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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Tritium trapping in silicon carbide in contact with solid breeder under high flux isotope reactor irradiation

The trapping of tritium in silicon carbide (SiC) injected from ceramic breeding materials was examined via tritium measurements using imaging plate (IP) techniques. Monolithic SiC in contact with ternary lithium oxide (lithium titanate and lithium aluminate) as a ceramic breeder was irradiated in the High Flux Isotope Reactor (HFIR) in Oak Ridge, Tennessee, USA. The distribution of photo-stimulated luminescence (PSL) of tritium in SiC was successfully obtained, which separated the contribution of 14C ß-rays to the PSL. The tritium incident from ceramic breeders was retained in the vicinity of the SiC surface even after irradiation at 1073 K over the duration of ~3000 h, while trapping of tritium was not observed in the bulk region. The PSL intensity near the SiC surface in contact with lithium titanate was higher than that obtained with lithium aluminate. The amount of the incident tritium and/or the formation of a Li2SiO3 phase on SiC due to the reaction with lithium aluminate under irradiation likely were responsible for this observation.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2012

Degradation of CYANEX 301 in Contact with Nitric Acid Media

The nature of the degradation product obtained upon contacting CYANEX 301 (bis(2,4,4-trimethylpentyl)dithiophosphinic acid) with nitric acid has been elucidated and found to be a disulfide derivative. The first step to the degradation of CYANEX 301 in toluene has been studied using 31P{1H} NMR after being contacted with nitric acid media. The spectrum of the degradation product exhibits a complex multiplet around dP = 80 ppm. A succession of purifications of CYANEX 301 has resulted in single crystals of the acidic form and the corresponding ammonium salt. Unlike the original CYANEX 301, which consists of a complex diastereomeric mixture displaying all possible combinations of chiral orientations at the 2-methyl positions, the purified crystals were shown by single-crystal X-ray diffraction to be racemates, containing 50:50 mixtures of the [R;R] and [S;S] diastereomers. The comparison between the 31P {1H} NMR spectra of the degradation products resulting from the diastereomerically pure CYANEX 301 and the original diastereomeric mixture has elucidated the influence of the isomeric composition on the multiplicity of the 31P {1H} NMR peak. These NMR data indicate the initial degradation leads to a disulfide-bridged condensation product displaying multiple resonances due to phosphorus–phosphorus coupling, which is caused by the inequivalence of the two P atoms as a result of their different chirality. A total of nine different NMR resonances, six of which display phosphorus–phosphorus coupling, could be assigned, and the identity of the peaks corresponding to phosphorus atoms coupled to each other was confirmed by 31P {1H} homodecoupled NMR analysis.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2012

Epitaxial Cr on n-SrTiO{sub 3}(001) - An ideal Ohmic contact

Epitaxial Cr metallizations grown on n-SrTiO{sub 3}(001) by molecular beam epitaxy are shown to result in an ordered interface with Cr bound to O in the terminal TiO{sub 2} layer, no reduction of the SrTiO{sub 3}, and a near-perfect Ohmic contact. Cr/n-SrTiO{sub 3}(001) thus constitutes an ideal interface between a pure metal and wide gap oxide in which interface redox chemistry does not occur, and the Fermi level remains unpinned.

36 MATERIALS SCIENCE↗
DOE OSTI2014

High performance TiN gate contact on AlGaN/GaN transistor using a mechanically strain induced P-doping

High performance titanium nitride sub-100 nm rectifying contact, deposited by sputtering on AlGaN/GaN high electron mobility transistors, shows a reverse leakage current as low as 38 pA/mm at V{sub GS} = −40 V and a Schottky barrier height of 0.95 eV. Based on structural characterization and 3D simulations, it is found that the polarization gradient induced by the gate metallization forms a P-type pseudo-doping region under the gate between the tensile surface and the compressively strained bulk AlGaN barrier layer. The strain induced by the gate metallization can compensate for the piezoelectric component. As a result, the gate contact can operate at temperatures as high as 700 °C and can withstand a large reverse bias of up to −100 V, which is interesting for high-performance transistors dedicated to power applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Temperature dependences of the contact resistivity in ohmic contacts to n{sup +}-InN

The temperature dependences of the contact resistivity (ρ{sub c}) of ohmic contacts based on the Au-Ti-Pd-InN system are measured at an InN doping level of 2 × 10{sup 18} cm{sup −3} in the temperature range of 4.2–300 K. At temperatures T > 150 K, linearly increasing dependences ρ{sub c}(T) are obtained. The dependences are explained within the mechanism of thermionic current flow through metal shunts associated with dislocations. Good agreement between theoretical and experimental dependences is achieved assuming that the flowing current is limited by the total resistance of the metal shunts, and the density of conductive dislocations is ∼5 × 10{sup 9} cm{sup −2}. Using the X-ray diffraction method, the density of screw and edge dislocations in the structure under study is measured: their total density exceeds 10{sup 10} cm{sup −2}.

36 MATERIALS SCIENCE↗
NASA NTRS1994

Comparison of Gap Elements and Contact Algorithm for 3D Contact Analysis of Spiral Bevel Gears

Three dimensional stress analysis of spiral bevel gears in mesh using the finite element method is presented. A finite element model is generated by solving equations that identify tooth surface coordinates. Contact is simulated by the automatic generation of nonpenetration constraints. This method is compared to a finite element contact analysis conducted with gap elements.

Bibel, G. D.↗
DOE OSTI2013

Method of forming contacts for a back-contact solar cell

Methods of forming contacts for back-contact solar cells are described. In one embodiment, a method includes forming a thin dielectric layer on a substrate, forming a polysilicon layer on the thin dielectric layer, forming and patterning a solid-state p-type dopant source on the polysilicon layer, forming an n-type dopant source layer over exposed regions of the polysilicon layer and over a plurality of regions of the solid-state p-type dopant source, and heating the substrate to provide a plurality of n-type doped polysilicon regions among a plurality of p-type doped polysilicon regions.

14 SOLAR ENERGY↗
DOE OSTI2018

Contact ion-pair structure in concentrated cesium chloride aqueous solutions: An extended X-ray absorption fine structure study

The hydration and ion pair structure of Cl- ion in aqueous cesium chloride solutions at 0.5, 6 and 11 mol/kg (H2O) has been studied using Extended X-ray Absorption Fine Structure (EXAFS) at the Cl K-edge. The co-refinement of multiple EXAFS datasets shows the hydration structure of the free Cl- ion is consistent with previously reported studies. In concentrated solution the Cl- ion is strongly associated with the cation forming contact ion pairs with 1.6 and 2.8 Cs ions in 6 and 11 mol/kg aqueous CsCl, respectively. The fact that the degree of ion pairing of Cs-Cl is higher than that of both aqueous RbCl and RbBr at the same concentration is an interesting result as it deviates from the Collins’s law of matching water affinities. The reported Cs-Cl ion-pair structure provides a basis for the development and testing of improved interaction potentials leading to more realistic structures from molecular dynamics (MD) simulations. ACKNOWLEDGEMENT VTP was supported by the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 103.99-2013.19. Work by JLF was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. The PNC/XSD facilities at the Advanced Photon Source, and research at these facilities, are supported by DOE/BES, the Canadian Light Source and its funding partners, the University of Washington, and the Advanced Photon Source. Use of the Advanced Photon Source, an Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory, was supported by the DOE under Contract No. DE-AC02-06CH11357.

Pham, Van-Thai↗