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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 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Effect of THz-bandwidth incoherent laser radiation on bulk damage in potassium dihydrogen phosphate crystals

Abstract The laser-damage performance characteristics of potassium dihydrogen phosphate (KDP) samples under exposure to a distinctive broadband incoherent laser pulse are investigated. A laser system providing such pulses is intended to explore improved energy-coupling efficiency on the target in direct-drive inertial confinement fusion experiments and provides incoherent bandwidths as large as 10 THz in a nanosecond pulse. A consequence of this bandwidth is very rapid fluctuations in intensity capable of reaching maxima much larger than the average intensity within the pulse. A custom damage-test station has been built to perform measurements with broadband incoherent pulses in order to determine what effect these fast and high-intensity oscillations have on laser damage. A set of experiments under different bandwidth and beam configurations shows the effect to be minimal when probing bulk damage in KDP. Modeling indicates this behavior is supported by long electron-relaxation times compared to the source-field fluctuations, following excitation of individual electrons in the conduction band. The results help better understand the laser-induced–damage mechanisms in KDP, and its ability to operate in broadband temporally incoherent high-energy lasers that may be particularly suitable for future laser-fusion energy systems.

36 MATERIALS SCIENCE↗
NASA NTRS1977

Consideration of encapsulants for photovoltaic arrays in terrestrial applications

Long-term survivability of photovoltaic arrays and components in terrestrial environments will require development of adequate protective systems. Highly considered are polymeric encapsulants, a method which was successfully employed in space and aerospace applications to protect critical electrical circuitry. To be employable, however, the polymer encapsulants must themselves be chemically and mechanically resistant to failure in terrestrial service. Chemical resistance includes stability to the degrading actions of ultraviolet light, oxygen, moisture and elevated temperatures in sun rich areas. Programs are underway to identify and develop chemically stable encapsulant candidates. Chemical considerations aside, mechanical failures of the encapsulants must also be avoided in array designs. This paper discusses design considerations for avoiding mechanical failures of polymeric encapsulants, with emphasis on biaxial properties, thermal fatigue, and anisotropy and nonhomogeneity of material properties. The general principles to be presented evolved from actual failures of polymeric materials in engineering applications. Also included are brief remarks on the permeability of polymer materials to atmospheric gases.

Cuddihy, E. F.↗
NASA NTRS1996

Impact Properties of Metal Fan Containment Materials Being Evaluated for the High-Speed Civil Transport (HSCT)

Under the Enabling Propulsion Materials (EPM) program - a partnership between NASA, Pratt & Whitney, and GE Aircraft Engines - the Materials and Structures Divisions of the NASA Lewis Research Center are involved in developing a fan-containment system for the High-Speed Civil Transport (HSCT). The program calls for a baseline system to be designed by the end of 1995, with subsequent testing of innovative concepts. Five metal candidate materials are currently being evaluated for the baseline system in the Structures Division's Ballistic Impact Facility. This facility was developed to provide the EPM program with cost-efficient and timely impact test data. At the facility, material specimens are impacted at speeds up to 350 m/sec by projectiles of various sizes and shapes to assess the specimens' ability to absorb energy and withstand impact. The tests can be conducted at either room or elevated temperatures. Posttest metallographic analysis is conducted to improve understanding of the failure modes. A dynamic finite element program is used to simulate the events and both guide the testing as well as aid in designing the fan-containment system.

Source record↗
DOE OSTI2014

Thin Silicon Solar Cells: A Path to 35% Shockley-Queisser Limits

Crystalline silicon technology is expected to remain the leading photovoltaic industry workhorse for decades. We present here the objectives and workplan of a recently launched project funded by the U.S. Department of Energy through the Foundational Program to Advance Cell Efficiency II (FPACE II), which aims at leading crystalline silicon to an efficiency breakthrough. The project will tackle fundamental approach of materials design, defect engineering, device simulations and materials growth and characterization. Among the main novelties, the implementation of carrier selective contacts made of wide bandgap material or stack of materials is investigated for improved passivation, carrier extraction and carrier transport. Based on an initial selection of candidate materials, preliminary experiments are conducted to verify the suitability of their critical parameters as well as preservation of the silicon substrate surface and bulk properties. The target materials include III-V and metal-oxide materials.

Ding, Laura↗
DOE OSTI2018

Uranium(VI) Sorption onto Montmorillonite Clay in the Presence of Ca2+/Calcite Impurities

The storage of nuclear waste creates a series of significant environmental risks. One attempt to minimize these potential impacts is the use of underground geological repositories, where waste containers are surrounded by geologic buffer materials creating an engineered barrier. One buffer material that has been of interest is bentonite, which is largely composed of montmorillonite clay. These barriers limit the mobility of radioactive contaminants, such as uranium(VI), into environmental systems based on contaminant sorption onto the clay material. System conditions, such as pH, the presence of mineral impurities such as calcite, and the concentrations of U(VI) and atmospheric CO2 also affect the sorption behavior of U(VI) onto these clay barriers. This study focuses on the effects of Ca2+ and calcite (CaCO3), a common impurity found in montmorillonite on the sorption behavior of U(VI). Computer simulations of the chemical solution species (chemical form) of U(VI), in the absence and presence of Ca2+/calcite impurities are performed in parallel with laboratory sorption experiments. Experimental data will be compared to modeling results to help obtain further insights regarding the impacts of Ca2+/calcite impurities on U(VI) solution speciation and sorption behavior onto montmorillonite.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Positron Annihilation Spectroscopy Investigation of Vacancy Clusters in Neutron-Irradiated 3C-SiC

Silicon carbide (SiC) has been widely applied or considered in nuclear systems as fuel and structural materials since 1960's, given its high-temperature stability, chemical inertness, and exceptional irradiation resistance. Chemically vapor deposited (CVD) SiC has been considered as the pressure vessel materials for the TRISO fuel particles used in high temperature gas-cooled reactors or novel accident tolerant fuel concepts for light water reactors. The use of SiC/SiC composites as primary structural materials has also been proposed in fusion reactors. Driven by the need to enlarge the safety margins of nuclear reactors in accident scenarios, R and D of accident-tolerant fuel has become an important topic in the nuclear engineering and materials community. A continuous fiber SiC/SiC composite is under consideration for Zr alloy cladding replacement. Microstructural development and mechanical property change in SiC subject to neutron and ion irradiation have been studied extensively and understood well. However, the information of small vacancy cluster (i.e., those invisible in TEM) evolution in SiC exposed to neutron irradiation is still lacking, and such small clusters is suspected to play an important role in swelling, radiation creep, and thermal conductivity degradation. In this study, positron annihilation spectroscopy is used to characterize the vacancy defects in 3C-SiC exposed to various neutron irradiation conditions to capture the dependence of temperature and irradiation dose. The obtained vacancy cluster distribution is then linked to the measured swelling behavior to provide insight into the relationship between microstructure and physical property of SiC. (authors)

36 MATERIALS SCIENCE↗
NASA NTRS1988

Structural analyses of engine wall cooling concepts and materials

The severe thermal environments under which hypersonic aircraft such as the National Aerospace Plane (NASP) will operate require cooling of the engine walls, especially in the combustor. A preliminary assessment is made of some candidate materials based on structural analyses for a number of convective cooling configurations. Three materials were studied: graphite/copper and tungsten/copper composite alloys with 50 percent fiber volume fractions and a wrought cobalt-base superalloy, Haynes 188. Anisotropic mechanical and thermal properties for the composites were obtained from a computer code, ICAN, which determines the composite material properties from the individual properties of the fiber and matrix materials. The structural analyses were performed by using the MARC nonlinear finite element code. Heat transfer analyses were conducted to calculate the metal temperature distributions.

Kaufman, Albert↗
DOE OSTI2013

Low Background Materials and Assay: A Supplement to the Cosmic Frontier CF1 Summary.

Executive Summary The next generation of direct detection dark matter experiments will require stringent radiopurity in their target materials, internal instrumentation, and shielding components. A survey of major material assay facilities worldwide and of anticipated assay needs of generation 2 (G2) experiments indicate the current assay capability is marginally adequate in sensitivity and inadequate in throughput. High purity germanium (HPGe) gamma-ray assay has been the workhorse for material screening. It appears hundreds of samples will require screening at the limits of current achievable HPGe sensitivity. Mass spectroscopy methods and neutron activation analysis have demonstrated superior assay sensitivity in some specific cases. However, they are also currently throughput limited. In addition, both alpha/beta screening and radon emanation analysis at or beyond the current achievable sensitivity levels will be needed for dozens of samples. Experiments that follow G2 will have even more stringent material radiopurity specifications, exceeding current assay capabilities in both sensitivity and throughput. These screening needs must precede the commissioning of experiments by 3-5 years to inform design and quality control of components. Achieving the radiopurity goals of the next decade’s experiments will require investment in new techniques and tools to improve material assay sensitivity and throughput. Engineered low-background materials are a significant R&D expenditure, requiring developmental lead-time, and should benefit many end-user experiments. Reserving underground real estate for assay methods affected by cosmic rays (e.g. HPGe) and engineered radiopure materials activated by cosmic rays (e.g. electroformed copper) is judicious forward planning. In many cases, these spaces will require radon-suppressed sample preparation and material storage space. The above-mentioned survey of material assay facilities indicated very little development is taking place to improve sensitivity or throughput capability. In order to create the necessary infrastructure, it may help to form a consortium of low-background assay centers in the U.S that is managed by a scientific board with representatives from the community. This would provide for common use of existing screening facilities and a unified plan for new infrastructure and site development (see the Facilities White Paper). Such a loose organization already exists as AARM (Assay and Acquisition of Radiopure Materials), which is currently populating a community-wide materials database with published assay information. A more formal organization such as a Consortium is being actively investigated with DOE and NSF. Eventually, results of all screening performed in Consortium assay centers could be input directly to the open-access database, reducing duplication and providing for more efficient vendor selection.

Cooley-Sekula, Jodi↗
NASA NTRS1984

Advanced high temperature materials for the energy efficient automotive Stirling engine

The Stirling Engine is under investigated jointly by the Department of Energy and NASA Lewis as an alternative to the internal combustion engine for automotive applications. The Stirling Engine is an external combustion engine that offers the advantage of high fuel economy, low emissions, low noise, and low vibrations compared to current internal combustion automotive engines. The most critical component from a materials viewpoint is the heater head consisting of the cylinders, heating tubes, and regenerator housing. Materials requirements for the heater head include compatibility with hydrogen, resistance to hydrogen permeation, high temperature oxidation/corrosion resistance and high temperature creep-rupture and fatigue properties. A continuing supporting materials research and technology program has identified the wrought alloys CG-27 and 12RN72 and the cast alloys XF-818 and NASAUT 4G-A1 as candidate replacements for the cobalt containing alloys used in current prototype engines. Based on the materials research program in support of the automotive Stirling engine it is concluded that manufacture of the engine is feasible from low cost iron-base alloys rather than the cobalt alloys rather than the cobalt alloys used in prototype engines. This paper will present results of research that led to this conclusion.

Titran, R. H.↗
NASA NTRS1980

3500-hour durability testing of ceramic materials for automotive gas turbine engines

A two-year durability program was performed by AiResearch Phoenix to evaluate four commercially available ceramic materials under simulated automotive gas turbine combustor discharge conditions. These conditions included extended cyclic thermal exposures up to 2500 F and 3500 hr. The four materials selected for evaluation were Norton NCX-34 hot pressed silicon nitride, AiResearch RBN 101 reaction bonded silicon nitride, Carborundum pressureless sintered alpha-SiC and Pure Carbon Co. (British Nuclear Fuels, Ltd.) Refel reaction sintered silicon carbide. These materials were initially exposed to 350 hr/1750 cycles at 1200 and 1370 C. Subsequent exposures to 1050, 2100 and 3500 hr were performed on those materials maintaining 50% of baseline strength after the initial exposure. Additional evaluations of exposed bars included dimensional and weight changes, dye penetrant, specific damping capacity changes, SEM fractography, and X-ray diffraction.

Carruthers, W. D.↗
DOE OSTI2019

Radiation Tolerance and Mechanical Properties of Nanostructured Amorphous-Ceramic/Metal Composites

The objective of this work was to use a radically non-traditional approach to design amorphous-ceramic/metal composites for service in extreme irradiation environments. The project was built on a strong integration among four research teams for materials synthesis and characterization, ion irradiation, mechanical evaluation, and atomic scale modeling. Rather than try to prevent microstructure changes in polycrystalline aggregates, the research team worked to evolve composite systems where one of the constituents is intentionally synthesized in a non-crystalline or “amorphous” state. Because amorphous materials possess no translational symmetry, such alloys do not contain conventional crystal defects such as vacancies, interstitials, or dislocations. These materials offer the possibility of eliminating the root cause responsible for radiation damage in polycrystalline solids - namely the production of point defects and clusters thereof in collision cascades - and could serve as the basis for developing a new class of structural materials with unprecedented resistance to radiation. The amorphous alloys were used to develop advanced amorphous-ceramic/metal composites with greatly improved radiation tolerance and stability above 500oC, and improved mechanical performance by combining the good properties of amorphous materials (high strength and elastic limit) with those of crystalline materials (high toughness, strain hardening). The ceramic component of the composite consisted of a high crystallization temperature and radiation tolerant amorphous alloy composed of Si-O-C, silicon oxycarbide, while the metal layer was Fe and Fe(Cr), chosen to serve as model materials for steel. A prime hypothesis that drove this work is that the composite interface, together with the composite constituents, would provide significantly enhanced radiation tolerance, similar to or superior to those observed in metallic nanolayered structures, in a more engineering relevant material system. As our experimental data and modeling show, we have successfully developed a new class of ceramic/metal composites that can be adapted for engineering applications, thus significantly impacting improved materials performance for advanced nuclear reactors.

36 MATERIALS SCIENCE↗
DOE OSTI2011

In-vitro Cell Exposure Studies for the Assessment of Nanoparticle Toxicity in the Lung - A Dialogue between Aerosol Science and Biology

The rapid introduction of engineered nanostructured materials into numerous industrial and consumer products will result in enhanced exposure to engineered nanoparticles. Workplace exposure has been identified as the most likely source of uncontrolled inhalation of engineered aerosolized nanoparticles, but release of engineered nanoparticles may occur at any stage of the lifecycle of consumer products. The dynamic development of new nanomaterials with possibly unknown toxicological effects poses a challenge for the assessment of nanoparticle induced toxicity and safety. In this consensus document from a workshop on in-vitro cell systems for nanotoxicity testing an overview is given of the main issues concerning inhalation exposure to nanoparticles, lung physiology, nanoparticle-related biological mechanisms, in-vitro cell exposure systems for nanoparticles and social aspects of nanotechnology. The workshop participants recognized the large potential of in-vitro cell exposure systems for reliable, high-throughput screening of nanotoxicity. For the investigation of pulmonary nanotoxicity, a strong preference was expressed for air-liquid interface (ALI) cell exposure systems (rather than submerged cell exposure systems) as they closely resemble in-vivo conditions in the lungs and they allow for unaltered and dosimetrically accurate delivery of aerosolized nanoparticles to the cells. The members of the workshop believe that further advances in in-vitro cell exposure studies would be greatly facilitated by a more active role of the aerosol scientists. The technical know-how for developing and running ALI in-vitro exposure systems is available in the aerosol community and at the same time biologists/toxicologists are required for proper assessment of the biological impact of nanoparticles.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2016

Genetically encoded sensors enable real-time observation of metabolite production

Advances in biotechnology are enabling engineers to harness natural processes for the production of valuable new chemicals and materials. Cells engineered for chemical production act as renewable factories and redefine what is possible in industries as diverse as manufacturing, pharmaceuticals, and energy. Despite this potential, long and uncertain timelines for biobased product development hinder progress. Engineering cells for chemical production is challenging because the complexity of biology necessitates many attempted designs before an optimal combination of genetic elements or culture conditions is discovered. In this work, we develop a framework that allows design evaluation to be performed with fluorescence such that microbial chemical production can be monitored in real time without the need for sample preparation or laborious analytical techniques.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Methods and materials for determination of distribution coefficients for separation materials

Methods and materials for determining the affinity of separation materials for targeted species are described. A composite separation medium is described that combines a separation material such as an ion exchange material or a sorbent with an SERS substrate. Methods and materials can be utilized to determine the distribution coefficient of a species for a separation material after running a single separation protocol followed by examination of the separation material of the protocol according to SERS. Disclosed methods can be utilized to determine the affinity of existing separation materials for targeted species as well as to determine the affinity of newly engineered separation materials to characterize species.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

PBX 9502 Literature Review: An Engineering Perspective

Engineering analysis for the stockpile systems requires that materials used in the stockpile be characterized properly. One of these materials is PBX 9502, an insensitive high explosive (IHE). The Los Alamos National Laboratory (LANL) is working to improve its engineering material modeling capability for PBX 9502.This effort includes the development of requirements for an engineering material model (or models), review of material models currently used for engineering simulations, and review of currently available thermal-mechanical test data. The information obtained will either help to enhance the existing models or help the development and implementation of a new model or models. This document summarizes a review of literature on PBX 9502 that was performed over the past several months. The review was focused primarily on literature dealing with the characterization of PBX 9502 from a thermo-mechanical standpoint. Literature dealing with the formulation, explosive performance, and sensitivity was not included in this report. It should be noted that, like most research of this nature, this literature review is not intended to be all-inclusive. However, it provides a detailed baseline of the information that is available and will be very useful to those seeking to expand the PBX 9502 knowledge base.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
NASA NTRS1966

Development of porous ionizer materials.

Porous structures for ion engine application, discussing ionizer materials preparation, based on powder metallurgy and two-phase tungsten base alloy

POWDER METALLURGY↗
NASA NTRS1994

High Temperature Solid Lubricant Materials for Heavy Duty and Advanced Heat Engines

Advanced engine designs incorporate higher mechanical and thermal loading to achieve efficiency improvements. This approach often leads to higher operating temperatures of critical sliding elements (e.g. piston ring/cylinder wall contacts and valve guides) which compromise the use of conventional and even advanced synthetic liquid lubricants. For these applications solid lubricants must be considered. Several novel solid lubricant composites and coatings designated PS/PM200 have been employed to dry and marginally oil lubricated contacts in advanced heat engines. These applications include cylinder kits of heavy duty diesels, and high temperature Stirling engines, sidewall seals of rotary engines, and various exhaust valve and exhaust component applications. This paper describes the tribological and thermophysical properties of these tribomaterials and reviews the results of applying them to engine applications. Other potential tribological materials and applications are also discussed with particular emphasis on heavy duty and advanced heat engines.

Dellacorte, C.↗