Electronic structure of Rh and Ru doped Sr2IrO4

NASA Astrophysics Data System (ADS)

Chikara, Shalinee; Fabbris, Gilberto; Terzic, Jasminka; Qi, Tongfei; Butrouna, Kamal; Veiga, Larissa; Souza Neto, Narcizo; Cao, Gang; Haskel, Daniel

2014-03-01

Sr2IrO4 is a spin-orbit interaction(SOI) assisted insulator. It has been proposed that the weaker SOI in the 4 d -substituted Sr2Ir1-x(Ru, Rh)xO4 closes the insulating gap, rendering it a paramagnetic metal. Rh(4d5) is isoelectronic to Ir(5d5) whereas Ru(4d4) has one less electron in the 4 d -band. The AFM-I/PM-M transition takes place at lower x for Ru than Rh, presumably due to the effect of hole doping. X-ray absorption near edge structure (XANES) and x-ray magnetic circular dichroism (XMCD) measurements at the Ir L2 , 3 edges show that < L . S > is non-zero and independent of x. This is indicative of a strong local 5 d spin orbit interaction that is rather insensitive to the 4 d doping. In contrast, measurements at the L2 , 3 edges of Ru and Rh show < L . S > ~ 0 for all x. The results point to the importance of local 4 d / 5 d - 2 p hybridization as opposed to 4 d - 5 d band formation in the Rh and Ru doped Sr2IrO4.

Novel thermoelectric properties of complex transition-metal oxides.

PubMed

Terasaki, Ichiro; Iwakawa, Manabu; Nakano, Tomohito; Tsukuda, Akira; Kobayashi, Wataru

2010-01-28

We report how the thermopower of complex transition-metal oxides is susceptible to small changes in material parameters. In the A-site ordered perovskite oxide R(2/3)Cu(3)Ti(3.6)Ru(0.4)O(12), the thermopower changes from 15 to -100 microV K(-1) at 300 K in going from R = La to Er. We associate this with the hybridization between Cu 3d and Ru 4d electrons, which depends on R. For stronger hybridization, the Cu 3d electrons become more itinerant leading to positive thermopower. In the A-site ordered perovskite cobalt oxide Sr(3)YCo(4)O(10.5), the spin state of the Co(3+) ions determines the magnitude of the thermopower, where partial isovalent substitution (Ca for Sr and Rh for Co) enhances the thermopower whilst keeping the resistivity intact. These substitutions stabilize the low spin state of the Co(3+) ions, which affects the thermopower through the entropy of the background for the carriers. We propose that the control of the magnetism plays a pivotal role in determining the thermopower in a certain class of complex oxides.

[Determination of ru, rh and Pd in 30% trialkyl phosphine oxide (TRPO)-kerosene by inductively coupled plasma-atomic emission spectrum (ICP-AES)].

PubMed

Wang, Jian-Chen; Zhang, Lin

2013-07-01

The determination method of Ru, Rh and Pd in 30% TRPO-kerosene ICP-AES was studied by using aqueous calibration reference solution and choosing ethanol as diluent. The effects of the contents of 30% TRPO-kerosene and aqueous solution and the concentration of HNO3 in 30% TRPO-kerosene on the intensities of Ru, Rh and Pd were described. The optimized condition for preparing samples and calibration solutions was chosen as follows: The contents of 30% TRPO-kerosene and aqueous phase were 10% (V/V) and 5% (V/V) respectively and the concentration of HNO3 30% TRPO-kerosene was 0.20 mol x L(-1). The determination method of Au, Ru and Pd was set up according to the above condition. The detection limit, precision and recovery ratio of Ru, Rh and Pd are well. The method is not only used in determination of Au, Ru and Pd in 30% TRPO-kerosene, but also used in other organic phases.

New Data on Some Short-Lived Isotopes of Ruthenium and Rhodium; NUEVOS DATOS SOBRE ALGUNOS ISOTOPOS DE RUTENIO Y RODIO DE VIDA CORTA

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

Baumgartner, F.; Bedmar, A.P.

1961-01-01

BS>Ru and Rh isotopes with mass numbers 107 and 108 and Rh/sup 109/ were obtained from fission products. Ru/sup 107/ was also prepared by the nuclear process Pd/sup 110/ (n, alpha ) Ru/sup 107/. Beta and gamma energies of these nuclides were studied spectrometrically and the gamma lines found for Ru/sup 107/ and Ru/sup 108/ (and daughter) were useful for the precise determination of their half lives. Rh/sup 109/ was identified through its daughter Pd/sup 109/ in the mixture of rhodium isotopes from fission products. lrradiation of natural paladium with fast neutrons led to an activity that may only bemore » attributed to Rh/ sup 110/. Neither its half life nor its decay energy was determined accurately. (auth)« less

Discovering the balance of steric and electronic factors needed to provide a new structural motif for photocatalytic hydrogen production from water.

PubMed

White, Travis A; Whitaker, Brittany N; Brewer, Karen J

2011-10-05

Ru,Rh,Ru supramolecules are known to undergo multielectron photoreduction and reduce H(2)O to H(2). Ru,Rh bimetallics were recently shown to photoreduce but not catalyze H(2)O reduction. Careful tuning of sterics and electronics for [(TL)(2)Ru(dpp)RhCl(2)(TL')](3+) produce active bimetallic photocatalysts (TL = terminal ligand). The system with TL,TL' = Ph(2)phen photocatalytically reduces H(2)O to H(2) while TL,TL' = phen,bpy or bpy,(t)Bu(2)bpy do not.

[Separation of [Rh-103m]-rhodocene derivatives from the parent [103Ru]ruthenocene derivatives and their organ distribution].

PubMed

Wenzel, M; Wu, Y F

1987-01-01

The radioactive decay of [103Ru]ruthenocene derivatives leads to 103mRh labelled rhodocinium derivatives, which can be separated by the extraction of a lipophilic solution of the ruthenocen derivate with water. The separation factor 103mRh/103Ru reaches values of 32:1 Rh3+ ions are not liberated and extracted. The organ distribution of the 103mRh labelled rhodocinium derivatives gained from ruthenocene and from N-isopropyl-ruthenocene amphetamine is different from the distribution of the parent ruthenocene compound. The liver and kidney uptake of the rhodocinium-amphetamine is much higher than the uptake with ruthenocene amphetamine.

Platinum-group elements fractionation by selective complexing, the Os, Ir, Ru, Rh-arsenide-sulfide systems above 1020 °C

NASA Astrophysics Data System (ADS)

Helmy, Hassan M.; Bragagni, Alessandro

2017-11-01

The platinum-group element (PGE) contents in magmatic ores and rocks are normally in the low μg/g (even in the ng/g) level, yet they form discrete platinum-group mineral (PGM) phases. IPGE (Os, Ir, Ru) + Rh form alloys, sulfides, and sulfarsenides while Pt and Pd form arsenides, tellurides, bismuthoids and antimonides. We experimentally investigate the behavior of Os, Ru, Ir and Rh in As-bearing sulfide system between 1300 and 1020 °C and show that the prominent mineralogical difference between IPGE (+Rh) and Pt and Pd reflects different chemical preference in the sulfide melt. At temperatures above 1200 °C, Os shows a tendency to form alloys. Ruthenium forms a sulfide (laurite RuS2) while Ir and Rh form sulfarsenides (irarsite IrAsS and hollingworthite RhAsS, respectively). The chemical preference of PGE is selective: IPGE + Rh form metal-metal, metal-S and metal-AsS complexes while Pt and Pd form semimetal complexes. Selective complexing followed by mechanical separation of IPGE (and Rh)-ligand from Pt- and Pd-ligand associations lead to PGE fractionation.

Atomic structure solution of the complex quasicrystal approximant Al77Rh15Ru8 from electron diffraction data.

PubMed

Samuha, Shmuel; Mugnaioli, Enrico; Grushko, Benjamin; Kolb, Ute; Meshi, Louisa

2014-12-01

The crystal structure of the novel Al77Rh15Ru8 phase (which is an approximant of decagonal quasicrystals) was determined using modern direct methods (MDM) applied to automated electron diffraction tomography (ADT) data. The Al77Rh15Ru8 E-phase is orthorhombic [Pbma, a = 23.40 (5), b = 16.20 (4) and c = 20.00 (5) Å] and has one of the most complicated intermetallic structures solved solely by electron diffraction methods. Its structural model consists of 78 unique atomic positions in the unit cell (19 Rh/Ru and 59 Al). Precession electron diffraction (PED) patterns and high-resolution electron microscopy (HRTEM) images were used for the validation of the proposed atomic model. The structure of the E-phase is described using hierarchical packing of polyhedra and a single type of tiling in the form of a parallelogram. Based on this description, the structure of the E-phase is compared with that of the ε6-phase formed in Al-Rh-Ru at close compositions.

Crystal structure, oxidation state and magnetism of Sr{sub x}La{sub 2−x}Cu{sub 0.5}Ru{sub 0.5}O{sub 4} (x=1, 1.5)

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

Lü, Minfeng, E-mail: m.f.lv@ciac.jl.cn; Deng, Xiaolong; Waerenborgh, João C.

2014-03-15

Sr{sub x}La{sub 2−x}Cu{sub 0.5}Ru{sub 0.5}O{sub 4} (x=1, 1.5) oxides with K{sub 2}NiF{sub 4}-type structure were prepared by solid state reaction and characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, magnetic and electrical resistivity measurements. The SrLaCu{sub 0.5}Ru{sub 0.5}O{sub 4} phase was obtained for the first time with a negligible amount of impurities. The octahedral Cu/RuO{sub 6} units are more elongated in SrLaCu{sub 0.5}Ru{sub 0.5}O{sub 4} than in Sr{sub 1.5}La{sub 0.5}Cu{sub 0.5}Ru{sub 0.5}O{sub 4} indicating a greater extent of static Jahn–Teller distortion. XPS suggests that mixed ion pairs Ru{sup 5+}/Ru{sup 4+}↔Cu{sup +}/Cu{sup 2+} are present in SrLaCu{sub 0.5}Ru{sub 0.5}O{sub 4}, whilemore » Ru remains as Ru{sup 5+} and Cu as Cu{sup 2+} in Sr{sub 1.5}La{sub 0.5}Cu{sub 0.5}Ru{sub 0.5}O{sub 4}. Both samples show spin-glass behavior, which can be explained by competition between ferromagnetic and antiferromagnetic superexchange interactions. The negative Weiss temperature estimated for SrLaCu{sub 0.5}Ru{sub 0.5}O{sub 4}, −318 K, is significantly lower than −11.5 K deduced for Sr{sub 1.5}La{sub 0.5}Cu{sub 0.5}Ru{sub 0.5}O{sub 4} which may be related to the higher static Jahn–Teller distortion in the former oxide. -- Graphical abstract: SrLaCu{sub 0.5}Ru{sub 0.5}O{sub 4} with K{sub 2}NiF{sub 4}-type structure show a larger static Jahn–Teller distortion than Sr{sub 1.5}La{sub 0.5}Cu{sub 0.5}Ru{sub 0.5}O{sub 4}, which may be related to stronger antiferromagnetic superexchange interactions. Highlights: • SrLaCu{sub 0.5}Ru{sub 0.5}O{sub 4} (I) larger Jahn–Teller (J–T) distortion than Sr{sub 1.5}La{sub 0.5}Cu{sub 0.5}Ru{sub 0.5}O{sub 4} (II). • Octahedral Cu/RuO{sub 6} units are more elongated in I than in II. • Mixed ion pairs Ru{sup 5+}/Ru{sup 4+}↔Cu{sup +}/Cu{sup 2+} are present in I, while Ru remains as Ru{sup 5+} and Cu as Cu{sup 2+} in II. • Negative Weiss temperature of I significantly lower, consistent with higher J–T distortion.« less

GRAVIMETRIC DETERMINATION OF PLATINIUM, PALLADIUM, RUTHENIUM, RHODIUM AS TlPtS$sub 3$, TlPd$sub 2$S$sub 3$, TlRu$sub 2$S$sub 6$, TlRh$sub 2$S$sub 4$ (in Russian)

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

Rudnev, N.A.; Malofeeva, G.I.

1963-07-01

Gravimetric methods were developed for the determination of microamounts of Ru, Rh, Pt, and Pd as TlRu/sub 2/S/sub 6/, TlRh/sub 2/S/sub 4/ TlPtS/sub 3/, and TlPd/sub 2/S/sub 3/. The methods are simpl e, rapid, and satisfactorily accurate. (auth)

Ru-core/Cu-shell bimetallic nanoparticles with controlled size formed in one-pot synthesis.

PubMed

Helgadottir, I; Freychet, G; Arquillière, P; Maret, M; Gergaud, P; Haumesser, P H; Santini, C C

2014-12-21

Suspensions of bimetallic nanoparticles (NPs) of Ru and Cu have been synthesized by simultaneous decomposition of two organometallic compounds in an ionic liquid. These suspensions have been characterized by Anomalous Small-Angle X-ray Scattering (ASAXS) at energies slightly below the Ru K-edge. It is found that the NPs adopt a Ru-core, a Cu-shell structure, with a constant Ru core diameter of 1.9 nm for all Ru : Cu compositions, while the Cu shell thickness increases with Cu content up to 0.9 nm. The formation of RuCuNPs thus proceeds through rapid decomposition of the Ru precursor into RuNPs of constant size followed by the reaction of the Cu precursor and agglomeration as a Cu shell. Thus, the different decomposition kinetics of precursors make possible the elaboration of core-shell NPs composed of two metals without chemical affinity.

Metal-insulator transition and superconductivity induced by Rh doping in the binary pnictides RuPn (Pn=P, As, Sb)

NASA Astrophysics Data System (ADS)

Hirai, Daigorou; Takayama, Tomohiro; Hashizume, Daisuke; Takagi, Hidenori

2012-04-01

Binary ruthenium pnictides, RuP and RuAs, with an orthorhombic MnP structure, were found to show a metal to a nonmagnetic insulator transition at TMI = 270 and 200 K, respectively. In the metallic region above TMI, a structural phase transition, accompanied with a weak anomaly in the resistivity and the magnetic susceptibility, indicative of a pseudogap formation, was identified at Ts = 330 and 280 K, respectively. These two transitions were suppressed by substituting Ru with Rh. We found superconductivity with a maximum Tc = 3.7 and 1.8 K in a narrow composition range around the critical point for the pseudogap phase, Rh content xc = 0.45 and 0.25 for Ru1-xRhxP and Ru1-xRhxAs, respectively, which may provide us with a nonmagnetic route to superconductivity at a quantum critical point.

Bounding Analysis of Effects of Fractionation of Radionuclides inFallout on Estimation of Doses to Atomic Veterans

DTIC Science & Technology

2007-05-04

140 Sm-156 Y-91m Rh - 103m Cd-115 Te-129 La-141 Eu-156 Y-91 Ru-105 In-115m I-130 Ce-141 Eu-157 Sr-92 Rh -105m Sn-121 Te-131m Ce-143 Gd-159 Y-92 Rh ...Tc-99m 6.02 h R 1.09E+00n (0.886) Ru-103 39.35 d V 2.04E-07 9.65E-01 6.81E-12 Rh - 103m 56.119 m V 1.00E+00n (0.997) 1.00E+00 Ru-105 4.44 h...08 1.24E-08 9.09E-09 Rh - 103m 6.36E-09 1.34E-08 1.23E-08 9.07E-09 Ru-105 1.20E-02 5.36E-02 4.05E-02 3.22E-02 2.90E-10 1.30E-09 9.79E-10 7.78E-10

First principles study of surface stability and segregation of PdRuRh ternary metal alloy system

NASA Astrophysics Data System (ADS)

Aspera, Susan Meñez; Arevalo, Ryan Lacdao; Nakanishi, Hiroshi; Kasai, Hideaki

2018-05-01

The recognized importance on the studies of alloyed materials is due to the high possibility of forming designer materials that caters to different applications. In any reaction and application, the stability and configuration of the alloy combination are important. In this study, we analyzed the surface stability and segregation of ternary metal alloy system PdRuRh through first principles calculation using density functional theory (DFT). We considered the possibility of forming phases as observed in the binary combinations of elements, i.e., completely miscible, and separating phases. With that, the model we analyzed for the ternary metal alloy slabs considers forming complete atomic miscibility, segregation of each component, and segregation of one component with mixing of the two other. Our results show that for the ternary combination of Pd, Rh and Ru, the Pd atoms have high tendency to segregate at the surface, while due to the high tendency of Ru and Rh to mix, core formation of a mixed RuRh is possible. Also, we determined that the trend of stability in the binary alloy system is a good determinant of stability in the ternary alloy system.

Skeletal Ru/Cu catalysts prepared from crystalline and quasicrystalline ternary alloy precursors: characterization by X-ray absorption spectroscopy and CO oxidation.

PubMed

Highfield, James; Liu, Tao; Loo, Yook Si; Grushko, Benjamin; Borgna, Armando

2009-02-28

The Ru/Cu system is of historical significance in catalysis. The early development and application of X-ray absorption spectroscopy (XAS) led to the original 'bimetallic cluster" concept for highly-immiscible systems. This work explores alkali leaching of Al-based ternary crystalline and quasicrystalline precursors as a potential route to bulk Ru/Cu alloys. Single-phase ternary alloys at 3 trial compositions; Al(71)Ru(22)Cu(7), Al(70.5)Ru(17)Cu(12.5), and Al(70)Ru(10)Cu(20), were prepared by arc melting of the pure metal components. After leaching, the bimetallic residues were characterized principally by transmission XAS, "as-leached" and after annealing in H(2) (and passivation) in a thermobalance. XRD and BET revealed a nanocrystalline product with a native structure of hexagonal Ru. XPS surface analysis of Ru(22)Cu(7) and Ru(17)Cu(12.5) found only slight enrichment by Cu in the as-leached forms, with little change upon annealing. Ru(10)Cu(20) was highly segregated as-leached. XANES data showed preferential oxidation of Cu in Ru(22)Cu(7), implying that it exists as an encapsulating layer. TG data supports this view since it does not show the distinct two-stage O(2) uptake characteristic of skeletal Ru. Cu K-edge EXAFS data for Ru(22)Cu(7) were unique in showing a high proportion of Ru neighbours. The spacing, d(CuRu) = 2.65 A, was that expected from a hypothetical (ideal) solid solution at this composition, but this is unlikely in such a bulk-immiscible system and Ru K-edge EXAFS failed to confirm bulk alloying. Furthermore its invariance under annealing was more indicative of an interfacial bond between bulk components, although partial alloying with retention of local order cannot entirely be ruled out. The XAS and XPS data were reconciled in a model involving surface and bulk segregation, Cu being present at both the grain exterior and in ultra-fine internal pores. This structure can be considered as the 3-dimensional analogue of the classical type. Preliminary studies in CO and H(2) oxidation were made in a DRIFTS flow reactor with on-line MS, and their activities and selectivities were compared against skeletal Ru and Cu controls, Ru/Al(2)O(3), and Au/Fe(2)O(3). All samples were active in CO oxidation above approximately 50 degrees C, showing light-off temperatures in the range 60-70 degrees C. Ru(22)Cu(7) and Ru(17)Cu(12.5) also showed good selectivities (vs. H(2) oxidation), attributed tentatively to Ru-modified Cu surfaces of varying thickness. These compositions are promising candidates to test in a (PROX) fuel processor to supply purified (CO-free) H(2) to a PEM fuel cell.

Growth and sacrificial oxidation of transition metal nanolayers

NASA Astrophysics Data System (ADS)

Tsarfati, Tim; Zoethout, Erwin; van de Kruijs, Robbert; Bijkerk, Fred

2009-04-01

Growth and oxidation of Au, Pt, Pd, Rh, Cu, Ru, Ni and Co layers of 0.3-4.3 nm thickness on Mo have been investigated with ARPES and AFM. Co and Ni layers oxidize while the Mo remains metallic. For nobler metals, the on top O and oxidation state of subsurface Mo increase, suggesting sacrificial e - donation by Mo. Au and Cu, in spite of their significantly lower surface free energy, grow in islands on Mo and actually promote Mo oxidation. Applications of the sacrificial oxidation in nanometer thin layers exist in a range of nanoscopic devices, such as nano-electronics and protection of e.g. multilayer X-ray optics for astronomy, medicine and lithography.

Platinum-group element concentrations in pyrite from the Main Sulfide Zone of the Great Dyke of Zimbabwe

NASA Astrophysics Data System (ADS)

Piña, R.; Gervilla, F.; Barnes, S.-J.; Oberthür, T.; Lunar, R.

2016-10-01

The Main Sulfide Zone (MSZ) of the Great Dyke of Zimbabwe hosts the world's second largest resource of platinum-group elements (PGE) after the Bushveld Complex in South Africa. The sulfide assemblage of the MSZ comprises pyrrhotite, pentlandite, chalcopyrite, and minor pyrite. Recently, several studies have observed in a number of Ni-Cu-PGE ore deposits that pyrite may host significant amounts of PGE, particularly Pt and Rh. In this study, we have determined PGE and other trace element contents in pyrite from the Hartley, Ngezi, Unki, and Mimosa mines of the Great Dyke by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Based on the textures and PGE contents, two types of pyrite can be differentiated. Py1 occurs as individual euhedral or subhedral grains or clusters of crystals mostly within chalcopyrite and pentlandite, in some cases in the form of symplectitic intergrowths, and is PGE rich (up to 99 ppm Pt and 61 ppm Rh; 1.7 to 47.1 ppm Ru, 0.1 to 7.8 ppm Os, and 1.2 to 20.2 ppm Ir). Py2 occurs as small individual euhedral or subhedral crystals within pyrrhotite, pentlandite, and less frequently within chalcopyrite and silicates and has low PGE contents (<0.11 ppm Pt, <0.34 ppm Rh, <2.5 ppm Ru, <0.37 ppm Ir, and <0.40 ppm Os). Py1 contains higher Os, Ir, Ru, Rh, and Pt contents than the associated pyrrhotite, pentlandite, and chalcopyrite, whereas Py2 has similar PGE contents as coexisting pyrrhotite and pentlandite. Based on the textural relationships, two different origins are attributed for each pyrite type. Py1 intergrowth with pentlandite and chalcopyrite is inferred to have formed by late, low temperature (<300 °C) decomposition of residual Ni-rich monosulfide solid solution, whereas Py2 is suggested to have formed by replacement of pyrrhotite and pentlandite caused by late magmatic/hydrothermal fluids.

What Factors Control Platinum-Group Element (PGE) Abundances in Basalts From the Ontong Java Plateau?

NASA Astrophysics Data System (ADS)

Chazey, W. J.; Neal, C. R.

2002-12-01

Eleven samples encompassing four sites drilled by Ocean Drilling Program Leg 192 to the Ontong Java Plateau (OJP) were analyzed for major, trace and platinum-group (PGEs: Ir, Ru, Rh, Pt, and Pd) elements. Based on major and trace element chemistry, these are divided into two groups: a primitive group, which was newly discovered on Leg 192, and Kwaimbaita-type basalts, which are ubiquitous on the OJP (cf. Tejada et al., 2002, J. Pet. 43:449). The primitive group is relatively enriched in MgO, Ni, and Cr and relatively depleted in incompatible elements compared to the Kwaimbaita-type basalts. Petrography indicates that the fractionating phases during emplacement of both types of basalts were olivine and Cr-spinel +/- plagioclase +/- cpx. Normalized PGE profiles are fractionated, but exhibit a flattening between Ru and Ir and occasionally an enrichment in Ir. It has been shown that chromite can preferentially incorporate Os and Ru (Kd ?150) over Ir (Kd ?100), which may account for the Ir and Ru systematics. We do not consider sulfide to be a factor in fractionating the PGEs because it is either absent or present as a trace phase in these basalts and the OJP basalts are sulfur undersaturated (Michael and Cornell, 1996, EOS 77:714). Additionally, the primitive samples from the OJP also have Cu/Pd ratios (4500-8000) that are roughly similar to primitive mantle (7300), and have a generally flat transition from Pd to Y on a primitive mantle-normalized plot. It is unlikely that these samples reached sulfur saturation. The Kwaimbaita-type basalts have slightly elevated Cu/Pd ratios (9000-14000). While there are subtle differences between the PGE profiles of basalts from the Leg 192 drill cores compared to OJP basalts from subaerial outcrops in the Solomon Islands (e.g., the former have general lower Pt/Rh and higher Rh/Ru ratios), it is apparent that silicate and oxide phases are controlling the PGE profiles and abundances. For example, the six samples analyzed from Site 1185 demonstrate a positive correlation of Ru and Ir with Cr and Ni, suggesting a close association of these elements with the observed olivine and Cr-spinel phenocrysts. For all OJP basalts for which we have PGE data, there is a general positive correlation using MgO (or Cr or Ni) as a fractionation index and PGE abundance as well as ratios such as Pt/Y. Therefore, fractional crystallization controls the PGE contents of the OJP basalts. However, as noted by Ely and Neal (2002, Chem. Geol., in press) the abundances require a source enriched in the PGEs over upper mantle and, in some cases, primitive mantle. Such sources require a PGE enriched component that could be from the outer core, although as noted by Parkinson et al. (2001, EOS 82:F1398) this component is not always required. Further work is underway to substantiate this.

DEEP, SHALLOW AND EYE LENS DOSES FROM 106Ru/106Rh-A COMPARSION.

PubMed

Kumar, Munish; Bakshi, A K; Rakesh, R B; Ratna, P; Kulkarni, M S; Datta, D

2017-11-01

106Ru/106Rh is unique amongst other commonly used beta sources such as 147Pm, 85Kr, 204Tl, 32P, natU and 90Sr/90Y in the sense that it is capable of simultaneously delivering shallow/skin, eye lens and deep/whole body doses (WBDs) and they differ from each other substantially. In view of this, the investigation of various quantities defined for individual monitoring is possible and this makes 106Ru/106Rh beta source, a classical example in radiation protection and dosimetry. This led us to estimate skin, eye lens and WBDs for 106Ru/106Rh beta source. Optically stimulated luminescence based ultra-thin α-Al2O3:C disc dosimeters were used in the present study. Typical values (relative) of the eye lens and whole body/deep doses with respective to the skin dose (100%) were experimentally measured as ~66 ± 4.6% and 17 ± 3.9%, respectively. The study shows that 106Ru/106Rh beta source is capable of delivering even WBD which is not the case with other beta sources. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Ultrathin Cr added Ru film as a seedless Cu diffusion barrier for advanced Cu interconnects

NASA Astrophysics Data System (ADS)

Hsu, Kuo-Chung; Perng, Dung-Ching; Yeh, Jia-Bin; Wang, Yi-Chun

2012-07-01

A 5 nm thick Cr added Ru film has been extensively investigated as a seedless Cu diffusion barrier. High-resolution transmission electron microscopy micrograph, X-ray diffraction (XRD) pattern and Fourier transform-electron diffraction pattern reveal that a Cr contained Ru (RuCr) film has a glassy microstructure and is an amorphous-like film. XRD patterns and sheet resistance data show that the RuCr film is stable up to 650 °C, which is approximately a 200 °C improvement in thermal stability as compared to that of the pure Ru film. X-ray photoelectron spectroscopy depth profiles show that the RuCr film can successfully block Cu diffusion, even after a 30-min 650 °C annealing. The leakage current of the Cu/5 nm RuCr/porous SiOCH/Si stacked structure is about two orders of magnitude lower than that of a pristine Ru sample for electric field below 1 MV/cm. The RuCr film can be a promising Cu diffusion barrier for advanced Cu metallization.

For cermet inert anode containing oxide and metal phases useful for the electrolytic production of metals

DOEpatents

Ray, Siba P.; Liu, Xinghua; Weirauch, Douglas A.

2002-01-01

A cermet inert anode for the electrolytic production of metals such as aluminum is disclosed. The inert anode comprises a ceramic phase including an oxide of Ni, Fe and M, where M is at least one metal selected from Zn, Co, Al, Li, Cu, Ti, V, Cr, Zr, Nb, Ta, W, Mo, Hf and rare earths, preferably Zn and/or Co. Preferred ceramic compositions comprise Fe.sub.2 O.sub.3, NiO and ZnO or CoO. The cermet inert anode also comprises a metal phase such as Cu, Ag, Pd, Pt, Au, Rh, Ru, Ir and/or Os. A preferred metal phase comprises Cu and Ag. The cermet inert anodes may be used in electrolytic reduction cells for the production of commercial purity aluminum as well as other metals.

Methods of reforming hydrocarbon fuels using hexaaluminate catalysts

DOEpatents

Gardner, Todd H [Morgantown, WV; Berry, David A [Morgantown, WV; Shekhawat, Dushyant [Morgantown, WV

2012-03-27

A metal substituted hexaaluminate catalyst for reforming hydrocarbon fuels to synthesis gas of the general formula AB.sub.yAl.sub.12-yO.sub.19-.delta., A being selected from alkali metals, alkaline earth metals and lanthanide metals or mixtures thereof. A dopant or surface modifier selected from a transitions metal, a spinel of an oxygen-ion conductor is incorporated. The dopant may be Ca, Cs, K, La, Sr, Ba, Li, Mg, Ce, Co, Fe, Ir, Rh, Ni, Ru, Cu, Pe, Os, Pd, Cr, Mn, W, Re, Sn, Gd, V, Ti, Ag, Au, and mixtures thereof. The oxygen-ion conductor may be a perovskite selected from M'RhO.sub.3, M'PtO.sub.3, M'PdO.sub.3, M'IrO.sub.3, M'RuO.sub.3 wherein M'=Mg, Sr, Ba, La, Ca; a spinel selected from MRh.sub.2O.sub.4, MPt.sub.2O.sub.4, MPd.sub.2O.sub.4, MIr.sub.2O.sub.4, MRu.sub.2O.sub.4 wherein M=Mg, Sr, Ba, La, Ca and mixtures thereof; a florite is selected from M''O.sub.2.

Structure and magnetic properties of Fe12X clusters

NASA Astrophysics Data System (ADS)

Gutsev, G. L.; Johnson, L. E.; Belay, K. G.; Weatherford, C. A.; Gutsev, L. G.; Ramachandran, B. R.

2014-02-01

The electronic and geometrical structures of a Fe12X family of binary clusters Fe12Al, Fe12Sc, Fe12Ti, Fe12V, Fe12Cr, Fe12Mn, Fe12Co, Fe12Ni, Fe12Cu, Fe12Zn, Fe12Y, Fe12Zr, Fe12Nb, Fe12Mo, Fe12Tc, Fe12Ru, Fe12Rh, Fe12Pd, Fe12Ag, Fe12Cd, and Fe12Gd are studied using density functional theory within generalized gradient approximation. It is found that the geometrical structures corresponding to the lowest total energy states found for the Fe12X clusters possess icosahedral shape with the substituent atom occupying the central or a surface site. The only exception presents Fe12Nb where a squeezed cage structure is the energetically most favorable. The substitution of an atom in the Fe13 cluster results in the decrease of its total spin magnetic moment of 44 μB, except for Fe12Mn and Fe12Gd. The Fe12X clusters are more stable than the parent Fe13 cluster when X = Al, Sc, Ti, V, Co, Y, Zr, Nb, Mo, Tc, Ru, and Rh.

Interfacial and Alloying Effects on Activation of Ethanol from First-Principles

DOE PAGES

An, Wei; Men, Yong; Wang, Jinguo; ...

2017-02-24

Here, we present a first-principles density-functional theory study of ethanol activation at oxide/Rh(111) interface and the alloying effect on mitigating carbon deposition, which are essential to direct ethanol fuel cell (DEFC) anode reaction and steam reforming of ethanol (SRE) reaction. Our calculated results show that charge can transfer from Rh(111) substrate to MO x chain (e.g., MoO 3 and MnO 2), or from MO x chain (e.g., MgO, SnO 2, ZrO 2, and TiO 2) to Rh(111) substrate. The OH-binding strength is increased exponentially with M δ+ charge ranging from 1.4 to 2.2, which renders MnO 2/Rh(111) and MgO/Rh(111) interfacesmore » weaker OH-binding, and thereby enhanced oxidizing functionality of OH* for promoting ethanol oxidation reaction (EOR) at DEFC anode. For efficient C–C bond breaking, a large number of Rh ensemble sizes are critically needed at the interface of MO x/Rh(111). We found that Rh 1Au 3 near surface alloy has the weakest C* and CO* binding, followed by Rh 1Cu 3 and Rh 1Pd 3 near surface alloys, while Rh 1Ir 3 and Rh 1Ru 3 surface alloys have C* and CO* binding strength similar to that of pure Rh metal. The general implication of this study is that by engineering alloyed structure of weakened C* and CO* binding complemented with metal oxides of weakened OH-binding, high-performance DEFC anode or SRE catalysts can be identified.« less

Synthesis and characterization of bimetallic metal-organic framework Cu-Ru-BTC with HKUST-1 structure.

PubMed

Gotthardt, Meike A; Schoch, Roland; Wolf, Silke; Bauer, Matthias; Kleist, Wolfgang

2015-02-07

The bimetallic metal-organic framework Cu-Ru-BTC with the stoichiometric formula Cu2.75Ru0.25(BTC)2·xH2O, which is isoreticular to HKUST-1, was successfully prepared in a direct synthesis using mild reaction conditions. The partial substitution of Cu(2+) by Ru(3+) centers in the paddlewheel structure and the absence of other Ru-containing phases was proven using X-ray absorption spectroscopy.

Platinum-ruthenium nanotubes and platinum-ruthenium coated copper nanowires as efficient catalysts for electro-oxidation of methanol

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

Zheng, Jie; Cullen, David A.; Forest, Robert V.

2015-01-15

The sluggish kinetics of methanol oxidation reaction (MOR) is a major barrier to the commercialization of direct methanol fuel cells (DMFCs). In this study, we report a facile synthesis of platinum–ruthenium nanotubes (PtRuNTs) and platinum–ruthenium-coated copper nanowires (PtRu/CuNWs) by galvanic displacement reaction using copper nanowires as a template. The PtRu compositional effect on MOR is investigated; the optimum Pt/Ru bulk atomic ratio is about 4 and surface atomic ratio about 1 for both PtRuNTs and PtRu/CuNWs. Enhanced specific MOR activities are observed on both PtRuNTs and PtRu/CuNWs compared with the benchmark commercial carbon-supported PtRu catalyst (PtRu/C, Hispec 12100). Finally, x-raymore » photoelectron spectroscopy (XPS) reveals a larger extent of electron transfer from Ru to Pt on PtRu/CuNWs, which may lead to a modification of the d-band center of Pt and consequently a weaker bonding of CO (the poisoning intermediate) on Pt and a higher MOR activity on PtRu/CuNWs.« less

The applicability of the catalytic wet-oxidation to CELSS

NASA Technical Reports Server (NTRS)

Takahashi, Y.; Nitta, K.; Ohya, H.; Oguchi, M.

1987-01-01

The wet oxidation catalysis of Au, Pd, Pt, Rh or Ru on a ceramic honeycomb carrier was traced in detail by 16 to 20 repetitive batch tests each. As a result, Pt or Pd on a honeycomb carrier was shown to catalyze complete nitrogen gasification as N2. Though the catalysts which realize both complete nitrogen gasification and complete oxidation could not be found, the Ru+Rh catalyst was found to be most promising. Ru honeycomb catalyzed both nitrification and nitrogen gasification.

Thermoelectric and magnetic properties of CeRh 1- xM xSn (M=Co, Ni, Ru)

NASA Astrophysics Data System (ADS)

Echizen, Yuji; Yamane, Kyotaro; Takabatake, Toshiro

2003-05-01

The thermopower S, electrical resistivity ρ, and magnetic susceptibility χ are reported on CeRh 1- xM xSn (M=Co, Ni, Ru; x⩽0.25). The Ni doping changes the valence-fluctuating behavior of χ( T) for x=0 to the Currie-Weiss type, whereas the Ru one to the Pauli-type. Nevertheless, all the substitutions result in a decrease of the rather large maximum of S=60 μV/ K for x = 0.

Superconductivity and Competing Ordered Phase in RuPn (Pn = As, P)

NASA Astrophysics Data System (ADS)

Hirai, Daigorou; Takayama, Tomohiro; Hashizume, Daisuke; Yamamoto, Ayako; Takagi, Hidenori

2011-03-01

Unconventional superconductivity likely manifests itself when some competing electronic phases are suppressed down to zero temperature such as cuprates and iron-pnictide superconductors. Therefore, the correlated metallic state neighboring a competing electronic ordering can be a promising playground for unconventional superconductivity. Here we report superconductivity emerging adjacent to electronically ordered phases of RuPn (Pn = As, P). We found that RuAs(P) exhibits phase transitions at 240 (265) K, which is discerned as a drop of magnetic susceptibility or a resistivity upturn. Such anomalies can be suppressed by substituting Rh to the Ru site. Accompanied by the disappearance of the electronic order, superconductivity was found to emerge below 1.8 K and 3.8 K for RuAs and RuP, respectively. The superconductivity in Rh substituted RuPn, which neighbors a competing electronic order, might exhibit an exotic pairing state as seen in the unconventional superconductors known to date.

Site Preference of Ternary Alloying Additions to AuTi

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Mosca, Hugo O.; Noebe, Ronald D.

2006-01-01

Atomistic modeling of the site substitution behavior of several alloying additions, namely. Na, Mg, Al, Si. Sc, V, Cr, Mn. Fe, Co, Ni, Cu, Zn, Y, Zr. Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, and Pt in B2 TiAu is reported. The 30 elements can be grouped according to their absolute preference for a specific site, regardless of concentration, or preference for available sites in the deficient sublattice. Results of large scale simulations are also presented, distinguishing between additions that remain in solution from those that precipitate a second phase.

CH4 dehydrogenation on Cu(1 1 1), Cu@Cu(1 1 1), Rh@Cu(1 1 1) and RhCu(1 1 1) surfaces: A comparison studies of catalytic activity

NASA Astrophysics Data System (ADS)

Zhang, Riguang; Duan, Tian; Ling, Lixia; Wang, Baojun

2015-06-01

In the CVD growth of graphene, the reaction barriers of the dehydrogenation for hydrocarbon molecules directly decide the graphene CVD growth temperature. In this study, density functional theory method has been employed to comparatively probe into CH4 dehydrogenation on four types of Cu(1 1 1) surface, including the flat Cu(1 1 1) surface (labeled as Cu(1 1 1)) and the Cu(1 1 1) surface with one surface Cu atom substituted by one Rh atom (labeled as RhCu(1 1 1)), as well as the Cu(1 1 1) surface with one Cu or Rh adatom (labeled as Cu@Cu(1 1 1) and Rh@Cu(1 1 1), respectively). Our results show that the highest barrier of the whole CH4 dehydrogenation process is remarkably reduced from 448.7 and 418.4 kJ mol-1 on the flat Cu(1 1 1) and Cu@Cu(1 1 1) surfaces to 258.9 kJ mol-1 on RhCu(1 1 1) surface, and to 180.0 kJ mol-1 on Rh@Cu(1 1 1) surface, indicating that the adsorbed or substituted Rh atom on Cu catalyst can exhibit better catalytic activity for CH4 complete dehydrogenation; meanwhile, since the differences for the highest barrier between Cu@Cu(1 1 1) and Cu(1 1 1) surfaces are smaller, the catalytic behaviors of Cu@Cu(1 1 1) surface are very close to the flat Cu(1 1 1) surface, suggesting that the morphology of Cu substrate does not obviously affect the dehydrogenation of CH4, which accords with the reported experimental observations. As a result, the adsorbed or substituted Rh atom on Cu catalyst exhibit a better catalytic activity for CH4 dehydrogenation compared to the pure Cu catalyst, especially on Rh-adsorbed Cu catalyst, we can conclude that the potential of synthesizing high-quality graphene with the help of Rh on Cu foils may be carried out at relatively low temperatures. Meanwhile, the adsorbed Rh atom is the reaction active center, namely, the CVD growth can be controlled by manipulating the graphene nucleation position.

Dendritic Core-Frame and Frame Multimetallic Rhombic Dodecahedra: A Comparison Study of Composition and Structure Effects on Electrocatalysis of Methanol Oxidation

DOE PAGES

Mathurin, Leanne E.; Tao, Jing; Xin, Huolin; ...

2017-11-03

The composition and structure of multimetallic nanostructures can be tailored to enhance electrocatalytic properties. This work reports a seed-mediated synthesis of novel multimetallic dendritic core-frame and frame nanostructures with a rhombic dodecahedral shape for enhanced methanol oxidation reaction (MOR). The synthesis involves in situ formation of Cu seeds and the subsequent selective deposition of Pt and Ru on the edges and vertices of the Cu seeds to generate CuPt and CuPtRu dendritic core-frame nanostructures. The core-frame nanostructures undergo a post acetic acid etching process to form the frame nanostructures. While transmission electron microscopy reveals the morphology and elemental distribution ofmore » the nanostructures, X-ray diffraction patterns confirm the alloy compositions of dendritic frames for both the core-frame and frame nanostructures. Compared to the bimetallic CuPt nanostructures, the trimetallic CuPtRu nanostructures lower the onset potential and completely suppress the peak current in the reverse scan for MOR. The CuPtRu alloyed frame nanostructures are the best to prevent Ru leaching compared to the CuPtRu core-frame nanostructures and PtRu catalysts. X-ray photoelectron spectroscopy reveals that all three elements become more electron rich in the frame nanostructures. Thus, further refining the composition ratio of the CuPtRu alloyed dendritic frame nanostructures can lead to more efficient catalysts at a lower cost for MOR.« less

Dendritic Core-Frame and Frame Multimetallic Rhombic Dodecahedra: A Comparison Study of Composition and Structure Effects on Electrocatalysis of Methanol Oxidation

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

Mathurin, Leanne E.; Tao, Jing; Xin, Huolin

The composition and structure of multimetallic nanostructures can be tailored to enhance electrocatalytic properties. This work reports a seed-mediated synthesis of novel multimetallic dendritic core-frame and frame nanostructures with a rhombic dodecahedral shape for enhanced methanol oxidation reaction (MOR). The synthesis involves in situ formation of Cu seeds and the subsequent selective deposition of Pt and Ru on the edges and vertices of the Cu seeds to generate CuPt and CuPtRu dendritic core-frame nanostructures. The core-frame nanostructures undergo a post acetic acid etching process to form the frame nanostructures. While transmission electron microscopy reveals the morphology and elemental distribution ofmore » the nanostructures, X-ray diffraction patterns confirm the alloy compositions of dendritic frames for both the core-frame and frame nanostructures. Compared to the bimetallic CuPt nanostructures, the trimetallic CuPtRu nanostructures lower the onset potential and completely suppress the peak current in the reverse scan for MOR. The CuPtRu alloyed frame nanostructures are the best to prevent Ru leaching compared to the CuPtRu core-frame nanostructures and PtRu catalysts. X-ray photoelectron spectroscopy reveals that all three elements become more electron rich in the frame nanostructures. Thus, further refining the composition ratio of the CuPtRu alloyed dendritic frame nanostructures can lead to more efficient catalysts at a lower cost for MOR.« less

Investigation of amorphous RuMoC alloy films as a seedless diffusion barrier for Cu/ p-SiOC:H ultralow- k dielectric integration

NASA Astrophysics Data System (ADS)

Jiao, Guohua; Liu, Bo; Li, Qiran

2015-08-01

Ultrathin RuMoC amorphous films prepared by magnetron co-sputtering with Ru and MoC targets in a sandwiched scheme Si/ p-SiOC:H/RuMoC/Cu were investigated as barrier in copper metallization. The evolution of final microstructure of RuMoC alloy films show sensitive correlation with the content of doped Mo and C elements and can be easily controlled by adjusting the sputtering power of the MoC target. There was no signal of interdiffusion between the Cu and SiOC:H layer in the sample of Cu/RuMoC/ p-SiOC:H/Si, even annealing up to 500 °C. Very weak signal of oxygen have been confirmed in the RuMoC barrier layer both as-deposited and after being annealed, and a good performance on preventing oxygen diffusion has been proved. Leakage current and resistivity evaluations also reveal the excellent thermal reliability of this Si/ p-SiOC:H/RuMoC/Cu film stack at the temperatures up to 500 °C, indicating its potential application in the advanced barrierless Cu metallization.

Electron microscope studies of nano-domain structures in Ru-based magneto-superconductors: RuSr(2)Gd(1.5)Ce(0.5)Cu(2)O(10-delta) (Ru-1222) and RuSr(2)GdCu(2)O(8) (Ru-1212).

PubMed

Yokosawa, Tadahiro; Awana, V P S Veer Pal Singh; Kimoto, Koji; Takayama-Muromachi, Eiji; Karppinen, Maarit; Yamauchi, Hisao; Matsui, Yoshio

2004-01-01

Microstructures of the RuSr(2)Gd(1.5)Ce(0.5)Cu(2)O(10-delta) (Ru-1222) and RuSr(2)GdCu(2)O(8) (Ru-1212) magneto-superconductors have been investigated by using selected-area electron diffraction, convergent-beam electron diffraction, dark-field electron microscopy and high-resolution electron microscopy at room temperature. Both Ru-1212 and Ru-1222 consist of nm-size domains stacked along the [Formula: see text] direction, where the domains are formed by two types of superstructures due to ordering of rotated RuO(6) octahedra about the c-axis. In Ru-1212, both primitive-and body-centered tetragonal superstructures (the possible space groups: P4/mbm and I4/mcm) are derived to form the corresponding nm-domains. It is of great interest that Ru-1212 consists of domains of two crystallographically different superstructures, while the similar domains observed in Ru-1222 have crystallographically identical superstructure with an orthorhombic symmetry (possible space group: Aeam), related by 90 degrees rotation around the c-axis (Yokosawa et al., 2003, submitted for publication).

Nanoamorphous carbon-based photonic crystal infrared emitters

DOEpatents

Norwood, Robert A [Tucson, AZ; Skotheim, Terje [Tucson, AZ

2011-12-13

Provided is a tunable radiation emitting structure comprising: a nanoamorphous carbon structure having a plurality of relief features provided in a periodic spatial configuration, wherein the relief features are separated from each other by adjacent recessed features, and wherein the nanoamorphous carbon comprises a total of from 0 to 60 atomic percent of one or more dopants of the dopant group consisting of: transition metals, lanthanoids, electro-conductive carbides, silicides and nitrides. In one embodiment, a dopant is selected from the group consisting of: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La and other lanthanides, Hf, Ta, W, Rh, Os, Ir, Pt, Au, and Hg. In one embodiment, a dopant is selected from the group consisting of: electro-conductive carbides (like Mo.sub.2C), silicides (like MoSi.sub.2) and nitrides (like TiN).

Stabilization of Pt monolayer catalysts under harsh conditions of fuel cells

DOE PAGES

Zhang, Xiaoming; Liu, Ping; Yu, Shansheng; ...

2015-05-21

We employed density functional theory (DFT) to explore the stability of core (M = Cu, Ru, Rh, Pd, Ag, Os, Ir, Au)-shell (Pt) catalysts under harsh conditions, including solutions and reaction intermediates involved in the oxygen reduction reaction (ORR) in fuel cells. A pseudomorphic surface alloy (PSA) with a Pt monolayer (Pt 1ML) supported on an M surface, Pt 1ML/M(111) or (001), was considered as a model system. Different sets of candidate M cores were identified to achieve a stable Pt 1ML shell depending on the conditions. In vacuum conditions, the Pt 1ML shell can be stabilized on the mostmore » of M cores except Cu, Ag, and Au. The situation varies under various electrochemical conditions. Depending on the solutions and the operating reaction pathways of the ORR, different M should be considered. Pd and Ir are the only core metals studied, being able to keep the Pt ML shell intact in perchloric acid, sulfuric acid, phosphoric acid, and alkaline solutions as well as under the ORR conditions via different pathways. Ru and Os cores should also be paid attention, which only fall during the ORR via the *OOH intermediate. Rh core works well as long as the ORR does not undergo the pathway via *O intermediate. Our results show that PSAs can behave differently from the near surface alloy, Pt 1ML/M 1ML/Pt(111), highlighting the importance of considering both chemical environments and the atomic structures in rational design of highly stable core-shell nanocatalysts. Finally, the roles that d-band center of a core M played in determining the stability of supported Pt 1ML shell were also discussed.« less

Stabilization of Pt monolayer catalysts under harsh conditions of fuel cells

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

Zhang, Xiaoming; Yu, Shansheng; Zheng, Weitao, E-mail: wtzheng@jlu.edu.cn, E-mail: pingliu3@bnl.gov

2015-05-21

We employed density functional theory to explore the stability of core (M = Cu, Ru, Rh, Pd, Ag, Os, Ir, Au)-shell (Pt) catalysts under harsh conditions, including solutions and reaction intermediates involved in the oxygen reduction reaction (ORR) in fuel cells. A pseudomorphic surface alloy (PSA) with a Pt monolayer (Pt{sub 1ML}) supported on an M surface, Pt{sub 1ML}/M(111) or (001), was considered as a model system. Different sets of candidate M cores were identified to achieve a stable Pt{sub 1ML} shell depending on the conditions. In vacuum conditions, the Pt{sub 1ML} shell can be stabilized on the most ofmore » M cores except Cu, Ag, and Au. The situation varies under various electrochemical conditions. Depending on the solutions and the operating reaction pathways of the ORR, different M should be considered. Pd and Ir are the only core metals studied, being able to keep the Pt{sub ML} shell intact in perchloric acid, sulfuric acid, phosphoric acid, and alkaline solutions as well as under the ORR conditions via different pathways. Ru and Os cores should also be paid attention, which only fall during the ORR via the *OOH intermediate. Rh core works well as long as the ORR does not undergo the pathway via *O intermediate. Our results show that PSAs can behave differently from the near surface alloy, Pt{sub 1ML}/M{sub 1ML}/Pt(111), highlighting the importance of considering both chemical environments and the atomic structures in rational design of highly stable core-shell nanocatalysts. Finally, the roles that d-band center of a core M played in determining the stability of supported Pt{sub 1ML} shell were also discussed.« less

Microscopic evidence for magnetic ordering in NdCu3Ru4O12 : 63,65Cu nuclear quadrupole resonance study

NASA Astrophysics Data System (ADS)

Yogi, M.; Niki, H.; Hedo, M.; Komesu, S.; Nakama, T.

2018-05-01

We have conducted 63,65Cu nuclear quadrupole resonance (NQR) measurements on A-site ordered perovskite compounds LaCu3Ru4O12 and NdCu3Ru4O12 to investigate their ground state and spin fluctuations. While there is only one Cu site in the crystal structure, multiple NQR resonance lines were observed. This is presumed to be due to the presence of slight distortion and lattice defects in the samples. The nuclear spin-lattice relaxation rate divided by temperature, 1 /T1 T , for LaCu3Ru4O12 showed almost constant value indicating the Fermi-liquid state. A remarkable increase in 1 /T1 T due to spin fluctuations was observed in NdCu3Ru4O12 . Furthermore, an evident magnetic phase transition at TM = 0.6 K was revealed from the distinct peak of 1 /T1 T and the broadening of the NQR spectrum.

Separation of 103Ru from a proton irradiated thorium matrix: A potential source of Auger therapy radionuclide 103mRh

DOE PAGES

Mastren, Tara; Radchenko, Valery; Hopkins, Philip D.; ...

2017-12-22

Ruthenium-103 is the parent isotope of 103mRh (t1/2 56.1 min), an isotope of interest for Auger electron therapy. During the proton irradiation of thorium targets, large amounts of 103Ru are generated through proton induced fission. Furthermore, the development of a two part chemical separation process to isolate 103Ru in high yield and purity from a proton irradiated thorium matrix on an analytical scale is described herein. The first part employed an anion exchange column to remove cationic actinide/lanthanide impurities along with the majority of the transition metal fission products. Secondly, an extraction chromatographic column utilizing diglycolamide functional groups was usedmore » to decontaminate 103Ru from the remaining impurities. This method then resulted in a final radiochemical yield of 83 ± 5% of 103Ru with a purity of 99.9%. Additionally, measured nuclear reaction cross sections for the formation of 103Ru and 106Ru via the 232Th(p,f) 103,106Ru reactions are reported within.« less

Separation of 103Ru from a proton irradiated thorium matrix: A potential source of Auger therapy radionuclide 103mRh

PubMed Central

Hopkins, Philip D.; Engle, Jonathan W.; Weidner, John W.; Copping, Roy; Brugh, Mark; Nortier, F. Meiring; Birnbaum, Eva R.; John, Kevin D.

2017-01-01

Ruthenium-103 is the parent isotope of 103mRh (t1/2 56.1 min), an isotope of interest for Auger electron therapy. During the proton irradiation of thorium targets, large amounts of 103Ru are generated through proton induced fission. The development of a two part chemical separation process to isolate 103Ru in high yield and purity from a proton irradiated thorium matrix on an analytical scale is described herein. The first part employed an anion exchange column to remove cationic actinide/lanthanide impurities along with the majority of the transition metal fission products. Secondly, an extraction chromatographic column utilizing diglycolamide functional groups was used to decontaminate 103Ru from the remaining impurities. This method resulted in a final radiochemical yield of 83 ± 5% of 103Ru with a purity of 99.9%. Additionally, measured nuclear reaction cross sections for the formation of 103Ru and 106Ru via the 232Th(p,f)103,106Ru reactions are reported within. PMID:29272318

Compositional effects in Ru, Pd, Pt, and Rh-doped mesoporous tantalum oxide catalysts for ammonia synthesis.

PubMed

Yue, Chaoyang; Qiu, Longhui; Trudeau, Michel; Antonelli, David

2007-06-11

A series of early metal-promoted Ru-, Pd-, Pt-, and Rh-doped mesoporous tantalum oxide catalysts were synthesized using a variety of dopant ratios and dopant precursors, and the effects of these parameters on the catalytic activity of NH3 synthesis from H2 and N2 were explored. Previous studies on this system supported an unprecedented mechanism in which N-N cleavage occurred at the Ta sites rather than on Ru. The results of the present study showed, for all systems, that Ba is a better promoter than Cs or La and that the nitrate is a superior precursor for Ba than the isopropoxide or the hydroxide. 15N-labeling studies showed that residual nitrate functions as the major ammonia source in the first hour but that it does not account for the ammonia produced after the nitrate is completely consumed. Ru3(CO)12 proved to be a better Ru precursor than RuCl(3).3H2O, and an almost linear increase in activity with increasing Ru loading level was observed at 350 degrees C (623 K). However, at 175 degrees C (448 K), the increase in Ru had no effect on the reaction rate. Pd functioned with comparable rates to Ru, while Pt and Rh functioned far less efficiently. The surprising activities for the Pd-doped catalysts, coupled with XPS evidence for low-valent Ta in this catalyst system, support a mechanism in which cleavage of the N-N triple bond occurs on Ta rather than the precious metal because the Ea value for N-N cleavage on Pd is 2.5 times greater than that for Ru, and the 9.3 kJ mol-1 Ea value measured previously for the Ru system suggests that N-N cleavage cannot occur at the Ru surface.

Heat flux measurements of Tb3M series (M=Co, Rh and Ru): Specific heat and magnetocaloric properties

NASA Astrophysics Data System (ADS)

Monteiro, J. C. B.; Lombardi, G. A.; dos Reis, R. D.; Freitas, H. E.; Cardoso, L. P.; Mansanares, A. M.; Gandra, F. G.

2016-12-01

We report on the magnetic properties and magnetocaloric effect (MCE) for the Tb3M series, with M=Co, Rh and Ru, obtained using a heat flux technique. The specific heat of Tb3Co and Tb3Rh are very similar, with a first order type transition occurring around 6 K below the magnetic ordering temperature without any corresponding feature on the magnetization. The slightly enhanced electronic specific heat, the Debye temperature around 150 K and the presence of the magnetic specific heat well above the ordering temperature are also characteristic of many other compounds of the R3M family (R=Rare Earth). The specific heat for Tb3Ru, however, presents two peaks at 37 K and 74 K. The magnetization shows that below the first peak the system presents an antiferromagnetic behavior and is paramagnetic above 74 K. We obtained a magnetocaloric effect for M=Co and Rh, -∆S=12 J/kg K, but for Tb3Ru it is less than 3 J/kg K (μ0∆H=5 T). We believe that the experimental results show that the MCE is directly related with the process of hybridization of the (R)5d-(M)d electrons that occurs in the R3M materials.

A highly sensitive luminescent probe based on Ru(II)-bipyridine complex for Cu2+, l-Histidine detection and cellular imaging.

PubMed

Zhang, Shi-Ting; Li, Panpan; Liao, Caiyun; Luo, Tingting; Kou, Xingming; Xiao, Dan

2018-05-02

A ruthenium(II) bipyridyl complex conjugated with functionalized Schiff base (RuA) has been synthesized and functioned as a luminescent probe. The luminescence of RuA was greatly quenched by Cu 2+ due to its molecular coordination with paramagnetic Cu 2+ . Subsequently, the addition of l-Histidine can turn on the luminescence of the RuA-Cu(II) ensemble, which can be attributed to the replacement of RuA in RuA-Cu(II) ensemble by l-Histidine. On the basis of the quenching and recovery of the luminescence of RuA, we proposed a rapid and highly sensitive on-off-on luminescent assay for sensing Cu 2+ and l-Histidine in aqueous solution. Under the optimal conditions, Cu 2+ and l-Histidine can be detected in the concentration range of 5 nM-9.0 μM and 50 nM-30 μM, respectively, and the corresponding detection limits were calculated to be 0.35 and 0.44 nM (S/N=3), separately. The proposed luminescent probe has been successfully utilized for the analysis of Cu 2+ and l-Histidine in real samples (drinking water and biological fluids). Furthermore, the probe revealed good photostability, low cytotoxicity and excellent permeability, making it a suitable candidate for cell imaging and labeling in vitro. Copyright © 2018 Elsevier B.V. All rights reserved.

Chemically engineered papain as artificial formate dehydrogenase for NAD(P)H regeneration.

PubMed

Haquette, Pierre; Talbi, Barisa; Barilleau, Laure; Madern, Nathalie; Fosse, Céline; Salmain, Michèle

2011-08-21

Organometallic complexes of the general formula [(η(6)-arene)Ru(N⁁N)Cl](+) and [(η(5)-Cp*)Rh(N⁁N)Cl](+) where N⁁N is a 2,2'-dipyridylamine (DPA) derivative carrying a thiol-targeted maleimide group, 2,2'-bispyridyl (bpy), 1,10-phenanthroline (phen) or ethylenediamine (en) and arene is benzene, 2-chloro-N-[2-(phenyl)ethyl]acetamide or p-cymene were identified as catalysts for the stereoselective reduction of the enzyme cofactors NAD(P)(+) into NAD(P)H with formate as a hydride donor. A thorough comparison of their effectiveness towards NAD(+) (expressed as TOF) revealed that the Rh(III) complexes were much more potent catalysts than the Ru(II) complexes. Within the Ru(II) complex series, both the N⁁N and arene ligands forming the coordination sphere had a noticeable influence on the activity of the complexes. Covalent anchoring of the maleimide-functionalized Ru(II) and Rh(III) complexes to the cysteine endoproteinase papain yielded hybrid metalloproteins, some of them displaying formate dehydrogenase activity with potentially interesting kinetic parameters.

Attosecond nanotechnology: NEMS of energy storage and nanostructural transformations in materials

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

Beznosyuk, Sergey A., E-mail: bsa1953@mail.ru; Maslova, Olga A., E-mail: maslova-o.a@mail.ru; Zhukovsky, Mark S., E-mail: zhukovsky@list.ru

2015-10-27

The attosecond technology of the nanoelectromechanical system (NEMS) energy storage as active center fast transformation of nanostructures in materials is considered. The self-organizing relaxation of the NEMS active center containing nanocube of 256-atoms limited by planes (100) in the FCC lattice matrix of 4d-transition metals (Ru, Rh, Pd) is described by the quantum NEMS-kinetics (NK) method. Typical for these metals change of the NEMS active center physicochemical characteristics during the time of relaxation is presented. There are three types of intermediate quasistationary states of the NEMS active center. Their forms are plainly distinguishable. The full relaxed NEMS active centers (Ru{submore » 256}, Rh{sub 256}, Pd{sub 256}) accumulate next storage energies: E{sub Ru} = 2.27 eV/at, E{sub Rh} = 1.67 eV/at, E{sub Pd} = 3.02 eV/at.« less

Potential of transition metal atoms embedded in buckled monolayer g-C3N4 as single-atom catalysts.

PubMed

Li, Shu-Long; Yin, Hui; Kan, Xiang; Gan, Li-Yong; Schwingenschlögl, Udo; Zhao, Yong

2017-11-15

We use first-principles calculations to systematically explore the potential of transition metal atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au) embedded in buckled monolayer g-C 3 N 4 as single-atom catalysts. We show that clustering of Sc and Ti on g-C 3 N 4 is thermodynamically impeded and that V, Cr, Mn, and Cu are much less susceptible to clustering than the other TM atoms under investigation. Strong bonding of the transition metal atoms in the cavities of g-C 3 N 4 and high diffusion barriers together are responsible for single-atom fixation. Analysis of the CO oxidation process indicates that embedding of Cr and Mn in g-C 3 N 4 gives rise to promising single-atom catalysts at low temperature.

Sulfide petrology and highly siderophile element geochemistry of abyssal peridotites: a coupled study of samples from the Kane Fracture Zone (45°W 23°20N, MARK area, Atlantic Ocean)

NASA Astrophysics Data System (ADS)

Luguet, Ambre; Lorand, Jean-Pierre; Seyler, Monique

2003-04-01

Nineteen samples from the Kane Fracture Zone have been studied for sulfide mineralogy and analyzed for S, Se, platinum-group elements (PGE), and Au to assess the effect of refertilization processes on the PGE systematics of abyssal peridotites. The lherzolites show broadly chondritic PGE ratios and sulfide modal abundances (0.01 to 0.03 wt%) consistent with partial melting models, although the few pyroxene-hosted sulfide inclusions and in situ LAM-ICPMS analyses provide evidence for in situ mobilization of a Cu-Ni-rich sulfide partial melt. The most refractory harzburgites (spinel Cr# > 29) are almost devoid of magmatic sulfides and show uniformly low Pd N/Ir N (<0.5) for variable Pt N/Ir N (0.8 to 1.2). The compatible behavior of Os, Ir, Ru, Rh, and Pt reflects the presence of primary Os-Ru alloys. Some harzburgites displaying petrographic evidence for refertilization by incremental melts en route to the surface are enriched in sulfides (up to 0.1 wt%). Some of these sulfides are concentrated in small veinlets of clinopyroxene and spinel crystallized from these melts. These S-rich harzburgites display superchondritic Pd N/Ir N (up to 2.04) positively correlated with sulfide modal contents. It is concluded that refertilization processes resulting in precipitation of metasomatic sulfides may significantly enhance Pd concentrations of abyssal peridotites while marginally affecting Pt (Pt N/Ir N ≤ 1.24) and Rh (Rh N/Ir N ≤ 1.23) as well. When the effects of such processes are screened out, our database suggests PGE relative abundances in the DMM (Depleted MORB Mantle; MORB: Mid-Ocean Ridge) within the uncertainty range of chondritic meteorites, without evidence of superchondritic Pt/Ir and/or Rh/Ir ratios.

Magnetic behavior in heterometallic one-dimensional chains or octanuclear complex regularly aligned with metal-metal bonds as -Rh-Rh-Pt-Cu-Pt

NASA Astrophysics Data System (ADS)

Uemura, Kazuhiro

2018-06-01

Heterometallic one-dimensional chains, [{Rh2(O2CCH3)4}{Pt2Cu(piam)4(NH3)4}]n(PF6)2n (1 and 2, piam = pivalamidate) and [{Rh2(O2CCH3)4}{Pt2Cu(piam)4(NH3)4}2](CF3CO2)2(ClO4)2·2H2O (3), are paramagnetic one-dimensional chains or octanuclear complexes that are either aligned as -Rh-Rh-Pt-Cu-Pt- (1 and 2) or as Pt-Cu-Pt-Rh-Rh-Pt-Cu-Pt (3) with metal-metal bonds. Compounds 1-3 have rare structures, from the standpoint of that the paramagnetic species of Cu atoms are linked by direct metal-metal bonds. Magnetic susceptibility measurements for 1-3 performed at temperatures of 2 K-300 K indicated that the unpaired electrons localize in the Cu 3dx2-y2 orbitals, where S = 1/2 Cu(II) atoms are weakly antiferromagnetically coupled with J = -0.35 cm-1 (1), -0.47 cm-1 (2), and -0.45 cm-1 (3).

Tuning the Photophysical Properties of Ru(II) Monometallic and Ru(II),Rh(III) Bimetallic Supramolecular Complexes by Selective Ligand Deuteration.

PubMed

Wagner, Alec T; Zhou, Rongwei; Quinn, Kevan S; White, Travis A; Wang, Jing; Brewer, Karen J

2015-07-02

A series of three new complexes of the design [(TL)2Ru(BL)](2+), two new complexes of the design [(TL)2Ru(BL)Ru(TL)2](4+), and three new complexes of the design [(TL)2Ru(BL)RhCl2(TL)](3+) (TL = bpy or d8-bpy; BL = dpp or d10-dpp; TL = terminal ligand; BL = bridging ligand; bpy = 2,2'-bipyridine; dpp = 2,3-bis(2-pyridyl)pyrazine) were synthesized and the (1)H NMR spectroscopy, electrochemistry, electronic absorbance spectroscopy, and photophysical properties studied. Incorporation of deuterated ligands into the molecular architecture simplifies the (1)H NMR spectra, allowing for complete (1)H assignment of [(d8-bpy)2Ru(dpp)](PF6)2 and partial assignment of [(bpy)2Ru(d10-dpp)](PF6)2. The electrochemistry for the deuterated and nondeuterated species showed nearly identical redox properties. Electronic absorption spectroscopy of the deuterated and nondeuterated complexes are superimposable with the lowest energy transition being Ru(dπ) → BL(π*) charge transfer in nature (BL = dpp or d10-dpp). Ligand deuteration impacts the excited-state properties with an observed increase in the quantum yield of emission (Φ(em)) and excited-state lifetime (τ) of the Ru(dπ) → d10-dpp(π*) triplet metal-to-ligand charge transfer ((3)MLCT) excited state when dpp is deuterated, and a decrease in the rate constant for nonradiative decay (knr). Choice of ligand deuteration between bpy and dpp strongly impacts the observed photophysical properties with BL = d10-dpp complexes showing an enhanced Φ(em) and τ, providing further support that the lowest electronic excited state populated via UV or visible excitation is the photoactive Ru(dπ) → dpp(π*) CT excited state. The Ru(II),Rh(III) complex incorporating the deuterated BL shows increased hydrogen production compared to the variants incorporating the protiated BL, while demonstrating identical dynamic quenching behaviors in the presence of sacrificial electron donor.

Realization of Ru-C Eutectic Point for Evaluation of W-Re and IrRh/Ir Thermocouples

NASA Astrophysics Data System (ADS)

Ogura, H.; Masuyama, S.; Izuchi, M.; Yamazawa, K.; Arai, M.

2015-03-01

Tungsten-rhenium (W-Re) thermocouples are widely used in industry for measurements at high temperatures, up to . Since the electromotive force (emf) of a W-Re thermocouple is known to change during exposure at high temperatures, evaluation of the emf stability is essential for measuring temperature precisely and for realizing precise temperature control used to ensure the quality of products subject to annealing processes. To evaluate precisely the thermoelectric stability around , two Ru-C cells (crucible and Ru-C eutectic alloy) were constructed in our laboratory. The key feature of the cells is that their dimensions are large to ensure there is sufficient immersion available to evaluate the homogeneity characteristics of the thermocouples. By using one of the Ru-C cells, the drift and inhomogeneity of Type C (tungsten-5 % rhenium vs tungsten-26 % rhenium) thermocouples during an exposure to high temperature around were evaluated. Furthermore, to explore possible applications of the eutectic point to other types of high-temperature thermocouples, the drift of an IrRh/Ir thermocouple (iridium-40 % rhodium vs iridium) was also evaluated using another Ru-C cell. The tests with W-Re and IrRh/Ir thermocouples demonstrate that the newly developed Ru-C cells can be used to successfully realize melting plateaux repeatedly. This enables the long-term drift measurements essential for the evaluation and improvement of high-temperature thermocouples. The results obtained in this study will also be useful for evaluating the uncertainty of thermocouple calibrations at around.

Platinum-group elements, S, Se and Cu in highly depleted abyssal peridotites from the Mid-Atlantic Ocean Ridge (ODP Hole 1274A): Influence of hydrothermal and magmatic processes

NASA Astrophysics Data System (ADS)

Marchesi, Claudio; Garrido, Carlos J.; Harvey, Jason; González-Jiménez, José María; Hidas, Károly; Lorand, Jean-Pierre; Gervilla, Fernando

2013-11-01

Highly depleted harzburgites and dunites were recovered from ODP Hole 1274A, near the intersection between the Mid-Atlantic Ocean Ridge and the 15°20'N Fracture Zone. In addition to high degrees of partial melting, these peridotites underwent multiple episodes of melt-rock reaction and intense serpentinization and seawater alteration close to the seafloor. Low concentrations of Se, Cu and platinum-group elements (PGE) in harzburgites drilled at around 35-85 m below seafloor are consistent with the consumption of mantle sulfides after high degrees (>15-20 %) of partial melting and redistribution of chalcophile and siderophile elements into PGE-rich residual microphases. Higher concentrations of Cu, Se, Ru, Rh and Pd in harzburgites from the uppermost and lowest cores testify to late reaction with a sulfide melt. Dunites were formed by percolation of silica- and sulfur-undersaturated melts into low-Se harzburgites. Platinum-group and chalcophile elements were not mobilized during dunite formation and mostly preserve the signature of precursor harzburgites, except for higher Ru and lower Pt contents caused by precipitation and removal of platinum-group minerals. During serpentinization at low temperature (<250 °C) and reducing conditions, mantle sulfides experienced desulfurization to S-poor sulfides (mainly heazlewoodite) and awaruite. Contrary to Se and Cu, sulfur does not record the magmatic evolution of peridotites but was mostly added in hydrothermal sulfides and sulfate from seawater. Platinum-group elements were unaffected by post-magmatic low-temperature processes, except Pt and Pd that may have been slightly remobilized during oxidative seawater alteration.

Effect of ultra-thin liner materials on copper nucleation/wetting and copper grain growth

NASA Astrophysics Data System (ADS)

Mueller, Justin E.

One of the key challenges facing future integrated circuit copper (Cu) interconnect manufacturing is to achieve uniform coverage of PVD Cu seed layer at minimum thickness on a liner and barrier. We have therefore characterized the nucleation and wetting of PVD Cu on various liner surfaces by monitoring in-situ the film's electrical conductance during the initial stages of deposition (0 to 25 nm). Our results showed that the Cu wetting is sensitive to the Cu/liner interfacial properties, while the nucleation depends on the liner microstructure. It was found that a ruthenium (Ru) liner has a good Cu wetting characteristic and allows at the onset nearly layer by layer Cu growth. Because of good wetting, Cu growth is not significantly affected by Ru liner grain size. Tantalum (Ta), however, exhibits poor Cu wetting, which results in an initial stage of three dimensional island growth of Cu. In this case, Cu island coalescing occurs sooner, at a smaller Cu film thickness, when the nucleation site density is increased with a smaller grain size Ta liner. To optimize the seed layer's conductance and step coverage, a liner with combined properties of Ta (for adhesion and barrier formation) and Ru (for wetting and grain growth) may be desired. A hybrid magnetron target has been developed for depositing TaRu liner films at various compositions. The microstructure of the compound liners and their effects on the overgrown Cu seed layer over a wide range of TaRu composition is presented. It was found that below 80% Ru concentration, TaRu films are amorphous. An amorphous liner results in poor Cu nucleation as compared with a crystalline Ta or Ru liner. A comparison of the microstructure of thin Cu films deposited on bcc alpha-Ta and tetragonal beta-Ta surfaces has been carried out. Cu resistivity is lower by 10-15%, accompanied by larger Cu grain size, in as-deposited Cu films of various thickness' (30-120 nm) on beta-Ta as compared to those deposited on alpha-Ta. This is due to the presence of an epitaxial relationship between Cu (111) and beta-Ta (002) planes. After annealing, the difference was only seen in films thinner than 60 nm. Results were confirmed when Cu film resistance was measured in-situ during deposition on each phase of Ta liner. Serpentine interconnect line structures of various line widths and aspect ratios were fabricated using either alpha- or beta-Ta liners, and subjected to a similar heat treatment. Results showed a similar ˜10% lower resistivity in the thinnest interconnects (˜40 nm) when a beta-Ta liner was used.

CuPt and CuPtRu Nanostructures for Ammonia Oxidation Reaction

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

Manso, R H.; Song, L.; Liang, Z.

Liquid fuels, such as methanol, ethanol, and ammonia, are attractive alternative to hydrogen for fuel cells due to their lower costs for storage and distribution. However, lack of sufficiently active catalysts for their oxidation reactions is a roadblock. Our previous study found that Pt 3Cu nanodendrites yielded higher activity and durability than Pt nanoparticles for methanol oxidation reaction (MOR) in acid. In this study, we synthesized two types of nanostructures of CuPt and CuPtRu catalysts via seed-mediated growth of Pt and Ru on Cu and tested their performance for ammonia oxidation reaction (AOR) in alkaline solution. Unlike for MOR, themore » nanodendrites do not promote AOR activity - CuPt performs similar to Pt and CuPtRu is less active than Pt. Interestingly, the AOR peak current is increased by 64% on CuPt nanowires and 330% on CuPtRu nanowires as compared to Pt nanoparticles. These results suggest that AOR prefers extended surface on long nanowires, distinctly differing from MOR. This can be contributed to two factors: NH 3 oxidization to N 2 involves dimerization of two N-containing intermediates to form the N-N bond and diffusion batters for adsorbed intermediates are generally lower on terrace than at low-coordination sites. This demonstrated strong effect of surface morphology will be further studied and utilized in developing advanced AOR nanocatalysts.« less

CuPt and CuPtRu Nanostructures for Ammonia Oxidation Reaction

DOE PAGES

Manso, R H.; Song, L.; Liang, Z.; ...

2018-04-01

Liquid fuels, such as methanol, ethanol, and ammonia, are attractive alternative to hydrogen for fuel cells due to their lower costs for storage and distribution. However, lack of sufficiently active catalysts for their oxidation reactions is a roadblock. Our previous study found that Pt 3Cu nanodendrites yielded higher activity and durability than Pt nanoparticles for methanol oxidation reaction (MOR) in acid. In this study, we synthesized two types of nanostructures of CuPt and CuPtRu catalysts via seed-mediated growth of Pt and Ru on Cu and tested their performance for ammonia oxidation reaction (AOR) in alkaline solution. Unlike for MOR, themore » nanodendrites do not promote AOR activity - CuPt performs similar to Pt and CuPtRu is less active than Pt. Interestingly, the AOR peak current is increased by 64% on CuPt nanowires and 330% on CuPtRu nanowires as compared to Pt nanoparticles. These results suggest that AOR prefers extended surface on long nanowires, distinctly differing from MOR. This can be contributed to two factors: NH 3 oxidization to N 2 involves dimerization of two N-containing intermediates to form the N-N bond and diffusion batters for adsorbed intermediates are generally lower on terrace than at low-coordination sites. This demonstrated strong effect of surface morphology will be further studied and utilized in developing advanced AOR nanocatalysts.« less

Single-reactor process for producing liquid-phase organic compounds from biomass

DOEpatents

Dumesic, James A.; Simonetti, Dante A.; Kunkes, Edward L.

2015-12-08

Disclosed is a method for preparing liquid fuel and chemical intermediates from biomass-derived oxygenated hydrocarbons. The method includes the steps of reacting in a single reactor an aqueous solution of a biomass-derived, water-soluble oxygenated hydrocarbon reactant, in the presence of a catalyst comprising a metal selected from the group consisting of Cr, Mn, Fe, Co, Ni, Cu, Mo, Tc, Ru, Rh, Pd, Ag, W, Re, Os, Ir, Pt, and Au, at a temperature, and a pressure, and for a time sufficient to yield a self-separating, three-phase product stream comprising a vapor phase, an organic phase containing linear and/or cyclic mono-oxygenated hydrocarbons, and an aqueous phase.

Single-reactor process for producing liquid-phase organic compounds from biomass

DOEpatents

Dumesic, James A [Verona, WI; Simonetti, Dante A [Middleton, WI; Kunkes, Edward L [Madison, WI

2011-12-13

Disclosed is a method for preparing liquid fuel and chemical intermediates from biomass-derived oxygenated hydrocarbons. The method includes the steps of reacting in a single reactor an aqueous solution of a biomass-derived, water-soluble oxygenated hydrocarbon reactant, in the presence of a catalyst comprising a metal selected from the group consisting of Cr, Mn, Fe, Co, Ni, Cu, Mo, Tc, Ru, Rh, Pd, Ag, W, Re, Os, Ir, Pt, and Au, at a temperature, and a pressure, and for a time sufficient to yield a self-separating, three-phase product stream comprising a vapor phase, an organic phase containing linear and/or cyclic mono-oxygenated hydrocarbons, and an aqueous phase.

Crystal phase-based epitaxial growth of hybrid noble metal nanostructures on 4H/fcc Au nanowires

NASA Astrophysics Data System (ADS)

Lu, Qipeng; Wang, An-Liang; Gong, Yue; Hao, Wei; Cheng, Hongfei; Chen, Junze; Li, Bing; Yang, Nailiang; Niu, Wenxin; Wang, Jie; Yu, Yifu; Zhang, Xiao; Chen, Ye; Fan, Zhanxi; Wu, Xue-Jun; Chen, Jinping; Luo, Jun; Li, Shuzhou; Gu, Lin; Zhang, Hua

2018-03-01

Crystal-phase engineering offers opportunities for the rational design and synthesis of noble metal nanomaterials with unusual crystal phases that normally do not exist in bulk materials. However, it remains a challenge to use these materials as seeds to construct heterometallic nanostructures with desired crystal phases and morphologies for promising applications such as catalysis. Here, we report a strategy for the synthesis of binary and ternary hybrid noble metal nanostructures. Our synthesized crystal-phase heterostructured 4H/fcc Au nanowires enable the epitaxial growth of Ru nanorods on the 4H phase and fcc-twin boundary in Au nanowires, resulting in hybrid Au-Ru nanowires. Moreover, the method can be extended to the epitaxial growth of Rh, Ru-Rh and Ru-Pt nanorods on the 4H/fcc Au nanowires to form unique hybrid nanowires. Importantly, the Au-Ru hybrid nanowires with tunable compositions exhibit excellent electrocatalytic performance towards the hydrogen evolution reaction in alkaline media.

Structural Stability of Diffusion Barriers in Cu/Ru/MgO/Ta/Si

PubMed Central

Hsieh, Shu-Huei; Chen, Wen Jauh; Chien, Chu-Mo

2015-01-01

Various structures of Cu (50 nm)/Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm)/Si were prepared by sputtering and electroplating techniques, in which the ultra-thin trilayer of Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm) is used as the diffusion barrier against the interdiffusion between Cu film and Si substrate. The various structures of Cu/Ru/MgO/Ta/Si were characterized by four-point probes for their sheet resistances, by X-ray diffractometers for their crystal structures, by scanning electron microscopes for their surface morphologies, and by transmission electron microscopes for their cross-section and high resolution views. The results showed that the ultra-thin tri-layer of Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm) is an effective diffusion barrier against the interdiffusion between Cu film and Si substrate. The MgO, and Ta layers as deposited are amorphous. The mechanism for the failure of the diffusion barrier is that the Ru layer first became discontinuous at a high temperature and the Ta layer sequentially become discontinuous at a higher temperature, the Cu atoms then diffuse through the MgO layer and to the substrate at the discontinuities, and the Cu3Si phases finally form. The maximum temperature at which the structures of Cu (50 nm)/Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm)/Si are annealed and still have low sheet resistance is from 550 to 750 °C for the annealing time of 5 min and from 500 to 700 °C for the annealing time of 30 min. PMID:28347099

Synthesis, crystal structure investigation and magnetism of the complex metal-rich boride series Crx(Rh1-yRuy)7-xB3 (x=0.88-1; y=0-1) with Th7Fe3-type structure

NASA Astrophysics Data System (ADS)

Misse, Patrick R. N.; Mbarki, Mohammed; Fokwa, Boniface P. T.

2012-08-01

Powder samples and single crystals of the new complex boride series Crx(Rh1-yRuy)7-xB3 (x=0.88-1; y=0-1) have been synthesized by arc-melting the elements under purified argon atmosphere on a water-cooled copper crucible. The products, which have metallic luster, were structurally characterized by single-crystal and powder X-ray diffraction as well as EDX measurements. Within the whole solid solution range the hexagonal Th7Fe3 structure type (space group P63mc, no. 186, Z=2) was identified. Single-crystal structure refinement results indicate the presence of chromium at two sites (6c and 2b) of the available three metal Wyckoff sites, with a pronounced preference for the 6c site. An unexpected Rh/Ru site preference was found in the Ru-rich region only, leading to two different magnetic behaviors in the solid solution: The Rh-rich region shows a temperature-independent (Pauli) paramagnetism whereas an additional temperature-dependent paramagnetic component is found in the Ru-rich region.

London penetration depth measurements in Ba (Fe 1-xT x) 2As 2(T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors

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

Gordon, Ryan T.

2011-01-01

The London penetration depth has been measured in various doping levels of single crystals of Ba(Fe 1-xT x) 2As 2 (T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors by utilizing a tunnel diode resonator (TDR) apparatus. All in-plane penetration depth measurements exhibit a power law temperature dependence of the form Δλ ab(T) = CT n, indicating the existence of low-temperature, normal state quasiparticles all the way down to the lowest measured temperature, which was typically 500 mK. Several different doping concentrations from the Ba(Fe 1-xT x) 2As 2 (T=Co,Ni) systems have been measured and the doping dependence of the power law exponent, n, is compared tomore » results from measurements of thermal conductivity and specific heat. In addition, a novel method has been developed to allow for the measurement of the zero temperature value of the in-plane penetration depth, λ ab(0), by using TDR frequency shifts. By using this technique, the doping dependence of λ ab(0) has been measured in the Ba(Fe 1-xCo x) 2As 2 series, which has allowed also for the construction of the doping-dependent superfluid phase stiffness, ρ s(T) = [λ(0)/λ(T)] 2. By studying the effects of disorder on these superconductors using heavy ion irradiation, it has been determined that the observed power law temperature dependence likely arises from pair-breaking impurity scattering contributions, which is consistent with the proposed s±-wave symmetry of the superconducting gap in the dirty scattering limit. This hypothesis is supported by the measurement of an exponential temperature dependence of the penetration depth in the intrinsically clean LiFeAs, indicative of a nodeless superconducting gap.« less

First-Principles Mechanistic Analysis of Dimethyl Ether Electro-Oxidation on Monometallic Single-Crystal Surfaces

DOE PAGES

Herron, Jeffrey A.; Ferrin, Peter; Mavrikakis, Manos

2014-08-27

Dimethyl ether is an attractive alternative to petroleum fuels due to its physical properties, comparable energy density to methanol and ethanol, and minimal deleterious environmental/toxicological effects. For direct fuel cells, it has a number of advantages over other prominent fuels, including easier storage with respect to hydrogen, lower toxicity and crossover when compared to methanol, and more facile complete oxidation as compared to ethanol (which includes a relatively difficult to break C–C bond). However, the dimethyl ether electro-oxidation reaction is poorly understood, hindering the development of improved electrocatalysts. Using periodic, self-consistent (PW91-GGA) density functional theory calculations, we evaluate the thermochemistrymore » of dimethyl ether (DME) electro-oxidation, at the elementary step level, on 12 model, closed-packed facets of pure transition metals: Au, Ag, Cu, Pt, Pd, Ni, Ir, Rh, Co, Os, Ru, and Re. From the calculated thermochemistry, we determine the most probable reaction paths on each of these surfaces, focusing on Pt as a model system. Our results predict two key electro-oxidation peaks. At lower potentials, there is a peak corresponding to partial oxidation of DME to CO (and other surface poisoning species) or complete oxidation to CO 2 via formic acid as a key intermediate. A second, higher-potential peak is due to complete oxidation of adsorbed CO (and other surface poisoning species) to CO 2. Assuming the catalysts remain in their metallic state during the DME electro-oxidation process, our results suggest that the onset potential of the surfaces increases in the order Cu < Ni < Os < Rh < Ir < Co < Ru < Pt < Ag < Pd < Re < Au. Using our results, we construct a theoretical phase diagram showing predicted catalyst activity based on two key reactivity descriptors, the free energies of adsorbed CO and OH. Here, we compare all results to methanol electro-oxidation to understand key mechanistic differences and their impacts on optimal catalyst design for direct DME fuel cells.« less

Carbon Dioxide Gas Sensors and Method of Manufacturing and Using Same

NASA Technical Reports Server (NTRS)

Hunter, Gary W. (Inventor); Xu, Jennifer C. (Inventor)

2014-01-01

A gas sensor comprises a substrate layer; a pair of interdigitated metal electrodes, said electrodes include upper surfaces, the electrodes selected from the group consisting of Pt, Pd, Au, Ir, Ag, Ru, Rh, In, Os, and their alloys. A first layer of solid electrolyte staying in between electrode fingers and partially on said upper surfaces of said electrodes, said first layer selected from NASICON, LISICON, KSICON and.beta.''-Alumina. A second layer of metal carbonate(s) as an auxiliary electrolyte engaging said upper surfaces of the electrodes and the first solid electrolyte. The metal carbonates selected from the group consisting of the following ions Na.sup.+, K.sup.+, Li.sup.+, Ag.sup.+, H.sup.+, Pb.sup.2+, Sr.sup.2+, Ba.sup.2+, and any combination thereof. An extra layer of metal oxide selected from the group consisting of SnO.sub.2, In.sub.2O.sub.3, TiO.sub.2, WO.sub.3, ZnO, Fe.sub.2O.sub.3, ITO, CdO, U.sub.3O.sub.8, Ta.sub.2O.sub.5, BaO, MoO.sub.2, MoO.sub.3, V.sub.2O.sub.5, Nb.sub.2O.sub.5, CuO, Cr.sub.2O.sub.3, La.sub.2O.sub.3, RuO.sub.3, RuO.sub.2, ReO.sub.2, ReO.sub.3, Ag.sub.2O, CoO, Cu.sub.2O, SnO, NiO, Pr.sub.2O.sub.3, BaO, PdO.sub.2, HfO.sub.3, HfO.sub.3 or other metal oxide and their mixtures residing above and in engagement with the second electrolyte to improve sensor performance and/or to reduce sensor heating power consumption.

Palladium, platinum, rhodium, iridium and ruthenium in chromite- rich rocks from the Samail ophiolite, Oman.

USGS Publications Warehouse

Page, N.J.; Pallister, J.S.; Brown, M.A.; Smewing, J.D.; Haffty, J.

1982-01-01

30 samples of chromitite and chromite-rich rocks from two stratigraphic sections, 250 km apart, through the basal ultramafic member of the Samail ophiolite were spectrographically analysed for platinum-group elements (PGE) and for Co, Cu, Ni and V. These data are reported as are Cr/(Cr + Al), Mg/(Mg + Fe) and wt.% TiO2 for most samples. The chromitite occurs as pods or lenses in rocks of mantle origin or as discontinuous layers at the base of the overlying cumulus sequence. PGE abundances in both sections are similar, with average contents in chromite-rich rocks: Pd 8 ppb, Pt 14 ppb, Rh 6 ppb, Ir 48 ppb and Ru 135 ppb. The PGE data, combined with major-element and petrographic data on the chromitite, suggest: 1) relatively larger Ir and Ru contents and highest total PGE in the middle part of each section; 2) PGE concentrations and ratios do not correlate with coexisting silicate and chromite abundances or chromite compositions; 3) Pd/PGE, on average, increases upward in each section; 4) Samail PGE concentrations, particularly Rh, Pt and Pd, are lower than the average values for chromite-rich rocks in stratiform intrusions. 2) suggests that PGEs occur in discrete alloy or sulphide phases rather than in the major oxides or silicates, and 4) suggests that chromite-rich rocks from the oceanic upper mantle are depleted in PGE with respect to chondrites. L.C.C.

Preparation of fine single crystals of magnetic superconductor RuSr2GdCu2O8-δ by partial melting

NASA Astrophysics Data System (ADS)

Yamaki, Kazuhiro; Bamba, Yoshihiro; Irie, Akinobu

2018-03-01

In this study, fine uniform RuSr2GdCu2O8-δ (RuGd-1212) single crystals have been successfully prepared by partial melting. Synthesis temperature could be lowered to a value not exceeding the decomposition temperature of RuGd-1212 using the Sr-Gd-Cu-O flux. The crystals grown by alumina boats are cubic, which coincides with the result of a previous study of RuGd-1212 single crystals using platinum crucibles. The single crystals were up to 15 × 15 × 15 µm3 in size and their lattice constants were consistent with those of polycrystalline samples reported previously. Although the present size of single crystals is not sufficient for measurements, the partial melting technique will be beneficial for future progress of research using RuGd-1212 single crystals. Appropriate nominal composition, sintering atmosphere, and temperature are essential factors for growing RuGd-1212 single crystals.

The valence of Ru, Ce and Eu ions in the magneto-superconductor Eu 1.5Ce 0.5RuSr 2Cu 2O 10

NASA Astrophysics Data System (ADS)

Felner, I.; Asaf, U.; Godart, C.; Alleno, E.

1999-01-01

The superconducting (T c∼32 K) Eu 1.5Ce 0.5RuSr 2Cu 2O 10 (Ru-2122) material is also magnetically ordered (T M∼122 K) with TM≫ Tc. Superconductivity (SC) is confined to the CuO 2 planes, whereas magnetism is due to the Ru sublattice. Mossbauer spectroscopy performed at 90 and 300 K on 151Eu shows a single narrow line with an isomer shift=0.69(2) and a quadrupole splitting of 1.84 mm/s, indicating that the Eu ions are trivalent with a nonmagnetic J=0 ground state. This is in agreement with X-ray-absorption spectroscopy (XAS) taken at L III edges of Eu, Ce which shows that Eu is trivalent and Ce is tetravalent. XAS experiments at the K edge of Ru indicate that Ru is pentavalent. This indicates, that in the M-2122 system, SC exists only for pentavalent M ions such as Ta, Nb and Ru.

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

Xie, Chao; Chen, Yongsheng; Engelhard, Mark H.

This work was conducted to clarify the influence of the type of metal and support on the sulfur tolerance and carbon resistance of supported noble metal catalysts in steam reforming of liquid hydrocarbons. Al2O3-supported noble metal catalysts (Rh, Ru, Pt, and Pd), Rh catalysts on different supports (Al2O3, CeO2, SiO2, and MgO), and Pt catalyst supported on CeO2 and Al2O3, were examined for steam reforming of a liquid hydrocarbon fuel (Norpar13 from Exxon Mobil) at 800 C for 55 h. The results indicate that (1) Rh/Al2O3 shows higher sulfur tolerance than the Ru, Pt, and Pd catalysts on the samemore » support; (2) both Al2O3 and CeO2 are promising supports for Rh catalyst to process sulfur-containing hydrocarbons; and (3) Pt/CeO2 exhibits better catalytic performance than Pt/Al2O3 in the reaction with sulfur. TEM results demonstrate that the metal particles in Rh/Al2O3 were better dispersed (mostly in 1-3 nm) compared with the other catalysts after reforming the sulfur-containing feed. As revealed by XPS, the binding energy of Rh 3d for Rh/Al2O3 is notably higher than that for Rh/CeO2, implying the formation of electron-deficient Rh particles in the former. The strong sulfur tolerance of Rh/Al2O3 may be related to the formation of well-dispersed electron-deficient Rh particles on the Al2O3 support. Sulfur K-edge XANES illustrates the preferential formation of sulfonate and sulfate on Rh/Al2O3, which is believed to be beneficial for improving its sulfur tolerance as their oxygen-shielded sulfur structure may hinder direct Rh-S interaction. Due to its strong sulfur tolerance, the carbon deposition on Rh/Al2O3 was significantly lower than that on the Al2O3-supported Ru, Pt, and Pd catalysts after the reaction with sulfur. The superior catalytic performance of CeO2-supported Rh and Pt catalysts in the presence of sulfur can be ascribed mainly to the promotion effect of CeO2 on carbon gasification, leading to much lower carbon deposition compared with the Rh/Al2O3, Rh/MgO, Rh/SiO2 and Pt/Al2O3 catalysts.« less

Influence of Electron Doping on Magnetic Order in CeRu 2Al 10

DOE PAGES

Kobayashi, Riki; Kaneko, Koji; Saito, Kotaro; ...

2014-09-17

The effect of electron doping by the substitution of Rh for Ru on unconventional magnetic order in CeRu 2Al 10 was investigated via neutron powder diffraction. In Ce(Ru 1-xRh x) 2Al 10 with x = 0.05, 0.12, and 0.2, reorientation of the ordered moment from the c- to the a-axis takes place in all samples, while the ordering vector q=(0 1 0) remains unchanged within this concentration range. The moment reorientation is accompanied by an enhancement in its size by a factor of ~2.4, from μ=0.43 μ B at x=0 to μ =1.06, 1.04, and 1.02 μ B for x=0.05,more » 0.12 and 0.2, respectively. The continuous decrease in N´eel temperature T 0(T N), despite an abrupt increase in μ , underlines the strong anisotropy in the exchange interaction in CeRu 2Al 10, and the fact that this anisotropy is easily suppressed by electron doping.« less

Ligand effects on the hydrogenation of biomass-inspired substrates with bifunctional Ru, Ir, and Rh complexes.

PubMed

Jansen, Eveline; Jongbloed, Linda S; Tromp, Dorette S; Lutz, Martin; de Bruin, Bas; Elsevier, Cornelis J

2013-09-01

We herein report on the application and structural investigation of a new set of complexes that contain bidentate N-heterocyclic carbenes (NHCs) and primary amine moieties of the type [M(arene)Cl(L)] [M=Ru, Ir, or Rh; arene=p-cymene or pentamethylcyclopentadienyl; L=1-(2-aminophenyl)-3-(n-alkyl)imidazol-2-ylidine]. These complexes were tested and compared in the hydrogenation of acetophenone with hydrogen. Structural variations in the chelate ring size of the heteroditopic ligand revealed that smaller chelate ring sizes in combination with ring conjugation in the ligand are beneficial for the activity of this type of catalyst, favoring an inner-sphere coordination pathway. Additionally, increasing the steric bulk of the alkyl substituent on the NHC aided the reaction, showing almost no induction period and formation of a more active catalyst for the n-butyl complex relative to complexes with smaller Me and Et substituents. As is common in hydrogenation reactions, the activity of the complexes decreases in the order Ru>Ir>Rh. The application of [Ru(p-cym)Cl(L)]PF6 , which outperforms its reported analogues, has been successfully extended to the hydrogenation of more challenging biomass-inspired substrates. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phase Structure and Site Preference Behavior of Ternary Alloying Additions to PdTi and PtTi Shape-Memory Alloys

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Mosca, Hugo O.; Noebe, Ronald D.

2006-01-01

The phasc structure and concentration dependence of the lattice parameter and energy of formation of ternary Pd-'I-X and Pt-Ti-X alloys for a large number of ternary alloying additions X (X = Na, Mg, Al, Si, Sc. V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ag, Cd, Hf, Ta, W, Re, Os, Ir) are investigated with an atomistic modeling approach. In addition, a detailed description of the site preference behavior of such additions showing that the elements can be grouped according to their absolute preference for a specific site, regardless of concentration, or preference for available sites in the deficient sublattice is provided.

Testing Room-Temperature Ionic Liquid Solutions for Depot Repair of Aluminum Coatings

DTIC Science & Technology

2011-05-01

Ne 3 Na Mg IIIB IVB VB VIB VIIB ------ VIIIB ------ IB IIB Al Si P S Cl Ar 4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 5 Rb Sr Y Zr Nb Mo Tc...Ru Rh Pd Ag Cd In Sn Sb Te I Xe 6 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 7 Fr Ra Ac Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np...Electroplating Bath Lid Arrangement ;:::::::::::=== Thermometer Purge gas vent Anode lead Cathode lead (Extractable from the lid) Purge feed gas

A dual-potential electrochemiluminescence ratiometric sensor for sensitive detection of dopamine based on graphene-CdTe quantum dots and self-enhanced Ru(II) complex.

PubMed

Fu, Xiaomin; Tan, Xingrong; Yuan, Ruo; Chen, Shihong

2017-04-15

A novel dual-potential ratiometric electrochemiluminescence (ECL) sensor was designed for detecting dopamine (DA) based on graphene-CdTe quantum dots (G-CdTe QDs) as the cathodic emitter and self-enhanced Ru(II) composite (TAEA-Ru) as the anodic emitter. TAEA-Ru was prepared by linking ruthenium(II) tris(2,2'-bipyridyl-4,4'-dicarboxylato) with tris(2-aminoethyl)amine. Firstly, 3-aminopropyltriethoxysilane founctionalized G-CdTe QDs was used as the substrate for capturing target DA via the specific recognition of the diol of DA to the oxyethyl group of APTES. Then, Cu 2 O nanocrystals supported TAEA-Ru was further bound by the strong interaction between amino groups of DA and carboxyl groups of the Cu 2 O-TAEA-Ru. With the increase in DA concentration, the loading of Cu 2 O-TAEA-Ru at the electrode increased. As a result, the anodic ECL signal from TAEA-Ru increased, and the cathodic ECL signal from G-CdTe QDs/O 2 system decreased correspondingly. Such a decrease was resulted from the ECL resonance energy transfer (RET) from G-CdTe QDs to TAEA-Ru as well as the dual quenching effects of Cu 2 O to G-CdTe QDs, namely the ECL-RET from G-CdTe QDs to Cu 2 O and the consumption of coreactant O 2 by Cu 2 O. Based on the ratio of two ECL signals, the determination of DA was achieved with a linear range from 10.0 fM to 1.0nM and a detection limit low to 2.9 fM (S/N=3). The combination of G-CdTe QDs/O 2 and TAEA-Ru would break the limitation of the same coreatant shared in previous ECL ratiometric systems and provide a potential application of ECL ratiometric sensor in the detection of biological small molecules with the assistance of the dual molecular recognition strategy. Copyright © 2016 Elsevier B.V. All rights reserved.

PALLADIUM, PLATINUM, RHODIUM, RUTHENIUM AND IRIDIUM IN PERIDOTITES AND CHROMITITES FROM OPHIOLITE COMPLEXES IN NEWFOUNDLAND.

USGS Publications Warehouse

Page, Norman J; Talkington, Raymond W.

1984-01-01

Samples of spinel lherzolite, harzburgite, dunite, and chromitite from the Bay of Islands, Lewis Hills, Table Mountain, Advocate, North Arm Mountain, White Hills Periodite Point Rousse, Great Bend and Betts Cove ophiolite complexes in Newfoundland were analyzed for the platinum-group elements (PGE) Pd, Pt, Rh, Ru and Ir. The ranges of concentration (in ppb) observed for all rocks are: less than 0. 5 to 77 (Pd), less than 1 to 120 (Pt), less than 0. 5 to 20 (Rh), less than 100 to 250 (Ru) and less than 20 to 83 (Ir). Chondrite-normalized PGE ratios suggest differences between rock types and between complexes. Samples of chromitite and dunite show relative enrichment in Ru and Ir and relative depletion in Pt and Pd.

Valence-Band Electronic Structures of High-Pressure-Phase PdF2-type Platinum-Group Metal Dioxides MO2 (M = Ru, Rh, Ir, and Pt)

NASA Astrophysics Data System (ADS)

Soda, Kazuo; Kobayashi, Daichi; Mizui, Tatsuya; Kato, Masahiko; Shirako, Yuichi; Niwa, Ken; Hasegawa, Masashi; Akaogi, Masaki; Kojitani, Hiroshi; Ikenaga, Eiji; Muro, Takayuki

2018-04-01

The valence-band electronic structures of high-pressure-phase PdF2-type (HP-PdF2-type) platinum-group metal dioxides MO2 (M = Ru, Rh, Ir, and Pt) were studied by synchrotron radiation photoelectron spectroscopy and first-principles calculations. The obtained photoelectron spectra for HP-PdF2-type RuO2, RhO2, and IrO2 agree well with the calculated valence-band densities of states (DOSs) for these compounds, indicating their metallic properties, whereas the DOS of HP-PdF2-type PtO2 (calculated in the presence and absence of spin-orbit interactions) predicts that this material may be metallic or semimetallic, which is inconsistent with the electric conductivity reported to date and the charging effect observed in current photoelectron measurements. Compared with the calculated results, the valence-band spectrum of PtO2 appears to have shifted toward the high-binding-energy side and reveals a gradual intensity decrease toward the Fermi energy EF, implying a semiconductor-like electronic structure. Spin-dependent calculations predict a ferromagnetic ground state with a magnetization of 0.475 μB per formula unit for HP-PdF2-type RhO2.

Precious metal enrichment at low-redox in terrestrial native Fe-bearing basalts investigated using laser-ablation ICP-MS

NASA Astrophysics Data System (ADS)

Howarth, Geoffrey H.; Day, James M. D.; Pernet-Fisher, John F.; Goodrich, Cyrena A.; Pearson, D. Graham; Luo, Yan; Ryabov, Viktor V.; Taylor, Lawrence A.

2017-04-01

Primary native Fe is a rare crystallizing phase from terrestrial basaltic magmas, requiring highly reducing conditions (fO2

Structure functions in decomposing CuRh systems

NASA Astrophysics Data System (ADS)

Prem, M.; Blaschko, O.; Rosta, L.

1997-02-01

The time evolution of a CuRh alloy quenched within the miscibility gap is investigated by small and wide angle neutron scattering techniques. Near fundamental Bragg reflections diffuse satellites arising from a lattice parameter modulation induced by the precipitation pattern are investigated. The results show that in CuRh the precipitation morphology and its time evolution are quite different from decomposition characteristics recently observed in the system AuPt. The results are discussed and related to the larger lattice misfit present in CuRh in comparison to AuPt.

Growth and structural characterization of single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) obtained by the partial melting technique

NASA Astrophysics Data System (ADS)

Yamaki, K.; Bamba, Y.; Mochiku, T.; Funahashi, S.; Matsushita, Y.; Irie, A.

2018-05-01

In this study, cubic single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) with typical dimensions of 100-150 μm in length were grown by the partial melting technique. Multiple 00l reflections were first observed by XRD measurements of the bulk RuGd-1212 single crystals. The resistivity of the obtained crystals was roughly estimated to be ∼24-80 mΩ cm and no superconducting transition was observed down to 4.2 K. From the XRD measurements and refinement of the crystal structure, it was apparent that the Ru and Sr sites of the single-crystal RuGd-1212 were partially substituted by Cu and Gd, respectively. Oxygen defects were found to be minor (δ ≈ 0.1). The lattice parameters a and c of the single crystals were found to be larger and smaller, respectively, than those of a polycrystalline sample.

Generation of a stable supramolecular hydrogen evolving photocatalyst by alteration of the catalytic center.

PubMed

Mengele, Alexander K; Kaufhold, Simon; Streb, Carsten; Rau, Sven

2016-04-21

A new dyad consisting of a Ru(II) chromophore, a tetrapyridophenazine bridging ligand and a Rh(Cp*)Cl catalytic center, [Ru(tbbpy)2(tpphz)Rh(Cp*)Cl]Cl(PF6)2, acts as durable photocatalyst for hydrogen production from water. Catalytic activity is observed for more than 650 hours. Electrochemical investigations reveal that up to two electrons can be transferred to the catalytic center by a thermodynamically favorable intramolecular process, which has so far not been reported for similar tpphz based supramolecular photocatalysts. Additionally, mercury poisoning tests indicate that the new dyad works as a homogeneous photocatalyst.

Platinum-group element geochemistry of the Forest Reef Volcanics, southeastern Australia: Implications for porphyry Au-Cu mineralisation

NASA Astrophysics Data System (ADS)

Lowczak, Jessica N.; Campbell, Ian H.; Cocker, Helen; Park, Jung-Woo; Cooke, David R.

2018-01-01

Platinum-group element concentrations in felsic to intermediate rocks from the Forest Reef Volcanics, Cadia-Neville region, southeastern Australia have been analysed by the Ni-S fire assay-isotope dilution method. The Forest Reef Volcanics are shoshonitic to calc-alkaline in composition and fractionated to produce a wide range of compositions, with MgO varying between 9.7 and 1.8 wt.%. The interest in this suite is that it is coeval with Au-Cu porphyry-style mineralisation in the Cadia mineral district. This study uses PGE geochemistry to determine the timing of sulfide saturation, relative to volatile (ore-fluid) saturation, in the magma that gave rise to the Forest Reef Volcanics and, in turn, to assess how this timing affected the mineralisation potential of the evolving magmatic system. The Forest Reef Volcanics can be subdivided, on the basis of their contrasting PGE geochemistry, into high-Mg (>6.8 wt.% MgO) and low-Mg suites (≤6.8 wt.% MgO). Platinum, Pd and Re concentrations increase in the high-Mg samples, whereas Ir and Ru decrease and Rh concentrations remain steady, with decreasing MgO. The coupled Ir, Ru and Rh depletion is attributed to the partitioning of these elements into magnetite. The rate of Pt and Pd enrichment is not possible by closed-system fractional crystallisation alone, which suggests that the parent magma was replenished by a Pt-Pd-rich melt. In contrast, the PGE concentrations in the low-Mg samples decrease with decreasing MgO indicating the onset of sulfide saturation at 6.8 wt.% MgO, which is confirmed by the presence of spheroidal sulfide inclusions in liquidus crystals (i.e. clinopyroxene, plagioclase, magnetite). The rate of Pd depletion is appreciably less than for any other sulfide saturated felsic system for which data are available. This requires either that the amount of sulfide melt to have precipitated was unusually low, or that the rate of Pd depletion was limited by the mass of silicate melt the sulfide melt reached equilibrium with, or both. In any event, the fraction of sulfide melt that precipitated was too small to have had a significant effect on the Cu and Au content of the magma so that both Cu and Au were available to enter the ore-forming fluid when the magma became volatile saturated at, or shortly after, it reached ca. 2.9 wt.% MgO.

Intrinsic Josephson effects in the magnetic superconductor RuSr2GdCu2O8.

PubMed

Nachtrab, T; Koelle, D; Kleiner, R; Bernhard, C; Lin, C T

2004-03-19

We have measured interlayer current transport in small-sized RuSr2GdCu2O8 single crystals. We find a clear intrinsic Josephson effect showing that the material acts as a natural superconductor-insulator-ferromagnet-insulator-superconductor superlattice. Thus far, we detected no unconventional behavior due to the magnetism of the RuO2 layers.

Platinum-group minerals in the LG and MG chromitites of the eastern Bushveld Complex, South Africa

NASA Astrophysics Data System (ADS)

Oberthür, Thomas; Junge, Malte; Rudashevsky, Nikolay; de Meyer, Eveline; Gutter, Paul

2016-01-01

The chromitites of the Bushveld Complex in South Africa contain vast resources of platinum-group elements (PGE); however, except for the economic upper group (UG)-2 chromitite seam, information on the distribution of the PGE in the ores and on the mineralogical nature, assemblages, and proportions of platinum-group minerals (PGM) is essentially missing. In the present geochemical and mineralogical study, PGE concentrates originating from the lower group (LG)-6 and middle group (MG)-1/2 chromitites were investigated with the intention to fill this gap of knowledge. Chondrite-normalized PGE patterns of bulk rock and concentrates are characterized by a positive slope from Os to Rh, a slight drop to Pt, and an increase to Pd again. The pronounced similarities of the PGE patterns indicate similar primary processes of PGE concentration in the chromitites, namely "sulfide control" of the PGE mineralization, i.e., co-precipitation of chromite and sulfide. Further, the primary control of PGE concentration in chromitites appears to be dual in character: (i) base-level concentrations of IPGE (up to ˜500 ppb) hosted within chromite and (ii) co-precipitation of chromite and sulfide, the latter containing virtually the entire remaining PGE budget. Sulfides (chalcopyrite, pentlandite, and pyrite; pyrrhotite is largely missing) are scarce within the chromitites and occur mainly interstitial to chromite grains. Pd and Rh contents in pentlandite are low and erratic. Essentially, the whole PGE inventory of the ores occurs in the form of discrete PGM. The PGM are almost always associated with sulfides. The dominant PGM are various Pt-Pd-Rh sulfides (cooperite/braggite [(Pt,Pd)S] and malanite/cuprorhodsite [CuPt2S4]/[CuRh2S4]), laurite [RuS2], the main carrier of the IPGE (Os, Ir, Ru), sulfarsenides [(Rh,Pt,Ir)AsS], sperrylite [PtAs2], Pt-Fe alloys, and a large variety of mainly Pd-rich PGM. The LG and MG chromitites have many characteristics in common and define a general, "typical" PGM spectrum of Bushveld chromitites. This PGM assemblage is characterized by the predominance of PGE-sulfides including elevated proportions of malanite, variable proportions of (sulf) arsenides, and Pt-Fe alloys in conjunction with a paucity of (bismutho)tellurides. The formation of this specific PGM spectrum is related to the distinct chromitite environment and its depositional and post-depositional history, whereby desulfurization reactions have probably played an important role. The LG-6 samples have higher contents of PGE-sulfides, including extraordinary high proportions of malanite but low PGE-arsenide and PGE-sulfarsenide contents compared to the MG-1/2 samples. This indicates a higher availability of arsenic either in the stratigraphically higher MG-1/2 samples (compared to the LG-6) or regionally in the chromitites south of the Steelpoort lineament.

Metal phosphide catalysts and methods for making the same and uses thereof

DOEpatents

Habas, Susan Ellen; Wang, Jun; Ruddy, Daniel A.; Baddour, Frederick Raymond Gabriel; Schaidle, Joshua

2017-05-02

The present disclosure relates to a method that includes heating a mixture that includes a metal phenylphosphine-containing precursor that includes at least one of Mo(PPh.sub.3).sub.2(CO).sub.4, Pd(PPh.sub.3).sub.4, Ru(PPh.sub.3).sub.3Cl.sub.2, Ru(PPh.sub.3).sub.2(CO).sub.2Cl.sub.2, Co(PPh.sub.3)(CO).sub.2(NO), and/or Rh(PPh.sub.3).sub.2(CO)Cl, a surfactant, and a solvent. The heating is to a target temperature to form a heated mixture containing a metal phosphide nanoparticle that includes at least one of MoP, Ru.sub.2P, Co.sub.2P, Rh.sub.2P, and/or Pd.sub.3P, and the metal phosphide nanoparticle is not hollow.

Pressure-induced structural phase transition in transition metal carbides TMC (TM = Ru, Rh, Pd, Os, Ir, Pt): a DFT study

NASA Astrophysics Data System (ADS)

Manikandan, M.; Rajeswarapalanichamy, R.; Iyakutti, K.

2018-03-01

First-principles calculations based on density functional theory was performed to analyse the structural stability of transition metal carbides TMC (TM = Ru, Rh, Pd, Os, Ir, Pt). It is observed that zinc-blende phase is the most stable one for these carbides. Pressure-induced structural phase transition from zinc blende to NiAs phase is predicted at the pressures of 248.5 GPa, 127 GPa and 142 GPa for OsC, IrC and PtC, respectively. The electronic structure reveals that RuC exhibits a semiconducting behaviour with an energy gap of 0.7056 eV. The high bulk modulus values of these carbides indicate that these metal carbides are super hard materials. The high B/G value predicts that the carbides are ductile in their most stable phase.

High turnover in a photocatalytic system for water reduction to produce hydrogen using a Ru,  Rh,  Ru photoinitiated electron collector.

PubMed

Arachchige, Shamindri M; Shaw, Ryan; White, Travis A; Shenoy, Vimal; Tsui, Hei-Man; Brewer, Karen J

2011-04-18

Covalent coupling of Ru(II) light absorbers to a Rh(III) electron collecting site through polyazine bridging ligands affords photocatalytic production of H(2) in the presence of visible light and a sacrificial electron donor. A robust photocatalytic system displaying a high turnover of the photocatalyst has been developed using the photoinitiated electron collector [{(bpy)(2)Ru(dpp)}(2)RhBr(2)](5+) (bpy=2,2'-bipyridine; dpp=2,3-bis(2-pyridyl)pyrazine) and N,N-dimethylaniline in DMF/H(2)O. Studies have shown that increased [DMA], the headspace volume, and the use of DMF solvent improves the systems performance and stability providing mechanistic insight into the deactivation routes of the photocatalytic system. Photolysis of the system at 460 nm generates 20 mL of H(2) in 19.5 h with a maximum Φ=0.023 based on H(2) produced and an overall Φ=0.014 and 280 turnovers of the photocatalyst. The photocatalytic system also displays long-term photostability with 30 mL of H(2) generated and 420 turnovers in 50 h under the same conditions. Prolonged photolysis provides 820 mol H(2) per mole of catalyst. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Platinum-group element contents of Karelian kimberlites: Implications for the PGE budget of the sub-continental lithospheric mantle

NASA Astrophysics Data System (ADS)

Maier, W. D.; O'Brien, H.; Peltonen, P.; Barnes, Sarah-Jane

2017-11-01

We present high-precision isotope dilution data for Os, Ir, Ru, Pt, Pd and Re in Group I and Group II kimberlites from the Karelian craton, as well as 2 samples of the Premier Group I kimberlite pipe from the Kaapvaal craton. The samples have, on average, 1.38 ppb Pt and 1.33 ppb Pd, with Pt/Pd around unity. These PGE levels are markedly lower, by as much as 80%, than those reported previously for kimberlites from South Africa, Brazil and India, but overlap with PGE results reported recently from Canadian kimberlites. Primitive-mantle-normalised chalcophile element patterns are relatively flat from Os to Pt, but Cu, Ni and, somewhat less so, Au are enriched relative to the PGE (e.g., Cu/Pd > 25.000). Pd/Ir ratios are 3,6 on average, lower than in most other mantle melts. The PGE systematics can be largely explained by two components, (i) harzburgite/lherzolite detritus of the SCLM with relatively high IPGE (Os-Ir-Ru)/PPGE (Rh-Pt-Pd) ratios, and (ii) a melt component that has high PPGE/IPGE ratios. By using the concentrations of iridium in the kimberlites as a proxy for the proportion of mantle detritus in the magma, we estimate that the analysed kimberlites contain 3-27% entrained and partially dissolved detritus from the sub-continental lithospheric mantle, consistent with previous estimates of kimberlites elsewhere (Tappe S. et al., 2016, Chem. Geol. 10.1016/j.chemgeo.2016.08.019).

Brachytherapy treatment simulation of strontium-90 and ruthenium-106 plaques on small size posterior uveal melanoma using MCNPX code

NASA Astrophysics Data System (ADS)

Barbosa, N. A.; da Rosa, L. A. R.; Facure, A.; Braz, D.

2014-02-01

Concave eye applicators with 90Sr/90Y and 106Ru/106Rh beta-ray sources are usually used in brachytherapy for the treatment of superficial intraocular tumors as uveal melanoma with thickness up to 5 mm. The aim of this work consisted in using the Monte Carlo code MCNPX to calculate the 3D dose distribution on a mathematical model of the human eye, considering 90Sr/90Y and 160Ru/160Rh beta-ray eye applicators, in order to treat a posterior uveal melanoma with a thickness 3.8 mm from the choroid surface. Mathematical models were developed for the two ophthalmic applicators, CGD produced by BEBIG Company and SIA.6 produced by the Amersham Company, with activities 1 mCi and 4.23 mCi respectively. They have a concave form. These applicators' mathematical models were attached to the eye model and the dose distributions were calculated using the MCNPX *F8 tally. The average doses rates were determined in all regions of the eye model. The *F8 tally results showed that the deposited energy due to the applicator with the radionuclide 106Ru/106Rh is higher in all eye regions, including tumor. However the average dose rate in the tumor region is higher for the applicator with 90Sr/90Y, due to its high activity. Due to the dosimetric characteristics of these applicators, the PDD value for 3 mm water is 73% for the 106Ru/106Rh applicator and 60% for 90Sr/90Y applicator. For a better choice of the applicator type and radionuclide it is important to know the thickness of the tumor and its location.

Significance of β-dehydrogenation in ethanol electro-oxidation on platinum doped with Ru, Rh, Pd, Os and Ir.

PubMed

Sheng, Tian; Lin, Wen-Feng; Hardacre, Christopher; Hu, P

2014-07-14

In the exploration of highly efficient direct ethanol fuel cells (DEFCs), how to promote the CO2 selectivity is a key issue which remains to be solved. Some advances have been made, for example, using bimetallic electrocatalysts, Rh has been found to be an efficient additive to platinum to obtain high CO2 selectivity experimentally. In this work, the mechanism of ethanol electrooxidation is investigated using the first principles method. It is found that CH3CHOH* is the key intermediate during ethanol electrooxidation and the activity of β-dehydrogenation is the rate determining factor that affects the completeness of ethanol oxidation. In addition, a series of transition metals (Ru, Rh, Pd, Os and Ir) are alloyed on the top layer of Pt(111) in order to analyze their effects. The elementary steps, α-, β-C-H bond and C-C bond dissociations, are calculated on these bimetallic M/Pt(111) surfaces and the formation potential of OH* from water dissociation is also calculated. We find that the active metals increase the activity of β-dehydrogenation but lower the OH* formation potential resulting in the active site being blocked. By considering both β-dehydrogenation and OH* formation, Ru, Os and Ir are identified to be unsuitable for the promotion of CO2 selectivity and only Rh is able to increase the selectivity of CO2 in DEFCs.

Influences of alkaline earth metal substitution on the crystal structure and physical properties of magnetic RuSr1.9A0.1GdCu2O8 (A = Ca, Sr, and Ba) superconductors.

PubMed

Hur, Su Gil; Park, Dae Hoon; Hwang, Seong-Ju; Kim, Seung Joo; Lee, J H; Lee, Sang Young

2005-11-24

We have investigated the effect of alkaline earth metal substitution on the crystal structure and physical properties of magnetic superconductors RuSr(1.9)A(0.1)GdCu(2)O(8) (A = Ca, Sr, and Ba) in order to probe an interaction between the magnetic coupling of the RuO(2) layer and the superconductivity of the CuO(2) layer. X-ray diffraction and X-ray absorption spectroscopic analyses demonstrate that the isovalent substitution of Sr ions with Ca or Ba ions makes it possible to tune the interlayer distance between the CuO(2) and the RuO(2) layers. From the measurements of electrical resistance and magnetic susceptibility, it was found that, in contrast to negligible change of magnetization, both of the alkaline earth metal substitutions lead to a notable depression of zero-resistance temperature T(c) (DeltaT(c) approximately 17-19 K). On the basis of the absence of a systematic correlation between the T(c) and the interlayer distance/magnetization, we have concluded that the internal magnetic field of the RuO(2) layer has insignificant influence on the superconducting property of the CuO(2) layer in the ruthenocuprate.

LA-ICP-MS Study of Trace Elements in the Chanuskij Metal

NASA Technical Reports Server (NTRS)

Petaev, Michail I.

2005-01-01

This progress report covers work done during the second year of the 3-year proposal. During this year we resolved many issues relevant to the analytical technique developed by us for measuring trace elements in meteoritic metals. This technique was used to measure concentrations of Fe, Ni, Co, Cr, Cu, Ga, Ge, As, Mo, Ru, Rh, Pd, Sb, W, Re, Os, Ir, Pt, and Au in eight large (120 - 160 microns) metal grains from both "igneous" and "metamorphic" lithologies of the Chanuskij silicate inclusions. The first application of OUT technique to metal grains from thin sections showed some limitations. Small thickness of metal grains in the thin section limited the signal to 3-4 time-slices instead of 10- 1 1 ones in polished sections of iron meteorites studied before.

Ternary oxide nanostructures and methods of making same

DOEpatents

Wong, Stanislaus S [Stony Brook, NY; Park, Tae-Jin [Port Jefferson, NY

2009-09-08

A single crystalline ternary nanostructure having the formula A.sub.xB.sub.yO.sub.z, wherein x ranges from 0.25 to 24, and y ranges from 1.5 to 40, and wherein A and B are independently selected from the group consisting of Ag, Al, As, Au, B, Ba, Br, Ca, Cd, Ce, Cl, Cm, Co, Cr, Cs, Cu, Dy, Er, Eu, F, Fe, Ga, Gd, Ge, Hf, Ho, I, In, Ir, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Nd, Ni, Os, P, Pb, Pd, Pr, Pt, Rb, Re, Rh, Ru, S, Sb, Sc, Se, Si, Sm, Sn, Sr, Ta, Tb, Tc, Te, Ti, Tl, Tm, U, V, W, Y, Yb, and Zn, wherein the nanostructure is at least 95% free of defects and/or dislocations.

Recommended values of clean metal surface work functions

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

Derry, Gregory N., E-mail: gderry@loyola.edu; Kern, Megan E.; Worth, Eli H.

2015-11-15

A critical review of the experimental literature for measurements of the work functions of clean metal surfaces of single-crystals is presented. The tables presented include all results found for low-index crystal faces except cases that were known to be contaminated surfaces. These results are used to construct a recommended value of the work function for each surface examined, along with an uncertainty estimate for that value. The uncertainties are based in part on the error distribution for all measured work functions in the literature, which is included here. The metals included in this review are silver (Ag), aluminum (Al), goldmore » (Au), copper (Cu), iron (Fe), iridium (Ir), molybdenum (Mo), niobium (Nb), nickel (Ni), palladium (Pd), platinum (Pt), rhodium (Rh), ruthenium (Ru), tantalum (Ta), and tungsten (W)« less

Synthesis and microstructural TEM investigation of CaCu{sub 3}Ru{sub 4}O{sub 12} ceramic and thin film

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

Brize, Virginie; STMicroelectronics, 16 rue P and M Curie, 37001 Tours; Autret-Lambert, Cecile, E-mail: cecile.autret-lambert@univ-tours.fr

2011-10-15

CaCu{sub 3}Ru{sub 4}O{sub 12} (CCRO) is a conductive oxide having the same structure as CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) and close lattice parameters. The later compound is strongly considered for high density parallel plates capacitors application due to its so-called colossal dielectric constant. The need for an electrode inducing CCTO epitaxial growth with a clean and sharp interface is therefore necessary, and CCRO is a good potential candidate. In this paper, the synthesis of monophasic CCRO ceramic is reported, as well as pulsed laser deposition of CCRO thin film onto (001) NdCaAlO{sub 4} substrate. Structural and physical properties of bulkmore » CCRO were studied by transmission electron microscopy and electron spin resonance. CCRO films and ceramic exhibited a metallic behavior down to low temperature. CCRO films were (001) oriented and promoted a CCTO film growth with the same orientation. - Graphical Abstract: Structure of CaCu{sub 3}Ru{sub 4}O{sub 12} showing the RuO{sub 6} octahedra and the square planar environment for Cu{sup 2+}. Highlights: > In this study, we investigate the structural properties and microstructure of ceramics CaCu{sub 3}Ru{sub 4}O{sub 12}. > We study the conduction properties of polycrystalline material. > Then we synthesize the conductive thin film which is deposited on a high K material with the same structure (CaCu{sub 3}Ti{sub 4}O{sub 12}).« less

Noble metal catalyzed aqueous phase hydrogenation and hydrodeoxygenation of lignin-derived pyrolysis oil and related model compounds.

PubMed

Mu, Wei; Ben, Haoxi; Du, Xiaotang; Zhang, Xiaodan; Hu, Fan; Liu, Wei; Ragauskas, Arthur J; Deng, Yulin

2014-12-01

Aqueous phase hydrodeoxygenation of lignin pyrolysis oil and related model compounds were investigated using four noble metals supported on activated carbon. The hydrodeoxygenation of guaiacol has three major reaction pathways and the demethylation reaction, mainly catalyzed by Pd, Pt and Rh, produces catechol as the products. The presence of catechol and guaiacol in the reaction is responsible for the coke formation and the catalysts deactivation. As expected, there was a significant decrease in the specific surface area of Pd, Pt and Rh catalysts during the catalytic reaction because of the coke deposition. In contrast, no catechol was produced from guaiacol when Ru was used so a completely hydrogenation was accomplished. The lignin pyrolysis oil upgrading with Pt and Ru catalysts further validated the reaction mechanism deduced from model compounds. Fully hydrogenated bio-oil was produced with Ru catalyst. Copyright © 2014 Elsevier Ltd. All rights reserved.

Highly Stable and Active Catalyst for Sabatier Reactions

NASA Technical Reports Server (NTRS)

Hu, Jianli; Brooks, Kriston P.

2012-01-01

Highly active Ru/TiO2 catalysts for Sabatier reaction have been developed. The catalysts have shown to be stable under repeated shutting down/startup conditions. When the Ru/TiO2 catalyst is coated on the engineered substrate Fe-CrAlY felt, activity enhancement is more than doubled when compared with an identically prepared engineered catalyst made from commercial Degussa catalyst. Also, bimetallic Ru-Rh/TiO2 catalysts show high activity at high throughput.

Electronic properties of hybrid Cu2S/Ru semiconductor/metallic-cage nanoparticles.

PubMed

Bekenstein, Yehonadav; Vinokurov, Kathy; Banin, Uri; Millo, Oded

2012-12-21

Hybrid inorganic nanoparticles, comprising a semiconducting Cu(2)S quantum-dot (QD) core encapsulated by a metallic Ru cage-like shell, and each of their individual components, are studied via scanning tunneling spectroscopy. Bare Cu(2)S QDs show nearly identical semiconducting-like I-V characteristics while the empty Ru cages exhibit single electron tunneling effects-the Coulomb blockade and staircase. Surprisingly, in some cases negative differential conductance features, with periodicity that correlates to the Coulomb staircase, were observed. The tunneling spectra measured on the hybrid QDs varies greatly along a single particle, manifesting synergetic electrical properties that originate from this unique semiconducting-metallic interface.

Steam reforming of fast pyrolysis-derived aqueous phase oxygenates over Co, Ni, and Rh metals supported on MgAl 2O 4

DOE PAGES

Xing, Rong; Dagle, Vanessa Lebarbier; Flake, Matthew; ...

2016-02-03

In this paper we examine the feasibility of steam reforming the mixed oxygenate aqueous fraction derived from fast pyrolysis bio-oils. Catalysts selective towards hydrogen formation and resistant to carbon formation utilizing feeds with relatively low steam-to-carbon (S/C) ratios are desired. Rh (5 wt%), Pt (5 wt%), Ru (5 wt%), Ir (5 wt%), Ni (15 wt%), and Co (15 wt%) metals supported on MgAl2O4 were evaluated for catalytic performance at 500 °C and 1 atm using a complex feed mixture comprising acids, polyols, cycloalkanes, and phenolic compounds. The Rh catalyst was found to be the most active and resistant to carbonmore » formation. The Ni and Co catalysts were found to be more active than the other noble metal catalysts investigated (Pt, Ru, and Ir).« less

Enhancement of ethanol oxidation at Pt and PtRu nanoparticles dispersed over hybrid zirconia-rhodium supports

NASA Astrophysics Data System (ADS)

Rutkowska, Iwona A.; Koster, Margaretta D.; Blanchard, Gary J.; Kulesza, Pawel J.

2014-12-01

A catalytic material for electrooxidation of ethanol that utilizes PtRu nanoparticles dispersed over thin films of rhodium-free and rhodium-containing zirconia (ZrO2) supports is described here. The enhancement of electrocatalytic activity (particularly in the potential range as low as 0.25-0.5 V vs. RHE), that has been achieved by dispersing PtRu nanoparticles (loading, 100 μg cm-2) over the hybrid Rh-ZrO2 support composed of nanostructured zirconia and metallic rhodium particles, is clearly evident from comparison of the respective voltammetric and chronoamperometric current densities recorded at room temperature (22 °C) in 0.5 mol dm-3 H2SO4 containing 0.5 mol dm-3 ethanol. Porous ZrO2 nanostructures, that provide a large population of hydroxyl groups in acidic medium in the vicinity of PtRu sites, are expected to facilitate the ruthenium-induced removal of passivating CO adsorbates from platinum, as is apparent from the diagnostic experiments with a small organic molecule such as methanol. Although Rh itself does not show directly any activity toward ethanol oxidation, the metal is expected to facilitate C-C bond splitting in C2H5OH. It has also been found during parallel voltammetric and chronoamperometric measurements that the hybrid Rh-ZrO2 support increases activity of the platinum component itself toward ethanol oxidation in the low potential range.

Preparation and characterization of the magnetic superconductor EuSr2RuCu2O8-δ (RuEu-1212) by partial melting

NASA Astrophysics Data System (ADS)

Yamaki, K.; Kitagawa, N.; Funahashi, S.; Bamba, Y.; Irie, A.

2018-07-01

In this study, fine single crystals of the magnetic superconductor EuSr2RuCu2O8-δ (RuEu-1212) were successfully prepared using the partial melting technique. The obtained single crystals had a cubic shape, which coincides with the results of previous studies of RuGd-1212 single crystals. The single crystals had a typical length of 20-30 μm and the diffraction pattern observed from a sample prepared by partial melting was consistent with patterns of previously reported polycrystalline RuEu-1212 samples. A sample subjected to prolonged sintering, which consisted of a large number of combined micro single crystals prepared by partial melting, exhibited a superconducting transition with Tc-onset of 30.9 K and Tc-zero of 10.5 K.

Introduction and Validation of Chromium-Free Consumables for Welding Stainless Steels. Version 2

DTIC Science & Technology

2015-04-14

12 4.3 Site-related Permits and Regulations .......................................................................... 13 TEST DESIGN ...109 Appendix K: X-ray Report on ENiCuRu Weld Test Assembly...60 Table 6.24 Radiographic Test Report on Baseline E308L-16 and Test ENiCuRu Weld Assemblies

One-Pot Process for Hydrodeoxygenation of Lignin to Alkanes Using Ru-Based Bimetallic and Bifunctional Catalysts Supported on Zeolite Y.

PubMed

Wang, Hongliang; Ruan, Hao; Feng, Maoqi; Qin, Yuling; Job, Heather; Luo, Langli; Wang, Chongmin; Engelhard, Mark H; Kuhn, Erik; Chen, Xiaowen; Tucker, Melvin P; Yang, Bin

2017-04-22

The synthesis of high-efficiency and low-cost catalysts for hydrodeoxygenation (HDO) of waste lignin to advanced biofuels is crucial for enhancing current biorefinery processes. Inexpensive transition metals, including Fe, Ni, Cu, and Zn, were severally co-loaded with Ru on HY zeolite to form bimetallic and bifunctional catalysts. These catalysts were subsequently tested for HDO conversion of softwood lignin and several lignin model compounds. Results indicated that the inexpensive earth-abundant metals could modulate the hydrogenolysis activity of Ru and decrease the yield of low-molecular-weight gaseous products. Among these catalysts, Ru-Cu/HY showed the best HDO performance, affording the highest selectivity to hydrocarbon products. The improved catalytic performance of Ru-Cu/HY was probably a result of the following three factors: (1) high total and strong acid sites, (2) good dispersion of metal species and limited segregation, and (3) high adsorption capacity for polar fractions, including hydroxyl groups and ether bonds. Moreover, all bifunctional catalysts proved to be superior over the combination catalysts of Ru/Al 2 O 3 and HY zeolite. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

One-pot process for hydrodeoxygenation of lignin to alkanes using Ru-based bimetallic and bifunctional catalysts supported on zeolite Y

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

Wang, Hongliang; Ruan, Hao; Feng, Maoqi

2017-02-22

Here, the synthesis of high-efficiency and low-cost catalysts for hydrodeoxygenation (HDO) of waste lignin to advanced biofuels is crucial for enhancing current biorefinery processes. Inexpensive transition metals, including Fe, Ni, Cu, and Zn, were severally co-loaded with Ru on HY zeolite to form bimetallic and bifunctional catalysts. These catalysts were subsequently tested for HDO conversion of softwood lignin and several lignin model compounds. Results indicated that the inexpensive earth-abundant metals could modulate the hydrogenolysis activity of Ru and decrease the yield of low-molecular-weight gaseous products. Among these catalysts, Ru-Cu/HY showed the best HDO performance, affording the highest selectivity to hydrocarbonmore » products. The improved catalytic performance of Ru-Cu/HY was probably a result of the following three factors: (1) high total and strong acid sites, (2) good dispersion of metal species and limited segregation, and (3) high adsorption capacity for polar fractions, including hydroxyl groups and ether bonds. Moreover, all bifunctional catalysts proved to be superior over the combination catalysts of Ru/Al 2O 3 and HY zeolite.« less

Synthesis and spectral studies of platinum metal complexes of benzoin thiosemicarbazone

NASA Astrophysics Data System (ADS)

Offiong, Offiong E.

1994-11-01

The platinum metal chelates of benzoin thiosemicarbazone obtained with Ru(III), Rh(III), Ir(III), Pd(II) and Pt(II) were prepared from their corresponding halide salts. The complexes were characterized by elemental analysis, conductance measurement, IR, Raman, 1H-NMR, 13C-NMR and UV-visible spectra studies. Various ligand field parameters and nephelauxetic parameters were also calculated. The mode of bonding and the geometry of the ligand environment around the metal ion have been discussed in the light of the available data obtained. Complexes of Ru(III), Rh(III) and Ir(III) are six-coordinate octahedral, while Pd(II) and Pt(II) halide complexes are four-coordinated with halides bridging.

Inert anode containing oxides of nickel iron and cobalt useful for the electrolytic production of metals

DOEpatents

Ray, Siba P.; Liu, Xinghua; Weirauch, Jr., Douglas A.

2002-01-01

An inert anode for the electrolytic production of metals such as aluminum is disclosed. The inert anode includes a ceramic oxide material preferably made from NiO, Fe.sub.2 O.sub.3 and CoO. The inert anode composition may comprise the following mole fractions of NiO, Fe.sub.2 O.sub.3 and CoO: 0.15 to 0.99 NiO; 0.0001 to 0.85 Fe.sub.2 O.sub.3 ; and 0.0001 to 0.45 CoO. The inert anode may optionally include other oxides and/or at least one metal phase, such as Cu, Ag, Pd, Pt, Au, Rh, Ru, Ir and/or Os. The Ni--Fe--Co--O ceramic material exhibits very low solubility in Hall cell baths used to produce aluminum.

Inert anode containing oxides of nickel, iron and zinc useful for the electrolytic production of metals

DOEpatents

Ray, Siba P.; Weirauch, Jr., Douglas A.; Liu, Xinghua

2002-01-01

An inert anode for the electrolytic production of metals such as aluminum is disclosed. The inert anode includes a ceramic oxide material preferably made from NiO, Fe.sub.2 O.sub.3 and ZnO. The inert anode composition may comprise the following mole fractions of NiO, Fe.sub.2 O.sub.3 and ZnO: 0.2 to 0.99 NiO; 0.0001 to 0.8 Fe.sub.2 O.sub.3 ; and 0.0001 to 0.3 ZnO. The inert anode may optionally include other oxides and/or at least one metal phase, such as Cu, Ag, Pd, Pt, Au, Rh, Ru, Ir and/or Os. The Ni--Fe--Co--O ceramic material exhibits very low solubility in Hall cell baths used to produce aluminum.

High-throughput screening of small-molecule adsorption in MOF-74

NASA Astrophysics Data System (ADS)

Thonhauser, T.; Canepa, P.

2014-03-01

Using high-throughput screening coupled with state-of-the-art van der Waals density functional theory, we investigate the adsorption properties of four important molecules, H2, CO2, CH4, and H2O in MOF-74-  with  = Be, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Zr, Nb, Ru, Rh, Pd, La, W, Os, Ir, and Pt. We show that high-throughput techniques can aid in speeding up the development and refinement of effective materials for hydrogen storage, carbon capture, and gas separation. The exploration of the configurational adsorption space allows us to extract crucial information concerning, for example, the competition of water with CO2 for the adsorption binding sites. We find that only a few noble metals--Rh, Pd, Os, Ir, and Pt--favor the adsorption of CO2 and hence are potential candidates for effective carbon-capture materials. Our findings further reveal significant differences in the binding characteristics of H2, CO2, CH4, and H2O within the MOF structure, indicating that molecular blends can be successfully separated by these nano-porous materials. Supported by DOE DE-FG02-08ER46491.

Interplay of structure and magnetism in ruthenocuprates: a Raman scattering and dilatometry study

NASA Astrophysics Data System (ADS)

Fainstein, A.; Ramos, C. A.; Pregliasco, R. G.; Butera, A.; Trodahl, H. J.; Williams, G. V. M.; Tallon, J. L.

2002-07-01

We present a Raman scattering and dilatometry study of polycrystalline samples of the magnetic superconducting ruthenocuprates RuSr 2Gd 2- xCe xCu 2O 10+ δ (RuGd 1222) and RuSr 2GdCu 2O 8 (RuGd 1212). In the Raman spectra a high-temperature diffusive-like laser-tail develops below the magnetic ordering temperature ( TM) into an underdamped peak which shifts up to ˜130 cm-1. A line assigned to O(Ru) phonons hardens, narrows and strengthens strongly below TM. Finally, a phonon peak appears below TM at ˜590 cm-1. These three magnetic-order-dependent features are observed for RuGd 1212 and for RuGd 1222 with x=1.0, but do not appear for x=0.5. Dilatometry measurements, on the other hand, evidence a change of the expansion coefficient at TM. These results point to a structural effect accompanying the magnetic order, and suggest a complex interplay of spin and lattice degrees of freedom in these ruthenocuprates.

The series of carbon-chain complexes {Ru(dppe)Cp*}₂{μ-(C≡C )x} (x = 4–8, 11): Synthesis, structures, properties and some reactions

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

Bruce, Michael I.; Cole, Marcus L.; Ellis, Benjamin G.

The construction of a series of compounds {Ru(dppe)Cp*} 2(μ-C 2x) (Ru*-C2x-Ru*, x = 4–8, 11)) is described. A direct reaction between RuCl(dppe)Cp* and Me 3Si(Ctriple bond; length of mdashC) 4SiMe 3 afforded Ru*-C8-Ru* in 89% yield. The Pd(0)/Cu(I)-catalysed coupling of Ru{Ctriple bond; length of mdashCCtriple bond; length of mdashCAu(PPh 3)}(dppe)Cp*Ru*-C4-Au (2 equiv.) with diiodoethyne gave Ru*-C10-Ru* (64%), or of 1 equiv. with I(Ctriple bond; length of mdashC) 3I gave Ru*-C14-Ru* (36%); similarly, Ru{(Ctriple bond; length of mdashC) 4Au(PPh 3)}(dppe)Cp*Ru*-C8-Au and I(Ctriple bond; length of mdashC) 3I gave Ru*-C22-Ru* (12%). Desilylation (TBAF) of Ru{(Ctriple bond; length of mdashC)xSiMe 3}(dppe)Cp*Ru*-C2x-Si (x =more » 3, 4) followed by oxidative coupling [Cu(OAc) 2/py] gave Ru*-C12-Ru* (82%) and Ru*-C16-Ru* (58%), respectively. Similar oxidative coupling of Ru(Ctriple bond; length of mdashCCtriple bond; length of mdashCH)(dppe)Cp* was a second route to Ru*-C8-Ru* (82%). Appropriate precursors are already known, or obtained by coupling of Ru*-C2x-Si (x = 2, 4) with AuCl(PPh 3)/NaOMe [Ru*-C4-Au, 95%; Ru*-C8-Au, 74%] or from Pd(0)/Cu(I) catalysed coupling of Ru*-C2x-Au (x = 2, 3) with I(Ctriple bond; length of mdashC) 2SiMe 3 (Ru*-C8-Si, 64%; Ru*-C10-Si, 2%). Reactions between Ru*-C2x-Ru* (x = 3, 4) and Fe 2(CO) 9 gave {Fe 3(CO) 9}{μ 3-CCtriple bond; length of mdashC[Ru(dppe)Cp*]} 2Fe(C 3-Ru*) 2 and {Fe 3(CO) 9}{μ 3-CCtriple bond; length of mdashC[Ru(dppe)Cp*]}{μ 3-C(Ctriple bond; length of mdashC) 2[Ru(dppe)Cp*]} Fe(C 3-Ru*)(C 5-Ru*), respectively. The redox properties of the series of complexes with 2x = 2–16 were measured and showed a diminution of the separation of the first two oxidation potentials, ΔE = E 2 - E 1, with increasing carbon chain length. The X-ray-determined molecular structures of Ru*-C8-Si, Ru*-C8-Ru*, Ru*-C14-Ru* (two C 6H 6 solvates), {Ru(PPh 3) 2Cp} 2{μ-(Ctriple bond; length of mdashC) 4}·4CHCl 3Ru-C 8-Ru·4CHCl 3 and of Fe(C 3-Ru*) 2 and Fe(C 3-Ru*)(C 5-Ru*) are reported.« less

Complex vibrations in arsenide skutterudites and oxyskutterudites

NASA Astrophysics Data System (ADS)

Bridges, F.; Car, B.; Sutton, L.; Hoffman-Stapleton, M.; Keiber, T.; Baumbach, R. E.; Maple, M. B.; Henkie, Z.; Wawryk, R.

2015-01-01

The local structure of two skutterudite families—Ce M4As12 (M =Fe , Ru, Os) and L n Cu3Ru4O12 (L n =La , Pr, and Nd)—have been studied using the extended x-ray absorption fine structure (EXAFS) technique with a focus on the lattice vibrations about the rare-earth "rattler atoms" and the extent to which these vibrations can be considered local modes, with the rattler vibrating inside a nearly rigid cage. X-ray absorption data at all the metal edges were collected over a temperature range of 4 to 300 K and analyzed using standard procedures. The pair distances from EXAFS results agree quite well with the average structure obtained from diffraction. The cage structure is formed by the M and As atoms in Ce M4As12 and by Cu, O, and Ru atoms in L n Cu3Ru4O12 . Although some of the bonds within the cage are quite stiff (correlated Debye temperatures, θcD, are ˜500 K for Ce M4As12 and above 800 K for L n Cu3Ru4O12 ), we show that the structure is not completely rigid. For the rattler atom the nearest-neighbor pairs have a relatively low Einstein temperature, θE:˜100 - 120 K for Ce-As and ˜130 K for L n -O . Surprisingly, the behaviors of the second-neighbor pairs are quite different: for Ce M4As12 the second-neighbor pairs (Ce -M ) have a weaker bond while for L n Cu3Ru4O12 the L n -Ru second-neighbor pair has a stiffer effective spring constant than the first-neighbor pair. In addition, we show that the As4 or CuO4 rings are relatively rigid units and that their vibrations are anisotropic within these cubic structures, with stiff restoring forces perpendicular to the rings and much weaker restoring forces in directions parallel to the rings. Consequently vibrations of the rings may also act as "rattlers" and help suppress thermal conductivity. In general neither the rigid-cage approximation nor the simple reduced-mass approximation are sufficient for describing rattler behavior.

Direct determination of platinum group elements and their distributions in geological and environmental samples at the ng g(-1) level using LA-ICP-IDMS.

PubMed

Boulyga, Sergei F; Heumann, Klaus G

2005-10-01

Laser ablation inductively coupled plasma isotope dilution mass spectrometry (LA-ICP-IDMS) was applied to the direct and simultaneous determination of the platinum group elements (PGEs) Pt, Pd, Ru, and Ir in geological and environmental samples. A special laser ablation system with high ablation rates was used, along with sector field ICP-MS. Special attention was paid to deriving the distributions of PGEs in the pulverized samples. IDMS could not be applied to the (mono-isotopic) Rh, but the similar ablation behavior of Ru and Rh allowed Rh to be simultaneously determined via relative sensitivity coefficients. The laser ablation process produces hardly any oxide ions (which usually cause interference in PGE analysis with liquid sample injection), so the ICP-MS can be run in its low mass resolution but high-sensitivity mode. The detection limits obtained for the geological samples were 0.16 ng g(-1), 0.14 ng g(-1), 0.08 ng g(-1), 0.01 ng g(-1) and 0.06 ng g(-1) for Ru, Rh, Pd, Ir and Pt, respectively. LA-ICP-IDMS was applied to different geological reference materials (TDB-1, WGB-1, UMT-1, WMG-1, SARM-7) and the road dust reference material BCR-723, which are only certified for some of the PGEs. Comparisons with certified values as well as with indicative values from the literature demonstrated the validity of the LA-ICP-IDMS method. The PGE concentrations in subsamples of the road dust reference material correspond to a normal distribution, whereas the distributions in the geological reference materials TDB-1, WGB-1, UMT-1, WMG-1, and SARM-7 are more complex. For example, in the case of Ru, a logarithmic normal distribution best fits the analyzed concentrations in TDB-1 subsamples, whereas a pronounced nugget effect was found for Pt in most geological samples.

Analysis of scattering lengths in Co/Cu/Co and Co/Cu/Co/Cu spin-valves using a Ru barrier

NASA Astrophysics Data System (ADS)

Strijkers, G. J.; Willekens, M. M. H.; Swagten, H. J. M.; de Jonge, W. J. M.

1996-10-01

We use uncoupled Co/Cu/Co and Co/Cu/Co/Cu spin-valve structures with a Ru barrier shifted through the top Co and Cu layer, respectively, to measure the longest of the electron mean free paths in Co and Cu as originally suggested by Parkin. From semiclassical transport calculations and careful analysis of the magnetoresistance data we conclude that the exponential behavior of ΔG is uniquely related to the longest of the Co and Cu mean free paths under the condition of effective spin-dependent filtering at the interfaces or in the bulk of the Co. In this regime we have compared λlong in Co and Cu with bulk conductivities (~λshort+λlong), yielding no strong evidence for bulk spin-dependent scattering in Co.

Electron scattering at interfaces in nano-scale vertical interconnects: A combined experimental and ab initio study

NASA Astrophysics Data System (ADS)

Lanzillo, Nicholas A.; Restrepo, Oscar D.; Bhosale, Prasad S.; Cruz-Silva, Eduardo; Yang, Chih-Chao; Youp Kim, Byoung; Spooner, Terry; Standaert, Theodorus; Child, Craig; Bonilla, Griselda; Murali, Kota V. R. M.

2018-04-01

We present a combined theoretical and experimental study on the electron transport characteristics across several representative interface structures found in back-end-of-line interconnect stacks for advanced semiconductor manufacturing: Cu/Ta(N)/Co/Cu and Cu/Ta(N)/Ru/Cu. In particular, we evaluate the impact of replacing a thin TaN barrier with Ta while considering both Co and Ru as wetting layers. Both theory and experiment indicate a pronounced reduction in vertical resistance when replacing TaN with Ta, regardless of whether a Co or Ru wetting layer is used. This indicates that a significant portion of the total vertical resistance is determined by electron scattering at the Cu/Ta(N) interface. The electronic structure of these nano-sized interconnects is analyzed in terms of the atom-resolved projected density of states and k-resolved transmission spectra at the Fermi level. This work further develops a fundamental understanding of electron transport and material characteristics in nano-sized interconnects.

Initial Reduction of CO2 on Pd-, Ru-, and Cu-Doped CeO2(111) Surfaces: Effects of Surface Modification on Catalytic Activity and Selectivity.

PubMed

Guo, Chen; Wei, Shuxian; Zhou, Sainan; Zhang, Tian; Wang, Zhaojie; Ng, Siu-Pang; Lu, Xiaoqing; Wu, Chi-Man Lawrence; Guo, Wenyue

2017-08-09

Surface modification by metal doping is an effective treatment technique for improving surface properties for CO 2 reduction. Herein, the effects of doped Pd, Ru, and Cu on the adsorption, activation, and reduction selectivity of CO 2 on CeO 2 (111) were investigated by periodic density functional theory. The doped metals distorted the configuration of a perfect CeO 2 (111) by weakening the adjacent Ce-O bond strength, and Pd doping was beneficial for generating a highly active O vacancy. The analyses of adsorption energy, charge density difference, and density of states confirmed that the doped metals were conducive for enhancing CO 2 adsorption, especially for Cu/CeO 2 (111). The initial reductive dissociation CO 2 → CO* + O* on metal-doped CeO 2 (111) followed the sequence of Cu- > perfect > Pd- > Ru-doped CeO 2 (111); the reductive hydrogenation CO 2 + H → COOH* followed the sequence of Cu- > perfect > Ru- > Pd-doped CeO 2 (111), in which the most competitive route on Cu/CeO 2 (111) was exothermic by 0.52 eV with an energy barrier of 0.16 eV; the reductive hydrogenation CO 2 + H → HCOO* followed the sequence of Ru- > perfect > Pd-doped CeO 2 (111). Energy barrier decomposition analyses were performed to identify the governing factors of bond activation and scission along the initial CO 2 reduction routes. Results of this study provided deep insights into the effect of surface modification on the initial reduction mechanisms of CO 2 on metal-doped CeO 2 (111) surfaces.

Highly reflective Ag-Cu alloy-based ohmic contact on p-type GaN using Ru overlayer.

PubMed

Son, Jun Ho; Jung, Gwan Ho; Lee, Jong-Lam

2008-12-15

We report on a metallization scheme of high reflectance, low resistance, and smooth surface morphology ohmic contact on p-type GaN. Ag-Cu alloy/Ru contact showed low contact resistivity as low as 6.2 x 10(-6) Ohms cm(2) and high reflectance of 91% at 460 nm after annealing at 400 degrees C in air ambient. The oxidation annealing promoted the out-diffusion of Ga atoms to dissolve in an Ag-Cu layer with the formation of an Ag-Ga solid solution, lowering the contact resistivity. The Ru overlayer acts as a diffusion barrier for excessive oxygen incorporation during oxidation annealing, resulting in high reflectance, good thermal stability, and smooth surface quality of the contact.

One-Pot Process for Hydrodeoxygenation of Lignin to Alkanes Using Ru-Based Bimetallic and Bifunctional Catalysts Supported on Zeolite Y

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

Wang, Hongliang; Ruan, Hao; Feng, Maoqi

2017-03-16

The synthesis of high-efficiency and low-cost multifunctional catalysts for hydrodeoxygenation (HDO) of waste lignin into advanced biofuels is crucial for enhancing current biorefinery processes. Inexpensive transition metals, including Fe, Ni, Cu, Zn, were severally co-loaded with Ru on HY zeolite to form bimetallic and bifunctional catalysts. These catalysts were subsequently tested for HDO conversion of softwood lignin and several lignin model compounds. Results indicated that the inexpensive earth abundant metals could modulate the hydrogenolysis activity of Ru and decrease the yield of low molecular weight gaseous side-products. Among all the prepared catalysts, Ru-Cu/HY showed the best HDO performance, giving themore » highest selectivity to hydrocarbon products. The improved catalytic performance of Ru-Cu/HY was probably due to the following three factors: (1) high total and strong acid sites, (2) good dispersion of metal species and limited segregation, (3) high adsorption capacity for polar fractions, including hydroxyl groups and ether bonds. Moreover, all the bifunctional catalysts were proven to be superior over the combination catalysts of Ru/Al2O3 and HY zeolite, and this could be attributed to the “intimacy criterion”. The practical use of the designed catalysts would be promising in lignin valorization.« less

Multi-mode humidity sensing with water-soluble copper phthalocyanine for increased sensitivity and dynamic range

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

Muckley, Eric S.; Jacobs, Christopher B.; Vidal, Keith

Aqueous solubility of copper phthalocyanine-3,4',4',4"'-tetrasulfonic acid tetrasodium salt (CuPcTs) enables fabrication of flexible electronic devices by low cost inkjet printing. We (1) investigate water adsorption kinetics on CuPcTs for better understanding the effects of relative humidity (RH) on hydrophilic phthalocyanines, and (2) assess CuPcTs as a humidity-sensing material. Reaction models show that H 2O undergoes 2-site adsorption which can be represented by a pair of sequentially-occurring pseudo-first order reactions. Using high frequency (300–700 THz) and low frequency (1–8 MHz) dielectric spectroscopy combined with gravimetric measurements and principal component analysis, we observe that significant opto-electrical changes in CuPcTs occur at RHmore » ≈ 60%. The results suggest that rapid H 2O adsorption takes place at hydrophilic sulfonyl/salt groups on domain surfaces at low RH, while slow adsorption and diffusion of H 2O into CuPcTs crystallites leads to a mixed CuPcTs-H 2O phase at RH > 60%, resulting in high frequency dielectric screening of the film by water and dissociation of Na+ from CuPc(SO 3-) 4 ions. Lastly, the CuPcTs-H 2O interaction can be tracked using a combination of gravimetric, optical, and electrical sensing modes, enabling accurate ( ± 2.5%) sensing in the ~0–95% RH range with a detection limit of less than 0.1% RH.« less

Multi-mode humidity sensing with water-soluble copper phthalocyanine for increased sensitivity and dynamic range

DOE PAGES

Muckley, Eric S.; Jacobs, Christopher B.; Vidal, Keith; ...

2017-08-30

Aqueous solubility of copper phthalocyanine-3,4',4',4"'-tetrasulfonic acid tetrasodium salt (CuPcTs) enables fabrication of flexible electronic devices by low cost inkjet printing. We (1) investigate water adsorption kinetics on CuPcTs for better understanding the effects of relative humidity (RH) on hydrophilic phthalocyanines, and (2) assess CuPcTs as a humidity-sensing material. Reaction models show that H 2O undergoes 2-site adsorption which can be represented by a pair of sequentially-occurring pseudo-first order reactions. Using high frequency (300–700 THz) and low frequency (1–8 MHz) dielectric spectroscopy combined with gravimetric measurements and principal component analysis, we observe that significant opto-electrical changes in CuPcTs occur at RHmore » ≈ 60%. The results suggest that rapid H 2O adsorption takes place at hydrophilic sulfonyl/salt groups on domain surfaces at low RH, while slow adsorption and diffusion of H 2O into CuPcTs crystallites leads to a mixed CuPcTs-H 2O phase at RH > 60%, resulting in high frequency dielectric screening of the film by water and dissociation of Na+ from CuPc(SO 3-) 4 ions. Lastly, the CuPcTs-H 2O interaction can be tracked using a combination of gravimetric, optical, and electrical sensing modes, enabling accurate ( ± 2.5%) sensing in the ~0–95% RH range with a detection limit of less than 0.1% RH.« less

Multi-mode humidity sensing with water-soluble copper phthalocyanine for increased sensitivity and dynamic range.

PubMed

Muckley, Eric S; Jacobs, Christopher B; Vidal, Keith; Lavrik, Nickolay V; Sumpter, Bobby G; Ivanov, Ilia N

2017-08-30

Aqueous solubility of copper phthalocyanine-3,4',4″,4″'-tetrasulfonic acid tetrasodium salt (CuPcTs) enables fabrication of flexible electronic devices by low cost inkjet printing. We (1) investigate water adsorption kinetics on CuPcTs for better understanding the effects of relative humidity (RH) on hydrophilic phthalocyanines, and (2) assess CuPcTs as a humidity-sensing material. Reaction models show that H 2 O undergoes 2-site adsorption which can be represented by a pair of sequentially-occurring pseudo-first order reactions. Using high frequency (300-700 THz) and low frequency (1-8 MHz) dielectric spectroscopy combined with gravimetric measurements and principal component analysis, we observe that significant opto-electrical changes in CuPcTs occur at RH ≈ 60%. The results suggest that rapid H 2 O adsorption takes place at hydrophilic sulfonyl/salt groups on domain surfaces at low RH, while slow adsorption and diffusion of H 2 O into CuPcTs crystallites leads to a mixed CuPcTs-H 2 O phase at RH > 60%, resulting in high frequency dielectric screening of the film by water and dissociation of Na + from CuPc(SO 3 - ) 4 ions. The CuPcTs-H 2 O interaction can be tracked using a combination of gravimetric, optical, and electrical sensing modes, enabling accurate ( ± 2.5%) sensing in the ~0-95% RH range with a detection limit of less than 0.1% RH.

Study of new mononuclear platinum group metal complexes containing η 5 and η 6 - Carbocyclic ligands and nitrogen based derivatives and formation of helices due to N sbnd H⋯Cl interactions

NASA Astrophysics Data System (ADS)

Gupta, Gajendra; Gloria, Sairem; Das, Babulal; Rao, Kollipara Mohan

2010-08-01

A quite general approach for the preparation of η 5- and η 6-cyclichydrocarbon platinum group metal complexes is reported. The dinuclear arene ruthenium complexes [(η 6-arene)Ru(μ-Cl)Cl] 2 (arene = C 6H 6, C 10H 14 and C 6Me 6) and η 5-pentamethylcyclopentadienyl rhodium and iridium complexes [(η 5-C 5Me 5)M(μ-Cl)Cl] 2 (M = Rh and Ir) reacts with two equivalents of the ligands 2-chloro-3-(pyrazolyl)quinoxaline ( L 1) and di-(2-pyridyl)amine ( L 2) in presence of NH 4PF 6 to afford the corresponding mononuclear complexes of the type [(η 6-arene)Ru(L 1)Cl]PF 6 {arene = C 6H 6 ( 1), C 10H 14 ( 2) and C 6Me 6 ( 3)}, [(η 6-arene)Ru(L 2)Cl]PF 6 {arene = C 6H 6 ( 4), C 10H 14 ( 5) and C 6Me 6 ( 6)}, and [(η 5-C 5Me 5)M(L 1)Cl]PF 6 {M = Rh ( 7), Ir ( 8)} and [(η 5-C 5Me 5)M(L 2)Cl]PF 6 {M = Rh ( 9), Ir ( 10)}. However the mononuclear η 5-cyclopentadienyl analogues such as [(η 5-C 5H 5)Ru(PPh 3) 2Cl], [(η 5-C 5H 5)Os(PPh 3) 2Br], [(η 5-C 5Me 5)Ru(PPh 3) 2Cl] and [(η 5-C 9H 7)Ru(PPh 3) 2Cl] complexes react in presence of one equivalent of ligands 2-chloro-3-(pyrazolyl)quinoxaline ( L 1) and di-(2-pyridyl)amine ( L 2) and one equivalent of NH 4PF 6 in methanol yielded mononuclear complexes [(η 5-C 5H 5)Ru(PPh 3)(L 1)]PF 6 ( 11), [(η 5-C 5H 5)Os(PPh 3)(L 1)]PF 6 ( 12), [(η 5-C 5Me 5)Ru(PPh 3)(L 1)]PF 6 ( 13) and [(η 5-C 9H 7)Ru(PPh 3)(L 1)]PF 6 ( 14) and [(η 5-C 5H 5)Ru(PPh 3)(L 2)]PF 6 ( 15), [(η 5-C 5H 5)Os(PPh 3)(L 2)]PF 6 ( 16), [(η 5-C 5Me 5)Ru(PPh 3)(L 2)]PF 6 ( 17) and [(η 5-C 9H 7)Ru(PPh 3)(L 2)]PF 6 ( 18) respectively. These compounds have been systematically characterized by IR, NMR and mass spectrometry. The molecular structures of 2, 4 and 15 have been established by single crystal X-ray diffraction study and some of the representative complexes have also been studied by UV-visible spectroscopy. The crystal packing diagram of complex 4 reveals that the cation [(η 6-C 6H 6)Ru(L 2)Cl] + is engaged in non-covalent interaction. This compound gives rise to a 1D helical architecture along the ' a' axis via intermolecular N sbnd H⋯Cl hydrogen bonds.

Investigation of the synthesis, activation, and isosteric heats of CO2 adsorption of the isostructural series of metal-organic frameworks M3(BTC)2 (M = Cr, Fe, Ni, Cu, Mo, Ru).

PubMed

Wade, Casey R; Dincă, Mircea

2012-07-14

The synthesis, activation, and heats of CO(2) adsorption for the known members of the M(3)(BTC)(2) (HKUST-1) isostructural series (M = Cr, Fe, Ni, Zn, Ni, Cu, Mo) were investigated to gain insight into the impact of CO(2)-metal interactions for CO(2) storage/separation applications. With the use of modified syntheses and activation procedures, improved BET surface areas were obtained for M = Ni, Mo, and Ru. The zero-coverage isosteric heats of CO(2) adsorption were measured for the Cu, Cr, Ni, Mo, and Ru analogues and gave values consistent with those reported for MOFs containing coordinatively unsaturated metal sites, but lower than for amine functionalized materials. Notably, the Ni and Ru congeners exhibited the highest CO(2) affinities in the studied series. These behaviors were attributed to the presence of residual guest molecules in the case of Ni(3)(BTC)(2)(Me(2)NH)(2)(H(2)O) and the increased charge of the dimetal secondary building unit in [Ru(3)(BTC)(2)][BTC](0.5).

Band gap tuning in transition metal oxides by site-specific substitution

DOEpatents

Lee, Ho Nyung; Chisholm, Jr., Matthew F; Jellison, Jr., Gerald Earle; Singh, David J; Choi, Woo Seok

2013-12-24

A transition metal oxide insulator composition having a tuned band gap includes a transition metal oxide having a perovskite or a perovskite-like crystalline structure. The transition metal oxide includes at least one first element selected form the group of Bi, Ca, Ba, Sr, Li, Na, Mg, K, Pb, and Pr; and at least one second element selected from the group of Ti, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Hf, Ta, W, Re, Os, Ir, and Pt. At least one correlated insulator is integrated into the crystalline structure, including REMO.sub.3, wherein RE is at least one Rare Earth element, and wherein M is at least one element selected from the group of Co, V, Cr, Ni, Mn, and Fe. The composition is characterized by a band gap of less of 4.5 eV.

Producing carbon-based boundary films from catalytically active lubricant additives

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

Erdemir, Ali; Mane, Anil U.; Elam, Jeffrey W.

A lubricant composition includes an oil including a plurality of long-chain hydrocarbon molecules. A quantity of a catalytically active metal-organic additive is mixed with the oil. The metal-organic additive is formulated to fragment the long-chain hydrocarbon molecules of the oil into at least one of dimers and trimers under the influence of at least one of a mechanical loading and a thermal loading. In some embodiments, the metal-organic additive includes a compound of formula II: ##STR00001## where: X is Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf,more » Ta, W, Re, Os, Ir, Pt, Au, Hg, Rf, Db, Sg, Bh, Hs, Mt, Ds, Rg or Cn, and R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are alkyl or alkyl halide.« less

Quantum anomalous Hall phase and half-metallic phase in ferromagnetic (111) bilayers of 4 d and 5 d transition metal perovskites

NASA Astrophysics Data System (ADS)

Chandra, Hirak Kumar; Guo, Guang-Yu

2017-04-01

Extraordinary electronic phases can form in artificial oxide heterostructures, which will provide a fertile ground for new physics and also give rise to novel device functions. Based on a systematic first-principles density functional theory study of the magnetic and electronic properties of the (111) superlattices (ABO3) 2/(AB'O3)10 of 4 d and 5 d transition metal perovskite (B = Ru, Rh, Ag, Re, Os, Ir, Au; AB'O3=LaAlO3 , SrTiO3) , we demonstrate that due to quantum confinement, bilayers (LaBO3)2 (B = Ru, Re, Os) and (SrBO3)2 (B = Rh, Os, Ir) are ferromagnetic with ordering temperatures up to room temperature. In particular, bilayer (LaOsO3)2 is an exotic spin-polarized quantum anomalous Hall insulator, while the other ferromagnetic bilayers are metallic with large Hall conductances comparable to the conductance quantum. Furthermore, bilayers (LaRuO3)2 and (SrRhO3)2 are half metallic, while the bilayer (SrIrO3)2 exhibits a peculiar colossal magnetic anisotropy. Our findings thus show that 4 d and 5 d metal perovskite (111) bilayers are a class of quasi-two-dimensional materials for exploring exotic quantum phases and also for advanced applications such as low-power nanoelectronics and oxide spintronics.

Platinum group elements and gold in ferromanganese crusts from Afanasiy-Nikitin seamount, equatorial Indian Ocean: Sources and fractionation

USGS Publications Warehouse

Banakar, V.K.; Hein, J.R.; Rajani, R.P.; Chodankar, A.R.

2007-01-01

The major element relationships in ferromanganese (Fe-Mn) crusts from Afanasiy-Nikitin seamount (ANS), eastern equatorial Indian Ocean, appear to be atypical. High positive correlations (r = 0.99) between Mn/Co and Fe/Co ratios, and lack of correlation of those ratios with Co, Ce, and Ce/Co, indicate that the ANS Fe-Mn crusts are distinct from Pacific seamount Fe-Mn crusts, and reflect region-specific chemical characteristics. The platinum group elements (PGE: Ir, Ru, Rh, Pt, and Pd) and Au in ANS Fe-Mn crusts are derived from seawater and are mainly of terrestrial origin, with a minor cosmogenic component. The Ru/Rh (0.5-2) and Pt/Ru ratios (7-28) are closely comparable to ratios in continental basalts, whereas Pd/Ir ratios exhibit values ( 0.75) correlations between water depth and Mn/Co, Fe/Co, Ce/Co, Co, and the PGEs. Fractionation of the PGE-Au from seawater during colloidal precipitation of the major-oxide phases is indicated by well-defined linear positive correlations (r > 0.8) of Co and Ce with Ir, Ru, Rh, and Pt; Au/Co with Mn/Co; and by weak or no correlations of Pd with water depth, Co-normalized major-element ratios, and with the other PGE (r < 0.5). The strong enrichment of Pt (up to 1 ppm) relative to the other PGE and its positive correlations with Ce and Co demonstrate a common link for the high concentrations of all three elements, which likely involves an oxidation reaction on the Mn-oxide and Fe-oxyhydroxide surfaces. The documented fractionation of PGE-Au and their positive association with redox sensitive Co and Ce may have applications in reconstructing past-ocean redox conditions and water masses.

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

Corredor, L.T.; Programa de Pós-Graduação em Ciências de Materiais-CCEN, Universidade Federal de Pernambuco, 50670-901 Recife, PE; Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, Bogotá D.C.

Highlights: • We investigated the effect of the dilution of magnetic Ru sub-lattice of RuSr{sub 2}GdCu{sub 2}O{sub 8}. • We synthesized the doped compound Rui{sub x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y}, for 3%, 6%, 9% and 12% Re. • Re would affect the electron coupling: just 3 and 6% samples were superconductor. • Superconductivity emergence strongly affects magnetic properties of 3 and 6% samples. • A weak ferromagnetic component is consistent with a globally antiferromagnetic system. - Abstract: Despite the discovery of new superconductors classes, high-Tc oxides continue to be a current topic, because of their complex phase diagrams and doping-dependantmore » effects (allowing one to investigate the interaction between orbitals), as well as structural properties such as lattice distortion and charge ordering, among many others. Ruthenocuprates are magnetic superconductors in which the magnetic transition temperature is much higher than the critical superconducting temperature, making them unique compounds. With the aim of investigating the dilution of the magnetic Ru sub-lattice, we proposed the synthesis of the Ru{sub 1−x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y} ruthenocuprate-type family, adapting the known two-step process (double perovskite + CuO) by directly doping the double perovskite, thus obtaining the perovskite compound Sr{sub 2}GdRu{sub 1−x}Re{sub x}O{sub y}, which represents a new synthesis process to the best of our knowledge. Our samples were structurally characterized through X-ray diffraction, and the patterns were analysed via Rietveld refinement. A complete magnetic characterization as a function of temperature and applied field, as well as transport measurements were carried out. We discuss our results in the light of the two-lattice model for ruthenocuprates, and a relation between RuO{sub 2} (magnetic) and CuO{sub 2} (superconductor) sub-lattices can clearly be observed.« less

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

Mastren, Tara; Radchenko, Valery; Hopkins, Philip D.

Ruthenium-103 is the parent isotope of 103mRh (t1/2 56.1 min), an isotope of interest for Auger electron therapy. During the proton irradiation of thorium targets, large amounts of 103Ru are generated through proton induced fission. Furthermore, the development of a two part chemical separation process to isolate 103Ru in high yield and purity from a proton irradiated thorium matrix on an analytical scale is described herein. The first part employed an anion exchange column to remove cationic actinide/lanthanide impurities along with the majority of the transition metal fission products. Secondly, an extraction chromatographic column utilizing diglycolamide functional groups was usedmore » to decontaminate 103Ru from the remaining impurities. This method then resulted in a final radiochemical yield of 83 ± 5% of 103Ru with a purity of 99.9%. Additionally, measured nuclear reaction cross sections for the formation of 103Ru and 106Ru via the 232Th(p,f) 103,106Ru reactions are reported within.« less

RRh2Al10 (R = Ce, Yb): New intermetallic compounds in the 1 : 2 : 10 stoichiometry series

NASA Astrophysics Data System (ADS)

Strydom, A. M.; Djoumessi, R. F.; Blinova, M.; Tursina, A.; Nesterenko, S.; Avzuragova, V.

2018-05-01

The orthorhombic, space group Cmcm YbFe2Al10 structure type series of compounds are known to form with practically the entire series of rare-earth elements R, but only with the three d - electron elements Fe, Ru, and Os. The Ce-derivatives in particular have been of much interest since the first reports of their highly unusual physical properties. Classified as Kondo insulators, CeRu2Al10 and CeOs2Al10 controversially order magnetically and with uncharacteristically high Néel temperatures of ≃ 28 K. CeFe2Al10 on the other hand shows pronounced semiconducting and Kondo features but remains paramagnetic. As part of our ongoing studies into the rich physics of this class of materials we have succeeded in synthesizing new members of the 1:2:10 stoichiometry involving the chemical element Rh for the first time. CeRh2Al10 is found to crystallize in the tetragonal system with space group I41 / amd . Yb Rh2Al10 on the other hand forms in the serial Cmcm orthorhombic structure type. We discuss important similarities between the two types. At 5.310 Å the shortest Ce-Ce distance is, likewise to the situation in CeRu2Al10 and CeOs2Al10 , also well above the Hill limit of 3.40 Å. Despite the cage-like structure and large rare-earth separation distances, this study reveals the onset of long-range magnetic ordering in CeRh2Al10 at 3.9 K. The magnetic ordering develops out of an incoherent Kondo state that dominates the electrical resistivity below about 40 K.

Low temperature synthesis of Ru-Cu alloy nanoparticles with the compositions in the miscibility gap

NASA Astrophysics Data System (ADS)

Martynova, S. A.; Filatov, E. Yu.; Korenev, S. V.; Kuratieva, N. V.; Sheludyakova, L. A.; Plusnin, P. E.; Shubin, Yu. V.; Slavinskaya, E. M.; Boronin, A. I.

2014-04-01

A complex salt [Ru(NH3)5Cl][Cu(C2O4)2H2O]-the precursor of nanoalloys combining ruthenium and copper was prepared. It crystallizes in the monoclinic space group P21/n. Thermal properties of the prepared salt were examined in different atmospheres (helium, hydrogen, oxygen). Thermal decomposition of the precursor in inert atmosphere was thoroughly examined and the intermediate products were characterized. Experimental conditions for preparation of copper-rich (up to 12 at% of copper) metastable solid solution CuxRu1-x (based on Ru structure) were optimized, what is in sharp contrast to the bimetallic miscibility gap known for the bulk counterparts in a wide composition range. Catalytic properties of copper-ruthenium oxide composite were tested in catalytic oxidation of CO.

Electrocatalytic Oxidation of Ammonia on Transition-Metal Surfaces: A First-Principles Study

DOE PAGES

Herron, Jeffrey A.; Ferrin, Peter; Mavrikakis, Manos

2015-02-20

Here, we investigate the catalytic electro-oxidation of ammonia on model close-packed surfaces of Au, Ag, Cu, Pd, Pt, Ni, Ir, Co, Rh, Ru, Os, and Re to derive insights for the reaction mechanism and evaluate the catalysts based on their energy efficiency and activity in the context of their application in fuel cells. Two mechanisms, which are differentiated by their N–N bond formation step, are compared: (1) a mechanism proposed by Gerischer and Mauerer, whereby the N–N bond formation occurs between hydrogenated NH x adsorbed species, and (2) a mechanism in which N–N bond formation occurs between N adatoms. Themore » results of our study show that the mechanism proposed by Gerischer and Mauerer is kinetically preferred and that the formation of N adatoms poisons the surface of the catalyst. On the basis of a simple Sabatier analysis, we predict that Pt is the most active monometallic catalyst followed by Ir and Cu, whereas all other metal surfaces studied here have significantly lower activity. We conclude by outlining some design principles for bimetallic alloy catalysts for NH 3 electro-oxidation.« less

Durable pd-based alloy and hydrogen generation membrane thereof

DOEpatents

Benn, Raymond C.; Opalka, Susanne M.; Vanderspurt, Thomas Henry

2010-02-02

A durable Pd-based alloy is used for a H.sub.2-selective membrane in a hydrogen generator, as in the fuel processor of a fuel cell plant. The Pd-based alloy includes Cu as a binary element, and further includes "X", where "X" comprises at least one metal from group "M" that is BCC and acts to stabilize the .beta. BCC phase for stability during operating temperatures. The metal from group "M" is selected from the group consisting of Fe, Cr, Nb, Ta, V, Mo, and W, with Nb and Ta being most preferred. "X" may further comprise at least one metal from a group "N" that is non-BCC, preferably FCC, that enhances other properties of the membrane, such as ductility. The metal from group "N" is selected from the group consisting of Ag, Au, Re, Ru, Rh, Y, Ce, Ni, Ir, Pt, Co, La and In. The at. % of Pd in the binary Pd--Cu alloy ranges from about 35 at. % to about 55 at. %, and the at. % of "X" in the higher order alloy, based on said binary alloy, is in the range of about 1 at. % to about 15 at. %. The metals are selected according to a novel process.

Chemical Mechanical Polishing of Ruthenium, Cobalt, and Black Diamond Films

NASA Astrophysics Data System (ADS)

Peethala, Brown Cornelius

Ta/TaN bilayer serves as the diffusion barrier as well as the adhesion promoter between Cu and the dielectric in 32 nm technology devices. A key concern of future technology devices (<32 nm) for Cu interconnects is the extendibility of TaN/Ta/Cu-seed to sustain the diffusion barrier performance without forming voids and meeting the requirements of low resistivity. These are very challenging requirements for the Ta/TaN bilayer at a thickness of < 5 nm. Hence, ruthenium (Ru) and cobalt (Co), among these, are being considered for replacing Ta/TaN as barrier materials for Cu interconnects in future technology devices. Both are very attractive for reasons such as the capability of direct electroplating of Cu, lower resistivity and for a single layer (vs. a bilayer of Ta/TaN) to act as a barrier. During patterning, they need to be planarized using conventional chemical mechanical polishing (CMP) to achieve a planar surface. However, CMP of these new barrier materials requires novel slurry compositions that provide adequate selectivity towards Cu and dielectric films, and minimize galvanic corrosion. Apart from the application as a barrier, Ru also has been proposed as a lower electrode material in metal-insulator-metal capacitors where high (> 50 nm/min) Ru removal rates (RRs) are required and as a stop layer in magnetic recording head fabrication where low (< 1 nm/min) Ru RRs are desired. A Ru removal rate of ˜60 nm/min was achieved with a colloidal silica-based slurry at pH 9 using potassium periodate (KIO4) as the oxidizer. At this pH, toxic RuO4 does not form eliminating a major challenge in Ru CMP. This removal rate was obtained by increasing the solubility of KIO4 by adding potassium hydroxide (KOH). It was also determined that increased the ionic strength is not responsible for the observed increase in Ru removal rate. Benzotirazole (BTA) and ascorbic acid were added to the slurry to reduce the open circuit potential (Eoc) difference between Cu and Ru to ˜20 mV from about 550 mV in the absence of additives. A removal mechanism with KIO4 as the oxidizing agent is proposed based on the formation of several ruthenium oxides, some of which formed residues on the polishing pad below a pH of ˜7. Next, a colloidal silica-based slurry with hydrogen peroxide (H 2O2) as the oxidizer (1 wt%), and arginine (0.5 wt%) as the complexing agent was developed to polish Co at pH 10. The Eoc between Cu and Co at the above conditions was reduced to ˜20 mV compared to ˜250 mV in the absence of additives, suggestive of reduced galvanic corrosion during the Co polishing. The slurry also has the advantages of good post-polish surface quality at pH 10, and no dissolution rate. BTA at a concentration of 5mM in this slurry inhibited Cu dissolution rates and yielded a Cu/Co RR ratio of ˜0.8:1 while the open potential difference between Cu and Co was further reduced to ˜10 mV. The role of H2O2, complexing agent (arginine), silica abrasives, and Co removal mechanism during polishing is discussed. Also, during the barrier CMP, a part of the underlying low-k (SiCOH) material has to be polished to remove any modified surface film. Black Diamond (BD) is a SiCOH type material with a dielectric constant of ˜2.9 and here, polishing of BD was investigated in order to understand the polishing behavior of SiCOH-based materials using the barrier slurries. The slurries that were developed for polishing Co and Ru in this work and Ta/TaN (earlier) were investigated for polishing the Black Diamond (BD) films. Here, it was found that ionic salts play a major role in enhancing the BD RRs to ˜65 nm/min compared to no removal rates in the absence of additives. A removal mechanism in the presence of ionic salts is proposed.

Creation of Novel Solid-Solution Alloy Nanoparticles on the Basis of Density-of-States Engineering by Interelement Fusion.

PubMed

Kobayashi, Hirokazu; Kusada, Kohei; Kitagawa, Hiroshi

2015-06-16

Currently 118 known elements are represented in the periodic table. Of these 118 elements, only about 80 elements are stable, nonradioactive, and widely available for our society. From the viewpoint of the "elements strategy", we need to make full use of the 80 elements to bring out their latent ability and create innovative materials. Furthermore, there is a strong demand that the use of rare or toxic elements be reduced or replaced while their important properties are retained. Advanced science and technology could create higher-performance materials even while replacing or reducing minor or harmful elements through the combination of more abundant elements. The properties of elements are correlated directly with their electronic states. In a solid, the magnitude of the density of states (DOS) at the Fermi level affects the physical and chemical properties. In the present age, more attention has been paid to improving the properties of materials by means of alloying elements. In particular, the solid-solution-type alloy is advantageous because the properties can be continuously controlled by tuning the compositions and/or combinations of the constituent elements. However, the majority of bulk alloys are of the phase-separated type under ambient conditions, where constituent elements are immiscible with each other. To overcome the challenge of the bulk-phase metallurgical aspects, we have focused on the nanosize effect and developed methods involving "nonequilibrium synthesis" or "a process of hydrogen absorption/desorption". We propose a new concept of "density-of-states engineering" for the design of materials having the most desirable and suitable properties by means of "interelement fusion". In this Account, we describe novel solid-solution alloys of Pd-Pt, Ag-Rh, and Pd-Ru systems in which the constituent elements are immiscible in the bulk state. The homogeneous solid-solution alloys of Pd and Pt were created from Pd core/Pt shell nanoparticles using a hydrogen absorption/desorption process as a trigger. Several atom percent replacements of Pd with Pt atoms resulted in a significantly enhanced hydrogen absorption capacity compared with Pd nanoparticles. AgxRh1-x and PdxRu1-x solid-solution alloy nanoparticles were also developed by nonequilibrium synthesis based on a polyol method. The AgxRh1-x nanoparticles demonstrated hydrogen storage properties, although pure metal nanoparticles of each constituent element do not adsorb hydrogen. AgxRh1-x is therefore considered to possess a similar electronic structure to Pd as a synthetic pseudo-palladium. The PdxRu1-x nanoparticles showed enhanced catalytic activity for CO oxidation, with the highest catalytic activity found using the equimolar Pd0.5Ru0.5 nanoparticles. The catalytic activity of the Pd0.5Ru0.5 nanoparticles exceeds that of the widely used and best-performing Ru catalysts for CO oxidation and is also higher than that of neighboring Rh on the periodic table. Our present work provides a guiding principle for the design of a suitable DOS shape according to the intended physical and/or chemical properties and a method for the development of novel solid-solution alloys.

Chemical composition and reactivity of water on hexagonal Pt-group metal surfaces.

PubMed

Shavorskiy, A; Gladys, M J; Held, G

2008-10-28

The dissociation behaviour and valence-electronic structure of water adsorbed on clean and oxygen-covered Ru{0001}, Rh{111}, Pd{111}, Ir{111} and Pt{111} surfaces has been studied by high-resolution X-ray photoelectron spectroscopy with the aim of identifying similarities and trends within the Pt-group metals. On average, we find higher reactivity for the 4d metals (Ru, Rh, Pd) as compared to 5d (Ir, Pt), which is correlated with characteristic shifts in the 1b(1) and 3a(1) molecular orbitals of water. Small amounts of oxygen (< 0.2 ML) induce dissociation of water on all five surfaces, for higher coverages (> 0.25 ML) only intact water is observed. Under UHV conditions these higher coverages can only be reached on the 4d metals, the 5d metals are, therefore, not passivated.

Diastereoselective formation of metallamacrocyclic (arene)Ru(II) and CpRh(III) complexes.

PubMed

Lehaire, Marie-Line; Scopelliti, Rosario; Herdeis, Lorenz; Polborn, Kurt; Mayer, Peter; Severin, Kay

2004-03-08

The reaction of [(arene)RuCl(2)](2) (arene = cymene, 1,3,5-C(6)H(3)Me(3)) and [CpRhCl(2)](2) half-sandwich complexes with tridentate heterocyclic ligands in the presence of base has been investigated. In all cases, the chloro-ligands were substituted to give metallacyclic products with ring sizes between 4 and 18 atoms. The cyclization occurs in a highly diastereoselective fashion with chiral recognition between the different metal fragments. The complexes were comprehensively characterized by elemental analysis, NMR spectroscopy, and single crystal X-ray crystallography. For 2-hydroxy-nicotinic acid and 2-amino-nicotinic acid, dinuclear structures were obtained (15-17) whereas for 2,3-dihydroxyquinoline, 2,3-dihydroxyquinoxaline, and 6-methyl-2,3-phenazinediol, trimeric assemblies were found (19-22), and for 4-imidazolecarboxylic acid, a tetrameric assembly (18) was found.

IMPACT OF Ce DOPING ON THE MAGNETIC AND TRANSPORT PROPERTIES OF Y1-xCexSr2Ru0.9Cu2.1O7.9; x = 0.05 AND 0.1

NASA Astrophysics Data System (ADS)

Balamurugan, S.

2012-11-01

The magnetic and transport properties of lightly Ce doped, Y1-xCexSr2Ru0.9Cu2.1 O7.9(x = 0.05 and 0.1) samples have been studied and their results are compared with the pristine rutheno-cuprate, YSr2Ru0.9Cu2.1O7.9. The electron doping due to Ce4+ for Y3+ ion impacts on the physical properties of the present system. The tetragonal stabilized samples exhibit magneto superconducting properties under zero field cooled condition (H = 10 Oe) and the diamagnetic onset transition, Td shift slightly towards higher temperature with the increase of "x". Weak antiferromagnetic like hysteresis curves are seen for these samples at 2 K in the magnetic field strength up to ±10 kOe and the magnetization moment, M(μB/Ru) decreases with increase of "x". While the magnetic property of the present system is due to canted Ru moments, the superconducting signal originates from CuO2 plane. Through electrical resistivity measurements we observe that none of the samples exhibit bulk superconductivity down to 2 K. However the x = 0.05 sample reveals lowest resistivity in the entire temperature range than x = 0 and 0.1 samples. The isothermal magnetoresistance, MR(H) measured at different temperatures vary with tuning of "x". While x = 0.1 doped sample shows lower -MR( 8%), the pristine sample exhibits maximum -MR(45%) at 2 K under ±90 kOe field condition.

Empirical constraints on partitioning of platinum group elements between Cr-spinel and primitive terrestrial magmas

NASA Astrophysics Data System (ADS)

Park, Jung-Woo; Kamenetsky, Vadim; Campbell, Ian; Park, Gyuseung; Hanski, Eero; Pushkarev, Evgeny

2017-11-01

Recent experimental studies and in situ LA-ICP-MS analysis on natural Cr-spinel have shown that Rh and IPGEs (Ir-group platinum group elements: Ru, Ir, Os) are enriched in the lattice of Cr-spinel. However, the factors controlling the partitioning behaviour of these elements are not well constrained. In this study, we report the Rh, IPGE, and trace element contents in primitive Cr-spinel, measured by LA-ICP-MS, from nine volcanic suites covering various tectonic settings including island arc picrites, boninites, large igneous province picrites and mid-ocean ridge basalts. The aim is to understand the factors controlling the enrichment of Rh and IPGEs in Cr-spinels, to estimate empirical partition coefficients between Cr-spinel and silicate melts, and to investigate the role of Cr-spinel fractional crystallization on the PGE geochemistry of primitive magmas during the early stages of fractional crystallization. There are systematic differences in trace elements, Rh and IPGEs in Cr-spinels from arc-related magmas (Arc Group Cr-spinel), intraplate magmas (Intraplate Group Cr-spinel), and mid-ocean ridge magmas (MORB Group Cr-spinel). Arc Group Cr-spinels are systematically enriched in Sc, Co and Mn and depleted in Ni compared to the MORB Group Cr-spinels. Intraplate Group Cr-spinels are distinguished from the Arc Group Cr-spinels by their high Ni contents. Both the Arc and Intraplate Group Cr-spinels have total Rh and IPGE contents of 22-689 ppb whereas the MORB Group Cr-spinels are depleted in Rh and IPGE (total < 20 ppb). Palladium and Pt contents are below detection limit for all of the studied Cr-spinels (<1-5 ppb). The time-resolved spectra of LA-ICP-MS data for Cr-spinels mostly show constant count rates for trace element and Rh and IPGEs, suggesting homogeneous distribution of these elements in Cr-spinels. The PGE spikes observed in several Cr-spinels were interpreted to be PGE-bearing mineral inclusions and excluded from calculating the PGE contents of the Cr-spinels. On primitive mantle normalized diagrams the Arc Group Cr-spinels are characterized by a fractionated pattern with high Rh and low Os. The Intraplate Group Cr-spinels show flat patterns with positive Ru anomalies. Our results, together with the experimental and empirical data from previous studies, show that PGE patterns of Cr-spinel largely mimic that of the rock in which they are found, and that Rh, Ir and Os contents increase with increasing Fe3+ contents (i.e. magnetite component) in Cr-spinel, although Ru does not. These observations suggest that the enrichment of Rh and IPGEs in Cr-spinel is controlled by a combination of the Rh and IPGE contents in parental melts and the magnetite component of the spinel. Empirical partition coefficients (D) for Rh and IPGEs between Cr-spinels and silicate melts were calculated using the Rh and IPGE contents of the Cr-spinel and their host volcanic rocks after subtracting the accumulation effect of Cr-spinel. The D values for the Intraplate and MORB Group Cr-spinels increase with increasing magnetite component in Cr-spinel and range from 6 to 512, which is consistent with previously reported experimental and empirical values. In contrast, the Arc Group Cr-spinels have significantly higher D values (e.g. up to ∼3700 for Ru) than those of the Intraplate and MORB Group at the same magnetite concentration in the Cr-spinel, suggesting Rh and IPGEs dissolved in silicate melt have stronger affinity for Cr spinel under arc magma conditions than in intraplate magmas. This may be partly attributed to the low temperature of arc magmas relative to intraplate magmas, which leads to the Arc Group Cr-spinels having more octahedral sites at the same magnetite components than the Intraplate Group Cr-spinels. Because of significantly higher D values for the Arc Group Cr-spinels, compared with the Intraplate Group and MORB Group spinels, fractional crystallization of Cr-spinel will more efficiently fractionate Rh and IPGE from Pd and Pt in arc systems than in intraplate and MORB systems, which accounts for the highly fractionated PGE patterns in arc basalts.

Copper amplification of prostaglandin E/sub 2/ stimulation of the release of luteinizing hormone-releasing hormone is a postreceptor event

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

Barnea, A.; Cho, G.

1987-01-01

The authors have shown that copper amplifies prostaglandin E/sub 2/ (PGE/sub 2/) stimulation of luteinizing hormone-releasing hormone (LH-RH) from explants of the median eminence area (MEA) and that this process is calcium-dependent. Since a Ca-cAMP pathway has been implicated in PGE/sub 2/ action on the LH-RH neuron, in this study the authors wished to ascertain if copper exerts its effect on the PGE/sub 2/ receptor or on a postreceptor component involved in PGE/sub 2/ action. MEA of adult male rats were incubated for 5 min with 200 ..mu..M Cu/histidine and then incubated for 15 min either with 10 ..mu..M PGE/submore » 2/ (Cu/PGE/sub 2/), 100 ..mu..M forskolin (Cu/forskolin), or 1 mM 8-bromoadenosine 3',5'-cyclic monophosphate (Cu/cAMP). Basal release of LH-RH was 4.6 +/- 0.45 pg/15 min per MEA determined by radioimmunoassay. Net stimulated release during the 15-min exposure to PGE/sub 2/, forskolin, or 8-bromoadenosine 3',5'-cyclic monophosphate was 3.6 +/- 0.52, 3.1 +/- 0.39, and 1.6 +/- 0.42 pg/15 min per MEA, respectively. Net stimulated release after exposure to Cu/PGE/sub 2/, Cu/forskolin, or Cu/cAMP indicated that copper amplifies the action of PGE/sub 2/ and forskolin but not cAMP action. When MEA were exposed to a mixture of PGE/sub 2/ and forskolin for 15 min, the effects of these two secretagogues on LH-RH release were not additive. In contrast to PGE/sub 2/ and forskolin, copper did not amplify K/sup +/ stimulation of OH-RH release. These results are supportive of the proposition that PGE/sub 2/ stimulation of OH-RH release is mediated by the Ca-cAMP pathway and that copper amplification of PGE/sub 2/ action is a postreceptor event.« less

High performance fuel electrodes fabricated by electroless plating of copper on BaZr0.8Ce0.1Y0.1O3-δ proton-conducting ceramic

NASA Astrophysics Data System (ADS)

Patki, Neil S.; Way, J. Douglas; Ricote, Sandrine

2017-10-01

The stability of copper at high temperatures in reducing and hydrocarbon-containing atmospheres makes it a good candidate for fabricating fuel electrodes on proton-conducting ceramics, such as BaZr0.9-xCexY0.1O3-δ (BZCY). In this work, the electrochemical performance of Cu-based electrodes fabricated by electroless plating (ELP) on BaZr0.8Ce0.1Y0.1O3-δ is studied with impedance spectroscopy. Three activation catalysts (Pd, Ru, and Cu) are investigated and ELP is compared to a commercial Cu paste (ESL 2312-G) for electrode fabrication. The area specific resistances (ASR) for Pd, Ru, and Cu activations at 700 °C in moist 5% H2 in Ar are 2.1, 3.2, and 13.4 Ω cm2, respectively. That is a 1-2 orders of magnitude improvement over the commercial Cu paste (192 Ω cm2). Furthermore, the ASR has contributions from electrode processes and charge transfer at the electrode/electrolyte interface. Additionally, the morphology of the as-fabricated electrode is unaffected by the activation catalyst. However, heat treatment at 750 °C in H2 for 24 h leads to sintering and large reorganization of the electrode fabricated with Cu activation (micron sized pores seen in the tested sample), while Pd and Ru activations are immune to such reorganization. Thus, Pd and Ru are identified as candidates for future work with improvements to charge transfer required for the former, and better electrode processes required for the latter.

Electronic screening in stacked graphene flakes revealed by scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Feng, Xiaofeng; Salmeron, Miquel

2013-02-01

Electronic doping and screening effects in stacked graphene flakes on Ru and Cu substrates have been observed using scanning tunneling microscopy (STM). The screening affects the apparent STM height of each flake in successive layers reflecting the density of states near the Fermi level and thus the doping level. It is revealed in this way that the strong doping of the first graphene layer on Ru(0001) is attenuated in the second one, and almost eliminated in the third and fourth layers. Similar effect is also observed in graphene flakes on Cu(111). In contrast, the strong doping effect is suppressed immediately by a water layer intercalated between the graphene and Ru.

Metal-insulator transition and superconductivity in the spinel-type Cu(Ir1-xRhx)2S4 system

NASA Astrophysics Data System (ADS)

Matsumoto, Nobuhiro; Endoh, Ryo; Nagata, Shoichi; Furubayashi, Takao; Matsumoto, Takehiko

1999-08-01

The normal thiospinel CuIr2S4 exhibits a temperature-induced metal-insulator (M-I) transition around 226 K with structural transformation, showing hysteresis on heating and cooling. It has been verified that d electrons of Ir atom on the octahedral B sites have a significant role for the M-I transition. On the other hand, CuRh2S4 is a superconductor with the transition temperature Tc=4.70 K, which is well understood on the basis of the BCS theory. It is important to investigate the effect on the M-I transition by substitution of Rh for Ir. We have systematically studied structural transformation and electrical and magnetic properties of Cu(Ir1-xRhx)2S4. The features of the M-I transition change with Rh concentration x. A phase diagram of temperature versus x will be proposed for the Cu(Ir1-xRhx)2S4 system. The sharp M-I transition temperature varies drastically from 226 to 93 K with x from 0.00 to 0.17 and disappears around x=0.20. In a region of 0.00<=x<=0.20, the magnetic susceptibility begins decreasing at a constant onset temperature 226 K on cooling process and shows rather broad temperature variation, even though the metallic state is kept in the resistivity. The sharp M-I transition can take place after the suppression of magnitude in the susceptibility has sufficiently developed far below 226 K. These experimental results are discussed with emphasis on the intrinsic difference between Cu(Ir1-xRhx)2S4 and CuIr2(S1-xSex)4 systems. Furthermore, we will mention the superconductivity for both systems of Cu(Ir1-xRhx)2S4 with high-Rh concentration region and Cu1-xNixRh2S4.

UV-Vis spectroscopy combined with chemometric study on the interactions of three dietary flavonoids with copper ions.

PubMed

Zhang, Liangliang; Liu, Yuchen; Wang, Yongmei; Xu, Man; Hu, Xinyu

2018-10-15

The complex formation between a copper ion and the dietary flavonoid quercetin (QU) and its two glycosides hyperin (HY) and rutin (RU) was studied by the combined use of spectroscopic measurement and the chemometric method. The spectral changes of pH titration revealed two successively formed deprotonated species of QU: the first formed species was proposed to be the 3-hydroxyl group deprotonated QU, and the second was the quinone form QU, which was formed by oxidation after the hydroxyl groups in the B-ring were deprotonated at high pH values. Similar results were obtained for HY and RU with two deprotonated species forming at high pH values. UV/visible spectroscopy showed successive formation of CuL 2 and CuL species of QU at pH 6.0, while only Cu 2 L was formed for HY and RU at this pH. Glycoside moieties in the C-ring of flavonoids decrease the conditional associated constants between flavonoids and Cu 2+ . Copyright © 2018 Elsevier Ltd. All rights reserved.

Electronic Structure, Mechanical and Dynamical Stability of Hexagonal Subcarbides M2C (M = Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt): Ab Initio Calculations

NASA Astrophysics Data System (ADS)

Suetin, D. V.; Shein, I. R.

2018-02-01

Ab initio calculations were used to study the properties of a series of hexagonal (Fe2N-like) subcarbides M2C, where M = Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt, and to calculate their equilibrium structural parameters, electronic properties, phase stability, elastic constants, compression modulus, shear modulus, Young's modulus, compressibility, Pugh's indicator, Poisson ratio, elastic anisotropy indices, and also hardness, Debye temperature, sound velocity, and low-temperature heat capacity. It is found based on these results that all the subcarbides are mechanically stable; however, their formation energies E form are positive with respect to a mixture of d-metal and graphite. In addition, the calculation of the phonon spectra of these subcarbides shows the existence of negative modes, which indicates their dynamical instability. Thus, a successful synthesis of these subcarbides at normal conditions is highly improbable.

Photoinitiated Electron Collection in Mixed-Metal Supramolecular Complexes: Development of Photocatalysts for Hydrogen Production. Final Report of Progress August 2017

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

Tanko, James M.

Mixed-metal supramolecular complexes containing one or two RuII light absorbing subunits coupled through polyazine bridging ligands to a RhIII reactive metal center were prepared for use as photocatalysts for the production of solar H 2 fuel from H 2O. The electrochemical, photophysical, and photochemical properties upon variation of the monodentate, labile ligands coordinated to the Rh reactive metal center were investigated.

p-Type CuRhO 2 as a Self-Healing Photoelectrode for Water Reduction under Visible Light

DOE PAGES

Gu, Jing; Krizan, Jason W.; Gibson, Quinn D.; ...

2013-12-30

Polycrystalline CuRhO 2 is investigated as a photocathode for the splitting of water under visible irradiation. The band edge positions of this material straddle the water oxidation and reduction redox potentials. Thus, photogenerated conduction band electrons are sufficiently energetic to reduce water, while the associated valence band holes are energetically able to oxidize water to O 2. Under visible illumination, H 2 production is observed with ~0.2 V underpotential in an air-saturated solution. In contrast, H 2 production in an Ar-saturated solution was found to be unstable. This instability is associated with the reduction of the semiconductor forming Cu(s). However,more » in the presence of air or O 2, bulk Cu(s) was not detected, implying that CuRhO 2 is self-healing when air is present. Here, this property allows for the stable formation of H 2 with ca. 80% Faradaic efficiency.« less

p-Type CuRhO 2 as a Self-Healing Photoelectrode for Water Reduction under Visible Light

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

Gu, Jing; Krizan, Jason W.; Gibson, Quinn D.

Polycrystalline CuRhO 2 is investigated as a photocathode for the splitting of water under visible irradiation. The band edge positions of this material straddle the water oxidation and reduction redox potentials. Thus, photogenerated conduction band electrons are sufficiently energetic to reduce water, while the associated valence band holes are energetically able to oxidize water to O 2. Under visible illumination, H 2 production is observed with ~0.2 V underpotential in an air-saturated solution. In contrast, H 2 production in an Ar-saturated solution was found to be unstable. This instability is associated with the reduction of the semiconductor forming Cu(s). However,more » in the presence of air or O 2, bulk Cu(s) was not detected, implying that CuRhO 2 is self-healing when air is present. Here, this property allows for the stable formation of H 2 with ca. 80% Faradaic efficiency.« less

Heterobimetallic acetylide bridged Cu(I)/Ru(II)-halide/pseudohalide hybrid complexes: Synthesis, structural characterization, luminescence and electrochemical studies

NASA Astrophysics Data System (ADS)

Lolage, Sanjay; Pawal, Sandip; Chavan, Sanjay

2018-01-01

A new series of heterobimetallic complexes [Cu(PPh3)(NC5H4HCdbnd NC6H4Ctbnd CC6H4Ctbnd CRu (dppe)2Cl)X] (1a-5a) have been prepared by the reaction of trans-(NC5H4HCdbnd NC6H4Ctbnd CC6H4Ctbnd C Ru(dppe)2Cl) with copper salts in presence of triphenylphosphine (where X = Cl, Br, I, N3, NCS). Our synthetic attempts and successes are discussed in combination with spectroscopic and electronic characterization of the compounds. Comparison between halides and pseudohalides were studied by thermal and electrochemical analysis where, thermally robust complexes demonstrate quasireversible redox behaviour analogous to CuI/II/RuII/III couple. Room temperature luminescence with varying electron donating and quenching abilities of halides and pseudohalides in blue-green region were observed. Concentration and solvent dependant emission displays positive solvatochromism at ambient temperature.

Theoretical study of adsorption of organic phosphines on transition metal surfaces

NASA Astrophysics Data System (ADS)

Lou, Shujie; Jiang, Hong

2018-04-01

The adsorption properties of organic phosphines on transition metal (TM) surfaces (Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au) have been studied to explore the possibility of building novel heterogeneous chiral catalytic systems based on organic phosphines. Preferred adsorption sites, adsorption energies and surface electronic structures of a selected set of typical organic phosphines adsorbed on TM surfaces are calculated with density-functional theory to obtain a systematic understanding on the nature of adsorption interactions. All organic phosphines considered are found to chemically adsorb on these TM surfaces with the atop site as the most preferred one, and the TM-P bond is formed via the lone-pair electrons of the P atom and the directly contacted TM atom. These findings imply that it is indeed possible to build heterogeneous chiral catalytic systems based on organic phosphines adsorbed on TM surfaces, which, however, requires a careful design of molecular structure of organic phosphines.

Synthesis, molecular structure, and C-C coupling reactions of carbeneruthenium(II) complexes with C5H5Ru(=CRR') and C5Me5Ru(=CRR') as molecular units.

PubMed

Braun, Thomas; Münch, Gerhard; Windmüller, Bettina; Gevert, Olaf; Laubender, Matthias; Werner, Helmut

2003-06-06

The ethene derivatives [(eta(5)-C(5)R(5))RuX(C(2)H(4))(PPh(3))] with R=H and Me, which have been prepared from the eta(3)-allylic compounds [(eta(5)-C(5)R(5))Ru(eta(3)-2-MeC(3)H(4))(PPh(3))] (1, 2) and acids HX under an ethene atmosphere, are excellent starting materials for the synthesis of a series of new halfsandwich-type ruthenium(II) complexes. The olefinic ligand is replaced not only by CO and pyridine, but also by internal and terminal alkynes to give (for X=Cl) alkyne, vinylidene, and allene compounds of the general composition [(eta(5)-C(5)R(5))RuCl(L)(PPh(3))] with L=C(2)(CO(2)Me)(2), Me(3)SiC(2)CO(2)Et, C=CHCO(2)R, and C(3)H(4). The allenylidene complex [(eta(5)-C(5)H(5))RuCl(=C=C=CPh(2))(PPh(3))] is directly accessible from 1 (R=H) in two steps with the propargylic alcohol HC triple bond CC(OH)Ph(2) as the precursor. The reactions of the ethene derivatives [(eta(5)-C(5)H(5))RuX(C(2)H(4))(PPh(3))] (X=Cl, CF(3)CO(2)) with diazo compounds RR'CN(2) yield the corresponding carbene complexes [(eta(5)-C(5)R(5))RuX(=CRR')(PPh(3))], while with ethyl diazoacetate (for X=Cl) the diethyl maleate compound [(eta(5)-C(5)H(5))RuCl[eta(2)-Z-C(2)H(2)(CO(2)Et)(2)](PPh(3))] is obtained. Halfsandwich-type ruthenium(II) complexes [(eta(5)-C(5)R(5))RuCl(=CHR')(PPh(3))] with secondary carbenes as ligands, as well as cationic species [(eta(5)-C(5)H(5))Ru(=CPh(2))(L)(PPh(3))]X with L=CO and CNtBu and X=AlCl(4) and PF(6), have also been prepared. The neutral compounds [(eta(5)-C(5)H(5))RuCl(=CRR')(PPh(3))] react with phenyllithium, methyllithium, and the vinyl Grignard reagent CH(2)=CHMgBr by displacement of the chloride and subsequent C-C coupling to generate halfsandwich-type ruthenium(II) complexes with eta(3)-benzyl, eta(3)-allyl, and substituted olefins as ligands. Protolytic cleavage of the metal-allylic bond in [(eta(5)-C(5)H(5))Ru(eta(3)-CH(2)CHCR(2))(PPh(3))] with acetic acid affords the corresponding olefins R(2)C=CHCH(3). The by-product of this process is the acetato derivative [(eta(5)-C(5)H(5))Ru(kappa(2)-O(2)CCH(3))(PPh(3))], which can be reconverted to the carbene complexes [(eta(5)-C(5)H(5))RuCl(=CR(2))(PPh(3))] in a one-pot reaction with R(2)CN(2) and Et(3)NHCl.

Microwave irradiation for the facile synthesis of transition-metal nanoparticles (NPs) in ionic liquids (ILs) from metal-carbonyl precursors and Ru-, Rh-, and Ir-NP/IL dispersions as biphasic liquid-liquid hydrogenation nanocatalysts for cyclohexene.

PubMed

Vollmer, Christian; Redel, Engelbert; Abu-Shandi, Khalid; Thomann, Ralf; Manyar, Haresh; Hardacre, Christopher; Janiak, Christoph

2010-03-22

Stable chromium, molybdenum, tungsten, manganese, rhenium, ruthenium, osmium, cobalt, rhodium, and iridium metal nanoparticles (M-NPs) have been reproducibly obtained by facile, rapid (3 min), and energy-saving 10 W microwave irradiation (MWI) under an argon atmosphere from their metal-carbonyl precursors [M(x)(CO)(y)] in the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF(4)]). This MWI synthesis is compared to UV-photolytic (1000 W, 15 min) or conventional thermal decomposition (180-250 degrees C, 6-12 h) of [M(x)(CO)(y)] in ILs. The MWI-obtained nanoparticles have a very small (<5 nm) and uniform size and are prepared without any additional stabilizers or capping molecules as long-term stable M-NP/IL dispersions (characterization by transmission electron microscopy (TEM), transmission electron diffraction (TED), and dynamic light scattering (DLS)). The ruthenium, rhodium, or iridium nanoparticle/IL dispersions are highly active and easily recyclable catalysts for the biphasic liquid-liquid hydrogenation of cyclohexene to cyclohexane with activities of up to 522 (mol product) (mol Ru)(-1) h(-1) and 884 (mol product) (mol Rh)(-1) h(-1) and give almost quantitative conversion within 2 h at 10 bar H(2) and 90 degrees C. Catalyst poisoning experiments with CS(2) (0.05 equiv per Ru) suggest a heterogeneous surface catalysis of Ru-NPs.

Pyridine synthesis by reactions of allyl amines and alkynes proceeding through a Cu(OAc)2 oxidation and Rh(III)-catalyzed N-annulation sequence.

PubMed

Kim, Dong-Su; Park, Jung-Woo; Jun, Chul-Ho

2012-11-28

A new methodology has been developed for the synthesis of pyridines from allyl amines and alkynes, which involves sequential Cu(II)-promoted dehydrogenation of the allylamine and Rh(III)-catalyzed N-annulation of the resulting α,β-unsaturated imine and alkyne.

Environmental application of millimeter-scale sponge iron (s-Fe(0)) particles (II): the effect of surface copper.

PubMed

Ju, Yongming; Liu, Xiaowen; Liu, Runlong; Li, Guohua; Wang, Xiaoyan; Yang, Yanyan; Wei, Dongyang; Fang, Jiande; Dionysiou, Dionysios D

2015-04-28

To enhance the catalytic reactivity of millimeter-scale particles of sponge iron (s-Fe(0)), Cu(2+) ions were deposited on the surface of s-Fe(0) using a simple direct reduction reaction, and the catalytic properties of the bimetallic system was tested for removal of rhodamine B (RhB) from an aqueous solution. The influence of Cu(0) loading, catalyst dosage, particle size, initial RhB concentration, and initial pH were investigated, and the recyclability of the catalyst was also assessed. The results demonstrate that the 3∼5 millimeter s-Fe(0) particles (s-Fe(0)(3∼5mm)) with 5wt% Cu loading gave the best results. The removal of RhB followed two-step, pseudo-first-order reaction kinetics. Cu(0)-s-Fe(0) showed excellent stability after five reuse cycles. Cu(0)-s-Fe(0) possesses great advantages compared to nanoscale zero-valent iron, iron power, and iron flakes as well as its bimetals. The surface Cu(0) apparently catalyzes the production of reactive hydrogen atoms for indirect reaction and generates Fe-Cu galvanic cells that enhance electron transfer for direct reaction. This bimetallic catalyst shows great potential for the pre-treatment of recalcitrant wastewaters. Additionally, some oxides containing iron element are selected to simulate the adsorption process. The results prove that the adsorption process of FeOOH, Fe2O3 and Fe3O4 played minor role for the removal of RhB. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis of noble metal/carbon nanotube composites in supercritical methanol.

PubMed

Sun, Zhenyu; Fu, Lei; Liu, Zhimin; Han, Buxing; Liu, Yunqi; Du, Jimin

2006-03-01

A simple and efficient route has been employed to deposit noble metal nanoparticles (Pt, Ru, Pt-Ru, Rh, Ru-Sn) onto carbon nanotubes (CNTs) in supercritical methanol solution. In this method, the inorganic metallic salts acted as metal precursors, and methanol as solvent as well as reductant for the precursors. The as-prepared nanocomposites were structurally and morphologically characterized by X-ray diffraction spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy, and X-ray photoelectron spectroscopy analyses. It was demonstrated that the CNTs were decorated by crystalline metal nanoparticles with uniform sizes and a narrow particle size distribution. The size and loading content of the nanoparticles on CNTs could be tuned by manipulating reaction parameters. Furthermore, the formation mechanism of the composites was also discussed.

Mean glandular dose coefficients (D(g)N) for x-ray spectra used in contemporary breast imaging systems.

PubMed

Nosratieh, Anita; Hernandez, Andrew; Shen, Sam Z; Yaffe, Martin J; Seibert, J Anthony; Boone, John M

2015-09-21

To develop tables of normalized glandular dose coefficients D(g)N for a range of anode-filter combinations and tube voltages used in contemporary breast imaging systems. Previously published mono-energetic D(g)N values were used with various spectra to mathematically compute D(g)N coefficients. The tungsten anode spectra from TASMICS were used; molybdenum and rhodium anode-spectra were generated using MCNPX Monte Carlo code. The spectra were filtered with various thicknesses of Al, Rh, Mo or Cu. An initial half value layer (HVL) calculation was made using the anode and filter material. A range of the HVL values was produced with the addition of small thicknesses of polymethyl methacrylate (PMMA) as a surrogate for the breast compression paddle, to produce a range of HVL values at each tube voltage. Using a spectral weighting method, D(g)N coefficients for the generated spectra were calculated for breast glandular densities of 0%, 12.5%, 25%, 37.5%, 50% and 100% for a range of compressed breast thicknesses from 3 to 8 cm. Eleven tables of normalized glandular dose (D(g)N) coefficients were produced for the following anode/filter combinations: W + 50 μm Ag, W + 500 μm Al, W + 700 μm Al, W + 200 μm Cu, W + 300 μm Cu, W + 50 μm Rh, Mo + 400 μm Cu, Mo + 30 μm Mo, Mo + 25 μm Rh, Rh + 400 μm Cu and Rh + 25 μm Rh. Where possible, these results were compared to previously published D(g)N values and were found to be on average less than 2% different than previously reported values.Over 200 pages of D(g)N coefficients were computed for modeled x-ray system spectra that are used in a number of new breast imaging applications. The reported values were found to be in excellent agreement when compared to published values.

Mean Glandular dose coefficients (DgN) for x-ray spectra used in contemporary breast imaging systems

PubMed Central

Nosratieh, Anita; Hernandez, Andrew; Shen, Sam Z.; Yaffe, Martin J.; Seibert, J. Anthony; Boone, John M.

2015-01-01

Purpose To develop tables of normalized glandular dose coefficients DgN for a range of anode–filter combinations and tube voltages used in contemporary breast imaging systems. Methods Previously published mono-energetic DgN values were used with various spectra to mathematically compute DgN coefficients. The tungsten anode spectra from TASMICS were used; Molybdenum and Rhodium anode-spectra were generated using MCNPx Monte Carlo code. The spectra were filtered with various thicknesses of Al, Rh, Mo or Cu. An initial HVL calculation was made using the anode and filter material. A range of the HVL values was produced with the addition of small thicknesses of polymethyl methacrylate (PMMA) as a surrogate for the breast compression paddle, to produce a range of HVL values at each tube voltage. Using a spectral weighting method, DgN coefficients for the generated spectra were calculated for breast glandular densities of 0%, 12.5%, 25%, 37.5%, 50% and 100% for a range of compressed breast thicknesses from 3 to 8 cm. Results Eleven tables of normalized glandular dose (DgN) coefficients were produced for the following anode/filter combinations: W + 50 μm Ag, W + 500 μm Al, W + 700 μm Al, W + 200 μm Cu, W + 300 μm Cu, W + 50 μm Rh, Mo + 400 μm Cu, Mo + 30 μm Mo, Mo + 25 μm Rh, Rh + 400 μm Cu and Rh + 25 μm Rh. Where possible, these results were compared to previously published DgN values and were found to be on average less than 2% different than previously reported values. Conclusion Over 200-pages of DgN coefficients were computed for modeled x-ray system spectra that are used in a number of new breast imaging applications. The reported values were found to be in excellent agreement when compared to published values. PMID:26348995

Computational investigation of half-Heusler compounds for spintronics applications

NASA Astrophysics Data System (ADS)

Ma, Jianhua; Hegde, Vinay I.; Munira, Kamaram; Xie, Yunkun; Keshavarz, Sahar; Mildebrath, David T.; Wolverton, C.; Ghosh, Avik W.; Butler, W. H.

2017-01-01

We present first-principles density functional calculations of the electronic structure, magnetism, and structural stability of 378 XYZ half-Heusler compounds (with X = Cr, Mn, Fe, Co, Ni, Ru, Rh; Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Ga, In, Si, Ge, Sn, P, As, Sb). We find that a "Slater-Pauling gap" in the density of states (i.e., a gap or pseudogap after nine states in the three atom primitive cell) in at least one spin channel is a common feature in half-Heusler compounds. We find that the presence of such a gap at the Fermi energy in one or both spin channels contributes significantly to the stability of a half-Heusler compound. We calculate the formation energy of each compound and systematically investigate its stability against all other phases in the open quantum materials database (OQMD). We represent the thermodynamic phase stability of each compound as its distance from the convex hull of stable phases in the respective chemical space and show that the hull distance of a compound is a good measure of the likelihood of its experimental synthesis. We find low formation energies and mostly correspondingly low hull distances for compounds with X = Co, Rh, or Ni, Y = Ti or V, and Z = P, As, Sb, or Si. We identify 26 18-electron semiconductors, 45 half-metals, and 34 near half-metals with negative formation energy that follow the Slater-Pauling rule of three electrons per atom. Our calculations predict several new, as-yet unknown, thermodynamically stable phases, which merit further experimental exploration—RuVAs, CoVGe, FeVAs in the half-Heusler structure, and NiScAs, RuVP, RhTiP in the orthorhombic MgSrSi-type structure. Further, two interesting zero-moment half-metals, CrMnAs and MnCrAs, are calculated to have negative formation energy. In addition, our calculations predict a number of hitherto unreported semiconducting (e.g., CoVSn and RhVGe), half-metallic (e.g., RhVSb), and near half-metallic (e.g., CoFeSb and CoVP) half-Heusler compounds to lie close to the respective convex hull of stable phases, and thus may be experimentally realized under suitable synthesis conditions, resulting in potential candidates for various semiconducting and spintronics applications.

Electrochemistry of mixed-metal bimetallic complexes containing the pentacyanoferrate(II) or pentaammineruthenium(II) metal center

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

Moore, K.J.; Lee, L.; Mabbott, G.A.

1983-03-30

The electrochemistry of a series of mixed-metal bimetallic complexes of the type B/sub 5/MLM'B'/sub 5/, where B/sub 5/M = (CNN)/sub 5/Fe/sup II/ or (NH/sub 3/)/sub 5/Ru/sup II/, L = pyrazine, 4,4'-bipyridine, or 4-cyanopyridine, M'B'/sub 5/ = Rh/sup III/(NH/sub 3/)/sub 5/ or Co/sup III/(CN)/sub 5/, is reported. The bimetallic complexes all have metal-to-ligand charge-transfer (MLCT) bands associated with the M-B unit (d/sub ..pi../M ..-->.. p/sub ..pi../*L). The effect of the remote metal center, M'B'/sub 5/, is to function as a Lewis acid, shifting the MLCT maximum to lower energy and shifting the M/sup III///sup II/ reduction potential more positive with respectmore » to free B/sub 5/ML. The remote metal influence is attenuated by longer bridging ligands and by reduced ..pi..-overlap. A comparison of the electrochemical data of the mixed-valence Fe(II)/Fe(III) and Ru(II)/Ru(III) complexes to the mixed-metal Fe(II)/Co(III) and Ru(II)/Rh(III) complexes has enabled a quantitative measure of the stabilization due to electron delocalization in the mixed-valence complexes. The results show that electron delocalization is greater for the ruthenium complexes than for the iron complexes, is a small contributor to the total stabilization of the mixed-valence state, and even in ruthenium drops off rapidly as the length of the bridge increases.« less

Metal organic frameworks enhanced graphene oxide electrode for humidity sensor

NASA Astrophysics Data System (ADS)

Zhang, Wen; Meng, Siyu; Wang, Hui; He, Yongning

2018-03-01

Copper benzene-1,3,5-tricarboxylate (Cu-BTC), a typical metal organic framework, is deposited on the graphene oxide (GO) film to prepare a resistance humidity sensor (Cu- BTC/GO) for improving humidity sensing. The characteristics of Cu-BTC, GO and Cu- BTC/GO were measured by scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen isotherm adsorption and electrochemical impedance spectroscopy (EIS). The humidity sensing properties of the Cu-BTC/GO were investigated in detail. The obtained Cu-BTC/GO demonstrates good sensitivity and repeatability over 11%-85% relative humidity (RH) measurements. The Cu-BTC/GO coated device shows high normalized response (S) value (6200%), which is much higher than that of pure GO coated device. Sensing mechanism of Cu- BTC/GO is discussed based on different RH and the results indicate that moderate amounts of Cu-BTC deposition can enhance sensing abilities of GO. High specific surface area and interfacial conductivity are crucial factors to fabricate humidity sensors with high performance.

Density functional theory calculations on transition metal atoms adsorbed on graphene monolayers

NASA Astrophysics Data System (ADS)

Dimakis, Nicholas; Flor, Fernando Antonio; Salgado, Andres; Adjibi, Kolade; Vargas, Sarah; Saenz, Justin

2017-11-01

Transition metal atom adsorption on graphene monolayers has been elucidated using periodic density functional theory under hybrid and generalized gradient approximation functionals. More specifically, we examined the adsorption of Cu, Fe, Zn, Ru, and Os on graphene monolayers by calculating, among others, the electronic density-of-states spectra of the adatom-graphene system and the overlap populations of the adatom with the nearest adsorbing graphene carbon atoms. These calculations reveal that Cu form primarily covalent bonds with graphene atoms via strong hybridization between the adatom orbitals and the sp band of the graphene substrate, whereas the interaction of the Ru and Os with graphene also contain ionic parts. Although the interaction of Fe with graphene atoms is mostly covalent, some charge transfer to graphene is also observed. The interaction of Zn with graphene is weak. Mulliken population analysis and charge contour maps are used to elucidate charge transfers between the adatom and the substrate. The adsorption strength is correlated with the metal adsorption energy and the height of the metal adatom from the graphene plane for the geometrically optimized adatom-graphene system. Our analysis shows that show that metal adsorption strength follows the adatom trend Ru ≈ Os > Fe > Cu > Zn, as verified by corresponding changes in the adsorption energies. The increased metal-carbon orbital overlap for the Ru relative to Os adatom is attributed to hybridization defects.

Improving The Efficiency Of Ammonia Electrolysis For Hydrogen Production

NASA Astrophysics Data System (ADS)

Palaniappan, Ramasamy

Given the abundance of ammonia in domestic and industrial wastes, ammonia electrolysis is a promising technology for remediation and distributed power generation in a clean and safe manner. Efficiency has been identified as one of the key issues that require improvement in order for the technology to enter the market phase. Therefore, this research was performed with the aim of improving the efficiency of hydrogen production by finding alternative materials for the cathode and electrolyte. 1. In the presence of ammonia the activity for hydrogen evolution reaction (HER) followed the trend Rh>Pt>Ru>Ni. The addition of ammonia resulted in lower rates for HER for Pt, Ru, and Ni, which have been attributed to competition from the ammonia adsorption reaction. 2. The addition of ammonia offers insight into the role of metal-hydrogen underpotential deposition (M-Hupd) on HER kinetics. In addition to offering competition via ammonia adsorption it resulted in fewer and weaker M-Hupd bonds for all metals. This finding substantiates the theory that M-Hupd bonds favor HER on Pt electrocatalyst. However, for Rh results suggest that M-Hupd bond may hinder the HER. In addition, the presence of unpaired valence shell electrons is suggested to provide higher activity for HER in the presence of ammonia. 3. Bimetals PtxM1-x (M = Ir, Ru, Rh, and Ni) offered lower overpotentials for HER compared to the unalloyed metals in the presence of ammonia. The activity of HER in the presence of ammonia follows the trend Pt-Ir>Pt-Rh>Pt-Ru>Pt-Ni. The higher activity of HER is attributed to the synergistic effect of the alloy, where ammonia adsorbs onto the more electropositive alloying metal leaving Pt available for Hupd formation and HER to take place. Additionally, this supports the theory that the presence of a higher number of unpaired electrons favors the HER in the presence of ammonia. 4. Potassium polyacrylate (PAA-K) was successfully used as a substitute for aqueous KOH for ammonia electrolysis. PAA-K allowed for a wider operating potential for the electrolytic cell while increasing the rate for HER at lower cell voltages. The conversion of ammonia improved from 16 % to 25 %, while the current efficiency for the consumption of ammonia increased from 92 +/- 1 % to 97 +/- 2 % by using PAA-K in lieu of KOH. The use of PAA-K also prevented the crossover of the hydrogen produced to the anode side, unlike aqueous KOH.

Noble metal abundances in komatiite suites from Alexo, Ontario and Gorgona Island, Colombia

NASA Astrophysics Data System (ADS)

Brügmann, G. E.; Arndt, N. T.; Hofmann, A. W.; Tobschall, H. J.

1987-08-01

The distribution of the chalcophile and siderophile metals Cu, Ni, Au, Pd, Ir, Os and Ru in an Archaean komatiite flow from Alexo, Ontario and in a Phanerozoic komatiitic suite of Gorgona Island, Colombia, provides new information about the geochemical behaviour of these elements. Copper, Au and Pd behave as incompatible elements during the crystallization of these ultramafic magmas. In contrast, Ni, Ir, Os and Ru concentrations systematically decrease with decreasing MgO contents, a pattern characteristic of compatible elements. These trends are most probably controlled by olivine crystallization, which implies that Ir, Os and Ru are compatible in olivine. Calculated partition coefficients for Ir, Os and Ru between olivine and the melt are about 1.8. Compared to primitive mantle, parental komatiitic liquids are enriched in (incompatible) Cu, Au and Pd and depleted in (compatible) Ir, Os and Ru. Within both Archaean and Phanerozoic komatiites, noble metal ratios such as Au/Pd, Ir/Os, Os/Ru and Ru/Ir and ratios of lithophile and siderophile elements such as Ti/Pd, Ti/Au are constant and similar to primitive mantle values. This implies that Au and Pd are moderately incompatible elements and that there has been no significant fractionation of siderophile and lithophile elements since the Archaean. Platinum-group element abundances of normal MORB are highly variable and always much lower than in komatiites, because MORB magma is saturated with sulfur and a variable but minor amount of sulfide segregated during mantle melting or during the ascent of magma to the surface. Sulfide deposits associated with komatiites display similar chalcophile element patterns to those of komatiites. Noble metal ratios such as Pd/Ir, Au/Ir, Pd/Os and Pd/Ru can be used to determine the composition of the host komatiite at the time of sulfide segregation.

Hydrogen production from bio-fuels using precious metal catalysts

NASA Astrophysics Data System (ADS)

Pasel, Joachim; Wohlrab, Sebastian; Rotov, Mikhail; Löhken, Katrin; Peters, Ralf; Stolten, Detlef

2017-11-01

Fuel cell systems with integrated autothermal reforming unit require active and robust catalysts for H2 production. Thus, an experimental screening of catalysts for autothermal reforming of commercial biodiesel fuel was performed. Catalysts consisted of a monolithic cordierite substrate, an oxide support (γ-Al2O3) and Pt, Ru, Ni, PtRh and PtRu as active phase. Experiments were run by widely varying the O2/C and H2O/C molar ratios at different gas hourly space velocities. Fresh and aged catalysts were characterized by temperature programmed methods and thermogravimetry to find correlations with catalytic activity and stability.

Oxidative demetalation of cyclohexadienyl ruthenium(II) complexes: a net Ru-mediated dearomatization.

PubMed

Pigge, F Christopher; Coniglio, John J; Rath, Nigam P

2003-05-29

[reaction: see text] An experimentally simple method for the demetalation of spirocyclic cyclohexadienylruthenium(II) complexes has been developed. Treatment of an alkoxy-substituted cyclohexadienyl complex with CuCl(2) affords either azaspiro[4.5]decane derivatives or heavily functionalized tetrahydroisoquinolines. The former reaction manifold completes a net Ru-mediated dearomatization as the organometallic starting materials are prepared from (eta(6)-arene)Ru(II) precursors. Both of these heterocyclic products are well suited for further synthetic elaboration.

Copper-based alloys, crystallographic and crystallochemical parameters of alloys in binary systems Cu-Me (Me=Co, Rh, Ir, Cu, Ag, Au, Ni, Pd, Pt)

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

Porobova, Svetlana, E-mail: porobova.sveta@yandex.ru; Loskutov, Oleg, E-mail: lom58@mail.ru; Markova, Tat’jana, E-mail: patriot-rf@mail.ru

2016-01-15

The article presents the results of the analysis of phase equilibrium of ordered phases in binary systems based on copper Cu- Me (where Me - Co, Rh, Ir, Ag, Au, Ni, Pd, Pt) to find correlations of crystallochemical and crystallographic factors. It is established that the packing index in disordered solid solutions in binary systems based on copper is close to the value of 0.74 against the background of an insignificant deviation of atomic volumes from the Zen’s law.

Organometallic conjugates of the drug sulfadoxine for combatting antimicrobial resistance

USDA-ARS?s Scientific Manuscript database

Fourteen new RuII, RhIII and IrIII complexes conjugated to the antimalarial drug sulfadoxine functionalised with either a pyridylimino- or quinolylimino- group to allow N,N’-chelation ligands have been synthesized and characterized. The effect of the arene/Cpx, planarity of imino group on sulfadoxin...

Electron-transfer quenching vs. exciplex-mediated quenching of the low-lying excited states in phthalocyanines

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

Prasad, D.R.; Ferraudi, G.

1983-05-25

Oxidative electron-transfer quenching of the lowest ligand-centered /sup 3/..pi pi..* of ruthenium (RU) phthalocyanines (pc)L/sub 2/, L = dimethylformamide (dmf) or pyridine (py), by a series of nitroaromatic compounds, viologen salts, and metal complexes has been investigated by laser and conventional flash photolysis. The quenching rate constants, treated according to Marcus-Hush and Rehm-Weller equations, gave self-exchange rate constants, k/sub exch/ approx. 10/sup 7/ M/sup -1/ s/sup -1/, for the electron exchange between the /sup 3/..pi pi..* and the ruthenium(II) ligand radical. The excited states of a number of phthalocyanines, e.g. Ru(pc)(dimethyl sulfoxide(Me/sub 2/SO)/sub 2/), Ru(pc)(dmf)CO, Ru(pc)(py)CO, and Rh(pc)(methanol(CH/sub 3/OH)chloride), undergomore » quenching mediated by exciplex formation. The formation of exciplexes is discussed in terms of the related exciplexes of the porphyrins.« less

Half-life of the electron-capture decay of {sup 97}Ru: Precision measurement shows no temperature dependence

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

Goodwin, J. R.; Golovko, V. V.; Iacob, V. E.

2009-10-15

We have measured the half-life of the electron-capture (ec) decay of {sup 97}Ru in a metallic environment, both at low temperature (19 K), and also at room temperature. We find the half-lives at both temperatures to be the same within 0.1%. This demonstrates that a recent claim that the ec decay half-life for {sup 7}Be changes by 0.9%{+-}0.2% under similar circumstances certainly cannot be generalized to other ec decays. Our results for the half-life of {sup 97}Ru, 2.8370(14) d at room temperature and 2.8382(14) d at 19 K, are consistent with, but much more precise than, previous room-temperature measurements. Inmore » addition, we have also measured the half-lives of the {beta}{sup -}-emitters {sup 103}Ru and {sup 105}Rh at both temperatures, and found them also to be unchanged.« less

Behaviour of Ni-PGE-Au-Cu in mafic-ultramafic volcanic suites of the 2.7 Ga Kambalda Sequence, Kalgoorlie Terrane, Yilgarn Craton

NASA Astrophysics Data System (ADS)

Said, Nuru; Kerrich, Robert; Maier, W. D.; McCuaig, Campbell

2011-05-01

The 2.7 Ga Kambalda Sequence comprises a mafic to ultramafic dominated volcanic rock sequence of the Kalgoorlie Terrane, Yilgarn Craton, Western Australia. The Sequence is divided into Lower and Upper Units separated by the Kambalda Komatiite Formation. Five basalt suites of the Lower Unit are tholeiitic where MgO spans 5-10 wt.% MgO, with minor assimilation-fractional crystallization (AFC), whereas six volcanic suites identified in the Upper Unit are tholeiitic to komatiitic-basalts with MgO 24-5 wt.% having generally greater degrees of AFC. Upper suites plot at Al 2O 3/TiO 2 (17-26) close to the primitive mantle ratio of 21, and Pt + Pd (19-31 ppb), whereas the PGE-depleted Lower basalts plot at generally lower Al 2O 3/TiO 2 (<16) and Pt + Pd (<10 ppb). Most suites have an average Pt/Pd ratio of 1.11, despite large variations in MgO contents, broadly consistent with the Pt/Pd ratio in the primitive mantle. On primitive mantle-normalised PGE plots, Upper suites generally display less fractionated patterns of the IPGE (Os, Ir, Ru and Rh) from the PPGE (Pt and Pd) relative to the Lower basalts. Most suites exhibit patterns with positive slopes reflecting relative enrichment of Pd, Pt, Au and Cu relative to Ni and IPGE. In suites of both Units, the concentrations of Ir and Ru fall with decreasing MgO contents, indicating their broadly compatible behaviour during magmatic evolution that involved AFC. Platinum and Pd behave as incompatible elements in the high-MgO suites, whereas Pt and Pd behave compatibly during crystallisation of the Lower basalt magmas, an interpretation consistent with progressively higher Cu/Pt and Cu/Pd ratios at decreasing MgO contents, and with falling Pt/Ti, collectively due to sulphur saturation induced by AFC as recorded in an antivariance of Pd/Ir with Nb/Th, a monitor of AFC. Collectively, the data suggest that several of the Lower Basalt suites crystallised under sulphide-saturated conditions, whereas most of the Upper Basalt Sequences remained sulphur undersaturated during magmatic evolution. Alteration, and fractional crystallisation of silicate and oxide phases, can be ruled out as factors governing PGE distribution in these mafic-ultramafic suites. Instead, the data suggest that discrete PGE-bearing phase (s) fractionated from the magmas. Such phases could be platinum group minerals (PGM; e.g., laurite) and/or alloys, or discrete PGE-rich nuggets or sulphides.

Effects of central metal ions on vibrational circular dichroism spectra of tris-(beta-diketonato)metal(III) complexes.

PubMed

Sato, Hisako; Taniguchi, Tohru; Nakahashi, Atsufumi; Monde, Kenji; Yamagishi, Akihiko

2007-08-06

Vibrational circular dichroism (VCD) spectra of a series of [M(III)(acac)3] (acac = acetylacetonato; M = Cr, Co, Ru, Rh, Ir, and Al) and [M(III)(acac)2(dbm)] (dbm = dibenzoylmethanato; M = Cr, Co, and Ru) have been investigated experimentally and/or theoretically in order to see the effect of the central metal ion on the vibrational dynamics of ligands. The optical antipodes give the mirror-imaged spectra in the region of 1700-1000 cm(-1). The remarkable effect of the central metal ion is observed experimentally on the VCD peaks due to C-O stretches (1500-1300 cm(-1)) for both [M(III)(acac)3] and [M(III)(acac)2(dbm)]. In the case of Delta-[M(III)(acac)3], for example, the order of frequency of two C-O stretches (E and A2 symmetries) is dependent on the kind of a central metal ion as follows: E (-) > A2 (+) for M = Co, Rh, and Ir, while A2 (+) > E (-) for M = Cr and Ru. In the case of Delta-[M(III)(acac)2(dbm)], the order of frequency of three C-O stretches (A, B, and B symmetries) is as follows: A (-) > B (+) > B (+) for Co(III), B (+) > A (-) > B (-) for Cr(III), and A (-) > B (+) > B (-) for Ru(III). These results imply that the energy levels of C-O stretches are delicately affected by the kind of central metal ion. Since such detailed information is not obtained from the IR spectra alone, the VCD spectrum can probe the effect of the central metal ion on interligand cooperative vibration modes.

Graphene wrapped Copper Phthalocyanine nanotube: Enhanced photocatalytic activity for industrial waste water treatment

NASA Astrophysics Data System (ADS)

Mukherjee, Moumita; Ghorai, Uttam Kumar; Samanta, Madhupriya; Santra, Angshuman; Das, Gour P.; Chattopadhyay, Kalyan K.

2017-10-01

To improve the photocatalytic performance of metal phthalocyanine based catalyst, Copper Phthalocyanine (CuPc) functionalized reduced graphene oxide (RGO) nanocomposite has been synthesized through a simple chemical approach. The obtained product was characterized by X-ray diffraction technique (XRD), Fourier transform infrared (FTIR) spectroscopy, Ultraviolet-visible spectroscopy (UV-vis) and High resolution transmission electron microscopy (HRTEM). The photocatalytic activity of the RGO/CuPc nanocomposite was performed by the degradation of Rhodamine B (RhB) under visible light irradiation. The photocatalytic studies revealed that the RGO/CuPc nanocomposite exhibits much stronger catalytic behavior than the pristine CuPc nanotube. A plausible mechanism for the photodegradation of Rhodamine B (RhB) was suggested. The RGO wrapped CuPc nanotube composite materials offer great potential as active photocatalysts for degradation of organic pollutions in industrial waste water.

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

Zhou, Yinghui; Lii-Rosales, Ann; Kim, Minsung

Here, we show that 3 metals – Dy, Ru, and Cu – can form multilayer intercalated (encapsulated) islands at the graphite (0001) surface if 2 specific conditions are met: Defects are introduced on the graphite terraces to act as entry portals, and the metal deposition temperature is well above ambient. Focusing on Dy as a prototype, we show that surface encapsulation is much different than bulk intercalation, because the encapsulated metal takes the form of bulk-like rafts of multilayer Dy, rather than the dilute, single-layer structure known for the bulk compound. Carbon-covered metallic rafts even form for relatively unreactive metalsmore » (Ru and Cu) which have no known bulk intercalation compound.« less

Switching properties of SrRuO3/Pb(Zr0.4Ti0.6)O3/SrRuO3 capacitor grown on Cu-coated Si substrate measured at various temperatures

NASA Astrophysics Data System (ADS)

Chen, J. H.; Liu, B. T.; Li, C. R.; Li, X. H.; Dai, X. H.; Guo, J. X.; Zhou, Y.; Wang, Y. L.; Zhao, Q. X.; Ma, L. X.

2014-09-01

SrRuO3(SRO)/Ni-Al/Cu/Ni-Al/SiO2/Si heterostructures annealed at various temperatures are found to remain intact after 750 \\circ\\text{C} annealing. Moreover, a SRO/Pb(Zr0.4Ti0.6)O3 (PZT)/SRO capacitor is grown on a Ni-Al/Cu/Ni-Al/SiO2/Si heterostructure, which is tested up to 100 \\circ\\text{C} to investigate the reliability of the memory capacitor. It is found that besides the good fatigue resistance and retention characteristic, the capacitor, measured at 5 V and room temperature, possesses a large remnant polarization of 25.0 μ \\text{C/cm}2 and a small coercive voltage of 0.83 V, respectively. Its dominant leakage current behavior satisfies the space-charge-limited conduction at various temperatures. Very clear interfaces can be observed from the cross-sectional images of transmission electron microscopy, indicating that the Ni-Al film can be used as a diffusion barrier layer for copper metallization as well as a conducting barrier layer between copper and oxide layer.

Cu-modified alkalinized g-C3N4 as photocatalytically assisted heterogeneous Fenton-like catalyst

NASA Astrophysics Data System (ADS)

Dong, Qimei; Chen, Yingying; Wang, Lingli; Ai, Shasha; Ding, Hanming

2017-12-01

Alkalinized graphitic carbon nitride (CNK-OH) has been synthesized by one-step thermal poly-condensation method, and Cu-modified alkalinized g-C3N4 (Cu-CNK-OH) has been prepared by impregnation approach over CNK-OH. These copper species in Cu-CNK-OH are embedded in the frame of CNK-OH mostly via the Cu-N bonds. Cu-CNK-OH has been employed as a heterogeneous Fenton-like catalyst to degrade rhodamine B (RhB). Both the production efficiency of hydroxyl radicals and the transformation rate of Cu(II)/Cu(I) redox pair increase under visible-light irradiation. As a result, Cu-CNK-OH exhibits improved Fenton-like catalytic activity on the degradation of RhB. The synergetic interaction between Fenton-like process and photocatalytic process also contributes such improvement. The hydroxyl radicals and holes are the major reactive species in the photocatalytically assisted Fenton-like process. This study provides a valuable strategy for metal modification of alkalinized g-C3N4 with enhanced Fenton-like catalytic performance for the degradation of organic contaminants.

One-Pot and Facile Fabrication of Hierarchical Branched Pt-Cu Nanoparticles as Excellent Electrocatalysts for Direct Methanol Fuel Cells.

PubMed

Cao, Yanqin; Yang, Yong; Shan, Yufeng; Huang, Zhengren

2016-03-09

Hierarchical branched nanoparticles are one promising nanostructure with three-dimensional open porous structure composed of integrated branches for superior catalysis. We have successfully synthesized Pt-Cu hierarchical branched nanoparticles (HBNDs) with small size of about 30 nm and composed of integrated ultrathin branches by using a modified polyol process with introduction of poly(vinylpyrrolidone) and HCl. This strategy is expected to be a general strategy to prepare various metallic nanostructures for catalysis. Because of the special open porous structure, the as-prepared Pt-Cu HBNDs exhibit greatly enhanced specific activity toward the methanol oxidation reaction as much as 2.5 and 1.7 times compared with that of the commercial Pt-Ru and Pt-Ru/C catalysts, respectively. Therefore, they are potentially applicable as electrocatalysts for direct methanol fuel cells.

Highly versatile heteroditopic ligand scaffolds for accommodating group 8, 9 & 11 heterobimetallic complexes.

PubMed

Gatus, Mark R D; Bhadbhade, Mohan; Messerle, Barbara A

2017-10-24

Two highly versatile xanthene scaffolds containing pairs of heteroditopic ligands were found to be capable of accommodating a range of transition metal ions, including Au(i), Ir(i), Ir(iii), Rh(i), and Ru(ii) to generate an array of heterobimetallic complexes. The metal complexes were fully characterised and proved to be stable in the solid and solution state, with no observed metal-metal scrambling. Heterobimetallic complexes containing the Rh(i)/Ir(i) combinations were tested as catalysts for the two-step dihydroalkoxylation reaction of alkynediols and sequential hydroamination/hydrosilylation reaction of alkynamines.

Utilization of Metal Sulfide Material of (CuGa)(1-x)Zn(2x)S2 Solid Solution with Visible Light Response in Photocatalytic and Photoelectrochemical Solar Water Splitting Systems.

PubMed

Kato, Takaaki; Hakari, Yuichiro; Ikeda, Satoru; Jia, Qingxin; Iwase, Akihide; Kudo, Akihiko

2015-03-19

Upon forming a solid solution between CuGaS2 and ZnS, we have successfully developed a highly active (CuGa)(1-x)Zn(2x)S2 photocatalyst for H2 evolution in the presence of sacrificial reagents under visible light irradiation. The Ru-loaded (CuGa)0.8Zn0.4S2 functioned as a H2-evolving photocatalyst in a Z-scheme system with BiVO4 of an O2-evolving photocatalyst and Co complexes of an electron mediator. The Z-scheme system split water into H2 and O2 under visible light and simulated sunlight irradiation. The (CuGa)(1-x)Zn(2x)S2 possessed a p-type semiconductor character. The photoelectrochemical cell with a Ru-loaded (CuGa)0.5ZnS2 photocathode and a CoO(x)-modified BiVO4 photoanode split water even without applying an external bias. Thus, we successfully demonstrated that the metal sulfide material group can be available for Z-scheme and electrochemical systems to achieve solar water splitting into H2 and O2.

Humidity sensitive polymers In solution processed adjustable pore-volume Cu(In,Ga)S2 photocathodes for solar hydrogen production

NASA Astrophysics Data System (ADS)

Zhang, Chuan; Luo, Wenjun; Wen, Xin; Guan, Zhongjie; Zou, Zhigang

2017-11-01

P-type Cu(In,Ga)S2 semiconductors are promising candidates to be used as photocathodes for solar water splitting. Porous structures have been widely used to improve the performances of photoelectrodes due to good minority carrier transport. However, a porous photoelectrode has longer transport distance of majority carriers, which limits its performance. Controlling pore volume of a photoelectrode can balance minority and majority carrier transport and improve the performance. Here, a porous Cu(In,Ga)S2 film is prepared by facile spin-coating method. The pore volume of Cu(In,Ga)S2 film is controlled by adjusting relative humidity (RH) of air during spin-coating process. Further studies suggest that polyvinyl acetate (PVAc) in precursor solution is a humidity sensitive polymer and plays a key role to form different pore volume. The 40% RH sample has the best performance due to its optimum pore volume. After further coated with CdS surface passivation layer and Pt electrocatalyst on the surface, a 40% RH Cu(In,Ga)S2 photocathode indicates a photocurrent density of 8.6 mA cm-2 at 0 V RHE, which is one of the highest photocurrents of Cu(In,Ga)S2 photocathodes. This new strategy for adjusting pore volume is also suitable to prepare other solution-processed inorganic materials.

Palladium, platinum, rhodium, ruthenium, and iridium in chromitites from the Massif du Sud and Tiebaghi massif, New Caledonia.

USGS Publications Warehouse

Page, N.J.; Cassard, D.; Haffty, J.

1982-01-01

The massive and disseminated podiform chromitites from 43 mines and other occurrences in the area contain up to (in ppb) Pd 9, Pt 45, Rh 31, Ir 410 and Ru 1300. The possble origins of the chromitites are discussed. -K.A.R.

Bimetallic poly- and oligo-nuclear complexes based on a rhodium(III) metalloligand

NASA Astrophysics Data System (ADS)

Vasilchenko, Danila B.; Venediktov, Anatoliy B.; Korenev, Sergey V.; Filatov, Evgeniy Yu.; Baidina, Iraida A.; Nadolinnyi, Vladimir A.

2012-10-01

Interaction of trans-[Rh(i-Nic)4Cl2]3- anions (i-Nic- - isonicotinate anion) with Cuaq2+ and Coaq2+ cations in water has afforded complex salts Co3[Rh(i-Nic)4Cl2]2·17H2O (1) and Cu3[Rh(i-Nic)4Cl2]2·14H2O (2). Oligonuclear character of 1 and 2 has been established. A coordination polymer Cu5[Rh(i-Nic)4Cl2]2(i-Nic)2(OH)2·2H2O (3) has been crystallized by hydrothermal treatment of 2 at 160 °C, and its structure was determined by X-ray structural analysis. EPR data for the complexes has been collected and interpreted. Thermal decomposition of the salts was studied by c-DTA. Bimetallic alloys rhodium-copper and rhodium-cobalt have been obtained as final products of thermal decomposition.

Effect of Precursors on the Synthesis of CuO Nanoparticles Under Microwave for Photocatalytic Activity Towards Methylene Blue and Rhodamine B Dyes.

PubMed

Sanjini, N S; Winston, B; Velmathi, S

2017-01-01

Copper oxide nanoparticles have been successfully synthesized by microwave assisted precipitation method. Different precursors like copper chloride, copper nitrate and copper sulphate were used for synthesis of CuO nanoparticles with different shape, size and catalytic activity. Sodium hydroxide acts as a capping agent and ethanol as solvent for the synthesis. The XRD study was conducted to confirm the single phase monoclinic structure of as-synthesized and annealed CuO nano particles. The morphology of the as-synthesized and annealed CuO samples was analyzed by high resolution field emission scanning electron microscope. Fourier transform infrared spectroscopy was done for all the synthesized CuO nanoparticles for functional group characterization. The wide band gap and photocatalytic activity were studied by UV-Visible spectroscopy. The photocatalytic degradation of Methylene blue (MB) and Rhodamine B (RhB) dyes in aqueous solution were investigated under UV light (254 nm). In all the cases annealed samples showed good catalytic activity compared to as-synthesized CuO nanoparticles. The CuO nanoparticles from CuCl2 precursor act as excellent photocatalyst for both MB and RhB compared to CuNO₃ and CuSO₄.

Novel 2D RuPt core-edge nanocluster catalyst for CO electro-oxidation

NASA Astrophysics Data System (ADS)

Grabow, Lars C.; Yuan, Qiuyi; Doan, Hieu A.; Brankovic, Stanko R.

2015-10-01

A single layer, bi-metallic RuPt catalyst on Au(111) is synthesized using surface limited red-ox replacement of underpotentially deposited Cu and Pb monolayers though a two-step process. The resulting 2D RuPt monolayer nanoclusters have a unique core-edge structure with a Ru core and Pt at the edge along the perimeter. The activity of this catalyst is evaluated using CO monolayer oxidation as the probe reaction. Cyclic voltammetry demonstrates that the 2D RuPt core-edge catalyst morphology is significantly more active than either Pt or Ru monolayer catalysts. Density functional theory calculations in combination with infra-red spectroscopy data point towards oscillating variations (ripples) in the adsorption energy landscape along the radial direction of the Ru core as the origin of the observed behavior. Both, CO and OH experience a thermodynamic driving force for surface migration towards the Ru-Pt interface, where they adsorb most strongly and react rapidly. We propose that the complex interplay between epitaxial strain, ligand and finite size effects is responsible for the formation of the rippled RuPt monolayer cluster, which provides optimal conditions for a quasi-ideal bi-functional mechanism for CO oxidation, in which CO is adsorbed mainly on Pt, and Ru provides OH to the active Pt-Ru interface.

Synthesis of Pd 9Ru@Pt nanoparticles for oxygen reduction reaction in acidic electrolytes

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

Sun, Yu; Hsieh, Yu -Chi; Chang, Li -Chung

2014-11-22

Nanoparticles of PdRu, Pd₃Ru, and Pd₉Ru are synthesized and impregnated on carbon black via a wet chemical reflux process. X-ray diffraction patterns of the as-synthesized samples, Pd xRu/C (x=1/3/9), suggest succesful formation of alloy without presence of individual Pd and Ru nanoparticles. Images from transmission electron microscope confirm irregularly-shaped nanoparticles with average size below 3 nm. Analysis from extended X-ray absorption fine structure on both Pd and Ru K-edge absorption profiles indicate the Ru atoms are enriched on the surface of Pd xRu/C. Among these samples, the Pd₉Ru/C exhibits the strongest electrocatalytic activity for oxygen reduction reaction (ORR) in anmore » oxygen-saturated 0.1 M aqueous HClO₄ solution. Subsequently, the Pd₉Ru/C undegoes Cu under potential deposition, followed by a galvanic displacement reaction to deposit a Pt monolayer on the Pd₉Ru surface (Pd₉Ru@Pt). The Pd₉Ru@Pt reveals better ORR performance than that of Pt, reaching a mass activity of 0.38 mA μg⁻¹ Pt, as compared to that of commercially available Pt nanoparticles (0.107 mA μg⁻¹ Pt). Thus, the mechanisms responsible for the ORR enhancement are attributed to the combined effects of lattice strain and ligand interaction. In addition, this core-shell Pd₉Ru@Pt electrocatalyst represents a substantial reduction in the amount of Pt consumption and raw material cost.« less

Synthesis of Pd9Ru@Pt nanoparticles for oxygen reduction reaction in acidic electrolytes

NASA Astrophysics Data System (ADS)

Sun, Yu; Hsieh, Yu-Chi; Chang, Li-Chung; Wu, Pu-Wei; Lee, Jyh-Fu

2015-03-01

Nanoparticles of PdRu, Pd3Ru, and Pd9Ru are synthesized and impregnated on carbon black via a wet chemical reflux process. X-ray diffraction patterns of the as-synthesized samples, PdxRu/C (x = 1/3/9), suggest successful formation of alloy without presence of individual Pd and Ru nanoparticles. Images from transmission electron microscope confirm irregularly-shaped nanoparticles with average size below 3 nm. Analysis from extended X-ray absorption fine structure on both Pd and Ru K-edge absorption profiles indicate the Ru atoms are enriched on the surface of PdxRu/C. Among these samples, the Pd9Ru/C exhibits the strongest electrocatalytic activity for oxygen reduction reaction (ORR) in an oxygen-saturated 0.1 M aqueous HClO4 solution. Subsequently, the Pd9Ru/C undergoes Cu under potential deposition, followed by a galvanic displacement reaction to deposit a Pt monolayer on the Pd9Ru surface (Pd9Ru@Pt). The Pd9Ru@Pt reveals better ORR performance than that of Pt, reaching a mass activity of 0.38 mA μg-1Pt, as compared to that of commercially available Pt nanoparticles (0.107 mA μg-1Pt). The mechanisms responsible for the ORR enhancement are attributed to the combined effects of lattice strain and ligand interaction. In addition, this core-shell Pd9Ru@Pt electrocatalyst represents a substantial reduction in the amount of Pt consumption and raw material cost.

Synthesis and microstructural TEM investigation of CaCu 3Ru 4O 12 ceramic and thin film

NASA Astrophysics Data System (ADS)

Brizé, Virginie; Autret-Lambert, Cécile; Wolfman, Jérôme; Gervais, Monique; Gervais, François

2011-10-01

CaCu 3Ru 4O 12 (CCRO) is a conductive oxide having the same structure as CaCu 3Ti 4O 12 (CCTO) and close lattice parameters. The later compound is strongly considered for high density parallel plates capacitors application due to its so-called colossal dielectric constant. The need for an electrode inducing CCTO epitaxial growth with a clean and sharp interface is therefore necessary, and CCRO is a good potential candidate. In this paper, the synthesis of monophasic CCRO ceramic is reported, as well as pulsed laser deposition of CCRO thin film onto (001) NdCaAlO 4 substrate. Structural and physical properties of bulk CCRO were studied by transmission electron microscopy and electron spin resonance. CCRO films and ceramic exhibited a metallic behavior down to low temperature. CCRO films were (001) oriented and promoted a CCTO film growth with the same orientation.

Investigation of energy band alignments and interfacial properties of rutile NMO2/TiO2 (NM = Ru, Rh, Os, and Ir) by first-principles calculations.

PubMed

Yang, Chen; Zhao, Zong-Yan

2017-11-08

In the field of photocatalysis, constructing hetero-structures is an efficient strategy to improve quantum efficiency. However, a lattice mismatch often induces unfavorable interfacial states that can act as recombination centers for photo-generated electron-hole pairs. If the hetero-structure's components have the same crystal structure, this disadvantage can be easily avoided. Conversely, in the process of loading a noble metal co-catalyst onto the TiO 2 surface, a transition layer of noble metal oxides is often formed between the TiO 2 layer and the noble metal layer. In this article, interfacial properties of hetero-structures composed of a noble metal dioxide and TiO 2 with a rutile crystal structure have been systematically investigated using first-principles calculations. In particular, the Schottky barrier height, band bending, and energy band alignments are studied to provide evidence for practical applications. In all cases, no interfacial states exist in the forbidden band of TiO 2 , and the interfacial formation energy is very small. A strong internal electric field generated by interfacial electron transfer leads to an efficient separation of photo-generated carriers and band bending. Because of the differences in the atomic properties of the components, RuO 2 /TiO 2 and OsO 2 /TiO 2 hetero-structures demonstrate band dividing, while RhO 2 /TiO 2 and IrO 2 /TiO 2 hetero-structures have a pseudo-gap near the Fermi energy level. Furthermore, NMO 2 /TiO 2 hetero-structures show upward band bending. Conversely, RuO 2 /TiO 2 and OsO 2 /TiO 2 hetero-structures present a relatively strong infrared light absorption, while RhO 2 /TiO 2 and IrO 2 /TiO 2 hetero-structures show an obvious absorption edge in the visible light region. Overall, considering all aspects of their properties, RuO 2 /TiO 2 and OsO 2 /TiO 2 hetero-structures are more suitable than others for improving the photocatalytic performance of TiO 2 . These findings will provide useful information for understanding the role and effects of a noble metal dioxide as a transition layer between a noble metal co-catalyst and a TiO 2 photocatalyst.

Enhancement of high dielectric permittivity in CaCu3Ti4O12/RuO2 composites in the vicinity of the percolation threshold

NASA Astrophysics Data System (ADS)

Mukherjee, Rupam; Lawes, Gavin; Nadgorny, Boris

2014-08-01

We observe the large enhancement in the dielectric permittivity near the percolation threshold in a composite nanoparticle system consisting of metallic RuO2 grains embedded into CaCu3Ti4O12 (CCTO) matrix and annealed at 1100 °C. To understand the nature of the dielectric response, we prepared CCTO by using standard solid state and sol-gel processes, with the relative permittivity found to be on the order of 103-104 at 10 kHz. For RuO2/CCTO composites, an increase in the real part of the dielectric permittivity by approximately an order of magnitude is observed in the vicinity of the percolation threshold, with moderate losses at room temperature. The critical exponent of dielectric permittivity and conductivity of these composites are lower than universal value (0.8-1). In these composite systems, both Maxwell-Wagner and percolation effects have been found responsible for the enhancement of dielectric permittivity.

Information Requirements for the VIMS (Vehicle Integrated Management System).

DTIC Science & Technology

1983-09-01

flj the decision setting and the...rl 4-1 -o to SH 0 en X r4 4J <D +J (U 4-1 3 s <u 3 a) r-\\ X 0 U H Jo (0 T3 (Ö TD <tf 0 +J c X i. 1 tt a C" rtJ rH XI x; X CO (0 Cn -4-1 i...tr •H CO en (0 CO •H <u rH O •H a CU > CU x: +j Ä O •H JC O 4J c o •P 4J td N •H C (TJ Oi P o P O CU CT> CO CO

Isonitrile radionuclide complexes for labelling and imaging agents

DOEpatents

Jones, Alun G.; Davison, Alan; Abrams, Michael J.

1984-06-04

A coordination complex of an isonitrile ligand and radionuclide such as Tc, Ru, Co, Pt, Fe, Os, Ir, W, Re, Cr, Mo, Mn, Ni, Rh, Pd, Nb and Ta, is useful as a diagnostic agent for labelling liposomes or vesicles, and selected living cells containing lipid membranes, such as blood clots, myocardial tissue, gall bladder tissue, etc.

Photochemical preparation of olefin addition catalysts

NASA Technical Reports Server (NTRS)

Gray, Harry B. (Inventor); Rembaum, Alan (Inventor); Gupta, Amitava (Inventor)

1978-01-01

Novel polymer supported catalysts are prepared by photo-irradiation of low valent transition metal compounds such as Co.sub.2 (CO).sub.8, Rh.sub.4 (CO).sub.12 or Ru.sub.3 (CO).sub.12 in the presence of solid polymers containing amine ligands such as polyvinyl pyridine. Hydroformylation of olefins to aldehydes at ambient conditions has been demonstrated.

Study of activation cross-sections of deuteron induced reactions on rhodium up to 40 MeV

NASA Astrophysics Data System (ADS)

Ditrói, F.; Tárkányi, F.; Takács, S.; Hermanne, A.; Yamazaki, H.; Baba, M.; Mohammadi, A.; Ignatyuk, A. V.

2011-09-01

In the frame of a systematic study of the activation cross-sections of deuteron induced nuclear reactions, excitation functions of the 103Rh(d,x) 100,101,103Pd, 100g,101m,101g,102m,102gRh and 103gRu reactions were determined up to 40 MeV. Cross-sections were measured with the activation method using a stacked foil irradiation technique. Excitation functions of the contributing reactions were calculated using the ALICE-IPPE, EMPIRE-II and TALYS codes. From the measured cross-section data integral production yields were calculated and compared with experimental integral yield data reported in the literature. From the measured cross-sections and previous data, activation curves were deduced to support thin layer activation (TLA) on rhodium and Rh containing alloys.

Interference removals on Pd, Ru and Au with ICP-QQQ-MS in PGE RM

NASA Astrophysics Data System (ADS)

Nadeem Hussain Bokhari, Syed; Meisel, Thomas; Walkner, Christoph

2015-04-01

Gold and platinum group elements (PGE) are essential industrial precious metals with high world demand due to their unique properties. Struggle for natural exploration of PGE is on great pace and recycling from industrial wastes, electronics and catalytic convertor is on the rise for PGE supply chain. Along with these developments it is becoming more challenging for analytical chemists to determine gold and PGE out of complex matrix which causes severe interferences. The current state of art is online analysis coupled with chromatographic separation of interferences. The ICP-QQQ-MS Agilent 8800 has the capability of using multi tunes and mass shifts. We aim to remove interferences on Pd+ (for direct and isotope dilution analysis) Au+ and Ru+ in lieu of chemical separations. YO+, SrOH+, ZnAr+, NiAr+, ZrO+, CuAr+, MoO+ , Ru+and Cd+ are expected interferences on Pd+ while Au+ is interfered by TaO+, HfOH+, GdAr+ and 102Ru+ ,104Ru+ by 102Pd+ ,104Pd+ etc. Initial test were performed on pure solutions of 1mg/l (interfering elements): 1 ng/l (Pd, Ru & Au) respectively. The outcomes of initial tests were applied on PGE reference material (RM) WMG-1 and SARM-7 (digested with Na2O2 sintering). The results obtained show that YO+, SrOH+ interfere (104Pd,105Pd), 104 Ru+ on (104Pd), ZnAr+ has slight interference on (104Pd and106Pd), ZrO+, NiAr+, CuAr+ interferences are negligible, MoO+ has severe interference on (108Pd, 110Pd) and that Cd+ has severe isobaric interference on (106Pd,108Pd, 110Pd). These interference have been removed by formation of Pd(NH3)3+complex. The TaO+, HfOH+ and GdAr+ interferences on Au+ are best removed by formation of Au(NH3)+ and Au(NH3)2+ complexes. 102Pd+,104Pd+interference on 102Ru+ ,104Ru+ can be removed by formation of Ru(NH3)4+ and RuO+ compounds. The results obtained comply with certified values of RM. The developed method is being tested on low concentration PGE reference materials. References: Sugiyama, N. " Removal of complex spectral interferences on noble metal isotopes." Agilent 8800 ICP-QQQ Application Handbook, 2014, 42-46.

Platinum-Group Elements in Soils and Street Dust of the Southeastern Administrative District of Moscow

NASA Astrophysics Data System (ADS)

Ladonin, D. V.

2018-03-01

The contents of five platinum-group metals (Ru, Rh, Pd, Ir, and Pt) in soils and street dust of the Southeastern administrative district (SEAD) of Moscow have been determined. The contents of these elements in soils may considerably exceed their natural abundances in the lithosphere and are characterized by considerable variability and asymmetric frequency distribution. A close correlation between Rh, Pd, and Pt contents in soils and street dust has been shown. The data on the contents of the elements and the ratios between them suggest that motor vehicles are the major source of pollution of soils and street dust in the studied district.

Tuned sensitivity towards H{sub 2}S and NH{sub 3} with Cu doped barium strontium titanate materials

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

Simion, C. E., E-mail: simion@infim.ro; Teodorescu, V. S.; Stănoiu, A.

2014-11-05

The different amount of Cu-doped Barium Strontium Titanate (BST) thick film materials have been tested for their gas-sensing performances towards NH{sub 3} and H{sub 2}S under dry and 50% relative humidity (RH) background conditions. The optimum NH{sub 3} sensitivity was attained with 0.1mol% Cu-doped BST whereas the selective detection of H{sub 2}S was highlighted using 5mol% Cu-doped BST material. No cross-sensitivity effects to CO, NO{sub 2}, CH{sub 4} and SO{sub 2} were observed for all tested materials operated at their optimum temperature (200°C) under humid conditions (50% RH). The presence of humidity clearly enhances the gas sensitivity to NH{sub 3}more » and H{sub 2}S detection.« less

Flower-like Rh/Cu superhydrophobic coating via electrodeposition and its self-cleaning property

NASA Astrophysics Data System (ADS)

Zhao, N.; Lu, S. X.; Xu, W. G.; Cheng, X. L.

2017-01-01

Rh/Cu superhydrophobic coatings with textured flower-like dual micro-nano structures were fabricated on copper substrates via electrodesposition of Rh followed by annealing treatment. The scanning electron microscopy and X-ray diffraction pattern were conducted to analyse the morphology and chemical composition of the coating surfaces, respectively. The water drops exhibited a water contact angle of 168±1° and a sliding angle of 0±1° on the coating surfaces which were obtained by etching in concentrated hydrochloric acid and nitric acid, electrodeposited at -1.0 V for 30 min and annealing in an oven at 180°C for 60 min. The prepared superhydrophobic coatings showed excellent water repellence and self-cleaning property due to its extremely high water contact angle.

Development of Navy Methodologies for Relating Logistics Resources to Materiel Readiness.

DTIC Science & Technology

1984-04-08

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Flux Crystal Growth of the RE 2Ru 3Ge 5 ( RE = La, Ce, Nd, Gd, Tb) Series and Their Magnetic and Metamagnetic Transitions

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

Bugaris, Daniel E.; Malliakas, Christos D.; Bud?ko, Sergey L.

Previously synthesized only as powders, single crystals of the RE 2Ru 3Ge 5 (RE = La, Ce, Nd, Gd, Tb) series of compounds have been now been obtained from molten In. We report that these materials crystallize with the U 2Co 3Si 5-type structure in orthorhombic space group Ibam with lattice parameters a ~ 10.00-9.77 Å (La-Tb), b ~ 12.51-12.35 Å, and c ~ 5.92-5.72 Å. The structure is a three-dimensional framework consisting of RuGe 5 and RuGe 6 units, as well as Ge-Ge zigzag chains. This structure type, along with the other five (Sc 2Fe 3Si 5, Lu 2Comore » 3Si 5, Y 2Rh 3Sn 5, Yb 2Ir 3Ge 5, and Yb 2Pt 3Sn 5) to compose the RE 2T 3X 5 phase space, are discussed in depth. For the three compounds with RE = Nd, Gd, and Tb, multiple magnetic transitions and metamagnetic behavior are observed. Lastly, electronic band structure calculations performed on La 2Ru 3Ge 5 indicate that these materials have a negative band gap and are semimetallic in nature.« less

Flux Crystal Growth of the RE 2Ru 3Ge 5 ( RE = La, Ce, Nd, Gd, Tb) Series and Their Magnetic and Metamagnetic Transitions

DOE PAGES

Bugaris, Daniel E.; Malliakas, Christos D.; Bud?ko, Sergey L.; ...

2017-11-21

Previously synthesized only as powders, single crystals of the RE 2Ru 3Ge 5 (RE = La, Ce, Nd, Gd, Tb) series of compounds have been now been obtained from molten In. We report that these materials crystallize with the U 2Co 3Si 5-type structure in orthorhombic space group Ibam with lattice parameters a ~ 10.00-9.77 Å (La-Tb), b ~ 12.51-12.35 Å, and c ~ 5.92-5.72 Å. The structure is a three-dimensional framework consisting of RuGe 5 and RuGe 6 units, as well as Ge-Ge zigzag chains. This structure type, along with the other five (Sc 2Fe 3Si 5, Lu 2Comore » 3Si 5, Y 2Rh 3Sn 5, Yb 2Ir 3Ge 5, and Yb 2Pt 3Sn 5) to compose the RE 2T 3X 5 phase space, are discussed in depth. For the three compounds with RE = Nd, Gd, and Tb, multiple magnetic transitions and metamagnetic behavior are observed. Lastly, electronic band structure calculations performed on La 2Ru 3Ge 5 indicate that these materials have a negative band gap and are semimetallic in nature.« less

Defect-mediated, thermally-activated encapsulation of metals at the surface of graphite

DOE PAGES

Zhou, Yinghui; Lii-Rosales, Ann; Kim, Minsung; ...

2017-11-04

Here, we show that 3 metals – Dy, Ru, and Cu – can form multilayer intercalated (encapsulated) islands at the graphite (0001) surface if 2 specific conditions are met: Defects are introduced on the graphite terraces to act as entry portals, and the metal deposition temperature is well above ambient. Focusing on Dy as a prototype, we show that surface encapsulation is much different than bulk intercalation, because the encapsulated metal takes the form of bulk-like rafts of multilayer Dy, rather than the dilute, single-layer structure known for the bulk compound. Carbon-covered metallic rafts even form for relatively unreactive metalsmore » (Ru and Cu) which have no known bulk intercalation compound.« less

2,5,8,11-Tetraalkenyl Perylene Bisimides: Direct Regioselective Synthesis and Enhanced π-π Stacking Interaction.

PubMed

Zhang, Li; He, Dezhi; Liu, Yudong; Wang, Kun; Guo, Zongxia; Lin, Jianbin; Zhang, Hui-Jun

2016-11-18

A series of 2,5,8,11-tetraalkenyl perylene bisimide (PBI) derivatives were synthesized through Ru(II)- or Rh(III)-catalyzed regio- and steroselective oxidative C-H olefination in one step. The optical electronic and self-assembly of the 2,5,8,11-substituted PBIs were investigated, which showed great potential in optoelectronic applications.

Thermally Stable TiO2 - and SiO2 -Shell-Isolated Au Nanoparticles for In Situ Plasmon-Enhanced Raman Spectroscopy of Hydrogenation Catalysts.

PubMed

Hartman, Thomas; Weckhuysen, Bert M

2018-03-12

Raman spectroscopy is known as a powerful technique for solid catalyst characterization as it provides vibrational fingerprints of (metal) oxides, reactants, and products. It can even become a strong surface-sensitive technique by implementing shell-isolated surface-enhanced Raman spectroscopy (SHINERS). Au@TiO 2 and Au@SiO 2 shell-isolated nanoparticles (SHINs) of various sizes were therefore prepared for the purpose of studying heterogeneous catalysis and the effect of metal oxide coating. Both SiO 2 - and TiO 2 -SHINs are effective SHINERS substrates and thermally stable up to 400 °C. Nano-sized Ru and Rh hydrogenation catalysts were assembled over the SHINs by wet impregnation of aqueous RuCl 3 and RhCl 3 . The substrates were implemented to study CO adsorption and hydrogenation under in situ conditions at various temperatures to illustrate the differences between catalysts and shell materials with SHINERS. This work demonstrates the potential of SHINS for in situ characterization studies in a wide range of catalytic reactions. © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Density-functional theory study of the initial oxygen incorporation in Pd(111)

NASA Astrophysics Data System (ADS)

Todorova, Mira; Reuter, Karsten; Scheffler, Matthias

2005-05-01

Pd(111) has recently been shown to exhibit a propensity to form a subnanometer thin surface oxide film already well before a full monolayer coverage of adsorbed O atoms is reached on the surface. Aiming at an atomic-scale understanding of this finding, we study the initial oxygen incorporation into the Pd(111) surface using density-functional theory. We find that oxygen incorporation into the sub-surface region starts at essentially the same coverage as formation of the surface oxide. This implies that the role of sub-surface oxygen should be considered as that of a metastable precursor in the oxidation process of the surface. The mechanisms found to play a role towards the ensuing stabilization of an ordered oxidic structure with a mixed on-surface/sub-surface site occupation follow a clear trend over the late 4d transition metal series, as seen by comparing our data to previously published studies concerned with oxide formation at the basal surface of Ru, Rh, and Ag. The formation of a linearly aligned O-TM-O trilayered structure (TM=Ru,Rh,Pd,Ag) , together with an efficient coupling to the underlying substrate seem to be key ingredients in this respect.

Slater-Pauling behavior within quaternary intermetallic borides of the Ti{sub 3}Co{sub 5}B{sub 2} structure-type

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

Burghaus, Jens; Dronskowski, Richard, E-mail: drons@HAL9000.ac.rwth-aachen.d; Miller, Gordon J.

2009-10-15

First-principles, density-functional studies of several intermetallic borides of the general type M{sub 2}M'Ru{sub 5-n}Rh{sub n}B{sub 2} (n=0-5; M=Sc, Ti, Nb; M'=Fe, Co) show that the variation in saturation magnetic moment with valence-electron count follows a Slater-Pauling curve, with a maximum moment occurring typically at 66 valence electrons. The magnetic moments in these compounds occur primarily from the 3d electrons of the magnetically active M' sites, with some contribution from the Ru/Rh sites via magnetic polarization. Electronic DOS curves reveal that a rigid-band approach is a reasonable approximation for the estimation of saturation moments and the analysis of orbital interactions inmore » this family of complex borides. COHP analyses of the M'-M' orbital interactions indicate optimized interactions in the minority spin states for Co-containing phases, but strong bonding interactions remaining in Fe-containing phases. - Graphical abstract: Theoretically determined (spin-polarized LMTO-GGA) local magnetic moments as a function of the chemical valence Z for various intermetallic borides.« less

Surface interaction between cubic phase NaNbO3 nanoflowers and Ru nanoparticles for enhancing visible-light driven photosensitized photocatalysis

NASA Astrophysics Data System (ADS)

Chen, Wei; Hu, Yin; Ba, Mingwei

2018-03-01

Ru nanoparticles supported on perovskite NaNbO3 with cubic crystal structure and nanoflower-like morphology was prepared by a convenient solvothermal method combined with photo-deposition technique. Crystal structure, chemical component and surface valence states determined by XRD, XPS, TEM and SEM demonstrated the metastable cubic phase of perovskite NaNbO3, and its modified surface by Ru species. Optical and electrochemical analysis, such as UV-vis DRS, OTCS and EIS, indicated the excellent photoelectrochemical properties and the efficient electron transfer of the composites. Compared with naked and Ru-doped NaNbO3, the composite photocatalyst exhibited outstanding performance for the degradation of RhB under visible light irradiation due to the dye self-photosensitization and the surface interaction between Ru metal nanoparticles and semiconductor. In-situ reduction of surface Ru oxide species in the photocatalytic process assisted the further improvement of the photocatalytic activity and stability. Investigation of the main active species during the photocatalysis confirmed the efficient transfer of the photo-generated electrons and the positive effect of oxygen defects in NaNbO3. Finally, possible mechanism of the present visible-light driven photocatalysis was proposed in detail. This work provided an alternative strategy to enhance the visible-light photocatalytic efficiency of the catalyst with wide band gap on the basis of the synergistic effect of dye self-photosensitization, interaction between NaNbO3 and its surface Ru nanoparticles, and the "self-doping" of oxygen defects in NaNbO3.

Effect of Alloying Elements on Nb-Rich Portion of Nb-Si-X Ternary Systems and In Situ Crack Observation of Nb-Si-Based Alloys

NASA Astrophysics Data System (ADS)

Miura, Seiji; Hatabata, Toru; Okawa, Takuya; Mohri, Tetsuo

2014-03-01

To find a new route for microstructure control and to find additive elements beneficial for improving high-temperature strength, a systematic investigation is performed on hypoeutectic Nb-15 at. pct Si-X ternary alloys containing a transition element, Fe, Co, Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, Pt, or Au. Information on phase equilibrium is classified in terms of phase stability of silicide phases, α Nb5Si3, Nb4SiX, and Nb3Si, and the relationship between microstructure and mechanical properties both at room temperature and high temperature is investigated. All the additive elements are found to stabilize either α Nb5Si3 or Nb4SiX but destabilize Nb3Si. A microstructure of Nbss/α Nb5Si3 alloy composed of spheroidized α Nb5Si3 phase embedded in the Nbss matrix is effective for toughening, regardless of the initial as-cast microstructure. Also the plastic deformation of Nbss dendrites may effectively suppress the propagation of longer cracks. High-temperature strength of alloys is governed by the deformation of Nbss phase and increases with higher melting point additives.

Understanding of catalyst deactivation caused by sulfur poisoning and carbon deposition in steam reforming of liquid hydrocarbon fuels

NASA Astrophysics Data System (ADS)

Xie, Chao

2011-12-01

The present work was conducted to develop a better understanding on the catalyst deactivation in steam reforming of sulfur-containing liquid hydrocarbon fuels for hydrogen production. Steam reforming of Norpar13 (a liquid hydrocarbon fuel from Exxon Mobile) without and with sulfur was performed on various metal catalysts (Rh, Ru, Pt, Pd, and Ni) supported on different materials (Al2O3, CeO2, SiO2, MgO, and CeO2- Al2O3). A number of characterization techniques were applied to study the physicochemical properties of these catalysts before and after the reactions. Especially, X-ray absorption near edge structure (XANES) spectroscopy was intensively used to investigate the nature of sulfur and carbon species in the used catalysts to reveal the catalyst deactivation mechanism. Among the tested noble metal catalysts (Rh, Ru, Pt, and Pd), Rh catalyst is the most sulfur tolerant. Al2O3 and CeO2 are much better than SiO2 and MgO as the supports for the Rh catalyst to reform sulfur-containing hydrocarbons. The good sulfur tolerance of Rh/Al2O3 can be attributed to the acidic nature of the Al2O3 support and its small Rh crystallites (1-3 nm) as these characteristics facilitate the formation of electron-deficient Rh particles with high sulfur tolerance. The good catalytic performance of Rh/CeO2 in the presence of sulfur can be ascribed to the promotion effect of CeO2 on carbon gasification, which significantly reduced the carbon deposition on the Rh/CeO2catalyst. Steam reforming of Norpar13 in the absence and presence of sulfur was further carried out over CeO2-Al2O3 supported monometallic Ni and Rh and bimetallic Rh-Ni catalysts at 550 and 800 °C. Both monometallic catalysts rapidly deactivated at 550 °C, iv and showed poor sulfur tolerance. Although ineffective for the Ni catalyst, increasing the temperature to 800 °C dramatically improved the sulfur tolerance of the Rh catalyst. Sulfur K-edge XANES revealed that metal sulfide and organic sulfide are the dominant sulfur species on the used Ni catalyst, while sulfonate and sulfate predominate on the used Rh catalyst. The superior sulfur tolerance of the Rh/CeO2-Al2O3 catalyst at 800 °C may be associated with its capability in sulfur oxidation. It is very likely that the oxygenshielded sulfur structure of sulfonate and sulfate can suppress the poisoning impact of sulfur on Rh through inhibiting direct rhodium-sulfur interaction. Although the Rh-Ni catalyst exhibited better sulfur tolerance than the monometallic ones at 550 °C, its catalytic performance was inferior compared with the Rh catalyst in the sulfur-containing reaction at 800 °C probably due to the severe carbon deposition on the bimetallic catalyst. The last part of this work focuses on the influence of sulfur on the carbon deposition in steam reforming of liquid hydrocarbon fuels over CeO2-Al2O3 supported monometallic Ni and Rh catalysts at 800 ºC. Though abundant carbon deposits can accumulate on the pure CeO2-Al2O3 support due to fuel thermal cracking, the metal addition substantially mitigated the carbon deposition in the sulfur-free reaction. The presence of sulfur increased the carbon deposition on both catalysts, which has a much more significant impact for the Ni catalyst. Our results indicate that (I) the presence of sulfur can suppress carbon gasification and promote the formation of graphitic carbon on reforming catalysts, and (II) the Rh catalyst possesses stronger capability to maintain carbon gasification activity than the Ni catalyst in the presence of sulfur.

Rattler behavior in As skutterudites and oxy-skutterudites

NASA Astrophysics Data System (ADS)

Bridges, Frank; Car, Brad; Hoffman-Stapleton, Mikaela; Keiber, Trevor; Sutton, Logan; Maple, M. Brian

2014-03-01

We report EXAFS measurements for the series CeX4As12 (X = Fe, Ru, Os) and NdCu3Ru4O12 as a function of temperature for most elements in the structure. In each case the rare earth atom is a ``rattler'' atom, with a low Einstein temperature while the skutterudite cage structure is relatively stiff. From temperature dependencies of the correlated Debye model for the cage atoms, one can estimate the effective spring constant for various atom pairs. We also find for the oxy-skutterudites that the planar CuO4 sub-structure is very stiff, and likely vibrates as a rigid unit. We compare the behavior of the As-skutterudites with other skutterudites and with the oxy-skutterudites, and discuss in terms of the rigid cage model. The second neighbor pair Ce-X for the As-skutterudites is softer than expected while for the oxy-skutterudites the second neighbor Nd-Ru pair is stiffer than the nearest neighbor Nd-O pair. Models are need to explore this behavior. Support: NSF DMR1005568.

Ruthenium Nanoparticles Mediated Electrocatalytic Reduction of UO22+ Ions for Its Rapid and Sensitive Detection in Natural Waters.

PubMed

Gupta, Ruma; Sundararajan, Mahesh; Gamare, Jayashree S

2017-08-01

Reduction of UO 2 2+ ions to U 4+ ions is difficult due to involvement of two axially bonded oxygen atoms, and often requires a catalyst to lower the activation barrier. The noble metal nanoparticles (NPs) exhibit high electrocatalytic activity, and could be employed for the sensitive and rapid quantifications of U0 2 2+ ions in the aqueous matrix. Therefore, the Pd, Ru, and Rh NPs decorated glassy carbon electrode were examined for their efficacy toward electrocatalytic reduction of UO 2 2+ ions and observed that Ru NPs mediate efficiently the electro-reduction of UO 2 2+ ions. The mechanism of the electroreduction of UO 2 2+ by the RuNPs/GC was studied using density functional theory calculations which pointed different approach of 5f metal ions electroreduction unlike 4p metal ions such as As(III). RuNP decorated on the glassy carbon would be hydrated, which in turn assist to adsorb the uranyl sulfates through hydrogen bonding thus facilitated electro-reduction. Differential pulse voltammetric (DPV) technique, was used for rapid and sensitive quantification of UO 2 2+ ions. The RuNPs/GC based DPV technique could be used to determine the concentration of uranyl in a few minutes with a detection limit of 1.95 ppb. The RuNPs/GC based DPV was evaluated for its analytical performance using seawater as well lake water and groundwater spiked with known amounts of UO 2 2+ .

Anomalous Change of Hall Coefficient in Overdoped La2-xSrxCu1-yZnyO4 around x = 0.2

NASA Astrophysics Data System (ADS)

Tonishi, Jun; Suzuki, Takao; Goto, Takayuki

2006-09-01

The Hall coefficient (RH) has been measured in 0.5% Zn-doped La2-xSrxCu0.995Zn0.005O4 under high magnetic fields up to 12 T. With decreasing temperature, RH increases and begins to decrease below a temperature TRH. This characteristic temperature TRH has the local maximum around x = 0.195, and this Sr-concentration coincides with that the superconducting transition temperature is slightly suppressed. This behavior is quite similar to the phenomena observed in the stripe phase in x ˜ 0.12. These results suggest that the anomalous decrease of RH around x = 0.195 observed in this study is responsible for the "1/4"-anomaly [as reported by Kakinuma et al., Phys. Rev. B 59, 1491 (1999).].

Catalytic combustion of methane over commercial catalysts in presence of ammonia and hydrogen sulphide.

PubMed

Hurtado, Paloma; Ordóñez, Salvador; Vega, Aurelio; Díez, Fernando V

2004-05-01

The performance of different commercially available catalysts (supported Pd, Pt, Rh, bimetallic Pd-Pt, and Cr-Cu-Ti oxide catalyst) for the oxidation of methane, alone and in presence of ammonia and hydrogen sulphide is studied in this work. Catalysts performance was evaluated both in terms of activity and resistance to poisoning. The main conclusions are that supported Pd and Rh, present the highest activities for methane oxidation, both alone and in presence of ammonia, whereas they are severely poisoned in presence of H2S. Pt and Cr-Cu-Ti are less active but more sulphur resistant, but their activity is lower than the residual activity of sulphur-deactivated Pd and Rh catalysts. The Pd-Pt catalyst exhibits low activity and it is quickly deactivated in presence of hydrogen sulphide.

Electrochemical Growth of Single-Crystal Metal Nanowires via a Two-Dimensional Nucleation and Growth Mechanism.

PubMed

Tian, Mingliang; Wang, Jinguo; Kurtz, James; Mallouk, Thomas E; Chan, M H W

2003-07-01

Metallic nanowires (Au, Ag, Cu, Ni, Co, and Rh) with an average diameter of 40 nm and a length of 3-5 μm have been fabricated by electrodeposition in the pores of track-etched polycarbonate membranes. Structural characterizations by transmission electron microscopy (TEM) and electron diffraction showed that nanowires of Au, Ag, and Cu are single-crystalline with a preferred [111] orientation, whereas Ni, Co, and Rh wires are polycrystalline. Possible mechanisms responsible for nucleation and growth for single-crystal noble metals versus polycrystalline group VIII-B metals are discussed.

Catalytic upgrading of duckweed biocrude in subcritical water.

PubMed

Zhang, Caicai; Duan, Peigao; Xu, Yuping; Wang, Bing; Wang, Feng; Zhang, Lei

2014-08-01

Herein, a duckweed biocrude produced from the hydrothermal liquefaction of Lemna minor was treated in subcritical water with added H₂. Effects of several different commercially available materials such as Ru/C, Pd/C, Pt/C, Pt/γ-Al₂O₃, Pt/C-sulfide, Rh/γ-Al₂O₃, activated carbon, MoS₂, Mo₂C, Co-Mo/γ-Al₂O₃, and zeolite on the yields of product fractions and the deoxygenation, denitrogenation, and desulfurization of biocrude at 350°C were examined, respectively. All the materials showed catalytic activity for deoxygenation and desulfurization of the biocrude and only Ru/C showed activity for denitrogenation. Of those catalysts examined, Pt/C showed the best performance for deoxygenation. Among all the upgraded oils, the oil produced with Ru/C shows the lowest sulfur, the highest hydrocarbon content (25.6%), the highest energy recovery (85.5%), and the highest higher heating value (42.6 MJ/kg). The gaseous products were mainly unreacted H₂, CH₄, CO₂, and C₂H6. Copyright © 2014 Elsevier Ltd. All rights reserved.

Estimation and Mitigation of Unmodeled Errors for a Pseudolite Based Reference System

DTIC Science & Technology

2005-03-01

42700− hs)× 10−6 5Ts∆hu [( 1− ∆hAPL 42700− hs )5 − ( 1− ∆hAPL + ∆hu 42700− hs )5] Ru + Ns × (13000− hs)× 10−6 5∆hu [( 1− ∆hAPL 13000− hs )5 − ( 1− ∆hAPL...hu 13000− hs )5] Ru (1.1) where Ns = 2.277(10 −6) RH T 2s ( 10 7.4475(Ts−273K) Ts−38.3K ) (1.2) and τAPL,u = tropospheric delay for mobile receiver...humidity (percent) Ns = surface refractivity 1-8 Bouska and Raquet [4] discuss the effects of tropospheric reduction efforts re- lating to DGPS and

Experimental Study of the Partitioning of Siderophile Elements in a Crystallizing Lunar Magma Ocean

NASA Technical Reports Server (NTRS)

Galenas, M.; Righter, K.; Danielson, L.; Pando, K.; Walker, R. J.

2012-01-01

The distributions of trace elements between the lunar interior and pristine crustal rocks were controlled by the composition of starting materials, lunar core formation, and crystallization of the lunar magma ocean (LMO) [1]. This study focuses on the partitioning of highly siderophile elements (HSE) including Re, Os, Ir, Ru, Pt, Rh, Pd and Au as well as the moderately siderophile elements Mo and W, and the lithophile elements of Hf and Sr. Our experiments also include Ga, which can be slightly siderophile, but is mostly considered to be chalcophile. Partitioning of these elements is not well known at the conditions of a crystallizing LMO. Previous studies of HSE partitioning in silicate systems have yielded highly variable results for differing oxygen fugacity (fO2) and pressure [2-4]. For example, under certain conditions Pt is compatible in clinopy-roxene [2] and Rh and Ru are compatible in olivine [3]. The silicate compositions used for these experiments were nominally basaltic. Ruthenium, Rh, and Pd are incompatible in plagioclase under these conditions[4]. However, this latter study was done at extremely oxidizing conditions and at atmospheric pressure, possibly limiting the applicability for consideration of conditions of a crystallizing LMO. In this study we address the effects of pressure and oxygen fugacity on the crystal/liquid partition coefficients of these trace elements. We are especially interested in the plagioclase/melt partition coefficients so that it may be possible to use reverse modeling to constrain the concentrations of these elements in the lunar mantle through their abundances in pristine crustal rocks.

USSR and Eastern Europe Scientific Abstracts Geophysics, Astronomy and Space No. 404

DTIC Science & Technology

1977-09-01

atmospheric circulation. A reliable linear correlation was established between the monthly fallout activity of 10^Ru + -^Rh and monthly precipitation and...therefore the washing out of this radionuclide from tropospheric air by precipitation is more important for its fallout. [153] ANALYTICAL...development of some methods for predicting definite weather phenomena (such as precipitation ), taking into account the evolution of the

Air core detectors for Cerenkov-free scintillation dosimetry of brachytherapy β-sources.

PubMed

Eichmann, Marion; Thomann, Benedikt

2017-09-01

Plastic scintillation detectors are used for dosimetry in small radiation fields with high dose gradients, e.g., provided by β-emitting sources like 106 Ru/ 106 Rh eye plaques. A drawback is a background signal caused by Cerenkov radiation generated by electrons passing the optical fibers (light guides) of this dosimetry system. Common approaches to correct for the Cerenkov signal are influenced by uncertainties resulting from detector positioning and calibration procedures. A different approach to avoid any correction procedure is to suppress the Cerenkov signal by replacing the solid core optical fiber with an air core light guide, previously shown for external beam therapy. In this study, the air core concept is modified and applied to the requirements of dosimetry in brachytherapy, proving its usability for measuring water energy doses in small radiation fields. Three air core detectors with different air core lengths are constructed and their performance in dosimetry for brachytherapy β-sources is compared with a standard two-fiber system, which uses a second fiber for Cerenkov correction. The detector systems are calibrated with a 90 Sr/ 90 Y secondary standard and tested for their angular dependence as well as their performance in depth dose measurements of 106 Ru/ 106 Rh sources. The signal loss relative to the standard detector increases with increasing air core length to a maximum value of 58.3%. At the same time, however, the percentage amount of Cerenkov light in the total signal is reduced from at least 12.1% to a value below 1.1%. There is a linear correlation between induced dose and measured signal current. The air core detectors determine the dose rates for 106 Ru/ 106 Rh sources without any form of correction for the Cerenkov signal. The air core detectors show advantages over the standard two-fiber system especially when measuring in radiation fields with high dose gradients. They can be used as simple one-fiber systems and allow for an almost Cerenkov-free scintillation dosimetry of brachytherapy β-sources. © 2017 American Association of Physicists in Medicine.

Solvothermal growth of a ruthenium metal-organic framework featuring HKUST-1 structure type as thin films on oxide surfaces.

PubMed

Kozachuk, Olesia; Yusenko, Kirill; Noei, Heshmat; Wang, Yuemin; Walleck, Stephan; Glaser, Thorsten; Fischer, Roland A

2011-08-14

Phase-pure crystalline thin films of a mixed-valence Ru(2)(II,III) metal-organic framework with 1,3,5-benzenetricarboxylate (btc) as a linker were solvothermally grown on amorphous alumina and silica surfaces. Based on the Rietveld refinement, the structure of Ru-MOF was assigned to be analogous to [Cu(3)(btc)(2)] (HKUST-1). This journal is © The Royal Society of Chemistry 2011

Determination of boron in blood, urine and bone by electrothermal atomic absorption spectrometry using zirconium and citric acid as modifiers

NASA Astrophysics Data System (ADS)

Burguera, Marcela; Burguera, José Luis; Rondón, Carlos; Carrero, Pablo

2001-10-01

A comparative study of various potential chemical modifiers (Au, Ba, Be, Ca, Cr, Ir, La, Lu, Mg, Ni, Pd, Pt, Rh, Ru, Sr, V, W, and Zr), and different 'coating' treatments (Zr, W, and W+Rh) of the pyrolytic graphite platform of a longitudinally heated graphite tube atomizer for thermal stabilization and determination of boron was undertaken. The use of Au, Ba, Be, Cr, Ir, Pt, Rh, Ru, Sr and V as modifiers, and of W+Rh coating produced erratic, and noisy signals, while the addition of La, Ni and Pd as modifiers, and the W coating had positive effects, but with too high background absorption signals, rendering their use unsuitable for boron determination even in aqueous solutions. The atomic absorption signal for boron was increased and stabilized when the platform was coated with Zr, and by the addition of Ca, Mg, Lu, W or Zr as modifiers. Only the addition of 10 μg of Zr as a modifier onto Zr-treated platforms allowed the use of a higher pyrolysis temperature without analyte losses. The memory effect was minimized by incorporating a cleaning step with 10 μl of 50 g l -1 NH 4F HF after every three boron measurements. The addition of 10 μl of 15 g l -1 citric acid together with Zr onto Zr-treated platforms significantly improved the characteristic mass to m0=282 pg, which is adequate for biological samples such as urine and bone, although the sensitivity was still inadequate for the determination of boron in blood of subjects without supplementary diet. Under optimized conditions, the detection limit (3σ) was 60 μg l -1. The amount of boron found in whole blood, urine and femur head samples from patients with osteoporosis was in agreement with values previously reported in the literature.

cis,cis-Muconic acid: separation and catalysis to bio-adipic acid for nylon-6,6 polymerization

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

Vardon, Derek R.; Rorrer, Nicholas A.; Salvachúa, Davinia

cis,cis-Muconic acid is a polyunsaturated dicarboxylic acid that can be produced renewably via the biological conversion of sugars and lignin-derived aromatic compounds. Subsequently, muconic acid can be catalytically converted to adipic acid -- the most commercially significant dicarboxylic acid manufactured from petroleum. Nylon-6,6 is the major industrial application for adipic acid, consuming 85% of market demand; however, high purity adipic acid (99.8%) is required for polymer synthesis. As such, process technologies are needed to effectively separate and catalytically transform biologically derived muconic acid to adipic acid in high purity over stable catalytic materials. To that end, this study: (1) demonstratesmore » bioreactor production of muconate at 34.5 g L-1 in an engineered strain of Pseudomonas putida KT2440, (2) examines the staged recovery of muconic acid from culture media, (3) screens platinum group metals (e.g., Pd, Pt, Rh, Ru) for activity and leaching stability on activated carbon (AC) and silica supports, (4) evaluates the time-on-stream performance of Rh/AC in a trickle bed reactor, and (5) demonstrates the polymerization of bio-adipic acid to nylon-6,6. Separation experiments confirmed AC effectively removed broth color compounds, but subsequent pH/temperature shift crystallization resulted in significant levels of Na, P, K, S and N in the crystallized product. Ethanol dissolution of muconic acid precipitated bulk salts, achieving a purity of 99.8%. Batch catalysis screening reactions determined that Rh and Pd were both highly active compared to Pt and Ru, but Pd leached significantly (1-9%) from both AC and silica supports. Testing of Rh/AC in a continuous trickle bed reactor for 100 h confirmed stable performance after 24 h, although organic adsorption resulted in reduced steady-state activity. Lastly, polymerization of bio-adipic acid with hexamethyldiamine produced nylon-6,6 with comparable properties to its petrochemical counterpart, thereby demonstrating a path towards bio-based nylon production via muconic acid.« less

Preparation, Iodometric Analysis, and Classroom Demonstration of Superconductivity in YBa2Cu3O8-x.

ERIC Educational Resources Information Center

Harris, Daniel C.; And Others

1987-01-01

Described is a student preparation of YBa2Cu3O8-x, a classroom demonstration of its superconductivity, and an analytical chemistry experiment dealing with the oxidation state of copper in the material. (RH)

Sensitization of TiO₂ nanosheets with Cu-biphenylamine frame work to enhance photocatalytic degradation performance of toxic organic contaminants: Synthesis, mechanism and kinetic studies.

PubMed

Khan, Muhammad Asim; Mutahir, Sadaf; Wang, Fengyun; Lei, Wu; Xia, Mingzhu

2018-06-25

TNS/Cu(X) composite materials were firstly synthesized via simple overnight stirring of TNS in the methanolic solution of Cu complexes. The developed TNS/Cu(X) composites having a well-designed nanostructure, in which TNS and Cu complexes were closely bounded with each other. Biphenylamine complexes fixed on TNS surface in form of Nano-capsules, which were confirmed by TEM and SEM, thus improving the surface area and subsequently charge separation. Innovatively merged photocatalysts of Cu complexes with TNS were successfully verified for photocatalytic mineralization of colored and colorless organic contaminants under the visible light degradation. As compared to original TNS, TNS/Cu(BA) showed prominent improvement in the catalytic actions. Kinetics i.e. t1/2 (half-life times period), Kapp, and R2 (linear regression co-efficient) were also studied. The amended materials created charge separation, by means of electrons gathering at the higher CB, and holes gathering at lower level VB of Cu complex, therefore improving mineralization efficiency of electrons and holes. TNS/Cu(BA) degrade 99% to 99.6% of MO & RhB dyes in 120 min, and 160 min, respectively, and 68 % of phenol and 53% of TCP were destroyed in 180 min. The resilient holes can directly destroy MO, RhB, phenol, and TCP. © 2018 IOP Publishing Ltd.

Enhanced performance of direct Z-scheme CuS-WO3 system towards photocatalytic decomposition of organic pollutants under visible light

NASA Astrophysics Data System (ADS)

Song, Chundong; Wang, Xiang; Zhang, Jing; Chen, Xuebing; Li, Can

2017-12-01

CuS-WO3 composites were synthesized by an in situ solution method at low temperature. The crystalline phase, morphology, particle size, and the optical properties of CuS-WO3 samples were characterized by XRD, SEM, XPS, and UV-vis diffuse reflectance spectra. CuS-WO3 composites showed much higher activity for photocatalytic degradation of RhB as compared with WO3 and CuS. The degradation rate constant over 1 wt% CuS-WO3 catalyst was 4.4 times and 9.2 times higher than that of WO3 and CuS, respectively. It is found that holes (h+) and superoxide radical anions (rad O2-) are the dominant reactive species by using methanol, disodium ethylenediaminetetraacetate (EDTA) and ascorbic acid as scavengers. Band structure analysis shows that bottom of CB of WO3 is very similar with and higher (ca. 0.01 eV) than the top of VB of CuS. The results of PL showed that the similarity renders the recombination between photogenerated holes on the VB of CuS and photogenerated electrons on the CB of WO3 possible and easy, forming a direct Z-scheme in CuS-WO3. This result in that more electrons in the CB of CuS and holes in the VB of WO3 survived, and then participated in the photocatalytic degradation of RhB, showing an increased activity.

Enhanced performance of direct Z-scheme CuS-WO 3 system towards photocatalytic decomposition of organic pollutants under visible light

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

Song, Chundong; Wang, Xiang; Zhang, Jing

CuS-WO 3 composites were synthesized by an in situ solution method at low temperature. The crystalline phase, morphology, particle size, and the optical properties of CuS-WO 3 samples were characterized by XRD, SEM, XPS, and UV–vis diffuse reflectance spectra. CuS-WO 3 composites showed much higher activity for photocatalytic degradation of RhB as compared with WO 3 and CuS. The degradation rate constant over 1 wt% CuS-WO 3 catalyst was 4.4 times and 9.2 times higher than that of WO 3 and CuS, respectively. It is found that holes (h+) and superoxide radical anions (O2-) are the dominant reactive species bymore » using methanol, disodium ethylenediaminetetraacetate (EDTA) and ascorbic acid as scavengers. Band structure analysis shows that bottom of CB of WO 3 is very similar with and higher (ca. 0.01 eV) than the top of VB of CuS. The results of PL showed that the similarity renders the recombination between photogenerated holes on the VB of CuS and photogenerated electrons on the CB of WO 3 possible and easy, forming a direct Z-scheme in CuS-WO 3. This result in that more electrons in the CB of CuS and holes in the VB of WO 3 survived, and then participated in the photocatalytic degradation of RhB, showing an increased activity.« less

Electron Flow through Proteins

PubMed Central

Gray, Harry B.; Winkler, Jay R.

2009-01-01

Electron transfers in photosynthesis and respiration commonly occur between metal-containing cofactors that are separated by large molecular distances. Employing laser flash-quench triggering methods, we have shown that 20-Å, coupling-limited FeII to RuIII and CuI to RuIII electron tunneling in Ru-modified cytochromes and blue copper proteins can occur on the microsecond timescale both in solutions and crystals. Redox equivalents can be transferred even longer distances by multistep tunneling, often called hopping, through intervening amino acid side chains. Our work has established that 20-Å hole hopping through an intervening tryptophan is two orders of magnitude faster than single-step electron tunneling in a Re-modified blue copper protein. PMID:20161522

Derivation of the P2T Criterion (in Closed Form) Based on the Frey Shear Band Mechanism

DTIC Science & Technology

1984-01-01

max 6d/d = G (12) max o u Pil < o .tlllilltt, >. X !5 < Q: o W) TJ C rH CU •H ed •P in -H 03 W 4-" FH cd C 03 Cu <U P...C 3 -H 10 T3 cd T3 O H s h ♦J 03 PH If) X3 -d rH fH ^H ed 03 OJ -H (1) •H -t-i Xi MH -H in c X’H <D ■M 43 • H 0 +J O...P o c a> rH X! 0 M 03 w C M •H O 03 u S & K <u TO S 0) +-> FH O ^—^ o3 W) y ^ cd i S: •H -H O -d T3 T3 iH CD *W P O nj

Monte Carlo Simulation of X-Ray Spectra in Mammography and Contrast-Enhanced Digital Mammography Using the Code PENELOPE

NASA Astrophysics Data System (ADS)

Cunha, Diego M.; Tomal, Alessandra; Poletti, Martin E.

2013-04-01

In this work, the Monte Carlo (MC) code PENELOPE was employed for simulation of x-ray spectra in mammography and contrast-enhanced digital mammography (CEDM). Spectra for Mo, Rh and W anodes were obtained for tube potentials between 24-36 kV, for mammography, and between 45-49 kV, for CEDM. The spectra obtained from the simulations were analytically filtered to correspond to the anode/filter combinations usually employed in each technique (Mo/Mo, Rh/Rh and W/Rh for mammography and Mo/Cu, Rh/Cu and W/Cu for CEDM). For the Mo/Mo combination, the simulated spectra were compared with those obtained experimentally, and for spectra for the W anode, with experimental data from the literature, through comparison of distribution shape, average energies, half-value layers (HVL) and transmission curves. For all combinations evaluated, the simulated spectra were also compared with those provided by different models from the literature. Results showed that the code PENELOPE provides mammographic x-ray spectra in good agreement with those experimentally measured and those from the literature. The differences in the values of HVL ranged between 2-7%, for anode/filter combinations and tube potentials employed in mammography, and they were less than 5% for those employed in CEDM. The transmission curves for the spectra obtained also showed good agreement compared to those computed from reference spectra, with average relative differences less than 12% for mammography and CEDM. These results show that the code PENELOPE can be a useful tool to generate x-ray spectra for studies in mammography and CEDM, and also for evaluation of new x-ray tube designs and new anode materials.

A Systematic Transport and Thermodynamic Study of Heavy Transition Metal Oxides with Hexagonal Structure

NASA Astrophysics Data System (ADS)

Butrouna, Kamal

There is no apparent, dominant interaction in heavy transition metal oxides (TMO), especially in 5d-TMO, where all relevant interactions are of comparable energy scales, and therefore strongly compete. In particular, the spin-orbit interaction (SOI) strongly competes with the electron-lattice and on-site Coulomb interaction (U). Therefore, any tool that allows one to tune the relative strengths of SOI and U is expected to offer an opportunity for the discovery and study of novel materials. BaIrO3 is a magnetic insulator driven by SOI, whereas the isostructural BaRuO3 is a paramagnetic metal. The contrasting ground states have been shown to result from the critical role of SOI in the iridate. This dissertation thoroughly examines a wide array of newly observed novel phenomena induced by adjusting the relative strengths of SOI and U via a systematic chemical substitution of the Ru4+(4d 4) ions for Ir4+(5d5) ions in BaIrO3, i.e., in high quality single crystals of BaIr1--x RuxO3(0.0 ≤ x ≤ 1.0). Our investigation of structural, magnetic, transport and thermal properties reveals that Ru substitution directly rebalances the competing energies so profoundly that it generates a rich phase diagram for BaIr 1--xRuxO 3 featuring two major effects: (1) Light Ru doping (0 ≤ x ≤ 0.15) prompts a simultaneous and precipitous drop in both the magnetic ordering temperature TC and the electrical resistivity, which exhibits metal-insulator transition at around TC. (2) Heavier Ru doping (0.41 ≤ x ≤ 0.82) induces a robust metallic and spin frustration state. For comparison and contrast, we also substituted Rh4+(4d 5) ions for Ir4+(5d5) ions in BaIrO3, i.e. in BaIr1--xRhxO 3(0.0 ≤ x ≤ 0.1), where Rh only reduces the SOI, but without altering the band filling. Hence, this system remains tuned at the Mott instability and is very susceptible to disorder scattering which gives rise to Anderson localization. KEYWORDS: spin-orbit interaction, heavy transition metal oxides, barium iridate, metal-insulator transition, magnetic order.

Radiosondes Corrected for Inaccuracy in RH Measurements

DOE Data Explorer

Miloshevich, Larry

2008-01-15

Corrections for inaccuracy in Vaisala radiosonde RH measurements have been applied to ARM SGP radiosonde soundings. The magnitude of the corrections can vary considerably between soundings. The radiosonde measurement accuracy, and therefore the correction magnitude, is a function of atmospheric conditions, mainly T, RH, and dRH/dt (humidity gradient). The corrections are also very sensitive to the RH sensor type, and there are 3 Vaisala sensor types represented in this dataset (RS80-H, RS90, and RS92). Depending on the sensor type and the radiosonde production date, one or more of the following three corrections were applied to the RH data: Temperature-Dependence correction (TD), Contamination-Dry Bias correction (C), Time Lag correction (TL). The estimated absolute accuracy of NIGHTTIME corrected and uncorrected Vaisala RH measurements, as determined by comparison to simultaneous reference-quality measurements from Holger Voemel's (CU/CIRES) cryogenic frostpoint hygrometer (CFH), is given by Miloshevich et al. (2006).

Infrared photorefractive effect in doped KNbO3 crystals

NASA Astrophysics Data System (ADS)

Medrano, C.; Zgonik, M.; Liakatas, I.; Günter, P.

1996-11-01

The photorefractive sensitivity of potassium niobate crystals doped with Ce, Co, Cu, Fe, Mn, Ni, and Rh and double-doped with Mn and Rh is investigated over an extended spectral range. We present experimental evidence on extrinsic properties important for the photorefractive effect, such as absorption and effective trap density. Photorefractive gratings are investigated with two-wave mixing experiments. Results on exponential gain, response time, and photorefractive sensitivity at near-infrared wavelengths are reported. The best photorefractive sensitivities at 860 and 1064 nm were obtained in crystals doped with Rh, Fe, Mn, and Mn-Rh. This makes them suitable for applications at laser-diode wavelengths; at 1064 nm, however, Rh:KNbO3 shows a better photorefractive sensitivity than the others. .

Kinetic and catalytic analysis of mesoporous metal oxides on the oxidation of Rhodamine B

NASA Astrophysics Data System (ADS)

Xaba, Morena S.; Noh, Ji-Hyang; Mokgadi, Keabetswe; Meijboom, Reinout

2018-05-01

In this study, we demonstrate the synthesis and catalytic activity of different mesoporous transition metal oxides, silica (SiO2), copper oxide (CuO), chromium oxide (Cr2O3), iron oxide (Fe2O3) cobalt oxide (Co3O4), cerium oxide (CeO2) and nickel oxide (NiO), on the oxidation of a pollutant dye, Rhodamine B (RhB). These metal oxides were synthesized by inverse micelle formation method and characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), adsorption-desorption isotherms (BET) and H2-temperature programmed reduction (TPR). UV-vis spectrophotometry was used to monitor the time-resolved absorbance of RhB at λmax = 554 nm. Mesoporous copper oxide was calcined at different final heating temperatures of 250, 350, 450 and 550 °C, and each mesoporous copper oxide catalyst showed unique physical properties and catalytic behavior. Mesoporous CuO-550 with the smallest characteristic path length δ, proved to be the catalyst of choice for the oxidation of RhB in aqueous media. We observed that the oxidation of RhB in aqueous media is dependent on the crystallite size and characteristic path length of the mesoporous metal oxide. The Langmuir-Hinshelwood model was used to fit the experimental data and to prove that the reaction occurs on the surface of the mesoporous CuO. The thermodynamic parameters, EA, ΔH#, ΔS# and ΔG# were calculated and catalyst recycling and reusability were demonstrated.

75 FR 6854 - Airworthiness Directives; Dassault-Aviation Model Falcon 900EX Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-12

... and passenger Right-Hand (RH) oxygen lines may both interfere with the frame 8 of the aeroplane structure. A subsequent design review of the oxygen lines routing has confirmed that, on certain aeroplanes, equipped in RH mid-cabin with a 115 cu-ft oxygen cylinder, the installation of the line support assembly at...

[Bifunctional chelates of Rh-105, Au-199, and other metallic radionuclides as potential radiotherapeutic agents

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

Not Available

1991-12-31

Progress during this period is reported under the following headings: Diethylenetriamine based and related bifunctional chelating agents and their complexation with Rh-105, Au-198, Pd-109, cu-67, In-111, and Co-57; studies of Pd-109, Rh-105 and Tc-99m with bifunctional chelates based on phenylenediamine; establishment of an appropriate protein assay method for conjugated proteins; studies of new bifunctional Bi, Tri and tetradentate amine oxime ligands with Rh-105; IgG and antibody B72.3 conjugation studies by HPLC Techniques with bifunctional metal chelates; and progress on ligand systems for Au(III).

(Bifunctional chelates of Rh-105, Au-199, and other metallic radionuclides as potential radiotherapeutic agents)

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

Not Available

1991-01-01

Progress during this period is reported under the following headings: Diethylenetriamine based and related bifunctional chelating agents and their complexation with Rh-105, Au-198, Pd-109, cu-67, In-111, and Co-57; studies of Pd-109, Rh-105 and Tc-99m with bifunctional chelates based on phenylenediamine; establishment of an appropriate protein assay method for conjugated proteins; studies of new bifunctional Bi, Tri and tetradentate amine oxime ligands with Rh-105; IgG and antibody B72.3 conjugation studies by HPLC Techniques with bifunctional metal chelates; and progress on ligand systems for Au(III).

Molecule-based magnets formed by bimetallic three-dimensional oxalate networks and chiral tris(bipyridyl) complex cations. The series [ZII(bpy)3][ClO4][MIICrIII(ox)3] (ZII = Ru, Fe, Co, and Ni; MII = Mn, Fe, Co, Ni, Cu, and Zn; ox = oxalate dianion).

PubMed

Coronado, E; Galán-Mascarós, J R; Gómez-García, C J; Martínez-Agudo, J M

2001-01-01

The synthesis, structure, and physical properties of the series of molecular magnets formulated as [ZII(bpy)3][ClO4][MIICrIII(ox)3] (ZII = Ru, Fe, Co, and Ni; MII = Mn, Fe, Co, Ni, Cu, and Zn; ox = oxalate dianion) are presented. All the compounds are isostructural to the [Ru(bpy)3][ClO4][MnCr(ox)3] member whose structure (cubic space group P4(1)32 with a = 15.506(2) A, Z = 4) consists of a three-dimensional bimetallic network formed by alternating MII and CrIII ions connected by oxalate anions. The identical chirality (lambda in the solved crystal) of all the metallic centers determines the 3D chiral structure adopted by these compounds. The anionic 3D sublattice leaves some holes where the chiral [Z(bpy)3]2+ and ClO4- counterions are located. These compounds behave as soft ferromagnets with ordering temperatures up to 6.6 K and coercive fields up to 8 mT.

A Readily Accessible Class of Chiral Cp Ligands and their Application in RuII -Catalyzed Enantioselective Syntheses of Dihydrobenzoindoles.

PubMed

Wang, Shou-Guo; Park, Sung Hwan; Cramer, Nicolai

2018-05-04

Chiral cyclopentadienyl (Cp x ) ligands have a large application potential in enantioselective transition-metal catalysis. However, the development of concise and practical routes to such ligands remains in its infancy. We present a convenient and efficient two-step synthesis of a novel class of chiral Cp x ligands with tunable steric properties that can be readily used for complexation, giving Cp x Rh I , Cp x Ir I , and Cp x Ru II complexes. The potential of this ligand class is demonstrated with the latter in the enantioselective cyclization of azabenzonorbornadienes with alkynes, affording dihydrobenzoindoles in up to 98:2 e.r., significantly outperforming existing binaphthyl-derived Cp x ligands. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Progesterone Directly and Rapidly Inhibits GnRH Neuronal Activity via Progesterone Receptor Membrane Component 1

PubMed Central

Bashour, Nicholas Michael

2012-01-01

GnRH neurons are essential for reproduction, being an integral component of the hypothalamic-pituitary-gonadal axis. Progesterone (P4), a steroid hormone, modulates reproductive behavior and is associated with rapid changes in GnRH secretion. However, a direct action of P4 on GnRH neurons has not been previously described. Receptors in the progestin/adipoQ receptor family (PAQR), as well as progesterone receptor membrane component 1 (PgRMC1) and its partner serpin peptidase inhibitor, clade E (nexin, plasminogen activator inhibitor type 1) mRNA binding protein 1 (SERBP1), have been shown to mediate rapid progestin actions in various tissues, including the brain. This study shows that PgRMC1 and SERBP1, but not PAQR, are expressed in prenatal GnRH neurons. Expression of PgRMC1 and SERBP1 was verified in adult mouse GnRH neurons. To investigate the effect of P4 on GnRH neuronal activity, calcium imaging was used on primary GnRH neurons maintained in explants. Application of P4 significantly decreased the activity of GnRH neurons, independent of secretion of gamma-aminobutyric acidergic and glutamatergic input, suggesting a direct action of P4 on GnRH neurons. Inhibition was not blocked by RU486, an antagonist of the classic nuclear P4 receptor. Inhibition was also maintained after uncoupling of the inhibitory regulative G protein (Gi/o), the signal transduction pathway used by PAQR. However, AG-205, a PgRMC1 ligand and inhibitor, blocked the rapid P4-mediated inhibition, and inhibition of protein kinase G, thought to be activated downstream of PgRMC1, also blocked the inhibitory activity of P4. These data show for the first time that P4 can act directly on GnRH neurons through PgRMC1 to inhibit neuronal activity. PMID:22822163

Ternary Pt9RhFex Nanoscale Alloys as Highly Efficient Catalysts with Enhanced Activity and Excellent CO-Poisoning Tolerance for Ethanol Oxidation.

PubMed

Wang, Peng; Yin, Shibin; Wen, Ying; Tian, Zhiqun; Wang, Ningzhang; Key, Julian; Wang, Shuangbao; Shen, Pei Kang

2017-03-22

To address the problems of high cost and poor stability of anode catalysts in direct ethanol fuel cells (DEFCs), ternary nanoparticles Pt 9 RhFe x (x = 1, 3, 5, 7, and 9) supported on carbon powders (XC-72R) have been synthesized via a facile method involving reduction by sodium borohydride followed by thermal annealing in N 2 at ambient pressure. The catalysts are physically characterized by X-ray diffraction, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy, and their catalytic performance for the ethanol oxidation reaction (EOR) is evaluated by cyclic and linear scan voltammetry, CO-stripping voltammograms, and chronopotentiometry. All the Pt 9 RhFe x /C catalysts of different atomic ratios produce high EOR catalytic activity. The catalyst of atomic ratio composition 9:1:3 (Pt/Rh/Fe) has the highest activity and excellent CO-poisoning tolerance. Moreover, the enhanced EOR catalytic activity on Pt 9 RhFe 3 /C when compared to Pt 9 Rh/C, Pt 3 Fe/C, and Pt/C clearly demonstrates the presence of Fe improves catalytic performance. Notably, the onset potential for CO oxidation on Pt 9 RhFe 3 /C (0.271 V) is ∼55, 75, and 191 mV more negative than on Pt 9 Rh/C (0.326 V), Pt 3 Fe/C (0.346 V), and Pt/C (0.462 V), respectively, which implies the presence of Fe atoms dramatically improves CO-poisoning tolerance. Meanwhile, compared to the commercial PtRu/C catalyst, the peak potential on Pt 9 RhFe 3 /C for CO oxidation was just slightly changed after several thousand cycles, which shows high stability against the potential cycling. The possible mechanism by which Fe and Rh atoms facilitate the observed enhanced performance is also considered herein, and we conclude Pt 9 RhFe 3 /C offers a promising anode catalyst for direct ethanol fuel cells.

A Reactive Oxide Overlayer on Rh Nanoparticles during CO Oxidation and Its Size Dependence Studied by in Situ Ambient Pressure XPS

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

Grass, Michael E.; Zhang, Yawen; Butcher, Derek R.

2008-09-15

CO oxidation is one of the most studied heterogeneous reactions, being scientifically and industrially important, particularly for removal of CO from exhaust streams and preferential oxidation for hydrogen purification in fuel cell applications. The precious metals Ru, Rh, Pd, Pt, and Au are most commonly used for this reaction because of their high activity and stability. Despite the wealth of experimental and theoretical data, it remains unclear what is the active surface for CO oxidation under catalytic conditions for these metals. In this communication, we utilize in situ synchrotron ambient pressure X-ray photoelectron spectroscopy (APXPS) to monitor the oxidation statemore » at the surface of Rh nanoparticles during CO oxidation and demonstrate that the active catalyst is a surface oxide, the formation of which is dependent on particle size. The amount of oxide formed and the reaction rate both increase with decreasing particle size.« less

Enhanced Photocatalytic Property of Cu Doped Sodium Niobate

DOE PAGES

Xu, Jianbin; Zhang, Feng; Sun, Bingyang; ...

2015-01-01

Here, we investigate the photocatalytic activity of Cu doped NaNbO 3 powder sample prepared by the modified polymer complex method. The photocatalytic activity of hydrogen evolution from methanol aqueous solution was improved by Cu 2.6 at% doping. The photocatalytic degradation of rhodamine B (RhB) under visible light irradiation was enhanced in comparison with pristine NaNbO 3. Cu introduction improved the adsorption property of NaNbO 3, judging from the Fourier transform infrared spectra. Moreover, the ultraviolet light excitation in Cu doped sample would accelerate the mineralized process.

Synthesis of borasiloxanes by oxidative hydrolysis of silanes and pinacolborane using Cu3(BTC)2 as a solid catalyst.

PubMed

Dhakshinamoorthy, Amarajothi; Asiri, Abdullah M; Concepcion, Patricia; Garcia, Hermenegildo

2017-09-05

A convenient method for the synthesis of borasiloxanes from silanes and pinacolboranes using Cu 3 (BTC) 2 as a heterogeneous catalyst in acetonitrile at 70 °C is reported. This procedure is more convenient than Ru and Pd based homogeneous catalysts because it avoids the use of noble metals, easy handling of starting materials and the catalyst can be reused.

Oxidative leaching process with cupric ion in hydrochloric acid media for recovery of Pd and Rh from spent catalytic converters.

PubMed

Nogueira, C A; Paiva, A P; Oliveira, P C; Costa, M C; da Costa, A M Rosa

2014-08-15

The recycling of platinum-group metals from wastes such as autocatalytic converters is getting growing attention due to the scarcity of these precious metals and the market pressure originated by increase of demand in current and emerging applications. Hydrometallurgical treatment of such wastes is an alternative way to the most usual pyrometallurgical processes based on smelter operations. This paper focuses on the development of a leaching process using cupric chloride as oxidising agent, in HCl media, for recovery of palladium and rhodium from a spent catalyst. The chloride media allows the adequate conditions for oxidising and solubilising the metals, as demonstrated by equilibrium calculations based on thermodynamic data. The experimental study of the leaching process revealed that Pd solubilisation is clearly easier than that of Rh. The factors temperature, time, and HCl and Cu(2+) concentrations were significant regarding Pd and Rh leaching, the latter requiring higher factor values to achieve the same results. Leaching yields of 95% Pd and 86% Rh were achieved under optimised conditions (T = 80 °C, t = 4h, [HCl] = 6M, [Cu(2+)] = 0.3M). Copyright © 2014 Elsevier B.V. All rights reserved.

Ni, Cu, Au, and platinum-group element contents of sulphides associated with intraplate magmatism: A synthesis

USGS Publications Warehouse

Barnes, S.-J.; Zientek, M.L.; Severson, M.J.

1997-01-01

The tectonic setting of intraplate magmas, typically a plume intersecting a rift, is ideal for the development of Ni - Cu - platinum-group element-bearing sulphides. The plume transports metal-rich magmas close to the mantle - crust boundary. The interaction of the rift and plume permits rapid transport of the magma into the crust, thus ensuring that no sulphides are lost from the magma en route to the crust. The rift may contain sediments which could provide the sulphur necessary to bring about sulphide saturation in the magmas. The plume provides large volumes of mafic magma; thus any sulphides that form can collect metals from a large volume of magma and consequently the sulphides will be metal rich. The large volume of magma provides sufficient heat to release large quantities of S from the crust, thus providing sufficient S to form a large sulphide deposit. The composition of the sulphides varies on a number of scales: (i) there is a variation between geographic areas, in which sulphides from the Noril'sk - Talnakh area are the richest in metals and those from the Muskox intrusion are poorest in metals; (ii) there is a variation between textural types of sulphides, in which disseminated sulphides are generally richer in metals than the associated massive and matrix sulphides; and (iii) the massive and matrix sulphides show a much wider range of compositions than the disseminated sulphides, and on the basis of their Ni/Cu ratio the massive and matrix sulphides can be divided into Cu rich and Fe rich. The Cu-rich sulphides are also enriched in Pt, Pd, and Au; in contrast, the Fe-rich sulphides are enriched in Fe, Os, Ir, Ru, and Rh. Nickel concentrations are similar in both. Differences in the composition between the sulphides from different areas may be attributed to a combination of differences in composition of the silicate magma from which the sulphides segregated and differences in the ratio of silicate to sulphide liquid (R factors). The higher metal content of the disseminated sulphides relative to the massive and matrix sulphides may be due to the fact that the disseminated sulphides equilibrated with a larger volume of magma than massive and matrix sulphides. The difference in composition between the Cu- and Fe-rich sulphides may be the result of the fractional crystallization of monosulphide solid solution from a sulphide liquid, with the Cu-rich sulphides representing the liquid and the Fe-rich sulphides representing the cumulate.

Raman study of transition-metal oxides with perovskite-like structure

NASA Astrophysics Data System (ADS)

Kolev, Nikolay Iliev

Perovskite-like oxides exhibit a rich variety of properties of fundamental scientific interest and potential application value. The motivation for this work is to contribute to our knowledge of perovskite-like systems and strongly correlated systems in general. The polarized Raman spectra of single crystal and thin film CaCu3Ti4O12, single crystal and thin film CaRuO3, microcrystals of La0.5Ca 0.5MnO3, and ceramic and thin film CaMnO3 have been investigated. In close comparison to results from lattice dynamics calculations most of the Raman lines in the CaCu3Ti4O12, CaRuO3, La0.5Ca0.5MnO3 and CaMnO 3 spectra, have been assigned to definite phonon modes. The validity of the model for twin orientation in the Pnma structure for CaRuO3 and La0.5Ca0.5MnO3 is confirmed. The analysis of the CaMnO3 spectra contributed to the development of a model, based on four basic distortions of the (distorted) perovskite structure. The temperature behavior of the CaCu3Ti4O 12 spectra shows that there is no evidence for structural phase transition in the temperature range 20--600 K, so such a transition cannot be responsible for the sharp drop in the dielectric constant below 100 K. The Raman spectra indirectly support the mechanism of formation of barrier layer capacitances in CaCu3Ti4O12.The observation of additional Raman mode of nominal Ag symmetry is discussed in terms of coexistence of domains of different atomic arrangement, or alternatively of non-stoichiometry (Cu deficiency). In the case of the thin film, the tetragonal distortions could be responsible for the greater separation of the additional Ag line. No anomalies in the temperature behavior of the Raman lines of CaRuO3 is observed, which is an indirect evidence for its lack of long-range magnetic ordering at low temperatures (depending on whether this ordering would be observable by Raman spectroscopy through spin-phonon coupling). In La0.5Ca0.5MnO 3 the appearance of several Raman lines below TN is analyzed in terms of ordering and freezing of the Jahn-Teller distortions in a superstructure. Polarized Raman spectra confirmed their usefulness in studying thin films and their properties.

Novel porous CuO microrods: synthesis, characterization, and their photocatalysis property

NASA Astrophysics Data System (ADS)

Huang, Jiarui; Fu, Guijun; Shi, Chengcheng; Wang, Xinyue; Zhai, Muheng; Gu, Cuiping

2014-09-01

Porous copper oxide microrods have been synthesized via calcining copper glycinate monohydrate microrod precursor which was prepared in mild conditions without any template or additive. Several techniques, such as X-ray diffraction, field emission scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller (BET) N2 adsorption-desorption analyses, were used to characterize the structure and morphology of the products. Scanning electron microscopy (SEM) analyses show that the precursor consists of a large quantity of uniform rod-like micro/nanostructures with typical lengths in the range of 25-40 μm and diameters in the range of 0.1-0.35 μm. The microrod-like precursors transformed into porous microrod products after calcination at 450 °C in flow air for 2 h. The BET surface area of the porous CuO microrods was calculated to be 8.5 m² g-1. In addition, the obtained porous CuO microrods were used as catalysts to photodegrade rhodamine B (RhB), methyl orange, methylene blue, eosin B, and p-nitrophenol. Compared with commercial CuO powders, the as-prepared porous CuO microrods exhibit superior properties on photocatalytic decomposition of RhB due to their porous hierarchical structures.

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

Xing, Rong; Dagle, Vanessa Lebarbier; Flake, Matthew

In this study we examine feasibility for steam reforming the mixed oxygenate aqueous fraction derived from mildly hydrotreated fast pyrolysis bio-oils. Catalysts selective towards hydrogen formation and resistant to carbon formation utilizing feeds with relatively low steam-to-carbon (S/C) ratios are desired. Rh (5 wt%), Pt (5 wt%), Ru (5 wt%), Ir (5 wt%), Ni (15 wt%), and Co (15 wt%) metals supported on MgAl 2O 4 were evaluated for catalytic performance at 500°C and 1 atm using a complex feed mixture comprising of acids, polyols, cycloalkanes, and phenolic compounds. The Rh catalyst was found to be the most active andmore » resistant to carbon formation. The Ni and Co catalysts were found to be more active than the other noble metal catalysts investigated (Pt, Ru, and Ir). However, Ni was found to form significantly more carbon (coke) on the catalyst surface. Furthermore, Co was found to be the most selective towards H 2 formation. Evaluating the effect of temperature on stability for the Rh catalyst we found that catalyst stability was best when operated at 500°C as compared to the higher temperatures investigated (700, 800°C). When operating at 700°C significantly more graphitic formation was observed on the spent catalyst surface. Operating at 800°C resulted in reactor plugging as a result of thermal decomposition of the reactants. Thus, a concept analogous to the petroleum industries’ use of a pre-reformer, operated at approximately 500°C for steam reforming of the heavier naphtha components, followed by a high temperature methane reforming operated in the 600-850°C temperature range, could be applied in the case of steam reforming biomass derived oxygenates. Moreover, stability evaluations were performed over the Rh, Ni, and Co catalysts at 500°C and 1 atm, under similar initial conversions, reveal the Co catalyst to be the most stable and selective towards H 2 production. Conversion and selectivity to CH 4 over Co remained relatively stable at approximately 80% and 1.2%, respectively. By contrast, the Rh and Ni catalysts CH 4 selectivity’s were approximately 7-8%. Thus suggesting that a Co type catalyst may be more suitable for the steam reforming of biomass derived oxygenates as compared to the more conventional Ni and Rh type steam reforming catalysts. However, deposition of carbon on the surface was observed. High resolution TEM on the spent catalysts revealed the formation of graphitic carbon on the Rh catalyst, and filamentous carbon formation was observed on both the Ni and Co catalysts, albeit less pronounced on Co. Thus there is certainly opportunity for improvement in Co catalyst design and/or with process optimization.« less

A Euclidean Perspective on the Unfolding of Azurin: Spatial Correlations

PubMed Central

Warren, Jeffrey J.; Gray, Harry B.; Winkler, Jay R.; Kozak, John J.

2013-01-01

We investigate the stability to structural perturbation of Pseudomonas aeruginosa azurin using a previously developed geometric model. Our analysis considers Ru(2,2′,6′,2″-terpyridine)(1,10-phenanthroline)(His83)-labeled wild-type azurin and five variants with mutations to Cu-ligating residues. We find that in the early stages of unfolding, the β-strands exhibit the most structural stability. The conserved residues comprising the hydrophobic core are dislocated only after nearly complete unfolding of the β-barrel. Attachment of the Ru-complex at His83 does not destabilize the protein fold, despite causing some degree of structural rearrangement. Notably, replacing the Cys112 and/or Met121 Cu ligands does not affect the conformational integrity of the protein. Notably, these results are in accord with experimental evidence, as well as molecular dynamics simulations of the denaturation of azurin. PMID:23853392

Bismuth oxychloride (BiOCl)/copper phthalocyanine (CuTNPc) heterostructures immobilized on electrospun polyacrylonitrile nanofibers with enhanced activity for floating photocatalysis.

PubMed

Guo, Xiaohui; Zhou, Xuejiao; Li, Xinghua; Shao, Changlu; Han, Chaohan; Li, Xiaowei; Liu, Yichun

2018-09-01

The 2,9,16,23-tetranitro phthalocyanine copper (II) nanostructures and bismuth oxychloride nanosheets were grown on electrospun polyacrylonitrile (PAN) nanofibers in sequence by solvothermal method. As a result, the BiOCl/CuTNPc heterostructures were uniformly immobilized on the PAN nanofibers. The obtained BiOCl/CuTNPc/PAN nanofibers had excellent photocatalytic activity for the degradation of rhodamine B (RhB) under UV-vis light irradiation. The first-order rate constant of the BiOCl/CuTNPc/PAN nanofibers was 5.86 and 6.31 times as much as CuTNPc/PAN and BiOCl/PAN nanofibers, respectively. The high photocatalytic activity could be attributed to the formation of BiOCl/CuTNPc heterostructures, which helped the separation of the photogenerated electron-hole pairs. Concurrently, the marcoporous structure of the BiOCl/CuTNPc/PAN nanofibers improved the photocatalytic activity due to the increased interface contacts between the photocatalyst and the RhB solution. The BiOCl/CuTNPc/PAN nanofibers did not need to be separated for reuse due to their flexible self-supporting properties originating from the PAN nanofibers. Moreover, the film-like BiOCl/CuTNPc/PAN nanofibers could float easily on the liquid and maximize the absorption of sunlight during photocatalysis. It was expected that the BiOCl/CuTNPc/PAN nanofibers with high photocatalytic activity and easily separable property will possess great potential in the field of industrial applications and environmental remediation. Copyright © 2018. Published by Elsevier Inc.

Spin-orbit tuned metal-insulator transitions in single-crystal Sr₂Ir 1–xRh xO₄ (0≤x≤1)

DOE PAGES

Qi, T. F.; Korneta, O. B.; Li, L.; ...

2012-09-06

Sr₂IrO₄ is a magnetic insulator driven by spin-orbit interaction (SOI) whereas the isoelectronic and isostructural Sr₂RhO₄ is a paramagnetic metal. The contrasting ground states have been shown to result from the critical role of the strong SOI in the iridate. Our investigation of structural, transport, magnetic, and thermal properties reveals that substituting 4d Rh⁴⁺ (4d⁵) ions for 5d Ir⁴⁺ (5d⁵) ions in Sr₂IrO₄ directly reduces the SOI and rebalances the competing energies so profoundly that it generates a rich phase diagram for Sr₂Ir 1–xRh xO₄ featuring two major effects: (1) Light Rh doping (0 ≤ x ≤ 0.16) prompts amore » simultaneous and precipitous drop in both the electrical resistivity and the magnetic ordering temperature TC, which is suppressed to zero at x = 0.16 from 240 K at x = 0. (2) However, with heavier Rh doping [0.24 < x < 0.85 (±0.05)] disorder scattering leads to localized states and a return to an insulating state with spin frustration and exotic magnetic behavior that only disappears near x = 1. The intricacy of Sr₂Ir 1–xRh xO₄ is further highlighted by comparison with Sr₂Ir 1–xRu xO₄ where Ru⁴⁺ (4d⁴) drives a direct crossover from the insulating to metallic states.« less

Characterization, Recovery Opportunities, and Valuation of Metals in Municipal Sludges from U.S. Wastewater Treatment Plants Nationwide.

PubMed

Westerhoff, Paul; Lee, Sungyun; Yang, Yu; Gordon, Gwyneth W; Hristovski, Kiril; Halden, Rolf U; Herckes, Pierre

2015-08-18

U.S. sewage sludges were analyzed for 58 regulated and nonregulated elements by ICP-MS and electron microscopy to explore opportunities for removal and recovery. Sludge/water distribution coefficients (KD, L/kg dry weight) spanned 5 orders of magnitude, indicating significant metal accumulation in biosolids. Rare-earth elements and minor metals (Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) detected in sludges showed enrichment factors (EFs) near unity, suggesting dust or soils as likely dominant sources. In contrast, most platinum group elements (i.e., Ru, Rh, Pd, Pt) showed high EF and KD values, indicating anthropogenic sources. Numerous metallic and metal oxide colloids (<100-500 nm diameter) were detected; the morphology of abundant aggregates of primary particles measuring <100 nm provided clues to their origin. For a community of 1 million people, metals in biosolids were valued at up to US$13 million annually. A model incorporating a parameter (KD × EF × $Value) to capture the relative potential for economic value from biosolids revealed the identity of the 13 most lucrative elements (Ag, Cu, Au, P, Fe, Pd, Mn, Zn, Ir, Al, Cd, Ti, Ga, and Cr) with a combined value of US $280/ton of sludge.

Biomonitoring of 37 trace elements in blood samples from inhabitants of northern Germany by ICP-MS.

PubMed

Heitland, Peter; Köster, Helmut D

2006-01-01

The trace elements Ag, As, Au, B, Ba, Be, Bi, Cd, Ce, Co, Cs, Cu, Ga, Hf, Hg, In, La, Mn, Mo, Ni, Pb, Pd, Rb, Rh, Ru, Sb, Se, Sn, Sr, Te, Th, Tl, U, V, W, Y and Zr were determined in 130 human blood samples from occupationally non-exposed volunteers living in the greater area of Bremen in northern Germany. The blood samples were collected in lithium heparin monovettes developed for trace metal determination and were analysed by inductively coupled plasma mass spectrometry (ICP-MS) with an octopole-based collision/reaction cell. For sample introduction into the ICP, the blood samples were diluted 1/10 (V/V) with a 0.1% Triton-X-100 and 0.5% (V/V) ammonia solution. The method validation of our developed routine method is described for all 37 elements and results about internal and external quality assurance are discussed. Information on exposure conditions of all human subjects were collected by questionnaire-based interviews, including smoking habits, seafood consumption and the type of dental alloys in the teeth. Mean values, geometric mean values, ranges and selected percentiles of all elemental concentrations in human blood are presented, which helps toxicologists and clinical chemists planning research about exposition to metals and health effects caused by exposition to metals.

Electrocatalytic Water Oxidation by a Homogeneous Copper Catalyst Disfavors Single-Site Mechanisms.

PubMed

Koepke, Sara J; Light, Kenneth M; VanNatta, Peter E; Wiley, Keaton M; Kieber-Emmons, Matthew T

2017-06-28

Deployment of solar fuels derived from water requires robust oxygen-evolving catalysts made from earth abundant materials. Copper has recently received much attention in this regard. Mechanistic parallels between Cu and single-site Ru/Ir/Mn water oxidation catalysts, including intermediacy of terminal Cu oxo/oxyl species, are prevalent in the literature; however, intermediacy of late transition metal oxo species would be remarkable given the high d-electron count would fill antibonding orbitals, making these species high in energy. This may suggest alternate pathways are at work in copper-based water oxidation. This report characterizes a dinuclear copper water oxidation catalyst, {[(L)Cu(II)] 2 -(μ-OH) 2 }(OTf) 2 (L = Me 2 TMPA = bis((6-methyl-2-pyridyl)methyl)(2-pyridylmethyl)amine) in which water oxidation proceeds with high Faradaic efficiency (>90%) and moderate rates (33 s -1 at ∼1 V overpotential, pH 12.5). A large kinetic isotope effect (k H /k D = 20) suggests proton coupled electron transfer in the initial oxidation as the rate-determining step. This species partially dissociates in aqueous solution at pH 12.5 to generate a mononuclear {[(L)Cu(II)(OH)]} + adduct (K eq = 0.0041). Calculations that reproduce the experimental findings reveal that oxidation of either the mononuclear or dinuclear species results in a common dinuclear intermediate, {[LCu(III)] 2 -(μ-O) 2 } 2+ , which avoids formation of terminal Cu(IV)═O/Cu(III)-O • intermediates. Calculations further reveal that both intermolecular water nucleophilic attack and redox isomerization of {[LCu(III)] 2 -(μ-O) 2 } 2+ are energetically accessible pathways for O-O bond formation. The consequences of these findings are discussed in relation to differences in water oxidation pathways between Cu catalysts and catalysts based on Ru, Ir, and Mn.

E-Selective Semi-Hydrogenation of Alkynes by Heterobimetallic Catalysis.

PubMed

Karunananda, Malkanthi K; Mankad, Neal P

2015-11-25

A unique cooperative H2 activation reaction by heterobimetallic (NHC)M'-MCp(CO)2 complexes (NHC = N-heterocyclic carbene, M' = Cu or Ag, M = Fe or Ru) has been leveraged to develop a catalytic alkyne semi-hydrogenation transformation. The optimal Ag-Ru catalyst gives high selectivity for converting alkynes to E-alkenes, a rare selectivity mode for reduction reactions with H2. The transformation is tolerant of many reducible functional groups. Computational analysis of H2 activation thermodynamics guided rational catalyst development. Bimetallic alkyne hydrogenation and alkene isomerization mechanisms are proposed.

Platinum group element abundances in the upper continental crust revisited - New constraints from analyses of Chinese loess

NASA Astrophysics Data System (ADS)

Park, Jung-Woo; Hu, Zhaochu; Gao, Shan; Campbell, Ian H.; Gong, Hujun

2012-09-01

Platinum group element (PGE) abundances in the upper continental crust (UCC) are poorly constrained with published values varying by up to an order of magnitude. We evaluated the validity of using loess to estimate PGE abundances in the UCC by measuring these elements in seven Chinese loess samples using a precise method that combines NiS fire assay with isotope dilution. Major and trace elements of the Chinese loess show a typical upper crustal composition and PGE abundances are consistent with literature data on Chinese loess, except for Ru, which is a factor of 10 lowe than published values. We suggest that the high Ru data and RuN/IrN values of Chinese loess reported by Peucker-Ehrenbrink and Jahn (2001) (Geochem. Geophys. Geosys.2, 2001GC000172) are an analytical artifact, rather than a true geochemical characteristic of loess because likely sources of loess are not significantly enriched in Ru and transport and deposition processes cannot preferentially enrich Ru in loess. The effect of eolian fractionation on PGE abundances in loess appears to be limited because Chinese loess from different locations shows similar PGE patterns and concentrations. This conclusion is supported by strong positive correlations between the PGE (except for Pt) and other compatible elements such as Fe2O3, Ni, Cr, Co. Using a compilation of PGE data for loess from China, Argentina and Europe, including our data but excluding one sample with an anomalously high Pt content, we propose average PGE abundances for global loess of Ir = 0.022 ppb (ng/g), Ru = 0.030 ppb, Rh = 0.018 ppb, Pt = 0.599 ppb, and Pd = 0.526 ppb, and suggest that these are the best current estimates for the PGE abundances of the UCC.

Electrochemical Migration Behavior of Copper-Clad Laminate and Electroless Nickel/Immersion Gold Printed Circuit Boards under Thin Electrolyte Layers

PubMed Central

Yi, Pan; Xiao, Kui; Ding, Kangkang; Dong, Chaofang; Li, Xiaogang

2017-01-01

The electrochemical migration (ECM) behavior of copper-clad laminate (PCB-Cu) and electroless nickel/immersion gold printed circuit boards (PCB-ENIG) under thin electrolyte layers of different thicknesses containing 0.1 M Na2SO4 was studied. Results showed that, under the bias voltage of 12 V, the reverse migration of ions occurred. For PCB-Cu, both copper dendrites and sulfate precipitates were found on the surface of FR-4 (board material) between two plates. Moreover, the Cu dendrite was produced between the two plates and migrated toward cathode. Compared to PCB-Cu, PCB-ENIG exhibited a higher tendency of ECM failure and suffered from seriously short circuit failure under high relative humidity (RH) environment. SKP results demonstrated that surface potentials of the anode plates were greater than those of the cathode plates, and those potentials of the two plates exhibited a descending trend as the RH increased. At the end of the paper, an electrochemical migration corrosion failure model of PCB was proposed. PMID:28772497

Magnetic and transport properties of the spin-state disordered oxide La0.8Sr0.2Co1-xRhxO3-δ

NASA Astrophysics Data System (ADS)

Shibasaki, Soichiro; Terasaki, Ichiro; Nishibori, Eiji; Sawa, Hiroshi; Lybeck, Jenni; Yamauchi, Hisao; Karppinen, Maarit

2011-03-01

We report measurements and analysis of magnetization, resistivity, and thermopower of polycrystalline samples of the perovskite-type Co/Rh oxide La0.8Sr0.2Co1-xRhxO3-δ. This system constitutes a solid solution for a full range of x, in which the crystal structure changes from rhombohedral to orthorhombic symmetry with increasing Rh content x. The magnetization data reveal that the magnetic ground state immediately changes upon Rh substitution from ferromagnetic to paramagnetic with increasing x near 0.25, which is close to the structural phase boundary. We find that one substituted Rh ion diminishes the saturation moment by 9 μB, which implies that one Rh3+ ion makes a few magnetic Co3+ ions nonmagnetic (the low-spin state) and causes disorder in the spin state and the highest occupied orbital. In this disordered composition (0.05⩽x⩽0.75), we find that the thermopower is anomalously enhanced below 50 K. In particular, the thermopower of x=0.5 is larger by a factor of 10 than those of x=0 and 1, and the temperature coefficient reaches 4 μV/K2, which is as large as that of heavy-fermion materials such as CeRu2Si2.

The behavior of Pt, Pd, Cu and Ni in the Se-sulfide system between 1050 and 700 °C and the role of Se in platinum-group elements fractionation in sulfide melts

NASA Astrophysics Data System (ADS)

Helmy, Hassan M.; Fonseca, Raúl O. C.

2017-11-01

The behavior of Pt, Pd, Ni and Cu in Se-sulfide system and the role of Se in platinum-group elements (PGE) fractionation have been experimentally investigated at temperatures between 1050 and 700 °C in evacuated silica tubes. At 1050 °C, Se partially partitions into a vapor phase. At 980 °C, monosulfide solid solution (mss) and sulfide melt are the only stable phases. No Pt or Pd-bearing discrete selenide phases form down to 700 °C. Instead cooperite (PtS) forms at 900 °C. Both mss and sulfide melt can accommodate wt.% levels of Se over the whole temperature range covered by the experiments. The addition of Se in the sulfide system leads to an increase in the activity coefficients of Ni and Pd in sulfide melt. This is reflected by an increase in the partition coefficients of Ni and Pd between mss and sulfide melt. The Pt-Se activity coefficient in sulfide melt is lower than that of Pt-S. Owing to selenium's high solubility in sulfides, there never become oversaturated in Se to the extent that discrete selenides form. As such, base metal sulfides are expected to control the geochemical behavior of Se in natural systems. Interestingly, partition coefficients for the platinum-group elements (Os, Ir, Ru, Pt, Rh, Pd) between mss and sulfide melt are undistinguishable regardless of whether Se is present or not. These results imply that Se plays little role in the fractionation of PGE as sulfide melt cools down and crystallize. Furthermore, our experimental results provide evidence that Se is volatile at magmatic temperature and is likely to be degassed like sulfur.

Studies of Metal-Metal Bonded Compounds in Catalysis

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

Berry, John F.

The overall goals of this research are (1) to define the fundamental coordination chemistry underlying successful catalytic transformations promoted by metal-metal bonded compounds, and (2) to explore new chemical transformations that occur at metal-metal bonded sites that could lead to the discovery of new catalytic processes. Transformations of interest include metal-promoted reactions of carbene, nitrene, or nitrido species to yield products with new C–C and C–N bonds, respectively. The most promising suite of transition metal catalysts for these transformations is the set of metal-metal bonded coordination compounds of Ru and Rh of the general formula M 2(ligand) 4, where Mmore » = Ru or Rh and ligand = a monoanionic, bridging ligand such as acetate. Development of new catalysts and improvement of catalytic conditions have been stymied by a general lack of knowledge about the nature of highly reactive intermediates in these reactions, the knowledge that is to be supplied by this work. Our three specific objectives for this year have been (A) to trap, isolate, and characterize new reactive intermediates of general relevance to catalysis, (B) to explore the electronic structure and reactivity of these unusual species, and how these two properties are interrelated, and (C) to use our obtained mechanistic knowledge to design new catalysts with a focus on Earth-abundant first-row transition metal compounds.« less

Study on separation of platinum group metals from high level liquid waste using macroporous (MOTDGA-TOA)/SiO{sub 2}-P silica-based absorbent

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

Ito, Tatsuya; Japan Atomic Energy Agency, Tokai-mura Naka-gun, Ibarak319-1195; Kim, Seong-Yun

2013-07-01

The recovery of platinum group metals (PGMs) from high level liquid waste (HLLW) by macroporous silica-based adsorbent, (MOTDGA-TOA)/SiO{sub 2}-P has been developed by impregnating two extractants of N,N'-dimethyl-N,N'-di-n-octyl-thio-diglycolamide (MOTDGA) and tri-n-octylamine (TOA) into a silica/polymer composite support (SiO{sub 2}-P). The adsorption of Ru(III), Rh(III) and Pd(II) have been investigated in simulated HLLW by batch method. The adsorbent has shown good uptake property for Pd(II). In addition, the combined use of MOTDGA and TOA improved the adsorption of Ru(III) and Rh(III) better than the individual use of them. The usability of adsorbent in radiation fields was further confirmed by irradiation experiments.more » The adsorbent remained to have the uptake capability for PGMs over the absorbed dose of 100 kGy, corresponding with one really adsorbed by the adsorbent, and showed good retention capability for Pd(II) even at the absorbed dose of 800 kGy. The chromatographic separation of metal ions was demonstrated with the adsorbent packed column, there is no influence of Re(VII) (instead of Tc) on the excellent separation behavior of Pd(II). (authors)« less

Changing Bureaucratic Behavior Acquisition Reform in the United States Army

DTIC Science & Technology

2000-01-01

I . Title. UC263.S32 2000 355.6��—dc21 99-39065 CIP RAND is a nonprofit...1 CO cu u a cu ■ä cu u a 1 2 a a .—1 CN i — I tN m •* in CO r~ 00 CT> rH l-H i —t 8 a o W CO CO. 1 cu cu ŗ J3 cu cu UJ E E ■S CU...p cu > äj § S3 ■43 ■n J3 X. CO cO rrl ■§ cu cu cu i o CO a CO a co a T3 O ■a ft o o o M 1*1 ■g ■g CO ’g ft ft) X II a a a. X V a E

Synthesis and Characterization of the First Cyclic Monothioether Derivative of 1,2-o-Carborane and Its Reactivity toward Phosphine Transition Metal Complexes.

PubMed

Viñas, Clara; Cirera, M. Rosa; Teixidor, Francesc; Kivekäs, Raikko; Sillanpää, Reijo; Llibre, Joan

1998-12-28

The first cyclic monothioether derivative of [C(2)B(9)H(12)](-) has been synthesized from 1-(SH)-1,2-C(2)B(10)H(11). Reaction of the latter with (n)BuLi and 1,3-dibromopropane leads to 1,2-&mgr;-(S(CH(2))(3))-1,2-C(2)B(10)H(10). Partial degradation leads to [7,8-&mgr;-(S(CH(2))(3))-7,8-C(2)B(9)H(10)](-). Reaction of [7,8-&mgr;-(S(CH(2))(3))-7,8-C(2)B(9)H(10)](-) with [PdCl(2)(PRR'(2))(2)] leads to different sets of compounds depending on the nature of R and R'. If R = R' = (t)Bu, a closo compound with one vertex occupied by "[Pd(P(t)Bu(3))(2)]" is obtained. When aryl groups are present in the starting phosphine complex, the zwitterionic non-metal-containing compounds are obtained. The crystal structure of one of them has been determined, and the compound has been proven to be 7,8-&mgr;-(S(CH(2))(3))-11-PPh(3)-7,8-C(2)B(9)H(9). The reaction of [7,8-&mgr;-(S(CH(2))(3))-7,8-C(2)B(9)H(10)](-) with [RhCl(PPh(3))(3)] leads to [Rh(7,8-&mgr;-(S(CH(2))(3))-7,8-C(2)B(9)H(10))(PPh(3))(2)]. An agostic B-Hright harpoon-up Rh interaction has been produced, identified by a (1)H{(11)B} NMR resonance at -4.78 ppm. In this instance the cluster is connected to "Rh" via the thioether and B(11)-H. The reaction of [7,8-&mgr;-(S(CH(2))(3))-7,8-C(2)B(9)H(10)](-) with [RuCl(2)(PPh(3))(3)] leads to a compound with two B-Hright harpoon-up Ru interactions. Contrarily to its noncyclic analogues, it seems that only one isomer has been obtained.

Rh-Catalyzed Annulations of N-Methoxybenzamides and Ketenimines: Sterically and Electronically Controlled Synthesis of Isoquinolinones and Isoindolinones.

PubMed

Zhou, Xiaorong; Zhang, Zhiyin; Zhao, Hongyang; Lu, Ping; Wang, Yanguang

2017-04-07

Rhodium-catalyzed C-H activation/annulation reactions of ketenimines with N-methoxybenzamides are reported. The outcome of reactions is dependent on the structure of ketenimines. The β-alkyl-substituted ketenimines furnish 3-iminoisoquinolin-1(2H)-ones in a formal [4 + 2] annulation manner, while the β-ester substituted ketenimines afford 3-aminoisoindolin-1-ones in a formal [4 + 1] annulation manner. The synthesized [4 + 2] products undergo an intramolecular Cu-catalyzed C-N coupling to be converted to benzo[4,5]imidazo[1,2-b]isoquinolin-11-ones, which can be directly prepared from ketenimines and N-methoxybenzamides by a one-pot Rh-catalyzed annulation/Cu-catalyzed C-N coupling sequence.

Evaluation of Pt Alloys as Electrocatalysts for Oxalic Acid Oxidation: A Combined Experimental and Computational Study

DOE PAGES

Perry, Albert; Babanova, Sofia; Matanovic, Ivana; ...

2016-07-14

Here in this study we combined experimental approaches and density functional theory to evaluate novel platinum-based materials as electrocatalysts for oxalic acid oxidation. Several Pt alloys, PtSn (1:1), PtSn (19:1), PtRu (1:4), PtRuSn (5:4:1), and PtRhSn (3:1:4), were synthetized using sacrificial support method and tested for oxidation of oxalic acid at pH 4. It was shown that PtSn (1:1) and PtRu (1:4) have higher mass activity relative to Pt. These two materials along with Pt and one of the least active alloys, PtSn (19:1), were further analyzed for the oxidation of oxalic acid at different pHs. The results show thatmore » all samples tested followed an identical trend of decreased onset potential with increased pH and increased catalytic activity with decreased pH. Density functional theory was further utilized to gain a fundamental knowledge about the mechanism of oxalic acid oxidation on Pt, PtSn (1:1), and PtRu (1:4). In conclusion, the results of the calculations along with the experimentally observed dependence of generated currents on the oxalic acid concentration indicate that the mechanism of oxalic acid oxidation on Pt proceeds without the participation of surface oxidizing species, while on Pt alloys it involves their participation.« less

Level, source identification, and risk analysis of heavy metal in surface sediments from river-lake ecosystems in the Poyang Lake, China.

PubMed

Zhang, Hua; Jiang, Yinghui; Ding, Mingjun; Xie, Zhenglei

2017-09-01

The concentrations, sources, and risks of heavy metals (Fe, Al, Mn, Cr, Co, Ni, Cu, Zn, As, Cd, W, Pb, and Tl) in sediments in five river-lake ecosystems in the Poyang Lake region were studied. The concentrations of the heavy metals varied spatially, with most of the highest concentrations in the Raohe river-lake ecosystem (RH). All heavy metals except As, Cd, W, and Tl were enriched in sediments possessing high total organic carbon contents or in finer sediments. Based on enrichment factors and statistical methods, it was found that Cd in sediments in the Xiushui (XS), Ganjiang (GJ), Xinjiang (XJ) river-lake ecosystems, and RH; Mn in the XS, GJ, and RH; and W in the XS and GJ were greatly affected by anthropogenic inputs. Moreover, the origins of Cu, Zn, and As require more attention due to the high concentrations found. The high enrichment factor of Cd in the sediments indicated that this metal might cause significant pollution in the environment. The results of the modified potential ecological risk index revealed that the XS, GJ, RH, and XJ were at considerable ecological risk, while the sediments in the Fuhe river-lake ecosystem (FH) were at moderate ecological risk, with Cd contributing the highest proportion of risk. The hazard score fundamentally validated the modified potential ecological risk analysis and revealed a mean toxicity of 57.80% to the benthic organisms in the RH.

Tin Whisker Growth and Mitigation with a Nanocrysytalline Nickel Coating

NASA Astrophysics Data System (ADS)

Janiuk, Szymon

Tin whiskers are a problem in the electronics industry since the EU banned the use of lead in Pb-Sn solders as part of the Restriction of Hazardous Substances (RoHS). The biggest concern with Sn whiskers is their ability to short-circuit electronics. High reliability applications such as the aerospace, defense, healthcare, and automotive industries are at most risk. This project explores Sn whisker mitigation and prevention with the use of nanocrystalline nickel coating over Sn surfaces. Sn was plated onto a pure Cu substrate using electroplating. A high temperature and high humidity condition, at 85°C and 85% RH, was effective at growing whiskers. A nNi coating was plated over Sn/Cu coupons. After subjecting the nNi/ Sn/Cu samples through 85°C/85% RH testing conditions, no whiskers were observed penetrating the surface. These results make nNi a viable material to use as a coating to prevent the growth of Sn whiskers in electronic assemblies.

Damage threshold of coating materials on x-ray mirror for x-ray free electron laser

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

Koyama, Takahisa, E-mail: koyama@spring8.or.jp; Yumoto, Hirokatsu; Tono, Kensuke

2016-05-15

We evaluated the damage threshold of coating materials such as Mo, Ru, Rh, W, and Pt on Si substrates, and that of uncoated Si substrate, for mirror optics of X-ray free electron lasers (XFELs). Focused 1 μm (full width at half maximum) XFEL pulses with the energies of 5.5 and 10 keV, generated by the SPring-8 angstrom compact free electron laser (SACLA), were irradiated under the grazing incidence condition. The damage thresholds were evaluated by in situ measurements of X-ray reflectivity degradation during irradiation by multiple pulses. The measured damage fluences below the critical angles were sufficiently high compared withmore » the unfocused SACLA beam fluence. Rh coating was adopted for two mirror systems of SACLA. One system was a beamline transport mirror system that was partially coated with Rh for optional utilization of a pink beam in the photon energy range of more than 20 keV. The other was an improved version of the 1 μm focusing mirror system, and no damage was observed after one year of operation.« less

Thermal stability of spin valves based on a synthetic antiferromagnet and Fe50Mn50 alloy

NASA Astrophysics Data System (ADS)

Milyaev, M. A.; Naumova, L. I.; Proglyado, V. V.; Chernyshova, T. A.; Blagodatkov, D. V.; Kamenskii, I. Yu.; Ustinov, V. V.

2015-11-01

Magnetron sputtering was used to prepare spin valves with the Ta/Ni80Fe20/Co90Fe10/Cu/Co90Fe10/Ru/Co90Fe10/Fe50Mn50/Ta composition. Changes in the functional characteristics of the spin valves were studied in a temperature range of-180 to +160°C. The maximum temperature at which the functional characteristics of spin valve remain unchanged was shown to depend on the relationship of thicknesses of Co90Fe10 layers separated by the Ru interlayer.

Physics of the N=Z and N=Z+1 Nuclei in the A = 80--100 Region

NASA Astrophysics Data System (ADS)

Bucurescu, D.

2007-04-01

A review of the experimental work performed at the GASP array with the purpose of the identification and first spectroscopic measurements of the heaviest even-even N=Z and odd-A N=Z+1 nuclei (mass larger than 80) is made. Systematic experiments in this mass region led to the first study of seven such nuclei: 88Ru, 81Zr, 85Mo, 89Ru, 91Rh, 93Pd, and 95Ag, and extensive data on many other nuclei in their neighborhood. The systematic evolution of the level structures in both even-even and odd-A nuclei, between N approx Z approx 40 and N approx Z approx 47 is briefly presented. The possibility that effects of the neutron-proton pairing have been observed, as well as the type of collectivity observed in this region are discussed.

Materials by Design - Computational Alloy Design for Corrosion

DTIC Science & Technology

2011-02-01

Es = + 0.33 eV Cs Rb K · ~·Ba Sr ::~ \\ H ~ YCd ./ G B FS A~ Zn " Be• ’f_ Ni?.Au SeA. ’\\ . At-v Rh Ru • Zr Ja Mo Tc _,. • • • pt • lr Nb w...Windows Air Conditioning Autoflight Electrical Power Navigation Engine Exhaust Stabilizer Doors Fuel system Nacelles/Pylons Power Plant Equip...p. 14 ASETSDefense 2011: Sustainable Surface Engineering for Aerospace and Defense Workshop Quantum Mechanics Insights into SCC resistance 3.5 -E 0

Enhancement of dielectric constant at percolation threshold in CaCu3 Ti4 O12 ceramic fabricated by both solid state and sol-gel process

NASA Astrophysics Data System (ADS)

Mukherjee, Rupam; Garcia, Lucia; Lawes, Gavin; Nadgorny, Boris

2014-03-01

We have investigated the large dielectric enhancement at the percolation threshold by introducing metallic RuO2 grains into a matrix of CaCu3Ti4O12 (CCTO). The intrinsic response of the pure CCTO samples prepared by solid state and sol-gel processes results in a dielectric constant on the order of 104 and 103 respectively with low loss. Scanning electron microscopy and energy dispersive x-ray spectroscopy indicate that a difference in the thickness of the copper oxide enriched grain boundary is the main reason for the different dielectric properties between these two samples. Introducing RuO2 metallic fillers in these CCTO samples yields a sharp increase of the dielectric constant at percolation threshold fc, by a factor of 6 and 3 respectively. The temperature dependence of the dielectric constant shows that the dipolar relaxation plays an important role in enhancing dielectric constant in composite systems.

Electrocatalysis of the HER in acid and alkaline media

DOE PAGES

Danilovic, Nemanja; Subbaraman, Ram; Strmcnik, Dusan; ...

2013-01-01

Trends in the HER are studied on selected metals (M= Cu, Ag, Au, Pt, Ru, Ir, Ti) in acid and alkaline environments. Here, we found that with the exception of Pt, Ir and Au, due to high coverage by spectator species on non-noble metal catalysts, experimentally established positions of Cu , Ag, Ru and Ti in the observed volcano relations are still uncertain. We also found that while in acidic solutions the M-Hupd binding energy most likely is controlling the activity trends, the trends in activity in alkaline solutions are controlled by a delicate balance between two descriptors: the M-Hadmore » interaction as well as the energetics required to dissociate water molecules. We confirm the importance of the second descriptor by introducing bifunctional catalysts such as M modified by Ni(OH); e.g. while the latter serves to enhance catalytic decomposition of water, the metal sites are required for collecting and recombining the produced hydrogen intermediates.« less

Theory of H bonding and vibration on close-packed metal surfaces

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

Feibelman, P.J.; Hamann, D.R.

1987-07-01

Self-consistent linearized augmented plane-wave calculations for H monolayers adsorbed on Pt(111), Ru(0001), Cu(111), and Cu(1 x 1)/Ru(0001) thin slabs predict the following: the H-atom equilibrium position on these substrates is generally in the face-centered cubic threefold hollow at a height above the surface where the clean-metal electron density is about 0.015 a.u. The symmetric stretch (SS) frequency lies in the range 130--165 meV, and is about 30% greater than the asymmetric stretch (AS) frequency on the same substrate. These results contradict the mode assignments of Baro et al. (A. M. Baro, H. Ibach, and H. D. Bruchman, Surf. Sci. 88,more » 384 (1979)) for H/Pt(111) which were based on the observation of weak dipole scattering by the low-lying mode, and of Barteau et al. (M. A. Barteau, J. Q. Broughton, and D. Menzel, Surf. Sci. 133, 443 (1983)) for H/Ru(0001). The pairwise spring model of H--metal vibration invoked by these groups in support of their mode assignments neglects a major component of the H--metal interaction, that between the adsorbed H and the delocalized electrons of a metal surface. It is this interaction which is responsible for the fact that the frequency of the SS vibration is greater than that of the AS.« less

Characterization of aqueous interactions of copper-doped phosphate-based glasses by vapour sorption.

PubMed

Stähli, Christoph; Shah Mohammadi, Maziar; Waters, Kristian E; Nazhat, Showan N

2014-07-01

Owing to their adjustable dissolution properties, phosphate-based glasses (PGs) are promising materials for the controlled release of bioinorganics, such as copper ions. This study describes a vapour sorption method that allowed for the investigation of the kinetics and mechanisms of aqueous interactions of PGs of the formulation 50P2O5-30CaO-(20-x)Na2O-xCuO (x=0, 1, 5 and 10mol.%). Initial characterization was performed using (31)P magic angle spinning nuclear magnetic resonance and attenuated total reflectance-Fourier transform infrared spectroscopy. Increasing CuO content resulted in chemical shifts of the predominant Q(2) NMR peak and of the (POP)as and (PO(-)) Fourier transform infrared absorptions, owing to the higher strength of the POCu bond compared to PONa. Vapour sorption and desorption were gravimetrically measured in PG powders exposed to variable relative humidity (RH). Sorption was negligible below 70% RH and increased exponentially with RH from 70 to 90%, where it exhibited a negative correlation with CuO content. Vapour sorption in 0% and 1% CuO glasses resulted in phosphate chain hydration and hydrolysis, as evidenced by protonated Q(0)(1H) and Q(1)(1H) species. Dissolution rates in deionized water showed a linear correlation (R(2)>0.99) with vapour sorption. Furthermore, cation release rates could be predicted based on dissolution rates and PG composition. The release of orthophosphate and short polyphosphate species corroborates the action of hydrolysis and was correlated with pH changes. In conclusion, the agreement between vapour sorption and routine characterization techniques in water demonstrates the potential of this method for the study of PG aqueous reactions. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Assessment of home environments with a fungal index using hydrophilic and xerophilic fungi as biologic sensors.

PubMed

Abe, K

2012-06-01

  Previously, the author proposed a 'fungal index' that quantifies the capacity for fungal growth in a test environment where a device (fungal detector) encapsulating spores of a xerophilic sensor fungus Eurotium herbariorum was placed. It was also found that an extremely xerophilic fungus, Aspergillus penicillioides, was suitable as a sensor fungus at sites with lower relative humidity (RH). In this report, the hydrophilic fungus Alternaria alternata was added to sensor fungi for the determination of the index in extremely humid environments. Measurements of the index and observations of the formation of spores by the sensor fungi were made in stable climates in moisture chambers, under natural conditions in homes, and in bathrooms prepared in an artificial climate chamber. Higher index values and earlier sporulation were obtained at higher RH in stable climates. The hydrophilic Alt. alternata showed the greatest response at 100% and 97.3% RH, the moderately xerophilic Eur. herbariorum, at 94%, 84%, and 75% RH, and the extremely xerophilic Asp. penicillioides, at 71% RH. In homes, the hydrophilic fungus was most active in water-usage areas, and the xerophilic fungi were most active in non-water-usage areas. Sporulation was observed on sensor fungi in fungal detectors placed in rooms where the index exceeded 18 ru/week after one-month exposure. Sites where the index exceeded 18 ru/week were referred to as damp, where fungal contamination seems to be unavoidable. Evaluations of ventilation systems in bathrooms with extremely humid climates showed typical examples of a countermeasure to fungal contamination. The purpose of this study is to establish a fungal index applicable in home environments with extremely high to relatively low relative humidity climates. The sensor fungus that showed the greatest response in a fungal detector (a device encapsulating spores of sensor fungi) served as not only a quantitative but also a qualitative indicator of the environment tested, indicating the type of fungi that would contaminate the site. A fungal index would be a good tool for detecting dampness that induces fungal contamination, which has adverse effects on human health. Evaluations of indoor climates would provide information useful to building owners, builders, designers, advisers, medical practitioners, and so on. Selection of the most suitable insulation systems in various buildings under different climates or evaluations of the drying process in water-damaged buildings could also be possible using fungal detectors and measurements of fungal indices. © 2011 John Wiley & Sons A/S.

Development and validation of an ICP-OES method for quantitation of elemental impurities in tablets according to coming US pharmacopeia chapters.

PubMed

Støving, Celina; Jensen, Henrik; Gammelgaard, Bente; Stürup, Stefan

2013-10-01

May 1, 2014 the United States Pharmacopeia (USP) will implement two new chapters stating limit concentrations of elemental impurities in pharmaceuticals applying inductively coupled plasma methods. In the present work an inductively coupled plasma optical emission spectrometry (ICP-OES) method for quantitation of As, Cd, Cu, Cr, Fe, Hg, Ir, Mn, Mo, Ni, Os, Pb, Pd, Pt, Rh, Ru, V and Zn in tablets according to the new USP chapters was developed. Sample preparation was performed by microwave-assisted acid digestion using a mixture of 65% HNO3 and 37% HCl (3:1, v/v). Limits of detection and quantitation were at least a factor of ten below the USP limit concentrations showing that the ICP-OES technique is well suited for quantitation of elemental impurities. Excluding Os, spike recoveries in the range of 85.3-103.8% were obtained with relative standard deviations (%RSD) ranging from 1.3 to 3.2%. Due to memory effects the spike recovery and %RSD of Os were 161.5% and 13.7%, respectively, thus the method will need further development with respect to elimination of the memory effect of Os. The method was proven to be specific but with potential spectral interference for Ir, Os, Pb, Pt and Rh necessitating visual examination of the spectra. Hg memory effect was handled by using lower spike levels combined with rinsing with 0.1M HCl. The tablets had a content of Fe and Pt of 182.8 ± 18.1 and 2.8 ± 0.2 μg/g, respectively and did therefore not exceed the limit concentration defined by USP. It is suggested that the developed method is applicable to pharmaceutical products with a composition and maximal amount of daily intake (g drug product/day) similar to the tablets used in this work. Copyright © 2013 Elsevier B.V. All rights reserved.

Feasibility Studies of Parametric X-rays Use in a Medical Environment

NASA Astrophysics Data System (ADS)

Sones, Bryndol; Danon, Yaron; Blain, Ezekiel

2009-03-01

Parametric X-rays (PXR) are produced from the interaction of relativistic electrons with the periodic structure of crystal materials. Smooth X-ray energy tunability is achieved by rotating the crystal with respects to the electron beam direction. Experiments at the Rensselaer Polytechnic Institute 60-MeV LINAC produce quasi-monochromatic X-rays (6-35 keV) from various target crystals to include highly oriented pyrolytic graphite (HOPG), LiF, Si, Ge, Cu, and W using electron beam currents up to 6 uA. These experiments demonstrate the first PXR images and some of the merits of thin metallic crystals. Recent experiments with a 100-μm thick Cu crystal improve the Cu PXR (with energy ˜12 keV) to Cu fluorescence ratio by a factor of 20 compared to a 1 mm-thick Cu crystal. This study uses Monte Carlo techniques to investigate (1) PXR dose compared to emissions from simulated Mo, Rh, and W anodes for mammography applications and (2) electron scattering effects when considering LiF111, Si111, and Cu111 PXR production using electron beams with energies of 20-30 MeV. Advantages in using monochromatic PXR compared to X-rays from Mo and Rh anodes in mammography applications result in a dose per incident photon reduction by a factor of 2. Using 20 MeV electrons, the thinner Cu111 crystal for 15 keV PXR production results in an electron scattering angle of 30.7+/-0.2 mrad offering the best potential for PXR from lower energy electrons.

Moisture barrier properties of single-layer graphene deposited on Cu films for Cu metallization

NASA Astrophysics Data System (ADS)

Gomasang, Ploybussara; Abe, Takumi; Kawahara, Kenji; Wasai, Yoko; Nabatova-Gabain, Nataliya; Thanh Cuong, Nguyen; Ago, Hiroki; Okada, Susumu; Ueno, Kazuyoshi

2018-04-01

The moisture barrier properties of large-grain single-layer graphene (SLG) deposited on a Cu(111)/sapphire substrate are demonstrated by comparing with the bare Cu(111) surface under an accelerated degradation test (ADT) at 85 °C and 85% relative humidity (RH) for various durations. The change in surface color and the formation of Cu oxide are investigated by optical microscopy (OM) and X-ray photoelectron spectroscopy (XPS), respectively. First-principle simulation is performed to understand the mechanisms underlying the barrier properties of SLG against O diffusion. The correlation between Cu oxide thickness and SLG quality are also analyzed by spectroscopic ellipsometry (SE) measured on a non-uniform SLG film. SLG with large grains shows high performance in preventing the Cu oxidation due to moisture during ADT.

Effects of Chloride and Sulfate Salts on the Inhibition or Promotion of Sucrose Crystallization in Initially Amorphous Sucrose-Salt Blends.

PubMed

Thorat, Alpana A; Forny, Laurent; Meunier, Vincent; Taylor, Lynne S; Mauer, Lisa J

2017-12-27

The effects of salts on the stability of amorphous sucrose and its crystallization in different environments were investigated. Chloride (LiCl, NaCl, KCl, MgCl 2 , CaCl 2 , CuCl 2 , FeCl 2 , FeCl 3 , and AlCl 3 ) and sulfate salts with the same cations (Na 2 SO 4 , K 2 SO 4 , MgSO 4 , CuSO 4 , Fe(II)SO 4 , and Fe(III)SO 4 ) were studied. Samples (sucrose controls and sucrose:salt 1:0.1 molar ratios) were lyophilized, stored in controlled temperature and relative humidity (RH) conditions, and monitored for one month using X-ray diffraction. Samples were also analyzed by differential scanning calorimetry, microscopy, and moisture sorption techniques. All lyophiles were initially amorphous, but during storage the presence of a salt had a variable impact on sucrose crystallization. While all samples remained amorphous when stored at 11 and 23% RH at 25 °C, increasing the RH to 33 and 40% RH resulted in variations in crystallization onset times. The recrystallization time generally followed the order monovalent cations < sucrose < divalent cations < trivalent cations. The presence of a salt typically increased water sorption as compared to sucrose alone when stored at the same RH; however, anticrystallization effects were observed for sucrose combined with salts containing di- and trivalent cations in spite of the increased water content. The cation valency and hydration number played a major role in dictating the impact of the added salt on sucrose crystallization.

Effects of Alloyed Metal on the Catalysis Activity of Pt for Ethanol Partial Oxidation: Adsorption and Dehydrogenation on Pt3M (M=Pt, Ru, Sn, Re, Rh, and Pd)

PubMed Central

Xu, Zhen-Feng; Wang, Yixuan

2011-01-01

The adsorption and dehydrogenation reactions of ethanol over bimetallic clusters, Pt3M (M = Pt, Ru, Sn, Re, Rh, and Pd), have been extensively investigated with density functional theory. Both the α-hydrogen and hydroxyl adsorptions on Pt as well as on the alloyed transition metal M sites of PtM were considered as initial reaction steps. The adsorptions of ethanol on Pt and M sites of some PtM via the α-hydrogen were well established. Although the α-hydrogen adsorption on Pt site is weaker than the hydroxyl, the potential energy profiles show that the dehydrogenation via the α-hydrogen path has much lower energy barrier than that via the hydroxyl path. Generally for the α-hydrogen path the adsorption is a rate-determining-step because of rather low dehydrogenation barrier for the α-hydrogen adsorption complex (thermodynamic control), while the hydroxyl path is determined by its dehydrogenation step (kinetic control). The effects of alloyed metal on the catalysis activity of Pt for ethanol partial oxidation, including adsorption energy, energy barrier, electronic structure, and eventually rate constant were discussed. Among all of the alloyed metals only Sn enhances the rate constant of the dehydrogenation via the α-hydrogen path on the Pt site of Pt3Sn as compared with Pt alone, which interprets why the PtSn is the most active to the oxidation of ethanol. PMID:22102920

Local suppression of the hidden-order phase by impurities in URu2Si2

NASA Astrophysics Data System (ADS)

Pezzoli, Maria E.; Graf, Matthias J.; Haule, Kristjan; Kotliar, Gabriel; Balatsky, Alexander V.

2011-06-01

We consider the effects of impurities on the enigmatic hidden order (HO) state of the heavy-fermion material URu2Si2. In particular, we focus on local effects of Rh impurities as a tool to probe the suppression of the HO state. To study local properties, we introduce a lattice free energy, where the time invariant HO order parameter Ψ and local antiferromagnetic (AFM) order parameter M are competing orders. Near each Rh atom, the HO order parameter is suppressed, creating a hole in which local AFM order emerges as a result of competition. These local holes are created in the fabric of the HO state like in a Swiss cheese and “filled” with droplets of AFM order. We compare our analysis with recent NMR results on U(RhxRu1-x)2Si2 and find good agreement with the data.

Resonant-enhanced spectroscopy of molecular rotations with a scanning tunneling microscope.

PubMed

Natterer, Fabian Donat; Patthey, François; Brune, Harald

2014-07-22

We use rotational excitation spectroscopy with a scanning tunneling microscope to investigate the rotational properties of molecular hydrogen and its isotopes physisorbed on the surfaces of graphene and hexagonal boron nitride (h-BN), grown on Ni(111), Ru(0001), and Rh(111). The rotational excitation energies are in good agreement with ΔJ = 2 transitions of freely spinning p-H2 and o-D2 molecules. The variations of the spectral line shapes for H2 among the different surfaces can be traced back to a molecular resonance-mediated tunneling mechanism. Our data for H2/h-BN/Rh(111) suggest a local intrinsic gating on this surface due to lateral static dipoles. Spectra on a mixed monolayer of H2, HD, and D2 display all three J = 0 → 2 rotational transitions, irrespective of tip position, thus pointing to a multimolecule excitation, or molecular mobility in the physisorbed close-packed layer.

Method to remove ammonia using a proton-conducting ceramic membrane

DOEpatents

Balachandran, Uthamalinga; Bose, Arun C

2003-10-07

An apparatus and method for decomposing NH.sub.3. A fluid containing NH.sub.3 is passed in contact with a tubular membrane that is a homogeneous mixture of a ceramic and a first metal, with the ceramic being selected from one or more of a cerate having the formula of M'Ce.sub.1-x M".sub.3-.delta., zirconates having the formula M'Zr.sub.1-x M"O.sub.3-.delta., stannates having the formula M'Sn.sub.1-x M'O.sub.3-.delta., where M' is a group IIA metal, M" is a dopant metal of one or more of Ca, Y, Yb, In, Nd, Gd or mixtures thereof and .delta. is a variable depending on the concentration of dopant and is in the range of from 0.001 to 0.5, the first metal is a group VIII or group IB element selected from the group consisting of Pt, Ag, Pd, Fe, Co, Cr, Mn, V, Ni, Au, Cu, Rh, Ru and mixtures thereof. The tubular membrane has a catalytic metal on the side thereof in contact with the fluid containing NH.sub.3 which is effective to cause NH.sub.3 to decompose to N.sub.2 and H.sub.2. When the H.sub.2 contacts the membrane H.sup.+ ions are formed which pass through the membrane driving the NH.sub.3 decomposition toward completion.

Using microkinetic analysis to search for novel anhydrous formaldehyde production catalysts

NASA Astrophysics Data System (ADS)

Li, Han-Jung; Lausche, Adam C.; Peterson, Andrew A.; Hansen, Heine A.; Studt, Felix; Bligaard, Thomas

2015-11-01

Direct dehydrogenation of methanol to produce anhydrous formaldehyde is investigated using periodic density functional theory (DFT) and combining the microkinetic model to estimate rates and selectivities on stepped (211) surfaces under a desired reaction condition. Binding energies of reaction intermediates and transition state energies for each elementary reaction can be accurately scaled with CHO and OH binding energies as the only descriptors. Based on these two descriptors, a steady-state microkinetic model is constructed with a piecewise adsorbate-adsorbate interaction model that explicitly includes the effects of adsorbate coverage on the rates and selectivities as well as the volcano plots are obtained. Our results show that most of the stepped (211) pure-metallic surfaces such as Au, Pt, Pd, Rh, Ru, Ni, Fe, and Co are located in a region of low activity and selectivity toward CH2O production due to higher rate for CH2O dehydrogenation than CH2O desorption. The selectivities toward CH2O production on Zn, Cu, and Ag surfaces are located on the boundary between the high and low selectivity regions. To find suitable catalysts for anhydrous CH2O production, a large number of A3B-type transition metal alloys are screened based on their predicted rates and selectivities, as well as their estimated stabilities and prices. We finally propose several promising candidates for the dehydrogenation of CH3OH.

A versatile in situ spectroscopic cell for fluorescence/transmission EXAFS and X-ray diffraction of heterogeneous catalysts in gas and liquid phase.

PubMed

Hannemann, Stefan; Casapu, Maria; Grunwaldt, Jan Dierk; Haider, Peter; Trüssel, Philippe; Baiker, Alfons; Welter, Edmund

2007-07-01

A new spectroscopic cell suitable for the analysis of heterogeneous catalysts by fluorescence EXAFS (extended X-ray absorption fine structure), transmission EXAFS and X-ray diffraction during in situ treatments and during catalysis is described. Both gas-phase and liquid-phase reactions can be investigated combined with on-line product analysis performed either by mass spectrometry or infrared spectroscopy. The set-up allows measurements from liquid-nitrogen temperature to 973 K. The catalysts are loaded preferentially as powders, but also as self-supporting wafers. The reaction cell was tested in various case studies demonstrating its flexibility and its wide applicability from model studies at liquid-nitrogen temperature to operando studies under realistic reaction conditions. Examples include structural studies during (i) the reduction of alumina-supported noble metal particles prepared by flame-spray pyrolysis and analysis of alloying in bimetallic noble metal particles (0.1%Pt-0.1%Pd/Al(2)O(3), 0.1%Pt-0.1%Ru/Al(2)O(3), 0.1%Pt-0.1%Rh/Al(2)O(3), 0.1%Au-0.1%Pd/Al(2)O(3)), (ii) reactivation of aged 0.8%Pt-16%BaO-CeO(2) NO(x) storage-reduction catalysts including the NO(x) storage/reduction cycle, and (iii) alcohol oxidation over gold catalysts (0.6%Au-20%CuO-CeO(2)).

Catalysts for the selective oxidation of hydrogen sulfide to sulfur

DOEpatents

Srinivas, Girish; Bai, Chuansheng

2000-08-08

This invention provides catalysts for the oxidation of hydrogen sulfide. In particular, the invention provides catalysts for the partial oxidation of hydrogen sulfide to elemental sulfur and water. The catalytically active component of the catalyst comprises a mixture of metal oxides containing titanium oxide and one or more metal oxides which can be selected from the group of metal oxides or mixtures of metal oxides of transition metals or lanthanide metals. Preferred metal oxides for combination with TiO.sub.2 in the catalysts of this invention include oxides of V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Tc, Ru, Rh, Hf, Ta, W, Au, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Catalysts which comprise a homogeneous mixture of titanium oxide and niobium (Nb) oxide are also provided. A preferred method for preparing the precursor homogenous mixture of metal hydroxides is by coprecipitation of titanium hydroxide with one or more other selected metal hydroxides. Catalysts of this invention have improved activity and/or selectivity for elemental sulfur production. Further improvements of activity and/or selectivity can be obtained by introducing relatively low amounts (up to about 5 mol %)of a promoter metal oxide (preferably of metals other than titanium and that of the selected second metal oxide) into the homogeneous metal/titanium oxide catalysts of this invention.

A Framework for Collaborative Quadrotor - Ground Robot Missions

DTIC Science & Technology

2011-12-01

corresponds to the following criteria (117) ( ) ( ) ( )X t AX t BU t  cK ( ) ( )cU t K X t  0 ( )T TJ X QX U RU dt      2 2 1 , 1,2...pattern (wanding process), whose edges have reflectors on the top, within the whole space trying to cover every possible view angle of each of the...BR RS  , where ( ) BS  is a skew symmetric matrix. The term ( )B BS V  is the Coriolis term and can be written as: ( )B B B B qw rv S V V ru

Production of Oxidation-Resistant Cu-Based Nanoparticles by Wire Explosion

PubMed Central

Kawamura, Go; Alvarez, Samuel; Stewart, Ian E.; Catenacci, Matthew; Chen, Zuofeng; Ha, Yoon-Cheol

2015-01-01

The low performance or high cost of commercially available conductive inks limits the advancement of printed electronics. This article studies the explosion of metal wires in aqueous solutions as a simple, low-cost, and environmentally friendly method to prepare metallic nanoparticles consisting of Cu and Cu alloys for use in affordable, highly conductive inks. Addition of 0.2 M ascorbic acid to an aqueous explosion medium prevented the formation of Cu2O shells around Cu nanoparticles, and allowed for the printing of conductive lines directly from these nanoparticles with no post-treatment. Cu alloy nanoparticles were generated from metal wires that were alloyed as purchased, or from two wires of different metals that were twisted together. Cu nanoparticles alloyed with 1% Sn, 5% Ag, 5% Ni and 30% Ni had electrical conductivities similar to Cu but unlike Cu, remained conductive after 24 hrs at 85 °C and 85% RH. PMID:26669447

Promotional effects of chemisorbed oxygen and hydroxide in the activation of C-H and O-H bonds over transition metal surfaces

NASA Astrophysics Data System (ADS)

Hibbitts, David; Neurock, Matthew

2016-08-01

Electronegative coadsorbates such as atomic oxygen (O*) and hydroxide (OH*) can act as Brønsted bases when bound to Group 11 as well as particular Group 8-10 metal surfaces and aid in the activation of X-H bonds. First-principle density functional theory calculations were carried out to systematically explore the reactivity of the C-H bonds of methane and surface methyl intermediates as well as the O-H bond of methanol directly and with the assistance of coadsorbed O* and OH* intermediates over Group 11 (Cu, Ag, and Au) and Group 8-10 transition metal (Ru, Rh, Pd, Os, Ir, and Pt) surfaces. C-H as well as O-H bond activation over the metal proceeds via a classic oxidative addition type mechanism involving the insertion of the metal center into the C-H or O-H bond. O* and OH* assist C-H and O-H activation over particular Group 11 and Group 8-10 metal surfaces via a σ-bond metathesis type mechanism involving the oxidative addition of the C-H or O-H bond to the metal along with a reductive deprotonation of the acidic C-H and O-H bond over the M-O* or M-OH* site pair. The O*- and OH*-assisted C-H activation paths are energetically preferred over the direct metal catalyzed C-H scission for all Group 11 metals (Cu, Ag, and Au) with barriers that are 0.4-1.5 eV lower than those for the unassisted routes. The barriers for O*- and OH*-assisted C-H activation of CH4 on the Group 8-10 transition metals, however, are higher than those over the bare transition metal surfaces by as much as 1.4 eV. The C-H activation of adsorbed methyl species show very similar trends to those for CH4 despite the differences in structure between the weakly bound methane and the covalently adsorbed methyl intermediates. The activation of the O-H bond of methanol is significantly promoted by O* as well as OH* intermediates over both the Group 11 metals (Cu, Ag, and Au) as well as on all Group 8-10 metals studied (Ru, Rh, Pd, Os, Ir, and Pt). The O*- and OH*-assisted CH3O-H barriers are 0.6 to 2.0 eV lower than unassisted barriers, with the largest differences occurring on Group 11 metals. The higher degree of O*- and OH*-promotion in activating methanol over that in methane and methyl is due to the stronger interaction between the basic O* and OH* sites and the acidic proton in the O-H bond of methanol versus the non-acidic H in the C-H bond of methane. A detailed analysis of the binding energies and the charges for O* and OH* on different metal surfaces indicates that the marked differences in the properties and reactivity of O* and OH* between the Group 11 and Group 8-10 metals is due to the increased negative charge on the O-atoms (in O* as well as OH*) bound to Group 11 metals. The promotional effects of O* and OH* are consistent with a proton-coupled electron transfer and the cooperative role of the metal-O* or metal-OH* pair in carrying out the oxidative addition and reductive deprotonation of the acidic C-H and O-H bonds. Ultimately, the ability of O* or OH* to act as a Brønsted base depends upon its charge, its binding energy on the metal surface (due to shifts in its position during X-H activation), and the acidity of the H-atom being abstracted.

Seismic stratigraphy of sedimentary cover in Amerasian Basin based on the results of Russian High Arctic expeditions

NASA Astrophysics Data System (ADS)

Poselov, Viktor; Kireev, Artem; Smirnov, Oleg; Butsenko, Viktor; Zholondz, Sergey; Savin, Vasily

2016-04-01

Massive amount of multichannel seismic (MCS) data were obtained by Russian High Arct ic expeditions "Arctica-2011", "Acrtica-2012" and "Arctica-2014". More than 40 MCS lines are located in the Amerasian basin and help to substantiate the seismic stratigraphy model of its sedimentary cover. The proposed seismic stratigraphy model was successively determined for the Cenozoic and pre-Cenozoic parts of the sedimentary section and was based on correlation of the Russian MCS data and seismic data documented by boreholes. Cenozoic part of the sedimentary cover is based on correlation of the Russian MCS data and AWI91090 section calibrated by ACEX-2004 boreholes on the Lomonosov Ridge. Two major unconformities are traced. The upper regional unconformity (RU) is associated with a major pre-Miocene hiatus. Another major hiatus is recorded in the borehole section between the Campanian and the Upper Paleocene units. It is recognized as the post-Campanian unconformity (pCU) in the seismic sections. Formation of the regional unconformities is associated with a fundamental change in depositional environment. Formation of RU was initiated by opening of the Fram Strait gateway at the Paleogene/Neogene boundary. Post-Campanian unconformity is linked with the initial stage of the Eurasian Basin opening between the Cretaceous and the Paleogene. Cenozoic sedimentary units are continuously traced from the East-Siberian and Chukchi sea shelves across the transit zone to the Amerasian basin. Paleogene unit (between pCU and RU) is formed under the neritic depositional environment and it is characterized by an extremely small thickness on the Lomonosov Ridge (less than 200 m), on the Mendeleev Rise and in the Podvodnikov Basin (not more than 300-400 m). Neogene unit (above RU) consists of hemipelagic deposits and occupies the essential part of thickness of the Cenozoic section in Podvodnikov and Makarov Basins. Interval velocities in the Paleogene unit vary within 2.8-3.2 km/s, in the Neogene unit they vary within 1.8-2.7 km/s. Pre-Cenozoic part of the sedimentary cover is based on tracing major unconformities from boreholes on the Chukchi shelf (Crackerjack, Klondike, Popcorn) to the North-Chuckchi Trough and further to the Mendeleev Rise as well as to the Vilkitsky Trough and the adjacent Podvodnikov Basin. Three regional unconformities are correlated: Jurassic (JU - top of the Upper Ellesmerian unit), Lower Cretaceous (LCU) and Brookian (BU - base of the Lower Brookian unit). Above the acoustic basement the pre-Cenozoic section is mainly represented by terrigenous units. Two major unconformities: RU and pCU are allocated on all MCS lines intersecting the Mendeleev Rise along its entire extent. BU is traced nearly everywhere along the rise excepting certain acoustic basement highs. All unconformities are also traced from the Mendeleev Rise to the continental structure of the Chuckchi Borderland. Sedimentary sequence between pCU and JU which underlies deposits of the Upper Ellesmerian unit is recorded as a synrift unit of the entire area of the Podvodnikov Basin. MCS data show a natural prolongation of the sedimentary cover from the shelf to the Podvodnikov Basin without any breaks and tectonic movements. Interval velocities in the Upper Cretaceous unit (between pCU and BU) vary within 3.2-3.9 km/s, in the pre-Upper Cretaceous units (between BU and the acoustic basement) vary within 4.1-4.8 km/s.

Synergistic effect of rice husk addition on hydrothermal treatment of sewage sludge: fate and environmental risk of heavy metals.

PubMed

Shi, Wansheng; Liu, Chunguang; Shu, Youju; Feng, Chuanping; Lei, Zhongfang; Zhang, Zhenya

2013-12-01

Hydrothermal treatment (HTT) at 200°C was applied to immobilize heavy metals (HMs) and the effect of rice husk (RH) addition was investigated based on total HMs concentration, fractionation and leaching tests. The results indicated that a synergistic effect of RH addition and HTT could be achieved on reducing the risk of HMs from medium and low risk to no risk. Metals were redistributed and transformed from weakly bounded state to stable state during the HTT process under RH addition. Notably at a RH/sludge ratio of 1/1.75 (d.w.), all the HMs showed no eco-toxicity and no leaching toxicity, with the concentrations of leachable Cr, Ni, Cu and Cd decreased by 17%, 89%, 95% and 93%, respectively. This synergistic effect of RH addition and HTT on the risk reduction of HMs implies that HTT process with RH addition could be a promising and safe disposal technology for sewage sludge treatment in practice. Copyright © 2013 Elsevier Ltd. All rights reserved.

Investigation of the physical properties of two Laves phase compounds HRh2 (H = Ca and La): A DFT study

NASA Astrophysics Data System (ADS)

Rahaman, Md. Zahidur; Rahman, Md. Atikur

2018-05-01

By using the first-principle calculations, the structural, elastic, electronic and optical properties of Laves phase intermetallic compounds CaRh2 and LaRh2 prototype with MgCu2 are investigated. The evaluated lattice parameters are consistent with the experimental values. The important elastic properties, such as bulk modulus B, shear modulus G, Young’s modulus Y and the Poisson’s ratio v, are computed by applying the Voigt-Reuss-Hill (VRH) approximation. The analysis of Pugh’s ratio exhibits the ductile nature of both the phases. Electronic conductivity is predicted for both the compounds. Most of the contribution comes from Rh-4d states. The study of bonding characteristics reveals the existence of ionic and metallic bonds in both intermetallics. The study of optical properties indicates that CaRh2 is a better dielectric material than LaRh2. Absorption quality of both the phases is good in the ultraviolet region.

Highly recyclable and ultra-rapid catalytic reduction of organic pollutants on Ag-Cu@ZnO bimetal nanocomposite synthesized via green technology

NASA Astrophysics Data System (ADS)

Gangarapu, Manjari; Sarangapany, Saran; Suja, Devipriya P.; Arava, Vijaya Bhaskara Rao

2018-04-01

In this study, synthesis of Ag-Cu alloy bimetal nanoparticles anchored on high surface and porous ZnO using a facile, greener and low-cost aqeous bark extract of Aglaia roxburghiana for highly active, ultra-rapid and stable catalyst is performed. The nanocomposite was scrupulously characterized using UV-Vis spectrophotometer, X-ray diffraction, Raman spectrophotometer, high-resolution transmission electron microscope, selected area (electron) diffraction, scanning electron microscope with energy dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy. The catalytic activity of the green synthesized Ag-Cu bimetal nanocomposite was evaluated in the reduction of 4-nitrophenol (4-NP), methylene blue (MB) and rhodamine B (Rh B) dyes. The different types of dye exhibited very high and effective catalytic activity within few seconds. The theoretical investigations reveal that the unique synergistic effect of Ag-Cu nanoparticles and immobilization over ZnO assists in the reduction of 4-NP, MB and Rh B. Loading and leaching of metal nanoparticles were obtained using inductively coupled plasma atomic emission spectroscopy. Moreover, the stable and efficient recyclability of nanocomposite by centrifugation after completion of the reaction was demonstrated. The results lead to the design different possible bimetal on ZnO with boosting and an effective catalyst for the environmental applications.

Facile synthesis of polyaniline-modified CuS with enhanced adsorbtion and photocatalytic activity

NASA Astrophysics Data System (ADS)

Wang, Xiufang; Chen, Shaohua; Shuai, Ying

2016-10-01

Novel hierarchical polyaniline-modified CuS (PANI-CuS) has been synthesized by simple assembling PANI on the surface of flower-like CuS spheres. The PANI modification enhances the adsorption properties of flower-like CuS. The prepared PANI-CuS composites exhibit higher visible-light-driven photocatalytic activities in degradation of rhodamine B (RhB) than that of neat CuS. The unusual photocatalytic activity could be attributed to the great adsorptivity of dyes, the extended photoresponse range, and the high migration efficiency of photoinduced electrons, which may effectively suppress the charge recombination. This work not only provides a simple strategy for fabricating highly efficient and stable CuS-based composites, but also proves that these unique structures are excellent platforms for significantly improving their visible- light-driven photoactivities, holding great promise for their applications in the field of purifying polluted water resources.

Field-induced phase transition in Ce3M4Sn13 with M = Co, Rh, and Ru

NASA Astrophysics Data System (ADS)

Ślebarski, Andrzej; Goraus, Jerzy

2018-05-01

Large electronic specific heat coefficient, C (T) / T , suggests that the family of Ce3M4Sn13 heavy-fermions (HF) is near a magnetic quantum critical point (QCP). We analyze the 4 f contribution to the specific heat in terms of the single-ion Kondo resonance model. An unexpected change in the Kondo temperature TK versus magnetic field B signals a field-induced phase transition between the magnetically correlated HF phase and a single-ion Kondo impurity state.

Nuclear Data Sheets for A = 91

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

Baglin, Coral M.

2013-10-15

Experimental nuclear structure and decay data for all known A=91 nuclides (As, Se, Br, Kr, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd) have been evaluated. This evaluation, covering data received by 1 September 2013, supersedes the 1998 evaluation by C. M. Baglin published in Nuclear Data Sheets86, 1 (1999) (15 December 1998 literature cutoff), and subsequent evaluations by C. M. Baglin added to the ENSDF database for Kr, Sr and Zr (29 December 2000 literature cutoff) and by B. Singh for {sup 91}Tc (6 November 2000 literature cutoff)

Attrition resistant fluidizable reforming catalyst

DOEpatents

Parent, Yves O [Golden, CO; Magrini, Kim [Golden, CO; Landin, Steven M [Conifer, CO; Ritland, Marcus A [Palm Beach Shores, FL

2011-03-29

A method of preparing a steam reforming catalyst characterized by improved resistance to attrition loss when used for cracking, reforming, water gas shift and gasification reactions on feedstock in a fluidized bed reactor, comprising: fabricating the ceramic support particle, coating a ceramic support by adding an aqueous solution of a precursor salt of a metal selected from the group consisting of Ni, Pt, Pd, Ru, Rh, Cr, Co, Mn, Mg, K, La and Fe and mixtures thereof to the ceramic support and calcining the coated ceramic in air to convert the metal salts to metal oxides.

Crossover between superconductivity and magnetism in SrRuO3 mesocrystal embedded YBa2Cu3O7-x heterostructures.

PubMed

Suresh, Vandrangi; Lin, Jheng-Cyuan; Liu, Heng-Jui; Zhang, Zaoli; Chiang, Ping-Chih; Hsun, Yu-Ching; Chen, Yi-Chun; Lin, Jiunn-Yuan; Chu, Ying-Hao

2016-11-03

The competition between superconductivity and ferromagnetism poses great challenges and has attracted renewed interest for applications in novel spintronic devices. In order to emphasize their interactions, we fabricated a heterostructure composed of superconducting YBa 2 Cu 3 O 7-δ (YBCO) film embedded with itinerant ferromagnetic SrRuO 3 (SRO) mesocrystals. Starting from a doping concentration of 10 vol% of SRO mesocrystal in a YBCO matrix, corresponding to the density of SRO nanocrystals ∼5 × 10 9 cm -2 , which exhibits the typical characteristic of a metal-superconductor transition, and then increasing the magnetic interactions as a function of SRO embedment, the electronic correlation and the interplay between superconductivity and magnetism throughout the temperature regime were investigated. A metal-insulator transition in the normal state of YBCO and a crossover between superconductivity and magnetism at low temperatures were found upon increasing the density of nano-size SRO crystallites in the YBCO matrix as a consequence of competing interactions between these two ordered phases.

Anode materials for lithium ion batteries

DOEpatents

Abouimrane, Ali; Amine, Khalil

2017-04-11

An electrochemical device includes a composite material of general Formula (1-x)J-(x)Q wherein: J is a metal carbon alloy of formula Sn.sub.zSi.sub.z'Met.sub.wMet'.sub.w'C.sub.t; Q is a metal oxide of formula A.sub..gamma.M.sub..alpha.M'.sub..alpha.'O.sub..beta.; and wherein: A is Li, Na, or K; M and M' are individually Ge, Mo, Al, Ga, As, Sb, Te, Ti, Ta, Zr, Ca, Mg, Sr, Ba, Li, Na, K, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Rt, Ru or Cd; Met and Met' are individually Ge, Mo, Al, Ga, As, Sb, Te, Ti, Ta, Zr, Ca, Mg, Sr, Ba, Li, Na, K, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Rt, Ru or Cd; 0

Heterobimetallic coordination polymers involving 3d metal complexes and heavier transition metals cyanometallates

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

Peresypkina, Eugenia V.; Samsonenko, Denis G.; Novosibirsk State University, Novosibirsk 630090

The results of the first steps in the design of coordination polymers based on penta- and heptacyanometallates of heavier d transitions metals are presented. The 2D structure of the coordination polymers: [(Mn(acacen)){sub 2}Ru(NO)(CN){sub 5}]{sub n} and two complexes composed of different cyanorhenates, [Ni(cyclam)]{sub 2}[ReO(OH)(CN){sub 4}](ClO{sub 4}){sub 2}(H{sub 2}O){sub 1.25} and [Cu(cyclam)]{sub 2}[Re(CN){sub 7}](H{sub 2}O){sub 12}, was confirmed by single crystal XRD study, the rhenium oxidation state having been proved by the magnetic measurements. An amorphism of [M(cyclam)]{sub 3}[Re(CN){sub 7}]{sub 2} (M=Ni, Cu) polymers does not allow to define strictly their dimensionality and to model anisotropic magnetic behavior of the compounds.more » However, with high probability a honey-comb like layer structure could be expected for [M(cyclam)]{sub 3}[Re(CN){sub 7}]{sub 2} complexes, studied in this work, because such an arrangement is the most common among the bimetallic assemblies of hexa- and octacyanometallates with a ratio [M(cyclam)]/[M(CN){sub n}]=3/2. For the first time was prepared and fully characterized a precursor (n-Bu{sub 4}N){sub 2}[Ru(NO)(CN){sub 5}], soluble in organic media. - Graphical abstract: The very first results in the design of 2D coordination polymers based on penta- and heptacyanometallates of 4d and5d transitions metals are presented. - Highlights: • Design of coordination polymers based on penta- and heptacyanometallates. • New Ru and Re cyanide based heterobimetallic coordination complexes. • Hydrolysis and ox/red processes involving [Re(CN){sub 7}]{sup 3+} during crystallization. • High magnetic anisotropy of [M(cyclam)]{sub 3}[Re(CN){sub 7}]{sub 2}(H{sub 2}O){sub n}, M=Cu, Ni, complexes.« less

Charge partitioning and anomalous hole doping in Rh-doped Sr 2 IrO 4

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

Chikara, S.; Fabbris, G.; Terzic, J.

2017-02-01

The simultaneous presence of sizable spin-orbit interactions and electron correlations in iridium oxides has led to predictions of novel ground states including Dirac semimetals, Kitaev spin liquids, and superconductivity. Electron and hole doping studies of spin-orbit assisted Mott insulator Sr2IrO4 are being intensively pursued due to extensive parallels with the La2CuO4 parent compound of cuprate superconductors. In particular, the mechanism of charge doping associated with replacement of Ir with Rh ions remains controversial with profound consequences for the interpretation of electronic structure and transport data. Using x-ray absorption near edge structure measurements at the Rh L, K, and Ir Lmore » edges we observe anomalous evolution of charge partitioning between Rh and Ir with Rh doping. The partitioning of charge between Rh and Ir sites progresses in a way that holes are initially doped into the J(eff) = 1/2 band at low x only to be removed from it at higher x values. This anomalous hole doping naturally explains the reentrant insulating phase in the phase diagram of Sr2Ir1-x Rh-x O-4 and ought to be considered when searching for superconductivity and other emergent phenomena in iridates doped with 4d elements.« less

Charge partitioning and anomalous hole doping in Rh-doped Sr 2 IrO 4

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

Chikara, Shalinee; Fabbris, G.; Terzic, J.

2017-02-15

The simultaneous presence of sizable spin-orbit interactions and electron correlations in iridium oxides has led to predictions of novel ground states including Dirac semimetals, Kitaev spin liquids, and superconductivity. Electron and hole doping studies of spin-orbit assisted Mott insulator Sr 2IrO 4 are being intensively pursued due to extensive parallels with the La 2CuO 4 parent compound of cuprate superconductors. In particular, the mechanism of charge doping associated with replacement of Ir with Rh ions remains controversial with profound consequences for the interpretation of electronic structure and transport data. Using x-ray absorption near edge structure measurements at the Rh L,more » K, and Ir L edges we observe anomalous evolution of charge partitioning between Rh and Ir with Rh doping. The partitioning of charge between Rh and Ir sites progresses in a way that holes are initially doped into the J eff = 1/2 band at low x only to be removed from it at higher x values. Furthermore, this anomalous hole doping naturally explains the reentrant insulating phase in the phase diagram of Sr 2Ir 1–xRh xO 4 and ought to be considered when searching for superconductivity and other emergent phenomena in iridates doped with 4d elements.« less

Development of Mesoporous Nanocatalysts for Production of Hydrogen and Fisher Tropsch Studies

NASA Astrophysics Data System (ADS)

Abrokwah, Richard Yeboah

The primary aim of this study was to develop mesoporous nanocatalysts for (i) hydrogen production via steam reforming of methanol (SRM) in a tubular reactor, and (ii) syngas conversion to hydrocarbons via Fisher-Tropsch synthesis using silicon microchannel microreactors. The mesoporous catalysts for SRM were prepared by an optimized one-pot hydrothermal synthesis procedure. The catalysts were investigated for SRM activity in a packed bed tubular reactor using metals, namely, Cu, Co, Ni, Pd, Zn, and Sn. The metals were incorporated in different supports -MCM-41, SBA-15, CeO2, TiO2, and ZrO2 to investigate the influence of support on catalyst properties. A sharp contrast in catalyst performance was noticed depending on the type of support employed. For example, in SRM at 250 °C, Cu supported on amorphous silica SBA-15 and MCM-41 produced significantly less CO (< 7%) compared to other crystalline supports Cu-TiO2 and Cu/ZrO2 that showed high CO selectivity of ˜56% and ˜37%, respectively. Amongst all the metals studied for SRM activity using 1:3 methanol:water mole ratio at 250 °C, 10%Cu-MCM-41 showed the best performance with 68% methanol conversion, 100% H2 , ˜6 % CO, 94% CO2 selectivities, and no methane formation. Furthermore, 10%Cu-CeO2 yielded the lowest CO selectivity of 1.84% and the highest CO2 selectivity of ˜98% at 250 °C. Stability studies of the catalysts conducted for time-on-stream of 40 h at 300 °C revealed that Cu-MCM41 was the most stable and displayed consistent steady state conversion of ˜74%. Our results indicate that, although coking played an influential role in deactivation of most catalysts, thermal sintering and changes in MCM-41 structure can be responsible for the catalyst deactivation. For monomtetallic systems, the MCM-41 supported catalysts especially Pd and Sn showed appreciable hydrothermal stability under the synthesis and reaction conditions. While bimetallic Pd-Co-MCM-41 and Cu-Ni-MCM-41 catalysts produced more CO, Cu-Zn-MCM-41 and Cu-Sn-MCM-41exhibited better SRM activity, and produced much less CO and CH4. In spite of the improved the stability and dispersion of the monometallic active sites in the support, no noticeable synergistic activity was observed in terms of H2 and CO selectivities in the multimetallic catalysts. For the Fisher-Tropsch (F-T) studies, Co-TiO 2, Fe-TiO2 and Ru-TiO2 catalysts were prepared by the sol-gel method and coated on 116 microchannels (50mum wide x 100mum deep) of a Si-microreactor. The F-T process parameters such as temperature, pressure and flow rates were controlled by an in-house setup programmed by LabVIEWRTM. The effect of temperature on F-T activity in the range of 150 to 300°C was investigated at 1 atm, a flow rate of 6 ml/min and a constant H2:CO molar ratio of 2:1. In our initial studies at 220 °C, 12%Ru-TiO2 showed higher CO conversion of 74% and produced the highest C2-C4 hydrocarbon selectivity-of ˜11% ethane, 22% propane and ˜17% butane. The overall catalyst stability and performance was in the order of 12%Ru-TiO2>> 12%Fe-TiO2 > 12%Co-TiO2.

An Experimental and Analytical Investigation of a Radial Face Seal

DTIC Science & Technology

1976-01-01

c \\]f’ n" •’ * TIMOTHY W. SWAFFORD h ; January 1976 Cjl...Vi 4J to c H Ö o Ö Ü (D M s Ö • H tfl 1-1 U a) :r^J. y^^^^^l 32 From NA iransparent tubing To seal ^xH— Globe valves Supply... c . 3 n) cNi a o cu <• C8 rH CC 1 A > o. U T-: 1 ^O J ^ ’ k 3 o a c ^ ^O TI —< r- -i! O 0) H - H rH H

Lordosis facilitated by GPER-1 receptor activation involves GnRH-1, progestin and estrogen receptors in estrogen-primed rats.

PubMed

Domínguez-Ordóñez, R; Garcia-Juárez, M; Lima-Hernández, F J; Gómora-Arrati, P; Domínguez-Salazar, E; Blaustein, J D; Etgen, A M; González-Flores, O

2018-02-01

The present study assessed the participation of membrane G-protein coupled estrogen receptor 1 (GPER-1) and gonadotropin releasing hormone 1 (GnRH-1) receptor in the display of lordosis induced by intracerebroventricular (icv) administration of G1, a GPER-1 agonist, and by unesterified 17β-estradiol (free E 2 ). In addition, we assessed the participation of both estrogen and progestin receptors in the lordosis behavior induced by G1 in ovariectomized (OVX), E 2 -benzoate (EB)-primed rats. In Experiment 1, icv injection of G1 induced lordosis behavior at 120 and 240min. In Experiment 2, icv injection of the GPER-1 antagonist G15 significantly reduced lordosis behavior induced by either G1 or free E 2 . In addition, Antide, a GnRH-1 receptor antagonist, significantly depressed G1 facilitation of lordosis behavior in OVX, EB-primed rats. Similarly, icv injection of Antide blocked the stimulatory effect of E 2 on lordosis behavior. In Experiment 3, systemic injection of either tamoxifen or RU486 significantly reduced lordosis behavior induced by icv administration of G1 in OVX, EB-primed rats. The results suggest that GnRH release activates both estrogen and progestin receptors and that this activation is important in the chain of events leading to the display of lordosis behavior in response to activation of GPER-1 in estrogen-primed rats. Copyright © 2018 Elsevier Inc. All rights reserved.

Chalcophile and siderophile elements in sulphide inclusions in eclogitic diamonds and metal cycling in a Paleoproterozoic subduction zone

NASA Astrophysics Data System (ADS)

Aulbach, Sonja; Stachel, Thomas; Seitz, Hans-Michael; Brey, Gerhard P.

2012-09-01

In the central Slave craton, eclogitic diamonds are suggested to have formed during Paleoproterozoic subduction in a meta-gabbroic substrate representing former lower oceanic crust that interacted with serpentinite-derived fluids at high fluid-rock ratios. In order to assess the behaviour of chalcophile and siderophile elements (CSE) during this process, we measured trace-element concentrations of sulphide inclusions in diamonds from the Diavik mine by laser ablation ICPMS. The nitrogen systematics of the diamonds (average N concentration of ˜600 ppm and aggregation state 4% N as B-aggregates) indicate average mantle residence temperatures of ˜1050 °C for a 1.85 Ga formation age, corresponding ˜170 km depth. Based on the available evidence from natural samples and experiments, we suggest that the highly siderophile elements (HSE: Os, Ir, Ru, Rh, Pd, Pt, Re) except Au behaved largely conservatively during fluid-induced metamorphism, which may point to a reducing and Cl-poor nature of the fluid. The abundances of the moderately siderophile and chalcophile elements Cr, Co, Ni, Cu, Ag, Sn, Mo and W may also have changed little, whereas As, Sb, Tl, Pb and Bi may have been mobilised from the subducting lower oceanic crust. The partitioning of CSE in eclogite and geochemical behaviour during oceanic crust formation was assessed for inferred conservative elements. Assuming an average sulphide mode of 0.3 wt.% for the oceanic crust, its abundances of HSE, Cu, Mo, Se and Te can mostly be accounted for by sulphide minerals alone. Lithophile behaviour of W, Cd, In and Sn and enrichment in residual melts may explain their lower abundances in the gabbroic eclogitic sulphide inclusions compared to MORB sulphide. These elements, as well as Cr, Co, Ni, Zn and Ga require additional host phases both in eclogite, where rutile partitions significant amounts of Cr, Zn, W, Ga and Sn, and in the oceanic crust.

A delafossite-based copper catalyst for sustainable Cl2 production by HCl oxidation.

PubMed

Mondelli, Cecilia; Amrute, Amol P; Schmidt, Timm; Pérez-Ramírez, Javier

2011-07-07

A copper catalyst based on a delafossite precursor (CuAlO(2)) displays high activity and extraordinary lifetime in the gas-phase oxidation of HCl to Cl(2), representing a cost-effective alternative to RuO(2)-based catalysts for chlorine recycling. This journal is © The Royal Society of Chemistry 2011

Natural sunlight irradiated flower-like CuS synthesized from DMF solvothermal treatment

NASA Astrophysics Data System (ADS)

Zhao, Wei; Wang, Zihao; Zhou, Lei; Liu, Nianqi; Wang, Hongxing

2016-09-01

Three-dimensional CuS hierarchical crystals with high catalytic activity had been successfully fabricated using a facile solvothermal process. The CuS microparticles showed different flower-like morphology and good dispersion by optimizing reaction conditions. It was found that using N,N-dimethylformamide (DMF) as the solvent reagent in the proper temperature conditions was favorable for the growth of hierarchically structured CuS. The hexagonal flower-like CuS synthesized at 170°C for 60 min displayed broad-spectrum photocatalytic properties under ultraviolet (UV) and visible irradiation. The as-prepared CuS crystals exhibited good performance to decolorize methylene blue (MB) solution under visible light irradiation. The total organic carbon (TOC) removal of rhodamine B (RhB) solution was nearly 60% after 5 h of the natural sunlight irradiation, and the property was stable after testing over four recycles, demonstrating a potential application in waster water treatment.

Nuclear Data Sheets for A = 92

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

Baglin, Coral M.

2012-10-15

Nuclear structure and decay data pertaining to all nuclides with mass number A = 92 (As, Se, Br, Kr, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd) have been compiled and evaluated, and incorporated into the ENSDF data file. All literature available by 15 September 2012 has been considered. This evaluation supersedes the previous publication for this mass chain (Coral M. Baglin, Nuclear Data Sheets 91, 423 (2000) (November 2000 cutoff date)), and subsequent unpublished reevaluations by C.M. Baglin for {sup 92}Kr (January 2004 literature cut-off) and {sup 92}Sr (August 2003 literature cut-off).

Dissolution of spent nuclear fuel in carbonate-peroxide solution

NASA Astrophysics Data System (ADS)

Soderquist, Chuck; Hanson, Brady

2010-01-01

This study shows that spent UO2 fuel can be completely dissolved in a room temperature carbonate-peroxide solution apparently without attacking the metallic Mo-Tc-Ru-Rh-Pd fission product phase. In parallel tests, identical samples of spent nuclear fuel were dissolved in nitric acid and in an ammonium carbonate, hydrogen peroxide solution. The resulting solutions were analyzed for strontium-90, technetium-99, cesium-137, europium-154, plutonium, and americium-241. The results were identical for all analytes except technetium, where the carbonate-peroxide dissolution had only about 25% of the technetium that the nitric acid dissolution had.

Development and validation of an ICP-MS method for the determination of elemental impurities in TP-6076 active pharmaceutical ingredient (API) according to USP 〈232〉/〈233〉.

PubMed

Chahrour, Osama; Malone, John; Collins, Mark; Salmon, Vrushali; Greenan, Catherine; Bombardier, Amy; Ma, Zhongze; Dunwoody, Nick

2017-10-25

The new guidelines of the United States pharmacopeia (USP), European pharmacopeia (EP) and international conference on harmonization (ICH) regulating elemental impurities limits in pharmaceuticals signify the end of unspecific analysis of metals as outlined in USP 〈231〉. The new guidelines specify both daily doses and concentration/limits of elemental impurities in pharmaceutical final products, active pharmaceutical ingredients (API) and excipients. In chapter USP 〈233〉 method implementation, validation and quality control during the analytical process are described. We herein report the use of a stabilising matrix that overcomes low spike recovery problem encountered with Os and allows the determination of all USP required elemental impurities (As, Cd, Hg, Pb, V, Cr, Ni, Mo, Cu, Pt, Pd, Ru, Rh, Os and Ir) in a single analysis. The matrix was used in the validation of a method to determine elemental impurities in TP-6076 active pharmaceutical ingredient (API) by ICP-MS according to the procedures defined in USP〈233〉 and to GMP requirements. This validation will support the regulatory submission of TP-6076 which is a novel tetracycline analogue effective against the most urgent multidrug-resistant gram-negative bacteria. Evaluation of TP-6076 in IND-enabling toxicology studies has led to the initiation of a phase 1 clinical trial. Copyright © 2017 Elsevier B.V. All rights reserved.

Src kinase signaling mediates estrous behavior induced by 5β-reduced progestins, GnRH, prostaglandin E2 and vaginocervical stimulation in estrogen-primed rats.

PubMed

Lima-Hernández, Francisco J; Beyer, Carlos; Gómora-Arrati, Porfirio; García-Juárez, Marcos; Encarnación-Sánchez, José L; Etgen, Anne M; González-Flores, Oscar

2012-11-01

The progesterone receptor (PR) is a dual function protein that acts in the nucleus as a transcriptional factor and at the cytoplasm as a scaffold for the Src-MAPK signaling pathway. Several agents lacking affinity for the PR, such as 5β-reduced progestins, GnRH or prostaglandin E(2) (PGE(2)) facilitate estrous behavior in ovariectomized (ovx), estrogen-primed rats yet their action is blocked by the antiprogestin RU486. We hypothesize that these agents act by using the PR-Src-mitogen activated protein kinase alternative pathway. To test this hypothesis we used PP2, a specific inhibitor of the Src kinase family. Intraventricular infusion of 30 μg of PP2, 30 min before behavioral testing, significantly attenuated estrous behaviors induced in estradiol benzoate (E(2)B)-primed rats by 5β-dihydroprogesterone (5β-DHP), 5β-pregnan-3β-ol-20-one (5β,3β-Pgl), GnRH, PGE(2) and by manual flank/vaginocervical stimulation. These results suggest that the Src signaling system, by activating mitogen-activated protein kinases, participates in the facilitation of estrous behavior in E(2)B-primed rats induced by agents lacking affinity for the PR. Copyright © 2012 Elsevier Inc. All rights reserved.

Stabilization of the Ti{sub 3}Co{sub 5}B{sub 2}-type structure for Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} through Si–Ti substitution

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

Xie, Weiwei, E-mail: weiweix@princeton.edu; Fuccillo, M.K.; Phelan, B.F.

2015-07-15

We report a route for designing and synthesizing Ti{sub 3}Co{sub 5}B{sub 2}-type compounds in the Ti–Ru–B system by using chemical substitution of Si for Ti to decrease the d-electron-based antibonding interactions that it is argued would otherwise drive an instability in this structure for unsubstituted Ti{sub 3}Ru{sub 5}B{sub 2}. Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} with x=0.75, 1.00 and 1.25 nominal compositions crystalizes in the Ti{sub 3}Co{sub 5}B{sub 2} structure type using arc melting methods, whereas at lower doping levels (x=0.0, 0.25 and 0.50) the more complex Zn{sub 11}Rh{sub 18}B{sub 8}-type structure is stable. Electronic structure calculations show that in hypothetical,more » unsubstituted Ti{sub 3}Ru{sub 5}B{sub 2} with the Ti{sub 3}Co{sub 5}B{sub 2}-type structure, the antibonding interactions are strong around the Fermi level between the Ti and Ru in the structure that form tetragonal prisms. We propose that weakening these strong interactions through the partial substitution of isovalent Si for Ti leads to the observed stability of the Ti{sub 3}Co{sub 5}B{sub 2}-type structure for Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} for x≈1. - Graphical abstract: We present the designing and synthesizing of Ti{sub 3}Co{sub 5}B{sub 2}-type compounds in the Ti–Ru–B system by using chemical substitution of Si for Ti to decrease the d-electron-based antibonding interactions that would otherwise drive an instability in this structure for unsubstituted Ti{sub 3}Ru{sub 5}B{sub 2}. Electronic structure calculations show that in hypothetical, unsubstituted Ti{sub 3}Ru{sub 5}B{sub 2} with the Ti{sub 3}Co{sub 5}B{sub 2}-type structure, the antibonding interactions are strong around the Fermi level between the Ti and Ru in the structure that form tetragonal prisms. We propose that weakening these strong interactions through the partial substitution of isovalent Si for Ti leads to the observed stability of the Ti{sub 3}Co{sub 5}B{sub 2}-type structure for Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} for x≈1. - Highlights: • New quaternary phase Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} in Ti{sub 3}Co{sub 5}B{sub 2}-type structure is reported. • Chemical substitution of isovalent Si for Ti is used to stabilize the phase. • Decreasing the d-electron-based antibonding interactions is proved by calculation. • Physical properties of Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} are presented down to 0.4 K.« less

Strong anisotropy within a Heisenberg model in the J eff = 1 2 insulating state of Sr 2 Ir 0.8 Ru 0.2 O 4

DOE PAGES

Calder, Stuart A.; Kim, J. W.; Taylor, Alice E.; ...

2016-12-28

The dispersive magnetic excitations in Sr 2IrO 4 have previously been well described within an isospin-1/2 Heisenberg model on a square lattice that revealed parallels with La 2CuO 4. In this paper, we investigate the inelastic spectra of Sr 2Ir 0.8Ru 0.2O 4 with resonant inelastic x-ray scattering (RIXS) at the Ir L 3 edge. The results are well described using linear spin-wave theory within a similar Heisenberg model applicable to Sr 2IrO 4; however, the disorder induced by the substitution of 20% Ir 4+ ions for Ru 4+ removes longer range exchange interactions. A large spin gap (40 meV)more » is measured indicating strong anisotropy from spin-orbit coupling that is manifest due to the altered magnetic structure in Sr 2Ir 0.8Ru 0.2O 4 with c-axis aligned moments compared to the basal plane moments in the parent. Finally, collectively the results indicate the robustness of a Heisenberg model description even when the magnetic structure is altered and the J eff = 1/2 moments are diluted.« less

On the Structure Sensitivity of Dimethyl Ether Electro-oxidation on Eight FCC Metals: A First-Principles Study

DOE PAGES

Herron, Jeffrey A.; Ferrin, Peter; Mavrikakis, Manos

2015-09-24

The electro-oxidation of dimethyl ether (DME) was investigated using periodic, self-consistent density functional theory (DFT) calculations on the (111) and (100) facets of eight fcc metals: Au, Ag, Cu, Pt, Pd, Ni, Ir, and Rh. The goal of this study is to understand the experimentally observed structure sensitivity of this reaction on Pt, and to predict trends in structure sensitivity of this reaction across the other seven metals studied. The main conclusion is that the enhanced activity of Pt(100) originates from more facile C–O bond breaking and removal of surface poisoning species, including CO and CH. When comparing C–O bondmore » breaking energetics, we do not find a universal trend where these elementary steps are always more exergonic on the (100) facet. However, we find that, at a given potential, DME can be dehydrogenated (prior to breaking the C–O bond) to a greater extent on the (100) facet. Additionally, we find that the reaction energy for C–O bond breaking in CHxOCHy-type species becomes increasingly exergonic as the species becomes increasingly dehydrogenated. Together, the more facile dehydrogenation on the (100) facets provides more favorable routes to C–O bond activation. Though we calculate a lower onset potential on Au(100), Ag(100), Cu(100), Pt(100), and Pd(100) than their respective (111) facets, the calculated onset potential for Ni(100), Ir(100), and Rh(100) are actually higher than for their respective (111) facets. Lastly, by constructing theoretical volcano plots, we conclude that Au(100), Ag(100), Cu(100), Pt(100), and Pd(100) should be more active than their respective (111) facets, while Ni(100), Rh(100), and Ir(100) will show the opposite trend.« less

The effect of pressure on the structural, electronic, magnetic, and thermodynamic properties of the Mn2RuGe inverse Heusler alloy

NASA Astrophysics Data System (ADS)

Song, Ting; Sun, Xiao-Wei; Tian, Jun-Hong; Wei, Xiao-Ping; Wan, Gui-Xin; Ma, Qin

2017-04-01

In the frame of density functional theory, first-principles calculations based on generalized gradient approximation and quasi-harmonic Debye approximation model in which the phononic effects are taken into account have been carried out to investigate the structural, electronic, magnetic, and thermodynamic properties of full-Heusler alloy Mn2RuGe in CuHg2Ti-type structure in the pressure range of 0-50 GPa. Present calculations predict that Mn2RuGe is a ferrimagnet with an optimized lattice parameter of 5.854 Å. The calculated total magnetic moment of 2.01 μB per formula unit is very close to integer value and agree well with the Slater-Pauling rule, where the partial spin moments of Mn (A) and Mn (B) which mainly contribute to the total magnetic moment are 2.66 μB and -0.90 μB, respectively. In the study of the energy band structures and density of states, Mn2RuGe exhibits half-metallicity with an indirect gap of 0.235 eV in the spin-down channels, and the shifting of bands towards higher energies in spin-down channel under high pressure. Meanwhile, the high-pressure thermodynamic properties of Mn2RuGe, such as the pressure-volume-temperature relationship, bulk modulus, thermal expansivity, heat capacity, Debye temperature, and Grüneisen parameter are evaluated systematically in the temperature range of 0-900 K. This set of data is considered as the useful information to understand the high-pressure and high-temperature properties for the Mn2RuZ-type Heusler alloy family.

Radioactivity levels in major French rivers: summary of monitoring chronicles acquired over the past thirty years and current status.

PubMed

Eyrolle, Frédérique; Claval, David; Gontier, Gilles; Antonelli, Christelle

2008-07-01

Since the beginning of the 1990 s, liquid releases of gamma-emitting radionuclides from French nuclear facilities have generally fallen by almost 85%. Almost 65% of gamma-emitting liquid effluents released into freshwater rivers concerned the River Rhône (Southeast France), with around 85% of this originating from the Marcoule spent fuel reprocessing plant. Upstream of French nuclear plants, artificial radionuclides still detected by gamma spectrometry in 2006, include (137)Cs, (131)I as well as (60)Co, (58)Co and (54)Mn in the case of the Rhine (Switzerland nuclear industries). In the wake of the fallout from the Chernobyl accident, (103)Ru, (106)Rh-Ru, (110 m)Ag, (141)Ce and (129)Te were detected in rivers in the east of France. Some of these radionuclides were found in aquatic plants until 1989. In eastern France, (137)Cs activity in river sediments and mosses is still today two to three times greater than that observed in similar environments in western France. No (134)Cs has been detected upstream of nuclear plants in French rivers since 2001. Downstream of nuclear plants, the gamma emitters still detected regularly in rivers in 2006 are (137)Cs, (134)Cs, (60)Co, (58)Co, (110 m)Ag, (54)Mn, (131)I, together with (241)Am downstream of the Marcoule spent fuel reprocessing plant. Alpha and beta emitters such as plutonium isotopes and (90)Sr first entered freshwaters at the early 1950s due to the leaching of soils contaminated by atmospheric fallout from nuclear testing. These elements were also introduced, in the case of the Rhône River, via effluent from the Marcoule reprocessing plant. Until the mid 1990 s, plutonium isotope levels observed in the lower reaches of the Rhône were 10 to 1000 times higher than those observed in other French freshwaters. Data gathered over a period of almost thirty years of radioecological studies reveal that the only radionuclides detected in fish muscles are (137)Cs, (90)Sr, plutonium isotopes and (241)Am. At the scale of the French territory, there is no significant difference since the mid 1990 s between (137)Cs activity observed downstream of nuclear facilities and that observed upstream, whether in sediments, mosses and fish. Finally, this study highlights that the natural radioactivity of surface freshwaters are around 25 times greater than artificial radioactivity from gamma emitters. However, non gamma emitters released by nuclear industries, such as (3)H, may lead to artificial activity levels 2 to 20 times higher than natural levels.

Heterobimetallic coordination polymers involving 3d metal complexes and heavier transition metals cyanometallates

NASA Astrophysics Data System (ADS)

Peresypkina, Eugenia V.; Samsonenko, Denis G.; Vostrikova, Kira E.

2015-04-01

The results of the first steps in the design of coordination polymers based on penta- and heptacyanometallates of heavier d transitions metals are presented. The 2D structure of the coordination polymers: [{Mn(acacen)}2Ru(NO)(CN)5]n and two complexes composed of different cyanorhenates, [Ni(cyclam)]2[ReO(OH)(CN)4](ClO4)2(H2O)1.25 and [Cu(cyclam)]2[Re(CN)7](H2O)12, was confirmed by single crystal XRD study, the rhenium oxidation state having been proved by the magnetic measurements. An amorphism of [M(cyclam)]3[Re(CN)7]2 (M=Ni, Cu) polymers does not allow to define strictly their dimensionality and to model anisotropic magnetic behavior of the compounds. However, with high probability a honey-comb like layer structure could be expected for [M(cyclam)]3[Re(CN)7]2 complexes, studied in this work, because such an arrangement is the most common among the bimetallic assemblies of hexa- and octacyanometallates with a ratio [M(cyclam)]/[M(CN)n]=3/2. For the first time was prepared and fully characterized a precursor (n-Bu4N)2[Ru(NO)(CN)5], soluble in organic media.

Charge partitioning and anomalous hole doping in Rh-doped Sr2IrO4

NASA Astrophysics Data System (ADS)

Chikara, S.; Fabbris, G.; Terzic, J.; Cao, G.; Khomskii, D.; Haskel, D.

2017-02-01

The simultaneous presence of sizable spin-orbit interactions and electron correlations in iridium oxides has led to predictions of novel ground states including Dirac semimetals, Kitaev spin liquids, and superconductivity. Electron and hole doping studies of spin-orbit assisted Mott insulator Sr2Ir O4 are being intensively pursued due to extensive parallels with the La2CuO4 parent compound of cuprate superconductors. In particular, the mechanism of charge doping associated with replacement of Ir with Rh ions remains controversial with profound consequences for the interpretation of electronic structure and transport data. Using x-ray absorption near edge structure measurements at the Rh L, K, and Ir L edges we observe anomalous evolution of charge partitioning between Rh and Ir with Rh doping. The partitioning of charge between Rh and Ir sites progresses in a way that holes are initially doped into the Jeff=1 /2 band at low x only to be removed from it at higher x values. This anomalous hole doping naturally explains the reentrant insulating phase in the phase diagram of Sr2Ir1 -xRhxO4 and ought to be considered when searching for superconductivity and other emergent phenomena in iridates doped with 4 d elements.

Photo-reduced Cu/CuO nanoclusters on TiO2 nanotube arrays as highly efficient and reusable catalyst

NASA Astrophysics Data System (ADS)

Jin, Zhao; Liu, Chang; Qi, Kun; Cui, Xiaoqiang

2017-01-01

Non-noble metal nanoparticles are becoming more and more important in catalysis recently. Cu/CuO nanoclusters on highly ordered TiO2 nanotube arrays are successfully developed by a surfactant-free photoreduction method. This non-noble metal Cu/CuO-TiO2 catalyst exhibits excellent catalytic activity and stability for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with the presence of sodium borohydride (NaBH4). The rate constant of this low-cost Cu/CuO based catalyst is even higher than that of the noble metal nanoparticles decorated on the same TiO2 substrate. The conversion efficiency remains almost unchanged after 7 cycles of recycling. The recycle process of this Cu/CuO-TiO2 catalyst supported by Ti foil is very simple and convenient compared with that of the common powder catalysts. This catalyst also exhibited great catalytic activity to other organic dyes, such as methylene blue (MB), rhodamine B (RhB) and methyl orange (MO). This highly efficient, low-cost and easily reusable Cu/CuO-TiO2 catalyst is expected to be of great potential in catalysis in the future.

Density-functional theory study of dimethyl carbonate synthesis by methanol oxidative carbonylation on single-atom Cu1/graphene catalyst

NASA Astrophysics Data System (ADS)

Sun, Wei; Shi, Ruina; Wang, Xuhui; Liu, Shusen; Han, Xiaoxia; Zhao, Chaofan; Li, Zhong; Ren, Jun

2017-12-01

The mechanism for dimethyl carbonate (DMC) synthesis by oxidation carbonylation of methanol on a single-atom Cu1/graphene catalyst was investigated by density-functional theory calculations. Carbon vacancies in graphene can significantly enhance the interaction between Cu atoms and graphene supports, and provide an increased transfer of electrons from Cu atoms to the graphene sheet. Compared with Cu-doped divacancy graphene (Cu/DG), Cu-doped monovacancy graphene (Cu/MG) provides a stronger interaction between adsorbents and the catalyst surface. Among the reaction processes over Cu1/graphene catalysts, CO insertion into methoxide was more favorable than dimethoxide. The rate-limiting step on the Cu/DG surface is the carbomethoxide reaction with methoxide, which is exothermic by 164.6 kJ mol-1 and has an activation barrier of 190.9 kJ mol-1 energy. Compared with that on the Cu crystal surface, Cu4 and Cu3Rh clusters, and the Cu2O(111) surface, the rate-determining step for DMC formation on Cu/MG, which is CO insertion into methoxide, needs to overcome the lowest barrier of 73.5 kJ mol-1 and is exothermic by 44.6 kJ mol-1. Therefore, Cu/MG was beneficial to the formation of DMC as a single-atom catalyst.

Selective borane reduction of phosphinoferrocene carbaldehydes to phosphinoalcohol-borane adducts. The coordination behaviour of 1-(diphenylphosphino)-1'-(methoxymethyl)ferrocene, a new ferrocene O,P-hybrid donor prepared from such an adduct.

PubMed

Stěpnička, Petr; Císařová, Ivana

2013-03-14

The reduction of ferrocene phosphino-aldehydes, R(2)PfcCHO (R = Ph, 2; Cy, 3; fc = ferrocene-1,1'-diyl, Cy = cyclohexyl) and (S(p))-[Fe(η(5)-C(5)H(3)-1-CHO-2-PPh(2))(η(5)-C(5)H(5))] ((S(p))-4), with BH(3)·THF or BH(3)·SMe(2) in THF at 0 °C selectively afforded the corresponding phosphinoalcohol-borane adducts, R(2)PfcCH(2)OH·BH(3) (R = Ph, 5; Cy, 6) and (S(p))-[Fe(η(5)-C(5)H(3)-1-CH(2)OH-2-PPh(2))(η(5)-C(5)H(5))]·BH(3) ((S(p))-7), in quantitative yields. In contrast, the reactions performed at elevated temperatures favoured the formation of methyl derivatives (e.g., Ph(2)PfcCH(3)·BH(3) (8)) resulting from overreduction (deoxygenation). The crystal structures of 3, 5, (S(p))-7, 8 and Cy(2)PfcBr (9) have been determined by single-crystal X-ray diffraction analysis. The crystal assemblies of adducts 5 and (S(p))-7 are built up by means of C-H...O contacts, O-H...HB dihydrogen bonds and other soft interactions but, surprisingly, not via the conventional O-H...O hydrogen bonds. Adduct 5 was smoothly deprotected to give the corresponding free phosphine, Ph(2)PfcCH(2)OH (1), and was further used for the preparation of a hybrid phosphinoether ligand, Ph(2)PfcCH(2)OMe (11). The latter compound was studied as a donor for Group 8-10 metal ions and for Cu(i), whereupon the following complexes were isolated and structurally characterised: [(η(6)-p-cymene)RuCl(2)(11-κP)] (12*), [(η(6)-p-cymene)RuCl(11-κP)(MeCN)][SbF(6)] (13*), [RhCl(cod)(11-κP)] (cod = η(2):η(2)-cycloocta-1,5-diene; 14), trans-[PdCl(2)(11-κP)(2)] (trans-15*), [PdCl(μ-Cl)(11-κP)](2) (16*), cis- and trans-[PtCl(2)(11-κP)(2)] (cis-17 and trans-17*), and [Cu(CF(3)SO(3)-κO)(11-κP)(H(2)O)] (18) (the asterisk indicates that the crystal structure was determined). In all these compounds, ligand 11 behaves as a P-monodentate donor while its ether group remains uncoordinated. This probably reflects structural flexibility of 11 resulting from the presence of the methylene linker and also distinguishes 11 from its known, non-spaced analogue Ph(2)PfcOMe.

New Polyazine-Bridged RuII,RhIII and RuII,RhI Supramolecular Photocatalysts for Water Reduction to Hydrogen Applicable for Solar Energy Conversion and Mechanistic Investigation of the Photocatalytic Cycle

NASA Astrophysics Data System (ADS)

Zhou, Rongwei

Underwater gliders are robust and long endurance ocean sampling platforms that are increasingly being deployed in coastal regions. This new environment is characterized by shallow waters and significant currents that can challenge the mobility of these efficient (but traditionally slow moving) vehicles. This dissertation aims to improve the performance of shallow water underwater gliders through path planning. The path planning problem is formulated for a dynamic particle (or "kinematic car") model. The objective is to identify the path which satisfies specified boundary conditions and minimizes a particular cost. Several cost functions are considered. The problem is addressed using optimal control theory. The length scales of interest for path planning are within a few turn radii. First, an approach is developed for planning minimum-time paths, for a fixed speed glider, that are sub-optimal but are guaranteed to be feasible in the presence of unknown time-varying currents. Next the minimum-time problem for a glider with speed controls, that may vary between the stall speed and the maximum speed, is solved. Last, optimal paths that minimize change in depth (equivalently, maximize range) are investigated. Recognizing that path planning alone cannot overcome all of the challenges associated with significant currents and shallow waters, the design of a novel underwater glider with improved capabilities is explored. A glider with a pneumatic buoyancy engine (allowing large, rapid buoyancy changes) and a cylindrical moving mass mechanism (generating large pitch and roll moments) is designed, manufactured, and tested to demonstrate potential improvements in speed and maneuverability.

Charge Order and Superconductivity in Underdoped YBa2 Cu3 O7 -δ under Pressure

NASA Astrophysics Data System (ADS)

Putzke, Carsten; Ayres, Jake; Buhot, Jonathan; Licciardello, Salvatore; Hussey, Nigel E.; Friedemann, Sven; Carrington, Antony

2018-03-01

In underdoped cuprates, an incommensurate charge density wave (CDW) order is known to coexist with superconductivity. A dip in Tc at the hole doping level where the CDW is strongest (np≃0.12 ) suggests that CDW order may suppress superconductivity. We investigate the interplay of charge order with superconductivity in underdoped YBa2 Cu3 O7 -δ by measuring the temperature dependence of the Hall coefficient RH(T ) at high magnetic field and at high hydrostatic pressure. We find that, although pressure increases Tc by up to 10 K at 2.6 GPa, it has very little effect on RH(T ). This suggests that pressure, at these levels, only weakly affects the CDW and that the increase in Tc with pressure cannot be attributed to a suppression of the CDW. We argue, therefore, that the dip in Tc at np≃0.12 at ambient pressure is probably not caused by the CDW formation.

Organic chemistry. A rhodium catalyst for single-step styrene production from benzene and ethylene.

PubMed

Vaughan, Benjamin A; Webster-Gardiner, Michael S; Cundari, Thomas R; Gunnoe, T Brent

2015-04-24

Rising global demand for fossil resources has prompted a renewed interest in catalyst technologies that increase the efficiency of conversion of hydrocarbons from petroleum and natural gas to higher-value materials. Styrene is currently produced from benzene and ethylene through the intermediacy of ethylbenzene, which must be dehydrogenated in a separate step. The direct oxidative conversion of benzene and ethylene to styrene could provide a more efficient route, but achieving high selectivity and yield for this reaction has been challenging. Here, we report that the Rh catalyst ((Fl)DAB)Rh(TFA)(η(2)-C2H4) [(Fl)DAB is N,N'-bis(pentafluorophenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene; TFA is trifluoroacetate] converts benzene, ethylene, and Cu(II) acetate to styrene, Cu(I) acetate, and acetic acid with 100% selectivity and yields ≥95%. Turnover numbers >800 have been demonstrated, with catalyst stability up to 96 hours. Copyright © 2015, American Association for the Advancement of Science.

Strongly suppressed proximity effect and ferromagnetism in topological insulator/ferromagnet/superconductor thin film trilayers of Bi2Se3/SrRuO3/underdoped YBa2Cu3O x : a possible new platform for Majorana nano-electronics

NASA Astrophysics Data System (ADS)

Koren, Gad

2018-07-01

We report properties of a topological insulator–ferromagnet–superconductor trilayers comprised of thin films of 20 nm thick {Bi}}2{Se}}3 on 10 nm SrRuO3 on 30 nm {YBa}}2{Cu}}3{{{O}}}x. As deposited trilayers are underdoped and have a superconductive transition with {{T}}{{c}} onset at 75 K, zero resistance at 65 K, {{T}}Cueri} at 150 K and {{T}}* of about 200 K. Further reannealing under vacuum yields the 60 K phase of {YBa}}2{Cu}}3{{{O}}}x which still has zero resistance below about 40 K. Only when 10 × 100 microbridges were patterned in the trilayer, some of the bridges showed resistive behavior all the way down to low temperatures. Magnetoresistance versus temperature of the superconductive ones showed the typical peak due to flux flow against pinning below {{T}}{{c}}, while the resistive ones showed only the broad leading edge of such a peak. All this indicates clearly weak-link superconductivity in the resistive bridges between superconductive {YBa}}2{Cu}}3{{{O}}}x grains via the topological and ferromagnetic cap layers. Comparing our results to those of a reference trilayer (RTL) with the topological {Bi}}2{Se}}3 layer substituted by a non-superconducting highly overdoped {La}}1.65{Sr}}0.35{CuO}}4, indicates that the superconductive proximity effect as well as ferromagnetism in the topological trilayer are actually strongly suppressed compared to the non-topological RTL. This strong suppression could originate in lattice and Fermi levels mismatch as well as in short coherence length and unfavorable effects of strong spin–orbit coupling in {Bi}}2{Se}}3 on the d-wave pairing of {YBa}}2{Cu}}3{{{O}}}x. Proximity induced edge currents in the SRO/YBCO layer could lead to Majorana bound states, a possible signature of which is observed in the present study as zero bias conductance peaks.

High-pressure synthesis and structural, physical properties of CaIr1-xPtxO3 and CaIr1-xRhxO3

NASA Astrophysics Data System (ADS)

Hirai, S.; Bromiley, G. D.; Klemme, S.; Irifune, T.; Ohfuji, H.; Attfield, P.; Nishiyama, N.

2010-12-01

Since the discovery of the perovskite to post-perovskite transition in MgSiO3 in a laser-heated DAC, wide attention has been focussed on the post-perovskite phase of MgSiO3. This is because the post-perovskite phase is likely to play a key role in Earth’s lowermost mantle, and because the perovskite to post-perovskite transition can explain many features of the D” seismic discontinuity. While it is meaningful to conduct further studies of MgSiO3, the post-perovskite phase of MgSiO3 cannot be quenched to ambient pressure/temperature conditions. Thus, further studies must be conducted using analogue compounds of MgSiO3 post-perovskite, which are quenchable to ambient pressure/temperature conditions. The post-perovskite phase of MgSiO3 crystallizes in a layered structure with CaIrO3-structure. Therefore, it is useful to investigate compounds with CaIrO3-structure. There are only four quenchable oxides with CaIrO3-structure reported to date: CaIrO3, CaPtO3, CaRhO3 and CaRuO3. CaIrO3 can be synthesized at ambient pressure, whilst the other three oxides can only be obtained at high pressure/temperature conditions using a multi-anvil apparatus. Further studies on these materials have revealed structural phase transitions at high P-T and a metal-insulator transition by hole doping. In the case of CaIrO3, The post-perovskite phase of CaIrO3 synthesized at 2GPa, 1373K transforms into a perovskite phase at 2GPa, 1673K. In other words, the perovskite phase can be synthesized at temperatures higher than those needed for synthesizing the post-perovskite phase. This is also the case for CaRhO3 (6GPa, 1873K) and CaRuO3 (23GPa, 1343K), while CaPtO3 remained post-perovskite at higher temperatures. We have succeeded in synthesizing solid solutions between CaIrO3, CaPtO3 and CaRhO3. We have found the systematic change in structural and physical properties of post-perovskite oxides, with composition and P-T, which broadens the future opportunity for studying post-perovskite systems in terms of materials science applications. To our knowledge, this will be the first report on structural, magnetic and charge-transport properties of B-site substituted solid solutions of post-perovskite oxides with 4d/5d transition metals. High-quality polycrystalline samples of CaIr1-xPtxO3 and CaIr1-xRhxO3 have been obtained at high pressures, and structural, magnetic and charge-transport properties of the compounds will be reported. ODF analysis reveals that solutions of CaIrO3, CaPtO3 and CaRhO3 exhibit similar grain growth features to the mother compound, although growth in [0 1 0] plays a more dominant role than the growth in [0 0 1] for the solid solutions. CaIrO3 is a characteristic hard magnet suitable for applications such as magnetic recording, with TN = 108K. A new phase of CaIr1-xPtxO3 synthesized at a high P/T condition has Raman modes which resemble those of CaIrO3 perovskite, suggesting this phase has a perovskite structure.The instability of the perovskite phase of CaIr1-xPtxO3 reveals why the post-perovskite to peovskite phase transition has not been observed for CaPtO3 unlike the case for CaIrO3, CaRhO3 and CaRuO3.

Surfactant-free Synthesis of CuO with Controllable Morphologies and Enhanced Photocatalytic Property

NASA Astrophysics Data System (ADS)

Wang, Xing; Yang, Jiao; Shi, Liuxue; Gao, Meizhen

2016-03-01

A green synthesis for nanoleave, nanosheet, spindle-like, rugby-like, dandelion-like and flower-like CuO nanostructures (from 2D to 3D) is successfully achieved through simply hydrothermal synthetic method without the assistance of surfactant. The morphology of CuO nanostructures can be easily tailored by adjusting the amount of ammonia and the source of copper. By designing a time varying experiment, it is verified that the flower- and dandelion-like CuO structures are synthesized by the self-assembly and Ostwald ripening mechanism. Structural and morphological evolutions are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-visible diffuse reflectance spectra. Additionally, the CuO nanostructures with different morphologies could serve as a potential photocatalyst on the photodecomposition of rhodamine B (RhB) aqueous solutions in the presence of H2O2 under visible light irradiation.

Partitioning of Ru, Rh, Pd, Re, Ir and Pt between liquid metal and silicate at high pressures and high temperatures - Implications for the origin of highly siderophile element concentrations in the Earth's mantle

NASA Astrophysics Data System (ADS)

Mann, Ute; Frost, Daniel J.; Rubie, David C.; Becker, Harry; Audétat, Andreas

2012-05-01

The apparent overabundance of the highly siderophile elements (HSEs: Pt-group elements, Re and Au) in the mantles of Earth, Moon and Mars has not been satisfactorily explained. Although late accretion of a chondritic component seems to provide the most plausible explanation, metal-silicate equilibration in a magma ocean cannot be ruled out due to a lack of HSE partitioning data suitable for extrapolations to the relevant high pressure and high temperature conditions. We provide a new data set of partition coefficients simultaneously determined for Ru, Rh, Pd, Re, Ir and Pt over a range of 3.5-18 GPa and 2423-2773 K. In multianvil experiments, molten peridotite was equilibrated in MgO single crystal capsules with liquid Fe-alloy that contained bulk HSE concentrations of 53.2-98.9 wt% (XFe = 0.03-0.67) such that oxygen fugacities of IW - 1.5 to IW + 1.6 (i.e. logarithmic units relative to the iron-wüstite buffer) were established at run conditions. To analyse trace concentrations of the HSEs in the silicate melt with LA-ICP-MS, two silicate glass standards (1-119 ppm Ru, Rh, Pd, Re, Ir, Pt) were produced and evaluated for this study. Using an asymmetric regular solution model we have corrected experimental partition coefficients to account for the differences between HSE metal activities in the multicomponent Fe-alloys and infinite dilution. Based on the experimental data, the P and T dependence of the partition coefficients (D) was parameterized. The partition coefficients of all HSEs studied decrease with increasing pressure and to a greater extent with increasing temperature. Except for Pt, the decrease with pressure is stronger below ˜6 GPa and much weaker in the range 6-18 GPa. This change might result from pressure induced coordination changes in the silicate liquid. Extrapolating the D values over a large range of potential P-T conditions in a terrestrial magma ocean (peridotite liquidus at P ⩽ 60-80 GPa) we conclude that the P-T-induced decrease of D would not have been sufficient to explain HSE mantle abundances by metal-silicate equilibration at a common set of P-T-oxygen fugacity conditions. Therefore, the mantle concentrations of most HSEs cannot have been established during core formation. The comparatively less siderophile Pd might have been partly retained in the magma ocean if effective equilibration pressures reached 35-50 GPa. To a much smaller extent this could also apply to Pt and Rh providing that equilibration pressures reached ⩾60 GPa in the late stage of accretion. With most of the HSE partition coefficients at 60 GPa still differing by 0.5-3 orders of magnitude, metal-silicate equilibration alone cannot have produced the observed near-chondritic HSE abundances of the mantles of the Earth as well as of the Moon or Mars. Our results show that an additional process, such as the accretion of a late veneer composed of some type of chondritic material, was required. The results, therefore, support recent hybrid models, which propose that the observed HSE signatures are a combined result of both metal-silicate partitioning as well as an overprint by late accretion.

Search of collectivity at N >= 52 via lifetime measurements in ^96-98Ru

NASA Astrophysics Data System (ADS)

Kharraja, B.; Garg, U.; Ghugre, S. S.; Frohlich, A.; Ahmad, I.; Amro, H.; Blumenthal, D.; Carpenter, M. P.; Crowell, B.; Fisher, S.; Janssens, R. V. F.; Khoo, T. L.; Lauritsen, T.; Nissius, D.; Reviol, W.; Mueller, W.; Govil, I. M.; Ma, W. C.; Kaczarowski, R.; Ruchowska, E.

1996-05-01

Level structures of nuclei with N ~ 50 and Z ~ 40 exhibit interesting interplay between the single particle and collective degrees of freedom. Lifetime measurements are crucial to ascertain the intrinsic structures of the observed level sequences in this region and, specificaly to verify the onset of collectivity. This motivated us to undertake lifetime measurements using the RDM technique for ^96-98Ru nuclei. These nuclei were populated via the ^65Cu(^36Si,pyn) reaction at 142 MeV, and the Argonne-Notre Dame γ-ray facility was employed in conjonction with the Notre Dame plunger. Data were connected in coincidence at 12 distances rangin from 10 μm to 1000 μm giving us an effective lifetime range 1 ps to 400 ps.

Tetragonal-antiprismatic coordination of transition metals in intermetallic compounds: ω1-Mn6Ga29 and its structuralrelationships

NASA Astrophysics Data System (ADS)

Antonyshyn, Iryna; Prots, Yurii; Margiolaki, Irene; Schmidt, Marcus Peter; Zhak, Olga; Oryshchyn, Stepan; Grin, Yuri

2013-03-01

The new phase ω1-Mn6Ga29 was synthesised in single-crystal form from the elements applying the high-temperature centrifugation-aided filtration technique. The crystal structure was determined using diffraction data collected from a twinned specimen: a new prototype, space group P1¯; a=6.3114(2) Å, b=9.9557(3) Å, c=18.920(1) Å, α=90.473(1)°, β=90.847(1)°, γ=90.396(1)°; R1=0.047, wR2=0.117 for 317 variable parameters and 7346 observed reflections; twinning matrix 0 0 -1/3, 0 -1 0, -3 0 0; twin domains ratio 0.830(3):0.170. All manganese atoms in the crystal structure of ω1-Mn6Ga29 are coordinated exclusively by Ga forming distorted tetragonal antiprisms. The monocapped [MnGa8+1] antiprisms condense into pairs by sharing their pseudo-quadratic faces and are interconnected via common apexes and edges to form a 3D framework. The relationship between the crystal structures of ω1-Mn6Ga29 and CuAl2, α-, β-CoSn3, PtSn4, Ti4MnBi2, PdGa5, Rh3Ga16, Rh4Ga21, Al7FeCu2, Co2Al9, and RhBi4 is discussed.

The influence of external factors on the corrosion resistance of high temperature superconductor thin films against moisture

NASA Astrophysics Data System (ADS)

Murugesan, M.; Obara, H.; Yamasaki, H.; Kosaka, S.

2006-12-01

High temperature superconductor (HTS) thin films have been systematically investigated for their corrosion resistance against moisture by studying the role of external factors such as temperature (T), relative humidity (RH), and the type of substrates in the corrosion. In general, (i) the corrosion is progressed monotonously with increasing T as well as RH, (ii) a threshold level of water vapor is needed to cause degradation, and (iii) between T and RH, the influence of T is more dominant. HTS films on SrTiO3 and CeO2 buffered sapphire (cbs) substrates showed better corrosion stability and a low rate of degradation in the critical current density as compared to that of the film grown on MgO substrate. Between DyBa2Cu3Oz (DBCO) and YBa2Cu3Oz, the former is reproducibly found to have many fold higher corrosion resistance against moisture. This observed enhancement in the corrosion resistance in DBCO could be explained by the improved microstructure in the films and the better lattice matching with the substrate. Thus, the dual advantage of DBCO/cbs films, i.e., the enhanced corrosion stability of DBCO and the appropriate dielectric properties of sapphire, can be readily exploited for the use of DBCO/cbs films in the microwave and power devices.

Effect of steam during Fischer–Tropsch Synthesis using biomass-derived syngas

Treesearch

Zi Wang; Khiet Mai; Nitin Kumar; Thomas Elder; Leslie H. Groom; James J. Spivey

2017-01-01

Fischer–Tropsch synthesis (FTS) with biomass- derived syngas was performed using both iron-based 100Fe/6Cu/4K/25Al catalyst and ruthenium-based 5 % Ru/SiO2 catalyst. During FTS, different concentrations of steam were co-fed with the biomass-derived syngas to promote the water gas shift reaction and increase the H2/ CO ratio...

Conductive buffer layers and overlayers for the thermal stability of coated conductors

NASA Astrophysics Data System (ADS)

Cantoni, C.; Aytug, T.; Verebelyi, D. T.; Paranthaman, M.; Specht, E. D.; Norton, D. P.; Christen, D. K.

2001-03-01

We analyze fundamental issues related to the thermal and electrical stability of a coated conductor during its operation. We address the role of conductive buffer layers in the stability of Ni-based coated conductors, and the effect of a metallic cap layer on the electrical properties of Ni alloy-based superconducting tapes. For the first case we report on the fabrication of a fully conductive RABiTS architecture formed of bilayers of conductive oxides SrRuO3 and LaNiO3 on textured Ni tapes. For the second case we discuss measurements of current-voltage relations on Ag/YBa2Cu3O7-d and Cu/Ag/ YBa2Cu3O7-d prototype multilayers on insulating substrates. Limitations on the overall tape structure and properties that are posed by the stability requirement are presented.

Growth and Characterization of Reduced Dimensionality Superconductor-Related Phases by Molecular Beam Epitaxy

DTIC Science & Technology

1998-02-01

BaTiO3 Ferromagnets M., = 1.4 g SrRuO3 Colossal Magnetoresistance AR/RH > 104~ (6 T) (La,Sr)MnO 3 3 submitted to JOM B4Ti 3O12 PbUiO 3 (Ba,K)BiO3 YBa2C...films, perhaps as a result of those films being closer to the correct Ba/Ti stoichiometric ratio. This is seen in Fig. 5, where data for the permittivity ...as a function of temperature is shown for a 60 nm thick BaTiO 3 film (Note Permittivity BSS-12 -- Ls BSS12 that as explained earlier, this film

Development of a complex of instrumental nuclear-physical methods to detect PGE, Re, Au, and Ag in hard-to-analyze rocks and complex ores

NASA Astrophysics Data System (ADS)

Kolmogorov, Yu. P.; Mezentsev, N. A.; Mironov, A. G.; Parkhomenko, V. S.; Spiridonov, A. M.; Shaporenko, A. D.; Yusupov, T. S.; Zhmodik, S. M.; Zolotarev, K. V.; Anoshin, G. N.

2009-05-01

A system of methods to detect platinum group elements (PGE): Re, Au, and Ag in hard-to-analyze rocks and complex ores has been developed. It applies the SRXRF for Ru, Rh, Pd, and Ag and the INAA method for Os, Ir, Pt and Ag and implies mechanoactivation of probes to study. The results of measurement of standard samples of carbonaceous rocks and ores in order to PGE, gold, and silver confirm the possibility of detecting some of the above-listed elements with a detection limit of 10 ppb.

Hydrogen peroxide-assisted synthesis of novel three-dimensional octagonal-like CuO nanostructures with enhanced visible-light-driven photocatalytic activity

NASA Astrophysics Data System (ADS)

Chen, Xiangyu; Chu, Deqing; Wang, Limin; Hu, Wenhui; Yang, Huifang; Sun, Jingjing; Zhu, Shaopeng; Wang, Guowei; Tao, Jian; Zhang, Songsong

2018-04-01

Novel three-dimensional octagonal-like CuO micro-/nanostructures with diameters ranging from 10 to 15 μm have been successfully prepared by hydrogen peroxide-assisted hydrothermal method and subsequent calcination. The product morphology can be changed by simply ordering the amount of hydrogen peroxide (H2O2). When the amounts of H2O2 is increased, the length of the corner portion is increased and the width is narrower. The obtained octagonal CuO nanostructures were evaluated for their ability for the degradation of hazardous organic contaminants in water under visible-light irradiation. Comparing with commercial CuO and other CuO products, the CuO octagonal nanostructures exhibit excellent performance for photocatalytic decomposition of RhB (Rhodamine B). It is well established that effective photocatalytic performance results from its unique 3D octagonal nanostructures. We believe that the present work will provide some ideas for further fabrication of other novel nanostructures and exploration of their applications.

Spin valves with spin-engineered domain-biasing scheme

NASA Astrophysics Data System (ADS)

Lu, Z. Q.; Pan, G.

2003-06-01

Synthetic spin-filter spin valves with spin-engineered biasing scheme "sub/Ta/NiFe/IrMn/NiFe/NOL/Cu1/CoFe/Cu2/CoFe/Ru/CoFe/IrMn/Ta" were developed. In the structure, the orthogonal magnetic configuration for biasing and pinning field was obtained by one-step magnetic annealing process by means of spin flop, which eliminated the need for two antiferromagnetic materials with distinctively different blocking temperatures and two-step magnetic annealing as in conventional exchange biasing scheme. The longitudinal domain biasing of spin valves was achieved by using interlayer coupling field through Cu1 spacer. By adjusting the thickness of the Cu1 layer, the interlayer coupling biasing field can provide domain stabilization and was sufficiently strong to constrain the magnetization in coherent rotation. This can prevent Barkhausen noises associated with magnetization reversal. We report here a proof of concept study of such a domain-biasing scheme, which has its important technological applications in nanoscale spin valve and magnetic tunneling junction read heads and other spintronic devices.

Origin of primary PGM assemblage in сhromitite from a mantle tectonite at Harold's Grave (Shetland Ophiolite Complex, Scotland)

NASA Astrophysics Data System (ADS)

Badanina, Inna Yu.; Malitch, Kreshimir N.; Lord, Richard A.; Meisel, Thomas C.

2013-12-01

In this paper we present textural and mineral chemistry data for a PGM inclusion assemblage and whole-rock platinum-group element (PGE) concentrations of chromitite from Harold's Grave, which occurrs in a dunite pod in a mantle tectonite at Unst in the Shetland Ophiolite Complex (SOC), Scotland. The study utilized a number of analytical techniques, including acid digestion and isotope dilution (ID) ICP-MS, hydroseparation and electron microprobe analysis. The chromitite contains a pronounced enrichment of refractory PGE (IPGE: Os, Ir and Ru) over less refractory PGE (PPGE: Rh, Pt and Pd), typical of mantle hosted `ophiolitic' chromitites. A `primary' magmatic PGM assemblage is represented by euhedrally shaped (up to 60 μm in size) single and composite inclusions in chromite. Polyphase PGM grains are dominated by laurite and osmian iridium, with subordinate laurite + osmian iridium + iridian osmium and rare laurite + Ir-Rh alloy + Rh-rich sulphide (possibly prassoite). The compositional variability of associated laurite and Os-rich alloys at Harold's Grave fit the predicted compositions of experiment W-1200-0.37 of Andrews and Brenan (Can Mineral 40: 1705-1716, 2002) providing unequivocal information on conditions of their genesis, with the upper thermal stability of laurite in equilibrium with Os-rich alloys estimated at 1200-1250 °C and f(S2) of 10-0.39-10-0.07.

Enhanced TiO2 Photocatalytic Processing of Organic Wastes for Green Space Exploration

NASA Technical Reports Server (NTRS)

Udom, I.; Goswami, D. Y.; Ram, M. K.; Stefanakos, E. K.; Heep, A. F.; Kulis, M. J.; McNatt, J. S.; Jaworske, D. A.; Jones, C. A.

2013-01-01

The effect of transition metal co-catalysts on the photocatalytic properties of TiO2 was investigated. Ruthenium (Ru), palladium, platinum, copper, silver, and gold, were loaded onto TiO2 powders (anatase and mixed-phase P25) and screened for the decomposition of rhodamine B (RhB) under broad-band irradiation. The morphology and estimated chemical composition of photocatalysts were determined by scanning electron microscopy and energy dispersive spectroscopy, respectively. Brunhauer, Emmett and Teller (BET) analysis measured mass-specific surface area(s). X-ray diffraction analysis was performed to confirm the identity of titania phase(s) present. The BET surface area of anatase TiO2/Ru 1% (9.2 sq m/gm) was one of the highest measured of all photocatalysts prepared in our laboratory. Photolyses conducted under air-saturated and nitrogen-saturated conditions revealed photodegradation efficiencies of 85 and 2 percent, respectively, after 60 min compared to 58 percent with no catalyst. The cause of low photocatalytic activity under an inert atmosphere is discussed. TiO2/Ru 1% showed a superior photocatalytic activity relative to P25-TiO2 under broad-band irradiation. A potential deployment of photocatalytic technologies on a mission could be a reactor with modest enhancement in solar intensity brought about by a trough-style reactor, with reactants and catalyst flowing along the axis of the trough and therefore being illuminated for a controlled duration based on the flow rate.

Summary of Available Hail Literature and the Effect of Hail on Aircraft in Flight

DTIC Science & Technology

1952-09-01

Delaware - District of Columbia area. D-58. Anon.: Estudios Superiores, Seccion de Investigaciones Meteorologicas. Observacion de la frecuencia...41 +> H d Üf"e 3 O •■» m cu -■gg p m 3 4) d CH H flü son ft o 3 cd ft Xl ■ V 41 > aj = 4) rH X! d B...d PH W lA i^o . CO CM CO * LT P * CO w CO rH w w en w O W CD *d m d EH * * CO P * &H CO E-i EH -=f LT\\ EH NO NO ON s N£> CO O

Thermodynamical study of boron doped CeX{sub 3} (X=Pd, Rh)

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

Sharma, Ramesh; Dwivedi, Shalini; Sharma, Yamini, E-mail: sharma.yamini62@gmail.com

2016-05-06

The structural, electronic, thermal, and optical properties of cubic non magnetic CeX{sub 3}(X=Pd, Rh) compounds which crystallize in the Au{sub 3}Cu structure have been studied using the projected augmented wave (PAW) method within the density functional theory (DFT) with generalized gradient approximation (GGA) for exchange correlation potential. In this paper we have calculated the band structure which are interpreted using the density of states. The optical properties such as extinction coefficients clearly illustrate the changes in CeX{sub 3} due to intercalation of boron. Lattice instability is observed in CePd{sub 3}B from the calculated dynamical properties.

Structural, electronic and elastic properties of heavy fermion YbRh2 Laves phase compound

NASA Astrophysics Data System (ADS)

Pawar, Harsha; Shugani, Mani; Aynyas, Mahendra; Sanyal, Sankar P.

2018-05-01

The structural, electronic and elastic properties of YbRh2 Laves phase intermetallic compound which crystallize in cubic (MgCu2-type) structure have been investigated using ab-initio full potential linearized augmented plane wave (FP- LAPW) method with LDA and LDA+U approximation. The calculated ground state properties such as lattice parameter (a0), bulk modulus (B) and its pressure derivative (B') are in good agreement with available experimental and theoretical data. The electronic properties are analyzed from band structures and density of states. Elastic constants are predicted first time for this compound which obeys the stability criteria for cubic system.

Highly Siderophile Element Abundances in Martian Meteorites

NASA Technical Reports Server (NTRS)

Jones, J. H.; Neal, C. R.; Ely, J. C.

2001-01-01

Critical evaluation of new and literature data for highly siderophile elements (HSE) in Martian (SNC) meteorites allows several first order conclusions to be drawn. (i) Re concentrations in SNC meteorites are nearly constant (within a factor of two) and do not correlate with rock type. Exceptions to this rule are Chassigny and Dar al Gani (DaG) 476, both of which are inferred to have experienced terrestrial Re contamination. (ii) Fractionations between Rh and Pd are small. Excluding Shergotty, the Rh/Pd ratio of the SNC suite is 0.22\\pm0.05. (iii) Os and Ir contents vary by about four orders of magnitude; and positive correlations with MgO, Cr, and Ni suggest that these variations are not controlled by sulfide fractionation. A possible exception is the orthopyroxenite ALH84001, whose HSE's (including Ni, which is compatible in opx) are very low. (iv) Zagami, Shergotty, and Nakhla have nearly identical HSE signatures. Shergotty and Zagami have experienced assimilation-fractional crystallization (AFC) and have "crustal" Sr and Nd isotopic signatures. Conversely, the Nakhla parent was a small degree partial melt of a depleted mantle that interacted little with the Martian crust. These observations suggest that "evolved" HSE signatures can be produced by either fractional crystallization or small degrees of partial melting. (v) Chassigny and other mafic SNC's have HSE signatures that are very distinct from those of Nakhla-Zagami-Shergotty. The HSE elemental ratios of mafic SNC's approach chondritic, implying that the Martian mantle has nearly chondritic relative abundances of the HSE's. (vi) This chondritic HSE signature is observed in SNC's of various ages, suggesting that this is an ancient feature that has not evolved over time. (vii) No correlation is observed between HSE's and signatures of crustal contamination (e.g., Sr isotopes), indicating that the HSE signatures of the SNC suite are not derived from the crust. (vii) The Ru/Pd for the SNC suite ratio is about 0.5 chondritic. We attribute this depletion of Ru to the presence of spinel in the SNC source regions. (viii) Assignment of this depletion of Ru to spinel seems to also imply that spinel is not the cause of Os and Ir fractionations, requiring some other mafic phase to account for the observed variations. -----.

Electrochemical Corrosion Studies for Modeling Metallic Waste Form Release Rates

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

Poineau, Frederic; Tamalis, Dimitri

The isotope 99Tc is an important fission product generated from nuclear power production. Because of its long half-life (t 1/2 = 2.13 ∙ 10 5 years) and beta-radiotoxicity (β⁻ = 292 keV), it is a major concern in the long-term management of spent nuclear fuel. In the spent nuclear fuel, Tc is present as an alloy with Mo, Ru, Rh, and Pd called the epsilon-phase, the relative amount of which increases with fuel burn-up. In some separation schemes for spent nuclear fuel, Tc would be separated from the spent fuel and disposed of in a durable waste form. Technetium wastemore » forms under consideration include metallic alloys, oxide ceramics and borosilicate glass. In the development of a metallic waste form, after separation from the spent fuel, Tc would be converted to the metal, incorporated into an alloy and the resulting waste form stored in a repository. Metallic alloys under consideration include Tc–Zr alloys, Tc–stainless steel alloys and Tc–Inconel alloys (Inconel is an alloy of Ni, Cr and iron which is resistant to corrosion). To predict the long-term behavior of the metallic Tc waste form, understanding the corrosion properties of Tc metal and Tc alloys in various chemical environments is needed, but efforts to model the behavior of Tc metallic alloys are limited. One parameter that should also be considered in predicting the long-term behavior of the Tc waste form is the ingrowth of stable Ru that occurs from the radioactive decay of 99Tc ( 99Tc → 99Ru + β⁻). After a geological period of time, significant amounts of Ru will be present in the Tc and may affect its corrosion properties. Studying the effect of Ru on the corrosion behavior of Tc is also of importance. In this context, we studied the electrochemical behavior of Tc metal, Tc-Ni alloys (to model Tc-Inconel alloy) and Tc-Ru alloys in acidic media. The study of Tc-U alloys has also been performed in order to better understand the nature of Tc in metallic spent fuel. Computational modeling and simulations were performed to shed light on experimental results and explain structural and kinetics trends.« less

Transparent metal selenide alloy counter electrodes for high-efficiency bifacial dye-sensitized solar cells.

PubMed

Duan, Yanyan; Tang, Qunwei; Liu, Juan; He, Benlin; Yu, Liangmin

2014-12-22

The exploration of cost-effective and transparent counter electrodes (CEs) is a persistent objective in the development of bifacial dye-sensitized solar cells (DSSCs). Transparent counter electrodes based on binary-alloy metal selenides (M-Se; M=Co, Ni, Cu, Fe, Ru) are now obtained by a mild, solution-based method and employed in efficient bifacial DSSCs. Owing to superior charge-transfer ability for the I(-) /I3 (-) redox couple, electrocatalytic activity toward I3 (-) reduction, and optical transparency, the bifacial DSSCs with CEs consisting of a metal selenide alloy yield front and rear efficiencies of 8.30 % and 4.63 % for Co0.85 Se, 7.85 % and 4.37 % for Ni0.85 Se, 6.43 % and 4.24 % for Cu0.50 Se, 7.64 % and 5.05 % for FeSe, and 9.22 % and 5.90 % for Ru0.33 Se in comparison with 6.18 % and 3.56 % for a cell with an electrode based on pristine platinum, respectively. Moreover, fast activity onset, high multiple start/stop capability, and relatively good stability demonstrate that these new electrodes should find applications in solar panels. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparison of the agglomeration behavior of thin metallic films on SiO2

NASA Astrophysics Data System (ADS)

Gadkari, P. R.; Warren, A. P.; Todi, R. M.; Petrova, R. V.; Coffey, K. R.

2005-07-01

The stability of continuous metallic thin films on insulating oxide surfaces is of interest to applications such as semiconductor interconnections and gate engineering. In this work, we report the study of the formation of voids and agglomeration of initially continuous Cu, Au, Ru and Pt thin films deposited on amorphous thermally grown SiO2 surfaces. Polycrystalline thin films having thicknesses in the range of 10-100 nm were ultrahigh vacuum sputter deposited on thermally grown SiO2 surfaces. The films were annealed at temperatures in the range of 150-800 °C in argon and argon+3% hydrogen gases. Scanning electron microscopy was used to investigate the agglomeration behavior, and transmission electron microscopy was used to characterize the microstructure of the as-deposited and annealed films. The agglomeration sequence in all of the films is found to follow a two step process of void nucleation and void growth. However, void growth in Au and Pt thin films is different from Cu and Ru thin films. Residual stress and adhesion were observed to play an important part in deciding the mode of void growth in Au and Pt thin films. Last, it is also observed that the tendency for agglomeration can be reduced by encapsulating the metal film with an oxide overlayer.

Biosorption of metal elements by exopolymer nanofibrils excreted from Leptothrix cells.

PubMed

Kunoh, Tatsuki; Nakanishi, Makoto; Kusano, Yoshihiro; Itadani, Atsushi; Ando, Kota; Matsumoto, Syuji; Tamura, Katsunori; Kunoh, Hitoshi; Takada, Jun

2017-10-01

Leptothrix species, aquatic Fe-oxidizing bacteria, excrete nano-scaled exopolymer fibrils. Once excreted, the fibrils weave together and coalesce to form extracellular, microtubular, immature sheaths encasing catenulate cells of Leptothrix. The immature sheaths, composed of aggregated nanofibrils with a homogeneous-looking matrix, attract and bind aqueous-phase inorganics, especially Fe, P, and Si, to form seemingly solid, mature sheaths of a hybrid organic-inorganic nature. To verify our assumption that the organic skeleton of the sheaths might sorb a broad range of other metallic and nonmetallic elements, we examined the sorption potential of chemically and enzymatically prepared protein-free organic sheath remnants for 47 available elements. The sheath remnants were found by XRF to sorb each of the 47 elements, although their sorption degree varied among the elements: >35% atomic percentages for Ti, Y, Zr, Ru, Rh, Ag, and Au. Electron microscopy, energy dispersive x-ray spectroscopy, electron and x-ray diffractions, and Fourier transform infrared spectroscopy analyses of sheath remnants that had sorbed Ag, Cu, and Pt revealed that (i) the sheath remnants comprised a 5-10 nm thick aggregation of fibrils, (ii) the test elements were distributed almost homogeneously throughout the fibrillar aggregate, (iii) the nanofibril matrix sorbing the elements was nearly amorphous, and (iv) these elements plausibly were bound to the matrix by ionic binding, especially via OH. The present results show that the constitutive protein-free exopolymer nanofibrils of the sheaths can contribute to creating novel filtering materials for recovering and recycling useful and/or hazardous elements from the environment. Copyright © 2017. Published by Elsevier Ltd.

[A novel yellow organic light-emitting device].

PubMed

Ma, Chen; Wang, Hua; Hao, Yu-Ying; Gao, Zhi-Xiang; Zhou, He-Feng; Xu, Bing-She

2008-07-01

The fabrication of a novel organic yellow-light-emitting device using Rhodamine B as dopant with double quantum-well (DQW) structure was introduced in the present article. The structure and thickness of this device is ITO/CuPc (6 nm) /NPB (20 nm) /Alq3 (3 nm)/Alq3 : Rhodamine B (3 nm) /Alq3 (3 nm) /Al q3 : Rhodamine B(3 nm) /Alq3 (30 nm) /Liq (5 nm)/Al (30 nm). With the detailed investigation of electroluminescence of the novel organic yellow-light-emitting device, the authors found that the doping concentration of Rhodamine B (RhB) had a very big influence on luminance and efficiency of the organic yellow-light-emitting device. When doping concentration of Rhodamine B (RhB) was 1.5 wt%, the organic yellow-light-emitting device was obtained with the maximum current efficiency of 1.526 cd x A(-1) and the maximum luminance of 1 309 cd x m(-2). It can be seen from the EL spectra of the devices that there existed energy transferring from Alq3 to RhB in the organic light-emitting layers. When the doping concentration of RhB increased, lambda(max) of EL spectra redshifted obviously. The phenomenon was attributed to the Stokes effect of quantum wells and self-polarization of RhB dye molecules.

Search for New Superconductors for Energy and Power Applications

DTIC Science & Technology

2014-10-21

superconductors, borides , carbides, silicides, and chalcogenides. In addition, a number of thin film systems have been explored: A15s, superlattices, arrays of...YBa2Cu3O7 Bi2Se3 Eu-Si-C ErRh4B4 Bi2Sr2CaCu2O8 (UD, OD) Sb2Se3 V-Si-C (Ga,Mn)As CuO ZrSe2 Sm-Si-C Hf(FeCo)P Y1-xCaxCrO3 Fe-Te-Se BORIDES Hf-Fe-C-P...Physics, Warsaw, Poland Table III New superconductors, discovered by UCSD MURI team. BORIDES Tc (K) Nb0.9Zr0.1B 11.2 ZrNbxB 9.0 ZrVxB 9.0

Evolution of magnetic and orbital properties in the magnetically diluted A -site spinel Cu1 -xZnxRh2O4

NASA Astrophysics Data System (ADS)

Zakrzewski, A. V.; Gangopadhyay, S.; MacDougall, G. J.; Aczel, A. A.; Calder, S.; Williams, T. J.

2018-06-01

In frustrated spinel antiferromagnets, dilution with nonmagnetic ions can be a powerful strategy for probing unconventional spin states or uncovering interesting phenomena. Here, we present x-ray, neutron scattering, and thermodynamic studies of the effects of magnetic dilution of the tetragonally distorted A -site spinel antiferromagnet, CuRh2O4 , with nonmagnetic Zn2 + ions. Our data confirm the helical spin order recently identified at low temperatures in this material, and further demonstrate a systematic suppression of the associated Néel temperature with increasing site dilution towards a continuous transition with critical doping of xspin˜0.44 . Interestingly, this critical doping is demonstrably distinct from a second structural critical point at xJ T˜0.6 , which is consistent with the suppression of orbital order on the A site through a classical percolative mechanism. This anomalously low value for xspin is confirmed via multiple measurements, and is inconsistent with predictions of classical percolation theory, suggesting that the spin transition in this material is driven by an enhancement of preexisting spin fluctuations with weak dilution.

Influence of hydrogen on the structure and stability of ultra-thin ZnO on metal substrates

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

Bieniek, Bjoern; Hofmann, Oliver T.; Institut für Festkörperphysik, TU Graz, 8010 Graz

2015-03-30

We investigate the atomic and electronic structure of ultra-thin ZnO films (1 to 4 layers) on the (111) surfaces of Ag, Cu, Pd, Pt, Ni, and Rh by means of density-functional theory. The ZnO monolayer is found to adopt an α-BN structure on the metal substrates with coincidence structures in good agreement with experiment. Thicker ZnO layers change into a wurtzite structure. The films exhibit a strong corrugation, which can be smoothed by hydrogen (H) adsorption. An H over-layer with 50% coverage is formed at chemical potentials that range from low to ultra-high vacuum H{sub 2} pressures. For the Agmore » substrate, both α-BN and wurtzite ZnO films are accessible in this pressure range, while for Cu, Pd, Pt, Rh, and Ni wurtzite films are favored. The surface structure and the density of states of these H passivated ZnO thin films agree well with those of the bulk ZnO(0001{sup ¯})-2×1-H surface.« less

Design and Investigation of Optical Properties of N-(Rhodamine-B)-Lactam-Ethylenediamine (RhB-EDA) Fluorescent Probe.

PubMed

Soršak, Eva; Volmajer Valh, Julija; Korent Urek, Špela; Lobnik, Aleksandra

2018-04-14

This study presents chemical modification of a Rhodamine B (RhB) sensor probe by ethylenediamine (EDA), and investigation of its spectral as well as sensor properties to the various metals. The synthesised N -(Rhodamine-B)-lactam-ethylenediamine (RhB-EDA) fluorescent probe shows interesting optical sensor properties, and high sensitivity and selectivity to Ag⁺ ions among all the tested metal ions (K⁺, Mg 2+ , Cu 2+ , Ni 2+ , Fe 2+ , Pb 2+ , Na⁺, Mn 2+ , Li⁺, Al 3+ , Co 2+ , Hg 2+ , Sr 2+ , Ca 2+ , Ag⁺, Cd 2+ and Zn 2+ ), while the well-known Rhodamine B (RhB) fluorescent probe shows much less sensitivity to Ag⁺ ions, but high sensitivity to Fe 2+ ions. The novel fluorescent sensor probe RhB-EDA has the capabilities to sense Ag⁺ ions up to µM ranges by using the fluorescence quenching approach. The probe displayed a dynamic response to Ag⁺ in the range of 0.43 × 10 -3 -10 -6 M with a detection limit of 0.1 μM. The sensing system of an RhB-EDA novel fluorescent probe was optimised according to the spectral properties, effect of pH and buffer, photostability, incubation time, sensitivity, and selectivity. Since all the spectral and sensing properties were tested in green aqueous media, although many other similar sensor systems rely on organic solvent solutions, the RhB-EDA sensing probe may be a good candidate for measuring Ag⁺ ions in real-life applications.

Solvothermal fabrication and enhanced visible light photocatalytic activity of Cu2O-reduced graphene oxide composite microspheres for photodegradation of Rhodamine B

NASA Astrophysics Data System (ADS)

Sun, Lingling; Wang, Guohong; Hao, Ruirui; Han, Deyan; Cao, Sheng

2015-12-01

The addition of graphene oxide (GO) in the semiconductors has been regarded as one of the effective methods to enhance their photocatalytic activity. In this study, Cu2O-reduced graphene oxide (Cu2O-rGO) composites with low loading (0-0.5 wt.%) of graphene oxide (GO) were produced by a one-step green solvothermal method in ethanol system by using Cu(NO3)2·3H2O and glutamic acid as copper precursor and reducing agent, respectively. During the solvothermal treatment, GO was reduced to rGO. The as-prepared Cu2O-reduced graphene oxide composite microspheres exhibited enhanced photocatalytic activity toward the degradation of RhB aqueous solution under visible light irradiation. At the optimal loading of graphene oxide (0.05 wt.%), Cu2O-rGO composites showed the highest photocatalytic activity, exceeding that of pure Cu2O and commercial Degussa P25 by a factor of 2.9 and 7.9, respectively. The enhanced photocatalytic activity may be ascribed to the strong coupling interaction between Cu2O particles and rGO nanosheets, which reduces the recombination of charge carriers.

9,10-phenanthrenesemiquinone radical complexes of ruthenium(III), osmium(III) and rhodium(III) and redox series.

PubMed

Biswas, Manas Kumar; Patra, Sarat Chandra; Maity, Amarendra Nath; Ke, Shyue-Chu; Weyhermüller, Thomas; Ghosh, Prasanta

2013-05-14

Reactions of 9,10-phenanthrenequinone (PQ) in toluene with [M(II)(PPh3)3X2] at 298 K afford green complexes, trans-[M(PQ)(PPh3)2X2] (M = Ru, X = Cl, 1; M = Os, X = Br, 2) in moderate yields. Reaction of anhydrous RhCl3 with PQ and PPh3 in boiling ethanol affords the dark brown paramagnetic complex, cis-[Rh(PQ)(PPh3)2Cl2] (3) in good yields. Diffusion of iodine solution in n-hexane to the trans-[Os(PQ) (PPh3)2(CO)(Br)] solution in CH2Cl2 generates the crystals of trans-[Os(PQ)(PPh3)2(CO)(Br)](+)I3(-), (4(+))I3(-)), in lower yields. Single crystal X-ray structure determinations of 1·2toluene, 2·CH2Cl2 and 4(+)I3(-), UV-vis/NIR absorption spectra, EPR spectra of 3, electrochemical activities and DFT calculations on 1, 2, trans-[Ru(PQ)(PMe3)2Cl2] (1Me), trans-[Os(PQ)(PMe3)2Br2] (2Me), cis-[Rh(PQ)(PMe3)2Cl2] (3Me) and their oxidized and reduced analogues including trans-[Os(PQ)(PMe3)2(CO)(Br)](+) (4Me(+)) substantiated that 1-3 are the 9,10-phenanthrenesemiquinone radical (PQ(˙-)) complexes of ruthenium(III), osmium(III) and rhodium(III) and are defined as trans/cis-[M(III)(PQ(˙-))(PPh3)2X2] with a minor contribution of the resonance form trans/cis-[M(II)(PQ)(PPh3)2X2]. Two comparatively longer C-O (1.286(4) Å) and the shorter C-C lengths (1.415(7) Å) of the OO-chelate of 1·2toluene and 2·CH2Cl2 and the isotropic fluid solution EPR signal at g = 1.999 of 3 are consistent with the existence of the reduced PQ(˙-) ligand in 1-3 complexes. Anisotropic EPR spectra of the frozen glasses (g11 = g22 = 2.0046 and g33 = 1.9874) and solids (g11 = g22 = 2.005 and g33 = 1.987) instigate the contribution of the resonance form, cis-[Rh(II)(PQ)(PPh3)2Cl2] in 3. DFT calculations established that the closed shell singlet (CSS) solutions of 1Me and 2Me are unstable due to open shell singlet (OSS) perturbation. However, the broken symmetry (BS) (1,1) Ms = 0 solutions of 1Me and 2Me are respectively 22.6 and 24.2 kJ mole(-1) lower in energy and reproduced the experimental bond parameters well prompting the coordination of PQ(˙-) to the M(III) ions. The comparatively shorter C-O lengths, 1.268(4) and 1.266(5) Å and the longer C-C length, 1.466(6) Å, are consistent with the PQ chelation to osmium(II) ion in 4(+). The reversible anodic waves at 0.22, 0.22, and 0.18 V of 1-3, referenced by the Fc(+)/Fc couple, are assigned to the PQ(˙-)/PQ couple forming PQ complexes as trans/cis-[M(III)(PQ)(PPh3)2X2](+) while the cathodic waves at -0.92 and -0.89 V of 2 and 3 are due to formations of PQ(2-) complexes as trans-[M(III)(PQ(2-))(PPh3)2X2](-). 1 displays two overlapping cathodic waves at -0.72(89), -1.0(120) V. EPR spectrum of the frozen glass of 1(-) along with DFT calculations detected the contribution of both the valence tautomers, trans-[Ru(III)(PQ(2-))(PPh3)2Cl2](-) (g1 = g2 = 2.456; g3 = 1.983) and trans-[Ru(II)(PQ(˙-))(PPh3)2X2](-) (g(iso) = 1.999) in the anion. The characteristic lower energy absorption bands of 1 and 2 at 700 nm were assigned to CSS-OSS perturbation MLCT those are absent in paramagnetic 3, 1(+), 2(+), 1(-), 2(-) and 4(+) complexes, investigated by spectro-electrochemical measurements and time dependent (TD) DFT calculations on 1Me, 2Me, 1Me(+) and 1Me(-).

Synthesis, spectroscopic and biological activities studies of acyclic and macrocyclic mono and binuclear metal complexes containing a hard-soft Schiff base

NASA Astrophysics Data System (ADS)

Abou-Hussein, Azza A. A.; Linert, Wolfgang

Mono- and bi-nuclear acyclic and macrocyclic complexes with hard-soft Schiff base, H2L, ligand derived from the reaction of 4,6-diacetylresorcinol and thiocabohydrazide, in the molar ratio 1:2 have been prepared. The H2L ligand reacts with Co(II), Ni(II), Cu(II), Zn(II), Mn(II) and UO2(VI) nitrates, VO(IV) sulfate and Ru(III) chloride to get acyclic binuclear complexes except for VO(IV) and Ru(III) which gave acyclic mono-nuclear complexes. Reaction of the acyclic mono-nuclear VO(IV) and Ru(III) complexes with 4,6-diacetylresorcinol afforded the corresponding macrocyclic mono-nuclear VO(IV) and Ru(IIII) complexes. Template reactions of the 4,6-diacetylresorcinol and thiocarbohydrazide with either VO(IV) or Ru(III) salts afforded the macrocyclic binuclear VO(IV) and Ru(III) complexes. The Schiff base, H2L, ligand acts as dibasic with two NSO-tridentate sites and can coordinate with two metal ions to form binuclear complexes after the deprotonation of the hydrogen atoms of the phenolic groups in all the complexes, except in the case of the acyclic mononuclear Ru(III) and VO(IV) complexes, where the Schiff base behaves as neutral tetradentate chelate with N2S2 donor atoms. The ligands and the metal complexes were characterized by elemental analysis, IR, UV-vis 1H-NMR, thermal gravimetric analysis (TGA) and ESR, as well as the measurements of conductivity and magnetic moments at room temperature. Electronic spectra and magnetic moments of the complexes indicate the geometries of the metal centers are either tetrahedral, square planar or octahedral. Kinetic and thermodynamic parameters were calculated using Coats-Redfern equation, for the different thermal decomposition steps of the complexes. The ligands and the metal complexes were screened for their antimicrobial activity against Staphylococcus aureus as Gram-positive bacteria, and Pseudomonas fluorescens as Gram-negative bacteria in addition to Fusarium oxysporum fungus. Most of the complexes exhibit mild antibacterial and antifungal activities against these organisms.

Synthesis, spectroscopic and biological activities studies of acyclic and macrocyclic mono and binuclear metal complexes containing a hard-soft Schiff base.

PubMed

Abou-Hussein, Azza A A; Linert, Wolfgang

2012-09-01

Mono- and bi-nuclear acyclic and macrocyclic complexes with hard-soft Schiff base, H(2)L, ligand derived from the reaction of 4,6-diacetylresorcinol and thiocabohydrazide, in the molar ratio 1:2 have been prepared. The H(2)L ligand reacts with Co(II), Ni(II), Cu(II), Zn(II), Mn(II) and UO(2)(VI) nitrates, VO(IV) sulfate and Ru(III) chloride to get acyclic binuclear complexes except for VO(IV) and Ru(III) which gave acyclic mono-nuclear complexes. Reaction of the acyclic mono-nuclear VO(IV) and Ru(III) complexes with 4,6-diacetylresorcinol afforded the corresponding macrocyclic mono-nuclear VO(IV) and Ru(IIII) complexes. Template reactions of the 4,6-diacetylresorcinol and thiocarbohydrazide with either VO(IV) or Ru(III) salts afforded the macrocyclic binuclear VO(IV) and Ru(III) complexes. The Schiff base, H(2)L, ligand acts as dibasic with two NSO-tridentate sites and can coordinate with two metal ions to form binuclear complexes after the deprotonation of the hydrogen atoms of the phenolic groups in all the complexes, except in the case of the acyclic mononuclear Ru(III) and VO(IV) complexes, where the Schiff base behaves as neutral tetradentate chelate with N(2)S(2) donor atoms. The ligands and the metal complexes were characterized by elemental analysis, IR, UV-vis (1)H-NMR, thermal gravimetric analysis (TGA) and ESR, as well as the measurements of conductivity and magnetic moments at room temperature. Electronic spectra and magnetic moments of the complexes indicate the geometries of the metal centers are either tetrahedral, square planar or octahedral. Kinetic and thermodynamic parameters were calculated using Coats-Redfern equation, for the different thermal decomposition steps of the complexes. The ligands and the metal complexes were screened for their antimicrobial activity against Staphylococcus aureus as Gram-positive bacteria, and Pseudomonas fluorescens as Gram-negative bacteria in addition to Fusarium oxysporum fungus. Most of the complexes exhibit mild antibacterial and antifungal activities against these organisms. Copyright © 2012 Elsevier B.V. All rights reserved.

Platinum Group Elements (PGE) geochemistry of komatiites and boninites from Dharwar Craton, India: Implications for mantle melting processes

NASA Astrophysics Data System (ADS)

Saha, Abhishek; Manikyamba, C.; Santosh, M.; Ganguly, Sohini; Khelen, Arubam C.; Subramanyam, K. S. V.

2015-06-01

High MgO volcanic rocks having elevated concentrations of Ni and Cr are potential hosts for platinum group elements (PGE) owing to their primitive mantle origin and eruption at high temperatures. Though their higher PGE abundance is economically significant in mineral exploration studies, their lower concentrations are also valuable geochemical tools to evaluate petrogenetic processes. In this paper an attempt has been made to evaluate the PGE geochemistry of high MgO volcanic rocks from two greenstone belts of western and eastern Dharwar Craton and to discuss different mantle processes operative at diverse geodynamic settings during the Neoarchean time. The Bababudan greenstone belt of western and Gadwal greenstone belt of eastern Dharwar Cratons are dominantly composed of high MgO volcanic rocks which, based on distinct geochemical characteristics, have been identified as komatiites and boninites respectively. The Bababudan komatiites are essentially composed of olivine and clinopyroxene with rare plagioclase tending towards komatiitic basalts. The Gadwal boninites contain clinopyroxene, recrystallized hornblende with minor orthopyroxene, plagioclase and sulphide minerals. The Bababudan komatiites are Al-undepleted type (Al2O3/TiO2 = 23-59) with distinctly high MgO (27.4-35.8 wt.%), Ni (509-1066 ppm) and Cr (136-3036 ppm) contents. These rocks have low ΣPGE (9-42 ppb) contents with 0.2-2.4 ppb Iridium (Ir), 0.2-1.4 ppb Osmium (Os) and 0.4-4.4 ppb Ruthenium (Ru) among Iridium group PGE (IPGE); and 1.4-16.2 ppb Platinum (Pt), 2.8-19 ppb Palladium (Pd) and 0.2-9.8 ppb Rhodium (Rh) among Platinum group PGE (PPGE). The Gadwal boninites are high-Ca boninites with CaO/Al2O3 ratios varying between 0.8 and 1.0, with 12-24 wt.% MgO, 821-1168 ppm Ni and 2307-2765 ppm Cr. They show higher concentration of total PGE (82-207 ppb) with Pt concentration ranging from 13 to 19 ppb, Pd between 65 and 180 ppb and Rh in the range of 1.4-3 ppb compared to the Bababudan komatiites. Ir, Os and Ru concentrations range from 0.6 to 2.2 ppb, 0.2 to 0.6 ppb and 1.4 to 2.6 ppb respectively in IPGE. The PGE abundances in Bababudan komatiites were controlled by olivine fractionation whereas that in Gadwal boninites were influenced by fractionation of chromite and sulphides. The Al-undepleted Bababudan komatiites are characterized by low CaO/Al2O3, (Gd/Yb)N, (La/Yb)N, with positive Zr, Hf, Ti anomalies and high Cu/Pd, Pd/Ir ratios at low Pd concentrations suggesting the derivation of parent magma by high degrees (>30%) partial melting of mantle under anhydrous conditions at shallow depth with garnet as a residual phase in the mantle restite. The komatiites are geochemically analogous to Al-undepleted Munro type komatiites and their PGE compositions are consistent with Alexo and Gorgona komatiites. The S-undersaturated character of Bababudan komatiites is attributed to decompression and assimilation of lower crustal materials during magma ascent and emplacement. In contrast, the higher Al2O3/TiO2, lower (Gd/Yb)N, for Gadwal boninites in combination with negative Nb, Zr, Hf, Ti anomalies and lower Cu/Pd at relatively higher Pd/Ir and Pd concentrations reflect high degree melting of refractory mantle wedge under hydrous conditions in an intraoceanic subduction zone setting. Higher Pd/Ir ratios and S-undersaturation of these boninites conform to influx of fluids derived by dehydration of subducted slab resulting into high fluid pressure and metasomatism of mantle wedge.

Management of agricultural waste for removal of heavy metals from aqueous solution: adsorption behaviors, adsorption mechanisms, environmental protection, and techno-economic analysis.

PubMed

Elhafez, S E Abd; Hamad, H A; Zaatout, A A; Malash, G F

2017-01-01

In the last decades, Egypt has been suffering from the phenomenon of black cloud resulting from burning rice husk and increasing the demand for water leading to the water crisis. An alternative, low-value and surplus agricultural byproduct (rice husk, RH) has an enormous potential for the removal of Cu(II) ions from water. The present study focuses on the chance of the use of rice husk as a bio-adsorbent without any chemical treatment instead of burning it and soiling the environment. The elemental, structural, morphological, surface functional, thermal, and textural characteristics of RH are determined by XRF, XRD, SEM, FT-IR, TGA, and BET surface area, respectively, and contributed to the understanding of the adsorption mechanism of Cu(II) ions in aqueous solution. Also, the performance analysis, adsorption mechanism, influencing factors, favorable conditions, etc. are discussed in this article. The results obtained from optimization by batch mode are achieved under the following conditions: initial concentration, 150 ppm; amount of rice husk, 1 g; average particle size, 0.25 mm; temperature, 25 °C; pH, 4; agitation rate, 180 rpm; and contact time, 60 min. RH exhibits a high degree of selectivity for Cu(II) adsorption. The adsorption isotherm is fitted well with Langmuir and Freundlich models with R 2 0.998 and 0.997, respectively. The adsorption is well governed by the pseudo-second-order kinetics. It is observed that the rate of adsorption improves with decreasing temperature, and the process is exothermic and non-spontaneous. Particular attention has being paid to factors as production processes, fixed/operational cost, production cost, and profit. The techno-economical analysis is presented in this study that provides precise demands on capital for a fixed investment, provisions for operational capital, and finally provisions for revenue. The social, economical, and environmental benefits by industrial point of view using low-cost adsorbent are also discussed.

Enhanced catalytic activity without the use of an external light source using microwave-synthesized CuO nanopetals

PubMed Central

Bajaj, Sonal; Nayak, Arpan Kumar; Pradhan, Debabrata; Tekade, Pradip

2017-01-01

We report enhanced catalytic activity of CuO nanopetals synthesized by microwave-assisted wet chemical synthesis. The catalytic reaction of CuO nanopetals and H2O2 was studied with the application of external light source and also under dark conditions for the degradation of the hazardous dye methylene blue. The CuO nanopetals showed significant catalytic activity for the fast degradation of methylene blue and rhodamine B (RhB) under dark conditions, without the application of an external light source. This increased catalytic activity was attributed to the co-operative role of H2O2 and the large specific surface area (≈40 m2·g−1) of the nanopetals. We propose a detail mechanism for this fast degradation. A separate study of the effect of different H2O2 concentrations for the degradation of methylene blue under dark conditions is also illustrated. PMID:28685117

Polynuclear complexes of copper(I) halides: coordination chemistry and catalytic transformations of alkynes

NASA Astrophysics Data System (ADS)

Mykhalichko, B. M.; Temkin, Oleg N.; Mys'kiv, M. G.

2000-11-01

Characteristic features of the coordination chemistry of Cu(I) and mechanisms of catalytic conversions of alkynes in the CuCl-MCl-H2O-HC≡CR system (MCl is alkali metal or ammonium chloride or amine hydrochloride; R=H, CH2OH, CH=CH2, etc.) are analysed based on studies of the compositions and structures of copper(I) chloride (bromide) complexes, alkyne π-complexes and ethynyl organometallic polynuclear compounds formed in this system in solutions and in the crystalline state. The role of polynuclear complexes in various reactions of alkynes is discussed. The bibliography includes 149 references.

Process for the regeneration of metallic catalysts

DOEpatents

Katzer, James R.; Windawi, Hassan

1981-01-01

A method for the regeneration of metallic hydrogenation catalysts from the class consisting of Ni, Rh, Pd, Ir, Pt and Ru poisoned with sulfur, with or without accompanying carbon deposition, comprising subjecting the catalyst to exposure to oxygen gas in a concentration of about 1-10 ppm. intermixed with an inert gas of the group consisting of He, A, Xe, Kr, N.sub.2 and air substantially free of oxygen to an extent such that the total oxygen molecule throughout is in the range of about 10 to 20 times that of the hydrogen sulfide molecular exposure producing the catalyst poisoning while maintaining the temperature in the range of about 300.degree. to 500.degree. C.

Spent fuel reaction - the behavior of the {epsilon}-phase over 3.1 years

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

Finn, P.A.; Hoh, J.C.; Wolf, S.F.

The release fractions of the five elements in the {epsilon}-phase ({sup 99}Tc, {sup 97}Mo, Ru, Rh, and Pd) as well as that of {sup 238}U are reported for the reaction of two oxide fuels (ATM-103 and ATM-106) in unsaturated tests under oxidizing conditions. The {sup 99}Tc release fractions provide a lower limit for the magnitude of the spent fuel reaction. The {sup 99}Tc release fractions indicate that a surface reaction might be the rate controlling mechanism for fuel reaction under unsaturated conditions and the oxidant is possibly H{sub 2}O{sub 2}, a product of alpha radiolysis of water.

Platinum-group element geochemistry of zoned ultramafic intrusive suites, Klamath Mountains, California and Oregon.

USGS Publications Warehouse

Gray, F.; Page, N.J.; Carlson, C.A.; Wilson, S.A.; Carlson, R.R.

1986-01-01

Analyses for platinum-group elements of the varied rock suites of three Alaskan-type ultramafic to mafic multi-intrusive bodies are reported. Ir and Ru are less than analytical sensitivities of 100 and 20 ppb; Rh is less than or near 1 ppb. Average Pd assays vary among the rocks within intrusive complexes and between the three complexes (6.3, 13.7, 36.4 ppb); average Pt assays vary little among the same samples (27.9, 60.9, 34.0 ppb). Statistically adjusted Pt/(Pt + Pd) ratios increase in each suite from gabbro through clinopyroxenite to olivine-rich rocks, possibly owing to Pd fractionation.-G.J.N.

Evaluations of catalysts for wet oxidation waste management in CELSS

NASA Astrophysics Data System (ADS)

Oguchi, Mitsuo; Nitta, Keiji

1992-11-01

A wet oxidation method is considered to be one of the most effective methods of waste processing and recycling in CELSS (Controlled Ecological Life Support System). The first test using rabbit waste as raw material was conducted under a decomposition temperature of 280 °C for 30 minutes and an initial pure oxygen pressure of 4.9 MPa (50 kgf/cm2) before heating, and the following results were obtained. The value of COD (Chemical Oxygen Demand) was reduced 82.5 % by the wet oxidation. And also the Kjeldahl nitrogen concentration was decreased 98.8%. However, the organic carbon compound in the residual solution was almost acetic acid and ammonia was produced. In order to activate the oxidation more strongly, the second tests using catalysts such as Pd, Ru and Ru+Rh were conducted. As the results of these tests, the effectiveness of catalysts for oxidizing raw material ws shown as follows: COD and the Kjeldahl nitrogen values were drastically decreased 99.65 % and 99.88 %, respectively. Furthermore, the quantity of acetic acid and ammonia were reduced considerably. On the other hand, nitrate was showed a value 30 times as much as without catalytic oxidation.

Giant Tunnel Magnetoresistance with a Single Magnetic Phase-Transition Electrode

NASA Astrophysics Data System (ADS)

Zhang, Jia; Chen, X. Z.; Song, C.; Feng, J. F.; Wei, H. X.; Lü, Jing-Tao

2018-04-01

The magnetic phase-transition tunnel-magnetoresistance (MPT-TMR) effect with a single magnetic electrode is investigated by first-principles calculations. The calculations show that the MPT-TMR of an α'-FeRh /MgO /Cu tunnel junction can be as high as hundreds of percent when the magnetic structure of α'-FeRh changes from G -type antiferromagnetic (G -AFM ) to ferromagnetic order. This type of MPT-TMR may be superior to the tunnel anisotropic magnetoresistance because of its huge magnetoresistance effect and similar structural simplicity. The main mechanism for the giant MPT-TMR can be attributed to the formation of interface resonant states at the G -AFM FeRh /MgO interface. A direct FeRh /MgO interface is found to be necessary for achieving a high MPT-TMR experimentally. Moreover, we find the α'-FeRh /MgO interface with FeRh in the ferromagnetic phase has nearly full spin polarization due to the negligible majority transmission and significantly different Fermi surface of two spin channels. Thus, it may act as a highly efficient and tunable spin injector. In addition, the electric-field-driven MPT of FeRh-based heteromagnetic nanostructures can be utilized to design various energy-efficient tunnel-junction structures and the corresponding lower-power-consumption devices. We also discuss the consequence of various junction defects on MPT-TMR. The interface oxygen layer is found to be detrimental to MPT-TMR. The sign of MPT-TMR is reversed with Rh termination due to the lack of contribution from the interface resonance states. However, the MPT-TMR may be robust against the oxygen vacancy inside of MgO and the shift of the Fermi energy. Our results will stimulate further experimental investigations of MPT-TMR and other fascinating phenomenon of FeRh-based tunnel junctions that may be promising in antiferromagnetic spintronics.

Highly Active and Stable MgAl2O4 Supported Rh and Ir Catalysts for Methane Steam Reforming: A Combined Experimental and Theoretical Study

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

Mei, Donghai; Glezakou, Vassiliki Alexandra; Lebarbier, Vanessa MC

2014-07-01

In this work we present a combined experimental and theoretical investigation of stable MgAl2O4 spinel-supported Rh and Ir catalysts for the steam methane reforming (SMR) reaction. Firstly, catalytic performance for a series of noble metal catalysts supported on MgAl2O4 spinel was evaluated for SMR at 600-850°C. Turnover rate at 850°C follows the order: Pd > Pt > Ir > Rh > Ru > Ni. However, Rh and Ir were found to have the best combination of activity and stability for methane steam reforming in the presence of simulated biomass-derived syngas. It was found that highly dispersed ~2 nm Rh andmore » ~1 nm Ir clusters were formed on the MgAl2O4 spinel support. Scanning Transition Electron Microscopy (STEM) images show that excellent dispersion was maintained even under challenging high temperature conditions (e.g. at 850°C in the presence of steam) while Ir and Rh catalysts supported on Al2O3 were observed to sinter at increased rates under the same conditions. These observations were further confirmed by ab initio molecular dynamics (AIMD) simulations which find that ~1 nm Rh and Ir particles (50-atom cluster) bind strongly to the MgAl2O4 surfaces via a redox process leading to a strong metal-support interaction, thus helping anchor the metal clusters and reduce the tendency to sinter. Density functional theory (DFT) calculations suggest that these supported smaller Rh and Ir particles have a lower work function than larger more bulk-like ones, which enables them to activate both water and methane more effectively than larger particles, yet have a minimal influence on the relative stability of coke precursors. In addition, theoretical mechanistic studies were used to probe the relationship between structure and reactivity. Consistent with the experimental observations, our theoretical modeling results also suggest that the small spinel-supported Ir particle catalyst is more active than the counterpart of Rh catalyst for SMR. This work was financially supported by the United States Department of Energy (DOE)’s Bioenergy Technologies Office (BETO) and performed at the Pacific Northwest National Laboratory (PNNL). PNNL is a multi-program national laboratory operated for DOE by Battelle Memorial Institute. Computing time was granted by a user proposal at the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) located at PNNL. Part of the computational time was provided by the National Energy Research Scientific Computing Center (NERSC).« less

NanoSIMS Determination of Carbon and Oxygen Isotopic Compositions of Presolar Graphites from the Murchison Meteorite

NASA Technical Reports Server (NTRS)

Stadermann, F. J.; Croat, T. K.; Bernatowicz, T.

2004-01-01

Graphite from the Murchison density separate KFC1 (2.15 - 2.20 g/cu cm) has previously been studied by combined SEM/EDX and ion microprobe analysis. These studies found several distinct morphological types of graphites and C isotopic compositions that vary over more than 3 orders of magnitude, clearly establishing their presolar origin. Subsequent TEM measurements of a subset of these particles found abundant embedded crystals of metal (Zr, Mo, Ti, Ru) carbides which were incorporated during the growth of the graphites. A new TEM study of a large set of KFC1 graphites led to the discovery of another type of presolar material, Ru-Fe metal. Here we report results of the C and O isotopic measurements in the same graphite sections, which makes it possible for the first time to directly correlate isotopic and TEM data of KFC1 grains.

Threshold for ion movements in wood cell walls below fiber saturation observed by X-ray fluorescence microscopy (XFM)

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

Zelinka, Samuel L.; Gleber, Sophie-Charlotte; Vogt, Stefan

Diffusion of chemicals and ions through the wood cell wall plays an important role in wood damage mechanisms. In the present work, free diffusion of ions through wood secondary walls and middle lamellae has been investigated as a function of moisture content (MC) and anatomical direction. Various ions (K, Cl, Zn, Cu) were injected into selected regions of 2 mu m thick wood sections with a microinjector and then the ion distribution was mapped by means of X-ray fluorescence microscopy with submicron spatial resolution. The MC of the wood was controlled in situ by means of climatic chamber with controlledmore » relative humidity (RH). For all ions investigated, there was a threshold RH below which the concentration profiles did not change. The threshold RH depended upon ionic species, cell wall layer, and wood anatomical orientation. Above the threshold RH, differences in mobility among ions were observed and the mobility depended upon anatomical direction and cell wall layer. These observations support a recently proposed percolation model of electrical conduction in wood. The results contribute to understanding the mechanisms of fungal decay and fastener corrosion that occur below the fiber saturation point.« less

Oxygen vacancy rich Cu2O based composite material with nitrogen doped carbon as matrix for photocatalytic H2 production and organic pollutant removal.

PubMed

Lu, Lele; Xu, Xinxin; Yan, Jiaming; Shi, Fa-Nian; Huo, Yuqiu

2018-02-06

A nitrogen doped carbon matrix supported Cu 2 O composite material (Cu/Cu2O@NC) was fabricated successfully with a coordination polymer as precursor through calcination. In this composite material, Cu 2 O particles with a size of about 6-10 nm were dispersed evenly in the nitrogen doped carbon matrix. After calcination, some coordinated nitrogen atoms were doped in the lattice of Cu 2 O and replace oxygen atoms, thus generating a large number of oxygen vacancies. In Cu/Cu2O@NC, the existence of oxygen vacancies has been confirmed by electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS). Under visible light irradiation, Cu/Cu2O@NC exhibits excellent H 2 production with the rate of 379.6 μmol h -1 g -1 . Its photocatalytic activity affects organic dyes, such as Rhodamine B (RhB) and methyl orange (MO). In addition to photocatalysis, Cu/Cu2O@NC also exhibits striking catalytic activity in reductive conversion of 4-nitrophenol to 4-aminophenol with in presence of sodium borohydride (NaBH 4 ). The conversion efficiency reaches almost 100% in 250 s with the quantity of Cu/Cu2O@NC as low as 5 mg. The outstanding H 2 production and organic pollutants removal are attributed to the oxygen vacancy. We expect that Cu/Cu2O@NC will find its way as a new resource for hydrogen energy as well as a promising material in water purification.

Screening of Possible Re-Substitutional Elements in Single-Crystal Ni-Based Superalloys: A Viewpoint From Interdiffusion Coefficients in Ni-Al-X Ternaries

NASA Astrophysics Data System (ADS)

Chen, Juan; Zhang, Lijun; Lu, Xiao-Gang

2018-07-01

A popular area of research in the field of high-temperature alloys concerns the search of substitutional elements for Re in order to manufacture single-crystal Ni-based superalloys with less or even no Re addition. To find the elements with similar or even lower diffusion coefficients than Re is an effective strategy. Based on 29 fcc diffusion couples in ternary Ni-Al-X (X = Re, Os, and Ir) systems, high-throughput measurement of composition- and temperature-dependent interdiffusivity matrices was performed using our recently developed numerical inverse method implemented in HitDIC software. The reliability of the determined interdiffusivities was validated by comprehensively comparing the model-predicted composition/interdiffusion flux profiles for each diffusion couple with the corresponding experimental data. Moreover, we also conducted a comparison with the interdiffusivities evaluated using the traditional Matano-Kirkaldy method as well as those from the literature and in boundary binary systems. After that, a comprehensive comparison of the interdiffusion coefficients in fcc Ni-2 wt pct Al-6 wt pct X (X = Ti, Co, Ni, Nb, Mo, Ru, Rh, Ta, W, Re, Os, Ir, and Pt) alloys at 1423 K to 1573 K was conducted. Results indicate that the diffusion rate of Re is lower than that of Os at 1473 K and 1523 K; but higher at 1573 K, while the diffusion rate of Ir is always slightly higher than those of Os and Re at 1473 K to 1573 K. Further analysis of the magnitude of the interdiffusion coefficient correlates with the alloying concentration, activation energy, atomic number, and atomic radius of different diffusing transition metal species ( i.e., Ti, Co, Ni, Nb, Mo, Ru, Rh, Ta, W, Re, Os, Ir, and Pt) was conducted, which is expected to provide useful information regarding element choice in the development of new-generation Ni-based single-crystal superalloys.

Screening of Possible Re-Substitutional Elements in Single-Crystal Ni-Based Superalloys: A Viewpoint From Interdiffusion Coefficients in Ni-Al-X Ternaries

NASA Astrophysics Data System (ADS)

Chen, Juan; Zhang, Lijun; Lu, Xiao-Gang

2018-05-01

A popular area of research in the field of high-temperature alloys concerns the search of substitutional elements for Re in order to manufacture single-crystal Ni-based superalloys with less or even no Re addition. To find the elements with similar or even lower diffusion coefficients than Re is an effective strategy. Based on 29 fcc diffusion couples in ternary Ni-Al-X (X = Re, Os, and Ir) systems, high-throughput measurement of composition- and temperature-dependent interdiffusivity matrices was performed using our recently developed numerical inverse method implemented in HitDIC software. The reliability of the determined interdiffusivities was validated by comprehensively comparing the model-predicted composition/interdiffusion flux profiles for each diffusion couple with the corresponding experimental data. Moreover, we also conducted a comparison with the interdiffusivities evaluated using the traditional Matano-Kirkaldy method as well as those from the literature and in boundary binary systems. After that, a comprehensive comparison of the interdiffusion coefficients in fcc Ni-2 wt pct Al-6 wt pct X (X = Ti, Co, Ni, Nb, Mo, Ru, Rh, Ta, W, Re, Os, Ir, and Pt) alloys at 1423 K to 1573 K was conducted. Results indicate that the diffusion rate of Re is lower than that of Os at 1473 K and 1523 K; but higher at 1573 K, while the diffusion rate of Ir is always slightly higher than those of Os and Re at 1473 K to 1573 K. Further analysis of the magnitude of the interdiffusion coefficient correlates with the alloying concentration, activation energy, atomic number, and atomic radius of different diffusing transition metal species (i.e., Ti, Co, Ni, Nb, Mo, Ru, Rh, Ta, W, Re, Os, Ir, and Pt) was conducted, which is expected to provide useful information regarding element choice in the development of new-generation Ni-based single-crystal superalloys.

Comparison between semiconducting and oxide layers as a reflection layer in spin-valve films

NASA Astrophysics Data System (ADS)

Dinia, A.; Schmerber, G.; Ulhaq, C.

2003-07-01

It is well established that appropriate oxide capping is effective in forming nano-oxide layers (NOL) in spin-valve films for specular enhancement of giant magnetoresistance (GMR) effect. However, the beneficial effect of a NOL is strongly dependent on its process of formation. Therefore, we are interested to use a nano-semiconducting layer (NSL) for specular reflection instead of oxide layers because its achievement is easier since no specific growth conditions are needed. Moreover, we intend to compare the efficiency of the electronic confinement inside the spin valve induced either by NSL or NOLs for structures with the same stack. We have prepared hard-soft spin valve structures by sputtering on glass substrates with the following stacking sequence: Fe6 nm/Cu3 nm/CoFe1.8 nmRu0.8 nmCoFe3 nmCu2 nmRu2 nm. The reflecting layers have been inserted in the middle of the Fe soft layer and on the top of the spin valve. The GMR effect is enhanced by 60% and 75% respectively for the NSL and the NOL. This shows that the NOL is more efficient in term of electronic confinement. To understand the origin of the difference between the NOL and NSL magnetization measurements as well as transmission electron microscopy are presented.

Adsorptive Separation of Methanol-Acetone on Isostructural Series of Metal-Organic Frameworks M-BTC (M = Ti, Fe, Cu, Co, Ru, Mo): A Computational Study of Adsorption Mechanisms and Metal-Substitution Impacts.

PubMed

Wu, Ying; Chen, Huiyong; Xiao, Jing; Liu, Defei; Liu, Zewei; Qian, Yu; Xi, Hongxia

2015-12-09

The adsorptive separation properties of M-BTC isostructural series (M = Ti, Fe, Cu, Co, Ru, Mo) for methanol-acetone mixtures were investigated by using various computational procedures of grand canonical Monte Carlo simulations (GCMC), density functional theory (DFT), and ideal adsorbed solution theory (IAST), following with comprehensive understanding of adsorbate-metal interactions on the adsorptive separation behaviors. The obtained results showed that the single component adsorptions were driven by adsorbate-framework interactions at low pressures and by framework structures at high pressures, among which the mass effects, electrostatics, and geometric accessibility of the metal sites also played roles. In the case of methanol-acetone separation, the selectivity of methanol on M-BTCs decreased with rising pressures due to the pressure-dependent separation mechanisms: the cooperative effects between methanol and acetone hindered the separation at low pressures, whereas the competitive effects of acetone further resulted in the lower selectivity at high pressures. Among these M-BTCs, Ti and Fe analogues exhibited the highest thermodynamic methanol/acetone selectivity, making them promising for adsorptive methanol/acetone separation processes. The investigation provides mechanistic insights on how the nature of metal centers affects the adsorption properties of MOFs, and will further promote the rational design of new MOF materials for effective gas mixture separation.

Carbon Isotope Fractionations Associated with Methanotrophic Growth with the Soluble and Particulate Methane Monooxygenases

NASA Technical Reports Server (NTRS)

Jahnke, Linda L.; Summons, Roger E.; Chang, Sherwood (Technical Monitor)

1996-01-01

Growth experiments with the RuMP-type methanotroph, Methylococcus capsulatus (Bath), have demonstrated that biomass and lipid biomarkers are significantly depleted in C-13 compared to the substrate methane and that the extent of fractionation is dependent on whether cells express the soluble (s) or particulate (p) methane monooxygenase (MMO). The presence or absence of the characteristic sMMO subunits was monitored using SDS-polyacrylamide gels. In M. capsulatus grown with no Cu supplementation, the characteristic sMMO subunits were observed in the soluble fraction throughout the entire growth period and biomass was depleted in C-13 by approximately 14,700 relative to substrate methane. In cells grown with 5uM Cu, no sMMO bands were observed and a greater fractionation of approximately 27,700 in resultant biomass was obtained. Methanol growth experiments with M. capsulatus and with a RuMP methylotroph, Methylophilus methylotrophus, in which biomass measurements yielded depletions in C-13 of 9 and 5%(sub o), respectively, suggest that oxidation of methane is the major fractionation step. Growth of M. capsulatus at a low level of oxygen, approximately 0.5%, had no significant effect on carbon isotope fractionation by either sMMO or pMMO. These observations are significant for identification of molecular biomarkers; and methanotrophic contributions to carbon isotope composition in natural environments.

Synthesis of CuO by Cu-CPPs with the determination of Cu(II) coordination modes from a novel complex of [Cu(terpyOH){sub 2}]·(HBTC)·2H{sub 2}O

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

Wang, Yu, E-mail: wangyu1012@hit.edu.cn; Chen, Gang, E-mail: gchen@hit.edu.cn; Han, Li

2013-10-15

In this study, we investigated the synthesis of CuO microrods by simple calcination of copper-based coordination polymer particles (Cu-CPPs) at high temperature in air. The photocatalytic activity of the CuO microrods was tested by the decomposition of aqueous solution of RhB, which was completely decomposed by irradiation with light. To analyze the relationship of metal ions and ligands in the Cu-CPPs, the single crystal of [Cu(terpyOH){sub 2}]∙(HBTC)∙2H{sub 2}O (1) (terpyOH=4′-hydroxy-2,2′:6′,2″-terpyridine, BTC=1,3,5-benzene tricarboxylate) was first prepared and characterized by X-ray single crystal structural analysis. A variety of hydrogen bonds constructing the 3D complex structure in [Cu(terpyOH){sub 2}]∙(HBTC)∙2H{sub 2}O (1) were observed.more » - Graphical abstract: Demonstrating a general method to synthesize CuO microrods via simple calcination of Cu-CPPs and Cu(II) coordination modes from a novel complex of [Cu(terpyOH){sub 2}]∙(HBTC)·2H{sub 2}O constructed by hydrogen bonding. Display Omitted - Highlights: • The formation of microrods CuO from thermal treatment of Cu-CPPs through an “escape-by-crafty-scheme” strategy has been studied. • Determination of Cu(II) coordination modes in Cu-CPPs from a novel complex of [Cu(terpyOH){sub 2}]∙(HBTC) 2H{sub 2}O. • Invested the behave of hydrogen bonding to construct the 3D complex structure. • Commendable photodegradation performance was observed.« less

Magmatic sulphides in Quaternary Ecuadorian arc magmas

NASA Astrophysics Data System (ADS)

Georgatou, Ariadni; Chiaradia, Massimo; Rezeau, Hervé; Wälle, Markus

2018-01-01

New petrographic and geochemical data on magmatic sulphide inclusions (MSIs) are presented and discussed for 15 Quaternary volcanic centers of the Ecuadorian frontal, main and back volcanic arc. MSIs occur mostly in Fe-Ti oxides (magnetite and/or magnetite-ilmenite pair) and to a lesser extent in silicate minerals (amphibole, plagioclase, and pyroxene). MSIs are present in all volcanic centers ranging in composition from basalt to dacite (SiO2 = 50-67 wt.%), indicating that sulphide saturation occurs at various stages of magmatic evolution and independently from the volcano location along the volcanic arc. MSIs also occur in dioritic, gabbroic and hornblenditic magmatic enclaves of the volcanic rocks. MSIs display variable sizes (1-30 μm) and shapes (globular, ellipsoidal, angular, irregular) and occur mostly as polymineralic inclusions composed of Fe-rich and Cu-poor (pyrrhotite) and Cu-rich (mostly chalcopyrite) phases. Aerial sulphide relative abundances range from 0.3 to 7 ppm in volcanic host rocks and from 13 to 24 ppm in magmatic enclaves. Electron microprobe analyses of MSIs indicate maximum metal contents of Cu = 65.7 wt.%, Fe = 65.2 wt.%, Ni = 10.1 wt.% for those hosted in the volcanic rocks and of Cu = 57.7 wt.%, Fe = 60.9 wt.%, Ni = 5.1 wt.%, for those hosted in magmatic enclaves. Relationships of the sulphide chemistry to the host whole rock chemistry show that with magmatic differentiation (e.g., increasing SiO2) the Cu and Ni content of sulphides decrease whereas the Fe and S contents increase. The opposite behavior is observed with the increase of Cu in the whole rock, because the latter is anti-correlated with the SiO2 whole rock content. Laser ablation ICP-MS analyses of MSIs returned maximum values of PGEs and noble metals of Pd = 30 ppm, Rh = 8.1 ppm, Ag = 92.8 ppm and Au = 0.6 ppm and Pd = 43 ppm, Rh = 22.6 ppm, Ag = 89 ppm and Au = 1 ppm for those hosted in volcanic rocks and magmatic enclaves, respectively. These PGE contents display a different range of values with respect to those in previously investigated magmatic sulphides. MSIs that are Cu- and PGE/Cu-rich are found in less evolved rocks (i.e., lower SiO2 contents) that also display a lower amount of sulphide inclusions. Cu-rich sulphide phases (chalcopyrite ± bornite) are mostly hosted by magnetite, whereas PGE-rich ones consist of a Cu-poor phase (pyrrhotite) hosted by plagioclase. However, no systematic changes in the chemistry of the host silicate mineral are observed in coincidence with the occurrence of MSIs. We use the results of our study to draw some implications on Cu (and other chalcophile elements) behavior during arc magmatic processes potentially associated with the formation of porphyry-type deposits.

Typology of mafic-ultramafic complexes in Hoggar, Algeria: Implications for PGE, chromite and base-metal sulphide mineralisation

NASA Astrophysics Data System (ADS)

Augé, Thierry; Joubert, Marc; Bailly, Laurent

2012-02-01

With the aims to bring new information about the typology and mineral potential of mafic-ultramafic complexes of the Hoggar, detailed petrological and chemical characterisation were performed on serpentinite bands and layered intrusions. The serpentinite bands locally contain pods, layers and disseminations of chromite showing all the characteristics (mode of occurrence, composition, nature and composition of silicate inclusions, etc.) of an "ophiolite" chromite. Some chromite concentrations in the serpentinite bands also contain inclusions of platinum-group minerals (described for the first time in the Hoggar) such as ruarsite (RuAsS), an Os, Ru, Ir alloy, and complex Os, Ir, Ru sulfarsenides and arsenides. The serpentinite probably corresponds to remnants of oceanic lithosphere—more specifically from the upper part of the mantle sequence, generally where chromitite pods are most abundant, and the basal part of the cumulate series with stratiform chromite concentrations—and marks suture zones; the rest of the oceanic crust has not been preserved. Considering the typology of the serpentinites bands, their potential for precious- and base-metals is suspected to be low. Of the two layered mafic-ultramafic intrusions that were studied, the In Tedeini intrusion has a wehrlite core intruded by olivine gabbronorite and surrounded by an olivine gabbro aureole; three orthocumulate units, containing disseminated magmatic base-metal sulphides and with a plagioclase composition varying around An 58.1 and An 63.3, that could have been derived from a single magma. The East Laouni intrusion has a basal unit of olivine gabbronorite with specific silicate oxide intergrowths, and an upper unit of more differentiated gabbro, both units containing disseminated magmatic Ni-Cu sulphides indicative of early sulphide immiscibility; the mineral composition of these two cumulate units indicates that they also could have been derived from a single magmatic episode. The characteristic of the two intrusions appears very favourable for the presence of a significant Ni-Cu-(PGE) sulphide mineralisation.

What can Andreev bound states tell us about superconductors?

PubMed

Millo, Oded; Koren, Gad

2018-08-06

Zero-energy Andreev bound states, which manifest themselves in the tunnelling spectra as zero-bias conductance peaks (ZBCPs), are abundant at interfaces between superconductors and other materials and on the nodal surface of high-temperature superconductors. In this review, we focus on the information such excitations can provide on the properties of superconductor systems. First, a general introduction to the physics of Andreev bound states in superconductor/normal metal interfaces is given with a particular emphasis on why they appear at zero energy in d -wave superconductors. Then, specific spectroscopic tunnelling studies of thin films, bilayers and junctions are described, focusing on the corresponding ZBCP features. Scanning tunnelling spectroscopy (STS) studies show that the ZBCPs on the c -axis YBa 2 Cu 3 O 7- δ (YBCO) films are correlated with the surface morphology and appear only in proximity to (110) facets. STS on c -axis La 1.88 Sr 0.12 CuO 4 (LSCO) films exhibiting the 1/8 anomaly shows spatially modulated peaks near zero bias associated with the anti-phase ordering of the d -wave order parameter predicted at this doping level. ZBCPs were also found in micrometre-size edge junctions of YBCO/SrRuO 3 /YBCO, where SrRuO 3 is ferromagnetic. Here, the results are consistent with a crossed Andreev reflection effect (CARE) at the narrow domain walls of the SrRuO 3 ZBCPs measured in STS studies of manganite/cuprate bilayers could not be attributed to CARE because the manganite's domain wall is much larger than the coherence length in YBCO, and instead are attributed to proximity-induced triplet-pairing superconductivity with non-conventional symmetry. And finally, ZBCPs found in junctions of non-intentionally doped topological insulator films of Bi 2 Se 3 and the s -wave superconductor NbN are attributed to proximity-induced p x  + ip y triplet order parameter in the topological material.This article is part of the theme issue 'Andreev bound states'. © 2018 The Author(s).

Platinum-group elements (Rh, Pt, Pd) and Au distribution in snow samples from the Kola Peninsula, NW Russia

NASA Astrophysics Data System (ADS)

Gregurek, Dean; Melcher, Frank; Niskavaara, Heikki; Pavlov, Vladimir A.; Reimann, Clemens; Stumpfl, Eugen F.

In April 1996 snowpack samples were collected from the surroundings of the ore roasting and dressing plant at Zapoljarnij and the nickel smelters at Nikel and Monchegorsk, Kola Peninsula, NW Russia. In the laboratory, filter residues of snowpack samples (fraction>0.45 μm) from 15 localities (close to the nickel processing centres) were chemically for precious metals (Rh, Pt, Pd, Au) and Te by graphite furnace atomic absorption spectrometry (GFAAS) analysis, and for Cu and Ni by ICP-MS. Values up to 2770 ng/l Pd, 650 ng/l Pt and 186 ng/l Au were found in the filter residues. Additionally, platinum-group elements (PGE) and Au contents in ore samples from Noril'sk , as well as in technogenic products ("Cu-Ni-feinstein" and copper concentrate) processed at the Monchegorsk smelter complex, were analysed using flameless atomic absorption spectroscopy (FAAS) for comparison with results obtained from snow. Rh, Pt, Pd and Au distribution data show the presence of two ore components (Noril'sk and Pechenga). Concentrations of these metals decrease with distance from the industrial sources and with the prevailing wind direction (generally north-south). Microscopic investigations and electron microprobe analysis of polished sections of snow filter residues (>0.45 μm) also reveal differences between particles from the two sources. To avoid confusion the term "Noril'sk" is used throughout the paper to denote material and/or data from the Noril'sk area and its sub-district, Noril'sk while Pechenga relates to the local ore.

Ternary Pt/Rh/SnO2 electrocatalysts for oxidizing ethanol to CO2.

PubMed

Kowal, A; Li, M; Shao, M; Sasaki, K; Vukmirovic, M B; Zhang, J; Marinkovic, N S; Liu, P; Frenkel, A I; Adzic, R R

2009-04-01

Ethanol, with its high energy density, likely production from renewable sources and ease of storage and transportation, is almost the ideal combustible for fuel cells wherein its chemical energy can be converted directly into electrical energy. However, commercialization of direct ethanol fuel cells has been impeded by ethanol's slow, inefficient oxidation even at the best electrocatalysts. We synthesized a ternary PtRhSnO(2)/C electrocatalyst by depositing platinum and rhodium atoms on carbon-supported tin dioxide nanoparticles that is capable of oxidizing ethanol with high efficiency and holds great promise for resolving the impediments to developing practical direct ethanol fuel cells. This electrocatalyst effectively splits the C-C bond in ethanol at room temperature in acid solutions, facilitating its oxidation at low potentials to CO(2), which has not been achieved with existing catalysts. Our experiments and density functional theory calculations indicate that the electrocatalyst's activity is due to the specific property of each of its constituents, induced by their interactions. These findings help explain the high activity of Pt-Ru for methanol oxidation and the lack of it for ethanol oxidation, and point to the way to accomplishing the C-C bond splitting in other catalytic processes.

Calculations of stopping powers of 100 eV-30 keV electrons in 31 elemental solids

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

Tanuma, S.; Powell, C. J.; Penn, D. R.

We present calculated electron stopping powers (SPs) for 31 elemental solids (Li, Be, glassy C, graphite, diamond, Na, Mg, K, Sc, Ti, V, Fe, Y, Zr, Nb, Mo, Ru, Rh, In, Sn, Cs, Gd, Tb, Dy, Hf, Ta, W, Re, Os, Ir, and Bi). These SPs were determined with an algorithm previously used for the calculation of electron inelastic mean free paths and from energy-loss functions (ELFs) derived from experimental optical data. The SP calculations were made for electron energies between 100 eV and 30 keV and supplement our earlier SP calculations for ten additional solids (Al, Si, Cr, Ni,more » Cu, Ge, Pd, Ag, Pt, and Au). Plots of SP versus atomic number for the group of 41 solids show clear trends. Multiple peaks and shoulders are seen that result from the contributions of valence-electron and various inner-shell excitations. Satisfactory agreement was found between the calculated SPs and values from the relativistic Bethe SP equation with recommended values of the mean excitation energy (MEE) for energies above 10 keV. We determined effective MEEs versus maximum excitation energy from the ELFs for each solid. Plots of effective MEE versus atomic number showed the relative contributions of valence-electron and different core-electron excitations to the MEE. For a maximum excitation energy of 30 keV, our effective MEEs agreed well for Be, graphite, Na, Al, and Si with recommended MEEs; a difference for Li was attributed to sample oxidation in the SP measurements for the recommended MEE. Substantially different effective MEEs were found for the three carbon allotropes (graphite, diamond, and glassy C)« less

Single d-metal atoms on F(s) and F(s+) defects of MgO(001): a theoretical study across the periodic table.

PubMed

Neyman, Konstantin M; Inntam, Chan; Matveev, Alexei V; Nasluzov, Vladimir A; Rösch, Notker

2005-08-24

Single d-metal atoms on oxygen defects F(s) and F(s+) of the MgO(001) surface were studied theoretically. We employed an accurate density functional method combined with cluster models, embedded in an elastic polarizable environment, and we applied two gradient-corrected exchange-correlation functionals. In this way, we quantified how 17 metal atoms from groups 6-11 of the periodic table (Cu, Ag, Au; Ni, Pd, Pt; Co, Rh, Ir; Fe, Ru, Os; Mn, Re; and Cr, Mo, W) interact with terrace sites of MgO. We found bonding with F(s) and F(s+) defects to be in general stronger than that with O2- sites, except for Mn-, Re-, and Fe/F(s) complexes. In M/F(s) systems, electron density is accumulated on the metal center in a notable fashion. The binding energy on both kinds of O defects increases from 3d- to 4d- to 5d-atoms of a given group, at variance with the binding energy trend established earlier for the M/O2- complexes, 4d < 3d < 5d. Regarding the evolution of the binding energy along a period, group 7 atoms are slightly destabilized compared to their group 6 congeners in both the F(s) and F(s+) complexes; for later transition elements, the binding energy increases gradually up to group 10 and finally decreases again in group 11, most strongly on the F(s) site. This trend is governed by the negative charge on the adsorbed atoms. We discuss implications for an experimental detection of metal atoms on oxide supports based on computed core-level energies.

Properties of real metallic surfaces: Effects of density functional semilocality and van der Waals nonlocality

PubMed Central

Patra, Abhirup; Bates, Jefferson E.; Sun, Jianwei; Perdew, John P.

2017-01-01

We have computed the surface energies, work functions, and interlayer surface relaxations of clean (111), (100), and (110) surfaces of Al, Cu, Ru, Rh, Pd, Ag, Pt, and Au. We interpret the surface energy from liquid metal measurements as the mean of the solid-state surface energies over these three lowest-index crystal faces. We compare experimental (and random phase approximation) reference values to those of a family of nonempirical semilocal density functionals, from the basic local density approximation (LDA) to our most advanced general purpose meta-generalized gradient approximation, strongly constrained and appropriately normed (SCAN). The closest agreement is achieved by the simplest density functional LDA, and by the most sophisticated one, SCAN+rVV10 (Vydrov–Van Voorhis 2010). The long-range van der Waals interaction, incorporated through rVV10, increases the surface energies by about 10%, and increases the work functions by about 3%. LDA works for metal surfaces through two known error cancellations. The Perdew–Burke–Ernzerhof generalized gradient approximation tends to underestimate both surface energies (by about 24%) and work functions (by about 4%), yielding the least-accurate results. The amount by which a functional underestimates these surface properties correlates with the extent to which it neglects van der Waals attraction at intermediate and long range. Qualitative arguments are given for the signs of the van der Waals contributions to the surface energy and work function. A standard expression for the work function in Kohn–Sham (KS) theory is shown to be valid in generalized KS theory. Interlayer relaxations from different functionals are in reasonable agreement with one another, and usually with experiment. PMID:29042509

Fast and direct screening of copper in micro-volumes of distilled alcoholic beverages by high-resolution continuum source graphite furnace atomic absorption spectrometry.

PubMed

Ajtony, Zsolt; Laczai, Nikoletta; Dravecz, Gabriella; Szoboszlai, Norbert; Marosi, Áron; Marlok, Bence; Streli, Christina; Bencs, László

2016-12-15

HR-CS-GFAAS methods were developed for the fast determination of Cu in domestic and commercially available Hungarian distilled alcoholic beverages (called pálinka), in order to decide if their Cu content exceeds the permissible limit, as legislated by the WHO. Some microliters of samples were directly dispensed into the atomizer. Graphite furnace heating programs, effects/amounts of the Pd modifier, alternative wavelengths (e.g., Cu I 249.2146nm), external calibration and internal standardization methods were studied. Applying a fast graphite furnace heating program without any chemical modifier, the Cu content of a sample could be quantitated within 1.5min. The detection limit of the method is 0.03mg/L. Calibration curves are linear up to 10-15mg/L Cu. Spike-recoveries ranged from 89% to 119% with an average of 100.9±8.5%. Internal calibration could be applied with the assistance of Cr, Fe, and/or Rh standards. The accuracy of the GFAAS results was verified by TXRF analyses. Copyright © 2016 Elsevier Ltd. All rights reserved.

Structural and Thermodynamic Factors of Suppressed Interdiffusion Kinetics in Multi-component High-entropy Materials

PubMed Central

Chang, Shou-Yi; Li, Chen-En; Huang, Yi-Chung; Hsu, Hsun-Feng; Yeh, Jien-Wei; Lin, Su-Jien

2014-01-01

We report multi-component high-entropy materials as extraordinarily robust diffusion barriers and clarify the highly suppressed interdiffusion kinetics in the multi-component materials from structural and thermodynamic perspectives. The failures of six alloy barriers with different numbers of elements, from unitary Ti to senary TiTaCrZrAlRu, against the interdiffusion of Cu and Si were characterized, and experimental results indicated that, with more elements incorporated, the failure temperature of the barriers increased from 550 to 900°C. The activation energy of Cu diffusion through the alloy barriers was determined to increase from 110 to 163 kJ/mole. Mechanistic analyses suggest that, structurally, severe lattice distortion strains and a high packing density caused by different atom sizes, and, thermodynamically, a strengthened cohesion provide a total increase of 55 kJ/mole in the activation energy of substitutional Cu diffusion, and are believed to be the dominant factors of suppressed interdiffusion kinetics through the multi-component barrier materials. PMID:24561911

Electrode kinetics of ethanol oxidation on novel CuNi alloy supported catalysts synthesized from PTFE suspension

NASA Astrophysics Data System (ADS)

Sen Gupta, S.; Datta, J.

An understanding of the kinetics and mechanism of the electrochemical oxidation of ethanol is of considerable interest for the optimization of the direct ethanol fuel cell. In this paper, the electro-oxidation of ethanol in sodium hydroxide solution has been studied over 70:30 CuNi alloy supported binary platinum electrocatalysts. These comprised mixed deposits of Pt with Ru or Mo. The electrodepositions were carried out under galvanostatic condition from a dilute suspension of polytetrafluoroethylene (PTFE) containing the respective metal salts. Characterization of the catalyst layers by scanning electron microscope (SEM)-energy dispersive X-ray (EDX) indicated that this preparation technique yields well-dispersed catalyst particles on the CuNi alloy substrate. Cyclic voltammetry, polarization study and electrochemical impedance spectroscopy were used to investigate the kinetics and mechanism of ethanol electro-oxidation over a range of NaOH and ethanol concentrations. The relevant parameters such as Tafel slope, charge transfer resistance and the reaction orders in respect of OH - ions and ethanol were determined.

Preface to highly siderophile element constraints on Earth and planetary processes

NASA Astrophysics Data System (ADS)

Riches, Amy J. V.

2017-11-01

The geochemical properties of the highly siderophile elements (HSEs; Os, Ir, Ru, Rh, Pt, Pd, Re and Au) - being strongly iron-loving, but also chalcophile (i.e., having an affinity for sulphide), and generally occurring at ultra trace levels in silicate rocks, their weathered products, and oceanic waters - mean that this suite of elements and their isotopic compositions are useful in tracing a wide variety of processes. Thus, the HSEs are useful probes with which to tackle major research questions pertinent to past and present day change at a variety of scales and in a range of Earth and other-worldly environments by constraining reservoir compositions, chemical drivers, and the timing of key events and/or transformation rates.

Method for fabricating beryllium-based multilayer structures

DOEpatents

Skulina, Kenneth M.; Bionta, Richard M.; Makowiecki, Daniel M.; Alford, Craig S.

2003-02-18

Beryllium-based multilayer structures and a process for fabricating beryllium-based multilayer mirrors, useful in the wavelength region greater than the beryllium K-edge (111 .ANG. or 11.1 nm). The process includes alternating sputter deposition of beryllium and a metal, typically from the fifth row of the periodic table, such as niobium (Nb), molybdenum (Mo), ruthenium (Ru), and rhodium (Rh). The process includes not only the method of sputtering the materials, but the industrial hygiene controls for safe handling of beryllium. The mirrors made in accordance with the process may be utilized in soft x-ray and extreme-ultraviolet projection lithography, which requires mirrors of high reflectivity (>60%) for x-rays in the range of 60-140 .ANG. (60-14.0 nm).

Measurement of activation cross-section of long-lived products in deuteron induced nuclear reactions on palladium in the 30-50MeV energy range.

PubMed

Ditrói, F; Tárkányi, F; Takács, S; Hermanne, A; Ignatyuk, A V

2017-10-01

Excitation functions were measured in the 31-49.2MeV energy range for the nat Pd(d,xn) 111,110m,106m,105,104g,103 Ag, nat Pd(d,x) 111m,109,101,100 Pd, nat Pd(d,x), 105,102m,102g,101m,101g,100,99m,99g Rh and nat Pd(d,x) 103,97 Ru nuclear reactions by using the stacked foil irradiation technique. The experimental results are compared with our previous results and with the theoretical predictions calculated with the ALICE-D, EMPIRE-D and TALYS (TENDL libraries) codes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Transition metal-modified zinc oxides for UV and visible light photocatalysis.

PubMed

Bloh, J Z; Dillert, R; Bahnemann, D W

2012-11-01

In order to use photocatalysis with solar light, finding more active and especially visible light active photocatalysts is a very important challenge. Also, studies of these photocatalysts should employ a standardized test procedure so that their results can be accurately compared and evaluated with one another. A systematic study of transition metal-modified zinc oxide was conducted to determine whether they are suitable as visible light photocatalysts. The photocatalytic activity of ZnO modified with eight different transition metals (Cu, Co, Fe, Mn, Ni, Ru, Ti, Zr) in three different concentrations (0.01, 0.1, and 1 at.%) was investigated under irradiation with UV as well as with visible light. The employed activity test is the gas-phase degradation of acetaldehyde as described by the ISO standard 22197-2. The results suggest that the UV activity can be improved with almost any modification element and that there exists an optimal modification ratio at about 0.1 at.%. Additionally, Mn- and Ru-modified ZnO display visible light activity. Especially the Ru-modified ZnO is highly active and surpasses the visible light activity of all studied titania standards. These findings suggest that modified zinc oxides may be a viable alternative to titanium dioxide-based catalysts for visible light photocatalysis. Eventually, possible underlying mechanisms are proposed and discussed.

Two intriguing hydroxy-copper(II) coordination polymers with bis(triazole) and bicarboxylate ligands: Syntheses, structures and photocatalytic degradation of organic dyes

NASA Astrophysics Data System (ADS)

Zhao, Shan; Zheng, Tian-Rui; Shi, Lu-Lu; Li, Ke; Li, Bao-Long; Li, Hai-Yan

2017-09-01

Two intriguing coordination polymers [Cu2(OH)(mbtx)(sip)(H2O)2]n (1) and {[Cu3(OH)2(mbtx)(nip)2]·H2O}n (2) were synthesized by the hydrothermal method and characterized by elementary analysis, IR, PXRD, diffuse reflectance spectra and single-crystal X-ray diffraction (mbtx = 1,3-bis(1,2,4-triazol-4-yl)benzene, sip = sulfoisophthalate, nip = 5-nitroisophthalate). 1 shows an unusual 3-connected 2D network based on the dimeric hydroxy-copper(II) cluster [Cu2(μ-OH)] with the point symbol of 63. 2 exhibits an unusual 3D network based on 1D hydroxyl-copper(II) chains [Cu3(OH)2]n. 1 and 2 are highly efficient and universal photocatalysts for the degradation of the organic dyes such as methyl orange (MO), methylene blue (MB) and rhodamine B (RhB) under UV irradiation. The photocatalytic mechanism was supposed.

Strongly reduced Ehrlich-Schwoebel barriers at the Cu (111) stepped surface with In and Pb surfactants

NASA Astrophysics Data System (ADS)

Hao, Jialei; Zhang, Lixin

2018-01-01

A surfactant can modify the properties of the surface and induce different mode of epitaxy growth. The atomistic mechanism is not fully understood yet. In this first-principles study, taking Cu homoepitaxy along (111) direction as an example, we show that the distribution of the surfactant atoms on the surface is the key. For In and Pb, they prefer to locate at the step edges and remain isolated. Once the growth is started, the distribution can be further modified by Cu adatoms. The uniquely decorated step edges have much lowered Ehrlich-Schwoebel (ES) barriers than that of the clean edges, thus the two dimensional growth on Cu (111) surface is promoted significantly. On the other hand, for Rh, Ir, and Au, these atoms are not favored at the step edges. The ES barriers can't be affected and these metals are not surfactants. The result is very helpful for searching of the optimal surfactants in metal homoepitaxy.

Department of the Navy Fiscal Year (FY) 2000/2001 Biennial Budget Estimates, Justification of Estimates, February 1999 Research, Development, Test & Evaluation, Navy Budget Activity 5.

DTIC Science & Technology

1999-02-01

jjAi id ß g§s(ö rH^^-H ■J a) wm 4J ft & ü o o P .y rHrH id CDrH (D 0, > id 01 _Ö <D pQw > a oi rr) OCD lj 01a id *^r5 CD ft...Old cu-O § d id u cu •H u d co P P CD 3 M Ol O rH -H (D &CÜH43P CD 5H d CtJ d CDrH CU O PrH P ■O CO d-H CD d U-H s ^ Id CD QH...H P CN CD P P I -H <D drH EH M43 CDrH H O P-H 10 CD S-0 >iP PS drH g IdrH > CD CD Id Ol Ä4JJJ3S P 01 CU C0-H >ld"H Ol

Edge-Selectively Functionalized Graphene-Like Platelets as a Co-curing Agent and a Nanoscale Additive to Epoxy Resin

DTIC Science & Technology

2012-08-12

21 For mass production , the Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden for the collection of information is...analyzer. The field emission scanning electron microscope ( FE -SEM) used in this work was a NanoSem 230 (FEI, USA). High-resolution transmission...WAXD) powder patterns were recorded with a Rigaku RU-200 diffractometer using Ni-filtered Cu K radiation (40 kV, 100 mA,  = 0.15418 nm). Dynamic

Maintenance Dredging of the Federal Navigation Channels in the St. Clair River, Michigan.

DTIC Science & Technology

1976-01-01

Detroit livers system today constitutes a major corridor for waterborne traffic, and therefore a central axis of settlement, it should not be surprising...0 C;U2 $4 2) ~ 4 .0 41 -4 0~ 0~ ~0 -4 144 .H ,.4ul0. ".4 -4 -4 4.42 0 0 4.44 -44 ’U r rU 0 54 4-’ 4 .14 1- 1 A N.~~- A. )0 > TABLE 14. Wildife in

Tunable photoluminescent metal-organic-frameworks and method of making the same

DOEpatents

Nenoff, Tina M.; Sava Gallis, Dorina Florentina; Rohwer, Lauren E.S.

2017-08-22

The present disclosure is directed to new photoluminescent metal-organic frameworks (MOFs). The newly developed MOFs include either non rare earth element (REE) transition metal atoms or limited concentrations of REE atoms, including: Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Ru, Ag, Cd, Sn, Sb, Ir, Pb, Bi, that are located in the MOF framework in site isolated locations, and have emission colors ranging from white to red, depending on the metal concentration levels and/or choice of ligand.

X-Ray Absorption Spectroscopy of Electrochemically Generated Species

DTIC Science & Technology

1989-01-27

constructed from gold minigrid, colloidal graphite, and reticulated vitreous carbon (RVC). The use of gold minigrid electrodes has been demonstrated for...jBF n (bipy= 2,2’-ipyridine, dmp= 2,9-dimethvl- 1,10-phenanthroline) in solution at reticulated vitreous carbon electrodes, and incorporated in...Fe(bipy)3(C104)2, Ru(bipy)3Cl2, and Cu(drp)2BF4 (bipy= 2,2’-bipyridine, dmp= 2, 9-dimethyl-l,10-phenanthroline) in solution at reticulated vitreous

[Advanced treatment of coking wastewater with a novel heterogeneous electro-Fenton technology].

PubMed

Li, Hai-Tao; Li, Yu-Ping; Zhang, An-Yang; Cao, Hong-Bin; Li, Xin-Gang; Zhang, Yi

2011-01-01

A novel electro-catalytic reactor, with oxygen-reduction cathode (PAQ/GF), dimensionally stable anode (IrO2-RuO2 -TiO2/ Ti) and heterogeneous catalysts, is developed for advanced treatment of coking wastewater after biological process, integrating cathodic and anodic simultaneous oxidation processes. A PAQ/GF electrode was synthesized by the electro-polymerization of 2-ethyl anthraquinone on graphite felt, which was characterized with cyclic voltametry measurements; the results indicated that the PAQ/GF electrode showed high reversibility for oxidation-reduction reaction of anthraquinone and catalytic activity for O2 reduction to H2O2; 13.5 mmol/L H2O2 was obtained after electrolysis for 6 h at -0.7 V (vs. SCE) and pH 6 with a current efficiency of 50% in a membrane reactor. Fe-Cu/Y350 catalysts, prepared by impregnation method, could catalyze the production of hydroxyl radicals (*OH) from H2O2, which was confirmed both by fading reaction of crystal violet and oxidation of *OH-probe compound (p-chlorobenzoic acid); Fe-Cu/Y350 also showed high catalytic-activity for the oxidation of organics by hypochlorous sodium, because COD removal of coking wastewater reached 26% in the catalytic process while only 11% of COD removal was obtained in the absence of Fe-Cu/Y350. COD removal of coking wastewater reached 49.4% (26.0% and 23.4% in cathodic system and anodic system, respectively) in the developed electrolytic-reactor, which was higher than that of conventional cathodic-anodic-oxidation process (29.8%). At optimal reaction condition of initial COD = 192 mg/L, I = 10A x m(-2) and pH 4-5, more than 50% COD were removed after electrolysis for 1 h. The mechanism might be as follows: in cathodic system, H2O2 is generated from reduction of O2 on PAQ/GF cathode, and catalyzed by Fe-Cu/Y350 for production of *OH, which causes mineralization and degradation of organic pollutants; in anodic system, Cl2 and HClO are generated from Cl- oxidation on IrO2-RuO2-TiO2/Ti anode and the organic pollutants are oxidized by Cl2, and HClO with Fe-Cu/Y350 catalysts or by direct anodic oxidation.

Pathways for tailoring the magnetostructural behavior of FeRh-based systems

NASA Astrophysics Data System (ADS)

Barua, Radhika

2014-03-01

The prediction of phase transition temperatures in functional materials provides dual benefits of supplying insight into fundamental drivers underlying the phase transition, as well as enabling new and improved technological applications that employ the material. In this work, studies focused on understanding the magnetostructural phase transition of FeRh as a function of elemental substitution, provides guidance for tailoring phase transitions in this compound, with possible extensions to other intermetallic-based magnetostructural compounds. Clear trends in the magnetostructural temperatures (Tt) of alloys of composition Fe(Rh1-xMx) or (Fe1-xMx) Rh (M = 3 d, 4 d or 5 d transition metals), as reported in literature since 1961, were identified and confirmed as a function of the valence band electron concentration ((s + d) electrons/atom) of the system. It is observed that substitution of 3 dor 4 delements (x <= 6.5 at%) into B2-ordered FeRh compounds causes Ttto increase to a maximum around a critical valence band electron concentration (ev *) of 8.50 electrons/atom and then decrease. Substitution of 5 delements echoes this trend but with an overall increase in Ttand a shift in ev * to 8.52 electrons/atom. For ev>8.65 electrons/atom, FeRh-based alloys cease to adopt the B2-ordered crystallographic structure in favor of the chemically disordered A1-type structure or the ordered L10-type structure. This phenomenological model has been confirmed through synthesis and characterization of FeRh alloys with Cu, Ni and Au additions. The success of this model in confirming existing data trends in chemically-substituted FeRh and predicting new composition-transition temperature correlations emphasizes the strong interplay between the electronic spin configuration, the electronic band structure, and crystal lattice of this system. Further these results provide pathways for tailoring the magnetostructural behavior and the associated functional response of FeRh-based systems for potential technological applications. Research was performed under the auspices of the U.S. Department of Energy (Contract No. DE-SC0005250).

Micrometer- and nanometer-sized platinum group nuggets in micrometeorites from deep-sea sediments of the Indian Ocean

NASA Astrophysics Data System (ADS)

Rudraswami, N. G.; Parashar, K.; Shyam Prasad, M.

2011-03-01

We examined 378 micrometeorites collected from deep-sea sediments of the Indian Ocean of which 175, 180, and 23 are I-type, S-type, and G-type, respectively. Of the 175 I-type spherules, 13 contained platinum group element nuggets (PGNs). The nuggets occur in two distinct sizes and have distinctly different elemental compositions: micrometer (μm)-sized nuggets that are >3 μm contain dominantly Ir, Os, and Ru (iridium-platinum group element or IPGE) and sub-μm (or nanometer)-sized (<1 μm) nuggets, which contain dominantly Pt, Rh, and Pd (palladium—PGE or PPGE). The μm-sized nuggets are found only one per spherule in the cross section observed and are usually found at the edge of the spherule. By contrast, there are hundreds of nanometer-sized nuggets distributed dominantly in the magnetite phases of the spherules, and rarely in the wüstite phases. Both the nugget types are found as separate entities in the same spherule and apparently, nugget formation is a common phenomenon among I-type micrometeorites. However, the μm-sized nuggets are seen in fewer specimens (˜2.5% of the observed I-type spherules). In all, we analyzed four nuggets of μm size and 213 nanometer-sized nuggets from 13 I-type spherules for platinum group elements. Chemically, the μm-sized PGNs contain chondritic ratios of Os/Ir, but are depleted in the more volatile PGE (Pt, Rh, and Pd) relative to chondritic ratios. On the other hand, the nanometer-sized nuggets contain dominantly Pt and Rh. Importantly, the refractory PGEs are conspicuous by their absence in these nanometer nuggets. Palladium, the most volatile PGE is highly depleted (<1.1%) with respect to chondritic ratios in the μm-sized PGNs, and is observed in only 17 of 213 nanometer nuggets with concentrations that are just above the detection limit (≥0.2%). Distinct fractionation of the PGE into IPGE (Ir, Os, Ru) and PPGE seems to take place during the short span of atmospheric entry. These observations suggest several implications: (1) The observation of fractionated PGE in an Fe-Ni system gives rise to the possibility that Earth’s core could contain fractionated PGE. (2) The present data support the processes suggested for the fractionated PGE patterns observed in the ejecta of ancient meteorite impacts. (3) Meteoric metals released in the troposphere could contain fractionated PGNs in large numbers.

Highly potent metallopeptide analogues of luteinizing hormone-releasing hormone.

PubMed Central

Bajusz, S; Janaky, T; Csernus, V J; Bokser, L; Fekete, M; Srkalovic, G; Redding, T W; Schally, A V

1989-01-01

Metal complexes related to the cytotoxic complexes cisplatin [cis-diamminedichloroplatinum(II)] and transbis(salicylaldoximato)copper(II) were incorporated into suitably modified luteinizing hormone-releasing hormone (LH-RH) analogues containing D-lysine at position 6. Some of the metallopeptides thus obtained proved to be highly active LH-RH agonists or antagonists. For instance, SB-40, a PtCl2-containing metallopeptide in which platinum is coordinated to an N epsilon-(DL-2,3-diaminopropionyl)-D-lysine residue [D-Lys(DL-A2pr] at position 6, showed 50 times higher LH-releasing potency than the native hormone. SB-95, [Ac-D-Nal(2)1,D-Phe(pCl)2, D-Pal(3)2, Arg5,D-Lys[DL-A2pr(Sal2Cu)]6,D-Ala10]LH-RH, where Nal(2) is 3-(2-naphthyl)alanine, Pal(3) is 3-(3-pyridyl)alanine, and copper(II) is coordinated to the salicylideneimino moieties resulting from condensation of salicylaldehyde with D-Lys(DL-A2pr)6, caused 100% inhibition of ovulation at a dose of 3 micrograms in rats. Most metallopeptide analogues of LH-RH showed high affinities for the membrane receptors of rat pituitary and human breast cancer cells. Some of these metallopeptides had cytotoxic activity against human breast cancer and prostate cancer cell lines in vitro (this will be the subject of a separate paper on cytotoxicity evaluation). Such cytostatic metallopeptides could be envisioned as targeted chemotherapeutic agents in cancers that contain receptors for LH-RH-like peptides. PMID:2548206

Highly potent metallopeptide analogues of luteinizing hormone-releasing hormone.

PubMed

Bajusz, S; Janaky, T; Csernus, V J; Bokser, L; Fekete, M; Srkalovic, G; Redding, T W; Schally, A V

1989-08-01

Metal complexes related to the cytotoxic complexes cisplatin [cis-diamminedichloroplatinum(II)] and transbis(salicylaldoximato)copper(II) were incorporated into suitably modified luteinizing hormone-releasing hormone (LH-RH) analogues containing D-lysine at position 6. Some of the metallopeptides thus obtained proved to be highly active LH-RH agonists or antagonists. For instance, SB-40, a PtCl2-containing metallopeptide in which platinum is coordinated to an N epsilon-(DL-2,3-diaminopropionyl)-D-lysine residue [D-Lys(DL-A2pr] at position 6, showed 50 times higher LH-releasing potency than the native hormone. SB-95, [Ac-D-Nal(2)1,D-Phe(pCl)2, D-Pal(3)2, Arg5,D-Lys[DL-A2pr(Sal2Cu)]6,D-Ala10]LH-RH, where Nal(2) is 3-(2-naphthyl)alanine, Pal(3) is 3-(3-pyridyl)alanine, and copper(II) is coordinated to the salicylideneimino moieties resulting from condensation of salicylaldehyde with D-Lys(DL-A2pr)6, caused 100% inhibition of ovulation at a dose of 3 micrograms in rats. Most metallopeptide analogues of LH-RH showed high affinities for the membrane receptors of rat pituitary and human breast cancer cells. Some of these metallopeptides had cytotoxic activity against human breast cancer and prostate cancer cell lines in vitro (this will be the subject of a separate paper on cytotoxicity evaluation). Such cytostatic metallopeptides could be envisioned as targeted chemotherapeutic agents in cancers that contain receptors for LH-RH-like peptides.

Chemistry of group 9 dimetallaborane analogues of octaborane(12).

PubMed

Barik, Subrat Kumar; Roy, Dipak Kumar; Ghosh, Sundargopal

2015-01-14

We report the synthesis, isolation and structural characterization of several moderately air stable nido-metallaboranes that represent boron rich open cage systems. The reaction of [Cp*CoCl]2, (Cp* = η(5)-C5Me5), with [BH3·thf] in toluene at ice cold temperature, followed by thermolysis in boiling toluene produced [(Cp*Co)B9H13], 1 [(Cp*Co)2B8H12], 2 and [(Cp*Co)2B6H10] 3. Building upon our earlier reactivity studies on rhodaboranes, we continue to explore the reactivity of dicobalt analogues of octaborane(12) cluster 3 with [Fe2(CO)9] and [Ru3(CO)12] at ambient conditions that yielded novel fused clusters [Fe2(CO)6(Cp*Co)2B6H10], 4 and [Ru4(CO)11(Cp*Co)2B3H3], 5 respectively. In an attempt to synthesize a heterometallic metallaborane compound we performed the reaction of [(Cp*Rh)2B6H10], 6 with [Cp*IrH4] that yielded a Ir-Ir double bonded compound [(Cp*Ir)2H3][B(OH)4], 7. All the new compounds have been characterized by IR, (1)H, (11)B, (13)C NMR spectroscopy, and the molecular structures were unambiguously established by X-ray diffraction analysis.

Validation of the Protected DMS Specifications

DTIC Science & Technology

1977-04-01

a, * 0 * p (« 0) o in P u tp rH 1 rd X <H • o a a) 0) tt) > U tt) to XI Tl O tt) •rl CO 4H Q) -H rH ’O (0 S •H p T) td C...Cu p P -H COO) D tt) S 0 -H O 4-> 4J •H tP X tn tn c •POO) td rd -H QurH rd tt) 0) tt) E U 0) •• . X X O X P U) ro EH EH...O w d-Hw CM <c ^, CQ 31 APP DIR (START) Subject 1 (at level W) W COEE <- EN f END J N N IL \\ N / TD ^ c W CODE «• IR W CODE i

Cycloruthenated complexes from imine-based heterocycles: synthesis, characterization, and reactivity toward alkynes.

PubMed

Cuesta, Luciano; Soler, Tatiana; Urriolabeitia, Esteban P

2012-11-19

Novel cycloruthenated complexes 2 a-c, 4 a-c, and 6 a, b based on heteroaromatic cores have been synthesized by reaction of a series of heterocycle-based imines with [{RuCl(η(6)-p-cymene)}(2)(μ-Cl)(2)] and Cu(OAc)(2). This approach has proved efficient for the cyclometalation of thiophene, benzothiophene, furan, benzofuran, pyrrole, and indole derivatives. In addition, even a double cyclometalation process over the same heterocyclic ring is possible, yielding unprecedented bimetallic complexes. These ruthenacycles react with 3-hexyne through an unexpected pathway, which involves the coupling of the original imino heterocycle and acetylene followed by dearomatization to afford fused hetero-hydropyridyl ligands bonded to the {Ru(p-cymene)} organometallic moiety (i.e., 7 a-c and 8 a-c). These complexes represent, as far as we know, the first examples of this type of compound within the context of cyclometalation, and an exhaustive analysis of their structure was carried out in solution and solid state. Furthermore, these unique species react with CuCl(2), which promotes the rearomatization and the release of highly valuable aromatic fused bis-heterocycles (i.e., 9 a-c, 10 a-c, 11 a, and 12 a/12 a'), providing a novel and appealing synthetic route to this extraordinary family of molecules. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Mukherjee, Rupam; Huang, Zhi-Feng; Nadgorny, Boris

Multiple percolation transitions are observed in a binary system of RuO{sub 2}-CaCu{sub 3}Ti{sub 4}O{sub 12} metal-semiconductor nanoparticle composites near percolation thresholds. Apart from a classical percolation transition, associated with the appearance of a continuous conductance path through RuO{sub 2} metal oxide nanoparticles, at least two additional tunneling percolation transitions are detected in this composite system. Such behavior is consistent with the recently emerged picture of a quantum conductivity staircase, which predicts several percolation tunneling thresholds in a system with a hierarchy of local tunneling conductance, due to various degrees of proximity of adjacent conducting particles distributed in an insulating matrix.more » Here, we investigate a different type of percolation tunneling staircase, associated with a more complex conductive and insulating particle microstructure of two types of non-spherical constituents. As tunneling is strongly temperature dependent, we use variable temperature measurements to emphasize the hierarchical nature of consecutive tunneling transitions. The critical exponents corresponding to specific tunneling percolation thresholds are found to be nonuniversal and temperature dependent.« less

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

Benson, David M.; Tsang, Chu F.; Sugar, Joshua Daniel

One method for the formation of nanofilms of materials, is Electrochemical atomic layer deposition (E-ALD), one atomic layer at a time. It uses the galvanic exchange of a less noble metal, deposited using underpotential deposition (UPD), to produce an atomic layer of a more noble element by reduction of its ions. This process is referred to as surface limited redox replacement and can be repeated in a cycle to grow thicker deposits. Previously, we performed it on nanoparticles and planar substrates. In the present report, E-ALD is applied for coating a submicron-sized powder substrate, making use of a new flowmore » cell design. E-ALD is used to coat a Pd powder substrate with different thicknesses of Rh by exchanging it for Cu UPD. Furthermore, cyclic voltammetry and X-ray photoelectron spectroscopy indicate an increasing Rh coverage with increasing numbers of deposition cycles performed, in a manner consistent with the atomic layer deposition (ALD) mechanism. Cyclic voltammetry also indicated increased kinetics of H sorption and desorption in and out of the Pd powder with Rh present, relative to unmodified Pd.« less

Measurement of the cross section of the residues from the 11B-induced reaction on 89Y and 93Nb: Production of 97Ru and Rhm101

NASA Astrophysics Data System (ADS)

Kumar, Deepak; Maiti, Moumita

2017-06-01

Background: The heavy-ion induced reactions on intermediate mass targets are complex in nature, even at the low energies. To understand those nuclear reaction phenomena in detail, more experimental studies are required in a wide range of energies. Purpose: Investigation of heavy-ion reactions by measuring production cross sections of the residues produced in the 11B-induced reactions on 89Y and 93Nb at low energies, near and above the barrier, and to check the effectiveness of the different nuclear models to explain them. Further, aim is also to optimize the production parameters of neutron deficient medically relevant 97Ru and Rhm101 radioisotopes produced in those reactions, respectively. Method: The 11B beam was allowed to impinge on 89Y and 93Nb foils supported by an aluminum (Al) catcher foil, arranged in a stack, in 27.5-58.7 and 30.6-62.3 MeV energy range, respectively. The off-line γ -ray spectrometry was carried out after the end of bombardment to measure the activity of the radionuclides produced in each foil and cross sections were calculated. Measured cross-sectional data were analyzed in terms of compound and precompound model calculations. Results: The measured cross sections of Ru,9597, 96,95,94Tc, Mom93, Ym90 radionuclides produced in the 11B+89Y reaction, and 101,100,99Pd, 101m,100,99mRh, 97Ru produced in the 11B+93Nb reaction showed good agreement with the model calculations based on the Hauser-Feshbach formulation and exciton model. Unlike theoretical estimation, consistent production of Ym90 was observed in the 11B+89Y reaction. Substantial pre-equilibrium contribution was noticed in the 3 n reaction channel in both reactions. Conclusions: Theoretical estimations confirmed that major production yields are mostly contributed by the compound reaction process. Pre-equilibrium emissions contributed at the high energy tail of the 3 n channel for both reactions. Moreover, an indirect signature of a direct reaction influence was also observed in the Ym90 production.

Evidence from bond lengths and bond angles for enneacovalence of cobalt, rhodium, iridium, iron, ruthenium, and osmium in compounds with elements of medium electronegativity.

PubMed

Pauling, L

1984-03-01

Enneacovalence of neutral atoms can be achieved for Co, Rh, and Ir by promoting some electrons from the nd orbital to the (n + 1)s and (n + 1)p orbitals and for Fe, Ru, and Os by a similar promotion together with the addition of an electron, which may be provided by an electron pair from a singly bonded carbonyl group or other group. The bond lengths and bond angles are predicted by the theory of enneacovalence to be significantly different for the different transition metals. Recently reported experimental values are shown to be in good agreement with the predicted values, providing support for the theory of enneacovalence and the theory of hybrid sp(3)d(5) bond orbitals.

PEM regenerative fuel cells

NASA Technical Reports Server (NTRS)

Swette, Larry L.; Laconti, Anthony B.; Mccatty, Stephen A.

1993-01-01

This paper will update the progress in developing electrocatalyst systems and electrode structures primarily for the positive electrode of single-unit solid polymer proton exchange membrane (PEM) regenerative fuel cells. The work was done with DuPont Nafion 117 in complete fuel cells (40 sq cm electrodes). The cells were operated alternately in fuel cell mode and electrolysis mode at 80 C. In fuel cell mode, humidified hydrogen and oxygen were supplied at 207 kPa (30 psi); in electrolysis mode, water was pumped over the positive electrode and the gases were evolved at ambient pressure. Cycling data will be presented for Pt-Ir catalysts and limited bifunctional data will be presented for Pt, Ir, Ru, Rh, and Na(x)Pt3O4 catalysts as well as for electrode structure variations.

Mono- and bimetallic nanoparticles decorated KTaO3 photocatalysts with improved Vis and UV-Vis light activity

NASA Astrophysics Data System (ADS)

Krukowska, Anna; Trykowski, Grzegorz; Winiarski, Michal Jerzy; Klimczuk, Tomasz; Lisowski, Wojciech; Mikolajczyk, Alicja; Pinto, Henry P.; Zaleska-Medynska, Adriana

2018-05-01

Novel mono- and bimetallic nanoparticles (MNPs and BNPs) decorated surface of perovskite-type KTaO3 photocatalysts were successfully synthesized by hydrothermal reaction of KTaO3 followed by photodeposition of MNPs/BNPs. The effect of noble metal type (MNPs = Au, Ag, Pt, Pd, Rh, Ru or BNPs = Au/Pt, Ag/Pd, Rh/Ru), amount of metal precursor (0.5, 1.0, 1.5 or 2.0 wt%) as well as photoreduction method (simultaneous (both) or subsequent (seq) deposition of two metals) on the physicochemical and photocatalytic properties of MNPs- and BNPs-KTaO3 have been investigated. All as-prepared photocatalysts were subsequently characterized by UV-Vis diffuse reflectance spectroscopy (DRS), Brunauer-Emmett-Teller (BET) specific surface area and pore size distribution measurement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (PXRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) emission spectroscopy. The crystal structure was performed using visualization for electronic and structural analysis (VESTA). The photocatalytic activity under Vis light irradiation was estimated in phenol degradation in aqueous phase and toluene removal in gas phase, while under UV-Vis light irradiation was measured amount of H2 generation from formic acid solution. The absorption properties of O2 and H2O molecules on KTaO3(1 0 0) surface supported by Au or Au/Pt NPs was also investigated using density-functional theory (DFT). The experimental results show that, both MNPs-KTaO3 and BNPs-KTaO3 exhibit greatly enhanced pollutant decomposition efficiency under Vis light irradiation and highly improved H2 production under UV-Vis light irradiation compared with pristine KTaO3. MNPs deposition on KTaO3 surface effects by disperse metal particle size ranging from 11 nm (Ru NPs) to 112 nm (Au NPs). Simultaneous addition of Au/Pt precursors results in formation of agglomerated larger metal nanoparticles (50-100 nm) on KTaO3 surface than subsequent deposition of Au/Pt with composition of concentrated smaller metal nanoparticles (>50 nm) on KTaO3 surface. The 0.5 Au/1.5 Pt-KTaO3_both and 2.0 Rh-KTaO3 reveal the highest Vis-induced activity among prepared samples in aqueous phase (14.75% of phenol decomposition after 90 min of irradiation) and gas phase (41.98% of toluene removal after 60 min of irradiation), respectively. The theoretical calculations confirmed that adsorption energy of O2 and H2O molecules was increased after loading of Au or Au/Pt NPs on KTaO3(1 0 0) surface. Control tests with scavengers show that O2rad - radical is significantly involved in phenol oxidation under Vis light irradiation, which proposed mechanism is based on direct electron transfer from MNPs/BNPs to conduction band of KTaO3. The highest amount of H2 evaluation is obtained also by 0.5 Au/1.5 Pt-KTaO3_both after 240 min of UV-Vis light irradiation (76.53 μmol/min), which is eleven times higher than for pristine KTaO3 (6.69 μmol/min). Moreover, the most photocatalytic samples for each model reaction present good repeatability and stability after subsequent three cycles. Summarized, MNPs- and BNPs-KTaO3 are promising material in advanced applications of photocatalysis.

Lattice dynamics and metastability of fcc metals in the hcp structure and the crucial role of spin-orbit coupling in platinum

NASA Astrophysics Data System (ADS)

Schönecker, Stephan; Li, Xiaoqing; Richter, Manuel; Vitos, Levente

2018-06-01

We investigate the lattice dynamical properties of Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au in the nonequilibrium hcp structure by means of density-functional simulations, wherein spin-orbit coupling (SOC) was considered for Ir, Pt, and Au. The determined dynamical properties reveal that all eight elements possess a metastable hcp phase at zero temperature and pressure. The hcp Ni, Cu, Rh, Pd, and Au previously observed in nanostructures support this finding. We make evident that the inclusion of SOC is mandatory for an accurate description of the phonon dispersion relations and dynamical stability of hcp Pt. The underlying sensitivity of the interatomic force constants is ascribed to a SOC-induced splitting of degenerate band states accompanied by a pronounced reduction of electronic density of states at the Fermi level. To give further insight into the importance of SOC in Pt, we (i) focus on phase stability and examine a lattice transformation related to optical phonons in the hcp phase and (ii) focus on the generalized stacking fault energy (GSFE) of the fcc phase pertinent to crystal plasticity. We show that the intrinsic stable and unstable fault energies of the GSFE scale as in other common fcc metals, provided that the spin-orbit interaction is taken into account.

Dimers of nineteen-electron sandwich compounds: crystal and electronic structures, and comparison of reducing strengths.

PubMed

Mohapatra, Swagat K; Fonari, Alexandr; Risko, Chad; Yesudas, Kada; Moudgil, Karttikay; Delcamp, Jared H; Timofeeva, Tatiana V; Brédas, Jean-Luc; Marder, Seth R; Barlow, Stephen

2014-11-17

The dimers of some Group 8 metal cyclopentadienyl/arene complexes and Group 9 metallocenes can be handled in air, yet are strongly reducing, making them useful n-dopants in organic electronics. In this work, the X-ray molecular structures are shown to resemble those of Group 8 metal cyclopentadienyl/pentadienyl or Group 9 metal cyclopentadienyl/diene model compounds. Compared to those of the model compounds, the DFT HOMOs of the dimers are significantly destabilized by interactions between the metal and the central CC σ-bonding orbital, accounting for the facile oxidation of the dimers. The lengths of these CC bonds (X-ray or DFT) do not correlate with DFT dissociation energies, the latter depending strongly on the monomer stabilities. Ru and Ir monomers are more reducing than their Fe and Rh analogues, but the corresponding dimers also exhibit much higher dissociation energies, so the estimated monomer cation/neutral dimer potentials are, with the exception of that of [RhCp2 ]2 , rather similar (-1.97 to -2.15 V vs. FeCp2 (+/0) in THF). The consequences of the variations in bond strength and redox potentials for the reactivity of the dimers are discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photochemistry of transition-metal phthalocyanines. Analysis of the photochemical and photophysical properties of the acido(phthalocyaninato)rhodium(III) complexes

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

Ferraudi, G.; Muralidharan, S.

1983-04-01

The ultraviolet photochemistry of the rhodium(II) phthalocyanines Rh(ph)(CH/sub 3/OH)X with X = Cl/sup -/, Br/sup -/, and I/sup -/ was investigated at different wavelengths. The same action spectrum for the photoinduced hydrogen abstraction was obtained for the three compounds. The photonic energy of the excitation is degraded in part by emission at short wavelengths, e.g. lambda/sub max/ approx. = 420 nm. Such a violet emission, observed with phthalocyanines of Al(III), Rh(III), Co(III), and Ru(II), has been attributed to the relaxation of an upper /sup 3/par. deltapar. delta* excited state. The emissions spectra at 77 K exhibited vibronic components with amore » separation between successive peaks ..delta nu.. approx. = 1.3 x 10/sup 3/ cm/sup -1/. A comparison between the excitation and action spectra shows the difference in the paths that populate the reactive npar. delta* and upper emissive par. deltapar. delta* states. An investigation of the time dependence of the upper /sup 3/par. deltapar. delta* emission and lowest /sup 3/par. deltapar. delta* absorptions reveals the participation of triplet sublevels in the degradation of the excitation energy. The relationship between photoemissive and photoreactive states is discussed.« less

Photochemistry of transition-metal phthalocyanines. Analysis of the photochemical and photophysical properties of the acido(phthalocyaninato)rhodium(III) complexes

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

Ferraudi, G.; Muralidharan, S.

1983-01-01

The ultraviolet photochemistry of the rhodium(III) phthalocyanines Rh(ph)(CH/sub 3/OH)X with X = Cl/sup -/, Br/sup -/, and I/sup -/ was investigated at different wavelengths. The same action spectrum for the photoinduced hydrogen abstraction was obtained for the three compounds. The photonic energy of the excitation is degraded in part by emission at short wavelengths, e.g. lambda/sub max/ approx. = 420 nm. Such a violet emission, observed with phthalocyanines of Al(III), Rh(III), Co(III), and Ru(II), has been attributed to the relaxation of an upper /sup 3/pipi* excited state. The emission spectra at 77 K exhibited vibronic components with a separation betweenmore » successive peaks ..delta..v approx. = 1.3 x 10/sup 3/ cm/sup -1/. A comparison between the excitation and action spectra shows the difference in the paths that populate the reactive npi* and upper emissive pipi* states. An investigation of the time dependence of the upper /sup 3/pipi* emission and lowest /sup 3/pipi* absorptions reveals the participation of triplet sublevels in the degradation of the excitation energy. The relationship between photoemissive and photoreactive states is discussed. 40 references, 6 figures, 2 tables.« less

Quantitative study of the f occupation in CeMIn 5 and other cerium compounds with hard X-rays

DOE PAGES

Sundermann, M.; Strigari, F.; Willers, T.; ...

2016-02-28

We present bulk-sensitive hard X-ray photoelectron spectroscopy (HAXPES) data of the Ce3d core levels and lifetime-reduced L-edge X-ray absorption spectroscopy (XAS) in the partial fluorescence yield (PFY) mode of the CeMIn 5 family with M = Co, Rh, and Ir. The HAXPES data are analyzed quantitatively with a combination of full multiplet and configuration interaction model which allows correcting for the strong plasmons in the CeMIn 5 HAXPES data, and reliable weights w n of the different f n contributions in the ground state are determined. The CeMIn 5 results are compared to HAXPES data of other heavy fermion compoundsmore » and a systematic decrease of the hybridization strength V eff from CePd 3 to CeRh 3B 2 to CeRu 2Si 2 is observed, while it is smallest for the three CeMIn 5 compounds. The f-occupation, however, increases in the same sequence and is close to one for the CeMIn 5 family. The PFY-XAS data confirm an identical f-occupation in the three CeMIn 5 compounds and a phenomenological fit to these PFY-XAS data combined with a configuration interaction model yields consistent results.« less

Fac and mer isomers of Ru(II) tris(pyrazolyl-pyridine) complexes as models for the vertices of coordination cages: structural characterisation and hydrogen-bonding characteristics.

PubMed

Metherell, Alexander J; Cullen, William; Stephenson, Andrew; Hunter, Christopher A; Ward, Michael D

2014-01-07

We have prepared a series of mononuclear fac and mer isomers of Ru(II) complexes containing chelating pyrazolyl-pyridine ligands, to examine their differing ability to act as hydrogen-bond donors in MeCN. This was prompted by our earlier observation that octanuclear cube-like coordination cages that contain these types of metal vertex can bind guests such as isoquinoline-N-oxide (K = 2100 M(-1) in MeCN), with a significant contribution to binding being a hydrogen-bonding interaction between the electron-rich atom of the guest and a hydrogen-bond donor site on the internal surface of the cage formed by a convergent set of CH2 protons close to a 2+ metal centre. Starting with [Ru(L(H))3](2+) [L(H) = 3-(2-pyridyl)-1H-pyrazole] the geometric isomers were separated by virtue of the fact that the fac isomer forms a Cu(I) adduct which the mer isomer does not. Alkylation of the pyrazolyl NH group with methyl iodide or benzyl bromide afforded [Ru(L(Me))3](2+) and [Ru(L(bz))3](2+) respectively, each as their fac and mer isomers; all were structurally characterised. In the fac isomers the convergent group of pendant -CH2R or -CH3 protons defines a hydrogen-bond donor pocket; in the mer isomer these protons do not converge and any hydrogen-bonding involving these protons is expected to be weaker. For both [Ru(L(Me))3](2+) and [Ru(L(bz))3](2+), NMR titrations with isoquinoline-N-oxide in MeCN revealed weak 1 : 1 binding (K ≈ 1 M(-1)) between the guest and the fac isomer of the complex that was absent with the mer isomer, confirming a difference in the hydrogen-bond donor capabilities of these complexes associated with their differing geometries. The weak binding compared to the cage however occurs because of competition from the anions, which are free to form ion-pairs with the mononuclear complex cations in a way that does not happen in the cage complexes. We conclude that (i) the presence of fac tris-chelate sites in the cage to act as hydrogen-bond donors, and (ii) exclusion of counter-ions from the central cavity leaving these hydrogen-bonding sites free to interact with guests, are both important design criteria for future coordination cage hosts.

Unique Pressure versus Temperature Phase Diagram for Antiferromagnets Eu2Ni3Ge5 and EuRhSi3

NASA Astrophysics Data System (ADS)

Nakashima, Miho; Amako, Yasushi; Matsubayashi, Kazuyuki; Uwatoko, Yoshiya; Nada, Masato; Sugiyama, Kiyohiro; Hagiwara, Masayuki; Haga, Yoshinori; Takeuchi, Tetsuya; Nakamura, Ai; Akamine, Hiromu; Tomori, Keisuke; Yara, Tomoyuki; Ashitomi, Yosuke; Hedo, Masato; Nakama, Takao; Ōnuki, Yoshichika

2017-03-01

We studied the magnetic properties of the antiferromagnets Eu2Ni3Ge5 and EuRhSi3 by measuring their electrical resistivity, specific heat, magnetic susceptibility, magnetization, and thermoelectric power, together with the electrical resistivities at high pressures of up to 15 GPa. These compounds have almost divalent Eu ions at ambient pressure and order antiferromagnetically with a successive change in the antiferromagnetic structure at TN = 19 K and T'N = 17 K in Eu2Ni3Ge5, and at TN = 49 K and T'N = 45 K in EuRhSi3. Magnetic field versus temperature (H-T) phase diagrams were constructed for both compounds from the magnetization measurements. The Néel temperature in Eu2Ni3Ge5 was found to increase up to 7 GPa but to decrease continuously with further increasing pressure, without the so-called valence transition. Under a high pressure of 15 GPa, Kondo-like behavior of the electrical resistivity was observed, suggesting the existence of the heavy-fermion state at low temperatures. A similar trend is likely to occur in EuRhSi3. The present P-T phase diagrams for both compounds are the first cases that are reminiscent of the phase diagram of EuCu2(SixGe1-x)2.

Elucidating photophysical attributes of alpha,alpha'-diimine ligands, rhodium(III) dicyano-bis (alpha,alpha'-diimine) and tris(alpha,alpha'-diimine) complexes via ab inition and density-functional calculations

NASA Astrophysics Data System (ADS)

Matz, Phillip Daniel

Based on crystal structure data, the recently developed density functional PBE1PBE predicts ground state equilibrium geometries in good agreement with experiments. Bond length and angle alpha,alpha'-diimine ligand Mean Absolute Deviation (MAD) values of 0.0077 A and 0.63° are obtained with the low-cost model chemistry PBE1PBE/6-21G. Theoretical trends, specifically the gs → 1pipi* absorption energies and 3pipi* → gs phosphorescence emission energies of the ligands also agree well with experiment. Computations on [Ru(II)(1,10-phenanthroline)3]2+ indicate that the Stuttgart ECP ECP28MWB is capable of reproducing adequately the geometries and photophysical characteristics of transition-metal complexes when paired with the DFT hybrid functional PBE1PBE and the Pople-style split-valence 6-21G basis set describing the ligands. Examination shows that the predicted photophysical properties of both [Rh(III)(s-NN)3](PF6) 3 and [Rh(III)(CN)2(s-NN)2](PF6) complexes agree with experimental evidence in many, but not all aspects. The experimentally observed spectroscopic trend for the gs → 1pipi* absorption energies is reproduced, namely the absorption bands of phenanthroline complexes containing progressively more methyl substituents are monotonically red-shifted relative to the parent phenanthroline in the following energy order: phen > 4-Mephen > 4,7-Me2phen > 3,4,7,8-Me4phen >> 5,6-Me 2phen. Also, the trend of the experimental 3pipi* → gs phosphorescence emission energies is reproduced by the calculations. Experimentally, the activation barriers for the onset of photochemistry in glycerol matrices are reported to be around 2500 cm-1 and 2000 cm-1 for the [Rh(III)(s-NN)3](PF 6)3 and [Rh(III)(CN)2(s-NN)2](PF 6) complexes, respectively. Calculations of the energy gap between the lowest 3pipi* states and the ligand-field states locate the ligand-field states ˜5000cm-1 above the 3pipi* manifolds in the [Rh(III)(s-NN)3](PF6) 3 complexes, far exceeding the experimentally observed values. Analogous calculations on [Rh(III)(CN)2(s-NN)2](PF6) complexes predict an energy gap closer to the experimentally observed activation barriers (˜2500 cm-1) and correctly reproduce the observed trend of increasing activation energy with increasing methyl-substitution, but the ligand field states are shown to possess substantial ligand-centered character.

Distribution and PGE mineralization in the formation of chromitite in ophiolite complexes (Ospina-Kitoi Kharanur and ultrabasic massifs of Eastern Sayan, Sousern Siberia)

NASA Astrophysics Data System (ADS)

Kiseleva, Olga; Zhmodik, Sergei

2015-04-01

New study of PGE in restitic ultrabasic (Kharanur and Ospin-Kitoi) massifs from North and South branches (Dobretsov et al., 1985) of the ophiolite complexes in south-eastern part of the Eastern Sayan show their presence in chromitites of both branches belonging to the different geodynamic settings. Modern concepts model includes several mechanisms of podiform chromitite origin reflected in the chemistry of Cr-spinels (Arai, Yurimoto, 1994; Ballhaus, 1998; Uysal et al., 2009 et al.): 1) partial melting of upper mantle rocks, 2) mixing of primitive melts with melts enriched in SiO2, 3) melt-rock interaction. We estimated the types of interaction of mafic melts with mantle peridotites, with the formation of chromite bodies. For ore chrome spinelides from northern branch (Al2O3) melt = 8 - 14 wt%, (TiO2) melt = 0 - 0,4 wt%, (Fe/Mg) melt = 0,5 - 2,4; Southern branch (Al2O3) melt = 10 - 13 wt%, (TiO2) melt = 0,1 wt%, (Fe/Mg) melt = 0,3 - 1 (Kiseleva, 2014). There are two types of PGE distribution Os-Ir-Ru (I) and Pt-Pd (II). Type I chromitites (mid-Al#Cr-spinels) revealed only Os-Ir-Ru distributions; type II (low-Al#Cr spinelides) show both Os-Ir-Ru and (Pt-Pd) distributions (Kiseleva et al., 2012, 2014). PGE distribution in ultramafic peridotites and chromitites reflects PGE fractionation during partial melting (Barnes et al., 1985; Rehkämper et al., 1997). Processes bringing to extreme fractionation of PGE, may be associated with fluid-saturated supra subduction environment where melting degree near 20% and above is sufficient for the release of PGE from the mantle source (Dick, Bullen, 1984; Naldrett, 2010). Enrichment in PPGE together with a high content of IPGE in same chromite bodies is attributed to the second step of melting, and formation of S-enriched and saturated in PGE melts (Hamlyn, Keays, 1986; Prichard et al., 1996). For type I chromitites platinum group minerals (PGM) are presented by Os-Ir-Ru system. In type II chromitites PGM are represented by Os-Ir-Ru-Rh-Pt system. Solid solutions Os-Ir-Ru and formed in the upper mantle RuS2 conditions together with chromite. The (Os-Ir-Ru)AsS minerals are forming on postmagmatic stage under the influence of S, As-containing fluids Under the influence of mantle reduced fluids the remobilization of PGE during desulfurization and deserpentinization early of "primary" PGM takes place. Changes of the redox environment from reducing to oxidizing condition is followed by creation of PGE together with As, Sb, Sn, and nickel arsenides, ferrichromie, chrommagnetite. The latter association reflects the redistribution of chromite and platinum group metals and formation of new mineral associations within the ultramafic substrate in crustal conditions (Kiseleva, 2014). Kiseleva O.N. Chromitite and PGE mineralization in ophiolites south-eastern part of the East Sayan (Ospina-Kitoi and Kharanur massifs), Thesis of PHD dissertation, Novosibirsk, 2014 IPGG SB RAS, 15p. Kiseleva O.N., Zhmodik SM, Damdinov BB, Agafonov LV, Belyanin D.K. 2014 The composition and evolution of platinum group mineralization in chromite ores Ilchir ophiolite complex (Ospin-Kitoi and Kharanur massifs, Eastern Sayan). Geology and Geophysics 55, 333 - 349.

Paragenesis of multiple platinum-group mineral populations in Shetland ophiolite chromitite: 3D X-ray tomography and in situ Os isotopes

NASA Astrophysics Data System (ADS)

Prichard, H. M.; Barnes, Stephen J.; Dale, C. W.; Godel, B.; Fisher, P. C.; Nowell, G. M.

2017-11-01

Chromitite from the Harold's Grave locality in the mantle section of the Shetland ophiolite complex is extremely enriched in Ru, Os and Ir, at μg/g concentrations. High-resolution X-ray computed tomography on micro-cores from these chromitites was used to determine the location, size, distribution and morphology of the platinum-group minerals (PGM). There are five generations of PGM in these chromitites. Small (average 5 μm in equivalent sphere diameter, ESD) euhedral laurites, often with Os-Ir alloys, are totally enclosed in the chromite and are likely to have formed first by direct crystallisation from the magma as the chromite crystallised. Also within the chromitite there are clusters of larger (50 μm ESD) aligned elongate crystals of Pt-, Rh-, Ir-, Os- and Ru-bearing PGM that have different orientations in different chromite crystals. These may have formed either by exsolution, or by preferential nucleation of PGMs in boundary layers around particular growing chromite grains. Thirdly there is a generation of large (100 μm ESD) composite Os-Ir-Ru-rich PGM that are all interstitial to the chromite grains and sometimes form in clusters. It is proposed that Os, Ir and Ru in this generation were concentrated in base metal sulfide droplets that were then re-dissolved into a later sulfide-undersaturated magma, leaving PGM interstitial to the chromite grains. Fourthly there is a group of almost spherical large (80 μm ESD) laurites, hosting minor Os-Ir-Ru-rich PGM that form on the edge or enclosed in chromite grains occurring in a sheet crosscutting a chromitite layer. These may be hosted in an annealed late syn- or post magmatic fracture. Finally a few of the PGM have been deformed in localised shear zones through the chromitites. The vast majority of the PGM - including small PGM enclosed within chromite, larger interstitial PGM and elongate aligned PGM - have Os isotope compositions that give Re-depletion model ages approximately equal to the age of the ophiolite at ∼492 Ma. A number of other PGM - not confined to a single textural group - fall to more or less radiogenic values, with four PGM giving anomalously unradiogenic Os corresponding to an older age of ∼1050 Ma. The 187Os/188Os isotopic ratios for PGM from Cliff and Quoys, from the same ophiolite section, are somewhat more radiogenic than those at Harold's Grave. This may be due to a distinct mantle source history or possibly the assimilation of radiogenic crustal Os.

Indented Cu2MoS4 nanosheets with enhanced electrocatalytic and photocatalytic activities realized through edge engineering.

PubMed

Chen, Bang-Bao; Ma, De-Kun; Ke, Qing-Ping; Chen, Wei; Huang, Shao-Ming

2016-03-07

Edges often play a role as active centers for catalytic reactions in some nanomaterials. Therefore it is highly desirable to enhance catalytic activity of a material through modulating the microstructure of the edges. However, the study associated with edge engineering is less investigated and still at its preliminary stage. Here we report that Cu2MoS4 nanosheets with indented edges can be fabricated through a simple chemical etching route at room temperature, using Cu2MoS4 nanosheets with flat ones as sacrifice templates. Taking the electrocatalytic hydrogen evolution reaction (HER), photocatalytic degradation of rhodamine B (RhB) and conversion of benzyl alcohol as examples, the catalytic activity of Cu2MoS4 indented nanosheets (INSs) obtained through edge engineering was comparatively studied with those of Cu2MoS4 flat nanosheets (FNSs) without any modification. The photocatalytic tests revealed that the catalytic active sites of Cu2MoS4 nanosheets were associated with their edges rather than basal planes. Cu2MoS4 INSs were endowed with larger electrochemically active surface area (ECSA), more active edges and better hydrophilicity through the edge engineering. As a result, the as-fabricated Cu2MoS4 INSs exhibited an excellent HER activity with a small Tafel slope of 77 mV dec(-1), which is among the best records for Cu2MoS4 catalysts. The present work demonstrated the validity of adjusting catalytic activity of the material through edge engineering and provided a new strategy for designing and developing highly efficient catalysts.

One-step synthesis of highly efficient nanocatalysts on the supports with hierarchical pores using porous ionic liquid-water gel.

PubMed

Kang, Xinchen; Zhang, Jianling; Shang, Wenting; Wu, Tianbin; Zhang, Peng; Han, Buxing; Wu, Zhonghua; Mo, Guang; Xing, Xueqing

2014-03-12

Stable porous ionic liquid-water gel induced by inorganic salts was created for the first time. The porous gel was used to develop a one-step method to synthesize supported metal nanocatalysts. Au/SiO2, Ru/SiO2, Pd/Cu(2-pymo)2 metal-organic framework (Cu-MOF), and Au/polyacrylamide (PAM) were synthesized, in which the supports had hierarchical meso- and macropores, the size of the metal nanocatalysts could be very small (<1 nm), and the size distribution was very narrow even when the metal loading amount was as high as 8 wt %. The catalysts were extremely active, selective, and stable for oxidative esterification of benzyl alcohol to methyl benzoate, benzene hydrogenation to cyclohexane, and oxidation of benzyl alcohol to benzaldehyde because they combined the advantages of the nanocatalysts of small size and hierarchical porosity of the supports. In addition, this method is very simple.

Nano-sized quaternary CuGa2In3S8 as an efficient photocatalyst for solar hydrogen production.

PubMed

Kandiel, Tarek A; Anjum, Dalaver H; Takanabe, Kazuhiro

2014-11-01

The synthesis of quaternary metal sulfide (QMS) nanocrystals is challenging because of the difficulty to control their stoichiometry and phase structure. Herein, quaternary CuGa2In3S8 photocatalysts with a primary particle size of ≈4 nm are synthesized using a facile hot-injection method by fine-tuning the sulfur source injection temperature and aging time. Characterization of the samples reveals that quaternary CuGa2In3S8 nanocrystals exhibit n-type semiconductor characteristics with a transition band gap of ≈1.8 eV. Their flatband potential is located at -0.56 V versus the standard hydrogen electrode at pH 6.0 and is shifted cathodically by 0.75 V in solutions with pH values greater than 12.0. Under optimized conditions, the 1.0 wt % Ru-loaded CuGa2In3S8 photocatalyst exhibits a photocatalytic H2 evolution response up to 700 nm and an apparent quantum efficiency of (6.9±0.5) % at 560 nm. These results indicate clearly that QMS nanocrystals have great potential as nano-photocatalysts for solar H2 production. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New SSMS Techniques for the Determination of Rhodium and Other Platinum- Group Elements in Carbonaceous Chondrites

NASA Astrophysics Data System (ADS)

Jochum, K. P.; Seufert, H. M.

1995-09-01

We have developed new spark source mass spectrometric (SSMS) techniques for simultaneous analysis of platinum-group elements (PGE) together with other trace elements in stony meteorites. We have measured elemental abundances of Rh, Ru, Os, Ir, Pt, Au in carbonaceous chondrites of different types including the two CI chondrites Orgueil and Ivuna. These data are relevant for the determination of solar-system abundances. Whereas the solar-system abundances of most PGE are well known, this is not the case for Rh, and no literature data exist for carbonaceous chondrites, mainly because of analytical difficulties. The SSMS techniques include new calibration procedures and the use of a recently developed multi-ion counting (MIC) system [1]. The mono-isotopic element Rh and the other PGE were determined by using internal standard elements (e.g., Nd, U) that were measured by isotope dilution in the same sample electrode material. The data were calibrated with certified standard solutions of PGE which were doped on trace-element poor rock samples. Ion abundances were measured using both the conventional photoplate detection and the ion-counting techniques. The new MIC technique that uses up to 20 small channeltrons for ion counting measurements has the advantage of improved precision, detection limits and analysis time compared to photoplate detection. Tab. 1 shows the Rh analyses for the meteorites Orgueil, Ivuna, Murchison, Allende and Karoonda obtained by conventional photoplate detection. These are the first Rh results for carbonaceous chondrites. The data for the two CI chondrites Orgueil and Ivuna are identical and agree within 4 % with the CI estimate of Anders and Grevesse [2] which was derived indirectly from analyses for H-chondrites. The PGE Os, Ir, Pt, Au and W, Re, Th, U concentrations were determined by both detection systems. Data obtained with the MIC system are more precise (about 4% for concentrations in the ppb range) compared to the photoplate detection system (about 10 - 15 %). Both data sets agree within error limits. Rhodium correlates well with Pt and other PGE indicating no significant fractionation between the different types of carbonaceous chondrites (Tab. 1). References: [1] Jochum K. P. et al. (1994) Fresenius J. Anal. Chem., 350, 642-644. [2] Anders E. and Grevesse N. (1989) GCA, 53, 197-214.

Theory of high-TC superconductivity: transition temperature

NASA Astrophysics Data System (ADS)

Harshman, Dale R.; Fiory, Anthony T.; Dow, John D.

2010-12-01

After reading over our published manuscript, we noticed that the discussion concerning the determination of σ for the ruthenate Ba2YRu0.9Cu0.1O6 in section 2.3.1 (3rd paragraph) is somewhat terse. Herein we provide an expanded analysis which better explains our estimate of γ (and thus σ) for this compound. All numbers, figures and conclusions remain unaltered. The ruthenate compounds A2YRu1-xCuxO6 (with A = Ba or Sr; x = 0.05-0.15) are double-perovskites containing no cuprate planes and with ν = μ = 1 [1] (reference [82] in the paper). The determination of γ follows from equation (2.5b), wherein rule 1b introduces the factor 1/2. In the lower limit, one expects a minimum of ~2 charges per Cu dopant, which are shared between two charge reservoirs of each layer type (AO and 1/2 (YRu1-xCuxO4)), producing a net factor of unity. Thus, for Ba2YRu0.9Cu0.1O6 (with TC0 ~ 30-40 K), we estimate γ = (1/2)(1) = 1/2, yielding σ = 0.05 as stated by equation (2.5c) in the paper. While one may expect an average effective charge state for Ru near +5, and that of Cu to be between +2 and +3 (post anneal) [2], the lower-limit estimation provided, which places the corresponding data point in figure 2 to the left of the line, appears sufficient to include the ruthenates with the other high-TC compounds found to follow equation (2.6) so far. Owing to the uncertainty in the experimental values for TC0, as well as the Ru and Cu valence states, however, this compound was excluded in the data analyses presented. Future research will attempt a more accurate determination of the charge per doped Cu, and thus σ. We would also like to point out a typographical correction in the definition of the corresponding ruthenate type II reservoir in the last column of table 1, which should read 1/2 (YRu0.9Cu0.1O4). An unrelated item is found in the fourth line of section 2.3.3, where Tb(O0.80F0.20)FeAs should read Tb(O0.80-yF0.20)FeAs. Additionally, reference [132] is now known and has the form: [132] Harshman D R and Fiory A T 2011 J. Phys.: Condens. Matter 23 315702 References [1] Parkinson N G, Hatton P D, Howard J A K, Ritter C, Chien F Z and Wu M-K 2003 J. Mater. Chem. 13 1468 [2] Rao S M, Wu M-K, Ren H C, Chen C L, Guo J-H, Hsu F C, Chen S Y, Chen Y Y, Chang C L and Liu H L 2011 in preparation

Efficient Synthesis of Differentiated syn-1,2-Diol Derivatives by Asymmetric Transfer Hydrogenation-Dynamic Kinetic Resolution of α-Alkoxy-Substituted β-Ketoesters.

PubMed

Monnereau, Laure; Cartigny, Damien; Scalone, Michelangelo; Ayad, Tahar; Ratovelomanana-Vidal, Virginie

2015-08-10

Asymmetric transfer hydrogenation was applied to a wide range of racemic aryl α-alkoxy-β-ketoesters in the presence of well-defined, commercially available, chiral catalyst Ru(II) -(N-p-toluenesulfonyl-1,2-diphenylethylenediamine) and a 5:2 mixture of formic acid and triethylamine as the hydrogen source. Under these conditions, dynamic kinetic resolution was efficiently promoted to provide the corresponding syn α-alkoxy-β-hydroxyesters derived from substituted aromatic and heteroaromatic aldehydes with a high level of diastereoselectivity (diastereomeric ratio (d.r.)>99:1) and an almost perfect enantioselectivity (enantiomeric excess (ee)>99 %). Additionally, after extensive screening of the reaction conditions, the use of Ru(II) - and Rh(III) -tethered precatalysts extended this process to more-challenging substrates that bore alkenyl-, alkynyl-, and alkyl substituents to provide the corresponding syn α-alkoxy-β-hydroxyesters with excellent enantiocontrol (up to 99 % ee) and good to perfect diastereocontrol (d.r.>99:1). Lastly, the synthetic utility of the present protocol was demonstrated by application to the asymmetric synthesis of chiral ester ethyl (2S)-2-ethoxy-3-(4-hydroxyphenyl)-propanoate, which is an important pharmacophore in a number of peroxisome proliferator-activated receptor α/γ dual agonist advanced drug candidates used for the treatment of type-II diabetes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stability of CIGS Solar Cells and Component Materials Evaluated by a Step-Stress Accelerated Degradation Test Method: Preprint

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

Pern, F. J.; Noufi, R.

A step-stress accelerated degradation testing (SSADT) method was employed for the first time to evaluate the stability of CuInGaSe2 (CIGS) solar cells and device component materials in four Al-framed test structures encapsulated with an edge sealant and three kinds of backsheet or moisture barrier film for moisture ingress control. The SSADT exposure used a 15oC and then a 15% relative humidity (RH) increment step, beginning from 40oC/40%RH (T/RH = 40/40) to 85oC/70%RH (85/70) as of the moment. The voluminous data acquired and processed as of total DH = 3956 h with 85/70 = 704 h produced the following results. Themore » best CIGS solar cells in sample Set-1 with a moisture-permeable TPT backsheet showed essentially identical I-V degradation trend regardless of the Al-doped ZnO (AZO) layer thickness ranging from standard 0.12 μm to 0.50 μm on the cells. No clear 'stepwise' feature in the I-V parameter degradation curves corresponding to the SSADT T/RH/time profile was observed. Irregularity in I-V performance degradation pattern was observed with some cells showing early degradation at low T/RH < 55/55 and some showing large Voc, FF, and efficiency degradation due to increased series Rs (ohm-cm2) at T/RH ≥ 70/70. Results of (electrochemical) impedance spectroscopy (ECIS) analysis indicate degradation of the CIGS solar cells corresponded to increased series resistance Rs (ohm) and degraded parallel (minority carrier diffusion/recombination) resistance Rp, capacitance C, overall time constant Rp*C, and 'capacitor quality' factor (CPE-P), which were related to the cells? p-n junction properties. Heating at 85/70 appeared to benefit the CIGS solar cells as indicated by the largely recovered CPE-P factor. Device component materials, Mo on soda lime glass (Mo/SLG), bilayer ZnO (BZO), AlNi grid contact, and CdS/CIGS/Mo/SLG in test structures with TPT showed notable to significant degradation at T/RH ≥ 70/70. At T/RH = 85/70, substantial blistering of BZO layers on CIGS cell pieces was observed that was not seen on BZO/glass, and a CdS/CIGS sample displayed a small darkening and then flaking feature. Additionally, standard AlNi grid contact was less stable than thin Ni grid contact at T/RH ≥ 70/70. The edge sealant and moisture-blocking films were effective to block moisture ingress, as evidenced by the good stability of most CIGS solar cells and device components at T/RH = 85/70 for 704 h, and by preservation of the initial blue color on the RH indicator strips. The SSADT experiment is ongoing to be completed at T/RH = 85/85.« less

Enhanced Kinetics of Electrochemical Hydrogen Uptake and Release by Palladium Powders Modified by Electrochemical Atomic Layer Deposition

DOE PAGES

Benson, David M.; Tsang, Chu F.; Sugar, Joshua Daniel; ...

2017-04-28

One method for the formation of nanofilms of materials, is Electrochemical atomic layer deposition (E-ALD), one atomic layer at a time. It uses the galvanic exchange of a less noble metal, deposited using underpotential deposition (UPD), to produce an atomic layer of a more noble element by reduction of its ions. This process is referred to as surface limited redox replacement and can be repeated in a cycle to grow thicker deposits. Previously, we performed it on nanoparticles and planar substrates. In the present report, E-ALD is applied for coating a submicron-sized powder substrate, making use of a new flowmore » cell design. E-ALD is used to coat a Pd powder substrate with different thicknesses of Rh by exchanging it for Cu UPD. Furthermore, cyclic voltammetry and X-ray photoelectron spectroscopy indicate an increasing Rh coverage with increasing numbers of deposition cycles performed, in a manner consistent with the atomic layer deposition (ALD) mechanism. Cyclic voltammetry also indicated increased kinetics of H sorption and desorption in and out of the Pd powder with Rh present, relative to unmodified Pd.« less

Evidence from bond lengths and bond angles for enneacovalence of cobalt, rhodium, iridium, iron, ruthenium, and osmium in compounds with elements of medium electronegativity

PubMed Central

Pauling, Linus

1984-01-01

Enneacovalence of neutral atoms can be achieved for Co, Rh, and Ir by promoting some electrons from the nd orbital to the (n + 1)s and (n + 1)p orbitals and for Fe, Ru, and Os by a similar promotion together with the addition of an electron, which may be provided by an electron pair from a singly bonded carbonyl group or other group. The bond lengths and bond angles are predicted by the theory of enneacovalence to be significantly different for the different transition metals. Recently reported experimental values are shown to be in good agreement with the predicted values, providing support for the theory of enneacovalence and the theory of hybrid sp3d5 bond orbitals. PMID:16593439

Observation of New Neutron-rich Isotopes among Fission Fragments from In-flight Fission of 345 MeV/nucleon 238U: Search for New Isotopes Conducted Concurrently with Decay Measurement Campaigns

NASA Astrophysics Data System (ADS)

Shimizu, Yohei; Kubo, Toshiyuki; Fukuda, Naoki; Inabe, Naohito; Kameda, Daisuke; Sato, Hiromi; Suzuki, Hiroshi; Takeda, Hiroyuki; Yoshida, Koichi; Lorusso, Giuseppe; Watanabe, Hiroshi; Simpson, Gary S.; Jungclaus, Andrea; Baba, Hidetada; Browne, Frank; Doornenbal, Pieter; Gey, Guillaunme; Isobe, Tadaaki; Li, Zhihuan; Nishimura, Shunji; Söderström, Pär-Anders; Sumikama, Toshiyuki; Taprogge, Jan; Vajta, Zsolt; Wu, Jin; Xu, Zhengyu; Odahara, Atsuko; Yagi, Ayumi; Nishibata, Hiroki; Lozeva, Radomira; Moon, Changbum; Jung, HyoSoon

2018-01-01

The search for new isotopes using the in-flight fission of a 238U beam has been conducted concurrently with decay measurements, during the so-called EURICA campaigns, at the RIKEN Nishina Center RI Beam Factory. Fission fragments were analyzed and identified in flight using the BigRIPS separator. We have identified the following 36 new neutron-rich isotopes: 104Rb, 113Zr, 116Nb, 118,119Mo, 121,122Tc, 125Ru, 127,128Rh, 129,130,131Pd, 132Ag, 134Cd, 136,137In, 139,140Sn, 141,142Sb, 144,145Te, 146,147I, 149,150Xe, 149,150,151Cs, 153,154Ba, and 154,155,156,157La.

Magnetic and electronic properties of the Cu-substituted Weyl semimetal candidate ZrCo₂Sn.

PubMed

Kushwaha, S K; Wang, Zhijun; Kong, Tai; Cava, Robert

2018-01-04

We report that the partial substitution of Cu for Co has a significant impact on the magnetic properties of the Heusler-phase Weyl fermion candidate ZrCo₂Sn. Polycrystalline samples of ZrCo_2-<i>x</i>Cu_<i>x</i>Sn (<i>x</i> = 0.0 to 1.0) exhibited a linearly decreasing ferromagnetic transition temperature and similarly decreasing saturated magnetic moment on increasing Cu substitution x. Materials with Cu contents near <i>x</i> = 1 and several other quaternary materials synthesized at the same <i>x</i> (ZrCo<i>T</i>'Sn (<i>T</i>' = Rh, Pd, Ni)) display what appears to be non-ferromagnetic magnetization behavior with spin glass characteristics. Electronic structure calculations suggest that the half-metallic nature of unsubstituted ZrCo₂Sn is disrupted significantly by the Cu substitutions, leading to the breakdown of the magnetization vs. electron count guidelines usually followed by Heusler phases, and a more typical metallic non-spin-polarized electronic structure at high <i>x</i>. © 2018 IOP Publishing Ltd.

Large-scale and green synthesis of octahedral flower-like cupric oxide nanocrystals with enhanced photochemical properties

NASA Astrophysics Data System (ADS)

Li, Shi-Kuo; Pan, Yu-Yi; Wu, Mi; Huang, Fang-Zhi; Li, Chuan-Hao; Shen, Yu-Hua

2014-10-01

In this work, a large-scale and green method is reported for the facile synthesis of octahedral flower-like CuO nanocrystals via a coordination-deposition route by using Fehling regents. Not any harmful organic chemicals were used during the reaction period. The obtained hierarchical nanostructure can be rationally tailored by varying the concentration of tartrate ions and reaction time. The typical flower-like CuO nanocrystals in the range of 200-250 nm are consisted of numerous small crystalline whiskers, which present a porous surface with a specific surface area of 32.12 m2/g and a narrow band gap of 1.5 eV. Importantly, the flower-like CuO nanocrystals show an enhanced photocatalytic activity toward decomposing Rhodamine B (RhB) molecules. The degradation rate is about 87.9% in 40 min under visible light irradiation, which is about 2.5 times for the commercial CuO powers (35.2%). Moreover, the uniform flower-like monolayered CuO film exhibits an excellent photoelectrochemical (PEC) performance with a maximum photocurrent density of 58.8 μA/cm2, which is nearly five times higher than the commercial CuO film. This novel synthesis approach provides a large-scale and green protocol for synthesizing hierarchical metal oxide nanocrystals that are useful for photocatalysis, PEC water splitting and photovoltaic device.

Cooperative magnetic behaviour in the new valence fluctuating compound Ce2Rh3Ge

NASA Astrophysics Data System (ADS)

Falkowski, M.; Strydom, A. M.

2015-10-01

In this study we report the physical properties of the new ternary compound Ce2Rh3Ge that crystallizes in the rhombohedral, triple hexagonal MgCu2-type of structure. The electronic ground state properties of Ce2Rh3Ge were characterized by magnetic susceptibility, specific heat, electrical resistivity and thermal transport measurements. The results indicate the presence of short range magnetic interaction, probably of ferromagnetic origin below T C  =  4 K. The shape of χ -1(T) deviates from the Curie-Weiss behavior with a broad minimum at about T\\min{{χ-1}}   =  450 K reminiscent of valence fluctuating cerium systems. At T  =  10 K, the magnetic part of the resistivity ρ 4 f (T) exhibits a shallow minimum followed by increase of resistivity ρ(T) \\propto   -lnT, which hints at a substantial Kondo screening effect. Ce2Rh3Ge belongs to a small group of strongly correlated cerium compounds in which the two competing effects of Kondo and RKKY interactions produce long-range magnetic order from strongly hybridized and intermediate-valent 4 f spins. At sufficiently low temperatures Ce2Rh3Ge scales well with the Kadowaki-Woods ratio A/γ 2 and the value of the Wilson ratio χ(T  →  0)/γ found for this compound classifies it as a mixed-valence compound. The presence of valence fluctuation and magnetic order it is rare for these attributes to be found simultaneously in same compound, in same temperature range. In our opinion a novelty of presented results of Ce2Rh3Ge is that this compound adds a new member to a small but growing class of systems bearing a strongly mixed- or intermediate-valent 4 f magnetic moment, but in which the lattice of spins nevertheless end up finding it possible to order magnetically.

pH-dependent release of trace elements including platinum group elements (PGEs) from gasoline and diesel catalysts

NASA Astrophysics Data System (ADS)

Sucha, Veronika; Mihaljevic, Martin; Ettler, Vojtech; Strnad, Ladislav

2014-05-01

The release of trace metals and platinum group elements (PGEs) from automobile exhaust catalysts represents a remarkable source of higly dispersed environmental contamination. Especially, PGEs have shown increasing research interest due to their possible bioaccessibility. In our research, we focused on leaching behaviour of trace metals from gasoline and diesel automobile catalysts. While catalysts for gasoline engines contain a mixture of Pt-Pd-Rh or Pd-Rh, catalysts for diesel engines are composed only of Pt. We used dust from two crushed gasoline and two crushed diesel catalysts (new and aged). The dust of gasoline catalysts contains significant concentrations of Pt (700 mg.kg-1), Pd (11 000 mg.kg-1) and Rh (700 mg.kg-1). And the dust of diesel catalysts are composed of Pt (3 900 mg.kg-1) and they contains negligible amounts of Pd dan Rh (< 0.5 mg.kg-1, < 0.1 mg.kg-1, respectively). To evaluate leaching of trace metals from dust we used pH-stat leaching test according to the European standard CEN/TS 14997. The concentrations of cations: PGEs (Pt, Pd a Rh), K, Na, Ca, Mg, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, La and Ce were determined by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS), and anions: F-, Cl-, SO42- and NO3- by high-performance liquid chromatography. Although the dusts from catalysts were relatively stable to acid/base influence, the leaching of trace metals from catalysts showed a dependence on pH. Generally, the highest concentrations were released under acidic conditions. The leaching of PGEs was higher for Pt in diesel catalysts and for Pd and Rh in gasoline catalysts. The highest concentrations of Zn and Pb were observed in old catalysts. The rare earth metals were released more from gasoline catalysts. Catalysts particles represent health risk especially with respect to their PGEs contents.

Kinetics of heterogeneous reactions of HO2 radical at ambient concentration levels with (NH4)2SO4 and NaCl aerosol particles.

PubMed

Taketani, Fumikazu; Kanaya, Yugo; Akimoto, Hajime

2008-03-20

The HO2 uptake coefficient (gamma) for inorganic submicrometer wet and dry aerosol particles ((NH4)2SO4 and NaCl) under ambient conditions (760 Torr and 296 +/- 2 K) was measured using an aerosol flow tube (AFT) coupled with a chemical conversion/laser-induced fluorescence (CC/LIF) technique. The CC/LIF technique enabled experiments to be performed at almost the same HO2 radical concentration as that in the atmosphere. HO2 radicals were injected into the AFT through a vertically movable Pyrex tube. Injector position-dependent profiles of LIF intensity were measured as a function of aerosol concentration. Measured gamma values for dry aerosols of (NH4)2SO4 were 0.04 +/- 0.02 and 0.05 +/- 0.02 at 20% and 45% relative humidity (RH), respectively, while those of NaCl were <0.01 and 0.02 +/- 0.01 at 20% and 53% RH, respectively. For wet (NH4)2SO4 aerosols, measured gamma values were 0.11 +/- 0.03, 0.15 +/- 0.03, 0.17 +/- 0.04, and 0.19 +/- 0.04, at 45%, 55%, 65%, and 75% RH, respectively, whereas for wet NaCl aerosols the values were 0.11 +/- 0.03, 0.09 +/- 0.02, and 0.10 +/- 0.02 for 53%, 63%, and 75% RH, respectively. Wet (NH4)2SO4 and NaCl aerosols doped with CuSO4 showed gamma values of 0.53 +/- 0.12 and 0.65 +/- 0.17, respectively. These results suggest that compositions, RH, and phase for aerosol particles are significant to HO2 uptake. Potential HO2 loss processes and their atmospheric contributions are discussed.

Copper stress-induced changes in leaf soluble proteome of Cu-sensitive and tolerant Agrostis capillaris L. populations.

PubMed

Hego, Elena; Vilain, Sébastien; Barré, Aurélien; Claverol, Stéphane; Dupuy, Jean-William; Lalanne, Céline; Bonneu, Marc; Plomion, Christophe; Mench, Michel

2016-05-01

Changes in leaf soluble proteome were explored in 3-month-old plants of metallicolous (M) and nonmetallicolous (NM) Agrostis capillaris L. populations exposed to increasing Cu concentrations (1-50 μM) to investigate molecular mechanisms underlying plant responses to Cu excess and tolerance of M plants. Plants were cultivated on perlite (CuSO4 spiked-nutrient solution). Soluble proteins, extracted by the trichloroacetic acid/acetone procedure, were separated with 2-DE (linear 4-7 pH gradient). Analysis of CCB-stained gels (PDQuest) reproducibly detected 214 spots, and 64 proteins differentially expressed were identified using LC-MS/MS. In both populations, Cu excess impacted both light-dependent (OEE, cytochrome b6-f complex, and chlorophyll a-b binding protein), and -independent (RuBisCO) photosynthesis reactions, more intensively in NM leaves (ferredoxin-NADP reductase and metalloprotease FTSH2). In both populations, upregulation of isocitrate dehydrogenase and cysteine/methionine synthases respectively suggested increased isocitrate oxidation and enhanced need for S-containing amino-acids, likely for chelation and detoxification. In NM leaves, an increasing need for energetic compounds was indicated by the stimulation of ATPases, glycolysis, pentose phosphate pathway, and Calvin cycle enzymes; impacts on protein metabolism and oxidative stress increase were respectively suggested by the rise of chaperones and redox enzymes. Overexpression of a HSP70 may be pivotal for M Cu tolerance by protecting protein metabolism. All MS data have been deposited in the ProteomeXchange with the dataset identifier PXD001930 (http//proteomecentral.proteomexchange.org/dataset/PXD001930). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bimetallic Cobalt-Based Phosphide Zeolitic Imidazolate Framework: CoP x Phase-Dependent Electrical Conductivity and Hydrogen Atom Adsorption Energy for Efficient Overall Water Splitting

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

Song, Junhua; Zhu, Chengzhou; Xu, Bo Z.

Cobalt-based bimetallic phosphide encapsulated in carbonized zeolitic imadazolate frameworks has been successfully synthesized and showed excellent activities toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Density functional theory calculation and electrochemical measurements reveal that the electrical conductivity and electrochemical activity are closely associated with the Co2P/CoP mixed phase behaviors upon Cu metal doping. This relationship is found to be the decisive factor for enhanced electrocatalytic performance. Moreover, the precise control of Cu content in Co-host lattice effectively alters the Gibbs free energy for H* adsorption, which is favorable for facilitating reaction kinetics. Impressively, an optimized performance hasmore » been achieved with mild Cu doping in Cu0.3Co2.7P/nitrogen-doped carbon (NC) which exhibits an ultralow overpotential of 0.19 V at 10 mA cm–2 and satisfying stability for OER. Cu0.3Co2.7P/NC also shows excellent HER activity, affording a current density of 10 mA cm–2 at a low overpotential of 0.22 V. In addition, a homemade electrolyzer with Cu0.3Co2.7P/NC paired electrodes shows 60% larger current density than Pt/ RuO2 couple at 1.74 V, along with negligible catalytic deactivation after 50 h operation. The manipulation of electronic structure by controlled incorporation of second metal sheds light on understanding and synthesizing bimetallic transition metal phosphides for electrolysis-based energy conversion.« less

About some processes of replacement of PGM from the placers of Southern Siberia

NASA Astrophysics Data System (ADS)

Shvedov, G. I.; Knyazev, V. N.; Nekos, V. V.

2003-04-01

Authors observed a series of replacement (conversions) in PGM from gold-bearing placers of southern part of Krasnoyarsk region. These facts have mineralogical and genetic interest. In researched placers primary PGM are presented by solid solutions Os-Ir-Ru with different ratios of main elements from osmium to iridium (by classification of D. Harris and L. Cabri /5 /. At smaller amounts Pt-Fe and sperrylite are presented, and other PGM were found in single cases. In minerals of Os-Ir-Ru system the main typical replacement is the forming of edgings of phase (Os,Ir,Ru)S_2 upon the edges of native Os, Ir, Ru or rutheniridosmine. Usually, the process of transformation takes place in grains in a direction of the best permeability, i.e. along deformational gaps or along planes of cleavage, because the phases of this system are chemically stable. The structures of replacements are diversified: fulfillment of gaps, formation of edgings around the grains, selective replacement, forming of metacrystalls or metagrains. The thickness of forming edgings is not stable; boundaries have corrosion textures with penetration inside of replaced grain. The chemical composition of cations of forming disulfides depends upon the composition of primary mineral first of all, but it cannot be subject to this rule. For example, grains from placer of Bolshoy Khailyk river (Western Sayan) have a composition adequate to ruthenium (tab., No. 1) and are replaced by laurite more often (tab., No. 1-1). In Kuznetsky Alatau (placer of Talanovaya river) authors observed simultaneous replacement of osmium (with admixtures of Ru and Ir) (tab., No. 2) by laurite (tab., No. 2-1) and irarsite (tab., No. 2-2) along gaps. This fact is explained by more affinity of ruthenium to sulfur, then iridium and osmium to sulfur /2/. In conditions of low fugitivity of sulfur the edgings with more rare composition (Ir,Os,Ru)_3S_2 (tab., No. 3-1) are formed. It was observed by the authors on iridium (tab., No. 3) from placer of Sysim river (Eastern Sayan). The similar composition of phase was described by S.A.Toma and S.Murphy /6/. In placer of Talanovaya river (Kuznetsky Alatau) the edging of idealized composition Os_2S (tab., No. 4-1) are develops on the grain of Os-Ir-ruthenium (tab., No.4). It indicates deficit of sulfur in a solution. In case of increased concentration of arsenic the minerals of Os-Ir-Ru system (tab., No. 5) are replaced by diarsenides (anduoite - omeiite series) (tab., No. 5-1) or sulfoarsenides of these elements as it was observed in PGM from placer of Rudnaya river (Western Sayan). In the extremely rare cases at superposition of sulfurless and arsenicless solutions the replacement of alloys Os-Ir-Ru by exotic phases can happen. For example, authors find the grain of native iridium, which was heavily deformed and impregnated on microgaps by phases of generalized composition from Pt(Ni,Cu,Fe)_2 to Ir(Ni,Fe,Cu)_3 in placer of Bolshoy Khaylik river /7/. The forming of similar phases can be initiated by very specific conditions: the extremely reducing conditions, very low fugitivity of sulfur and oxygen, absence of other anion-forming elements, high activity of a nickel, iron and cooper. The similar phases were found in streak-schlieren chromitic ores in one massif of alpine-type ultramafic rocks of Koryak Highland /3/. Also rather rare replacement of platinum with the high contents of ruthenium and iridium (platruthenosmiridium by old nomenclature) (tab., No.6) by Pt-Fe alloys (tab., No.6-1). It was observed by authors in PGM from placer of Talanovaya river (Kuznetsky Alatau). In the system Pt-Fe most widespread placer-forming minerals are ferriferous platinum, tetraferroplatinum and isoferroplatinum. In placers that were investigated by the authors the Pt-Fe alloys most frequently is replaced by cuperite, which forms the various thickness edgings. It usual phenomenon in some cases becomes complicated by forming of narrow (first microns) intermittent band of high-standard gold on the boundary of cuperite and Pt-Fe alloy. Same edgings of gold round the grains of alloys with consequent overlap by a more broad band of cuperite were observed by S.A. Shcheka with the co-authors in PGM from placers of Far East /4/. According to these authors the forming of edgings of gold is connected to effect of gold-bearing solutions with low fugitivity of S and As on the Pt-Fe alloy. Hereinafter under the opinion of the quoted authors the concentrations of S and As have increased and cuperite or arsenides (sulfoarsenides) of platinum were formed. On ours opinion the forming of edgings of gold between PtS and Pt-Fe alloy may occur by two ways. At the first, the allocation of the bands of high-standard gold on the boundary Pt-Fe alloy and PtS was simultaneously with replacement. It is connected that the gold and silver was included in the crystalline of Pt-Fe alloys primary and at the time of replacement of this mineral these elements reduced to native phase because the entry to the lattice of cuperite is impossible. Such process can be presented as the following equation: (Pt,Pd,Au,Ag)_3Fe + 2S_2 =3(Pt,Pd)S + 3(Au,Ag)^0 + FeS There aren't crystallochemical prohibitions for such process. At the second, the gold from later solutions may penetrate deep into the grain through porous edging of cuperite and locate at the boundary of PtS and Pt-Fe alloy. Probability of these processes must be test by experiments. The cuperite edgings on Pt-Fe alloys are acquired by the band or metacrystalls of sperrilite later. It is connected to occurrence of arsenic in the system. A feature of the composition of these sperrylites is increased contents of those elements, which originally were included in the lattice of Pt-Fe alloys (Rh, Ir, Os). The complex replacements of Pt-Fe alloys were observed by the authors in placer Sysim river. Pt-Fe alloys from this placer are presented by small-sized isomeric grains and contain increased contents of rhodium (tab., No.7). This feature was reflected in phases of replacement. In one case the edgings of Rh-sperrylite thickness 15-30 microns rounds the grain of Pt-Fe alloy and between these minerals the thin intermittent band of mineral with adequate RhAs (cherepanovite?) composition is situated (tab., No.7-1). This association is complicated by formation of small-sized selections hollingworthite (tab., No.7-2). In the near-drift placers sperrylite occurs frequently. This mineral is brittle and havn't transported on distant distances, but it is chemically very stable phase. Nevertheless, it mineral is replaced by native platinum on the edgings frequently, that was observed by authors in placers of the rivers Coloromo, Danilovsky (Yenisei Ridge), Caragan (East Sayan) etc. This process can be finished by formation of the native platinum. According to T.L. Evstigneeva with co-authors /1/ the de-arsenization of sperrylite can happen only at rather high temperatures more 400^oC;. Therefore it cannot be attributed to process of low-temperature replacement in solid condition, and it is necessary to connect with temperature burning of sperrylite. The native platinum which was formed in it process differs from primary magmatic in high cleanness of composition and absence of any admixtures, except for As (tab., No.8, 8-1). References: 1.T.L.Evstigneeva, A.A.Kim, I.Ay.Nekrasov (1990) //About de-arsenization of sperrylite in nature. Mineralogical Zhurnal, vol.12, No3, pp.90-96 (in Russian). 2. A.A.Marakushev, N.I.Bezmen Thermodynamics of sulfides and oxides in connection with problems of ore-forming. - M., Nauka, 1972. - 230p (in Russian). 3. A.G.Mochalov, G.G.Dmitrenko, I.V.Zhernovskii, N.S.Rudashevskii (1985) New iridium-osmium-ruthenium type (solid solutions of rare platinum-group elements with iron) of platinum-group mineralization in chromium spinel-group minerals of alpine-type ultramafic rocks of Koryak Highland. - Zapiski Vses. Mineral. Obshch., 114, pp.544-554 (in Russian). 4. S.A.Shcheka, A.A.Vrzhosek, V.I. Sapin, N.I.Kiryukhina (1991) Trasformations of platinum-group minerals from Primor'ye placers. - Mineralogical Zhurnal, vol.13, No1, pp.31-40 (in Russian). 5. D.C.Harris, L.J.Cabri (1991) Nomenclature of platinum-group-element alloys: review and revision. - Canadian Mineralogist, vol.29, pp.231-237. 6. L.J.Cabri (ed.) (1978) Unnamed platinum-group minerals. In: Platinum-group elements: mineralogy, geology, recovery. - Canadian Institute of Mining and Metallurgy, Montreal, pp.177-195. 7. G.I.Shvedov, V.N.Knyazev Unnamed PGE Phases from Gold Placer Deposits of South Siberia, Russia. - 9th International Platinum Symposium, July 21-25, Billings, Montana, USA, 2002 (http://www.duke.edu/˜boudreau/IPS_Abstracts.htm).

Biomonitoring of 30 trace elements in urine of children and adults by ICP-MS.

PubMed

Heitland, Peter; Köster, Helmut D

2006-03-01

The paper provides physicians and clinical chemists with statistical data (concentration ranges, geometric mean values, selected percentiles, etc.) about 30 urinary trace elements in order to determine whether people have trace element deficiencies or have been exposed to higher elemental concentrations. Morning urine samples of 72 children and 87 adults from two geographical areas of Germany were collected and the elements Li, Be, V, Cr, Mn, Ni, Co, Cu, Zn, Ga, As, Se, Rb, Sr, Mo, Rh, Pd, Ag, Cd, In, Sn, Sb, Cs, Ba, Pt, Au, Pb, Tl, Bi and U were determined by inductively coupled plasma mass spectrometry (ICP-MS) with a new octopole based collision/reaction cell. The urine samples were analysed directly after a simple 1/5 (V/V) dilution with deionised water and nitric acid. Information on exposure conditions of all human subjects were collected by questionnaire-based interviews. The described concentration data down to the ng/l range are very useful for the formulation of reference values. For some elements either new data are described (e.g., for V, Ga, In, Bi, Rh, Mn) or differences to earlier studies were found (e.g., for Be, As). For other elements (e.g., Sb, Se, Mo, Ba, Cu, Zn, Li) our results are in good correlation with previous studies and also complemented with urinary trace element concentrations for children.

Thermodynamical and thermoelectric properties of boron doped YPd{sub 3} and YRh{sub 3}

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

Dwivedi, Shalini; Sharma, Yamini, E-mail: sharma.yamini62@gmail.com; Sharma, Ramesh

2016-05-23

The structural, electronic, thermal, and optical properties of borides of cubic non-magnetic YX{sub 3} (X=Rh, Pd) compounds and their borides which crystallize in the AuCu{sub 3} structure have been studied using the density functional theory (DFT). The flat bands in the vicinity of E{sub F} which are associated with superconductivity appear in YPd{sub 3} and YRh{sub 3} band structures. However, the B s-states enhance the flat band only in YRh{sub 3}B. The optical properties clearly show that boron insertion modifies the absorption and transmittance. The YX{sub 3} alloys and their borides exhibit valuable changes in the thermopower and ZT. Itmore » is observed that the properties of the Y-X intermetallics change significantly for the Y-Rh and Y-Pd alloys and the presence of single boron atom modifies the properties to a great extent.« less

Traffic and catalytic converter - related atmospheric contamination in the metropolitan region of the city of Rio de Janeiro, Brazil.

PubMed

da Silva, Lílian Irene Dias; de Souza Sarkis, Jorge Eduardo; Zotin, Fátima Maria Zanon; Carneiro, Manuel Castro; Neto, Arnaldo Alcover; da Silva, Alzira dos Santos Amaral Gomes; Cardoso, Mauri José Baldini; Monteiro, Maria Inês Couto

2008-03-01

In this work, 24-h PM10 samples were collected in Rio de Janeiro, Brazil, and analysed for trace elements (Cd, Ce, Cu, La, Mo, Ni, Pb, Pd, Rh, Sb and Sn). The sampling was carried out at five locations (Bonsucesso; Centro, downtown city; Copacabana; Nova Iguaçu and Sumaré) with different traffic densities and anthropogenic activities. An analytical method based on the EPA method for the determination of trace elements in airborne particulate matter (PM), using ultrasonic-assisted extraction and inductively coupled plasma mass spectrometry (ICP-MS) was applied. Our results suggest that vehicular traffic is the most important source of environmental pollution at the studied sites. The presence of Mo, Pd and Rh in the analysed filters reflects an additional source of pollution caused by the erosion and deterioration of automotive catalytic converters.

Correlation effects in nanoparticle composites: Percolation, packing and tunneling

NASA Astrophysics Data System (ADS)

Mukherjee, Rupam

Percolation is one of the most fundamental and far-reaching physical phenomena, with major implications in a vast variety of fields. The work described in this thesis aims to understand the role of percolation effects in various, seemingly unrelated phenomena, such as the dielectric permittivity of metal-insulator composites, tunneling percolation, and the relationship between percolation and filling factors. Specifically, we investigated 1) the very large enhancement of the dielectric permittivity of a composite metal -- insulator system, RuO2 - CaCu3Ti4O12 (CCTO) near the percolation threshold. For RuO2/CCTO composites, an increase in the real part of the dielectric permittivity (initially about 10 3-104 at 10 kHz) by approximately an order of magnitude is observed in the vicinity of the percolation threshold. 2) In the same system, apart from a classical percolation transition associated with the appearance of a continuous conductance path through RuO2 nanoparticles, at least two additional tunneling percolation transitions are detected. Such behavior is consistent with the recently emerged picture of a quantum conductivity staircase, which predicts several percolation tunneling thresholds in a system with a hierarchy of local tunneling conductance, due to various degrees of proximity of adjacent conducting particles distributed in an insulating matrix. 3) The filling factors of the composites of nanoparticles with different shapes have been studied as a function of volume fraction. Interestingly, like percolation, filling factors also obey critical power law behavior as a function of size ratio of constituent particles.

Hall effect in high- Tc Y 1Ba 2Cu 3O 7-δ superconductor

NASA Astrophysics Data System (ADS)

Vezzoli, G. C.; Burke, T.; Moon, B. M.; Lalevic, B.; Safari, A.; Sundar, H. G. K.; Bonometti, R.; Alexander, C.; Rau, C.; Waters, K.

1989-04-01

We have performed point-by-point and continuous Hall effect experiments as a function of temperature in polycrystalline Y 1Ba 2Cu 3O 7-δ. We have shown that the positive Hall constant shows an abrupt increase upon decreasing temperature at a value just above Tc. This temperature corresponds to where the resistance versus temperature data deviates from linearity. At very high fields of 6.8 and 15 T we observe a subsequent decrease in RH. We interpret these data as supportive of a contribution toward the superconductivity mechanism arising from internal excitions or change transfer excitations such that the bound exciton concentration increases near Tc at the expense of positive carries which are reflected in both bound and free holes.

Nanocomposites Derived From a Low-Color Aromatic Polyimide (CP2) and Amine-Functionalized Vapor-Grown Carbon Nanofibers: In Situ Polymerization and Characterization (Preprint)

DTIC Science & Technology

2007-01-01

small metal catalyst (e.g., ferrocene, Fe (CO)5, etc.). They have an outer diameter of 60-200 nm, a hollow core of 30-90 nm, and length on the order...diffractions (WAXS) of compression-molded samples were recorded with a Rigaku RU-200 diffractometer using Ni-filtered Cu KR radiation (40 kV, 100 mA, λ...attributable to the sp3 C-H and sp2 C-H defects as methane is used as the major component in the feedstock for its production . Based on hydrogen

Heavy Fermions

NASA Astrophysics Data System (ADS)

Sugiyama, K.; Ónuki, Y.

Recent experimental results of high-field magnetization and de Haas-van Alphen experiments in f-electron systems are presented. The magnetic moment and the electronic state are simultaneously discussed because both properties are connected with each other. The first example is a drastic change of the Fermi surface in the antiferromagnet NdIn3. The second is the metamagnetic transition based on the quadrupolar interaction in PrCu2. The third is the metamagnetic transition in a typical heavy fermion compound CeRu2Si2, together with the heavy fermion uranium compounds such as UPd2Al3, URu2Si2 and UPt3.

Enhanced photocatalytic activity of ternary CuInS2 nanocrystals synthesized from the combination of a binary Cu(I)S precursor and InCl3

NASA Astrophysics Data System (ADS)

Mondal, Gopinath; Santra, Ananyakumari; Jana, Sumanta; Pramanik, Nimai Chand; Mondal, Anup; Bera, Pulakesh

2018-04-01

Ternary copper indium sulfide (CIS) nanocrystals (NCs) have been synthesized by mixing of binary precursor [CuI(bdpa)2][CuICl2] ( 1) and/or [CuI(mdpa)2][CuICl2] ( 2) (where, mdpa and bdpa represent methyl and benzyl ester of 3,5-dimethyl pyrazole-1-dithioic acid, respectively) with InCl3 in a low-temperature solvothermal process. The +1 oxidation state of copper and the atomic ratio Cu to S (1:2) is atomically maintained in the pyrazole-based Cu(I)-S precursor to synthesize phase pure CuInS2. Coordinating solvents like ethylene diamine (EN) and ethylene glycol (EG) have been used in the synthesis without any surfactants. No use of external surfactants in the synthesis of CIS nanoparticles reveals that precursor acts as stabilizing agent. The synthesized nanocrystals were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray spectroscopy (EDX) studies. The optical property of the nanocrystals shows a pronounced quantum confinement effect in the particles with band gap energy ca. 1.5 eV. The formation mechanism of ternary CIS has been proposed. The pore size distributions of the particles show the average pore diameters 13.1 nm from 1 and 5.3 nm from 2. The calculated values of the specific surface area are 8.123 and 9.577 m2/g for 1 and 2, respectively. The excellent photocatalytic degradation of rose bengal (RB) and rhodamine B (RhB) was demonstrated by the porous CIS nanocrystals. [Figure not available: see fulltext.

Efficient photocatalytic degradation of rhodamine-B by Fe doped CuS diluted magnetic semiconductor nanoparticles under the simulated sunlight irradiation

NASA Astrophysics Data System (ADS)

Sreelekha, N.; Subramanyam, K.; Amaranatha Reddy, D.; Murali, G.; Rahul Varma, K.; Vijayalakshmi, R. P.

2016-12-01

The present work is planned for a simple, inexpensive and efficient approach for the synthesis of Cu1-xFexS (x = 0.00, 0.01, 0.03, 0.05 and 0.07) nanoparticles via simplistic chemical co-precipitation route by using ethylene diamine tetra acetic acid (EDTA) as a capping molecules. As synthesized nanoparticles were used as competent catalysts for degradation of rhodamine-B organic dye pollutant. The properties of prepared samples were analyzed with energy dispersive analysis of X-rays (EDAX), X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible optical absorption spectroscopy, Fourier transform infrared (FTIR) spectra, Raman spectra and vibrating sample magnetometer (VSM). EDAX spectra corroborated the existence of Fe in prepared nanoparticles within close proximity to stoichiometric ratio. XRD, FTIR and Raman patterns affirmed that configuration of single phase hexagonal crystal structure as that of (P63/mmc) CuS, without impurity crystals. The average particle size estimated by TEM scrutiny is in the assortment of 5-10 nm. UV-visible optical absorption measurements showed that band gap narrowing with increasing the Fe doping concentration. VSM measurements revealed that 3% Fe doped CuS nanoparticles exhibited strong ferromagnetism at room temperature and changeover of magnetic signs from ferromagnetic to the paramagnetic nature with increasing the Fe doping concentration in CuS host lattice. Among all Fe doped CuS nanoparticles, 3% Fe inclusion CuS sample shows better photocatalytic performance in decomposition of RhB compared with the pristine CuS. Thus as synthesized Cu0·97Fe0·03S nanocatalysts are tremendously realistic compounds for photocatalytic fictionalization in the direction of organic dye degradation under visible light.

Electrochemically assisted fabrication of size-exclusion films of organically modified silica and application to the voltammetry of phospholipids.

PubMed

Mehdi, B Layla; Rutkowska, Iwona A; Kulesza, Pawel J; Cox, James A

2013-06-01

Modification of electrodes with nm-scale organically modified silica films with pores diameters controlled at 10- and 50-nm is described. An oxidation catalyst, mixed-valence ruthenium oxide with cyano crosslinks or gold nanoparticles protected by dirhodium-substituted phosophomolybdate (AuNP-Rh 2 PMo 11 ), was immobilized in the pores. These systems comprise size-exclusion films at which the biological compounds, phosphatidylcholine and cardiolipin, were electrocatalytically oxidized without interference from surface-active concomitants such as bovine serum albumin. 10-nm pores were obtained by adding generation-4 poly(amidoamine) dendrimer, G4-PAMAM, to a (CH 3 ) 3 SiOCH 3 sol. 50-nm pores were obtained by modifying a glassy carbon electrode (GC) with a sub-monolayer film of aminopropyltriethoxylsilane, attaching 50-nm diameter poly(styrene sulfonate), PSS, spheres to the protonated amine, transferring this electrode to a (CH 3 ) 3 SiOCH 3 sol, and electrochemically generating hydronium at uncoated GC sites, which catalyzed ormosil growth around the PSS. Voltammetry of Fe(CN) 6 3- and Ru(NH 3 ) 6 3+ demonstrated the absence of residual charge after removal of the templating agents. With the 50-nm system, the pore structure was sufficiently defined to use layer-by-layer electrostatic assembly of AuNP-Rh 2 PMo 11 therein. Flow injection amperometry of phosphatidylcholine and cardiolipin demonstrated analytical utility of these electrodes.

Translocation of iron from lysosomes to mitochondria during acetaminophen-induced hepatocellular injury: Protection by starch-desferal and minocycline.

PubMed

Hu, Jiangting; Kholmukhamedov, Andaleb; Lindsey, Christopher C; Beeson, Craig C; Jaeschke, Hartmut; Lemasters, John J

2016-08-01

Acetaminophen (APAP) overdose causes hepatotoxicity involving mitochondrial dysfunction and the mitochondrial permeability transition (MPT). Iron is a critical catalyst for ROS formation, and reactive oxygen species (ROS) play an important role in APAP-induced hepatotoxicity. Previous studies show that APAP disrupts lysosomes, which release ferrous iron (Fe(2+)) into the cytosol to trigger the MPT and cell killing. Here, our aim was to investigate whether iron released from lysosomes after APAP is then taken up into mitochondria via the mitochondrial electrogenic Ca(2+), Fe(2+) uniporter (MCFU) to cause mitochondrial dysfunction and cell death. Hepatocytes were isolated from fasted male C57BL/6 mice. Necrotic cell killing was assessed by propidium iodide fluorimetry. Mitochondrial membrane potential (ΔΨ) was visualized by confocal microscopy of rhodamine 123 (Rh123) and tetramethylrhodamine methylester (TMRM). Chelatable Fe(2+) was monitored by quenching of calcein (cytosol) and mitoferrofluor (MFF, mitochondria). ROS generation was monitored by confocal microscopy of MitoSox Red and plate reader fluorimetry of chloromethyldihydrodichlorofluorescein diacetate (cmH2DCF-DA). Administered 1h before APAP (10mM), the lysosomally targeted iron chelator, starch-desferal (1mM), and the MCFU inhibitors, Ru360 (100nM) and minocycline (4µM), decreased cell killing from 83% to 41%, 57% and 53%, respectively, after 10h. Progressive quenching of calcein and MFF began after ~4h, signifying increased cytosolic and mitochondrial chelatable Fe(2+). Mitochondria then depolarized after ~10h. Dipyridyl, a membrane-permeable iron chelator, dequenched calcein and MFF fluorescence after APAP. Starch-desferal, but not Ru360 and minocycline, suppressed cytosolic calcein quenching, whereas starch-desferal, Ru360 and minocycline all suppressed mitochondrial MFF quenching and mitochondrial depolarization. Starch-desferal, Ru360 and minocycline also each decreased ROS formation. Moreover, minocycline 1h after APAP decreased cell killing by half. In conclusion, release of Fe(2+) from lysosomes followed by uptake into mitochondria via MCFU occurs during APAP hepatotoxicity. Mitochondrial iron then catalyzes toxic hydroxyl radical formation, which triggers the MPT and cell killing. The efficacy of minocycline post-treatment shows minocycline as a possible therapeutic agent against APAP hepatotoxicity. Copyright © 2016 Elsevier Inc. All rights reserved.

Fabrication and characterization of SnO2/ZnO gas sensors for detecting toluene gas.

PubMed

Min, Byung-Sam; Park, Young-Ho; Lee, Chang-Seop

2014-11-01

This study investigates the use of SnO2, ZnO, Ag, Au, Cu, In, Pd, Ru and carbon black to improve the sensitivity of a gas sensor for detecting toluene gas. Metal-SnO2/ZnO thick films were screen-printed onto Al2O3 substrates with platinum electrodes. The physico-chemical properties of the sensor materials were characterized using SEM/EDS, XRD, and BET analyses. Measuring the electrical resistance of each sensor as a function of the gas concentration determined the sensing characteristics. The sensors were tested using toluene, benzene, xylene, ethanol, methanol, ammonia and trimethylamine vapors with concentrations of 1-2000 ppm. The gas sensing properties of metal-SnO2/ZnO thick films depended on the content and variety of metals and the content of carbon black. The optimum condition of sensor material for toluene gas detection is operation temperature 300 degrees C and when metal catalyst Cu and carbon black were added. The best sensitivity and selectivity for toluene gas at 300 degrees C resulted from doping with 5 wt.% carbon black, 1 wt.% Cu and 20 wt.% ZnO to SnO2.

Magnetic proximity effect at the interface between a cuprate superconductor and an oxide spin valve

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

Ovsyannikov, G. A., E-mail: gena@hitech.cplire.ru; Demidov, V. V.; Khaydukov, Yu. N.

2016-04-15

A heterostructure that consists of the YBa{sub 2}Cu{sub 3}O{sub 7–δ} cuprate superconductor and the SrRuO{sub 3}/La{sub 0.7}Sr{sub 0.3}MnO{sub 3} ruthenate/manganite spin valve is investigated using SQUID magnetometry, ferromagnetic resonance, and neutron reflectometry. It is shown that a magnetic moment is induced due to the magnetic proximity effect in the superconducting part of the heterostructure, while the magnetic moment in the composite ferromagnetic interlayer is suppressed. The magnetization emerging in the superconductor coincides in order of magnitude with the results of calculations taking into account the induced magnetic moment of Cu atoms because of orbital reconstruction at the interface between themore » superconductor and the ferromagnet, as well as with the results of the model taking into account the variations in the density of states at a distance on the order of the coherence length in the superconductor. The experimentally obtained characteristic penetration depth of the magnetic moment in the superconductor considerably exceeds the coherence length of the cuprate superconductor, which indicates the predominance of the mechanism of induced magnetic moment of Cu atoms.« less

Coupling between crystal structure and magnetism in transition-metal oxides

NASA Astrophysics Data System (ADS)

Barton, Phillip Thomas

Transition-metal oxides exhibit a fascinating array of phenomena ranging from superconductivity to negative thermal expansion to catalysis. This dissertation focuses on magnetism, which is integral to engineering applications such as data storage, electric motors/generators, and transformers. The investigative approach follows structure-property relationships from materials science and draws on intuition from solid-state chemistry. The interplay between crystal structure and magnetic properties is studied experimentally in order to enhance the understanding of magnetostructural coupling mechanisms and provide insight into avenues for tuning behavior. A combination of diffraction and physical property measurements were used to study structural and magnetic phase transitions as a function of chemical composition, temperature, and magnetic field. The systems examined are of importance in Li-ion battery electrochemistry, condensed-matter physics, solid-state chemistry, and p-type transparent conducting oxides. The materials were prepared by solid-state reaction of powder reagents at high temperatures for periods lasting tens of hours. The first project discussed is of a solid solution between NiO, a correlated insulator, and LiNiO2, a layered battery cathode. Despite the deceptive structural and compositional simplicity of this system, a complete understanding of its complex magnetic properties has remained elusive. This study shows that nanoscale domains of chemical order form at intermediate compositions, creating interfaces between antiferromagnetism and ferrimagnetism that give rise to magnetic exchange bias. A simple model of the magnetism is presented along with a comprehensive phase diagram. The second set of investigations focus on the Ge-Co-O system where the spin-orbit coupling of Co(II) plays a significant role. GeCo2O 4 is reported to exhibit unusual magnetic behavior that arises from Ising spin in its spinel crystal structure. Studies by variable-temperature synchrotron X-ray diffraction reveal a magnetostructural transition and capacitance measurements show evidence for magnetodielectric behavior. The above work uncovered a Co10Ge3O16 phase that had a known structure but whose physical properties were largely uncharacterized. This project examined its metamagnetic properties using detailed magnetometry experiments. Upon the application of a magnetic field, this material goes through a first-order phase transition from a noncollinear antiferromagnet to an unknown ferrimagnetic state. Lastly, this thesis explored the chemical dilution of magnetism in some perovskite and delafossite solid solutions. In the perovskite structure, compositions intermediate to the endmembers SrRuO3, a ferromagnetic metal, and LaRhO3, a diamagnetic semiconductor, were investigated. While the magnetism of this system is poised between localized and itinerant behavior, a compositionally-driven metal to insulator transition, revealed by electrical resistivity measurements, did not strongly impact the magnetic properties. Instead, both octahedral tilting and magnetic dilution had strong effects, and comparison of this characterization to Sr1-- x CaxRuO3 reinforces the important role of structural distortions in determining magnetic ground state. The final materials studied were of composition CuAl1-- xCrxO2 (0 < x < 1) in the delafossite structure. The primary interest was the geometric frustration of antiferromagnetism in CuCrO 2 and significant short-range correlations were observed above TN. The analysis found that reducing the number of degenerate states through Al substitution did not enhance magnetic ordering because of the weakening of magnetic exchange.

Effects of alloying element and temperature on the stacking fault energies of dilute Ni-base superalloys.

PubMed

Shang, S L; Zacherl, C L; Fang, H Z; Wang, Y; Du, Y; Liu, Z K

2012-12-19

A systematic study of stacking fault energy (γ(SF)) resulting from induced alias shear deformation has been performed by means of first-principles calculations for dilute Ni-base superalloys (Ni(23)X and Ni(71)X) for various alloying elements (X) as a function of temperature. Twenty-six alloying elements are considered, i.e., Al, Co, Cr, Cu, Fe, Hf, Ir, Mn, Mo, Nb, Os, Pd, Pt, Re, Rh, Ru, Sc, Si, Ta, Tc, Ti, V, W, Y, Zn, and Zr. The temperature dependence of γ(SF) is computed using the proposed quasistatic approach based on a predicted γ(SF)-volume-temperature relationship. Besides γ(SF), equilibrium volume and the normalized stacking fault energy (Γ(SF) = γ(SF)/Gb, with G the shear modulus and b the Burgers vector) are also studied as a function of temperature for the 26 alloying elements. The following conclusions are obtained: all alloying elements X studied herein decrease the γ(SF) of fcc Ni, approximately the further the alloying element X is from Ni on the periodic table, the larger the decrease of γ(SF) for the dilute Ni-X alloy, and roughly the γ(SF) of Ni-X decreases with increasing equilibrium volume. In addition, the values of γ(SF) for all Ni-X systems decrease with increasing temperature (except for Ni-Cr at higher Cr content), and the largest decrease is observed for pure Ni. Similar to the case of the shear modulus, the variation of γ(SF) for Ni-X systems due to various alloying elements is traceable from the distribution of (magnetization) charge density: the spherical distribution of charge density around a Ni atom, especially a smaller sphere, results in a lower value of γ(SF) due to the facility of redistribution of charges. Computed stacking fault energies and the related properties are in favorable accord with available experimental and theoretical data.

Unconventional quantum criticality emerging as a new common language of transition-metal compounds, heavy-fermion systems, and organic conductors.

PubMed

Imada, Masatoshi; Misawa, Takahiro; Yamaji, Youhei

2010-04-28

We analyze and overview some of the different types of unconventional quantum criticalities by focusing on two origins. One origin of the unconventionality is the proximity to first-order transitions. The border between the first-order and continuous transitions is described by a quantum tricritical point (QTCP) for symmetry breaking transitions. One of the characteristic features of the quantum tricriticality is the concomitant divergence of an order parameter and uniform fluctuations, in contrast to the conventional quantum critical point (QCP). The interplay of these two fluctuations generates unconventionality. Several puzzling non-Fermi-liquid properties in experiments are taken to be accounted for by the resultant universality, as in the cases of Y bRh(2)Si(2), CeRu(2)Si(2) and β-Y bAlB(4). Another more dramatic unconventionality appears again at the border of the first-order and continuous transitions, but in this case for topological transitions such as metal-insulator and Lifshitz transitions. This border, the marginal quantum critical point (MQCP), belongs to an unprecedented universality class with diverging uniform fluctuations at zero temperature. The Ising universality at the critical end point of the first-order transition at nonzero temperatures transforms to the marginal quantum criticality when the critical temperature is suppressed to zero. The MQCP has a unique feature with a combined character of symmetry breaking and topological transitions. In the metal-insulator transitions, the theoretical results are supported by experimental indications for V(2 - x)Cr(x)O(3) and an organic conductor κ-(ET)(2)Cu[N(CN)(2)]Cl. Identifying topological transitions also reveals how non-Fermi liquid appears as a phase in metals. The theory also accounts for the criticality of a metamagnetic transition in ZrZn(2), by interpreting it as an interplay of Lifshitz transition and correlation effects. We discuss the common underlying physics in these examples.

Effect of silicon on trace element partitioning in iron-bearing metallic melts

NASA Astrophysics Data System (ADS)

Chabot, Nancy L.; Safko, Trevor M.; McDonough, William F.

2010-08-01

Despite the fact that Si is considered a potentially important metalloid in planetary systems, little is known about the effect of Si in metallic melts on trace element partitioning behavior. Previous studies have established the effects of S, C, and P, nonmetals, through solid metal/liquid metal experiments in the corresponding Fe binary systems, but the Fe-Si system is not appropriate for similar experiments because of the high solubility of Si in solid metal. In this work, we present the results from 0.1MPa experiments with two coexisting immiscible metallic liquids in the Fe-S-Si system. By leveraging the extensive available knowledge about the effect of S on trace element partitioning behavior, we explore the effect of Si. Results for 22 trace elements are presented. Strong Si avoidance behavior is demonstrated by As, Au, Ga, Ge, Sb, Sn, and Zn. Iridium, Os, Pt, Re, Ru, and W exhibit weak Si avoidance tendencies. Silicon appears to have no significant effect on the partitioning behaviors of Ag, Co, Cu, Cr, Ni, Pd, and V, all of which had similar partition coefficients over a wide range of Si liquid concentrations from Si-free to 13 wt%. The only elements in our experiments to show evidence of a potentially weak attraction to Si were Mo and Rh. Applications of the newly determined effects of Si to problems in planetary science indicate that (1) The elements Ni, Co, Mo, and W, which are commonly used in planetary differentiation models, are minimally affected by the presence of Si in the metal, especially in comparison to other effects such as from oxygen fugacity. 2) Reduced enstatite-rich meteorites may record a chemical signature due to Si in the metallic melts during partial melting, and if so, elements identified by this study as having strong Si avoidance may offer unique insight into unraveling the history of these meteorites.

Multi-elemental analysis of Lentinula edodes mushrooms available in trade.

PubMed

Mleczek, Mirosław; Siwulski, Marek; Rzymski, Piotr; Niedzielski, Przemysław; Gąsecka, Monika; Jasińska, Agnieszka; Budzyńska, Sylwia; Budka, Anna

2017-03-04

The present study investigated the content of 62 elements in the fruiting bodies of Lentinula edodes (Shiitake mushroom) cultivated commercially in Poland on various substrates from 2007-2015. The general mean content (mg kg -1 dry weight (DW)) of the studied elements ranked in the following order: K (26,335) > P (11,015) > Mg (2,284) > Ca (607) > Na (131) > Zn (112) > Fe (69) > Mn (33) > B (32) > Rb (17) > Cu (14.5) > Al (11.2) > Te (2.9) > As (1.80) > Cd (1.76) > Ag (1.73) > Nd (1.70) > Sr (1.46) > Se (1.41) > U (1.11) > Pt (0.90) > Ce (0.80) > Ba (0.61) > Co (0.59) > Tl (0.58) > Er (0.50) > Pb (0.42) > Li (0.40) > Pr (0.39) > Ir (0.37) > In (0.35) > Mo (0.31) > Cr (0.29) > Ni (0.28) > Sb (0.26) > Re (0.24) > Ti (0.19) > Bi (0.18) > Th (0.12) > La (0.10) = Pd (0.10) > Os (0.09) = Zr (0.09) > Rh (0.08) > Ho (0.07) > Ru (0.06) > Sm (0.04) = Eu (0.04) = Tm (0.04) > Gd (0.03) > Sc (0.02) = Y (0.02) > Lu (0.01) = Yb (0.01) = V (0.01). The contents of Au, Be, Dy, Ga, Ge, Hf, and Tb were below the limits of detection (0.02, 0.02, 0.01, 0.01, 0.01, 0.01, 0.02 mg kg -1 respectively). The concentrations of Al, As, B, Ba, Ca, Cd, Cr, Er, Fe, In, Lu, Mn, Nd, Sr, Ti, Tm, and Zr were comparable over the period the mushrooms were cultivated. The study revealed that Lentinula edodes contained As and Cd at levels potentially adverse to human health. This highlights the need to monitor these elements in food products obtained from this mushroom species and ensure that only low levels of these elements are present in cultivation substrates.

The iron-nickel-phosphorus system: Effects on the distribution of trace elements during the evolution of iron meteorites

NASA Astrophysics Data System (ADS)

Corrigan, Catherine M.; Chabot, Nancy L.; McCoy, Timothy J.; McDonough, William F.; Watson, Heather C.; Saslow, Sarah A.; Ash, Richard D.

2009-05-01

To better understand the partitioning behavior of elements during the formation and evolution of iron meteorites, two sets of experiments were conducted at 1 atm in the Fe-Ni-P system. The first set examined the effect of P on solid metal/liquid metal partitioning behavior of 22 elements, while the other set explored the effect of the crystal structures of body-centered cubic (α)- and face-centered cubic (γ)-solid Fe alloys on partitioning behavior. Overall, the effect of P on the partition coefficients for the majority of the elements was minimal. As, Au, Ga, Ge, Ir, Os, Pt, Re, and Sb showed slightly increasing partition coefficients with increasing P-content of the metallic liquid. Co, Cu, Pd, and Sn showed constant partition coefficients. Rh, Ru, W, and Mo showed phosphorophile (P-loving) tendencies. Parameterization models were applied to solid metal/liquid metal results for 12 elements. As, Au, Pt, and Re failed to match previous parameterization models, requiring the determination of separate parameters for the Fe-Ni-S and Fe-Ni-P systems. Experiments with coexisting α and γ Fe alloy solids produced partitioning ratios close to unity, indicating that an α versus γ Fe alloy crystal structure has only a minor influence on the partitioning behaviors of the trace element studied. A simple relationship between an element's natural crystal structure and its α/γ partitioning ratio was not observed. If an iron meteorite crystallizes from a single metallic liquid that contains both S and P, the effect of P on the distribution of elements between the crystallizing solids and the residual liquid will be minor in comparison to the effect of S. This indicates that to a first order, fractional crystallization models of the Fe-Ni-S-P system that do not take into account P are appropriate for interpreting the evolution of iron meteorites if the effects of S are appropriately included in the effort.

Comparative proteomic analysis of rd29A:RdreB1BI transgenic and non-transgenic strawberries exposed to low temperature.

PubMed

Gu, Xianbin; Gao, Zhihong; Zhuang, Weibing; Qiao, Yushan; Wang, Xiuyun; Mi, Lin; Zhang, Zhen; Lin, Zhilin

2013-05-01

Low-temperature stress is one of the major abiotic stresses in plants worldwide, and the dehydration responsive element binding protein (DREB) transcription factor induces expression of genes involved in environmental stress tolerance in plants. A proteomic approach based on two-dimensional gel electrophoresis (2-DE) and subsequent mass spectrometric identification was used to study the changes in the leaf proteome profiles of rd29A:RdreB1BI transgenic and non-transgenic strawberries exposed to low-temperature conditions. By comparing the proteomic profiles, we located 21 protein spots that were reproducibly up- or down-regulated by more than twofold between transgenic and non-transgenic strawberries. Eight identified proteins function in energy and metabolism, four in biosynthetic processes, four were stress and defense related, three spots were identified as cold-stress related expressed sequence tags (ESTs), and two were unknown proteins. The change patterns of low-temperature tolerance proteins, including photosynthetic proteins (RuBisCO large subunit and RuBisCO activase), cytoplasmic Cu/Zn-superoxide dismutase (Cu/Zn-SOD), late embryogenesis abundant protein 14-A (Lea14-A), eukaryotic translation initiation factor 5A (eIF5A), and cold-stress related ESTs, were differentially regulated between non-transgenic and rd29A:RdreB1BI transgenic strawberries. They are likely important gene products in the regulatory network of the RdreB1BI gene. Consequently, this study provides the first characterization of the transgenic strawberry proteome and the predicted target proteins of the RdreB1BI gene by using proteomic approaches. Copyright © 2013 Elsevier GmbH. All rights reserved.

Document Image Compression and Analysis

DTIC Science & Technology

1997-04-01

F3 ’Q>F6BUKXYU󈨐&2:38’CZ3 O ’[5>:H3Z3 O > F3 /3 O 󈧵LA\\+󈨊Ś...H2$6SH0A#BU+’K3 O >3V2:@BCg’�%8h^’U�U+���𔄁%8’�6BH’C N4O RH O 2+H7H#&%<@B󈨍 N ’�󈨐�> 9&%2$382:3E;9B’�>F6BU�>�H�>F6BURU&> F3 ’D9B> F3 ...38#&%’>F6BUD6&2$3Q6&2$RCg’>F6SU�C O 2$#&0RUI3 O 𔄁%8𔃿=2:%8’W@B’ H2:6BCgRU𔄁%8’_U N ŗ ODO "! O

Solution hardened platinum alloy flexure materials for improved performance and reliability of MEMS devices

NASA Astrophysics Data System (ADS)

Brazzle, John D.; Taylor, William P.; Ganesh, Bala; Price, James J.; Bernstein, Jonathan J.

2005-01-01

Solution hardened platinum alloys are presented for use as a MEMS flexure material. Two Pt alloys are discussed in this work; Pt alloyed with 15% Rh and 6% Ru (known as Alloy 851) and an alloy of Pt with 10% Ir. These alloys do not require protective masking, resulting in fewer fabrication steps because the alloys can be exposed to fluorine, chlorine and oxygen plasmas as well as wet chemical etches without damage. These alloys combine many desirable properties such as biocompatibility, extreme corrosion resistance, good electrical/thermal conductivity, high Young's modulus, high yield strength [1], low hysteresis and fatigue, and they are non-ferromagnetic. Compositional profiles for the sputtered films are described, as well as stress control during deposition. Nanoindentation experiments were performed to measure mechanical properties. The mechanical performance of these Pt alloy flexures as supports for rotating micromirror structures is described.

Synthesis of acetic acid via methanol hydrocarboxylation with CO2 and H2.

PubMed

Qian, Qingli; Zhang, Jingjing; Cui, Meng; Han, Buxing

2016-05-11

Acetic acid is an important bulk chemical that is currently produced via methanol carbonylation using fossil based CO. Synthesis of acetic acid from the renewable and cheap CO2 is of great importance, but state of the art routes encounter difficulties, especially in reaction selectivity and activity. Here we report a route to produce acetic acid from CO2, methanol and H2. The reaction can be efficiently catalysed by Ru-Rh bimetallic catalyst using imidazole as the ligand and LiI as the promoter in 1,3-dimethyl-2-imidazolidinone (DMI) solvent. It is confirmed that methanol is hydrocarboxylated into acetic acid by CO2 and H2, which accounts for the outstanding reaction results. The reaction mechanism is proposed based on the control experiments. The strategy opens a new way for acetic acid production and CO2 transformation, and represents a significant progress in synthetic chemistry.

Systems and methods for treating material

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

Scheele, Randall D; McNamara, Bruce K

Systems for treating material are provided that can include a vessel defining a volume, at least one conduit coupled to the vessel and in fluid communication with the vessel, material within the vessel, and NF.sub.3 material within the conduit. Methods for fluorinating material are provided that can include exposing the material to NF.sub.3 to fluorinate at least a portion of the material. Methods for separating components of material are also provided that can include exposing the material to NF.sub.3 to at least partially fluorinate a portion of the material, and separating at least one fluorinated component of the fluorinated portionmore » from the material. The materials exposed to the NF.sub.3 material can include but are not limited to one or more of U, Ru, Rh, Mo, Tc, Np, Pu, Sb, Ag, Am, Sn, Zr, Cs, Th, and/or Rb.« less

Metal-isonitrile adducts for preparing radionuclide complexes for labelling and imaging agents

DOEpatents

Jones, Alun G.; Davison, Alan; Abrams, Michael J.

1987-01-01

A method for preparing a coordination complex of an isonitrile ligand and radionuclide such as Tc, Ru, Co, Pt, Fe, Os, Ir, W, Re, Cr, Mo, Mn, Ni, Rh, Pd, Nb and Ta is disclosed. The method comprises preparing a soluble metal adduct of said isonitrile ligand by admixing said ligand with a salt of a displaceable metal having a complete d-electron shell selected from the group consisting of Zn, Ga, Cd, In, Sn, Hg, Tl, Pb and Bi to form a soluble metal-isonitrile salt, and admixing said metal isonitrile salt with a salt comprising said radioactive metal in a suitable solvent to displace said displaceable metal with the radioactive metal thereby forming said coordination. The complex is useful as a diagnostic agent for labelling liposomes or vesicles, and selected living cells containing lipid membranes, such as blood clots, myocardial tissue, gall bladder tissue, etc.

Vibrational spectra of carboxylato complexes—III. Trinuclear 'basic' acetates and formates of chromium(III), iron(III) and other transition metals

NASA Astrophysics Data System (ADS)

Johnson, M. K.; Powell, D. B.; Cannon, R. D.

The i.r. and Raman spectra of a series of complexes [M III3O(OOCR) 6L 3]X· xH 2O (M = Cr, Fe, Mn, Ru, Rh; L = H 2O, pyridine, γ-picoline; X = Cl, Br, I, NO 3, ClO 3, ClO 4, BF 4) have been analysed in detail. The vibrational modes of the central M 3O and the three surrounding MO 4 units, are identified. The metal—nitrogen stretching vibrations and the MOH 2 modes are assigned. The 'basic' chromium(III) formate is shown to be [Cr 3O(OOCH) 6(OH 2) 2(OOCH)] xH 2O, containing monodentate, inner-sphere coordinated formate ion. The use of the symmetric and asymmetric OCO stretching frequencies in characterizing bridging carboxylate ions is discussed.

Wet-oxidation waste management system for CELSS

NASA Technical Reports Server (NTRS)

Takahashi, Y.; Ohya, H.

1986-01-01

A wet oxidation system will be useful in the Closed Ecological Life Support System (CELSS) as a facility to treat organic wastes and to redistribute inorganic compounds and elements. However at rather higher temperatures needed in this reaction, for instance, at 260 deg C, only 80% of organic in a raw material can be oxidized, and 20% of it will remain in the liquid mainly as acetic acid, which is virtually noncombustible. Furthermore, nitrogen is transformed to ammonium ions which normally cannot be absorbed by plants. To resolve these problems, it becomes necessary to use catalysts. Noble metals such as Ru, Rh and so on have proved to be partially effective as these catalysts. That is, oxidation does not occur completely, and the unexpected denitrification, instead of the expected nitrification, occurs. So, it is essential to develop the catalysts which are able to realize the complete oxidation and the nitrification.

Superconductivity in YTE2Ge2 compounds (TE = d-electron transition metal)

NASA Astrophysics Data System (ADS)

Chajewski, G.; Samsel-Czekała, M.; Hackemer, A.; Wiśniewski, P.; Pikul, A. P.; Kaczorowski, D.

2018-05-01

Polycrystalline samples of YTE2Ge2 with TE = Co, Ni, Ru, Rh, Pd and Pt were synthesized and characterized by means of X-ray powder diffraction and low-temperature electrical resistivity and specific heat measurements, supplemented by fully relativistic full-potential local-orbital band structure calculations. We confirm that most of the compounds studied crystallize in a body-centered tetragonal ThCr2S2 -type structure (space group I 4 / mmm) and have three-dimensional Fermi surfaces, while only one of them (YPt2Ge2) forms with a primitive tetragonal CaBe2Ge2 -type unit cell (space group P 4 / nmm) and possesses quasi-two-dimensional Fermi surface sheets with some nesting. Physical properties data show conventional superconductivity in the phases with TE = Co, Pd and Pt, i.e. independently of the structure type (and hence the dimensionality of the Fermi surface).

Nano-structured noble metal catalysts based on hexametallate architecture for the reforming of hydrocarbon fuels

DOEpatents

Gardner, Todd H.

2015-09-15

Nano-structured noble metal catalysts based on hexametallate lattices, of a spinel block type, and which are resistant to carbon deposition and metal sulfide formation are provided. The catalysts are designed for the reforming of hydrocarbon fuels to synthesis gas. The hexametallate lattices are doped with noble metals (Au, Pt, Rh, Ru) which are atomically dispersed as isolated sites throughout the lattice and take the place of hexametallate metal ions such as Cr, Ga, In, and/or Nb. Mirror cations in the crystal lattice are selected from alkali metals, alkaline earth metals, and the lanthanide metals, so as to reduce the acidity of the catalyst crystal lattice and enhance the desorption of carbon deposit forming moieties such as aromatics. The catalysts can be used at temperatures as high as 1000.degree. C. and pressures up to 30 atmospheres. A method for producing these catalysts and applications of their use also is provided.

Photochemical methods to assay DNA photocleavage using supercoiled pUC18 DNA and LED or xenon arc lamp excitation.

PubMed

Prussin, Aaron J; Zigler, David F; Jain, Avijita; Brown, Jared R; Winkel, Brenda S J; Brewer, Karen J

2008-04-01

Methods for the study of DNA photocleavage are illustrated using a mixed-metal supramolecular complex [{(bpy)(2)Ru(dpp)}(2)RhCl(2)]Cl(5). The methods use supercoiled pUC18 plasmid as a DNA probe and either filtered light from a xenon arc lamp source or monochromatic light from a newly designed, high-intensity light-emitting diode (LED) array. Detailed methods for performing the photochemical experiments and analysis of the DNA photoproduct are delineated. Detailed methods are also given for building an LED array to be used for DNA photolysis experiments. The Xe arc source has a broad spectral range and high light flux. The LEDs have a high-intensity, nearly monochromatic output. Arrays of LEDs have the advantage of allowing tunable, accurate output to multiple samples for high-throughput photochemistry experiments at relatively low cost.

Catalytic wet-oxidation of human wastes produced in space: the effects of temperature elevation.

PubMed

Takeda, N; Takahashi, Y

1992-01-01

The filtrate of non-catalytical wet-oxidation sewage sludge was wet-oxidized again at 290 degrees C and 300 degrees C with a Ru-Rh catalyst. At each temperature, repeated batch tests were carried out. Both oxidation and denitrification efficiency of organic matter in the raw material were studied. In the 16 times batch tests at 300 degrees C, high and stable oxidation occurred. 98.0% of organic carbon in the raw material was oxidized and 98.3% of organic nitrogen was denitrified. At 290 degrees C, though high and stable denitrification occurred, oxidation did not occur highly and stably. A catalytic wet-oxidation system studied at 300 degrees C will be useful as a waste management system for a human life support system, where almost all food is resupplied from the earth. This system can prevent organic waste accumulation in the life support system.

Atomic scale modelling of hexagonal structured metallic fission product alloys

PubMed Central

Middleburgh, S. C.; King, D. M.; Lumpkin, G. R.

2015-01-01

Noble metal particles in the Mo-Pd-Rh-Ru-Tc system have been simulated on the atomic scale using density functional theory techniques for the first time. The composition and behaviour of the epsilon phases are consistent with high-entropy alloys (or multi-principal component alloys)—making the epsilon phase the only hexagonally close packed high-entropy alloy currently described. Configurational entropy effects were considered to predict the stability of the alloys with increasing temperatures. The variation of Mo content was modelled to understand the change in alloy structure and behaviour with fuel burnup (Mo molar content decreases in these alloys as burnup increases). The predicted structures compare extremely well with experimentally ascertained values. Vacancy formation energies and the behaviour of extrinsic defects (including iodine and xenon) in the epsilon phase were also investigated to further understand the impact that the metallic precipitates have on fuel performance. PMID:26064629

Electrocatalytic activity of spots of electrodeposited noble-metal catalysts on carbon nanotubes modified glassy carbon.

PubMed

Chen, Xingxing; Eckhard, Kathrin; Zhou, Min; Bron, Michael; Schuhmann, Wolfgang

2009-09-15

A strategy for the screening of the electrocatalytic activity of electrocatalysts for possible application in fuel cells and other devices is presented. In this approach, metal nanoclusters (Pt, Au, Ru, and Rh and their codeposits) were prepared using a capillary-based droplet-cell by pulsed electrodeposition in a diffusion-restricted viscous solution. A glassy carbon surface was modified with carbon nanotubes (CNTs) by electrophoretic accumulation and was used as substrate for metal nanoparticle deposition. The formed catalyst spots on the CNT-modified glassy carbon surface were investigated toward their catalytic activity for oxygen reduction as a test reaction employing the redox competition mode of scanning electrochemical microscopy (RC-SECM). Qualitative information on the electrocatalytic activity of the catalysts was obtained by varying the potential applied to the substrate; semiquantitative evaluation was based on the determination of the electrochemically deposited catalyst loading by means of the charge transferred during the metal nanoparticle deposition. Qualitatively, Au showed the highest electrocatalytic activity toward the oxygen reduction reaction (ORR) in phosphate buffer among all investigated single metal catalysts which was attributed to the much higher loading of Au achieved during electrodeposition. Coelectrodeposited Au-Pt catalysts showed a more positive onset potential (-150 mV in RC-SECM experiments) of the ORR in phosphate buffer at pH 6.7. After normalizing the SECM image by the charge during the metal nanocluster deposition which represents the mass loading of the catalyst, Ru showed a higher electrocatalytic activity toward the ORR than Au.

Green synthesis of the Cu/Fe3O4 nanoparticles using Morinda morindoides leaf aqueous extract: A highly efficient magnetically separable catalyst for the reduction of organic dyes in aqueous medium at room temperature

NASA Astrophysics Data System (ADS)

Nasrollahzadeh, Mahmoud; Atarod, Monireh; Sajadi, S. Mohammad

2016-02-01

This paper reports the green and in-situ preparation of the Cu/Fe3O4 magnetic nanocatalyst synthesized using Morinda morindoides leaf extract without stabilizers or surfactants. The catalyst was characterized by XRD, SEM, EDS, UV-visible, TEM, VSM and TGA-DTA. The catalytic performance of the resulting nanocatalyst was examined for the reduction of 4-nitrophenol (4-NP), Congo red (CR) and Rhodamine B (RhB) in an environmental friendly medium at room temperature. The catalyst was recovered using an external magnet and reused several times without appreciable loss of its catalytic activity. In addition, the stability of the recycled catalyst has been proved by SEM and EDS techniques.

Determination of Elemental Composition of Malabar spinach, Lettuce, Spinach, Hyacinth Bean, and Cauliflower Vegetables Using Proton Induced X-Ray Emission Technique at Savar Subdistrict in Bangladesh

PubMed Central

Fahad, S. M.; Islam, A. F. M. Mahmudul; Ahmed, Mahiuddin; Alam, Md. Rezaul; Alam, Md. Ferdous; Khalik, Md. Farhan; Hossain, Md. Lokman; Abedin, Md. Joynal

2015-01-01

The concentrations of 18 different elements (K, Ca, Fe, Cl, P, Zn, S, Mn, Ti, Cr, Rb, Co, Br, Sr, Ru, Si, Ni, and Cu) were analyzed in five selected vegetables through Proton Induced X-ray Emission (PIXE) technique. The objective of this study was to provide updated information on concentrations of elements in vegetables available in the local markets at Savar subdistrict in Bangladesh. These elements were found in varying concentrations in the studied vegetables. The results also indicated that P, Cl, K, Ca, Mn, Fe, and Zn were found in all vegetables. Overall, K and Ca exhibited the highest concentrations. Cu and Ni exhibited the lowest concentrations in vegetables. The necessity of these elements was also evaluated, based on the established limits of regulatory standards. The findings of this study suggest that the consumption of these vegetables is not completely free of health risks. PMID:26229953

Hexavalent Americium Recovery Using Copper(III) Periodate

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

McCann, Kevin; Brigham, Derek M.; Morrison, Samuel

2016-11-21

Separation of americium from the lanthanides is considered one of the most difficult separation steps in closing the nuclear fuel cycle. One approach to this separation could involve oxidizing americium to the hexavalent state to form a linear dioxo cation while the lanthanides remain as trivalent ions. This work considers aqueous soluble Cu3+ periodate as an oxidant under molar nitric acid conditions to separate hexavalent Am with diamyl amylphosphonate (DAAP) in n-dodecane. Initial studies assessed the kinetics of Cu3+ periodate auto-reduction in acidic media to aid in development of the solvent extraction system. Following characterization of the Cu3+ periodate oxidant,more » solvent extraction studies optimized the recovery of Am from varied nitric acid media and in the presence of other fission product, or fission product surrogate, species. Short aqueous/organic contact times encouraged successful recovery of Am (distribution values as high as 2) from nitric acid media in the absence of redox active fission products. In the presence of a post-PUREX simulant aqueous feed, precipitation of tetravalent species (Ce, Ru, Zr) occurred and the distribution values of 241Am were suppressed, suggesting some oxidizing capacity of the Cu3+ periodate is significantly consumed by other redox active metals in the simulant. The manuscript demonstrates Cu3+ periodate as a potentially viable oxidant for Am oxidation and recovery and notes the consumption of oxidizing capacity observed in the presence of the post-PUREX simulant feed will need to be addressed for any approach seeking to oxidize Am for separations relevant to the nuclear fuel cycle.« less

Singularity in the positive Hall coeffcient near pre-onset temperatures in high-Tc superconductors

NASA Astrophysics Data System (ADS)

Vezzoli, G. C.; Chen, M. F.; Craver, F.; Moon, B. M.; Safari, A.; Burke, T.; Stanley, W.

1990-10-01

Hall measurements using continuous extremely slow cooling and reheating rates as well as employing eqiulibrium point-by-point conventional techniques reveals a clear anomally in RH at pre-onset temperatures near Tc in polycrystalline samples Y1Ba2Cu3O7 and Bi2Sr2Ca2Cu3O10. The anomaly has the appearance of a singularity of Dirac-delta function which parallels earlier work on La1-xSrxCuO4. Recent single crystal work on the Bi-containing high-Tc superconductor is in accord with a clearcut anomaly. The singularity is tentatively interpreted to be associated (upon cooling) with initially the removal of positive holes from the hopping conduction system of the normal state such as from the increased concentration of bound virtual excitons due to increased exciton and hole lifetimes at low temperature. Subsequently the formation of Cooper pairs by mediation from these centers (bound-holes) and/or bound excitons) may cause an ionization of these bound virtual excitons thereby re-introducing holes and electrons into the conduction system at Tc.

IMPACT OF NOBLE METALS AND MERCURY ON HYDROGEN GENERATION DURING HIGH LEVEL WASTE PRETREATMENT AT THE SAVANNAH RIVER SITE

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

Stone, M; Tommy Edwards, T; David Koopman, D

2009-03-03

The Defense Waste Processing Facility (DWPF) at the Savannah River Site vitrifies radioactive High Level Waste (HLW) for repository internment. The process consists of three major steps: waste pretreatment, vitrification, and canister decontamination/sealing. HLW consists of insoluble metal hydroxides (primarily iron, aluminum, calcium, magnesium, manganese, and uranium) and soluble sodium salts (carbonate, hydroxide, nitrite, nitrate, and sulfate). The pretreatment process in the Chemical Processing Cell (CPC) consists of two process tanks, the Sludge Receipt and Adjustment Tank (SRAT) and the Slurry Mix Evaporator (SME) as well as a melter feed tank. During SRAT processing, nitric and formic acids are addedmore » to the sludge to lower pH, destroy nitrite and carbonate ions, and reduce mercury and manganese. During the SME cycle, glass formers are added, and the batch is concentrated to the final solids target prior to vitrification. During these processes, hydrogen can be produced by catalytic decomposition of excess formic acid. The waste contains silver, palladium, rhodium, ruthenium, and mercury, but silver and palladium have been shown to be insignificant factors in catalytic hydrogen generation during the DWPF process. A full factorial experimental design was developed to ensure that the existence of statistically significant two-way interactions could be determined without confounding of the main effects with the two-way interaction effects. Rh ranged from 0.0026-0.013% and Ru ranged from 0.010-0.050% in the dried sludge solids, while initial Hg ranged from 0.5-2.5 wt%, as shown in Table 1. The nominal matrix design consisted of twelve SRAT cycles. Testing included: a three factor (Rh, Ru, and Hg) study at two levels per factor (eight runs), three duplicate midpoint runs, and one additional replicate run to assess reproducibility away from the midpoint. Midpoint testing was used to identify potential quadratic effects from the three factors. A single sludge simulant was used for all tests and was spiked with the required amount of noble metals immediately prior to performing the test. Acid addition was kept effectively constant except to compensate for variations in the starting mercury concentration. SME cycles were also performed during six of the tests.« less

Synthesis of PtRu/Ru heterostructure for efficient methanol electrooxidation: The role of extra Ru

NASA Astrophysics Data System (ADS)

Bai, Lei

2018-03-01

Platinum-ruthenium (PtRu) nanocubes and PtRu/Ru heterostructure via epitaxial growth were synthesized by varying the amount of Ru precursor. As model catalysts, the PtRu/Ru heterostructure demonstrated the highest catalytic performance in electrooxidation of methanol, which was possibly due to the more hydroxyl species produced from the extra Ru nanoparticles as well as enhanced adsorption of methanol of PtRu alloys in the PtRu/Ru heterostructure. The catalytic performance of the catalysts was closely related with the structure, which was well characterized by a series of methods. It was expected that the present work could provide a new insight for the synthesis of PtRu based nanocatalysts.

(Pt1-xCux)3Cu2B and Pt9Cu3B5, the first examples of copper platinum borides. Observation of superconductivity in a novel boron filled β-Mn-type compound

NASA Astrophysics Data System (ADS)

Salamakha, Leonid P.; Sologub, Oksana; Stöger, Berthold; Michor, Herwig; Bauer, Ernst; Rogl, Peter F.

2015-09-01

New ternary copper platinum borides have been synthesized by arc melting of pure elements followed by annealing at 600 °C. The structures have been studied by X-ray single crystal and powder diffraction. (Pt1-xCux)3Cu2B (x=0.33) forms a B-filled β-Mn-type structure (space group P4132; a=0.6671(1) nm). Cu atoms are distributed preferentially on the 8c atom sites, whereas the 12d site is randomly occupied by Pt and Cu atoms (0.670(4) Pt±0.330(4) Cu). Boron is located in octahedral voids of the parent β-Mn-type structure. Pt9Cu3B5 (space group P-62m; a=0.9048(3) nm, c=0.2908(1) nm) adopts the Pt9Zn3B5-δ-type structure. It has a columnar architecture along the short translation vector exhibiting three kinds of [Pt6] trigonal prism columns (boron filled, boron semi-filled and empty) and Pt channels with a pentagonal cross section filled with Cu atoms. The striking structural feature is a [Pt6] cluster in form of an empty trigonal prism at the origin of the unit cell, which is surrounded by coupled [BPt6] and [Pt6] trigonal prisms, rotated perpendicularly to the central one. There is no B-B contact as well as Cu-B contact in the structure. The relationships of Pt9Cu3B5 structure with the structure of Ti1+xOs2-xRuB2 as well as with the structure families of metal sulfides and aluminides have been elucidated. (Pt1-xCux)3Cu2B (x=0.3) (B-filled β-Mn-type structure) is a bulk superconductor with a transition temperature of about 2.06 K and an upper critical field μ0HC2(0)WHH of 1.2 T, whereas no superconducting transition has been observed up to 0.3 K in Pt9Cu3B5 (Pt9Zn3B5-δ-type structure) from electrical resistivity measurements.

Roadside Accumulation of Pt, Pd, Rh and Other Trace Elements From Automobiles: Catalytic Converter Attrition and Platinum-Group Element Mobility in the Roadside Environment.

NASA Astrophysics Data System (ADS)

Ely, J. C.; Dahlheimer, S. R.; Neal, C. R.

2003-12-01

Elemental abundances of Pt, Pd and Rh have been documented across the industrialized world in roadside environments due to attrition of automotive catalytic converters (Zereini and Alt, 2000, Anthropogenic PGE Emissions, Springer, 308pp; Ely et al., 2001, EnvSci&Tech, 35:3816-3822; Whiteley and Murray, 2003, SciTotEnv, in press). In our ongoing study, the highest reported roadside Pt abundance 1.8 ppm has been found immediately adjacent to the road at a field site in South Bend, IN, USA. Furthermore, initial studies show positive correlations of Pt, Pd and Rh with some trace elements (Ni, Cu, Zn and Pb), which has been confirmed by further analysis for these and other elements (Ce, Cr). It has been demonstrated that elements such as Ce are present in catalytic converters at concentrations of 100's ppm to 3-wt.%. These elements are also being attrited with Pt, Pd and Rh and aerially transported and deposited. Our field site was established next to US-933 adjacent to the Notre Dame campus. Areas were cleared of the top 2-4 cm of soil (removing surficial Pt, Pd and Rh) at 1, 5, 10 and 50 meters from the roadside. Within 3 months the 1-meter site contained 67% of the initial Rh and Pt concentrations and 100% of the initial Pd concentration. The sites at 5, 10 and 50 meters showed similar results, in some cases exceeding the initial concentrations. After 6 months the concentrations of Pt, Pd and Rh were all within error of the initial concentrations, indicating steady state abundances had probably been reached. Grass samples from each site showed that washed vs. unwashed samples were within error of each other, and there may be a slight enrichment (approx. 1 ppb) in the grasses of Pd and Pt, but this enrichment was independent of distance from the road. The steady-state situation suggests that the PGEs are being removed from the immediate roadside environment, which requires that the metals are being oxidized and/or complexed in such a way to facilitate transport. The environmental effects of such processes are unknown, but Pt complexes are known carcinogens. Electron microprobe and SEM analysis are being used to isolate particles using these surrogate trace elements in an ongoing effort to determine the oxidation state (using XANES) of Pt, Pd and Rh in the natural environment.

Photochemical pathways of the dimeric, mixed dimer, and monomeric sulfophthalocyanines of cobalt(III) and iron(II)

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

Ferraudi, G.

1979-04-01

The photochemical reactivity of the dimeric, mixed dimer, and monomeric sulfophthalocyanines of cobalt (III) and iron (II) was investigated by steady-state and flash irradiations. The dimeric species photodissociated into sulfophthalocyanine radicals which were coordinated to either Co(III) or Fe(II) metal centers. Reactions of such intermediates were investigated by interception with alcohols and O/sub 2/. Also, photoredox reactions were detected with monomeric acidocobalt(III) sulfophtahlocyanines. These processes produce the oxidation of the acido ligands (Cl/sup -/, Br/sup -/, N/sub 3//sup -/, I/sup -/) and the reduction of the metal center. The photoredox dissociation was also investigated by using mixed dimers of themore » cobalt sulfophthalocyanines with Cr(bpy)/sub 3//sup 3 +/ and Ru(bpy)/sub 3//sup 2 +/. The photogeneration of sulfophthalocyanine radicals was observed as a general reaction which was produced by excitation of either the Cr(bby)/sub 3//sup 3 +/ or Ru(bpy)/sub 3//sup 2 +/ units in the mixed dimer. The nature of the reactive excited states involved in the various photochemical reactions of the sulfophthalocyanines of Co(II), Co(III), Cu(II), and Fe(II) is discussed.« less

Routes to heavy-fermion superconductivity

NASA Astrophysics Data System (ADS)

Steglich, F.; Stockert, O.; Wirth, S.; Geibel, C.; Yuan, H. Q.; Kirchner, S.; Si, Q.

2013-07-01

Superconductivity in lanthanide- and actinide-based heavy-fermion (HF) metals can have different microscopic origins. Among others, Cooper pair formation based on fluctuations of the valence, of the quadrupole moment or of the spin of the localized 4f/5f shell have been proposed. Spin-fluctuation mediated superconductivity in CeCu2Si2 was demonstrated by inelastic neutron scattering to exist in the vicinity of a spin-density-wave (SDW) quantum critical point (QCP). The isostructural HF compound YbRh2Si2 which is prototypical for a Kondo-breakdown QCP has so far not shown any sign of superconductivity down to T ≈ 10 mK. In contrast, results of de-Haas-van-Alphen experiments by Shishido et al. (J. Phys. Soc. Jpn. 74, 1103 (2005)) suggest superconductivity in CeRhIn5 close to an antiferromagnetic QCP beyond the SDW type, at which the Kondo effect breaks down. For the related compound CeCoIn5 however, a field-induced QCP of SDW type is extrapolated to exist inside the superconducting phase.

The role of sulfides in the fractionation of highly siderophile and chalcophile elements during the formation of martian shergottite meteorites

NASA Astrophysics Data System (ADS)

Baumgartner, Raphael J.; Fiorentini, Marco L.; Lorand, Jean-Pierre; Baratoux, David; Zaccarini, Federica; Ferrière, Ludovic; Prašek, Marko K.; Sener, Kerim

2017-08-01

The shergottite meteorites are ultramafic to mafic igneous rocks whose parental magmas formed from partial melting of the martian mantle. This study reports in-situ laser ablation inductively coupled plasma mass spectrometry analyses for siderophile and chalcophile major and trace elements (i.e., Co, Ni, Cu, As, Se, Ag, Sb, Te, Pb, Bi, and the highly siderophile platinum-group elements, PGE: Os, Ir, Ru, Rh, Pt and Pd) of magmatic Fe-Ni-Cu sulfide assemblages from four shergottite meteorites. They include three geochemically similar incompatible trace element- (ITE-) depleted olivine-phyric shergottites (Yamato-980459, Dar al Gani 476 and Dhofar 019) that presumably formed from similar mantle and magma sources, and one distinctively ITE-enriched basaltic shergottite (Zagami). The sulfides in the shergottites have been variably modified by alteration on Earth and Mars, as well as by impact shock-shock related melting/volatilization during meteorite ejection. However, they inherit and retain their magmatic PGE signatures. The CI chondrite-normalized PGE concentration patterns of sulfides reproduce the whole-rock signatures determined in previous studies. These similarities indicate that sulfides exerted a major control on the PGE during shergottite petrogenesis. However, depletions of Pt (and Ir) in sulfide relative to the other PGE suggest that additional phases such discrete Pt-Fe-Ir alloys have played an important role in the concentration of these elements. These alloys are expected to have enhanced stability in reduced and FeO-rich shergottite magmas, and could be a common feature in martian igneous systems. A Pt-rich PGM was found to occur in a sulfide assemblage in Dhofar 019. However, its origin may be related to impact shock-related sulfide melting and volatilisation during meteorite ejection. In the ITE-depleted olivine-phyric shergottites, positive relationships exist between petrogenetic indicators (e.g., whole-rock Mg-number) and most moderately to strongly siderophile and chalcophile elements in sulfides. These variations extend to incompatible elements like Te and Pd. The whole-rock concentrations of Pd derived from mass-balance calculations decrease by one order of magnitude in the order Y-980459, DaG 476 and Dhofar 019, and broadly overlap the trends in previously published whole-rock analyses. Mantle heterogeneities, and the timing of sulfide saturation as function of mantle melting and/or magma fractionation following ascent from the mantle, may have been the controlling factors of the siderophile and chalcophile element systematics in the analyzed shergottites.

Geochemistry and mineralogy of Pd in the magnetitite layer within the upper gabbro of the Mesoarchean Nuasahi Massif (Orissa, India)

NASA Astrophysics Data System (ADS)

Prichard, Hazel M.; Mondal, Sisir K.; Mukherjee, Ria; Fisher, Peter C.; Giles, Nicolas

2018-04-01

Palladium concentrations of 1-3 ppm with an average Pt/Pd ratio of 0.15 have been located for the first time in a magnetitite layer in the Nuasahi Massif in Orissa India. This layer occurs at a high stratigraphic level in the complex and is nearly 4-km long and 5-12-m thick. The sections of the Pd-rich zone identified to date extend over a distance of 1 km at the southern end of the layer. Several phases of mineralization are evident. The first, primary assemblage of platinum-group minerals (PGM) contains Pd-sulfides (vysotskite), Pd-Pb alloys (zvyagintsevite), and a Pd-In alloy, a mineral probably new to mineralogy. These PGM are confined to central magnetite grains in the magnetitites. The magnetite grains with exsolved fine laths of ilmenite at centers are referred to as central magnetite grains. These central magnetite grains are commonly surrounded by blebs of ilmenite and magnetite that contain the majority of the PGM. These are dominated by Pd-antimonides, variably altered to Pd-oxides, and other PGM including PtAs2 (sperrylite), RuS2 (laurite), and IrRhAsS (irarsite/hollingwothite). Many of these PGM also occur in the interstitial silicates, with rare occurrences in the central magnetite grains. We propose that the platinum-group elements (PGE) crystallized during a minor sulfide saturation event that occurred as the magnetitites crystallized. This event produced the minor Cu-sulfides in these magnetitites. Later introduction of antimony and arsenic, during the alteration event that produced the blebby ilmenite and magnetite, led to the more primary PGM being succeeded by the main PGM assemblage, dominated by Pd-antimonides. These are associated with secondary Cu minerals and sperrylite. Subsequent oxidation during weathering in the hot wet Indian climate produced the Pd-oxides. The Nuasahi Massif is a sill-like Archean layered ultramafic-mafic intrusion genetically linked to high-Mg siliceous basalt or boninites and is characterized by unusually thick layers of chromitite. PGE are concentrated in these chromitites and in the base metal sulfide-bearing breccias in the overlying gabbro. The Pd in the magnetitites described here indicates the presence of a third level where PGE are concentrated and a magma that crystallized to produce PGE concentrations at three stratigraphic levels in the massif. This indicates that similar thin sill-like intrusions, hosting unusually thick chromitites, may also have PGE concentrations at a number of stratigraphic levels.