Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Cr”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Cr(RhSe2)2 by Materials Project

Cr(RhSe2)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Cr2+ is bonded to six Se2- atoms to form CrSe6 octahedra that share corners with twelve equivalent RhSe6 octahedra, edges with two equivalent CrSe6 octahedra, and faces with two equivalent RhSe6 octahedra. The corner-sharing octahedra tilt angles range from 50–52°. There are four shorter (2.58 Å) and two longer (2.62 Å) Cr–Se bond lengths. Rh3+ is bonded to six Se2- atoms to form RhSe6 octahedra that share corners with six equivalent CrSe6 octahedra, edges with six equivalent RhSe6 octahedra, and a faceface with one CrSe6 octahedra. The corner-sharing octahedra tilt angles range from 50–52°. There are a spread of Rh–Se bond distances ranging from 2.47–2.62 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to one Cr2+ and three equivalent Rh3+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent Cr2+ and three equivalent Rh3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(WO4)3 by Materials Project

Cr(WO4)3 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are three inequivalent W6+ sites. In the first W6+ site, W6+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 18–29°. There are a spread of W–O bond distances ranging from 1.92–1.95 Å. In the second W6+ site, W6+ is bonded to six O2- atoms to form distorted WO6 octahedra that share corners with two equivalent WO6 octahedra and corners with four equivalent CrO6 octahedra. The corner-sharing octahedra tilt angles range from 22–31°. There are a spread of W–O bond distances ranging from 1.79–2.20 Å. In the third W6+ site, W6+ is bonded to six O2- atoms to form distorted WO6 octahedra that share corners with two equivalent CrO6 octahedra and corners with four equivalent WO6 octahedra. The corner-sharing octahedra tilt angles range from 18–29°. There are a spread of W–O bond distances ranging from 1.78–2.23 Å. Cr6+ is bonded to six O2- atoms to form distorted CrO6 octahedra that share corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 23–31°. There are a spread of Cr–O bond distances ranging from 1.65–2.12 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one W6+ and one Cr6+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two W6+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two W6+ atoms. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to one W6+ and one Cr6+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two W6+ atoms. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one W6+ and one Cr6+ atom. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to one W6+ and one Cr6+ atom. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to two W6+ atoms. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to one W6+ and one Cr6+ atom. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to two W6+ atoms. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to two W6+ atoms. In the twelfth O2- site, O2- is bonded in a distorted single-bond geometry to one W6+ and one Cr6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(Te2Rh)2 by Materials Project

Cr(RhTe2)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Cr2+ is bonded to six Te2- atoms to form CrTe6 octahedra that share corners with twelve equivalent RhTe6 octahedra, edges with two equivalent CrTe6 octahedra, and faces with two equivalent RhTe6 octahedra. The corner-sharing octahedra tilt angles range from 52–53°. There are four shorter (2.78 Å) and two longer (2.80 Å) Cr–Te bond lengths. Rh3+ is bonded to six Te2- atoms to form RhTe6 octahedra that share corners with six equivalent CrTe6 octahedra, edges with six equivalent RhTe6 octahedra, and a faceface with one CrTe6 octahedra. The corner-sharing octahedra tilt angles range from 52–53°. There are a spread of Rh–Te bond distances ranging from 2.67–2.76 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Cr2+ and three equivalent Rh3+ atoms. In the second Te2- site, Te2- is bonded in a 4-coordinate geometry to one Cr2+ and three equivalent Rh3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(ReO3)2 by Materials Project

Cr(ReO3)2 is beta Vanadium nitride-derived structured and crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with eight equivalent ReO6 octahedra and edges with two equivalent ReO6 octahedra. The corner-sharing octahedra tilt angles range from 41–51°. There is two shorter (1.89 Å) and four longer (2.00 Å) Cr–O bond length. Re+4.50+ is bonded to six O2- atoms to form ReO6 octahedra that share corners with four equivalent CrO6 octahedra, corners with four equivalent ReO6 octahedra, an edgeedge with one CrO6 octahedra, and an edgeedge with one ReO6 octahedra. The corner-sharing octahedra tilt angles range from 41–51°. There are a spread of Re–O bond distances ranging from 1.97–2.04 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Cr3+ and two equivalent Re+4.50+ atoms. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to one Cr3+ and two equivalent Re+4.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(PO3)4 by Materials Project

Cr(PO3)4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Cr4+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Cr–O bond distances ranging from 2.00–2.05 Å. There are four inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form corner-sharing PO4 tetrahedra. There is two shorter (1.51 Å) and two longer (1.59 Å) P–O bond length. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent CrO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 41–44°. There are a spread of P–O bond distances ranging from 1.50–1.61 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent CrO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 29–37°. There are a spread of P–O bond distances ranging from 1.50–1.63 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent CrO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 6–44°. There are a spread of P–O bond distances ranging from 1.49–1.62 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one P5+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cr4+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr4+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cr4+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two P5+ atoms. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr4+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cr4+ and one P5+ atom. In the ninth O2- site, O2- is bonded in a single-bond geometry to one P5+ atom. In the tenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two P5+ atoms. In the eleventh O2- site, O2- is bonded in a linear geometry to one Cr4+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(Fe2Sb5)2 by Materials Project

Cr(Fe2Sb5)2 crystallizes in the monoclinic P2/m space group. The structure is three-dimensional. Cr6+ is bonded to six Sb+1.80- atoms to form CrSb6 octahedra that share corners with eight FeSb6 octahedra and edges with two equivalent CrSb6 octahedra. The corner-sharing octahedra tilt angles range from 50–52°. There are one shorter (2.67 Å) and five longer (2.68 Å) Cr–Sb bond lengths. There are five inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six Sb+1.80- atoms to form a mixture of corner and edge-sharing FeSb6 octahedra. The corner-sharing octahedra tilt angles range from 50–51°. There are a spread of Fe–Sb bond distances ranging from 2.58–2.61 Å. In the second Fe3+ site, Fe3+ is bonded to six Sb+1.80- atoms to form a mixture of corner and edge-sharing FeSb6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are two shorter (2.59 Å) and four longer (2.61 Å) Fe–Sb bond lengths. In the third Fe3+ site, Fe3+ is bonded to six Sb+1.80- atoms to form FeSb6 octahedra that share corners with four equivalent CrSb6 octahedra, corners with four equivalent FeSb6 octahedra, and edges with two equivalent FeSb6 octahedra. The corner-sharing octahedra tilt angles range from 50–51°. There are a spread of Fe–Sb bond distances ranging from 2.55–2.60 Å. In the fourth Fe3+ site, Fe3+ is bonded to six Sb+1.80- atoms to form FeSb6 octahedra that share corners with eight equivalent CrSb6 octahedra and edges with two equivalent FeSb6 octahedra. The corner-sharing octahedra tilt angles range from 50–52°. There are two shorter (2.52 Å) and four longer (2.57 Å) Fe–Sb bond lengths. In the fifth Fe3+ site, Fe3+ is bonded to six Sb+1.80- atoms to form a mixture of corner and edge-sharing FeSb6 octahedra. The corner-sharing octahedra tilt angles range from 50–51°. There are a spread of Fe–Sb bond distances ranging from 2.59–2.61 Å. There are ten inequivalent Sb+1.80- sites. In the first Sb+1.80- site, Sb+1.80- is bonded in a 3-coordinate geometry to one Cr6+ and two equivalent Fe3+ atoms. In the second Sb+1.80- site, Sb+1.80- is bonded in a 3-coordinate geometry to one Cr6+ and two equivalent Fe3+ atoms. In the third Sb+1.80- site, Sb+1.80- is bonded in a 4-coordinate geometry to three Fe3+ atoms. In the fourth Sb+1.80- site, Sb+1.80- is bonded in a 6-coordinate geometry to three Fe3+ atoms. In the fifth Sb+1.80- site, Sb+1.80- is bonded in a 6-coordinate geometry to three Fe3+ atoms. In the sixth Sb+1.80- site, Sb+1.80- is bonded in a 3-coordinate geometry to two equivalent Cr6+ and one Fe3+ atom. In the seventh Sb+1.80- site, Sb+1.80- is bonded in a 3-coordinate geometry to two equivalent Cr6+ and one Fe3+ atom. In the eighth Sb+1.80- site, Sb+1.80- is bonded in a 3-coordinate geometry to three Fe3+ atoms. In the ninth Sb+1.80- site, Sb+1.80- is bonded in a 6-coordinate geometry to three Fe3+ atoms. In the tenth Sb+1.80- site, Sb+1.80- is bonded in a 6-coordinate geometry to three Fe3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(BMo)2 by Materials Project

Cr(MoB)2 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Mo2+ is bonded in a distorted hexagonal planar geometry to six equivalent B3- atoms. There are two shorter (2.33 Å) and four longer (2.34 Å) Mo–B bond lengths. Cr2+ is bonded in a square co-planar geometry to four equivalent B3- atoms. All Cr–B bond lengths are 2.35 Å. B3- is bonded in a 9-coordinate geometry to six equivalent Mo2+, two equivalent Cr2+, and one B3- atom. The B–B bond length is 1.88 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(FeAs3)2 by Materials Project

Cr(FeAs3)2 crystallizes in the monoclinic P2/m space group. The structure is three-dimensional. Cr4+ is bonded to six As+1.67- atoms to form CrAs6 octahedra that share corners with eight FeAs6 octahedra and edges with two equivalent CrAs6 octahedra. The corner-sharing octahedra tilt angles range from 52–54°. There are five shorter (2.47 Å) and one longer (2.49 Å) Cr–As bond lengths. There are three inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six As+1.67- atoms to form a mixture of edge and corner-sharing FeAs6 octahedra. The corner-sharing octahedral tilt angles are 53°. There are two shorter (2.39 Å) and four longer (2.40 Å) Fe–As bond lengths. In the second Fe3+ site, Fe3+ is bonded to six As+1.67- atoms to form FeAs6 octahedra that share corners with four equivalent CrAs6 octahedra, corners with four equivalent FeAs6 octahedra, and edges with two equivalent FeAs6 octahedra. The corner-sharing octahedra tilt angles range from 52–53°. There are a spread of Fe–As bond distances ranging from 2.37–2.41 Å. In the third Fe3+ site, Fe3+ is bonded to six As+1.67- atoms to form FeAs6 octahedra that share corners with eight equivalent CrAs6 octahedra and edges with two equivalent FeAs6 octahedra. The corner-sharing octahedra tilt angles range from 52–54°. There are two shorter (2.35 Å) and four longer (2.37 Å) Fe–As bond lengths. There are six inequivalent As+1.67- sites. In the first As+1.67- site, As+1.67- is bonded in a 4-coordinate geometry to one Cr4+ and two equivalent Fe3+ atoms. In the second As+1.67- site, As+1.67- is bonded in a 4-coordinate geometry to one Cr4+ and two equivalent Fe3+ atoms. In the third As+1.67- site, As+1.67- is bonded in a 4-coordinate geometry to three Fe3+ atoms. In the fourth As+1.67- site, As+1.67- is bonded in a 4-coordinate geometry to two equivalent Cr4+ and one Fe3+ atom. In the fifth As+1.67- site, As+1.67- is bonded in a 4-coordinate geometry to two equivalent Cr4+ and one Fe3+ atom. In the sixth As+1.67- site, As+1.67- is bonded in a 4-coordinate geometry to three Fe3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(Mo3Se4)2 by Materials Project

Cr(Mo3Se4)2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are three inequivalent Mo+2.17+ sites. In the first Mo+2.17+ site, Mo+2.17+ is bonded to five Se2- atoms to form a mixture of edge and corner-sharing MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.55–2.70 Å. In the second Mo+2.17+ site, Mo+2.17+ is bonded to five Se2- atoms to form a mixture of edge and corner-sharing MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.54–2.70 Å. In the third Mo+2.17+ site, Mo+2.17+ is bonded to five Se2- atoms to form a mixture of edge and corner-sharing MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.55–2.71 Å. Cr3+ is bonded in a body-centered cubic geometry to eight Se2- atoms. There are a spread of Cr–Se bond distances ranging from 2.51–3.16 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to four Mo+2.17+ and one Cr3+ atom. In the second Se2- site, Se2- is bonded in a 1-coordinate geometry to three Mo+2.17+ and one Cr3+ atom. In the third Se2- site, Se2- is bonded in a 5-coordinate geometry to four Mo+2.17+ and one Cr3+ atom. In the fourth Se2- site, Se2- is bonded in a 5-coordinate geometry to four Mo+2.17+ and one Cr3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(SbO3)2 by Materials Project

Cr(SbO3)2 is zeta iron carbide-derived structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Cr6+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with twelve equivalent SbO6 octahedra. The corner-sharing octahedra tilt angles range from 50–54°. There are two shorter (2.13 Å) and four longer (2.33 Å) Cr–O bond lengths. Sb3+ is bonded to six O2- atoms to form SbO6 octahedra that share corners with six equivalent CrO6 octahedra and edges with three equivalent SbO6 octahedra. The corner-sharing octahedra tilt angles range from 50–54°. There are a spread of Sb–O bond distances ranging from 2.01–2.04 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Cr6+ and two equivalent Sb3+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Cr6+ and two equivalent Sb3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(ClO)2 by Materials Project

CrO2Cl2 is Silicon tetrafluoride-derived structured and crystallizes in the monoclinic P2_1 space group. The structure is zero-dimensional and consists of two CrO2Cl2 clusters. Cr6+ is bonded in a tetrahedral geometry to two O2- and two Cl1- atoms. Both Cr–O bond lengths are 1.59 Å. There are one shorter (2.12 Å) and one longer (2.13 Å) Cr–Cl bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Cr6+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one Cr6+ atom. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one Cr6+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Cr6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Fatigue Performance of an Improved Creep Strength 10%Cr Steel

The deployment of 9-12% Cr steels for elevated temperature applications up to 650 °C presents a cost-effective alternative to more expensive nickel-based alloys in steam turbine power generation. To enhance creep resistance at this temperature range, a novel ferritic-martensitic steel, designated CPJ7, was developed and fabricated at the National Energy Technology Laboratory. The alloy design aimed to mitigate the transformation of strengthening carbides into deleterious phases that degrade creep performance. Results have demonstrated that CPJ7 exhibits favorable creep and oxidation resistance at 650 °C. However, its fatigue performance remains unexplored. This study builds upon prior research by evaluating the low cycle fatigue behavior of CPJ7 and verifying that modifications beneficial to creep performance were not detrimental to the fatigue performance. The alloy was tested at both 650 °C and ambient temperature under fully reversed bending conditions (R = − 1) and a load ratio of 0.05. Furthermore, the alloy exhibits cyclic softening, a behavior consistent with other 9-10 wt.% Cr steels. Analysis of the microstructure and hysteresis loops further corroborate cyclic softening mechanisms typical of ferritic-martensitic steels. Overall, the fatigue performance of CPJ7 meets or exceeds that of P91 steel, demonstrating its potential for high-temperature structural applications.

9% Cr ferritic-martensitic steel↗
DOE OSTI2022

Effect of heavy ion irradiation dose rate and temperature on α' precipitation in high purity Fe-18%Cr alloy

Cr-rich alpha prime precipitates (CrRP) induce hardening and embrittlement of FeCr alloys, but the kinetics of CrRP formation due to particle irradiation are not well understood. In this study, Fe18wt.%Cr alloy in solid solution state and pre-aged to produce relatively coarse CrRP was irradiated with 8 MeV Fe ions. The irradiation conditions involved two midrange doses of 0.37 and 3.7 displacements per atom (dpa), a wide range of dose rates (10 -5 –10 -3 dpa/s) and temperatures (300–450 °C). The distributions of CrRP after irradiation were studied with atom probe tomography (APT). The critical irradiation conditions to suppress CrRP formation were identified as 300 °C and 10-3 dpa/s; CrRP formation occurred readily at lower dose rates or higher temperatures. From 0.37 to 3.7 dpa, CrRP were observed to slightly grow at 350 °C and strongly coarsen at 450 °C. Specimens with pre-existing CrRP evolved into a similar precipitate distribution as detected after ion irradiation on solution annealed specimens at 300–350 °C to 0.37 dpa, indicating that the precipitate microstructure approaches a quasi-equilibrium for doses <1 dpa. Limited shrinking of pre-existing CrRP was observed after irradiation at 450 °C to 0.37 dpa, indicating a higher recovery rate at this temperature. Additionally, the evolution of CrRP is quantitatively explained by employing corrections to the historic Nelson-Hudson-Mazey precipitate stability model, and a radiation modified precipitation mechanism is proposed to account for the competition between radiation enhanced diffusion and ballistic dissolution which results in the modifications on both size and solute concentration of CrRP.

36 MATERIALS SCIENCE↗
DOE OSTI2021

In situ preparation of visible-light-driven carbon quantum dots/NaBiO 3 hybrid materials for the photoreduction of Cr(VI)

Here, different carbon quantum dots (CQDs)/NaBiO 3 hybrid materials were synthesized as photocatalysts to effectively utilize visible light for the photocatalytic degradation of contaminants effectively. These hybrid materials exhibit an enhanced photocatalytic reduction of hexavalent chromium (Cr(VI)) in the aqueous medium. Zero-dimensional nanoparticles of CQDs were embedded within the two-dimensional NaBiO 3 nanosheets by the hydrothermal process. Compared with that of the pure NaBiO 3 nanosheets, the photocatalytic performance of the hybrid catalysts was significantly high and 6 wt.% CQDs/NaBiO 3 catalyst exhibited better photocatalytic performance. We performed the first-principles density functional theory calculations to study the interfacial properties of pure NaBiO 3 nanosheets and hybrid photocatalysts, and confirmed the CQDs played an important role in the CQDs/NaBiO 3 composites. The experimental results indicated that the enhanced reduction of Cr(VI) was probably due to the high loading of CQDs (electron acceptor) on NaBiO 3 , which made NaBiO 3 nanomaterials to respond in visible light and significantly improved their electron-hole separation efficiency.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

The influence of hydrothermal synthesis temperature on the electronic structure and luminescence property of Cr-doped ZnGa 2 O 4 nanoparticles

Cr-doped ZnGa 2 O 4 (CZGO) is a near-infrared-emitting material with long-lasting persistent luminescence. This unique property makes it a great candidate in optical imaging and sensing for various biomedical applications. Nanosized CZGO can be synthesized via a hydrothermal approach, but the reaction temperatures reported in existing literature vary from 120°C to 220°C, approaching the highest temperature allowed for a standard autoclave vessel. The reason for choosing a particular hydrothermal synthesis temperature has rarely been discussed, and it is unclear whether the resulting CZGO possess the same optical properties. This work compares CZGO nanoparticles synthesized at temperatures from the lowest reported 120°C and to as high as 220°C. We find that although all the synthesized CZGO are light emitting, they exhibit different luminescence intensities and respond differently to the change of excitation energy. X-ray absorption fine structure (XAFS) analysis is employed to investigate the local chemical environment around Zn, Ga and Cr, respectively. We found synthesis temperature strongly influences the Ga species formed in these particles. The energy transfer mechanism is further elucidated using X-ray excited optical luminescence (XEOL) in combination with element-specific XAFS. Two energy transfer paths are identified, which explains the different excitation energy dependencies of the observed photoluminescence.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Influence of grain size on α' Cr precipitation in an isothermally aged Fe-21Cr-5Al alloy

Cr-rich α' precipitation during aging typically leads to hardening and accordingly embrittlement of FeCrAl alloys, which needs to be suppressed. The influence of grain size on α' precipitation was studied by aging coarse-grained (CG), ultra-fine grained (UFG), and nanocrystalline (NC) ferritic Kanthal-D [KD; Fe-21Cr-5Al (wt.%) alloy] at 450, 500 and 550 °C for 500 h. After aging at 450 and 500 °C, less hardening was observed in the UFG KD than in CG KD. Atom probe tomography indicated a lower number density and larger sized intragranular α' in the UFG versus the CG alloy. The smaller grain size and higher defect (vacancy and dislocation) density in the UFG KD facilitated diffusion and accordingly enhanced precipitation kinetics, leading to coarsening of precipitates, as well as saturation of precipitation at lower temperatures, as compared to those in CG KD. No hardening occurred in UFG and CG KD after aging at 550 °C, indicating that the miscibility gap is between 500 and 550 °C. NC KD exhibited softening after aging owing to grain growth. α' precipitation occurred in NC KD aged at 450 °C but not at 500 °C, indicating that miscibility gap is between 450 and 500 °C. Thus, the significantly smaller grain size in NC KD decreased the miscibility gap, as compared to that in CG and UFG KD. Finally, this is attributed to the absorption of vacancies by migrating grain boundaries during aging, suppressing α' nucleation and enhancing Cr solubility.

36 MATERIALS SCIENCE↗
NASA NTRS2022

Vacuum Melt Infiltration of 2D Tyranno SA3® Ceramic Matrix Composites with Cr-25(wt.%)Si Intermetallic Alloy

The potential and limitations of vacuum melt infiltrating woven preforms of 2D Tyranno SA3 fibers with Cr-25(wt.%)Si alloy were investigated. Microstructural observations revealed that the volume fractions of open voids infiltrated by the molten metal varied between 3.7 and 10.0% irrespective of the magnitudes of the melt infiltration temperatures and hold times, which was attributed in part to substantial volatilization of the silicide charge based on computational thermodynamics. In the absence of experimental data, poor wettability of the melt could not be ruled out unambiguously. Other possible reasons are carefully examined and discarded. Ring microstructures were observed around the fibers mainly at the outer surfaces of the infiltrated preform, where the BN and chemical vapor infiltrated SiC coatings had vaporized in the high vacuum environment. In contrast, they were absent in the interior of the preform, where the coatings were still present with no evidence of molten metal attack of the coatings. Details of thermodynamic calculations are presented to confirm the volatilization of the BN and CVI SiC coatings thereby resulting in the ring microstructures due to the filling of voids by the molten silicide. It is concluded that successful melt infiltration of Tyranno SA3® with Cr-25%Si can be only achieved under sufficient positive pressure to prevent volatilization of the coatings and the molten silicide.

Cr-25%Si↗
DOE OSTI2023

Widely Tunable Berry Curvature in the Magnetic Semimetal Cr 1+ δ Te 2

Abstract Magnetic semimetals have increasingly emerged as lucrative platforms hosting spin‐based topological phenomena in real and momentum spaces. Cr 1+ δ Te 2 is a self‐intercalated magnetic transition metal dichalcogenide (TMD), which exhibits topological magnetism and tunable electron filling. While recent studies have explored real‐space Berry curvature effects, similar considerations of momentum‐space Berry curvature are lacking. Here, the electronic structure and transport properties of epitaxial Cr 1+ δ Te 2 thin films are systematically investigated over a range of doping, δ (0.33 – 0.71). Spectroscopic experiments reveal the presence of a characteristic semi‐metallic band region, which shows a rigid like energy shift with δ. Transport experiments show that the intrinsic component of the anomalous Hall effect (AHE) is sizable and undergoes a sign flip across δ. Finally, density functional theory calculations establish a link between the doping evolution of the band structure and AHE: the AHE sign flip is shown to emerge from the sign change of the Berry curvature, as the semi‐metallic band region crosses the Fermi energy. These findings underscore the increasing relevance of momentum‐space Berry curvature in magnetic TMDs and provide a unique platform for intertwining topological physics in real and momentum spaces.

36 MATERIALS SCIENCE↗