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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Vapor-Liquid Partitioning of Methylmercury Compounds: Fundamental Data to Support the Savannah River Site Liquid Waste System: Henry's Law, Solubility and Vapor Pressure Determination for Representative Methylmercury Compounds

The Savannah River Site (SRS) Liquid Waste System (LWS) contains approximately 66 tons of mercury within the liquids, salts, and sludges that are currently being processed into final wasteforms for disposal. Mercury concentrations within the system exceed those typically experienced in environmental or industrial systems; thus, management of mercury compounds continues to be a priority for SRS. In the LWS, waste is vitrified into a borosilicate glass wasteform that contains most of the radioactivity, while the lower activity solutions are dispositioned in a low-level grout wasteform, or “saltstone”. The alkaline, high ionic strength caustic wastes are pumped, evaporated, and otherwise managed throughout the LWS and Defense Waste Processing Facility (DWPF) as they are stored and prepared for conversion to the final wasteforms. Because of the complexity of this system, a key component of effective mercury management in the LWS requires analysis of mercury in various physical phases. The high concentration of mercury within the SRS LWS has the potential to generate vapor-phase contamination. Elemental mercury (Hg 0 ), dimethylmercury ((CH 3 ) 2 Hg), and methylmercury (CH 3 Hg + ) are among species known or suspected to contribute to the flux of mercury from liquid to vapor phase (Iverfeldt and Lindquist, 1982). Chemical speciation affects not only mercury behavior in LWS operations but may also affect the performance of mercury treatment and removal technologies in the LWS.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Vapor and Liquid ( p –ρ– T–x ) Measurements of Binary Refrigerant Blends Containing R-32, R-152a, R-227ea, R-1234yf, and R-1234ze(E)

In this article, The pressure–density–temperature–composition (p–ρ–T–x) data of binary refrigerant mixtures containing R-32 (difluoromethane), R-152a (1,1,-difluoroethane), R-227ea (1,1,1,2,3,3,3-heptafluoropropane), R-1234yf (2,3,3,3-tetrafluoropropene), and R-1234ze(E) (trans-1,3,3,3-tetrafluoropropene) were measured in both the vapor and liquid phases using a two-sinker, magnetic suspension densimeter. The specific samples in this study comprised two compositions of approximately (0.3/0.7) and (0.7/0.3) mole fraction for each of the following four binary refrigerant blends: R-32 + R-1234yf, R-32 + R-1234ze(E), R-1234yf + R-152a, and R-1234ze(E) + R-227ea. Single-phase vapor densities were measured over a temperature range of approximately 253 to 293 K and pressures from 0.05 to 0.98 MPa. Single-phase liquid and supercritical densities were measured over a temperature range of approximately 230 to 400 K and pressures up to 22 MPa; for refrigerant blends containing R-1234yf, the maximum pressure was limited to 14 MPa. Overall relative combined, expanded (k = 2) uncertainties in density ranged from 0.025 to 0.191%, with an average uncertainty of approximately 0.05%. Here, we present measurement results, along with comparisons to available literature data and to default equations of state and mixture models included in REFPROP.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

High intensity vacuum ultraviolet and extreme ultraviolet production by noncollinear mixing in laser vaporized media

A method is described for generating intense pulsed vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) laser radiation by resonance enhanced four-wave mixing of commercial pulsed nanosecond lasers in laser vaporized mercury under windowless conditions. By employing noncollinear mixing of the input beams, the need of dispersive elements such as gratings for separating the VUV/XUV from the residual UV and visible beams is eliminated. A number of schemes are described, facilitating access to the 9.9–14.6 eV range. A simple and convenient scheme for generating wavelengths of 125 nm, 112 nm, and 104 nm (10 eV, 11 eV, and 12 eV) using two dye lasers without the need for dye changes is described.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Effect of water vapor on plasma morphology, OH and H 2 O 2 production in He and Ar atmospheric pressure dielectric barrier discharges

Although atmospheric pressure dielectric barrier discharges (DBDs) have a long history, the effects of water vapor on the discharge morphology and kinetics have not been studied intensively. We report a simultaneous investigation of discharge morphology, OH and H 2 O 2 production in Ar and He DBDs operated at different water vapor concentrations and powers. The combined study allows us to assess the impact of the discharge morphology and power on the concentration dependence of the OH and H 2 O 2 production. The morphology of the discharge is investigated by ICCD images and current–voltage waveforms. These diagnostics are complemented by broadband absorption and a colorimetric method to measure the gas temperature and the OH and H 2 O 2 concentrations. The number of filaments in Ar DBD increases with increasing water concentration and power. The surface discharge part of the micro-discharge also reduces with increasing water concentration most likely due to a change in surface conductivity of the dielectric with changing water concentration. The OH density in the case of Ar is approximately double the OH density in He for similar power and water admixture. In contrast to the root square dependence of the OH density on the water concentration in He similar to diffuse RF discharges, the OH density in Ar increases for small water concentrations followed by a saturation and reduces for higher water concentrations. Furthermore, this dependence of OH density on water concentration is found to correlate with changes in discharge morphology. An analytical balance of the production and destruction mechanism of H 2 O 2 is shown to be able to reproduce the ratio of the measured OH and H 2 O 2 density for realistic values of electron densities.

42 ENGINEERING↗
DOE OSTI2021

Optimization of Source Material for in-situ Arsenic Doping via Vapor Transport Deposition of CdTe Films

In-situ doping of CdTe/CdSeTe films with arsenic is performed using pre-doped source material prepared by high pressure Bridgman (HPB) melt growth. Arsenic level in the source material is varied from 1018-1020 cm-3. Correspondingly, dopant incorporation in the films prepared using vapor transport deposition (VTD) varied from 3x1017 cm-3–1x1018cm-3. In this range, dopant activation is found to inversely correlate with the dopant incorporation, suggesting compensation. The results from this study indicate film properties can be adjusted by source material.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2018

Modeling physical vapor deposition of energetic materials

Morphology and microstructure of organic explosive films formed using physical vapor deposition (PVD) processes strongly depends on local surface temperature during deposition. Currently, there is no accurate means of quantifying the local surface temperature during PVD processes in the deposition chambers. This study focuses on using a multiphysics computational fluid dynamics tool, STARCCM+, to simulate pentaerythritol tetranitrate (PETN) deposition. The PETN vapor and solid phase were simulated using the volume of fluid method and its deposition in the vacuum chamber on spinning silicon wafers was modeled. The model also included the spinning copper cooling block where the wafers are placed along with the chiller operating with forced convection refrigerant. Implicit time-dependent simulations in two- and three-dimensional were performed to derive insights in the governing physics for PETN thin film formation. PETN is deposited at the rate of 14 nm/s at 142.9 °C on a wafer with an initial temperature of 22 °C. The deposition of PETN on the wafers was calculated at an assumed heat transfer coefficient (HTC) of 400 W/m 2 K. This HTC proved to be the most sensitive parameter in determining the local surface temperature during deposition. Previous experimental work found noticeable microstructural changes with 0.5 mm fused silica wafers in place of silicon during the PETN deposition. This work showed that fused silica slows initial wafer cool down and results in ~10 °C difference for the surface temperature at 500 μm PETN film thickness. It was also found that the deposition surface temperature is insensitive to the cooling power of the copper block due to the copper block's very large heat capacity and thermal conductivity relative to the heat input from the PVD process. Future work should incorporate the addition of local stress during PETN deposition. Lastly, based on simulation results, it is also recommended to investigate the impact of wafer surface energy on the PETN microstructure and morphology formation.

36 MATERIALS SCIENCE↗
DOE OSTI2019

An Analysis of the Processes Affecting Rapid Near-Surface Water Vapor Increases during the Afternoon to Evening Transition in Oklahoma

Abstract This study used 20 years of Oklahoma Mesonet data to investigate the changes of near-surface water vapor mixing ratio qυ during the afternoon to evening transition (AET). Similar to past studies, increases in qυ are found to occur near sunset. However, the location, magnitude, and timing of the qυ maximum occurring during the AET are shown to be dependent on the seasonal growth and harvest of vegetation across Oklahoma in the spring and summer months. Particularly, the late spring harvest of winter wheat grown in Oklahoma appears to modify the relative contribution of local and nonlocal processes on qυ. By analyzing time series of qυ during the AET, it is found that the likelihood of a presunset qυ maximum is strongly dependent upon vegetation, soil moisture, wind speed, and cloud cover. Analysis also reveals that the increase in qυ during the AET can increase the parcel conditional instability despite the surface cooling produced by loss of insolation. Next to known changes in low-level wind shear, these changes in instability and moisture demonstrate new ways the AET can modify the presence of the key ingredients relevant to explaining the climatological increase in severe convective storm hazards around sunset.

Blumberg, W. G.↗
DOE OSTI2022

Lower Temperature Annealing of Vapor Diffused Nb₃Sn for Accelerator Cavities

Nb₃Sn is a next-generation superconducting material for the accelerator cavities with higher critical temperature and superheating field, both twice compared to Nb. It promises superior performance and higher operating temperature than Nb, resulting in significant cost reduction. So far, the Sn vapor diffusion method is the most preferred and successful technique to coat niobium cavities with Nb₃Sn. Although several post-coating techniques (chemical, electrochemical, mechanical) have been explored to improve the surface quality of the coated surface, an effective process has yet to be found. Since there are only a few studies on the post-coating heat treatment at lower temperatures, we annealed Nb₃Sn-coated samples at 800 C - 1000 C to study the effect of heat treatments on surface properties, primarily aimed at removing surface Sn residues. This paper discusses the systematic surface analysis of coated samples after annealing at temperatures between 850 C and 950 C.

43 PARTICLE ACCELERATORS↗
NASA NTRS1995

AMTEC vapor-vapor series connected cells

An alkali metal thermoelectric converter (AMTEC) having a plurality of cells structurally connected in series to form a septum dividing a plenum into two chambers, and electrically connected in series, is provided with porous metal anodes and porous metal cathodes in the cells. The cells may be planar or annular, and in either case a metal alkali vapor at a high temperature is provided to the plenum through one chamber on one side of the wall and returned to a vapor boiler after condensation at a chamber on the other side of the wall in the plenum. If the cells are annular, a heating core may be placed along the axis of the stacked cells. This arrangement of series-connected cells allows efficient generation of power at high voltage and low current.

Underwood, Mark L.↗