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At least 1,405 records · Page 78
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Electrical resistivity of some palladium-silver alloys containing hydrogen at 4.2 K

The electrical resistivities of the alloys 90at.%Pd - 10at.%Ag, 80at.%Pd - 20at.%Ag, 70at.%Pd - 30at.%Ag, 60at.%Pd - 40at.%Ag, and 50at.%Pd - 50at.%Ag were measured as functions of absorbed hydrogen x at 4.2 K. These results show a minimum in the resistivity for all the alloys except 90Pd-10Ag; they show a maximum for all the alloys except for 50Pd-Ag. We associate the shapes of the plots with a modification of the Pd D-band because of the substitutional alloying of Ag and the interstitial absorption of hydrogen.

Smith, R. J.↗
NASA NTRS1991

Recovery of precious metals from space

The overall objective is to develop efficient and economical separation and recovery methods for the platinum group and other precious metals. The separation of Pd(II) from Pt(II), Ir(III), and Rh(III) with trioctylphosphine oxide (TOPO) in heptane using centrifugal partition chromatography (CPC) was investigated. Activities to achieve this objective focussed on selection and evaluation of extraction systems for the PGM and modification of selected systems for multistage operation with a view to scaling up to desired macro levels. On the basis of preliminary evaluation of a series of simple metal complexing agents and chelating agents, the TOPO in heptane was selected as a likely system for isolating of Pd(II) and Pt(II) from the other PGM. A multistage apparatus capable of configuration as a simple rugged device, a centrifugal partition chromatograph (CPC), was shown to be effective. The extraction of Pd(II) was studied by CPC and batch solvent extraction. The distribution ratios for Pd(II) determined by both methods agree well. In low HCl concentrations (less than 0.1 M), the extracted species was PdCl2.(TOPO)2, irrespective of the chloride concentration, while at acid concentrations above 0.1 M, the Pd was extracted as the ion pair, 2(TOPO.H+).(PdCl4)2-. Base line separation of Pd(II) and Pt(II) in CPC was obtained under a variety of chloride and HCl concentration. It was demonstrated that the efficiency of CPC for metal separation was limited by chemical kinetic factors rather than instrumental factors, strongly suggesting that dramatic improvements can be achieved by studying reaction kinetics of formation and dissociation of the extractable metal complex.

Freiser, Henry↗
NASA NTRS1993

The solubility of gold in silicate melts: First results

The effects of oxygen fugacity and temperature on the solubility of Au in silicate melts were determined. Pd-Au alloys were equilibrated with silicate of anorthite-diopside eutectic composition at different T-fO2 conditions. The behavior of Au was found to be similar to that of Pd reported recently. Au solubilities for alloys with 30 to 40 at. percent Au decrease at 1400 C from 12 ppm in air to 160 ppb at a log fO2 = -8.7. The slope of the log(Me-solubility) vs. log(fO2) curve is close to 1/4 for Au and the simultaneously determined Pd suggesting a formal valence of Au and Pd of 1+. Near the IW buffer Pd and Au solubilities become even less dependent on fO2 perhaps reflecting the presence of some metallic Au and Pd.

Borisov, A.↗
NASA NTRS1998

X-Ray Photoelectron Spectroscopy Study of the Heating Effects on Pd/6H-SiC Schottky Structure

X-ray photoelectron spectroscopy is used to study the effects of heat treatment on the Pd/6H-SiC Schottky diode structure. After heating the structure at 425 C for 140 h, a very thin surface layer of PdO mixed with SiO(x) formed on the palladium surface of the Schottky structure. Heat treatment promoted interfacial diffusion and reaction which significantly broadened the interfacial region. In the interfacial region, the palladium concentration decreases with depth, and the interfacial products are Pd(x)Si (x = 1,2,3,4). In the high Pd concentration regions, Pd4Si is the major silicide component while gr and Pd2Si are major components in the low Pd concentration region. At the center of the interface, where the total palladium concentration equals that of silicon, the concentrations of palladium associated with various palladium silicides (Pd(x)Si, x= 1,2,3,4) are approximately equal. The surface passivation layer composed of PdO and SiO, may significantly affect the electronic and catalytic properties of the surface of the Schottky diode which plays a major role in gas detection. The electronic properties of the Schottky structure may be dominated by a (Pd+Pd(x)Si)/SiC interface. In order to stabilize the properties of the Schottky structure the surface and interface diffusion and reactions must be controlled.

Chen, Liang-Yu↗
NASA NTRS1998

Gait variability and basal ganglia disorders: stride-to-stride variations of gait cycle timing in Parkinson's disease and Huntington's disease

The basal ganglia are thought to play an important role in regulating motor programs involved in gait and in the fluidity and sequencing of movement. We postulated that the ability to maintain a steady gait, with low stride-to-stride variability of gait cycle timing and its subphases, would be diminished with both Parkinson's disease (PD) and Huntington's disease (HD). To test this hypothesis, we obtained quantitative measures of stride-to-stride variability of gait cycle timing in subjects with PD (n = 15), HD (n = 20), and disease-free controls (n = 16). All measures of gait variability were significantly increased in PD and HD. In subjects with PD and HD, gait variability measures were two and three times that observed in control subjects, respectively. The degree of gait variability correlated with disease severity. In contrast, gait speed was significantly lower in PD, but not in HD, and average gait cycle duration and the time spent in many subphases of the gait cycle were similar in control subjects, HD subjects, and PD subjects. These findings are consistent with a differential control of gait variability, speed, and average gait cycle timing that may have implications for understanding the role of the basal ganglia in locomotor control and for quantitatively assessing gait in clinical settings.

Non-NASA Center↗
DOE OSTI2021

Partial discharge detector

A partial discharge (PD) detection system includes a PD sensor configured to sense a PD event of an electrical system and to generate a sensor signal in response to the PD event. An envelope generator is coupled to receive the sensor signal from the PD sensor. The envelope generator extracts an envelope signal from the sensor signal. A digitizer is configured to convert the envelope signal to a digital representation of the PD event.

Karin, Todd↗
DOE OSTI2020

Deep Understanding of Strong Metal Interface Confinement: A Journey of Pd/FeO x Catalysts

Tuning the atomic interface configuration of noble metals (NMs) and transition-metal oxides is an effective straightforward yet challenging strategy to modulate the activity and stability of heterogeneous catalysts. Herein, Pd supported on mesoporous Fe 2 O 3 with a high specific surface area was rationally designed and chosen to construct the Pd/iron oxide interface. As a versatile model, the physicochemical environments of Pd nanoparticles (NPs) could be precisely controlled by taming the reduction temperature. The experimental and density functional theory calculation results unveiled that the catalyst in the support–metal interface confinement (SMIC) state showed significantly enhanced catalytic activity and sintering resistance for CO oxidation. The constructed Fe sites at the interfaces between FeO x overlayers and Pd NPs not only provided additional coordinative unsaturated ferrous sites for the adsorption and activation of O 2 , thereby facilitating the activation efficiency of O 2 , but also impressively changed the reaction pathway of CO oxidation. As a result, the catalyst followed the Pd/Fe dual-site mechanism instead of the classical Mars–van Krevelen mechanism. For the catalyst in the strong metal–support interaction (SMSI) state, its catalytic activity was seriously suppressed because of the excessive encapsulation of the active Pd sites by FeO x overlayers. Thus, the present study therefore provides detailed insights into the SMIC and SMSI in ferric oxide-supported Pd catalysts, which could guide the preparation of highly efficient supported catalysts for practical applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on TbGaPd by Materials Project

TbPdGa crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Tb is bonded in a 1-coordinate geometry to five equivalent Pd and six equivalent Ga atoms. There are a spread of Tb–Pd bond distances ranging from 2.92–3.16 Å. There are a spread of Tb–Ga bond distances ranging from 3.11–3.24 Å. Pd is bonded in a 9-coordinate geometry to five equivalent Tb and four equivalent Ga atoms. There are three shorter (2.62 Å) and one longer (2.76 Å) Pd–Ga bond lengths. Ga is bonded in a 10-coordinate geometry to six equivalent Tb and four equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on DyBPd3 by Materials Project

DyPd3B is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Dy is bonded to twelve equivalent Pd atoms to form DyPd12 cuboctahedra that share corners with twelve equivalent DyPd12 cuboctahedra, faces with six equivalent DyPd12 cuboctahedra, and faces with eight equivalent BPd6 octahedra. All Dy–Pd bond lengths are 3.05 Å. Pd is bonded to four equivalent Dy and two equivalent B atoms to form a mixture of distorted corner, edge, and face-sharing PdDy4B2 octahedra. The corner-sharing octahedra tilt angles range from 0–60°. Both Pd–B bond lengths are 2.16 Å. B is bonded to six equivalent Pd atoms to form BPd6 octahedra that share corners with six equivalent BPd6 octahedra and faces with eight equivalent DyPd12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ErBPd3 by Materials Project

ErPd3B is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Er is bonded to twelve equivalent Pd atoms to form ErPd12 cuboctahedra that share corners with twelve equivalent ErPd12 cuboctahedra, faces with six equivalent ErPd12 cuboctahedra, and faces with eight equivalent BPd6 octahedra. All Er–Pd bond lengths are 3.04 Å. Pd is bonded to four equivalent Er and two equivalent B atoms to form a mixture of distorted edge, corner, and face-sharing PdEr4B2 octahedra. The corner-sharing octahedra tilt angles range from 0–60°. Both Pd–B bond lengths are 2.15 Å. B is bonded to six equivalent Pd atoms to form BPd6 octahedra that share corners with six equivalent BPd6 octahedra and faces with eight equivalent ErPd12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NdBPd3 by Materials Project

NdPd3B is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Nd is bonded to twelve equivalent Pd atoms to form NdPd12 cuboctahedra that share corners with twelve equivalent NdPd12 cuboctahedra, faces with six equivalent NdPd12 cuboctahedra, and faces with eight equivalent BPd6 octahedra. All Nd–Pd bond lengths are 3.10 Å. Pd is bonded to four equivalent Nd and two equivalent B atoms to form a mixture of distorted edge, face, and corner-sharing PdNd4B2 octahedra. The corner-sharing octahedra tilt angles range from 0–60°. Both Pd–B bond lengths are 2.19 Å. B is bonded to six equivalent Pd atoms to form BPd6 octahedra that share corners with six equivalent BPd6 octahedra and faces with eight equivalent NdPd12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TmBPd3 by Materials Project

TmPd3B is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Tm is bonded to twelve equivalent Pd atoms to form TmPd12 cuboctahedra that share corners with twelve equivalent TmPd12 cuboctahedra, faces with six equivalent TmPd12 cuboctahedra, and faces with eight equivalent BPd6 octahedra. All Tm–Pd bond lengths are 3.04 Å. Pd is bonded to four equivalent Tm and two equivalent B atoms to form a mixture of distorted corner, edge, and face-sharing PdTm4B2 octahedra. The corner-sharing octahedra tilt angles range from 0–60°. Both Pd–B bond lengths are 2.15 Å. B is bonded to six equivalent Pd atoms to form BPd6 octahedra that share corners with six equivalent BPd6 octahedra and faces with eight equivalent TmPd12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on YbBPd3 by Materials Project

YbPd3B is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Yb is bonded to twelve equivalent Pd atoms to form YbPd12 cuboctahedra that share corners with twelve equivalent YbPd12 cuboctahedra, faces with six equivalent YbPd12 cuboctahedra, and faces with eight equivalent BPd6 octahedra. All Yb–Pd bond lengths are 3.03 Å. Pd is bonded to four equivalent Yb and two equivalent B atoms to form a mixture of distorted corner, edge, and face-sharing PdYb4B2 octahedra. The corner-sharing octahedra tilt angles range from 0–60°. Both Pd–B bond lengths are 2.14 Å. B is bonded to six equivalent Pd atoms to form BPd6 octahedra that share corners with six equivalent BPd6 octahedra and faces with eight equivalent YbPd12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgSbPd by Materials Project

MgPdSb is half-Heusler structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Mg is bonded to four equivalent Pd and six equivalent Sb atoms to form a mixture of distorted face and corner-sharing MgSb6Pd4 tetrahedra. All Mg–Pd bond lengths are 2.75 Å. All Mg–Sb bond lengths are 3.18 Å. Pd is bonded in a body-centered cubic geometry to four equivalent Mg and four equivalent Sb atoms. All Pd–Sb bond lengths are 2.75 Å. Sb is bonded in a 10-coordinate geometry to six equivalent Mg and four equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(GePd)2 by Materials Project

Np(PdGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np is bonded in a 8-coordinate geometry to eight equivalent Pd and eight equivalent Ge atoms. All Np–Pd bond lengths are 3.38 Å. All Np–Ge bond lengths are 3.21 Å. Pd is bonded to four equivalent Np and four equivalent Ge atoms to form a mixture of distorted corner, edge, and face-sharing PdNp4Ge4 tetrahedra. All Pd–Ge bond lengths are 2.53 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Np, four equivalent Pd, and one Ge atom. The Ge–Ge bond length is 2.45 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PrPPd by Materials Project

PrPdP is hexagonal omega structure-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Pr is bonded to six equivalent Pd and six equivalent P atoms to form a mixture of edge and face-sharing PrP6Pd6 cuboctahedra. All Pr–Pd bond lengths are 3.16 Å. All Pr–P bond lengths are 3.16 Å. Pd is bonded in a 9-coordinate geometry to six equivalent Pr and three equivalent P atoms. All Pd–P bond lengths are 2.46 Å. P is bonded in a 9-coordinate geometry to six equivalent Pr and three equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SmPPd by Materials Project

SmPdP is hexagonal omega structure-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Sm is bonded to six equivalent Pd and six equivalent P atoms to form a mixture of edge and face-sharing SmP6Pd6 cuboctahedra. All Sm–Pd bond lengths are 3.11 Å. All Sm–P bond lengths are 3.11 Å. Pd is bonded in a 9-coordinate geometry to six equivalent Sm and three equivalent P atoms. All Pd–P bond lengths are 2.44 Å. P is bonded in a 9-coordinate geometry to six equivalent Sm and three equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnAlPd2 by Materials Project

Pd2MnAl is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Mn is bonded in a body-centered cubic geometry to eight equivalent Pd atoms. All Mn–Pd bond lengths are 2.68 Å. Pd is bonded in a body-centered cubic geometry to four equivalent Mn and four equivalent Al atoms. All Pd–Al bond lengths are 2.68 Å. Al is bonded in a body-centered cubic geometry to eight equivalent Pd atoms.

36 MATERIALS SCIENCE↗