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All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Syntheses, crystal structures, and comparisons of rare-earth oxyapatites Ca2RE8(SiO4)6O2 (RE = La, Nd, Sm, Eu, Yb) and NaLa9(SiO4)6O2

Six different rare-earth oxyapatites including Ca2RE8(SiO4)6O2 (RE = La, Nd, Sm, Eu, Yb) and NaLa9(SiO4)6O2 were synthesized using solution-based processes followed by heat treatments. The crystal structures of the synthesized oxyapatites were solved from X-ray powder diffraction (XRD) and electron probe microanalysis (EPMA). All the oxyapatites were isostructural with the hexagonal space group P63/m and showed similar unit cell parameters. The isolated [SiO4]4- tetrahedra in each crystal are linked by the cations at 4f and 6h sites occupied by RE3+ and Ca2+ in Ca2RE8(SiO4)6O2 or La3+ and Na+ in NaLa9(SiO4)6O2. The lattice parameters, cell volumes, and densities of the synthesized oxyapatites fit well to the trendlines calculated from literature values. The compositions of crystals were verified with EPMA measurements.

oxyapatite↗
DOE OSTI2021

Structural, vibrational, thermal, and magnetic properties of mullite-type NdMnTiO 5 ceramic

Mullite-type $R$Mn 2 O 5 ($R$ = Y, rare-earth element) ceramics are of ongoing research attention because of their interesting crystal-chemical and magnetic properties. We report nuclear and magnetic structures of NdMnTiO 5 together with its spectroscopic, thermogravimetric, and magnetic properties. The polycrystalline sample is prepared by solid-state synthesis and characterized from neutron and X-ray powder diffraction data Rietveld refinements. NdMnTiO 5 crystallizes in the orthorhombic space group $Pbam$ with metric parameter $a$ = 755.20(1) pm, $b$ = 869.91(1) pm, $c$ = 582.42(1) pm, and $V$ = 382.62(1) 10 6 pm 3 . The Mn 3+ and Ti 4+ cations are observed to be located in the octahedral and pyramidal sites, respectively. The vibrational features in these polyhedral sites are characterized by Raman and Fourier transform infrared spectroscopes. The higher decomposition temperature of NdMnTiO 5 , compared to other $R$Mn 2 O 5 phases, is explained in terms of the higher bond strength of Ti-O bonds than those of Mn-O bonds. Temperature-dependent DC magnetic susceptibility suggests a paramagnetic to antiferromagnetic phase transition at 43(1) K. Inverse susceptibility in the paramagnetic region above 120 K follows the Curie-Weiss law, resulting in a magnetic moment of 6.33(1) μ B per formula unit. Neutron diffraction data collected at 7.5 K reveal that the magnetic moments of Nd 3+ and Mn 3+ in NdMnTiO 5 are incommensurately ordered with a propagation vector $k$ = (0, 0.238, 0.117).

36 MATERIALS SCIENCE↗
DOE OSTI2020

Design of higher valency in covalent organic frameworks

The valency (connectivity) of building units in covalent organic frameworks (COFs) has been primarily 3 and 4, corresponding to triangles and squares or tetrahedrons, respectively. We report a strategy for making COFs with valency 8 (cubes) and “infinity” (rods). The linker 1,4-boronophenylphosphonic acid—designed to have boron and phosphorus as an isoelectronic combination of carbon-group elements—was condensed into a porous, polycubane structure (BP-COF- 1 ) formulated as (–B 4 P 4 O 12 –)(–C 6 H 4 –) 4 . It was characterized by x-ray powder diffraction techniques, which revealed cubes linked with phenyls. The isoreticular forms (BP-COF- 2 to 5 ) were similarly prepared and characterized. Large single crystals of a constitutionally isomeric COF (BP-COF- 6 ), composed of rod units, were also synthesized using the same strategy, thus propelling COF chemistry into a new valency regime.

Gropp, Cornelius↗
DOE OSTI2017

pH-Dependent Single-Step Rapid Synthesis of CuO Nanoparticles and Their Optical Behavior

This paper reports the pH-dependent growth of copper oxide (CuO) nanoparticles by wet chemical precipitation method using pH value of the samples as the only variable parameter. The phase purity, morphology, optical behavior, and elemental analysis of synthesized nanoparticles are shown to be critically dependent on the pH of the samples. Scanning electron microscope (SEM) results shows that a higher pH results well-defined CuO nanoflakes. X-ray powder diffraction (XRD) results disclosed that the growth of pure CuO with monoclinic structure at higher pH 8, whereas mixed phase was formed at lower pH 7. The average crystallite size of samples prepared at pH 8 to 10 was varying from 23.36 to 25.78 nm. The infrared spectroscopy showed that the O–H stretching peaks become narrow with an increase in the pH value. Optical results revealed the existence of the sharp absorption edges with precise excitonic features and photoluminescence bands both located at visible and near infrared spectral region attributed to the excellent optical behavior and narrow size distribution of particles. The additional near infrared band in photoluminescence spectrum located at 860 nm is attributed the defect-related luminescence. The growth mechanism of CuO nanostructures was discussed in the light of our findings.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Structure and thermal behavior of a nickel complex based on a V-shaped bis(4-(1H-imidazol-1-yl)phenyl)amine ligand

A new coordination polymer ([Ni(BIPA)(bpdc)(H{sub 2}O){sub 2}]){sub n} has been prepared based on a new V-shaped bis(4-(1H-imidazol-1-yl)phenyl)amine (BIPA) ligand. Complex was characterized by elemental analysis, IR spectra, X-ray powder diffraction, thermal analysis and single crystal X-ray analysis. Complex exhibits a 1D → 3D structure. Hydrogen bonds play an important role in the formation of supramolecular network structure. Thermal analysis indicates that complex exhibits a high thermal stability.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Total-scattering pair-distribution function analysis of zinc from high-energy synchrotron data

The crystal structure of zinc metal deviates from the ideal hexagonal close packing structure by a significantly increased axial ratio (c/a). The local atomic structure of zinc metal is investigated using the total scattering atomic pair distribution function (PDF) analysis based on X-ray powder diffraction data collected at ambient conditions. The X-ray total scattering PDF analysis confirms that the crystal structure of zinc can be described in terms of wurtzite structure, but with an anomalously atomic displacement parameters U 33 , indicating a significant displacement disorder along the c-axis. For the long r-range PDF refinements, the thermal motion of zinc shows a notable anisotropy as expressed by the ratio U 33 /U 11 of 2.5 at ambient conditions. This average distortion level along the c-axis, was not reflected locally for the features below 5.0 Å as it fits the high r region. Based on PDF refinements over different r-ranges, we measure an interesting increase of the U 33 value with decreasing the r-range of the refinement. Finally, this suggests that the local structure features in zinc metal differ from the average structure ones.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Thermal annealing of natural, radiation-damaged pyrochlore

Abstract Radiation damage in minerals is caused by the α-decay of incorporated radionuclides, such as U and Th and their decay products. The effect of thermal annealing (400–1000 K) on radiation-damaged pyrochlores has been investigated by Raman scattering, X-ray powder diffraction (XRD), and combined differential scanning calorimetry/thermogravimetry (DSC/TG). The analysis of three natural radiation-damaged pyrochlore samples from Miass/Russia [6.4 wt% Th, 23.1·10

nuclear (including radiation effects), materials a↗
DOE OSTI2020

Multi-Scale Lithofacies and Chemostratigraphic Analysis of Two Middle Devonian Marcellus Shale Wells in Northern West Virginia, USA

The Marcellus Shale Energy and Environmental Laboratory (MSEEL) consists of two project areas within the dry gas producing region of the Marcellus shale play in Monongalia County, West Virginia. MSEEL is a collaborative field project led by West Virginia University, with Northeast Natural Energy LLC, several industrial partners, and sponsored by the US Department of Energy National Energy Technology Laboratory. The study areas are drilled approximately 8.5 miles apart to better understand the vertical and lateral changes in stratigraphy over a short distance. Two vertical pilot wells, MIP-3H and Boggess 17H were drilled in the fall of 2015 and spring of 2019, respectively. Core was recovered from the MIP-3H (API: 47-061-01707-00-00) 112 feet (34m) between depths of 7445 to 7557 feet, and from the Boggess 17H (API: 47-061-01812-00-00) 139 feet (42m) between depths of 7908 and 8012 ft. A full suite of triple combo (gamma ray, neutron, density logs), image logs, and advanced logging tools were run in both wells and calibrated to core analysis. Core analysis includes medical computed tomography (CT) scans, mineralogy and chemostratigraphy determined from handheld X-Ray fluorescence (hhXRF) and X-Ray powder diffraction (XRD) measurements, and determination of total organic content (TOC). Lithofacies were determined at core-scale using traditional core description techniques and medical CT-scan images. Log-scale facies are based on mineralogy and TOC data and developed using petrophysical logging data calibrated to core data (XRD and pyrolysis data). Chemostratigraphic analysis utilized hhXRF data to determine the major and trace element trends in the cores. In the two wells six shale lithofacies were recognized at the core and log scale. Both wells show organic-rich facies (TOC > 6.5%) primarily in the middle and lower Marcellus, with a slight decrease in thickness of this interval in the Boggess 17H. This interval is interpreted as an increase in paleo-productivity (increased Ni, Zn, and V), decreased sedimentation (decreased detrital proxies), and anoxic to euxinic conditions (increased Mo and chalcophile elements). Paleo-redox conditions in both wells are dynamic throughout deposition transitioning between euxinic/anoxic to dysoxic/oxic. This trend is seen through elemental proxies and calcite/pyrite concretion distributions.

03 NATURAL GAS↗
DOE OSTI2016

Elasticity and phase transformation at high pressure in coesite from experiments and first-principles calculations

Here, the crystal structure and equation of state of coesite (space group C2/ c ) and its high pressure polymorph coesite-II (space group P2 1 / n ) under pressure have been studied using X-ray powder diffraction in a diamond anvil cell (DAC) up to 31 GPa at room temperature and first-principles calculations at 0 K up to 45 GPa. New diffraction peaks appear above 20 GPa, indicating the formation of coesite-II structure. The calculated enthalpies provide theoretical support for the pressure-induced phase transformation from coesite to coesite-II at ~21.4 GPa. Compared with coesite, the coesite-II structure is characterized by a ‘doubled’ b -axis and the breakdown of the linear Si1-O1-Si1 angle in coesite into two distinct angles - one is ~176°, close to linear, whereas the other decreases by 22° to 158°. Coesite is very anisotropic with the a -axis the shortest and twice more compressible than the b- and c-axis. By comparison, coesite-II is not so anisotropic with similar compressibilities in its a-, b-, and c -axis. As analyzed by a third-order Eulerian finite strain equation of state, the bulk modulus of coesite at 21.4 GPa is 182.3GPa, and that of coesite-II is 140.8 GPa, indicating that coesite-II is much more compressible than coesite. Furthermore, the existence of coesite-II in the coldest subduction zone will change the elasticity and anisotropic properties of the subducting materials dramatically.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Bobfinchite, Na[(UO2)8O3(OH)11]·10H2O, a new Na-bearing member of the schoepite family

Abstract The new mineral bobfinchite (IMA2020-082), Na[(UO2)8O3(OH)11]·10H2O, was found in the Burro mine, Slick Rock district, San Miguel County, Colorado, U.S.A., where it occurs as an oxidation product of uraninite on asphaltite matrix in intimate association with gypsum, natrozippeite, metaschoepite, and uranopilite. Bobfinchite crystals are transparent to translucent, yellow, lozenge-shaped disks up to 0.3 mm wide. Crystals are flattened on [100] and exhibit the forms {100}, {011}, {021}, {021}, and {011}. Bobfinchite has a pale-yellow streak and emits very dim yellow fluorescence under 365 nm ultraviolet illumination. The crystals are brittle with very good {100} cleavage and irregular, stepped fracture. The Mohs hardness is ca. 2 based on scratch tests. The calculated density is 5.044 g/cm3 based on the empirical formula and 5.036 g/cm3 for the ideal formula. Bobfinchite is optically biaxial (–), with α = 1.690(5), β = 1.7205(5), and γ = 1.730(5) (white light). The measured 2V, estimated from the interference figure, is 55(5)° and the calculated value is 59.1°. Dispersion is moderate, r > v; orientation: X = a, Y = b, Z = c; pleochroism: X nearly colorless, Y yellow, Z yellow; X < Y ≈Z. Electron microprobe analysis provided the empirical formula (Na0.99Pb0.02)[(UO2)7.99O3(OH)11]·10H2O. The five strongest X-ray powder diffraction lines are [dobs in Å(I)(hkl)]: 7.34(100)(200), 3.59(50)(024), 3.23(60)(224), 3.18(36)(240), and 2.01(23)(624,551,208,640,346). Bobfinchite is orthorhombic, Pbcn, a = 14.6249(9), b = 14.0389(10), c = 16.6923(10) Å, V = 3427.2(4) Å3, and Z = 4. The structure of bobfinchite (R1 = 0.0330 for 3770 I > 4σI) is built from uranyl oxide-hydroxide sheets that adopt the fourmarierite topology, with interlayer Na+ and H2O groups. Both the sheet and interlayer topology mimic those observed in natural and synthetic Na-metaschoepites studied previously, and as seen in other uranyl oxide hydrate minerals, charge balance is achieved at specific sites in the sheet through the substitution O2– ↔ (OH)–.

Geochemistry & Geophysics↗
DOE OSTI2013

High-pressure phase transitions of Fe 3-x Ti x O 4 solid solution up to 60 GPa correlated with electronic spin transition

The structural phase transition of the titanomagnetite (Fe 3–x Ti x O 4 ) solid solution under pressures up to 60 GPa has been clarified by single-crystal and powder diffraction studies using synchrotron radiation and a diamond-anvil cell. Present Rietveld structure refinements of the solid solution prove that the prefered cation distribution is based on the crystal field preference rather than the magnetic spin ordering in the solid solution. The Ti-rich phases in 0.734 ≤ x ≤1.0 undergo a phase transformation from the cubic spinel of Fd3m to the tetragonal spinel structure of I4 1 /amd with c/a < 1.0. The transition is driven by a Jahn-Teller effect of IV Fe 2+ (3d 6 ) on the tetrahedral site. The c/a < 1 ratio is induced by lifting of the degeneracy of the e orbitals by raising the d x2-y2 orbital below the energy of the d z2 orbital. The distortion characterized by c/a < 1 is more pronounced with increasing Ti content in the Fe 3–x Ti x O 4 solid solutions and with increasing pressure. An X-ray emission experiment of Fe 2 TiO 4 at high pressures confirms the spin transition of FeKβ from high spin to intermediate spin (IS) state. The high spin (HS)-to-low spin (LS) transition starts at 14 GPa and the IS state gradually increases with compression. The VI Fe 2+ in the octahedral site is more prone for the HS-to-LS transition, compared with Fe 2+ in the fourfold- or eightfold-coordinated site. The transition to the orthorhombic post-spinel structure with space group Cmcm has been confirmed in the whole compositional range of Fe 3–x Ti x O 4 . The transition pressure decreases from 25 GPa (x = 0.0) to 15 GPa (x = 1.0) with increasing Ti content. There are two cation sites in the orthorhombic phase: M1 and M2 sites of eightfold and sixfold coordination, respectively. Fe 2+ and Ti 4+ are disordered on the M2 site. This structural change is accelerated at higher pressures due to the spin transition of Fe 2+ in the octahedral site. This is because the ionic radius of VI Fe 2+ becomes 20% shortened by the spin transition. At 53 GPa, the structure transforms to another high-pressure polymorph with Pmma symmetry with the ordered structure of Ti and Fe atoms in the octahedral site. This structure change results from the order-disorder transition.

Yamanaka, Takamitsu↗
DOE OSTI2013

Novel dense membrane for hydrogen separation for energy applications

The main objectives of this project are: (1) Characterization of the thermo mechanical properties of the novel dense HTM bulk sample; (2) Development of a correlation among the intrinsic factors (such as grain size and phase distribution), and the extrinsic factors (such as temperature and atmosphere) and the thermo-mechanical properties (such as strengths and stress) to predict the performance of a HTM system (HTM membrane and porous substrate) ; and (3) Evaluation of the stability of the novel HTM membrane and its property correlations after thermal cycling. Based on all results and analysis of the thermo mechanical properties for the HTM cermet bulk samples, several important conclusions were made. The mean σfs at room temperature is approximately 356 MPa for the HTM cermet. The mean σfs value decreases to 284 MPa as the temperature increases to 850?C. The Difference difference in atmosphere, such as air or N2, had an insignificant effect on the flexural strength values at 850?C for the HTM cermet. The HTM cermet samples at room temperature and at 500?C fractured without any significant plastic deformation. Whereas, at 850?C, the HTM cermet samples fractured, preceded by an extensive plastic deformation. It seems that the HTM cermet behaves more like an elastic material such as a nonmetal ceramic at the room temperature, and more like a ductile material at increased temperature (850?C). The exothermic peak during the TG/DTA tests centered at 600?C is most likely associated with both the enthalpy change of transformation from the amorphous phase into crystalline zirconia and the oxidation of Pd phase in HTM cermet in air. The endothermic peak centered at 800?C is associated with the dissociation of PdO to Pd for the HTM cermet sample in both inert N2 environment and air. There is a corresponding weight gain as oxidation occurs for palladium (Pd) phase to form palladium oxide (PdO) and there is a weight loss as the unstable PdO is dissociated back to Pd and oxygen. The normal stress and shear stresses from the Mohr?s circle indicate that the residual stress in the HTM cermet sample is mainly as compressive residual stress in the magnitude of -135 to -155 MP, and with very little shear stress (in the magnitude of 10 MPa). The magnitude of change in the normal stress and the shear stress is insignificant in the HTM after 120 thermal cycles. However, the principle normal stress changes from compressive to tensile residual stress and there is a significant increase in the shear stress after 500 thermal cycles. The calculated value based on the equation and the Mohr?s circle is found to be consistent with the experimental value for the as-received HTM cermet samples. At some rotation (φ) angle, the residual stress was found to be as tensile stress. Most ceramic material is weak in tension, and develops microscopic cracks. With treatment of 120 thermal cycles between 50?850?C, the HTM- sample exhibited thermally-induced cracks on the surface. Visually observable cracks appeared on the surface of HTM cermet with continuous thermal cycling, after 500 thermal cycles. The XRD powder diffraction analysis indicated an increased amount of crystalline PdO crystalline in HTM cermet after 120 and 500 thermal cycles as compare to the as-received samples. The Pd crystalline peaks were found to significantly decrease in peak intensity with thermal cycling. Higher peak intensity for PdO phase was observed with increased number of thermal cycles. A Monoclinic monoclinic zirconia phase was first identified in the as-received HTM as-received sample. However, with thermal cycling treatment of both 120 and 500 thermal cycles, the M-ZrO2 phase is transformed to the tetragonal YSZ, which is consistent with the thermal analysis results by TG/DTA. Correlations of the microstructural and thermo-mechanical properties of both selected reference material and ANL-3e HTM cermet bulk sample are affected mainly by porosity and microstructural features, such as grain size and pore size/distribution. The Young?s Modulus (E-value), especially, is positively proportional to the flexural strength for materials with similar crystallographic structure. For different crystallographic materials, physical properties such as E and density are independent of mechanical properties, such as flexural strength.. Microstructural properties, particularly, grain size and crystallographic structure, and thermodynamic properties are the main factors affecting the mechanical properties at both room and high temperatures. The oxidation and the plasticity of Pd phase mainly affect the mechanical properties of HTM cermet at high temperature or with thermal cycling treatment. Changes in the residual stress and microstructure affect the mechanical properties of HTM when subjected to high temperature or thermal cycling treatment.

08 HYDROGEN↗
DOE OSTI2015

A hard X-ray study of a manganese-terpyridine catalyst in a chromium-based Metal Organic Framework

Hydrogen produced from water splitting is a promising source of clean energy. However, a robust catalyst is necessary to carry out the water oxidation step of water splitting. In this study, the catalyst studied was [(terpy)Mn(μ-O)2Mn(terpy)] 3+ (MnTD) synthesized in the Metal Organic Framework (MOF) MIL-101(Cr), and the method used for analysis was hard X-ray powder diffraction. The diffraction data was used to detect the presence of MOF in different catalytic stages, and lattice parameters were assigned to the samples containing MOF. Fourier maps were constructed with GSAS II to determine the contents of the MOF as preliminary studies suggested that MnTD may not be present. Results showed that MOF is present before catalysis occurs but disappears by the time 45 minutes of catalysis has ensued. Changes in the MOF’s lattice parameters and location of electron density in the Fourier maps suggest attractions between the MOF and catalyst that may lead to MOF degradation. Fourier maps also revealed limited, if any, amounts of MnTD, even before catalysis occurred. Molecular manganese oxide may be the source of the high rate of water oxidation catalysis in the studied system.

08 HYDROGEN↗
DOE OSTI2015

A Hard X-ray Study of a Manganese-Terpyridine Dimer Catalyst in a Chromium-Based Metal Organic Framework

Much of today’s scientific research is geared toward discovering clean energy from renewable sources. A promising approach is to split water into its fundamental elements – hydrogen and oxygen. The hydrogen produced from this process is a source of clean energy. Plants carry out this water splitting routinely as a part of photosynthesis, but we cannot do this readily as the reaction requires a lot of energy, negating the value of cleaner and plentiful energy from hydrogen. Adding a catalyst provides an alternative pathway for the reaction so that it can proceed with lower energy input. Many such catalysts have been developed; the one used in this study is manganese based and is called manganese-terpyridine dimer (MnTD). The problem is that when individual molecules of MnTD interact they destroy each other, which limits practical use of the catalyst. However, by placing the catalyst in a Metal Organic Framework (MOF), the molecules of MnTD can be separated so that, in principle, they do not interact with each other and only interact with water. The MOF is essentially a repetition of boxes, and each box should contain one MnTD molecule. However, preliminary studies showed that a different molecule, not MnTD, may be inside the boxes. My research focused on identifying which molecules are present in the MOF. The primary method of analysis used was x-ray powder diffraction, a technique in which x-rays are scattered by a sample, and the intensity of the scattered radiation is measured as a function of scattering angle. Three samples were analyzed; one contained only the MOF, one contained the MOF and catalyst before catalysis, and one contained the MOF and catalyst during catalysis. The diffraction experiments were carried out at the Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC National Accelerator Laboratory. Initial results revealed that the MOF structure falls apart during catalysis. To further analyze the data, I used several computer programs, including GSAS II, FOX, and VESTA. These programs allowed me to create maps that showed regions of electron density within the MOF and gave me clues as to which molecules were present. I found that MnTD was not the catalytic molecule in the MOF. The preliminary studies showed that manganese oxide is likely present, which is consistent with by data. However, the catalytic rate for this system is much higher than that reported for manganese oxide, and thus future studies are needed to verify the identity of the catalytic molecule and determine the reasons for its unusually high rate of catalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

A Hard X-ray Study of a Manganese-Terpyridine Dimer Catalyst in a Chromium-based Metal Organic Framework - Oral Presentation [Slides]

Cleaner forms of energy are needed, and H 2 produced from water splitting is a possible source. However, a robust catalyst is necessary to carry out the water oxidation reaction. Plants utilize Photosystem II to catalyze water oxidation as a part of photosynthesis, and many synthetic water oxidation catalysts use Photosystem II as a model. In this study, the catalyst of interest was [(terpy)Mn(μ-O)2Mn(terpy)]3+ (MnTD), which was synthesized in a chromium-based Metal Organic Framework (MOF) to avoid degradation of MnTD molecules. Hard X-ray powder diffraction was the primary method of analysis. The diffraction data was used to detect the presence of MOF in samples at different catalytic stages, and lattice parameters were assigned to the samples containing MOF. Fourier maps were constructed to determine the contents of the MOF as preliminary studies suggested that MnTD may not be present. Results showed that MOF is present before catalysis occurs, but disappears in the initial stages of catalysis. Changes in the MOF’s lattice parameters suggest attractive interactions between the MOF and catalyst; these interactions may lead to the observed MOF degradation. Fourier maps also reveal limited, if any, amounts of MnTD in the system. Molecular manganese oxide may be the source of the high rate of water oxidation catalysis in the studied system.

08 HYDROGEN↗
DOE OSTI2016

Additive Manufacturing of Near-net Shaped Permanent Magnets

The technical objective of this technical collaboration phase I proposal is to fabricate near net-shaped permanent magnets using alloy powders utilizing direct metal deposition technologies at the ORNL MDF. Direct Manufacturing using the POM laser system was used to consolidate Nd 2 Fe 14 B (NdFeB) magnet powders into near net-shape parts efficiently and with virtually no wasted material as part of the feasibility study. We fabricated builds based on spherical NdFeB magnet particles. The results show that despite the ability to fabricate highly reactive materials in the laser deposition process, the magnetic coercivity and remanence of the NdFeB hard magnets is significantly reduced. X-ray powder diffraction in conjunction with electron microscopy showed that the material experienced a primary Nd 2 Fe 17 B x solidification due to the undercooling effect (>60K). Consequently the presence of alpha iron phase resulted in deterioration of the build properties. Further optimization of the processing parameters is needed to maintain the Nd 2 Fe 14 B phase during fabrication.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Nuclear Technology Research and Development (NTRD) Technical Monthly December FY18

Neutron time-of-flight powder diffraction was conducted on three U-Si samples with nominal compositions of USi 1.70 , U 3 Si 2.00 , and U 3 Si 2.01 between room temperature and 1100°C. The data will provide information on the crystal structure evolution over this temperature range, thus covering operation as well as accident temperatures. The main phase, U 3 Si 5 (USi 1.67 ), has a hexagonal crystal structure and the diffraction analysis will provide the thermal expansion coefficients for the a and c crystal axes separa tely, which have not been determined in the literature to date. Furthermore, atomic positions and anisotropic thermal motion parameters will be determined, from which parameters such as bond lengths can be derived as a function of temperature.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

28ID1 - PDF Beamline Radiation Shielding Analysis

The high flux hard x-ray damping wiggler (DW100) located in cell 28-ID provides a synchrotron source for the X-ray Powder Diffraction (XPD) beamline and the Pair Distribution Function (PDF) beamline. The primary purpose of these beamlines is the quantitative characterization of the atomic structure of complex materials; not just carefully prepared ideal systems, but materials as they are actually used.

36 MATERIALS SCIENCE↗