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Sample records for rhodium silicides

  1. Rhodium-rich silicides RERh{sub 6}Si{sub 4} (RE=La, Nd, Tb, Dy, Er, Yb)

    Energy Technology Data Exchange (ETDEWEB)

    Vosswinkel, Daniel; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

    2017-07-01

    Polycrystalline RERh{sub 6}Si{sub 4} (RE=La, Nd, Tb, Dy, Er, Yb) samples can be synthesized by arc-melting of the elements. Single crystals of LaRh{sub 6}Si{sub 4}, NdRh{sub 6}Si{sub 4} and YbRh{sub 6}Si{sub 4} were synthesized from the elements in bismuth fluxes (non-reactive flux medium). The structures were refined on the basis of single-crystal X-ray diffractometer data: LiCo{sub 6}P{sub 4} type, P anti 6m2, a=700.56(3), c=380.55(1) pm, wR2=0.0257, 317 F{sup 2} values, 19 variables for LaRh{sub 6}Si{sub 4}, a=698.4(5), c=377.7(2) pm, wR2=0.0578, 219 F{sup 2} values, 19 variables for NdRh{sub 6}Si{sub 4} and a=696.00(3), c=371.97(1) pm, wR2=0.0440, 309 F{sup 2} values, 19 variables for YbRh{sub 6}Si{sub 4}. The rhodium and silicon atoms build up three-dimensional, covalently bonded [Rh{sub 6}Si{sub 4}]{sup δ-} polyanionic networks with Rh-Si distances ranging from 239 to 249 pm. The rare earth atoms fill larger cavities within channels of these networks and they are coordinated by six silicon and twelve rhodium atoms in the form of hexa-capped hexagonal prisms.

  2. Rhodium. Suppl. Vol. B1

    International Nuclear Information System (INIS)

    Griffith, W.P.; Jehn, H.; McCleverty, J.A.; Raub, C.J.; Robinson, S.D.

    1982-01-01

    The present rhodium vol. B1 is concerned largely with linary compounds and coordination complexes of this important metal, which is used either alone or in alloy form for fabrication of other materials or for heterogeneous catalysis. In first two chapters are devoted for hydrides, oxides, ternary and quaternary oxorhodates. Third chapter is on different type of complexes with nitrogen. From chapter four to seven is on halogen complexes with this metal. Next chapters are on sulphides, sulphoxide and sulphito complexes, sulphates and sulphato complexes, selenides and tellurides, borides, borane complexes, carbides, carbonato, cyno, fulminato and thiocyanato complexes. Finally, silicide, phosphides, phosphito and arsenides are treated over here. (AB)

  3. Rhodium thioacetate complexes

    International Nuclear Information System (INIS)

    Baranovskij, I.B.; Golubnichaya, M.A.; Mazo, G.Ya.

    1976-01-01

    Thioacetato-complexes of rhodium(II) were prepared by the reaction of thioacetic acid with rhodium(II) carboxylates. Diamagnetic compounds of the type Rh 2 (CH 3 COS) 4 2A, where A=H 2 O, Py, N 2 H 4 .HCl, Thio, KNCS, DMSO, CH 3 CN, CsCl, or CH 3 COSH, were isolated. Their infrared spectra were recorded, and the principal vibrational wavenumbers assigned. The X-ray electron spectra confirm that rhodium is divalent. The thioacetato-complexes are dimeric, with a metal-metal bond. [Rh(NH 3 ) 5 (CH 3 COS)]I 2 was prepared, and its properties studied. The significant decrease in the strength of the bonds formed by the axial ligands with rhodium is due to the strong trans-influence of the covalent rhodium-rhodium sigma-bond

  4. Refractory silicides for integrated circuits

    International Nuclear Information System (INIS)

    Murarka, S.P.

    1980-01-01

    Transition metal silicides have, in the past, attracted attention because of their usefulness as high temperature materials and in integrated circuits as Schottky barrier and ohmic contacts. More recently, with the increasing silicon integrated circuits (SIC) packing density, the line widths get narrower and the sheet resistance contribution to the RC delay increases. The possibility of using low resistivity silicides, which can be formed directly on the polysilicon, makes these silicides highly attractive. The usefulness of a silicide metallization scheme for integrated circuits depends, not only on the desired low resistivity, but also on the ease with which the silicide can be formed and patterned and on the stability of the silicides throughout device processing and during actual device usage. In this paper, various properties and the formation techniques of the silicides have been reviewed. Correlations between the various properties and the metal or silicide electronic or crystallographic structure have been made to predict the more useful silicides for SIC applications. Special reference to the silicide resistivity, stress, and oxidizability during the formation and subsequent processing has been given. Various formation and etching techniques are discussed

  5. Surface morphology of erbium silicide

    International Nuclear Information System (INIS)

    Lau, S.S.; Pai, C.S.; Wu, C.S.; Kuech, T.F.; Liu, B.X.

    1982-01-01

    The surface of rare-earth silicides (Er, Tb, etc.), formed by the reaction of thin-film metal layers with a silicon substrate, is typically dominated by deep penetrating, regularly shaped pits. These pits may have a detrimental effect on the electronic performance of low Schottky barrier height diodes utilizing such silicides on n-type Si. This study suggests that contamination at the metal-Si or silicide-Si interface is the primary cause of surface pitting. Surface pits may be reduced in density or eliminated entirely through either the use of Si substrate surfaces prepared under ultrahigh vacuum conditions prior to metal deposition and silicide formation or by means of ion irradiation techniques. Silicide layers formed by these techniques possess an almost planar morphology

  6. Rhodium Catalyzed Decarbonylation

    DEFF Research Database (Denmark)

    Garcia Suárez, Eduardo José; Kahr, Klara; Riisager, Anders

    2017-01-01

    Rhodium catalyzed decarbonylation has developed significantly over the last 50 years and resulted in a wide range of reported catalyst systems and reaction protocols. Besides experimental data, literature also includes mechanistic studies incorporating Hammett methods, analysis of kinetic isotope...

  7. Rhodium platings – experimental study

    OpenAIRE

    Rudolf, R.; Budić, B.; Stamenković, D.; Čolić, M.; Ivanič, A.; Kosec, B.

    2013-01-01

    Modern rhodium plating solutions are based on either sulphate or phosphate. Although in theory there are four possible combinations, in practice only three different rhodium electrolytes are used. These are based on dilutions of rhodium sulphate or phosphate concentrates with added sulphuric or phosphoric acid. These processes are be discussed in this paper with a demonstration of Rh platings in the Slovenian firm Zlatarna Celje d.d.

  8. Rhodium platings – experimental study

    Directory of Open Access Journals (Sweden)

    R. Rudolf

    2013-07-01

    Full Text Available Modern rhodium plating solutions are based on either sulphate or phosphate. Although in theory there are four possible combinations, in practice only three different rhodium electrolytes are used. These are based on dilutions of rhodium sulphate or phosphate concentrates with added sulphuric or phosphoric acid. These processes are be discussed in this paper with a demonstration of Rh platings in the Slovenian firm Zlatarna Celje d.d.

  9. High temperature structural silicides

    International Nuclear Information System (INIS)

    Petrovic, J.J.

    1997-01-01

    Structural silicides have important high temperature applications in oxidizing and aggressive environments. Most prominent are MoSi 2 -based materials, which are borderline ceramic-intermetallic compounds. MoSi 2 single crystals exhibit macroscopic compressive ductility at temperatures below room temperature in some orientations. Polycrystalline MoSi 2 possesses elevated temperature creep behavior which is highly sensitive to grain size. MoSi 2 -Si 3 N 4 composites show an important combination of oxidation resistance, creep resistance, and low temperature fracture toughness. Current potential applications of MoSi 2 -based materials include furnace heating elements, molten metal lances, industrial gas burners, aerospace turbine engine components, diesel engine glow plugs, and materials for glass processing

  10. Rhodium complexes as therapeutic agents.

    Science.gov (United States)

    Ma, Dik-Lung; Wang, Modi; Mao, Zhifeng; Yang, Chao; Ng, Chan-Tat; Leung, Chung-Hang

    2016-02-21

    The landscape of inorganic medicinal chemistry has been dominated by the investigation of platinum, and to a lesser extent ruthenium, complexes over the past few decades. Recently, complexes based on other metal centers such as rhodium have attracted attention due to their tunable chemical and biological properties as well as distinct mechanisms of action. This perspective highlights recent examples of rhodium complexes that show diverse biological activities against various targets, including enzymes and protein-protein interactions.

  11. Rhodium-103m generator

    International Nuclear Information System (INIS)

    Mamadaliev, N.; Levin, V.I.; Malinin, A.B.

    1978-01-01

    103 Pd separated from metal rhodium irradiated with deuterons has been used without a carrier for sup( 03m)Rh generator The generator of sup(103m)Rh is a column 6mm in diameter filled with an anionite in Cl - form (Dowex-2,8,200-400 mesh) with an adsorbed parent isotope of 103 Pd. As a result of its decay, a 103 Rh daughter isotope is accumulated, which can be washed out from the generator from time to time with a corresponding solution. To prepare the generator, 0.5g of the resin with an adsorbed 103 Pd is charged into the column containing 1g of the same resin. Washing out with 2N HCl yields more than 90% of sup(103m)Rh with a radionuclide purity of more than 99.99%

  12. Rhodium segregation in dilute silver-rhodium alloys

    International Nuclear Information System (INIS)

    Krolas, K.; Sternik, M.

    1995-01-01

    Segregation of Rh in Ag-based alloys has been studied using the perturbed angular correlation of γ-rays emitted in the nuclear decay of radioactive 111 In. The formation of impurity complexes, consisting of an 111 In probe atom and one or more Rh atoms, was observed as a function of annealing time and temperature. Rhodium atom aggregation starts at about 600 K. From the fraction of 111 In bound to isolated Rh atoms the solute rhodium atom concentration was determined. It increases with the nominal alloy concentration up to about 0.04 at.% and then it is essentially constant for the nominal Rh concentration varying between 0.1 and 0.5 at.%. The solute rhodium atom concentration is 3 times larger at the melting point than at 750 K

  13. Measurement of the hyperfine magnetic field on rhodium in chromium

    International Nuclear Information System (INIS)

    Peretto, P.; Teisseron, G.; Berthier, J.

    1978-01-01

    Hyperfine magnetic field of rhodium in a chromium matrix is studied. Anisotropy of rhodium 100 is + 0.17. Time dependence of angular correlation is given with a sample containing 145 ppm of rhodium despite the short life [fr

  14. Synthesis and characterization of the Rhodium (II) citrate complex

    International Nuclear Information System (INIS)

    Najjar, R.; Santos, F.S. dos; Seidel, W.

    1987-01-01

    The preparation and characterization of the rhodium (II) citrate is described. Rhodium citrate was prepared by reacting citric acid trihydrated (3,4 g, 16 mmols) with anhydrous rhodium acetate (0,44 g, 1 mmol). Th electronic instruments, thermogravimetric curve and spectrum of rhodium (II) citrate are analysed. (M.J.C.) [pt

  15. Reactivity of rhodium during co-deposition of rhodium and carbon

    International Nuclear Information System (INIS)

    Marot, Laurent; Steiner, Roland; De Temmerman, Gregory; Oelhafen, Peter

    2009-01-01

    The detailed characterizations of rhodium/carbon films prepared by co-deposition using a dual magnetron sputtering have been carried out on silicon substrates at room temperature. Effects of the carbon incorporated in the film on the chemical bonding state, optical reflectivity and crystallinity were investigated using XPS, reflectivity measurements, XRD and SEM. The incorporation of carbon changes the films' crystallinity and thus producing amorphous films. The reflectivity of the films decreases linearly as the rhodium concentration decreases. It is important to note that no chemical bonding was observed between rhodium and carbon whatever the deposition conditions, even at high deposition temperature. Concerning the reactivity of rhodium films with oxygen, after long term storage in air the rhodium surface is covered with a thin rhodium oxide (few nanometers). However, for these films no variation of the optical reflectivity was observed after long air storage.

  16. Room temperature ferromagnetic gadolinium silicide nanoparticles

    Science.gov (United States)

    Hadimani, Magundappa Ravi L.; Gupta, Shalabh; Harstad, Shane; Pecharsky, Vitalij; Jiles, David C.

    2018-03-06

    A particle usable as T1 and T2 contrast agents is provided. The particle is a gadolinium silicide (Gd5Si4) particle that is ferromagnetic at temperatures up to 290 K and is less than 2 .mu.m in diameter. An MRI contrast agent that includes a plurality of gadolinium silicide (Gd.sub.5Si.sub.4) particles that are less than 1 .mu.m in diameter is also provided. A method for creating gadolinium silicide (Gd5Si4) particles is also provided. The method includes the steps of providing a Gd5Si4 bulk alloy; grinding the Gd5Si4 bulk alloy into a powder; and milling the Gd5Si4 bulk alloy powder for a time of approximately 20 minutes or less.

  17. Reprocessing of LEU silicide fuel at Dounreay

    International Nuclear Information System (INIS)

    Cartwright, P.

    1996-01-01

    UKAEA have recently reprocessed two LEU silicide fuel elements in their MTR fuel reprocessing plant at Dounreay. The reprocessing was undertaken to demonstrate UKAEA's commitment to the world-wide research reactor communities future needs. Reprocessing of LEU silicide fuel is seen as a waste treatment process, resulting in the production of a liquid feed suitable for conditioning in a stable form of disposal. The uranium product from the reprocessing can be used as a blending feed with the HEU to produce LEU for use in the MTR cycle. (author)

  18. Rhodium(I) catalysis in olefin photoreactions

    International Nuclear Information System (INIS)

    Salomon, R.G.; El Sanadi, N.

    1975-01-01

    The photorearrangement (254 nm) of 1,5-cyclooctadiene (1) in the presence of rhodium(I) chloride to give 1,4-cyclooctadiene (4) was found by deuterium labeling to involve an intramolecular [1,3] shift of hydrogen. A rate-determining cleavage of an allylic C--H bond is indicated by a deuterium isotope effect, k/sub H//k/sub D/ = 1.55 +- 0.03 for the 1 → 4 rearrangement. The acyclic 1,5-diene, 3,3-dimethyl-1,5-hexadiene (8), rearranges in the presence of rhodium(I) chloride upon uv irradiation (254 nm) to give cis-3,3-dimethyl-1,4-hexadiene (10) and the trans isomer 11 in a 1:4 ratio, respectively. This observation supports a mechanism for the photorearrangement of olefins catalyzed by rhodium(I) involving an initial photodissociation of one of two rhodium(I) coordinated carbon-carbon double bonds. This results in an increase in the coordinative unsaturation of rhodium(I) and enhances the proclivity of this d/sub s/ metal atom toward oxidative addition of an allylic C--H bond. A eta 3 -allylrhodium hydride intermediate then gives rearranged olefin by reductive elimination. Lastly, a novel photochemical, rhodium(I) catalyzed hydrogen transfer is reported which gives cyclooctene (7) from cyclooctadienes under unprecedentedly mild conditions. (auth)

  19. Synthesis and design of silicide intermetallic materials

    Energy Technology Data Exchange (ETDEWEB)

    Petrovic, J.J.; Castro, R.G.; Butt, D.P. [Los Alamos National Lab., NM (United States)] [and others

    1997-04-01

    The overall objective of this program is to develop structural silicide-based materials with optimum combinations of elevated temperature strength/creep resistance, low temperature fracture toughness, and high temperature oxidation and corrosion resistance for applications of importance to the U.S. processing industry. A further objective is to develop silicide-based prototype industrial components. The ultimate aim of the program is to work with industry to transfer the structural silicide materials technology to the private sector in order to promote international competitiveness in the area of advanced high temperature materials and important applications in major energy-intensive U.S. processing industries. The program presently has a number of developing industrial connections, including a CRADA with Schuller International Inc. targeted at the area of MoSi{sub 2}-based high temperature materials and components for fiberglass melting and processing applications. The authors are also developing an interaction with the Institute of Gas Technology (IGT) to develop silicides for high temperature radiant gas burner applications, for the glass and other industries. Current experimental emphasis is on the development and characterization of MoSi{sub 2}-Si{sub 3}N{sub 4} and MoSi{sub 2}-SiC composites, the plasma spraying of MoSi{sub 2}-based materials, and the joining of MoSi{sub 2} materials to metals.

  20. Quantification of Rhodium in a Series of Inorganic and ...

    African Journals Online (AJOL)

    NICO

    ... such as rhodium hydridocarbonyl tristriphenylphosphine, [HRh(CO)(PPh3)3], .... The selection of the most suitable wavelengths for rhodium, yttrium and cobalt ... chloride ions were removed from the CRM samples as chlorine gas with the ...

  1. Preparation of rhodium target for cyclone-30 accelerator

    International Nuclear Information System (INIS)

    Deng Xuesong; Li Dakang; Xie Xiangqian; Li Chao

    2002-01-01

    The rhodium target for Cyclone-30 accelerator is prepared by pulse electroplating method. The effects of pulse parameters, rhodium concentration, acidity and temperature on the properties of the target layer are studied, and the optimal process is determined. The rhodium target, mass thickness is more than 150 mg/cm 2 , adapts to producing 103 Pd on Cyclone-30 accelerator

  2. Irradiation behavior of miniature experimental uranium silicide fuel plates

    International Nuclear Information System (INIS)

    Hofman, G.L.; Neimark, L.A.; Mattas, R.F.

    1983-01-01

    Uranium silicides, because of their relatively high uranium density, were selected as candidate dispersion fuels for the higher fuel densities required in the Reduced Enrichment Research and Test Reactor (RERTR) Program. Irradiation experience with this type of fuel, however, was limited to relatively modest fission densities in the bulk from, on the order of 7 x 10 20 cm -3 , far short of the approximately 20 x 10 20 cm -3 goal established for the RERTR program. The purpose of the irradiation experiments on silicide fuels on the ORR, therefore, was to investigate the intrinsic irradiation behavior of uranium silicide as a dispersion fuel. Of particular interest was the interaction between the silicide particles and the aluminum matrix, the swelling behavior of the silicide particles, and the maximum volume fraction of silicide particles that could be contained in the aluminum matrix

  3. Palladium silicide - a new contact for semiconductor radiation detectors

    International Nuclear Information System (INIS)

    Totterdell, D.H.J.

    1981-11-01

    Silicide layers can be used as low resistance contacts in semiconductor devices. The formation of a metal rich palladium silicide Pd 2 Si is discussed. A palladium film 100A thick is deposited at 300 0 C and the resulting silicide layer used as an ohmic contact in an n + p silicon detector. This rugged contact has electrical characteristics comparable with existing evaporated gold contacts and enables the use of more reproducible bonding techniques. (author)

  4. Solvent extraction studies of RERTR silicide fuels

    International Nuclear Information System (INIS)

    Gouge, Anthony P.

    1983-01-01

    Uranium silicide fuels, which are candidate RERTR fuel compositions, may require special considerations in solvent extraction reprocessing. Since Savannah River Plant may be reprocessing RERTR fuels as early as 1985, studies have been conducted at Savannah River Laboratory to demonstrate the solvent extraction behavior of this fuel. Results of solvent extraction studies with both unirradiated and irradiated fuel are presented along with the preliminary RERTR solvent extraction reprocessing flow sheet for Savannah River Plant. (author)

  5. Uranium silicide activities at Babcock and Wilcox

    International Nuclear Information System (INIS)

    Noel, W.W.; Freim, J.B.

    1983-01-01

    Babcock and Wilcox, Naval Nuclear Fuel Division (NNFD) in conjunction with Argonne National Laboratory (ANL) is actively involved in the Reduced Enrichment Research Test Reactor (RERTR) Program to produce low enriched fuel elements for research reactors. B and W and ANL have undertaken a joint effort in which NNFD will fabricate two low enriched uranium (LEU), Oak Ridge Reactor (ORR) elements with uranium silicide fuel furnished by ANL. These elements are being fabricated for irradiation testing at Oak Ridge National Laboratory (ORNL). Concurrently with this program, NNFD is developing and implementing the uranium silicide and uranium aluminide fuel fabrication technology. NNFD is fabricating the uranium silicide ORR elements in a two-phase program, Development and Production. To summarize: 1. Full size fuel plates can be made with U 3 SiAl but the fabricator must prevent oxidation of the compact prior to hot roll bonding; 2. Providing the ANL U 3 Si x irradiation results are successful, NNFD plans to provide two ORR elements during February 1983; 3. NNFD is developing and implementing U 3 Si x and UAI x fuel fabrication technology to be operational in 1983; 4. NNFD can supply U 3 O 8 high enriched uranium (HEU) or low enriched uranium (LEU) research reactor elements; 5. NNFD is capable of providing high quality, cost competitive LEU or HEU research reactor elements to meet the needs of the customer

  6. Room temperature ferromagnetic gadolinium silicide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hadimani, Magundappa Ravi L.; Gupta, Shalabh; Harstad, Shane; Pecharsky, Vitalij; Jiles, David C.

    2018-03-06

    A particle usable as T1 and T2 contrast agents is provided. The particle is a gadolinium silicide (Gd5Si4) particle that is ferromagnetic at temperatures up to 290 K and is less than 2 .mu.m in diameter. An MRI contrast agent that includes a plurality of gadolinium silicide (Gd.sub.5Si.sub.4) particles that are less than 1 .mu.m in diameter is also provided. A method for creating gadolinium silicide (Gd5Si4) particles is also provided. The method includes the steps of providing a Gd5Si4 bulk alloy; grinding the Gd5Si4 bulk alloy into a powder; and milling the Gd5Si4 bulk alloy powder for a time of approximately 20 minutes or less.

  7. Line profile analyses of rhodium metal obtained by decomposition of rhodium carbonyl

    International Nuclear Information System (INIS)

    Chandra, D.; Mandalia, H.; Garner, M.L.; Blakely, M.K.; Lau, K.H.

    1995-01-01

    Metal carbonyls are important for chemical vapor deposition (CVD) of metals and alloys and formation of high surface area metallic particles which have potential applications as catalysts. Rhodium carbonyl [Rh 6 (CO) 16 ] produces high surface area metallic particles whose structure has been reported as monoclinic (I2/a) with lattice dimensions, a=17.00(±0.03)Angstrom, b=9.78(±0.02)Angstrom, c=17.53(±0.03)Angstrom and Β=121 degrees 45' ± 30' at room temperature. Generally, metal carbonyl crystals dissociate under vacuum as carbonyl gas and decompose to metallic crystals and carbon monoxide at higher temperatures. However, the behavior of rhodium carbonyl crystals is different; they decompose directly to metallic rhodium without the formation of rhodium carbonyl gas in vacuum. Several residual fine grains of rhodium metal are found after the decomposition in vacuum at relatively low temperatures. The metallic samples of rhodium were obtained from vapor pressure experiments using torsion Knudsen-effusion apparatus. X-ray diffraction analyses performed on these gains showed severely broadened Bragg reflections indicative of small particle size and/or lattice microgram. In this study, a comparison of lattice strains and domain sizes obtained by integral breadth and Fourier methods has been made. In addition a comparison of the lattice strains and domain sizes has been made between the Cauchy, Gaussian, Cauchy-Gaussian and Aqua integral breadth methods

  8. Superconductivity in zirconium-rhodium alloys

    Science.gov (United States)

    Zegler, S. T.

    1969-01-01

    Metallographic studies and transition temperature measurements were made with isothermally annealed and water-quenched zirconium-rhodium alloys. The results clarify both the solid-state phase relations at the Zr-rich end of the Zr-Rh alloy system and the influence upon the superconducting transition temperature of structure and composition.

  9. Rhodium-Catalyzed Decarbonylation of Aldoses

    DEFF Research Database (Denmark)

    Monrad, Rune; Madsen, Robert

    2007-01-01

    A catalytic procedure is described for decarbonylation of unprotected aldoses to afford alditols with one less carbon atom. The reaction is performed with the rhodium complex Rh(dppp)2Cl in a refluxing diglyme - DMA solution. A slightly improved catalyst turnover is observed when a catalytic amount...

  10. Correction of rhodium detector signals for comparison to design calculations

    International Nuclear Information System (INIS)

    Judd, J.L.; Chang, R.Y.; Gabel, C.W.

    1989-01-01

    Rhodium detectors are used in many commercial pressurized water reactors PWRs [pressurized water reactor] as in-core neutron detectors. The signals from the detectors are the result of neutron absorption in 103 Rh and the subsequent beta decay of 104 Rh to 104 Pd. The rhodium depletes ∼1% per full-power month, so corrections are necessary to the detector signal to account for the effects of the rhodium depletion. These corrections result from the change in detector self-shielding with rhodium burnup and the change in rhodium concentration itself. Correction for the change in rhodium concentration is done by multiplication of the factor N(t)/N 0 , where N(t) is the rhodium concentration at time t and N 0 is the initial rhodium concentration. The calculation of the self-shielding factor is more complicated and is presented. A self-shielding factor based on the fraction of rhodium remaining was calculated with the CASMO-3 code. The results obtained from our comparisons of predicted and measured in-core detector signals show that the CASMO-3/SIMULATE-3 code package is an effective tool for estimating pin peaking and power distributions

  11. Reaction pathways for reduction of nitrate ions on platinum, rhodium, and platinum-rhodium alloy electrodes

    International Nuclear Information System (INIS)

    Cunha, M.C.P.M. da; De Souza, J.P.I.; Nart, F.C.

    2000-01-01

    The reduction of nitrate ions on platinum, rhodium, and platinum-rhodium alloy electrodes has been investigated using differential electrochemical mass spectrometry and in situ FTIR measurements. For 3 M HNO 3 concentration it has been found that nitrate starts the reduction with partial N-O bond dissociation and N-N bond formation generating NO and N 2 O. At potentials lower than 0.2 V the reaction proceeds forming dissolved NH 4 + . For potentials lower than 0 V the reduction continues via a multiple pathway reaction leading to the nonselective production of N 2 , NH 2 OH, and N 2 H 2 . On the alloyed electrodes, the production of NO and N 2 O has been observed in both cathodic and anodic scans, while on pure platinum and rhodium electrodes the reaction has been observed only during the cathodic scan. Contrasting with the pure platinum and rhodium alloys, where the N-O bond break starts forming NO and N 2 O, on the alloys HNO 2 has been observed as the first reaction step. For alloys with higher rhodium composition, like Pt 75 Rh 25 , no N 2 has been detected for potentials lower than 0 V

  12. Investigation into cathode polarization during deposition of rhodium-nickel and rhodium-indium alloys

    International Nuclear Information System (INIS)

    Evdokimova, N.V.; Byacheslavov, P.M.; Lokshtanova, O.G.

    1979-01-01

    The results of kinetic regularities experimental investigations during electrodeposition of rhodium-nickel and rhonium-indium alloys are presented. Methods of general and partial polarization curves have been used to show the nature of polarization during the rhonium-nickel and rhodium-indium alloys deposition. It is shown that indium into the rhodium-indium alloy and nickel into the rhodium-nickel alloy deposit with great depolarization ( PHIsub(In)sup(0)=-0.33B, PHIsub(Ni)sup(0)=-0.23B). Indium and nickel in pure form do not deposit from the electrolytes of the given composition (H 2 SO 4 - 50 g/l, HNH 2 SO 3 -10 g/l). The recalculation of partial polarization curve of indium precipitation into the rhodium-indium alloy in the mixed kinetics coordinates gives a straight line with 40 mV inclination angle. This corresponds to the delayed stage of the second electron addition with the imposition of diffusion limitations

  13. Molybdenum silicide based materials and their properties

    International Nuclear Information System (INIS)

    Yao, Z.; Stiglich, J.; Sudarshan, T.S.

    1999-01-01

    Molybdenum disilicide (MoSi 2 ) is a promising candidate material for high temperature structural applications. It is a high melting point (2030 C) material with excellent oxidation resistance and a moderate density (6.24 g/cm 3 ). However, low toughness at low temperatures and high creep rates at elevated temperatures have hindered its commercialization in structural applications. Much effort has been invested in MoSi 2 composites as alternatives to pure molybdenum disilicide for oxidizing and aggressive environments. Molybdenum disilicide-based heating elements have been used extensively in high-temperature furnaces. The low electrical resistance of silicides in combination with high thermal stability, electron-migration resistance, and excellent diffusion-barrier characteristics is important for microelectronic applications. Projected applications of MoSi 2 -based materials include turbine airfoils, combustion chamber components in oxidizing environments, missile nozzles, molten metal lances, industrial gas burners, diesel engine glow plugs, and materials for glass processing. On this paper, synthesis, fabrication, and properties of the monolithic and composite molybdenum silicides are reviewed

  14. Distribution of Rhodium in Mice Submitted to Treatment With the Adduct of Rhodium Propionate and Sodium Isonicotinate

    OpenAIRE

    de Souza, Aparecido Ribeiro; Najjar, Renato; de Oliveira, Elizabeth; Zyngier, Szulim Ber

    1997-01-01

    The distribution of rhodium in Balb/c mice following intraperitoneal (ip) administration of a solution of adduct of rhodium propionate and sodium isonicotinate has been investigated. The metal concentration was determined in blood and in the following organ tissues: brain, heart, lung, liver, spleen, kidney, testes, and uterus/ovary, and the rhodium concentration was obtained by Inductively Coupled Argon Atomic Emission Spectroscopy (ICP-AES). The metal was detected in all organ tissues exami...

  15. Subsurface contributions in epitaxial rare-earth silicides

    Energy Technology Data Exchange (ETDEWEB)

    Luebben, Olaf; Shvets, Igor V. [Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), School of Physics, Trinity College, Dublin (Ireland); Cerda, Jorge I. [Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, Cantoblanco, Madrid (Spain); Chaika, Alexander N. [Institute of Solid State Physics, RAS, Chernogolovka (Russian Federation)

    2015-07-01

    Metallic thin films of heavy rare-earth silicides epitaxially grown on Si(111) substrates have been widely studied in recent years because of their appealing properties: unusually low values of the Schottky barrier height, an abrupt interface, and a small lattice mismatch. Previous studies also showed that these silicides present very similar atomic and electronic structures. Here, we examine one of these silicides (Gd{sub 3}Si{sub 5}) using scanning tunneling microscopy (STM) image simulations that go beyond the Tersoff-Hamann approach. These simulations strongly indicate an unusual STM depth sensitivity for this system.

  16. Production of Mo-99 using low-enriched uranium silicide

    International Nuclear Information System (INIS)

    Hutter, J.C.; Srinivasan, B.; Vicek, M.; Vandegrift, G.F.

    1994-01-01

    Over the last several years, uranium silicide fuels have been under development as low-enriched uranium (LEU) targets for Mo-99. The use of LEU silicide is aimed at replacing the UAl x alloy in the highly-enriched uranium dissolution process. A process to recover Mo-99 from low-enriched uranium silicide is being developed at Argonne National Laboratory. The uranium silicide is dissolved in alkaline hydrogen peroxide. Experiments performed to determine the optimum dissolution procedure are discussed, and the results of dissolving a portion of a high-burnup (>40%) U 3 Si 2 miniplate are presented. Future work related to Mo-99 separation and waste disposal are also discussed

  17. Rare earth silicide nanowires on silicon surfaces

    International Nuclear Information System (INIS)

    Wanke, Martina

    2008-01-01

    The growth, structure and electronic properties of rare earth silicide nanowires are investigated on planar and vicinal Si(001) und Si(111) surfaces with scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and angle-resolved photoelectron spectroscopy (ARPES). On all surfaces investigated within this work hexagonal disilicides are grown epitaxially with a lattice mismatch of -2.55% up to +0.83% along the hexagonal a-axis. Along the hexagonal c-axis the lattice mismatch is essentially larger with 6.5%. On the Si(001)2 x 1 surface two types of nanowires are grown epitaxially. The socalled broad wires show a one-dimensional metallic valence band structure with states crossing the Fermi level. Along the nanowires two strongly dispersing states at the anti J point and a strongly dispersing state at the anti Γ point can be observed. Along the thin nanowires dispersing states could not be observed. Merely in the direction perpendicular to the wires an intensity variation could be observed, which corresponds to the observed spacial structure of the thin nanowires. The electronic properties of the broad erbium silicide nanowires are very similar to the broad dysprosium silicide nanowires. The electronic properties of the DySi 2 -monolayer and the Dy 3 Si 5 -multilayer on the Si(111) surface are investigated in comparison to the known ErSi 2 /Si(111) and Er 3 Si 5 /Si(111) system. The positions and the energetic locations of the observed band in the surface Brillouin zone will be confirmed for dysprosium. The shape of the electron pockets in the vector k parallel space is elliptical at the anti M points, while the hole pocket at the anti Γ point is showing a hexagonal symmetry. On the Si(557) surface the structural and electronic properties depend strongly on the different preparation conditions likewise, in particular on the rare earth coverage. At submonolayer coverage the thin nanowires grow in wide areas of the sample surface, which are oriented

  18. Far-infrared spectroscopy of thermally annealed tungsten silicide films

    International Nuclear Information System (INIS)

    Amiotti, M.; Borghesi, A.; Guizzetti, G.; Nava, F.; Santoro, G.

    1991-01-01

    The far-infrared transmittance spectrum of tungsten silicide has been observed for the first time. WSi 2 polycrystalline films were prepared by coevaporation and chemical-vapour deposition on silicon wafers, and subsequently thermally annealed at different temperatures. The observed structures are interpreted, on the basis of the symmetry properties of the crystal, such as infrared-active vibrational modes. Moreover, the marked lineshape dependence on annealing temperature enables this technique to analyse the formation of the solid silicide phases

  19. Hydroformylation of methyl oleate catalyzed by rhodium complexes

    International Nuclear Information System (INIS)

    Mendes, Ana Nery Furlan; Rosa, Ricardo Gomes da; Gregorio, Jose Ribeiro

    2012-01-01

    In this work, we describe the hydroformylation of methyl oleate catalyzed by several rhodium complexes. Parameters including total pressure, phosphorous/rhodium and CO/H 2 ratio, temperature and phosphorous ligands were scanned. Total conversion of the starting double bonds was achieved while maintaining excellent selectivity in aldehydes. (author)

  20. Cyclopentadiene-mediated hydride transfer from rhodium complexes.

    Science.gov (United States)

    Pitman, C L; Finster, O N L; Miller, A J M

    2016-07-12

    Attempts to generate a proposed rhodium hydride catalytic intermediate instead resulted in isolation of (Cp*H)Rh(bpy)Cl (1), a pentamethylcyclopentadiene complex, formed by C-H bond-forming reductive elimination from the fleeting rhodium hydride. The hydride transfer ability of diene 1 was explored through thermochemistry and hydride transfer reactions, including the reduction of NAD(+).

  1. Determination of accurate metal silicide layer thickness by RBS

    International Nuclear Information System (INIS)

    Kirchhoff, J.F.; Baumann, S.M.; Evans, C.; Ward, I.; Coveney, P.

    1995-01-01

    Rutherford Backscattering Spectrometry (RBS) is a proven useful analytical tool for determining compositional information of a wide variety of materials. One of the most widely utilized applications of RBS is the study of the composition of metal silicides (MSi x ), also referred to as polycides. A key quantity obtained from an analysis of a metal silicide is the ratio of silicon to metal (Si/M). Although compositional information is very reliable in these applications, determination of metal silicide layer thickness by RBS techniques can differ from true layer thicknesses by more than 40%. The cause of these differences lies in how the densities utilized in the RBS analysis are calculated. The standard RBS analysis software packages calculate layer densities by assuming each element's bulk densities weighted by the fractional atomic presence. This calculation causes large thickness discrepancies in metal silicide thicknesses because most films form into crystal structures with distinct densities. Assuming a constant layer density for a full spectrum of Si/M values for metal silicide samples improves layer thickness determination but ignores the underlying physics of the films. We will present results of RBS determination of the thickness various metal silicide films with a range of Si/M values using a physically accurate model for the calculation of layer densities. The thicknesses are compared to scanning electron microscopy (SEM) cross-section micrographs. We have also developed supporting software that incorporates these calculations into routine analyses. (orig.)

  2. Recent Advances in Nb-silicide in-situ composites

    International Nuclear Information System (INIS)

    Bewlay, B.P.; Jackson, M.R.; Subramanian, P.R.; Briant, C.L.

    2001-01-01

    In-situ composites based on Nb silicides have great potential for future high-temperature applications. These Nb-silicide composites combine a ductile Nb-based matrix with high-strength silicides. With the appropriate combination of alloying elements, such as Ti, Hf, Cr, AI, it is possible to achieve a promising balance of fracture toughness, high-temperature creep performance, and oxidation resistance. This paper will describe the effect of volume fraction of silicide on microstructure, high-temperature creep performance, and oxidation resistance. The ratio of Nb:(W+Ti) is critical in determining both creep rate and oxidation performance. If this ratio goes below ∼1.5, the creep rate increases substantially. In more complex silicide-based systems, other intermetallics, such as laves phases and a boron-rich T-2 phase, are added for oxidation resistance. To understand the role of each phase on the creep resistance and oxidation performance of these composites, we determined the creep and oxidation behavior of the individual phases and composites at temperatures up to 1200 o C. These data allow quantification of the load-bearing capability of the individual phases in the Nb-silicide based in-situ composites. (author)

  3. Influence of impurities on silicide contact formation

    International Nuclear Information System (INIS)

    Kazdaev, Kh.R.; Meermanov, G.B.; Kazdaev, R.Kh.

    2002-01-01

    Research objectives of this work are to investigate the influence of light impurities implantation on peculiarities of the silicides formation in molybdenum monocrystal implanted by silicon, and in molybdenum films sputtered on silicon substrate at subsequent annealing. Implantation of the molybdenum samples was performed with silicon ions (90 keV, 5x10 17 cm -2 ). Phase identification was performed by X ray analysis with photographic method of registration. Analysis of the results has shown the formation of the molybdenum silicide Mo 3 Si at 900 deg. C. To find out the influence of impurities present in the atmosphere (C,N,O) on investigated processes we have applied combined implantation. At first, molybdenum was implanted with ions of the basic component (silicon) and then -- with impurities ions. Acceleration energies (40keV for C, 45 keV for N and 50 keV for O) were chosen to obtain the same distribution profiles for basic and impurities ions. Ion doses were 5x10 17 cm -2 for Si-ions and 5x10 16 cm -2 - for impurities. The most important results are reported here. The first, for all three kinds of impurities the decreased formation temperatures of the phase Mo 3 Si were observed; in the case of C and N it was ∼100 deg. and in the case of nitrogen - ∼200 deg. Further, simultaneously with the Mo 3 Si phase, the appearance of the rich-metal phase Mo 5 Si 3 was registered (not observed in the samples without additional implantation). In case of Mo/Si-structure, the implantation of the impurities (N,O) was performed to create the peak concentration (∼4at/%) located in the middle of the molybdenum film (∼ 150nm) deposited on silicon substrate. Investigation carried out on unimplanted samples showed the formation of the silicide molybdenum MoSi 2 , observed after annealing at temperatures 900/1000 deg. C, higher than values 500-600 deg. C reported in other works. It is discovered that electrical conductivity of Mo 5 Si 3 -films synthesized after impurities

  4. Dinuclear ditertiary phosphite derivatives of rhodium

    International Nuclear Information System (INIS)

    Meintjies, E.

    1981-08-01

    The overall objective of the research described in this thesis was the design, synthesis, characterization and chemistry of dinuclear complexes of rhodium in which the metal atoms are held in close proximity to each other. Complexes of this nature are of considerable interest owing, in part, to their potential as models for multicentred metal catalysts, as well as to the highly novel and unusual chemistry already discovered for a number of them. A survey of dinuclear complexes of rhodium containing carbonyl and group V donor ligands has been presented as a background introduction to the research reported in this thesis. The coordination behaviour of the diphosphazane ligands, (RO) 2 PN(R')P(OR) 2 (R=Ph or Me, R' = Et; R = Et or Pr/i, R' = Me), and the ditertiary phosphite ligand, (EtO) 2 POP(OEt) 2 , towards certain rhodium precursors has been investigated. A number of highly unusual neutral dinuclear complexes of rhodium, in which these ligands bridge-bond the two rhodium atoms, have been synthesized. Two types of monocarbonyl decarbonylation products are observed for compounds of the type, [Rh 2 Cl 2 (CO) 2 (μ-diphosphazane) 2 ]. 1 H and 31 P[ 1 H] n.m.r. spectral studies have been carried out with the object of establishing the nature of the bridging halogen ligands in the tricarbonyl species. Asymetric zerovalent dinuclear species of the type, [Rh 2 (CO) 3 -[μ-(RO) 2 PN(R')P(OR) 2 ] 2 ] (R = Ph or Me, R' = Et; R = Pr/i, R' = Me), are obtained. A single crystal X-ray analysis has been carried out. Homoleptic cationic species are obtained by reaction of the alkoxydiphosphazane ligands with [Rh(C 8 H 12 )(solvent)(n)] + under the appropriate reaction conditions. The solution and solid-state infrared spectra and the 31 P[ 1 H] n.m.r. spectra of all new compounds synthesized in this study are discussed in terms of possible structures for these compounds. Where appropriate, the n.m.r. spectral data are also discussed in terms of fluxional behaviour

  5. Phase transformations in Higher Manganese Silicides

    Energy Technology Data Exchange (ETDEWEB)

    Allam, A. [MADIREL, UMR 7246 CNRS - Universite Aix-Marseille, av Normandie-Niemen, 13397 Marseille Cedex 20 (France); IM2NP, UMR 7334 CNRS - Universite Aix-Marseille, av Normandie-Niemen, Case 142, 13397 Marseille Cedex 20 (France); Boulet, P. [MADIREL, UMR 7246 CNRS - Universite Aix-Marseille, av Normandie-Niemen, 13397 Marseille Cedex 20 (France); Nunes, C.A. [Departamento de Engenharia de Materiais (DEMAR), Escola de Engenharia de Lorena (EEL), Universidade de Sao Paulo - USP, Caixa Postal 116, 12600-970 Lorena, Sao Paulo (Brazil); Sopousek, J.; Broz, P. [Masaryk University, Faculty of Science, Department of Chemistry, Kolarska 2, 611 37 Brno (Czech Republic); Masaryk University, Central European Institute of Technology, CEITEC, Kamenice 753/5, 625 00 Brno (Czech Republic); Record, M.-C., E-mail: m-c.record@univ-cezanne.fr [IM2NP, UMR 7334 CNRS - Universite Aix-Marseille, av Normandie-Niemen, Case 142, 13397 Marseille Cedex 20 (France)

    2013-02-25

    Highlights: Black-Right-Pointing-Pointer The phase transitions of the Higher Manganese Silicides were investigated. Black-Right-Pointing-Pointer The samples were characterised by XRD, DTA and DSC. Black-Right-Pointing-Pointer Mn{sub 27}Si{sub 47} is the stable phase at room temperature and under atmospheric pressure. Black-Right-Pointing-Pointer At around 800 Degree-Sign C, Mn{sub 27}Si{sub 47} is transformed into Mn{sub 15}Si{sub 26}. Black-Right-Pointing-Pointer The phase transition is of a second order. - Abstract: This work is an investigation of the phase transformations of the Higher Manganese Silicides in the temperature range [100-1200 Degree-Sign C]. Several complementary experimental techniques were used, namely in situ X-ray Diffraction (XRD), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC). The evolution of both the lattice parameters and the thermal expansion coefficients was determined from in situ XRD measurements. The stability of the samples was investigated by thermal analysis (DTA) and Cp measurements (DSC). This study shows that Mn{sub 27}Si{sub 47} which is the stable phase at room temperature and under atmospheric pressure undergoes a phase transformation at around 800 Degree-Sign C. Mn{sub 27}Si{sub 47} is transformed into Mn{sub 15}Si{sub 26}. This phase transformation seems to be of a second order one. Indeed it was not evidenced by DTA and by contrast it appears on the Cp curve.

  6. Analyses on Silicide Coating for LOCA Resistant Cladding

    Energy Technology Data Exchange (ETDEWEB)

    Sweidan, Faris B.; Lee, You Ho; Ryu, Ho Jin [KAIST, Daejeon (Korea, Republic of)

    2015-10-15

    A particular focus of accident-tolerant fuel has been cladding due to the rapid high-temperature oxidation of zirconium-based cladding with the evolution of H2 when steam is a reactant. Some key features of the coated cladding include high-temperature resistance to oxidation, lower processing temperatures, and a high melting point of the coating. Zirconium alloys exhibit a reasonably high melting temperature, so a coating for the cladding is appealing if the coating increases the high-temperature resistance to oxidation. In this case, the cladding is protected from complete oxidation. The cladding coating involves the application of zirconium silicide onto Zr-based cladding. Zirconium silicide coating is expected to produce a glassy layer that becomes more protective at elevated temperature. For this reason, silicide coatings on cladding offer the potential for improved reliability at normal operating temperatures and at the higher transient temperatures encountered during accidents. Although ceramic coatings are brittle and may have weak points to be used as coating materials, several ceramic coatings were successful and showed adherent behavior and high resistance to oxidation. In this study, the oxidation behavior of zirconium silicide and its oxidation kinetics are analyzed. Zirconium silicide is a new suggested material to be used as coatings on existing Zr-based cladding alloys, the aim of this study is to evaluate if zirconium silicide is applicable to be used, so they can be more rapidly developed using existing cladding technology with some modifications. These silicide coatings are an attractive alternative to the use of coatings on zirconium claddings or to the lengthy development of monolithic ceramic or ceramic composite claddings and coatings.

  7. Analyses on Silicide Coating for LOCA Resistant Cladding

    International Nuclear Information System (INIS)

    Sweidan, Faris B.; Lee, You Ho; Ryu, Ho Jin

    2015-01-01

    A particular focus of accident-tolerant fuel has been cladding due to the rapid high-temperature oxidation of zirconium-based cladding with the evolution of H2 when steam is a reactant. Some key features of the coated cladding include high-temperature resistance to oxidation, lower processing temperatures, and a high melting point of the coating. Zirconium alloys exhibit a reasonably high melting temperature, so a coating for the cladding is appealing if the coating increases the high-temperature resistance to oxidation. In this case, the cladding is protected from complete oxidation. The cladding coating involves the application of zirconium silicide onto Zr-based cladding. Zirconium silicide coating is expected to produce a glassy layer that becomes more protective at elevated temperature. For this reason, silicide coatings on cladding offer the potential for improved reliability at normal operating temperatures and at the higher transient temperatures encountered during accidents. Although ceramic coatings are brittle and may have weak points to be used as coating materials, several ceramic coatings were successful and showed adherent behavior and high resistance to oxidation. In this study, the oxidation behavior of zirconium silicide and its oxidation kinetics are analyzed. Zirconium silicide is a new suggested material to be used as coatings on existing Zr-based cladding alloys, the aim of this study is to evaluate if zirconium silicide is applicable to be used, so they can be more rapidly developed using existing cladding technology with some modifications. These silicide coatings are an attractive alternative to the use of coatings on zirconium claddings or to the lengthy development of monolithic ceramic or ceramic composite claddings and coatings

  8. Rare earth silicide nanowires on silicon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wanke, Martina

    2008-11-10

    The growth, structure and electronic properties of rare earth silicide nanowires are investigated on planar and vicinal Si(001) und Si(111) surfaces with scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and angle-resolved photoelectron spectroscopy (ARPES). On all surfaces investigated within this work hexagonal disilicides are grown epitaxially with a lattice mismatch of -2.55% up to +0.83% along the hexagonal a-axis. Along the hexagonal c-axis the lattice mismatch is essentially larger with 6.5%. On the Si(001)2 x 1 surface two types of nanowires are grown epitaxially. The socalled broad wires show a one-dimensional metallic valence band structure with states crossing the Fermi level. Along the nanowires two strongly dispersing states at the anti J point and a strongly dispersing state at the anti {gamma} point can be observed. Along the thin nanowires dispersing states could not be observed. Merely in the direction perpendicular to the wires an intensity variation could be observed, which corresponds to the observed spacial structure of the thin nanowires. The electronic properties of the broad erbium silicide nanowires are very similar to the broad dysprosium silicide nanowires. The electronic properties of the DySi{sub 2}-monolayer and the Dy{sub 3}Si{sub 5}-multilayer on the Si(111) surface are investigated in comparison to the known ErSi{sub 2}/Si(111) and Er{sub 3}Si{sub 5}/Si(111) system. The positions and the energetic locations of the observed band in the surface Brillouin zone will be confirmed for dysprosium. The shape of the electron pockets in the (vector)k {sub parallel} space is elliptical at the anti M points, while the hole pocket at the anti {gamma} point is showing a hexagonal symmetry. On the Si(557) surface the structural and electronic properties depend strongly on the different preparation conditions likewise, in particular on the rare earth coverage. At submonolayer coverage the thin nanowires grow in wide areas

  9. Relaxation of polarized nuclei in superconducting rhodium

    DEFF Research Database (Denmark)

    Knuuttila, T.A.; Tuoriniemi, J.T.; Lefmann, K.

    2000-01-01

    Nuclear spin lattice relaxation rates were measured in normal and superconducting (sc) rhodium with nuclear polarizations up to p = 0.55. This was sufficient to influence the sc state of Rh, whose T, and B-c, are exceptionally low. Because B-c ... is unchanged, the nuclear spin entropy was fully sustained across the sc transition. The relaxation in the sc state was slower at all temperatures without the coherence enhancement close to T-c. Nonzero nuclear polarization strongly reduced the difference between the relaxation rates in the sc and normal...

  10. Adhesion of rhodium films on metallic substrates

    International Nuclear Information System (INIS)

    Marot, L.; Covarel, G.; Tuilier, M.-H.; Steiner, R.; Oelhafen, P.

    2008-01-01

    Rhodium coated metallic films were prepared by magnetron sputtering on metallic substrates. All films were elaborated in same conditions on copper, molybdenum and stainless steel. Adhesion strength tests were carried out by scratch test. The results reveal that the adhesion strength between the film and the substrate is influenced by the hardness of the substrate. Increase of deposition temperature improves the adhesion of the coating. In addition, pre-treatment of substrates by a filtered cathodic vacuum arc and the layer thickness have has some effects on the final adhesion strength

  11. Adhesion of rhodium films on metallic substrates

    Energy Technology Data Exchange (ETDEWEB)

    Marot, L. [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)], E-mail: laurent.marot@unibas.ch; Covarel, G.; Tuilier, M.-H. [Laboratoire Mecanique, Materiaux et Procedes de Fabrication, Pole STIC-SPI-Math 61 rue Albert Camus, Universite de Haute-Alsace, F-68093 - Mulhouse Cedex (France); Steiner, R.; Oelhafen, P. [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)

    2008-09-01

    Rhodium coated metallic films were prepared by magnetron sputtering on metallic substrates. All films were elaborated in same conditions on copper, molybdenum and stainless steel. Adhesion strength tests were carried out by scratch test. The results reveal that the adhesion strength between the film and the substrate is influenced by the hardness of the substrate. Increase of deposition temperature improves the adhesion of the coating. In addition, pre-treatment of substrates by a filtered cathodic vacuum arc and the layer thickness have has some effects on the final adhesion strength.

  12. Irradiation behavior of experimental miniature uranium silicide fuel plates

    International Nuclear Information System (INIS)

    Hofman, Gerard L.; Neimark, L.A.; Mattas, R.F.

    1983-01-01

    Uranium silicides, because of their relatively high uranium density, were selected as candidate dispersion fuels for the higher fuel densities required in the Reduced Enrichment Research and Test Reactor (RERTR) Program. Irradiation experience with this type of fuel, however, was limited to relatively modest fission densities in the bulk form, on the order of 7 x 10 20 cm -3 , far short of he approximately 20 x 10 20 cm -3 goal established for the RERTR Program. The purpose of the irradiation experiments on silicide fuels in the ORR, therefore, was to investigate the intrinsic irradiation behavior of uranium silicide as a dispersion fuel. Of particular interest was the interaction between the silicide particles and the aluminum matrix, the swelling behavior of the silicide particles, and the maximum volume fraction of silicide particles that could be contained in the aluminum matrix. The first group of experimental 'mini' fuel plates have recently reached the program's goal burnup and are in various stages of examination. Although the results to date indicate some limitations, it appears that within the range of parameters examined thus far the uranium silicide dispersion holds promise for satisfying most of the needs of the RERTR Program. The twelve experimental silicide dispersion fuel plates that were irradiated to approximately their goal exposure show the 30-vol % U 3 Si-Al plates to be in a stage of relatively rapid fission-gas-driven swelling at a fission density of 2 x 10 20 cm -3 . This fuel swelling will likely result in unacceptably large plate-thickness increases. The U 3 Si plates appear to be superior in this respect; however, they, too, are starting to move into the rapid fuel-swelling stage. Analysis of the currently available post irradiation data indicates that a 40-vol % dispersed fuel may offer an acceptable margin to the onset of unstable thickness changes at exposures of 2 x 10 21 fission/cm 3 . The interdiffusion between fuel and matrix

  13. Electronic and magnetic properties of ultrathin rhodium nanowires

    CERN Document Server

    Wang Bao Lin; Ren-Yun; Sun Hou Qian; Chen Xiao Shuang; Zhao Ji Jun

    2003-01-01

    The structures of ultrathin rhodium nanowires are studied using empirical molecular dynamics simulations with a genetic algorithm. Helical multishell cylindrical and pentagonal packing structures are found. The electronic and magnetic properties of the rhodium nanowires are calculated using an spd tight-binding Hamiltonian in the unrestricted Hartree-Fock approximation. The average magnetic moment and electronic density of states are obtained. Our results indicate that the electronic and magnetic properties of the rhodium nanowires depend not only on the size of the wire but also on the atomic structure. In particular, centred pentagonal and hexagonal structures can be unusually ferromagnetic.

  14. Ferromagnetic properties of manganese doped iron silicide

    Science.gov (United States)

    Ruiz-Reyes, Angel; Fonseca, Luis F.; Sabirianov, Renat

    We report the synthesis of high quality Iron silicide (FeSi) nanowires via Chemical Vapor Deposition (CVD). The materials exhibits excellent magnetic response at room temperature, especially when doped with manganese showing values of 2.0 X 10-04 emu for the FexMnySi nanowires. SEM and TEM characterization indicates that the synthesized nanowires have a diameter of approximately 80nm. MFM measurements present a clear description of the magnetic domains when the nanowires are doped with manganese. Electron Diffraction and XRD measurements confirms that the nanowires are single crystal forming a simple cubic structure with space group P213. First-principle calculations were performed on (111) FeSi surface using the Vienna ab initio simulation package (VASP). The exchange correlations were treated under the Ceperley-Alder (CA) local density approximation (LDA). The Brillouin Zone was sampled with 8x8x1 k-point grid. A total magnetic moment of about 10 μB was obtained for three different surface configuration in which the Iron atom nearest to the surface present the higher magnetization. To study the effect of Mn doping, Fe atom was replaced for a Mn. Stronger magnetization is presented when the Mn atom is close to the surface. The exchange coupling constant have been evaluated calculating the energy difference between the ferromagnetic and anti-ferromagnetic configurations.

  15. Submicron Features in Higher Manganese Silicide

    Directory of Open Access Journals (Sweden)

    Yatir Sadia

    2013-01-01

    Full Text Available The world energy crisis had increased the demand for alternative energy sources and as such is one of the topics at the forefront of research. One way for reducing energy consumption is by thermoelectricity. Thermoelectric effects enable direct conversion of thermal into electrical energy. Higher manganese silicide (HMS, MnSi1.75 is one of the promising materials for applications in the field of thermoelectricity. The abundance and low cost of the elements, combined with good thermoelectric properties and high mechanical and chemical stability at high temperatures, make it very attractive for thermoelectric applications. Recent studies have shown that Si-rich HMS has improved thermoelectric properties. The most interesting of which is the unusual reduction in thermal conductivity. In the current research, transmission (TEM and scanning (SEM electron microscopy as well as X-ray diffraction methods were applied for investigation of the govern mechanisms resulting in very low thermal conductivity values of an Si-rich HMS composition, following arc melting and hot-pressing procedures. In this paper, it is shown that there is a presence of sub-micron dislocations walls, stacking faults, and silicon and HMS precipitates inside each other apparent in the matrix, following a high temperature (0.9 Tm hot pressing for an hour. These are not just responsible for the low thermal conductivity values observed but also indicate the ability to create complicate nano-structures that will last during the production process and possibly during the application.

  16. Nickel silicide formation in silicon implanted nickel

    Science.gov (United States)

    Rao, Z.; Williams, J. S.; Pogany, A. P.; Sood, D. K.; Collins, G. A.

    1995-04-01

    Nickel silicide formation during the annealing of very high dose (≥4.5×1017 ions/cm2) Si implanted Ni has been investigated, using ion beam analytical techniques, electron microscopy, and x-ray diffraction analysis. An initial amorphous Si-Ni alloy, formed as a result of high dose ion implantation, first crystallized to Ni2Si upon annealing in the temperature region of 200-300 °C. This was followed by the formation of Ni5Si2 in the temperature region of 300-400 °C and then by Ni3Si at 400-600 °C. The Ni3Si layer was found to have an epitaxial relationship with the substrate Ni, which was determined as Ni3Si∥Ni and Ni3Si∥Ni for Ni(100) samples. The minimum channeling yield in the 2 MeV He Rutherford backscattering and channeling spectra of this epitaxial layer improved with higher annealing temperatures up to 600 °C, and reached a best value measured at about 8%. However, the epitaxial Ni3Si dissolved after long time annealing at 600 °C or annealing at higher temperatures to liberate soluble Si into the Ni substrate. The epitaxy is attributed to the excellent lattice match between the Ni3Si and the Ni. The annealing behavior follows the predictions of the Ni-Si phase diagram for this nickel-rich binary system.

  17. Characterization of uranium silicide powder using XRD

    International Nuclear Information System (INIS)

    Garcia, Rafael H.L.; Saliba-Silva, Adonis M.; Carvalho, Elita F.U.; Lima, Nelson B.; Ichikawa, Rodrigo U.; Martinez, Luiz G.

    2013-01-01

    Uranium silicide (U 3 Si 2 ) is an intermetallic used as nuclear fuel in most modern MTR - Materials Test Reactor. Dispersed in aluminum, this fuel allows high uranium densities, up to 4.8 gU/cm 3 . At IPEN, the fabrication of fuel elements based on U 3 Si 2 for the IEA-R1 reactor is carried out in the Nuclear Fuel Center (CCN), by vacuum induction melting of uranium and silicon, followed by grinding. Before employed in a nuclear reactor, U 3 Si 2 must be submitted to a strict quality control, which includes granulometry, density, X-ray radiography for dispersion homogeneity, chemical and crystallographic characterization. Concerning phase composition for a qualified fuel, the fraction of U 3 Si 2 should be higher than 80wt.%. Aiming at the development of a routine methodology for quantification of phases via analysis of XRD data using the Rietved method, six samples from two production baths of CCN were submitted to X-ray diffraction. The data were analyzed using software GSAS and line profile analysis methods. The results suggest that fusion product have preferred orientation and grinding step is important for a better refinement. (author)

  18. Trace metal assay of uranium silicide fuel

    International Nuclear Information System (INIS)

    Kulkarni, M.J.; Argekar, A.A.; Thulasidas, S.K.; Dhawale, B.A.; Rajeswari, B.; Adya, V.C.; Purohit, P.J.; Neelam, G.; Bangia, T.R.; Page, A.G.; Sastry, M.D.; Iyer, R.H.

    1994-01-01

    A comprehensive trace metal assay of uranium silicide, a fuel for nuclear research reactors that employs low-enrichment uranium, is carried out by atomic spectrometry. Of the list of specification elements, 21 metallic elements are determined by a direct current (dc) arc carrier distillation technique; the rare earths yttrium and zirconium are chemically separated from the major matrix followed by a dc arc/inductively coupled argon plasma (ICP) excitation technique in atomic emission spectrometry (AES); silver is determined by electrothermal atomization-atomic absorption spectrometry (ETA-AAS) without prior chemical separation of the major matrix. Gamma radioactive tracers are used to check the recovery of rare earths during the chemical separation procedure. The detection limits for trace metallics vary in the 0.1- to 40-ppm range. The precision of the determinations as evaluated from the analysis of the synthetic sample with intermediate range analyte concentration is better than 25% relative standard deviation (RSD) for most of the elements employing dc arc-AES, while that for silver determination by ETS-AAS is 10% RSD. The precision of the determinations for four crucially important rare earths by ICP-AES is better than 3% RSD

  19. Structural properties of small rhodium clusters

    Energy Technology Data Exchange (ETDEWEB)

    Soon, Yee Yeen; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

    2015-04-24

    We report a systematic study of the structural properties of rhodium clusters at the atomistic level. A novel global-minimum search algorithm, known as parallel tempering multicanonical basin hopping plus genetic algorithm (PTMBHGA), is used to obtain the geometrical structures with lowest minima at the semi-empirical level where Gupta potential is used to describe the atomic interaction among the rhodium atoms. These structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA). The structures are optimized for different spin multiplicities. The ones with lowest energies will be taken as ground-state structures. In most cases, we observe only minor changes in the geometry and bond length of the clusters as a result of DFT-level re-optimization. Only in some limited cases, the initial geometries obtained from the PTMBHGA are modified by the re-optimization. The variation of structural properties, such as ground-state geometry, symmetry and binding energy, with respect to the cluster size is studied and agreed well with other results available in the literature.

  20. Si-Ge Nano-Structured with Tungsten Silicide Inclusions

    Science.gov (United States)

    Mackey, Jon; Sehirlioglu, Alp; Dynys, Fred

    2014-01-01

    Traditional silicon germanium high temperature thermoelectrics have potential for improvements in figure of merit via nano-structuring with a silicide phase. A second phase of nano-sized silicides can theoretically reduce the lattice component of thermal conductivity without significantly reducing the electrical conductivity. However, experimentally achieving such improvements in line with the theory is complicated by factors such as control of silicide size during sintering, dopant segregation, matrix homogeneity, and sintering kinetics. Samples are prepared using powder metallurgy techniques; including mechanochemical alloying via ball milling and spark plasma sintering for densification. In addition to microstructural development, thermal stability of thermoelectric transport properties are reported, as well as couple and device level characterization.

  1. Magnesium silicide production and silane synthesis on its basis

    International Nuclear Information System (INIS)

    Taurbaev, T.I.; Mukashev, F.A.; Manakov, S.M.; Francev, U.V.; Kalblanbekov, B.M.; Akhter, P.; Abbas, M.; Hussain, A.

    2003-01-01

    We had developed an alternative method of production of magnesium silicide with use of ferroalloys of silicon. Magnesium silicide is raw material for silane synthesis. The essence of the method consist of sintering FS -75 (ferrosilicium with 75 % of silicon and 25 % of iron, made by ferroalloy factories) with metal magnesium at temperature of 650 deg. C. The X-ray analysis has shown formation of magnesium silicide. That is further used for synthesis of silane. The output of silane is 60 % in respect of the contents of silicon. After removing the water vapors the mass-spectrometer analysis has estimated the purity of silane as 99.95 % with no detection of phosphine and diborane. (author)

  2. TiSi2 integrity within a doped silicide process step

    International Nuclear Information System (INIS)

    Crean, G.M.; Cole, P.D.; Stoemenos, J.

    1993-01-01

    Degradation of arsenic implanted titanium silicide (TiSi 2 ) thin films as a result of thermal processing for shallow junction formation is investigated. Significant arsenic diffusion from the silicide overlayer into the silicon substrate has been detected by Rutherford Backscattering Spectrometry at drive-in temperatures > 1,050 C. Cross-sectional transmission electron micrographs have shown the silicide film become increasingly non-uniform as the thermal budget increases, ultimately leading to discontinuities forming in the silicide film. This observed degradation of the titanium silicide film is also supported by sheet resistance measurements which show the film to degrade significantly above a threshold thermal budget

  3. Morphology of Si/tungsten-silicides/Si interlayers

    International Nuclear Information System (INIS)

    Theodore, N.; Secco d'Aragona, F.; Blackstone, S.

    1992-01-01

    Tungsten and tungsten-silicides are of interest for semiconductor technology because of their refractory nature, low electrical-resistivity and high electromigration-resistance. This paper presents the first formation of buried tungsten-silicide layers in silicon, by proximity adhesion. The interlayers, created by a combination of chemical vapor-deposition (CVD) and proximity-adhesion were studied using transmission electron-microscopy (TEM). The behavior of the layers in the presence and absence of an adjacent silicon-dioxide interlayer was also investigated. Buried silicide layers were successfully formed with or without the adjacent silicon-dioxide. The silicide formed continuous layers with single grains encompassing the width of the interlayer. Individual grains were globular, with cusps at grain boundaries. This caused interlayer-thicknesses to be non-uniform, with lower thickness values being present at the cusps. Occasional voids were observed at grain-boundary cusps. The voids were smaller and less frequent in the presence of an adjacent oxide-layer, due to flow of the oxide during proximity adhesion. Electron-diffraction revealed a predominance of tungsten-disilicide in the interlayers, with some free tungsten being present. Stresses in the silicide layers caused occasional glide dislocations to propagate into the silicon substrate beneath the interlayers. The dislocations propagate only ∼100 nm into the substrate and therefore should not be detrimental to use of the buried layers. Occasional precipitates were observed at the end of glide-loops. These possibly arise due to excess tungsten from the interlayer diffusion down the glide dislocation to finally precipitate out as tungsten-silicide

  4. Rhodium-Catalyzed Dehydrogenative Borylation of Cyclic Alkenes

    Science.gov (United States)

    Kondoh, Azusa; Jamison, Timothy F.

    2010-01-01

    A rhodium-catalyzed dehydrogenative borylation of cyclic alkenes is described. This reaction provides direct access to cyclic 1-alkenylboronic acid pinacol esters, useful intermediates in organic synthesis. Suzuki-Miyaura cross-coupling applications are also presented. PMID:20107646

  5. Low gravity containerless processing of immiscible gold rhodium alloys

    Science.gov (United States)

    Andrews, J. Barry

    1986-01-01

    Under normal one-g conditions immiscible alloys segregate extensively during solidification due to sedementation of the more dense of the immiscible liquid phases. However, under low-g conditions it should be possible to form a dispersion of the two immiscible liquids and maintain this dispersed structure during solidification. Immiscible (hypermonotectic) gold-rhodium alloys were processed in the Marshall Space Flight Center 105 meter drop tube in order to investigate the influence of low gravity, containerless solidification on their microstructure. Hypermonotectic alloys composed of 65 atomic % rhodium exhibited a tendency for the gold rich liquid to wet the outer surface of the containerless processed samples. This tendency led to extensive segregation in several cases. However, well dispersed microstructures consisting of 2 to 3 micron diameter rhodium-rich spheres in a gold-rich matrix were produced in 23.4 atomic % rhodium alloys. This is one of the best dispersions obtained in research on immiscible alloy-systems to data.

  6. Oxidation behavior of molybdenum silicides and their composites

    International Nuclear Information System (INIS)

    Natesan, K.; Deevi, S. C.

    2000-01-01

    A key materials issue associated with the future of high-temperature structural silicides is the resistance of these materials to oxidation at low temperatures. Oxidation tests were conducted on Mo-based silicides over a wide temperature range to evaluate the effects of alloy composition and temperature on the protective scaling characteristics and testing regime for the materials. The study included Mo 5 Si 3 alloys that contained several concentrations of B. In addition, oxidation characteristics of MoSi 2 -Si 3 N 4 composites that contained 20--80 vol.% Si 3 N 4 were evaluated at 500--1,400 C

  7. Formation of silicides in a cavity applicator microwave system

    International Nuclear Information System (INIS)

    Thompson, D.C.; Kim, H.C.; Alford, T.L.; Mayer, J.W.

    2003-01-01

    Metal silicides of nickel and cobalt are formed in a cavity applicator microwave system with a magnetron power of 1200 W and a frequency of 2.45 GHz. X-ray diffraction, Rutherford backscattering spectrometry, and four-point-probe measurements are used to identify the silicide phase present and layer thicknesses. Additional processing confirmed that the products attained from heating by microwaves do not differ appreciably from those attained in heating by thermal processes. Materials properties are used to explain microwave power absorption and demonstrate how to tailor a robust process in which thin film reactions can be attained and specific products isolated

  8. The influence of rhodium burn-up on the sensitivity of rhodium self-powered neutron detectors

    International Nuclear Information System (INIS)

    Erben, O.

    1980-01-01

    Depression and self-shielding coefficients are presented for thermal and epithermal neutron flux densities. Functions are shown describing the distribution of beta particle sources on the emitter cross section for 0 to 50% rhodium burnup. The values are calculated of detector sensitivity to thermal and epithermal neutron flux densities for the said burnup for main types of rhodium SPN detectors made by SODERN. (J.B.)

  9. Making of fission 99Mo from LEU silicide(s): A radiochemists' view

    International Nuclear Information System (INIS)

    Kolar, Z.I.; Wolterbeek, H.Th.

    2005-01-01

    The present-day industrial scale production of 99 Mo is fission based and involves thermal-neutron irradiation in research reactors of highly enriched uranium (HEU, > 20 % 235 U) containing targets, followed by radiochemical processing of the irradiated targets resulting in the final product: a 99 Mo containing chemical compound of molybdenum. In 1978 a program (RERTR) was started to develop a substitute for HEU reactor fuel i.e. a low enriched uranium (LEU, 235 U) one. In the wake of that program studies were undertaken to convert HEU into LEU based 99 Mo production. Both new targets and radiochemical treatments leading to 99 Mo compounds were proposed. One of these targets is based on LEU silicide, U 3 Si 2 . Present paper aims at comparing LEU U 3 Si 2 and LEU U 3 Si with another LEU target i.e. target material and arriving at some preferences pertaining to 99 Mo production. (author)

  10. Rhodium and Hafnium Influence on the Microstructure, Phase Composition, and Oxidation Resistance of Aluminide Coatings

    OpenAIRE

    Maryana Zagula-Yavorska; Małgorzata Wierzbińska; Jan Sieniawski

    2017-01-01

    A 0.5 μm thick layer of rhodium was deposited on the CMSX 4 superalloy by the electroplating method. The rhodium-coated superalloy was hafnized and aluminized or only aluminized using the Chemical vapour deposition method. A comparison was made of the microstructure, phase composition, and oxidation resistance of three aluminide coatings: nonmodified (a), rhodium-modified (b), and rhodium- and hafnium-modified (c). All three coatings consisted of two layers: the additive layer and the interdi...

  11. Silicide Schottky Contacts to Silicon: Screened Pinning at Defect Levels

    Energy Technology Data Exchange (ETDEWEB)

    Drummond, T.J.

    1999-03-11

    Silicide Schottky contacts can be as large as 0.955 eV (E{sub v} + 0.165 eV) on n-type silicon and as large as 1.05 eV (E{sub c} {minus} 0.07 eV) on p-type silicon. Current models of Schottky barrier formation do not provide a satisfactory explanation of occurrence of this wide variation. A model for understanding Schottky contacts via screened pinning at defect levels is presented. In the present paper it is shown that most transition metal silicides are pinned approximately 0.48 eV above the valence band by interstitial Si clusters. Rare earth disilicides pin close to the divacancy acceptor level 0.41 eV below the conduction band edge while high work function silicides of Ir and Pt pin close to the divacancy donor level 0.21 eV above the valence band edge. Selection of a particular defect pinning level depends strongly on the relative positions of the silicide work function and the defect energy level on an absolute energy scale.

  12. The electronic structure of 4d and 5d silicides

    NARCIS (Netherlands)

    Speier, W.; Kumar, L.; Sarma, D.D.; Groot, R.A. de; Fuggle, J.C.

    1989-01-01

    A systematic experimental and theoretical study of the electronic structure of stoichiometric silicides with Nb, Mo, Ta and W is presented. We have employed x-ray photoemission and bremsstrahlung isochromat spectroscopy as experimental techniques and interpreted the measured data by calculation of

  13. Neutronic design of the RSG-GAS silicide core

    Energy Technology Data Exchange (ETDEWEB)

    Sembiring, T.M.; Kuntoro, I.; Hastowo, H. [Center for Development of Research Reactor Technology National Nuclear Energy Agency BATAN, PUSPIPTEK Serpong Tangerang, 15310 (Indonesia)

    2002-07-01

    The objective of core conversion program of the RSG-GAS multipurpose reactor is to convert the fuel from oxide, U{sub 3}O{sub 8}-Al to silicide, U{sub 3}Si{sub 2}-Al. The aim of the program is to gain longer operation cycle by having, which is technically possible for silicide fuel, a higher density. Upon constraints of the existing reactor system and utilization, an optimal fuel density in amount of 3.55 g U/cc was found. This paper describes the neutronic parameter design of the silicide equilibrium core and the design of its transition cores as well. From reactivity control point of view, a modification of control rod system is also discussed. All calculations are carried out by means of diffusion codes, Batan-EQUIL-2D, Batan-2DIFF and -3DIFF. The silicide core shows that longer operation cycle of 32 full power days can be achieved without decreasing the safety criteria and utilization capabilities. (author)

  14. Texture in thin film silicides and germanides: A review

    Energy Technology Data Exchange (ETDEWEB)

    De Schutter, B., E-mail: bob.deschutter@ugent.be; De Keyser, K.; Detavernier, C. [Department of Solid State Sciences, Ghent University, Ghent (Belgium); Lavoie, C. [IBM Research Division, T.J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598 (United States)

    2016-09-15

    Silicides and germanides are compounds consisting of a metal and silicon or germanium. In the microelectronics industry, silicides are the material of choice for contacting silicon based devices (over the years, CoSi{sub 2}, C54-TiSi{sub 2}, and NiSi have been adopted), while germanides are considered as a top candidate for contacting future germanium based electronics. Since also strain engineering through the use of Si{sub 1−x}Ge{sub x} in the source/drain/gate regions of MOSFET devices is an important technique for improving device characteristics in modern Si-based microelectronics industry, a profound understanding of the formation of silicide/germanide contacts to silicon and germanium is of utmost importance. The crystallographic texture of these films, which is defined as the statistical distribution of the orientation of the grains in the film, has been the subject of scientific studies since the 1970s. Different types of texture like epitaxy, axiotaxy, fiber, or combinations thereof have been observed in such films. In recent years, it has become increasingly clear that film texture can have a profound influence on the formation and stability of silicide/germanide contacts, as it controls the type and orientation of grain boundaries (affecting diffusion and agglomeration) and the interface energy (affecting nucleation during the solid-state reaction). Furthermore, the texture also has an impact on the electrical characteristics of the contact, as the orientation and size of individual grains influences functional properties such as contact resistance and sheet resistance and will induce local variations in strain and Schottky barrier height. This review aims to give a comprehensive overview of the scientific work that has been published in the field of texture studies on thin film silicide/germanide contacts.

  15. Texture in thin film silicides and germanides: A review

    International Nuclear Information System (INIS)

    De Schutter, B.; De Keyser, K.; Detavernier, C.; Lavoie, C.

    2016-01-01

    Silicides and germanides are compounds consisting of a metal and silicon or germanium. In the microelectronics industry, silicides are the material of choice for contacting silicon based devices (over the years, CoSi_2, C54-TiSi_2, and NiSi have been adopted), while germanides are considered as a top candidate for contacting future germanium based electronics. Since also strain engineering through the use of Si_1_−_xGe_x in the source/drain/gate regions of MOSFET devices is an important technique for improving device characteristics in modern Si-based microelectronics industry, a profound understanding of the formation of silicide/germanide contacts to silicon and germanium is of utmost importance. The crystallographic texture of these films, which is defined as the statistical distribution of the orientation of the grains in the film, has been the subject of scientific studies since the 1970s. Different types of texture like epitaxy, axiotaxy, fiber, or combinations thereof have been observed in such films. In recent years, it has become increasingly clear that film texture can have a profound influence on the formation and stability of silicide/germanide contacts, as it controls the type and orientation of grain boundaries (affecting diffusion and agglomeration) and the interface energy (affecting nucleation during the solid-state reaction). Furthermore, the texture also has an impact on the electrical characteristics of the contact, as the orientation and size of individual grains influences functional properties such as contact resistance and sheet resistance and will induce local variations in strain and Schottky barrier height. This review aims to give a comprehensive overview of the scientific work that has been published in the field of texture studies on thin film silicide/germanide contacts.

  16. Texture in thin film silicides and germanides: A review

    Science.gov (United States)

    De Schutter, B.; De Keyser, K.; Lavoie, C.; Detavernier, C.

    2016-09-01

    Silicides and germanides are compounds consisting of a metal and silicon or germanium. In the microelectronics industry, silicides are the material of choice for contacting silicon based devices (over the years, CoSi2, C54-TiSi2, and NiSi have been adopted), while germanides are considered as a top candidate for contacting future germanium based electronics. Since also strain engineering through the use of Si1-xGex in the source/drain/gate regions of MOSFET devices is an important technique for improving device characteristics in modern Si-based microelectronics industry, a profound understanding of the formation of silicide/germanide contacts to silicon and germanium is of utmost importance. The crystallographic texture of these films, which is defined as the statistical distribution of the orientation of the grains in the film, has been the subject of scientific studies since the 1970s. Different types of texture like epitaxy, axiotaxy, fiber, or combinations thereof have been observed in such films. In recent years, it has become increasingly clear that film texture can have a profound influence on the formation and stability of silicide/germanide contacts, as it controls the type and orientation of grain boundaries (affecting diffusion and agglomeration) and the interface energy (affecting nucleation during the solid-state reaction). Furthermore, the texture also has an impact on the electrical characteristics of the contact, as the orientation and size of individual grains influences functional properties such as contact resistance and sheet resistance and will induce local variations in strain and Schottky barrier height. This review aims to give a comprehensive overview of the scientific work that has been published in the field of texture studies on thin film silicide/germanide contacts.

  17. About the extraction recovery of fission rhodium from radioactive wastes

    International Nuclear Information System (INIS)

    Khaperskaya, A.V.; Renard, E.V.; Koltunov, V.S.

    2000-01-01

    The report will cover a radically new approach to the problem of rhodium recovery from HLLW after the transformation of kinetically inert poly-aqua cation of trivalent rhodium (which is not recoverable by the majority known extractants) to Rh (IV) form by chemical methods. Presented are the research results of Rh (IV) extraction from nitric acid solutions by several extractants that are of considerable current use in noble metals and radiochemical industries (tri-n-butyl phosphate, di-octyl-sulphide, tri-n-octylamine, quaternary ammonium bases). High level of rhodium extraction has been found for the above extractants: for several systems, for example, tri-n-octylamine - diethyl-benzene, rhodium distribution coefficient achieves high values (10-plus), as well as the sufficient extraction kinetics. Rhodium extraction increases with a decrease of the acidity, a rise in phase mixing time and in the following series: tri-n-butyl phosphate → di-octyl-sulphide → quaternary ammonium bases → tri-n-octylamine. Rh (IV) can be easily reduced to non-extractable Rh (III) by such reductants as Fe (II), HCOOH, C 6 H 8 O 6 , NH 2 OH, N 2 H 4 et al, that may be applied for the re-extraction process. (authors)

  18. Block copolymer lithography of rhodium nanoparticles for high temperature electrocatalysis.

    Science.gov (United States)

    Boyd, David A; Hao, Yong; Li, Changyi; Goodwin, David G; Haile, Sossina M

    2013-06-25

    We present a method for forming ordered rhodium nanostructures on a solid support. The approach makes use of a block copolymer to create and assemble rhodium chloride nanoparticles from solution onto a surface; subsequent plasma and thermal processing are employed to remove the polymer and fully convert the nanostructures to metallic rhodium. Films cast from a solution of the triblock copolymer poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) dissolved in toluene with rhodium(III) chloride hydrate were capable of producing a monolayer of rhodium nanoparticles of uniform size and interparticle spacing. The nanostructures were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The electrocatalytic performance of the nanoparticles was investigated with AC impedance spectroscopy. We observed that the addition of the particles to a model solid oxide fuel cell anode provided up to a 14-fold improvement in the anode activity as evidenced by a decrease in the AC impedance resistance. Examination of the anode after electrochemical measurement revealed that the basic morphology and distribution of the particles were preserved.

  19. Evaluation of anomalies during nickel and titanium silicide formation using the effective heat of formation mode

    CSIR Research Space (South Africa)

    Pretorius, R

    1993-11-01

    Full Text Available , as well as the observed sequence of growth of different silicide phases, are not in agree- ment with thermodynamic considerations [26]. In the case of the nickel silicides Ni,Si is nearly always found to be the first... to determine how the oxygen content in the silicon affects phase formation. We also show how the anomalous behaviour of titanium and nickel silicide formation can be explained thermodynamically by using the ?effective heat...

  20. Kalman filtering for rhodium self-powered neutron detectors

    International Nuclear Information System (INIS)

    Kantrowitz, M.L.

    1988-01-01

    Rhodium self-powered neutron detectors are utilized in many pressurized water reactors to determine the neutronic behavior within the core. In order to compensate for the inherent time delay associated with the response of these detectors, a dynamic compensation algorithm is currently used in Combustion Engineering plants to reconstruct the dynamic flux signal which is being sensed by the rhodium detectors. This paper describes a new dynamic compensation algorithm, based on Kalman filtering, which improves on the noise gain and response time characteristics of the algorithm currently used, and offers the possibility of utilizing the proven rhodium detector based fixed in-core detector system as an integral part of advanced core control and/or protection systems

  1. Antagonizing STAT3 dimerization with a rhodium(III) complex.

    Science.gov (United States)

    Ma, Dik-Lung; Liu, Li-Juan; Leung, Ka-Ho; Chen, Yen-Ting; Zhong, Hai-Jing; Chan, Daniel Shiu-Hin; Wang, Hui-Min David; Leung, Chung-Hang

    2014-08-25

    Kinetically inert metal complexes have arisen as promising alternatives to existing platinum and ruthenium chemotherapeutics. Reported herein, to our knowledge, is the first example of a substitutionally inert, Group 9 organometallic compound as a direct inhibitor of signal transducer and activator of transcription 3 (STAT3) dimerization. From a series of cyclometalated rhodium(III) and iridium(III) complexes, a rhodium(III) complex emerged as a potent inhibitor of STAT3 that targeted the SH2 domain and inhibited STAT3 phosphorylation and dimerization. Significantly, the complex exhibited potent anti-tumor activities in an in vivo mouse xenograft model of melanoma. This study demonstrates that rhodium complexes may be developed as effective STAT3 inhibitors with potent anti-tumor activity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Chemical Posttranslational Modification with Designed Rhodium(II) Catalysts.

    Science.gov (United States)

    Martin, S C; Minus, M B; Ball, Z T

    2016-01-01

    Natural enzymes use molecular recognition to perform exquisitely selective transformations on nucleic acids, proteins, and natural products. Rhodium(II) catalysts mimic this selectivity, using molecular recognition to allow selective modification of proteins with a variety of functionalized diazo reagents. The rhodium catalysts and the diazo reactivity have been successfully applied to a variety of protein folds, the chemistry succeeds in complex environments such as cell lysate, and a simple protein blot method accurately assesses modification efficiency. The studies with rhodium catalysts provide a new tool to study and probe protein-binding events, as well as a new synthetic approach to protein conjugates for medical, biochemical, or materials applications. © 2016 Elsevier Inc. All rights reserved.

  3. Gas cluster ion beam assisted NiPt germano-silicide formation on SiGe

    Energy Technology Data Exchange (ETDEWEB)

    Ozcan, Ahmet S., E-mail: asozcan@us.ibm.com [IBM Almaden Research Center, 650 Harry Road, San Jose, California 95120 (United States); Lavoie, Christian; Jordan-Sweet, Jean [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, New York 10598 (United States); Alptekin, Emre; Zhu, Frank [IBM Semiconductor Research and Development Center, 2070 Route 52, Hopewell Junction, New York 12533 (United States); Leith, Allen; Pfeifer, Brian D.; LaRose, J. D.; Russell, N. M. [TEL Epion Inc., 900 Middlesex Turnpike, Bldg. 6, Billerica, Massachusetts 01821 (United States)

    2016-04-21

    We report the formation of very uniform and smooth Ni(Pt)Si on epitaxially grown SiGe using Si gas cluster ion beam treatment after metal-rich silicide formation. The gas cluster ion implantation process was optimized to infuse Si into the metal-rich silicide layer and lowered the NiSi nucleation temperature significantly according to in situ X-ray diffraction measurements. This novel method which leads to more uniform films can also be used to control silicide depth in ultra-shallow junctions, especially for high Ge containing devices, where silicidation is problematic as it leads to much rougher interfaces.

  4. A study of CoSix silicide formed by recoil implantation

    International Nuclear Information System (INIS)

    Kwok, H.L.

    1989-01-01

    This work investigated the formation of CoSi x silicides on n-Si by recoil implantation through a thin cobalt layer using an inert gas ion beam. The results suggest the formation of a very shallow (35 to 45 nm) silicide surface layer under the specific conditions of preparation. The surface layer resistivity was comparable to values reported for Co 2 Si and CoSi, although below the surface, the resistivity decreased. This appeared to suggest a change-over from cobalt-rich silicides near the surface to a more conducting silicide (CoSi 2 ) at the interface. (author)

  5. Analysis of reactivity accidents of the RSG-GAS core with silicide fuel

    International Nuclear Information System (INIS)

    Tukiran

    2002-01-01

    The fuels of RSG-GAS reactor is changed from uranium oxide to uranium silicide. For time being, the fuel of RSG-GAS core are mixed up between oxide and silicide fuels with 250 gr of loading and 2.96 g U/cm 3 of density, respectively. While, silicide fuel with 300 gr of loading is still under research. The advantages of silicide fuels are can be used in high density, so that, it can be stayed longer in the core at higher burn-up, therefore, the length of cycle is longer. The silicide fuel in RSG-GAS core is used in step-wise by using mixed up core. Firstly, it is used silicide fuel with 250 gr of loading and then, silicide fuel with 300 gr of loading (3.55 g U/cm 3 of density). In every step-wise of fuel loading must be analysed its safety margin. In this occasion, it is analysed the reactivity accident of RSG-GAS core with 300 gr of silicide fuel loading. The calculation was done by using POKDYN code which available at P2TRR. The calculation was done by reactivity insertion at start up and power rangers. From all cases which were have been done, the results of analysis showed that there is no anomaly and safety margin break at RSG-GAS core with 300 gr silicide fuel loading

  6. Fuel-cycle cost comparisons with oxide and silicide fuels

    International Nuclear Information System (INIS)

    Matos, J.E.; Freese, K.E.

    1982-01-01

    This paper addresses fuel cycle cost comparisons for a generic 10 MW reactor with HEU aluminide fuel and with LEU oxide and silicide fuels in several fuel element geometries. The intention of this study is to provide a consistent assessment of various design options from a cost point of view. Fuel cycle cost benefits could result if a number of reactors were to utilize fuel elements with the same number or different numbers of the same standard fuel plate. Data are presented to quantify these potential cost benefits. This analysis shows that there are a number of fuel element designs using LEU oxide or silicide fuels that have either the same or lower total fuel cycle costs than the HEU design. Use of these fuels with the uranium densities considered requires that they are successfully demonstrated and licensed

  7. RA-3 core with uranium silicide fuel elements

    International Nuclear Information System (INIS)

    Abbate, Maximo J.; Sbaffoni, Maria M.

    2000-01-01

    Following on with studies on uranium silicide fuel elements, this paper reports some comparisons between the use of standard ECN [U 3 O 8 ] fuel elements and type P-06 [from U 3 Si 2 ] fuel elements in the RA-3 core.The first results showed that the calculated overall mean burn up is in agreement with that reported for the facility, which gives more confidence to the successive ones. Comparing the mentioned cores, the silicide one presents several advantages such as: -) a mean burn up increase of 18 %; -) an extraction burn up increase of 20 %; -) 37.4 % increase in full power days, for mean burn up. All this is meritorious for this fuel. Moreover, grouped and homogenized libraries were prepared for CITVAP code that will be used for planning experiments and other bidimensional studies. Preliminary calculations were also performed. (author)

  8. Snapshot analysis for rhodium fixed incore detector using BEACON methodology

    International Nuclear Information System (INIS)

    Cha, Kyoon Ho; Choi, Yu Sun; Lee, Eun Ki; Park, Moon Ghu; Morita, Toshio; Heibel, Michael D.

    2004-01-01

    The purpose of this report is to process the rhodium detector data of the Yonggwang nuclear unit 4 cycle 5 core for the measured power distribution by using the BEACON methodology. Rhodium snapshots of the YGN 4 cycle 5 have been analyzed by both BEACON/SPINOVA and CECOR to compare the results of both codes. By analyzing a large number of snapshots obtained during normal plant operation. Reviewing the results of this analysis, the BEACON/SPNOVA can be used for the snapshot analysis of Korean Standard Nuclear Power (KSNP) plants

  9. Rhodium-catalyzed regioselective olefination directed by a carboxylic group.

    Science.gov (United States)

    Mochida, Satoshi; Hirano, Koji; Satoh, Tetsuya; Miura, Masahiro

    2011-05-06

    The ortho-olefination of benzoic acids can be achieved effectively through rhodium-catalyzed oxidative coupling with alkenes. The carboxylic group is readily removable to allow ortho-olefination/decarboxylation in one pot. α,β-Unsaturated carboxylic acids such as methacrylic acid also undergo the olefination at the β-position. Under the rhodium catalysis, the cine-olefination of heteroarene carboxylic acids such as thiophene-2-carboxylic acid proceeds smoothly accompanied by decarboxylation to selectively produce the corresponding vinylheteroarene derivatives. © 2011 American Chemical Society

  10. Secondary neutral mass spectrometry depth profile analysis of silicides

    International Nuclear Information System (INIS)

    Beckmann, P.; Kopnarski, M.; Oechsner, H.

    1985-01-01

    The Direct Bombardment Mode (DBM) of Secondary Neutral Mass Spectrometry (SNMS) has been applied for depth profile analysis of two different multilayer systems containing metal silicides. Due to the extremely high depth resolution obtained with low energy SNMS structural details down to only a few atomic distances are detected. Stoichiometric information on internal oxides and implanted material is supplied by the high quantificability of SNMS. (Author)

  11. Fracture of niobium-base silicide coated alloy

    International Nuclear Information System (INIS)

    Davydova, A.D.; Zotov, Yu.P.; Ivashchenko, O.V.; Kushnareva, N.P.; Yarosh, I.P.

    1990-01-01

    Mechanical properties and character of fracture of Nb-W-Mo-Zr-C alloy composition with complex by composition and structure silicide coating under different states of stage-by-stage coating are studied. Structural features, character of fracture from ductile to quasibrittle transcrystalline one and, respectively, the composition plasticity level are defined by interrelation of fracture processes in coating, matrix plastic flow and possibility and way of stress relaxation on their boundary

  12. Development of Silicide Coating on Molybdenum Alloy Cladding

    International Nuclear Information System (INIS)

    Lim, Woojin; Ryu, Ho Jin

    2015-01-01

    The molybdenum alloy is considered as one of the accident tolerant fuel (ATF) cladding materials due to its high temperature mechanical properties. However, molybdenum has a weak oxidation resistance at elevated temperatures. To modify the oxidation resistance of molybdenum cladding, silicide coating on the cladding is considered. Molybdenum silicide layers are oxidized to SiO 2 in an oxidation atmosphere. The SiO 2 protective layer isolates the substrate from the oxidizing atmosphere. Pack cementation deposition technique is widely adopted for silicide coating for molybdenum alloys due to its simple procedure, homogeneous coating quality and chemical compatibility. In this study, the pack cementation method was conducted to develop molybdenum silicide layers on molybdenum alloys. It was found that the Mo 3 Si layer was deposited on substrate instead of MoSi 2 because of short holding time. It means that through the extension of holding time, MoSi 2 layer can be formed on molybdenum substrate to enhance the oxidation resistance of molybdenum. The accident tolerant fuel (ATF) concept is to delay the process following an accident by reducing the oxidation rate at high temperatures and to delay swelling and rupture of fuel claddings. The current research for Atf can be categorized into three groups: First, modification of existing zirconium-based alloy cladding by improving the high temperature oxidation resistance and strength. Second, replacing Zirconium based alloys with alternative metallic materials such as refractory elements with high temperature oxidation resistance and strength. Third, designing alternative fuel structures using ceramic and composite systems

  13. Detailed analysis of uranium silicide dispersion fuel swelling

    International Nuclear Information System (INIS)

    Hofmann, G.L.; Ryu, Woo-Seog

    1991-01-01

    Swelling of U 3 Si and U 3 Si 2 is analyzed. The growth of fission gas bubbles appears to be affected by fission rate, fuel loading, and micro structural change taking place in the fuel compounds during irradiation. Several mechanisms are explored to explain the observations. The present work is aimed at a better understanding of the basic swelling phenomenon in order to accurately model irradiation behavior of uranium silicide dispersion fuel. (orig.)

  14. Detailed analysis of uranium silicide dispersion fuel swelling

    International Nuclear Information System (INIS)

    Hofman, G.L.; Ryu, Woo-Seog.

    1989-01-01

    Swelling of U 3 Si and U 3 Si 2 is analyzed. The growth of fission gas bubbles appears to be affected by fission rate, fuel loading, and microstructural change taking place in the fuel compounds during irradiation. Several mechanisms are explored to explain the observations. The present work is aimed at a better understanding of the basic swelling phenomenon in order to accurately model irradiation behavior of uranium silicide disperson fuel. 5 refs., 10 figs

  15. Rhodium enalcarbenoids: direct synthesis of indoles by rhodium(II)-catalyzed [4+2] benzannulation of pyrroles.

    Science.gov (United States)

    Dawande, Sudam Ganpat; Kanchupalli, Vinaykumar; Kalepu, Jagadeesh; Chennamsetti, Haribabu; Lad, Bapurao Sudam; Katukojvala, Sreenivas

    2014-04-14

    Disclosed herein is the design of an unprecedented electrophilic rhodium enalcarbenoid which results from rhodium(II)-catalyzed decomposition of a new class of enaldiazo compounds. The synthetic utility of these enalcarbenoids has been successfully demonstrated in the first transition-metal-catalyzed [4+2] benzannulation of pyrroles, thus leading to substituted indoles. The new benzannulation has been applied to the efficient synthesis of the natural product leiocarpone as well as a potent adipocyte fatty-acid binding protein inhibitor. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Electronic and magnetic properties of small rhodium clusters

    Energy Technology Data Exchange (ETDEWEB)

    Soon, Yee Yeen; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

    2015-04-24

    We report a theoretical study of the electronic and magnetic properties of rhodium-atomic clusters. The lowest energy structures at the semi-empirical level of rhodium clusters are first obtained from a novel global-minimum search algorithm, known as PTMBHGA, where Gupta potential is used to describe the atomic interaction among the rhodium atoms. The structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof generalized gradient approximation. For the purpose of calculating the magnetic moment of a given cluster, we calculate the optimized structure as a function of the spin multiplicity within the DFT framework. The resultant magnetic moments with the lowest energies so obtained allow us to work out the magnetic moment as a function of cluster size. Rhodium atomic clusters are found to display a unique variation in the magnetic moment as the cluster size varies. However, Rh{sub 4} and Rh{sub 6} are found to be nonmagnetic. Electronic structures of the magnetic ground-state structures are also investigated within the DFT framework. The results are compared against those based on different theoretical approaches available in the literature.

  17. Ring Expansion and Rearrangements of Rhodium(II) Azavinyl Carbenes

    Science.gov (United States)

    Selander, Nicklas; Worrell, Brady T.

    2013-01-01

    An efficient, regioselective and convergent method for the ring expansion and rearrangement of 1-sulfonyl-1,2,3-triazoles under rhodium(II)-catalyzed conditions is described. These denitrogenative reactions form substituted enaminone and olefin-based products, which in the former case can be further functionalized to unique products rendering the sulfonyl triazole traceless. PMID:23161725

  18. In vitro permeation of platinum and rhodium through Caucasian skin.

    Science.gov (United States)

    Franken, A; Eloff, F C; Du Plessis, J; Badenhorst, C J; Jordaan, A; Du Plessis, J L

    2014-12-01

    During platinum group metals (PGMs) refining the possibility exists for dermal exposure to PGM salts. The dermal route has been questioned as an alternative route of exposure that could contribute to employee sensitisation, even though literature has been focused on respiratory exposure. This study aimed to investigate the in vitro permeation of platinum and rhodium through intact Caucasian skin. A donor solution of 0.3mg/ml of metal, K2PtCl4 and RhCl3 respectively, was applied to the vertical Franz diffusion cells with full thickness abdominal skin. The receptor solution was removed at various intervals during the 24h experiment, and analysed with high resolution ICP-MS. Skin was digested and analysed by ICP-OES. Results indicated cumulative permeation with prolonged exposure, with a significantly higher mass of platinum permeating after 24h when compared to rhodium. The mass of platinum retained inside the skin and the flux of platinum across the skin was significantly higher than that of rhodium. Permeated and skin retained platinum and rhodium may therefore contribute to sensitisation and indicates a health risk associated with dermal exposure in the workplace. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Kinetic method of determination of rhodium trace amounts

    International Nuclear Information System (INIS)

    Kalinina, V.E.; Lyakushina, V.M.; Rybina, A.E.

    1978-01-01

    A catalytic action of rhodium compounds has been detected and studied in the reaction of copper (2) tellurate oxidation with hypobromite to ditelluratocuprate (3) in an alkaline medium. The relationships between the reaction rate and concentrations of copper, tellurate, and hypobromite have been established. The optimum concentrations of the used compounds have been found: Csub(Cu(2))=4x10 -5 g-ion/l; Csub(OHsup(-))=3.0 g-ion/l; Csub(Te)=1.4x10 -2 g-ion/l; Csub(NaBrO)=2.17x10 -3 M. It has been established for chloride, sulphate, and perchlorate solutions of rhodium (3) and (4) that the reaction sensitivity increases by 2-3-fold with a temperature rise from 25-60 deg C. The technique of determining rhodium traces has been developed based on its catalytic action. The low limit of determined rhodium amounts is about 10 -3 mkg/ml

  20. Extraction of fission product rhodium from nitric acid solutions. 1

    International Nuclear Information System (INIS)

    Gorski, B.; Beer, M.; Russ, L.

    1988-01-01

    The extraction of noble metals from nitric acid solutions represents one problem of separating valueable substances from nuclear wastes in nuclear fuel reprocessing. Results of distribution experiments demonstrate the possibility of solvent extraction of rhodium using tertiary amines in presence of nitrite. Even short mixing times realize high distribution coefficients allowing quantitative separation from aqueous solutions. (author)

  1. Rhodium(iii)-catalyzed ortho-olefination of aryl phosphonates.

    Science.gov (United States)

    Chary, Bathoju Chandra; Kim, Sunggak

    2013-09-25

    Rhodium(iii)-catalyzed C-H olefination of aryl phosphonic esters is reported for the first time. In this mild and efficient process, the phosphonic ester group is utilized successfully as a new directing group. In addition, mono-olefination for aryl phosphonates is observed using a phosphonic diamide directing group.

  2. Rhodium trichloride as a homogeneous catalyst for isotopic hydrogen exchange. Comparison with heterogeneous rhodium in the deuteriation of aromatic compounds and alkanes

    Energy Technology Data Exchange (ETDEWEB)

    Blake, M R; Garnett, J L; Gregor, I K; Hannan, W; Hoa, K; Long, M A [New South Wales Univ., Kensington (Australia)

    1975-12-03

    The use of rhodium trichloride as a homogeneous catalyst for the exchange of aromatic compounds and alkanes is described; comparison of the results with corresponding data from heterogeneous rhodium metal and other homogeneous systems, e.g., platinum and iridium, supports the proposal that specific type of ..pi..-complex mechanisms are common to all such exchange systems.

  3. Mechanoactivation of chromium silicide formation in the SiC-Cr-Si system

    Directory of Open Access Journals (Sweden)

    Vlasova M.

    2002-01-01

    Full Text Available The processes of simultaneous grinding of the components of a SiC-Cr-Si mixture and further temperature treatment in the temperature range 1073-1793 K were studied by X-ray phase analysis, IR spectroscopy, electron microscopy, and X-ray microanalysis. It was established that, during grinding of the mixture, chromium silicides form. A temperature treatment completes the process. Silicide formation proceeds within the framework of the diffusion of silicon into chromium. In the presence of SiO2 in the mixture, silicide formation occurs also as a result of the reduction of silica by silicon and silicon carbide. The sintering of synthesized composite SiC-chromium silicides powders at a high temperature under a high pressure (T = 2073 K, P = 5 GPa is accompanied by the destruction of cc-SiC particles, the cc/3 transition in silicon carbide and deformation distortions of the lattices of chromium silicides.

  4. Structure of Rhodium in an Ultradispersed Rhodium/Alumina Catalyst as Studied by EXAFS and Other Technique

    NARCIS (Netherlands)

    Koningsberger, D.C.; Blik, H.F.J. van 't; Zon, J.B.A.D. van; Huizinga, T.; Vis, J.C.; Prins, R.

    1985-01-01

    The structure of rhodium in an ultradispersed 0.57 wt % Rh/y-Al,O, catalyst before and after CO adsorption was studied with extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), temperature programmed reduction (TPR), CO infrared

  5. Neutronic Analysis and Radiological Safety of RSG-GAS Reactor on 300 Grams Uranium Silicide Core

    International Nuclear Information System (INIS)

    Pande Made Udiyani; Lily Suparlina; Rokhmadi

    2007-01-01

    As starting of usage silicide U 250 g fuel element in the core of RSG-GAS and will be continued with usage of silicide U 300 g fuel element, hence done beforehand neutronic analyse and radiological safety of RSG-GAS. Calculation done by ORIGEN2.1 code to calculate source term, and also by PC-COSYMA code to calculate radiological safety of radioactive dispersion from RSG-GAS. Calculation of radioactive dispersion done at condition of reactor is postulated be happened an accident of LOCA causing one fuel element to melt. Neutronic analysis indicate that silicide U 250 g full core shall to be operated beforehand during 625 MWD before converted to silicide U 300 g core. During operation of transition core with mixture of silicide U 250 g and 300 g, all parameter fulfill criterion of safety Designed Balance core of silicide U 300 g will be reached at the time of fifth full core. Result of calculation indicate that through mixture core of silicide U 250 and 300 g proposed can form silicide U 300 g balance core of reactor RSG-GAS safely. Calculation of radiology safety by deterministic for silicide U 300 g balance core, and accident postulation which is equal to core of silicide U 250 g yield output in the form of radiation activity (radionuclide concentration in the air and deposition on the ground), radiation dose (collective and individual), radiation effect (short- and long-range), which accepted by society in each perceived sector. Result of calculation indicated that dose accepted by society is not pass permitted boundary for public society if happened accident. (author)

  6. Exploitation of a self-limiting process for reproducible formation of ultrathin Ni1-xPtx silicide films

    International Nuclear Information System (INIS)

    Zhang Zhen; Zhu Yu; Rossnagel, Steve; Murray, Conal; Jordan-Sweet, Jean; Yang, Bin; Gaudet, Simon; Desjardins, Patrick; Kellock, Andrew J.; Ozcan, Ahmet; Zhang Shili; Lavoie, Christian

    2010-01-01

    This letter reports on a process scheme to obtain highly reproducible Ni 1-x Pt x silicide films of 3-6 nm thickness formed on a Si(100) substrate. Such ultrathin silicide films are readily attained by sputter deposition of metal films, metal stripping in wet chemicals, and final silicidation by rapid thermal processing. This process sequence warrants an invariant amount of metal intermixed with Si in the substrate surface region independent of the initial metal thickness, thereby leading to a self-limiting formation of ultrathin silicide films. The crystallographic structure, thickness, uniformity, and morphological stability of the final silicide films depend sensitively on the initial Pt fraction.

  7. Local Electric Field Effects on Rhodium-Porphyrin and NHC-Gold Catalysts

    Science.gov (United States)

    2015-01-05

    AFRL-OSR-VA-TR-2015-0023 (NII) - Local Electric Field Effects on Rhodium -Porphyrin and NHC-Gold Catalysts MATTHEW KANAN LELAND STANFORD JUNIOR UNIV...Effects on Rhodium -Porphyrin and NHC-Gold Catalysts Principal Investigator: Matthew W. Kanan Project Publications: 1. “An Electric Field–Induced Change...Stanford University Grant/Contract Title The full title of the funded effort. (NII)-Local Electric Field Effects on Rhodium -Porphyrin and NHC-Gold

  8. Rhodium self-powered neutron detector's lifetime for korean standard nuclear power plants

    International Nuclear Information System (INIS)

    Yoo, Choon Sung; Kim, Byoung Chul; Park, Jong Ho; Fero, Arnold H.; Anderson, S. L.

    2005-01-01

    A method to estimate the relative sensitivity of a self-powered rhodium detector for an upcoming cycle is developed by combining the rhodium depletion data from a nuclear design with the site measurement data. This method can be used both by nuclear power plant designers and by site staffs of Korean standard nuclear power plants for determining which rhodium detectors should be replaced during overhauls

  9. Mechanochemical synthesis and spark plasma sintering of the cerium silicides

    Energy Technology Data Exchange (ETDEWEB)

    Alanko, Gordon A.; Jaques, Brian; Bateman, Allyssa [Department of Materials Science and Engineering, College of Engineering, Boise State University, 1910 University Drive, Boise, ID 83725 (United States); Butt, Darryl P., E-mail: darrylbutt@boisestate.edu [Department of Materials Science and Engineering, College of Engineering, Boise State University, 1910 University Drive, Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Boulevard, Idaho Falls, ID 83401 (United States)

    2014-12-15

    Highlights: • Ce{sub 5}Si{sub 3}, Ce{sub 3}Si{sub 2}, CeSi, CeSi{sub 2−x} and CeSi{sub 2} were mechanochemically synthesized. • Temperature and pressure were monitored to investigate reaction progress. • All syntheses proceeded through a MSR event followed by rapid solid-state diffusion. • Milling time before MSR correlates well with effective heat of formation. • Some synthesized material was densified by spark plasma sintering. - Abstract: The cerium silicides, Ce{sub 5}Si{sub 3}, Ce{sub 3}Si{sub 2}, CeSi, CeSi{sub 2−y}, and CeSi{sub 2−x}, have been prepared from the elements by mechanochemical processing in a planetary ball mill. Preparation of the cerium silicide Ce{sub 5}Si{sub 4} was unsuccessfully attempted and potential reasons for this are discussed. Temperature and pressure of the milling vial were monitored in situ to gain insight into the mechanochemical reaction kinetics, which include a mechanically-induced self-propagating reaction (MSR). Some prepared powders were consolidated by spark plasma sintering to high density. Starting materials, as-milled powders, and consolidated samples were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results obtained help elucidate key questions in mechanochemical processing of intermetallics, showing first phase formation similar to thin films, MSR ignition times that are composition- and milling speed-dependent, and sensitivity of stable compound formation on the impact pressure. The results demonstrate mechanochemical synthesis as a viable technique for rare earth silicides.

  10. Immobilization of Uranium Silicide in Sintered Iron-Phosphate Glass

    International Nuclear Information System (INIS)

    Mateos, Patricia; Russo, Diego; Rodriguez, Diego; Heredia, A; Sanfilippo, M.; Sterba, Mario

    2003-01-01

    This work is a continuation of a previous one performed in vitrification of uranium silicide in borosilicate and iron-silicate glasses, by sintering.We present the results obtained with an iron-phosphate glass developed at our laboratory and we compare this results with those obtained with the above mentioned glasses. The main objective was to develop a method as simple as possible, so as to get a monolithic glass block with the appropriate properties to be disposed in a deep geological repository.The thermal transformation of the uranium silicide was characterized by DTA/TG analysis and X-ray diffraction.We determined the evolution of the crystalline phases and the change in weight.Calcined uranium silicide was mixed with natural U 3 O 8 , the amount of U 3 O 8 was calculated to simulate an isotopic dilution of 4%.This material was mixed with powdered iron-phosphate glass (in wt.%: 64,9 P 2 O 5 ; 22,7 Fe 2 O 3 ; 8,1 Al 2 O 3 ; 4,3 Na 2 O) in different proportions (in wt%): 7%, 10% y 15%.The powders were pressed and sintered at temperatures between 585 y 670 °C. Samples of the sintered pellet were prepared for the lixiviation tests (MCC-1P: monolithic samples; deionised water; 90° C; 7, 14 and 28 days).The samples showed a quite good durability (0,6 g.m -2 .day -1 ), similar to borosilicate glasses.The microstructure of the glass samples showed that the uranium particles are much better integrated to the glass matrix in the iron-phosphate glasses than in the borosilicate or iron-silicate glasses.We can conclude that the sintered product obtained could be a good alternative for the immobilization of nuclear wastes with high content of uranium, as the ones arising from the conditioning of research reactors spent fuels

  11. Neutronic calculations of PARR-1 cores using LEU silicide fuel

    International Nuclear Information System (INIS)

    Arshad, M.; Bakhtyar, S.; Hayat, T.; Salahuddin, A.

    1991-08-01

    Detailed neutronic calculations have been carried out for different PARR-1 cores utilizing low enriched uranium (LEU) silicide fuel and operating at an upgraded power of 9 MW. The calculations include the search for critical loadings in open and stall ends of the pool, neutronic analysis of the first full equilibrium core and calculations cores. The burnup study of inventory have also been carried out. Further, the reactivity coefficients of the first full power operation core are evaluated for use in the accident analysis. 14 figs. (author)

  12. Postirradiation analysis of experimental uranium-silicide dispersion fuel plates

    International Nuclear Information System (INIS)

    Hofman, G.L.; Neimark, L.A.

    1985-01-01

    Low-enriched uranium silicide dispersion fuel plates were irradiated to maximum burnups of 96% of 235 U. Fuel plates containing 33 v/o U 3 Si and U 3 Si 2 behaved very well up to this burnup. Plates containing 33 v/o U 3 Si-Al pillowed between 90 and 96% burnup of the fissile atoms. More highly loaded U 3 Si-Al plates, up to 50 v/o were found to pillow at lower burnups. Plates containing 40 v/o U 3 Si showed an increase swelling rate around 85% burnup. 5 refs., 10 figs

  13. Progress in doping of ruthenium silicide (Ru2Si3)

    International Nuclear Information System (INIS)

    Vining, C.B.; Allevato, C.E.

    1992-01-01

    This paper reports that ruthenium silicide (Ru 2 Si 3 ) is currently under development as a promising thermoelectric material suitable for space power applications. Key to realizing the potentially high figure of merit values of this material is the development of appropriate doping techniques. In this study, manganese and iridium have been identified as useful p- and n-type dopants, respectively. Resistivity values have been reduced by more than 3 orders of magnitude. Anomalous Hall effect results, however, complicate interpretation of some of the results and further effort is required to achieve optimum doping levels

  14. Microstructure and mechanical properties of molybdenum silicides with Al additions

    International Nuclear Information System (INIS)

    Rosales, I.; Bahena, D.; Colin, J.

    2007-01-01

    Several molybdenum silicides alloys with different aluminum additions were produced by the arc-cast method. Microstructure observed in the alloys presented a variation of the precipitated second phase respect to the aluminum content. Evaluation of the compressive behavior at high temperature of the alloys shows an important improvement in its ductility, approximately of 20%. Fracture toughness was increased proportionally with Al content. In addition at room temperature the alloys show a better mechanical behavior in comparison with the sample unalloyed. In general, Al additions result to be a good alternative to improve the resistance of these intermetallic alloys. The results are interpreted on the base of the analysis of second phase strengthening

  15. Structural and electronic properties of rare-earth silicide thin films at Si(111)

    Energy Technology Data Exchange (ETDEWEB)

    Dues, Christof; Schmidt, Wolf Gero; Sanna, Simone [Lehrstuhl fuer Theoretische Physik, Universitaet Paderborn (Germany)

    2016-07-01

    Rare-earth (RE) silicides thin films on silicon surfaces are currently of high interest. They grow nearly defect-free because of the small lattice mismatch, and exhibit very low Schottky-barriers on n-type silicon. They even give rise to the self-organized formation of RE silicide nanowires on the Si(001) and vicinal surfaces. Depending on the amount of deposited RE atoms, a plethora of reconstructions are observed for the RE silicide. While one monolayer leads to the formation of a 1 x 1-reconstruction, several monolayer thick silicides crystallize in a √(3) x √(3) R30 {sup circle} superstructure. Submonolayer RE deposition leads to different periodicities. In this work we investigate the formation of RE silicides thin films on Si(111) within the density functional theory. The energetically favored adsorption site for RE adatoms is determined calculating the potential energy surface. As prototypical RE, Dysprosium is used. Additional calculations are performed for silicides formed by different RE elements. We calculate structural properties, electronic band structures and compare measured and simulated STM images. We consider different terminations for the 5 x 2 reconstruction occurring in the submonolayer regime and investigate their stability by means of ab initio thermodynamics. The same method is employed to predict the stable silicide structure as a function of the deposited RE atoms.

  16. Interfacial bonding stabilizes rhodium and rhodium oxide nanoparticles on layered Nb oxide and Ta oxide supports.

    Science.gov (United States)

    Strayer, Megan E; Binz, Jason M; Tanase, Mihaela; Shahri, Seyed Mehdi Kamali; Sharma, Renu; Rioux, Robert M; Mallouk, Thomas E

    2014-04-16

    Metal nanoparticles are commonly supported on metal oxides, but their utility as catalysts is limited by coarsening at high temperatures. Rhodium oxide and rhodium metal nanoparticles on niobate and tantalate supports are anomalously stable. To understand this, the nanoparticle-support interaction was studied by isothermal titration calorimetry (ITC), environmental transmission electron microscopy (ETEM), and synchrotron X-ray absorption and scattering techniques. Nanosheets derived from the layered oxides KCa2Nb3O10, K4Nb6O17, and RbTaO3 were compared as supports to nanosheets of Na-TSM, a synthetic fluoromica (Na0.66Mg2.68(Si3.98Al0.02)O10.02F1.96), and α-Zr(HPO4)2·H2O. High surface area SiO2 and γ-Al2O3 supports were also used for comparison in the ITC experiments. A Born-Haber cycle analysis of ITC data revealed an exothermic interaction between Rh(OH)3 nanoparticles and the layered niobate and tantalate supports, with ΔH values in the range -32 kJ·mol(-1) Rh to -37 kJ·mol(-1) Rh. In contrast, the interaction enthalpy was positive with SiO2 and γ-Al2O3 supports. The strong interfacial bonding in the former case led to "reverse" ripening of micrometer-size Rh(OH)3, which dispersed as 0.5 to 2 nm particles on the niobate and tantalate supports. In contrast, particles grown on Na-TSM and α-Zr(HPO4)2·H2O nanosheets were larger and had a broad size distribution. ETEM, X-ray absorption spectroscopy, and pair distribution function analyses were used to study the growth of supported nanoparticles under oxidizing and reducing conditions, as well as the transformation from Rh(OH)3 to Rh nanoparticles. Interfacial covalent bonding, possibly strengthened by d-electron acid/base interactions, appear to stabilize Rh(OH)3, Rh2O3, and Rh nanoparticles on niobate and tantalate supports.

  17. Activation of heterogenised rhodium carbonylation catalyst infrared spectroscopic study

    Energy Technology Data Exchange (ETDEWEB)

    Scurrell, M S

    1977-01-01

    In a study related to heterogeneous versions of homogeneous catalysts active in carbonylation of methanol to acetic acid, the catalyst consisted of 1Vertical Bar3< rhodium as rhodium trichloride supported on 13X zeolite and evacuated at 437/sup 0/K. Contacting the catalyst with carbon monoxide caused two bands, at 2025 and 2095 cm/sup -1/, to appear. Contact with a mixture of carbon monoxide and methyl iodide (the usual promoter) caused bands at 2085, 1710, 1440, and 1370 cm/sup -1/ to appear; the first two correspond to the bands at 2062 and 1711 cm/sup -1/ in homogeneous catalysts attributed to the formation of Rh(CH/sup 3/CO)(CO)X/sup 2/I/sup -/. Spectra.

  18. Antitumor effect and toxicity of free rhodium (II) citrate and rhodium (II) citrate-loaded maghemite nanoparticles in mice bearing breast cancer.

    Science.gov (United States)

    Carneiro, Marcella Lemos Brettas; Peixoto, Raphael C A; Joanitti, Graziela A; Oliveira, Ricardo G S; Telles, Luis A M; Miranda-Vilela, Ana L; Bocca, Anamélia L; Vianna, Leonora M S; da Silva, Izabel C R; de Souza, Aparecido R; Lacava, Zulmira G M; Báo, Sônia N

    2013-02-16

    Magnetic fluids containing superparamagnetic iron oxide nanoparticles represent an attractive platform as nanocarriers in chemotherapy. Recently, we developed a formulation of maghemite nanoparticles coated with rhodium (II) citrate, which resulted in in vitro cytotoxicity enhanced up to 4.6 times when compared to free rhodium (II) citrate formulation on breast carcinoma cells. In this work, we evaluate the antitumor activity and toxicity induced by these formulations in Balb/c mice bearing orthotopic 4T1 breast carcinoma. Mice were evaluated with regard to the treatments' toxicity through analyses of hemogram, serum levels of alanine aminotransferase, iron, and creatinine; DNA fragmentation and cell cycle of bone marrow cells; and liver, kidney and lung histology. In addition, the antitumor activity of rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate was verified by tumor volume reduction, histology and immunohistochemistry. Regarding the treatments' toxicity, no experimental groups had alterations in levels of serum ALT or creatinine, and this suggestion was corroborated by the histopathologic examination of liver and kidney of mice. Moreover, DNA fragmentation frequency of bone marrow cells was lower than 15% in all experimental groups. On the other hand, the complexes rhodium (II) citrate-functionalized maghemite and free rhodium (II) citrate led to a marked growth inhibition of tumor and decrease in CD31 and Ki-67 staining. In summary, we demonstrated that both rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate formulations exhibited antitumor effects against 4T1 metastatic breast cancer cell line following intratumoral administration. This antitumor effect was followed by inhibition of both cell proliferation and microvascularization and by tumor tissue injury characterized as necrosis and fibrosis. Remarkably, this is the first published report demonstrating the therapeutic efficacy of maghemite

  19. Influence of IR-laser irradiation on α-SiC-chromium silicides ceramics

    International Nuclear Information System (INIS)

    Vlasova, M.; Marquez Aguilar, P.A.; Resendiz-Gonzalez, M.C.; Kakazey, M.; Bykov, A.; Gonzalez Morales, I.

    2005-01-01

    This project investigated the influence of IR-laser irradiation (λ = 1064 nm, P = 240 mW) on composite ceramics SiC-chromium silicides (CrSi 2 , CrSi, Cr 5 Si 3 ) by methods of X-ray diffraction, electron microscopy, atomic force microscopy, and X-ray microanalysis. Samples were irradiated in air. It was established that a surface temperature of 1990 K was required to melt chromium silicides, evaporate silicon from SiC, oxidize chromium silicides, and enrich superficial layer by carbon and chromium oxide

  20. Fuel cycle cost comparisons with oxide and silicide fuels

    Energy Technology Data Exchange (ETDEWEB)

    Matos, J E; Freese, K E [RERTR Program, Argonne National Laboratory (United States)

    1983-09-01

    This paper addresses fuel cycle cost comparisons for a generic 10 MW reactor with HEU aluminide fuel and with LEU oxide and silicide fuels in several fuel element geometries. The intention of this study is to provide a consistent assessment of various design options from a cost point of view. The status of the development and demonstration of the oxide and silicide fuels are presented in several papers in these proceedings. Routine utilization of these fuels with the uranium densities considered here requires that they are successfully demonstrated and licensed. Thermal-hydraulic safety margins, shutdown margins, mixed cores, and transient analyses are not addressed here, but analyses of these safety issues are in progress for a limited number of the most promising design options. Fuel cycle cost benefits could result if a number of reactors were to utilize fuel elements with the same number or different numbers of the same standard fuel plate. Data is presented to quantify these potential cost benefits. This analysis shows that there are a number of fuel element designs using LEU oxide or silicide fuels that have either the same or lower total fuel cycle costs than the HEU design. Use of these fuels with the uranium densities considered requires that they are successfully demonstrated and licensed. All safety criteria for the reactor with these fuel element designs need to be satisfied as well. With LEU oxide fuel, 31 g U/cm{sup 3} 1 and 0.76 mm--thick fuel meat, elements with 18-22 plates 320-391 g {sup 235}U) result in the same or lower total costs than with the HEU element 23 plates, 280 g {sup 235}U). Higher LEU loadings (more plates per element) are needed for larger excess reactivity requirements. However, there is little cost advantage to using more than 20 of these plates per element. Increasing the fuel meat thickness from 0.76 mm to 1.0 mm with 3.1 g U/cm{sup 3} in the design with 20 plates per element could result in significant cost reductions if the

  1. Bioenvironmental aspects of europium and rhodium: a selected bibliography

    International Nuclear Information System (INIS)

    Fore, C.S.; Carrier, R.F.; Talmage, S.S.; Fielden, J.M.; Daniel, E.W.

    1983-09-01

    This bibliography of 428 abstracted references represents a summary of the domestic and foreign literature relevant to the biological and environmental aspects of europium and rhodium. The collected data are organized by current NAEG interests - research highlighting inventory and distribution of the radionulcides, ecological studies covering terrestrial and aquatic systems, and biological studies in both man and animals. Studies that focus directly on research conducted at specific sites (e.g., the Nevada Test Site) are emphasized throughout the bibliography

  2. Diphosphinoazine Rhodium(I) and Iridium(I) Complexes

    Czech Academy of Sciences Publication Activity Database

    Pošta, Martin; Čermák, Jan; Vojtíšek, P.; Císařová, I.

    2006-01-01

    Roč. 71, č. 2 (2006), s. 197-206 ISSN 0010-0765 R&D Projects: GA ČR(CZ) GA203/01/0554; GA ČR(CZ) GA203/99/M037 Institutional research plan: CEZ:AV0Z40720504 Keywords : diphosphinoazines * rhodium complexes * iridium complexes Subject RIV: CC - Organic Chemistry Impact factor: 0.881, year: 2006

  3. Arylation of Rhodium(II) Azavinyl Carbenes with Boronic Acids

    Science.gov (United States)

    Selander, Nicklas; Worrell, Brady T.; Chuprakov, Stepan; Velaparthi, Subash; Fokin, Valery V.

    2013-01-01

    A highly efficient and stereoselective arylation of in situ generated azavinyl carbenes affording 2,2-diaryl enamines at ambient temperatures has been developed. These transition metal carbenes are directly produced from readily available and stable 1-sulfonyl-1,2,3-triazoles in the presence of a rhodium carboxylate catalyst. In several cases, the enamines generated in this reaction can be cyclized into substituted indoles employing copper catalysts. PMID:22913576

  4. Rhodium(II)-catalyzed enantioselective synthesis of troponoids.

    Science.gov (United States)

    Murarka, Sandip; Jia, Zhi-Jun; Merten, Christian; Daniliuc, Constantin-G; Antonchick, Andrey P; Waldmann, Herbert

    2015-06-22

    We report a rhodium(II)-catalyzed highly enantioselective 1,3-dipolar cycloaddition reaction between the carbonyl moiety of tropone and carbonyl ylides to afford troponoids in good to high yields with excellent enantioselectivity. We demonstrate that α-diazoketone-derived carbonyl ylides, in contrast to carbonyl ylides derived from diazodiketoesters, undergo [6+3] cycloaddition reactions with tropone to yield the corresponding bridged heterocycles with excellent stereoselectivity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Inter-diffusion study of rhodium and tantalum by RBS

    International Nuclear Information System (INIS)

    Nuttens, V.E.; Hubert, R.L.; Bodart, F.; Lucas, S.

    2005-01-01

    The inter-diffusion of rhodium and tantalum has been studied with the goal of synthesizing an alloy acting as a diffusion barrier for high temperature applications. Rh/Ta sandwiched samples were annealed in vacuum at temperature ranging from 800 to 900 deg. C and from 1000 to 1075 deg. C. The diffusion profiles were obtained by RBS. They suggest the formation of two clearly different phases in each temperature range considered

  6. Rhodium coated mirrors deposited by magnetron sputtering for fusion applications

    International Nuclear Information System (INIS)

    Marot, L.; De Temmerman, G.; Oelhafen, P.; Covarel, G.; Litnovsky, A.

    2007-01-01

    Metallic mirrors will be essential components of all optical spectroscopy and imaging systems for ITER plasma diagnostics. Any change in the mirror performance, in particular, its reflectivity, due to erosion of the surface by charge exchange neutrals or deposition of impurities will influence the quality and reliability of the detected signals. Due to its high reflectivity in the visible wavelength range and its low sputtering yield, rhodium appears as an attractive material for first mirrors in ITER. However, the very high price of the raw material calls for using it in the form of a film deposited onto metallic substrates. The development of a reliable technique for the preparation of high reflectivity rhodium films is therefore of the highest importance. Rhodium layers with thicknesses of up to 2 μm were produced on different substrates of interest (Mo, stainless steel, Cu) by magnetron sputtering. Produced films exhibit a low roughness and crystallite size of about 10 nm with a dense columnar structure. No impurities were detected on the surface after deposition. Scratch tests demonstrate that adhesion properties increase with substrate hardness. Detailed optical characterizations of Rh-coated mirrors as well as results of erosion tests performed both under laboratory conditions and in the TEXTOR tokamak are presented in this paper

  7. DNA Mismatch Binding and Antiproliferative Activity of Rhodium Metalloinsertors

    Science.gov (United States)

    Ernst, Russell J.; Song, Hang; Barton, Jacqueline K.

    2009-01-01

    Deficiencies in mismatch repair (MMR) are associated with carcinogenesis. Rhodium metalloinsertors bind to DNA base mismatches with high specificity and inhibit cellular proliferation preferentially in MMR-deficient cells versus MMR-proficient cells. A family of chrysenequinone diimine complexes of rhodium with varying ancillary ligands that serve as DNA metalloinsertors has been synthesized, and both DNA mismatch binding affinities and antiproliferative activities against the human colorectal carcinoma cell lines HCT116N and HCT116O, an isogenic model system for MMR deficiency, have been determined. DNA photocleavage experiments reveal that all complexes bind to the mismatch sites with high specificities; DNA binding affinities to oligonucleotides containing single base CA and CC mismatches, obtained through photocleavage titration or competition, vary from 104 to 108 M−1 for the series of complexes. Significantly, binding affinities are found to be inversely related to ancillary ligand size and directly related to differential inhibition of the HCT116 cell lines. The observed trend in binding affinity is consistent with the metalloinsertion mode where the complex binds from the minor groove with ejection of mismatched base pairs. The correlation between binding affinity and targeting of the MMR-deficient cell line suggests that rhodium metalloinsertors exert their selective biological effects on MMR-deficient cells through mismatch binding in vivo. PMID:19175313

  8. Scalar Relativistic Study of the Structure of Rhodium Acetate

    Directory of Open Access Journals (Sweden)

    Emily E. Edwards

    2004-01-01

    Full Text Available Abstract: Rhodium acetate, related rhodium carboxylates, and rhodium amide complexes are powerful catalysts for carbene chemistry. They readily promote the decomposition of diazo compounds and transfer the resulting carbene to a variety of substrates. There have been several quantum chemistry studies of these compounds, particularly of the acetate. These have all used non-relativistic methods, and all have shown optimized Rh-Rh bond lengths significantly longer than the experimental value. In this study we have surveyed several scalar relativistic DFT methods using Gaussian, Slater, and numerical basis functions (in DGAUSS, ADF, and DMOL3. Several combinations of exchange-correlation functionals with relativistic and non-relativistic effective core potentials (ECP were investigated, as were non-relativistic and all electron scalar relativistic methods. The combination of the PW91 exchange and PW91 correlation functional with the Christiansen-Ermler ECP gave the best results: 2.3918 Å compared to the experimental value of 2.3855±0.0005 Å.

  9. Electrochemical behavior of rhodium(III) in 1-butyl-3-methylimidazolium chloride ionic liquid

    Energy Technology Data Exchange (ETDEWEB)

    Jayakumar, M.; Venkatesan, K.A. [Fuel Chemistry Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Srinivasan, T.G. [Fuel Chemistry Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)], E-mail: tgs@igcar.gov.in

    2008-02-15

    Electrochemical behavior of rhodium(III) chloride in 1-butyl-3-methylimidazolium chloride was investigated by various electrochemical transient techniques at glassy carbon working electrode at different temperatures (343-373 K). Cyclic voltammogram of rhodium(III) in bmimCl consisted of a surge in reduction current occurring at a potential of -0.48 V (vs. Pd) is due to the reduction of Rh(III) to metallic rhodium and a very small oxidation wave occurring at -0.1 V. Increase of scan rate increases the peak current and remarkably shifts the cathodic peak potential (E{sub p}{sup c1}) in negative direction indicating the irreversibility of electroreduction of rhodium(III). The diffusion coefficient of rhodium(III) in bmimCl ({approx}10{sup -9} cm{sup 2}/s) was determined and the energy of activation ({approx}25 kJ/mol) was deduced from cyclic voltammograms at various temperatures. The cathodic ({tau}{sub r}) and anodic ({tau}{sub o}) transition times were measured from chronopotential transients and the ratio {tau}{sub o}/{tau}{sub r} was found to be 1:7. Electrowinning of rhodium from bmimCl medium results in a deposition of metallic rhodium with lower (20-25%) Faradaic efficiency. A separation factor of rhodium from co-existing noble metal fission product palladium in bmimCl was determined during electrodeposition.

  10. Inhibiting prolyl isomerase activity by hybrid organic-inorganic molecules containing rhodium(II) fragments.

    Science.gov (United States)

    Coughlin, Jane M; Kundu, Rituparna; Cooper, Julian C; Ball, Zachary T

    2014-11-15

    A small molecule containing a rhodium(II) tetracarboxylate fragment is shown to be a potent inhibitor of the prolyl isomerase FKBP12. The use of small molecules conjugates of rhodium(II) is presented as a general strategy for developing new protein inhibitors based on distinct structural and sequence features of the enzyme active site. Copyright © 2014 Elsevier Ltd. All rights reserved.

  11. Energetic driving force of H spillover between rhodium and titania surfaces : a DFT view

    NARCIS (Netherlands)

    Conradie, J.; Gracia, J.; Niemantsverdriet, J.W.

    2012-01-01

    Hydrogen spillover from a rhodium particle, over the most stable (111) surface, to a TiO2 rutile support occurs at low hydrogen coverage because the adsorption energy of H atoms at low hydrogen coverage on rutile is larger than that on rhodium. H diffuses over the support with an activation barrier

  12. The isomerization of allylrhodium intermediates in the rhodium-catalyzed nucleophilic allylation of cyclic imines.

    Science.gov (United States)

    Hepburn, Hamish B; Lam, Hon Wai

    2014-10-20

    Allylrhodium species generated from potassium allyltrifluoroborates can undergo isomerization by 1,4-rhodium(I) migration to give more complex isomers, which then react with cyclic imines to provide products with up to three new stereochemical elements. High enantioselectivities are obtained using chiral diene-rhodium complexes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. "On-water" rhodium-catalysed hydroformylation for the production of linear alcohols

    NARCIS (Netherlands)

    Diebolt, O.H.; Müller, Christian; Vogt, D.

    2012-01-01

    Optimisation of the reaction conditions for the rhodium-catalysed aldehyde hydrogenation under hydroformylation conditions showed that water used as co-solvent enhances both rate and selectivity towards primary alcohols. One-pot hydroformylation–hydrogenation using rhodium as the only transition

  14. Prediction of barrier inhomogeneities and carrier transport in Ni-silicided Schottky diode

    International Nuclear Information System (INIS)

    Saha, A.R.; Dimitriu, C.B.; Horsfall, A.B.; Chattopadhyay, S.; Wright, N.G.; O'Neill, A.G.; Maiti, C.K.

    2006-01-01

    Based on Quantum Mechanical (QM) carrier transport and the effects of interface states, a theoretical model has been developed to predict the anomalous current-voltage (I-V) characteristics of a non-ideal Ni-silicided Schottky diode at low temperatures. Physical parameters such as barrier height, ideality factor, series resistance and effective Richardson constant of a silicided Schottky diode were extracted from forward I-V characteristics and are subsequently used for the simulation of both forward and reverse I-V characteristics using a QM transport model in which the effects of interface state and bias dependent barrier reduction are incorporated. The present analysis indicates that the effects of barrier inhomogeneity caused by incomplete silicide formation at the junction and the interface states may change the conventional current transport process, leading to anomalous forward and reverse I-V characteristics for the Ni-silicided Schottky diode

  15. NMOS contact resistance reduction with selenium implant into NiPt silicide

    Science.gov (United States)

    Rao, K. V.; Khaja, F. A.; Ni, C. N.; Muthukrishnan, S.; Darlark, A.; Lei, J.; Peidous, I.; Brand, A.; Henry, T.; Variam, N.; Erokhin, Y.

    2012-11-01

    A 25% reduction in NMOS contact resistance (Rc) was achieved by Selenium implantation into NiPt silicide film in VIISta Trident high-current single-wafer implanter. The Trident implanter is designed for shallow high-dose implants with high beam currents to maintain high throughput (for low CoO), with improved micro-uniformity and no energy contamination. The integration of Se implant was realized using a test chip dedicated to investigating silicide/junction related electrical properties and testable after silicidation. The silicide module processes were optimized, including the pre-clean (prior to RF PVD NiPt dep) and pre- and post-implant anneals. A 270°C soak anneal was used for RTP1, whereas a msec laser anneal was employed for RTP2 with sufficient process window (800-850°C), while maintaining excellent junction characteristics without Rs degradation.

  16. Further data of silicide fuel for the LEU conversion of JMTR

    International Nuclear Information System (INIS)

    Saito, M.; Futamura, Y.; Nakata, H.; Ando, H.; Sakurai, F.; Ooka, N.; Sakakura, A.; Ugajin, M.; Shirai, E.

    1990-01-01

    Silicide fuel data for the safety assessment of the JMTR LEU fuel conversion are being measured. The data include fission product release, thermal properties, behaviour under accident conditions, and metallurgical characteristics. The methods used in the experiments are discussed. Results of fission products release at high temperature are described. The release of iodine from the silicide fuel is considerably lower than for U-Al alloy fuel

  17. Evaluation of the oxide and silicide fuels reactivity in the RSG-GAS core

    International Nuclear Information System (INIS)

    S, Tukiran; M S, Tagor; S, Lily; Pinem, S.

    2000-01-01

    Fuel exchange of The RSG-GAS reactor core from uranium oxide to uranium silicide in the same loading, density, and enrichment, that is, 250 gr, 2.98 gr/cm 3 , and 19.75 % respectively, will be performed in-step wise. In every cycle of exchange with 5/l mode, it is needed to evaluate the parameter of reactor core operation. One of the important operation parameters is fuel reactivity that gives effect to the core reactivity. The experiment was performed at core no. 36, BOC, low power which exist 2 silicide fuels. The evaluation was done based on the RSG-GAS control rod calibration consisting of 40 fuels and 8 control rod.s. From 40 fuels in the core, there are 2 silicide fuels, RI-225/A-9 and RI-224/C-3. For inserting 2 silicide fuels, the reactivity effect to the core must be know. To know this effect , it was performed fuels reactivity experiment, which based on control rod calibration. But in this case the RSG-GAS has no other fresh oxide fuel so that configuration of the RSG-GAS core was rearranged by taking out the both silicide fuels and this configuration is used as reference core. Then silicide fuel RI-224 was inserted to position F-3 replacing the fresh oxide fuel RI-260 so the different reactivity of the fuels is obtained. The experiment result showed that the fuel reactivity change is in amount of 12.85 cent (0.098 % ) The experiment result was compared to the calculation result, using IAFUEL code which amount to 13.49 cent (0.103 %) The result showed that the reactivity change of oxide to silicide fuel is small so that the fuel exchange from uranium oxide to uranium silicide in the first step can be done without any significant change of the operation parameter

  18. Information for irradiation and post-irradiation of the silicide fuel element prototype P-07

    International Nuclear Information System (INIS)

    Abbate, Maximo J.; Sbaffoni, Maria M.

    2003-01-01

    Included in the 'Silicides' Project, developed by the Nuclear Fuels Department of the National Atomic Energy Commission (CNEA), it is foreseen the qualification of this type of fuel for research reactors in order to be used in the Argentine RA-3 reactor and to confirm the CNEA as an international supplier. The paper presents basic information on several parameters corresponding to the new silicide prototype, called P-07, to be taken into account for its irradiation, postirradiation and qualification. (author)

  19. Thermoelectric characteristics of Pt-silicide/silicon multi-layer structured p-type silicon

    International Nuclear Information System (INIS)

    Choi, Wonchul; Jun, Dongseok; Kim, Soojung; Shin, Mincheol; Jang, Moongyu

    2015-01-01

    Electric and thermoelectric properties of silicide/silicon multi-layer structured devices were investigated with the variation of silicide/silicon heterojunction numbers from 3 to 12 layers. For the fabrication of silicide/silicon multi-layered structure, platinum and silicon layers are repeatedly sputtered on the (100) silicon bulk substrate and rapid thermal annealing is carried out for the silicidation. The manufactured devices show ohmic current–voltage (I–V) characteristics. The Seebeck coefficient of bulk Si is evaluated as 195.8 ± 15.3 μV/K at 300 K, whereas the 12 layered silicide/silicon multi-layer structured device is evaluated as 201.8 ± 9.1 μV/K. As the temperature increases to 400 K, the Seebeck coefficient increases to 237.2 ± 4.7 μV/K and 277.0 ± 1.1 μV/K for bulk and 12 layered devices, respectively. The increase of Seebeck coefficient in multi-layered structure is mainly attributed to the electron filtering effect due to the Schottky barrier at Pt-silicide/silicon interface. At 400 K, the thermal conductivity is reduced by about half of magnitude compared to bulk in multi-layered device which shows the efficient suppression of phonon propagation by using Pt-silicide/silicon hetero-junctions. - Highlights: • Silicide/silicon multi-layer structured is proposed for thermoelectric devices. • Electric and thermoelectric properties with the number of layer are investigated. • An increase of Seebeck coefficient is mainly attributed the Schottky barrier. • Phonon propagation is suppressed with the existence of Schottky barrier. • Thermal conductivity is reduced due to the suppression of phonon propagation

  20. Free Rhodium (II) citrate and rhodium (II) citrate magnetic carriers as potential strategies for breast cancer therapy

    Science.gov (United States)

    2011-01-01

    Background Rhodium (II) citrate (Rh2(H2cit)4) has significant antitumor, cytotoxic, and cytostatic activity on Ehrlich ascite tumor. Although toxic to normal cells, its lower toxicity when compared to carboxylate analogues of rhodium (II) indicates Rh2(H2cit)4 as a promising agent for chemotherapy. Nevertheless, few studies have been performed to explore this potential. Superparamagnetic particles of iron oxide (SPIOs) represent an attractive platform as carriers in drug delivery systems (DDS) because they can present greater specificity to tumor cells than normal cells. Thus, the association between Rh2(H2cit)4 and SPIOs can represent a strategy to enhance the former's therapeutic action. In this work, we report the cytotoxicity of free rhodium (II) citrate (Rh2(H2cit)4) and rhodium (II) citrate-loaded maghemite nanoparticles or magnetoliposomes, used as drug delivery systems, on both normal and carcinoma breast cell cultures. Results Treatment with free Rh2(H2cit)4 induced cytotoxicity that was dependent on dose, time, and cell line. The IC50 values showed that this effect was more intense on breast normal cells (MCF-10A) than on breast carcinoma cells (MCF-7 and 4T1). However, the treatment with 50 μM Rh2(H2cit)4-loaded maghemite nanoparticles (Magh-Rh2(H2cit)4) and Rh2(H2cit)4-loaded magnetoliposomes (Lip-Magh-Rh2(H2cit)4) induced a higher cytotoxicity on MCF-7 and 4T1 than on MCF-10A (p rhodium (II) citrate-loaded maghemite nanoparticles and magnetoliposomes induced more specific cytotoxicity on breast carcinoma cells than on breast normal cells, which is the opposite of the results observed with free Rh2(H2cit)4 treatment. Thus, magnetic nanoparticles represent an attractive platform as carriers in Rh2(H2cit)4 delivery systems, since they can act preferentially in tumor cells. Therefore, these nanopaticulate systems may be explored as a potential tool for chemotherapy drug development. PMID:21443799

  1. An Extended X-ray Absorption Fine Structure Study of Rhodium-Oxygen Bonds in a Highly Dispersed Rhodium/Aluminum Oxide Catalyst

    NARCIS (Netherlands)

    Koningsberger, D.C.; Zon, J.B.A.D. van; Blik, H.F.J. van 't; Visser, G.J.; Prins, R.; Mansour, A.N.; Sayers, D.E.; Short, D.R.

    1985-01-01

    Analysis of in situ EXAFS measurements on a 2.4 wt % Rh/A120, catalyst, reduced at 473 K after calcination at 623 K, shows the presence of two different rhodium-oxygen bonds (viz. 2.05 and 2.68 A). The oxygen neighbors of rhodium at a distance of 2.05 A disappear after reduction at 673 K. The

  2. Kinetics of nickel silicide growth in silicon nanowires: From linear to square root growth

    International Nuclear Information System (INIS)

    Yaish, Y. E.; Beregovsky, M.; Katsman, A.; Cohen, G. M.

    2011-01-01

    The common practice for nickel silicide formation in silicon nanowires (SiNWs) relies on axial growth of silicide along the wire that is initiated from nickel reservoirs at the source and drain contacts. In the present work the silicide intrusions were studied for various parameters including wire diameter (25-50 nm), annealing time (15-120 s), annealing temperature (300-440 deg. C), and the quality of the initial Ni/Si interface. The silicide formation was investigated by high-resolution scanning electron microscopy, high-resolution transmission electron microscopy (TEM), and atomic force microscopy. The main part of the intrusion formed at 420 deg. C consists of monosilicide NiSi, as was confirmed by energy dispersive spectroscopy STEM, selected area diffraction TEM, and electrical resistance measurements of fully silicided SiNWs. The kinetics of nickel silicide axial growth in the SiNWs was analyzed in the framework of a diffusion model through constrictions. The model calculates the time dependence of the intrusion length, L, and predicts crossover from linear to square root time dependency for different wire parameters, as confirmed by the experimental data.

  3. Attempt to produce silicide fuel elements in Indonesia

    International Nuclear Information System (INIS)

    Soentono, S.; Suripto, A.

    1991-01-01

    After the successful experiment to produce U 3 Si 2 powder and U 3 Si 2 -Al fuel plates using depleted U and Si of semiconductor quality, silicide fuel was synthesized using x -Al available at the Fuel Element Production Installation (FEPI) at Serpong, Indonesia. Two full-size U 3 Si 2 -Al fuel elements, having similar specifications to the ones of U 3 O 8 -Al for the RSG-GAS (formerly known as MPR-30), have been produced at the FEPI. All quality controls required have been imposed to the feeds, intermediate, as well as final products throughout the production processes of the two fuel elements. The current results show that these fuel elements are qualified from fabrication point of view, therefore it is expected that they will be permitted to be tested in the RSG-GAS, sometime by the end of 1989, for normal (∝50%) and above normal burn-up. (orig.)

  4. Status of the atomized uranium silicide fuel development at KAERI

    Energy Technology Data Exchange (ETDEWEB)

    Kim, C.K.; Kim, K.H.; Park, H.D.; Kuk, I.H. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1997-08-01

    While developing KMRR fuel fabrication technology an atomizing technique has been applied in order to eliminate the difficulties relating to the tough property of U{sub 3}Si and to take advantage of the rapid solidification effect of atomization. The comparison between the conventionally comminuted powder dispersion fuel and the atomized powder dispersion fuel has been made. As the result, the processes, uranium silicide powdering and heat treatment for U{sub 3}Si transformation, become simplified. The workability, the thermal conductivity and the thermal compatibility of fuel meat have been investigated and found to be improved due to the spherical shape of atomized powder. In this presentation the overall developments of atomized U{sub 3}Si dispersion fuel and the planned activities for applying the atomizing technique to the real fuel fabrication are described.

  5. Characterization of tungsten silicides formed by rapid thermal annealing

    International Nuclear Information System (INIS)

    Siegal, M.; Santiago, J.J.; VanDerSpiegel, J.

    1986-01-01

    Tungsten silicide samples were formed by sputter depositing 80 nm W metal onto (100) oriented, 5 ohm-cm Si wafers. After deposition, the samples were fast radiatively processed in an RTA system using quartz-halogen tungsten lamps as radiation sources for time intervals ranging from 20 to 60s under high vacuum. Films processed at 22-25 W/cm 2 radiation with the film side of the samples oriented away from the lamps result in films which are metallic or cloudy in color, and have mixed composition as evidenced by x-ray diffraction (W, W 5 Si 3 and WSi 2 ). Films processed with the film side oriented toward the lamps show the occurrence of a phase transformation clearly nucleated at the film edge

  6. Development of molecular dynamics potential for uranium silicide fuels

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Jianguo; Zhang, Yongfeng; Hales, Jason D.

    2016-09-01

    Use of uranium–silicide (U-Si) in place of uranium dioxide (UO2) is one of the promising concepts being proposed to increase the accident tolerance of nuclear fuels. This is due to a higher thermal conductivity than UO2 that results in lower centerline temperatures. U-Si also has a higher fissile density, which may enable some new cladding concepts that would otherwise require increased enrichment limits to compensate for their neutronic penalty. However, many critical material properties for U-Si have not been determined experimentally. For example, silicide compounds (U3Si2 and U3Si) are known to become amorphous under irradiation. There was clear independent experimental evidence to support a crystalline to amorphous transformation in those compounds. However, it is still not well understood how the amorphous transformation will affect on fuel behavior. It is anticipated that modeling and simulation may deliver guidance on the importance of various properties and help prioritize experimental work. In order to develop knowledge-based models for use at the engineering scale with a minimum of empirical parameters and increase the predictive capabilities of the developed model, inputs from atomistic simulations are essential. First-principles based density functional theory (DFT) calculations will provide the most reliable information. However, it is probably not possible to obtain kinetic information such as amorphization under irradiation directly from DFT simulations due to size and time limitations. Thus, a more feasible way may be to employ molecular dynamics (MD) simulation. Unfortunately, so far no MD potential is available for U-Si to discover the underlying mechanisms. Here, we will present our recent progress in developing a U-Si potential from ab initio data. This work is supported by the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program funded by the U.S. Department of Energy, Office of Nuclear Energy.

  7. Nickel silicide thin films as masking and structural layers for silicon bulk micro-machining by potassium hydroxide wet etching

    International Nuclear Information System (INIS)

    Bhaskaran, M; Sriram, S; Sim, L W

    2008-01-01

    This paper studies the feasibility of using titanium and nickel silicide thin films as mask materials for silicon bulk micro-machining. Thin films of nickel silicide were found to be more resistant to wet etching in potassium hydroxide. The use of nickel silicide as a structural material, by fabricating micro-beams of varying dimensions, is demonstrated. The micro-structures were realized using these thin films with wet etching using potassium hydroxide solution on (1 0 0) and (1 1 0) silicon substrates. These results show that nickel silicide is a suitable alternative to silicon nitride for silicon bulk micro-machining

  8. Industrial tests of rhodium self-powered detectors: the Golfech 2 experimentation

    International Nuclear Information System (INIS)

    Mourlevat, J.L.; Janvier, D.; Warren, H.D.

    2000-01-01

    In co-operation with Electricite de France (EDF), FRAMATOME has been testing two in-core strings which are equipped with rhodium self-powered detectors (SPDs) in the Golfech Unit 2 reactor (1300 MW, 4L plant) since August 1997. The rhodium SPDs and the strings which support them were designed and built by the US FRAMATOME subsidiary FRAMATOME-COGEMA-FUEL (FCF). The rhodium signals and some other plant parameters are acquired through the use of a specific device designed by the CEA (Commissariat a l'Energie Atomique) and are processed off-line by FRAMATOME. This demonstration test is planned to last until mid-2000. The following presentation is focused on the results obtained during the first demonstration cycle (from 08/97 to 12/98). The tests that have been conducted consist of checking the rhodium depletion and of comparing the rhodium signals to the movable probes. In order to compensate for the delay in the rhodium signals, a deconvolution algorithm has also been tested. Up to now, the results are very satisfactory and a future large scale industrial application is being discussed with the EDF. The main objective of the next experimentation phase is to test - under industrial conditions - a prototype of an on-line monitoring unit known as the Partial In-Core Monitoring System (PIMS). This system will include 16 rhodium in-core strings and will use an on-line 3-D core model. (authors)

  9. Methane Steam Reforming Kinetics for a Rhodium-Based Catalyst

    DEFF Research Database (Denmark)

    Jakobsen, Jon Geest; Jakobsen, M.; Chorkendorff, Ib

    2010-01-01

    Methane steam reforming is the key reaction to produce synthesis gas and hydrogen at the industrial scale. Here the kinetics of methane steam reforming over a rhodium-based catalyst is investigated in the temperature range 500-800 A degrees C and as a function of CH4, H2O and H-2 partial pressures....... The methane steam reforming reaction cannot be modeled without taking CO and H coverages into account. This is especially important at low temperatures and higher partial pressures of CO and H-2. For methane CO2 reforming experiments, it is also necessary to consider the repulsive interaction of CO...

  10. A Recyclable Nanoparticle-Supported Rhodium Catalyst for Hydrogenation Reactions

    Directory of Open Access Journals (Sweden)

    Maria Michela Dell’Anna

    2010-05-01

    Full Text Available Catalytic hydrogenation under mild conditions of olefins, unsaturated aldeydes and ketones, nitriles and nitroarenes was investigated, using a supported rhodium complex obtained by copolymerization of Rh(cod(aaema [cod: 1,5-cyclooctadiene, aaema–: deprotonated form of 2-(acetoacetoxyethyl methacrylate] with acrylamides. In particular, the hydrogenation reaction of halonitroarenes was carried out under 20 bar hydrogen pressure with ethanol as solvent at room temperature, in order to minimize hydro-dehalogenation. The yields in haloanilines ranged from 85% (bromoaniline to 98% (chloroaniline.

  11. Hydrogen adsorption on skeletal rhodium-tantalum electrodes-catalysts

    International Nuclear Information System (INIS)

    Tsinstevich, V.M.; Krejnina, N.M.

    1975-01-01

    Skeleton rhodium-tantalic catalyst electrodes with a tantalum mass percentage of 0 to 100 have been obtained by the methodology of Crupp and others. The hydrogen adsorption is studied through the method of removing the galvano-static and potentiodynamic curves of charging in sulfuric acid and potassium hydroxide. It has been discovered that the maximum adsorption ability relatively to the hydrogen can be observed in an alloy with a 5% tantalum contents. The energetic characteristics of the alloys are higher in alkali than in acid

  12. Rhodium in car exhaust tips by total automatic activation analysis

    International Nuclear Information System (INIS)

    Grass, F.; Westphal, G.P.; Lemmel, H.; Sterba, J.

    2007-01-01

    Exhaust systems of modern cars contain catalysts for the reduction of CO, NO x and hydrocarbons. These catalysts are made of ceramic materials with a large surface on which platinum metals catalyse the oxidation. The catalysts contain approximately 2 g of platinum and 0.4 g of rhodium. Recently platinum is being replaced by palladium. During driving the platinum-group elements (PGEs) are expelled from the tip in fine particles and are deposited in the environment. For a projected study of emissions from cars driven on streets and highways it is important to know which elements can be measured by short time activation analysis without any chemical procedure. (author)

  13. Molecular recognition in protein modification with rhodium metallopeptides

    Science.gov (United States)

    Ball, Zachary T.

    2015-01-01

    Chemical manipulation of natural, unengineered proteins is a daunting challenge which tests the limits of reaction design. By combining transition-metal or other catalysts with molecular recognition ideas, it is possible to achieve site-selective protein reactivity without the need for engineered recognition sequences or reactive sites. Some recent examples in this area have used ruthenium photocatalysis, pyridine organocatalysis, and rhodium(II) metallocarbene catalysis, indicating that the fundamental ideas provide opportunities for using diverse reactivity on complex protein substrates and in complex cell-like environments. PMID:25588960

  14. Technology CAD of silicided Schottky barrier MOSFET for elevated source-drain engineering

    International Nuclear Information System (INIS)

    Saha, A.R.; Chattopadhyay, S.; Bose, C.; Maiti, C.K.

    2005-01-01

    Technology CAD has been used to study the performance of a silicided Schottky barrier (SB) MOSFET with gate, source and drain contacts realized with nickel-silicide. Elevated source-drain structures have been used towards the S/D engineering of CMOS devices. A full process-to-device simulation has been employed to predict the performance of sub-micron SB n-MOSFETs for the first time. A model for the diffusion and alloy growth kinetics has been incorporated in SILVACO-ATLAS and ATHENA to explore the processing and design parameter space for the Ni-silicided MOSFETs. The temperature and concentration dependent diffusion model for NiSi have been developed and necessary material parameters for nickel-silicide and epitaxial-Si have been incorporated through the C-interpreter function. Two-dimensional (2D) process-to-device simulations have also been used to study the dc and ac (RF) performance of silicided Schottky barrier (SB) n-MOSFETs. The extracted sheet resistivity, as a function of annealing temperature of the silicided S/D contacts, is found to be lower than the conventional contacts currently in use. It is also shown that the Technology CAD has the full capability to predict the possible dc and ac performance enhancement of a MOSFET with elevated S/D structures. While the simulated dc performance shows a clear enhancement, the RF analyses show no performance degradation in the cut-off frequency/propagation delay and also improve the ac performance due to the incorporation of silicide contacts in the S/D region

  15. Technology CAD of silicided Schottky barrier MOSFET for elevated source-drain engineering

    Energy Technology Data Exchange (ETDEWEB)

    Saha, A.R. [Department of Electronics and ECE, IIT, Kharagpur 721302 (India)]. E-mail: ars.iitkgp@gmail.com; Chattopadhyay, S. [Department of Electronics and ECE, IIT, Kharagpur 721302 (India); School of Electrical, Electronics and Computer Engineering, University of Newcastle, Newcastle upon Tyne (United Kingdom); Bose, C. [Department of Electronics and Telecommunication Engineering, Jadavpur University, Calcutta 700032 (India); Maiti, C.K. [Department of Electronics and ECE, IIT, Kharagpur 721302 (India)

    2005-12-05

    Technology CAD has been used to study the performance of a silicided Schottky barrier (SB) MOSFET with gate, source and drain contacts realized with nickel-silicide. Elevated source-drain structures have been used towards the S/D engineering of CMOS devices. A full process-to-device simulation has been employed to predict the performance of sub-micron SB n-MOSFETs for the first time. A model for the diffusion and alloy growth kinetics has been incorporated in SILVACO-ATLAS and ATHENA to explore the processing and design parameter space for the Ni-silicided MOSFETs. The temperature and concentration dependent diffusion model for NiSi have been developed and necessary material parameters for nickel-silicide and epitaxial-Si have been incorporated through the C-interpreter function. Two-dimensional (2D) process-to-device simulations have also been used to study the dc and ac (RF) performance of silicided Schottky barrier (SB) n-MOSFETs. The extracted sheet resistivity, as a function of annealing temperature of the silicided S/D contacts, is found to be lower than the conventional contacts currently in use. It is also shown that the Technology CAD has the full capability to predict the possible dc and ac performance enhancement of a MOSFET with elevated S/D structures. While the simulated dc performance shows a clear enhancement, the RF analyses show no performance degradation in the cut-off frequency/propagation delay and also improve the ac performance due to the incorporation of silicide contacts in the S/D region.

  16. Atmosphere-Controlled Chemoselectivity: Rhodium-Catalyzed Alkylation and Olefination of Alkylnitriles with Alcohols.

    Science.gov (United States)

    Li, Junjun; Liu, Yuxuan; Tang, Weijun; Xue, Dong; Li, Chaoqun; Xiao, Jianliang; Wang, Chao

    2017-10-17

    The chemoselective alkylation and olefination of alkylnitriles with alcohols have been developed by simply controlling the reaction atmosphere. A binuclear rhodium complex catalyzes the alkylation reaction under argon through a hydrogen-borrowing pathway and the olefination reaction under oxygen through aerobic dehydrogenation. Broad substrate scope is demonstrated, permitting the synthesis of some important organic building blocks. Mechanistic studies suggest that the alkylation product may be formed through conjugate reduction of an alkene intermediate by a rhodium hydride, whereas the formation of olefin product may be due to the oxidation of the rhodium hydride complex with molecular oxygen. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Reclamation and reuse of LEU silicide fuel from manufacturing scrap

    International Nuclear Information System (INIS)

    Gale, G.R.; Pace, B.W.; Evans, R.S.

    2004-01-01

    In order to provide an understanding of the organization which is the sole supplier of United States plate type research and test reactor fuel and LEU core conversions, a brief description of the structure and history is presented. Babcock and Wilcox (B and W) is a part of McDermott International, Inc. which is a large diversified corporation employing over 20,000 people primarily in engineering and construction for the off-shore oil and power generation industries throughout the world. B and W provides many energy related products requiring precision machining and high quality systems. This is accomplished by using state-of-the-art equipment, technology and highly skilled people. The RTRFE group within B and W has the ability to produce various complexly shaped fuel elements with a wide variety of fuels and enrichments. B and W RTRFE has fabricated over 200,000 plates since 1981 and gained the diversified experience necessary to satisfy many customer requirements. This accomplishment was possible with the support of McDermott International and all of its resources. B and W has always had a commitment to high quality and integrity. This is apparent by the success and longevity (125 years) of the company. A lower cost to convert cores to LEU provides direct support to RERTR and demonstrates Babcock and Wilcox's commitment to the program. As a supporter of RERTR reactor conversion from HEU to LEU, B and W has contributed a significant amount of R and D money to improve the silicide fuel process which ultimately lowers the LEU core costs. In the most recent R and D project, B and W is constructing a LEU silicide reclamation facility to re-use the unirradiated fuel scrap generated from the production process. Remanufacturing use of this fuel completes the fuel cycle and provides a contribution to LEU cores by reducing scrap inventory and handling costs, lowering initial purchase of fuel due to increasing the process yields, and lowering the replacement costs. This

  18. Capacitance-voltage characterization of fully silicided gated MOS capacitor

    International Nuclear Information System (INIS)

    Wang Baomin; Ru Guoping; Jiang Yulong; Qu Xinping; Li Bingzong; Liu Ran

    2009-01-01

    This paper investigates the capacitance-voltage (C-V) measurement on fully silicided (FUSI) gated metal-oxide-semiconductor (MOS) capacitors and the applicability of MOS capacitor models. When the oxide leakage current of an MOS capacitor is large, two-element parallel or series model cannot be used to obtain its real C-V characteristic. A three-element model simultaneously consisting of parallel conductance and series resistance or a four-element model with further consideration of a series inductance should be used. We employed the three-element and the four-element models with the help of two-frequency technique to measure the Ni FUSI gated MOS capacitors. The results indicate that the capacitance of the MOS capacitors extracted by the three-element model still shows some frequency dispersion, while that extracted by the four-element model is close to the real capacitance, showing little frequency dispersion. The obtained capacitance can be used to calculate the dielectric thickness with quantum effect correction by NCSU C-V program. We also investigated the influence of MOS capacitor's area on the measurement accuracy. The results indicate that the decrease of capacitor area can reduce the dissipation factor and improve the measurement accuracy. As a result, the frequency dispersion of the measured capacitance is significantly reduced, and real C-V characteristic can be obtained directly by the series model. In addition, this paper investigates the quasi-static C-V measurement and the photonic high-frequency C-V measurement on Ni FUSI metal gated MOS capacitor with a thin leaky oxide. The results indicate that the large tunneling current through the gate oxide significantly perturbs the accurate measurement of the displacement current, which is essential for the quasi-static C-V measurement. On the other hand, the photonic high-frequency C-V measurement can bypass the leakage problem, and get reliable low-frequency C-V characteristic, which can be used to

  19. Microstructure and mechanical properties of metal/oxide and metal/silicide interfaces

    International Nuclear Information System (INIS)

    Shaw, L.; Miracle, D.; Abbaschian, R.

    1995-01-01

    Fracture energies of Al 2 O 3 /Nb interfaces and MoSi 2 /Nb interfaces with and without Al 2 O 3 coating were measured using sandwich-type chevron-notched specimens. The relations between the mechanical properties, microstructures, types of bonds at the interface and processing routes were explored. The fracture energy of the Al 2 O 3 /Nb interface was determined to be 9 J/m 2 and changed to 16 J/m 2 when Nb was pre-oxidized before the formation of the Al 2 O 3 /Nb interface. The fracture energy of the MoSi 2 /Nb interface could not be determined directly because of the formation of the interfacial compounds. However, the fracture energy at the MoSi 2 /Nb interfacial region was found to depend on the interfacial bond strength, roughness of interfaces and microstructure of interfacial compounds. The interfacial fracture energies of Al 2 O 3 with silicides, MoSi 2 , Nb 5 Si 3 , or (Nb, Mo)Si 2 were estimated to be about 16 J/m 2 , while the interfacial fracture energies between two silicides or between Nb and a silicide were larger than 34 J/m 2 . The measured fracture energies between two silicides or between Nb and a silicide were larger than 34 J/m 2 . The measured fracture energies of the various interfaces are discussed in terms of the interfacial microstructures and types of bonds at the interfaces

  20. Improvement of Silicide Coating Method as Diffusion Barrier for U-Mo Dispersion Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Nam, Ji Min; Kim, Sunghwan; Lee, Kyu Hong; Park, Jong Man [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-10-15

    The excessive interaction between the U-Mo alloys and their surrounding Al matrix lead to excessive local swelling called 'pillowing'. For this reason, KAERI suggested several remedies such as alloying U-Mo with Ti, or Al matrix with Si. In addition, silicide or nitride coatings on the surface of U-Mo particles have also been proposed to hinder the growth of the interaction layer. In this study, centrifugally atomized U-Mo-Ti alloy powders were coated with silicide layers. The coating process was improved when compared to the previous coating in terms of the ball milling and heat treatment conditions. Subsequently, silicide coated U-Mo-Ti powders and pure aluminum powders were mixed and made into a compact for the annealing test. The compacts were annealed at 550 .deg. C for 2hr, and characterized using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). 1. Uniform, homogeneous, thickness controllable silicide layers were successfully coated on the surface of U-7wt%Mo-1wt%Ti powders. 2. U{sub 3}Si, U{sub 3}Si{sub 2} silicide layers formed on the surface of U-7wt%Mo-1wt%Ti powders, and were identified by XRD and EDS analyses.

  1. Synthesis of molybdenum borides and molybdenum silicides in molten salts and their oxidation behavior in an air-water mixture

    NARCIS (Netherlands)

    Kuznetsov, S.A.; Kuznetsova, S.V.; Rebrov, E.V.; Mies, M.J.M.; Croon, de M.H.J.M.; Schouten, J.C.

    2005-01-01

    The formation of various coatings in molybdenum-boron and molybdenum-silicon systems was investigated. Boronizing and siliciding treatments were conducted in molten salts under inert gas atm. in the 850-1050 DegC temp. range for 7 h. The presence of boride (e.g. Mo2B, MoB, Mo2B5) and silicide

  2. Neutronic design of mixed oxide-silicide cores for the core conversion of rsg-gas reactor

    International Nuclear Information System (INIS)

    Sembiring, Tagor Malem; Tukiran; Pinem surian; Febrianto

    2001-01-01

    The core conversion of rsg-gas reactor from an all-oxide (U 3 O 8 -Al) core, through a series of mixed oxide-silicide core, to an all-silicide (U 3 Si 2 -Al) core for the same meat density of 2.96 g U/cc is in progress. The conversion is first step of the step-wise conversion and will be followed by the second step that is the core conversion from low meat density of silicide core, through a series of mixed lower-higher density of silicide core, to an all-higher meat density of 3.55 g/cc core. Therefore, the objectives of this work is to design the mixed cores on the neutronic performance to achieve safety a first full-silicide core for the reactor with the low uranium meat density of 2.96gU/cc. The neutronic design of the mixed cores was performed by means of Batan-EQUIL-2D and Batan-3DIFF computer codes for 2 and 3 dimension diffusion calculation, respectively. The result shows that all mixed oxide-silicide cores will be feasible to achieve safety a fist full-silicide core. The core performs the same neutronic core parameters as those of the equilibrium silicide core. Therefore, the reactor availability and utilization during the core conversion is not changed

  3. Nanoscale investigation of the interface situation of plated nickel and thermally formed nickel silicide for silicon solar cell metallization

    Energy Technology Data Exchange (ETDEWEB)

    Mondon, A., E-mail: andrew.mondon@ise.fraunhofer.de [Fraunhofer ISE, Heidenhofst. 2, D-79110 Freiburg (Germany); Wang, D. [Karlsruhe Nano Micro Facility (KNMF), H.-von-Helmholz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); Zuschlag, A. [Universität Konstanz FB Physik, Jacob-Burckhardt-Str. 27, D-78464 Konstanz (Germany); Bartsch, J.; Glatthaar, M.; Glunz, S.W. [Fraunhofer ISE, Heidenhofst. 2, D-79110 Freiburg (Germany)

    2014-12-30

    Highlights: • Adhesion of metallization of fully plated nickel–copper contacts on silicon solar cells can be achieved by formation of nickel silicide at the cost of degraded cell performance. • Understanding of silicide growth mechanisms and controlled growth may lead to high performance together with excellent adhesion. • Silicide formation is well known from CMOS production from PVD-Ni on flat surfaces. Yet the deposition methods and therefore layer characteristics and the surface topography are different for plated metallization. • TEM analysis is performed for differently processed samples. • A nickel silicide growth model is created for plated Ni on textured silicon solar cells. - Abstract: In the context of nickel silicide formation from plated nickel layers for solar cell metallization, there are several open questions regarding contact adhesion and electrical properties. Nanoscale characterization by transmission electron microscopy has been employed to support these investigations. Interfacial oxides and silicide phases were investigated on differently prepared samples by different analytical methods associated with transmission electron microscopy analysis. Processing variations included the pre-treatment of samples before nickel plating, the used plating solution and the thermal budget for the nickel–silicon solid-state reaction. It was shown that interface oxides of only few nm thickness on both silicon and nickel silicide are present on the samples, depending on the chosen process sequence, which have been shown to play an important role in adhesion of nickel on silicide in an earlier publication. From sample pretreatment variations, conclusions about the role of an interfacial oxide in silicide formation and its influence on phase formation were drawn. Such an oxide layer hinders silicide formation except for pinhole sites. This reduces the availability of Ni and causes a silicide with low Ni content to form. Without an interfacial oxide

  4. Rhodium-Catalyzed Enantioselective Cyclopropanation of Olefins with N-Sulfonyl 1,2,3-Triazoles

    Science.gov (United States)

    Chuprakov, Stepan; Kwok, Sen Wai; Zhang, Li; Lercher, Lukas; Fokin, Valery V.

    2009-01-01

    N-Sulfonyl 1,2,3-triazoles readily form rhodium(II) azavinyl carbenes, which react with olefins to produce cyclopropanes with excellent diastereo- and enantioselectivity and in high yield. PMID:19928917

  5. First-principles study of hydrogen diffusion in transition metal Rhodium

    International Nuclear Information System (INIS)

    Bao, Wulijibilige; Cui, Xin; Wang, Zhi-Ping

    2015-01-01

    In this study, the diffuse pattern and path of hydrogen in transition metal rhodium are investigated by the first-principles calculations. Density functional theory is used to calculate the system energies of hydrogen atom occupying different positions in rhodium crystal lattice. The results indicate that the most stable position of hydrogen atom in rhodium crystal lattice locates at the octahedral interstice, and the tetrahedral interstice is the second stable site. The activation barrier energy for the diffusion of atomic hydrogen in transition metal rhodium is quantified by determining the most favorable path, i.e., the minimum-energy pathway for diffusion, that is the indirect octahedral-tetrahedral-octahedral (O-T-O) pathway, and the activation energy is 0.8345eV

  6. Rhodium-catalyzed Chemo- and Regioselective Cross-dimerization of Two Terminal Alkynes

    Science.gov (United States)

    Xu, Hua-Dong; Zhang, Ren-Wei; Li, Xiaoxun; Huang, Suyu; Tang, Weiping; Hu, Wen-Hao

    2013-01-01

    Cross-dimerization of terminal arylacetylenes and terminal propargylic alcohols/amides has been achieved in the effect of a rhodium catalyst. This method features high chemo- and regioselectivities rendering convenient and atom economical access to functionalized enynes. PMID:23356993

  7. Crystal structures of fac-tri?chlorido?tris?(tri?methyl?phosphane-?P)rhodium(III) monohydrate and fac-tri?chlorido?tris?(tri?methyl?phosphane-?P)rhodium(III) methanol hemisolvate: rhodium structures that are isotypic with their iridium analogs

    OpenAIRE

    Merola, Joseph S.; Franks, Marion A.

    2015-01-01

    The crystal structures of two solvates of fac-tri-chlorido-tris-(tri-methyl-phosphane-κP)rhodium(III) are reported, i.e. one with water in the crystal lattice, fac-[RhCl3(Me3P)3]·H2O, and one with methanol in the crystal lattice, fac-[RhCl3(Me3P)3]·0.5CH3OH. These rhodium compounds exhibit distorted octahedral coordination spheres at the metal and are isotypic with the analogous iridium compounds previously reported by us [Merola et al. (2013 ▶). Polyhedron, 54, 67-73]. Comparison is made bet...

  8. Irradiation of an uranium silicide prototype in RA-3 reactor

    International Nuclear Information System (INIS)

    Calabrese, R.; Estrik, G.; Notari, C.

    1996-01-01

    The factibility of irradiation of an uranium silicide (U 3 Si 2 ) prototype in the RA-3 reactor was studied. The standard RA-3 fuel element uses U 3 O 8 as fissible material. The enrichment of both standard and prototype is the same: 20% U 235 and also the frame geometry and number of plates is identical. The differences are in the plate dimensions and the fissile content which is higher in the prototype. The cooling conditions of the core allow the insertion of the prototype in any core position, even near the water trap, if the overall power is kept below 5Mw. Nevertheless, the recommendation was to begin irradiation near the periphery and later on move the prototype towards more central positions in order to increase the burnup rate. The prototype was effectively introduced in a peripheral position and the thermal fluxes were measured between plates with the foil activation technique. These were also evaluated with the fuel management codes and a reasonable agreement was found. (author). 5 refs., 3 figs., 3 tabs

  9. Milling uranium silicide powder for dispersion nuclear fuels

    Energy Technology Data Exchange (ETDEWEB)

    Vieira, E.; Silva, D.G.; Souza, J.A.B.; Durazzo, M. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Riella, H.G. [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil)

    2009-07-01

    Full text: Uranium silicide (U3Si2) is presently considered the best fuel qualified so far in terms of uranium loading and performance. Stability of the U3Si2 fuel with uranium density of 4.8 g/cm3 was confirmed by burnup stability tests performed during the Reduced Enrichment for Research and Test Reactors (RERTR) program. This fuel was chosen to compose the first core of the new Brazilian Multipurpose Research Reactor (RMB), planned to be constructed in the next years. This new reactor will consume bigger quantities of U3Si2 powder, when compared with the small consumption of the IEA-R1 research reactor of IPEN-CNEN/SP, the unique MTR type research reactor operating in the country. At the present time, the milling operation of U3Si2 ingots is made manually. In order to increase the powder production capacity, the manual milling must be replaced by an automated procedure. This paper describes a new milling machine and procedure developed to produce U3Si2 powder with higher efficiency. (author)

  10. Mixing of Al into uranium silicides reactor fuels

    International Nuclear Information System (INIS)

    Ding, F.R.; Birtcher, R.C.; Kestel, B.J.; Baldo, P.M.

    1996-11-01

    SEM observations have shown that irradiation induced interaction of the aluminum cladding with uranium silicide reactor fuels strongly affects both fission gas and fuel swelling behaviors during fuel burn-up. The authors have used ion beam mixing, by 1.5 MeV Kr, to study this phenomena. RBS and the 27 Al(p, γ) 28 Si resonance nuclear reaction were used to measure radiation induced mixing of Al into U 3 Si and U 3 Si 2 after irradiation at 300 C. Initially U mixes into the Al layer and Al mixes into the U 3 Si. At a low dose, the Al layer is converted into UAl 4 type compound while near the interface the phase U(Al .93 Si .07 ) 3 grows. Under irradiation, Al diffuses out of the UAl 4 surface layer, and the lower density ternary, which is stable under irradiation, is the final product. Al mixing into U 3 Si 2 is slower than in U 3 Si, but after high dose irradiation the Al concentration extends much farther into the bulk. In both systems Al mixing and diffusion is controlled by phase formation and growth. The Al mixing rates into the two alloys are similar to that of Al into pure uranium where similar aluminide phases are formed

  11. Simulated Fission Gas Behavior in Silicide Fuel at LWR Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Yinbin [Argonne National Lab. (ANL), Argonne, IL (United States); Mo, Kun [Argonne National Lab. (ANL), Argonne, IL (United States); Yacout, Abdellatif [Argonne National Lab. (ANL), Argonne, IL (United States); Harp, Jason [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-09-15

    As a promising candidate for the accident tolerant fuel (ATF) used in light water reactors (LWRs), the fuel performance of uranium silicide (U3Si2) at LWR conditions needs to be well-understood. However, existing experimental post-irradiation examination (PIE) data are limited to the research reactor conditions, which involve lower fuel temperature compared to LWR conditions. This lack of appropriate experimental data significantly affects the development of fuel performance codes that can precisely predict the microstructure evolution and property degradation at LWR conditions, and therefore evaluate the qualification of U3Si2 as an AFT for LWRs. Considering the high cost, long timescale, and restrictive access of the in-pile irradiation experiments, this study aims to utilize ion irradiation to simulate the inpile behavior of the U3Si2 fuel. Both in situ TEM ion irradiation and ex situ high-energy ATLAS ion irradiation experiments were employed to simulate different types of microstructure modifications in U3Si2. Multiple PIE techniques were used or will be used to quantitatively analyze the microstructure evolution induced by ion irradiation so as to provide valuable reference for the development of fuel performance code prior to the availability of the in-pile irradiation data.

  12. Modifiers in rhodium catalysts for carbon monoxide hydrogenation: Structure-activity relationships

    Energy Technology Data Exchange (ETDEWEB)

    Bhore, N. A.

    1989-05-01

    This report is aimed at identifying interesting modified rhodium systems and elucidating structure-activity relationships in these systems with the overall goal of understanding the scientific issues in the catalytic conversion of syngas to oxygenates. Specific additives (sodium and molybdenum) are selected based on the scoping experiments. The effect of the additives on supported rhodium catalysts is then investigated. Throughout the investigation, experiments and analysis were performed on real systems instead of ideal systems. 374 refs., 82 figs., 57 tabs.

  13. Rhodium-Catalyzed Linear Codimerization and Cycloaddition of Ketenes with Alkynes

    Directory of Open Access Journals (Sweden)

    Teruyuki Kondo

    2010-06-01

    Full Text Available A novel rhodium-catalyzed linear codimerization of alkyl phenyl ketenes with internal alkynes to dienones and a novel synthesis of furans by an unusual cycloaddition of diaryl ketenes with internal alkynes have been developed. These reactions proceed smoothly with the same rhodium catalyst, RhCl(PPh33, and are highly dependent on the structure and reactivity of the starting ketenes.

  14. Nanoscale investigation of the interface situation of plated nickel and thermally formed nickel silicide for silicon solar cell metallization

    Science.gov (United States)

    Mondon, A.; Wang, D.; Zuschlag, A.; Bartsch, J.; Glatthaar, M.; Glunz, S. W.

    2014-12-01

    In the context of nickel silicide formation from plated nickel layers for solar cell metallization, there are several open questions regarding contact adhesion and electrical properties. Nanoscale characterization by transmission electron microscopy has been employed to support these investigations. Interfacial oxides and silicide phases were investigated on differently prepared samples by different analytical methods associated with transmission electron microscopy analysis. Processing variations included the pre-treatment of samples before nickel plating, the used plating solution and the thermal budget for the nickel-silicon solid-state reaction. It was shown that interface oxides of only few nm thickness on both silicon and nickel silicide are present on the samples, depending on the chosen process sequence, which have been shown to play an important role in adhesion of nickel on silicide in an earlier publication. From sample pretreatment variations, conclusions about the role of an interfacial oxide in silicide formation and its influence on phase formation were drawn. Such an oxide layer hinders silicide formation except for pinhole sites. This reduces the availability of Ni and causes a silicide with low Ni content to form. Without an interfacial oxide a continuous nickel silicide of greater depth, polycrystalline modification and expected phase according to thermal budget is formed. Information about the nature of silicide growth on typical solar cell surfaces could be obtained from silicide phase and geometric observations, which were supported by FIB tomography. The theory of isotropic NiSi growth and orientation dependent NiSi2 growth was derived. By this, a very well performing low-cost metallization for silicon solar cells has been brought an important step closer to industrial introduction.

  15. Analysis of impurity effect on Silicide fuels of the RSG-GAS core

    International Nuclear Information System (INIS)

    Tukiran-Surbakti

    2003-01-01

    Simulation of impurity effect on silicide fuel of the RSG-GAS core has been done. The aim of this research is to know impurity effect of the U-234 and U-236 isotopes in the silicide fuels on the core criticality. The silicide fuels of 250 g U loading and 19.75 of enrichment is used in this simulation. Cross section constant of fuels and non-structure material of core are generated by WIMSD/4 computer code, meanwhile impurity concentration was arranged from 0.01% to 2%. From the result of analysis can be concluded that the isotopes impurity in the fuels could make trouble in the core and the core can not be operated at critical after a half of its cycle length (350 MW D)

  16. Self-organized patterns along sidewalls of iron silicide nanowires on Si(110) and their origin

    Energy Technology Data Exchange (ETDEWEB)

    Das, Debolina; Mahato, J. C.; Bisi, Bhaskar; Dev, B. N., E-mail: msbnd@iacs.res.in [Department of Materials Science, Indian Association for the Cultivation of Science, Kolkata 700032 (India); Satpati, B. [Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)

    2014-11-10

    Iron silicide (cubic FeSi{sub 2}) nanowires have been grown on Si(110) by reactive deposition epitaxy and investigated by scanning tunneling microscopy and scanning/transmission electron microscopy. On an otherwise uniform nanowire, a semi-periodic pattern along the edges of FeSi{sub 2} nanowires has been discovered. The origin of such growth patterns has been traced to initial growth of silicide nanodots with a pyramidal Si base at the chevron-like atomic arrangement of a clean reconstructed Si(110) surface. The pyramidal base evolves into a comb-like structure along the edges of the nanowires. This causes the semi-periodic structure of the iron silicide nanowires along their edges.

  17. Evaluation Of Oxide And Silicide Mixed Fuels Of The RSG-GAS Core

    International Nuclear Information System (INIS)

    Tukiran; Sembiring, Tagor Malem; Suparlina, Lily

    2000-01-01

    Fuel exchange of the RSG-GAS reactor core from uranium oxide to uranium silicide in the same loading, density, and enrichment, that is 250 gr, 2.98 gr/cm 3 , and 19.75%, respectively, will be performed in-step wise. In every cycle of exchange with 5/1 mode, it is needed to evaluate the parameter of reactor core operation. The parameters of the reactor operation observed are criticality mass of fuels, reactivity balance, and fuel reactivity that give effect to the reactor operation. The evaluation was done at beginning of cycle of the first and second transition core with compared between experiment and calculation results. The experiments were performed at transition core I and II, BOC, and low power. At transition core I, there are 2 silicide fuels (RI-224 and R1-225) in the core and then, added five silicide fuels (R1-226, R1-252, R1-263, and R1-264) to the core, so that there are seven silicide fuels in the transition core II. The evaluation was done based on the experiment of criticality, control rod calibration, fuel reactivity of the RSG-GAS transition core. For inserting 2 silicide fuels in the transition core I dan 7 fuels in the transition core II, the operation of RSG-GAS core fulfilled the safety margin and the parameter of reactor operation change is not occur drastically in experiment and calculation results. So that, the reactor was operated during 36 days at 15 MW, 540 MWD at the first transition core. The general result showed that the parameter of reactor operation change is small so that the fuel exchange from uranium oxide to uranium silicide in the next step can be done

  18. A Study on Silicide Coatings as Diffusion barrier for U-7Mo Dispersion Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Won, Ju Jin; Kim, Sung Hwan; Lee, Kyu Hong; Jeong, Yong Jin; Kim, Ki Nam; Park, Jong Man; Lee, Chong Tak [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    Gamma phase U-Mo alloys are regarded as one of the promising candidates for advanced research reactor fuel when it comes to the irradiation performance. However, it has been reported that interaction layer formation between the UMo alloys and Al matrix degrades the irradiation performance of U-Mo dispersion fuel. The excessive interaction between the U-Mo alloys and their surrounding Al matrix lead to excessive local swelling called 'pillowing'. For this reason, KAERI suggested several remedies such as alloying U-Mo with Al matrix with Si. In addition, silicide or nitride coatings on the surface of U-Mo particles have also been proposed to hinder the growth of the interaction layer. In this study, centrifugally atomized U-7Mo alloy powders were coated with silicide layers at 900 .deg. C for 1hr. U-Mo alloy powder was mixed with MoSi{sub 2}, Si and ZrSi{sub 2} powders and subsequently heat-treated to form uranium-silicide coating layers on the surface of U-Mo alloy particles. Silicide coated U-Mo powders and characterized using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS) and X-ray diffractometer (XRD). The ZrSi{sub 2} coating layers has a thickness of about 1∼ 2μm. The surface of a silicide coated particle was very rough and silicide powder attached to the surface of the coating layer. 3. The XRD analysis of the coating layers showed that, they consisted of compounds such as U3Si{sub 2}, USi{sub 2}.

  19. Effects of Silicide Coating on the Interdiffusion between U-7Mo and Al

    Energy Technology Data Exchange (ETDEWEB)

    Nam, Ji Min; Kim, Ji Hyun; Kim, Sunghwan; Lee, Kyu Hong; Park, Jong Man; Jeong, Yong Jin; Kim, Ki Nam [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    The excessive interaction between the U-Mo alloys and their surrounding Al matrix lead to and excessive local swelling called 'pillowing'. For this reason, KAERI suggested several remedies such as alloying U-Mo with Ti, or Al matrix with Si. In addition, silicide, or nitride coatings on the surface of U-Mo particles have also been proposed to hinder the growth of interaction layer. In this study, centrifugally atomized U-7Mo alloy powders were coated with silicide layers at varying T (T = 900 and 1000 .deg. C) for 30 min, respectively. U-Mo alloy powder was blended with Si powders and subsequently heat-treated to form uranium-silicide coating layers on the surface of U-Mo alloy particles. For an annealing test, silicide-coated U-Mo alloy powders were made into a compact, and Al powders were used as a matrix. From EDS results, transformed uranium aluminide intermetallic compounds were mainly U(Al,Si)3. U(Al,Si)3 phase left the silicide coating layer behind, and formed inside of U-7Mo particles, as shown in Fig. 3(a) and (b). In the case of sample B, Al could not penetrate the silicide coating layer and the coating layers were remained constant, as shown in Fig. 3(c) and (d). From the results, we made a comparison between the compacts of sample A and B, and it was shown that Al can easily diffuse into unreacted Si and U{sub 3}Si{sub 5} mixed layer while U{sub 3}Si{sub 2} acted as a good diffusion barrier at 550 .deg. C though those layers had the same thickness.

  20. Effects of Silicide Coating on the Interdiffusion between U-7Mo and Al

    International Nuclear Information System (INIS)

    Nam, Ji Min; Kim, Ji Hyun; Kim, Sunghwan; Lee, Kyu Hong; Park, Jong Man; Jeong, Yong Jin; Kim, Ki Nam

    2015-01-01

    The excessive interaction between the U-Mo alloys and their surrounding Al matrix lead to and excessive local swelling called 'pillowing'. For this reason, KAERI suggested several remedies such as alloying U-Mo with Ti, or Al matrix with Si. In addition, silicide, or nitride coatings on the surface of U-Mo particles have also been proposed to hinder the growth of interaction layer. In this study, centrifugally atomized U-7Mo alloy powders were coated with silicide layers at varying T (T = 900 and 1000 .deg. C) for 30 min, respectively. U-Mo alloy powder was blended with Si powders and subsequently heat-treated to form uranium-silicide coating layers on the surface of U-Mo alloy particles. For an annealing test, silicide-coated U-Mo alloy powders were made into a compact, and Al powders were used as a matrix. From EDS results, transformed uranium aluminide intermetallic compounds were mainly U(Al,Si)3. U(Al,Si)3 phase left the silicide coating layer behind, and formed inside of U-7Mo particles, as shown in Fig. 3(a) and (b). In the case of sample B, Al could not penetrate the silicide coating layer and the coating layers were remained constant, as shown in Fig. 3(c) and (d). From the results, we made a comparison between the compacts of sample A and B, and it was shown that Al can easily diffuse into unreacted Si and U 3 Si 5 mixed layer while U 3 Si 2 acted as a good diffusion barrier at 550 .deg. C though those layers had the same thickness

  1. Separation of carrier-free rhodium isotopes from ruthenium cyclotron targets by the extraction of nitrosylruthenium from hydrochloric acid solution

    International Nuclear Information System (INIS)

    Haasbroek, F.J.; Strelow, F.W.E.; Van der Walt, T.N.

    1981-01-01

    A method is presented for the separation of rhodium isotopes from ruthenium cyclotron targets. After bombardment with deuterons and dissolution of the target material, the ruthenium is converted into a nitrosyl complex by treatment with hydroxylammonium chloride. Aluminium and other elements which have been introduced in the dissolution step, are separated by cation exchange. Ruthenium is then separated by extraction with a mixture of tri-n-butyl phosphate and hexane (4:1), leaving the rhodium in the aqueous phase. No ruthenium is found in the rhodium fraction and the recovery of rhodium is better than 90 per cent [af

  2. The effects of primary beam filters on the analysis of rhodium and cadmium using a rhodium target x-ray tube

    International Nuclear Information System (INIS)

    Anzelmo, J.A.; Boyer, B.W.

    1986-01-01

    Since its introduction in 1964, the thin end-window rhodium target x-ray tube has been considered to be an excellent general purpose source of excitation. Heavy elements are efficiently excited by high Bremsstrahlung and the K lines of rhodium while the light elements are excited by the L lines of rhodium. The ability to efficiently excite both heavy and light elements is essential to special applications such as auto catalysts, which are composed of precious metals in a clay-like matrix. Close control of the light elements, including sodium, phosphorous, aluminum and silicon, and the heavy element precious metals, such as rhodium, are necessary to keep operating characteristics and manufacturing expense at desired levels. A quick survey of typical x-ray tube targets shows that some targets are more efficient for light elements while others are more efficient for heavy elements. The few general purpose x-ray tubes that are available have characteristic lines which overlap on elements to be determined. The rhodium target, which is a good excitation source for most of the elements mentioned, contains line overlaps on cadmium (RHKB) and rhodium (RHKA). When using a sequential wavelength dispersive XRF spectrometer, the characteristic lines of the tube scattered from the sample can be removed by a programmable primary beam filter having an absorption edge just higher in wavelength than the wavelengths to be removed. The thickness and composition of the filter, as well as the choice of KV and MA, will determine the operating parameter necessary to achieve the optimum precision and lowest limits of detection. For this study, synthetic samples are made up using Kaolin as the matrix

  3. Formation of copper silicides by high dose metal vapor vacuum arc ion implantation

    International Nuclear Information System (INIS)

    Rong Chun; Zhang Jizhong; Li Wenzhi

    2003-01-01

    Si(1 1 1) was implanted by copper ions with different doses and copper distribution in silicon matrix was obtained. The as-implanted samples were annealed at 300 and 540 deg. C, respectively. Formation of copper silicides in as-implanted and annealed samples were studied. Thermodynamics and kinetics of the reaction were found to be different from reaction at copper-silicon interface that was applied in conventional studies of copper-silicon interaction. The defects in silicon induced by implantation and formation of copper silicides were recognized by Si(2 2 2) X-ray diffraction (XRD)

  4. The influence of alloying on the phase formation sequence of ultra-thin nickel silicide films and on the inheritance of texture

    Science.gov (United States)

    Geenen, F. A.; Solano, E.; Jordan-Sweet, J.; Lavoie, C.; Mocuta, C.; Detavernier, C.

    2018-05-01

    The controlled formation of silicide materials is an ongoing challenge to facilitate the electrical contact of Si-based transistors. Due to the ongoing miniaturisation of the transistor, the silicide is trending to ever-thinner thickness's. The corresponding increase in surface-to-volume ratio emphasises the importance of low-energetic interfaces. Intriguingly, the thickness reduction of nickel silicides results in an abrupt change in phase sequence. This paper investigates the sequence of the silicides phases and their preferential orientation with respect to the Si(001) substrate, for both "thin" (i.e., 9 nm) and "ultra-thin" (i.e., 3 nm) Ni films. Furthermore, as the addition of ternary elements is often considered in order to tailor the silicides' properties, additives of Al, Co, and Pt are also included in this study. Our results show that the first silicide formed is epitaxial θ-Ni2Si, regardless of initial thickness or alloyed composition. The transformations towards subsequent silicides are changed through the additive elements, which can be understood through solubility arguments and classical nucleation theory. The crystalline alignment of the formed silicides with the substrate significantly differs through alloying. The observed textures of sequential silicides could be linked through texture inheritance. Our study illustrates the nucleation of a new phase drive to reduce the interfacial energy at the silicide-substrate interface as well as at the interface with the silicide which is being consumed for these sub-10 nm thin films.

  5. Synthesis and characterization of rhodium sulfide nanoparticles and thin films

    International Nuclear Information System (INIS)

    Sosibo, Ndabenhle M.; Revaprasadu, Neerish

    2008-01-01

    The synthesis and characterization of a rhodium complex, [Rh(S 2 CNEt 2 ) 2 ] is described. The complex was thermolysed at a high temperature (280 deg. C) in the presence of capping agent, hexadecylamine (HDA) to form Rh 2 S 3 nanoparticles. Rod-shaped Rh 2 S 3 nanoparticles with an average length of 26.7 nm and an average breadth of 7.8 nm were synthesized. The complex was also used as a single molecule precursor for the deposition of Rh 2 S 3 thin films on a glass substrate at 350 deg. C and 450 deg. C using the Aerosol Assisted Chemical Vapour Deposition (AACVD) technique. The resultant thin films showed temperature dependent morphologies and showed (0 2 2), (4 1 1) and (6 1 1) lattice planes characteristic of to the orthorhombic Rh 2 S 3 phase. X-ray diffraction and scanning electron microscopy techniques were used to characterize the films

  6. Irradiation behavior of uranium-silicide dispersion fuels

    International Nuclear Information System (INIS)

    Hofman, G.L.; Neimark, L.A.

    1984-01-01

    This paper describes and analyzes the irradiation behavior of experimental fuel plates containing U 3 Si, U 3 Si-1.5 w/o Al, and U 3 Si 2 particulate fuel dispersed and clad in aluminum. The fuel is nominally 19.9%-enriched 235 U and the fuel volume fraction in the central ''meat'' section of the plates is approximately 33%. Sets of fuel plates were removed from the Oak Ridge Research reactor at burnup levels of 35, 83, and 94% 235 U depletion and examined at the Alpha-Gamma Hot-Cell Facility at Argonne National Laboratory. The results of the examination may be summarized as follows. The dimensional stability of the U 3 Si 2 and pure U 3 Si fuel was excellent throughout the entire burnup range, with uniform plate thickness increases up to a maximum of 4 mils at the highest burnup level (94% 235 U depletion). This corresponds to a meat volume increase of 11%. The swelling was partially due to solid fission products but to a larger extent to fission gas bubbles. The fission gas bubbles in U 3 Si 2 were small (submicrometer size) and very uniformly distributed, indicating great stability. To a large extent this was also the case for U 3 Si; however, larger bubbles ( 3 Si-1.5 w/o Al fuel became unstable at the higher burnup levels. Fission gas bubbles were larger than in the other two fuels and were present throughout the fuel particles. At 94% 235 U depletion, the formation of fission gas bubbles with diameters up to 20 mils caused the plates to pillow. It is proposed that aluminum in U 3 Si destabilizes fission gas bubble formation to the point of severe breakaway swelling in the prealloyed silicide fuel. (author)

  7. Radiation Re-solution Calculation in Uranium-Silicide Fuels

    International Nuclear Information System (INIS)

    Matthews, Christopher; Andersson, Anders David Ragnar; Unal, Cetin

    2017-01-01

    The release of fission gas from nuclear fuels is of primary concern for safe operation of nuclear power plants. Although the production of fission gas atoms can be easily calculated from the fission rate in the fuel and the average yield of fission gas, the actual diffusion, behavior, and ultimate escape of fission gas from nuclear fuel depends on many other variables. As fission gas diffuses through the fuel grain, it tends to collect into intra-granular bubbles, as portrayed in Figure 1.1. These bubbles continue to grow due to absorption of single gas atoms. Simultaneously, passing fission fragments can cause collisions in the bubble that result in gas atoms being knocked back into the grain. This so called ''re-solution'' event results in a transient equilibrium of single gas atoms within the grain. As single gas atoms progress through the grain, they will eventually collect along grain boundaries, creating inter-granular bubbles. As the inter-granular bubbles grow over time, they will interconnect with other grain-face bubbles until a pathway is created to the outside of the fuel surface, at which point the highly pressurized inter-granular bubbles will expel their contents into the fuel plenum. This last process is the primary cause of fission gas release. From the simple description above, it is clear there are several parameters that ultimately affect fission gas release, including the diffusivity of single gas atoms, the absorption and knockout rate of single gas atoms in intra-granular bubbles, and the growth and interlinkage of intergranular bubbles. Of these, the knockout, or re-solution rate has an particularly important role in determining the transient concentration of single gas atoms in the grain. The re-solution rate will be explored in the following sections with regards to uranium-silicide fuels in order to support future models of fission gas bubble behavior.

  8. Analysis Of Core Management For The Transition Cores Of RSG-GAS Reactor To Full-Silicide Core

    International Nuclear Information System (INIS)

    Malem Sembiring, Tagor; Suparlina, Lily; Tukiran

    2001-01-01

    The core conversion of RSG-GAS reactor from oxide to silicide core with meat density of 2.96 g U/cc is still doing. At the end of 2000, the reactor has been operated for 3 transition cores which is the mixed core of oxide-silicide. Based on previous work, the calculated core parameter for the cores were obtained and it is needed 10 transition cores to achieve a full-silicide core. The objective of this work is to acquire the effect of the increment of the number of silicide fuel on the core parameters such as excess reactivity and shutdown margin. The measurement of the core parameters was carried out using the method of compensation of couple control rods. The experiment shows that the excess reactivity trends lower with the increment of the number of silicide fuel in the core. However, the shutdown margin is not change with the increment of the number of silicide fuel. Therefore, the transition cores can be operated safety to a full-silicide core

  9. The Accident Analysis Due to Reactivity Insertion of RSG GAS 3.55 g U/cc Silicide Core

    International Nuclear Information System (INIS)

    Endiah Puji-Hastuti; Surbakti, Tukiran

    2004-01-01

    The fuels of RSG-GAS reactor was changed from uranium oxide with 250 g U of loading or 2.96 g U/cc of fuel loading to uranium silicide with the same loading. The silicide fuels can be used in higher density, staying longer in the reactor core and hence having a longer cycle length. The silicide fuel in RSG-GAS core was made up in step-wise by using mixed up core Firstly, it was used silicide fuel with 250 g U of loading and then, silicide fuel with 300 g U of loading (3.55 g U/cc of fuel loading). In every step-wise of fuel loading, it must be analyzed its safety margin. In this occasion, the reactivity accident of RSG-GAS core with 300 g U of silicide fuel loading is analyzed. The calculation was done using EUREKA-2/RR code available at P2TRR. The calculation was done by reactivity insertion at start up and power rangers. The worst case accident is transient due to control rod with drawl failure at start up by means of lowest initial power (0.1 W), either in power range. From all cases which have been done, the results of analysis showed that there is no anomaly and safety margin break at RSG-GAS core with 300 g U silicide fuel loading. (author)

  10. Thermal stability of Ni-Pt-Ta alloy silicides on epi-Si{sub 1-x}C{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Jung-Ho; Chang, Hyun-Jin [Department of Ceramic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Min, Byoung-Gi [Department of Ceramic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Jusung Engineering Co., Ltd., 49, Neungpyeong-ri, Opo-eup, Gwangju-Si, Kyunggi-do 464-892 (Korea, Republic of); Ko, Dae-Hong [Department of Ceramic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)], E-mail: dhko@yonsei.ac.kr; Cho, Mann-Ho [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Sohn, Hyunchul [Department of Ceramic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Lee, Tae-Wan [Jusung Engineering Co., Ltd., 49, Neungpyeong-ri, Opo-eup, Gwangju-Si, Kyunggi-do 464-892 (Korea, Republic of)

    2008-12-05

    We investigated the silicide formation in Ni/epi-Si{sub 1-x}C{sub x} systems. Ni-Pt and Ni-Pt-Ta films were deposited on epi-Si{sub 1-x}C{sub x}/Si substrates by DC magnetron sputtering and processed at various temperatures. The sheet resistance of the silicide from the Ni alloy/epi-Si{sub 1-x}C{sub x} systems was maintained at low values compared to that from Ni/Si systems. By TEM and EDS analyses, we confirmed the presence of a Pt alloy layer at the top of the Ni-silicide layer. The stability of the silicide layer in the Ni alloy/epi-Si{sub 1-x}C{sub x} system is explained by not only the Pt rich layer on the top of the Ni-silicide layer, but also by the presence of a small amount of Pt in the Ni-silicide layer or at the grain boundaries. And both the thermal stability and the morphology of silicide were greatly improved by the addition of Ta in Ni-Pt films.

  11. Thermal stability of Ni-Pt-Ta alloy silicides on epi-Si1-xCx

    International Nuclear Information System (INIS)

    Yoo, Jung-Ho; Chang, Hyun-Jin; Min, Byoung-Gi; Ko, Dae-Hong; Cho, Mann-Ho; Sohn, Hyunchul; Lee, Tae-Wan

    2008-01-01

    We investigated the silicide formation in Ni/epi-Si 1-x C x systems. Ni-Pt and Ni-Pt-Ta films were deposited on epi-Si 1-x C x /Si substrates by DC magnetron sputtering and processed at various temperatures. The sheet resistance of the silicide from the Ni alloy/epi-Si 1-x C x systems was maintained at low values compared to that from Ni/Si systems. By TEM and EDS analyses, we confirmed the presence of a Pt alloy layer at the top of the Ni-silicide layer. The stability of the silicide layer in the Ni alloy/epi-Si 1-x C x system is explained by not only the Pt rich layer on the top of the Ni-silicide layer, but also by the presence of a small amount of Pt in the Ni-silicide layer or at the grain boundaries. And both the thermal stability and the morphology of silicide were greatly improved by the addition of Ta in Ni-Pt films

  12. A study on the sensitivity depletion laws for rhodium self-powered neutron detectors

    International Nuclear Information System (INIS)

    Kim, Gil Gon

    1999-02-01

    The rhodium self-powered neutron detectors (SPND) in a reactor core provide the operator with the on-line 3-dimensional nuclear power distribution. The signal produced by rhodium SPND is interpreted into the local neutron flux by using a sensitivity depletion law and the local neutron flux is interpreted into the local power by using a power conversion factor. This work on the sensitivity depletion laws for rhodium self-powered neutron detectors (SPND) is performed to improve the uncertainty of the sensitivity depletion law used in ABB-CE reactors employing a rhodium SPND and to develop a calculational tool for providing the sensitivity depletion laws to interpret the signal of the newly designed rhodium SPND into the local neutron flux. The calculational tools for a time dependent neutron flux distribution in the rhodium emitter during depletion and for a time dependent beta escape probability that a beta generated in the emitter is escaped into the collector were developed. Due to the cost, the exposure to the radiation, and the longer fuel cycle, there is a strong incentive that the loading density of an in-core instrumentation is reduced and the lifetime of the detector is lengthened. These objectives can be achieved by reducing the uncertainty which is amplified as it depletes. The calculational tools above provide the sensitivity depletion law and show the reduction of the uncertainty to about 1 % in interpreting the signal into the local neutron flux compared to the method employed by ABB-CE. The reduction in the uncertainty of 1 % in interpreting the signal into the local neutron flux is equivalent to the reduction in the uncertainty of 1 % or more in interpreting the signal into the local power and to the extension of the lifetime of rhodium SPND to about 10 % as reported by ABB-CE

  13. Impact of Nickel silicide Rear Metallization on Series Resistance of Crystalline Silicon Solar Cells

    KAUST Repository

    Bahabry, Rabab R; Hanna, Amir N; Kutbee, Arwa T; Gumus, Abdurrahman; Hussain, Muhammad Mustafa

    2018-01-01

    the electrical characteristics of nickel mono-silicide (NiSi)/Cu-Al ohmic contact on the rear side of c-Si solar cells. We observe a significant enhancement in the fill factor of around 6.5% for NiSi/Cu-Al rear contacts leading to increasing the efficiency by 1.2

  14. Pilot plant production at Riso of LEU silicide fuel for the Danish reactor DR3

    International Nuclear Information System (INIS)

    Toft, P.; Borring, J.; Adolph, E.

    1988-01-01

    A pilot plant for fabricating LEU silicide fuel elements has been established at Riso National Laboratory. Three test elements for the Danish reactor DR3 have been fabricated, based on 19.88% enriched U 3 Si 2 powder that has been purchased elsewhere. The pilot plant has been set up and 3 test elements fabricated without any major difficulties

  15. Role of Ti 3 Al/silicides on tensile properties of Timetal 834 at ...

    Indian Academy of Sciences (India)

    Extremely fine coherent precipitates of ordered Ti3Al and relatively coarse incoherent precipitates of 2 silicide exist together in the near -titanium alloy, Timetal 834, in the dual phase matrix of primary and transformed . In order to assess the role of these precipitates, three heat treatments viz. WQ, WQ–A and WQ–OA, ...

  16. Core-hole effects in the x-ray-absorption spectra of transition-metal silicides

    NARCIS (Netherlands)

    WEIJS, PJW; CZYZYK, MT; VANACKER, JF; SPEIER, W; GOEDKOOP, JB; VANLEUKEN, H; HENDRIX, HJM; DEGROOT, RA; VANDERLAAN, G; BUSCHOW, KHJ; WIECH, G; FUGGLE, JC

    1990-01-01

    We report systematic differences between the shape of the Si K x-ray-absorption spectra of transition-metal silicides and broadened partial densities of Si p states. We use a variety of calculations to show that the origin of these discrepancies is the core-hole potential appropriate to the final

  17. Cross-Bridge Kelvin Resistor (CBKR) structures for silicide-semiconductor junctions characterization

    NARCIS (Netherlands)

    Stavitski, N.; van Dal, M.J.H.; Klootwijk, J.H.; Wolters, Robertus A.M.; Kovalgin, Alexeij Y.; Schmitz, Jurriaan

    2006-01-01

    Analyzing the contact geometry factors for the conventional CBKR structures, it appeared that the contact geometries conventionally used for the metal-to-silicide contact resistance measurements were not always satisfactory to reveal the specific contact resistance values. To investigate these

  18. X-ray-emission studies of chemical bonding in transition-metal silicides

    NARCIS (Netherlands)

    Weijs, P.J.W.; Leuken, H. van; Groot, R.A. de; Fuggle, J.C.; Reiter, S.; Wiech, G.; Buschow, K.H.J.

    1991-01-01

    We present Si L2,3 emission-band spectra of a series of 3d and 4d transition-metal (TM) silicides, together wtih Si K emission-band spectra of four 3d TM disilicides. The data are compared with augmented-spherical-wave density-of-states (DOS) calculations, and good agreement is found. The trends we

  19. Kinetics of low pressure chemical vapor deposition of tungsten silicide from dichlorocilane reduction of tungsten hexafluoride

    International Nuclear Information System (INIS)

    Srinivas, D.; Raupp, G.B.; Hillman, J.

    1990-01-01

    The authors report on experiments to determine the intrinsic surface reaction rate dependences and film properties' dependence on local reactant partial pressures and wafer temperature in low pressure chemical vapor deposition (LPCVD) of tungsten silicide from dichlorosilane reduction of tungsten hexafluoride. Films were deposited in a commercial-scale Spectrum CVD cold wall single wafer reactor under near differential, gradientless conditions. Over the range of process conditions investigated, deposition rate was found to be first order in dichlorosillane and negative second order in tungsten hexafluoride partial pressure. The apparent activation energy in the surface reaction limited regime was found to be 70-120 kcal/mol. The silicon to tungsten ratio of as deposited silicide films ranged from 1.1 to 2.4, and increased with increasing temperature and dichlorosillane partial pressure, and decreased with increasing tungsten hexafluoride pressure. These results suggest that the apparent silicide deposition rate and composition are controlled by the relative rates of at least two competing reactions which deposit stoichiometric tungsten silicides and/or silicon

  20. Waste Photovoltaic Panels for Ultrapure Silicon and Hydrogen through the Low-Temperature Magnesium Silicide.

    Czech Academy of Sciences Publication Activity Database

    Dytrych, Pavel; Bumba, Jakub; Kaštánek, František; Fajgar, Radek; Koštejn, Martin; Šolcová, Olga

    Roč. 56, č. 45 ( 2017 ), s. 12863-12869 ISSN 0888-5885 R&D Projects: GA ČR GA15-14228S Institutional support: RVO:67985858 Keywords : magnesium silicide * waste photovoltaic panels * ultrapure silicon Subject RIV: CI - Industrial Chemistry, Chemical Engineering OBOR OECD: Chemical process engineering Impact factor: 2.843, year: 2016

  1. High pressure studies on uranium and thorium silicide compounds: Experiment and theory

    DEFF Research Database (Denmark)

    Yagoubi, S.; Heathman, S.; Svane, A.

    2013-01-01

    The actinide silicides ThSi, USi and USi2 have been studied under high pressure using both theory and experiment. High pressure synchrotron X-ray diffraction experiments were performed on polycrystalline samples in diamond anvil cells at room temperature and for pressures up to 54, 52 and 26 GPa...

  2. Electrodeposition of carrier-free 57Co on rhodium as an approach to the preparation of Moessbauer sources

    International Nuclear Information System (INIS)

    Cieszykowska, Izabela; ZoLtowska, MaLgorzata; Mielcarski, MieczysLaw

    2011-01-01

    Electrodeposition of carrier-free 57 Co on a rhodium matrix as the first step of preparing Moessbauer sources was studied. To optimize the plating parameters, the influences of current density, volume and pH of the electrolyte solution, shape, thickness, and surface area of the rhodium cathode, mode of cathode pretreatment, concentration of 57 Co and duration of electrolysis were investigated.

  3. Transient-response study of CO insertion into CHx surface intermediates on a vanadium-promoted rhodium catalyst

    NARCIS (Netherlands)

    Koerts, T.; Santen, van R.A.

    1992-01-01

    The rate of CO insertion into surface CHx species was investigated on silica-supported rhodium and rhodium-vanadium catalysts. Isotopically labelled 13CO was used in a transient kinetic experiment under steady-state conditions. A main conclusion is that vanadium promotion does not affect the rate of

  4. Hydroformylation of methyl oleate catalyzed by rhodium complexes; Hidroformilacao do oleato de metila catalisada por complexos de rodio

    Energy Technology Data Exchange (ETDEWEB)

    Mendes, Ana Nery Furlan [Universidade Federal do Espirito Santo (UFES), Sao Mateus, ES (Brazil). Centro Universitario Norte do Espirito Santo. Dept. de Ciencias Naturais; Rosa, Ricardo Gomes da; Gregorio, Jose Ribeiro, E-mail: jrg@iq.ufrgs.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Inst. de Quimica

    2012-07-01

    In this work, we describe the hydroformylation of methyl oleate catalyzed by several rhodium complexes. Parameters including total pressure, phosphorous/rhodium and CO/H{sub 2} ratio, temperature and phosphorous ligands were scanned. Total conversion of the starting double bonds was achieved while maintaining excellent selectivity in aldehydes. (author)

  5. Near surface silicide formation after off-normal Fe-implantation of Si(001) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Khanbabaee, B., E-mail: khanbabaee@physik.uni-siegen.de; Pietsch, U. [Solid State Physics, University of Siegen, D-57068 Siegen (Germany); Lützenkirchen-Hecht, D. [Fachbereich C - Physik, Bergische Universität Wuppertal, D-42097 Wuppertal (Germany); Hübner, R.; Grenzer, J.; Facsko, S. [Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden (Germany)

    2014-07-14

    We report on formation of non-crystalline Fe-silicides of various stoichiometries below the amorphized surface of crystalline Si(001) after irradiation with 5 keV Fe{sup +} ions under off-normal incidence. We examined samples prepared with ion fluences of 0.1 × 10{sup 17} and 5 × 10{sup 17} ions cm{sup −2} exhibiting a flat and patterned surface morphology, respectively. Whereas the iron silicides are found across the whole surface of the flat sample, they are concentrated at the top of ridges at the rippled surface. A depth resolved analysis of the chemical states of Si and Fe atoms in the near surface region was performed by combining X-ray photoelectron spectroscopy and X-ray absorption spectroscopy (XAS) using synchrotron radiation. The chemical shift and the line shape of the Si 2p core levels and valence bands were measured and associated with the formation of silicide bonds of different stoichiometric composition changing from an Fe-rich silicides (Fe{sub 3}Si) close to the surface into a Si-rich silicide (FeSi{sub 2}) towards the inner interface to the Si(001) substrate. This finding is supported by XAS analysis at the Fe K-edge which shows changes of the chemical environment and the near order atomic coordination of the Fe atoms in the region close to surface. Because a similar Fe depth profile has been found for samples co-sputtered with Fe during Kr{sup +} ion irradiation, our results suggest the importance of chemically bonded Fe in the surface region for the process of ripple formation.

  6. Interaction between water-soluble rhodium complex RhCl(CO)(TPPTS)₂ and surfactants probed by spectroscopic methods.

    Science.gov (United States)

    Zhou, Li-Mei; Guo, Cai-Hong; Fu, Hai-Yan; Jiang, Xiao-Hui; Chen, Hua; Li, Rui-Xiang; Li, Xian-Jun

    2012-07-01

    The interactions of rhodium complex RhCl(CO)(TPPTS)(2) [TPPTS=P(m-C(6)H(4)SO(3)Na)(3)] with cationic, nonionic, and anionic surfactants have been investigated by UV-vis, fluorescence and (1)H NMR measurements. The presence of four different species of RhCl(CO)(TPPTS)(2) in cationic cetyltrimethylammonium (CTAB) solution has been demonstrated: free rhodium complex, rhodium complex bound to CTAB monomer, rhodium complex bound to CTAB premicelles, rhodium complex bound to CTAB micelles. The spectroscopy data show that RhCl(CO)(TPPTS)(2) can adsorb on the interface of cationic CTAB micelles by strong electrostatic attraction, weakly bind to the nonionic polyoxyethylene (20) sorbitan monolaurate (Tween 20) micelles by hydrophobic interaction, and does not interact with anion sodium dodecyl sulfate (SDS) micelles due to the strong electrostatic repulsion. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. Rhodium mediated bond activation: from synthesis to catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Hung-An [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    Recently, our lab has developed monoanionic tridentate ligand, ToR, showing the corresponding coordination chemistry and catalyst reactivity of magnesium, zirconium, zinc and iridium complexes. This thesis details synthetic chemistry, structural study and catalytic reactivity of the ToR-supported rhodium compounds. Tl[ToR] has been proved to be a superior ligand transfer agent for synthesizing rhodium complexes. The salt metathesis route of Tl[ToM] with [Rh(μ-Cl)(CO)]2 and [Rh(μ- Cl)(COE)]2 gives ToMRh(CO)2 (2.2) and ToMRhH(β3-C8H13) (3.1) respectively while Tl[ToM] with [Rh(μ-Cl)(CO)]2 affords ToPRh(CO)2 (2.3). 2.2 reacts with both strong and weak electrophiles, resulting in the oxazoline N-attacked and the metal center-attacked compounds correspondingly. Using one of the metal center-attacked electrophiles, 2.3 was demonstrated to give high diastereoselectivity. Parallel to COE allylic C-H activation complex 3.1, the propene and allylbenzene allylic C-H activation products have also been synthesized. The subsequent functionalization attempts have been examined by treating with Brønsted acids, Lewis acids, electrophiles, nucleophiles, 1,3-dipolar reagents and reagents containing multiple bonds able to be inserted. Various related complexes have been obtained under these conditions, in which one of the azide insertion compounds reductively eliminates to give an allylic functionalization product stoichiometrically. 3.1 reacts with various primary alcohols to give the decarbonylation dihydride complex ToMRh(H)2CO (4.1). 4.1 shows catalytic reactivity for primary alcohol decarbonylation under a photolytic condition. Meanwhile, 2.2 has been found to be more reactive than 4.1 for catalytic alcohol decarbonylation under the same condition. Various complexes and primary

  8. Electron spectroscopy in the X-ray range for occupied and free levels and the application to transition metal silicides

    International Nuclear Information System (INIS)

    Speier, W.

    1988-03-01

    Intermetallic compounds of transition metals are investigated by means of XPS, Bremsstrahlung Isochromate Spectroscopy and XAS. Occupied and free levels are characterized and moreover a systematic overview over the electronic structure of the transition element silicides is given. (BHO)

  9. Exposure of the German general population to platinum and rhodium - Urinary levels and determining factors.

    Science.gov (United States)

    Munker, Sven; Kilo, Sonja; Röß, Christoph; Jeitner, Peter; Schierl, Rudolf; Göen, Thomas; Drexler, Hans

    2016-11-01

    In this study the exposure of the general population in Germany to platinum and rhodium and its determinants was investigated in 259 participants (subdivided in three groups) by urine analyses and assessment of the dental status. Complementary, an interview including questions characterising possible exposure to traffic exhaust was conducted. The median excretion was 2.42ng platinum/g creatinine and 7.27ng rhodium/g creatinine. The detailed analysis of the collected data showed significant higher platinum excretion values with increasing number of surfaces covered with restorations containing precious metals (R=0.389; prhodium excretion values (median=7.27ng/g; 95th percentile=13.5 ng/g). In summary, the study showed that exhaust emissions have an influence on platinum and rhodium excretion, but for platinum this influence is rather low compared to the influence of precious metals containing restorations. Copyright © 2016 Elsevier GmbH. All rights reserved.

  10. Co-deposition of rhodium and tungsten films for the first-mirror on ITER

    International Nuclear Information System (INIS)

    Marot, Laurent; Steiner, Roland; Gantenbein, Markus; Mathys, Daniel; Meyer, Ernst

    2011-01-01

    The detailed characterizations of rhodium/tungsten films prepared by co-deposition using a dual magnetron sputtering have been carried out on silicon substrates at room temperature. Effects of the tungsten incorporated in the film on the chemical bonding state, optical reflectivity and crystallinity were investigated using X-ray photoelectron spectroscopy (XPS), reflectivity measurements, X-rays diffraction (XRD) and scanning electron microscopy (SEM). The incorporation of tungsten changes the films crystalline structure i.e. leading to Rh 3 W formation. The reflectivity of the films decreases linearly with the decrease of rhodium concentration. XPS and ultraviolet photoemission spectroscopy (UPS) measurements show a positive shift of the core level binding energy of rhodium which is coupled to a shift of the Rh d-band ΔE d away from the Fermi level. Opposite shifts are observed for tungsten.

  11. Rhodium(III)-Catalyzed Amidation of Unactivated C(sp(3) )-H Bonds.

    Science.gov (United States)

    Wang, He; Tang, Guodong; Li, Xingwei

    2015-10-26

    Nitrogenation by direct functionalization of C-H bonds represents an important strategy for constructing C-N bonds. Rhodium(III)-catalyzed direct amidation of unactivated C(sp(3) )-H bonds is rare, especially under mild reaction conditions. Herein, a broad scope of C(sp(3) )-H bonds are amidated under rhodium catalysis in high efficiency using 3-substituted 1,4,2-dioxazol-5-ones as the amide source. The protocol broadens the scope of rhodium(III)-catalyzed C(sp(3) )-H activation chemistry, and is applicable to the late-stage functionalization of natural products. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Monodisperse Platinum and Rhodium Nanoparticles as Model Heterogeneous Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Grass, Michael Edward [Univ. of California, Berkeley, CA (United States)

    2008-09-01

    Model heterogeneous catalysts have been synthesized and studied to better understand how the surface structure of noble metal nanoparticles affects catalytic performance. In this project, monodisperse rhodium and platinum nanoparticles of controlled size and shape have been synthesized by solution phase polyol reduction, stabilized by polyvinylpyrrolidone (PVP). Model catalysts have been developed using these nanoparticles by two methods: synthesis of mesoporous silica (SBA-15) in the presence of nanoparticles (nanoparticle encapsulation, NE) to form a composite of metal nanoparticles supported on SBA-15 and by deposition of the particles onto a silicon wafer using Langmuir-Blodgett (LB) monolayer deposition. The particle shapes were analyzed by transmission electron microscopy (TEM) and high resolution TEM (HRTEM) and the sizes were determined by TEM, X-ray diffraction (XRD), and in the case of NE samples, room temperature H2 and CO adsorption isotherms. Catalytic studies were carried out in homebuilt gas-phase reactors. For the nanoparticles supported on SBA-15, the catalysts are in powder form and were studied using the homebuilt systems as plug-flow reactors. In the case of nanoparticles deposited on silicon wafers, the same systems were operated as batch reactors. This dissertation has focused on the synthesis, characterization, and reaction studies of model noble metal heterogeneous catalysts. Careful control of particle size and shape has been accomplished though solution phase synthesis of Pt and Rh nanoparticles in order to elucidate further structure-reactivity relationships in noble metal catalysis.

  13. Synthesis and characterization of rhodium sulfide nanoparticles and thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sosibo, Ndabenhle M. [Department of Chemistry, University of Zululand, Private Bag X1001, KwaDlangezwa 3886 (South Africa); Revaprasadu, Neerish [Department of Chemistry, University of Zululand, Private Bag X1001, KwaDlangezwa 3886 (South Africa)], E-mail: nrevapra@pan.uzulula.za

    2008-05-15

    The synthesis and characterization of a rhodium complex, [Rh(S{sub 2}CNEt{sub 2}){sub 2}] is described. The complex was thermolysed at a high temperature (280 deg. C) in the presence of capping agent, hexadecylamine (HDA) to form Rh{sub 2}S{sub 3} nanoparticles. Rod-shaped Rh{sub 2}S{sub 3} nanoparticles with an average length of 26.7 nm and an average breadth of 7.8 nm were synthesized. The complex was also used as a single molecule precursor for the deposition of Rh{sub 2}S{sub 3} thin films on a glass substrate at 350 deg. C and 450 deg. C using the Aerosol Assisted Chemical Vapour Deposition (AACVD) technique. The resultant thin films showed temperature dependent morphologies and showed (0 2 2), (4 1 1) and (6 1 1) lattice planes characteristic of to the orthorhombic Rh{sub 2}S{sub 3} phase. X-ray diffraction and scanning electron microscopy techniques were used to characterize the films.

  14. The UV Plasmonic Behavior of Distorted Rhodium Nanocubes

    Directory of Open Access Journals (Sweden)

    Yael Gutiérrez

    2017-12-01

    Full Text Available For applications of surface-enhanced spectroscopy and photocatalysis, the ultraviolet (UV plasmonic behavior and charge distribution within rhodium nanocubes is explored by a detailed numerical analysis. The strongest plasmonic hot-spots and charge concentrations are located at the corners and edges of the nanocubes, exactly where they are the most spectroscopically and catalytically active. Because intense catalytic activity at corners and edges will reshape these nanoparticles, distortions of the cubical shape, including surface concavity, surface convexity, and rounded corners and edges, are also explored to quantify how significantly these distortions deteriorate their plasmonic and photocatalytic properties. The fact that the highest fields and highest carrier concentrations occur in the corners and edges of Rh nanocubes (NCs confirms their tremendous potential for plasmon-enhanced spectroscopy and catalysis. It is shown that this opportunity is fortuitously enhanced by the fact that even higher field and charge concentrations reside at the interface between the metal nanoparticle and a dielectric or semiconductor support, precisely where the most chemically active sites are located.

  15. Biological effects of simple changes in functionality on rhodium metalloinsertors

    Science.gov (United States)

    Weidmann, Alyson G.; Komor, Alexis C.; Barton, Jacqueline K.

    2013-01-01

    DNA mismatch repair (MMR) is crucial to ensuring the fidelity of the genome. The inability to correct single base mismatches leads to elevated mutation rates and carcinogenesis. Using metalloinsertors–bulky metal complexes that bind with high specificity to mismatched sites in the DNA duplex–our laboratory has adopted a new chemotherapeutic strategy through the selective targeting of MMR-deficient cells, that is, those that have a propensity for cancerous transformation. Rhodium metalloinsertors display inhibitory effects selectively in cells that are deficient in the MMR machinery, consistent with this strategy. However, a highly sensitive structure–function relationship is emerging with the development of new complexes that highlights the importance of subcellular localization. We have found that small structural modifications, for example a hydroxyl versus a methyl functional group, can yield profound differences in biological function. Despite similar binding affinities and selectivities for DNA mismatches, only one metalloinsertor shows selective inhibition of cellular proliferation in MMR-deficient versus -proficient cells. Studies of whole-cell, nuclear and mitochondrial uptake reveal that this selectivity depends upon targeting DNA mismatches in the cell nucleus. PMID:23776288

  16. Tandem rhodium catalysis: exploiting sulfoxides for asymmetric transition-metal catalysis.

    Science.gov (United States)

    Kou, K G M; Dong, V M

    2015-06-07

    Sulfoxides are uncommon substrates for transition-metal catalysis due to their propensity to inhibit catalyst turnover. In a collaborative effort with Ken Houk, we developed the first dynamic kinetic resolution (DKR) of allylic sulfoxides using asymmetric rhodium-catalyzed hydrogenation. A detailed mechanistic analysis of this transformation using both experimental and theoretical methods revealed rhodium to be a tandem catalyst that promoted both hydrogenation of the alkene and racemization of the allylic sulfoxide. Using a combination of deuterium labelling and DFT studies, a novel mode of allylic sulfoxide racemization via a Rh(III)-π-allyl intermediate was identified.

  17. The extraction of rhodium from aqueous nitric acid by dinonylnaphthalene sulphonic acid

    International Nuclear Information System (INIS)

    Patel, N.M.; Miles, J.H.; Thornback, J.R.

    1987-01-01

    The extraction of rhodium from aqueous nitric acid using dinonylnaphthalene sulphonic acid has been investigated. The extraction occurs readily from 0.1 M to 1.0 M nitric acid and, since the rhodium is extracted as {Rh(H 2 O) 6 } 3+ into the inverted micelles of the organic solution, equilibration times are less than 5 minutes. Extraction is enhanced by addition of nitrite ion to form {Rh(H 2 O) 5 NO 2 } 2+ as the extracted species. (author)

  18. Sorption properties study of nitron fibre S-3 relative to rhodium (III)

    International Nuclear Information System (INIS)

    Rustamov, S.; Khusainov, A.D.; Shadieva, S.F.

    2001-01-01

    The purpose of present work is studying of sorption properties of nitron fibre S-3 relative to rhodium (III) from chloride solutions. Nitron sorbent S-3 was synthesised by reprocessing of wastes of production of nitron fibre by sulfited compound Na 2 Sn:NH 4 SCN=50:50 during 3 hours at temperature 90 d ig C . The sulfur containing in the sorbent was about 9%. During investigation by authors was determined that fibre nitron-S has good kinetic characteristics relative to rhodium (III), limitative stage of sorption process is diffusion and kinetics of sorption has mixed-diffusion character

  19. Rhodium-catalyzed C-H alkynylation of arenes at room temperature.

    Science.gov (United States)

    Feng, Chao; Loh, Teck-Peng

    2014-03-03

    The rhodium(III)-catalyzed ortho C-H alkynylation of non-electronically activated arenes is disclosed. This process features a straightforward and highly effective protocol for the synthesis of functionalized alkynes and represents the first example of merging a hypervalent iodine reagent with rhodium(III) catalysis. Notably, this reaction proceeds at room temperature, tolerates a variety of functional groups, and more importantly, exhibits high selectivity for monoalkynylation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. A Concise Synthesis of the Erythrina Alkaloid 3–Demethoxyerythratidinone via Combined Rhodium Catalysis

    Science.gov (United States)

    Joo, Jung Min; David, Ramoncito A.; Yuan, Yu; Lee, Chulbom

    2010-01-01

    The total synthesis of the erythrina alkaloid 3–demethoxyerythratidinone has been achieved via a strategy based on combined rhodium catalysis. The catalytic tandem cyclization effected by the interplay of alkynyl and vinylidene rhodium species allows for efficient access to the A and B rings of the tetracyclic erythrinane skeleton in a single step. The synthesis also features rapid preparation of the requisite precursor for the double ring closure and thus has been completed in only 7 total steps in 41% overall yield. PMID:21090648

  1. Evaluation of In-Core Fuel Management for the Transition Cores of RSG-GAS Reactor to Full-Silicide Core

    International Nuclear Information System (INIS)

    S, Tukiran; MS, Tagor; P, Surian

    2003-01-01

    The core conversion of RSG-GAS reactor from oxide to silicide core with meat density of 2.96 gU/cc has been done. The core-of RSG-GAS reactor has been operated full core of silicide fuels which is started with the mixed core of oxide-silicide start from core 36. Based on previous work, the calculated core parameter for the cores were obtained and it is needed 9 transition cores (core 36 - 44) to achieve a full-silicide core (core 45). The objective of this work is to acquire the effect of the increment of the number of silicide fuel on the core parameters. Conversion core was achieved by transition cores mixed oxide-silicide fuels. Each transition core is calculated and measured core parameter such as, excess reactivity and shutdown margin. Calculation done by Batan-EQUIL-2D code and measurement of the core parameters was carried out using the method of compensation of couple control rods. The results of calculation and experiment shows that the excess reactivity trends lower with the increment of the number of silicide fuel in the core. However, the shutdown margin is not change with the increment of the number of silicide fuel. Therefore, the transition cores can be operated safely to a full-silicide core

  2. Spectrophotometric determination of ruthenium(III) and rhodium(III) after extraction of their cyclohexylthioglycolate complexes into chloroform

    International Nuclear Information System (INIS)

    Rao, A.L.J.; Gupta, Usha; Puri, B.K.

    1986-01-01

    Cyclohexylthioglycolate has been used as a reagent for the spectrophotometric determination of ruthenium(III) and rhodium(III) after the extraction of their complexes into chloroform. Various parameters involved in the extraction have been studied and the composition of the extracted complex has been established in each instance. Ruthenium and rhodium complexes are extracted into chloroform in the pH ranges 5.0-9.0 and 9.0-12.5, respectively. The ruthenium complex absorbs strongly at 365 nm, whereas the rhodium complex shows a maximum absorption at 345 nm. Beer's law is obeyed over the concentration range 6-96 μg for ruthenium and 2-41 μg for rhodium in 10 ml of the chloroform solution. The molar absorptivities are 5.02 x 10 3 l mol -1 cm -1 for ruthenium and 1.60 x 10 4 l mol -1 cm -1 for rhodium. Ten replicate determinations on a sample solution containing 60.3 μg of ruthenium or 20.6 μg of rhodium gave mean absorbances of 0.300 and 0.320 with standard deviations of 0.0021 and 0.0025 and relative standard deviations of 0.70% and 0.78%, respectively. The interference of various ions has been studied and the method has been applied to the determination of the metals in various synthetic samples. Conditions have also been developed for the simultaneous determination of ruthenium and rhodium. (author)

  3. Spectrophotometric determination of ruthenium (III) and rhodium (III) with 9,10-phenanthrenequinone monoxime after extraction into molten naphthalene

    International Nuclear Information System (INIS)

    Wasey, A.; Bansal, R.K.; Puri, B.K.; Satake, Masatada.

    1983-01-01

    9,10-Phenanthrenequinone monoxime has been used as a reagent for the spectrophotometric determination of ruthenium(III) and rhodium(III) after extraction into molten naphthalene. The extracted mixture of the metal complex and naphthalene was dissolved in chloroform and ruthenium and rhodium were determined spectrophotometrically. Beer's law holds in the concentration range of 0.2-4.1 μg/cm 3 for ruthenium and 0.3-5.3 μg/cm 3 for rhodium in 10 cm 3 of the final solution. The molar absorptivities and Sandell sensitivities are calculated to be 9.70 x 10 3 l mol -1 cm -1 and 0.01 μg/cmsup(2 ) (660 nm) for ruthenium and 1.13 x 10 4 l mol -1 cm -1 and 0.009 μg/cm 2 (410 nm) for rhodium respectively. Aliquots containing 2.0 μg of ruthenium and 4.1 μg of rhodium give mean absorbances of 0.192 and 0.451 with standard deviations of 0.0017 and 0.0039, respectively. Interference of various ions has been studied and the method has been applied to the determination of ruthenium and rhodium in various synthetic mixtures. This procedure is also applied to the simultaneous determination of ruthenium and rhodium present together in a solution. (author)

  4. Reactivity And Neutron Flux At Silicide Fuel Element In The Core Of RSG-GAS

    International Nuclear Information System (INIS)

    Hamzah, Amir

    2000-01-01

    In order to 4.8 and 5.2 gr U/cm exp 3 loading of U 3 Si 2 --Al fuel plates characterization, he core reactivity change and neutron flux depression had been done. Control rod calibration method was used to reactivity change measurement and neutron flux distribution was measured using foil activation method. Measurement of insertion of A-type of testing fuel element with U-loading above cannot be done due to technical reason, so the measurement using full type silicide fuel element of 2.96 gr U/cm exp 3 loading. The reactivity change measurement result of insertion in A-9 and C-3 is + 2.67 cent. The flux depression at silicide fuel in A-9 is 1.69 times bigger than oxide and in C-3 is 0.68 times lower than oxide

  5. Babcock and Wilcox plate fabrication experience with uranium silicide spherical fuel

    International Nuclear Information System (INIS)

    Todd, Lawrence E.; Pace, Brett W.

    1996-01-01

    This report is written to present the fuel fabrication experience of Babcock and Wilcox using atomized spherical uranium silicide powder. The intent is to demonstrate the ability to fabricate fuel plates using spherical powder and to provide useful information proceeding into the next phase of work using this type of fuel. The limited quantity of resources- spherical powder and time, did not allow for much process optimizing in this work scope. However, the information contained within provides optimism for the future of spherical uranium silicide fuel plate fabrication at Babcock and Wilcox.The success of assembling fuel elements with spherical powder will enable Babcock and Wilcox to reduce overall costs to its customers while still maintaining our reputation for providing high quality research and test reactor products. (author)

  6. The formation of magnetic silicide Fe{sub 3}Si clusters during ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Balakirev, N. [Kazan National Research Technological University, K.Marx st. 68, Kazan 420015 (Russian Federation); Zhikharev, V., E-mail: valzhik@mail.ru [Kazan National Research Technological University, K.Marx st. 68, Kazan 420015 (Russian Federation); Gumarov, G. [Zavoiskii Physico-Technical Institute of Russian Academy of Sciences, 10/7 Sibirskii trakt st., Kazan 420029 (Russian Federation)

    2014-05-01

    A simple two-dimensional model of the formation of magnetic silicide Fe{sub 3}Si clusters during high-dose Fe ion implantation into silicon has been proposed and the cluster growth process has been computer simulated. The model takes into account the interaction between the cluster magnetization and magnetic moments of Fe atoms random walking in the implanted layer. If the clusters are formed in the presence of the external magnetic field parallel to the implanted layer, the model predicts the elongation of the growing cluster in the field direction. It has been proposed that the cluster elongation results in the uniaxial magnetic anisotropy in the plane of the implanted layer, which is observed in iron silicide films ion-beam synthesized in the external magnetic field.

  7. The formation of magnetic silicide Fe3Si clusters during ion implantation

    Science.gov (United States)

    Balakirev, N.; Zhikharev, V.; Gumarov, G.

    2014-05-01

    A simple two-dimensional model of the formation of magnetic silicide Fe3Si clusters during high-dose Fe ion implantation into silicon has been proposed and the cluster growth process has been computer simulated. The model takes into account the interaction between the cluster magnetization and magnetic moments of Fe atoms random walking in the implanted layer. If the clusters are formed in the presence of the external magnetic field parallel to the implanted layer, the model predicts the elongation of the growing cluster in the field direction. It has been proposed that the cluster elongation results in the uniaxial magnetic anisotropy in the plane of the implanted layer, which is observed in iron silicide films ion-beam synthesized in the external magnetic field.

  8. RA-3 reactor core with uranium silicide fuel elements P-07 type

    International Nuclear Information System (INIS)

    Abbate, Maximo J.; Sbaffoni, Maria M.

    2003-01-01

    Following the studies on the utilization of fuel elements (FE) containing uranium silicide, core of the RA-3 was analyzed with several calculation models. At first, the present situation, i.e. the core charged with normal FE (U 3 O 8 ), has been analyzed to validate the simulation methodology comparing with experimental results and to establish reference data to 5 and 10 MW able to be compared with future new situations. Also, CITVAP's nuclear data libraries to be used in irradiation experiment planning were completed. The results were satisfactory and were applied to the study of the core containing P-07 FE [U 3 Si 2 ], in face of a future core change. Comparing with the performance of the U 3 O 8 FE, the silicides ones show the following advantages: - average burnup: 45 % greater; -extraction burnup increase 12 %; and, -the residence time [in full power days] could be a 117 % greater. (author)

  9. The formation of magnetic silicide Fe3Si clusters during ion implantation

    International Nuclear Information System (INIS)

    Balakirev, N.; Zhikharev, V.; Gumarov, G.

    2014-01-01

    A simple two-dimensional model of the formation of magnetic silicide Fe 3 Si clusters during high-dose Fe ion implantation into silicon has been proposed and the cluster growth process has been computer simulated. The model takes into account the interaction between the cluster magnetization and magnetic moments of Fe atoms random walking in the implanted layer. If the clusters are formed in the presence of the external magnetic field parallel to the implanted layer, the model predicts the elongation of the growing cluster in the field direction. It has been proposed that the cluster elongation results in the uniaxial magnetic anisotropy in the plane of the implanted layer, which is observed in iron silicide films ion-beam synthesized in the external magnetic field

  10. A long-term ultrahigh temperature application of layered silicide coated Nb alloy in air

    Science.gov (United States)

    Sun, Jia; Fu, Qian-Gang; Li, Tao; Wang, Chen; Huo, Cai-Xia; Zhou, Hong; Yang, Guan-Jun; Sun, Le

    2018-05-01

    Nb-based alloy possessed limited application service life at ultrahigh temperature (>1400 °C) in air even taking the effective protective coating strategy into consideration for last decades. In this work a long duration of above 128 h at 1500 °C in air was successfully achieved on Nb-based alloy thanked to multi-layered silicide coating. Through optimizing interfaces, the MoSi2/NbSi2 silicide coating with Al2O3-adsorbed-particles layer exhibited three-times higher of oxidation resistance capacity than the one without it. In MoSi2-Al2O3-NbSi2 multilayer coating, the Al2O3-adsorbed-particles layer playing as an element-diffusion barrier role, as well as the formed porous Nb5Si3 layer as a stress transition zone, contributed to the significant improvement.

  11. Study of optical and luminescence properties of silicon — semiconducting silicide — silicon multilayer nanostructures

    International Nuclear Information System (INIS)

    Galkin, N.G.; Galkin, K.N.; Dotsenko, S.A.; Goroshko, D.L.; Shevlyagin, A.V.; Chusovitin, E.A.; Chernev, I.M.

    2017-01-01

    By method of in situ differential spectroscopy it was established that at the formation of monolayer Fe, Cr, Ca, Mg silicide and Mg stannide islands on the atomically clean silicon surface an appearance of loss peaks characteristic for these materials in the energy range of 1.1-2.6 eV is observed. An optimization of growth processes permit to grow monolithic double nanoheterostructures (DNHS) with embedded Fe, Cr and Ca nanocrystals, and also polycrystalline DNHS with NC of Mg silicide and Mg stannide and Ca disilicide. By methods of optical spectroscopy and Raman spectroscopy it was shown that embedded NC form intensive peaks in the reflectance spectra at energies up to 2.5 eV and Raman peaks. In DNS with β-FeSi2 NC a photoluminescence and electroluminescence at room temperature were firstly observed.

  12. High-Temperature Compatible Nickel Silicide Thermometer And Heater For Catalytic Chemical Microreactors

    DEFF Research Database (Denmark)

    Jensen, Søren; Quaade, U.J.; Hansen, Ole

    2005-01-01

    Integration of heaters and thermometers is important for agile and accurate control and measurement of the thermal reaction conditions in microfabricated chemical reactors (microreactors). This paper describes development and operation of nickel silicide heaters and temperature sensors...... for temperatures exceeding 700 °C. The heaters and thermometers are integrated with chemical microreactors for heterogeneous catalytic conversion of gasses, and thermally activated catalytic conversion of CO to CO2 in the reactors is demonstrated. The heaters and thermometers are shown to be compatible...

  13. Optical anisotropy of quasi-1D rare-earth silicide nanostructures on Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Chandola, S., E-mail: sandhya.chandola@isas.de [Leibniz-Institut für Analytische Wissenschaften – ISAS – e.V., Schwarzschildstraße 8, 12489 Berlin (Germany); Speiser, E.; Esser, N. [Leibniz-Institut für Analytische Wissenschaften – ISAS – e.V., Schwarzschildstraße 8, 12489 Berlin (Germany); Appelfeller, S.; Franz, M.; Dähne, M. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin (Germany)

    2017-03-31

    Highlights: • Reflectance anisotropy spectroscopy (RAS) is capable of distinguishing optically between the semiconducting wetting layer and the metallic nanowires of rare earth (Tb and Dy) silicide nanostructures grown on vicinal Si(001). • The spectra of the wetting layer show a distinctive line shape with a large peak appearing at 3.8 eV, which is assigned to the formation of 2 × 3 and 2 × 4-like subunits of the 2 × 7 reconstruction. The spectra of the metallic nanowires show peaks at the E{sub 1} and E{sub 2} transitions of bulk Si which is assigned to strong substrate strain induced by the nanowires. • The optical anisotropy of the Tb nanowires is larger than for the Dy nanowires, which is related to the preferential formation of more strained bundles as well as larger areas of clean Si surfaces in the case of Tb. • RAS is shown to be a powerful addition to surface science techniques for studying the formation of rare-earth silicide nanostructures. Its surface sensitivity and rapidity of response make it an ideal complement to the slower but higher resolution of scanning probes of STM and AFM. - Abstract: Rare earth metals are known to interact strongly with Si(001) surfaces to form different types of silicide nanostructures. Using STM to structurally characterize Dy and Tb silicide nanostructures on vicinal Si(001), it will be shown that reflectance anisotropy spectroscopy (RAS) can be used as an optical fingerprint technique to clearly distinguish between the formation of a semiconducting two-dimensional wetting layer and the metallic one-dimensional nanowires. Moreover, the distinctive spectral features can be related to structural units of the nanostructures. RAS spectra of Tb and Dy nanostructures are found to show similar features.

  14. Neutronic study on conversion of SAFARI-1 to LEU silicide fuel

    International Nuclear Information System (INIS)

    Ball, G.; Pond, R.; Hanan, N.; Matos, J.

    1995-01-01

    This paper marks the initial study into the technical and economic feasibility of converting the SAFARI-1 reactor in South Africa to LEU silicide fuel. Several MTR assembly geometries and LEU uranium densities have been studied and compared with MEU and HEU fuels. Two factors of primary importance for conversion of SAFARI-1 to LEU fuel are the economy of the fuel cycle and the performance of the incore and excore irradiation positions

  15. Techno-economic study on conversion of SAFARI-1 to LEU silicide fuel

    International Nuclear Information System (INIS)

    Ball, G.; Malherbe, F.J.

    2004-01-01

    This paper marks the conclusion of the techno-economic study into the conversion of SAFARI-1 reactor in South Africa to LEU silicide fuel. Several different fuel types were studied and their characteristics compared to the current HEU fuel. The technical feasibility of operating SAFARI-1 with the different fuels as well as the overall economic impact of the fuels is discussed and conclusions drawn.(author)

  16. Behavior of silicon in nitric media. Application to uranium silicides fuels reprocessing

    International Nuclear Information System (INIS)

    Cheroux, L.

    2001-01-01

    Uranium silicides are used in some research reactors. Reprocessing them is a solution for their cycle end. A list of reprocessing scenarios has been set the most realistic being a nitric dissolution close to the classic spent fuel reprocessing. This uranium silicide fuel contains a lot of silicon and few things are known about polymerization of silicic acid in concentrated nitric acid. The study of this polymerization allows to point out the main parameters: acidity, temperature, silicon concentration. The presence of aluminum seems to speed up heavily the polymerization. It has been impossible to find an analytical technique smart and fast enough to characterize the first steps of silicic acid polymerization. However the action of silicic species on emulsions stabilization formed by mixing them with an organic phase containing TBP has been studied, Silicon slows down the phase separation by means of oligomeric species forming complex with TBP. The existence of these intermediate species is short and heating can avoid any stabilization. When non irradiated uranium silicide fuel is attacked by a nitric solution, aluminum and uranium are quickly dissolved whereas silicon mainly stands in solid state. That builds a gangue of hydrated silica around the uranium silicide particulates without preventing uranium dissolution. A small part of silicon passes into the solution and polymerize towards the highly poly-condensed forms, just 2% of initial silicon is still in molecular form at the end of the dissolution. A thermal treatment of the fuel element, by forming inter-metallic phases U-Al-Si, allows the whole silicon to pass into the solution and next to precipitate. The behavior of silicon in spent fuels should be between these two situations. (author)

  17. Formation of (Nd,Y)-silicides by sequential channeled implantation of Y and Nd ions

    International Nuclear Information System (INIS)

    Jin, S.; Bender, H.; Wu, M.F.; Vantomme, A.; Langouche, G.

    2000-01-01

    A buried hexagonal Nd 0.32 Y 0.68 Si 1.7 layer is formed by a sequential implantation of Y and Nd ions into (1 1 1)-oriented silicon wafers. The orientation relationship between the epitaxial Nd 0.32 Y 0.68 Si 1.7 and the silicon is (0 0 0 1) Nd 0.32 Y 0.68 Si 1.7 //(1 1 1) Si with Nd 0.32 Y 0.68 Si 1.7 // Si . High temperature annealing (1000 deg. C) results in a gradual transition into an orthorhombic ternary (Nd,Y)-silicide. Between the orthorhombic (Nd,Y)-silicide and the Si a preferential orientation relationship exists: (1 1 0) orth //(1 1(bar) 0) Si with orth // Si . However, as not all orthorhombic silicide grains follow this epitaxial relationship, the minimum yield in the Rutherford backscattering spectrometry (RBS) spectrum increases compared to the results after a low temperature annealing

  18. Formation of (Nd,Y)-silicides by sequential channeled implantation of Y and Nd ions

    Science.gov (United States)

    Jin, S.; Bender, H.; Wu, M. F.; Vantomme, A.; Langouche, G.

    2000-03-01

    A buried hexagonal Nd0.32Y0.68Si1.7 layer is formed by a sequential implantation of Y and Nd ions into (1 1 1)-oriented silicon wafers. The orientation relationship between the epitaxial Nd0.32Y0.68Si1.7 and the silicon is (0 0 0 1)Nd0.32Y0.68Si1.7//(1 1 1)Si with Nd0.32Y0.68Si1.7//Si. High temperature annealing (1000°C) results in a gradual transition into an orthorhombic ternary (Nd,Y)-silicide. Between the orthorhombic (Nd,Y)-silicide and the Si a preferential orientation relationship exists: (1 1 0)orth//(1 1¯ 0)Si with orth//Si. However, as not all orthorhombic silicide grains follow this epitaxial relationship, the minimum yield in the Rutherford backscattering spectrometry (RBS) spectrum increases compared to the results after a low temperature annealing.

  19. Pt silicide/poly-Si Schottky diodes as temperature sensors for bolometers

    Energy Technology Data Exchange (ETDEWEB)

    Yuryev, V. A., E-mail: vyuryev@kapella.gpi.ru; Chizh, K. V.; Chapnin, V. A.; Mironov, S. A.; Dubkov, V. P.; Uvarov, O. V.; Kalinushkin, V. P. [A. M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov Street, Moscow 119991 (Russian Federation); Senkov, V. M. [P. N. Lebedev Physical Institute of the Russian Academy of Sciences, 53 Leninskiy Avenue, Moscow 119991 (Russian Federation); Nalivaiko, O. Y. [JSC “Integral” – “Integral” Holding Management Company, 121A, Kazintsa I. P. Street, Minsk 220108 (Belarus); Novikau, A. G.; Gaiduk, P. I. [Belarusian State University, 4 Nezavisimosti Avenue, 220030 Minsk (Belarus)

    2015-05-28

    Platinum silicide Schottky diodes formed on films of polycrystalline Si doped by phosphorus are demonstrated to be efficient and manufacturable CMOS-compatible temperature sensors for microbolometer detectors of radiation. Thin-film platinum silicide/poly-Si diodes have been produced by a CMOS-compatible process on artificial Si{sub 3}N{sub 4}/SiO{sub 2}/Si(001) substrates simulating the bolometer cells. Layer structure and phase composition of the original Pt/poly-Si films and the Pt silicide/poly-Si films synthesized by a low-temperature process have been studied by means of the scanning transmission electron microscopy; they have also been explored by means of the two-wavelength X-ray structural phase analysis and the X-ray photoelectron spectroscopy. Temperature coefficient of voltage for the forward current of a single diode is shown to reach the value of about −2%/ °C in the temperature interval from 25 to 50 °C.

  20. Multi-layered silicides coating for vanadium alloys for generation IV reactors

    International Nuclear Information System (INIS)

    Mathieu, S.; Chaia, N.; Vilasi, M.; Le Flem, M.

    2012-01-01

    The halide-activated pack-cementation technique was employed to fabricate a diffusion coating that is resistant both to isothermal and to cyclic oxidation in air at 650 degrees C on the surface of the V-4Cr-4Ti vanadium alloy that is a potential core component of future nuclear systems. A thermodynamic assessment determined the deposit conditions in terms of master alloy, activator, filler and temperature. The partial pressures of the main gaseous species (SiCl 4 , SiCl 2 and VCl 2 ) in the pack were calculated with the master alloy Si and the mixture VSi 2 + Si. The VSi 2 + Si master alloy was used to limit vanadium loss from the surface. The obtained coating consisted of multi-layered V x Si y silicides with an outer layer of VSi 2 . This silicide developed a protective layer of silica at 650 degrees C in air and was not susceptible to the pest phenomenon, unlike other refractory silicides (MoSi 2 , NbSi 2 ). We suggest that VSi 2 exhibits no risk of rapid degradation in the gas fast reactor (GFR) conditions. (authors)

  1. Silicide/Silicon Heterointerfaces, Reaction Kinetics and Ultra-short Channel Devices

    Science.gov (United States)

    Tang, Wei

    Nickel silicide is one of the electrical contact materials widely used on very large scale integration (VLSI) of Si devices in microelectronic industry. This is because the silicide/silicon interface can be formed in a highly controlled manner to ensure reproducibility of optimal structural and electrical properties of the metal-Si contacts. These advantages can be inherited to Si nanowire (NW) field-effect transistors (FET) device. Due to the technological importance of nickel silicides, fundamental materials science of nickel silicides formation (Ni-Si reaction), especially in nanoscale, has raised wide interest and stimulate new insights and understandings. In this dissertation, in-situ transmission electron microscopy (TEM) in combination with FET device characterization will be demonstrated as useful tools in nano-device fabrication as well as in gaining insights into the process of nickel silicide formation. The shortest transistor channel length (17 nm) fabricated on a vapor-liquid-solid (VLS) grown silicon nanowire (NW) has been demonstrated by controlled reaction with Ni leads on an in-situ transmission electron microscope (TEM) heating stage at a moderate temperature of 400 ºC. NiSi2 is the leading phase, and the silicide-silicon interface is an atomically sharp type-A interface. At such channel lengths, high maximum on-currents of 890 (microA/microm) and a maximum transconductance of 430 (microS/microm) were obtained, which pushes forward the performance of bottom-up Si NW Schottky barrier field-effect transistors (SB-FETs). Through accurate control over the silicidation reaction, we provide a systematic study of channel length dependent carrier transport in a large number of SB-FETs with channel lengths in the range of (17 nm -- 3.6 microm). Our device results corroborate with our transport simulations and reveal a characteristic type of short channel effects in SB-FETs, both in on- and off-state, which is different from that in conventional MOSFETs

  2. Olefins hydro-formylation catalysed by rhodium complexes using ionic liquids; Hydroformylation des olefines par les complexes du rhodium dans les liquides ioniques

    Energy Technology Data Exchange (ETDEWEB)

    Favre, F.

    2000-10-26

    Biphasic long chain olefins hydro-formylation catalysed by rhodium complexes using ionic liquids allows a selective reaction and an easy separation of the products from the catalyst. This study reports the synthesis of ionic liquids that were used as the catalyst's solvent. Their physical and chemical properties (melting point, solubility of organic substrates) can be varied with the structure of the organic cation (imidazolium, pyridinium, pyrrolydinium) and with its substituents (nature, length, number). It depends also on the nature of the inorganic anion (hexa-fluoro-phosphate, tetrafluoroborate, tri-fluoro-acetate, triflate, bistriflylamidure...). The use of phosphorus ligands bearing ionic functions proved to be efficient to maintain the onerous rhodium catalyst in the ionic liquid phase. Phosphines, phosphites and phosphinites including anionic (sulfonate, carboxylate) or cationic (imidazolium, pyridinium, guanidinium, phosphonium) groups have been synthesised. Finally, the influences of the ligand and of the ionic liquid on the catalytic system performances are described. Selectivities in aldehydes and reaction rates proved to be highly dependent on the nature of the ligand and of the ionic liquid. The different possibilities of recycling the ionic phase containing the rhodium catalyst have been also studied. (author)

  3. Direct C-H alkylation and indole formation of anilines with diazo compounds under rhodium catalysis.

    Science.gov (United States)

    Mishra, Neeraj Kumar; Choi, Miji; Jo, Hyeim; Oh, Yongguk; Sharma, Satyasheel; Han, Sang Hoon; Jeong, Taejoo; Han, Sangil; Lee, Seok-Yong; Kim, In Su

    2015-12-18

    The rhodium(III)-catalyzed direct functionalization of aniline C-H bonds with α-diazo compounds is described. These transformations provide a facile construction of ortho-alkylated anilines with diazo malonates or highly substituted indoles with diazo acetoacetates.

  4. Activity of iridium-ruthenium and iridium-rhodium adsorption catalysts in decomposition of hydrogen peroxide

    Energy Technology Data Exchange (ETDEWEB)

    Zubovich, I A; Mikhaylov, V A; Migulina, N N [Yaroslavskij Politekhnicheskij Inst. (USSR)

    1976-06-01

    Experimental data for the activities of iridium-ruthenium and iridium-rhodium adsorption catalysts in the decomposition of hydrogen peroxide are considered and the results of magnetic susceptibility measurements are presented. It is concluded that surface structures (complexes) may be formed and that micro-electronic feaures play a role in heterogeneous catalysis.

  5. Rhodium(II)-Catalyzed Asymmetric Sulfur(VI) Reduction of Diazo Sulfonylamidines

    OpenAIRE

    Selander, Nicklas; Fokin, Valery V.

    2012-01-01

    Diazo sulfonylamidines readily undergo enantioselective oxygen transfer from sulfur to carbon atom in the presence of chiral rhodium(II) carboxylates resulting in chiral sulfinylamidines. This unusual asymmetric atom transfer “reduction” occurs rapidly under mild conditions, and sulfinylamidines are obtained in excellent yield.

  6. Enantioselective rhodium enolate protonations. A new methodology for the synthesis of beta2-amino acids.

    Science.gov (United States)

    Sibi, Mukund P; Tatamidani, Hiroto; Patil, Kalyani

    2005-06-23

    [reaction: see text] Rhodium-catalyzed conjugate addition of an aryl boronic acid to alpha-methylamino acrylates followed by enantioselective protonation of the oxa-pi-allylrhodium intermediate provides access to aryl-substituted beta(2)-amino acids. The impact of the different variables of the reaction on the levels of enantioselectivity has been assessed.

  7. Rhodium-catalyzed chemo- and regioselective decarboxylative addition of β-ketoacids to alkynes.

    Science.gov (United States)

    Li, Changkun; Grugel, Christian P; Breit, Bernhard

    2016-04-30

    A highly efficient rhodium-catalyzed chemo- and regioselective addition of β-ketoacids to alkynes is reported. Applying a Rh(i)/(S,S)-DIOP catalyst system, γ,δ-unsaturated ketones were prepared with exclusively branched selectivity under mild conditions. This demonstrates that readily available alkynes can be an alternative entry to allyl electrophiles in transition-metal catalyzed allylic alkylation reactions.

  8. Immobilization of rhodium complexes at thiolate monolayers on gold surfaces : Catalytic and structural studies

    NARCIS (Netherlands)

    Belser, T; Stöhr, Meike; Pfaltz, A

    2005-01-01

    Chiral rhodium-diphosphine complexes have been incorporated into self-assembled thiolate monolayers (SAMS) on gold colloids. Catalysts of this type are of interest because they combine properties of homogeneous and heterogeneous systems. In addition, it should be possible to influence the catalytic

  9. The Role of the Element Rhodium in the Hyperbolic Law of the Periodic Table of Elements

    Directory of Open Access Journals (Sweden)

    Albert Khazan

    2008-07-01

    Full Text Available The role of the element rhodium as an independent affirmation of calculations by the Hyperbolic Law and validity of all its relations is shown herein. The deviation in calculation by this method of the atomic mass of heaviest element is 0.0024%, and its coefficient of scaling 0.001-0.005%.

  10. STABLE SILICA-GRAFTED POLYMER-BOUND BULKY-PHOSPHITE MODIFIED RHODIUM HYDROFORMYLATION CATALYSTS

    NARCIS (Netherlands)

    JONGSMA, T; VANAERT, H; FOSSEN, M; CHALLA, G; VANLEEUWEN, PWNM

    1993-01-01

    The present study demonstrates that silica-grafted polymer-bound phosphite modified rhodium complexes can be used in continuous flow reactors. The hydroformylation of styrene was carried out at moderate pressure (p(CO/H-2) = 30 bar) and temperature (T = 100-degrees-C), yielding constant conversions

  11. A NEW TYPE OF HIGHLY-ACTIVE POLYMER-BOUND RHODIUM HYDROFORMYLATION CATALYST

    NARCIS (Netherlands)

    JONGSMA, T; KIMKES, P; CHALLA, G; VANLEEUWEN, PWNM

    1992-01-01

    A new route of attaching phosphites to a (co)polymer chain is described. These copolymers are used for the preparation of a rhodium phosphite hydroformylation catalyst. The catalytic activity of this polymer-bound system is identical to that of the low molecular weight analogue. The catalysts show a

  12. Komplexe zouten van trans-1-2-diaminocyclohexaan met driewaardig rhodium en kobalt

    NARCIS (Netherlands)

    Bijkerk, Lucas

    1937-01-01

    Some complex salts of trans-I-2-díominocyclohexane with trivalent cobaltum and rhodium were prepared and their properties described in detail. Diaminocyclohexanwe as obtained by the following series of reactions: cyclohexanone --> cyclohexanone-I-oxalylicester --> cyclohexonone-I-carboxylicester-2

  13. Rhodium Phosphine-π-Arene Intermediates in the Hydroamination of Alkenes

    Science.gov (United States)

    Liu, Zhijian; Yamamichi, Hideaki; Madrahimov, Sherzod T.; Hartwig, John F.

    2011-01-01

    A detailed mechanistic study of the intramolecular hydroamination of alkenes with amines catalyzed by rhodium complexes of a biaryldialkylphosphine are reported. The active catalyst is shown to contain the phosphine ligand bound in a κ1, η6 form in which the arene is π-bound to rhodium. Addition of deuterated amine to an internal olefin showed that the reaction occurs by trans addition of the N-H bond across the C=C bond, and this stereochemistry implies that the reaction occurs by nucleophilic attack of the amine on a coordinated alkene. Indeed, the cationic rhodium fragment binds the alkene over the secondary amine, and the olefin complex was shown to be the catalyst resting state. The reaction was zero-order in substrate, when the concentration of olefin was high, and a primary isotope effect was observed. The primary isotope effect, in combination with the observation of the alkene complex as the resting state, implies that nucleophilic attack of the amine on the alkene is reversible and is followed by turnover-limiting protonation. This mechanism constitutes an unusual pathway for rhodium-catalyzed additions to alkenes and is more closely related to the mechanism for palladium-catalyzed addition of amide N-H bonds to alkenes. PMID:21309512

  14. A MECHANISTIC STUDY OF RHODIUM TRI(ORTHO-TERT-BUTYLPHENYL)PHOSPHITE COMPLEXES AS HYDROFORMYLATION CATALYSTS

    NARCIS (Netherlands)

    JONGSMA, T; CHALLA, G; VANLEEUWEN, PWNM

    1991-01-01

    A mechanistic study of the hydroformylation cycle with a rhodium tri(o-t-butylphenyl)phosphite complex as catalyst is presented. Spectroscopic experiments prove that under hydroformylation conditions this complex is coordinated by only one phosphite. The complex has a high activity in the

  15. Enantioselective Rhodium Enolate Protonations. A New Methodology for the Synthesis of β2-Amino Acids

    Science.gov (United States)

    Sibi, Mukund P.; Tatamidani, Hiroto; Patil, Kalyani

    2008-01-01

    Rhodium catalyzed conjugate addition of an aryl boronic acid to α-methylamino acrylates followed by enantioselective protonation of the oxa-π-allylrhodium intermediate provides access to aryl substituted β2-amino acids. The impact of the different variables of the reaction on the levels of enantioselectivity has been assessed. PMID:15957893

  16. Double-spin-flip resonance of rhodium nuclei at positive and negative spin temperatures

    DEFF Research Database (Denmark)

    Tuoriniemi, J.T.; Knuuttila, T.A.; Lefmann, K.

    2000-01-01

    Sensitive SQUID-NMR measurements were used to study the mutual interactions in the highly polarized nuclear-spin system of rhodium metal. The dipolar coupling gives rise to a weak double-spin-flip resonance. The observed frequency shifts allow deducing separately the dipolarlike contribution...

  17. Rhodium Catalyzed Annulation of N-Benzoylsulfonamide with Isocyanide via C-H Activation

    Science.gov (United States)

    Zhu, Chen; Xie, Weiqing; Falck, John R.

    2012-01-01

    Isocyanide insertion: the first rhodium-catalyzed annulation of N-benzoylsulfonamide incorporating with isocyanide via C-H activation is described. The transformation is broadly compatible with N-benzoylsulfonamides bearing various electron-properties as well as isocyanides. From practical point of view, this methodology provides the most straightforward approach to a series of 3-(imino)isoindolinones. PMID:21972033

  18. Rhodium-Catalyzed Regioselective C7-Olefination of Indazoles Using an N-Amide Directing Group.

    Science.gov (United States)

    Guo, Lei; Chen, Yanyu; Zhang, Rong; Peng, Qiujun; Xu, Lanting; Pan, Xianhua

    2017-02-01

    A rhodium-catalyzed regioselective C-H olefination of indazole is described. This protocol relies on the use of an efficient and removable N,N-diisopropylcarbamoyl directing group, which offers facile access to C7-olefinated indazoles with high regioselectivity, ample substrate scope and broad functional group tolerance. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. The influence of pH on the in vitro permeation of rhodium through human skin.

    Science.gov (United States)

    Jansen Van Rensburg, Sané; Franken, Anja; Du Plessis, Jeanetta; Du Plessis, Johannes Lodewykus

    2017-06-01

    Workers in precious metals refineries are at risk of exposure to salt compounds of the platinum group metals through inhalation, as well as through the skin. Rhodium salt permeation through the skin has previously been proven using rhodium trichloride (RhCl 3 ) dissolved in synthetic sweat at a pH of 6.5. However, the skin surface pH of refinery workers may be lower than 6.5. The aim of this study was to investigate the influence of pH 6.5 and 4.5 on the in vitro permeation of rhodium through intact Caucasian skin using Franz diffusion cells. A concentration of 0.3 mg mL -1 rhodium was used and analyses were performed using inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectrometry. Results indicated a cumulative increase in permeation over 24 h. Rhodium permeation after 12 h was significantly greater at pH 4.5 (1.56 ± 0.24 ng cm -2 ) than at 6.5 (0.85 ± 0.13 ng cm -2 ; p = 0.02). At both pH levels, there was a highly significant difference ( p rhodium remaining in the skin (1428.68 ± 224.67 ng cm -2 at pH 4.5 and 1029.90 ± 115.96 ng cm -2 at pH 6.5) and the mass that diffused through (0.88 ± 0.17 ng cm -2 at pH 4.5 and 0.62 ± 0.10 ng cm -2 at pH 6.5). From these findings, it is evident that an acidic working environment or low skin surface pH may enhance permeation of rhodium salts, contributing to sensitization and adverse health effects.

  20. Chemo- and regioselective homogeneous rhodium-catalyzed hydroamidomethylation of terminal alkenes to N-alkylamides.

    Science.gov (United States)

    Raoufmoghaddam, Saeed; Drent, Eite; Bouwman, Elisabeth

    2013-09-01

    A rhodium/xantphos homogeneous catalyst system has been developed for direct chemo- and regioselective mono-N-alkylation of primary amides with 1-alkenes and syngas through catalytic hydroamidomethylation with 1-pentene and acetamide as model substrates. For appropriate catalyst performance, it appears to be essential that catalytic amounts of a strong acid promoter, such as p-toluenesulfonic acid (HOTs), as well as larger amounts of a weakly acidic protic promoter, particularly hexafluoroisopropyl alcohol (HOR(F) ) are applied. Apart from the product N-1-hexylacetamide, the isomeric unsaturated intermediates, hexanol and higher mass byproducts, as well as the corresponding isomeric branched products, can be formed. Under optimized conditions, almost full alkene conversion can be achieved with more than 80% selectivity to the product N-1-hexylamide. Interestingly, in the presence of a relatively high concentration of HOR(F) , the same catalyst system shows a remarkably high selectivity for the formation of hexanol from 1-pentene with syngas, thus presenting a unique example of a selective rhodium-catalyzed hydroformylation-hydrogenation tandem reaction under mild conditions. Time-dependent product formation during hydroamidomethylation batch experiments provides evidence for aldehyde and unsaturated intermediates; this clearly indicates the three-step hydroformylation/condensation/hydrogenation reaction sequence that takes place in hydroamidomethylation. One likely role of the weakly acidic protic promoter, HOR(F) , in combination with the strong acid HOTs, is to establish a dual-functionality rhodium catalyst system comprised of a neutral rhodium(I) hydroformylation catalyst species and a cationic rhodium(III) complex capable of selectively reducing the imide and/or ene-amide intermediates that are in a dynamic, acid-catalyzed condensation equilibrium with the aldehyde and amide in a syngas environment. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Efficient Synthesis of Spirobarbiturates and Spirothiobarbiturates Bearing Cyclopropane Rings by Rhodium(II)-Catalyzed Reactions of Cyclic Diazo Compounds

    International Nuclear Information System (INIS)

    Wang, Xue; Lee, Yong Rok

    2013-01-01

    Rhodium(II)-catalyzed reactions of cyclic diazo compounds derived from barbituric acid and thiobarbituric acid with a variety of styrene moieties were examined. These reactions provide rapid synthetic routes to the preparations of spirobarbiturates and spirothiobarbiturates bearing cyclopropane rings

  2. Efficient Synthesis of Spirobarbiturates and Spirothiobarbiturates Bearing Cyclopropane Rings by Rhodium(II)-Catalyzed Reactions of Cyclic Diazo Compounds

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xue; Lee, Yong Rok [Yeungnam Univ., Gyeongsan (Korea, Republic of)

    2013-06-15

    Rhodium(II)-catalyzed reactions of cyclic diazo compounds derived from barbituric acid and thiobarbituric acid with a variety of styrene moieties were examined. These reactions provide rapid synthetic routes to the preparations of spirobarbiturates and spirothiobarbiturates bearing cyclopropane rings.

  3. Burnup Estimation of Rhodium Self-Powered Neutron Detector Emitter in VVER Reactor Core Using Monte Carlo Simulations

    OpenAIRE

    Khrutchinsky, А. А.; Kuten, S. A.; Babichev, L. F.

    2011-01-01

    Estimation of burn-up in a rhodium-103 emitter of self-powered neutron detector in VVER-1000 reactor core has been performed using Monte Carlo simulations within approximation of a constant neutron flux.

  4. Safeguarding subcriticality during loading and shuffling operations in the higher density of the RSG-GAS's silicide core

    International Nuclear Information System (INIS)

    Sembiring, T.M.; Kuntoro, I.

    2003-01-01

    The core conversion program of the RSG-GAS reactor is to convert the all-oxide to all-silicide core. The silicide equilibrium core with fuel meat density of 3.55 gU cm -3 is an optimal core for RSG-GAS reactor and it can significantly increase the operation cycle length from 25 to 32 full power days. Nevertheless, the subcriticality of the shutdown core and the shutdown margin are lower than of the oxide core. Therefore, the deviation of subcriticality condition in the higher silicide core caused by the fuel loading and shuffling error should be reanalysed. The objective of this work is to analyse the sufficiency of the subcriticality condition of the shutdown core to face the worst condition caused by an error during loading and shuffling operations. The calculations were carried out using the 2-dimensional multigroup neutron diffusion code of Batan-FUEL. In the fuel handling error, the calculated results showed that the subcriticality condition of the shutdown higher density silicide equilibrium core of RSG-GAS can be maintained. Therefore, all fuel management steps are fixed in the present reactor operation manual can be applied in the higher silicide equilibrium core of RSG-GAS reactor. (author)

  5. Local solid phase growth of few-layer graphene on silicon carbide from nickel silicide supersaturated with carbon

    International Nuclear Information System (INIS)

    Escobedo-Cousin, Enrique; Vassilevski, Konstantin; Hopf, Toby; Wright, Nick; O'Neill, Anthony; Horsfall, Alton; Goss, Jonathan; Cumpson, Peter

    2013-01-01

    Patterned few-layer graphene (FLG) films were obtained by local solid phase growth from nickel silicide supersaturated with carbon, following a fabrication scheme, which allows the formation of self-aligned ohmic contacts on FLG and is compatible with conventional SiC device processing methods. The process was realised by the deposition and patterning of thin Ni films on semi-insulating 6H-SiC wafers followed by annealing and the selective removal of the resulting nickel silicide by wet chemistry. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to confirm both the formation and subsequent removal of nickel silicide. The impact of process parameters such as the thickness of the initial Ni layer, annealing temperature, and cooling rates on the FLG films was assessed by Raman spectroscopy, XPS, and atomic force microscopy. The thickness of the final FLG film estimated from the Raman spectra varied from 1 to 4 monolayers for initial Ni layers between 3 and 20 nm thick. Self-aligned contacts were formed on these patterned films by contact photolithography and wet etching of nickel silicide, which enabled the fabrication of test structures to measure the carrier concentration and mobility in the FLG films. A simple model of diffusion-driven solid phase chemical reaction was used to explain formation of the FLG film at the interface between nickel silicide and silicon carbide.

  6. Selective catalytic reduction system and process for treating NOx emissions using a palladium and rhodium or ruthenium catalyst

    Science.gov (United States)

    Sobolevskiy, Anatoly [Orlando, FL; Rossin, Joseph A [Columbus, OH; Knapke, Michael J [Columbus, OH

    2011-07-12

    A process for the catalytic reduction of nitrogen oxides (NOx) in a gas stream (29) in the presence of H.sub.2 is provided. The process comprises contacting the gas stream with a catalyst system (38) comprising zirconia-silica washcoat particles (41), a pre-sulfated zirconia binder (44), and a catalyst combination (40) comprising palladium and at least one of rhodium, ruthenium, or a mixture of ruthenium and rhodium.

  7. Dihydropyranone Formation by Ipso C–H Activation in a Glucal 3-Carbamate-Derived Rhodium Acyl Nitrenoid

    Science.gov (United States)

    Hurlocker, Brisa; Abascal, Nadia C.; Repka, Lindsay M.; Santizo-Deleon, Elsy; Smenton, Abigail L.; Baranov, Victoria; Gupta, Ritu; Bernard, Sarah E.; Chowdhury, Shenjuti; Rojas, Christian M.

    2011-01-01

    By using (N-tosyloxy)-3-O-carbamoyl-D-glucal 10, which removes the need for a hypervalent iodine(III) oxidant, we provide evidence for rhodium nitrenoid-mediated ipso C–H activation as the origin of a C3-oxidized dihydropyranone product 3. This system may be especially susceptible to such a pathway due to the ease of forming a cation upon hydride transfer to the rhodium-complexed acyl nitrene. PMID:21381715

  8. Homoleptic mono- and dinuclear cationic alkoxydiphosphazane derivatives of rhodium

    International Nuclear Information System (INIS)

    Edwards, K.J.; Haines, R.J.; Meintjies, E.; Sigwarth, B.

    1990-01-01

    Treatment of the solvento species [Rh(C 8 H 12 )(solvent) 2 ][SbF 6 ] (solvent = methanol, ethanol, or tetrahydrofuran) with a twice-molar amount of the diphosphazane ligands (RO) 2 PN(R') P(OR) 2 (R' = Me or Et; R = Me, Et, or Pr i ) in the appropriate solvent leads to the ready formation of monocationic [Rh{(RO) 2 PN(R')P(OR) 2 } 2 ] + and/or dicationic [Rh 2 {μ-(RO) 2 PN(R')P(OR) 2 } 2 {(RO) 2 PN(R')P(OR) 2 } 2 ] 2+ hexafluoroantimonate salts, with the tendency to afford dinuclear derivatives decreasing along the series Me>Et>Pr i . Carbon monoxide readily forms addition products with these ionic species, giving rise to five-coordinate derivatives of the type [Rh(CO){(RO) 2 PN(R')P (OR) 2 } 2 ][SbF 6 ] in the case of the mononuclear derivatives, and inserting across the two rhodium atoms to afford [Rh 2 (μ-CO){μ-(MeO) 2 PN(Et)P(OMe) 2 } 2 {(MeO) 2 PN(Et)P(OMe) 2 } 2 ][SbF 6 ] 2 in the case of [Rh 2 {μ-(MeO) 2 PN (Et)P(OMe) 2 } 2 {(MeO) 2 PN(Et)P(OMe) 2 } 2 ][SbF 6 ] 2 . These mono- and dicationic derivatives also react readily with iodine affording [RhI 2 {(RO) 2 PN(R')P(OR) 2 } 2 ][SbF 6 ] and [Rh 2 (μ-I){μ-(MeO) 2 PN(Et)P(OMe) 2 } 2 {(MeO) 2 PN(Et)P(OMe) 2 } 2 ][SbF 6 ] n (n = 2 or 3) respectively. The coordination behaviour of the diphosphorus ligands (MeO) 2 PCH 2 P(OMe) 2 and Me 2 PCH 2 PMe 2 towards [Rh(C 8 H 12 )(solvent) 2 ][SbF 6 ] has also been investigated. 1 fig., 1 tab., 19 refs

  9. Relationship between electronic structure and electric conductivity of double rhodium oxides from X-ray spectral data

    International Nuclear Information System (INIS)

    Firsov, M.N.; Nefedov, V.I.; Shaplygin, I.S.

    1983-01-01

    Quantum yield spectra of X-ray photoemission of O K - and Rh M 3 -bands of double rhodium oxides with Be, Mg, Ca, Sr, Ba, Cd, V, Nb, Ta, Mo, W are obtained. Quantum yield spectra are analogous to absorption spectra and reflect vacant states in a crystal, in particular, the quantum yield spectrum of O K-band is associated with oxygen vacant states of p-symmetry while Rh M 3 -band spectrum with rhomium vacant states of d-symmetry. In all rhodium compounds investigated the first vacant band is formed by the rhodium 4d-states. The forbidden zone between the last occupied and first free states of rhodiUm has a small width (eV fractions), which explains the semiconductor character of electric conductivity of the investigated compounds. Electric resistance variation in investigated series of rhodium compounds is in agreement with peculiarities of their electronic structure and entirely depends on variation in the electron density on rhodium atoms

  10. Post-pulse detail metallographic examinations of low-enriched uranium silicide plate-type miniature fuel

    International Nuclear Information System (INIS)

    Yanagisawa, Kazuaki

    1991-10-01

    Pulse irradiation at Nuclear Safety Research Reactor (NSRR) was performed using low-enriched (19.89 w% 235 U) unirradiated silicide plate-type miniature fuel which had a density of 4.8 gU/cm 3 . Experimental aims are to understand the dimensional stability and to clarify the failure threshold of the silicide plate-type miniature fuel under power transient conditions through post-pulse detail metallographic examinations. A silicide plate-type miniature fuel was loaded into an irradiation capsule and irradiated by a single pulse. Deposited energies given in the experiments were 62, 77, 116 and 154 cal/g·fuel, which lead to corresponding peak fuel plate temperatures, 201 ± 28degC, 187 ± 10degC, 418 ± 74degC and 871 ± 74degC, respectively. Below 400degC, reliability and dimensional stability of the silicide plate fuel was sustained, and the silicide plate fuel was intact. Up to 540degC, wall-through intergranular crackings occurred in the Al-3%Mg alloy cladding. With the increase of the temperature, the melting of the aluminum cladding followed by recrystallization, the denudation of fuel core and the plate-through intergranular cracking were observed. With the increase of the temperature beyond 400degC, the bowing of fuel plate became significant. Above the temperature of 640degC molten aluminum partially reacted with the fuel core, partially flowed downward under the influence of surface tension and gravity, and partially formed agglomerations. Judging from these experimental observations, the fuel-plate above 400degC tends to reduce its dimensional stability. Despite of the apparent silicide fuel-plate failure, neither generation of pressure pulse nor that of mechanical energy occurred at all. (J.P.N.)

  11. Quantitative EPMA of Nano-Phase Iron-Silicides in Apollo 16 Lunar Regolith

    Science.gov (United States)

    Gopon, P.; Fournelle, J.; Valley, J. W.; Pinard, P. T.; Sobol, P.; Horn, W.; Spicuzza, M.; Llovet, X.; Richter, S.

    2013-12-01

    Until recently, quantitative EPMA of phases under a few microns in size has been extremely difficult. In order to achieve analytical volumes to analyze sub-micron features, accelerating voltages between 5 and 8 keV need to be used. At these voltages the normally used K X-ray transitions (of higher Z elements) are no longer excited, and we must rely of outer shell transitions (L and M). These outer shell transitions are difficult to use for quantitative EPMA because they are strongly affected by different bonding environments, the error associated with their mass attenuation coefficients (MAC), and their proximity to absorption edges. These problems are especially prevalent for the transition metals, because of the unfilled M5 electron shell where the Lα transition originates. Previous studies have tried to overcome these limitations by using standards that almost exactly matched their unknowns. This, however, is cumbersome and requires accurate knowledge of the composition of your sample beforehand, as well as an exorbitant number of well characterized standards. Using a 5 keV electron beam and utilizing non-standard X-ray transitions (Ll) for the transition metals, we are able to conduct accurate quantitative analyses of phases down to ~300nm. The Ll transition in the transition metals behaves more like a core-state transition, and unlike the Lα/β lines, is unaffected by bonding effects and does not lie near an absorption edge. This allows for quantitative analysis using standards do not have to exactly match the unknown. In our case pure metal standards were used for all elements except phosphorus. We present here data on iron-silicides in two Apollo 16 regolith grains. These plagioclase grains (A6-7 and A6-8) were collected between North and South Ray Craters, in the lunar highlands, and thus are associated with one or more large impact events. We report the presence of carbon, nickel, and phosphorus (in order of abundance) in these iron-silicide phases

  12. The fabrication and performance of Canadian silicide dispersion fuel for test reactors

    International Nuclear Information System (INIS)

    Sears, D.F.; Wood, J.C.; Berthiaume, L.C.; Herbert, L.N.; Schaefer, J.D.

    1985-01-01

    Fuel fabrication effort is now concentrated on the commissioning of large-scale process equipment, defining product specifications, developing a quality assurance plan, and setting up a mini-computer material accountancy system. In the irradiation testing program, full-size NRU assemblies containing 20% enriched silicide dispersion fuel have been Irradiated successfully to burnups in the range 65-80 atomic percent. Irradiations have also been conducted on mini-elements having 1.2 mm diameter holes In their mid-sections, some drilled before irradiation and others after irradiation to 22-83 atomic percent burnup. Uranium was lost to the coolant in direct proportion to the surface area of exposed core material. Pre-irradiation in the intact condition appeared to reduce in-reactor corrosion. Fuel cores developed for the NRU reactor are dimensionally very stable, swelling by only 6-8% at the very high burnup of 93 atomic percent. Two important factors contributing to this good performance are cylindrical clad restraint and coarse silicide particles. Thermal ramping tests were conducted on irradiated silicide aspersion fuels. Small segments of fuel cores released 85 Kr starting at about 520 deg. C and peaking at about 680 deg C. After a holding period of 1 hour at 720 deg. C a secondary 85 Kr peak occurred during cooling (at about 330 deg. C) probably due to thermal contraction cracking. Whole mini-elements irradiated to 93 atomic percent burnup were also ramped thermally, with encouraging results. After about 0.25 h at 530 deg. C the aluminum cladding developed very localized small blisters, some with penetrating pin-hole cracks preventing gross pillowing or ballooning. (author)

  13. Silicon-germanium and platinum silicide nanostructures for silicon based photonics

    Science.gov (United States)

    Storozhevykh, M. S.; Dubkov, V. P.; Arapkina, L. V.; Chizh, K. V.; Mironov, S. A.; Chapnin, V. A.; Yuryev, V. A.

    2017-05-01

    This paper reports a study of two types of silicon based nanostructures prospective for applications in photonics. The first ones are Ge/Si(001) structures forming at room temperature and reconstructing after annealing at 600°C. Germanium, being deposited from a molecular beam at room temperature on the Si(001) surface, forms a thin granular film composed of Ge particles with sizes of a few nanometers. A characteristic feature of these films is that they demonstrate signs of the 2 x 1 structure in their RHEED patterns. After short-term annealing at 600°C under the closed system conditions, the granular films reconstruct to heterostructures consisting of a Ge wetting layer and oval clusters of Ge. A mixed type c(4x2) + p(2x2) reconstruction typical to the low-temperature MBE (Tgr Ge. The other type of the studied nanostructures is based on Pt silicides. This class of materials is one of the friendliest to silicon technology. But as silicide film thickness reaches a few nanometers, low resistivity becomes of primary importance. Pt3Si has the lowest sheet resistance among the Pt silicides. However, the development of a process of thin Pt3Si films formation is a challenging task. This paper describes formation of a thin Pt3Si/Pt2Si structures at room temperature on poly-Si films. Special attention is paid upon formation of poly-Si and amorphous Si films on Si3N4 substrates at low temperatures.

  14. The fabrication and performance of Canadian silicide dispersion fuel for test reactors

    Energy Technology Data Exchange (ETDEWEB)

    Sears, D F; Wood, J C; Berthiaume, L C; Herbert, L N; Schaefer, J D

    1985-07-01

    Fuel fabrication effort is now concentrated on the commissioning of large-scale process equipment, defining product specifications, developing a quality assurance plan, and setting up a mini-computer material accountancy system. In the irradiation testing program, full-size NRU assemblies containing 20% enriched silicide dispersion fuel have been Irradiated successfully to burnups in the range 65-80 atomic percent. Irradiations have also been conducted on mini-elements having 1.2 mm diameter holes In their mid-sections, some drilled before irradiation and others after irradiation to 22-83 atomic percent burnup. Uranium was lost to the coolant in direct proportion to the surface area of exposed core material. Pre-irradiation in the intact condition appeared to reduce in-reactor corrosion. Fuel cores developed for the NRU reactor are dimensionally very stable, swelling by only 6-8% at the very high burnup of 93 atomic percent. Two important factors contributing to this good performance are cylindrical clad restraint and coarse silicide particles. Thermal ramping tests were conducted on irradiated silicide aspersion fuels. Small segments of fuel cores released {sup 85}Kr starting at about 520 deg. C and peaking at about 680 deg C. After a holding period of 1 hour at 720 deg. C a secondary {sup 85}Kr peak occurred during cooling (at about 330 deg. C) probably due to thermal contraction cracking. Whole mini-elements irradiated to 93 atomic percent burnup were also ramped thermally, with encouraging results. After about 0.25 h at 530 deg. C the aluminum cladding developed very localized small blisters, some with penetrating pin-hole cracks preventing gross pillowing or ballooning. (author)

  15. X-ray photoemission spectromicroscopy of titanium silicide formation in patterned microstructures

    International Nuclear Information System (INIS)

    Singh, S.; Solak, H.; Cerrina, F.

    1997-01-01

    Titanium silicide has the lowest resistivity of all the refractory metal silicides and has good thermal stability as well as excellent compatibility with Al metallization. It is used as an intermediate buffer layer between W vias and the Si substrate to provide good electrical contact in ULSI technology, whose submicron patterned features form the basis of the integrated circuits of today and tomorrow, in the self aligned silicide (salicide) formation process. TiSi 2 exists in two phases: a metastable C49 base-centered orthorhombic phase with specific resistivity of 60-90 μΩ-cm that is formed at a lower temperature (formation anneal) and the stable 12-15 μΩ-cm resistivity face-centered orthorhombic C54 phase into which C49 is transformed with a higher temperature (conversion anneal) step. C54 is clearly the target for low resistivity VLSI interconnects. However, it has been observed that when dimensions shrink below 1/mic (or when the Ti thickness drops below several hundred angstroms), the transformation of C49 into C54 is inhibited and agglomeration often occurs in fine lines at high temperatures. This results in a rise in resistivity due to incomplete transformation to C54 and because of discontinuities in the interconnect line resulting from agglomeration. Spectromicroscopy is an appropriate tool to study the evolution of the TiSi2 formation process because of its high resolution chemical imaging ability which can detect bonding changes even in the absence of changes in the relative amounts of species and because of the capability of studying thick open-quotes as isclose quotes industrial samples

  16. X-ray photoemission spectromicroscopy of titanium silicide formation in patterned microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Singh, S.; Solak, H.; Cerrina, F. [Univ. of Wisconsin-Madison, Stoughton, WI (United States)] [and others

    1997-04-01

    Titanium silicide has the lowest resistivity of all the refractory metal silicides and has good thermal stability as well as excellent compatibility with Al metallization. It is used as an intermediate buffer layer between W vias and the Si substrate to provide good electrical contact in ULSI technology, whose submicron patterned features form the basis of the integrated circuits of today and tomorrow, in the self aligned silicide (salicide) formation process. TiSi{sub 2} exists in two phases: a metastable C49 base-centered orthorhombic phase with specific resistivity of 60-90 {mu}{Omega}-cm that is formed at a lower temperature (formation anneal) and the stable 12-15 {mu}{Omega}-cm resistivity face-centered orthorhombic C54 phase into which C49 is transformed with a higher temperature (conversion anneal) step. C54 is clearly the target for low resistivity VLSI interconnects. However, it has been observed that when dimensions shrink below 1/mic (or when the Ti thickness drops below several hundred angstroms), the transformation of C49 into C54 is inhibited and agglomeration often occurs in fine lines at high temperatures. This results in a rise in resistivity due to incomplete transformation to C54 and because of discontinuities in the interconnect line resulting from agglomeration. Spectromicroscopy is an appropriate tool to study the evolution of the TiSi2 formation process because of its high resolution chemical imaging ability which can detect bonding changes even in the absence of changes in the relative amounts of species and because of the capability of studying thick {open_quotes}as is{close_quotes} industrial samples.

  17. Antitumor effect of free rhodium (II) citrate and rhodium (II) citrate-loaded maghemite nanoparticles on mice bearing breast cancer: a systemic toxicity assay.

    Science.gov (United States)

    Peixoto, Raphael Cândido Apolinário; Miranda-Vilela, Ana Luisa; de Souza Filho, José; Carneiro, Marcella Lemos' Brettas; Oliveira, Ricardo G S; da Silva, Matheus Oliveira; de Souza, Aparecido R; Báo, Sônia Nair

    2015-05-01

    Breast cancer is one of the most prevalent cancer types among women. The use of magnetic fluids for specific delivery of drugs represents an attractive platform for chemotherapy. In our previous studies, it was demonstrated that maghemite nanoparticles coated with rhodium (II) citrate (Magh-Rh2Cit) induced in vitro cytotoxicity and in vivo antitumor activity, followed by intratumoral administration in breast carcinoma cells. In this study, our aim was to follow intravenous treatment to evaluate the systemic antitumor activity and toxicity induced by these formulations in Balb/c mice bearing orthotopic 4T1 breast carcinoma. Female Balb/c mice were evaluated with regard to toxicity of intravenous treatments through analyses of hemogram, serum levels of alanine aminotransferase, iron, and creatinine and liver, kidney, and lung histology. The antitumor activity of rhodium (II) citrate (Rh2Cit), Magh-Rh2Cit, and maghemite nanoparticles coated with citrate (Magh-Cit), used as control, was evaluated by tumor volume reduction, histology, and morphometric analysis. Magh-Rh2Cit and Magh-Cit promoted a significant decrease in tumor area, and no experimental groups presented hematotoxic effects or increased levels of serum ALT and creatinine. This observation was corroborated by the histopathological examination of the liver and kidney of mice. Furthermore, the presence of nanoparticles was verified in lung tissue with no morphological changes, supporting the idea that our nanoformulations did not induce toxicity effects. No studies about the systemic action of rhodium (II) citrate-loaded maghemite nanoparticles have been carried out, making this report a suitable starting point for exploring the therapeutic potential of these compounds in treating breast cancer.

  18. Tungsten silicide contacts to polycrystalline silicon and silicon-germanium alloys

    International Nuclear Information System (INIS)

    Srinivasan, G.; Bain, M.F.; Bhattacharyya, S.; Baine, P.; Armstrong, B.M.; Gamble, H.S.; McNeill, D.W.

    2004-01-01

    Silicon-germanium alloy layers will be employed in the source-drain engineering of future MOS transistors. The use of this technology offers advantages in reducing series resistance and decreasing junction depth resulting in reduction in punch-through and SCE problems. The contact resistance of metal or metal silicides to the raised source-drain material is a serious issue at sub-micron dimensions and must be minimised. In this work, tungsten silicide produced by chemical vapour deposition has been investigated as a contact metallization scheme to both boron and phosphorus doped polycrystalline Si 1- x Ge x , with 0 ≤x ≤ 0.3. Cross bridge Kelvin resistor (CKBR) structures were fabricated incorporating CVD WSi 2 and polycrystalline SiGe. Tungsten silicide contacts to control polysilicon CKBR structures have been shown to be of high quality with specific contact resistance ρ c values 3 x 10 -7 ohm cm 2 and 6 x 10 -7 ohm cm 2 obtained to boron and phosphorus implanted samples respectively. The SiGe CKBR structures show that the inclusion of Ge yields a reduction in ρ c for both dopant types. The boron doped SiGe exhibits a reduction in ρ c from 3 x 10 -7 to 5 x 10 -8 ohm cm 2 as Ge fraction is increased from 0 to 0.3. The reduction in ρ c has been shown to be due to (i) the lowering of the tungsten silicide Schottky barrier height to p-type SiGe resulting from the energy band gap reduction, and (ii) increased activation of the implanted boron with increased Ge fraction. The phosphorus implanted samples show less sensitivity of ρ c to Ge fraction with a lowest value in this work of 3 x 10 -7 ohm cm 2 for a Ge fraction of 0.3. The reduction in specific contact resistance to the phosphorus implanted samples has been shown to be due to increased dopant activation alone

  19. The series production in a standardized fabrication line for silicide fuels and commercial aspects

    International Nuclear Information System (INIS)

    Wehner, E.L.; Hassel, H.W.

    1987-01-01

    NUKEM has been responsible for the development and fabrication of LEU fuel elements for MTR reactors under the frame of the German AF program since 1979. The AF program is part of the international RERTR efforts, which were initiated by the INFCE Group in 1978. This paper describes the actual status of development and the transition from the prototype to the series production in a standardized manufacturing line for silicide fuels at NUKEM. Technical provisions and a customer oriented standardized product range aim at an economized manufacturing. (Author)

  20. Current enhancement in crystalline silicon photovoltaic by low-cost nickel silicide back contact

    KAUST Repository

    Bahabry, R. R.; Gumus, A.; Kutbee, A. T.; Wehbe, N.; Ahmed, S. M.; Ghoneim, M. T.; Lee, K. -T.; Rogers, J. A.; Hussain, M. M.

    2016-01-01

    We report short circuit current (Jsc) enhancement in crystalline silicon (C-Si) photovoltaic (PV) using low-cost Ohmic contact engineering by integration of Nickel mono-silicide (NiSi) for back contact metallization as an alternative to the status quo of using expensive screen printed silver (Ag). We show 2.6 mA/cm2 enhancement in the short circuit current (Jsc) and 1.2 % increment in the efficiency by improving the current collection due to the low specific contact resistance of the NiSi on the heavily Boron (B) doped Silicon (Si) interface.

  1. Current enhancement in crystalline silicon photovoltaic by low-cost nickel silicide back contact

    KAUST Repository

    Bahabry, R. R.

    2016-11-30

    We report short circuit current (Jsc) enhancement in crystalline silicon (C-Si) photovoltaic (PV) using low-cost Ohmic contact engineering by integration of Nickel mono-silicide (NiSi) for back contact metallization as an alternative to the status quo of using expensive screen printed silver (Ag). We show 2.6 mA/cm2 enhancement in the short circuit current (Jsc) and 1.2 % increment in the efficiency by improving the current collection due to the low specific contact resistance of the NiSi on the heavily Boron (B) doped Silicon (Si) interface.

  2. Estimations on uranium silicide fuel prototypes for their irradiation and postirradiation

    International Nuclear Information System (INIS)

    Sbaffoni, Maria M.

    2000-01-01

    The 'Silicide' project includes the qualification of this type of research reactor fuel to be used i.e. in the Argentine RA-3 and to confirm CNEA's role as an international supplier. The present paper shows complementary basic information for P-04 prototype post-irradiation, which is already under way, and some parameter values related to the new P-06 prototype to be taken into account for planning its irradiation and post-irradiation. The reliability of these values has been evaluated through comparison with experimental results. The reported results contribute, also, to a parallel study on the nuclear data libraries used in calculations for this type of reactor. (author)

  3. Selective Cytotoxicity of Rhodium Metalloinsertors in Mismatch Repair-Deficient Cells†

    Science.gov (United States)

    Ernst, Russell J.; Komor, Alexis C.; Barton, Jacqueline K.

    2011-01-01

    Mismatches in DNA occur naturally during replication and as a result of endogenous DNA damaging agents, but the mismatch repair (MMR) pathway acts to correct mismatches before subsequent rounds of replication. Rhodium metalloinsertors bind to DNA mismatches with high affinity and specificity and represent a promising strategy to target mismatches in cells. Here we examine the biological fate of rhodium metalloinsertors bearing dipyridylamine ancillary ligands in cells deficient in MMR versus those that are MMR-proficient. These complexes are shown to exhibit accelerated cellular uptake which permits the observation of various cellular responses, including disruption of the cell cycle, monitored by flow cytometry assays, and induction of necrosis, monitored by dye exclusion and caspase inhibition assays, that occur preferentially in the MMR-deficient cell line. These cellular responses provide insight into the mechanisms underlying the selective activity of this novel class of targeted anti-cancer agents. PMID:22103240

  4. Enantioselective rhodium/ruthenium photoredox catalysis en route to chiral 1,2-aminoalcohols.

    Science.gov (United States)

    Ma, Jiajia; Harms, Klaus; Meggers, Eric

    2016-08-09

    A rhodium-based chiral Lewis acid catalyst combined with [Ru(bpy)3](PF6)2 as a photoredox sensitizer allows for the visible-light-activated redox coupling of α-silylamines with 2-acyl imidazoles to afford, after desilylation, 1,2-amino-alcohols in yields of 69-88% and with high enantioselectivity (54-99% ee). The reaction is proposed to proceed via an electron exchange between the α-silylamine (electron donor) and the rhodium-chelated 2-acyl imidazole (electron acceptor), followed by a stereocontrolled radical-radical reaction. Substrate scope and control experiments reveal that the trimethylsilyl group plays a crucial role in this reductive umpolung of the carbonyl group.

  5. Asymmetric Synthesis of Hydrocarbazoles Catalyzed by an Octahedral Chiral-at-Rhodium Lewis Acid.

    Science.gov (United States)

    Huang, Yong; Song, Liangliang; Gong, Lei; Meggers, Eric

    2015-12-01

    A bis-cyclometalated chiral-at-metal rhodium complex catalyzes the Diels-Alder reaction between N-Boc-protected 3-vinylindoles (Boc = tert-butyloxycarbonyl) and β-carboxylic ester-substituted α,β-unsaturated 2-acyl imidazoles with good-to-excellent regioselectivity (up to 99:1) and excellent diastereoselectivity (>50:1 d.r.) as well as enantioselectivity (92-99% ee) under optimized conditions. The rhodium catalyst serves as a chiral Lewis acid to activate the 2-acyl imidazole dienophile by two-point binding and overrules the preferred regioselectivity of the uncatalyzed reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Effects of human serun albumin in some biological properties of rhodium(II complexes

    Directory of Open Access Journals (Sweden)

    Espósito Breno P.

    2000-01-01

    Full Text Available The affinities for human albumin (HSA of five rhodium(II complexes of general formula [Rh2(bridge4] (bridge = acetate, propionate, butyrate, trifluoroacetate and trifluoroacetamidate were determined by spectrophotometry. In the case of the alkylcarboxylates, an inverse correlation of affinity with their liposolubilities was observed. Diffusion of the free or protein-bound complexes into Ehrlich cells in vitro seems to be primarily governed by the hydrophobic character of the complex. The complex [Rh2(tfc4] exhibited affinity towards the protein (K = 214.1 as well as cell partition both in the absence (32.1% and presence (48.6% of HSA. The compound HSA: [Rh2(tfc4] has had its antitumoral action in tumor-bearing Balb-c mice investigated, showing that HSA can be a drug reservoir for the rhodium complex.

  7. Extraction of ruthenium thiocyanate and its separation from rhodium by polyurethane foam

    International Nuclear Information System (INIS)

    Al-Bazi, S.J.; Chow, A.

    1984-01-01

    Conditions for the formation and extraction of the thiocyanate complex of ruthenium are reported. Distribution coefficients of more than 10 4 and a capacity of about 0.24 mole per kg of foam were obtained. The effect of the chloride salts of various univalent cations on the extraction of Ru(SCN) 6 3- indicated that the efficiency of ruthenium extraction depends on how well the cation fits into the polyether segment of the polyurethane foam, which agrees with the 'cation-chelation' mechanism. The separation of ruthenium and rhodium indicated that more than 95% of the rhodium remained in the aqueous phase and about 95% of the ruthenium was retained by the polyurethane foam and could be easily recovered. (author)

  8. Complexes of technetium, rhenium, and rhodium with sexidentate Schiff-base ligands

    International Nuclear Information System (INIS)

    Hunter, G.; Kilcullen, N.

    1989-01-01

    The monocationic technetium (IV) and rhenium (IV) complexes with the sexidentate Schiff-base ligands tris[2-(2'-hydroxybenzylideneethyl)]amine and its substituted derivatives have been prepared and their electrochemical properties studied. The variable-temperature 90.6 MHz 13 C-{ 1 H} n.m.r. spectrum of the rhodium (III) complex of tris[2-(2-hydroxy-5'-isopropylbenzylideneethyl)-amine] has been observed, indicating fluxionality at temperatures above 218 K. (author)

  9. Bifunctional Rhodium Intercalator Conjugates as Mismatch-Directing DNA Alkylating Agents

    OpenAIRE

    Schatzschneider, Ulrich; Barton, Jacqueline K.

    2004-01-01

    A conjugate of a DNA mismatch-specific rhodium intercalator, containing the bulky chrysenediimine ligand, and an aniline mustard has been prepared, and targeting of mismatches in DNA by this conjugate has been examined. The preferential alkylation of mismatched over fully matched DNA is found by a mobility shift assay at concentrations where untethered organic mustards show little reaction. The binding site of the Rh intercalator was determined by DNA photocleavage, and the position of covale...

  10. Dynamical model of computation of the rhodium self-powered neutron detector current

    International Nuclear Information System (INIS)

    Erben, O.; Slovacek, M.; Zerola, L.

    1992-01-01

    A model is presented for the calculation of the rhodium self-powered neutron detector current in dependence on the neutron flux density during reactor core transients. The total signal consists of a beta emission, prompt, and gamma component and a background signal. The model has been verified by means of experimental data obtained during measurements on the LVR-15 research reactor and at the Dukovany nuclear power plant. (author) 9 figs., 21 refs

  11. Rhodium-catalyzed asymmetric hydroboration of γ,δ-unsaturated amide derivatives: δ-borylated amides.

    Science.gov (United States)

    Hoang, G L; Zhang, S; Takacs, J M

    2018-05-08

    γ,δ-Unsaturated amides in which the alkene moiety bears an aryl or heteroaryl substituent undergo regioselective rhodium-catalyzed δ-borylation by pinacolborane to afford chiral secondary benzylic boronic esters. The results contrast the γ-borylation of γ,δ-unsaturated amides in which the disubstituted alkene moiety bears only alkyl substituents; the reversal in regiochemistry is coupled with a reversal in the sense of π-facial selectivity.

  12. Substrate-induced antiferromagnetism of ultrathin iron overlayers on the iridium and rhodium (001) surfaces

    Czech Academy of Sciences Publication Activity Database

    Máca, František; Kudrnovský, Josef; Drchal, Václav; Turek, Ilja; Bengone, O.; Redinger, J.

    2009-01-01

    Roč. 11, - (2009), s. 38-40 ISSN 1642-6037 R&D Projects: GA ČR GA202/07/0456; GA MŠk OC09028 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z20410507 Keywords : iridium * rhodium * iron * magnetismus in thin layers * density functional calculations Subject RIV: BM - Solid Matter Physics ; Magnetism

  13. Examining Rhodium Catalyst complexes for Use with Conducting Polymers Designed for Fuel Cells in Preparing Biosensors

    Energy Technology Data Exchange (ETDEWEB)

    Carpio, M.M.; Kerr, J.B.

    2005-01-01

    Biosensing devices are important because they can detect, record, and transmit information regarding the presence of, or physiological changes in, different chemical or biological materials in the environment. The goal of this research is to prepare a biosensing device that is effective, quick, and low cost. This is done by examining which chemicals will work best when placed in a biosensor. The first study involved experimenting on a rhodium catalyst complexed with ligands such as bipyridine and imidazole. The rhodium catalyst is important because it is reduced from RhIII to RhI, forms a hydride by reaction with water and releases the hydride to react with nicotinamide adenine dinucleotide (NAD+) to selectively produce 1,4-NADH, the reduced form of NAD+. The second study looked at different types of ketones and enzymes for the enzyme-substrate reaction converting a ketone into an alcohol. Preliminary results showed that the rhodium complexed with bipyridine was able to carry out all the reactions, while the rhodium complexed with imidazole was not able to produce and release hydrides. In addition, the most effective ketone to use is benzylacetone with the enzyme alcohol dehydrogenase from baker’s yeast. Future work includes experimenting with bis-imidazole, which mimics the structure of bipyridine to see if it has the capability to reduce and if the reduction rate is comparable to the bipyridine complex. Once all testing is completed, the fastest catalysts will be combined with polymer membranes designed for fuel cells to prepare biosensing devices that can be used in a variety of applications including ones in the medical and environmental fields.

  14. Identification of short-lived neutron-rich ruthenium and rhodium isotopes in fission

    International Nuclear Information System (INIS)

    Franz, G.; Herrmann, G.

    1975-01-01

    Short-lived ruthenium and rhodium isotopes ( 107 Ru, 108 Ru, 108 Rh, 109 Ru, 109 Rh, 110 Ru, 110 Rh, 111 Ru, 111 Rh, 112 Ru, 112 Rh, 113 Ru) have been separated from fission products by a rapid chemical procedure and identified by means of γ-ray spectroscopy. Nuclides with half-lives down to 3 sec were accessible. Ruthenium isotopes up to mass number 113 have been identified. (author)

  15. Rhodium-catalyzed C-H functionalization with N-acylsaccharins.

    Science.gov (United States)

    Wu, Hongxiang; Liu, Tingting; Cui, Ming; Li, Yue; Jian, Junsheng; Wang, Hui; Zeng, Zhuo

    2017-01-18

    A rhodium-catalyzed C-H functionalization with activated amides by decarbonylation has been developed. Notably, this is the first C-H arylation employing N-acylsaccharins as coupling partners to give biaryls in good to excellent yields. The highlight of the work is the high tolerance of functional groups such as formyl, ester, and vinyl and the use of a removable directing group.

  16. Rhodium-catalyzed asymmetric hydrogenation of unprotected NH imines assisted by a thiourea.

    Science.gov (United States)

    Zhao, Qingyang; Wen, Jialin; Tan, Renchang; Huang, Kexuan; Metola, Pedro; Wang, Rui; Anslyn, Eric V; Zhang, Xumu

    2014-08-04

    Asymmetric hydrogenation of unprotected NH imines catalyzed by rhodium/bis(phosphine)-thiourea provided chiral amines with up to 97% yield and 95% ee. (1)H NMR studies, coupled with control experiments, implied that catalytic chloride-bound intermediates were involved in the mechanism through a dual hydrogen-bonding interaction. Deuteration experiments proved that the hydrogenation proceeded through a pathway consistent with an imine. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Regioselective syntheses of 1,2-benzothiazines by rhodium-catalyzed annulation reactions.

    Science.gov (United States)

    Cheng, Ying; Bolm, Carsten

    2015-10-12

    Rhodium-catalyzed directed carbene insertions into aromatic CH bonds of S-aryl sulfoximines lead to intermediates, which upon dehydration provide 1,2-benzothiazines in excellent yields. The domino-type process is regioselective and shows a high functional-group tolerance. It is scalable, and the only by-products are dinitrogen and water. Three illustrative transformations underscore the synthetic value of the products. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Rhodium-catalyzed chemo-, regio-, and enantioselective addition of 2-pyridones to terminal allenes.

    Science.gov (United States)

    Li, Changkun; Kähny, Matthias; Breit, Bernhard

    2014-12-08

    A rhodium-catalyzed chemo-, regio-, and enantioselective addition of 2-pyridones to terminal allenes to give branched N-allyl 2-pyridones is reported. Preliminary mechanistic studies support the hypothesis that the reaction was initiated from the more acidic 2-hydroxypyridine form, and the initial kinetic O-allylation product was finally converted into the thermodynamically more stable N-allyl 2-pyridones. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Rhodium-catalyzed triarylphosphine synthesis via cross-coupling of aryl iodides and acylphosphines

    Directory of Open Access Journals (Sweden)

    Jiefang Yang

    2018-01-01

    Full Text Available Rhodium(I-catalyzed C–P cross-coupling reaction with aryl iodides and acylphosphines was disclosed for a straight forward synthesis of triarylphosphines. The acylphosphines were successfully employed as both the phosphorus source and the ligand to the Rh(I catalyst. The triarylphosphines could be afforded in a yield up to 98% with good toleration of wide functional groups.

  20. Divergent Reactivity of Rhodium(I) Carbenes Derived from Indole Annulations.

    Science.gov (United States)

    Li, Xiaoxun; Li, Hui; Song, Wangze; Tseng, Po-Sen; Liu, Lingyan; Guzei, Ilia A; Tang, Weiping

    2015-10-26

    Rhodium(I) carbenes were generated from propargylic alcohol derivatives as the result of a dehydrative indole annulation. Depending on the choice of the electron-withdrawing group on the aniline nitrogen nucleophile, either a cyclopropanation product or dimerization product was obtained chemoselectively. Intramolecular hydroamidation occurred for the same type of propargylic alcohol derivatives when other transition-metal catalysts were employed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Ammonia synthesis in the presence of rhodium-ruthenium-iridium carbonyl clusters

    International Nuclear Information System (INIS)

    Fedoseev, I.V.; Solov'ev, N.V.

    2007-01-01

    Researches in the field of platinum metal coordination compounds, where nitrogen enters as a ligand in coordination sphere of metal, are discussed. Results of experiments on the ammonia synthesis during the CO+N 2 mixture passing through alkali solution containing mixture of carbonyl clusters of rhodium, ruthenium and iridium at atmospheric pressure are given. Technique of the experiment and steps of assumed reactions of nitrogen fixation by Rh, Ir and Ru carbonyl clusters are demonstrated [ru

  2. Rhodium SPND's Error Reduction using Extended Kalman Filter combined with Time Dependent Neutron Diffusion Equation

    International Nuclear Information System (INIS)

    Lee, Jeong Hun; Park, Tong Kyu; Jeon, Seong Su

    2014-01-01

    The Rhodium SPND is accurate in steady-state conditions but responds slowly to changes in neutron flux. The slow response time of Rhodium SPND precludes its direct use for control and protection purposes specially when nuclear power plant is used for load following. To shorten the response time of Rhodium SPND, there were some acceleration methods but they could not reflect neutron flux distribution in reactor core. On the other hands, some methods for core power distribution monitoring could not consider the slow response time of Rhodium SPND and noise effect. In this paper, time dependent neutron diffusion equation is directly used to estimate reactor power distribution and extended Kalman filter method is used to correct neutron flux with Rhodium SPND's and to shorten the response time of them. Extended Kalman filter is effective tool to reduce measurement error of Rhodium SPND's and even simple FDM to solve time dependent neutron diffusion equation can be an effective measure. This method reduces random errors of detectors and can follow reactor power level without cross-section change. It means monitoring system may not calculate cross-section at every time steps and computing time will be shorten. To minimize delay of Rhodium SPND's conversion function h should be evaluated in next study. Neutron and Rh-103 reaction has several decay chains and half-lives over 40 seconds causing delay of detection. Time dependent neutron diffusion equation will be combined with decay chains. Power level and distribution change corresponding movement of control rod will be tested with more complicated reference code as well as xenon effect. With these efforts, final result is expected to be used as a powerful monitoring tool of nuclear reactor core

  3. Rhodium SPND's Error Reduction using Extended Kalman Filter combined with Time Dependent Neutron Diffusion Equation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jeong Hun; Park, Tong Kyu; Jeon, Seong Su [FNC Technology Co., Ltd., Yongin (Korea, Republic of)

    2014-05-15

    The Rhodium SPND is accurate in steady-state conditions but responds slowly to changes in neutron flux. The slow response time of Rhodium SPND precludes its direct use for control and protection purposes specially when nuclear power plant is used for load following. To shorten the response time of Rhodium SPND, there were some acceleration methods but they could not reflect neutron flux distribution in reactor core. On the other hands, some methods for core power distribution monitoring could not consider the slow response time of Rhodium SPND and noise effect. In this paper, time dependent neutron diffusion equation is directly used to estimate reactor power distribution and extended Kalman filter method is used to correct neutron flux with Rhodium SPND's and to shorten the response time of them. Extended Kalman filter is effective tool to reduce measurement error of Rhodium SPND's and even simple FDM to solve time dependent neutron diffusion equation can be an effective measure. This method reduces random errors of detectors and can follow reactor power level without cross-section change. It means monitoring system may not calculate cross-section at every time steps and computing time will be shorten. To minimize delay of Rhodium SPND's conversion function h should be evaluated in next study. Neutron and Rh-103 reaction has several decay chains and half-lives over 40 seconds causing delay of detection. Time dependent neutron diffusion equation will be combined with decay chains. Power level and distribution change corresponding movement of control rod will be tested with more complicated reference code as well as xenon effect. With these efforts, final result is expected to be used as a powerful monitoring tool of nuclear reactor core.

  4. Effect of Utilization of Silicide Fuel with the Density 4.8 gU/cc on the Kinetic Parameters of RSG-GAS Reactor

    International Nuclear Information System (INIS)

    Setiyanto; Sembiring, Tagor M.; Pinem, Surian

    2007-01-01

    Presently, the RSG-GAS reactor using silicide fuel element of 2.96 gU/cc. For increasing reactor operation time, its planning to change to higher density fuel. The kinetic calculation of silicide core with density 4.8 gU/cc has been carried out, since it has an influence on the reactor operation safety. The calculated kinetic parameters are the effective delayed neutron fraction, the delayed neutron decay constant, prompt neutron lifetime and feedback reactivity coefficient very important for reactor operation safety. the calculation is performed in 2-dimensional neutron diffusion-perturbation method using modified Batan-2DIFF code. The calculation showed that the effective delayed neutron fraction is 7. 03256x10 -03 , total delay neutron time constant is 7.85820x10 -02 s -1 and the prompt neutron lifetime is 55.4900 μs. The result of prompt neutron lifetime smaller 10 % compare with silicide fuel of 4.8 gU/cc. The calculated results showed that all of the feedback reactivity coefficient silicide core 4.8 gU/cc is negative. Totally, the feedback reactivity coefficient of silicide fuel of 4.8 gU/cc is 10% less than that of silicide fuel of 2.96 gU/cc. The results shown that kinetic parameters result decrease compared with the silicide core with density 2.96 gU/cc, but no significant influence in the RSG-GAS reactor operation. (author)

  5. Selectivity of a heterogeneous rhodium catalyst for the carbonylation of monohydric alcohols

    Energy Technology Data Exchange (ETDEWEB)

    Christensen, B; Scurrell, M S

    1977-01-01

    Selectivity of a heterogeneous rhodium catalyst for the carbonylation of monohydric alcohols with carbon monoxide in the presence of the corresponding alkyl iodides as promotors was studied in a glass reactor at approx. 0.05:1 alcohol/carbon monoxide ratio. The 1% by wt rhodium-zeolite catalyst was prepared by immersing a Linde molecular sieve zeolite Type 13X in rhodium trichloride at 80/sup 0/C for 15 hr. Methanol was converted to methyl acetate at 433/sup 0/-513/sup 0/K with selectivites > 90% even at the highest temperatures, and dimethyl ether was by-produced. In the absence of methyl iodide, the carbonylation rate decreased drastically but the dehydration was virtually unaffected. The selectivity for ethanol carbonylation decreased from 99% at 383/sup 0/K to 6% at 523/sup 0/K due to the formation of ethylene (predominant at > 470/sup 0/K) and diethyl ether. The only product of the reaction with propan-2-ol studied at 433/sup 0/ or 473/sup 0/K was propene with 100% conversion at 473/sup 0/K. These results are consistent with the relative ease of reactant dehydration on polar catalysts. Table and 13 references.

  6. Spatial and temporal distribution of platinum, palladium and rhodium in Zagreb air.

    Science.gov (United States)

    Rinkovec, Jasmina; Pehnec, Gordana; Godec, Ranka; Davila, Silvije; Bešlić, Ivan

    2018-09-15

    Platinum (Pt), palladium (Pd) and rhodium (Rh) are most widely used in the production of automotive catalytic converters that serve to reduce toxic emissions from motor vehicles. The aim of this study was to quantitatively determine the levels of platinum, palladium and rhodium in the PM 10 and PM 2.5 fraction of airborne particle matter and find their spatial and temporal distribution at different polluted areas of the city of Zagreb, Croatia. The method used in this paper included weekly sampling of airborne particle matter on quartz filters, microwave digestion in acid under high pressure and temperature, and analysis by inductively coupled plasma mass spectrometry (ICP MS). The results have shown that the highest mean values at all three sampling stations (North, Center, South) were obtained for palladium (3.856 pg m -3 , 5.396 pg m -3 , 5.600 pg m -3 ) and the lowest for rhodium (0.444 pg m -3 , 0.643 pg m -3 , 0.750 pg m -3 ). The average mass concentrations of platinum group elements (PGE) in PM 10 increased for all three elements in the direction North Zagreb are the first results of their kind for this area and will provide insights into the contribution of catalytic converters to the presence of these elements in the environment. Copyright © 2018 Elsevier B.V. All rights reserved.

  7. Rhodium self-powered detector for monitoring neutron fluence, energy production, and isotopic composition of fuel

    International Nuclear Information System (INIS)

    Sokolov, A.P.; Pochivalin, G.P.; Shipovskikh, Yu.M.; Garusov, Yu.V.; Chernikov, O.G.; Shevchenko, V.G.

    1993-01-01

    The use of self-powered detectors (SPDs) with a rhodium emitter customarily involves monitoring of neutron fields in the core of a nuclear reactor. Since current in an SPD is generated primarily because of the neutron flux, which is responsible for the dynamics of particular nuclear transformations, including fission reactions of heavy isotopes, the detector signal can be attributed unambiguously to energy release at the location of the detector. Computation modeling performed with the KOMDPS package of programs of the current formation in a rhodium SPD along with the neutron-physical processes that occur in the reactor core makes it possible to take account of the effect of the principal factors characterizing the operating conditions and the design features of the fuel channel and the detector, reveal quantitative relations between the generated signal and individual physical parameters, and determine the metrological parameters of the detector. The formation and transport of changed particles in the sensitive part of the SPC is calculated by the Monte Carlo method. The emitter activation, neutron transport, and dynamics of the isotopic composition in the fuel channel containing the SPD are determined by solving the kinetic equation in the multigroup representation of the neutron spectrum, using the discrete ordinate method. In this work the authors consider the operation of a rhodium SPD in a bundle of 49 fuel channels of the RBMK-1000 reactor with a fuel enrichment of 2.4% from the time it is inserted into a fresh channel

  8. Stereoselective hydrogenation of olefins using rhodium-substituted carbonic anhydrase--a new reductase.

    Science.gov (United States)

    Jing, Qing; Okrasa, Krzysztof; Kazlauskas, Romas J

    2009-01-01

    One useful synthetic reaction missing from nature's toolbox is the direct hydrogenation of substrates using hydrogen. Instead nature uses cofactors like NADH to reduce organic substrates, which adds complexity and cost to these reductions. To create an enzyme that can directly reduce organic substrates with hydrogen, researchers have combined metal hydrogenation catalysts with proteins. One approach is an indirect link where a ligand is linked to a protein and the metal binds to the ligand. Another approach is direct linking of the metal to protein, but nonspecific binding of the metal limits this approach. Herein, we report a direct hydrogenation of olefins catalyzed by rhodium(I) bound to carbonic anhydrase (CA-[Rh]). We minimized nonspecific binding of rhodium by replacing histidine residues on the protein surface using site-directed mutagenesis or by chemically modifying the histidine residues. Hydrogenation catalyzed by CA-[Rh] is slightly slower than for uncomplexed rhodium(I), but the protein environment induces stereoselectivity favoring cis- over trans-stilbene by about 20:1. This enzyme is the first cofactor-independent reductase that reduces organic molecules using hydrogen. This catalyst is a good starting point to create variants with tailored reactivity and selectivity. This strategy to insert transition metals in the active site of metalloenzymes opens opportunities to a wider range of enzyme-catalyzed reactions.

  9. Functionalized cyclopentadienyl rhodium(III) bipyridine complexes: synthesis, characterization, and catalytic application in hydrogenation of ketones.

    Science.gov (United States)

    Wang, Wan-Hui; Suna, Yuki; Himeda, Yuichiro; Muckerman, James T; Fujita, Etsuko

    2013-07-14

    A series of highly functionalized cyclopentadienyl rhodium(III) complexes, [Cp'Rh(bpy)Br](ClO4) (Cp' = substituted cyclopentadienyl), was synthesized from various multi-substituted cyclopentadienes (Cp'H). [Rh(cod)Cl]2 and Cp'H were firstly converted to [Cp'Rh(cod)] complexes, which were then treated with Br2 to give the rhodium(III) dibromides [Cp'RhBr2]2. The novel complexes [Cp'Rh(bpy)Br](ClO4) were obtained readily by the reaction of 2,2'-bipyridine with [Cp'RhBr2]2. These rhodium complexes [Cp'Rh(bpy)Br](ClO4) were fully characterized and utilized in the hydrogenation of cyclohexanone and acetophenone with generally high yields, but they did not exhibit the same reactivity trends for the two substrate ketones. The different activity of these complexes for the different substrates may be due to the influence of the substituents on the Cp' rings.

  10. Rhodium (II) cycle alkanecarboxylate: synthesis, spectroscopic and thermo analytic studies and evaluation of the antitumor potential

    International Nuclear Information System (INIS)

    Souza, Aparecido Ribeiro de

    1995-01-01

    Four new rhodium(II) carboxylates (cyclopropane, cyclobutane, cyclopentane, and cyclohexanecarboxylate), and other already known rhodium (II) carboxylates (acetate, propionate, butyrate, metoxyacetate, dichloroacetate, and trifluoroacetate), have been prepared for study in this work. The compounds were characterized by elementary and thermogravimetric analysis, magnetic susceptibility, and electronic, Raman, and infrared spectroscopy. The reaction of Rh CL 3 .aq with the sodium carboxylates was studied aiming to improve the understanding of the redox process involved. Spectroscopy studies (Raman and electronic) were made to examine the transition involved in the Rh-Rh and Rh-O bonds. The results have shown a direct relation between the force of the carboxylic acid and the Rh-O force, but show a inverse relation with the Rh-Rh bond force. Thermal analysis studies were undertaken and the obtained date show a resemblance of the TG/DTG curves with that found in literature. In the other hand, the DSC curves show a different results: in open crucible, the peaks associated with the cage breakdown are exothermic and, in closed crucible this peaks are endothermic. The thermodecomposition products were analyzed. The evolved gases were identified by GC?MS and 1 H and 13 C NMR spectra. The residues were analyzed by X-ray diffraction. Antitumor activity of rhodium cyclopropanecarboxylate was evaluated in vitro (cell cultures K562 and Ehrlich) and in vivo (Balb-c mice with ascite Ehrlich tumor), indicating an increased life span (87.5%) of the treated animals. (author)

  11. Rhodium-coated mirrors deposited by magnetron sputtering for fusion applications

    International Nuclear Information System (INIS)

    Marot, L.; Temmermann, G. de; Oelhafen, P.; Mathys, D.; Covarel, G.; Litnovsky, A.

    2007-01-01

    Metallic mirrors will be essential components of all optical spectroscopy and imaging systems for plasma diagnostics that will be used in ITER. Any change in the mirror performance, in particular its reflectivity, will influence the quality and reliability of detected signals. Due to its high reflectivity in the visible wavelength range and its low sputtering yield, rhodium may be a good candidate material for first mirrors in ITER. However, the very high price of the raw material calls for using it in the form of a film deposited onto metallic substrates. The development of a reliable technique for the preparation of high reflectivity rhodium films is therefore of the highest importance. Rhodium layers with thicknesses of up to 2 μm were produced on different relevant substrates (Mo, Stainless Steel, Cu) by magnetron sputtering. Produced films exhibit a low roughness, crystallite size of about 10 nm with a dense columnar structure. No impurities were detected on the surface after deposition. Scratch test results demonstrate that adhesion properties increase with the substrate hardness. The detailed optical characterizations of Rh coated mirrors as well as the results of erosion tests performed both under laboratory conditions and in TEXTOR will be presented in this paper. (orig.)

  12. Cell-Selective Biological Activity of Rhodium Metalloinsertors Correlates with Subcellular Localization

    Science.gov (United States)

    Komor, Alexis C.; Schneider, Curtis J.; Weidmann, Alyson G.; Barton, Jacqueline K.

    2013-01-01

    Deficiencies in the mismatch repair (MMR) pathway are associated with several types of cancers, as well as resistance to commonly used chemotherapeutics. Rhodium metalloinsertors have been found to bind DNA mismatches with high affinity and specificity in vitro, and also exhibit cell-selective cytotoxicity, targeting MMR-deficient cells over MMR-proficient cells. Ten distinct metalloinsertors with varying lipophilicities have been synthesized and their mismatch binding affinities and biological activities determined. Although DNA photocleavage experiments demonstrate that their binding affinities are quite similar, their cell-selective antiproliferative and cytotoxic activities vary significantly. Inductively coupled plasma mass spectrometry (ICP-MS) experiments have uncovered a relationship between the subcellular distribution of these metalloinsertors and their biological activities. Specifically, we find that all of our metalloinsertors localize in the nucleus at sufficient concentrations for binding to DNA mismatches. However, the metalloinsertors with high rhodium localization in the mitochondria show toxicity that is not selective for MMR-deficient cells, whereas metalloinsertors with less mitochondrial rhodium show activity that is highly selective for MMR-deficient versus proficient cells. This work supports the notion that specific targeting of the metalloinsertors to nuclear DNA gives rise to their cell-selective cytotoxic and antiproliferative activities. The selectivity in cellular targeting depends upon binding to mismatches in genomic DNA. PMID:23137296

  13. Intramolecular Hydroamination of Unbiased and Functionalized Primary Aminoalkenes Catalyzed by a Rhodium Aminophosphine Complex

    Science.gov (United States)

    Julian, Lisa D.; Hartwig, John F.

    2010-01-01

    We report a rhodium catalyst that exhibits high reactivity for the hydroamination of primary aminoalkenes that are unbiased toward cyclization and that possess functional groups that would not be tolerated in hydroaminations catalyzed by more electrophilic systems. This catalyst contains an unusual diaminophosphine ligand that binds to rhodium in a κ3-P,O,P mode. The reactions catalyzed by this complex typically proceed at mild temperatures (room temperature to 70 °C), occur with primary aminoalkenes lacking substituents on the alkyl chain that bias the system toward cyclization, occur with primary aminoalkenes containing chloride, ester, ether, enolizable ketone, nitrile, and unprotected alcohol functionality, and occur with primary aminoalkenes containing internal olefins. Mechanistic data imply that these reactions occur with a turnover-limiting step that is different from that of reactions catalyzed by late transition metal complexes of Pd, Pt, and Ir. This change in the turnover-limiting step and resulting high activity of the catalyst stem from favorable relative rates for protonolysis of the M-C bond to release the hydroamination product vs reversion of the aminoalkyl intermediate to regenerate the acyclic precursor. Probes for the origin of the reactivity of the rhodium complex of L1 imply that the aminophosphine groups lead to these favorable rates by effects beyond steric demands and simple electron donation to the metal center. PMID:20839807

  14. Column preconcentration and electrothermal atomic absorption spectrometric determination of rhodium in some food and standard samples.

    Science.gov (United States)

    Taher, Mohammad Ali; Pourmohammad, Fatemeh; Fazelirad, Hamid

    2015-12-01

    In the present work, an electrothermal atomic absorption spectrometric method has been developed for the determination of ultra-trace amounts of rhodium after adsorption of its 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol/tetraphenylborate ion associated complex at the surface of alumina. Several factors affecting the extraction efficiency such as the pH, type of eluent, sample and eluent flow rates, sorption capacity of alumina and sample volume were investigated and optimized. The relative standard deviation for eight measurements of 0.1 ng/mL of rhodium was ±6.3%. In this method, the detection limit was 0.003 ng/mL in the original solution. The sorption capacity of alumina and the linear range for Rh(III) were evaluated as 0.8 mg/g and 0.015-0.45 ng/mL in the original solution, respectively. The proposed method was successfully applied for the extraction and determination of rhodium content in some food and standard samples with high recovery values. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Preliminary investigations on the use of uranium silicide targets for fission Mo-99 production

    Energy Technology Data Exchange (ETDEWEB)

    Cols, H.; Cristini, P.; Marques, R.

    1997-08-01

    The National Atomic Energy Commission (CNEA) of Argentine Republic owns and operates an installation for production of molybdenum-99 from fission products since 1985, and, since 1991, covers the whole national demand of this nuclide, carrying out a program of weekly productions, achieving an average activity of 13 terabecquerel per week. At present they are finishing an enlargement of the production plant that will allow an increase in the volume of production to about one hundred of terabecquerel. Irradiation targets are uranium/aluminium alloy with 90% enriched uranium with aluminium cladding. In view of international trends held at present for replacing high enrichment uranium (HEU) for enrichment values lower than 20 % (LEU), since 1990 the authors are in contact with the RERTR program, beginning with tests to adapt their separation process to new irradiation target conditions. Uranium silicide (U{sub 3}Si{sub 2}) was chosen as the testing material, because it has an uranium mass per volume unit, so that it allows to reduce enrichment to a value of 20%. CNEA has the technology for manufacturing miniplates of uranium silicide for their purposes. In this way, equivalent amounts of Molybdenum-99 could be obtained with no substantial changes in target parameters and irradiation conditions established for the current process with Al/U alloy. This paper shows results achieved on the use of this new target.

  16. Microstructure of the irradiated U 3Si 2/Al silicide dispersion fuel

    Science.gov (United States)

    Gan, J.; Keiser, D. D.; Miller, B. D.; Jue, J.-F.; Robinson, A. B.; Madden, J. W.; Medvedev, P. G.; Wachs, D. M.

    2011-12-01

    The silicide dispersion fuel of U 3Si 2/Al is recognized as the best performance fuel for many nuclear research and test reactors with up to 4.8 gU/cm 3 fuel loading. An irradiated U 3Si 2/Al dispersion fuel ( 235U ˜ 75%) from the high-flux side of a fuel plate (U0R040) from the Reduced Enrichment for Research and Test Reactors (RERTR)-8 test was characterized using transmission electron microscopy (TEM). The fuel was irradiated in the Advanced Test Reactor (ATR) for 105 days. The average irradiation temperature and fission density of the U 3Si 2 fuel particles for the TEM sample are estimated to be approximately 110 °C and 5.4 × 10 27 f/m 3. The characterization was performed using a 200-kV TEM. The U/Si ratio for the fuel particle and (Si + Al)/U for the fuel-matrix-interaction layer are approximately 1.1 and 4-10, respectively. The estimated average diameter, number density and volume fraction for small bubbles (<1 μm) in the fuel particle are ˜94 nm, 1.05 × 10 20 m -3 and ˜11%, respectively. The results and their implication on the performance of the U 3Si 2/Al silicide dispersion fuel are discussed.

  17. Prospect of Uranium Silicide fuel element with hypostoichiometric (Si ≤3.7%)

    International Nuclear Information System (INIS)

    Suripto, A.; Sardjono; Martoyo

    1996-01-01

    An attempt to obtain high uranium-loading in silicide dispersion fuel element using the fabrication technology applicable nowadays can reach Uranium-loading slightly above 5 gU/cm 3 . It is difficult to achieve a higher uranium-loading than that because of fabricability constraints. To overcome those difficulties, the use of uranium silicide U 3 Si based is considered. The excess of U is obtained by synthesising U 3 Si 2 in Si-hypostoichiometric stage, without applying heat treatment to the ingot as it can generate undesired U 3 Si. The U U will react with the matrix to form U al x compound, that its pressure is tolerable. This experiment is to consider possibilities of employing the U 3 Si 2 as nuclear fuel element which have been performed by synthesising U 3 Si 2 -U with the composition of 3.7 % weigh and 3 % weigh U. The ingot was obtained and converted into powder form which then was fabricated into experimental plate nuclear fuel element. The interaction between free U and Al-matrix during heat-treatment is the rolling phase of the fuel element was observed. The study of the next phase will be conducted later

  18. CEMS Investigations of Fe-Silicide Phases Formed by the Method of Concentration Controlled Phase Selection

    Energy Technology Data Exchange (ETDEWEB)

    Moodley, M. K.; Bharuth-Ram, K. [University of Durban-Westville, Physics Department (South Africa); Waal, H. de; Pretorius, R. [University of Stellenbosch, Physics Department (South Africa)

    2002-03-15

    Conversion electron Moessbauer spectroscopy (CEMS) measurements have been made on Fe-silicide samples formed using the method of concentration controlled phase selection. To prepare the samples a 10 nm layer of Fe{sub 30}M{sub 70} (M=Cr, Ni) was evaporated onto Si(100) surfaces, followed by evaporation of a 60 nm Fe layer. Diffusion of the Fe into the Si substrate and the formation of different Fe-Si phases was achieved by subjecting the evaporated samples to a series of heating stages, which consisted of (a) a 10 min anneal at 800 deg. C plus etch of the residual surface layer, (b) a further 3 hr anneal at 800 deg. C, (c) a 60 mJ excimer laser anneal to an energy density of 0.8 J/cm{sup 2}, and (d) a final 3 hr anneal at 800 deg. C. CEMS measurements were used to track the Fe-silicide phases formed. The CEMS spectra consisted of doublets which, based on established hyperfine parameters, could be assigned to {alpha}- or {beta}-FeSi{sub 2} or cubic FeSi. The spectra showed that {beta}-FeSi{sub 2} had formed already at the first annealing stage. Excimer laser annealing resulted in the formation of a phase with hyperfine parameters consistent with those of {alpha}-FeSi{sub 2}. A further 3 hr anneal at 800 deg. C resulted in complete reversal to the semiconducting {beta}-FeSi{sub 2} phase.

  19. Mössbauer spectroscopy study of surfactant sputtering induced Fe silicide formation on a Si surface

    Energy Technology Data Exchange (ETDEWEB)

    Beckmann, C.; Zhang, K. [2nd Institute of Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany); Hofsäss, H., E-mail: hans.hofsaess@phys.uni-goettingen.de [2nd Institute of Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany); Brüsewitz, C.; Vetter, U. [2nd Institute of Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany); Bharuth-Ram, K. [Physics Department, Durban University of Technology, Durban 4001 (South Africa)

    2015-12-01

    Highlights: • We study the formation of self-organized nanoscale dot and ripple patterns on Si. • Patterns are created by keV noble gas ion irradiation and simultaneous {sup 57}Fe co-deposition. • Ion-induced phase separation and the formation of a-FeSi{sub 2} is identified as relevant process. - Abstract: The formation of Fe silicides in surface ripple patterns, generated by erosion of a Si surface with keV Ar and Xe ions and simultaneous co-deposition of Fe, was investigated with conversion electron Mössbauer spectroscopy, atomic force microscopy and Rutherford backscattering spectrometry. For the dot and ripple patterns studied, we find an average Fe concentration in the irradiated layer between 6 and 25 at.%. The Mössbauer spectra clearly show evidence of the formation of Fe disilicides with Fe content close to 33 at.%, but very little evidence of the formation of metallic Fe particles. The results support the process of ion-induced phase separation toward an amorphous Fe disilicide phase as pattern generation mechanism. The observed amorphous phase is in agreement with thermodynamic calculations of amorphous Fe silicides.

  20. Impact of Nickel silicide Rear Metallization on Series Resistance of Crystalline Silicon Solar Cells

    KAUST Repository

    Bahabry, Rabab R

    2018-01-11

    The Silicon-based solar cell is one of the most important enablers toward high efficiency and low-cost clean energy resource. Metallization of silicon-based solar cells typically utilizes screen printed silver-Aluminium (Ag-Al) which affects the optimal electrical performance. To date, metal silicide-based ohmic contacts are occasionally used as an alternative candidate only to the front contact grid lines in crystalline silicon (c-Si) based solar cells. In this paper, we investigate the electrical characteristics of nickel mono-silicide (NiSi)/Cu-Al ohmic contact on the rear side of c-Si solar cells. We observe a significant enhancement in the fill factor of around 6.5% for NiSi/Cu-Al rear contacts leading to increasing the efficiency by 1.2% compared to Ag-Al. This is attributed to the improvement of the parasitic resistance in which the series resistance decreased by 0.737 Ω.cm². Further, we complement experimental observation with a simulation of different contact resistance values, which manifests NiSi/Cu-Al rear contact as a promising low-cost metallization for c-Si solar cells with enhanced efficiency.

  1. Magnesium and Manganese Silicides For Efficient And Low Cost Thermo-Electric Power Generation

    Energy Technology Data Exchange (ETDEWEB)

    Trivedi, Sudhir B. [Brimrose Technology Corporation; Kutcher, Susan W. [Brimrose Technology Corporation; Rosemeier, Cory A. [Brimrose Technology Corporation; Mayers, David [Brimrose Technology Corporation; Singh, Jogender [Pennsylvania State University

    2013-12-02

    Thermoelectric Power Generation (TEPG) is the most efficient and commercially deployable power generation technology for harvesting wasted heat from such things as automobile exhausts, industrial furnaces, and incinerators, and converting it into usable electrical power. We investigated the materials magnesium silicide (Mg2Si) and manganese silicide (MnSi) for TEG. MgSi2 and MnSi are environmentally friendly, have constituent elements that are abundant in the earth's crust, non-toxic, lighter and cheaper. In Phase I, we successfully produced Mg2Si and MnSi material with good TE properties. We developed a novel technique to synthesize Mg2Si with good crystalline quality, which is normally very difficult due to high Mg vapor pressure and its corrosive nature. We produced n-type Mg2Si and p-type MnSi nanocomposite pellets using FAST. Measurements of resistivity and voltage under a temperature gradient indicated a Seebeck coefficient of roughly 120 V/K on average per leg, which is quite respectable. Results indicated however, that issues related to bonding resulted in high resistivity contacts. Determining a bonding process and bonding material that can provide ohmic contact from room temperature to the operating temperature is an essential part of successful device fabrication. Work continues in the development of a process for reproducibly obtaining low resistance electrical contacts.

  2. The reaction mechanism of the partial oxidation of methane to synthesis gas: a transient kinetic study over rhodium and a comparison with platinum

    NARCIS (Netherlands)

    Mallens, E.P.J.; Hoebink, J.H.B.J.; Marin, G.B.M.M.

    1997-01-01

    The partial oxidation of methane to synthesis gas over rhodium sponge has been investigated by admitting pulses of pure methane and pure oxygen as well as mixtures of methane and oxygen to rhodium sponge at temperatures from 873 to 1023 K. Moreover, pulses of oxygen followed by methane and vice

  3. Controlled Oxygen Chemisorption on an Alumina Supported Rhodium Catalyst. The Formation of a New Metal-Metal Oxide Interface Determined with EXAFS.

    NARCIS (Netherlands)

    Koningsberger, D.C.; Martens, J.H.A.; Prins, R.

    1989-01-01

    An alumina-supported rhodium catalyst has been studied with EXAFS. After reduction and evacuation, oxygen was admitted at 100 and 300 K. EXAFS spectra of the catalyst after oxygen admission at 100 K indicated the beginning of oxidation. At 300 K only a small part of the rhodium particles remained

  4. Influence of iron and beryllium additions on heat resistance of silicide coatings on TsMB-30 molybdenum alloy

    International Nuclear Information System (INIS)

    Zajtseva, A.L.; Fedorchuk, N.M.; Lazarev, Eh.M.; Korotkov, N.A.

    1985-01-01

    Alloying of titanium modified silicide coatings on TsMB-30 molybdenum alloy with iron or beryllium is stated to improve their protective properties. Coatings with low content of alloying elements have the best protective properties. Service life of coatings is determined by the formed oxide film and phase transformations taking place in the coating

  5. Aluminium alloyed iron-silicide/silicon solar cells: A simple approach for low cost environmental-friendly photovoltaic technology.

    Science.gov (United States)

    Kumar Dalapati, Goutam; Masudy-Panah, Saeid; Kumar, Avishek; Cheh Tan, Cheng; Ru Tan, Hui; Chi, Dongzhi

    2015-12-03

    This work demonstrates the fabrication of silicide/silicon based solar cell towards the development of low cost and environmental friendly photovoltaic technology. A heterostructure solar cells using metallic alpha phase (α-phase) aluminum alloyed iron silicide (FeSi(Al)) on n-type silicon is fabricated with an efficiency of 0.8%. The fabricated device has an open circuit voltage and fill-factor of 240 mV and 60%, respectively. Performance of the device was improved by about 7 fold to 5.1% through the interface engineering. The α-phase FeSi(Al)/silicon solar cell devices have promising photovoltaic characteristic with an open circuit voltage, short-circuit current and a fill factor (FF) of 425 mV, 18.5 mA/cm(2), and 64%, respectively. The significant improvement of α-phase FeSi(Al)/n-Si solar cells is due to the formation p(+-)n homojunction through the formation of re-grown crystalline silicon layer (~5-10 nm) at the silicide/silicon interface. Thickness of the regrown silicon layer is crucial for the silicide/silicon based photovoltaic devices. Performance of the α-FeSi(Al)/n-Si solar cells significantly depends on the thickness of α-FeSi(Al) layer and process temperature during the device fabrication. This study will open up new opportunities for the Si based photovoltaic technology using a simple, sustainable, and los cost method.

  6. Towards the improvement of the oxidation resistance of Nb-silicides in situ composites: A solid state diffusion approach

    International Nuclear Information System (INIS)

    Mathieu, S.; Knittel, S.; François, M.; Portebois, L.; Mathieu, S.; Vilasi, M.

    2014-01-01

    Highlights: •Local equilibrium is attained during oxidation at phase boundaries (steady state conditions). •A solid state diffusion model explains the oxidation mechanism of Nb-silicides composites. •The Nb ss fraction is not the only parameters governing the oxidation rate of Nb-silicides. •Aluminium increases the thermodynamic activity of Si in the Nb-silicides composites. •The results indicate the need to develop a Nb–Ti–Hf–Al–Cr–Si thermodynamic database. -- Abstract: The present study focuses on the oxidation mechanism of Nb-silicide composites and on the effect of the composition on the oxidation rate at 1100 °C. A theoretical approach is proposed based on experimental results and used to optimise the oxidation resistance. The growth model based on multiphase diffusion was experimentally tested and confirmed by manufacturing seven composites with different compositions. It was also found that the effect of the composition has to be evaluated at 1100 °C within a short time duration (50 h), where the oxide scale and the internal oxidation zone both grow according to parabolic kinetics

  7. Determination of rhodium in metallic alloy and water samples using cloud point extraction coupled with spectrophotometric technique

    Science.gov (United States)

    Kassem, Mohammed A.; Amin, Alaa S.

    2015-02-01

    A new method to estimate rhodium in different samples at trace levels had been developed. Rhodium was complexed with 5-(4‧-nitro-2‧,6‧-dichlorophenylazo)-6-hydroxypyrimidine-2,4-dione (NDPHPD) as a complexing agent in an aqueous medium and concentrated by using Triton X-114 as a surfactant. The investigated rhodium complex was preconcentrated with cloud point extraction process using the nonionic surfactant Triton X-114 to extract rhodium complex from aqueous solutions at pH 4.75. After the phase separation at 50 °C, the surfactant-rich phase was heated again at 100 °C to remove water after decantation and the remaining phase was dissolved using 0.5 mL of acetonitrile. Under optimum conditions, the calibration curve was linear for the concentration range of 0.5-75 ng mL-1 and the detection limit was 0.15 ng mL-1 of the original solution. The enhancement factor of 500 was achieved for 250 mL samples containing the analyte and relative standard deviations were ⩽1.50%. The method was found to be highly selective, fairly sensitive, simple, rapid and economical and safely applied for rhodium determination in different complex materials such as synthetic mixture of alloys and environmental water samples.

  8. Adducts of nitrogenous ligands with rhodium(II) tetracarboxylates and tetraformamidinate: NMR spectroscopy and density functional theory calculations.

    Science.gov (United States)

    Cmoch, Piotr; Głaszczka, Rafał; Jaźwiński, Jarosław; Kamieński, Bohdan; Senkara, Elżbieta

    2014-03-01

    Complexation of tetrakis(μ2-N,N'-diphenylformamidinato-N,N')-di-rhodium(II) with ligands containing nitrile, isonitrile, amine, hydroxyl, sulfhydryl, isocyanate, and isothiocyanate functional groups has been studied in liquid and solid phases using (1)H, (13)C and (15)N NMR, (13)C and (15)N cross polarisation-magic angle spinning NMR, and absorption spectroscopy in the visible range. The complexation was monitored using various NMR physicochemical parameters, such as chemical shifts, longitudinal relaxation times T1 , and NOE enhancements. Rhodium(II) tetraformamidinate selectively bonded only unbranched amine (propan-1-amine), pentanenitrile, and (1-isocyanoethyl)benzene. No complexation occurred in the case of ligands having hydroxyl, sulfhydryl, isocyanate, and isothiocyanate functional groups, and more expanded amine molecules such as butan-2-amine and 1-azabicyclo[2.2.2]octane. Such features were opposite to those observed in rhodium(II) tetracarboxylates, forming adducts with all kind of ligands. Special attention was focused on the analysis of Δδ parameters, defined as a chemical shift difference between signal in adduct and corresponding signal in free ligand. In the case of (1)H NMR, Δδ values were either negative in adducts of rhodium(II) tetraformamidinate or positive in adducts of rhodium(II) tetracarboxylates. Experimental findings were supported by density functional theory molecular modelling and gauge independent atomic orbitals chemical shift calculations. The calculation of chemical shifts combined with scaling procedure allowed to reproduce qualitatively Δδ parameters. Copyright © 2013 John Wiley & Sons, Ltd.

  9. Influence of Al addition on phase transformation and thermal stability of nickel silicides on Si(0 0 1)

    International Nuclear Information System (INIS)

    Huang, Shih-Hsien; Twan, Sheng-Chen; Cheng, Shao-Liang; Lee, Tu; Hu, Jung-Chih; Chen, Lien-Tai; Lee, Sheng-Wei

    2014-01-01

    Highlights: ► The presence of Al slows down the Ni 2 Si–NiSi phase transformation but significantly promotes the NiSi 2−x Al x formation. ► The behavior of phase transformation strongly depends on the Al concentration of the initial Ni 1−x Al x alloys. ► The Ni 0.91 Al 0.09 /Si system exhibits remarkably improved thermal stability, even after high temperature annealing for 1000 s. ► The relationship between microstructures, electrical property, and thermal stability of Ni(Al) silicides is discussed. -- Abstract: The influence of Al addition on the phase transformation and thermal stability of Ni silicides on (0 0 1)Si has been systematically investigated. The presence of Al atoms is found to slow down the Ni 2 Si–NiSi phase transformation but significantly promote the NiSi 2−x Al x formation during annealing. The behavior of phase transformation strongly depends on the Al concentration of the initial Ni 1−x Al x alloys. Compared to the Ni 0.95 Pt 0.05 /Si and Ni 0.95 Al 0.05 /Si system, the Ni 0.91 Al 0.09 /Si sample exhibits remarkably enhanced thermal stability, even after high temperature annealing for 1000 s. The relationship between microstructures, electrical property, and thermal stability of Ni silicides is discussed to elucidate the role of Al during the Ni 1−x Al x alloy silicidation. This work demonstrated that thermally stable Ni 1−x Al x alloy silicides would be a promising candidate as source/drain (S/D) contacts in advanced complementary metal–oxide-semiconductor (CMOS) devices

  10. A multi-target caffeine derived rhodium(i) N-heterocyclic carbene complex: evaluation of the mechanism of action.

    Science.gov (United States)

    Zhang, Jing-Jing; Muenzner, Julienne K; Abu El Maaty, Mohamed A; Karge, Bianka; Schobert, Rainer; Wölfl, Stefan; Ott, Ingo

    2016-08-16

    A rhodium(i) and a ruthenium(ii) complex with a caffeine derived N-heterocyclic carbene (NHC) ligand were biologically investigated as organometallic conjugates consisting of a metal center and a naturally occurring moiety. While the ruthenium(ii) complex was largely inactive, the rhodium(i) NHC complex displayed selective cytotoxicity and significant anti-metastatic and in vivo anti-vascular activities and acted as both a mammalian and an E. coli thioredoxin reductase inhibitor. In HCT-116 cells it increased the reactive oxygen species level, leading to DNA damage, and it induced cell cycle arrest, decreased the mitochondrial membrane potential, and triggered apoptosis. This rhodium(i) NHC derivative thus represents a multi-target compound with promising anti-cancer potential.

  11. Core conversion study from silicide to molybdenum fuel in the Indonesian 30 MW multipurpose reactor G.A. Siwabessy (RSG-GAS)

    International Nuclear Information System (INIS)

    Sembiring, T.M.; Kuntoro, I.

    2005-01-01

    This paper describes the core conversion from silicide to molybdenum core through a series of silicide (2.96 gU cm -3 ) - molybdenum (3.55 gUcm -3 ) mixed transition cores for the Indonesian 30 MW-Multipurpose G.A. Siwabessy (RSGGAS) reactor. The core calculations are carried out using the two-dimensional multigroup neutron diffusion method code of Batan-EQUIL-2D. The calculated results showed that the proposed silicide-molybdenum mixed transition cores, using the same refueling/reshuffling scheme, meet the safety criteria and it can be used in safely converting from an all-silicide core to an all-molybdenum core. (author)

  12. Understanding and Improving High-Temperature Structural Properties of Metal-Silicide Intermetallics

    Energy Technology Data Exchange (ETDEWEB)

    Bruce S. Kang

    2005-10-10

    The objective of this project was to understand and improve high-temperature structural properties of metal-silicide intermetallic alloys. Through research collaboration between the research team at West Virginia University (WVU) and Dr. J.H. Schneibel at Oak Ridge National Laboratory (ORNL), molybdenum silicide alloys were developed at ORNL and evaluated at WVU through atomistic modeling analyses, thermo-mechanical tests, and metallurgical studies. In this study, molybdenum-based alloys were ductilized by dispersing MgAl2O4 or MgO spinel particles. The addition of spinel particles is hypothesized to getter impurities such as oxygen and nitrogen from the alloy matrix with the result of ductility improvement. The introduction of fine dispersions has also been postulated to improve ductility by acting as a dislocation source or reducing dislocation pile-ups at grain boundaries. The spinel particles, on the other hand, can also act as local notches or crack initiation sites, which is detrimental to the alloy mechanical properties. Optimization of material processing condition is important to develop the desirable molybdenum alloys with sufficient room-temperature ductility. Atomistic analyses were conducted to further understand the mechanism of ductility improvement of the molybdenum alloys and the results showed that trace amount of residual oxygen may be responsible for the brittle behavior of the as-cast Mo alloys. For the alloys studied, uniaxial tensile tests were conducted at different loading rates, and at room and elevated temperatures. Thermal cycling effect on the mechanical properties was also studied. Tensile tests for specimens subjected to either ten or twenty thermal cycles were conducted. For each test, a follow-up detailed fractography and microstructural analysis were carried out. The test results were correlated to the size, density, distribution of the spinel particles and processing time. Thermal expansion tests were carried out using thermo

  13. Mechanism of intermolecular hydroacylation of vinylsilanes catalyzed by a rhodium(I) olefin complex: a DFT study.

    Science.gov (United States)

    Meng, Qingxi; Shen, Wei; Li, Ming

    2012-03-01

    Density functional theory (DFT) was used to investigate the Rh(I)-catalyzed intermolecular hydroacylation of vinylsilane with benzaldehyde. All intermediates and transition states were optimized completely at the B3LYP/6-31G(d,p) level (LANL2DZ(f) for Rh). Calculations indicated that Rh(I)-catalyzed intermolecular hydroacylation is exergonic, and the total free energy released is -110 kJ mol(-1). Rh(I)-catalyzed intermolecular hydroacylation mainly involves the active catalyst CA2, rhodium-alkene-benzaldehyde complex M1, rhodium-alkene-hydrogen-acyl complex M2, rhodium-alkyl-acyl complex M3, rhodium-alkyl-carbonyl-phenyl complex M4, rhodium-acyl-phenyl complex M5, and rhodium-ketone complex M6. The reaction pathway CA2 + R2 → M1b → T1b → M2b → T2b1 → M3b1 → T4b → M4b → T5b → M5b → T6b → M6b → P2 is the most favorable among all reaction channels of Rh(I)-catalyzed intermolecular hydroacylation. The reductive elimination reaction is the rate-determining step for this pathway, and the dominant product predicted theoretically is the linear ketone, which is consistent with Brookhart's experiments. Solvation has a significant effect, and it greatly decreases the free energies of all species. The use of the ligand Cp' (Cp' = C(5)Me(4)CF(3)) decreased the free energies in general, and in this case the rate-determining step was again the reductive elimination reaction.

  14. Purification in the interaction between yttria mould and Nb-silicide-based alloy during directional solidification: A novel effect of yttrium

    International Nuclear Information System (INIS)

    Ma, Limin; Tang, Xiaoxia; Wang, Bin; Jia, Lina; Yuan, Sainan; Zhang, Hu

    2012-01-01

    Nb-silicide-based alloys were directionally solidified in yttria moulds. As a result of thermal dissociation of yttria, the alloys were slightly contaminated with oxygen, which caused a competitive oxidation between yttrium and hafnium. The addition of 0.15 at.% yttrium reduced the oxygen increment by 42%, because the buoyant inclusions concentrated around the top surface. The yttrium addition caused a significant purification of the interaction between the yttria mould and the Nb-silicide-based alloys during the directional solidification.

  15. Moessbauer spectroscopic characterisation of catalysts obtained by interaction between tetra-n-butyl-tin and silica or silica supported rhodium

    International Nuclear Information System (INIS)

    Millet, J.M.M.; Toyir, J.; Didillon, B.; Candy, J.P.; Nedez, C.; Basset, J.M.

    1997-01-01

    Moessbauer spectroscopy at 78 K was used to study the interaction between tetra-n-butyl-tin and the surfaces of silica or silica supported rhodium. At room temperature, the tetra-n-butyl-tin was physically adsorbed on the surfaces. After reaction under hydrogen at 373 K, the formation of grafted organometallic fragments on the Rh surface was confirmed whereas with pure silica, ≡SiO-Sn(n-C 4 H 9 ) 3 moieties were observed. After treatment at 523 K, the rhodium grafted organometallic species was completely decomposed and there was formation of a defined bimetallic RhSn compound

  16. Electrooxidative Rhodium-Catalyzed C-H/C-H Activation: Electricity as Oxidant for Cross-Dehydrogenative Alkenylation.

    Science.gov (United States)

    Qiu, Youai; Kong, Wei-Jun; Struwe, Julia; Sauermann, Nicolas; Rogge, Torben; Scheremetjew, Alexej; Ackermann, Lutz

    2018-04-06

    Rhodium(III) catalysis has enabled a plethora of oxidative C-H functionalizations, which predominantly employ stoichiometric amounts of toxic and/or expensive metal oxidants. In contrast, we describe the first electrochemical C-H activation by rhodium catalysis that avoids hazardous chemical oxidants. Thus, environmentally-benign twofold C-H/C-H functionalizations were accomplished with weakly-coordinating benzoic acids and benzamides, employing electricity as the terminal oxidant with H2 as the sole byproduct. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. The Leakage Current Improvement of a Ni-Silicided SiGe/Si Junction Using a Si Cap Layer and the PAI Technique

    International Nuclear Information System (INIS)

    Chang Jian-Guang; Wu Chun-Bo; Ji Xiao-Li; Ma Hao-Wen; Yan Feng; Shi Yi; Zhang Rong

    2012-01-01

    We investigate the leakage current of ultra-shallow Ni-silicided SiGe/Si junctions for 45 nm CMOS technology using a Si cap layer and the pre-amorphization implantation (PAI) process. It is found that with the conventional Ni silicide method, the leakage current of a p + (SiGe)—n(Si) junction is large and attributed to band-to-band tunneling and the generation-recombination process. The two leakage contributors can be suppressed quite effectively when a Si cap layer is added in the Ni silicide method. The leakage reduction is about one order of magnitude and could be associated with the suppression of the agglomeration of the Ni germano-silicide film. In addition, the PAI process after the application of a Si cap layer has little effect on improving the junction leakage but reduces the sheet resistance of the silicide film. As a result, the novel Ni silicide method using a Si cap combined with PAI is a promising choice for SiGe junctions in advanced technology. (cross-disciplinary physics and related areas of science and technology)

  18. Interaction of copper metallization with rare-earth metals and silicides

    International Nuclear Information System (INIS)

    Molnar, G. L.; Peto, G.; Zsoldos, E.; Horvath, Z. E.

    2001-01-01

    Solid-phase reactions of copper films with underlying gadolinium, erbium, and erbium - silicide layers on Si(100) substrates were investigated. For the phase analysis, x-ray diffraction and cross-sectional transmission electron microscopy were used. In the case of Cu/Gd/Si(100), an orthorhombic GdSi 2 formed, and, at higher temperatures, copper aggregated into islands. Annealed Cu/Er/Si(100) samples resulted in a hexagonal Er 5 Si 3 phase. In the Cu/ErSi 2-x /Si system, the copper catalyzes the transformation of the highly oriented hexagonal ErSi 2-x phase into hexagonal Er 5 Si 3 . Diverse phase developments of the samples with Gd and Er are based on reactivity differences of the two rare-earth metals. [copyright] 2001 American Institute of Physics

  19. A study of strain in thin epitaxial films of yttrium silicide on Si(111)

    Science.gov (United States)

    Siegal, Michelle F.; Martínez-Miranda, L. J.; Santiago-Avilés, J. J.; Graham, W. R.; Siegal, M. P.

    1994-02-01

    We present the results of an x-ray diffraction analysis of epitaxial yttrium silicide films grown on Si(111), with thicknesses ranging from 14 to 100 Å. The macroscopic strain along the out-of-plane direction for films containing pits or pinholes follows the trend observed previously in films of thicknesses up to 510 Å. The out-of-plane lattice parameter decreases linearly with film thickness. We show preliminary evidence that pinhole-free films do not follow the above trend, and that strain in these films has the opposite sign than in films with pinholes. Finally, our results also indicate that the mode of growth, coupled to the interfacial thermal properties of the films, affects the observed value for the strain in the films.

  20. A study of strain in thin epitaxial films of yttrium silicide on Si(111)

    International Nuclear Information System (INIS)

    Siegal, M.F.; Martinez-Miranda, L.J.; Santiago-Aviles, J.J.; Graham, W.R.; Siegal, M.P.

    1994-01-01

    We present the results of an x-ray diffraction analysis of epitaxial yttrium silicide films grown on Si(111), with thicknesses ranging from 14 to 100 A. The macroscopic strain along the out-of-plane direction for films containing pits or pinholes follows the trend observed previously in films of thicknesses up to 510 A. The out-of-plane lattice parameter decreases linearly with film thickness. We show preliminary evidence that pinhole-free films do not follow the above trend, and that strain in these films has the opposite sign than in films with pinholes. Finally, our results also indicate that the mode of growth, coupled to the interfacial thermal properties of the films, affects the observed value for the strain in the films

  1. Safety analysis of RSG-GAS Silicide core using one line cooling system

    International Nuclear Information System (INIS)

    Endiah-Puji-Hastuti

    2003-01-01

    In the frame of minimizing the operation-cost, operation mode using one line cooling system is being evaluated. Maximum reactor has been determined and to continuing this program, steady state and transient analysis were done. The analysis was done by means of a core thermal hydraulic code, COOLOD-N, and PARET. The codes solves core thermal hydraulic equation at steady state conditions and transient, respectively. By using silicide core data and coast down flow rate as the input, thermal hydraulics parameters such as fuel cladding and fuel meat temperatures as well as safety margin against flow instability were calculated. Imposing the safety criteria to the results of steady state and transient analysis, maximum permissible power for this operation was obtained as much as 17.1 MW

  2. The fabrication of metal silicide nanodot arrays using localized ion implantation

    International Nuclear Information System (INIS)

    Han, Jin; Kim, Tae-Gon; Min, Byung-Kwon; Lee, Sang Jo

    2010-01-01

    We propose a process for fabricating nanodot arrays with a pitch size of less than 25 nm. The process consists of localized ion implantation in a metal thin film on a Si wafer using a focused ion beam (FIB), followed by chemical etching. This process utilizes the etching resistivity changes of the ion beam irradiated region that result from metal silicide formation by ion implantation. To control the nanodot diameter, a threshold ion dose model is proposed using the Gaussian distribution of the ion beam intensities. The process is verified by fabricating nanodots with various diameters. The mechanism of etching resistivity is investigated via x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES).

  3. Study of surface segregation of Si on palladium silicide using Auger electron spectroscopy

    International Nuclear Information System (INIS)

    Abhaya, S; Amarendra, G; Gopalan, Padma; Reddy, G L N; Saroja, S

    2004-01-01

    The transformation of Pd/Si to Pd 2 Si/Si is studied using Auger electron spectroscopy over a wide temperature range of 370-1020 K. The Pd film gets totally converted to Pd 2 Si upon annealing at 520 K, and beyond 570 K, Si starts segregating on the surface of silicide. It is found that the presence of surface oxygen influences the segregation of Si. The time evolution study of Si segregation reveals that segregation kinetics is very fast and the segregated Si concentration increases as the temperature is increased. Scanning electron microscopy measurements show that Pd 2 Si is formed in the form of islands, which grow as the annealing temperature is increased

  4. Hydrogen generation systems utilizing sodium silicide and sodium silica gel materials

    Science.gov (United States)

    Wallace, Andrew P.; Melack, John M.; Lefenfeld, Michael

    2015-07-14

    Systems, devices, and methods combine reactant materials and aqueous solutions to generate hydrogen. The reactant materials can sodium silicide or sodium silica gel. The hydrogen generation devices are used in fuels cells and other industrial applications. One system combines cooling, pumping, water storage, and other devices to sense and control reactions between reactant materials and aqueous solutions to generate hydrogen. Multiple inlets of varied placement geometries deliver aqueous solution to the reaction. The reactant materials and aqueous solution are churned to control the state of the reaction. The aqueous solution can be recycled and returned to the reaction. One system operates over a range of temperatures and pressures and includes a hydrogen separator, a heat removal mechanism, and state of reaction control devices. The systems, devices, and methods of generating hydrogen provide thermally stable solids, near-instant reaction with the aqueous solutions, and a non-toxic liquid by-product.

  5. Contributions to the preparation of 241americium metal and a few 241americium silicides

    International Nuclear Information System (INIS)

    Wittmann, F.D.

    1980-01-01

    In order to take a closer look at the americium-silicon system, three further silicides of americium: Am 5 Si 3 , Am 2 Si 3 and AmSi 2 were prepared in addition to the already known americium monosilicide and starting from the knowledge gained from the latters preparation. Radiographic investigations were carried out into the temperature region of 900 0 C. They showed no change of structure in the three compounds. It was possible to prepare residue-free americium metal by reducing AmF 3 with Si, whereby the SiF 4 formed can be easily separated off as volatile compound, and the Am metal is brought into a very pure form by sublimation suitable for spectrochemical investigations. Attempts to prepare binary germanides and gallides of 241 americium were unsuccessful. (RB) [de

  6. First-principles investigations of the physical properties of binary uranium silicide alloys

    International Nuclear Information System (INIS)

    Yang, Jin; Long, Jianping; Yang, Lijun; Li, Dongmei

    2013-01-01

    Graphical abstract: Total density of states for USi 2 . Display Omitted -- Abstract: The structural, elastic properties and the Debye temperature of binary Uranium Silicide (U-Si) alloys are investigated by using the first-principles plane-wave pseudopotential density function theory within the generalized gradient approximation (GGA). The ground states properties are found to agree with the available experimental data. The mechanical properties like shear modulus, Young’s modulus, Poisson’s ratio σ and ratio B/G are also calculated. Finally, The averaged sound velocity (v m ), the longitudinal sound velocity (v l ), transverse sound velocity (v t ) and the Debye temperature (θ D ) are obtained. However, the theoretical values are slightly different from few existed experiment data because the latter was obtained at room temperature while the former one at 0 K

  7. Hydrogen generation systems and methods utilizing sodium silicide and sodium silica gel materials

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, Andrew P.; Melack, John M.; Lefenfeld, Michael

    2017-12-19

    Systems, devices, and methods combine thermally stable reactant materials and aqueous solutions to generate hydrogen and a non-toxic liquid by-product. The reactant materials can sodium silicide or sodium silica gel. The hydrogen generation devices are used in fuels cells and other industrial applications. One system combines cooling, pumping, water storage, and other devices to sense and control reactions between reactant materials and aqueous solutions to generate hydrogen. Springs and other pressurization mechanisms pressurize and deliver an aqueous solution to the reaction. A check valve and other pressure regulation mechanisms regulate the pressure of the aqueous solution delivered to the reactant fuel material in the reactor based upon characteristics of the pressurization mechanisms and can regulate the pressure of the delivered aqueous solution as a steady decay associated with the pressurization force. The pressure regulation mechanism can also prevent hydrogen gas from deflecting the pressure regulation mechanism.

  8. X-ray absorption fine structure (XAFS) studies of cobalt silicide thin films

    International Nuclear Information System (INIS)

    Naftel, S.J.; Coulthard, I.; Hu, Y.; Sham, T.K.; Zinke-Allmang, M.

    1998-01-01

    Cobalt silicide thin films, prepared on Si(100) wafers, have been studied by X-ray absorption near edge structures (XANES) at the Si K-, L 2,3 - and Co K-edges utilizing both total electron (TEY) and fluorescence yield (FLY) detection as well as extended X-ray absorption fine structure (EXAFS) at the Co K-edge. Samples made using DC sputter deposition on clean Si surfaces and MBE were studied along with a bulk CoSi 2 sample. XANES and EXAFS provide information about the electronic structure and morphology of the films. It was found that the films studied have essentially the same structure as bulk CoSi 2 . Both the spectroscopy and materials characterization aspects of XAFS (X-ray absorption fine structures) are discussed

  9. Burn-up analysis of uranium silicide fuels 20% 235U, in the LFR facility

    International Nuclear Information System (INIS)

    Amor, Ricardo A.; Bouza, Edgardo; Cabrejas, Julian L.; Devida, Claudio A.; Gil, Daniel A.; Stankevicius, Alejandro; Gautier, Eduardo; Garavaglia, Ricardo N.; Lobo, Alfredo

    2003-01-01

    The LFR Facility is a laboratory designed and constructed with a Hot-Cells line, a Globe-Box and a Fume-Hood, all of them suited to work with radioactive materials such as samples of irradiated silicide MTR fuel elements. A series of dissolutions of this material was performed. From the resulting solutions, two fractions were separated by HPLC. One contained U + Pu, and other the fission product Nd. The concentrations of these elements were obtained by isotopic dilution and mass spectrometry (IDMS). It is concluded that this technique is very powerful and accurate when properly applied, and makes the validation of burn-up calculation codes possible. It is worth remarking the Lfr capacity to carry on different Research and Development (R + D) tasks in the Nuclear Fuel Cycle field. (author)

  10. Intermetallic nickel silicide nanocatalyst-A non-noble metal-based general hydrogenation catalyst.

    Science.gov (United States)

    Ryabchuk, Pavel; Agostini, Giovanni; Pohl, Marga-Martina; Lund, Henrik; Agapova, Anastasiya; Junge, Henrik; Junge, Kathrin; Beller, Matthias

    2018-06-01

    Hydrogenation reactions are essential processes in the chemical industry, giving access to a variety of valuable compounds including fine chemicals, agrochemicals, and pharmachemicals. On an industrial scale, hydrogenations are typically performed with precious metal catalysts or with base metal catalysts, such as Raney nickel, which requires special handling due to its pyrophoric nature. We report a stable and highly active intermetallic nickel silicide catalyst that can be used for hydrogenations of a wide range of unsaturated compounds. The catalyst is prepared via a straightforward procedure using SiO 2 as the silicon atom source. The process involves thermal reduction of Si-O bonds in the presence of Ni nanoparticles at temperatures below 1000°C. The presence of silicon as a secondary component in the nickel metal lattice plays the key role in its properties and is of crucial importance for improved catalytic activity. This novel catalyst allows for efficient reduction of nitroarenes, carbonyls, nitriles, N-containing heterocycles, and unsaturated carbon-carbon bonds. Moreover, the reported catalyst can be used for oxidation reactions in the presence of molecular oxygen and is capable of promoting acceptorless dehydrogenation of unsaturated N-containing heterocycles, opening avenues for H 2 storage in organic compounds. The generality of the nickel silicide catalyst is demonstrated in the hydrogenation of over a hundred of structurally diverse unsaturated compounds. The wide application scope and high catalytic activity of this novel catalyst make it a nice alternative to known general hydrogenation catalysts, such as Raney nickel and noble metal-based catalysts.

  11. The ability of silicide coating to delay the catastrophic oxidation of vanadium under severe conditions

    Energy Technology Data Exchange (ETDEWEB)

    Chaia, N., E-mail: nabil.chaia@univ-lorraine.fr [Université de Lorraine, Institut Jean Lamour – UMR7198, Boulevard des Aiguillettes, BP70239, 54506 Vandoeuvre-lès-Nancy Cedex (France); Mathieu, S., E-mail: stephane.mathieu@univ-lorraine.fr [Université de Lorraine, Institut Jean Lamour – UMR7198, Boulevard des Aiguillettes, BP70239, 54506 Vandoeuvre-lès-Nancy Cedex (France); Rouillard, F., E-mail: fabien.rouillard@cea.fr [CEA, DEN, DPC, SCCME, Laboratoire d’Etude de la Corrosion Non Aqueuse, F-91191 Gif-sur-Yvette (France); Vilasi, M., E-mail: michel.vilasi@univ-lorraine.fr [Université de Lorraine, Institut Jean Lamour – UMR7198, Boulevard des Aiguillettes, BP70239, 54506 Vandoeuvre-lès-Nancy Cedex (France)

    2015-02-15

    Highlights: • Oxidation protection is due to the formation of a pure silica layer. • V–4Cr–4Ti with V{sub x}Si{sub y} silicide coating withstands 400 1-h cycles (1100 °C-T{sub amb}) in air. • Three-point flexure testing at 950 °C and 75 MPa does not induce coating breakdown. • No delamination between coating and substrate is observed in any test. - Abstract: V–4Cr–4Ti vanadium alloy is a potential cladding material for sodium-cooled fast-neutron reactors (SFRs). However, its affinity for oxygen and the subsequent embrittlement that oxygen induces causes a need for an oxygen diffusion barrier, which can be obtained by manufacturing a multi-layered silicide coating. The present work aims to evaluate the effects of thermal cycling (using a cyclic oxidation device) and tensile and compressive stresses (using the three-point flexure test) on the coated alloy system. Tests were performed in air up to 1100 °C, which is 200 °C higher than the accidental temperature for SFR applications. The results showed that the VSi{sub 2} coating was able to protect the vanadium substrate from oxidation for more than 400 1-h cycles between 1100 °C and room temperature. The severe bending applied to the coated alloy at 950 °C using a load of 75 MPa did not lead to specimen breakage. It can be suggested that the VSi{sub 2} coating has mechanical properties compatible with the V–4Cr–4Ti alloy for SFR applications.

  12. Permeation of platinum and rhodium nanoparticles through intact and damaged human skin

    International Nuclear Information System (INIS)

    Mauro, Marcella; Crosera, Matteo; Bianco, Carlotta; Adami, Gianpiero; Montini, Tiziano; Fornasiero, Paolo; Jaganjac, Morana; Bovenzi, Massimo; Filon, Francesca Larese

    2015-01-01

    The aim of the study was to evaluate percutaneous penetration of platinum and rhodium nanoparticles (PtNPs: 5.8 ± 0.9 nm, RhNPs: 5.3 ± 1.9 nm) through human skin. Salts compounds of these metals are sensitizers and some also carcinogenic agents. In vitro permeation experiments were performed using Franz diffusion cells with intact and damaged skin. PtNPs and RhNPs, stabilized with polyvinylpyrrolidone, were synthesized by reduction of Na 2 PtC l6 and RhCl 3 ·3H 2 O respectively. Suspensions with a concentration of 2.0 g/L of PtNPs and RhNPs were dispersed separately in synthetic sweat at pH 4.5 and applied as donor phases to the outer surface of the skin for 24 h. Measurements of the content of the metals in the receiving solution and in the skin were performed subsequently. Rhodium skin permeation was demonstrated through damaged skin, with a permeation flux of 0.04 ± 0.04 μg cm −2  h −1 and a lag time of 7.9 ± 1.1 h, while no traces of platinum were found in receiving solutions. Platinum and rhodium skin-analysis showed significantly higher concentrations of the metals in damaged skin. Rh and Pt applied as NPs can penetrate the skin barrier and Rh can be found in receiving solutions. These experiments pointed out the need for skin contamination prevention, since even a minor injury to the skin barrier can significantly increase penetration

  13. Thermodynamic assessment of the rhodium-ruthenium-oxygen (Rh-Ru-O) system

    Science.gov (United States)

    Gossé, S.; Bordier, S.; Guéneau, C.; Brackx, E.; Domenger, R.; Rogez, J.

    2018-03-01

    Ruthenium (Ru) and rhodium (Rh) are abundant platinum-group metals formed during burn-up of nuclear fuels. Under normal operating conditions, Rh and Ru accumulate and predominantly form metallic precipitates with other fission products like Mo, Pd and Tc. In the framework of vitrification of high-level nuclear waste, these fission products are poorly soluble in molten glasses. They precipitate as metallic particles and oxide phases. Moreover, these Ru and Rh rich phases strongly depend on temperature and the oxygen fugacity of the glass melt. In case of severe accidental conditions with air ingress, oxidation of the Ru and Rh is possible. At low temperatures (T 1422 K for rhodium sesquioxide and T > 1815 K for ruthenium dioxide), they may decompose into (Rh)-FCC or (Ru)-HCP metallic phases and radiotoxic volatile gaseous species. A thermodynamic assessment of the Rh-Ru-O system will enable the prediction of: (1) the metallic and oxide phases that form during the vitrification of high-level nuclear wastes and (2) the release of volatile gaseous species during a severe accident. The Calphad method developed herein employs a thermodynamic approach in the investigation of the thermochemistry of rhodium and ruthenium at high temperatures. Current literature on the thermodynamic properties and phase diagram data enables preliminary thermodynamic assessments of the Rh-O and Ru-O systems. Additionally, select compositions in the ternary Rh-Ru-O system underwent experimental tests to complement data found in literature and to establish the phase equilibria in the ternary system.

  14. A rhodium(III)-based inhibitor of autotaxin with antiproliferative activity.

    Science.gov (United States)

    Kang, Tian-Shu; Wang, Wanhe; Zhong, Hai-Jing; Liang, Jia-Xin; Ko, Chung-Nga; Lu, Jin-Jian; Chen, Xiu-Ping; Ma, Dik-Lung; Leung, Chung-Hang

    2017-02-01

    Cancer of the skin is by far the most common of all cancers. Melanoma accounts for only about 1% of skin cancers but causes a large majority of skin cancer deaths. Autotaxin (ATX), also known as ectonucleotide pyrophosphatase/phosphodiesterase 2 (ENPP2), regulates physiological and pathological functions of lysophosphatidic acid (LPA), and is thus an important therapeutic target. We synthesized ten metal-based complexes and a novel cyclometalated rhodium(III) complex 1 was identified as an ATX enzymatic inhibitor using multiple methods, including ATX enzymatic assay, thermal shift assay, western immunoblotting and so on. Protein thermal shift assays showed that 1 increased the melting temperature (T m ) of ATX by 3.5°C. 1 also reduced ATX-LPA mediated downstream survival signal pathway proteins such as ERK and AKT, and inhibited the activation of the transcription factor nuclear factor κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3). 1 also exhibited strong anti-proliferative activity against A2058 melanoma cells (IC 50 =0.58μM). Structure-activity relationship indicated that both the rhodium(III) center and the auxiliary ligands of complex 1 are important for bioactivity. 1 represents a promising scaffold for the development of small-molecule ATX inhibitors for anti-tumor applications. To our knowledge, complex 1 is the first metal-based ATX inhibitor reported to date. Rhodium complexes will have the increased attention in therapeutic and bioanalytical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Permeation of platinum and rhodium nanoparticles through intact and damaged human skin

    Energy Technology Data Exchange (ETDEWEB)

    Mauro, Marcella [University of Trieste, Clinical Unit of Occupational Medicine, Department of Medical Sciences (Italy); Crosera, Matteo; Bianco, Carlotta; Adami, Gianpiero; Montini, Tiziano; Fornasiero, Paolo [University of Trieste, Department of Chemical and Pharmaceutical Sciences (Italy); Jaganjac, Morana [Rudjer Boskovic Institute, Laboratory for Oxidative Stress, Department of Molecular Medicine (Croatia); Bovenzi, Massimo; Filon, Francesca Larese, E-mail: larese@units.it [University of Trieste, Clinical Unit of Occupational Medicine, Department of Medical Sciences (Italy)

    2015-06-15

    The aim of the study was to evaluate percutaneous penetration of platinum and rhodium nanoparticles (PtNPs: 5.8 ± 0.9 nm, RhNPs: 5.3 ± 1.9 nm) through human skin. Salts compounds of these metals are sensitizers and some also carcinogenic agents. In vitro permeation experiments were performed using Franz diffusion cells with intact and damaged skin. PtNPs and RhNPs, stabilized with polyvinylpyrrolidone, were synthesized by reduction of Na{sub 2}PtC{sub l6} and RhCl{sub 3}·3H{sub 2}O respectively. Suspensions with a concentration of 2.0 g/L of PtNPs and RhNPs were dispersed separately in synthetic sweat at pH 4.5 and applied as donor phases to the outer surface of the skin for 24 h. Measurements of the content of the metals in the receiving solution and in the skin were performed subsequently. Rhodium skin permeation was demonstrated through damaged skin, with a permeation flux of 0.04 ± 0.04 μg cm{sup −2} h{sup −1} and a lag time of 7.9 ± 1.1 h, while no traces of platinum were found in receiving solutions. Platinum and rhodium skin-analysis showed significantly higher concentrations of the metals in damaged skin. Rh and Pt applied as NPs can penetrate the skin barrier and Rh can be found in receiving solutions. These experiments pointed out the need for skin contamination prevention, since even a minor injury to the skin barrier can significantly increase penetration.

  16. Synthesis and structural study of the transition metal doped rhodium perovskites

    International Nuclear Information System (INIS)

    Ting, J.; Kennedy, B.; Zhang, Z.

    2009-01-01

    Full text: One of the most common structures encountered in solid state chemistry is the perovskite structure. With a general formula of AB0 3, the A-type cations are 12-coordinate within a cubo-octahedral environment, while the B-type cations are 6-coordinate, forming an interconnecting three-dimensional octahedral network with neighbouring oxygen anions. While the ideal perovskite structure is cubic in Pm 3 m, many perovskites exhibit symmetry lowering tilting of the corner-sharing B0 6o ctahedral units as a result of A- and B-type cation size disparity. This is also evident in substituted perovskites, where two cations occupy the smaller octahedral site, AB 1- xB' x0 3' Electronic effects can also lower the symmetry. The two most commonly observed effects are the polarisation of the B-cation with a d 0 electronic configuration and Jahn-Teller distortion where the B-cation has a d 4 or d 9 electronic configuration, such as Mn 3+ or Cu 2+ respectively. Manganese containing perovskites have been shown in some compounds to exhibit long-range orbital ordering, giving rise to interesting properties. Heavier transition metals such as ruthenium and iridium have been previously incorporated into these perovskites as an avenue to regulate the properties of these materials. Two orthorhombic rhodium perovskite structures are presented, LaMn 0 . 5 Rh 0 . 5 O 3 and LaCu 05 Rh 0 . 5 O 3 ' A combination of synchrotron x-ray and neutron powder diffraction has been used to elucidate their structures, and have shown both B- and B'-type cations to be disordered across the same crystallographic site for both compounds. x-ray absorption spectroscopy measurements have been used to provide an insight into the valence states of the cations, which show a valency of +3.5 for rhodium due to an extensive charge delocalisation between copper and rhodium.

  17. Trans-Selective Rhodium Catalysed Conjugate Addition of Organoboron Reagents to Dihydropyranones

    Directory of Open Access Journals (Sweden)

    Hannah J. Edwards

    2015-04-01

    Full Text Available The selective synthesis of 2,6-trans-tetrahydropyran derivatives employing the rhodium catalysed addition of organoboron reagents to dihydropyranone templates, derived from a zinc-catalysed hetero-Diels-Alder reaction, is reported. The addition of both arylboronic acids and potassium alkenyltrifluoroborates have been accomplished in high yields using commercially-available [Rh(cod(OH]2 catalyst. The selective formation of the 2,6-trans-tetrahydropyran stereoisomer is consistent with a mechanism involving alkene association and carbometalation on the less hindered face of the dihydropyranone.

  18. Experimental demonstration of H∞ filter performance for dynamic compensation of rhodium neutron detectors

    International Nuclear Information System (INIS)

    Park, Moon-Ghu; Choi, Yu-Sun; Lee, Kwang-Dae

    2008-01-01

    This paper describes the experimental demonstration of the theoretical result of the previous work on LMI (linear matrix inequality) based H ∞ filter for time-delay compensation of self-powered neutron detectors. The filter gains are optimized in the sense of noise attenuation level of H ∞ setting. By introducing bounded real lemma, the conventional algebraic Riccati inequalities are converted into linear matrix inequalities (LMIs). Finally, the filter design problem is solved via the convex optimization framework using LMIs. The experimental measurements of rhodium detector signal from a research reactor show that the predicted theoretical filter performance is verified by showing successful reconstruction of the reference power signal

  19. Rhodium deposition onto a 4-mercaptopyridine SAM on Au(1 1 1)

    Energy Technology Data Exchange (ETDEWEB)

    Manolova, M. [Institute of Electrochemistry, University of Ulm, 89069 Ulm (Germany); Kayser, M. [Institute of Electrochemistry, University of Ulm, 89069 Ulm (Germany); Kolb, D.M. [Institute of Electrochemistry, University of Ulm, 89069 Ulm (Germany)]. E-mail: dieter.kolb@uni-ulm.de; Boyen, H.-G. [Institute of Solid State Physics, University of Ulm, 89069 Ulm (Germany); Ziemann, P. [Institute of Solid State Physics, University of Ulm, 89069 Ulm (Germany); Mayer, D. [BASF Electronic Materials GmbH, 67056 Ludwigshafen (Germany); Wirth, A. [BASF Electronic Materials GmbH, 67056 Ludwigshafen (Germany)

    2007-02-10

    The application of a recently developed method for the deposition of Pd and Pt on top of a SAM, has been successfully extended to Rh, thus proving the versatility of the new concept. Experimental evidence from cyclic voltammetry, in situ STM and ex situ X-ray photoemission spectroscopy is presented for the deposition of monoatomic high rhodium islands onto a 4-mercaptopyridine self-assembled monolayer on a Au(1 1 1) electrode. By repetitive complexation of the Rh ions to the ring-nitrogen and reduction in a Rh-ion free solution, an almost completely covered SAM is obtained. The consequences of making contacts for molecular electronics are briefly discussed.

  20. Study of heat transfer parameters on rhodium target for 103Pd production

    International Nuclear Information System (INIS)

    Sadeghi, M.; Tenreiro, C.; Van den Winkel, P.

    2009-01-01

    The efficiency of cooling and the particle beam characteristics are important when high beam current irradiations are intended for production of radionuclides. The efficiency of cooling is determined by both the target carrier geometry and the flow rate of coolant, while the beam characteristics deal with the current density distribution on the irradiated surface area. Heat transfer on rhodium target to produce 103 Pd via the 103 Rh(p,n) 103 Pd reaction was investigated and the beam current was obtained more than 500 μA. (authors)

  1. Predictable and Regioselective Insertion of Internal Unsymmetrical Alkynes in Rhodium-Catalyzed Cycloadditions with Alkenyl Isocyanates

    Science.gov (United States)

    Friedman, Rebecca Keller; Rovis, Tomislav

    2009-01-01

    A regioselective, rhodium-catalyzed cycloaddition between a variety of internal, unsymmetrical alkynes is described. We document the impact of both steric and electronic properties of the alkyne on reaction course, efficiency and enantioselectivity. The substituent that better stabilizes a positive charge or the larger group, all else being equal, inserts distal to the carbonyl moiety in a predictable and controllable fashion. The reaction scope is broad and the enantioselectivities are high, providing an ‘instruction manual’ for substrate choice when utilizing this reaction as a synthetic tool. PMID:19569692

  2. Rhodium(III) as a potentiator of the effects of X-rays on cells

    Energy Technology Data Exchange (ETDEWEB)

    Richmond, R C; Centilli, M A; Cross, M H; Powers, E L

    1986-08-01

    A rhodium compound, Rh(NH/sub 3/)/sub 3/Cl/sub 3/, does not sensitize the spores of Bacillus megaterium to X-rays. However, it is a very effective sensitizer of vegetative cells of Staphylococcus aureus, raising the sensitivity four times in O/sub 2/ and over 100 times in anoxia. The inhibition by oxygen of the sensitizing action of Rh(III), which operates over a wide range of (O/sub 2/), is noteworthy. These experiments were performed in saline-phosphate buffer using 50 kVp X-rays. The results are discussed in terms of the known radiation chemistry of this compound.

  3. Stereoselective 1,3-Insertions of Rhodium(II) Azavinyl Carbenes

    Science.gov (United States)

    Chuprakov, Stepan; Worrell, Brady T.; Selander, Nicklas; Sit, Rakesh K.; Fokin, Valery V.

    2014-01-01

    Rhodium(II) azavinyl carbenes, conveniently generated from 1-sulfonyl-1,2,3-triazoles, undergo a facile, mild and convergent formal 1,3-insertion into N–H and O–H bonds of primary and secondary amides, various alcohols, and carboxylic acids to afford a wide range of vicinally bis-functionalized Z-olefins with perfect regio- and stereoselectively. Utilizing the distinctive functionality installed through these reactions, a number of subsequent rearrangements and cyclizations expand the repertoire of valuable organic building blocks constructed by reactions of transition metal carbene complexes, including α-allenyl ketones and amino-substituted heterocycles. PMID:24295389

  4. Platinum, palladium, and rhodium in volcanic and plutonic rocks from the Gravina-Nutzotin belt, Alaska

    Science.gov (United States)

    Page, Norman J; Berg, Henry C.; Haffty, Joseph

    1977-01-01

    The Gravina-Nutzotin belt of Middle (?) Jurassic to middle Cretaceous sedimentary and volcanic rocks in south and southeastern Alaska includes concentrically zoned ultramafic complexes known to contain platinum-group metals. Previous isotopic, petrologic, and geologic studies suggested a close relation in time and space between the volcanic rocks and the ultramafic complexes. Interpretation of 40 analyses for platinum, palladium, and rhodium in volcanic and plutonic rocks of the belt indicates a strong geochemical correlation between the two groups of rocks and is in support of their being cogenetic either from directly connected magma chambers and flows or indirectly by selective concentration processes from similar mantle material.

  5. Hydrolysis of Letrozole catalyzed by macrocyclic Rhodium (I) Schiff-base complexes.

    Science.gov (United States)

    Reddy, P Muralidhar; Shanker, K; Srinivas, V; Krishna, E Ravi; Rohini, R; Srikanth, G; Hu, Anren; Ravinder, V

    2015-03-15

    Ten mononuclear Rhodium (I) complexes were synthesized by macrocyclic ligands having N4 and N2O2 donor sites. Square planar geometry is assigned based on the analytical and spectral properties for all complexes. Rh(I) complexes were investigated as catalysts in hydrolysis of Nitrile group containing pharmaceutical drug Letrozole. A comparative study showed that all the complexes are efficient in the catalysis. The percent yields of all the catalytic reaction products viz. drug impurities were determined by spectrophotometric procedures and characterized by spectral studies. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Enantioselective Access to Spirocyclic Sultams by Chiral Cp(x) -Rhodium(III)-Catalyzed Annulations.

    Science.gov (United States)

    Pham, Manh V; Cramer, Nicolai

    2016-02-12

    Chiral spirocyclic sultams are a valuable compound class in organic and medicinal chemistry. A rapid entry to this structural motif involves a [3+2] annulation of an N-sulfonyl ketimine and an alkyne. Although the directing-group properties of the imino group for C-H activation have been exploited, the developments of related asymmetric variants have remained very challenging. The use of rhodium(III) complexes equipped with a suitable atropchiral cyclopentadienyl ligand, in conjunction with a carboxylic acid additive, enables an enantioselective and high yielding access to such spirocyclic sultams. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Sensitivity change of rhodium self -powered detectors with burn-up

    International Nuclear Information System (INIS)

    Girgis, R.; Akimov, I.S.; Hamouda, I.

    1976-01-01

    The scope of the present paper is to obtain the calculation formulae to evaluate the rate of sensitivity change of the neutron self-powered detectors with burn-up. A code written in FORTRAN 4 was developed to be operational on the IBM-1130 computer. It has been established in the case of rhodium detectors that neglecting the β-particle absorption in the calculations leads to the underestimation of the detector sensitivity decrease up to 40%. The derived formulae can be used for other self-powered detectors. (author)

  8. Redox-Neutral Rhodium-Catalyzed [4+1] Annulation through Formal Dehydrogenative Vinylidene Insertion.

    Science.gov (United States)

    Liu, Huan; Song, Shengjin; Wang, Cheng-Qiang; Feng, Chao; Loh, Teck-Peng

    2017-01-10

    A synthetic protocol for the expedient construction of 5-methylene-1H-pyrrol-2(5H)-one derivatives through rhodium-catalyzed [4+1] annulation with gem-difluoroacrylate as the C 1 component was reported. By taking advantage of the twofold C-F bond cleavage occurring during the annulation, this reaction not only allows the synthesis of these heterocyclic compounds under overall oxidant-free conditions but also renders the transformation stereospecific. The very mild reaction conditions employed ensure compatibility with a wide variety of synthetically useful functional groups. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Rhodium-catalyzed redox-neutral coupling of phenidones with alkynes.

    Science.gov (United States)

    Fan, Zhoulong; Lu, Heng; Li, Wei; Geng, Kaijun; Zhang, Ao

    2017-07-21

    A switchable synthesis of N-substituted indole derivatives from phenidones via rhodium-catalyzed redox-neutral C-H activation has been achieved. In this protocol, we firstly disclosed that the reactivity of Rh(iii) catalysis could be enhanced through employing palladium acetate as an additive. Some representative features include external oxidant-free, applicable to terminal alkynes, short reaction time and operational simplicity. The utility of this method is further showcased by the economical synthesis of potent anticancer PARP-1 inhibitors.

  10. Platinum, palladium, and rhodium analyses of ultramafic and mafic rocks from the Stillwater Complex, Montana

    Science.gov (United States)

    Page, Norman J; Riley, Leonard Benjamin; Haffty, Joseph

    1969-01-01

    Analyses by a combination fire- assay-solution-optical-emission spectrographic method of 137 rocks from the Stillwater Complex, Mont., indicate that platinum, palladium, and rhodium are preferentially concentrated in chromitite zones. The A chromitite zone (21 samples) has an average of 988.9 ppb (pans per billion, 10-9) Pt, 2290.2 ppb Pd, and 245.9 ppb Rh and reaches a maximum (to date) of 8,000 ppb Pt, 11,000 ppb Pd, and 1,700 ppb Rh.

  11. Complexation of diphenyl(phenylacetenyl)phosphine to rhodium(III) tetraphenyl porphyrins

    DEFF Research Database (Denmark)

    Stulz, Eugen; Scott, Sonya M; Bond, Andrew D

    2003-01-01

    ). The methylide on rhodium in 3 is not displaced, leading selectively to the mono-phosphine complex (DPAP)(Me)Rh(TPP) (5). The first and second association constants, as determined by isothermal titration calorimetry and UV-vis titrations, are in the range 10(4)-10(7) M(-1) (in CH(2)Cl(2)). Using LDI-TOF mass....... The largest values of DeltaG degrees are found for 6. The thermodynamic and UV-vis data reveal that the methylide and the phosphine ligand have an almost identical electronic trans-influence on the sixth ligand....

  12. Light-induced reduction of rhodium(III) and palladium(II) on titanium dioxide dispersions and the selective photochemical separation and recovery of gold(III), platinum(IV), and rhodium(III) in chloride media

    Energy Technology Data Exchange (ETDEWEB)

    Borgarello, E.; Serpone, N.; Emo, G.; Harris, R.; Pelizzetti, E.; Minero, C.

    1986-12-03

    Irradiation of aqueous TiO/sub 2/ dispersions containing palladium(II) or rhodium(III) chloride salts with AM1 simulated sunlight leads to the photoreduction of these metals, which are deposited on the semiconductor particle surface. Oxygen is detrimental to the photoreduction of rhodium(III) but not the photoreduction of palladium(II). However, in both cases the reduction process is most efficient if the solution contains CH/sub 3/OH, which acts to scavenge valence band holes of the illuminated TiO/sub 2/ semiconductor. The selective photoreduction and recovery of precious metals from a dilute solution (as might be found in industrial wastes) have been investigated for a mixture of gold(III), platinum(IV), and rhodium(III) chloride salts as a function of various parameters (pH, presence or absence of O/sub 2/, presence or absence of a hole scavenger, and the concentration of the semiconductor). At pH 0, gold is easily separated from platinum and rhodium. The rate of photoreduction of gold(III) on TiO/sub 2/ is nearly independent of the concentration of the semiconductor, under the experimental conditions employed; the limiting rate is 2.7 x 10/sup -7/ M s/sup -1/. The potential utility of this selective photochemical technique is discussed.

  13. Excess Substrate is a Spectator Ligand in a Rhodium-Catalyzed Asymmetric [2+2+2] Cycloaddition of Alkenyl Isocyanates with Tolanes

    Science.gov (United States)

    Oinen, Mark Emil; Yu, Robert T.; Rovis, Tomislav

    2009-01-01

    Excess substrate has been identified as an unintended spectator ligand affecting enantioselectivity in the [2+2+2] cycloaddition of alkenyl isocyanates with tolanes. Replacement of excess substrate with an exogenous additive affords products with consistent and higher ee’s. The increase in enantioselectivity is the result of a change in composition of a proposed rhodium(III) intermediate on the catalytic cycle. The net result is a rational probe of a short-lived rhodium(III) intermediate, and gives insight that may have applications in many rhodium catalyzed reactions. PMID:19803471

  14. Oxidation-resistant Ge-doped silicide coating on Cr-Cr2Nb alloys by pack cementation

    International Nuclear Information System (INIS)

    He Yirong

    1997-01-01

    The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating on Cr-Cr 2 Nb alloys in a single processing step. The morphology and composition of the coating depended both on the pack composition and processing schedule and also on the composition and microstructure of the substrate. Higher Ge content in the pack suppressed the formation of CrSi 2 and reduced the growth kinetics of the coating. Ge was not homogeneously distributed in the coatings. Under cyclic and isothermal oxidation conditions, the Ge-doped silicide coating protected the Cr-Nb alloys from significant oxidation and from pesting by the formation of a Ge-doped silica film. (orig.)

  15. Optical metrology of Ni and NiSi thin films used in the self-aligned silicidation process

    International Nuclear Information System (INIS)

    Kamineni, V. K.; Bersch, E. J.; Diebold, A. C.; Raymond, M.; Doris, B. B.

    2010-01-01

    The thickness-dependent optical properties of nickel metal and nickel monosilicide (NiSi) thin films, used for self-aligned silicidation process, were characterized using spectroscopic ellipsometry. The thickness-dependent complex dielectric function of nickel metal films is shown to be correlated with the change in Drude free electron relaxation time. The change in relaxation time can be traced to the change in grain boundary (GB) reflection coefficient and grain size. A resistivity based model was used as the complementary method to the thickness-dependent optical model to trace the change in GB reflection coefficient and grain size. After silicidation, the complex dielectric function of NiSi films exhibit non-Drude behavior due to superimposition of interband absorptions arising at lower frequencies. The Optical models of the complete film stack were refined using x-ray photoelectron spectroscopy, Rutherford backscattered spectroscopy, and x-ray reflectivity (XRR).

  16. Fuel element burnup measurements for the equilibrium LEU silicide RSG GAS (MPR-30) core under a new fuel management strategy

    International Nuclear Information System (INIS)

    Pinem, Surian; Liem, Peng Hong; Sembiring, Tagor Malem; Surbakti, Tukiran

    2016-01-01

    Highlights: • Burnup measurement of fuel elements comprising the new equilibrium LEU silicide core of RSG GAS. • The burnup measurement method is based on a linear relationship between reactivity and burnup. • Burnup verification was conducted using an in-house, in-core fuel management code BATAN-FUEL. • A good agreement between the measured and calculated burnup was confirmed. • The new fuel management strategy was confirmed and validated. - Abstract: After the equilibrium LEU silicide core of RSG GAS was achieved, there was a strong need to validate the new fuel management strategy by measuring burnup of fuel elements comprising the core. Since the regulatory body had a great concern on the safety limit of the silicide fuel element burnup, amongst the 35 burnt fuel elements we selected 22 fuel elements with high burnup classes i.e. from 20 to 53% loss of U-235 (declared values) for the present measurements. The burnup measurement method was based on a linear relationship between reactivity and burnup where the measurements were conducted under subcritical conditions using two fission counters of the reactor startup channel. The measurement results were compared with the declared burnup evaluated by an in-house in-core fuel management code, BATAN-FUEL. A good agreement between the measured burnup values and the calculated ones was found within 8% uncertainties. Possible major sources of differences were identified, i.e. large statistical errors (i.e. low fission counters’ count rates), variation of initial U-235 loading per fuel element and accuracy of control rod indicators. The measured burnup of the 22 fuel elements provided the confirmation of the core burnup distribution planned for the equilibrium LEU silicide core under the new fuel management strategy.

  17. Evaluation of powder metallurgical processing routes for multi-component niobium silicide-based high-temperature alloys

    Energy Technology Data Exchange (ETDEWEB)

    Seemueller, Hans Christoph Maximilian

    2016-03-22

    Niobium silicide-based composites are potential candidates to replace nickel-base superalloys for turbine applications. The goal of this work was to evaluate the feasibility and differences in ensuing properties of various powder metallurgical processing techniques that are capable of manufacturing net-shape turbine components. Two routes for powder production, mechanical alloying and gas atomization were combined with compaction via hot isostatic pressing and powder injection molding.

  18. Carbonyl complexes of rhodium with N-donor ligands: factors determining the formation of terminal versus bridging carbonyls

    NARCIS (Netherlands)

    Dzik, W.I.; Creusen, C.; de Gelder, R.; Peters, T.P.J.; Smits, J.M.M.; de Bruin, B.

    2010-01-01

    Cationic rhodium carbonyl complexes supported by a series of different N-3- and N-4-donor ligands were prepared, and their ability to form carbonyl-bridged species was evaluated. Complex [Rh(K3-bpa)(cod)r (1(+)) (bpa = bis(2-picolyBamine, cod = cis,cis-1,5-cyclooctadiene) reacts with I bar of CO to

  19. Extraction of carrier-free 103Pd from thin rhodium wire irradiated with a proton beam in U-150 cyclotron

    International Nuclear Information System (INIS)

    Yuldashev, B.S.; Khudajbergenov, U.; Gulamov, I.R.; Mirzarva, M.A.; Rylov, A.A.

    2003-01-01

    A procedure for preparation of 103 Pd isotope of 99.9 % purity from a thin rhodium wire irradiated by 21 MeV proton beam in a cyclotron was developed. The desired product was prepared by electrolytic dissolution of the irradiated target in 6 M HCl with subsequent extraction of 103 Pd isotope without carrier by dimethylglyoxime in chloroform [ru

  20. Solvent extraction of no-carrier-added 103Pd from irradiated rhodium target with α-furyldioxime

    International Nuclear Information System (INIS)

    Mahdi Sadeghi; Behrouz Shirazi; Nami Shadanpour

    2006-01-01

    Solvent extraction of no-carrier-added 103 Pd was investigated from irradiated rhodium target with a-furyldioxime in chloroform from diluted hydrochloric acid. Extraction yield was 85.3% for a single extraction from 0.37M HCl and 103 Pd purity was better than 99%. (author)

  1. Dispersive oxidation of rhodium clusters in Na-Y by the combined action of zeolite protons and carbon monoxide

    International Nuclear Information System (INIS)

    Wong, T.T.T.; Sachtler, W.M.H.; Stakheev, A.Yu.

    1992-01-01

    This paper uses x-ray photoelectron spectroscopy, fourier transform infrared spectroscopy and temperature programmed mass-spectrometric analysis to study the interaction of Na-Y supported rhodium with hydrogen, carbon monoxide, and zeolite protons. This report attempts to clarify the mechanism of dispersive oxidation of reduced Rh particles in the presence of CO, leading to the formation of Rh + (CO) 2 cations

  2. PipPhos and MorfPhos : Privileged monodentate phosphoramidite ligands for rhodium-catalyzed asymmetric hydrogenation

    NARCIS (Netherlands)

    Bernsmann, Heiko; van den Berg, M; Hoen, Robert; Minnaard, AJ; Mehler, G; Reetz, MT; De Vries, JG; Feringa, BL

    2005-01-01

    A library of 20 monodentate phosphoramidite ligands has been prepared and applied in rhodium-catalyzed asymmetric hydrogenation. This resulted in the identification of two ligands, PipPhos and MorfPhos, that afford excellent and in several cases unprecedented enantioselectivities in the

  3. Reversible switching of the sol- gel transition with ultrasound in rhodium(I) and iridium(I) coordination networks

    NARCIS (Netherlands)

    Paulusse, J.M.J.; Beek, van D.J.M.; Sijbesma, R.P.

    2007-01-01

    Reversible coordination networks were prepared by combining diphenylphosphinite telechelic polytetrahydrofuran (2) with [RhCl(COD)]2 or [IrCl(COD)]2 in chloroform. Both systems resulted in stable gels at concentrations above 50 and 30 g/L for the rhodium(I) and iridium(I) networks, respectively. The

  4. The Rôle of the Element Rhodium in the Hyperbolic Law of the Periodic Table of Elements

    Directory of Open Access Journals (Sweden)

    Khazan A.

    2008-07-01

    Full Text Available The role of the element rhodium as an independent affirmation of calculations by the Hyperbolic Law and validity of all its relations is shown herein. The deviation in cal- culation by this method of the atomic mass of heaviest element is 0.0024%, and its coefficient of scaling 0.001–0.005%

  5. Mono and dinuclear iridium, rhodium and ruthenium complexes containing chelating carboxylato pyrazine ligands: Synthesis, molecular structure and electrochemistry

    Czech Academy of Sciences Publication Activity Database

    Govindaswamy, P.; Therrien, B.; Süss-Fink, G.; Štěpnička, P.; Ludvík, Jiří

    2007-01-01

    Roč. 692, č. 8 (2007), s. 1661-1671 ISSN 0022-328X R&D Projects: GA MŠk LC510; GA MŠk(CZ) LC06070 Institutional research plan: CEZ:AV0Z40400503 Keywords : dinuclear complexes * iridium * rhodium * ruthenium * electrochemistry Subject RIV: CG - Electrochemistry Impact factor: 2.168, year: 2007

  6. Intermolecular rhodium-catalyzed [2 + 2 + 2] carbocyclization reactions of 1,6-enynes with symmetrical and unsymmetrical alkynes†

    Science.gov (United States)

    Andrew Evans, P.; Sawyer, James R.; Lai, Kwong Wah; Huffman, John C.

    2006-01-01

    The crossed intermolecular rhodium-catalyzed [2 + 2 + 2] carbocyclization of carbon and heteroatom tethered 1,6-enynes can be accomplished with symmetrical and unsymmetrical alkynes, to afford the corresponding bicyclohexadienes in an efficient and highly selective manner. PMID:16075089

  7. Direct Synthesis of 5-Aryl Barbituric Acids by Rhodium(II)-Catalyzed Reactions of Arenes with Diazo Compounds**

    Science.gov (United States)

    Best, Daniel; Burns, David J; Lam, Hon Wai

    2015-01-01

    A commercially available rhodium(II) complex catalyzes the direct arylation of 5-diazobarbituric acids with arenes, allowing straightforward access to 5-aryl barbituric acids. Free N—H groups are tolerated on the barbituric acid, with no complications arising from N—H insertion processes. This method was applied to the concise synthesis of a potent matrix metalloproteinase (MMP) inhibitor. PMID:25959544

  8. Complexation of rhodium(II) tetracarboxylates with aliphatic diamines in solution: 1H and 13C NMR and DFT investigations.

    Science.gov (United States)

    Jaźwiński, Jarosław; Sadlej, Agnieszka

    2013-10-01

    The complexation of rhodium(II) tetraacetate, tetrakistrifluoroaceate and tetrakisoctanoate with a set of diamines (ethane-1,diamine, propane-1,3-diamine and nonane-1,9-diamine) and their N,N'-dimethyl and N,N,N',N'-tetramethyl derivatives in chloroform solution has been investigated by (1) H and (13) C NMR spectroscopy and density functional theory (DFT) modelling. A combination of two bifunctional reagents, diamines and rhodium(II) tetracarboxylates, yielded insoluble coordination polymers as main products of complexation and various adducts in the solution, being in equilibrium with insoluble material. All diamines initially formed the 2 : 1 (blue), (1 : 1)n oligomeric (red) and 1 : 2 (red) axial adducts in solution, depending on the reagents' molar ratio. Adducts of primary and secondary diamines decomposed in the presence of ligand excess, the former via unstable equatorial complexes. The complexation of secondary diamines slowed down the inversion at nitrogen atoms in NH(CH3 ) functional groups and resulted in the formation of nitrogenous stereogenic centres, detectable by NMR. Axial adducts of tertiary diamines appeared to be relatively stable. The presence of long aliphatic chains in molecules (adducts of nonane-1,9-diamines or rhodium(II) tetrakisoctanoate) increased adduct solubility. Hypothetical structures of the equatorial adduct of rhodium(II) tetraacetate with ethane-1,2-diamine and their NMR parameters were explored by means of DFT calculations. Copyright © 2013 John Wiley & Sons, Ltd.

  9. Controlling the formation and stability of ultra-thin nickel silicides - An alloying strategy for preventing agglomeration

    Science.gov (United States)

    Geenen, F. A.; van Stiphout, K.; Nanakoudis, A.; Bals, S.; Vantomme, A.; Jordan-Sweet, J.; Lavoie, C.; Detavernier, C.

    2018-02-01

    The electrical contact of the source and drain regions in state-of-the-art CMOS transistors is nowadays facilitated through NiSi, which is often alloyed with Pt in order to avoid morphological agglomeration of the silicide film. However, the solid-state reaction between as-deposited Ni and the Si substrate exhibits a peculiar change for as-deposited Ni films thinner than a critical thickness of tc = 5 nm. Whereas thicker films form polycrystalline NiSi upon annealing above 450 ° C , thinner films form epitaxial NiSi2 films that exhibit a high resistance toward agglomeration. For industrial applications, it is therefore of utmost importance to assess the critical thickness with high certainty and find novel methodologies to either increase or decrease its value, depending on the aimed silicide formation. This paper investigates Ni films between 0 and 15 nm initial thickness by use of "thickness gradients," which provide semi-continuous information on silicide formation and stability as a function of as-deposited layer thickness. The alloying of these Ni layers with 10% Al, Co, Ge, Pd, or Pt renders a significant change in the phase sequence as a function of thickness and dependent on the alloying element. The addition of these ternary impurities therefore changes the critical thickness tc. The results are discussed in the framework of classical nucleation theory.

  10. A Study on Characterization of Light-Induced Electroless Plated Ni Seed Layer and Silicide Formation for Solar Cell Application

    Science.gov (United States)

    Takaloo, Ashkan Vakilipour; Joo, Seung Ki; Es, Firat; Turan, Rasit; Lee, Doo Won

    2018-03-01

    Light-induced electroless plating (LIEP) is an easy and inexpensive method that has been widely used for seed layer deposition of Nickel/Copper (Ni/Cu)-based metallization in the solar cell. In this study, material characterization aspects of the Ni seed layer and Ni silicide formation at different bath conditions and annealing temperatures on the n-side of a silicon diode structure have been examined to achieve the optimum cell contacts. The effects of morphology and chemical composition of Ni film on its electrical conductivity were evaluated and described by a quantum mechanical model. It has been found that correlation exists between the theoretical and experimental conductivity of Ni film. Residual stress and phase transformation of Ni silicide as a function of annealing temperature were evaluated using Raman and XRD techniques. Finally, transmission line measurement (TLM) technique was employed to determine the contact resistance of Ni/Si stack after thermal treatment and to understand its correlation with the chemical-structural properties. Results indicated that low electrical resistive mono-silicide (NiSi) phase as low as 5 mΩ.cm2 was obtained.

  11. Electrical and optical properties of sub-10 nm nickel silicide films for silicon solar cells

    International Nuclear Information System (INIS)

    Brahmi, Hatem; Ravipati, Srikanth; Yarali, Milad; Wang, Weijie; Ryou, Jae-Hyun; Mavrokefalos, Anastassios; Shervin, Shahab

    2017-01-01

    Highly conductive and transparent films of ultra-thin p-type nickel silicide films have been prepared by RF magnetron sputtering of nickel on silicon substrates followed by rapid thermal annealing in an inert environment in the temperature range 400–600 °C. The films are uniform throughout the wafer with thicknesses in the range of 3–6 nm. The electrical and optical properties are presented for nickel silicide films with varying thickness. The Drude–Lorentz model and Fresnel equations were used to calculate the dielectric properties, sheet resistance, absorption and transmission of the films. These ultrathin nickel silicide films have excellent optoelectronic properties for p-type contacts with optical transparencies up to 80% and sheet resistance as low as ∼0.15 µΩ cm. Furthermore, it was shown that the use of a simple anti-reflection (AR) coating can recover most of the reflected light approaching the values of a standard Si solar cell with the same AR coating. Overall, the combination of ultra-low thickness, high transmittance, low sheet resistance and ability to recover the reflected light by utilizing standard AR coating makes them ideal for utilization in silicon based photovoltaic technologies as a p-type transparent conductor. (paper)

  12. Electrical and optical properties of sub-10 nm nickel silicide films for silicon solar cells

    Science.gov (United States)

    Brahmi, Hatem; Ravipati, Srikanth; Yarali, Milad; Shervin, Shahab; Wang, Weijie; Ryou, Jae-Hyun; Mavrokefalos, Anastassios

    2017-01-01

    Highly conductive and transparent films of ultra-thin p-type nickel silicide films have been prepared by RF magnetron sputtering of nickel on silicon substrates followed by rapid thermal annealing in an inert environment in the temperature range 400-600 °C. The films are uniform throughout the wafer with thicknesses in the range of 3-6 nm. The electrical and optical properties are presented for nickel silicide films with varying thickness. The Drude-Lorentz model and Fresnel equations were used to calculate the dielectric properties, sheet resistance, absorption and transmission of the films. These ultrathin nickel silicide films have excellent optoelectronic properties for p-type contacts with optical transparencies up to 80% and sheet resistance as low as ~0.15 µΩ cm. Furthermore, it was shown that the use of a simple anti-reflection (AR) coating can recover most of the reflected light approaching the values of a standard Si solar cell with the same AR coating. Overall, the combination of ultra-low thickness, high transmittance, low sheet resistance and ability to recover the reflected light by utilizing standard AR coating makes them ideal for utilization in silicon based photovoltaic technologies as a p-type transparent conductor.

  13. Gravimetric preparation and characterization of primary reference solutions of molybdenum and rhodium.

    Science.gov (United States)

    Kaltenbach, Angela; Noordmann, Janine; Görlitz, Volker; Pape, Carola; Richter, Silke; Kipphardt, Heinrich; Kopp, Gernot; Jährling, Reinhard; Rienitz, Olaf; Güttler, Bernd

    2015-04-01

    Gravimetrically prepared mono-elemental reference solutions having a well-known mass fraction of approximately 1 g/kg (or a mass concentration of 1 g/L) define the very basis of virtually all measurements in inorganic analysis. Serving as the starting materials of all standard/calibration solutions, they link virtually all measurements of inorganic analytes (regardless of the method applied) to the purity of the solid materials (high-purity metals or salts) they were prepared from. In case these solid materials are characterized comprehensively with respect to their purity, this link also establishes direct metrological traceability to The International System of Units (SI). This, in turn, ensures the comparability of all results on the highest level achievable. Several national metrology institutes (NMIs) and designated institutes (DIs) have been working for nearly two decades in close cooperation with commercial producers on making an increasing number of traceable reference solutions available. Besides the comprehensive characterization of the solid starting materials, dissolving them both loss-free and completely under strict gravimetric control is a challenging problem in the case of several elements like molybdenum and rhodium. Within the framework of the European Metrology Research Programme (EMRP), in the Joint Research Project (JRP) called SIB09 Primary standards for challenging elements, reference solutions of molybdenum and rhodium were prepared directly from the respective metals with a relative expanded uncertainty associated with the mass fraction of U rel(w) methods required to assist with the preparation and as dissemination tools.

  14. Ion flotation of rhodium(III) and palladium(II) with anionic surfactants.

    Science.gov (United States)

    He, X C

    1991-03-01

    The ion flotation of rhodium(III) and palladium(II) with some anionic surfactants has been investigated. Two flotation procedures are proposed for the separation of some platinum metals, based on differences in the kinetic properties of the chloro-complexes of rhodium(III), palladium(II) and platinum(IV). The first involves the selective flotation of Rh(H(2)O)(3+)(6) from PdCl(2-)(4) and PtCl(2-)(6) in dilute hydrochloric acid with sodium dodecylbenzenesulfonate (SDBS). After precipitation of the hydroxide and redissolution in dilute acid, the Rh(III) is converted into Rh(H(2)O)(3+)(6), Pd(II) and Pt(IV) remaining as PdCl(2-)(4) and PtCl(2-)(6) respectively, and separation is achieved by floating the Rh(H(2)O)(3+)(6) with SDBS. The second is for separation of Pd(II). Prior to flotation, the solution of PdCl(2-)(4) and PtCl(2-)(6) is heated with ammonium acetate to convert PdCl(2-)(4) into Pd(NH(3))(2+)(4). The chloro-complex of Pt(IV) is unaffected. The complex cation, Pd(NH(3))(2+)(4), is then selectively floated with SDBS. The procedures are fast, simple and do not require expensive reagents and apparatus.

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

    Science.gov (United States)

    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.

  16. Rhodium-catalysed syn-carboamination of alkenes via a transient directing group.

    Science.gov (United States)

    Piou, Tiffany; Rovis, Tomislav

    2015-11-05

    Alkenes are the most ubiquitous prochiral functional groups--those that can be converted from achiral to chiral in a single step--that are accessible to synthetic chemists. For this reason, difunctionalization reactions of alkenes (whereby two functional groups are added to the same double bond) are particularly important, as they can be used to produce highly complex molecular architectures. Stereoselective oxidation reactions, including dihydroxylation, aminohydroxylation and halogenation, are well established methods for functionalizing alkenes. However, the intermolecular incorporation of both carbon- and nitrogen-based functionalities stereoselectively across an alkene has not been reported. Here we describe the rhodium-catalysed carboamination of alkenes at the same (syn) face of a double bond, initiated by a carbon-hydrogen activation event that uses enoxyphthalimides as the source of both the carbon and the nitrogen functionalities. The reaction methodology allows for the intermolecular, stereospecific formation of one carbon-carbon and one carbon-nitrogen bond across an alkene, which is, to our knowledge, unprecedented. The reaction design involves the in situ generation of a bidentate directing group and the use of a new cyclopentadienyl ligand to control the reactivity of rhodium. The results provide a new way of synthesizing functionalized alkenes, and should lead to the convergent and stereoselective assembly of amine-containing acyclic molecules.

  17. Correlation between the Stereochemistry and Bioactivity in Octahedral Rhodium Prolinato Complexes.

    Science.gov (United States)

    Rajaratnam, Rajathees; Martin, Elisabeth K; Dörr, Markus; Harms, Klaus; Casini, Angela; Meggers, Eric

    2015-08-17

    Controlling the relative and absolute configuration of octahedral metal complexes constitutes a key challenge that needs to be overcome in order to fully exploit the structural properties of octahedral metal complexes for applications in the fields of catalysis, materials sciences, and life sciences. Herein, we describe the application of a proline-based chiral tridentate ligand to decisively control the coordination mode of an octahedral rhodium(III) complex. We demonstrate the mirror-like relationship of synthesized enantiomers and differences between diastereomers. Further, we demonstrate, using the established pyridocarbazole pharmacophore ligand as part of the organometallic complexes, the importance of the relative and absolute stereochemistry at the metal toward chiral environments like protein kinases. Protein kinase profiling and inhibition data confirm that the proline-based enantiopure rhodium(III) complexes, despite having all of the same constitution, differ strongly in their selectivity properties despite their unmistakably mutual origin. Moreover, two exemplary compounds have been shown to induce different toxic effects in an ex vivo rat liver model.

  18. Rate Theory Modeling and Simulations of Silicide Fuel at LWR Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Yinbin [Argonne National Lab. (ANL), Argonne, IL (United States); Ye, Bei [Argonne National Lab. (ANL), Argonne, IL (United States); Mei, Zhigang [Argonne National Lab. (ANL), Argonne, IL (United States); Hofman, Gerard [Argonne National Lab. (ANL), Argonne, IL (United States); Yacout, Abdellatif [Argonne National Lab. (ANL), Argonne, IL (United States)

    2015-12-10

    Uranium silicide (U3Si2) fuel has higher thermal conductivity and higher uranium density, making it a promising candidate for the accident-tolerant fuel (ATF) used in light water reactors (LWRs). However, previous studies on the fuel performance of U3Si2, including both experimental and computational approaches, have been focusing on the irradiation conditions in research reactors, which usually involve low operation temperatures and high fuel burnups. Thus, it is important to examine the fuel performance of U3Si2 at typical LWR conditions so as to evaluate the feasibility of replacing conventional uranium dioxide fuel with this silicide fuel material. As in-reactor irradiation experiments involve significant time and financial cost, it is appropriate to utilize modeling tools to estimate the behavior of U3Si2 in LWRs based on all those available research reactor experimental references and state-of-the-art density functional theory (DFT) calculation capabilities at the early development stage. Hence, in this report, a comprehensive investigation of the fission gas swelling behavior of U3Si2 at LWR conditions is introduced. The modeling efforts mentioned in this report was based on the rate theory (RT) model of fission gas bubble evolution that has been successfully applied for a variety of fuel materials at devious reactor conditions. Both existing experimental data and DFT-calculated results were used for the optimization of the parameters adopted by the RT model. Meanwhile, the fuel-cladding interaction was captured by the coupling of the RT model with simplified mechanical correlations. Therefore, the swelling behavior of U3Si2 fuel and its consequent interaction with cladding in LWRs was predicted by the rate theory modeling, providing valuable information for the development of U3Si2 fuel as an accident

  19. Reactivity management and burn-up management on JRR-3 silicide-fuel-core

    International Nuclear Information System (INIS)

    Kato, Tomoaki; Araki, Masaaki; Izumo, Hironobu; Kinase, Masami; Torii, Yoshiya; Murayama, Yoji

    2007-08-01

    On the conversion from uranium-aluminum-dispersion-type fuel (aluminide fuel) to uranium-silicon-aluminum-dispersion-type fuel (silicide fuel), uranium density was increased from 2.2 to 4.8 g/cm 3 with keeping uranium-235 enrichment of 20%. So, burnable absorbers (cadmium wire) were introduced for decreasing excess reactivity caused by the increasing of uranium density. The burnable absorbers influence reactivity during reactor operation. So, the burning of the burnable absorbers was studied and the influence on reactor operation was made cleared. Furthermore, necessary excess reactivity on beginning of operation cycle and the time limit for restart after unplanned reactor shutdown was calculated. On the conversion, limit of fuel burn-up was increased from 50% to 60%. And the fuel exchange procedure was changed from the six-batch dispersion procedure to the fuel burn-up management procedure. The previous estimation of fuel burn-up was required for the planning of fuel exchange, so that the estimation was carried out by means of past operation data. Finally, a new fuel exchange procedure was proposed for effective use of fuel elements. On the procedure, burn-up of spent fuel was defined for each loading position. The average length of fuel's staying in the core can be increased by two percent on the procedure. (author)

  20. The whole-core LEU silicide fuel demonstration in the JMTR

    Energy Technology Data Exchange (ETDEWEB)

    Aso, Tomokazu; Akashi, Kazutomo; Nagao, Yoshiharu [Japan Atomic Energy Research Institute, Ibaraki-ken (Japan)] [and others

    1997-08-01

    The JMTR was fully converted to LEU silicide (U{sub 3}Si{sub 2}) fuel with cadmium wires as burnable absorber in January, 1994. The reduced enrichment program for the JMTR was initiated in 1979, and the conversion to MEU (enrichment ; 45%) aluminide fuel was carried out in 1986 as the first step of the program. The final goal of the program was terminated by the present LEU conversion. This paper describes the results of core physics measurement through the conversion phase from MEU fuel core to LEU fuel core. Measured excess reactivities of the LEU fuel cores are mostly in good agreement with predicted values. Reactivity effect and burnup of cadmium wires, therefore, were proved to be well predicted. Control rod worth in the LEU fuel core is mostly less than that in the MEU fuel core. Shutdown margin was verified to be within the safety limit. There is no significant difference in temperature coefficient of reactivity between the MEU and LEU fuel cores. These results verified that the JMTR was successfully and safely converted to LEU fuel. Extension of the operating cycle period was achieved and reduction of spend fuel elements is expected by using the fuel with high uranium density.

  1. Status of core conversion with LEU silicide fuel in JRR-4

    Energy Technology Data Exchange (ETDEWEB)

    Nakajima, Teruo; Ohnishi, Nobuaki; Shirai, Eiji [Japan Atomic Energy Research Institute, Ibaraki-ken (Japan)

    1997-08-01

    Japan Research Reactor No.4 (JRR-4) is a light water moderated and cooled, 93% enriched uranium ETR-type fuel used and swimming pool type reactor with thermal output of 3.5MW. Since the first criticality was achieved on January 28, 1965, JRR-4 has been used for shielding experiments, radioisotope production, neutron activation analyses, training for reactor engineers and so on for about 30 years. Within the framework of the RERTR Program, the works for conversion to LEU fuel are now under way, and neutronic and thermal-hydraulic calculations emphasizing on safety and performance aspects are being carried out. The design and evaluation for the core conversion are based on the Guides for Safety Design and Evaluation of research and testing reactor facilities in Japan. These results show that the JRR-4 will be able to convert to use LEU fuel without any major design change of core and size of fuel element. LEU silicide fuel (19.75%) will be used and maximum neutron flux in irradiation hole would be slightly decreased from present neutron flux value of 7x10{sup 13}(n/cm{sup 2}/s). The conversion works are scheduled to complete in 1998, including with upgrade of the reactor building and utilization facilities.

  2. Status of core conversion with LEU silicide fuel in JRR-4

    International Nuclear Information System (INIS)

    Nakajima, Teruo; Ohnishi, Nobuaki; Shirai, Eiji

    1997-01-01

    Japan Research Reactor No.4 (JRR-4) is a light water moderated and cooled, 93% enriched uranium ETR-type fuel used and swimming pool type reactor with thermal output of 3.5MW. Since the first criticality was achieved on January 28, 1965, JRR-4 has been used for shielding experiments, radioisotope production, neutron activation analyses, training for reactor engineers and so on for about 30 years. Within the framework of the RERTR Program, the works for conversion to LEU fuel are now under way, and neutronic and thermal-hydraulic calculations emphasizing on safety and performance aspects are being carried out. The design and evaluation for the core conversion are based on the Guides for Safety Design and Evaluation of research and testing reactor facilities in Japan. These results show that the JRR-4 will be able to convert to use LEU fuel without any major design change of core and size of fuel element. LEU silicide fuel (19.75%) will be used and maximum neutron flux in irradiation hole would be slightly decreased from present neutron flux value of 7x10 13 (n/cm 2 /s). The conversion works are scheduled to complete in 1998, including with upgrade of the reactor building and utilization facilities

  3. Experimental studies of thermal and chemical interactions between oxide and silicide nuclear fuels with water

    Energy Technology Data Exchange (ETDEWEB)

    farahani, A.A.; Corradini, M.L. [Univ. of Wisconsi, Madison, WI (United States)

    1995-09-01

    Given some transient power/cooling mismatch is a nuclear reactor and its inability to establish the necessary core cooling, energetic fuel-coolant interactions (FCI`s commonly called `vapor explosions`) could occur as a result of the core melting and coolant contact. Although a large number of studies have been done on energetic FCI`s, very few experiments have been performed with the actual fuel materials postulated to be produced in severe accidents. Because of the scarcity of well-characterized FCI data for uranium allows in noncommercial reactors (cermet and silicide fuels), we have conducted a series of experiments to provide a data base for the foregoing materials. An existing 1-D shock-tube facility was modified to handle depleted radioactive materials (U{sub 3}O{sub 8}-Al, and U{sub 3}Si{sub 2}-Al). Our objectives have been to determine the effects of the initial fuel composition and temperature and the driving pressure (triggering) on the explosion work output, dynamic pressures, transient temperatures, and the hydrogen production. Experimental results indicate limited energetics, mainly thermal interactions, for these fuel materials as compared to aluminum where more chemical reactions occur between the molten aluminum and water.

  4. Oxidation behavior of niobium aluminide intermetallics protected by aluminide and silicide diffusion coatings

    International Nuclear Information System (INIS)

    Li, Y.; Soboyejo, W.; Rapp, R.A.

    1999-01-01

    The isothermal and cyclic oxidation behavior of a new class of damage-tolerant niobium aluminide (Nb 3 Al-xTi-yCr) intermetallics is studied between 650 C and 850 C. Protective diffusion coatings were deposited by pack cementation to achieve the siliciding or aluminizing of substrates with or without intervening Mo or Ni layers, respectively. The compositions and microstructures of the resulting coatings and oxidized surfaces were characterized. The isothermal and cyclic oxidation kinetics indicate that uncoated Nb-40Ti-15Al-based intermetallics may be used up to ∼750 C. Alloying with Cr improves the isothermal oxidation resistance between 650 C and 850 C. The most significant improvement in oxidation resistance is achieved by the aluminization of electroplated Ni interlayers. The results suggest that the high-temperature limit of niobium aluminide-based alloys may be increased to 800 C to 850 C by aluminide-based diffusion coatings on ductile Ni interlayers. Indentation fracture experiments also indicate that the ductile nickel interlayers are resistant to crack propagation in multilayered aluminide-based coatings

  5. The Comparison Of Silicon Analysis For The Uranium Silicide Fuel Using Spectrophotometrical And Gravimetrical Methods

    International Nuclear Information System (INIS)

    Putro, P. K.; Suripto, A.; Putra, S.; Gunanjar

    1996-01-01

    The analysis of silicon content in the uranium silicide fuel spectro-photometrical and gravimetrical method have been performed. The nitrous oxide-acetylene was used in the atomic absorption spectrophotometry (AAS) on the wave length of 251.6 nm, and the mixture of ammonium hepta molybdate complexes and SnC1 2 as reductor were applied during analysis by UV-VIS spectrophotometry (UV-VIS) on the wave length of 757.5 mm. The reagent of HCLO 4 and HNO 3 were used for determining Si content by gravimetrical methods. The results of this comparison is as follows: the accuracy result is around 96.37 % + 0.24 % for the Si concentration up to 300 ppm (the AAS), is 138.60 % = 0.43 % for the Si concentration range between 0.1-1.5 ppm (UV-VIS), and is 51.13 % + 0.8 % for 1 gram of Si (gravimetry). The results also show that the lowest analytical error is obtained by AAS method

  6. Silicide formation by Ar/sup +/ ion bombardment of Pd/Si

    Energy Technology Data Exchange (ETDEWEB)

    Lee, R Y; Whang, C N; Kim, H K; Smith, R J

    1988-08-01

    Palladium films, 45 nm thick, evaporated on to Si(111) were irradiated to various doses with 78 keV Ar/sup +/ ions to promote silicide formation. Rutherford backscattering spectroscopy (RBS) shows that intermixing has occurred across the Pd/Si interface at room temperature. The mixing behaviour is increased with dose which coincides well with the theoretical model of cascade mixing. The absence of deep RBS tails for palladium and the small area of this for silicon spectra indicate that short-range mixing occurs. From the calculated damage profiles computed with TRIM code, the dominant diffusion species is found to be silicon atoms in the Pd/Si system. It is also found that the initial compound formed by Ar/sup +/ irradiation is Pd/sub 2/Si which increases with dose. At a dose of 1 x 10/sup 16/ Ar/sup +/ cm/sup -2/, a 48 nm thickness of Pd/sub 2/Si was formed by ion-beam mixing at room temperature.

  7. Analysis Of Temperature Effects On Reactivity Of The Rsg-Gas Core Using Silicide Fuels

    International Nuclear Information System (INIS)

    Surbakti, Tukiran; Pinem, Surian

    2001-01-01

    RSG-GAS has been operating using new silicide fuels so that it is necessary to estimate and to measure the effect of temperature on reactivity of the core. The parameters to be determined due to temperature effect are reactivity coefficient of moderator temperature, temperature coefficient of fuel element and power reactivity coefficient. By doing a couple compensation method, determination of reactivity coefficient as well as the reactivity coefficient of moderator temperature can be obtained. Furthermore, coefficient of the reactivity was successfully estimated using the combination of WIMS-D4 and Batan-2DIFF. The cell calculation was done by using WIMS-D4 code to get macroscopic cross section and Batan-2DIFF code is used for core calculation. The calculation and experimental results of reactivity coefficient do not show any deviation from RSG-GAS safety margin. The results are -2,84 sen/ o C, -1,29 sen/MW and -0,64 sen/ o C for reactivity coefficients of temperature, power, fuel element and moderator temperature, respectively. All of 3 parameters are absolutely met with safety criteria

  8. Prompt Neutron Decay Constant Determination Of Silicide Transition Core Using Noise Method

    International Nuclear Information System (INIS)

    Jujuratisbela, Uju; Yulianto, Yusi Eko; Cahyana

    2001-01-01

    Chairman of BATAN had decided to replace the Oxide fuel element type of RSG-GAS into silicide element type step by step. The replacement will create core transitions. Kinetic characteristic of the transition cores have to be monitored in order to know the deviation of core behavior. For that reason, the kinetic parameters have to be measured. Prompt neutron decay constant (alpha) is one of the kinetic parameters that has to be monitored continuously in the transition cores. In order not to disturb the normal operation of reactor, alpha parameter should be measured by using noise analysis method. The voltage of neutron flux at power of 15 MW is connected to preamplifier and filter then to the Dynamic Signal Analyzer Version-2 and then the auto power spectral density (APSD) was determined by using Fast Fourier transform. From the APSD curve of each channel of JKT03, the cut off frequency of each channel can be determined by using linear regression technique such that the prompt neutron decay constant can be estimated

  9. Large-format platinum silicide microwave kinetic inductance detectors for optical to near-IR astronomy.

    Science.gov (United States)

    Szypryt, P; Meeker, S R; Coiffard, G; Fruitwala, N; Bumble, B; Ulbricht, G; Walter, A B; Daal, M; Bockstiegel, C; Collura, G; Zobrist, N; Lipartito, I; Mazin, B A

    2017-10-16

    We have fabricated and characterized 10,000 and 20,440 pixel Microwave Kinetic Inductance Detector (MKID) arrays for the Dark-speckle Near-IR Energy-resolved Superconducting Spectrophotometer (DARKNESS) and the MKID Exoplanet Camera (MEC). These instruments are designed to sit behind adaptive optics systems with the goal of directly imaging exoplanets in a 800-1400 nm band. Previous large optical and near-IR MKID arrays were fabricated using substoichiometric titanium nitride (TiN) on a silicon substrate. These arrays, however, suffered from severe non-uniformities in the TiN critical temperature, causing resonances to shift away from their designed values and lowering usable detector yield. We have begun fabricating DARKNESS and MEC arrays using platinum silicide (PtSi) on sapphire instead of TiN. Not only do these arrays have much higher uniformity than the TiN arrays, resulting in higher pixel yields, they have demonstrated better spectral resolution than TiN MKIDs of similar design. PtSi MKIDs also do not display the hot pixel effects seen when illuminating TiN on silicon MKIDs with photons with wavelengths shorter than 1 µm.

  10. Characterization of titanium silicide thin films by X-ray diffraction techniques

    International Nuclear Information System (INIS)

    Morimoto, N.J.

    1987-01-01

    This thesis deals with characterization techniques of thin films by means of X-ray diffraction. This includes phase identification and residual stress, microstress and crystallite size calculations. The techniques developed were applied on the study of the titanium silicide formation obtained by means of Rapidy Thermal Processing (RTP) pf Ti films deposited on silicon substratum. The different phases were studied in relation with processing temperature and time in one and two anneling steps. The low resistivity TiSi 2 phase was observed for temperature of 700 0 C and higher. The experimental results indicate that the residual stress of TiSi 2 films doesn't vary significantly with the annealing conditions. On the other hand, the microstress is reduced with annealing time at 800 0 C, while the crystallite size is almost not affected. For the microstress and the crystallite size determination technique, two methods were implemented and compared. The Riella's method appeared to be very efficient, while the Gangulle's method seemed to be inadequate, because the results oscillate too much [pt

  11. Neutron irradiated uranium silicides studied by neutron diffraction and Rietveld analysis

    International Nuclear Information System (INIS)

    Birtcher, R.C.; Mueller, M.H.; Richardson, J.W. Jr.; Faber, J. Jr.

    1989-11-01

    Uranium silicides have been considered for use as reactor fuels in both high power and low enrichment applications. However, U 3 Si was found to become amorphous under irradiation and to become mechanically unstable to rapid growth by plastic flow. U 2 Si 2 appears to be stable against amorphization at low displacement rates, but the extent of this stability is uncertain. Although the mechanisms responsible for plastic flow in U 3 Si and other amorphous systems are unknown, as is the importance of crystal structure for amorphization, it may not be surprising that these materials amorphize, in light of the fact that many radioactive nuclide - containing minerals are known to metaminctize (lose crystallinity) under irradiation. The present experiment follows the detailed changes in the crystal structures of U 3 Si and U 3 Si 2 introduced by neutron bombardment and subsequent uranium fission at room temperature. U-Si seems the ideal system for a neutron diffraction investigation since the crystallographic and amorphous forms can be studied simultaneously by combining conventional Rietveld refinement of the crystallographic phases with Fourier-filtering of the non-crystalline scattering component

  12. New data on some short-lived isotopes of ruthenium and rhodium

    International Nuclear Information System (INIS)

    Baumgartner, F.; Plata Bedmar, A.

    1961-01-01

    Ru and Rd isotopes with mass numbers 107 and 108 and 1 09Rh, has been obtained from fission products. 1 07 Ru has also been prepared by the nuclear process 1 10Pd (n,α) 1 07 Ru. Beta and gamma energies of these nuclides have been studied spectropolarimetry and the gamma lines found for 1 07 Ru and 1 08Ru ( and daughter) have been very useful for the precise determination of their half-lives. 1 09Rh has been identified through its daughter 1 09Pd in the mixture of rhodium isotopes from fission products. Irradiation of natural palladium with fast neutrons has lead to an activity that may only be attributed to 1 10rh. Neither its half life nor its decay energy have been possible to determine accurately. (Author) 1 refs

  13. Electrochemical and mass variation behaviour of rhodium oxide electrodes prepared by the polymeric precursor method

    International Nuclear Information System (INIS)

    Santos, M.C.; Oliveira, R.T.S.; Pereira, E.C.; Bulhoes, L.O.S.

    2005-01-01

    This paper describes an investigation of the charging processes of Rh 2 O 3 electrodes in acidic medium using Electrochemical Quartz Crystal Microbalance. The Rh 2 O 3 was prepared by the Pechini method. The microstructural characterization of the rhodium oxide was performed using Scanning Electron Microscopy and the structure was determined by X-ray diffraction. The Rh 2 O 3 oxidizes at potentials higher than 0.8 V. A mass loss of 60 ng was observed during the anodic sweep. The same amount is gained during the cathodic sweep indicating that the process is reversible. From the mass versus charge plots a slope of 8.5 g mol -1 is calculated. Considering a process that involves a two-electron transfer, the oxidation of Rh 2 O 3 to RhO 2 with the loss of a water molecule (18 g mol -1 ) is proposed

  14. Scanning tunneling microscopy studies of organic monolayers adsorbed on the rhodium(111) crystal surface

    Energy Technology Data Exchange (ETDEWEB)

    Cernota, Paul Davis [Univ. of California, Berkeley, CA (United States)

    1999-08-01

    Scanning Tunneling Microscopy studies were carried out on ordered overlayers on the (111) surface of rhodium. These adsorbates include carbon monoxide (CO), cyclohexane, cyclohexene, 1,4-cyclohexadiene, para-xylene, and meta-xylene. Coadsorbate systems included: CO with ethylidyne, CO with para- and meta-xylene, and para-xylene with meta-xylene. In the case of CO, the structure of the low coverage (2x2) overlayer has been observed. The symmetry of the unit cell in this layer suggests that the CO is adsorbed in the 3-fold hollow sites. There were also two higher coverage surface structures with (√7x√7) unit cells. One of these is composed of trimers of CO and has three CO molecules in each unit cell. The other structure has an additional CO molecule, making a total of four. This extra CO sits on a top site.

  15. Mapping of the radiation field of a mammography equipment using molybdenum and rhodium filters

    International Nuclear Information System (INIS)

    Barreira, Jacqueline S.; Campos, Daniela; Vivolo, Vitor

    2014-01-01

    The use of X rays for diagnostic radiology is very common and important to Medicine, including mammographic diagnosis focusing decreasing of the doses applied to the patients and preserving high quality of the diagnostic image. A quality control program of the irradiation systems it is very necessary. The Instruments Calibration Laboratory (LCI) of IPEN perform calibration in dosemeters used in radiation dosimetry (in diagnostic radiology) for many years. The objective of that paper is determining the point of greatest intensity of the beam issued by the mammography equipment. Exposures were made with filters Rhodium and Molybdenum. That mapping is important before applied a routine quality control program of the mammography equipment and the calibration of instruments in the diagnosis. (author)

  16. Hydroformylation and kinetics of 1-hexene over ruthenium, cobalt and rhodium zerolite catalysts

    International Nuclear Information System (INIS)

    Wang, C.; Wei, W.

    1989-01-01

    In this paper, six kinds of catalysts were prepared by cation exchange with rhodium, ruthenium and cobalt chloropentaamino dichoride and zeolites. Effects such as support materials, PPH 3 to metal ratio, reaction temperature, total pressure, H 2 /CO ratio, reaction time and solvents have been investigated in an autoclave. The most favorable results of 1-hexene hydroformylation were obtained in the temperature range 100-150 degrees C at a pressure of 5.0MPa (H 2 /CO=1:1) and the addition of free PPh 3 . The bimetallic catalysts showed high catalytic activing for hydroformylation because of the synergistic effect of bimetallic systems. This paper reports the results of experiments and catalysts characterization by means of IR and XRD spectroscopy

  17. Bifunctional rhodium intercalator conjugates as mismatch-directing DNA alkylating agents.

    Science.gov (United States)

    Schatzschneider, Ulrich; Barton, Jacqueline K

    2004-07-21

    A conjugate of a DNA mismatch-specific rhodium intercalator, containing the bulky chrysenediimine ligand, and an aniline mustard has been prepared, and targeting of mismatches in DNA by this conjugate has been examined. The preferential alkylation of mismatched over fully matched DNA is found by a mobility shift assay at concentrations where untethered organic mustards show little reaction. The binding site of the Rh intercalator was determined by DNA photocleavage, and the position of covalent modification was established on the basis of the enhanced depurination associated with N-alkylation. The site-selective alkylation at mismatched DNA renders these conjugates useful tools for the covalent tagging of DNA base pair mismatches and new chemotherapeutic design.

  18. An investigation of models of rhodium emitter used in self-powered neutron detector

    International Nuclear Information System (INIS)

    Borisenko, V.I.; Piontkovskij, Yu.F.; Goranchuk, V.V.

    2017-01-01

    he paper presents the results of MCNP simulation of the self-powered neutron detector (SPND) signal formation as a result of emitter nuclei activation under the irradiation with neutrons generated in the fuel assemblies. To account for the non-uniformity of emitter burnup along the radius, its model was divided radially into 10 layers of equal thickness. It has been shown that the main contribution of about 88 % of SPND signal is provided by the four peripheral emitter layers. The contribution of different parts of emitter to the SPND signal formation throughout the lifetime of the SPND in the In-Core Monitoring System was found. Simulation results allow us to determine the SPND signal when the spectral characteristics of the neutron flux at the detector location change during the fuel campaign. The study has investigated and proposed a SPND model with the higher neutron sensitivity even though a smaller amount of expensive rhodium is used.

  19. Mathematical model of rhodium self-powered detectors and algorithms for correction of their time delay

    International Nuclear Information System (INIS)

    Bur'yan, V.I.; Kozlova, L.V.; Kuzhil', A.S.; Shikalov, V.F.

    2005-01-01

    The development of algorithms for correction of self-powered neutron detector (SPND) inertial is caused by necessity to increase the fast response of the in-core instrumentation systems (ICIS). The increase of ICIS fast response will permit to monitor in real time fast transient processes in the core, and in perspective - to use the signals of rhodium SPND for functions of emergency protection by local parameters. In this paper it is proposed to use mathematical model of neutron flux measurements by means of SPND in integral form for creation of correction algorithms. This approach, in the case, is the most convenient for creation of recurrent algorithms for flux estimation. The results of comparison for estimation of neutron flux and reactivity by readings of ionization chambers and SPND signals, corrected by proposed algorithms, are presented [ru

  20. Dimerisation, rhodium complex formation and rearrangements of N-heterocyclic carbenes of indazoles

    Directory of Open Access Journals (Sweden)

    Zong Guan

    2014-04-01

    Full Text Available Deprotonation of indazolium salts at low temperatures gives N-heterocyclic carbenes of indazoles (indazol-3-ylidenes which can be trapped as rhodium complexes (X-ray analysis. In the absence of Rh, the indazol-3-ylidenes spontaneously dimerize under ring cleavage of one of the N,N-bonds and ring closure to an indazole–indole spiro compound which possesses an exocyclic imine group. The E/Z isomers of the imines can be separated by column chromatography when methanol is used as eluent. We present results of a single crystal X-ray analysis of one of the E-isomers, which equilibrate in solution as well as in the solid state. Heating of the indazole–indole spiro compounds results in the formation of quinazolines by a ring-cleavage/ring-closure sequence (X-ray analysis. Results of DFT calculations are presented.

  1. Optimization of Rhodium-Based Catalysts for Mixed Alcohol Synthesis – 2012 Progress Report

    Energy Technology Data Exchange (ETDEWEB)

    Gerber, Mark A.; Gray, Michel J.; Albrecht, Karl O.; Thompson, Becky L.

    2012-11-01

    Pacific Northwest National Laboratory has been conducting research to investigate the feasibility of producing mixed alcohols from biomass-derived synthesis gas (syngas). In recent years, this research has primarily involved the further development of catalysts containing rhodium and manganese based on the results of earlier catalyst screening tests. Testing continued in FY 2012 to further improve the Ir-promoted RhMn catalysts on both silica and carbon supports for producing mixed oxygenates from synthesis gas. This testing re-examined selected alternative silica and carbon supports to follow up on some uncertainties in the results with previous test results. Additional tests were conducted to further optimize the total and relative concentrations of Rh, Mn, and Ir, and to examine selected promoters and promoter combinations based on earlier results. To establish optimum operating conditions, the effects of the process pressure and the feed gas composition also were evaluated.

  2. Rhodium Nanoparticle-mesoporous Silicon Nanowire Nanohybrids for Hydrogen Peroxide Detection with High Selectivity

    Science.gov (United States)

    Song, Zhiqian; Chang, Hucheng; Zhu, Weiqin; Xu, Chenlong; Feng, Xinjian

    2015-01-01

    Developing nanostructured electrocatalysts, with low overpotential, high selectivity and activity has fundamental and technical importance in many fields. We report here rhodium nanoparticle and mesoporous silicon nanowire (RhNP@mSiNW) hybrids for hydrogen peroxide (H2O2) detection with high electrocatalytic activity and selectivity. By employing electrodes that loaded with RhNP@mSiNW nanohybrids, interference caused from both many electroactive substances and dissolved oxygen were eliminated by electrochemical assaying at an optimal potential of +75 mV. Furthermore, the electrodes exhibited a high detection sensitivity of 0.53 μA/mM and fast response (< 5 s). This high-performance nanohybrid electrocatalyst has great potential for future practical application in various oxidase-base biosensors. PMID:25588953

  3. Highly Stereoselective Synthesis of Cyclopentanes bearing Four Stereocenters by a Rhodium Carbene–Initiated Domino Sequence

    Science.gov (United States)

    Parr, Brendan T.; Davies, Huw M. L.

    2014-01-01

    Stereoselective synthesis of a cyclopentane nucleus by convergent annulations constitutes a significant challenge for synthetic chemists. Though a number of biologically relevant cyclopentane natural products are known, more often than not, the cyclopentane core is assembled in a stepwise fashion due to lack of efficient annulation strategies. Herein, we report the rhodium-catalyzed reactions of vinyldiazoacetates with (E)-1,3-disubstituted 2-butenols generate cyclopentanes, containing four new stereogenic centers with very high levels of stereoselectivity (99% ee, >97 : 3 dr). The reaction proceeds by a carbene–initiated domino sequence consisting of five distinct steps: rhodium–bound oxonium ylide formation, [2,3]-sigmatropic rearrangement, oxy-Cope rearrangement, enol–keto tautomerization, and finally an intramolecular carbonyl ene reaction. A systematic study is presented detailing how to control chirality transfer in each of the four stereo-defining steps of the cascade, consummating in the development of a highly stereoselective process. PMID:25082301

  4. Ionic Liquids as Solvents for Rhodium and Platinum Catalysts Used in Hydrosilylation Reaction

    Directory of Open Access Journals (Sweden)

    Witold Zielinski

    2016-08-01

    Full Text Available A group of imidazolium and pyridinium based ionic liquids has been synthetized, and their ability to dissolve and activate the catalysts used in hydrosilylation reaction of 1-octane and 1,1,1,3,5,5,5-heptamethyltrisiloxane was investigated. An organometallic catalyst as well as inorganic complexes of platinum and rhodium dissolved in ionic liquids were used, forming liquid solutions not miscible with the substrates or with the products of the reaction. The results show that application of such a simple biphasic catalytic system enables reuse of ionic liquid phase with catalysts in multiple reaction cycles reducing the costs and decreasing the amount of catalyst needed per mole of product.

  5. Impurities determination in precious metals like rhodium, palladium and platinum by neutron activation without separation

    International Nuclear Information System (INIS)

    May, S.; Piccot, D.; Pinte, G.

    1978-01-01

    The possibilities of the method explored using an installation of gamma or X ray spectrometry of good performance. The irradiations were realized in the reactors EL.3 (flux approximately 6.10 12 n.cm -2 .s -1 ) and Osiris (flux > 10 14 n.cm -2 .s -1 ) of the CEN Saclay. In rhodium the presence of iridium limits the analysis possibilities. However gold, silver and platinum are easily determined, just as the other elements (As, Br, Cl, Co, Mn, Na, Sb). In platinum it is possible to determine the elements of long period, especially antimony, silver, cobalt, iridium, tantalum and zinc. As for palladium the principal impurities are gold, silver and ruthenium for what is of precious metals and particularly zinc among the other metals. For the three matrices considered the detection limits of a certain number of elements are indicated [fr

  6. Exploring cellular uptake of iron oxide nanoparticles associated with rhodium citrate in breast cancer cells.

    Science.gov (United States)

    Chaves, Natalia L; Estrela-Lopis, Irina; Böttner, Julia; Lopes, Cláudio Ap; Guido, Bruna C; de Sousa, Aparecido R; Báo, Sônia N

    2017-01-01

    Nanocarriers have the potential to improve the therapeutic index of currently available drugs by improving their efficacy and achieving therapeutic steady-state levels over an extended period. The association of maghemite-rhodium citrate (MRC) nanoparticles (NPs) has the potential to increase specificity of the cytotoxic action. However, the interaction of these NPs with cells, their uptake mechanism, and subcellular localization need to be elucidated. This work evaluates the uptake mechanism of MRC NPs in metastatic and nonmetastatic breast cancer-cell models, comparing them to a nontumor cell line. MRC NPs uptake in breast cancer cells was more effective than in normal cells, with regard to both the amount of internalized material and the achievement of more strategic intracellular distribution. Moreover, this process occurred through a clathrin-dependent endocytosis pathway with different basal expression levels of this protein in the cell lines tested.

  7. Water resistant rhodium plated reflectors for use in the DIRC BaBar Cherenkov detector

    CERN Document Server

    Benkebil, M; Plaszczynski, S; Schune, M H; Wormser, G

    2000-01-01

    Early simulation studies showed that reflectors mounted on the photomultipliers would be useful for the DIRC BaBar Cherenkov detector, showing a gain between 20% and 30% in the number of Cherenkov photons. The proof of principle for these reflectors has been obtained during the beam test of a large-scale prototype of the DIRC detector. An extensive R and D has been conducted in order to test different metallization procedures. Indeed, the challenge was to find a metallization technique which can resist the pure de-ionized water (>15 M OMEGA) up to 10 yr. The chosen technology was rhodium plated reflectors. During the first BaBar cosmic run, the measured performance confirmed the results of the simulation, the prototype-II and the R and D.

  8. Highly enantioselective rhodium(I)-catalyzed carbonyl carboacylations initiated by C-C bond activation.

    Science.gov (United States)

    Souillart, Laetitia; Cramer, Nicolai

    2014-09-01

    The lactone motif is ubiquitous in natural products and pharmaceuticals. The Tishchenko disproportionation of two aldehydes, a carbonyl hydroacylation, is an efficient and atom-economic access to lactones. However, these reaction types are limited to the transfer of a hydride to the accepting carbonyl group. The transfer of alkyl groups enabling the formation of CC bonds during the ester formation would be of significant interest. Reported herein is such asymmetric carbonyl carboacylation of aldehydes and ketones, thus affording complex bicyclic lactones in excellent enantioselectivities. The rhodium(I)-catalyzed transformation is induced by an enantiotopic CC bond activation of a cyclobutanone and the formed rhodacyclic intermediate reacts with aldehyde or ketone groups to give highly functionalized lactones. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Selective rhodium-catalyzed reduction of tertiary amides in amino acid esters and peptides.

    Science.gov (United States)

    Das, Shoubhik; Li, Yuehui; Bornschein, Christoph; Pisiewicz, Sabine; Kiersch, Konstanze; Michalik, Dirk; Gallou, Fabrice; Junge, Kathrin; Beller, Matthias

    2015-10-12

    Efficient reduction of the tertiary amide bond in amino acid derivatives and peptides is described. Functional group selectivity has been achieved by applying a commercially available rhodium precursor and bis(diphenylphosphino)propane (dppp) ligand together with phenyl silane as a reductant. This methodology allows for specific reductive derivatization of biologically interesting peptides and offers straightforward access to a variety of novel peptide derivatives for chemical biology studies and potential pharmaceutical applications. The catalytic system tolerates a variety of functional groups including secondary amides, ester, nitrile, thiomethyl, and hydroxy groups. This convenient hydrosilylation reaction proceeds at ambient conditions and is operationally safe because no air-sensitive reagents or highly reactive metal hydrides are needed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Conclusive evidence on the mechanism of the rhodium-mediated decyanative borylation.

    Science.gov (United States)

    Esteruelas, Miguel A; Oliván, Montserrat; Vélez, Andrea

    2015-09-30

    The stoichiometric reactions proposed in the mechanism of the rhodium-mediated decyanative borylation have been performed and all relevant intermediates isolated and characterized including their X-ray structures. Complex RhCl{xant(P(i)Pr2)2} (1, xant(P(i)Pr2)2 = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene) reacts with bis(pinacolato)diboron (B2pin2), in benzene, to give the rhodium(III) derivative RhHCl(Bpin){xant(P(i)Pr2)2} (4) and PhBpin. The reaction involves the oxidative addition of B2pin2 to 1 to give RhCl(Bpin)2{xant(P(i)Pr2)2}, which eliminates ClBpin generating Rh(Bpin){xant(P(i)Pr2)2} (2). The reaction of the latter with the solvent yields PhBpin and the monohydride RhH{xant(P(i)Pr2)2} (6), which adds the eliminated ClBpin. Complex 4 and its catecholboryl counterpart RhHCl(Bcat){xant(P(i)Pr2)2} (7) have also been obtained by oxidative addition of HBR2 to 1. Complex 2 is the promoter of the decyanative borylation. Thus, benzonitrile and 4-(trifluoromethyl)benzonitrile insert into the Rh-B bond of 2 to form Rh{C(R-C6H4)═NBpin}{xant(P(i)Pr2)2} (R = H (8), p-CF3 (9)), which evolve into the aryl derivatives RhPh{xant(P(i)Pr2)2} (3) and Rh(p-CF3-C6H4){xant(P(i)Pr2)2} (10), as a result of the extrusion of CNBpin. The reactions of 3 and 10 with B2pin2 yield the arylBpin products and regenerate 2.

  11. Bibliographies on radiation chemistry. 9. Metal ions and complexes. Part A: Cobalt, rhodium, iridium

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, M Z; Ross, A B

    1986-01-01

    The one-electron oxidation and reduction of metal ions and complexes can yield species in unusual oxidation states, and ligand-radicals coordinated to the central metal. These often unstable species can be mechanistically important intermediates in thermal, photochemical, and electrochemical reactions involving metal-containing substances. Their generation via radiolysis provides an alternate means of characterizing them using kinetic and spectroscopic techniques. We hope these bibliographies on the radiation chemistry of metal ions and complexes, presented according to periodic groups, will prove useful to researchers in metallo-redox chemistry. These bibliographies contain only primary literature sources; reviews are not included. However, a list of general review articles on the radiation chemistry of metal ions and complexes is presented here in the first section which covers cobalt, rhodium and iridium, Group 9 in the new IUPAC notation. Additional parts of the bibliography are planned, covering other periodic groups. Part A of the bibliography was prepared by a search of the Radiation Chemistry Data Center Bibliographic Data Base (RCDCbib) through January 1986 for papers on rhodium, iridium and cobalt compounds, and radiolysis (both continuous and pulsed). Papers in which the use of metal compounds was incidental to the primary objective of the study were excluded. Excluded also were publications in unrefereed and obscure sources such as meeting proceedings, internal reports, dissertations, and patents. The majority of the studies in the resultant compilation deal with experiments performed on solutions, mainly aqueous, although a substantial fraction is devoted to solid-state esr measurements. The references are listed in separate sections for each of the metals, and are presented in approximate chronological order.

  12. Rhodium target preparation from homemade chloride plating baths used for the industrial cyclotron production of palladium-L03

    International Nuclear Information System (INIS)

    Sadeghi, M.; Van den Winkel, P.; Afarideh, H.; Haji-Saeid, M.; Syrafi Nafis, H.

    2004-01-01

    Purpose: To avoid acquisition problems of commercially available western rhodium plating solutions in developing countries, a new plating/recovery cycle for Rh-103 electroplated target material (1 g Rh per target) used for the industrial cyclotron production of Pd-103 was developed. Rhodium chloride plating solutions can be prepared by dissolution of the analytical grade compound or from rhodium recovery solutions obtained after electrosolubilisation of irradiated targets and extraction of palladium. Methods: The technology involves the selective removal of the copper target backing of an irradiated target in concentrated nitric acid using a homemade flow-through stripper. The resulting rhodium fragments are dissolved in a constant-volume (40 ml), homemade graphite centrifugal ac-electrodissolution mini-reactor operating at 90 degree C, 2 A.cm-2 and 1000-rpm rotation speed. The system allows time-controlled 99 % solubilisation of up to 3g rhodium (as fragments, powder or small pieces of wire) in less than 3 hours when 12 N hydrochloric acid is applied. Upon solvent-solvent extraction of the non-carrier added Pd-103 from the resulting HCI solution; the following procedure can be used for the simultaneous preparation of 4 targets showing a surface area of 11.69 cm 2 and a physical thickness of 48 Um. Dissolve an amount of hydrated RhC13 containing 2.8 g of rhodium in 400 ml of water. Alternatively, the filtered (0.45 μm filter) combined recovery solutions containing the same weight of rhodium can be evaporated to near dryness (350 degree C at the start, 150 degree C near the end) and residue taken up (gentle stirring, 50 degree C) in 400 ml of distilled water, After filtration, a stress reducing agent (sulfamic acid) is added and the pH sodium hydroxide. Upon make up to volume (450 ml) adjusted to the optimum value (pH = 2) with and preheating to 40 degree C, the resulting solution is introduced in a cylindrical home-made constant-volume, 4- target plating vessel

  13. Steady-state thermal hydraulic analysis and flow channel blockage accident analysis of JRR-3 silicide core

    International Nuclear Information System (INIS)

    Kaminaga, Masanori

    1997-03-01

    JRR-3 is a light water moderated and cooled, beryllium and heavy water reflected pool type research reactor using low enriched uranium (LEU) plate-type fuels. Its thermal power is 20 MW. The core conversion program from uranium-aluminum (UAl x -Al) dispersion type fuel (aluminide fuel) to uranium-silicon-aluminum (U 3 Si 2 -Al) dispersion type fuel (silicide fuel) is currently conducted at the JRR-3. This report describes about the steady-state thermal hydraulic analysis results and the flow channel blockage accident analysis result. In JRR-3, there are two operation mode. One is high power operation mode up to 20 MW, under forced convection cooling using the primary and the secondary cooling systems. The other is low power operation mode up to 200 kW, under natural circulation cooling between the reactor core and the reactor pool without the primary and the secondary cooling systems. For the analysis of the flow channel blockage accident, COOLOD code was used. On the other hand, steady-state thermal hydraulic analysis for both of the high power operation mode under forced convection cooling and low power operation under natural convection cooling, COOLOD-N2 code was used. From steady-state thermal hydraulic analysis results of both forced and natural convection cooling, fuel temperature, minimum DNBR etc. meet the design criteria and JRR-3 LEU silicide core has enough safety margin under normal operation conditions. Furthermore, flow channel blockage accident analysis results show that one channel flow blockage accident meet the safety criteria for accident conditions which have been established for JRR-3 LEU silicide core. (author)

  14. Initial Stages in the Rhodium(III)-Catalyzed C-H Bond Activation of Primary Alcohols in Aqueous Solution

    DEFF Research Database (Denmark)

    Eriksen, J.; Monsted, L.; Monsted, O.

    2010-01-01

    The mechanism of the catalytic HID exchange in primary alcohol substrates derived from aldopentoses, promoted by a macrocyclic rhodium(III) complex, has been shown to occur by a reversible redox reaction that gives aldehyde and a rhodium hydride complex. Hydride exchange in the latter complex...... promotes the introduction of solvent hydrogen in the primary alcohol formed by the reverse reaction. The hydride complex has been crystallographically characterized as a trifluoromethanesulfonate salt that contains the trans-[Rh(cycb)(H)(OH2)](2+) (cycb = rac-5,5,7,12,12,14-hexamethyl-1......,4,8,11-tetraazacyclotetradecane) cation. The hydride complex is stable for extended periods of time in acidic solution in the absence of oxidants. In basic solutions a series of base-catalyzed reactions take place to yield ultimately the same mixture of [Rh(cycb)(OH)(2)](+) isomers as produced by base hydrolysis of the trans...

  15. A Mixed-Ligand Chiral Rhodium(II) Catalyst Enables the Enantioselective Total Synthesis of Piperarborenine B.

    Science.gov (United States)

    Panish, Robert A; Chintala, Srinivasa R; Fox, Joseph M

    2016-04-11

    A novel, mixed-ligand chiral rhodium(II) catalyst, Rh2(S-NTTL)3(dCPA), has enabled the first enantioselective total synthesis of the natural product piperarborenine B. A crystal structure of Rh2(S-NTTL)3(dCPA) reveals a "chiral crown" conformation with a bulky dicyclohexylphenyl acetate ligand and three N-naphthalimido groups oriented on the same face of the catalyst. The natural product was prepared on large scale using rhodium-catalyzed bicyclobutanation/ copper-catalyzed homoconjugate addition chemistry in the key step. The route proceeds in ten steps with an 8% overall yield and 92% ee. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. On the interdiffusion in multilayered silicide coatings for the vanadium-based alloy V-4Cr-4Ti

    Energy Technology Data Exchange (ETDEWEB)

    Chaia, N., E-mail: nabil.chaia@usp.br [Escola de Engenharia de Lorena, Universidade de São Paulo, Pólo Urbo-Industrial Gleba AI-6, 12602-810 Lorena, SP (Brazil); Portebois, L., E-mail: leo.portebois@univ-lorraine.fr [Université de Lorraine, Institut Jean Lamour, UMR7198, Boulevard des Aiguillettes, BP70239, 54506 Vandoeuvre-lès-Nancy, Cedex (France); Mathieu, S., E-mail: stephane.mathieu@univ-lorraine.fr [Université de Lorraine, Institut Jean Lamour, UMR7198, Boulevard des Aiguillettes, BP70239, 54506 Vandoeuvre-lès-Nancy, Cedex (France); David, N., E-mail: nicolas.david@univ-lorraine.fr [Université de Lorraine, Institut Jean Lamour, UMR7198, Boulevard des Aiguillettes, BP70239, 54506 Vandoeuvre-lès-Nancy, Cedex (France); Vilasi, M., E-mail: michel.vilasi@univ-lorraine.fr [Université de Lorraine, Institut Jean Lamour, UMR7198, Boulevard des Aiguillettes, BP70239, 54506 Vandoeuvre-lès-Nancy, Cedex (France)

    2017-02-15

    To provide protection against corrosion at high temperatures, silicide diffusion coatings were developed for the V-4Cr-4Ti alloy, which can be used as the fuel cladding in next-generation sodium-cooled fast breeder reactors. The multilayered coatings were prepared by halide-activated pack cementation using MgF{sub 2} as the transport agent and pure silicon (high activity) as the master alloy. Coated pure vanadium and coated V-4Cr-4Ti alloy were studied and compared as substrates. In both cases, the growth of the silicide layers (V{sub 3}Si, V{sub 5}Si{sub 3}, V{sub 6}Si{sub 5} and VSi{sub 2}) was controlled exclusively by solid-state diffusion, and the growth kinetics followed a parabolic law. Wagner's analysis was adopted to calculate the integrated diffusion coefficients for all silicides. The estimated values of the integrated diffusion coefficients range from approximately 10{sup −9} to 10{sup −13} cm{sup 2} s{sup −1}. Then, a diffusion-based numerical approach was used to evaluate the growth and consumption of the layers when the coated substrates were exposed at critical temperatures. The estimated lifetimes of the upper VSi{sub 2} layer were 400 h and 280 h for pure vanadium and the V-4Cr-4Ti alloy, respectively. The result from the numeric simulation was in good agreement with the layer thicknesses measured after aging the coated samples at 1150 °C under vacuum. - Highlights: • The pack cementation technique is implemented to study interdiffusion in V/Si and V-4Cr-4Ti/Si couples. • Interdiffusion coefficients of vanadium silicides were experimentally determined within the range 1100–1250 °C. • For either V/Si or V-4Cr-4Ti/Si couples, the VSi{sub 2} layer has the highest growth rate. • The Cr and Ti alloying elements mainly modified the V{sub 5}Si{sub 3} and V{sub 6}Si{sub 5} growth rate. • Numerical simulation allows for a confident assessment of the VSi{sub 2} coating lifetime on V-4Cr-4Ti.

  17. Enantioselective synthesis of chiral 3-aryl-1-indanones through rhodium-catalyzed asymmetric intramolecular 1,4-addition.

    Science.gov (United States)

    Yu, Yue-Na; Xu, Ming-Hua

    2013-03-15

    Enantioselective synthesis of potentially useful chiral 3-aryl-1-indanones was achieved through a rhodium-catalyzed asymmetric intramolecular 1,4-addition of pinacolborane chalcone derivatives using extraordinary simple MonoPhos as chiral ligand under relatively mild conditions. This novel protocol offers an easy access to a wide variety of enantioenriched 3-aryl-1-indanone derivatives in high yields (up to 95%) with excellent enantioselectivities (up to 95% ee).

  18. Enantioselective Construction of 3-Hydroxypiperidine Scaffolds by Sequential Action of Light and Rhodium upon N-Allylglyoxylamides.

    Science.gov (United States)

    Ishida, Naoki; Nečas, David; Masuda, Yusuke; Murakami, Masahiro

    2015-06-15

    3-Hydroxypiperidine scaffolds were enantioselectively constructed in an atom-economical way by sequential action of light and rhodium upon N-allylglyoxylamides. In a formal sense, the allylic C-H bond was selectively cleaved and enantioselectively added across the ketonic carbonyl group with migration of the double bond (carbonyl-ene-type reaction). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Sequential rhodium/palladium catalysis: enantioselective formation of dihydroquinolinones in the presence of achiral and chiral ligands.

    Science.gov (United States)

    Zhang, Lei; Qureshi, Zafar; Sonaglia, Lorenzo; Lautens, Mark

    2014-12-08

    Compatible combinations of achiral and chiral ligands can be used in rhodium/palladium catalysis to achieve highly enantioselective domino reactions. The difference in rates of catalysis and minimal effects of ligand interference confer control in the domino sequence. The "all-in-one" 1,4-conjugate arylation and C-N cross-coupling through sequential Rh/Pd catalysis provides access to enantioenriched dihydroquinolinone building blocks. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Applying Adjacent Hyperbolas to Calculation of the Upper Limit of the Periodic Table of Elements, with Use of Rhodium

    Directory of Open Access Journals (Sweden)

    Khazan A.

    2011-01-01

    Full Text Available In the earlier study (Khazan A. Upper Limit in Mendeleev’s Periodic Table — Ele- ment No. 155. 2nd ed., Svenska fysikarkivet, Stockholm, 2010 the author showed how Rhodium can be applied to the hyperbolic law of the Periodic Table of Elements in or- der to calculate, with high precision, all other elements conceivable in the Table. Here we obtain the same result, with use of fraction linear functions (adjacent hyperbolas.

  1. Construction of axial chirality by rhodium-catalyzed asymmetric dehydrogenative Heck coupling of biaryl compounds with alkenes.

    Science.gov (United States)

    Zheng, Jun; You, Shu-Li

    2014-11-24

    Enantioselective construction of axially chiral biaryls by direct C-H bond functionalization reactions has been realized. Novel axially chiral biaryls were synthesized by the direct C-H bond olefination of biaryl compounds, using a chiral [Cp*Rh(III)] catalyst, in good to excellent yields and enantioselectivities. The obtained axially chiral biaryls were found as suitable ligands for rhodium-catalyzed asymmetric conjugate additions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Rhodium(III)-catalyzed three-component reaction of imines, alkynes, and aldehydes through C-H activation.

    Science.gov (United States)

    Huang, Ji-Rong; Song, Qiang; Zhu, Yu-Qin; Qin, Liu; Qian, Zhi-Yong; Dong, Lin

    2014-12-15

    An efficient rhodium(III)-catalyzed tandem three-component reaction of imines, alkynes and aldehydes through CH activation has been developed. High stereo- and regioselectivity, as well as good yields were obtained in most cases. The simple and atom-economical approach offers a broad scope of substrates, providing polycyclic skeletons with potential biological properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Applying Adjacent Hyperbolas to Calculation of the Upper Limit of the Periodic Table of Elements, with Use of Rhodium

    Directory of Open Access Journals (Sweden)

    Khazan A.

    2011-01-01

    Full Text Available In the earlier study (Khazan A. Upper Limit in Mendeleev's Periodic Table - Element No.155. 2nd ed., Svenska fysikarkivet, Stockholm, 2010 the author showed how Rhodium can be applied to the hyperbolic law of the Periodic Table of Elements in order to calculate, with high precision, all other elements conceivable in the Table. Here we obtain the same result, with use of fraction linear functions (adjacent hyperbolas.

  4. The liquid-liquid extraction of chloro-(trichlorostannato)-rhodium(I/III) and -ruthenium (II) complexes from dilute hydrochloric acid into 4-methylpentan-2-one

    International Nuclear Information System (INIS)

    Wyrley-Birch, J.M.

    1984-10-01

    The effect of stannous chloride on the liquid-liquid extraction of rhodium and ruthenium from hydrochloric acid solutions into 4-methyl-pentan-2-one (MIBK)/hexane mixtures was studied in detail. Stannous chloride concentrations were found to considerably increase the efficiency of the extraction of rhodium and ruthenium into the organic phase. Chloro-(trichlorostannato)-rhodium (I/III) complexes were formed at room temperature. The rate of chloro-(trichlorostannato)-ruthenium (II) complex formation was extremely slow at room temperature, but increased on heating of the aqueous solutions. The amount of rhodium and ruthenium extracted into the organic phase depend on the Sn(II):M molar ratio, the HCl, H sup(+) and Cl sup(-) concentrations, as well as the equilibration time. A 119 Sn NMR study of the MIBK extracts, showed that the stoichiometry of the chloro-(trichlorostannato)-rhodium (I/III) complexes extracted into the organic phase was dependent on the Sn(II):Rh(III) molar ratio as well as the HCl, H sup(+) and Cl sup(-) concentrations in the aqueous phase. The predominant species observed in the organic phase from HCl solutions containing Sn(II):Rh(III) ratios >= 5:1, was shown to be an hydrido complex having the form [RhH(SnCl 3 ) 4 Cl] 3 sup(-) or [RhH(SnCl 3 ) 4 ]2 sup(-). An essentially quantitative separation of rhodium and ruthenium was achieved utilising the variation in the rates of rhodium-tin and ruthenium-tin complex formation

  5. Catalytic wet oxidation of ammonia solution: Activity of the nanoscale platinum-palladium-rhodium composite oxide catalyst

    International Nuclear Information System (INIS)

    Hung, C.-M.

    2009-01-01

    Aqueous solutions of 400-1000 mg/L of ammonia were oxidized in a trickle-bed reactor (TBR) in this study of nanoscale platinum-palladium-rhodium composite oxide catalysts, which were prepared by the co-precipitation of H 2 PtCl 6 , Pd(NO 3 ) 3 and Rh(NO 3 ) 3 . Hardly any of the dissolved ammonia was removed by wet oxidation in the absence of any catalyst, whereas about 99% of the ammonia was reduced during wet oxidation over nanoscale platinum-palladium-rhodium composite oxide catalysts at 503 K in an oxygen partial pressure of 2.0 MPa. A synergistic effect exists in the nanoscale platinum-palladium-rhodium composite structure, which is the material with the highest ammonia reduction activity. The nanometer-sized particles were characterized by TEM, XRD and FTIR. The effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid hourly space velocity of under 9 h -1 in the wet catalytic processes

  6. Catalytic wet oxidation of ammonia solution: Activity of the nanoscale platinum-palladium-rhodium composite oxide catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Hung, C.-M. [Department of Industry Engineering and Management, Yung-Ta Institute of Technology and Commerce, 316 Chung-shan Road, Linlo, Pingtung 909, Taiwan (China)], E-mail: hungcm1031@gmail.com

    2009-04-15

    Aqueous solutions of 400-1000 mg/L of ammonia were oxidized in a trickle-bed reactor (TBR) in this study of nanoscale platinum-palladium-rhodium composite oxide catalysts, which were prepared by the co-precipitation of H{sub 2}PtCl{sub 6}, Pd(NO{sub 3}){sub 3} and Rh(NO{sub 3}){sub 3}. Hardly any of the dissolved ammonia was removed by wet oxidation in the absence of any catalyst, whereas about 99% of the ammonia was reduced during wet oxidation over nanoscale platinum-palladium-rhodium composite oxide catalysts at 503 K in an oxygen partial pressure of 2.0 MPa. A synergistic effect exists in the nanoscale platinum-palladium-rhodium composite structure, which is the material with the highest ammonia reduction activity. The nanometer-sized particles were characterized by TEM, XRD and FTIR. The effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid hourly space velocity of under 9 h{sup -1} in the wet catalytic processes.

  7. Catalytic wet oxidation of ammonia solution: activity of the nanoscale platinum-palladium-rhodium composite oxide catalyst.

    Science.gov (United States)

    Hung, Chang-Mao

    2009-04-15

    Aqueous solutions of 400-1000 mg/L of ammonia were oxidized in a trickle-bed reactor (TBR) in this study of nanoscale platinum-palladium-rhodium composite oxide catalysts, which were prepared by the co-precipitation of H(2)PtCl(6), Pd(NO(3))(3) and Rh(NO(3))(3). Hardly any of the dissolved ammonia was removed by wet oxidation in the absence of any catalyst, whereas about 99% of the ammonia was reduced during wet oxidation over nanoscale platinum-palladium-rhodium composite oxide catalysts at 503 K in an oxygen partial pressure of 2.0 MPa. A synergistic effect exists in the nanoscale platinum-palladium-rhodium composite structure, which is the material with the highest ammonia reduction activity. The nanometer-sized particles were characterized by TEM, XRD and FTIR. The effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid hourly space velocity of under 9 h(-1) in the wet catalytic processes.

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

    Science.gov (United States)

    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.

  9. The determination, by atomic-absorption spectrophotometry using electrothermal atomization, of platinum, palladium, rhodium, ruthenium, and iridium

    International Nuclear Information System (INIS)

    Haines, J.; Robert, R.V.D.

    1982-01-01

    A method that involves measurement by atomic-absorption spectrophotometry using electrothermal atomization has been developed for the determination of trace quantities of platinum, palladium, rhodium, ruthenium, and iridium in mineralogical samples. The elements are separated and concentrated by fusion, nickel sulphide being used as the collector, and the analyte elements are measured in the resulting acid solution. An organic extraction procedure was found to offer no advantages over the proposed method. Mutual interferences between the five platinum-group metals examined, as well as interferences from gold, silver, and nickel were determined. The accuracy of the measurement was established by the analysis of a platinum-ore reference material. The lower limits of determination of each of the analyte elements in a sample material are as follows: platinum 1,6μg/l, palladium 0,2μg/1, rhodium 0,5μg/l, ruthenium 3μg/l, and iridium 2,5μg/l. The relative standard deviations range from 0,05 for rhodium to 0.08 for iridium. The method, which is described in detail in the Appendix, is applicable to the determination of these elements in ores, tailings, and geological materials in which the total concentration of the noble metals is less than 1g/t

  10. In Situ Structure-Function Studies of Oxide Supported Rhodium Catalysts by Combined Energy Dispersive XAFS and DRIFTS Spectroscopies

    International Nuclear Information System (INIS)

    Evans, John; Dent, Andrew J.; Diaz-Moreno, Sofia; Fiddy, Steven G.; Jyoti, Bhrat; Tromp, Moniek; Newton, Mark A.

    2007-01-01

    The techniques of energy dispersive EXAFS (EDE), diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) and mass spectrometry (MS) have been combined to study the structure and function of an oxide supported metal catalyst, namely 5 wt% Rh/Al2O3. Using a FreLoN camera as the EDE detector and a rapid-scanning IR spectrometer, experiments could be performed with a repetition rate of 50 ms. The results show that the nature of the rhodium centers is a function of the partial pressures of the reacting gases (CO and NO) and also temperature. This combination of gases oxidizes metallic rhodium particles to Rh(CO)2 at room temperature. The proportion of the rhodium adopting this site increases as the temperature is raised (up to 450 K). Above that temperature the dicarbonyl decomposes and the metal reclusters. Once this condition is met, catalysis ensues. Gas switching techniques show that at 573 K with NO in excess, the clusters can be oxidized rapidly to afford a linear nitrosyl complex; re-exposure to CO also promotes reclustering and the CO adopts terminal (atop) and bridging (2-fold) sites

  11. Photocatalytic carbon dioxide reduction with rhodium-based catalysts in solution and heterogenized within metal-organic frameworks.

    Science.gov (United States)

    Chambers, Matthew B; Wang, Xia; Elgrishi, Noémie; Hendon, Christopher H; Walsh, Aron; Bonnefoy, Jonathan; Canivet, Jérôme; Quadrelli, Elsje Alessandra; Farrusseng, David; Mellot-Draznieks, Caroline; Fontecave, Marc

    2015-02-01

    The first photosensitization of a rhodium-based catalytic system for CO2 reduction is reported, with formate as the sole carbon-containing product. Formate has wide industrial applications and is seen as valuable within fuel cell technologies as well as an interesting H2 -storage compound. Heterogenization of molecular rhodium catalysts is accomplished via the synthesis, post-synthetic linker exchange, and characterization of a new metal-organic framework (MOF) Cp*Rh@UiO-67. While the catalytic activities of the homogeneous and heterogeneous systems are found to be comparable, the MOF-based system is more stable and selective. Furthermore it can be recycled without loss of activity. For formate production, an optimal catalyst loading of ∼10 % molar Rh incorporation is determined. Increased incorporation of rhodium catalyst favors thermal decomposition of formate into H2 . There is no precedent for a MOF catalyzing the latter reaction so far. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Loading rate and test temperature effects on fracture of in situ niobium silicide-niobium composites

    International Nuclear Information System (INIS)

    Rigney, J.D.; Lewandowski, J.J.

    1996-01-01

    Arc cast, extruded, and heat-treated in situ composites of niobium silicide (Nb 5 Si 3 ) intermetallic with niobium phases (primary--Nb p and secondary--Nb s ) exhibited high fracture resistance in comparison to monolithic Nb 5 Si 3 . In toughness tests conducted at 298 K and slow applied loading rates, the fracture process proceeded by the microcracking of the Nb 5 Si 3 and plastic deformation of the Nb p and Nb s phases, producing resistance-curve behavior and toughnesses of 28 MPa√m with damage zone lengths less than 500 microm. The effects of changes in the Nb p yield strength and fracture behavior on the measured toughnesses were investigated by varying the loading rates during fracture tests at both 77 and 298 K. Quantitative fractography was utilized to completely characterize each fracture surface created at 298 K in order to determine the type of fracture mode (i.e., dimpled, cleavage) exhibited by the Nb p . Specimens tested at either higher loading rates or lower test temperatures consistently exhibited a greater amount of cleavage fracture in the Nb p , while the Nb s always remained ductile. However, the fracture toughness values determined from experiments spanning six orders of magnitude in loading rate at 298 and 77 K exhibited little variation, even under conditions when the majority of Nb p phases failed by cleavage at 77 K. The changes in fracture mode with increasing loading rate and/or decreasing test temperature and their effects on fracture toughness are rationalized by comparison to existing theoretical models

  13. Effects of ball milling on microstructures and thermoelectric properties of higher manganese silicides

    International Nuclear Information System (INIS)

    Chen, Xi; Shi, Li; Zhou, Jianshi; Goodenough, John B.

    2015-01-01

    Highlights: • The already low κ L of HMS can be suppressed further by decreasing the grain size. • The ball milling process can lead to the formation of secondary MnSi and W/C-rich phases. • The formation of the MnSi ad W/C rich phases is found to suppress the thermoelectric power factor. - Abstract: Bulk nanostructured higher manganese silicide (HMS) samples with different grain size are prepared by melting, subsequent ball milling (BM), and followed by spark plasma sintering (SPS). The effects of BM time on the microstructures and thermoelectric properties of these samples are investigated. It is found that BM effectively reduces the grain size to about 90 nm in the sample after SPS, which leads to a decrease in both the thermal conductivity and electrical conductivity. By prolonging the BM time, MnSi and tungsten/carbon-rich impurity phases are formed due to the impact-induced decomposition of HMS and contamination from the tungsten carbide jar and balls during the BM, respectively. These impurities result in a reduced Seebeck coefficient and increased thermal conductivity above room temperature. The measured size-dependent lattice thermal conductivities agree qualitatively with the reported calculation results based on a combined phonon and diffuson model. The size effects are found to be increasingly significant as temperature decreases. Because of the formation of the impurity phases and a relatively large grain size, the ZT values are not improved in the ball-milled HMS samples. These findings suggest the need of alternative approaches for the synthesis of pure HMS with further reduced grain size and controlled impurity doping in order to enhance the thermoelectric figure-of-merit of HMS via nanostructuring

  14. Development of silicide coating over molybdenum based refractory alloy and its characterization

    International Nuclear Information System (INIS)

    Chakraborty, S.P.; Banerjee, S.; Sharma, I.G.; Suri, A.K.

    2010-01-01

    Molybdenum based refractory alloys are potential candidate materials for structural applications in high temperature compact nuclear reactors and fusion reactors. However, these alloys being highly susceptible to oxidation in air or oxygen at elevated temperature, undergoes severe losses from highly volatile molybdenum trioxide species. Present investigation, therefore, examines the feasibility of development of silicide type of coating over molybdenum base TZM alloy shape (Mo > 99 wt.%) using pack cementation coating technique. TZM alloy was synthesized in this laboratory from oxide intermediates of MoO 2 , TiO 2 and ZrO 2 in presence of requisite amount of carbon, by alumino-thermic reduction smelting technique. The arc melted and homogenized samples of TZM alloy substrate was then embedded in the chosen and intimately mixed pack composition consisting of inert matrix (Al 2 O 3 ), coating powder (Si) and activator (NH 4 Cl) taken in the judicious proportion. The sealed charge packs contained in an alumina crucible were heated at temperatures of 1000 o C for 8-16 h heating cycle to develop the coating. The coating phase was confirmed to be of made of MoSi 2 by XRD analysis. The morphology of the coating was studied by SEM characterization. It had revealed that the coating was diffusion bonded where Si from coating diffused inward and Mo from TZM substrate diffused outward to form the coating. The coating was found to be resistant to oxidation when tested in air up to 1200 o C. A maximum 100 μm of coating thickness was achieved on each side of the substrate.

  15. Fuel loading and homogeneity analysis of HFIR design fuel plates loaded with uranium silicide fuel

    International Nuclear Information System (INIS)

    Blumenfeld, P.E.

    1995-08-01

    Twelve nuclear reactor fuel plates were analyzed for fuel loading and fuel loading homogeneity by measuring the attenuation of a collimated X-ray beam as it passed through the plates. The plates were identical to those used by the High Flux Isotope Reactor (HFIR) but were loaded with uranium silicide rather than with HFIR's uranium oxide fuel. Systematic deviations from nominal fuel loading were observed as higher loading near the center of the plates and underloading near the radial edges. These deviations were within those allowed by HFIR specifications. The report begins with a brief background on the thermal-hydraulic uncertainty analysis for the Advanced Neutron Source (ANS) Reactor that motivated a statistical description of fuel loading and homogeneity. The body of the report addresses the homogeneity measurement techniques employed, the numerical correction required to account for a difference in fuel types, and the statistical analysis of the resulting data. This statistical analysis pertains to local variation in fuel loading, as well as to ''hot segment'' analysis of narrow axial regions along the plate and ''hot streak'' analysis, the cumulative effect of hot segment loading variation. The data for all twelve plates were compiled and divided into 20 regions for analysis, with each region represented by a mean and a standard deviation to report percent deviation from nominal fuel loading. The central regions of the plates showed mean values of about +3% deviation, while the edge regions showed mean values of about -7% deviation. The data within these regions roughly approximated random samplings from normal distributions, although the chi-square (χ 2 ) test for goodness of fit to normal distributions was not satisfied

  16. Electronic structure and bonding in the ternary silicide YNiSi3

    International Nuclear Information System (INIS)

    Sung, Gi Hong; Kang, Dae Bok

    2003-01-01

    An analysis of the electronic structure and bonding in the ternary silicide YNiSi 3 is made, using extended Hueckel tight-binding calculations. The YNiSi 3 structure consists of Ni-capped Si 2 dimer layers and Si zigzag chains. Significant bonding interactions are present between the silicon atoms in the structure. The oxidation state formalism of (Y 3+ )(Ni 0 )(Si 3 ) 3- for YNiSi 3 constitutes a good starting point to describe its electronic structure. Si atoms receive electrons form the most electropositive Y in YNiSi 3 , and Ni 3d and Si 3p states dominate below the Fermi level. There is an interesting electron balance between the two Si and Ni sublattices. Since the π orbitals in the Si chain and the Ni d and s block levels are almost completely occupied, the charge balance for YNiSi 3 can be rewritten as (Y 3+ )(Ni 2- )(Si 2- )(Si-Si) + , making the Si 2 layers oxidized. These results suggest that the Si zigzag chain contains single bonds and the Si 2 double layer possesses single bonds within a dimer with a partial double bond character. Stronger Si-Si and Ni-Si bonding interactions are important for giving stability to the structure, while essentially no metal-metal bonding exists at all. The 2D metallic behavior of this compound is due to the Si-Si interaction leading to dispersion of the several Si 2 π bands crossing the Fermi level in the plane perpendicular to the crystallographic b axis

  17. Rate Theory Modeling and Simulation of Silicide Fuel at LWR Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Yinbin [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Ye, Bei [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Hofman, Gerard [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Yacout, Abdellatif [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Gamble, Kyle [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation; Mei, Zhi-Gang [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division

    2016-08-29

    As a promising candidate for the accident tolerant fuel (ATF) used in light water reactors (LWRs), the fuel performance of uranium silicide (U3Si2) at LWR conditions needs to be well understood. In this report, rate theory model was developed based on existing experimental data and density functional theory (DFT) calculations so as to predict the fission gas behavior in U3Si2 at LWR conditions. The fission gas behavior of U3Si2 can be divided into three temperature regimes. During steady-state operation, the majority of the fission gas stays in intragranular bubbles, whereas the dominance of intergranular bubbles and fission gas release only occurs beyond 1000 K. The steady-state rate theory model was also used as reference to establish a gaseous swelling correlation of U3Si2 for the BISON code. Meanwhile, the overpressurized bubble model was also developed so that the fission gas behavior at LOCA can be simulated. LOCA simulation showed that intragranular bubbles are still dominant after a 70 second LOCA, resulting in a controllable gaseous swelling. The fission gas behavior of U3Si2 at LWR conditions is benign according to the rate theory prediction at both steady-state and LOCA conditions, which provides important references to the qualification of U3Si2 as a LWR fuel material with excellent fuel performance and enhanced accident tolerance.

  18. Synthesis and characterization of β-phase iron silicide nano-particles by chemical reduction

    International Nuclear Information System (INIS)

    Sen, Sabyasachi; Gogurla, Narendar; Banerji, Pallab; Guha, Prasanta K.; Pramanik, Panchanan

    2015-01-01

    Graphical abstract: - Highlights: • β-FeSi 2 nano-particle was synthesized by reducing with Mg and by diluting with MgO. • XRD profile shows the iron di-silicide phase to be semiconducting β-FeSi 2 . • HRTEM and FESEM images indicate the β-FeSi 2 average particle size to be 60–70 nm. • Absorption, reflectance and PL spectroscopy show band gap to be direct 0.87 eV. • Nano-β-FeSi 2 is p-type with hole density of 4.38 × 10 18 cm −3 and mobility 8.9 cm 2 /V s. - Abstract: Nano-particles of β-FeSi 2 have been synthesized by chemical reduction of a glassy phase of [Fe 2 O 3 , 4SiO 2 ] by Mg-metal where MgO is used as diluent to prevent the agglomeration of nano crystallites into micro-particles and also act as a negative catalyst for the formation of other phases. The sample is characterized by XRD, FESEM, HRTEM, EDX, ultra-violet-visible-infrared and PL spectroscopy and electronic properties have been investigated by Hall measurement. XRD profile shows that the synthesized powder consists of purely β-FeSi 2 semiconducting phase. The average crystallite size of β-FeSi 2 is determined to be around 65.4 nm from XRD peaks as well as from FESEM also. The optical absorption and PL spectroscopy shows that synthesized β-FeSi 2 phase is a direct band gap semiconductor with a value of 0.87 eV. Hall measurements show that β-FeSi 2 nano-particles is p-type with hole concentration of 4.38 × 10 18 cm −3 and average hole mobility of 8.9 cm 2 /V s at 300 K

  19. Effects of ball milling on microstructures and thermoelectric properties of higher manganese silicides

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xi [Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712 (United States); Shi, Li, E-mail: lishi@mail.utexas.edu [Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712 (United States); Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78712 (United States); Zhou, Jianshi; Goodenough, John B. [Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712 (United States); Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78712 (United States)

    2015-08-25

    Highlights: • The already low κ{sub L} of HMS can be suppressed further by decreasing the grain size. • The ball milling process can lead to the formation of secondary MnSi and W/C-rich phases. • The formation of the MnSi ad W/C rich phases is found to suppress the thermoelectric power factor. - Abstract: Bulk nanostructured higher manganese silicide (HMS) samples with different grain size are prepared by melting, subsequent ball milling (BM), and followed by spark plasma sintering (SPS). The effects of BM time on the microstructures and thermoelectric properties of these samples are investigated. It is found that BM effectively reduces the grain size to about 90 nm in the sample after SPS, which leads to a decrease in both the thermal conductivity and electrical conductivity. By prolonging the BM time, MnSi and tungsten/carbon-rich impurity phases are formed due to the impact-induced decomposition of HMS and contamination from the tungsten carbide jar and balls during the BM, respectively. These impurities result in a reduced Seebeck coefficient and increased thermal conductivity above room temperature. The measured size-dependent lattice thermal conductivities agree qualitatively with the reported calculation results based on a combined phonon and diffuson model. The size effects are found to be increasingly significant as temperature decreases. Because of the formation of the impurity phases and a relatively large grain size, the ZT values are not improved in the ball-milled HMS samples. These findings suggest the need of alternative approaches for the synthesis of pure HMS with further reduced grain size and controlled impurity doping in order to enhance the thermoelectric figure-of-merit of HMS via nanostructuring.

  20. Significant enhancement in thermoelectric performance of nanostructured higher manganese silicides synthesized employing a melt spinning technique.

    Science.gov (United States)

    Muthiah, Saravanan; Singh, R C; Pathak, B D; Avasthi, Piyush Kumar; Kumar, Rishikesh; Kumar, Anil; Srivastava, A K; Dhar, Ajay

    2018-01-25

    The limited thermoelectric performance of p-type Higher Manganese Silicides (HMS) in terms of their low figure-of-merit (ZT), which is far below unity, is the main bottle-neck for realising an efficient HMS based thermoelectric generator, which has been recognized as the most promising material for harnessing waste-heat in the mid-temperature range, owing to its thermal stability, earth-abundant and environmentally friendly nature of its constituent elements. We report a significant enhancement in the thermoelectric performance of nanostructured HMS synthesized using rapid solidification by optimizing the cooling rates during melt-spinning followed by spark plasma sintering of the resulting melt-spun ribbons. By employing this experimental strategy, an unprecedented ZT ∼ 0.82 at 800 K was realized in spark plasma sintered 5 at% Al-doped MnSi 1.73 HMS, melt spun at an optimized high cooling rate of ∼2 × 10 7 K s -1 . This enhancement in ZT represents a ∼25% increase over the best reported values thus far for HMS and primarily originates from a nano-crystalline microstructure consisting of a HMS matrix (20-40 nm) with excess Si (3-9 nm) uniformly distributed in it. This nanostructure, resulting from the high cooling rates employed during the melt-spinning of HMS, introduces a high density of nano-crystallite boundaries in a wide spectrum of nano-scale dimensions, which scatter the low-to-mid-wavelength heat-carrying phonons. This abundant phonon scattering results in a significantly reduced thermal conductivity of ∼1.5 W m -1 K -1 at 800 K, which primarily contributes to the enhancement in ZT.

  1. Evaluation of steam corrosion and water quenching behavior of zirconium-silicide coated LWR fuel claddings

    Science.gov (United States)

    Yeom, Hwasung; Lockhart, Cody; Mariani, Robert; Xu, Peng; Corradini, Michael; Sridharan, Kumar

    2018-02-01

    This study investigates steam corrosion of bulk ZrSi2, pure Si, and zirconium-silicide coatings as well as water quenching behavior of ZrSi2 coatings to evaluate its feasibility as a potential accident-tolerant fuel cladding coating material in light water nuclear reactor. The ZrSi2 coating and Zr2Si-ZrSi2 coating were deposited on Zircaloy-4 flats, SiC flats, and cylindrical Zircaloy-4 rodlets using magnetron sputter deposition. Bulk ZrSi2 and pure Si samples showed weight loss after the corrosion test in pure steam at 400 °C and 10.3 MPa for 72 h. Silicon depletion on the ZrSi2 surface during the steam test was related to the surface recession observed in the silicon samples. ZrSi2 coating (∼3.9 μm) pre-oxidized in 700 °C air prevented substrate oxidation but thin porous ZrO2 formed on the coating. The only condition which achieved complete silicon immobilization in the oxide scale in aqueous environments was the formation of ZrSiO4 via ZrSi2 coating oxidation in 1400 °C air. In addition, ZrSi2 coatings were beneficial in enhancing quenching heat transfer - the minimum film boiling temperature increased by 6-8% in the three different environmental conditions tested. During repeated thermal cycles (water quenching from 700 °C to 85 °C for 20 s) performed as a part of quench tests, no spallation and cracking was observed and the coating prevented oxidation of the underlying Zircaloy-4 substrate.

  2. Hot wire chemical vapor deposition: limits and opportunities of protecting the tungsten catalyzer from silicide with a cavity

    International Nuclear Information System (INIS)

    Frigeri, P.A.; Nos, O.; Bengoechea, S.; Frevert, C.; Asensi, J.M.; Bertomeu, J.

    2009-01-01

    Hot Wire Chemical Vapor Deposition (HW-CVD) is one of the most promising techniques for depositing the intrinsic microcrystalline silicon layer for the production of micro-morph solar cells. However, the silicide formation at the colder ends of the tungsten wire drastically reduces the lifetime of the catalyzer, thus limiting its industrial exploitation. A simple but interesting strategy to decrease the silicide formation is to hide the electrical contacts of the catalyzer in a long narrow cavity which reduces the probability of the silane molecules to reach the colder ends of the wire. In this paper, the working mechanism of the cavity is elucidated. Measurements of the thickness profile of the silicon deposited in the internal walls of the cavity have been compared with those predicted using a simple diffusion model based on the assumption of Knudsen flow. A lifetime study of the protected and unprotected wires has been carried out. The different mechanisms which determine the deterioration of the catalyzer have been identified and discussed.

  3. Silicide induced surface defects in FePt nanoparticle fcc-to-fct thermally activated phase transition

    International Nuclear Information System (INIS)

    Chen, Shu; Lee, Stephen L.; André, Pascal

    2016-01-01

    Magnetic nanoparticles (MnPs) are relevant to a wide range of applications including high density information storage and magnetic resonance imaging to name but a few. Among the materials available to prepare MnPs, FePt is attracting growing attention. However, to harvest the strongest magnetic properties of FePt MnPs, a thermal annealing is often required to convert face-centered cubic as synthesized nPs into its tetragonal phase. Rarely addressed are the potential side effects of such treatments on the magnetic properties. In this study, we focus on the impact of silica shells often used in strategies aiming at overcoming MnP coalescence during the thermal annealing. While we show that this shell does prevent sintering, and that fcc-to-fct conversion does occur, we also reveal the formation of silicide, which can prevent the stronger magnetic properties of fct-FePt MnPs from being fully realised. This report therefore sheds lights on poorly investigated and understood interfacial phenomena occurring during the thermal annealing of MnPs and, by doing so, also highlights the benefits of developing new strategies to avoid silicide formation.

  4. Silicide induced surface defects in FePt nanoparticle fcc-to-fct thermally activated phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Shu; Lee, Stephen L. [School of Physics and Astronomy, SUPA, University of St Andrews, St Andrews KY16 9SS (United Kingdom); André, Pascal, E-mail: pjpandre@riken.jp [School of Physics and Astronomy, SUPA, University of St Andrews, St Andrews KY16 9SS (United Kingdom); RIKEN, Wako 351-0198 (Japan); Department of Physics, CNRS-Ewha International Research Center (CERC), Ewha W. University, Seoul 120-750 (Korea, Republic of)

    2016-11-01

    Magnetic nanoparticles (MnPs) are relevant to a wide range of applications including high density information storage and magnetic resonance imaging to name but a few. Among the materials available to prepare MnPs, FePt is attracting growing attention. However, to harvest the strongest magnetic properties of FePt MnPs, a thermal annealing is often required to convert face-centered cubic as synthesized nPs into its tetragonal phase. Rarely addressed are the potential side effects of such treatments on the magnetic properties. In this study, we focus on the impact of silica shells often used in strategies aiming at overcoming MnP coalescence during the thermal annealing. While we show that this shell does prevent sintering, and that fcc-to-fct conversion does occur, we also reveal the formation of silicide, which can prevent the stronger magnetic properties of fct-FePt MnPs from being fully realised. This report therefore sheds lights on poorly investigated and understood interfacial phenomena occurring during the thermal annealing of MnPs and, by doing so, also highlights the benefits of developing new strategies to avoid silicide formation.

  5. Surface effect on the electronic and the magnetic properties of rock-salt alkaline-earth metal silicides

    International Nuclear Information System (INIS)

    Bialek, Beata; Lee, Jaeil

    2011-01-01

    An all electron ab-initio method was employed to study the electronic and the magnetic properties of the (001) surface of alkaline-earth metal silicides, CaSi, SrSi, and BaSi, in the rock-salt structure. The three compounds retain their ferromagnetic metallic properties at the surface. Due to the surface effects, the magnetism of the topmost layer is changed as compared with the bulk. This is a short-range effect. In CaSi, the magnetism of the surface layer is noticeably reduced, as compared with the bulk: magnetic moments (MMs) on both Ca and Si atoms are reduced. In SrSi (001), the polarization of electrons in the surface atoms is similar to that in the bulk atoms, and the values of MMs on the component atoms in the topmost layer do not change as much as in CaSi. In BaSi (001), the magnetic properties of Si surface atoms are enhanced slightly, and the magnetism of Ba atoms is not affected considerably by the surface effect. The calculated densities of states confirm the short-range effect of the surface on the electronic properties of the metal silicides.

  6. Ytterbium silicide (YbSi{sub 2}). A promising thermoelectric material with a high power factor at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Tanusilp, Sora-at; Ohishi, Yuji; Muta, Hiroaki [Graduate School of Engineering, Osaka University, Suita, Osaka (Japan); Yamanaka, Shinsuke [Graduate School of Engineering, Osaka University, Suita, Osaka (Japan); Research Institute of Nuclear Engineering, University of Fukui, Tsuruga (Japan); Nishide, Akinori [Graduate School of Engineering, Osaka University, Suita, Osaka (Japan); Center for Exploratory Research, Research and Development Group, Hitachi, Ltd., Kokubunji, Tokyo (Japan); Hayakawa, Jun [Center for Exploratory Research, Research and Development Group, Hitachi, Ltd., Kokubunji, Tokyo (Japan); Kurosaki, Ken [Graduate School of Engineering, Osaka University, Suita, Osaka (Japan); Research Institute of Nuclear Engineering, University of Fukui, Tsuruga (Japan); JST, PRESTO, Kawaguchi, Saitama (Japan)

    2018-02-15

    Metal silicide-based thermoelectric (TE) materials have attracted attention in the past two decades, because they are less toxic, with low production cost and high chemical stability. Here, we study the TE properties of ytterbium silicide YbSi{sub 2} with a specific layered structure and the mixed valence state of Yb{sup 2+} and Yb{sup 3+}. YbSi{sub 2} exhibits large Seebeck coefficient, S, accompanied by high electrical conductivity, σ, leading to high power factor, S{sup 2}σ, of 2.2 mW m{sup -1} K{sup -2} at room temperature, which is comparable to those of state-of-the-art TE materials such as Bi{sub 2}Te{sub 3} and PbTe. Moreover, YbSi{sub 2} exhibits high Grueneisen parameter of 1.57, which leads to relatively low lattice thermal conductivity, κ{sub lat}, of 3.0 W m{sup -1} K{sup -1} at room temperature. The present study reveals that YbSi{sub 2} can be a good candidate of TE materials working near room temperature. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Technical report: technical development on the silicide plate-type fuel experiment at nuclear safety research reactor

    International Nuclear Information System (INIS)

    Yanagisawa, Kazuaki; Soyama, Kazuhiko; Ichikawa, Hiroki

    1991-08-01

    According to a reduction of fuel enrichment from 45 w/o 235 U to 20 w/o, an aluminide plate-type fuel used currently in the domestic research and material testing reactors will be replaced by a silicide plate-type one. One of the major concern arisen from this alternation is to understand the fuel behavior under simulated reactivity initiated accident (RIA) conditions, this is strongly necessary from the safety and licensing point of view. The in-core RIA experiments are, therefore, carried out at Nuclear Safety Research Reactor (NSRR) in Japan Atomic Energy Research Institute (JAERI). The silicide plate-type fuel consisted of the ternary alloy of U-Al-Si as a meat with uranium density up to 4.8 g/cm 3 having thickness by 0.51 mm and the binary alloy of Al-3%Mg as a cladding by thickness of 0.38 mm. Comparison of the physical properties of this metallic plate fuel with the UO 2 -zircaloy fuel rod used conventionally in commercial light water reactors shows that the heat conductivity of the former is of the order of about 13 times greater than the latter, however the melting temperature is only one-half (1570degC). Prior to in-core RIA experiments, there were some difficulties lay in our technical path. This report summarized the technical achievements obtained through our four years work. (J.P.N.)

  8. High-temperature oxidation of silicide-aluminide layer on the TiAl6V4 alloy prepared by liquid-phase siliconizing

    Czech Academy of Sciences Publication Activity Database

    Kubatík, Tomáš František

    2016-01-01

    Roč. 50, č. 2 (2016), s. 257-261 ISSN 1580-2949 Institutional support: RVO:61389021 Keywords : TiAl6V4 * silicides * high-temperature oxidation * liquid-phase silicon izing Subject RIV: JG - Metallurgy Impact factor: 0.436, year: 2016

  9. Phase analyses of silicide or nitride coated U–Mo and U–Mo–Ti particle dispersion fuel after out-of-pile annealing

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Woo Jeong [Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong, Daejeon 305-353 (Korea, Republic of); Palancher, Hervé [CEA, DEN, DEC, F-13108 Saint Paul Lez Durance Cedex (France); Ryu, Ho Jin, E-mail: hojinryu@kaist.ac.kr [Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong, Daejeon 305-701 (Korea, Republic of); Park, Jong Man; Nam, Ji Min [Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong, Daejeon 305-353 (Korea, Republic of); Bonnin, Anne [CEA, DEN, DEC, F-13108 Saint Paul Lez Durance Cedex (France); ESRF, 6, rue J. Horowitz, F-38000 Grenoble Cedex (France); Honkimäki, Veijo [ESRF, 6, rue J. Horowitz, F-38000 Grenoble Cedex (France); Charollais, François [CEA, DEN, DEC, F-13108 Saint Paul Lez Durance Cedex (France); Lemoine, Patrick [CEA, DEN, DISN, 91191 Gif sur Yvette (France)

    2014-03-15

    Highlights: • Silicide or nitride layers were coated on atomized U–Mo or U–Mo–Ti powder. • The constituent phases after annealing were identified through high-energy XRD. • U{sub 3}Si{sub 5} and U{sub 4}Mo(Mo{sub x}Si{sub 1−x})Si{sub 2} were identified in the silicide coating layers. • UN was identified for U–Mo particles and UN and U{sub 4}N{sub 7} formed on U–Mo–Ti particles. -- Abstract: The coating of silicide or nitride layers on U–7 wt%Mo or U–7 wt%Mo–1 wt%Ti particles has been proposed for the minimization of the interaction phase growth in U–Mo/Al dispersion fuel during irradiation. Out-of-pile annealing tests show reduced inter-diffusion by forming silicide or nitride protective layers on U–Mo and U–Mo–Ti particles. To characterize the constituent phases of the coated layers on U–Mo and U–Mo–Ti particles and the interaction phases of coated U–Mo and U–Mo–Ti particle dispersed Al matrix fuel, synchrotron X-ray diffraction experiments have been performed. It was identified that silicide coating layers consisted mainly of U{sub 3}Si{sub 5} and U{sub 4}Mo(Mo{sub x}Si{sub 1−x})Si{sub 2}, and nitride coating layers were composed of mainly UN and U{sub 4}N{sub 7}. The interaction phases obtained after annealing of coated U–Mo and U–Mo–Ti particle dispersion samples were identical to those found in U–Mo/Al–Si and U–Mo/Al systems. Nitride-coated particles showed less interaction formation than silicide-coated particles after annealing at 580 °C for 1 h owing to the higher susceptibility to breakage of the silicide coating layers during hot extrusion.

  10. Synthesis and structures of a pincer-type rhodium(iii) complex: reactivity toward biomolecules.

    Science.gov (United States)

    Milutinović, Milan M; Bogojeski, Jovana V; Klisurić, Olivera; Scheurer, Andreas; Elmroth, Sofi K C; Bugarčić, Živadin D

    2016-10-04

    A novel rhodium(iii) complex [Rh III (H 2 L tBu )Cl 3 ] (1) (H 2 L tBu = 2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)pyridine) containing a pincer type, tridentate nitrogen-donor chelate system was synthesized. Single crystal X-ray structure analysis revealed that 1 crystallizes in the orthorhombic space group Pbcn with a = 20.7982(6), b = 10.8952(4), c = 10.9832(4) Å, V = 2488.80(15) Å 3 , and eight molecules in the unit cell. The rhodium center in the complex [Rh III (H 2 L tBu )Cl 3 ] (1) is coordinated in a slightly distorted octahedral geometry by the tridentate N,N,N-donor and three chloro ligands, adopting a mer arrangement with an essentially planar ligand skeleton. Due to the tridentate coordination of the N,N,N-donor, the central nitrogen atom N1 is located closer to the Rh III center. The reactivity of the synthesized complex toward small biomolecules (l-methionine (l-Met), guanosine-5'-monophosphate (5'-GMP), l-histidine (l-His) and glutathione (GSH)) and to a series of duplex DNAs and RNA was investigated. The order of reactivity of the studied small biomolecules is: 5'-GMP > GSH > l-Met > l-His. Duplex RNA reacts faster with the [Rh III (H 2 L tBu )Cl 3 ] complex than duplex DNA, while shorter duplex DNA (15mer GG) reacts faster compared with 22mer GG duplex DNA. In addition, a higher reactivity is achieved with a DNA duplex with a centrally located GG-sequence than with a 22GTG duplex DNA, in which the GG-sequence is separated by a T base. Furthermore, the interaction of this metal complex 1 with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) was examined by absorption (UV-Vis) and emission spectral studies (EthBr displacement studies). Overall, the studied complex exhibited good DNA and BSA interaction ability.

  11. Thermal expansion and elastic moduli of the silicide based intermetallic alloys Ti5Si3(X) and Nb5Si3

    International Nuclear Information System (INIS)

    Zhang, L.; Wu, J.

    1997-01-01

    Silicides are among those potential candidates for high temperature application because of their high melting temperature, low density and good oxidation resistance. Recent interest is focused on molybdenum silicides and titanium silicides. Extensive investigation has been carried out on MoSi 2 , yet comparatively less work was performed on titanium silicides such as Ti 5 Si 3 and Ti 3 and TiSi 2 which are of lower density than MoSi 2 . Fundamental understanding of the titanium silicides' properties for further evaluation their potential for practical application are thus needed. The thermal expansion coefficients and elastic moduli of intermetallic compounds are two properties important for evaluation as a first step. The thermal expansion determines the possible stress that might arise during cooling for these high melting point compounds, which is crucial to the preparation of defect free specimens; and the elastic moduli are usually reflections of the cohesion in crystal. In Frommeyer's work and some works afterwards, the coefficients of thermal expansion were measured on both polycrystalline and single crystal Ti 5 Si 3 . The elastic modulus of polycrystalline Ti 5 Si 3 was measured by Frommeyer and Rosenkranz. However, in the above works, the referred Ti 5 Si 3 was the binary one, no alloying effect has been reported on this matter. Moreover, the above parameters (coefficient of thermal expansion and elastic modulus) of Nb 5 Si 3 remain unreported so far. In this paper, the authors try to extend the knowledge of alloyed Ti 5 Si 3 compounds with Nb and Cr additions. Results on the coefficients of thermal expansion and elastic moduli of Ti 5 Si 3 compounds and Nb 5 Si 3 are presented and the discussion is focused on the alloying effect

  12. Effects of (Al,Ge) double doping on the thermoelectric properties of higher manganese silicides

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xi; Salta, Daniel; Zhang, Libin [Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712 (United States); Weathers, Annie [Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States); Zhou, Jianshi; Goodenough, John B.; Shi, Li [Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712 (United States); Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States)

    2013-11-07

    Experiments and analysis have been carried out to investigate the effects of Al and (Al,Ge) doping on the microstructure and thermoelectric properties of polycrystalline higher manganese silicide (HMS) samples, which were prepared by solid-state reaction, ball milling, and followed by spark plasma sintering. It has been found that Al doping effectively increases the hole concentration, which leads to an increase in the electrical conductivity and power factor. By introducing the second dopant Ge into Al-doped HMS, the electrical conductivity is increased, and the Seebeck coefficient is decreased as a result of further increased hole concentration. The peak power factor is found to occur at a hole concentration between 1.8 × 10{sup 21} and 2.2 × 10{sup 21} cm{sup −3} measured at room temperature. The (Al,Ge)-doped HMS samples show lower power factors owing to their higher hole concentrations. The mobility of Mn(Al{sub 0.0035}Ge{sub y}Si{sub 0.9965-y}){sub 1.8} with y = 0.035 varies approximately as T{sup −3/2} above 200 K, suggesting acoustic phonon scattering is the dominant scattering mechanism. The thermal conductivity of HMS does not change appreciably by Al or (Al,Ge) doping. The maximum ZT of (Al,Ge)-doped HMS is 0.57 at 823 K, which is similar to the highest value found in the Al-doped HMS samples. The ZT values were reduced in the Mn(Al{sub 0.0035}Ge{sub y}Si{sub 0.9965-y}){sub 1.8} samples with high Ge concentration of y = 0.025 and 0.035, because of reduced power factor. In addition, a two-band model was employed to show that the hole contribution to the thermal conductivity dominates the bipolar and electron contributions for all samples from 300 to 823 K and accounts for about 12% of the total thermal conductivity at about 800 K.

  13. Effects of (Al,Ge) double doping on the thermoelectric properties of higher manganese silicides

    International Nuclear Information System (INIS)

    Chen, Xi; Salta, Daniel; Zhang, Libin; Weathers, Annie; Zhou, Jianshi; Goodenough, John B.; Shi, Li

    2013-01-01

    Experiments and analysis have been carried out to investigate the effects of Al and (Al,Ge) doping on the microstructure and thermoelectric properties of polycrystalline higher manganese silicide (HMS) samples, which were prepared by solid-state reaction, ball milling, and followed by spark plasma sintering. It has been found that Al doping effectively increases the hole concentration, which leads to an increase in the electrical conductivity and power factor. By introducing the second dopant Ge into Al-doped HMS, the electrical conductivity is increased, and the Seebeck coefficient is decreased as a result of further increased hole concentration. The peak power factor is found to occur at a hole concentration between 1.8 × 10 21 and 2.2 × 10 21  cm −3 measured at room temperature. The (Al,Ge)-doped HMS samples show lower power factors owing to their higher hole concentrations. The mobility of Mn(Al 0.0035 Ge y Si 0.9965-y ) 1.8 with y = 0.035 varies approximately as T −3/2 above 200 K, suggesting acoustic phonon scattering is the dominant scattering mechanism. The thermal conductivity of HMS does not change appreciably by Al or (Al,Ge) doping. The maximum ZT of (Al,Ge)-doped HMS is 0.57 at 823 K, which is similar to the highest value found in the Al-doped HMS samples. The ZT values were reduced in the Mn(Al 0.0035 Ge y Si 0.9965-y ) 1.8 samples with high Ge concentration of y = 0.025 and 0.035, because of reduced power factor. In addition, a two-band model was employed to show that the hole contribution to the thermal conductivity dominates the bipolar and electron contributions for all samples from 300 to 823 K and accounts for about 12% of the total thermal conductivity at about 800 K

  14. Elucidation of structural isomers from the homogeneous rhodium-catalyzed isomerization of vegetable oils.

    Science.gov (United States)

    Andjelkovic, Dejan D; Min, Byungrok; Ahn, Dong; Larock, Richard C

    2006-12-13

    The structural isomers formed by the homogeneous rhodium-catalyzed isomerization of several vegetable oils have been elucidated. A detailed study of the isomerization of the model compound methyl linoleate has been performed to correlate the distribution of conjugated isomers, the reaction kinetics, and the mechanism of the reaction. It has been shown that [RhCl(C8H8)2]2 is a highly efficient and selective isomerization catalyst for the production of highly conjugated vegetable oils with a high conjugated linoleic acid (CLA) content, which is highly desirable in the food industry. The combined fraction of the two major CLA isomers [(9Z,11E)-CLA and (10E,12Z)-CLA] in the overall CLA mixture is in the range from 76.2% to 93.4%. The high efficiency and selectivity of this isomerization method along with the straightforward purification process render this approach highly promising for the preparation of conjugated oils and CLA. Proposed improvements in catalyst recovery and reusability will only make this method more appealing to the food, paint, coating, and polymer industries in the future.

  15. Separation of Hydridocarbonyltris(triphenylphosphine) Rhodium (I) Catalyst Using Solvent Resistant Nano filtration Membrane

    International Nuclear Information System (INIS)

    Razak, N.S.A.; Hilmi Mukhtar; Maizatul, S. Shaharun; Mohd, F. Taha

    2013-01-01

    An investigation was conducted into the nano filtration of rhodium tris(triphenyl-phosphine) [HRh(CO)(PPh3)3] catalyst used in the hydroformylation of olefins. The large size of the catalyst (>400 Da) - relative to other components of the reaction provides the opportunity for a membrane separation based on retention of the catalyst species while permeating the solvent. The compatibility of the solvent-polyimide membrane (STARMEMTM 122 and STARMEMTM 240) combinations was assessed in terms of the membrane stability in solvent plus non-zero solvent flux at 2.0 MPa. The morphology of the membrane was studied by field emission scanning electron microscopy (FESEM). The solvent flux and membrane rejection of HRh(CO)(PPh3)3 was then determined for the catalyst-solvent-membrane combination in a dead-end pressure cell. Good HRh(CO)(PPh3)3 rejection (>0.93) coupled with good solvent fluxes (>72 L/ m 2 h 1 at 2.0 MPa) were obtained in one of the systems tested. The effect of pressure and catalyst concentration on the solvent flux and catalyst rejection was conducted. Increasing pressure substantially improved both solvent flux and catalyst rejection, while increasing catalyst concentration was found to be beneficial in terms of substantial increases in catalyst rejection without significantly affecting the solvent flux. (author)

  16. Enhanced electrocatalytic oxidation of isoniazid at electrochemically modified rhodium electrode for biological and pharmaceutical analysis.

    Science.gov (United States)

    Cheemalapati, Srikanth; Chen, Shen-Ming; Ali, M Ajmal; Al-Hemaid, Fahad M A

    2014-09-01

    A simple and sensitive electrochemical method has been proposed for the determination of isoniazid (INZ). For the first time, rhodium (Rh) modified glassy carbon electrode (GCE) has been employed for the determination of INZ by linear sweep voltammetry technique (LSV). Compared with the unmodified electrode, the proposed Rh modified electrode provides strong electrocatalytic activity toward INZ with significant enhancement in the anodic peak current. Scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM) results reveal the morphology of Rh particles. With the advantages of wide linearity (70-1300μM), good sensitivity (0.139μAμM(-1)cm(-2)) and low detection limit (13μM), this proposed sensor holds great potential for the determination of INZ in real samples. The practicality of the proposed electrode for the detection of INZ in human urine and blood plasma samples has been successfully demonstrated using LSV technique. Through the determination of INZ in commercially available pharmaceutical tablets, the practical applicability of the proposed method has been validated. The recovery results are found to be in good agreement with the labeled amounts of INZ in tablets, thus showing its great potential for use in clinical and pharmaceutical analysis. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Laser cleaning of pulsed laser deposited rhodium films for fusion diagnostic mirrors

    International Nuclear Information System (INIS)

    Uccello, A.; Maffini, A.; Dellasega, D.; Passoni, M.

    2013-01-01

    Highlights: ► Pulsed laser deposition is exploited to produce Rh films for first mirrors. ► Pulsed laser deposition is exploited to produce tokamak-like C contaminants. ► Rh laser damage threshold has been evaluated for infrared pulses. ► Laser cleaning of C contaminated Rh films gives promising results. -- Abstract: In this paper an experimental investigation on the laser cleaning process of rhodium films, potentially candidates to be used as tokamak first mirrors (FMs), from redeposited carbon contaminants is presented. A relevant issue that lowers mirror's performance during tokamak operations is the redeposition of sputtered material from the first wall on their surface. Among all the possible techniques, laser cleaning, in which a train of laser pulses is launched to the surface that has to be treated, is a method to potentially mitigate this problem. The same laser system (Q-switched Nd:YAG laser with a fundamental wavelength of 1064-nm and 7-ns pulses) has been employed with three aims: (i) production by pulsed laser deposition (PLD) of Rh film mirrors, (ii) production by PLD of C deposits with controlled morphology, and (iii) investigation of the laser cleaning method onto C contaminated Rh samples. The evaluation of Rh films laser damage threshold, as a function of fluence and number of pulses, is discussed. Then, the C/Rh films have been cleaned by the laser beam. The exposed zones have been characterized by visual inspection and scanning electron microscopy (SEM), showing promising results

  18. Comparative analysis for the measured and the predicted relative sensitivity of rhodium In core detector

    International Nuclear Information System (INIS)

    Moon, Sang Rae; Cha, Kyoon Ho; Bae, Seong Man

    2012-01-01

    Self-powered neutron detector (SPND) is widely used as in-core flux monitoring in nuclear power plants. OPR1000 has applied a rhodium (Rh) as the emitter of the SPND. The SPND contains a neutron-sensitive metallic emitter surrounded by a ceramic insulator. When capturing a neutron, the Rh will be decayed by emitting some electrons which is crossing the sheath and produce current. This current can be measured externally using pico-ammeter. The sensitivity of detectors is closely related with the geometry and material of the detectors. The lifetime of in-core detector is determined by calculating the relative sensitivity of Rh detector. It is required that the Rh detector should be replaced before the burn-up of Rh detector has reached 66% of its original compositions. To predict Rh detector's relative sensitivity ANC code, advanced nodal code capable of two-dimensional and three-dimensional calculations, is used. It is determined that the Rh detectors should be replaced on the basis of the predicted sensitivity value calculated by ANC code. When evaluating the life of Rh detectors using ANC code, it is assumed that the uncertainty of the sensitivity calculation include the measurement error of 5%. As a result of the analysis of measured and predicted data for the Rh detector's relative sensitivity, it is possible to reduce the assumed uncertainty

  19. Size effects on rhodium nanoparticles related to hydrogen-storage capability.

    Science.gov (United States)

    Song, Chulho; Yang, Anli; Sakata, Osami; Kumara, L S R; Hiroi, Satoshi; Cui, Yi-Tao; Kusada, Kohei; Kobayashi, Hirokazu; Kitagawa, Hiroshi

    2018-06-06

    To unveil the origin of the hydrogen-storage properties of rhodium nanoparticles (Rh NPs), we investigated the electronic and crystal structures of the Rh NPs using various synchrotron based X-ray techniques. Electronic structure studies revealed that the hydrogen-storage capability of Rh NPs could be attributed to their more unoccupied d-DOSs than that of the bulk near the Fermi level. Crystal structure studies indicated that lattice distortion and mean-square displacement increase while coordination number decreases with decreasing particle size and the hydrogen-absorption capability of Rh NPs improves to a greater extent with increased structural disorder in the local structure than with that in the mean structure. The smallest Rh NPs, having the largest structural disorder/increased vacancy spaces and the smallest coordination number, exhibited excellent hydrogen-storage capacity. Finally, from the bond-orientational order analysis, we confirmed that the localized disordering is distributed more over the surface part than the core part and hydrogen can be trapped on the surface part of Rh NPs which increases with a decrease in NP diameter.

  20. Manifestation of external size reduction effects on the yield point of nanocrystalline rhodium using nanopillars approach

    International Nuclear Information System (INIS)

    Alshehri, Omar; Yavuz, Mustafa; Tsui Ting

    2013-01-01

    In this study, pure rhodium was fabricated and mechanically investigated at the nanoscale for the first time. The nanopillars approach was employed to study the effects of size on the yield point. Nanopillars with different diameters were fabricated using electroplating followed by uniaxial compression tests. Scanning electron microscopy (SEM) was used as a quality control technique by imaging the pillars before and after compression to ensure the absence of cracks, buckling, barrelling or any other problems. Transmission electron microscopy and SEM were used as microstructural characterization techniques. Due to substrate-induced effects, only the plastic region of the stress–strain curves were investigated, and it was revealed that the yield point increases with size reduction up to certain limit, then decreases with further reduction of the nanopillar size (diameter). The later weakening effect is consistent with the literature, which demonstrates the reversed size effect (the failure of the plasticity theory) in nanocrystalline metals, i.e. smaller is weaker. In this study, however, the effect of size reduction is not only weakening, but is strengthening-then-weakening, which the authors believe is the true behavior of nanocrystalline materials.

  1. Reactivity Control of Rhodium Cluster Ions by Alloying with Tantalum Atoms.

    Science.gov (United States)

    Mafuné, Fumitaka; Tawaraya, Yuki; Kudoh, Satoshi

    2016-02-18

    Gas phase, bielement rhodium and tantalum clusters, RhnTam(+) (n + m = 6), were prepared by the double laser ablation of Rh and Ta rods in He carrier gas. The clusters were introduced into a reaction gas cell filled with nitric oxide (NO) diluted with He and were subjected to collisions with NO and He at room temperature. The product species were observed by mass spectrometry, demonstrating that the NO molecules were sequentially adsorbed on the RhnTam(+) clusters to form RhnTam(+)NxOx (x = 1, 2, 3, ...) species. In addition, oxide clusters, RhnTam(+)O2, were also observed, suggesting that the NO molecules were dissociatively adsorbed on the cluster, the N atoms migrated on the surface to form N2, and the N2 molecules were released from RhnTam(+)N2O2. The reactivity, leading to oxide formation, was composition dependent: oxide clusters were dominantly formed for the bielement clusters containing both Rh and Ta atoms, whereas such clusters were hardly formed for the single-element Rhn(+) and Tam(+) clusters. DFT calculations indicated that the Ta atoms induce dissociation of NO on the clusters by lowering the dissociation energy, whereas the Rh atoms enable release of N2 by lowering the binding energy of the N atoms on the clusters.

  2. Comparative analysis for the measured and the predicted relative sensitivity of rhodium In core detector

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Sang Rae; Cha, Kyoon Ho; Bae, Seong Man [Nuclear Reactor Safety Lab., KHNP Central Research Institute, Daejeon (Korea, Republic of)

    2012-10-15

    Self-powered neutron detector (SPND) is widely used as in-core flux monitoring in nuclear power plants. OPR1000 has applied a rhodium (Rh) as the emitter of the SPND. The SPND contains a neutron-sensitive metallic emitter surrounded by a ceramic insulator. When capturing a neutron, the Rh will be decayed by emitting some electrons which is crossing the sheath and produce current. This current can be measured externally using pico-ammeter. The sensitivity of detectors is closely related with the geometry and material of the detectors. The lifetime of in-core detector is determined by calculating the relative sensitivity of Rh detector. It is required that the Rh detector should be replaced before the burn-up of Rh detector has reached 66% of its original compositions. To predict Rh detector's relative sensitivity ANC code, advanced nodal code capable of two-dimensional and three-dimensional calculations, is used. It is determined that the Rh detectors should be replaced on the basis of the predicted sensitivity value calculated by ANC code. When evaluating the life of Rh detectors using ANC code, it is assumed that the uncertainty of the sensitivity calculation include the measurement error of 5%. As a result of the analysis of measured and predicted data for the Rh detector's relative sensitivity, it is possible to reduce the assumed uncertainty.

  3. Electrochemical behavior of rhodium acetamidate immobilized on a carbon paste electrode: a hydrazine sensor

    Directory of Open Access Journals (Sweden)

    Gil Eric de S.

    2000-01-01

    Full Text Available The electrochemical behavior of rhodium acetamidate immobilized in carbon paste electrode and the consequences for sensor construction were evaluated. The electrode showed good stability and redox properties. Two reversible redox couples with midpoint potentials between 0.15 and 0.55 V vs SCE were observed. However, peak resolution in voltammetric studies was very dependent on the supporting electrolyte. The correlation between coordinating power of the electrolyte and peak potential suggests that the electrolyte can coordinate through the axial position of the complexes. Furthermore, the axial position may be also the catalytic site, as a catalytical response was observed for hydrazine oxidation. A good linear response range for hydrazine was fit by the equation i = 23.13 (± 0.34 c , where i = current in mA and c = concentration in mol dm-3 in the range of 10-5 up to 10-2 mol dm-3. The low applied potential (<300 mV indicates a good device for hydrazine sensor, minimizing interference problems. The short response time (~1 s may be useful in flow injection analysis. Furthermore, this system was very stable presenting good repeatability even after 30 measurements with a variance of 0.5 %.

  4. Rhodium metalloinsertor binding generates a lesion with selective cytotoxicity for mismatch repair-deficient cells.

    Science.gov (United States)

    Bailis, Julie M; Weidmann, Alyson G; Mariano, Natalie F; Barton, Jacqueline K

    2017-07-03

    The DNA mismatch repair (MMR) pathway recognizes and repairs errors in base pairing and acts to maintain genome stability. Cancers that have lost MMR function are common and comprise an important clinical subtype that is resistant to many standard of care chemotherapeutics such as cisplatin. We have identified a family of rhodium metalloinsertors that bind DNA mismatches with high specificity and are preferentially cytotoxic to MMR-deficient cells. Here, we characterize the cellular mechanism of action of the most potent and selective complex in this family, [Rh(chrysi)(phen)(PPO)] 2+ (Rh-PPO). We find that Rh-PPO binding induces a lesion that triggers the DNA damage response (DDR). DDR activation results in cell-cycle blockade and inhibition of DNA replication and transcription. Significantly, the lesion induced by Rh-PPO is not repaired in MMR-deficient cells, resulting in selective cytotoxicity. The Rh-PPO mechanism is reminiscent of DNA repair enzymes that displace mismatched bases, and is differentiated from other DNA-targeted chemotherapeutics such as cisplatin by its potency, cellular mechanism, and selectivity for MMR-deficient cells.

  5. Versatile deprotonated NHC: C,N-bridged dinuclear iridium and rhodium complexes

    Directory of Open Access Journals (Sweden)

    Albert Poater

    2016-01-01

    Full Text Available Bearing the versatility of N-heterocyclic carbene (NHC ligands, here density functional theory (DFT calculations unravel the capacity of coordination of a deprotonated NHC ligand (pNHC to generate a doubly C2,N3-bridged dinuclear complex. Here, in particular the discussion is based on the combination of the deprotonated 1-arylimidazol (aryl = mesityl (Mes with [M(cod(μ-Cl] (M = Ir, Rh generated two geometrical isomers of complex [M(cod{µ-C3H2N2(Mes-κC2,κN3}]2. The latter two isomers display conformations head-to-head (H-H and head-to-tail (H-T of CS and C2 symmetry, respectively. The isomerization from the H-H to the H-T conformation is feasible, whereas next substitutions of the cod ligand by CO first, and PMe3 later confirm the H-T coordination as the thermodynamically preferred. It is envisaged the exchange of the metal, from iridium to rhodium, confirming here the innocence of the nature of the metal for such arrangements of the bridging ligands.

  6. The effects of rhodium on the renal function of female Wistar rats.

    Science.gov (United States)

    Iavicoli, Ivo; Leso, Veruscka; Fontana, Luca; Marinaccio, Alessandro; Bergamaschi, Antonio; Calabrese, Edward J

    2014-06-01

    In recent years, the increased use of rhodium (Rh) as an active catalyst material in modern three-way automobile catalytic converters has led to a parallel rise in environmental levels of this metal. In spite of this, the literature contains few studies of the effects of Rh on human health. The aim of this study is to assess the effects of Rh on the renal function of female Wistar rats. Our findings show that sub-acute exposure to six increasing concentrations, ranging from 0.001 to 1 mg L(-1), of Rh (III) chloride hydrate in drinking water does not induce alterations in urinary albumin levels, while, at concentrations from 0.1 to 1 mg L(-1), a significant rise in urinary levels of Retinol Binding Protein is evident and an increasing trend in urinary β2-microglobulin, which becomes significant at 1 mg L(-1), is observed. These results therefore demonstrate a nephrotoxic action of Rh at tubular level in a wide range of doses. Interestingly, because of the recent increase in environmental Rh levels, these findings may have relevant implications both for occupationally exposed subjects and for the general population, especially children. Copyright © 2013 Elsevier Ltd. All rights reserved.

  7. trans-Carbonylchloridobis[dicyclohexyl(4-isopropylphenylphosphane]rhodium(I acetone monosolvate

    Directory of Open Access Journals (Sweden)

    Sizwe Makhoba

    2011-09-01

    Full Text Available The title rhodium Vaska-type complex, trans-[RhCl{P(C6H112(C6H4-4-C3H72}2(CO], crystallizes with an accompanying acetone solvent molecule. The metal atom shows a distorted square-planar coordination environment with selected important geometrical parameters of Rh—P = 2.3237 (6 and 2.3253 (6 Å, Rh—Cl = 2.3724 (6 Å, Rh—C = 1.802 (2 Å, P—Rh—P = 173.42 (2° and Cl—Rh—C = 179.13 (7°. Effective cone angles for the two P atoms are 165 and 161°, respectively. Both isopropyl groups and the acetone molecule are disordered with occupancy values of 0.523 (5:0.477 (5, 0.554 (8:0.446 (8 and 0.735 (4:0.265 (4, respectively. The crystal packing is stabilized by weak C—H...O and C—H...Cl contacts.

  8. Rhodium(I)-catalyzed cyclization of allenynes with a carbonyl group through unusual insertion of a C-O bond into a rhodacycle intermediate.

    Science.gov (United States)

    Oonishi, Yoshihiro; Yokoe, Takayuki; Hosotani, Akihito; Sato, Yoshihiro

    2014-01-20

    Rhodium(I)-catalyzed cyclization of allenynes with a tethered carbonyl group was investigated. An unusual insertion of a CO bond into the C(sp(2) )-rhodium bond of a rhodacycle intermediate occurs via a highly strained transition state. Direct reductive elimination from the obtained rhodacyle intermediate proceeds to give a tricyclic product containing an 8-oxabicyclo[3.2.1]octane skeleton, while β-hydride elimination from the same intermediate gives products that contain fused five- and seven-membered rings in high yields. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. The divergent synthesis of nitrogen heterocycles by rhodium(II)-catalyzed cycloadditions of 1-sulfonyl 1,2,3-triazoles with 1,3-dienes.

    Science.gov (United States)

    Shang, Hai; Wang, Yuanhao; Tian, Yu; Feng, Juan; Tang, Yefeng

    2014-05-26

    The first rhodium(II)-catalyzed aza-[4+3] cycloadditions of 1-sulfonyl 1,2,3-triazoles with 1,3-dienes have been developed, and enable the efficient synthesis of highly functionalized 2,5-dihydroazepines from readily available precursors. In some cases, the reaction pathway could divert to formal aza-[3+2] cycloadditions, thus leading to 2,3-dihydropyrroles. In this context, the titled reaction represents a capable tool for the divergent synthesis of two types of synthetically valuable aza-heterocycles from common rhodium(II) iminocarbene intermediates. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. One-pot synthesis of 2,5-dihydropyrroles from terminal alkynes, azides, and propargylic alcohols by relay actions of copper, rhodium, and gold.

    Science.gov (United States)

    Miura, Tomoya; Tanaka, Takamasa; Matsumoto, Kohei; Murakami, Masahiro

    2014-12-01

    Relay actions of copper, rhodium, and gold formulate a one-pot multistep pathway, which directly gives 2,5-dihydropyrroles starting from terminal alkynes, sulfonyl azides, and propargylic alcohols. Initially, copper-catalyzed 1,3-dipolar cycloaddition of terminal alkynes with sulfonyl azides affords 1-sulfonyl-1,2,3-triazoles, which then react with propargylic alcohols under the catalysis of rhodium. The resulting alkenyl propargyl ethers subsequently undergo the thermal Claisen rearrangement to give α-allenyl-α-amino ketones. Finally, a gold catalyst prompts 5-endo cyclization to produce 2,5-dihydropyrroles. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Oxidative Olefination of Anilides with Unactivated Alkenes Catalyzed by an (Electron-Deficient η(5) -Cyclopentadienyl)Rhodium(III) Complex Under Ambient Conditions.

    Science.gov (United States)

    Takahama, Yuji; Shibata, Yu; Tanaka, Ken

    2015-06-15

    The oxidative olefination of sp(2) C-H bonds of anilides with both activated and unactivated alkenes using an (electron-deficient η(5) -cyclopentadienyl)rhodium(III) complex is reported. In contrast to reactions using this electron-deficient rhodium(III) catalyst, [Cp*RhCl2 ]2 showed no activity against olefination with unactivated alkenes. In addition, the deuterium kinetic isotope effect (DKIE) study revealed that the C-H bond cleavage step is thought to be the turnover-limiting step. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Construction of a four tip scanning tunneling microscope/scanning electron microscope combination and conductivity measurements of silicide nanowires

    International Nuclear Information System (INIS)

    Zubkov, Evgeniy

    2013-01-01

    In this work the combination of a four-tip scanning tunneling microscope with a scanning electron microscope is presented. By means of this apparatus it is possible to perform the conductivity measurements on the in-situ prepared nanostructures in ultra-high vacuum. With the aid of a scanning electron microscope (SEM), it becomes possible to position the tunneling tips of the four-tip scanning tunneling microscope (STM), so that an arrangement for a four-point probe measurement on nanostructures can be obtained. The STM head was built according to the novel coaxial Beetle concept. This concept allows on the one hand, a very compact arrangement of the components of the STM and on the other hand, the new-built STM head has a good mechanical stability, in order to achieve atomic resolution with all four STM units. The atomic resolution of the STM units was confirmed by scanning a Si(111)-7 x 7 surface. The thermal drift during the STM operation, as well as the resonant frequencies of the mechanical structure of the STM head, were determined. The scanning electron microscope allows the precise and safe navigation of the tunneling tips on the sample surface. Multi tip spectroscopy with up to four STM units can be performed synchronously. To demonstrate the capabilities of the new-built apparatus the conductivity measurements were carried out on metallic yttrium silicide nanowires. The nanowires were prepared by the in-situ deposition of yttrium on a heated Si(110) sample surface. Current-voltage curves were recorded on the nanowires and on the wetting layer in-between. The curves indicate an existence of the Schottky barrier between the yttrium silicide nanowires and the silicon bulk. By means of the two-tip measurements with a gate, the insulating property of the Schottky barrier has been confirmed. Using this Schottky barrier, it is possible to limit the current to the nanowire and to prevent it from flowing through the silicon bulk. A four-tip resistance measurement

  13. Electrochemical Sensor Based on Rh(III) Ion-Imprinted Polymer as a New Modifying Agent for Rhodium Determination.

    Science.gov (United States)

    Bai, Huiping; Xiong, Caiyun; Wang, Chunqiong; Liu, Peng; Dong, Su; Cao, Qiue

    2018-05-01

    A rhodium (III) ion carbon paste electrode (CPE) based on an ion imprinted polymer (IIP) as a new modifying agent has been prepared and studied. Rh(III) ion imprinted polymer was synthesized by copolymerization of acrylamide-Rh(III) complex and ethylene glycol dimethacrylate according to the precipitation polymerization. Acrylamide acted as both functional monomer and complexing agent to create selective coordination sites in a cross-linked polymer. The ion imprinted carbon paste electrode (IIP-CPE) was prepared by mixing rhodium IIP-nanoparticles and graphite powder in n-eicosane as an adhesive and then embedding them in a Teflon tube. Amperometric i-t curve method was applied as the determination technique. Several parameters, including the functional monomer, molar ratio of template, monomer and cross-linking agent, the amounts of IIP, the applied potential, the buffer solution and pH have been studied. According to the results, IIP-CPE showed a considerably higher response in comparison with the electrode embedded with non-imprinted polymer (NIP), indicating the formation of suitable recognition sites in the IIP structure during the polymerization stage. The introduced electrode showed a linear range of 1.00×10-8~3.0×10-5 mol·L-1 and detection limit of 6.0 nmol L-1 (S/N = 3). The IIP-CPE was successfully applied for the trace rhodium determination in catalyst and plant samples with RSD of less than 3.3% (n = 5) and recoveries in the range of 95.5~102.5%.

  14. Rhodium-Catalyzed Insertion Reaction of PhP Group of Pentaphenylcyclopentaphosphine with Acyclic and Cyclic Disulfides.

    Science.gov (United States)

    Arisawa, Mieko; Sawahata, Kyosuke; Yamada, Tomoki; Sarkar, Debayan; Yamaguchi, Masahiko

    2018-02-16

    Organophosphorus compounds with a phosphorus atom attached to a phenyl group and two organothio/organoseleno groups were synthesized using the rhodium-catalyzed insertion reaction of the PhP group of pentaphenylcyclopentaphosphine (PhP) 5 with acyclic disulfides and diselenides. The method was applied to the synthesis of heterocyclic compounds containing the S-P-S group by the reaction of (PhP) 5 and cyclic disulfides such as 1,2-dithietes, 1,2-dithiocane, 1,4,5-dithiopane, and 1,2-dithiolanes.

  15. Rhodium catalyzed regioselective arene homologation of aryl urea via double C-H bond activation and migratory insertion of alkyne

    Institute of Scientific and Technical Information of China (English)

    Yan Wang; Hao Zhou; Ke Xu; Mei-Hua Shen; Hua-Dong Xu

    2017-01-01

    A convenient rhodium catalyzed oxidative arene homologation of aniline derivatives with symmetrical or unsymmetrical alkynes using Cu(OAc)2 as oxidant is described.Urea group is shown to be effective as a directing group for initial ortho C-H activation.Two migratory insertion events of alkyne into Rh-C bond occur successively,both with complete regioselectivity.This method is particularly useful for synthesis of polyarenes with different substituents,which has not been reported with conventional protocol.A mechanism has been proposed to explain the observed data.

  16. Rhodium-catalyzed annulation of arenes with alkynes through weak chelation-assisted C-H activation.

    Science.gov (United States)

    Yang, Yudong; Li, Kaizhi; Cheng, Yangyang; Wan, Danyang; Li, Mingliang; You, Jingsong

    2016-02-18

    The purpose of this article is to give a brief review of weak chelation-assistance as a powerful means for the rhodium-catalyzed annulation of arenes with alkynes. The use of commonly occurring functional groups (e.g., ketones, aldehydes, carboxylic acids and alcohols) as the directing groups enriches the versatility of auxiliary ligands and extends the scope of products. This short article offers an overview on emerging procedures, highlights their advantages and limitations, and covers the latest progress in the rapid synthesis of organic functional materials and natural products.

  17. Rhodium-catalyzed enantioselective intramolecular C-H silylation for the syntheses of planar-chiral metallocene siloles.

    Science.gov (United States)

    Zhang, Qing-Wei; An, Kun; Liu, Li-Chuan; Yue, Yuan; He, Wei

    2015-06-01

    Reported herein is the rhodium-catalyzed enantioselective C-H bond silylation of the cyclopentadiene rings in Fe and Ru metallocenes. Thus, in the presence of (S)-TMS-Segphos, the reactions took place under very mild conditions to afford metallocene-fused siloles in good to excellent yields and with ee values of up to 97%. During this study it was observed that the steric hindrance of chiral ligands had a profound influence on the reactivity and enantioselectivity of the reaction, and might hold the key to accomplishing conventionally challenging asymmetric C-H silylations. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Regio- and enantioselective synthesis of N-substituted pyrazoles by rhodium-catalyzed asymmetric addition to allenes.

    Science.gov (United States)

    Haydl, Alexander M; Xu, Kun; Breit, Bernhard

    2015-06-08

    The rhodium-catalyzed asymmetric N-selective coupling of pyrazole derivatives with terminal allenes gives access to enantioenriched secondary and tertiary allylic pyrazoles, which can be employed for the synthesis of medicinally important targets. The reaction tolerates a large variety of functional groups and labelling experiments gave insights into the reaction mechanism. This new methodology was further applied in a highly efficient synthesis of JAK 1/2 inhibitor (R)-ruxolitinib. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Rhodium-catalyzed Asymmetric Hydrogenation of α-Dehydroamino Ketones: A General Approach to Chiral α-amino Ketones.

    Science.gov (United States)

    Gao, Wenchao; Wang, Qingli; Xie, Yun; Lv, Hui; Zhang, Xumu

    2016-01-01

    Rhodium/DuanPhos-catalyzed asymmetric hydrogenation of aliphatic α-dehydroamino ketones has been achieved and afforded chiral α-amino ketones in high yields and excellent enantioselectives (up to 99 % ee), which could be reduced further to chiral β-amino alcohols by LiAlH(tBuO)3 with good yields. This protocol provides a readily accessible route for the synthesis of chiral α-amino ketones and chiral β-amino alcohols. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Synthesis and structural studies of Cp{sup *} rhodium and Cp{sup *} iridium complexes of picolinic hydrazine ligand

    Energy Technology Data Exchange (ETDEWEB)

    Palepu, Narasinga Rao; Kollipara, Mohan Rao [Centre for Advanced Studies in Chemistry, North-Eastern Hill University, Shillong (India); Kaminsky Werner [Dept. of Chemistry, University of Washington, Seattle (United States)

    2017-01-15

    A series of Cp{sup *}Rh and Cp{sup *}Ir complexes of picolinic hydrazine ligand are synthesized and characterized. Picolinic hydrazine has yielded only dinuclear complexes in the case of rhodium metal whereas both mono and dinuclear complexes with iridium metal. Iridium complexes are formed as quaternary salts by the migration of the N–H proton onto the adjacent amine group of the hydrazine after binding to the metal. Picolinic hydrazine acts as nitrogen and oxygen donor ligand in the form of bi and tetradentate bonding modes.