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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
NASA NTRS1993

Monolithic catalytic igniters

Catalytic igniters offer the potential for excellent reliability and simplicity for use with the diergolic bipropellant oxygen/hydrogen as well as with the monopropellant hydrazine. State-of-the-art catalyst beds - noble metal/granular pellet carriers - currently used in hydrazine engines are limited by carrier stability, which limits the hot-fire temperature, and by poor thermal response due to the large thermal mass. Moreover, questions remain with regard to longevity and reliability of these catalysts. In this work, Ultramet investigated the feasibility of fabricating monolithic catalyst beds that overcome the limitations of current catalytic igniters via a combination of chemical vapor deposition (CVD) iridium coatings and chemical vapor infiltration (CVI) refractory ceramic foams. It was found that under all flow conditions and O2:H2 mass ratios tested, a high surface area monolithic bed outperformed a Shell 405 bed. Additionally, it was found that monolithic catalytic igniters, specifically porous ceramic foams fabricated by CVD/CVI processing, can be fabricated whose catalytic performance is better than Shell 405 and with significantly lower flow restriction, from materials that can operate at 2000 C or higher.

La Ferla, R.↗
NASA NTRS1991

Low cost high efficiency GaAs monolithic RF module for SARSAT distress beacons

Low cost high performance (5 Watts output) 406 MHz beacons are urgently needed to realize the maximum utilization of the Search and Rescue Satellite-Aided Tracking (SARSAT) system spearheaded in the U.S. by NASA. Although current technology can produce beacons meeting the output power requirement, power consumption is high due to the low efficiency of available transmitters. Field performance is currently unsatisfactory due to the lack of safe and reliable high density batteries capable of operation at -40 C. Low cost production is also a crucial but elusive requirement for the ultimate wide scale utilization of this system. Microwave Monolithics Incorporated (MMInc.) has proposed to make both the technical and cost goals for the SARSAT beacon attainable by developing a monolithic GaAs chip set for the RF module. This chip set consists of a high efficiency power amplifier and a bi-phase modulator. In addition to implementing the RF module in Monolithic Microwave Integrated Circuit (MMIC) form to minimize ultimate production costs, the power amplifier has a power-added efficiency nearly twice that attained with current commercial technology. A distress beacon built using this RF module chip set will be significantly smaller in size and lighter in weight due to a smaller battery requirement, since the 406 MHz signal source and the digital controller have far lower power consumption compared to the 5 watt power amplifier. All the program tasks have been successfully completed. The GaAs MMIC RF module chip set has been designed to be compatible with the present 406 MHz signal source and digital controller. A complete high performance low cost SARSAT beacon can be realized with only additional minor iteration and systems integration.

Petersen, W. C.↗
NASA NTRS2000

Characteristics of Monolithically Integrated InGaAs Active Pixel Imager Array

Switching and amplifying characteristics of a newly developed monolithic InGaAs Active Pixel Imager Array are presented. The sensor array is fabricated from InGaAs material epitaxially deposited on an InP substrate. It consists of an InGaAs photodiode connected to InP depletion-mode junction field effect transistors (JFETs) for low leakage, low power, and fast control of circuit signal amplifying, buffering, selection, and reset. This monolithically integrated active pixel sensor configuration eliminates the need for hybridization with silicon multiplexer. In addition, the configuration allows the sensor to be front illuminated, making it sensitive to visible as well as near infrared signal radiation. Adapting the existing 1.55 micrometer fiber optical communication technology, this integration will be an ideal system of optoelectronic integration for dual band (Visible/IR) applications near room temperature, for use in atmospheric gas sensing in space, and for target identification on earth. In this paper, two different types of small 4 x 1 test arrays will be described. The effectiveness of switching and amplifying circuits will be discussed in terms of circuit effectiveness (leakage, operating frequency, and temperature) in preparation for the second phase demonstration of integrated, two-dimensional monolithic InGaAs active pixel sensor arrays for applications in transportable shipboard surveillance, night vision, and emission spectroscopy.

Kim, Q.↗
NASA NTRS1997

Monolithically Integrated SiGe/Si PIN-HBT Front-End Transimpedance Photoreceivers

The demand for monolithically integrated photoreceivers based on Si-based technology keeps increasing as low cost and high reliability products are required for the expanding commercial market. Higher speed and wider operating frequency range are expected when SiGe/Si heterojunction is introduced to the circuit design. In this paper, a monolithic SiGe/Si PIN-HBT front-end transimpedance photoreceiver is demonstrated for the first time. For this purpose, mesa-type SiGe/Si PIN-HBT technology was developed. Fabricated HBTs exhibit f(sub max) of 34 GHz with DC gain of 25. SiGe/Si PIN photodiodes, which share base and collector layers of HBTs, demonstrate responsivity of 0.3 A/W at lambda=850 nm and bandwidth of 450 MHz. Based on these devices, single- and dual-feedback transimpedance amplifiers were fabricated and they exhibited the bandwidth of 3.2 GHz and 3.3 GHz with the transimpedance gain of 45.2 dB(Omega) and 47.4 dB(Omega) respectively. Monolithically integrated single-feedback PIN-HBT photoreceivers were implemented and the bandwidth was measured to be approx. 0.5 GHz, which is limited by the bandwidth of PIN photodiodes.

Rieh, J.-S.↗
DOE OSTI2012

Recent Accomplishments in the Irradiation Testing of Engineering-Scale Monolithic Fuel Specimens

The US fuel development team is focused on qualification and demonstration of the uranium-molybdenum monolithic fuel including irradiation testing of engineering-scale specimens. The team has recently accomplished the successful irradiation of the first monolithic multi-plate fuel element assembly within the AFIP-7 campaign. The AFIP-6 MKII campaign, while somewhat truncated by hardware challenges, exhibited successful irradiation of a large-scale monolithic specimen under extreme irradiation conditions. The channel gap and ultrasonic data are presented for AFIP-7 and AFIP-6 MKII, respectively. Finally, design concepts are summarized for future irradiations such as the base fuel demonstration and design demonstration experiment campaigns.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2014

Shutdown-induced tensile stress in monolithic miniplates as a possible cause of plate pillowing at very high burnup

Post-irradiation examination of Reduced Enrichment for Research and Test Reactors (RERTR)-12 miniplates showed that in-reactor pillowing occurred in at least 4 plates, rendering performance of these plates unacceptable. To address in-reactor failures, efforts are underway to define the mechanisms responsible for in-reactor pillowing, and to suggest improvements to the fuel plate design and operational conditions. To achieve these objectives, the mechanical response of monolithic fuel to fission and thermally-induced stresses was modeled using a commercial finite element analysis code. Calculations of stresses and deformations in monolithic miniplates during irradiation and after the shutdown revealed that the tensile stress generated in the fuel increased from 2 MPa to 100 MPa at shutdown. The increase in tensile stress at shutdown possibly explains in-reactor pillowing of several RERTR-12 miniplates irradiated to the peak local burnup of up to 1.11x1022 fissions/cm3 . This paper presents the modeling approach and calculation results, and compares results with post-irradiation examinations and mechanical testing of irradiated fuel. The implications for the safe use of the monolithic fuel in research reactors are discussed, including the influence of fuel burnup and power on the magnitude of the shutdown-induced tensile stress.

rertr↗
DOE OSTI2017

Graphene-supported metal oxide monolith

A composition comprising at least one graphene-supported metal oxide monolith, said monolith comprising a three-dimensional structure of graphene sheets crosslinked by covalent carbon bonds, wherein the graphene sheets are coated by at least one metal oxide such as iron oxide or titanium oxide. Also provided is an electrode comprising the aforementioned graphene-supported metal oxide monolith, wherein the electrode can be substantially free of any carbon-black and substantially free of any binder.

36 MATERIALS SCIENCE↗
DOE OSTI2017

High-density 3D graphene-based monolith and related materials, methods, and devices

A composition comprising at least one high-density graphene-based monolith, said monolith comprising a three-dimensional structure of graphene sheets crosslinked by covalent carbon bonds and having a density of at least 0.1 g/cm.sup.3. Also provided is a method comprising: preparing a reaction mixture comprising a suspension and at least one catalyst, said suspension selected from a graphene oxide (GO) suspension and a carbon nanotube suspension; curing the reaction mixture to produce a wet gel; drying the wet gel to produce a dry gel, said drying step is substantially free of supercritical drying and freeze drying; and pyrolyzing the dry gel to produce a high-density graphene-based monolith. Exceptional combinations of properties are achieved including high conductive and mechanical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Metal oxide nanorod arrays on monolithic substrates

A metal oxide nanorod array structure according to embodiments disclosed herein includes a monolithic substrate having a surface and multiple channels, an interface layer bonded to the surface of the substrate, and a metal oxide nanorod array coupled to the substrate surface via the interface layer. The metal oxide can include ceria, zinc oxide, tin oxide, alumina, zirconia, cobalt oxide, and gallium oxide. The substrate can include a glass substrate, a plastic substrate, a silicon substrate, a ceramic monolith, and a stainless steel monolith. The ceramic can include cordierite, alumina, tin oxide, and titania. The nanorod array structure can include a perovskite shell, such as a lanthanum-based transition metal oxide, or a metal oxide shell, such as ceria, zinc oxide, tin oxide, alumina, zirconia, cobalt oxide, and gallium oxide, or a coating of metal particles, such as platinum, gold, palladium, rhodium, and ruthenium, over each metal oxide nanorod. Structures can be bonded to the surface of a substrate and resist erosion if exposed to high velocity flow rates.

36 MATERIALS SCIENCE↗
DOE OSTI2018

High-density carbon nanotube-based monolith and related materials, methods, and devices

Disclosed here is a composition comprising at least one high-density carbon-nanotube-based monolith, said monolith comprising carbon nanotubes crosslinked by nanoparticles and having a density of at least 0.2 g/cm 3 . Also provided is a method for making the composition comprising: preparing a reaction mixture comprising a suspension and at least one catalyst, said suspension is a carbon nanotube suspension; curing the reaction mixture to produce a wet gel; drying the wet gel to produce a dry gel, said drying step is substantially free of supercritical drying and freeze drying; and pyrolyzing the dry gel to produce the composition comprising a high-density carbon-nanotube-based monolith. Exceptional combinations of properties are achieved including high conductive and mechanical properties.

Worsley, Marcus A.↗
DOE OSTI2018

MONTE CARLO NEUTRONICS ANALYSIS OF THE SNS STS MONOLITH

Neutronics analysis for the Oak Ridge National Laboratory Spallation Neutron Source second target station monolith conceptual design was performed entirely with the Monte Carlo method. It has been demonstrated that even though the monolith provides ~peta-scale attenuation of the dose rates, Monte Carlo simulations are within reach of computing capabilities of relatively inexpensive Linux clusters. Several monolith configurations achieved or exceeded design requirements and provide basis for the final design.

Remec, Igor↗
DOE OSTI2019

Monte Carlo Neutronics Analysis of the SNS STS Monolith

The neutronics analysis for the Oak Ridge National Laboratory’s Spallation Neutron Source second target station monolith conceptual design was performed entirely with the Monte Carlo method. It has been demonstrated that even though the monolith provides approximately peta-scale attenuation of the dose rates, Monte Carlo simulations are within reach of computing capabilities of relatively inexpensive Linux clusters. Several monolith configurations achieved or exceeded design requirements and provide basis for the final design.

Remec, Igor↗
DOE OSTI2023

3D printed zeolite monoliths for CO 2 removal

Carbon dioxide (CO 2 ) capture materials comprising one or more 3D-printed zeolite monoliths for the capture and or removal of CO 2 from air or gases in enclosed compartments, including gases or mixtures of gases having less than about 5% CO 2 . Methods for preparing 3D-printed zeolite monoliths useful as CO 2 capture materials and filters, as well as methods of removing CO 2 from a gas or mixture of gases in an enclosed compartment using 3D-printed zeolite monoliths are provided.

Rezaei, Fateme↗
DOE OSTI2018

Monte Carlo neutronics analysis of the SNS STS monolith - 25684

Neutronics analysis for the Oak Ridge National Laboratory's Spallation Neutron Source second target station monolith conceptual design was performed entirely with the Monte Carlo method. It has been demonstrated that even though the monolith provides ∼peta-scale attenuation of the dose rates, Monte Carlo simulations are within reach of computing capabilities of relatively inexpensive Linux clusters. Several monolith configurations achieved or exceeded design requirements and provide basis for the final design. (authors)

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Impacts of annealing treatment on the microstructure of U-Mo monolithic fuel plates

The objective of this paper is to analyze the effect of different heat treatments on the fuel microstructure and texture in laboratory scale monolithic U-Mo fuel plates. Such analyses are relevant as they could possibly inform future fabrication methods for the optimization of microstructure and of material properties to ultimately improve fuel performance during irradiation. For this reason, detail characterization including Energy x-ray dispersive spectroscopy (EDS) and electron backscattered diffraction (EBSD) techniques were applied on U-Mo plates fabricated with different heat treatments to understand the influence of fabrication on fuel microstructure. Here, U-Mo fresh fuel specimens with or without annealing treatments (homogenization and stress release annealing) after rolling were analyzed in this work. In this study for the first time EBSD was systematically used to analyze the heat treatments influence on texture present in fresh fuel monolithic U-Mo fuel plates. Such changes were connected to other known microstructural and chemical changes. In this work minimization of molybdenum concentration variation and gamma phase decomposition of the U-Mo fuel core after homogenization was observed. Also, an increase in the interaction layer of the U-Mo fuel core with the Zr interlayer diffusion barrier was observed with the UZr 2 growing up to 1 µm in thickness. Such microstructural changes were aligned to the changes in texture and grain structure. Indeed, common texture observed in body-centered cubic (BCC) metal after cold rolling (e.g., α, ξ, γ fibers) were minimized by the annealing/homogenization process. Moreover, grain structure was influenced by the fabrication route with elongated grains formed in the rolled sample and equiaxed grains found after annealing. Such features are relevant since the formation of microstructural features formed during fuel fabrication can impact fuel performance in reactor.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Template-free fabrication of fractal porous Y 2 O 3 monolithic foam and its functional modification by Ni-doping

Fractal structures which display nearly the same character at every scale exist widely in nature, however, it is still a great challenge to fabricate a fractal nanostructure. Herein, a Y 2 O 3 monolith with unique hierarchically fractal porous structure was fabricated via calcination of a fractal porous coordination polymer precursor. The monolith exhibits porous feature with the pore-size ranging from micrometers to nanometers. Interestingly, each level of the pore-wall is composed of secondary porous structures, whose pore-wall is composed of sub-level self-similar porous feature. Moreover, by Ni-doping in the coordination polymer precursor, fractal porous Ni@Y 2 O 3 was prepared, and exhibited enhanced activity in ethanol steam reforming compared with that of a common supported NiO catalyst.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Layer structured bifunctional monolith catalysts for energy-efficient conversion of CO 2 to dimethyl ether

A monolith supported bifunctional catalyst for the direct conversion of CO 2 to dimethyl ether was developed and evaluated. The catalyst consists of a layer structured configuration, in which a CuO/ZnO/ZrO 2 component for methanol synthesis using CO 2 as feedstock and a Ferrierite zeolite component for the subsequent dehydration reaction are washcoated onto the channel surfaces of a metallic monolith substrate as two consecutive layers. The metal substrate provides heat conduction to regulate the catalyst bed temperature. The layered configuration significantly improves the synergistic effects of the two components, resulting in a 20% increase in the productivity for dimethyl ether at 240 °C as compared with the conventional catalysts with the two components being blended in various levels of proximity. Furthermore, the layer structured design minimizes the undesirable interaction between the two components and drastically improves the on-stream durability of the catalyst. No activity decline was observed in a 146-h performance test.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Possible impacts of Mo chemical banding and second phase impurities on the irradiation behavior of monolithic U-10Mo fuels

This study investigated the microstructural behavior of both full-size and mini-size monolithic U-10Mo fuel plates irradiated to high burnup with a focus on the evolution of the second phase impurities in monolithic U-Mo using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and wavelength dispersive spectroscopy (WDS). Key indicators of possible mechanical and thermal compromise include cracks, large fission gas porosity, and interconnection of fission gas pores. For the fission densities evaluated in this work (3.5 × 10 21 fissions/cm 3 -5.1 × 10 21 fissions/cm 3 ), fine porosity can develop along the UC phase boundary; however, the size of the fission gas pores is no more than those observed in the U-Mo fuel phase. Further, other inclusions such as Si-rich second-phase impurities found in the as-fabricated microstructure were difficult to resolve post-irradiation because they can become overshadowed by porosity development in the fuel phase. Additionally, the presence of a Fe-rich sublayer formed in the Zr diffusion layer during fabrication remained enriched in the Zr layer in the irradiated U-10Mo microstructures near the U-Mo/Zr interface; however, based on the burnup assessed in this study the identified impurities did not appear to contribute to notable microstructural degradation.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗