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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Statistical Multiobjective Optimization of Thiospinel CoNi 2 S 4 Nanocrystal Synthesis via Design of Experiments

Thiospinels, such as CoNi 2 S 4 , are showing promise for numerous applications, including as catalysts for the hydrogen evolution reaction, hydrodesulfurization, and oxygen evolution and reduction reactions; however, CoNi 2 S 4 has not been synthesized as small, colloidal nanocrystals with high surface-area-to-volume ratios. Traditional optimization methods to control nanocrystal attributes such as size typically rely upon one variable at a time (OVAT) methods that are not only time and labor intensive but also lack the ability to identify higher-order interactions between experimental variables that affect target outcomes. Herein, we demonstrate that a statistical design of experiments (DoE) approach can optimize the synthesis of CoNi 2 S 4 nanocrystals, allowing for control over the responses of nanocrystal size, size distribution, and isolated yield. After implementing a 2 5–2 fractional factorial design, the statistical screening of five different experimental variables identified temperature, Co:Ni precursor ratio, Co:thiol ratio, and their higher-order interactions as the most critical factors in influencing the aforementioned responses. Second-order design with a Doehlert matrix yielded polynomial functions used to predict the reaction parameters needed to individually optimize all three responses. A multiobjective optimization, allowing for the simultaneous optimization of size, size distribution, and isolated yield, predicted the synthetic conditions needed to achieve a minimum nanocrystal size of 6.1 nm, a minimum polydispersity (σ/$\bar{d}$) of 10%, and a maximum isolated yield of 99%, with a desirability of 96%. The resulting model was experimentally verified by performing reactions under the specified conditions. Furthermore, our work illustrates the advantage of multivariate experimental design as a powerful tool for accelerating control and optimization in nanocrystal syntheses.

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

Materials Data on CoNi(PS3)2 by Materials Project

CoNi(PS3)2 crystallizes in the monoclinic C2 space group. The structure is two-dimensional and consists of one CoNi(PS3)2 sheet oriented in the (0, 0, 1) direction. Co1+ is bonded to six S2- atoms to form CoS6 octahedra that share edges with three equivalent NiS6 octahedra. There are four shorter (2.34 Å) and two longer (2.35 Å) Co–S bond lengths. Ni1+ is bonded to six S2- atoms to form NiS6 octahedra that share edges with three equivalent CoS6 octahedra. There are four shorter (2.43 Å) and two longer (2.44 Å) Ni–S bond lengths. P5+ is bonded in a trigonal planar geometry to three S2- atoms. There are two shorter (2.06 Å) and one longer (2.07 Å) P–S bond lengths. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted trigonal non-coplanar geometry to one Co1+, one Ni1+, and one P5+ atom. In the second S2- site, S2- is bonded in a distorted trigonal non-coplanar geometry to one Co1+, one Ni1+, and one P5+ atom. In the third S2- site, S2- is bonded in a distorted trigonal non-coplanar geometry to one Co1+, one Ni1+, and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Minor Elements and Solidification Cracking During Laser Powder-Bed Fusion of a High $\gamma ^{\prime }$ CoNi-Base Superalloy

Here, the cracking behavior of a high γ' volume fraction CoNi-base superalloy fabricated via laser powder bed fusion (LPBF) is studied in relation to the content of carbon and boron. Severe cracking occurred with the increase in boron content from 0.08 to 0.16 at. pct (0.015 to 0.029 wt pct), while compositions with 0.1 to 0.36 at. pct C (0.02 to 0.076 wt pct) and 0.08 at. pct B exhibited minimal cracking. Assessment of cracks in the high-boron composition shows a variation in crack density with printing parameters, and alignment of the cracks with the build direction. Scanning electron microscopy (SEM) of the crack surfaces shows evidence of a solidification cracking mode. Differential thermal analysis (DTA) reveals a decreased incipient melting temperature for the high-boron composition, and atom probe tomography (APT) is used to measure the enrichment at grain boundaries, revealing distinct boron segregation. Scheil-Gulliver solidification simulations for the different C and B levels are consistent with the incipient melting behavior observed with DTA. Evaluation of the solidification cracking susceptibility from the simulations allow for comparison of the CoNi alloy behavior to Ni-base superalloys studied for LPBF fabrication and displays how such metrics may aid in the design of new precipitation-strengthened superalloys for additive manufacturing (AM).

36 MATERIALS SCIENCE↗
DOE OSTI2024

Understanding the influence of boron in additively manufactured GammaPrint®-700 CoNi-based superalloy

Boron is commonly added to superalloys in small amounts to enhance creep resistance, but can lead to cracking at high concentrations, especially during the additive manufacturing process. Two variants of CoNi-based GammaPrint®-700 superalloy with different B contents (0.08 at% vs 0.16 at%) were printed via laser powder bed fusion (LPBF) with the same printing parameters, with only the high B alloy exhibiting solidification cracking. Atom probe tomography (APT) revealed stronger segregation behaviors in the high B alloy compared to the low B alloy at both the inter-dendritic regions and grain boundaries (GBs). The segregation behavior at inter-dendritic regions was well captured with Scheil simulation and can correlate with the existing cracking susceptibility index (CSI) on cracking tendencies, although high angle GBs are where cracking occurs according to electron backscatter diffraction (EBSD) measurements. Additionally, the extent of GB segregation was compared between the high B and low B alloy. Higher B additions led to significantly more GB B segregation in the high B alloy compared to the low B alloy. Further, for the high B alloy, the cracked region of one GB exhibited higher levels of B compared to the uncracked region of the same GB. However, much higher B contents were also found in two other uncracked GBs in the high B alloy, which demonstrates that higher GB B concentrations are not fully responsible for the cracking. A much larger variance in GB B segregation content was found in the high B alloy compared to the low B alloy. These phenomena were explained with a solidification model with the GB segregation content expressed explicitly by a modified Langmuir-McLean equation. This model linked the GB segregation content with solidification undercooling, which can be used as quantitative cracking criteria for future builds.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoNi by Materials Project

CoNi is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Co is bonded in a body-centered cubic geometry to eight equivalent Ni atoms. All Co–Ni bond lengths are 2.43 Å. Ni is bonded in a body-centered cubic geometry to eight equivalent Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y2(CoNi)5 by Materials Project

Y2(CoNi)5 crystallizes in the orthorhombic Pmmm space group. The structure is three-dimensional. there are two inequivalent Y sites. In the first Y site, Y is bonded in a 6-coordinate geometry to six Co and twelve Ni atoms. There are four shorter (2.83 Å) and two longer (2.87 Å) Y–Co bond lengths. There are eight shorter (3.15 Å) and four longer (3.16 Å) Y–Ni bond lengths. In the second Y site, Y is bonded in a 6-coordinate geometry to ten Co and eight equivalent Ni atoms. There are a spread of Y–Co bond distances ranging from 2.81–3.16 Å. All Y–Ni bond lengths are 3.15 Å. There are three inequivalent Co sites. In the first Co site, Co is bonded in a 12-coordinate geometry to three Y, five Co, and four equivalent Ni atoms. There are a spread of Co–Co bond distances ranging from 2.40–2.86 Å. All Co–Ni bond lengths are 2.45 Å. In the second Co site, Co is bonded in a 12-coordinate geometry to three Y, two equivalent Co, and six Ni atoms. There are two shorter (2.43 Å) and four longer (2.44 Å) Co–Ni bond lengths. In the third Co site, Co is bonded to four equivalent Y, four equivalent Co, and four equivalent Ni atoms to form CoY4Co4Ni4 cuboctahedra that share corners with four equivalent CoY4Co4Ni4 cuboctahedra, corners with twelve NiY4Co5Ni3 cuboctahedra, edges with two equivalent CoY4Co4Ni4 cuboctahedra, edges with eight equivalent NiY4Co5Ni3 cuboctahedra, faces with two equivalent CoY4Co4Ni4 cuboctahedra, and faces with eight equivalent NiY4Co5Ni3 cuboctahedra. All Co–Ni bond lengths are 2.44 Å. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded to four equivalent Y, four equivalent Co, and four equivalent Ni atoms to form NiY4Co4Ni4 cuboctahedra that share corners with four equivalent CoY4Co4Ni4 cuboctahedra, corners with twelve NiY4Co5Ni3 cuboctahedra, edges with ten NiY4Co5Ni3 cuboctahedra, and faces with ten NiY4Co4Ni4 cuboctahedra. All Ni–Ni bond lengths are 2.45 Å. In the second Ni site, Ni is bonded to four Y, five Co, and three Ni atoms to form NiY4Co5Ni3 cuboctahedra that share corners with two equivalent CoY4Co4Ni4 cuboctahedra, corners with fourteen NiY4Co4Ni4 cuboctahedra, edges with two equivalent CoY4Co4Ni4 cuboctahedra, edges with eight NiY4Co5Ni3 cuboctahedra, faces with two equivalent CoY4Co4Ni4 cuboctahedra, and faces with eight NiY4Co4Ni4 cuboctahedra. Both Ni–Ni bond lengths are 2.46 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho2(CoNi)5 by Materials Project

Ho2(CoNi)5 crystallizes in the orthorhombic Pmmm space group. The structure is three-dimensional. there are two inequivalent Ho sites. In the first Ho site, Ho is bonded in a 6-coordinate geometry to six Co and twelve Ni atoms. There are four shorter (2.83 Å) and two longer (2.86 Å) Ho–Co bond lengths. There are eight shorter (3.14 Å) and four longer (3.15 Å) Ho–Ni bond lengths. In the second Ho site, Ho is bonded in a 6-coordinate geometry to ten Co and eight equivalent Ni atoms. There are a spread of Ho–Co bond distances ranging from 2.81–3.15 Å. All Ho–Ni bond lengths are 3.14 Å. There are three inequivalent Co sites. In the first Co site, Co is bonded in a 12-coordinate geometry to three Ho, two equivalent Co, and four equivalent Ni atoms. Both Co–Co bond lengths are 2.40 Å. All Co–Ni bond lengths are 2.44 Å. In the second Co site, Co is bonded in a 12-coordinate geometry to three Ho and six Ni atoms. There are four shorter (2.42 Å) and two longer (2.43 Å) Co–Ni bond lengths. In the third Co site, Co is bonded to four equivalent Ho, four equivalent Co, and four equivalent Ni atoms to form CoHo4Co4Ni4 cuboctahedra that share corners with four equivalent CoHo4Co4Ni4 cuboctahedra, corners with twelve NiHo4Co5Ni3 cuboctahedra, edges with two equivalent CoHo4Co4Ni4 cuboctahedra, edges with eight equivalent NiHo4Co5Ni3 cuboctahedra, faces with two equivalent CoHo4Co4Ni4 cuboctahedra, and faces with eight equivalent NiHo4Co5Ni3 cuboctahedra. All Co–Ni bond lengths are 2.45 Å. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded to four equivalent Ho, four equivalent Co, and four equivalent Ni atoms to form NiHo4Co4Ni4 cuboctahedra that share corners with four equivalent CoHo4Co4Ni4 cuboctahedra, corners with twelve NiHo4Co5Ni3 cuboctahedra, edges with ten NiHo4Co5Ni3 cuboctahedra, and faces with ten NiHo4Co4Ni4 cuboctahedra. All Ni–Ni bond lengths are 2.45 Å. In the second Ni site, Ni is bonded to four Ho, five Co, and three Ni atoms to form NiHo4Co5Ni3 cuboctahedra that share corners with two equivalent CoHo4Co4Ni4 cuboctahedra, corners with fourteen NiHo4Co4Ni4 cuboctahedra, edges with two equivalent CoHo4Co4Ni4 cuboctahedra, edges with eight NiHo4Co4Ni4 cuboctahedra, faces with two equivalent CoHo4Co4Ni4 cuboctahedra, and faces with eight NiHo4Co4Ni4 cuboctahedra. There are one shorter (2.44 Å) and one longer (2.46 Å) Ni–Ni bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoNi(AsS)2 by Materials Project

CoNi(AsS)2 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. Co2+ is bonded to three As and three S2- atoms to form CoAs3S3 octahedra that share corners with four equivalent CoAs3S3 octahedra, corners with eight equivalent NiAs3S3 octahedra, corners with three AsCoNi2S tetrahedra, and corners with three SCoNi2As tetrahedra. The corner-sharing octahedra tilt angles range from 62–65°. There are a spread of Co–As bond distances ranging from 2.34–2.37 Å. There are one shorter (2.28 Å) and two longer (2.29 Å) Co–S bond lengths. Ni2+ is bonded to three As and three S2- atoms to form NiAs3S3 octahedra that share corners with four equivalent NiAs3S3 octahedra, corners with eight equivalent CoAs3S3 octahedra, corners with three AsCoNi2S tetrahedra, and corners with three SCoNi2As tetrahedra. The corner-sharing octahedra tilt angles range from 63–65°. There are two shorter (2.40 Å) and one longer (2.42 Å) Ni–As bond lengths. There are a spread of Ni–S bond distances ranging from 2.32–2.34 Å. There are two inequivalent As sites. In the first As site, As is bonded to one Co2+, two equivalent Ni2+, and one S2- atom to form distorted AsCoNi2S tetrahedra that share a cornercorner with one CoAs3S3 octahedra, corners with two equivalent NiAs3S3 octahedra, corners with six AsCoNi2S tetrahedra, and corners with nine SCoNi2As tetrahedra. The corner-sharing octahedra tilt angles range from 77–80°. The As–S bond length is 2.32 Å. In the second As site, As is bonded to two equivalent Co2+, one Ni2+, and one S2- atom to form distorted AsCo2NiS tetrahedra that share a cornercorner with one NiAs3S3 octahedra, corners with two equivalent CoAs3S3 octahedra, corners with six AsCoNi2S tetrahedra, and corners with nine SCoNi2As tetrahedra. The corner-sharing octahedra tilt angles range from 78–81°. The As–S bond length is 2.33 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded to one Co2+, two equivalent Ni2+, and one As atom to form distorted SCoNi2As tetrahedra that share a cornercorner with one CoAs3S3 octahedra, corners with two equivalent NiAs3S3 octahedra, corners with six SCoNi2As tetrahedra, and corners with nine AsCoNi2S tetrahedra. The corner-sharing octahedra tilt angles range from 77–80°. In the second S2- site, S2- is bonded to two equivalent Co2+, one Ni2+, and one As atom to form distorted SCo2NiAs tetrahedra that share a cornercorner with one NiAs3S3 octahedra, corners with two equivalent CoAs3S3 octahedra, corners with six SCoNi2As tetrahedra, and corners with nine AsCoNi2S tetrahedra. The corner-sharing octahedra tilt angles range from 78–81°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr2(CoNi)5 by Materials Project

Pr2(CoNi)5 crystallizes in the orthorhombic Pmmm space group. The structure is three-dimensional. there are two inequivalent Pr sites. In the first Pr site, Pr is bonded in a 6-coordinate geometry to six Co and twelve Ni atoms. All Pr–Co bond lengths are 2.88 Å. All Pr–Ni bond lengths are 3.19 Å. In the second Pr site, Pr is bonded in a 6-coordinate geometry to ten Co and eight equivalent Ni atoms. There are a spread of Pr–Co bond distances ranging from 2.87–3.19 Å. All Pr–Ni bond lengths are 3.19 Å. There are three inequivalent Co sites. In the first Co site, Co is bonded in a 12-coordinate geometry to three Pr, two equivalent Co, and four equivalent Ni atoms. Both Co–Co bond lengths are 2.45 Å. All Co–Ni bond lengths are 2.45 Å. In the second Co site, Co is bonded in a 12-coordinate geometry to three Pr and six Ni atoms. All Co–Ni bond lengths are 2.45 Å. In the third Co site, Co is bonded to four equivalent Pr, four equivalent Co, and four equivalent Ni atoms to form CoPr4Co4Ni4 cuboctahedra that share corners with four equivalent CoPr4Co4Ni4 cuboctahedra, corners with twelve NiPr4Co5Ni3 cuboctahedra, edges with two equivalent CoPr4Co4Ni4 cuboctahedra, edges with eight equivalent NiPr4Co5Ni3 cuboctahedra, faces with two equivalent CoPr4Co4Ni4 cuboctahedra, and faces with eight equivalent NiPr4Co5Ni3 cuboctahedra. All Co–Ni bond lengths are 2.49 Å. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded to four equivalent Pr, four equivalent Co, and four equivalent Ni atoms to form NiPr4Co4Ni4 cuboctahedra that share corners with four equivalent CoPr4Co4Ni4 cuboctahedra, corners with twelve NiPr4Co5Ni3 cuboctahedra, edges with ten NiPr4Co5Ni3 cuboctahedra, and faces with ten NiPr4Co4Ni4 cuboctahedra. All Ni–Ni bond lengths are 2.49 Å. In the second Ni site, Ni is bonded to four Pr, five Co, and three Ni atoms to form NiPr4Co5Ni3 cuboctahedra that share corners with two equivalent CoPr4Co4Ni4 cuboctahedra, corners with fourteen NiPr4Co4Ni4 cuboctahedra, edges with two equivalent CoPr4Co4Ni4 cuboctahedra, edges with eight NiPr4Co4Ni4 cuboctahedra, faces with two equivalent CoPr4Co4Ni4 cuboctahedra, and faces with eight NiPr4Co4Ni4 cuboctahedra. Both Ni–Ni bond lengths are 2.49 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoNi by Materials Project

CoNi is alpha La-derived structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are three inequivalent Co sites. In the first Co site, Co is bonded to six equivalent Co and six equivalent Ni atoms to form CoCo6Ni6 cuboctahedra that share corners with twelve CoCo6Ni6 cuboctahedra, edges with twelve CoCo6Ni6 cuboctahedra, edges with twelve equivalent NiCo6Ni6 cuboctahedra, faces with six equivalent CoCo6Ni6 cuboctahedra, and faces with twelve equivalent NiCo6Ni6 cuboctahedra. All Co–Co bond lengths are 2.48 Å. All Co–Ni bond lengths are 2.49 Å. In the second Co site, Co is bonded to six equivalent Co and six Ni atoms to form CoCo6Ni6 cuboctahedra that share corners with five equivalent NiCo6Ni10 cuboctahedra, corners with twelve CoCo6Ni6 cuboctahedra, edges with ten NiCo6Ni6 cuboctahedra, edges with twelve CoCo6Ni6 cuboctahedra, faces with six equivalent CoCo6Ni6 cuboctahedra, and faces with fifteen NiCo6Ni6 cuboctahedra. All Co–Co bond lengths are 2.48 Å. All Co–Ni bond lengths are 2.49 Å. In the third Co site, Co is bonded to six equivalent Co and six Ni atoms to form CoCo6Ni6 cuboctahedra that share corners with five equivalent NiCo6Ni10 cuboctahedra, corners with twelve CoCo6Ni6 cuboctahedra, edges with ten NiCo6Ni6 cuboctahedra, edges with twelve CoCo6Ni6 cuboctahedra, faces with six equivalent CoCo6Ni6 cuboctahedra, and faces with fifteen NiCo6Ni6 cuboctahedra. All Co–Co bond lengths are 2.48 Å. All Co–Ni bond lengths are 2.49 Å. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded to six Co and six equivalent Ni atoms to form NiCo6Ni6 cuboctahedra that share corners with twelve NiCo6Ni6 cuboctahedra, edges with twelve CoCo6Ni6 cuboctahedra, edges with twelve NiCo6Ni6 cuboctahedra, faces with six equivalent NiCo6Ni6 cuboctahedra, and faces with twelve CoCo6Ni6 cuboctahedra. All Ni–Ni bond lengths are 2.48 Å. In the second Ni site, Ni is bonded to six Co and ten equivalent Ni atoms to form NiCo6Ni10 cuboctahedra that share corners with ten CoCo6Ni6 cuboctahedra, corners with twelve NiCo6Ni6 cuboctahedra, edges with eight CoCo6Ni6 cuboctahedra, edges with sixteen NiCo6Ni6 cuboctahedra, faces with sixteen equivalent NiCo6Ni10 cuboctahedra, and faces with eighteen CoCo6Ni6 cuboctahedra. There are a spread of Ni–Ni bond distances ranging from 2.48–4.96 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Bottom‐Up Synthesis of Metallic CoNi Nanoplatelets with Magnetic Vortex‐Like Spin Configurations

Magnetic nanoplatelets hold significant potential for various technical applications due to their ability to switch between a fully magnetized state with high magnetization and a vortex‐like configuration that eliminates stray fields in the absence of an external field. This study presents the synthesis of uniform CoNi nanoplatelets through the topotactic reduction of metal hydroxides using hydrogen plasma. The reduction process is analyzed via magnetometry, leveraging the transition from paramagnetic hydroxide to ferromagnetic metal. Lorentz transmission electron microscopy and scanning transmission X‐ray microscopy confirm the presence of magnetic vortex‐like structures in isolated Co 0.85 Ni 0.15 nanoplatelets at ambient temperature. Additionally, micromagnetic simulations are conducted to further explore the magnetic properties of the nanoplatelets, revealing the formation of magnetic vortex remanent states at diameters between 200 nm and 1 μm and a thickness of around 12 nm. Notably, structural defects and thickness variations do not directly destabilize the magnetic vortex configurations.

Kräenbring, Mena‐Alexander [Faculty of Physics and↗
DOE OSTI2022

Hydrogen generation via ammonia decomposition on highly efficient and stable Ru-free catalysts: approaching complete conversion at 450 °C

We report Hydrogen (H 2 ) is a prospective zero-carbon and high-energy-density fuel alternative to fossil fuels for generating power and clean energy. Ammonia (NH 3 ) is a promising H 2 (17.7%) carrier, which can easily overcome the challenges associated with H 2 storage and transportation. Thermocatalytic ammonia decomposition reaction (ADR) is an effective way to produce clean H 2 but it relies on the use of expensive and rare ruthenium (Ru)-based catalysts at elevated temperatures (>500 °C), hence is not sustainable and economically feasible. Herein, we report a synergistic strategy to design a heterostructured Ru-free catalyst, consisting of CoNi alloy nanoparticles well-dispersed on a MgO–CeO 2 –SrO mixed oxide support with potassium promotion. The resulting K–CoNi alloy –MgO–CeO 2 –SrO catalyst presents 97.7% and 87.5% NH 3 conversion efficiency at 450 °C at gas hourly space velocities (GHSVs) of 6000- and 12 000-mL h -1 g cat -1 , respectively. At 500 °C, the H 2 production rate (57.75 mmol g cat -1 min -1 ) becomes comparable to that of most of the reported Ru-based catalysts. The catalyst stability has been successfully demonstrated in both a fixed-bed reactor under high pressure (120 h at 5.0 bar) and a membrane reactor prototype (600 h at 1.5 bar) at 500 °C. High-temperature in situ XPS analysis, temperature-programmed desorption/reduction, and density functional theory calculations have been carried out to elucidate the possible active sites and performance enhancement mechanisms. This work highlights the importance of constructing optimal interfaces between active metal nanoparticles and oxide support for boosting the NH 3 to H 2 conversion efficiency and long-term stability.

25 ENERGY STORAGE↗
DOE OSTI2020

Planar Hall Driven Torque in a Ferromagnet/Nonmagnet/Ferromagnet System

An important goal of spintronics is to covert a charge current into a spin current with a controlled spin polarization that can exert torques on an adjacent magnetic layer. Here we demonstrate such torques in a two ferromagnet system. A CoNi multilayer is used as a spin current source in a sample with structure CoNi/Au/CoFeB. Spin torque ferromagnetic resonance is used to measure the torque on the CoFeB layer. The response as a function of the applied field angle and current is consistent with the symmetry expected for a torque produced by the planar Hall effect originating in CoNi. We find the strength of this effect to be comparable to that of the spin Hall effect in platinum, indicating that the planar Hall effect holds potential as a spin current source with a controllable polarization direction.

ferromagnetic resonance↗
DOE OSTI2026

Edge dislocation mediated anomalous charge transfer in face centered cubic high entropy alloys

The charge transfer in alloys dictates their structural and functional properties. The presence of the line defect can influence the charge transfer characteristics in alloys. The edge dislocation-volume misfit interaction in high entropy alloys is a critical area of interest concerning the development of accurate solid solution strengthening models for these materials. The evolution of the volume misfit of atoms is either studied empirically using Vegard's law or mechanistically using \emph{ab initio} calculations, without considering the effect of edge dislocation on charge transfer explicitly. In this work, we show the influence of edge dislocation on the charge transfer in CoCrFeMnNi, CoCrNi and CoNi using large-scale \emph{ab initio} calculations. The anomalous charge transfer characteristics, in terms of deviations from electronegativity trends, are demonstrated, which are dictated by electronegativity equalisation rather than pair-atom interactions. The deviation of atomic volume in the compressive and tensile stress regions of the edge dislocation is rationalised in terms of anomalous magneto-volume fluctuations in such alloys.

Ghosh, Swarnava [ORNL] (ORCID:0000000338005264)↗
DOE OSTI2021

Core-shell metallic alloy nanopillars-in-dielectric hybrid metamaterials with magneto-plasmonic coupling

Combining plasmonic and magnetic properties, namely magneto-plasmonic coupling, inspires great research interest and the search for magneto-plasmonic nanostructure becomes considerably critical. In this work, we designed a nanopillar-in-matrix structure with core–shell alloyed nanopillars for both BaTiO 3 (BTO)-Au 0.5 Co 0.5 (AuCo) and BTO-Au 0.25 Cu 0.25 Co 0.25 Ni 0.25 (AuCuCoNi) hybrid systems, i.e., ferromagnetic alloy cores (e.g., Co or CoNi) with plasmonic shells (e.g., Au or Au/Cu). These core–shell alloy nanopillars are uniformly embedded into a dielectric BTO matrix to form a vertically aligned nanocomposite (VAN) structure. Both hybrid systems present excellent epitaxial quality and interesting multi-functionality, e.g., high magnetic anisotropy, magneto-optical coupling response, tailorable plasmonic resonance wavelength, tunable hyperbolic properties and strong optical anisotropy. These alloyed nanopillars-in-matrix designs provide enormous potential for complex hybrid material designs with multi-functionality and demonstrate strong interface enabled magneto-plasmonic coupling along with plasmonic and magnetic performance.

36 MATERIALS SCIENCE↗
DOE OSTI2026

High-temperature mechanical properties of a γ′-strengthened Co-based superalloy designed for additive manufacturing

GammaPrint®-700 is a recently developed high γ′ (∼70% volume fraction) CoNi-based superalloy designed to combine high-temperature mechanical performance with laser powder bed fusion processability. Room-temperature yield strength ranged from 610 to 658 MPa and increased to 661 MPa (longitudinal) and 730 MPa (transverse) at 760 °C. The creep behavior compared favorably to high-γ′ Ni-based superalloys manufactured via laser powder bed fusion such as Incoloy® 939 and Inconel® 738LC. In-situ neutron diffraction data measured during creep revealed that plastic deformation was largely localized to the γ phase at 760 °C, allowing the γ’ phase to elastically compensate and maintain creep strain resistance. Furthermore, at 900 °C, this load sharing behavior was weakened, contributing to accelerated creep rate and rupture.

Creep↗
DOE OSTI2024

Target Configuration Effect on Microstructures and Properties of Vertically Aligned Nanocomposites

Vertically aligned nanocomposites (VANs) are unique thin films with vertical nanostructures embedded in a matrix material, allowing for the integration of two distinct materials. These nanocomposites offer novel combined physical properties, such as nanocomposite-based multiferroics and strongly coupled physical properties, such as magneto-optic coupling. Much work has been conducted in exploring different two-phase combinations and various processing conditions to achieve novel tunable properties that cannot be obtained by any single-phase material alone. Here, in this work, the target configuration effects are explored for the growth of LaFeO 3 –CoNi 2 O 4 VANs. Both mixed and pie-shaped targets are utilized to compare the target configuration effects on the phase separation, morphology tuning, and their resulting physical properties, including optical and magnetic properties. This work suggests that the target configuration is another important parameter for achieving the desired VAN morphology and can be used to design different two-phase VANs with tailorable properties.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A defect-resistant Co–Ni superalloy for 3D printing

Abstract Additive manufacturing promises a major transformation of the production of high economic value metallic materials, enabling innovative, geometrically complex designs with minimal material waste. The overarching challenge is to design alloys that are compatible with the unique additive processing conditions while maintaining material properties sufficient for the challenging environments encountered in energy, space, and nuclear applications. Here we describe a class of high strength, defect-resistant 3D printable superalloys containing approximately equal parts of Co and Ni along with Al, Cr, Ta and W that possess strengths in excess of 1.1 GPa in as-printed and post-processed forms and tensile ductilities of greater than 13% at room temperature. These alloys are amenable to crack-free 3D printing via electron beam melting (EBM) with preheat as well as selective laser melting (SLM) with limited preheat. Alloy design principles are described along with the structure and properties of EBM and SLM CoNi-base materials.

36 MATERIALS SCIENCE↗