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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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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Measurement of detonation temperature of hydrogen-oxygen mixture by CARS (Coherent Anti-Stokes Raman Spectroscopy)

It was confirmed that CARS is very useful as a temperature measurement method of detonation. By revising the detecting system so that a lot of information can be handled simultaneously like an optical multi-channel analyzer, it is possible to obtain information concerning the detailed three dimensional structure of detonation which has never been obtained.

Tezaki, Atsumu↗
NASA NTRS1988

The use of four-photon Raman spectroscopy for the remote sensing of natural objects

The results of the laboratory simulation of optical Kerr effect/Raman spectroscopy for the purpose of remote sensing are presented. The experimental setup is described, and measurements of the vibrational spectra of various liquids obtained. Attention is paid to the possibility of using the proposed method to detect trace hydrocarbons in water, and the spectrum of petroleum is obtained. Full-scale measurements using a laser spectrometer were made on the Black Sea.

Bunkin, A. F.↗
NASA NTRS1987

Amorphous silicon deposition diagnostics using coherent anti-Stokes Raman spectroscopy

This paper reports on an in situ silicon deposition process diagnostics, using CARS performed at state-of-the-art a-Si:H film deposition conditions in a reactor designed for a-Si:H solar cell fabrication. The diagnostics procedure measures the silane depletion in an RF plasma as a function of the silane flow rate (where the relationship is linear between 50-percent depletion, at a flow rate of 5.6 sccm, and about 8-percent depletion, at 80 sccm) and the RF power (where the silane depletion is linearly dependent on the RF power in the region of 4 to 12 W). The linear RF power dependence of the silane depletion is considered to be consistent with the mechanism of silane decomposition primarily by electron impact dissociations, while the flow rate dependence is interpreted in terms of the residence time of the SiH4 molecules in the glow discharge region, where an increase of the residence time at a low flow rate results in a high depletion ratio.

Shing, Y. H.↗
NASA NTRS2004

Petrology and Raman Spectroscopy of Shocked Phases in the Gujba CB Chondrite and the Shock History of the CB Parent Body

The CB chondrites are metal-rich chondritic meteorites having characteristics that sharply distinguish them from other chondrites [1], including (1) high metal abundances (60-80 vol.% metal), (2) most chondrules have cryptocrystalline or barred textures, (3) moderately volatile lithophile elements are highly depleted and (4) nitrogen is enriched in the heavy isotope. Similarities in mineral composition, as well as oxygen and nitrogen isotopic compositions of the CB to CR and CH chondrites are consistent with derivation of these chondrite groups from a common nebular reservoir, hence their grouping in the CR clan [1, 2, 3, 4]. CB chondrites have been divided into CBa (Gujba, Bencubbin, Weatherford) and CBb (Hammadah al Hamra 237 and QUE 94411) subgroups based on petrologic characteristics.

Weisberg, M. K.↗
NASA NTRSDate not supplied

Potential Discovery of Amphibole in Miller Range (MIL) 090292 via Raman Spectroscopy

Ungrouped carbonaceous chondrites have the potential to provide insights into processes on their parent bodies that may not be accessible through studying established groups. Miller Range (MIL) 090292 is an extensively aqueously altered ungrouped carbonaceous chondrite, which provides the potential to reveal new information about alteration processes on carbonaceous chondrite-like asteroids. The meteorite MIL090292 was initially classified as a CR1 chondrite. It experienced heavy aqueous alteration and, texturally, the meteorite is highly brecciated. MIL 090292 was reclassified as a C1 ungrouped chondrite after it was found that the Δ17O values of its magnetite grains do not plot along the CR mixing line. Furthermore, there is a lack of calcium carbonate grains in the sample, which are common in aqueously altered CRs –calcium is found in andradite and hedenbergite (which are not found in CRs) and phosphates. However, beyond this basic mineralogical information, there is a lack of knowledge about the petrogenetic history of the meteorite or its parent body.

Meteorite↗
DOE OSTI2023

Synthesis and Thermal Oxidation Resistance of Boron-Rich Boron–Carbide Material

A boron-rich boron–carbide material (B4+δC) was synthesized by spark plasma sintering of a ball-milled mixture of high-purity boron powder and graphitic carbon at a pressure of 7 MPa and a temperature of 1930 °C. This high-pressure, high-temperature synthesized material was recovered and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Vickers hardness measurements, and thermal oxidation studies. The X-ray diffraction studies revealed a single-phase rhombohedral structure (space group R-3m) with lattice parameters in hexagonal representation as a = 5.609 ± 0.007 Å and c = 12.082 ± 0.02 Å. The experimental lattice parameters result in a value of δ = 0.55, or the composition of the synthesized compound as B4.55C. The high-resolution scans of boron binding energy reveal the existence of a B-C bond at 188.5 eV. Raman spectroscopy reveals the existence of a 386 cm−1 vibrational mode representative of C-B-B linear chain formation due to excess boron in the lattice. The measured Vickers microhardness at a load of 200 gf shows a high hardness value of 33.8 ± 2.3 GPa. Thermal gravimetric studies on B4.55C were conducted at a temperature of 1300 °C in a compressed dry air environment, and its behavior is compared to other high-temperature ceramic materials such as high-entropy transition metal boride. The high neutron absorption cross section, high melting point, high mechanical strength, and thermal oxidation resistance make this material ideal for applications in extreme environments.

36 MATERIALS SCIENCE↗