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All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

The effects of Cr, Co, Al, Mo and Ta on the cyclic oxidation behavior of a prototype cast Ni-base superalloy based on a 2(5) composite statistically designed experiment

A series of cast Ni-base superalloys were systematically varied at selected levels of Co, Cr, Mo, Ta, and Al. The elemental levels varied were Mo, 0 to 4 percent; Cr, 6 to 18 percent; Co, 0 to 20 percent, Ta, 0 to 8 percent; and Al, 3.25 to 6.25 percent. The cyclic oxidation resistance was determined from specific weight change data as a function of time for 1 hr cycles in static air at 1100 C. The significant terms in decreasing order of their importance were Al, Ta, Cr2, Al-Cr, Cr-Co, Co2, Al-Mo, Cr-Mo, Al-Al, and Mo-Ta. The Al term alone accounted for close to 82 percent of the explained variability. The estimating equation showed that the Al level was the most important and should be at its 6.25 wt % maximum value. The Mo and Ta levels should also be at their maximum 4 and 8 wt % respectively. The cobalt composition should be as low as possible, i.e., 0 wt%. The Cr level optimum varies depending on the other 4 levels. The X-ray diffaction results indicate the most protective scales are alumina/aluminate spinel stabilizized with a tri-rutile oxide high in Ta and Mo.

Barrett, C. A.↗
NASA NTRS1985

Orientation and temperature dependence of some mechanical properties of the single-crystal nickel-base superalloy Rene N4. 3: Tension-compression anisotropy

Single crystal superalloy specimens with various crystallographic directions along their axes were tested in compression at room temperature, 650, 760, 870, and 980 deg C. These results are compared with the tensile behavior studied previously. The alloy, Rene N4, was developed for gas turbine engine blades and has the nominal composition 3.7 Al, 4.2 Ti, 4 Ta, 0.5 Nb, 6 W, 1.5 Mo 9 Cr. 7.5 Co, balance Ni, in weight percent. Slip trace analysis showed that primary cube slip occurred even at room temperature for the 111 specimens. With increasing test temperature more orientations exhibited primary cube slip, until at 870 deg C only the 100 and 011 specimens exhibited normal octahedral slip. The yield strength for octahedral slip was numerically analysed using a model proposed by Lall, Chin, and Pope to explain deviations from Schmid's Law in the yielding behavior of a single phase Gamma prime alloy, Ni3(Al, Nb). The Schmid's Law deviations in Rene N4 were found to be largely due to a tension-compression anisotropy. A second effect, which increases trength for orientations away from 001, was found to be small in Rene N4. Analysis of recently published data on the single crystal superalloy PWA 1480 yielded the same result.

Miner, R. V.↗
NASA NTRS1986

Orientation and temperature dependence of some mechanical properties of the single-crystal nickel-base superalloy Rene N4. I - Tensile behavior

Single crystal specimens of a nickel-base superalloy with axes near 001, 011, and -112 were tested in tension at room temperature, 760, and 980 C. The alloy Rene N-4, was developed for gas turbine engine blades and has the nominal composition 3.7 Al, 4.2 Ti, 4 Ta, 0.5 Nb, 6 W, 1.5 Mo, 9 Cr, 7.5 Co, balance Ni, (all in weight percent). Analysis of slip band traces, specimen axis rotation, and dislocation Burgers vectors showed that at 760 and 980 C primary cube slip supplanted normal octahedral slip for the -112 line-oriented specimens. The other two orientations, which have lower resolved shear stresses on the cube system, exhibited octahedral slip at all three temperatures. The critical resolved shear stress is considerably greater on the cube system than on the octahedral system at room temperature. However, at 760 and 980 C the critical resolved shear stresses on the two systems are about the same. While the room temperature and 980 C yield strengths for the two orientations exhibiting octahedral slip could be rationalized on the basis of resolved shear stress, those at 760 C could not. Such violations of Schmid's law have previously been observed in other superalloys and single phase gamma-prime.

Miner, R. V.↗
DOE OSTI2024

K–Co–Mo–S x chalcogel: high-capacity removal of Pb 2+ and Ag + and the underlying mechanisms

Chalcogenide-based aerogels, known as chalcogels, represent a novel class of nanoparticle-based porous amorphous materials characterized by high surface polarizability and Lewis base properties, exhibiting promising applications in clean energy and separation science. This work presents a K–Co–Mo–S x (KCMS) chalcogel as a highly efficient sorbent for heavy metal ions and details its sorption mechanisms. Its incoherent structure comprises Mo 2 V (S 2 ) 6 and Mo 3 IV S(S 6 ) 2 anion-like clusters with four- and six-coordinated Co–S polyhedra, forming a Co–Mo–S covalent network that hosts K + ions through electrostatic attraction. The interactions of KCMS with heavy metal ions, particularly Pb 2+ and Ag + , reveal that KCMS is exceptionally effective in removing these ions from ppm concentrations down to trace levels (≤5 ppb). KCMS rapidly removes Ag + (≈81.7%) and Pb 2+ (≈99.5%) within five minutes, achieving >99.9% removal within an hour, with a distribution constant K d ≥10 8 mL g -1 . KCMS exhibits an impressive removal capacity of 1378 mg g -1 for Ag + and 1146 mg g -1 for Pb 2+ , establishing it as one of the most effective materials known to date for heavy metal removal. This material is also effective for the removal of Ag + and Pb 2+ along with Hg 2+ , Ni 2+ , Cu 2+ , and Cd 2+ from various water sources even in the presence of highly concentrated and chemically diverse cations, anions, and organic species. Analysis of the post-interacted KCMS by synchrotron X-ray pair distribution function (PDF), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS) revealed that the sorption of Pb 2+ , Ag + , and Hg 2+ mainly occurs by the exchange of K + and Co 2+ . Despite being amorphous, this material exhibits unprecedented ion-exchange mechanisms both for the ionically and covalently bound K + and Co 2+ , respectively. In conclusion, this discovery advances our knowledge of amorphous gels and guides material synthesis principles for the highly selective and efficient removal of heavy metal ions from water.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Materials Data on GaCo(Mo3O20)2 by Materials Project

Co(MoO4)6GaO12(O2)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two oxygen molecules, one Co(MoO4)6 cluster, and one GaO12 cluster. In the Co(MoO4)6 cluster, there are three inequivalent Mo sites. In the first Mo site, Mo is bonded in a 4-coordinate geometry to six O atoms. There are a spread of Mo–O bond distances ranging from 1.73–2.68 Å. In the second Mo site, Mo is bonded in a 4-coordinate geometry to six O atoms. There are a spread of Mo–O bond distances ranging from 1.72–2.50 Å. In the third Mo site, Mo is bonded in a 4-coordinate geometry to six O atoms. There are a spread of Mo–O bond distances ranging from 1.72–2.54 Å. Co is bonded in an octahedral geometry to six O atoms. There are a spread of Co–O bond distances ranging from 1.77–1.91 Å. There are twelve inequivalent O sites. In the first O site, O is bonded in a distorted trigonal non-coplanar geometry to two Mo and one Co atom. In the second O site, O is bonded in a bent 120 degrees geometry to two Mo atoms. In the third O site, O is bonded in a single-bond geometry to one Mo atom. In the fourth O site, O is bonded in a single-bond geometry to one Mo atom. In the fifth O site, O is bonded in a distorted single-bond geometry to two Mo and one Co atom. In the sixth O site, O is bonded in a bent 120 degrees geometry to two Mo atoms. In the seventh O site, O is bonded in a single-bond geometry to one Mo atom. In the eighth O site, O is bonded in a single-bond geometry to one Mo atom. In the ninth O site, O is bonded in a distorted single-bond geometry to two Mo and one Co atom. In the tenth O site, O is bonded in a bent 120 degrees geometry to two Mo atoms. In the eleventh O site, O is bonded in a single-bond geometry to one Mo atom. In the twelfth O site, O is bonded in a single-bond geometry to one Mo atom. In the GaO12 cluster, Ga is bonded in a distorted linear geometry to six O atoms. There are two shorter (1.73 Å) and four longer (2.55 Å) Ga–O bond lengths. There are six inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to one Ga and one O atom. The O–O bond length is 1.31 Å. In the second O site, O is bonded in a bent 120 degrees geometry to one Ga and one O atom. The O–O bond length is 1.23 Å. In the third O site, O is bonded in a single-bond geometry to one Ga atom. In the fourth O site, O is bonded in a single-bond geometry to one O atom. The O–O bond length is 1.27 Å. In the fifth O site, O is bonded in a single-bond geometry to one O atom. In the sixth O site, O is bonded in a bent 120 degrees geometry to two O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hf9CoMo4 by Materials Project

Hf9Mo4Co crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Hf sites. In the first Hf site, Hf is bonded in a 1-coordinate geometry to four Mo and one Co atom. There are a spread of Hf–Mo bond distances ranging from 2.92–3.09 Å. The Hf–Co bond length is 2.56 Å. In the second Hf site, Hf is bonded in a 2-coordinate geometry to two equivalent Mo atoms. Both Hf–Mo bond lengths are 2.89 Å. There are two inequivalent Mo sites. In the first Mo site, Mo is bonded to six equivalent Hf and six equivalent Mo atoms to form face-sharing MoHf6Mo6 cuboctahedra. All Mo–Mo bond lengths are 2.69 Å. In the second Mo site, Mo is bonded in a 12-coordinate geometry to eight Hf and four Mo atoms. Both Mo–Mo bond lengths are 2.91 Å. Co is bonded in a 6-coordinate geometry to six equivalent Hf atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

How the Bioinspired Fe 2 Mo 6 S 8 Chevrel Breaks Electrocatalytic Nitrogen Reduction Scaling Relations

The nitrogen reduction reaction (NRR) is a renewable alternative to the energy- and CO 2 -intensive Haber–Bosch NH 3 synthesis process but is severely limited by the low activity and selectivity of studied electrocatalysts. The Chevrel phase Fe 2 Mo 6 S 8 has a surface Fe–S–Mo coordination environment that mimics the nitrogenase FeMo-cofactor and was recently shown to provide state-of-the-art activity and selectivity for NRR. Here, we elucidate the previously unknown NRR mechanism on Fe 2 Mo 6 S 8 via grand-canonical density functional theory (GC-DFT) that realistically models solvated and biased surfaces. Fe sites of Fe 2 Mo 6 S 8 selectively stabilize the key *NNH intermediate via a narrow band of free-atom-like surface d-states that selectively hybridize with p-states of *NNH, which results in Fe sites breaking NRR scaling relationships. These sharp d-states arise from an Fe–S bond dissociation during N 2 adsorption that mimics the mechanism of the nitrogenase FeMo-cofactor. Furthermore, we developed a new GC-DFT-based approach for calculating transition states as a function of bias (GC-NEB) and applied it to produce a microkinetic model for NRR at Fe 2 Mo 6 S 8 that predicts high activity and selectivity, in close agreement with experiments. Furthermore, our results suggest new design principles that may identify effective NRR electrocatalysts that minimize the barriers for *N 2 protonation and *NH 3 desorption and that may be broadly applied to the rational discovery of stable, multinary electrocatalysts for other reactions where narrow bands of surface d-states can be tuned to selectively stabilize key reaction intermediates and guide selectivity toward a target product. Furthermore, our results highlight the importance of using GC-DFT and GC-NEB to accurately model electrocatalytic reactions.

10 SYNTHETIC FUELS↗
DOE OSTI2020

Materials Data on CoMo4N5 by Materials Project

Mo4CoN5 is Tungsten Carbide-derived structured and crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are four inequivalent Mo+3.25+ sites. In the first Mo+3.25+ site, Mo+3.25+ is bonded to six N3- atoms to form a mixture of distorted corner, edge, and face-sharing MoN6 pentagonal pyramids. There are two shorter (2.13 Å) and four longer (2.18 Å) Mo–N bond lengths. In the second Mo+3.25+ site, Mo+3.25+ is bonded to six N3- atoms to form a mixture of distorted corner, edge, and face-sharing MoN6 pentagonal pyramids. There are four shorter (2.18 Å) and two longer (2.19 Å) Mo–N bond lengths. In the third Mo+3.25+ site, Mo+3.25+ is bonded to six N3- atoms to form a mixture of distorted corner, edge, and face-sharing MoN6 pentagonal pyramids. There are four shorter (2.16 Å) and two longer (2.19 Å) Mo–N bond lengths. In the fourth Mo+3.25+ site, Mo+3.25+ is bonded to six N3- atoms to form a mixture of distorted corner, edge, and face-sharing MoN6 pentagonal pyramids. There are four shorter (2.16 Å) and two longer (2.17 Å) Mo–N bond lengths. Co2+ is bonded in a 6-coordinate geometry to six N3- atoms. There are four shorter (2.07 Å) and two longer (2.36 Å) Co–N bond lengths. There are five inequivalent N3- sites. In the first N3- site, N3- is bonded in a 6-coordinate geometry to two equivalent Mo+3.25+ and four equivalent Co2+ atoms. In the second N3- site, N3- is bonded to six Mo+3.25+ atoms to form a mixture of distorted corner, edge, and face-sharing NMo6 pentagonal pyramids. In the third N3- site, N3- is bonded to six Mo+3.25+ atoms to form a mixture of distorted corner, edge, and face-sharing NMo6 pentagonal pyramids. In the fourth N3- site, N3- is bonded to six Mo+3.25+ atoms to form a mixture of distorted corner, edge, and face-sharing NMo6 pentagonal pyramids. In the fifth N3- site, N3- is bonded in a 6-coordinate geometry to four equivalent Mo+3.25+ and two equivalent Co2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr16Fe6Co2Mo8O45 by Materials Project

Sr16Mo8Fe6Co2O45 is Orthorhombic Perovskite-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are sixteen inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form distorted SrO12 cuboctahedra that share corners with eight SrO12 cuboctahedra, faces with five SrO12 cuboctahedra, faces with two equivalent CoO6 octahedra, faces with four MoO6 octahedra, and faces with two equivalent FeO5 square pyramids. There are a spread of Sr–O bond distances ranging from 2.64–3.15 Å. In the second Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form distorted SrO12 cuboctahedra that share corners with eight SrO12 cuboctahedra, faces with five SrO12 cuboctahedra, faces with four MoO6 octahedra, and faces with four CoO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.57–3.13 Å. In the third Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form distorted SrO12 cuboctahedra that share corners with eight SrO12 cuboctahedra, faces with five SrO12 cuboctahedra, faces with two equivalent CoO6 octahedra, faces with four MoO6 octahedra, and faces with two equivalent FeO5 square pyramids. There are a spread of Sr–O bond distances ranging from 2.65–3.17 Å. In the fourth Sr2+ site, Sr2+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of Sr–O bond distances ranging from 2.57–3.24 Å. In the fifth Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form distorted SrO12 cuboctahedra that share corners with eight SrO12 cuboctahedra, faces with five SrO12 cuboctahedra, faces with four MoO6 octahedra, and faces with four CoO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.58–3.14 Å. In the sixth Sr2+ site, Sr2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sr–O bond distances ranging from 2.55–3.02 Å. In the seventh Sr2+ site, Sr2+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of Sr–O bond distances ranging from 2.56–3.19 Å. In the eighth Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form distorted SrO12 cuboctahedra that share corners with four equivalent SrO12 cuboctahedra, faces with two equivalent MoO6 octahedra, faces with two equivalent FeO6 octahedra, faces with two equivalent FeO5 square pyramids, and faces with two equivalent MoO5 trigonal bipyramids. There are a spread of Sr–O bond distances ranging from 2.63–3.17 Å. In the ninth Sr2+ site, Sr2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sr–O bond distances ranging from 2.54–2.99 Å. In the tenth Sr2+ site, Sr2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sr–O bond distances ranging from 2.59–3.02 Å. In the eleventh Sr2+ site, Sr2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sr–O bond distances ranging from 2.66–3.08 Å. In the twelfth Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form distorted SrO12 cuboctahedra that share corners with four equivalent SrO12 cuboctahedra, faces with two equivalent MoO6 octahedra, faces with two equivalent FeO6 octahedra, faces with two equivalent FeO5 square pyramids, and faces with two equivalent MoO5 trigonal bipyramids. There are a spread of Sr–O bond distances ranging from 2.63–3.18 Å. In the thirteenth Sr2+ site, Sr2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sr–O bond distances ranging from 2.49–3.08 Å. In the fourteenth Sr2+ site, Sr2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sr–O bond distances ranging from 2.61–3.01 Å. In the fifteenth Sr2+ site, Sr2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sr–O bond distances ranging from 2.65–3.04 Å. In the sixteenth Sr2+ site, Sr2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Sr–O bond distances ranging from 2.52–3.08 Å. There are eight inequivalent Mo+4.50+ sites. In the first Mo+4.50+ site, Mo+4.50+ is bonded to six O2- atoms to form MoO6 octahedra that share a cornercorner with one FeO6 octahedra, a cornercorner with one CoO6 octahedra, corners with four equivalent FeO5 square pyramids, and faces with four SrO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mo–O bond distances ranging from 1.87–2.06 Å. In the second Mo+4.50+ site, Mo+4.50+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with five CoO6 octahedra, a cornercorner with one FeO5 square pyramid, and faces with eight SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–17°. There are a spread of Mo–O bond distances ranging from 1.89–1.99 Å. In the third Mo+4.50+ site, Mo+4.50+ is bonded to six O2- atoms to form MoO6 octahedra that share a cornercorner with one FeO6 octahedra, corners with five CoO6 octahedra, and faces with four SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–18°. There are a spread of Mo–O bond distances ranging from 1.93–1.97 Å. In the fourth Mo+4.50+ site, Mo+4.50+ is bonded to five O2- atoms to form MoO5 square pyramids that share a cornercorner with one CoO6 octahedra and corners with four equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 0–21°. There are a spread of Mo–O bond distances ranging from 1.89–2.03 Å. In the fifth Mo+4.50+ site, Mo+4.50+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with two FeO6 octahedra, corners with four equivalent FeO5 square pyramids, and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedral tilt angles are 1°. There are a spread of Mo–O bond distances ranging from 1.86–2.09 Å. In the sixth Mo+4.50+ site, Mo+4.50+ is bonded to five O2- atoms to form MoO5 trigonal bipyramids that share corners with four equivalent FeO6 octahedra, a cornercorner with one FeO5 square pyramid, and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 16–26°. There are a spread of Mo–O bond distances ranging from 1.89–2.01 Å. In the seventh Mo+4.50+ site, Mo+4.50+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with two FeO6 octahedra, corners with four equivalent FeO5 square pyramids, and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–1°. There are a spread of Mo–O bond distances ranging from 1.89–2.06 Å. In the eighth Mo+4.50+ site, Mo+4.50+ is bonded to five O2- atoms to form MoO5 trigonal bipyramids that share corners with four equivalent FeO6 octahedra, a cornercorner with one FeO5 square pyramid, and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 16–24°. There is three shorter (1.89 Å) and two longer (2.03 Å) Mo–O bond length. There are six inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two MoO6 octahedra and corners with four equivalent MoO5 square pyramids. The corner-sharing octahedral tilt angles are 1°. There are a spread of Fe–O bond distances ranging from 2.04–2.22 Å. In the second Fe3+ site, Fe3+ is bonded to five O2- atoms to form FeO5 square pyramids that share corners with four equivalent MoO6 octahedra, a cornercorner with one MoO5 trigonal bipyramid, and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 15–17°. There are a spread of Fe–O bond distances ranging from 1.99–2.09 Å. In the third Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two MoO6 octahedra, corners with four equivalent MoO5 trigonal bipyramids, and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–1°. There are a spread of Fe–O bond distances ranging from 2.06–2.22 Å. In the fourth Fe3+ site, Fe3+ is bonded to five O2- atoms to form FeO5 square pyramids that share corners with five MoO6 octahedra and faces with four SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 1–15°. There are a spread of Fe–O bond distances ranging from 2.00–2.17 Å. In the fifth Fe3+ site, Fe3+ is bonded to five O2- atoms to form FeO5 square pyramids that share corners with four equivalent MoO6 octahedra, a cornercorner with one MoO5 trigonal bipyramid, and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 15–16°. There are a spread of Fe–O bond distances ranging from 2.00–2.14 Å. In the sixth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two MoO6 octahedra, corners with four equivalent MoO5 trigonal bipyramids, and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–1°. There are a spread of Fe–O bond distances ranging from 2.05–2.22 Å. There are two inequivalent Co2+ sites. In the first Co2+ site, Co2+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six MoO6 octahedra and faces with eight SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–17°. There are a spread of Co–O bond distances ranging from 2.06–2.13 Å. In the second Co2+ site, Co2+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with five MoO6 octahedra, a cornercorner with one MoO5 square pyramid, and faces with four SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–18°. There are a spread of Co–O bond distances ranging from 1.97–2.15 Å. There are forty-five inequivalent O2- sites. In the first O2- site, O2- is bonded to four Sr2+, one Mo+4.50+, and one Co2+ atom to form distorted corner-sharing OSr4CoMo octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the second O2- site, O2- is bonded in a 4-coordinate geometry to four Sr2+, one Mo+4.50+, and one Co2+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to four Sr2+, one Mo+4.50+, and one Co2+ atom. In the fourth O2- site, O2- is bonded in a distorted linear geometry to four Sr2+, one Mo+4.50+, and one Co2+ atom. In the fifth O2- site, O2- is bonded in a distorted linear geometry to four Sr2+, one Mo+4.50+, and one Fe3+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to four Sr2+, one Mo+4.50+, and one Co2+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to four Sr2+, one Mo+4.50+, and one Co2+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to four Sr2+, one Mo+4.50+, and one Co2+ atom. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to four Sr2+, one Mo+4.50+, and one Co2+ atom. In the tenth O2- site, O2- is bonded in a distorted linear geometry to four Sr2+, one Mo+4.50+, and one Fe3+ atom. In the eleventh O2- site, O2- is bonded in a distorted linear geometry to four Sr2+, one Mo+4.50+, and one Co2+ atom. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to four Sr2+, one Mo+4.50+, and one Co2+ atom. In the thirteenth O2- site, O2- is bonded in a 4-coordinate geometry to four Sr2+, one Mo+4.50+, and one Fe3+ atom. In the fourteenth O2- site, O2- is bonded in a 4-coordinate geometry to four Sr2+, one Mo+4.50+, and one Co2+ atom. In the fifteenth O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+, one Mo+4.50+, and one Fe3+ atom. In the sixteenth O2- site, O2- is bonded in a distorted linear geometry to four Sr2+, one Mo+4.50+, and one Co2+ atom. In the seventeenth O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+, one Mo+4.50+, and one Fe3+ atom. In the eighteenth O2- site, O2- is bonded in a 6-coordinate geometry to four Sr2+, one Mo+4.50+, and one Fe3+ atom. In the nineteenth O2- site, O2- is bonded in a 6-coordinate geometry to four Sr2+, one Mo+4.50+, and one Fe3+ atom. In the twentieth O2- site, O2- is bonded in a 6-coordinate geometry

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba2CoMoO6 by Materials Project

Ba2CoMoO6 is (Cubic) Perovskite-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with twelve equivalent BaO12 cuboctahedra, faces with six equivalent BaO12 cuboctahedra, faces with four equivalent MoO6 octahedra, and faces with four equivalent CoO6 octahedra. There are four shorter (2.87 Å) and eight longer (2.92 Å) Ba–O bond lengths. Mo6+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with six equivalent CoO6 octahedra and faces with eight equivalent BaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Mo–O bond lengths are 1.96 Å. Co2+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six equivalent MoO6 octahedra and faces with eight equivalent BaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.09 Å) and two longer (2.26 Å) Co–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Mo6+, and one Co2+ atom. In the second O2- site, O2- is bonded to four equivalent Ba2+, one Mo6+, and one Co2+ atom to form a mixture of distorted edge and corner-sharing OBa4CoMo octahedra. The corner-sharing octahedra tilt angles range from 0–6°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co3Te(MoO7)6 by Materials Project

(CoO6)3Te(MoO4)6 is T-50 Boron-derived structured and crystallizes in the trigonal R-3c space group. The structure is zero-dimensional and consists of eighteen cobalt;hexahydrate molecules and six Te(MoO4)6 clusters. In each Te(MoO4)6 cluster, Mo is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Mo–O bond distances ranging from 1.74–2.36 Å. Te is bonded in an octahedral geometry to six equivalent O atoms. All Te–O bond lengths are 1.95 Å. There are four inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one Mo atom. In the second O site, O is bonded in a bent 120 degrees geometry to two equivalent Mo atoms. In the third O site, O is bonded in a single-bond geometry to one Mo atom. In the fourth O site, O is bonded in a distorted trigonal non-coplanar geometry to two equivalent Mo and one Te atom.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Anomalous lattice expansion of bcc Ta in helium-loaded diamond anvil cells

Anomalous lattice expansion of bcc Ta is observed in helium-loaded diamond anvil cell (DAC) experiments near 6 GPa and above 400 K, while co-loaded W, Mo, and Au exhibit normal thermal expansion. The Ta volume expansion increases with temperature, reaching ~14% near 650 K before plateauing, and is largely retained after recovery to ambient conditions. Time-resolved measurements at 500 K reveal progressive expansion over several hours, consistent with gradual, thermally activated He incorporation. The largely retained expansion during subsequent cooling and holding at 400 K indicates that the incorporated He is predominantly kinetically trapped. The data reveal two distinct regimes: below ~550 K, modest and spatially uniform expansion consistent with interstitial He trapping at isolated, randomly distributed vacancies; above ~550 K, He-vacancy cluster growth producing dramatically larger expansion, peak broadening, and a core–shell microstructure revealed by micron-resolution X-ray diffraction mapping. These results demonstrate that He is not always a passive pressure medium in DAC experiments and reveal a previously unrecognized regime of He-mediated lattice modification in Ta, complementing conventional ion-implantation studies relevant to nuclear and fusion structural materials.

Diamond anvil cell↗
DOE OSTI2025

Stepwise impregnation of bimetallic catalysts for carbon nanotube synthesis

Supported bimetallic catalysts are widely used for carbon nanotube (CNT) synthesis, yet the effects of impregnation procedure remain underexplored. Here, we investigated how the sequence of metal impregnation affects CNT synthesis. We prepared cobalt-molybdenum (Co-Mo) bimetallic catalysts on alumina supports via co- and stepwise impregnation, then compared their CNT synthesis performance under identical conditions. Stepwise-impregnated catalysts exhibited higher carbon yields than those prepared by co-impregnation. Notably, impregnating Mo after Co achieved the highest yield despite the lowest BET surface area. Synchrotron X-ray diffraction and visible/UV-Raman spectroscopy revealed that only this catalyst contained Al 2 (MoO 4 ) 3 with a MoO 4 structure. X-ray photoelectron spectroscopy clarified the surface chemistry: the catalyst with the highest CNT productivity exposed Mo entirely as Mo 6+ in Al 2 (MoO 4 ) 3 and CoMoO 4 , whereas the others contained both Mo 4+ and Mo 6+ . The MoO x species like Al 2 (MoO 4 ) 3 is known to suppress Co sintering during CNT synthesis, delaying catalyst deactivation and enhancing the carbon yield. Moreover, an inverse relationship was observed between carbon yield and the CoMoO 4 content. This is attributed to the consumption of catalytically active Co during CoMoO 4 formation, which reduces active sites for CNT growth. ICP-OES further confirmed higher Co and Mo loadings for stepwise catalysts, contributing to superior catalyst performance. The extent of CoMoO 4 formation strongly depended on the metal introduction sequence. In conclusion, this trend is illustrated by considering the relationship between the point of zero charge of support and the pH of the metal precursor solutions.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Thermodynamic Trends for Reduction of CO by Molecular Complexes

Selective reduction of CO 2 into fuels and chemical feedstocks is highly desirable to reduce our dependence on fossil fuels. Most molecular catalysts afford 2e – reduction products, such as CO or HCO 2 – , as opposed to more reduced products. Here we present an analysis of the thermodynamic limitations for reduction of the CO ligand in the form of a series of isostructural group 6 carbonyl complexes, Cp*M(CO) 3 (P(OMe) 3 ) + (M = Cr, Mo, and W). Additionally, the free energy for stepwise transfer of a hydride (H – ) and a proton (H + ) to the CO ligand, resulting in a hydroxycarbene (CHOH) complex, was measured by equilibration with H – /H + donors and acceptors with known hydricity or acidity. Together, these two reaction steps are equivalent to a net addition of H 2 across the CO ligand. A large and unfavorable free energy for H 2 addition (Δ G ° H2 ) was measured for all three complexes and decreases in the order Cr > Mo > W. The trend for these complexes is opposite to the trend previously reported for group 7 carbonyl complexes, for which Δ G ° H2 decreases moving up the group, Re > Mn. Computational analysis indicates the trends can be described in terms of electrostatic effects, where a low Δ G ° H2 is obtained in complexes that balance the atomic charges of the M–C≡O fragment of the complex. These findings can be used to design metal carbonyl complexes with a more energetically accessible H 2 addition, which will facilitate the development of molecular catalysts for reduction of CO.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Tuning Thermal Stability through Dopant Size in Chemically Doped DPP–Thiophene Polymers

Molecular doping of conjugated polymers (CPs) is a key strategy for improving the performance of organic electronics devices, particularly thermoelectrics. Doped donor–acceptor (D–A) conjugated polymers, characterized by a tunable energy gap between the Fermi level and the transport band, show great promise in achieving high electrical conductivity (σ) while preserving a favorable Seebeck coefficient (S). Despite the promising performance enhancement of chemically doped D–A polymers, their thermal stability remains largely underexplored, a crucial consideration for the long-term operation of organic thermoelectric devices. In this study, we investigated the dopant size-dependent thermal stability of a diketopyrrolopyrrole-thiophene (DPP-T) D–A copolymer, utilizing two p-dopants: 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4 TCNQ) and Mo(tfd-CO 2 Me) 3 . Temperature-dependent UV–vis–NIR spectroscopy revealed that DPP-T/F 4 TCNQ is more prone to dedoping under a high temperature thermal stress than DPP-T/Mo(tfd-CO 2 Me) 3 . Although the F 4 TCNQ doped polymer shows higher initial in-plane conductivity than its Mo(tfd-CO 2 Me) 3 counterpart, it undergoes a conductivity loss of more than an order of magnitude after annealing at 120 °C for 30 min. In contrast, the in-plane conductivity of DPP-T/Mo(tfd-CO 2 Me) 3 remains stable under the same thermal conditions. Thermogravimetric analysis ruled out dopant sublimation as a primary contributor to dedoping, leading us to attribute the conductivity loss in F 4 TCNQ-doped DPP-T to dopant phase separation and migration. This observation was further confirmed by X-ray scattering studies and nanoscale infrared microscopy and spectroscopy studies. This work could provide further insights into the thermal stability of doped conjugated polymers and suggests that incorporating bulkier dopants is an effective strategy to enhance the thermal robustness of doped DPP-type systems.

Conjugated polymers↗
DOE OSTI2025

Heterointercalation in Chevrel-Phase Sulfides: A Model Periodic Solid for the Investigation of Chain Electron Transfer

Modulation of electron density localization on periodic crystal solids through electron transfer from interstitial cations can directly influence the bonding configurations of small-molecule intermediates at the catalyst binding site. This study presents the microwave-assisted solid-state synthesis of four heterointercalant Chevrel-phase (CP) sulfides with varying metal cation intercalants with compositional and electronic structure investigations of the electron density redistribution as a result of intercalation. The heterointercalant CP sulfides, with the general formula Cu x M y Mo 6 S 8 (where M = Cr, Mn, Fe, Ni; x, y = 1.5−2.5), are presented here for the probe reaction of electrochemical CO 2 reduction. A change in product selectivity is observed toward the production of methanol at low overpotentials of −0.5 V vs reversible hydrogen electrode (RHE), as a result of the intercalant combination present within the CP interstitial cavity. Structural confirmation of all materials was examined through Rietveld refinement of the powder X-ray diffraction (PXRD) data, high-resolution transmission electron microscopy (HR-TEM), and selected-area electron diffraction (SAED). Electron transfer from the intercalated metal cations to the Mo 6 S 8 cluster was investigated via X-ray photoelectron spectroscopy (XPS) of the intercalated metal cations and the chalcogenide cluster. Electron transfer was further confirmed through X-ray absorption analysis (XAS) of the K-edges of Mo and intercalants. Intermediate studies of electrochemical reduction of formaldehyde to methanol resulted in a faradaic efficiency of ∼78% methanol production on Cu x Ni y Mo 6 S 8 . The results presented herein identify distinct principles for materials design that can be utilized in other compositional spaces within the broad families of periodic crystal solids.

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

Materials Data on CoMoP2 by Materials Project

MoCoP2 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Mo4+ is bonded to six equivalent P3- atoms to form edge-sharing MoP6 octahedra. All Mo–P bond lengths are 2.49 Å. Co2+ is bonded in a 6-coordinate geometry to six equivalent P3- atoms. All Co–P bond lengths are 2.27 Å. P3- is bonded in a 3-coordinate geometry to three equivalent Mo4+, three equivalent Co2+, and one P3- atom. The P–P bond length is 2.45 Å.

36 MATERIALS SCIENCE↗