Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Yb”

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 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Yb2S3 by Materials Project

Yb2S3 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. there are four inequivalent Yb3+ sites. In the first Yb3+ site, Yb3+ is bonded to six S2- atoms to form a mixture of edge and corner-sharing YbS6 octahedra. There are a spread of Yb–S bond distances ranging from 2.66–3.02 Å. In the second Yb3+ site, Yb3+ is bonded in a 6-coordinate geometry to six S2- atoms. There are a spread of Yb–S bond distances ranging from 2.69–3.09 Å. In the third Yb3+ site, Yb3+ is bonded to seven S2- atoms to form distorted YbS7 pentagonal bipyramids that share a cornercorner with one YbS6 octahedra, edges with two equivalent YbS6 octahedra, and edges with three equivalent YbS7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 89°. There are a spread of Yb–S bond distances ranging from 2.69–3.08 Å. In the fourth Yb3+ site, Yb3+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Yb–S bond distances ranging from 2.77–3.03 Å. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to three Yb3+ and one S2- atom. The S–S bond length is 2.10 Å. In the second S2- site, S2- is bonded in a 5-coordinate geometry to four Yb3+ and one S2- atom. The S–S bond length is 2.11 Å. In the third S2- site, S2- is bonded in a 1-coordinate geometry to six Yb3+ atoms. In the fourth S2- site, S2- is bonded in a 6-coordinate geometry to six Yb3+ atoms. In the fifth S2- site, S2- is bonded in a distorted tetrahedral geometry to three Yb3+ and one S2- atom. In the sixth S2- site, S2- is bonded in a 5-coordinate geometry to four Yb3+ and one S2- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on YbHo3 by Materials Project

YbHo3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb is bonded to twelve Ho atoms to form YbHo12 cuboctahedra that share corners with four equivalent YbHo12 cuboctahedra, corners with eight equivalent HoYb4Ho8 cuboctahedra, edges with eight equivalent YbHo12 cuboctahedra, edges with sixteen equivalent HoYb4Ho8 cuboctahedra, faces with four equivalent YbHo12 cuboctahedra, and faces with fourteen HoYb4Ho8 cuboctahedra. There are four shorter (3.56 Å) and eight longer (3.57 Å) Yb–Ho bond lengths. There are two inequivalent Ho sites. In the first Ho site, Ho is bonded to four equivalent Yb and eight Ho atoms to form HoYb4Ho8 cuboctahedra that share corners with twelve equivalent HoYb4Ho8 cuboctahedra, edges with eight equivalent YbHo12 cuboctahedra, edges with sixteen HoYb4Ho8 cuboctahedra, faces with four equivalent YbHo12 cuboctahedra, and faces with fourteen HoYb4Ho8 cuboctahedra. There are four shorter (3.56 Å) and four longer (3.57 Å) Ho–Ho bond lengths. In the second Ho site, Ho is bonded to four equivalent Yb and eight equivalent Ho atoms to form HoYb4Ho8 cuboctahedra that share corners with four equivalent HoYb4Ho8 cuboctahedra, corners with eight equivalent YbHo12 cuboctahedra, edges with twenty-four HoYb4Ho8 cuboctahedra, faces with six equivalent YbHo12 cuboctahedra, and faces with twelve HoYb4Ho8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb4CdS7 by Materials Project

Yb4CdS7 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are four inequivalent Yb3+ sites. In the first Yb3+ site, Yb3+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Yb–S bond distances ranging from 2.71–3.34 Å. In the second Yb3+ site, Yb3+ is bonded to seven S2- atoms to form distorted YbS7 pentagonal bipyramids that share corners with six YbS6 octahedra, edges with two equivalent CdS6 octahedra, edges with four YbS6 octahedra, and faces with two equivalent YbS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 11–49°. There are a spread of Yb–S bond distances ranging from 2.72–3.13 Å. In the third Yb3+ site, Yb3+ is bonded to six S2- atoms to form YbS6 octahedra that share a cornercorner with one YbS6 octahedra, a cornercorner with one CdS6 octahedra, corners with four equivalent YbS7 pentagonal bipyramids, edges with two equivalent YbS6 octahedra, and an edgeedge with one YbS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 77–80°. There are a spread of Yb–S bond distances ranging from 2.68–2.87 Å. In the fourth Yb3+ site, Yb3+ is bonded to six S2- atoms to form YbS6 octahedra that share a cornercorner with one YbS6 octahedra, corners with two equivalent CdS6 octahedra, corners with two equivalent YbS7 pentagonal bipyramids, edges with two equivalent YbS6 octahedra, edges with three equivalent CdS6 octahedra, and edges with three equivalent YbS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 2–80°. There are a spread of Yb–S bond distances ranging from 2.66–2.95 Å. Cd2+ is bonded to six S2- atoms to form distorted CdS6 octahedra that share corners with three YbS6 octahedra, edges with two equivalent CdS6 octahedra, edges with three equivalent YbS6 octahedra, and edges with two equivalent YbS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 2–77°. There are a spread of Cd–S bond distances ranging from 2.52–3.04 Å. There are seven inequivalent S2- sites. In the first S2- site, S2- is bonded in a 6-coordinate geometry to four Yb3+, one Cd2+, and one S2- atom. The S–S bond length is 2.13 Å. In the second S2- site, S2- is bonded in a 4-coordinate geometry to three Yb3+, two equivalent Cd2+, and one S2- atom. The S–S bond length is 2.11 Å. In the third S2- site, S2- is bonded in a 5-coordinate geometry to four Yb3+ and one S2- atom. In the fourth S2- site, S2- is bonded in a 5-coordinate geometry to four Yb3+ and one S2- atom. In the fifth S2- site, S2- is bonded in a rectangular see-saw-like geometry to three Yb3+ and one Cd2+ atom. In the sixth S2- site, S2- is bonded to four Yb3+ atoms to form SYb4 trigonal pyramids that share corners with two equivalent SYb4 trigonal pyramids and edges with two equivalent SYb4Cd2 octahedra. In the seventh S2- site, S2- is bonded to four Yb3+ and two equivalent Cd2+ atoms to form SYb4Cd2 octahedra that share edges with two equivalent SYb4Cd2 octahedra and edges with two equivalent SYb4 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb2TeO6 by Materials Project

Yb2TeO6 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are four inequivalent Yb3+ sites. In the first Yb3+ site, Yb3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Yb–O bond distances ranging from 2.36–2.58 Å. In the second Yb3+ site, Yb3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Yb–O bond distances ranging from 2.31–2.82 Å. In the third Yb3+ site, Yb3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Yb–O bond distances ranging from 2.25–2.66 Å. In the fourth Yb3+ site, Yb3+ is bonded in a 4-coordinate geometry to seven O2- atoms. There are a spread of Yb–O bond distances ranging from 2.20–2.73 Å. There are two inequivalent Te6+ sites. In the first Te6+ site, Te6+ is bonded in a distorted octahedral geometry to six O2- atoms. All Te–O bond lengths are 1.95 Å. In the second Te6+ site, Te6+ is bonded in a distorted octahedral geometry to six O2- atoms. There are a spread of Te–O bond distances ranging from 1.87–2.39 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Yb3+ and one Te6+ atom. In the second O2- site, O2- is bonded to three Yb3+ and one Te6+ atom to form distorted corner-sharing OYb3Te tetrahedra. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Yb3+ and one Te6+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to three Yb3+ and one Te6+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two Yb3+, one Te6+, and one O2- atom. The O–O bond length is 1.42 Å. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two Yb3+ and one Te6+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to two Yb3+, one Te6+, and one O2- atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to three Yb3+ and one Te6+ atom. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Yb3+ and one Te6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

A New Class of Proton Conductors with Dramatically Enhanced Stability and High Conductivity for Reversible Solid Oxide Cells

Reversible solid oxide cells based on proton conductors (P-ReSOCs) have potential to be the most efficient and low-cost option for large-scale energy storage and power generation, holding promise as an enabler for the implementation of intermittent renewable energy technologies and the widespread utilization of hydrogen. Here, the rational design of a new class of hexavalent Mo/W-doped proton-conducting electrolytes with excellent durability while maintaining high conductivity is reported. Specifically, BaMo(W) 0.03 Ce 0.71 Yb 0.26 O 3-δ exhibits dramatically enhanced chemical stability against high concentrations of steam and carbon dioxide than the state-of-the-art electrolyte materials while retaining similar ionic conductivity. In addition, P-ReSOCs based on BaW 0.03 Ce 0.71 Yb 0.26 O 3-δ demonstrate high peak power densities of 1.54, 1.03, 0.72, and 0.48 W cm –2 at 650, 600, 550, and 500 °C, respectively, in the fuel cell mode. During steam electrolysis, a high current density of 2.28 A cm –2 is achieved at a cell voltage of 1.3 V at 600 °C, and the electrolysis cell can operate stably with no noticeable degradation when exposed to high humidity of 30% H 2 O at –0.5 A cm –2 and 600 °C for over 300 h. Altogether, this work demonstrates the promise of donor doping for obtaining proton conductors with both high conductivity and chemical stability for P-ReSOCs.

25 ENERGY STORAGE↗
DOE OSTI2021

A systematic study of lanthanide titanates (A 2 Ti 2 O 7 ) chemical durability: corrosion mechanisms and control parameters

Dense lanthanide titanates ranging from La 2 Ti 2 O 7 to Yb 2 Ti 2 O 7 were synthesized by spark plasma sintering with similar micro-sized microstructure, and their chemical durability and degradation mechanisms were investigated by semi-dynamic leaching tests. Different corrosion mechanisms from incongruent to congruent dissolution were observed with preferential elemental releases of lanthanides in A 2 Ti 2 O 7 (A = La to Gd) and Ti in Er 2 Ti 2 O 7 and Yb 2 Ti 2 O 7 . Initial leaching was controlled by surface dissolution and long-term dissolution shifted to a diffusion-controlled mechanism for titanate pyrochlores from Sm 2 Ti 2 O 7 to Yb 2 Ti 2 O 7 . Both short-term and long-term leaching rates decreased from La 2 Ti 2 O 7 to Yb 2 Ti 2 O 7 , and materials became more corrosion resistant with decreasing ionic radius ratios of the rare-earth elements and titanium. Amorphous passivation films of several nm-thick enriched with Ti formed on the surfaces of the corroded materials, and the formation mechanisms were governed either by surface reorganization with preferential release of lanthanides or dissolution-precipitation from saturated bulk solutions with preferential release of titanium. Finally, these results demonstrate that the ionic size plays a dominant role in determining chemical durability of lanthanide titanates and a strong correlation is established among chemical composition/structural variation, passivation film formation and corrosion mechanisms, and materials chemical durability.

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

On plasticity-enhanced interfacial toughness in bonded joints

Here, the performance and reliability of many structures and components depend on the integrity of interfaces between dissimilar materials. Interfacial toughness Γ is the key material parameter that characterizes resistance to interfacial crack growth, and Γ is known to depend on many factors including temperature. For example, previous work showed that the toughness of an epoxy/aluminum interface decreased 40 % as the test temperature was increased from -60 °C to room temperature (RT). Interfacial integrity at elevated temperatures is of considerable practical importance. Recent measurements show that instead of continuing to decrease with increasing temperature, Γ increases when test temperature is above RT. Cohesive zone finite element calculations of an adhesively bonded, asymmetric double cantilever beam specimen of the type used to measure Γ suggest that this increase in toughness may be a result of R-curve behavior generated by plasticity-enhanced toughening during stable subcritical crack growth with interfacial toughness defined as the critical steady-state limit value. In these calculations, which used an elastic-perfectly plastic epoxy model with a temperature-dependent yield strength, the plasticity-enhanced increase in Γ above its intrinsic value Γ o depended on the ratio of interfacial strength σ* to the yield strength σyb of the bond material. There is a nonlinear relationship between Γ/Γ o and σ*/σ yb with the value Γ/Γ o increasing rapidly above a threshold value of σ*/σ yb . The predicted increase in toughness can be significant. For example, there is nearly a factor of two predicted increase in Γ/Γ o during micrometer-scale crack-growth when σ*/σ yb = 2 (a reasonable choice for σ*/σ yb ). Furthermore, contrary to other reported results, plasticity-enhanced toughening can occur prior to crack advance as the cohesive zone forms and the peak stress at the tip of the original crack tip translates to the tip of the fully formed cohesive zone. These results suggest that plasticity-enhanced toughening should be considered when modeling interfaces at elevated temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2023

DFT-based investigation of solvation of Nd(III)/Yb(III) cations in room-temperature ionic-liquid

We report a DFT study on the solvation of bare rare-earth (RE) cations [Nd(III) and Yb(III)] in the room-temperature ionic-liquid (RTIL) based on 1,3-dimethyl-imidazolium + , PF 6 - , [MMI][PF 6 ]. In the present article, we aim to investigate whether the chosen RTIL can preferentially solvate any of the RE cations under study. First, the RTIL binding to the RE cation is studied in the gas phase, and then explored with continuum solvation model employing RTIL parameters. First, we considered the formation of the first solvation shell, where the PF 6 - anions directly bond with the Ln(III) cation. We then further surrounded the first solvation shell with [MMI]+ cations to form the second solvation shell. The stability of PF 6 - coordinated complexes is studied by calculating the binding energy values. The number of PF 6 - anions for both Ln(III) cations starts with three ligands and goes until the maximum binding energy in the RTIL medium is reached. The coordination number and binding modes of PF 6 - depend on the size of the RE cation. Comparing the binding energy values between the RE cations for the first solvation shell complexes, it is noticed that Yb-complexes have relatively greater binding energy than Nd-complexes. We have further performed a Boltzmann population analysis to find out the most dominant conformer among each category of PF 6 - coordinated complexes. A study using Natural Population Analysis shows that after complexation with PF 6 - the charge on the Yb-centers lower to a greater extent than Nd-centers, implying stronger bonding between Yb and PF 6 - , which is in harmony with the binding energy analysis. Overall, the computational investigation provides an in-depth understanding of the complexation phenomena of RE cations in RTIL, which can be useful for the practical separation of RE cations using RTIL.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Towards understanding the magnetic properties of the breathing pyrochlore compound Ba3Yb2Zn5O11through single-crystal studies

Abstract Ba 3 Yb 2 Zn 5 O 11 is exceptional among breathing pyrochlore compounds for being in the nearly-decoupled limit where inter-tetrahedron interactions are weak, hosting isolated clusters or molecular magnet-like tetrahedra of magnetic ytterbium (Yb 3+ ) ions. In this work, we present the study carried out on single-crystal samples of the breathing pyrochlore Ba 3 Yb 2 Zn 5 O 11 , using a variety of magnetometry and neutron scattering techniques along with theoretical modeling. We employ inelastic neutron scattering to investigate the magnetic dynamics as a function of applied field (with respect to both magnitude and direction) down to a temperature of 70 mK, where inelastic scattering reveals dispersionless bands of excitations as found in earlier powder sample studies, in good agreement with a single-tetrahedron model. However, diffuse neutron scattering at zero field and dc-susceptibility at finite field exhibit features suggesting the presence of excitations at low-energy that are not captured by the single tetrahedron model. Analysis of the local structure down to 2 K via pair distribution function analysis finds no evidence of structural disorder. We conclude that effects beyond the single tetrahedron model are important in describing the low-energy, low-temperature physics of Ba 3 Yb 2 Zn 5 O 11 , but their nature remains undetermined.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Finding the order in complexity: The electronic structure of 14-1-11 zintl compounds

Yb 14 MnSb 11 and Yb 14 MgSb 11 have rapidly risen to prominence as high-performing p-type thermoelectric materials. However, the fairly complex crystal structure of A 14 MX 11 Zintl compounds renders the interpretation of the electronic band structure obscure, making it difficult to chemically guide band engineering and optimization efforts. In this work, we delineate the valence-balanced Zintl chemistry of A 14 MX 11 compounds using the molecular orbital theory. By analyzing the electronic band structures of Yb 14 MgSb 11 and Yb 14 AlSb 11 , we show that the conduction band minimum is composed of either an antibonding molecular orbital originating from the (Sb 3 ) 7– trimer or a mix of atomic orbitals of A, M, and X. The singly degenerate valence band is comprised of non-bonding Sb pz orbitals primarily from the Sb atoms in the (MSb 4 ) m– tetrahedra and of isolated Sb atoms distributed throughout the unit cell. Such a chemical understanding of the electronic structure enables strategies to engineer electronic properties (e.g., the bandgap) of A 14 MX 11 compounds.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Magnetic structure and multiferroicity of Sc-substituted hexagonal YbFeO 3

The hexagonal rare-earth ferrite RFeO 3 family represents a unique class of multiferroics exhibiting weak ferromagnetism, and a strong coupling between magnetism and structural trimerization is predicted. However, the hexagonal structure for RFeO 3 remains metastable in conventional conditions. We have succeeded in stabilizing the hexagonal structure of polycrystalline YbFeO 3 by partial Sc substitution of Yb. Using bulk magnetometry and neutron diffraction, we find that Yb 0.42 Sc 0.58 FeO 3 orders into a canted antiferromagnetic state with the Néel temperature T N ~ 165K, below which the Fe 3+ moments form the triangular configuration in the ab plane and their in-plane projections are parallel to the [100] axis, consistent with magnetic space group P6 3 c'm'. It is determined that the spin canting is aligned along the c axis, giving rise to the weak ferromagnetism. Furthermore, the Fe 3+ moments reorient toward a new direction below reorientation temperature T R ~ 40K, satisfying magnetic subgroup P6 3 , while the Yb 3+ moments order independently and ferrimagnetically along the c axis at the characteristic temperature T Yb ~ 15K. Interestingly, reproducible modulation of electric polarization induced by magnetic field at low temperature is achieved, suggesting that the delicate structural distortion associated with two-up/one-down buckling of the Yb/Sc planes and tilting of the FeO 5 bipyramids may mediate the coupling between ferroelectric and magnetic orders under magnetic field. Furthermore, the present work represents substantial progress to search for high-temperature multiferroics in hexagonal ferrites and related materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Probing New Bosons and Nuclear Structure with Ytterbium Isotope Shifts

In this Letter, we present mass-ratio measurements on highly charged Yb 42+ ions with a precision of 4 ×10 -12 and isotope-shift measurements on Yb + on the 2 S 1/2 → 2 D 5/2 and 2 S 1/2 → 2 F 7/2 transitions with a precision of 4 ×10 -9 for the isotopes 168,170,172,174,176 Yb. We present a new method that allows us to extract higher-order changes in the nuclear charge distribution along the Yb isotope chain, benchmarking ab initio nuclear structure calculations. Additionally, we perform a King plot analysis to set bounds on a fifth force in the keV/c 2 to MeV/c 2 range coupling to electrons and neutrons.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2024

Holistic comparison of environmental barrier coating material candidates through design of a figure of merit

The first figure of merit for environmental barrier coating (EBC) materials was designed through a ranking system for material properties pertaining to established EBC failure modes in service. Seven past, present, and novel EBC candidate materials were used in the figure of merit design: SiO 2 , Ba 0.75 Sr 0.25 Al 2 Si 2 O 8 (BSAS), HfSiO 4 , Yb 2 Si 2 O 7 , Yb 2 SiO 5 , Yb 2 O 3 , and YbPO 4 . Utilizing compiled data from the literature, the presented figure of merit verified Yb 2 Si 2 O 7 as the state-of-the-art candidate with optimal EBC properties and inferred that YbPO 4 should be considered as a potentially viable EBC material candidate. Further, the figure of merit allows for a holistic comparison of EBC candidates and informs experimental and computational search efforts for next-generation complex EBCs. Clear knowledge gaps found through this work include CaO–MgO–Al 2 O 3 –SiO 2 (CMAS)-resistant coatings, EBC lifetimes before delamination, and oxidant diffusion rates in relevant EBC microstructures. It was shown that while some materials show promise for solving a single key failure mode for EBCs (i.e., CMAS reactivity), a community-wide goal should be placed on materials development to achieve acceptable resistance against all major failure modes, which are interconnected. Novel compositionally complex EBC materials, in addition to layered EBC architectures, show promise for the optimization of material properties for long-lifetime EBCs in combustion environments.

36 MATERIALS SCIENCE↗
DOE OSTI2026

All-ceramic channel waveguides fabricated via 3D printing

All-ceramic channel waveguides (CWGs) in Yb:YAG transparent ceramics have been fabricated for the first time, to the best of our knowledge, via direct ink write (DIW) and their laser performance has been demonstrated. Single filaments of Yb:YAG nanoparticle-loaded ink were extruded into undoped YAG; the Yb:YAG filaments formed the CWGs, surrounded by undoped cladding. Elemental mapping confirmed the Yb doping profile and waveguide integrity. Optical characterization showed low cladding scatter losses (<1.3%/cm at 1.3 µm), and laser testing with a 940 nm Ti:sapphire pump demonstrated efficient lasing at 1030 nm. The best-performing waveguide, with an elliptical cross-section (100 µm × 60 µm and a length of 1.4 cm), achieved a slope efficiency of 61% and a roundtrip loss of 12.4%. These results identify DIW as a promising approach for fabricating high-performance channel waveguides in transparent ceramics.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Vectors of Efficiency in Hybrid Poplar Genotype Testing

Abstract The Natural Resources Research Institute Hybrid Poplar Program breeds and tests genetically improved clones for bio-mass production and environmental services. The testing process progresses from Nursery Progeny Tests (NPT) to Family Field Trials (FFT) to Clone Trials (CT) to Yield Blocks (YB), with limited replication of many clones in FFT and CT and a limited number of highly selected clones set out in monoclonal blocks (YB) to approximate the conditions of commercial plantations. We used correlation vectors, R 2 (coefficient of determination) and r s (Spearman’s Coefficient) for growth (DBH 2 ) and McFadden’s Pseudo R 2 for canker severity score, to determine where testing times could be altered (age – age correlations) and whole testing steps eliminated. FFT can be shortened from 5 years to 4 years. In CT, rank correlations between age 5 (half-rotation) and age 9/10 (full rotation) were significant (R 2 = 0.39 – 0.72), but age 5 selection missed 44 % of the top ten clones at age 9/10. Clone rank in CT at full, but not half, rotation was correlated with rank at full rotation in YB. Choosing clones at 9 years in CT adds 4 years but allows possible elimination of YB for clone selection. Both FFT and CT are necessary. Canker abundance and severity in CT at full rotation cannot be determined at earlier ages. An aggressive strategy saves 6 years of testing.

Forestry↗
NASA NTRS1992

The effects of RF plasma ashing on zinc orthotitanate/potassium silicate thermal control coatings

Samples of YB-71, a white thermal control coating composed of zinc orthotitanate pigment in a potassium silicate binder, were exposed in air plasma and in oxygen plasma to determine optical property and surface chemistry changes. Results show that YB-71 undergoes a significant reflectance decrease upon exposure to the simulated LEO atomic oxygen environment provided by an air plasma asher. YB-71 samples exposed to the same effective fluence in oxygen plasma, or in a UV screening Faraday cage in air or oxygen, do not undergo as severe reflectance decreases as the samples exposed in the air plasma asher environment. The UV and VUV radiation present in the plasma ashers affects the YB-71 degradation. It is noted that, when using plasma ashers to determine LEO degradation, it is necessary to take into account the sensitivity of the material to the synergistic effects of atomic oxygen and accelerated UV radiation.

Dever, Joyce A.↗
NASA NTRS2006

Effects of Doping on Thermal Conductivity of Pyrochlore Oxides for Advanced Thermal Barrier Coatings

Pyrochlore oxides of general composition, A2B2O7, where A is a 3(+) cation (La to Lu) and B is a 4(+) cation (Zr, Hf, Ti, etc.) have high melting point, relatively high coefficient of thermal expansion, and low thermal conductivity which make them suitable for applications as high-temperature thermal barrier coatings. The effect of doping at the A site on the thermal conductivity of a pyrochlore oxide La2Zr2O7, has been investigated. Oxide powders of various compositions La2Zr2O7, La(1.7)Gd(0.3)Zr2O7, La(1.7)Yb(0.3)Zr2O7 and La(1.7)Gd(0.15)Yb(0.15)Zr2O7 were synthesized by the citric acid sol-gel method. These powders were hot pressed into discs and used for thermal conductivity measurements using a steady-state laser heat flux test technique. The rare earth oxide doped pyrochlores La(1.7)Gd(0.3)Zr2O7, La(1.7)Yb(0.3)Zr2O7 and La(1.7)Gd(0.15)Yb(0.15)Zr2O7 had lower thermal conductivity than the un-doped La2Zr2O7. The Gd2O3 and Yb2O3 co-doped composition showed the lowest thermal conductivity.

Bansal, Narottam P.↗
DOE OSTI2020

Materials Data on YbCo3B2 by Materials Project

YbCo3B2 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Yb2+ is bonded to two equivalent Yb2+ and six equivalent B3- atoms to form a mixture of edge and corner-sharing YbYb2B6 hexagonal bipyramids. Both Yb–Yb bond lengths are 2.76 Å. All Yb–B bond lengths are 2.98 Å. Co+1.33+ is bonded in a square co-planar geometry to four equivalent B3- atoms. All Co–B bond lengths are 2.03 Å. B3- is bonded in a 6-coordinate geometry to three equivalent Yb2+ and six equivalent Co+1.33+ atoms.

36 MATERIALS SCIENCE↗