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DOE OSTI2022

Tuning the Placement of Pt “Single Atoms” on a Mixed CeO 2 –TiO 2 Support

Defect sites on the oxide supports can be used to anchor and activate "single-atoms" catalysts (SACs). By engineering the anchoring sites for supporting SACs, one can alter their electronic and atomic structures which, in turn, define their activity, selectivity, and stability for catalytic reactions. To create and tune unique sites for Pt SACs on CeO 2 support, in this work, we synthesized a system consisting of CeO 2 decorated on TiO 2 nano-oxides for supporting the Pt SACs and investigated the effect of Pt weight loading. Here, a combination of multiple structural characterization methods including diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) were employed to characterize the distribution of charge states of single atoms and evaluate the heterogeneity of their binding sites. We have found that the placement of Pt atoms can be tuned on a mixed oxide surface by changing the weight loading of Pt.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2018

Creep and Tensile Properties of Direct Metal Laser Sintered (DMLS) Inconel 738LC Coupons and Comparison to Cast Properties

Due to the nature of sCO2 power cycles, a number of turbine parts must have good mechanical properties at elevated temperatures. For recompression cycles, the turbine inlet temperature is between 600°C - 750°C, which puts nearly all high-temperature turbine parts into a creep regime. The high-strength parts in these applications are often composed of materials having high nickel or chrome contents, and are often termed superalloys. At these temperatures, the blades must survive mechanical loads due to centrifugal stress and blade loading. While centrifugal stress is primarily a function of tip velocity and its associated centrifugal acceleration, blade loading is a function of power density. Since sCO2 turbomachinery is approaching the power density of rocket engines, blade loading tends to be quite large. Another result of this high power density is that blade passages for 1-10 MW turbines tend to be quite small, making conventional fabrication methods challenging and costly; this leads engineers to pioneer new techniques to address these challenges. The authors of the current work are addressing this challenge by applying additive manufacturing techniques in the production of a 10 MW radial inflow impeller. While a comprehensive database exists for the mechanical properties of forged and cast superalloys, data is sparse for superalloys fashioned by direct metal laser sintering (DMLS) or other additive manufacturing methods. For the remainder of this work, the term printed will refer to components manufactured using one of these processes for brevity. The current work stems from the desire to manufacture a radial inflow turbine impeller using additive manufactured (AM) Inconel 738. While Siemens has adopted the use of DMLS printed Inconel 738 for use in select aviation engine parts, creep and tensile properties have not been published to the extent needed to validate a given design. The current work will show creep and tensile properties of AM Inconel 738 in the horizontal and vertical build directions and their respective comparison to cast Inconel 738 properties.

wilkes, Jason↗

DOE OSTI2019

Development of Molybdenum Phosphide Catalysts for Higher Alcohol Synthesis from Syngas by Exploiting Support and Promoter Effects

Molybdenum phosphide (MoP) catalysts have recently gained attention because of their robust methanol synthesis activity from CO/CO 2 . Synthesis strategies are used to steer MoP selectivity toward higher alcohols by investigating the promotion effects of alkali (K) and CO-dissociating (Co, Ni) and non-CO-dissociating (Pd) metals. Systematic research with transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy (XAS) showed that critical parameters governing the activity of MoP catalysts are P/Mo ratio and K loading, both facilitating MoP formation. The kinetic studies of mesoporous silica-supported MoP catalysts show a twofold role of K, which also acts as an electronic promoter by increasing the total alcohol selectivity and chain length. Palladium (Pd) increases CO conversion, but decreases alcohol chain length. The use of mesoporous carbon (MC) support has the most significant effect on catalyst performance and yields a KMoP/MC catalyst that ranks among the state-of-the-art in terms of selectivity to higher alcohols.

10 SYNTHETIC FUELS↗

DOE OSTI2025

An Integrated High-Speed Microstructural Characterization Method Using Simultaneous XRD, Stereo-DIC, and PCI

High-speed characterization of the deformation mechanisms in polycrystalline metals requires the quantification of full strain fields and local microstructural evolutions simultaneously. In this paper, we present a novel experimental method to integrate phase-contrast imaging (PCI), stereographic digital image correlation (stereo-DIC), and full-ring X-ray diffraction (XRD) to allow for the simultaneous characterization of polycrystalline metals at 1MHz or higher. A Kolsky bar was integrated into the synchrotron X-ray source in Sector 32 ID-B at the Advance Photon Source (APS) at Argonne National Laboratory. When the sample is dynamically loaded, the diagnostic methods of full-ring XRD, PCI, and stereo-DIC are properly synchronized to record the deformation behavior at both continuum and microstructural scales as a function of the loading history. An advanced high-strength steel (AHSS) is used as a model material to demonstrate the capabilities of this new experimental method.

36 MATERIALS SCIENCE↗

DOE OSTI2021

The nature of yielding and anelasticity in metals

Not provided.

Materials Science↗

DOE OSTI2022

Multiscale dynamic experiments on fiber-reinforced composites with damage assessment using high-speed synchrotron X-ray phase-contrast imaging

We report fiber-reinforced composites (FRCs) have been widely used as protection materials to replace heavier metals. However, predictive capabilities for the impact-induced failure of FRCs have not been well-developed. In this work, we introduced an integrated technique to visualize the dynamic failure of FRCs, with the modified Kolsky bar loading and the high-speed synchrotron X-ray phase-contrast imaging (PCI). We summarize our experimental studies across the FRCs’ structural levels by using this integrated technique, including single-fiber tensile experiments, fiber/matrix debonding experiments, and single-edge notched bending experiments on composite laminates. It is revealed that the high-speed synchrotron X-ray PCI technique possesses sufficient spatial resolution to identify the failure behavior of a single fiber in the 10-μm scale level, as well as temporal resolution to identify the time sequence of internal dynamic damage evolution. The technique can penetrate through the opaque composite sample and provide real-time visualization of small-scale damaging mechanisms such as the embedded fiber’s sliding in the matrix and the fiber’s transverse debonding with the matrix. At an expanding scale, the technique can identify the crack initiation and track the cracking behavior inside a single ply or between different plies of a composite laminate. High-speed visualization inside the material by this integrated technique provides critical deformation and failure information to develop physical understanding of the damage inside composites under impact.

47 OTHER INSTRUMENTATION↗

DOE OSTI2018

Fatigue-driven acceleration of abnormal grain growth in nanocrystalline wires

In this study, molecular dynamics simulations were employed to simulate the mechanical response and grain evolution in a Ni nanowire for both static and cyclic loading conditions at both 300 and 500 K for periods of 40 ns. The loading conditions included thermal annealing with no deformation, constant 1% extension (creep loading) and cyclic loading with strain amplitudes of 0.5% and 1% for 200 cycles. Under cyclic loading, the stress–strain response showed permanent deformation and cyclic hardening behavior. At 300 K, modest grain evolution was observed at all conditions within the 40 ns simulations. At 500 K, substantial grain growth is observed in all cases, but is most pronounced under cyclic loading. This may result mechanistically from a net motion of the boundaries associated with boundary ratcheting. Finally, there is a striking qualitative consistency between the present simulation results and the experimental observation of abnormal grain growth in nanocrystalline metals as a precursor to fatigue crack initiation.

36 MATERIALS SCIENCE↗

NASA NTRS1972

Mechanically prestressed windows

A method was developed for mechanically prestressing glass used in spacecraft windows so that surface imperfections of the glass will not propagate under stress. A metal ring, in tension, is placed around the periphery of the glass where the interference fit between the ring and glass fixes the glass in a state of uniform compression. When the glass is subjected to a pressure loading, the compressive prestress prevents tension loading of the outer surface and, therefore, eliminates the tendency for propagation of surface imperfections.

Keathley, W. H.↗

NASA NTRS1973

Filament-wound composite vessels material technology

Programs are reviewed that were conducted to establish a technology base for applying advanced fibers or resins to high performance filament-wound pressure vessels for containment of cryogens and high pressure gases. Materials evaluated included boron, graphite, PRD 49-1 and 3/epoxy and S-glass/polyimide composites. Closed-end cylindrical, and oblate spheroid-shaped vessels were fabricated in 4- and 8-inch diameter sizes. Vessels were subjected to single-cycle burst, low-cycle fatigue, and sustained loading tests over a -423 F to room temperature range for epoxy composites and a -423 to 500 F temperature range for the polyimide composites. Vessels tested at cryogenic and/or 500 F had thin (3 to 20 mils) metallic liners whereas vessels tested at room temperature had elastomeric liners. Correlations between acoustic emissions and burst and cyclic properties of PRD 49-1 filament-wound vessels are discussed.

Lark, R. F.↗

NASA NTRS1979

Fastener for easy installation and removal of tiles

Mating strips, one with metal hooks and one with metal loops, allow convenient mounting and removal on many kinds of modules. Principle is adaptable to applications where shear-resistant, compliants, removable fastening is needed in hard-to-reach places, especially when attached part is lightly loaded or fragile.

Maletz, L. H.↗

NASA NTRS1984

Ceramic-to-metal bonding for pressure transducers

A solid-state diffusion technique involving the placement of a gold foil between INCONEL X-750 and a machinable glass-ceramic "MACOR" was shown to be successful in bonding these two materials. This technique was selected after an exhaustive literature search on ceramic-metal bonding methods. Small expansion mismatch between the Inconel and the MACOR resulted in fracture of the MACOR when the bonded body was subjected to tensile stress of 535 psi. The bonded parts were submitted to a cyclic loading test in an air atmosphere at 1 Hz from 0 to 60 KPa. Failure was observed after 700,000 cycles at 650 C. Ceramic-Inconel bonding was not achieved with this method for boron nitride and silica glass.

Mackenzie, J. D.↗

NASA NTRS1989

The isothermal fatigue behavior of a unidirectional SiC/Ti composite and the Ti alloy matrix

The high temperature fatigue behavior of a metal matrix composite (MMC) consisting of Ti-15V-3Cr-3Al-3Sn (Ti-15-3) matrix reinforced by 33 vol percent of continuous unidirectional SiC fibers was experimentally and analytically evaluated. Isothermal MMC fatigue tests with constant amplitude loading parallel to the fiber direction were performed at 300 and 550 C. Comparative fatigue tests of the Ti-15-3 matrix alloy were also conducted. Composite fatigue behavior and the in-situ stress state of the fiber and matrix were analyzed with a micromechanical model, the Concentric Cylinder Model (CCM). The cyclic stress-strain response of the composite was stable at 300 C. However, an increase in cyclic mean strain foreshortened MMC fatigue life at high strain ranges at 550 C. Fatigue tests of the matrix alloy and CCM analyses indicated this response was associated with stress relaxation of the matrix in the composite.

Gayda, John, Jr.↗

NASA NTRS1988

Materials and structures for hypersonic vehicles

The development of low-density materials with higher strength and stiffness, and more efficient engine and airframe structures is considered enabling technology for reusable hypersonic vehicles. Advanced structural concepts are required for minimum weight hot structures that will be fully reusable. Key design drivers are maximum heating rate, duration of heating, total heat load, flight envelope and type of propulsion system, mission life requirements, and containment of liquid hydrogen. For hot-structures applications in the range from 600-1800°F, advanced alloys of titanium, titanium and nickel aluminides, and metal-matrix composites are leading candidates because of their high specific properties. For temperatures in excess of 2000°F carbon-carbon and ceramic-matrix composites are the most structurally efficient materials. This paper addresses the technology issues for light weight hot structures, gives brief assessments of the state of the art, presents selected highlights of current research, and identifies areas requiring additional development.

Hypersonic Vehicles↗

NASA NTRS1990

Preloaded Composite-Strut/End-Fitting Joint

Proposed structural joint between composite strut and metal end fitting strong and light in weight. Joint configured to distribute stresses fairly uniformly, with little interlaminar stress. Composite-strut/metal-fitting joint built up integrally with strut in layup process. Joint remains tight under reversals of loads and changes in temperature.

Monitor, Dean S.↗

NASA NTRS1990

Hazards protection for space suits and spacecraft

A flexible multi-layered covering article for protection against the hazards of exposure to the environment of outer space is disclosed. The covering includes an outer layer section comprising an outermost lamina of woven expanded tetrafluoroethylene yarns (Gore Tex) for protecting against abrasion and tearing, an underlying weave of meta-aramid yarns (Nomex) and para-aramid yarns (Kevlar) for particle impart protection, and electrostatic charge dissipation and control system incorporated therein, and a chemical contaminants control barrier applied as a coating. A middle section includes a succession of thermal insulating layers of polymeric thermoplastic or thermoforming material, each of which is coated with a metal deposit of high infra-red emissivity and low solar radiation absorption characteristics and separated from adjacent insulating layers by a low thermal conductance material. The covering further includes a radiation attenuating layer of a tungsten-loaded polymeric elastomer binder for protecting against bremsstrahlung radiation and an inner layer of rip-stop polyester material for abrasion protection. A chloroprene coating may be supplied the polyester-material for added micrometeroid protection. Securing means of low heat conductance material secures the multi-layers together as a laminar composite.

Kosmo, Joseph J.↗

NASA NTRS1989

Materials and structures for hypersonic vehicles

Hypersonic Vehicles↗

NASA NTRS1990

The isothermal fatigue behavior of a unidirectional SiC/Ti composite and the Ti alloy matrix

The high temperature fatigue behavior of a metal matrix composite (MMC) consisting of Ti-15V-3Cr-3Al-3Sn(Ti-15-3) matrix reinforced by 33 volume percent of continuous unidirectional SiC fibers was experimentally and analytically evaluated. Isothermal MMC fatigue tests with constant amplitude loading parallel to the fiber direction were performed at 300 and 550 C. Comparative fatigue tests of the Ti-15-3 matrix alloy were also performed. Composite fatigue behavior and the in situ stress state of the fiber and matrix were analyzed with a micromechanical model, the Concentric Cylinder Model (CCM). The cyclic stress-strain response of the composite was stable at 300 C. However, an increase in cyclic mean strain foreshortened MMC fatigue life at high strain ranges at 550 C. Fatigue tests of the matrix alloy and CCM analyses indicated this response was associated with stress relaxation of the matrix in the composite and subsequent load shedding to the fibers.

Gayda, John↗

NASA NTRS1992

Screen Cage Ion Plating (SCIP) and scratch testing of polycrystalline aluminum oxide

A screen cage ion plating (SCIP) technique was developed to apply silver films on electrically nonconducting aluminum oxide. It is shown that SCIP has remarkable throwing power; surfaces to be coated need not be in direct line of sight with the evaporation source. Scratch tests, employing a diamond stylus with a 200 micro m radius tip, were performed on uncoated and on silver coated alumina. Subsequent surface analysis show that a significant amount of silver remains on the scratched surfaces, even in areas where high stylus load produced severe crack patterns in the ceramic. Friction coefficients were lowered during the scratch tests on the coated alumina indicating that this modification of the ion planting process should be useful for applying lubricating films of soft metals to electrical insulating materials. The very good throwing power of SCIP also strongly suggests general applicability of this process in other areas of technology, e.g., electronics, in addition to tribology.

Spalvins, Talivaldis↗