2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Mg is bonded to four equivalent Bi atoms to form MgBi4 tetrahedra that share corners with six equivalent SmBi6 octahedra, corners with six equivalent MgBi4 tetrahedra, edges with three equivalent SmBi6 octahedra, and edges with three equivalent MgBi4 tetrahedra. The corner-sharing octahedra tilt angles range from 15–58°. There are three shorter (2.94 Å) and one longer (2.98 Å) Mg–Bi bond lengths. Sm is bonded to six equivalent Bi atoms to form SmBi6 octahedra that share corners with twelve equivalent MgBi4 tetrahedra, edges with six equivalent SmBi6 octahedra, and edges with six equivalent MgBi4 tetrahedra. All Sm–Bi bond lengths are 3.33 Å. Bi is bonded to four equivalent Mg and three equivalent Sm atoms to form a mixture of distorted corner and edge-sharing BiSm3Mg4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Mechanically strengthened heterogeneous Sm-Co sintered magnets

Samarium-cobalt sintered magnets offer excellent magnetic properties, thermal stability, and corrosion resistance. They are used in a variety of defense and civilian applications, especially when elevated operation temperatures (e.g., 200 ºC to 550 ºC) are required. However, the utilization of these materials is restricted by their brittleness. Improving their mechanical resilience would make them more cost-effective, efficient, and robust in decarbonization and other function-related applications while reducing the pressure on critical material supply chains. In this paper, we engineer a series of novel heterogeneous microstructures, such as laminated coarse grain (CG)/fine grain (FG) and core/shell CG/FG microstructures, to produce unprecedented combinations of superior mechanical and magnetic properties without altering the chemical compositions of the magnets or common heat treatment procedures. Further, a 60% flexural strength enhancement is obtained using heterogeneous Sm 2 (CoFeCuZr) 17 sintered magnets with little impact on their magnetic properties. The mechanically robust heterogeneous Sm-Co sintered magnets have a minor (e.g., less than 4.6%) reduction in the energy product (BH) max due to a slightly reduced squareness of the demagnetization curve, with no decrease in either the remanence (B r ) or the intrinsic coercivity (H ci ). The flexural strengths of these heterogeneous Sm-Co magnets depend on the volume ratios and mean grain sizes of the FG/CG regions, as well as their microstructural architectures. The fine-grained regions act as mechanical strengthening sites, which can be strategically used when designing the magnet for different applications. This technology is highly compatible with existing magnet manufacturing processes and thus can be adopted readily by the magnet industry.

36 MATERIALS SCIENCE↗
NASA NTRS2015

Soil Moisture Active Passive (SMAP) Mission Level 4 Surface and Root Zone Soil Moisture (L4_SM) Product Specification Document

This is the Product Specification Document (PSD) for Level 4 Surface and Root Zone Soil Moisture (L4_SM) data for the Science Data System (SDS) of the Soil Moisture Active Passive (SMAP) project. The L4_SM data product provides estimates of land surface conditions based on the assimilation of SMAP observations into a customized version of the NASA Goddard Earth Observing System, Version 5 (GEOS-5) land data assimilation system (LDAS). This document applies to any standard L4_SM data product generated by the SMAP Project. The Soil Moisture Active Passive (SMAP) mission will enhance the accuracy and the resolution of space-based measurements of terrestrial soil moisture and freeze-thaw state. SMAP data products will have a noteworthy impact on multiple relevant and current Earth Science endeavors. These include: Understanding of the processes that link the terrestrial water, the energy and the carbon cycles, Estimations of global water and energy fluxes over the land surfaces, Quantification of the net carbon flux in boreal landscapes Forecast skill of both weather and climate, Predictions and monitoring of natural disasters including floods, landslides and droughts, and Predictions of agricultural productivity. To provide these data, the SMAP mission will deploy a satellite observatory in a near polar, sun synchronous orbit. The observatory will house an L-band radiometer that operates at 1.40 GHz and an L-band radar that operates at 1.26 GHz. The instruments will share a rotating reflector antenna with a 6 meter aperture that scans over a 1000 km swath.

L4-SM↗
DOE OSTI2021

3D printing of anisotropic Sm–Fe–N nylon bonded permanent magnets

Abstract Fabricating a bonded magnet with a near‐net shape in suitable thermoplastic polymer binders is of paramount importance in the development of cost‐effective energy technologies. In this work, anisotropic Sm 2 Fe 17 N 3 (Sm–Fe–N) bonded magnets are additively printed using SmFeN anisotropic magnetic particles in a polymeric binder polyamide‐12 (PA12). The anisotropic SmFeN bonded magnets are fabricated by Big Area Additive Manufacturing followed by post‐printing alignment in a magnetic field. Optimal post‐alignment results in an enhanced remanence of ∼0.68 T in PA12 reflected in a parallel‐oriented (aligned) measured direction. The maximum energy product achieved for the additively printed anisotropic bonded magnet of Sm–Fe–N in PA12 polymer is 78.8 KJ m −3 . Our results show advanced processing flexibility with 3D printing of the development of SmFeN nylon bonded magnets designed for applications with no critical rare earth magnets.

42 ENGINEERING↗
DOE OSTI2022

Chemical separation of 146 Sm for half-life determination

Here, although methods for the chemical separation of samarium from a rock matrix are well established, chemical separation of samarium from non-natural isotopic impurities for the purpose of 146 Sm half-life measurement requires modifications to these procedures, as well as additional checks for effective separation. This work describes the chemical purification procedures associated with the 146 Sm source and the results from gamma spectroscopy. The purification procedure allowed for the quantitative determination of the number of 146Sm atoms using a modified isotope dilution technique. Alpha-decay counting of the sample will be applied in the future to determine the half-life of 146 Sm.

146Sm↗