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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Synergistic Effects of Molten Salt Corrosion and Proton Irradiation on Grain Boundary Strength in Ni-20Cr

Nickel-based alloys are leading contenders for use as structural materials in molten salt reactors. While there have been extensive studies on the impact of fluoride/chloride-based molten salt corrosion on the microstructural evolution of various nickel-based alloys, the effects of simultaneous molten salt corrosion and radiation on the mechanical integrity of grain boundaries (GBs) remain underexplored. In this study, we use a Ni-20Cr model alloy to investigate this issue, subjecting it to simultaneous molten fluoride salt corrosion and proton irradiation. We performed cross-sectional and chemically-sensitive electron microscopy characterization of the microstructures of these materials, identifying the characteristic corrosion-induced microstructure and local chemical heterogeneity near GBs. After developing a sample preparation method for reliable characterization of GB strength, we assess the mechanical degradation of GBs using in situ push-to-pull micro tensile tests. Our findings reveal that voids induced by corrosion are the primary influence on the failure mode of GBs, regardless of whether proton irradiation is present. For materials that exhibit ductile fracture, those subjected to simultaneous corrosion and radiation exhibit lower yield strengths than those exposed to corrosion alone, which may be linked to the previously observed phenomenon of proton irradiation-decelerated intergranular corrosion in molten salt.

36 - MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni(AsO3)2 by Materials Project

NiAs2O6 is zeta iron carbide-derived structured and crystallizes in the trigonal P-31m space group. The structure is three-dimensional. Ni2+ is bonded to six equivalent O2- atoms to form NiO6 octahedra that share corners with twelve equivalent AsO6 octahedra. The corner-sharing octahedral tilt angles are 52°. All Ni–O bond lengths are 2.14 Å. As5+ is bonded to six equivalent O2- atoms to form AsO6 octahedra that share corners with six equivalent NiO6 octahedra and edges with three equivalent AsO6 octahedra. The corner-sharing octahedral tilt angles are 52°. All As–O bond lengths are 1.86 Å. O2- is bonded in a distorted trigonal planar geometry to one Ni2+ and two equivalent As5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni(AgO)2 by Materials Project

Ag2NiO2 is Calaverite-derived structured and crystallizes in the trigonal R-3m space group. The structure is two-dimensional and consists of three Ag2NiO2 sheets oriented in the (0, 0, 1) direction. Ni2+ is bonded to six equivalent O2- atoms to form edge-sharing NiO6 octahedra. All Ni–O bond lengths are 2.06 Å. Ag1+ is bonded in a 3-coordinate geometry to three equivalent O2- atoms. All Ag–O bond lengths are 2.42 Å. O2- is bonded to three equivalent Ni2+ and three equivalent Ag1+ atoms to form a mixture of edge and corner-sharing ONi3Ag3 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni(SbO3)2 by Materials Project

NiSb2O6 is Hydrophilite-derived structured and crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Ni2+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with eight equivalent SbO6 octahedra and edges with two equivalent SbO6 octahedra. The corner-sharing octahedral tilt angles are 51°. All Ni–O bond lengths are 2.07 Å. Sb5+ is bonded to six O2- atoms to form SbO6 octahedra that share corners with four equivalent NiO6 octahedra, corners with four equivalent SbO6 octahedra, an edgeedge with one NiO6 octahedra, and an edgeedge with one SbO6 octahedra. The corner-sharing octahedra tilt angles range from 48–51°. There are two shorter (2.00 Å) and four longer (2.02 Å) Sb–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to one Ni2+ and two equivalent Sb5+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ni2+ and two equivalent Sb5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni(BMo)2 by Materials Project

Mo2NiB2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Mo2+ is bonded in a 6-coordinate geometry to six equivalent B3- atoms. There are four shorter (2.33 Å) and two longer (2.54 Å) Mo–B bond lengths. Ni2+ is bonded in a square co-planar geometry to four equivalent B3- atoms. All Ni–B bond lengths are 2.10 Å. B3- is bonded in a 9-coordinate geometry to six equivalent Mo2+, two equivalent Ni2+, and one B3- atom. The B–B bond length is 1.84 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni(CO)6 by Materials Project

Ni(C)2(CO)4O2 crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of sixteen formaldehyde molecules, four hydrogen peroxide molecules, eight methane molecules, and four nickel molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni(N3O2)2 by Materials Project

NiO4N2(N2)2 is Cyanogen Chloride-derived structured and crystallizes in the monoclinic C2/m space group. The structure is zero-dimensional and consists of four nitrogen molecules and two NiO4N2 clusters. In each NiO4N2 cluster, Ni2+ is bonded in a linear geometry to two equivalent O2- atoms. Both Ni–O bond lengths are 2.02 Å. N1+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.22 Å) and one longer (1.29 Å) N–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Ni2+ and one N1+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one N1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni(AsO2)2 by Materials Project

NiAs2O4 crystallizes in the tetragonal P4_2/mbc space group. The structure is three-dimensional. Ni2+ is bonded to six O2- atoms to form edge-sharing NiO6 octahedra. There are four shorter (2.04 Å) and two longer (2.14 Å) Ni–O bond lengths. As3+ is bonded in a 3-coordinate geometry to three O2- atoms. There is one shorter (1.76 Å) and two longer (1.89 Å) As–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ni2+ and one As3+ atom. In the second O2- site, O2- is bonded in a trigonal planar geometry to one Ni2+ and two equivalent As3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni(N4O3)2 by Materials Project

Ni(N4O3)2 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional and consists of four raney alloy molecules and one N4O3 framework. In the N4O3 framework, there are two inequivalent N1+ sites. In the first N1+ site, N1+ is bonded to six equivalent O2- atoms to form corner-sharing NO6 octahedra. The corner-sharing octahedral tilt angles are 0°. All N–O bond lengths are 1.96 Å. In the second N1+ site, N1+ is bonded in a distorted rectangular see-saw-like geometry to four equivalent O2- atoms. All N–O bond lengths are 1.96 Å. O2- is bonded to six N1+ atoms to form a mixture of edge and corner-sharing ON6 octahedra. The corner-sharing octahedra tilt angles range from 0–5°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni(PtO2)3 by Materials Project

NiPt3O6 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are two inequivalent Pt+3.33+ sites. In the first Pt+3.33+ site, Pt+3.33+ is bonded in a square co-planar geometry to four O2- atoms. There is two shorter (1.97 Å) and two longer (1.98 Å) Pt–O bond length. In the second Pt+3.33+ site, Pt+3.33+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing PtO6 octahedra. The corner-sharing octahedral tilt angles are 60°. There are a spread of Pt–O bond distances ranging from 2.03–2.09 Å. Ni2+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Ni–O bond distances ranging from 2.17–2.50 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Pt+3.33+ and two equivalent Ni2+ atoms to form ONi2Pt2 tetrahedra that share corners with ten ONi2Pt2 tetrahedra and edges with three ONiPt3 tetrahedra. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Pt+3.33+ and one Ni2+ atom. In the third O2- site, O2- is bonded to three Pt+3.33+ and one Ni2+ atom to form distorted ONiPt3 tetrahedra that share corners with eight ONiPt3 tetrahedra and edges with two equivalent ONi2Pt2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni(NF2)2 by Materials Project

NiF4N2 is (La,Ba)CuO4 structured and crystallizes in the tetragonal I4/mmm space group. The structure is two-dimensional and consists of four ammonia molecules and two NiF4 sheets oriented in the (0, 0, 1) direction. In each NiF4 sheet, Ni2+ is bonded to six F1- atoms to form corner-sharing NiF6 octahedra. The corner-sharing octahedral tilt angles are 0°. There is two shorter (1.83 Å) and four longer (1.90 Å) Ni–F bond length. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a linear geometry to two equivalent Ni2+ atoms. In the second F1- site, F1- is bonded in a single-bond geometry to one Ni2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Improved Creep and Tensile Properties of a Corrosion Resistant Ni-Based Superalloy Using High Temperature Aging and Nb/Ta Additions

Resistance to creep deformation is essential for cast and wrought Ni-based superalloys in next generation energy systems due to the considerable exposure times required at the operating temperature. Here the amount of precipitate strengthening was increased in variants to Inconel alloy 725 (IN725), a corrosion resistant alloy, to improve its elevated temperature mechanical strength. Additions of Nb or Ta coupled with a high temperature aging (HTA) heat treatment promoted the formation of γ" precipitates and grain boundary phases which led to significant increases in time to failure. The HTA increased the creep life of various alloy formulations as compared to the standard aging heat treatment with a maximum improvement of 371%. The Nb and Ta additions lowered the minimum creep rate (MCR) and had a similar effect on increasing creep life. The positive effect of the additions was more pronounced when coupled with the HTA which employed a higher temperature in the first step of the heat treatment to promote precipitate phase formation. The Ti/Al ratio was used to design alloys with preferential formation of ' or γ" precipitates. Compact morphology precipitates were formed in the alloys with a low Ti/Al ratio. While a low Ti/Al ratio was primarily associated with lower MCRs, the effect on the creep life was less evident than that of the HTA. By using additions of Nb or Ta and a HTA heat treatment, the creep life of IN725 for testing at 973 K (700 °C) and 483 MPa was improved by up to 256%.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A creep-resistant additively manufactured Al-Ce-Ni-Mn alloy

Existing additively manufactured aluminum alloys exhibit poor creep resistance due to coarsening of their strengthening phases and refined grain structures. In this paper, we report on a novel additively manufactured Al-10.5Ce-3.1Ni-1.2Mn wt.% alloy which displays excellent creep resistance relative to cast high-temperature aluminum alloys at 300–400 °C. In this work, the creep resistance of this alloy is attributed to a high volume fraction (~35%) of submicron intermetallic strengthening phases which are coarsening-resistant for hundreds of hours at 350 °C. The results herein demonstrate that additive manufacturing provides opportunities for development of creep-resistant aluminum alloys that may be used in bulk form in the 250–400 °C temperature range. Pathways for further development of such alloys are identified.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Multiscale investigation of thermomechanical and compositional developments in Ni alloy 718 under laser processing

Laser processing has been widely employed in various applications due to its exceptional spatial resolution. However, the rapid temperature gradients generated in localized areas present significant challenges for experimental characterization using conventional instruments. To characterize Ni alloy 718 during laser processing, we employed in-situ synchrotron X-ray diffraction with a high-speed detector, a method particularly well-suited for probing processes with high temporal and spatial resolution. Through a series of in-situ experiments, we investigated the local variations in the evolution of microstructures and thermomechanical behaviors within a keyhole mode melt pool. The in situ macroscopic thermomechanical behaviors were quantified using an empirical model derived from diffraction patterns, with experimental results showing reasonable agreement with finite element analysis. Various laser parameters were tested to assess their influences on the residual strains in the melt pools. The results revealed that the residual strain in the keyhole mode melt pool is relatively insensitive to variations in the parameters and is smaller than that in the melt pool created under conduction mode laser scanning. Additionally, we analyzed the shapes of individual diffraction spots, providing insights into the plastic behaviors and compositional developments in the resolidified alloy. The analysis confirmed that compositional variations in a dendritic microstructure manifest as asymmetric broadening of the diffraction spots.

Ni alloy 718↗
DOE OSTI2020

Multi-scale microstructural investigation of a laser 3D printed Ni-based superalloy

The heterogeneous microstructure of a laser 3D printed Ni-based superalloy was examined at multiple length scales. The sub-millimeter-sized columnar crystal grains are composed of micron-sized cellular colonies. The crystal grains grow in epitaxy with the substrate under the large temperature gradient and high cooling rate. The cell boundaries, decorated with γ/γ' eutectics, μ-phase precipitates and high density of dislocations, show enrichment of γ' forming elements and low-angle misorientations. Dislocations trapped in the intra-cellular regions are characterized as statistically stored dislocations with no detectable contribution to lattice curvature, and are the results of the interaction between dislocations and γ' precipitates.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Partial oxidation of isobutylene using Ni TiO x

In this work, we report an aerobic partical oxidation of isobutylene into isoprene, acetone, and p-xylene using a mesoporous Ni TiO x catalytic material. In this work, two catalysts were found to synthesize two of these three valuable products with high selectivity, with p-xylene being synthesized with a selectivity of 46.0% and isoprene being synthesized with a selectivity of 64.7%, with overall conversions of isobutylene being 34.0% and 11.9% respectively. These reactions were done at relatively low temperatures. (300°C or below) and are conducted at flow rates of 10 sccm oxygen and isobutylene. The nickel titania catalysts were studied extensively using various characterization methodologies such as TEM, Raman, XRD, and XRF.

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

Towards synthetic L 1 0 -FeNi: Detecting the absence of cubic symmetry in Laser-Ablated Fe-Ni nanoparticles

The L 1 0 crystal structure underlines an important class of chemically ordered alloys that exhibits uniaxial magnetocrystalline anisotropy. The near-equiatomic L 1 0 -FeNi extracted from meteorites has demonstrated intriguing magnetic properties for permanent magnet applications. However, the synthesis of this chemically ordered non-cubic structure has been a longstanding challenge. Here, in this work, we demonstrate the absence of cubic symmetry in near-equiatomic Fe-Ni nanoparticles synthesized by picosecond-pulsed laser ablation in liquids. The non-cubic phase detected in these particles can only be L 1 0 -FeNi or hexagonal close-packed (HCP) FeNi, and the absence of cubic symmetry was unequivocal. The orientation relationship between the non-cubic phase and the adjacent cubic phase was characterized by a series of transmission electron microscopy (TEM) techniques, which consistently suggests that the formation of the non-cubic phase involves a martensitic transformation process.

36 MATERIALS SCIENCE↗
DOE OSTI2023

High Temperature Oxidation Behavior of Ni-based High Entropy Superalloys

A new class of polycrystalline gamma-prime strengthened superalloys with alloy compositions of (wt%) Ni-20Co-13Cr-6Fe-4Al-3W-2Mo-(4-x)Nb-(x)Ti (x = 0,1,2) were subjected to cyclic oxidation exposures in dry air at 800 °C for 3600 h. The alloys were borderline chromia/alumina formers, showing good oxidation resistance relative to commercially available materials of similar composition. While all alloys formed alumina scales initially, only the alloy with the lowest Ti/Nb ratio retained an alumina scale for the duration of the exposure. Formation of a continuous layer of rutile TiO 2 at the alumina/alloy interface is proposed to cause eventual alumina failure for the alloys containing Ti.

36 MATERIALS SCIENCE↗