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All sourcesNASA NTRSDOE OSTI
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↗
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↗
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↗
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↗
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↗
DOE OSTI2021

Synthesis of Ti 3 C 2 T z MXene from low-cost and environmentally friendly precursors

Herein we report an approach to synthesis Ti 3 AlC 2 MAX phase and Ti 3 C 2 T z MXene from low-cost precursors, viz. recycled carbon recovered from waste tire, recycled aluminum scrap, and titanium oxide. By adjusting the ratios of the initial materials, we determined that 3TiO 2 +6Al+1.9C resulted in the purest sample of Ti 3 AlC 2 when heated at 1,350 °C for 1 h. The MXene phase was synthesized by modified minimally intensive layer delamination and acid etching under N2 purging. The final Ti 3 C 2 T z films demonstrated conductivity of 5857 ± 680 S/cm and capacitance of 285 F/g (1,012 F/cm 3 ) at 20 mV/s scan rates, which are comparable with that produced from MAX phase of high-purity elemental precursors (viz. Ti, Al and C). Choosing readily available and inexpensive precursor materials such as these allows for a drastic reduction in production cost of the MXene, as well as reducing the environmental impact of the industry.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Modeling of thermal pressurization in tight claystone using sequential THM coupling: Benchmarking and validation against in-situ heating experiments in COx claystone

We apply thermoporoelasticity and a sequentially coupling technique for modeling thermally-driven coupled Thermo-Hydro-Mechanical (THM) processes in tight claystone. A THM benchmark case with a corresponding analytic solution for thermoporoelasticity under a constant heat loading verifies the model. Thereafter, two in situ heating experiments are simulated for model validation: a smaller-scale heating experiment (TED experiment) and a larger-scale experiment (ALC experiment) in Callovo-Oxfordian (COx) claystone at the Meuse/Haute-Marne underground research laboratory in France. The model exhibits good performance to match the observed temperature and pore pressure evolution for the smaller-scale TED experiment. For the larger-scale ALC experiment, general trends of thermal-pressurization are captured in the modeling, but pressure is underestimated at some monitoring points during cool-down. This indicates that the THM response in the field may be affected by the variability of rock's properties or irreversible or time-dependent mechanical processes that are not included in the current thermoporoelastic model. The main contributions of this work are as follows: (1) we verify and validate the numerical simulator, TOUGH-FLAC, to be a valuable coupled THM modeling tool; (2) prove that the laboratory determined material parameters can be used as reference values for upscaling experiments. However, to better identify and quantify THM processes with modeling of in situ tests, more emphasize should be dedicated to obtaining high-quality mechanical deformation data.

58 GEOSCIENCES↗
DOE OSTI2020

Materials Data on Zr3Al3C5 by Materials Project

Zr3Al3C5 crystallizes in the hexagonal P6_3/mmc space group. The structure is two-dimensional and consists of two AlC sheets oriented in the (0, 0, 1) direction and two Zr3(AlC2)2 sheets oriented in the (0, 0, 1) direction. In each AlC sheet, Al3+ is bonded in a trigonal planar geometry to three equivalent C4- atoms. All Al–C bond lengths are 1.91 Å. C4- is bonded in a trigonal planar geometry to three equivalent Al3+ atoms. In each Zr3(AlC2)2 sheet, there are two inequivalent Zr+3.67+ sites. In the first Zr+3.67+ site, Zr+3.67+ is bonded to six equivalent C4- atoms to form a mixture of corner and edge-sharing ZrC6 octahedra. The corner-sharing octahedral tilt angles are 3°. All Zr–C bond lengths are 2.37 Å. In the second Zr+3.67+ site, Zr+3.67+ is bonded to six C4- atoms to form a mixture of corner and edge-sharing ZrC6 octahedra. The corner-sharing octahedral tilt angles are 3°. There are three shorter (2.29 Å) and three longer (2.59 Å) Zr–C bond lengths. Al3+ is bonded in a trigonal non-coplanar geometry to three equivalent C4- atoms. All Al–C bond lengths are 2.09 Å. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded in a 3-coordinate geometry to three equivalent Zr+3.67+ and three equivalent Al3+ atoms. In the second C4- site, C4- is bonded to six Zr+3.67+ atoms to form a mixture of corner and edge-sharing CZr6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsAl by Materials Project

AlCs is Zintl Phase structured and crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional and consists of two AlCs frameworks. Cs is bonded to four equivalent Al atoms to form distorted corner-sharing CsAl4 tetrahedra. All Cs–Al bond lengths are 3.62 Å. Al is bonded to four equivalent Cs atoms to form distorted corner-sharing AlCs4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Trace Chemical Detection Using Intercalated MXenes as a Signal Enhancing Substrate in Optical Probes

MXenes are 2D materials composed of layered transition metal nitrides or carbides. These materials are synthesized by HF exfoliation from MAX phases (Ti{sub 3}AlC{sub 2}). The 2D nanomaterial was synthesized by the removal of the 'A' element, resulting in a Mxene product (Ti{sub 3}C{sub 2}). MXenes have the general formula M{sub n+1}X{sub n}T{sub x}, where M is an early transition metal, X is Carbon and/or Nitrogen, and T accounts for surface terminated functional groups such as Fluoride, hydroxyl, and oxygen. These materials have very unique properties, similar to graphene, that allows them to be applied in a variety of trace detection techniques including surface-enhanced Raman spectroscopy (SERS). MXenes have also been demonstrated to selectively uptake uranyl ion, UO{sub 2}{sup 2+}. If this property can be combined with SERS or fluorescence detection, it may be possible to use MXenes as the basis for an alternative method to kinetic phosphorescence analysis (KPA) for trace uranyl measurements. Objectives: To confirm that MXene Nano materials are suitable substrates for SERS and sensor development by enhancing Raman signaling. To determine if certain MXene preparation methods yield materials that are more suitable for trace sensing methods. To determine uranyl uptake properties of these MXene materials and test them for analytical signals. Sample Preparation: Preparation of Ti{sub 3}C{sub 2}MXene (at FSU). MXenes were prepared by etching Al from Ti{sub 3}AlC{sub 2} (MAX phase)material. Two etching techniques yield different MXene products: LiF/HCl: Milder reaction, larger MXene flakes. HF: Harsher reaction, smaller flakes, larger layer separation. Products washed to remove etchant, vacuum filtered, and dried. Dried MXene flakes are air-stable. Film preparation for sensor testing (at SRNL): Suspend powder in diH{sub 2}O, purge with Ar, sonicate for 30 min. Centrifuge and collect supernate with suspended particles. Observed LiF-etched Mxene yielded a higher density of particles and darker collected solution. Drop-cast (4 ml) supernate onto slides and dried with Ar. For Rhodamine B (RhB) testing, drop-cast 4 ml drops onto Mxene spots and dried with Ar. Scanning Electron Microscopy conditions: 10 kV Beam energy, high vacuum; Working distance of 8 mm; beam penetration depth appx. 4 microns, beam spot size appx. 2 nanometers. Results: Detection of aluminum correlates with bright spots on image. Presence of aluminum shows that LiF/HCl etching was less thorough than HF etching. Trace Cl detection in LiF images suggests incomplete rinsing. HF has smaller feature size, more layer structure, and increased homogeneity, consistent with expectations. Macroscopic Raman spectroscopy measurements: 532 nm excitation, ∼50 mW with a ∼100 micron spot size (InPhotonics RPB probe). Kaiser Optical Holospec f/1.8 spectrometer with cooled (-60 deg.C) Andor iDus OE420 CCD. LiF 1x supernate showed good signal for trace measurements of Rhodamine B. HF and 1/4x LiF supernates showed little Mxene or Rhodamine B signal. Low deposition densities led to excess background signal from glass slides. For LiF film, response is linear with Rhodamine B concentration over range tested. Will retest with Raman microscope (∼1 micron spot size) to characterize SERS of more dilute LiF and HF etched Mxenes. Conclusions: The LiF etched material was more suitable for macroscopic SERS measurements because it was more concentrated, resulting in a thicker film than the HF etched Mxene and diluted LiF sample. However, the other materials may give greater SERS enhancements, which we hope to determine from measurements with the Raman microscope. From characterization with SEM we concluded that the HF etched Mxene is more uniform/homogenous and has smaller particle size than the LiF etched Mxene. There is still aluminum present in both samples indicating that etching wasn't complete, but the removal of the aluminum was more efficient in the HF method. Path Forward: Observe SERS with Raman microscopy, to obtain better signals for the more diluted samples and be able to compare enhancement effects for the different MXenes. Characterize uranyl sorption into MXene films and test Raman and fluorescence signals. Revisit the etching conditions to improve removal of aluminum. FSU and SRNL will continue to collaborate to create and characterize different Mxene materials and test their usefulness for sensor applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Synthesis of new two-dimensional titanium carbonitride Ti 2 C 0.5 N 0.5 T x MXene and its performance as an electrode material for sodium-ion battery

Two-dimensional (2D) layered transition metal carbides/nitrides, called MXenes, are attractive alternative electrode materials for electrochemical energy storage. Owing to their metallic electrical conductivity and low ion diffusion barrier, MXenes are promising anode materials for sodium-ion batteries (SIBs). Herein, we report on a new 2D carbonitride MXene, viz ., Ti 2 C 0.5 N 0.5 T x (T x stands for surface terminations), and the only second carbonitride after Ti 3 CNT x so far. A new type of in situ HF (HCl/KF) etching condition was employed to synthesize multilayer Ti 2 C 0.5 N 0.5 T x powders from Ti 2 AlC 0.5 N 0.5 . Spontaneous intercalation of tetramethylammonium followed by sonication in water allowed for large-scale delamination of this new titanium carbonitride into 2D sheets. Multilayer Ti 2 C 0.5 N 0.5 T x powders showed higher specific capacities and larger electroactive surface area than those of Ti 2 CT x powders. Multilayer Ti 2 C 0.5 N 0.5 T x powders show a specific capacity of 182 mAh g -1 at 20 mA g -1 , the highest among all reported MXene electrodes as SIBs with excellent cycling stability.

25 ENERGY STORAGE↗