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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Effect of heating method on stress-rupture life

The effect of radiant(furnace), resistance(electric current), burner(hot gas stream), and a combination of resistance and burner heating on intermediate time (100 to 300 hr) stress-rupture life and reduction of area was evaluated. All heating methods were studied using the nickel-based alloy Udimet 700 while all but burner heating were evaluated with the cobalt-based alloy Mar-M 509. Limited test results of eight other superalloys were also included in this study. Resistance heated specimens had about 20 to 30 percent of the stress-rupture life of radiant heated specimens. The limited burner heating data showed about a 50 percent life reduction as compared to the radiant heated tests. A metallurgical examination gave no explanation for these reductions.

Bizon, P. T.↗
NASA NTRS2003

Methane Clathrate Hydrate Prospecting

A method of prospecting for methane has been devised. The impetus for this method lies in the abundance of CH4 and the growing shortages of other fuels. The method is intended especially to enable identification of subpermafrost locations where significant amounts of methane are trapped in the form of methane gas hydrate (CH4(raised dot)6H2O). It has been estimated by the U.S. Geological Survey that the total CH4 resource in CH4(raised dot) 6H2O exceeds the energy content of all other fossil fuels (oil, coal, and natural gas from non-hydrate sources). Also, CH4(raised dot)6H2O is among the cleanest-burning fuels, and CH4 is the most efficient fuel because the carbon in CH4 is in its most reduced state. The method involves looking for a proxy for methane gas hydrate, by means of the combination of a thermal-analysis submethod and a field submethod that does not involve drilling. The absence of drilling makes this method easier and less expensive, in comparison with prior methods of prospecting for oil and natural gas. The proposed method would include thermoprospecting in combination with one more of the other non-drilling measurement techniques, which could include magneto-telluric sounding and/or a subsurface-electrical-resistivity technique. The method would exploit the fact that the electrical conductivity in the underlying thawed region is greater than that in the overlying permafrost.

Duxbury, N.↗
NASA NTRS1989

Strong, Low-Resistance Bonds For AMTEC Electrodes

Heat of operating cell helps form contacts. Strong, low-electrical-resistance contacts between elements of current-collection grid in alkali-metal thermoelectric converter (AMTEC) cell obtained by simple in-place thermocompression bonding. Bonds formed between porous electrode of molybdenum film, nickel or cobalt strips overlying film, and molybdenum tie wires running at right angles to strips. Bonding method also works on films of tungsten or tungsten/platinum.

Williams, Roger M.↗
DOE OSTI2020

In situ and laboratory evidence for high electrical anisotropy in marine gas hydrate

Marine gas hydrate is electrically resistive compared to the surrounding hydrate-free formation, a property that is exploited in borehole logging and also by marine controlled-source electromagnetic (CSEM) surveys. Well logging shows that hydrate can be electrically anisotropic, with vertical resistivities up to 10 times higher than horizontal resistivities, although the use of logging tools capable of measuring anisotropy is the exception rather than the rule. Marine CSEM methods are well known to be sensitive to anisotropy in seafloor sediments, and, for example, we have observed anisotropies of more than an order of magnitude using CSEM to map offshore relic permafrost.

02 PETROLEUM↗
NASA NTRS2004

Embedded Heaters for Joining or Separating Plastic Parts

A proposed thermal-bonding technique would make it possible to join or separate thermoplastic parts quickly and efficiently. The technique would eliminate the need for conventional welding or for such conventional fastening components as bolted flanges or interlocking hooks. The technique could be particularly useful in the sign industry (in which large quantities of thermoplastics are used) or could be used to join plastic pipes. A thin sheet of a suitable electrically conductive material would be formed to fit between two thermoplastic parts to be joined (see figure). The electrically conductive sheet and the two parts would be put together tightly, then an electrical current would be sent through the conductor to heat the thermoplastic locally. The magnitude of the current and the heating time would be chosen to generate just enough heat to cause the thermoplastic to adhere to both sides of the electrically conductive sheet. Optionally, the electrically conductive sheet could contain many small holes to provide purchase or to increase electrical resistance to facilitate the generation of heat. After thermal bonding, the electrically conductive sheet remains as an integral part of the structure. If necessary, the electrically conductive sheet can be reheated later to separate the joined thermoplastic parts.

Bryant, Melvin A., III↗
DOE OSTI2020

Effect of controlled pointlike disorder induced by 2.5-MeV electron irradiation on the nematic resistivity anisotropy of hole-doped (Ba,K)Fe 2 As 2

In-plane anisotropy of electrical resistivity was studied in samples of the hole-doped Ba 1–x K x Fe 2 As 2 in the composition range 0.21 ≤ x ≤ 0.26 where anisotropy changes sign. Low-temperature (~20 K) irradiation with relativistic 2.5 MeV electrons was used to control the level of disorder and residual resistivity of the samples. Modification of the stress-detwinning technique enabled measurements of the same samples before and after irradiation, leading to the conclusion of anisotropic character of predominantly inelastic scattering processes. Our main finding is that the resistivity anisotropy is of the same sign irrespective of residual resistivity, and remains the same in the orthorhombic C 2 phase above the reentrant tetragonal transition. Unusual T-linear dependence of the anisotropy Δρ ≡ ρ a (T) – ρ b (T) is found in pristine samples with x = 0.213 and x = 0.219 , without similar signatures in either ρ a (T) or ρ b (T). In this paper, we show that this feature can be reproduced by a phenomenological model of R. M. Fernandes et al. We speculate that onset of fluctuations of nematic order on approaching the instability towards the reentrant tetragonal phase contributes to this unusual dependence.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1987

Amorphous Insulator Films With Controllable Properties

In experiments described in report, amorphous hydrogenated carbon films grown at room temperature by low-frequency plasma deposition, using methane or butane gas. Films have unique array of useful properties; (a) adhere to wide variety of materials; (b) contain only carbon and hydrogen; (c) smooth and free of pinholes; (d) resistant to attack by moisture and chemicals; and (e) have high electric-breakdown strength and electrical resistivity. Two of optical properties and hardness of this film controlled by deposition conditions. Amorphous a-C:H and BN films used for hermetic sealing and protection of optical, electronic, magnetic, or delicate mechanical systems, and for semiconductor field dielectrics.

Alterovitz, Samuel A.↗
DOE OSTI2024

Groundwater Circulation Within the Mountain Block: Combining Flow and Transport Models With Magnetotelluric Observations to Untangle Its Nested Nature

Abstract Mountains are vital water sources for humans and ecosystems, continuously replenishing lowland aquifers through surface runoff and mountain recharge. Quantifying these fluxes and their relative importance is essential for sustainable water resource management. However, our mechanistic understanding of the flow and transport processes determining the connection between the mountain block and the basin aquifer remains limited. Traditional conceptualizations assume groundwater circulation within the mountain block is predominantly shallow. This view neglects the role of deep groundwater flowpaths significantly contributing to the water, solute, and energy budgets. Overcoming these limitations requires a holistic characterization of the multiscale nature of groundwater flow along the mountain‐to‐valley continuum. As a proof‐of‐concept, we use a coupled groundwater flow and transport model to design a series of numerical experiments that explore the role of geology, topography, and weathering rates in groundwater circulation and their resulting resistivity patterns. Our results show that accumulating solutes near stagnation zones create contrasting electrical resistivity patterns that separate local, intermediate, and regional flow cells, presenting a target for magnetotelluric observations. To demonstrate the sensitivity of magnetotelluric data to features in our resistivity models, we use the MARE2DEM electromagnetic modeling code to perform forward and inverse simulations. This study highlights the potential of magnetotelluric surveys to image the resistivity structure resulting from multiscale groundwater circulation through relatively impervious crystalline basement rocks in mountainous terrains. This capability could change our understanding of the critical zone, offering a holistic perspective that includes deep groundwater circulation and its role in conveying solutes and energy.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Cryogenic C-band wavelength division multiplexing system using an AIM Photonics Foundry process design kit

Cryogenic environments make superconducting computing possible by reducing thermal noise, electrical resistance and heat dissipation. Heat generated by the electronics and thermal conductivity of electrical transmission lines to the outside world constitute two main sources of thermal load in such systems. As a result, higher data rates require additional transmission lines which come at an increasingly higher cooling power cost. Hybrid or monolithic integration of silicon photonics with the electronics can be the key to higher data rates and lower power costs in these systems. We present a 4-channel wavelength division multiplexing photonic integrated circuit (PIC) built from modulators in the AIM Photonics process development kit (PDK) that operate at 25 Gbps at room temperature and 10 Gbps at 40 K. We further demonstrate 2-channel operation for 20 Gbps aggregate data rate at 40 K using two different modulators/wavelengths, with the potential for higher aggregate bit rates by utilizing additional channels.

42 ENGINEERING↗
NASA NTRS1978

Contact Whiskers for Millimeter Wave Diodes

Several techniques are investigated for making short conical tips on wires (whiskers) used for contacting millimeter-wave Schottky diodes. One procedure, using a phosphoric and chromic acid etching solution (PCE), is found to give good results on 12 microns phosphor-bronze wires. Full cone angles of 60 degrees-80 degrees are consistently obtained, compared with the 15 degrees-20 degrees angles obtained with the widely used sodium hydroxide etch. Methods are also described for cleaning, increasing the tip diameter (i.e. blunting), gold plating, and testing the contact resistance of the whiskers. The effects of the whisker tip shape on the electrical resistance, inductance, and capacitance of the whiskers are studied, and examples given for typical sets of parameters.

Kerr, A. R.↗
NASA NTRS1980

Collector temperature effects on the performance of advanced thermionic converters and nuclear electric propulsion systems

The specific weight of a thermionic nuclear electric propulsion (NEP) system depends on the collector temperature because of changes in power density, efficiency and the temperature of heat rejection. Increasing the collector temperature above the value for maximum converter performance decreases both the efficiency and the power density of the converters, but the specific weight of the total system is decreased because of the reduction in radiator weight due to the increased heat rejection temperature. The effect of collector temperature on the performance of thermionic converters was investigated. The behavior of conventional ignited mode converters as well as advanced converters with lower collector work functions; the specific mass of an 'uninsulated' NEP system design was then evaluated as a function of collector temperature. The uninsulated design uses the electrical resistance of the heat pipes between the converters and the reactor to provide electrical insolation, eliminating the need for ceramic insulators at emitter temperature and providing other design advantages. The results indicate that an optimum collector temperature, which minimizes system weight, exists at a temperature above the optimum temperature for converter performance.

Dick, R. S.↗
NASA NTRS1989

Graphite Fluoride Fiber Composites For Heat Sinking

Graphite fluoride fiber/polymer composite materials consist of graphite fluoride fibers in epoxy, polytetrafluoroethylene, or polyimide resin. Combines high electrical resistivity with high thermal conductivity and solves heat-transfer problems of many electrical systems. Commercially available in powder form, for use as dry lubricant or cathode material in lithium batteries. Produced by direct fluorination of graphite powder at temperature of 400 to 650 degree C. Applications include printed-circuit boards for high-density power electronics, insulators for magnetic-field cores like those found in alternators and transformers, substrates for thin-film resistors, and electrical-protection layers in aircraft de-icers.

Hung, Ching-Cheh↗
NASA NTRS2009

Modeling Joule Heating Effect on Lunar O2 Generation via Electrolytic Reduction.

Kennedy Space Center is leading research work on lunar O2 generation via electrolytic reduction of regolith; the metal oxide present in the regolith is dissociated in oxygen anions and metal cations leading to the generation of gaseous oxygen at the anode and liquid metal at the cathode. Electrical resistance of molten regolith is high, leading to heating of the melt when electrical current is applied between the electrodes (Joule heating). The authors have developed a 3D model using a rigorous approach for two coupled physics (thermal and electrical potential) to not only study the effect of Joule heating on temperature distribution throughout the molten regolith but also to evaluate and optimize the design of the electrolytic cells. This paper presents the results of the thermal analysis performed on the model and used to validate the design of the electrolytic cell.

Dominquez, Jesus↗
NASA NTRS1972

Evaluation of zirconia, thoria and zirconium diboride for advanced resistojet use

A literature survey was conducted to collect material properties data on all advanced high temperature materials. Three of these, Y2O3-stabilized ZrO2, ThO2, and ZrB2 with additives of C and SiC were selected for further study. Stabilized ZrO2 and ThO2 were found to have higher temperature oxidation resistance than any metal and great potential for use in advanced biowaste resistojets. ZrO2 has a lower electrical resistivity and sublimation and a higher creep endurance strength. ZrO2 and ThO2 tubular heat exchangers, electrically heated indirectly, were evaluated in short tests to about 1900 K in flowing CO2. ZrO2 was subjected to N2, H2, H2O and vacuum as well. X-ray diffraction and fluorescence analyses were made. The metal-to-ceramic seal technology for ZrO2 and ThO2 was developed using chemical vapor deposition of tantalum for metallizing and 82 Au - 18 Ni filler braze.

Page, R. J.↗
DOE OSTI2021

Coupled physics simulation of fracture in nuclear fuel pellets induced by resistive heating

While it is well known that the UO 2 fuel used in light-water reactors cracks early in its life in the reactor, it is very difficult to collect in-reactor data regarding fuel cracking initiation and propagation to validate fracture models in fuel performance codes. Most fracture data comes from the post-irradiation examination of fuel that has been subjected to long and complex power histories. Replicating the thermal gradients experienced in this fuel to study crack initiation and propagation in a laboratory environment is challenging. This is primarily because the fuel is heated volumetrically by fission, which is difficult to replicate. One way to approximate this volumetric heating out of the reactor is to use electrical resistance (or Joule heating). An electrical conductivity model has been developed and coupled with the existing thermomechanical modeling capability in the BISON nuclear fuel performance code. This will permit simulation of experiments that use resistive heating for the purpose of validating fracture models in BISON. The modeling approach developed here is applied to simulate both historical and current resistive heating experiments on ceramic nuclear fuel.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1991

Deposition Of Diamondlike Films By ECR Microwave Plasma

Hard, amorphous hydrogenated carbon films of diamondlike quality deposited at room temperature on silicon, optical glass, and quartz through decomposition of CH4 in electron-cyclotron-resonance (ECR) microwave plasma of CH4 diluted with H2. Technique provides hard, abrasion-resistant coatings for lenses and other optical components. Films chemically inert and posses high electrical resistivity and breakdown fields, valuable properties in microelectronics applications.

Pool, Frederick S.↗