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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Thermodynamics and Magnetism of SmFe 12 Compound Doped with Zr, Ce, Co and Ni: An Ab Initio Study

Alloys that are Ni-doped, such as the (Sm 1—y Zr y )(Fe 1—x Co x ) 12 and (Ce 0.5 Sm 0.5 )Fe 10 Co 2 systems, are studied because of their magnetic properties. The (Sm 1—y Zr y )(Fe 1—x Co x ) 11—z Ti z and (Ce. 1—x Sm x )Fe 9 Co 2 Ti alloys are considered contenders for vastly effective permanent magnets because of their anisotropy field and Curie temperature. Ti can act as a stabilizer for the SmFe 12 compound but substantially suppresses saturation magnetization. To maintain the saturation magnetization in the scope of 1.3–1.5 T, we propose substituting a particular quantity of Fe and Co in the (Sm 1—y Zr y )(Fe 1—x Co x ) 12 and (Ce 0.5 Sm 0.5 )Fe 10 Co 2 alloys with Ni. By performing ab initio calculations, we show that Ni incorporation results in increased thermodynamic stability and, in contrast to Ti, has a parallel spin moment aligned to the moment of the SmFe 12 compound and improves its saturation magnetization without affecting the anisotropy field or Curie temperature.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1975

Deposition rate and substrate temperature effects on the structure and properties of bulk-sputtered OFHC Cu and Cu-0.15Zr

Bulk-sputtered OFHC Cu and Cu-0.15 Zr used as inner walls of advanced regeneratively cooled thrust chambers are evaluated as to microstructure, surface topography, and fractography. It is found that under conditions of low substrate temperature, crystallite size and openness of the structure increase with increasing deposition rate for both materials. At elevated temperatures, an equiaxed ductile structure of OFHC Cu is produced only at low deposition rates; at higher deposition rate, open structures are observed with recrystallized equiaxed grains within large poorly bonded crystallites. The Cu-0.15 Zr alloy sputtered from the hollow cathode using a diode discharge shows open-type structures for all conditions evaluated. The use of a triode discharge in generating a dense non-voided structure of Cu-0.15 Zr is discussed.

Hecht, R. J.↗
NASA NTRS1976

Zr-Hf fractionation in chemically defined lunar rock groups

Zirconium and hafnium, a geochemically coherent pair of elements, are strongly fractionated in lunar rocks, as evidenced by a wide range of Zr/Hf mass ratios from 12 for the anorthosite 60015,65A to 50 for the KREEP breccia 14321. This may be explained in part by selective reduction of Zr(4+) to Zr(3+) and exclusion of the Zr(3+) from early crystallized Fe-Ti minerals.

Garg, A. N.↗
NASA NTRS1988

Oxidation behavior of FeAl+Hf,Zr,B

The oxidation behavior of Fe-40Al-1Hf, Fe-40Al-1Hf-0.4B, and Fe-40Al-0.1Zr-0.4B (at. percent) alloys was characterized after 900, 1000, and 100 C exposures. Isothermal tests revealed parabolic kinetics after a period of transitional theta-alumina scale growth. The parabolic growth rates for the subsequent alpha-alumina scales were about five times higher than those for NiAl+0.1Zr alloys. The isothermally grown scales showed a propensity toward massive scale spallation due to both extensive rumpling from growth stresses and to an inner layer of HfO2. Cyclic oxidation for 200 1-hr cycles produced little degradation at 900 or 1000 C, but caused significant spallation at 1100 C in the form of small segments of the outer scale. The major difference in the cyclic oxidation of the three FeAl alloys was increased initial spallation for FeAl+Zr,B. Although these FeAl alloys showed many similarities to NiAl alloys, they were generally less oxidation resistant. It is believed that this resulted from nonoptimal levels of dopants and larger thermal expansion mismatch stresses.

Smialek, James L.↗
NASA NTRS1989

Creep strength of niobium alloys, Nb-1%Zr and PWC-11

A study is being conducted at NASA Lewis Research Center to determine the feasibility of using a carbide particle strengthened Nb-1 percent Zr base alloy to meet the anticipated temperature and creep resistance requirements of proposed near term space power systems. In order to provide information to aid in the determination of the suitability of the PWC-11 alloy as an alternative to Nb-1 percent Zr in space power systems this study investigated: (1) the long-time high-vacuum creep behavior of the PWC-11 material and the Nb-1 percent Zr alloy, (2) the effect of prior stress-free thermal aging on this creep behavior, (3) the effect of electron beam (EB) welding on this creep behavior, and (4) the stability of creep strengthening carbide particles.

Titran, Robert H.↗
NASA NTRS1989

Microstructure and tensile properties of Fe-40 at. pct Al alloys with C, Zr, Hf, and B additions

The influence of small additions of C, Zr, and Hf, alone or in combination with B, on the microstructure and tensile behavior of substoichiometric FeAl was investigated. Tensile properties were determined from 300 to 1100 K on powder which was consolidated by hot extrusion. All materials possessed some ductility at room temperature, although ternary additions generally reduced ductility compared to the binary alloy. Adding B to the C- and Zr-containing alloys changed the fracture mode from intergranular to transgranular and restored the ductility to approximately 5 percent elongation. Additions of Zr and Hf increased strength up to about 900 K. Fe6Al6Zr and Fe6Al6Hf precipitates, both with identical body-centered tetragonal structures, were identified as the principal second phase in these alloys. Strength decreased steadily as temperature increased above 700 K, as diffusion-assisted mechanisms became operative. Although all alloys had similar strengths at 1100 K, Hf additions significantly improved high-temperature ductility by suppressing cavitation.

Gaydosh, D. J.↗
NASA NTRS1989

Oxidation behavior of FeAl+Hf,Zr,B

The oxidation behavior of Fe-40Al-1Hf, Fe-40Al-1Hf-0.4B, and Fe-40Al-0.1Zr-0.4B (at. percent) alloys was characterized after 900, 1000, and 100 C exposures. Isothermal tests revealed parabolic kinetics after a period of transitional theta-alumina scale growth. The parabolic growth rates for the subsequent alpha-alumina scales were about five times higher than those for NiAl+0.1Zr alloys. The isothermally grown scales showed a propensity toward massive scale spallation due to both extensive rumpling from growth stresses and to an inner layer of Hf02. Cyclic oxidation for 200 1-hr cycles produced little degradation at 900 or 1000 C, but caused significant spallation at 1100 C in the form of small segments of the outer scale. The major difference in the cyclic oxidation of the three FeAl alloys was increased initial spallation for FeAl+Zr,B. Although these FeAl alloys showed many similarities to NiAl alloys, they were generally less oxidation resistant. It is believed that this resulted from nonoptimal levels of dopants and larger thermal expansion mismatch stresses.

Smialek, James L.↗
NASA NTRS1992

Correlation of deformation mechanisms with the tensile and compressive behavior of NiAl and NiAl(Zr) intermetallic alloys

To identify the mechanisms controlling strength and ductility in powder-extruded NiAl and NiAl + 0.05 at. pct Zr, tensile and compressive testing was performed from 300 to 1300 K for several grain sizes. Grain size refinement significantly increased yield stress in both alloys and, in some cases, slightly lowered the ductile-to-brittle transition temperature (DBTT), although no room-temperature tensile ductility was observed even in the finest grain size specimens. The small Zr addition increased the DBTT and changed the low-temperature fracture mode from intergranular in NiAl to a combination of intergranular and transgranular in the Zr-doped alloy. Scanning electron microscopy of compression specimens deformed at room temperature revealed the presence of grain-boundary cracks in both alloys. These cracks were due to the incompatibility of strain in the polycrystalline material, owing to the lack of five independent slip systems. The tendency to form grain-boundary cracks, in addition to the low fracture stress of these alloys, contributed to the lack of tensile ductility at low temperatures.

Bowman, R. R.↗
NASA NTRS1994

Effects of thermomechanical processing on tensile and long-time creep behavior of Nb-1 percent Zr-0.1 percent C sheet

Effects of thermomechanical processing on the mechanical properties of Nb-1 wt. percent Zr-0.1 wt. percent C, a candidate alloy for use in advanced space power systems, were investigated. Sheet bars were cold rolled into 1-mm thick sheets following single, double, or triple extrusion operations at 1900 K. All the creep and tensile specimens were given a two-step heat treatment 1 hr at 1755 K + 2 hr 1475 K prior to testing. Tensile properties were determined at 300 as well as at 1350 K. Microhardness measurements were made on cold rolled, heat treated, and crept samples. Creep tests were carried out at 1350 K and 34.5 MPa for times of about 10,000 to 19,000 hr. The results show that the number of extrusions had some effects on both the microhardness and tensile properties. However, the long-time creep behavior of the samples were comparable, and all were found to have adequate properties to meet the design requirements of advanced power systems regardless of thermomechanical history. The results are discussed in correlation with processing and microstructure, and further compared to the results obtained from the testing of Nb-1 wt. percent Zr and Nb-1 wt. percent Zr-0.06 wt. percent C alloys.

Titran, Robert H.↗
NASA NTRS2006

Observations Of A Cast Cu-Cr-Zr Alloy

The calculated phase diagram and observations of Zeng et al were confirmed. 1) Additional X-ray diffraction peaks for aged sample indicates possibility that additional metastable phases may form; 2) Cu5Zr was observed rather than the Cu9Zr2 proposed for the binary Cu-Zr phase diagram. Despite similarities between Zr and Nb, Cu-Cr-Zr does not appear to be a good candidate alloy system for rocket engine applications.

Ellis, David L.↗
DOE OSTI2024

Thermal Conductivity Degradation in High Burnup U-Pu-Zr Fuel

Recent advancements in the characterization of irradiated U-Pu-Zr fuels have revealed complexities that challenge existing understanding of constituent redistribution. Traditionally, models have proposed three concentric regions within the fuel, each characterized by distinctive phases and porosity. However, through detailed analysis of high burnup U-Pu-Zr, we discovered the presence of four distinct constituent redistribution regions. Particularly novel is the observation of significant Pu redistribution, a previously unreported phenomenon that necessitates a reevaluation of current models. This work aims to delve deeper into these findings, seeking to correlate mesoscale measurements of thermal diffusivity and respective thermal conductivity with the phases present in each redistribution region. To achieve this objective, we employed mesoscale thermoreflectance methods using the unique, Idaho National Laboratory (INL) developed, Thermal Conductivity Microscope (TCM) at INL’s Irradiated Materials Characterization Laboratory. The TCM employs two tightly focused lasers: one for heating to generate periodic thermal waves in the substrate, and another spatially separated probe laser to detect changes in the optical reflectivity of the gold-coated substrate resulting from thermal wave diffusion. We conducted several thermal diffusivity measurements within each region of constituent redistribution of a U-19Pu-10Zr fuel pin cross section irradiated to 11 at. % burnup. The TCM measurement positions strategically aligned with transmission electron microscopy (TEM) lift-out locations previously collected from the fuel sample. Complementary microstructural analysis techniques such as optical and scanning electron microscopy (OM/SEM), electron probe microanalysis for chemical compositions, and TEM-based selective area electron diffraction (SAED) analysis for crystallographic insights into each phase were also utilized. This comprehensive approach allowed us to correlate local thermal diffusivity data with microstructural characteristics, enabling the computation of local thermal conductivity at each position. The significance of this contribution lies in its pioneering use of the TCM for ternary fuel mesoscale examination, shedding light on the previously overlooked effects of Pu redistribution on local thermal conductivity. By informing current models capturing constituent redistribution and heat transfer, our findings pave the way for more accurate predictions of metallic fuel performance. Moreover, this work sets the stage for future comparisons with similar TCM examinations on U-19Pu-10Zr fuels at ultra-low burnup, facilitating a comprehensive understanding of thermal property changes across different burnup levels. Ultimately, our study not only enriches our understanding of the thermophysical properties of individual redistribution regions within U-Pu-Zr fuel but also offers valuable insights for the design and operational parameters of proposed next-generation fast reactors.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Materials Data on Zr(NiP)2 by Materials Project

Zr(NiP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Zr2+ is bonded in a distorted body-centered cubic geometry to eight equivalent P3- atoms. All Zr–P bond lengths are 2.85 Å. Ni2+ is bonded to four equivalent P3- atoms to form a mixture of edge and corner-sharing NiP4 tetrahedra. All Ni–P bond lengths are 2.24 Å. P3- is bonded in a 9-coordinate geometry to four equivalent Zr2+, four equivalent Ni2+, and one P3- atom. The P–P bond length is 2.25 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr(SO4)2 by Materials Project

Zr(SO4)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Zr4+ is bonded to seven O2- atoms to form distorted ZrO7 pentagonal bipyramids that share corners with seven SO4 tetrahedra. There are a spread of Zr–O bond distances ranging from 2.09–2.30 Å. There are two inequivalent S6+ sites. In the first S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three equivalent ZrO7 pentagonal bipyramids. There are a spread of S–O bond distances ranging from 1.43–1.50 Å. In the second S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with four equivalent ZrO7 pentagonal bipyramids. There is three shorter (1.48 Å) and one longer (1.49 Å) S–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one Zr4+ and one S6+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Zr4+ and one S6+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Zr4+ and one S6+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one S6+ atom. In the fifth O2- site, O2- is bonded in a distorted linear geometry to one Zr4+ and one S6+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Zr4+ and one S6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr(FeSi)2 by Materials Project

Zr(FeSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Zr2+ is bonded in a distorted body-centered cubic geometry to eight equivalent Si4- atoms. All Zr–Si bond lengths are 2.98 Å. Fe3+ is bonded to four equivalent Si4- atoms to form a mixture of corner and edge-sharing FeSi4 tetrahedra. All Fe–Si bond lengths are 2.24 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Zr2+, four equivalent Fe3+, and one Si4- atom. The Si–Si bond length is 2.40 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr(SeCl6)2 by Materials Project

Zr(SeCl6)2 crystallizes in the orthorhombic Fdd2 space group. The structure is three-dimensional. Zr4+ is bonded to six Cl1- atoms to form ZrCl6 octahedra that share corners with two equivalent SeCl6 octahedra and edges with two equivalent SeCl6 octahedra. The corner-sharing octahedral tilt angles are 46°. There are a spread of Zr–Cl bond distances ranging from 2.47–2.52 Å. Se4+ is bonded to six Cl1- atoms to form distorted SeCl6 octahedra that share a cornercorner with one ZrCl6 octahedra and an edgeedge with one ZrCl6 octahedra. The corner-sharing octahedral tilt angles are 46°. There are a spread of Se–Cl bond distances ranging from 2.19–2.96 Å. There are six inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a distorted single-bond geometry to one Zr4+ and one Se4+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Se4+ atom. In the third Cl1- site, Cl1- is bonded in a single-bond geometry to one Se4+ atom. In the fourth Cl1- site, Cl1- is bonded in a distorted water-like geometry to one Zr4+ and one Se4+ atom. In the fifth Cl1- site, Cl1- is bonded in a distorted water-like geometry to one Zr4+ and one Se4+ atom. In the sixth Cl1- site, Cl1- is bonded in a single-bond geometry to one Se4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr(MoO4)2 by Materials Project

ZrMo2O8 crystallizes in the trigonal P-31c space group. The structure is two-dimensional and consists of two ZrMo2O8 sheets oriented in the (0, 0, 1) direction. there are two inequivalent Zr4+ sites. In the first Zr4+ site, Zr4+ is bonded to six O2- atoms to form ZrO6 octahedra that share corners with six equivalent MoO4 tetrahedra. All Zr–O bond lengths are 2.11 Å. In the second Zr4+ site, Zr4+ is bonded to six equivalent O2- atoms to form ZrO6 octahedra that share corners with six equivalent MoO4 tetrahedra. All Zr–O bond lengths are 2.11 Å. Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three ZrO6 octahedra. The corner-sharing octahedra tilt angles range from 11–21°. There is one shorter (1.73 Å) and three longer (1.82 Å) Mo–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the second O2- site, O2- is bonded in a linear geometry to one Zr4+ and one Mo6+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Zr4+ and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a linear geometry to one Zr4+ and one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr(SiNi)2 by Materials Project

Zr(NiSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Zr4+ is bonded in a distorted body-centered cubic geometry to eight equivalent Si4- atoms. All Zr–Si bond lengths are 2.90 Å. Ni2+ is bonded to four equivalent Si4- atoms to form a mixture of edge and corner-sharing NiSi4 tetrahedra. All Ni–Si bond lengths are 2.27 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Zr4+, four equivalent Ni2+, and one Si4- atom. The Si–Si bond length is 2.33 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr(CuP)2 by Materials Project

Zr(CuP)2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Zr4+ is bonded to six equivalent P3- atoms to form ZrP6 octahedra that share corners with twelve equivalent CuP4 tetrahedra, edges with six equivalent ZrP6 octahedra, and edges with six equivalent CuP4 tetrahedra. All Zr–P bond lengths are 2.70 Å. Cu1+ is bonded to four equivalent P3- atoms to form CuP4 tetrahedra that share corners with six equivalent ZrP6 octahedra, corners with six equivalent CuP4 tetrahedra, edges with three equivalent ZrP6 octahedra, and edges with three equivalent CuP4 tetrahedra. The corner-sharing octahedra tilt angles range from 18–55°. There are three shorter (2.30 Å) and one longer (2.40 Å) Cu–P bond lengths. P3- is bonded to three equivalent Zr4+ and four equivalent Cu1+ atoms to form a mixture of distorted edge and corner-sharing PZr3Cu4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗