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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Studies of an artificially shock-loaded H group chondrite

SEM and TEM, together with thermoluminescence (TL), are used to study five samples of the naturally unshocked Kernouve (H6) meteorite that were shock-loaded to pressures of 70, 165, 270, and 390 kbar. Attention is given to olivine and orthopyroxene deformation mechanisms at these pressure levels. The microhardness of the kamacite in the samples increases with shock pressure, and it is noted that annealed kamacite displays incipient crystallinity, while alpha-martensite and taenite sometimes contain slip lines. At pressures over 200 kbar, there was a systematic decrease in both natural TL and TL sensitivity. Changes in the ratio of these two values for various regions of the TL glow curve suggest that two processes were effective during shock: thermal drainage of electron traps and a reduction in the effective trap density. Thermal effects with widespread annealing are noted in the case of a sample subjected to shock pulse.

Sears, D. W.↗
NASA NTRS1984

Thermoluminescence and the shock and reheating history of meteorites. II - Annealing studies of the Kernouve meteorite

Samples of the unshocked, equilibrated chondrite, Kernouve (H6), have been annealed for 1-100 hours at 500-1200 C, their thermoluminescence sensitivity measured and Na, K, Mn, Ca, and Sc determined by instrumental neutron activation analysis. The TL sensitivity decreased with temperature until by 1000 C it had fallen by 40 percent. The process responsible has an activation energy of 8 kcal/mole and probably involves diffusion. Samples annealed 1000-1200 C had TL sensitivities 0.01 times the unannealed values, most of the decrease occurring at 1100 C. This process has an activation energy of 100 kcal/mole and is probably related to the melting of the TL phosphor, feldspar, with some decomposition and loss of Cs, Na and K. Meteorites whose petrography indicates heating above 1100 C by natural shock heating events (shock facies d-f), have TL sensitivities similar to samples annealed above 1100 C.

Sears, D. W. G.↗
NASA NTRS1986

Chemical and physical studies of type 3 chondrites. VII - Annealing studies of the Dhajala H3.8 chondrite and the thermal history of chondrules and chondrites

Samples of the Dhajala meteorite were annealed at 600-1000 C for 1, 2, 10, 20 and 100 h and their thermoluminescence (TL) properties were measured. After annealing at less than 900 deg, the TL sensitivity decreased by a factor of two; at higher temperatures, it fell by an order of magnitude. Data indicate that the annealing treatment caused the low-temperature feldspar in Dhajala to be converted to feldspar of a high-temperature (disordered) form. Low-temperature feldspar was found in the meteorite's TL-sensitive chondrules which comprised about 20 percent of those separated. It is suggested that these chondrules suffered greater crystallization of their mesostasis than the other chondrules, and equilibrated to lower temperatures. Based on TL data, there appears to be no relationship between post-metamorphic cooling rate and petrologic type for the 3.5-3.9 chondrites.

Keck, B. D.↗
NASA NTRS1986

A thermoluminescence study of experimentally shock-loaded oligoclase and bytownite

The thermoluminescence (TL) properties of a terrestrial oligoclase and a bytownite shock-loaded to pressures of 10.5-45 GPa are measured. Glow curves and TL sensitivity levels for the oligoclase and bytownite samples are presented and analyzed; it is detected that shock causes a decrease in the TL sensitivity and changes the shape of the glow curve. The causes of the decrease in TL sensitivity and peak temperature and width variations are examined. Shock-induced disordering of the Al, Si chain, and ordinary chondrite shocks are studied.

Hartmetz, Christopher P.↗
NASA NTRS1991

Chemical and physical studies of type 3 chondrites. XI - Metamorphism, pairing, and brecciation of ordinary chondrites

The present study reports recent measurements of the induced thermoluminescence (TL) properties of 69 type-3 ordinary chondrites, bringing to 125 the number of type-3 ordinary chondrites for which TL data are available. The samples include several of the particularly low petrographic type and many breccias, some of them gas-rich. The significance of the data with respect to the physical conditions affecting metamorphism is discussed. The TL data, olivine heterogeneity, carbon content, and inert-gas content were used to assign the samples to petrologic types. Twelve meteorites were identified as being type 3.0-3.2, and 10 of the breccias were found to contain material that may also be of this type. The temperature and width of the induced TL peak are also related to thermal history, with type 3.2-3.4 chondrites tending to have narrower peaks at lower glow curve temperatures than the type 3.6-3.9 chondrites. Type 3 H chondrites were found to be a higher petrographic type than the type 3 L and LL chondrites.

Sears, D. W. G.↗
NASA NTRS1992

Observation of alloy solidification using high-speed video

A high-speed video instrumentation system was used to observe solidification of undercooled Ti-51 at. pct Al. The camera system developed by Battelle is capable of operation at rates up to 12,000 frames per second. The system digitizes and stores video images acquired by a 64 x 64 pixel silicon photodiode array. In a joint effort with Vanderbilt University the camera was used to observe three transformations of the undercooled alloys, using containerless processing by electromagnetic levitation. The first was solidification where nucleation was induced at an undercooling of 9 percent Tl, where Tl is the liquidus temperature of the alloy, and the second was solidification where nucleation was spontaneous at an undercooling of 15 percent Tl. The third event was a solid-state nucleation and growth transformation following the solidification at an undercooling of 15 percent Tl.

Bassler, B. T.↗
NASA NTRS1994

The natural thermoluminescence of meteorites. 7: Ordinary chondrites from the Elephant Moraine region, Antarctica

We report natural and induced thermoluminescence (TL) measurements for meteorites from the Elephant Moraine region (76 deg 17 min S, 157 deg 20 min E) of Antarctica. We use our data to identify fragmented meteorites (i.e., 'pairings'); our dataset of 107 samples represents at most 73 separate meteorite falls. Pairing groups are generally confined to single icefields, or to adjacent icefields, but a small proportion cross widely separated icefields in the region, suggesting that the fields can be considered as a single unit. Meteorites from this region have high natural TL levels, which indicates that they have small terrestrial surface exposure ages (less than 12,500 years). There do not appear to be significant differences in natural TL levels (and hence surface exposure ages) between individual blue icefields in the region. The proportion of reheated meteorites from the Elephant Moraine region is similar to that of other Antarctic sites and modern falls, consistent with the uniformity of the meteoritic flux in this regard. An unusual subset of H-chondrites, with high induced TL peak temperatures, is absent among the data for meteorites collected in the Elephant Moraine region, which stresses their similarity to modern falls. We suggest that the Elephant Moraine region, which stresses their similarity to modern falls. We suggest that the Elephant Moraine icefields formed through shallow ablation of the ice. Unlike the Allan Hills sites to the south, lateral transport is probably less important relative to the infall of meteorites in concentrating meteorites on these icefields.

Benoit, P. H.↗
NASA NTRS1996

The Thermal and Radiation Exposure History of Lunar Meteorites

We have measured the natural and induced thermoluminescence (TL) of seven lunar meteorites in order to examine their crystallization, irradiation, and recent thermal histories. Lunar meteorites have induced TL properties similar to Apollo samples of the same provenance (highland or mare), indicating similar crystallization and metamorphic histories. MacAlplne Hills 88104/5 has experienced the greatest degree of impact/regolith processing among the highland-dominated meteorites. The basaltic breccia QUE 94281 is dominated by mare component but may also contain a significant highland component. For the mare-dominated meteorites, EET 87521 may have a significant highland impact-melt component, while Asuka 881757 and Y-793169 have been heavily shocked. The thermal history of Y-793169 included slow cooling, either during impact processing or during its initial crystallization. Our natural TL data indicate that most lunar meteorites have apparently been irradiated in space a few thousand years, with most less than 15,000 a. Elephant Moraine 87521 has the lowest irradiation exposure time, being less than 1,000 a. Either the natural TL of ALHA81005, Asuka 881757 and Y-82192 was only partially reset by lunar ejection or these meteorites were in small perihelia orbits (less than or equal to 0.7 AU).

Benoit, Paul H.↗
NASA NTRS2015

Acoustically Tailored Composite Rotorcraft Fuselage Panels

A rotorcraft roof sandwich panel has been redesigned to optimize sound power transmission loss (TL) and minimize structure-borne sound for frequencies between 1 and 4 kHz where gear meshing noise from the transmission has the most impact on speech intelligibility. The roof section, framed by a grid of ribs, was originally constructed of a single honeycomb core/composite face sheet panel. The original panel has coincidence frequencies near 700 Hz, leading to poor TL across the frequency range of 1 to 4 kHz. To quiet the panel, the cross section was split into two thinner sandwich subpanels separated by an air gap. The air gap was sized to target the fundamental mass-spring-mass resonance of the double panel system to less than 500 Hz. The panels were designed to withstand structural loading from normal rotorcraft operation, as well as 'man-on-the-roof' static loads experienced during maintenance operations. Thin layers of VHB 9469 viscoelastomer from 3M were also included in the face sheet ply layups, increasing panel damping loss factors from about 0.01 to 0.05. Measurements in the NASA SALT facility show the optimized panel provides 6-11 dB of acoustic transmission loss improvement, and 6-15 dB of structure-borne sound reduction at critical rotorcraft transmission tonal frequencies. Analytic panel TL theory simulates the measured performance quite well. Detailed finite element/boundary element modeling of the baseline panel simulates TL slightly more accurately, and also simulates structure-borne sound well.

Hambric, Stephen↗
NASA NTRSDate not supplied

Development of Acoustic Mufflers for Cabin Noise Reduction in Orion Spacecraft

Controlling cabin acoustic noise levels in the Crew Module (CM) of the Orion spacecraft is critical to ensure adequate speech intelligibility, to avoid fatigue, and prevent any possibility of temporary and permanent hearing loss to the crew. The primary source of cabin noise for the on-orbit phase of the mission is from the Environmental Control and Life Support System (ECLSS) which recycles and conditions breathing air and maintains cabin pressurization through its duct network and components. Unfortunately, as a side effect, noise from the ECLSS fans propagates through theses ducts and emanate into the cabin habitable volume via the ECLSS inlet and outlets. To mitigate excessive duct-borne noise, two ECLSS mufflers have been designed to provide significant acoustic transmission loss (TL) so that the cabin noise requirements can be met. Each muffler is meant to be installed in the ducting of the ECLSS air inlet and outlet sides, respectively. Packaging constraints and tight volume requirements necessitated the mufflers to be of complex geometry and compatible with the bends of the ECLSS duct layout. To design and characterize the acoustic performance of the inlet and outlet mufflers, computational acoustic models were developed using the Finite Element Method (FEM) with 𝑤𝑎𝑣𝑒଺ vibroacoustic software. Characterization of the acoustic material and perforations in the mufflers were addressed with poroelastic theory. Once the mufflers were designed on paper and its TL predicted, prototypes of these mufflers were created using additive manufacturing. The muffler prototypes were subsequently tested for acoustic TL in the laboratory with various con-figurations of acoustic materials. Comparing the analytical predictions to the test performance yielded excellent correlation for acoustic TL and demonstrated significant broadband noise attenuation. The ECLSS mufflers are currently scheduled to be installed on the Artemis II Crew Module (CM) of the Orion spacecraft and will provide significant cabin comfort to crew during the mission.

Indranil Dandaroy↗
DOE OSTI2020

Materials Data on Sc3TlB by Materials Project

Sc3TlB is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Sc is bonded in a linear geometry to four equivalent Tl and two equivalent B atoms. All Sc–Tl bond lengths are 3.32 Å. Both Sc–B bond lengths are 2.35 Å. Tl is bonded to twelve equivalent Sc atoms to form TlSc12 cuboctahedra that share corners with twelve equivalent TlSc12 cuboctahedra, faces with six equivalent TlSc12 cuboctahedra, and faces with eight equivalent BSc6 octahedra. B is bonded to six equivalent Sc atoms to form BSc6 octahedra that share corners with six equivalent BSc6 octahedra and faces with eight equivalent TlSc12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ErTl by Materials Project

ErTl is Tetraauricupride structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Er is bonded in a distorted body-centered cubic geometry to eight equivalent Tl atoms. All Er–Tl bond lengths are 3.29 Å. Tl is bonded in a distorted body-centered cubic geometry to eight equivalent Er atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca3TlN by Materials Project

TlNCa3 is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ca is bonded in a linear geometry to four equivalent Tl and two equivalent N atoms. All Ca–Tl bond lengths are 3.50 Å. Both Ca–N bond lengths are 2.48 Å. Tl is bonded to twelve equivalent Ca atoms to form TlCa12 cuboctahedra that share corners with twelve equivalent TlCa12 cuboctahedra, faces with six equivalent TlCa12 cuboctahedra, and faces with eight equivalent NCa6 octahedra. N is bonded to six equivalent Ca atoms to form NCa6 octahedra that share corners with six equivalent NCa6 octahedra and faces with eight equivalent TlCa12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm3TlC by Materials Project

Sm3TlC is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Sm is bonded in a linear geometry to four equivalent Tl and two equivalent C atoms. All Sm–Tl bond lengths are 3.58 Å. Both Sm–C bond lengths are 2.53 Å. Tl is bonded to twelve equivalent Sm atoms to form TlSm12 cuboctahedra that share corners with twelve equivalent TlSm12 cuboctahedra, faces with six equivalent TlSm12 cuboctahedra, and faces with eight equivalent CSm6 octahedra. C is bonded to six equivalent Sm atoms to form CSm6 octahedra that share corners with six equivalent CSm6 octahedra and faces with eight equivalent TlSm12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu3TlC by Materials Project

Lu3TlC is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Lu is bonded in a linear geometry to four equivalent Tl and two equivalent C atoms. All Lu–Tl bond lengths are 3.38 Å. Both Lu–C bond lengths are 2.39 Å. Tl is bonded to twelve equivalent Lu atoms to form TlLu12 cuboctahedra that share corners with twelve equivalent TlLu12 cuboctahedra, faces with six equivalent TlLu12 cuboctahedra, and faces with eight equivalent CLu6 octahedra. C is bonded to six equivalent Lu atoms to form CLu6 octahedra that share corners with six equivalent CLu6 octahedra and faces with eight equivalent TlLu12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on DyTl by Materials Project

DyTl is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Dy is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Dy–Tl bond lengths are 3.29 Å. Tl is bonded in a body-centered cubic geometry to eight equivalent Dy atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TlHg3 by Materials Project

Hg3Tl is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Hg is bonded in a square co-planar geometry to four equivalent Tl atoms. All Hg–Tl bond lengths are 3.45 Å. Tl is bonded to twelve equivalent Hg atoms to form a mixture of corner and face-sharing TlHg12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LaTl by Materials Project

LaTl is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. La is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All La–Tl bond lengths are 3.46 Å. Tl is bonded in a body-centered cubic geometry to eight equivalent La atoms.

36 MATERIALS SCIENCE↗