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Results for “Er-Ho”

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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6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Radiative Performance of Rare Earth Garnet Thin Film Selective Emitters

In this paper we present the first emitter efficiency results for the thin film 40 percent Er-1.5 percent Ho YAG (Yttrium Aluminum Garnet, Y3Al5O12) and 25 percent Ho YAG selective emitter at 1500 K with a platinum substrate. Spectral emittance and emissive power measurements were made (1.2 less than lambda less than 3.2 microns). Emitter efficiency and power density are significantly improved with the addition of multiple rare earth dopants. Predicted efficiency results are presented for an optimized (equal power density in the Er, (4)I(sub 15/2)-(4)I(sub 13/2) at 1.5 microns, and Ho, (5)I(sub 7)-(5)I(sub 8) at 2.0 micron emission bands) Er-Ho YAG thin film selective emitter.

Lowe, Roland A.↗
DOE OSTI2020

Materials Data on Ho3Er by Materials Project

ErHo3 is Magnesium-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Er is bonded to twelve equivalent Ho atoms to form ErHo12 cuboctahedra that share corners with six equivalent ErHo12 cuboctahedra, corners with twelve equivalent HoHo8Er4 cuboctahedra, edges with eighteen equivalent HoHo8Er4 cuboctahedra, faces with eight equivalent ErHo12 cuboctahedra, and faces with twelve equivalent HoHo8Er4 cuboctahedra. There are six shorter (3.49 Å) and six longer (3.59 Å) Er–Ho bond lengths. Ho is bonded to four equivalent Er and eight equivalent Ho atoms to form HoHo8Er4 cuboctahedra that share corners with four equivalent ErHo12 cuboctahedra, corners with fourteen equivalent HoHo8Er4 cuboctahedra, edges with six equivalent ErHo12 cuboctahedra, edges with twelve equivalent HoHo8Er4 cuboctahedra, faces with four equivalent ErHo12 cuboctahedra, and faces with sixteen equivalent HoHo8Er4 cuboctahedra. There are four shorter (3.49 Å) and four longer (3.59 Å) Ho–Ho bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoEr by Materials Project

ErHo is Magnesium-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Er is bonded to six equivalent Er and six equivalent Ho atoms to form ErHo6Er6 cuboctahedra that share corners with eighteen equivalent ErHo6Er6 cuboctahedra, edges with six equivalent ErHo6Er6 cuboctahedra, edges with twelve equivalent HoHo6Er6 cuboctahedra, faces with eight equivalent ErHo6Er6 cuboctahedra, and faces with twelve equivalent HoHo6Er6 cuboctahedra. All Er–Er bond lengths are 3.57 Å. All Er–Ho bond lengths are 3.51 Å. Ho is bonded to six equivalent Er and six equivalent Ho atoms to form HoHo6Er6 cuboctahedra that share corners with eighteen equivalent HoHo6Er6 cuboctahedra, edges with six equivalent HoHo6Er6 cuboctahedra, edges with twelve equivalent ErHo6Er6 cuboctahedra, faces with eight equivalent HoHo6Er6 cuboctahedra, and faces with twelve equivalent ErHo6Er6 cuboctahedra. All Ho–Ho bond lengths are 3.57 Å.

36 MATERIALS SCIENCE↗
NASA NTRS1990

A search for eclipses of HD 114762 by a low-mass companion

HD 114762 has an unseen companion with a dynamical mass that satisfies the constraint mass sin i = 2.5 x 10 to the 31st gm. The companion is a good candidate for a planetary-mass object, but the inclination of its orbit is unknown and its mass is indeterminate. Tests were conducted for the specific case of a nearly edge-on orbit by looking for eclipses of HD 114762 by the companion. Although the a priori probability of an eclipse is low, this is a crucial case because the companion has its minimum mass if the orbit is edge on. No eclipses were found with a depth greater than 0.01 mag and, therefore, the inclination of the orbit of HD 114762 is less than 89 deg.

Robinson, Edward L.↗
NASA NTRS1993

HW Virginis - A short period eclipsing binary containing an sdB star

Simultaneous photometry of the binary star HW Vir, a detached system with an orbital period of 2 h 48 min is described. The new UBVR light curves obtained using the Wilson-Devinney code are found to constrain the orbital inclination of the system within the narrow range of 80.6 +/-0.2 deg. The temperature of the primary star is between 29,000 and 36,000 K, and the temperature of the secondary star is near 3,700 K. The possible masses and radii of the two stars are calculated using the published amplitude of the radial velocity curve of the primary star, 87.9 +/-4.8 km/s. It is found that, for the primary star log g1 is greater than 4.8 and less than or equal to 5.8. From the temperature and gravity of the primary star, its distance is found to be in the range between 42 and 151 pc. It is suggested that the system will begin mass transfer when the orbital period has decreased enough to bring the secondary star into contact with its Roche lobe.

Wood, Janet H.↗
NASA NTRS1994

The ultraviolet pulsations of the cataclysmic variable AE Aquarii as observed with the Hubble Space Telescope

We present the results of high time resolution UV spectroscopy and simultaneous high-speed UBVR photometry of AE Aqr. The UV spectra were obtained with the Faint Object Spectrograph aboard the Hubble Space Telescope (HST), and the photometry was carried out with the 82 sec telescope at McDonald Observatory. Our study focuses on the coherent 33 sceond oscillations, whose amplitude is found to be very large in the UV (40% of the mean quiescent level). The mean pulse profile has two broad unequal peaks spaced by half an oscillation cycle. The pulse profiles in the UV and optical bands appear quite similar in shape, with no discernible shifts. The orbital delay curve of the UV pulses establishes the white dwarf as their origin. The (UV+optical) spectrum of the pulsations is well described by a white dwarf atmosphere model with a temperature of about 26,000 K. We find no oscillations in the UV emission-line fluxes, nor in their velocities, down to a limit of 800 km/s. Based on the properties of the UV and optical pulsations we suggest that they originate in the X-ray heated magnetic polar caps of the white dwarf. Under this assumption we produce maximum entropy maps of the brightness distribution of the white dwarf surface. Using this model we are able to reproduce the observed mean pulse profile and interpret fluctuations in the oscillation amplitude as small fluctuations in the accretion rate. We find that the amplitudes and profiles of the pulses are not strongly affectd by the large aperiodic flares exhibited by the system. This suggests that the large flares are not related to the process of depositing material onto the white dwarf and argues against models that place their origin at the white dwarf magnetosphere.

Eracleous, Michael↗