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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on HfTi by Materials Project

HfTi crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Hf is bonded to six equivalent Hf and six equivalent Ti atoms to form distorted HfHf6Ti6 cuboctahedra that share corners with eighteen equivalent HfHf6Ti6 cuboctahedra, edges with six equivalent HfHf6Ti6 cuboctahedra, edges with twelve equivalent TiHf6Ti6 cuboctahedra, faces with eight equivalent HfHf6Ti6 cuboctahedra, and faces with twelve equivalent TiHf6Ti6 cuboctahedra. All Hf–Hf bond lengths are 3.09 Å. All Hf–Ti bond lengths are 3.01 Å. Ti is bonded to six equivalent Hf and six equivalent Ti atoms to form distorted TiHf6Ti6 cuboctahedra that share corners with eighteen equivalent TiHf6Ti6 cuboctahedra, edges with six equivalent TiHf6Ti6 cuboctahedra, edges with twelve equivalent HfHf6Ti6 cuboctahedra, faces with eight equivalent TiHf6Ti6 cuboctahedra, and faces with twelve equivalent HfHf6Ti6 cuboctahedra. All Ti–Ti bond lengths are 3.09 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HfScGe4 by Materials Project

ScHfGe4 is Zirconium Disilicide-derived structured and crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. Sc is bonded in a 10-coordinate geometry to ten Ge atoms. There are a spread of Sc–Ge bond distances ranging from 2.79–3.12 Å. Hf is bonded in a 10-coordinate geometry to ten Ge atoms. There are a spread of Hf–Ge bond distances ranging from 2.79–3.13 Å. There are four inequivalent Ge sites. In the first Ge site, Ge is bonded in a 4-coordinate geometry to four equivalent Sc, two equivalent Hf, and two equivalent Ge atoms. Both Ge–Ge bond lengths are 2.61 Å. In the second Ge site, Ge is bonded in a 4-coordinate geometry to two equivalent Sc, four equivalent Hf, and two equivalent Ge atoms. In the third Ge site, Ge is bonded in a 8-coordinate geometry to two equivalent Sc, two equivalent Hf, and four equivalent Ge atoms. All Ge–Ge bond lengths are 2.71 Å. In the fourth Ge site, Ge is bonded in a 8-coordinate geometry to two equivalent Sc, two equivalent Hf, and four equivalent Ge atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hf3Bi by Materials Project

Hf3Bi is Uranium Silicide-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Hf is bonded to eight equivalent Hf and four equivalent Bi atoms to form distorted HfHf8Bi4 cuboctahedra that share corners with four equivalent BiHf12 cuboctahedra, corners with fourteen equivalent HfHf8Bi4 cuboctahedra, edges with six equivalent BiHf12 cuboctahedra, edges with twelve equivalent HfHf8Bi4 cuboctahedra, faces with four equivalent BiHf12 cuboctahedra, and faces with sixteen equivalent HfHf8Bi4 cuboctahedra. There are a spread of Hf–Hf bond distances ranging from 3.08–3.25 Å. There are two shorter (3.16 Å) and two longer (3.22 Å) Hf–Bi bond lengths. Bi is bonded to twelve equivalent Hf atoms to form BiHf12 cuboctahedra that share corners with six equivalent BiHf12 cuboctahedra, corners with twelve equivalent HfHf8Bi4 cuboctahedra, edges with eighteen equivalent HfHf8Bi4 cuboctahedra, faces with eight equivalent BiHf12 cuboctahedra, and faces with twelve equivalent HfHf8Bi4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HfGaRh by Materials Project

HfRhGa crystallizes in the trigonal P31m space group. The structure is three-dimensional. Hf is bonded in a 11-coordinate geometry to five Rh and six equivalent Ga atoms. There are four shorter (2.79 Å) and one longer (2.86 Å) Hf–Rh bond lengths. There are a spread of Hf–Ga bond distances ranging from 2.94–3.03 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 9-coordinate geometry to three equivalent Hf and six equivalent Ga atoms. There are three shorter (2.59 Å) and three longer (2.60 Å) Rh–Ga bond lengths. In the second Rh site, Rh is bonded in a 9-coordinate geometry to six equivalent Hf and three equivalent Ga atoms. All Rh–Ga bond lengths are 2.68 Å. Ga is bonded in a 10-coordinate geometry to six equivalent Hf and four Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Microseismic Monitoring of Laboratory Hydraulic Fracturing Experiments in Granitic Rocks for Different Fracture Propagation Regimes

While hydraulic fracturing (HF) is a widely employed process, the underlying fracturing processes are still heavily contested. The attributes of the HF generated fracture network can exhibit substantial variation when dealing with specific HF propagation regimes encountered in the field. In this study, HF experiments were performed on true-triaxially loaded Barre granite cubes, with microseismic monitoring, to identify and characterize the fracturing mechanisms associated with different viscosity injection fluids. Utilizing fluids with high (oil/1450 cP) and low (water/1 cP) viscosity represented two key HF propagation regimes: viscosity- and toughness-dominated. The experiments conducted with oil involved higher breakdown pressures, larger fluid volumes, and slower fracture propagation speeds. Furthermore, the frequency–magnitude distribution (b value) for all experiments (1.9–2.3) was similar to those encountered for large-scale operations. Slightly larger b values were encountered during the initiation phase (2.4–2.7) relative to the fracture propagation and post-fracturing phases (1.9–2.2). Techniques such as polarity and moment-tensor inversion were utilized to characterize the source mechanisms. For the HF experiments with oil, tensile fractures were most dominant (92%) in the initiation phase compared to fracture propagation and post-fracturing phases (70–75%). Similar tensile fracturing dominancy was not observed with water, attributable to fluid permeation and leak-off. Regardless of the injection fluid or classification criteria employed, tensile fractures were the dominant type consistently, with fewer occurring in water experiments but the specific ratio of crack types varied with different source mechanism criteria employed.

58 GEOSCIENCES↗
DOE OSTI2022

Active learning with multifidelity modeling for efficient rare event simulation

Here, while multifidelity modeling provides a cost-effective way to conduct uncertainty quantification with computationally expensive models, much greater efficiency can be achieved by adaptively deciding the number of required high-fidelity (HF) simulations, depending on the type and complexity of the problem and the desired accuracy in the results. We propose a framework for active learning with multifidelity modeling emphasizing the efficient estimation of rare events. Our framework works by fusing a low-fidelity (LF) prediction with an HF-inferred correction, filtering the corrected LF prediction to decide whether to call the high-fidelity model, and for enhanced subsequent accuracy, adapting the correction for the LF prediction after every HF model call. The framework does not make any assumptions as to the LF model type or its correlations with the HF model. In addition, for improved robustness when estimating smaller failure probabilities, we propose using dynamic active learning functions that decide when to call the HF model. We demonstrate our framework using several academic case studies (including some high-dimensional problems) and two finite element model case studies: estimating Navier-Stokes velocities using the Stokes approximation and estimating stresses in a transversely isotropic model subjected to displacements via a coarsely meshed isotropic model. Across these case studies, not only did the proposed framework estimate the failure probabilities accurately, but compared with either Monte Carlo or a standard variance reduction method, it also required only a small fraction of the calls to the HF model.

42 ENGINEERING↗
DOE OSTI2020

Machine-Learning-Assisted Synthesis of Polar Racemates

Racemates have recently received attention as nonlinear optical and piezoelectric materials. We report a machine-learning-assisted composition space approach was applied to synthesize the missing M = Ti, Zr members of the Δ,Λ-[Cu(bpy) 2 (H 2 O)] 2 [MF 6 ] 2·3 H 2 O (M = Ti, Zr, Hf; bpy = 2,2'-bipyridine) family (space group: Pna2 1 ). In each (CuO, MO 2 )/bpy/HF(aq) (M = Ti, Zr, Hf) system, the polar noncentrosymmetric racemate (M-NCS) forms in competition with a centrosymmetric one-dimensional chain compound (M-CS) based on alternating Cu(bpy)(H 2 O) 2 2+ and MF 6 2– basic building units (space groups: Ti-CS (Pnma), Zr-CS (P1̅), Hf-CS (P2/n)). Machine learning models were trained on reaction parameters to gain unbiased insight into the underlying statistical trends in each composition space. A human-interpretable decision tree shows that phase selection is driven primarily by the bpy:CuO molar ratio for reactions containing Zr or Hf, and predicts that formation of the Ti-NCS compound requires that the amount of HF present be decreased to raise the pH, which we verified experimentally. Predictive leave-one-metal-out (LOO) models further confirm that behavior in the Ti system is distinct from that of the Zr and Hf systems. The chemical origin of this distinction was probed via fluorine K-edge X-ray absorption spectroscopy. Pre-edge features in the F1s X-ray absorption spectra reveal the strong ligand-to-metal π bonding between Ti(3d – t 2g ) and F(2p) states that distinguishes the TiF 6 2– anion from the ZrF 6 2– and HfF 6 2– anions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

A Simple Space Vector Modulation of High-Frequency AC Linked Three-Phase-to-Single-Phase/DC Converter

High frequency (HF) ac linked converter functions well to interface between buses with different voltage types. Using a three-phase-to-single-phase matrix converter, a single-phase cyclo converter, and a HF transformer, we can compose a HF ac linked converter to interface between three-phase ac grids and single-phase ac or dc distributed generations (DGs). In this paper, a novel space vector modulation (SVM) method is proposed for such kind of converter. The proposed SVM method converts the mains three-phase ac voltage to a HF ac voltage at the primary side of transformer, and then unfolds the HF ac voltage to a single-phase ac or dc voltage at the secondary side of transformer. Without need to compute separate switching signals for the primary and secondary converters and then coordinate their operations elaborately, the proposed SVM method can be easily implemented by incorporating the HF chopping into the SVM of traditional indirect matrix converter. Therefore, no complicated duty cycle computation or elaborate switching states combination is required. Simulation and hardware-in-loop implementation demonstrate the validity of the proposed method.

42 ENGINEERING↗
DOE OSTI2021

Analysis and Integration of the Hydraulic Fracturing Test Site-2 (HFTS-2) Comprehensive Dataset

Hydraulic Fracturing Test Site-2 (HFTS-2) is a field-based research experiment performed in the Permian (Delaware) Basin. The unique aspect of this program was the acquisition of a unique, comprehensive, diagnostic dataset. Additionally, shorter parent wells drilled three years before the child wells offered clear distinction between the stages influenced by parent-child effects and the stages without any effects. The goal of this study was to analyze and integrate this comprehensive diagnostic dataset to understand the areal and vertical extent of hydraulic fractures (HF). The paper also provides insights on the effects of parent wells’ depletion on child well HF geometry based on various monitoring methods and subsurface models. Areal and vertical coverage for all HFTS-2 wells during stimulation and depletion was estimated based on analysis and interpretation of diagnostics and advanced modeling results. HFTS-2 diagnostics included microseismic (MS), pre- and post-stimulation logs and cores, bottomhole gauges, and fiber optic (FO) data. The diagnostics results (MS, FO, image logs) were integrated and used to calibrate subsurface models. Additional field tests were designed and implemented for depletion monitoring. The tailored program for monitoring depletion included vertical and slant well pressures, interference testing, and a vertical strain depletion trial. Areal Coverage: Conventional MS (and FO MS) were used to compute HF dimensions, which were compared with diagnostics (FO strain, gauge, image logs) observations and calibrated subsurface models. A post-production interference test did not show offset well communication. Vertical Coverage: Vertical coverage during stimulation was monitored using a vertical monitoring well. The stronger mechanical strain signals showed good correlation with MS event intensities, geomechanical properties, and gauge inferences. Vertical depletion was estimated based on vertical/slant well gauges and strain depletion tests. Parent-Child Effects: Diagnostics and calibrated subsurface models show asymmetry in child well fracture geometries for stages that overlap parent wells. Child well image logs serve as a good indicator for parent Downloaded from http://onepetro.org/URTECONF/proceedings-pdf/21URTC/2-21URTC/D021S031R004/2477423/urtec-2021-5241-ms.pdf/1 by Carol Worster on 28 February 2022 URTeC 5241 well HF tracking. Child well MS events had an eastward bias, in line with pre-stimulation image logs, and was confirmed by parent well frac hits. Novel/Additive Information: The dataset presents a unique, over-constrained problem space to compare independent techniques to arrive at HF metrics (i.e., stimulation height and/or half-length), unlike a single source dataset, in which calibration is done using available data to guide predictions. Here, the asymmetry in HF geometry seen in the stages influenced by parent-child effects offers unique insights into well spacing and landing, which are key capital decisions the unconventional resources industry is seeking to optimize.

58 GEOSCIENCES↗
DOE OSTI2022

Multi-principal element grain boundaries: Stabilizing nanocrystalline grains with thick amorphous complexions

Amorphous complexions have recently been demonstrated to simultaneously enhance the ductility and stability of certain nanocrystalline alloys. In this study, three quinary alloys (Cu–Zr–Hf–Mo–Nb, Cu–Zr–Hf–Nb–Ti, and Cu–Zr–Hf–Mo–W) are studied to test the hypothesis that increasing the chemical complexity of the grain boundaries will result in thicker amorphous complexions and further stabilize a nanocrystalline microstructure. Significant boundary segregation of Zr, Nb, and Ti is observed in the Cu–Zr–Hf–Nb–Ti alloy, which creates a quaternary interfacial composition that limits average grain size to 63 nm even after 1 week at ~ 97% of the melting temperature. This high level of thermal stability is attributed to the complex grain boundary chemistry and amorphous structure resulting from multi-component segregation. Furthermore, high-resolution transmission electron microscopy reveals that the increased chemical complexity of the grain boundary region in the Cu–Zr–Hf–Nb–Ti alloy results in an average amorphous complexion thickness of 2.44 nm, approximately 44% and 32% thicker than amorphous complexions previously observed in Cu–Zr and Cu–Zr–Hf alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HfVGe by Materials Project

HfVGe crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Hf is bonded in a 5-coordinate geometry to four equivalent V and five equivalent Ge atoms. All Hf–V bond lengths are 3.16 Å. There are four shorter (2.73 Å) and one longer (2.82 Å) Hf–Ge bond lengths. V is bonded to four equivalent Hf, four equivalent V, and four equivalent Ge atoms to form a mixture of distorted corner and face-sharing VHf4V4Ge4 cuboctahedra. All V–V bond lengths are 2.63 Å. All V–Ge bond lengths are 2.62 Å. Ge is bonded in a 9-coordinate geometry to five equivalent Hf and four equivalent V atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HfSiPt by Materials Project

HfPtSi crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Hf is bonded in a 11-coordinate geometry to six equivalent Pt and five equivalent Si atoms. There are a spread of Hf–Pt bond distances ranging from 2.98–3.11 Å. There are three shorter (2.75 Å) and two longer (2.85 Å) Hf–Si bond lengths. Pt is bonded in a 12-coordinate geometry to six equivalent Hf and four equivalent Si atoms. There are a spread of Pt–Si bond distances ranging from 2.48–2.58 Å. Si is bonded in a 9-coordinate geometry to five equivalent Hf and four equivalent Pt atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HfSiPd by Materials Project

HfPdSi crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Hf is bonded in a 11-coordinate geometry to six equivalent Pd and five equivalent Si atoms. There are a spread of Hf–Pd bond distances ranging from 2.99–3.14 Å. There are a spread of Hf–Si bond distances ranging from 2.74–2.83 Å. Pd is bonded in a 12-coordinate geometry to six equivalent Hf, two equivalent Pd, and four equivalent Si atoms. Both Pd–Pd bond lengths are 2.87 Å. There are a spread of Pd–Si bond distances ranging from 2.49–2.59 Å. Si is bonded in a 9-coordinate geometry to five equivalent Hf and four equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HfSnPd by Materials Project

PdHfSn is half-Heusler structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Hf is bonded to four equivalent Pd and six equivalent Sn atoms to form a mixture of distorted corner and face-sharing HfSn6Pd4 tetrahedra. All Hf–Pd bond lengths are 2.76 Å. All Hf–Sn bond lengths are 3.18 Å. Pd is bonded in a body-centered cubic geometry to four equivalent Hf and four equivalent Sn atoms. All Pd–Sn bond lengths are 2.76 Å. Sn is bonded in a 10-coordinate geometry to six equivalent Hf and four equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HfBeSi by Materials Project

BeHfSi crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Be is bonded in a distorted trigonal planar geometry to six equivalent Hf and three equivalent Si atoms. All Be–Hf bond lengths are 2.79 Å. All Be–Si bond lengths are 2.14 Å. Hf is bonded to six equivalent Be and six equivalent Si atoms to form a mixture of edge and face-sharing HfBe6Si6 cuboctahedra. All Hf–Si bond lengths are 2.79 Å. Si is bonded in a distorted trigonal planar geometry to three equivalent Be and six equivalent Hf atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hf2CS by Materials Project

Hf2SC is H-Phase structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Hf is bonded to three equivalent C and three equivalent S atoms to form a mixture of edge, face, and corner-sharing HfC3S3 octahedra. The corner-sharing octahedra tilt angles range from 0–43°. All Hf–C bond lengths are 2.29 Å. All Hf–S bond lengths are 2.66 Å. C is bonded to six equivalent Hf atoms to form CHf6 octahedra that share corners with six equivalent SHf6 pentagonal pyramids, edges with six equivalent CHf6 octahedra, and edges with six equivalent SHf6 pentagonal pyramids. S is bonded to six equivalent Hf atoms to form distorted SHf6 pentagonal pyramids that share corners with six equivalent CHf6 octahedra, edges with six equivalent CHf6 octahedra, and edges with six equivalent SHf6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 11°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HfSiRh by Materials Project

HfRhSi crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Hf is bonded in a 11-coordinate geometry to six equivalent Rh and five equivalent Si atoms. There are a spread of Hf–Rh bond distances ranging from 2.93–3.04 Å. There are three shorter (2.79 Å) and two longer (2.80 Å) Hf–Si bond lengths. Rh is bonded in a 4-coordinate geometry to six equivalent Hf and four equivalent Si atoms. There are a spread of Rh–Si bond distances ranging from 2.44–2.50 Å. Si is bonded in a 9-coordinate geometry to five equivalent Hf and four equivalent Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HfSiSe by Materials Project

HfSiSe crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Hf is bonded in a 4-coordinate geometry to four equivalent Si and five equivalent Se atoms. All Hf–Si bond lengths are 2.78 Å. There are four shorter (2.75 Å) and one longer (3.27 Å) Hf–Se bond lengths. Si is bonded in a 8-coordinate geometry to four equivalent Hf and four equivalent Si atoms. All Si–Si bond lengths are 2.54 Å. Se is bonded in a 4-coordinate geometry to five equivalent Hf atoms.

36 MATERIALS SCIENCE↗