Magnetocaloric behavior in ternary europium indides EuT 5In: Probing the design capability of first-principles-based methods on the multifaceted magnetic materials

DOE PAGES

Bigun, Inna; Steinberg, Simon; Smetana, Volodymyr; ...

2017-01-27

The most favorable structures and the types of magnetic ordering predicted from first-principles-based methods in a family of closely related transition-metal-rich indides EuT 5In (T = Cu, Ag, Au) are gauged against relevant experiments. The EuT5In compounds adopt a different structure for each different coinage metal—EuCu 5In ( hR42; Rmore » $$\\overline{3}$$m, a = 5.0933(7), c = 30.557(6) Å), EuAg 5In ( oP28; Pnma, a = 9.121(2), b = 5.645(1), c = 11.437(3) Å), and EuAu 5In ( tI14; I4/ mmm, a = 7.1740(3), c = 5.4425(3) Å)—and crystallize with the Sr 5Al 9, CeCu 6, and YbMo 2Al 4 structure types, respectively. EuCu 5In and EuAg 5In order antiferromagnetically at T N = 12 and 6 K, respectively, whereas EuAu 5In is ferromagnetic below T C = 13 K. EuCu 5In exhibits complex magnetism: after the initial drop at T N, the magnetization rises again below 8 K, and a weak metamagnetic-like transition occurs at 2 K in μ 0H = 1.8 T. The electronic heat capacity of EuCu 5In, γ = ~400 mJ/(mol K 2), points to strong electronic correlations. Spin-polarized densities of states suggest that the magnetic interactions in the three materials studied are supported via mixing 4 f and 5 d states of Eu. As a result, a chemical bonding analysis based on the Crystal Orbital Hamilton populations reveals the tendency to maximize overall bonding as a driving force to adopt a particular type of crystal structure.« less

Comment on "A hydrogen-rich early Earth atmosphere".

PubMed

Catling, David C

2006-01-06

Tian et al. (Reports, 13 May 2005, p. 1014) proposed a hydrogen-rich early atmosphere with slow hydrogen escape from a cold thermosphere. However, their model neglects the ultraviolet absorption of all gases other than H2. The model also neglects Earth's magnetic field, which affects the temperature and density of ions and promotes nonthermal escape of neutral hydrogen.

Assessing rare earth elements in quartz rich geological samples.

PubMed

Santoro, A; Thoss, V; Ribeiro Guevara, S; Urgast, D; Raab, A; Mastrolitti, S; Feldmann, J

2016-01-01

Sodium peroxide (Na2O2) fusion coupled to Inductively Coupled Plasma Tandem Mass Spectrometry (ICP-MS/MS) measurements was used to rapidly screen quartz-rich geological samples for rare earth element (REE) content. The method accuracy was checked with a geological reference material and Instrumental Neutron Activation Analysis (INAA) measurements. The used mass-mode combinations presented accurate results (only exception being (157)Gd in He gas mode) with recovery of the geological reference material QLO-1 between 80% and 98% (lower values for Lu, Nd and Sm) and in general comparable to INAA measurements. Low limits of detection for all elements were achieved, generally below 10 pg g(-1), as well as measurement repeatability below 15%. Overall, the Na2O2/ICP-MS/MS method proved to be a suitable lab-based method to quickly and accurately screen rock samples originating from quartz-rich geological areas for rare earth element content; particularly useful if checking commercial viability. Copyright © 2015 Elsevier Ltd. All rights reserved.

METHOD OF MAKING ALLOYS OF SECOND RARE EARTH SERIES METALS

DOEpatents

Baker, R.D.; Hayward, B.R.

1963-01-01

>This invention relates to a process for alloying the second rare earth series metals with Mo, Nb, or Zr. A halide of the rare earth metal is mixed with about 1 to 20 at.% of an oxide of Mo, Nb, or Zr. Iodine and an alkali or alkaline earth metal are added, and the resulting mixture is heated in an inert atmosphere to 350 deg C. (AEC)

Method for treating rare earth-transition metal scrap

DOEpatents

Schmidt, Frederick A.; Peterson, David T.; Wheelock, John T.; Jones, Lawrence L.

1992-12-29

Rare earth-transition metal (e.g., iron) scrap (e.g., Nd-Fe-B scrap) is flux (slag) remelted to reduce tramp non-metallic impurities, such as oxygen and nitrogen, and metallic impurities, such as Li, Na, Al, etc., picked up by the scrap from previous fabrication operations. The tramp impurities are reduced to concentrations acceptable for reuse of the treated alloy in the manufacture of end-use articles, such as permanent magnets. The scrap is electroslag or inductoslag melted using a prefused, rare earth fluoride-bearing flux of CaF.sub.2, CaCl.sub.2 or mixtures thereof or the slag resulting from practice of the thermite reduction process to make a rare earth-iron alloy.

Method for treating rare earth-transition metal scrap

DOEpatents

Schmidt, F.A.; Peterson, D.T.; Wheelock, J.T.; Jones, L.L.

1992-12-29

Rare earth-transition metal (e.g., iron) scrap (e.g., Nd-Fe-B scrap) is flux (slag) remelted to reduce tramp non-metallic impurities, such as oxygen and nitrogen, and metallic impurities, such as Li, Na, Al, etc., picked up by the scrap from previous fabrication operations. The tramp impurities are reduced to concentrations acceptable for reuse of the treated alloy in the manufacture of end-use articles, such as permanent magnets. The scrap is electroslag or inductoslag melted using a rare earth fluoride-bearing flux of CaF[sub 2], CaCl[sub 2] or mixtures thereof or the slag resulting from practice of the thermite reduction process to make a rare earth-iron alloy. 3 figs.

Rare-earth metal prices in the USA ca. 1960 to 1994

USGS Publications Warehouse

Hedrick, James B.

1997-01-01

Rare-earth metal prices were compiled from the late 1950s and early 1960s through 1994. Although commercial demand for rare-earth metals began in 1908, as the alloy mischmetal, commercial quantities of a wide range of individual rare-earth metals were not available until the late 1950s. The discovery of a large, high-grade rare-earth deposit at Mountain Pass. CA, USA, in 1949, was significant because it led to the production of commercial quantities or rare-earth elements that reduced prices and encouraged wider application of the materials. The availability of ore from Mountain Pass, and other large rare-earth deposits, especially those in Australia and China, has provided the world with abundant resources for rare-earth metal production. This availability, coupled with improved technology from Government and private-sector metallurgical research, has resulted in substantial decreases in rare-earth metal prices since the late 1950s and early 1960s. Price series for the individual rare-earth metals (except promethium) are quoted on a kilogram basis from the late 1950s and early 1960s through 1994. Prices are given in US dollars on an actual and constant dollar basis. Industrial and economic factors affecting prices during this time period are examined.

Rare-earth metal prices in the USA ca. 1960 to 1994

USGS Publications Warehouse

Hedrick, J.B.

1997-01-01

Rare-earth metal prices were compiled from the late 1950s and early 1960s through 1994. Although commercial demand for rare-earth metals began in 1908, as the alloy mischmetal, commercial quantities of a wide range of individual rare-earth metals were not available until the late 1950s. The discovery of a large, high-grade rare-earth deposit at Mountain Pass, CA, USA, in 1949, was significant because it led to the production of commercial quantities of rare-earth elements that reduced prices and encouraged wider application of the materials. The availability of ore from Mountain Pass, and other large rare-earth deposits, especially those in Australia and China, has provided the world with abundant resources for rare-earth metal production. This availability, coupled with improved technology from Government and private-sector metallurgical research, has resulted in substantial decreases in rare-earth metal prices since the late 1950s and early 1960s. Price series for the individual rare-earth metals (except promethium) are quoted on a kilogram basis from the late 1950s and early 1960s through 1994. Prices are given in US dollars on an actual and constant dollar basis. Industrial and economic factors affecting prices during this time period are examined.

Syntheses and structures of alkaline earth metal bis(diphenylamides).

PubMed

Gärtner, Martin; Fischer, Reinald; Langer, Jens; Görls, Helmar; Walther, Dirk; Westerhausen, Matthias

2007-06-11

Various preparative procedures are employed in order to synthesize alkaline earth metal bis(diphenylamides) such as (i) metalation of HNPh2 with the alkaline earth metal M, (ii) metalation of HNPh2 with MPh2, (iii) metathesis reaction of MI2 with KNPh2, (iv) metalation of HNPh2 with PhMI in THF, and (v) metathesis reaction of PhMI with KNPh2 followed by a dismutation reaction yielding MPh2 and M(NPh2)2. The magnesium compounds [(diox)MgPh2]infinity (1) and (thf)2Mg(NPh2)2 (2) show tetracoordinate metal atoms, whereas in (dme)2Ca(NPh2)2 (3), (thf)4Sr(NPh2)2 (4), and (thf)4Ba(NPh2)2 (5) the metals are 6-fold coordinated. Additional agostic interactions between an ipso-carbon of one of the phenyl groups of the amide ligand and the alkaline earth metal atom lead to unsymmetric coordination of the NPh2 anions with two strongly different M-N-C angles in 3-5.

Variable Stars In the Unusual, Metal-Rich Globular Cluster

NASA Technical Reports Server (NTRS)

Pritzl, Barton J.; Smith, Horace A.; Catelan, Marcio; Sweigart, Allen V.; Oegerle, William R. (Technical Monitor)

2002-01-01

We have undertaken a search for variable stars in the metal-rich globular cluster NGC 6388 using time-series BV photometry. Twenty-eight new variables were found in this survey, increasing the total number of variables found near NGC 6388 to approx. 57. A significant number of the variables are RR Lyrae (approx. 14), most of which are probable cluster members. The periods of the fundamental mode RR Lyrae are shown to be unusually long compared to metal-rich field stars. The existence of these long period RRab stars suggests that the horizontal branch of NGC 6388 is unusually bright. This implies that the metallicity-luminosity relationship for RR Lyrae stars is not universal if the RR Lyrae in NGC 6388 are indeed metal-rich. We consider the alternative possibility that the stars in NGC 6388 may span a range in [Fe/H]. Four candidate Population II Cepheids were also found. If they are members of the cluster, NGC 6388 would be the most metal-rich globular cluster to contain Population II Cepheids. The mean V magnitude of the RR Lyrae is found to be 16.85 +/- 0.05 resulting in a distance of 9.0 to 10.3 kpc, for a range of assumed values of (M(sub V)) for RR Lyrae. We determine the reddening of the cluster to be E(B - V) = 0.40 +/- 0.03 mag, with differential reddening across the face of the cluster. We discuss the difficulty in determining the Oosterhoff classification of NGC 6388 and NGC 6441 due to the unusual nature of their RR Lyrae, and address evolutionary constraints on a recent suggestion that they are of Oosterhoff type II.

Metal sulfide and rare-earth phosphate nanostructures and methods of making same

DOEpatents

Wong, Stanislaus; Zhang, Fen

2016-06-28

The present invention provides a method of producing a crystalline rare earth phosphate nanostructure. The method comprising: providing a rare earth metal precursor solution and providing a phosphate precursor solution; placing a porous membrane between the metal precursor solution and the phosphate precursor solution, wherein metal cations of the metal precursor solution and phosphate ions of the phosphate precursor solution react, thereby producing a crystalline rare earth metal phosphate nanostructure.

Experimentally determined Si isotope fractionation between silicate and Fe metal and implications for Earth's core formation

NASA Astrophysics Data System (ADS)

Shahar, Anat; Ziegler, Karen; Young, Edward D.; Ricolleau, Angele; Schauble, Edwin A.; Fei, Yingwei

2009-10-01

Stable isotope fractionation amongst phases comprising terrestrial planets and asteroids can be used to elucidate planet-forming processes. To date, the composition of the Earth's core remains largely unknown though cosmochemical and geophysical evidence indicates that elements lighter than iron and nickel must reside there. Silicon is often cited as a light element that could explain the seismic properties of the core. The amount of silicon in the core, if any, can be deduced from the difference in 30Si/ 28Si between meteorites and terrestrial rocks if the Si isotope fractionation between silicate and Fe-rich metal is known. Recent studies (e.g., [Georg R.B., Halliday A.N., Schauble E.A., Reynolds B.C., 2007. Silicon in the Earth's core. Nature 447 (31), 1102-1106.]; [Fitoussi, C., Bourdon, B., Kleine, T., Oberli, F., Reynolds, B. C., 2009. Si isotope systematics of meteorites and terrestrial peridotites: implications for Mg/Si fractionation in the solar nebula and for Si in the Earth's core. Earth Planet. Sci. Lett. 287, 77-85.]) showing (sometimes subtle) differences between 30Si/ 28Si in meteorites and terrestrial rocks suggest that Si missing from terrestrial rocks might be in the core. However, any conclusion based on Earth-meteorite comparisons depends on the veracity of the 30Si/ 28Si fractionation factor between silicates and metals at appropriate conditions. Here we present the first direct experimental evidence that silicon isotopes are not distributed uniformly between iron metal and rock when equilibrated at high temperatures. High-precision measurements of the silicon isotope ratios in iron-silicon alloy and silicate equilibrated at 1 GPa and 1800 °C show that Si in silicate has higher 30Si/ 28Si than Si in metal, by at least 2.0‰. These findings provide an experimental foundation for using isotope ratios of silicon as indicators of terrestrial planet formation processes. They imply that if Si isotope equilibrium existed during segregation of Earth

Thermophysical properties of liquid rare earth metals

NASA Astrophysics Data System (ADS)

Thakor, P. B.; Sonvane, Y. A.; Patel, H. P.; Jani, A. R.

2013-06-01

The thermodynamical properties like long wavelength limit S(0), iso-thermal compressibility (χT), thermal expansion coefficient (αV), thermal pressure coefficient (γV), specific heat at constant volume (CV) and specific heat at constant pressure (CP) are calculated for liquid rare earth metals. Our newly constructed parameter free model potential is used to describe the electron ion interaction due to Sarkar et al (S) local field correction function. Lastly, we conclude that our newly constructed model potential is capable to explain the thermophysical properties of liquid rare earth metals.

The Stability of Hydrogen-Rich Atmospheres of Earth-Like Planets

NASA Technical Reports Server (NTRS)

Zahnle, Kevin

2016-01-01

Understanding hydrogen escape is essential to understanding the limits to habitability, both for liquid water where the Sun is bright, but also to assess the true potential of H2 as a greenhouse gas where the Sun is faint. Hydrogen-rich primary atmospheres of Earth-like planets can result either from gravitational capture of solar nebular gases (with helium), or from impact shock processing of a wide variety of volatile-rich planetesimals (typically accompanied by H2O, CO2, and under the right circumstances, CH4). Most studies of hydrogen escape from planets focus on determining how fast the hydrogen escapes. In general this requires solving hydro- dynamic equations that take into account the acceleration of hydrogen through a critical transonic point and an energy budget that should include radiative heating and cooling, thermal conduction, the work done in lifting the hydrogen against gravity, and the residual heat carried by the hydrogen as it leaves. But for planets from which hydrogen escape is modest or insignificant, the atmosphere can be approximated as hydrostatic, which is much simpler, and for which a relatively full-featured treatment of radiative cooling by embedded molecules, atoms, and ions such as CO2 and H3+ is straightforward. Previous work has overlooked the fact that the H2 molecule is extremely efficient at exciting non-LTE CO2 15 micron emission, and thus that radiative cooling can be markedly more efficient when H2 is abundant. We map out the region of phase space in which terrestrial planets keep hydrogen-rich atmospheres, which is what we actually want to know for habitability. We will use this framework to reassess Tian et al's hypothesis that H2-rich atmospheres may have been rather long-lived on Earth itself. Finally, we will address the empirical observation that rocky planets with thin or negligible atmospheres are rarely or never bigger than 1.6 Earth radii.

40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting under...

40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting under...

40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting under...

40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting under...

40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting under...

Metal Based Synthetic Strategies and the Examination of Structure Determining Factors in Alkaline Earth Metal Compounds

NASA Astrophysics Data System (ADS)

Takahashi, Yuriko

Last decades have witnessed a large expansion of the organometallic heavier alkaline earth metal species. However, continued growth of this promising area of chemistry has been slowed by severe restrictions and limitations in viable synthetic methodologies leading to difficulties in preparing and characterizing the target compounds. There is clearly a need for the further development of synthetic methodologies and detailed structure function analysis that will promote the further advancement of organoalkaline earth metal chemistry in applications as diverse as materials chemistry and catalysis. This thesis work greatly extends the synthetic options currently available towards organoalkaline earth metal species by introducing redox transmetallation protolysis (RTP), a reaction based on the readily available Ph3Bi as a non-toxic transmetallation agent. Based on a straightforward one-pot procedure and work-up, Ph3Bi based RTP presents a powerful synthetic alternative for the facile preparation of a large variety of heavy alkaline earth metal compounds. The second part of the thesis explores the effect of secondary non covalent interactions on the coordination chemistry as well as thermal properties of a series of novel alkali, alkaline earth, rare earth as well as heterobimetallic alkali/alkaline earth fluoroalkoxides. These compounds showcase the significance of non-covalent M···F-C and agostic interactions on metal stabilization and structural features, providing critical input on ligand design for the design of advanced metal organic vapor deposition (MOCVD) precursor materials. This work also showcases the impact of M···F-C interactions over M---co-ligand coordination, a critical precursor design element as well.

Multiple populations in more metal-rich galactic globular clusters

NASA Astrophysics Data System (ADS)

Cordero, Maria J.

In this thesis we present chemical abundances for bright stars in the intermediate metallicity globular cluster (GC) M5, and the relatively metal-rich GCs M71 and 47 Tuc with the goal of improving the understanding of chemical evolution in the metallicity regime sampled by these three GCs. The first chapter presents a brief historical overview in light element abundance variations in globular clusters. In the second chapter we present the results obtained for 47 Tuc, the most-metal rich cluster of my sample. 47 Tuc is an ideal target to study chemical evolution and GC formation in massive more metal-rich GCs since it is the closest massive GC. Chemical abundances for O, Na, Al, Si, Ca, Ti, Fe, Ni, La, and Eu were determined for 164 red giant branch (RGB) stars in 47 Tuc using spectra obtained with both the Hydra multi-fiber spectrograph at the Blanco 4-m telescope and the FLAMES multi-object spectrograph at the ESO Very Large Telescope. The average [Fe/H]= --0.79+/-0.09 dex is consistent with literature values, as well as over-abundances of alpha-elements ([alpha/Fe] ~ 0.3 dex). The n-capture process elements indicate that 47 Tuc is r-process dominated ([Eu/La]=+0.24), and the light elements O, Na, and Al exhibit star-to-star variations. The Na-O anti-correlation, a signature typically seen in Galactic GCs, is present in 47 Tuc, and extends to include a small number of stars with [O/Fe] ~ --0.5. Additionally, the [O/Na] ratios of our sample reveal that the cluster stars can be separated into three distinct populations. A KS-test demonstrates that the O-poor/Na-rich stars are more centrally concentrated than the O-rich/Na-poor stars. The observed number and radial distribution of 47 Tuc's stellar populations, as distinguished by their light element composition, agrees closely with the results obtained from photometric data. We do not find evidence supporting a strong Na-Al correlation in 47 Tuc, which is consistent with current models of AGB nucleosynthesis yields

METAL-POOR LITHIUM-RICH GIANTS IN THE RADIAL VELOCITY EXPERIMENT SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruchti, Gregory R.; Fulbright, Jon P.; Wyse, Rosemary F. G.

We report the discovery of eight lithium-rich field giants found in a high-resolution spectroscopic sample of over 700 metal-poor stars ([Fe/H] < -0.5) selected from the Radial Velocity Experiment survey. The majority of the Li-rich giants in our sample are very metal-poor ([Fe/H] {approx}< -1.9), and have a Li abundance (in the form of {sup 7}Li), A(Li) = log (n(Li)/n(H)) + 12, between 2.30 and 3.63, well above the typical upper red giant branch (RGB) limit, A(Li) < 0.5, while two stars, with A(Li) {approx} 1.7-1.8, show similar lithium abundances to normal giants at the same gravity. We further includedmore » two metal-poor, Li-rich globular cluster giants in our sample, namely the previously discovered M3-IV101 and newly discovered (in this work) M68-A96. This comprises the largest sample of metal-poor Li-rich giants to date. We performed a detailed abundance analysis of all stars, finding that the majority of our sample stars have elemental abundances similar to that of Li-normal halo giants. Although the evolutionary phase of each Li-rich giant cannot be definitively determined, the Li-rich phase is likely connected to extra mixing at the RGB bump or early asymptotic giant branch that triggers cool bottom processing in which the bottom of the outer convective envelope is connected to the H-burning shell in the star. The surface of a star becomes Li-enhanced as {sup 7}Be (which burns to {sup 7}Li) is transported to the stellar surface via the Cameron-Fowler mechanism. We discuss and discriminate among several models for the extra mixing that can cause Li production, given the detailed abundances of the Li-rich giants in our sample.« less

40 CFR 421.270 - Applicability: Description of the primary rare earth metals subcategory.

Code of Federal Regulations, 2014 CFR

2014-07-01

... primary rare earth metals subcategory. 421.270 Section 421.270 Protection of Environment ENVIRONMENTAL... CATEGORY Primary Rare Earth Metals Subcategory § 421.270 Applicability: Description of the primary rare earth metals subcategory. The provisions of this subpart are applicable to discharges resulting from the...

40 CFR 421.270 - Applicability: Description of the primary rare earth metals subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... primary rare earth metals subcategory. 421.270 Section 421.270 Protection of Environment ENVIRONMENTAL... CATEGORY Primary Rare Earth Metals Subcategory § 421.270 Applicability: Description of the primary rare earth metals subcategory. The provisions of this subpart are applicable to discharges resulting from the...

40 CFR 421.270 - Applicability: Description of the primary rare earth metals subcategory.

Code of Federal Regulations, 2012 CFR

2012-07-01

... primary rare earth metals subcategory. 421.270 Section 421.270 Protection of Environment ENVIRONMENTAL... CATEGORY Primary Rare Earth Metals Subcategory § 421.270 Applicability: Description of the primary rare earth metals subcategory. The provisions of this subpart are applicable to discharges resulting from the...

40 CFR 421.270 - Applicability: Description of the primary rare earth metals subcategory.

Code of Federal Regulations, 2011 CFR

2011-07-01

... primary rare earth metals subcategory. 421.270 Section 421.270 Protection of Environment ENVIRONMENTAL... CATEGORY Primary Rare Earth Metals Subcategory § 421.270 Applicability: Description of the primary rare earth metals subcategory. The provisions of this subpart are applicable to discharges resulting from the...

40 CFR 421.270 - Applicability: Description of the primary rare earth metals subcategory.

Code of Federal Regulations, 2013 CFR

2013-07-01

... primary rare earth metals subcategory. 421.270 Section 421.270 Protection of Environment ENVIRONMENTAL... CATEGORY Primary Rare Earth Metals Subcategory § 421.270 Applicability: Description of the primary rare earth metals subcategory. The provisions of this subpart are applicable to discharges resulting from the...

Olivine-rich asteroids in the near-Earth space

NASA Astrophysics Data System (ADS)

Popescu, Marcel; Perna, D.; Barucci, M. A.; Fornasier, S.; Doressoundiram, A.; Lantz, C.; Merlin, F.; Belskaya, I. N.; Fulchignoni, M.

2018-06-01

In the framework of a 30-night spectroscopic survey of small near-Earth asteroids (NEAs), we present new results regarding the identification of olivine-rich objects. The following NEAs were classified as A-type using visible spectra obtained with 3.6-m New Technology Telescope: (293726) 2007 RQ17, (444584) 2006 UK, 2012 NP, 2014 YS34, 2015 HB117, 2015 LH, 2015 TB179, 2015 TW144. We determined a relative abundance of 5.4 per cent (8 out of 147 observed targets) A-types at a 100-m size range of NEA population. The ratio is at least five times larger compared with the previously known A-types, which represent less than ˜ 1 per cent of NEAs taxonomically classified. By taking into account that part of our targets may not be confirmed as olivine-rich asteroids by their near-infrared spectra, or they can have a nebular origin, our result provides an upper-limit estimation of mantle fragments at size ranges below 300 m. Our findings are compared with the `battered-to-bits' scenario, claiming that at small sizes the olivine-rich objects should be more abundant when compared with basaltic and iron ones.

Rare-Earth Metals and Their Applications in Aviation

DTIC Science & Technology

1984-08-01

metals are not as common as iron and steel which are visible everywhere, yet they are not unfamiliar to us. We often encounter them in everyday life...the flint of a lighter. It is an alloy of rare-earth metal and iron . It contains about 30% iron and the remainder is a composite rare-earth alloy...used to manufacture the detonators of bullets and shells as well as the pyrophoric alloys of firing devices. This type of alloy has a 49.5% content of

Process optimization and kinetics for leaching of rare earth metals from the spent Ni-metal hydride batteries.

PubMed

Meshram, Pratima; Pandey, B D; Mankhand, T R

2016-05-01

Nickel-metal hydride batteries (Ni-MH) contain not only the base metals, but valuable rare earth metals (REMs) viz. La, Sm, Nd, Pr and Ce as well. In view of the importance of resource recycling and assured supply of the contained metals in such wastes, the present study has focussed on the leaching of the rare earth metals from the spent Ni-MH batteries. The conditions for the leaching of REMs from the spent batteries were optimized as: 2M H2SO4, 348K temperature and 120min of time at a pulp density (PD) of 100g/L. Under this condition, the leaching of 98.1% Nd, 98.4% Sm, 95.5% Pr and 89.4% Ce was achieved. Besides the rare earth metals, more than 90% of base metals (Ni, Co, Mn and Zn) were also leached out in this condition. Kinetic data for the dissolution of all the rare earth metals showed the best fit to the chemical control shrinking core model. The leaching of metals followed the mechanism involving the chemical reaction proceeding on the surface of particles by the lixiviant, which was corroborated by the XRD phase analysis and SEM-EDS studies. The activation energy of 7.6, 6.3, 11.3 and 13.5kJ/mol was acquired for the leaching of neodymium, samarium, praseodymium and cerium, respectively in the temperature range 305-348K. From the leach liquor, the mixed rare earth metals were precipitated at pH∼1.8 and the precipitated REMs was analyzed by XRD and SEM studies to determine the phases and the morphological features. Copyright © 2015. Published by Elsevier Ltd.

Gaia Reveals a Metal-rich, in situ Component of the Local Stellar Halo

NASA Astrophysics Data System (ADS)

Bonaca, Ana; Conroy, Charlie; Wetzel, Andrew; Hopkins, Philip F.; Kereš, Dušan

2017-08-01

We use the first Gaia data release, combined with the RAVE and APOGEE spectroscopic surveys, to investigate the origin of halo stars within ≲ 3 kpc from the Sun. We identify halo stars kinematically as moving at a relative speed of at least 220 km s-1 with respect to the local standard of rest. These stars are generally less metal-rich than the disk, but surprisingly, half of our halo sample is comprised of stars with [{Fe}/{{H}}]> -1. The orbital directions of these metal-rich halo stars are preferentially aligned with the disk rotation, in sharp contrast with the intrinsically isotropic orbital distribution of the metal-poor halo stars. We find similar properties in the Latte cosmological zoom-in simulation of a Milky Way-like galaxy from the FIRE project. In Latte, metal-rich halo stars formed primarily inside of the solar circle, whereas lower-metallicity halo stars preferentially formed at larger distances (extending beyond the virial radius). This suggests that metal-rich halo stars in the solar neighborhood actually formed in situ within the Galactic disk, rather than having been accreted from satellite systems. These stars, currently on halo-like orbits, therefore have likely undergone substantial radial migration/heating.

Color-magnitude diagrams for six metal-rich, low-latitude globular clusters

NASA Technical Reports Server (NTRS)

Armandroff, Taft E.

1988-01-01

Colors and magnitudes for stars on CCD frames for six metal-rich, low-latitude, previously unstudied globular clusters and one well-studied, metal-rich cluster (47 Tuc) have been derived and color-magnitude diagrams have been constructed. The photometry for stars in 47 Tuc are in good agreement with previous studies, while the V magnitudes of the horizontal-branch stars in the six program clusters do not agree with estimates based on secondary methods. The distances to these clusters are different from prior estimates. Redding values are derived for each program cluster. The horizontal branches of the program clusters all appear to lie entirely redwards of the red edge of the instability strip, as is normal for their metallicities.

New stable ternary alkaline-earth metal Pb(II) oxides: Ca / Sr / BaPb 2 O 3 and BaPbO 2

DOE PAGES

Li, Yuwei; Zhang, Lijun; Singh, David J.

2017-10-16

The different but related chemical behaviors of Pb(II) oxides compared to Sn(II) oxides, and the existence of known alkali/alkali-earth metal Sn(II) ternary phases, suggest that there should be additional ternary Pb(II) oxide phases. Here, we report structure searches on the ternary alkaline-earth metal Pb(II) oxides leading to four new phases. These are two ternary Pb(II) oxides, SrPb 2O 3 and BaPb 2O 3, which have larger chemical potential stability ranges compared with the corresponding Sn(II) oxides, and additionally two other ternary Pb(II) oxides, CaPb 2O 3 and BaPbO 2, for which there are no corresponding Sn(II) oxides. Those Pb(II) oxidesmore » are stabilized by Pb-rich conditions. These structures follow the Zintl behavior and consist of basic structural motifs of (PbO 3) 4- anionic units separated and stabilized by the alkaline-earth metal ions. They show wide band gaps ranging from 2.86 to 3.12 eV, and two compounds (CaPb 2O 3 and SrPb 2O 3) show rather light hole effective masses (around 2m 0). The valence band maxima of these compounds have a Pb-6s/O-2p antibonding character, which may lead to p-type defect (or doping) tolerant behavior. This then suggests alkaline-earth metal Pb(II) oxides may be potential p-type transparent conducting oxides.« less

New stable ternary alkaline-earth metal Pb(II) oxides: Ca / Sr / BaPb 2 O 3 and BaPbO 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yuwei; Zhang, Lijun; Singh, David J.

The different but related chemical behaviors of Pb(II) oxides compared to Sn(II) oxides, and the existence of known alkali/alkali-earth metal Sn(II) ternary phases, suggest that there should be additional ternary Pb(II) oxide phases. Here, we report structure searches on the ternary alkaline-earth metal Pb(II) oxides leading to four new phases. These are two ternary Pb(II) oxides, SrPb 2O 3 and BaPb 2O 3, which have larger chemical potential stability ranges compared with the corresponding Sn(II) oxides, and additionally two other ternary Pb(II) oxides, CaPb 2O 3 and BaPbO 2, for which there are no corresponding Sn(II) oxides. Those Pb(II) oxidesmore » are stabilized by Pb-rich conditions. These structures follow the Zintl behavior and consist of basic structural motifs of (PbO 3) 4- anionic units separated and stabilized by the alkaline-earth metal ions. They show wide band gaps ranging from 2.86 to 3.12 eV, and two compounds (CaPb 2O 3 and SrPb 2O 3) show rather light hole effective masses (around 2m 0). The valence band maxima of these compounds have a Pb-6s/O-2p antibonding character, which may lead to p-type defect (or doping) tolerant behavior. This then suggests alkaline-earth metal Pb(II) oxides may be potential p-type transparent conducting oxides.« less

Crystallographic phases in heavy rare earth metals under megabar pressures

NASA Astrophysics Data System (ADS)

Samudrala, G. K.; Vohra, Y. K.

2012-07-01

Experiments aimed at understanding the crystallographic phases of heavy rare earth metals were carried out in a diamond anvil cell at the Advanced Photon Source, Argonne National Laboratory. Heavy rare earth metals dysprosium (Dy), holmium (Ho), erbium (Er) and thulium (Tm) were compressed to multi-megabar pressures. The rare earth crystal sequence hcp→Sm-type→dhcp→distorted-fcc (dfcc) is observed in all four elements. Upon further compression, a structural transformation to a monoclinic C2/m phase has been observed. We summarize the results from these experiments and present Rietveld structural refinements on high pressure phases for the specific case of dysprosium.

Generation of copper rich metallic phases from waste printed circuit boards.

PubMed

Cayumil, R; Khanna, R; Ikram-Ul-Haq, M; Rajarao, R; Hill, A; Sahajwalla, V

2014-10-01

The rapid consumption and obsolescence of electronics have resulted in e-waste being one of the fastest growing waste streams worldwide. Printed circuit boards (PCBs) are among the most complex e-waste, containing significant quantities of hazardous and toxic materials leading to high levels of pollution if landfilled or processed inappropriately. However, PCBs are also an important resource of metals including copper, tin, lead and precious metals; their recycling is appealing especially as the concentration of these metals in PCBs is considerably higher than in their ores. This article is focused on a novel approach to recover copper rich phases from waste PCBs. Crushed PCBs were heat treated at 1150°C under argon gas flowing at 1L/min into a horizontal tube furnace. Samples were placed into an alumina crucible and positioned in the cold zone of the furnace for 5 min to avoid thermal shock, and then pushed into the hot zone, with specimens exposed to high temperatures for 10 and 20 min. After treatment, residues were pulled back to the cold zone and kept there for 5 min to avoid thermal cracking and re-oxidation. This process resulted in the generation of a metallic phase in the form of droplets and a carbonaceous residue. The metallic phase was formed of copper-rich red droplets and tin-rich white droplets along with the presence of several precious metals. The carbonaceous residue was found to consist of slag and ∼30% carbon. The process conditions led to the segregation of hazardous lead and tin clusters in the metallic phase. The heat treatment temperature was chosen to be above the melting point of copper; molten copper helped to concentrate metallic constituents and their separation from the carbonaceous residue and the slag. Inert atmosphere prevented the re-oxidation of metals and the loss of carbon in the gaseous fraction. Recycling e-waste is expected to lead to enhanced metal recovery, conserving natural resources and providing an environmentally

A volatile topic: Parsing out the details of Earth's formation through experimental metal-silicate partitioning of volatile and moderately volatile elements

NASA Astrophysics Data System (ADS)

Mahan, B. M.; Siebert, J.; Blanchard, I.; Badro, J.; Sossi, P.; Moynier, F.

2017-12-01

Volatile and moderately volatile elements display different volatilities and siderophilities, as well as varying sensitivity to thermodynamic controls (X, P, T, fO2) during metal-silicate differentiation. The experimental determination of the metal-silicate partitioning of these elements permits us to evaluate processes controlling the distribution of these elements in Earth. In this work, we have combined metal-silicate partitioning data and results for S, Sn, Zn and Cu, and input these characterizations into Earth formation models. Model parameters such as source material, timing of volatile delivery, fO2 path, and degree of impactor equilibration were varied to encompass an array of possible formation scenarios. These models were then assessed to discern plausible sets of conditions that can produce current observed element-to-element ratios (e.g. S/Zn) in the Earth's present-day mantle, while also satisfying current estimates on the S content of the core, at no more than 2 wt%. The results of our models indicate two modes of accretion that can maintain chondritic element-to-element ratios for the bulk Earth and can arrive at present-day mantle abundances of these elements. The first mode requires the late addition of Earth's entire inventory of these elements (assuming a CI-chondritic composition) and late-stage accretion that is marked by partial equilibration of large impactors. The second, possibly more intuitive mode, requires that Earth accreted - at least initially - from volatile poor material preferentially depleted in S relative to Sn, Zn, and Cu. From a chemical standpoint, this source material is most similar to type I chondrule rich (and S poor) materials (Hewins and Herzberg, 1996; Mahan et al., 2017; Amsellem et al., 2017), such as the metal-bearing carbonaceous chondrites.

Gaia reveals a metal-rich in-situ component of the local stellar halo

NASA Astrophysics Data System (ADS)

Bonaca, Ana; Conroy, Charlie; Wetzel, Andrew; Hopkins, Philip; Keres, Dusan

2018-01-01

We use the first Gaia data release, combined with RAVE and APOGEE spectroscopic surveys, to investigate the origin of halo stars within ~3 kpc from the Sun. We identify halo stars kinematically, as moving with a relative speed of at least 220 km/s with respect to the local standard of rest. These stars are in general more metal-poor than the disk, but surprisingly, half of our halo sample is comprised of stars with [Fe/H]>-1. The orbital directions of these metal-rich halo stars are preferentially aligned with the disk rotation, in sharp contrast with the isotropic orbital distribution of the more metal-poor halo stars. We find similar properties in the Latte cosmological zoom-in simulation of a Milky Way-like galaxy from the FIRE project. In Latte, metal-rich halo stars formed primarily inside of the solar circle, while lower-metallicity halo stars preferentially formed at larger distances (extending beyond the virial radius). This suggests that metal-rich halo stars in the Solar neighborhood in fact formed in situ within the Galactic disk rather than having been accreted from satellite systems. These stars, currently on halo-like orbits, therefore have likely undergone substantial radial migration/heating.

Asymmetric Catalysis with bis(hydroxyphenyl)diamides/rare-earth metal complexes.

PubMed

Kumagai, Naoya; Shibasaki, Masakatsu

2013-01-02

A series of asymmetric catalysts composed of conformationally flexible amide-based chiral ligands and rare-earth metals was developed for proton-transfer catalysis. These ligands derived from amino acids provide an intriguing chiral platform for the formation of asymmetric catalysts upon complexation with rare-earth metals. The scope of this arsenal of catalysts was further broadened by the development of heterobimetallic catalytic systems. The cooperative function of hydrogen bonding and metal coordination resulted in intriguing substrate specificity and stereocontrol, and the dynamic nature of the catalysts led to a switch of their function. Herein, we summarize our recent exploration of this class of catalysts. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rare earth-transition metal scrap treatment method

DOEpatents

Schmidt, Frederick A.; Peterson, David T.; Wheelock, John T.; Jones, Lawrence L.; Lincoln, Lanny P.

1992-02-11

Rare earth-transition metal (e.g. iron) scrap (e.g. Nd-Fe-B scrap) is melted to reduce the levels of tramp oxygen and nitrogen impurities therein. The tramp impurities are reduced in the melt by virtue of the reaction of the tramp impurities and the rare earth to form dross on the melt. The purified melt is separated from the dross for reuse. The oxygen and nitrogen of the melt are reduced to levels acceptable for reuse of the treated alloy in the manufacture of end-use articles, such as permanent magnets.

Rare earth-transition metal scrap treatment method

DOEpatents

Schmidt, F.A.; Peterson, D.T.; Wheelock, J.T.; Jones, L.L.; Lincoln, L.P.

1992-02-11

Rare earth-transition metal (e.g. iron) scrap (e.g. Nd-Fe-B scrap) is melted to reduce the levels of tramp oxygen and nitrogen impurities therein. The tramp impurities are reduced in the melt by virtue of the reaction of the tramp impurities and the rare earth to form dross on the melt. The purified melt is separated from the dross for reuse. The oxygen and nitrogen of the melt are reduced to levels acceptable for reuse of the treated alloy in the manufacture of end-use articles, such as permanent magnets. 3 figs.

Biomimetic mineral self-organization from silica-rich spring waters.

PubMed

García-Ruiz, Juan Manuel; Nakouzi, Elias; Kotopoulou, Electra; Tamborrino, Leonardo; Steinbock, Oliver

2017-03-01

Purely inorganic reactions of silica, metal carbonates, and metal hydroxides can produce self-organized complex structures that mimic the texture of biominerals, the morphology of primitive organisms, and that catalyze prebiotic reactions. To date, these fascinating structures have only been synthesized using model solutions. We report that mineral self-assembly can be also obtained from natural alkaline silica-rich water deriving from serpentinization. Specifically, we demonstrate three main types of mineral self-assembly: (i) nanocrystalline biomorphs of barium carbonate and silica, (ii) mesocrystals and crystal aggregates of calcium carbonate with complex biomimetic textures, and (iii) osmosis-driven metal silicate hydrate membranes that form compartmentalized, hollow structures. Our results suggest that silica-induced mineral self-assembly could have been a common phenomenon in alkaline environments of early Earth and Earth-like planets.

Studies of high temperature ternary phases in mixed-metal-rich early transition metal sulfide and phosphide systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marking, Gregory Allen

1994-01-04

Investigations of ternary mixed early transition metal-rich sulfide and phosphide systems resulted in the discovery of new structures and new phases. A new series of Zr and Hf - group V transition metal - sulfur K-phases was synthesized and crystallographically characterized. When the group V transition metal was Nb or Ta, the unit cell volume was larger than any previously reported K-phase. The presence of adventitious oxygen was determined in two K-phases through a combination of neutron scattering and X-ray diffraction experiments. A compound Hf 10Ta 3S 3 was found to crystallize in a new-structure type similar to the knownmore » gamma brasses. This structure is unique in that it is the only reported "stuffed" gamma-brass type structure. The metal components, Hf and Ta, are larger in size and more electropositive than the metals found in normal gamma brasses (e.g. Cu and Zn) and because of the larger metallic radii, sulfur can be incorporated into the structure where it plays an integral role in stabilizing this phase relative to others. X-ray single-crystal, X-ray powder and neutron powder refinements were performed on this structure. A new structure was found in the ternary Nb-Zr-P system which has characteristics in common with many known early transition metal-rich sulfides, selenides, and phosphides. This structure has the simplest known interconnection of the basic building blocks known for this structural class. Anomalous scattering was a powerful tool for differentiating between Zr and Nb when using Mo Kα X-radiation. The compounds ZrNbP and HfNbP formed in the space group Prima with the simple Co 2Si structure which is among the most common structures found for crystalline solid materials. Solid solution compounds in the Ta-Nb-P, Ta-Zr-P, Nb-Zr-P, Hf-Nb-P, and Hf-Zr-S systems were crystallographically characterized. The structural information corroborated ideas about bonding in metal-rich compounds.« less

Alkali and alkaline earth metal salts of tetrazolone: structurally interesting and excellently thermostable.

PubMed

He, Piao; Wu, Le; Wu, Jin-Ting; Yin, Xin; Gozin, Michael; Zhang, Jian-Guo

2017-07-04

Tetrazolone (5-oxotetrazole) was synthesized by a moderate strategy through three steps (addition, cyclization and catalytic hydrogenation) avoiding the unstable intermediate diazonium, as reported during the previous preparation. Alkali and alkaline earth metal salts with lithium (1), sodium (2), potassium (3), rubidium (4) caesium (5), magnesium (6), calcium (7), strontium (8) and barium (9) were prepared and fully characterized using elemental analysis, IR and NMR spectroscopy, DSC and TG analysis. All metal salts were characterized via single-crystal X-ray diffraction. They crystallize in common space groups with high densities ranging from 1.479 (1) to 3.060 g cm -3 (5). Furthermore, the crystal structures of 7, 8 and 9 reveal interesting porous energetic coordination polymers with strong hydrogen bond interactions. All new salts have good thermal stabilities with decomposition temperature between 215.0 °C (4) and 328.2 °C (7), significantly higher than that of the reported nitrogen-rich salt neutral tetrazolone. The sensitivities towards impact and friction were tested using standard methods, and all the tetrazolone-based compounds investigated can be classified into insensitive. The flame test of these metal salts supports their potential use as perchlorate-free pyrotechnics or eco-friendly insensitive energetic materials.

Catalysts Based on Earth-Abundant Metals for Visible Light-Driven Water Oxidation Reaction.

PubMed

Lin, Junqi; Han, Qing; Ding, Yong

2018-06-04

Exploration of water oxidation catalyst (WOC) with excellent performance is the key for the overall water splitting reaction, which is a feasible strategy to convert solar energy to chemical energy. Although some compounds composed of noble metals, mainly Ru and Ir, have been reported to catalyze water oxidation with high efficiency, catalysts based on low-cost and earth-abundant transition metals are essential for realizing economical and large-scale light-driven water splitting. Various WOCs containing earth-abundant metals (mainly Mn, Fe, Co, Ni, Cu) have been utilized for visible light-driven water oxidation in recent years. In this Personal Account, we summarize our recent developments in WOCs based on earth-abundant transition metals including polyoxometalates (POMs), metal oxides or bimetal oxides, and metal complexes containing multidentate ligand scaffolds for visible light-driven water oxidation reaction. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Metal-rich meteorites from the aubrite parent body

NASA Technical Reports Server (NTRS)

Casanova, I.; Mccoy, T. J.; Keil, K.

1993-01-01

Three metal-rich meteorites - Mt. Egerton, Horse Creek, and LEW 88055 - were studied and it is suggested that they formed in the aubrite parent body. LEW 85369 and 88631 may also have a common origin, but these rocks have not yet been studied in detail. This body was probably heated to about 1600 C by a very strong heat source. While molten, metal agglomerated into sizeable nodules which never segregated efficiently to form a core, but were trapped in the silicate mantle. Different clasts and lithologies in aubrites solidified and cooled under local equilibrium conditions of oxygen fugacity, and with different thermal histories. Impacts mixed clasts from throughout the parent body, creating the typical aubrite breccias.

The composition of Earth's core from equations of state, metal-silicate partitioning, and core formation modeling

NASA Astrophysics Data System (ADS)

Fischer, Rebecca; Campbell, Andrew; Ciesla, Fred

2016-04-01

The Earth accreted in a series of increasingly large and violent collisions. Simultaneously, the metallic core segregated from the silicate mantle, acquiring its modern composition through high pressure (P), high temperature (T) partitioning reactions. Here we present a model that couples these aspects of early planetary evolution, building on recent accretion simulations and metal-silicate partitioning experiments, constrained by density measurements of Fe-rich alloys. Previously, the equations of state of FeO, Fe-9Si, Fe-16Si, and FeSi were measured to megabar pressures and several thousand K using a laser-heated diamond anvil cell. With these equations of state, we determined that the core's density can be reproduced through the addition of 11.3 +/- 0.6 wt% silicon or 8.1 +/- 1.1 wt% oxygen to an Fe-Ni alloy (Fischer et al., 2011, 2014). Metal-silicate partitioning experiments of Ni, Co, V, Cr, Si, and O have been performed in a diamond anvil cell to 100 GPa and 5700 K, allowing the effects of P, T, and composition on the partitioning behaviors of these elements to be parameterized (Fischer et al., 2015; Siebert et al., 2012). Here we apply those experimental results to model Earth's core formation, using N-body simulations to describe the delivery, masses, and original locations of planetary building blocks (Fischer and Ciesla, 2014). As planets accrete, their core and mantle compositions are modified by high P-T reactions with each collision (Rubie et al., 2011). For partial equilibration of the mantle at 55% of the evolving core-mantle boundary pressure and the liquidus temperature, we find that the core contains 5.4 wt% Si and 1.9 wt% O. This composition is consistent with the seismologically-inferred density of Earth's core, based on comparisons to our equations of state, and indicate that the core cannot contain more than ~2 wt% S or C. Earth analogues experience 1.2 +/- 0.2 log units of oxidation during accretion, due to both the effects of high P

Process for preparing higher oxides of the alkali and alkaline earth metals

NASA Technical Reports Server (NTRS)

Sadhukhan, P.; Bell, A. (Inventor)

1978-01-01

High purity inorganic higher oxides of the alkali and alkaline earth metals are prepared by subjecting the hydroxide of the alkali and alkaline earth metal to a radio frequency discharge sustained in oxygen. The process is particulary adaptable to the production of high purity potassium superoxide by subjecting potassium hydroxide to glow discharge sustained in oxygen under the pressure of about 0.75 to 1.00 torr.

Metal-rich SX Phe stars in the Kepler field

NASA Astrophysics Data System (ADS)

Nemec, James M.; Balona, Luis A.; Murphy, Simon J.; Kinemuchi, Karen; Jeon, Young-Beom

2017-04-01

A spectroscopic and photometric analysis has been carried out for 32 candidate SX Phe variable blue straggler stars in the Kepler field. Radial velocities (RVs), space motions (U, V, W), projected rotation velocities (vsin I), spectral types and atmospheric characteristics (Teff, log g, [Fe/H], ξt, ζRT, etc.) are presented for 30 of the 32 stars. Although several stars are metal-weak with extreme halo orbits, the mean [Fe/H] of the sample is near-solar, thus the stars are more metal-rich than expected for a typical sample of Pop. II stars and more like halo metal-rich A-type stars. Two-thirds of the stars are fast rotators with vsin I > 50 km s-1, including four stars with vsin I > 200 km s-1. Three of the stars have (negative) RVs > 250 km s-1, five have retrograde space motions and 21 have total speeds (relative to the Local Standard of Rest) >400 km s-1. All but one of the 30 stars have positions in a Toomre diagram consistent with the kinematics of bona fide halo stars (the exception being a thick-disc star). Observed Rømer time delays, pulsation frequency modulations and light curves suggest that at least one-third of the stars are in binary (or triple) systems with orbital periods ranging from 2.3 d to more than four years.

Raman microscopy of lithium-manganese-rich transition metal oxide cathodes

DOE PAGES

Ruther, Rose E.; Callender, Andrew F.; Zhou, Hui; ...

2014-11-15

Lithium-rich and manganese-rich (LMR) layered transition metal (TM) oxide composites with general formula xLi 2MnO 3·(1-x)LiMO 2 (M = Ni, Co, Mn) are promising cathode candidates for high energy density lithium ion batteries. Lithium-manganese-rich TM oxides crystallize as a nanocomposite layered phase whose structure further evolves with electrochemical cycling. Raman spectroscopy is a powerful tool to monitor the crystal chemistry and correlate phase changes with electrochemical behavior. While several groups have reported Raman spectra of lithium rich TM oxides, the data show considerable variability in terms of both the vibrational features observed and their interpretation. In this paper, Raman microscopymore » is used to investigate lithium-rich and manganese-rich TM cathodes as a function of voltage and electrochemical cycling at various temperatures. No growth of a spinel phase is observed within the cycling conditions. However, analysis of the Raman spectra does indicate the structure of LMR-NMC deviates significantly from an ideal layered phase. Finally, the results also highlight the importance of using low laser power and large sample sizes to obtain consistent data sets.« less

Deep-Earth Equilibration between Molten Iron and Solid Silicates

NASA Astrophysics Data System (ADS)

Brennan, M.; Zurkowski, C. C.; Chidester, B.; Campbell, A.

2017-12-01

Elemental partitioning between iron-rich metals and silicate minerals influences the properties of Earth's deep interior, and is ultimately responsible for the nature of the core-mantle boundary. These interactions between molten iron and solid silicates were influential during planetary accretion, and persist today between the mantle and liquid outer core. Here we report the results of diamond anvil cell experiments at lower mantle conditions (40 GPa, >2500 K) aimed at examining systems containing a mixture of metals (iron or Fe-16Si alloy) and silicates (peridotite). The experiments were conducted at pressure-temperature conditions above the metallic liquidus but below the silicate solidus, and the recovered samples were analyzed by FIB/SEM with EDS to record the compositions of the coexisting phases. Each sample formed a three-phase equilibrium between bridgmanite, Fe-rich metallic melt, and an oxide. In one experiment, using pure Fe, the quenched metal contained 6 weight percent O, and the coexisting oxide was ferropericlase. The second experiment, using Fe-Si alloy, was highly reducing; its metal contained 10 wt% Si, and the coexisting mineral was stishovite. The distinct mineralogies of the two experiments derived from their different starting metals. These results imply that metallic composition is an important factor in determining the products of mixed phase iron-silicate reactions. The properties of deep-Earth interfaces such as the core-mantle boundary could be strongly affected by their metallic components.

Properties of the moon, Mars, Martian satellites, and near-earth asteroids

NASA Technical Reports Server (NTRS)

Taylor, Jeffrey G.

1989-01-01

Environments and surface properties of the moon, Mars, Martian satellites, and near-earth asteroids are discussed. Topics include gravity, atmospheres, surface properties, surface compositions, seismicity, radiation environment, degradation, use of robotics, and environmental impacts. Gravity fields vary from large fractions of the earth's field such as 1/3 on Mars and 1/6 on the moon to smaller fractions of 0.0004 g on an asteroid 1 km in diameter. Spectral data and the analogy with meteor compositions suggest that near-earth asteroids may contain many resources such as water-rich carbonaceous materials and iron-rich metallic bodies. It is concluded that future mining and materials processing operations from extraterrestrial bodies require an investment now in both (1) missions to the moon, Mars, Phobos, Deimos, and near-earth asteroids and (2) earth-based laboratory research in materials and processing.

When VSEPR Fails: Experimental and Theoretical Investigations of the Behavior of Alkaline-Earth-Metal Acetylides

PubMed Central

Guino-o, Marites A.; Alexander, Jacob S.; McKee, Michael L.; Hope, Håkon; Englich, Ulrich B.

2014-01-01

The synthesis, structural, and spectral characterization as well as a theoretical study of a family of alkaline-earth-metal acetylides provides insights into synthetic access and the structural and bonding characteristics of this group of highly reactive compounds. Based on our earlier communication that reported unusual geometry for a family of triphenylsilyl-substituted alkaline-earth-metal acetylides, we herein present our studies on an expanded family of target derivatives, providing experimental and theoretical data to offer new insights into the intensively debated theme of structural chemistry in heavy alkaline-earth-metal chemistry. PMID:19844925

Application of Freeze-Dried Powders of Genetically Engineered Microbial Strains as Adsorbents for Rare Earth Metal Ions.

PubMed

Moriwaki, Hiroshi; Masuda, Reiko; Yamazaki, Yuki; Horiuchi, Kaoru; Miyashita, Mari; Kasahara, Jun; Tanaka, Tatsuhito; Yamamoto, Hiroki

2016-10-12

The adsorption behaviors of the rare earth metal ions onto freeze-dried powders of genetically engineered microbial strains were compared. Cell powders obtained from four kinds of strains, Bacillus subtilis 168 wild type (WT), lipoteichoic acid-defective (ΔLTA), wall teichoic acid-defective (ΔWTA), and cell wall hydrolases-defective (EFKYOJLp) strains, were used as an adsorbent of the rare earth metal ions at pH 3. The adsorption ability of the rare earth metal ions was in the order of EFKYOJLp > WT > ΔLTA > ΔWTA. The order was the same as the order of the phosphorus quantity of the strains. This result indicates that the main adsorption sites for the ions are the phosphate groups and the teichoic acids, LTA and WTA, that contribute to the adsorption of the rare earth metal ions onto the cell walls. The contribution of WTA was clearly greater than that of LTA. Each microbial powder was added to a solution containing 16 kinds of rare earth metal ions, and the removals (%) of each rare earth metal ion were obtained. The scandium ion showed the highest removal (%), while that of the lanthanum ion was the lowest for all the microbial powders. Differences in the distribution coefficients between the kinds of lanthanide ions by the EFKYOJLp and ΔWTA powders were greater than those of the other strains. Therefore, the EFKYOJLp and ΔWTA powders could be applicable for the selective extraction of the lanthanide ions. The ΔLTA powder coagulated by mixing with a rare earth metal ion, although no sedimentation of the WT or ΔWTA powder with a rare earth metal ion was observed under the same conditions. The EFKYOJLp powder was also coagulated, but its flocculating activity was lower than that of ΔLTA. The ΔLTA and EFKYOJLp powders have a long shape compared to those of the WT or ΔWTA strain. The shapes of the cells will play an important role in the sedimentation of the microbial powders with rare earth metal ions. As the results, three kinds of the genetically

Environmental Defects And Economic Impact On Global Market Of Rare Earth Metals

NASA Astrophysics Data System (ADS)

Charalampides, G.; Vatalis, K.; Karayannis, V.; Baklavaridis, A.

2016-11-01

Rare earth elements include the 14 lanthanides as well as lanthanium and often yttrium. Actually, most of them are not very rare and occur widely dispersed in a variety of rocks. Rare earth metals are vital to some of the world's faster growing industries: catalysts, Nd-magnets, ceramics, glass, metallurgy, battery alloys, electronics and phosphors. Worldwide, the main countries for distribution of rare earths deposits include China, USA, Russia, Brasil, India, Australia, Greenland and Malaysia. The mining and processing of rare earth metals usually result in significant environmental defects. Many deposits are associated with high concentrations of radioactive elements such as uranium and thorium, which requires separate treatment and disposal. The accumulation of rare earth elements in soils has occurred due to pollution caused by the exploitation of rare earth resources and the wide use of rare earths as fertilizers in agriculture. This accumulation has a toxic effect on the soil microfauna community. However, there are large differences in market prices due to the degree of purity determined by the specifications in the applications. The main focus of this article is to overview Rare Earth Metals’ overall impact on global economy and their environmental defects on soils during processing techniques and as they are used as fertilizers.

Assessment of radionuclide and metal contamination in a thorium rich area in Norway.

PubMed

Popic, Jelena Mrdakovic; Salbu, Brit; Strand, Terje; Skipperud, Lindis

2011-06-01

The Fen Central Complex in southern Norway, a geologically well investigated area of magmatic carbonatite rocks, is assumed to be among the world largest natural reservoirs of thorium ((232)Th). These rocks, also rich in iron (Fe), niobium (Nb), uranium ((238)U) and rare earth elements (REE), were mined in several past centuries. Waste locations, giving rise to enhanced levels of both radionuclides and metals, are now situated in the area. Estimation of radionuclide and metal contamination of the environment and radiological risk assessment were done in this study. The average outdoor gamma dose rate measured in Fen, 2.71 μGy h(-1), was significantly higher than the world average dose rate of 0.059 μGy h(-1). The annual exposure dose from terrestrial gamma radiation, related to outdoor occupancy, was in the range 0.18-9.82 mSv. The total activity concentrations of (232)Th and (238)U in soil ranged from 69 to 6581 and from 49 to 130 Bq kg(-1), respectively. Enhanced concentrations were also identified for metals, arsenic (As), lead (Pb), chromium (Cr) and zinc (Zn), in the vicinity of former mining sites. Both radionuclide and heavy metal concentrations suggested leaching, mobilization and distribution from rocks into the soil. Correlation analysis indicated different origins for (232)Th and (238)U, but same or similar for (232)Th and metals As, Cr, Zn, nickel (Ni) and cadmium (Cd). The results from in situ size fractionation of water demonstrated radionuclides predominately present as colloids and low molecular mass (LMM) species, being potentially mobile and available for uptake in aquatic organisms of Norsjø Lake. Transfer factors, calculated for different plant species, showed the highest radionuclide accumulation in mosses and lichens. Uptake in trees was, as expected, lower. Relationship analysis of (232)Th and (238)U concentrations in moss and soil samples showed a significant positive linear correlation.

Fluorine and Sodium in C-rich Low-metallicity Stars

NASA Astrophysics Data System (ADS)

Lucatello, Sara; Masseron, Thomas; Johnson, Jennifer A.; Pignatari, Marco; Herwig, Falk

2011-03-01

We present the N, O, F, and Na abundance and 12C/13C isotopic ratio measurements or upper limits for a sample of 10 C-rich, metal-poor giant stars: 8 enhanced in s-process (CEMP-s) elements and 2 poor in n-capture elements (CEMP-no). The abundances are derived from IR, K-band, high-resolution CRIRES@VLT obtained spectra. The metallicity of our sample ranges from [Fe/H] = -3.4 to -1.3. F abundance could be measured only in two CEMP-s stars. With [F/Fe] = 0.64, one is mildly F-overabundant, while the other is F-rich, at [F/Fe] = 1.44. For the remaining eight objects, including both CEMP-no stars in our sample, only upper limits on F abundance could be placed. Our measurements and upper limits show that there is a spread in the [F/C+N] ratio in CEMP-s stars as predicted by theory. Predictions from nucleosynthetic models for low-mass, low-metallicity asymptotic giant branch (AGB) stars account for the derived F abundances, while the upper limits on F content derived for most of the stars are lower than the predicted values. The measured Na content is accounted for by AGB models in the 1.25-1.75 M sun range, confirming that the stars responsible for the peculiar abundance pattern observed in CEMP-s stars are low-mass, low-metallicity AGB stars in agreement with the most accepted astrophysical scenario. We conclude that the mechanism of F production in current state-of-the-art low-metallicity low-mass AGB models needs further scrutiny and that F measurements in a larger number of metal-poor stars are needed to better constrain the models. Based on observations made with ESO Telescopes at Paranal Observatories under program ID 080.D-0606A. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center, funded by the National Aeronautics and Space Administration and the National Science Foundation.

Lithium-rich very metal-poor stars discovered with LAMOST and Subaru

NASA Astrophysics Data System (ADS)

Aoki, Wako; Li, Haining; Matsuno, Tadafumi; Kumar, Yerra Bharat; Shi, Jianrong; Suda, Takuma; Zhao, Gang

2018-04-01

Lithium is a unique element that is produced in the Big Bang nucleosynthesis but is destroyed by nuclear reactions inside stars. As a result, almost constant lithium abundance is found in unevolved main-sequence metal-poor stars, although the value is systematically lower than that expected from the standard Big Bang nucleosynthesis models, whereas lithium abundances of red giants are more than one order of magnitudes lower than those of unevolved stars. There are, however, a small fraction of metal-poor stars that show extremely high lithium abundances, which is not explained by standard stellar evolution models. We have discovered 12 new very metal-poor stars that have enhancement of lithium by more than 10 times compared with typical metal-poor stars at similar evolutionary stages by the large-scale spectroscopic survey with LAMOST and the follow-up high-resolution spectroscopy with the Subaru Telescope. The sample shows a wide distribution of evolutionary stages from subgiants to red giants with the metallicity of -3.3 <[Fe/H]< -1.6. The chemical abundance ratios of other elements have been obtained by our spectroscopic study, and an estimate of the binary frequency by radial velocity monitoring is ongoing. The observational results provide new constraints on the scenarios to explain lithium-rich metal-poor stars, such as extra mixing during the evolution along the red giant branch, mass-transfer from a companion AGB star, and engulfment of planet-like objects. These explanations are very unlikely for at least some of lithium-rich objects in our sample, suggesting a new mechanism that enhances lithium during the low-mass star evolution.

Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites.

PubMed

Van Kooten, Elishevah M M E; Wielandt, Daniel; Schiller, Martin; Nagashima, Kazuhide; Thomen, Aurélien; Larsen, Kirsten K; Olsen, Mia B; Nordlund, Åke; Krot, Alexander N; Bizzarro, Martin

2016-02-23

The short-lived (26)Al radionuclide is thought to have been admixed into the initially (26)Al-poor protosolar molecular cloud before or contemporaneously with its collapse. Bulk inner Solar System reservoirs record positively correlated variability in mass-independent (54)Cr and (26)Mg*, the decay product of (26)Al. This correlation is interpreted as reflecting progressive thermal processing of in-falling (26)Al-rich molecular cloud material in the inner Solar System. The thermally unprocessed molecular cloud matter reflecting the nucleosynthetic makeup of the molecular cloud before the last addition of stellar-derived (26)Al has not been identified yet but may be preserved in planetesimals that accreted in the outer Solar System. We show that metal-rich carbonaceous chondrites and their components have a unique isotopic signature extending from an inner Solar System composition toward a (26)Mg*-depleted and (54)Cr-enriched component. This composition is consistent with that expected for thermally unprocessed primordial molecular cloud material before its pollution by stellar-derived (26)Al. The (26)Mg* and (54)Cr compositions of bulk metal-rich chondrites require significant amounts (25-50%) of primordial molecular cloud matter in their precursor material. Given that such high fractions of primordial molecular cloud material are expected to survive only in the outer Solar System, we infer that, similarly to cometary bodies, metal-rich carbonaceous chondrites are samples of planetesimals that accreted beyond the orbits of the gas giants. The lack of evidence for this material in other chondrite groups requires isolation from the outer Solar System, possibly by the opening of disk gaps from the early formation of gas giants.

Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

PubMed Central

Van Kooten, Elishevah M. M. E.; Wielandt, Daniel; Schiller, Martin; Nagashima, Kazuhide; Thomen, Aurélien; Olsen, Mia B.; Nordlund, Åke; Krot, Alexander N.; Bizzarro, Martin

2016-01-01

The short-lived 26Al radionuclide is thought to have been admixed into the initially 26Al-poor protosolar molecular cloud before or contemporaneously with its collapse. Bulk inner Solar System reservoirs record positively correlated variability in mass-independent 54Cr and 26Mg*, the decay product of 26Al. This correlation is interpreted as reflecting progressive thermal processing of in-falling 26Al-rich molecular cloud material in the inner Solar System. The thermally unprocessed molecular cloud matter reflecting the nucleosynthetic makeup of the molecular cloud before the last addition of stellar-derived 26Al has not been identified yet but may be preserved in planetesimals that accreted in the outer Solar System. We show that metal-rich carbonaceous chondrites and their components have a unique isotopic signature extending from an inner Solar System composition toward a 26Mg*-depleted and 54Cr-enriched component. This composition is consistent with that expected for thermally unprocessed primordial molecular cloud material before its pollution by stellar-derived 26Al. The 26Mg* and 54Cr compositions of bulk metal-rich chondrites require significant amounts (25–50%) of primordial molecular cloud matter in their precursor material. Given that such high fractions of primordial molecular cloud material are expected to survive only in the outer Solar System, we infer that, similarly to cometary bodies, metal-rich carbonaceous chondrites are samples of planetesimals that accreted beyond the orbits of the gas giants. The lack of evidence for this material in other chondrite groups requires isolation from the outer Solar System, possibly by the opening of disk gaps from the early formation of gas giants. PMID:26858438

Fluorescent probes and bioimaging: alkali metals, alkaline earth metals and pH.

PubMed

Yin, Jun; Hu, Ying; Yoon, Juyoung

2015-07-21

All living species and life forms have an absolute requirement for bio-functional metals and acid-base equilibrium chemistry owing to the critical roles they play in biological processes. Hence, a great need exists for efficient methods to detect and monitor biometals and acids. In the last few years, great attention has been paid to the development of organic molecule based fluorescent chemosensors. The availability of new synthetic fluorescent probes has made fluorescence microscopy an indispensable tool for tracing biologically important molecules and in the area of clinical diagnostics. This review highlights the recent advances that have been made in the design and bioimaging applications of fluorescent probes for alkali metals and alkaline earth metal cations, including lithium, sodium and potassium, magnesium and calcium, and for pH determination within biological systems.

Pal 12 - A metal-rich globular cluster in the outer halo

NASA Technical Reports Server (NTRS)

Cohen, J. G.; Frogel, J. A.; Persson, S. E.; Zinn, R.

1980-01-01

New optical and infrared observations of several stars in the distant globular cluster Pal 12 show that they have CO strengths and heavy element abundances only slightly less than in M 71, one of the more metal-rich globular clusters. Pal 12 thus has a metal abundance near the high end of the range over which globular clusters exist and lies in the outer galactic halo. Its red horizontal branch is not anomalous in view of the abundance that has been found.

Water-rich planets: How habitable is a water layer deeper than on Earth?

NASA Astrophysics Data System (ADS)

Noack, L.; Höning, D.; Rivoldini, A.; Heistracher, C.; Zimov, N.; Journaux, B.; Lammer, H.; Van Hoolst, T.; Bredehöft, J. H.

2016-10-01

Water is necessary for the origin and survival of life as we know it. In the search for life-friendly worlds, water-rich planets therefore are obvious candidates and have attracted increasing attention in recent years. The surface H2O layer on such planets (containing a liquid water ocean and possibly high-pressure ice below a specific depth) could potentially be hundreds of kilometres deep depending on the water content and the evolution of the proto-atmosphere. We study possible constraints for the habitability of deep water layers and introduce a new habitability classification relevant for water-rich planets (from Mars-size to super-Earth-size planets). A new ocean model has been developed that is coupled to a thermal evolution model of the mantle and core. Our interior structure model takes into account depth-dependent thermodynamic properties and the possible formation of high-pressure ice. We find that heat flowing out of the silicate mantle can melt an ice layer from below (in some cases episodically), depending mainly on the thickness of the ocean-ice shell, the mass of the planet, the surface temperature and the interior parameters (e.g. radioactive mantle heat sources). The high pressure at the bottom of deep water-ice layers could also impede volcanism at the water-mantle boundary for both stagnant lid and plate tectonics silicate shells. We conclude that water-rich planets with a deep ocean, a large planet mass, a high average density or a low surface temperature are likely less habitable than planets with an Earth-like ocean.

Yttrium and rare earth stabilized fast reactor metal fuel

DOEpatents

Guon, Jerold; Grantham, LeRoy F.; Specht, Eugene R.

1992-01-01

To increase the operating temperature of a reactor, the melting point and mechanical properties of the fuel must be increased. For an actinide-rich fuel, yttrium, lanthanum and/or rare earth elements can be added, as stabilizers, to uranium and plutonium and/or a mixture of other actinides to raise the melting point of the fuel and improve its mechanical properties. Since only about 1% of the actinide fuel may be yttrium, lanthanum, or a rare earth element, the neutron penalty is low, the reactor core size can be reduced, the fuel can be burned efficiently, reprocessing requirements are reduced, and the nuclear waste disposal volumes reduced. A further advantage occurs when yttrium, lanthanum, and/or other rare earth elements are exposed to radiation in a reactor, they produce only short half life radioisotopes, which reduce nuclear waste disposal problems through much shorter assured-isolation requirements.

Environmental assessment and management of metal-rich wastes generated in acid mine drainage passive remediation systems.

PubMed

Macías, Francisco; Caraballo, Manuel A; Nieto, José Miguel

2012-08-30

As acid mine drainage (AMD) remediation is increasingly faced by governments and mining industries worldwide, the generation of metal-rich solid residues from the treatments plants is concomitantly raising. A proper environmental management of these metal-rich wastes requires a detailed characterization of the metal mobility as well as an assessment of this new residues stability. The European standard leaching test EN 12457-2, the US EPA TCLP test and the BCR sequential extraction procedure were selected to address the environmental assessment of dispersed alkaline substrate (DAS) residues generated in AMD passive treatment systems. Significant discrepancies were observed in the hazardousness classification of the residues according to the TCLP or EN 12457-2 test. Furthermore, the absence of some important metals (like Fe or Al) in the regulatory limits employed in both leaching tests severely restricts their applicability for metal-rich wastes. The results obtained in the BCR sequential extraction suggest an important influence of the landfill environmental conditions on the metals released from the wastes. To ensure a complete stability of the pollutants in the studied DAS-wastes the contact with water or any other leaching solutions must be avoided and a dry environment needs to be provided in the landfill disposal selected. Copyright © 2012 Elsevier B.V. All rights reserved.

Data gaps in anthropogenically driven local-scale species richness change studies across the Earth's terrestrial biomes.

PubMed

Murphy, Grace E P; Romanuk, Tamara N

2016-05-01

There have been numerous attempts to synthesize the results of local-scale biodiversity change studies, yet several geographic data gaps exist. These data gaps have hindered ecologist's ability to make strong conclusions about how local-scale species richness is changing around the globe. Research on four of the major drivers of global change is unevenly distributed across the Earth's biomes. Here, we use a dataset of 638 anthropogenically driven species richness change studies to identify where data gaps exist across the Earth's terrestrial biomes based on land area, future change in drivers, and the impact of drivers on biodiversity, and make recommendations for where future studies should focus their efforts. Across all drivers of change, the temperate broadleaf and mixed forests and the tropical moist broadleaf forests are the best studied. The biome-driver combinations we have identified as most critical in terms of where local-scale species richness change studies are lacking include the following: land-use change studies in tropical and temperate coniferous forests, species invasion and nutrient addition studies in the boreal forest, and warming studies in the boreal forest and tropics. Gaining more information on the local-scale effects of the specific human drivers of change in these biomes will allow for better predictions of how human activity impacts species richness around the globe.

Chemoselective single-site Earth-abundant metal catalysts at metal–organic framework nodes

PubMed Central

Manna, Kuntal; Ji, Pengfei; Lin, Zekai; Greene, Francis X.; Urban, Ania; Thacker, Nathan C.; Lin, Wenbin

2016-01-01

Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal–organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C–H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturated metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals. PMID:27574182

Chemoselective single-site Earth-abundant metal catalysts at metal–organic framework nodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manna, Kuntal; Ji, Pengfei; Lin, Zekai

2016-08-30

Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal–organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C–H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturatedmore » metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals.« less

Metal-Rich Transition Metal Diborides as Electrocatalysts for Hydrogen Evolution Reactions in a Wide Range of pH

DOE PAGES

Sitler, Steven J.; Raja, Krishnan S.; Charit, Indrajit

2016-09-23

Solid solutions of HfB 2-ZrB 2 mixtures were prepared by high-energy ball milling of diboride and additive powders followed by spark plasma sintering (SPS). A mixture of stoichiometric 1:1 HfB 2-ZrB 2 borides was the base composition to which Hf, Zr, Ta, LaB 6 or Gd 2O 3 was added. Hf, Zr and Ta were added in order to bring the boron-to-metal ratio down to 1.86, rendering the boride as MeB 1.86. In the case of LaB 6 and Gd 2O 3, 1.8 mol% was added. Electroanalytical behavior of hydrogen evolution reactions was evaluated in 1 M H 2SO 4more » and 1 M NaOH solutions. The LaB 6 additive material showed Tafel slopes of 125 and 90 mV/decade in acidic and alkaline solutions respectively. The Hf and Zr rich samples showed Tafel slopes of about 120 mV/decade in both electrolytes. The over potentials of hydrogen evolution reactions (at 10 mA/cm 2) in the alkaline solution were about 100 mV lower than those in acidic solution. The metal-rich diborides and addition of LaB 6 showed better hydrogen evolution reaction (HER) activities than the base 1:1 HfB 2-ZrB 2 stoichiometric diboride solid solution. Furthermore, the higher activity of metal-rich borides could be attributed to the increased electron population at the d-orbitals of the metal shown by band structure modeling calculations using the Density Functional Theory approach.« less

Selective extraction and recovery of rare earth metals from phosphor powders in waste fluorescent lamps using an ionic liquid system.

PubMed

Yang, Fan; Kubota, Fukiko; Baba, Yuzo; Kamiya, Noriho; Goto, Masahiro

2013-06-15

The recycling of rare earth metals from phosphor powders in waste fluorescent lamps by solvent extraction using ionic liquids was studied. Acid leaching of rare earth metals from the waste phosphor powder was examined first. Yttrium (Y) and europium (Eu) dissolved readily in the acid solution; however, the leaching of other rare earth metals required substantial energy input. Ionization of target rare earth metals from the waste phosphor powders into the leach solution was critical for their successful recovery. As a high temperature was required for the complete leaching of all rare earth metals, ionic liquids, for which vapor pressure is negligible, were used as an alternative extracting phase to the conventional organic diluent. An extractant, N, N-dioctyldiglycol amic acid (DODGAA), which was recently developed, showed a high affinity for rare earth metal ions in liquid-liquid extraction although a conventional commercial phosphonic extractant did not. An effective recovery of the rare earth metals, Y, Eu, La and Ce, from the metal impurities, Fe, Al and Zn, was achieved from the acidic leach solution of phosphor powders using an ionic liquid containing DODGAA as novel extractant system. Copyright © 2013 Elsevier B.V. All rights reserved.

THE EFFECT OF SECOND-GENERATION POPULATIONS ON THE INTEGRATED COLORS OF METAL-RICH GLOBULAR CLUSTERS IN EARLY-TYPE GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, Chul; Lee, Sang-Yoon; Yoon, Suk-Jin

2013-05-20

The mean color of globular clusters (GCs) in early-type galaxies is in general bluer than the integrated color of halo field stars in host galaxies. Metal-rich GCs often appear more associated with field stars than metal-poor GCs, yet show bluer colors than their host galaxy light. Motivated by the discovery of multiple stellar populations in Milky Way GCs, we present a new scenario in which the presence of second-generation (SG) stars in GCs is responsible for the color discrepancy between metal-rich GCs and field stars. The model assumes that the SG populations have an enhanced helium abundance as evidenced bymore » observations, and it gives a good explanation of the bluer optical colors of metal-rich GCs than field stars as well as strong Balmer lines and blue UV colors of metal-rich GCs. Ours may be complementary to the recent scenario suggesting the difference in stellar mass functions (MFs) as an origin for the GC-to-star color offset. A quantitative comparison is given between the SG and MF models.« less

First-principles study on interlayer state in alkali and alkaline earth metal atoms intercalated bilayer graphene

NASA Astrophysics Data System (ADS)

Kaneko, Tomoaki; Saito, Riichiro

2017-11-01

Energetics and electronic structures of alkali metal (Li, Na, K, Rb, and Cs) and alkaline earth metal (Be, Mg, Ca, Sr, and Ba) atoms intercalated bilayer graphene are systematically investigated using first-principles calculations based on density functional theory. Formation of alkali and alkaline earth metal atoms intercalated bilayer graphene is exothermic except for Be and Mg. The interlayer state between two graphene layers is occupied for K, Rb, Cs, Ca, Sr, and Ba. We find that the energetic position of the interlayer states between bilayer graphene monotonically shifts downward with increasing of interlayer distance. The interlayer distances of more than 4.5 Å and 4.0 Å, respectively, are necessary for the occupation of the interlayer state in bilayer graphene for alkali and alkaline earth metal atoms, which is almost independent of the intercalant metal species. We discuss the relevance to occurrence of superconductivity for the metal intercalated bilayer graphene in terms of the occupation of the interlayer state and the phonon frequency of metal ions.

Molten metal containment vessel with rare earth oxysulfide protective coating thereon and method of making same

DOEpatents

Krikorian, Oscar H.; Curtis, Paul G.

1992-01-01

An improved molten metal containment vessel is disclosed in which wetting of the vessel's inner wall surfaces by molten metal is inhibited by coating at least the inner surfaces of the containment vessel with one or more rare earth oxysulfide or rare earth sulfide compounds to inhibit wetting and or adherence by the molten metal to the surfaces of the containment vessel.

Inner Edges of Compact Debris Disks around Metal-rich White Dwarfs

NASA Astrophysics Data System (ADS)

Rafikov, Roman R.; Garmilla, José A.

2012-12-01

A number of metal-rich white dwarfs (WDs) are known to host compact, dense particle disks, which are thought to be responsible for metal pollution of these stars. In many such systems, the inner radii of disks inferred from their spectra are so close to the WD that particles directly exposed to starlight must be heated above 1500 K and are expected to be unstable against sublimation. To reconcile this expectation with observations, we explore particle sublimation in H-poor debris disks around WDs. We show that because of the high metal vapor pressure the characteristic sublimation temperature in these disks is 300-400 K higher than in their protoplanetary analogs, allowing particles to survive at higher temperatures. We then look at the structure of the inner edges of debris disks and show that they should generically feature superheated inner rims directly exposed to starlight with temperatures reaching 2500-3500 K. Particles migrating through the rim toward the WD (and rapidly sublimating) shield the disk behind them from strong stellar heating, making the survival of solids possible close to the WD. Our model agrees well with observations of WD+disk systems provided that disk particles are composed of Si-rich material such as olivine, and have sizes in the range ~0.03-30 cm.

Heavy Metal - Exploring a magnetised metallic asteroid

NASA Astrophysics Data System (ADS)

Wahlund, Jan-Erik; Andrews, David; Futaana, Yoshifumi; Masters, Adam; Thomas, Nicolas; De Sanctis, Maria Cristina; Herique, Alain; Retherford, Kurt; Tortora, Paolo; Trigo-Rodriguez, Joseph; Ivchenko, Nickolay; Simon, Sven

2017-04-01

We propose a spacecraft mission (Heavy Metal) to orbit and explore (16) Psyche - the largest M-class metallic asteroid in the main belt. Recent estimates of the shape, 279×232×189 km and mass, 2.7×10(19) kg make it one of the largest and densest of asteroids, and together with the high surface radar reflectivity and the spectral data measured from Earth it is consistent with a bulk composition rich in iron-nickel. The M5 mission Heavy Metal will investigate if (16) Psyche is the exposed metallic core of a planetesimal, formed early enough to melt and differentiate. High-resolution mapping of the surface in optical, IR, UV and radar wavebands, along with the determination of the shape and gravity field will be used to address the formation and subsequent evolution of (16) Psyche, determining the origin of metallic asteroids. It is conceivable that a cataclysmic collision with a second body led to the ejection of all or part of the differentiated core of the parent body. Measurements at (16) Psyche therefore provide a possibility to directly examine an iron-rich planetary core, similar to that expected at the center of all the major planets including Earth. A short-lived dynamo producing a magnetic field early in the life of (16) Psyche could have led to a remnant field (of tens of micro Tesla) being preserved in the body today. (16) Psyche is embedded in the variable flow of the solar wind. Whereas planetary magnetospheres and induced magnetospheres are the result of intense dynamo fields and dense conductive ionospheres presenting obstacles to the solar wind, (16) Psyche may show an entirely new 'class' of interaction as a consequence of its lack of a significant atmosphere, the extremely high bulk electrical conductivity of the asteroid, and the possible presence of intense magnetic fields retained in iron-rich material. The small characteristic scale of (16) Psyche ( 200 km) firmly places any solar wind interaction in the "sub-MHD" scale, in which kinetic

Metal-rich or misclassified? The case of four RR Lyrae stars

NASA Astrophysics Data System (ADS)

Molnar, L.; Juhasz, A. L.; Plachy, E.; Szabo, R.

2016-06-01

We analysed the light curve of four, apparently extremely metal-rich fundamenta-mode RR Lyrae stars. We identified two stars, MT Tel and ASAS J091803-3022.6 as RRc (first-overtone) pulsators that were misclassified as RRab ones in the ASAS survey. In the case of the other two stars, V397 Gem and ASAS J075127-4136.3, we could not decide conclusively, as they are outliers in the period-Fourier-coefficient space from the loci of both classes, but their photometric metallicities also favour the RRc classification.

Low frequency vibrational spectra and the nature of metal-oxygen bond of alkaline earth metal acetylacetonates

NASA Astrophysics Data System (ADS)

Fakheri, Hamideh; Tayyari, Sayyed Faramarz; Heravi, Mohammad Momen; Morsali, Ali

2017-12-01

Theoretical quantum chemistry calculations were used to assign the observed vibrational band frequencies of Be, Mg, Ca, Sr, and Ba acetylacetonates complexes. Density functional theory (DFT) calculations have been carried out at the B3LYP level, using LanL2DZ, def2SVP, and mixed, GenECP, (def2SVP for metal ions and 6-311++G** for all other atoms) basis sets. The B3LYP level, with mixed basis sets, was utilized for calculations of vibrational frequencies, IR intensity, and Raman activity. Analysis of the vibrational spectra indicates that there are several bands which could almost be assigned mainly to the metal-oxygen vibrations. The strongest Raman band in this region could be used as a measure of the stability of the complex. The effects of central metal on the bond orders and charge distributions in alkaline earth metal acetylacetonates were studied by the Natural Bond Orbital (NBO) method for fully optimized compounds. Optimization were performed at the B3LYP/6-311++G** level for the lighter alkaline earth metal complexes (Be, Mg, and Ca acetylacetonates) while the B3LYP level, using LanL2DZ (extrabasis, d and f on oxygen and metal atoms), def2SVP and mixed (def2SVP on metal ions and 6-311++G** for all other atoms) basis sets for all understudy complexes. Calculations indicate that the covalence nature of metal-oxygen bonds considerably decreases from Be to Ba complexes. The nature of metal-oxygen bond was further studied by using Atoms In Molecules (AIM) analysis. The topological parameters, Wiberg bond orders, natural charges of O and metal ions, and also some vibrational band frequencies were correlated with the stability constants of understudy complexes.

High Pressure Phase Transformations in Heavy Rare Earth Metals and Connections to Actinide Crystal Structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vohra, Yogesh K.; Sangala, Bagvanth Reddy; Stemshorn, Andrew K.

2008-07-01

High-pressure studies have been performed on heavy rare earth metals Terbium (Tb) to 155 GPa and Holmium (Ho) to 134 GPa in a diamond anvil cell at room temperature. The following crystal structure sequence was observed in both metals hcp {yields} Sm-type {yields} dhcp {yields} distorted fcc (hR-24) {yields} monoclinic (C2/m) with increasing pressure. The last transformation to a low symmetry monoclinic phase is accompanied by a volume collapse of 5 % for Tb at 51 GPa and a volume collapse of 3 % for Ho at 103 GPa. This volume collapse under high pressure is reminiscent of f-shell delocalizationmore » in light rare earth metal Cerium (Ce), Praseodymium (Pr), and heavy actinide metals Americium (Am) and Curium (Cm). The orthorhombic Pnma phase that has been reported in Am and Cm after f-shell delocalization is not observed in heavy rare earth metals under high pressures. (authors)« less

Design of ternary alkaline-earth metal Sn(II) oxides with potential good p-type conductivity

DOE PAGES

Du, Mao -Hua; Singh, David J.; Zhang, Lijun; ...

2016-04-19

Oxides with good p-type conductivity have been long sought after to achieve high performance all-oxide optoelectronic devices. Divalent Sn(II) based oxides are promising candidates because of their rather dispersive upper valence bands caused by the Sn-5s/O-2p anti-bonding hybridization. There are so far few known Sn(II) oxides being p-type conductive suitable for device applications. Here, we present via first-principles global optimization structure searches a material design study for a hitherto unexplored Sn(II)-based system, ternary alkaline-earth metal Sn(II) oxides in the stoichiometry of MSn 2O 3 (M = Mg, Ca, Sr, Ba). We identify two stable compounds of SrSn 2O 3 andmore » BaSn 2O 3, which can be stabilized by Sn-rich conditions in phase stability diagrams. Their structures follow the Zintl behaviour and consist of basic structural motifs of SnO 3 tetrahedra. Unexpectedly they show distinct electronic properties with band gaps ranging from 1.90 (BaSn 2O 3) to 3.15 (SrSn 2O 3) eV, and hole effective masses ranging from 0.87 (BaSn 2O 3) to above 6.0 (SrSn 2O 3) m0. Further exploration of metastable phases indicates a wide tunability of electronic properties controlled by the details of the bonding between the basic structural motifs. Lastly, this suggests further exploration of alkaline-earth metal Sn(II) oxides for potential applications requiring good p-type conductivity such as transparent conductors and photovoltaic absorbers.« less

A volatile-rich Earth's core inferred from melting temperature of core materials

NASA Astrophysics Data System (ADS)

Morard, G.; Andrault, D.; Antonangeli, D.; Nakajima, Y.; Auzende, A. L.; Boulard, E.; Clark, A. N.; Lord, O. T.; Cervera, S.; Siebert, J.; Garbarino, G.; Svitlyk, V.; Mezouar, M.

2016-12-01

Planetary cores are mainly constituted of iron and nickel, alloyed with lighter elements (Si, O, C, S or H). Understanding how these elements affect the physical and chemical properties of solid and liquid iron provides stringent constraints on the composition of the Earth's core. In particular, melting curves of iron alloys are key parameter to establish the temperature profile in the Earth's core, and to asses the potential occurrence of partial melting at the Core-Mantle Boundary. Core formation models based on metal-silicate equilibration suggest that Si and O are the major light element components1-4, while the abundance of other elements such as S, C and H is constrained by arguments based on their volatility during planetary accretion5,6. Each compositional model implies a specific thermal state for the core, due to the different effect that light elements have on the melting behaviour of Fe. We recently measured melting temperatures in Fe-C and Fe-O systems at high pressures, which complete the data sets available both for pure Fe7 and other binary alloys8. Compositional models with an O- and Si-rich outer core are suggested to be compatible with seismological constraints on density and sound velocity9. However, their crystallization temperatures of 3650-4050 K at the CMB pressure of 136 GPa are very close to, if not higher than the melting temperature of the silicate mantle and yet mantle melting above the CMB is not a ubiquitous feature. This observation requires significant amounts of volatile elements (S, C or H) in the outer core to further reduce the crystallisation temperature of the core alloy below that of the lower mantle. References 1. Wood, B. J., et al Nature 441, 825-833 (2006). 2. Siebert, J., et al Science 339, 1194-7 (2013). 3. Corgne, A., et al Earth Planet. Sc. Lett. 288, 108-114 (2009). 4. Fischer, R. a. et al. Geochim. Cosmochim. Acta 167, 177-194 (2015). 5. Dreibus, G. & Palme, H. Geochim. Cosmochim. Acta 60, 1125-1130 (1995). 6. Mc

Tracing the Chemical Evolution of Metal-rich Galactic Bulge Globular Clusters

NASA Astrophysics Data System (ADS)

Munoz Gonzalez, Cesar; Saviane, Ivo; Geisler, Doug; Villanova, Sandro

2018-01-01

We present in this poster the metallicity characterization of the four metal rich Bulge Galactic Gobular Clusters, which have controversial metallicities. We analyzed our high-resolution spectra (using UVES-580nm and GIRAFFE-HR13 setups) for a large sample of RGB/AGB targets in each cluster in order to measure their metallicity and prove or discard the iron spread hypothesis. We have also characterized chemically stars with potentially different iron content by measuring light (O, Na, Mg, Al), alpha (Si, Ca, Ti), iron–peak (V, Cr, Ni, Mn) and s and r process (Y, Zr, Ba, Eu) elements. We have identified possible channels responsible for the chemical heterogeneity of the cluster populations, like AGB or massive fast-rotating stars contamination, or SN explosion. Also, we have analyzed the origin and evolution of these bulge GCs and their connection with the bulge itself.

Trace Metal Associations with Manganese-Rich Surface Coatings of Lead Service Lines

EPA Science Inventory

Analysis of lead service line samples from U. S. Environmental Protection Agency’s long-term research program to evaluate control and metal release from domestic drinking water service lines has revealed that Manganese-rich solids also contain Iron and sometimes Aluminum have fre...

Mitigation effects of silicon rich amendments on heavy metal accumulation in rice (Oryza sativa L.) planted on multi-metal contaminated acidic soil

USDA-ARS?s Scientific Manuscript database

The mechanisms of stabilization by silicon-rich amendments of cadmium, zinc, copper and lead in a multi-metal contaminated acidic soil and the mitigation of metal accumulation in rice were investigated in this study. The results from a pot experiment indicated that the application of fly ash (20 and...

Rare-earth metal oxide doped transparent mesoporous silica plates under non-aqueous condition as a potential UV sensor.

PubMed

Lee, Sang-Joon; Park, Sung Soo; Lee, Sang Hyun; Hong, Sang-Hyun; Ha, Chang-Sik

2013-11-01

Transparent mesoporous silica plates doped with rare-earth metal oxide were prepared using solvent-evaporation method based on the self-organization between structure-directing agent and silicate in a non-aqueous solvent. A triblock copolymer, Pluronic (F127 or P123), was used as the structure-directing agent, while tetraethyl orthosilicate (TEOS) was used as a silica source. The pore diameter and the surface area of the mesoporous silica plate prepared with the optimized conditions were ca 40 A and 600 m2 g(-1), respectively, for both structure-directing agent. Rare-earth metal oxides (Eu, Tb, Tm oxide) in mesochannel were formed via one-step synthetic route based on the preparation method of a silica plate. Optical properties of rare-earth metal oxide-doped mesoporous silica plates were investigated by UV irradiation and photoluminescence (PL) spectroscopy. Under the exitation wavelength of 254 nm, the doped mesoporous silica plates emitted red, green and blue for Eu, Tb and Tm oxides, respectively. Rare-earth metal oxide-doped mesoporous silica plates showed enhanced PL intensity compared to that of the bulk rare-earth metal oxide.

Adsorption Behavior of Rare Earth Metal Cations in the Interlayer Space of γ-ZrP.

PubMed

Takei, Takahiro; Iidzuka, Kiyoaki; Miura, Akira; Yanagida, Sayaka; Kumada, Nobuhiro; Magome, Eisuke; Moriyoshi, Chikako; Kuroiwa, Yoshihiro

2016-10-04

Adsorption competencies of rare earth metal cations in γ-zirconium phosphate were examined by ICP, synchrotron X-ray diffraction (SXRD), and ab initio simulation. The adsorption amounts are around 0.06-0.10 per zirconium phosphate. From the SXRD patterns of the adsorbed samples, the basal spacing estimated by c sin β increased linearly with an increasing ionic radius of rare earth metal cation, though a and b lattice constants show no change. These SXRD patterns can be classified into four groups that have different super lattices. The four superlattices have multiplicities of x131, x241, and x221 for the xabc axis, and the location of the rare earth metal cation in the original unit cell changes depending on the superlattice cell. In the x131 superlattice, Yb and Er occupied the site near the zirconium phosphate layer, though La and Ce in the x221 superlattice remained in the center position between the phosphate sheet. For the ab initio simulation of γ-ZrP with the typical rare earth metal cations (Tb, Eu, Dy, and La), the results of simulation show a similar tendency of the position estimated by SXRD refinements.

Comparative Transcriptomic Analysis of the Response of Dunaliella acidophila (Chlorophyta) to Short-Term Cadmium and Chronic Natural Metal-Rich Water Exposures.

PubMed

Puente-Sánchez, Fernando; Olsson, Sanna; Aguilera, Angeles

2016-10-01

Heavy metals are toxic compounds known to cause multiple and severe cellular damage. However, acidophilic extremophiles are able to cope with very high concentrations of heavy metals. This study investigated the stress response under natural environmental heavy metal concentrations in an acidophilic Dunaliella acidophila. We employed Illumina sequencing for a de novo transcriptome assembly and to identify changes in response to high cadmium concentrations and natural metal-rich water. The photosynthetic performance was also estimated by pulse amplitude-modulated (PAM) fluorescence. Transcriptomic analysis highlights a number of processes mainly related to a high constitutive expression of genes involved in oxidative stress and response to reactive oxygen species (ROS), even in the absence of heavy metals. Photosynthetic activity seems to be unaltered under short-term exposition to Cd and chronic exposure to natural metal-rich water, probably due to an increase in the synthesis of structural photosynthetic components preserving their functional integrity. An overrepresentation of Gene Ontology (GO) terms related to metabolic activities, transcription, and proteosomal catabolic process was observed when D. acidophila grew under chronic exposure to natural metal-rich water. GO terms involved in carbohydrate metabolic process, reticulum endoplasmic and Golgi bodies, were also specifically overrepresented in natural metal-rich water library suggesting an endoplasmic reticulum stress response.

High pressure phase transitions in the rare earth metal erbium to 151 GPa.

PubMed

Samudrala, Gopi K; Thomas, Sarah A; Montgomery, Jeffrey M; Vohra, Yogesh K

2011-08-10

High pressure x-ray diffraction studies have been performed on the heavy rare earth metal erbium (Er) in a diamond anvil cell at room temperature to a pressure of 151 GPa and Er has been compressed to 40% of its initial volume. The rare earth crystal structure sequence hcp → Sm type → dhcp → distorted fcc (hcp: hexagonal close packed; fcc: face centered cubic; dhcp: double hcp) is observed in Er below 58 GPa. We have carried out Rietveld refinement of crystal structures in the pressure range between 58 GPa and 151 GPa. We have examined various crystal structures that have been proposed for the distorted fcc (dfcc) phase and the post-dfcc phase in rare earth metals. We find that the hexagonal hR 24 structure is the best fit between 58 and 118 GPa. Above 118 GPa, a structural transformation from hR 24 phase to a monoclinic C 2/m phase is observed with a volume change of - 1.9%. We have also established a clear trend for the pressure at which a post-dfcc phase is formed in rare earth metals and show that there is a monotonic increase in this pressure with the filling of 4f shell.

High pressure phase transitions in the rare earth metal erbium to 151 GPa

NASA Astrophysics Data System (ADS)

Samudrala, Gopi K.; Thomas, Sarah A.; Montgomery, Jeffrey M.; Vohra, Yogesh K.

2011-08-01

High pressure x-ray diffraction studies have been performed on the heavy rare earth metal erbium (Er) in a diamond anvil cell at room temperature to a pressure of 151 GPa and Er has been compressed to 40% of its initial volume. The rare earth crystal structure sequence {hcp} \\to {Sm}~ {type} \\to {dhcp} \\to {distorted} fcc (hcp: hexagonal close packed; fcc: face centered cubic; dhcp: double hcp) is observed in Er below 58 GPa. We have carried out Rietveld refinement of crystal structures in the pressure range between 58 GPa and 151 GPa. We have examined various crystal structures that have been proposed for the distorted fcc (dfcc) phase and the post-dfcc phase in rare earth metals. We find that the hexagonal hR 24 structure is the best fit between 58 and 118 GPa. Above 118 GPa, a structural transformation from hR 24 phase to a monoclinic C 2/m phase is observed with a volume change of - 1.9%. We have also established a clear trend for the pressure at which a post-dfcc phase is formed in rare earth metals and show that there is a monotonic increase in this pressure with the filling of 4f shell.

Pore-Environment Engineering with Multiple Metal Sites in Rare-Earth Porphyrinic Metal-Organic Frameworks.

PubMed

Zhang, Liangliang; Yuan, Shuai; Feng, Liang; Guo, Bingbing; Qin, Jun-Sheng; Xu, Ben; Lollar, Christina; Sun, Daofeng; Zhou, Hong-Cai

2018-04-23

Multi-component metal-organic frameworks (MOFs) with precisely controlled pore environments are highly desired owing to their potential applications in gas adsorption, separation, cooperative catalysis, and biomimetics. A series of multi-component MOFs, namely PCN-900(RE), were constructed from a combination of tetratopic porphyrinic linkers, linear linkers, and rare-earth hexanuclear clusters (RE 6 ) under the guidance of thermodynamics. These MOFs exhibit high surface areas (up to 2523 cm 2  g -1 ) and unlimited tunability by modification of metal nodes and/or linker components. Post-synthetic exchange of linear linkers and metalation of two organic linkers were realized, allowing the incorporation of a wide range of functional moieties. Two different metal sites were sequentially placed on the linear linker and the tetratopic porphyrinic linker, respectively, giving rise to an ideal platform for heterogeneous catalysis. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Metal-rich fluid inclusions provide new insights into unconformity-related U deposits (Athabasca Basin and Basement, Canada)

NASA Astrophysics Data System (ADS)

Richard, Antonin; Cathelineau, Michel; Boiron, Marie-Christine; Mercadier, Julien; Banks, David A.; Cuney, Michel

2016-02-01

alteration. Finally, the metal concentrations in the NaCl-rich and CaCl2-rich brines are among the highest recorded compared to present-day sedimentary formation waters and fluid inclusions from basin-hosted base metal deposits (up to 600 ppm U, 3000 ppm Mn, 4000 ppm Zn, 6000 ppm Cu, 8000 ppm Pb, and 10,000 ppm Fe). The CaCl2-rich brine carries up to one order of magnitude more metal than the NaCl-rich brine. Though the exact origin of major cations and metals of the two brines remains uncertain, their contrasting compositions indicate that the two brines had distinct flow paths and fluid-rock interactions. Large-scale circulation of the brines in the Athabasca Basin and Basement was therefore a key parameter for metal mobility (including U) and formation of unconformity-related U deposits.

Behaviour of Rare Earth Elements during the Earth's core formation

NASA Astrophysics Data System (ADS)

Faure, Pierre; Bouhifd, Mohamed Ali; Boyet, Maud; Hammouda, Tahar; Manthilake, Geeth

2017-04-01

Rare Earth Elements (REE) are classified in the refractory group, which means that they have a high temperature condensation and their volatility-controlled fractionation is limited to high-temperature processes. Anomalies have been measured for Eu, Yb and Sm, which are the REE with the lowest condensation temperatures in CAIs and chondrules (e.g. [1]). REE are particularly abundant in the sulfides of enstatite chondrites, 100 to 1000 times the CI value [e.g. 2,3], proving that these elements are not strictly lithophile under extremely reducing conditions. However by investigating experimentally the impact of Earth's core formation on the behavior of Sm and Nd, we have shown the absence of fractionation between Sm and Nd during the segregation of the metallic phase [4]. Recently, Wohlers and Wood [5] proposed that Nd and Sm could be fractionated in presence of a S-rich alloy phase. However, their results were obtained at pressure and temperature conditions below the plausible conditions of the Earth's core formation. Clearly, large pressure range needs to be covered before well-constrained model can be expected. Furthermore, our preliminary metal-silicate partitioning results show that Ce and Eu have higher metal/silicate partition coefficients than their neighboring elements, and that the presence of sulphur enhances the relative difference between partition coefficients. In this presentation, we will present and discuss new metal-silicate partition coefficients of all REE at a deep magma ocean at pressures ranging from those of the uppermost upper mantle ( 5 GPa) to a maximum pressure expected in the range of 20 GPa, temperatures ranging from 2500 to about 3000 K, and oxygen fugacities within IW-1 to IW-5 (1 to 5 orders of magnitude lower than the iron-wüstite buffer). We will discuss the effect of S, as well as the effect of H2O on the behaviour of REE during the Earth's core formation: recent models suggest that contrary to currently accepted beliefs, the

Pentadienyl chemistry of the heavy alkaline-earth metals revisited.

PubMed

Reiners, Matthias; Fecker, Ann Christin; Freytag, Matthias; Jones, Peter G; Walter, Marc D

2014-05-14

Open-metallocenes of the heavy alkaline-earth metals [(η(5)-Pdl')2M(thf)n] (M = Ca (1), Sr (2), n = 1; M = Ba (3), n = 2; Pdl' = 2,4-tBu2C5H5) are readily prepared by salt-metathesis between MI2 and KPdl' and characterized by NMR spectroscopy and X-ray diffraction studies.

Computational Studies of Thermodynamics and Kinetics of Metal Oxides in Li-Ion Batteries and Earth's Lower Mantle Materials

NASA Astrophysics Data System (ADS)

Xu, Shenzhen

Metal oxide materials are ubiquitous in nature and in our daily lives. For example, the Earth's mantle layer that makes up about 80% of our Earth's volume is composed of metal oxide materials, the cathode materials in the lithium-ion batteries that provide power for most of our mobile electronic devices are composed of metal oxides, the chemical components of the passivation layers on many kinds of metal materials that protect the metal from further corrosion are metal oxides. This thesis is composed of two major topics about the metal oxide materials in nature. The first topic is about our computational study of the iron chemistry in the Earth's lower mantle metal oxide materials, i.e. the bridgmanite (Fe-bearing MgSiO3 where iron is the substitution impurity element) and the ferropericlase (Fe-bearing MgO where iron is the substitution impurity element). The second topic is about our multiscale modeling works for understanding the nanoscale kinetic and thermodynamic properties of the metal oxide cathode interfaces in Li-ion batteries, including the intrinsic cathode interfaces (intergrowth of multiple types of cathode materials, compositional gradient cathode materials, etc.), the cathode/coating interface systems and the cathode/electrolyte interface systems. This thesis uses models based on density functional theory quantum mechanical calculations to explore the underlying physics behind several types of metal oxide materials existing in the interior of the Earth or used in the applications of lithium-ion batteries. The exploration of this physics can help us better understand the geochemical and seismic properties of our Earth and inspire us to engineer the next generation of electrochemical technologies.

Effect of composition on the structure of lithium- and manganese-rich transition metal oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shukla, Alpesh Khushalchand; Ramasse, Quentin M.; Ophus, Colin

In this work, we establish a definitive structural model for lithium- and manganese-rich transition metal oxides and demonstrate the effect of composition on their bulk as well as the surface structure.

Effect of composition on the structure of lithium- and manganese-rich transition metal oxides

DOE PAGES

Shukla, Alpesh Khushalchand; Ramasse, Quentin M.; Ophus, Colin; ...

2018-01-01

In this work, we establish a definitive structural model for lithium- and manganese-rich transition metal oxides and demonstrate the effect of composition on their bulk as well as the surface structure.

Effect of rare earth metal on the spin-orbit torque in magnetic heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ueda, Kohei; Pai, Chi-Feng; Tan, Aik Jun

2016-06-06

We report the effect of the rare earth metal Gd on current-induced spin-orbit torques (SOTs) in perpendicularly magnetized Pt/Co/Gd heterostructures, characterized using harmonic measurements and spin-torque ferromagnetic resonance (ST-FMR). By varying the Gd metal layer thickness from 0 nm to 8 nm, harmonic measurements reveal a significant enhancement of the effective fields generated from the Slonczewski-like and field-like torques. ST-FMR measurements confirm an enhanced effective spin Hall angle and show a corresponding increase in the magnetic damping constant with increasing Gd thickness. These results suggest that Gd plays an active role in generating SOTs in these heterostructures. Our finding may lead tomore » spin-orbitronics device application such as non-volatile magnetic random access memory, based on rare earth metals.« less

Theoretical Study of pKa Values for Trivalent Rare-Earth Metal Cations in Aqueous Solution.

PubMed

Yu, Donghai; Du, Ruobing; Xiao, Ji-Chang; Xu, Shengming; Rong, Chunying; Liu, Shubin

2018-01-18

Molecular acidity of trivalent rare-earth metal cations in aqueous solution is an important factor dedicated to the efficiency of their extraction and separation processes. In this work, the aqueous acidity of these metal ions has been quantitatively investigated using a few theoretical approaches. Our computational results expressed in terms of pK a values agree well with the tetrad effect of trivalent rare-earth ions extensively reported in the extraction and separation of these elements. Strong linear relationships have been observed between the acidity and quantum electronic descriptors such as the molecular electrostatic potential on the acidic nucleus and the sum of the valence natural atomic orbitals energies of the dissociating proton. Making use of the predicted pK a values, we have also predicted the major ionic forms of these species in the aqueous environment with different pH values, which can be employed to rationalize the behavior difference of different rare-earth metal cations during the extraction process. Our present results should provide needed insights not only for the qualitatively understanding about the extraction and separation between yttrium and lanthanide elements but also for the prediction of novel and more efficient rare-earth metal extractants in the future.

Theoretical study of the alkaline-earth metal superoxides BeO2 through SrO2

NASA Technical Reports Server (NTRS)

Bauschlicher, Charles W., Jr.; Partridge, Harry; Sodupe, Mariona; Langhoff, Stephen R.

1992-01-01

Three competing bonding mechanisms have been identified for the alkaline-earth metal superoxides: these result in a change in the optimal structure and ground state as the alkaline-earth metal becomes heavier. For example, BeO2 has a linear 3Sigma(-)g ground-state structure, whereas both CaO2 and SrO2 have C(2v)1A1 structures. For MgO2, the theoretical calculations are less definitive, as the 3A2 C(2v) structure is computed to lie only about 3 kcal/mol above the 3Sigma(-)g linear structure. The bond dissociation energies for the alkaline-earth metal superoxides have been computed using extensive Gaussian basis sets and treating electron correlation at the modified coupled-pair functional or coupled-cluster singles and doubles level with a perturbational estimate of the triple excitations.

Alkaline earth metal doped tin oxide as a novel oxygen storage material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Qiang, E-mail: dong@tagen.tohoku.ac.jp; Yin, Shu; Yoshida, Mizuki

2015-09-15

Alkaline earth metal doped tin oxide (SnO{sub 2}) hollow nanospheres with a diameter of 50 nm have been synthesized successfully via a facial solvothermal route in a very simple system composed of only ethanol, acetic acid, SnCl{sub 4}·5H{sub 2}O and A(NO{sub 3}){sub 2}·xH{sub 2}O (A = Mg, Ca, Sr, Ba). The synthesized undoped SnO{sub 2} and A-doped SnO{sub 2} hollow nanospheres were characterized by the oxygen storage capacity (OSC), X-ray diffraction, transmission electron microscopy and the Brunauer–Emmet–Teller (BET) technique. The OSC values of all samples were measured using thermogravimetric-differential thermal analysis. The incorporation of alkaline earth metal ion into tinmore » oxide greatly enhanced the thermal stability and OSC. Especially, Ba-doped SnO{sub 2} hollow nanospheres calcined at 1000 °C for 20 h with a BET surface area of 61 m{sup 2} g{sup −1} exhibited the considerably high OSC of 457 μmol-O g{sup −1} and good thermal stability. Alkaline earth metal doped tin oxide has the potential to be a novel oxygen storage material.« less

Blending Non-Group-3 Transition Metal and Rare-Earth Metal into a C80 Fullerene Cage with D5h Symmetry.

PubMed

Wei, Tao; Jin, Fei; Guan, Runnan; Huang, Jing; Chen, Muqing; Li, Qunxiang; Yang, Shangfeng

2018-02-11

Rare-earth metals have been mostly entrapped into fullerene cages to form endohedral clusterfullerenes, whereas non-Group-3 transition metals that can form clusterfullerenes are limited to titanium (Ti) and vanadium (V), and both are exclusively entrapped within an I h -C 80 cage. Non-Group-3 transition-metal-containing endohedral fullerenes based on a C 80 cage with D 5h symmetry, V x Sc 3-x N@D 5h -C 80 (x=1, 2), have now been synthesized, which exhibit two variable cluster compositions. The molecular structure of VSc 2 N@D 5h -C 80 was unambiguously determined by X-ray crystallography. According to a comparative study with the reported Ti- and V-containing clusterfullerenes based on a I h -C 80 cage and the analogous D 5h -C 80 -based metal nitride clusterfullerenes containing rare-earth metals only, the decisive role of the non-Group-3 transition metal on the formation of the corresponding D 5h -C 80 -based clusterfullerenes is unraveled. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Particle size dependence of alkali and alkaline earth metal enrichment in marine aerosols from Bermuda

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoffman, E.J.; Hoffman, G.L.; Duce, R.A.

1980-10-20

Three cascade impactor samples were collected from a 20-m-high tower on the southeastern coast of Bermuda. These samples were analyzed for Na, K, Ca, Mg, and Fe by atomic absorption spectrophotometry. When the alkali-alkakine earth metal concentrations are corrected for a soil-derived component, utilizing the atmospheric Fe concentrations, Mg, Ca, and Na are found to be present in the same relative abundances as in seawater for all particle sizes sampled. Potassium also shows no deviation from a bulk seawater composition for particles with radii greater than approx.0.5 ..mu..m. However, excess K above that expected from either a bulk seawater ormore » soil source is observed on particles with radii less than approx.0.5 ..mu..m. While oceanic chemical fractionation processes during bubble bursting may be responsible for this excess small particle K, it is most likely due to long-range transport of K-rich particles of terrestrial vegetative origin.« less

High-pressure metallization of FeO and implications for the earth's core

NASA Technical Reports Server (NTRS)

Knittle, Elise; Jeanloz, Raymond

1986-01-01

The phase diagram of FeO has been experimentally determined to pressures of 155 GPa and temperatures of 4000 K using shock-wave and diamond-cell techniques. A metallic phase of FeO is observed at pressures greater than 70 GPa and temperatures exceeding 1000 K. The metallization of FeO at high pressures implies that oxygen can be present as the light alloying element of the earth's outer core, in accord with the geochemical predictions of Ringwood (1977 and 1979). The high pressures necessary for this metallization suggest that the core has acquired its composition well after the initial stages of the earth's accretion. Direct experimental observations at elevated pressures and temperatures indicate that core-forming alloy can react chemically with oxides such as those forming the mantle. The core and mantle may never have reached complete chemical equilibrium, however. If this is the case, the core-mantle boundary is likely to be a zone of active chemical reactions.

Non-LTE line-blanketed model atmospheres of hot stars. 2: Hot, metal-rich white dwarfs

NASA Technical Reports Server (NTRS)

Lanz, T.; Hubeny, I.

1995-01-01

We present several model atmospheres for a typical hot metal-rich DA white dwarf, T(sub eff) = 60,000 K, log g = 7.5. We consider pure hydrogen models, as well as models with various abundances of two typical 'trace' elements-carbon and iron. We calculte a number of Local Thermodynamic Equilibrium (LTE) and non-LTE models, taking into account the effect of numerous lines of these elements on the atmospheric structure. We demostrate that while the non-LTE effects are notvery significant for pure hydrogen models, except for describing correctly the central emission in H-alpha they are essential for predicting correctly the ionization balance of metals, such as carbon and iron. Previously reported discrepancies in LTE abundances determinations using C III and C IV lines are easily explained by non-LTE effects. We show that if the iron abundance is larger than 10(exp -5), the iron line opacity has to be considered not only for the spectrum synthesis, but also in the model construction itself. For such metal abundances, non-LTE metal line-blanketed models are needed for detailed abundance studies of hot, metal-rich white dwarfs. We also discuss the predicted Extreme Ultraviolet (EUV) spectrum and show that it is very sensitive to metal abundances, as well as to non-LTE effects.

Carbon and oxygen abundances in cool metal-rich exoplanet hosts: A case study of the C/O ratio of 55 Cancri

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teske, Johanna K.; Cunha, Katia; Schuler, Simon C.

2013-12-01

The super-Earth exoplanet 55 Cnc e, the smallest member of a five-planet system, has recently been observed to transit its host star. The radius estimates from transit observations, coupled with spectroscopic determinations of mass, provide constraints on its interior composition. The composition of exoplanetary interiors and atmospheres are particularly sensitive to elemental C/O ratio, which to first order can be estimated from the host stars. Results from a recent spectroscopic study analyzing the 6300 Å [O I] line and two C I lines suggest that 55 Cnc has a carbon-rich composition (C/O = 1.12 ± 0.09). However, oxygen abundances derivedmore » using the 6300 Å [O I] line are highly sensitive to a Ni I blend, particularly in metal-rich stars such as 55 Cnc ([Fe/H] =0.34 ± 0.18). Here, we further investigate 55 Cnc's composition by deriving the carbon and oxygen abundances from these and additional C and O absorption features. We find that the measured C/O ratio depends on the oxygen lines used. The C/O ratio that we derive based on the 6300 Å [O I] line alone is consistent with the previous value. Yet, our investigation of additional abundance indicators results in a mean C/O ratio of 0.78 ± 0.08. The lower C/O ratio of 55 Cnc determined here may place this system at the sensitive boundary between protoplanetary disk compositions giving rise to planets with high (>0.8) versus low (<0.8) C/O ratios. This study illustrates the caution that must applied when determining planet host star C/O ratios, particularly in cool, metal-rich stars.« less

Nd3Ge1.18In0.82 and Sm3Ge1.33In0.67 - New ternary indides with La3GeIn type structure

NASA Astrophysics Data System (ADS)

Kravets, Oksana; Nychyporuk, Galyna; Muts, Ihor; Hlukhyy, Viktor; Pöttgen, Rainer; Zaremba, Vasyl'

2014-06-01

New indides, Nd3Ge1.18In0.82 and Sm3Ge1.33In0.67, were synthesized from the elements by arc-melting and subsequent annealing at 870 K. Single crystals were grown through special annealing procedures in sealed tantalum tubes in a resistance furnace. Both compounds were investigated on the basis of X-ray powder and single crystal data: La3GeIn type structure, Pearson code tI80, space group I4/mcm; a = 1200.1(1), c = 1562.8(1) pm, wR2 = 0.0781, 716 F2 values, 34 variables for Nd3Ge1.18In0.82 and a = 1184.7(2), c = 1537.0(3) pm, wR2 = 0.0305, 911 F2 values, 34 variables for Sm3Ge1.33In0.67. The crystal chemistry in Nd3Ge1.18In0.82 is discussed from a geometrical point of view and in terms of LMTO band structure calculations.

Extraterrestrial amino acids identified in metal-rich CH and CB carbonaceous chondrites from Antarctica

NASA Astrophysics Data System (ADS)

Burton, Aaron S.; Elsila, Jamie E.; Hein, Jason E.; Glavin, Daniel P.; Dworkin, Jason P.

2013-03-01

Carbonaceous chondrites contain numerous indigenous organic compounds and could have been an important source of prebiotic compounds required for the origin of life on Earth or elsewhere. Extraterrestrial amino acids have been reported in five of the eight groups of carbonaceous chondrites and are most abundant in CI, CM, and CR chondrites but are also present in the more thermally altered CV and CO chondrites. We report the abundance, distribution, and enantiomeric and isotopic compositions of simple primary amino acids in six metal-rich CH and CB carbonaceous chondrites that have not previously been investigated for amino acids: Allan Hills (ALH) 85085 (CH3), Pecora Escarpment (PCA) 91467 (CH3), Patuxent Range (PAT) 91546 (CH3), MacAlpine Hills (MAC) 02675 (CBb), Miller Range (MIL) 05082 (CB), and Miller Range (MIL) 07411 (CB). Amino acid abundances and carbon isotopic values were obtained by using both liquid chromatography time-of-flight mass spectrometry and fluorescence, and gas chromatography isotope ratio mass spectrometry. The δ13C/12C ratios of multiple amino acids fall outside of the terrestrial range and support their extraterrestrial origin. Extracts of CH chondrites were found to be particularly rich in amino acids (13-16 parts per million, ppm) while CB chondrite extracts had much lower abundances (0.2-2 ppm). The amino acid distributions of the CH and CB chondrites were distinct from the distributions observed in type 2 and 3 CM and CR chondrites and contained elevated levels of β-, γ-, and δ-amino acids compared to the corresponding α-amino acids, providing evidence that multiple amino acid formation mechanisms were important in CH and CB chondrites.

Extraterrestrial Amino Acids Identified in Metal-Rich CH and CB Carbonaceous Chondrites from Antarctica

NASA Technical Reports Server (NTRS)

Burton, Aaron S.; Elsila, Jamie E.; Hein, Jason E.; Glavin, Daniel P.; Dworkin, Jason P.

2013-01-01

Carbonaceous chondrites contain numerous indigenous organic compounds and could have been an important source of prebiotic compounds required for the origin of life on Earth or elsewhere. Extraterrestrial amino acids have been reported in five of the eight groups of carbonaceous chondrites and are most abundant in CI, CM, and CR chondritesbut are also present in the more thermally altered CV and CO chondrites. We report the abundance, distribution, and enantiomeric and isotopic compositions of simple primary amino acids in six metal-rich CH and CB carbonaceous chondrites that have not previously been investigated for amino acids: Allan Hills (ALH) 85085 (CH3), Pecora Escarpment(PCA) 91467 (CH3), Patuxent Range (PAT) 91546 (CH3), MacAlpine Hills (MAC) 02675(CBb), Miller Range (MIL) 05082 (CB), and Miller Range (MIL) 07411 (CB). Amino acid abundances and carbon isotopic values were obtained by using both liquid chromatography time-of-flight mass spectrometry and fluorescence, and gas chromatography isotope ratiomass spectrometry. The (delta D, delta C-13, delta N-15) ratios of multiple amino acids fall outside of the terrestrial range and support their extraterrestrial origin. Extracts of CH chondrites were found to be particularly rich in amino acids (1316 parts per million, ppm) while CB chondrite extracts had much lower abundances (0.22 ppm). The amino acid distributions of the CH and CB chondrites were distinct from the distributions observed in type 2 and 3 CM and CR chondrites and contained elevated levels of beta-, gamma-, and delta-amino acids compared to the corresponding alpha-amino acids, providing evidence that multiple amino acid formation mechanisms were important in CH and CB chondrites.

Carbon and sulfur budget of the silicate Earth explained by accretion of differentiated planetary embryos

NASA Astrophysics Data System (ADS)

Li, Yuan; Dasgupta, Rajdeep; Tsuno, Kyusei; Monteleone, Brian; Shimizu, Nobumichi

2016-10-01

The abundances of volatile elements in the Earth's mantle have been attributed to the delivery of volatile-rich material after the main phase of accretion. However, no known meteorites could deliver the volatile elements, such as carbon, nitrogen, hydrogen and sulfur, at the relative abundances observed for the silicate Earth. Alternatively, Earth could have acquired its volatile inventory during accretion and differentiation, but the fate of volatile elements during core formation is known only for a limited set of conditions. Here we present constraints from laboratory experiments on the partitioning of carbon and sulfur between metallic cores and silicate mantles under conditions relevant for rocky planetary bodies. We find that carbon remains more siderophile than sulfur over a range of oxygen fugacities; however, our experiments suggest that in reduced or sulfur-rich bodies, carbon is expelled from the segregating core. Combined with previous constraints, we propose that the ratio of carbon to sulfur in the silicate Earth could have been established by differentiation of a planetary embryo that was then accreted to the proto-Earth. We suggest that the accretion of a Mercury-like (reduced) or a sulfur-rich (oxidized) differentiated body--in which carbon has been preferentially partitioned into the mantle--may explain the Earth's carbon and sulfur budgets.

Composite nanoparticles containing rare earth metal and methods of preparation thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kandapallil, Binil Itty Ipe; Krishnan, Lakshmi; Johnson, Francis

The present invention is directed to composite nanoparticles comprising a metal, a rare earth element, and, optionally, a complexing ligand. The invention is also directed to composite nanoparticles having a core-shell structure and to processes for preparation of composite nanoparticles of the invention.

An Earth-sized exoplanet with a Mercury-like composition

NASA Astrophysics Data System (ADS)

Santerne, A.; Brugger, B.; Armstrong, D. J.; Adibekyan, V.; Lillo-Box, J.; Gosselin, H.; Aguichine, A.; Almenara, J.-M.; Barrado, D.; Barros, S. C. C.; Bayliss, D.; Boisse, I.; Bonomo, A. S.; Bouchy, F.; Brown, D. J. A.; Deleuil, M.; Delgado Mena, E.; Demangeon, O.; Díaz, R. F.; Doyle, A.; Dumusque, X.; Faedi, F.; Faria, J. P.; Figueira, P.; Foxell, E.; Giles, H.; Hébrard, G.; Hojjatpanah, S.; Hobson, M.; Jackman, J.; King, G.; Kirk, J.; Lam, K. W. F.; Ligi, R.; Lovis, C.; Louden, T.; McCormac, J.; Mousis, O.; Neal, J. J.; Osborn, H. P.; Pepe, F.; Pollacco, D.; Santos, N. C.; Sousa, S. G.; Udry, S.; Vigan, A.

2018-05-01

Earth, Venus, Mars and some extrasolar terrestrial planets1 have a mass and radius that is consistent with a mass fraction of about 30% metallic core and 70% silicate mantle2. At the inner frontier of the Solar System, Mercury has a completely different composition, with a mass fraction of about 70% metallic core and 30% silicate mantle3. Several formation or evolution scenarios are proposed to explain this metal-rich composition, such as a giant impact4, mantle evaporation5 or the depletion of silicate at the inner edge of the protoplanetary disk6. These scenarios are still strongly debated. Here, we report the discovery of a multiple transiting planetary system (K2-229) in which the inner planet has a radius of 1.165 ± 0.066 Earth radii and a mass of 2.59 ± 0.43 Earth masses. This Earth-sized planet thus has a core-mass fraction that is compatible with that of Mercury, although it was expected to be similar to that of Earth based on host-star chemistry7. This larger Mercury analogue either formed with a very peculiar composition or has evolved, for example, by losing part of its mantle. Further characterization of Mercury-like exoplanets such as K2-229 b will help to put the detailed in situ observations of Mercury (with MESSENGER and BepiColombo8) into the global context of the formation and evolution of solar and extrasolar terrestrial planets.

Metallic rare-earth silicide nanowires on silicon surfaces.

PubMed

Dähne, Mario; Wanke, Martina

2013-01-09

The formation, atomic structure, and electronic properties of self-assembled rare-earth silicide nanowires on silicon surfaces were studied by scanning tunneling microscopy and angle-resolved photoelectron spectroscopy. Metallic dysprosium and erbium silicide nanowires were observed on both the Si(001) and Si(557) surfaces. It was found that they consist of hexagonal rare-earth disilicides for both surface orientations. On Si(001), the nanowires are characterized by a one-dimensional band structure, while the electronic dispersion is two-dimensional for the nanowires formed on Si(557). This behavior is explained by the different orientations of the hexagonal c axis of the silicide leading to different conditions for the carrier confinement. By considering this carrier confinement it is demonstrated how the one-dimensional band structure of the nanowires on Si(001) can be derived from the two-dimensional one of the silicide monolayer on Si(111).

METAL-RICH PLANETARY NEBULAE IN THE OUTER REACHES OF M31

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balick, B.; Kwitter, K. B.; Corradi, R. L. M.

2013-09-01

Spectroscopic data of two relatively [O III]-luminous planetary nebulae (PNe) have been obtained with the 10.4 m Gran Telescopio Canarias. M174 and M2496 are each {approx}1 Degree-Sign from the center of M31 along opposite sides of its minor axis. The ensemble of these 2 distant PNe plus 16 similarly luminous outer-disk PNe published previously by Kwitter et al. forms a homogeneous group in luminosity, metal content, progenitor mass, age, and kinematics. The main factual findings of our work are (1) O/H (and other low-mass {alpha} elements and their ratios to O) is uniformly solar-like in all 18 PNe ((12 +more » log(O/H)) = 8.62 {+-} 0.14); (2) the general sky distribution and kinematics of the ensemble much more closely resemble the rotation pattern of the classical disk of M31 than its halo or bulge; (3) the O/H gradient is surprisingly flat beyond R{sub g} {approx} 20 kpc. The PNe are too metal-rich to be bona fide members of M31's disk or halo, and (4) the abundance patterns of the sample are distinct from those in the spiral galaxies M33, M81, and NGC 300. Using standard PN age diagnostic methods, we suggest that all of the PNe formed {approx}2 Gyr ago in a starburst of metal-rich interstellar medium that followed an M31-M33 encounter about 3 Gyr ago. We review supporting evidence from stellar studies. Other more prosaic explanations, such as dwarf galaxy assimilation, are unlikely.« less

Rare earth element recycling from waste nickel-metal hydride batteries.

PubMed

Yang, Xiuli; Zhang, Junwei; Fang, Xihui

2014-08-30

With an increase in number of waste nickel-metal hydride batteries, and because of the importance of rare earth elements, the recycling of rare earth elements is becoming increasingly important. In this paper, we investigate the effects of temperature, hydrochloric acid concentration, and leaching time to optimize leaching conditions and determine leach kinetics. The results indicate that an increase in temperature, hydrochloric acid concentration, and leaching time enhance the leaching rate of rare earth elements. A maximum rare earth elements recovery of 95.16% was achieved at optimal leaching conditions of 70°C, solid/liquid ratio of 1:10, 20% hydrochloric acid concentration, -74μm particle size, and 100min leaching time. The experimental data were best fitted by a chemical reaction-controlled model. The activation energy was 43.98kJ/mol and the reaction order for hydrochloric acid concentration was 0.64. The kinetic equation for the leaching process was found to be: 1-(1-x)(1/3)=A/ρr0[HCl](0.64)exp-439,8008.314Tt. After leaching and filtration, by adding saturated oxalic solution to the filtrate, rare earth element oxalates were obtained. After removing impurities by adding ammonia, filtering, washing with dilute hydrochloric acid, and calcining at 810°C, a final product of 99% pure rare earth oxides was obtained. Copyright © 2014 Elsevier B.V. All rights reserved.

How Does Boiling in the Earth's Crust Influence Metal Speciation and Transport?

NASA Astrophysics Data System (ADS)

Kam, K.; Lemke, K.

2014-12-01

The presence of large quantities of precious metals, such as gold and copper, near the Earth's surface (upper crust) is commonly attributed to transport in aqueous solution and precipitation upon variations in temperature and pressure. As a consequence, gold exploration is closely linked to solution chemistry, i.e. hydrothermal processes involving aqueous fluids with densities of around unity. However, as crustal fluids buoyantly ascend, boiling produces a coexisting low-density aqueous liquid with fundamentally different physical and chemical properties, and a, most importantly, a high affinity for coinage metals (Heinrich et al., Econ Geol., 1992, 87, 1566). From recent experimental studies of Au (Hurtig and Williams-Jones, 2014, Geochim. Cosmochim. Acta,, 127, 304), we know that metal speciation in this low-density phase differs fundamentally from that observed in bulk solution, clearly, with important implications for Au, and metal speciation in general, transport and ore concentrations processes (these processes would also be operable in industrial geothermal plants given the quite special solvent properties of steam). In brief, this study focuses on the speciation of select metal halides in bulk solution as well as in water vapor, and is driven by our need to understand the solvent properties of around 2.0x109 cubic kilometers of free water (or 2,500 times as much water as stored in all lakes and rivers) present in the Earth's crust. The scope of this study has particular applications in the geothermal and oil industries, as both deal with high temperature low-density aqueous fluids. Understanding how metal halide species behave upon boiling can also provide insight into how metals, such as copper and silver, coat turbine equipment and steam piping in geothermal plants, ultimately rendering these components inoperable. This study will also provide preliminary results from mass spectrometric experiments of transition metal halides, and will be augmented with

Experimental constraints on Earth's core formation

NASA Astrophysics Data System (ADS)

Bouhifd, Mohamed Ali

2017-04-01

The Earth contains a Fe-rich metallic core that segregated from the primitive silicate mantle very early in its 4.5 billion year history. One major consequence of this segregation is the depletion of the Earth's mantle from the siderophile elements "high core affinity" relative to primitive solar system abundances. The way in which siderophile elements partition between metal and silicate depends strongly on pressure (P), temperature (T), oxygen fugacity (fO2) and chemical compositions of both metal and silicate phases. In the present presentation, I will discuss the experimental results of metal-silicate partitioning of Ni and Co that show a marked change with increasing pressure (e.g. Bouhifd and Jephcoat, 2011; Siebert et al., 2012; Fischer et al., 2015 for the most recent studies). This behavior coincides with a change in the coordination of silicon (in a basaltic melt composition) from 4-fold coordination under ambient conditions to 6-fold coordination at about 35 GPa, indicating that melt compressibility may controls siderophile-element partitioning (Sanloup et al., 2013). I will also discuss the impact of Earth's core formation on "lithophile" elements such as Sm, Nd, Ta and Nb (e.g. Bouhifd et al. 2015; Cartier et al., 2014), as well as the impact of sulphur on the behavior of various elements during core formation (e.g. Boujibar et al., 2014; Wohlers and Wood, 2015). By combining the metal-silicate partitioning data from siderophile, lithophile and chalcophile elements I will present and discuss the most plausible conditions for Earth's core formation. References Bouhifd and Jephcoat (2011) EPSL, 307, 341-348. Bouhifd et al. (2015) EPSL 413, 158-166. Boujibar et al. (2014) EPSL 391, 42-54. Cartier et al. (2014) Nature Geoscience, 7, 573-576. Fischer et al. (2015) GCA 167, 177-194. Sanloup et al. (2013) Nature, 503, 104-107. Siebert et al. (2012) EPSL 321-322, 189-197. Wohlers and Wood (2015) Nature 520, 337-340.

High-pressure phase transitions in rare earth metal thulium to 195 GPa.

PubMed

Montgomery, Jeffrey M; Samudrala, Gopi K; Tsoi, Georgiy M; Vohra, Yogesh K

2011-04-20

We have performed image plate x-ray diffraction studies on a heavy rare earth metal, thulium (Tm), in a diamond anvil cell to a pressure of 195 GPa and volume compression V/V₀ = 0.38 at room temperature. The rare earth crystal structure sequence, hcp →Sm-type→ dhcp →fcc → distorted fcc, is observed in Tm below 70 GPa with the exception of a pure fcc phase. The focus of our study is on the ultrahigh-pressure phase transition and Rietveld refinement of crystal structures in the pressure range between 70 and 195 GPa. The hexagonal hR-24 phase is seen to describe the distorted fcc phase between 70 and 124 GPa. Above 124 ± 4 GPa, a structural transformation from hR 24 phase to a monoclinic C 2/m phase is observed with a volume change of -1.5%. The equation of state data shows rapid stiffening above the phase transition at 124 GPa and is indicative of participation of f-electrons in bonding. We compare the behavior of Tm to other heavy rare-earths and heavy actinide metals under extreme conditions of pressure.

High-pressure phase transitions in rare earth metal thulium to 195 GPa

NASA Astrophysics Data System (ADS)

Montgomery, Jeffrey M.; Samudrala, Gopi K.; Tsoi, Georgiy M.; Vohra, Yogesh K.

2011-04-01

We have performed image plate x-ray diffraction studies on a heavy rare earth metal, thulium (Tm), in a diamond anvil cell to a pressure of 195 GPa and volume compression V/Vo = 0.38 at room temperature. The rare earth crystal structure sequence, {hcp}\\to {Sm {-}type} \\to {dhcp} \\to {fcc} \\to distorted fcc, is observed in Tm below 70 GPa with the exception of a pure fcc phase. The focus of our study is on the ultrahigh-pressure phase transition and Rietveld refinement of crystal structures in the pressure range between 70 and 195 GPa. The hexagonal hR- 24 phase is seen to describe the distorted fcc phase between 70 and 124 GPa. Above 124 ± 4 GPa, a structural transformation from hR 24 phase to a monoclinic C 2/m phase is observed with a volume change of - 1.5%. The equation of state data shows rapid stiffening above the phase transition at 124 GPa and is indicative of participation of f-electrons in bonding. We compare the behavior of Tm to other heavy rare-earths and heavy actinide metals under extreme conditions of pressure.

Dynamical Correlation In Some Liquid Alkaline Earth Metals Near Melting

NASA Astrophysics Data System (ADS)

Thakore, B. Y.; Suthar, P. H.; Khambholja, S. G.; Gajjar, P. N.; Jani, A. R.

2010-12-01

The study of dynamical variables: velocity autocorrelation function (VACF) and power spectrum of liquid alkaline earth metals (Ca, Sr, and Ba) have been presented based on the static harmonic well approximation. The effective interatomic potential for liquid metals is computed using our well recognized model potential with the exchange correlation functions due to Hartree, Taylor, Ichimaru and Utsumi, Farid et al. and Sarkar et al. It is observed that the VACF computed using Sarkar et al. gives the good agreement with available molecular dynamics simulation (MD) results [Phys Rev. B 62, 14818 (2000)]. The shoulder of the power spectrum depends upon the type of local field correlation function used.

Wüstite in the fusion crust of Almahata Sitta sulfide-metal assemblage MS-166: Evidence for oxygen in metallic melts

NASA Astrophysics Data System (ADS)

Horstmann, Marian; Humayun, Munir; Harries, Dennis; Langenhorst, Falko; Chabot, Nancy L.; Bischoff, Addi; Zolensky, Michael E.

2013-05-01

Meteorite fusion crusts form during the passage of a meteoroid through the Earth's atmosphere and are highly oxidized intergrowths as documented by the presence of e.g., oxides. The porous and irregular fusion crust surrounding the Almahata Sitta sulfide-metal assemblage MS-166 was found highly enriched in wüstite (Fe1-xO). Frictional heating of the outer portions of the assemblage caused partial melting of predominantly the Fe-sulfide and minor amounts of the outer Ni-rich portions of the originally zoned metal in MS-166. Along with melting significant amounts of oxygen were incorporated into the molten fusion crust and mainly FeS was oxidized and desulfurized to form wüstite. Considerable amounts of FeS were lost due to ablation, whereas the cores of the large metal grains appear largely unmelted leaving behind metal grains and surrounding wüstite-rich material (matte). Metal grains along with the surrounding matte typically form an often highly porous framework of globules interconnected with the matte. Although textures and chemical composition suggest that melting of Fe,Ni metal occurred only partially (Ni-rich rims), there is a trace elemental imprint of siderophile element partitioning influenced by oxygen in the metallic melt as indicated by the behavior of W and Ga, the two elements significantly affected by oxygen in a metallic melt. It is remarkable that MS-166 survived the atmospheric passage as troilite inclusions in iron meteorites are preferentially destroyed.

Separation of rare earths from transition metals by liquid-liquid extraction from a molten salt hydrate to an ionic liquid phase.

PubMed

Rout, Alok; Binnemans, Koen

2014-02-28

The solvent extraction of trivalent rare-earth ions and their separation from divalent transition metal ions using molten salt hydrates as the feed phase and an undiluted fluorine-free ionic liquid as the extracting phase were investigated in detail. The extractant was tricaprylmethylammonium nitrate, [A336][NO3], and the hydrated melt was calcium nitrate tetrahydrate, Ca(NO3)2·4H2O. The extraction behavior of rare-earth ions was studied for solutions of individual elements, as well as for mixtures of rare earths in the hydrated melt. The influence of different extraction parameters was investigated: the initial metal loading in the feed phase, percentage of water in the feed solution, equilibration time, and the type of hydrated melt. The extraction of rare earths from Ca(NO3)2·4H2O was compared with extraction from CaCl2·4H2O by [A336][Cl] (Aliquat 336). The nitrate system was found to be the better one. The extraction and separation of rare earths from the transition metals nickel, cobalt and zinc were also investigated. Remarkably high separation factors of rare-earth ions over transition metal ions were observed for extraction from Ca(NO3)2·4H2O by the [A336][NO3] extracting phase. Furthermore, rare-earth ions could be separated efficiently from transition metal ions, even in melts with very high concentrations of transition metal ions. Rare-earth oxides could be directly dissolved in the Ca(NO3)2·4H2O phase in the presence of small amounts of Al(NO3)3·9H2O or concentrated nitric acid. The efficiency of extraction after dissolving the rare-earth oxides in the hydrated nitrate melt was identical to extraction from solutions with rare-earth nitrates dissolved in the molten phase. The stripping of the rare-earth ions from the loaded ionic liquid phase and the reuse of the recycled ionic liquid were also investigated in detail.

ACFER 182/207/214 A Metal-rich, Volatile-poor Chondritic Meteorite, Similar to ALH85085

NASA Astrophysics Data System (ADS)

Palme, H.; Spettel, B.

1992-07-01

low temperatures, after the chondrule-forming process had transformed silicate grains into chondrules and fine metal grains into coarser metal. Partial loss of volatiles during chondrule formation or reheating of a metal-silicate assemblage with high volatile element abundances are very unlikely to produce the observed depletion sequence as argued by Grossman et al. (1988) for ALH85085. In addition, experiments on artificially heated meteorites produce losses of volatiles that are strongly dependent on fO(sub)2 and are incompatible with the patterns observed in ACFER182 (Wulf and Palme 1991). For example, the observed depletion of Mn in Acfer182 is 0.35 (i.e., 65 % are not condensed). However, Mn loss was never observed in the heating experiments, while large losses of Ga, Se, and Zn were found at temperatures up to 1300 degrees C. At temperatures required for Mn-volatilisation most other moderately volatiles would be quantitatively removed. However, the delicate pattern of moderate volatiles excludes ACFER182 as being a simple mixture of volatile-rich and volatile-poor material. Chemically, ACFER182 and ALHA85085 are related to CR-chondrites. These meteorites follow a trend of increasingly lower contents of volatile elements (e.g., Se, Zn) with decreasing contents of refractory element contents (e.g., Sc), opposite to the major trend in carbonaceous chondrites (from CI to CV). The ACFER182 and ALH85085 meteorites with their low Zn and Se contents and their low Sc abundances appear to form an endmember of this trend. Additional similarities with CR-meteorites in texture, mineralogy, and O, C, and N isotopic compositions (Bischoff et al. 1992; Prinz and Weisberg 1992 and references therein) may indicate that these meteorites are not as unique as originally thought. References: Bischoff A., Palme H., Schultz L., Weber D., Weber H.W. and Spettel B. (submitted to Geochim. Cosmochim. Acta 1992). Grossman J.N., Rubin A.E., MacPherson G.J. (1988) Earth Planet. Sci. Lett. 91

Thermodynamic Considerations of Direct Oxygen Removal from Titanium by Utilizing the Deoxidation Capability of Rare Earth Metals

NASA Astrophysics Data System (ADS)

Okabe, Toru H.; Zheng, Chenyi; Taninouchi, Yu-ki

2018-06-01

Oxygen removal from metallic Ti is extremely difficult and, currently, there is no commercial process for effectively deoxidizing Ti or its alloys. The oxygen concentration in Ti scraps is normally higher than that in virgin metals such as in Ti sponges produced by the Kroll process. When scraps are remelted with virgin metals for producing primary ingots of Ti or its alloys, the amount of scrap that can be used is limited owing to the accumulation of oxygen impurities. Future demands of an increase in Ti production and of mitigating environmental impacts require that the amount of scrap recycled as a feed material of Ti ingots should also increase. Therefore, it is important to develop methods for removing oxygen directly from Ti scraps. In this study, we evaluated the deoxidation limit for β-Ti using Y or light rare earth metals (La, Ce, Pr, or Nd) as a deoxidant. Thermodynamic considerations suggest that extra-low-oxygen Ti, with an oxygen concentration of 100 mass ppm or less can be obtained using a molten salt equilibrating with rare earth metals. The results presented herein also indicate that methods based on molten salt electrolysis for producing rare earth metals can be utilized for effectively and directly deoxidizing Ti scraps.

Simultaneous recovery of benzene-rich oil and metals by steam pyrolysis of metal-poly(ethylene terephthalate) composite waste.

PubMed

Kumagai, Shogo; Grause, Guido; Kameda, Tomohito; Yoshioka, Toshiaki

2014-03-18

The possibility of simultaneous recovery of benzene and metals from the hydrolysis of poly(ethylene terephthalate) (PET)-based materials such as X-ray films, magnetic tape, and prepaid cards under a steam atmosphere at a temperature of 450 °C was evaluated. The hydrolysis resulted in metal-containing carbonaceous residue and volatile terephthalic acid (TPA). The effects of metals and additives on the recovery process were also investigated. All metals were quantitatively recovered, and silver, maghemite (γ-Fe2O3), and anatase (TiO2) were recovered without any changes in their crystal structures or compositions. In a second step, TPA was decarboxylized in the presence of calcium oxide (CaO) at 700 °C, producing benzene with an average yield of 34% and purity of 76%. Maghemite (γ-Fe2O3) incorporated in magnetic tape and prepaid cards could decarboxylate TPA. Aluminum present in the prepaid cards produced hydrogen by the reaction with steam. However, the presence of metals had no adverse influence on the recovery of benzene-rich oil in the presence of CaO. Therefore, this method can be applied to PET-based materials containing inorganic substances, which cannot be recycled effectively otherwise.

Voltage Control of Rare-Earth Magnetic Moments at the Magnetic-Insulator-Metal Interface

NASA Astrophysics Data System (ADS)

Leon, Alejandro O.; Cahaya, Adam B.; Bauer, Gerrit E. W.

2018-01-01

The large spin-orbit interaction in the lanthanides implies a strong coupling between their internal charge and spin degrees of freedom. We formulate the coupling between the voltage and the local magnetic moments of rare-earth atoms with a partially filled 4 f shell at the interface between an insulator and a metal. The rare-earth-mediated torques allow the power-efficient control of spintronic devices by electric-field-induced ferromagnetic resonance and magnetization switching.

Disturbances to metal partitioning during toxicity testing of iron(II)-rich estuarine pore waters and whole sediments.

PubMed

Simpson, Stuart L; Batley, Graeme E

2003-02-01

Metal partitioning is altered when suboxic estuarine sediments containing Fe(II)-rich pore waters are disturbed during collection, preparation, and toxicity testing. Experiments with model Fe(II)-rich pore waters demonstrated the rates at which adsorptive losses of Cd, Cu, Ni, Mn, Pb, and Zn occur upon exposure to air. Experiments with Zn-contaminated estuarine sediments demonstrated large and often unpredictable changes to metal partitioning during sediment storage, removal of organisms, and homogenization before testing. Small modifications to conditions, such as aeration of overlying waters, caused large changes to the metal partitioning. Disturbances caused by sediment collection required many weeks for reestablishment of equilibrium. Bioturbation by benthic organisms led to oxidation of pore-water Fe(II) and lower Zn fluxes because of the formation of Fe hydroxide precipitates that adsorb pore-water Zn. For five weeks after the addition of organisms to sediments, Zn fluxes increased slowly as the organisms established themselves in the sediments, indicating that the establishment of equilibrium was not rapid. The results are discussed in terms of the dynamic nature of suboxic, Fe(II)-rich estuarine sediments, how organisms perturb their environment, and the importance of understanding chemistry in toxicity testing with whole sediments or pore water. Recommendations are provided for the handling of sediments for toxicity testing.

A hydrogen-rich early Earth atmosphere.

PubMed

Tian, Feng; Toon, Owen B; Pavlov, Alexander A; De Sterck, H

2005-05-13

We show that the escape of hydrogen from early Earth's atmosphere likely occurred at rates slower by two orders of magnitude than previously thought. The balance between slow hydrogen escape and volcanic outgassing could have maintained a hydrogen mixing ratio of more than 30%. The production of prebiotic organic compounds in such an atmosphere would have been more efficient than either exogenous delivery or synthesis in hydrothermal systems. The organic soup in the oceans and ponds on early Earth would have been a more favorable place for the origin of life than previously thought.

V, Cr, and Mn in the Earth, Moon, EPB, and SPB and the origin of the Moon: Experimental studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drake, M.J.; Capobianco, C.J.; Newsom, H.E.

1989-08-01

The abundances of V, Cr, and Mn inferred for the mantles of the Earth and Moon decrease in that order and are similar, but are distinct from those inferred for the mantles of the Eucrite Parent Body (EPB) and Shergottite Parent Body (SPB). This similarity between Earth and Moon has been used to suggest that the Moon is derived substantially or entirely from Earth mantle material following terrestrial core formation. To test this hypothesis, the authors have determined the partitioning of V, Cr, and Mn between solid iron metal, S-rich metallic liquid, and synthetic basaltic silicate liquid at 1,260{degree}C andmore » one bar pressure. The sequence of compatibility in the metallic phases is Cr > V > Mn at high oxygen fugacity and V > Cr > Mn at low oxygen fugacities. Solubilities in liquid metal always exceed solubilities in solid metal. These partition coefficients suggest that the abundances of V, Cr, and Mn do not reflect core formation in the Earth. Rather, they are consistent with the relative volatilities of these elements. The similarity in the depletion patterns of V, Cr, and Mn inferred for the mantles of the Earth and Moon is a necessary, but not sufficient, condition for the Moon to have been derived wholly or in part from the Earth's mantle.« less

Adsorption of alkali and alkaline earth metal atoms and dimers on monolayer germanium carbide

NASA Astrophysics Data System (ADS)

Gökçe, Aytaç Gürhan; Ersan, Fatih

2017-01-01

First-principles plane wave calculations have been performed to study the adsorption of alkali and alkaline earth metals on monolayer germanium carbide (GeC). We found that the favourable adsorption sites on GeC sheet for single alkali and alkaline earth adatoms are generally different from graphene or germanene. Among them, Mg, Na and their dimers have weakly bounded to GeC due to their closed valence electron shells, so they may have high mobility on GeC. Two different levels of adatom coverage (? and ?) have been investigated and we concluded that different electronic structures and magnetic moments for both coverages owing to alkali and alkaline earth atoms have long range electrostatic interactions. Lithium atom prefers to adsorbed on hollow site similar to other group-IV monolayers and the adsorption results in metallisation of GeC instead of semiconducting behaviour. Na and K adsorption can induce 1 ? total magnetic moment on GeC structures and they have shown semiconductor property which may have potential use in spintronic devices. We also showed that alkali or alkaline earth metal atoms can form dimer on GeC sheet. Calculated adsorption energies suggest that clustering of alkali and alkaline earth atoms is energetically favourable. All dimer adsorbed GeC systems have nonmagnetic semiconductor property with varying band gaps from 0.391 to 1.311 eV which are very suitable values for various device applications.

Identification of New Neutron-Rich Isotopes in the Rare-Earth Region Produced by 345 MeV/nucleon 238U

NASA Astrophysics Data System (ADS)

Fukuda, Naoki; Kubo, Toshiyuki; Kameda, Daisuke; Inabe, Naohito; Suzuki, Hiroshi; Shimizu, Yohei; Takeda, Hiroyuki; Kusaka, Kensuke; Yanagisawa, Yoshiyuki; Ohtake, Masao; Tanaka, Kanenobu; Yoshida, Koichi; Sato, Hiromi; Baba, Hidetada; Kurokawa, Meiko; Ohnishi, Tetsuya; Iwasa, Naohito; Chiba, Ayuko; Yamada, Taku; Ideguchi, Eiji; Go, Shintaro; Yokoyama, Rin; Fujii, Toshihiko; Nishibata, Hiroki; Ieki, Kazuo; Murai, Daichi; Momota, Sadao; Nishimura, Daiki; Sato, Yoshiteru; Hwang, Jongwon; Kim, Sunji; Tarasov, Oleg B.; Morrissey, David J.; Simpson, Gary

2018-01-01

A search for new isotopes in the neutron-rich rare-earth region has been carried out using a 345 MeV/nucleon 238U beam at the RIKEN Nishina Center RI Beam Factory. Fragments produced were analyzed and identified using the BigRIPS in-flight separator. We observed a total of 29 new neutron-rich isotopes: 153Ba, 154,155,156La, 156,157,158Ce, 156,157,158,159,160,161Pr, 162,163Nd, 164,165Pm, 166,167Sm, 169Eu, 171Gd, 173,174Tb, 175,176Dy, 177,178Ho, and 179,180Er.

Determination of Thermodynamic Properties of Alkaline Earth-liquid Metal Alloys Using the Electromotive Force Technique

PubMed Central

Nigl, Thomas P.; Smith, Nathan D.; Lichtenstein, Timothy; Gesualdi, Jarrod; Kumar, Kuldeep; Kim, Hojong

2017-01-01

A novel electrochemical cell based on a CaF2 solid-state electrolyte has been developed to measure the electromotive force (emf) of binary alkaline earth-liquid metal alloys as functions of both composition and temperature in order to acquire thermodynamic data. The cell consists of a chemically stable solid-state CaF2-AF2 electrolyte (where A is the alkaline-earth element such as Ca, Sr, or Ba), with binary A-B alloy (where B is the liquid metal such as Bi or Sb) working electrodes, and a pure A metal reference electrode. Emf data are collected over a temperature range of 723 K to 1,123 K in 25 K increments for multiple alloy compositions per experiment and the results are analyzed to yield activity values, phase transition temperatures, and partial molar entropies/enthalpies for each composition. PMID:29155770

Ground-state properties of rare-earth metals: an evaluation of density-functional theory.

PubMed

Söderlind, Per; Turchi, P E A; Landa, A; Lordi, V

2014-10-15

The rare-earth metals have important technological applications due to their magnetic properties, but are scarce and expensive. Development of high-performance magnetic materials with less rare-earth content is desired, but theoretical modeling is hampered by complexities of the rare earths electronic structure. The existence of correlated (atomic-like) 4f electrons in the vicinity of the valence band makes any first-principles theory challenging. Here, we apply and evaluate the efficacy of density-functional theory for the series of lanthanides (rare earths), investigating the influence of the electron exchange and correlation functional, spin-orbit interaction, and orbital polarization. As a reference, the results are compared with those of the so-called 'standard model' of the lanthanides in which electrons are constrained to occupy 4f core states with no hybridization with the valence electrons. Some comparisons are also made with models designed for strong electron correlations. Our results suggest that spin-orbit coupling and orbital polarization are important, particularly for the magnitude of the magnetic moments, and that calculated equilibrium volumes, bulk moduli, and magnetic moments show correct trends overall. However, the precision of the calculated properties is not at the level of that found for simpler metals in the Periodic Table of Elements, and the electronic structures do not accurately reproduce x-ray photoemission spectra.

Temperate Earth-sized planets transiting a nearby ultracool dwarf star

NASA Astrophysics Data System (ADS)

Gillon, Michaël; Jehin, Emmanuël; Lederer, Susan M.; Delrez, Laetitia; de Wit, Julien; Burdanov, Artem; Van Grootel, Valérie; Burgasser, Adam J.; Triaud, Amaury H. M. J.; Opitom, Cyrielle; Demory, Brice-Olivier; Sahu, Devendra K.; Bardalez Gagliuffi, Daniella; Magain, Pierre; Queloz, Didier

2016-05-01

Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as ‘ultracool dwarfs’. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the Sun. Core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disks, there should be a large but hitherto undetected population of terrestrial planets orbiting them—ranging from metal-rich Mercury-sized planets to more hospitable volatile-rich Earth-sized planets. Here we report observations of three short-period Earth-sized planets transiting an ultracool dwarf star only 12 parsecs away. The inner two planets receive four times and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star. Our data suggest that 11 orbits remain possible for the third planet, the most likely resulting in irradiation significantly less than that received by Earth. The infrared brightness of the host star, combined with its Jupiter-like size, offers the possibility of thoroughly characterizing the components of this nearby planetary system.

Temperate Earth-sized planets transiting a nearby ultracool dwarf star.

PubMed

Gillon, Michaël; Jehin, Emmanuël; Lederer, Susan M; Delrez, Laetitia; de Wit, Julien; Burdanov, Artem; Van Grootel, Valérie; Burgasser, Adam J; Triaud, Amaury H M J; Opitom, Cyrielle; Demory, Brice-Olivier; Sahu, Devendra K; Bardalez Gagliuffi, Daniella; Magain, Pierre; Queloz, Didier

2016-05-12

Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as 'ultracool dwarfs'. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the Sun. Core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disks, there should be a large but hitherto undetected population of terrestrial planets orbiting them--ranging from metal-rich Mercury-sized planets to more hospitable volatile-rich Earth-sized planets. Here we report observations of three short-period Earth-sized planets transiting an ultracool dwarf star only 12 parsecs away. The inner two planets receive four times and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star. Our data suggest that 11 orbits remain possible for the third planet, the most likely resulting in irradiation significantly less than that received by Earth. The infrared brightness of the host star, combined with its Jupiter-like size, offers the possibility of thoroughly characterizing the components of this nearby planetary system.

The Electronic Structure and Optical Properties of Anatase TiO₂ with Rare Earth Metal Dopants from First-Principles Calculations.

PubMed

Xie, Kefeng; Jia, Qiangqiang; Wang, Yizhe; Zhang, Wenxue; Xu, Jingcheng

2018-01-24

The electronic and optical properties of the rare earth metal atom-doped anatase TiO₂ have been investigated systematically via density functional theory calculations. The results show that TiO₂ doped by Ce or Pr is the optimal choice because of its small band gap and strong optical absorption. Rare earth metal atom doping induces several impurity states that tune the location of valence and conduction bands and an obvious lattice distortion that should reduce the probability of electron-hole recombination. This effect of band change originates from the 4 f electrons of the rare earth metal atoms, which leads to an improved visible light absorption. This finding indicates that the electronic structure of anatase TiO₂ is tuned by the introduction of impurity atoms.

Were micrometeorites a source of prebiotic molecules on the early Earth?

PubMed

Maurette, M; Brack, A; Kurat, G; Perreau, M; Engrand, C

1995-03-01

"Interplanetary Dust Particles" with sizes approximately 10 micrometers collected in the stratosphere (IDPs), as well as much larger "giant" micrometeorites retrieved from Antarctic ice melt water (AMMs), are mostly composed of unequilibrated assemblages of minerals, thus being related to primitive unequilibrated meteorites. Two independent evaluations of the mass flux of micrometeorites measuring approximately 50 micrometers to approximately 200 micrometers, recovered from either the Greenland or the Antarctic ice sheets have been reported (approximately 20,000 tons/a). A comparison with recent evaluation of the flux of meteorites reaching the Earth's surface (up to masses of 10,000 tons), indicates that micrometeorites represent about 99.5% of the extraterrestrial material falling on the Earth's surface each year. As they show carbon concentrations exceeding that of the most C-rich meteorite (Orgueil), they are the major contributors of extraterrestrial C-rich matter accreting to the Earth today. Moreover they are complex microstructured aggregates of grains. They contain not only a variety of C-rich matter, such as a new "dirty" magnetite phase enriched in P, S, and minor elements, but also a diversity of potential catalysts (hydrous silicates, oxides, sulfides and metal grains of Fe/Ni composition, etc.). They could have individually functioned on the early Earth, as "micro-chondritic-reactors" for the processing of prebiotic organic molecules in liquid water. Future progress requires the challenging development of meaningful laboratory simulation experiments, and a better understanding of the partial reprocessing of micrometeorites in the atmosphere.

Thermodynamic Investigation of the Reduction-Distillation Process for Rare Earth Metals Production

NASA Astrophysics Data System (ADS)

Judge, W. D.; Azimi, G.

2017-10-01

Owing to their high vapor pressure, the four rare earth metals samarium, europium, thulium, and ytterbium are produced by reduction-distillation whereby their oxides are reduced with metallic lanthanum in vacuo, and the produced metal is subsequently vaporized off. Here, we performed a thorough thermodynamic investigation to establish a fundamental understanding of the reduction-distillation process. Thermodynamic functions including vapor pressures, Gibbs free energies, and enthalpies of reaction were calculated and compared with available experimental data. Furthermore, the kinetics of the process was explored and theoretical evaporation rates were calculated from thermodynamic data. The thermodynamic model developed in this work can help optimize processing conditions to maximize the yield and improve the overall process.

Distribution behavior of uranium, neptunium, rare-earth elements ( Y, La, Ce, Nd, Sm, Eu, Gd) and alkaline-earth metals (Sr,Ba) between molten LiClKCI eutectic salt and liquid cadmium or bismuth

NASA Astrophysics Data System (ADS)

Kurata, M.; Sakamura, Y.; Hijikata, T.; Kinoshita, K.

1995-12-01

Distribution coefficients of uranium neptunium, eight rare-earth elements (Y, La, Ce, Pr, Nd, Sm, Eu and Gd) and two alkaline-earth metals (Sr and Ba) between molten LiCl-KCI eutectic salt and either liquid cadmium or bismuth were measured at 773 K. Separation factors of trivalent rare-earth elements to uranium or neptunium in the LiCl-KCl/Bi system were by one or two orders of magnitude larger than those in the LiCl-KCl/Cd system. On the contrary, the separation factors of alkaline-earth metals and divalent rare-earth elements to trivalent rare-earth elements were by one or two orders of magnitude smaller in the LiCl-KCl/Bi system.

The RAVE Survey: Rich in Very Metal-poor Stars

NASA Astrophysics Data System (ADS)

Fulbright, Jon P.; Wyse, Rosemary F. G.; Ruchti, Gregory R.; Gilmore, G. F.; Grebel, Eva; Bienaymé, O.; Binney, J.; Bland-Hawthorn, J.; Campbell, R.; Freeman, K. C.; Gibson, B. K.; Helmi, A.; Munari, U.; Navarro, J. F.; Parker, Q. A.; Reid, W.; Seabroke, G. M.; Siebert, A.; Siviero, A.; Steinmetz, M.; Watson, F. G.; Williams, M.; Zwitter, T.

2010-11-01

Very metal-poor stars are of obvious importance for many problems in chemical evolution, star formation, and galaxy evolution. Finding complete samples of such stars which are also bright enough to allow high-precision individual analyses is of considerable interest. We demonstrate here that stars with iron abundances [Fe/H] <-2 dex, and down to below -4 dex, can be efficiently identified within the Radial Velocity Experiment (RAVE) survey of bright stars, without requiring additional confirmatory observations. We determine a calibration of the equivalent width of the calcium triplet lines measured from the RAVE spectra onto true [Fe/H], using high spectral resolution data for a subset of the stars. These RAVE iron abundances are accurate enough to obviate the need for confirmatory higher-resolution spectroscopy. Our initial study has identified 631 stars with [Fe/H] <=-2, from a RAVE database containing approximately 200,000 stars. This RAVE-based sample is complete for stars with [Fe/H] lsim-2.5, allowing statistical sample analysis. We identify three stars with [Fe/H] lsim-4. Of these, one was already known to be "ultra metal-poor," one is a known carbon-enhanced metal-poor star, but we obtain [Fe/H] = -4.0, rather than the published [Fe/H] = -3.3, and derive [C/Fe] = +0.9, and [N/Fe] = +3.2, and the third is at the limit of our signal-to-noise ratio. RAVE observations are ongoing and should prove to be a rich source of bright, easily studied, very metal-poor stars. Based in part on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile, in the framework of proposals 081.B-0900 and 080.B-0927.

New technology of extracting the amount of rare earth metals from the red mud

NASA Astrophysics Data System (ADS)

Martoyan, G. A.; Karamyan, G. G.; Vardan, G. A.

2016-01-01

The paper outlined the environmental and economic problems associated with red mud - the waste generated in processing of bauxite ore for aluminum production. The chemical analysis of red mud has identified a number of useful elements including rare earth metals. The electromembrane technology of red mud processing with extraction of valuable elements is described. A possible scheme of separation of these metals through electrolysis is also given.

Alkali or alkaline earth metal promoted catalyst and a process for methanol synthesis using alkali or alkaline earth metals as promoters

DOEpatents

Tierney, J.W.; Wender, I.; Palekar, V.M.

1995-01-31

The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a heterogeneous catalyst comprising reduced copper chromite impregnated with an alkali or alkaline earth metal. There is thus no need to add a separate alkali or alkaline earth compound. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100--160 C and the pressure range of 40--65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H[sub 2]/CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

Alkali or alkaline earth metal promoted catalyst and a process for methanol synthesis using alkali or alkaline earth metals as promoters

DOEpatents

Tierney, John W.; Wender, Irving; Palekar, Vishwesh M.

1995-01-01

The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a heterogeneous catalyst comprising reduced copper chromite impregnated with an alkali or alkaline earth metal. There is thus no need to add a separate alkali or alkaline earth compound. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100.degree.-160.degree. C. and the pressure range of 40-65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H.sub.2 /CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

Neutron Diffraction Studies of Some Rare Earth-Transition Metal Deuterides.

DTIC Science & Technology

1986-05-01

RD-A168 M NEUTRON DIFFRACTION STUDIES OF SONE RARE EARTH-TRANSITION METAL DEUTERIDES(U) MISSOURI UNIV-ROLLR MATERIALS RESEARCH CENTER N J JAMES MY 86...REPORT William J. James OTtO -il May 1986 ZLECTEJU U. S. Army Research Office DAAG29-83-K-01 59 ".;’ Graduate Center for Materials Research ...9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT, PROJECT. TASK AREA & WORK UNIT NUMBERS 2* Graduate Center for Materials Research

Stabilized Lithium-Metal Surface in a Polysulfide-Rich Environment of Lithium-Sulfur Batteries.

PubMed

Zu, Chenxi; Manthiram, Arumugam

2014-08-07

Lithium-metal anode degradation is one of the major challenges of lithium-sulfur (Li-S) batteries, hindering their practical utility as next-generation rechargeable battery chemistry. The polysulfide migration and shuttling associated with Li-S batteries can induce heterogeneities of the lithium-metal surface because it causes passivation by bulk insulating Li2S particles/electrolyte decomposition products on a lithium-metal surface. This promotes lithium dendrite formation and leads to poor lithium cycling efficiency with complicated lithium surface chemistry. Here, we show copper acetate as a surface stabilizer for lithium metal in a polysulfide-rich environment of Li-S batteries. The lithium surface is protected from parasitic reactions with the organic electrolyte and the migrating polysulfides by an in situ chemical formation of a passivation film consisting of mainly Li2S/Li2S2/CuS/Cu2S and electrolyte decomposition products. This passivation film also suppresses lithium dendrite formation by controlling the lithium deposition sites, leading to a stabilized lithium surface characterized by a dendrite-free morphology and improved surface chemistry.

Hydrogen Abundances in Metal Grains from the Hammadah Al Hamra (HaH) 237 Metal-rich Chondrite: A Test of the Nebular-Formation Theory

NASA Technical Reports Server (NTRS)

Lauretta, D. S.; Guan, Y.; Leshin, L. A.

2005-01-01

The Bencubbin-like (CB) chondrites are metal-rich, primitive meteorites [1,2]. Some of these chondrites (HaH 237, QUE 94411) contain compositionally zoned metal grains with near-chondritic bulk compositions. Thermodynamic modeling of the zoning patterns in these grains suggests that they were formed by condensation in a region of the solar nebula with enhanced dust/gas ratios and a total pressure of 10(exp -4) bars at temperatures between 1400 - 1500 K [3]. If these predictions are correct than the metal grains would have been exposed to abundant H2 gas, which comprises the bulk of nebular systems. Since Fe-based alloys can absorb significant quantities of H, metal grains formed in the solar nebula should contain measurable abundances of H.

Heavy Metal - Exploring a magnetised metallic asteroid

NASA Astrophysics Data System (ADS)

Wahlund, J.-E.; Andrews, D. J.

2017-09-01

We propose an ESA/M5 spacecraft mission to orbit and explore (16) Psyche - the largest M-class metallic asteroid in the main belt. Recent estimates of the shape, 279×232×189 km and mass, 2.7×1019 kg of (16) Psyche make it one of the largest and densest of asteroids, 4.5 g cm-3, and together with the high surface radar reflectivity and the spectral data measured from Earth it is consistent with a bulk composition rich in iron-nickel. (16) Psyche orbits the Sun with semi-major axis 2.9 AU, 3º inclination, and is as yet unexplored in-situ.

Characterization of metal binding sites onto biochar using rare earth elements as a fingerprint.

PubMed

Pourret, Olivier; Houben, David

2018-02-01

The ability of biochar to immobilize metals relies on the amount of functional groups at its surface but the contribution of each functional groups (e.g. carboxylic, phenolic) to metal bonding is poorly known. Using a new approach based on previous works on rare earth element (REE) interactions with humic substances, we aim at elucidating the relative contribution of these binding sites to metal sorption under various conditions (i.e. pH and ionic strengths, IS). Using batch experiments, REE sorption onto biochar was analyzed from pH 3 to 9 and IS 10 -1 mol/L to 10 -3 mol/L. Rare earth element patterns show a Middle REE (MREE) downward concavity at acidic pH and low ionic strength. These patterns are in good agreement with existing datasets quantifying REE binding with humic substances. Indeed, the MREE downward concavity displayed by REE-biochar complexation pattern compares well with REE patterns with various organic compounds. This similarity in the REE complexation pattern shapes suggests that carboxylic groups are the main binding sites of REE in biochar. Overall, our results indicate that the strength of the metal bonding with biochar increases when pH and IS increase, suggesting that biochar is more efficient for long-term metal immobilization at near neutral pH and high ionic strength.

Oxidation behavior of Cr(III) during thermal treatment of chromium hydroxide in the presence of alkali and alkaline earth metal chlorides.

PubMed

Mao, Linqiang; Gao, Bingying; Deng, Ning; Liu, Lu; Cui, Hao

2016-02-01

The oxidation behavior of Cr(III) during the thermal treatment of chromium hydroxide in the presence of alkali and alkaline earth metal chlorides (NaCl, KCl, MgCl2, and CaCl2) was investigated. The amounts of Cr(III) oxidized at various temperatures and heating times were determined, and the Cr-containing species in the residues were characterized. During the transformation of chromium hydroxide to Cr2O3 at 300 °C approximately 5% of the Cr(III) was oxidized to form intermediate compounds containing Cr(VI) (i.e., CrO3), but these intermediates were reduced to Cr2O3 when the temperature was above 400 °C. Alkali and alkaline earth metals significantly promoted the oxidation of Cr(III) during the thermal drying process. Two pathways were involved in the influences the alkali and alkaline earth metals had on the formation of Cr(VI). In pathway I, the alkali and alkaline earth metals were found to act as electron transfer agents and to interfere with the dehydration process, causing more intermediate Cr(VI)-containing compounds (which were identified as being CrO3 and Cr5O12) to be formed. The reduction of intermediate compounds to Cr2O3 was also found to be hindered in pathway I. In pathway II, the alkali and alkaline earth metals were found to contribute to the oxidation of Cr(III) to form chromates. The results showed that the presence of alkali and alkaline earth metals significantly increases the degree to which Cr(III) is oxidized during the thermal drying of chromium-containing sludge. Copyright © 2015 Elsevier Ltd. All rights reserved.

High-temperature corrosion of metals in the salt and metallic melts containing rare earths

NASA Astrophysics Data System (ADS)

Karpov, V. V.; Abramov, A. V.; Zhilyakov, A. Yu.; Belikov, S. V.; Volkovich, V. A.; Polovov, I. B.; Rebrin, O. I.

2016-09-01

A complex of independent methods was employed to study the corrosion resistance of molybdenum, zirconium, tantalum and tungsten in chloride, chloride-fluoride and fluoride-oxide melts based on LiCl, CaCl2, NaCl- KCl, LiF, and containing rare earths. Tests were conducted for 30 h at 750-1050 °C. The metals showed excellent corrosion resistance in fused chlorides (the corrosion rates were below 0.0005 g/(m2 h). Despite the presence of chemically active fluoride ions in the chloride-fluoride melts, the metals studied also showed very low corrosion rates, except molybdenum, for which the rate of corrosion was 0,8 g/(m2 h). The corrosion resistance of tantalum was considerably reduced in the fluoride-oxide melts; the corrosion rate was over 1 g/(m2 h) corresponding to the 8-th grade of stability and placing tantalum to the group of "low stability" materials.

Alkaline and alkaline earth metal phosphate halides and phosphors

DOEpatents

Lyons, Robert Joseph; Setlur, Anant Achyut; Cleaver, Robert John

2012-11-13

Compounds, phosphor materials and apparatus related to nacaphite family of materials are presented. Potassium and rubidium based nacaphite family compounds and phosphors designed by doping divalent rare earth elements in the sites of alkaline earth metals in the nacaphite material families are descried. An apparatus comprising the phosphors based on the nacaphite family materials are presented herein. The compounds presented is of formula A.sub.2B.sub.1-yR.sub.yPO.sub.4X where the elements A, B, R, X and suffix y are defined such that A is potassium, rubidium, or a combination of potassium and rubidium and B is calcium, strontium, barium, or a combination of any of calcium, strontium and barium. X is fluorine, chlorine, or a combination of fluorine and chlorine, R is europium, samarium, ytterbium, or a combination of any of europium, samarium, and ytterbium, and y ranges from 0 to about 0.1.

Silicon rich nitride ring resonators for rare - earth doped telecommunications-band amplifiers pumped at the O-band.

PubMed

Xing, P; Chen, G F R; Zhao, X; Ng, D K T; Tan, M C; Tan, D T H

2017-08-22

Ring resonators on silicon rich nitride for potential use as rare-earth doped amplifiers pumped at 1310 nm with amplification at telecommunications-band are designed and characterized. The ring resonators are fabricated on 300 nm and 400 nm silicon rich nitride films and characterized at both 1310 nm and 1550 nm. We demonstrate ring resonators exhibiting similar quality factors exceeding 10,000 simultaneously at 1310 nm and 1550 nm. A Dysprosium-Erbium material system exhibiting photoluminescence at 1510 nm when pumped at 1310 nm is experimentally demonstrated. When used together with Dy-Er co-doped particles, these resonators with similar quality factors at 1310 nm and 1550 nm may be used for O-band pumped amplifiers for the telecommunications-band.

Analysis of the world distribution of metal-rich subsea manganese nodules

USGS Publications Warehouse

McKelvey, Vincent Ellis; Wright, Nancy A.; Bowen, Roger W.

1983-01-01

Publicly available data on the composition of subsea manganese nodules extend previous reports of differences in average metal contents from ocean to ocean and of variations related to latitude and depth. Pacific Ocean nodules have the highest average manganese, nickel, and copper contents, and Atlantic Ocean nodules have the highest average iron content. The average manganese, nickel, and copper contents generally increase toward the equator in both hemispheres, and iron content generally decreases. The variation of metal content with water depth is not linear; instead, there appears to be a threshold depth of about 2,900 to 3,000 m, above which combined nickel and copper contents are generally less than 1 percent and below which cobalt content is generally less than about 0.6 percent. The composition of the nodules varies widely, but three rarely overlapping types that are of possible economic interest can be recognized. (1) Nodules containing more than about 1 percent combined nickel and copper only exceptionally contain more than 0.5 percent cobalt and 35 percent manganese. (2) Nodules containing more than 0.5 percent cobalt rarely contain more than 1 percent combined nickel and copper and 35 percent manganese. (3) Nodules containing more than 35 percent manganese only exceptionally contain more than 0.5 percent cobalt, although they average nearly 1.1 percent combined nickel and copper. Current economic interest in nodule mining is focused on the Clarion-Clipperton zone in the northeastern equatorial Pacific Ocean, the largest known area in which nodules average 1.8 percent or more combined nickel and copper. Several other areas in which nodules are rich in these metals are found in the Pacific and Indian Oceans and may be viewed as targets for exploration. Nearly 60 chemical elements have been found in manganese nodules, many in concentrations far exceeding their crustal abundances. The amounts in which many minor elements are present vary with the amounts of

THE OPTICAL COLORS OF GIANT ELLIPTICAL GALAXIES AND THEIR METAL-RICH GLOBULAR CLUSTERS INDICATE A BOTTOM-HEAVY INITIAL MASS FUNCTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goudfrooij, Paul; Diederik Kruijssen, J. M., E-mail: goudfroo@stsci.edu, E-mail: kruijssen@mpa-garching.mpg.de

2013-01-10

We report a systematic and statistically significant offset between the optical (g - z or B - I) colors of seven massive elliptical galaxies and the mean colors of their associated massive metal-rich globular clusters (GCs) in the sense that the parent galaxies are redder by {approx}0.12-0.20 mag at a given galactocentric distance. However, spectroscopic indices in the blue indicate that the luminosity-weighted ages and metallicities of such galaxies are equal to that of their averaged massive metal-rich GCs at a given galactocentric distance, to within small uncertainties. The observed color differences between the red GC systems and their parentmore » galaxies cannot be explained by the presence of multiple stellar generations in massive metal-rich GCs, as the impact of the latter to the populations' integrated g - z or B - I colors is found to be negligible. However, we show that this paradox can be explained if the stellar initial mass function (IMF) in these massive elliptical galaxies was significantly steeper at subsolar masses than canonical IMFs derived from star counts in the solar neighborhood, with the GC colors having become bluer due to dynamical evolution, causing a significant flattening of the stellar MF of the average surviving GC.« less

Stellar abundances and ages for metal-rich Milky Way globular clusters. Stellar parameters and elemental abundances for 9 HB stars in NGC 6352

NASA Astrophysics Data System (ADS)

Feltzing, S.; Primas, F.; Johnson, R. A.

2009-01-01

Context: Metal-rich globular clusters provide important tracers of the formation of our Galaxy. Moreover, and not less important, they are very important calibrators for the derivation of properties of extra-galactic metal-rich stellar populations. Nonetheless, only a few of the metal-rich globular clusters in the Milky Way have been studied using high-resolution stellar spectra to derive elemental abundances. Additionally, Rosenberg et al. identified a small group of metal-rich globular clusters that appeared to be about 2 billion years younger than the bulk of the Milky Way globular clusters. However, it is unclear if like is compared with like in this dataset as we do not know the enhancement of α-elements in the clusters and the amount of α-elements is well known to influence the derivation of ages for globular clusters. Aims: We derive elemental abundances for the metal-rich globular cluster NGC 6352 and we present our methods to be used in up-coming studies of other metal-rich globular clusters. Methods: We present a study of elemental abundances for α- and iron-peak elements for nine HB stars in the metal-rich globular cluster NGC 6352. The elemental abundances are based on high-resolution, high signal-to-noise spectra obtained with the UVES spectrograph on VLT. The elemental abundances have been derived using standard LTE calculations and stellar parameters have been derived from the spectra themselves by requiring ionizational as well as excitational equilibrium. Results: We find that NGC 6352 has [Fe/H] = -0.55, is enhanced in the α-elements to about +0.2 dex for Ca, Si, and Ti relative to Fe. For the iron-peak elements we find solar values. Based on the spectroscopically derived stellar parameters we find that an E(B-V) = 0.24 and (m-M) ≃ 14.05 better fits the data than the nominal values. An investigation of log gf-values for suitable Fe i lines lead us to the conclusion that the commonly used correction to the May et al. (1974) data should not be

A mini-review on rare earth metal-doped TiO2 for photocatalytic remediation of wastewater.

PubMed

Saqib, Najm Us; Adnan, Rohana; Shah, Irfan

2016-08-01

Titanium dioxide (TiO2) has been considered a useful material for the treatment of wastewater due to its non-toxic character, chemical stability and excellent electrical and optical properties which contribute in its wide range of applications, particularly in environmental remediation technology. However, the wide band gap of TiO2 photocatalyst (anatase phase, 3.20 eV) limits its photocatalytic activity to the ultraviolet region of light. Besides that, the electron-hole pair recombination has been found to reduce the efficiency of the photocatalyst. To overcome these problems, tailoring of TiO2 surface with rare earth metals to improve its surface, optical and photocatalytic properties has been investigated by many researchers. The surface modifications with rare earth metals proved to enhance the efficiency of TiO2 photocatalyts by way of reducing the band gap by shifting the working wavelength to the visible region and inhibiting the anatase-to-rutile phase transformations. This review paper summarises the attempts on modification of TiO2 using rare earth metals describing their effect on the photocatalytic activities of the modified TiO2 photocatalyst.

Dual Functionalization of White Phosphorus: Formation, Characterization, and Reactivity of Rare-Earth-Metal Cyclo-P3 Complexes.

PubMed

Du, Shanshan; Yin, Jianhao; Chi, Yue; Xu, Ling; Zhang, Wen-Xiong

2017-12-11

The [3+1] fragmentation reaction of rare-earth metallacyclopentadienes 1 a-c with 0.5 equivalents of P 4 affords a series of rare-earth metal cyclo-P 3 complexes 2 a-c and a phospholyl anion 3. 2 a-c demonstrate an unusual η 3 coordination mode with one P-P bond featuring partial π-bonding character. 2 a-c are the first cyclo-P 3 complexes of rare-earth metals, and also the first organo-substituted polyphosphides in the category of Group 3 and f-block elements. Rare-earth metallacyclopentadienes play a dual role in the combination of aromatization and Diels-Alder reaction. Compounds 2 a-c can coordinate to one or two [W(CO) 5 ] units, yielding 4 a-c or 5 c, respectively. Furthermore, oxidation of 2 a with p-benzoquinone produces its corresponding phospholyllithium and regenerated P 4 . © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The tremendous potential of deep-sea mud as a source of rare-earth elements.

PubMed

Takaya, Yutaro; Yasukawa, Kazutaka; Kawasaki, Takehiro; Fujinaga, Koichiro; Ohta, Junichiro; Usui, Yoichi; Nakamura, Kentaro; Kimura, Jun-Ichi; Chang, Qing; Hamada, Morihisa; Dodbiba, Gjergj; Nozaki, Tatsuo; Iijima, Koichi; Morisawa, Tomohiro; Kuwahara, Takuma; Ishida, Yasuyuki; Ichimura, Takao; Kitazume, Masaki; Fujita, Toyohisa; Kato, Yasuhiro

2018-04-10

Potential risks of supply shortages for critical metals including rare-earth elements and yttrium (REY) have spurred great interest in commercial mining of deep-sea mineral resources. Deep-sea mud containing over 5,000 ppm total REY content was discovered in the western North Pacific Ocean near Minamitorishima Island, Japan, in 2013. This REY-rich mud has great potential as a rare-earth metal resource because of the enormous amount available and its advantageous mineralogical features. Here, we estimated the resource amount in REY-rich mud with Geographical Information System software and established a mineral processing procedure to greatly enhance its economic value. The resource amount was estimated to be 1.2 Mt of rare-earth oxide for the most promising area (105 km 2  × 0-10 mbsf), which accounts for 62, 47, 32, and 56 years of annual global demand for Y, Eu, Tb, and Dy, respectively. Moreover, using a hydrocyclone separator enabled us to recover selectively biogenic calcium phosphate grains, which have high REY content (up to 22,000 ppm) and constitute the coarser domain in the grain-size distribution. The enormous resource amount and the effectiveness of the mineral processing are strong indicators that this new REY resource could be exploited in the near future.

An easy access to nanocrystalline alkaline earth metal fluorides - just by shaking

NASA Astrophysics Data System (ADS)

Dreger, M.; Scholz, G.; Kemnitz, E.

2012-04-01

High energy ball milling as fast, direct and solvent free method allows an easy access to nanocrystalline alkaline earth metal fluorides MF2 (M: Mg, Ca, Sr, Ba). Comparable metal sources (acetates, carbonates, hydroxides, alkoxides) were used for the reaction with NH4F as fluorinating agent. Even very simple manual shaking experiments between NH4F and the corresponding hydroxides in the stoichiometric ratio (M:F = 1:2, M: Ca, Sr, Ba) give phase pure fluorides. Moreover, comparable classical thermal reactions in closed crucibles at higher temperatures provide phase pure crystalline fluorides in nearly all cases as well.

Unravelling structural ambiguities in lithium- and manganese-rich transition metal oxides

DOE PAGES

Shukla, Alpesh Khushalchand; Ramasse, Quentin M.; Ophus, Colin; ...

2015-10-29

Although Li- and Mn-rich transition metal oxides have been extensively studied as high-capacity cathode materials for Li-ion batteries, the crystal structure of these materials in their pristine state is not yet fully understood. Here we apply complementary electron microscopy and spectroscopy techniques at multi-length scale on well-formed Li1.2(Ni0.13Mn0.54Co0.13)O2 crystals with two different morphologies as well as two commercially available materials with similar compositions, and unambiguously describe the structural make-up of these samples. Systematically observing the entire primary particles along multiple zone axes reveals that they are consistently made up of a single phase, save for rare localized defects and amore » thin surface layer on certain crystallographic facets. Finally and more specifically, we show the bulk of the oxides can be described as an aperiodic crystal consisting of randomly stacked domains that correspond to three variants of monoclinic structure, while the surface is composed of a Co- and/or Ni-rich spinel with antisite defects.« less

Abundances in the Very Metal Poor s-Process-rich Star CS 22183-015

NASA Astrophysics Data System (ADS)

Johnson, Jennifer A.; Bolte, Michael

2002-11-01

We report on the abundances for 13 elements in CS 22183-015, the most metal-poor, s-process-rich star yet discovered. We measure [Fe/H]=-3.12 and large overabundances compared to scaled solar values for 11 heavy elements with s-process origin. The low luminosity of the star suggests that it is a CH star, a giant that has accreted s-processed material from an evolved, very metal poor companion. We find a [Pb/Ba] value of 1.1 dex and, more generally, that the ratio of heavy to light s-process elements is larger than seen in the solar system. This result is consistent with theoretical expectations for the s-process in metal-poor stars. [Eu/La] is higher than predicted from the solar system s-process abundance ratios. We argue that the s-process in metal-poor stars is more efficient at producing Eu that in asymptotic giant branch stars of solar metallicity. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Pathways to Earth-like atmospheres. Extreme ultraviolet (EUV)-powered escape of hydrogen-rich protoatmospheres.

PubMed

Lammer, Helmut; Kislyakova, K G; Odert, P; Leitzinger, M; Schwarz, R; Pilat-Lohinger, E; Kulikov, Yu N; Khodachenko, M L; Güdel, M; Hanslmeier, M

2011-12-01

We discuss the evolution of the atmosphere of early Earth and of terrestrial exoplanets which may be capable of sustaining liquid water oceans and continents where life may originate. The formation age of a terrestrial planet, its mass and size, as well as the lifetime in the EUV-saturated early phase of its host star play a significant role in its atmosphere evolution. We show that planets even in orbits within the habitable zone of their host stars might not lose nebular- or catastrophically outgassed initial protoatmospheres completely and could end up as water worlds with CO2 and hydrogen- or oxygen-rich upper atmospheres. If an atmosphere of a terrestrial planet evolves to an N2-rich atmosphere too early in its lifetime, the atmosphere may be lost. We show that the initial conditions set up by the formation of a terrestrial planet and by the evolution of the host star's EUV and plasma environment are very important factors owing to which a planet may evolve to a habitable world. Finally we present a method for studying the discussed atmosphere evolution hypotheses by future UV transit observations of terrestrial exoplanets.

Effects of pH on frog gustatory responses to chloride salts of alkali-metal and alkali-earth-metal.

PubMed

Kumai, T; Nomura, H

1980-01-01

The pH effects on frog gustatory responses to alkali-metal and alkali-earth-metal chloride salts were examined using single fungi-form papilla preparations. Responses to 0.1-0.5 M NaCl were clearly dependent upon the pH of the stimulating solutions. The responses increased as the pH decreased from 6.5 to 4.5 and were almost completely suppressed at pH's above 6.5. There was no significant difference in the pH dependency of the response among alkali-metal chlorides. HCl solutions elicited only a poor response under conditions in which the water response was suppressed by the simultaneous presence of a low NaCl concentration. Responses to alkali-earth-metal chlorides varied in their pH dependency. Response to CaCl2 was slightly affected by pH changes from 4.5 to 9.0, response to SrCl2 was considerably suppressed in the alkaline region, and responses to BaCl2 and MgCl2 were strongly suppressed at pH's above 6.5. BeCl2 solutions showed less marked stimulating effects over the pH range tested. The differences in pH dependency described above suggest the existence of two kinds of receptor sites, one being pH-insensitive sites responsible for the calcium response and the other pH-sensitive sites responsible for the sodium response. A cross-adaptation test appeared to support this possibility. Assuming that the pH effect mentioned is related to changes in the state of ionization of the receptor molecule, the pKa of the ionizable group responsible for the sodium response was determined to be approximately 5.5.

Temperate Earth-sized planets transiting a nearby ultracool dwarf star

PubMed Central

Gillon, Michaël; Jehin, Emmanuël; Lederer, Susan M.; Delrez, Laetitia; de Wit, Julien; Burdanov, Artem; Van Grootel, Valérie; Burgasser, Adam; Triaud, Amaury H. M. J.; Opitom, Cyrielle; Demory, Brice-Olivier; Sahu, Devendra K.; Bardalez Gagliuffi, Daniella; Magain, Pierre; Queloz, Didier

2017-01-01

Stellar-like objects with effective temperatures of 2700K and below are referred to as “ultracool dwarfs”1. This heterogeneous group includes both extremely low-mass stars and brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15% of the stellar-like objects in the vicinity of the Sun2. Based on the small masses and sizes of their protoplanetary disks3,4, core-accretion theory for ultracool dwarfs predicts a large, but heretofore undetected population of close-in terrestrial planets5, ranging from metal-rich Mercury-sized planets6 to more hospitable volatile-rich Earth-sized planets7. Here we report the discovery of three short-period Earth-sized planets transiting an ultracool dwarf star 12 parsecs away using data collected by the TRAPPIST8 telescope as part of an ongoing prototype transit survey9. The inner two planets receive four and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star10. Eleven orbits remain possible for the third planet based on our data, the most likely resulting in an irradiation significantly smaller than Earth's. The infrared brightness of the host star combined with its Jupiter-like size offer the possibility of thoroughly characterizing the components of this nearby planetary system. PMID:27135924

The Electronic Structure and Optical Properties of Anatase TiO2 with Rare Earth Metal Dopants from First-Principles Calculations

PubMed Central

Xie, Kefeng; Jia, Qiangqiang; Wang, Yizhe; Zhang, Wenxue; Xu, Jingcheng

2018-01-01

The electronic and optical properties of the rare earth metal atom-doped anatase TiO2 have been investigated systematically via density functional theory calculations. The results show that TiO2 doped by Ce or Pr is the optimal choice because of its small band gap and strong optical absorption. Rare earth metal atom doping induces several impurity states that tune the location of valence and conduction bands and an obvious lattice distortion that should reduce the probability of electron–hole recombination. This effect of band change originates from the 4f electrons of the rare earth metal atoms, which leads to an improved visible light absorption. This finding indicates that the electronic structure of anatase TiO2 is tuned by the introduction of impurity atoms. PMID:29364161

Mitigation effects of silicon rich amendments on heavy metal accumulation in rice (Oryza sativa L.) planted on multi-metal contaminated acidic soil.

PubMed

Gu, Hai-Hong; Qiu, Hao; Tian, Tian; Zhan, Shu-Shun; Deng, Teng-Hao-Bo; Chaney, Rufus L; Wang, Shi-Zhong; Tang, Ye-Tao; Morel, Jean-Louis; Qiu, Rong-Liang

2011-05-01

The mechanisms of stabilization by silicon-rich amendments of cadmium, zinc, copper and lead in a multi-metal contaminated acidic soil and the mitigation of metal accumulation in rice were investigated in this study. The results from a pot experiment indicated that the application of fly ash (20 and 40gkg(-1)) and steel slag (3 and 6gkg(-1)) increased soil pH from 4.0 to 5.0-6.4, decreased the phytoavailability of heavy metals by at least 60%, and further suppressed metal uptake by rice. Diffusion gradient in thin-film measurement showed the heavy metal diffusion fluxes from soil to solution decreased by greater than 84% after remediation. X-ray diffraction analysis indicated the mobile metals were mainly deposited as their silicates, phosphates and hydroxides in amended treatments. Moreover, it was found metal translocation from stem to leaf was dramatically restrained by adding amendments, which might be due to the increase of silicon concentration and co-precipitation with heavy metals in stem. Finally, a field experiment showed the trace element concentrations in polished rice treated with amendments complied with the food safety standards of China. These results demonstrated fly ash and steel slag could be effective in mitigating heavy metal accumulation in rice grown on multi-metal contaminated acidic soils. Copyright © 2011 Elsevier Ltd. All rights reserved.

Formation of an integrated holding company to produce rare-earth metal articles

NASA Astrophysics Data System (ADS)

Bogdanov, S. V.; Grishaev, S. I.

2013-12-01

The possibility of formation of a Russian holding company for the production of rare-earth metal articles under conditions of its increasing demand on the world market is considered. It is reasonable to ensure stable business operation on the market under conditions of state-private partnership after the fraction of soled products is determined and supported by the competitive advantages of Russian products.

Highly efficient hydrophosphonylation of aldehydes and unactivated ketones catalyzed by methylene-linked pyrrolyl rare earth metal amido complexes.

PubMed

Zhou, Shuangliu; Wu, Zhangshuan; Rong, Jiewei; Wang, Shaowu; Yang, Gaosheng; Zhu, Xiancui; Zhang, Lijun

2012-02-27

A series of rare earth metal amido complexes bearing methylene-linked pyrrolyl-amido ligands were prepared through silylamine elimination reactions and displayed high catalytic activities in hydrophosphonylations of aldehydes and unactivated ketones under solvent-free conditions for liquid substrates. Treatment of [(Me(3)Si)(2)N](3)Ln(μ-Cl)Li(THF)(3) with 2-(2,6-Me(2)C(6)H(3)NHCH(2))C(4)H(3)NH (1, 1 equiv) in toluene afforded the corresponding trivalent rare earth metal amides of formula {(μ-η(5):η(1)):η(1)-2-[(2,6-Me(2)C(6)H(3))NCH(2)](C(4)H(3)N)LnN(SiMe(3))(2)}(2) [Ln=Y (2), Nd (3), Sm (4), Dy (5), Yb (6)] in moderate to good yields. All compounds were fully characterized by spectroscopic methods and elemental analyses. The yttrium complex was also characterized by (1)H NMR spectroscopic analyses. The structures of complexes 2, 3, 4, and 6 were determined by single-crystal X-ray analyses. Study of the catalytic activities of the complexes showed that these rare earth metal amido complexes were excellent catalysts for hydrophosphonylations of aldehydes and unactivated ketones. The catalyzed reactions between diethyl phosphite and aldehydes in the presence of the rare earth metal amido complexes (0.1 mol%) afforded the products in high yields (up to 99%) at room temperature in short times of 5 to 10 min. Furthermore, the catalytic addition of diethyl phosphite to unactivated ketones also afforded the products in high yields of up to 99% with employment of low loadings (0.1 to 0.5 mol%) of the rare earth metal amido complexes at room temperature in short times of 20 min. The system works well for a wide range of unactivated aliphatic, aromatic or heteroaromatic ketones, especially for substituted benzophenones, giving the corresponding α-hydroxy diaryl phosphonates in moderate to high yields. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Production method for making rare earth compounds

DOEpatents

McCallum, R.W.; Ellis, T.W.; Dennis, K.W.; Hofer, R.J.; Branagan, D.J.

1997-11-25

A method of making a rare earth compound, such as a earth-transition metal permanent magnet compound, without the need for producing rare earth metal as a process step, comprises carbothermically reacting a rare earth oxide to form a rare earth carbide and heating the rare earth carbide, a compound-forming reactant (e.g., a transition metal and optional boron), and a carbide-forming element (e.g., a refractory metal) that forms a carbide that is more thermodynamically favorable than the rare earth carbide whereby the rare earth compound (e.g., Nd{sub 2}Fe{sub 14}B or LaNi{sub 5}) and a carbide of the carbide-forming element are formed.

Production method for making rare earth compounds

DOEpatents

McCallum, R. William; Ellis, Timothy W.; Dennis, Kevin W.; Hofer, Robert J.; Branagan, Daniel J.

1997-11-25

A method of making a rare earth compound, such as a earth-transition metal permanent magnet compound, without the need for producing rare earth metal as a process step, comprises carbothermically reacting a rare earth oxide to form a rare earth carbide and heating the rare earth carbide, a compound-forming reactant (e.g. a transition metal and optional boron), and a carbide-forming element (e.g. a refractory metal) that forms a carbide that is more thermodynamically favorable than the rare earth carbide whereby the rare earth compound (e.g. Nd.sub.2 Fe.sub.14 B or LaNi.sub.5) and a carbide of the carbide-forming element are formed.

Metal-silicate Partitioning and Its Role in Core Formation and Composition on Super-Earths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schaefer, Laura; Petaev, M. I.; Sasselov, Dimitar D.

We use a thermodynamic framework for silicate-metal partitioning to determine the possible compositions of metallic cores on super-Earths. We compare results using literature values of the partition coefficients of Si and Ni, as well as new partition coefficients calculated using results from laser shock-induced melting of powdered metal-dunite targets at pressures up to 276 GPa, which approaches those found within the deep mantles of super-Earths. We find that larger planets may have little to no light elements in their cores because the Si partition coefficient decreases at high pressures. The planet mass at which this occurs will depend on themore » metal-silicate equilibration depth. We also extrapolate the equations of state (EOS) of FeO and FeSi alloys to high pressures, and present mass–radius diagrams using self-consistent planet compositions assuming equilibrated mantles and cores. We confirm the results of previous studies that the distribution of elements between mantle and core will not be detectable from mass and radius measurements alone. While observations may be insensitive to interior structure, further modeling is sensitive to compositionally dependent properties, such as mantle viscosity and core freeze-out properties. We therefore emphasize the need for additional high pressure measurements of partitioning as well as EOSs, and highlight the utility of the Sandia Z-facilities for this type of work.« less

The metal-rich abundance pattern - spectroscopic properties and abundances for 107 main-sequence stars

NASA Astrophysics Data System (ADS)

Ivanyuk, O. M.; Jenkins, J. S.; Pavlenko, Ya. V.; Jones, H. R. A.; Pinfield, D. J.

2017-07-01

We report results from the high-resolution spectral analysis of the 107 metal-rich (mostly [Fe/H] ≥ 7.67 dex) target stars from the Calan-Hertfordshire Extrasolar Planet Search programme observed with HARPS. Using our procedure of finding the best fit to the absorption line profiles in the observed spectra, we measure the abundances of Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Ni, Cu and Zn, and then compare them with known results from different authors. Most of our abundances agree with these works at the level of ±0.05 dex or better for the stars we have in common. However, we do find systematic differences that make direct inferences difficult. Our analysis suggests that the selection of line lists and atomic line data along with the adopted continuum level influence these differences the most. At the same time, we confirm the positive trends of abundances versus metallicity for Na, Mn, Ni and, to a lesser degree, Al. A slight negative trend is observed for Ca, whereas Si and Cr tend to follow iron. Our analysis allows us to determine the positively skewed normal distribution of projected rotational velocities with a maximum peaking at 3 km s-1. Finally, we obtained a Gaussian distribution of microturbulent velocities that has a maximum at 1.2 km s-1 and a full width at half-maximum Δv1/2 = 0.35 km s-1, indicating that metal-rich dwarfs and subgiants in our sample have a very restricted range in microturbulent velocity.

Promoting effect of alkaline earth metal doping on catalytic activity of HC and NOx conversion over Pd-only three-way catalyst.

PubMed

Yang, Linyan; Lin, Siyu; Yang, Xue; Fang, Weimin; Zhou, Renxian

2014-08-30

The influence of alkaline earth metal (M=Mg, Ca, Sr and Ba) promoter on the structural/textural properties of Ce0.67Zr0.33O2 (designated as CZ) and the catalytic behavior of its supported Pd-only three-way catalyst (Pd/CZM) have been investigated. The results show that the modification with alkaline earth metal obviously improves the catalytic activity for hydrocarbon (HC) and nitrogen oxides (NOx) conversion, especially the introduction of Ba. Furthermore, the operation window of the promoted catalysts has also been widened. The doping of alkaline earth metal leads to the formation of more homogeneous Ce-Zr-M ternary solid solution with higher surface area and smaller crystallite size, and the corresponding Pd/CZM catalysts present improved reducibility of PdO species. The modification with Ca, Sr and Ba improves the thermal aging resistance, especially Ba. DRIFTS results reveal that the doping of alkaline earth metal enhances the oxygen and electron transfer ability and favors the dissociation of NO, which promotes the activation and storage capacity of the acidic atoms like NOx, and leads to enhanced catalytic activity performance. Copyright © 2014 Elsevier B.V. All rights reserved.

On the metallicity dependence of crystalline silicates in oxygen-rich asymptotic giant branch stars and red supergiants

NASA Astrophysics Data System (ADS)

Jones, O. C.; Kemper, F.; Sargent, B. A.; McDonald, I.; Gielen, C.; Woods, Paul M.; Sloan, G. C.; Boyer, M. L.; Zijlstra, A. A.; Clayton, G. C.; Kraemer, K. E.; Srinivasan, S.; Ruffle, P. M. E.

2012-12-01

We investigate the occurrence of crystalline silicates in oxygen-rich evolved stars across a range of metallicities and mass-loss rates. It has been suggested that the crystalline silicate feature strength increases with increasing mass-loss rate, implying a correlation between lattice structure and wind density. To test this, we analyse Spitzer Infrared Spectrograph and Infrared Space Observatory Short Wavelength Spectrometer spectra of 217 oxygen-rich asymptotic giant branch and 98 red supergiants in the Milky Way, the Large and Small Magellanic Clouds, and Galactic globular clusters. These encompass a range of spectral morphologies from the spectrally rich which exhibit a wealth of crystalline and amorphous silicate features to 'naked' (dust-free) stars. We combine spectroscopic and photometric observations with the GRAMS grid of radiative transfer models to derive (dust) mass-loss rates and temperature. We then measure the strength of the crystalline silicate bands at 23, 28 and 33 μm. We detect crystalline silicates in stars with dust mass-loss rates which span over 3 dex, down to rates of ˜10-9 M⊙ yr-1. Detections of crystalline silicates are more prevalent in higher mass-loss rate objects, though the highest mass-loss rate objects do not show the 23-μm feature, possibly due to the low temperature of the forsterite grains or it may indicate that the 23-μm band is going into absorption due to high column density. Furthermore, we detect a change in the crystalline silicate mineralogy with metallicity, with enstatite seen increasingly at low metallicity.

Enrichment of rare earth metal ions by the highly selective adsorption of phytate intercalated layered double hydroxide.

PubMed

Jin, Cheng; Liu, Huimin; Kong, Xianggui; Yan, Hong; Lei, Xiaodong

2018-02-27

Phytate intercalated MgAl layered double hydroxide (MgAl-LDH) was prepared by an anion exchange method with the precursor NO 3 - containing MgAl-LDH. The final as-synthesized product [Mg 0.69 Al 0.31 (OH) 2 ] (phytateNa 6 ) 0.05 (NO 3 ) 0.01 ·mH 2 O (phytate-LDH) has highly selective adsorption ability for some metal ions and can be used to enrich rare earth metal ions in mixed solution, such as Pr 3+ and Ce 3+ from a mixed solution of them with Pb 2+ and Co 2+ . At first, phytate-LDH has good adsorption performance for these ions in single metal ion solutions. At low concentration (below 10 mg L -1 ), all the capture rates of the four metal ions were more than 97%, for highly toxic Pb 2+ it was even up to nearly 100%, and a high capture rate (99.87%) was maintained for Pb 2+ at a high concentration (100 mg L -1 ). When all the four metal ions are co-existing in aqueous solution, the selectivity order is Pb 2+ ≫ Pr 3+ ≈ Ce 3+ > Co 2+ . In a solution containing mixtures of the three metal ions of Pr 3+ , Ce 3+ , and Co 2+ , the selectivity order is Pr 3+ ≈ Ce 3+ ≫ Co 2+ , and in a solution containing mixtures of Pr 3+ with Co 2+ and Ce 3+ with Co 2+ , the selectivity orders are Pr 3+ ≫ Co 2+ and Ce 3+ ≫ Co 2+ , respectively. The high selectivity and adsorption capacities for Pb 2+ , Co 2+ , Pr 3+ , and Ce 3+ result in the efficient removal of Pb 2+ and enrichment of the rare earth metal ions Pr 3+ and Ce 3+ by phytate-LDH. Based on the elemental analysis, it is found that the difference of the adsorption capacities is mainly due to the different coordination number of them with phytate-LDH. With molecular simulation, we believe that the adsorption selectivity is due to the difference of the binding energy between the metal ion and phytate-LDH. Therefore, the phytate-LDH is promising for the enrichment and/or purification of the rare earth metal ions and removal of toxic metal ions from waste water.

Rare earth element and rare metal inventory of central Asia

USGS Publications Warehouse

Mihalasky, Mark J.; Tucker, Robert D.; Renaud, Karine; Verstraeten, Ingrid M.

2018-03-06

Rare earth elements (REE), with their unique physical and chemical properties, are an essential part of modern living. REE have enabled development and manufacture of high-performance materials, processes, and electronic technologies commonly used today in computing and communications, clean energy and transportation, medical treatment and health care, glass and ceramics, aerospace and defense, and metallurgy and chemical refining. Central Asia is an emerging REE and rare metals (RM) producing region. A newly compiled inventory of REE-RM-bearing mineral occurrences and delineation of areas-of-interest indicate this region may have considerable undiscovered resources.

Effect of metal cation replacement on the electronic structure of metalorganic halide perovskites: Replacement of lead with alkaline-earth metals

NASA Astrophysics Data System (ADS)

Pazoki, Meysam; Jacobsson, T. Jesper; Hagfeldt, Anders; Boschloo, Gerrit; Edvinsson, Tomas

2016-04-01

Organic and inorganic lead halogen perovskites, and in particular, C H3N H3Pb I3 , have during the last years emerged as a class of highly efficient solar cell materials. Herein we introduce metalorganic halogen perovskite materials for energy-relevant applications based on alkaline-earth metals. Based on the classical notion of Goldschmidt's rules and quantum mechanical considerations, the three alkaline-earth metals, Ca, Sr, and Ba, are shown to be able to exchange lead in the perovskite structure. The three alkaline-earth perovskites, C H3N H3Ca I3,C H3N H3Sr I3 , and C H3N H3Ba I3 , as well as the reference compound, C H3N H3Pb I3 , are in this paper investigated with density functional theory (DFT) calculations, which predict these compounds to exist as stable perovskite materials, and their electronic properties are explored. A detailed analysis of the projected molecular orbital density of states and electronic band structure from DFT calculations were used for interpretation of the band-gap variations in these materials and for estimation of the effective masses of the electrons and holes. Neglecting spin-orbit effects, the band gap of MACa I3,MASr I3 , and MABa I3 were estimated to be 2.95, 3.6, and 3.3 eV, respectively, showing the relative change expected for metal cation exchange. The shifts in the conduction band (CB) edges for the alkaline-earth perovskites were quantified using scalar relativistic DFT calculations and tight-binding analysis, and were compared to the situation in the more extensively studied lead halide perovskite, C H3N H3Pb I3 , where the change in the work function of the metal is the single most important factor in tuning the CB edge and band gap. The results show that alkaline-earth-based organometallic perovskites will not work as an efficient light absorber in photovoltaic applications but instead could be applicable as charge-selective contact materials. The rather high CB edge and the wide band gap together with the large

Discovery of Extended Blue Horizontal Branches in Two Metal-rich Globular Clusters

NASA Astrophysics Data System (ADS)

Rich, R. Michael; Sosin, Craig; Djorgovski, S. George; Piotto, Giampaolo; King, Ivan R.; Renzini, Alvio; Phinney, E. Sterl; Dorman, Ben; Liebert, James; Meylan, Georges

1997-07-01

We have used WFPC2 to construct B, V color-magnitude diagrams of four metal-rich globular clusters, NGC 104 (47 Tuc), NGC 5927, NGC 6388, and NGC 6441. All four clusters have well populated red horizontal branches (RHB), as expected for their metallicity. However, NGC 6388 and 6441 also exhibit a prominent blue horizontal-branch (BHB) extension, including stars reaching as faint in V as the turnoff luminosity. This discovery demonstrates directly for the first time that a major population of hot horizontal-branch (HB) stars can exist in old, metal-rich systems. This may have important implications for the interpretation of the integrated spectra of elliptical galaxies. The cause of the phenomenon remains uncertain. We examine the possibility that NGC 6388 and 6441 are older than the other clusters, but a simple difference in age may not be sufficient to produce the observed distributions along the HB. The high central densities in NGC 6388 and 6441 suggest that the existence of the BHB tails might be caused by stellar interactions in the dense cores of these clusters, which we calculate to have two of the highest collision rates among globular clusters in the Galaxy. Tidal collisions might act in various ways to enhance loss of envelope mass and therefore populate the blue side of the HB. However, the relative frequency of tidal collisions does not seem large enough (compared to that of the clusters with pure RHBs) to account for such a drastic difference in HB morphology. While a combination of an age difference and dynamical interactions may help, prima facie the lack of a radial gradient in the BHB/RHB star ratio seems to argue against dynamical effects playing a role. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

Magnetic Fe, Si, Al-Rich Impact Spherules from the P-T Boundary Layer at Graphite Peak, Antarctica

NASA Technical Reports Server (NTRS)

Petaev, M. I.; Jacobsen, S. B.; Basu, A. R.; Becker, L.

2004-01-01

The geological boundary between Triassic and Permian strata coincides with the greatest life extinction in the Earth's history. Although the cause of the extinction is still the subject of intense debates, recent discoveries in the P-T boundary layer of shocked quartz grains, fullerenes with the extraterrestrial noble gases, Fe metal nuggets, and chondritic meteorite fragments all point to a powerful collision of Earth with a celestial body in the late Permian. Here we report the discovery of magnetic Fe, Si, Al-rich impact spherules which accompany the chondritic meteorite fragments in some samples from the P-T boundary layer at Graphite Peak, Antarctica.

Bond-length distributions for ions bonded to oxygen: alkali and alkaline-earth metals.

PubMed

Gagné, Olivier Charles; Hawthorne, Frank Christopher

2016-08-01

Bond-length distributions have been examined for 55 configurations of alkali-metal ions and 29 configurations of alkaline-earth-metal ions bonded to oxygen, for 4859 coordination polyhedra and 38 594 bond distances (alkali metals), and for 3038 coordination polyhedra and 24 487 bond distances (alkaline-earth metals). Bond lengths generally show a positively skewed Gaussian distribution that originates from the variation in Born repulsion and Coulomb attraction as a function of interatomic distance. The skewness and kurtosis of these distributions generally decrease with increasing coordination number of the central cation, a result of decreasing Born repulsion with increasing coordination number. We confirm the following minimum coordination numbers: ([3])Li(+), ([3])Na(+), ([4])K(+), ([4])Rb(+), ([6])Cs(+), ([3])Be(2+), ([4])Mg(2+), ([6])Ca(2+), ([6])Sr(2+) and ([6])Ba(2+), but note that some reported examples are the result of extensive dynamic and/or positional short-range disorder and are not ordered arrangements. Some distributions of bond lengths are distinctly multi-modal. This is commonly due to the occurrence of large numbers of structure refinements of a particular structure type in which a particular cation is always present, leading to an over-representation of a specific range of bond lengths. Outliers in the distributions of mean bond lengths are often associated with anomalous values of atomic displacement of the constituent cations and/or anions. For a sample of ([6])Na(+), the ratio Ueq(Na)/Ueq(bonded anions) is partially correlated with 〈([6])Na(+)-O(2-)〉 (R(2) = 0.57), suggesting that the mean bond length is correlated with vibrational/displacement characteristics of the constituent ions for a fixed coordination number. Mean bond lengths also show a weak correlation with bond-length distortion from the mean value in general, although some coordination numbers show the widest variation in mean bond length for zero distortion, e.g. Li(+) in

One-process fabrication of metal hierarchical nanostructures with rich nanogaps for highly-sensitive surface-enhanced Raman scattering.

PubMed

Liu, Gui-qiang; Yu, Mei-dong; Liu, Zheng-qi; Liu, Xiao-shan; Huang, Shan; Pan, Ping-ping; Wang, Yan; Liu, Mu-lin; Gu, Gang

2015-05-08

One-process fabrication of highly active and reproducible surface-enhanced Raman scattering (SERS) substrates via ion beam deposition is reported. The fabricated metal-dielectric-metal (MDM) hierarchical nanostructure possesses rich nanogaps and a tunable resonant cavity. Raman scattering signals of analytes are dramatically strengthened due to the strong near-field coupling of localized surface plasmon resonances (LSPRs) and the strong interaction of LSPRs of metal NPs with surface plasmon polaritons (SPPs) on the underlying metal film by crossing over the dielectric spacer. The maximum Raman enhancement for the highest Raman peak at 1650 cm(-1) is 13.5 times greater than that of a single metal nanoparticle (NP) array. Moreover, the SERS activity can be efficiently tailored by varying the size and number of voids between adjacent metal NPs and the thickness of the dielectric spacer. These findings may broaden the scope of SERS applications of MDM hierarchical nanostructures in biomedical and analytical chemistry.

Metal uptake by native plants and revegetation potential of mining sulfide-rich waste-dumps.

PubMed

Gomes, Patrícia; Valente, Teresa; Pamplona, Jorge; Braga, Maria Amália Sequeira; Pissarra, José; Gil, José António Grande; de la Torre, Maria Luisa

2014-01-01

Waste dumps resulting from metal exploitation create serious environmental damage, providing soil and water degradation over long distances. Phytostabilization can be used to remediate these mining sites. The present study aims to evaluate the behavior of selected plant species (Erica arborea, Ulex europaeus, Agrostis delicatula, and Cytisus multiflorus) that grow spontaneously in three sulfide-rich waste-dumps (Lapa Grande, Cerdeirinha, and Penedono, Portugal). These sites represent different geological, climatic and floristic settings. The results indicate distinctive levels and types of metal contamination: Penedono presents highest sulfate and metal contents, especially As, with low levels of Fe. In contrast, at Lapa Grande and Cerdeirinha Fe, Mn, and Zn are the dominant metals. In accordance, each waste dump develops a typical plant community, providing a specific vegetation inventory. At Penedono, Agrostis delicatula accumulates As, Pb, Cu, Mn, and Zn, showing higher bioaccumulation factors (BF) for Mn (32.1) and As (24.4). At Cerdeirinha, Ulex europaeus has the highest BF for Pb (984), while at Lapa Grande, Erica arborea presents high BF for Mn (9.8) and Pb (8.1). Regarding TF, low values were obtained for most of the metals, especially As (TF < 1). Therefore, the results obtained from representative plant species suggest appropriate behavior for phytostabilization measures.

Origins of ultralow velocity zones through slab-derived metallic melt

PubMed Central

Liu, Jiachao; Li, Jie; Smith, Jesse S.

2016-01-01

Understanding the ultralow velocity zones (ULVZs) places constraints on the chemical composition and thermal structure of deep Earth and provides critical information on the dynamics of large-scale mantle convection, but their origin has remained enigmatic for decades. Recent studies suggest that metallic iron and carbon are produced in subducted slabs when they sink beyond a depth of 250 km. Here we show that the eutectic melting curve of the iron−carbon system crosses the current geotherm near Earth’s core−mantle boundary, suggesting that dense metallic melt may form in the lowermost mantle. If concentrated into isolated patches, such melt could produce the seismically observed density and velocity features of ULVZs. Depending on the wetting behavior of the metallic melt, the resultant ULVZs may be short-lived domains that are replenished or regenerated through subduction, or long-lasting regions containing both metallic and silicate melts. Slab-derived metallic melt may produce another type of ULVZ that escapes core sequestration by reacting with the mantle to form iron-rich postbridgmanite or ferropericlase. The hypotheses connect peculiar features near Earth's core−mantle boundary to subduction of the oceanic lithosphere through the deep carbon cycle. PMID:27143719

Hydrometallurgical separation of rare earth elements, cobalt and nickel from spent nickel-metal-hydride batteries

NASA Astrophysics Data System (ADS)

Rodrigues, Luiz Eduardo Oliveira Carmo; Mansur, Marcelo Borges

The separation of rare earth elements, cobalt and nickel from NiMH battery residues is evaluated in this paper. Analysis of the internal content of the NiMH batteries shows that nickel is the main metal present in the residue (around 50% in weight), as well as potassium (2.2-10.9%), cobalt (5.1-5.5%), rare earth elements (15.3-29.0%) and cadmium (2.8%). The presence of cadmium reveals that some Ni-Cd batteries are possibly labeled as NiMH ones. The leaching of nickel and cobalt from the NiMH battery powder with sulfuric acid is efficient; operating variables temperature and concentration of H 2O 2 has no significant effect for the conditions studied. A mixture of rare earth elements is separated by precipitation with NaOH. Finally, solvent extraction with D2EHPA (di-2-ethylhexyl phosphoric acid) followed by Cyanex 272 (bis-2,4,4-trimethylpentyl phosphinic acid) can separate cadmium, cobalt and nickel from the leach liquor. The effect of the main operating variables of both leaching and solvent extraction steps are discussed aiming to maximize metal separation for recycling purposes.

Heterogeneous Delivery of Silicate and Metal to the Earth via Large Planetesimals

NASA Astrophysics Data System (ADS)

Marchi, S.; Canup, R. M.; Walker, R. J.

2017-12-01

Earth's mantle abundances of at least some highly siderophile elements, (HSE; Re, Os, Ir, Ru, Pt, Rh, Pd, and Au), are much higher than would result from metal-silicate equilibration during terrestrial core formation, and can be better explained as a result of late accretion of a minimum of 0.5% Earth's masses after core formation was complete. Traditional models assume that HSEs delivered by late projectiles completely mixed and chemically equilibrated with the Earth's mantle. This appears likely for undifferentiated, well-mixed projectiles, or for relatively small, differentiated projectiles. However several arguments suggest that late projectiles may have been large (> 1500 km in diameter) and differentiated, and in this case, portions of the projectile's core may merge with the Earth's core, rather than being mixed into the Earth's mantle. We investigate projectile mixing with a suite of SPH simulations of differentiated planetesimal colliding with the Earth. A range of outcomes emerge from our simulations suggesting that for large impactors (>1500 km), the delivery of HSE to the Earth's mantle may be disproportionate with the overall delivery of mass. For impacts with impact angles < 45° , between ˜ 20% to 80% of the impactor's core may merge directly with the Earth's core; while for impact angle > 60°, most of the impactor core escapes for moderate impact speeds. An implication is that the late accreted mass inferred from terrestrial HSE abundances may be a substantial underestimate, by a factor 2-5. In addition, partial mixing of projectiles result in an enrichment in mantle vs core material delivered to the bulk silicate Earth, implying substantial compositional variations in the accreted mass. Such variations could produce initially localized domains in Earth's mantle with distinct, mass independent isotopic signatures, given the isotopic variability resulting from nucleosynthetic heterogeneities among genetically diverse meteorites. In general we find

Comparison of the optical responses of O-poor and O-rich thermochromic VOX films during semiconductor-to-metal transition

NASA Astrophysics Data System (ADS)

Luo, Zhenfei; Wu, Zhiming; Wang, Tao; Xu, Xiangdong; Li, Weizhi; Li, Wei; Jiang, Yadong

2012-09-01

O-poor and O-rich thermochromic vanadium oxide (VOX) nanostructured thin films were prepared by applying reactive direct current magnetron sputtering and post-annealing in oxygen ambient. UV-visible spectrophotometer and spectroscopic ellipsometry were used to investigate the optical properties of films. It was found that, when the O-poor VOX thin film underwent semiconductor-to-metal transition, the values of optical conductivity and extinction coefficient in the visible region increased due to the existence of occupied band-gap states. This noticeable feature, however, was not observed for the O-rich film, which showed a similar optical behavior with the stoichiometric crystalline VO2 films reported in the literatures. Moreover, the O-poor VOX film exhibits consistent variations of transmission values in the visible/near-infrared region when it undergoes semiconductor-to-metal transition.

Earth Observations taken by the Expedition 22 Crew

NASA Image and Video Library

2010-01-14

ISS022-E-026137 (14 Jan. 2010) --- Open Pit Mines in southern Arizona are featured in this image photographed by an Expedition 22 crew member on the International Space Station. The State of Arizona is the United States? largest producer of the metal copper, primarily mined from ore bodies known as porphyry copper deposits. Copper is a good conductor of electricity and heat, and is a vital element of virtually all of our electronic devices and components. A porphyry copper deposit is a geological structure formed by crystal-rich magma moving upwards through pre-existing rock layers. As the magma cools and crystallizes, it forms an igneous rock with large crystals embedded in a fine-grained matrix, known as porphyry. Hot fluids circulate through the magma and surrounding rocks via fractures, depositing copper-bearing and other minerals in characteristic spatial patterns that signal the nature of the ore body to a geologist. The most common approach to extracting metal-bearing ore from a porphyry copper deposit is by open-pit mining. For more details, please refer to http://earth.jsc.nasa.gov/EarthObservatory/OpenPitMinesSouthernArizona.htm.

Uncovering the Chemistry of Earth-like Planets

NASA Astrophysics Data System (ADS)

Zeng, Li; Jacobsen, Stein; Sasselov, Dimitar D.

2015-01-01

We propose to use evidence from our solar system to understand exoplanets, and in particular, to predict their surface chemistry and thereby the possibility of life. An Earth-like planet, born from the same nebula as its host star, is composed primarily of silicate rocks and an iron-nickel metal core, and depleted in volatile content in a systematic manner. The more volatile (easier to vaporize or dissociate into gas form) an element is in an Earth-like planet, the more depleted the element is compared to its host star. After depletion, an Earth-like planet would go through the process of core formation due to heat from radioactive decay and collisions. Core formation depletes a planet's rocky mantle of siderophile (iron-loving) elements, in addition to the volatile depletion. After that, Earth-like planets likely accrete some volatile-rich materials, called 'late veneer'. The late veneer could be essential to the origins of life on Earth and Earth-like planets, as it also delivers the volatiles such as nitrogen, sulfur, carbon and water to the planet's surface, which are crucial for life to occur. We plan to build an integrative model of Earth-like planets from the bottom up. We would like to infer their chemical compositions from their mass-radius relations and their host stars' elemental abundances, and understand the origins of volatile contents (especially water) on their surfaces, and thereby shed light on the origins of life on them.

Kinetics of the mechanochemical synthesis of alkaline-earth metal amides

NASA Astrophysics Data System (ADS)

Garroni, Sebastiano; Takacs, Laszlo; Leng, Haiyan; Delogu, Francesco

2014-07-01

A phenomenological framework is developed to model the kinetics of the formation of alkaline-earth metal amides by the ball milling induced reaction of their hydrides with gaseous ammonia. It is shown that the exponential character of the kinetic curves is modulated by the increase of the total volume of the powder inside the reactor due to the substantially larger molar volume of the products compared to the reactants. It is claimed that the volume of powder effectively processed during each collision connects the transformation rate to the physical and chemical processes underlying the mechanochemical transformations.

Complete phase diagram of rare-earth nickelates from first-principles

NASA Astrophysics Data System (ADS)

Varignon, Julien; Grisolia, Mathieu N.; Íñiguez, Jorge; Barthélémy, Agnès; Bibes, Manuel

2017-12-01

The structural, electronic and magnetic properties of AMO3 perovskite oxides, where M is a 3d transition metal, are highly sensitive to the geometry of the bonds between the metal-d and oxygen-p ions (through octahedra rotations and distortions) and to their level of covalence. This is particularly true in rare-earth nickelates RNiO3 that display a metal-insulator transition with complex spin orders tunable by the rare-earth size, and are on the border line between dominantly ionic (lighter elements) and covalent characters (heavier elements). Accordingly, computing their ground state is challenging and a complete theoretical description of their rich phase diagram is still missing. Here, using first-principles simulations, we successfully describe the electronic and magnetic experimental ground state of nickelates. We show that the insulating phase is characterized by a split of the electronic states of the two Ni sites (i.e., resembling low-spin 4+ and high-spin 2+) with a concomitant shift of the oxygen-2p orbitals toward the depleted Ni cations. Therefore, from the point of view of the charge, the two Ni sites appear nearly identical whereas they are in fact distinct. Performing such calculations for several nickelates, we built a theoretical phase diagram that reproduces all their key features, namely a systematic dependence of the metal-insulator transition with the rare-earth size and the crossover between a second to first order transition for R = Pr and Nd. Finally, our results hint at strategies to control the electronic and magnetic phases of perovskite oxides by fine tuning of the level of covalence.

Uncovering the Chemistry of Earth-like Planets

NASA Astrophysics Data System (ADS)

Zeng, L.; Jacobsen, S. B.; Sasselov, D. D.

2015-12-01

We propose to use the evidence from our solar system to understand exoplanets, and in particular, to predict their surface chemistry and thereby the possibility of life. An Earth-like planet, born from the same nebula as its host star, is composed primarily of silicate rocks and an iron-nickel metal core, and depleted in volatile content in a systematic manner. The more volatile (easier to vaporize or dissociate into gas form) an element is in an Earth-like planet, the more depleted the element is compared to its host star. After depletion, an Earth-like planet would go through the process of core formation due to heat from radioactive decay and collisions. Core formation depletes a planet's rocky mantle of siderophile (iron-loving) elements, in addition to the volatile depletion. After that, Earth-like planets likely accrete some volatile-rich materials, called "late veneer". The late veneer could be essential to the origins of life on Earth and Earth-like planets, as it also delivers the volatiles such as nitrogen, sulfur, carbon and water to the planet's surface, which are crucial for life to occur. Here we build an integrative model of Earth-like planets from the bottom up. Thus the chemical compositions of Earth-like planets could be inferred from their mass-radius relations and their host stars' elemental abundances, and the origins of volatile contents (especially water) on their surfaces could be understood, and thereby shed light on the origins of life on them. This elemental abundance model could be applied to other rocky exoplanets in exoplanet systems.

Partitioning of Oxygen During Core Formation on Earth and Mars

NASA Astrophysics Data System (ADS)

Rubie, D. C.; Gessmann, C. K.; Frost, D. J.

2003-12-01

Core formation on Earth and Mars involved the physical separation of Fe-Ni metal alloy from silicate, most likely in deep magma oceans. Although core-formation models explain many aspects of mantle geochemistry, they do not account for large differences between the compositions of the mantles of Earth ( ˜8 wt% FeO) and Mars ( ˜18 wt% FeO) or the much smaller mass fraction of the Martian core. Here we explain these differences using new experimental results on the solubility of oxygen in liquid Fe-Ni alloy, which we have determined at 5-23 GPa, 2100-2700 K and variable oxygen fugacities using a multianvil apparatus. Oxygen solubility increases with increasing temperature and oxygen fugacity and decreases with increasing pressure. Thus, along a high temperature adiabat (e.g. after formation of a deep magma ocean on Earth), oxygen solubility is high at depths up to about 2000 km but decreases strongly at greater depths where the effect of high pressure dominates. For modeling oxygen partitioning during core formation, we assume that Earth and Mars both accreted from oxidized chondritic material with a silicate fraction initially containing around 18 wt% FeO. In a terrestrial magma ocean, 1200-2000 km deep, high temperatures resulted in the extraction of FeO from the silicate magma ocean, due to the high solubility of oxygen in the segregating metal, leaving the mantle with its present FeO content of ˜8 wt%. Lower temperatures of a Martian magma ocean resulted in little or no extraction of FeO from the mantle, which thus remained unchanged at about 18 wt%. The mass fractions of segregated metal are consistent with the mass fraction of the Martian core being small relative to that of the Earth. FeO extracted from the Earth's magma ocean by segregating core-forming liquid may have contributed to chemical heterogeneities in the lowermost mantle, a FeO-rich D'' layer and the light element budget of the core.

Dehydrogenation of secondary amines: synthesis, and characterization of rare-earth metal complexes incorporating imino- or amido-functionalized pyrrolyl ligands.

PubMed

Li, Qinghai; Zhou, Shuangliu; Wang, Shaowu; Zhu, Xiancui; Zhang, Lijun; Feng, Zhijun; Guo, Liping; Wang, Fenhua; Wei, Yun

2013-02-28

The dehydrogenation of pyrrolyl-functionalized secondary amines initiated by rare-earth metal amides was systematically studied. Reactions of the rare-earth metal amides [(Me(3)Si)(2)N](3)RE(μ-Cl)Li(THF)(3) with pyrrolyl-functionalized secondary amines 2-(t)BuNHCH(2)-5-R-C(4)H(2)NH (R = H (1), R = (t)Bu (2)) led to dehydrogenation of the secondary amines with isolation of imino-functionalized pyrrolyl rare-earth metal complexes [2-(t)BuN=CH-5-R-C(4)H(2)N](2)REN(SiMe(3))(2) (R = H, RE = Y (3a), Dy (3b), Yb (3c), Eu (3d); R = (t)Bu, RE = Y (4a), Dy (4b), Er (4c)). The mixed ligands erbium complex [2-(t)BuNCH(2)-5-(t)Bu-C(4)H(2)N]Er[2-(t)BuN=CH-5-(t)BuC(4)H(2)N](2)ClLi(2)(THF) (4c') was isolated in a short reaction time for the synthesis of complex 4c. Reaction of the deuterated pyrrolyl-functionalized secondary amine 2-((t)BuNHCHD)C(4)H(3)NH with yttrium amide [(Me(3)Si)(2)N](3)Y(μ-Cl)Li(THF)(3) further proved that pyrrolyl-amino ligands were transferred to pyrrolyl-imino ligands. Treatment of 2-((t)BuNHCH(2))C(4)H(3)NH (1) with excess (Me(3)Si)(2)NLi gave the only pyrrole deprotonated product {[η(5):η(2):η(1)-2-((t)BuNHCH(2))C(4)H(3)N]Li(2)N(SiMe(3))(2)}(2) (5), indicating that LiN(SiMe(3))(2) could not dehydrogenate the secondary amines to imines and rare-earth metal ions had a decisive effect on the dehydrogenation. The reaction of the rare-earth metal amides [(Me(3)Si)(2)N](3)RE(μ-Cl)Li(THF)(3) with 1 equiv. of more bulky pyrrolyl-functionalized secondary amine 2-[(2,6-(i)Pr(2)C(6)H(3))NHCH(2)](C(4)H(3)NH) (6) in toluene afforded the only amine and pyrrole deprotonated dinuclear rare-earth metal amido complexes {(μ-η(5):η(1)):η(1)-2-[(2,6-(i)Pr(2)C(6)H(3))NCH(2)]C(4)H(3)N]LnN(SiMe(3))(2)}(2) (RE = Nd (7a), Sm (7b), Er (7c)), no dehydrogenation of secondary amine to imine products were observed. On the basis of experimental results, a plausible mechanism for the dehydrogenation of secondary amines to imines was proposed.

Extraction of trivalent rare-earth metal nitrates by solutions of tributyl phosphate and diisooctylmethylphosphonate in kerosene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pyartman, A.K.; Puzikov, E.A.; Kopyrin, A.A.

1995-01-01

Isotherms of extraction of trivalent rare-earth metal nitrates in the series lanthanum-lutetium, yttrium by 0.5-2.5 M solutions of tri-n-buty1 phosphate and diisooctyl methylphosphonate in kerosene at 298.15 K, pH 2 are presented. The influence of the ionic strength of aqueous phase and extractant concentration on the concentration extraction constants in the case of formation of metal(III) trisolvates in organic phase is given by equation.

The adsorption kinetics of metal ions onto different microalgae and siliceous earth.

PubMed

Schmitt, D; Müller, A; Csögör, Z; Frimmel, F H; Posten, C

2001-03-01

In the present work the adsorption kinetics of the six metal ions aluminum, zinc, mercury, lead, copper, and cadmium onto living microalgae were measured. The freshwater green microalga Scenedesmus subspicatus, the brackish water diatom Cyclotella cryptica, the seawater diatom Phaeodactylum tricornutum, and the seawater red alga Porphyridium purpureum were the subject of investigation. In most cases the adsorption rate of the metals could be well described by using the equation of the Langmuir adsorption rate expression. Inverse parameter estimation allowed the determination of the rate constants of the adsorption process and the maximum metal content of the algae. The highest values for the rate constant were obtained for Porphyridium purpureum followed by Phaeodactylum tricornutum. High values for the maximum content were obtained for Cyclotella cryptica and Scenedesmus subspicatus. The maximum rate constant was 24.21 h-1 for the adsorption of Hg to Porphyridium purpureum whereas the maximum metal content (0.243 g g-1) was obtained for Zn on Cyclotella cryptica. A comparison of these values with those obtained for the mineral siliceous earth exhibiting low maximum content and high adsorption rates reveals that the mechanism of adsorption onto the algae is a mixture of adsorption and accumulation.

Metal oxide films on metal

DOEpatents

Wu, Xin D.; Tiwari, Prabhat

1995-01-01

A structure including a thin film of a conductive alkaline earth metal oxide selected from the group consisting of strontium ruthenium trioxide, calcium ruthenium trioxide, barium ruthenium trioxide, lanthanum-strontium cobalt oxide or mixed alkaline earth ruthenium trioxides thereof upon a thin film of a noble metal such as platinum is provided.

Lattice vibrations and electronic transitions in the rare-earth metals: yttrium, gadolinium and lutetium.

PubMed

Olijnyk, Helmut

2005-01-12

Lattice vibrations in high-pressure phases of Y, Gd and Lu were studied by Raman spectroscopy. The observed phonon frequencies decrease towards the transitions to the dhcp and fcc phases. There is evidence that the entire structural sequence [Formula: see text] under pressure for the individual regular rare-earth metals and along the lanthanide series at ambient pressure involve softening of certain acoustic and optical phonon modes and of the elastic shear modulus C(44). Comparison is made to transitions between close-packed lattices in other metals, and possible correlations to s-d electron transfer are discussed.

Determination of robust metallicities for metal-rich red giant branch stars. An application to the globular cluster NGC 6528

NASA Astrophysics Data System (ADS)

Liu, C.; Ruchti, G.; Feltzing, S.; Primas, F.

2017-05-01

Context. The study of the Milky Way relies on our ability to interpret the light from stars correctly. With the advent of the astrometric ESA mission Gaia we will enter a new era where the study of the Milky Way can be undertaken on much larger scales than currently possible. In particular we will be able to obtain full 3D space motions of red giant stars at large distances. This calls for a reinvestigation of how reliably we can determine, for example, iron abundances in such stars and how well they reproduce those of dwarf stars. Aims: Here we explore robust ways of determining the iron content of metal-rich giant stars. We aim to understand what biases and shortcomings the widely applied methods suffer from. Methods: In this study we were mainly concerned with standard methods of analysing stellar spectra. These include the analysis of individual lines to determine stellar parameters, and analysis of the broad wings of certain lines (e.g. Hα and calcium lines) to determine effective temperature and surface gravity for the stars. Results: For NGC 6528 we find that [Fe/H] = + 0.04 dex with a scatter of σ = 0.07 dex, which gives an error in the derived mean abundance of 0.02 dex. Conclusions: Our work has two important conclusions for analysis of metal-rich red giant branch stars. Firstly, for spectra with S/N of below about 35 per reduced pixel, [Fe/H] becomes too high. Secondly, determination of Teff using the wings of the Hα line results in [Fe/H] values about 0.1 dex higher than if excitational equilibrium is used. The last conclusion is perhaps unsurprising, as we expect the NLTE effect to become more prominent in cooler stars and we can not use the wings of the Hα line to determine Teff for the cool stars in our sample. We therefore recommend that in studies of metal-rich red giant stars care should be taken to obtain sufficient calibration data to enable use of the cooler stars. Based on observations made with the ESO/VLT, at Paranal Observatory, under

A seismologically consistent compositional model of Earth's core.

PubMed

Badro, James; Côté, Alexander S; Brodholt, John P

2014-05-27

Earth's core is less dense than iron, and therefore it must contain "light elements," such as S, Si, O, or C. We use ab initio molecular dynamics to calculate the density and bulk sound velocity in liquid metal alloys at the pressure and temperature conditions of Earth's outer core. We compare the velocity and density for any composition in the (Fe-Ni, C, O, Si, S) system to radial seismological models and find a range of compositional models that fit the seismological data. We find no oxygen-free composition that fits the seismological data, and therefore our results indicate that oxygen is always required in the outer core. An oxygen-rich core is a strong indication of high-pressure and high-temperature conditions of core differentiation in a deep magma ocean with an FeO concentration (oxygen fugacity) higher than that of the present-day mantle.

MOST Detects Transits of HD 97658b, a Warm, Likely Volatile-rich Super-Earth

NASA Astrophysics Data System (ADS)

Dragomir, Diana; Matthews, Jaymie M.; Eastman, Jason D.; Cameron, Chris; Howard, Andrew W.; Guenther, David B.; Kuschnig, Rainer; Moffat, Anthony F. J.; Rowe, Jason F.; Rucinski, Slavek M.; Sasselov, Dimitar; Weiss, Werner W.

2013-07-01

Through photometric monitoring of the extended transit window of HD 97658b with the MOST space telescope, we have found that this exoplanet transits with an ephemeris consistent with that predicted from radial velocity measurements. The mid-transit times are 5.6σ earlier than those of the unverified transit-like signals reported in 2011, and we find no connection between the two sets of events. The transit depth together with our determined stellar radius (R_\\star = 0.703^{+0.039}_{-0.034}\\ R_\\odot) indicates a 2.34^{+0.18}_{-0.15} R ⊕ super-Earth. When combined with the radial velocity determined mass of 7.86 ± 0.73 M ⊕, our radius measure allows us to derive a planet density of 3.44^{+0.91}_{-0.82} g cm-3. Models suggest that a planet with our measured density has a rocky core that is enveloped in an atmosphere composed of lighter elements. The star of the HD 97658 system is the second brightest known to host a transiting super-Earth, facilitating follow-up studies of this not easily daunted, warm and likely volatile-rich exoplanet. Based on data from the MOST satellite, a Canadian Space Agency mission operated by Microsatellite Systems Canada Inc. (MSCI; former Dynacon Inc.) and the Universities of Toronto and British Columbia, with the assistance of the University of Vienna.

Recommendations from the Investigational New Drug/Investigational Device Exemption Task Force of the clInical and Translational Science Award Consortium: developing and implementing a sponsor-investigators training program.

PubMed

Holbein, M E Blair; Berglund, Jelena Petrovic; O'Reilly, Erin K; Hartman, Karen; Speicher, Lisa A; Adamo, Joan E; O'Riordan, Gerri; Brown, Jennifer Swanton; Schuff, Kathryn G

2014-06-01

The objective of this study was to provide recommendations for provision of training for sponsor and investigators at Academic Health Centers. A subgroup of the Investigational New Drug/Investigational Device Exemption (IND/IDE) Task Force of the Clinical and Translational Science Award (CTSA) program Regulatory Knowledge Key Function Committee was assembled to specifically address how clinical investigators who hold an IND/IDE and thus assume the role of sponsor-investigators are adequately trained to meet the additional regulatory requirements of this role. The participants who developed the recommendations were representatives of institutions with IND/IDE support programs. Through an informal survey, the task force determined that a variety and mix of models are used to provide support for IND/IDE holders within CTSA institutions. In addition, a CTSA consortium-wide resources survey was used. The participants worked from the models and survey results to develop consensus recommendations to address institutional support, training content, and implementation. The CTSA IND/IDE Task Force recommendations are as follows: (1) Institutions should assess the scope of Food and Drug Administration-regulated research, perform a needs analysis, and provide resources to implement a suitable training program; (2) The model of training program should be tailored to each institution; (3) The training should specifically address the unique role of sponsor-investigators, and the effectiveness of training should be evaluated regularly by methods that fit the model adopted by the institution; and (4) Institutional leadership should mandate sponsor-investigator training and effectively communicate the necessity and availability of training.

Proteins in Load-Bearing Junctions: The Histidine-Rich Metal-Binding Protein of Mussel Byssus†,‡

PubMed Central

Zhao, Hua; Waite, J. Herbert

2007-01-01

Building complex load-bearing scaffolds depends on effective ways of joining functionally different biomacromolecules. The junction between collagen fibers and foamlike adhesive plaques in mussel byssus is robust despite the strikingly dissimilar connected structures. mcfp-4, the matrix protein from this junction, and its presecreted form from the foot tissue of Mytilus californianus were isolated and characterized. mcfp-4 has a mass of ∼93 kDa as determined by MALDI-TOF mass spectrometry. Its composition is dominated by histidine (22 mol %), but levels of lysine, arginine, and aspartate are also significant. A small amount of 3,4-dihydroxyphenyl-L-alanine (2 mol %) can be detected by amino acid analysis and redox cycling assays. The cDNA-deduced sequence of mcfp-4 reveals multiple variants with highly repetitive internal structures, including ∼36 tandemly repeated His-rich decapeptides (e.g., HVHTHRVLHK) in the N-terminal half and 16 somewhat more degenerate aspartate-rich undecapeptides (e.g., DDHVNDIAQTA) in the C-terminal half. Incubation of a synthetic peptide based on the His-rich decapeptide with Fe3+, Co2+, Ni2+, Zn2+, and Cu2+ indicates that only Cu is strongly bound. MALDI-TOF mass spectrometry of the peptide modified with diethyl pyrocarbonate before and after Cu binding suggests that histidine residues dominate Cu binding. In contrast, the aspartate-rich undecapeptides preferentially bind Ca2+. mcfp-4 is strategically positioned to function as a macromolecular bifunctional linker by using metal ions to couple its own His-rich domains to the His-rich termini of the preCOLs. Ca2+ may mediate coupling of the C-terminus to other calcium-binding plaque proteins. PMID:17115717

Polyoxometalate electrocatalysts based on earth-abundant metals for efficient water oxidation in acidic media

NASA Astrophysics Data System (ADS)

Blasco-Ahicart, Marta; Soriano-López, Joaquín; Carbó, Jorge J.; Poblet, Josep M.; Galan-Mascaros, J. R.

2018-01-01

Water splitting is a promising approach to the efficient and cost-effective production of renewable fuels, but water oxidation remains a bottleneck in its technological development because it largely relies on noble-metal catalysts. Although inexpensive transition-metal oxides are competitive water oxidation catalysts in alkaline media, they cannot compete with noble metals in acidic media, in which hydrogen production is easier and faster. Here, we report a water oxidation catalyst based on earth-abundant metals that performs well in acidic conditions. Specifically, we report the enhanced catalytic activity of insoluble salts of polyoxometalates with caesium or barium counter-cations for oxygen evolution. In particular, the barium salt of a cobalt-phosphotungstate polyanion outperforms the state-of-the-art IrO2 catalyst even at pH < 1, with an overpotential of 189 mV at 1 mA cm-2. In addition, we find that a carbon-paste conducting support with a hydrocarbon binder can improve the stability of metal-oxide catalysts in acidic media by providing a hydrophobic environment.

Super earth interiors and validity of Birch's Law for ultra-high pressure metals and ionic solids

NASA Astrophysics Data System (ADS)

Ware, Lucas Andrew

2015-01-01

Super Earths, recently detected by the Kepler Mission, expand the ensemble of known terrestrial planets beyond our Solar System's limited group. Birch's Law and velocity-density systematics have been crucial in constraining our knowledge of the composition of Earth's mantle and core. Recently published static diamond anvil cell experimental measurements of sound velocities in iron, a key deep element in most super Earth models, are inconsistent with each other with regard to the validity of Birch's Law. We examine the range of validity of Birch's Law for several metallic elements, including iron, and ionic solids shocked with a two-stage light gas gun into the ultra-high pressure, temperature fluid state and make comparisons to the recent static data.

AN ANCIENT EXTRASOLAR SYSTEM WITH FIVE SUB-EARTH-SIZE PLANETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campante, T. L.; Davies, G. R.; Chaplin, W. J.

The chemical composition of stars hosting small exoplanets (with radii less than four Earth radii) appears to be more diverse than that of gas-giant hosts, which tend to be metal-rich. This implies that small, including Earth-size, planets may have readily formed at earlier epochs in the universe's history when metals were more scarce. We report Kepler spacecraft observations of Kepler-444, a metal-poor Sun-like star from the old population of the Galactic thick disk and the host to a compact system of five transiting planets with sizes between those of Mercury and Venus. We validate this system as a true five-planetmore » system orbiting the target star and provide a detailed characterization of its planetary and orbital parameters based on an analysis of the transit photometry. Kepler-444 is the densest star with detected solar-like oscillations. We use asteroseismology to directly measure a precise age of 11.2 ± 1.0 Gyr for the host star, indicating that Kepler-444 formed when the universe was less than 20% of its current age and making it the oldest known system of terrestrial-size planets. We thus show that Earth-size planets have formed throughout most of the universe's 13.8 billion year history, leaving open the possibility for the existence of ancient life in the Galaxy. The age of Kepler-444 not only suggests that thick-disk stars were among the hosts to the first Galactic planets, but may also help to pinpoint the beginning of the era of planet formation.« less

Processing of Phosphorus Slag with Recovery of Rare Earth Metals and Obtaining Silicon Containing Cake

NASA Astrophysics Data System (ADS)

Karshigina, Zaure; Abisheva, Zinesh; Bochevskaya, Yelena; Akcil, Ata; Sharipova, Aynash; Sargelova, Elmira

2016-10-01

The present research is devoted to the processing of slag generating during the yellow phosphorus production. In this paper are presented studies on leaching of phosphorus production slag by nitric acid with recovery of rare earth metals (REMs) into solution. REMs recovery into the solution achieved 98 % during the leaching process with using 7.5 mol/L of HNO3, liquid-to-solid ratio is 2.6:1, temperature is 60°C, process duration is 1 hour and stirrer speed is 500 rpm. Behaviour during the leaching of associated components such as calcium, aluminium, and iron was studied. After the leaching cake contains ∼⃒75-85 % of SiO2 and it might be useful for obtaining of precipitated silicon dioxide. With the purpose of separation from the impurities, recovery and concentrating of REMs, the obtained solution after leaching was subjected to extraction processing methods. The influence of ratio of organic and aqueous phases (O: A) on the extraction of rare earth metals by tributyl phosphate (TBP) with concentrations from 20 up to 100 % was studied. The REMs extraction with increasing TBP concentration under changes O:A ratio from 1:20 down to 1:1 into the organic phase from the solutions after nitric acid leaching increased from 22.2 up to 99.3%. The duration effect of REMs extraction process was studied by tributyl phosphate. It is revealed that with increasing of duration of the extraction process from 10 to 30 minutes REMs recovery into the organic phase almost did not changed. The behaviour of iron in the extraction process by TBP was studied. It was found that such accompanying components as calcium and aluminium by tributyl phosphate didn't extracted. To construct isotherm of REMs extraction of by tributyl phosphate was used variable volume method. It was calculated three-step extraction is needed for REMs recovery from the solutions after nitric acid leaching of phosphorus production slag. The process of the three-steps counter current extraction of rare earth

Solvation structures and dynamics of alkaline earth metal halides in supercritical water: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Keshri, Sonanki; Mandal, Ratnamala; Tembe, B. L.

2016-09-01

Constrained molecular dynamics simulations of alkaline earth metal halides have been carried out to investigate their structural and dynamical properties in supercritical water. Potentials of mean force (PMFs) for all the alkaline earth metal halides in supercritical water have been computed. Contact ion pairs (CIPs) are found to be more stable than all other configurations of the ion pairs except for MgI2 where solvent shared ion pair (SShIP) is more stable than the CIP. There is hardly any difference in the PMFs between the M2+ (M = Mg, Ca, Sr, Ba) and the X- (X = F, Cl, Br, I) ions whether the second X- ion is present in the first coordination shell of the M2+ ion or not. The solvent molecules in the solvation shells diffuse at a much slower rate compared to the bulk. Orientational distribution functions of solvent molecules are sharper for smaller ions.

Richness, coverage and concentration of heavy metals in vascular epiphytes along an urbanization gradient.

PubMed

Becker, Diego Fedrizzi Petry; Linden, Rafael; Schmitt, Jairo Lizandro

2017-04-15

Richness, coverage and concentration of heavy metals in vascular epiphytes were analyzed in isolated trees along an urbanization gradient in Southern Brazil. A total of 20 phorophytes were sampled in the main street of each site. Concentrations of chromium, cadmium, lead, manganese, nickel and zinc were measured in the leaves of Tillandsia recurvata L. using Graphite Furnace Atomic Absorption Spectrophotometry. A decreasing gradient of epiphyte richness and coverage was observed as urbanization increased. Vehicle fleet and demographic density were the parameters most correlated with the reduction of epiphytic diversity. In T. recurvata, significantly higher values of cadmium, lead and zinc were recorded in the most urbanized areas, and were strongly related to the vehicle fleet and to the demographic density in these sites. The results demonstrated that these parameters could be applied to the diagnosis of environmental quality in urban areas, allowing standardized analyses in other regions. Copyright © 2017 Elsevier B.V. All rights reserved.

Hg and Pt-metals in meteorite carbon-rich residues - Suggestions for possible host phase for Hg

NASA Technical Reports Server (NTRS)

Jovanovic, S.; Reed, G. W., Jr.

1980-01-01

Carbon-rich and oxide residual phases have been isolated from Allende and Murchison by acid demineralization for the determination of their Hg, Pt-metal, Cr, Sc, Co, and Fe contents. Experimental procedures used eliminated the possibility of exogenous and endogenous contaminant trace elements from coprecipitating with the residues. Large enrichments of Hg and Pt-metals were found in Allende but not in Murchison residues. Hg-release profiles from stepwise heating experiments suggest a sulfide as the host for Hg. Diffusion calculations for Hg based on these experiments indicate an activation energy of 7-8 kcal/mol, the same as that for Hg in troilite from an iron meteorite. This is further support for a sulfide host phase for Hg. Equilibration of Hg with this phase at approximately 900 K is indicated. Reasons for the presence of Pt-metals in noncosmic relative abundances are explored.

Uncovering the Chemistry of Earth-like Planets

NASA Astrophysics Data System (ADS)

Zeng, Li; Sasselov, Dimitar; Jacobsen, Stein

2015-08-01

We propose to use the evidence from our solar system to understand exoplanets, and in particular, to predict their surface chemistry and thereby the possibility of life. An Earth-like planet, born from the same nebula as its host star, is composed primarily of silicate rocks and an iron-nickel metal core, and depleted in volatile content in a systematic manner. The more volatile (easier to vaporize or dissociate into gas form) an element is in an Earth-like planet, the more depleted the element is compared to its host star. After depletion, an Earth-like planet would go through the process of core formation due to heat from radioactive decay and collisions. Core formation depletes a planet’s rocky mantle of siderophile (iron-loving) elements, in addition to the volatile depletion. After that, Earth-like planets likely accrete some volatile-rich materials, called “late veneer”. The late veneer could be essential to the origins of life on Earth and Earth-like planets, as it also delivers the volatiles such as nitrogen, sulfur, carbon and water to the planet’s surface, which are crucial for life to occur. Here we build an integrative model of Earth-like planets from the bottom up. Thus the chemical compositions of Earth-like planets could be inferred from their mass-radius relations and their host stars’ elemental abundances, and the origins of volatile contents (especially water) on their surfaces could be understood, and thereby shed light on the origins of life on them. This elemental abundance model could be applied to other rocky exoplanets in exoplanet systems.

Transfer of rare earth elements from natural metalliferous (copper and cobalt rich) soils into plant shoot biomass of metallophytes from Katanga (Democratic Republic of Congo)

NASA Astrophysics Data System (ADS)

Pourret, Olivier; Lange, Bastien; Jitaru, Petru; Mahy, Grégory; Faucon, Michel-Pierre

2014-05-01

The geochemical behavior of rare earth elements (REE) is generally assessed for the characterization of the geological systems where these elements represent the best proxies of processes involving the occurrence of an interface between different media. REE behavior is investigated according to their concentrations normalized with respect to the upper continental crust. In this study, the geochemical fingerprint of REE in plant shoot biomass of an unique metallicolous flora (i.e., Crepidorhopalon tenuis and Anisopappus chinensis) was investigated. The plants originate from extremely copper and cobalt rich soils, deriving from Cu and Co outcrops in Katanga, Democratic Republic of Congo. Some of the species investigated in this study are able to accumulate high amounts of Cu and Co in shoot hence being considered as Cu and Co hyperaccumulators. Therefore, assessing the behavior of REE may lead to a better understanding of the mechanisms of metal accumulation by this flora. The data obtained in this study indicate that REE uptake by plants is not primarily controlled by their concentration and speciation in the soil as previously shown in the literature (Brioschi et al. 2013). Indeed, the REE patterns in shoots are relatively flat whereas soils patterns are Middle REE enriched. In addition, it is worth noting that Eu enrichments occur in aerial parts of the plants. These positive Eu anomalies suggest that Eu3 + can form stable organic complexes replacing Ca2 + in several biological processes as in xylem fluids associated with the general nutrient flux. Therefore, is is possible that the Eu mobility in these fluids is enhanced by its reductive speciation as Eu2 +. Eventually, the geochemical behavior of REE illustrates that metals accumulation in aerial parts of C. tenuis and A. chinensis is mainly driven by dissolved complexation. Brioschi, L., Steinmann, M., Lucot, E., Pierret, M., Stille, P., Prunier, J., Badot, P., 2013. Transfer of rare earth elements (REE) from

Lattice vibrations and electronic transitions in the rare-earth metals: yttrium, gadolinium and lutetium

NASA Astrophysics Data System (ADS)

Olijnyk, Helmut

2005-01-01

Lattice vibrations in high-pressure phases of Y, Gd and Lu were studied by Raman spectroscopy. The observed phonon frequencies decrease towards the transitions to the dhcp and fcc phases. There is evidence that the entire structural sequence {\\mathrm {hcp \\to Sm\\mbox {-}type \\to dhcp \\to fcc}} under pressure for the individual regular rare-earth metals and along the lanthanide series at ambient pressure involve softening of certain acoustic and optical phonon modes and of the elastic shear modulus C44. Comparison is made to transitions between close-packed lattices in other metals, and possible correlations to s-d electron transfer are discussed.

Comparison of metallothionein concentrations and tissue distribution of trace metals in crabs (Pachygrapsus marmoratus) from a metal-rich estuary, in and out of the reproductive season.

PubMed

Mouneyrac, C; Amiard-Triquet, C; Amiard, J C; Rainbow, P S

2001-07-01

Crabs, Pachygrapsus marmoratus, were sampled in June 1997 and February 1998 from two sites (at the mouth and 25 km upstream) in the metal-rich Gironde estuary, France. Gills and hepatopancreas were analysed for metal (Cd, Cu, Zn) and metallothionein (MT) contents, in order to examine the influence of both biological and environmental factors on the physico-chemical forms of detoxified metal storage in the crabs. The concentrations of MT and both cytosolic and insoluble metals were not greatly different between males and females, and the influence of organ weights was also minimal. Intersite differences were observed, probably resulting from the gradient of salinity in the estuary, which interacts with both the chemical speciation and bioavailability of metals, and the general protein metabolism of the crabs. Seasonal changes were also important, probably in interaction with the moult and reproductive cycles. In February, concentrations of insoluble metals were generally higher than in June, in both organs, suggesting that essential metals, particularly Zn, are stored during winter then remobilised during the breeding season. The natural variability in the concentrations of MT often concealed any relationship with accumulated metal concentrations. Thus MT in crabs cannot be considered as a useful biomarker of metal pollution.

Hyperfine structure of 2Σ molecules containing alkaline-earth-metal atoms

NASA Astrophysics Data System (ADS)

Aldegunde, Jesus; Hutson, Jeremy M.

2018-04-01

Ultracold molecules with both electron spin and an electric dipole moment offer new possibilities in quantum science. We use density-functional theory to calculate hyperfine coupling constants for a selection of molecules important in this area, including RbSr, LiYb, RbYb, CaF, and SrF. We find substantial hyperfine coupling constants for the fermionic isotopes of the alkaline-earth-metal and Yb atoms. We discuss the hyperfine level patterns and Zeeman splittings expected for these molecules. The results will be important both to experiments aimed at forming ultracold open-shell molecules and to their applications.

Liquefaction process for solid carbonaceous materials containing alkaline earth metal humates

DOEpatents

Epperly, William R.; Deane, Barry C.; Brunson, Roy J.

1982-01-01

An improved liquefaction process wherein wall scale and particulate agglomeration during the liquefaction of solid carbonaceous materials containing alkaline earth metal humates is reduced and/or eliminated by subjecting the solid carbonaceous materials to controlled cyclic cavitation during liquefaction. It is important that the solid carbonaceous material be slurried in a suitable solvent or diluent during liquefaction. The cyclic cavitation may be imparted via pressure cycling, cyclic agitation and the like. When pressure cycling or the like is employed an amplitude equivalent to at least 25 psia is required to effectively remove scale from the liquefaction vessel walls.

A stable lithium-rich surface structure for lithium-rich layered cathode materials

PubMed Central

Kim, Sangryun; Cho, Woosuk; Zhang, Xiaobin; Oshima, Yoshifumi; Choi, Jang Wook

2016-01-01

Lithium ion batteries are encountering ever-growing demand for further increases in energy density. Li-rich layered oxides are considered a feasible solution to meet this demand because their specific capacities often surpass 200 mAh g−1 due to the additional lithium occupation in the transition metal layers. However, this lithium arrangement, in turn, triggers cation mixing with the transition metals, causing phase transitions during cycling and loss of reversible capacity. Here we report a Li-rich layered surface bearing a consistent framework with the host, in which nickel is regularly arranged between the transition metal layers. This surface structure mitigates unwanted phase transitions, improving the cycling stability. This surface modification enables a reversible capacity of 218.3 mAh g−1 at 1C (250 mA g−1) with improved cycle retention (94.1% after 100 cycles). The present surface design can be applied to various battery electrodes that suffer from structural degradations propagating from the surface. PMID:27886178

Preferential growth of short aligned, metallic-rich single-walled carbon nanotubes from perpendicular layered double hydroxide film.

PubMed

Zhao, Meng-Qiang; Tian, Gui-Li; Zhang, Qiang; Huang, Jia-Qi; Nie, Jing-Qi; Wei, Fei

2012-04-07

Direct bulk growth of single-walled carbon nanotubes (SWCNTs) with required properties, such as diameter, length, and chirality, is the first step to realize their advanced applications in electrical and optical devices, transparent conductive films, and high-performance field-effect transistors. Preferential growth of short aligned, metallic-rich SWCNTs is a great challenge to the carbon nanotube community. We report the bulk preferential growth of short aligned SWCNTs from perpendicular Mo-containing FeMgAl layered double hydroxide (LDH) film by a facile thermal chemical vapor deposition with CH(4) as carbon source. The growth of the short aligned SWCNTs showed a decreased growth velocity with an initial value of 1.9 nm s(-1). Such a low growth velocity made it possible to get aligned SWCNTs shorter than 1 μm with a growth duration less than 15 min. Raman spectra with different excitation wavelengths indicated that the as-grown short aligned SWCNTs showed high selectivity of metallic SWCNTs. Various kinds of materials, such as mica, quartz, Cu foil, and carbon fiber, can serve as the substrates for the growth of perpendicular FeMoMgAl LDH films and also the growth of the short aligned SWCNTs subsequently. These findings highlight the easy route for bulk preferential growth of aligned metallic-rich SWCNTs with well defined length for further bulk characterization and applications. This journal is © The Royal Society of Chemistry 2012

Biogeochemical characterization of an undisturbed highly acidic, metal-rich bryophyte habitat, east-central Alaska, U.S.A.

USGS Publications Warehouse

Gough, L.P.; Eppinger, R.G.; Briggs, P.H.; Giles, S.

2006-01-01

We report on the geochemistry of soil and bryophyte-laden sediment and on the biogeochemistry of willows growing in an undisturbed volcanogenic massive sulfide deposit in the Alaska Range ecoregion of east-central Alaska. We also describe an unusual bryophyte assemblage found growing in the acidic metal-rich waters that drain the area. Ferricrete-cemented silty alluvial sediments within seeps and streams are covered with the liverwort Gymnocolea inflata whereas the mosses Polytrichum commune and P. juniperinum inhabit the area adjacent to the water and within the splash zone. Both the liverwort-encrusted sediment and Polytrichum thalli have high concentrations of major and trace metal cations (e.g., Al, As, Cu, Fe, Hg, La, Mn, Pb, and Zn). Soils in the area do not reflect the geochemical signature of the mineral deposit and we postulate they are influenced by the chemistry of eolian sediments derived from outside the deposit area. The willow, Salix pulchra, growing mostly within and adjacent to the larger streams, has much higher concentrations of Al, As, Cd, Cr, Fe, La, Pb, and Zn when compared to the same species collected in non-mineralized areas of Alaska. The Cd levels are especially high and are shown to exceed, by an order of magnitude, levels demonstrated to be toxic to ptarmigan in Colorado. Willow, growing in this naturally occurring metal-rich Red Mountain alteration zone, may adversely affect the health of browsing animals. ?? 2006 Regents of the University of Colorado.

Rare earth element scavenging in seawater

NASA Astrophysics Data System (ADS)

Byrne, Robert H.; Kim, Ki-Hyun

1990-10-01

Examinations of rare earth element (REE) adsorption in seawater, using a variety of surface-types, indicated that, for most surfaces, light rare earth elements (LREEs) are preferentially adsorbed compared to the heavy rare earths (HREEs). Exceptions to this behavior were observed only for silica phases (glass surfaces, acid-cleaned diatomaceous earth, and synthetic SiO 2). The affinity of the rare earths for surfaces can be strongly affected by thin organic coatings. Glass surfaces which acquired an organic coating through immersion in Tampa Bay exhibited adsorptive behavior typical of organic-rich, rather than glass, surfaces. Models of rare earth distributions between seawater and carboxylate-rich surfaces indicate that scavenging processes which involve such surfaces should exhibit a strong dependence on pH and carbonate complexation. Scavenging models involving carboxylate surfaces produce relative REE abundance patterns in good general agreement with observed shale-normalized REE abundances in seawater. Scavenging by carboxylate-rich surfaces should produce HREE enrichments in seawater relative to the LREEs and may produce enrichments of lanthanum relative to its immediate trivalent neighbors. Due to the origin of distribution coefficients as a difference between REE solution complexation (which increases strongly with atomic number) and surface complexation (which apparently also increases with atomic number) the relative solution abundance patterns of the REEs produced by scavenging reactions can be quite complex.

Recovery of Rare Earths, Precious Metals and Other Critical Materials from Geothermal Waters with Advanced Sorbent Structures

DOE Data Explorer

Pamela M. Kinsey

2015-09-30

The work evaluates, develops and demonstrates flexible, scalable mineral extraction technology for geothermal brines based upon solid phase sorbent materials with a specific focus upon rare earth elements (REEs). The selected organic and inorganic sorbent materials demonstrated high performance for collection of trace REEs, precious and valuable metals. The nanostructured materials typically performed better than commercially available sorbents. Data contains organic and inorganic sorbent removal efficiency, Sharkey Hot Springs (Idaho) water chemsitry analysis, and rare earth removal efficiency from select sorbents.

The Toxicological Geochemistry of Dusts, Soils, and Other Earth Materials: Insights From In Vitro Physiologically-based Geochemical Leach Tests

NASA Astrophysics Data System (ADS)

Plumlee, G. S.; Ziegler, T. L.; Lamothe, P.; Meeker, G. P.; Sutley, S.

2003-12-01

Exposure to mineral dusts, soils, and other earth materials results in chemical reactions between the materials and different body fluids that include, depending upon the exposure route, lung fluids, gastrointestinal fluids, and perspiration. In vitro physiologically-based geochemical leach tests provide useful insights into these chemical reactions and their potential toxicological implications. We have conducted such leach tests on a variety of earth materials, including asbestos, volcanic ash, dusts from dry lake beds, mine wastes, wastes left from the roasting of mercury ores, mineral processing wastes, coal dusts and coal fly ash, various soils, and complex dusts generated by the World Trade Center collapse. Size-fractionated samples of earth materials that have been well-characterized mineralogically and chemically are reacted at body temperature (37 C) for periods from 2 hours up to multiple days with various proportions of simulated lung, gastric, intestinal, and/or plasma-based fluids. Results indicate that different earth materials may have quite different solubility and dissolution behavior in vivo, depending upon a) the mineralogic makeup of the material, and b) the exposure route. For example, biodurable minerals such as asbestos and volcanic ash particles, whose health effects result because they dissolve very slowly in vivo, bleed off low levels of trace metals into the simulated lung fluids; these include metals such as Fe and Cr that are suspected by health scientists of contributing to the generation of reactive oxygen species and resulting DNA damage in vivo. In contrast, dry lake bed dusts and concrete-rich dusts are highly alkaline and bioreactive, and cause substantial pH increases and other chemical changes in the simulated body fluids. Many of the earth materials tested contain a variety of metals that can be quite soluble (bioaccessible), depending upon the material and the simulated body fluid composition. For example, due to their acidic

Dissolved Massive Metal-rich Globular Clusters Can Cause the Range of UV Upturn Strengths Found among Early-type Galaxies

NASA Astrophysics Data System (ADS)

Goudfrooij, Paul

2018-04-01

I discuss a scenario in which the ultraviolet (UV) upturn of giant early-type galaxies (ETGs) is primarily due to helium-rich stellar populations that formed in massive metal-rich globular clusters (GCs), which subsequently dissolved in the strong tidal field in the central regions of the massive host galaxy. These massive GCs are assumed to show UV upturns similar to those observed recently in M87, the central giant elliptical galaxy in the Virgo cluster of galaxies. Data taken from the literature reveal a strong correlation between the strength of the UV upturn and the specific frequency of metal-rich GCs in ETGs. Adopting a Schechter function parameterization of GC mass functions, simulations of long-term dynamical evolution of GC systems show that the observed correlation between UV upturn strength and GC specific frequency can be explained by variations in the characteristic truncation mass {{ \\mathcal M }}{{c}} such that {{ \\mathcal M }}{{c}} increases with ETG luminosity in a way that is consistent with observed GC luminosity functions in ETGs. These findings suggest that the nature of the UV upturn in ETGs and the variation of its strength among ETGs are causally related to that of helium-rich populations in massive GCs, rather than intrinsic properties of field stars in massive galactic spheroids. With this in mind, I predict that future studies will find that [N/Fe] decreases with increasing galactocentric radius in massive ETGs, and that such gradients have the largest amplitudes in ETGs with the strongest UV upturns.

Physical Theory of Voltage Fade in Lithium- and Manganese-Rich Transition Metal Oxides

DOE PAGES

Rinaldo, Steven G.; Gallagher, Kevin G.; Long, Brandon R.; ...

2015-03-04

Lithium- and manganese-rich (LMR) transition metal oxide cathodes are of interest for lithium-ion battery applications due to their increased energy density and decreased cost. However, the advantages in energy density and cost are offset, in part, due to the phenomena of voltage fade. Specifically, the voltage profiles (voltage as a function of capacity) of LMR cathodes transform from a high energy configuration to a lower energy configuration as they are repeatedly charged (Li removed) and discharged (Li inserted). Here, we propose a physical model of voltage fade that accounts for the emergence of a low voltage Li phase due tomore » the introduction of transition metal ion defects within a parent Li phase. The phenomenological model was re-cast in a general form and experimental LMR charge profiles were de-convoluted to extract the evolutionary behavior of various components of LMR capacitance profiles. Evolution of the voltage fade component was found to follow a universal growth curve with a maximal voltage fade capacity of ≈ 20% of the initial total capacity.« less

THE DOMINANCE OF METAL-RICH STREAMS IN STELLAR HALOS: A COMPARISON BETWEEN SUBSTRUCTURE IN M31 AND {lambda}CDM MODELS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilbert, Karoline M.; Font, Andreea S.; Johnston, Kathryn V.

2009-08-10

Extensive photometric and spectroscopic surveys of the Andromeda galaxy (M31) have discovered tidal debris features throughout M31's stellar halo. We present stellar kinematics and metallicities in fields with identified substructure from our on-going SPLASH survey of M31 red giant branch stars with the DEIMOS spectrograph on the Keck II 10 m telescope. Radial velocity criteria are used to isolate members of the kinematically cold substructures. The substructures are shown to be metal-rich relative to the rest of the dynamically hot stellar population in the fields in which they are found. We calculate the mean metallicity and average surface brightness ofmore » the various kinematical components in each field, and show that, on average, higher surface brightness features tend to be more metal-rich than lower surface brightness features. Simulations of stellar halo formation via accretion in a cosmological context are used to illustrate that the observed trend can be explained as a natural consequence of the observed dwarf galaxy mass-metallicity relation. A significant spread in metallicity at a given surface brightness is seen in the data; we show that this is due to time effects, namely, the variation in the time since accretion of the tidal streams' progenitor onto the host halo. We show that in this theoretical framework a relationship between the alpha-enhancement and surface brightness of tidal streams is expected, which arises from the varying times of accretion of the progenitor satellites onto the host halo. Thus, measurements of the alpha-enrichment, metallicity, and surface brightness of tidal debris can be used to reconstruct the luminosity and time of accretion onto the host halo of the progenitors of tidal streams.« less

Alkali-earth metal bridges formed in biofilm matrices regulate the uptake of fluoroquinolone antibiotics and protect against bacterial apoptosis.

PubMed

Kang, Fuxing; Wang, Qian; Shou, Weijun; Collins, Chris D; Gao, Yanzheng

2017-01-01

Bacterially extracellular biofilms play a critical role in relieving toxicity of fluoroquinolone antibiotic (FQA) pollutants, yet it is unclear whether antibiotic attack may be defused by a bacterial one-two punch strategy associated with metal-reinforced detoxification efficiency. Our findings help to assign functions to specific structural features of biofilms, as they strongly imply a molecularly regulated mechanism by which freely accessed alkali-earth metals in natural waters affect the cellular uptake of FQAs at the water-biofilm interface. Specifically, formation of alkali-earth-metal (Ca 2+ or Mg 2+ ) bridge between modeling ciprofloxacin and biofilms of Escherichia coli regulates the trans-biofilm transport rate of FQAs towards cells (135-nm-thick biofilm). As the addition of Ca 2+ and Mg 2+ (0-3.5 mmol/L, CIP: 1.25 μmol/L), the transport rates were reduced to 52.4% and 63.0%, respectively. Computational chemistry analysis further demonstrated a deprotonated carboxyl in the tryptophan residues of biofilms acted as a major bridge site, of which one side is a metal and the other is a metal girder jointly connected to the carboxyl and carbonyl of a FQA. The bacterial growth rate depends on the bridging energy at anchoring site, which underlines the environmental importance of metal bridge formed in biofilm matrices in bacterially antibiotic resistance. Copyright © 2016 Elsevier Ltd. All rights reserved.

Experimental investigation of the partitioning of phosphorus between metal and silicate phases - Implications for the earth, moon and eucrite parent body

NASA Technical Reports Server (NTRS)

Newsom, H. E.; Drake, M. J.

1983-01-01

An experimental study is reported of the partitioning of Phosphorus between solid metal and basaltic silicate liquid as a function of temperature and oxygen fugacity and of the implications for the earth, moon and eucrite parent body (EPB). The relationship established between the partition coefficient and the fugacity is given at 1190 C by log D(P) = -1.12 log fO2 - 15.95 and by log D(P) = -1.53 log fO2 17.73 at 1300 C. The partition coefficient D(P) was determined, and it is found to be consistent with a valence state of 5 for P in the molten silicate. Using the determined coefficient the low P/La ratios of the earth, moon, and eucrites relative to C1 chondrites can be explained. The lowering of the P/La ratio in the eucrites relative to Cl chondrite by a factor of 40 can be explained by partitioning P into 20-25 wt% sulfur-bearing metallic liquid corresponding to 5-25% of the total metal plus silicate system. The low P/La and W/La ratios in the moon may be explained by the partitioning of P and W into metal during formation of a small core by separation of liquid metal from silicate at low degrees of partial melting of the silicates. These observations are consistent with independent formation of the moon and the earth.

Haze production rates in super-Earth and mini-Neptune atmosphere experiments

NASA Astrophysics Data System (ADS)

Hörst, Sarah M.; He, Chao; Lewis, Nikole K.; Kempton, Eliza M.-R.; Marley, Mark S.; Morley, Caroline V.; Moses, Julianne I.; Valenti, Jeff A.; Vuitton, Véronique

2018-04-01

Numerous Solar System atmospheres possess photochemically generated hazes, including the characteristic organic hazes of Titan and Pluto. Haze particles substantially impact atmospheric temperature structures and may provide organic material to the surface of a world, potentially affecting its habitability. Observations of exoplanet atmospheres suggest the presence of aerosols, especially in cooler (<800 K), smaller (<0.3× Jupiter's mass) exoplanets. It remains unclear whether the aerosols muting the spectroscopic features of exoplanet atmospheres are condensate clouds or photochemical hazes1-3, which is difficult to predict from theory alone4. Here, we present laboratory haze simulation experiments that probe a broad range of atmospheric parameters relevant to super-Earth- and mini-Neptune-type planets5, the most frequently occurring type of planet in our galaxy6. It is expected that photochemical haze will play a much greater role in the atmospheres of planets with average temperatures below 1,000 K (ref. 7), especially those planets that may have enhanced atmospheric metallicity and/or enhanced C/O ratios, such as super-Earths and Neptune-mass planets8-12. We explored temperatures from 300 to 600 K and a range of atmospheric metallicities (100×, 1,000× and 10,000× solar). All simulated atmospheres produced particles, and the cooler (300 and 400 K) 1,000× solar metallicity (`H2O-dominated' and CH4-rich) experiments exhibited haze production rates higher than our standard Titan simulation ( 10 mg h-1 versus 7.4 mg h-1 for Titan13). However, the particle production rates varied greatly, with measured rates as low as 0.04 mg h-1 (for the case with 100× solar metallicity at 600 K). Here, we show that we should expect great diversity in haze production rates, as some—but not all—super-Earth and mini-Neptune atmospheres will possess photochemically generated haze.

Haze production rates in super-Earth and mini-Neptune atmosphere experiments

NASA Astrophysics Data System (ADS)

Hörst, Sarah M.; He, Chao; Lewis, Nikole K.; Kempton, Eliza M.-R.; Marley, Mark S.; Morley, Caroline V.; Moses, Julianne I.; Valenti, Jeff A.; Vuitton, Véronique

2018-03-01

Numerous Solar System atmospheres possess photochemically generated hazes, including the characteristic organic hazes of Titan and Pluto. Haze particles substantially impact atmospheric temperature structures and may provide organic material to the surface of a world, potentially affecting its habitability. Observations of exoplanet atmospheres suggest the presence of aerosols, especially in cooler (<800 K), smaller (<0.3× Jupiter's mass) exoplanets. It remains unclear whether the aerosols muting the spectroscopic features of exoplanet atmospheres are condensate clouds or photochemical hazes1-3, which is difficult to predict from theory alone4. Here, we present laboratory haze simulation experiments that probe a broad range of atmospheric parameters relevant to super-Earth- and mini-Neptune-type planets5, the most frequently occurring type of planet in our galaxy6. It is expected that photochemical haze will play a much greater role in the atmospheres of planets with average temperatures below 1,000 K (ref. 7), especially those planets that may have enhanced atmospheric metallicity and/or enhanced C/O ratios, such as super-Earths and Neptune-mass planets8-12. We explored temperatures from 300 to 600 K and a range of atmospheric metallicities (100×, 1,000× and 10,000× solar). All simulated atmospheres produced particles, and the cooler (300 and 400 K) 1,000× solar metallicity (`H2O-dominated' and CH4-rich) experiments exhibited haze production rates higher than our standard Titan simulation ( 10 mg h-1 versus 7.4 mg h-1 for Titan13). However, the particle production rates varied greatly, with measured rates as low as 0.04 mg h-1 (for the case with 100× solar metallicity at 600 K). Here, we show that we should expect great diversity in haze production rates, as some—but not all—super-Earth and mini-Neptune atmospheres will possess photochemically generated haze.

A Search for the Optimum Lithium Rich Layered Metal Oxide Cathode Material for Li-Ion Batteries

PubMed Central

Ates, Mehmet Nurullah; Mukerjee, Sanjeev; Abraham, K. M.

2015-01-01

We report the results of a comprehensive study of the relationship between electrochemical performance in Li cells and chemical composition of a series of Li rich layered metal oxides of the general formula xLi2MnO3 · (1-x)LiMn0.33Ni0.33Co0.33O2 in which x = 0,1, 0.2, 0,3, 0.5 or 0.7, synthesized using the same method. In order to identify the cathode material having the optimum Li cell performance we first varied the ratio between Li2MnO3 and LiMO2 segments of the composite oxides while maintaining the same metal ratio residing within their LiMO2 portions. The materials with the overall composition 0.5Li2MnO3 · 0.5LiMO2 containing 0.5 mole of Li2MnO3 per mole of the composite metal oxide were found to be the optimum in terms of electrochemical performance. The electrochemical properties of these materials were further tuned by changing the relative amounts of Mn, Ni and Co in the LiMO2 segment to produce xLi2MnO3 · (1-x)LiMn0.50Ni0.35Co0.15O2 with enhanced capacities and rate capabilities. The rate capability of the lithium rich compound in which x = 0.3 was further increased by preparing electrodes with about 2 weight-percent multiwall carbon nanotube in the electrode. Lithium cells prepared with such electrodes were cycled at the 4C rate with little fade in capacity for over one hundred cycles. PMID:26478598

Enhanced pinning in mixed rare earth-123 films

DOEpatents

Driscoll, Judith L [Los Alamos, NM; Foltyn, Stephen R [Los Alamos, NM

2009-06-16

An superconductive article and method of forming such an article is disclosed, the article including a substrate and a layer of a rare earth barium cuprate film upon the substrate, the rare earth barium cuprate film including two or more rare earth metals capable of yielding a superconductive composition where ion size variance between the two or more rare earth metals is characterized as greater than zero and less than about 10.times.10.sup.-4, and the rare earth barium cuprate film including two or more rare earth metals is further characterized as having an enhanced critical current density in comparison to a standard YBa.sub.2Cu.sub.3O.sub.y composition under identical testing conditions.

Labile rhizosphere soil solution fraction for prediction of bioavailability of heavy metals and rare earth elements to plants.

PubMed

Shan, Xiao-Quan; Wang, Zhongwen; Wang, Weisheng; Zhang, Shuzhen; Wen, Bei

2003-02-01

A labile rhizosphere soil solution fraction has been recommended to predict the bioavailability of heavy metals and rare earth elements to plants. This method used moist rhizosphere soil in combination with a mixture of 0.01 mol L(-1) of low-molecular-weight organic acids (LMWOAs) as extractant. The extracted soil solutions were fractionated into two colloidal fractions of <0.45 microm (F(3)) and <0.2 microm (F(2)), and one truly dissolved fraction including free metal ions and inorganic and organic complexes (fractionmetals and rare earth elements in F(2) and F(3) were quite similar. However, the mean concentrations of Cr, Ni, Zn, Cu, Pb, Cd, La, Ce, Pr, and Nd in F(lrss) accounted for 79.9%, 91.3%, 90.8%, 60.1%, 77.5%, 75.3%, 81.2%, 77.2%, 80.3%, and 79.5%, respectively, of their concentrations in F(2). In contrast, there were no differences in the extractable metal concentrations between the three fractions while the first step of the method recommended by the European Community of Reference (BCR), where 0.1 mol L(-1) acetic acid was used as an extractant. The single correlation analysis was made between metal concentrations in the different fractions of soil solutions and their concentrations in wheat. If the first step of BCR method was used there was no good correlation between heavy metals in soil pools and that in wheat shoots and roots. When LMWAOs were used a good correlation was obtained between the concentrations of heavy metals in soil pools and that in wheat roots, which followed a general order of r(1 kD, LMWOAs) >r(0.2 microm, LMWOAs) approximately r(0.45 microm, LMWOAs). In the case of rare earth elements the good correlation was obtained for both the wheat roots and shoots. Generally, the correlation coefficients

Polymer Nanocomposite Film with Metal Rich Surface Prepared by In Situ Single-Step Formation of Palladium Nanoparticles: An Interesting Way to Combine Specific Functional Properties.

PubMed

Thompson, David; Kranbuehl, David; Espuche, Eliane

2016-10-18

This paper presents a continuous single-step route that permits preparation of a thermostable polymer/metal nanocomposite film and to combine different functional properties in a unique material. More precisely, palladium nanoparticles are in situ generated in a polyimide matrix thanks to a designed curing cycle which is applied to a polyamic acid/metal precursor solution cast on a glass plate. A metal-rich surface layer which is strongly bonded to the bulk film is formed in addition to homogeneously dispersed metal nanoparticles. This specific morphology leads to obtaining an optically reflective film. The metal nanoparticles act as gas diffusion barriers for helium, oxygen, and carbon dioxide; they induce a tortuosity effect which allows dividing the gas permeation coefficients by a factor near to 2 with respect to the neat polyimide matrix. Moreover, the ability of the in situ synthesized palladium nanoparticles to entrap hydrogen is evidenced. The nanocomposite film properties can be modulated as a function of the location of the film metal-rich surface with respect to the hydrogen feed. The synthesized nanocomposite could represent a major interest for a wide variety of applications, from specific coatings for aerospace or automotive industry, to catalysis applications or sensors.

Iron-carbonate interaction at Earth's core-mantle boundary

NASA Astrophysics Data System (ADS)

Dorfman, S. M.; Badro, J.; Nabiei, F.; Prakapenka, V.; Gillet, P.

2015-12-01

Carbon storage and flux in the deep Earth are moderated by oxygen fugacity and interactions with iron-bearing phases. The amount of carbon stored in Earth's mantle versus the core depends on carbon-iron chemistry at the core-mantle boundary. Oxidized carbonates subducted from Earth's surface to the lowermost mantle may encounter reduced Fe0 metal from disproportionation of Fe2+ in lower mantle silicates or mixing with the core. To understand the fate of carbonates in the lowermost mantle, we have performed experiments on sandwiches of single-crystal (Ca0.6Mg0.4)CO3 dolomite and Fe foil in the laser-heated diamond anvil cell at lower mantle conditions of 49-110 GPa and 1800-2500 K. Syntheses were conducted with in situ synchrotron X-ray diffraction to identify phase assemblages. After quench to ambient conditions, samples were sectioned with a focused Ga+ ion beam for composition analysis with transmission electron microscopy. At the centers of the heated spots, iron melted and reacted completely with the carbonate to form magnesiowüstite, iron carbide, diamond, magnesium-rich carbonate and calcium carbonate. In samples heated at 49 and 64 GPa, the two carbonates exhibit a eutectoid texture. In the sample heated at 110 GPa, the carbonates form rounded ~150-nm-diameter grains with a higher modal proportion of interspersed diamonds. The presence of reduced iron in the deep lower mantle and core-mantle boundary region will promote the formation of diamonds in carbonate-bearing subducted slabs. The complete reaction of metallic iron to oxides and carbides in the presence of mantle carbonate supports the formation of these phases at the Earth's core-mantle boundary and in ultra-low velocity zones.

Cluster synthesis and direct ordering of rare-earth transition-metal nanomagnets.

PubMed

Balasubramanian, Balamurugan; Skomski, Ralph; Li, Xingzhong; Valloppilly, Shah R; Shield, Jeffrey E; Hadjipanayis, George C; Sellmyer, David J

2011-04-13

Rare-earth transition-metal (R-TM) alloys show superior permanent magnetic properties in the bulk, but the synthesis and application of R-TM nanoparticles remains a challenge due to the requirement of high-temperature annealing above about 800 °C for alloy formation and subsequent crystalline ordering. Here we report a single-step method to produce highly ordered R-TM nanoparticles such as YCo(5) and Y(2)Co(17), without high-temperature thermal annealing by employing a cluster-deposition system and investigate their structural and magnetic properties. The direct ordering is highly desirable to create and assemble R-TM nanoparticle building blocks for future permanent-magnet and other significant applications.

The influence of heavy metals on the polymorphs of dicalcium silicate in the belite-rich clinkers produced from electroplating sludge.

PubMed

Chen, Ying-Liang; Shih, Pai-Haung; Chiang, Li-Choung; Chang, Yi-Kuo; Lu, Hsing-Cheng; Chang, Juu-En

2009-10-15

The purpose of this study is to utilize an electroplating sludge for belite-rich clinker production and to observe the influence of heavy metals on the polymorphs of dicalcium silicate (C(2)S). Belite-rich clinkers prepared with 0.5-2% of NiO, ZnO, CuO, and Cr(2)O(3) were used to investigate the individual effects of the heavy metals in question. The Reference Intensity Ratio (RIR) method was employed to determine the weight fractions of gamma-C(2)S and beta-C(2)S in the clinkers, and their microstructures were examined by the transmission electron microscopy (TEM). The results showed that nickel, zinc, and chromium have positive effects on beta-C(2)S stabilization (Cr(3+)>Ni(2+)>Zn(2+)), whereas copper has a negative effect. The addition of up to 10% electroplating sludge did not have any negative influence on the formation of C(2)S. It was observed that gamma-C(2)S decreased while beta-C(2)S increased with a rise in the addition of the electroplating sludge. Moreover, nickel and chromium mainly contributed to stabilizing beta-C(2)S in the belite-rich clinkers produced from the electroplating sludge.

IUPAC-NIST Solubility Data Series. 100. Rare Earth Metal Fluorides in Water and Aqueous Systems. Part 1. Scandium Group (Sc, Y, La)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mioduski, Tomasz; Gumiński, Cezary, E-mail: cegie@chem.uw.edu.pl; Zeng, Dewen, E-mail: dewen-zeng@hotmail.com

2014-03-15

This work presents an assessment of solubility data for rare earth metal fluorides (generally of trivalent metals and of CeF{sub 4}) in water and in aqueous ternary systems. Compilations of all available experimental data are introduced for each rare earth metal fluoride with a corresponding critical evaluation. Every such evaluation contains a collection of all solubility results in water, a selection of suggested solubility data, and a brief discussion of the multicomponent systems. Because the ternary systems were seldom studied more than once, no critical evaluations of such data were possible. Only simple fluorides (no complexes or binary salts) aremore » treated as the input substances in this report. The literature has been covered through the end of 2013.« less

Abundances in metal-rich stars. Detailed abundance analysis of 47 G and K dwarf stars with [Me/H] > 0.10 dex

NASA Astrophysics Data System (ADS)

Feltzing, S.; Gustafsson, B.

1998-04-01

a decreasing abundance of the s-elements relative to iron for the most metal-rich dwarf stars. We discuss our results in the context of recent models of galactic chemical evolution. In our sample we have included a few very metal rich stars, sometimes called SMR (super metal rich) stars. We find these stars to be among the most iron-rich in our sample but far from as metal-rich as indicated by their photometric metallicities. SMR stars on highly eccentric orbits, alleged to trace the evolution of the chemical evolution in the galactic Bulge, have previously been found overabundant in O, Mg and Si. We have included three such stars from the study by \\cite[Barbuy & Grenon (1990)]{Bar90}. We find them to be less metal rich and the other elemental abundances remain puzzling. Detailed spectroscopic abundance analyses of K dwarf stars are rare. Our study includes 5 K dwarf stars and has revealed what appears to be a striking example of overionization. The overionization is especially prominent for Ca, Cr and Fe. The origin of this apparent overionization is not clear and we discuss different explanations in some detail. Based on observations at the McDonald Observatory.

The Effect of Alkaline Earth Metal on the Cesium Loading of Ionsiv(R) IE-910 and IE-911

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fondeur, F.F.

2001-01-16

This study investigated the effect of variances in alkaline earth metal concentrations on cesium loading of IONSIV(R) IE-911. The study focused on Savannah River Site (SRS) ''average'' solution with varying amounts of calcium, barium and magnesium.

Clouds Composition in Super-Earth Atmospheres: Chemical Equilibrium Calculations

NASA Astrophysics Data System (ADS)

Kempton, Eliza M.-R.; Mbarek, Rostom

2015-12-01

Attempts to determine the composition of super-Earth atmospheres have so far been plagued by the presence of clouds. Yet the theoretical framework to understand these clouds is still in its infancy. For the super-Earth archetype GJ 1214b, KCl, Na2S, and ZnS have been proposed as condensates that would form under the condition of chemical equilibrium, if the planet’s atmosphere has a bulk composition near solar. Condensation chemistry calculations have not been presented for a wider range of atmospheric bulk composition that is to be expected for super-Earth exoplanets. Here we provide a theoretical context for the formation of super-Earth clouds in atmospheres of varied composition by determining which condensates are likely to form, under the assumption of chemical equilibrium. We model super-Earth atmospheres assuming they are formed by degassing of volatiles from a solid planetary core of chondritic material. Given the atomic makeup of these atmospheres, we minimize the global Gibbs free energy of over 550 gases and condensates to obtain the molecular composition of the atmospheres over a temperature range of 350-3,000 K. Clouds should form along the temperature-pressure boundaries where the condensed species appear in our calculations. The super-Earth atmospheres that we study range from highly reducing to oxidizing and have carbon to oxygen (C:O) ratios that are both sub-solar and super-solar, thereby spanning a diverse range of atmospheric composition that is appropriate for low-mass exoplanets. Some condensates appear across all of our models. However, the majority of condensed species appear only over specific ranges of H:O and C:O ratios. We find that for GJ 1214b, KCl is the primary cloud-forming condensate at solar composition, in agreement with previous work. However, for oxidizing atmospheres, where H:O is less than unity, K2SO4 clouds form instead. For carbon-rich atmospheres with super-solar C:O ratios, graphite clouds additionally appear. At

Europium-activated phosphors containing oxides of rare-earth and group-IIIB metals and method of making the same

DOEpatents

Comanzo, Holly Ann; Setlur, Anant Achyut; Srivastava, Alok Mani

2006-04-04

Europium-activated phosphors comprise oxides of at least a rare-earth metal selected from the group consisting of gadolinium, yttrium, lanthanum, and combinations thereof and at least a Group-IIIB metal selected from the group consisting of aluminum, gallium, indium, and combinations thereof. A method for making such phosphors comprises adding at least a halide of at least one of the selected Group-IIIB metals in a starting mixture. The method further comprises firing the starting mixture in an oxygen-containing atmosphere. The phosphors produced by such a method exhibit improved absorption in the UV wavelength range and improved quantum efficiency.

Europium-activated phosphors containing oxides of rare-earth and group-IIIB metals and method of making the same

DOEpatents

Comanzo, Holly Ann; Setlur, Anant Achyut; Srivastava, Alok Mani; Manivannan, Venkatesan

2004-07-13

Europium-activated phosphors comprise oxides of at least a rare-earth metal selected from the group consisting of gadolinium, yttrium, lanthanum, and combinations thereof and at least a Group-IIIB metal selected from the group consisting of aluminum, gallium, indium, and combinations thereof. A method for making such phosphors comprises adding at least a halide of at least one of the selected Group-IIIB metals in a starting mixture. The method further comprises firing the starting mixture in an oxygen-containing atmosphere. The phosphors produced by such a method exhibit improved absorption in the UV wavelength range and improved quantum efficiency.

Effect of H2O on metal-silicate partitioning of Ni, Co, V, Cr, Mn and Fe: Implications for the oxidation state of the Earth and Mars

NASA Astrophysics Data System (ADS)

Clesi, V.; Bouhifd, M. A.; Bolfan-Casanova, N.; Manthilake, G.; Fabbrizio, A.; Andrault, D.

2016-11-01

This study investigates the metal-silicate partitioning of Ni, Co, V, Cr, Mn and Fe during core mantle differentiation of terrestrial planets under hydrous conditions. For this, we equilibrated a molten hydrous CI chondrite model composition with various Fe-rich alloys in the system Fe-C-Ni-Co-Si-S in a multi-anvil over a range of P, T, fO2 and water content (5-20 GPa, 2073-2500 K, from 1 to 5 log units below the iron-wüstite (IW) buffer and for XH2O varying from 500 ppm to 1.5 wt%). By comparing the present experiments with the available data sets on dry systems, we observes that the effect of water on the partition coefficients of moderately siderophile elements is only moderate. For example, for iron we observed a decrease in the partition coefficient of Fe (Dmet/silFe) from 9.5 to 4.3, with increasing water content of the silicate melt, from 0 to 1.44 wt%, respectively. The evolution of metal-silicate partition coefficients of Ni, Co, V, Cr, Mn and Fe are modelled based on sets of empirical parameters. These empirical models are then used to refine the process of core segregation during accretion of Mars and the Earth. It appears that the likely presence of 3.5 wt% water on Mars during the core-mantle segregation could account for ∼74% of the FeO content of the Martian mantle. In contrast, water does not play such an important role for the Earth; only 4-6% of the FeO content of its mantle could be due to the water-induced Fe-oxidation, for a likely initial water concentration of 1.8 wt%. Thus, in order to reproduce the present-day FeO content of 8 wt% in the mantle, the Earth could initially have been accreted from a large fraction (between 85% and 90%) of reducing bodies (similar to EH chondrites), with 10-15% of the Earth's mass likely made of more oxidized components that introduced the major part of water and FeO to the Earth. This high proportion of enstatite chondrites in the original constitution of the Earth is consistent with the 17O,48Ca,50Ti,62Ni

Unambiguously identifying spin states of transition-metal ions in the Earth (Invited)

NASA Astrophysics Data System (ADS)

Hsu, H.

2010-12-01

The spin state of a transition-metal ion in crystalline solids, defined by the number of unpaired electrons in the ion’s incomplete 3d shell, may vary with many factors, such as temperature, pressure, strain, and the local atomic configuration, to name a few. Such a phenomenon, known as spin-state crossover, plays a crucial role in spintronic materials. Recently, the pressure-induced spin-state crossover in iron-bearing minerals has been recognized to affect the minerals’ structural and elastic properties. However, the detailed mechanism of such crossover in iron-bearing magnesium silicate perovskite, the most abundant mineral in the Earth, remains unclear. A significant part of this confusion arises from the difficulty in reliably extracting the spin state from experiments. For the same reason, the thermally-induced spin-state crossover in lanthanum cobaltite (LaCoO3) has been controversial for more than four decades. In this talk, I will discuss how first-principle calculations can help clarifying these long-standing controversies. In addition to the total energy, equation of state, and elastic properties of each spin state, first-principle calculations also predict the electric field gradient (EFG) at the nucleus of each transition-metal ion. Our calculations showed that the nuclear EFG, a quantity that can be measured via Mössbauer or nuclear magnetic resonance (NMR) spectroscopy, depends primarily on the spin state, irrespective of the concentration or configuration of transition-metal ions. Such robustness makes EFG a unique fingerprint to identify the spin state. The combination of first-principle calculations and Mössbauer/NMR spectroscopy can therefore be a reliable and efficient approach in tackling spin-state crossover problems in the Earth. This work was primarily supported by the MRSEC Program of NSF under Awards Number DMR-0212302 and DMR-0819885, and partially supported by NSF under ATM-0428774 (V-Lab), EAR-1019853, and EAR-0810272. The

Coordination chemistry of vitamin C. Part I. Interaction of L-ascorbic acid with alkaline earth metal ions in the crystalline solid and aqueous solution.

PubMed

Tajmir-Riahi, H A

1990-10-01

The interaction of L-ascorbic acid with alkaline earth metal ions has been investigated in aqueous solution at pH 6-7. The solid salts of the type Mg(L-ascorbate)2.4H2O, Ca(L-ascorbate)2.2H2O, Sr(L-ascorbate)2.2H2O and Ba(L-ascorbate)2.2H2O were isolated and characterized by means of 13C NMR and FT-IR spectroscopy. Spectroscopic and other evidence suggested that in aqueous solution, the binding of the alkaline earth metal ions is through the O-3 atom of the ascorbate anion, while in the solid state the binding of the Mg(II) is different from those of the other alkaline earth metal ion salts. The Mg(II) ion binds to the O-3, O-1 atom of the two ascorbate anions and to two H2O molecules, while the eight-coordination around the Ca(II), Sr(II), and Ba(II) ions would be completed by the coordination of three acid anions, through O-5, O-6 of the first, O-3, O-5, O-6 of the second and O-1 of the third anion as well as to two H2O molecules. The structural properties of the alkaline earth metal-ascorbate salts are different in the solid and aqueous solution.

Organic chemistry in a CO2 rich early Earth atmosphere

NASA Astrophysics Data System (ADS)

Fleury, Benjamin; Carrasco, Nathalie; Millan, Maëva; Vettier, Ludovic; Szopa, Cyril

2017-12-01

The emergence of life on the Earth has required a prior organic chemistry leading to the formation of prebiotic molecules. The origin and the evolution of the organic matter on the early Earth is not yet firmly understood. Several hypothesis, possibly complementary, are considered. They can be divided in two categories: endogenous and exogenous sources. In this work we investigate the contribution of a specific endogenous source: the organic chemistry occurring in the ionosphere of the early Earth where the significant VUV contribution of the young Sun involved an efficient formation of reactive species. We address the issue whether this chemistry can lead to the formation of complex organic compounds with CO2 as only source of carbon in an early atmosphere made of N2, CO2 and H2, by mimicking experimentally this type of chemistry using a low pressure plasma reactor. By analyzing the gaseous phase composition, we strictly identified the formation of H2O, NH3, N2O and C2N2. The formation of a solid organic phase is also observed, confirming the possibility to trigger organic chemistry in the upper atmosphere of the early Earth. The identification of Nitrogen-bearing chemical functions in the solid highlights the possibility for an efficient ionospheric chemistry to provide prebiotic material on the early Earth.

Heavily-hydrated lithic clasts in CH chondrites and the related, metal-rich chondrites Queen Alexandra Range 94411 and Hammadah al Hamra 237

NASA Astrophysics Data System (ADS)

Greshake, A.; Krot, A. N.; Meibom, A.; Weisberg, M. K.; Zolensky, M. E.; Keil, K.

2002-02-01

Fine-grained, heavily-hydrated lithic clasts in the metal-rich (CB) chondrites Queen Alexandra Range (QUE) 94411 and Hammadah al Hamra 237 and CH chondrites, such as Patuxent Range (PAT) 91546 and Allan Hills (ALH) 85085, are mineralogically similar suggesting genetic relationship between these meteorites. These clasts contain no anhydrous silicates and consist of framboidal and platelet magnetite, prismatic sulfides (pentlandite and pyrrhotite), and Fe-Mn-Mg-bearing Ca-carbonates set in a phyllosilicate-rich matrix. Two types of phyllosilicates were identified: serpentine, with basal spacing of ?0.73 nm, and saponite, with basal spacings of about 1.1-1.2 nm. Chondrules and FeNi-metal grains in CB and CH chondrites are believed to have formed at high temperature (>1300 K) by condensation in a solar nebula region that experienced complete vaporization. The absence of aqueous alteration of chondrules and metal grains in CB and CH chondrites indicates that the clasts experienced hydration in an asteroidal setting prior to incorporation into the CH and CB parent bodies. The hydrated clasts were either incorporated during regolith gardening or accreted together with chondrules and FeNi-metal grains after these high-temperature components had been transported from their hot formation region to a much colder region of the solar nebula.

Dominance of 'Gallionella capsiferriformans' and heavy metal association with Gallionella-like stalks in metal-rich pH 6 mine water discharge

USGS Publications Warehouse

Fabisch, Maria; Freyer, Gina; Johnson, Carol A.; Buchel, Georg; Akob, Denise M.; Neu, Thomas R.; Kusel, Kirsten

2016-01-01

Heavy metal-contaminated, pH 6 mine water discharge created new streams and iron-rich terraces at a creek bank in a former uranium-mining area near Ronneburg, Germany. The transition from microoxic groundwater with ~5 mm Fe(II) to oxic surface water may provide a suitable habitat for microaerobic iron-oxidizing bacteria (FeOB). In this study, we investigated the potential contribution of these FeOB to iron oxidation and metal retention in this high-metal environment. We (i) identified and quantified FeOB in water and sediment at the outflow, terraces, and creek, (ii) studied the composition of biogenic iron oxides (Gallionella-like twisted stalks) with scanning and transmission electron microscopy (SEM, TEM) as well as confocal laser scanning microscopy (CLSM), and (iii) examined the metal distribution in sediments. Using quantitative PCR, a very high abundance of FeOB was demonstrated at all sites over a 6-month study period. Gallionella spp. clearly dominated the communities, accounting for up to 88% ofBacteria, with a minor contribution of other FeOB such as Sideroxydans spp. and ‘Ferrovum myxofaciens’. Classical 16S rRNA gene cloning showed that 96% of the Gallionella-related sequences had ≥97% identity to the putatively metal-tolerant ‘Gallionella capsiferriformans ES-2’, in addition to known stalk formers such as Gallionella ferruginea and Gallionellaceae strain R-1. Twisted stalks from glass slides incubated in water and sediment were composed of the Fe(III) oxyhydroxide ferrihydrite, as well as polysaccharides. SEM and scanning TEM-energy-dispersive X-ray spectroscopy revealed that stalk material contained Cu and Sn, demonstrating the association of heavy metals with biogenic iron oxides and the potential for metal retention by these stalks. Sequential extraction of sediments suggested that Cu (52–61% of total sediment Cu) and other heavy metals were primarily bound to the iron oxide fractions. These results show the importance of �

Synthesis, structure, and catalytic activity of novel trinuclear rare-earth metal amido complexes incorporating μ-η5:η1 bonding indolyl and μ3-oxo groups.

PubMed

Yang, Song; Zhu, Xiancui; Zhou, Shuangliu; Wang, Shaowu; Feng, Zhijun; Wei, Yun; Miao, Hui; Guo, Liping; Wang, Fenhua; Zhang, Guangchao; Gu, Xiaoxia; Mu, Xiaolong

2014-02-14

The reactions of different pyrrolyl-functionalized indoles with rare-earth metal(III) amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Er, Dy, Eu, Y) produced different kinds of rare-earth metal amido complexes. Reactions of N-((1H-pyrrol-2-yl)methylene)-2-(1H-indol-3-yl)ethanamine with rare-earth metal amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Er, Dy, Eu, Y) in toluene or THF at temperatures of 75-80 °C afforded the novel trinuclear rare-earth metal amido complexes incorporating the indolyl ligand in μ-η(5):η(1) bonding modes and a μ3-O group, which is believed to originate from cleavage of the THF ring based on experimental results. Reactions of 2-(1H-indol-3-yl)-N-((1-methyl-1H-pyrrol-2-yl)methylene)ethanamine with rare-earth metal(III) amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Dy) produced mononuclear ytterbium and dysprosium amides having the indolyl ligand in an η(1) bonding fashion. The results indicate that substituents not only have an influence on reactivity, but also have an influence on the bonding of the indolyl ligands with metals. The catalytic activities of the novel lanthanide amido complexes for the hydrophosphonylation of both aromatic and aliphatic aldehydes and ketones were explored. The results indicate that these complexes display a high catalytic activity for the C-P bond formation under mild conditions when using low catalyst loadings (0.1 mol% for aldehydes and ketones). Thus, it provides a potential way to prepare α-hydroxy phosphonates.

Water inventories on Earth and Mars: Clues to atmosphere formation

NASA Technical Reports Server (NTRS)

Carr, M. H.

1992-01-01

Water is distributed differently on Earth and on Mars and the differences may have implications for the accretion of the two planets and the formation of their atmospheres. The Earth's mantle appears to contain at least several times the water content of the Martian mantle even accounting for differences in plate tectonics. One explanation is that the Earth's surface melted during accretion, as a result of development of a steam atmosphere, thereby allowing impact-devolitalized water at the surface to dissolve into the Earth's interior. In contrast, because of Mars' smaller size and greater distance from the Sun, the Martian surface may not have melted, so that the devolatilized water could not dissolve into the surface. A second possibility is suggested by the siderophile elements in the Earth's mantle, which indicates the Earth acquired a volatile-rich veneer after the core formed. Mars may have acquired a late volatile-rich veneer, but it did not get folded into the interior as with the Earth, but instead remained as a water rich veneer. This perception of Mars with a wet surface but dry interior is consistent with our knowledge of Mars' geologic history.

Carbon-rich supramolecular metallacycles and metallacages

PubMed Central

Northrop, Brian H.; Chercka, Dennis; Stang, Peter J.

2008-01-01

Coordination-driven self-assembly via the directional-bonding approach utilizes rigid transition metal acceptors and electron-rich donors to allow for complex, nanoscale 2D polygons and 3D polyhedra to be prepared under mild conditions and in high yields. To ensure proper rigidity and directionality, many acceptor and donor precursors contain largely carbon-rich aromatic and/or acetylenic moieties. This article introduces self-assembly as an alternative means of synthesizing carbon-rich materials and discusses the development, design, synthesis, and applications of carbon-rich supramolecular metallacycles and metallacages as well as the self-assembly of new diastereomeric carbon-rich supramolecular triangles. PMID:20011029

Regio- and Stereochemical Control in Ocimene Polymerization by Half-Sandwich Rare-Earth Metal Dialkyl Complexes.

PubMed

Peng, Deqian; Du, Gaixia; Zhang, Pengfei; Yao, Bo; Li, Xiaofang; Zhang, Shaowen

2016-06-01

The polymerization of ocimene has been first achieved by half-sandwich rare-earth metal dialkyl complexes in combination with activator and Al(i) Bu3 . The regio- and stereoselectivity in the ocimene polymerization can be controlled by tuning the cyclopentadienyl ligand and the central metal of the complex. The chiral cyclopentadienyl-ligated Sc complex 1 prepares syndiotactic cis-1,4-polyocimene (cis-1,4-selectivity up to 100%, rrrr = 100%), while the corresponding Lu, Y, and Dy complexes 2-4 and the achiral pentamethylcyclopentadienyl Sc, Lu, and Y complexes 5-7 afford isotactic trans-1,2-polyocimenes (trans-1,2-selectivity up to 100%, mm = 100%). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polar Misunderstandings: Earth's Dynamic Dynamo

ERIC Educational Resources Information Center

DiSpezio, Michael A.

2011-01-01

This article discusses the movement of Earth's north and south poles. The Earth's poles may be a bit more complex and dynamic than what many students and teachers believe. With better understanding, offer them up as a rich landscape for higher-level critical analysis and subject integration. Possible curriculum tie-ins include magnets, Earth…

Metal/Silicate Partitioning, Melt Speciation, Accretion, and Core Formation in the Earth

NASA Astrophysics Data System (ADS)

Drake, M. J.; Hillgren, V. J.; Dearo, J. A.; Capobianco, C. J.

1993-07-01

Core formation in terrestrial planets was concomitant with accretion. Siderophile and chalcophile element signatures in the mantles of planets are the result of these processes. For Earth, abundances of most siderophile and chalcophile elements are elevated relative to predictions from simple metal/silicate equilibria at low pressures [1]. This observation has led to three hypotheses for how these abundances were established: heterogeneous accretion [2], inefficient core formation [3], and metal/silicate equilibria at magma ocean pressures and temperatures [4]. Knowledge of speciation of siderophile elements in silicate melts in equilibrium with metal may help distinguish between these hypotheses. But there is some uncertainty regarding speciation. For example, Ni and Co have been reported to be present as 1+ or zero valence species in silicate melts at redox states appropriate to planetary accretion, rather than the expected 2+ state [5-7]. Independent metal/silicate partitioning experiments by three members of this group using two different experimental designs on both synthetic and natural compositions do not show evidence for Ni and Co in valence states other than 2+ over a wide range of redox states. For example, solid metal/silicate melt partition coefficients for Ni at 1260 degrees C obtained by VJH from experiments investigating the partitioning of Ni, Co, Mo, W, and P are indistinguishable from those obtained by JAD in similar experiments investigating the partitioning of Ni, Ge, and Sn. Both datasets define a line with the equation: log D(Ni) = - 0.54log fO2 - 3.14 with r^2 > 0.995. (Note that fO2 was calculated in both studies from thermodynamic data and phase compositions. A small, systematic offset from the true fO2 as measured by a solid electrolyte cell affects both equations similarly, but does not diminish their close agreement.) The valence of Ni in the silicate melt is obtained by multiplying the slope of the line by -4, indicating divalent Ni in

Hybridization wave as the cause of the metal-insulator transition in rare earth nickelates

NASA Astrophysics Data System (ADS)

Park, Hyowon; Marianetti, Chris A.; Millis, Andrew J.

2012-02-01

The metal-insulator transition driven by varying rare earth (Re) ion in ReNiO3 has been a longstanding challenge to materials theory. Experimental evidence suggesting charge order is seemingly incompatible with the strong Mott-Hubbard correlations characteristic of transition metals. We present density functional, Hartree-Fock and Dynamical Mean field calculations showing that the origin of the insulating phase is a hybridization wave, in which a two sublattice ordering of the oxygen breathing mode produces two Ni sites with almost identical Ni d-charge densities but very different magnetic moments and other properties. The high temperature crystal structure associated with smaller Re ions such as Lu is shown to be more susceptible to the distortion than the high temperature structure associated with larger Re ions such as La.

Wide-band-gap, alkaline-earth-oxide semiconductor and devices utilizing same

DOEpatents

Abraham, Marvin M.; Chen, Yok; Kernohan, Robert H.

1981-01-01

This invention relates to novel and comparatively inexpensive semiconductor devices utilizing semiconducting alkaline-earth-oxide crystals doped with alkali metal. The semiconducting crystals are produced by a simple and relatively inexpensive process. As a specific example, a high-purity lithium-doped MgO crystal is grown by conventional techniques. The crystal then is heated in an oxygen-containing atmosphere to form many [Li].degree. defects therein, and the resulting defect-rich hot crystal is promptly quenched to render the defects stable at room temperature and temperatures well above the same. Quenching can be effected conveniently by contacting the hot crystal with room-temperature air.

Earth's earliest atmospheres.

PubMed

Zahnle, Kevin; Schaefer, Laura; Fegley, Bruce

2010-10-01

Earth is the one known example of an inhabited planet and to current knowledge the likeliest site of the one known origin of life. Here we discuss the origin of Earth's atmosphere and ocean and some of the environmental conditions of the early Earth as they may relate to the origin of life. A key punctuating event in the narrative is the Moon-forming impact, partly because it made Earth for a short time absolutely uninhabitable, and partly because it sets the boundary conditions for Earth's subsequent evolution. If life began on Earth, as opposed to having migrated here, it would have done so after the Moon-forming impact. What took place before the Moon formed determined the bulk properties of the Earth and probably determined the overall compositions and sizes of its atmospheres and oceans. What took place afterward animated these materials. One interesting consequence of the Moon-forming impact is that the mantle is devolatized, so that the volatiles subsequently fell out in a kind of condensation sequence. This ensures that the volatiles were concentrated toward the surface so that, for example, the oceans were likely salty from the start. We also point out that an atmosphere generated by impact degassing would tend to have a composition reflective of the impacting bodies (rather than the mantle), and these are almost without exception strongly reducing and volatile-rich. A consequence is that, although CO- or methane-rich atmospheres are not necessarily stable as steady states, they are quite likely to have existed as long-lived transients, many times. With CO comes abundant chemical energy in a metastable package, and with methane comes hydrogen cyanide and ammonia as important albeit less abundant gases.

Geochemistry of metal-rich brines from central Mississippi Salt Dome basin, U.S.A.

USGS Publications Warehouse

Kharaka, Y.K.; Maest, A.S.; Carothers, W.W.; Law, L.M.; Lamothe, P.J.; Fries, T.L.

1987-01-01

Oil-field brines are the most favored ore-forming solutions for the sediment-hosted Mississippi Valley-type ore deposits. Detailed inorganic and organic chemical and isotope analyses of water and gas samples from six oil fields in central Mississippi, one of the very few areas with high metal brines, were conducted to study the inorganic and organic complexes responsible for the high concentrations of these metals. The samples were obtained from production zones consisting of sandstone and limestone that range in depth from 1900 to 4000 m (70-120??C) and in age from Late Cretaceous to Late Jurassic. Results show that the waters are dominantly bittern brines related to the Louann Salt. The brines have extremely high salinities that range from 160,000 to 320,000 mg/l total dissolved solids and are NaCaCl-type waters with very high concentrations of Ca (up to 48,000 mg/l) and other alkaline-earth metals, but with low concentrations of aliphatic acid anions. The concentrations of metals in many water samples are very high, reaching values of 70 mg/l for Pb, 245 mg/l for Zn, 465 mg/l for Fe and 210 mg/l for Mn. The samples with high metal contents have extremely low concentrations (<0.02 mg/l) of H2S. Samples obtained from the Smackover Formation (limestone) have low metal contents that are more typical of oil-field waters, but have very high concentrations (up to 85 mg/l) of H2S. Computations with the geochemical code SOLMINEQ.87 give the following results: (1) both Pb and Zn are present predominantly as aqueous chloride complexes (mainly as PbCl42- and ZnCl42-, respectively); (2) the concentrations of metals complexed with short-chained aliphatic acid anions and reduced S species are minor; (3) organic acid anions are important in controlling the concentrations of metals because they affect the pH and buffer capacity of the waters at subsurface conditions; and (4) galena and sphalerite solubilities control the concentrations of Pb and Zn in these waters. ?? 1988.

High contents of rare earth elements (REEs) in stream waters of a Cu-Pb-Zn mining area.

PubMed

Protano, G; Riccobono, F

2002-01-01

Stream waters draining an old mining area present very high rare earth element (REE) contents, reaching 928 microg/l as the maximum total value (sigmaREE). The middle rare earth elements (MREEs) are usually enriched with respect to both the light (LREEs) and heavy (HREEs) elements of this group, producing a characteristic "roof-shaped" pattern of the shale Post-Archean Australian Shales-normalized concentrations. At the Fenice Capanne Mine (FCM), the most important base metal mine of the study area, the REE source coincides with the mine tailings, mostly the oldest ones composed of iron-rich materials. The geochemical history of the REEs released into Noni stream from wastes in the FCM area is strictly determined by the pH, which controls the REE speciation and in-stream processes. The formation of Al-rich and mainly Fe-rich flocs effectively scavenges the REEs, which are readily and drastically removed from the solution when the pH approaches neutrality. Leaching experiments performed on flocs and waste materials demonstrate that Fe-oxides/oxyhydroxides play a key role in the release of lanthanide elements into stream waters. The origin of the "roof-shaped" REE distribution pattern as well as the peculiar geochemical behavior of some lanthanide elements in the aqueous system are discussed.

Evaluation of shielding parameters for heavy metal fluoride based tellurite-rich glasses for gamma ray shielding applications

NASA Astrophysics Data System (ADS)

Sayyed, M. I.; Lakshminarayana, G.; Kityk, I. V.; Mahdi, M. A.

2017-10-01

In this work, we have evaluated the γ-ray shielding parameters such as mass attenuation coefficient (μ/ρ), effective atomic number (Zeff), half value layer (HVL), mean free path (MFP) and exposure buildup factors (EBF) for heavy metal fluoride (PbF2) based tellurite-rich glasses. In addition, neutron total macroscopic cross sections (∑R) for these glasses were also calculated. The maximum value for μ/ρ, Zeff and ∑R was found for heavy metal (Bi2O3) oxide introduced glass. The results of the selected glasses have been compared, in terms of MFP with different glass systems. The shielding effectiveness of the selected glasses is found comparable or better than of common ones, which indicates that these glasses with suitable oxides could be developed for gamma ray shielding applications.

KEPLER EXOPLANET CANDIDATE HOST STARS ARE PREFERENTIALLY METAL RICH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlaufman, Kevin C.; Laughlin, Gregory, E-mail: kcs@ucolick.org, E-mail: laughlin@ucolick.org

We find that Kepler exoplanet candidate (EC) host stars are preferentially metal rich, including the low-mass stellar hosts of small-radius ECs. The last observation confirms a tentative hint that there is a correlation between the metallicity of low-mass stars and the presence of low-mass and small-radius exoplanets. In particular, we compare the J-H-g-r color-color distribution of Kepler EC host stars with a control sample of dwarf stars selected from the {approx}150, 000 stars observed during Q1 and Q2 of the Kepler mission but with no detected planets. We find that at J - H = 0.30 characteristic of solar-type stars,more » the average g-r color of stars that host giant ECs is 4{sigma} redder than the average color of the stars in the control sample. At the same J - H color, the average g-r color of solar-type stars that host small-radius ECs is indistinguishable from the average color of the stars in the control sample. In addition, we find that at J - H = 0.62 indicative of late K dwarfs, the average g-r color of stars that host small-radius ECs is 4{sigma} redder than the average color of the stars in the control sample. These offsets are unlikely to be caused by differential reddening, age differences between the two populations, or the presence of giant stars in the control sample. Stellar models suggest that the first color offset is due to a 0.2 dex enhancement in [Fe/H] of the giant EC host population at M{sub *} {approx} 1 M{sub sun}, while Sloan photometry of M 67 and NGC 6791 suggests that the second color offset is due to a similar [Fe/H] enhancement of the small-radius EC host population at M{sub *} {approx} 0.7 M{sub sun}. These correlations are a natural consequence of the core-accretion model of planet formation.« less

K2-155: A Bright Metal-poor M Dwarf with Three Transiting Super-Earths

NASA Astrophysics Data System (ADS)

Hirano, Teruyuki; Dai, Fei; Livingston, John H.; Fujii, Yuka; Cochran, William D.; Endl, Michael; Gandolfi, Davide; Redfield, Seth; Winn, Joshua N.; Guenther, Eike W.; Prieto-Arranz, Jorge; Albrecht, Simon; Barragan, Oscar; Cabrera, Juan; Cauley, P. Wilson; Csizmadia, Szilard; Deeg, Hans; Eigmüller, Philipp; Erikson, Anders; Fridlund, Malcolm; Fukui, Akihiko; Grziwa, Sascha; Hatzes, Artie P.; Korth, Judith; Narita, Norio; Nespral, David; Niraula, Prajwal; Nowak, Grzegorz; Pätzold, Martin; Palle, Enric; Persson, Carina M.; Rauer, Heike; Ribas, Ignasi; Smith, Alexis M. S.; Van Eylen, Vincent

2018-03-01

We report on the discovery of three transiting super-Earths around K2-155 (EPIC 210897587), a relatively bright early M dwarf (V = 12.81 mag) observed during Campaign 13 of the NASA K2 mission. To characterize the system and validate the planet candidates, we conducted speckle imaging and high-dispersion optical spectroscopy, including radial velocity measurements. Based on the K2 light curve and the spectroscopic characterization of the host star, the planet sizes and orbital periods are {1.55}-0.17+0.20 {R}\\oplus and 6.34365 ± 0.00028 days for the inner planet; {1.95}-0.22+0.27 {R}\\oplus and 13.85402 ± 0.00088 days for the middle planet; and {1.64}-0.17+0.18 {R}\\oplus and 40.6835 ± 0.0031 days for the outer planet. The outer planet (K2-155d) is near the habitable zone, with an insolation 1.67 ± 0.38 times that of the Earth. The planet’s radius falls within the range between that of smaller rocky planets and larger gas-rich planets. To assess the habitability of this planet, we present a series of three-dimensional global climate simulations, assuming that K2-155d is tidally locked and has an Earth-like composition and atmosphere. We find that the planet can maintain a moderate surface temperature if the insolation proves to be smaller than ∼1.5 times that of the Earth. Doppler mass measurements, transit spectroscopy, and other follow-up observations should be rewarding, as K2-155 is one of the optically brightest M dwarfs known to harbor transiting planets.

Anomalous positive flatband voltage shifts in metal gate stacks containing rare-earth oxide capping layers

NASA Astrophysics Data System (ADS)

Caraveo-Frescas, J. A.; Hedhili, M. N.; Wang, H.; Schwingenschlögl, U.; Alshareef, H. N.

2012-03-01

It is shown that the well-known negative flatband voltage (VFB) shift, induced by rare-earth oxide capping in metal gate stacks, can be completely reversed in the absence of the silicon overlayer. Using TaN metal gates and Gd2O3-doped dielectric, we measure a ˜350 mV negative shift with the Si overlayer present and a ˜110 mV positive shift with the Si overlayer removed. This effect is correlated to a positive change in the average electrostatic potential at the TaN/dielectric interface which originates from an interfacial dipole. The dipole is created by the replacement of interfacial oxygen atoms in the HfO2 lattice with nitrogen atoms from TaN.

Origin of low sodium capacity in graphite and generally weak substrate binding of Na and Mg among alkali and alkaline earth metals.

PubMed

Liu, Yuanyue; Merinov, Boris V; Goddard, William A

2016-04-05

It is well known that graphite has a low capacity for Na but a high capacity for other alkali metals. The growing interest in alternative cation batteries beyond Li makes it particularly important to elucidate the origin of this behavior, which is not well understood. In examining this question, we find a quite general phenomenon: among the alkali and alkaline earth metals, Na and Mg generally have the weakest chemical binding to a given substrate, compared with the other elements in the same column of the periodic table. We demonstrate this with quantum mechanics calculations for a wide range of substrate materials (not limited to C) covering a variety of structures and chemical compositions. The phenomenon arises from the competition between trends in the ionization energy and the ion-substrate coupling, down the columns of the periodic table. Consequently, the cathodic voltage for Na and Mg is expected to be lower than those for other metals in the same column. This generality provides a basis for analyzing the binding of alkali and alkaline earth metal atoms over a broad range of systems.

Chondritic Mn/Na ratio and limited post-nebular volatile loss of the Earth

NASA Astrophysics Data System (ADS)

Siebert, Julien; Sossi, Paolo A.; Blanchard, Ingrid; Mahan, Brandon; Badro, James; Moynier, Frédéric

2018-03-01

The depletion pattern of volatile elements on Earth and other differentiated terrestrial bodies provides a unique insight as to the nature and origin of planetary building blocks. The processes responsible for the depletion of volatile elements range from the early incomplete condensation in the solar nebula to the late de-volatilization induced by heating and impacting during planetary accretion after the dispersion of the H2-rich nebular gas. Furthermore, as many volatile elements are also siderophile (metal-loving), it is often difficult to deconvolve the effect of volatility from core formation. With the notable exception of the Earth, all the differentiated terrestrial bodies for which we have samples have non-chondritic Mn/Na ratios, taken as a signature of post-nebular volatilization. The bulk silicate Earth (BSE) is unique in that its Mn/Na ratio is chondritic, which points to a nebular origin for the depletion; unless the Mn/Na in the BSE is not that of the bulk Earth (BE), and has been affected by core formation through the partitioning of Mn in Earth's core. Here we quantify the metal-silicate partitioning behavior of Mn at deep magma ocean pressure and temperature conditions directly applicable to core formation. The experiments show that Mn becomes more siderophile with increasing pressure and temperature. Modeling the partitioning of Mn during core formation by combining our results with previous data at lower P-T conditions, we show that the core likely contains a significant fraction (20 to 35%) of Earth's Mn budget. However, we show that the derived Mn/Na value of the bulk Earth still lies on the volatile-depleted end of a trend defined by chondritic meteorites in a Mn/Na vs Mn/Mg plot, which tend to higher Mn/Na with increasing volatile depletion. This suggests that the material that formed the Earth recorded similar chemical fractionation processes for moderately volatile elements as chondrites in the solar nebula, and experienced limited post

Implications for Core Formation of the Earth from High Pressure-Temperature Au Partitioning Experiments

NASA Technical Reports Server (NTRS)

Danielson, L. R.; Sharp, T. G.; Hervig, R. L.

2005-01-01

Siderophile elements in the Earth.s mantle are depleted relative to chondrites. This is most pronounced for the highly siderophile elements (HSEs), which are approximately 400x lower than chondrites. Also remarkable is the relative chondritic abundances of the HSEs. This signature has been interpreted as representing their sequestration into an iron-rich core during the separation of metal from silicate liquids early in the Earth's history, followed by a late addition of chondritic material. Alternative efforts to explain this trace element signature have centered on element partitioning experiments at varying pressures, temperatures, and compositions (P-T-X). However, first results from experiments conducted at 1 bar did not match the observed mantle abundances, which motivated the model described above, a "late veneer" of chondritic material deposited on the earth and mixed into the upper mantle. Alternatively, the mantle trace element signature could be the result of equilibrium partitioning between metal and silicate in the deep mantle, under P-T-X conditions which are not yet completely identified. An earlier model determined that equilibrium between metal and silicate liquids could occur at a depth of approximately 700 km, 27(plus or minus 6) GPa and approximately 2000 (plus or minus 200) C, based on an extrapolation of partitioning data for a variety of moderately siderophile elements obtained at lower pressures and temperatures. Based on Ni-Co partitioning, the magma ocean may have been as deep as 1450 km. At present, only a small range of possible P-T-X trace element partitioning conditions has been explored, necessitating large extrapolations from experimental to mantle conditions for tests of equilibrium models. Our primary objective was to reduce or remove the additional uncertainty introduced by extrapolation by testing the equilibrium core formation hypothesis at P-T-X conditions appropriate to the mantle.

On the Chemical Abundances of Miras in Clusters: V1 in the Metal-rich Globular NGC 5927

NASA Astrophysics Data System (ADS)

D’Orazi, V.; Magurno, D.; Bono, G.; Matsunaga, N.; Braga, V. F.; Elgueta, S. S.; Fukue, K.; Hamano, S.; Inno, L.; Kobayashi, N.; Kondo, S.; Monelli, M.; Nonino, M.; Przybilla, N.; Sameshima, H.; Saviane, I.; Taniguchi, D.; Thevenin, F.; Urbaneja-Perez, M.; Watase, A.; Arai, A.; Bergemann, M.; Buonanno, R.; Dall’Ora, M.; Da Silva, R.; Fabrizio, M.; Ferraro, I.; Fiorentino, G.; Francois, P.; Gilmozzi, R.; Iannicola, G.; Ikeda, Y.; Jian, M.; Kawakita, H.; Kudritzki, R. P.; Lemasle, B.; Marengo, M.; Marinoni, S.; Martínez-Vázquez, C. E.; Minniti, D.; Neeley, J.; Otsubo, S.; Prieto, J. L.; Proxauf, B.; Romaniello, M.; Sanna, N.; Sneden, C.; Takenaka, K.; Tsujimoto, T.; Valenti, E.; Yasui, C.; Yoshikawa, T.; Zoccali, M.

2018-03-01

We present the first spectroscopic abundance determination of iron, α-elements (Si, Ca, and Ti), and sodium for the Mira variable V1 in the metal-rich globular cluster NGC 5927. We use high-resolution (R ∼ 28,000), high signal-to-noise ratio (∼200) spectra collected with WINERED, a near-infrared (NIR) spectrograph covering simultaneously the wavelength range 0.91–1.35 μm. The effective temperature and the surface gravity at the pulsation phase of the spectroscopic observation were estimated using both optical (V) and NIR time-series photometric data. We found that the Mira is metal-rich ([Fe/H] = ‑0.55 ± 0.15) and moderately α-enhanced ([α/Fe] = 0.15 ± 0.01, σ = 0.2). These values agree quite well with the mean cluster abundances based on high-resolution optical spectra of several cluster red giants available in the literature ([Fe/H] = ‑ 0.47 ± 0.06, [α/Fe] = + 0.24 ± 0.05). We also found a Na abundance of +0.35 ± 0.20 that is higher than the mean cluster abundance based on optical spectra (+0.18 ± 0.13). However, the lack of similar spectra for cluster red giants and that of corrections for departures from local thermodynamical equilibrium prevents us from establishing whether the difference is intrinsic or connected with multiple populations. These findings indicate a strong similarity between optical and NIR metallicity scales in spite of the difference in the experimental equipment, data analysis, and in the adopted spectroscopic diagnostics. Based on spectra collected with the WINERED spectrograph available as a visitor instrument at the ESO New Technology Telescope (NTT), La Silla, Chile (ESO Proposal: 098.D-0878(A), PI: G. Bono).

Rare earth elements and critical metal content of extracted landfilled material and potential recovery opportunities.

PubMed

Gutiérrez-Gutiérrez, Silvia C; Coulon, Frédéric; Jiang, Ying; Wagland, Stuart

2015-08-01

Rare earth elements (REEs), Platinum group metals (PGMs) and other critical metals currently attract significant interest due to the high risks of supply shortage and substantial impact on the economy. Their uses in many applications have made them present in municipal solid waste (MSW) and in commercial and industrial waste (C&I), since several industrial processes produce by-products with high content of these metals. With over 4000 landfills in the UK alone, the aim of this study was to assess the existence of these critical metals within landfills. Samples collected from four closed landfills in UK were subjected to a two-step acid digestion to extract 27 metals of interest. Concentrations across the four landfill sites were 58±6mgkg(-1) for REEs comprising 44±8mgkg(-1) for light REEs, 11±2mgkg(-1) for heavy REEs and 3±1mgkg(-1) for Scandium (Sc) and 3±1.0mgkg(-1) of PGMs. Compared to the typical concentration in ores, these concentrations are too low to achieve a commercially viable extraction. However, content of other highly valuable metals (Al and Cu) was found in concentrations equating to a combined value across the four landfills of around $400 million, which increases the economic viability of landfill mining. Presence of critical metals will mainly depend on the type of waste that was buried but the recovery of these metals through landfill mining is possible and is economically feasible only if additional materials (plastics, paper, metallic items and other) are also recovered for reprocessing. Copyright © 2015 Elsevier Ltd. All rights reserved.

Metal transports and enrichments in iron depositions hosted in basaltic rocks. II: Metal rich fluids and Fe origin

NASA Astrophysics Data System (ADS)

Zhang, Ronghua; Zhang, Xuetong; Hu, Shumin

2015-12-01

This study focuses on revealing the mechanism of metal transport, enrichment and Fe origin of iron deposition during water basalt interactions occurred in basaltic rocks. Observations of the iron deposits (anhydrite-magnetite-pyroxene type deposits) hosted in K-rich basaltic rocks in the Mesozoic volcanic area of the Middle-Lower Yangtze River valley, China, indicate that the mechanism of metal transport and enrichment for those deposits are significant objective to scientists, and the Fe origin problem is not well resolved. Here the metal transport, enrichment and iron origin have been investigated in high temperature experiments of water basaltic interactions. These deposits were accompanying a wide zone with metal alteration. The effects of hydrothermal alteration on major rock-forming element concentrations in basaltic rock were investigated by systematically comparing the chemical compositions of altered rocks with those of fresh rocks. In the deposits, these metals are distributed throughout altered rocks that exhibit vertical zoning from the deeper to the shallow. Then, combined with the investigations of the metal-alterations, we performed kinetic experiments of water-basaltic rock interactions using flow-through reactors in open systems at temperatures from 20 °C to 550 °C, 23-34 MPa. Release rates for the rock-forming elements from the rocks have been measured. Experiments provide the release rates for various elements at a large temperature range, and indicate that the dissolution rates (release rates) for various elements vary with temperature. Si, Al, and K have high release rates at temperatures from 300 °C to 500 °C; the maximum release rates (RMX) for Si are reached at temperatures from 300 °C to 400 °C. The RMXs for Ca, Mg, and Fe are at low temperatures from 20 °C to 300 °C. Results demonstrate that Fe is not released from 400 °C to 550 °C, and indicate that when deep circling fluids passed through basaltic rocks, Fe was not mobile, and

Versatile reactivities of rare-earth metal dialkyl complexes supported by a neutral pyrrolyl-functionalized β-diketiminato ligand.

PubMed

Zhu, Xiancui; Li, Yang; Guo, Dianjun; Wang, Shaowu; Wei, Yun; Zhou, Shuangliu

2018-03-12

Herein, rare-earth metal dialkyl complexes supported by a neutral pyrrolyl-functionalized β-diketiminato ligand with the formula LRE(CH 2 SiMe 3 ) 2 (thf) (RE = Y (1a), Dy (1b), Er (1c), Yb (1d); L = MeC(NDipp)CHC(Me)NCH 2 CH 2 NC 4 H 2 -2,5-Me 2 , Dipp = 2,6- i Pr 2 C 6 H 3 ) were synthesized via the reactions of the β-diketimine HL with the rare-earth metal trialkyl complexes RE(CH 2 SiMe 3 ) 3 (thf) 2 in high yields. The reactivities of 1 with pyridine derivatives, unsaturated substrates, and elemental sulfur were investigated, and some interesting chemical transformations were observed. Ligand exchange and activation of sp 2 and sp 3 C-H bonds occurred during the reactions with pyridine derivatives to afford different types of mononuclear rare-earth metal pyridyl complexes, namely, LEr(CH 2 SiMe 3 ) 2 (η 1 -NC 5 H 4 ) (2c), LRE(η 3 -CH 2 -2-NC 5 H 2 -4,6-Me 2 ) 2 (RE = Y (3a), Er (3c)), and LRE(CH 2 SiMe 3 )(η 2 -(C,N)-2-(2-C 6 H 4 NC 5 H 4 )) (RE = Er (4c), Yb = (4d)). Similarly, activation of the sp C-H bond occurred during the reaction of phenylacetylene with 1c to produce the dinuclear erbium alkynyl complex [LEr(CH 2 SiMe 3 )(μ-C[triple bond, length as m-dash]CPh)] 2 (5c). The mixed amidinate-β-diketiminato ytterbium complex LYb[(Dipp)NC(CH 2 SiMe 3 )N(Dipp)](CH 2 SiMe 3 ) (6d) was obtained by the insertion of bis(2,6-diisopropylphenyl)carbodiimide into a Yb-alkyl bond, as well as via the direct alkane elimination of a CH 2 SiMe 3 moiety with bis(2,6-diisopropylphenyl)formamidine to afford the erbium complex LEr(DippNCHNDipp)(CH 2 SiMe 3 ) (7c). A rare sp 2 C-H bond oxidation of the β-diketiminato backbone with elemental sulfur insertion was detected to provide the unprecedented dinuclear rare-earth metal thiolate complexes (LRE) 2 (μ-SCH 2 SiMe 3 ) 2 (μ-SCC(Me)(NDipp)C(Me)NCH 2 CH 2 NC 4 H 2 Me 2 -2,5) (RE = Y (8a), Er (8c)) in the reactions of S 8 with 1a and 1c, respectively. The molecular structures of the complexes 1-8 were determined by

Large-Grain Tin-Rich Perovskite Films for Efficient Solar Cells via Metal Alloying Technique.

PubMed

Tavakoli, Mohammad Mahdi; Zakeeruddin, Shaik Mohammed; Grätzel, Michael; Fan, Zhiyong

2018-03-01

Fast research progress on lead halide perovskite solar cells has been achieved in the past a few years. However, the presence of lead (Pb) in perovskite composition as a toxic element still remains a major issue for large-scale deployment. In this work, a novel and facile technique is presented to fabricate tin (Sn)-rich perovskite film using metal precursors and an alloying technique. Herein, the perovskite films are formed as a result of the reaction between Sn/Pb binary alloy metal precursors and methylammonium iodide (MAI) vapor in a chemical vapor deposition process carried out at 185 °C. It is found that in this approach the Pb/Sn precursors are first converted to (Pb/Sn)I 2 and further reaction with MAI vapor leads to the formation of perovskite films. By using Pb-Sn eutectic alloy, perovskite films with large grain sizes up to 5 µm can be grown directly from liquid phase metal. Consequently, using an alloying technique and this unique growth mechanism, a less-toxic and efficient perovskite solar cell with a power conversion efficiency (PCE) of 14.04% is demonstrated, while pure Sn and Pb perovskite solar cells prepared in this manner yield PCEs of 4.62% and 14.21%, respectively. It is found that this alloying technique can open up a new direction to further explore different alloy systems (binary or ternary alloys) with even lower melting point. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A molecular cross-linking approach for hybrid metal oxides.

PubMed

Jung, Dahee; Saleh, Liban M A; Berkson, Zachariah J; El-Kady, Maher F; Hwang, Jee Youn; Mohamed, Nahla; Wixtrom, Alex I; Titarenko, Ekaterina; Shao, Yanwu; McCarthy, Kassandra; Guo, Jian; Martini, Ignacio B; Kraemer, Stephan; Wegener, Evan C; Saint-Cricq, Philippe; Ruehle, Bastian; Langeslay, Ryan R; Delferro, Massimiliano; Brosmer, Jonathan L; Hendon, Christopher H; Gallagher-Jones, Marcus; Rodriguez, Jose; Chapman, Karena W; Miller, Jeffrey T; Duan, Xiangfeng; Kaner, Richard B; Zink, Jeffrey I; Chmelka, Bradley F; Spokoyny, Alexander M

2018-04-01

There is significant interest in the development of methods to create hybrid materials that transform capabilities, in particular for Earth-abundant metal oxides, such as TiO 2 , to give improved or new properties relevant to a broad spectrum of applications. Here we introduce an approach we refer to as 'molecular cross-linking', whereby a hybrid molecular boron oxide material is formed from polyhedral boron-cluster precursors of the type [B 12 (OH) 12 ] 2- . This new approach is enabled by the inherent robustness of the boron-cluster molecular building block, which is compatible with the harsh thermal and oxidizing conditions that are necessary for the synthesis of many metal oxides. In this work, using a battery of experimental techniques and materials simulation, we show how this material can be interfaced successfully with TiO 2 and other metal oxides to give boron-rich hybrid materials with intriguing photophysical and electrochemical properties.

A molecular cross-linking approach for hybrid metal oxides

NASA Astrophysics Data System (ADS)

Jung, Dahee; Saleh, Liban M. A.; Berkson, Zachariah J.; El-Kady, Maher F.; Hwang, Jee Youn; Mohamed, Nahla; Wixtrom, Alex I.; Titarenko, Ekaterina; Shao, Yanwu; McCarthy, Kassandra; Guo, Jian; Martini, Ignacio B.; Kraemer, Stephan; Wegener, Evan C.; Saint-Cricq, Philippe; Ruehle, Bastian; Langeslay, Ryan R.; Delferro, Massimiliano; Brosmer, Jonathan L.; Hendon, Christopher H.; Gallagher-Jones, Marcus; Rodriguez, Jose; Chapman, Karena W.; Miller, Jeffrey T.; Duan, Xiangfeng; Kaner, Richard B.; Zink, Jeffrey I.; Chmelka, Bradley F.; Spokoyny, Alexander M.

2018-03-01

There is significant interest in the development of methods to create hybrid materials that transform capabilities, in particular for Earth-abundant metal oxides, such as TiO2, to give improved or new properties relevant to a broad spectrum of applications. Here we introduce an approach we refer to as `molecular cross-linking', whereby a hybrid molecular boron oxide material is formed from polyhedral boron-cluster precursors of the type [B12(OH)12]2-. This new approach is enabled by the inherent robustness of the boron-cluster molecular building block, which is compatible with the harsh thermal and oxidizing conditions that are necessary for the synthesis of many metal oxides. In this work, using a battery of experimental techniques and materials simulation, we show how this material can be interfaced successfully with TiO2 and other metal oxides to give boron-rich hybrid materials with intriguing photophysical and electrochemical properties.

Monitoring of photoluminescence decay by alkali and alkaline earth metal cations using a photoluminescent bolaamphiphile self-assembly as an optical probe.

PubMed

Kim, Sunhyung; Kwak, Jinyoung; Lee, Sang-Yup

2014-05-01

Photoluminescence (PL) decay induced by the displacement of an ionic fluorescence component, Tb(3+), with alkali and alkaline earth metal cations was investigated using photoluminescent spherical self-assemblies as optical probes. The photoluminescent spherical self-assembly was prepared by the self-organization of a tyrosine-containing bolaamphiphile molecule with a photosensitizer and Tb(3+) ion. The lanthanide ion, Tb(3+), electrically bound to the carboxyl group of the bolaamphiphile molecule, was displaced by alkali and alkaline earth metal cations that had stronger electrophilicity. The PL of the self-assembly decayed remarkably due to the substitution of lanthanide ions with alkali and alkaline earth metal cations. The PL decay showed a positive correlation with cation concentration and was sensitive to the cation valency. Generally, the PL decay was enhanced by the electrophilicity of the cations. However, Ca(2+) showed greater PL decay than Mg(2+) because Ca(2+) could create various complexes with the carboxyl groups of the bolaamphiphile molecule. Microscopic and spectroscopic investigations were conducted to study the photon energy transfer and displacement of Tb(3+) by the cation exchange. This study demonstrated that the PL decay by the displacement of the ionic fluorescent compound was applied to the detection of various cations in aqueous media and is applicable to the development of future optical sensors. Copyright © 2014 Elsevier B.V. All rights reserved.

Effects of metal-rich particulate matter exposure on exogenous and endogenous viral sequence methylation in healthy steel-workers.

PubMed

Mercorio, Roberta; Bonzini, Matteo; Angelici, Laura; Iodice, Simona; Delbue, Serena; Mariani, Jacopo; Apostoli, Pietro; Pesatori, Angela Cecilia; Bollati, Valentina

2017-11-01

Inhaled particles have been shown to produce systemic changes in DNA methylation. Global hypomethylation has been associated to viral sequence reactivation, possibly linked to the activation of pro-inflammatory pathways occurring after exposure. This observation provides a rationale to investigate viral sequence (both exogenous and endogenous) methylation in association to metal-rich particulate matter exposure. To verify this hypothesis, we chose the Wp promoter of the Epstein-Barr Virus (EBV-Wp) and the promoter of the human-endogenous-retrovirus w (HERV-w), respectively as a paradigm of an exogenous and an endogenous retroviral sequence, to be investigated by bisulfite PCR Pyrosequencing. We enrolled 63 male workers in an electric furnace steel plant, exposed to high level of metal-rich particulate matter. Comparing samples obtained in the first day of a work week (time 0-baseline, after 2 days off work) and the samples obtained after 3 days of work (time 1-post exposure), the mean methylation of EBV-Wp was significantly higher at baseline compared to post-exposure (mean baseline = 56.7%5mC; mean post-exposure = 47.9%5mC; p-value = 0.009), whereas the mean methylation of HERV-w did not significantly differ. Individual exposure to inhalable particles and metals was estimated based on measures in all working areas and time spent by the study subjects in each area. In a regression model adjusted for age, body mass index and smoking, PM and metal components had a positive association with EBV-Wp methylation (i.e. PM10: β = 5.99, p-value < 0.038; nickel: β = 17.82, p-value = 0.02; arsenic: β = 13.59, p-value < 0.015). The difference observed comparing baseline and post-exposure samples may be suggestive of a rapid change in EBV methylation induced by air particles, while correlation between EBV methylation and PM/metal exposure may represent a more stable adaptive mechanism. Future studies investigating a larger panel of viral sequences could better elucidate

Alkaline earth metal complexes of a phosphine-borane-stabilized carbanion: synthesis, structures, and stabilities.

PubMed

Izod, Keith; Wills, Corinne; Clegg, William; Harrington, Ross W

2007-05-14

The reaction between either MgI2 or CaI2 and 2 equiv of [(Me3Si)2{Me2(H3B)P}C]K (2) in toluene gives the corresponding organo-alkaline earth metal compounds [(Me3Si)2{Me2(H3B)P}C]2M in moderate to good yields [M = Mg (3), Ca (4)]. Compound 3 crystallizes solvent-free, whereas X-ray quality crystals of 4 could not be obtained in the absence of coordinating solvents; crystallization of 4 from cold methylcyclohexane/THF gives the solvate [(Me3Si)2{Me2(H3B)P}C]2Ca(THF)4 (4a). The corresponding heavier alkaline earth metal complexes [(Me3Si)2{Me2(H3B)P}C]2M(THF)5 [M = Sr (7), Ba (8)] are obtained from the reaction between MI2 and 2 equiv of 2 in THF, followed by recrystallization from cold methylcyclohexane/THF. Compound 3 degrades over a period of several weeks at room-temperature both in the solid state and in toluene solution to give the free phosphine-borane (Me3Si)2{Me2(H3B)P}CH (5) as the sole phosphorus-containing product. In addition, compounds 3, 4, and 4a react rapidly with THF in toluene solution, yielding 5 as the sole phosphorus-containing product; in contrast, compounds 7 and 8 are stable toward this solvent.

Endangered New Caledonian endemic mushroom coral Cantharellus noumeae in turbid, metal-rich, natural and artificial environments.

PubMed

Gilbert, Antoine; Heintz, Tom; Hoeksema, Bert W; Benzoni, Francesca; Fernandez, Jean Michel; Fauvelot, Cécile; Andréfouët, Serge

2015-11-15

Since its description in 1984, little attention has been paid to the New Caledonian endemic mushroom coral Cantharellus noumeae (Fungiidae), an IUCN Red-listed, endangered coral species. Our study presents the first ever quantitative assessment conducted on C. noumeae populations for two contrasting sites in the same turbid bay. Sites differed by their substrates of artificial or natural origins. Metal concentrations of superficial sediment were measured. C. noumeae was found in high densities in metal-rich and turbid environments at both locations, reaching up to 288 individuals per 50m(2). It was 3.5 times more abundant on natural rock than on artificial substrates. Recruitment was also higher proportionally on rock (47% vs 7-14%). The composition of the associated coral communities included 30-37 species occurring in low densities. Our findings clarify the environmental niche of this species and its colonization potential, in order to eventually better characterize its conservation status. Copyright © 2015 Elsevier Ltd. All rights reserved.

Calculating the Magnetic Anisotropy of Rare-Earth-Transition-Metal Ferrimagnets

NASA Astrophysics Data System (ADS)

Patrick, Christopher E.; Kumar, Santosh; Balakrishnan, Geetha; Edwards, Rachel S.; Lees, Martin R.; Petit, Leon; Staunton, Julie B.

2018-03-01

Magnetocrystalline anisotropy, the microscopic origin of permanent magnetism, is often explained in terms of ferromagnets. However, the best performing permanent magnets based on rare earths and transition metals (RE-TM) are in fact ferrimagnets, consisting of a number of magnetic sublattices. Here we show how a naive calculation of the magnetocrystalline anisotropy of the classic RE-TM ferrimagnet GdCo5 gives numbers that are too large at 0 K and exhibit the wrong temperature dependence. We solve this problem by introducing a first-principles approach to calculate temperature-dependent magnetization versus field (FPMVB) curves, mirroring the experiments actually used to determine the anisotropy. We pair our calculations with measurements on a recently grown single crystal of GdCo5 , and find excellent agreement. The FPMVB approach demonstrates a new level of sophistication in the use of first-principles calculations to understand RE-TM magnets.

Calculating the Magnetic Anisotropy of Rare-Earth-Transition-Metal Ferrimagnets.

PubMed

Patrick, Christopher E; Kumar, Santosh; Balakrishnan, Geetha; Edwards, Rachel S; Lees, Martin R; Petit, Leon; Staunton, Julie B

2018-03-02

Magnetocrystalline anisotropy, the microscopic origin of permanent magnetism, is often explained in terms of ferromagnets. However, the best performing permanent magnets based on rare earths and transition metals (RE-TM) are in fact ferrimagnets, consisting of a number of magnetic sublattices. Here we show how a naive calculation of the magnetocrystalline anisotropy of the classic RE-TM ferrimagnet GdCo_{5} gives numbers that are too large at 0 K and exhibit the wrong temperature dependence. We solve this problem by introducing a first-principles approach to calculate temperature-dependent magnetization versus field (FPMVB) curves, mirroring the experiments actually used to determine the anisotropy. We pair our calculations with measurements on a recently grown single crystal of GdCo_{5}, and find excellent agreement. The FPMVB approach demonstrates a new level of sophistication in the use of first-principles calculations to understand RE-TM magnets.

Extending FEAST-METAL for analysis of low content minor actinide bearing and zirconium rich metallic fuels for sodium fast reactors

NASA Astrophysics Data System (ADS)

Karahan, Aydın

2011-07-01

Computational models in FEAST-METAL fuel behaviour code have been upgraded to simulate minor actinide bearing zirconium rich metallic fuels for use in sodium fast reactors. Increasing the zirconium content to 20-40 wt.% causes significant changes in fuel slug microstructure affecting thermal, mechanical, chemical, and fission gas behaviour. Inclusion of zirconium rich phase reduces the fission gas swelling rate significantly in early irradiation. Above the threshold fission gas swelling, formation of micro-cracks, and open pores increase material compliancy enhance diffusivity, leading to rapid fuel gas swelling, interconnected porosity development and release of the fission gases and helium. Production and release of helium was modelled empirically as a function of americium content and fission gas production, consistent with previous Idaho National Laboratory studies. Predicted fuel constituent redistribution is much smaller compared to typical U-Pu-10Zr fuel operated at EBR-II. Material properties such as fuel thermal conductivity, modulus of elasticity, and thermal expansion coefficient have been approximated using the available database. Creep rate and fission gas diffusivity of high zirconium fuel is lowered by an order of magnitude with respect to the reference low zirconium fuel based on limited database and in order to match experimental observations. The new code is benchmarked against the AFC-1F fuel assembly post irradiation examination results. Satisfactory match was obtained for fission gas release and swelling behaviour. Finally, the study considers a comparison of fuel behaviour between high zirconium content minor actinide bearing fuel and typical U-15Pu-6Zr fuel pins with 75% smear density. The new fuel has much higher fissile content, allowing for operating at lower neutron flux level compared to fuel with lower fissile density. This feature allows the designer to reach a much higher burnup before reaching the cladding dose limit. On the other

Migration-driven diversity of super-Earth compositions

NASA Astrophysics Data System (ADS)

Raymond, Sean N.; Boulet, Thibault; Izidoro, Andre; Esteves, Leandro; Bitsch, Bertram

2018-06-01

A leading model for the origin of super-Earths proposes that planetary embryos migrate inward and pile up on close-in orbits. As large embryos are thought to preferentially form beyond the snow line, this naively predicts that most super-Earths should be very water-rich. Here we show that the shortest-period planets formed in the migration model are often purely rocky. The inward migration of icy embryos through the terrestrial zone accelerates the growth of rocky planets via resonant shepherding. We illustrate this process with a simulation that provided a match to the Kepler-36 system of two planets on close orbits with very different densities. In the simulation, two super-Earths formed in a Kepler-36-like configuration; the inner planet was pure rock while the outer one was ice-rich. We conclude from a suite of simulations that the feeding zones of close-in super-Earths are likely to be broad and disconnected from their final orbital radii.

Structural, mechanical and corrosion studies of Cr-rich inclusions in 152 cladding of dissimilar metal weld joint

NASA Astrophysics Data System (ADS)

Li, Yifeng; Wang, Jianqiu; Han, En-Hou; Yang, Chengdong

2018-01-01

Cr-rich inclusions were discovered in 152 cladding at the inner wall of domestic dissimilar metal weld joint, and their morphologies, microstructures, mechanical properties and corrosion behaviors were systematically characterized by SEM, TEM, nanoindentation and FIB. The results indicate that the Cr-rich inclusions originate from large-size Cr particles in 152 welding electrode flux, and they are 50-150 μm in size in most cases, and there is a continuous transition zone of 2-5 μm in width between the Cr inclusion core and 152 cladding matrix, and the transition zone consists of Ni & Fe-rich dendritic austenite and Cr23C6 and Cr matrix. The transition zone has the highest nanoindentation hardness (7.66 GPa), which is much harder than the inclusion core (5.14 GPa) and 152 cladding (3.71 GPa). In-situ microscopic tensile tests show that cracks initialize preferentially in transition zone, and then propagate into the inclusion core, and creep further into 152 cladding after penetrating the core area. The inclusion core and its transition zone both share similar oxide film structure with nickel-base 152 cladding matrix in simulated primary water, while those two parts present better general corrosion resistance than 152 cladding matrix due to higher Cr concentration.

Laminated rare earth structure and method of making

DOEpatents

Senor, David J [West Richland, WA; Johnson, Roger N [Richland, WA; Reid, Bruce D [Pasco, WA; Larson, Sandra [Richland, WA

2002-07-30

A laminated structure having two or more layers, wherein at least one layer is a metal substrate and at least one other layer is a coating comprising at least one rare earth element. For structures having more than two layers, the coating and metal substrate layers alternate. In one embodiment of the invention, the structure is a two-layer laminate having a rare earth coating electrospark deposited onto a metal substrate. In another embodiment of the invention, the structure is a three-layer laminate having the rare earth coating electrospark deposited onto a first metal substrate and the coating subsequently abonded to a second metal substrate. The bonding of the coating to the second metal substrate may be accomplished by hot pressing, hot rolling, high deformation rate processing, or combinations thereof. The laminated structure may be used in nuclear components where reactivity control or neutron absorption is desired and in non-nuclear applications such as magnetic and superconducting films.

Origin of spinel-rich chondrules and inclusions in carbonaceous and ordinary chondrites

NASA Technical Reports Server (NTRS)

Kornacki, A. S.; Fegley, B., Jr.

1984-01-01

The evaluation of three models of the origin of spinel-rich chondrules and inclusions presented here includes new calculations of the major-element refractory mineral condensation sequence from a gas of solar composition over a wide pressure interval. Condensation calculations show that spinel-rich chondrules did not crystallize from metastable liquid condensates, and that spinel-rich inclusions are not aggregates of refractory nebular condensates. It is proposed that spinel-rich objects are fractionated distillation residues of small aggregates of primitive dust that lost Ca, Si-rich partial melts by evaporation, ablation, or splashing during collisions. This model also explains why spinel-rich chondrules and inclusions (1) are usually smaller than melilite-rich chondrules and inclusions; (2) often have highly fractionated trace-element compositions; and (3) usually do not contain Pt-metal nuggets even when they are more enriched in the Pt-group metals than nugget-bearing melilite-rich objects.

Fracture-induced flow and liquid metal transport during core formation

NASA Astrophysics Data System (ADS)

Jones, V.; Petford, N.; Rushmer, T.; Wertheim, D.

2008-12-01

The most important event in the early history of the earth was the separation of its iron-rich core. Core formation induced profound chemical fractionations and extracted into the core most of Earth's iron and siderophile elements (Ni, Co, Au, Pt, W, Re), leaving the silicate crust and mantle with strong depletions of these elements relative to primitive planetary material. Recent measurements of radiogenic 182W anomalies in the silicate Earth, Mars and differentiated meteorites imply that planetesimals segregated metallic cores within a few Myr of the origin of the solar system. Various models have been put forward to explain the physical nature of the segregation mechanism (Fe-diapirs, 'raining' through a magma ocean), and more recently melt flow via fractures. In this contribution we present the initial results of a numerical study into Fe segregation in a deforming silicate matrix that captures the temperature-dependent effect of liquid metal viscosity on the transport rate. Flow is driven by pressure gradients associated with impact deformation in a growing planetesimal and the fracture geometry is constrained by experimental data on naturally deformed H6 chondrite. Early results suggest that under dynamic conditions, fracture-driven melt flow can in principle be extremely rapid, leading to a significant draining of the Fe-liquid metal and siderophile trace element component on a timescale of hours to days. Fluid transport in planetesimals where deformation is the driving force provides an attractive and simple way of segregating Fe from host silicate as both precursor and primary agent of core formation

Ternary metal-rich sulfide with a layered structure

DOEpatents

Franzen, Hugo F.; Yao, Xiaoqiang

1993-08-17

A ternary Nb-Ta-S compound is provided having the atomic formula, Nb.sub.1.72 Ta.sub.3.28 S.sub.2, and exhibiting a layered structure in the sequence S-M3-M2-M1-M2-M3-S wherein S represents sulfur layers and M1, M2, and M3 represent Nb/Ta mixed metal layers. This sequence generates seven sheets stacked along the [001] direction of an approximate body centered cubic crystal structure with relatively weak sulfur-to-sulfur van der Waals type interactions between adjacent sulfur sheets and metal-to-metal bonding within and between adjacent mixed metal sheets.

Molecular electrocatalysts for oxidation of hydrogen using earth-abundant metals: shoving protons around with proton relays.

PubMed

Bullock, R Morris; Helm, Monte L

2015-07-21

Sustainable, carbon-neutral energy is needed to supplant the worldwide reliance on fossil fuels in order to address the persistent problem of increasing emissions of CO2. Solar and wind energy are intermittent, highlighting the need to develop energy storage on a huge scale. Electrocatalysts provide a way to convert between electrical energy generated by renewable energy sources and chemical energy in the form of chemical bonds. Oxidation of hydrogen to give two electrons and two protons is carried out in fuel cells, but the typical catalyst is platinum, a precious metal of low earth abundance and high cost. In nature, hydrogenases based on iron or iron/nickel reversibly oxidize hydrogen with remarkable efficiencies and rates. Functional models of these enzymes have been synthesized with the goal of achieving electrocatalytic H2 oxidation using inexpensive, earth-abundant metals along with a key feature identified in the [FeFe]-hydrogenase: an amine base positioned near the metal. The diphosphine ligands P(R)2N(R')2 (1,5-diaza-3,7-diphosphacyclooctane with alkyl or aryl groups on the P and N atoms) are used as ligands in Ni, Fe, and Mn complexes. The pendant amines facilitate binding and heterolytic cleavage of H2, placing the hydride on the metal and the proton on the amine. The pendant amines also serve as proton relays, accelerating intramolecular and intermolecular proton transfers. Electrochemical oxidations and deprotonations by an exogeneous amine base lead to catalytic cycles for oxidation of H2 (1 atm) at room temperature for catalysts derived from [Ni(P(Cy)2N(R')2)2](2+), Cp(C6F5)Fe(P(tBu)2N(Bn)2)H, and MnH(P(Ph)2N(Bn)2)(bppm)(CO) [bppm = (PAr(F)2)2CH2]. In the oxidation of H2 catalyzed by [Ni(P(Cy)2N(R')2)2](2+), the initial product observed experimentally is a Ni(0) complex in which two of the pendant amines are protonated. Two different pathways can occur from this intermediate; deprotonation followed by oxidation occurs with a lower overpotential than

Improved method for preparing rare earth sesquichalcogenides

DOEpatents

Takeshita, T.; Beaudry, B.J.; Gschneidner, K.A. Jr.

1982-04-14

An improved method for the preparation of high purity rare earth sesquichalcogenides is described. The rare earth, as one or more pieces of the metal, is sealed under a vacuum with a stoichiometric amount of sulfur or selenium and a small amount of iodine into a quartz reaction vessel. The sealed vessel is then heated to above the vaporization temperature of the chalcogen and below the melting temperature of the rare earth metal and maintained until the product has been formed. The iodine is then vaporized off leaving a pure product. The rare earth sulfides and selenides thus formed are useful as semiconductors and as thermoelectric generators. 3 tables.

Alaska's rare earth deposits and resource potential

USGS Publications Warehouse

Barker, James C.; Van Gosen, Bradley S.

2012-01-01

Alaska’s known mineral endowment includes some of the largest and highest grade deposits of various metals, including gold, copper and zinc. Recently, Alaska has also been active in the worldwide search for sources of rare earth elements (REE) to replace exports now being limitedby China. Driven by limited supply of the rare earths, combined with their increasing use in new ‘green’ energy, lighting, transportation, and many other technological applications, the rare earth metals neodymium, europium and, in particular, the heavy rare earth elements terbium, dysprosium and yttrium are forecast to soon be in critical short supply (U.S. Department of Energy, 2010).

Behavior and Distribution of Heavy Metals Including Rare Earth Elements, Thorium, and Uranium in Sludge from Industry Water Treatment Plant and Recovery Method of Metals by Biosurfactants Application

PubMed Central

Gao, Lidi; Kano, Naoki; Sato, Yuichi; Li, Chong; Zhang, Shuang; Imaizumi, Hiroshi

2012-01-01

In order to investigate the behavior, distribution, and characteristics of heavy metals including rare earth elements (REEs), thorium (Th), and uranium (U) in sludge, the total and fractional concentrations of these elements in sludge collected from an industry water treatment plant were determined and compared with those in natural soil. In addition, the removal/recovery process of heavy metals (Pb, Cr, and Ni) from the polluted sludge was studied with biosurfactant (saponin and sophorolipid) elution by batch and column experiments to evaluate the efficiency of biosurfactant for the removal of heavy metals. Consequently, the following matters have been largely clarified. (1) Heavy metallic elements in sludge have generally larger concentrations and exist as more unstable fraction than those in natural soil. (2) Nonionic saponin including carboxyl group is more efficient than sophorolipid for the removal of heavy metals in polluted sludge. Saponin has selectivity for the mobilization of heavy metals and mainly reacts with heavy metals in F3 (the fraction bound to carbonates) and F5 (the fraction bound to Fe-Mn oxides). (3) The recovery efficiency of heavy metals (Pb, Ni, and Cr) reached about 90–100% using a precipitation method with alkaline solution. PMID:22693485

Novel condensation of Au-centered trigonal prisms in rare-earth-metal-rich tellurides: Er7Au2Te2 and Lu7Au2Te2.

PubMed

Gupta, Shalabh; Corbett, John D

2010-07-14

A new monoclinic structure occurs for Er(7)Au(2)Te(2) according to X-ray diffraction analysis of single crystals grown at 1200 degrees C: C2/m, Z = 4, a = 17.8310(9) A, b = 3.9819(5) A, c = 16.9089(9) A, beta = 104.361(4) degrees. The isostructural Lu(7)Au(2)Te(2) also exists according to X-ray powder pattern means, a = 17.536(4) A, b = 3.9719(4) A, c = 16.695(2) A, beta = 104.33(1) degrees. The structure contains zigzag chains of condensed, Au-centered tricapped trigonal prisms (TCTP) of Er along c that also share basal faces along b to generate puckered sheets. Further bi-face-capping Er atoms between these generate the three dimensional network along a, with tellurium in cavities outlined by augmented trigonal prismatic Er polyhedra. Bonding analysis via LMTO-DFT methods reveal very significant Er-Au bonding interactions, as quantified by their energy-weighted Hamilton overlap populations (-ICOHP), approximately 49% of the total for all interactions. These and similar Er-Te contributions sharply contrast with the small Er-Er population, only approximately 14% of the total in spite of the high proportion of Er-Er contacts. The strong polar bonding of Er to the electronegative Au and Te leaves Er relatively oxidized, with many of its 5d states falling above the Fermi level and empty. The contradiction with customary representations of structures that highlight rare-earth metal clusters is manifest. The large Er-Au Hamilton overlap population is in accord with the strong bonding between early and late transition metals first noted by Brewer in 1973. The relationship of this structure to the more distorted orthorhombic (Imm2) structure type of neighboring Dy(7)Ir(2)Te(2) is considered.

CLOUDS IN SUPER-EARTH ATMOSPHERES: CHEMICAL EQUILIBRIUM CALCULATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mbarek, Rostom; Kempton, Eliza M.-R., E-mail: mbarekro@grinnell.edu, E-mail: kemptone@grinnell.edu

Recent studies have unequivocally proven the existence of clouds in super-Earth atmospheres. Here we provide a theoretical context for the formation of super-Earth clouds by determining which condensates are likely to form under the assumption of chemical equilibrium. We study super-Earth atmospheres of diverse bulk composition, which are assumed to form by outgassing from a solid core of chondritic material, following Schaefer and Fegley. The super-Earth atmospheres that we study arise from planetary cores made up of individual types of chondritic meteorites. They range from highly reducing to oxidizing and have carbon to oxygen (C:O) ratios that are both sub-solarmore » and super-solar, thereby spanning a range of atmospheric composition that is appropriate for low-mass exoplanets. Given the atomic makeup of these atmospheres, we minimize the global Gibbs free energy of formation for over 550 gases and condensates to obtain the molecular composition of the atmospheres over a temperature range of 350–3000 K. Clouds should form along the temperature–pressure boundaries where the condensed species appear in our calculation. We find that the composition of condensate clouds depends strongly on both the H:O and C:O ratios. For the super-Earth archetype GJ 1214b, KCl and ZnS are the primary cloud-forming condensates at solar composition, in agreement with previous work. However, for oxidizing atmospheres, K{sub 2}SO{sub 4} and ZnO condensates are favored instead, and for carbon-rich atmospheres with super-solar C:O ratios, graphite clouds appear. For even hotter planets, clouds form from a wide variety of rock-forming and metallic species.« less

Clouds in Super-Earth Atmospheres: Chemical Equilibrium Calculations

NASA Astrophysics Data System (ADS)

Mbarek, Rostom; Kempton, Eliza M.-R.

2016-08-01

Recent studies have unequivocally proven the existence of clouds in super-Earth atmospheres. Here we provide a theoretical context for the formation of super-Earth clouds by determining which condensates are likely to form under the assumption of chemical equilibrium. We study super-Earth atmospheres of diverse bulk composition, which are assumed to form by outgassing from a solid core of chondritic material, following Schaefer & Fegley. The super-Earth atmospheres that we study arise from planetary cores made up of individual types of chondritic meteorites. They range from highly reducing to oxidizing and have carbon to oxygen (C:O) ratios that are both sub-solar and super-solar, thereby spanning a range of atmospheric composition that is appropriate for low-mass exoplanets. Given the atomic makeup of these atmospheres, we minimize the global Gibbs free energy of formation for over 550 gases and condensates to obtain the molecular composition of the atmospheres over a temperature range of 350-3000 K. Clouds should form along the temperature-pressure boundaries where the condensed species appear in our calculation. We find that the composition of condensate clouds depends strongly on both the H:O and C:O ratios. For the super-Earth archetype GJ 1214b, KCl and ZnS are the primary cloud-forming condensates at solar composition, in agreement with previous work. However, for oxidizing atmospheres, K2SO4 and ZnO condensates are favored instead, and for carbon-rich atmospheres with super-solar C:O ratios, graphite clouds appear. For even hotter planets, clouds form from a wide variety of rock-forming and metallic species.

Byproduct metals and rare-earth elements used in the production of light-emitting diodes—Overview of principal sources of supply and material requirements for selected markets

USGS Publications Warehouse

Wilburn, David R.

2012-01-01

The use of light-emitting diodes (LEDs) is expanding because of environmental issues and the efficiency and cost savings achieved compared with use of traditional incandescent lighting. The longer life and reduced power consumption of some LEDs have led to annual energy savings, reduced maintenance costs, and lower emissions of carbon dioxide, sulfur dioxide, and nitrogen oxides from powerplants because of the resulting decrease in energy consumption required for lighting applications when LEDs are used to replace less-energy-efficient sources. Metals such as arsenic, gallium, indium, and the rare-earth elements (REEs) cerium, europium, gadolinium, lanthanum, terbium, and yttrium are important mineral materials used in LED semiconductor technology. Most of the world's supply of these materials is produced as byproducts from the production of aluminum, copper, lead, and zinc. Most of the rare earths required for LED production in 2011 came from China, and most LED production facilities were located in Asia. The LED manufacturing process is complex and is undergoing much change with the growth of the industry and the changes in demand patterns of associated commodities. In many respects, the continued growth of the LED industry, particularly in the general lighting sector, is tied to its ability to increase LED efficiency and color uniformity while decreasing the costs of producing, purchasing, and operating LEDs. Research is supported by governments of China, the European Union, Japan, the Republic of Korea, and the United States. Because of the volume of ongoing research in this sector, it is likely that the material requirements of future LEDs may be quite different than LEDs currently (2011) in use as industry attempts to cut costs by reducing material requirements of expensive heavy rare-earth phosphors and increasing the sizes of wafers for economies of scale. Improved LED performance will allow customers to reduce the number of LEDs in automotive, electronic

Na, Rb and Cs partitioning between metal, silicate and sulfide: Implications for volatile depletion in terrestrial planets

NASA Astrophysics Data System (ADS)

Boujibar, A.; Fei, Y.; Du, Z.; Righter, K.; Bullock, E. S.

2017-12-01

Inner Solar System materials are known for their depletion in volatile elements, including the moderately volatile alkalis: Na, K, Rb, and Cs. The origin of this depletion is still uncertain, as several processes could have been involved, during the nebular condensation or planetary accretion. Volatile depletion is commonly estimated through comparison of alkali concentrations relatively to those of chondrites, assuming they remain in planetary mantles during core segregation. However, experimental studies show that substantial K can partition into metals that are enriched in sulfur and oxygen. Several models have also suggested that sulfides may have played an important role during episodes of sulfide segregation from a crystallizing magma ocean (sulfide matte) or accretion of S-rich planetary embryos. For Mercury, a sulfide layer could be present between core and mantle, due to immiscibility between Si-rich and S-rich metals. Therefore, here we investigate whether alkali elements (Na, Cs and Rb) could be partly sequestered in planetary cores during their differentiation. We conducted experiments at high pressure and temperature (1 to 5 GPa and up to 1900 °C) to determine partition coefficients of Na, Rb and Cs between metal and silicate. Our results show that pressure, temperature, sulfur and oxygen in metals enhance the partitioning of Na, Rb and Cs into metals, as previously found for K. For all three investigated alkalis (Na, Rb and Cs), we found a maximum partition coefficient of 1 between sulfides containing 13 wt% O and silicate melt. Therefore, S-rich cores or sulfide layers formed due to immiscibility in Fe-S-O systems could have acted as important geochemical reservoirs for alkali elements. Using our experimental data and different assumptions on initial bulk abundances, we evaluate volatile depletion in terrestrial planets, by comparing resulting mantle alkali concentrations after core segregation, with actual concentrations in the Earth's mantle.

A miniature single element effusion cell for the vacuum deposition of transition-metal and rare-earth elements

NASA Astrophysics Data System (ADS)

Harris, V. G.; Koon, N. C.

1997-08-01

A miniature single element effusion cell has been fabricated and tested that allows for the high-vacuum deposition of a variety of transition-metal and rare-earth elements. The cell is designed to operate under high-vacuum conditions, ≈10-9 Torr, with low power demands, <200 W. The virtues of this evaporator are the simplicity of design and ease of fabrication, assembly, maintenance, and operation.

Half-sandwich rare-earth-catalyzed olefin polymerization, carbometalation, and hydroarylation.

PubMed

Nishiura, Masayoshi; Guo, Fang; Hou, Zhaomin

2015-08-18

The search for new catalysts for more efficient, selective chemical transformations and for the synthesis of new functional materials has been a long-standing research subject in both academia and industry. To develop new generations of catalysts that are superior or complementary to the existing ones, exploring the potential of untapped elements is an important strategy. Rare-earth elements, including scandium, yttrium, and the lanthanides (La-Lu), constitute one important frontier in the periodic table. Rare-earth elements possess unique chemical and physical properties that are different from those of main-group and late-transition metals. The development of rare-earth-based catalysts by taking the advantage of these unique properties is of great interest and importance. The most stable oxidation state of rare-earth metals is 3+, which is difficult to change under many reaction conditions. The oxidative addition and reductive elimination processes often observed in catalytic cycles involving late transition metals are generally difficult in the case of rare-earth complexes. The 18-electron rule that is applicable to late-transition-metal complexes does not fit rare-earth complexes, whose structures are mainly governed by the sterics (rather than the electron numbers) of the ligands. In the lanthanide series (La-Lu), the ionic radius gradually decreases with increasing atomic number because of the influence of the 4f electrons, which show poor shielding of nuclear charge. Rare-earth metal ions generally show strong Lewis acidity and oxophilicity. Rare-earth metal alkyl and hydride species are highly reactive, showing both nucleophilicity and basicity. The combination of these features, such as the strong nucleophilicity and moderate basicity of the alkyl and hydride species and the high stability, strong Lewis acidity, and unsaturated C-C bond affinity of the 3+ metal ions, can make rare-earth metals unique candidates for the formation of excellent single

Distribution of rare-earth (Y, La, Ce) and other heavy metals in the profiles of the podzolic soil group

NASA Astrophysics Data System (ADS)

Vodyanitskii, Yu. N.; Goryachkin, S. V.; Savichev, A. T.

2011-05-01

Along with Fe and Al, many heavy metals (Mn, Cr, Zn, Cu, and Ni) show a markedly pronounced eluvial-illuvial redistribution in the profiles of soils of the podzolic group. The intensity of the redistribution of the bulk forms of these metals is comparable with that of Fe and exceeds that of Al. Although the podzolic soils are depleted of rare-earth metals, the latter respond readily to soil podzolization. The inactive participation of Al is explained by an insignificant portion of the active reaction-capable fraction. Podzolization does not influence the profile distribution of Sr and Ba. The leaching degree of heavy metals such as Mn, Cr, Zn, Ni, and Zr is noticeably higher in the sandy podzols than in the loamy podzolic soils. Leaching of heavy metals from the podzolic horizons is of geochemical importance, whereas the depletion of metals participating in plant nutrition and biota development is of ecological importance. The leaching of heavy metals is related to the destruction of clay particles in the heavy-textured podzolic soils; the effect of the soil acidity on the leaching of heavy metals is less significant.

A Time-domain Analysis of Nitrogen-rich Quasars.

NASA Astrophysics Data System (ADS)

Dittmann, Alexander; Liu, Xin; Shen, Yue; Jiang, Linhua

2018-01-01

A small population of quasars exhibit anomalously high nitrogen-to-carbon ratios (N/C) in their emission lines. These “nitrogen-rich” (N-rich) quasars have been difficult to explain. Few of the possible mechanism are natural, since stellar populations with abnormally high metallicities are required to produce an N-rich interstellar medium. N-rich quasars are also more likely to be “radio-loud” than average quasars, which is difficult to explain by invoking higher metallicity alone. Recently, tidal disruption events (TDEs) have been proposed as a mechanism for N-rich quasars. Such a TDE would occur between a supersolar mass star and a supermassive black hole. The CNO cycle creates a surplus of N-rich and carbon-deficient material that could naturally explain the N/C observed in N-rich quasars. The TDE hypothesis explains N-rich quasars without requiring extremely exotic stellar populations. A testable difference differentiating the TDE explanation and exotic stellar population scenarios is that TDEs do not produce enough N-rich material to pollute the quasar environment for extended periods of time, in which case N-rich phenomena in quasars would be transient. By analyzing changes in nitrogen and carbon line widths in time-separated spectra of N-rich quasars, we have studied nitrogen abundance in quasars which had previously been identified as nitrogen rich. We have found that over time-frames of greater than one year in the quasar rest frame, nitrogen abundance tends to systematically decrease. The observed decrease is larger than our estimate of the effects of noise based on spectra separated by smaller time frames. Additionally, x-ray observations of one N-rich quasar have demonstrated that its x-ray emission is an outlier among the quasar population, but similar to confirmed TDEs.

REVIEWS OF TOPICAL PROBLEMS: Universal viscosity growth in metallic melts at megabar pressures: the vitreous state of the Earth's inner core

NASA Astrophysics Data System (ADS)

Brazhkin, Vadim V.; Lyapin, A. G.

2000-05-01

Experimental data on and theoretical models for the viscosity of various types of liquids and melts under pressure are reviewed. Experimentally, the least studied melts are those of metals, whose viscosity is considered to be virtually constant along the melting curve. The authors' new approach to the viscosity of melts involves the measurement of the grain size in solidified samples. Measurements on liquid metals at pressures up to 10 GPa using this method show, contrary to the empirical approach, that the melt viscosity grows considerably along the melting curves. Based on the experimental data and on the critical analysis of current theories, a hypothesis of a universal viscosity behavior is introduced for liquids under pressure. Extrapolating the liquid iron results to the pressures and temperatures at the Earth's core reveals that the Earth's outer core is a very viscous melt with viscosity values ranging from 102 Pa s to 1011 Pa s depending on the depth. The Earth's inner core is presumably an ultraviscous (>1011 Pa s) glass-like liquid — in disagreement with the current idea of a crystalline inner core. The notion of the highly viscous interior of celestial bodies sheds light on many mysteries of planetary geophysics and astronomy. From the analysis of the pressure variation of the melting and glass-transition temperatures, an entirely new concept of a stable metallic vitreous state arises, calling for further experimental and theoretical study.

Tunable magnetic and magnetocaloric properties in heavy rare-earth based metallic glasses through the substitution of similar elements

NASA Astrophysics Data System (ADS)

Zhang, Huiyan; Li, Ran; Zhang, Leilei; Zhang, Tao

2014-04-01

The influence of interchangeable substitution of similar heavy rare-earth-elements (HRE), i.e., Gd-Ho, Gd-Er, and Ho-Er, on the magnetic and magnetocaloric properties of HRE55Al27.5Co17.5 metallic glasses was evaluated. The magnetic transition temperature (TC) can be tuned in a wide temperature range from 8 K to 93 K by adjusting the substitutional concentration in the resulting metallic glasses. A roughly linear correlation between peak value of magnetic entropy change (|ΔSMpk|) and TC-2/3 was obtained in the three systems. This kind of substitutional adjustment provides a useful method for designing desirable candidates in metallic glasses with high magnetic entropy change, large magnetic cooling efficiency, and tunable TC for magnetic refrigerant in nitrogen and hydrogen liquefaction temperature ranges.

Catalysis using hydrous metal oxide ion exchanges

DOEpatents

Dosch, Robert G.; Stephens, Howard P.; Stohl, Frances V.

1985-01-01

In a process which is catalyzed by a catalyst comprising an active metal on a carrier, said metal being active as a catalyst for the process, an improvement is provided wherein the catalyst is a hydrous, alkali metal or alkaline earth metal titanate, zirconate, niobate or tantalate wherein alkali or alkaline earth metal cations have been exchanged with a catalytically effective amount of cations of said metal.

Catalysis using hydrous metal oxide ion exchangers

DOEpatents

Dosch, R.G.; Stephens, H.P.; Stohl, F.V.

1983-07-21

In a process which is catalyzed by a catalyst comprising an active metal on a carrier, said metal being active as a catalyst for the process, an improvement is provided wherein the catalyst is a hydrous, alkali metal or alkaline earth metal titanate, zirconate, niobate or tantalate wherein alkali or alkaline earth metal cations have been exchanged with a catalytically effective amount of cations of said metal.

Thermochemistry and Photochemistry in Thick Atmospheres on Super Earths and Mini Neptunes

NASA Astrophysics Data System (ADS)

Hu, R.; Seager, S.

2013-12-01

Dectection and characterization of low-mass exoplanets is poised to accelerate in the coming decade. Some low-mass exoplanets, namely super Earths and some mini Neptunes, will likely have thick atmospheres that are not H2-dominated. We have developed a photochemistry-thermochemistry model for exploring the compositions of thick atmospheres on super Earths and mini Neptunes, applicable for both H2-dominated atmospheres and non-H2-dominated atmospheres. Using this model, we have simulated the molecular composition of thick atmospheres on warm and hot super Earths/mini Neptunes, and classified thick atmospheres into hydrogen-rich atmospheres, water-rich atmospheres, oxygen-rich atmospheres, and hydrocarbon-rich atmospheres, depending on the hydrogen abundance and the carbon to oxygen abundance ratio. We find that carbon has to be in the form of CO2 rather than CH4 or CO in an H2-depleted water-dominated thick atmosphere, and that the preferred loss of light elements from an oxygen-poor carbon-rich atmosphere leads to formation of unsaturated hydrocarbons. For future observations, we find for GJ 1214b that (1) C2H2 features at 1.0 and 1.5 μm in transmission are diagnostic for hydrocarbon-rich atmospheres; (2) a constraint on the thermal emission at 4.5 μm could differentiate water-rich atmospheres versus hydrocarbon-rich atmospheres; (3) a detection of water-vapor features and a confirmation of nonexistence of methane features would provide sufficient evidence for a water-dominated atmosphere. For a hot super Earth like 55 Cnc e, the diagnostic features of water-rich atmospheres (H2O) and the diagnostic features of hydrocarbon-rich atmospheres (CO and C2H2) are well separated in transmission spectra at 0.6-5 μm, which would enable straightforward characterization. In general, our simulations show that chemical stability has to be taken into account when interpreting the spectrum of a super Earth/mini Neptune. Theoretical transmission spectra and thermal emission

Coordination Polymerization of Renewable 3-Methylenecyclopentene with Rare-Earth-Metal Precursors.

PubMed

Liu, Bo; Li, Shihui; Wang, Meiyan; Cui, Dongmei

2017-04-10

Coordination polymerization of renewable 3-methylenecyclopentene has been investigated for the first time using rare-earth metal-based precursors bearing various bulky ligands. All the prepared complexes catalyze controllable polymerization of 3-methylenecyclopentene into high molecular weight polymers, of which the NPN- and NSN-tridentate non-Cp ligated lutetium-based catalytic systems exhibited extremely high activities up to 11 520 kg/(mol Lu ⋅h) in a dilute toluene solution (3.2 g/100 mL) at room temperature. The resultant polymers have pure 1,4-regioregularity (>99 %) and tailorable number average molecular weights (1-20×10 4 ) with narrow molecular weight distributions (polydispersity index (PDI)=1.45-1.79). DFT simulations were employed to study the polymerization mechanism and stereoregularity control. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Neutron diffraction studies of some rare earth-transition metal deuterides

NASA Astrophysics Data System (ADS)

James, W. J.

1984-04-01

Neutron diffraction studies of the ternary alloy system Y6(Fel-xMnx)23 reveal that the unusual magnetic behavior upon substitution of Mn or Fe into the end members, is a consequence of atomic ordering wherein there is strong site preference of Mn for the f sub 2 sites and of Fe for the f sub 1 sites. In the Mn-rich compositions, Fe is found to have no spontaneous moments. Therefore, the long range magnetic ordering arises solely from Mn-Mn interactions. Upon substitution of Mn into the Fe-rich ternaries, the Fe moments are considerably reduced. Neutron diffraction studies of Y6Mn23D23 show that a transition occurs below 180K from a fcc structure to a primitive tetragonal structure, space group P4/mmm with the onset of antiferromagnetic ordering. The Mn moments are directed along the c-axis. The transition probably results from atomic ordering of the D atoms at low temperature which induces c axis magnetic ordering. The question of the appropriate space group of LaNi4.5Al0.5D4.5, P6/mmm or P3/m has been resolved by a careful refinement and analysis of neutron diffraction data. The preferred space group is P6/mmm. Neutron powder diffraction and thermal magnetization measurements on small single crystals of ErNi3, ErCo3, and ErFe3 (space group R3m) show that the magnetocrystalline properties are a consequence of competing local site anisotropies between the two non-equivalent crystallographic sites of Er and two of the three non-equivalent sites of the 3d-transition metal.

Anaerobic digestion of nitrogen rich poultry manure: Impact of thermophilic biogas process on metal release and microbial resistances.

PubMed

Anjum, Reshma; Grohmann, Elisabeth; Krakat, Niclas

2017-02-01

Poultry manure is a nitrogen rich fertilizer, which is usually recycled and spread on agricultural fields. Due to its high nutrient content, chicken manure is considered to be one of the most valuable animal wastes as organic fertilizer. However, when chicken litter is applied in its native form, concerns are raised as such fertilizers also include high amounts of antibiotic resistant pathogenic Bacteria and heavy metals. We studied the impact of an anaerobic thermophilic digestion process on poultry manure. Particularly, microbial antibiotic resistance profiles, mobile genetic elements promoting the resistance dissemination in the environment as well as the presence of heavy metals were focused in this study. The initiated heat treatment fostered a community shift from pathogenic to less pathogenic bacterial groups. Phenotypic and molecular studies demonstrated a clear reduction of multiple resistant pathogens and self-transmissible plasmids in the heat treated manure. That treatment also induced a higher release of metals and macroelements. Especially, Zn and Cu exceeded toxic thresholds. Although the concentrations of a few metals reached toxic levels after the anaerobic thermophilic treatment, the quality of poultry manure as organic fertilizer may raise significantly due to the elimination of antibiotic resistance genes (ARG) and self-transmissible plasmids. Copyright © 2016 Elsevier Ltd. All rights reserved.

A new carbon-rich phase (COPS) in Antarctic micrometeorites

NASA Technical Reports Server (NTRS)

Engrand, C.; Maurette, M.; Kurat, G.; Brandstatter, F.; Perreau, M.

1993-01-01

The contemporary flux of micrometeorites with sizes greater than 50 microns reaching the Earth's surface each year (about 20,000 tons/a) is much greater than the value of approximately 100 tons/a reported for conventional meteorites up to masses of approximately 10,000 tons. Moreover, on the average, Antarctic micrometeorites contain at least as much carbon as does Orgueil, the most C-rich meteorite. Micrometeorites are thus responsible for most of the carbon accreted by the Earth. In this paper we report SEM observations of a new C-rich 'dirty magnetite' phase observed as tiny inclusions in both melted and unmelted micrometeorites. This phase, which is enriched in C, O, P, S, Fe, frequently shows Ni contents in excess of 0.2 percent, strongly suggestive of an 'extraterrestrial' origin. We also discovered this 'COPS' phase in the fusion crust of Murchison. It appears likely that COPS is a product of meteoroid reprocessing during frictional heating in the Earth's atmosphere and/or its fast 'weathering' in the upper atmosphere. Upon 'catalyzed' hydrolysis this phase might have facilitated the functioning of micrometeorites as 'micro-chondritic-reactors' for the synthesis of prebiotic molecules on the early Earth.

An abundance of small exoplanets around stars with a wide range of metallicities.

PubMed

Buchhave, Lars A; Latham, David W; Johansen, Anders; Bizzarro, Martin; Torres, Guillermo; Rowe, Jason F; Batalha, Natalie M; Borucki, William J; Brugamyer, Erik; Caldwell, Caroline; Bryson, Stephen T; Ciardi, David R; Cochran, William D; Endl, Michael; Esquerdo, Gilbert A; Ford, Eric B; Geary, John C; Gilliland, Ronald L; Hansen, Terese; Isaacson, Howard; Laird, John B; Lucas, Philip W; Marcy, Geoffrey W; Morse, Jon A; Robertson, Paul; Shporer, Avi; Stefanik, Robert P; Still, Martin; Quinn, Samuel N

2012-06-13

The abundance of heavy elements (metallicity) in the photospheres of stars similar to the Sun provides a 'fossil' record of the chemical composition of the initial protoplanetary disk. Metal-rich stars are much more likely to harbour gas giant planets, supporting the model that planets form by accumulation of dust and ice particles. Recent ground-based surveys suggest that this correlation is weakened for Neptunian-sized planets. However, how the relationship between size and metallicity extends into the regime of terrestrial-sized exoplanets is unknown. Here we report spectroscopic metallicities of the host stars of 226 small exoplanet candidates discovered by NASA's Kepler mission, including objects that are comparable in size to the terrestrial planets in the Solar System. We find that planets with radii less than four Earth radii form around host stars with a wide range of metallicities (but on average a metallicity close to that of the Sun), whereas large planets preferentially form around stars with higher metallicities. This observation suggests that terrestrial planets may be widespread in the disk of the Galaxy, with no special requirement of enhanced metallicity for their formation.

Ecological transfer of radionuclides and metals to free-living earthworm species in natural habitats rich in NORM.

PubMed

Mrdakovic Popic, Jelena; Salbu, Brit; Skipperud, Lindis

2012-01-01

Transfer of radionuclides ((232)Th and (238)U) and associated metals (As, Cd, Pb and Cr) from soil to free-living earthworm species was investigated in a thorium ((232)Th) rich area in Norway. Sampling took place within former mining sites representing the technologically enhanced naturally occurring radioactive materials (TENORM), at undisturbed site with unique bedrock geology representing the naturally occurring radioactive materials (NORM) and at site outside the (232)Th rich area taken as reference Background site. Soil analysis revealed the elevated levels of investigated elements at NORM and TENORM sites. Based on sequential extraction, uranium ((238)U) and cadmium (Cd) were quite mobile, while the other elements were strongly associated with mineral components of soil. Four investigated earthworm species (Aporrectodea caliginosa, Aporrectodea rosea, Dendrodrilus rubidus and Lumbricus rubellus) showed large individual variability in the accumulation of radionuclides and metals. Differences in uptake by epigeic and endogeic species, as well as differences within same species from the NORM, TENORM and Background sites were also seen. Based on total concentrations in soil, the transfer factors (TF) were in ranges 0.03-0.08 and 0.09-0.25, for (232)Th and (238)U, respectively. TFs for lead (Pb), chromium (Cr) and arsenic (As) were low (less than 0.5), while TFs for Cd were higher (about 10). Using the ERICA tool, the estimated radiation exposure dose rate of the earthworms ranged from 2.2 to 3.9 μGy/h. The radiological risk for investigated earthworms was low (0.28). The obtained results demonstrated that free-living earthworm species can survive in soil containing elevated (232)Th and (238)U, as well As, Cd, Pb and Cr levels, although certain amount of radionuclides was accumulated within their bodies. The present investigation contributes to general better understanding of complex soil-to-biota transfer processes of radionuclides and metals and to assessment

Evolution of electronic structure across the rare-earth RNiO 3 series

DOE PAGES

Freeland, John W.; van Veenendaal, Michel; Chakhalian, Jak

2015-07-31

Here, the perovksite rare-earth nickelates, RNiO 3 (R = La… Lu), are a class of materials displaying a rich phase-diagram of metallic and insulating phases associated with charge and magnetic order. Being in the charge transfer regime, Ni 3+ in octahedral coordination displays a strong hybridization with oxygen to form 3d-2p mixed states, which results in a strong admixture of 3d 8L_ into 3d 7, where L_ denotes a hole on the oxygen. To understand the nature of this strongly hybridized ground state, we present a detailed study of the Ni and O electronic structure using high-resolution soft X-ray absorptionmore » spectroscopy (XAS). Through a comparison of the evolution of the XAS line-shape at Ni L- and O K-edges across the phase diagram, we explore the changes in the electronic signatures in connection with the insulating and metallic phases that support the idea of hybridization playing a fundamental role.« less

SEPARATION OF METAL SALTS BY ADSORPTION

DOEpatents

Gruen, D.M.

1959-01-20

It has been found that certain metal salts, particularly the halides of iron, cobalt, nickel, and the actinide metals, arc readily absorbed on aluminum oxide, while certain other salts, particularly rare earth metal halides, are not so absorbed. Use is made of this discovery to separate uranium from the rare earths. The metal salts are first dissolved in a molten mixture of alkali metal nitrates, e.g., the eutectic mixture of lithium nitrate and potassium nitrate, and then the molten salt solution is contacted with alumina, either by slurrying or by passing the salt solution through an absorption tower. The process is particularly valuable for the separation of actinides from lanthanum-group rare earths.

Does the linear conversion between calcium infrared triplet and metallicity of globular clusters in early-type galaxies hold in the whole range of metallicity?

NASA Astrophysics Data System (ADS)

Chung, Chul; Yoon, Suk-Jin; Lee, Young-Wook; Lee, Sang-Yoon

2015-01-01

The calcium infrared triplet (CaT) is one of the prominent absorption features in the infrared wavelength regime. Recently, these absorption features have been getting attention in the prediction of metallicity of globular clusters (GCs) in early-type galaxies (ETGs) because of its strong sensitivity to the metallicity and calcium abundance of a star. However, based on our population synthesis model for CaT, we find that measuring metallicity directly from CaT is inaccurate because the formation mechanism of Ca II ionised line is very inefficient in the cool stars which are abundant in metal-rich stellar populations. This characteristics of Ca II ionised line make the CaT-metallicity relation to converge around 8 angstrom in the metal-rich regime. This is why the metallicity of simple stellar populations, such as GCs, greater than [Fe/H]~-0.5 is unreliable when the linear conversion between CaT and metallicity is applied to derive metallicity. In addition, we have successfully simulated the metal-rich CaT peaks found in GCs in ETGs by using the nonlinear CaT-metallicity relation in the metal-rich regime. This can also explain the difference between color and CaT distributions of GCs in various ETGs. Based on these results, we suggest that CaT is not a good metallicity indicator for the metal-rich stellar populations.

Measuring DAC metal-silicate partitioning experiments by electron microprobe: Thickness, fluorescence, and oxide spheres

NASA Astrophysics Data System (ADS)

Jennings, E. S.; Wade, J.; Laurenz, V.; Kearns, S.; Buse, B.; Rubie, D. C.

2017-12-01

The process by which the Earth's core segregated, and its resulting composition, can be inferred from the composition of the bulk silicate Earth if the partitioning of various elements into metal at relevant conditions is known. As such, partitioning experiments between liquid metal and liquid silicate over a wide range of pressures and temperatures are frequently performed to constrain the partitioning behaviour of many elements. The use of diamond anvil cell experiments to access more extreme conditions than those achievable by larger volume presses is becoming increasingly common. With a volume several orders of magnitude smaller than conventional samples, these experiments present unique analytical challenges. Typically, sample preparation is performed by FIB as a 2 mm thick slice, containing a small iron ball surrounded by a layer of silicate melt. This implies that analyses made by EPMA will be made near boundaries where fluoresced X-rays from the neighbouring phase may be significant. By measuring and simulating synthetic samples, we investigate thickness and fluorescence limitations. We find that for typical sample geometries, a thickness of 2 μm contains the entire analytical volume for standard 15kV analyses of metals. Fluoresced X-rays from light elements into the metal are below detection limits if there is no direct electron interaction with the silicate. Continuum fluorescence from higher atomic number elements from the metal into silicate poses significant difficulties [1]. This can cause metal-silicate partition coefficients of siderophile elements to be underestimated. Finally, we examine the origin and analytical consequences of oxide-rich exsolutions that are frequently found in the metal phase of such experiments. These are spherical with diameters of 100 nm and can be sparsely to densely packed. They appear to be carbon-rich and result in low analytical totals by violating the assumption of homogeneity in matrix corrections (e.g. φρz), which

Google Earth and Geo Applications: A Toolset for Viewing Earth's Geospatial Information

NASA Astrophysics Data System (ADS)

Tuxen-Bettman, K.

2016-12-01

Earth scientists measure and derive fundamental data that can be of broad general interest to the public and policy makers. Yet, one of the challenges that has always faced the Earth science community is how to present their data and findings in an easy-to-use and compelling manner. Google's Geo Tools offer an efficient and dynamic way for scientists, educators, journalists and others to both access data and view or tell stories in a dynamic three-dimensional geospatial context. Google Earth in particular provides a dense canvas of satellite imagery on which can be viewed rich vector and raster datasets using the medium of Keyhole Markup Language (KML). Through KML, Google Earth can combine the analytical capabilities of Earth Engine, collaborative mapping of My Maps, and storytelling of Tour Builder and more to make Google's Geo Applications a coherent suite of tools for exploring our planet.https://earth.google.com/https://earthengine.google.com/https://mymaps.google.com/https://tourbuilder.withgoogle.com/https://www.google.com/streetview/

Recovery of rare earths from spent NdFeB magnets of wind turbine: Leaching and kinetic aspects.

PubMed

Kumari, Aarti; Sinha, Manish Kumar; Pramanik, Swati; Sahu, Sushanta Kumar

2018-05-01

Increasing demands of rare earth (RE) metals for advanced technological applications coupled with the scarcity of primary resources have led to the development of processes to treat secondary resources like scraps or end of life products that are often rich in such metals. Spent NdFeB magnet may serve as a potential source of rare earths containing around ∼30% of neodymium and other rare earths. In the present investigation, a pyro-hydrometallurgical process has been developed to recover rare earth elements (Nd, Pr and Dy) from the spent wind turbine magnet. The spent magnet is demagnetized and roasted at 1123 K to convert rare earths and iron to their respective oxides. Roasting of the magnet not only provides selectivity, but enhances the leaching efficiency also. The leaching of the roasted sample with 0.5 M hydrochloric acid at 368 K, 100 g/L pulp density and 500 rpm for 300 min selectively recovers the rare earth elements almost quantitatively leaving iron oxide in the residue. Leaching of rare earth elements with hydrochloric acid follows the mixed controlled kinetic model with activation energy (E a ) of 30.1 kJ/mol in the temperature range 348-368 K. The leaching mechanism is further established by characterizing the leach residues obtained at different time intervals by scanning electron microscopy- energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction (XRD). Individual rare earth elements from the leach solution containing 16.8 g/L of Nd, 3.8 g/L Pr, 0.28 g/L of Dy and other minor impurity elements could be separated by solvent extraction. However, mixed rare earth oxide of 99% purity was produced by oxalate precipitation followed by roasting. The leach residue comprising of pure hematite has a potential to be used as pigment or can find other applications. Copyright © 2018 Elsevier Ltd. All rights reserved.

Rare Earth Polyoxometalates.

PubMed

Boskovic, Colette

2017-09-19

Longstanding and important applications make use of the chemical and physical properties of both rare earth metals and polyoxometalates of early transition metals. The catalytic, optical, and magnetic features of rare earth metal ions are well-known, as are the reversible multielectron redox and photoredox capabilities of polyoxomolybdates and polyoxotungstates. The combination of rare earth ions and polyoxometalates in discrete molecules and coordination polymers is of interest for the unique combination of chemical and physical properties that can arise. This Account surveys our efforts to synthesize and investigate compounds with rare earth ions and polyoxometalates (RE-POMs), sometimes with carboxylate-based organic coligands. Our general synthetic approach is "bottom-up", which affords well-defined nanoscale molecules, typically in crystalline form and amenable to single-crystal X-ray diffraction for structure determination. Our particular focus is on elucidation of the physical properties conferred by the different structural components with a view to ultimately being able to tune these properties chemically. For this purpose, we employ a variety of spectroscopic, magnetochemical, electrochemical, and scattering techniques in concert with theoretical modeling and computation. Studies of RE-POM single-molecule magnets (SMMs) have utilized magnetic susceptibility, inelastic neutron scattering, and ab initio calculations. These investigations have allowed characterization of the crystal field splitting of the rare earth(III) ions that is responsible for the SMM properties of slow magnetic relaxation and magnetization quantum tunneling. Such SMMs are promising for applications in quantum computing and molecular spintronics. Photophysical measurements of a family of hybrid RE-POMs with organic ligands have afforded insights into sensitization of Tb(III) and Eu(III) emission through both organic and polyoxometalate chromophores in the same molecule. Detailed

A combined calorimetric and computational study of the energetics of rare earth substituted UO 2 systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Lei; Solomon, Jonathan M.; Asta, Mark

2015-09-01

The energetics of rare earth substituted UO2 solid solutions (U1-xLnxO2-0.5x+y, where Ln = La, Y, and Nd) are investigated employing a combination of calorimetric measurements and density functional theory based computations. Calculated and measured formation enthalpies agree within 10 kJ/mol for stoichiometric oxygen/metal compositions. To better understand the factors governing the stability and defect binding in rare earth substituted urania solid solutions, systematic trends in the energetics are investigated based on the present results and previous computational and experimental thermochemical studies of rare earth substituted fluorite oxides (A1-xLnxO2-0.5x, where A = Hf, Zr, Ce, and Th). A consistent trend towardsmore » increased energetic stability with larger size mismatch between the smaller host tetravalent cation and the larger rare earth trivalent cation is found for both actinide and non-actinide fluorite oxide systems where aliovalent substitution of Ln cations is compensated by oxygen vacancies. However, the large exothermic oxidation enthalpy in the UO2 based systems favors oxygen rich compositions where charge compensation occurs through the formation of uranium cations with higher oxidation states.« less

Rare Earths; The Fraternal Fifteen (Rev.)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gschneidner, Jr., Karl A.

1966-01-01

Rare earths are a set of 15 elements: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. They are not rare and not earths; they are metals and quite abundant. They are studied to develop commercial products which are beneficial to mankind, and because some rare earths are important to fission products.

Magnetocaloric effect in heavy rare-earth elements doped Fe-based bulk metallic glasses with tunable Curie temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jiawei; Huo, Juntao; Chang, Chuntao, E-mail: ctchang@nimte.ac.cn, E-mail: dujun@nimte.ac.cn

2014-08-14

The effects of heavy rare earth (RE) additions on the Curie temperature (T{sub C}) and magnetocaloric effect of the Fe-RE-B-Nb (RE = Gd, Dy and Ho) bulk metallic glasses were studied. The type of dopping RE element and its concentration can easily tune T{sub C} in a large temperature range of 120 K without significantly decreasing the magnetic entropy change (ΔS{sub M}) and refrigerant capacity (RC) of the alloys. The observed values of ΔS{sub M} and RC of these alloys compare favorably with those of recently reported Fe-based metallic glasses with enhanced RC compared to Gd{sub 5}Ge{sub 1.9}Si{sub 2}Fe{sub 0.1}. The tunable T{submore » C} and large glass-forming ability of these RE doped Fe-based bulk metallic glasses can be used in a wide temperature range with the final required shapes.« less

Empirical links between trace metal cycling and marine microbial ecology during a large perturbation to Earth's carbon cycle

NASA Astrophysics Data System (ADS)

Owens, Jeremy D.; Reinhard, Christopher T.; Rohrssen, Megan; Love, Gordon D.; Lyons, Timothy W.

2016-09-01

Understanding the global redox state of the oceans and its cause-and-effect relationship with periods of widespread organic-carbon deposition is vital to interpretations of Earth's climatic and biotic feedbacks during periods of expanded oceanic oxygen deficiency. Here, we present a compilation of new and published data from an organic-rich locality within the proto-North Atlantic Ocean during the Cenomanian-Turonian boundary event that shows a dramatic drawdown of redox-sensitive trace elements. Iron geochemistry independently suggests euxinic deposition (i.e., anoxic and sulfidic bottom waters) for the entire section, thus confirming its potential as an archive of global marine metal inventories. In particular, depleted molybdenum (Mo) and vanadium (V) concentrations effectively record the global expansion of euxinic and oxygen-deficient but non-sulfidic waters, respectively. The V drawdown precedes the OAE, fingerprinting an expansion of oxygen deficiency prior to an expansion of euxinia. Molybdenum drawdown, in contrast, is delayed with respect to V and coincides with the onset of OAE2. Parallel lipid biomarker analyses provide evidence for significant and progressive reorganization of marine microbial ecology during the OAE in this region of the proto-North Atlantic, with the smallest relative eukaryotic contributions to total primary production occurring during metal-depleted intervals. This relationship may be related to decreasing supplies of enzymatically important trace elements. Similarly, box modeling suggests that oceanic drawdown of Mo may have approached levels capable of affecting marine nitrogen fixation. Predictions of possible nitrogen stress on eukaryotic production, locally and globally, are consistent with the low observed levels of Mo and a rise in 2-methylhopane index values during the peak of the OAE. At the same time, the environmental challenge presented by low dissolved oxygen and euxinia coincides with increased turnover rates of

Impact of biostimulated redox processes on metal dynamics in an iron-rich creek soil of a former uranium mining area.

PubMed

Burkhardt, Eva-Maria; Akob, Denise M; Bischoff, Sebastian; Sitte, Jana; Kostka, Joel E; Banerjee, Dipanjan; Scheinost, Andreas C; Küsel, Kirsten

2010-01-01

Understanding the dynamics of metals and radionuclides in soil environments is necessary for evaluating risks to pristine sites. An iron-rich creek soil of a former uranium-mining district (Ronneburg, Germany) showed high porewater concentrations of heavy metals and radionuclides. Thus, this study aims to (i) evaluate metal dynamics during terminal electron accepting processes (TEAPs) and (ii) characterize active microbial populations in biostimulated soil microcosms using a stable isotope probing (SIP) approach. In biostimulated soil slurries, concentrations of soluble Co, Ni, Zn, As, and unexpectedly U increased during Fe(III)-reduction. This suggests that there was a release of sorbed metals and As during reductive dissolution of Fe(III)-oxides. Subsequent sulfate-reduction was concurrent with a decrease of U, Co, Ni, and Zn concentrations. The relative contribution of U(IV) in the solid phase changed from 18.5 to 88.7% after incubation. The active Fe(III)-reducing population was dominated by delta-Proteobacteria (Geobacter) in (13)C-ethanol amended microcosms. A more diverse community was present in (13)C-lactate amended microcosms including taxa related to Acidobacteria, Firmicutes, delta-Proteobacteria, and beta-Proteobacteria. Our results suggested that biostimulated Fe(III)-reducing communities facilitated the release of metals including U to groundwater which is in contrast to other studies.

Non-rare earth magnetic nanoparticles

DOEpatents

Carpenter, Everett E.; Huba, Zachary J.; Carroll, Kyler J.; Farghaly, Ahmed; Khanna, Shiv N.; Qian, Meichun; Bertino, Massimo

2017-09-26

Continuous flow synthetic methods are used to make single phase magnetic metal alloy nanoparticles that do not contain rare earth metals. Soft and hard magnets made from the magnetic nanoparticles are used for a variety of purposes, e.g. in electric motors, communication devices, etc.

Cross-Cutting Interoperability in an Earth Science Collaboratory

NASA Technical Reports Server (NTRS)

Lynnes, Christopher; Ramachandran, Rahul; Kuo, Kuo-Sen

2011-01-01

An Earth Science Collaboratory is: A rich data analysis environment with: (1) Access to a wide spectrum of Earth Science data, (3) A diverse set of science analysis services and tools, (4) A means to collaborate on data, tools and analysis, and (5)Supports sharing of data, tools, results and knowledge

Mineral resource of the month: rare earth elements

USGS Publications Warehouse

,

2011-01-01

The article provides information on rare earth elements, which are group of 17 natural metallic elements. The rare earth elements are scandium, yttrium and lanthanides and classified into light rare earth elements (LREE) and heavy rate earth elements (HREE). The principal ores of the rare earth elements are identified. An overview of China's production of 97 percent of the rare earths in the world is provided. Commercial applications of rare earths are described.

β-decay half-lives of new neutron-rich rare-earth isotopes 159Pm,162Sm, and 166Gd

NASA Astrophysics Data System (ADS)

Ichikawa, S.; Asai, M.; Tsukada, K.; Haba, H.; Nagame, Y.; Shibata, M.; Sakama, M.; Kojima, Y.

2005-06-01

The new neutron-rich rare-earth isotopes 159Pm, 162Sm, and 166Gd produced in the proton-induced fission of 238U were identified using the JAERI on-line isotope separator (JAERI-ISOL) coupled to a gas-jet transport system. The half-lives of 159Pm, 162Sm, and 166Gd were determined to be 1.5 ± 0.2, 2.4 ± 0.5, and 4.8 ± 1.0 s respectively. The partial decay scheme of 166Gd was constructed from γγ-coincidence data. A more accurate half-life value of 25.6 ± 2.2 s was obtained for the previously identified isotope 166Tb. The half-lives measured in the present study are in good agreement with the theoretical predictions calculated by the second generation of the gross theory with the atomic masses evaluated by Audi and Wapstra.

Stability and anisotropy of (FexNi1-x)2O under high pressure and implications in Earth's and super-Earths' core.

PubMed

Huang, Shengxuan; Wu, Xiang; Qin, Shan

2018-01-10

Oxygen is thought to be an important light element in Earth's core but the amount of oxygen in Earth's core remains elusive. In addition, iron-rich iron oxides are of great interest and significance in the field of geoscience and condensed matter physics. Here, static calculations based on density functional theory demonstrate that I4/mmm-Fe 2 O is dynamically and mechanically stable and becomes energetically favorable with respect to the assemblage of hcp-Fe and [Formula: see text]-FeO above 270 GPa, which indicates that I4/mmm-Fe 2 O can be a strong candidate phase for stable iron-rich iron oxides at high pressure, perhaps even at high temperature. The elasticity and anisotropy of I4/mmm-(Fe x Ni 1-x ) 2 O at high pressures are also determined. Based on these results, we have derived the upper limit of oxygen to be 4.3 wt% in Earth's lower outer core. On the other hand, I4/mmm-(Fe x Ni 1-x ) 2 O with high AV S is likely to exist in a super-Earth's or an ocean planet's solid core causing the locally seismic heterogeneity. Our results not only give some clues to explore and synthesize novel iron-rich iron oxides but also shed light on the fundamental information of oxygen in the planetary core.

The Rare Earth Magnet Industry and Rare Earth Price in China

NASA Astrophysics Data System (ADS)

Ding, Kaihong

2014-07-01

In the past four years, the price of rare earth metal fluctuates sharply for many reasons. Currently, it has become more stable and more reasonable. This presentation is focused on the effect about the rare earth metal price. Some motor manufacturers have shifted from rare earth permanent magnet to ferrite magnet. Many motor manufacturers changed the design for the motor cooling system to make the motor function at a lower temperature. Thus the consumption of Dy can be markedly reduced. As for manufacturer of NdFeB magnet, we are also trying to optimize our process to reduce to dependence of HREE such as Dy and Tb. HS process have been introduced to solve the problem. With more and more people focusing and engaging on the REE industry, the price of REE will be more transparent without too many fluctuations. China is considering the problems of balancing the environment, energy sources, and labor sources. The application field about NdFeB such as wind turbine generator, HEV/EV, FA /OA is flourishing.

Efficiently Communicating Rich Heterogeneous Geospatial Data from the FeMO2008 Dive Cruise with FlashMap on EarthRef.org

NASA Astrophysics Data System (ADS)

Minnett, R. C.; Koppers, A. A.; Staudigel, D.; Staudigel, H.

2008-12-01

EarthRef.org is comprehensive and convenient resource for Earth Science reference data and models. It encompasses four main portals: the Geochemical Earth Reference Model (GERM), the Magnetics Information Consortium (MagIC), the Seamount Biogeosciences Network (SBN), and the Enduring Resources for Earth Science Education (ERESE). Their underlying databases are publically available and the scientific community has contributed widely and is urged to continue to do so. However, the net result is a vast and largely heterogeneous warehouse of geospatial data ranging from carefully prepared maps of seamounts to geochemical data/metadata, daily reports from seagoing expeditions, large volumes of raw and processed multibeam data, images of paleomagnetic sampling sites, etc. This presents a considerable obstacle for integrating other rich media content, such as videos, images, data files, cruise tracks, and interoperable database results, without overwhelming the web user. The four EarthRef.org portals clearly lend themselves to a more intuitive user interface and has, therefore, been an invaluable test bed for the design and implementation of FlashMap, a versatile KML-driven geospatial browser written for reliability and speed in Adobe Flash. FlashMap allows layers of content to be loaded and displayed over a streaming high-resolution map which can be zoomed and panned similarly to Google Maps and Google Earth. Many organizations, from National Geographic to the USGS, have begun using Google Earth software to display geospatial content. However, Google Earth, as a desktop application, does not integrate cleanly with existing websites requiring the user to navigate away from the browser and focus on a separate application and Google Maps, written in Java Script, does not scale up reliably to large datasets. FlashMap remedies these problems as a web-based application that allows for seamless integration of the real-time display power of Google Earth and the flexibility of

Metal concentrations in the tissues of the hydrothermal vent mussel Bathymodiolus: reflection of different metal sources.

PubMed

Koschinsky, Andrea; Kausch, Matteo; Borowski, Christian

2014-04-01

Hydrothermal vent mussels of the genus Bathymodiolus are ideally positioned for the use of recording hydrothermal fluxes at the hydrothermal vent sites they inhabit. Barium, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Pb, Sr, and U concentrations in tissue sections of Bathymodiolus mussels from several hydrothermal fields between 15°N and 9°S at the Mid-Atlantic Ridge were determined and compared to the surrounding fluids and solid substrates in the habitats. Elements generally enriched in hydrothermal fluids, such as Fe, Cu, Zn, Pb and Cd, were significantly enriched in the gills and digestive glands of the hydrothermal mussels. The rather small variability of Zn (and Mn) and positive correlation with K and earth alkaline metals may indicate a biological regulation of accumulation. Enrichments of Mo and U in many tissue samples indicate that particulate matter such as hydrothermal mineral particles from the plumes can play a more important role as a metal source than dissolved metals. Highest enrichments of Cu in mussels from the Golden Valley site indicate a relation to the ≥400 °C hot heavy-metal rich fluids emanating in the vicinity. In contrast, mussels from the low-temperature Lilliput field are affected by the Fe oxyhydroxide sediment of their habitat. In a comparison of two different sites within the Logatchev field metal distributions in the tissues reflected small-scale local variations in the metal content of the fluids and the particulate material. Copyright © 2014 Elsevier Ltd. All rights reserved.

A carbon-rich region in Miller Range 091004 and implications for ureilite petrogenesis

NASA Astrophysics Data System (ADS)

Day, James M. D.; Corder, Christopher A.; Cartigny, Pierre; Steele, Andrew M.; Assayag, Nelly; Rumble, Douglas; Taylor, Lawrence A.

2017-02-01

Ureilite meteorites are partially melted asteroidal-peridotite residues, or more rarely, cumulates that can contain greater than three weight percent carbon. Here we describe an exceptional C-rich lithology, composed of 34 modal % large (up to 0.8 mm long) crystalline graphite grains, in the Antarctic ureilite meteorite Miller Range (MIL) 091004. This C-rich lithology is embedded within a silicate region composed dominantly of granular olivine with lesser quantities of low-Ca pyroxene, and minor FeNi metal, high-Ca pyroxene, spinel, schreibersite and troilite. Petrological evidence indicates that the graphite was added after formation of the silicate region and melt depletion. Associated with graphite is localized reduction of host olivine (Fo88-89) to nearly pure forsterite (Fo99), which is associated with FeNi metal grains containing up to 11 wt.% Si. The main silicate region is typical of ureilite composition, with highly siderophile element (HSE) abundances ∼0.3 × chondrite, 187Os/188Os of 0.1260-0.1262 and Δ17O of -0.81 ± 0.16‰. Mineral trace-element analyses reveal that the rare earth elements (REE) and the HSE are controlled by pyroxene and FeNi metal phases in the meteorite, respectively. Modeling of bulk-rock REE and HSE abundances indicates that the main silicate region experienced ∼6% silicate and >50% sulfide melt extraction, which is at the lower end of partial melt removal estimated for ureilites. Miller Range 091004 demonstrates heterogeneous distribution of carbon at centimeter scales and a limited range in Mg/(Mg + Fe) compositions of silicate grain cores, despite significant quantities of carbon. These observations demonstrate that silicate rim reduction was a rapid disequilibrium process, and came after silicate and sulfide melt removal in MIL 091004. The petrography and mineral chemistry of MIL 091004 is permissive of the graphite representing late-stage C-rich melt that pervaded silicates, or carbon that acted as a lubricant during

THEORETICAL TRANSIT SPECTRA FOR GJ 1214b AND OTHER 'SUPER-EARTHS'

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howe, Alex R.; Burrows, Adam S., E-mail: arhowe@astro.princeton.edu, E-mail: burrows@astro.princeton.edu

2012-09-10

We present new calculations of transit spectra of super-Earths that allow for atmospheres with arbitrary proportions of common molecular species and haze. We test this method with generic spectra, reproducing the expected systematics and absorption features, then apply it to the nearby super-Earth GJ 1214b, which has produced conflicting observational data, leaving the questions of a hydrogen-rich versus hydrogen-poor atmosphere and the water content of the atmosphere ambiguous. We present representative transit spectra for a range of classes of atmosphere models for GJ 1214b. Our analysis supports a hydrogen-rich atmosphere with a cloud or haze layer, although a hydrogen-poor modelmore » with {approx}<10% water is not ruled out. Several classes of models are ruled out, however, including hydrogen-rich atmospheres with no haze, hydrogen-rich atmospheres with a haze of {approx}0.01 {mu}m tholin particles, and hydrogen-poor atmospheres with major sources of absorption other than water. We propose an observational test to distinguish hydrogen-rich from hydrogen-poor atmospheres. Finally, we provide a library of theoretical transit spectra for super-Earths with a broad range of parameters to facilitate future comparison with anticipated data.« less

Tutorial on the Role of Cyclopentadienyl Ligands in the Discovery of Molecular Complexes of the Rare-Earth and Actinide Metals in New Oxidation States

DOE PAGES

Evans, William J.

2016-09-15

A fundamental aspect of any element is the range of oxidation states accessible for useful chemistry. This tutorial describes the recent expansion of the number of oxidation states available to the rare-earth and actinide metals in molecular complexes that has resulted through organometallic chemistry involving the cyclopentadienyl ligand. These discoveries demonstrate that the cyclopentadienyl ligand, which has been a key component in the development of organometallic chemistry since the seminal discovery of ferrocene in the 1950s, continues to contribute to the advancement of science. Lastly, we present background information on the rare-earth and actinide elements, as well as the sequencemore » of events that led to these unexpected developments in the oxidation state chemistry of these metals.« less

Tutorial on the Role of Cyclopentadienyl Ligands in the Discovery of Molecular Complexes of the Rare-Earth and Actinide Metals in New Oxidation States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evans, William J.

A fundamental aspect of any element is the range of oxidation states accessible for useful chemistry. This tutorial describes the recent expansion of the number of oxidation states available to the rare-earth and actinide metals in molecular complexes that has resulted through organometallic chemistry involving the cyclopentadienyl ligand. These discoveries demonstrate that the cyclopentadienyl ligand, which has been a key component in the development of organometallic chemistry since the seminal discovery of ferrocene in the 1950s, continues to contribute to the advancement of science. Lastly, we present background information on the rare-earth and actinide elements, as well as the sequencemore » of events that led to these unexpected developments in the oxidation state chemistry of these metals.« less

Selectivity sequences and sorption capacities of phosphatic clay and humus rich soil towards the heavy metals present in zinc mine tailing.

PubMed

Chaturvedi, Pranav Kumar; Seth, Chandra Shekhar; Misra, Virendra

2007-08-25

Sorption efficacy of phosphatic clay and humus rich soil alone and on combination were tested towards heavy metals present in zinc mine tailing (Zawar Zinc Mine), Udaipur (India). Characterization of the zinc mine tailing sample indicated the presence of Pb, Cu, Zn and Mn in the concentration of 637, 186, 720 and 577microg(-1), respectively. For sorption efficacy, the zinc mine tailing soil were properly amended with phosphatic clay and humus rich soil separately and in combination and leachability study was performed by batch experiment at different pH range from 3 to 9. The data showed that the percent leachability of heavy metal in non-amended soil was 75-90%. After amendment with phosphatic clay percent leachability of heavy metals became 35-45%. Further, the addition of humus soil to phosphatic clay decreased the percent leachability up to 5-15% at all tested pH. Column leachability experiment was performed to evaluate the rate of leachability. The shape of cumulative curves of Pb, Cu, Zn and Mn showed an increase in its concavity in following order: PbCu>Zn>Mn. Further, Langmuir isotherms applied for the sorption studies indicated that phosphatic clay in the presence of humus soil had high affinity for Pb followed by Cu, Zn and Mn, with sorption capacities (b) 139.94, 97.02, 83.32 and 67.58microgg(-1), respectively.

The episodic influx of tin-rich cosmic dust particles during the last ice age

NASA Astrophysics Data System (ADS)

LaViolette, Paul A.

2015-12-01

was found to contain tin-rich particles with a similar platy morphology and to have Sn and Pb weight abundances averaging 39% and 7.5% respectively, again approximating the interstellar Sn:Pb ratio. The relative absence of cosmic microspheres and the unmelted appearance of the tin-rich particles in both of these samples suggests that these particles entered the Earth's atmosphere at low velocity, implicating a gradual accumulation of dust from a dispersed state in the near Earth space environment. The unusual enhancement of Sn and Pb could be explained if these dust particles were originally present in the solar system's interstellar environment in a superconducting native metal state and were preferentially concentrated through Meissner effect forces by the passage of cosmic ray driven hydromagnetic shocks which may also have transported them into the solar system. The 49 kyrs BP event is estimated to have lasted over 6 years and to have deposited dust onto the Earth at a rate 104-105 times higher than present rates. This had a significant cooling effect on climate and resulted in a transient 33 fold increase in snow accumulation. Future discovery of these events in ice cores at other locations should void any lingering thoughts that this heavy metal enhancement may be due to sample contamination.

Board on Earth Sciences and Resources and its Activities

NASA Technical Reports Server (NTRS)

Schiffries, Craig M.

1997-01-01

The Board will provide oversight of the earth science and resource activities within the National Research Council, provide a review of research and public activities in the solid-earth sciences, and provide analyses and recommendations relevant to the supply, delivery, and associated impacts of and issues related to hydrocarbon, metallic, and non-metallic mineral resources. The Board will monitor the status of the earth sciences, assess the health of the disciplines, and identify research opportunities, and will respond to specific agency requests.

Alkaline-earth metal carboxylates characterized by 43Ca and 87Sr solid-state NMR: impact of metal-amine bonding.

PubMed

Burgess, Kevin M N; Xu, Yang; Leclerc, Matthew C; Bryce, David L

2014-01-06

A series of calcium and strontium complexes featuring aryl carboxylate ligands has been prepared and characterized by alkaline-earth ((43)Ca and (87)Sr) solid-state NMR experiments in a magnetic field of 21.1 T. In the 11 compounds studied as part of this work, a range of coordination motifs are observed including nitrogen atom binding to Ca(2+) and Sr(2+), a binding mode which has not been investigated previously by (43)Ca or (87)Sr solid-state NMR. (43)Ca isotopic enrichment has enabled the full characterization of the (43)Ca electric field gradient (EFG) and chemical shift tensors of the two calcium sites in calcium p-aminosalicylate (Ca(pams)), where both NMR interactions are affected by the presence of a nitrogen atom in the first coordination sphere of one of the metal sites. The (43)Ca isotropic chemical shift is sensitive to the Ca-N distance as exemplified by the NMR parameters of a second form of Ca(pams) and density functional theory (DFT) calculations. Studies of the strontium analogue, Sr(pams), confirm a similar sensitivity of the (87)Sr EFG tensor to the presence or absence of nitrogen in the first coordination sphere. To our knowledge, this is the first systematic (87)Sr NMR study of strontium complexes featuring organic ligands. The |CQ((87)Sr)| values are found to be sensitive to the coordination number about Sr(2+). In general, this work has also established a larger data set of reliable experimental |CQ((43)Ca)| values which correlate well with those obtained using gauge-including projector-augmented-wave (GIPAW) DFT calculations. It is found that the use of a recently recommended quadrupole moment for (43)Ca, -44.4 mbarn, improves the agreement with experimental values. This contribution lays the groundwork for the interpretation of (43)Ca and (87)Sr NMR spectra of more challenging systems, particularly where nitrogen-alkaline earth metal bonding is occurring.

Metal loading levels influence on REE distribution on humic acid: Experimental and Modelling approach

NASA Astrophysics Data System (ADS)

Marsac, R.; Davranche, M.; Gruau, G.; Dia, A.

2009-04-01

In natural organic-rich waters, rare earth elements (REE) speciation is mainly controlled by organic colloids such as humic acid (HA). Different series of REE-HA complexation experiments performed at several metal loading (REE/C) displayed two pattern shapes (i) at high metal loading, a middle-REE (MREE) downward concavity, and (ii) at low metal loading, a regular increase from La to Lu (e.g. Sonke and Salters, 2006; Pourret et al., 2007). Both REE patterns might be related to REE binding with different surface sites on HA. To understand REE-HA binding, REE-HA complexation experiments at various metals loading were carried out using ultrafiltration combined with ICP-MS measurements, for the 14 REE simultaneously. The patterns of the apparent coefficients of REE partition between HA and the inorganic solution (log Kd) evolved regularly according to the metal loading. The REE patterns presented a MREE downward concavity at low loading and a regular increase from La to Lu at high loading. The dataset was modelled with Model VI by adjusting two specific parameters, log KMA, the apparent complexation constant of HA low affinity sites and DLK2, the parameter increasing high affinity sites binding strength. Experiments and modelling provided evidence that HA high affinity sites controlled the REE binding with HA at low metal loading. The REE-HA complex could be as multidentate complexes with carboxylic or phenolic sites or potentially with sites constituted of N, P or S as donor atoms. Moreover, these high affinity sites could be different for light and heavy REE, because heavy REE have higher affinity for these sites, in low density, and could saturate them. These new Model VI parameter sets allowed the prediction of the REE-HA pattern shape evolution on a large range of pH and metal loading. According to the metal loading, the evolution of the calculated REE patterns was similar to the various REE pattern observed in natural acidic organic-rich waters (pH<7 and DOC>10

An Operationally Simple Method for Separating the Rare-Earth Elements Neodymium and Dysprosium.

PubMed

Bogart, Justin A; Lippincott, Connor A; Carroll, Patrick J; Schelter, Eric J

2015-07-06

Rare-earth metals are critical components of electronic materials and permanent magnets. Recycling of consumer materials is a promising new source of rare earths. To incentivize recycling there is a clear need for simple methods for targeted separations of mixtures of rare-earth metal salts. Metal complexes of a tripodal nitroxide ligand [{(2-(t) BuNO)C6 H4 CH2 }3 N](3-) (TriNOx(3-) ), feature a size-sensitive aperture formed of its three η(2) -(N,O) ligand arms. Exposure of metal cations in the aperture induces a self-associative equilibrium comprising [M(TriNOx)thf]/ [M(TriNOx)]2 (M=rare-earth metal). Differences in the equilibrium constants (Keq ) for early and late metals enables simple Nd/Dy separations through leaching with a separation ratio SNd/Dy =359. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetic ordering temperatures in rare earth metal dysprosium under ultrahigh pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.

Magnetic ordering temperatures in heavy rare earth metal Dysprosium (Dy) have been studied using an ultrasensitive electrical transport measurement technique in a designer diamond anvil cell to extreme conditions of pressure to 69 GPa and temperature to 10 K. Previous studies using magnetic susceptibility measurements at high pressures were only able to track magnetic ordering temperature till 7 GPa in the hexagonal close packed ( hcp) phase of Dy. Our studies indicate that the magnetic ordering temperature shows an abrupt drop of 80 K at the hcp-Sm phase transition followed by a gradual decrease that continues till 17 GPa. Thismore » is followed by a rapid increase in the magnetic ordering temperatures in the double hexagonal close packed phase and finally leveling off in the distorted face centered cubic phase of Dy. Lastly, our studies reaffirm that 4f-shell remain localized in Dy and there is no loss of magnetic moment or 4f-shell delocalization for pressures up to 69 GPa.« less

Magnetic ordering temperatures in rare earth metal dysprosium under ultrahigh pressures

DOE PAGES

Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.; ...

2014-04-03

Magnetic ordering temperatures in heavy rare earth metal Dysprosium (Dy) have been studied using an ultrasensitive electrical transport measurement technique in a designer diamond anvil cell to extreme conditions of pressure to 69 GPa and temperature to 10 K. Previous studies using magnetic susceptibility measurements at high pressures were only able to track magnetic ordering temperature till 7 GPa in the hexagonal close packed ( hcp) phase of Dy. Our studies indicate that the magnetic ordering temperature shows an abrupt drop of 80 K at the hcp-Sm phase transition followed by a gradual decrease that continues till 17 GPa. Thismore » is followed by a rapid increase in the magnetic ordering temperatures in the double hexagonal close packed phase and finally leveling off in the distorted face centered cubic phase of Dy. Lastly, our studies reaffirm that 4f-shell remain localized in Dy and there is no loss of magnetic moment or 4f-shell delocalization for pressures up to 69 GPa.« less

Binary rare earth element-Ni/Co metallic glasses with distinct β-relaxation behaviors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Z. G.; Wang, Z.; Wang, W. H., E-mail: whw@iphy.ac.cn

2015-10-21

We report the formation of a series of rare earth element (RE)-Ni/Co binary metallic glasses (MGs) with unusual distinct β-relaxation peak compared with that of most of the reported MGs which usually exhibit as an excess wing or a shoulder. The β-relaxation behavior of RE-Ni/Co MGs is sensitive to the composition and the atomic radii of the RE and can be tuned through changing the fraction of RE-Ni (or Co) atomic pairs. The novel RE-Ni/Co MGs with distinct β-relaxation can serve as model system to investigate the nature of the β-relaxation as well as its relations with other physical andmore » mechanical properties of MGs.« less

Oxidative stress and reduced responsiveness of challenged circulating leukocytes following pulmonary instillation of metal-rich particulate matter in rats

PubMed Central

2014-01-01

Welding fume is an exposure that consists of a mixture of metal-rich particulate matter with gases (ozone, carbon monoxide) and/or vapors (VOCs). Data suggests that welders are immune compromised. Given the inability of pulmonary leukocytes to properly respond to a secondary infection in animal models, the question arose whether the dysfunction persisted systemically. Our aim was to evaluate the circulating leukocyte population in terms of cellular activation, presence of oxidative stress, and functionality after a secondary challenge, following welding fume exposure. Rats were intratracheally instilled (ITI) with PBS or 2 mg of welding fume collected from a stainless steel weld. Rats were sacrificed 4 and 24 h post-exposure and whole blood was collected. Whole blood was used for cellular differential counts, RNA isolation with subsequent microarray and Ingenuity Pathway Analysis, and secondary stimulation with LPS utilizing TruCulture technology. In addition, mononuclear cells were isolated 24 h post-exposure to measure oxidative stress by flow cytometry and confocal microscopy. Welding fume exposure had rapid effects on the circulating leukocyte population as identified by relative mRNA expression changes. Instillation of welding fume reduced inflammatory protein production of circulating leukocytes when challenged with the secondary stimulus LPS. The effects were not related to transcription, but were observed in conjunction with oxidative stress. These findings support previous studies of an inadequate pulmonary immune response following a metal-rich exposure and extend those findings showing leukocyte dysfunction occurs systemically. PMID:25123171

Oxidative stress and reduced responsiveness of challenged circulating leukocytes following pulmonary instillation of metal-rich particulate matter in rats.

PubMed

Erdely, Aaron; Antonini, James M; Young, Shih-Houng; Kashon, Michael L; Gu, Ja K; Hulderman, Tracy; Salmen, Rebecca; Meighan, Terence; Roberts, Jenny R; Zeidler-Erdely, Patti C

2014-08-15

Welding fume is an exposure that consists of a mixture of metal-rich particulate matter with gases (ozone, carbon monoxide) and/or vapors (VOCs). Data suggests that welders are immune compromised. Given the inability of pulmonary leukocytes to properly respond to a secondary infection in animal models, the question arose whether the dysfunction persisted systemically. Our aim was to evaluate the circulating leukocyte population in terms of cellular activation, presence of oxidative stress, and functionality after a secondary challenge, following welding fume exposure. Rats were intratracheally instilled (ITI) with PBS or 2 mg of welding fume collected from a stainless steel weld. Rats were sacrificed 4 and 24 h post-exposure and whole blood was collected. Whole blood was used for cellular differential counts, RNA isolation with subsequent microarray and Ingenuity Pathway Analysis, and secondary stimulation with LPS utilizing TruCulture technology. In addition, mononuclear cells were isolated 24 h post-exposure to measure oxidative stress by flow cytometry and confocal microscopy. Welding fume exposure had rapid effects on the circulating leukocyte population as identified by relative mRNA expression changes. Instillation of welding fume reduced inflammatory protein production of circulating leukocytes when challenged with the secondary stimulus LPS. The effects were not related to transcription, but were observed in conjunction with oxidative stress. These findings support previous studies of an inadequate pulmonary immune response following a metal-rich exposure and extend those findings showing leukocyte dysfunction occurs systemically.

Combustion synthesis of low exothermic component rich composites

DOEpatents

Halverson, Danny C.; Lum, Beverly Y.; Munir, Zuhair A.

1991-01-01

A self-sustaining combustion synthesis process for producing hard, tough, lightweight, low exothermic potential product (LEPP)/high exothermic potential product (HEPP) composites is based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the LEPP and HEPP reactants. For lightweight products the composition must be relatively rich in the LEPP component. LEPP rich composites are obtained by varying the initial temperature of the reactants. The product is hard, porous material whose toughness can be enhanced by filling the pores with aluminum or other metal phases using a liquid metal infiltration process. The process can be extended to the formation of other composites having a low exothermic component.

Anthropogenic accumulation of metals and metalloids in carbonate-rich sediments: Insights from the ancient harbor setting of Tyre (Lebanon)

NASA Astrophysics Data System (ADS)

Elmaleh, A.; Galy, A.; Allard, T.; Dairon, R.; Day, J. A.; Michel, F.; Marriner, N.; Morhange, C.; Couffignal, F.

2012-04-01

The Antique and Byzantine sediments of the northern harbor of Tyre (Lebanon) store high amounts of metals and metalloids as the result of a millennial anthropogenic contamination as well as of efficient trapping and immobilization processes. Geochemical and mineralogical analyses reveal the contrasted patterns for the accumulation of trace metal(loid)s in the sedimentary sequence recovered by coring the inner part, now emerged, of the ancient harbor. Lead, Sn, Cu and Ag concentrations can be as high as 3000, 150, 1000, and 1.2 μg/g, respectively. Enrichment factors were calculated with respect to (1) Th and (2) the chemistry of the substratum and appear to be driven by anthropogenic inputs. Indeed, a drastic change in both excess concentrations and concentration ratios is observed through Roman and Byzantine times, pointing to major intensification of the trade and use of metals in Tyre, coherent with historical data. Good preservation of the archeological signal, despite (1) sediment disturbances that have caused age depth inversions, and (2) the large time lapse since the time of deposition of anthropogenic trace metal(loid)s is probably due to the reducing character of the sediments. Tyre's sedimentary sequence provides an interesting analog for modern carbonate-rich harbor environments, in which a millenary accumulation of trace metal(loid)s has been overall well preserved and suggests a restricted mobility of anthropogenic contamination for a period of time in excess of 1500 years.

Chemical study of the metal-rich globular cluster NGC 5927

NASA Astrophysics Data System (ADS)

Mura-Guzmán, A.; Villanova, S.; Muñoz, C.; Tang, B.

2018-03-01

Globular clusters (GCs) are natural laboratories where stellar and chemical evolution can be studied in detail. In addition, their chemical patterns and kinematics can tell us to which Galactic structure (disc, bulge, halo or extragalactic) the cluster belongs to. NGC 5927 is one of most metal-rich GCs in the Galaxy and its kinematics links it to the thick disc. We present abundance analysis based on high-resolution spectra of seven giant stars. The data were obtained using Fibre Large Array Multi Element Spectrograph/Ultraviolet Echelle Spectrograph (UVES) spectrograph mounted on UT2 telescope of the European Southern Observatory. The principal objective of this work is to perform a wide and detailed chemical abundance analysis of the cluster and look for possible Multiple Populations (MPs). We determined stellar parameters and measured 22 elements corresponding to light (Na, Al), alpha (O, Mg, Si, Ca, Ti), iron-peak (Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), and heavy elements (Y, Zr, Ba, Ce, Nd, Eu). We found a mean iron content of [Fe/H] = -0.47 ± 0.02 (error on the mean). We confirm the existence of MPs in this GC with an O-Na anti-correlation, and moderate spread in Al abundances. We estimate a mean [α/Fe] = 0.25 ± 0.08. Iron-peak elements show no significant spread. The [Ba/Eu] ratios indicate a predominant contribution from SNeII for the formation of the cluster.

Partitioning of carbon between Fe-rich alloy melt and silicate melt in a magma ocean - Implications for the abundance and origin of volatiles in Earth, Mars, and the Moon

NASA Astrophysics Data System (ADS)

Chi, Han; Dasgupta, Rajdeep; Duncan, Megan S.; Shimizu, Nobumichi

2014-08-01

The budget and origin of carbon in Earth and other terrestrial planets are debated and one of the key unknowns is the fate of carbon during early planetary processes including accretion, core formation, and magma ocean (MO) crystallization. Here we determine, experimentally, the solubility of carbon in coexisting Fe-Ni alloy melt and basaltic silicate melt in shallow MO conditions, i.e., at 1-3 GPa, 1500-1800 °C. Oxygen fugacity of the experiments, estimated based on Fe (in metallic alloy melt)-FeO (in silicate melt) equilibrium, varied between ∼IW-0.4 and IW-1.0, where IW refers to the oxygen fugacity imposed by the coexistence of iron and wüstite. Four different starting mixes, each with 7:3 silicate:metal mass ratio and silicate melt NBO/T (estimated proportion of non-bridging oxygen with respect to tetrahedral cations; NBO/T=2×/total OT -4, where T = Si + Ti + Al + Cr + P) ranging from 0.81 to 1.54 were studied. Concentrations of carbon in the alloy melt were determined using electron microprobe whereas carbon contents of quenched basaltic glasses were determined using secondary ionization mass spectrometry (SIMS). Identification of carbon and hydrogen-bearing species in silicate glasses was performed using Raman and Fourier Transformed Infrared (FTIR) spectroscopy. Our results show that carbon in the metallic melt varies between 4.4 wt.% and 7.4 wt.% and increases with increasing temperature and modestly with increasing pressure but decreases with increasing Ni content of the alloy melt. Carbon concentration in the silicate melts, on the other hand, varies from 11 ± 1 ppm to 111 ± 7 ppm and is negatively correlated with pressure but positively correlated with temperature, the NBO/T, the oxygen fugacity and the water content of the silicate melts. Raman and FTIR results show that at our experimental conditions, carbon in silicate melt is dissolved both as hydrogenated species and CO32-. The calculated carbon partition coefficient DCmetal/silicate varies

Isotopes as clues to the origin and earliest differentiation history of the Earth.

PubMed

Jacobsen, Stein B; Ranen, Michael C; Petaev, Michael I; Remo, John L; O'Connell, Richard J; Sasselov, Dimitar D

2008-11-28

Measurable variations in (182)W/(183)W, (142)Nd/(144)Nd, (129)Xe/(130)Xe and (136)XePu/(130)Xe in the Earth and meteorites provide a record of accretion and formation of the core, early crust and atmosphere. These variations are due to the decay of the now extinct nuclides (182)Hf, (146)Sm, (129)I and (244)Pu. The (l82)Hf-(182)W system is the best accretion and core-formation chronometer, which yields a mean time of Earth's formation of 10Myr, and a total time scale of 30Myr. New laser shock data at conditions comparable with those in the Earth's deep mantle subsequent to the giant Moon-forming impact suggest that metal-silicate equilibration was rapid enough for the Hf-W chronometer to reliably record this time scale. The coupled (146)Sm-(147)Sm chronometer is the best system for determining the initial silicate differentiation (magma ocean crystallization and proto-crust formation), which took place at ca 4.47Ga or perhaps even earlier. The presence of a large (129)Xe excess in the deep Earth is consistent with a very early atmosphere formation (as early as 30Myr); however, the interpretation is complicated by the fact that most of the atmospheric Xe may be from a volatile-rich late veneer.

Realizing high-rate sulfur reduction under sulfate-rich conditions in a biological sulfide production system to treat metal-laden wastewater deficient in organic matter.

PubMed

Sun, Rongrong; Zhang, Liang; Zhang, Zefeng; Chen, Guang-Hao; Jiang, Feng

2017-12-22

Biological sulfur reduction can theoretically produce sufficient sulfide to effectively remove and recover heavy metals in the treatment of organics-deficient sulfate-rich metal-laden wastewater such as acid mine drainage and metallurgic wastewater, using 75% less organics than biological sulfate reduction. However, it is still unknown whether sulfur reduction can indeed compete with sulfate reduction, particularly under high-strength sulfate conditions. The aim of this study was to investigate the long-term feasibility of biological sulfur reduction under high sulfate conditions in a lab-scale sulfur-reducing biological sulfide production (BSP) system with sublimed sulfur added. In the 169-day trial, an average sulfide production rate (SPR) as high as 47 ± 9 mg S/L-h was achieved in the absence of sulfate, and the average SPR under sulfate-rich conditions was similar (53 ± 10 mg S/L-h) when 1300 mg S/L sulfate were fed with the influent. Interestingly, sulfate was barely reduced even at such a high strength and contributed to only 1.5% of total sulfide production. Desulfomicrobium was identified as the predominant sulfidogenic bacterium in the bioreactor. Batch tests further revealed that this sulfidogenic bacteria used elemental sulfur as the electron acceptor instead of the highly bioavailable sulfate, during which polysulfide acted as an intermediate, leading to an even higher bioavailability of sulfur than sulfate. The pathway of sulfur to sulfide conversion via polysulfide in the presence of both sulfur and sulfate was discussed. Collectively, when conditions favor polysulfide formation, sulfur reduction can be a promising and attractive technology to realize a high-rate and low-cost BSP process for treating sulfate-rich metal-laden wastewater. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dinuclear rare-earth metal alkyl complexes supported by indolyl ligands in μ-η(2) :η(1) :η(1) hapticities and their high catalytic activity for isoprene 1,4-cis-polymerization.

PubMed

Zhang, Guangchao; Wei, Yun; Guo, Liping; Zhu, Xiancui; Wang, Shaowu; Zhou, Shuangliu; Mu, Xiaolong

2015-02-02

Two series of new dinuclear rare-earth metal alkyl complexes supported by indolyl ligands in novel μ-η(2) :η(1) :η(1) hapticities are synthesized and characterized. Treatment of [RE(CH2 SiMe3 )3 (thf)2 ] with 1 equivalent of 3-(tBuN=CH)C8 H5 NH (L1 ) in THF gives the dinuclear rare-earth metal alkyl complexes trans-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH(CH2 SiMe3 )}Ind)RE(thf)(CH2 SiMe3 )]2 (Ind=indolyl, RE=Y, Dy, or Yb) in good yields. In the process, the indole unit of L1 is deprotonated by the metal alkyl species and the imino C=N group is transferred to the amido group by alkyl CH2 SiMe3 insertion, affording a new dianionic ligand that bridges two metal alkyl units in μ-η(2) :η(1) :η(1) bonding modes, forming the dinuclear rare-earth metal alkyl complexes. When L1 is reduced to 3-(tBuNHCH2 )C8 H5 NH (L2 ), the reaction of [Yb(CH2 SiMe3 )3 (thf)2 ] with 1 equivalent of L2 in THF, interestingly, generated the trans-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH2 }Ind)Yb(thf)(CH2 SiMe3 )]2 (major) and cis-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH2 }Ind)Yb(thf)(CH2 SiMe3 )]2 (minor) complexes. The catalytic activities of these dinuclear rare-earth metal alkyl complexes for isoprene polymerization were investigated; the yttrium and dysprosium complexes exhibited high catalytic activities and high regio- and stereoselectivities for isoprene 1,4-cis-polymerization. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Metal-rich, Metal-poor: Updated Stellar Population Models for Old Stellar Systems

NASA Astrophysics Data System (ADS)

Conroy, Charlie; Villaume, Alexa; van Dokkum, Pieter G.; Lind, Karin

2018-02-01

We present updated stellar population models appropriate for old ages (>1 Gyr) and covering a wide range in metallicities (‑1.5 ≲ [Fe/H] ≲ 0.3). These models predict the full spectral variation associated with individual element abundance variation as a function of metallicity and age. The models span the optical–NIR wavelength range (0.37–2.4 μm), include a range of initial mass functions, and contain the flexibility to vary 18 individual elements including C, N, O, Mg, Si, Ca, Ti, and Fe. To test the fidelity of the models, we fit them to integrated light optical spectra of 41 Galactic globular clusters (GCs). The value of testing models against GCs is that their ages, metallicities, and detailed abundance patterns have been derived from the Hertzsprung–Russell diagram in combination with high-resolution spectroscopy of individual stars. We determine stellar population parameters from fits to all wavelengths simultaneously (“full spectrum fitting”), and demonstrate explicitly with mock tests that this approach produces smaller uncertainties at fixed signal-to-noise ratio than fitting a standard set of 14 line indices. Comparison of our integrated-light results to literature values reveals good agreement in metallicity, [Fe/H]. When restricting to GCs without prominent blue horizontal branch populations, we also find good agreement with literature values for ages, [Mg/Fe], [Si/Fe], and [Ti/Fe].

Elucidating electrolyte decomposition under electron-rich environments at the lithium-metal anode.

PubMed

Camacho-Forero, Luis E; Balbuena, Perla B

2017-11-22

The lithium metal anode is one of the key components of the lithium-sulfur (Li-S) batteries, which are considered one of the most promising candidates for the next generation of battery systems. However, one of the main challenges that have prevented Li-metal anodes from becoming feasible to be used in commercial batteries is the continuous decomposition of the electrolyte due to its high reactivity, which leads to the formation of solid-electrolyte interphase (SEI) layers. The properties of the SEI can dramatically affect the performance of the batteries. Thus, a rigorous understanding of the electrolyte decomposition is crucial to elucidate improvements in performance of the Li-S technology. In this work, using density functional theory (DFT) and ab initio molecular dynamics simulations (AIMD), we investigate the effect of electron-rich environments on the decomposition mechanism of electrolyte species in pure 1,2-dimethoxyethane (DME) solvent and 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(fluorosulfonyl)imide (LiFSI) salt solutions. It is found that systems with pure DME require an average environment of at least ∼0.9 |e| per molecule for a DME to decompose into CH 3 O - and C 2 H 4 2- via a 4-electron transfer. In the case of mixtures, the salts are very prone to react with any excess of electrons. In addition, DME dehydrogenation due to reactions with fragments coming from the salt decompositions was detected. Formation of oligomer anionic species from DME and salt fragments were also identified from the AIMD simulations. Finally, the thermodynamics and kinetics of the most relevant electrolyte decomposition reactions were characterized. DME decomposition reactions predicted from the AIMD simulations were found to be thermodynamically favorable under exposure to Li atoms and/or by reactions with salt fragments. In most cases, these reactions were shown to have low to moderate activation barriers.

Origins of ultralow velocity zones through slab-derived metallic melt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jiachao; Li, Jie; Hrubiak, Rostislav

2016-05-03

Understanding the ultralow velocity zones (ULVZs) places constraints on the chemical composition and thermal structure of deep Earth and provides critical information on the dynamics of large-scale mantle convection, but their origin has remained enigmatic for decades. Recent studies suggest that metallic iron and carbon are produced in subducted slabs when they sink beyond a depth of 250 km. Here we show that the eutectic melting curve of the iron-carbon system crosses the current geotherm near Earth’s core-mantle boundary, suggesting that dense metallic melt may form in the lowermost mantle. If concentrated into isolated patches, such melt could produce themore » seismically observed density and velocity features of ULVZs. Depending on the wetting behavior of the metallic melt, the resultant ULVZs may be short-lived domains that are replenished or regenerated through subduction, or long-lasting regions containing both metallic and silicate melts. Slab-derived metallic melt may produce another type of ULVZ that escapes core sequestration by reacting with the mantle to form iron-rich post-bridgmanite or ferropericlase. The hypotheses connect peculiar features near Earth’s core-mantle boundary to subduction of the oceanic lithosphere through the deep carbon cycle.« less

A molecular cross-linking approach for hybrid metal oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, Dahee; Saleh, Liban A. M.; Berkson, Zachariah J.

Developing methods to create hybrid materials to maximize their transformative capabilities has been the subject of significant interest. In particular, several key methods have been developed to manipulate earth abundant metal oxides such as TiO 2 to produce hybrid materials with improved or new properties relevant to a broad spectrum of applications. Here, we introduce a new approach we refer to as “molecular doping”, whereby a hybrid molecular boron oxide material is formed from polyhedral boron cluster precursors of the type [B 12(OH) 12] 2-. This new approach is enabled by the inherent robustness of the boron cluster molecular buildingmore » block, which is compatible with harsh thermal and oxidizing conditions that are necessary for the synthesis of many metal oxides. In this work, we show how this material can be successfully interfaced with TiO 2, resulting in boron-rich hybrid materials with unprecedented photophysical and electrochemical properties.« less

Uranium, thorium and REE partitioning into sulfide liquids at high pressure and high temperature: Implications for reduced, S-rich planetary bodies

NASA Astrophysics Data System (ADS)

Wohlers, A.; Wood, B. J.

2017-12-01

Based on models of the young solar nebula it is likely that the inner planets went through an early reduced phase of accretion with high metal/silicate ratio and low volatile element contents. Mercury is an existing example of a large planetary embryo with these characteristics but also with a very high S content. In order to investigate the geochemical evolution of Mercury-like bodies we experimentally determined the partitioning of lithophile elements (U, Th, Eu, Sm, Nd, Zr, La, Ce, Yb) between sulfide liquid, low-S metals and silicate melt at 1.5 GPa and 1400-2100˚C. Our results, when combined with those of Wohlers and Wood (2015) show that under highly reducing conditions (FeOsilicate<1wt%) U, Sm, Nd and other lithophile elements partition strongly into FeS liquids relative to silicate melts. The dependences of D's on the FeS contents of the metal and FeO contents of the silicate may be understood in terms of exchange reactions: UO2 + 2FeS = 2FeO + US2silicate sulfide silicate sulfideHigh concentrations of FeSmetal and low FeO contents of the silicate melts drive the reaction to the right, yielding high US2 in the sulfide and high DU. A second effect which raises DU (and other lithophile D's) is the S content of the silicate melt. The latter increases rapidly at low FeO contents and reaches 11wt %. This greatly reduces the activity coefficient of FeO, displacing the reaction further to the right. At 1.5GPa and 1400˚C we obtain sulfide-silicate partitioning with DNd/DSm 1.4 and DTh 0.1DU. As temperature increases to 2100˚C, DNd/DSm declines to 1.0 and DTh/DU increases to 0.3. We estimated the effects of accreting a reduced sulfur-rich component (with FeS core) added to early Earth. The results at 1400˚C imply the possibility of a significant ( 11ppm) 142Nd anomaly in silicate Earth and the addition of >8 ppb U to the core, but require an unreasonably high Th/U of silicate Earth (4.54). Results at 2100˚C lead to a 142Nd anomaly of 0 but addition of such a

Volatile accretion history of the Earth.

PubMed

Wood, B J; Halliday, A N; Rehkämper, M

2010-10-28

It has long been thought that the Earth had a protracted and complex history of volatile accretion and loss. Albarède paints a different picture, proposing that the Earth first formed as a dry planet which, like the Moon, was devoid of volatile constituents. He suggests that the Earth's complement of volatile elements was only established later, by the addition of a small veneer of volatile-rich material at ∼100 Myr (here and elsewhere, ages are relative to the origin of the Solar System). Here we argue that the Earth's mass balance of moderately volatile elements is inconsistent with Albarède's hypothesis but is well explained by the standard model of accretion from partially volatile-depleted material, accompanied by core formation.

Geochemical Constraints on Core Formation in the Earth

NASA Technical Reports Server (NTRS)

Jones, John H.; Drake, Michael J.

1986-01-01

New experimental data on the partitioning of siderophile and chalcophile elements among metallic and silicate phases may be used to constrain hypotheses of core formation in the Earth. Three current hypotheses can explain gross features of mantle geochemistry, but none predicts siderophile and chalcophile element abundances to within a factor of two of observed values. Either our understanding of metal-silicate interactions and/or our understanding of the early Earth requires revision.

Crew Earth Observations: Twelve Years of Documenting Earth from the International Space Station

NASA Technical Reports Server (NTRS)

Evans, Cynthia A.; Stefanov, William L.; Willis, Kimberley; Runco, Susan; Wilkinson, M. Justin; Dawson, Melissa; Trenchard, Michael

2012-01-01

The Crew Earth Observations (CEO) payload was one of the initial experiments aboard the International Space Station, and has been continuously collecting data about the Earth since Expedition 1. The design of the experiment is simple: using state-of-the-art camera equipment, astronauts collect imagery of the Earth's surface over defined regions of scientific interest and also document dynamic events such as storms systems, floods, wild fires and volcanic eruptions. To date, CEO has provided roughly 600,000 images of Earth, capturing views of features and processes on land, the oceans, and the atmosphere. CEO data are less rigorously constrained than other remote sensing data, but the volume of data, and the unique attributes of the imagery provide a rich and understandable view of the Earth that is difficult to achieve from the classic remote sensing platforms. In addition, the length-of-record of the imagery dataset, especially when combined with astronaut photography from other NASA and Russian missions starting in the early 1960s, provides a valuable record of changes on the surface of the Earth over 50 years. This time period coincides with the rapid growth of human settlements and human infrastructure.

Electrochemistry and the Earth's Core-Mantle Boundary

NASA Astrophysics Data System (ADS)

Kavner, A.; Walker, D.

2001-12-01

timescales. A second set of experiments examined the behavior of iron-silicate interfaces subjected to electric fields of 1-10 V, applied for times ranging from several minutes to several days. The samples were quenched from high temperatures, mounted, and examined using both light and electron microscopy. When the iron/iron-sulfide end is charged positively (+1-2 V) with respect to the silicate, oxides form around the platinum electrode embedded within the iron metal, suggesting the reaction Fe->Fe+2+2e- occurs in the metal. When the electric field is reversed, the silicate and MgO surrounding the + electrode turns red, implying the reaction Fe+2\\rightarrowFe^{+3}+e^{-}$ occurs at the silicate (anode end) of the sample. The richness of electrical and electrically activated chemical behavior observed at metal-silicate interfaces may be relevant to the Earth's core mantle boundary.

Controlled synthesis of racemic indenyl rare-earth metal complexes via the cooperation between the intramolecular coordination of donor atoms and a bridge.

PubMed

Zhou, Shuangliu; Wu, Zhangshuan; Zhou, Lingmin; Wang, Shaowu; Zhang, Lijun; Zhu, Xiancui; Wei, Yun; Zhai, Jinhua; Wu, Jie

2013-06-03

The reactions of Me2Si(C9H6CH2CH2-DG)2 (DG = NMe2 (1), CH2NMe2 (2), OMe (3), and N(CH2CH2)2O (4)) with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 in toluene afforded a series of racemic divalent rare-earth metal complexes: {η(5):η(1):η(5):η(1)-Me2Si(C9H5CH2CH2-DG)2}RE (DG = NMe2, RE = Yb (6) and Eu (7); DG = CH2NMe2, RE = Yb (8), Eu (9), and Sm (10); DG = OMe, RE = Yb (11) and Eu (12); DG = N(CH2CH2)2O, RE = Yb (13) and Eu (14)). Similarly, the racemic divalent rare-earth metal complexes {η(5):η(1):η(5):η(1)-Me2Si(C9H5CH2CH2CH2NMe2)(C9H5CH2CH2OMe)}RE (RE = Yb (15) and Eu (16)) were also obtained. The reaction of Me2Si(C9H5CH2CH2OMe)2Li2 with NdCl3 gave a racemic dimeric neodymium chloride {η(5):η(1):η(5)-Me2Si(C9H5CH2CH2OMe)2NdCl}2 (17), whereas the reaction of Me2Si(C9H5CH2CH2NMe2)2Li2 with SmCl3 afforded a racemic dinuclear samarium chloride bridged by lithium chloride {η(5):η(1):η(5):η(1)-Me2Si(C9H5CH2CH2NMe2)2SmCl}2(μ-LiCl) (18). Further reaction of complex 18 with LiCH2SiMe3 provided an unexpected rare-earth metal alkyl complex {η(5):η(1):η(5):η(1):σ-Me2Si(C9H5CH2CH2NMe2)[(C9H5CH2CH2N(CH2)Me]}Sm (19) through the activation of an sp(3) C-H bond α-adjacent to the nitrogen atom. Complexes 19 and {η(5):η(1):η(5):η(1):σ-Me2Si(C9H5CH2CH2NMe2)[(C9H5CH2CH2N(CH2)Me]}Y (20) were also obtained by one-pot reactions of Me2Si(C9H5CH2CH2NMe2)2Li2 with RECl3 followed by treatment with LiCH2SiMe3. All compounds were fully characterized by spectroscopic methods and elemental analysis. Complexes 6-10 and 14-20 were further characterized by single-crystal X-ray diffraction analysis. All of the prepared rare-earth metal complexes were racemic, suggesting that racemic organo rare-earth metal complexes could be controllably synthesized by the cooperation between a bridge and the intramolecular coordination of donor atoms.

How life shaped Earth.

PubMed

Gross, Michael

2015-10-05

Earth is much more complex than all the other solar system objects that we know. Thanks to its rich and diverse geology, our planet can offer habitats to a wide range of living species. Emerging insights suggest that this is not just a happy coincidence, but that life itself has in many ways helped to shape the planet.

Stable Hydrogen-rich Atmospheres of Young Rocky Planets

NASA Astrophysics Data System (ADS)

Zahnle, K. J.; Catling, D. C.; Gacesa, M.

2016-12-01

SourceURL:file://localhost/Volumes/Lexar/Zahnle_AGU_2016.docx Understanding hydrogen escape is essential to understanding the limits to habitability, both for liquid water where the Sun is bright, but also to assess the true potential of H2 as a greenhouse gas where the Sun is faint. Hydrogen-rich primary atmospheres of Earth-like planets can result either from gravitational capture of solar nebular gases (with helium), or from impact shock processing of a wide variety of volatile-rich planetesimals (typically accompanied by H2O, CO2, and under the right circumstances, CH4). Most studies of hydrogen escape from planets focus on determining how fast the hydrogen escapes. In general this requires solving hydrodynamic equations that take into account the acceleration of hydrogen through a critical transonic point and an energy budget that should include radiative heating and cooling, thermal conduction, the work done in lifting the hydrogen against gravity, and the residual heat carried by the hydrogen as it leaves. But for planets from which hydrogen escape is modest or insignificant, the atmosphere can be approximated as hydrostatic, which is much simpler, and for which a relatively full-featured treatment of radiative cooling by embedded molecules, atoms, and ions such as CO2 and H3+ is straightforward. Previous work has overlooked the fact that the H2 molecule is extremely efficient at exciting non-LTE CO2 15 micron emission, and thus that radiative cooling can be markedly more efficient when H2 is abundant. We map out the region of phase space in which terrestrial planets keep hydrogen-rich atmospheres, which is what we actually want to know for habitability. We will use this framework to reassess Tian et al's (Science 308, pp. 1014-1017, 2005) hypothesis that H2-rich atmospheres may have been rather long-lived on Earth itself. Finally, we will address the empirical observation that rocky planets with thin or negligible atmospheres are rarely or never bigger than

Coercivity of domain wall motion in thin films of amorphous rare earth-transition metal alloys

NASA Technical Reports Server (NTRS)

Mansuripur, M.; Giles, R. C.; Patterson, G.

1991-01-01

Computer simulations of a two dimensional lattice of magnetic dipoles are performed on the Connection Machine. The lattice is a discrete model for thin films of amorphous rare-earth transition metal alloys, which have application as the storage media in erasable optical data storage systems. In these simulations, the dipoles follow the dynamic Landau-Lifshitz-Gilbert equation under the influence of an effective field arising from local anisotropy, near-neighbor exchange, classical dipole-dipole interactions, and an externally applied field. Various sources of coercivity, such as defects and/or inhomogeneities in the lattice, are introduced and the subsequent motion of domain walls in response to external fields is investigated.

Nickel(0)-Catalyzed Inert C-O Bond Functionalization: Organo Rare-Earth Metal Complex as the Coupling Partner.

PubMed

Yan, Xiangqian; Yang, Fanzhi; Cai, Guilong; Meng, Qingwei; Li, Xiaofang

2018-02-02

An organo rare-earth metal complex has been employed as a highly efficient nucleophile in Ni(0)-catalyzed C-O bond functionalization. The optimized catalytic system which consists of Ni(cod) 2 , PCy 3 , and t-BuONa could smoothly convert 1 equiv of naphthyl ethers to alkylated naphthalene analogues with 0.4 equiv of Ln(CH 2 SiMe 3 ) 3 (THF) 2 , delivering good to excellent yields. The reaction system could also activate the ArCH 2 -O bond with mild base.

Electroluminescence color tuning between green and red from metal-oxide-semiconductor devices fabricated by spin-coating of rare-earth (terbium + europium) organic compounds on silicon

NASA Astrophysics Data System (ADS)

Matsuda, Toshihiro; Hattori, Fumihiro; Iwata, Hideyuki; Ohzone, Takashi

2018-04-01

Color tunable electroluminescence (EL) from metal-oxide-semiconductor devices with the rare-earth elements Tb and Eu is reported. Organic compound liquid sources of (Tb + Ba) and Eu with various Eu/Tb ratios from 0.001 to 0.4 were spin-coated on an n+-Si substrate and annealed to form an oxide insulator layer. The EL spectra had only peaks corresponding to the intrashell Tb3+/Eu3+ transitions in the spectral range from green to red, and the intensity ratio of the peaks was appropriately tuned using the appropriate Eu/Tb ratios in liquid sources. Consequently, the EL emission colors linearly changed from yellowish green to yellowish orange and eventually to reddish orange on the CIE chromaticity diagram. The gate current +I G current also affected the EL colors for the medium-Eu/Tb-ratio device. The structure of the surface insulator films analyzed by cross-sectional transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, and X-ray photoelectron spectroscopy (XPS) has four layers, namely, (Tb4O7 + Eu2O3), [Tb4O7 + Eu2O3 + (Tb/Eu/Ba)SiO x ], (Tb/Eu/Ba)SiO x , and SiO x -rich oxide. The EL mechanism proposed is that electrons injected from the Si substrate into the SiO x -rich oxide and Tb/Eu/Ba-silicate layers become hot electrons accelerated in a high electric field, and then these hot electrons excite Tb3+ and Eu3+ ions in the Tb4O7/Eu2O3 layers resulting in EL emission from Tb3+ and Eu3+ intrashell transitions.

A Liquid Chromatography Detector for Transition and Rare-Earth Metal Ions Based on a Cupric Ion-Selective Electrode

DTIC Science & Technology

1981-05-01

RARE-EARTH METAL IONS BASED ON A CUPRIC ION-SELECTIVE ELECTRODE By - 4 R. CAMERON DOREY TECHNICAL REPORT FJSRL-TR-81-0005 MAY 1981 Approved for public...FORM . REPORT NUMBER 12. GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER FJSRL-TR-81-0005BO CO ENGO 4 . TITLE (and Subtitle) 5. TYPE OF REPORT & PERIOD...common anions, including halide ions, is shown, and the advantages and limitations of the system are discussed. II ’ 4 UNCLASSIFIED SECURITY

Crystalline rare-earth activated oxyorthosilicate phosphor

DOEpatents

McClellan, Kenneth J.; Cooke, D. Wayne

2004-02-10

Crystalline, transparent, rare-earth activated lutetium oxyorthosilicate phosphor. The phosphor consists essentially of lutetium yttrium oxyorthosilicate activated with a rare-earth metal dopant M and having the general formula Lu(.sub.2-x-z)Y.sub.x M.sub.z SiO.sub.5, wherein 0.00.ltoreq.x.ltoreq.1.95, wherein 0.001.ltoreq.z.ltoreq.0.02, and wherein M is selected from Sm, Tb, Tm, Eu, Yb, and Pr. The phosphor also consists essentially of lutetium gadolinium oxyorthosilicate activated with a rare-earth metal dopant M and having the general formula Lu(.sub.2-x-z)Gd.sub.x M.sub.z SiO.sub.5, wherein 0.00.ltoreq.x.ltoreq.1.95, wherein 0.001.ltoreq.z.ltoreq.0.02, and wherein M is selected from Sm, Tb, Tm, Eu, Yb, and Pr. The phosphor also consists essentially of gadolinium yttrium oxyorthosilicate activated with a rare-earth metal dopant M and having the general formula Gd(.sub.2-x-z)Y.sub.x M.sub.z SiO.sub.5, wherein 0.00.ltoreq.x.ltoreq.1.95, wherein 0.001.ltoreq.z.ltoreq.0.02, and wherein M is selected from Sm, Tb, Tm, Eu, Yb, and Pr. The phosphor may be optically coupled to a photodetector to provide a radiation detector.

Utility of Lithium in Rare-Earth Metal Reduction Reactions to Form Nontraditional Ln2+ Complexes and Unusual [Li(2.2.2-cryptand)]1+ Cations.

PubMed

Huh, Daniel N; Darago, Lucy E; Ziller, Joseph W; Evans, William J

2018-02-19

The utility of lithium compared to other alkali metals in generating Ln 2+ rare-earth metal complexes via reduction of Ln 3+ precursors in reactions abbreviated as LnA 3 /M (Ln = rare-earth metal; A = anionic ligand; M = alkali metal) is described. Lithium reduction of Cp' 3 Ln (Cp' = C 5 H 4 SiMe 3 ; Ln = Y, Tb, Dy, Ho) under Ar in the presence of 2.2.2-cryptand (crypt) forms new examples of crystallographically characterizable Ln 2+ complexes of these metals, [Li(crypt)][Cp' 3 Ln]. In each complex, lithium is found in an N 2 O 4 donor atom coordination geometry that is unusual for the cryptand ligand. Magnetic susceptibility data on these new examples of nontraditional divalent lanthanide complexes are consistent with 4f n 5d 1 electronic configurations. The Dy and Ho complexes have exceptionally high single-ion magnetic moments, 11.35 and 11.67 μ B , respectively. Lithium reduction of Cp' 3 Y under N 2 at -35 °C forms the Y 2+ complex (Cp' 3 Y) 1- , which reduces dinitrogen upon warming to room temperature to generate the (N 2 ) 2- complex [Cp' 2 Y(THF)] 2 (μ-η 2 :η 2 -N 2 ). These results provide insight on the factors that lead to reduced dinitrogen complexes and/or stable divalent lanthanide complexes as a function of the specific reducing agent and conditions.

Synthesis and structures of metal chalcogenide precursors

NASA Technical Reports Server (NTRS)

Hepp, Aloysius F.; Duraj, Stan A.; Eckles, William E.; Andras, Maria T.

1990-01-01

The reactivity of early transition metal sandwich complexes with sulfur-rich molecules such as dithiocarboxylic acids was studied. Researchers recently initiated work on precursors to CuInSe2 and related chalcopyrite semiconductors. Th every high radiation tolerance and the high absorption coefficient of CuInSe2 makes this material extremely attractive for lightweight space solar cells. Their general approach in early transition metal chemistry, the reaction of low-valent metal complexes or metal powders with sulfur and selenium rich compounds, was extended to the synthesis of chalcopyrite precursors. Here, the researchers describe synthesis, structures, and and routes to single molecule precursors to metal chalcogenides.

Metal-Silicate Segregation in Asteroidal Meteorites

NASA Technical Reports Server (NTRS)

Herrin, Jason S.; Mittlefehldt, D. W.

2006-01-01

A fundamental process of planetary differentiation is the segregation of metal-sulfide and silicate phases, leading eventually to the formation of a metallic core. Asteroidal meteorites provide a glimpse of this process frozen in time from the early solar system. While chondrites represent starting materials, iron meteorites provide an end product where metal has been completely concentrated in a region of the parent asteroid. A complimentary end product is seen in metal-poor achondrites that have undergone significant igneous processing, such as angrites, HED's and the majority of aubrites. Metal-rich achondrites such as acapulcoite/lodranites, winonaites, ureilites, and metal-rich aubrites may represent intermediate stages in the metal segregation process. Among these, acapulcoite-lodranites and ureilites are examples of primary metal-bearing mantle restites, and therefore provide an opportunity to observe the metal segregation process that was captured in progress. In this study we use bulk trace element compositions of acapulcoites-lodranites and ureilites for this purpose.

Models of the Earth's Core.

PubMed

Stevenson, D J

1981-11-06

Combined inferences from seismology, high-pressure experiment and theory, geomagnetism, fluid dynamics, and current views of terrestrial planetary evolution lead to models of the earth's core with the following properties. Core formation was contemporaneous with earth accretion; the core is not in chemical equilibrium with the mantle; the outer core is a fluid iron alloy containing significant quantities of lighter elements and is probably almost adiabatic and compositionally uniform; the more iron-rich inner solid core is a consequence of partial freezing of the outer core, and the energy release from this process sustains the earth's magnetic field; and the thermodynamic properties of the core are well constrained by the application of liquid-state theory to seismic and laboratory data.

Models of the earth's core

NASA Technical Reports Server (NTRS)

Stevenson, D. J.

1981-01-01

Combined inferences from seismology, high-pressure experiment and theory, geomagnetism, fluid dynamics, and current views of terrestrial planetary evolution lead to models of the earth's core with five basic properties. These are that core formation was contemporaneous with earth accretion; the core is not in chemical equilibrium with the mantle; the outer core is a fluid iron alloy containing significant quantities of lighter elements and is probably almost adiabatic and compositionally uniform; the more iron-rich inner solid core is a consequence of partial freezing of the outer core, and the energy release from this process sustains the earth's magnetic field; and the thermodynamic properties of the core are well constrained by the application of liquid-state theory to seismic and labroatory data.

Which Type of Planets do We Expect to Observe in the Habitable Zone?

PubMed

Adibekyan, Vardan; Figueira, Pedro; Santos, Nuno C

2016-11-01

We used a sample of super-Earth-like planets detected by the Doppler spectroscopy and transit techniques to explore the dependence of orbital parameters of the planets on the metallicity of their host stars. We confirm the previous results (although still based on small samples of planets) that super-Earths orbiting around metal-rich stars are not observed to be as distant from their host stars as we observe their metal-poor counterparts to be. The orbits of these super-Earths with metal-rich hosts usually do not reach into the Habitable Zone (HZ), keeping them very hot and inhabitable. We found that most of the known planets in the HZ are orbiting their GK-type hosts which are metal-poor. The metal-poor nature of planets in the HZ suggests a high Mg abundance relative to Si and high Si abundance relative to Fe. These results lead us to speculate that HZ planets might be more frequent in the ancient Galaxy and had compositions different from that of our Earth.

Metal mining and the environment

USGS Publications Warehouse

Hudson, Travis L.; Fox, Frederick D.; Plumlee, Geoffrey S.

1999-01-01

The booklet, Metal Mining and the Environment, and the colorful companion poster offer new tools for raising awareness and understanding of the impact and issues surrounding metal mining and the environment. The 64-page full-color booklet contains a copy of the poster which includes a student activity on the back. This booklet and poster can help you: illustrate the importance of our natural and environmental resources; provide a geoscience perspective on metal mining and the environment; improve Earth science literacy; and increase student understandings of Earth resources and systems.

METAL PHTHALOCYANINES

DOEpatents

Frigerio, N.A.

1962-03-27

A process is given for preparing heavy metal phthalocyanines, sulfonated or not. The process comprises mixing an inorganic metal salt with dimethyl formamide or methyl sulfoxide; separating the metal complex formed from the solution; mixing the complex with an equimolar amount of sodium, potassium, lithium, magnesium, or beryllium sulfonated or unsulfonated phthalocyanine whereby heavy-metal phthalocyanine crystals are formed; and separating the crystals from the solution. Uranyl, thorium, lead, hafnium, and lanthanide rare earth phthalocyanines can be produced by the process. (AEC)

Robust and Porous β-Diketiminate-Functionalized Metal–Organic Frameworks for Earth-Abundant-Metal-Catalyzed C–H Amination and Hydrogenation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thacker, Nathan C.; Lin, Zekai; Zhang, Teng

We have designed a strategy for postsynthesis installation of the β-diketiminate (NacNac) functionality in a metal–organic framework (MOF) of UiO-topology. Metalation of the NacNac-MOF (I) with earth-abundant metal salts afforded the desired MOF-supported NacNac-M complexes (M = Fe, Cu, and Co) with coordination environments established by detailed EXAFS studies. The NacNac-Fe-MOF catalyst, I•Fe(Me), efficiently catalyzed the challenging intramolecular sp 3 C–H amination of a series of alkyl azides to afford α-substituted pyrrolidines. The NacNac-Cu-MOF catalyst, I•Cu(THF), was effective in promoting the intermolecular sp 3 C–H amination of cyclohexene using unprotected anilines to provide access to secondary amines in excellent selectivity.more » Finally, the NacNac-Co-MOF catalyst, I•Co(H), was used to catalyze alkene hydrogenation with turnover numbers (TONs) as high as 700 000. All of the NacNac-M-MOF catalysts were more effective than their analogous homogeneous catalysts and could be recycled and reused without a noticeable decrease in yield. The NacNac-MOFs thus provide a novel platform for engineering recyclable earth-abundant-element-based single-site solid catalysts for many important organic transformations.« less

Antibacterial, Antifungal and Nematicidal Activities of Rare Earth Ions.

PubMed

Wakabayashi, Tokumitsu; Ymamoto, Ayumi; Kazaana, Akira; Nakano, Yuta; Nojiri, Yui; Kashiwazaki, Moeko

2016-12-01

Despite the name, rare earth elements are relatively abundant in soil. Therefore, these elements might interact with biosphere during the history of life. In this study, we have examined the effect of rare earth ions on the growth of bacteria, fungi and soil nematode. All rare earth ions, except radioactive promethium that we have not tested, showed antibacterial and antifungal activities comparable to that of copper ions, which is widely used as antibacterial metals in our daily life. Rare earth ions also have nematicidal activities as they strongly perturb the embryonic development of the nematode, Caenorhabditis elegans. Interestingly, the nematicidal activity increased with increasing atomic number of lanthanide ions. Since the rare earth ions did not show high toxicity to the human lymphoblastoid cell line or even stimulate the growth of the cultured cells at 1 mM, it raised the possibility that we can substitute rare earth elements for the antibacterial metals usually used because of their safety.

Mechanisms of iron photoreduction in a metal-rich, acidic stream (St. Kevin Gulch, Colorado, U.S.A.)

USGS Publications Warehouse

Kimball, B.A.; McKnight, Diane M.; Wetherbee, G.A.; Harnish, R.A.

1992-01-01

Iron photoreduction in metal-rich, acidic streams affected by mine drainage accounts for some of the variability in metal chemistry of such streams, producing diel variations in Fe(II). Differentiation of the mechanisms of the Fe photoreduction reaction by a series of in-stream experiments at St. Kevin Gulch, Colorado, indicates that a homogeneous, solution-phase reaction can occur in the absence of suspended particulate Fe and bacteria, and the rate of reaction is increased by the presence of Fe colloids in the stream water. In-stream Fe photoreduction is limited during the diel cycle by the available Fe(III) in the water column and streambed. The quantum yield of Fe(II) was reproducible in diel measurements: the quantum yield, in mol E-1 (from 300 to 400 nm) was 1.4 ?? 10-3 in 1986, 0.8 ?? 10-3 in 1988 and 1.2 ?? 10-3 in 1989, at the same location and under similar streamflow and stream-chemistry conditions. In a photolysis control experiment, there was no detectable production of Fe(II) above background concentrations in stream-water samples that were experimentally excluded from sunlight. ?? 1992.

Ternary alkali-metal and transition metal or metalloid acetylides as alkali-metal intercalation electrodes for batteries

DOEpatents

Nemeth, Karoly; Srajer, George; Harkay, Katherine C; Terdik, Joseph Z

2015-02-10

Novel intercalation electrode materials including ternary acetylides of chemical formula: A.sub.nMC.sub.2 where A is alkali or alkaline-earth element; M is transition metal or metalloid element; C.sub.2 is reference to the acetylide ion; n is an integer that is 0, 1, 2, 3 or 4 when A is alkali element and 0, 1, or 2 when A is alkaline-earth element. The alkali elements are Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs) and Francium (Fr). The alkaline-earth elements are Berilium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra). M is a transition metal that is any element in groups 3 through 12 inclusive on the Periodic Table of Elements (elements 21 (Sc) to element 30 (Zn)). In another exemplary embodiment, M is a metalloid element.

Torsional Oscillations of the Earths's Core

NASA Technical Reports Server (NTRS)

Hide, Raymond; Boggs, Dale H.; Dickey, Jean O.

1997-01-01

Torsional oscillations of the Earth's liquid metallic outer core are investigated by diving the core into twenty imaginary e1qui-volume annuli coaxial with the axis of ratation of the Earth and determining temproal fluctuations in the axial component of angular memonetum of each annulus under the assumption of iso-rotation on cylindrical surfaces.

Earth's inner core nucleation paradox

NASA Astrophysics Data System (ADS)

Huguet, Ludovic; Van Orman, James A.; Hauck, Steven A.; Willard, Matthew A.

2018-04-01

The conventional view of Earth's inner core is that it began to crystallize at Earth's center when the temperature dropped below the melting point of the iron alloy and has grown steadily since that time as the core continued to cool. However, this model neglects the energy barrier to the formation of the first stable crystal nucleus, which is commonly represented in terms of the critical supercooling required to overcome the barrier. Using constraints from experiments, simulations, and theory, we show that spontaneous crystallization in a homogeneous liquid iron alloy at Earth's core pressures requires a critical supercooling of order 1000 K, which is too large to be a plausible mechanism for the origin of Earth's inner core. We consider mechanisms that can lower the nucleation barrier substantially. Each has caveats, yet the inner core exists: this is the nucleation paradox. Heterogeneous nucleation on a solid metallic substrate tends to have a low energy barrier and offers the most straightforward solution to the paradox, but solid metal would probably have to be delivered from the mantle and such events are unlikely to have been common. A delay in nucleation, whether due to a substantial nucleation energy barrier, or late introduction of a low energy substrate, would lead to an initial phase of rapid inner core growth from a supercooled state. Such rapid growth may lead to distinctive crystallization texturing that might be observable seismically. It would also generate a spike in chemical and thermal buoyancy that could affect the geomagnetic field significantly. Solid metal introduced to Earth's center before it reached saturation could also provide a nucleation substrate, if large enough to escape complete dissolution. Inner core growth, in this case, could begin earlier and start more slowly than standard thermal models predict.

PRODUCTION OF METALS

DOEpatents

Spedding, F.H.; Wilhelm, H.A.; Keller, W.H.

1961-09-19

A process is described producing metallic thorium, titanium, zirconium, or hafnium from the fluoride. In the process, the fluoride is reduced with alkali or alkaline earth metal and a booster compound (e.g. iodine or a decomposable oxysalt) in a sealed bomb at superatmospheric pressure and a temperature above the melting point of the metal to be produced.

Electronic and structural properties of Lu under pressure: Relation to structural phases of the rare-earth metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Min, B.I.; Oguchi, T.; Jansen, H.J.F.

1986-07-15

Ground-state electronic and structural properties of Lu under pressure are investigated with use of the self-consistent all-electron total-energy linear muffin-tin orbital band-structure method within a local-density-functional approximation. Pressure-induced structural transitions are found to occur in the following sequence: hcp--(Sm-type)--dhcp--fcc, which is the same as that observed in the crystal structures of the trivalent rare-earth metals with decreasing atomic number. This structural transition is correlated with the increase in the number of d-italic electrons under pressure.

Hyporheic Microbial Biofilms as Indicators of Heavy and Rare Earth Metals in the Clark Fork Basin, Montana

NASA Astrophysics Data System (ADS)

Barnhart, E. P.; Hornberger, M.; Hwang, C.; Dror, I.; Bouskill, N.; Short, T.; Cain, D.; Fields, M. W.

2016-12-01

The ability to effectively monitor the impact of hard rock mining activities on rivers and streams is a growing concern given the large number of active and abandoned mines in the western United States. One such example, the Clark Fork Basin (CFB), western Montana, was extensively mined for copper in the early 20th century: it is now one of largest U.S. EPA superfund sites. Microbial biofilms are at the base of the lotic food chain and may provide a useful biomonitoring tool for the assessment of metal toxicity due to their environmental ubiquity, rapidity of response to environmental perturbation, and importance in determining metal mobility. Hyporheic microbial biofilms from the CFB were sampled in 2014, concurrent with the USGS National Research Programs (NRP) long-term site monitoring of metals in bed sediment and aquatic benthic insects. Integration of the DNA sequencing results from the hyporheic biofilms with the sediment and insect metal concentrations correlated several bacterial phyla with metal contamination. For example, the genus Lysobacter was strongly associated with copper (Cu) bioaccumulation in the aquatic insect Hydropsyche. These results support previous studies identifying Lysobacter as a bacterial genus that is resistant to Cu ions. Our analysis is the first to indicate that specific microorganisms can act as biomarkers of Cu contamination in rivers. Moreover, our work demonstrates that changes at the microbial community level in the hyporheic zone can be coupled to observed perturbations across higher trophic levels. In 2015, extensive remediation occurred at several of the sites sampled in 2014, providing an excellent opportunity to revisit the sites and examine the temporal variability of identified biomarkers and the short-term effectiveness of remediation. In addition, samples were analyzed for rare earth metals, of which little is known, and could provide additional insight into other metals that change the microbial community structure.

New Insight into the Solar System’s Transition Disk Phase Provided by the Metal-rich Carbonaceous Chondrite Isheyevo

NASA Astrophysics Data System (ADS)

Morris, Melissa A.; Garvie, Laurence A. J.; Knauth, L. Paul

2015-03-01

Many aspects of planet formation are controlled by the amount of gas remaining in the natal protoplanetary disks (PPDs). Infrared observations show that PPDs undergo a transition stage at several megayears, during which gas densities are reduced. Our Solar System would have experienced such a stage. However, there is currently no data that provides insight into this crucial time in our PPD’s evolution. We show that the Isheyevo meteorite contains the first definitive evidence for a transition disk stage in our Solar System. Isheyevo belongs to a class of metal-rich meteorites whose components have been dated at almost 5 Myr after formation of Ca, Al-rich inclusions, and exhibits unique sedimentary layers that imply formation through gentle sedimentation. We show that such layering can occur via the gentle sweep-up of material found in the impact plume resulting from the collision of two planetesimals. Such sweep-up requires gas densities consistent with observed transition disks (10-12-10-11 g cm-3). As such, Isheyevo presents the first evidence of our own transition disk and provides new constraints on the evolution of our solar nebula.

Nitrogen solubility in the deep mantle and the origin of Earth's primordial nitrogen budget

NASA Astrophysics Data System (ADS)

Yoshioka, Takahiro; Wiedenbeck, Michael; Shcheka, Svyatoslav; Keppler, Hans

2018-04-01

The solubility of nitrogen in the major minerals of the Earth's transition zone and lower mantle (wadsleyite, ringwoodite, bridgmanite, and Ca-silicate perovskite) coexisting with a reduced, nitrogen-rich fluid phase was measured. Experiments were carried out in multi-anvil presses at 14 to 24 GPa and 1100 to 1800 °C close to the Fe-FeO buffer. Starting materials were enriched in 15N and the nitrogen concentrations in run products were measured by secondary ion mass spectrometry. Observed nitrogen (15N) solubilities in wadsleyite and ringwoodite typically range from 10 to 250 μg/g and strongly increase with temperature. Nitrogen solubility in bridgmanite is about 20 μg/g, while Ca-silicate perovskite incorporates about 30 μg/g under comparable conditions. Partition coefficients of nitrogen derived from coexisting phases are DNwadsleyite/olivine = 5.1 ± 2.1, DNringwoodite/wadsleyite = 0.49 ± 0.29, and DNbridgmanite/ringwoodite = 0.24 (+ 0.30 / - 0.19). Nitrogen solubility in the solid, iron-rich metal phase coexisting with the silicates was also measured and reached a maximum of nearly 1 wt.% 15N at 23 GPa and 1400 °C. These data yield a partition coefficient of nitrogen between iron metal and bridgmanite of DNmetal/bridgmanite ∼ 98, implying that in a lower mantle containing about 1% of iron metal, about half of the nitrogen still resides in the silicates. The high nitrogen solubility in wadsleyite and ringwoodite may be responsible for the low nitrogen concentrations often observed in ultradeep diamonds from the transition zone. Overall, the solubility data suggest that the transition zone and the lower mantle have the capacity to store at least 33 times the mass of nitrogen presently residing in the atmosphere. By combining the nitrogen solubility data in minerals with data on nitrogen solubility in silicate melts, mineral/melt partition coefficients of nitrogen can be estimated, from which the behavior of nitrogen during magma ocean crystallization can

Alkali Metal/Salt Thermal-Energy-Storage Systems

NASA Technical Reports Server (NTRS)

Phillips, Wayne W.; Stearns, John W.

1987-01-01

Proposed thermal-energy-storage system based on mixture of alkali metal and one of its halide salts; metal and salt form slurry of two immiscible melts. Use of slurry expected to prevent incrustations of solidified salts on heat-transfer surfaces that occur where salts alone used. Since incrustations impede heat transfer, system performance improved. In system, charging heat-exchanger surface immersed in lower liquid, rich in halide-salt, phase-charge material. Discharging heat exchanger surface immersed in upper liquid, rich in alkali metal.

Ohmic contacts to Al-rich AlGaN heterostructures

DOE PAGES

Douglas, E. A.; Reza, S.; Sanchez, C.; ...

2017-06-06

Due to the ultra-wide bandgap of Al-rich AlGaN, up to 5.8 eV for the structures in this study, obtaining low resistance ohmic contacts is inherently difficult to achieve. A comparative study of three different fabrication schemes is presented for obtaining ohmic contacts to an Al-rich AlGaN channel. Schottky-like behavior was observed for several different planar metallization stacks (and anneal temperatures), in addition to a dry-etch recess metallization contact scheme on Al 0.85Ga 0.15N/Al 0.66Ga 0.34N. However, a dry etch recess followed by n +-GaN regrowth fabrication process is reported as a means to obtain lower contact resistivity ohmic contacts onmore » a Al 0.85Ga 0.15N/Al 0.66Ga 0.34N heterostructure. In conclusion, specific contact resistivity of 5×10 -3 Ω cm 2 was achieved after annealing Ti/Al/Ni/Au metallization.« less

Unique Moon Formation Model: Two Impacts of Earth and After Moon's Birth

NASA Astrophysics Data System (ADS)

Miura, Y.

2018-04-01

The Moon rocks are mixed with two impact-processes of Earth's impact breccias and airless Moon's impact breccias; discussed voids-rich texture and crust-like composition. The present model might be explained as cave-rich interior on the airless-and waterless Moon.

Exotic Earths: forming habitable worlds with giant planet migration.

PubMed

Raymond, Sean N; Mandell, Avi M; Sigurdsson, Steinn

2006-09-08

Close-in giant planets (e.g., "hot Jupiters") are thought to form far from their host stars and migrate inward, through the terrestrial planet zone, via torques with a massive gaseous disk. Here we simulate terrestrial planet growth during and after giant planet migration. Several-Earth-mass planets also form interior to the migrating jovian planet, analogous to recently discovered "hot Earths." Very-water-rich, Earth-mass planets form from surviving material outside the giant planet's orbit, often in the habitable zone and with low orbital eccentricities. More than a third of the known systems of giant planets may harbor Earth-like planets.

Heterobimetallic transition metal/rare earth metal bifunctional catalysis: a Cu/Sm/Schiff base complex for syn-selective catalytic asymmetric nitro-Mannich reaction.

PubMed

Handa, Shinya; Gnanadesikan, Vijay; Matsunaga, Shigeki; Shibasaki, Masakatsu

2010-04-07

The full details of a catalytic asymmetric syn-selective nitro-Mannich reaction promoted by heterobimetallic Cu/Sm/dinucleating Schiff base complexes are described, demonstrating the effectiveness of the heterobimetallic transition metal/rare earth metal bifunctional catalysis. The first-generation system prepared from Cu(OAc)(2)/Sm(O-iPr)(3)/Schiff base 1a = 1:1:1 with an achiral phenol additive was partially successful for achieving the syn-selective catalytic asymmetric nitro-Mannich reaction. The substrate scope and limitations of the first-generation system remained problematic. After mechanistic studies on the catalyst prepared from Sm(O-iPr)(3), we reoptimized the catalyst preparation method, and a catalyst derived from Sm(5)O(O-iPr)(13) showed broader substrate generality as well as higher reactivity and stereoselectivity compared to Sm(O-iPr)(3). The optimal system with Sm(5)O(O-iPr)(13) was applicable to various aromatic, heteroaromatic, and isomerizable aliphatic N-Boc imines, giving products in 66-99% ee and syn/anti = >20:1-13:1. Catalytic asymmetric synthesis of nemonapride is also demonstrated using the catalyst derived from Sm(5)O(O-iPr)(13).

Fate and transport of trace metals and rare earth elements in the Snake River, an AMD/ARD-impacted watershed. Montezuma, Colorado USA.

NASA Astrophysics Data System (ADS)

McKnight, D. M.; Rue, G.

2017-12-01

Recent research in Snake River Watershed, located near the historic boomtown of Montezuma and adjacent the Continental Divide in the Colorado Rocky Mountains, has revealed the distinctive occurrence of rare earth elements (REE) at high concentrations. Here the weathering of the mineralized lithology naturally generates acid rock drainage (ARD) in addition to drainage recieved from abandoned mine adits throughout the area, results in aqueous REE concentrations three orders of magnitude higher than in most major rivers. The dominant mechanism responsible for this enrichment; their dissolution from secondary and accessory mineral stocks, abundant in REEs, promoted by the low pH waters generated from geochemical weathering of disseminated sulfide minerals. While REEs behave conservatively in acidic conditions, as well as in the presence of stabilizing ligands such as sulfate, downstream circumneutral inputs from pristine streams and a rising pH are resulting in observed fractional losses of heavy rare earth elements as well as partitioning towards colloidal and solid phases. These finding in combination with the established role of dissolved organic matter (DOM) in binding with both trace metals and REEs, suggest that competitive interactions, complexation, and scavenging are likely contributing to these proportional losses. However, outstanding questions yet remain regarding the effects of an increasing flux of trace metals as well as REEs from the Snake River Watershed into Dillon Reservoir, a major drinking water supply for the City of Denver, in part due to hydroclimatological drivers that are enhancing geochemical weathering and reducing groundwater recharge in alpine areas across the Colorado Rockies. Based on these findings also we seek to broaden this body of work to further investigate the behavior of rare earth elements (REE) in other aquatic environment as well the influence of trace metals, DOM, and pH in altering their reactivity and subsequent watershed

Magnetic Partitioning Nanofluid for Rare Earth Extraction from Geothermal Fluids

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGrail, Bernard P.; Thallapally, Praveen K.; Liu, Jian

Rare earth metals are critical materials in a wide variety of applications in generating and storing renewable energy and in designing more energy efficient devices. Extracting rare earth metals from geothermal brines is a very challenging problem due to the low concentrations of these elements and engineering challenges with traditional chemical separations methods involving packed sorbent beds or membranes that would impede large volumetric flow rates of geothermal fluids transitioning through the plant. We are demonstrating a simple and highly cost-effective nanofluid-based method for extracting rare earth metals from geothermal brines. Core-shell composite nanoparticles are produced that contain a magneticmore » iron oxide core surrounded by a shell made of silica or metal-organic framework (MOF) sorbent functionalized with chelating ligands selective for the rare earth elements. By introducing the nanoparticles at low concentration (≈0.05 wt%) into the geothermal brine after it passes through the plant heat exchanger, the brine is exposed to a very high concentration of chelating sites on the nanoparticles without need to pass through a large and costly traditional packed bed or membrane system where pressure drop and parasitic pumping power losses are significant issues. Instead, after a short residence time flowing with the brine, the particles are effectively separated out with an electromagnet and standard extraction methods are then applied to strip the rare earth metals from the nanoparticles, which are then recycled back to the geothermal plant. Recovery efficiency for the rare earths at ppm level has now been measured for both silica and MOF sorbents functionalized with a variety of chelating ligands. A detailed preliminary techno-economic performance analysis of extraction systems using both sorbents showed potential to generate a promising internal rate of return (IRR) up to 20%.« less

Silylation of C-H bonds in aromatic heterocycles by an Earth-abundant metal catalyst

NASA Astrophysics Data System (ADS)

Toutov, Anton A.; Liu, Wen-Bo; Betz, Kerry N.; Fedorov, Alexey; Stoltz, Brian M.; Grubbs, Robert H.

2015-02-01

Heteroaromatic compounds containing carbon-silicon (C-Si) bonds are of great interest in the fields of organic electronics and photonics, drug discovery, nuclear medicine and complex molecule synthesis, because these compounds have very useful physicochemical properties. Many of the methods now used to construct heteroaromatic C-Si bonds involve stoichiometric reactions between heteroaryl organometallic species and silicon electrophiles or direct, transition-metal-catalysed intermolecular carbon-hydrogen (C-H) silylation using rhodium or iridium complexes in the presence of excess hydrogen acceptors. Both approaches are useful, but their limitations include functional group incompatibility, narrow scope of application, high cost and low availability of the catalysts, and unproven scalability. For this reason, a new and general catalytic approach to heteroaromatic C-Si bond construction that avoids such limitations is highly desirable. Here we report an example of cross-dehydrogenative heteroaromatic C-H functionalization catalysed by an Earth-abundant alkali metal species. We found that readily available and inexpensive potassium tert-butoxide catalyses the direct silylation of aromatic heterocycles with hydrosilanes, furnishing heteroarylsilanes in a single step. The silylation proceeds under mild conditions, in the absence of hydrogen acceptors, ligands or additives, and is scalable to greater than 100 grams under optionally solvent-free conditions. Substrate classes that are difficult to activate with precious metal catalysts are silylated in good yield and with excellent regioselectivity. The derived heteroarylsilane products readily engage in versatile transformations enabling new synthetic strategies for heteroaromatic elaboration, and are useful in their own right in pharmaceutical and materials science applications.

Release of Nitrogen during Planetary Accretion Explains Missing Nitrogen in Earth's Mantle

NASA Astrophysics Data System (ADS)

Liu, J.; Dorfman, S.; Lv, M.; Li, J.; Kono, Y.

2017-12-01

Nitrogen and carbon are essential elements for life on Earth, and their relative abundances in planetary bodies (C/N ratios) are important for understanding planetary evolution and habitability1,2. However, the high C/N ratio in the bulk silicate Earth relative to CI chondrites and other volatile-rich chondrites is difficult to explain with partitioning behavior between silicate and metallic liquid or solubility in silicate melt, and has thus been a major unsolved problem in geochemistry1-5. Because core formation does not explain nitrogen depletion in the mantle, another process is required to match the observed BSE C/N ratio, such as devolatilization of metallic liquid. Previous studies have examined the Fe-C phase diagram extensively (e.g. ref. 6), but very limited melting data is available for the Fe-N system7. Here we examine melting relations for four Fe-N-C compositions with 1-7 wt% nitrogen up to 7 GPa and 2200 K in the Paris-Edinburgh press by a combination of in-situ X-ray radiography, X-ray diffraction and ex-situ electron microprobe techniques. In striking contrast to the Fe-C system, near-surface melting in all compositions in the Fe-N-C system entails release of nitrogen fluid and depletion of nitrogen from the liquid alloy. This could provide a pathway for nitrogen to escape the magma ocean in the accretion stage while carbon is retained. On the basis of our experimental results, we propose a new quantitative model of mantle nitrogen evolution during the core formation stage to explain the high BSE C/N ratios and resolve the paradox of missing mantle nitrogen1-5. Although nitrogen itself is not a greenhouse gas, the nitrogen released to the atmosphere from metallic melt early in Earth's history could amplify the greenhouse effect through collision-enhanced absorption8,9, which may help to explain warm surface temperatures during the Hadean and Archean eras on Earth when the solar luminosity was 25-30% lower than the present10. References1. Bergin et

Elucidating electrolyte decomposition under electron-rich environments at the lithium-metal anode

DOE PAGES

Camacho-Forero, Luis E.; Balbuena, Perla B.

2017-11-07

The lithium metal anode is one of the key components of the lithium–sulfur (Li–S) batteries, which are considered one of the most promising candidates for the next generation of battery systems. However, one of the main challenges that have prevented Li-metal anodes from becoming feasible to be used in commercial batteries is the continuous decomposition of the electrolyte due to its high reactivity, which leads to the formation of solid–electrolyte interphase (SEI) layers. The properties of the SEI can dramatically affect the performance of the batteries. Thus, a rigorous understanding of the electrolyte decomposition is crucial to elucidate improvements inmore » performance of the Li–S technology. Here, in this work, using density functional theory (DFT) and ab initio molecular dynamics simulations (AIMD), we investigate the effect of electron-rich environments on the decomposition mechanism of electrolyte species in pure 1,2-dimethoxyethane (DME) solvent and 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(fluorosulfonyl)imide (LiFSI) salt solutions. It is found that systems with pure DME require an average environment of at least ~0.9 |e| per molecule for a DME to decompose into CH 3O - and C 2H 4 2-via a 4-electron transfer. In the case of mixtures, the salts are very prone to react with any excess of electrons. In addition, DME dehydrogenation due to reactions with fragments coming from the salt decompositions was detected. Formation of oligomer anionic species from DME and salt fragments were also identified from the AIMD simulations. Finally, the thermodynamics and kinetics of the most relevant electrolyte decomposition reactions were characterized. DME decomposition reactions predicted from the AIMD simulations were found to be thermodynamically favorable under exposure to Li atoms and/or by reactions with salt fragments. Lastly, in most cases, these reactions were shown to have low to moderate activation barriers.« less

Elucidating electrolyte decomposition under electron-rich environments at the lithium-metal anode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Camacho-Forero, Luis E.; Balbuena, Perla B.

The lithium metal anode is one of the key components of the lithium–sulfur (Li–S) batteries, which are considered one of the most promising candidates for the next generation of battery systems. However, one of the main challenges that have prevented Li-metal anodes from becoming feasible to be used in commercial batteries is the continuous decomposition of the electrolyte due to its high reactivity, which leads to the formation of solid–electrolyte interphase (SEI) layers. The properties of the SEI can dramatically affect the performance of the batteries. Thus, a rigorous understanding of the electrolyte decomposition is crucial to elucidate improvements inmore » performance of the Li–S technology. Here, in this work, using density functional theory (DFT) and ab initio molecular dynamics simulations (AIMD), we investigate the effect of electron-rich environments on the decomposition mechanism of electrolyte species in pure 1,2-dimethoxyethane (DME) solvent and 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(fluorosulfonyl)imide (LiFSI) salt solutions. It is found that systems with pure DME require an average environment of at least ~0.9 |e| per molecule for a DME to decompose into CH 3O - and C 2H 4 2-via a 4-electron transfer. In the case of mixtures, the salts are very prone to react with any excess of electrons. In addition, DME dehydrogenation due to reactions with fragments coming from the salt decompositions was detected. Formation of oligomer anionic species from DME and salt fragments were also identified from the AIMD simulations. Finally, the thermodynamics and kinetics of the most relevant electrolyte decomposition reactions were characterized. DME decomposition reactions predicted from the AIMD simulations were found to be thermodynamically favorable under exposure to Li atoms and/or by reactions with salt fragments. Lastly, in most cases, these reactions were shown to have low to moderate activation barriers.« less

High Performance High Temperature Thermoelectric Composites with Metallic Inclusions

NASA Technical Reports Server (NTRS)

Firdosy, Samad A. (Inventor); Kaner, Richard B. (Inventor); Ma, James M. (Inventor); Fleurial, Jean-Pierre (Inventor); Star, Kurt (Inventor); Bux, Sabah K. (Inventor); Ravi, Vilupanur A. (Inventor)

2017-01-01

The present invention provides a composite thermoelectric material. The composite thermoelectric material can include a semiconductor material comprising a rare earth metal. The atomic percent of the rare earth metal in the semiconductor material can be at least about 20%. The composite thermoelectric material can further include a metal forming metallic inclusions distributed throughout the semiconductor material. The present invention also provides a method of forming this composite thermoelectric material.

Earth Science in 1970

ERIC Educational Resources Information Center

Geotimes, 1971

1971-01-01

Reviews advancements in earth science during 1970 in each of these areas: economic geology (fuels), economic geology (metals), economic geology (nonmetals), environmental geology, geochemistry, manpower, hydrology, mapping, marine geology, mineralogy, paleontology, plate tectonics, politics and geology, remote sensing, and seismology. (PR)

Water in the Earth's Interior: Distribution and Origin

NASA Astrophysics Data System (ADS)

Peslier, Anne H.; Schönbächler, Maria; Busemann, Henner; Karato, Shun-Ichiro

2017-10-01

The concentration and distribution of water in the Earth has influenced its evolution throughout its history. Even at the trace levels contained in the planet's deep interior (mantle and core), water affects Earth's thermal, deformational, melting, electrical and seismic properties, that control differentiation, plate tectonics and volcanism. These in turn influenced the development of Earth's atmosphere, oceans, and life. In addition to the ubiquitous presence of water in the hydrosphere, most of Earth's "water" actually occurs as trace amounts of hydrogen incorporated in the rock-forming silicate minerals that constitute the planet's crust and mantle, and may also be stored in the metallic core. The heterogeneous distribution of water in the Earth is the result of early planetary differentiation into crust, mantle and core, followed by remixing of lithosphere into the mantle after plate-tectonics started. The Earth's total water content is estimated at 18_{-15}^{+81} times the equivalent mass of the oceans (or a concentration of 3900_{-3300}^{+32700} ppm weight H2O). Uncertainties in this estimate arise primarily from the less-well-known concentrations for the lower mantle and core, since samples for water analyses are only available from the crust, the upper mantle and very rarely from the mantle transition zone (410-670 km depth). For the lower mantle (670-2900 km) and core (2900-4500 km), the estimates rely on laboratory experiments and indirect geophysical techniques (electrical conductivity and seismology). The Earth's accretion likely started relatively dry because it mainly acquired material from the inner part of the proto-planetary disk, where temperatures were too high for the formation and accretion of water ice. Combined evidence from several radionuclide systems (Pd-Ag, Mn-Cr, Rb-Sr, U-Pb) suggests that water was not incorporated in the Earth in significant quantities until the planet had grown to ˜60-90% of its current size, while core formation

Rare earths, the lanthanides, yttrium and scandium

USGS Publications Warehouse

Bedinger, G.; Bleiwas, D.

2012-01-01

In 2011, rare earths were recovered from bastnasite concentrates at the Mountain Pass Mine in California. Consumption of refined rare-earth products decreased in 2011 from 2010. U.S. rare-earth imports originated primarily from China, with lesser amounts from Austria, Estonia, France and Japan. The United States imported all of its demand for yttrium metal and yttrium compounds, with most of it originating from China. Scandium was imported in various forms and processed domestically.

Infrasound: Connecting the Solid Earth, Oceans, and Atmosphere

NASA Astrophysics Data System (ADS)

Hedlin, M. A. H.; Walker, K.; Drob, D. P.; de Groot-Hedlin, C. D.

2012-05-01

The recently reinvigorated field of infrasonics is poised to provide insight into atmospheric structure and the physics of large atmospheric phenomena, just as seismology has shed considerable light on the workings and structure of Earth's solid interior. Although a natural tool to monitor the atmosphere and shallow Earth for nuclear explosions, it is becoming increasingly apparent that infrasound also provides another means to monitor a suite of natural hazards. The frequent observation of geophysical sources—such as the unsteady sea surface, volcanoes, and earthquakes—that radiate energy both up into the atmosphere and down into the liquid or solid Earth and transmission of energy across Earth's boundaries reminds us that Earth is an interconnected system. This review details the rich history of the unheard sound in the atmosphere and the role that infrasonics plays in helping us understand the Earth system.

PROCESS OF PRODUCING ACTINIDE METALS

DOEpatents

Magel, T.T.

1959-07-14

The preparation of actinide metals in workable, coherent form is described. In general, the objects of the invention are achieved by heating a mixture of an oxide and a halide of an actinide metal such as uranium with an alkali metal on alkaline earth metal reducing agent in the presence of iodine.

Alkali and alkaline earth metallic (AAEM) species leaching and Cu(II) sorption by biochar.

PubMed

Li, Mi; Lou, Zhenjun; Wang, Yang; Liu, Qiang; Zhang, Yaping; Zhou, Jizhi; Qian, Guangren

2015-01-01

Alkali and alkaline earth metallic (AAEM) species water leaching and Cu(II) sorption by biochar prepared from two invasive plants, Spartina alterniflora (SA) and water hyacinth (WH), were explored in this work. Significant amounts of Na and K can be released (maximum leaching for Na 59.0 mg g(-1) and K 79.9 mg g(-1)) from SA and WH biochar when they are exposed to contact with water. Cu(II) removal by biochar is highly related with pyrolysis temperature and environmental pH with 600-700 °C and pH of 6 showing best performance (29.4 and 28.2 mg g(-1) for SA and WH biochar). Cu(II) sorption exerts negligible influence on Na/K/Mg leaching but clearly promotes the release of Ca. Biochars from these two plant species provide multiple benefits, including nutrient release (K), heavy metal immobilization as well as promoting the aggregation of soil particles (Ca) for soil amelioration. AAEM and Cu(II) equilibrium concentrations in sorption were analyzed by positive matrix factorization (PMF) to examine the factors underlying the leaching and sorption behavior of biochar. The identified factors can provide insightful understanding on experimental phenomena. Copyright © 2014 Elsevier Ltd. All rights reserved.

Porous metallic bodies

DOEpatents

Landingham, R.L.

1984-03-13

Porous metallic bodies having a substantially uniform pore size of less than about 200 microns and a density of less than about 25 percent theoretical, as well as the method for making them, are disclosed. Group IIA, IIIB, IVB, VB, and rare earth metal hydrides a

CADMIUM-RARE EARTH BORATE GLASS AS REACTOR CONTROL MATERIAL

DOEpatents

Ploetz, G.L.; Ray, W.E.

1958-11-01

A reactor control rod fabricated from a cadmiumrare earth-borate glass is presented. The rare earth component of this glass is selected from among those rare earths having large neutron capture cross sections, such as samarium, gadolinium or europium. Partlcles of this glass are then dispersed in a metal matrix by standard powder metallurgy techniques.

Influence of rare earth content on Mm-based AB 5 metal hydride alloys for Ni-MH batteries-An X-ray fluorescence study

NASA Astrophysics Data System (ADS)

Ananth, M. V.; Raju, M.; Manimaran, K.; Balachandran, G.; Nair, Lekshmi M.

AB 5-type MH alloys with Mm (Misch metal) as the A part (with varied rare earth contents in Mm) were investigated for rare earth by XRF analysis and battery performance by life cycle tests with an objective of understanding the influence of rare earth content on electrochemical hydrogen storage. The La/Ce ratio was found to vary from 0.51 to 18.73. The capacity output varied between 179 and 266 mAh g -1. The results show that the La/Ce ratio has a strong influence on the performance, with the best performance realized with samples having an La/Ce ratio of around 12. La enhancement facilitates easy activation due to refinement in grain size and interstitial dimensions. Also, an orderly influence on crystalline structure could be seen. The study demonstrates that the rare earth content is an essential factor in determining the maximum capacity output because of its influence on crystal orientation as well as an increase in the radius of the interstitials, lattice constants and cell volumes.

Spin-orbit qubits of rare-earth-metal ions in axially symmetric crystal fields.

PubMed

Bertaina, S; Shim, J H; Gambarelli, S; Malkin, B Z; Barbara, B

2009-11-27

Contrary to the well-known spin qubits, rare-earth-metal qubits are characterized by a strong influence of crystal field due to large spin-orbit coupling. At low temperature and in the presence of resonance microwaves, it is the magnetic moment of the crystal-field ground state which nutates (for several micros) and the Rabi frequency Omega(R) is anisotropic. Here, we present a study of the variations of Omega(R)(H(0)) with the magnitude and direction of the static magnetic field H(0) for the odd 167Er isotope in a single crystal CaWO(4):Er(3+). The hyperfine interactions split the Omega(R)(H(0)) curve into eight different curves which are fitted numerically and described analytically. These "spin-orbit qubits" should allow detailed studies of decoherence mechanisms which become relevant at high temperature and open new ways for qubit addressing using properly oriented magnetic fields.

K2-111 b - a short period super-Earth transiting a metal poor, evolved old star