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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Sm4Fe27Co7C2 by Materials Project

Sm4Fe27Co7C2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are four inequivalent Sm sites. In the first Sm site, Sm is bonded in a distorted single-bond geometry to ten Fe, four Co, and one C atom. There are a spread of Sm–Fe bond distances ranging from 3.03–3.32 Å. There are a spread of Sm–Co bond distances ranging from 3.07–3.34 Å. The Sm–C bond length is 2.55 Å. In the second Sm site, Sm is bonded in a distorted single-bond geometry to eleven Fe, three Co, and one C atom. There are a spread of Sm–Fe bond distances ranging from 3.04–3.31 Å. There are one shorter (3.27 Å) and two longer (3.34 Å) Sm–Co bond lengths. The Sm–C bond length is 2.56 Å. In the third Sm site, Sm is bonded in a distorted single-bond geometry to eleven Fe, three Co, and one C atom. There are a spread of Sm–Fe bond distances ranging from 3.04–3.30 Å. There are one shorter (3.27 Å) and two longer (3.34 Å) Sm–Co bond lengths. The Sm–C bond length is 2.56 Å. In the fourth Sm site, Sm is bonded in a distorted single-bond geometry to eleven Fe, three Co, and one C atom. There are a spread of Sm–Fe bond distances ranging from 3.03–3.30 Å. There are one shorter (3.27 Å) and two longer (3.34 Å) Sm–Co bond lengths. The Sm–C bond length is 2.55 Å. There are seventeen inequivalent Fe sites. In the first Fe site, Fe is bonded in a single-bond geometry to five Fe, two equivalent Co, and one C atom. There are four shorter (2.55 Å) and one longer (2.67 Å) Fe–Fe bond lengths. Both Fe–Co bond lengths are 2.48 Å. The Fe–C bond length is 1.93 Å. In the second Fe site, Fe is bonded in a single-bond geometry to five Fe, two equivalent Co, and one C atom. There are four shorter (2.56 Å) and one longer (2.66 Å) Fe–Fe bond lengths. Both Fe–Co bond lengths are 2.47 Å. The Fe–C bond length is 1.92 Å. In the third Fe site, Fe is bonded to three Sm, seven Fe, and two Co atoms to form distorted FeSm3Fe7Co2 cuboctahedra that share corners with five CoSm2Fe10 cuboctahedra, corners with seven FeSm3Fe7Co2 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with three FeSm3Fe7Co2 cuboctahedra, edges with three CoSm2Fe10 cuboctahedra, faces with three CoSm2Fe10 cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, and a faceface with one CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 66–70°. There are a spread of Fe–Fe bond distances ranging from 2.54–2.67 Å. There are one shorter (2.47 Å) and one longer (2.48 Å) Fe–Co bond lengths. In the fourth Fe site, Fe is bonded to three Sm, seven Fe, and two Co atoms to form distorted FeSm3Fe7Co2 cuboctahedra that share corners with five CoSm2Fe10 cuboctahedra, corners with seven FeSm3Fe7Co2 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with three FeSm3Fe7Co2 cuboctahedra, edges with three CoSm2Fe10 cuboctahedra, faces with three CoSm2Fe9Co cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, and a faceface with one CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 66–70°. There are a spread of Fe–Fe bond distances ranging from 2.54–2.67 Å. Both Fe–Co bond lengths are 2.47 Å. In the fifth Fe site, Fe is bonded in a single-bond geometry to five Fe, two equivalent Co, and one C atom. There are two shorter (2.56 Å) and one longer (2.66 Å) Fe–Fe bond lengths. Both Fe–Co bond lengths are 2.48 Å. The Fe–C bond length is 1.92 Å. In the sixth Fe site, Fe is bonded in a single-bond geometry to four Fe, three Co, and one C atom. Both Fe–Fe bond lengths are 2.55 Å. There are two shorter (2.47 Å) and one longer (2.64 Å) Fe–Co bond lengths. The Fe–C bond length is 1.92 Å. In the seventh Fe site, Fe is bonded to three Sm, six Fe, and three Co atoms to form distorted FeSm3Fe6Co3 cuboctahedra that share corners with five CoSm2Fe10 cuboctahedra, corners with seven FeSm3Fe7Co2 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with three FeSm3Fe7Co2 cuboctahedra, edges with three CoSm2Fe9Co cuboctahedra, faces with three CoSm2Fe9Co cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, and a faceface with one CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 66–70°. There are a spread of Fe–Fe bond distances ranging from 2.53–2.67 Å. There are a spread of Fe–Co bond distances ranging from 2.46–2.63 Å. In the eighth Fe site, Fe is bonded to three Sm, seven Fe, and two Co atoms to form distorted FeSm3Fe7Co2 cuboctahedra that share corners with five CoSm2Fe10 cuboctahedra, corners with seven FeSm3Fe7Co2 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with three FeSm3Fe7Co2 cuboctahedra, edges with three CoSm2Fe10 cuboctahedra, faces with three CoSm2Fe10 cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, and a faceface with one CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 66–70°. There are a spread of Fe–Fe bond distances ranging from 2.54–2.67 Å. Both Fe–Co bond lengths are 2.47 Å. In the ninth Fe site, Fe is bonded in a single-bond geometry to six Fe, two equivalent Co, and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.47–2.74 Å. Both Fe–Co bond lengths are 2.44 Å. The Fe–C bond length is 1.85 Å. In the tenth Fe site, Fe is bonded in a single-bond geometry to five Fe, three Co, and one C atom. There are two shorter (2.47 Å) and one longer (2.73 Å) Fe–Fe bond lengths. There are two shorter (2.44 Å) and one longer (2.74 Å) Fe–Co bond lengths. The Fe–C bond length is 1.84 Å. In the eleventh Fe site, Fe is bonded in a 12-coordinate geometry to two Sm, eight Fe, and two Co atoms. There are a spread of Fe–Fe bond distances ranging from 2.48–2.75 Å. There are one shorter (2.43 Å) and one longer (2.44 Å) Fe–Co bond lengths. In the twelfth Fe site, Fe is bonded in a 12-coordinate geometry to two Sm, seven Fe, and three Co atoms. There are one shorter (2.49 Å) and one longer (2.73 Å) Fe–Fe bond lengths. There are a spread of Fe–Co bond distances ranging from 2.42–2.73 Å. In the thirteenth Fe site, Fe is bonded in a 12-coordinate geometry to two Sm, seven Fe, and three Co atoms. There are one shorter (2.50 Å) and one longer (2.73 Å) Fe–Fe bond lengths. There are a spread of Fe–Co bond distances ranging from 2.42–2.75 Å. In the fourteenth Fe site, Fe is bonded in a 12-coordinate geometry to two Sm, eight Fe, and two Co atoms. There are a spread of Fe–Fe bond distances ranging from 2.49–2.75 Å. There are one shorter (2.43 Å) and one longer (2.44 Å) Fe–Co bond lengths. In the fifteenth Fe site, Fe is bonded in a 5-coordinate geometry to one Sm, ten Fe, and three Co atoms. The Fe–Fe bond length is 2.36 Å. All Fe–Co bond lengths are 2.64 Å. In the sixteenth Fe site, Fe is bonded in a 5-coordinate geometry to one Sm, ten Fe, and three Co atoms. There are one shorter (2.64 Å) and two longer (2.65 Å) Fe–Co bond lengths. In the seventeenth Fe site, Fe is bonded in a 1-coordinate geometry to one Sm, nine Fe, and four Co atoms. There are a spread of Fe–Co bond distances ranging from 2.33–2.66 Å. There are five inequivalent Co sites. In the first Co site, Co is bonded to two Sm, nine Fe, and one Co atom to form distorted CoSm2Fe9Co cuboctahedra that share corners with four FeSm3Fe7Co2 cuboctahedra, corners with four CoSm2Fe10 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with four FeSm3Fe7Co2 cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, and faces with four CoSm2Fe9Co cuboctahedra. The corner-sharing octahedral tilt angles are 45°. The Co–Co bond length is 2.63 Å. In the second Co site, Co is bonded to two Sm and ten Fe atoms to form distorted CoSm2Fe10 cuboctahedra that share corners with four FeSm3Fe7Co2 cuboctahedra, corners with four CoSm2Fe10 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with four FeSm3Fe7Co2 cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, and faces with four CoSm2Fe9Co cuboctahedra. The corner-sharing octahedral tilt angles are 45°. In the third Co site, Co is bonded to two Sm and ten Fe atoms to form distorted CoSm2Fe10 cuboctahedra that share corners with four CoSm2Fe10 cuboctahedra, corners with eight FeSm3Fe7Co2 cuboctahedra, edges with four FeSm3Fe7Co2 cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, faces with four CoSm2Fe10 cuboctahedra, and faces with two equivalent CSm2Fe4 octahedra. In the fourth Co site, Co is bonded to two Sm, nine Fe, and one Co atom to form distorted CoSm2Fe9Co cuboctahedra that share corners with four CoSm2Fe9Co cuboctahedra, corners with eight FeSm3Fe7Co2 cuboctahedra, edges with four FeSm3Fe7Co2 cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, faces with four CoSm2Fe9Co cuboctahedra, and faces with two equivalent CSm2Fe4 octahedra. The Co–Co bond length is 2.65 Å. In the fifth Co site, Co is bonded in a 1-coordinate geometry to one Sm, ten Fe, and three Co atoms. There are two inequivalent C sites. In the first C site, C is bonded to two Sm and four Fe atoms to form CSm2Fe4 octahedra that share corners with two CoSm2Fe9Co cuboctahedra, corners with eight FeSm3Fe7Co2 cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, and faces with four equivalent CoSm2Fe10 cuboctahedra. In the second C site, C is bonded to two Sm and four Fe atoms to form CSm2Fe4 octahedra that share corners with two CoSm2Fe9Co cuboctahedra, corners with eight FeSm3Fe7Co2 cuboctahedra, faces with four FeSm3Fe6Co3 cuboctahedra, and faces with four equivalent CoSm2Fe9Co cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeCoSn by Materials Project

FeCoSn crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Fe is bonded in a 8-coordinate geometry to two equivalent Fe, six equivalent Co, and six equivalent Sn atoms. Both Fe–Fe bond lengths are 2.60 Å. All Fe–Co bond lengths are 2.80 Å. All Fe–Sn bond lengths are 2.80 Å. Co is bonded in a 5-coordinate geometry to six equivalent Fe and five equivalent Sn atoms. There are three shorter (2.48 Å) and two longer (2.60 Å) Co–Sn bond lengths. Sn is bonded in a 11-coordinate geometry to six equivalent Fe and five equivalent Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeCoGe by Materials Project

CoFeGe crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Fe is bonded in a 6-coordinate geometry to two equivalent Fe, six equivalent Co, and six equivalent Ge atoms. Both Fe–Fe bond lengths are 2.52 Å. All Fe–Co bond lengths are 2.67 Å. All Fe–Ge bond lengths are 2.67 Å. Co is bonded in a 5-coordinate geometry to six equivalent Fe and five equivalent Ge atoms. There are three shorter (2.35 Å) and two longer (2.52 Å) Co–Ge bond lengths. Ge is bonded in a 11-coordinate geometry to six equivalent Fe and five equivalent Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Editors’ Choice—Rapid Deactivation Convolutes Electrochemical CO 2 Reduction Selectivity Measurements on Gold Rotating Ring Disk Electrodes

Voltammetric measurements of electrochemical CO 2 reduction reaction (CO 2 RR) selectivity on rotating ring disk electrodes (RRDE) are a rapid and sensitive method for quantifying an electrocatalyst’s selectivity, i.e. faradaic efficiency (FE). This method has been applied to polycrystalline Au electrocatalysts where a Au disk electrode catalyzes both the CO 2 RR and hydrogen evolution reaction while the concentric Au ring electrode selectively senses CO by oxidizing CO back to CO 2 . Such measurements enabled fundamental mechanistic studies but suffer from poor inter-laboratory reproducibility. This work identifies causes of variability in RRDE selectivity measurements by comparing protocols with different electrochemical methods, reagent purities, and glassware cleaning procedures. We observed FE CO decrease by 56% during 5 min chronoamperometry measurements, a phenomenon that is not readily apparent in voltammetric scans due to their dynamic nature. Electroplating of electrolyte impurities onto the disk and ring surfaces were identified as a major contributor to Au deactivation. Additionally, the oxygen reduction reaction may lead to higher disk currents in inadequately purged electrolytes, causing an apparent underestimation of FE CO at low overpotentials. Lastly, we propose operational bounds for CO 2 RR selectivity measurements on Au using the RRDE method and provide suggestions on steps for improving the accuracy of this technique.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Evolution of Bonding and Magnetism via Changes in Valence Electron Count in CuFe 2– x Co x Ge 2

A series of solid solutions, CuFe 2–x Co x Ge 2 (x = 0, 0.2, 0.4, 0.8, and 1.0), have been synthesized by arc-melting and characterized by powder X-ray and neutron diffraction, magnetic measurements, Mössbauer spectroscopy, and electronic band structure calculations. All compounds crystallize in the CuFe 2 Ge 2 structure type, which can be considered as a three-dimensional framework built of fused MGe6 octahedra and MGe 5 trigonal bipyramids (M = Fe and Co), with channels filled by rows of Cu atoms. As the Co content (x) increases, the unit cell volume decreases in an anisotropic fashion: the b and c lattice parameters decrease while the a parameter increases. The changes in all the parameters are nearly linear, thus following Vegard’s law. CuFe 2 Ge 2 exhibits two successive antiferromagnetic (AFM) orderings, corresponding to the formation of a commensurate AFM structure, followed by an incommensurate AFM structure observed at lower temperatures. Additionally, as the Co content increases, the AFM ordering temperature (TN) gradually decreases, and only one AFM transition is observed for x ≥ 0.2. The magnetic behavior of unsubstituted CuFe 2 Ge 2 was found to be sensitive to the preparation method. The temperature-dependent zero-field 57 Fe Mössbauer spectra reveal two hyperfine split components that evolve in agreement with the two consecutive AFM orderings observed in magnetic measurements. In contrast, the field-dependent spectra obtained for fields ≥ 2 T reveal a parallel arrangement of the moments associated with the two crystallographically unique metal sites. Electronic band structure calculations and chemical bonding analysis reveal a mix of strong M–M antibonding and non-bonding states at the Fermi level, in support of the overall AFM ordering observed in zero field. The substitution of Co for Fe reduces the population of the M–M antibonding states and the overall density of states at the Fermi level, thus suppressing the T N value.

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

Mechanical and Corrosion Response of 316SS in Supercritical CO 2

The supercritical carbon dioxide (s-CO 2 ) Brayton cycle is currently being explored as a replacement for the steam Rankine cycle due to its potential for higher efficiency and lower cycle cost. 316 stainless steel is a candidate alloy for use in s-CO 2 up to roughly 600 °C, but the mechanical effects of prolonged exposure of base and welded material in s-CO 2 have not been analyzed. The potential for carburization makes this an important concern for the implementation of 316 and similar austenitic stainless steels in the s-CO 2 environment. In this study, welded and base material of two types of 316–316L and 316H–were exposed in either s-CO 2 or argon at 550 °C or 750 °C for 1000 h. 550 °C s-CO 2 exposure yielded a thin (< 1 µm) Cr oxide with occasional nodules of duplex Fe oxide and Fe–Cr spinel that were up to 5 microns thick. However, tensile results from s-CO –2 exposure matched those of 550 °C thermal aging in Ar, indicating that no mechanically detrimental carburization occurred in either 316 variant after 1000 h exposure. Conversely, 750 °C s-CO 2 exposure produced roughly 10 × the oxide thickness, with a more substantial Fe oxide (3–5 µm) on the majority of the surface and nodules of up to 40 µm thick. In comparison to aged samples, tensile testing of 750 °C CO 2 -exposed samples revealed ductility loss attributed to carburization. As a result, projections of 316L performance in s-CO 2 indicate that mechanically detrimental carburization—equal to that shown here for 750 °C, 1000 h—will likely be present after 7–14 years of service at 550 °C.

316 stainless steel↗
DOE OSTI2021

Corrosion behavior in aluminum/galvanized steel resistance spot welds and self-piercing riveting joints in salt spray environment

Here, this paper underlined the corrosion behavior of aluminum alloy/galvanized steel joints fabricated by resistance spot welding (RSW) and self-piercing riveting (SPR) exposed to different salt-spray cycles. It was found that the crevice generated by different joining methods has an important impact on corrosion behavior. Compared with the RSW joint, less corrosion happened on the coupled regions in SPR joints because of the higher local pH value resulted from the smaller crevice. The crevice, however, has less impact on the types of corrosion products. Galvanic corrosion happened in the coupled region for both RSW and SPR joints. The Pourbaix diagram explained the stable corrosion products of Al and Zn—Fe alloy, which are Al 2 O 3 , ZnO, and Fe 3 O 4 . Additional corrosion products observed from the experiment included α-Al(OH) 3 , Ca 4 Al 2 (CO 3 )(OH) 12 (H 2 O) 5 , Zn 5 (OH) 8 Cl 2 (H 2 O), Zn 5 (CO 3 ) 2 (OH) 6 , and Fe 2 (OH) 2 (CO 3 ), which can be understood by considering the metastable corrosion products, Pourbaix diagram, and possible chemical reactions.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Unraveling Site Selective Magnetic Properties of Cobalt Sites in Critical Elements Lean RE(TM)5 Magnet Materials

We report here our discovery of crystallographic and interstitial sites and onsite electron correlation propelled intrinsic and derived permanent magnetic properties of critical elements lean RE(TM) 5 (RE = La, Ce and TM = Fe, Co) magnet materials. A full potential linearized augmented plane wave (FP-LAPW) method within the local density approximation (LDA) is used to investigate and analyze the electronic structure and magnetism of these RE(TM) 5 type structures. To better correlate the experimental results, the effective Coulomb (U) and exchange (J) interactions (Hubbard parameters) are crucial at the transition metal sites. Results show that the main propeller of magnetic anisotropy in these compounds is the cobalt atoms at the 2c sites not the 3g sites. This site-specific property and site preference energetics are used to replace 3g sites with non-critical elements such as iron that exhibits a larger magnetic moment. Based on this strategic replacement, we predict two new compounds that have a larger hardness parameter with a relatively large energy product due to the atomic dilution caused by interstitial addition of nitrogen in the compounds: CeCo 2 Fe 3 N 2 and LaCo 2 Fe 3 N 2 .

Rare-earths↗
DOE OSTI2024

Methods of forming bilayer cathodes for electrochemical cells

Materials for electrochemical cells are provided. BaZr 0.4 Ce 0.4 M 0.2 O 3 compounds, where M represents one or more rare earth elements, are provided for use as electrolytes. PrBa 0.5 Sr 0.5 Co 2−x Fe x O 5+δ is provided for use as a cathode. Also provided are electrochemical cells, such as protonic ceramic fuel cells, incorporating the compounds as electrolytes and cathodes.

Haile, Sossina M.↗
DOE OSTI2024

Effect of pretreatment conditions on Fe-ZSM-5 properties and performance for Fischer–Tropsch synthesis

Iron supported on ZSM-5 is a widely studied catalyst for Fischer–Tropsch synthesis (FTS). Iron is activated with H 2 , CO, or a mixture of CO and H 2 prior to FTS, resulting in phase transformations that make it challenging to understand structure–property relationships. Furthermore, in this work, we demonstrate that increasing the pretreatment temperature of Fe–Na-ZSM-5 reduces CO conversion irrespective of the reductant, but the product selectivity, iron particle size, composition, CO adsorption properties, and zeolite structure is dependent on both the pretreatment temperature and reductant. Pretreatment of Fe–Na-ZSM-5 in H 2 induces sintering of iron particles, increasing C 2 –C 4 olefins and C 5+ hydrocarbons selectivity from 19.0% and 14.0% at 350 °C to 28.2% and 25.4% at 770 °C, respectively. Conversely, CO pretreatment facilitates carbide formation, coke deposition, and CH 4 formation.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Evolution of microstructure and strength of a high entropy alloy undergoing the strain-induced martensitic transformation

In a recent work, we have reported outstanding strength and work hardening exhibited by a metastable high entropy alloy (HEA), Fe 42 Mn 28 Co 10 Cr 15 Si 5 (in at. %), undergoing the strain-induced martensitic transformation from metastable gamma austenite (γ) to stable epsilon martensite (ε). However, the alloy exhibited poor ductility, which was attributed to the presence of the brittle sigma (σ) phase in its microstructure. The present work reports the evolution of microstructure, strength, and ductility of a similar HEA, Fe 38.5 Mn 20 Co 20 Cr 15 Si 5 Cu 1.5 (in at. %), designed to suppress the formation of σ phase. A cast and then rolled plate of the alloy was processed into four conditions by annealing for 10 and 30 min at 1100 °C and by friction stir processing (FSP) at tool rotation rates of 150 and 400 revolutions per minute (RPM) to facilitate detailed examinations of variable initial grain structures. Neutron diffraction and electron microscopy were employed to characterize the microstructure and texture evolution. The initial materials had variable grain size but nearly 100% γ structure. Diffusionless strain induced γ→ε phase transformation took place under compression with higher rate initially and slower rate at the later stages of deformation, independent on the initial grain size. The transformation facilitated part of plastic strain accommodation and rapid strain hardening owing to a transformation-induced dynamic Hall-Petch-type barrier effect, increase in dislocation density, and texture. Here, the peak strength of nearly 2 GPa was achieved under compression using the structure created by double pass FSP (150 RPM followed by 150 RPM). Remarkably, the tensile elongation exhibited by the alloy was nearly 20% with fracture surfaces featuring a combination of ductile dimples and cleavage.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li8FeCo9O20 by Materials Project

Li8FeCo9O20 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share a cornercorner with one FeO6 octahedra, corners with five CoO6 octahedra, an edgeedge with one FeO6 octahedra, edges with four LiO6 octahedra, and edges with five CoO6 octahedra. The corner-sharing octahedra tilt angles range from 5–12°. There are a spread of Li–O bond distances ranging from 2.06–2.20 Å. In the second Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with six CoO6 octahedra, an edgeedge with one FeO6 octahedra, edges with five LiO6 octahedra, and edges with five CoO6 octahedra. The corner-sharing octahedra tilt angles range from 6–12°. There are a spread of Li–O bond distances ranging from 2.07–2.20 Å. In the third Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share a cornercorner with one FeO6 octahedra, corners with five CoO6 octahedra, edges with five LiO6 octahedra, and edges with six CoO6 octahedra. The corner-sharing octahedra tilt angles range from 5–12°. There are a spread of Li–O bond distances ranging from 2.07–2.21 Å. In the fourth Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share a cornercorner with one FeO6 octahedra, corners with five CoO6 octahedra, edges with four LiO6 octahedra, and edges with six CoO6 octahedra. The corner-sharing octahedra tilt angles range from 6–11°. There are a spread of Li–O bond distances ranging from 2.06–2.18 Å. Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six LiO6 octahedra, edges with four LiO6 octahedra, and edges with six CoO6 octahedra. The corner-sharing octahedra tilt angles range from 5–11°. There are a spread of Fe–O bond distances ranging from 1.92–1.95 Å. There are five inequivalent Co+3.22+ sites. In the first Co+3.22+ site, Co+3.22+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with five LiO6 octahedra, edges with five LiO6 octahedra, and edges with six CoO6 octahedra. The corner-sharing octahedra tilt angles range from 6–11°. There are a spread of Co–O bond distances ranging from 1.90–1.95 Å. In the second Co+3.22+ site, Co+3.22+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with four LiO6 octahedra, edges with two equivalent FeO6 octahedra, edges with four CoO6 octahedra, and edges with five LiO6 octahedra. The corner-sharing octahedra tilt angles range from 7–12°. There are a spread of Co–O bond distances ranging from 1.89–1.95 Å. In the third Co+3.22+ site, Co+3.22+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with four LiO6 octahedra, edges with five LiO6 octahedra, and edges with six CoO6 octahedra. The corner-sharing octahedra tilt angles range from 5–12°. There are a spread of Co–O bond distances ranging from 1.89–1.94 Å. In the fourth Co+3.22+ site, Co+3.22+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with five LiO6 octahedra, an edgeedge with one FeO6 octahedra, edges with five LiO6 octahedra, and edges with five CoO6 octahedra. The corner-sharing octahedra tilt angles range from 6–12°. There are a spread of Co–O bond distances ranging from 1.90–1.96 Å. In the fifth Co+3.22+ site, Co+3.22+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six LiO6 octahedra, edges with four LiO6 octahedra, and edges with six CoO6 octahedra. The corner-sharing octahedra tilt angles range from 6–10°. There is two shorter (1.92 Å) and four longer (1.93 Å) Co–O bond length. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded to two Li1+ and three Co+3.22+ atoms to form OLi2Co3 square pyramids that share corners with two OLi3Co3 octahedra, corners with seven OLi2FeCo2 square pyramids, edges with six OLi3Co3 octahedra, and edges with two OLi2Co3 square pyramids. The corner-sharing octahedra tilt angles range from 2–4°. In the second O2- site, O2- is bonded to two Li1+, one Fe3+, and two equivalent Co+3.22+ atoms to form OLi2FeCo2 square pyramids that share corners with two OLi3Co3 octahedra, corners with seven OLi2Co3 square pyramids, edges with five OLi3Co3 octahedra, and edges with three OLi2FeCo2 square pyramids. The corner-sharing octahedra tilt angles range from 2–5°. In the third O2- site, O2- is bonded to three Li1+ and three Co+3.22+ atoms to form OLi3Co3 octahedra that share corners with two OLi3FeCo2 octahedra, corners with four OLi2Co3 square pyramids, edges with five OLi3Co3 octahedra, and edges with seven OLi2Co3 square pyramids. The corner-sharing octahedra tilt angles range from 1–4°. In the fourth O2- site, O2- is bonded to two Li1+, one Fe3+, and two Co+3.22+ atoms to form OLi2FeCo2 square pyramids that share corners with three OLi3Co3 octahedra, corners with six OLi2Co3 square pyramids, edges with four OLi3FeCo2 octahedra, and edges with four OLi2FeCo2 square pyramids. The corner-sharing octahedra tilt angles range from 1–5°. In the fifth O2- site, O2- is bonded to three Li1+, one Fe3+, and two Co+3.22+ atoms to form OLi3FeCo2 octahedra that share corners with three OLi3Co3 octahedra, corners with three OLi2FeCo2 square pyramids, edges with four OLi3Co3 octahedra, and edges with eight OLi2Co3 square pyramids. The corner-sharing octahedra tilt angles range from 0–4°. In the sixth O2- site, O2- is bonded to three Li1+ and three Co+3.22+ atoms to form OLi3Co3 octahedra that share corners with two OLi3FeCo2 octahedra, corners with four OLi2Co3 square pyramids, edges with five OLi3Co3 octahedra, and edges with seven OLi2FeCo2 square pyramids. The corner-sharing octahedra tilt angles range from 1–5°. In the seventh O2- site, O2- is bonded to two Li1+ and three Co+3.22+ atoms to form OLi2Co3 square pyramids that share corners with three OLi3FeCo2 octahedra, corners with six OLi2Co3 square pyramids, edges with four OLi3Co3 octahedra, and edges with four OLi2Co3 square pyramids. The corner-sharing octahedra tilt angles range from 1–3°. In the eighth O2- site, O2- is bonded to two Li1+ and three Co+3.22+ atoms to form OLi2Co3 square pyramids that share corners with two OLi3Co3 octahedra, corners with seven OLi2FeCo2 square pyramids, edges with six OLi3FeCo2 octahedra, and edges with two OLi2FeCo2 square pyramids. The corner-sharing octahedra tilt angles range from 2–5°. In the ninth O2- site, O2- is bonded to three Li1+ and three Co+3.22+ atoms to form OLi3Co3 octahedra that share corners with three OLi3Co3 octahedra, corners with three OLi2FeCo2 square pyramids, edges with four OLi3Co3 octahedra, and edges with eight OLi2Co3 square pyramids. The corner-sharing octahedra tilt angles range from 0–5°. In the tenth O2- site, O2- is bonded to two Li1+ and three Co+3.22+ atoms to form OLi2Co3 square pyramids that share corners with two OLi3Co3 octahedra, corners with seven OLi2Co3 square pyramids, edges with five OLi3Co3 octahedra, and edges with three OLi2Co3 square pyramids. The corner-sharing octahedra tilt angles range from 3–5°.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Observation of electron orbital signatures of single atoms within metal-phthalocyanines using atomic force microscopy

Resolving the electronic structure of a single atom within a molecule is of fundamental importance for understanding and predicting chemical and physical properties of functional molecules such as molecular catalysts. However, the observation of the orbital signature of an individual atom is challenging. We report here the direct identification of two adjacent transition-metal atoms, Fe and Co, within phthalocyanine molecules using high-resolution noncontact atomic force microscopy (HR-AFM). HR-AFM imaging reveals that the Co atom is brighter and presents four distinct lobes on the horizontal plane whereas the Fe atom displays a “square” morphology. Pico-force spectroscopy measurements show a larger repulsion force of about 5 pN on the tip exerted by Co in comparison to Fe. Our combined experimental and theoretical results demonstrate that both the distinguishable features in AFM images and the variation in the measured forces arise from Co’s higher electron orbital occupation above the molecular plane. The ability to directly observe orbital signatures using HR-AFM should provide a promising approach to characterizing the electronic structure of an individual atom in a molecular species and to understand mechanisms of certain chemical reactions.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Influence of Solidification Velocity on Partitioning and Precipitate Evolution in a Multicomponent, Soft Magnetic Alloy Processed by Laser Melting

Multicomponent alloys have recently been shown to overcome the structural-functional barrier associated with soft magnetic materials. Here, single laser tracks have been used to investigate the effects of solidification velocity on the Al 7 Fe 32.6 Co 27.7 Ni 27.7 Ta 5 (at pct) alloy. Ta-rich cell wall partitioning was shown to affect the final distribution and size of the precipitating L1 2 phase, after aging. These findings demonstrate that solidification rate control offers the potential to tailor localized performance in alloys with size-dependent precipitation properties.

Brookins, Jeffrey M. [Oak Ridge National Laborator↗
DOE OSTI2023

Cluster-Spin-Glass Magnetic Behavior and Morphology in the Coordination Polymer Alloys Fe y Co 1– y BTT

We report the synthesis of a series of pseudo-1D coordination polymer (CP) materials with the formula Fe y Co 1–y BTT (BTT = 1,3,5-benzenetrithiolate). These materials were structurally characterized by PXRD Rietveld, EXAFS, and PDF analyses, revealing that the CP superstructure enables a continuous and isomorphous alloy between the two homometallic compounds. Lower Fe loadings exhibit emergent spin glass magnetic behavior, such as memory effects and composition-dependent spin glass response time constants ranging from 6.9 × 10 –9 s to 1.8 × 10 –6 s. These data are consistent with the formation of spin clusters within the lattice. The magnetic behavior in these materials was modeled via replica exchange Monte Carlo simulation, which provides a good match for the experimentally measured spin glassing and magnetic phase transitions. Furthermore, these findings underscore how the rigid superstructure of CP and MOF scaffolds can enable the systematic tuning of physical properties, such as the spin glass behavior described here.

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

Materials Data on Sm2Fe5Co12C by Materials Project

Sm2Fe5Co12C crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Sm is bonded in a distorted single-bond geometry to four Fe, ten Co, and one C atom. There are a spread of Sm–Fe bond distances ranging from 3.07–3.33 Å. There are a spread of Sm–Co bond distances ranging from 2.99–3.28 Å. The Sm–C bond length is 2.54 Å. There are three inequivalent Fe sites. In the first Fe site, Fe is bonded in a 5-coordinate geometry to one Sm, four Fe, and nine Co atoms. There are a spread of Fe–Fe bond distances ranging from 2.35–2.62 Å. There are a spread of Fe–Co bond distances ranging from 2.62–2.69 Å. In the second Fe site, Fe is bonded to two equivalent Sm, two equivalent Fe, and eight Co atoms to form distorted FeSm2Fe2Co8 cuboctahedra that share corners with four equivalent FeSm2Fe2Co8 cuboctahedra, corners with four equivalent CoSm3Fe3Co6 cuboctahedra, corners with two equivalent CSm2Co4 octahedra, edges with four equivalent CoSm3Fe3Co6 cuboctahedra, faces with four equivalent FeSm2Fe2Co8 cuboctahedra, and faces with four equivalent CoSm3Fe3Co6 cuboctahedra. The corner-sharing octahedral tilt angles are 47°. There are four shorter (2.39 Å) and four longer (2.43 Å) Fe–Co bond lengths. In the third Fe site, Fe is bonded to two equivalent Sm, two equivalent Fe, and eight Co atoms to form distorted FeSm2Fe2Co8 cuboctahedra that share corners with four FeSm2Fe2Co8 cuboctahedra, corners with eight equivalent CoSm3Fe3Co6 cuboctahedra, edges with four equivalent CoSm3Fe3Co6 cuboctahedra, faces with four FeSm2Fe2Co8 cuboctahedra, faces with four equivalent CoSm3Fe3Co6 cuboctahedra, and faces with two equivalent CSm2Co4 octahedra. There are a spread of Fe–Co bond distances ranging from 2.39–2.47 Å. There are four inequivalent Co sites. In the first Co site, Co is bonded in a single-bond geometry to three Fe, four Co, and one C atom. All Co–Co bond lengths are 2.56 Å. The Co–C bond length is 1.84 Å. In the second Co site, Co is bonded to three equivalent Sm, three Fe, and six Co atoms to form distorted CoSm3Fe3Co6 cuboctahedra that share corners with five FeSm2Fe2Co8 cuboctahedra, corners with seven equivalent CoSm3Fe3Co6 cuboctahedra, corners with two equivalent CSm2Co4 octahedra, edges with three FeSm2Fe2Co8 cuboctahedra, edges with three equivalent CoSm3Fe3Co6 cuboctahedra, faces with three FeSm2Fe2Co8 cuboctahedra, faces with four equivalent CoSm3Fe3Co6 cuboctahedra, and a faceface with one CSm2Co4 octahedra. The corner-sharing octahedra tilt angles range from 65–71°. There are a spread of Co–Co bond distances ranging from 2.49–2.66 Å. In the third Co site, Co is bonded in a single-bond geometry to four Fe, four Co, and one C atom. Both Co–Co bond lengths are 2.41 Å. The Co–C bond length is 1.86 Å. In the fourth Co site, Co is bonded in a 12-coordinate geometry to two equivalent Sm, four Fe, and six Co atoms. The Co–Co bond length is 2.41 Å. C is bonded to two equivalent Sm and four Co atoms to form CSm2Co4 octahedra that share corners with two equivalent FeSm2Fe2Co8 cuboctahedra, corners with eight equivalent CoSm3Fe3Co6 cuboctahedra, faces with four equivalent FeSm2Fe2Co8 cuboctahedra, and faces with four equivalent CoSm3Fe3Co6 cuboctahedra.

36 MATERIALS SCIENCE↗
NASA NTRS2009

Late Reduction Textures in Almahata Sitta Ureilite

The Almahata Sitta ureilite, derived from asteroid 2008 TC3, consists of many individual fragments recovered from the Nubian dessert strewn field [1]. Like most ureilites, it contains abundant carbon and exhibits examples of disequilibrium textures that record a late reduction event accompanied by rapid cooling (tens of degC/h) from high temperatures (1150-1300 C). Variations in Fe/Mg of silicate minerals are accompanied by variations in Fe/Mn, indicating loss of Fe into metal [2]. In coarser-grained fragments of Almahata Sitta, olivine exhibits irregular high mg# rims in contact with networks of interstitial metal 5- 20 microns in typical thickness. This is a common ureilite texture thought to be driven by the reaction of graphite to a CO gas phase and the concurrent reduction of FeO in olivine to Fe metal, with excess silica going primarily into pyroxene (2MgFeSiO4 + C approaches MgSiO4 + MgSiO3 + 2Fe + CO) [3, see also 4,5,6]. Other fragments of Almahata Sitta exhibit anomalous textures such as fine grain size, high porosity, and abundant graphite. Within these fragments pyroxene locally exhibits high-mg# rims in contact with metal and a discreet silica phase, suggesting that the reduction mechanism MgFeSi2O6 + C approaches MgSiO3 + Fe + SiO2 + CO. Metals in Almahata Sitta are particularly unaltered in comparison to ureilite finds. Variations in minor and trace element composition of this metal might partly result from localized dilution as iron is supplied by reduction of silicates.

Herrin, J. S.↗