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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

A Simulated Evaluation of Powder Flowability Through a Partially Obstructed Consumable in Blown Powder Directed Energy Deposition Systems

Abstract In the interest of continued industrialization of metal additive manufacturing in modern production environments, cost is often referenced as a primary deterrent to new adopters. Conventional economic models for additive systems, processes, and supply chains often focus on specific process applications with little generalizability, or they neglect significant costs associated with production such as machine maintenance and consumable part replacement. Compounding the latter issue are substantial knowledge gaps in consumable part wear characterization for additive and other convergent manufacturing systems. In coaxial blown powder directed energy deposition systems, gas atomized metal powder is wasted during material deposition at a rate that is partly dependent on present wear phenomena in a consumable nozzle housed in the cladding head assembly. The price and lead time required to replace the nozzle incentivizes its reuse even when visibly worn. Often this initiates a process quality decline in the form of underbuilt geometry and internal defects due to losses in powder catchment efficiency. While depositing H13 steel using a hybrid manufacturing machine tool equipped with such a deposition system, a unique partial clog with a bridge-like structure formed at the consumable nozzle exit when supporting argon gas flows failed mid-process. To further understand coaxial multi-phase powder flow in the event of support gas failure, a computational fluid dynamics simulation is tailored to relevant process parameters, H13 powder material profile, and machine operator observations collected after the incident. The resulting differences in powder flow compared to control gas flow parameters is presented and discussed. The powder flowability and performance of the clogged nozzle is then assessed by using an optical profilometer to extract the profile of the clog and recreate the clog geometry within the simulation environment. In past work this simulation has been experimentally validated for a 316L steel powder material profile and used specifically for analyzing powder stream geometry and catchment efficiency. After the initial powder flow characterization, the clog is removed, and the nozzle is reprofiled. After removing the obstructing clog, the newly unobstructed nozzle geometry, the original off the shelf nozzle geometry, and additional nozzle profiles exploring different consumable refurbishment strategies are reevaluated in the simulation. Powder catchment efficiency for all variant nozzle geometries and relevant flow variables are compared and discussed, along with potential mitigation strategies for optimizing powder flowability with worn consumables. This work expands on the known morphology of blown powder obstructions and wear defects present in consumable coaxial nozzles while discussing pragmatic simulation driven responses to unanticipated subsystem failure in hybrid manufacturing machining platforms.

DeWitte, Lisa↗
DOE OSTI2020

Influence of Hydrogen and Oxygen on the Structure and Properties of Sputtered Magnesium Zirconium Oxynitride Thin Films

Nitride materials with mixed ionic and covalent bonding character and resulting good charge transport properties are attractive for optoelectronic devices. Recently, Mg-based ternary nitride materials were found to have large dielectric constants and high absorption coefficients with bandgaps appropriate for photovoltaic applications. However, their degenerate carrier concentrations still hinder their possible applications in solar cells and related optoelectronic devices. Therefore, further understanding and engineering of the parameters controlling the material properties of these ternary nitrides is highly desirable. In this paper we report that the structural, optical and electrical properties of magnesium zirconium oxynitride (MZNO) thin films synthesized by combinatorial sputtering with a wide range of cation compositions can be affected by incorporation of oxygen and hydrogen. Excess oxygen improved the crystallinity of MZNO thin films whereas hydrogen attracted oxygen and formed Mg-rich oxide layers at the grain boundaries which in turn reduced the conductivity. On the other hand, optical properties are more sensitive to the composition – both cation and anion ratios – rather than the presence of hydrogen. Compared to cation-stoichiometric MZNO (10 19 –10 20 cm -3 ), substantial reduction of carrier concentration down to ~10 14 cm -3 was achieved under Mg-rich conditions by supplying hydrogen during growth. Photoluminescence measurements showed that the films prepared with hydrogen were optoelectronically active. Overall, this study demonstrates that the material properties of MZN thin films can be significantly influenced by incorporation of oxygen and hydrogen.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1972

Scatter factor and reliability of aircraft structures

The concept of time to first failure is utilized to perform a parameter study of scatter factors of aircraft structures. The Weibull distribution is used for estimation of characteristic and certifiable lives. Scatter factors for various Weibull-shaped parameters, fleet sizes and level of reliabilities are calculated. It is concluded that the currently used range of scatter factors (2 through 4) is too narrow for the estimation of a safe life and that a safe and economical design for structural materials with shape parameters less than 2 does not seem feasible except for very small fleet sizes and low levels of reliability.

Schueller, G. I.↗
NASA NTRS1991

Analytical studies of the Space Shuttle orbiter nose-gear tire

A computational procedure is presented for evaluating the analytic sensitivity derivatives of the tire response with respect to material and geometrical properties of the tire. The tire is modeled by using a two-dimensional laminated anisotropic shell theory with the effects of variation in material and geometric parameters included. The computational procedure is applied to the case of the Space Shuttle orbiter nose-gear tire subjected to uniform inflation pressure. Numerical results are presented which show the sensitivity of the different tire response quantities to variations in the material characteristics of both the cord and rubber.

Noor, Ahmed K.↗
NASA NTRS2006

Probabilistic Structural Evaluation of Uncertainties in Radiator Sandwich Panel Design

The Jupiter Icy Moons Orbiter (JIMO) Space System is part of the NASA's Prometheus Program. As part of the JIMO engineering team at NASA Glenn Research Center, the structural design of the JIMO Heat Rejection Subsystem (HRS) is evaluated. An initial goal of this study was to perform sensitivity analyses to determine the relative importance of the input variables on the structural responses of the radiator panel. The desire was to let the sensitivity analysis information identify the important parameters. The probabilistic analysis methods illustrated here support this objective. The probabilistic structural performance evaluation of a HRS radiator sandwich panel was performed. The radiator panel structural performance was assessed in the presence of uncertainties in the loading, fabrication process variables, and material properties. The stress and displacement contours of the deterministic structural analysis at mean probability was performed and results presented. It is followed by a probabilistic evaluation to determine the effect of the primitive variables on the radiator panel structural performance. Based on uncertainties in material properties, structural geometry and loading, the results of the displacement and stress analysis are used as an input file for the probabilistic analysis of the panel. The sensitivity of the structural responses, such as maximum displacement and maximum tensile and compressive stresses of the facesheet in x and y directions and maximum VonMises stresses of the tube, to the loading and design variables is determined under the boundary condition where all edges of the radiator panel are pinned. Based on this study, design critical material and geometric parameters of the considered sandwich panel are identified.

Kuguoglu, Latife↗
DOE OSTI2020

The Influence of Processing Parameters on the Transition Zone for Blended Material 3D Printing

The use of Multiple Materials (MM) in Additive Manufacturing (AM) is increasingly important for expanding the range of applications in the manufacturing industry, particularly for large-format processes. Typically, polymer-based AM incorporates MM transitions through discrete interfaces between layers. This arrangement significantly increases the occurrence of layer delamination failures due to decreased bonding between dissimilar polymers. Elimination of discrete material interfaces by continuously transitioning from Material A to B provides a possible solution. Such continuous gradients could be used to create functionally graded structures that take full advantage of AM’s capability to deliberately impart site-specific properties. Cincinnati’s Big Area Additive Manufacturing (BAAM) system at Oak Ridge National Lab has been equipped with a dual-hopper system that enables in-situ material switching specifically intended for functionally graded and MM printing. The resulting material transition exhibits varied behavior based on printing conditions, which can have an impact on part design and resulting mechanical properties. In this work, the transition zone is characterized as a function of the printing screw speed (related to volumetric flow) and the screw geometry.

Brackett, James↗
NASA NTRS1965

Evaluation of materials in entry heating simulation

The effects of several environmental parameters on the behavior of ablation materials have been examined. Practically all the entry heating parameters such as enthalpy, pressure, heating rate, aerodynamic shear, and so forth, affect material performance. However, the significance of the effects depends to a large extent upon the type of material. Inasmuch as it is rarely possible to simulate several environment effects simultaneously, the primary inputs must be determined and the test simulation must account for the effects of these inputs. The particular materials of concern must be characterized by test and analysis to determine which of the many environmental inputs are the most significant.

Simulation↗
DOE OSTI2021

On the progress of 3D-printed hydrogels for tissue engineering

Additive manufacturing or more commonly known as 3D printing, is currently driving innovations and applications in diverse fields such as prototyping, manufacturing, aerospace, education, and medicine. Recent technological and materials research breakthroughs have enabled 3D bioprinting, where biomaterials and cells are used to create scaffolds and functional living tissues (e.g. skin, cartilage, etc.). This prospective focuses on the classification and applications of hydrogels, and design considerations in their production (i.e. physical and biological parameters). Herein, the materials for 3D printing of hydrogels, such as biopolymers, synthetic polymers, and nanocomposites, are mainly discussed. More importantly, future perspectives on 3D printing hydrogels including new materials, 4D printing, emerging printing technologies, etc. and their importance in biomedical and bioengineering applications are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Controlled Dy-doping to nickel-rich cathode materials in high temperature aerosol synthesis

Layered nickel-rich materials are promising next-generation cathode materials for lithium ion batteries due to their high capacity and low cost. However, the poor thermal stability and longtime cycling performance hinders the commercial applications of high nickel materials. Doping with heteroatoms has been an effective approach for improving electrochemical performance of cathode materials. Controlling doping concentration and geometrical distribution is desired for optimal electrochemical performance, but it is challenging in traditional co-precipitation methods. In this work, controlled dysprosium (Dy) doping to NCM811 was studied in an aerosol synthesis method by controlling the precursor concentrations and heating parameters. The obtained materials were characterized by SEM, XRD, and XPS, and their electrochemical properties and thermal stability were evaluated. By controlling the doping concentration (1.5%), Dy-doped NCM811 was improved simultaneously in long-term cycling and high-rate performance. Here, the thermal-chemical stability of the Dy-doped cathode materials was examined in a microflow reactor with a mass spectrometer. The results showed that Dy-doping shifted the O 2 onset temperature to a higher temperature and reduced O 2 release by 80%, thus dramatically increasing the thermal-chemical stability and improving the fire safety of cathode materials. Since high temperature aerosol synthesis is a low-cost and scalable method, the findings in this work have broad implications for commercial synthesis of novel materials with controlled doping modification to achieve high electrochemical performance and safety in lithium ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2025

Performance Evaluation of LPBF Manufactured 316H Components

This work represents the continuation of a benchmark study that includes modeling, fabrication and characterization as demonstration to support industry’s adoption of advanced manufacturing processes in a variety of structures. This comprehensive study investigated the feasibility of using additive manufacturing (AM) technologies, specifically Laser Powder Direct Energy Deposition (LP-DED) and Laser Powder Bed Fusion (LPBF), to produce complex nuclear microreactor components using 316H stainless steel. The research focused on manufacturing an expanded elbow pipe component with transitioning sections, which are traditionally difficult and costly to produce through conventional manufacturing methods. The overall study’s primary objectives are therefore demonstrating AM viability for nuclear applications, optimizing process parameters, developing comprehensive material characterization protocols, validating computational modeling approaches, and establishing manufacturing guidelines for complex geometries. Although the initial work included the phased approach of cubical, upscaled cylindrical components, it is to enable to obtain more knowledge for the printing of the expanded elbow structure. The project achieved significant progress in process development by successfully optimizing LP-DED parameters to achieve 99.16-99.97% relative density in 316H stainless steel components. Through systematic evaluation of sixteen cube samples with varied laser powers (400-700W) and scan speeds (600-900 mm/min), optimal processing windows were identified at 500-550W with 600-700 mm/min or 650-700W with 650-900 mm/min scan speeds. The DED manufactured 316H demonstrated mechanical properties comparable or superior to wrought materials, with Young's modulus ranging from 153-208 GPa and controlled microstructural characteristics including greater than 95% face-centered cubic (FCC) phases and engineered cellular structures with sizes between 3.23-6.17 µm.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Interplay between magnetism and superconductivity in UTe 2

Time-reversal symmetry breaking (TRSB) in UTe 2 was inferred from observations of a spontaneous Kerr response in the superconducting state after cooling in zero magnetic field, while a finite c-axis magnetic field training was further used to determine the nature of the nonunitary composite order parameter of this material. Here, we present an extensive study of the magnetic-field-trained Kerr effect, which unveils a unique critical state of pinned “ferromagnetic vortices.” We show that a remanent Kerr signal appears following the removal of a training magnetic field, which reflects the response to the TRSB order parameter and the external magnetic field through the paramagnetic susceptibility. Furthermore, this unambiguously demonstrates the importance of the magnetic fluctuations and their intimate relation to the composite order parameter. Focusing the beam on the center of the sample, we are able to accurately determine the maximum field that is screened by the critical state and the respective critical current. Measurements in the presence of magnetic field show the tendency of the superconductor to produce shielding currents that oppose the increase in vortex-induced magnetization due to the diverging paramagnetic susceptibility.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Laser Additive Manufacturing Process Development for Bismuth Telluride Thermoelectric Material

Thermoelectric generators have strong potential for aerospace and aircraft applications. However, traditional manufacturing methods for thermoelectric devices severely limit device adaptability and consequently marketability. Laser powder bed fusion is an additive manufacturing method which shows promising potential for producing thermoelectric devices. Thermoelectric materials pose unique challenges compared to metals because of low thermal conductivity, brittle fracture characteristics, and irregular powder particle morphologies. Herein, we communicate processing procedures to fabricate thermoelectric parts of Bi 2 Te 3 through laser powder bed fusion. In this study, we identify the successful combination of key process parameters—laser power, scan speed, hatch distance, and powder layer thickness—to achieve high-quality parts in terms of density and physical properties, and we demonstrate the impact of process parameter variation on built part quality. While it cannot exclusively determine part quality, the volumetric energy density is a useful guide in deciding process parameters for thermoelectric materials, and the optimal value is between 9 and 11 J/mm 3 for Bi 2 Te 3 . We demonstrate successful fabrication of different freeform geometries of Bi 2 Te 3 powders. The results suggest it is possible to extend this method more broadly to other semiconductor materials, including thermoelectric power generation materials applicable for space applications.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Composite Development and Applications for RLV Tankage

The development of polymer composite cryogenic tanks is a critical step in creating the next generation of launch vehicles. Future launch vehicles need to minimize the gross liftoff weight (GLOW), which is possible due to the 28%-41% reduction in weight that composite materials can provide over current aluminum technology. The development of composite cryogenic tanks, feedlines, and unpressurized structures are key enabling technologies for performance and cost enhancements for Reusable Launch Vehicles (RLVs). The technology development of composite tanks has provided direct and applicable data for feedlines, unpressurized structures, material compatibility, and cryogenic fluid containment for highly loaded complex structures and interfaces. All three types of structure have similar material systems, processing parameters, scaling issues, analysis methodologies, NDE development, damage tolerance, and repair scenarios. Composite cryogenic tankage is the most complex of the 3 areas and provides the largest breakthrough in technology. A building block approach has been employed to bring this family of difficult technologies to maturity. This approach has built up composite materials, processes, design, analysis and test methods technology through a series of composite test programs beginning with the NASP program to meet aggressive performance goals for reusable launch vehicles. In this paper, the development and application of advanced composites for RLV use is described.

Wright, Richard J.↗
DOE OSTI2021

Temperature dependence of London penetration depth anisotropy in superconductors with anisotropic order parameters

Here, we study the effects of anisotropic order parameters on the temperature dependence of London penetration depth anisotropy γ λ ( T ) . After MgB 2 , this dependence is commonly attributed to distinct gaps on multiband Fermi surfaces in superconductors. We have found, however, that the anisotropy parameter may depend on temperature also in one-band materials with anisotropic order parameters Δ ( T , k F ) ; a few such examples are given. We have also found that for different order parameters, the temperature dependence of Δ ( T ) / Δ ( 0 ) can be represented with good accuracy by the interpolation suggested by Einzel, which simplifies considerably the evaluation of γ λ ( T ) . Of particular interest are mixed order parameters of two symmetries for which γ λ ( T ) may go through a maximum for a certain relative weight of two phases. Also, for this case we find that the ratio Δ max ( 0 ) / T c may exceed substantially the weak-coupling limit of 1.76. It, however, does not imply strong coupling; rather, it is due to significantly anisotropic angular variation of Δ .

36 MATERIALS SCIENCE↗
DOE OSTI2020

1D to 2D Transition in Tellurium Observed by 4D Electron Microscopy

A new microwave-enhanced synthesis method for the production of tellurium nanostructures is reported here—with control over products from the 1D regime (sub-5 nm diameter nanowires), to nanoribbons, to the 2D tellurene regime—along with a new methodology for local statistical quantification of the crystallographic parameters of these materials at the nanometer scale. Using a direct electron detector and image-corrected microscope, large and robust 4D scanning transmission electron microscopy datasets for accurate structural analysis are obtained. These datasets allow the adaptation of quantitative techniques originally developed for X-ray diffraction (XRD) refinement analyses to transmission electron microscopy, enabling the first demonstration of sub-picometer accuracy lattice parameter extraction while also obtaining both the size of the coherent crystallite domains and the nanostrain, which is observed to decrease as nanowires transition to tellurene. This new local analysis is commensurate with global powder XRD results, indicating the robustness of both the new synthesis approach and new structural analysis methodology for future scalable production of 2D tellurene and characterization of nanomaterials.

2D materials↗
NASA NTRS1980

Long-time creep behavior of the niobium alloy C-103

The creep behavior of C-103 was studied as a function of stress, temperature, and grain size for test times to 19000 hr. Over the temperature range 827 to 1204 C and the stress range 6.89 to 138 MPa, only tertiary (accelerating) creep was observed. The creep strain epsilon can be related to time t by an exponential relation epsilon = epsilon(0) + K e raised to power (st) - 1), where epsilon (0) is initial creep strain, K is the tertiary creep strain parameter, and s is the tertiary creep rate parameter. The observed stress exponent 2.87 is similar to the three power law generally observed for secondary (linear) creep of Class I solid solutions. The apparent activation energy 374 kj/g mol is close to that observed for self diffusion of pure niobium. The initial tertiary creep rate was slightly faster for fine grained than for coarse-grained material. The strain parameter K can be expressed as a combination of power functions of stress and grain size and an exponential function of temperature. Strain time curves generated by using calculated values for K and s showed reasonable agreement with observed curves to strains of at least 4 percent. The time to 1 percent strain was related to stress, temperature, and grain size in a similar manner as the initial tertiary creep rate.

Titran, R. H.↗
DOE OSTI2025

Thickness scaling and ferroelectric switching in wurtzite structure zinc magnesium oxide thin films

This study reports the thickness scaling of sputtered ferroelectric Zn 0.61 Mg 0.39 O (ZMO) thin films down to 43 nm. Encapsulated IrO 2 /ZMO/Ir capacitors exhibited switchable polarizations exceeding 50 μC cm −2 and coercive fields that increased from 3.9 to 4.4 MV cm −1 as the thickness decreased. Switching kinetics are best described by the simultaneous non-linear nucleation and the growth model. Bimodal switching is prevalent at low thicknesses, with the fastest switching times measured to be approximately 400 ns. Device encapsulation made ZMO switching kinetics more abrupt, potentially due to changes in the concentration of atmosphere-induced defects such as hydroxides. These results demonstrate stable ferroelectricity and sub-microsecond switching in sub-50 nm wurtzite ZMO, highlighting its potential as a low-voltage ferroelectric for integrated nonvolatile memory applications.

36 MATERIALS SCIENCE↗