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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on MoSI by Materials Project

MoSI crystallizes in the cubic F-43m space group. The structure is three-dimensional. Mo3+ is bonded to three equivalent S2- and three equivalent I1- atoms to form distorted edge-sharing MoS3I3 octahedra. All Mo–S bond lengths are 2.37 Å. All Mo–I bond lengths are 2.96 Å. S2- is bonded in a 12-coordinate geometry to three equivalent Mo3+ atoms. I1- is bonded in a distorted trigonal non-coplanar geometry to three equivalent Mo3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Additive Manufacturing of Corrosion Resistant UHTC Materials for Chloride Salt-to-sCO2 Brayton Cycle Heat Exchangers

The objectives of the project include: (1) screen high-purity, high density ultra-high-temperature ceramics (UHTCs) for chloride salt corrosion resistance, (2) develop binder-jet additive manufacturing and sintering for ZrB 2 -MoSi 2 blends using literature and experiments to demonstrate feasibility, and (3) evaluate chloride salt corrosion resistance of additively manufactured ZrB 2 -MoSi 2 . These initial objectives support the development of a durable and reliable ultra-compact high-efficiency salt-to-sCO 2 heat exchanger for closed-loop Brayton power cycles based on corrosion resistant, high-strength, thermally conductive UHTC materials and novel designs enabled by additive manufacturing. The UHTC materials are also abrasion resistant so that they could be applicable to all three thermal carrier media pathways identified in the CSP Gen3 Roadmap.

36 MATERIALS SCIENCE↗
NASA NTRS1986

Prototyping and implementing flight qualifiable semicustom CMOS P-well bulk integrated circuits in the JPL environment

Presently, there are many difficulties associated with implementing application specific custom or semi-custom (standard cell based) integrated circuits (ICs) into JPL flight projects. One of the primary difficulties is developing prototype semi-custom integrated circuits for use and evaluation in engineering prototype flight hardware. The prototype semi-custom ICs must be extremely cost-effective and yet still representative of flight qualifiable versions of the design. A second difficulty is encountered in the transport of the design from engineering prototype quality to flight quality. Normally, flight quality integrated circuits have stringent quality standards, must be radiation resistant and should consume minimal power. It is often not necessary or cost effective, however, to impose such stringent quality standards on engineering models developed for systems analysis in controlled lab environments. This article presents work originally initiated for ground based applications that also addresses these two problems. Furthermore, this article suggests a method that has been shown successful in prototyping flight quality semi-custom ICs through the Metal Oxide Semiconductor Implementation Service (MOSIS) program run by the University of Southern California's Information Sciences Institute. The method has been used successfully to design and fabricate through the MOSIS three different semi-custom prototype CMOS p-well chips. The three designs make use of the work presented and were designed consistent with design techniques and structures that are flight qualifiable, allowing one hour transfer of the design from engineering model status to flight qualifiable foundry-ready status through methods outlined in this article.

Olson, E. M.↗
DOE OSTI2022

Exploring Material Solutions for Supercritical CO 2 Applications above 800 °C

There has been recent interest in exploring revolutionary supercritical CO 2 (sCO 2 ) power cycles, and this exploratory investigation was seeking materials with CO 2 compatibility at up to 1200 °C. Here, initial exposures were conducted at 0.1 and 2 MPa CO 2 for up to 1000 h at 900–1200 °C. As expected, specimens of Mo and W that might be used as matrix materials in cermets were rapidly attacked under these conditions. Even an alumina-forming FeCrAlMo alloy showed high mass gains in less than 100 h at 1200 °C due to the formation of Fe-rich oxide. However, at 900–1100 °C, more protective behavior was observed for FeCrAlMo specimens, with or without pre-oxidation, in 0.1 MPa CO 2 , but increased attack was observed in 2 MPa CO 2 . In contrast, most Ni-based alloys exposed at 900–1100 °C showed higher mass gains and thicker reaction products than formed in air. Thus, Ni-based alloys appear less compatible with CO 2 environments above 800 °C compared to lower temperatures. Low mass gains were observed for CVD SiC at 900–1200 °C, but MoSi 2 and Mo(Si,Al) 2 specimens did not form protective scales under these conditions at 1000 and 1100 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Binder jet additive manufacturing of ceramic heat exchangers for concentrating solar power applications with thermal energy storage in molten chlorides

Triply periodic minimal surface (TPMS) geometries can only be fabricated by additive manufacturing methods and are of interest for heat exchangers. Ceramic TPMS heat exchangers can operate at higher temperatures and pressures with superior performance and increased operating efficiencies compared to metal heat exchangers. The properties of ultra-high temperature ceramic (UHTC) materials are also favorable for heat exchangers and potentially suited to concentrated solar power (CSP) systems, such as those based on a molten chloride salt thermal energy storage (TES) medium used to heat CO 2 in a closed-loop Brayton power cycle. We intended to demonstrate binder jet additive manufacturing feasibility of a UHTC-TPMS structure by printing and sintering a null candidate. We aimed to achieve parts with a relative density ≥ 92 % of theoretical and to provide a TPMS part demonstration. The target density indicates the transition from intermediate to final stage sintering, a requirement to inhibit gas permeability and for sintering complex near net shapes to full density with sinter-HIP technology. The goal of the TPMS part demonstration was to determine if printing and sintering parameters developed from test coupons apply to the complex geometries that will eventually be used in a heat exchanger design. Our objective was to print cubic TPMS parts with a 9 cm 3 volume and sinter it without distorting and cracking. We report we were able to sinter ZrB 2 -MoSi 2 composite parts based on the Schwarz-D TPMS and achieve isotropic shrinkage up to 60 % by volume, resulting in densities ranging from 92 % to 96 % of theoretical.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Current activated reactive ultrafast joining (CARUJ) of silicon carbide

In this work we propose and demonstrate a novel approach for rapid fabrication of ceramic-ceramic joint assemblies, using sintered Silicon Carbide (SiC) as an initial example. Current Activated Reactive Ultrafast Joining (CARUJ) utilizes resistive heating of carbon-based materials to apply localized heat at or around the joint zone at heating rates of 101– 103 °C/min. CARUJ is used to fabricate SiC-SiC joints with a Si-SiC interface using minimal pressure (1–2 MPa) at time scales considerably shorter (several minutes opposed to hours) than conventional approaches for similar systems. The reaction of an interfacial precursor based on elemental silicon and carbon leads to in-situ SiC formation to produce a continuous and dense bond in a single step. Measured average joint strengths of roughly 15 MPa are achieved when tested in single lap offset (SLO) compressive shear. Optional additions of refractory metals such as molybdenum can be utilized to introduce secondary inclusions such as MoSi 2 within the joint interface. We further demonstrate SiC-SiC joining using Active Brazing Alloys (ABA) and proof of concept joining of tubular geometries. The localized and rapid heat application realizes a versatile material joining technique that could be extended for joining components at the plant site.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Delayed onset of discontinuous precipitation-based phase transformation in U10Mo alloys doped with Silicon

A uranium-10 wt% molybdenum (U-10Mo) alloy is one of the primary candidates for metallic fuels that would use low-enriched uranium in place of highly enriched uranium, to support nuclear nonproliferation efforts. Optimal performance of a U-based metallic nuclear fuel can be achieved by retaining the high-temperature, body-centered cubic (bcc) allotrope (γ-U) at room temperature, which can be accomplished in the U-10Mo alloy. However, presence of minor alloying elements can influence the final constitution of room-temperature phases in the U10Mo alloy, specifically, formation of α-U phase which results in anisotropic behavior of the fuel in reactor. Further, through a detailed transmission electron microscopy analysis, the present study reports the constituent phases that are present in a U10Mo alloy containing ~0.1 wt% Si after it is subjected to homogenization heat treatment and thermomechanical processing. For comparison, results from an undoped U10Mo alloy are also included. The experimental results reveal that γ-UMo solid solution is the major phase in a hot-rolled, Si-doped U10Mo alloy metallic fuel foil, along with U 2 MoSi 2 C, UC, and U 2 Mo, after isothermal annealing at 460 °C for 10h. In contrast, after the same heat treatment, the undoped U10Mo alloy metallic fuel had formed a noticeable amount of α-U along prior γ-UMo grain boundaries through discontinuous precipitation (DP, area fraction: ~27.9%) with characteristic lamellar morphology, together with γ-UMo, UC, and U 2 Mo. This result indicates that doping with Si could mitigate the DP reaction in U10Mo alloy and prevent formation of undesirable α-U. This work sheds light on optimizing Si-doping–dominated microstructure in U10Mo fuels and facilitates designing and tuning of microstructures of U10Mo alloys for tailoring the final designed performance of the fuel under irradiation.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2021

Forming mechanism of equilibrium and non-equilibrium metallurgical phases in dissimilar aluminum/steel (Al–Fe) joints

Abstract Forming metallurgical phases has a critical impact on the performance of dissimilar materials joints. Here, we shed light on the forming mechanism of equilibrium and non-equilibrium intermetallic compounds (IMCs) in dissimilar aluminum/steel joints with respect to processing history (e.g., the pressure and temperature profiles) and chemical composition, where the knowledge of free energy and atomic diffusion in the Al–Fe system was taken from first-principles phonon calculations and data available in the literature. We found that the metastable and ductile (judged by the presently predicted elastic constants) Al 6 Fe is a pressure ( P ) favored IMC observed in processes involving high pressures. The MoSi 2 -type Al 2 Fe is brittle and a strong P -favored IMC observed at high pressures. The stable, brittle η-Al 5 Fe 2 is the most observed IMC (followed by θ-Al 13 Fe 4 ) in almost all processes, such as fusion/solid-state welding and additive manufacturing (AM), since η-Al 5 Fe 2 is temperature-favored, possessing high thermodynamic driving force of formation and the fastest atomic diffusivity among all Al–Fe IMCs. Notably, the ductile AlFe 3 , the less ductile AlFe, and most of the other IMCs can be formed during AM, making AM a superior process to achieve desired IMCs in dissimilar materials. In addition, the unknown configurations of Al 2 Fe and Al 5 Fe 2 were also examined by machine learning based datamining together with first-principles verifications and structure predictions. All the IMCs that are not P- favored can be identified using the conventional equilibrium phase diagram and the Scheil-Gulliver non-equilibrium simulations.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Intrinsic ferromagnetism and restrictive thermodynamic stability in MA$_{2}$N$_{4}$ and Janus VSiGeN$_{4}$ monolayers

The seminal experimental discovery of the remarkably stable MoSi 2 N 4 monolayer has led to a handful of predicted magnetic two-dimensional (2D) materials in the MA 2 Z 4 family (M = transition metals, A = Si, Ge, and Z = N, P, As). These magnetic monolayers were predicted to be dynamically stable, but none of them has been synthesized to date. In this Research Letter, from first-principles thermodynamic stability analysis, we demonstrate that only the nitrides are thermodynamically stable and this occurs under N-rich conditions. Based on this finding, we propose two ferromagnetic, semiconducting Janus monolayers in the family: VSiGeN 4 and VSiSnN 4 . They are both dynamically and thermally stable, but only the former is thermodynamically stable. Intriguingly, Janus VSiGeN 4 and VSiSnN 4 monolayers show weak in-plane anisotropy compared with the VSi 2 N 4 monolayer. Furthermore, these two emerging Janus magnetic semiconductors offer opportunities for studying 2D magnetism and spin control for spintronics applications.

2-dimensional systems↗
DOE OSTI2020

Materials Data on SiMo by Materials Project

MoSi is Tungsten Carbide structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Mo4+ is bonded to six equivalent Si4- atoms to form a mixture of distorted corner, edge, and face-sharing MoSi6 pentagonal pyramids. All Mo–Si bond lengths are 2.52 Å. Si4- is bonded to six equivalent Mo4+ atoms to form a mixture of distorted corner, edge, and face-sharing SiMo6 pentagonal pyramids.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Integrated CMOS RF amplifier

This paper reports an integrated 2.0 micron CMOS RF amplifier designed for amplification in the 420-450 MHz frequency band. Design techniques are shown for the test amplifier configuration. Problems of decreased amplifier bandwidth, gain element instability, and low Q values for the inductors were encountered. Techniques used to overcome these problems are discussed. Layouts of the various elements are described and a summary of the simulation results are included. Test circuits have been submitted to MOSIS for fabrication.

Charity, C.↗
NASA NTRS1990

CMOS output buffer wave shaper

As the switching speeds and densities of Digital CMOS integrated circuits continue to increase, output switching noise becomes more of a problem. A design technique which aids in the reduction of switching noise is reported. The output driver stage is analyzed through the use of an equivalent RLC circuit. The results of the analysis are used in the design of an output driver stage. A test circuit based on these techniques is being submitted to MOSIS for fabrication.

Albertson, L.↗
NASA NTRS1992

Analog/digital pH meter system I.C.

The project utilizes design automation software tools to design, simulate, and fabricate a pH meter integrated circuit (IC) system including a successive approximation type seven-bit analog to digital converter circuits using a 1.25 micron N-Well CMOS MOSIS process. The input voltage ranges from 0.5 to 1.0 V derived from a special type pH sensor, and the output is a three-digit decimal number display of pH with one decimal point.

Vincent, Paul↗
NASA NTRS1995

High-temperature oxidation behavior of reaction-formed silicon carbide ceramics

The oxidation behavior of reaction-formed silicon carbide (RFSC) ceramics was investigated in the temperature range of 1100 to 1400 C. The oxidation weight change was recorded by TGA; the oxidized materials were examined by light and electron microscopy, and the oxidation product by x-ray diffraction analysis (XRD). The materials exhibited initial weight loss, followed by passive weight gain (with enhanced parabolic rates, k(sub p)), and ending with a negative (logarithmic) deviation from the parabolic law. The weight loss arose from the oxidation of residual carbon, and the enhanced k(sub p) values from internal oxidation and the oxidation of residual silicon, while the logarithmic kinetics is thought to have resulted from crystallization of the oxide. The presence of a small amount of MoSi, in the RFSC material caused a further increase in the oxidation rate. The only solid oxidation product for all temperatures studied was silica.

Ogbuji, Linus U. J. T.↗