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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Gd(AlC)3 by Materials Project

Gd(AlC)3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Gd3+ is bonded to six equivalent C4- atoms to form GdC6 octahedra that share corners with six equivalent AlC4 tetrahedra, edges with six equivalent GdC6 octahedra, and edges with six equivalent AlC4 tetrahedra. All Gd–C bond lengths are 2.59 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four C4- atoms to form AlC4 tetrahedra that share corners with three equivalent GdC6 octahedra, corners with seven equivalent AlC4 tetrahedra, and edges with three equivalent GdC6 octahedra. The corner-sharing octahedral tilt angles are 20°. There are one shorter (2.02 Å) and three longer (2.11 Å) Al–C bond lengths. In the second Al3+ site, Al3+ is bonded in a trigonal planar geometry to three equivalent C4- atoms. All Al–C bond lengths are 1.99 Å. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded in a 6-coordinate geometry to three equivalent Gd3+ and three equivalent Al3+ atoms. In the second C4- site, C4- is bonded to five Al3+ atoms to form corner-sharing CAl5 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AlC by Materials Project

AlC crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of twenty-four aluminium molecules and one AlC5 sheet oriented in the (0, 0, 1) direction. In the AlC5 sheet, there are six inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded in a distorted L-shaped geometry to three C3- atoms. There are a spread of Al–C bond distances ranging from 2.17–2.46 Å. In the second Al3+ site, Al3+ is bonded in a 2-coordinate geometry to two C3- atoms. There are one shorter (2.05 Å) and one longer (2.31 Å) Al–C bond lengths. In the third Al3+ site, Al3+ is bonded in a 2-coordinate geometry to two C3- atoms. There are one shorter (2.05 Å) and one longer (2.32 Å) Al–C bond lengths. In the fourth Al3+ site, Al3+ is bonded in a water-like geometry to two C3- atoms. Both Al–C bond lengths are 2.27 Å. In the fifth Al3+ site, Al3+ is bonded in a single-bond geometry to one C3- atom. The Al–C bond length is 2.07 Å. In the sixth Al3+ site, Al3+ is bonded in a single-bond geometry to one C3- atom. The Al–C bond length is 2.07 Å. There are thirty inequivalent C3- sites. In the first C3- site, C3- is bonded to one Al3+ and three C3- atoms to form distorted corner-sharing CAlC3 tetrahedra. There are a spread of C–C bond distances ranging from 1.51–1.60 Å. In the second C3- site, C3- is bonded to one Al3+ and three C3- atoms to form corner-sharing CAlC3 tetrahedra. There are a spread of C–C bond distances ranging from 1.53–1.59 Å. In the third C3- site, C3- is bonded to one Al3+ and three C3- atoms to form corner-sharing CAlC3 tetrahedra. There is one shorter (1.44 Å) and two longer (1.57 Å) C–C bond length. In the fourth C3- site, C3- is bonded in a distorted trigonal non-coplanar geometry to three C3- atoms. There are a spread of C–C bond distances ranging from 1.44–1.56 Å. In the fifth C3- site, C3- is bonded in a 5-coordinate geometry to two Al3+ and three C3- atoms. There are a spread of C–C bond distances ranging from 1.53–1.63 Å. In the sixth C3- site, C3- is bonded in a distorted pentagonal planar geometry to two Al3+ and three C3- atoms. Both C–C bond lengths are 1.63 Å. In the seventh C3- site, C3- is bonded in a distorted trigonal non-coplanar geometry to three C3- atoms. There is one shorter (1.55 Å) and one longer (1.56 Å) C–C bond length. In the eighth C3- site, C3- is bonded to one Al3+ and three C3- atoms to form corner-sharing CAlC3 tetrahedra. Both C–C bond lengths are 1.57 Å. In the ninth C3- site, C3- is bonded to one Al3+ and three C3- atoms to form corner-sharing CAlC3 tetrahedra. There is one shorter (1.58 Å) and one longer (1.59 Å) C–C bond length. In the tenth C3- site, C3- is bonded to one Al3+ and three C3- atoms to form distorted corner-sharing CAlC3 tetrahedra. There is one shorter (1.58 Å) and one longer (1.60 Å) C–C bond length. In the eleventh C3- site, C3- is bonded in a 4-coordinate geometry to one Al3+ and four C3- atoms. Both C–C bond lengths are 1.53 Å. In the twelfth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. There is one shorter (1.55 Å) and one longer (1.56 Å) C–C bond length. In the thirteenth C3- site, C3- is bonded to four C3- atoms to form corner-sharing CC4 tetrahedra. There is one shorter (1.53 Å) and one longer (1.54 Å) C–C bond length. In the fourteenth C3- site, C3- is bonded to four C3- atoms to form corner-sharing CC4 tetrahedra. There is one shorter (1.53 Å) and one longer (1.54 Å) C–C bond length. In the fifteenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. There is one shorter (1.55 Å) and one longer (1.56 Å) C–C bond length. In the sixteenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. Both C–C bond lengths are 1.52 Å. In the seventeenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. There is one shorter (1.53 Å) and one longer (1.56 Å) C–C bond length. In the eighteenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. Both C–C bond lengths are 1.54 Å. In the nineteenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. There is one shorter (1.53 Å) and one longer (1.56 Å) C–C bond length. In the twentieth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. Both C–C bond lengths are 1.52 Å. In the twenty-first C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-second C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-third C3- site, C3- is bonded in a water-like geometry to two C3- atoms. In the twenty-fourth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-fifth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-sixth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-seventh C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-eighth C3- site, C3- is bonded in a water-like geometry to two C3- atoms. In the twenty-ninth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the thirtieth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2026

2D in-Plane Ordered MXene Nanosheets Derived from (Mo 2/3 Er 1/3 ) 2 AlC Rare-Earth i-MAX for Energy Storage Applications

MXenes have become one of the most versatile families of two-dimensional (2D) materials due to their high conductivity, hydrophilicity, and remarkable electrochemical performance. This has stimulated intense efforts to design and synthesize MXenes, including structurally unique in-plane ordered 2D MXenes called i-MXenes. Here, we have synthesized the quaternary rare earth (RE)-based i-MAX phase (Mo 2/3 Er 1/3 ) 2 AlC using an arc melting method, and the corresponding 2D i-MXene was then obtained through a LiF/HCl soft etching process. Literature studies have shown that Al and the RE element are etched out during the etching process, leading to the formation of pure vacancy-ordered Mo1.33C 2D i-MXene. However, our investigation reveals that upon exposure to a fluorine solution, the i-MAX phase forms RE fluoride impurities, which are challenging to remove through HCl−DI water washing and persist in the final product, resulting in impure Mo 1.33 C@Er i-MXene. These results were confirmed by various characterizations such as X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning transmission electron microscopy. Although the Mo 1.33 C@Er electrode showed a 24-fold increase in specific capacitance compared to its parent i-MAX phase, it still exhibited a high charge-transfer resistance arising from the insulating nature of RE fluoride byproducts, which adversely influence the overall capacitance behavior of the synthesized 2D Mo 1.33 C@Er i-MXenes. This study contributes to identifying pathways for the preparation of pure 2D i-MXenes from RE-based i-MAX phases and developing improved synthesis methods. With additional process optimization, the 2D i-MXene holds a strong potential for electrochemical energy storage applications. Additionally, the electronic structures of Mo 1.33 C were theoretically studied using first-principles density functional theory calculations, which revealed that pristine Mo 1.33 C is metallic, and this metallic nature is preserved even with −O, −F, and mixed functionalization.

chemical structure↗
NASA NTRS1988

The computed spectrum of AlC

The low-lying (up to about 40,000/cm) doublet and quartet states of AlC have been studied at the CASSCF and MRCI levels of theory. The bonding in the X4Sigma(-) state is shown to involve three one-electron bonds. The first excited state, a 2Pi, lies about 8700/cm higher and like the X4Sigma(-) state is derived from ground state Al and C, but has a two-electron pi bond leading to a much shorter bond length.

Bauschlicher, Charles W., Jr.↗
DOE OSTI2020

Materials Data on Sc(AlC)3 by Materials Project

ScAl3C3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Sc3+ is bonded to six equivalent C4- atoms to form ScC6 octahedra that share corners with six equivalent AlC4 tetrahedra, edges with six equivalent ScC6 octahedra, and edges with six equivalent AlC4 tetrahedra. All Sc–C bond lengths are 2.42 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four C4- atoms to form AlC4 tetrahedra that share corners with three equivalent ScC6 octahedra, corners with seven equivalent AlC4 tetrahedra, and edges with three equivalent ScC6 octahedra. The corner-sharing octahedral tilt angles are 17°. There are one shorter (2.03 Å) and three longer (2.07 Å) Al–C bond lengths. In the second Al3+ site, Al3+ is bonded in a trigonal planar geometry to three equivalent C4- atoms. All Al–C bond lengths are 1.94 Å. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded to three equivalent Sc3+ and three equivalent Al3+ atoms to form distorted CSc3Al3 octahedra that share corners with three equivalent CSc3Al3 octahedra, corners with three equivalent CAl5 trigonal bipyramids, and edges with nine equivalent CSc3Al3 octahedra. The corner-sharing octahedral tilt angles are 0°. In the second C4- site, C4- is bonded to five Al3+ atoms to form CAl5 trigonal bipyramids that share corners with six equivalent CSc3Al3 octahedra and corners with six equivalent CAl5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 70°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(AlC)3 by Materials Project

UAl3C3 crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. U3+ is bonded to six C4- atoms to form UC6 octahedra that share corners with six AlC4 tetrahedra, edges with six equivalent UC6 octahedra, and edges with six AlC4 tetrahedra. There are three shorter (2.54 Å) and three longer (2.57 Å) U–C bond lengths. There are three inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four C4- atoms to form AlC4 tetrahedra that share corners with three equivalent UC6 octahedra, corners with seven AlC4 tetrahedra, and edges with three equivalent UC6 octahedra. The corner-sharing octahedral tilt angles are 19°. There are one shorter (2.02 Å) and three longer (2.08 Å) Al–C bond lengths. In the second Al3+ site, Al3+ is bonded to four C4- atoms to form AlC4 tetrahedra that share corners with three equivalent UC6 octahedra, corners with seven AlC4 tetrahedra, and edges with three equivalent UC6 octahedra. The corner-sharing octahedral tilt angles are 22°. There are one shorter (2.04 Å) and three longer (2.06 Å) Al–C bond lengths. In the third Al3+ site, Al3+ is bonded in a trigonal planar geometry to three equivalent C4- atoms. All Al–C bond lengths are 1.96 Å. There are three inequivalent C4- sites. In the first C4- site, C4- is bonded to three equivalent U3+ and three equivalent Al3+ atoms to form distorted CU3Al3 octahedra that share corners with three equivalent CAl5 trigonal bipyramids and edges with six equivalent CU3Al3 octahedra. In the second C4- site, C4- is bonded in a 3-coordinate geometry to three equivalent U3+ and three equivalent Al3+ atoms. In the third C4- site, C4- is bonded to five Al3+ atoms to form CAl5 trigonal bipyramids that share corners with three equivalent CU3Al3 octahedra and corners with six equivalent CAl5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 70°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sc(AlC)3 by Materials Project

ScAl3C3 crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. Sc3+ is bonded to six C4- atoms to form ScC6 octahedra that share corners with six AlC4 tetrahedra, edges with six equivalent ScC6 octahedra, and edges with six AlC4 tetrahedra. There are three shorter (2.39 Å) and three longer (2.47 Å) Sc–C bond lengths. There are three inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four C4- atoms to form AlC4 tetrahedra that share corners with three equivalent ScC6 octahedra, corners with seven AlC4 tetrahedra, and edges with three equivalent ScC6 octahedra. The corner-sharing octahedral tilt angles are 20°. There are one shorter (2.04 Å) and three longer (2.05 Å) Al–C bond lengths. In the second Al3+ site, Al3+ is bonded to four C4- atoms to form AlC4 tetrahedra that share corners with three equivalent ScC6 octahedra, corners with seven AlC4 tetrahedra, and edges with three equivalent ScC6 octahedra. The corner-sharing octahedral tilt angles are 14°. There are one shorter (2.02 Å) and three longer (2.09 Å) Al–C bond lengths. In the third Al3+ site, Al3+ is bonded in a distorted trigonal planar geometry to four C4- atoms. There are three shorter (1.95 Å) and one longer (2.58 Å) Al–C bond lengths. There are three inequivalent C4- sites. In the first C4- site, C4- is bonded to five Al3+ atoms to form CAl5 trigonal bipyramids that share corners with three equivalent CSc3Al3 octahedra and corners with six equivalent CAl5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 68°. In the second C4- site, C4- is bonded in a 3-coordinate geometry to three equivalent Sc3+ and four Al3+ atoms. In the third C4- site, C4- is bonded to three equivalent Sc3+ and three equivalent Al3+ atoms to form CSc3Al3 octahedra that share corners with three equivalent CAl5 trigonal bipyramids and edges with six equivalent CSc3Al3 octahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(AlC)2 by Materials Project

Al2MgC2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Mg2+ is bonded to six equivalent C4- atoms to form MgC6 octahedra that share corners with twelve equivalent AlC4 tetrahedra, edges with six equivalent MgC6 octahedra, and edges with six equivalent AlC4 tetrahedra. All Mg–C bond lengths are 2.51 Å. Al3+ is bonded to four equivalent C4- atoms to form AlC4 tetrahedra that share corners with six equivalent MgC6 octahedra, corners with six equivalent AlC4 tetrahedra, edges with three equivalent MgC6 octahedra, and edges with three equivalent AlC4 tetrahedra. The corner-sharing octahedra tilt angles range from 25–51°. There are three shorter (2.01 Å) and one longer (2.21 Å) Al–C bond lengths. C4- is bonded in a 7-coordinate geometry to three equivalent Mg2+ and four equivalent Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(AlC)3 by Materials Project

YbAl3C3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Yb3+ is bonded to six equivalent C4- atoms to form YbC6 octahedra that share corners with six equivalent AlC4 tetrahedra, edges with six equivalent YbC6 octahedra, and edges with six equivalent AlC4 tetrahedra. All Yb–C bond lengths are 2.63 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded in a trigonal planar geometry to three equivalent C4- atoms. All Al–C bond lengths are 1.98 Å. In the second Al3+ site, Al3+ is bonded to four C4- atoms to form AlC4 tetrahedra that share corners with three equivalent YbC6 octahedra, corners with seven equivalent AlC4 tetrahedra, and edges with three equivalent YbC6 octahedra. The corner-sharing octahedral tilt angles are 24°. There are one shorter (2.03 Å) and three longer (2.07 Å) Al–C bond lengths. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded in a 3-coordinate geometry to three equivalent Yb3+ and three equivalent Al3+ atoms. In the second C4- site, C4- is bonded to five Al3+ atoms to form corner-sharing CAl5 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(AlC)3 by Materials Project

YbAl3C3 crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. Yb3+ is bonded to six C4- atoms to form YbC6 octahedra that share corners with six AlC4 tetrahedra, edges with six equivalent YbC6 octahedra, and edges with six AlC4 tetrahedra. There are three shorter (2.61 Å) and three longer (2.65 Å) Yb–C bond lengths. There are three inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four C4- atoms to form AlC4 tetrahedra that share corners with three equivalent YbC6 octahedra, corners with seven AlC4 tetrahedra, and edges with three equivalent YbC6 octahedra. The corner-sharing octahedral tilt angles are 26°. There are one shorter (2.05 Å) and three longer (2.06 Å) Al–C bond lengths. In the second Al3+ site, Al3+ is bonded to four C4- atoms to form AlC4 tetrahedra that share corners with three equivalent YbC6 octahedra, corners with seven AlC4 tetrahedra, and edges with three equivalent YbC6 octahedra. The corner-sharing octahedral tilt angles are 23°. There are one shorter (2.03 Å) and three longer (2.08 Å) Al–C bond lengths. In the third Al3+ site, Al3+ is bonded in a distorted trigonal planar geometry to four C4- atoms. There are three shorter (1.98 Å) and one longer (2.54 Å) Al–C bond lengths. There are three inequivalent C4- sites. In the first C4- site, C4- is bonded to five Al3+ atoms to form corner-sharing CAl5 trigonal bipyramids. In the second C4- site, C4- is bonded in a 3-coordinate geometry to three equivalent Yb3+ and four Al3+ atoms. In the third C4- site, C4- is bonded in a 6-coordinate geometry to three equivalent Yb3+ and three equivalent Al3+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS2007

Deep Space Network Antenna Logic Controller

The Antenna Logic Controller (ALC) software controls and monitors the motion control equipment of the 4,000-metric-ton structure of the Deep Space Network 70-meter antenna. This program coordinates the control of 42 hydraulic pumps, while monitoring several interlocks for personnel and equipment safety. Remote operation of the ALC runs via the Antenna Monitor & Control (AMC) computer, which orchestrates the tracking functions of the entire antenna. This software provides a graphical user interface for local control, monitoring, and identification of faults as well as, at a high level, providing for the digital control of the axis brakes so that the servo of the AMC may control the motion of the antenna. Specific functions of the ALC also include routines for startup in cold weather, controlled shutdown for both normal and fault situations, and pump switching on failure. The increased monitoring, the ability to trend key performance characteristics, the improved fault detection and recovery, the centralization of all control at a single panel, and the simplification of the user interface have all reduced the required workforce to run 70-meter antennas. The ALC also increases the antenna availability by reducing the time required to start up the antenna, to diagnose faults, and by providing additional insight into the performance of key parameters that aid in preventive maintenance to avoid key element failure. The ALC User Display (AUD) is a graphical user interface with hierarchical display structure, which provides high-level status information to the operation of the ALC, as well as detailed information for virtually all aspects of the ALC via drill-down displays. The operational status of an item, be it a function or assembly, is shown in the higher-level display. By pressing the item on the display screen, a new screen opens to show more detail of the function/assembly. Navigation tools and the map button allow immediate access to all screens.

Ahlstrom, Harlow↗
NASA NTRS2023

Crystallographic and TEM Features of a TBC/Ti2AlC MAX Phase Interface after 1300°C Burner Rig Oxidation

A FIB/STEM interfacial study was performed on a TBC/Ti 2 AlC MAX phase system, oxidized in an aggressive burner rig test (Mach 0.3 at 1300 °C for 500 h). The 7YSZ TBC, α-Al 2 O 3 TGO, and MAXthal 211 TM Ti 2 AlC base were variously characterized by TEM/STEM, EDS, SADP, and HRTEM. The YSZ was a mix of “clean” featureless and “faulted” high contrast grains. The latter exhibited ferro-elastic domains of high Y content tetragonal t″ variants. No martensite was observed. The TGO was essentially a duplex α-Al 2 O 3 structure of inner columnar plus outer equiaxed grains. It maintained a perfectly intact, clean interface with the Ti 2 AlC substrate. The Ti 2 AlC substrate exhibited no interfacial Al-depletion zone but, rather, numerous faults along the basal plane of the hexagonal structure. These are believed to offer a means of depleting Al by forming crystallographic, low-Al planar defects, proposed as Ti 2.5 AlC 1.5 . These characterizations support and augment prior optical, SEM, and XRD findings that demonstrated remarkable durability for the YSZ/Ti 2 AlC MAX phase system in aggressive burner tests.

TI2AlC↗
DOE OSTI2021

The Area Localized Coupled Model for Analytical Mean Flow Prediction in Arbitrary Wind Farm Geometries

This work introduces the area localized coupled (ALC) model, which extends the applicability of approaches that couple classical wake superposition models and atmospheric boundary layer models to wind farms with arbitrary layouts. Coupling wake and top–down boundary layer models is particularly challenging since the latter requires averaging over planform areas associated with turbine-specific regions of the flow that need to be specified. The ALC model uses Voronoi tessellation to define this local area around each turbine. A top–down description of a developing internal boundary layer is then applied over Voronoi cells upstream of each turbine to estimate the local mean velocity profile. Coupling between the velocity at hub-height based on this localized top–down model and a wake model is achieved by enforcing a minimum least-square-error in mean velocity in each cell. The wake model in the present implementation takes into account variations in wind farm inflow velocity and represents the wake profile behind each turbine as a super-Gaussian function that smoothly transitions between a top-hat shape in the region immediately following the turbine to a Gaussian profile downstream. Detailed comparisons to large-eddy simulation (LES) data from two different wind farms demonstrate the efficacy of the model in accurately predicting both wind farm power output and local turbine hub-height velocity for different wind farm geometries. These validations using data generated from two different LES codes demonstrate the model's versatility with respect to capturing results from different simulation setups and wind farm configurations.

49 EE - Wind and Water Power Program - Wind (EE-4W↗
NASA NTRS1982

A quantitative model of geomagnetic activity

A quantitative model of geomagnetic activity is developed and utilized to investigate the causes of the diurnal, seasonal, and IMF sector variations in the AL index records. This auroral index was chosen for study because of its high sensitivity to the strength of the westward electrojet and, hence, magnetospheric substorm activity. After the introduction of corrections for processes not related to substorms, ability of the function Bs to the 0.85th power x V squared to produce the observed variations in AL was examined. The annual variation of Bs was determined by superposing the contributions to Bs due to the inclination of the magnetic axis (Russell and McPherron, 1973) on an empirical mean distribution of Bz. V was assumed constant. The predicted values of ALc have been compared with observed averages for 9 years of solar cycle 20. The predicted annual variation of ALc for toward and away sectors are in good agreement with observation. While the predicted semi-annual component of ALc is in phase with observation, it is less than half the observed amplitude. The predicted diurnal variation of ALc for June is in satisfactory agreement with observation.

Holzer, R. E.↗
DOE OSTI2024

Robust Solar Receivers Using MAX Phase Materials

This work was supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy under the Solar Energy Technologies Office Award Number 35928. The objective of the proposed effort was to develop and optimize additive manufacturing technologies for low-cost fabrication of high-temperature receivers using MAX phase-based materials (Ti 3 SiC 2 and Ti 3 AlC 2 ). MAX phase materials are a group of ternary metal carbides and nitrides where M stands for an early transition metal element, A is a group 13–16 element, and X is C and/or N. In Phase 1, the binder jetting additive manufacturing process was used to synthesize and characterize the Ti 3 SiC 2 MAX phase material. The typical process involved first producing a TiC preform using binder jetting followed by infiltration of the preform with silicon melt to form Ti 3 SiC 2 in situ. The reaction-infiltrated samples showed formation of MAX phase in the sample core; however, the surface showed cracking. Various process conditions—cooling rates, hold times, Si proportion, etc.—were varied to minimize the surface cracking. The fabricated MAX phase core was characterized by microstructure analysis and evaluations of mechanical properties such as hardness and thermal shock. In Phase 2, the focus included fabrication of Ti 3 SiC 2 MAX phase materials by spark plasma sintering (SPS) and synthesis of Ti 3 AlC 2 MAX phase materials by the Al melt infiltration process. It is expected that Al infiltration will not cause sample cracking, since Al does not expand during solidification. In addition, other processing approaches were investigated to fabricate the MAX phase materials, such as SPS with a graphite bedding approach for producing short-length Ti 3 AlC 2 MAX phase tubes for demonstration of prototypical Concentrating Solar Power receiver tubes. Fabricated samples underwent thermo-mechanical testing to validate the materials for the solar receiver application at temperatures >1000°C. In Phase 3, the effort focused on the development and optimization of the Ti-Al-C MAX phase composite material using the Al melt infiltration approach. We started with optimization of precursor powders and making preform structures by either pressing them in a die or using the binder jetting additive manufacturing process followed by Al melt infiltration. In addition, we investigated the formation of preform structures by cold isostatic pressing followed by Al melt infiltration for making Ti-Al-C MAX phase composite. Thermo-mechanical characterizations, such as creep, strength, and thermal shock, were conducted to establish the structures’ performance.

36 MATERIALS SCIENCE↗
NASA NTRS1993

RACE pulls for shared control

Maintaining and supporting an aircraft fleet, in a climate of reduced manpower and financial resources, dictates effective utilization of robotics and automation technologies. To help develop a winning robotics and automation program the Air Force Logistics Command created the Robotics and Automation Center of Excellence (RACE). RACE is a command wide focal point. Race is an organic source of expertise to assist the Air Logistic Center (ALC) product directorates in improving process productivity through the judicious insertion of robotics and automation technologies. RACE is a champion for pulling emerging technologies into the aircraft logistic centers. One of those technology pulls is shared control. Small batch sizes, feature uncertainty, and varying work load conspire to make classic industrial robotic solutions impractical. One can view ALC process problems in the context of space robotics without the time delay. The ALC's will benefit greatly from the implementation of a common architecture that supports a range of control actions from fully autonomous to teleoperated. Working with national laboratories and private industry, we hope to transition shared control technology to the depot floor. This paper provides an overview of the RACE internal initiatives and customer support, with particular emphasis on production processes that will benefit from shared control technology.

Leahy, M. B., Jr.↗
DOE OSTI2022

Modeling the non-Schmid crystallographic slip in MAX phases

We present a crystal plasticity constitutive relation for the description of experimentally observed non-Schmid crystallographic slip in a class of ternary carbides and nitrides commonly referred to as MAX phases. In the constitutive relation, we assume that the evolution of the slip system strength in MAX phases has two components – a classical component that depends on the Taylor cumulative shear strain and a non-Schmid component that depends on the stress normal to the slip plane. The non-Schmid crystal plasticity constitutive relation is then used to carry out finite element simulations of micropillar compression of single crystals of two MAX phases, Ti 2 AlC and Ti 3 AlC 2 . The finite element simulations not only quantitatively predict the stress – strain response of a wide range of crystallographic orientations of the micropillars but also rationalize the non-uniform deformation and the deformed shape of the micropillars observed in the experiments for the two materials. As a result, parametric studies are also carried out to quantify the role of the non-Schmid effect and understand the effects of key experimental parameters on the stress – strain response of the micropillars of the two MAX phases.

36 MATERIALS SCIENCE↗