Effect of band structure on the Ruderman- Kittel-Kasuya-Yosida interaction in the heavy rare earths
Rare earth energy band structure effect on RKKY magnetic interaction between atomic spins
Bambakidis, G.↗
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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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Multilayer Thermal Barrier Coating (TBC) Architectures Utilizing Rare Earth Doped YSZ and Rare Earth Pyrochlores
To allow for increased gas turbine efficiencies, new insulating thermal barrier coatings (TBCs) must be developed to protect the underlying metallic components from higher operating temperatures. This work focused on using rare earth doped (Yb and Gd) yttria stabilized zirconia (t' Low-k) and Gd2Zr2O7 pyrochlores (GZO) combined with novel nanolayered and thick layered microstructures to enable operation beyond the 1200 C stability limit of current 7 wt% yttria stabilized zirconia (7YSZ) coatings. It was observed that the layered system can reduce the thermal conductivity by approximately 45 percent with respect to YSZ after 20 hr of testing at 1316 C. The erosion rate of GZO is shown to be an order to magnitude higher than YSZ and t' Low-k, but this can be reduced by almost 57 percent when utilizing a nanolayered structure. Lastly, the thermal instability of the layered system is investigated and thought is given to optimization of layer thickness.
Thermal Barrier Coating↗
Rare Earth elements in individual minerals in Shergottites
Shergottites (i.e., Shergotty, Zagami, EETA79001, ALHA77005, and LEW88516) are an important set of achondrites because they comprise the majority of the SNC group of meteorites (nine, in total, known to us), which are likely to be samples of the planet Mars. Study of these meteorites may therefore provide valuable information about petrogenetic processes on a large planetary body other than Earth. Rare earth element (REE) distributions between various mineral phases were found to be useful in geochemically modeling the petrogenesis of various rock types (terrestrial and meteoritic). However, with the exception of a few ion microprobe studies and analyses of mineral separates, there has previously not been any comprehensive effort to characterize and directly compare REE in individual minerals in each of the five known shergottites. Ion microprobe analyses were made on thin sections of each of the shergottites. Minerals analyzed were pyroxenes (pigeonite and augite), maskelynite, and whitlockite. The REE concentrations in each mineral type in each shergottite is given.
Wadhwa, Meenakshi↗
Investigation of rare earth ions - Spectroscopic relaxation processes of rare earth ions in crystals Final report, 1 Mar. - 31 Jul. 1969
Relaxation effects of rare earth ions in crystals
Moos, H. W.↗
Alkali, alkaline earth, and rare-earth element concentrations in some Apollo 12 soils, rocks, and separated phases
Apollo 12 lunar soils, rocks and core samples, determining rare earth, alkali and alkaline earth elements concentrations
Philpotts, J. A.↗
Thermal Expansion and Thermal Conductivity of Rare Earth Silicates
Rare earth silicates are considered promising candidate materials for environmental barrier coatings applications at elevated temperature for ceramic matrix composites. High temperature thermophysical properties are of great importance for coating system design and development. In this study, the thermal expansion and thermal conductivity of hot-pressed rare earth silicate materials were characterized at temperatures up to 1400 C. The effects of specimen porosity, composition and microstructure on the properties were also investigated. The materials processing and testing issues affecting the measurements will also be discussed.
Zhu, Dongming↗
Meteoritic, solar, and terrestrial rare-earth distribution
Rare earth element distributions in meteoritic, solar, and terrestrial matter
METEORITIC COMPOSITION↗
Correlation of molecular structure with fluorescence spectra in rare earth chelates. I.
Rare earth chelates fluorescence spectra correlation with molecular structure, analyzing emission spectrum internal Stark splitting of tetramethylammonium tetrakis /dibenzoylmethido/europate microcrystals
Bjorklund, S.↗
Partitioning of rare earth elements between hibonite and melt and implications for nebular condensation of the rare earth elements
The effect of oxygen fugacity on the partitioning of REEs between hibonite and silicate melt is investigated in hibonite-growth experiments at 1470 C. The experimental procedures and apparatus are described, and the results are presented in extensive tables and graphs and characterized in detail. The absolute activity coefficients in hibonite are estimated as 330 for La, 1200 for Eu(3+), and 24,000 for Yb. It is inferred that ideal solution behavior cannot be assumed when calculating REE condensation temperatures for (Ca, Al)-rich inclusions in carbonaceous chondrites.
Drake, Michael J.↗
Selective Emitter Pumped Rare Earth Laser
A selective emitter pumped rare earth laser provides an additional type of laser for use in many laser applications. Rare earth doped lasers exist which are pumped with flashtubes or laser diodes. The invention uses a rare earth emitter to transform thermal energy input to a spectral band matching the absorption band of a rare earth in the laser in order to produce lasing.
Chubb, Donald L.↗
High temperature rare earth solid lubricants
Rare earth trifluorides have potential use as lubricating fillers for mechanical carbons and as coatings on metallic substrates. Friction experiments show that they are effective in reducing metallic wear.
Sliney, H. E.↗
Thermoelectric properties of rare earth chalcogenides
The rare earth chalcogenides are important thermoelectric materials due to their high melting points, self-doping capabilities, and low thermal conductivities. Lanthanum sulfides and lanthanum tellurides have been synthesized in quartz ampules, hot-pressed into samples, and measured. The n-type Seebeck coefficients, electrical resistivities, and power factors generally all increased as the temperature increased from 200 to 1000 C. The figure-of-merit for nonstoichiometric lanthanum telluride was 0.001/deg C at 1000 C, considerably higher than for silicon-germanium. Thermoelectric measurements were made for LaTe(2) and YbS(1.4), and p-type behavior was observed for these compounds from 300 to 1100 C.
Danielson, L. R.↗
Anomalous Hall Effect in a Feromagnetic Rare-Earth Cobalite
Rare-Earth manganites and cobalites with the perovskite structure have been a subject of great recent interest because their electrical resistance changes significantly when a magnetic field is applied...we have studied the Hall effect in thin film La(sub 0.5)Ca(sub 0.5)CoO(sub 3) material and have obtained convincing evidence fo the so called anomalous Hall effect, typical for magnetic metals...Our results suggest that near the ferromagnetic ordering temperature, the dominant electron scattering mechanism is the spin fluctuation.
manganites cobalites perovskite structures magneti↗
Dynamical properties of some rare earth- intermeallic compounds
Dynamic properties of rare earth intermetallic compounds - large J second half rare earth
DYNAMIC PROPERTY↗
Rare Earth Optical Temperature Sensor
A rare earth optical temperature sensor is disclosed for measuring high temperatures. Optical temperature sensors exist that channel emissions from a sensor to a detector using a light pipe. The invention uses a rare earth emitter to transform the sensed thermal energy into a narrow band width optical signal that travels to a detector using a light pipe. An optical bandpass filter at the detector removes any noise signal outside of the band width of the signal from the emitter.
Donald L Chubb↗
Condensation and fractionation of rare earths in the solar nebula
The condensation behavior of the rare earth elements in the solar nebula is calculated on the basis of the most recent thermodynamic data in order to construct a model explaining group II rare earth element patterns in Allende inclusions. Models considered all involve the removal of large fractions of the more refractory heavy rare earth elements in an early condensate, followed by the condensation of the remainder at a lower temperature. It is shown that the model of Boynton (1975) in which one rare earth element component is dissolved nonideally in perovskite according to relative activity coefficients can not reasonably be made to fit the observed group II patterns. A model in which two rare earth components control the patterns and dissolve ideally in perovskite is proposed and shown to be able to account for the 20 patterns by variations of the perovskite removal temperature and the relative proportions of the two components.
Davis, A. M.↗
The Development of HfO2-Rare Earth Based Oxide Materials and Barrier Coatings for Thermal Protection Systems
Advanced hafnia-rare earth oxides, rare earth aluminates and silicates have been developed for thermal environmental barrier systems for aerospace propulsion engine and thermal protection applications. The high temperature stability, low thermal conductivity, excellent oxidation resistance and mechanical properties of these oxide material systems make them attractive and potentially viable for thermal protection systems. This paper will focus on the development of the high performance and high temperature capable ZrO2HfO2-rare earth based alloy and compound oxide materials, processed as protective coating systems using state-or-the-art processing techniques. The emphasis has been in particular placed on assessing their temperature capability, stability and suitability for advanced space vehicle entry thermal protection systems. Fundamental thermophysical and thermomechanical properties of the material systems have been investigated at high temperatures. Laser high-heat-flux testing has also been developed to validate the material systems, and demonstrating durability under space entry high heat flux conditions.
Ceramic Matrix Composites↗
Thermochemistry of Rare Earth Silicates for Environmental Barrier Coatings
Rare earth silicates are promising candidates as environmental protective coatings (EBCs) for silica-forming ceramics and composites in combustion environments since they are predicted to have lower reactivity with the water vapor combustion products. The reactivity of rare earth silicates is assessed by the thermodynamic activity of the silica component which is best measured by Knudsen effusion mass spectrometry (KEMS). Here, we discuss a novel method based on a reducing agent to increase the partial pressure of SiO(g) which is then used to calculate thermodynamic activity of silica in Y2O3-SiO2 and Yb2O3-SiO2 systems. After the KEMS measurements, samples were probed by X-ray diffraction and their phase content was calculated from Rietveld refinement.
Rare Earth Silicates↗