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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 1,243 records · Page 69
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

INVESTIGATION OF TITANIUM BONDED GRAPHITE FOAM COMPOSITES FOR MICRO ELECTRONIC MECHANICAL SYSTEMS (MEMS) APPLICATIONS

PiMEMS Inc. (Santa Barbara, CA) in collaboration with ORNL investigated the use of Titanium Bonded Graphite Foam Composites (TBGC) for thermal mitigation in Micro Electronic Mechanical Systems (MEMS) applications. Also considered were potentially new additive manufacturing routes to producing novel high surface area micro features and diverse shaped heat transfer components for numerous lightweight MEMs applications.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Surface analysis of model systems: From a metal-graphite interface to an intermetallic catalyst

This thesis summarizes research completed on two different model systems. In the first system, we investigate the deposition of the elemental metal dysprosium on highly-oriented pyrolytic graphite (HOPG) and its resulting nucleation and growth. The goal of this research is to better understand the metal-carbon interactions that occur on HOPG and to apply those to an array of other carbon surfaces. This insight may prove beneficial to developing and using new materials for electronic applications, magnetic applications and catalysis.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Surface analysis of model systems: From a metal-graphite interface to an intermetallic catalyst

This thesis summarizes research completed on two different model systems. In the first system, we investigate the deposition of the elemental metal dysprosium on highlyoriented pyrolytic graphite (HOPG) and its resulting nucleation and growth. The goal of this research is to better understand the metal-carbon interactions that occur on HOPG and to apply those to an array of other carbon surfaces. This insight may prove beneficial to developing and using new materials for electronic applications, magnetic applications and catalysis. In the second system, we investigate the intermetallic single crystal NaAu2. We conducted a characterization of the clean (111) surface along with a determination of the effects of gas exposures on the surface. No surfaces of bulk NaAu2 have been previously characterized, although the closely related system of Na films on Au(111) has been investigated. NaAu2 is an active catalyst for CO oxidation. To better understand the catalytic reaction occurring, we studied the NaAu2 surface after exposure to O 2 ,g, CO g , CO 2,g ,and H 2 O g . The goal of this research is to find a possible alternative for supported gold catalysts by utilizing an Au-rich intermetallic compound and to determine how its catalytic reaction proceeds. This insight may be valuable in determining other catalytic alternatives as well as helping understand catalytic reactions that occur with other intermetallic compounds. In order to characterize and examine these systems, we utilized several ultrahigh vacuum (UHV) techniques, including scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Review of Thermal Contact Resistance of Flexible Graphite Materials for Thermal Interfaces in High Heat Flux Applications

In this report the data is reviewed on thermal contact conductance (TCC) and/or thermal contact resistance (TCR) at material interfaces which employs flexible graphite (FG) materials as thermal interface materials (TIM). FG materials are often used as TIM due to their conforming nature. While the overall TCR can be estimated straightforward from measured data, the interface TCR is much more difficult to obtain. The report also discusses the interfacial thermal contact conductance between FG-tungsten and FG-Glidcop-Al15, which are envisioned for high-heat flux applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Neural Thermal Scattering (NeTS) Modules for Graphite & Beryllium [Slides]

This presentation discusses the motivations behind the project, which include facilitating compact formulation for TSL data, extending AI knowledge, and providing advanced reactor simulation framework. It also discusses how the project accounts for beryllium and graphite complexity, including atomistic, dynamical, and neural. Additionally, new material-informed neural thermal scattering (NeTS) Modules are examined. The implications, conclusions, and plan future work for the project are also discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Secondary Pion Production using the LINAC Beam on Graphite and Tungsten Targets

The Fermilab 400-MeV Linac primary proton beam can produce precision, single-species secondary beams using a production target in the MeV Test Area experimental hall; specifically, pions from 4 up to 120 MeV kinetic energy. (These low energy pions rapidly decay into a muon beam in a secondary collection and transport beamline.) Although graphite is a standard production target material given its ultra-high temperature tolerance and low impact on the post-target primary beam, secondary pion/muon total production cross sections increase approximately as Z1/3 for positive muons and N2/3 for negative muons. Higher mass targets such as tungsten can potentially increase low-energy m+ and m- rates by factors of 3 and 8, respectively. Initial production studies have confirmed higher muon yield from heavy targets (tungsten vs carbon), but also, surprisingly, show significant differences in pion production between modern hadronic models (GENIEhad) and between GEANT and MCNP, state of the art production modeling codes. This project will further investigate the production discrepancies between these two target materials and between different physics models with high-statistics runs using the GEANT-based code, G4Beamline to better quantify the results and compare with production data which will be obtained using the MTA secondary beamline.

Ahmed, Shiza↗
DOE OSTI2016

The Analysis of Results from 3-Point Flexure Testing of Irradiated AGC-1 Graphite Creep Specimens

Here we report the analysis of test data from AGC-1 specimen 3-pt flexure testing. At this time all mechanical (flexural) testing of AGC-1 specimens has been completed. Individual force-extension curves are available as .txt files recorded electronically from the author (burchelltd@ornl.gov). This Technical Memorandum meets Idaho National Laboratories statement of Work No. 10752 Rev. 3 deliverable 4.4C “Issue a draft ORNL TM report summarizing the results and data analysis of all mechanical testing to INL no later than May 15, 2015.” The data and analysis was provided in a timely fashion as an excel s/s with data analysis plots. This TM follows on and formalizes transmission of the data. The major conclusion from this analysis is that there is no additional effect of creep strain on the flexure strength of graphite.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Experimental Plan for NBG-18 Graphite Bi-axial Strength Testing in the Second and Third Stress Quadrants

The plan for test system's shake down and eventual (funding permitting) bi-axial testing of grade NBG-18 graphite in the second and third stress quadrant are reported. Testing in the first and fourth stress quadrants was previously reported. Details of the specimen and test system design are given along with the anticipated stress ratios to be tested, including specimen numbers are reported. The estimated test pressures needed to attain the planned stress ratios are reported.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Robust Statistical Approach for Determination of Graphite Nitridation Using Bayesian Model Comparison

A better estimation of surface reaction efficiency of semiconductor-grade graphite with atomic nitrogen, as well as the calibration error are calculated using Bayesian updating based on experimental data. Compared with a conventional deterministic model, the stochastic model approach is a powerful tool in the sense that the model is capable of taking into account underlying error correlations among the data quantities. In this paper, we investigate four different stochastic models (called “stochastic system model classes” herein) corresponding to different descriptions of modeling and measurement error structures, given one deterministic physical model. These stochastic system model classes differ in the covariance matrix structure that is used in the uncertainty model to represent uncertainties associated with the physical model and experimental measurements. For each model class, Bayesian inference is used to estimate the posterior probabilities of the physical model parameters as well as of the stochastic model parameters. Model comparison and selection are then applied based on two measures including Bayesian evidence and Bayesian information criterion, as well as the deviance information criterion. Both measures suggest the stochastic model class, which considers that a correlation between errors in two data quantities among different data points is the most plausible. With the stochastic model class, the range of uncertainty in surface reaction efficiency is estimated to be about two orders of magnitude at [Formula: see text].

Engineering↗
DOE OSTI2020

Improving Heat Conduction of Insulated Metal Substrate with Thermal Pyrolytic Graphite Core for SiC Power Module Packaging

TPG-core IMS concept was jointly explored in this study. Integrating high thermally conductive TPG graphite core into IMS is expected to simultaneously achieve high thermal conductivity from TPG and electrical functionalities from IMS. Nearly 2x thermal conductivity and 30% weight saving was demonstrated on TPG-core IMS compared to conventional Cu-core IMS. Significant junction temperature reduction (11°C) in steady state and power cycling was revealed by the thermal analysis as the result of improved thermal spreading in plane and through the thickness. The study also proved the manufacturability and compatibility of this TPG-core IMS structure to the existing IMS production and power module assembling. Finally, the integration of TPG and IMS paves a new packaging route to increase heat load, improve reliability, simplify module design and reduce assembling cost and number of steps.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effect of boronization on plasma-facing graphite surfaces and its correlation with the plasma behavior in NSTX-U

Boronization is a Plasma Facing Component (PFC) conditioning technique widely used in tokamak machines. The National Spherical Torus Experiment-Upgrade (NSTX-U) applied this conditioning, using a plasma glow with a deuterated Trimethyl-boron (d-TMB) and He mixture. The use of boronization during the campaign improved the plasma performance, allowing longer plasma discharges and H-mode access. The chemical state of an ATJ graphite sample, used as a proxy for the NSTX-U PFCs, was monitored in-situ using the Materials Analysis Particle Probe (MAPP) diagnostic and X-ray Photoelectron Spectroscopy (XPS). The XPS data showed a progressive rise (from + fluence increased. Filterscopes were used to measure the light emitted by oxygen impurities in the plasma near the surface of the PFC. An increase in the registered magnitude of the OII line, normalized to the Dγ intensity, was observed as the concentration of O on the ATJ surface increased. The plasma performance was found to be strongly correlated to oxygen impurity concentrations at the plasma edge and on the PFC surface, as measured by the discharge length and access to the H-mode regime. In this work, we present a quantitative analysis of the evolution of the chemistry of the ATJ surface, and the oxygen presence in the plasma-material interface, and report relevant plasma parameters observed during the same period of time.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1965

Graphite element serves as radiant heat source

Radiators using a graphite heating element as a radiant heat source have high heat flux and long operational lives. They are used to test the thermal resistance of materials.

Source record↗
NASA NTRS1966

Carbon and graphite

Mechanical properties, plastic deformation, and tensile creep rate in carbon and graphite

TENSILE CREEP↗