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

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)

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.

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

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.)

A cerium(IV)-carbon multiple bond

Energy Technology Data Exchange (ETDEWEB)

Gregson, Matthew; Lu, Erli; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T. [Nottingham Univ. (United Kingdom). School of Chemistry

2013-12-02

Straightforward access to a cerium(IV)-carbene complex was provided by one-electron oxidation of an anionic ''ate'' cerium(III)-carbene precursor, thereby avoiding decomposition reactions that plague oxidations of neutral cerium(III) compounds. The cerium(IV)-carbene complex is the first lanthanide(IV)-element multiple bond and involves a twofold bonding interaction of two electron pairs between cerium and carbon. [German] Auf direktem Wege zu einem Cer(IV)-Carbenkomplex gelangt man durch die Einelektronenoxidation einer anionischen Carben-Cerat(III)-Vorstufe. So werden Zersetzungsprozesse vermieden, die die Oxidation neutraler Cer(III)-Verbindungen erschweren. Der Cer(IV)-Carbenkomplex enthaelt die erste Lanthanoid(IV)-Element-Mehrfachbindung; dabei binden Cer und Kohlenstoff ueber zwei Elektronenpaare.

Calcination of the cerium concentrate to be cerium oxide

International Nuclear Information System (INIS)

Suyanti; MV Purwani

2016-01-01

Calcination of the cerium concentrate to be cerium oxide has done. The cerium concentrate were obtained from the Ce making process wear KBrO_3 and without using KBrO_3. The calcination were done with a variation of time 1, 2, 3 and 4 hours with the temperature variations of 700, 800 and 900°C. The easiest calcination of Ce concentrates to be CeO_2 containing majority of Ce(OH)_4 and contains least impurities as Th(OH)_4, (NH_4)_2Y(NO_3), H_4N_5O_1_2La, H_1_2N_3NdO_1_5 and N_3O_9Sm. On the calcination of Ce concentrates process results without using KBrO_3 1, the calcination temperature 900°C was obtained CeO_2 content of 73.53% for calcination time of 4 hours, has little difference when compared with the predictions and calculation result of complete calcination was equal 73.84%. (author)

Cerium and jojoba in engines?; Cerium et jojoba dans les moteurs?

Energy Technology Data Exchange (ETDEWEB)

Massy-Delhotel, E.

1996-10-01

The Belgium company CreaTel proposes a new system, called Forac, which can lead to a 10% reduction of fuel consumption in thermal engines together with a quasi-complete reduction of CO, HC, NOx pollutants and CO{sub 2} particulates emission. The system comprises a steam production device and an admission pipe with a cerium alloy whorl inside. The steam produced is mixed with the admission air and tears cerium particles from the inside of the admission pipe to the combustion chamber. The cerium particles act as a catalyst which favours the complete combustion of the fuel. The same company proposes also lubricant additives made from liquid jojoba wax which allow the reduction of pollutant emissions, fuel consumption and noise emissions of diesel engines. (J.S.)

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.

Cerium and rare earth separation process

International Nuclear Information System (INIS)

Martin, M.; Rollat, M.

1986-01-01

An aqueous solution containing cerium III and rare earths is oxidized in the anodic compartment of an electrolytic cell, cerium IV is extracted by an organic solvent, the organic phase containing Ce IV is reduced in the catodic compartment of the same electrolytic cell and cerium III is extracted in a nitric aqueous phase [fr

Multifunctional cerium-based nanomaterials and methods for producing the same

Science.gov (United States)

O'Keefe, Matthew J.; Castano Londono, Carlos E.; Fahrenholtz, William G.

2018-01-09

Embodiments relate to a cerium-containing nano-coating composition, the composition including an amorphous matrix including one or more of cerium oxide, cerium hydroxide, and cerium phosphate; and crystalline regions including one or more of crystalline cerium oxide, crystalline cerium hydroxide, and crystalline cerium phosphate. The diameter of each crystalline region is less than about 50 nanometers.

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.

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)

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

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)

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.

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

Some Environmentally Relevant Reactions of Cerium Oxide

Directory of Open Access Journals (Sweden)

Janoš Pavel

2014-12-01

Full Text Available Reactive forms of cerium oxide were prepared by a thermal decomposition of various precursors, namely carbonates, oxalates and citrates, commercially available nanocrystalline cerium oxide (nanoceria was involved in the study for comparison. Scanning electron microscopy (SEM and x-ray diffraction analysis (XRD were used to examine the morphology and crystallinity of the samples, respectively, whereas the Brunauer-Emmett-Teller (BET method of nitrogen adsorption was used to determine surface areas. Interactions of cerium oxide with some phosphorus-containing compounds were investigated. Some of the examined samples, especially those prepared by annealing from carbonate precursors, exhibited an outstanding ability to destroy highly toxic organophosphates, such as pesticides (parathion methyl, or nerve agents (soman, VX. There were identified some relations between the degradation efficiency of cerium oxides and their crystallinity. It was also shown that cerium oxide is able to destroy one of widely used flame retardants - triphenyl phosphate. A phosphatase-mimetic activity of various cerium oxides was examined with the aid of a standardized phosphatase test.

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.

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.

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

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.

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.

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

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)

Local Structure of Cerium in Aluminophosphate and Silicophosphate Glasses

International Nuclear Information System (INIS)

Rygel, Jennifer L.; Chen, Yongsheng; Pantano, Carlo G.; Shibata, Tomohiro; Du, Jincheng; Kokou, Leopold; Woodman, Robert; Belcher, James

2011-01-01

The local structure of cerium in two systematic compositional series of glasses, nominally CeP 3 O 9 -AlP 3 O 9 and CeP 3 O 9 -SiP 2 O 7 , was interrogated using X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) spectroscopy. XPS revealed that, for glasses melted in air, ≥95% of cerium ions are Ce 3+ . This was independently confirmed using X-ray absorption near edge spectroscopy (XANES). Ce K-edge extended X-ray absorption fine structure (EXAFS) has been used to determine the local structure of Ce 3+ . Near the metaphosphate composition, cerium was found to have an average cerium coordination number of ∼7.0 and an average cerium-oxygen bond length of 2.41 (angstrom). The average cerium coordination number and average cerium-oxygen bond distance were found to increase with decreasing cerium concentration in both compositional series. Rare-earth clustering is suggested based on numerical calculations for glasses containing ≥14 and ≥15 mol% Ce 2 O 3 for the aluminophosphate and silicophosphate series, respectively.

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.

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.

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

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

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

Metabolism of cerium 144 in rat. Distribution - elimination - dosimetry; Metabolisme du cerium 144 chez le rat. Distribution - elimination - dosimetrie

Energy Technology Data Exchange (ETDEWEB)

Remy, Jacques

1959-07-01

This academic report concerns a study during which cerium 144 has been intravenously injected to three-month old rats under the form of cerium chloride in aqueous solution with pH of 9,5. Rats have then been sacrificed at different times after the injection, and organ or tissue samplings have been performed to study the isotope distribution in their bodies. This allowed the calculation of internal irradiation doses locally received by the animal, and also to identify critical organs with respect to cerium 144. Thus, until the twentieth day after injection, liver is the critical organ. After, it is the skeleton, for the rest of the animal's life. The bone internal irradiation is the highest danger for an internal cerium 144 contamination, due to threats on body hematopoietic functions [French] Le Cerium 144 est injecte a des rats de trois mois par voie intraveineuse, sous forme de chlorure en solution aqueuse a pH = 9,5. Une telle solution est colloidale. Les rats sont sacrifies par groupe de 5 a des temps differents apres l'injection et des prelevements d'organes ou de tissus sont effectues qui permettent d'etudier la distribution de l'isotope dans l'organisme. Cette etude de la distribution du Cerium 144 dans l'organiqme du rat a permis egalement le calcul des doses d'irradiation interne recues localement par l'animal. Ces donnees permettent de definir les organes critiques de l'organisme pour le Cerium 144: Jusqu'au 20eme jour l'organe critique est le foie. Ce sera ensuite le squelette, et ce, pendant toute la vie de l'animal. L'irradiation interne de l'os constitue, en raison des menaces qu'elle comporte pour les fonctions hematopoietiques de l'organisme, le plus grand danger d'une contamination interne par le Cerium 144.

Structural, optical, morphological and dielectric properties of cerium oxide nanoparticles

International Nuclear Information System (INIS)

Prabaharan, Devadoss Mangalam Durai Manoharadoss; Sadaiyandi, Karuppasamy; Mahendran, Manickam; Sagadevan, Suresh

2016-01-01

Cerium oxide (CeO 2 ) nanoparticles were prepared by the precipitation method. The average crystallite size of cerium oxide nanoparticles was calculated from the X-ray diffraction (XRD) pattern and found to be 11 nm. The FT-IR spectrum clearly indicated the strong presence of cerium oxide nanoparticles. Raman spectrum confirmed the cubic nature of the cerium oxide nanoparticles. The Scanning Electron Microscopy (SEM) analysis showed that the nanoparticles agglomerated forming spherical-shaped particles. The Transmission Electron Microscopic (TEM) analysis confirmed the prepared cerium oxide nanoparticles with the particle size being found to be 16 nm. The optical absorption spectrum showed a blue shift by the cerium oxide nanoparticles due to the quantum confinement effect. The dielectric properties of cerium oxide nanoparticles were studied for different frequencies at different temperatures. The dielectric constant and the dielectric loss of the cerium oxide nanoparticles decreased with increase in frequency. The AC electrical conductivity study revealed that the conduction depended on both the frequency and the temperature. (author)

Structural, optical, morphological and dielectric properties of cerium oxide nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Prabaharan, Devadoss Mangalam Durai Manoharadoss [Department of Physics, NPR College of Engineering and Technology, Natham, Dindigul, Tamil Nadu (India); Sadaiyandi, Karuppasamy [Department of Physics, Alagappa Government Arts College, Karaikudi, Sivaganga, Tamil Nadu (India); Mahendran, Manickam [Department of Physics, Thiagarajar College of Engineering, Madurai, Tamil Nadu (India); Sagadevan, Suresh, E-mail: duraiphysics2011@gmail.com [Department of Physics, AMET University (India)

2016-03-15

Cerium oxide (CeO{sub 2}) nanoparticles were prepared by the precipitation method. The average crystallite size of cerium oxide nanoparticles was calculated from the X-ray diffraction (XRD) pattern and found to be 11 nm. The FT-IR spectrum clearly indicated the strong presence of cerium oxide nanoparticles. Raman spectrum confirmed the cubic nature of the cerium oxide nanoparticles. The Scanning Electron Microscopy (SEM) analysis showed that the nanoparticles agglomerated forming spherical-shaped particles. The Transmission Electron Microscopic (TEM) analysis confirmed the prepared cerium oxide nanoparticles with the particle size being found to be 16 nm. The optical absorption spectrum showed a blue shift by the cerium oxide nanoparticles due to the quantum confinement effect. The dielectric properties of cerium oxide nanoparticles were studied for different frequencies at different temperatures. The dielectric constant and the dielectric loss of the cerium oxide nanoparticles decreased with increase in frequency. The AC electrical conductivity study revealed that the conduction depended on both the frequency and the temperature. (author)

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

Electrochemical reduction of cerium oxides in molten salts

International Nuclear Information System (INIS)

Claux, B.; Serp, J.; Fouletier, J.

2011-01-01

This brief article describes a pyrochemical process that is used by CEA to turn actinide oxides into metal actinides. This process is applied to Cerium oxides (CeO 2 ) that simulate actinide oxides well chemically as cerium belongs to the lanthanide family. The process is in fact an electrolysis of cerium oxide in a bath of molten calcium chloride salt whose temperature is between 800 and 900 Celsius degrees. At those temperatures calcium chloride becomes a ionic liquid (Ca 2+ and Cl - ) that is a good electrical conductor and is particularly well-adapted as solvent to an electrolytic process. The electrolysis current allows the transformation of solvent Ca 2+ ions into metal calcium which, in turn, can reduce cerium oxide into metal cerium through chromatically. Experimental data shows the reduction of up to 90% of 10 g samples of CeO 2 in a 6 hour long electrolysis while the best reduction rate ever known was 80% so far. This result is all the more promising that cerium oxides are more difficult to reduce than actinide oxides from the thermodynamical perspective

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

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

Valence instabilities in cerium intermetallics

International Nuclear Information System (INIS)

Dijkman, W.H.

1982-01-01

The primary purpose of this investigation was to study the magnetic behaviour of cerium in intermetallic compounds, that show an IV behaviour, e.g. CeSn 3 . In the progress of the investigations, it became of interest to study the effect of changes in the lattice of the IV compound by substituting La or Y for Ce, thus constituting the Cesub(1-x)Lasub(x)Sn 3 and Cesub(1-x)Ysub(x)Sn 3 quasibinary systems. A second purpose was to examine the possibility of introducing instabilities in the valency of a trivalent intermetallic cerium compound: CeIn 3 , also by La and Y-substitutions in the lattice. Measurements on the resulting Cesub(1-x)Lasub(x)In 3 and Cesub(1-x)Ysub(x)In 3 quasibinaries are described. A third purpose was to study the (gradual) transition from a trivalent cerium compound into an IV cerium compound. This was done by examining the magnetic properties of the CeInsub(x)Snsub(3-x) and CePbsub(x)Snsub(3-x) systems. Finally a new possibility was investigated: that of the occurrence of IV behaviour in CeSi 2 , CeSi, and in CeGa 2 . (Auth.)

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.

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.

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.

Determination of silver and cerium in the liver and the kidney from a severely burned infant treated with silver sulfadiazine and cerium nitrate

International Nuclear Information System (INIS)

Hirakawa, Keiko

1983-01-01

Silver and cerium in the liver and the kidney from severely burned infant were analyzed by neutron activation method. The patient was treated topically with cerium nitrate/silver sulfadiazine cream and cerium nitrate solution for 3 months. Then, the treatment with these drugs was stopped because o f abdominal distention. The patient died 1 month after the cessation of the treatment with these drugs. The tissue specimens, blank liver sample and reference standards were irradiated with TRIGA MARK II Reactor of Rikkyo University. About 1 month after the irradiation, the activities were measured with a Ge(Li) detector coupled to a 4096 channel pulse height analyzer. A large amount of silver was detected both in the liver and in the kidney and a trace of cerium only in the liver. A considerable amount of silver was detected in the liver and its quantity was about 1600 times more than that of normal livers reported by Hamilton, Minski and Cleary (1972 -- 73). Neither silver nor cerium were detected in the blank liver. These results suggest that prolonged topical chemotherapy of cerium nitrate/silver sulfadiazine cream and cerium nitrate solution for the extensive burn injuries causes considerable absorption of silver and cerium into the liver and the kidney. (author)

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

Membrane assisted liquid-liquid extraction of cerium

International Nuclear Information System (INIS)

Soldenhoff, K.M.

2000-02-01

Membrane assisted liquid-liquid extraction of cerium was investigated, with emphasis placed on the study of the reaction chemistry and the kinetics of non-dispersive solvent extraction and stripping with microporous membranes. A bulk liquid membrane process was developed for the purification of cerium(IV) from sulfate solutions containing other rare earth elements. The cerium process was studied in both a flat sheet contained liquid membrane configuration and with hollow fibre contactors. Di-2-ethylhexyl phosphoric acid (DEHPA) was identified as a suitable extractant for cerium(IV) from sulfuric acid solution, with due consideration of factors such as extraction ability, resistance to degradation, solvent selectivity and potential for sulfate transfer into a strip solution. A detailed study of the extraction of cerium(IV) with DEHPA defined the extraction reaction chemistry. The Ce/DEHPA/sulfate system was also investigated with a flat sheet bulk liquid membrane configuration, using both sulfuric and hydrochloric acid as receiver solutions. These tests identified that hydrophobic membranes provide better mass transfer for extraction and hydrophilic membranes are better for stripping. The presence of an impurity, mono 2-ethylhexyl phosphoric acid (MEHPA), was found to have a dramatic accelerating effect on the rate of the chemical extraction reaction. This was attributed to its higher interfacial activity and population compared to DEHPA, and the fact that MEHPA was also found to be an active carrier for cerium(IV). The mass transfer rate of membrane assisted extraction and stripping of cerium, using hydrophobic and hydrophilic microporous membranes, respectively, was investigated using a modified Lewis-type cell. It was quantitatively demonstrated that the extraction process was mainly controlled by membrane diffusion and the stripping process was controlled by the chemical reaction rate, with membrane diffusion becoming important at low distribution coefficients

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

Obtainment of cerium dioxide for use as spectrochemical standard

International Nuclear Information System (INIS)

Silva Queiroz, C.A. da; Hespanhol, E.C.B.; Abrao, A.

1992-01-01

This paper describes a simple method for cerium separation and purification. Cerium is previously precipitated with N H 3 /air/H 2 O 2 system in a mixed chlorides solution obtained from Brazilian monazite treatment. The cerium fraction as cerium chloride is run down throughout a strong cationic resin bed and then the rare earth impurities separation is done by elution of the resin with separation ammonium salt of EDTA. None retainer ion is used in the purification technique by ion exchange. (author)

Selected cerium phase diagrams

International Nuclear Information System (INIS)

Gschneidner, K.A. Jr.; Verkade, M.E.

1974-09-01

A compilation of cerium alloy phase equilibria data based on the most reliable information available is presented. The binary systems selected are those of cerium with each of the following twenty nine elements which might be commonly found in steels: Al, Sb, As, Bi, Ca, C, Cr, Co, Nb, Cu, Fe, Pb, Mg, Mn, Mo, Ni, N, O, P, Se, Si, Ag, S, Te, Sn, Ti, W, and Zn. A brief discussion, a summary of crystal lattice parameters where applicable, and a list of references is included for each element surveyed. (U.S.)

Novel in situ coordinated cerium salt/acrylonitrile-butadiene rubber composite

International Nuclear Information System (INIS)

Han, Jianjun; Lu, Haifeng; Zhang, Jie; Feng, Shengyu

2012-01-01

A novel rubber composite of acrylonitrile-butadiene rubber (NBR) filled with cerium salt particles was vulcanized via in situ coordination for the first time. The resulting materials exhibit good mechanical properties. Curing characteristics analysis, differential scanning calorimetry, X-ray photoelectron spectroscopy, tensile testing, and an equilibrium swelling method were used for the characterization of the composite. The results in this paper indicate that the composite is a kind of elastomer based on the in situ coordination crosslinking interactions between the nitrile groups (–CN) of NBR and cerium ions. The mechanical properties of vulcanized cerium salt/ NBR rubber are altered when changing the sorts of cerium salt. Moreover, these materials show good irradiation resistance because of the introduction of the cerium salt. -- Highlights: ► Cerium salts were firstly used to vulcanize the acrylonitrile-butadiene rubber. ► Cerium salts act as not only crosslink agents but also reinforcing fillers in the matrix. ► These materials show good irradiation resistance and mechanical properties at same time.

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

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

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.

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.

Two-phase titration of cerium(3) by permanganate

International Nuclear Information System (INIS)

Lazarev, A.I.; Lazareva, V.I.; Gerko, V.V.

1986-01-01

Reaction of cerium (3) and permanganate was investigated at a room temperature depending on PH, concentrations of pyrophosphate, cerium (3), tetraphenylphosphonium and foreign compounds. Selective method of two-phase titration determination of cerium (3) by permanganate without using silver compounds, preliminary separation of chlorides, nitrates, was developed. The method was tested using alloys based on iron, nickel, REE, copper, cobalt (S r ≤0.008). Correctness is proved with method of standard additives

Novel in situ coordinated cerium salt/acrylonitrile-butadiene rubber composite

Energy Technology Data Exchange (ETDEWEB)

Han, Jianjun [Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Lu, Haifeng, E-mail: lhf@sdu.edu.cn [Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Zhang, Jie [Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Feng, Shengyu, E-mail: fsy@sdu.edu.cn [Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China)

2012-09-14

A novel rubber composite of acrylonitrile-butadiene rubber (NBR) filled with cerium salt particles was vulcanized via in situ coordination for the first time. The resulting materials exhibit good mechanical properties. Curing characteristics analysis, differential scanning calorimetry, X-ray photoelectron spectroscopy, tensile testing, and an equilibrium swelling method were used for the characterization of the composite. The results in this paper indicate that the composite is a kind of elastomer based on the in situ coordination crosslinking interactions between the nitrile groups (-CN) of NBR and cerium ions. The mechanical properties of vulcanized cerium salt/ NBR rubber are altered when changing the sorts of cerium salt. Moreover, these materials show good irradiation resistance because of the introduction of the cerium salt. -- Highlights: Black-Right-Pointing-Pointer Cerium salts were firstly used to vulcanize the acrylonitrile-butadiene rubber. Black-Right-Pointing-Pointer Cerium salts act as not only crosslink agents but also reinforcing fillers in the matrix. Black-Right-Pointing-Pointer These materials show good irradiation resistance and mechanical properties at same time.

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

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

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

Preparation of cerium oxide for lens polishing powder

International Nuclear Information System (INIS)

Injarean, Uthaiwan; Rodthongkom, Chouvana; Pichestapong, Pipat; Changkrurng, Kalaya

2003-10-01

Cerium is an element of rare earth group which is called lanthanide series. It is found in the ores like monazite and xenotime which are the tailings of tin mines in the south of Thailand. Cerium is used mostly as lens polishing powder besides the applications in other industries. In this study, cerium extracted from monazite ore breakdown by alkaline process was used for the preparation of lens polishing powder. Cerium hydroxide cake from the process was dissolved by hydrochloric acid and precipitated with oxalic acid. The oxalate precipitate then was calcined to oxide powder and its particle size was measured. Precipitation conditions being studied are concentration of feed cerium chloride solution, concentration of oxalic acid used for the precipitation, concentration of sulfuric acid used as precipitation control reagent and the precipitation temperature. It was found that the appropriate precipitation conditions yielded the fine oxide powder with particle size about 12μm. The oxide powder can be ground to the size of 1-3 μm which is suitable for making lens polishing powder

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.

Bordoni relaxation and magnetic transformation in cerium and cerium-lanthanum alloys

Energy Technology Data Exchange (ETDEWEB)

Postnikov, V S; Polner, G L; Sharshakov, I M

1975-11-01

The internal friction in pure cerium and cerium-base alloys with 2.5 and 12 weight percent of lanthanum added at temperature ranging from 4.2 deg up to 77/sup 0/K is described. Amplitude-independent internal friction has been measured with an inverse torsion pendulum with a specimen oscillation frequency of 1-30 hz in vacuum not less than 1.10/sup -5/ torr. A temperature of the specimen has been determined with a capacitance-type sensor and a gas gage. A curve showing the dependence of internal friction upon a temperature of pure cerium has two distinct peaks; the first at 12.5/sup 0/K, the second at 45/sup 0/K. The 12.5/sup 0/K peak is accounted for by a transition of antiferromagnetic ..beta..-Ce into a paramagnetic state. The 45/sup 0/K peak is a Bordoni maximum. The paper describes an influence of additions, specimen oscillation frequency variations, deformation and annealing upon the peak behavor. Added lanthanum reduces not only a peak temperature but a height as well. Studies of the 45/sup 0/K peak have shown that its temperature location depends upon the specimen oscillation frequency. As the frequency increases the peak tends to a range of high temperatures which confirms its relaxation nature.

Dissolution properties of cerium dibutylphosphate corrosion inhibitors

NARCIS (Netherlands)

Soestbergen, van M.; Erich, S.J.F.; Huinink, H.P.; Adan, O.C.G.

2013-01-01

The corrosion inhibitor cerium dibutylphosphate, Ce(dbp)3, prevents corrosion by cerium and dbp deposition at the alkaline cathode and acidic anode respectively. The pH dependent Ce(dbp)3 solubility seems to play an essential role in the inhibition degree. We found that Ce(dbp)3 scarcely dissolves

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

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.

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

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

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)

Fundamental aspects of regenerative cerium oxide nanoparticles and their applications in nanobiotechnology

Science.gov (United States)

Patil, Swanand D.

Cerium oxide has been used extensively for various applications over the past two decades. The use of cerium oxide nanoparticles is beneficial in present applications and can open avenues for future applications. The present study utilizes the microemulsion technique to synthesize uniformly distributed cerium oxide nanoparticles. The same technique was also used to synthesize cerium oxide nanoparticles doped with trivalent elements (La and Nd). The fundamental study of cerium oxide nanoparticles identified variations in properties as a function of particle size and also due to doping with trivalent elements (La and Nd). It was found that the lattice parameter of cerium oxide nanoparticles increases with decrease in particle size. Also Raman allowed mode shift to lower energies and the peak at 464 cm-1 becomes broader and asymmetric. The size dependent changes in cerium oxide were correlated to increase in oxygen vacancy concentration in the cerium oxide lattice. The doping of cerium oxide nanoparticles with trivalent elements introduces more oxygen vacancies and expands the cerium oxide lattice further (in addition to the lattice expansion due to the size effect). The lattice expansion is greater for La-doped cerium oxide nanoparticles compared to Nd-doping due to the larger ionic radius of La compared to Nd, the lattice expansion is directly proportional to the dopant concentration. The synthesized cerium oxide nanoparticles were used to develop an electrochemical biosensor of hydrogen peroxide (H2O2). The sensor was useful to detect H2O2 concentrations as low as 1muM in water. Also the preliminary testing of the sensor on tomato stem and leaf extracts indicated that the sensor can be used in practical applications such as plant physiological studies etc. The nanomolar concentrations of cerium oxide nanoparticles were also found to be useful in decreasing ROS (reactive oxygen species) mediated cellular damages in various in vitro cell cultures. Cerium oxide

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.

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.

Cerium-modified Aurivillius-type sodium lanthanum bismuth titanate with enhanced piezoactivities

International Nuclear Information System (INIS)

Wang Chunming; Zhao Liang; Wang Jinfeng; Zheng Limei; Du Juan; Zhao Minglei; Wang Chunlei

2009-01-01

The electrical, piezoelectric and dielectric properties of cerium-modified Aurivillius-type sodium lanthanum bismuth titanate (Na 0.5 La 0.5 Bi 4 Ti 4 O 15 , NLBT) ceramics were investigated. It was found the piezoelectric activities of NLBT ceramics were significantly improved by cerium modification. The piezoelectric coefficient d 33 and Curie temperature T c for the 0.50 wt.% cerium-modified NLBT were found to be 29 pC/N and 573 deg. C, respectively. The reasons for piezoelectric activities improvement by cerium modification were given. A small dielectric abnormity was observed in NLBT ceramics, which can be suppressed by cerium modification.

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}.

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)

Specific Features of the Response of Cerium to Pulsed Actions

Science.gov (United States)

Atroshenko, S. A.; Zubareva, A. N.; Morozov, V. A.; Savenkov, G. G.; Utkin, A. V.

2018-02-01

Experimental studies of cerium at high rates and nanosecond durations of action have been performed. The isomorphic phase transition was studied upon shock compression. The spall strength of cerium has been determined. Cerium demonstrates anomalous compressibility upon dynamic loading. Stress waves dampen under action of a high-current electron beam due to the energy dissipation during fragmentation and twinning.

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...

A contribution to the radiologic findings in cerium pneumoconiosis

International Nuclear Information System (INIS)

Hecht, F.M.; Wesch, H.; Deutsches Krebsforschungszentrum, Heidelberg

1980-01-01

Report on a 69 year old man, who had been employed as photographer in the printing industry and who had been exposed to Cerium for 40 years. The chest X-ray which was performed 9 years after the end of the exposure displayes striate densities of the lungs, which must be considered as a late stage of Cerium-pneumoconiosis. The changes which were found fulfill the code 't 1/0 RO, RM, RU, LO, LM, LU, p 0/1 RO, RM, LO, LM, em, tbu' according to the 'ILO U/C 1971 classification of pneumoconiosis'. The diagnosis could be substantiated by measureing Cerium in the lung parenchyma qualitatively and quantitatively using neutrone activating analysis. The radiolgic findings of the Cerium pneumoconiosis are discussed. (orig.) [de

Electronic state of cerium-based catalysts studied by spectroscopic methods (XPS, XAS)

International Nuclear Information System (INIS)

Le Normand, F.; Bernhardt, P.; Hilaire, L.; Kili, K.; Maire, G.; Krill, G.

1987-01-01

X-ray Photoelectron Spectroscopy (XPS) of the 3d core level of cerium and X-ray Absorption Spectroscopy (XAS) of the L III absorption edge of cerium have been used to study Pd/CeO 2 , Pd-Ce/γAl 2 O 3 and Ce/γAl 2 O 3 catalysts. The oxidation state of cerium was found to decrease with decreasing amounts of cerium on the surface. It was quite close to III for very low contents of cerium (2-3%). For higher cerium contents the oxidation state was nearer to IV but differences between the two methods were found, owing to the fact that XAS is a volume sensitive probe. The oxidation state of cerium was also lower for Pd-Ce/γAl 2 O 3 than for Ce/γAl 2 O 3 , suggesting the formation of Ce III OCl, chlorine coming from the precursor salt of palladium. 15 refs.; 5 figs.; 1 table

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.

Adsorption of Some Hazardous Radionuclides on Cerium(IV) Antimonate

International Nuclear Information System (INIS)

Aly, H.F.; Zakaria, E.S.; Shady, S.A.; El-Naggar, I.M.

1999-01-01

Cerium(IV) antimonate had been prepared by the dropwise addition of 0.6 M antimony pentachloride and 0.6 M cerium ammonium nitrate solutions by a molar radio of Ce/Sb 0.75. Exchange isotherms for H +/ Co 2+ , H +/ Cs +, H +/ Zn 2+ , H +/ Sr 2+ and H +/ Eu 3+ have been determined at 25, 40 and 60 degree. Besides it was proved that europium is physically adsorbed while zinc, strontium, cobalt and cesium are chemically adsorbed. Moreover, the heat of adsorption of zinc, strontium, cobalt and cesium on cerium(IV) antimonate had been calculated and indicated that cerium(IV) antimonate is of endothermic behaviour towards these ions. Also the distribution coefficients of these ions were determined and it was found that the selectivity in the order: Eu 3+ >Sr 2+ > Cs +> Na +

Metabolism of cerium 144 in rat. Distribution - elimination - dosimetry

International Nuclear Information System (INIS)

Remy, Jacques

1959-01-01

This academic report concerns a study during which cerium 144 has been intravenously injected to three-month old rats under the form of cerium chloride in aqueous solution with pH of 9,5. Rats have then been sacrificed at different times after the injection, and organ or tissue samplings have been performed to study the isotope distribution in their bodies. This allowed the calculation of internal irradiation doses locally received by the animal, and also to identify critical organs with respect to cerium 144. Thus, until the twentieth day after injection, liver is the critical organ. After, it is the skeleton, for the rest of the animal's life. The bone internal irradiation is the highest danger for an internal cerium 144 contamination, due to threats on body hematopoietic functions [fr

Investigation of AA2024-T3 surfaces modified by cerium compounds: A localized approach

International Nuclear Information System (INIS)

Paussa, L.; Andreatta, F.; De Felicis, D.; Bemporad, E.; Fedrizzi, L.

2014-01-01

Highlights: •The precipitation of cerium compounds occurs on the entire AA2024-T3 surface. •The matrix is less involved in the cerium precipitation. •Cerium intensely precipitates on Mg-rich IM particles. •The electrochemical behavior of Mg-rich IM particles influences the mechanism of cerium precipitation. -- Abstract: The precipitation of cerium compounds on polished AA2024-T3 surfaces was investigated following an electrochemical and microstructural localized approach. It was found that cerium precipitation occurs on the entire surface covering intermetallic particles and the matrix as well. The matrix is the region where the precipitation of cerium is less favoured. The highest amount of cerium was observed on magnesium-rich intermetallic particles. The localized analyses suggest that precipitation of cerium on magnesium-rich intermetallic particles could happen following two mechanisms: the former based on a potential reversal of the intermetallic particles and the latter due to a partial magnesium dissolution

Electrochemical redox processes involving soluble cerium species

International Nuclear Information System (INIS)

Arenas, L.F.; Ponce de León, C.; Walsh, F.C.

2016-01-01

Highlights: • The relevance of cerium in laboratory and industrial electrochemistry is considered. • The history of fundamental electrochemical studies and applications is considered. • The chemistry, redox thermodynamics and electrode kinetics of cerium are summarised. • The uses of cerium ions in synthesis, energy storage, analysis and environmental treatment are illustrated. • Research needs and development perspectives are discussed. - Abstract: Anodic oxidation of cerous ions and cathodic reduction of ceric ions, in aqueous acidic solutions, play an important role in electrochemical processes at laboratory and industrial scale. Ceric ions, which have been used for oxidation of organic wastes and off-gases in environmental treatment, are a well-established oxidant for indirect organic synthesis and specialised cleaning processes, including oxide film removal from tanks and process pipework in nuclear decontamination. They also provide a classical reagent for chemical analysis in the laboratory. The reversible oxidation of cerous ions is an important reaction in the positive compartment of various redox flow batteries during charge and discharge cycling. A knowledge of the thermodynamics and kinetics of the redox reaction is critical to an understanding of the role of cerium redox species in these applications. Suitable choices of electrode material (metal or ceramic; coated or uncoated), geometry/structure (2-or 3-dimensional) and electrolyte flow conditions (hence an acceptable mass transport rate) are critical to achieving effective electrocatalysis, a high performance and a long lifetime. This review considers the electrochemistry of soluble cerium species and their diverse uses in electrochemical technology, especially for redox flow batteries and mediated electrochemical oxidation.

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

Lattice dynamics of α-cerium

International Nuclear Information System (INIS)

Smith, G.S.

1985-01-01

The lattice dynamics of the fcc α-phase of cerium metal was investigated using inelastic neutron scattering techniques. This phase of cerium is an example of a mixed-valent system. Various physical properties of α-Ce suggest that there may be coupling between the phonons and the f d transitions associated with the mixed valence phenomenon. These measurements of the dispersion curves provide important information about the electron-phonon interaction in this phase of cerium. These studies were not performed in the past because single crystals of α-Ce were not available. We were able to prepare a single α-Ce crystal using a high temperature, high pressure technique. The sample was of sufficient size for inelastic neutron scattering experiments, but the measurements were complicated because of the large mosaic spread (approx.7.0 0 ) of the crystal. It was possible, however, to obtain a set of dispersion curves along the [00zeta], [zeta,zeta,0], and [zeta,zeta,zeta] symmetry directions. Comparison of the dispersion curves with those of fcc γ-Ce indicate that the branches exhibit anomalous features that may be related to the mixed-valence effects

Systems of cerium(3) nitrate-dimethyl amine nitrate-water and cerium(3) nitrate-dimethyl amine nitrate-water

International Nuclear Information System (INIS)

Mininkov, N.E.; Zhuravlev, E.F.

1976-01-01

Solubility of solid phases in the systems cerium(3)nitrate-water-dimethyl amine nitrate and cerium(3)nitrate-water-dimethyl amine nitrate has been st ed by the method of isothermal sections at 25 and 50 deo. C. It has been shown that one anhydrous compound is formed in each system with a ratio of cerium(3) nitrate to amine nitrate 1:5. The compounds formed in the systems have been separated from the corresponding solutions and studied by microcrystalloscopic, X-ray phase, thermal and infrared spectroscopic methods. On the basis of spectroscopic studies the following formula has been assigned to the compound: [(CH 3 ) 2 NH 2 + ] 5 x[Ce(NO 3 ) 8 ]. The thermal analysis of the compound has shown that its melting point is 106 deg C. The solubility isotherms in the system Ce(NO 3 ) 3 -H 2 O-(C 2 H 5 ) 2 NHxHNO 3 consist of three branches which intersect in two eutonic points

Method of cerium separation from other lanthanides and yttrium

International Nuclear Information System (INIS)

Tran, Duc Hiep; Mostecky, J.

1988-01-01

Cerium is separated from a suspension produced during the aerial oxidation process. The suspension is subject to a cyclic process of two-stage fractional dissolution. Following the first dissolution, almost all cerium remains undissolved while 95% of the other lanthanides pass into the solution. The filtrate of the second stage of dissolution containing about 5% of ceriumm is returned for oxidation with the next batch of hydroxide mixed concentrate. Following oxidation, the two-stage fractional dissolution is repeated. This cycling provides quantitative cerium separation from other rare earth elements. (E.S.)

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.)

Characterization of platinized and unplatinized cerium dioxide and other cerium containing catalyst supports

International Nuclear Information System (INIS)

Daniel, D.W.

1984-01-01

The adsorption of CO on platinized cerium dioxide has been investigated by FTIR (Fourier Transform Infrared Spectroscopy). Four active surface sites and two adsorption geometries were found for the oxidized catalyst. Although the metallic sites and both geometries, linear and bridged, were retained upon reduction the two cationic sites were not. During stepwise desorption, CO dissociates leaving behind adsorbed carbon inhibiting readsorption. At elevated temperatures CeO 2 oxidizes Pt. The large decrease in CO adsorption resulting from high temperature reduction was reversed by reoxidation. XPS (X-ray Photoelectron Spectroscopy) data provided no evidence of encapsulation and XRD (X-ray Diffraction) showed the retention of a constant particle size. The results were interpreted as electronic metal-support interaction. The addition of H 2 or D 2 to adsorbed CO at 25 0 C caused spillover of the CO onto the support and a decrease in CO band frequency. When O 2 was added to preadsorbed CO a new band associated with oxygen and CO coadsorbed on a single Pt atom appeared. Carbon dioxide dissociation at room temperature is proposed to occur via a Langmuir-Hinshelwood mechanism. CO adsorption on platinized titania, silica, ceria/titania, ceria/silica, and cerium titanate has also been studied by the same techniques. The adsorption/desorption behavior of the cerium/titania and the single oxide systems paralleled that of Pt/CeO 2

Stepwise hydrochloric acid extraction of monazite hydroxides for the recovery of cerium lean rare earths, cerium, uranium and thorium

International Nuclear Information System (INIS)

Swaminathan, T.V.; Nair, V.R.; John, C.V.

1988-01-01

Monazite sand is normally processed by the caustic soda route to produce mixed rare earth chloride, thorium hydroxide and trisodium phosphate. Bulk of the mixed rare earth chloride is used for the preparation of FC catalysts. Recently some of the catalyst producers have shown preference to cerium depleted (lanthanum enriched) rare earth chloride rather than the natural rare earth chloride obtained from monazite. Therefore, a process for producing cerium depleted rare earth chloride, cerium, thorium and uranium from rare earth + thorium hydroxide obtained by treating monazite, based on stepwise hydrochloric acid extraction, was developed in the authors laboratory. The process involves drying of the mixed rare earth-thorium hydroxide cake obtained by monazite-caustic soda process followed by stepwise extraction of the dried cake with hydrochloric acid under specified conditions

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)

Studies on the promotion of nickel—alumina coprecipitated catalysts: III. Cerium oxide

NARCIS (Netherlands)

Lansink Rotgerink, H.G.J.; Slaa, J.C.; van Ommen, J.G.; Ross, J.R.H.

1988-01-01

Three series of cerium-promoted nickel—alumina catalysts with different nickel-to-aluminium ratios each containing different amounts of cerium have been prepared and characterized. The calcination and reduction behaviour were found not to be altered by the presence of cerium. Part of the promoter

Cerium-doped scintillating fused-silica fibers

Science.gov (United States)

Akchurin, N.; Cowden, C.; Damgov, J.; Dragoiu, C.; Dudero, P.; Faulkner, J.; Kunori, S.

2018-04-01

We report on a set of measurements made on (scintillating) cerium-doped fused-silica fibers using high-energy particle beams. These fibers were uniformly embedded in a copper absorber in order to utilize electromagnetic showers as a source of charged particles for generating signals. This new type of cerium-doped fiber potentially offers myriad new applications in calorimeters in high-energy physics, tracking systems, and beam monitoring detectors for future applications. The light yield, pulse shape, attenuation length, and light propagation speeds are given and discussed. Possible future applications are also explored.

Preparation of high-purity cerium nitrate; Preparacao de nitrato de cerio de alta pureza

Energy Technology Data Exchange (ETDEWEB)

Avila, Daniela Moraes; Silva Queiroz, Carlos Alberto da; Santos Mucillo, Eliana Navarro dos [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)

1995-12-31

The preparation of high-purity cerium nitrate has been carried out Cerium oxide has been prepared by fractioned precipitation and ionic exchange techniques, using a concentrate with approximately 85% of cerium oxide from NUCLEMON as raw material. Five sequential ion-exchange columns with a retention capacity of 170 g each have been used. The ethylenediamine-tetraacetic acid (EDTA) was used as eluent. The cerium content has been determined by gravimetry and iodometry techniques. The resulting cerium oxide has a purity > 99%. This material was transformed in cerium nitrate to be used as precursor for the preparation of Zirconia-ceria ceramics by the coprecipitation technique. (author) 2 tabs.

Synthesis and crystal kinetics of cerium oxide nanocrystallites prepared by co-precipitation process

International Nuclear Information System (INIS)

Shih, C.J.; Chen, Y.J.; Hon, M.H.

2010-01-01

Cerium oxide nanocrystallites were synthesized at a relatively low temperature using cerium nitrate as starting materials in a water solution by a co-precipitation process. Effect of calcination temperature on the crystallite growth of cerium oxide nano-powders was investigated by X-ray diffraction, transmission electron microscopy and electron diffraction. The crystallization temperature of the cerium oxide powders was estimated to be about 273 K by XRD analysis. When calcined from 473 to 1273 K, the crystallization of the face-centered cubic phase was observed by XRD. The crystallite size of the cerium oxide increased from 10.0 to 43.8 nm with calcining temperature increasing from 673 to 1273 K. The activation energy for growth of cerium oxide nanoparticles was found to be 16.0 kJ mol -1 .

Synthesis and crystal kinetics of cerium oxide nanocrystallites prepared by co-precipitation process

Energy Technology Data Exchange (ETDEWEB)

Shih, C.J., E-mail: cjshih@kmu.edu.tw [Department of Fragrance and Cosmetics Science, Kaohsiung Medical University, 100 Shi-Chuan 1st Road, Kaohsiung 807, Taiwan (China); Chen, Y.J. [Institute of Biomedical Sciences, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Hon, M.H. [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)

2010-05-15

Cerium oxide nanocrystallites were synthesized at a relatively low temperature using cerium nitrate as starting materials in a water solution by a co-precipitation process. Effect of calcination temperature on the crystallite growth of cerium oxide nano-powders was investigated by X-ray diffraction, transmission electron microscopy and electron diffraction. The crystallization temperature of the cerium oxide powders was estimated to be about 273 K by XRD analysis. When calcined from 473 to 1273 K, the crystallization of the face-centered cubic phase was observed by XRD. The crystallite size of the cerium oxide increased from 10.0 to 43.8 nm with calcining temperature increasing from 673 to 1273 K. The activation energy for growth of cerium oxide nanoparticles was found to be 16.0 kJ mol{sup -1}.

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.

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

Synthesis and characterization of magnesium doped cerium oxide for the fuel cell application

International Nuclear Information System (INIS)

Kumar, Amit; Kumari, Monika; Kumar, Mintu; Kumar, Sacheen; Kumar, Dinesh

2016-01-01

Cerium oxide has attained much attentions in global nanotechnology market due to valuable application for catalytic, fuel additive, and widely as electrolyte in solid oxide fuel cell. Doped cerium oxide has large oxygen vacancies that allow for greater reactivity and faster ion transport. These properties make cerium oxide suitable material for SOFCs application. Cerium oxide electrolyte requires lower operation temperature which shows improvement in processing and the fabrication technique. In our work, we synthesized magnesium doped cerium oxide by the co-precipitation method. With the magnesium doping catalytic reactivity of CeO_2 was increased. Synthesized nanoparticle were characterized by the XRD and UV absorption techniques.

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.

Thin film ionic conductors based on cerium oxide

International Nuclear Information System (INIS)

Haridoss, P.; Hellstrom, E.; Garzon, F.H.; Brown, D.R.; Hawley, M.

1994-01-01

Fluorite and perovskite structure cerium oxide based ceramics are a class of materials that may exhibit good oxygen ion and/or protonic conductivity. The authors have successfully deposited thin films of these materials on a variety of substrates. Interesting orientation relationships were noticed between cerium oxide films and strontium titanate bi-crystal substrates. Near lattice site coincidence theory has been used to study these relationships

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)

Antimicrobial cerium ion-chitosan crosslinked alginate biopolymer films: A novel and potential wound dressing.

Science.gov (United States)

Kaygusuz, Hakan; Torlak, Emrah; Akın-Evingür, Gülşen; Özen, İlhan; von Klitzing, Regine; Erim, F Bedia

2017-12-01

Wound dressings require good antiseptic properties, mechanical strength and, more trustably, natural material ingredients. Antimicrobial properties of cerium ions and chitosan are known and alginate based wound dressings are commercially available. In this study, the advantages of these materials were combined and alginate films were crosslinked with cerium(III) solution and chitosan added cerium(III) solution. Films were characterized by Fourier transform infrared spectroscopy (FTIR), light transmittance, scanning electron microscopy (SEM), swelling experiments, water vapor transmittance tests, and mechanical stretching tests. The antibacterial and physical properties of the films were compared with those of conventional calcium alginate films. Both cerium ion crosslinked and cerium ion-chitosan crosslinked alginate films gained antibacterial activity against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. Cerium alginate-chitosan films showed high resistance to being deformed elastically. Results show that cerium alginate-chitosan films can be flexible, ultraviolet-protecting, and antibacterial wound dressings. Copyright © 2017 Elsevier B.V. All rights reserved.

Casting Characteristics of High Cerium Content Aluminum Alloys

Energy Technology Data Exchange (ETDEWEB)

Weiss, D; Rios, O R; Sims, Z C; McCall, S K; Ott, R T

2017-09-05

This paper compares the castability of the near eutectic aluminum-cerium alloy system to the aluminum-silicon and aluminum-copper systems. The alloys are compared based on die filling capability, feeding characteristics and tendency to hot tear in both sand cast and permanent mold applications. The castability ranking of the binary Al–Ce systems is as good as the aluminum-silicon system with some deterioration as additional alloying elements are added. In alloy systems that use cerium in combination with common aluminum alloying elements such as silicon, magnesium and/or copper, the casting characteristics are generally better than the aluminum-copper system. In general, production systems for melting, de-gassing and other processing of aluminum-silicon or aluminum-copper alloys can be used without modification for conventional casting of aluminum-cerium alloys.

Effect of adduct formation on valent state of cerium in its ν-diketonates

International Nuclear Information System (INIS)

Spitsyn, V.I.; Martynenko, L.I.; Pechurova, N.I.; Snezhko, N.I.; Murav'eva, I.A.; Anufrieva, S.I.

1982-01-01

Physicochemical investigation of the system cerium (III, IV)-ν-diketone-additional ligand shows that ν-diketonate ability to adduct formation decreases in the series tenoyltrifluoro-acetonate > acetylacetonate > dibenzoylmethanate > benzoylmethanate. Adduct formation of the cerium (III, IV) ν-diketonates stabilizes cerium in trivalent condition, while oxidation degree 4+ is stable in tetrakis-ν-diketonates. The additional ligands are arranged in the series: tributhylphosphate < trioctyl-phosphineoxide < triphenylphosphineoxide < α, α'-dipyridyl < o-phenanthroline by the effect on cerium (III) stabilization in its ν-diketonates

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)

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

Effect of adduct formation on valent state of cerium in its. beta. -diketonates

Energy Technology Data Exchange (ETDEWEB)

Spitsyn, V.I.; Martynenko, L.I.; Pechurova, N.I.; Snezhko, N.I.; Murav' eva, I.A.; Anufrieva, S.I. (Moskovskij Gosudarstvennyj Univ. (USSR))

1982-04-01

Physicochemical investigation of the system cerium (III, IV)-..beta..-diketone-additional ligand shows that ..beta..-diketonate ability to adduct formation decreases in the series tenoyltrifluoro-acetonate > acetylacetonate > dibenzoylmethanate > benzoylmethanate. Adduct formation of the cerium (III, IV) ..beta..-diketonates stabilizes cerium in trivalent condition, while oxidation degree 4+ is stable in tetrakis-..beta..-diketonates. The additional ligands are arranged in the series: tributhylphosphate < trioctyl-phosphineoxide < triphenylphosphineoxide < ..cap alpha.., ..cap alpha..'-dipyridyl < o-phenanthroline by the effect on cerium (III) stabilization in its ..beta..-diketonates.

Tuning Reactivity and Electronic Properties through Ligand Reorganization within a Cerium Heterobimetallic Framework

Energy Technology Data Exchange (ETDEWEB)

Robinson, Jerome R.; Gordon, Zachary; Booth, Corwin H.; Carroll, Patrick J.; Walsh, Patrick J.; Schelter, Eric J.

2014-06-24

Cerium compounds have played vital roles in organic, inorganic, and materials chemistry due to their reversible redox chemistry between trivalent and tetravalent oxidation states. However, attempts to rationally access molecular cerium complexes in both oxidation states have been frustrated by unpredictable reactivity in cerium(III) oxidation chemistry. Such oxidation reactions are limited by steric saturation at the metal ion, which can result in high energy activation barriers for electron transfer. An alternative approach has been realized using a rare earth/alkali metal/1,1'-BINOLate (REMB) heterobimetallic framework, which uses redox-inactive metals within the secondary coordination sphere to control ligand reorganization. The rational syntheses of functionalized cerium(IV) products and a mechanistic examination of the role of ligand reorganization in cerium(III) oxidation are presented.

Comparison of Titration ICP and XRF Spectrometry Methods in Determination of Cerium in Lens Polishing Powder

International Nuclear Information System (INIS)

Ninlaphruk, Sumalee; Pichestapong, Pipat; Mungpayabal, Harinate; Jiyavaranant, Thitima; Srisukho, Supapan; Chaisai, Prapassurn

2004-10-01

Three analytical methods in determination of cerium in cerium oxide separated from monazite ore for producing lens polishing powder were compared. These methods are titration ICP and XRF spectrometry techniques. The cerium oxide sample with estimated 45% cerium content needed to be digested and converted into solution before the analysis. The analytical results shown significantly no difference between each method. However, the titration method was found to be more convenient and suitable for quality control in the production of cerium oxide as it does not require standard cerium and the complicated analytical instruments

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)

Direct growth of cerium oxide nanorods on diverse substrates for superhydrophobicity and corrosion resistance

International Nuclear Information System (INIS)

Cho, Young Jun; Jang, Hanmin; Lee, Kwan-Soo; Kim, Dong Rip

2015-01-01

Graphical abstract: - Highlights: • Cerium oxide nanorods were uniformly grown on diverse substrates. • Changes in growth conditions led to morphology evolution of cerium oxide nanostructures. • The grown cerium oxide nanostructures were single or poly crystalline. • Direct growth of cerium oxide nanorods made the diverse substrates superhydrophobic and anti-corrosive without any surface modifiers. - Abstract: Superhydrophobic surfaces with anti-corrosion properties have attracted great interest in many industrial fields, particularly to enhance the thermal performance of offshore applications such as heat exchangers, pipelines, power plants, and platform structures. Nanostructures with hydrophobic materials have been widely utilized to realize superhydrophobicity of surfaces, and cerium oxide has been highlighted due to its good corrosion resistive and intrinsically hydrophobic properties. However, few studies of direct growth of cerium oxide nanostructures on diverse substrates have been reported. Herein we report a facile hydrothermal method to directly grow cerium oxide nanorods on diverse substrates, such as aluminum alloy, stainless steel, titanium, and silicon. Diverse substrates with cerium oxide nanorods exhibited superhydrophobicity with no hydrophobic modifiers on their surfaces, and showed good corrosion resistive properties in corrosive medium. We believe our method could pave the way for realization of scalable and sustainable corrosion resistive superhydrophobic surfaces in many industrial fields

Direct growth of cerium oxide nanorods on diverse substrates for superhydrophobicity and corrosion resistance

Energy Technology Data Exchange (ETDEWEB)

Cho, Young Jun; Jang, Hanmin; Lee, Kwan-Soo [School of Mechanical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Kim, Dong Rip, E-mail: dongrip@hanyang.ac.kr [School of Mechanical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Institute of Nano Science and Technology, Hanyang University, Seoul 133-791 (Korea, Republic of)

2015-06-15

Graphical abstract: - Highlights: • Cerium oxide nanorods were uniformly grown on diverse substrates. • Changes in growth conditions led to morphology evolution of cerium oxide nanostructures. • The grown cerium oxide nanostructures were single or poly crystalline. • Direct growth of cerium oxide nanorods made the diverse substrates superhydrophobic and anti-corrosive without any surface modifiers. - Abstract: Superhydrophobic surfaces with anti-corrosion properties have attracted great interest in many industrial fields, particularly to enhance the thermal performance of offshore applications such as heat exchangers, pipelines, power plants, and platform structures. Nanostructures with hydrophobic materials have been widely utilized to realize superhydrophobicity of surfaces, and cerium oxide has been highlighted due to its good corrosion resistive and intrinsically hydrophobic properties. However, few studies of direct growth of cerium oxide nanostructures on diverse substrates have been reported. Herein we report a facile hydrothermal method to directly grow cerium oxide nanorods on diverse substrates, such as aluminum alloy, stainless steel, titanium, and silicon. Diverse substrates with cerium oxide nanorods exhibited superhydrophobicity with no hydrophobic modifiers on their surfaces, and showed good corrosion resistive properties in corrosive medium. We believe our method could pave the way for realization of scalable and sustainable corrosion resistive superhydrophobic surfaces in many industrial fields.

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)

Dielectric parameters of blood plasma of rats treated with cerium-144 and external irradiation

International Nuclear Information System (INIS)

Hadzhidekova, E.; Kiradzhiev, G.; Paskalev, Z.; Miloslavov, V.

1988-01-01

Investigation was carried out of the dielectric parameters of blood plasma of male Wistar rats treated with cerium 144 in doses of 370 kBq/animal and external gamma irradiation in doses of 200 cGy and 400 cGy. The radioactive cerium was introduced intraperitoneally 1 h after the external irradiation with dose rate of 1,6 cGy/sec. The permittivity ε, the time of relaxation τ and the coefficient of Debaye κ of plasma protein molecules were determined at the 1st, 3rd, 10th, 15th, and 30th days after treatement for frequence ranges of 1,4, 2,2, 3,6 and 6 MHz. At the same terms the content of cerium 144 was measured in the organs of predilectional accumulation of cerium. It was established that the treatment only with cerium lead to most essential changes of dielectric parameters at frequence of 3,6 MHz. The external irradiation didn't influence essentially the kinetics of absorbed cerium. In combination of both radiation factors the action of cerium was predominant

Critical indices for reversible gamma-alpha phase transformation in metallic cerium

Science.gov (United States)

Soldatova, E. D.; Tkachenko, T. B.

1980-08-01

Critical indices for cerium have been determined within the framework of the pseudobinary solution theory along the phase equilibrium curve, the critical isotherm, and the critical isobar. The results obtained verify the validity of relationships proposed by Rushbrook (1963), Griffiths (1965), and Coopersmith (1968). It is concluded that reversible gamma-alpha transformation in metallic cerium is a critical-type transformation, and cerium has a critical point on the phase diagram similar to the critical point of the liquid-vapor system.

Characterization of microstructure and catalytic of cerium oxide obtained by colloidal solution

International Nuclear Information System (INIS)

Senisse, C.A.L.; Bergmann, C.P.; Alves, A.K.

2012-01-01

This study investigated to obtain particles of cerium oxide, for use as catalysts for the combustion of methane using the technique of through polymeric colloidal solution. Obtaining the colloidal system is based on hydrolysis of salts such as cerium acetylacetonate, cerium nitrate in the presence of additives such as polyvinylbutyral (PVB), polyvinylpyrrolidone (PVP) and polyvinyl acetate (PVA), at concentrations of 5, 10 and 15% in aqueous or alcoholic medium. These solutions containing ions of interest were subjected to a heat treatment at 650° C for 30 minutes, with heating rate of 2 ° C/ min. After heat treatment, the fibers were characterized according to their morphology, surface area, crystallinity, weight loss and catalytic activity. Samples obtained from cerium acetylacetonate were more reactive than the cerium nitrate to the combustion of methane, as showed greater conversions and higher temperatures reached during the process, which is of utmost importance since the combustion catalytic methane is used for generating thermal energy. After the reaction with methane, the samples underwent significant change in surface area, probably due to the intensity of combustion reactions of the nitrate and the generation of heat involved in this reaction, which gave rise to coarse particles. During the combustion process using the obtained from particles of cerium acetylacetonate, there was the release of large quantities of nitrogen compared to the results of assays with the particles obtained with cerium nitrate. (author)

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

Nanoparticulate cerium dioxide and cerium dioxide-titanium dioxide composite thin films on glass by aerosol assisted chemical vapour deposition

International Nuclear Information System (INIS)

Qureshi, Uzma; Dunnill, Charles W.; Parkin, Ivan P.

2009-01-01

Two series of composite thin films were deposited on glass by aerosol assisted chemical vapour deposition (AACVD)-nanoparticulate cerium dioxide and nanoparticulate cerium dioxide embedded in a titanium dioxide matrix. The films were analysed by a range of techniques including UV-visible absorption spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive analysis by X-rays. The AACVD prepared films showed the functional properties of photocatalysis and super-hydrophilicity. The CeO 2 nanoparticle thin films displaying photocatalysis and photo-induced hydrophilicity almost comparable to that of anatase titania.

Berkelium (4) and cerium (4) extraction with tertiary amines

International Nuclear Information System (INIS)

Milyukova, M.S.; Malikov, D.A.; Myasoedov, B.V.

1978-01-01

Oxidation of indicator quantities of berkelium and cerium by a mixture of silver nitrate and ammonium persulfate in the solutions of nitric and sulfuric acid has been examined. The stability of the elements in a tetravalent state and their extraction by the solutions of ternary amines have been investigated. It has been established that berkelium and cerium oxidation under these conditions occurs under the effect of ions of divalent silver which is formed owing to oxidation of monovalent silver by peroxide sulfate ions. The following supposition has been put forward: a difference in the behaviour of tetravalent berkelium and cerium during their extraction by ternary amines is explained by their different stability in this state, but not by the formation of complex compounds with nitrate ions

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

Separation of cerium and fractionation of rare earths from mixed chlorides

International Nuclear Information System (INIS)

Silva Queiroz, C.A. da; Sood, S.P.; Abrao, A.

1982-01-01

The separation of cerium from rare earths chlorides solutions by precipitation with hydrogen peroxide/air/dil. ammonium hydroxide; purification of cerium; fractionation by ion exchange and analytical control of the process are presented. (A.R.H.) [pt

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)

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

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.

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)

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)

Two-phase titration of cerium(III) by permanganate

International Nuclear Information System (INIS)

Lazarev, A.I.; Lazareva, V.I.; Gerko, V.V.

1987-01-01

This paper presents a method for the two-phase titrimetric determination of cerium(III) with permanganate which does not require an expenditure of sugar and preliminary removal of chlorides and nitrates. The interaction of cerium(III) with permanganate at room temperature was studied as a function of the pH, the concentration of pyrophosphate, tetraphenylphosphonium (TPP), permanganate, and extraneous compounds, the rate of titration, and the time of stay of the solution in air before titration. The investigations were conducted according to the following methodology: water, solution of cerium(III) pyrophosphate, and TPP were introduced into an Erlenmeyer flask with a side branch near the bottom for clearer observation of the color of the chloroform phase. The authors established the given pH value, poured the water into a volume of 50 ml, and added chloroform. The result was titrated with permanganate solutions of various concentrations until a violet color appeared in the chloroform phase

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

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.

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

Processing and Characterization of Sol-Gel Cerium Oxide Microspheres

Energy Technology Data Exchange (ETDEWEB)

McClure, Zachary D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Padilla Cintron, Cristina [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2016-09-27

Of interest to space exploration and power generation, Radioisotope Thermoelectric Generators (RTGs) can provide long-term power to remote electronic systems without the need for refueling or replacement. Plutonium-238 (Pu-238) remains one of the more promising materials for thermoelectric power generation due to its high power density, long half-life, and low gamma emissions. Traditional methods for processing Pu-238 include ball milling irregular precipitated powders before pressing and sintering into a dense pellet. The resulting submicron particulates of Pu-238 quickly accumulate and contaminate glove boxes. An alternative and dust-free method for Pu-238 processing is internal gelation via sol-gel techniques. Sol-gel methodology creates monodisperse and uniform microspheres that can be packed and pressed into a pellet. For this study cerium oxide microspheres were produced as a surrogate to Pu-238. The similar electronic orbitals between cerium and plutonium make cerium an ideal choice for non-radioactive work. Before the microspheres can be sintered and pressed they must be washed to remove the processing oil and any unreacted substituents. An investigation was performed on the washing step to find an appropriate wash solution that reduced waste and flammable risk. Cerium oxide microspheres were processed, washed, and characterized to determine the effectiveness of the new wash solution.

Cerium; crystal structure and position in the periodic table.

Science.gov (United States)

Johansson, Börje; Luo, Wei; Li, Sa; Ahuja, Rajeev

2014-09-17

The properties of the cerium metal have intrigued physicists and chemists for many decades. In particular a lot of attention has been directed towards its high pressure behavior, where an isostructural volume collapse (γ phase → α phase) has been observed. Two main models of the electronic aspect of this transformation have been proposed; one where the 4f electron undergoes a change from being localized into an itinerant metallic state, and one where the focus is on the interaction between the 4f electron and the conduction electrons, often referred to as the Kondo volume collapse model. However, over the years it has been repeatedly questioned whether the cerium collapse really is isostructural. Most recently, detailed experiments have been able to remove this worrisome uncertainty. Therefore the isostructural aspect of the α-γ transition has now to be seriously addressed in the theoretical modeling, something which has been very much neglected. A study of this fundamental characteristic of the cerium volume collapse is made in present paper and we show that the localized [rlhar2 ] delocalized 4f electron picture provides an adequate description of this unique behavior. This agreement makes it possible to suggest that an appropriate crossroad position for cerium in The Periodic Table.

Cerium oxide and platinum nanoparticles protect cells from oxidant-mediated apoptosis

International Nuclear Information System (INIS)

Clark, Andrea; Zhu Aiping; Sun Kai; Petty, Howard R.

2011-01-01

Catalytic nanoparticles represent a potential clinical approach to replace or correct aberrant enzymatic activities in patients. Several diseases, including many blinding eye diseases, are promoted by excessive oxidant stress due to reactive oxygen species (ROS). Cerium oxide and platinum nanoparticles represent two potentially therapeutic nanoparticles that de-toxify ROS. In the present study, we directly compare these two classes of catalytic nanoparticles. Cerium oxide and platinum nanoparticles were found to be 16 ± 2.4 and 1.9 ± 0.2 nm in diameter, respectively. Using surface plasmon-enhanced microscopy, we find that these nanoparticles associate with cells. Furthermore, cerium oxide and platinum nanoparticles demonstrated superoxide dismutase catalytic activity, but did not promote hemolytic or cytolytic pathways in living cells. Importantly, both cerium oxide and platinum nanoparticles reduce oxidant-mediated apoptosis in target cells as judged by the activation of caspase 3. The ability to diminish apoptosis may contribute to maintaining healthy tissues.

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)

Thermal Treatment of Cerium Oxide and Its Properties: Adsorption Ability versus Degradation Efficiency

Directory of Open Access Journals (Sweden)

Pavel Janoš

2014-01-01

Full Text Available Cerium oxide belongs to the most important heterogeneous catalysts, but its applicability as so-called reactive sorbent for the degradation of toxic chemicals was only recently discovered. For these purposes, cerium oxide is prepared by precipitation of insoluble cerium salts (carbonates with a subsequent thermal decomposition. Properties of cerium oxide prepared from the carbonate precursor are strongly affected by the temperature during the calcination. Main physicochemical properties of cerium oxide (specific surface area, crystallinity, and surface chemistry were examined in dependence on the calcination temperature. As the adsorptive properties of CeO2 are undoubtedly of great importance in the abovementioned applications, the adsorption ability was studied using an azo dye Acid Orange 7 (AO7 as a model compound. The highest sorption efficiency towards AO7 exhibited sorbents prepared at temperatures below 700°C, which was attributed mainly to the presence of hydroxyl groups on the oxide surface. A strong correlation was found between an adsorption efficiency of cerium oxides and their degradation efficiency for organophosphate pesticide parathion methyl. The >Ce–OH groups on the sorbent surface are responsible for the dye binding by the surface-complexation mechanism, and probably also for the nucleophilic cleavage of the P–O–aryl bond in the pesticide molecule.

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)

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.

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

An Economic Model and Experiments to Understand Aluminum-Cerium Alloy Recycling

Science.gov (United States)

Iyer, Ananth V.; Lim, Heejong; Rios, Orlando; Sims, Zachary; Weiss, David

2018-04-01

We provide an economic model to understand the impact of adoption, sorting and pricing of scrap on the recycling of a new aluminum-cerium (AlCe) alloy for use in engine blocks in the automobile industry. The goal of the laboratory portion of this study is to investigate possible effects of cerium contamination on well-established aluminum recycling streams. Our methodology includes three components: (1) focused data gathering from industry supply chain participants, (2) experimental data through laboratory experiments to understand the impact of cerium on existing alloys and (3) an economic model to understand pricing incentives on a recycler's separation of AlCe engine blocks.

Extraction-differential-photometric method to determine rare earths of cerium subgroup

International Nuclear Information System (INIS)

Askerov, D.N.; Gusejnov, I.K.; Melikov, A.A.

1985-01-01

The extraction - photometric method to determine great quantities of rare earths of the cerium subgroup as a complex with antipyrine A and diphenylguanidine is developed. Isobutyl and n-butyl alcohols are used as extractants. It is established that proportional dependence between relative optical density and concentration of rare earths of the cerium subgroup in the solution takes place in the concentration interval of 10.3-14.7 μg of rare earths in 1 ml of the solution. Determination error is+-1.12%. The technique is used to determine rare earths of the cerium subgroup in rare earth oxides of a mixed composition, as well as in monozite and loparite

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)

Spectrophotometric determination of cerium with methylthymol blue in the presence of oxalate and cyanide as masking agents

Energy Technology Data Exchange (ETDEWEB)

Cabrera-Martin, A; Izquierdo-Hornillos, R; Quejido-Cabezas, A J; Peral-Fernandez, J L [Universidad Complutense de Madrid (Spain). Facultad de Ciencias Quimicas

1983-04-01

The spectrophotometric determination of cerium can be carried out by several methods, which involve either the formation of complexes of cerium(III) and cerium(IV) or the oxidation of suitable reagents by cerium(IV) and further measuring the intensity of the colour of the oxidised matter. The latter methods show a lack of selectivity and low sensitivity owing to the nature of the redox reaction. The methods that involve the formation of complexes have also been shown to have low selectivity and sensitivity. However, the most useful methods are those based on the complexes of cerium(III) with Xylenol Orange and Methylthymol Blue (MTB), but they are affected by many interferences. In this work the reaction of cerium(III) with MTB in the presence of oxalate and cyanide ions was studied at pH 10.2, which improves the sensitivity and the selectivity of the determination of cerium.

Inhibition of pH fronts in corrosion cells due to the formation of cerium hydroxide

NARCIS (Netherlands)

Soestbergen, M. van; Erich, S.J.F.; Huinink, H.P.; Adan, O.C.G.

2013-01-01

The effect of cerium-based corrosion inhibitors on the pH front between the alkaline cathode and acidic anode in corrosion cells has been studied. The cerium component of these inhibitors can affect the pH front since it precipitates in an alkaline environment as cerium hydroxide, which is important

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.

Solvent extraction of cerium (III) with high molecular weight amines

International Nuclear Information System (INIS)

Chatterjee, A.; Basu, S.

1992-01-01

The use of high molecular weight amines in the extraction of cerium (III) as EDTA complex from neutral aqueous medium is reported. The extraction condition was optimised from the study of effects of several variables like concentration of amine and EDTA pH nature of diluents etc. The method has been applied for the determination of cerium in few mineral samples. (author). 7 refs., 5 tabs

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

Study of cerium diffusion in undoped lithium-6 enriched glass with Rutherford backscattering spectrometry

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiaodong, E-mail: xzhang39@utk.edu [Department of Nuclear Engineering, University of Tennessee, TN 37996 (United States); Moore, Michael E.; Lee, Kyung-Min; Lukosi, Eric D. [Department of Nuclear Engineering, University of Tennessee, TN 37996 (United States); Hayward, Jason P. [Department of Nuclear Engineering, University of Tennessee, TN 37996 (United States); Oak Ridge National Lab, Oak Ridge, TN 37831 (United States)

2016-07-01

Undoped lithium-6 enriched glasses coated with pure cerium (99.9%) with a gold protection layer on top were heated at three different temperatures (500, 550, and 600 °C) for varied durations (1, 2, and 4 h). Diffusion profiles of cerium in such glasses were obtained with the conventional Rutherford backscattering technique. Through fitting the diffusion profiles with the thin-film solution of Fick’s second law, diffusion coefficients of cerium with different annealing temperatures and durations were solved. Then, the activation energy of cerium for the diffusion process in the studied glasses was found to be 114 kJ/mol with the Arrhenius equation.

Optical properties of cerium oxide (CeO2) nanoparticles synthesized by hydroxide mediated method

Science.gov (United States)

Ali, Mawlood Maajal; Mahdi, Hadeel Salih; Parveen, Azra; Azam, Ameer

2018-05-01

The nanoparticles of cerium oxide have been successfully synthesized by hydroxide mediated method, using cerium nitrate and sodium hydroxide as precursors. The microstructural properties were analyzed by X-ray diffraction technique (XRD). The X-ray diffraction results show that the cerium oxide nanoparticles were in cubic structure. The optical absorption spectra of cerium oxide were recorded by UV-VIS spectrophotometer in the range of 320 to 600 nm and photoluminescence spectra in the range of 400-540 nm and have been presented. The energy band gap was determined by Tauc relationship. The crystallite size was determined from Debye-Scherer equation and came out to be 6.4 nm.

Study of cerium diffusion in undoped lithium-6 enriched glass with Rutherford backscattering spectrometry

Science.gov (United States)

Zhang, Xiaodong; Moore, Michael E.; Lee, Kyung-Min; Lukosi, Eric D.; Hayward, Jason P.

2016-07-01

Undoped lithium-6 enriched glasses coated with pure cerium (99.9%) with a gold protection layer on top were heated at three different temperatures (500, 550, and 600 °C) for varied durations (1, 2, and 4 h). Diffusion profiles of cerium in such glasses were obtained with the conventional Rutherford backscattering technique. Through fitting the diffusion profiles with the thin-film solution of Fick's second law, diffusion coefficients of cerium with different annealing temperatures and durations were solved. Then, the activation energy of cerium for the diffusion process in the studied glasses was found to be 114 kJ/mol with the Arrhenius equation.

Study of phase transitions in cerium in shock-wave experiments

Directory of Open Access Journals (Sweden)

Zhernokletov M.V.

2015-01-01

Full Text Available Cerium has a complex phase diagram that is explained by the presence of structure phase transitions. Planar gauges were used in various combinations in experiments for determination of sound velocity dependence on pressure in cerium by the technique of PVDF gauge. The data of time dependence on pressure profiles with use of x(t diagrams and the D(u relation for cerium allowed the definition of the Lagrangian velocity of the unloading wave CLagr and the Eulerian velocity CEul by taking into account the compression σ. These results accords with data obtained by using the technique of VISAR and a manganin-based gauge, and calculated pressure dependence of isentropic sound velocity according to the VNIITF EOS. Metallography analysis of post-experimental samples did not find any changes in a phase composition.

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

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

The solvent extraction of cerium from sulphate solution - mini plant trials

International Nuclear Information System (INIS)

Soldenhoff, K.; Wilkins, D.; Ring, R.

1998-01-01

Full text: The Mt. Weld deposit in Western Australia has a complex rare earth mineralisation. The rare earth phosphate minerals, which include monazite, are amenable to conventional caustic cracking followed by hydrochloric acid dissolution of the trivalent rare earths. The presence of the mineral cerianite in the ore, which is unaffected by the alkali attack, results in rejection of a considerable proportion of the cerium to the acid leach residue. The recovery of cerium from a sulphate solution, resulting from the processing of such a residue, is the subject of the current paper. The liquor treated by solvent extraction contained 63 g L -1 rare earths and the cerium to total rare earth ratio was 75%. Other impurities, including Fe and Th, totalled 2000 ppm. A solvent mixture of commercially available extractants in a low aromatic content diluent was used to extract Ce 4+ selectively over the trivalent rare earths. Partial co-extraction of Fe and Th occurred but it was found that these elements were not easily stripped and therefore selective back extraction of cerium was possible. The cerium was stripped from the organic phase by hydrochloric acid and hydrogen peroxide. In continuous counter-current trials two extraction stages and three strip stages were used. In order to produce two grades of strip liquor, stripping was divided into two circuits. The first strip circuit consisting of a single stage, contained proportionally more of the trivalent rare earths. The second strip circuit, consisting of two stages, removed the remaining cerium with proportionally less of the rare earths. A bleed solvent stream was treated for removal of impurities to prevent build-up in the solvent. In the continuous counter current trials, 95% Ce 4+ extraction was achieved and the Ce to total rare earth ratio was upgraded to > 99%

Spectrofluorimetric determination of cerium by flow injection analysis

International Nuclear Information System (INIS)

Liu Shaorong; Meng Jian; Liu Wenhua

1990-01-01

A spectrofluorimetric method for the determination of cerium (λ ex/em:251/365 nm) in hydrochloric acid solution by flow injection analysis is presented. It has well developed the normal spectrofluorimetric method for determination of cerium and has made: 1, the determination procedure shortened; 2, the determination speed increased to about 180 samples per hour; 3, the determination range widened to 0.05-100.0 ppm CeO 2 , abouot two times as wide as the normal spectrofluorimetric method; and 4, the relative standard deviation lessened (about 0.47% for 0.1 ppm CeO 2 , n = 13)

Environmental Geochemistry of Cerium: Applications and Toxicology of Cerium Oxide Nanoparticles

Directory of Open Access Journals (Sweden)

Jessica T. Dahle

2015-01-01

Full Text Available Cerium is the most abundant of rare-earth metals found in the Earth’s crust. Several Ce-carbonate, -phosphate, -silicate, and -(hydroxide minerals have been historically mined and processed for pharmaceutical uses and industrial applications. Of all Ce minerals, cerium dioxide has received much attention in the global nanotechnology market due to their useful applications for catalysts, fuel cells, and fuel additives. A recent mass flow modeling study predicted that a major source of CeO2 nanoparticles from industrial processing plants (e.g., electronics and optics manufactures is likely to reach the terrestrial environment such as landfills and soils. The environmental fate of CeO2 nanoparticles is highly dependent on its physcochemical properties in low temperature geochemical environment. Though there are needs in improving the analytical method in detecting/quantifying CeO2 nanoparticles in different environmental media, it is clear that aquatic and terrestrial organisms have been exposed to CeO2 NPs, potentially yielding in negative impact on human and ecosystem health. Interestingly, there has been contradicting reports about the toxicological effects of CeO2 nanoparticles, acting as either an antioxidant or reactive oxygen species production-inducing agent. This poses a challenge in future regulations for the CeO2 nanoparticle application and the risk assessment in the environment.

Electrorefining of Cerium in LiCl-KCl Molten Salts

International Nuclear Information System (INIS)

Campbell-Kelly, R.P.; Paget, T.J.

2010-01-01

Electrorefining of cerium from cerium-gallium alloys has been demonstrated in lithium chloride-potassium chloride salts at temperatures below 500 deg. C, with excellent current efficiencies and high product yields. These experiments are being carried out as non-active trials for a process for the purification of impure actinide metals. The results reported show anodic current efficiencies consistently close to 100%, and in several experiments complete oxidation of the cerium in the feed occurred. The cathodic product is hard and metallic, and incorporates a significant amount of salt into its structure. The product can be consolidated into a dense, pure metal by melting under calcium chloride at 850 deg. C. The yield of this consolidation step varies between 16 and 75%, seeming to depend on the total mass of metal being consolidated and the quality of inert atmosphere. A small-scale electrochemical cell has been demonstrated which will be used in initial active experiments. (authors)

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.

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

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.

Corrosion resistance of flaky aluminum pigment coated with cerium oxides/hydroxides in chloride and acidic electrolytes

International Nuclear Information System (INIS)

Niroumandrad, S.; Rostami, M.; Ramezanzadeh, B.

2015-01-01

Graphical abstract: - Highlights: • Flaky aluminum pigments were modified with cerium nitrate salt. • pH value of 3.0 was chosen as the optimized pH for the cerium solution. • Corrosion resistance of the pigment significantly increased after modification. • Alkaline pre-treatment prior to modification affected the cerium layer performance. - Abstract: The objective of this study was to enhance the corrosion resistance of lamellar aluminum pigment through surface treatment by cerium oxides/hydroxides. The surface composition of the pigments was studied by energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the pigment was evaluated by conventional hydrogen evolution measurements in acidic solution and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. Results showed that the Ce-rich coating composed of Ce 2 O 3 and CeO 2 was precipitated on the pigment surface after immersion in the cerium solution. The corrosion resistance of pigment was significantly enhanced after modification with cerium layer.

Corrosion resistance of flaky aluminum pigment coated with cerium oxides/hydroxides in chloride and acidic electrolytes

Energy Technology Data Exchange (ETDEWEB)

Niroumandrad, S. [Institute for Color Science and Technology (ICST), PO 16765-654, Tehran (Iran, Islamic Republic of); Rostami, M. [Department of Nanomaterials and Nanocoatings, Institute for Color Science and Technology (ICST), PO 16765-654, Tehran (Iran, Islamic Republic of); Ramezanzadeh, B., E-mail: ramezanzadeh-bh@icrc.ac.ir [Department of Surface Coatings and Corrosion, Institute for Color Science and Technology (ICST), PO 16765-654, Tehran (Iran, Islamic Republic of)

2015-12-01

Graphical abstract: - Highlights: • Flaky aluminum pigments were modified with cerium nitrate salt. • pH value of 3.0 was chosen as the optimized pH for the cerium solution. • Corrosion resistance of the pigment significantly increased after modification. • Alkaline pre-treatment prior to modification affected the cerium layer performance. - Abstract: The objective of this study was to enhance the corrosion resistance of lamellar aluminum pigment through surface treatment by cerium oxides/hydroxides. The surface composition of the pigments was studied by energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the pigment was evaluated by conventional hydrogen evolution measurements in acidic solution and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. Results showed that the Ce-rich coating composed of Ce{sub 2}O{sub 3} and CeO{sub 2} was precipitated on the pigment surface after immersion in the cerium solution. The corrosion resistance of pigment was significantly enhanced after modification with cerium layer.

The developments and challenges of cerium half-cell in zinc–cerium redox flow battery for energy storage

International Nuclear Information System (INIS)

Xie, Zhipeng; Liu, Qingchao; Chang, Zhiwen; Zhang, Xinbo

2013-01-01

Zinc–cerium redox flow batteries (ZCBs) are emerging as a very promising new technology with the potential to store a large amount of energy economically and efficiently, thanking to its highest thermodynamic open-circuit cell voltage among all the currently studied aqueous redox flow batteries. However, there are numerous scientific and technical challenges that must be overcome if this alluring promise is to turn into reality, from designing the battery structure, to optimizing the electrolyte compositions and elucidating the complex chemical reactions that occur during charge and discharge. This review article is the first summary of the most significant developments and challenges of cerium half-cell and the current understanding of their chemistry. We are certain that this review will be of great interest to audience over a broad range, especially in fields of energy storage, electrochemistry, and chemical engineering

Molecular and physiological responses to titanium dioxide and cerium oxide nanoparticles in Arabidopsis

Science.gov (United States)

- Changes in tissue transcriptomes and productivity of Arabidopsis thaliana were investigated during exposure of plants to two widely-used engineered metal oxide nanoparticles, titanium dioxide (nano-titanium) and cerium dioxide (nano-cerium). Microarray analyses confirmed that e...

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.

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

Electrochemical reduction of cerium oxide into metal

Energy Technology Data Exchange (ETDEWEB)

Claux, Benoit [CEA, Valduc, F-21120 Is-sur-Tille (France); Universite de Grenoble, LEPMI-ENSEEG, 1130 rue de la Piscine, BP75, F-38402 St Martin d' Heres Cedex (France); Serp, Jerome, E-mail: jerome.serp@cea.f [CEA, Valduc, F-21120 Is-sur-Tille (France); Fouletier, Jacques [Universite de Grenoble, LEPMI-ENSEEG, 1130 rue de la Piscine, BP75, F-38402 St Martin d' Heres Cedex (France)

2011-02-28

The Fray Farthing and Chen (FFC) and Ono and Suzuki (OS) processes were developed for the reduction of titanium oxide to titanium metal by electrolysis in high temperature molten alkali chloride salts. The possible transposition to CeO{sub 2} reduction is considered in this study. Present work clarifies, by electro-analytical techniques, the reduction pathway leading to the metal. The reduction of CeO{sub 2} into metal was feasible via an indirect mechanism. Electrolyses on 10 g of CeO{sub 2} were carried out to evaluate the electrochemical process efficiency. Ca metal is electrodeposited at the cathode from CaCl{sub 2}-KCl solvent and reacts chemically with ceria to form not only metallic cerium, but also cerium oxychloride.

Energy-dispersive X-ray fluorescence analysis of cerium in ferrosilicon

International Nuclear Information System (INIS)

Marbec, E.R.

1987-01-01

The cerium was determined in ferrosilicon samples by energy-dispersive X-ray fluorescence techniques (XRF) techniques, with a secondary target of gadolinium. The methods employed were: comparison and linear regression with reference materials with cerium concentration between 0.4 and 1.0%. The samples were prepared in the form of pellets and the analytical results are reported as an average of five determinations with a confidence limits at 95% probability. (Author) [es

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

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

Analysis of the effects of cerium on calcium ion in the protoplasts of ...

African Journals Online (AJOL)

Administrator

2011-09-12

Sep 12, 2011 ... African Journal of Biotechnology Vol. 10(52), pp. ... Paper. Analysis of the effects of cerium on calcium ion in the .... plasma membrane (Zeng et al., 2003). Recently .... cerium on vegetable growth of wheat (Triticum aestivum L.).

Study on the uranium-cerium extraction and his application to the treatment of irradiated uranium

International Nuclear Information System (INIS)

Lobao, Afonso dos Santos Tome

1979-01-01

It was made a study on the behavior of uranium and cerium(IV) extraction, using the latter element as a plutonium simulator in a flowsheet of the treatment of irradiated uranium. Cerium(IV) was used under the same conditions as a plutonium in the Purex process because the admitted similar properties. An experimental work was initiated to determine the equilibrium curves of uranium, under the following conditions: concentration of 1 to 20 g U/1 and acidity varying from 1 to 5M in HNO 3 . Other parameters studied were the volumetric ratio of the phases and the influence of the concentration of TBP (tri-n-butyl phosphate). To guarantee the cerium(IV) extraction, the diluent (varsol) was previously treated with 10% potassium dichromate in perchloric acid, potassium permanganate in 1M sulphuric acid and concentrated sulphuric acid at 70 deg to eliminate reducing compounds. The results obtained for cerium extraction, allowed a better understanding of its behavior in solution. The results permitted to conclude that the decontamination for cerium are very high in the first Purex extraction cycle. The easy as cerium(IV) is reduced to the trivalent state contributes a great deal to its decontamination. (author)

Influences of the main anodic electroplating parameters on cerium oxide films

Energy Technology Data Exchange (ETDEWEB)

Yang, Yang; Yang, Yumeng; Du, Xiaoqing; Chen, Yu [Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang (China); Zhang, Zhao, E-mail: eaglezzy@zjuem.zju.edu.cn [Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang (China); Zhang, Jianqing [Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang (China); State Key Laboratory for Corrosion and Protection of Metals, Shenyang 110016 (China)

2014-06-01

Cerium oxide thin films were fabricated onto 316 L stainless steel via a potentiostatically anodic electrodeposition approach in the solutions containing cerium(III) nitrate (0.05 M), ammonia acetate (0.1 M) and ethanol (10% V/V). The electrochemical behaviors and deposition parameters (applied potential, bath temperature, dissolving O{sub 2} and bath pH) have been investigated. Results show that, the electrochemical oxidation of Ce{sup 3+} goes through one electrochemical step, which is under charge transfer control. The optimum applied potential for film deposition is 0.8 V. Bath temperature plays a significant effect on the deposition rate, composition (different colors of the film) and surface morphology of the deposits. Due to the hydrolysis of Ce{sup 3+}, cerous hydroxide is facility to form when the bath temperature is higher than 60 °C. The electroplating bath pH is another key role for the anodic deposition of cerium oxide thin films, and the best bath pH is around 6.20. N{sub 2} or O{sub 2} purged into the bath will result in film porosities and O{sub 2} favors cerium oxide particles and film generation.

Growth and characterization of Sm3+ doped cerium oxalate single crystals

Directory of Open Access Journals (Sweden)

Minu Mary C

2016-07-01

Full Text Available Single crystals of Sm3+ doped cerium oxalate decahydrate were synthesized using single diffusion gel technique and the conditions influencing the size, morphology, nucleation density and quality of the crystals were optimized. Highly transparent single crystals of average size 3 mm × 2 mm × 1 mm with well-defined hexagonal morphology were grown during a time period of two weeks. X-ray powder diffraction analysis revealed that the grown crystals crystallize in the monoclinic system with space group P21/c as identical with the pure cerium oxalate. The various functional groups of the oxalate ligand and the water of crystallization were identified by Fourier transform infrared spectroscopy. The photoluminescence spectrum of the Sm3+ doped cerium oxalate indicated that the Sm3+ ions are optically active in the cerium oxalate matrix. The crystal has a strong and efficient orange red emission with a wavelength peak at 595 nm and hence can be effectively used for optical amplification. Microhardness measurements of the crystal revealed that they belong to the soft material category.

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

Synthesis, characterization and antibacterial activity of hybrid chitosan-cerium oxide nanoparticles: As a bionanomaterials.

Science.gov (United States)

Senthilkumar, R P; Bhuvaneshwari, V; Ranjithkumar, R; Sathiyavimal, S; Malayaman, V; Chandarshekar, B

2017-11-01

The hybrid chitosan cerium oxide nanoparticles were prepared for the first time by green chemistry approach using plant leaf extract. The intense peak observed around 292nm in the UV-vis spectrum indicate the formation of cerium oxide nanoparticles. The XRD pattern revealed that the hybrid chitosan-cerium oxide nanoparticles have a polycrystalline structure with cubic fluorite phase. The FTIR spectrum of prepared samples showed the formation of Ce-O bonds and chitosan main chains COC and CO. The FESEM image of hybrid chitosan cerium oxide nanoparticles revealed that the particles are spherical in shape with grains size varying from 23.12nm to 89.91nm. EDAX analysis confirmed the presence of Ce, O, C and N elements in the prepared sample. TEM images showed that the prepared hybrid chitosan-cerium oxide nanoparticles are predominantly uniform in size and most of the particles are spherical in shape with less agglomeration and the particles size varies from 3.61nm to 24.40nm. The prepared chitosan cerium oxide nanoparticles of 50μL concentration showed good antibacterial properties against test pathogens, which was confirmed by the FESEM analysis. The prepared small particle size facilitate that these hybrid ChiCO 2 NPs could effectively be used in biomedical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

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.)

Oxochloroalkoxide of the Cerium (IV and Titanium (IV as oxides precursor

Directory of Open Access Journals (Sweden)

Machado Luiz Carlos

2002-01-01

Full Text Available The Cerium (IV and Titanium (IV oxides mixture (CeO2-3TiO2 was prepared by thermal treatment of the oxochloroisopropoxide of Cerium (IV and Titanium (IV. The chemical route utilizing the Cerium (III chloride alcoholic complex and Titanium (IV isopropoxide is presented. The compound Ce5Ti15Cl16O30 (iOPr4(OH-Et15 was characterized by elemental analysis, FTIR and TG/DTG. The X-ray diffraction patterns of the oxides resulting from the thermal decomposition of the precursor at 1000 degreesC for 36 h indicated the formation of cubic cerianite (a = 5.417Å and tetragonal rutile (a = 4.592Å and (c = 2.962 Å, with apparent crystallite sizes around 38 and 55nm, respectively.

Procedure for the separation of cerium from crude phosphates and rare earth concentrates

International Nuclear Information System (INIS)

Richter, H.; Koenig, O.; Schmitt, A.; Grauss, H.; Freitag, S.

1986-01-01

The invention has to do with a procedure for the separation of cerium from crude phosphates and rare earth phosphate concentrates originating from the partial neutralization of nitric crude phosphate decomposition solutions. It is aimed at the cerium separation from the raw material at an early stage of reprocessing without preceding elimination of other components and impurities. The rare earth phosphate concentrates or crude phosphates are dissolved in nitric acid, the Ce 3+ is oxidized with potassium permanganate or magnanese(IV) hydroxide, and cerium(IV) phosphate is precipitated as pure substance by decreasing the acidity of the solution

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.

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)

Oxidative stress induced by cerium oxide nanoparticles in cultured BEAS-2B cells

International Nuclear Information System (INIS)

Park, Eun-Jung; Choi, Jinhee; Park, Young-Kwon; Park, Kwangsik

2008-01-01

Cerium oxide nanoparticles of different sizes (15, 25, 30, 45 nm) were prepared by the supercritical synthesis method, and cytotoxicity was evaluated using cultured human lung epithelial cells (BEAS-2B). Exposure of the cultured cells to nanoparticles (5, 10, 20, 40 μg/ml) led to cell death, ROS increase, GSH decrease, and the inductions of oxidative stress-related genes such as heme oxygenase-1, catalase, glutathione S-transferase, and thioredoxin reductase. The increased ROS by cerium oxide nanoparticles triggered the activation of cytosolic caspase-3 and chromatin condensation, which means that cerium oxide nanoparticles exert cytotoxicity by an apoptotic process. Uptake of the nanoparticles to the cultured cells was also tested. It was observed that cerium oxide nanoparticles penetrated into the cytoplasm and located in the peri-region of the nucleus as aggregated particles, which may induce the direct interaction between nanoparticles and cellular molecules to cause adverse cellular responses

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.

Effect of correlation on the band structure of α-cerium

International Nuclear Information System (INIS)

Rao, R.S.; Singh, R.P.

1975-01-01

The electronic band structure of f.c.c. phase of the rare earth metal cerium (α-cerium) has been calculated using a formulation of the crystal potential where correlation also has been included in addition to exchange. The Green's function method of Korringa-Kohn and Rostoker has been used due to obvious advantages in calculation. The calculations indicate that the s-d bands are hybridized with the f-levels but the f-bands are fairly narrow and lie slightly above the Fermi level. The structure of the bands is qualitatively similar to those of calculations by others except for a general shift of the entire set of bands by about 0.1 Ryd. Thd density of states has also been calculated from the bands obtained. The spin susceptibility of α-cerium has also been calculated using the Kohn-Sham method. However, the calculated additional contributions to the band structure values cannot still explain the large experimental values reported in the literature. (author)

Solid-soluted content of cerium in solid solution of sphene

International Nuclear Information System (INIS)

Zhao Wei; Teng Yuancheng; Li Yuxiang; Ren Xuetan; Huang Junjun

2010-01-01

The sphene solid solution was synthesized by solid-state method,with calcium carbonate, silica, titanium dioxide, cerium oxalate and alumina as raw materials. The solid-soluted content of cerium in sphene was researched by means of X-ray diffraction (XRD), backscattering scanning electron microscopy (BSE), energy dispersive spectroscopy (EDS) and so on. The influence of A l3+ ion introduction to sphene on the solid-soluted content of cerium in sphene solid solution was studied. The results indicate that when introducing Al 3+ to sphene as electrovalence compensation, Ce 4+ could be well solidified to Ca 1-x Ce x Ti 1-2x A l2x SiO 5 , and the solid-soluted content is approximately 12.61%. With no electrovalence compensation, Ce 4+ could be solidified to Ca 1-2x Ce x TiSiO 5 , and the solid-soluted content is approximately 10.98%. The appropriate synthesis temperature of sphene solid solution is 1 260 degree C.(authors)

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

Production of cerium dioxide microspheres by an internal gelation sol–gel method

Energy Technology Data Exchange (ETDEWEB)

Katalenich, Jeffrey A.

2017-03-27

An internal gelation sol-gel technique was used to prepare cerium dioxide microspheres with uniform diameters near 100 µm. In this process, chilled aqueous solutions containing cerium, hexamethylenetetramine (HMTA), and urea are transformed into a solid gel by heat addition and are subsequently washed, dried, and sintered to produce pure cerium dioxide. Cerous nitrate and ceric ammonium nitrate solutions were compared for their usefulness in microsphere production. Gelation experiments were performed with both cerous nitrate and ceric ammonium nitrate to determine desirable concentrations of cerium, HMTA, and urea in feed solutions as well as the necessary quantity of ammonium hydroxide added to cerium solutions. Analysis of the pH before and after sample gelation was found to provide a quantitative metric for optimal parameter selection along with subjective evaluations of gel qualities. The time necessary for chilled solutions to gel upon inserting into a hot water bath was determined for samples with a variety of parameters and also used to determine desirable formulations for microsphere production. A technique for choosing the optimal mixture of ceric ammonium nitrate, HMTA, and urea was determined using gelation experiments and used to produce microspheres by dispersion of the feed solution into heated silicone oil. Gelled spheres were washed to remove excess reactants and reaction products before being dried and sintered. X-ray diffraction of air-dried microspheres, sintered microspheres, and commercial CeO₂ powders indicated that air-dried and sintered spheres were pure CeO₂.

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)

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

Effects of PEG4000 template on sol-gel synthesis of porous cerium titanate photocatalyst

Science.gov (United States)

Zhang, Wenjie; Tao, Yingjie; Li, Chuanguo

2018-04-01

Porous cerium titanate was synthesized by sol-gel method, using polyethylene glycol (PEG4000) as template agent. Brannerite structured CeTi2O6 in monoclinic system is the major substance formed in the materials. Formation of CeO2 and rutile TiO2 depends on the amount of PEG4000. The addition of PEG4000 leads to production of fine particles in the samples, but it does not apparently affect the band gap energy. Pore volume of the cerium titanate sample continuously increases with rising PEG4000 amount. The sample obtained using 3.5 g PEG4000 has BET surface area of 16.2 m2/g and pore volume of 0.0232 cm3/g. The addition of PEG4000 can obviously promote photocatalytic activity of cerium titanate, which can be proven by both enhanced production of hydroxyl radical and ofloxacin degradation efficiency. As much as 95.2% of the initial ofloxacin molecules are removed from the solution after 50 min of photocatalytic degradation on the cerium titanate obtained using 3.5 g PEG4000, while only 48.4% ofloxacin is removed on cerium titanate obtained without PEG4000.

Analysis of cerium-composite polymer-electrolyte membranes during and after accelerated oxidative-stability test

Science.gov (United States)

Shin, Dongwon; Han, Myungseong; Shul, Yong-Gun; Lee, Hyejin; Bae, Byungchan

2018-02-01

The oxidative stability of membranes constructed from a composite of pristine sulfonated poly(arylene ether sulfone) and cerium was investigated by conducting an accelerated oxidative-stability test at the open-circuit voltage (OCV). The membranes were analyzed in situ through OCV and impedance measurements, cyclic voltammetry, and linear-sweep voltammetry to monitor the electrochemical properties during the stability test. Although the high-frequency resistance of a composite membrane was slightly higher than that of a pristine membrane because of the exchange of protons from the sulfonic acid with cerium ions, the composite membrane maintained its potential for much longer than the pristine membrane. The effect of the cerium ions as radical scavengers was confirmed by analyzing the drain water and chemical structure after operation. These post-operation analyses confirmed that cerium ions improved the oxidative stability of the hydrocarbon-based polymer during fuel-cell operation. It is clear that the cerium-based radical scavengers prevented chemical degradation of the polymer membrane as well as the electrode in terms of hydrogen cross-over, polymer-chain scission, and the electrochemical surface area, while they rarely diffused outward from the membrane.

Immobilization of simulated radioactive soil waste containing cerium by self-propagating high-temperature synthesis

International Nuclear Information System (INIS)

Mao, Xianhe; Qin, Zhigui; Yuan, Xiaoning; Wang, Chunming; Cai, Xinan; Zhao, Weixia; Zhao, Kang; Yang, Ping; Fan, Xiaoling

2013-01-01

A simulated radioactive soil waste containing cerium as an imitator element has been immobilized by a thermite self-propagating high-temperature synthesis (SHS) process. The compositions, structures, and element leaching rates of products with different cerium contents have been characterized. To investigate the influence of iron on the chemical stability of the immobilized products, leaching tests of samples with different iron contents with different leaching solutions were carried out. The results showed that the imitator element cerium mainly forms the crystalline phases CeAl 11 O 18 and Ce 2 SiO 5 . The leaching rate of cerium over a period of 28 days was 10 −5 –10 −6 g/(m 2 day). Iron in the reactants, the reaction products, and the environment has no significant effect on the chemical stability of the immobilized SHS products

Immobilization of simulated radioactive soil waste containing cerium by self-propagating high-temperature synthesis

Science.gov (United States)

Mao, Xianhe; Qin, Zhigui; Yuan, Xiaoning; Wang, Chunming; Cai, Xinan; Zhao, Weixia; Zhao, Kang; Yang, Ping; Fan, Xiaoling

2013-11-01

A simulated radioactive soil waste containing cerium as an imitator element has been immobilized by a thermite self-propagating high-temperature synthesis (SHS) process. The compositions, structures, and element leaching rates of products with different cerium contents have been characterized. To investigate the influence of iron on the chemical stability of the immobilized products, leaching tests of samples with different iron contents with different leaching solutions were carried out. The results showed that the imitator element cerium mainly forms the crystalline phases CeAl11O18 and Ce2SiO5. The leaching rate of cerium over a period of 28 days was 10-5-10-6 g/(m2 day). Iron in the reactants, the reaction products, and the environment has no significant effect on the chemical stability of the immobilized SHS products.

Synthesis of cerium oxide catalysts supported on MCM-41 molecular sieve

International Nuclear Information System (INIS)

Souza, E.L.S.; Barros, T.R.B.; Sousa, B.V. de

2016-01-01

Porous materials have been widely studied as catalysts and catalyst support. The MCM-41 structure is the one that has been most studied because of its application possibilities in chemical processes. This work aimed to obtain and characterize cerium oxide catalysts supported on MCM-41 molecular sieve. The molecular sieve was synthesized by the conventional method with the following molar composition: 1 SiO2: 0.30 CTABr: NH3 11: 144 H2O. Then, 25% w/w cerium was incorporated into the MCM-41 using the wet impregnation process and the material obtained was activated by calcination. From the XRD patterns was confirmed the structure of the molecular sieve, and were identified the cerium oxide phases in its structure. The textural catalysts characteristics were investigated by isotherms of N2 adsorption/desorption (BET method). (author)

Imidazolium ionic liquids as solvents for cerium(IV)-mediated oxidation reactions

OpenAIRE

Mehdi, Hasan; Bodor, Andrea; Lantos, Diana; Horváth, István T; De Vos, Dirk; Binnemans, Koen

2007-01-01

Use of imidazolium ionic liquids as solvents for organic transformations with tetravalent cerium salts as oxidizing agents was evaluated. Good solubility was found for ammonium hexanitratocerate(IV) (ceric ammonium nitrate, CAN) and cerium(IV) triflate in 1-alkyl-3-methylimidazolium triflate ionic liquids. Oxidation of benzyl alcohol to benzaldehyde in 1-ethyl-3-methylimidazolium triflate was studied by in-situ FTIR spectroscopy and 13C NMR spectroscopy on carbon-13-labeled benzyl alcohol. Ca...

Procedure for the separation of cerium from rare earth phosphate mixtures

International Nuclear Information System (INIS)

Richter, H.; Grauss, H.; Schmitt, A.; Schade, H.; Lindeholz, M.; Lorenz, E.; Weickart, J.

1986-01-01

The invention is concerned with a procedure for the separation of cerium from rare earth concentrates originating from the partial neutralization of nitric crude phosphate decomposition solutions without preceding elimination of impurities from the raw material. The rare earth phosphates are treated with an excess of concentrated nitric acid through which the Ce 3+ , contained in the solution, is oxidized to Ce 4+ and precipitated as cerium(IV) phosphate by neutralization with alkalis

Synthesis and structure of cerium nitrosocarbonylcyanmethanid complex

International Nuclear Information System (INIS)

Gerasimenko, H.; Scopenko, V.V.; Kapshuk, A.A.

1998-01-01

Full text: The complex compound [CeL 4 Dy 2 ]Na*2Ac (where L- nitrosocarbonylcyanmethanid, Dy -- dipyridile, Ac - acetone) were synthesised by interaction of cerium chloride and sodium nitrosocarbonylcyanmethanid from acetone solution. After two hours of mixing the dipyridil solution in acetone was added for complex stabilization. After filtration solution was put to desiccator for crystallisation. The complex was studied using IR- and UV-spectroscopy. The structure of the complex was determined using X-ray structure analysis. It was found that the structure of the complex belongs to orthorhombic Pna2(1) syngony with the unit cell parameters 17.010, 16.280 and 16.340Angstroms, respectively. It was found that cerium in the compound was eight co-ordinated. Four nitroso ligands were co-ordinated by bidentate bridge method and two dipyridiles by bidentate-cycle method

Fixation of radioactive cerium-144 on white blood cells. Possibilities for use in physiopathology; Fixation du cerium radioactif ({sup 144}Ce) sur les globules blancs. Possibilites d'emploi en physiopathologie

Energy Technology Data Exchange (ETDEWEB)

Aeberhardt, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

From the study of the means of transport of cerium in the blood of various laboratory animals, after intra-venous injection of {sup 144}Ce-{sup 144}Pr without carrier, we have been able to show up the part played by the white cells in the transport of this fission product during its passage in the blood. This observation has led to the study, in vitro, of the methods of cerium fixation on the white cells, with a view to determining the possibilities of using this property for white cell labelling, the methods used up to the present not being entirely satisfactory. Using the method for the separation of the known constituents of the blood proposed by us in 1956, we have studied the cerium fixation under various conditions: - on suspensions of white cells from the rabbit, - on a suspension of human white cells, - on the white cells in whole from the rabbit. (author) [French] L'etude du mode de transport du cerium dans le sang chez differents animaux de laboratoire, apres injection intra-veineuse de {sup 144}Ce-{sup 144}Pr sans entraineur, nous a permis de mettre en evidence le rale des globules blancs dans le transport de ce produit de fission au cours de son passage dans le sang. Cette constatation nous a conduit a etudier, in vitro, les modalites de la fixation du cerium sur les globules blancs afin de preciser les possibilites d'utilisation de cette propriete pour le marquage des globules blancs, les methodes employees jusqu'ici ne donnant pas entiere satisfaction. Disposant de la methode de separation des elements figures du sang que nous avons proposee en 1956, nous avons etudie la fixation du cerium, dans diverses conditions: - sur des suspensions de globules blancs de lapin, - sur une suspension de globules blancs humains, - sur les globules blancs dans le sang total de lapin. (auteur)

Purification of cerium, neodymium and gadolinium for low background experiments

Directory of Open Access Journals (Sweden)

Boiko R.S.

2014-01-01

Full Text Available Cerium, neodymium and gadolinium contain double beta active isotopes. The most interesting are 150Nd and 160Gd (promising for 0ν2β search, 136Ce (2β+ candidate with one of the highest Q2β. The main problem of compounds containing lanthanide elements is their high radioactive contamination by uranium, radium, actinium and thorium. The new generation 2β experiments require development of methods for a deep purification of lanthanides from the radioactive elements. A combination of physical and chemical methods was applied to purify cerium, neodymium and gadolinium. Liquid-liquid extraction technique was used to remove traces of Th and U from neodymium, gadolinium and for purification of cerium from Th, U, Ra and K. Co-precipitation and recrystallization methods were utilized for further reduction of the impurities. The radioactive contamination of the samples before and after the purification was tested by using ultra-low-background HPGe gamma spectrometry. As a result of the purification procedure the radioactive contamination of gadolinium oxide (a similar purification efficiency was reached also with cerium and neodymium oxides was decreased from 0.12 Bq/kg to 0.007 Bq/kg in 228Th, from 0.04 Bq/kg to <0.006 Bq/kg in 226Ra, and from 0.9 Bq/kg to 0.04 Bq/kg in 40K. The purification methods are much less efficient for chemically very similar radioactive elements like actinium, lanthanum and lutetium.

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.

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

Investigating the Influence of the Cerium loading in prepared Y zeolite from Iraqi kaolin on its Catalytic Performance

Directory of Open Access Journals (Sweden)

Karim Khalifa Esgair

2018-01-01

Full Text Available In this study, the effects of different loading doses of cerium in the prepared NaY zeolite from Iraqi kaolin were investigated. Al-Duara refinery atmospheric residue fluid catalytic cracking was selected as palpation reaction for testing the catalytic activity of cerium loading NaY zeolite. The insertion of cerium in NaY zeolites has been synthesized by simple ion exchange methods. Three samples of modified zeolite Y have been obtained by replacing the sodium ions in the original sample with cerium and the weight percent added are 0.35, 0.64, and 1.06 respectively. The effects of cerium loading to zeolite Y in different weight percent on the cracking catalysts were studied by employing a laboratory fluidized bed reactor. The experiments have been performed with weight hourly space velocity (WHSV range from 6 to 24 h-1, and the temperature range from 450 to 510 oC. The activity of the catalyst with 1.06 wt% cerium has been shown to be much greater than that of the sample parent NaY. Also it was observed that the addition of the cerium causes an increase in the thermal stability of the zeolite.

Synthesis of cerium oxide (CeO{sub 2}) nanoparticles using simple CO-precipitation method

Energy Technology Data Exchange (ETDEWEB)

Farahmandjou, M.; Zarinkamar, M.; Firoozabadi, T. P., E-mail: farahamndjou@iauvaramin.ac.ir [Islamis Azad University, Varamin-Phisva Branch, Department of Physics, Varamin (Iran, Islamic Republic of)

2016-11-01

Synthesis of cerium oxide (CeO{sub 2}) nanoparticles was studied by new and simple co-precipitation method. The cerium oxide nanoparticles were synthesized using cerium nitrate and potassium carbonate precursors. Their physicochemical properties were characterized by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (Sem), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (Ftir) and UV-Vis spectrophotometer. XRD pattern showed the cubic structure of the cerium oxide nanoparticles. The average particle size of CeO{sub 2} was around 20 nm as estimated by XRD technique and direct HRTEM observations. The surface morphological studies from Sem and Tem depicted spherical particles with formation of clusters. The sharp peaks in Ftir spectrum determined the existence of CeO{sub 2} stretching mode and the absorbance peak of UV-Vis spectrum showed the bandgap energy of 3.26 eV. (Author)

Direct growth of cerium oxide nanorods on diverse substrates for superhydrophobicity and corrosion resistance

Science.gov (United States)

Cho, Young Jun; Jang, Hanmin; Lee, Kwan-Soo; Kim, Dong Rip

2015-06-01

Superhydrophobic surfaces with anti-corrosion properties have attracted great interest in many industrial fields, particularly to enhance the thermal performance of offshore applications such as heat exchangers, pipelines, power plants, and platform structures. Nanostructures with hydrophobic materials have been widely utilized to realize superhydrophobicity of surfaces, and cerium oxide has been highlighted due to its good corrosion resistive and intrinsically hydrophobic properties. However, few studies of direct growth of cerium oxide nanostructures on diverse substrates have been reported. Herein we report a facile hydrothermal method to directly grow cerium oxide nanorods on diverse substrates, such as aluminum alloy, stainless steel, titanium, and silicon. Diverse substrates with cerium oxide nanorods exhibited superhydrophobicity with no hydrophobic modifiers on their surfaces, and showed good corrosion resistive properties in corrosive medium. We believe our method could pave the way for realization of scalable and sustainable corrosion resistive superhydrophobic surfaces in many industrial fields.

Study of the effect of cerium nitrate on AA2024-T3 by means of electrochemical micro-cell technique

International Nuclear Information System (INIS)

Paussa, L.; Andreatta, F.; Rosero Navarro, N.C.; Durán, A.; Fedrizzi, L.

2012-01-01

Highlights: ► We evaluate the cerium nitrate effect on the electrochemical behavior of AA2024-T3. ► We examine how AA2024-T3 microstructure affects cerium precipitation mechanism. ► The entire AA2024-T3 surface is involved in cerium precipitation. ► Anodic and cathodic inhibitions are both provided by cerium precipitation. ► Mg-rich intermetallics are preferential sites for cerium precipitation. - Abstract: This work evaluates the effect of cerium nitrate as corrosion inhibitor for AA2024-T3 in the view of its introduction in sol–gel coatings able to provide self-healing ability. Since it is well established that deposition of Ce species is activated by the local pH increase, the objective of this paper is to investigate the behavior of AA2024-T3 (open circuit potential and polarization curves) in the presence of Ce species in aggressive solutions by means of a local technique, the electrochemical micro-cell. This technique enables the investigation of small areas with resolution in the micrometer range by the use of glass capillaries to define the working electrode area. The micro-cell results clearly displayed that the entire AA2024-T3 area exposed to the cerium-containing electrolyte was involved in the cerium precipitation mechanism. The heterogeneous electrochemical behavior of the microstructure is minimized by the formation of a cerium-containing layer able to protect the metal substrate.

Determination of trace amounts of cerium in silicate rocks based on its candoluminescence in a calcium oxide based matrix

International Nuclear Information System (INIS)

Belcher, R.; Nasser, T.A.K.; Polo-Diez, L.; Townshend, A.

1977-01-01

A very sensitive method for the determination of cerium (above 10 ng ml -1 ) has been developed (Belcher et al., Analyst;100:415(1975)), based on the measurement of the green candoluminescence produced by cerium in a calcium oxide-calcium sulphate matrix, with sulphuric acid as a coactivator, when the matrix is inserted into a hydrogen-nitrogen-air flame. This paper describes the application of this method to the determination of trace amounts of cerium in rocks. It involves the fusion of the sample with lithium metaborate, and does not require the isolation of cerium from other components of the rock, before measuring the candoluminescence intensity of the cerium. (author)

Methods study of homogeneity and stability test from cerium oxide CRM candidate

International Nuclear Information System (INIS)

Samin; Susanna TS

2016-01-01

The methods study of homogeneity and stability test from cerium oxide CRM candidate has been studied based on ISO 13258 and KAN DP. 01. 34. The purpose of this study was to select the test method homogeneity and stability tough on making CRM cerium oxide. Prepared 10 sub samples of cerium oxide randomly selected types of analytes which represent two compounds, namely CeO_2 and La_2O_3. At 10 sub sample is analyzed CeO_2 and La_2O_3 contents in duplicate with the same analytical methods, by the same analyst, and in the same laboratory. Data analysis results calculated statistically based on ISO 13528 and KAN DP.01.34. According to ISO 13528 Cerium Oxide samples said to be homogeneous if Ss ≤ 0.3 σ and is stable if | Xr – Yr | ≤ 0.3 σ. In this study, the data of homogeneity test obtained CeO_2 is Ss = 2.073 x 10-4 smaller than 0.3 σ (0.5476) and the stability test obtained | Xr - Yr | = 0.225 and the price is < 0.3 σ. Whereas for La_2O_3, the price for homogeneity test obtained Ss = 1.649 x 10-4 smaller than 0.3 σ (0.4865) and test the stability of the price obtained | Xr - Yr | = 0.2185 where the price is < 0.3 σ. Compared with the method from KAN, a sample of cerium oxide has also been homogenized for Fcalc < Ftable and stable, because | Xi - Xhm | < 0.3 x n IQR. Provided that the results of the evaluation homogeneity and stability test from CeO_2 CRM candidate test data were processed using statistical methods ISO 13528 is not significantly different with statistical methods from KAN DP.01.34, which together meet the requirements of a homogeneous and stable. So the test method homogeneity and stability test based on ISO 13528 can be used to make CRM cerium oxide. (author)

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

Phase segregation in cerium-lanthanum solid solutions

NARCIS (Netherlands)

Belliere, V.; Joorst, G; Stephan, O; de Groot, FMF; Weckhuysen, BM

2006-01-01

Electron energy-loss spectroscopy (EELS) in combination with scanning transmission electron microscopy ( STEM) reveals that the La enrichment at the surface of cerium-lanthanum solid solutions is an averaged effect and that segregation occurs in a mixed oxide phase. This separation occurs within a

Effect of cerium on structure modifications of a hybrid sol–gel coating, its mechanical properties and anti-corrosion behavior

International Nuclear Information System (INIS)

Cambon, Jean-Baptiste; Esteban, Julien; Ansart, Florence; Bonino, Jean-Pierre; Turq, Viviane; Santagneli, S.H.; Santilli, C.V.; Pulcinelli, S.H.

2012-01-01

Highlights: ► New sol–gel routes to replace chromates for corrosion protection of aluminum. ► Effect of cerium concentration on the microstructure of xerogel. ► Electrochemical and mechanical performances of hybrid coating with different cerium contents. ► Good correlation between the different results with an optimal cerium content of 0.01 M. -- Abstract: An organic–inorganic hybrid coating was developed to improve the corrosion resistance of the aluminum alloy AA 2024-T3. Organic and inorganic coatings derived from glycidoxypropyl-trimethoxysilane (GPTMS) and aluminum tri-sec-butoxide Al(O s Bu) 3 , with different cerium contents, were deposited onto aluminum by dip-coating process. Corrosion resistance and mechanical properties were investigated by electrochemical impedance measurements and nano-indentation respectively. An optimal cerium concentration of 0.01 M was evidenced. To correlate and explain the hybrid coating performances in relation to the cerium content, NMR experiments were performed. It has been shown that when the cerium concentration in the hybrid is higher than 0.01 M there are important modifications in the hybrid structure that account for the mechanical properties and anti-corrosion behavior of the sol–gel coating.

Dry sliding wear behaviour of Al-12Si-4Mg alloy with cerium addition

International Nuclear Information System (INIS)

Anasyida, A.S.; Daud, A.R.; Ghazali, M.J.

2010-01-01

The purpose of this work is to understand the effect of cerium addition on wear resistance behaviour of as-cast alloys. Al-12Si-4 Mg alloys with 1-5 wt% cerium addition were prepared using the casting technique. A sliding wear test was carried out under applied loads of 10 N, 30 N and 50 N at a fixed sliding speed of 1 m/s using a pin-on-disc configuration. The wear test was conducted in dry conditions at room temperature of ∼25 o C. Detailed analysis of the microstructure, worn surface, collected debris and microhardness was undertaken in order to investigate the differences between the as-cast alloys with different levels of cerium addition. The addition of 1-5 wt% cerium was found to lead to the precipitation of intermetallic phases (Al-Ce), resulting a needle-like structures. Increasing cerium content up to 2 wt% improved both wear resistance and microhardness of as-cast alloys. Addition of more than 2 wt% cerium, however, led to a decrease in microhardness, resulting in lower wear resistance of the alloys. Moderate wear was observed at all loads, with specific wear rates (K') ranging from 6.82 x 10 -5 with 2 wt% Ce at applied load of 50 N to 21.48 x 10 -5 mm 3 /N m without added Ce at an applied load of 10 N. Based on K' ranges, the as-cast alloys exhibited moderate wear regimes, and the mechanism of wear is a combination of abrasion and adhesion. Alloy containing 2 wt% Ce, with the highest hardness and lowest K' value, showed the greatest wear resistance.

Corrosion electrochemical behaviors of silane coating coated magnesium alloy in NaCl solution containing cerium nitrate

Energy Technology Data Exchange (ETDEWEB)

Luo, F.; Li, Q.; Zhong, X.K.; Gao, H.; Dai, Y.; Chen, F.N. [School of Chemistry and Chemical Engineering, Southwest University Chongqing (China)

2012-02-15

Sol-gel coatings cannot provide adequate corrosion protection for metal/alloys in the corrosive environments due to their high crack-forming potential. This paper demonstrates the possibility to employ cerium nitrate as inhibitor to decrease the corrosion development of sol-gel-based silane coating on the magnesium alloy in NaCl solution. Cerium nitrate was added into the NaCl solution where the silane coating coated magnesium alloy was immersed. Scanning electron microscopy (SEM) was used to examine surface morphology of the silane coating coated magnesium alloy immersed in NaCl solutions doped and undoped with cerium nitrate. The corrosion electrochemical behaviors were investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests. The results showed that the introduction of cerium nitrate into NaCl solution could effectively inhibit the corrosion of the silane coating coated magnesium alloy. Moreover, the influence of concentration of cerium nitrate on the corrosion inhibition and the possible inhibiting mechanism were also discussed in detail. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Effect of cerium substitution on structural and magnetic properties of magnetite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Padalia, Diwakar, E-mail: Padalia.diwakar@gmail.com [Department of Physics, G.B.Pant University of Agriculture & Technology, Pantnagar, Uttrakhand (India); Johri, U.C. [Department of Physics, G.B.Pant University of Agriculture & Technology, Pantnagar, Uttrakhand (India); Zaidi, M.G.H. [Supercritical Fluid Processing Laboratory, Department of Chemistry, G.B.Pant University of Agriculture & Technology, Pantnagar, Uttrakhand (India)

2016-02-01

The current work presents the synthesis and properties of cerium doped magnetite (Fe{sub 3}O{sub 4}) nanoparticles synthesized by standard chemical co-precipitation method using NH{sub 4}OH as co-precipitating agent. The effects of cerium ion substitution on structural and magnetic properties of magnetite (Fe{sub 3}O{sub 4}) nanoparticles were reported. These materials were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM). The cerium content has a significant influence on structural and magnetic properties. The X-ray diffraction study confirmed the formation of single-phase magnetite with space group Fd3m and crystallite size ranging from 39 to 58 nm. The addition of cerium resulted in a reduction of crystallite size and an increase of cell parameters. FTIR measurements confirmed the formation of different samples and suggested that the reduction of Fe{sup +3} to Fe{sup +2} preferred on a site adjacent to Ce{sup +4}. Magnetic measurements revealed that the saturation magnetization (Ms) and remanence (M{sub r}) decreased while the coercivity (H{sub C}) and squareness (M{sub r}/M{sub S}) increased with increasing cerium content. - Highlights: • There is an increase in cell parameters and strain with Ce-content. • Samples show the presence of secondary phase after 1.0% doping level. • Ce-ions prefer octahedral sites and charge neutrality is accompanied by Fe{sup +3} → Fe{sup +2}. • Magnetization decreases due to weakening of the super exchange interactions. • Squareness and coercivity start to increase with Ce content.

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.)

Effect of calcination temperature on the crystallite growth of cerium oxide nano-powders prepared by the co-precipitation process

Energy Technology Data Exchange (ETDEWEB)

Chen, Jian-Chih [Department of Orthopaedics, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China); Chen, Wen-Cheng [School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Tien, Yin-Chun [Department of Orthopaedics, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China); Shih, Chi-Jen, E-mail: cjshih@kmu.edu.t [Department of Fragrance and Cosmetics Science, Kaohsiung Medical University, 100 Shi-Chuan1st Road, Kaohsiung 80708, Taiwan (China)

2010-04-30

Cerium oxide nanocrystallites were synthesized by a co-precipitation process at a relatively low temperature, using cerium (III) nitrate as the starting material in a water solution with pH in the range of 8-9. The effect of calcination temperature on the crystallite growth of cerium oxide nano-powders was investigated by X-ray diffraction, transmission electron microscopy and electron diffraction. The crystallization temperature of the cerium oxide powders was estimated to be about 273 K, by XRD analysis. When calcined at temperatures from 473 to 1273 K, face-centered cubic phase crystallization was observed by XRD. The crystallite size of the cerium oxide increased from 12.0 to 48 nm as the calcining temperature increased from 473 to 1273 K, in the pH range 8-9. The activation energy for the growth of cerium oxide nanoparticles was found to have very low values of 17.5 kJ/mol for pH = 8 and 16.0 kJ/mol for pH = 9.

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)

Mesoporous cerium oxide nanospheres for the visible-light driven photocatalytic degradation of dyes

Directory of Open Access Journals (Sweden)

Subas K. Muduli

2014-04-01

Full Text Available A facile, solvothermal synthesis of mesoporous cerium oxide nanospheres is reported for the purpose of the photocatalytic degradation of organic dyes and future applications in sustainable energy research. The earth-abundant, relatively affordable, mixed valence cerium oxide sample, which consists of predominantly Ce7O12, has been characterized by powder X-ray diffraction, X-ray photoelectron and UV–vis spectroscopy, and transmission electron microscopy. Together with N2 sorption experiments, the data confirms that the new cerium oxide material is mesoporous and absorbs visible light. The photocatalytic degradation of rhodamin B is investigated with a series of radical scavengers, suggesting that the mechanism of photocatalytic activity under visible-light irradiation involves predominantly hydroxyl radicals as the active species.

Assessement of the effect of Pyrimetin in combined injury with external irradiation and oral cerium-144 incorporation

International Nuclear Information System (INIS)

Kiradzhiev, G.; Khadzhidekova, E.

1985-01-01

The effect of the preparation Pyrimetin on rats, subjected to external irradiation combined with oral cerium 144 incorporation was studied. LD 50/30 of cerium-144 was used as biological criterion. It was shown that by this criterion Pyrimetin essentially abolished the potentiated by external radiation effect of cerium. Probably, the preparation leads to normalization of the gastro-intestinal motor function and the dose loading of the colon

Obtainment of cerium dioxide for use as spectrochemical standard. Obtencao de dioxido de cerio para uso como padrao espectroquimico

Energy Technology Data Exchange (ETDEWEB)

Silva Queiroz, C.A. da; Hespanhol, E C.B.; Abrao, A [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)

1992-01-01

This paper describes a simple method for cerium separation and purification. Cerium is previously precipitated with N H{sub 3}/air/H{sub 2} O{sub 2} system in a mixed chlorides solution obtained from Brazilian monazite treatment. The cerium fraction as cerium chloride is run down throughout a strong cationic resin bed and then the rare earth impurities separation is done by elution of the resin with separation ammonium salt of EDTA. None retainer ion is used in the purification technique by ion exchange. (author).

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

First heats of cerium solution in liquid aluminium, gallium, indium, tin, lead and bismuth

International Nuclear Information System (INIS)

Yamshchikov, L.F.; Lebedev, V.A.; Nichkov, I.F.; Raspopin, S.P.; Shein, V.G.

1983-01-01

Cerium solution heats in liquid alluminium, gallium, indium, tin, lead and bismuth are determined in high temperature mixing calorimeter with an isothermal shell. The statistical analysis carried out proves that values of cerium solution heat in fusible metals obtained by the methods of electric motive forces and calorimety give a satisfactory agreement

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...

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)

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)

Decontamination of alpha contaminated metallic waste by cerium IV redox process

International Nuclear Information System (INIS)

Shah, J.G.; Dhami, P.S.; Gandhi, P.M.; Wattal, P.K.

2012-01-01

Decontamination of alpha contaminated metallic waste is an important aspect in the management of waste generated during dismantling and decommissioning of nuclear facilities. Present work on cerium redox process targets decontamination of alpha contaminated metallic waste till it qualifies for the non alpha waste category for disposal in near surface disposal facility. Recovery of the alpha radio nuclides and cerium from aqueous secondary waste streams was also studied deploying solvent extraction process and established. The alpha-lean secondary waste stream has been immobilised in cement based matrix for final disposal. (author)

LUMINESCENT PROPERTIES OF SILICATE GLASSES WITH CERIUM IONS AND ANTIMONY

Directory of Open Access Journals (Sweden)

A. M. Klykova

2014-05-01

Full Text Available The paper deals with the results of an experimental study of luminescence excitation spectra and luminescence of silicate glasses containing cerium ions and antimony. The aim of this work was to study the features of the luminescence and the effect of UV irradiation and heat treatment on luminescence and the state of cerium ions and antimony in glass. We investigated glass system Na2O-ZnO-Al2O3-SiO2-NaF-NaBr with additives CeO2 and Sb2O3. Synthesis was carried out in platinum crucibles in the air at 14500C. The samples were polished glass plates with a thickness of 0.5-1 mm. UV irradiation was carried out with a mercury lamp having a wide range of radiation in the spectral range 240-390 nm. It was conducted in a Nabertherm muffle furnaces. Luminescence spectra and excitation spectra were measured using a spectrofluorimeter MPF-44A (PerkinElmer at the room temperature. Measured luminescence spectra were corrected in view of the spectral sensitivity of the photodetector for spectrofluorimeter. Adjustment of the excitation spectra for the spectral dependence of the intensity of the excitation source was not carried out. During the experiments it was found that in silicate glasses Sb3+ ions can exist in two energy states, which corresponds to a different environment with oxygen ions. Heat treatment of these glasses in an oxidizing atmosphere leads to an increase in ion concentration of Sb3+ ions with a greater amount of oxygen in the environment. In glasses containing antimony and cerium ions, ultraviolet irradiation causes a change in the valence of cerium ions and antimony, which is accompanied by luminescence quenching. Subsequent heat treatment of glass leads to the inverse processes and restore luminescence excitation spectra. The study of fluorescent properties of silicate glasses with cerium and antimony ions led to the conclusion of the practical significance of this work. Promising multifunctional materials can be created on the basis of

Enhanced hot ductility of a Cr–Mo low alloy steel by rare earth cerium

International Nuclear Information System (INIS)

Jiang, X.; Song, S.-H.

2014-01-01

The hot ductility of a 1Cr–0.5Mo low alloy steel is investigated over a temperature range of 700–1050 °C using a Gleeble thermomechanical simulator in conjunction with various characterization techniques. The steel samples undoped and doped with cerium are heated at 1300 °C for 3 min and then cooled with a rate of 5 K s −1 down to different test temperatures, followed by tensile deformation until fracture. The results show that the hot ductility of the steel, evaluated by the reduction in area, can be substantially enhanced by a minor addition of cerium, especially in the range 800–1000 °C. In the austenite–ferrite dual-phase region, cerium may delay the formation of proeutectoid ferrite layers along austenite grain boundaries, thereby increasing the hot ductility of the steel. In the single austenite region, grain boundary segregation of cerium may increase the grain boundary cohesion, toughening the steel and thus raising the resistance to grain boundary sliding as well as promoting dynamic recrystallization. Consequently, the hot ductility of the steel is enhanced

Contribution to research on the metabolism of fission product. Studies on the physico-chemical state and the metabolic fate of radio-cerium solution

International Nuclear Information System (INIS)

Aeberhardt, A.

1961-01-01

This paper describes a study of the physico-chemical state of radio-cerium in dilute solutions on the tracer scale, as a function of the pH of the solution. The way in which this radioelement is transported in the blood is studied in vitro and in vivo, with reference to the ionic or colloidal state of the radio-cerium used. The distribution of cerium amongst the various components of the blood is studied by a new method of blood fractionation and by paper electrophoresis. Evidence of a cerium globulin connection is shown in the case of ionic cerium. A study of the initial distribution of radio-cerium in rats, after intravenous administration of ionic or colloidal solutions, shows considerable differences according to the physico-chemical state of the cerium injected. (author) [fr

The effects of cerium doping on the size, morphology, and optical properties of α-hematite nanoparticles for ultraviolet filtration

Energy Technology Data Exchange (ETDEWEB)

Cardillo, Dean [Institute for Superconducting and Electronic Materials, AIIM Facility, University of Wollongong Innovation Campus, Squires Way, North Wollongong, NSW 2500 (Australia); Konstantinov, Konstantin, E-mail: konstan@uow.edu.au [Institute for Superconducting and Electronic Materials, AIIM Facility, University of Wollongong Innovation Campus, Squires Way, North Wollongong, NSW 2500 (Australia); Devers, Thierry [Centre de Recherche sur la Matière Divisée, Institut de Physique, site de Chartres, Université d’Orléans (France)

2013-11-15

Highlights: • Possible application of cerium-doped α-hematite as ultraviolet filter. • Nanoparticles obtained through co-precipitation technique using various cerium doping levels followed by annealing. • Comprehensive materials characterisation utilizing XRD, DSC/TGA, STEM, UV–vis spectroscopy. • Increasing cerium content reduces particle sizing and alters morphology. • Solubility of cerium in hematite seen between 5 and 10% doping, 10% cerium doping greatly enhances attenuation in ultraviolet region and increases optical bandgap. - Abstract: Metal oxide nanoparticles have potential use in energy storage, electrode materials, as catalysts and in the emerging field of nanomedicine. Being able to accurately tailor the desirable properties of these nanoceramic materials, such as particle size, morphology and optical bandgap (E{sub g}) is integral in the feasibility of their use. In this study we investigate the altering of both the structure and physical properties through the doping of hematite (α-Fe{sub 2}O{sub 3}) nanocrystals with cerium at a range of concentrations, synthesised using a one-pot co-precipitation method. This extremely simple synthesis followed by thermal treatment results in stable Fe{sub 2−x}Ce{sub x}O{sub y} nanoceramics resulting from the burning of any unreacted precursors and transformation of goethite-cerium doped nanoparticle intermediate. The inclusion of Ce into the crystal lattice of these α-Fe{sub 2}O{sub 3} nanoparticles causes a significantly large reduction in mean crystalline size and alteration in particle morphology with increasing cerium content. Finally we report an increase optical semiconductor bandgap, along with a substantial increase in the ultraviolet attenuation found for a 10% Ce-doping concentration which shows the potential application of cerium-doped hematite nanocrystals to be used as a pigmented ultraviolet filter for cosmetic products.

Ceria nanoparticles vis-à-vis cerium nitrate as corrosion inhibitors for silica-alumina hybrid sol-gel coating

Energy Technology Data Exchange (ETDEWEB)

Lakshmi, R.V. [Surface Engineering Division, Council of Scientific and Industrial Research – National Aerospace Laboratories, HAL Airport Road, Kodihalli, Bengaluru 560017 (India); Aruna, S.T., E-mail: staruna194@gmail.com [Surface Engineering Division, Council of Scientific and Industrial Research – National Aerospace Laboratories, HAL Airport Road, Kodihalli, Bengaluru 560017 (India); Sampath, S. [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bengaluru 560012 (India)

2017-01-30

Highlights: • Corrosion protection efficiency comparison of ceria nanoparticles and cerium nitrate. • Silica-alumina hybrid coating exhibited good barrier protection. • Detailed XPS study confirm the hybrid structure and presence of Ce species in coating. • Loss of cerium ions not prevalent in ceria doped coating unlike that of cerium nitrate. • Ceria increased the coating integrity, corrosion inhibition and barrier protection. - Abstract: The present work provides a comparative study on the corrosion protection efficiency of defect free sol-gel hybrid coating containing ceria nanoparticles and cerium nitrate ions as corrosion inhibitors. Less explored organically modified alumina-silica hybrid sol-gel coatings are synthesized from 3-glycidoxypropyltrimethoxysilane and aluminium-tri-sec-butoxide. The microemulsion derived nanoparticles and the hybrid coatings are characterized and compared with coatings containing cerium nitrate. Corrosion inhibiting capability is assessed using electrochemical impedance spectroscopy. Scanning Kelvin probe measurements are also conducted on the coatings for identifying the apparent corrosion prone regions. Detailed X-ray photoelectron spectroscopy (XPS) analysis is carried out to comprehend the bonding and corrosion protection rendered by the hybrid coatings.

Effects of uncoated and citric acid coated cerium oxide nanoparticles, bulk cerium oxide, cerium acetate, and citric acid on tomato plants

International Nuclear Information System (INIS)

Barrios, Ana Cecilia; Rico, Cyren M.; Trujillo-Reyes, Jesica; Medina-Velo, Illya A.; Peralta-Videa, Jose R.; Gardea-Torresdey, Jorge L.

2016-01-01

Little is known about the physiological and biochemical responses of plants exposed to surface modified nanomaterials. In this study, tomato (Solanum lycopersicum L.) plants were cultivated for 210 days in potting soil amended with uncoated and citric acid coated cerium oxide nanoparticles (nCeO_2, CA + nCeO_2) bulk cerium oxide (bCeO_2), and cerium acetate (CeAc). Millipore water (MPW), and citric acid (CA) were used as controls. Physiological and biochemical parameters were measured. At 500 mg/kg, both the uncoated and CA + nCeO_2 increased shoot length by ~ 9 and ~ 13%, respectively, while bCeO_2 and CeAc decreased shoot length by ~ 48 and ~ 26%, respectively, compared with MPW (p ≤ 0.05). Total chlorophyll, chlo-a, and chlo-b were significantly increased by CA + nCeO_2 at 250 mg/kg, but reduced by bCeO_2 at 62.5 mg/kg, compared with MPW. At 250 and 500 mg/kg, nCeO_2 increased Ce in roots by 10 and 7 times, compared to CA + nCeO_2, but none of the treatments affected the Ce concentration in above ground tissues. Neither nCeO_2 nor CA + nCeO_2 affected the homeostasis of nutrient elements in roots, stems, and leaves or catalase and ascorbate peroxidase in leaves. CeAc at 62.5 and 125 mg/kg increased B (81%) and Fe (174%) in roots, while at 250 and 500 mg/kg, increased Ca in stems (84% and 86%, respectively). On the other hand, bCeO_2 at 62.5 increased Zn (152%) but reduced P (80%) in stems. Only nCeO_2 at 62.5 mg/kg produced higher total number of tomatoes, compared with control and the rest of the treatments. The surface coating reduced Ce uptake by roots but did not affect its translocation to the aboveground organs. In addition, there was no clear effect of surface coating on fruit production. To our knowledge, this is the first study comparing the effects of coated and uncoated nCeO_2 on tomato plants. - Highlights: • At 500 mg/kg, coated and bare NPs increased stem length by 13 and 9%, respectively. • Coated NPs at 500 mg/kg increased CAT activity in

Effects of uncoated and citric acid coated cerium oxide nanoparticles, bulk cerium oxide, cerium acetate, and citric acid on tomato plants

Energy Technology Data Exchange (ETDEWEB)

Barrios, Ana Cecilia [Department of Chemistry, The University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968 (United States); Rico, Cyren M. [Department of Chemistry, The University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN), The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); Trujillo-Reyes, Jesica [Department of Chemistry, The University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968 (United States); Medina-Velo, Illya A. [Department of Chemistry, The University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN), The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); Peralta-Videa, Jose R. [Department of Chemistry, The University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968 (United States); Environmental Science and Engineering Ph.D. Program, The University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN), The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); Gardea-Torresdey, Jorge L., E-mail: jgardea@utep.edu [Department of Chemistry, The University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968 (United States); Environmental Science and Engineering Ph.D. Program, The University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN), The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States)

2016-09-01

Little is known about the physiological and biochemical responses of plants exposed to surface modified nanomaterials. In this study, tomato (Solanum lycopersicum L.) plants were cultivated for 210 days in potting soil amended with uncoated and citric acid coated cerium oxide nanoparticles (nCeO{sub 2}, CA + nCeO{sub 2}) bulk cerium oxide (bCeO{sub 2}), and cerium acetate (CeAc). Millipore water (MPW), and citric acid (CA) were used as controls. Physiological and biochemical parameters were measured. At 500 mg/kg, both the uncoated and CA + nCeO{sub 2} increased shoot length by ~ 9 and ~ 13%, respectively, while bCeO{sub 2} and CeAc decreased shoot length by ~ 48 and ~ 26%, respectively, compared with MPW (p ≤ 0.05). Total chlorophyll, chlo-a, and chlo-b were significantly increased by CA + nCeO{sub 2} at 250 mg/kg, but reduced by bCeO{sub 2} at 62.5 mg/kg, compared with MPW. At 250 and 500 mg/kg, nCeO{sub 2} increased Ce in roots by 10 and 7 times, compared to CA + nCeO{sub 2}, but none of the treatments affected the Ce concentration in above ground tissues. Neither nCeO{sub 2} nor CA + nCeO{sub 2} affected the homeostasis of nutrient elements in roots, stems, and leaves or catalase and ascorbate peroxidase in leaves. CeAc at 62.5 and 125 mg/kg increased B (81%) and Fe (174%) in roots, while at 250 and 500 mg/kg, increased Ca in stems (84% and 86%, respectively). On the other hand, bCeO{sub 2} at 62.5 increased Zn (152%) but reduced P (80%) in stems. Only nCeO{sub 2} at 62.5 mg/kg produced higher total number of tomatoes, compared with control and the rest of the treatments. The surface coating reduced Ce uptake by roots but did not affect its translocation to the aboveground organs. In addition, there was no clear effect of surface coating on fruit production. To our knowledge, this is the first study comparing the effects of coated and uncoated nCeO{sub 2} on tomato plants. - Highlights: • At 500 mg/kg, coated and bare NPs increased stem length by 13 and 9

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

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

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.

Jet formation in cerium metal to examine material strength

Energy Technology Data Exchange (ETDEWEB)

Jensen, B. J., E-mail: bjjensen@lanl.gov; Cherne, F. J.; Prime, M. B.; Yeager, J. D.; Ramos, K. J.; Hooks, D. E.; Cooley, J. C.; Dimonte, G. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Fezzaa, K. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Iverson, A. J.; Carlson, C. A. [National Security Technologies LLC, Los Alamos, New Mexico 87544 (United States)

2015-11-21

Examining the evolution of material properties at extreme conditions advances our understanding of numerous high-pressure phenomena from natural events like meteorite impacts to general solid mechanics and fluid flow behavior. Recent advances in synchrotron diagnostics coupled with dynamic compression platforms have introduced new possibilities for examining in-situ, spatially resolved material response with nanosecond time resolution. In this work, we examined jet formation from a Richtmyer-Meshkov instability in cerium initially shocked into a transient, high-pressure phase, and then released to a low-pressure, higher-temperature state. Cerium's rich phase diagram allows us to study the yield stress following a shock induced solid-solid phase transition. X-ray imaging was used to obtain images of jet formation and evolution with 2–3 μm spatial resolution. From these images, an analytic method was used to estimate the post-shock yield stress, and these results were compared to continuum calculations that incorporated an experimentally validated equation-of-state (EOS) for cerium coupled with a deviatoric strength model. Reasonable agreement was observed between the calculations and the data illustrating the sensitivity of jet formation on the yield stress values. The data and analysis shown here provide insight into material strength during dynamic loading which is expected to aid in the development of strength aware multi-phase EOS required to predict the response of matter at extreme conditions.

Investigation of cerium salt/sulfuric acid anodizing technology for 1420 aluminum alloy

Energy Technology Data Exchange (ETDEWEB)

Di Li; Yue Peng Deng; Bao Lan Guo; Guo Qiang Li [Beijing Univ. of Aeronautics and Astronautics (China). Dept. of Mater. Sci. and Eng.

2000-07-01

In this paper, the effect of cerium addition agent on the property of anodized coating of 1420 Al alloy has been studied by corrosion experiment (immersion test and neutral salt spray test), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and measurement of polarization curves. The result show that only pitting could be observed in all corrosion tests while intergranular corrosion and exfoliation corrosion did not appear on 1420 Al-Li alloys. When organic carboxylic acid S or the cerium (IV) salt was added into sulfuric acid anodizing electrolyte separately, there was no significant improvement in corrosion resistance of anodized film. However, in the case of adding them into sulfuric acid anodizing electrolyte together, the corrosion resistance of anodized film increased greatly owing to synergistic effect. The synergistic effect may relate to the formation of cerium-organic carboxylic acid S complex compound and its effects on film growth and film structure. (orig.)

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)

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.

Charge transfer cross sections for dysprosium and cerium

Energy Technology Data Exchange (ETDEWEB)

Adachi, Hajime; Tamura, Koji; Okazaki, Tetsuji; Shibata, Takemasa [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

1998-06-01

Symmetric resonant charge transfer cross sections between singly ionized ions and the parent atoms were measured for dysprosium and cerium in the impact energy of 200-2000eV. The cross sections were determined from the ratio between the number of ions produced by charge transfer and those in primary ion beam. The primary ion beam was produced by a laser ion source in which their atoms were ionized by laser resonant photo-ionization. The slow ions produced by charge transfer and fast primary ions were detected with Faraday cups. The obtained cross sections were (1.82{+-}0.14) x 10{sup -14} cm{sup 2} for dysprosium and (0.88{+-}0.12) x 10{sup -14} cm{sup 2} for cerium in the above energy range. The difference of these values can mostly be explained by considering the electron configurations of these atoms and ions. (author)

Charge transfer cross sections for dysprosium and cerium

International Nuclear Information System (INIS)

Adachi, Hajime; Tamura, Koji; Okazaki, Tetsuji; Shibata, Takemasa

1998-06-01

Symmetric resonant charge transfer cross sections between singly ionized ions and the parent atoms were measured for dysprosium and cerium in the impact energy of 200-2000eV. The cross sections were determined from the ratio between the number of ions produced by charge transfer and those in primary ion beam. The primary ion beam was produced by a laser ion source in which their atoms were ionized by laser resonant photo-ionization. The slow ions produced by charge transfer and fast primary ions were detected with Faraday cups. The obtained cross sections were (1.82±0.14) x 10 -14 cm 2 for dysprosium and (0.88±0.12) x 10 -14 cm 2 for cerium in the above energy range. The difference of these values can mostly be explained by considering the electron configurations of these atoms and ions. (author)

Exposure, Health and Ecological Effects Review of Engineered Nanoscale Cerium and Cerium Oxide Associated with its Use as a Fuel Additive

Science.gov (United States)

Advances of nanoscale science have produced nanomaterials with unique physical and chemical properties at commercial levels which are now incorporated into over 1000 products. Nanoscale cerium (di) oxide (CeO(2)) has recently gained a wide range of applications which includes coa...

Thermometric titrimetry Studies of the cerium(IV) oxidation of alpha-mercaptocarboxylic acids.

Science.gov (United States)

Alexander, W A; Mash, C J; McAuley, A

1969-04-01

The cerium(IV) oxidation of thioglycollic, thiolactic and thiomalic acids has been examined by thermometric titration. The titration curves indicate stoichiometries of more than 1 mole of cerium(IV) per mole of alpha-thiol, suggesting possible side-reactions. In the presence of methyl acrylate, however, the expected ratio is observed. The overall heat of each reaction has been derived. Only with a titration method of this kind where allowance can be made for side-reactions can the heats of reaction for these systems be measured.

Fabrication of mesoporous cerium dioxide films by cathodic electrodeposition.

Science.gov (United States)

Kim, Young-Soo; Lee, Jin-Kyu; Ahn, Jae-Hoon; Park, Eun-Kyung; Kim, Gil-Pyo; Baeck, Sung-Hyeon

2007-11-01

Mesoporous cerium dioxide (Ceria, CeO2) thin films have been successfully electrodeposited onto ITO-coated glass substrates from an aqueous solution of cerium nitrate using CTAB (Cetyltrimethylammonium Bromide) as a templating agent. The synthesized films underwent detailed characterizations. The crystallinity of synthesized CeO2 film was confirmed by XRD analysis and HR-TEM analysis, and surface morphology was investigated by SEM analysis. The presence of mesoporosity in fabricated films was confirmed by TEM and small angle X-ray analysis. As-synthesized film was observed from XRD analysis and HR-TEM image to have well-crystallized structure of cubic phase CeO2. Transmission electron microscopy and small angle X-ray analysis revealed the presence of uniform mesoporosity with a well-ordered lamellar phase in the CeO2 films electrodeposited with CTAB templating.

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.

Catalysts with Cerium in a Membrane Reactor for the Removal of Formaldehyde Pollutant from Water Effluents

Directory of Open Access Journals (Sweden)

Mirella Gutiérrez-Arzaluz

2016-05-01

Full Text Available We report the synthesis of cerium oxide, cobalt oxide, mixed cerium, and cobalt oxides and a Ce–Co/Al2O3 membrane, which are employed as catalysts for the catalytic wet oxidation (CWO reaction process and the removal of formaldehyde from industrial effluents. Formaldehyde is present in numerous waste streams from the chemical industry in a concentration low enough to make its recovery not economically justified but high enough to create an environmental hazard. Common biological degradation methods do not work for formaldehyde, a highly toxic but refractory, low biodegradability substance. The CWO reaction is a recent, promising alternative that also permits much lower temperature and pressure conditions than other oxidation processes, resulting in economic benefits. The CWO reaction employing Ce- and Co-containing catalysts was carried out inside a slurry batch reactor and a membrane reactor. Experimental results are reported. Next, a mixed Ce–Co oxide film was supported on an γ-alumina membrane used in a catalytic membrane reactor to compare formaldehyde removal between both types of systems. Catalytic materials with cerium and with a relatively large amount of cerium favored the transformation of formaldehyde. Cerium was present as cerianite in the catalytic materials, as indicated by X-ray diffraction patterns.

Exposure of cerium oxide nanoparticles to kidney bean shows disturbance in the plant defense mechanisms

Energy Technology Data Exchange (ETDEWEB)

Majumdar, Sanghamitra [Department of Chemistry, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN) (United States); Peralta-Videa, Jose R. [Department of Chemistry, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); Environmental Science and Engineering PhD Program, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN) (United States); Bandyopadhyay, Susmita [Environmental Science and Engineering PhD Program, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN) (United States); Castillo-Michel, Hiram [European Synchrotron Radiation Facility, B.P. 220-38043 Grenoble, Cedex (France); Hernandez-Viezcas, Jose-Angel [Department of Chemistry, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN) (United States); Sahi, Shivendra [Department of Biology, Western Kentucky University, Bowling Green, KY 42101 (United States); Gardea-Torresdey, Jorge L., E-mail: jgardea@utep.edu [Department of Chemistry, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); Environmental Science and Engineering PhD Program, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN) (United States)

2014-08-15

Graphical abstract: - Highlights: • Kidney bean roots uptake nCeO{sub 2} primarily without biotransformation. • Cerium reached the root vascular tissues through gaps in the Casparian strip. • On longer exposure to high concentration, roots demonstrate stress response. • In leaves, guaiacol peroxidase plays a major role in ROS scavenging. - Abstract: Overwhelming use of engineered nanoparticles demands rapid assessment of their environmental impacts. The transport of cerium oxide nanoparticles (nCeO{sub 2}) in plants and their impact on cellular homeostasis as a function of exposure duration is not well understood. In this study, kidney bean plants were exposed to suspensions of ∼8 ± 1 nm nCeO{sub 2} (62.5 to 500 mg/L) for 15 days in hydroponic conditions. Plant parts were analyzed for cerium accumulation after one, seven, and 15 days of nCeO{sub 2} exposure. The primary indicators of stress like lipid peroxidation, antioxidant enzyme activities, total soluble protein and chlorophyll contents were studied. Cerium in tissues was localized using scanning electron microscopy and synchrotron μ-XRF mapping, and the chemical forms were identified using μ-XANES. In the root epidermis, cerium was primarily shown to exist as nCeO{sub 2}, although a small fraction (12%) was biotransformed to Ce(III) compound. Cerium was found to reach the root vascular tissues and translocate to aerial parts with time. Upon prolonged exposure to 500 mg nCeO{sub 2}/L, the root antioxidant enzyme activities were significantly reduced, simultaneously increasing the root soluble protein by 204%. In addition, leaf's guaiacol peroxidase activity was enhanced with nCeO{sub 2} exposure in order to maintain cellular homeostasis.

Cerium, uranium, and plutonium behavior in glass-bonded sodalite, a ceramic nuclear waste form

International Nuclear Information System (INIS)

Lewis, M. A.; Lexa, D.; Morss, L. R.; Richmann, M. K.

1999-01-01

Glass-bonded sodalite is being developed as a ceramic waste form (CWF) to immobilize radioactive fission products, actinides, and salt residues from electrometallurgical treatment of spent nuclear reactor fuel. The CWF consists of about 75 mass % sodalite, 25 mass % glass, and small amounts of other phases. This paper presents some results and interpretation of physical measurements to characterize the CWF structure, and dissolution tests to measure the release of matrix components and radionuclides from the waste form. Tests have been carried out with specimens of the CWF that contain rare earths at concentrations similar to those expected in the waste form. Parallel tests have been carried out on specimens that have uranium or plutonium as well as the rare earths at concentrations similar to those expected in the waste forms; in these specimens UCl 3 forms UO 2 and PuCl 3 forms PuO 2 . The normalized releases of rare earths in dissolution tests were found to be much lower than those of matrix elements (B, Si, Al, Na). When there is no uranium in the CWF, the release of cerium is two to ten times lower than the release of the other rare earths. The low release of cerium may be due to its tetravalent state in uranium-free CWF. However, when there is uranium in the CWF, the release of cerium is similar to that of the other rare earths. This trivalent behavior of cerium is attributed to charge transfer or covalent interactions among cerium, uranium, and oxygen in (U,Ce)O 2

Synthesis and characterization of platinum supported on alumina doped with cerium catalyst

International Nuclear Information System (INIS)

Yusof Abdullah; Abd Fatah Awang Mat; Mohd Ali Sufi; Sarimah Mahat; Razali Kassim; Nurhaslinda Abdullah.

1996-03-01

The synthesis and characterization of gamma-alumina doped with cerium as platinum support for the automobile exhaust catalyst are described. Platinum/alumina/ceria catalyst were prepared by impregnation of hexachloroplatinic acid and sintered at 500 degree Celsius to obtain metal dispersions of 1.0 wt%. Catalyst distribution inside the powder and the effects of the addition of cerium to alumina were analyzed by the scanning electron microscopy (SEM) and x-ray fluorescence spectroscopy (XRF). The results showed that the alumina - supported catalysts contained well dispersion of the noble metal

Cerium fluoride nanoparticles protect cells against oxidative stress

International Nuclear Information System (INIS)

Shcherbakov, Alexander B.; Zholobak, Nadezhda M.; Baranchikov, Alexander E.; Ryabova, Anastasia V.; Ivanov, Vladimir K.

2015-01-01

A novel facile method of non-doped and fluorescent terbium-doped cerium fluoride stable aqueous sols synthesis is proposed. Intense green luminescence of CeF 3 :Tb nanoparticles can be used to visualize these nanoparticles' accumulation in cells using confocal laser scanning microscopy. Cerium fluoride nanoparticles are shown for the first time to protect both organic molecules and living cells from the oxidative action of hydrogen peroxide. Both non-doped and terbium-doped CeF 3 nanoparticles are shown to provide noteworthy protection to cells against the vesicular stomatitis virus. - Highlights: • Facile method of CeF 3 and CeF 3 :Tb stable aqueous sols synthesis is proposed. • Naked CeF 3 nanoparticles are shown to be non-toxic and to protect cells from the action of H 2 O 2 . • CeF 3 and CeF 3 :Tb nanoparticles are shown to protect living cells against the vesicular stomatitis virus

Cerium fluoride nanoparticles protect cells against oxidative stress

Energy Technology Data Exchange (ETDEWEB)

Shcherbakov, Alexander B.; Zholobak, Nadezhda M. [Zabolotny Institute of Microbiology and Virology, National Academy of Sciences of Ukraine, Kyiv D0368 (Ukraine); Baranchikov, Alexander E. [Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, Moscow 119991 (Russian Federation); Ryabova, Anastasia V. [Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow 119991 (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow 115409 (Russian Federation); Ivanov, Vladimir K., E-mail: van@igic.ras.ru [Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, Moscow 119991 (Russian Federation); National Research Tomsk State University, Tomsk 634050 (Russian Federation)

2015-05-01

A novel facile method of non-doped and fluorescent terbium-doped cerium fluoride stable aqueous sols synthesis is proposed. Intense green luminescence of CeF{sub 3}:Tb nanoparticles can be used to visualize these nanoparticles' accumulation in cells using confocal laser scanning microscopy. Cerium fluoride nanoparticles are shown for the first time to protect both organic molecules and living cells from the oxidative action of hydrogen peroxide. Both non-doped and terbium-doped CeF{sub 3} nanoparticles are shown to provide noteworthy protection to cells against the vesicular stomatitis virus. - Highlights: • Facile method of CeF{sub 3} and CeF{sub 3}:Tb stable aqueous sols synthesis is proposed. • Naked CeF{sub 3} nanoparticles are shown to be non-toxic and to protect cells from the action of H{sub 2}O{sub 2}. • CeF{sub 3} and CeF{sub 3}:Tb nanoparticles are shown to protect living cells against the vesicular stomatitis virus.

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

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

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.

Reactive removal of 2-chloroethyl ethyl sulfide vapors under visible light irradiation by cerium oxide modified highly porous zirconium (hydr) oxide

Energy Technology Data Exchange (ETDEWEB)

Mitchell, Joshua K.; Arcibar-Orozco, Javier A.; Bandosz, Teresa J., E-mail: tbandosz@ccny.cuny.edu

2016-12-30

Highlights: • Microporous zirconium-cerium (hydr) oxides were synthetized. • Ce presence narrowed the band gap of the materials. • The samples showed a high efficiency for removal of CEES vapors. • 1,2-Bis (ethyl thio) ethane and ethyl vinyl sulfide were the main reaction products. • 5% (Ce/Zr mol) addition of cerium oxide results in the best performing material. - Abstract: Highly porous cerium oxide modified Zr(OH){sub 4} samples were synthesized using a simple one stage urea precipitation method. The amorphicity level of zirconium hydroxide did not change upon addition of cerium oxide particles. A unique aspect of the cerium oxide-modified materials is the presence of both the oxide (CeO{sub 2}) and hydroxide (Zr(OH){sub 4}) phases resulting in a unique microporous structure of the final material. Extensive characterization using various chemical and physical methods revealed significant differences in the surface features. All synthesized materials were microporous and small additions of cerium oxide affected the surface chemistry. These samples were found as effective catalysts for a decontamination of mustard gas surrogate, 2-chloroethyl ethyl sulfide (CEES). Cerium oxide addition significantly decreased the band gap of zirconium hydroxide. Ethyl vinyl sulfide and 1,2-bis (Ethyl thio) ethane were identified as surface reaction products.

The study on preparation of high dispersion and pure cerium dioxide for producing automotive exhaust catalysts

International Nuclear Information System (INIS)

Le Minh Tuan; Nguyen Trong Hung; Nguyen Thanh Chung

2003-01-01

The multi-stage counter-current solvent extraction process using TBP as the solvent has been carried out for purifying cerium and the ammonium carbonate precipitation method has been used to produce the cerium oxide of high dispersion and pure. The flow sheet of extraction system includes 3 extraction stages with O/A = 0.7,2 stripping stages and 4 scrubbing stages with O/A = 5. The condition for ammonium carbonate precipitation, drying and calcination have been investigated and a procedure that seem to be practically suitable to prepare cerium dioxide powder with great specific surface area for producing automotive exhaust catalyst has been proposed. (LMT)

Corrosion resistance of flaky aluminum pigment coated with cerium oxides/hydroxides in chloride and acidic electrolytes

Science.gov (United States)

Niroumandrad, S.; Rostami, M.; Ramezanzadeh, B.

2015-12-01

The objective of this study was to enhance the corrosion resistance of lamellar aluminum pigment through surface treatment by cerium oxides/hydroxides. The surface composition of the pigments was studied by energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the pigment was evaluated by conventional hydrogen evolution measurements in acidic solution and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. Results showed that the Ce-rich coating composed of Ce2O3 and CeO2 was precipitated on the pigment surface after immersion in the cerium solution. The corrosion resistance of pigment was significantly enhanced after modification with cerium layer.

Complex formation of transferrin with tetravalent plutonium and cerium

International Nuclear Information System (INIS)

Subramanian, M.S.; Oomen, I.K.

1981-01-01

Gel filtration experiments with 239 Pu labelled In Vitro bovine serum showed that the metal ion is bound to the transferrin of the serum proteins as in the case of iron labelled serum. This was confirmed by polyacrylamide gel electrophoresis. The ovotransferrin prepared from chicken egg white which was devoid of hemopexin contaminant was found to complex both tetravalent plutonium and cerium giving visible absorption peak at 365 and 435 nm respectively. The binding capacity of ovotransferrin with tetravalent plutonium and cerium, determined by spectrophotometric titration indicates that two metal ions are bound to each protein molecule as in the case of iron. The average molecular weight computed from this binding capacity measurements was found to be 71,000-75,000. The number of protons liberated for each metal ion bound was found to be three as in the case of iron. (author)

Synthesis and ion-exchange properties of cerium(IV) molybdate

Energy Technology Data Exchange (ETDEWEB)

Srivastava, S K; Singh, Raj Pal; Agrawal, Sushma; Kumar, Satish [Roorkee Univ. (India). Dept. of Chemistry

1977-01-01

The synthesis, ion exchange properties, and the separation of a number of cation pairs on the columns of cerium (IV) molybdate is discussed. In order to obtain the product in gel form showing a high exchange capacity and suitable for column operation, preliminary experiments were performed to determine the optimum conditions of precipitation, i.e., the concentration of ceric and molybdate solutions, mixing ratio, pH of precipitation and the order of mixing. Cerium (IV) molybdate, prepared under the optimum conditions of concentration, acidity etc., shows exchange capacity of 0.96 meg per g of exchanger. The sorption of a large number of metal ions has been investigated and the compound shows promising behaviour as cation exchanger. Numerous separations of analytical and radiochemical interest have been performed on the column of this exchanger with great efficiency.

Synthesis and ion-exchange properties of cerium(IV) molybdate

International Nuclear Information System (INIS)

Srivastava, S.K.; Raj Pal Singh; Sushma Agrawal; Satish Kumar

1977-01-01

The synthesis, ion exchange properties, and the separation of a number of cation pairs on the columns of cerium (IV) molybdate is discussed. In order to obtain the product in gel form showing a high exchange capacity and suitable for column operation, preliminary experiments were performed to determine the optimum conditions of precipitation, i.e., the concentration of ceric and molybdate solutions, mixing ratio, pH of precipitation and the order of mixing. Cerium (IV) molybdate, prepared under the optimum conditions of concentration, acidity etc., shows exchange capacity of 0.96 meg per g of exchanger. The sorption of a large number of metal ions has been investigated and the compound shows promising behaviour as cation exchanger. Numerous separations of analytical and radiochemical interest have been performed on the column of this exchanger with great efficiency. (T.G.)

Crystalline cerium(IV) phosphates

International Nuclear Information System (INIS)

Herman, R.G.; Clearfield, A.

1976-01-01

The ion exchange behaviour of seven crystalline cerium(IV) phosphates towards some of the alkali metal cations is described. Only two of the compounds (A and C) possess ion exchange properties in acidic solutions. Four others show some ion exchange characteristics in basic media with some of the alkali cations. Compound G does not behave as an ion exchanger in solutions of pH + , but show very little Na + uptake. Compound E undergoes ion exchange with Na + and Cs + , but not with Li+. Both Li + and Na + are sorbed by compounds A and C. The results are indicative of structures which show steric exclusion phenomena. (author)

Appearance of minimum on the curve of cerium melting

International Nuclear Information System (INIS)

Boguslavskij, Yu.Ya.; Grigor'ev, S.B.

1986-01-01

It is shown by means of simple and obvious thermodynamical considerations that the reduced stability line continues up to the solid phase boundary. The existence of this line causes the appearance of minimum on the fcc cerium melting curve

Study of cerium doped magnetite (Fe 3O 4:Ce)/PMMA nanocomposites

Science.gov (United States)

Padalia, Diwakar; Johri, U. C.; Zaidi, M. G. H.

2012-03-01

The paper presents the synthesis and properties of polymer nanocomposite material based on cerium doped magnetite (Fe 3O 4) as filler material and poly methyl methacrylate (PMMA) as host matrix. The magnetite (Fe 3O 4) particles were synthesized by co-precipitation route using stable ferrous and ferric salts with ammonium hydroxide as precipitating agent. Further, they doped by cerium oxide (CeO 2) non-stoichiometrically. The composite material was fabricated by solvent evaporation method. Here 2.4 GHz microwaves were used to study the effect of microwaves heating on polymerization. The phase and crystal structure is determined by X-ray diffraction (XRD). The average crystallite size of the composites varies from 28 to 35 nm. The chemical structure is confirmed by Fourier transform infrared (FTIR) spectroscopy. The magnetic and thermal properties are investigated by vibrating sample magnetometer (VSM) and differential scanning calorimetry (DSC). The thermal study shows that the microwave heated samples possess higher glass transition temperature ( Tg). The magnetic results suggest that coercivity ( HC) and squareness ( Mr/ Ms) of the loop increases with increasing doping percent of cerium.

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.

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.

Fabrication of Cerium Oxide and Uranium Oxide Microspheres for Space Nuclear Power Applications

Energy Technology Data Exchange (ETDEWEB)

Jeffrey A. Katalenich; Michael R. Hartman; Robert C. O' Brien

2013-02-01

Cerium oxide and uranium oxide microspheres are being produced via an internal gelation sol-gel method to investigate alternative fabrication routes for space nuclear fuels. Depleted uranium and non-radioactive cerium are being utilized as surrogates for plutonium-238 (Pu-238) used in radioisotope thermoelectric generators and for enriched uranium required by nuclear thermal rockets. While current methods used to produce Pu-238 fuels at Los Alamos National Laboratory (LANL) involve the generation of fine powders that pose a respiratory hazard and have a propensity to contaminate glove boxes, the sol-gel route allows for the generation of oxide microsphere fuels through an aqueous route. The sol-gel method does not generate fine powders and may require fewer processing steps than the LANL method with less operator handling. High-quality cerium dioxide microspheres have been fabricated in the desired size range and equipment is being prepared to establish a uranium dioxide microsphere production capability.

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, ...

Citric complexes of trivalent cerium and berkelium

International Nuclear Information System (INIS)

Boulhassa, S.

1977-01-01

The extraction by thenoyltrifluoroacetone (TTA) in benzene of trivalent cerium, berkelium and californium, at the indicator scale, hydrolysis and complexation by citric acid of these cations are studied. The radionuclides used were 144 Ce, 249 Bk and 249 Cf respectively γ, β and α emitters. The solvent extraction technique of the elements by TTA in benzene from a perchloric medium at the ionic stength 0.1 was employed. The distribution coefficients D were measured by the γ, β or α radiometry. Cerium and berkelium, which have a comparable redox behavior, show in solution a relatively stable valency IV. Therefore the study by solvent extraction of their trivalent form required the standing up of complete reducing conditions of these elements and their stabilization in solution at the valency III. The thermodynamic data obtained for berkelium and californium contribute to understand the chemistry of these elements and permit to complete the third 'tetrad branch' of 5f elements from Cm 3+ to Es 3+ . This tetrad effect is a manifestation of thermodynamic consequence of the 'nephelauxetic effect'. As for Ce(III), the data confirm the pronounced acid property and may be show no neglected ligand effect for f 1 configuration [fr

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

Cerium concentrate and mixed rare earth chloride by the oxidative decomposition of bastnaesite in molten sodium hydroxide

International Nuclear Information System (INIS)

Iijima, Toshio; Kato, Kazuhiro; Kuno, Toyohiko; Okuwaki, Akitsugu; Umetsu, Yoshiaki; Okabe, Taijiro

1993-01-01

Bastnaesite was treated in molten NaOH at 623-777 K for 10-60 min under atmosphere. Cerium-(III) in the ore was easily oxidized 95% or more within 30 min to give an oxidation product composed of solid solutions of CeO 2 -rich and CeO 2 -lean phases and Ce-free rare earth oxide phase. Simultaneously fluoride ion was removed 97% or more. Cerium concentrate was prepared from the oxidation product by leaching with 0.1-3 M HCl solution. The yield of cerium concentrate and the CeO 2 content reached 55-57% and 70-72%, respectively. Mixed rare earth chloride is composed of about 90% rare earth chloride and 10% alkaline earth chloride, and the contents of CeCl 3 , LaCl 3 , NdCl 3 , and PrCl 3 are 11.5, 58.5, 14.4, and 5.4%, respectively. The particle size of resulting cerium concentrate was fairly uniform and about 0.1 μm

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

Synthesis of mesoporous cerium-zirconium mixed oxides by hydrothermal templating method

Institute of Scientific and Technical Information of China (English)

无

2008-01-01

Mesoporous cerium-zirconium mixed oxides were prepared by hydrothermal method using cetyl trimethyl ammonium bromide (CTAB) as template.The effects of amount of template,pH value of solution and hydrothermal temperature on mesostructure of samples were systematically investigated.The final products were characterized by XRD,TEM,FT-IR,and BET.The results indicate that all the cerium-zirconium mixed oxides present a meso-structure.At molar ratio of n(CTAB)/n((Ce)+(Zr))=0.15,pH value of 9,and hydrothermal temperature of 120 ℃,the samples obtained possess a specific surface area of 207.9 m2/g with pore diameter of 3.70 nm and pore volume of 0.19 cm3/g.

Synergism between cerium nitrate and sodium dodecylbenzenesulfonate on corrosion of AA5052 aluminium alloy in 3 wt.% NaCl solution

Energy Technology Data Exchange (ETDEWEB)

Liu, Jie; Wang, Dapeng; Gao, Lixin; Zhang, Daquan, E-mail: zhdq@sh163.net

2016-12-15

Highlights: • Effectively prevent corrosion of AA5052 alloy by using the mixture of cerium nitrate and sodium dodecylbenzenesulfonate. • Synergistic mechanism of the combination of cerium nitrate and sodium dodecylbenzenesulfonate. • Structure of the complex formed between cerium ions and dodecylbenzenesulfonate. • The optimal adsorption model of dodecylbenzenesulfonate on the Al{sub 2}O{sub 3} and CeO{sub 2} surface. - Abstract: The synergistic inhibition effect of rare earth cerium nitrate and sodium dodecylbenzenesulfonate (DBS) on corrosion of AA5052 aluminium alloy in 3 wt.% NaCl solution was investigated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curve, scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR). The results show that the single cerium nitrate or DBS has a limited inhibition effect against corrosion of AA5052 alloy. The combination cerium ions with DBS produced strong synergistic effect on corrosion inhibition for AA5052 alloy and rendered a negaitve shift of the corrosion potential. The formation of the complex of Al(DBS){sub 3} and Ce(DBS){sub 3} stabilized the passive film of Al{sub 2}O{sub 3} and CeO{sub 2}, retarding both the cathodic and anodic processes of AA5052 alloy corrosion reaction significantly.

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)

Nanostructured sol-gel coatings doped with cerium nitrate as pre-treatments for AA2024-T3

International Nuclear Information System (INIS)

Zheludkevich, M.L.; Serra, R.; Montemor, M.F.; Yasakau, K.A.; Salvado, I.M. Miranda; Ferreira, M.G.S.

2005-01-01

Nanostructured hybrid sol-gel coatings doped with cerium ions were investigated in the present work as pre-treatments for the AA2024-T3 alloy. The sol-gel films have been synthesized from tetraethylorthosilicate (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) precursors. Additionally the hybrid sol was doped with zirconia nanoparticles prepared from hydrolyzed tetra-n-propoxyzirconium (TPOZ). Cerium nitrate, as corrosion inhibitor, was added into the hybrid matrix or into the oxide nanoparticles. The chemical composition and the structure of the hybrid sol-gel films were studied by XPS (X-ray photoelectron spectroscopy) and AFM (atomic force microscopy), respectively. The evolution of the corrosion protection properties of the sol-gel films was studied by EIS (electrochemical impedance spectroscopy), which can provide quantitative information on the role of the different pre-treatments. Different equivalent circuits, for different stages of the corrosion processes, were used in order to model the coating degradation. The models were supported by SEM (scanning electron microscopy) measurements. The results show that the sol-gel films containing zirconia nanoparticles present improved barrier properties. Doping the hybrid nanostructured sol-gel coatings with cerium nitrate leads to additional improvement of the corrosion protection. The zirconia particles present in the sol-gel matrix seem to act as nanoreservoirs providing a prolonged release of cerium ions. The nanostructured sol-gel films doped with cerium nitrate can be proposed as a potential candidate for substitution of the chromate pre-treatments for AA2024-T3

Effect of cerium oxide addition on electrical properties of ZnO

Energy Technology Data Exchange (ETDEWEB)

Ibrahim, D.M. [National Research Center, Dokki, Giza (Egypt). Dept. of Ceramics; Mounir, M. [Dept. of Physics, Cairo Univ., Giza (Egypt); Mahgoub, A.S. [Cairo Univ., Giza (Egypt). Dept. of Chemistry; Turky, G. [Dept. of Physics, National Research Center, Dokki, Giza (Egypt); El-Desouky, O.A. [Cer. Cleopatra Co., Ramadan City (Egypt)

2002-07-01

Mixtures of ZnO and Ce{sub 6} O{sub 11} as additive were prepared by solid state reaction from the calcined oxides with the following proportions: 0.03, 0.08, 0.1, 0.2 and 0.4 mole. Disc specimens 1.2 cm 5 cm in diameter and 0.3 cm thickness were processed under a force of 70 kN and fired at 1150 C/ 30 minutes. XRD revealed the presence of limited solid solution of cerium in ZnO, as evident from the shift in the peaks [0.03-0.04 A ] up to 0.1 mole addition and remains constant. SEM revealed the presence of inter-granular phase. EDAX showed it to be a mixture of ZnO and Ce{sub 6}O{sub 11}. Also cerium was detected in the ZnO grains confirming the XRD results. RCL circuit was used to measure the capacitance and resistance at different frequencies at room temperature. The dielectric constant and conductivity were calculated. The change in resistivity with temperature was followed up to 523 K. The change in dielectric strength with temperature at spot frequency of 10 kHz is demonstrated. The electrical conductivity was found to increase with the proportion of cerium oxide up to 0.2 mole then decreased. (orig.)

Cerium Modified Pillared Montmorillonite Supported Cobalt Catalysts for Fischer Tropsch Synthesis

International Nuclear Information System (INIS)

Ahmad, N.; Ali, Z.; Abbas, S. M.; Hussain, F.

2015-01-01

Fischer-Tropsch (FT) synthesis was accomplished over Al-pillared Montmorillonite supported 20 wt% Co modified with different weight% of cerium catalysts. These catalysts were prepared by impregnation method while structural characterizations of the prepared samples were performed by XRD, TPR, NH/sub 3/TPD, TGA, BET, XRF and SEM techniques. The Fischer Tropsch reaction was studied in fixed bed micro catalytic reactor at temperature range of 220, 260 and 275 degree C and at different pressure (1, 5 and 10 bars). From the activity results, it was found that by pillaring NaMMT with Al higher catalytic activity and lower methane selectivity of NaMMT was achieved. Furthermore, the results of FT synthesis reaction revealed that cerium incorporation increased the dispersion of Co/sub 3/O/sub 4/ on the surface and consequently resulted in enhanced catalytic activity. Additionally, the C/sub 5/-C/sub 12/ hydrocarbons and methane selectivity increased while C/sub 22+/ hydrocarbons selectivity was decreased over cerium modified catalysts. Higher reaction temperature (>220 degree C) resulted in significant enhancement in CO conversion and methane selectivity. Though, increase in pressure from 1 to 10 bars eventually resulted in increase in C/sub 5+/ hydrocarbons and decrease in methane and C/sub 2/-C/sub 5/ hydrocarbons selectivity. (author)

Influence of agglomeration of cerium oxide nanoparticles and speciation of cerium(III) on short term effects to the green algae Chlamydomonas reinhardtii

Energy Technology Data Exchange (ETDEWEB)

Röhder, Lena A. [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Environmental Toxicology, Dübendorf 8600 (Switzerland); ETH-Zurich, Institute of Biogeochemistry and Pollutant Dynamics, Zürich 8092 (Switzerland); Brandt, Tanja [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Environmental Toxicology, Dübendorf 8600 (Switzerland); Sigg, Laura [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Environmental Toxicology, Dübendorf 8600 (Switzerland); ETH-Zurich, Institute of Biogeochemistry and Pollutant Dynamics, Zürich 8092 (Switzerland); Behra, Renata, E-mail: Renata.behra@eawag.ch [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Environmental Toxicology, Dübendorf 8600 (Switzerland)

2014-07-01

Highlights: • Phosphate-dispersed CeO₂ NP did not affect photosynthetic yield in C. reinhardtii. • Agglomerated CeO₂ NP slightly decreased photosynthetic yield. • Cerium(III) was shown to affect photosynthetic yield and intracellular ROS level. • Slight effects of CeO₂ NP were caused by dissolved Ce³⁺ ions present in suspensions. • Wild type and cell wall free mutant of C. reinhardtii showed the same sensitivity. - Abstract: Cerium oxide nanoparticles (CeO₂ NP) are increasingly used in industrial applications and may be released to the aquatic environment. The fate of CeO₂ NP and effects on algae are largely unknown. In this study, the short term effects of CeO₂ NP in two different agglomeration states on the green algae Chlamydomonas reinhardtii were examined. The role of dissolved cerium(III) on toxicity, its speciation and the dissolution of CeO₂ NP were considered. The role of cell wall of C. reinhardtii as a barrier and its influence on the sensitivity to CeO₂ NP and cerium(III) was evaluated by testing both, the wild type and the cell wall free mutant of C. reinhardtii. Characterization showed that CeO₂ NP had a surface charge of ~0 mV at physiological pH and agglomerated in exposure media. Phosphate stabilized CeO₂ NP at pH 7.5 over 24 h. This effect was exploited to test CeO₂ NP dispersed in phosphate with a mean size of 140 nm and agglomerated in absence of phosphate with a mean size of 2000 nm. The level of dissolved cerium(III) in CeO₂ NP suspensions was very low and between 0.1 and 27 nM in all tested media. Exposure of C. reinhardtii to Ce(NO₃)₃ decreased the photosynthetic yield in a concentration dependent manner with EC₅₀ of 7.5 ± 0.84 μM for wild type and EC₅₀ of 6.3 ± 0.53 μM for the cell wall free mutant. The intracellular level of reactive oxygen species (ROS) increased upon exposure to Ce(NO₃)₃ with effective concentrations similar to those inhibiting photosynthesis. The agglomerated Ce

Extraction of Cerium (IV) Using Di–n-butylsulfoxide in Chloroform ...

African Journals Online (AJOL)

NICO

2015-01-12

Jan 12, 2015 ... Cerium is the most abundant among rare earth metals and is extracted from monazite, allanite and ... Variamine blue, 2,4, dihydroxy benzophenoe benzoic hydrazone, ... thoroughly for colour development. The reagent blank ...

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)

Thermodynamic Studies of the Phase Relationships of Nonstoichiometric Cerium Oxides at Higher Temperatures

DEFF Research Database (Denmark)

Sørensen, Ole Toft

1976-01-01

Partial molar thermodynamic quantities for oxygen in nonstoichiometric cerium oxides were determined by thermogravimetric analysis in CO/CO2 mixtures in the temperature range 900–1400°C. Under these conditions compositions within the range 2.00 greater-or-equal, slanted O/M greater-or-equal, slan......Partial molar thermodynamic quantities for oxygen in nonstoichiometric cerium oxides were determined by thermogravimetric analysis in CO/CO2 mixtures in the temperature range 900–1400°C. Under these conditions compositions within the range 2.00 greater-or-equal, slanted O/M greater...

Moissanite (SiC) with metal-silicide and silicon inclusions from tuff of Israel: Raman spectroscopy and electron microscope studies

Science.gov (United States)

Dobrzhinetskaya, Larissa; Mukhin, Pavel; Wang, Qin; Wirth, Richard; O'Bannon, Earl; Zhao, Wenxia; Eppelbaum, Lev; Sokhonchuk, Tatiana

2018-06-01

Here, we present studies of natural SiC that occurs in situ in tuff related to the Miocene alkaline basalt formation deposited in northern part of Israel. Raman spectroscopy, SEM and FIB-assisted TEM studies revealed that SiC is primarily hexagonal polytypes 4H-SiC and 6H-SiC, and that the 4H-SiC polytype is the predominant phase. Both SiC polytypes contain crystalline inclusions of silicon (Sio) and inclusions of metal-silicide with varying compositions (e.g. Si58V25Ti12Cr3Fe2, Si41Fe24Ti20Ni7V5Zr3, and Si43Fe40Ni17). The silicides crystal structure parameters match Si2TiV5 (Pm-3m space group, cubic), FeSi2Ti (Pbam space group, orthorhombic), and FeSi2 (Cmca space group, orthorhombic) respectively. We hypothesize that SiC was formed in a local ultra-reduced environment at respectively shallow depths (60-100 km), through a reaction of SiO2 with highly reducing fluids (H2O-CH4-H2-C2H6) arisen from the mantle "hot spot" and passing through alkaline basalt magma reservoir. SiO2 interacting with the fluids may originate from the walls of the crustal rocks surrounding this magmatic reservoir. This process led to the formation of SiC and accompanied by the reducing of metal-oxides to native metals, alloys, and silicides. The latter were trapped by SiC during its growth. Hence, interplate "hot spot" alkali basalt volcanism can now be included as a geological environment where SiC, silicon, and silicides can be found.

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

Determination of Ideal Broth Formulations Needed to Prepare Hydrous Cerium Oxide Microspheres via the Internal Gelation Process

Energy Technology Data Exchange (ETDEWEB)

Collins, Jack Lee [ORNL; Chi, Anthony [ORNL

2009-02-01

A simple test tube methodology was used to determine optimum process parameters for preparing hydrous cerium oxide microspheres via the internal gelation process.1 Broth formulations of cerium ammonium nitrate [(NH4)2Ce(NO3)6], hexamethylenetetramine, and urea were found that can be used to prepare hydrous cerium oxide gel spheres in the temperature range of 60 to 90 C. A few gel-forming runs were made in which microspheres were prepared with some of these formulations to be able to equate the test-tube gelation times to actual gelation times. These preparations confirmed that the test-tube methodology is reliable for determining the ideal broth formulations.

Effect of cerium and thermomechanical processing on microstructure

Indian Academy of Sciences (India)

The effect of cerium content and thermomechanical processing on structure and properties of Fe–10.5 wt.%Al–0.8 wt%C alloy has been investigated. Alloys were prepared by a combination of air induction melting with flux cover (AIMFC) and electroslag remelting (ESR). The ESR ingots were hot-forged and hotrolled at ...

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

Using cerium anomaly as an indicator of redox reactions in constructed wetland

Science.gov (United States)

Liang, R.

2013-12-01

The study area, Chiayi County located in southern Taiwan, has highly developed livestock. The surface water has very low dissolved oxygen and high NH4. Under the situation, constructed wetland becomes the most effective and economic choice to treat the wastewater in the natural waterways. Hebao Island free surface constructed wetland started to operate in late 2006. It covers an area of 0.28 km2 and is subdivided into 3 major cells, which are sedimentation cell, 1st aeration cell with rooted plants and 2nd aeration cell with float plants. The water depth of cells ranges from 0.6 m to 1.2 m. The total hydraulic retention time is about a half day. In this study, the water samples were sequentially collected along the flow path. The results of hydrochemical analysis show that the untreated inflow water can be characterized with enriched NH4 (11 ppm), sulfate (6 ppm) and arsenic (50 ppb). The removal efficiency of NH4 in the first two cells is arsenic is still higher than the permissible limits recommended by WHO (10 ppb). The wetland operation should be tuned to take more arsenic away in the future. As demonstrated in the above, oxidation reaction is the most dominant mechanism to remove pollutants from the wastewater; therefore, dissolved oxygen is traditionally considered as an important indicator to evaluate the operation efficiency of wetland. However, it would need longer time to achieve equilibrium state of redox reaction involving dissolved oxygen due to the slower reaction rate. For example, the input water in this study has fairly high dissolved oxygen (5 ppm) but the NH4 content is still high, which indicates a non-equilibrium condition. In this study, the cerium anomaly is alternatively utilized to evaluate the water redox state. The results demonstrate that the input water has the negative cerium anomaly of -0.16. Along the flow path, the cerium negative anomaly does not change in the first two cells and dramatically becomes -0.23 in cell 3. The trend of

Study of cerium doped magnetite (Fe3O4:Ce)/PMMA nanocomposites

International Nuclear Information System (INIS)

Padalia, Diwakar; Johri, U.C.; Zaidi, M.G.H.

2012-01-01

The paper presents the synthesis and properties of polymer nanocomposite material based on cerium doped magnetite (Fe 3 O 4 ) as filler material and poly methyl methacrylate (PMMA) as host matrix. The magnetite (Fe 3 O 4 ) particles were synthesized by co-precipitation route using stable ferrous and ferric salts with ammonium hydroxide as precipitating agent. Further, they doped by cerium oxide (CeO 2 ) non-stoichiometrically. The composite material was fabricated by solvent evaporation method. Here 2.4 GHz microwaves were used to study the effect of microwaves heating on polymerization. The phase and crystal structure is determined by X-ray diffraction (XRD). The average crystallite size of the composites varies from 28 to 35 nm. The chemical structure is confirmed by Fourier transform infrared (FTIR) spectroscopy. The magnetic and thermal properties are investigated by vibrating sample magnetometer (VSM) and differential scanning calorimetry (DSC). The thermal study shows that the microwave heated samples possess higher glass transition temperature (T g ). The magnetic results suggest that coercivity (H C ) and squareness (M r /M s ) of the loop increases with increasing doping percent of cerium.

Thermal decomposition study of uranyl nitrate and cerium hydroxide in a spray dryer

International Nuclear Information System (INIS)

Silva Wildhagen, G.R. da.

1993-05-01

A study, in a spray dryer system based on drying and thermal decomposition of uranyl nitrate solutions aiming the production of uranium trioxide adequate for the use in posterior steps of reduction and hydro fluorination in nuclear fuel cycle; and cerium hydroxide suspensions for the production of cerium oxide with high surface area is presented. Thus, the project and construction of a countercurrent spray dryer was elaborated for capacity of 10 Kg U O 3 /h and 3,5 k Ce O 2 /h. The methodology used in these experiments consisted in the analysis of several parameters (concentration and flow rate of the feed, atomization pressure and inlet temperature of the dryer) over the physical and chemical properties of the products. Using the obtained results, with the help of a mathematical model, it was developed the project of a continuous pilot unity for the production of uranium trioxide or cerium oxide, with capacity of 20 Kg U O 3 /h or 10 Kg Ce O 2 /h, respectively. (author)

Cerium valence change in the solid solutions Ce(Rh1-xRux)Sn

International Nuclear Information System (INIS)

Niehaus, Oliver; Riecken, Jan F.; Winter, Florian; Poettgen, Rainer; Muenster Univ.; Abdala, Paula M.; Chevalier, Bernard

2013-01-01

The solid solutions Ce(Rh 1-x Ru x )Sn were investigated by means of susceptibility measurements, specific heat, electrical resistivity, X-ray absorption spectroscopy (XAS), and 119 Sn Moessbauer spectroscopy. Magnetic measurements as well as XAS data show a cerium valence change in dependence on the ruthenium content. Higher ruthenium content causes an increase from 3.22 to 3.45 at 300 K. Furthermore χ and χ -1 data indicate valence fluctuation for cerium as a function of temperature. For example, Ce(Rh 0.8 Ru 0.2 )Sn exhibits valence fluctuations between 3.42 and 3.32 in the temperature range of 10 to 300 K. This could be proven by using the interconfiguration fluctuation (ICF) model introduced by Sales and Wohlleben. Cerium valence change does not influence the tin atoms as proven by 119 Sn Moessbauer spectroscopy, but it influences the electrical properties. Ce(Rh 0.9 Ru 0.1 )Sn behaves like a typical valence fluctuating compound, and higher ruthenium content causes an increase of the metallic behavior. (orig.)

Fixation of radioactive cerium-144 on white blood cells. Possibilities for use in physiopathology

International Nuclear Information System (INIS)

Aeberhardt, A.

1958-01-01

From the study of the means of transport of cerium in the blood of various laboratory animals, after intra-venous injection of 144 Ce- 144 Pr without carrier, we have been able to show up the part played by the white cells in the transport of this fission product during its passage in the blood. This observation has led to the study, in vitro, of the methods of cerium fixation on the white cells, with a view to determining the possibilities of using this property for white cell labelling, the methods used up to the present not being entirely satisfactory. Using the method for the separation of the known constituents of the blood proposed by us in 1956, we have studied the cerium fixation under various conditions: - on suspensions of white cells from the rabbit, - on a suspension of human white cells, - on the white cells in whole from the rabbit. (author) [fr

Indirect flow injection determination of N-acetyl-L-cysteine using cerium(IV) and ferroin

International Nuclear Information System (INIS)

Vieira, Heberth Juliano; Fatibello-Filho, Orlando

2005-01-01

An indirect flow injection spectrophotometric procedure is proposed for the determination of N-acetyl-L-cysteine in pharmaceutical formulations. In this system, ferroin ([Fe(II)-(fen) 2 ] 2+ ) in excess, with a strong absorption at 500 nm, is oxidized by cerium(IV) yielding cerium(III) and [Fe(III)-(fen) 2 ] 3+ (colorless), thus producing a baseline. When N-acetyl-L-cysteine solution is introduced into the flow injection system, it reacts with cerium(IV) increasing the analytical signal in proportion to the drug concentration. Under optimal experimental conditions, the linearity of the analytical curve for N-acetyl-L-cysteine ranged from 6.5x10 -6 to 1.3x10 -4 mol L -1 . The detection limit was 5.0x10 -6 mol L -1 and recoveries between 98.0 and 106% were obtained. The sampling frequency was 60 determinations per hour and the RSD was smaller than 1.4% for 2.2x10 -5 mol L -1 N-acetyl-L-cysteine. (author)

Corrosion behaviors in physiological solution of cerium conversion coatings on AZ31 magnesium alloy

International Nuclear Information System (INIS)

Cui Xiufang; Yang Yuyun; Liu Erbao; Jin Guo; Zhong Jinggao; Li Qingfen

2011-01-01

In this paper, a non-toxic Ce-based conversion coating was obtained on the surface of bio-medical AZ31 magnesium alloys. The micro-morphology of the coating prepared with optimal technical parameters and immersed in physiological solution (Hank's solution) in different time was observed by scanning electron microscopy (SEM), composition of the cerium conversion coating and corrosion products in Hank's solution were characterized by X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS), respectively. In addition, the corrosion property in Hank's solution was studied by electrochemical experiment and immersion test. The results show that the dense Ce-based conversion coating is obtained on the surface of AZ31 magnesium alloys in optimal technical parameters and the conversion coating consists of a mass of trivalent and tetravalent cerium oxides. The cerium conversion coating can provide obvious protection of magnesium alloys and can effectively reduce the degradation speed in Hank's solution. Also the degradation products have little influence on human body.

Cerium-loaded algae exoskeletons for active corrosion protection of coated AA2024-T3

International Nuclear Information System (INIS)

Denissen, Paul J.; Garcia, Santiago J.

2017-01-01

Highlights: •Nanoporous diatom algae exoskeletons allow for local inhibitor loading. •Cerium loaded exoskeletons show diffusion controlled release from coatings. •In-situ opto-electrochemical analysis allows for accurate corrosion evaluation. •Raman spectroscopy allows for precise identification of Ce at IMs in a scribe. •High levels of protection were obtained with the Ce-diatom coatings. -- Abstract: The use of micron sized nanoporous diatom algae exoskeletons for inhibitor storage and sustained corrosion protection of coated aluminium structures upon damage is presented. In this concept the algae exoskeleton allows local inhibitor loading, limits the interaction between the cerium and the epoxy/amine coating and allows for diffusion-controlled release of the inhibitor when needed. The inhibitor release and corrosion protection by loaded exoskeletons was evaluated by UV/Vis spectrometry, a home-built optical-electrochemical setup, and Raman spectroscopy. Although this concept has been proven for a cerium-epoxy-aluminium alloy system the main underlying principle can be extrapolated to other inhibitor-coating-metal systems.

Eucalyptus tolerance mechanisms to lanthanum and cerium: subcellular distribution, antioxidant system and thiol pools.

Science.gov (United States)

Shen, Yichang; Zhang, Shirong; Li, Sen; Xu, Xiaoxun; Jia, Yongxia; Gong, Guoshu

2014-12-01

Guanglin 9 (Eucalyptus grandis × Eucalyptus urophlla) and Eucalyptus grandis 5 are two eucalyptus species which have been found to grow normally in soils contaminated with lanthanum and cerium, but the tolerance mechanisms are not clear yet. In this study, a pot experiment was conducted to investigate the tolerance mechanisms of the eucalyptus to lanthanum and cerium. Cell walls stored 45.40-63.44% of the metals under lanthanum or cerium stress. Peroxidase and catalase activities enhanced with increasing soil La or Ce concentrations up to 200 mg kg(-1), while there were no obvious changes in glutathione and ascorbate concentrations. Non-protein thiols concentrations increased with increasing treatment levels up to 200 mg kg(-1), and then decreased. Phytochelatins concentrations continued to increase under La or Ce stress. Therefore, the two eucalyptus species are La and Ce tolerant plants, and the tolerance mechanisms include cell wall deposition, antioxidant system response, and thiol compound synthesis. Copyright © 2014 Elsevier Ltd. All rights reserved.

Electrolytic technique for the chemical decontamination process with sulfuric acid-cerium (IV) for decommissioning

International Nuclear Information System (INIS)

Wei, Tsong-Yang; Hsieh, Jung-Chun.

1992-01-01

An electrolyzer with an ion-exchange membrane as the separator has been used to study the electrolytic redox reaction of Ce 4+ / Ce 3+ in sulfuric acid solution, which is a reagent for predismantling system decontamination. Influencing factors such as current density, cerium concentration, acidity, electrolyte flow rate, membrane type and electrode material were studied experimentally. The results indicate that the redox can be achieved with high conversion even as the cerium concentration is below 0.005 M. However, the current efficiency strongly depends on the cerium concentration. In addition, the acid content and the electrolyte flow rate show little influence on the redox reaction. Both cation and anion membrane are feasible for this process. Therefore, the operation conditions are widely applicable. Moreover, two different electrode materials, platinized titanium meshes and graphite, were used. The results show that the platinized titanium meshes is preferable to the graphite for higher current efficiency. (author)

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

Effect of ultrasound on the structural and textural properties of copper-impregnated cerium-modified zirconium-pillared bentonite

International Nuclear Information System (INIS)

Tomul, Fatma

2011-01-01

In this study, the synthesis of zirconium-pillared bentonite modified with cerium was performed via two different methods by the application of conventional and ultrasonic treatments during the intercalation stage. To synthesise copper-impregnated pillared clays by wet impregnation, cerium-modified zirconium-pillared clays were used as supportive materials after being calcined at 300 °C. Ultrasonic treatment significantly decreased the required processing time compared with the conventional treatment of the synthesised pillared bentonites. Chemical analysis confirmed the incorporation of Zr 4+ , Ce 4+ and Cu 2+ species into the pillared bentonites. X-ray diffraction (XRD) patterns of zirconium- and cerium/zirconium-pillared bentonites prepared by conventional treatment show that one large d-spacing above 3.5 nm corresponds to the mesoporous delaminated part, and another small d-spacing above 1.7 nm is indicative of the microporous pillared part. Zirconium- and cerium/zirconium-pillared bentonites prepared via ultrasonic treatment exhibited similar results, with the same high d-spacing but with a second low-intensity d-spacing above 1.9 nm. The delaminated structures of the pillared bentonites synthesised by both methods were conserved after copper impregnation. Nitrogen-adsorption isotherm analysis showed that the textural characteristics of products synthesised by ultrasonic treatment were comparable to those of products synthesised by conventional treatment. Fourier-transform infrared spectroscopy (FTIR) analyses showed the presence of Brønsted- and Lewis-acid sites, and zirconium-pillared clays synthesised by conventional treatment exhibited increased numbers of Brønsted- and Lewis-acid sites after cerium addition and copper impregnation. However, the products synthesised by ultrasonic treatment exhibited an increased number of Brønsted- and Lewis-acid sites after cerium addition, but a decreased number of acid sites after copper impregnation.

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

Effect of HCl pre-treatment on corrosion resistance of cerium-based conversion coatings on magnesium and magnesium alloys

International Nuclear Information System (INIS)

Brunelli, Katya; Dabala, Manuele; Calliari, Irene; Magrini, Maurizio

2005-01-01

The corrosion protection afforded by a cerium conversion coating, formed by immersion in a solution containing rare earth salt and hydrogen peroxide, on pure magnesium and two magnesium alloys, AZ91 and AM50, has been studied. The effect of HCl pre-treatments on the morphology and on the corrosion resistance of the cerium conversion layer was investigated. A thicker and more homogeneous distribution of the conversion coating was obtained when the sample surface was pre-treated with acid. Higher amounts of cerium on the surface of the pre-treated samples were detected. The cerium conversion coating increased the corrosion resistance of the alloys because it ennobled the corrosion potential and decreased both the anodic and cathodic current. The acid pre-treatment further increased the corrosion resistance of the coated alloys. After five days of immersion in chloride environment the untreated samples showed localized corrosion while the chemical conversion coated samples appeared unaffected

Zirconia dispersion as a toughening agent in alumina - Influence of the cerium oxide

International Nuclear Information System (INIS)

Gritti, Olivier

1987-01-01

The improvement of mechanical properties of alumina can be obtained by fine dispersion of zirconia particles. The addition of cerium oxide as a stabilizer of the tetragonal phase has been examined. Different powder preparations, based on impregnation of the alumina powder by zirconium and cerium precursor salts, have been studied. Parameters, such as properties of alumina powder and cerium oxide content, for the production of reactive powders have been determined by two laboratory processes. The sintering of these powders in air at 1600 deg. C has resulted in dense materials with homogeneous microstructure. The mechanical properties, in particular the biaxial flexure strength and the toughness, have been determined in the temperature range 20 deg. C-900 deg. C. A reinforcement of about 80 pc in comparison with alumina is achieved. The optimal composition is (Al 2 O 3 ) 0.8 (ZrO 2 ) 0.18 (CeO 2 ) 0.02 . In the other hand, powder preparation by spray drying has been chosen for an approach to a larger scale process. The sintered ceramics made with these powders present a double microstructure which does not affect the mechanical properties. The presence of cerium oxide produces the following improvements: - increased mobility of the intergranular zirconia inclusions which results in a faster densification; - stabilization of a tetragonal phase without prohibiting the stress induced transformation; - increase of the critical sizes of the tetragonal → monoclinic transformation; - a large decrease in the transformation kinetic in water at 300 deg. C in comparison with that observed for alumina-zirconia doped with yttrium oxide. (author) [fr

Soil organic matter influences cerium translocation and physiological processes in kidney bean plants exposed to cerium oxide nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Majumdar, Sanghamitra [Department of Chemistry, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN), El Paso, TX (United States); Peralta-Videa, Jose R. [Department of Chemistry, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); Environmental Science and Engineering PhD Program, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN), El Paso, TX (United States); Trujillo-Reyes, Jesica [Department of Chemistry, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); Sun, Youping [Texas AgriLife Research Center at El Paso, Texas A& M University System, 1380 A & M Circle, El Paso, TX 79927 (United States); Barrios, Ana C. [Department of Chemistry, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); Niu, Genhua [Texas AgriLife Research Center at El Paso, Texas A& M University System, 1380 A & M Circle, El Paso, TX 79927 (United States); Margez, Juan P. Flores- [Autonomous University of Ciudad Juarez, Departamento de Química y Biología, Instituto de Ciencias Biomédicas, Anillo envolvente PRONAF y Estocolmo, Ciudad Juarez, Chihuahua 32310, México (Mexico); Gardea-Torresdey, Jorge L., E-mail: jgardea@utep.edu [Department of Chemistry, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); Environmental Science and Engineering PhD Program, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN), El Paso, TX (United States)

2016-11-01

Soil organic matter plays a major role in determining the fate of the engineered nanomaterials (ENMs) in the soil matrix and effects on the residing plants. In this study, kidney bean plants were grown in soils varying in organic matter content and amended with 0–500 mg/kg cerium oxide nanoparticles (nano-CeO{sub 2}) under greenhouse condition. After 52 days of exposure, cerium accumulation in tissues, plant growth and physiological parameters including photosynthetic pigments (chlorophylls and carotenoids), net photosynthesis rate, transpiration rate, and stomatal conductance were recorded. Additionally, catalase and ascorbate peroxidase activities were measured to evaluate oxidative stress in the tissues. The translocation factor of cerium in the nano-CeO{sub 2} exposed plants grown in organic matter enriched soil (OMES) was twice as the plants grown in low organic matter soil (LOMS). Although the leaf cover area increased by 65–111% with increasing nano-CeO{sub 2} concentration in LOMS, the effect on the physiological processes were inconsequential. In OMES leaves, exposure to 62.5–250 mg/kg nano-CeO{sub 2} led to an enhancement in the transpiration rate and stomatal conductance, but to a simultaneous decrease in carotenoid contents by 25–28%. Chlorophyll a in the OMES leaves also decreased by 27 and 18% on exposure to 125 and 250 mg/kg nano-CeO{sub 2}. In addition, catalase activity increased in LOMS stems, and ascorbate peroxidase increased in OMES leaves of nano-CeO{sub 2} exposed plants, with respect to control. Thus, this study provides clear evidence that the properties of the complex soil matrix play decisive roles in determining the fate, bioavailability, and biological transport of ENMs in the environment. - Highlights: • Ce translocation to leaves was facilitated by higher organic matter (OM) in soil. • Lower soil OM increased leaf cover area in nano-CeO{sub 2} exposed plants. • Nano-CeO{sub 2} effects on metabolic processes were more

The Ce-Ni-Si system as a representative of the rare earth-Ni-Si family: Isothermal section and new rare-earth nickel silicides

Energy Technology Data Exchange (ETDEWEB)

Morozkin, A.V., E-mail: morozkin@tech.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, Moscow, GSP-1, 119991 (Russian Federation); Knotko, A.V.; Garshev, A.V. [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, Moscow, GSP-1, 119991 (Russian Federation); Faculty of Materials Science, Moscow State University, Leninskie Gory, House 1, Building 73, Moscow, GSP-1, 119991 (Russian Federation); Yapaskurt, V.O. [Department of Petrology, Geological Faculty Moscow State University, Leninskie Gory, Moscow 119991 (Russian Federation); Nirmala, R. [Indian Institute of Technology Madras, Chennai 600036 (India); Quezado, S.; Malik, S.K. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal, 59082-970 (Brazil)

2016-11-15

Si{sub 2}; while no appreciable solubility was observed for the other binary compounds of the Ce-Ni-Si system. As a prolongation of Rare Earth-Ni-Si system’s isostructural rows, LaNi{sub 7}Si{sub 6} and YNi{sub 6.6}Si{sub 6.1} (GdNi{sub 7}Si{sub 6}-type), ScNi{sub 6}Si{sub 6} (YCo{sub 6}Ge{sub 6}-type), NdNi{sub 6}Si{sub 6} (YNi{sub 6}Si{sub 6}-type), (Tb, Ho){sub 2}Ni{sub 15}Si{sub 2} (Th{sub 2}Zn{sub 17}-type), Nd{sub 2}Ni{sub 2.3}Si{sub 0.7} and Sm{sub 2}Ni{sub 2.2}Si{sub 0.8} (Mo{sub 2}NiB{sub 2}-type), Nd{sub 3}Ni{sub 2.55}Si{sub 1.45} (W{sub 3}CoB{sub 3}-type) and (Tb, Dy){sub 7}Ni{sub 50}Si{sub 19} (Y{sub 7}Ni{sub 49}Si{sub 20}-type) compounds were synthesized and investigated. Magnetic properties of the CeNi{sub 6}Si{sub 6}, CeNi{sub 7}Si{sub 6}, CeNi{sub 8.8}Si{sub 4.2}, Ce{sub 6}Ni{sub 7}Si{sub 4}, CeNi{sub 5}Si, Ce{sub 2}Ni{sub 2.5}Si{sub 0.5}, Nd{sub 2}Ni{sub 2.3}Si{sub 0.7} and Dy{sub 7}Ni{sub 50}Si{sub 19} compounds have also been investigated and are presented here. - Highlights: • Ce-Ni-Si isothermal section was obtained at 870/1070 K. • Twenty one known ternary cerium nickel silicides were confirmed in Ce-Ni-Si. • Five new cerium nickel silicides were detected in Ce-Ni-Si. • Eleven new rare earth nickel silicides were detected in R-Ni-Si. • Magnetic properties of eight rare earth nickel silicides were investigated.

Corrosion inhibition of 7000 series aluminium alloys with cerium diphenyl phosphate

Energy Technology Data Exchange (ETDEWEB)

Hill, Julie-Anne [Department of Materials Engineering and Australian Centre of Excellence for Electromaterials Science, Wellington Rd, Monash University, Clayton, Victoria (Australia); Markley, Tracey [Department of Materials Engineering and Australian Centre of Excellence for Electromaterials Science, Wellington Rd, Monash University, Clayton, Victoria (Australia); CSIRO, Division of Materials Science and Technology, Clayton, Victoria (Australia); Forsyth, Maria, E-mail: maria.forsyth@deakin.edu.au [Department of Materials Engineering and Australian Centre of Excellence for Electromaterials Science, Wellington Rd, Monash University, Clayton, Victoria (Australia); Howlett, Patrick C. [Department of Materials Engineering and Australian Centre of Excellence for Electromaterials Science, Wellington Rd, Monash University, Clayton, Victoria (Australia); Hinton, Bruce R.W. [Department of Materials Engineering and Australian Centre of Excellence for Electromaterials Science, Wellington Rd, Monash University, Clayton, Victoria (Australia); Defence Science and Technology Organisation, Melbourne, Victoria (Australia)

2011-02-03

Graphical abstract: Scanning electron micrographs of microtomed surface shows pristine surface free of corrosion related 'mud cracking' inset for an inhibited AA7050 specimen when only 150 ppm Ce(dpp)3 is present in 0.1 M NaCl solution. Display Omitted Research highlights: > The thin film of hydrolysis products of Ce(dpp)3 and aluminium oxide is proposed to cause the inhibition. > The film consists of discrete Ce rich particles and a thin film over the matrix of Ce, P and Al oxides. > Discrete deposition of Ce is specifically influenced by Cu rich intermetallics. - Abstract: Cerium diphenyl phosphate (Ce(dpp){sub 3}) has previously been shown to be a strong corrosion inhibitor for aluminium-copper magnesium alloy AA2024-T3 and AA7075 in chloride solutions. Surface characterisation including SEM and ToF-SIMS coupled with electrochemical impedance spectroscopy (EIS) measurements are used to propose a mechanism of corrosion inhibition which appears to involve the formation of a complex oxide film of aluminium and cerium also incorporating the organophosphate component. The formation of a thin complex film consisting of hydrolysis products of the Ce(dpp){sub 3} compound and aluminium oxide is proposed to lead to the observed inhibition. SEM analysis shows that some intermetallics favour the creation of thicker deposits predominantly containing cerium oxide compounds.

Bioavailability of cerium oxide nanoparticles to Raphanus sativus L. in two soils.

Science.gov (United States)

Zhang, Weilan; Musante, Craig; White, Jason C; Schwab, Paul; Wang, Qiang; Ebbs, Stephen D; Ma, Xingmao

2017-01-01

Cerium oxide nanoparticles (CeO 2 NP) are a common component of many commercial products. Due to the general concerns over the potential toxicity of engineered nanoparticles (ENPs), the phytotoxicity and in planta accumulation of CeO 2 NPs have been broadly investigated. However, most previous studies were conducted in hydroponic systems and with grain crops. For a few studies performed with soil grown plants, the impact of soil properties on the fate and transport of CeO 2 NPs was generally ignored even though numerous previous studies indicate that soil properties play a critical role in the fate and transport of environmental pollutants. The objectives of this study were to evaluate the soil fractionation and bioavailability of CeO 2 NPs to Raphanus sativus L (radish) in two soil types. Our results showed that the silty loam contained slightly higher exchangeable fraction (F1) of cerium element than did loamy sand soil, but significantly lower reducible (F2) and oxidizable (F3) fractions as CeO 2 NPs concentration increased. CeO 2 NPs associated with silicate minerals or the residue fraction (F4) dominated in both soils. The cerium concentration in radish storage root showed linear correlation with the sum of the first three fractions (r 2  = 0.98 and 0.78 for loamy sand and silty loam respectively). However, the cerium content in radish shoots only exhibited strong correlations with F1 (r 2  = 0.97 and 0.89 for loamy sand and silty loam respectively). Overall, the results demonstrated that soil properties are important factors governing the distribution of CeO 2 NPs in soil and subsequent bioavailability to plants. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Coulometric microdetermination of organic compounds with manganese(III) and cerium(IV)

International Nuclear Information System (INIS)

Chateau-Gosselin, M.; Patriarche, G.J.

1977-01-01

The oxidation of compounds such as hydroquinon, p-aminophenol, paracetamol and phenacetin was performed using cerium(IV) and manganese(III) coulometrically electrogenerated. Quantitative results obtained are excellent even at the microscale level. (author)

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).

Effect of coating parameters on the microstructure of cerium oxide conversion coatings

Energy Technology Data Exchange (ETDEWEB)

Johnson, Benedict Y.; Edington, Joe; O' Keefe, Matthew J

2003-11-25

The microstructure and morphology of cerium oxide conversion coatings prepared under different deposition conditions were characterized by transmission electron microscopy (TEM). The coatings were formed by a spontaneous reaction between a water-based solution containing CeCl{sub 3} and aluminum alloy 7075-T6 substrates. Microstructural characterization was performed to determine the crystallinity of the coatings and to obtain a better understanding of the deposition parameters on coating microstructure. The results of TEM imaging and electron diffraction analysis indicated that the as-deposited coating was composed of nanocrystalline particles of a previously unreported cerium compound. The particles of the coatings produced using glycerol as an additive were found to be much finer than those of the coatings prepared in the absence of glycerol. This indicates that glycerol may act as a grain refiner and/or growth inhibitor during coating deposition. After deposition, the coated panels were treated for 5 min in a phosphate sealing solution. The sealing treatment converted the as-deposited coating into hydrated cerium phosphate. Panels coated from solutions containing no glycerol followed by phosphate sealing performed poorly in salt fog tests. With glycerol addition, the corrosion resistance of the coatings that were phosphate sealed improved considerably, achieving an average passing rate of 85%.

Ultrathin, epitaxial cerium dioxide on silicon

Energy Technology Data Exchange (ETDEWEB)

Flege, Jan Ingo, E-mail: flege@ifp.uni-bremen.de; Kaemena, Björn; Höcker, Jan; Schmidt, Thomas; Falta, Jens [Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen (Germany); Bertram, Florian [Photon Science, Deutsches Elektronensynchrotron (DESY), Notkestraße 85, 22607 Hamburg (Germany); Wollschläger, Joachim [Department of Physics, University of Osnabrück, Barbarastraße 7, 49069 Osnabrück (Germany)

2014-03-31

It is shown that ultrathin, highly ordered, continuous films of cerium dioxide may be prepared on silicon following substrate prepassivation using an atomic layer of chlorine. The as-deposited, few-nanometer-thin Ce{sub 2}O{sub 3} film may very effectively be converted at room temperature to almost fully oxidized CeO{sub 2} by simple exposure to air, as demonstrated by hard X-ray photoemission spectroscopy and X-ray diffraction. This post-oxidation process essentially results in a negligible loss in film crystallinity and interface abruptness.

Evaluation of mechanically treated cerium (IV) oxides as corrosion inhibitors for galvanized steel

Energy Technology Data Exchange (ETDEWEB)

Deflorian, F., E-mail: flavio.deflorian@ing.unitn.it [Department of Materials Engineering and Industrial Technology, University of Trento, Via Mesiano 77, 38123 Trento (Italy); Fedel, M.; Rossi, S. [Department of Materials Engineering and Industrial Technology, University of Trento, Via Mesiano 77, 38123 Trento (Italy); Kamarchik, P. [PPG Industries, Coatings Innovation Center, 4325 Rosanna Drive, Allison Park, PA 15101 (United States)

2011-09-30

The use of cerium salts as corrosion inhibitors for hot dip galvanized steel has been object of a numerous studies in the last few years. The role of cerium ions as corrosion inhibitors was proved: cerium is able to block the cathodic sites of the metal, forming insoluble hydroxides and oxides on the zinc surface. This fact leads to a dramatic decrease of the cathodic current densities and, therefore, to a reduction the overall corrosion processes. On the other hand, the potential of cerium oxides as corrosion inhibitors was also proposed. However, the real effectiveness of this kind of anticorrosive pigments has not been clarified yet. In this work cerium (IV) oxides are considered as corrosion inhibitors for galvanized steel. The corrosion inhibition mechanism of mechanically treated (milled) CeO{sub 2} alone and in combination with milled SiO{sub 2} nanoparticles was investigated. For this purpose milled CeO{sub 2}, CeO{sub 2} and SiO{sub 2} milled together and milled SiO{sub 2} particles were studied as corrosion inhibitors in water solution. Therefore, the different mechanically treated particles were dispersed in 0.1 M NaCl solution to test their effectiveness as corrosion inhibitors for galvanized steel. The galvanized steel was immersed in the different solutions and the corrosion inhibition efficiency of the different particles was measured by means of electrochemical techniques. For this purpose, electrochemical impedance spectroscopy (EIS) measurements were carried out, monitoring the evolution of the corrosion processes occurring at the metal surface with the immersion time in the solution. The effect of the different pigments was also investigated by carrying out anodic and cathodic polarization measurements. The polarization curves were acquired under conditions of varied pH. The experimental measurements suggest that the mechanical treatment performed on the SiO{sub 2} and CeO{sub 2} particles promote the formation of an effective corrosion pigment

EXAFS and XANES analysis of plutonium and cerium edges from titanate ceramics for fissile materials disposal

International Nuclear Information System (INIS)

Fortner, J. A.; Kropf, A. J.; Bakel, A. J.; Hash, M. C.; Aase, S. B.; Buck, E. C.; Chamerlain, D. B.

1999-01-01

We report x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) spectra from the plutonium L III edge and XANES from the cerium L II edge in prototype titanate ceramic hosts. The titanate ceramics studied are based upon the hafnium-pyrochlore and zirconolite mineral structures and will serve as an immobilization host for surplus fissile materials, containing as much as 10 weight % fissile plutonium and 20 weight % (natural or depleted) uranium. Three ceramic formulations were studied: one employed cerium as a ''surrogate'' element, replacing both plutonium and uranium in the ceramic matrix, another formulation contained plutonium in a ''baseline'' ceramic formulation, and a third contained plutonium in a formulation representing a high-impurity plutonium stream. The cerium XANES from the surrogate ceramic clearly indicates a mixed III-IV oxidation state for the cerium. In contrast, XANES analysis of the two plutonium-bearing ceramics shows that the plutonium is present almost entirely as Pu(IV) and occupies the calcium site in the zirconolite and pyrochlore phases. The plutonium EXAFS real-space structure shows a strong second-shell peak, clearly distinct from that of PuO 2 , with remarkably little difference in the plutonium crystal chemistry indicated between the baseline and high-impurity formulations

Implementation of a complex multi-phase equation of state for cerium and its correlation with experiment

Energy Technology Data Exchange (ETDEWEB)

Cherne, Frank J [Los Alamos National Laboratory; Jensen, Brian J [Los Alamos National Laboratory; Elkin, Vyacheslav M [VNIITF

2009-01-01

The complexity of cerium combined with its interesting material properties makes it a desirable material to examine dynamically. Characteristics such as the softening of the material before the phase change, low pressure solid-solid phase change, predicted low pressure melt boundary, and the solid-solid critical point add complexity to the construction of its equation of state. Currently, we are incorporating a feedback loop between a theoretical understanding of the material and an experimental understanding. Using a model equation of state for cerium we compare calculated wave profiles with experimental wave profiles for a number of front surface impact (cerium impacting a plated window) experiments. Using the calculated release isentrope we predict the temperature of the observed rarefaction shock. These experiments showed that the release state occurs at different magnitudes, thus allowing us to infer where dynamic {gamma} - {alpha} phase boundary is.

Colloidal stabilization of cerium-gadolinium oxide (CGO) suspensions via rheology

DEFF Research Database (Denmark)

Marani, Debora; Sudireddy, Bhaskar Reddy; Bentzen, Janet Jonna

2015-01-01

colloidally stable state. The method was applied to explore the ability of four commercial dispersants (acidic affine, neutral, basic affine, and polyvinylpyrrolidone (PVP)) to disperse cerium-gadolinium oxide (CGO) in ethanol. Only the acidic affine and the PVP dispersants were found to efficiently disperse...

Gas sensing behaviour of cerium oxide and magnesium aluminate

Indian Academy of Sciences (India)

Gas sensing behaviour of cerium oxide and magnesium aluminate composites ... A lone pairof the electron state was identified from the electro paramagnetic ... carbon monoxide (CO) (at 0.5, 1.0 and 1.5 bar) and ethanol (at 50 and 100 ppm) was ... The magnitude of the temperature varied linearly regardless of the gas ...

Exposure and Health Effects Review of Engineered Nanoscale Cerium and Cerium Dioxide Associated with its Use as a Fuel Additive - NOW IN PRINT IN THE JOURNAL

Science.gov (United States)

Advances of nanoscale science have produced nanomaterials with unique physical and chemical properties at commercial levels that are now incorporated into over 1000 products. Nanoscale cerium (di) oxide (Ce02) has recently gained a wide range of applications which includes coatin...

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.

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

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.

Study of cyclic oxidation for stainless steels AISI 309 T 253 M A, with low additions of cerium

International Nuclear Information System (INIS)

Velazquez F, G.L.; Martinez, M.; Ruiz, A.

1998-01-01

It has been detected that the addition of small amounts (<1%) of the so called 'reactive elements' such as Cerium to Fe-Cr alloys that was utilized in oxidating environment at high temperatures improving its resistance to oxidation under isothermal and cyclic conditions. In this work, it was evaluated the behavior under cyclic oxidation conditions for an austenitic stainless steel at chromium-nickel (253MA) with cerium addition, and comparing it with the AISI 310S austenitic stainless steel. The cyclic oxidation essays consist of five cycles by 24 hours each one, following of a cooling in air until ambient temperature from the temperatures of 850, 900 and 950 Centigrade, registering the gain mass of the specimen at end of each cycle. In order to this were prepared samples with dimensions of 20 mm. x 10 mm. x 1 mm. Later to the oxidation essays was evaluated the morphology of the corrosion products layer by scanning electron microscopy. The present phases were identified by X-ray diffraction and by chemical microanalysis by Dispersive energy (EDAX). The results obtained show that the steel with cerium addition, presents a higher adherence and resistance to the spalling noting that the cerium promotes the casting anchor of the oxides layer to matrix and by reducing the grain size of the layer improving its plasticity. Additionally the cerium promotes the preferential oxidation of the forming elements of protective layers like the chromium. (Author)

Influence of preliminary deformation and phase strengthening on γ reversible α transformation kinetics in cerium under pressure

International Nuclear Information System (INIS)

Larionov, L.V.; Livshits, L.D.; Peresada, G.I.; AN SSSR, Moscow. Inst. Fiziki Zemli)

1985-01-01

Using the methods of piezo- and resistometry the influence of preliminary plastic deformation, phase transformation induced strengthening and heat treatment on kinetics of γ reversible α transformation in cerium is studied. It is shown, that the used methods of preliminary treatment of sample material do not change pressure value of γ → α and α →γ transformation initiation and do not affect hysteresis value, but affect considerably its kinetics. Preliminary plastic deformation and structural strengthening increase the average formation rate of a new phase. According to the data of tensile tests, structural strengthening, apprearing as a result of one cycle of γ → α → γ transformation, increases cerium strength characteristics 6y 30-50% with simultaneous decrease in plasticity. Metallographic studies confirm martensitic character of γ → α → γ transformations in cerium

Photocatalytic action of cerium molybdate and iron-titanium oxide hollow nanospheres on Escherichia coli

Energy Technology Data Exchange (ETDEWEB)

Kartsonakis, I. A., E-mail: ikartsonakis@ims.demokritos.gr; Kontogiani, P.; Pappas, G. S.; Kordas, G. [NCSR ' DEMOKRITOS' , Sol-Gel Laboratory, Institute of Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems (Greece)

2013-06-15

This study is focused on the production of hollow nanospheres that reveal antibacterial action. Cerium molybdate and iron-titanium oxide hollow nanospheres with a diameter of 175 {+-} 15 and 221 {+-} 10 nm, respectively, were synthesized using emulsion polymerization and the sol-gel process. Their morphology characterization was accomplished using scanning electron microscopy. Their antibacterial action was examined on pure culture of Escherichia coli considering the loss of their viability. Both hollow nanospheres presented photocatalytic action after illumination with blue-black light, but those of cerium molybdate also demonstrated photocatalytic action in the dark. Therefore, the produced nanospheres can be used for antibacterial applications.

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.

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.

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)

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.

Evaluation of Antiproliferative Potential of Cerium Oxide Nanoparticles on HeLa Human Cervical Tumor Cell

Directory of Open Access Journals (Sweden)

Zoriţa Diaconeasa

2015-05-01

Full Text Available Cerium oxide nanoparticles (CeO2 nanoparticles as nanomaterials have promising biomedical applications. In this paper, the cytotoxicity induced by CONPs human cervical tumor cells was investigated. Cerium oxide nanoparticles were synthesized using the precipitation method. The nanoparticles were found to inhibit the proliferation of HeLa human cervical tumor cells in a dose dependent manner but did not showed to be cytotoxic as analyzed by MTT assay. The administrated treatment decreased the HeLa cell viability cells from 100% to 65% at the dose of 100 μg/mL.

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...

The kinetics of the cerium(IV)-uranium(IV) reaction at low sulfate concentrations

International Nuclear Information System (INIS)

Michaille, P.; Kikindai, T.

1977-01-01

The rate of oxidation of uranium(IV) by cerium(IV) was measured with a stopped-flow spectrophotometer at sulfuric acid concentrations of 2 x 10 -6 to 0.5 M. At a constant hydrogen ion concentration of 0.5 M, the maximum rate constant was observed for 2 x 10 -3 M sulfuric acid; at that concentration, two sulfate ions were involved in the activated complex. The dependence of the rate constant on the hydrogen ion concentration showed that the reaction paths involving one or two sulfate ions also involved one hydroxyl ion, whereas one hydrogen ion was involved in the five sulfate dependent path. Spectrophotometric measurements supported the existence of a hydrolyzed monosulfatocomplex of cerium(IV). (author)

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

Correlation of the oxidation state of cerium in sol-gel glasses as a function of thermal treatment via optical spectroscopy and XANES studies.

Science.gov (United States)

Assefa, Zerihun; Haire, R G; Caulder, D L; Shuh, D K

2004-07-01

Sol-gel glass matrices containing lanthanides have numerous technological applications and their formation involves several chemical facets. In the case of cerium, its ability to exist in two different oxidation states or in mixed valence state provides additional complexities for the sol-gel process. The oxidation state of cerium present during different facets of preparation of sol-gel glasses, and also as a function of the starting oxidation state of cerium added, were studied both by optical spectroscopy and X-ray absorption near-edge structures (XANES). The findings acquired by each approach were compared. The primary focus was on the redox chemistries associated with sample preparation, gelation, and thermal treatment. When Ce3+ is introduced into the starting sols, the trivalent state normally prevails in the wet and room temperature-dried gels. Heating in air at >100 degrees C can generate a light yellow coloration with partial oxidation to the tetravalent state. Above 200 degrees C and up to approximately 1000 degrees C, cerium is oxidized to its tetravalent state. In contrast, when tetravalent cerium is introduced into the sol, both the wet and room temperature-dried gels lose the yellow-brown color of the initial ceric ammonium nitrate solution. When the sol-gel is heated to 110 degrees C it turns yellowish as the cerium tends to be re-oxidized. The yellow color is believed to represent the effect of oxidation and oligomerization of the cerium-silanol units in the matrix. The luminescence properties are also affected by these changes, the details of which are reported herein.

Thermal expansion and transformation behavior of cerium and plutonium alloys: an application of the Aptekar-Ponyatovsky regular solution model.

Science.gov (United States)

Lawson, A C; Lashley, J C

2011-09-14

In this paper we apply the Aptekar-Ponyatovsky (AP) regular solution thermodynamic model to the analysis of experimental data for the coefficient of thermal expansion (CTE) and determine the AP model parameters for unalloyed cerium metal, Ce-Th-La alloys, and Pu-Ga alloys. We find that the high temperature CTE of cerium metal follows the predictions of the AP model based on low temperature, high pressure data. For Ce-Th-La alloys we use the AP parameters to track the suppression of the first-order γ-α cerium transition. We show the AP model accounts for the negative CTE observed for Pu-Ga alloys and is equivalent to an earlier invar model. Finally, we apply the AP parameters obtained for Pu-Ga alloys to rationalize the observed δ-α transformation pressures of these alloys. We show that the anomalous values of the Grüneisen and Grüneisen-Anderson parameters are important features of the thermal properties of plutonium. A strong analogy between the properties of plutonium and cerium is confirmed.

Electrochemical separation of cerium and yttrium in molten chlorides on liquid-metallic electrodes

International Nuclear Information System (INIS)

Yamshchikov, L.F.; Lebedev, V.A.; Nichkov, I.F.

1978-01-01

An estimating calculation of the coefficients of separation of cerium and yttrium in the process of electrolysis in molten salts on liquid electrodes of aluminium, gallium, indium, lead, tin, antimonium and zinc is carried out. The calculation of the separation coefficients was carried out according to the known values of activation coefficients of cerium and yttrium in fusible metals. The electrolysis was carried out at 973 K in the argon air in the cell with an eutectic mixture of NaCl and KCl as an elactrolyte. It is shown that the salten phase is concentrated by yttrium, and the melallic one- by cerium on all the electrodes. The value of the separation coefficient of Ce and Y is considerably high and continuously increases on the fusible metals in the Zn, In, Ga, Al, Pb, Sn, Sb series. The experimental values of the separation coefficients practically coincide with the theoretically calculated ones, testifying to the possibility of the effective separation of elements even in a single-staged possibility of the effective separation of elements even in a single-staged process. An electrolysis of molten salts is not inferior in its selectivity to the universally recognized methods of the fine purification of substances permitting to separate Ce and Y with the Ksub(sep) approximately equal to 10

Morphological and electrical properties of self-assembled iron silicide nanoparticles on Si(0 0 1) and Si(1 1 1) substrates

International Nuclear Information System (INIS)

Molnár, G.; Dózsa, L.; Erdélyi, R.; Vértesy, Z.; Osváth, Z.

2015-01-01

Highlights: • Epitaxial iron silicide nanostructures were grown on Si(1 1 1) and Si(0 0 1) substrates. • The size and shape of the particles are the function of the thickness and annealing. • The local current–voltage characteristics were measured by conductive AFM. • The different size and shape nanoparticles show similar I–V characteristics. • The tip current is dominated in few nm size sites, visible in the AFM phase image. - Abstract: Epitaxial iron silicide nanostructures are grown by solid phase epitaxy on Si(0 0 1) and Si(1 1 1), and by reactive deposition epitaxy on Si(0 0 1) substrates. The formation process is monitored by reflection high-energy electron diffraction. The morphology, size, and electrical properties of the nanoparticles are investigated by scanning electron microscopy, by electrically active scanning probe microscopy, and by confocal Raman spectroscopy. The results show that the shape, size, orientation, and density of the nanoobjects can be tuned by self-assembly, controlled by the lattice misfit between the substrates and iron silicides. The size distribution and shape of the grown nanoparticles depend on the substrate orientation, on the initial thickness of the evaporated iron, on the temperature and time of the annealing, and on the preparation method. The so-called Ostwald ripening phenomena, which state that the bigger objects develop at the expense of smaller ones, controls the density of the nanoparticles. Raman spectra show the bigger objects do not contain β-FeSi 2 phase. The different shape nanoparticles exhibit small, about 100 mV barrier compared to the surrounding silicon. The local leakage current of the samples measured by conductive AFM using a Pt coated Si tip is localized in a few nanometers size sites, and the sites which we assume are very small silicide nanoparticles or point defects.

Study of cerium doped magnetite (Fe{sub 3}O{sub 4}:Ce)/PMMA nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Padalia, Diwakar, E-mail: Padalia.diwakar@gmail.com [Department of Physics, G.B. Pant University of Agriculture and Technology, Pantnagar, Uttrakhand (India); Johri, U.C. [Department of Physics, G.B. Pant University of Agriculture and Technology, Pantnagar, Uttrakhand (India); Zaidi, M.G.H. [Supercritical Fluid Processing Laboratory, Department of Chemistry, G.B. Pant University of Agriculture and Technology, Pantnagar, Uttrakhand (India)

2012-03-01

The paper presents the synthesis and properties of polymer nanocomposite material based on cerium doped magnetite (Fe{sub 3}O{sub 4}) as filler material and poly methyl methacrylate (PMMA) as host matrix. The magnetite (Fe{sub 3}O{sub 4}) particles were synthesized by co-precipitation route using stable ferrous and ferric salts with ammonium hydroxide as precipitating agent. Further, they doped by cerium oxide (CeO{sub 2}) non-stoichiometrically. The composite material was fabricated by solvent evaporation method. Here 2.4 GHz microwaves were used to study the effect of microwaves heating on polymerization. The phase and crystal structure is determined by X-ray diffraction (XRD). The average crystallite size of the composites varies from 28 to 35 nm. The chemical structure is confirmed by Fourier transform infrared (FTIR) spectroscopy. The magnetic and thermal properties are investigated by vibrating sample magnetometer (VSM) and differential scanning calorimetry (DSC). The thermal study shows that the microwave heated samples possess higher glass transition temperature (T{sub g}). The magnetic results suggest that coercivity (H{sub C}) and squareness (M{sub r}/M{sub s}) of the loop increases with increasing doping percent of cerium.

Characterization of composite metal-ceramic of nickel-oxide cerium doped gadolinium

International Nuclear Information System (INIS)

Silva, M.L.A. da; Varela, M.C.R.S.

2016-01-01

Composite nickel doped cerium oxide are used in SOFC anode materials. In this study we evaluated the effect of the presence of gadolinium on the properties of composite nickel and ceria and. The supports were synthesized by sol-gel method. The impregnation with nickel nitrate was taken sequentially, followed by calcination. The materials were characterized by X-ray diffraction, measurement of specific surface area, temperature programmed reduction, Raman spectroscopy. The presence of gadolinium retained the fluorite structure of ceria by forming a solid solution, also not influencing significantly on the specific surface area of the support. On the other hand, there was a decrease in the area catalysts, which can be attributed to sintering of nickel. Furthermore, addition of gadolinium favored the formation of intrinsic and extrinsic vacancies in cerium oxide, which leads to an increase in the ionic conductivity of the solid, desirable property for an SOFC anode catalyst. (author)

Growth of monodisperse nanocrystals of cerium oxide during synthesis and annealing

International Nuclear Information System (INIS)

Ghosh, Swapankumar; Divya, Damodaran; Remani, Kottayilpadi C.; Sreeremya, Thadathil S.

2010-01-01

Monodisperse cerium oxide nanocrystals have been successfully synthesised using simple ammonia precipitation technique from cerium(III) nitrate solution at different temperatures in the range 35-80 o C. The activation energy for growth of CeO 2 nanocrystals during the precipitation is calculated as 11.54 kJ/mol using Arrhenius plot. Average crystal diameter was obtained from XRD analysis, HR-TEM and light scattering (PCS). The analysis of size data from HR-TEM images and PCS clearly indicated the formation of highly crystalline CeO 2 particles in narrow size range. CeO 2 nanocrystals precipitated at 35 o C were further annealed at temperatures in the range 300-700 o C. The activation energy for crystal growth during annealing is also calculated and is close to the reported values. An effort is made to predict the mechanism of crystal growth during the precipitation and annealing.

Molecular absorption spectra of beryllium, cerium, lanthanum, iron, and platinum salts

International Nuclear Information System (INIS)

Daidoji, Hidehiro

1980-01-01

The absorption spectra of some salts of beryllium, cerium, lanthanum, iron and platinum in air-acetylene flame were measured in the wavelength range from 200 to 400 nm. A Hitachi 207 type atomic absorption spectrophotometer was used. A deuterium lamp, a home-made continuous radiation lamp and some hollow cathode lamps were used as light sources. The new molecular absorption spectra of cerium, lanthanum and platinum and the absorption spectra due to Be(OH) 2 , LaO, PtH, FeO and FeCl in 200-400 nm region were obtained. Emission spectra of CeO, LaO and FeOH were also obtained. These molecular absorption bands were estimated as absorption errors of maximum 15 times to the sensitivity of each elements in atomic absorption spectrometry. In addition, spectral line interferences of iron were observed in atomic absorption spectrometry of Zn, Cd, Ni, Cu and Cr. (author)

Preparation and characterization of gelatin/cerium(Ⅲ) film

Institute of Scientific and Technical Information of China (English)

黄崇军; 黄雅钦; 田娜; 童元建; 殷瑞贤

2010-01-01

A novel gelatin film with antibacterial activity was prepared by electrostatic crosslinking using cerium (Ⅲ) nitrate hexahydrate as the crosslinking agent. The structure and properties of the films were investigated by Fourier transform infrared spectra, tensile tests, thermogravimetric analysis, static drop contact angle and disc diffusion method. The results showed that cross-linking could not only improve the thermal and mechanical properties and lower the hydrophilic property of the films, but also make...

Photocatalytic action of cerium molybdate and iron-titanium oxide hollow nanospheres on Escherichia coli

International Nuclear Information System (INIS)

Kartsonakis, I. A.; Kontogiani, P.; Pappas, G. S.; Kordas, G.

2013-01-01

This study is focused on the production of hollow nanospheres that reveal antibacterial action. Cerium molybdate and iron-titanium oxide hollow nanospheres with a diameter of 175 ± 15 and 221 ± 10 nm, respectively, were synthesized using emulsion polymerization and the sol–gel process. Their morphology characterization was accomplished using scanning electron microscopy. Their antibacterial action was examined on pure culture of Escherichia coli considering the loss of their viability. Both hollow nanospheres presented photocatalytic action after illumination with blue–black light, but those of cerium molybdate also demonstrated photocatalytic action in the dark. Therefore, the produced nanospheres can be used for antibacterial applications.

Influence of layout parameters on snapback characteristic for a gate-grounded NMOS device in 0.13-μm silicide CMOS technology

International Nuclear Information System (INIS)

Jiang Yuxi; Li Jiao; Ran Feng; Cao Jialin; Yang Dianxiong

2009-01-01

Gate-grounded NMOS (GGNMOS) devices with different device dimensions and layout floorplans have been designed and fabricated in 0.13-μm silicide CMOS technology. The snapback characteristics of these GGNMOS devices are measured using the transmission line pulsing (TLP) measurement technique. The relationships between snapback parameters and layout parameters are shown and analyzed. A TCAD device simulator is used to explain these relationships. From these results, the circuit designer can predict the behavior of the GGNMOS devices under high ESD current stress, and design area-efficient ESD protection circuits to sustain the required ESD level. Optimized layout rules for ESD protection in 0.13-μm silicide CMOS technology are also presented. (semiconductor devices)

Preparation of Carbon-Platinum-Ceria and Carbon-Platinum-Cerium catalysts and its application in Polymer Electrolyte Fuel Cell: Hydrogen, Methanol, and Ethanol

Science.gov (United States)

Guzman Blas, Rolando Pedro

This thesis is focused on fuel cells using hydrogen, methanol and ethanol as fuel. Also, in the method of preparation of catalytic material for the anode: Supercritical Fluid Deposition (SFD) and impregnation method using ethylenediaminetetraacetic acid (EDTA) as a chelating agent. The first part of the thesis describes the general knowledge about Hydrogen Polymer Exchange Membrane Fuel Cell (HPEMFC),Direct Methanol Fuel Cell (DMFC) and Direct Ethanol Fuel Cell (DEFC), as well as the properties of Cerium and CeO2 (Ceria). The second part of the thesis describes the preparation of catalytic material by Supercritical Fluid Deposition (SFD). SFD was utilized to deposit Pt and ceria simultaneously onto gas diffusion layers. The Pt-ceria catalyst deposited by SFD exhibited higher methanol oxidation activity compared to the platinum catalyst alone. The linear sweep traces of the cathode made for the methanol cross over study indicate that Pt-Ceria/C as the anode catalyst, due to its better activity for methanol, improves the fuel utilization, minimizing the methanol permeation from anode to cathode compartment. The third and fourth parts of the thesis describe the preparation of material catalytic material Carbon-Platinum-Cerium by a simple and cheap impregnation method using EDTA as a chelating agent to form a complex with cerium (III). This preparation method allows the mass production of the material catalysts without additional significant cost. Fuel cell polarization and power curves experiments showed that the Carbon-Platinum-Cerium anode materials exhibited better catalytic activity than the only Vulcan-Pt catalysts for DMFC, DEFC and HPEMFC. In the case of Vulcan-20%Pt-5%w Cerium, this material exhibits better catalytic activity than the Vulcan-20%Pt in DMFC. In the case of Vulcan-40% Pt-doped Cerium, this material exhibits better catalytic activity than the Vulcan-40% Pt in DMFC, DEFC and HPEMFC. Finally, I propose a theory that explains the reason why the

Ab initio molecular dynamics study of the properties of cerium in liquid sodium at 1000 K temperature

Energy Technology Data Exchange (ETDEWEB)

Samin, Adib; Li, Xiang; Zhang, Jinsuo [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, 201 W 19th Avenue, Columbus, Ohio 43210 (United States); Mariani, R. D. [Idaho National Laboratory, Materials and Fuels Complex, Idaho Falls, Idaho 83415 (United States); Unal, Cetin [Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, New Mexico 87545 (United States)

2015-12-21

For liquid-sodium-cooled fast nuclear reactor systems, it is crucial to understand the behavior of lanthanides and other potential fission products in liquid sodium or other liquid metal solutions such as liquid cesium-sodium. In this study, we focus on lanthanide behavior in liquid sodium. Using ab initio molecular dynamics, we found that the solubility of cerium in liquid sodium at 1000 K was less than 0.78 at. %, and the diffusion coefficient of cerium in liquid sodium was calculated to be 5.57 × 10{sup −9} m{sup 2}/s. Furthermore, it was found that cerium in small amounts may significantly alter the heat capacity of the liquid sodium system. Our results are consistent with the experimental results for similar materials under similar conditions.

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

Performance characteristics of silver cerium vanadate batteries

OpenAIRE

Arof , Abdul; Kamaluddin , Burhanuddin; Radhakrishna , S.

1993-01-01

Stoichiometric ratios of AR grade AgI, Ag2O, V2O5 and CeO2 were melted in a furnace and the melt was rapidly quenched to liquid nitrogen temperature to form a glass. The glassy nature of the sample has been confirmed by powder X-ray diffraction technique. The microstructure and microanalysis studies of the silver cerium vanadate (SCV) have been carried out by scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX). The SEM micrograph of the as-quenched melt showed c...

Growth of monodisperse nanocrystals of cerium oxide during synthesis and annealing

Energy Technology Data Exchange (ETDEWEB)

Ghosh, Swapankumar, E-mail: swapankumar.ghosh2@mail.dcu.ie; Divya, Damodaran [National Institute for Interdisciplinary Science and Technology (NIIST), Council of Scientific and Industrial Research (CSIR) (India); Remani, Kottayilpadi C. [Sree Neelakanda Government Sanskrit College, Department of Chemistry (India); Sreeremya, Thadathil S. [National Institute for Interdisciplinary Science and Technology (NIIST), Council of Scientific and Industrial Research (CSIR) (India)

2010-06-15

Monodisperse cerium oxide nanocrystals have been successfully synthesised using simple ammonia precipitation technique from cerium(III) nitrate solution at different temperatures in the range 35-80 {sup o}C. The activation energy for growth of CeO{sub 2} nanocrystals during the precipitation is calculated as 11.54 kJ/mol using Arrhenius plot. Average crystal diameter was obtained from XRD analysis, HR-TEM and light scattering (PCS). The analysis of size data from HR-TEM images and PCS clearly indicated the formation of highly crystalline CeO{sub 2} particles in narrow size range. CeO{sub 2} nanocrystals precipitated at 35 {sup o}C were further annealed at temperatures in the range 300-700 {sup o}C. The activation energy for crystal growth during annealing is also calculated and is close to the reported values. An effort is made to predict the mechanism of crystal growth during the precipitation and annealing.

In-pile test results of U-silicide or U-nitride coated U-7Mo particle dispersion fuel in Al

Science.gov (United States)

Kim, Yeon Soo; Park, J. M.; Lee, K. H.; Yoo, B. O.; Ryu, H. J.; Ye, B.

2014-11-01

U-silicide or U-nitride coated U-Mo particle dispersion fuel in Al (U-Mo/Al) was in-pile tested to examine the effectiveness of the coating as a diffusion barrier between the U-7Mo fuel kernels and Al matrix. This paper reports the PIE data and analyses focusing on the effectiveness of the coating in terms of interaction layer (IL) growth and general fuel performance. The U-silicide coating showed considerable success, but it also provided evidence for additional improvement for coating process. The U-nitride coated specimen showed largely inefficient results in reducing IL growth. From the test, important observations were also made that can be utilized to improve U-Mo/Al fuel performance. The heating process for coating turned out to be beneficial to suppress fuel swelling. The use of larger fuel particles confirmed favorable effects on fuel performance.

In-pile test results of U-silicide or U-nitride coated U-7Mo particle dispersion fuel in Al

Energy Technology Data Exchange (ETDEWEB)

Kim, Yeon Soo, E-mail: yskim@anl.gov [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Park, J.M.; Lee, K.H.; Yoo, B.O. [Korea Atomic Energy Research Institute, 989-111 Daedeokdaero, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Ryu, H.J. [Dept. of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Ye, B. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)

2014-11-15

U-silicide or U-nitride coated U-Mo particle dispersion fuel in Al (U-Mo/Al) was in-pile tested to examine the effectiveness of the coating as a diffusion barrier between the U-7Mo fuel kernels and Al matrix. This paper reports the PIE data and analyses focusing on the effectiveness of the coating in terms of interaction layer (IL) growth and general fuel performance. The U-silicide coating showed considerable success, but it also provided evidence for additional improvement for coating process. The U-nitride coated specimen showed largely inefficient results in reducing IL growth. From the test, important observations were also made that can be utilized to improve U-Mo/Al fuel performance. The heating process for coating turned out to be beneficial to suppress fuel swelling. The use of larger fuel particles confirmed favorable effects on fuel performance.

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.

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.

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.

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.

An Auger and XPS survey of cerium active corrosion protection for AA2024-T3 aluminum alloy

Energy Technology Data Exchange (ETDEWEB)

Uhart, A. [IPREM-ECP-UMR CNRS 5254, Université de Pau et des Pays de l' Adour, Technopole Hélioparc, 2 Avenue Président Pierre Angot, 64053 Pau Cedex 09 (France); Ledeuil, J.B. [IPREM-ECP-UMR CNRS 5254, Université de Pau et des Pays de l' Adour, Technopole Hélioparc, 2 Avenue Président Pierre Angot, 64053 Pau Cedex 09 (France); Université de Toulouse, UPS-INP-CNRS, Institut Carnot CIRIMAT, 118 Route de Narbonne, 31062 Toulouse Cedex 09 (France); Gonbeau, D. [IPREM-ECP-UMR CNRS 5254, Université de Pau et des Pays de l' Adour, Technopole Hélioparc, 2 Avenue Président Pierre Angot, 64053 Pau Cedex 09 (France); Dupin, J.C., E-mail: dupin@univ-pau.fr [IPREM-ECP-UMR CNRS 5254, Université de Pau et des Pays de l' Adour, Technopole Hélioparc, 2 Avenue Président Pierre Angot, 64053 Pau Cedex 09 (France); Bonino, J.P.; Ansart, F. [Université de Toulouse, UPS-INP-CNRS, Institut Carnot CIRIMAT, 118 Route de Narbonne, 31062 Toulouse Cedex 09 (France); Esteban, J. [Messier-Bugatti-Dowty, Etablissement de Molsheim, 3, rue Antoine de St Exupéry, 67129 Molsheim (France)

2016-12-30

Graphical abstract: Coupled SAM/SEM survey of cerium inhibitor migration towards corrosion pits in a conversion coating over AA2024-T3 substrate. - Highlights: • XPS evidenced the proximity of the inhibitor with the surface AA2024 alloy. • Cerium conversion coatings with [Ce] = 0.1 M offer the best corrosion resistance. • SAM shown the migration of Ce + III entities towards the corrosion pits or crevices. • High resolution analyses (Auger) connecting the nano-scale order with the chemical distribution.

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)

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

Cerium chloride stimulated controlled conversion of B-to-Z DNA in self-assembled nanostructures

International Nuclear Information System (INIS)

Bhanjadeo, Madhabi M.; Nayak, Ashok K.; Subudhi, Umakanta

2017-01-01

DNA adopts different conformation not only because of novel base pairs but also while interacting with inorganic or organic compounds. Self-assembled branched DNA (bDNA) structures or DNA origami that change conformation in response to environmental cues hold great promises in sensing and actuation at the nanoscale. Recently, the B-Z transition in DNA is being explored to design various nanomechanical devices. In this communication we have demonstrated that Cerium chloride binds to the phosphate backbone of self-assembled bDNA structure and induce B-to-Z transition at physiological concentration. The mechanism of controlled conversion from right-handed to left-handed has been assayed by various dye binding studies using CD and fluorescence spectroscopy. Three different bDNA structures have been identified to display B-Z transition. This approach provides a rapid and reversible means to change bDNA conformation, which can be used for dynamic and progressive control at the nanoscale. - Highlights: • Cerium-induced B-to-Z DNA transition in self-assembled nanostructures. • Lower melting temperature of Z-DNA than B-DNA confirmed by CD spectroscopy. • Binding mechanism of cerium chloride is explained using fluorescence spectroscopy. • Right-handed to left-handed DNA conformation is also noticed in modified bDNA structure.

Assessment of the abatement of acelsulfame K using cerium doped ZnO as photocatalyst

International Nuclear Information System (INIS)

Calza, P.; Gionco, C.; Giletta, M.; Kalaboka, M.; Sakkas, V.A.; Albanis, T.; Paganini, M.C.

2017-01-01

Highlights: • Hydrothermal synthesis and characterization of Ce doped ZnO. • The abatement of ACE K is assessed in ultrapure water and in river water matrix. • Demonstrated higher degradation activity than P25 under visible light. • The degradation activity is less affected in river water than for P25. - Abstract: In the present study, we investigated the possibility to abate Acesulfame K, a persistent emerging contaminant, in aqueous media using zinc oxide based materials. For this purpose, bare and Ce-doped zinc oxide was prepared via an easy and cheap hydrothermal process using different cerium salts as precursors. Their photocatalytic performance was evaluated in different media, namely ultrapure and river water under both UV–vis and visible light. Commercial TiO_2 P25 was also employed and used as a reference photocatalyst for comparison purposes. The obtained results pointed out that cerium doped zinc oxide composites exhibit higher performance than TiO_2 P25, especially under visible light and in the presence of organic matter, when the activity of the latter is greatly depressed. In particular, ZnO doped with cerium (1%) was the most effective material, and could be a promising alternative to TiO_2 P25, especially in the treatment of natural waters.

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.

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

Microstructure and electrochemical behavior of cerium conversion coating modified with silane agent on magnesium substrates

Science.gov (United States)

Lei, Li; Shi, Jing; Wang, Xin; Liu, Dan; Xu, Haigang

2016-07-01

The cerium conversion coating with and without different concentrations of silane agent bis-(γ-triethoxysilylpropyl)-tetrasulfide (BTESPT) modification is obtained on magnesium alloys. Detailed properties of the coatings and the role of BTESPT as an additive are studied and followed with careful discussion. The coating morphology, wettability, chemical composition and corrosion resistance are characterized by scanning electronic microscope (SEM), water contact-angle, X-ray photoelectron spectroscopy (XPS), potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of the coatings is investigated using EIS. The results indicate that the coating morphology and composition can be controlled by changing silane concentration. The combination of cerium ions and silane molecules could promote the formation of more homogenous and higher hydrophobic coating. The coating turns to be more compact and the adhesive strength between the coating and the magnesium substrate are strongly improved with the formation of Sisbnd Osbnd Si and Sisbnd Osbnd M chemical bonds. The optimum corrosion resistance of the coating in the corrosive media is obtained by 25 ml L-1 BTESPT modification. This whole study implies that the cerium conversion coating modified with certain silane agent deserves cautiousness before its application for corrosion resistance.

Preparation and Characterization of Cerium (III Doped Captopril Nanoparticles and Study of their Photoluminescence Properties

Directory of Open Access Journals (Sweden)

Ghamami Shahriar

2016-01-01

Full Text Available In this research Ce3+ doped Captopril nanoparticles (Ce3+ doped CAP-NP were prepared by a cold welding process and have been studied. Captopril may be applied in the treatment of hypertension and some types of congestive heart failure and for preventing kidney failure due to high blood pressure and diabetes. CAP-NP was synthesized by a cold welding process. The cerium nitrate was added at a ratio of 10% and the optical properties have been studied by photoluminescence (PL. The synthesized compounds were characterized by Fourier transform infrared spectroscopy. The size of CAP-NP was calculated by X-ray diffraction (XRD. The size of CAP-NP was in the range of 50 nm. Morphology of surface of synthesized nanoparticles was studied by scanning electron microscopy (SEM. Finally the luminescence properties of undoped and doped CAP-NP were compared. PL spectra from undoped CAP-NP show a strong pack in the range of 546 nm after doped cerium ion into the captopril appeared two bands at 680 and 357 nm, which is ascribed to the well-known 5d–4f emission band of the cerium.

Electron donating and acid-base properties of cerium oxide and its mixed oxides with alumina

International Nuclear Information System (INIS)

Sugunan, S.; Jalaja, J.M.

1994-01-01

The electron donating properties of cerium oxide activated at 300, 500 and 800 degC and of its mixed oxides with alumina were examined based on the adsorption of electron acceptors exhibiting different electron affinities. The surface acidity/basicity of the oxides was determined by titrimetry; the H 0,max values are given. The limit of electron transfer from the oxide surface lies within the region of 1.77 and 2.40 eV in terms of the electron affinity of the electron acceptor. Cerium oxide promotes the electron donor nature of alumina while leaving the limit of electron transfer unchanged. 2 tabs., 4 figs., 13 refs

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.

The heat capacity and entropy of the lithium silicides Li17Si4 and Li16.42Si4 in the temperature range from (2 to 873) K

International Nuclear Information System (INIS)

Thomas, Daniel; Zeilinger, Michael; Gruner, Daniel; Hüttl, Regina; Seidel, Jürgen; Wolter, Anja U.B.; Fässler, Thomas F.; Mertens, Florian

2015-01-01

Highlights: • High quality experimental heat capacities of the new lithium rich silicides Li 17 Si 4 and Li 16.42 Si 4 are reported. • Two different calorimeters have been used to cover the broad temperature range from (2 to 873) K. • Samples were prepared and characterized (XRD) by the original authors who firstly described these new silicide phases in 2013. • Supply of polynomial heat capacity functions for four temperature intervals. • Calculation of standard entropies and entropies of formation of the lithium silicides. - Abstract: This work presents the heat capacities and standard entropies of the recently described lithium rich silicide phases Li 17 Si 4 and Li 16.42 Si 4 as a function of temperature in the range from (2 to 873) K. The measurements were carried out using two different calorimeters. The heat capacities were determined in the range from T = (2 to 300) K by a relaxation technique using a Physical Properties Measurement System (PPMS) from Quantum Design, and in the range from T = (283 to 873) K by means of a Sensys DSC from Setaram applying the C p -by-step method. The experimental data are given with an accuracy of (1 to 2)% above T = 20 K and the error increases up to 7% below T = 20 K. The results of the measurements at low temperatures permit the calculation of additional thermodynamic parameters such as the standard entropy as well as the temperature coefficients of electronic and lattice contributions to the heat capacity. Additionally, differential scanning calorimetric (DSC) measurements were carried out to verify the phase transition temperatures of the studied lithium silicide phases. The results represent a significant contribution to the data basis for thermodynamic calculations (e.g. CALPHAD) and to the understanding of the phase equilibria in the (Li + Si) system, especially in the lithium rich region

Nutritional quality assessment of tomato fruits after exposure to uncoated and citric acid coated cerium oxide nanoparticles, bulk cerium oxide, cerium acetate and citric acid.

Science.gov (United States)

Barrios, Ana Cecilia; Medina-Velo, Illya A; Zuverza-Mena, Nubia; Dominguez, Osvaldo E; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge L

2017-01-01

Little is known about the effects of surface modification on the interaction of nanoparticles (NPs) with plants. Tomato (Solanum lycopersicum L.) plants were cultivated in potting soil amended with bare and citric acid coated nanoceria (nCeO 2, nCeO 2 +CA), cerium acetate (CeAc), bulk cerium oxide (bCeO 2 ) and citric acid (CA) at 0-500 mg kg -1 . Fruits were collected year-round until the harvesting time (210 days). Results showed that nCeO 2 +CA at 62.5, 250 and 500 mg kg -1 reduced dry weight by 54, 57, and 64% and total sugar by 84, 78, and 81%. At 62.5, 125, and 500 mg kg -1 nCeO 2 +CA decreased reducing sugar by 63, 75, and 52%, respectively and at 125 mg kg -1 reduced starch by 78%, compared to control. The bCeO 2 at 250 and 500 mg kg -1 , increased reducing sugar by 67 and 58%. In addition, when compared to controls, nCeO 2 at 500 mg kg -1 reduced B (28%), Fe (78%), Mn (33%), and Ca (59%). At 125 mg kg -1 decreased Al by 24%; while nCeO 2 +CA at 125 and 500 mg kg -1 increased B by 33%. On the other hand, bCeO 2 at 62.5 mg kg -1 increased Ca (267%), but at 250 mg kg -1 reduced Cu (52%), Mn (33%), and Mg (58%). Fruit macromolecules were mainly affected by nCeO 2 +CA, while nutritional elements by nCeO 2 ; however, all Ce treatments altered, in some way, the nutritional quality of tomato fruit. To our knowledge, this is the first study comparing effects of uncoated and coated nanoceria on tomato fruit quality. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Cyclic thermochemical process for producing hydrogen using cerium-titanium compounds

Science.gov (United States)

Bamberger, C.E.

A thermochemical cyclic process for producing hydrogen employs the reaction between ceric oxide and titanium dioxide to form cerium titanate and oxygen. The titanate is treated with an alkali metal hydroxide to give hydrogen, ceric oxide, an alkali metal titanate and water. Alkali metal titanate and water are boiled to give titanium dioxide which, along with ceric oxide, is recycled.

Cerium compounds in the fashion of the light actinides

International Nuclear Information System (INIS)

Koelling, D.D.

1984-01-01

Researchers familiar with the light actinides easily recognize in cerium compounds a microcosm of the rich variety of properties seen in the light actinides. The parallelism seen between comparable cerium and actinide compounds strongly suggests that the same physical models are applicable. The most significant is the relative size of the f-orbital. Localization is generally tighter in Ce compounds than uranium compounds, making Ce roughly analogous to Np through Am. A way to see the actinide parallelism is to compare Hill plots. Compounds in the different regions of the plots (representing different physics) are isostructural compounds with the same companion (B) elements. The most common materials exhibiting a direct f-f interaction are the cubic Laves compounds. Accordingly, we have determined the band structures of CeRu 2 , CeRh 2 , CeIr 2 , CeOs 2 , and CeNi 2 . Compounds illustrative of the interaction of f-orbitals with ligand orbitals are the Cu 3 Au structured materials. Materials calculated in this class are CeRh 3 , CePd 3 , and CeSn 3 - the materials of much interest as mixed valent. Although the focus is on the Ce compounds, calculations performed on uranium isomorphs are used to highlight the interesting physics

Analysis Influence of Mixing Gd2O3 in the Silicide Fuel Element to Core Excess Reactivity of RSG-GAS

International Nuclear Information System (INIS)

Susilo, Jati

2004-01-01

Gadolinium (Gd 2 O 3 ) is a burnable poison material mixed in the pin fuel element of the LWR core used to decrease core excess reactivity. In this research, analysis influence of mixing Gd 2 O 3 in the silicide fuel element to excess reactivity of the RSG-GAS core had been done. Equivalent cell of the equilibrium core developed by L.E.Strawbridge from Westing House Co. burn-up calculation has been done using SRAC-PIJ computer code achieve infinite multiplication factor (k x ). Value of Gd 2 O 3 concentration in the fuel element (pcm) showed by mass ratio of Gd 2 O 3 (gram) to that U 3 Si 2 (gram) times 10 5 , that is 0 pcm ∼ 100 pcm. From the calculation results analysis showed that Gd 2 O 3 concentration added should be considered. because a large number of Gd 2 O 3 will result in not achieving criticality at the Beginning Of Cycle. The maximum concentration of Gd 2 O 3 for RSG-GAS equilibrium fueled silicide 2.96 grU/cc is 80 pcm or 52.02 mgram/fuel plate. Maximum reduction of core excess reactivity due to mixing of Gd 2 O 3 in the RSG-GAS silicide fuels was around 1.502 %Δk/k, and hence not achieving the standard nominal excess reactivity for RSG-GAS core using high density of U 3 Si 2 -Al fuel. (author)

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)

Far infrared properties of PbTe doped with cerium

International Nuclear Information System (INIS)

Nikolic, P.M.; Koenig, W.; Vujatovic, S.S.; Blagojevic, V.; Lukovic, D.; Savic, S.; Radulovic, K.; Urosevic, D.; Nikolic, M.V.

2007-01-01

Single crystal samples of lead telluride doped with cerium were made using the Bridgman method. Far infrared reflectivity spectra in the temperature range from 10 to 300 K are presented. The experimental data were numerically analyzed using a fitting procedure based on the plasmon-phonon interaction model and optical parameters were determined. Two additional local modes were observed at about 138 and 337 cm -1 . The origin of these local vibrational impurity modes was discussed

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.

Selective anodic dissolution of cerium from aluminium alloys under potentiostatic conditions

International Nuclear Information System (INIS)

Gol'dshtejn, S.L.; Raspopin, S.P.; Seleznev, V.D.; Tunin, A.V.; Fedorov, V.A.

1975-01-01

A study was made of selective anodic dissolution of aluminum alloys containing cerium in concentrations from 0.5 to 10% by mass. The electropurification was carried out with the aid of a potentiostatic setup at 700 deg C in atmosphere of purified argon. Liquid aluminum served as the cathode, with chlorine half-cell as reference electrode and the melt of equimolar KCl-NaCl mixture as the electrolyte. The ''current-time'' plots are presented for selective ionization of cerium from aluminum alloys at preset potential values on the installation. For PHIsub(preset)=-2.04 v the current of potentiostatic electrolysis fades out to that of the supporting electrolyte, and the process itself proceeds at a rate that provides maximal extraction of cerium from the alloy (csub9finite)approximately equal to 0.002% by mass) at minimal ionization of the metalsolvent (Δ Msub(Al)approximately equal to 0.2). Alloys containing not less then 1% by mass of Ce exhibit a characteristic abrupt change of the attenuation coefficient apparently owing to nonlinear dependence of unbalance (ΔE) of signals at the input of the potentiostat. The ''ΔE-c'' function for Al alloy containing 0.5% by mass of Ce can be approximated by linear function. In this case the current of potentiostatic electrolysis approaches the value of the limiting diffusion current. To obtain the relationship between the magnitude of the limiting current of Ce ionization and the initial composition of the dissolving alloy, measurements were made under potentiodynamic conditions at a scanning rate of approximately equal to 500 mv/min. The results indicate that isub(intermediate) is directly proportional to csub(initial). It was shown that under the conditions employed, practically complete (csub(finite)<=0.004% by mass) extraction of the electronegative component is possible without noticeable ionization of the metal-solvent

Influence of annealing on texture properties of cerium oxide thin films

International Nuclear Information System (INIS)

Arunkumar, P.; Suresh Babu, K.; Ramaseshan, R.; Dash, S.

2013-01-01

Future power demand needs an energy source with higher efficiency, better power density, clean energy and fuel flexibility. Solid oxide fuel cell (SOFC) is one of the potential sources for future needs. Though the polymer and direct methanol based electrolyte are much suitable, for versatile applications (portable devices) they are having major challenges such as design, platinum based catalyst, lower power density and fuel flexibility (free from hydrocarbons). However, in SOFC the high operating temperature is the only major issue. Operating temperature of SOFC could be reduced by proper selection of electrolyte material which should have minimum ionic conductivity of 0.1 Scm -1 at reduced activation energy. This can be achieved by thin film based doped cerium oxide electrolyte for SOFC, leads to Intermediate Temperature Solid Oxide Fuel Cell (ITSOFC). In the present work, we focus on the synthesis of cerium oxide and 20 mol % samarium doped cerium oxide (SDC) nanoparticles by co-precipitation method and to synthesis thin films of the same. Pellets of those powders were heat treated at different temperatures and used as targets for e-beam evaporation to fabricate thin film based electrolyte. Stoichiometry of both powders and thin films were confirmed by XRF and EPMA. GIXRD profiles of ceria and SDC thin films are shown below and a preferred orientation effect is observed in SDC films. In SDC films the X-ray peaks have a shift towards lower angles, due to the difference in ionic radii of Ce 4+ and Sm 3+ . The band gap of CeO 2 (2.88 eV) from optical absorption technique indicates the presence of Ce 3+ with Ce 4+ , indirectly shows the concentration of oxygen vacancies which is required for the thin film electrolyte

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.

Energy transfer and thermal studies of Pr 3+ doped cerium oxalate ...

Indian Academy of Sciences (India)

The analysis of energy level diagrams of cerium and praseodymium ions indicates that the energy gap between the sensitizer and the activator ions varies in a small range suggesting a possible energy transfer from the Ce3+ to Pr3+. The emission and absorption spectra of these crystals were recorded. The overlapping of ...

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

Nanoceria and bulk cerium oxide effects on the germination of asplenium adiantum-nigrum spores

Directory of Open Access Journals (Sweden)

Aranzazu Gomez-Garay

2016-12-01

Full Text Available Aim of study: The effect of cerium oxide engineered nanoparticles on the spore germination of the fern. Asplenium adiantum-nigrum. Area of study: France, Britanny Region, Finistére Department, Plougonvelin, in rocks near the sea. Material and methods: Asplenium spores were cultured in vitro on agar medium with Nano-CeO2 (less than 25 nm particle size and bulk-CeO2. The addition of each nano- and bulk particles ranged from 0 to 3000 mg L-1. Observations on rhizoidal and prothallial cells during first stages of gametophyte development were made. The No-Observed-Adverse-Effect concentration (NOAEC and Lowest-Observed-Adverse-Effect-Concentration (LOEC values for spore germination rate data were analyzed.  Main results: Germination was speeded up by 100 to 2000 mg L-1 nanoceria, while bulk cerium oxide had the same effect for 500 to 200 mg L-1 concentrations. Present results showed cellular damage in the protonema while rhizoid cells seemed not to be affected, as growth and membrane integrity remained. Research highlights: Both nanosized and bulk cerium oxide are toxic for the fern Asplenium adiantum-nigrum, although diverse toxicity patterns were shown for both materials. Diverse toxic effects have been observed: chloroplast membrane damage and lysis, cell wall and membrane disruption which leads to cell lysis; and alterations in morphology and development. Keywords: Nanoparticles; rhizoid; prothallus; chloroplast; fern.

Nanoceria and bulk cerium oxide effects on the germination of asplenium adiantum-nigrum spores

Energy Technology Data Exchange (ETDEWEB)

Gomez-Garay, A.; Pintos, B.; Manzanera, J.A.; Prada, C.; Martin, L.; Gabriel y Galan, J.M.

2016-07-01

Aim of the study: The effect of cerium oxide engineered nanoparticles on the spore germination of the fern. Asplenium adiantum-nigrum. Area of study: France, Britanny Region, Finistére Department, Plougonvelin, in rocks near the sea. Material and methods: Asplenium spores were cultured in vitro on agar medium with Nano-CeO2 (less than 25 nm particle size) and bulk-CeO2. The addition of each nano- and bulk particles ranged from 0 to 3000 mg L-1. Observations on rhizoidal and prothallial cells during first stages of gametophyte development were made. The No-Observed-Adverse-Effect concentration (NOAEC) and Lowest-Observed-Adverse-Effect-Concentration (LOEC) values for spore germination rate data were analyzed. Main results: Germination was speeded up by 100 to 2000 mg L-1 nanoceria, while bulk cerium oxide had the same effect for 500 to 200 mg L-1 concentrations. Present results showed cellular damage in the protonema while rhizoid cells seemed not to be affected, as growth and membrane integrity remained. Research highlights: Both nanosized and bulk cerium oxide are toxic for the fern Asplenium adiantum-nigrum, although diverse toxicity patterns were shown for both materials. Diverse toxic effects have been observed: chloroplast membrane damage and lysis, cell wall and membrane disruption which leads to cell lysis; and alterations in morphology and development. (Author)

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.)

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.

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.

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.

Temperature and thickness dependence of the grain boundary scattering in the Ni–Si silicide films formed on silicon substrate at 500 °C by RTA

International Nuclear Information System (INIS)

Utlu, G.; Artunç, N.; Selvi, S.

2012-01-01

Highlights: ► It is a systematic study of various thicknesses (18–290 nm) of Ni–Si silicide films. ► The temperature-dependent resistivity measurements of the films are studied. ► Resistivity variation of the films with temperature exhibits an unusual behavior. ► Parallel-resistor formula is reduced to Matthiessen's rule in this study. ► Reflection coefficients have been found in a wide temperature and thickness range. - Abstract: The temperature-dependent resistivity measurements of Ni–Si silicide films with 18–290 nm thicknesses are studied as a function of temperature and film thickness over the temperature range of 100–900 K. The most striking behavior is that the variation of the resistivity of the films with temperature exhibits an unusual behavior. The total resistivity of the Ni–Si silicide films in this work increases linearly with temperature up to a T m temperature, thereafter decreases rapidly and finally reaches zero. Our analyses have shown that in the temperature range of 100 to T m (K), parallel-resistor formula reduces to Matthiessen's rule and θ D Debye temperature becomes independent of the temperature for the given thickness range, whereas at high temperatures (above T m ) it increases slightly with thickness. θ D Debye temperature have been found to be about 400–430 K for the films. We have also shown that for temperature range of 100 to T m (K), linear variation of the resistivity of the silicide films with temperature has been caused from both grain-boundary scattering and electron–phonon scattering. That is why, resistivity data could have been analyzed in terms of the Mayadas–Schatzkes (M–S) model successfully. Theoretical and experimental values of reflection coefficients have been calculated by analyzing resistivity data using M–S model. According to our analysis, R increases with decreasing film thickness for a given temperature, while it is almost constant for the thickness range of 200–67 nm and 47�

Density-functional theory for f-electron systems. The α-γ phase transition in cerium

International Nuclear Information System (INIS)

Casadei, Marco

2013-01-01

Rare earths are technologically important and scientifically highly interesting elements. The description of the volume collapse exhibited by some rare earth metals poses a great challenge to density-functional theory (DFT) since local/semi-local functionals (LDA/GGA) only partially capture the associated phase transitions. In this work this problem is approached by treating all electrons at the same quantum mechanical level, using both hybrid functionals (e.g. PBE0 and HSE06) and exact-exchange plus correlation in the random-phase approximation (EX+cRPA). The performance of recently developed beyond RPA schemes is also assessed. The isostructural α-γ phase transition in cerium is the most studied. The exact exchange contribution in PBE0 and HSE06 is crucial to produce two distinct solutions that can be associated with the α and γ phases. The two solutions emerge in bulk as well as in cluster calculations. Most notable is their presence in the cerium dimer. However, quantitative agreement with the extrapolated phase diagram requires EX+cRPA. So far the EX+cRPA correction can only be applied to cerium clusters and not to the bulk. A cluster of 19 atoms cut from the fcc crystal structure (the same that characterizes the α and γ phases) was therefore determined as representative. (EX+cRPA) rate at PBE0 for Ce 19 provides good agreement with the extrapolated transition pressure to zero temperature. We predict that a pressure induced phase transition should exist at or close to zero. A finite temperature phase diagram can be drawn in reasonable agreement with experiment by adding entropic effects. The cerium neighbors are also studied: lanthanum, which has no f electrons, praseodymium, with three f electrons and a volume collapse, and neodymium, with four f electrons and no volume collapse. Multiple solutions are also present for these f electron elements, confirming the importance of exact-exchange for f electron systems.

Cerium sorption in grounds modified by anti-deflation treatment

International Nuclear Information System (INIS)

Firsova, L.P.; Bogatyrev, I.O.

2001-01-01

Influence of soils and grounds treatment by anti-deflation compositions on the size of the soil particles was studied. Under static conditions sorption of 144 Ce by turf-podsolic soils prior to an after their modification by the anti-deflation reagents, i.e. bitumens and insoluble in water polyelectrolytic complexes, was considered. Degrees of 144 Ce sorption in the soil-solution systems, depending on solutions pH, presence of alkali metal carbonates and cerium concentration, were determined [ru

Far infrared properties of PbTe doped with cerium

Energy Technology Data Exchange (ETDEWEB)

Nikolic, P.M. [Institute of Technical Sciences SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia)]. E-mail: nikolic@sanu.ac.yu; Koenig, W. [Max Planck Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 7000 Stuttgart 80 (Germany); Vujatovic, S.S. [Institute of Technical Sciences SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia); Blagojevic, V. [Faculty of Electronic Engineering, University of Belgrade, Bulevar Kralja Aleksandra 73, 11000 Belgrade (Serbia); Lukovic, D. [Institute of Technical Sciences SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia); Savic, S. [Institute of Technical Sciences SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia); Radulovic, K. [Institute of Technical Sciences SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia); Urosevic, D. [Mathematical Institute SASA, Knez Mihailova 35/I, 11000 Belgrade (Serbia); Nikolic, M.V. [Center for Multidisciplinary Studies of the University of Belgrade, Kneza Viseslava 1, Belgrade (Serbia)

2007-05-16

Single crystal samples of lead telluride doped with cerium were made using the Bridgman method. Far infrared reflectivity spectra in the temperature range from 10 to 300 K are presented. The experimental data were numerically analyzed using a fitting procedure based on the plasmon-phonon interaction model and optical parameters were determined. Two additional local modes were observed at about 138 and 337 cm{sup -1}. The origin of these local vibrational impurity modes was discussed.

Cerium oxide nanoparticles stimulate proliferation of primary mouse embryonic fibroblasts in vitro

Energy Technology Data Exchange (ETDEWEB)

Popov, Anton L., E-mail: antonpopovleonid@gmail.com [Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow region (Russian Federation); Popova, Nelly R. [Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow region (Russian Federation); Selezneva, Irina I. [Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow region (Russian Federation); Pushchino State Institute of Natural sciences, Pushchino, Moscow region (Russian Federation); Akkizov, Azamat Y. [Kabardino-Balkarian State University, Nalchik (Russian Federation); Ivanov, Vladimir K. [Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow (Russian Federation); National Research Tomsk State University, Tomsk (Russian Federation)

2016-11-01

The increasing application of cell therapy technologies in the treatment of various diseases requires the development of new effective methods for culturing primary cells. The major limitation for the efficient use of autologous cell material is the low rate of cell proliferation. Successful cell therapy requires sufficient amounts of cell material over a short period of time with the preservation of their differentiation and proliferative potential. In this regard, the development of novel, highly efficient stimulators of proliferative activity in stem cells is a truly urgent task. In this paper we have demonstrated that citrate-stabilized cerium oxide nanoparticles (nanoceria) enhance the proliferative activity of primary mouse embryonic fibroblasts in vitro. Cerium oxide nanoparticles stimulate cell proliferation in a wide range of concentrations (10{sup −3} M–10{sup −9} M) through reduction of intracellular levels of reactive oxygen species (ROS) during the lag phase of cell growth and by modulating the expression level of the major antioxidant enzymes. We found the optimal concentration of nanoceria, which provides the greatest acceleration of cell proliferation in vitro, while maintaining the levels of intracellular ROS and mRNA of antioxidant enzymes in the physiological range. Our results confirm that nanocrystalline ceria can be considered as a basis for effective and inexpensive supplements in cell culturing. - Highlights: • Citrate-stabilized cerium oxide nanoparticles are shown to stimulate proliferation of primary embryonic cells in vitro. • Some of mechanisms involved in stimulating of the proliferation by CeO{sub 2} have been uncovered. • The most effective (optimal) concentration of CeO{sub 2} nanoparticles for stimulation of proliferation was determined.

Further results on cerium fluoride crystals

International Nuclear Information System (INIS)

Anderson, S.; Auffray, E.; Aziz, T.; Baccaro, S.; Banerjee, S.; Bareyre, P.; Barone, L.E.; Borgia, B.; Boutet, D.; Burq, J.P.; Chemarin, M.; Chipaux, R.; Dafinei, I.; D'Atanasio, P.; De Notaristefani, F.; Dezillie, B.; Dujardin, C.; Dutta, S.; Faure, J.L.; Fay, J.; Ferrere, D.; Francescangeli, O.; Fuchs, B.A.; Ganguli, S.N.; Gillespie, G.; Goyot, M.; Gupta, S.K.; Gurtu, A.; Heck, J.; Herve, A.; Hillemanns, H.; Holdener, F.; Ille, B.; Joensson, L.; Kierstead, J.; Krenz, W.; Kway, W.; Le Goff, J.M.; Lebeau, M.; Lebrun, P.; Lecoq, P.; Lemoigne, Y.; Loomis, G.; Lubelsmeyer, K.; Madjar, N.; Majni, G.; El Mamouni, H.; Mangla, S.; Mares, J.A.; Martin, J.P.; Mattioli, M.; Mauger, G.J.; Mazumdar, K.; Mengucci, P.; Merlo, J.P.; Moine, B.; Nikl, N.; Pansart, J.P.; Pedrini, C.; Poinsignon, J.; Polak, K.; Raghavan, R.; Rebourgeard, P.; Rinaldi, D.; Rosa, J.; Rosowsky, A.; Sahuc, P.; Samsonov, V.; Sarkar, S.; Schegelski, V.; Schmitz, D.; Schneegans, M.; Seliverstov, D.; Stoll, S.; Sudhakar, K.; Svensson, A.; Tonwar, S.C.; Topa, V.; Vialle, J.P.; Vivargent, M.; Wallraff, W.; Weber, M.J.; Winter, N.; Woody, C.; Wuest, C.R.; Yanovski, V.

1993-01-01

A systematic investigation of the properties of cerium fluoride monocrystals has been performed by the 'Crystal Clear' collaboration in view of a possible use of such crystals for the construction of high precision electromagnetic calorimeters for the future generation of high luminosity accelerators. A large sample of different crystals grown by several producers has been studied. The spectroscopic characteristics, the transmission, luminescence and excitation spectra and the decay time curves are analysed. The light yield of the different crystals is measured with photomultipliers and Si photodiodes and compared to reference standards like BGO and NaI(Tl). The radiation damage behaviour is then presented for γ and neutron irradiations, at different doses and dose rates, including thermal and optical bleaching. (orig.)

Vertically grown multiwalled carbon nanotube anode and nickel silicide integrated high performance microsized (1.25 μl) microbial fuel cell

KAUST Repository

Mink, Justine E.

2012-02-08

Microbial fuel cells (MFCs) are an environmentally friendly method for water purification and self-sustained electricity generation using microorganisms. Microsized MFCs can also be a useful power source for lab-on-a-chip and similar integrated devices. We fabricated a 1.25 μL microsized MFC containing an anode of vertically aligned, forest type multiwalled carbon nanotubes (MWCNTs) with a nickel silicide (NiSi) contact area that produced 197 mA/m 2 of current density and 392 mW/m 3 of power density. The MWCNTs increased the anode surface-to-volume ratio, which improved the ability of the microorganisms to couple and transfer electrons to the anode. The use of nickel silicide also helped to boost the output current by providing a low resistance contact area to more efficiently shuttle electrons from the anode out of the device. © 2012 American Chemical Society.

Cerium and yttrium oxide nanoparticles are neuroprotective

International Nuclear Information System (INIS)

Schubert, David; Dargusch, Richard; Raitano, Joan; Chan, S.-W.

2006-01-01

The responses of cells exposed to nanoparticles have been studied with regard to toxicity, but very little attention has been paid to the possibility that some types of particles can protect cells from various forms of lethal stress. It is shown here that nanoparticles composed of cerium oxide or yttrium oxide protect nerve cells from oxidative stress and that the neuroprotection is independent of particle size. The ceria and yttria nanoparticles act as direct antioxidants to limit the amount of reactive oxygen species required to kill the cells. It follows that this group of nanoparticles could be used to modulate oxidative stress in biological systems

Cerium oxide for the destruction of chemical warfare agents: A comparison of synthetic routes

Czech Academy of Sciences Publication Activity Database

Janos, P.; Henych, Jiří; Pelant, O.; Pilařová, V.; Vrtoch, L.; Kormunda, M.; Mazanec, K.; Štengl, Václav

2016-01-01

Roč. 304, MAR (2016), s. 259-268 ISSN 0304-3894 Institutional support: RVO:61388980 Keywords : Cerium oxide * Chemical warfare agents * Organophosphate compounds * Decontamination Subject RIV: CA - Inorganic Chemistry Impact factor: 6.065, year: 2016

Effect of Thickness on the Morphology and Corrosion Behavior of Cerium-Based Conversion Coatings on AZ31B Magnesium Alloy

Science.gov (United States)

Castano, Carlos E.; Maddela, Surender; O'Keefe, Matthew J.; Wang, Yar-Ming

Cerium-based conversion coatings (CeCCs) were deposited onto AZ31B magnesium alloy substrates using a spontaneous reaction of CeCl3, H2O2 and gelatin in a water-based solution. The coating thickness was adjusted by controlling the immersion time in the deposition solution. Prior to deposition, the AZ31B substrates were treated using an acid pickling in nitric acid and then an alkaline cleaning in sodium metasilicate pentahydrate. After deposition, the coated samples were immersed in a phosphate bath that converted cerium oxide/hydroxide into cerium phosphate. Electrochemical impedance spectroscopy, potentiodynamic polarization and neutral salt spray testing studies indicated that 100 nm thick CeCC had better corrosion performance than 400 nm coatings. Characterization of the CeCCs by transmission electron microscopy (TEM) revealed a three layer structure with different compositions.

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).

Cerium compounds in the fashion of the light actinides

International Nuclear Information System (INIS)

Koelling, D.D.

1985-01-01

Researchers familiar with the light actinides easily recognize in cerium compounds a microcosm of the rich variety of properties seen in the light actinides. The parallelism seen between comparable cerium and actinide compounds strongly suggests that the same physical models are applicable. The most significant is the relative size of the f-orbital. Localization is generally tighter in Ce compounds than uranium compounds, making Ce roughly analogous to Np through Am. A way to see the actinide parallelism is to compare Hill plots. Compounds in the different regions of the plots (representing different physics) are isostructural compounds with the same companion (B) elements. The most common materials expected to exhibit direct f-f interaction are the cubic Laves compounds. Accordingly, we have determined the band structures of CeRu 2 , CeRh 2 , CeIr 2 , and CeNi 2 . Surprisingly, it was found that an f-d interaction overshadows any direct f-f interaction in these systems. Compounds illustrative of the interaction of f-orbitals with ''ligand'' orbitals are the Cu 3 Au structured materials. Materials calculated in this class are CeRh 3 , CePd 3 , and CeSn 3 - the materials of much interest as ''mixed valent''. Although the focus is on the Ce compounds, calculations performed on uranium isomorphs are used to highlight the interesting physics. (orig.)

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

Effect of cerium additive and secondary phase analysis on Ag0.5Bi0 ...

Indian Academy of Sciences (India)

Technical University of Madrid (UPM), Madrid 28012, Spain. MS received 27 ... XRD analysis showed the presence of pyrochlore structure and secondary phase when more .... The present work reports the effect of incorporation of cerium in ...

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

Separation of uranium(V I) from binary solution mixtures with thorium(IV), zirconium(IV) and cerium(III) by foaming

International Nuclear Information System (INIS)

Shakir, K.; Aziz, M.; Benyamin, K.

1992-01-01

Foam separation has been investigated for the removal of uranium(V I), thorium(IV), zirconium(IV) and cerium(III) from dilute aqueous solutions at pH values ranging from about I to about II. Sodium laurel sulphate (Na L S) and acetyl trimethyl ammonium bromide (CTAB), being a strong anionic and a strong cationic surfactants, were used as collectors. The results indicate that Na L S can efficiently remove thorium(IV), zirconium(IV) and cerium(III) but not uranium(V I). CTAB, on the other hand, can successfully float only uranium(V I) and zirconium(IV). These differences in flotation properties of the different cations could be used to establish methods for the separation of uranium(V I) from binary mixtures with thorium(IV), zirconium(IV) or cerium(III). The results are discussed in terms of the hydrolytic behaviour of the tested cations and properties of used collectors.2 fig., 1 tab

Sodium nitrate-cerium nitrate-water ternary system at 25 deg C

International Nuclear Information System (INIS)

Fedorenko, T.P.; Onishchenko, M.K.

1978-01-01

Solubility isotherm of sodium nitrate-cerium nitrate-water system at 25 deg C consists of three crystallization branches of initial salts and double compound of the composition 2NaNO 3 xCe(NO 3 ) 3 x2H 2 O. Sodium nitrate introduced in the solution strengthens complexing. Physico-chemical characteristics are in a good agreement with solubility curve

Effects of ethylenediaminetetraacetic acid (EDTA)and diethylenetriaminepentaacetic acid (DTPA) derivatives on penetration of ytterbium-169 and cerium-144 into the rat offspring

Energy Technology Data Exchange (ETDEWEB)

Baltrukiewicz, Z; Burakowski, T; Derecki, J [Wojskowy Inst. Higieny i Epidemiologii, Warsaw (Poland)

1976-01-01

Penetration of radioactive ytterbum-169 and cerium-144 into fetuses was determined at the end of pregnancy and penetration into the organism of suckling rats was studied during feeding with the milk of exposed mothers when EDTA or DTPA derivatives were being administered. Injection of ytterbum-169 as a complex with EDTA or DTPA or injection of Na/sub 2/Ca EDTA or Na/sub 3/Ca DTPA 1h after administration of cerium-144 to mothers reduced penetration of both radionuclides into offsprings in relation to the animals receiving no complex compounds. It was observed that the action of DTPA was stronger than that of EDTA. Passage of ytterbium with milk and across the placenta was greater than the passage of cerium.

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.

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

Unusual kinetics of poly(ethylene glycol) oxidation with cerium(IV) ions in sulfuric acid medium and implications for copolymer synthesis.

Science.gov (United States)

Szymański, Jan K; Temprano-Coleto, Fernando; Pérez-Mercader, Juan

2015-03-14

The cerium(IV)-alcohol couple in an acidic medium is an example of a redox system capable of initiating free radical polymerization. When the alcohol has a polymeric nature, the outcome of such a process is a block copolymer, a member of a class of compounds possessing many useful properties. The most common polymer with a terminal -OH group is poly(ethylene glycol) (PEG); however, the detailed mechanism of its reaction with cerium(IV) remains underexplored. In this paper, we report our findings for this reaction based on spectrophotometric measurements and kinetic modeling. We find that both the reaction order and the net rate constant for the oxidation process depend strongly on the nature of the acidic medium used. In order to account for the experimental observations, we postulate that protonation of PEG decreases its affinity for some of the cerium(IV)-sulfate complexes formed in the system.

Cerium(III-Selective Membrane Electrode Based on Dibenzo-24-crown-8 as a Neutral Carrier

Directory of Open Access Journals (Sweden)

Susheel K. Mittal

2010-01-01

Full Text Available Cerium(III-selective membrane electrodes have been prepared using dibenzo-24-crown-8 (DB24C8 as an electroactive material. A membrane having a composition: DB24C8 (4.5%, plasticizer (NPOE, 62.5% and PVC (33% gives the best performance. It works well over a wide Ce(III ion-concentration range of 1x10-5 M to 1x10-1 M with a Nernstian slope of 19.0 mV/decade and a detection limit of 3x10-5 M. It has a fast response time of 20 seconds and has an average lifetime of four months. The internal solution concentration does not have a significant effect on the response of the electrode except for a change in intercept of the calibration curves. The working pH range for Ce(III solutions (1x10-2 M and 1x10-3 M is 3.5-8.0. The proposed sensor shows a good selectivity for cerium(III with respect to alkali, alkaline earth, some transition and rare earth metal ions that are normally present along with cerium in its ores. The proposed sensor was investigated in partially non-aqueous media using acetone, methanol and DMSO mixtures with water. The electrode was further used as an indicator electrode for the potentiometric titration of Ce(III solution against oxalic acid solution.

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)

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

Cerium intermetallics CeTX. Review III

Energy Technology Data Exchange (ETDEWEB)

Poettgen, Rainer; Janka, Oliver [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Chevalier, Bernard [Bordeaux Univ., Pessac (France). Inst. de Chimie de la Matiere Condensee de Bordeaux

2016-05-01

The structure-property relationships of CeTX intermetallics with structures other than the ZrNiAl and TiNiSi type are systematically reviewed. These CeTX phases form with electron-poor and electron-rich transition metals (T) and X = Mg, Zn, Cd, Hg, Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, Sb, and Bi. The review focusses on the crystal chemistry, the chemical bonding peculiarities, and the magnetic and transport properties. Furthermore {sup 119}Sn Moessbauer spectroscopic data, high-pressure studies, hydrogenation reactions and the formation of solid solutions are reviewed. This paper is the third of a series of four reviews on equiatomic intermetallic cerium compound [Part I: R. Poettgen, B. Chevalier, Z. Naturforsch. 2015, 70b, 289; Part II: R. Poettgen, B. Chevalier, Z. Naturforsch. 2015, 70b, 695].

Mixed mode and sequential oscillations in the cerium-bromate-4-aminophenol photoreaction

Energy Technology Data Exchange (ETDEWEB)

Bell, Jeffrey G.; Wang Jichang [Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4 (Canada)

2013-09-15

Cerium was introduced to the bromate-aminophenol photochemical oscillator to implement coupled autocatalytic feedbacks. Mixed mode and sequential oscillations emerged in the studied system, making it one of the few chemical oscillators known to support consecutive bifurcations in a batch system. The complex reaction behavior showed a strong dependence on the intensity of illumination supplied to the system. Removal of illumination during an oscillatory window affected both the frequency and amplitude of the oscillation but did not fully extinguish them, indicating that the cerium-bromate-4-aminophenol oscillator was photosensitive rather than photo-controlled. A moderate light intensity allowed for a slow evolution of the system, which proved to be critical for the emergence of transient complex oscillations. Variation of individual reaction parameters was carried out, which indicated that the development of complex oscillations occur in a narrow region and a phase diagram in the 4-aminophenol and sulfuric acid plane demonstrated this. Simulations provide strong support that transient complex oscillations observed experimentally arise from the coupling of two autocatalytic cycles.

Microstructure and electrochemical behavior of cerium conversion coating modified with silane agent on magnesium substrates

Energy Technology Data Exchange (ETDEWEB)

Lei, Li; Shi, Jing, E-mail: shijing@ouc.edu.cn; Wang, Xin, E-mail: wangxin.hd@163.com; Liu, Dan; Xu, Haigang

2016-07-15

Graphical abstract: The unmodified coating shows averaged static water contact angles of a little more than 50º, which is clearly hydrophilic for water solutions. With the silane concentration increases, the water contact angles show an increase tendency. Especially, when the silane addition is increased to 25 ml L-1, the coating surface presents a hydrophobic feature, with static water contact angle of more than 110º. - Highlights: • BTESPT modification can effectively improve the uniformity, hydrophobic performance, chemical stability and corrosion inhibition capability of traditional cerium conversion coating. • Si-O-Si linkage builds a robust structure to increase of the coating density. Si−O−Mg bonds strengthen the adhesion between the coating/substrate. • The system modified with 25 ml L{sup −1} BTESPT displays the optimum corrosion protection performance. - Abstract: The cerium conversion coating with and without different concentrations of silane agent bis-(γ-triethoxysilylpropyl)-tetrasulfide (BTESPT) modification is obtained on magnesium alloys. Detailed properties of the coatings and the role of BTESPT as an additive are studied and followed with careful discussion. The coating morphology, wettability, chemical composition and corrosion resistance are characterized by scanning electronic microscope (SEM), water contact-angle, X-ray photoelectron spectroscopy (XPS), potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of the coatings is investigated using EIS. The results indicate that the coating morphology and composition can be controlled by changing silane concentration. The combination of cerium ions and silane molecules could promote the formation of more homogenous and higher hydrophobic coating. The coating turns to be more compact and the adhesive strength between the coating and the magnesium substrate are strongly improved with the formation of Si−O−Si and Si�

Microstructure and electrochemical behavior of cerium conversion coating modified with silane agent on magnesium substrates

International Nuclear Information System (INIS)

Lei, Li; Shi, Jing; Wang, Xin; Liu, Dan; Xu, Haigang

2016-01-01

Graphical abstract: The unmodified coating shows averaged static water contact angles of a little more than 50º, which is clearly hydrophilic for water solutions. With the silane concentration increases, the water contact angles show an increase tendency. Especially, when the silane addition is increased to 25 ml L-1, the coating surface presents a hydrophobic feature, with static water contact angle of more than 110º. - Highlights: • BTESPT modification can effectively improve the uniformity, hydrophobic performance, chemical stability and corrosion inhibition capability of traditional cerium conversion coating. • Si-O-Si linkage builds a robust structure to increase of the coating density. Si−O−Mg bonds strengthen the adhesion between the coating/substrate. • The system modified with 25 ml L"−"1 BTESPT displays the optimum corrosion protection performance. - Abstract: The cerium conversion coating with and without different concentrations of silane agent bis-(γ-triethoxysilylpropyl)-tetrasulfide (BTESPT) modification is obtained on magnesium alloys. Detailed properties of the coatings and the role of BTESPT as an additive are studied and followed with careful discussion. The coating morphology, wettability, chemical composition and corrosion resistance are characterized by scanning electronic microscope (SEM), water contact-angle, X-ray photoelectron spectroscopy (XPS), potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of the coatings is investigated using EIS. The results indicate that the coating morphology and composition can be controlled by changing silane concentration. The combination of cerium ions and silane molecules could promote the formation of more homogenous and higher hydrophobic coating. The coating turns to be more compact and the adhesive strength between the coating and the magnesium substrate are strongly improved with the formation of Si−O−Si and Si−O−M chemical

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)

Sorption studies of radionuclides on a modified mesoporous cerium(IV) silicate

International Nuclear Information System (INIS)

Sepehrian, H.; Tarbiat Moallem University, Tehran; Ghannadi-Maragheh, M.; Yavari, R.; Khanchi, A.R.; Waqif-Husain, S.

2008-01-01

Five different samples of a new sorbent, modified mesoporous cerium(IV) silicate have been prepared with various mole ratios of Si/Ce and Cetyltrimethylammonium bromide (CTMABr) as template. XRD, nitrogen sorption, SEM, IR, thermogravimetry and sorption of radionuclides have been studied. Separation of Hg(II)-Th(IV), Hg(II)-Zr(IV) and Rb(I)-Zr(IV) have been developed on columns of this novel sorbent. (author)

Behavior of silicon in nitric media. Application to uranium silicides fuels reprocessing; Comportement du silicium en milieu nitrique. Application au retraitement des combustibles siliciures d'uranium

Energy Technology Data Exchange (ETDEWEB)

Cheroux, L

2001-07-01

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)

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)

Atomic layer deposition of cerium oxide for potential use in diesel soot combustion

Energy Technology Data Exchange (ETDEWEB)

Ivanova, Tatiana V., E-mail: tatiana.ivanova@lut.fi, E-mail: ivanova.tatyana.v@gmail.com; Toivonen, Jenni; Maydannik, Philipp S.; Kääriäinen, Tommi; Sillanpää, Mika [ASTRaL Team, Laboratory of Green Chemistry, School of Engineering Science, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland); Homola, Tomáš; Cameron, David C. [R& D Centre for Low-Cost Plasma and Nanotechnology Surface Modification, Masaryk University, Kotlářská 267/2, 611 37 Brno (Czech Republic)

2016-05-15

The particulate soot emission from diesel motors has a severe impact on the environment and people's health. The use of catalytic convertors is one of the ways to minimize the emission and decrease the hazard level. In this paper, the activity of cerium oxide for catalytic combustion of diesel soot was studied. Thin films of cerium dioxide were synthesized by atomic layer deposition using tetrakis(2,2,6,6-tetramethyl-3,5-heptanedionato)cerium [Ce(thd){sub 4}] and ozone as precursors. The characteristics of the films were studied as a function of deposition conditions within the reaction temperature range of 180–350 °C. Thickness, crystallinity, elemental composition, and morphology of the CeO{sub 2} films deposited on Si (100) were characterized by ellipsometry, x-ray diffraction, x-ray photoelectron spectroscopy, atomic force microscopy, and field emission scanning electron microscopy, respectively. The growth rate of CeO{sub 2} was observed to be 0.30 Å/cycle at temperatures up to 250 °C with a slight increase to 0.37 Å/cycle at 300 °C. The effect of CeO{sub 2} films grown on stainless steel foil supports on soot combustion was measured with annealing tests. Based on the analysis of these, in catalytic applications, CeO{sub 2} has been shown to be effective in lowering the soot combustion temperature from 600 °C for the uncoated substrates to 370 °C for the CeO{sub 2} coated ones. It was found that the higher deposition temperatures had a positive effect on the catalyst performance.

Magnetic and Mössbauer Study of Cerium-Based Reactive Sorbent

Czech Academy of Sciences Publication Activity Database

Jirásková, Yvonna; Buršík, Jiří; Životský, O.; Luňáček, J.; Janos, P.

2017-01-01

Roč. 131, č. 4 (2017), s. 1096-1098 ISSN 0587-4246. [CSMAG 2016 - Czech and Slovak Conference on Magnetism /16./. Košice, 13.06.2016-17.06.2016] R&D Projects: GA MŠk(CZ) LQ1601 Institutional support: RVO:68081723 Keywords : Cerium-based sorbent * magnetic properties * phase composition * composite Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 0.469, year: 2016

Simultaneous aluminizing and chromizing of steels to form (Fe,Cr){sub 3}Al coatings and Ge-doped silicide coatings of Cr-Zr base alloys

Energy Technology Data Exchange (ETDEWEB)

Zheng, M.; He, Y.R.; Rapp, R.A. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering

1997-12-01

A halide-activated cementation pack involving elemental Al and Cr powders has been used to achieve surface compositions of approximately Fe{sub 3}Al plus several percent Cr for low alloy steels (T11, T2 and T22) and medium carbon steel (1045 steel). A two-step treatment at 925 C and 1150 C yields the codeposition and diffusion of aluminum and chromium to form dense and uniform ferrite coatings of about 400 {micro}m thickness, while preventing the formation of a blocking chromium carbide at the substrate surfaces. Upon cyclic oxidation in air at 700 C, the coated steel exhibits a negligible 0.085 mg/cm{sup 2} weight gain for 1900 one-hour cycles. Virtually no attack was observed on coated steels tested at ABB in simulated boiler atmospheres at 500 C for 500 hours. But coatings with a surface composition of only 8 wt% Al and 6 wt% Cr suffered some sulfidation attack in simulated boiler atmospheres at temperatures higher than 500 C for 1000 hours. Two developmental Cr-Zr based Laves phase alloys (CN129-2 and CN117(Z)) were silicide/germanide coated. The cross-sections of the Ge-doped silicide coatings closely mimicked the microstructure of the substrate alloys. Cyclic oxidation in air at 1100 C showed that the Ge-doped silicide coating greatly improved the oxidation resistance of the Cr-Zr based alloys.

Monte Carlo radiative transfer simulation of a cavity solar reactor for the reduction of cerium oxide

Energy Technology Data Exchange (ETDEWEB)

Villafan-Vidales, H.I.; Arancibia-Bulnes, C.A.; Dehesa-Carrasco, U. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Privada Xochicalco s/n, Col. Centro, A.P. 34, Temixco, Morelos 62580 (Mexico); Romero-Paredes, H. [Departamento de Ingenieria de Procesos e Hidraulica, Universidad Autonoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco No.186, Col. Vicentina, A.P. 55-534, Mexico D.F 09340 (Mexico)

2009-01-15

Radiative heat transfer in a solar thermochemical reactor for the thermal reduction of cerium oxide is simulated with the Monte Carlo method. The directional characteristics and the power distribution of the concentrated solar radiation that enters the cavity is obtained by carrying out a Monte Carlo ray tracing of a paraboloidal concentrator. It is considered that the reactor contains a gas/particle suspension directly exposed to concentrated solar radiation. The suspension is treated as a non-isothermal, non-gray, absorbing, emitting, and anisotropically scattering medium. The transport coefficients of the particles are obtained from Mie-scattering theory by using the optical properties of cerium oxide. From the simulations, the aperture radius and the particle concentration were optimized to match the characteristics of the considered concentrator. (author)

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)

Extraordinary superconductor with nearly trivalent cerium, CeCu2Si2

International Nuclear Information System (INIS)

Ishikawa, M.; Jaccard, D.; Jorda, J.-L.

1982-01-01

Concentrating on the ternary phase diagram, the authors have performed a complementary investigation on CeCu 2 Si 2 and confirm that the compound containing nearly trivalent cerium ions is a new type of superconductor with Tsub(c) around 0.5 K. The analyses of the upper critical field curve support the description of the compound by heavy fermion quasiparticles. Other particular features of this compound are also presented. (Auth.)

Some observations concerning the direct titration of nitrite with cerium(IV)

International Nuclear Information System (INIS)

Muralikrishna, U.; Subrahmanyam, K.; Suryanarayana, M.V.S.; Krishnamurthy, M.

1983-01-01

Direct titration of nitrite with cerium(IV), with ferroin as indicator, is shown to give satisfactory results if the acidity is kept between 0.033 and 0.055 M at the end-point. Loss of nitrous acid owing to volatilization and decomposition is discussed. From 10 to 60 mg of sodium nitrite can be estimated with a standard deviation of 5 μg and an average error of 0.2%. (author)

Phenotypic and genomic responses to titanium dioxide and cerium oxide nanoparticles in Arabidopsis germinants

Science.gov (United States)

The effects of exposure to two nanoparticles (NPs) -titanium dioxide (nano-titania) and cerium oxide (nano-ceria) at 500 mg NPs L-1 on gene expression and growth in Arabidopsis thaliana germinants were studied using microarrays and phenotype studies. After 12 days post treatment,...

Electrospun cerium-based TiO2 nanofibers for photocatalytic oxidation of elemental mercury in coal combustion flue gas.

Science.gov (United States)

Wang, Lulu; Zhao, Yongchun; Zhang, Junying

2017-10-01

Photocatalytic oxidation is an attractive method for Hg-rich flue gas treatment. In the present study, a novel cerium-based TiO 2 nanofibers was prepared and selected as the catalyst to remove mercury in flue gas. Accordingly, physical/chemical properties of those nanofibers were clarified. The effects of some important parameters, such as calcination temperature, cerium dopant content and different illumination conditions on the removal of Hg 0 using the photocatalysis process were investigated. In addition, the removal mechanism of Hg 0 over cerium-based TiO 2 nanofibers focused on UV irradiation was proposed. The results show that catalyst which was calcined at 400 °C exhibited better performance. The addition of 0.3 wt% Ce into TiO 2 led to the highest removal efficiency at 91% under UV irradiation. As-prepared samples showed promising stability for long-term use in the test. However, the photoluminescence intensity of nanofibers incorporating ceria was significantly lower than TiO 2 , which was attributed to better photoelectron-hole separation. Although UV and O 2 are essential factors, the enhancement of Hg 0 removal is more obviously related to the participation of catalyst. The coexistence of Ce 3+ and Ce 4+ , which leads to the efficient oxidation of Hg 0 , was detected on samples. Hg 2+ is the final product in the reaction of Hg 0 removal. As a consequence, the emissions of Hg 0 from flue gas can be significantly suppressed. These indicate that combining photocatalysis technology with cerium-based TiO 2 nanofibers is a promising strategy for reducing Hg 0 efficiently. Copyright © 2017 Elsevier Ltd. All rights reserved.

Altering properties of cerium oxide thin films by Rh doping

International Nuclear Information System (INIS)

Ševčíková, Klára; Nehasil, Václav; Vorokhta, Mykhailo; Haviar, Stanislav; Matolín, Vladimír

2015-01-01

Highlights: • Thin films of ceria doped by rhodium deposited by RF magnetron sputtering. • Concentration of rhodium has great impact on properties of Rh–CeO x thin films. • Intensive oxygen migration in films with low concentration of rhodium. • Oxygen migration suppressed in films with high amount of Rh dopants. - Abstract: Ceria containing highly dispersed ions of rhodium is a promising material for catalytic applications. The Rh–CeO x thin films with different concentrations of rhodium were deposited by RF magnetron sputtering and were studied by soft and hard X-ray photoelectron spectroscopies, Temperature programmed reaction and X-ray powder diffraction techniques. The sputtered films consist of rhodium–cerium mixed oxide where cerium exhibits a mixed valency of Ce 4+ and Ce 3+ and rhodium occurs in two oxidation states, Rh 3+ and Rh n+ . We show that the concentration of rhodium has a great influence on the chemical composition, structure and reducibility of the Rh–CeO x thin films. The films with low concentrations of rhodium are polycrystalline, while the films with higher amount of Rh dopants are amorphous. The morphology of the films strongly influences the mobility of oxygen in the material. Therefore, varying the concentration of rhodium in Rh–CeO x thin films leads to preparing materials with different properties

EMISSION REDUCTION FROM A DIESEL ENGINE FUELED BY CERIUM OXIDE NANO-ADDITIVES USING SCR WITH DIFFERENT METAL OXIDES COATED CATALYTIC CONVERTER

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B. JOTHI THIRUMAL

2015-11-01

Full Text Available This paper reports the results of experimental investigations on the influence of the addition of cerium oxide in nanoparticle form on the major physiochemical properties and the performance of diesel. The fuel is modified by dispersing the catalytic nanoparticle by ultrasonic agitation. The physiochemical properties of sole diesel fuel and modified fuel are tested with ASTM standard procedures. The effects of the additive nanoparticles on the individual fuel properties, the engine performance, and emissions are studied, and the dosing level of the additive is optimized. Cerium oxide acts as an oxygen-donating catalyst and provides oxygen for the oxidation of CO during combustion. The active energy of cerium oxide acts to burn off carbon deposits within the engine cylinder at the wall temperature and prevents the deposition of non-polar compounds on the cylinder wall which results in reduction in HC emission by 56.5%. Furthermore, a low-cost metal oxide coated SCR (selective catalyst reduction, using urea as a reducing agent, along with different types of CC (catalytic converter, has been implemented in the exhaust pipe to reduce NOx. It was observed that a reduction in NOx emission is 50–60%. The tests revealed that cerium oxide nanoparticles can be used as an additive in diesel to improve complete combustion of the fuel and reduce the exhaust emissions significantly.

Micromagnetic simulation of the influence of grain boundary on cerium substituted Nd-Fe-B magnets

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D. Liu

2017-05-01

Full Text Available A three-dimensional finite element model was performed to study the magnetization reversal of (CexNd1-x2Fe14B nanocomposite permanent magnets. The influences of volume fraction, width and performance parameters of the grain boundary (GB composition on the coercivity were analyzed by the method of micromagnetic simulation. The calculation results indicate that the structure and chemistry of GB phase play important roles in Nd2Fe14B-based magnets. An abnormal increase in the value of coercivity is found to be connected with the GB phase, approximately when the percentage of doped cerium is between 20% and 30%. While the coercivity decreases directly with the increase in cerium content instead of being abnormal when there is no GB phase in magnets at all or the value of magnetocrystalline anisotropy or exchange integral is too large.

Corrosion of Zn5Al and Zn55Al alloys with cerium, praseodymium and neodymium

International Nuclear Information System (INIS)

Alikhanova, S.D.

2017-01-01

The present work is devoted to corrosion of Zn5Al and Zn55Al alloys with cerium, praseodymium and neodymium. The purpose of present work is elaboration of optimal composition of zinc-aluminium alloys Zn5Al and Zn55Al alloyed by rare-earth metals of cerium subgroup which are used as anode covers for protection of steel from corrosion. Therefore, the regularities of change of corrosion-electrochemical properties in various corrosive mediums have been determined; processes mechanisms of high temperature oxidation of alloys in solid state have been studied; in the products of alloys oxidation their phase components have been defined and their role in the corrosion process have been revealed; the optimal compositions of zinc-aluminium alloys alloyed by rare earth metals, which are protected by two patents of the Republic of Tajikistan have been elaborated.

Protective effects of Curcuma longa against neurobehavioral and neurochemical damage caused by cerium chloride in mice.

Science.gov (United States)

Kadri, Yamina; Nciri, Riadh; Brahmi, Noura; Saidi, Saber; Harrath, Abdel Halim; Alwasel, Saleh; Aldahmash, Waleed; El Feki, Abdelfatteh; Allagui, Mohamed Salah

2018-05-07

Cerium chloride (CeCl 3 ) is considered an environmental pollutant and a potent neurotoxic agent. Medicinal plants have many bioactive compounds that provide protection against damage caused by such pollutants. Curcuma longa is a bioactive compound-rich plant with very important antioxidant properties. To study the preventive and healing effects of Curcuma longa on cerium-damaged mouse brains, we intraperitoneally injected cerium chloride (CeCl 3 , 20 mg/kg BW) along with Curcuma longa extract, administrated by gavage (100 mg/kg BW), into mice for 60 days. We then examined mouse behavior, brain tissue damage, and brain oxidative stress parameters. Our results revealed a significant modification in the behavior of the CeCl 3 -treated mice. In addition, CeCl 3 induced a significant increment in lipid peroxidation, carbonyl protein (PCO), and advanced oxidation protein product levels, as well as a significant reduction in superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities. Acetylcholinesterase (AChE) activity remarkably increased in the brain of CeCl 3 -treated mice. Histopathological observations confirmed these results. Curcuma longa attenuated CeCl 3 -induced oxidative stress and increased the activities of antioxidant enzymes. It also decreased AChE activity in the CeCl 3 -damaged mouse brain that was confirmed by histopathology. In conclusion, this study suggests that Curcuma longa has a neuroprotective effect against CeCl 3 -induced damage in the brain.

The study of interaction of lanthanum-, cerium- and neodymium chlorides with sodium borohydride in pyridine- and tetrahydrofuran medium

International Nuclear Information System (INIS)

Mirsaidov, U.; Rotenberg, T.G.; Dymova, T.N.

1976-01-01

Bis-tetrahydrofurans of lanthanum and neodymium borohydrides and bis-pyridinates of lanthanum, cerium and neodymium borohydrides were obtained by interacting sodium borohydride with lanthanum-, cerium and neodymium chlorides in pyridine and tetrahydrofuran media. All operations involving reagent combination, sampling and phase separation are performed in inert atmosphere using argonvacuum equipment. The reaction in pyridine was virtually instantaneous and accompanied by flocculanet precipitation. The interaction of lanthanum chloride and neodymium chloride with sodium borohydride in tetrahydrofuran (THF) was a slow (23-30 hr) heterophase process. The interaction rate was affected by size reduction of the intial substances, temperature, reagent proportion and mixing rate. The reaction time was twice reduced with boiling tetrahydrofuran

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

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.

Synthesis and Characterization of Hybrid Silica-Zirconia Coatings with Cerium Inhibitor on Aluminum 6061

Directory of Open Access Journals (Sweden)

M. Bahrami

2016-12-01

Full Text Available Organic–inorganic hybrid coatings were prepared by sol–gel method and deposited on aluminum alloy 6061. Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR spectroscopy and Scanning Electron Microscopy (SEM were used for structural study of the hybrid coatings. Adhesive strength of sol–gel coatings to the substrate was evaluated quantitatively and qualitatively. Corrosion behavior of the samples was studied by cyclic potentiodynamic and linear polarization tests. Results showed that adhesion strength of the coatings to the substrates was increased with increasing tetrapropoxide of zirconium (TPOZ and cerium content. Corrosion tests showed that corrosion current density of coated samples were decreased three to seven orders of magnitude in comparison with uncoated aluminum alloy 6061. Decreasing in corrosion current density and increasing in polarization resistance was observed by increasing zirconia and cerium content. Unlike the uncoated aluminum alloy 6061, the crack-free coatings did not show pitting tendency. 

Effect of cerium (IV) ions on the anticorrosion properties of siloxane-poly(methyl methacrylate) based film applied on tin coated steel

Energy Technology Data Exchange (ETDEWEB)

Suegama, P.H. [Departamento de Engenharia Quimica, Escola Politecnica, Universidade de Sao Paulo, CP 61548, 05424-970 Sao Paulo, SP (Brazil); Sarmento, V.H.V. [Departamento Fisico-Quimica, Instituto de Quimica, Universidade Estadual Paulista, UNESP, CP 355, 14801-970 Araraquara, SP (Brazil); Montemor, M.F. [ICEMS, Instituto Superior Tecnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Benedetti, A.V. [Departamento Fisico-Quimica, Instituto de Quimica, Universidade Estadual Paulista, UNESP, CP 355, 14801-970 Araraquara, SP (Brazil); de Melo, H.G.; Aoki, I.V. [Departamento de Engenharia Quimica, Escola Politecnica, Universidade de Sao Paulo, CP 61548, 05424-970 Sao Paulo, SP (Brazil); Santilli, C.V., E-mail: santilli@iq.unesp.b [Departamento Fisico-Quimica, Instituto de Quimica, Universidade Estadual Paulista, UNESP, CP 355, 14801-970 Araraquara, SP (Brazil)

2010-07-15

This work investigates the influence of the addition of cerium (IV) ions on the anticorrosion properties of organic-inorganic hybrid coatings applied to passivated tin coated steel. In order to evaluate the specific effect of cerium (IV) addition on nanostructural features of the organic and inorganic phases of the hybrid coating, the hydrolytic polycondensation of silicon alkoxide and the radical polymerization of the methyl methacrylate (MMA) function were induced separately. The corrosion resistance of the coatings was evaluated by means of linear polarization, Tafel type curves and electrochemical impedance measurements. The impedance results obtained for the hybrid coatings were discussed based on an electrical equivalent circuit used to fit the experimental data. The electrochemical results clearly showed the improvement of the protective properties of the organic-inorganic hybrid coating mainly when the cerium (IV) was added to the organic phase solution precursor, which seemed to be due to the formation of a more uniform and densely reticulated siloxane-PMMA film.

Effect of cerium (IV) ions on the anticorrosion properties of siloxane-poly(methyl methacrylate) based film applied on tin coated steel

International Nuclear Information System (INIS)

Suegama, P.H.; Sarmento, V.H.V.; Montemor, M.F.; Benedetti, A.V.; de Melo, H.G.; Aoki, I.V.; Santilli, C.V.

2010-01-01

This work investigates the influence of the addition of cerium (IV) ions on the anticorrosion properties of organic-inorganic hybrid coatings applied to passivated tin coated steel. In order to evaluate the specific effect of cerium (IV) addition on nanostructural features of the organic and inorganic phases of the hybrid coating, the hydrolytic polycondensation of silicon alkoxide and the radical polymerization of the methyl methacrylate (MMA) function were induced separately. The corrosion resistance of the coatings was evaluated by means of linear polarization, Tafel type curves and electrochemical impedance measurements. The impedance results obtained for the hybrid coatings were discussed based on an electrical equivalent circuit used to fit the experimental data. The electrochemical results clearly showed the improvement of the protective properties of the organic-inorganic hybrid coating mainly when the cerium (IV) was added to the organic phase solution precursor, which seemed to be due to the formation of a more uniform and densely reticulated siloxane-PMMA film.

Study on recovering directly the commercial cerium oxide and total of residue rare earths from Dongpao bastnasite concentrate

International Nuclear Information System (INIS)

Nguyen Trong Hung; Nguyen Thanh Chung; Luu Xuan Dinh

2003-01-01

A technology for decomposition roasting and sequential leaching processes of Dong Pao bastnasite concentrate to recover directly commercial cerium oxide and total of residue rare earth elements from the leaching solution of the roasted product have been investigated. The bastnasite concentrate is initially roasted at temperature range of 600 - 650 degC and for time of 4 hrs in order to decompose and convert the hardly soluble carbonate forms of ore into easily soluble oxide. The roasted solid is then leached with sulfuric acid solution of 6N at 60 degC for 4 hrs to convert rare earths in oxide and fluoride form into rare earth sulfate. The recovery yield of rare earths of these stages is more than 95%. The attention has especially been paid on recovering directly the commercial cerium oxide and total of residue rare earth element from the above leaching solution. Complex ions of CeSO 4 2+ , Ce(SO 4 ) 2 , Ce(SO 4 ) 3 2- and Ce(SO 4 ) 4 4- exist in aqueous solution of cerium (IV) sulfate. Based on the property, the method of ion - sieve with DOWEX cation resin column has been applied to estimating separation of the ceric complex anions from Ln(III). The survey showed that most of the ceric complex anions are separated from total of residue rare earths. The latter which are absorbed in the cation column are recovered by elution of HCl of 4N. The recovery yield of cerium can only be reached 20% but the purity of that is very high, can be reached 99.6%. About 5 kg of CeO 2 of high grade and 5 kg of TREO of commercial specification have been produced. (author)

Submicron Features in Higher Manganese Silicide

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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.

Development of Self-Healing Zirconium-Silicide Coatings for Improved Performance Zirconium-Alloy Fuel Cladding

Energy Technology Data Exchange (ETDEWEB)

Sridharan, Kumar [University of Wisconsin-Madison; Mariani, Robert [Idaho National Lab. (INL), Idaho Falls, ID (United States); Bai, Xianming [Idaho National Lab. (INL), Idaho Falls, ID (United States); Xu, Peng [Westinghouse Electric Company; Lahoda, Ed [Westinghouse Electric Company

2018-03-31

Given the long-term goal of developing such coatings for use with nuclear reactor fuel cladding, this work describes results of oxidation and corrosion behavior of bulk zirconium-silicide and fabrication of zirconium-silicide coatings on zirconium-alloy test flats, tube configurations, and SiC test flats. In addition, boiling heat transfer of these modified surfaces (including ZrSi2 coating) during clad quenching experiments is discussed in detail. Oxidation of bulk ZrSi2 was found to be negligible compared to Zircaloy-4 (a common Zr-alloy cladding material) and mechanical integrity of ZrSi2 was superior to that of bulk Zr2Si at high temperatures in ambient air. Very interesting and unique multi-nanolayered composite of ZrO2 and SiO2 were observed. Physical model for the oxidation has been proposed wherein Zr–Si–O mixture undergoes a spinodal phase decomposition into ZrO2 and SiO2, which is manifested as a nanoscale assembly of alternating layer of the two oxides. Steam corrosion at high pressure (10.3 MPa) led to weight loss of ZrSi2 and produced oxide scale with depletion of silicon, possibly attributed to volatile silicon hydroxide, gaseous silicon monoxide, and a solubility of silicon dioxide in water. Only Zircon phase (ZrSiO4) formed during oxidation of ZrSi2 at 1400°C in air, and allowed for immobilization silicon species in oxide scale in the aqueous environments. Zirconium-silicide coatings (on zirconium-alloy substrates) investigated in this study were deposited primarily using magnetron sputter deposition method and slurry method, although powder spray deposition processes cold spray and thermal spray methods were also investigated. The optimized ZrSi2 sputtered coating exhibited a highly protective nature at elevated temperatures in ambient air by mitigating oxygen permeation to the underlying zirconium alloy substrate. The high oxidation resistance of the coating has been shown to be due to nanocrystalline SiO2 and ZrSiO4 phases in the amorphous

Tribological characteristics of monodispersed cerium borate nanospheres in biodegradable rapeseed oil lubricant

Energy Technology Data Exchange (ETDEWEB)

Boshui, Chen, E-mail: boshuichen@163.com; Kecheng, Gu; Jianhua, Fang; Jiang, Wu; Jiu, Wang; Nan, Zhang

2015-10-30

Graphical abstract: - Highlights: • Monodispersed stearic acid-capped cerium borate composite nanoparticles were prepared by hydrothermal method. Their morphologies, element compositions, size distributions, crystal and chemical structures, hydrophobic characteristics were also characterized. • The surface-capped cerium borate nanoparticles exhibited excellent dispersing stability in rapeseed oil. As new lubricating additives, they were also outstanding in enhancing friction-reducing and anti-wear capacities of rapeseed oil in biodegradable rapeseed oil. The results presented in this paper would be of important significance for developing green lubricants and lubricant additives. • The prominent tribological performances of SA/CeBO{sub 3} in rapeseed oil were investigated and attributed to the formation of a composite boundary lubrication film mainly composed of lubricous tribochemical species on the tribo-surfaces. - Abstract: Stearic acid-capped cerium borate composite nanoparticles, abbreviated as SA/CeBO{sub 3}, were prepared by hydrothermal method. The morphologies, element compositions, size distributions, crystal and chemical structures, hydrophobic characteristics, of SA/CeBO{sub 3} were characterized by scanning electron microscope, energy dispersive X-ray spectrometer, dynamic laser particle size analyzer, X-ray diffraction, and Fourier transform infrared spectrometer, respectively. The friction and wear performances of SA/CeBO{sub 3} as a lubricating additive in a rapeseed oil were evaluated on a four-ball tribo-tester. The tribochemical characteristics of the worn surfaces were investigated by X-ray photoelectron spectroscopy. The results showed that the hydrophobic SA/CeBO{sub 3} were monodispersed nanospheres with an average diameter of 8 nm, and exhibited excellent dispersing stability in rapeseed oil. Meanwhile, SA/CeBO{sub 3} nanospheres were outstanding in enhancing friction-reducing and anti-wear capacities of rapeseed oil. The prominent

Cerium(III) pivalate [Ce(Piv)3(HPiv)3]2: synthesis, crystal structure, and thermal stability

International Nuclear Information System (INIS)

Khudyakov, M.Yu.; Kuz'mina, N.P.; Pisarevskij, A.P.; Martynenko, L.I.

2002-01-01

Complex [Ce(Piv) 3 (HPiv) 3 ] 2 was prepared by precipitation of cerium(III) nitrate aqueous solution with salt NH 4 (Piv) (HPiv = pivalic acid) and subsequent recrystallization from 5% HPiv solution in hexane. According to data of X-ray diffraction analysis and IR spectroscopy crystal structure of the complex is built of centrally symmetric dimers, in which cerium atoms are bound by four bridge pivalate ligands. Thermal analysis suggests that heating of the complex in nitrogen atmosphere results first in splitting off six HPiv molecules in the range of 90-190 deg C and then in thermolysis of Ce(Piv) 3 formed at 290-450 deg C. Sublimation of Ce(Piv) 3 occurs in the range of 290-350 deg C along with thermolysis during heating in vacuum (0.01 mm Hg), which permits preparing CeO 2 films by the method of chemical precipitation from gaseous phase [ru

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

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

Cerium(terbium, erbium)chloride-choline chloride aqueous systems

International Nuclear Information System (INIS)

Gajfutdinova, R.K.; Zhuravlev, E.F.; Bikbaeva, G.G.; Domrachev, V.N.; Vanskova, G.I.

1985-01-01

To clarify the effect of rare earth nature on mutual solubility of rare earth salts and amines the solubility of solid phases in the systems, consisting of choline chloride, water and cerium, terbium, erbium chlorides, has been studied. It is established, that solubility isotherms of all the systems, testify to the formation of new solid phases of the composition: Ce(Tb, Er)xCl 3 x2C 5 H 14 ONClx3H 2 O. Individuality of new solid phases is proved by DTA method, the composition is confirmed by chemical analysis and data of PMR spectra, for choline chloride and its complexes with rare earth chlorides of the given composition PMR and IR spectra are studied

Cerium(III) molybdate nanoparticles: Synthesis, characterization and radionuclides adsorption studies

Energy Technology Data Exchange (ETDEWEB)

Yousefi, Taher, E-mail: Taher_yosefy@yahoo.com [NFCRS, Nuclear Science and Technology Institute, Kargher Ave, Tehran (Iran, Islamic Republic of); Tarbiat Moallem University, Mofatteh Ave, Tehran (Iran, Islamic Republic of); Khanchi, Ali Reza; Ahmadi, Seyed Javad [NFCRS, Nuclear Science and Technology Institute, Kargher Ave, Tehran (Iran, Islamic Republic of); Rofouei, Mohamad Kazem [Tarbiat Moallem University, Mofatteh Ave, Tehran (Iran, Islamic Republic of); Yavari, Ramin; Davarkhah, Reza; Myanji, Behzad [NFCRS, Nuclear Science and Technology Institute, Kargher Ave, Tehran (Iran, Islamic Republic of)

2012-05-15

Highlights: Black-Right-Pointing-Pointer A new inorganic nanoparticles with average size about 40 nm were synthesized by chemical method. Black-Right-Pointing-Pointer The morphology studies reveal existing nanowires among dense nanoparticles. Black-Right-Pointing-Pointer Investigation shows it has high stability in rough media and high affinity for Cs(I), U(VI), and Th(IV). Black-Right-Pointing-Pointer It was used for adsorption of radionuclides and removal of {sup 134}Cs from real sample. Black-Right-Pointing-Pointer These findings are important for evaluating human and environmental risk assessment. - Abstract: Cerium(III) molybdate nanostructure with average size about 40 nm was prepared by adding cerium(III) chloride and ammonium molybdate solutions under varying conditions. The product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA) and Brunauere Emmette Teller (BET) techniques. Ion exchange capacity of the sample for potassium ion and distribution coefficients (K{sub d}) for 23 metal ions were determined, the K{sub d} values for Tl(I), Pb(II), Th(IV), U(VI), and Cs(I) ions were found to be sufficiently high for their removal from various effluents. The adsorption behavior of the sample towards Cs(I){sub 134} species were studied. Finally, the binary separation of Dy(III)-U(VI), Sm(III)-Th(IV) and Cs(I)-Rb(I) and removal of Cs(I){sub 134} from the real sample were successfully achieved.

A phosphate-dependent shift in redox state of cerium oxide nanoparticles and its effects on catalytic properties

Energy Technology Data Exchange (ETDEWEB)

Singh, Sanjay; Dosani, Talib; Karakoti, Ajay S.; Kumar, Amit; Seal, Sudipta; Self, William

2011-10-01

Cerium oxide nanoparticles (CeNPs) have shown promise as catalytic antioxidants in cell culture and animal models as both superoxide dismutase and catalase mimetics. The reactivity of the cerium (Ce) atoms at the surface of its oxide particle is critical to such therapeutic properties, yet little is known about the potential for a protein or small molecule corona to form on these materials in vivo. Moreover Ce atoms in these active sites have the potential to interact with small molecule anions, peptides, or sugars when administered in culture or animal models. Several nanomaterials have been shown to alter or aggregate under these conditions, rendering them less useful for biomedical applications. In this work we have studied the change in catalytic properties of CeNPs when exposed to various biologically relevant conditions in vitro. We have found that CeNPs are resistant to broad changes in pH and also not altered by incubation in cell culture medium. However to our surprise phosphate anions significantly altered the characteristics of these nanomaterials and shifted the catalytic behavior due to the binding of phosphate anions to cerium. Given the abundance of phosphate in biological systems in an inorganic form, it is likely that the action of CeNPs as a catalyst may be strongly influenced by the local concentration of phosphate in the cells and/or tissues in which it has been introduced.

Defect states and room temperature ferromagnetism in cerium oxide nanopowders prepared by decomposition of Ce-propionate

DEFF Research Database (Denmark)

Mihalache, V.; Grivel, J. C.; Secu, M.

2018-01-01

. An improvement of ferromagnetism and intensity of defect-related PL emission was observed when annealing the products in which nanocrystalline cerium oxide coexists with Ce - oxicarbonate traces, Ce2O2CO3. The experimental results were explained based on the following considerations: room temperature......Four batches of cerium oxide powders (with nanocrystallite size of 6.9 nm–572 nm) were prepared from four precursor nanopowders by thermal decomposition of Ce-propionate and annealing in air between 250 °C–1200 °C for 10 min–240 min. Ceria formation reactions, structure, vibrational, luminescence...... and magnetic properties were investigated by differential scanning calorimetry, x-ray diffraction, electron microscopy, infrared spectroscopy, photoluminescence and SQUID. All the samples exhibit room temperature ferromagnetism, RTFM, (with coercivity, Hc, of 8 Oe - 121 Oe and saturation magnetization, Ms...

Corrosion behaviour of nanometre sized cerium oxide and titanium oxide incorporated aluminium in NaCl solution

International Nuclear Information System (INIS)

Ashraf, P. Muhamed; Edwin, Leela

2013-01-01

Highlights: ► Corrosion resistant aluminium incorporated with nano oxides of cerium and titanium. ► 0.2% nano CeO 2 and 0.05% nano TiO 2 showed increased corrosion resistance. ► Nano TiO 2 concentration influenced the optimum performance of the material. ► Comparison of Micro and nano CeO 2 and TiO 2 aluminium showed the latter is best. - Abstract: The study highlights the development of an aluminium matrix composite by incorporating mixture of nanometre sized cerium oxide and titanium oxide in pure aluminium and its corrosion resistance in marine environment. The mixed nanometre sized oxides incorporated aluminium exhibited improved microstructure and excellent corrosion resistance. Corrosion resistance depends on the concentration of nanometre sized titanium oxide. Electrochemical characteristics improved several folds in nanometre sized mixed oxides incorporated aluminium than micrometre sized oxides incorporated aluminium.

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

Electric dipole transitions for four-times ionized cerium (Ce V)

Energy Technology Data Exchange (ETDEWEB)

Usta, Betül Karaçoban, E-mail: bkaracoban@sakarya.edu.tr; Akgün, Elif, E-mail: elif.akgun@ogr.sakarya.edu.tr; Alparslan, Büşra, E-mail: busra.alparslan1@ogr.sakarya.edu.tr [Physics Department, Sakarya University, 54187, Sakarya (Turkey)

2016-03-25

We have calculated the transition parameters, such as wavelengths, oscillator strengths, and transition probabilities (or rates), for the electric dipole (E1) transitions in four-times ionized cerium (Ce V, Z = 58) by using the multiconfiguration Hartree-Fock method within the framework of Breit-Pauli (MCHF+BP) relativistic corrections and the relativistic Hartree-Fock (HFR) method. The obtained results have been compared with other works available in literature. A discussion of these calculations for Ce V in this study has also been in view of the MCHF+BP and HFR methods.

Program description for the qualification of CNEA - Argentina as a supplier of LEU silicide fuel and post-irradiation examinations plan for the first prototype irradiated in Argentina

International Nuclear Information System (INIS)

Rugirello, Gabriel; Adelfang, Pablo; Denis, Alicia; Zawerucha, Andres; Marco, Agustin di; Guillaume, Eduardo; Sbaffoni, Monica; Lacoste, Pablo

1998-01-01

In this report we present a description of the ongoing and future stages of the program for the qualification of CNEA, Argentina, as a supplier of low enriched uranium silicide fuel elements for research reactor. Particularly we will focus on the characteristics of the future irradiation experiment on a new detachable prototype, the post-irradiation examinations (PIE) plan for the already irradiated prototype PO4 and an overview of the recently implemented PIE facilities and equipment. The program is divided in several steps, some of which have been already completed. It concludes: development of the uranium silicide fissile material, irradiation and PIE of several full-scale prototypes. Important investments have been already carried out in the facilities for the FE production and PIE. (author)

Identification of the lines in the L emission spectrum of cerium and samarium

International Nuclear Information System (INIS)

Shrivastava, B.D.; Singh, D.

1992-01-01

The occurrence of a line at 2.1556 A in the L emission spectrum of cerium and two lines at 1.6679 and 1.8379 A in the L emission spectrum of samarium, reported many years ago, has remained a puzzle. These have now been identified as EXAFS minima occurring at the L absorption edges of the respective elements. (author)

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.

Brain suppression of AP-1 by inhaled diesel exhaust and reversal by cerium oxide nanoparticles

NARCIS (Netherlands)

Lung, Shyang; Cassee, Flemming R; Gosens, Ilse; Campbell, Arezoo

One of the uses of cerium oxide nanoparticles (nanoceria, CeO2) is as a diesel fuel additive to improve fuel efficiency. Gene/environment interactions are important determinants in the etiology of age-related disorders. Thus, it is possible that individuals on high-fat diet and genetic

Gene-expression changes in cerium chloride-induced injury of mouse hippocampus.

Directory of Open Access Journals (Sweden)

Zhe Cheng

Full Text Available Cerium is widely used in many aspects of modern society, including agriculture, industry and medicine. It has been demonstrated to enter the ecological environment, is then transferred to humans through food chains, and causes toxic actions in several organs including the brain of animals. However, the neurotoxic molecular mechanisms are not clearly understood. In this study, mice were exposed to 0.5, 1, and 2 mg/kg BW cerium chloride (CeCl(3 for 90 consecutive days, and their learning and memory ability as well as hippocampal gene expression profile were investigated. Our findings suggested that exposure to CeCl(3 led to hippocampal lesions, apoptosis, oxidative stress and impairment of spatial recognition memory. Furthermore, microarray data showed marked alterations in the expression of 154 genes involved in learning and memory, immunity and inflammation, signal transduction, apoptosis and response to stress in the 2 mg/kg CeCl(3 exposed hippocampi. Specifically, the significant up-regulation of Axud1, Cdc37, and Ube2v1 caused severe apoptosis, and great suppression of Adcy8, Fos, and Slc5a7 expression led to impairment of mouse cognitive ability. Therefore, Axud1, Cdc37, Ube2v1, Adcy8, Fos, and Slc5a7 may be potential biomarkers of hippocampal toxicity caused by CeCl3 exposure.

Synthesis of cerium oxide catalysts supported on MCM-41 molecular sieve; Sintese de catalisadores de oxido de cerio suportados na peneira molecular MCM-41

Energy Technology Data Exchange (ETDEWEB)

Souza, E.L.S.; Barros, T.R.B.; Sousa, B.V. de, E-mail: emylle.souza@gmail.com [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Unidade Academica de Engenharia Quimica

2016-07-01

Porous materials have been widely studied as catalysts and catalyst support. The MCM-41 structure is the one that has been most studied because of its application possibilities in chemical processes. This work aimed to obtain and characterize cerium oxide catalysts supported on MCM-41 molecular sieve. The molecular sieve was synthesized by the conventional method with the following molar composition: 1 SiO2: 0.30 CTABr: NH3 11: 144 H2O. Then, 25% w/w cerium was incorporated into the MCM-41 using the wet impregnation process and the material obtained was activated by calcination. From the XRD patterns was confirmed the structure of the molecular sieve, and were identified the cerium oxide phases in its structure. The textural catalysts characteristics were investigated by isotherms of N2 adsorption/desorption (BET method). (author)

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.

Assessing Covalency in Cerium and Uranium Hexachlorides: A Correlated Wavefunction and Density Functional Theory Study

Directory of Open Access Journals (Sweden)

Reece Beekmeyer

2015-11-01

Full Text Available The electronic structure of a series of uranium and cerium hexachlorides in a variety of oxidation states was evaluated at both the correlated wavefunction and density functional (DFT levels of theory. Following recent experimental observations of covalency in tetravalent cerium hexachlorides, bonding character was studied using topological and integrated analysis based on the quantum theory of atoms in molecules (QTAIM. This analysis revealed that M–Cl covalency was strongly dependent on oxidation state, with greater covalency found in higher oxidation state complexes. Comparison of M–Cl delocalisation indices revealed a discrepancy between correlated wavefunction and DFT-derived values. Decomposition of these delocalisation indices demonstrated that the origin of this discrepancy lay in ungerade contributions associated with the f-manifold which we suggest is due to self-interaction error inherent to DFT-based methods. By all measures used in this study, extremely similar levels of covalency between complexes of U and Ce in the same oxidation state was found.

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.)

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.

Long range ordered alloys modified by addition of niobium and cerium

International Nuclear Information System (INIS)

Liu, C.T.

1987-01-01

A long range ordered alloy composition is described consisting essentially of iron, nickel, cobalt, vanadium and a ductility enhancing metal, having the nominal composition (Fe, Ni,Co)/sub 3/(V,M) where M is the ductility enhancing metal selected from the group Ti, Zr, Hf and mixtures thereof. Effective amounts of creep property enhance elements selected from the group cerium, niobium and mixtures thereof sufficient to enhance creep properties in the resulting alloy without adversely affecting the fabrication of the alloy

The biological effects of subacute inhalation of diesel exhaust following addition of cerium oxide nanoparticles in atherosclerosis-prone mice

International Nuclear Information System (INIS)

Cassee, Flemming R.; Campbell, Arezoo; Boere, A. John F.; McLean, Steven G.; Duffin, Rodger; Krystek, Petra; Gosens, Ilse; Miller, Mark R.

2012-01-01

Background: Cerium oxide (CeO 2 ) nanoparticles improve the burning efficiency of fuel, however, little is known about health impacts of altered emissions from the vehicles. Methods: Atherosclerosis-prone apolipoprotein E knockout (ApoE −/− ) mice were exposed by inhalation to diluted exhaust (1.7 mg/m 3 , 20, 60 or 180 min, 5 day/week, for 4 weeks), from an engine using standard diesel fuel (DE) or the same diesel fuel containing 9 ppm cerium oxide nanoparticles (DCeE). Changes in hematological indices, clinical chemistry, atherosclerotic burden, tissue levels of inflammatory cytokines and pathology of the major organs were assessed. Results: Addition of CeO 2 to fuel resulted in a reduction of the number (30%) and surface area (10%) of the particles in the exhaust, whereas the gaseous co-pollutants were increased (6–8%). There was, however, a trend towards an increased size and complexity of the atherosclerotic plaques following DE exposure, which was not evident in the DCeE group. There were no clear signs of altered hematological or pathological changes induced by either treatment. However, levels of proinflammatory cytokines were modulated in a brain region and liver following DCeE exposure. Conclusions: These results imply that addition of CeO 2 nanoparticles to fuel decreases the number of particles in exhaust and may reduce atherosclerotic burden associated with exposure to standard diesel fuel. From the extensive assessment of biological parameters performed, the only concerning effect of cerium addition was a slightly raised level of cytokines in a region of the central nervous system. Overall, the use of cerium as a fuel additive may be a potentially useful way to limit the health effects of vehicle exhaust. However, further testing is required to ensure that such an approach is not associated with a chronic inflammatory response which may eventually cause long-term health effects.

The biological effects of subacute inhalation of diesel exhaust following addition of cerium oxide nanoparticles in atherosclerosis-prone mice

Energy Technology Data Exchange (ETDEWEB)

Cassee, Flemming R., E-mail: flemming.cassee@rivm.nl [National Institute for Public Health and the Environment, PO box 1, 3720 BA Bilthoven (Netherlands); Campbell, Arezoo, E-mail: acampbell@westernu.edu [Western University of Health Sciences, Pomona, CA (United States); Boere, A. John F., E-mail: john.boere@rivm.nl [National Institute for Public Health and the Environment, PO box 1, 3720 BA Bilthoven (Netherlands); McLean, Steven G., E-mail: smclean1@staffmail.ed.ac.uk [BHF/University Centre for Cardiovascular Sciences, University of Edinburgh, Edinburgh (United Kingdom); Duffin, Rodger, E-mail: Rodger.Duffin@ed.ac.uk [MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh (United Kingdom); Krystek, Petra, E-mail: petra.krystek@philips.com [Philips Innovation Services, Eindhoven (Netherlands); Gosens, Ilse, E-mail: Ilse.gosens@rivm.nl [National Institute for Public Health and the Environment, PO box 1, 3720 BA Bilthoven (Netherlands); Miller, Mark R., E-mail: Mark.Miller@ed.ac.uk [BHF/University Centre for Cardiovascular Sciences, University of Edinburgh, Edinburgh (United Kingdom)

2012-05-15

Background: Cerium oxide (CeO{sub 2}) nanoparticles improve the burning efficiency of fuel, however, little is known about health impacts of altered emissions from the vehicles. Methods: Atherosclerosis-prone apolipoprotein E knockout (ApoE{sup -/-}) mice were exposed by inhalation to diluted exhaust (1.7 mg/m{sup 3}, 20, 60 or 180 min, 5 day/week, for 4 weeks), from an engine using standard diesel fuel (DE) or the same diesel fuel containing 9 ppm cerium oxide nanoparticles (DCeE). Changes in hematological indices, clinical chemistry, atherosclerotic burden, tissue levels of inflammatory cytokines and pathology of the major organs were assessed. Results: Addition of CeO{sub 2} to fuel resulted in a reduction of the number (30%) and surface area (10%) of the particles in the exhaust, whereas the gaseous co-pollutants were increased (6-8%). There was, however, a trend towards an increased size and complexity of the atherosclerotic plaques following DE exposure, which was not evident in the DCeE group. There were no clear signs of altered hematological or pathological changes induced by either treatment. However, levels of proinflammatory cytokines were modulated in a brain region and liver following DCeE exposure. Conclusions: These results imply that addition of CeO{sub 2} nanoparticles to fuel decreases the number of particles in exhaust and may reduce atherosclerotic burden associated with exposure to standard diesel fuel. From the extensive assessment of biological parameters performed, the only concerning effect of cerium addition was a slightly raised level of cytokines in a region of the central nervous system. Overall, the use of cerium as a fuel additive may be a potentially useful way to limit the health effects of vehicle exhaust. However, further testing is required to ensure that such an approach is not associated with a chronic inflammatory response which may eventually cause long-term health effects.

The biological effects of subacute inhalation of diesel exhaust following addition of cerium oxide nanoparticles in atherosclerosis-prone mice.

Science.gov (United States)

Cassee, Flemming R; Campbell, Arezoo; Boere, A John F; McLean, Steven G; Duffin, Rodger; Krystek, Petra; Gosens, Ilse; Miller, Mark R

2012-05-01

Cerium oxide (CeO(2)) nanoparticles improve the burning efficiency of fuel, however, little is known about health impacts of altered emissions from the vehicles. Atherosclerosis-prone apolipoprotein E knockout (ApoE(-/-)) mice were exposed by inhalation to diluted exhaust (1.7 mg/m(3), 20, 60 or 180 min, 5 day/week, for 4 weeks), from an engine using standard diesel fuel (DE) or the same diesel fuel containing 9 ppm cerium oxide nanoparticles (DCeE). Changes in hematological indices, clinical chemistry, atherosclerotic burden, tissue levels of inflammatory cytokines and pathology of the major organs were assessed. Addition of CeO(2) to fuel resulted in a reduction of the number (30%) and surface area (10%) of the particles in the exhaust, whereas the gaseous co-pollutants were increased (6-8%). There was, however, a trend towards an increased size and complexity of the atherosclerotic plaques following DE exposure, which was not evident in the DCeE group. There were no clear signs of altered hematological or pathological changes induced by either treatment. However, levels of proinflammatory cytokines were modulated in a brain region and liver following DCeE exposure. These results imply that addition of CeO(2) nanoparticles to fuel decreases the number of particles in exhaust and may reduce atherosclerotic burden associated with exposure to standard diesel fuel. From the extensive assessment of biological parameters performed, the only concerning effect of cerium addition was a slightly raised level of cytokines in a region of the central nervous system. Overall, the use of cerium as a fuel additive may be a potentially useful way to limit the health effects of vehicle exhaust. However, further testing is required to ensure that such an approach is not associated with a chronic inflammatory response which may eventually cause long-term health effects. Copyright © 2012 Elsevier Inc. All rights reserved.

Development of electrolytic process in molten salt media for light rare-earth metals production. The metallic cerium electrodeposition

International Nuclear Information System (INIS)

Restivo, T.A.G.

1994-01-01

The development of molten salt process and the respective equipment aiming rare-earth metals recovery was described. In the present case, the liquid cerium metal electrodeposition in a molten electrolytes of cerium chloride and an equimolar mixture of sodium and potassium chlorides in temperatures near 800 C was studied. Due the high chemical reactivity of the rare-earth metals in the liquid state and their molten halides, an electrolytic cell was constructed with controlled atmosphere, graphite crucibles and anodes and a tungsten cathode. The electrolytic process variables and characteristics were evaluated upon the current efficiency and metallic product purity. Based on this evaluations, were suggested some alterations on the electrolytic reactor design and upon the process parameters. (author). 90 refs, 37 figs, 20 tabs

Yttrium and lanthanum recovery from low cerium carbonate, yttrium carbonate and yttrium concentrate

International Nuclear Information System (INIS)

Vasconcelos, Mari Estela de

2006-01-01

In this work, separation, enrichment and purification of lanthanum and yttrium were performed using as raw material a commercial low cerium rare earth concentrate named LCC (low cerium carbonate), an yttrium concentrate named 'yttrium carbonate', and a third concentrated known as 'yttrium earths oxide. The first two were industrially produced by the late NUCLEMON - NUCLEBRAS de Monazita e Associados Ltda, using Brazilian monazite. The 'yttrium earths oxide' come from a process for preparation of lanthanum during the course of the experimental work for the present thesis. The following techniques were used: fractional precipitation with urea; fractional leaching of the LCC using ammonium carbonate; precipitation of rare earth peroxycarbonates starting from the rare earth complex carbonates. Once prepared the enriched rare earth fractions the same were refined using the ion exchange chromatography with strong cationic resin without the use of retention ion and elution using the ammonium salt of ethylenediaminetetraacetic acid. With the association of the above mentioned techniques were obtained pure oxides of yttrium (>97,7%), lanthanum (99,9%), gadolinium (96,6%) and samarium (99,9%). The process here developed has technical and economic viability for the installation of a large scale unity. (author)

Synergistic properties of graphitic carbon nitride/cerium molybdate nanocomposites for enhanced photocatalytic activity

Science.gov (United States)

Bhargava, V. S.; Singh, Gajendar; Sharma, Manu

2018-05-01

A polymeric semiconductor (g-C3N4), based nanocomposites have been achieved much attention due to its excellent thermal, chemical stability and suitable band positions for water splitting. g-C3N4 based nanocomposites show good performance in the field of photocatalysis, sensors, Li-ion batteries, supercapacitors and water purification technology. In this work, a series of novel g-C3N4/CeM nano composites were synthesized using a facile one-step ultra-sonication method. X-ray diffraction (XRD) pattern confirms the formation of g-C3N4 and cerium molybdate. The photocatalytic activity of nanocomposites indicated the substantial degradation of Methylene Blue (MB) dye up to 97% over the surface of g-C3N4/CeM under visible light illumination. All the g-C3N4/CeM composites possess higher photocatalytic activity than pure cerium molybdate. The proposed mechanism demonstrated that the different weight ratios of photocatalyst were most likely attributed to a synergistic effect between g-C3N4 and CeM. This approach is very simple, cost effective, and free from any surfactant that makes it valuable catalyst for various future applications.

Thermally stimulated iron oxide transformations and magnetic behaviour of cerium dioxide/iron oxide reactive sorbents

Czech Academy of Sciences Publication Activity Database

Luňáček, J.; Životský, O.; Jirásková, Yvonna; Buršík, Jiří; Janoš, P.

2016-01-01

Roč. 120, OCT (2016), s. 295-303 ISSN 1044-5803 R&D Projects: GA MŠk(CZ) LQ1601 Institutional support: RVO:68081723 Keywords : Oxide -nano-composites * Mössbauer spectroscopy * TEM * Cerium oxide * Magnetic parameters Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.714, year: 2016

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

Using EIS to analyse samples of Al-Mg alloy AA5083 treated by thermal activation in cerium salt baths

International Nuclear Information System (INIS)

Bethencourt, M.; Botana, F.J.; Cano, M.J.; Marcos, M.; Sanchez-Amaya, J.M.; Gonzalez-Rovira, L.

2008-01-01

This paper describes a study undertaken of the morphological and anticorrosive characteristics of surface layers formed on the Al-Mg alloy AA5083 from solutions of Ce(III), by means of various heat treatments while immersed in baths of cerium salts. SEM/EDS studies have demonstrated the existence of a heterogeneous layer formed by a film of aluminium oxide/hydroxide on the matrix and a series of dispersed islands of cerium deposited on the cathodic intermetallics. With the object of evaluating the degree of protection provided by the layers formed and of characterising the particular contribution of the electrochemical response of the system in NaCl, the results obtained by means of EIS are presented and discussed

Nanoporous cerium oxide thin film for glucose biosensor.

Science.gov (United States)

Saha, Shibu; Arya, Sunil K; Singh, S P; Sreenivas, K; Malhotra, B D; Gupta, Vinay

2009-03-15

Nanoporous cerium oxide (CeO(2)) thin film deposited onto platinum (Pt) coated glass plate using pulsed laser deposition (PLD) has been utilized for immobilization of glucose oxidase (GOx). Atomic force microscopy studies reveal the formation of nanoporous surface morphology of CeO(2) thin film. Response studies carried out using differential pulsed voltammetry (DPV) and optical measurements show that the GOx/CeO(2)/Pt bio-electrode shows linearity in the range of 25-300 mg/dl of glucose concentration. The low value of Michaelis-Menten constant (1.01 mM) indicates enhanced enzyme affinity of GOx to glucose. The observed results show promising application of the nanoporous CeO(2) thin film for glucose sensing application without any surface functionalization or mediator.

Chemical and structural analyses of subsurface crevices formed during spontaneous deposition of cerium-based conversion coatings

Energy Technology Data Exchange (ETDEWEB)

Heller, Daimon K, E-mail: dkheller@mmm.com; Fahrenholtz, William G., E-mail: billf@mst.edu; O' Keefe, Matthew J., E-mail: mjokeefe@mst.edu

2011-11-15

Subsurface crevices formed during the deposition of cerium-based conversion coatings were analyzed in cross-section to assess the effect of deposition and post-treatment on the structure and chemistry of phases present. An Al-O containing phase, believed to be amorphous Al(OH){sub 3}, was formed in crevices during coating deposition. Analysis by energy dispersive X-ray spectroscopy revealed the presence of up to 1.6 at.% chlorine within the Al-O phase, which was likely a product of soluble chlorides that were present in the coating solution. Cerium was not detected within crevices. After post-treatment in an 85 deg. C aqueous phosphate solution, the chloride concentration was reduced to {<=} 0.30 at.% and electron diffraction of the Al-O phase produced ring patterns, indicating it had crystallized. Some diffraction patterns could be indexed to gibbsite (Al(OH){sub 3}), but others are believed to be a combination of hydrated aluminum hydroxides and/or oxides. Aluminum phosphate was not identified. Separately from its effect on cerium-based conversion coatings, phosphate post-treatment improved the corrosion resistance of Al 2024-T3 substrates by acting to crystallize Al(OH){sub 3} present on interior surfaces of crevices and by reducing the chloride concentration in this phase. - Highlights: {yields} Analysis of subsurface crevices formed during deposition of Ce-based conversion coatings. {yields} Phosphate post-treatment improved corrosion protection in salt spray testing. {yields} Post-treatment affected the composition and structure of regions within crevices. {yields} Crystallized Al(OH){sub 3} within crevices acted as a more effective barrier to chloride ions.

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.

Bimetallic low thermal-expansion panels of Co-base and silicide-coated Nb-base alloys for high-temperature structural applications

International Nuclear Information System (INIS)

Rhein, R.K.; Novak, M.D.; Levi, C.G.; Pollock, T.M.

2011-01-01

Research highlights: → Low net thermal expansion bimetallic structural lattice constructed. → Temperatures on the order of 1000 deg. C reached. → Improved silicide coating for niobium alloy developed. - Abstract: The fabrication and high temperature performance of low thermal expansion bimetallic lattices composed of Co-base and Nb-base alloys have been investigated. A 2D sheet lattice with a coefficient of thermal expansion (CTE) lower than the constituent materials of construction was designed for thermal cycling to 1000 deg. C with the use of elastic-plastic finite element analyses. The low CTE lattice consisted of a continuous network of the Nb-base alloy C-103 with inserts of high CTE Co-base alloy Haynes 188. A new coating approach wherein submicron alumina particles were incorporated into (Nb, Cr, Fe) silicide coatings was employed for oxidation protection of the Nb-base alloy. Thermal gravimetric analysis results indicate that the addition of submicron alumina particles reduced the oxidative mass gain by a factor of four during thermal cycling, increasing lifetime. Bimetallic cells with net expansion of 6 x 10 -6 /deg. C and 1 x 10 -6 /deg. C at 1000 deg. C were demonstrated and their measured thermal expansion characteristics were consistent with analytical models and finite element analysis predictions.

A new oxidimetric reagent: potassium dichromate in a strong phosphoric acid medium--VII. Photometric titration of vanadium(IV) and of cerium(III) alone and in mixtures with iroN(II).

Science.gov (United States)

Rao, G G; Rao, P K

1967-01-01

Vanadium(IV) can be accurately titrated with potassium dichromate in media containing phosphoric acid of 3-12M concentration: the change in absorption of vanadium(IV) is followed in the region 660 mmicro using a red filter. It is more convenient to carry out the titration in 3M phosphoric acid because at higher concentrations chloride, nitrate, cerium(III) and manganese(II) may interfere. Photoelcetric titration is more convenient than potentiometric because the former can be made in a 3M phosphoric acid medium, whereas the latter is possible only in 12M phosphoric acid. The simultaneous differential photometric titration of iron(II) and vanadium(IV) is also possible. Conditions have been found for the photometric titration of cerium(III) and of cerium(III) plus iron(II). The titration is carried out (at 450 mmicro or with a blue filter) in about 10.5M phosphoric acid. Application of the method to a cerium mineral is considered.

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

Absolute transition probabilities for 559 strong lines of neutral cerium

Energy Technology Data Exchange (ETDEWEB)

Curry, J J, E-mail: jjcurry@nist.go [National Institute of Standards and Technology, Gaithersburg, MD 20899-8422 (United States)

2009-07-07

Absolute radiative transition probabilities are reported for 559 strong lines of neutral cerium covering the wavelength range 340-880 nm. These transition probabilities are obtained by scaling published relative line intensities (Meggers et al 1975 Tables of Spectral Line Intensities (National Bureau of Standards Monograph 145)) with a smaller set of published absolute transition probabilities (Bisson et al 1991 J. Opt. Soc. Am. B 8 1545). All 559 new values are for lines for which transition probabilities have not previously been available. The estimated relative random uncertainty of the new data is +-35% for nearly all lines.

The effect of post-treatment time and temperature on cerium-based conversion coatings on Al 2024-T3

Energy Technology Data Exchange (ETDEWEB)

Heller, Daimon K [Missouri University of Science and Technology, 101 Straumanis Hall, 401 West 16th Street, Rolla, MO 65409 (United States)], E-mail: dkhvwb@mst.edu; Fahrenholtz, William G. [Missouri University of Science and Technology, 101 Straumanis Hall, 401 West 16th Street, Rolla, MO 65409 (United States)], E-mail: billf@mst.edu; O' Keefe, Matthew J. [Missouri University of Science and Technology, 101 Straumanis Hall, 401 West 16th Street, Rolla, MO 65409 (United States)

2010-02-15

Corrosion performance, morphology, and electrochemical characteristics of cerium-based conversion coatings on Al 2024-T3 were examined as a function of phosphate post-treatment time and temperature. Corrosion resistance improved after post-treatment in 2.5 wt.% NH{sub 4}H{sub 2}PO{sub 4} for times up to 10 min or temperatures up to 85 deg. C. Electrochemical impedance spectroscopy and polarization testing correlated to neutral salt spray corrosion performance. Hydrated cerium oxide and peroxide species present in the as-deposited coatings were transformed to CePO{sub 4}.H{sub 2}O for post-treatments at longer times and/or higher temperatures. Based on these results, processes active during post-treatment are kinetically dependent and strongly influenced by the post-treatment time and temperature.

Contribution to research on the metabolism of fission product. Studies on the physico-chemical state and the metabolic fate of radio-cerium solution; Contribution a l'etude du metabolisme des produits de fission. Recherches sur l'etat physico-chimique et le devenir metabolique des solutions de radiocerium

Energy Technology Data Exchange (ETDEWEB)

Aeberhardt, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-07-01

This paper describes a study of the physico-chemical state of radio-cerium in dilute solutions on the tracer scale, as a function of the pH of the solution. The way in which this radioelement is transported in the blood is studied in vitro and in vivo, with reference to the ionic or colloidal state of the radio-cerium used. The distribution of cerium amongst the various components of the blood is studied by a new method of blood fractionation and by paper electrophoresis. Evidence of a cerium globulin connection is shown in the case of ionic cerium. A study of the initial distribution of radio-cerium in rats, after intravenous administration of ionic or colloidal solutions, shows considerable differences according to the physico-chemical state of the cerium injected. (author) [French] Ce travail presente une etude de l'etat physico-chimique du radiocerium en solutions diluees a l'echelle des indicateurs, en fonction du pH de la solution. En fonction de l'etat ionique ou colloidal du radiocerium utilise, le mode de transport de ce radioelement dans le sang est etudie in vitro et in vivo. La distribution du cerium entre les differents constituants du sang est etudiee par une methode nouvelle de fractionnement du sang et par electrophorese sur papier. L'existence d'une liaison cerium-globuline est mise en evidence dans le cas du cerium ionique. L'etude de la distribution initiale du radiocerium, chez le rat apres administration par voie veineuse de solutions ionique ou colloidale, montre des differences importantes en fonction de l'etat physico-chimique du cerium injecte. (auteur)

Cerium dioxide as a new reactive sorbent for fast degradation of parathion methyl and some other organophosphates

Czech Academy of Sciences Publication Activity Database

Janos, P.; Kuráň, P.; Kormunda, M.; Štengl, Václav; Matys Grygar, Tomáš; Došek, M.; Šťastný, M.; Ederer, J.; Pilařová, V.; Vrtoch, L.

2014-01-01

Roč. 32, č. 4 (2014), s. 360-370 ISSN 1002-0721 Institutional support: RVO:61388980 Keywords : cerium dioxide * carbonate precursor * lanthanides * organophosphate pesticide * parathion methyl * chemical warfare agents Subject RIV: CA - Inorganic Chemistry Impact factor: 1.261, year: 2014

Chemiluminescence behavior based on oxidation reaction of rhodamine B with cerium(IV) in sulfuric acid medium

International Nuclear Information System (INIS)

Ma Yongjun; Jin Xiaoyong; Zhou Min; Zhang Ziyu; Teng Xiulan; Chen Hui

2003-01-01

The chemiluminescence (CL) of the rhodamine B (RhB)-cerium(IV) system was investigated by flow-injection. Rhodamine B was suggested to be a suitable chemiluminescent reagent in acidic conditions. When the concentration of rhodamine B was 100 mg l -1 and cerium sulfate was 1.6 mmol l -1 in sulfuric acid, the chemiluminescent intensity was found to be highest by using 0.3 mol l -1 sulfuric acid as a carrier solution. The particular chemiluminescent system could tolerate such distinct acidic environments that it was utilized for detecting many compounds that are stable in acidic solutions. Furthermore, by virtue of IR, UV-Vis and luminescence spectroscopic measurements, the chemiluminescent behavior of rhodamine B was studied and a possible mechanism for this chemiluminescent reaction was proposed. The emitter was affirmed to be a radical species due to one of the oxidation products of RhB; the chemiluminescent emissive wavelength was about 425 nm

Chemiluminescence behavior based on oxidation reaction of rhodamine B with cerium(IV) in sulfuric acid medium

Energy Technology Data Exchange (ETDEWEB)

Ma Yongjun; Jin Xiaoyong; Zhou Min; Zhang Ziyu; Teng Xiulan; Chen Hui

2003-08-18

The chemiluminescence (CL) of the rhodamine B (RhB)-cerium(IV) system was investigated by flow-injection. Rhodamine B was suggested to be a suitable chemiluminescent reagent in acidic conditions. When the concentration of rhodamine B was 100 mg l{sup -1} and cerium sulfate was 1.6 mmol l{sup -1} in sulfuric acid, the chemiluminescent intensity was found to be highest by using 0.3 mol l{sup -1} sulfuric acid as a carrier solution. The particular chemiluminescent system could tolerate such distinct acidic environments that it was utilized for detecting many compounds that are stable in acidic solutions. Furthermore, by virtue of IR, UV-Vis and luminescence spectroscopic measurements, the chemiluminescent behavior of rhodamine B was studied and a possible mechanism for this chemiluminescent reaction was proposed. The emitter was affirmed to be a radical species due to one of the oxidation products of RhB; the chemiluminescent emissive wavelength was about 425 nm.

Effect of Pressure on the Ferromagnetic Cerium Compound CeCu9Sn4

International Nuclear Information System (INIS)

Ishii, Y.; Mori, N.; Hedo, M.; Uwatoko, Y.

2003-01-01

Electrical resistivity measurements under hydrostatic pressure up to 2.2 GPa was carried out for a ferromagnetic ternary cerium compound CeCu 9 Sn 4 . The ferromagnetic transition temperature increases with increasing pressure up to 0.8 GPa and then decreases with increasing pressure above 1 GPa. Origins of this pressure dependence may be the competition between magnetic interaction in the c-plane and along the c-direction. (author)

Ab initio MCHF structural calculations of Mg-like cerium

Science.gov (United States)

Wajid, Abdul; Jabeen, S.; Husain, Abid

2018-05-01

Energy levels and emission line wavelengths of high-Z materials are useful for impurity diagnostics in the next generation fusion devices. For this here we have calculated E1, M2 transitions, oscillator strengths, and transition probabilities for transitions among the terms belonging to the 2p63s2, 2p63s3p, 2p63p2 and 2p63s3d for the Magnesium like cerium (Ce XLVII) using the GRASP2K package based on the fully relativistic multi-configuration Dirac-Fock method. The electron correlation effects, Breit interaction and quantum electrodynamics effects to the atomic state wave functions and the corresponding energies have been taken into account.