Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “RE”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

Re-Engineering the Tropical Rainfall Measuring Mission (TRMM) Satellite Utilizing Goddard Space Flight Center (GSFC) Mission Services Center (GMSEC) Middleware Based Technology to Enable Lights Out Operations and Autonomous Re-Dump of Lost Telemetry Data

The Tropical Rainfall Measuring Mission (TRMM) spacecraft was launched in November of 1996 in order to obtain unique three dimensional radar cross sectional observations of cloud structures with particular interest in hurricanes. The TRMM mission life was recently extended with current estimates that operations will continue through the 2012-2013 timeframe. Faced with this extended mission profile, the project has embarked on a technology refresh and re-engineering effort. TRMM has recently implemented a re-engineering effort to expand a middleware based messaging architecture to enable fully redundant lights-out of flight operations activities. The middleware approach is based on the Goddard Mission Services Evolution Center (GMSEC) architecture, tools and associated open-source Applications Programming Interface (API). Middleware based messaging systems are useful in spacecraft operations and automation systems because private node based knowledge (such as that within a telemetry and command system) can be broadcast on the middleware messaging bus and hence enable collaborative decisions to be made by multiple subsystems. In this fashion, private data is made public and distributed within the local area network and multiple nodes can remain synchronized with other nodes. This concept is useful in a fully redundant architecture whereby one node is monitoring the processing of the 'prime' node so that in the event of a failure the backup node can assume operations of the prime, without loss of state knowledge. This paper will review and present the experiences, architecture, approach and lessons learned of the TRMM re-engineering effort centered on the GMSEC middleware architecture and tool suite. Relevant information will be presented that relates to the dual redundant parallel nature of the Telemetry and Command (T and C) and Front-End systems and how these systems can interact over a middleware bus to achieve autonomous operations including autonomous commanding to recover missing science data during the same spacecraft contact.

Marius, Julio L.↗
DOE OSTI2019

Preparation of RE(DBM){sub 3}·Phen (RE=Eu{sup 3+},Tb{sup 3+}) Plate-Loading Fe{sub 3}O{sub 4} Nanospheres and their Magnetic-Optic Bifunctional Property

A facile wet chemical method has been used to synthesize bifunctional core-shell nanoparticles of Fe{sub 3}O{sub 4}@RE(DBM){sub 3}·Phen (RE=Eu{sup 3+},Tb{sup 3+}) showing an interesting combination of magnetic and luminescent properties. This method is convenient, cheap, and efficient. The morphology, structure, luminescent, and magnetic properties of the nanoparticles were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis absorption, fluorescence emission, and superconducting quantum interference device magnetometer (SQUID-VSM). The maximum emission peaks of novel Eu{sup 3+} and Tb{sup 3+} nanocomposites are at 618 nm and at 514 nm, respectively. And their corresponding special saturation magnetization Ms. are 25.853 emu/g and 24.015 emu/g, respectively. For the nanoparticles, it is shown that there have better magnetic behavior and they may act as red- and green-emitting material with potential application for fluorescent magnetic particle testing. Moreover, this chemical route could be used to obtain the development of several bifunctional systems of other rare earth ions for practical application.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

A single-composition CaSi{sub 2}O{sub 2}N{sub 2}:RE (RE=Ce{sup 3+}/Tb{sup 3+}, Eu{sup 2+}, Mn{sup 2+}) phosphor nanofiber mat: Energy transfer, luminescence and tunable color properties

CaSi{sub 2}O{sub 2}N{sub 2}:RE (RE = Ce{sup 3+}/Tb{sup 3+}, Eu{sup 2+}, Mn{sup 2+}) phosphor nanofiber mat has been prepared via the electrospinning process and further annealing treatment. The diameter of nanofiber precursors are generally in a range of 400–600 nm, which exhibits smooth and uniform surface morphology. After removing the polymer template by high temperature treatment, the fabricated mats have been transformed into a phosphor film and maintain uniform nanofiber network microstructures. Photoluminescence (PL) properties of CaSi{sub 2}O{sub 2}N{sub 2} phosphor nanofiber mat have been activated by Ce{sup 3+}/Tb{sup 3+}, Eu{sup 2+} and Mn{sup 2+}. The emission color of CaSi{sub 2}O{sub 2}N{sub 2}:Ce{sup 3+}/Tb{sup 3+}, Eu{sup 2+}, Mn{sup 2+} phosphor mats can be adjusted by modifying the concentration of doped Tb{sup 3+}/Mn{sup 2+}/Eu{sup 2+} and the resultant energy transfer process. Owing to the energy transfer of Ce{sup 3+}-Tb{sup 3+}, the emitting color of the phosphor mat can be changed from blue to green. Meanwhile, we still found that the switching of emitting colors from blue to red and blue to yellow can be achieved via the energy transfer of Ce{sup 3+}-Mn{sup 2+} and Ce{sup 3+}-Eu{sup 2+}, respectively. We demonstrated a white light emission phosphor nanofiber mat by using CaSi{sub 2}O{sub 2}N{sub 2} system, which exhibited promising applications for near-UV WLEDs. - Graphical abstract: CIE chromaticity coordinates of CaSi{sub 2}O{sub 2}N{sub 2}:Ce{sup 3+}/Tb{sup 3+}, Eu{sup 2+}, Mn{sup 2+} samples. The lighting optical images with a drive current of 100 mA: three LEDs with nanofiber mats of CaSi{sub 2}O{sub 2}N{sub 2}: 0.02Ce{sup 3+}, 0.03Tb{sup 3+}(b), CaSi{sub 2}O{sub 2}N{sub 2}: 0.02Ce{sup 3+}, 0.01Eu{sup 2+}(c) and CaSi{sub 2}O{sub 2}N{sub 2}: 0.02Ce{sup 3+}, 0.12Mn{sup 2+}(d). Display Omitted.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Mechanism of Me–Re Bond Addition to Platinum(II) and Dioxygen Activation by the Resulting Pt–Re Bimetallic Center

Unusual cis-oxidative addition of methyltrioxorhenium (MTO) to [PtMe 2 (bpy)], (bpy = 2,2'-bipyridine) (1) is described. Addition of MTO to 1 first gives the Lewis acid–base adduct [(bpy)Me 2 Pt–Re(Me)(O) 3 ] (2) and subsequently affords the oxidative addition product [(bpy)Me 3 PtReO 3 ] (3). All complexes 1, MTO, 2, and 3 are in equilibrium in solution. The structure of 2 was confirmed by X-ray crystallography, and its dissociation constant in solution is 0.87 M. The structure of 3 was confirmed by extended X-ray absorption fine structure and X-ray absorption near-edge structure in tandem with one- and two-dimensional NMR spectroscopy augmented by deuterium and 13 C isotope-labeling studies. Kinetics of formation of compound 3 revealed saturation kinetics dependence on [MTO] and first-order in [Pt], complying with prior equilibrium formation of 2 with oxidative addition of Me–Re being the rate-determining step. Exposure of 3 to molecular oxygen or air resulted in the insertion of an oxygen atom into the platinum–rhenium bond forming [(bpy)Me 3 PtOReO 3 ] (4) as final product. In conclusion, density functional theory analysis on oxygen insertion pathways leading to complex 4, merited on the basis of Russell oxidation pathway, revealed the involvement of rhenium peroxo species.'

Pichaandi, Kothanda Rama↗
DOE OSTI2025

Efficient Self-Sensitized Photochemical CO 2 Reduction Using [Re(bpy 2+ )(CO) 3 (I)] 2+ and [Re(bpy 2+ )(CO) 3 (CH 3 CN)] 3+ Photocatalysts with Pendent Ammonium Cations

Rhenium(I) tricarbonyl complexes fac-[Re(bpy)(CO) 3 (L)]n + are the classical examples of self-sensitized photocatalysts capable of the dual roles of light absorption and catalysis. Here, in this work, a series of dicationic halido or tricationic solvento complexes fac-[Re(bpy 2+ )(CO) 3 X] n+ (PF 6 ) n (where X = Cl - or I - (n = 2), or CH 3 CN (n = 3) and bpy 2+ is bipyridine modified by two -CH 2 -(NMe3) + tetra-alkylammonium cations) have been investigated as self-sensitized and sensitized CO 2 reduction photocatalysts. Four structural isomers differing in the cation position have been tested in N,Nʹ-dimethylacetamide solvent (DMA) using 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzimidazole (BIH) as the electron donor, and the position of the cationic pendants has a significant impact on the catalyst turnover number and quantum efficiency (ϕ). Up to 455 self-sensitized turnovers of CO and a high photon efficiency (ϕ CO ) of 22% have been achieved. Time-resolved infrared spectroscopy and theoretical calculations were used to characterize the catalytic cycle including the ligand exchange between one-electron reduced (OER) halido and solvento species as well as the binding of CO 2 to the putative two-electron reduced (TER) species. The CO 2 -reactive TER catalyst was formed by disproportionation or intramolecular electron transfer between two forms of the OER catalyst as indicated by the formation of the fully oxidized catalyst concurrent with CO 2 binding. When [Ru(bpy) 3 ] 2+ was used as a sensitizer, catalyst durability improved, and the selectivity toward formate increased as high as 3.3:1 over CO (total TON = 1370) due to acidification of the reaction, which promotes formation of the hydride intermediate, as BIH was consumed and deprotonated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Chemical ordering in substituted fluorite oxides: a computational investigation of Ho 2 Zr 2 O 7 and RE 2 Th 2 O 7 (RE=Ho, Y, Gd, Nd, La)

Fluorite-structured oxides find widespread use for applications spanning nuclear energy and waste containment, energy conversion, and sensing. In such applications the host tetravalent cation is often partially substituted by trivalent cations, with an associated formation of charge-compensating oxygen vacancies. The stability and properties of such materials are known to be influenced strongly by chemical ordering of the cations and vacancies, and the nature of such ordering and associated energetics are thus of considerable interest. Here we employ density-functional theory (DFT) calculations to study the structure and energetics of cation and oxygen-vacancy ordering in Ho 2 Zr 2 O 7 . In a recent neutron total scattering study, solid solutions in this system were reported to feature local chemical ordering based on the fluorite-derivative weberite structure. The calculations show a preferred chemical ordering qualitatively consistent with these findings, and yield values for the ordering energy of 9.5 kJ/mol-cation. Similar DFT calculations are applied to additional RE 2 Th 2 O 7 '' fluorite compounds, spanning a range of values for the ratio of the tetravalent and trivalent (RE) cation radii. Finally, the results demonstrate that weberite-type order becomes destabilized with increasing values of this size ratio, consistent with an increasing energetic preference for the tetravalent cations to have higher oxygen coordination.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Synthesis, crystal structure and physical properties of the solid solutions Ca 14– x RE x CdSb 11 ( RE = La–Nd, Sm, Gd–Yb, x ≈ 0.85±0.15)

This article presents new antimonides represented with the general formula Ca 14– x RE x CdSb 11 ( RE =La–Nd, Sm, Gd–Yb, x ≈ 0.85±0.15). The 12 studied compounds constitute a nearly complete series of rare-earth metal substituted variants of the ternary Ca 14 CdSb 11 phase. All have been synthesized from the respective elements, employing high-temperature reactions under molten flux conditions. The structures have been fully characterized by single-crystal X-ray diffraction methods. All materials crystallize in the tetragonal Ca 14 AlSb 11 structure type (space group I 4 1 / acd , No. 142, Z =8). Rare-earth element atoms randomly substitute Ca atoms on the four available crystallographic sites, with a noted preference for the Ca2 site in case of the light (La–Nd) rare-earth elements and the Ca1 site in case of the heavier (Sm, Gd–Yb) ones. The electronic structure calculations and resistivity measurements indicate title compounds as degenerated semiconductors. Magnetization measurements at varied temperature show Curie-Weiss paramagnetic behavior consistent with local-moment magnetism due to the 3+ ground state for the rare-earth metal ions. In the case of the Yb-containing sample, a mixed-valence Yb 2+/3+ state is apparent. Furthermore, the measured charge transport properties suggest small bandgap degenerate semiconductor-like behavior and suitability for thermoelectrics.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Re-Side Right: A Systems Approach to High-Performance Re-Siding Projects

The objectives of this project were to test and validate the incorporation of an air barrier and 1” of continuous thermal insulation into standard re-siding jobs to create a more durable, better performing envelope as part of a retrofit project that homeowners will do anyway.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2017

RE Light Re Mix

The RE Light process is a process that recycles fluorescent lamps for their rare earth and mercury. There is a limited U.S. market for recycled rare earth materials and current rare earth prices make domestic production cost-prohibitive.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Structure and thermodynamics of calcium rare earth silicate oxyapatites, Ca 2 RE 8 (SiO 4 ) 6 O 2 (RE = Pr, Tb, Ho, Tm)

Calcium rare earth silicate oxyapatites, (Ca 2 RE 8 (SiO 4 ) 6 O 2 ), are of interest as components of glass-ceramic nuclear waste forms. To assess their long-term behavior in a geologic repository, it is essential to determine their structure and thermodynamic stability at relevant conditions. Here, in this work, we performed detailed structural and thermodynamic investigations on Ca 2 Pr 8 (SiO 4 ) 6 O 2 , Ca 2 Tb 8 (SiO 4 ) 6 O 2 , Ca 2 Ho 8 (SiO 4 ) 6 O 2 , and Ca 2 Tm 8 (SiO 4 ) 6 O 2 by high energy synchrotron powder X-ray diffraction combined with Rietveld analysis and high temperature oxide melt drop solution calorimetry. Enthalpies of formation from constituent oxides (ΔH f,ox ) were determined to be -765.1 ± 22.8 kJ/mol for Ca 2 Pr 8 (SiO 4 ) 6 O 2 ; -638.9 ± 20.5 kJ/mol for Ca 2 Tb 8 (SiO 4 ) 6 O 2 ; -643.3 ± 10.3 kJ/mol for Ca 2 Ho 8 (SiO 4 ) 6 O 2 ; and -403.2 ± 5.1 kJ/mol for Ca 2 Tm 8 (SiO 4 ) 6 O 2 . These thermodynamic parameters were used in assessing the thermochemical stability of these phases in the presence of water vapor from room temperature to 600 K, as encountered in the subsurface environments of a geological repository.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Observation of Anomalously High Seebeck Coefficients in the Family of Zintl Phase Semiconductors Ca 10 RE CdSb 9 ( RE = Rare-Earth Metal)

This work reports the synthesis, structure and thermoelectric transport properties of the hole-dominated semiconductors with a general formula Ca 10 RECdSb 9 (RE = Y, Ce, Nd, Sm, and Lu). These materials feature unexpectedly high Seebeck coeffi-cients, up to 650 µV/K at 600 K, and electrical resistivities on the order of 1–1000 mΩ·cm, which is an indication of a degen-erate semiconducting state. For example, the Seebeck coeffi-cient observed in Ca 10 NdCdSb 9 (309 µV/K at 600 K) is accom-panied by low and metallic-like electrical resistivity (6 mΩ·cm) and a carrier concentration n = 4.68×10 20 cm –3 . The calculated power factor PF in Ca 10 NdCdSb 9 is 0.88 µW/cm·K 2 at 300 K, and calculations based on the single parabolic band model indi-cate that an optimum PF opt of 1.68 μW/cm·K 2 can be achieved at that temperature for a carrier concentration n opt = 6.62 × 10 19 cm –3 . Here, the estimated thermoelectric figure of merit zT in this material, when properly tuned is expected to surpass zT = 1 at 600 K.

36 MATERIALS SCIENCE↗