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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.

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14 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Acoustic and electrical properties of Fe-Ti oxides with application to the deep lunar mantle

The overturn of titanium-rich mantle cumulates has been invoked to explain the structure and dynamics of the Moon. These dense cumulates are stable at the core-mantle boundary (CMB) and could explain field observations inferred from geophysical studies. Here, we report acoustic and electrical experiments on natural ilmenite-rutile aggregates up to 4.5 GPa and 1920 K. Seismic velocities show a weak pressure and temperature dependence, with Vs ~ 4.2 (+/-0.2) km/s and Vp ~8.0 (+/-0.2) km/s at the CMB conditions. Conductivity increases by a factor of 10 4 from 373 to 1920 K and is >10(3) S/m above 1573 K. Seismic and electrical models for the lunar mantle based on our results, considering mixtures of Fe-Ti oxides and olivine, indicate that field velocity and conductivity estimates are reproduced satisfactorily with 3-16 vol.% Fe-Ti oxides and 20 vol.% melt. Interactions between a Ti-rich, melt-bearing layer and the adjacent core likely affect the cooling and magnetic history of the Moon.

58 GEOSCIENCES↗
DOE OSTI2026

Use of friction stir processing to synthesize nanocrystalline, grain boundary segregating Fe-Ti alloys

Grain boundary segregating alloys, a class of alloys designed such that nanocrystalline grain sizes are thermodynamically stabilized by the presence of high segregation energy solutes at the grain boundaries, are typically produced through geometrically limited processing techniques such as equal channel angular extrusion or thin film sputtering. Here, this study explores the use of friction stir processing (FSP) as a novel means of studying and producing these alloys using a test system of Fe-6at%Ti. Spot FSPs with a range of processing parameter sets were produced on bulk, coarse grained bars of material and optimal parameters were identified. Microscopy identified a range of processed materials which achieved nanocrystalline grains on the order of 100 nm, delineating a critical window of processing parameters which limit heat input while inducing sufficient plastic deformation for grain refinement. The finest grained nanocrystalline Fe-Ti achieved a hardness of 7.68 GPa, a significant increase in hardness over pure Fe with a similar microstructure due to increased dislocation density from FSP as well as several strengthening mechanisms produced through the presence and segregation of Ti. These results demonstrated the feasibility of using FSP to produce nanocrystalline grain boundary segregating alloys.

Fe alloys↗
DOE OSTI2021

A high-pressure Raman study of FeTiO 3 ilmenite: Fermi resonance as a manifestation of Fe-Ti charge transfer

In this work, we investigated the 300 K high-pressure behavior of ilmenite using Raman spectroscopy to 54 GPa. Upon compression, we observe a Fermi resonance between the lowest frequency A g symmetry peaks (ν 4 and ν 5 ) between ~ 10 and ~ 30 GPa: bands that involve major components of Ti–O and Fe–O-related displacements, respectively. The peaks’ relative intensities switch at ~ 18 GPa and they also reach their minimum separation at ~ 20 GPa, indicating that their maximum resonance occurs between 18 and 20 GPa. The negative shift of the Ti–O-associated ν 4 vibration under compression is fully consistent with a shift in valence of Ti from 4 + to 3 + under compression. Anomalously small mode shifts of other, more localized vibrations are also consistent with a charge transfer from Fe to Ti under compression. At higher pressures, we have not found definitive evidence for a transition to the perovskite-structure at 300 K, which has been well characterized at high pressures and temperatures. At 40 GPa, we observe an apparent reversible disordering that persists up to our highest pressure. The 300 K mode shifts of the Raman active modes in FeTiO 3 under pressure are notably different from those of other ABO 3 compounds (where A = Mg, Mn and B = Ti, Si); in other ilmenite-structured compounds, the peaks shift at a faster rate and there has not been any observation of Fermi resonance. Thus, iron’s complex electronic structure, and its charge transfer with titanium, appears to play a primary role in the behavior of phonons in FeTiO 3 ilmenite.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Enhanced Strength of 304 SS-Ti6Al4V Laser-Welded Joints Containing Composite Interlayers

This paper investigates the microstructural characterization of the fracture propagation edge during laser beam welding of Ti6Al4V and 304 stainless steel using Cu, V, and Ni interlayers as a single Cu interlayer and composite interlayer structures with different Cu interlayer thicknesses. This study attempts to increase the Ti-SS joint strength through the use of the composite interlayers. X-ray diffraction characterization based on a 0.5-mm-thick Cu interlayer showed that the SS/Cu/Ti joint contained considerable brittle IMCs; however, the fracture surface of the SS/Cu-V/Ti composite interlayer sample did not contain any Fe-Ti IMCs or Cr{sub 2}Ti. EBSD observation indicated that the crack propagated transgranularly from solidified CuTi in the interdendritic regions of the FeTi compounds in the composite interlayer sample; however, the crack propagated intergranularly along Fe{sub 2}Ti grain boundaries in the single interlayer sample. The investigation based on a 1-mm-thick Cu interlayer showed that the SS/Ni-Cu1/Ti sample was stronger than the SS/Cu1/Ti sample due to a lack of CuTi at 3.5 kW. The tensile strength of the SS/Cu1-V/Ti joint was greater than that of the SS/Ni-Cu1/Ti joint due to the formation of ductile NiTi instead of brittle NiTi{sub 2}. The microstructures of the fracture edges after tensile testing illustrated that the eutectic CuTi + CuTi{sub 2} fractured at the SS/Cu1/Ti joint after tensile testing, while CuTi{sub 2} and eutectoid αTi + CuTi{sub 2} compounds fractured during the tensile experiment at the SS/Ni-Cu1/Ti and SS/Cu1-V/Ti joints, respectively. Investigations based on both the 0.5- and 1-mm-thick Cu interlayers showed that the tensile strength and elongation of the composite interlayer joints at a laser power of 3.5 kW were greater than those of the single interlayer joints.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Investigation on Microstructure and Mechanical Properties of TA10–Q245R Composite Plate Formed by Explosive Welding

The titanium alloy TA10 and the carbon steel Q245R are welded by explosive welding, and post-weld heat treatment (PWHT) is carried out for the TA10–Q245R composite plate. Microstructure and mechanical properties of the composite plate are investigated both in as-welded (AW) condition and after PWHT, respectively. Results show that, in AW condition, the bonding interface of composite plate presents wavy morphology, and at both sides of the interface plastic deformation is generated to a certain degree. Near the interface interdiffusion zone of alloying elements exists, and no Fe-Ti intermetallic compound is produced at the interface. SEM images indicate that the tensile fracture of composite plate presents the characteristic of ductile fracture, and no defects such as gas pores or impurities are found on the surface of shear fracture. After PWHT, the interfacial microstructure of the composite plate is obviously changed. Compared with the mechanical properties of the composite plate in AW condition, both tensile strength and shear strength of the composite plate are decreased to a certain extent after PWHT. With various factors into consideration, the suitable heat treatment procedure of TA10–Q245R composite plate is determined as follows: 550 °C × 1.5 h.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Design of an additively manufactured functionally graded material of 316 stainless steel and Ti-6Al-4V with Ni-20Cr, Cr, and V intermediate compositions

This study presents a method for designing a computationally informed gradient pathway to fabricate a functionally graded material (FGM) with terminal alloys of 316 stainless steel (SS316) and Ti-6Al-4V via directed energy deposition additive manufacturing with powder feedstock. In this work, the grading is accomplished through the introduction of intermediate elements and alloys (Ni-20Cr, Cr, and V) to avoid the brittle Fe-Ti intermetallic phases that form in the direct liquid phase joining of Ti-alloys and stainless steels. Using a combination of equilibrium calculations and Scheil-Gulliver simulations, a compositional pathway was designed to avoid deleterious phases. FGM samples were fabricated and experimentally characterized to determine the viability of the pathway. A change in phases from fcc to bcc was predicted to occur within the Ni-20Cr/Cr gradient region, and this was validated through experimental characterization. No detrimental phases (intermetallic, Laves, or σ phases) formed along the gradient path, demonstrating a successful computationally-informed design and fabrication of an FGM from SS316 to Ti-6Al-4V.

36 MATERIALS SCIENCE↗
DOE OSTI2023

The Oxidation State of Sulfur in Apatite of Martian Meteorite—Shergotty

Apatite can incorporate sulfur in its reduced form (S 2− ) when apatite equilibrates with a silicate melt under reducing conditions. Incorporation of sulfate (S 6+ ) has been observed in terrestrial apatite under oxidizing conditions. Thus, it has been suggested that the proportions of S 6+ /S 2− in apatite may record the oxygen fugacity ( f O 2 ) during the formation and/or equilibration of apatite grains with a silicate melt in a wide variety of igneous and metamorphic rocks, including from Earth, Mars, the Moon, and in materials from the asteroid belt. Martian rocks, which record f O 2 values intermediate between those recorded by rocks from the Moon and Earth, may have apatite that contains only S 2− or mixtures of S 6+ and S 2− . Here, we present new measurements of the oxidation state of sulfur in apatite grains in the basaltic shergottite, Shergotty, which exhibits spectral features consistent with the presence of sulfide (S 2− ) structurally bound in apatite, and no evidence for the presence of sulfite (S 4+ ) or sulfate (S 6+ ). Further, the presence of sulfide-only apatite in Shergotty is consistent with other mineralogical records of f O 2 in this meteorite, which are calculated from other late-stage crystallizing phases like Fe-Ti oxides as well as from early crystallizing phases like clinopyroxene ( D Eu Cpx/melt ) of ΔIW + 1.9 to ΔIW + 3.5. At these f O 2 values, S is present in silicate melts as only S 2− , and this suggests that the oxidation state of sulfur records and preserves the f O 2 during the igneous crystallization of apatite reinforcing the idea that sulfur in apatite can be used as an igneous oxybarometer.

58 GEOSCIENCES↗
DOE OSTI2017

Materials Data on TiFe2 by Materials Project

Fe2Ti is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ti is bonded in a 12-coordinate geometry to four equivalent Ti and twelve Fe atoms. There are one shorter (2.92 Å) and three longer (2.93 Å) Ti–Ti bond lengths. There are three shorter (2.78 Å) and nine longer (2.80 Å) Ti–Fe bond lengths. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to six equivalent Ti and six equivalent Fe atoms to form a mixture of edge, face, and corner-sharing FeTi6Fe6 cuboctahedra. All Fe–Fe bond lengths are 2.40 Å. In the second Fe site, Fe is bonded to six equivalent Ti and six Fe atoms to form a mixture of edge, face, and corner-sharing FeTi6Fe6 cuboctahedra. There are two shorter (2.35 Å) and two longer (2.43 Å) Fe–Fe bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiFe by Materials Project

FeTi is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ti is bonded in a body-centered cubic geometry to eight equivalent Fe atoms. All Ti–Fe bond lengths are 2.56 Å. Fe is bonded in a body-centered cubic geometry to eight equivalent Ti atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Materials Data on TiFe4 by Materials Project

TiFe4 is alpha La-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ti is bonded to four equivalent Ti and eight equivalent Fe atoms to form TiTi4Fe8 cuboctahedra that share corners with four equivalent TiTi4Fe8 cuboctahedra, corners with eight equivalent FeFe12 cuboctahedra, edges with twenty-four FeTi4Fe8 cuboctahedra, faces with eight equivalent TiTi4Fe8 cuboctahedra, and faces with ten FeTi4Fe8 cuboctahedra. All Ti–Ti bond lengths are 2.52 Å. All Ti–Fe bond lengths are 2.72 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to four equivalent Ti and eight Fe atoms to form FeTi4Fe8 cuboctahedra that share corners with twelve FeTi4Fe8 cuboctahedra, edges with eight equivalent TiTi4Fe8 cuboctahedra, edges with sixteen FeTi4Fe8 cuboctahedra, faces with four equivalent TiTi4Fe8 cuboctahedra, and faces with fourteen FeTi4Fe8 cuboctahedra. There are four shorter (2.48 Å) and four longer (2.52 Å) Fe–Fe bond lengths. In the second Fe site, Fe is bonded to twelve Fe atoms to form FeFe12 cuboctahedra that share corners with four equivalent TiTi4Fe8 cuboctahedra, corners with eight FeTi4Fe8 cuboctahedra, edges with four equivalent TiTi4Fe8 cuboctahedra, edges with twenty FeTi4Fe8 cuboctahedra, a faceface with one TiTi4Fe8 cuboctahedra, and faces with seventeen FeTi4Fe8 cuboctahedra. There are four shorter (2.52 Å) and four longer (2.59 Å) Fe–Fe bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Materials Data on Ti3Fe by Materials Project

Ti3Fe crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. there are two inequivalent Ti sites. In the first Ti site, Ti is bonded to twelve Ti atoms to form a mixture of corner, edge, and face-sharing TiTi12 cuboctahedra. There are six shorter (2.87 Å) and six longer (3.00 Å) Ti–Ti bond lengths. In the second Ti site, Ti is bonded in a 12-coordinate geometry to three equivalent Ti and three equivalent Fe atoms. All Ti–Fe bond lengths are 2.45 Å. Fe is bonded in a 6-coordinate geometry to six equivalent Ti atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Materials Data on TiFe by Materials Project

FeTi crystallizes in the orthorhombic Cmmm space group. The structure is two-dimensional and consists of two FeTi sheets oriented in the (0, 1, 0) direction. Ti is bonded in a 4-coordinate geometry to four equivalent Fe atoms. All Ti–Fe bond lengths are 2.48 Å. Fe is bonded in a 4-coordinate geometry to four equivalent Ti atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti2Fe by Materials Project

Ti2Fe crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. there are two inequivalent Ti sites. In the first Ti site, Ti is bonded in a 12-coordinate geometry to six equivalent Ti and six equivalent Fe atoms. All Ti–Ti bond lengths are 2.87 Å. All Ti–Fe bond lengths are 2.46 Å. In the second Ti site, Ti is bonded in a 2-coordinate geometry to ten Ti and four equivalent Fe atoms. There are four shorter (2.96 Å) and four longer (3.01 Å) Ti–Ti bond lengths. There are two shorter (2.59 Å) and two longer (2.86 Å) Ti–Fe bond lengths. Fe is bonded in a 12-coordinate geometry to nine Ti atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti4Fe by Materials Project

FeTi4 crystallizes in the orthorhombic Fmmm space group. The structure is three-dimensional. there are two inequivalent Ti sites. In the first Ti site, Ti is bonded in a distorted L-shaped geometry to two equivalent Ti and two equivalent Fe atoms. Both Ti–Ti bond lengths are 2.90 Å. Both Ti–Fe bond lengths are 2.40 Å. In the second Ti site, Ti is bonded in a distorted body-centered cubic geometry to eight Ti atoms. There are two shorter (2.78 Å) and four longer (2.82 Å) Ti–Ti bond lengths. Fe is bonded in a distorted square co-planar geometry to four equivalent Ti atoms.

36 MATERIALS SCIENCE↗