WorldWideScience

Sample records for chromium silicides

  1. 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.

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

    OpenAIRE

    Vlasova M.; Kakazey M.; Gonzales-Rodriguez J.G.; Dominguez G.; Ristić Momčilo M.; Scherbina O.; Tomila T.; Isaeva L.; Timofeeva I.I.; Bukov A.

    2002-01-01

    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 ...

  3. Interdiffusion and growth of chromium silicide at the interface of Cr/Si(As) system during rapid thermal annealing

    International Nuclear Information System (INIS)

    In this work, the solid-state reaction between a thin film of chromium and silicon has been studied using Rutherford backscattering spectroscopy, X-ray diffraction and the sheet resistance measurements. The thickness of 100 nm chromium layer has been deposited by electronic bombardment on Si (100) substrates, part of them had previously been implanted with arsenic ions of 1015 at/cm2 doses and an energy of 100 keV. The samples were heat treated under rapid thermal annealing at 500 oC for time intervals ranging from 15 to 60 s. The rapid thermal annealing leads to a reaction at the interface Cr/Si inducing the formation and the growth of the unique silicide CrSi2, but no other phase can be detected. For samples implanted with arsenic, the saturation value of the sheet resistance is approximately 1.5 times higher than for the non-implanted case.

  4. Chromium

    Science.gov (United States)

    ... health risks of too much chromium? Chromium and medication interactions Supplemental sources of chromium Chromium and Healthful Diets References Disclaimer What foods provide chromium? Chromium is widely distributed in the ...

  5. Reprocessing RERTR silicide fuels

    International Nuclear Information System (INIS)

    The Reduced Enrichment Research and Test Reactor Program is one element of the United States Government's nonproliferation effort. High-density, low-enrichment, aluminum-clad uranium silicide fuels may be substituted for the highly enriched aluminum-clad alloy fuels now in use. Savannah River Laboratory has performed studies which demonstrate reprocessability of spent RERTR silicide fuels at Savannah River Plant. Results of dissolution and feed preparation tests and solvent extraction processing demonstrations with both unirradiated and irradiated uranium silicide fuels are presented

  6. Metal silicide nanowires

    Science.gov (United States)

    Chen, Lih-Juann; Wu, Wen-Wei

    2015-07-01

    The growth, properties and applications of metal silicide nanowires (NWs) have been extensively investigated. The investigations have led to significant advance in the understanding of one-dimensional (1D) metal silicide systems. For example, CoSi is paramagnetic in bulk form, but ferromagnetic in NW geometry. In addition, the helimagnetic phase and skyrmion state in MnSi are stabilized by NW morphology. The influencing factors on the growth of silicide phase have been elucidated for Ni-Si, Pt-Si, and Mn-Si systems. Promising results were obtained for spintronics, non-volatile memories, field emitter, magnetoresistive sensor, thermoelectric generator and solar cells. However, the main thrust has been in microelectronic devices and integrated circuits. Transistors of world-record small size have been fabricated. Reconfigurable Si NW transistors, dually active Si NW transistors and circuits with equal electron and hole transport have been demonstrated. Furthermore, multifunctional devices and logic gates with undoped Si NWs were reported. It is foreseen that practical applications will be realized in the near future.

  7. High temperature structural silicides

    International Nuclear Information System (INIS)

    Structural silicides have important high temperature applications in oxidizing and aggressive environments. Most prominent are MoSi2-based materials, which are borderline ceramic-intermetallic compounds. MoSi2 single crystals exhibit macroscopic compressive ductility at temperatures below room temperature in some orientations. Polycrystalline MoSi2 possesses elevated temperature creep behavior which is highly sensitive to grain size. MoSi2-Si3N4 composites show an important combination of oxidation resistance, creep resistance, and low temperature fracture toughness. Current potential applications of MoSi2-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

  8. Effect of P+ ions on the microstructure and the nature of the formed silicides in the Cr/Si system

    International Nuclear Information System (INIS)

    The effect of the phosphorus on the microstructure and on the nature of the formed silicide in the annealed Cr/Si system is studied. The chromium layer is deposited by electron gun evaporation on the undoped and P+ doped monocrystalline silicon. Cross-sectional transmission electron microscopy (XTEM) investigation of the samples, annealed at 475 deg. C for different times, shows that the presence of phosphorus leads to the formation of CrSi2 disilicide, free of defects, and Cr3Si silicide for lower and higher annealing times, respectively. In the case of undoped substrate the formed CrSi2 disilicide is stable and contains a high concentration of stacking faults when the chromium is partially consumed

  9. On Silicides in High Temperature Titanium Alloys

    Directory of Open Access Journals (Sweden)

    C. Ramachandra

    1986-04-01

    Full Text Available High temperature titanium alloys like IMI 685 contain small amounts of silicon (~ 0.25 wt. per cent to improve creep resistance. Different types of silicides, namely Ti5Si3 (TiZr5Si3(S1 and (TiZr6 Si3 (S2, have been observed to precipitate in various silicon-bearing titanium alloys depending upon their composition and heat treatment. The precipitation of silicides, their orientation relationship with the matrix in different alloys, and the beneficial influence of thermo-mechanical treatment on the distribution of silicides have been pointed out. The effect of silicides on mechanical properties and fracture of the commercial alloy IMI 685 is also indicated.

  10. LEU silicide programs at Babcock and Wilcox

    International Nuclear Information System (INIS)

    The low enriched silicide development project at Babcock and Wilcox has matured into a production operation that has resulted in the completion of fuel elements for three research reactors; ORR, R-2 Studsvik and SAPHIR. Characteristic anomalies of silicide fuel which make the fabrication of fuel plates and elements more difficult than UAlx, have either been avoided, eliminated or significantly improved. One such anomaly is the reaction between uranium silicide fuel and aluminum matrix material. A detailed analysis was performed to characterize the extent of this reaction. Data suggests that a solid state diffusion of aluminum atoms into the uranium silicide lattice results in the formation of several intermediate Al-Si-U phases before forming a stable UAl4 phase

  11. Nanoscale contact engineering for Si/Silicide nanowire devices

    OpenAIRE

    Lin, Yung-chen

    2012-01-01

    Metal silicides have been used in silicon technology as contacts to achieve high device performance and desired device functions. The growth and applications of silicide materials have recently attracted increasing interest for nanoscale device applications. Nanoscale silicide materials have been demonstrated with various synthetic approaches. Solid state reaction wherein high quality silicides form through diffusion of metal atoms into silicon nano-templates and the subsequent phase transfor...

  12. Robust micromachining of compliant mechanisms using silicides

    International Nuclear Information System (INIS)

    We introduce an innovative sacrificial surface micromachining process that enhances the mechanical robustness of freestanding microstructures and compliant mechanisms. This process facilitates the fabrication, and improves the assembly yield of the out-of-plane micro sensors and actuators. Fabrication of a compliant mechanism using conventional sacrificial surface micromachining results in a non-planar structure with a step between the structure and its anchor. During mechanism actuation or assembly, stress accumulation at the structure step can easily exceed the yield strength of the material and lead to the structure failure. Our process overcomes this topographic issue by virtually eliminating the step between the structure and its anchor, and achieves planarization without using chemical mechanical polishing. The process is based on low temperature and post-CMOS compatible nickel silicide technology. We use a layer of amorphous silicon (a-Si) as a sacrificial layer, which is locally converted to nickel silicide to form the anchors. High etch selectivity between silicon and nickel silicide in the xenon difluoride gas (sacrificial layer etchant) enables us to use the silicide to anchor the structures to the substrate. The formed silicide has the same thickness as the sacrificial layer; therefore, the structure is virtually flat. The maximum measured step between the anchor and the sacrificial layer is about 10 nm on a 300 nm thick sacrificial layer. (paper)

  13. New silicides for new niobium protective coatings

    International Nuclear Information System (INIS)

    Efforts to improve at high temperature the oxidation resistance of pure niobium or commercial niobium alloys have led to the development of a pack cementation process for the co-deposition of Si, Ti, Cr and Fe. Owing to the knowledge of the quaternary Nb(Ti)-T-Cr-Si phase diagrams (T=Fe or Co or Ni) and of the crystallographic features of phases present in the silicide coatings, new protective coatings have been applied on pure niobium and Cb752 alloy. The results of the crystallographic study of three new silicides isostructural with Nb3Fe3CrSi6, in which Nb is substituted by Ti and Fe by Co or Ni are reported. The oxidation performances of two new coatings mainly consisting of such a silicide are also outlined. (orig.)

  14. On Silicides in High Temperature Titanium Alloys

    OpenAIRE

    Ramachandra, C.; Vakil Singh; P. Rama Rao

    1986-01-01

    High temperature titanium alloys like IMI 685 contain small amounts of silicon (~ 0.25 wt. per cent) to improve creep resistance. Different types of silicides, namely Ti5Si3 (TiZr)5Si3(S1) and (TiZr)6 Si3 (S2), have been observed to precipitate in various silicon-bearing titanium alloys depending upon their composition and heat treatment. The precipitation of silicides, their orientation relationship with the matrix in different alloys, and the beneficial influence of thermo-mechanical treatm...

  15. On the kinetics of platinum silicide formation

    NARCIS (Netherlands)

    Faber, Erik J.; Wolters, Rob A.M.; Schmitz, Jurriaan

    2011-01-01

    In this work, the kinetics of platinum silicide formation for thin Pt films (50 nm) on monocrystalline <100> silicon is investigated via in situ resistance measurements under isothermal (197–275 °C) conditions. For Pt2Si diffusion limited growth was observed. For PtSi formation, however, no linear r

  16. Challenges of nickel silicidation in CMOS technologies

    Energy Technology Data Exchange (ETDEWEB)

    Breil, Nicolas [IBM Semiconductor Research and Development Center (SRDC), East Fishkill, NY (United States); Lavoie, Christian [IBM T.J. Watson Research Center, Yorktown Heights, NY (United States); Ozcan, Ahmet [IBM Semiconductor Research and Development Center (SRDC), East Fishkill, NY (United States); Baumann, Frieder [IBM Semiconductor Research and Development Center (SRDC), East Fishkill, NY (United States); Klymko, Nancy [IBM Semiconductor Research and Development Center (SRDC), East Fishkill, NY (United States); Nummy, Karen [IBM Semiconductor Research and Development Center (SRDC), East Fishkill, NY (United States); Sun, Bing [IBM Semiconductor Research and Development Center (SRDC), East Fishkill, NY (United States); Jordan-Sweet, Jean [IBM T.J. Watson Research Center, Yorktown Heights, NY (United States); Yu, Jian [IBM Semiconductor Research and Development Center (SRDC), East Fishkill, NY (United States); Zhu, Frank [IBM Semiconductor Research and Development Center (SRDC), East Fishkill, NY (United States); Narasimha, Shreesh [IBM Semiconductor Research and Development Center (SRDC), East Fishkill, NY (United States); Chudzik, Michael [IBM Semiconductor Research and Development Center (SRDC), East Fishkill, NY (United States)

    2015-04-01

    In our paper, we review some of the key challenges associated with the Ni silicidation process in the most recent CMOS technologies. The introduction of new materials (e.g.SiGe), and of non-planar architectures bring some important changes that require fundamental investigation from a material engineering perspective. Following a discussion of the device architecture and silicide evolution through the last CMOS generations, we focus our study on a very peculiar defect, termed NiSi-Fangs. We describe a mechanism for the defect formation, and present a detailed material analysis that supports this mechanism. We highlight some of the possible metal enrichment processes of the nickel monosilicide such as oxidation or various RIE (Reactive Ion Etching) plasma process, leading to a metal source available for defect formation. Furthermore, we investigate the NiSi formation and re-formation silicidation differences between Si and SiGe materials, and between (1 0 0) and (1 1 1) orientations. Finally, we show that the thermal budgets post silicidation can lead to the formation of NiSi-Fangs if the structure and the processes are not optimized. Beyond the understanding of the defect and the discussion on the engineering solutions used to prevent its formation, the interest of this investigation also lies in the fundamental learning within the Ni–Pt–Si–Ge system and some additional perspective on Ni-based contacts to advanced microelectronic devices.

  17. 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.

  18. New Manganese Silicide Mineral Phase in an Interplanetary Dust Particle

    Science.gov (United States)

    Nakamura-Messenger, K.; Keller, L. P.; Clemett, S. J.; Jones, J. H.; Palma, R. L.; Pepin, R. O.; Kloeck, W.; Zolensky, M. E.; Messenger, S.

    2008-01-01

    Comet 26P/Grigg-Skjellerup was identified as a source of an Earth-crossing dust stream with low Earth-encounter velocities, with peak anticipated fluxes during April in 2003 and 2004 [1]. In response to this prediction, NASA performed dedicated stratospheric dust collections using high altitude aircraft to target potential interplanetary dust particles (IDPs) from this comet stream in April 2003. Several IDPs from this collection have shown unusually low noble gas abundances [2] consistent with the predicted short space exposure ages of Grigg-Skjellerup dust particles [1]. High abundances of large D enrichments [3] and presolar grains [4] in IDPs from this collection are also consistent with an origin from the comet Grigg-Skjellerup. Here we report a new mineral from one of the cluster IDPs of the "Grigg-Skjellerup" collection, L2055. Our report focuses on an unusual manganese-iron-chromium silicide phase that, to our knowledge, has not been observed previously in nature. This unique phase may also shed light on the genesis of the enigmatic low-Fe,Mn-enriched (LIME) olivine that has been previously reported in IDPs and meteorites [5].

  19. Irradiation behavior of miniature experimental uranium silicide fuel plates

    International Nuclear Information System (INIS)

    Uranium silicides, because of their relatively high uranium density, were selected as candidate dispersion fuels for the higher fuel densities required in the Reduced Enrichment Research and Test Reactor (RERTR) Program. Irradiation experience with this type of fuel, however, was limited to relatively modest fission densities in the bulk from, on the order of 7 x 1020 cm-3, far short of the approximately 20 x 1020 cm-3 goal established for the RERTR program. The purpose of the irradiation experiments on silicide fuels on the ORR, therefore, was to investigate the intrinsic irradiation behavior of uranium silicide as a dispersion fuel. Of particular interest was the interaction between the silicide particles and the aluminum matrix, the swelling behavior of the silicide particles, and the maximum volume fraction of silicide particles that could be contained in the aluminum matrix

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

    International Nuclear Information System (INIS)

    Silicide layers can be used as low resistance contacts in semiconductor devices. The formation of a metal rich palladium silicide Pd2Si is discussed. A palladium film 100A thick is deposited at 3000C and the resulting silicide layer used as an ohmic contact in an n + p silicon detector. This rugged contact has electrical characteristics comparable with existing evaporated gold contacts and enables the use of more reproducible bonding techniques. (author)

  1. Formation and properties of nanometer-thick platinum silicide layers

    OpenAIRE

    Conforto, Egle

    1996-01-01

    Platinum silicide films are widely used in silicon devices for ohmic and Schottky contacts. It has been demonstrated in the recent years that Schottky barriers employing ultra-thin platinum silicide films (thickness < 10 nm) are useful for photodetection in the near infrared. We have studied the formation of thin platinum silicide films and their electrical properties as a function of the annealing temperature in presence of an interfacial native sili...

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

    International Nuclear Information System (INIS)

    Over the last several years, uranium silicide fuels have been under development as low-enriched uranium (LEU) targets for Mo-99. The use of LEU silicide is aimed at replacing the UAlx alloy in the highly-enriched uranium dissolution process. A process to recover Mo-99 from low-enriched uranium silicide is being developed at Argonne National Laboratory. The uranium silicide is dissolved in alkaline hydrogen peroxide. Experiments performed to determine the optimum dissolution procedure are discussed, and the results of dissolving a portion of a high-burnup (>40%) U3Si2 miniplate are presented. Future work related to Mo-99 separation and waste disposal are also discussed

  3. Fusion silicide coatings for tantalum alloys.

    Science.gov (United States)

    Warnock, R. V.; Stetson, A. R.

    1972-01-01

    Calculation of the performance of fusion silicide coatings under simulated atmospheric reentry conditions to a maximum temperature of 1810 K (2800 F). Both recently developed and commercially available coatings are included. Data are presented on oxidation rate with and without intentional defecting, the influence of the coatings on the ductile-brittle bend transition temperature, and the mechanical properties. Coatings appear capable of affording protection for at least 100 simulated cycles to 2600 F and 63 cycles to 2800 F.

  4. Microanalysis of tungsten silicide/polysilicon interface

    International Nuclear Information System (INIS)

    The presence of a thin (10-30 Angstrom) oxide (native oxide) layer on a silicon surface prior to the deposition of another film on that surface can contribute to difficulties with subsequent device processing steps, e.g. contact metallization and high-temperature annealing or oxidation. Thus the in situ process capability of native oxide removal affords advantage over the conventional method of aqueous hydrofluoric acid cleaning prior to a film deposition step. The paper describes such a technique, in which an in situ pre-deposition clean with C2F6 gas, using reactive ion etching (RIE) prior to tungsten silicide deposition, is employed. This technique allows post-silicide deposition high-temperature heat treatment and wet oxidation without loss of film adhesion or other obvious degradative effects. We also report the use of Secondary Ion Mass Spectrometry (SIMS) to show that this procedure has been effective in the removal of the oxide layer prior to silicide deposition. This study includes definition of the RIE etch parameters which provide acceptable etch selectivity of the oxide to silicon, and avoidance of excessive fluoropolymer formation on the silicon surface

  5. Silicides and germanides for nano-CMOS applications

    Energy Technology Data Exchange (ETDEWEB)

    Kittl, J.A. [IMEC, Kapeldreef 75, 3001 Leuven (Belgium)], E-mail: kittlj@imec.be; Opsomer, K.; Torregiani, C.; Demeurisse, C.; Mertens, S.; Brunco, D.P.; Van Dal, M.J.H.; Lauwers, A. [IMEC, Kapeldreef 75, 3001 Leuven (Belgium)

    2008-12-05

    An overview of silicides and germanides for nano-CMOS applications is presented. The historical evolution describing the migration from the use of Ti silicide to Co silicide to Ni silicide as contacting material is first discussed. These changes in silicide material were mainly motivated by the inability to form the target low resistivity silicide phase in small structures due to low nucleation density. This issue was found first for the low resistivity C54 TiSi{sub 2} at linewidths below 200 nm and later for the low resistivity CoSi{sub 2}, at linewidths below 40 nm. A detailed description of scalability and thermal stability issues for NiSi is then presented. No nucleation issues were found in small structures for NiSi, which grows by diffusion or interface limited kinetics with Ni as main moving species. However, silicidation can be excessive in small structures due to Ni diffusion from surrounding areas, resulting in thicker films than targeted in small devices. This can be controlled by using a silicidation process with two rapid thermal processing steps, the first one to control the amount of Ni reacted and the second one to convert the silicide to the target low resistivity monosilicide phase. One of the main issues for applications of NiSi is its low thermal stability: thin NiSi films agglomerate at relatively low temperatures. The process window and thermal stability of Ni and Pt-based films reacted with Si, Si:Ge and Si:C substrates is reviewed. Addition of Ge is shown to degrade thermal stability while addition of C or Pt improves it. Contact resistivity considerations and implementation of dual band-edge silicides are discussed, as well as promising results for the extension of Ni-based silicides to future nodes. Finally a brief overview of germanides is presented discussing NiGe and PdGe as main candidates.

  6. High temperature protective silicide coatings for titanium-niobium alloys

    International Nuclear Information System (INIS)

    The accomplished investigation of heat resistance of silicide coatings on titanium - (30-50)% niobium alloys has revealed that the coatings ensure reliable corrosion protection up to 1100 deg due to formation of heat resistant disilicides and a silicon dioxide layer on alloy surface. Silicide coatings possess particular ductility

  7. Pack cementation Cr-Al coating of steels and Ge-doped silicide coating of Cr-Nb alloy

    Energy Technology Data Exchange (ETDEWEB)

    He, Y.R.; Zheng, M.H.; Rapp, R.A. [Ohio State Univ., Columbus, OH (United States)

    1995-08-01

    Carbon steels or low-alloy steels used in utility boilers, heat exchangers, petrochemical plants and coal gasification systems are subjected to high temperature corrosion attack such as oxidation, sulfidation and hot corrosion. The pack cementation coating process has proven to be an economical and effective method to enhance the corrosion resistance by modifying the surface composition of steels. With the aid of a computer program, STEPSOL, pack cementation conditions to produce a ferrite Cr-Al diffusion coating on carbon-containing steels by using elemental Cr and Al powders have been calculated and experimentally verified. The cyclic oxidation kinetics for the Cr-Al coated steels are presented. Chromium silicide can maintain high oxidation resistance up to 1100{degrees}C by forming a SiO{sub 2} protective scale. Previous studies at Ohio State University have shown that the cyclic oxidation resistance of MOSi{sub 2} and TiSi{sub 2} can be further improved by Ge addition introduced during coating growth. The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating in a single processing step for the ORNL-developed Cr-Nb advanced intermetallic alloy. The oxidation behavior of the silicide-coated Cr-Nb alloy was excellent: weight gain of about 1 mg/cm{sup 2} upon oxidation at 1100{degrees}C in air for 100 hours.

  8. Nano-Borides and Silicide Dispersed Composite Coating on AISI 304 Stainless Steel by Laser-Assisted HVOF Spray Deposition

    Science.gov (United States)

    Sharma, Prashant; Majumdar, Jyotsna Dutta

    2014-10-01

    The study concerned a detailed microstructural investigation of nano-borides (Cr2B and Ni3B) and nano-silicide (Ni2Si) dispersed γ-nickel composite coating on AISI 304 stainless steel by HVOF spray deposition of the NiCrBSi precursor powder and subsequent laser surface melting. A continuous wave diode laser with an applied power of 3 kW and scan speed of 20 mm/s in argon shroud was employed. The characterization of the surface in terms of microstructure, microtexture, phases, and composition were carried out and compared with the as-coated (high-velocity oxy-fuel sprayed) surface. Laser surface melting led to homogenization and refinement of microstructures with the formation of few nano-silicides of nickel along with nano-borides of nickel and chromium (Ni3B, Cr2B, and Cr2B3). A detailed microtexture analysis showed the presence of no specific texture in the as-sprayed and laser-melted surface of Cr2B and Ni3B phases. The average microhardness was improved to 750-900 VHN as compared to 250 VHN of the as-received substrate. Laser surface melting improved the microhardness further to as high as 1400 VHN due to refinement of microstructure and the presence of silicides.

  9. Infrared spectra of semiconducting silicides nanolayers

    Energy Technology Data Exchange (ETDEWEB)

    Baleva, M; Atanassov, A [Faculty of Physics, St. Kl. Ohridski University of Sofia, 5 J. Bourchier Blvd., 1164 Sofia (Bulgaria); Marinova, M [Solid State Physics Section, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)], E-mail: baleva@phys.uni-sofia.bg

    2008-05-01

    The infrared absorption is studied of samples consisting of a Si matrix with unburied nanolayers of the semiconducting silicides {beta}-FeSi{sub 2} and Mg{sub 2}Si. Features additional to those due to the transversal optical phonons of the compounds are observed. The features are interpreted in the framework of the appearance of surface and interface phonon polaritons, which absorb the light. Insofar as the frequencies of the longitudinal optical (LO) phonon-polariton modes are close to those of the LO phonon frequencies, the infrared transmittance of nanolayers can be regarded as a method for direct determination of these frequencies.

  10. 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.

  11. Thermoelectric performance of higher manganese silicide nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Saleemi, M. [Department of Materials and Nano Physics, KTH Royal Institute of Technology, Kista, Stockholm (Sweden); Famengo, A.; Fiameni, S.; Boldrini, S.; Battiston, S. [CNR, Institute for Energetics and Interphases (IENI-CNR), Corso Stati Uniti 4, I-35127 Padua (Italy); Johnsson, M. [Department of Materials and Environmental Chemistry, Stockholm University, Stockholm (Sweden); Muhammed, M.; Toprak, M.S. [Department of Materials and Nano Physics, KTH Royal Institute of Technology, Kista, Stockholm (Sweden)

    2015-01-15

    Highlights: • Fabrication of p-type higher manganese silicide by mechanical alloying. • Different concentrations Ytterbium (Yb) was used to form HMS nanocomposites. • HMS nanostructures were preserved by using spark plasma sintering (SPS). • HMS–Yb nanocomposites showed improved electrical performance. - Abstract: Higher manganese silicides (HMS) are proven to be promising candidates as p-type thermoelectric material in the temperature range of 400–700 K. In this work, a series of nanostructured (NS) bulk MnSi{sub 1.73} with different levels of Ytterbium inclusions were fabricated via ball milling and the solid state reaction was completed by spark plasma sintering (SPS). Nanopowders and SPS consolidated Yb–HMS nanocomposites (NC) were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to reveal the crystal structure and morphology respectively. High resolution transmission electron microscopy (HRTEM) coupled with energy dispersive X-ray spectroscopy (EDS) was used to investigate the material composition in bulk grains. Yb was observed to stay as nanoinclusions at the grain boundaries. TE transport properties, including Seebeck coefficient, electrical resistivity, and thermal diffusivity as well as charge carrier concentrations were evaluated. Thermal conductivity decreased with increasing Yb content, while the electrical conductivity improved for the highest Yb content. A highest figure of merit (ZT) of 0.42 at 600 °C was achieved for 1% Yb–HMS NC sample.

  12. Rare earth silicide nanowires on silicon surfaces

    International Nuclear Information System (INIS)

    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 DySi2-monolayer and the Dy3Si5-multilayer on the Si(111) surface are investigated in comparison to the known ErSi2/Si(111) and Er3Si5/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 in the same

  13. Heterogeneous chromium catalysts

    OpenAIRE

    2005-01-01

    The present invention relates to a heterogeneous chromium catalyst system for the polymerisation of ethylene and/or alpha olefins prepared by the steps of: (a) providing a silica-containing support, (b) treating the silica-containing support with a chromium compound to form a chromium-based silica-containing support, (c) activating the chromium-based silica-containing support, (d) chemically reducing the activated chromium-based silica-containing support to produce a precursor catalyst, (e) r...

  14. Thermal compatibility studies of unirradiated uranium silicide dispersed in aluminum

    International Nuclear Information System (INIS)

    Powder metallurgy dispersions of uranium silicides in an aluminum matrix have been developed by the international Reduced Enrichment for Research and Test Reactors program as a new generation of proliferation-resistant fuels. A major issue of concern is the compatibility of the fuel with the matrix material and the dimensional stability of this fuel type. A total of 45 miniplate-type fuel plates were annealed at 4000C for up to 1981 hours. A data base for the thermal compatibility of unirradiated uranium silicide dispersed in aluminum was established. No modification tested of a standard fuel plate showed any significant reduction of the plate swelling. The cause of the thermal growth of silicide fuel plates was determined to be a two-step process: (1) the reaction of the uranium silicide with aluminum to form U(AlSi)3 and (2) the release of hydrogen and subsequent creep and pillowing of the fuel plate. 9 references, 4 figures, 6 tables

  15. 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.

  16. 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

  17. Hexavalent Chromium Workshop

    Science.gov (United States)

    EPA is developing an updated IRIS assessment of hexavalent chromium. This assessment will evaluate the potential health effects of hexavalent chromium from oral and inhalation exposures. An important component of determining the cancer causing potential of ingested hexavalent chr...

  18. Chromium and Genomic Stability

    OpenAIRE

    Wise, Sandra S.; Wise, John Pierce

    2011-01-01

    Many metals serve as micronutrients which protect against genomic instability. Chromium is most abundant in its trivalent and hexavalent forms. Trivalent chromium has historically been considered an essential element, though recent data indicate that while it can have pharmacological effects and value, it is not essential. There are no data indicating that trivalent chromium promotes genomic stability and, instead may promote genomic instability. Hexavalent chromium is widely accepted as high...

  19. Irradiation behavior of experimental miniature uranium silicide fuel plates

    International Nuclear Information System (INIS)

    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 1020 cm-3, far short of he approximately 20 x 1020 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 % U3Si-Al plates to be in a stage of relatively rapid fission-gas-driven swelling at a fission density of 2 x 1020 cm-3. This fuel swelling will likely result in unacceptably large plate-thickness increases. The U3Si 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 1021 fission/cm3. The interdiffusion between fuel and matrix aluminum was found

  20. Plasmon dispersion in dysprosium silicide nanowires

    International Nuclear Information System (INIS)

    By depositing Dy at around half monolayer coverage on single domain Si(001) surfaces miscut by 4 towards [110], we have grown DySi2 nanowires in the submonolayer regime. Their plasmon spectrum has been studied by a combination of high resolution EELS and spot profile analysis of LEED in one instrument (ELS-LEED) which enables us to measure characteristic losses with high momentum resolution. Ultraclean conditions (P≤1 x 10-10 mbar during Dy deposition) allowed growth of high quality structures with minimal oxidation of Dy. Deposition of Dy at 500 C results in the formation of single DySi2 nanowires on each terrace, leaving the periodicity of the clean Si surface unchanged. In contrast, deposition at room temperature and subsequent annealing to 500 C reduces the average terrace width by up to 20%. Clearest results in EELS were obtained for a silicide layer with 0.4 ML of Dy deposited at 500 C. Broad loss features in the range between 0 and 1 eV with typical dipole characteristics were detected, their position being strongly dependent on momentum transfer. As expected these characteristic losses have no dispersion normal to the wires, while parallel to the wires the dispersion is non-linear and goes to zero at zero momentum transfer. Thus the typical behavior of onedimensional surface plasmons is found

  1. Submicron Features in Higher Manganese Silicide

    Directory of Open Access Journals (Sweden)

    Yatir Sadia

    2013-01-01

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

  2. 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.

  3. Reaction layers structure of silicide coatings on niobium alloys

    International Nuclear Information System (INIS)

    This paper reports on fused silicide coatings that are used to protect niobium alloys against high temperature oxidation. Quantitative electron microprobe analysis was used to characterize the complex multilayer structure of Si-20w/oFE-20w/oCR fused silicide coating on four niobium containing alloys: niobium, Cb752, WC3009, and Nb-46.5 Ti. The outer coating layer structure on all four alloys was similar, consisting of either two or three phases. The three phase outer coating layer on the niobium, WC3009, and the Nb-Ti substrate alloys was determined to be made of two MSi phases and one MSi2 phase. This outer MSi2 phase contained base alloy elements. Coated samples were compared using cyclic oxidation testing. The fused silicide coating structure and protectiveness were determined to be a function of the base alloy composition

  4. Oxidation resistance of composite silicide coatings on niobium

    International Nuclear Information System (INIS)

    This paper reports the oxidation of NbSi2-MoSi2 composite silicide coatings produced by diffusive siliconizing of molybdenum films on a niobium surface. Molybdenum-coated niobium was siliconized and an x-ray microspectral analysis of the composite silicide coating showed the phase composition to be an ca 80-um-thick outer molybdenum disilicide film with a characteristic coarsely crystalline columnar structure, and inner ca 20-um film of niobium disilicide consisting of the tiny columnar crystals, and a substrate/coating interface comprising a thin, 2-3 um film of lower silicide, i.e., Nb5Si3. The average grain sizes, unit cell parameters, and x-ray determined densities of the Mo films obtained by various methods are shown

  5. Transition Metal Silicide Nanowires Growth and Electrical Characterization

    Institute of Scientific and Technical Information of China (English)

    PENG Zu-Lin; LIANG S.; DENG Luo-Gen

    2009-01-01

    We report the characterization of self-assembled epitaxially grown transition metal,Fe,Co,Ni,silicide nanowires(TM-NW)growth and electrical transport properties.NWs grown by reactive deposition epitaxy on various silicon surfaces show a dimension of 10nm by 5nm,and several micrometers in length.NW orientations strongly depend on substrate crystal orientation,and follow the substrate symmetry.By using conductive-AFM(c-AFM),the electron transport properties of one single NW were measured,the resistivity of crystalline nickel silicide NW was estimated to be 2×10~(-2) Ω·cm.

  6. Oxidation behavior of molybdenum silicides and their composites

    International Nuclear Information System (INIS)

    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 Mo5Si3 alloys that contained several concentrations of B. In addition, oxidation characteristics of MoSi2-Si3N4 composites that contained 20--80 vol.% Si3N4 were evaluated at 500--1,400 C

  7. TiSi2 integrity within a doped silicide process step

    International Nuclear Information System (INIS)

    Degradation of arsenic implanted titanium silicide (TiSi2) thin films as a result of thermal processing for shallow junction formation is investigated. Significant arsenic diffusion from the silicide overlayer into the silicon substrate has been detected by Rutherford Backscattering Spectrometry at drive-in temperatures > 1,050 C. Cross-sectional transmission electron micrographs have shown the silicide film become increasingly non-uniform as the thermal budget increases, ultimately leading to discontinuities forming in the silicide film. This observed degradation of the titanium silicide film is also supported by sheet resistance measurements which show the film to degrade significantly above a threshold thermal budget

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

    International Nuclear Information System (INIS)

    The present-day industrial scale production of 99Mo is fission based and involves thermal-neutron irradiation in research reactors of highly enriched uranium (HEU, > 20 % 235U) containing targets, followed by radiochemical processing of the irradiated targets resulting in the final product: a 99Mo 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, 235U) one. In the wake of that program studies were undertaken to convert HEU into LEU based 99Mo production. Both new targets and radiochemical treatments leading to 99Mo compounds were proposed. One of these targets is based on LEU silicide, U3Si2. Present paper aims at comparing LEU U3Si2 and LEU U3Si with another LEU target i.e. target material and arriving at some preferences pertaining to 99Mo production. (author)

  9. Silicon and silicide nanowires applications, fabrication, and properties

    CERN Document Server

    Tu, King-Ning

    2013-01-01

    This book comprises theoretical and experimental analysis of various properties of silicon nanocrystals, research methods and preparation techniques, and some promising applications. It comprises nine chapters. The first three are based on processing, the next three on properties, and the last three on applications of nanowires of silicon and silicides.

  10. A swelling model of LEU silicide fuel for KMRR

    International Nuclear Information System (INIS)

    A lot of efforts have been made internationally to understand the irradiation behavior and the safety characteristics of uranium silicide fuel. One of the important irradiation performance characteristics of the silicide dispersion fuel element is the diametral increase resulting from fuel swelling. This paper represents an attempt to develop the physical model for the swelling, DFSWELL, by modelling the basic irradiation behavior observed from in-reactor experiments. The most important part of developing the swelling model is the identification of the controlling physical processes. The swelling of the silicide fuel is comprised of the volume change due to three major components; (i) the formation of an interfacial layer between the fuel particle and matrix, (ii) the accumulation of gas bubble nucleation, (iii) the accumulation of solid fission products. In this study, the swelling of the fuel element is quantitatively estimated by considering temperature, fission rate, solid fission product build-up and gas bubble behavior. The DFSWELL model which takes into account the above physical components predicts well the absolute magnitude of silicide fuel swelling in accordance with the power histories in comparison with the experimental data

  11. Nickel silicides in semiconductor processing: thermal budget considerations

    International Nuclear Information System (INIS)

    Nickel silicide (NiSi) is emerging to be the choice material for contact application in semiconductor device processing for 65 nm technology node and beyond. However, process integration issues are yet to be completely understood and addressed. The focus of present work is to facilitate better understanding of the influence of thermal budget on nickel silicide solid-state reaction. The reaction couple consists of single-crystal silicon wafers with nickel layers deposited on them. Requirements for low temperature anneal and improved within wafer sheet resistance uniformity pose challenges for conventional lamp-based rapid thermal processing (RTP) due to lamp response effects on temperature controllability. Extendibility of such a system is presented with emphasis on process chamber technology. Low temperature 'spike' anneal is demonstrated for temperatures 2Si changes as a function of thermal exposure during the first anneal step; this plays an important role in determining the thermal stability of the low resistance mono-silicide during integration. It is postulated that lowering the Ni2Si/Si interface energy favors the delay (in temperature) of the agglomeration of the NiSi. RTP performance stability of less than 1 deg. C is presented for a sub-300 deg. C process. Understanding and resolving the issues around process monitoring methodologies for low temperature anneal are important. The ability to monitor the total thermal exposure down to sub-200 deg. C regime may be necessary for successful integration of nickel silicide in device manufacturing flow

  12. Deposition of aluminide and silicide based protective coatings on niobium

    International Nuclear Information System (INIS)

    We compare aluminide and alumino-silicide composite coatings on niobium using halide activated pack cementation (HAPC) technique for improving its oxidation resistance. The coated samples are characterized by SEM, EDS, EPMA and hardness measurements. We observe formation of NbAl3 in aluminide coating of Nb, though the alumino-silicide coating leads to formation primarily of NbSi2 in the inner layer and a ternary compound of Nb-Si-Al in the outer layer, as reported earlier (Majumdar et al. ). Formation of niobium silicide is preferred over niobium aluminide during alumino-silicide coating experiments, indicating Si is more strongly bonded to Nb than Al, although equivalent quantities of aluminium and silicon powders were used in the pack chemistry. We also employ first-principles density functional pseudopotential-based calculations to calculate the relative stability of these intermediate phases and the adhesion strength of the Al/Nb and Si/Nb interfaces. NbSi2 exhibits much stronger covalent character as compared to NbAl3. The ideal work of adhesion for the relaxed Al/Nb and Si/Nb interfaces are calculated to be 3226 mJ/m2 and 3545 mJ/m2, respectively, indicating stronger Nb-Si bonding across the interface.

  13. Deposition of aluminide and silicide based protective coatings on niobium

    Science.gov (United States)

    Majumdar, S.; Arya, A.; Sharma, I. G.; Suri, A. K.; Banerjee, S.

    2010-11-01

    We compare aluminide and alumino-silicide composite coatings on niobium using halide activated pack cementation (HAPC) technique for improving its oxidation resistance. The coated samples are characterized by SEM, EDS, EPMA and hardness measurements. We observe formation of NbAl3 in aluminide coating of Nb, though the alumino-silicide coating leads to formation primarily of NbSi2 in the inner layer and a ternary compound of Nb-Si-Al in the outer layer, as reported earlier (Majumdar et al. [11]). Formation of niobium silicide is preferred over niobium aluminide during alumino-silicide coating experiments, indicating Si is more strongly bonded to Nb than Al, although equivalent quantities of aluminium and silicon powders were used in the pack chemistry. We also employ first-principles density functional pseudopotential-based calculations to calculate the relative stability of these intermediate phases and the adhesion strength of the Al/Nb and Si/Nb interfaces. NbSi2 exhibits much stronger covalent character as compared to NbAl3. The ideal work of adhesion for the relaxed Al/Nb and Si/Nb interfaces are calculated to be 3226 mJ/m2 and 3545 mJ/m2, respectively, indicating stronger Nb-Si bonding across the interface.

  14. Oxidation of chromium telluride

    International Nuclear Information System (INIS)

    The authors study the interaction between chromium telluride and oxygen at elevated temperatures in view of its application in semiconductor technology. Thermodynamic analysis of the oxidation process and experimental data showed that the alloys of chromium telluride suffer oxidation in the presence of even traces of oxygen in a gaseous medium. Chromium telluride oxidation is a complex process that gives rise to various oxides and is accompanied by partial sublimation

  15. Oxidation of chromium telluride

    Energy Technology Data Exchange (ETDEWEB)

    Pakhomovskaya, N.S.; Iorga, E.V.; Sheveleva, T.F.; Solov' eva, A.E.

    1986-03-01

    The authors study the interaction between chromium telluride and oxygen at elevated temperatures in view of its application in semiconductor technology. Thermodynamic analysis of the oxidation process and experimental data showed that the alloys of chromium telluride suffer oxidation in the presence of even traces of oxygen in a gaseous medium. Chromium telluride oxidation is a complex process that gives rise to various oxides and is accompanied by partial sublimation.

  16. Nanoscale contact engineering for Silicon/Silicide nanowire devices

    Science.gov (United States)

    Lin, Yung-Chen

    Metal silicides have been used in silicon technology as contacts to achieve high device performance and desired device functions. The growth and applications of silicide materials have recently attracted increasing interest for nanoscale device applications. Nanoscale silicide materials have been demonstrated with various synthetic approaches. Solid state reaction wherein high quality silicides form through diffusion of metal atoms into silicon nano-templates and the subsequent phase transformation caught significant attention for the fabrication of nanoscale Si devices. Very interestingly, studies on the diffusion and phase transformation processes at nanoscale have indicated possible deviations from the bulk and the thin film system. Here we studied growth kinetics, electronic properties and device applications of nanoscale silicides formed through solid state reaction. We have grown single crystal PtSi nanowires and PtSi/Si/PtSi nanowire heterostructures through solid state reaction. TEM studies show that the heterostructures have atomically sharp interfaces free of defects. Electrical measurement of PtSi nanowires shows a low resistivity of ˜28.6 μΩ·cm and a high breakdown current density beyond 108 A/cm2. Furthermore, using single-crystal PtSi/Si/PtSi nanowire heterostructures with atomically clean interfaces, we have fabricated p-channel enhancement mode transistors with the best reported performance for intrinsic silicon nanowires to date. In our results, silicide can provide a clean and no Fermi level pinning interface and then silicide can form Ohmic-contact behavior by replacing the source/drain metal with PtSi. It has been proven by our experiment by contacting PtSi with intrinsic Si nanowires (no extrinsic doping) to achieve high performance p-channel device. By utilizing the same approach, single crystal MnSi nanowires and MnSi/Si/MnSi nanowire heterojunction with atomically sharp interfaces can also been grown. Electrical transport studies on Mn

  17. Ni based silicides for 45 nm CMOS and beyond

    Energy Technology Data Exchange (ETDEWEB)

    Lauwers, Anne [IMEC, Kapeldreef 75, 3001 Leuven (Belgium)]. E-mail: lauwersa@imec.be; Kittl, Jorge A. [IMEC, Texas Instruments (Belgium); Van Dal, Mark J.H. [IMEC, Philips Research Leuven (Belgium); Chamirian, Oxana [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Pawlak, Malgorzata A. [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Potter, Muriel de [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Lindsay, Richard [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Raymakers, Toon [Philips Research Laboratories, Prof. Holstlaan 4, 5656 AA Eindhoven (Netherlands); Pages, Xavier [IMEC, ASM Belgium (Belgium); Mebarki, Bencherki [Applied Materials (Belgium); Mandrekar, Tushar [Applied Materials Inc., Santa Clara, CA (United States); Maex, Karen [IMEC, Kapeldreef 75, 3001 Leuven (Belgium)

    2004-12-15

    Material issues that impact the applicability of Ni based silicides to CMOS flows were studied, including the excessive silicidation of narrow features, the growth kinetics of Ni{sub 2}Si and NiSi on single-crystalline and poly-crystalline silicon and the thermal degradation mechanisms. Ni{sub 2}Si was found to grow by diffusion controlled kinetics with an activation energy of about 1.55 eV on single-crystalline Si. As a result, the excessive silicidation in small features can be reduced in a 2-step Ni-silicide process by reducing the thermal budget of the first RTP step. The mechanisms of thermal degradation of NiSi were studied. Thin NiSi films were found to degrade morphologically while still in the monosilicide phase. Thick NiSi films degrade morphologically at low temperatures and by transformation to NiSi{sub 2} at high temperatures. The reaction of Ni with SiGe substrates and the effect of Ge on the thermal degradation of the Ni-germanosilicide were investigated. Activation energies for the thermal degradation of Ni(SiGe) on SiGe were found to be significantly smaller than the values found for the thermal degradation of NiSi on pure Si. The effect of alloying Ni with Pt or Ta was studied. NiSi films alloyed with Pt or Ta are found to be thermally more stable compared to pure NiSi. Alloying with Pt was found to improve the thermal stability of NiSi on narrow poly-Si gates. The kinetics of Ni{sub 2}Si and NiSi formation on poly silicon were determined as well as their dependence on dopants. The presence of B in high doses was found to slow down the silicide formation significantly. Dopant segregation to the NiSi/oxide interface was observed, which is believed to be responsible for the observed shifts in work function. The sheet resistance of fully Ni-silicided 100 nm poly Si/oxide stacks is found to be stable up to 800 deg. C.

  18. Ni based silicides for 45 nm CMOS and beyond

    International Nuclear Information System (INIS)

    Material issues that impact the applicability of Ni based silicides to CMOS flows were studied, including the excessive silicidation of narrow features, the growth kinetics of Ni2Si and NiSi on single-crystalline and poly-crystalline silicon and the thermal degradation mechanisms. Ni2Si was found to grow by diffusion controlled kinetics with an activation energy of about 1.55 eV on single-crystalline Si. As a result, the excessive silicidation in small features can be reduced in a 2-step Ni-silicide process by reducing the thermal budget of the first RTP step. The mechanisms of thermal degradation of NiSi were studied. Thin NiSi films were found to degrade morphologically while still in the monosilicide phase. Thick NiSi films degrade morphologically at low temperatures and by transformation to NiSi2 at high temperatures. The reaction of Ni with SiGe substrates and the effect of Ge on the thermal degradation of the Ni-germanosilicide were investigated. Activation energies for the thermal degradation of Ni(SiGe) on SiGe were found to be significantly smaller than the values found for the thermal degradation of NiSi on pure Si. The effect of alloying Ni with Pt or Ta was studied. NiSi films alloyed with Pt or Ta are found to be thermally more stable compared to pure NiSi. Alloying with Pt was found to improve the thermal stability of NiSi on narrow poly-Si gates. The kinetics of Ni2Si and NiSi formation on poly silicon were determined as well as their dependence on dopants. The presence of B in high doses was found to slow down the silicide formation significantly. Dopant segregation to the NiSi/oxide interface was observed, which is believed to be responsible for the observed shifts in work function. The sheet resistance of fully Ni-silicided 100 nm poly Si/oxide stacks is found to be stable up to 800 deg. C

  19. Hair chromium concentration and chromium excretion in tannery workers.

    OpenAIRE

    Saner, G; Yüzbasiyan, V; Cigdem, S

    1984-01-01

    Hair and urine samples were collected from 34 male tannery workers and from 12 normal adults. Eighteen of the workers dealt directly with chromium and the remaining 16 (controls) worked in the offices and kitchen of the same factory. All were found to be clinically healthy. Chromium was determined by flameless atomic absorption spectroscopy. When compared with normal adult values, urinary chromium concentration, Cr/Creatinine ratio, daily chromium excretion, and hair chromium, concentrations ...

  20. High-Purity Chromium Targets

    OpenAIRE

    Rudoy, A.; Milman, Yu.; Korzhova, N.

    1995-01-01

    A procedure for producing large-scale chromium ingots by means of induction-arc melting was developed. From the high-purity, low-alloyed chromium ingots obtained, chromium targets were produced by of thermoplastic treatment techniques. The method of electron-beam evaporation of high-purity chromium was also used for production of targets.

  1. Weld embrittlement in a silicide-coated tantalum alloy

    International Nuclear Information System (INIS)

    Certain weld configurations of Ta-10W alloy can become severely embrittled after a silicide coating procedure. The source of this embrittlement is shown to be a result of pronounced carbide precipitation at grain boundaries in the fusion zones of the weld. The source of carbon is the nitrocellulose lacquer that is contained in the slurry of metal powders used to provide the silicide coating. In certain weld configurations, the nitrocellulose can flash ahead of the remainder of the coating mixture, and the carbon constituent can diffuse down grain boundaries in subsequent thermal treatments. It is demonstrated that this embrittlement can be avoided if lacquers other than nitrocellulose are used or if weld configurations containing tight-fitting overlaps are avoided. The possible role of hydrogen embrittlement is also discussed. (author)

  2. RA-3 core with uranium silicide fuel elements

    International Nuclear Information System (INIS)

    Following on with studies on uranium silicide fuel elements, this paper reports some comparisons between the use of standard ECN [U3O8] fuel elements and type P-06 [from U3Si2] 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)

  3. Tailoring of nickel silicide contacts on silicon carbide

    International Nuclear Information System (INIS)

    Co-deposition technique by means of simultaneous ion beam sputtering of nickel and silicon onto SiC was performed for tailoring of Ni-silicide/SiC contacts. The prepared samples were analysed by means of XRD and XPS in order to obtain information about the surface and interface chemistry. Depth profiling was used in order to analyse in-depth information and chemical distribution of the specimens. XRD results showed that the main phase formed is Ni2Si. The XPS analysis confirmed the formation of the silicide on the surface and showed details about the chemical composition of the layer and layer/substrate interface. Moreover, the XPS depth profiles with detailed analysis of XPS peaks suggested that tailoring of C distribution could be monitored by the co-deposition technique employed

  4. Development and Oxidation Resistance of B-doped Silicide Coatings on Nb-based Alloy

    International Nuclear Information System (INIS)

    Halide-activated pack cementation was utilized to deposit B-doped silicide coating. The pack powders were consisted of 3 Wt.%NH4Cl, 7 Wt.%Si, 90 Wt.%Al2O3+TiB2. B-doped silicide coating was consisted of two layers, an outer layer of NbSi2 and an inner layer of Nb5Si3. Isothermal oxidation resistance of B-doped silicide coating was tested at 1250 .deg. C in static air. B-doped silicide coating had excellent oxidation resistance, because continuous SiO2 scale which serves as obstacle of oxygen diffusion was formed after oxidation

  5. A study of CoSix silicide formed by recoil implantation

    International Nuclear Information System (INIS)

    This work investigated the formation of CoSix silicides on n-Si by recoil implantation through a thin cobalt layer using an inert gas ion beam. The results suggest the formation of a very shallow (35 to 45 nm) silicide surface layer under the specific conditions of preparation. The surface layer resistivity was comparable to values reported for Co2Si and CoSi, although below the surface, the resistivity decreased. This appeared to suggest a change-over from cobalt-rich silicides near the surface to a more conducting silicide (CoSi2) at the interface. (author)

  6. Nickel silicides and germanides: Phases formation, kinetics and thermal expansion

    International Nuclear Information System (INIS)

    Thin film germanide reactions are often declared to be the same as silicides reactions which were far more studied. In this paper, we present a comparative study of the phase formation and kinetics of nickel silicides and nickel germanides by several experimental techniques. The samples, composed of a nanometric nickel film (50 nm) deposited on silicon or germanium substrates, have been examined by several 'in situ' real time measurements: X-ray diffraction (XRD), and differential scanning calorimetry (DSC). These original DSC and 'in situ' XRD measurements have allowed us to determine the interfacial reaction rate for Ni2Si using a linear-parabolic law. During the relatively fast DSC ramp, the growth is mainly controlled by the interface while isothermal heat treatments lead to a mainly diffusion control. In contrary to what is usually found for nickel silicide and germanides, a simultaneous growth of Ni5Ge3 and NiGe has been found during 'in situ' XRD measurements. The different behavior between the Ni-Si system (sequential formation) and the Ni-Ge system (simultaneous formation) is interpreted in term of diffusion and interface controlled growth. In addition, in devices, the film stability and the stress of the silicides or the germanides can be affected by an important physical characteristic that is the anisotropy of dilatation coefficient. In this work, the lattice parameters and linear thermal expansion coefficients (γa, γb and γc) of the orthorhombic Ni(Si1-XGeX) compounds with 0 ≤ X ≤ 1 were determined from high temperature X-ray diffraction data (298-1073 K). A negative thermal expansion coefficient of the b lattice parameter of Ni(Si1-XGeX) for all the studied Ge concentration was observed: the magnitude of this negative thermal expansion coefficient is decreasing with increasing Ge concentration

  7. Detailed analysis of uranium silicide dispersion fuel swelling

    International Nuclear Information System (INIS)

    Swelling of U3Si and U3Si2 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.)

  8. Stacked Metal Silicide/Silicon Far-Infrared Detectors

    Science.gov (United States)

    Maserjian, Joseph

    1988-01-01

    Selective doping of silicon in proposed metal silicide/silicon Schottky-barrier infrared photodetector increases maximum detectable wavelength. Stacking layers to form multiple Schottky barriers increases quantum efficiency of detector. Detectors of new type enhance capabilities of far-infrared imaging arrays. Grows by molecular-beam epitaxy on silicon waferscontaining very-large-scale integrated circuits. Imaging arrays of detectors made in monolithic units with image-preprocessing circuitry.

  9. Fracture of niobium-base silicide coated alloy

    International Nuclear Information System (INIS)

    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

  10. Silicidation of Niobium Deposited on Silicon by Physical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Coumba Ndoye, Kandabara Tapily, Marius Orlowski, Helmut Baumgart, Diefeng Gu

    2011-07-01

    Niobium was deposited by physical vapor deposition (PVD) using e-beam evaporation on bare (100) silicon substrates and SiO2 surfaces. The formation of niobium silicide was investigated by annealing PVD Nb films in the temperatures range 400–1000°C. At all elevated annealing temperatures the resistivity of Nb silicide is substantially higher than that of Nb. The Nb silicidation as a function of temperature has been investigated and different NbXSiy compounds have been characterized. It has been observed that the annealing of the Nb film on Si is accompanied by a strong volume expansion of about 2.5 of the resulting reacted film. The films' structural properties were studied using X-Ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM), which was not previously presented in the context of the extant NbSi literature. The X-Ray diffraction characterization of the Nb on Si sample annealed at 1000°C, showed the presence of hexagonal Nb5Si3 phases, with a dominant peak at the (200) plane, and NbSi2 phases. Fractal dimension calculations indicate a distinct transition from Stranski-Krastanov to Volmer-Weber film growth for NbSi formation at the annealing temperature of 600°C and above.

  11. Microstructural characterisation of chromium slags

    OpenAIRE

    Burja, J.; F. Tehovnik; Vode, F.; Arh, B.

    2015-01-01

    In this chromium slags that form during melting of chromium alloyed steels are examined. During melting and oxidation of these steel grades a considerable amount of chromium is lost, and gained back with slag reduction. Laboratory experiments were performed to study the mechanism of chromium oxide reduction by silicon. Slags chemistry and phase composition have a strong effect on the steelmaking process. Phase analysis revealed two types of chromium oxides, calcium chromites and chromite spin...

  12. Substoichiometric extraction of chromium

    International Nuclear Information System (INIS)

    Substoichiometric extraction of chromium with tetraphenylarsonium chloride (TPACl), tri-n-octylamine (TNOA), diethylammonium diethyldithiocarbamate (DDDC) and ammonium pyrrolidinedithiocarbamate (APDC) was examined in detail. Chromium can be extracted substoichiometrically in a pH range, which is 1.1-2.6 for the TPACl compound, 0.6-2.3 for the TNOA compound, 5.1-6.4 for the DDDC chelate and 3.9-4.9 for the APDC chelate. Chromium in high-purity calcium carbonate, Orchard Leaves (NBS SRM-1571) and Brewers Yeast (NBS SRM-1569) was determined by neutron activation analysis combined with substoichiometric extraction by DDDC and APDC. The values of 2.0+-0.02 ppm and 2.6+-0.2 ppm were obtained for Brewers Yeast and Orchard Leaves, respectively. These values were in good agreement with those reported by NBS. The reaction mechanism and the reaction ratio between hexavalent chromium and dithiocarbamate are also discussed. (author)

  13. Chromium in diet

    Science.gov (United States)

    ... Chromium deficiency may be seen as impaired glucose tolerance. It occurs in older people with type 2 ... PhD, and the A.D.A.M. Editorial team. Related MedlinePlus Health Topics Minerals Browse the Encyclopedia ...

  14. The carcinogenicity of chromium

    OpenAIRE

    Norseth, Tor

    1981-01-01

    The carcinogenicity of chromium compounds is reviewed with specific attention to the gaps in knowledge for risk estimation and research needs. The most important problems at present are whether trivalent chromium compounds cause cancer, and whether there is a difference in cancer causing effects between the soluble and the slightly soluble hexavalent compounds in the practical exposure situation. Dose estimates for risk estimation based on epidemiological investigations are also lacking. Pres...

  15. Fuel management strategy for the new equilibrium silicide core design of RSG GAS (MPR-30)

    International Nuclear Information System (INIS)

    The design procedure and fuel management strategy were proposed for converting the oxide core of RSG GAS (MPR-30) to the new equilibrium silicide core using higher uranium loading. The obtained silicide core gave significant extension of the core cycle length and thus increasing the reactor availability and utilisation. (author)

  16. Obtaining decorative chromium plating from trivalent chromium solutions

    OpenAIRE

    Óscar Javier Suárez García

    2010-01-01

    The present work was aimed at a qualitative evaluation, in the laboratory, of different alternatives for assembling and operating a trivalent chromium bath for decorative chromium plating. Different chromium concentration solutions and different complexing agents were used. The initial result of this analysis was that chloride, formate and acetate solutions produced the best results. Solution preparation conditions were evaluated: temperature, chromium III complex formation time and also ...

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

    International Nuclear Information System (INIS)

    Highlights: • Ce5Si3, Ce3Si2, CeSi, CeSi2−x and CeSi2 were mechanochemically synthesized. • Temperature and pressure were monitored to investigate reaction progress. • All syntheses proceeded through a MSR event followed by rapid solid-state diffusion. • Milling time before MSR correlates well with effective heat of formation. • Some synthesized material was densified by spark plasma sintering. - Abstract: The cerium silicides, Ce5Si3, Ce3Si2, CeSi, CeSi2−y, and CeSi2−x, have been prepared from the elements by mechanochemical processing in a planetary ball mill. Preparation of the cerium silicide Ce5Si4 was unsuccessfully attempted and potential reasons for this are discussed. Temperature and pressure of the milling vial were monitored in situ to gain insight into the mechanochemical reaction kinetics, which include a mechanically-induced self-propagating reaction (MSR). Some prepared powders were consolidated by spark plasma sintering to high density. Starting materials, as-milled powders, and consolidated samples were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results obtained help elucidate key questions in mechanochemical processing of intermetallics, showing first phase formation similar to thin films, MSR ignition times that are composition- and milling speed-dependent, and sensitivity of stable compound formation on the impact pressure. The results demonstrate mechanochemical synthesis as a viable technique for rare earth silicides

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-12-15

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

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

    International Nuclear Information System (INIS)

    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 U3O8, the amount of U3O8 was calculated to simulate an isotopic dilution of 4%.This material was mixed with powdered iron-phosphate glass (in wt.%: 64,9 P2O5; 22,7 Fe2O3; 8,1 Al2O3; 4,3 Na2O) 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

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

    International Nuclear Information System (INIS)

    This letter reports on a process scheme to obtain highly reproducible Ni1-xPtx 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.

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

    International Nuclear Information System (INIS)

    Low-enriched uranium silicide dispersion fuel plates were irradiated to maximum burnups of 96% of 235U. Fuel plates containing 33 v/o U3Si and U3Si2 behaved very well up to this burnup. Plates containing 33 v/o U3 Si-Al pillowed between 90 and 96% burnup of the fissile atoms. More highly loaded U3Si Al plates, up to 50 v/o, were found to pillow at lower burnups. Plates containing 40 v/o U3Si showed an increased swelling rate around 85% burnup. (author)

  2. Pt redistribution during Ni(Pt) silicide formation

    OpenAIRE

    Demeulemeester, Jelle; Smeets, D.; Van Bockstael, C; Detavernier, C.; Comrie, C. M.; Barradas, N. P.; Vieira, A; Vantomme, André

    2008-01-01

    We report on a real-time Rutherford backscattering spectrometry study of the erratic redistribution of Pt during Ni silicide formation in a solid phase reaction. The inhomogeneous Pt redistribution in Ni(Pt)Si films is a consequence of the low solubility of Pt in Ni2Si compared to NiSi and the limited mobility of Pt in NiSi. Pt further acts as a diffusion barrier and resides in the Ni2Si grain boundaries, significantly slowing down the Ni2Si and NiSi growth kinetics. Moreover, the observed in...

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

    International Nuclear Information System (INIS)

    Low-enriched uranium silicide dispersion fuel plates were irradiated to maximum burnups of 96% of 235U. Fuel plates containing 33 v/o U3Si and U3Si2 behaved very well up to this burnup. Plates containing 33 v/o U3Si-Al pillowed between 90 and 96% burnup of the fissile atoms. More highly loaded U3Si-Al plates, up to 50 v/o were found to pillow at lower burnups. Plates containing 40 v/o U3Si showed an increase swelling rate around 85% burnup. 5 refs., 10 figs

  4. Safety assessment of KUR low-enriched uranium silicide core

    International Nuclear Information System (INIS)

    Kyoto University Research Reactor (KUR) is a light-water moderated and cooled tank-type reactor operated at the rated thermal power of 5 MW. The operation of KUR with highly enriched uranium fuel ended on February 23, 2006 after its successful operation for 42 years. Since then, the conversion processes to the use of low-enriched uranium fuel have been performed. The operation of KUR with low-enriched uranium fuel is due to begin in the second half of FY2009. This report describes the abnormal transient and accident analysis for the safety assessment of KUR silicide core which have been carried out as a part of KUR silicide fuel project. The following 10 cases for the anticipated operational transients and accidents have been selected and analyzed for the safety assessment. Anticipated operational transients: (1) Due to reactivity or power distribution changes in the core. 1) Uncontrolled control rod withdrawal (from zero power, during natural circulation operation, during steady-state operation), 2) Reactivity insertion by cold water insertion, 3) Reactivity insertion by removal of irradiation samples. (2) Due to heat generation or heat removal changes in the core. 1) Primary coolant pump failure and flow coast down, 2) Secondary coolant pump failure and flow coast down, 3) Loss of commercial electric power supply. Accidents: Due to the effluent of primary coolant or the significant change of heat removal in the core. 1) Reactivity insertion by mishandling of a fuel assembly, 2) Effluent of primary coolant due to pipe rapture, 3) Primary coolant pump abrupt failure without coast down, 4) Flow channel blockage in the core. The transient analysis for the safety assessment of KUR silicide core after the earthquake was also carried out in present study. The analyses have been performed by THYDE-W, EUREA-2/RR and COOLOD-N2. Various operational conditions were studied to obtain critical results in the analyses. The results show that all cases meet the safety criteria

  5. The analytical biochemistry of chromium.

    OpenAIRE

    Katz, S A

    1991-01-01

    The essentiality and carcinogenicity of chromium depend on its chemical form. Oxidation state and solubility are particularly important in determining the biological effects of chromium compounds. For this reason, total chromium measurements are of little value in assessing its nutritional benefits or its toxicological hazards. Aqueous sodium carbonate-sodium hydroxide solutions have been successfully used for extracting hexavalent chromium from a variety of environmental and biological matri...

  6. Transient and End Silicide Phase Formation in Thin Film Ni/polycrystalline-Si Reactions for Fully Silicided Gate Applications

    Energy Technology Data Exchange (ETDEWEB)

    Kittl,J.; Pawlak, M.; Torregiani, C.; Lauwers, A.; Demeurisse, C.; Vrancken, C.; Absil, P.; Biesemans, S.; Coia, C.; et. al

    2007-01-01

    The Ni/polycrystalline-Si thin film reaction was monitored by in situ x-ray diffraction during ramp annealings, obtaining a detailed view of the formation and evolution of silicide phases in stacks of interest for fully silicided gate applications. Samples consisted of Ni (30-170 nm)/polycrystalline-Si (100 nm)/SiO2 (10-30 nm) stacks deposited on (100) Si. The dominant end phase (after full silicidation) was found to be well controlled by the deposited Ni to polycrystalline-Si thickness ratio (tNi/tSi), with formation of NiSi2 ( {approx} 600 C), NiSi ( {approx} 400 C), Ni3Si2 ( {approx} 500 C), Ni2Si, Ni31Si12 ( {approx} 420 C), and Ni3Si ( {approx} 600 C) in stacks with tNi/tSi of 0.3, 0.6, 0.9, 1.2, 1.4, and 1.7, respectively. NiSi and Ni31Si12 were observed to precede formation of NiSi2 and Ni3Si, respectively, as expected for the phase sequence conventionally reported. Formation of Ni2Si was observed at early stages of the reaction. These studies revealed, in addition, the formation of transient phases that appeared and disappeared in narrow temperature ranges, competing with formation of the phases expected in the conventional phase sequence. These included the transient formation of NiSi and Ni31Si12 in stacks in which these phases are not expected to form (e.g., tNi/tSi of 1.7 and 0.9, respectively), at temperatures similar to those in which these phases normally grow.

  7. Chromium in potatoes

    International Nuclear Information System (INIS)

    Chromium concentration in potatoes was determined, and tubes were labeled either intrinsically or extrinsically with radioactive chromate (51Cr). A labeled chromium complex was isolated from preparations of raw, baked, or fried potatoes and chromatographed on gel permeation media. Potato pulp and peel contained 1.63 and 2.70 μg of Cr/g tissue, respectively. There was no correlation between the two, nor did they respond similarly to changes of variety or locations. No significant differences were apparent in relative migration of the isolated complexes except between raw and cooked extrinsically labeled preparations

  8. Nonuniformity effects in a hybrid platinum silicide imaging device

    Science.gov (United States)

    Dereniak, Eustace L.; Perry, David L.

    1992-05-01

    The objective of this project was twofold. The first objective was to characterize the Hughes Aircraft Company CRC-365 platinum silicide imaging device in a starting infrared sensor system. The CRC-365 is a hybrid 256 x 256 IR focal plane array that operates in the 3-5 micrometer thermal infrared band. A complete sensor and computer interface were built for these tests, using, plans provided by the Rome Laboratory at Hanscom AFB. Testing of the device revealed largely satisfactory performance, with notable exception in the areas of temporal response, temporal noise, and electrical crosstalk. The second objective of this research was to advance the understanding of how detector nonuniformity effects reduce the performance of sensors of this type. Notable accomplishments in this area included a complete linear analysis of corrected thermal imaging in platinum silicide sensors, a nonlinear analysis of the CRC-365's expected performance, analysis of its actual performance when operated with nonuniformity correction, and the development of a new figure of merit. It was demonstrated that the CRC-365 is capable of maintaining background-noise-limited performance over at least a 40 K target temperature range, when operated with two-point nonuniformity correction.

  9. Atomic size effects studied by transport in single silicide nanowires

    Science.gov (United States)

    Miccoli, I.; Edler, F.; Pfnür, H.; Appelfeller, S.; Dähne, M.; Holtgrewe, K.; Sanna, S.; Schmidt, W. G.; Tegenkamp, C.

    2016-03-01

    Ultrathin metallic silicide nanowires with extremely high aspect ratios can be easily grown, e.g., by deposition of rare earth elements on semiconducting surfaces. These wires play a pivotal role in fundamental research and open intriguing perspectives for CMOS applications. However, the electronic properties of these one-dimensional systems are extremely sensitive to atomic-sized defects, which easily alter the transport characteristics. In this study, we characterized comprehensively TbSi2 wires grown on Si(100) and correlated details of the atomic structure with their electrical resistivities. Scanning tunneling microscopy (STM) as well as all transport experiments were performed in situ using a four-tip STM system. The measurements are complemented by local spectroscopy and density functional theory revealing that the silicide wires are electronically decoupled from the Si template. On the basis of a quasiclassical transport model, the size effect found for the resistivity is quantitatively explained in terms of bulk and surface transport channels considering details of atomic-scale roughness. Regarding future applications the full wealth of these robust nanostructures will emerge only if wires with truly atomically sharp interfaces can be reliably grown.

  10. Chromium and aging

    Science.gov (United States)

    Aging is associated with increased blood glucose, insulin, blood lipids, and fat mass, and decreased lean body mass leading to increased incidences of diabetes and cardiovascular diseases. Improved chromium nutrition is associated with improvements in all of these variables. Insulin sensitivity de...

  11. The Formation and Growth Process of Ru Silicide on Si(111) Surface

    Science.gov (United States)

    Toramaru, Masamitsu; Kobayashi, Naoto; Ohno, Shinya; Shudo, Kenichi; Miyamoto, Yasuyoshi; Kawamura, Norikazu

    Formation process of nanoscale ruthenium silicide islands on a Si(111) surfaces was studied with scanning tunneling microscopy for the first time. The ruthenium silicide islands were formed and grown on the only disorder-region, and small island grew up in three dimensions by incorporation of clusters including Ru exist on disorder-region and silicon atoms during thermal annealing. As the sizes of islands approaches 400 nm2 or more, the growth in two dimensional in a plane was limited, and it grew up in the direction of height. We will discuss about the formation process of ruthenium silicide on a Si(111) surface.

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

    OpenAIRE

    Yuryev, V. A.; Chizh, K. V.; Chapnin, V.A.; Mironov, S.A.; Dubkov, V. P.; Uvarov, O. V.; Kalinushkin, V. P.; Senkov, V. M.; Nalivaiko, O. Y.; Novikau, A. G.; Gaiduk, P. I.

    2015-01-01

    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$_3$N$_4$/SiO$_2$/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...

  13. Formation and Oxidation Resistance of Silicide Coatings for Mo and Mo-Based Alloys

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The forming process of silicide coatings on pure Mo and Mo-base alloys, obtained by the gasphase deposition method, has been studied by examining the microstructure of coatings and the relationship between coating thickness and process parameters. It was shown that the growth of coatings was diffusion-controlled, the diffusion of silicon to be coated into Mo or Mo-base alloys was mainly responsible for the formation of silicide. The relationship between initial silicide thickness and oxidation resistance was also investigated, and the equation of service life of the coatings at high temperature in air is presented.

  14. Influence Of The Gas Multipurpose Reactor Core Conversion From Oxide To Silicide On The GAMMA Density

    International Nuclear Information System (INIS)

    In order to prepare the reactor core conversion from oxide to silicide, analysis of the gamma heat generation in the fuel plate and its influence on the gamma density in the reactor core using the GAMSET computer code have been done. The heat generation was evaluated for oxide (U3O8-Al) and silicide (U3Si2-Al) plate for different uranium loading. The calculation result shows that the heat generation in the silicide fuel plate contains 400 gram of U-235 per fuel element increase of 10.64% related to the normal oxide plate. This means that the gamma density in the reactor core will consequently decrease. Regarding this result, it can be concluded that the core conversion from oxide to silicide fuel with higher uranium loading will be followed by the heat generation increases in the fuel plate and the gamma density decreases in the reactor core

  15. Formation of interface silicides at room temperature in pulsed laser deposited Ti thin films on Si

    International Nuclear Information System (INIS)

    Interface characterization of pulsed laser deposited (PLD) Ti thin films on Si substrates using secondary ion mass spectrometry (SIMS), grazing incidence X-ray diffraction (GIXRD) and grazing incidence X-ray reflectivity (GIXRR) reveals the growth of titanium silicides (predominantly C54-TiSi2) layers at room temperature. These silicides nucleate and grow only at higher temperatures if deposited by other physical vapor deposition techniques. The films have been subjected to isothermal and isochronal annealing under vacuum with a view to enhancing interface reaction and interdiffusion. The silicide phase formation at room temperature is due to the energetic Ti species available in PLD plume. The silicides formed in PLD have exhibited high thermal stability

  16. Stress Evolution During Ni-Si Compound Formation for Fully Silicided (FUSI) Gates

    Energy Technology Data Exchange (ETDEWEB)

    Torregiani,C.; Van Bockstael, C.; Detavernier, C.; Lavoie, C.; Lauwers, A.; Maex, K.; Kittl, J.

    2007-01-01

    The stress (force) evolution during the formation of different Ni silicide phases was monitored by in situ curvature measurements, for the reaction of thin Ni films of various thicknesses with 100 nm polycrystalline-Si deposited on oxidized (1 0 0) Si substrates. The silicide phase formation was also monitored by in situ X-ray diffraction, allowing to match and interpret the stress evolution in terms of the formation of the different silicide phases. We found that stresses developed during the formation of the different silicides can be explained qualitatively in terms of the corresponding volume changes at the reacting interfaces. Furthermore, the matching between XRD and force curve reveals that the highest compressive stress is related to the formation of the Ni31Si12 phase, and that the stress formed is relaxed when the reaction is completed.

  17. Measurement of thermal conductivity of uranium silicide - aluminum dispersion fuel

    International Nuclear Information System (INIS)

    In conjunction with reducing enrichment program for JMTR, thermal conductivity of uranium silicide - aluminum (U3Si2-Al) dispersion fuel was measured in the temperature range of 25degC ∼ 400degC for the safety evaluation of low enriched uranium fuel. Since thermal conductivity is determined as the product of thermal diffusivity, heat capacity and density, these three properties were individually measured. Thermal diffusivity and heat capacity of the specimen were measured by the laser flash method. Temperature dependence of density was obtained by measuring the thermal linear expansion with differential dilatometer. Obtained results show that conductivity of the U3Si2-Al dispersion fuel slightly increases as temperature increases, and tends to reach the maximum around 300degC. (author)

  18. Capping of rare earth silicide nanowires on Si(001)

    International Nuclear Information System (INIS)

    The capping of Tb and Dy silicide nanowires grown on Si(001) was studied using scanning tunneling microscopy and cross-sectional high-resolution transmission electron microscopy. Several nanometers thick amorphous Si films deposited at room temperature allow an even capping, while the nanowires maintain their original structural properties. Subsequent recrystallization by thermal annealing leads to more compact nanowire structures and to troughs in the Si layer above the nanowires, which may even reach down to the nanowires in the case of thin Si films, as well as to V-shaped stacking faults forming along (111) lattice planes. This behavior is related to strain due to the lattice mismatch between the Si overlayer and the nanowires

  19. 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.

  20. Capping of rare earth silicide nanowires on Si(001)

    Science.gov (United States)

    Appelfeller, Stephan; Franz, Martin; Kubicki, Milan; Reiß, Paul; Niermann, Tore; Schubert, Markus Andreas; Lehmann, Michael; Dähne, Mario

    2016-01-01

    The capping of Tb and Dy silicide nanowires grown on Si(001) was studied using scanning tunneling microscopy and cross-sectional high-resolution transmission electron microscopy. Several nanometers thick amorphous Si films deposited at room temperature allow an even capping, while the nanowires maintain their original structural properties. Subsequent recrystallization by thermal annealing leads to more compact nanowire structures and to troughs in the Si layer above the nanowires, which may even reach down to the nanowires in the case of thin Si films, as well as to V-shaped stacking faults forming along {111} lattice planes. This behavior is related to strain due to the lattice mismatch between the Si overlayer and the nanowires.

  1. Pt redistribution during Ni(Pt) silicide formation

    International Nuclear Information System (INIS)

    We report on a real-time Rutherford backscattering spectrometry study of the erratic redistribution of Pt during Ni silicide formation in a solid phase reaction. The inhomogeneous Pt redistribution in Ni(Pt)Si films is a consequence of the low solubility of Pt in Ni2Si compared to NiSi and the limited mobility of Pt in NiSi. Pt further acts as a diffusion barrier and resides in the Ni2Si grain boundaries, significantly slowing down the Ni2Si and NiSi growth kinetics. Moreover, the observed incorporation of a large amount of Pt in the NiSi seeds indicates that Pt plays a major role in selecting the crystallographic orientation of these seeds and thus in the texture of the resulting Ni1-xPtxSi film

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1985-01-01

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

  3. Attempt to produce silicide fuel elements in Indonesia

    International Nuclear Information System (INIS)

    After the successful experiment to produce U3Si2 powder and U3Si2-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 U3Si2-Al fuel elements, having similar specifications to the ones of U3O8-Al for the RSG-GAS (formerly known as MPR-30), have been produced at the FEPI. All quality controls required have been imposed to the feeds, intermediate, as well as final products throughout the production processes of the two fuel elements. The current results show that these fuel elements are qualified from fabrication point of view, therefore it is expected that they will be permitted to be tested in the RSG-GAS, sometime by the end of 1989, for normal (∝50%) and above normal burn-up. (orig.)

  4. Capping of rare earth silicide nanowires on Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Appelfeller, Stephan; Franz, Martin; Kubicki, Milan; Dähne, Mario [Institut für Festkörperphysik, Technische Universität Berlin, 10623 Berlin (Germany); Reiß, Paul; Niermann, Tore; Lehmann, Michael [Institut für Optik und Atomare Physik, Technische Universität Berlin, 10623 Berlin (Germany); Schubert, Markus Andreas [IHP–Leibniz-Institut für innovative Mikroelektronik, 15236 Frankfurt (Oder) (Germany)

    2016-01-04

    The capping of Tb and Dy silicide nanowires grown on Si(001) was studied using scanning tunneling microscopy and cross-sectional high-resolution transmission electron microscopy. Several nanometers thick amorphous Si films deposited at room temperature allow an even capping, while the nanowires maintain their original structural properties. Subsequent recrystallization by thermal annealing leads to more compact nanowire structures and to troughs in the Si layer above the nanowires, which may even reach down to the nanowires in the case of thin Si films, as well as to V-shaped stacking faults forming along (111) lattice planes. This behavior is related to strain due to the lattice mismatch between the Si overlayer and the nanowires.

  5. SiGeHBTs on Bonded SOI Incorporating Buried Silicide Layers

    OpenAIRE

    Bain, M.; El Mubarek, H A; Bonar, J. M.; Wang, Y.; Buiu, O.; Gamble, H.; Armstrong, B M; Hemment, P L; Hall, S.; Ashburn, P.

    2005-01-01

    A technology is described for fabricating SiGe hetero-junction bipolar transistors (HBTs) on wafer-bonded silicon-on-insulator (SOI) substrates that incorporate buried tungsten silicide layers for collector resistance reduction or buried groundplanes for crosstalk suppression. The physical structure of the devices is characterized using cross section transmission electron microscopy, and the electrical properties of the buried tungsten silicide layer are characterized using sheet resistance m...

  6. SiGe HBTs on bonded SOI incorporating buried silicide layers

    OpenAIRE

    Bain, M.; El Mubarek, A. W.; Bonar, J. M.; Wang, Y.; Buiu, O.; Gamble, H.; Armstrong, B M; Hemment, P. L. F.; Hall, Steven; Ashburn, Peter

    2005-01-01

    A technology is described for fabricating SiGe heterojunction bipolar transistors (HBTs) on wafer-bonded silicon-on-insulator (SOI) substrates that incorporate buried tungsten silicide layers for collector resistance reduction or buried groundplanes for crosstalk suppression. The physical structure of the devices is characterized using cross section transmission electron microscopy, and the electrical properties of the buried tungsten silicide layer are characterized using sheet resistance me...

  7. Advanced Lightweight Silicide and Nitride Based Materials for Turbo-Engine Applications.

    OpenAIRE

    Drawin, S.; Justin, J.F.

    2011-01-01

    International audience Refractory metal silicides and nitride-based ceramics combine two properties that may lead to substantial reductions in aircraft fuel consumption : compared to the most advanced nickel-based superalloys presently used in aeronautical turbines, they can withstand higher temperatures and may have lower densities. Niobium silicide-based alloys and silicon nitride / molybdenum disilicide composites are currently being developed for turbine hot section components for both...

  8. Deposition of magnesium silicide nanoparticles by the combination of vacuum evaporation and hydrogen plasma treatment

    Czech Academy of Sciences Publication Activity Database

    Stuchlík, Jiří; Stuchlíková, The-Ha; Artemenko, Anna; Remeš, Zdeněk

    Tokyo : The Japan Society of Applied Physics, 2015 - (Asano, T.), "011301-1"-"011301-5" ISBN 978-4-86348-491-7. [International Conference and Summer School on Advanced Silicide Technology 2014. Tokyo (JP), 19.07.2014-21.07.2014] R&D Projects: GA ČR(CZ) GA14-05053S; GA MŠk(CZ) LD14011; GA MŠk LH12236 Institutional support: RVO:68378271 Keywords : plasma treatment * silicides Subject RIV: BM - Solid Matter Physics ; Magnetism

  9. Facile Preparation of a Platinum Silicide Nanoparticle-Modified Tip Apex for Scanning Kelvin Probe Microscopy

    OpenAIRE

    Lin, Chun-Ting; Chen, Yu-Wei; Su, James; Wu, Chien-Ting; Hsiao, Chien-Nan; Shiao, Ming-Hua; Chang, Mao-Nan

    2015-01-01

    In this study, we propose an ultra-facile approach to prepare a platinum silicide nanoparticle-modified tip apex (PSM tip) used for scanning Kelvin probe microscopy (SKPM). We combined a localized fluoride-assisted galvanic replacement reaction (LFAGRR) and atmospheric microwave annealing (AMA) to deposit a single platinum silicide nanoparticle with a diameter of 32 nm on the apex of a bare silicon tip of atomic force microscopy (AFM). The total process was completed in an ambient environment...

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

    International Nuclear Information System (INIS)

    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

  11. Neutronic design for the conversion of ETRR-2 Reactor from oxide fuel to silicide fuel

    International Nuclear Information System (INIS)

    The neutronic design of Egypt second research reactor (ETRR-2) core conversion from oxide (U3 O8 - Al) fuel to silicide (U3Si2-Al) was carried out. The silicide fuel was chosen for the core conversion because of its high maximum fuel meat density (4.8 gu/cm3) which expected to increase the operation cycle length to meet the higher reactor availability and utilization. Analysis of ETRR-2 core was done first for the conversion from oxide (U3 O8 - Al) core, through a series of mixed oxide-silicide cores, to an all silicide (U3Si2 - Al) core with the same meat density of 3.017 gU/cm3. The second analysis was done for the conversion from low meat density (3.017/gU/cm3) silicide core, through a series of lower-higher meat density silicide cores , to an all higher meat density (3.54 gU/cm3) silicide core. The standard computer codes such as WIMSD4 code and diffusion code CITVAP (new version of CITATION II developed by INVAP's nuclear engineering division) were used in core neutronic calculations. The calculation results show the safe operation conditions of the intermediate or transition cores and equilibrium cores. With higher density silicide fuel, ETRR-2 core operation cycle length was increased from 15 (full power days)FPDs to 20 FPDs which reduce the total cost of fuel element, number of spent fuel elements, and times of core refueling. Also, the reactor utilization and production of radioisotopes can be increased.

  12. Research on behaviour of the irradiated uranium silicide for fission Mo-99 production

    International Nuclear Information System (INIS)

    This paper shows the results of purification of Mo-99 obtained by U-235 fission contained in uranium silicide (Si2U3) targets. These are the first tests carried out with irradiated targets. The separation method was previously developed employing non-irradiated uranium silicide with and with tracer addition. These tests were made trying to preserve the stages of the present method for fission Mo-99 production in the Argentine Republic. (author)

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

    International Nuclear Information System (INIS)

    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)

  14. Studies of chromium gettering

    International Nuclear Information System (INIS)

    Preliminary results have shown that hydrogen pumping by chromium is a surface effect. Unlike with titanium, the getter material used in many present day tokamaks, there is no significant diffusion into the bulk. Additional experiments have been carried out to measure the basic characteristics of chromium films for gases of interest in tokamak research. These gases include deuterium, oxygen and nitrogen. A vacuum system is described which allowed precise control of the test gas, a constant wall temperature and determination of the projected getter surface area. A quadrupole mass spectrometer, rather than simply a total pressure gauge, was utilized to measure the partial pressure of the test gas as well as the residual gas composition in the system. A quartz crystal monitor was used to measure film thickness. Pumping speeds and sticking coefficients are given as a function of surface coverage for each test gas. A comparison will be made with titanium films deposited in the same vacuum system and under similar conditions

  15. Synthesis of Co-silicides and fabrication of microwavepower device using MEVVA source implantation

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Tonghe(张通和); WU; Yuguang(吴瑜光); QIAN; Weidong(钱卫东); LIU; Yaodong(刘要东); ZHANG; Xu(张旭)

    2002-01-01

    Co synthesis silicides with good properties were prepared using MEVVA ion implantation with flux of 25-125 mA/cm2 to does of 5×1017/cm2. The structure of the silicides was investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM analysis shows that if the ion dose is greater than 2×1017/cm2, a continuous silicide layer will be formed. The sheet resistance of Co silicide decreases with an increase in ion flux and ion dose. The formation of silicides with CoSi and CoSi2 are identified by XRD analysis. After annealing, the sheet resistance decreases further. A continuous silicide layer with a width of 90-133 nm is formed. The optimal implantation condition is that the ion flux and dose are 50 mA/cm2 and 5×1017/cm2, respectively. The optimal annealing temperature and time are 900℃ and 10 s, respectively. The ohmic contact for power microwave transistors is fabricated using Co ion implantation technique for the first time. The emitter contact resistance and noise of the transistors decrease markedly; the microwave property has been improved obviously.

  16. On the size-dependent magnetism and all-optical magnetization switching of transition-metal silicide nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Glushkov, G. I.; Tuchin, A. V.; Popov, S. V.; Bityutskaya, L. A., E-mail: me144@phys.vsu.ru [Voronezh State University (Russian Federation)

    2015-12-15

    Theoretical investigations of the electronic structure, synthesis, and all-optical magnetization switching of transition-metal silicide nanostructures are reported. The magnetic moment of the nanostructures is studied as a function of the silicide cluster size and configuration. The experimentally demonstrated magnetization switching of nanostructured nickel silicide by circularly polarized light makes it possible to create high-speed storage devices with high density data recording.

  17. Effects of temperature dependent pre-amorphization implantation on NiPt silicide formation and thermal stability on Si(100)

    Energy Technology Data Exchange (ETDEWEB)

    Ozcan, Ahmet S.; Wall, Donald [IBM Semiconductor Research and Development Center, 2070 Route 52, Hopewell Junction, New York 12533 (United States); Jordan-Sweet, Jean; Lavoie, Christian [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, New York 10598 (United States)

    2013-04-29

    Using temperature controlled Si and C ion implantation, we studied the effects of pre-amorphization implantation on NiPt alloy silicide phase formation. In situ synchrotron x-ray diffraction and resistance measurements were used to monitor phase and morphology evolution in silicide films. Results show that substrate amorphization strongly modulate the nucleation of silicide phases, regardless of implant species. However, morphological stability of the thin films is mainly enhanced by C addition, independently of the amorphization depth.

  18. Catalytic Spectrophotometric Determination of Chromium

    OpenAIRE

    STOYANOVA, Angelina Miltcheva

    2005-01-01

    The catalytic effect of chromium(III) and chromium(VI) on the oxidation of sulfanilic acid by hydrogen peroxide was studied. The reaction was followed spectrophotometrically by measuring the absorbance of the reaction product at 360 nm. Under the optimum conditions 2 calibration graphs (for chromium(III) up to 100 ng mL-1, and for chromium(VI) up to 200 ng mL-1) were obtained, using the ``fixed time'' method with detection limits of 4.9 ng mL-1 and 3.8 ng mL-1, respectively...

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

    International Nuclear Information System (INIS)

    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

  20. Theory of Interface States at Silicon / Transition - - Silicide Interfaces.

    Science.gov (United States)

    Lim, Hunhwa

    The Si/NiSi(,2)(111) interface is of both fundamental and techno- logical interest: From the fundamental point of view, it is the best characterized of all semiconductor/metal interfaces, with two well-determined geometries (A and B) involving nearly perfect bonding. (This is because Si and NiSi(,2) have nearly the same lattice spacing.) Consequently, a theoretical treatment of this system makes sense--as it would not for messier systems--and one can have some confidence that the theoretical predictions are relevant to experimental observa- tions. From the technological point of view, Si/NiSi(,2) is representative of the class of semiconductor/metal interfaces that are currently of greatest interest in regard to electronic devices--Si/transition -metal-silicide interfaces. The calculations of this dissertation are for the intrinsic interface states of Si/NiSi(,2)-A geometry. These calculations also provide a foundation for later studies of defects at this interface, and for studies of other related systems, such as CoSi(,2). The calculations employ empirical tight-binding Hamiltonians for both Si and NiSi(,2) (with the parameters fitted to prior calculations of the bulk band structures, which appear to be in agreement with the available experimental data on bulk Si and NiSi(,2)). They also employ Green's function techniques--in particular, the subspace Hamiltonian technique. Our principal results are the following: (1) Interface state disper- sion curves are predicted along the symmetry lines (')(GAMMA)(')M, (')M(')K and (')K(')(GAMMA) of the surface Brillouin zone. (2) A prominent band of interface states is found which disperses downward from an energy within the Si band gap to an energy below the Si valence band edge E(,(upsilon)) as the planar wavevector (')k increases from (')(GAMMA) ((')k = 0) to (')M or (')K (symmetry points at boundary of the surface Brillouin zone). This band of inter- face states should be observable. It produces a peak in the surface

  1. CHROMIUM, METABOLIC SYNDROME AND DIABESITY

    Science.gov (United States)

    Suboptimal intakes of the essential nutrient, chromium, are characterized by elevated blood glucose, insulin resistance, obesity, hypertriglyceridemia, and low HDL. These are also signs and symptoms of the metabolic syndrome. Improvements due to increased intake of chromium are related to the degr...

  2. Groundwater contaminant by hexavalent chromium

    Energy Technology Data Exchange (ETDEWEB)

    Parsons, C. [Univ. of Texas, Austin, TX (United States)

    1995-11-01

    Oxidation of trivalent chromium to hexavalent chromium has been investigated as a function of total manganese in soils as well as various incubation conditions. Chromium and manganese contents were analyzed by atomic absorption (graphite furnace and flame emission respectively) following acid digestion. Total hexavalent chromium generation capacity was determined by addition of 0.001 M CrCL3, incubation, and analysis by s-diphenyl carbazide. Samples were then leached with CaSO{sub 4} and MgSO{sub 4} and incubated in various environments (oven, freeze-drier, field moist, ultrafreeze) to test for geogenic generation of Cr(IV). The degree of geogenic generation of hexavalent chromium was compared with total Mn and Cr content as well as hexavalent generational capacity.

  3. Role of paramagnetic chromium in chromium(VI)-induced damage in cultured mammalian cells.

    OpenAIRE

    Sugiyama, M

    1994-01-01

    Chromium(VI) compounds are known to be potent toxic and carcinogenic agents. Because chromium(VI) is easily taken up by cells and is subsequently reduced to chromium(III), the formation of paramagnetic chromium such as chromium(V) and chromium(III) is believed to play a role in the adverse biological effects of chromium(VI) compounds. The present report, uses electron spin resonance (ESR) spectroscopy; the importance of the role of paramagnetic chromium in chromium(VI)-induced damage in intac...

  4. Mixing of Al into uranium silicides reactor fuels

    International Nuclear Information System (INIS)

    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 27Al(p, γ) 28Si resonance nuclear reaction were used to measure radiation induced mixing of Al into U3Si and U3Si2 after irradiation at 300 C. Initially U mixes into the Al layer and Al mixes into the U3Si. At a low dose, the Al layer is converted into UAl4 type compound while near the interface the phase U(Al.93Si.07)3 grows. Under irradiation, Al diffuses out of the UAl4 surface layer, and the lower density ternary, which is stable under irradiation, is the final product. Al mixing into U3Si2 is slower than in U3Si, 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

  5. KUR core conversion to use LEU silicide fuel

    International Nuclear Information System (INIS)

    As one of possible future programs for the Kyoto University Research Reactor (KUR), the Research Reactor Institute of Kyoto University (KURRI) has a plan for core conversion to the use of low-enriched uranium (LEU) fuel. A feasibility study for this conversion started in November, 1983, as a part of the joint study between KURRI and Argonne National Laboratory (ANL).Thermal-hydraulic analysis on the use of LEU fuels in the KUR was performed in 1984, and neutronic calculation in 1985. The conversion is to be from the current highly enriched uranium HEU (93.15%, UAl-alloy 0.586 gU/cm3) to LEU (19.75%, U3Si2-Al, 3.2 gU/cm3). The results indicate that the core can be converted without significant difficulties. Prior to the safety review application for the full core conversion with LEU silicide fuel, we are planning to demonstrate the use of two full size LEU suicide fuel elements among the current HEU elements. The safety analysis report for the two-element demonstration is to be submitted to the government shortly. The full core conversion is anticipated in 1993.(author)

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

    International Nuclear Information System (INIS)

    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

  7. Strategy for silicon based hot-wire chemical vapor deposition without wire silicide formation

    Energy Technology Data Exchange (ETDEWEB)

    Laukart, Artur, E-mail: artur.laukart@ist.fraunhofer.de; Harig, Tino; Höfer, Markus; Schäfer, Lothar

    2015-01-30

    Silicide formation of wires during hot-wire chemical vapor deposition (HWCVD) of silicon based coatings is a key challenge which has to be overcome before HWCVD can be transferred successfully into industry. Silicide formation of tungsten wires is not occurring at temperatures of approximately 1900 °C and above when maintaining a silane partial pressure below approximately 1 Pa. Proceeding silicide formation at the cold ends where the wires are electrically contacted was completely prevented by continuously moving the cold ends of the wires into the hot deposition zone, resulting in a retransformation of the tungsten phase. Thus the maintenance period of a HWCVD manufacturing tool can be freed from wire lifetime.

  8. Anisotropic thermal expansion of Ni, Pd and Pt germanides and silicides

    Science.gov (United States)

    Geenen, F. A.; Knaepen, W.; Moens, F.; Brondeel, L.; Leenaers, A.; Van den Berghe, S.; Detavernier, C.

    2016-07-01

    Silicon or germanium-based transistors are nowadays used in direct contact with silicide or germanide crystalline alloys for semiconductor device applications. Since these compounds are formed at elevated temperatures, accurate knowledge of the thermal expansion of both substrate and the contact is important to address temperature depending effects such as thermal stress. Here we report the linear coefficients of thermal expansion of Ni-, Pd- and Pt-based mono-germanides, mono-silicides and di-metal-silicides as determined by powder-based x-ray diffraction between 300 and 1225 K. The investigated mono-metallic compounds, all sharing the MnP crystal structure, as well as Pd2Si and Pt2Si exhibit anisotropic expansion. By consequence, this anisotropic behaviour should be taken into account for evaluating the crystal unit’s cell at elevated temperatures.

  9. Kinetics and mechanism of hydrogen evolution reaction on cobalt silicides in alkaline solutions

    International Nuclear Information System (INIS)

    Cathodic polarisation curves and impedance spectra for cobalt silicides Co2Si and CoSi2 in 0.5–2 M KOH at ambient temperature were obtained. It was shown that electrocatalytic activity of both silicides in hydrogen evolution reaction (HER) is higher than that of cobalt. The dependences of equivalent circuit elements on the electrode potential were analysed. The conclusion was made that the atomic hydrogen adsorption on the surface of cobalt silicides is described by the Langmuir isotherm, and hydrogen evolution proceeds through the Volmer–Heyrovsky mechanism (at α1 ≠ α2 for Co2Si and α1 = α2 for CoSi2; α1 and α2 are the transfer coefficients for the Volmer and Heyrovsky steps respectively). The Heyrovsky reaction is probably the rate-determining step. The values of the kinetic parameters of HER on Co2Si and CoSi2 in 1 M KOH were estimated

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

    International Nuclear Information System (INIS)

    Iron silicide (cubic FeSi2) 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 FeSi2 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

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

    International Nuclear Information System (INIS)

    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)

  12. 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.

  13. Comparison of JRR-4 core neutronic performance between silicide fuel and TRIGA fuel

    International Nuclear Information System (INIS)

    Neutronic analyses on the JRR-4 core loaded with 20 wt% Low Enriched Uranium (LEU) fuels have been performed using SRAC code system. The LEU fuels studied in this work are ETR type silicide one and TRIGA one. For each type of them, parametrical analyses were done as the function of uranium loading in the fuel element to see changes of core excess reactivity, thermal neutron flux, fuel burnup and so on. From many cell and whole core calculations, following results have obtained. (a) A uranium density of 3.8 g/cm3 is a good value of the Silicide fuel for JRR-4. (b) In the case of TRIGA fuel, a uranium weight fraction of 40% to the total TRIGA fuel pin weight is one of adequate values. (c) The silicide core shows a good performance on the thermal neutron flux (d) and the TRIGA core can achieve a very high burnup. (author)

  14. Role of Ti3Al/silicides on tensile properties of Timetal 834 at various temperatures

    Indian Academy of Sciences (India)

    K V Sai Srinadh; Nidhi Singh; V Singh

    2007-12-01

    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, were given to have no precipitates, Ti3Al and silicide and only silicide precipitates in the respective conditions. Tensile properties in the above three heat treated conditions were determined at room temperature, 673 K and 873 K. It was observed that largely Ti3Al precipitates were responsible for increase in the yield strength and decrease in ductility in this alloy.

  15. Fate and transport of chromium through soil

    International Nuclear Information System (INIS)

    Chromium chemistry relevant to the problem facing state of New Jersey (Usa) was examined. Transport of chromium through soil depends on its chemical forms. Transformation of chromium within bulk of soil depends on soil constituents, soil condition, such as pH, Eh and organic compounds applied onto soil or present in soil. Total chromium in soil can be determined. Speciation of chromium based on ionization, hydrolysis, complex formation, redox reactions and adsorption is predicted using MINIQ program

  16. Release of Chromium from Orthopaedic Arthroplasties

    OpenAIRE

    Afolaranmi, G.A.; Tettey, J; Meek, R.M.D; Grant, M.H

    2008-01-01

    Many orthopaedic implants are composed of alloys containing chromium. Of particular relevance is the increasing number of Cobalt Chromium bearing arthroplasies being inserted into young patients with osteoarthritis. Such implants will release chromium ions. These patients will be exposed to the released chromium for over 50 years in some cases. The subsequent chromium ion metabolism and redistribution in fluid and tissue compartments is complex. In addition, the potential biological effects o...

  17. Chromium isotope variations

    DEFF Research Database (Denmark)

    D'Arcy, Joan Mary

    Chromium (Cr) stable isotopes are a useful tracer of changes in redox conditions because changes in its oxidation state are accompanied by an isotopic fractionation. For this reason the Cr isotope system is being developed as a potential tool for paleo-redox reconstruction. Dissolved Cr in seawater...... is incorporated into carbonates. Hence, ancient carbonates can potentially record the Cr isotopic composition (δ53Cr ‰) of seawater in the geological past. Reliable application and interpretation of this proxy requires a detailed knowledge about processes that fractionate Cr on the Earth’s surface......, and the quantification the Cr isotope composition of major Cr fluxes into and out of ocean. This thesis adds to the current knowledge of the Cr isotope system and is divided into two studies. The focus of the first study was to determine what processes control the Cr isotopic compositionof river...

  18. 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.

  19. Progress in alkaline peroxide dissolution of low-enriched uranium metal and silicide targets

    International Nuclear Information System (INIS)

    This paper reports recent progress on two alkaline peroxide dissolution processes: the dissolution of low-enriched uranium metal and silicide (U3Si2) targets. These processes are being developed to substitute low-enriched for high-enriched uranium in targets used for production of fission-product 9'9Mo. Issues that are addressed include (1) dissolution kinetics of silicide targets, (2) 99Mo lost during aluminum dissolution, (3) modeling of hydrogen peroxide consumption, (4) optimization of the uranium foil dissolution process, and (5) selection of uranium foil barrier materials. Future work associated with these two processes is also briefly discussed. (author)

  20. Silicide Nanopowders as Low-Cost and High-Performance Thermoelectric Materials

    Science.gov (United States)

    Chen, Renkun

    2013-06-01

    Thermoelectric devices directly convert heat into electricity and are very attractive for waste heat recovery and solar energy utilization. If thermoelectric devices can be made sufficiently efficient and inexpensive, then they will become a transformative energy technology that can tap a significant portion (10-20%) of the vast amount of heat existing in nature as well as industrial processes. Nanopowders of Earth-abundant, silicide-based materials, such as Mg2Si and its alloys, provide a unique opportunity to realize this goal. This article will present an overview of recent advances in the synthesis and thermoelectric properties of silicide-based nanostructured materials.

  1. Low enriched aluminide and silicide fuel element technology at B and W (USA)

    International Nuclear Information System (INIS)

    Babcock and Wilcox is fabricating full size fuel elements with low enriched uranium silicide and uranium aluminide. BandW also provides high enrichred U3O8 and UA Lsub(x) for United States Research Reactors, and Test Research and Training Reactors (TRTR). BandW and Argonne National Laboratry (ANL) are actively involved in the Reduced Enrichment Research and Test Reactor (RERTR) Program and have undertaken a joint effort in which BandW is fabricating two Oak Ridge Reactor (ORR ) elements with uranium silicide fuel. During plate development, fuel plates were fabricated with compacts containing U3SiAl and U3Si2 fuel. (author)

  2. Carbon mediated reduction of silicon dioxide and growth of copper silicide particles in uniform width channels

    OpenAIRE

    Pizzocchero, Filippo; Bøggild, Peter; Booth, Tim

    2013-01-01

    We show that surface arc-discharge deposited carbon plays a critical intermediary role in the breakdown of thermally grown oxide diffusion barriers of 90 nm on a silicon wafer at 1035°C in an Ar/H2 atmosphere, resulting in the formation of epitaxial copper silicide particles in ≈ 10 μm wide channels, which are aligned with the intersections of the (100) surface of the wafer and the {110} planes on an oxidized silicon wafer, as well as endotaxial copper silicide nanoparticles within the wafer ...

  3. Effect of copper on phase formation process in boron-silicide layers on niobium and tantalum

    International Nuclear Information System (INIS)

    The influence of copper additions on regularities of growth, phase- and structure formation of borosilicide coatings produced by siliconizing preliminarily borated niobium and tantalum was studied. Rolled sheets of niobium and tantalum with impurity content less than 0.02 % (mass) were used for the coating application. Copper introduction into saturating medium affects growth rate, phase- and structure formation of silicide phases on niobium and tantalum. It also permits obtaining alternating boride and silicide layers, which is probably the only way of the composition fabrication, which can be of interest, when developing coatings with preset properties

  4. Physical and electrical properties of ultra-thin nickel silicide Schottky diodes on Si (100)

    International Nuclear Information System (INIS)

    The physical and electrical properties of Ni silicides, reactively formed by a thin Ni layer of 3 nm, have been investigated. The existence of NiSi2 phase has been confirmed at low temperature annealing by x-ray photoelectron spectroscopy. The silicides have shown flat surfaces up to an annealing temperature of 800 °C and a stable sheet resistance can be achieved. The Schottky barrier heights extracted from diode characteristics have shown stable values against annealing temperature owing to the stability of the film with an ideality factor nearly to unit.

  5. Silicon Framework-Based Lithium Silicides at High Pressures.

    Science.gov (United States)

    Zhang, Shoutao; Wang, Yanchao; Yang, Guochun; Ma, Yanming

    2016-07-01

    The bandgap and optical properties of diamond silicon (Si) are not suitable for many advanced applications such as thin-film photovoltaic devices and light-emitting diodes. Thus, finding new Si allotropes with better bandgap and optical properties is desirable. Recently, a Si allotrope with a desirable bandgap of ∼1.3 eV was obtained by leaching Na from NaSi6 that was synthesized under high pressure [Nat. Mater. 2015, 14, 169], paving the way to finding new Si allotropes. Li is isoelectronic with Na, with a smaller atomic core and comparable electronegativity. It is unknown whether Li silicides share similar properties, but it is of considerable interest. Here, a swarm intelligence-based structural prediction is used in combination with first-principles calculations to investigate the chemical reactions between Si and Li at high pressures, where seven new compositions (LiSi4, LiSi3, LiSi2, Li2Si3, Li2Si, Li3Si, and Li4Si) become stable above 8.4 GPa. The Si-Si bonding patterns in these compounds evolve with increasing Li content sequentially from frameworks to layers, linear chains, and eventually isolated Si ions. Nearest-neighbor Si atoms, in Cmmm-structured LiSi4, form covalent open channels hosting one-dimensional Li atom chains, which have similar structural features to NaSi6. The analysis of integrated crystal orbital Hamilton populations reveals that the Si-Si interactions are mainly responsible for the structural stability. Moreover, this structure is dynamically stable even at ambient pressure. Our results are also important for understanding the structures and electronic properties of Li-Si binary compounds at high pressures. PMID:27302244

  6. Review of research and development work into silicide fuels

    International Nuclear Information System (INIS)

    Available data on the behaviour of silicide fuels under irradiation were judged as satisfactory (Safety Evaluation Report - NUREG - 1313) to initiate, in 1989, the procedure of conversion authorisation for OSIRIS reactor. Nevertheless, it was believed essential to check the performance of fuel elements manufactured according to the specifications for the OSIRIS reactor under irradiation and in defined conditions. To schedule specific experiments to answer the safety authority team specific questions. In addition, the question of increasing the density (above the reference density of 4.8 Utot/cm3) was examined in collaboration with CERCA as part of a research program. All these reflections led the CEA to undertake a large-scale irradiation programme. Analytical experiments have shown: No cladding failure was detected during the experiment; The thick core plate expanding is similar as nominal thickness core plates; The tests carried out confirm that U3Si2 fuel (4,8 g Utot/cm3) performs well under irradiation; Some of the manufacturing tolerances without any doubt can be increased without altering performance under irradiation. This will not take place for a further 1 or 2 years. e are waiting for the analysis of the results from the EPSILON irradiation experiment to make possible modifications to the OSIRIS cladding failure detection thresholds detection system. Once the tests presently scheduled have been completed, it might be possible to use a fuel with a uranium density about 30% greater than the reference fuel. This will make possible to meet economical targets. The aim of converting ORPHEE and RHF type reactors cannot be achieved merely by optimising actual technology because of the additional density increasing. Now the question is to be sure that research into density increasing should be continued. If so, for which purpose and for which reactors? It is not planed in the next ten years to implement and qualify a new manufacture process. Then an international

  7. Water splitting and electricity with semiconducting silicides in sunlight

    Energy Technology Data Exchange (ETDEWEB)

    Demuth, Martin [Max-Planck-Institut fuer Bioanorganische Chemie, Muelheim an der Ruhr (Germany); H2 Solar GmbH, Loerrach (Germany); Kerpen, Klaus; Kuklya, Andriy; Wuestkamp, Marc-Andre [Max-Planck-Institut fuer Kohlenforschung, Muelheim an der Ruhr (Germany)

    2010-07-01

    Generation of hydrogen and oxygen from water is described using mainly the semiconductor titanium disilicide as catalyst and halogen light which closely mimics solar radiation. The reactions are carried out under non-aerobic conditions, i.e., under nitrogen. High efficiencies are reached at 1.1-1.2 bar pressure. In the first phase of these reactions the catalytically active centers are built up. During this phase of reaction the kinetics of the water splitting process is growing in and leads to a linear dependence in the further course of the reactions which consists of >96% water splitting to yield hydrogen and oxygen in a 2:1 ratio. Hydrogen is partially and reversibly stored physically, depending on temperature. Oxygen behaves differently since it is stored entirely under the applied reaction conditions (50-80 C and light) and can be liberated from storage upon heating the slurries in the dark. This allows convenient separation of hydrogen and oxygen. The stability of titanium disilicide has been positively tested over several months. This material is abundant and inexpensive besides that it absorbs most of the solar radiation. Further, XRD and XPS studies show that titanium disilicide is 80% crystalline and the oxide formation is limited to a few molecular layers in depth. By using labeled water it was shown that labeled dioxygen appears in the gas phase of such reactions, this showing definitively that hydrogen evolution occuring here stems from photochemical splitting of water. Further, water splitting is part of a project which involves photoelectrochemistry and in which the silicides are used as light-receiving electrode and transition metal-coated anodes serve to split water. (orig.)

  8. Chromium reduction in Pseudomonas putida.

    OpenAIRE

    Ishibashi, Y.; Cervantes, C; Silver, S

    1990-01-01

    Reduction of hexavalent chromium (chromate) to less-toxic trivalent chromium was studied by using cell suspensions and cell-free supernatant fluids from Pseudomonas putida PRS2000. Chromate reductase activity was associated with soluble protein and not with the membrane fraction. The crude enzyme activity was heat labile and showed a Km of 40 microM CrO4(2-). Neither sulfate nor nitrate affected chromate reduction either in vitro or with intact cells.

  9. Chromium reduction in Pseudomonas putida.

    Science.gov (United States)

    Ishibashi, Y; Cervantes, C; Silver, S

    1990-01-01

    Reduction of hexavalent chromium (chromate) to less-toxic trivalent chromium was studied by using cell suspensions and cell-free supernatant fluids from Pseudomonas putida PRS2000. Chromate reductase activity was associated with soluble protein and not with the membrane fraction. The crude enzyme activity was heat labile and showed a Km of 40 microM CrO4(2-). Neither sulfate nor nitrate affected chromate reduction either in vitro or with intact cells. PMID:2389940

  10. Real-time monitoring of the silicidation process of tungsten filaments at high temperature used as catalysers for silane decomposition

    International Nuclear Information System (INIS)

    The scope of this work is the systematic study of the silicidation process affecting tungsten filaments at high temperature (1900 °C) used for silane decomposition in the hot-wire chemical vapour deposition technique (HWCVD). The correlation between the electrical resistance evolution of the filaments, Rfil(t), and the different stages of the their silicidation process is exposed. Said stages correspond to: the rapid formation of two WSi2 fronts at the cold ends of the filaments and their further propagation towards the middle of the filaments; and, regarding the hot central portion of the filaments: an initial stage of silicon dissolution into the tungsten bulk, with a random duration for as-manufactured filaments, followed by the inhomogeneous nucleation of W5Si3 (which is later replaced by WSi2) and its further growth towards the filaments core. An electrical model is used to obtain real-time information about the current status of the filaments silicidation process by simply monitoring their Rfil(t) evolution during the HWCVD process. It is shown that implementing an annealing pre-treatment to the filaments leads to a clearly repetitive trend in the monitored Rfil(t) signatures. The influence of hydrogen dilution of silane on the filaments silicidation process is also discussed. - Highlights: • The silicidation process of tungsten filaments at 1900 °C has been elucidated. • The silicidation process is correlated with the electrical resistance evolution. • Hydrogen dilution of silane delays the precipitation of silicides. • A thermal treatment of the filaments makes the silicidation process repeatable. • Raman spectroscopy and EDX analysis allow the tungsten silicides identification

  11. Hydrogen permeation through chromium

    International Nuclear Information System (INIS)

    Steady state and non-steady state measurements of hydrogen permeation through metallic chromium are reported. The experiments have been conducted by use of hydrogen and deuterium within a pressure range of 10-8 - 1 bar and temperatures between 600 - 8000C. Numerical values for the physical quantities permeability, diffusion constant and solubility could be derived. At an upstream pressure above around 10-3 bar classical Sieverts-low was found (permeation rate proportional √p) with activation energies Qsub(perm) = 65 kJoule/mole, Qsub(Diff) = 4-8 kJoule/mole, Qsub(Sol) = 57-61 kJoule/mole for the respective processes involved. The isotopic effect between H and D of the permeabilities could be represented by a factor of 1,5 independence on temperature. All non steady-state measurements could be approximated reasonably well by classical diffusion kinetics. Below up-stream pressures of approx.= 10-7 bar the kinetics was no longer diffusion controlled, the dependence on up-stream pressure changed from √p -> p, the activation energy for permetation increased to 127 kJoule/mole and the isotopic factor resulted in about 2-3. (orig.)

  12. Schottky barrier MOSFET structure with silicide source/drain on buried metal

    Institute of Scientific and Technical Information of China (English)

    Li Ding-Yu; Sun Lei; Zhang Sheng-Dong; Wang Yi; Liu Xiao-Yan; Han Ru-Qi

    2007-01-01

    In this paper, we propose a novel Schottky barrier MOSFET structure, in which the silicide source/drain is designed on the buried metal (SSDOM). The source/drain region consists of two layers of silicide materials. Two Schottky barriers are formed between the silicide layers and the silicon channel. In the device design, the top barrier is lower and the bottom is higher. The lower top contact barrier is to provide higher on-state current, and the higher bottom contact barrier to reduce the off-state current. To achieve this, ErSi is proposed for the top silicide and CoSi2 for the bottom in the n-channel case. The 50 nm n-channel SSDOM is thus simulated to analyse the performance of the SSDOM device. In the simulations, the top contact barrier is 0.2e V (for ErSi) and the bottom barrier is 0.6 eV (for CoSi2).Compared with the corresponding conventional Schottky barrier MOSFET structures (CSB), the high on-state current of the SSDOM is maintained, and the off-state current is efficiently reduced. Thus, the high drive ability (1.2 mA/μm at Vds = 1 V, Vgs = 2 V) and the high Ion/Imin ratio (106) are both achieved by applying the SSDOM structure.

  13. Mechanism for silicide formation in Ag(Cu)/Si and Ag(Co)/Si upon annealing

    International Nuclear Information System (INIS)

    Ag(Co) alloy and Ag(Cu) alloy films were prepared on HF-cleaned Si by using DC magnetron sputtering and were then annealed in vacuum (3 X 10-5 Torr) to investigate the effects of Co and Cu precipitation on the material properties of the Ag alloy films and on the reaction between alloy element (Co, Cu) and Si. The annealing of a Ag(Cu)/Si structure for 30 min at 200 .deg. C produced a uniform Cu3Si layer at the Ag(Cu)-Si interface, as a result of reaction of the segregated Cu with Si. This lowered the resistivity from 5.3 to 3.2 μΩ-cm, and also led to improved adhesion properties. In contrast, the annealing of a Ag(Co)/Si structure at 400 .deg. C produced a cobalt silicide in the Ag(Co) film, resulting from reaction of the diffused Si with Co precipitates, probably at the grain boundaries. The Co silicide formed at 400 .deg. C slightly increased the resistivity, which continued to decrease at temperatures of 500 .deg. C and higher. The different diffusing species in formation of Co silicide and Cu silicide may be attributed to the difference in the temperature of silicde formation and the mobility of the species.

  14. Electronic structure of dysprosium silicide films grown on a Si(1 1 1) surface

    International Nuclear Information System (INIS)

    The thickness-dependent electronic structures of Dy silicide films grown on a Si(1 1 1) surface have been investigated by angle-resolved photoelectron spectroscopy. Two (1x1) periodic bands, both of them cross the Fermi level, have been observed in the silicide films formed by Dy coverages of 1.0 monolayer and below, and more than five (√(3)x√(3)) periodic bands have been observed in thicker films. Taking the (2√(3)x2√(3)) periodic structure of Dy atoms in the submonolayer silicide film into account, the periodicity of the two metallic bands indicate that they mainly originate from the orbitals of Si atoms, which form a (1x1) structure. Of the (√(3)x√(3)) periodic bands observed in thick films, four of them are well explained by the folding of the (1x1) bands into a (√(3)x√(3)) periodicity. Regarding the other band, the three (√(3)x√(3)) periodic bands would originate from the electronic states related to the inner Si layers that form a (√(3)x√(3)) structure, and the one observed in the 3.0 ML film only might originate from the electron located at the interface between bulk Si and the Dy silicide film.

  15. 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

    , for ThSi, USi and USi2, respectively. At ambient conditions, the uranium silicides crystallize in tetragonal structures (space groups: I4/mmm for USi and I41/amd for USi2), while ThSi adopts an orthorhombic structure (space group: Pbnm) (including an anharmonic analysis of the silicon). These...

  16. Nanoscale metal-silicide films prepared by surfactant sputtering and analyzed by RBS

    International Nuclear Information System (INIS)

    Surfactant sputtering has been applied to modify the surface structure of Si substrates and to produce ultrathin metal-silicide films with nickel and platinum surfactants, utilizing the steady state coverage of a Si-substrate surface with surfactant atoms simultaneously during sputter erosion by combined ion irradiation and surfactant atom deposition. Si (1 0 0) substrates were eroded using 5 keV Xe-ions and 10-30 keV Ar ions at incident angles of 65o and 70o with fluences of up to 2 x 1018/cm2 under continuous sputter deposition of platinum and nickel from targets irradiated simultaneously by the same ion beam. These surfactant atoms form metal-silicides in the surface near region and strongly modify the substrate sputter yield and the surface nanostructure. Atomic force microscopy and scanning electron microscopy were carried out to observe a transition of surface topography from ripple to relief patterns, granular patterns or smooth surfaces. The Si and metal sputter yield as function of the steady state metal coverage were determined by combination of Rutherford-backscattering spectroscopy (RBS) and profilometry. The composition and the depth distributions of metal-silicide films were analyzed via high-resolution RBS and transmission electron microscopy. We show that RBS results in comparison with SRIM and TRIDYN sputter yield simulations allows us to identify the silicide surface structure on the nanometer scale.

  17. Quantitative determination of crystalline phases in the silicide fuel by the Rietveld method

    International Nuclear Information System (INIS)

    Uranium silicide has been used as nuclear fuel in modern research reactors. The nuclear fuel is based on a dispersion of uranium silicide and aluminum powder to form a fuel meat fabricated according to powder metallurgy techniques. The U3Si2 powder should attend technical specifications referring to the major crystalline constituent, which must be more than 80 wt% of U3Si2. IPEN/CNEN-SP currently produces the U3Si2-Al fuel to supply the IEA-R1 research reactor, which operates at 3.5 MW in order to produce primary radioisotopes used in nuclear medicine. The uranium concentration in the fuel should be increased from 3.0 gU/cm3 to 4.8 gU/cm3 in order to guarantee future fuel supplying for a new research reactor designed for radioisotope production, the Brazilian Multipurpose Research Reactor - RMB, which is planned to be constructed in the country. The new fuel will operate under much more severe conditions than the ones found currently in IEA-R1 reactor. So, the increasing of uranium concentration into the fuel requests urgent development of a new technology to qualify the uranium silicide powder produced by IPEN-CNEN/SP, referring to the characterization of crystalline phases. This paper describes a methodology developed to quantify crystalline phases in the silicide fuel powder, which is based in the Rietveld method for crystalline structures refinement. (author)

  18. Synthesis and characterization of silicide coating on niobium alloy produced using molten salt method

    International Nuclear Information System (INIS)

    Nb based alloys are promising structural materials for high temperature reactors due to their strength at higher temperatures. However Nb based alloys undergoes substantial oxidation at high temperatures. In order to improve its oxidation resistance property at high temperatures (>400 °C) a protective layer must be provided to avoid direct contact of the component to atmospheric oxygen. In the present work, attempts have been made to obtain silicide coatings on Nb alloy using molten salt method. In this method, deposition of silicon is a multistep process. Metallic Si produced by the subsequent reactions in the molten salt diffuses and an oxidation resistant silicide coating forms on the surface of substrate. To study the variation in the thickness of coated layer on the Nb alloy, experiments were carried out at different temperature and time periods. These silicide coated samples were characterized using optical, SEM and XRD techniques. Based on these results mechanism of silicide coating on Nb alloys has been discussed in detail. (author)

  19. Mechanical properties of niobium alloy with molybdenum-hafnium-silicide coating

    International Nuclear Information System (INIS)

    The method of bending loading permits studying mechanical characteristics (σ σ0.2 and deflection f) in the composite of niobium alloy with silicide coating on molybdenum and hafnium base. Results of mechanical characteristics are compared with microstructural peculiarities of the failure development. Criteria which determine strength and plastic properties of the composite as dependent on the structural state are established

  20. A thermodynamic assessment for synthesizing transition metal silicides by the combustion synthesis process

    International Nuclear Information System (INIS)

    Transition metal silicides have important applications in various disciplines. These include uses as interconnects in chips, as coatings, as heating elements, etc. As their uses increased, various processing techniques were adopted to produce them. These vary from chemical/physical vapor deposition, rapid thermal processing, and sputtering for thin film processing; traditional vacuum casting and powder metallurgical routes are used to produce bulk samples. In this paper, the authors are interested in those transition metal silicides which have the potential for use in the bulk form, possibly in the aerospace or other demanding applications. The primary requirements are high refractoriness, low density, high strength and good oxidation resistance. It is the oxidation resistance that makes the silicides better candidates as compared to the other intermetallics. Meschter argued that most engineering materials retain substantial strength up to 80% of their melting points. Therefore, for an operating temperature of 1500C, the melting point of the typical candidate may be 1950C, while the limit in density can be defined by the density of Ni (8.75 gn/cc). As an alterative, combustion synthesis (CS) processing may prove to be a viable route for producing these transition metal silicides. In this process, and exothermic reaction is initiated in a compact containing stoichiometric mixture of elemental powders

  1. Trivalent chromium sorption on alginate beads

    OpenAIRE

    Araújo, M. Manuela; Teixeira, J.A.

    1997-01-01

    The applicability of trivalent chromium removal from aqueous solutions using calcium alginate beads was studied. The equilibrium isotherms were plotted at two temperatures. The relationship between the chromium sorbed and the calcium released was determined as well as the effect of alginate amount and initial pH on the equilibrium results. Chromium sorption kinetics were evaluated as a function of chromium initial concentration and temperature. Transport properties of trival...

  2. On texture formation of chromium electrodeposits

    DEFF Research Database (Denmark)

    Nielsen, Christian Bergenstof; Leisner, Peter; Horsewell, Andy

    1998-01-01

    The microstructure, texture and hardness of electrodeposited hard, direct current (DC) chromium and pulsed reversed chromium has been investigated. These investigations suggest that the growth and texture of hard chromium is controlled by inhibition processes and reactions. Further, it has been...

  3. Exchange reactions of plutonium with silicides and estimation of the enthalpy of the formation of Pu5Si3

    International Nuclear Information System (INIS)

    An approximate ΔHof,298 value has been determined for Pu5Si3 through a study of exchange reactions of selected metal silicides with plutonium. The reactions were carried out by arc-melting. Results show that Pu5Si3 is intermediate in stability between V3Si and Mo3Si, and has a ΔHof,298 of -52±13 kJ/g-atom. Estimates of ΔHof,298 for the higher plutonium silicides are: Pu3Si2 -54, PuSi -60, Pu3Si5 -58, and PuSi2 -56 kJ/g-atom with uncertainties of ±18 kJ/g-atom. The plutonium silicides are found to be more stable than both the thorium and uranium silicides. (orig.)

  4. Chromium Salen Mediated Alkene Epoxidation

    DEFF Research Database (Denmark)

    Petersen, Kaare Brandt; Norrby, Per-Ola; Daly, Adrian M.; Gilheany, Declan G.

    2002-01-01

    The mechanism of alkene epoxidation by chromium(v) oxo salen complexes has been studied by DFT and experimental methods. The reaction is compared to the closely related Mn-catalyzed process in an attempt to understand the dramatic difference in selectivity between the two systems. Overall, the......-spin surface. The low-spin addition of metal oxo species to an alkene leads to an intermediate which forms epoxide either with a barrier on the low-spin surface or without a barrier after spin inversion. Supporting evidence for this intermediate was obtained by using vinylcyclopropane traps. The chromium...

  5. Chromium content of selected Greek foods.

    Science.gov (United States)

    Bratakos, Michael S; Lazos, Evangelos S; Bratakos, Sotirios M

    2002-05-01

    The total chromium content of a wide variety of Greek foods was determined by graphite furnace atomic absorption spectroscopy (GFAAS). Meat, fish and seafood, cereals and pulses were rich sources of chromium (>0.100 microg/g). Fruits, milk, oils and fats and sugar were poor sources. Differences in chromium content were found between different food classes from Greece and those from some other countries. Based on available food consumption data and chromium levels in this study, it was estimated that the chromium intake of Greeks is 143 microg/day, with vegetables, cereals and meat being the main contributors. PMID:12083715

  6. Determination of chromium combined with DNA, RNA and protein in chromium-rich brewer's yeast

    International Nuclear Information System (INIS)

    The contents of chromium in the DNA, RNA and protein fractions separated from chromium-rich and normal brewer's yeast were determined with the neutron activation analysis in order to study the combination of Cr with DNA, RNA and protein in chromium-rich brewer's yeast. The results showed that the extracting rats and concentrations of DNA, RNA and protein had no significant difference in two types of yeast, but the chromium contents of DNA, RNA and protein in the chromium-rich yeast were significantly higher than those in the normal. In addition, the content of chromium in DNA was much higher than that in RNA and protein, which indicated that the inorganic chromium compounds entered into the yeast cell, during the yeast cultivation in the culture medium containing chromium were converted into organic chromium compounds combined with DNA, RNA and protein

  7. Photoluminescence from neodymium silicide thin films formed by MEVVA ion source

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Neodymium silicides were synthesized by Nd ion implanted into Si substrates with the aid of a metal vaporvacuum arc (MEVVA) ion source. The blender of Nd5Si4 and NdSi2was formed in a neodymium-implanted silicon thinfilm during the as-implanted state, but there was only single neodymium silicide compound in the post-annealed state,and the phase changed from NdSi2 to Nd5Si4 with increasing annealing temperature. The blue-violetluminescence excited by ultra-violet was observed at the room temperature (RT), and the intensity of photoluminescence(PL) increased with increasing the neodymium ion fluence. Moreover,the photoluminescence was closely dependent onthe temperature of rapid thermal annealing (RTA). A mechanism ofphotoluminescence was discussed.

  8. Development of fused slurry silicide coatings for tantalum reentry heat shields

    Science.gov (United States)

    Warnock, R. V.; Stetson, A. R.

    1972-01-01

    A fused slurry silicide coating was developed to provide atmospheric reentry protection for the 90Ta-lOW alloy. Overlaying the silicide with a highly refractory glass greatly improved total lifetime and reliability of the coating system. Low pressure, slow cycle lifetimes in excess of 100 cycles were consistently recorded for 1700 K - 13 and 1300 N/sq m test conditions. A minimum of 25 cycles was obtained for 1810 K - 1300 N/sq m conditions. About 50 simulated reentry cycles (variable temperature, pressure, and stress) were endured by coated 1-inch miniature heat shield panels when exposed to a maximum of 1700 K and either internal or external pressure conditions.

  9. Development of a fused slurry silicide coating for the protection of tantalum alloys

    Science.gov (United States)

    Packer, C. M.; Perkins, R. A.

    1974-01-01

    Results are reported of a research program to develop a reliable high-performance, fused slurry silicide protective coating for a tantalum-10 tungsten alloy for use at 1427 to 1538 C at 0.1 to 10 torr air pressure under cyclic temperature conditions. A review of silicide coating performance under these conditions indicated that the primary wear-out mode is associated with widening of hairline fissures in the coating. Consideration has been given to modifying the oxidation products that form on the coating surface to provide a seal for these fissures and to minimize their widening. On the basis of an analysis of the phase relationships between silica and various other oxides, a coating having the slurry composition 2.5Mn-33Ti-64.5Si was developed that is effective in the pressure range from 1 to 10 torr.

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

    Science.gov (United States)

    Beckmann, C.; Zhang, K.; Hofsäss, H.; Brüsewitz, C.; Vetter, U.; Bharuth-Ram, K.

    2015-12-01

    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.

  11. Leakage current and deep levels in CoSi{sub 2} silicided junctions

    Energy Technology Data Exchange (ETDEWEB)

    Codegoni, D. [ST Microelectronics Via Olivetti 2, 20041 Agrate Brianza, Milan (Italy); Carnevale, G.P. [ST Microelectronics Via Olivetti 2, 20041 Agrate Brianza, Milan (Italy); De Marco, C. [ST Microelectronics Via Olivetti 2, 20041 Agrate Brianza, Milan (Italy); Mica, I. [ST Microelectronics Via Olivetti 2, 20041 Agrate Brianza, Milan (Italy); Polignano, M.L. [ST Microelectronics Via Olivetti 2, 20041 Agrate Brianza, Milan (Italy)]. E-mail: marialuisa.polignano@st.com

    2005-12-05

    In this work the leakage current of junctions with a self-aligned cobalt silicide is studied. It is shown that junctions with a self-aligned CoSi{sub 2} layer show a leakage current excess which is strongly reduced by increasing the PAI energy. This indicates that the observed leakage current excess is related to the CoSi{sub 2} formation conditions. The mechanism responsible for the leakage of CoSi{sub 2} junctions is investigated by current versus temperature measurements and by deep level transient spectroscopy. In addition, the role of the mechanical stress is investigated by comparing different isolation structures and by numerical stress calculations. It is concluded that the shallow trench isolation (STI) induced stress and the cobalt silicide formation concur to produce a junction leakage current increase by creating a deep level in silicon located close to midgap. This level can possibly identified with a level ascribed to a point defect excess.

  12. Synthesis of silicon nanotubes with cobalt silicide ends using anodized aluminum oxide template

    International Nuclear Information System (INIS)

    Silicon nanotubes (SiNTs) are compatible with Si-based semiconductor technology. In particular, the small diameters and controllable structure of such nanotubes are remaining challenges. Here we describe a method to fabricate SiNTs intrinsically connected with cobalt silicide ends based on highly ordered anodic aluminum oxide (AAO) templates. Size and growth direction of the SiNTs can be well controlled via the templates. The growth of SiNTs is catalyzed by the Co nanoparticles reduced on the pore walls of the AAO after annealing, with a controllable thickness at a given growth temperature and time. Simultaneously, cobalt silicide forms on the bottom side of the SiNTs.

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

    International Nuclear Information System (INIS)

    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)

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

    International Nuclear Information System (INIS)

    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 (U3O8), 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 [U3Si2], in face of a future core change. Comparing with the performance of the U3O8FE, 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)

  15. Formation of rare earth silicide clusters on Si(111)7 x 7

    International Nuclear Information System (INIS)

    Magic clusters on surfaces are of high interest because of their fascinating quantum properties and their possible application in future nanodevices. Here, the formation process as well as the structural and electronic properties of dysprosium silicide clusters on the Si(111)7 x 7 surface were studied using scanning tunneling microscopy (STM). The dysprosium silicide clusters were grown by molecular beam epitaxy using the 7 x 7 reconstructed Si(111) surface as a template for cluster formation using submonolayer metal coverages and moderate annealing temperatures. It was found that the clusters grow self-organized preferentially on the faulted halves of the 7 x 7 unit cells, and a variety of cluster shapes could be observed. At appropriate growth conditions, the formation of magic clusters, which appear centered on the 7 x 7 half unit cells, could be achieved.

  16. Silicide Coating Fabricated by HAPC/SAPS Combination to Protect Niobium Alloy from Oxidation.

    Science.gov (United States)

    Sun, Jia; Fu, Qian-Gang; Guo, Li-Ping; Wang, Lu

    2016-06-22

    A combined silicide coating, including inner NbSi2 layer and outer MoSi2 layer, was fabricated through a two-step method. The NbSi2 was deposited on niobium alloy by halide activated pack cementation (HAPC) in the first step. Then, supersonic atmospheric plasma spray (SAPS) was applied to obtain the outer MoSi2 layer, forming a combined silicide coating. Results show that the combined coating possessed a compact structure. The phase constitution of the combined coating prepared by HAPC and SAPS was NbSi2 and MoSi2, respectively. The adhesion strength of the combined coating increased nearly two times than that for single sprayed coating, attributing to the rougher surface of the HAPC-bond layer whose roughness increased about three times than that of the grit-blast substrate. After exposure at 1200 °C in air, the mass increasing rate for single HAPC-silicide coating was 3.5 mg/cm(2) because of the pest oxidation of niobium alloy, whereas the combined coating displayed better oxidation resistance with a mass gain of only 1.2 mg/cm(2). Even more, the combined coating could significantly improve the antioxidation ability of niobium based alloy at 1500 °C. The good oxidation resistance of the combined silicide coating was attributed to the integrity of the combined coating and the continuous SiO2 protective scale provided by the oxidation of MoSi2. PMID:27243944

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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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)

  19. Carbon mediated reduction of silicon dioxide and growth of copper silicide particles in uniform width channels

    DEFF Research Database (Denmark)

    Pizzocchero, Filippo; Bøggild, Peter; Booth, Tim

    2013-01-01

    channels, which are aligned with the intersections of the (100) surface of the wafer and the {110} planes on an oxidized silicon wafer, as well as endotaxial copper silicide nanoparticles within the wafer bulk. We apply energy dispersive x-ray spectroscopy, in combination with scanning and transmission...... electron microscopy of focused ion beam fabricated lammelas and trenches in the structure to elucidate the process of their formation....

  20. Formation of silicide based oxidation resistant coating over Mo-30 wt. % W alloy

    International Nuclear Information System (INIS)

    Silicide based oxidation resistant coatings were developed over Mo-30 W alloy using halide activated pack cementation process. Coated samples were characterized by SEM, optical microscopy, EDX and hardness measurements. Isothermal oxidation tests of coated alloy performed at 1000 deg C for 25h revealed a smaller weight gain at the initial stage of oxidation followed by no weight change indicating the protective nature of the coating. (author)

  1. Calculation of xenon 135 poisoning reactivity of RSG-GAS silicide fuelled

    International Nuclear Information System (INIS)

    Calculation of xenon 135 poisoning reactivity of RSG-GAS silicide fuelled. One of the important reactivity effects during reactor operation is a xenon poisoning, the reactivity depends on the power and time operation of reactor. The calculation was performed for RSG-GAS oxide 2,96 gr U/cc, silicide 2,96 gr U/cc silicide 3,55 gr U/cc fuelled using Xen Sam code, that is the xen sam code reform. In Xen Sam code, the xenon concentration is obtained by solving the simultaneous differential equation by means of limit different method. The results showed that the calculation values are close to the experiments. The equilibrium xenon reactivity will be higher if there is the increasing in the uranium density, while there is no significant change in the peak of xenon and dead time of the reactor. It shown that there is no influence in xenon reactivity for the same power levels and operation time more than 50 hours. At the other hand, if the operation time lest than 50 hours, there will be influences in equilibrium xenon reactivity, peak xenon and dead time reactor. For different power levels with the same operation time will be a significant influence to the xenon reactivity

  2. 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.

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

    Science.gov (United States)

    Yuryev, V. A.; Chizh, K. V.; Chapnin, V. A.; Mironov, S. A.; Dubkov, V. P.; Uvarov, O. V.; Kalinushkin, V. P.; Senkov, V. M.; Nalivaiko, O. Y.; Novikau, A. G.; Gaiduk, P. I.

    2015-05-01

    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 Si3N4/SiO2/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.

  4. Effect of TiOx on the formation of titanium silicide layer

    International Nuclear Information System (INIS)

    The Al/TiOx/Si, Ti/TiOx/Si, and Mo/TiOx/Si interfaces are studied, before and after thermal treatment, by secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. The metal layer is selected with regard to the formation of a titanium silicide layer. The reductive nature of the metal was found to be very significant in the interdiffusion of Si and Ti (from titanium oxide). This interdiffusion has the advantage to form a thin titanium silicide layer, which is known to have low contact resistivity. The SIMS, RBS, XPS, and XRD analyses show that after annealing for 10 min at 850 deg. C under hydrogen ambient, titanium silicide interfacial layers such as Ti5Si3 and TiSi2 C54 were formed in the case of Al/TiOx/Si and Ti/TiOx/Si structures, respectively. There is no significant reaction between Mo and TiOx and no Ti and Si interfacial reaction in the Mo/TiOx/Si system. With thermodynamic considerations, we confirm all the results found in this study

  5. Durability of Silicide-Based Thermoelectric Modules at High Temperatures in Air

    Science.gov (United States)

    Funahashi, Ryoji; Matsumura, Yoko; Barbier, Tristan; Takeuchi, Tomonari; Suzuki, Ryosuke O.; Katsuyama, Shigeru; Yamamoto, Atsushi; Takazawa, Hiroyuki; Combe, Emmanuel

    2015-08-01

    Thermoelectric modules consisting of n-type Mn2.7Cr0.3Si4Al2 and p-type MnSi1.75 legs have been fabricated by use of composite pastes of Ag with Pt or Pd. For the module prepared by Ni-B plating and with Ag paste, the specific power density reached 370 mW/cm2 at a heat-source temperature of 873 K. Ni-B plating 5 μm thick on the surfaces of the silicide legs reduced both the internal resistance and degradation of the power generated by silicide modules at temperatures up to 873 K in air. This is because of oxidation of Al diffusing into the n-type legs and reaching the Ag electrodes on both the hot and cold sides. Ni-B plating can suppress Al diffusion into n-type legs. However, cracking was observed parallel to the contact surface in the middle of the Ni-B plating layer on the p-type legs. It was also found that incorporating Pt or Pd into the Ag paste effectively suppressed degradation of the contact resistance between the silicide legs and the Ag electrodes.

  6. Palladium silicide formation under the influence of nitrogen and oxygen impurities

    Science.gov (United States)

    Ho, K. T.; Lien, C.-D.; Nicolet, M.-A.

    1985-01-01

    The effect of impurities on the growth of the Pd2Si layer upon thermal annealing of a Pd film on 100 line-type and amorphous Si substrates is investigated. Nitrogen and oxygen impurities are introduced into either Pd or Si which are subsequently annealed to form Pd2Si. The complementary techniques of Rutherford backscattering spectrometry, and N-15(p, alpha)C-12 or O-18(p, alpha)N-15 nuclear reaction, are used to investigate the behavior of nitrogen or oxygen and the alterations each creates during silicide formation. Both nitrogen and oxygen retard the silicide growth rate if initially present in Si. When they are initially in Pd, there is no significant retardation; instead, an interesting snow-plowing effect of N or O by the reaction interface of Pd2Si is observed. By using N implanted into Si as a marker, Pd and Si appear to trade roles as the moving species when the silicide front reaches the nitrogen-rich region.

  7. Tissues and urinary chromium concentrations in rats fed high-chromium diets

    International Nuclear Information System (INIS)

    Complete text of publication follows. Chromium is an essential trace elements and enhances the function of insulin as a form of chromodulin. In the subjects with a certain type of diabetics, 200 to 1,000 μg/d of chromium is administered to reduced the symptoms of diabetics. However, although there are not any health-promotive effects of chromium-administration in healthy subjects, various types of chromium supplements are commercially available in many countries; the adverse effects caused by an excessive chromium intake are feared. In the present study, to clarify the tolerable upper limit of chromium, tissue and urinary chromium concentrations, liver function and iron status were examined in rats fed high-chromium diets. Thirty-six male 4-weeks Wistar rats were divided into six groups and fed casein-based diets containing 1, 10 or 100 μg/g of chromium as chromium chloride (CrCl3) or chromium picolinate (CrPic) for 4 weeks. After the feeding, chromium concentrations in liver, kidney, small intestine and tibia were determined by inductively coupled plasma-mass spectrometry. In addition, urine samples were collected on 3rd to 4th week and their chromium concentrations were also determined. Chromium concentrations in liver, kidney, small intestine and tibia were elevated with increase of dietary chromium concentration. Urinary chromium excretion was also elevated with the increase of dietary chromium and the rate of urinary chromium excretion was less than 2% to dietary chromium intake in all the experimental groups. In the administration of 100 μg/g of chromium, rats given CrCl3 showed significantly higher tibia chromium concentration and lower urinary chromium excretion than those given CrPic. There were not any differences in iron status among the experimental groups. Activities of serum aspartate aminotransferase and alanine aminotransferase in rats fed diet containing 100 μg/g of chromium as CrPic were significantly higher than those in rats fed other diets.

  8. Food Chromium Contents, Chromium Dietary Intakes And Related Biological Variables In French Free-Living Elderly

    Science.gov (United States)

    Chromium (Cr III), an essential trace element, functions in potentiating insulin sensitivity, regulating glucose homeostasis, improving lipid profile, and maintaining lean body mass. Glucose intolerance and chromium deficiency increase with age, and could be aggravating factors of the metabolic synd...

  9. Soils contaminated with hexavalent chromium

    OpenAIRE

    Fonseca, Bruna Catarina da Silva

    2011-01-01

    Tese de doutoramento em Engenharia Química e Biológica The interest in environmental soil science has been growing in the last years due to the continuous degradation of this major natural resource. With this in mind, and because chromium and lead are two of the most toxic heavy metals frequently detected as soil contaminants in the Portuguese territory, the study and development of few remediation techniques and the indissociable description of the sorption and migration of...

  10. Carbon, chromium and molybdenum contents

    International Nuclear Information System (INIS)

    This work describes solidification experiments on white cast iron, with 15 and 20% of chromium, 2.3, 3.0 and 3.6 % of carbon and 0.0, 1.5 and 2.5 % of molybdenum in test de samples with 30 mm diameter. Measurements were performed on the austenite and eutectic formation arrests, the number of the eutectic carbide particles relative to the total and the eutectic volumes, and the volume fraction of the primary austenite

  11. Preparation and Characterization of Nanocrystalline Hard Chromium Coatings Using Eco-Friendly Trivalent Chromium Bath

    OpenAIRE

    V. S. Protsenko; V. O Gordiienko; Danilov, F. I.; Kwon, S.C.

    2011-01-01

    A new aqueous sulfate trivalent chromium bath is described. The chromium bath contains formic acid and carbamide as complexing agents. Chromium was deposited at a temperature of 30÷40 oC and a cathode current density of 10÷25 A dm-2. The bath allows obtaining thick (up to several hundred micrometers) hard chromium coatings with nanocrystalline structure. The electrodeposition rate reaches 0.8÷0.9 µm min-1.

  12. REMOVAL OF HEXAVALENT CHROMIUM FROM DRINKING WATER

    OpenAIRE

    A. R. Asgari ، F. Vaezi ، S. Nasseri ، O. Dördelmann ، A. H. Mahvi ، E. Dehghani Fard

    2008-01-01

    Removal of chromium can be accomplished by various methods but none of them is cost-effective in meeting drinking water standards. For this study, granular ferric hydroxide was used as adsorbent for removal of hexavalent chromium. Besides, the effects of changing contact time, pH and concentrations of competitive anions were determined for different amounts of granular ferric hydroxide. It was found that granular ferric hydroxide has a high capacity for adsorption of hexavalent chromium from ...

  13. Inoculation of chromium white cast iron

    Directory of Open Access Journals (Sweden)

    D. Kopyciński

    2009-01-01

    Full Text Available It has been proved that an addition of boron carbide introduced as an inoculant to the chromium white cast iron changes the structureof castings. Castings after inoculation revealed a different structure with numerous grains. Primary precipitates of chromium carbide also appeared, reducing the mechanical properties of as-cast parts. Properly established heat treatment regime makes chromium iron castings regain their, originally high, mechanical properties.

  14. Inoculation of chromium white cast iron

    OpenAIRE

    D. Kopyciński

    2009-01-01

    It has been proved that an addition of boron carbide introduced as an inoculant to the chromium white cast iron changes the structureof castings. Castings after inoculation revealed a different structure with numerous grains. Primary precipitates of chromium carbide also appeared, reducing the mechanical properties of as-cast parts. Properly established heat treatment regime makes chromium iron castings regain their, originally high, mechanical properties.

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

    International Nuclear Information System (INIS)

    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)

  16. Thin Ni silicide formation by low temperature-induced metal atom reaction with ion implanted amorphous silicon

    International Nuclear Information System (INIS)

    We have extended our recent work on buried silicide formation by Ni diffusion into a buried amorphous silicon layer to the case where silicide formation is at lower temperatures on silicon substrates which have been preamorphized. The reaction of metal atoms from a 12 nm Ni film evaporated on top of a 65 nm thick surface amorphous layer formed by 35 keV Si+ ion implantation has been investigated at temperature ≤400C. Rutherford Backscattering Spectrometry (RBS) with channeling, cross-sectional transmission electron microscopy (XTEM), x-ray diffraction and four-point-probe measurements were used to determine structure, interfacial morphology, composition and resistivity of the silicide films. It has been found that an increased rate of silicidation occurs for amorphous silicon with respect to crystalline areas permitting a selective control of the silicon area to be contacted during silicide growth. Vacuum furnace annealing at 360C for 8 hours followed by an additional step at 400C for one hour produces a continuos NiSi2 layer with a resistivity 44 μΩ cm

  17. A two-step annealing process for Ni silicide formation in an ultra-thin body RF SOI MOSFET

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Chang-Geun [Nano-Bio Electric Devices Team, IT Convergence Technology Research Division, ETRI, 161 Gajeong-dong, Yuseong-gu, Daejeon 305-350 (Korea, Republic of)], E-mail: cgahn@etri.re.kr; Kim, Tae-Youb; Yang, Jong-Heon; Baek, In-Bok [Nano-Bio Electric Devices Team, IT Convergence Technology Research Division, ETRI, 161 Gajeong-dong, Yuseong-gu, Daejeon 305-350 (Korea, Republic of); Cho, Won-ju [Department of Electronic Materials Engineering, Kwangwoon University, Seoul 139-701 (Korea, Republic of); Lee, Seongjae [Quantum Photonic Science Research Center and BK21 Program Division of Advanced Research and Education in Physics, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2008-02-15

    A two-step annealing process for Ni silicide formation in an ultra-thin body (UTB) RF SOI MOSFET is proposed to prevent a dramatic increase of the gate leakage current from the in-diffusion of Ni into the channel. The first step of the annealing process was performed at a low temperature for di-nickel silicide (Ni{sub 2}Si) formation, resulting in no in-diffusion of Ni into the channel. Next, the second step of the annealing process was performed at 500 deg. C for the formation of mono-nickel silicide (NiSi). Finally, the optimized Ni silicide SD with low resistance (5 {omega}/{open_square}) and a low leakage current was achieved on the UTB. Using the proposed two-step silicide process, UTB RF MOSFET with a gate length of 50 nm a 20-nm UTB was successfully fabricated and showed the good RF properties with a cut-off frequency of 138 GHz.

  18. Permeation of chromium salts through human skin in vitro

    DEFF Research Database (Denmark)

    Gammelgaard, Bente; Fullerton, A; Avnstorp, C;

    1992-01-01

    of the dichromate solution. Chromium skin levels increased with increasing concentrations of applied chromium salts up to 0.034 M Cr. The amount of chromium in recipient phase and skin layers increased with increasing pH when the applied solution contained potassium dichromate. This was ascribed to a decreased skin...... barrier function of the skin. The amount of chromium found in all skin layers after application of chromium chloride decreased with increasing pH due to lower solubility of the salt. The % of chromium found in the recipient phase as chromium(VI) increased with increasing total chromium concentration...... indicating a limited reduction ability of the skin in vitro....

  19. Investigation of diffusion silicide coatings interaction with substrate out of the molybdenum alloy TsM6 at elevated temperatures

    International Nuclear Information System (INIS)

    Researched have been the growth kinetics, structure and composition of the intermediate phases, being formed during the reaction of the MoSi2-based coating with the TsM6 molybdenum alloy at 1300, 1600 and 1800 deg C in the vacuum and in the inert gas medium. It is established that during the annealing of the TsM6 alloy silicide coatings in the 1300-1800 deg C temperature range, the molybdenum disilicide reacts with the alloy base, whereupon lower-silicide-based phases appear. The annealing of the MoB boron-substratum silicide coatings causes the formation of the Mo2B phase at the alloy-MoB boundary and a Mosub(x)(BSi)sub(y) complicated composition phase at the MoB-Mo5Si3 boundary

  20. Chromium in aqueous nitrate plutonium process streams: Corrosion of 316 stainless steel and chromium speciation

    International Nuclear Information System (INIS)

    This study was undertaken to determine if chromium(+6) could exist in plutonium process solutions under normal operating conditions. Four individual reactions were studied: the rate of dissolution of stainless steel, which is the principal source of chromium in process solutions; the rate of oxidation of chromium(+3) to chromium(+6) by nitric acid; and the reduction of chromium(+6) back to chromium(+3) by reaction with stainless steel and with oxalic acid. The stainless steel corrosion rate was found to increase with increasing nitric acid concentration, increasing hydrofluoric acid concentration, and increasing temperature. Oxidation of chromium(+3) to chromium(+6) was negligible at room temperature and only became significant in hot concentrated nitric acid. The rate of reduction of chromium(+6) back to chromium(+3) by reaction with stainless steel or oxalic acid was found to be much greater than the rate of the reverse oxidation reaction. Based on these findings and taking into account normal operating conditions, it was determined that although there would be considerable chromium in plutonium process streams it would rarely be found in the (+6) oxidation state and would not exist in the (+6) state in the final process waste solutions

  1. 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.

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

    International Nuclear Information System (INIS)

    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 85Kr 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 85Kr 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)

  3. The new ternary silicide Gd5CoSi2: Structural, magnetic and magnetocaloric properties

    International Nuclear Information System (INIS)

    Gd5CoSi2 was prepared by annealing at 1003 K. Its investigation by the X-ray powder diffraction shows that the ternary silicide crystallizes in a tetragonal structure deriving from the Cr5B3-type (I4/mcm space group; a=7.5799(4) and c=13.5091(12) A as unit cell parameters). The Rietveld refinement shows a mixed occupancy on the (8h) site between Si and Co atoms. Magnetization and specific heat measurements performed on Gd5CoSi2 reveal a ferromagnetic behaviour below TC=168 K. This magnetic ordering is associated to an interesting magnetocaloric effect; the adiabatic temperature change ΔTad is about 3.1 and 5.9 K, respectively, for a magnetic field change of 2 and 4.6 T. -- Graphical abstract: The adiabatic temperature change ΔTad was determined by combining the heat capacity measurements and the magnetization data. As expected, a peak near the Curie temperature of the Gd5CoSi2 ternary silicide is observed, with a maximum of ΔTad around 3.1 and 5.9 K for ΔH=2 and 4.6 T, respectively. Display Omitted Research Highlights: → We prepare and characterize for the first time the ternary silicide Gd5CoSi2. → Gd5CoSi2 crystallizes in the tetragonal structure deriving from the Cr5B3-type. → Gd5CoSi2 shows a ferromagnetic behaviour below 168 K associated with magnetocaloric properties.

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

    Energy Technology Data Exchange (ETDEWEB)

    Yagoubi, S., E-mail: said.yagoubi@u-psud.fr [European Commission, Joint Research Centre, Institute for Transuranium Elements, Postfach 2340, D-76125 Karlsruhe (Germany); LEEL SIS2M UMR 3299 CEA-CNRS, CEA Saclay, F-91191 Gif-Sur-Yvette (France); Departement de Chimie, Universite Paris-Sud 11, 91405 Orsay (France); Heathman, S. [European Commission, Joint Research Centre, Institute for Transuranium Elements, Postfach 2340, D-76125 Karlsruhe (Germany); Svane, A. [Department of Physics, University of Aarhus, DK 8000, Aarhus C (Denmark); Vaitheeswaran, G. [ACRHEM, University of Hyderabad, Hyderabad 500 046, Andhra Pradesh (India); Heines, P.; Griveau, J.-C. [European Commission, Joint Research Centre, Institute for Transuranium Elements, Postfach 2340, D-76125 Karlsruhe (Germany); Le Bihan, T. [European Synchrotron Radiation Facility, 38043 Grenoble (France); Idiri, M.; Wastin, F.; Caciuffo, R. [European Commission, Joint Research Centre, Institute for Transuranium Elements, Postfach 2340, D-76125 Karlsruhe (Germany)

    2013-01-05

    Highlights: Black-Right-Pointing-Pointer High pressure studies on uranium and thorium silicide compounds. Black-Right-Pointing-Pointer Bulk modulus B{sub 0} at ambient pressure are obtained from the measured P-V relations. Black-Right-Pointing-Pointer Experimental results are well reproduced by the calculated equation of state. Black-Right-Pointing-Pointer The electronic densities of states are calculated for ThSi, USi and USi2. - Abstract: The actinide silicides ThSi, USi and USi{sub 2} 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, for ThSi, USi and USi{sub 2}, respectively. At ambient conditions, the uranium silicides crystallize in tetragonal structures (space groups: I4/mmm for USi and I4{sub 1}/amd for USi{sub 2}), while ThSi adopts an orthorhombic structure (space group: Pbnm) (including an anharmonic analysis of the silicon). These structures are found to be stable with no structural transitions observed up to the highest pressures achieved. The zero-pressure bulk modulus B{sub 0} and its pressure derivative B{sub 0}{sup Prime} at ambient pressure are obtained from the measured P-V relations. The experiments are accompanied by first principles calculations using the full-potential linear muffin-tin orbital method within the generalized gradient approximation for exchange-correlation effects. Experimental results are well reproduced by the calculated equation of state and ground state properties.

  5. Combustion synthesis of molybdenum silicides and borosilicides for ultrahigh-temperature structural applications

    Science.gov (United States)

    Alam, Mohammad Shafiul

    Molybdenum silicides and borosilicides are promising structural materials for gas-turbine power plants. A major challenge, however, is to simultaneously achieve high oxidation resistance and acceptable mechanical properties at high temperatures. For example, molybdenum disilicide (MoSi2) has excellent oxidation resistance and poor mechanical properties, while Mo-rich silicides such as Mo5Si3 (called T 1) have much better mechanical properties but poor oxidation resistance. One approach is based on the fabrication of MoSi2-T 1 composites that combine high oxidation resistance of MoSi2 and good mechanical properties of T1. Another approach involves the addition of boron to Mo-rich silicides for improving their oxidation resistance through the formation of a borosilicate surface layer. In particular, Mo 5SiB2 (called T2) phase is considered as an attractive material. In the thesis, MoSi2-T1 composites and materials based on T2 phase are obtained by mechanically activated SHS. Use of SHS compaction (quasi-isostatic pressing) significantly improves oxidation resistance of the obtained MoSi2-T1 composites. Combustion of Mo-Si-B mixtures for the formation of T2 phase becomes possible if the composition is designed for the addition of more exothermic reactions leading to the formation of molybdenum boride. These mixtures exhibit spin combustion, the characteristics of which are in good agreement with the spin combustion theory. Oxidation resistance of the obtained Mo-Si-B materials is independent on the concentration of Mo phase in the products so that the materials with a higher Mo content are preferable because of better mechanical properties. Also, T2 phase has been obtained by the chemical oven combustion synthesis technique.

  6. Alkane dehydrogenation over supported chromium oxide catalysts

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Schoonheydt, R.A.

    1999-01-01

    The dehydrogenation of alkanes over supported chromium oxide catalysts in the absence of oxygen is of high interest for the industrial production of propene and isobutene. In this review, a critical overview is given of the current knowledge nowadays available about chromium-based dehydrogenation ca

  7. Effect of Annealing Temperature on the Formation of Silicides and the Surface Morphologies of PtSi Films

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The effect of annealing temperature on the formation of the PtSi phase, distribution of silicides and the surface morphologies of silicides films is investigated by XPS, AFM. It is shown that the phase sequences of the films change from Pt-Pt2Si-PtSi-Si to Pt+Pt2Si+PtSi-PtSi-Si or Pt+Pt2Si+PtSi-PtSi-Si with an increase of annealing temperature and the reason for the formation of mixed layers is discussed.

  8. Electrochemical deposition of coating from carbide, boride and silicide of IV-VIA group metals in ion melts

    International Nuclear Information System (INIS)

    The prehistory of the development of methods of production of metal-like refractory coatings (titanium, tantalum, niobium, vanadium, zirconium carbides, borides and silicides) with the help of high-temperature electrochemical synthesis (HTES) in ionic melts is described. A review is made on studies into the process of HTES of refractory metal borides, carbides and silicides, manufacture conditions for the coatings and electrolyte compositions (oxide, oxide-fluoride, chloride, chloride-fluoride melts). Structure and properties of coatings produced by the method of HTES are under consideration

  9. Silicidation of Mo-alloyed ytterbium: Mo alloying effects on microstructure evolution and contact properties

    International Nuclear Information System (INIS)

    In this study, we investigated the effects of Mo addition to Yb as a contact material with Si for metal–oxide-semiconductor field-effect transistors (MOSFETs) to mitigate oxidation problems, a persistent problem for rare-earth metal-based contacts (such as Yb/Si and Er/Si). Our thorough materials characterization using transmission electron microscopy and X-ray diffraction unravels Mo segregation during silicidation and its effect against oxidation. I–V characteristics, measured from Schottky diodes produced from the samples, reflect such microstructure evolution and demonstrate a strong improvement in contact properties at high temperatures

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

    International Nuclear Information System (INIS)

    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)

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

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasan, G. [Northern Ireland Semiconductor Research Centre, School of Electrical and Electronic Engineering, Queen' s University, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland (United Kingdom)]. E-mail: g.srinivasan@ee.qub.ac.uk; Bain, M.F. [Northern Ireland Semiconductor Research Centre, School of Electrical and Electronic Engineering, Queen' s University, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland (United Kingdom); Bhattacharyya, S. [Northern Ireland Semiconductor Research Centre, School of Electrical and Electronic Engineering, Queen' s University, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland (United Kingdom); Baine, P. [Northern Ireland Semiconductor Research Centre, School of Electrical and Electronic Engineering, Queen' s University, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland (United Kingdom); Armstrong, B.M. [Northern Ireland Semiconductor Research Centre, School of Electrical and Electronic Engineering, Queen' s University, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland (United Kingdom); Gamble, H.S. [Northern Ireland Semiconductor Research Centre, School of Electrical and Electronic Engineering, Queen' s University, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland (United Kingdom); McNeill, D.W. [Northern Ireland Semiconductor Research Centre, School of Electrical and Electronic Engineering, Queen' s University, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland (United Kingdom)

    2004-12-15

    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{sub 1-} {sub x} Ge {sub x} , with 0 {<=}x {<=} 0.3. Cross bridge Kelvin resistor (CKBR) structures were fabricated incorporating CVD WSi{sub 2} and polycrystalline SiGe. Tungsten silicide contacts to control polysilicon CKBR structures have been shown to be of high quality with specific contact resistance {rho} {sub c} values 3 x 10{sup -7} ohm cm{sup 2} and 6 x 10{sup -7} ohm cm{sup 2} obtained to boron and phosphorus implanted samples respectively. The SiGe CKBR structures show that the inclusion of Ge yields a reduction in {rho} {sub c} for both dopant types. The boron doped SiGe exhibits a reduction in {rho} {sub c} from 3 x 10{sup -7} to 5 x 10{sup -8} ohm cm{sup 2} as Ge fraction is increased from 0 to 0.3. The reduction in {rho} {sub 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 {rho} {sub c} to Ge fraction with a lowest value in this work of 3 x 10{sup -7} ohm cm{sup 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.

  12. Modeling the band structure of the higher manganese silicides starting from Mn$_4$Si$_7$

    OpenAIRE

    V., Vijay Shankar; Tseng, Yu-Chih; Kee, Hae-Young

    2016-01-01

    The higher manganese silicides (HMS), with the chemical formula MnSi$_x$($x \\approx 1.73 - 1.75$), have been attracted a lot of attention due to their potential application as thermoelectric materials. While the electronic band structures of HMS have been previously studied using first principle calculations, the relation between crystal structures of Mn and Si atoms and their band structures is not well understood. Here we study Mn$_4$Si$_7$ using first principle calculations and show that a...

  13. Transient behavior of silicide plate-type fuel during reactivity initiated accident conditions

    International Nuclear Information System (INIS)

    The results of transient experiments using a low enriched uranium silicide mini-plate fuel (19 w/o 235U, 4.8gU/c.c.) for research reactors are described. Studies were addressed mainly to clarifying 1) fuel failure threshold and failure mechanism, and 2) dimensional stability of the fuel plate at the temperature ranged from 140degC to 970degC. The pulse irradiation of the mini-plate fuels was performed in the Nuclear Safety Research Reactor (NSRR) at the Japan Atomic Energy Research Institute (JAERI). (author)

  14. Synthesis of metallic silicide fullerenes and the characteristics thereof by mass spectrometry

    Institute of Scientific and Technical Information of China (English)

    CHEN YiChi; GUO Liang; ZHU LiQun

    2007-01-01

    Direct current arc discharge is used for the study on the synthesis of metallofullerenes (MFs) to discover whether there exist metallic silicide fullerenes and silicon fullerenes. The resultant components are isolated by the multistage high-performance liquid chromatography (HPLC) and analyzed with the Time-of-Flight (TOF) mass spectrometry. Results show that there exist fullerenes such as SiC69, YSi2C64, YSi2C78, Y3Si2C78 as well as Y2Si2C90 which are structurally similar to (Y2C2)@C82.

  15. Synthesis of metallic silicide fullerenes and the characteristics thereof by mass spectrometry

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Direct current arc discharge is used for the study on the synthesis of metallo-fullerenes (MFs) to discover whether there exist metallic silicide fullerenes and silicon fullerenes. The resultant components are isolated by the multistage high-performance liquid chromatography (HPLC) and analyzed with the Time-of-Flight (TOF) mass spectrometry. Results show that there exist fullerenes such as SiC69, YSi2C64, YSi2C78, Y3Si2C78 as well as Y2Si2C90 which are structurally similar to (Y2C2)@C82.

  16. Neutronic calculations of PARR-1 cores using leu-silicide fuel. [leu (low enriched uranium)

    Energy Technology Data Exchange (ETDEWEB)

    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 power operation and the equilibrium cores. The burnup study of the equilibrium core and calculations for discharged fuel 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.

  17. Oxidation resistant silicide coatings for Nbss/Nb5Si3 in-situ composites

    International Nuclear Information System (INIS)

    Oxidation protective silicide coatings for the new Nbss/Nb5Si3 in-situ composites were prepared by molten salt method. The experiment results indicated that the majority phase in the coating was NbSi2. More Nb5Si3 was formed at the interface between the substrate and NbSi2 layer during the oxidation. The oxidation resistance of the composites was improved by the coating, significantly. The improvement in the oxidation resistance of the composites maybe mainly attributed to the formation of large amount of SiO2 and Al2O3 on surface of coating. (orig.)

  18. Neutron scattering and models: Chromium

    International Nuclear Information System (INIS)

    Differential neutron elastic-scattering cross sections of elemental chromium are measured from 4.5 ∼ 10 MeV in steps of ∼ 0.5 MeV and at ≥ 40 scattering angles distributed between ∼ 17 degree--160 degree. Concurrently differential cross sections for the inelastic neutron excitation of the yrast 2+ (1.434 MeV) level in d52Cr are determined. In addition, broad inelastically-scattered neutron groups are observed corresponding to composite excitation of levels up to ∼ 5.5 MeV in the various chromium isotopes. These experimental results are combined with low-energy values previously reported from this laboratory, with recent ∼ 8 → 15 MeV data measured at the Physikalisch-Technische Bundesanstalt and with a 21.6 MeV result from the literature to form an extensive neutron-scattering data base which is interpreted in the context of spherical-optical and coupled-channels (rotational and vibrational) models. These models reasonably describe the observables but indicate rather large energy-dependent parameter trends at low energies similar to those previously reported near the peak of the So strength function in studies at this laboratory. The physical implications of the measurements and models are discussed including deformation, coupling, dispersive and asymmetry effects

  19. Chemical Stability of Chromium Carbide and Chromium Nitride Powders Compared with Chromium Metal in Synthetic Biological Solutions

    OpenAIRE

    Tao Jiang; Inger Odnevall Wallinder; Gunilla Herting

    2012-01-01

    Chromium carbide (Cr-C) and chromium nitride (Cr-N) powders were compared with a chromium metal powder (Cr-metal) to evaluate their chemical stability in solution. All three powders were exposed in five different synthetic biological solutions of varying pH and chemical composition simulating selected human exposure conditions. Characterisation of the powders, using GI-XRD, revealed that the predominant bulk crystalline phases were Cr7C3 and Cr2N for Cr-C and Cr-N respectively. The outermost ...

  20. Low-chromium reduced-activation chromium-tungsten steels

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Alexander, D.J.; Maziasz, P.J. [Oak Ridge National Lab., TN (United States)

    1996-10-01

    Bainitic microstructures formed during continuous cooling can differ from classical upper and lower bainite formed during isothermal transformation. Two types of non-classical bainite were observed depending on the cooling rate: carbide-free acicular bainite at rapid cooling rates and granular bainite at slower cooling rates. The Charpy impact toughness of the acicular ferrite was found to be considerably better than for the granular bainite. It was postulated that alloying to improve the hardenability of the steel would promote the formation of acicular bainite, just as increasing the cooling rate does. To test this, chromium and tungsten were added to the 2 1/4Cr-2W and 2 1/4Cr-2WV steel compositions to increase their hardenability, and the microstructures and mechanical properties were examined.

  1. Uranium silicide pellet fabrication by powder metallurgy for accident tolerant fuel evaluation and irradiation

    Science.gov (United States)

    Harp, Jason M.; Lessing, Paul A.; Hoggan, Rita E.

    2015-11-01

    In collaboration with industry, Idaho National Laboratory is investigating uranium silicide for use in future light water reactor fuels as a more accident resistant alternative to uranium oxide base fuels. Specifically this project was focused on producing uranium silicide (U3Si2) pellets by conventional powder metallurgy with a density greater than 94% of the theoretical density. This work has produced a process to consistently produce pellets with the desired density through careful optimization of the process. Milling of the U3Si2 has been optimized and high phase purity U3Si2 has been successfully produced. Results are presented from sintering studies and microstructural examinations that illustrate the need for a finely ground reproducible particle size distribution in the source powder. The optimized process was used to produce pellets for the Accident Tolerant Fuel-1 irradiation experiment. The average density of these pellets was 11.54 ± 0.06 g/cm3. Additional characterization of the pellets by scanning electron microscopy and X-ray diffraction has also been performed. Pellets produced in this work have been encapsulated for irradiation, and irradiation in the Advanced Test Reactor is expected soon.

  2. Uranium silicide pellet fabrication by powder metallurgy for accident tolerant fuel evaluation and irradiation

    International Nuclear Information System (INIS)

    In collaboration with industry, Idaho National Laboratory is investigating uranium silicide for use in future light water reactor fuels as a more accident resistant alternative to uranium oxide base fuels. Specifically this project was focused on producing uranium silicide (U3Si2) pellets by conventional powder metallurgy with a density greater than 94% of the theoretical density. This work has produced a process to consistently produce pellets with the desired density through careful optimization of the process. Milling of the U3Si2 has been optimized and high phase purity U3Si2 has been successfully produced. Results are presented from sintering studies and microstructural examinations that illustrate the need for a finely ground reproducible particle size distribution in the source powder. The optimized process was used to produce pellets for the Accident Tolerant Fuel-1 irradiation experiment. The average density of these pellets was 11.54 ±0.06 g/cm3. Additional characterization of the pellets by scaning electron microscopy and X-ray diffraction has also been performed. As a result, pellets produced in this work have been encapsulated for irradiation, and irradiation in the Advanced Test Reactor is expected soon

  3. Effect of annealing on magnetic properties and silicide formation at Co/Si interface

    Indian Academy of Sciences (India)

    Shivani Agarwal; V Ganesan; A K Tyagi; I P Jain

    2006-11-01

    The interaction of Co (30 nm) thin films on Si (100) substrate in UHV using solid state mixing technique has been studied. Cobalt was deposited on silicon substrate using electron beam evaporation at a vacuum of 4 × 10-8 Torr having a deposition rate of about 0.1 Å/s. Reactivity at Co/Si interface is important for the understanding of silicide formation in thin film system. In the present paper, cobalt silicide films were characterized by atomic force microscopy (AFM) and secondary ion mass spectroscopy (SIMS) in terms of the surface and interface morphologies and depth profile, respectively. The roughness of the samples was found to increase up to temperature, 300°C and then decreased with further rise in temperature, which was due to the formation of crystalline CoSi2 phase. The effect of mixing on magnetic properties such as coercivity, remanence etc at interface has been studied using magneto optic Kerr effect (MOKE) techniques at different temperatures. The value of coercivity of pristine sample and 300°C annealed sample was found to be 66 Oe and 40 Oe, respectively, while at high temperature i.e. 748°C, the hysteresis disappears which indicates the formation of CoSi2 compound.

  4. 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.

  5. Mitigation of interfacial silicide reactions for electroplated CoPt films on Si substrates

    Science.gov (United States)

    Oniku, Ololade D.; Arnold, David P.

    2015-12-01

    We report in this paper the influence of film thickness on the material and magnetic properties of electroplated CoPt permanent magnets. Layers of CoPt magnets with film thicknesses ranging from 0.5 μm to 5 μm are deposited into photoresist molds (3.5 mm x 3.5 mm square and 5 μm x 50 μm arrays) on a (100)Si substrate coated with 10 nm/100 nm Ti/Cu adhesion/seed layer. Results show an unexpected reduction in magnetic properties for films below 2 μm thick. This effect is determined to be a consequence of metal-silicide reactions at the substrate interface during annealing leading to the formation of a non-magnetic layer at the interface. Subsequently, a TiN diffusion-barrier layer is added to inhibit the silicide reaction and thereby maintain strong magnetic properties (Hci ∼800 kA/m, Mr/Ms = 0.8) in micron- thick electroplated CoPt layers.

  6. Prediction of Stable Ruthenium Silicides from First-Principles Calculations: Stoichiometries, Crystal Structures, and Physical Properties.

    Science.gov (United States)

    Zhang, Chuanzhao; Kuang, Xiaoyu; Jin, Yuanyuan; Lu, Cheng; Zhou, Dawei; Li, Peifang; Bao, Gang; Hermann, Andreas

    2015-12-01

    We present results of an unbiased structure search for stable ruthenium silicide compounds with various stoichiometries, using a recently developed technique that combines particle swarm optimization algorithms with first-principles calculations. Two experimentally observed structures of ruthenium silicides, RuSi (space group P2(1)3) and Ru2Si3 (space group Pbcn), are successfully reproduced under ambient pressure conditions. In addition, a stable RuSi2 compound with β-FeSi2 structure type (space group Cmca) was found. The calculations of the formation enthalpy, elastic constants, and phonon dispersions demonstrate the Cmca-RuSi2 compound is energetically, mechanically, and dynamically stable. The analysis of electronic band structures and densities of state reveals that the Cmca-RuSi2 phase is a semiconductor with a direct band gap of 0.480 eV and is stabilized by strong covalent bonding between Ru and neighboring Si atoms. On the basis of the Mulliken overlap population analysis, the Vickers hardness of the Cmca structure RuSi2 is estimated to be 28.0 GPa, indicating its ultra-incompressible nature. PMID:26576622

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

    International Nuclear Information System (INIS)

    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/cm3. It is difficult to achieve a higher uranium-loading than that because of fabricability constraints. To overcome those difficulties, the use of uranium silicide U3Si based is considered. The excess of U is obtained by synthesising U3Si2 in Si-hypostoichiometric stage, without applying heat treatment to the ingot as it can generate undesired U3Si. The U U will react with the matrix to form U alx compound, that its pressure is tolerable. This experiment is to consider possibilities of employing the U3Si2 as nuclear fuel element which have been performed by synthesising U3Si2-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

  8. Facile Preparation of a Platinum Silicide Nanoparticle-Modified Tip Apex for Scanning Kelvin Probe Microscopy.

    Science.gov (United States)

    Lin, Chun-Ting; Chen, Yu-Wei; Su, James; Wu, Chien-Ting; Hsiao, Chien-Nan; Shiao, Ming-Hua; Chang, Mao-Nan

    2015-12-01

    In this study, we propose an ultra-facile approach to prepare a platinum silicide nanoparticle-modified tip apex (PSM tip) used for scanning Kelvin probe microscopy (SKPM). We combined a localized fluoride-assisted galvanic replacement reaction (LFAGRR) and atmospheric microwave annealing (AMA) to deposit a single platinum silicide nanoparticle with a diameter of 32 nm on the apex of a bare silicon tip of atomic force microscopy (AFM). The total process was completed in an ambient environment in less than 3 min. The improved potential resolution in the SKPM measurement was verified. Moreover, the resolution of the topography is comparable to that of a bare silicon tip. In addition, the negative charges found on the PSM tips suggest the possibility of exploring the use of current PSM tips to sense electric fields more precisely. The ultra-fast and cost-effective preparation of the PSM tips provides a new direction for the preparation of functional tips for scanning probe microscopy. PMID:26471480

  9. 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.

  10. Geometry-dependent phase, stress state and electrical properties in nickel-silicide nanowires

    Science.gov (United States)

    Wang, C. C.; Lai, W. T.; Hsiao, Y. Y.; Chen, I. H.; George, T.; Li, P. W.

    2016-05-01

    We report that the geometry of single-crystalline Si nanowires (NWs) prior to salicidation at 500 °C is the key factor controlling the phase, stress state, and electrical resistivity of the resulting Ni x Si y NWs of width less than 100 nm. This is a radical departure from previous observations of a single phase formation for nickel silicides generated from the silicidation of bulk Si substrates. The phase transition from NiSi for large NWs ( W Si NW  =  250–450 nm) to Ni2Si for small NWs ( W Si NW  =  70–100 nm) is well correlated with the observed volumetric expansion and electrical resistivity variation with the NW width. For the extremely small dimensions of Ni x Si y NWs, we propose that the preeminent, kinetics-based Zhang and d’Heurle model for salicidation be modified to a more thermodynamically-governed, volume-expansion dependent Ni x Si y phase formation. A novel, plastic deformation mechanism is proposed to explain the observed, geometry-dependent Ni x Si y NW phase formation that also strongly influences the electrical performance of the NWs.

  11. Study of temperature dependent zirconium silicide phases in Zr/Si structure by differential scanning calorimetry

    International Nuclear Information System (INIS)

    The differential scanning calorimetry (DSC) technique is employed to study the formation of different silicide compounds of Zr thin-film deposited on a 100 μm-thick Si (1 0 0) substrate by dc sputtering. A detailed analysis shows that silicide layers start growing at  ∼246 °C that changes to stable ZrSi2 at 627 °C via some compounds with different stoichiometric ratios of Zr and Si. It is further observed that oxygen starts reacting with Zr at  ∼540 °C but a stoichiometric ZrO2 film is formed after complete consumption of Zr metal at 857 °C. A further rise in temperature changes a part of ZrSi2 to Zr-Silicate. The synchrotron radiation-based grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy studies also corroborate the above findings. Atomic force microscopy is also carried out on the samples. It is evident from the observations that an intermixing and nucleation of Zr and Si occur at lower temperature prior to the formation of the interfacial silicate layer. Zr-Silicate formation takes place only at a higher temperature. (paper)

  12. Two-dimensional electronic structure of dysprosium silicide nanowires on Si(557)

    International Nuclear Information System (INIS)

    Rare earth silicide nanostructures are of high interest because of their extremely low Schottky barriers on n-Si(111) and the formation of nanowires with one-dimensional metallicity on Si(001). In this work, the self-organized growth of monolayer-thick dysprosium silicide nanowires on Si(557) has been studied by scanning tunnelling microscopy and angle-resolved photoelectron spectroscopy. The bare Si(557) surface is characterized by (111) and (112) facets. Accordingly, we observed the nanowires forming on the (111) facets. For coverages of 2A dysprosium, nanowire lengths exceeding 1μm and widths around 5 nm were found. Their electronic structure shows a strong dispersion both parallel and perpendicular to the nanowires, which is assigned to the band structure of DySi2 monolayers on Si(111). At higher coverages similar nanowires are observed at the (111) facets, which show characteristic structural properties of the multilayer growth and also the Dy3Si5 multilayer band structure

  13. Bainitic chromium-tungsten steels with 3 pct chromium

    International Nuclear Information System (INIS)

    Previous work on 3Cr-1.5MoV (nominally Fe-3Cr-2.5Mo-0.25V-0.1C), 2.25Cr-2W (Fe-2.25Cr-2W-0.1C), and 2.25Cr-2WV (Fe-2.25Cr-2W-0.25V-0.1C) steels indicated that the impact toughness of these steels depended on the microstructure of the bainite formed during continuous cooling from the austenization temperature. Microstructures formed during continuous cooling can differ from classical upper and lower bainite formed during isothermal transformation. Two types of nonclassical microstructures were observed depending on the cooling rate: carbide-free acicular bainite at rapid cooling rates and granular bainite at slower cooling rates. The Charpy impact toughness of the acicular ferrite was considerably better than for the granular bainite. It was postulated that alloying to improve the hardenability of the steel would promote the formation of acicular bainite, just as increasing the cooling rate does. To test this, chromium and tungsten were added to the 2.25Cr-2W and 2.25Cr-2WV steel compositions to increase their hardenability. Charpy testing indicated that the new 3Cr-W and 3Cr-WV steels had improved impact toughness, as demonstrated by lower ductile-brittle transition temperatures and higher upper-shelf energies. This improvement occurred with less tempering than was necessary to achieve similar toughness for the 2.25Cr steels and for high-chromium (9 to 12 pct Cr) Cr-W and Cr-Mo steels

  14. Reproductive toxicological aspects of chromium in males

    International Nuclear Information System (INIS)

    To expand our present understanding of the effects of chromium on male fertility a number of studies were designed to achieve this through the use of chromium intoxicated experimental animals and through investigation of sexual hormones and sperm quality in welders. Also in view of the lack of an experimental model for effects of noxious substance on the epididymal spermatozoa the main objectives of the series of studies reviewed here were: A. To establish a model for evaluation of epididymal sperm count and motility in the rat. B. To investigate and compare the effects of tri- and hexavalent chromium on epididymal spermatozoa. Further to describe the effects of low-dose long-time exposure of rats to the most toxicological interesting chromium oxidative state - hexavalent chromium. C. By the use of autoradiography and γ-countinuing to expand the present knowledge on the distribution of chromium in the body with special reference to the male reproductive organs. D. To describe the effects of exposure to hexavalent chromium in welding fume on levels of sexual hormones and semen parameters in welders. (EG)

  15. Synthesis of Chromium (Ⅲ) 5-aminosalicylate

    Institute of Scientific and Technical Information of China (English)

    LI Wei; HAO Er-jun; JIANG Yu-qin

    2004-01-01

    As we all known that diabetes is a chronic disease with major health consequences.Research has revealed that the occurrence of diabetes have great thing to do with the chromium deficient. Almost 40 years after the first report of glucose tolerance factor(GTF) [1], no conclusive evidence for an isolable ,biologically active form of chromium exited. Three materials have been proposed to be the biologically active form of chromium: "glucose tolerance factor", chromium Picolinate and low-molecular-weight chromium-binding substance (LWMCr) [2] . So there is potential for the design of new chromium drugs .5-Aminosalicylic acid (5-ASA) is identified as an active component in the therapy of inflammatory bowel disease (IBD) such as Crohn's disease and ulcerative colitis . The therapeutic action of 5-ASA is believed to be coupled to its ability to act as a free radical scavenger [3-4],acting locally on the inflamed colonic mucosa [5-7]. However, the clinical use of 5-ASA is limited, since orally administered 5-ASA is rapidly and completely absorbed from the upper gastrointestinal tract and therefore the local therapeutic effects of 5-ASA in the colon is hardly expected.In this paper, we report the synthesis of chromium(Ⅲ)5-aminosalicylate from 5-ASA and CrCl3. 6H2O.The synthesis route is as follow:The complex has been characterized by elemental analysis, IR spectra, X-ray powder diffractionand TG-DTA . They indicate that the structure is tris(5-ASA) Chromium . Experiments show that thecomplex has a good activity for supplement tiny dietary chromium, lowering blood glucose levels,lowering serum lipid levels and in creasing lean body mass .

  16. Formation of Mg silicides on amorphous Si. Origin and role of high pressure in the film growth

    International Nuclear Information System (INIS)

    Growth of Mg film on amorphous Si (a-Si) at room temperature in UHV conditions was studied in situ with optical differential reflection spectroscopy and electron energy loss spectroscopy. The phase composition of the film was also studied by high-resolution transmission electron microscopy. The mechanism of silicide film growth on a-Si is considered. The origin of internal stress within the growing film and its role in the silicide film growth process are discussed. Due to high pressure occurring within the growing film, the first phase to form is the hexagonal silicide phase h-Mg2Si. According to the DRS data, the phase h-Mg2Si is semiconducting. The new peak in the differential reflectance spectrum is assigned to the h-Mg2Si. At later stages of Mg deposition the cubic silicide phase c-Mg2Si grows. - Highlights: • The film growth by UHV deposition of Mg on amorphous Si layer was studied. • Two Mg2Si phases, hexagonal and cubic, were formed on amorphous Silicon. • The metastable h-Mg2Si forms first, due to very high stress inside the film. • The stress is induced by chemical forces during intermixing of Mg with Si. • The film growth stages are clearly seen by Differential Reflectance Spectroscopy

  17. 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

    2015-12-01

    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/cm2, 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.

  18. Chromium in leather footwear-risk assessment of chromium allergy and dermatitis

    DEFF Research Database (Denmark)

    Thyssen, Jacob P; Strandesen, Maria; Poulsen, Pia B;

    2012-01-01

    Background. Chromium-tanned leather footwear, which releases >3 ppm hexavalent Cr(VI), may pose a risk of sensitizing and eliciting allergic dermatitis. Objectives. To determine the content and potential release of chromium in leather footwear and to discuss the prevention of chromium contact...... allergy and dermatitis. Methods. Sixty pairs of leather shoes, sandals and boots (20 children's, 20 men's, and 20 women's) were purchased in Copenhagen and examined with X-ray fluorescence spectroscopy. Chromium was extracted according to the International Standard, ISO 17075. The detection level for Cr......(VI) was 3 ppm. Results. Chromium was identified in 95% of leather footwear products, the median content being 1.7% (range 0-3.3%). No association with store category or footwear category was found. A tendency for there to be a higher chromium content in footwear with high prices was shown (p(trend) = 0...

  19. Characteristics of chromium-allergic dermatitis patients prior to regulatory intervention for chromium in leather

    DEFF Research Database (Denmark)

    Bregnbak, David; Thyssen, Jacob P; Zachariae, Claus;

    2014-01-01

    BACKGROUND: Chromium-tanned leather articles currently constitute the most important cause of contact allergy to chromium in Denmark. A regulation on the content of hexavalent chromium in leather was adopted in November 2013 by the EU member states. OBJECTIVES: To characterize patients with...... chromium allergy and their disease, to serve as a baseline for future studies on the potential effect of the new regulation on chromium in leather. METHODS: A questionnaire case-control study was performed on 155 dermatitis patients with positive patch test reactions to potassium dichromate and a matched...... control group of 621 dermatitis patients. Comparisons were made by use of a χ(2) -test and the Mann-Whitney U-test. Logistic regression analyses were used to test for associations. RESULTS: Sixty-six per cent of chromium-allergic patients had a positive history of contact dermatitis caused by leather...

  20. Chromium intensification of a processed dental radiograph

    International Nuclear Information System (INIS)

    This study was undertaken to determine (1) the usefulness of chromium intensifier to improve the diagnostic quality of light radiograph; (2) the effect of chromium intensifier on density contrast; and (3) the effect of various chemical concentrations on density. The following results obtained: 1. CHROMIUM INTENSIFIER is useful for intensifying and improving the diagnostic quality of a light dental radiograph. 2. The degree of intensification can be controlled by varying bleaching time, repeating the processing, varying the proportions of the potassium bicarbonate and hydrochloric acid solutions. 3. The image produced is black and permanent. 4. The intensifier increases density and contrast

  1. Chromium (VI) adsorption on boehmite

    Energy Technology Data Exchange (ETDEWEB)

    Granados-Correa, F. [Instituto Nacional de Investigaciones Nucleares, Apartado Postal 18-1027 Col., Escandon, Delegacion Miguel Hidalgo, C.P. 11801 Mexico, D.F. (Mexico)], E-mail: fgc@nuclear.inin.mx; Jimenez-Becerril, J. [Instituto Nacional de Investigaciones Nucleares, Apartado Postal 18-1027 Col., Escandon, Delegacion Miguel Hidalgo, C.P. 11801 Mexico, D.F. (Mexico)

    2009-03-15

    Boehmite was synthesized and characterized in order to study the adsorption behavior and the removal of Cr(VI) ions from aqueous solutions as a function of contact time, initial pH solution, amount of adsorbent and initial metal ion concentration, using batch technique. Adsorption data of Cr(VI) on the boehmite were analyzed according to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) adsorption models. Thermodynamic parameters for the adsorption system were determinated at 293, 303, 313 and 323 K temperatures. The kinetic values and thermodynamic parameters from the adsorption process show that the Cr(VI) ions adsorption on boehmite is an endothermic and spontaneous process. These results show that the boehmite could be considered as a potential adsorbent for chromium ions in aqueous solutions.

  2. Chromium – An essential mineral

    Directory of Open Access Journals (Sweden)

    Merlin D Lindemann

    2009-09-01

    Full Text Available The status of chromium (Cr is not a new question. Cr is clearly an essential nutrient; this is a position that has been held for over three decades by individual scientists, groups of scientists, and governmental committees. The most uniform response across species with regard to Cr deficiency symptoms that are responsive to Cr supplementation are alterations in glucose metabolism with special reference to peripheral tissue sensitivity to insulin. Because the body’s ability to control blood glucose is critical to many life functions, and loss of ability to adequately control blood glucose can lead to many health debilitations, a consequence of Cr supplementation can be improved health and reproductive outcomes as well as improved survival rate or life span.

  3. Occupational asthma due to chromium.

    Science.gov (United States)

    Leroyer, C; Dewitte, J D; Bassanets, A; Boutoux, M; Daniel, C; Clavier, J

    1998-01-01

    We describe a 28-year-old subject employed as a roofer in a construction company since the age of 19, who developed work-related symptoms of a cough, shortness of breath, wheezing, rhinitis and headaches. A description of a usual day at work suggested that the symptoms worsened while he was sawing corrugated fiber cement. Baseline spirometry was normal, and there was a mild bronchial hyperresponsiveness to carbachol. A skin patch test to chromium was negative. A specific inhalation challenge showed a boderline fall in forced expiratory volume in 1 s (FEV1) after exposure to fiber cement dust. Exposure to nebulization of potassium dichromate (K2Cr2O7), at 0.1 mg.ml-1 for 30 min, was followed by an immediate fall by 20% FEV1. Simultaneously, a significant increase in bronchial hyperresponsiveness was demonstrated. PMID:9782225

  4. Chromium isotope uptake in carbonates

    DEFF Research Database (Denmark)

    Rodler, Alexandra

    Chromium (Cr) is a redox sensitive element potentially capable of tracing fine-scale fluctuations of the oxygenation of Earth’s early surface environments and seawater. The Cr isotope composition of carbonates could perhaps be used as paleo-redox proxy to elucidate changes in the geological past....... Processes that potentially fractionate Cr isotopes, perhaps during deposition, burial and alteration need to be constrained.Previous studies have shown that Cr isotopes are fractionated during oxidative weathering on land, where heavy Cr isotopes are preferentially removed with Cr(VI) while residual soils...... retain an isotopically light Cr signature. Cr(VI) enriched in heavy Cr isotopes is then transported via river waters to the oceans and sequestered into marine sediments. Marine chemical sediments such asbanded iron formations and modern marine carbonates have proven useful in recording the Cr isotope...

  5. Corrosion behaviors of a γ-toughened Cr13Ni5Si2/Cr3Ni5Si2 multi-phase ternary metal silicide alloy in NaCl solution

    International Nuclear Information System (INIS)

    Corrosion behaviors of a novel corrosion-resistant γ-toughened Cr13Ni5Si2/Cr3Ni5Si2 multi-phase ternary metal silicide alloy and properties of the passive film formed in NaCl solution were examined by anodic polarization, cyclic polarization and electrochemical impedance spectroscopy (EIS) experiments as well as X-ray photoelectron spectroscopy (XPS) and potentiostatic polarization measurements. Effects of immersion time and chloride ion concentration on corrosion behaviors of the alloy were also evaluated. Results indicated that the alloy exhibited excellent corrosion resistance in NaCl solution due to the spontaneous formation of a compact and protective passive film composed mainly of chromium (III) oxide as well as the high chemical stability and strong inter-atomic bonds inherent to Cr13Ni5Si2 and Cr3Ni5Si2 intermetallic phases. Moreover, corrosion resistance of the alloy was quite insensitive to the increase of chloride ion concentration and was improved noticeably with the increasing immersion time

  6. Influence of Al addition on phase transformation and thermal stability of nickel silicides on Si(0 0 1)

    International Nuclear Information System (INIS)

    Highlights: ► The presence of Al slows down the Ni2Si–NiSi phase transformation but significantly promotes the NiSi2−xAlx formation. ► The behavior of phase transformation strongly depends on the Al concentration of the initial Ni1−xAlx alloys. ► The Ni0.91Al0.09/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 Ni2Si–NiSi phase transformation but significantly promote the NiSi2−xAlx formation during annealing. The behavior of phase transformation strongly depends on the Al concentration of the initial Ni1−xAlx alloys. Compared to the Ni0.95Pt0.05/Si and Ni0.95Al0.05/Si system, the Ni0.91Al0.09/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 Ni1−xAlx alloy silicidation. This work demonstrated that thermally stable Ni1−xAlx alloy silicides would be a promising candidate as source/drain (S/D) contacts in advanced complementary metal–oxide-semiconductor (CMOS) devices

  7. Simultaneous determination of chromium(III) and chromium(VI) in aqueous solutions by ion chromatography and chemiluminescence detection

    DEFF Research Database (Denmark)

    Gammelgaard, Bente; Jøns, O; Nielsen, B

    1992-01-01

    A method for the simultaneous determination of chromium(iii) and chromium(vi) in a flow system based on chemiluminescence was developed. A Dionex cation-exchange guard column was used to separate chromium(iii) from chromium(vi), and chromium(vi) was reduced by potassium sulfite, whereupon both sp....... The detection limit was 0.5 micrograms l-1 for both species. Data were in agreement with Zeeman-effect background corrected atomic absorption spectrometry measurements....

  8. AEROSOL BEHAVIOR IN CHROMIUM WASTE INCINERATION

    Institute of Scientific and Technical Information of China (English)

    Suyuan Yu

    2003-01-01

    Cr2O3 is considered as the dominant incineration product during the combustion disposal of chromium waste. A hydrogen/air diffusion flame was employed to simulate the industrial process of incineration. Cr2O3 aerosols were generated inside the flame by the gas phase reaction of chromium and oxygen. Chromium came from the rapid decomposition of chromium hexacarbonyl (Cr(CO)6) at room temperature and was carried into the combustion chamber by hydrogen. Aerosol and clusters can then be easily formed in the flame by nucleation and coagulation. A two dimensional Discrete-Sectional Model (DSM) was adopted to calculate the Cr2O3 aerosol behavior. The experimental measurement method was Dynamic Light Scattering. The numerically predicted results agreed well with those of the experimental measurement. Both results show that the Cr2O3 aerosol size reached about 70 nanometers at the flame top.

  9. Potentiometry: A Chromium (III) -- EDTA Complex

    Science.gov (United States)

    Hoppe, J. I.; Howell, P. J.

    1975-01-01

    Describes an experiment that involves the preparation of a chromium (III)-EDTA compound, a study of its infrared spectrum, and the potentiometric determination of two successive acid dissociation constants. (Author/GS)

  10. 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

  11. Bioremediation of chromium solutions and chromium containing wastewaters.

    Science.gov (United States)

    Malaviya, Piyush; Singh, Asha

    2016-08-01

    Cr(VI) represents a serious threat to human health, living resources and ecological system as it is persistent, carcinogenic and toxic, whereas, Cr(III), another stable oxidation state of Cr, is less toxic and can be readily precipitated out of solution. The conventional methods of Cr(VI) removal from wastewaters comprise of chemical reduction followed by chemical precipitation. However, these methods utilize large amounts of chemicals and generate toxic sludge. This necessitates the need for devising an eco-technological strategy that would use the untapped potential of the biological world for remediation of Cr(VI) containing wastewaters. Among several viable approaches, biotransformation of Cr(VI) to relatively non-toxic Cr(III) by chromium resistant bacteria offers an economical- and environment-friendly option for its detoxification. Various studies on use of Cr(VI) tolerant viable bacterial isolates for treatment of Cr(VI) containing solutions and wastewater have been reported. Therefore, a detailed account of mechanisms and processes involved in bioreduction of Cr(VI) from solutions and wastewaters by bacterial isolates are the focus of this review article in addition to a discussion on toxicity of Cr(VI) on bacterial strains and various factors affecting Cr(VI) bioreduction. PMID:25358056

  12. Modified fused silicide coatings for tantalum (Ta-10W) reentry heat shields

    Science.gov (United States)

    Packer, C. M.; Perkins, R. A.

    1973-01-01

    Results are presented of a program of research to develop a reliable, high performance, fused slurry silicide coating for the Ta-10W alloy. The effort was directed toward developing new and improved formulations for use at 2600 to 2800 F (1700 to 1811 K) in an atmospheric reentry thermal protection system with a 100-mission capability. Based on a thorough characterization of isothermal and cyclic oxidation behavior, bend transition temperatures, room- and elevated-temperature tensile properties, and creep behavior, a 2.5 Mn-33Ti-64.5Si coating (designated MTS) provides excellent protection for the Ta-10W alloy in simulated reentry environments. An extensive analysis of the oxidation behavior and characteristics of the MTS coating in terms of fundamental mechanisms also is presented.

  13. Formation of pinhole-free epitaxial yttrium silicide on silicon (111)

    International Nuclear Information System (INIS)

    This paper reports the growth of structurally continuous, pinhole-free epitaxial YSi2-x films on Si(111) substrates as thin as 30 Angstrom. This is accomplished by depositing both yttrium and silicon in the appropriate stoichiometric ratio onto substrates held near room temperature, which is apparently below the activation energy for the nucleation of a reaction between a deposited Y film and a Si substrate. Diffusion of Si atoms from an evaporation source into a thin Y layer occurs below this barrier energy, allowing the layer by layer formation of YSi2-x without the removal of silicon from the substrate, maintaining a relatively low interface free energy between the growing silicide film and the Si(111) substrate. Samples have been annealed to 500-900 degrees C to improve epitaxy without the creation of pinholes. Use of the template method allows for the growth of thicker films also free of pinholes

  14. The fabrication of metal silicide nanodot arrays using localized ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jin; Kim, Tae-Gon; Min, Byung-Kwon; Lee, Sang Jo, E-mail: bkmin@yonsei.ac.kr [School of Mechanical Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2010-12-03

    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).

  15. Rare-earth silicide thin films on the Si(111) surface

    Science.gov (United States)

    Sanna, S.; Dues, C.; Schmidt, W. G.; Timmer, F.; Wollschläger, J.; Franz, M.; Appelfeller, S.; Dähne, M.

    2016-05-01

    Rare-earth induced layered structures on the Si(111) surface are investigated by a combined approach consisting of ab initio thermodynamics, electron and x-ray diffraction experiments, angle-resolved photoelectron spectroscopy, and scanning tunneling microscopy. Our density functional theory calculations predict the occurrence of structures with different periodicity, depending on the rare-earth availability. Microscopic structural models are assigned to the different silicide phases on the basis of stability criteria. The thermodynamically stable theoretical models are then employed to interpret the experimental results. The agreement between the simulated and measured scanning tunneling microscopy images validates the proposed structural models. The electronic properties of the surfaces are discussed on the basis of the calculated electronic band structure and photoelectron spectroscopy data.

  16. Fabrication of uranium silicide dispersion fuel by atomization for research reactor

    International Nuclear Information System (INIS)

    Atomizing technology has been developed to eliminate the difficulties in comminution of the tough U3Si and to take advantage of the spherical shape and the rapid solidification. The comparison between the conventional dispersion fuel with comminuted powder and the newly developed fuel with atomized powder has been made. As a result, the processes, powdering uranium silicide and heat treatment to U3Si, become simplified. The extruding pressure of blended powder with atomized powder was lower than that of blended powder with comminuted powder. The elongation of the atomization processed fuel meat was much higher than that of comminution processed fuel meats. It appears that the loading density of U3Si in fuel meat can be increased by using atomized U3Si powder. The thermal conductivity and the thermal compatibility of fuel meat have been investigated and found to be much improved due to the spherical shape of atomized powder. (author)

  17. 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.

  18. Hydrogen generation systems and methods utilizing sodium silicide and sodium silica gel materials

    Science.gov (United States)

    Wallace, Andrew P.; Melack, John M.; Lefenfeld, Michael

    2015-08-11

    Systems, devices, and methods combine thermally stable reactant materials and aqueous solutions to generate hydrogen and a non-toxic liquid by-product. The reactant materials can sodium silicide or sodium silica gel. The hydrogen generation devices are used in fuels cells and other industrial applications. One system combines cooling, pumping, water storage, and other devices to sense and control reactions between reactant materials and aqueous solutions to generate hydrogen. Springs and other pressurization mechanisms pressurize and deliver an aqueous solution to the reaction. A check valve and other pressure regulation mechanisms regulate the pressure of the aqueous solution delivered to the reactant fuel material in the reactor based upon characteristics of the pressurization mechanisms and can regulate the pressure of the delivered aqueous solution as a steady decay associated with the pressurization force. The pressure regulation mechanism can also prevent hydrogen gas from deflecting the pressure regulation mechanism.

  19. Chemical vapour deposition of tungsten and tungsten silicide layers for applications in novel silicon technology

    CERN Document Server

    Li, F X

    2002-01-01

    This work was a detailed investigation into the Chemical Vapour Deposition (CVD) of tungsten and tungsten silicide for potential applications in integrated circuit (IC) and other microelectronic devices. These materials may find novel applications in contact schemes for transistors in advanced ICs, buried high conductivity layers in novel Silicon-On-Insulator (SOI) technology and in power electronic devices. The CVD techniques developed may also be used for metal coating of recessed or enclosed features which may occur in novel electronic or electromechanical devices. CVD of tungsten was investigated using the silicon reduction reaction of WF sub 6. W layers with an optimum self-limiting thickness of 100 nm and resistivity 20 mu OMEGA centre dot cm were produced self-aligned to silicon. A hydrogen passivation technique was developed as part of the wafer pre-clean schedule and proved essential in achieving optimum layer thickness. Layers produced by this approach are ideal for intimate contact to shallow junct...

  20. Diminishing Chromium Use on Combined Chromium-Gambier Tanning Process Upon the Characteristics of Tanned Leather

    Directory of Open Access Journals (Sweden)

    A. Kasim

    2014-04-01

    Full Text Available The research was aimed to investigate the influence of minimizing chromium use on combined chromium-gambier process upon the characteristics of tanned leather. At the first stage of tanning process, chromium was used and in the second stage it was replaced by gambier. The raw material used was dried saline-preserved goat skin. The treatments applied on the tanning process were the different concentrations of chromium ranging from the highest level of 6% to the lowest level of 1% which was then re-tanned by using 8% concentration of gambier. The examination parameters included chemical and physical properties as well as visual investigation on the tanned leather in accordance with SNI-06-0463-1989-A. The result showed that the tanning process by using 2% chromium in the first step and 8% gambier in the second step was a treatment combination producing tanned leather that met the standard. The examination on tanned leather resulted from such treatment showed 56.33% rawhide, 17.45% of bound tannin, 31.22% of tanning level, tensile strength 386.30 kg/cm2, flexibility 31.91%, leather width 1.3 mm, density 0.75 g/cm3, the leather was quite elastic with light brownish color. In conclusion, minimizing the use of chromium in the combined tanning process of chromium and gambier can be implemented to the lowest of 2% chromium concentration and 8% gambier in the first and second step, respectively.

  1. Discovery of Brownleeite: a New Manganese Silicide Mineral in an Interplanetary Dust Particle

    Science.gov (United States)

    Keller, Lindsay P.; Nakamura-Messenger, Keiko; Clemett, Simon J.; Messenger, Scott; Jones, John H.; Palma, Russell L.; Pepin, Robert O.; Klock, Wolfgang; Zolensky, Michael E.; Tatsuoka, Hirokazu

    2011-01-01

    The Earth accretes approximately 40,000 tons of cosmic dust annually, originating mainly from the disintegration of comets and collisions among asteroids. This cosmic dust, also known as interplanetary dust particles (IDPs), is a subject of intense interest since it is made of the original building blocks of our Solar System. Although the specific parent bodies of IDPs are unknown, the anhydrous chondritic-porous IDPs (CP-IDPs) subset has been potentially linked to a cometary source. The CP-IDPs are extremely primitive materials based on their unequilibrated mineralogy, C-rich chemistry, and anomalous isotopic signatures. In particular, some CP-IDPs escaped the thermal, aqueous and impact shock processing that has modified or destroyed the original mineralogy of meteorites. Thus, the CP-IDPs represent some of the most primitive solar system materials available for laboratory study. Most CP-IDPs are comprised of minerals that are common on Earth. However, in the course of an examination of one of the CP-IDPs, we encountered three sub-micrometer sized grains of manganese silicide (MnSi), a phase that has heretofore not been found in nature. In the seminar, we would like to focus on IDP studies and this manganese silicide phase that has been approved as the first new mineral identified from a comet by the International Mineralogical Association (IMA) in 2008. The mineral is named in honour of Donald E. Brownlee, an American astronomer and a founder of the field of cosmic dust research who is the principal investigator of the NASA Stardust Mission that collected dust samples from Comet 81P/Wild-2 and returned them to Earth. Much of our current view and understanding of the early solar system would not exist without the pioneering work of professor Don Brownlee in the study of IDPs.

  2. In Situ Study of the Formation of Silicide Phases in Amorphous Co–Si Mixed Layers

    Energy Technology Data Exchange (ETDEWEB)

    Van Bockstael, C.; De Keyser, K; Demeulemeester, J; Vantomme, A; Van Meirhaeghe, R; Detavernier, C; Jordan-Sweet, J; Lavoie, C

    2010-01-01

    We investigate Co silicide phase formation when extra Si is added within an as deposited 50 nm Co film. The addition of Si is investigated for both the Co/SiO{sub 2} and Co/Si(1 0 0) system. A series of 10 Co-Si mixed films with a Si content varying from 21 to 59 at.% was prepared and investigated during annealing with in situ X-ray diffraction. The oxide system is used as reference system to identify phases that initially crystallize in an amorphous mixture of a given composition. Multiple phases can nucleate, and the temperature of crystallization depends on the Co-Si atomic ratio. Upon heating of the Co(Si)/Si system, the first reaction is a similar crystallization reaction of the Co(Si) mixture. Once the first phase is formed, one has the normal system of a silicide phase in contact with an unlimited amount of Si from the substrate, and the sequential phase formation towards CoSi{sub 2} is established. For deposited layers of composition ranging from 48%Si to 52%Si, the CoSi is the first phase to form and increasing the amount of Si leads to a remarkable improvement of the thermal stability of CoSi on Si(1 0 0). CoSi{sub 2} nucleation was extensively delayed by 150 C compared to the reaction observed from a pure Co film on Si(1 0 0). Electron backscatter diffraction measurements reveal that in this range, the gradual Si increase systematically leads to bigger CoSi grains (up to 20 {micro}m). This shows that the grain size of the CoSi precursor strongly affects the nucleation of the following CoSi{sub 2} phase. Laser-light scattering measurements suggest that adding more than 42%Si reduces the roughness of the CoSi{sub 2} layer.

  3. Lateral stress evolution in chromium sulfide cermets with varying excess chromium

    Science.gov (United States)

    Petel, O. E.; Appleby-Thomas, G. J.; Wood, D. C.; Capozzi, A.; Nabavi, A.; Goroshin, S.; Frost, D. L.; Hazell, P. J.

    2016-04-01

    The shock response of chromium sulfide-chromium, a cermet of potential interest as a matrix material for ballistic applications, has been investigated at two molar ratios. Using a combustion synthesis technique allowed for control of the molar ratio of the material, which was investigated under near-stoichiometric (cermet) and excess chromium (interpenetrating composite) conditions, representing chromium:sulfur molar ratios of 1.15:1 and 4:1, respectively. The compacts were investigated via the plate-impact technique, which allowed the material to be loaded under a one-dimensional state of strain. Embedded manganin stress gauges were employed to monitor the temporal evolution of longitudinal and lateral components of stress in both materials. Comparison of these two components has allowed assessment of the variation of material shear strength both with impact pressure/strain-rate and time for the two molar ratio conditions. The two materials exhibited identical material strength despite variations in their excess chromium contents.

  4. The enriched chromium neutrino source for GALLEX

    International Nuclear Information System (INIS)

    The preparation and study of an intense source of neutrinos in the form of neutron irradiated materials which are enriched in Cr-50 for use in the GALLEX solar neutrino experiment are discussed. Chromyl fluoride gas is enriched in the Cr-50 isotope by gas centrifugation and subsequently converted to a very stable form of chromium oxide. The results of neutron activation analyses of such chromium samples indicate low levels of any long-lived activities, but show that short-lived activities, in particular Na-24, may be of concern. These results show that irradiating chromium oxide enriched in Cr-50 is preferable to irradiating either natural chromium or argon gas as a means of producing a neutrino source to calibrate the GALLEX detector. These results of the impurity level analysis of the enriched chromyl fluoride gas and its conversion to the oxide are also of interest to work in progress by other members of the Collaboration investigating an alternative conversion of the enriched gas to chromium metal. 35 refs., 12 figs., 5 tabs

  5. Serum chromium levels in gestational diabetes mellitus

    Directory of Open Access Journals (Sweden)

    P G Sundararaman

    2012-01-01

    Full Text Available Objective: To measure serum chromium level in women with gestational diabetes mellitus (GDM from Chennai, South India. Materials and Methods: Thirty women with gestational diabetes, 60 age matched controls. Inclusion criteria: Gestational age 22-28 weeks, age group 20-35 years. Exclusion Criteria: Gestational age beyond 28 weeks, malnutrition or presence of infection. Serum chromium was measured using inductive couple plasma emission spectrometer. Results: Serum chromium levels of women with GDM, 1.59+/-0.02 ng/ml (range: 0.16-4.0 ng/ml were lower than in controls (4.58+/-0.62 ng/ml; range 0.82-5.33 ng/ml (P < 0.001. However, there were no significant differences among cases and controls when subdivided by parity. Conclusions: Women with GDM from a South Indian city had lower levels of serum chromium compared to pregnant women without GDM. Studies may be done whether chromium supplementation is useful in this group of women.

  6. Occupational exposure to chromium(VI compounds

    Directory of Open Access Journals (Sweden)

    Jolanta Skowroń

    2015-07-01

    Full Text Available This article discusses the effect of chromium(VI (Cr(VI on human health under conditions of acute and chronic exposure in the workplace. Chromium(VI compounds as carcinogens and/or mutagens pose a direct danger to people exposed to them. If carcinogens cannot be eliminated from the work and living environments, their exposure should be reduced to a minimum. In the European Union the proposed binding occupational exposure limit value (BOELV for chromium(VI of 0.025 mg/m³ is still associated with high cancer risk. Based on the Scientific Commitee of Occupational Exposure Limits (SCOEL document chromium(VI concentrations at 0.025 mg/m³ increases the risk of lung cancer in 2–14 cases per 1000 exposed workers. Exposure to chromium(VI compounds expressed in Cr(VI of 0.01 mg Cr(VI/m3 is responsible for the increased number of lung cancer cases in 1–6 per 1000 people employed in this condition for the whole period of professional activity. Med Pr 2015;66(3:407–427

  7. [Occupational exposure to chromium(VI) compounds].

    Science.gov (United States)

    Skowroń, Jolanta; Konieczko, Katarzyna

    2015-01-01

    This article discusses the effect of chromium(VI) (Cr(VI)) on human health under conditions of acute and chronic exposure in the workplace. Chromium(VI) compounds as carcinogens and/or mutagens pose a direct danger to people exposed to them. If carcinogens cannot be eliminated from the work and living environments, their exposure should be reduced to a minimum. In the European Union the proposed binding occupational exposure limit value (BOELV) for chromium(VI) of 0.025 mg/m³ is still associated with high cancer risk. Based on the Scientific Commitee of Occupational Exposure Limits (SCOEL) document chromium(VI) concentrations at 0.025 mg/m³ increases the risk of lung cancer in 2-14 cases per 1000 exposed workers. Exposure to chromium(VI) compounds expressed in Cr(VI) of 0.01 mg Cr(VI)/m3; is responsible for the increased number of lung cancer cases in 1-6 per 1000 people employed in this condition for the whole period of professional activity. PMID:26325053

  8. Selective silicide or boride film formation by reaction of vapor phase TiCl4 with silicon or boron

    International Nuclear Information System (INIS)

    Methods for selectively forming titanium silicide and titanium boride by vapor phase reaction of titanium chloride precursors with silicon or boron substrate surfaces are examined. By passing TiCl4 through a heated chamber packed with titanium metal turnings within the reactor tube, a reduced titanium halide is generated. It was found that the silicide or boride formation in the reactor can thus be controlled at a much lower temperature. Also, excessive silicon erosion normally encountered at the higher operating temperature (> 775 degrees C) required for the direct TiCl4 reaction is minimized. Characterization of the resulting films was conducted by use of scanning and transmission electron microscopy, sheet resistance measurements, and x-ray diffraction

  9. Oxidation-resistant Ge-doped silicide coating on Cr-Cr2Nb alloys by pack cementation

    International Nuclear Information System (INIS)

    The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating on Cr-Cr2Nb 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 CrSi2 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.)

  10. Flashlamp-pumped lasing of chromium-doped GSG garnet

    International Nuclear Information System (INIS)

    The implications for the practical use of chromium:GSGG in lamp-pumped tunable lasers are discussed in this paper. The authors report here some major improvements in the performance of the flashlamp-pumped chromium:GSGG laser

  11. Surface Chemistry and Spectroscopy of Chromium in Inorganic Oxides

    OpenAIRE

    Weckhuysen, B. M.; Wachs, I.E.; Schoonheydt, R. A.

    1996-01-01

    Focuses on the surface chemistry and spectroscopy of chromium in inorganic oxides. Characterization of the molecular structures of chromium; Mechanics of hydrogenation-dehydrogenation reactions; Mobility and reactivity on oxidic surfaces.

  12. Production Cycle for Large Scale Fission Mo-99 Separation by the Processing of Irradiated LEU Uranium Silicide Fuel Element Targets

    OpenAIRE

    Abdel-Hadi Ali Sameh

    2013-01-01

    Uranium silicide fuels proved over decades their exceptional qualification for the operation of higher flux material testing reactors with LEU elements. The application of such fuels as target materials, particularly for the large scale fission Mo-99 producers, offers an efficient and economical solution for the related facilities. The realization of such aim demands the introduction of a suitable dissolution process for the applied U3Si2 compound. Excellent results are achieved by the oxidiz...

  13. Studies of Some Novel Chromium Pyridine Dicarboxylate Complexes

    OpenAIRE

    Chauhan Jayprakash S; Patel Rameshchandra P; Pandya Ajit V

    2014-01-01

    Chromium pyridine di-carboxylate complexes are synthesized from Chromium (III) with pyridine 2, 6- dicarboxylic acid, pyridine 2, 3 and 2, 5- dicarboxylic acids. Chromium forms colored complexes. Chromium (III) forms a violate complex with pyridine 2, 6- dicarboxylic acid and purple violate complex with pyridine 2, 3 and 2, 5- dicarboxylic acids. The job’s method indicates metal ligand ratio to be 1:2. The interpretation of UV-VIS spectra indicates octahedral geometry and IR spectra give clue...

  14. Dimensional stability of low enriched uranium silicide plate-type fuel for research reactors at transient conditions

    Energy Technology Data Exchange (ETDEWEB)

    Yanagisawa, Kazuaki; Fujishiro, Toshio; Horiki, Oichiro; Soyama, Kazuhiko; Ichikawa, Hiroki; Kodaira, Tsuneo (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment)

    1992-03-01

    This paper describes the result of transient experiments using low enriched uranium silicide plate-type fuel for research reactors. The pulse irradiation was carried out at Nuclear Safety Research Reactor (NSRR) in Japan Atomic Energy Research Institute. The results obtained were: (1) At fuel plate temperature of below 400degC, a good dimensional stability of the tested fuel was kept. No fuel failure occurred. (2) At a plate temperature of about 540degC, a local crack was initiated on the Al-3% Mg alloy cladding. Once the cladding temperature exceeded the melting point of 640degC, the fuel plate was degraded much by increased bowing and cracking of the denuded fuel meat occurred after relocation of molten Al cladding. Despite of these degradation, neither fragmentation of the fuel plate nor mechanical energy generation occurred up to the cladding temperature of 971degC. (3) At the temperatures of around 925degC, the reaction of silicide particles with molten Al in the matrix and that of cladding occurred, forming Al riched U (Al, Si) compounds and Si riched (U, Si) compounds at the outermost surface of the silicide particles. (author).

  15. Dimensional stability of low enriched uranium silicide plate-type fuel for research reactors at transient conditions

    International Nuclear Information System (INIS)

    This paper describes the result of transient experiments using low enriched uranium silicide plate-type fuel for research reactors. The pulse irradiation was carried out at Nuclear Safety Research Reactor (NSRR) in Japan Atomic Energy Research Institute. The results obtained were: (1) At fuel plate temperature of below 400degC, a good dimensional stability of the tested fuel was kept. No fuel failure occurred. (2) At a plate temperature of about 540degC, a local crack was initiated on the Al-3% Mg alloy cladding. Once the cladding temperature exceeded the melting point of 640degC, the fuel plate was degraded much by increased bowing and cracking of the denuded fuel meat occurred after relocation of molten Al cladding. Despite of these degradation, neither fragmentation of the fuel plate nor mechanical energy generation occurred up to the cladding temperature of 971degC. (3) At the temperatures of around 925degC, the reaction of silicide particles with molten Al in the matrix and that of cladding occurred, forming Al riched U (Al, Si) compounds and Si riched (U, Si) compounds at the outermost surface of the silicide particles. (author)

  16. Determination of chromium combined with DNA, RNA and proteins in chromium-rich brewer's yeast by NAA

    International Nuclear Information System (INIS)

    The content of chromium in the DNA, RNA and protein fractions separated from chromium-rich and normal brewer's yeast was determined by neutron activation analysis (NAA). Our results show that the extracted relative amounts and concentrations of DNA, RNA and proteins have no significant difference for two types of yeast, but the chromium content in DNA, RNA and proteins fractions extracted from the chromium-rich yeast are substantially higher than those from the normal. In addition, the concentration of chromium in DNA is much higher than that in RNA and proteins. It is evident that the inorganic chromium compounds can enter the yeast cell during the yeast cultivation in the chromium-containing culture medium and are converted into organic chromium species, which are combined with DNA, RNA and proteins. (author)

  17. Chromium allergy and dermatitis: prevalence and main findings

    DEFF Research Database (Denmark)

    Bregnbak, David; Johansen, Jeanne D.; Jellesen, Morten Stendahl;

    2015-01-01

    The history of chromium as an allergen goes back more than a century, and includesan interventional success with national legislation that led to significant changes inthe epidemiology of chromium allergy in construction workers. The 2015 EU Leather Regulation once again put a focus on chromium...

  18. 21 CFR 73.1326 - Chromium hydroxide green.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium hydroxide green. 73.1326 Section 73.1326... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide...

  19. 21 CFR 73.2326 - Chromium hydroxide green.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium hydroxide green. 73.2326 Section 73.2326... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity and specifications.The color additive chromium hydroxide green shall conform in identity and specifications to...

  20. Thermodynamic properties of chromium bearing slags and minerals. A review

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Yanping; Holappa, L.

    1996-12-31

    In this report, the thermodynamic properties of chromium bearing slags and minerals were reviewed based on the available information in the literature. It includes the analysing methods for oxidation state of chromium in slags, oxidation state of chromium and activities of chromium oxides in slags and minerals. The phase diagrams of chromium oxide systems and chromium distributions between slag and metal phases are also covered ill this review. Concerning the analysing methods, it was found that most of the available approaches are limited to iron free slag systems and the sample preparation is very sensitive to the analysing results. In silicate slags under reducing atmosphere, divalent and trivalent chromium co-exist in the slags. It is agreed that the fraction of divalent chromium to total chromium increases with higher temperature, lower slag basicity and oxygen potential. For the slags under oxidising atmosphere, trivalent, pentavalent and hexavalent states were reported to be stable. The activities of CrO and CrO{sub 1.5} were concluded to have positive deviation from ideal solution. Slag basicity has a positive effect and temperature has a negative effect on the activities of chromium oxides. The phase diagrams of the Cr-O, binary, and ternary chromium containing oxide systems have been examined systematically. The analysis shows that the data on the quaternary and quinary systems are insufficient, and require further investigation. The most important features of the chromium containing silicate slags are the large miscibility gaps and the stability of the chromite spinel. (orig.) (76 refs.)

  1. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium-cobalt-aluminum oxide. 73.1015 Section 73... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1015 Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide is a blue-green pigment obtained by calcining...

  2. Hexavalent and trivalent chromium in leather: What should be done?

    Science.gov (United States)

    Moretto, Angelo

    2015-11-01

    Trivalent chromium compounds are used for leather tanning, and chromium may be released during use of leather goods. In certain instances, small amounts of hexavalent chromium can be formed and released. Both trivalent and hexavalent chromium can elicit allergic skin reaction in chromium sensitised subjects, the latter being significantly more potent. Induction of sensitisation only occurs after exposure to hexavalent chromium. A minority of subjects are sensitised to chromium, and in a fraction of these subjects allergic skin reaction have been described after wearing leather shoes or, less frequently, other leather goods. The evidence that in all these cases the reaction is related to hexavalent chromium is not always strong. The content of hexavalent chromium in leather is regulated in European Union, but rate of release rather than content is relevant for allergic skin reaction. The role of trivalent chromium appear much less relevant if at all. Modern tanning procedure do not pose significant risk due to either hexavalent or trivalent chromium. Dismissing bad quality and worn-off leather goods is relevant in reducing or eliminating the skin reaction. It should also be pointed out that shoe components or substances other than chromium in leather may cause allergic/irritative skin reactions. PMID:26361854

  3. SAFETY OF TRIVALENT CHROMIUM COMPLEXES USED IN NUTRIENT SUPPLEMENTS

    Science.gov (United States)

    Toxicity studies regarding trivalent chromium have often been completed under conditions that are not designed to reflect conditions that would be encountered under normal physiological conditions. We have shown that the incorporation of chromium into tissues of rats from chromium chloride and chro...

  4. Strategies for chromium bioremediation of tannery effluent.

    Science.gov (United States)

    Garg, Satyendra Kumar; Tripathi, Manikant; Srinath, Thiruneelakantan

    2012-01-01

    Bioremediation offers the possibility of using living organisms (bacteria, fungi, algae,or plants), but primarily microorganisms, to degrade or remove environmental contaminants, and transform them into nontoxic or less-toxic forms. The major advantages of bioremediation over conventional physicochemical and biological treatment methods include low cost, good efficiency, minimization of chemicals, reduced quantity of secondary sludge, regeneration of cell biomass, and the possibility of recover-ing pollutant metals. Leather industries, which extensively employ chromium compounds in the tanning process, discharge spent-chromium-laden effluent into nearby water bodies. Worldwide, chromium is known to be one of the most common inorganic contaminants of groundwater at pollutant hazardous sites. Hexavalent chromium poses a health risk to all forms of life. Bioremediation of chromium extant in tannery waste involves different strategies that include biosorption, bioaccumulation,bioreduction, and immobilization of biomaterial(s). Biosorption is a nondirected physiochemical interaction that occurs between metal species and the cellular components of biological species. It is metabolism-dependent when living biomass is employed, and metabolism-independent in dead cell biomass. Dead cell biomass is much more effective than living cell biomass at biosorping heavy metals, including chromium. Bioaccumulation is a metabolically active process in living organisms that works through adsorption, intracellular accumulation, and bioprecipitation mechanisms. In bioreduction processes, microorganisms alter the oxidation/reduction state of toxic metals through direct or indirect biological and chemical process(es).Bioreduction of Cr6+ to Cr3+ not only decreases the chromium toxicity to living organisms, but also helps precipitate chromium at a neutral pH for further physical removal,thus offering promise as a bioremediation strategy. However, biosorption, bioaccumulation, and

  5. Collisional properties of trapped cold chromium atoms

    CERN Document Server

    Pavlovich, Z; Côté, R; Sadeghpour, H R; Pavlovic, Zoran; Roos, Bjoern O.; Côté, Robin

    2004-01-01

    We report on calculations of the elastic cross section and thermalization rate for collision between two maximally spin-polarized chromium atoms in the cold and ultracold regimes, relevant to buffer-gas and magneto-optical cooling of chromium atoms. We calculate ab initio potential energy curves for Cr2 and the van der Waals coefficient C6, and construct interaction potentials between two colliding Cr atoms. We explore the effect of shape resonances on elastic cross section, and find that they dramatically affect the thermalization rate. Our calculated value for the s-wave scattering length is compared in magnitude with a recent measurement at ultracold temperatures.

  6. Reactivity insertion transient analysis for KUR low-enriched uranium silicide fuel core

    International Nuclear Information System (INIS)

    Highlights: • A simulation model for KUR LEU silicide core was established. • Safety analyses for reactivity insertion transients were performed by EUREKA-2/RR. • Accidental control rod withdrawal transients were analyzed. • Cold water injection induced reactivity insertion transients were analyzed. • Reactivity insertion transients due to removal of irradiation samples were analyzed. - Abstract: The purpose of this study is to realize the full core conversion from the use of High Enriched Uranium (HEU) fuels to the use of Low Enriched Uranium (LEU) fuels in Kyoto University Research Reactor (KUR). Although the conversion of nuclear energy sources is required to keep the safety margins and reactor reliability based on KUR HEU core, the uranium density (3.2 gU/cm3) and enrichment (20%) of LEU fuel (U3Si2–AL) are quite different from the uranium density (0.58 gU/ (cm3)) and enrichment (93%) of HEU fuel (U–Al), which may result in the changes of heat transfer response and neutronic characteristic in the core. So it is necessary to objectively re-assess the feasibility of LEU silicide fuel core in KUR by using various numerical simulation codes. This paper established a detailed simulation model for the LEU silicide core and provided the safety analyses for the reactivity insertion transients in the core by using EUREKA-2/RR code. Although the EUREKA-2/RR code is a proven and trusted code, its validity was further confirmed by the comparison with the predictions from another two thermal hydraulic codes, COOLOD-N2 and THYDE-W at steady state operation. The steady state simulation also verified the feasibility of KUR to be operated at rated thermal power of 5 MW. In view of the core loading patterns, the operational conditions and characteristics of the reactor protection system in KUR, the accidental control rod withdrawal transients at natural circulation and forced circulation modes, the cold water injection induced reactivity insertion transient and the

  7. Influence of nitrogen on the structure and properties of chromium, chromium-molybdenum and chromium-manganese steels

    International Nuclear Information System (INIS)

    Phase transformations, precipitation processes and properties of the chromium, chromium-molybdenum and chromium-manganese steels with a high content of nitrogen as the dependence on thermal treatment were investigated. In case of Fe-0.08C-18Cr-18Mn-N and Fe-0.08C-18Cr-18Mn-2Mo-N steels the samples in the state after solution at temperature 1050oC and 1150oC and 1250oC and after subsequent annealing in 600oC and 800oC were investigated. heat treatment of the Fe-0.5C-10Cr-N and Fe-0.5C-10Cr-1Mo-N steels included austenitizment from 1000oC with air cooling and hardening from 1000oC with oil cooling and tempering in 650oC and 750oC in two hours with cooling in the air. These investigations show that the influence of nitrogen as an alloy element on the phase transformations, precipitation processes, mechanical and corrosion properties is connected with the presence of molybdenum and chromium in the steel. Nitrogen with these elements creates complex ions with the coordinate number 6. This statement is formed on the base of both calculations and investigation results. (author)

  8. 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

  9. Electrodeposition of black chromium thin films from trivalent chromium-ionic liquid solution

    OpenAIRE

    Eugénio, S.; Vilar, Rui; C. M. Rangel; Baskaran, I.

    2009-01-01

    In the present study, black chromium thin films were electrodeposited from a solution of 1-butyl-3- methylimidazolium tetrafluoroborate ([BMIm][BF4] ionic liquid containing trivalent chromium (Cr(III)). Homogeneous and well adherent coatings have been obtained on nickel, copper and stainless steel substrates. The nucleation and growth of the films were investigated by cyclic voltammetry and current-density/time transient techniques. SEM/EDS, XPS and XRD were used to study the morphology, chem...

  10. Reduction of Hexavalent Chromium by Viable Cells of Chromium Resistant Bacteria Isolated from Chromite Mining Environment

    OpenAIRE

    Satarupa Dey; Baishali Pandit; A. K. Paul

    2014-01-01

    Environmental contamination of hexavalent chromium [Cr(VI)] is of serious concern for its toxicity as well as mutagenic and carcinogenic effects. Bacterial chromate reduction is a cost-effective technology for detoxification as well as removal of Cr(VI) from polluted environment. Chromium resistant and reducing bacteria, belonging to Arthrobacter, Pseudomonas, and Corynebacterium isolated from chromite mine overburden and seepage samples of Orissa, India, were found to tolerate 12–18 mM Cr(VI...

  11. Reduction of Chromium-VI by Chromium Resistant Lactobacilli: A Prospective Bacterium for Bioremediation

    OpenAIRE

    Mishra, Ritesh; Sinha, Vartika; Kannan, Ambrose; Upreti, Raj K.

    2012-01-01

    Chromium is a toxic heavy metal, which primarily exists in two inorganic forms, Cr (VI) and Cr (III). Highly soluble hexavalent chromium is carcinogenic due to its oxidizing nature. It is well established that the intestinal bacteria including Lactobacilli have regulatory effect on intestinal homeostasis and a breakdown in the relationship between intestinal cells and bacteria results in the manifestation of gastrointestinal (GI) disorders. In this study Cr (VI) resistance was developed in La...

  12. Mechanical properties of metal-ceramic systems from nickel-chromium and cobalt-chromium alloys

    OpenAIRE

    Mirković Nemanja

    2007-01-01

    Background/Aim. Metal-ceramic bond strength and alloys' elastic modulus clearly determine the potential of alloy application, because the ceramic integrity during mastication depends on these two characteristics. The aim of this study was to evaluate metal-ceramic bond strength and elastic modulus of cobalt-chromium alloys in making porcelainfused- to-metal restorations, regarding the application of the most frequent nickel-chromium alloy. Methods. The research was performed as an experimenta...

  13. Chromium-manganese steels of transition class

    International Nuclear Information System (INIS)

    Possibilities of nickel replacing by manganese and preparing the same level of mechanical properties as in chromium-nickel steels due to γ-α transformations taking place during property tests, are studied. Chromium-manganese steels with the composition of 0.05-0.1%C, 13-14%Cr, 5.0-6.5%Mn, 0.2-0.5%Si, 0.03-0.13%N, 0.05-0.01%Al and additionally alloyed 0.3-2.0%Cu, 0.05-0.6%V, 0.3-1.0%Mo, 0.02-0.05%Ca in various combinations have been melted. It is shown, that using alloying and heat treatment one can control the phase composition, austenite resistance to martensite transformation during loading and mechanical properties of chromium-manganese steels of the transition class. The use of the phase transformation in the process of testing determines the level of mechanical properties. The optimum development of the transformation accompanied by a sufficient development of processes of hardening and microstresses relaxation permits to obtain a high level of mechanical properties: σsub(B)=1500 MPa, σsub(0.2)-1130MPa, delta=15%, psi=37%, asub(H)=1000 kJ/msup(2) which exceeds the level for chromium-nickel steels. Steels have a lower cost and do not require any complecated heat treatment regime

  14. Defect structure of electrodeposited chromium layers

    International Nuclear Information System (INIS)

    Positron annihilation spectroscopy was applied to study the effects of pre-treatment and composition of substrates on the quality and defect structure of electrodeposited thick chromium coatings. The results show that both parameters are important, and a scenario is proposed why the mechanically polished substrate gives more defective film than the electro polished one.

  15. Defect structure of electrodeposited chromium layers

    CERN Document Server

    Marek, T; Vertes, A; El-Sharif, M; McDougall, J; Chisolm, C U

    2000-01-01

    Positron annihilation spectroscopy was applied to study the effects of pre-treatment and composition of substrates on the quality and defect structure of electrodeposited thick chromium coatings. The results show that both parameters are important, and a scenario is proposed why the mechanically polished substrate gives more defective film than the electro polished one.

  16. Flashlamp-pumped lasing of chromium: GSGG

    International Nuclear Information System (INIS)

    Lasing action in chromium-doped gadolinium scandium gallium garnet (Cr:GSGG) is well established for both CW/sup (1)/ and flashlamp/sup (2)/ pumping. This paper describes an investigation of flashlamp-pumped Cr:GSGG lasers and indicates some of the factors which limit performance

  17. Trace Elements Excluding Iron - Chromium and Zinc

    Science.gov (United States)

    The percentage of middle-aged US adults who are participating in leisure-time physical activities is growing. These adults also seek credible information about specific supplements that the public press routinely describes as necessary to enable increases in physical performance. Chromium and zinc a...

  18. HEALTH ASSESSMENT DOCUMENT FOR CHROMIUM. FINAL REPORT

    Science.gov (United States)

    The full document represents a comprehensive data base that considers all sources of chromium in the environment, the likelihood for its exposure to humans, and the possible consequences to man and lower organisms from its absorption. This information is integrated into a format ...

  19. 29 CFR 1926.1126 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... CFR 1926.51 Where skin contact with chromium (VI) occurs, the employer shall provide washing facilities in conformance with 29 CFR 1926.51. Eating and drinking areas provided by the employer shall also... requirements of the Hazard Communication Standard, 29 CFR 1910.1200. (3) Cleaning and replacement. (i)...

  20. 29 CFR 1910.1026 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... CFR 1910.141. Where skin contact with chromium (VI) occurs, the employer shall provide washing facilities in conformance with 29 CFR 1910.141. Eating and drinking areas provided by the employer shall also... requirements of the Hazard Communication Standard, 29 CFR 1910.1200. (3) Cleaning and replacement. (i)...

  1. 29 CFR 1915.1026 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... CFR 1910.141. Where skin contact with chromium (VI) occurs, the employer shall provide washing facilities in conformance with 29 CFR 1915.97. Eating and drinking areas provided by the employer shall also... requirements of the Hazard Communication Standard, 29 CFR 1910.1200. (3) Cleaning and replacement. (i)...

  2. Chromium(III) and chromium(VI) surface treated galvanized steel for outdoor constructions: environmental aspects.

    Science.gov (United States)

    Lindström, David; Hedberg, Yolanda; Odnevall Wallinder, Inger

    2010-06-01

    The long-term degradation of chromium(III) (Zn-Cr(III)) and chromium(VI)-based (Zn-Cr(VI)) surface treatments on galvanized steel and their capacities to hinder the release of zinc induced by atmospheric corrosion at nonsheltered urban and marine exposure conditions for 2 years are investigated. Compared to bare zinc sheet, both surface treatments revealed high corrosion protection abilities and capacities to hinder the release of zinc, still evident after 2 years of exposure. The zinc barrier properties of the thinner Zn-Cr(VI) (10 nm) treatment were during the first 100 days of urban exposure slightly improved compared with Zn-Cr(III) (35 nm). However, their long-term protection capacities were inverse. Released concentrations of total chromium correspond to annual release rates less than 0.000032 (Zn-Cr(III)) and 0.00014 g Cr m(-2) yr(-1) (Zn-Cr(VI)) after 1 year of urban exposure. Aging by indoor storage of the surface treatments prior to outdoor exposure reduced the released Cr concentrations from the surface treatments. No Cr(VI) was released from the aged surfaces but from the freshly exposed Zn-Cr(VI). Marine exposure conditions resulted in a faster reduction of chromate to chromium(III)oxide compared with urban conditions, and a significantly lower amount of both chromium(III) and chromium(VI) released from Zn-Cr(VI) at the marine site compared with the urban site. PMID:20462267

  3. Biological groundwater treatment for chromium removal at low hexavalent chromium concentrations.

    Science.gov (United States)

    Mamais, Daniel; Noutsopoulos, Constantinos; Kavallari, Ioanna; Nyktari, Eleni; Kaldis, Apostolos; Panousi, Eleni; Nikitopoulos, George; Antoniou, Kornilia; Nasioka, Maria

    2016-06-01

    The objective of this work is to develop and evaluate biological groundwater treatment systems that will achieve hexavalent chromium reduction and total chromium removal from groundwater at hexavalent chromium (Cr(VI)) groundwater concentrations in the 0-200 μg/L range. Three lab-scale units operated, as sequencing batch reactors (SBR) under aerobic, anaerobic and anaerobic-aerobic conditions. All systems received groundwater with a Cr(VI) content of 200 μg/L. In order to support biological growth, groundwater was supplemented with milk, liquid cheese whey or a mixture of sugar and milk to achieve a COD concentration of 200 mg/L. The results demonstrate that a fully anaerobic system or an anaerobic-aerobic system dosed with simple or complex external organic carbon sources can lead to practically complete Cr(VI) reduction to Cr(III). The temperature dependency of maximum Cr(VI) removal rates can be described by the Arrhenius relationship. Total chromium removal in the biological treatment systems was not complete because a significant portion of Cr(III) remained in solution. An integrated system comprising of an anaerobic SBR followed by a sand filter achieved more than 95% total chromium removal thus resulting in average effluent total and dissolved chromium concentrations of 7 μg/L and 3 μg/L, respectively. PMID:26971177

  4. Nephrotoxic and hepatotoxic effects of chromium compounds in rats

    Energy Technology Data Exchange (ETDEWEB)

    Laborda, R.; Diaz-Mayans, J.; Nunez, A.

    1986-03-01

    The nephrotoxic, hepatotoxic and cardiotoxic actions of hexavalent chromium compounds, as well as their effects on lung, blood and circulation may contribute to the fatal outcome of chromium intoxication. Although trivalent chromium have been regarded as relatively biologically inert, there are a few salts of chromium III that have been found to be carcinogenic when inhaled, ingested or brought in contact with the tissues. Sensitive persons and industry workers have been subjects of dermatitis, respiratory tract injuries and digestive ulcers due to chromium compounds. In this work, the authors have studied the effect of trivalent and hexavalent chromium compounds on rats measuring the transaminases (GOT and GPT), urea and creatinine levels in serum of chromium poisoned animals at different times.

  5. A Kinetic Model of Chromium in a Flame

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Chromium has been identified as a carcinogenic metal.Incineration is the useful method for disposal of toxic chromium hazard waste and a chromium kinetic model in a flame is very important to study chromium oxidation.Chromium chemical kinetics over a range of temperatures of a hydrogen/air flame is proposed.Nine chromium compounds and fifty-eight reversible chemical reactions were considered The forward reaction rates are calculated based on the molecular collision approach for unknown ones and Arrhenius's Law for known ones.The backward reaction rates were calculated according to forward reaction rates, the equilibrium constants and chemical thermodynamics.It is verified by several equilibrium cases and is tested by a hydrogen/air diffusion flame.The results show that the kinetic model could be used in cases in which the chromium kinetics play an important role in a flame

  6. The Chromium is an essential element in the human

    International Nuclear Information System (INIS)

    The Chromium is an essential element for human and animals, because it a preponderant function in the insulin metabolism as a glucose tolerance factor (GTF). The deficiency of chromium engenders a deterioration in the glucose metabolism due to bad efficiency of insulin. Because the importance of this element an exhaustive reference review was made and this presents some studies realized in laboratory animals and in human beings where it is prove with resuits the effect of chromium over the improvement of patients with non-insulin dependant diabetes. Three substances are presented as chromium active biological forms: a material rich in chromium known as glucose tolerance factor, chromium picolinate and a substance of low molecular weight LMWCr in its forms of apo and holo that contains chromium and it links the insulin receptor and improves its activity. Also this paper presents information about the condition of diabetes in Costa Rica. (Author)

  7. The ability of silicide coating to delay the catastrophic oxidation of vanadium under severe conditions

    Science.gov (United States)

    Chaia, N.; Mathieu, S.; Rouillard, F.; Vilasi, M.

    2015-02-01

    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 VSi2 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 VSi2 coating has mechanical properties compatible with the V-4Cr-4Ti alloy for SFR applications.

  8. Molybdenum, Tungsten, and Aluminium Substitution for Enhancement of the Thermoelectric Performance of Higher Manganese Silicides

    Science.gov (United States)

    Nhi Truong, D. Y.; Berthebaud, David; Gascoin, Franck; Kleinke, Holger

    2015-10-01

    An easy and efficient process involving ball milling under soft conditions and spark plasma sintering was used to synthesize higher manganese silicide (HMS)-based compounds, for example MnSi1.75Ge0.02, with different molybdenum, tungsten, and aluminium substitution. The x-ray diffraction patterns of the samples after sintering showed the main phase to be HMS with the presence of some side products. Molybdenum substitution enlarges the unit cells more than tungsten substitution, owing to its greater solubility in the HMS structure, whereas substitution with aluminium did not substantially alter the cell parameters. The electrical resistivity of HMS-based compounds was reduced by <10% by this substitution, because of increased carrier concentrations. Changes of the Seebeck coefficient were insignificant after molybdenum and aluminium substitution whereas tungsten substitution slightly reduced the thermopower of the base material by approximately 8% over the whole temperature range; this was ascribed to reduced carrier mobility as a result of enhanced scattering. Substitution with any combination of two of these elements resulted in no crucial modification of the electrical properties of the base material. Large decreases of lattice thermal conductivity were observed, because of enhanced phonon scattering, with the highest reduction up to 25% for molybdenum substitution; this resulted in a 20% decrease of total thermal conductivity, which contributed to improvement of the figure of merit ZT of the HMS-based materials. The maximum ZT value was approximately 0.40 for the material with 2 at.% molybdenum substitution at the Mn sites.

  9. The Comparison Of Silicon Analysis For The Uranium Silicide Fuel Using Spectrophotometrical And Gravimetrical Methods

    International Nuclear Information System (INIS)

    The analysis of silicon content in the uranium silicide fuel spectro-photometrical and gravimetrical method have been performed. The nitrous oxide-acetylene was used in the atomic absorption spectrophotometry (AAS) on the wave length of 251.6 nm, and the mixture of ammonium hepta molybdate complexes and SnC12 as reductor were applied during analysis by UV-VIS spectrophotometry (UV-VIS) on the wave length of 757.5 mm. The reagent of HCLO4 and HNO3 were used for determining Si content by gravimetrical methods. The results of this comparison is as follows: the accuracy result is around 96.37 % + 0.24 % for the Si concentration up to 300 ppm (the AAS), is 138.60 % = 0.43 % for the Si concentration range between 0.1-1.5 ppm (UV-VIS), and is 51.13 % + 0.8 % for 1 gram of Si (gravimetry). The results also show that the lowest analytical error is obtained by AAS method

  10. Burnup determination of silicide MTR fuel elements (20% 235U) in the LFR laboratory

    International Nuclear Information System (INIS)

    The LFR facility is a radiochemical laboratory designed and constructed with a hot-cells line, a glove-box and a fume hood, all of them suited to work radioactive materials. At the beginning of the LFR operation a series of dissolutions of MTR irradiated silicide fuel elements was performed, and determined its isotopic composition of 235U, 239Pu and 148Nd (the last one as burn up monitor), by the thermal ionization mass spectrometry (TIMS). These assays are linked to the IAEA RLA/4/018 Regional Project 'Management of Spent Fuel from Research Reactors'. It is concluded that this technique of burn up measurement is powerful and accurate when properly applied, and permit to validate the calculation codes when isotopic dilution is performed. It is worth noticed the LFR capacity to carry on different research and development programs in the nuclear fuel cycle field, such as the previously mentioned absolute burn up measurements, or the evaluation of radioactive waste immobilization processes and researches on burnable poisons. (author)

  11. A Computational Study on the Ground and Excited States of Nickel Silicide.

    Science.gov (United States)

    Schoendorff, George; Morris, Alexis R; Hu, Emily D; Wilson, Angela K

    2015-09-17

    Nickel silicide has been studied with a range of computational methods to determine the nature of the Ni-Si bond. Additionally, the physical effects that need to be addressed within calculations to predict the equilibrium bond length and bond dissociation energy within experimental error have been determined. The ground state is predicted to be a (1)Σ(+) state with a bond order of 2.41 corresponding to a triple bond with weak π bonds. It is shown that calculation of the ground state equilibrium geometry requires a polarized basis set and treatment of dynamic correlation including up to triple excitations with CR-CCSD(T)L resulting in an equilibrium bond length of only 0.012 Å shorter than the experimental bond length. Previous calculations of the bond dissociation energy resulted in energies that were only 34.8% to 76.5% of the experimental bond dissociation energy. It is shown here that use of polarized basis sets, treatment of triple excitations, correlation of the valence and subvalence electrons, and a Λ coupled cluster approach is required to obtain a bond dissociation energy that deviates as little as 1% from experiment. PMID:26301835

  12. The whole-core LEU silicide fuel demonstration in the JMTR

    Energy Technology Data Exchange (ETDEWEB)

    Aso, Tomokazu; Akashi, Kazutomo; Nagao, Yoshiharu [Japan Atomic Energy Research Institute, Ibaraki-ken (Japan)] [and others

    1997-08-01

    The JMTR was fully converted to LEU silicide (U{sub 3}Si{sub 2}) fuel with cadmium wires as burnable absorber in January, 1994. The reduced enrichment program for the JMTR was initiated in 1979, and the conversion to MEU (enrichment ; 45%) aluminide fuel was carried out in 1986 as the first step of the program. The final goal of the program was terminated by the present LEU conversion. This paper describes the results of core physics measurement through the conversion phase from MEU fuel core to LEU fuel core. Measured excess reactivities of the LEU fuel cores are mostly in good agreement with predicted values. Reactivity effect and burnup of cadmium wires, therefore, were proved to be well predicted. Control rod worth in the LEU fuel core is mostly less than that in the MEU fuel core. Shutdown margin was verified to be within the safety limit. There is no significant difference in temperature coefficient of reactivity between the MEU and LEU fuel cores. These results verified that the JMTR was successfully and safely converted to LEU fuel. Extension of the operating cycle period was achieved and reduction of spend fuel elements is expected by using the fuel with high uranium density.

  13. Status of core conversion with LEU silicide fuel in JRR-4

    Energy Technology Data Exchange (ETDEWEB)

    Nakajima, Teruo; Ohnishi, Nobuaki; Shirai, Eiji [Japan Atomic Energy Research Institute, Ibaraki-ken (Japan)

    1997-08-01

    Japan Research Reactor No.4 (JRR-4) is a light water moderated and cooled, 93% enriched uranium ETR-type fuel used and swimming pool type reactor with thermal output of 3.5MW. Since the first criticality was achieved on January 28, 1965, JRR-4 has been used for shielding experiments, radioisotope production, neutron activation analyses, training for reactor engineers and so on for about 30 years. Within the framework of the RERTR Program, the works for conversion to LEU fuel are now under way, and neutronic and thermal-hydraulic calculations emphasizing on safety and performance aspects are being carried out. The design and evaluation for the core conversion are based on the Guides for Safety Design and Evaluation of research and testing reactor facilities in Japan. These results show that the JRR-4 will be able to convert to use LEU fuel without any major design change of core and size of fuel element. LEU silicide fuel (19.75%) will be used and maximum neutron flux in irradiation hole would be slightly decreased from present neutron flux value of 7x10{sup 13}(n/cm{sup 2}/s). The conversion works are scheduled to complete in 1998, including with upgrade of the reactor building and utilization facilities.

  14. Ion-beam nanopatterning of silicon surfaces under codeposition of non-silicide-forming impurities

    Science.gov (United States)

    Moon, B.; Yoo, S.; Kim, J.-S.; Kang, S. J.; Muñoz-García, J.; Cuerno, R.

    2016-03-01

    We report experiments on surface nanopatterning of Si targets which are irradiated with 2-keV Ar+ ions impinging at near-glancing incidence, under concurrent codeposition of Au impurities simultaneously extracted from a gold target by the same ion beam. Previous recent experiments by a number of groups suggest that silicide formation is a prerequisite for pattern formation in the presence of metallic impurities. In spite of the fact that Au is known not to form stable compounds with the Si atoms, ripples nonetheless emerge in our experiments with nanometric wavelengths and small amplitudes, and with an orientation that changes with distance to the Au source. We provide results of sample analysis through Auger electron and energy-dispersive x-ray spectroscopies for their space-resolved chemical composition, and through atomic force, scanning transmission electron, and high-resolution transmission microscopies for their morphological properties. We discuss these findings in the light of current continuum models for this class of systems. The composition of and the dynamics within the near-surface amorphized layer that ensues is expected to play a relevant role to account for the unexpected formation of these surface structures.

  15. Experimental studies of thermal and chemical interactions between oxide and silicide nuclear fuels with water

    International Nuclear Information System (INIS)

    Given some transient power/cooling mismatch is a nuclear reactor and its inability to establish the necessary core cooling, energetic fuel-coolant interactions (FCI's commonly called 'vapor explosions') could occur as a result of the core melting and coolant contact. Although a large number of studies have been done on energetic FCI's, very few experiments have been performed with the actual fuel materials postulated to be produced in severe accidents. Because of the scarcity of well-characterized FCI data for uranium allows in noncommercial reactors (cermet and silicide fuels), we have conducted a series of experiments to provide a data base for the foregoing materials. An existing 1-D shock-tube facility was modified to handle depleted radioactive materials (U3O8-Al, and U3Si2-Al). Our objectives have been to determine the effects of the initial fuel composition and temperature and the driving pressure (triggering) on the explosion work output, dynamic pressures, transient temperatures, and the hydrogen production. Experimental results indicate limited energetics, mainly thermal interactions, for these fuel materials as compared to aluminum where more chemical reactions occur between the molten aluminum and water

  16. Prompt Neutron Decay Constant Determination Of Silicide Transition Core Using Noise Method

    International Nuclear Information System (INIS)

    Chairman of BATAN had decided to replace the Oxide fuel element type of RSG-GAS into silicide element type step by step. The replacement will create core transitions. Kinetic characteristic of the transition cores have to be monitored in order to know the deviation of core behavior. For that reason, the kinetic parameters have to be measured. Prompt neutron decay constant (alpha) is one of the kinetic parameters that has to be monitored continuously in the transition cores. In order not to disturb the normal operation of reactor, alpha parameter should be measured by using noise analysis method. The voltage of neutron flux at power of 15 MW is connected to preamplifier and filter then to the Dynamic Signal Analyzer Version-2 and then the auto power spectral density (APSD) was determined by using Fast Fourier transform. From the APSD curve of each channel of JKT03, the cut off frequency of each channel can be determined by using linear regression technique such that the prompt neutron decay constant can be estimated

  17. Experimental studies of thermal and chemical interactions between oxide and silicide nuclear fuels with water

    Energy Technology Data Exchange (ETDEWEB)

    farahani, A.A.; Corradini, M.L. [Univ. of Wisconsi, Madison, WI (United States)

    1995-09-01

    Given some transient power/cooling mismatch is a nuclear reactor and its inability to establish the necessary core cooling, energetic fuel-coolant interactions (FCI`s commonly called `vapor explosions`) could occur as a result of the core melting and coolant contact. Although a large number of studies have been done on energetic FCI`s, very few experiments have been performed with the actual fuel materials postulated to be produced in severe accidents. Because of the scarcity of well-characterized FCI data for uranium allows in noncommercial reactors (cermet and silicide fuels), we have conducted a series of experiments to provide a data base for the foregoing materials. An existing 1-D shock-tube facility was modified to handle depleted radioactive materials (U{sub 3}O{sub 8}-Al, and U{sub 3}Si{sub 2}-Al). Our objectives have been to determine the effects of the initial fuel composition and temperature and the driving pressure (triggering) on the explosion work output, dynamic pressures, transient temperatures, and the hydrogen production. Experimental results indicate limited energetics, mainly thermal interactions, for these fuel materials as compared to aluminum where more chemical reactions occur between the molten aluminum and water.

  18. Enhanced power factor of higher manganese silicide via melt spin synthesis method

    International Nuclear Information System (INIS)

    We report on the thermoelectric properties of the higher manganese silicide MnSi1.75 synthesized by means of a one-step non-equilibrium method. The ultrahigh cooling rate generated from the melt-spin technique is found to be effective in reducing second phases, which are inevitable during the traditional solid state diffusion processes. Aside from being detrimental to thermoelectric properties, second phases skew the revealing of the intrinsic properties of this class of materials, for example, the optimal level of carrier concentration. With this melt-spin sample, we are able to formulate a simple model based on a single parabolic band that can well describe the carrier concentration dependence of the Seebeck coefficient and power factor of the data reported in the literature. An optimal carrier concentration around 5 × 1020 cm−3 at 300 K is predicted according to this model. The phase-pure melt-spin sample shows the largest power factor at high temperature, resulting in the highest zT value among the three samples in this paper

  19. Status of core conversion with LEU silicide fuel in JRR-4

    International Nuclear Information System (INIS)

    Japan Research Reactor No.4 (JRR-4) is a light water moderated and cooled, 93% enriched uranium ETR-type fuel used and swimming pool type reactor with thermal output of 3.5MW. Since the first criticality was achieved on January 28, 1965, JRR-4 has been used for shielding experiments, radioisotope production, neutron activation analyses, training for reactor engineers and so on for about 30 years. Within the framework of the RERTR Program, the works for conversion to LEU fuel are now under way, and neutronic and thermal-hydraulic calculations emphasizing on safety and performance aspects are being carried out. The design and evaluation for the core conversion are based on the Guides for Safety Design and Evaluation of research and testing reactor facilities in Japan. These results show that the JRR-4 will be able to convert to use LEU fuel without any major design change of core and size of fuel element. LEU silicide fuel (19.75%) will be used and maximum neutron flux in irradiation hole would be slightly decreased from present neutron flux value of 7x1013(n/cm2/s). The conversion works are scheduled to complete in 1998, including with upgrade of the reactor building and utilization facilities

  20. Crystal structure of the ternary silicide Gd2Re3Si5

    Directory of Open Access Journals (Sweden)

    Vitaliia Fedyna

    2014-12-01

    Full Text Available A single crystal of the title compound, the ternary silicide digadolinium trirhenium pentasilicide, Gd2Re3Si5, was isolated from an alloy of nominal composition Gd20Re30Si50 synthesized by arc melting and investigated by X-ray single-crystal diffraction. Its crystal structure belongs to the U2Mn3Si5 structure type. All atoms in the asymmetric lie on special positions. The Gd site has site symmetry m..; the two Mn atoms have site symmetries m.. and 2.22; the three Si atoms have site symmetries m.., ..2 and 4.. . The coordination polyhedra of the Gd atoms have 21 vertices, while those of the Re atoms are cubooctahedra and 13-vertex polyhedra. The Si atoms are arranged as tricapped trigonal prisms, bicapped square antiprisms, or 11-vertex polyhedra. The crystal structure of the title compound is also related to the structure types CaBe2Ge2 and W5Si3. It can be represented as a stacking of Gd-centred polyhedra of composition [GdSi9]. The Re atoms form infinite chains with an Re—Re distance of 2.78163 (5 Å and isolated squares with an Re—Re distance of 2.9683 (6 Å.

  1. Oxidation behavior of niobium aluminide intermetallics protected by aluminide and silicide diffusion coatings

    International Nuclear Information System (INIS)

    The isothermal and cyclic oxidation behavior of a new class of damage-tolerant niobium aluminide (Nb3Al-xTi-yCr) intermetallics is studied between 650 C and 850 C. Protective diffusion coatings were deposited by pack cementation to achieve the siliciding or aluminizing of substrates with or without intervening Mo or Ni layers, respectively. The compositions and microstructures of the resulting coatings and oxidized surfaces were characterized. The isothermal and cyclic oxidation kinetics indicate that uncoated Nb-40Ti-15Al-based intermetallics may be used up to ∼750 C. Alloying with Cr improves the isothermal oxidation resistance between 650 C and 850 C. The most significant improvement in oxidation resistance is achieved by the aluminization of electroplated Ni interlayers. The results suggest that the high-temperature limit of niobium aluminide-based alloys may be increased to 800 C to 850 C by aluminide-based diffusion coatings on ductile Ni interlayers. Indentation fracture experiments also indicate that the ductile nickel interlayers are resistant to crack propagation in multilayered aluminide-based coatings

  2. Magnetic structure of the ferromagnetic new ternary silicide Nd5CoSi2.

    Science.gov (United States)

    Mayer, C; Gaudin, E; Gorsse, S; Porcher, F; André, G; Chevalier, B

    2012-04-01

    Nd(5)CoSi(2) was obtained from the elements by arc-melting followed by annealing at 883 K. Its investigation by single-crystal x-ray and neutron powder diffraction shows that this ternary silicide crystallizes as Nd(5)Si(3) in a tetragonal structure deriving from the Cr(5)B(3)-type (I4/mcm space group; a = 7.7472(2) and c = 13.5981(5) Å as unit cell parameters). The structural refinements confirm the mixed occupancy on the 8h site between Si and Co atoms, as already observed for Gd(5)CoSi(2). Magnetization and specific heat measurements reveal a ferromagnetic behavior below T(C) = 55 K for Nd(5)CoSi(2). This magnetic ordering is further evidenced by neutron powder diffraction investigation revealing between 1.8 K and T(C) a canted ferromagnetic structure in the direction of the c-axis described by a propagation vector k = (0 0 0). At 1.8 K, the two Nd(3+) ions carry ordered magnetic moments equal respectively to 1.67(7) and 2.37(7) μ(B) for Nd1 and Nd2; these two moments exhibit a canting angle of θ = 4.3(6)°. This magnetic structure presents some similarities with that reported for Nd(5)Si(3). PMID:22392874

  3. Characterization of novel heterophasic powdered silicide-type material for high-temperature protection systems

    International Nuclear Information System (INIS)

    Novel multicomponent heterophasic powdered material of silicide-type is presented. The powdered material is intended for forming high-temperature protective multifunction coatings able to protect different hot-loaded structural elements of aerospace industry from refractory metals alloys under severe oxidizing conditions in high-enthalpy and super/hypersonic oxygen-containing gas flows. The powdered material base on complexly composition of Si-Ti-Mo system modified with B,Y,W. Technological conception of its obtaining and powder making process are examined. The powders were worked out in accordance with early performed functional structural model of special materials for coatings with the increased self-healing ability. The coatings can be deposited from the specially prepared abovementioned powders by plasma spraying processes or any one of other coating methods ensuring the conservation of morphological peculiarities of microstructure and phase composition of powdered material (detonation spraying technique, from slurry ...). Finally the results of some properties of novel heterophasic silicidetype powders and some properties of protective coating deposited on the niobium base alloys by means of plasma spraying technique are presented. (author)

  4. Lanthanide silicide-carbide phases of composition La5Si3Csub(x)

    International Nuclear Information System (INIS)

    Alloys of lanthanide elements (La, Ce, Nd, Gd, Ho, Er and Y) with silicon have been prepared around the composition Ln5Si3. These have been investigated by single-crystal and powder x-ray diffraction, neutron diffraction, thermal analysis, micro hardness and hydrolytic techniques. For the light lanthanides (La, Ce), no Cr5B3-type phase was observed, but several new phases have been identified. The Nd-compound has a complicated behaviour and is a borderline element between the light and heavy lanthanides. Lanthanides heavier than Nd produce the 5:3 silicide, crystallizing in the Mn5Si3 (D88)-type structure. The solubility of carbon and its effect on the D88 structure have been investigated by x-ray, metallographic and hardness measurements. Also, the corrosion products arising from attack by H2O vapour and by HNO3 have been analysed. X-ray single-crystal analysis was achieved for two ordered superstructures, Er28Si16C4 and Er90Si54C18, despite serious problems from absorption and the presence of heavy atoms. A neutron powder profile analysis for these structures failed because of the screening effect and low resolution. The addition of carbon to the D88 structure in the range x = 0 to 2 in Ln5Si3Csub(x) produces quite complex phase changes which are reported and discussed. (author)

  5. Reaction of chromium(VI) with glutathione or with hydrogen peroxide: identification of reactive intermediates and their role in chromium(VI)-induced DNA damage.

    OpenAIRE

    Aiyar, J; Berkovits, H J; Floyd, R A; Wetterhahn, K E

    1991-01-01

    The types of reactive intermediates generated upon reduction of chromium(VI) by glutathione or hydrogen peroxide and the resulting DNA damage have been determined. In vitro, reaction of chromium(VI) with glutathione led to formation of two chromium(V) complexes and the glutathione thiyl radical. When chromium(VI) was reacted with DNA in the presence of glutathione, chromium-DNA adducts were obtained, with no DNA strand breakage. The level of chromium-DNA adduct formation correlated with chrom...

  6. Design and performance of chromium mist generator

    Directory of Open Access Journals (Sweden)

    Tirgar Aram

    2006-01-01

    Full Text Available Chromium mist generator is an essential tool for conducting researches and making science-based recommendations to evaluate air pollution and its control systems. The purpose of this research was to design and construct a homogenous chromium mist generator and the study of some effective factors including sampling height and distances between samplers in side-by-side sampling on chromium mist sampling method. A mist generator was constructed, using a chromium electroplating bath in pilot scale. Concentration of CrO3 and sulfuric acid in plating solution was 125 g L-1 and 1.25 g L-1, respectively. In order to create permanent air sampling locations, a Plexiglas cylindrical chamber (75 cm height, 55 cm i.d was installed the bath overhead. Sixty holes were produced on the chamber in 3 rows (each 20. The distance between rows and holes was 15 and 7.5 cm, respectively. Homogeneity and effective factors were studied via side-by-side air sampling method. So, 48 clusters of samples were collected on polyvinyl chloride (PVC filters housed in sampling cassettes. Cassettes were located in 35, 50, and 65 cm above the solution surface with less than 7.5 and/or 7.5-15 cm distance between heads. All samples were analyzed according to the NIOSH method 7600. According to the ANOVA test, no significant differences were observed between different sampling locations in side-by-side sampling (P=0.82 and between sampling heights and different samplers distances (P=0.86 and 0.86, respectively. However, there were notable differences between means of coefficient of variations (CV in various heights and distances. It is concluded that the most chromium mist homogeneity could be obtained at height 50 cm from the bath solution surface and samplers distance of < 7.5 cm.

  7. Chromium supplementation improved post-stroke brain infarction and hyperglycemia.

    Science.gov (United States)

    Chen, Wen-Ying; Mao, Frank Chiahung; Liu, Chia-Hsin; Kuan, Yu-Hsiang; Lai, Nai-Wei; Wu, Chih-Cheng; Chen, Chun-Jung

    2016-04-01

    Hyperglycemia is common after acute stroke and is associated with a worse outcome of stroke. Thus, a better understanding of stress hyperglycemia is helpful to the prevention and therapeutic treatment of stroke. Chromium is an essential nutrient required for optimal insulin activity and normal carbohydrate and lipid metabolism. Beyond its nutritional effects, dietary supplement of chromium causes beneficial outcomes against several diseases, in particular diabetes-associated complications. In this study, we investigated whether post-stroke hyperglycemia involved chromium dynamic mobilization in a rat model of permanent focal cerebral ischemia and whether dietary supplement of chromium improved post-stroke injury and alterations. Stroke rats developed brain infarction, hyperglycemia, hyperinsulinemia, glucose intolerance, and insulin resistance. Post-stroke hyperglycemia was accompanied by elevated secretion of counter-regulatory hormones including glucagon, corticosterone, and norepinephrine, decreased insulin signaling in skeletal muscles, and increased hepatic gluconeogenesis. Correlation studies revealed that counter-regulatory hormone secretion showed a positive correlation with chromium loss and blood glucose increased together with chromium loss. Daily chromium supplementation increased tissue chromium levels, attenuated brain infarction, improved hyperglycemia, and decreased plasma levels of glucagon and corticosterone in stroke rats. Our findings suggest that stroke rats show disturbance of tissue chromium homeostasis with a net loss through urinary excretion and chromium mobilization and loss might be an alternative mechanism responsible for post-stroke hyperglycemia. PMID:26477944

  8. Femtosecond laser surface structuring and oxidation of chromium thin coatings: Black chromium

    Energy Technology Data Exchange (ETDEWEB)

    Kotsedi, L., E-mail: Kotsedi@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Nuru, Z.Y. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Mthunzi, P. [National Laser Centre, Council for Scientific and Industrial Research, 0001 Pretoria (South Africa); Muller, T.F.G. [University of the Western Cape, Physics Department, Bellville, 7535 Cape Town (South Africa); Eaton, S.M. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Julies, B. [University of the Western Cape, Physics Department, Bellville, 7535 Cape Town (South Africa); Manikandan, E. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Ramponi, R. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Maaza, M. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa)

    2014-12-01

    Highlights: • Oxidation of the chromium thin film to chromium oxide by femtosecond laser with a fundamental wavelength of 1064 nm. • Solar absorber from chromium oxide that low percentage reflectance. • Femtosecond laser oxidation, with a de-focused laser. • Chromium oxide formation by femtosecond laser in normal ambient. - Abstract: In view of their potential applications as selective solar absorbers, chromium coatings on float glass substrates were nano/micro structured by femtosecond laser in air. Raman and X-rays diffraction investigations confirmed the formation of an ultra-porous α-Cr{sub 2}O{sub 3} layer at the surface; higher is the input laser power, enhanced is the crystallinity of the α-Cr{sub 2}O{sub 3} layer. The α-Cr{sub 2}O{sub 3} layer with the Cr underneath it in addition to the photo-induced porosity acted as a classical ceramic–metal nano-composite making the reflectance to decrease significantly within the spectral range of 190–1100 nm. The average reflectance decreased from 70 to 2%.

  9. Femtosecond laser surface structuring and oxidation of chromium thin coatings: Black chromium

    International Nuclear Information System (INIS)

    Highlights: • Oxidation of the chromium thin film to chromium oxide by femtosecond laser with a fundamental wavelength of 1064 nm. • Solar absorber from chromium oxide that low percentage reflectance. • Femtosecond laser oxidation, with a de-focused laser. • Chromium oxide formation by femtosecond laser in normal ambient. - Abstract: In view of their potential applications as selective solar absorbers, chromium coatings on float glass substrates were nano/micro structured by femtosecond laser in air. Raman and X-rays diffraction investigations confirmed the formation of an ultra-porous α-Cr2O3 layer at the surface; higher is the input laser power, enhanced is the crystallinity of the α-Cr2O3 layer. The α-Cr2O3 layer with the Cr underneath it in addition to the photo-induced porosity acted as a classical ceramic–metal nano-composite making the reflectance to decrease significantly within the spectral range of 190–1100 nm. The average reflectance decreased from 70 to 2%

  10. Production of basic chromium sulfate by using recovered chromium from ashes of thermally treated leather.

    Science.gov (United States)

    Dettmer, Aline; Nunes, Keila Guerra Pacheco; Gutterres, Mariliz; Marcílio, Nilson Romeu

    2010-04-15

    Leather wastes tanned with chromium are generated during the production process of leather, hence the wastes from hand crafted goods and footwear industries are a serious environmental problem. The thermal treatment of leather wastes can be one of the treatment options because the wastes are rich in chromium and can be used as a raw material for sodium chromate production and further to obtain several chromium compounds. The objective of this study was to utilize the chromium from leather wastes via basic chromium sulfate production to be subsequently applied in a hide tanning. The obtained results have shown that this is the first successful attempt to achieve desired base properties of the product. The result was achieved when the following conditions were applied: a molar ratio between sodium sulfite and sodium dichromate equal to 6; reaction time equal to 5 min before addition of sulfuric acid; pH of sodium dichromate solution equal to 2. Summarizing, there is an opportunity to utilize the dangerous wastes and reused them in the production scheme by minimizing or annulling the environmental impact and to attend a sustainable process development concept. PMID:20031309

  11. Synthesis and characterization of β-phase iron silicide nano-particles by chemical reduction

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • β-FeSi2 nano-particle was synthesized by reducing with Mg and by diluting with MgO. • XRD profile shows the iron di-silicide phase to be semiconducting β-FeSi2. • HRTEM and FESEM images indicate the β-FeSi2average particle size to be 60–70 nm. • Absorption, reflectance and PL spectroscopy show band gap to be direct 0.87 eV. • Nano-β-FeSi2is p-type with hole density of 4.38 × 1018 cm−3 and mobility 8.9 cm2/V s. - Abstract: Nano-particles of β-FeSi2 have been synthesized by chemical reduction of a glassy phase of [Fe2O3, 4SiO2] by Mg-metal where MgO is used as diluent to prevent the agglomeration of nano crystallites into micro-particles and also act as a negative catalyst for the formation of other phases. The sample is characterized by XRD, FESEM, HRTEM, EDX, ultra-violet-visible-infrared and PL spectroscopy and electronic properties have been investigated by Hall measurement. XRD profile shows that the synthesized powder consists of purely β-FeSi2 semiconducting phase. The average crystallite size of β-FeSi2 is determined to be around 65.4 nm from XRD peaks as well as from FESEM also. The optical absorption and PL spectroscopy shows that synthesized β-FeSi2 phase is a direct band gap semiconductor with a value of 0.87 eV. Hall measurements show that β-FeSi2 nano-particles is p-type with hole concentration of 4.38 × 1018 cm−3 and average hole mobility of 8.9 cm2/V s at 300 K

  12. Fuel loading and homogeneity analysis of HFIR design fuel plates loaded with uranium silicide fuel

    International Nuclear Information System (INIS)

    Twelve nuclear reactor fuel plates were analyzed for fuel loading and fuel loading homogeneity by measuring the attenuation of a collimated X-ray beam as it passed through the plates. The plates were identical to those used by the High Flux Isotope Reactor (HFIR) but were loaded with uranium silicide rather than with HFIR's uranium oxide fuel. Systematic deviations from nominal fuel loading were observed as higher loading near the center of the plates and underloading near the radial edges. These deviations were within those allowed by HFIR specifications. The report begins with a brief background on the thermal-hydraulic uncertainty analysis for the Advanced Neutron Source (ANS) Reactor that motivated a statistical description of fuel loading and homogeneity. The body of the report addresses the homogeneity measurement techniques employed, the numerical correction required to account for a difference in fuel types, and the statistical analysis of the resulting data. This statistical analysis pertains to local variation in fuel loading, as well as to ''hot segment'' analysis of narrow axial regions along the plate and ''hot streak'' analysis, the cumulative effect of hot segment loading variation. The data for all twelve plates were compiled and divided into 20 regions for analysis, with each region represented by a mean and a standard deviation to report percent deviation from nominal fuel loading. The central regions of the plates showed mean values of about +3% deviation, while the edge regions showed mean values of about -7% deviation. The data within these regions roughly approximated random samplings from normal distributions, although the chi-square (χ2) test for goodness of fit to normal distributions was not satisfied

  13. Ab initio studies of structural, electronic, magnetic and mechanical properties of alkali earth metal silicides

    International Nuclear Information System (INIS)

    Alkali earth metal silicides MSi (M = Mg, Ca, Sr, Ba) are multi-phase compound and exist simultaneously in CrB, CsCl, NaCl or rock salt (RS) and zinc blende (zb) structures. In the CrB and CsCl phases, their behavior is metallic in the non-magnetic (NM) as well as the ferromagnetic (FM) structure. The total spin magnetic moment of these compounds in the zb phase is more than that in the corresponding RS phase; therefore, detailed studies for the zb phase are presented in this paper. This study includes structural, electronic and mechanical properties by using the full potential linear augmented plain wave scheme with local orbitals. Ferromagnetic CaSi, SrSi and BaSi show true half-metallic character. For a better understanding of the half-metallicity in the above-mentioned sp-type compounds, their band structures have been calculated and densities of state plots have been produced. The FM structures are more stable and harder than the corresponding NM structures. The magnetic moment corresponding to equilibrium lattice constants is calculated as 2 µB for FM CaSi, SrSi and BaSi, which are in accordance with the earlier work on the sp-type compounds CaC, SrC and BaC. The FM character changes to the paramagnetic character as the lattice parameter decreases. The general trend is that the values of the elastic constants C11, C12 and C44 increase with increasing hydrostatic pressure

  14. Effects of ball milling on microstructures and thermoelectric properties of higher manganese silicides

    International Nuclear Information System (INIS)

    Highlights: • The already low κL of HMS can be suppressed further by decreasing the grain size. • The ball milling process can lead to the formation of secondary MnSi and W/C-rich phases. • The formation of the MnSi ad W/C rich phases is found to suppress the thermoelectric power factor. - Abstract: Bulk nanostructured higher manganese silicide (HMS) samples with different grain size are prepared by melting, subsequent ball milling (BM), and followed by spark plasma sintering (SPS). The effects of BM time on the microstructures and thermoelectric properties of these samples are investigated. It is found that BM effectively reduces the grain size to about 90 nm in the sample after SPS, which leads to a decrease in both the thermal conductivity and electrical conductivity. By prolonging the BM time, MnSi and tungsten/carbon-rich impurity phases are formed due to the impact-induced decomposition of HMS and contamination from the tungsten carbide jar and balls during the BM, respectively. These impurities result in a reduced Seebeck coefficient and increased thermal conductivity above room temperature. The measured size-dependent lattice thermal conductivities agree qualitatively with the reported calculation results based on a combined phonon and diffuson model. The size effects are found to be increasingly significant as temperature decreases. Because of the formation of the impurity phases and a relatively large grain size, the ZT values are not improved in the ball-milled HMS samples. These findings suggest the need of alternative approaches for the synthesis of pure HMS with further reduced grain size and controlled impurity doping in order to enhance the thermoelectric figure-of-merit of HMS via nanostructuring

  15. M(5)-silicon (M= titanium, niobium, molybdenum) based transition-metal silicides for high temperature applications

    Science.gov (United States)

    Tang, Zhihong

    2007-12-01

    Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600ºC. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti5Si3-based alloys was investigated. Oxidation behavior of Ti5Si3-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters the oxidation behavior of Ti5Si3 by nucleation and growth of nitride subscale. Ti5Si3.2 and Ti5Si3C0.5 alloys exhibited an excellent oxidation resistance in nitrogen bearing atmosphere due to limited dissolution of nitrogen and increased Si/Ti activity ratio. MoSi2 coating developed by pack cementation to protect Mo-based Mo-Si-B composites was found to be effective up to 1500ºC. Shifting coating composition to T1+T2+Mo3Si region showed the possibility to extend the coating lifetime above 1500ºC by more than ten times via formation of slow growing Mo3Si or T2 interlayer without sacrificing the oxidation resistance of the coating. The phase equilibria in the Nb-rich portion of Nb-B system has been evaluated experimentally using metallographic analysis and differential thermal analyzer (DTA). It was shown that Nbss (solid solution) and NbB are the only two primary phases in the 0-40 at.% B composition range, and the eutectic reaction L ↔ Nbss + NbB was determined to occur at 2104+/-5°C by DTA.

  16. Inelastic Scattering of Neutrons in Chromium

    International Nuclear Information System (INIS)

    The phonon spectrum of chromium has been studied by neutron inelastic scattering. The dispersion curves are very similar, in form to those of tungsten and molybdenum, indicating similar interionic force constants. The neutron groups broaden but do not shift appreciably when the temperature is raised. No effect has been observed which can be attributed to the interaction between the phonons and the crystal magnetization in the antiferromagnetic phase. (author)

  17. Observational Approach to Chromium Site Remediation - 13266

    International Nuclear Information System (INIS)

    Production reactors at the U.S. Department of Energy's (DOE) Hanford Site in Richland, Washington, required massive quantities of water for reactor cooling and material processing. To reduce corrosion and the build-up of scale in pipelines and cooling systems, sodium dichromate was added to the water feedstock. Spills and other releases at the makeup facilities, as well as leaks from miles of pipelines, have led to numerous areas with chromium-contaminated soil and groundwater, threatening fish populations in the nearby Columbia River. Pump-and-treat systems have been installed to remove chromium from the groundwater, but significant contamination remain in the soil column and poses a continuing threat to groundwater and the Columbia River. Washington Closure Hanford, DOE, and regulators are working on a team approach that implements the observational approach, a strategy for effectively dealing with the uncertainties inherent in subsurface conditions. Remediation of large, complex waste sites at a federal facility is a daunting effort. It is particularly difficult to perform the work in an environment of rapid response to changing field and contamination conditions. The observational approach, developed by geotechnical engineers to accommodate the inherent uncertainties in subsurface conditions, is a powerful and appropriate method for site remediation. It offers a structured means of quickly moving into full remediation and responding to the variations and changing conditions inherent in waste site cleanups. A number of significant factors, however, complicate the application of the observational approach for chromium site remediation. Conceptual models of contamination and site conditions are difficult to establish and get consensus on. Mid-stream revisions to the design of large excavations are time-consuming and costly. And regulatory constraints and contract performance incentives can be impediments to the flexible responses required under the observational

  18. Stainless chromium-nickel steels. Chapter I

    International Nuclear Information System (INIS)

    The chemical composition is tabulated of 90 chromium-nickel stainless steels and alloys given in volume %. The values are also given of the corrosion resistance of the steels and alloys. The tables show data on the surface condition or the methods of material working, types and chemical composition of the medium where corrosion resistance tests were carried out, temperature, pressure, time of tests, corrosion rates, corrosion types, and literature references. A total of 35 references is given. (J.B.)

  19. Loading chromium atoms in a magnetic guide

    OpenAIRE

    Greiner, A; Sebastian, J.; Rehme, P.; Aghajani-Talesh, A.; Griesmaier, A.; Pfau, T.

    2007-01-01

    We have realized a magnetic guide for ultracold chromium atoms by continuously loading atoms directly from a Zeeman slower into a horizontal guide. We observe an atomic flux of $2 \\cdot 10^7$ atoms/s and are able to control the mean velocity of the guided atoms between 0 m/s and 3 m/s. We present our experimental results on loading and controlling the mean velocity of the guided atoms and discuss the experimental techniques that are used.

  20. X-616 Chromium Sludge Lagoons pictorial overview, Piketon, Ohio

    International Nuclear Information System (INIS)

    The Portsmouth Gaseous Diffusion Plant uses large quantities of water for process cooling. The X-616 Liquid Effluent Control Facility was placed in operation in December 1976 to treat recirculation cooling water blowdown from the process cooling system. A chromium-based corrosion inhibitor was used in the cooling water system. A chromium sludge was produced in a clarifier to control chromium levels in the water. Chromium sludge produced by this process was stored in two surface impoundments called the X-616 Chromium Sludge Lagoons. The sludge was toxic due to its chromium concentration and therefore required treatment. The sludge was treated, turning it into a sanitary waste, and buried in an Ohio EPA approved landfill. The plant's process cooling water system has changed to a more environmentally acceptable phosphate-based inhibitor. Closure activities at X-616 began in August 1990, with all construction activities completed in June 1991, at a total cost of $8.0 million

  1. Chromium oxidation state mapping in human cells

    Science.gov (United States)

    Ortega, R.; Fayard, B.; Salomé, M.; Devès, G.; Susini, J.

    2003-03-01

    The widespread use of chromium in industrial applications such as chemical production of pigments, refractory brick production, tanning, metallurgy, electroplating, and combustion of fuels has lead to human occupational exposure and to its increased introduction into the environment. Hexavalent chromium compounds are established carcinogens but their mechanism of cell transformation is not known. Up to now, no microanalytical technique was sensitive enough to allow the observation of chromium distribution, and oxidation state identification, within isolated cells at carcinogenic concentrations. In this experiment, we used successfully the ID-21 X-ray microscope to map Cr(VI) and total Cr distributions in cells exposed in vitro to soluble, and insoluble, Cr(VI) compounds. Exposure to soluble compounds, weak carcinogens, resulted in a homogeneous intracellular distribution of Cr, confirming by in situ measurement that Cr is present in the cell nucleus. Cr(VI) was never detected in cells which suggests a mechanism of rapid intracellular reducticn. On the other hand, exposure to insoluble compounds, strong carcinogens, also resulted in a homogeneous distribution of reduced forms of Cr in cells, and their nucleus. However, in this case, Cr(VI)-rich structures were observed into the cells suggesting that carcinogenicity is enhanced when oxidation reactions due to Cr(VI) chronic exposure are associated to Cr-DNA alterations.

  2. Dimensionally Controlled Lithiation of Chromium Oxide

    Energy Technology Data Exchange (ETDEWEB)

    Fister, Tim T. [Argonne National Lab. (ANL), Argonne, IL (United States); Hu, Xianyi [Northwestern Univ., Evanston, IL (United States); Esbenshade, Jennifer [Univ. of Illinois, Urbana-Champaign, IL (United States); Chen, Xiao [Northwestern Univ., Evanston, IL (United States); Wu, Jinsong [Northwestern Univ., Evanston, IL (United States); Dravid, Vinayak [Northwestern Univ., Evanston, IL (United States); Bedzyk, Michael [Northwestern Univ., Evanston, IL (United States); Long, Brandon [Argonne National Lab. (ANL), Argonne, IL (United States); Gewirth, Andrew A. [Univ. of Illinois, Urbana-Champaign, IL (United States); Shi, Bing [Argonne National Lab. (ANL), Argonne, IL (United States); Schlepütz, Christian M. [Argonne National Lab. (ANL), Argonne, IL (United States); Fenter, Paul [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-01-12

    Oxide conversion reactions are an alternative approach for high capacity lithium ion batteries but are known to suffer from structural irreversibility associated with the phase separation and reconstitution of reduced metal species and Li2O. In particular, the morphology of the reduced metal species is thought to play a critical role in the electrochemical properties of a conversion material. Here we use a model electrode with alternating layers of chromium and chromium oxide to better understand and control these phase changes in real-time and at molecular length scales. Despite lacking crystallinity at the atomic scale, this superstructure is observed (with X-ray reflectivity, XR) to lithiate and delithiate in a purely one-dimensional manner, preserving the layered structure. The XR data show that the metal layers act as nucleation sites for the reduction of chromium in the conversion reaction. Irreversibility during delithiation is due to the formation of a ternary phase, LiCrO2, which can be further delithiated at higher potentials. The results reveal that the combination of confining lithiation to nanoscale sheets of Li2O and the availability of reaction sites in the metal layers in the layered structure is a strategy for improving the reversibility and mass transport properties that can be used in a wide range of conversion materials.

  3. Chromium--a material for fusion technology

    International Nuclear Information System (INIS)

    Due to their low neutron-induced radioactivity chromium based materials are considered to be candidates for structure materials in fusion technology. In this paper investigations are presented of unirradiated chromium with a purity of 99.96% (DUCROPUR) and a dispersion strengthened chromium alloy Cr5Fe1Y2O3 (DUCROLLOY). Both materials have been produced in a powder metallurgical route. Mechanical tests of smooth and pre-cracked specimens have been performed in a wide temperature range. Below 280 deg. C the fracture toughness values of DUCROPUR are very low (1/2), above the transition temperature they exceed 500 MPa m1/2. Large plastic deformations have been observed. DUCROLLOY does not indicate such a significant increase of fracture toughness in the tested temperature range. But above 400 deg. C large plastic deformations can be obtained in bending samples, too. The fatigue crack propagation behaviour of DUCROPUR at 300 deg. C is similar to that of a ductile metal

  4. A REVIEW OF BIOSORPTION OF CHROMIUM IONS BY MICROORGANISMS

    OpenAIRE

    Inga Zinicovscaia

    2012-01-01

    Due to its widespread industrial use, chromium has become a serious pollutant in diverse environmental settings. The main source of chromium pollution including the Republic o Moldova is industry. It is a great need to develop new eco-friendly methods of chromium removal. Biosorption of heavy metals is a most promising technology involved in the removal of toxic metals from industrial waste streams and natural waters. This article is an extended abstract of a communication presented at the...

  5. CHROMIUM INDUCED CYTOTOXICITY IN BLACKGRAM (VIGNA MUNGO L.)

    OpenAIRE

    A. Chidambaram ، P. Sundaramoorthy ، A. Murugan ، K. Sankar Ganesh ، L. Baskaran

    2009-01-01

    Chromium is known to be highly toxic to biological systems. This study was designed to determine the mutagenic effects of different concentrations (0, 10, 25, 50, 100 and 200 mg/L) of hexavalent chromium on root tip cells of blackgram (Vigna mungo L. Hepper). The blackgram seeds were equi-spacially arranged in sterilized petriplates lined with filter paper and they were treated with different concentrations of chromium solution. In germination studies, the morphological growth parameters such...

  6. Processes affecting the remediation of chromium-contaminated sites.

    OpenAIRE

    Palmer, C.D.; Wittbrodt, P R

    1991-01-01

    The remediation of chromium-contaminated sites requires knowledge of the processes that control the migration and transformation of chromium. Advection, dispersion, and diffusion are physical processes affecting the rate at which contaminants can migrate in the subsurface. Heterogeneity is an important factor that affects the contribution of each of these mechanisms to the migration of chromium-laden waters. Redox reactions, chemical speciation, adsorption/desorption phenomena, and precipitat...

  7. Analysis of molybdenum, chromium, vanadium and iron by polarographic techniques

    International Nuclear Information System (INIS)

    The application of direct current Tast polarograph, differential pulse polarography and phase-selective alternative current Tast polarography to the problem of determining molybdenum, chromium, vanadium and iron in various supporting electrolytes is reported. The effect of the supporting electrolyte on the wave/peak potential and sensitivity of the metal ion have been examined. The polarographic methods were applied for simultaneous determination of chromium (3)/chromium (6), vanadium (4), vanadium (5) and iron (2)/iron (3) in different supporting electrolytes

  8. Production of a chromium Bose-Einstein condensate

    OpenAIRE

    Griesmaier, Axel; Stuhler, Jürgen; Pfau, Tilman

    2005-01-01

    The recent achievement of Bose-Einstein condensation of chromium atoms [1] has opened longed-for experimental access to a degenerate quantum gas with long-range and anisotropic interaction. Due to the large magnetic moment of chromium atoms of 6 {$\\mu$}B, in contrast to other Bose- Einstein condensates (BECs), magnetic dipole-dipole interaction plays an important role in a chromium BEC. Many new physical properties of degenerate gases arising from these magnetic forces have been predicted in ...

  9. Removal of chromium(VI) from saline wastewaters by

    OpenAIRE

    AKSU, Zümriye

    2002-01-01

    Some industrial wastewaters contain higher quantities of salts besides chromium(VI) ions so the effect of these salts on the biosorption of chromium(VI) should be investigated. The biosorption of chromium (VI) from saline solutions on two strains of living Dunaliella algae were tested under laboratory conditions as a function of pH, initial metal ion and salt (NaCl) concentrations in a batch system. The biosorption capacity of both Dunaliella strains strongly de...

  10. Increase of chromium utilization in stainless steel melting

    International Nuclear Information System (INIS)

    The processes of deoxidizing when melting stainless 18-10 steels in electric are furnaces by the method of remelting with wastes are investigated. The dependences of amount of reduced chromium on silicon consumption are made more precise. It is shown that it is useful to apply aluminium for deoxidation of acid high-chromium slags. Based on the data on pilot melts the extent to which aluminium can be used as a reducing agent for chromium is estimated. 3 refs., 2 figs

  11. Scientific Opinion on ChromoPrecise® cellular bound chromium yeast added for nutritional purposes as a source of chromium in food supplements and the bioavailability of chromium from this source

    OpenAIRE

    EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS)

    2012-01-01

    The Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re-evaluating the safety of ChromoPrecise® cellular bound chromium yeast added for nutritional purposes as a source of chromium in food supplements and the bioavailability of chromium from this source. ChromoPrecise® is a yeast preparation with an enriched trivalent chromium content, obtained by culture of Saccharomyces cerevisiae in the presence of chromium chloride. A daily intake of 100 µg ch...

  12. Chromium depletion from stainless steels during vacuum annealing

    International Nuclear Information System (INIS)

    The behaviour of chromium during selective evaporation by high temperature vacuum annealing has been investigated by means of energy dispersive X-ray analysis and by neutron activation analysis. It was established that the rate of chromium loss from austenitic stainless steels 316 and 321 is controlled by chromium inter-diffusion rather than tracer diffusion in the alloy. Two important parameters in selective removal of chromium from alloy steels are the variation in the chromium surface concentration with time and the depletion profile in the alloy. The present work gives support for the model in which loss of chromium is dependent on its diffusivity in the alloy and on an interface transfer coefficient. The results showed that the surface concentration of chromium decreased with increasing vacuum annealing time. The chromium depletion profile in the metal was in accord with the previous derived model, apart from an anomalous near surface region. Here the higher resolution of a neutron activation technique indicated a region within approximately 2 microns of the surface where the chromium concentration decreased more steeply than expected. (author)

  13. Stabilization and solidification of chromium-contaminated soil

    Energy Technology Data Exchange (ETDEWEB)

    Cherne, C.A.; Thomson, B.M. [Univ. of New Mexico, Albuquerque, NM (United States). Civil Engineering Dept.; Conway, R. [Sandia National Labs., Albuquerque, NM (United States)

    1997-11-01

    Chromium-contaminated soil is a common environmental problem in the United States as a result of numerous industrial processes involving chromium. Hexavalent chromium [Cr(VI)] is the species of most concern because of its toxicity and mobility in groundwater. One method of diminishing the environmental impact of chromium is to reduce it to a trivalent oxidation state [Cr(III)], in which it is relatively insoluble and nontoxic. This study investigated a stabilization and solidification process to minimize the chromium concentration in the Toxicity Characteristic Leaching Procedure (TCLP) extract and to produce a solidified waste form with a compressive strength in the range of 150 to 300 pounds per square inch (psi). To minimize the chromium in the TCLP extract, the chromium had to be reduced to the trivalent oxidation state. The average used in this study was an alluvium contaminated with chromic and sulfuric acid solutions. The chromium concentration in the in the in situ soil was 1212 milligrams per kilogram (mg/kg) total chromium and 275 mg/kg Cr(VI). The effectiveness of iron, ferrous sulfate to reduce Cr(VI) was tested in batch experiments.

  14. Method of trivalent chromium concentration determination by atomic spectrometry

    Science.gov (United States)

    Reheulishvili, Aleksandre N.; Tsibakhashvili, Neli Ya.

    2006-12-12

    A method is disclosed for determining the concentration of trivalent chromium Cr(III) in a sample. The addition of perchloric acid has been found to increase the atomic chromium spectrometric signal due to Cr(III), while leaving the signal due to hexavalent chromium Cr(VI) unchanged. This enables determination of the Cr(III) concentration without pre-concentration or pre-separation from chromium of other valences. The Cr(III) concentration may be measured using atomic absorption spectrometry, atomic emission spectrometry or atomic fluorescence spectrometry.

  15. Tribological Characteristics of Chromium-active Carbon Electroplated Composite Coatings

    Institute of Scientific and Technical Information of China (English)

    GUKa-fi; HUAMeng; Yi-min

    2004-01-01

    A process of chromium electroplating using a standard bath with additives and active carbon particles was reported, and the tribological behaviors of the composite coatings using the pin-on-disk tester and the table wear tester were i nvestig(aed. Experimental results indicate that the electroplated chromium-active carbon composite coatings exhibited the low friction coefficient anti excellent anti-wear properties whets coffered with the normal chromium electroplated ones. The formation of active carbon particles within the chromium matrices can be explained by SEM analysis and the mechanis of wear resistance of the composite coatings were studied.

  16. Defect transformation in GSGG crystals during chromium ion activation

    International Nuclear Information System (INIS)

    Absorption and induced absorption spectra, dose dependence of induced absorption, thermoluminescence of GSGG crystals, nominally pure and activated with chromium and neodymium ions in different concentrations, are investigated. It is shown that it is chromium ion presence in large concentration that decreases the induced coloration in GSGG crystals after γ-irradiation at 300 K. Optimum concentration of chromium ions for the minimum of induced coloration are found. The mechanism of decrease of induced coloration consisting in Fermi level displacement by chromium ion activation is established. Defect concentration and localization and recombination possibilities of electrons and holes in GSGG crystals are estimated by computer simulation

  17. Oral bioavailability of chromium from a specific site.

    OpenAIRE

    Witmer, C M; Harris, R.; Shupack, S I

    1991-01-01

    Analysis of soil from a specific site in New Jersey indicated a low level of sodium and chromium present as a calcium compound. Chromium was then administered orally to young, mature male rats at a level of 240 micrograms/kg for 14 days as chromium-contaminated soil, as CaCrO4, and as an equimolar mixture of the soil and calcium salts for 14 days. The rats were sacrificed 24 hr after the last dosing, and tissues were taken immediately for chromium analysis. Blood, muscle, and liver contained ...

  18. MICRO-SEGREGATION OF CHROMIUM IN Fe-Cr ALLOY

    OpenAIRE

    Igata, N.; Sato, S; ANDO, T.; H. Doi; Nishikawa, O.; Shibata, M.

    1984-01-01

    The objective of this investigation is to clarify the behavior of chromium atoms in iron-5at.% chromium alloy. When the specimens were quenched after soultion annealing at 1150°C for 1hr, FIM image was only a bright area, but when they were tempered from 450°C to 650°C, both bright areas and dark areas were observed in the FIM image. In these quenched specimens there was microsegregation of chromium atoms : In bright areas the chromium concentration was lower, and in dark areas it was higher ...

  19. Influence of Chelating Agents on Chromium Fate in Sediment

    Institute of Scientific and Technical Information of China (English)

    WANGXIAOCHANG; SUNJINHE; 等

    1996-01-01

    A laboratory investigation on reaction between chelating agents and chromium was conducted to evaluate the effect of chelating agents on the adsorption and desorption of chromium in sediment.The amount of adsorbed chromium(VI) in sediment decreased slightly by 5%-10% because of addition of chelating agents.Chelating agents inhibited the removal of Cr(Ⅲ)by sediment from solutions and the inhibiting effect was in the order:citric acid>tartaric acid>EDTA,Salicylic acid.No effect of chelating agents on desorption of chromium in sediment was observed.

  20. Analysing the chromium-chromium multiple bond using multiconfigurational quantum chemistry

    OpenAIRE

    Brynda, Marcin; Gagliardi, Laura; Roos, Björn O.

    2009-01-01

    This Letter discusses the nature of the chemical bond between two chromium atoms in different di-chromium complexes with the metal atoms in different oxidation states. Starting with the Cr diatom, with its formally sextuple bond and oxidation number zero, we proceed to analyse the bonding in some Cr(I)–Cr(I) XCrCrX complexes with X varying from F, to Phenyl, and Aryl. The bond distance in these complexes varies over a large range: 1.65–1.83 Å and we suggest explanations for these variations. ...

  1. The effect of chromium picolinate on serum cholesterol and apolipoprotein fractions in human subjects.

    OpenAIRE

    Press, R. I.; Geller, J.; Evans, G. W.

    1990-01-01

    Chromium has been implicated as a cofactor in the maintenance of normal lipid and carbohydrate metabolism. A deficiency of chromium results from diets low in biologically available chromium. Picolinic acid, a metabolite of tryptophan, forms stable complexes with transitional metal ions, which results in an improved bioavailability of the metal ion chromium. To determine whether or not chromium picolinate is effective in humans, 28 volunteer subjects were given either chromium tripicolinate (3...

  2. Oxide mediated liquid-solid growth of high aspect ratio aligned gold silicide nanowires on Si(110) substrates

    International Nuclear Information System (INIS)

    Silicon nanowires grown using the vapor-liquid-solid method are promising candidates for nanoelectronics applications. The nanowires grow from an Au-Si catalyst during silicon chemical vapor deposition. In this paper, the effect of temperature, oxide at the interface and substrate orientation on the nucleation and growth kinetics during formation of nanogold silicide structures is explained using an oxide mediated liquid-solid growth mechanism. Using real time in situ high temperature transmission electron microscopy (with 40 ms time resolution), we show the formation of high aspect ratio (∼15.0) aligned gold silicide nanorods in the presence of native oxide at the interface during in situ annealing of gold thin films on Si(110) substrates. Steps observed in the growth rate and real time electron diffraction show the existence of liquid Au-Si nano-alloy structures on the surface besides the un-reacted gold nanostructures. These results might enable us to engineer the growth of nanowires and similar structures with an Au-Si alloy as a catalyst.

  3. Technical report: technical development on the silicide plate-type fuel experiment at nuclear safety research reactor

    International Nuclear Information System (INIS)

    According to a reduction of fuel enrichment from 45 w/o 235U 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/cm3 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 UO2-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.)

  4. Effects of nitrogen annealing on surface structure, silicide formation and magnetic properties of ultrathin films of Co on Si(100)

    Indian Academy of Sciences (India)

    Ganesh K Rajan; Shivaraman Ramaswamy; C Gopalakrishnan; D John Thiruvadigal

    2012-02-01

    Effects of nitrogen annealing on structural and magnetic properties of Co/Si (100) up to 700°C has been studied in this paper. Ultrathin Co films having a constant thickness of 50 Å were grown on Si (100) substrates using electron-beam evaporation under very high vacuum conditions at room temperature. Subsequently, the samples were annealed at temperatures ranging from 100–700°C in a nitrogen environment at atmospheric pressure. Sample quality and surface morphology were examined using atomic force microscopy. Silicide formation and the resultant variation in crystallographic arrangement were studied using X-ray diffractometer. The magnetization measurements done using a vibrating sample magnetometer indicate a decrease in coercivity and retentivity values with increase in annealing temperature. Resistivity of the samples measured using a four-point probe set up shows a decrease in resistivity with increase in annealing temperature. Formation of various silicide phases at different annealing temperatures and the resultant variation in the magnetic susceptibility has been thoroughly studied and quantified in this work.

  5. Surface effect on the electronic and the magnetic properties of rock-salt alkaline-earth metal silicides

    International Nuclear Information System (INIS)

    An all electron ab-initio method was employed to study the electronic and the magnetic properties of the (001) surface of alkaline-earth metal silicides, CaSi, SrSi, and BaSi, in the rock-salt structure. The three compounds retain their ferromagnetic metallic properties at the surface. Due to the surface effects, the magnetism of the topmost layer is changed as compared with the bulk. This is a short-range effect. In CaSi, the magnetism of the surface layer is noticeably reduced, as compared with the bulk: magnetic moments (MMs) on both Ca and Si atoms are reduced. In SrSi (001), the polarization of electrons in the surface atoms is similar to that in the bulk atoms, and the values of MMs on the component atoms in the topmost layer do not change as much as in CaSi. In BaSi (001), the magnetic properties of Si surface atoms are enhanced slightly, and the magnetism of Ba atoms is not affected considerably by the surface effect. The calculated densities of states confirm the short-range effect of the surface on the electronic properties of the metal silicides.

  6. Thermal Stability and Growth Behavior of Erbium Silicide Nanowires Self-Assembled on a Vicinal Si(001) Surface

    Institute of Scientific and Technical Information of China (English)

    DING Tao; SONG Jun-Qiang; LI Juan; CAI Qun

    2011-01-01

    Erbium silicide nanowires are self-assembled on vicinal Si(Ool) substrates after electron beam evaporation and post annealing at 63(fC In-situ scanning tunneling microscopy investigations manifest that the nanowires will successively shrink and transform into a nanoisland with annealing prolonged. Meanwhile, a structural transition from hexagonal AIB2 phase to tetragonal ThSi'2 phase is revealed with high-resolution transmission electron microscopy. It is also found that the nanowires gradually expand to embed into the substrates during the growth process, which has much influence on the shape instability of nanowires. Additionally, a multiple deposition-annealing treatment is given as a novel growth method to strengthen the controlled fabrication of nanowires.%@@ Erbium silicide nanowires are self-assembled on vicinal Si(001) substrates after electron beam evaporation and post annealing at 630℃ In-situ scanning tunneling microscopy investigations manifest that the nanowires will successively shrink and transform into a nanoisland with annealing prolonged.Meanwhile, a structural transition from hexagonal AlB phase to tetragonal ThSi phase is revealed with high-resolution transmission electron microscopy.It is also found that the nanowires gradually expand to embed into the substrates during the growth process, which has much influence on the shape instability of nanowires.Additionally, a multiple deposition- annealing treatment is given as a novel growth method to strengthen the controlled fabrication of nanowires.

  7. The Effect of Chromium Added into Basal Diet on Serum Total Protein, Urea, Triglyceride, Cholesterol and Serum and Tissue Chromium, Zinc, Copper Levels in Rabbits

    OpenAIRE

    *, Kâzim ŞAHİN; *, Talat GÜLER; +, N. ŞAHİN; *, O. N. ERTAS; +, N. ERKAL

    1999-01-01

    This study was conducted to determine the effect of supplemantal dietary chromium on serum total protein, urea, triglycerides, cholesterol, and serum and tissue chromium, zinc, and copper contents of pregnant rabbits, their offspring and their young rabbits. Treatment groups consisted of chromium level as follows: Control Group no supplementation chromium into basal diet, Treatment I (200 ppb Group) contained 200 ppb of supplemental chromium into basal diet, and Treatment II (400 ppb Group...

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

    Institute of Scientific and Technical Information of China (English)

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

    2009-01-01

    r 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.

  9. Narrow bandgap semiconducting silicides: Intrinsic infrared detectors on a silicon chip

    Science.gov (United States)

    Mahan, John E.

    1990-01-01

    Work done during the final report period is presented. The main technical objective was to achieve epitaxial growth on silicon of two semiconducting silicides, ReSi2 and CrSi2. ReSi2 thin films were grown on (001) silicon wafers by vacuum evaporation of rhenium onto hot substrates in ultrahigh vacuum. The preferred epitaxial relationship was found to be ReSi2(100)/Si(001) with ReSi2(010) parallel to Si(110). The lattice matching consists of a common unit mesh of 120 A(sup 2) area, and a mismatch of 1.8 percent. Transmission electron microscopy revealed the existence of rotation twins corresponding to two distinct but equivalent azimuthal orientations of the common unit mesh. MeV He(+) backscattering spectrometry revealed a minimum channeling yield of 2 percent for an approximately 1,500 A thick film grown at 650 C. Although the lateral dimension of the twins is on the order of 100 A, there is a very high degree of alignment between the ReSi2(100) and the Si(001) planes. Highly oriented films of CrSi2 were grown on (111) silicon substrates, with the matching crystallographic faces being CrSi2(001)/Si(111). The reflection high-energy electron diffraction (RHEED) patterns of the films consist of sharp streaks, symmetrically arranged. The predominant azimuthal orientation of the films was determined to be CrSi2(210) parallel to Si(110). This highly desirable heteroepitaxial relationship has been obtained previously by others; it may be described with a common unit mesh of 51 A(sup 2) and mismatch of 0.3 percent. RHEED also revealed the presence of limited film regions of a competing azimuthal orientation, CrSi2(110) parallel to Si(110). A channeling effect for MeV He(+) ions was not found for this material. Potential commercial applications of this research may be found in silicon-integrated infrared detector arrays. Optical characterizations showed that semiconducting ReSi2 is a strong absorber of infrared radiation, with the adsorption constant increasing above 2 x

  10. Synthesis and characterization of β-phase iron silicide nano-particles by chemical reduction

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Sabyasachi [Department of Electronics & Electrical Communication Engineering, Indian Institute of Technology, Kharagpur 721302 (India); Gogurla, Narendar [Department of Physics, Indian Institute of Technology, Kharagpur 721302 (India); Banerji, Pallab [Materials Science Centre, Indian Institute of Technology, Kharagpur 721302 (India); Guha, Prasanta K. [Department of Electronics & Electrical Communication Engineering, Indian Institute of Technology, Kharagpur 721302 (India); Pramanik, Panchanan, E-mail: pramanik1946@gmail.com [Department of Basic Science, MCKV Institute of Engineering, Howrah, Liluah 711204 (India)

    2015-10-15

    Graphical abstract: - Highlights: • β-FeSi{sub 2} nano-particle was synthesized by reducing with Mg and by diluting with MgO. • XRD profile shows the iron di-silicide phase to be semiconducting β-FeSi{sub 2}. • HRTEM and FESEM images indicate the β-FeSi{sub 2}average particle size to be 60–70 nm. • Absorption, reflectance and PL spectroscopy show band gap to be direct 0.87 eV. • Nano-β-FeSi{sub 2}is p-type with hole density of 4.38 × 10{sup 18} cm{sup −3} and mobility 8.9 cm{sup 2}/V s. - Abstract: Nano-particles of β-FeSi{sub 2} have been synthesized by chemical reduction of a glassy phase of [Fe{sub 2}O{sub 3}, 4SiO{sub 2}] by Mg-metal where MgO is used as diluent to prevent the agglomeration of nano crystallites into micro-particles and also act as a negative catalyst for the formation of other phases. The sample is characterized by XRD, FESEM, HRTEM, EDX, ultra-violet-visible-infrared and PL spectroscopy and electronic properties have been investigated by Hall measurement. XRD profile shows that the synthesized powder consists of purely β-FeSi{sub 2} semiconducting phase. The average crystallite size of β-FeSi{sub 2} is determined to be around 65.4 nm from XRD peaks as well as from FESEM also. The optical absorption and PL spectroscopy shows that synthesized β-FeSi{sub 2} phase is a direct band gap semiconductor with a value of 0.87 eV. Hall measurements show that β-FeSi{sub 2} nano-particles is p-type with hole concentration of 4.38 × 10{sup 18} cm{sup −3} and average hole mobility of 8.9 cm{sup 2}/V s at 300 K.

  11. STABILITY AND ABSORPTION OF CHROMIUM AND ABSORPTION OF CHROMIUM HISTIDINE BY HUMANS

    Science.gov (United States)

    Increased intake of chromium has been shown to lead to improvements in glucose, insulin, lipids, and related variables in studies involving humans, experimental and farm animals. However, the results are often variable depending not only upon the selection of subjects, but also dietary conditions a...

  12. Chromium and Polyphenols From Cinnamon Improve Insulin Sensitivity

    Science.gov (United States)

    Naturally occurring compounds that have been shown to improve insulin sensitivity include chromium and polyphenols found in cinnamon. These compounds also have similar effects on insulin signaling and glucose control. The signs of chromium deficiency are similar to those for the metabolic syndrome ...

  13. IRIS Toxicological Review of Hexavalent Chromium (2010 External Review Draft)

    Science.gov (United States)

    [UPDATE] New Schedule for IRIS Hexavalent Chromium Assessment In Feb 2012, EPA developed a new schedule for completing the IRIS hexavalent chromium assessment. Based on the recommendations of the external peer review panel, which met in May 2011 to review the dra...

  14. Composition and structure of plasma sprayed chromium steel powders

    Czech Academy of Sciences Publication Activity Database

    Schneeweiss, O.; Voleník, Karel; Kolman, Blahoslav Jan

    Praha, 2005, s. 105-111. ISBN 1899072 18 7. [EURO Powder Metallurgy Congress & Exhibition. Prague (CZ), 02.10.2005-05.10.2005] Institutional research plan: CEZ:AV0Z20430508 Keywords : chromium steel * plasma spraying * chromium depletion * Mössbauer spectroscopy Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  15. Safety, absorption, and antioxidant effects of chromium histidine

    Science.gov (United States)

    Supplemental chromium has been shown to be involved in the alleviation of the metabolic syndrome, glucose intolerance, polycystic ovary syndrome, depression, excess body fat, and gestational, steroid-induced, and type 2 diabetes. Chromium amino acid complexes that contained histidine displayed cons...

  16. Toxicity and adaptation of Dictyosphaerium chlorelloides to extreme chromium contamination.

    Science.gov (United States)

    Sánchez-Fortún, Sebastián; López-Rodas, Victoria; Navarro, Macarena; Marvá, Fernando; D'ors, Ana; Rouco, Mónica; Haigh-Florez, David; Costas, Eduardo

    2009-09-01

    Metals are often spilled by industries into inland water environments, with adverse consequences. Numerous papers have reported that heavy metals produce massive destruction of algae. Nevertheless, algal populations seem to become tolerant when they have had previous exposures to heavy metals. Because the mechanisms allowing heavy metal tolerance of algae are not yet known, the present study analyzed the effect of hexavalent chromium on growth and photosynthetic performance of Dictyosphaerium chlorelloides, stressing on the adaptation mechanisms to chromium contamination. Growth and photosynthetic performance of algal cells were inhibited by Cr(VI) at 10 mg/L, and the 72-h median inhibition concentration was established as 1.64 and 1.54 mg/L, respectively. However, after further incubation for a three month period in an environment with 25 mg/L of chromium, some rare, chromium-resistant cells occasionally were found. A Luria-Delbrück fluctuation analysis was performed to distinguish between resistant algae arising from rare, spontaneous mutations and resistant algae arising from physiological adaptation and other adaptive mechanisms. Resistant cells arose only by spontaneous mutations before the addition of chromium, with a rate of 1.77 x 10(-6) mutants per cell division. From a practical point of view, the use of both chromium-sensitive and chromium-resistant genotypes could make possible a specific algal biosensor for chromium. PMID:19323601

  17. Residual Chromium in Leather by Instrumental Neutron Activation Analysis

    Directory of Open Access Journals (Sweden)

    S. Okoh

    2012-01-01

    Full Text Available Problem statement: Most tanning processes employ the use of chromium sulphate. For chromium tanned leather, finished products may contain high amount of residual chromium. This may pose some health hazards, since chromium is known to be toxic at elevated concentration. This justifies the need for the study. Approach: Various samples of leather were collected from a tannery, a leather crafts market, a leather dump site and from local tanners all in Kano, Nigeria in 2009. The samples were irradiated for 6 h in the inner site of the Nigerian Research Reactor (NIRR-1 at a flux of 5×1011 ncm-2 sec-1. Results: After evaluating the spectrum, the mean results for chromium in the samples were determined as 2.33±0.3, 2.23±0.3 and 2.93±0.4% for samples from the tannery, leather crafts market and leather dump sites respectively. Chromium concentration in samples collected from local tanners who use tannins from Acacia nilotica as tanning agent was below the detection limit of Instrumental Neutron Activation Analysis (INAA technique used in the study. Conclusion: Although, the concentrations of chromium in the analysed samples were not much higher than what were obtained in literature, they may be enough to sensitize the population that is allergic to chromium.

  18. AMORPHOUS ALLOY SURFACE COATINGS FOR HARD CHROMIUM REPLACEMENT - PHASE I

    Science.gov (United States)

    Hard chromium coatings (0.25 to10 mil thick) are used extensively for imparting wear and erosion resistance to components in both industrial and military applications. The most common means of depositing hard chromium has been through the use of chromic acid baths containing ...

  19. ADVANCES IN HEXAVALENT CHROMIUM REMOVAL AT HANFORD

    Energy Technology Data Exchange (ETDEWEB)

    NESHEM DO; RIDDELLE J

    2012-01-30

    At the Hanford Site, chromium was used as a corrosion inhibitor in the reactor cooling water and was introduced into the groundwater as a result of planned and unplanned discharges from reactors during plutonium production since 1944. Beginning in 1995, groundwater treatment methods were evaluated leading to the use of pump and treat facilities with ion exchange using Dowex 21 K, a regenerable strong base anion exchange resin. This required regeneration of the resin, which is currently performed offsite. Resin was installed in a 4 vessel train, with resin removal required from the lead vessel approximately once a month. In 2007, there were 8 trains (32 vessels) in operation. In 2008, DOE recognized that regulatory agreements would require significant expansion in the groundwater chromium treatment capacity. Previous experience from one of the DOE project managers led to identification of a possible alternative resin, and the contractor was requested to evaluate alternative resins for both cost and programmatic risk reductions. Testing was performed onsite in 2009 and 2010, using a variety of potential resins in two separate facilities with groundwater from specific remediation sites to demonstrate resin performance in the specific groundwater chemistry at each site. The testing demonstrated that a weak base anion single-use resin, ResinTech SIR-700, was effective at removing chromium, had a significantly higher capacity, could be disposed of efficiently on site, and would eliminate the complexities and programmatic risks from sampling, packaging, transportation and return of resin for regeneration. This resin was installed in Hanford's newest groundwater treatment facility, called 100-DX, which began operations in November, 2010, and used in a sister facility, 100-HX, which started up in September of 2011. This increased chromium treatment capacity to 25 trains (100 vessels). The resin is also being tested in existing facilities that utilize Dowex 21 K for

  20. Chromium-Makes stainless steel stainless

    Science.gov (United States)

    Kropschot, S.J.; Doebrich, Jeff

    2010-01-01

    Chromium, a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point, is a silvery white, hard, and bright metal plating on steel and other material. Commonly known as chrome, it is one of the most important and indispensable industrial metals because of its hardness and resistance to corrosion. But it is used for more than the production of stainless steel and nonferrous alloys; it is also used to create pigments and chemicals used to process leather.

  1. The electronic structure of antiferromagnetic chromium

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt

    1981-01-01

    The author has used the local spin density formalism to perform self-consistent calculations of the electronic structure of chromium in the non-magnetic and commensurate antiferromagnetic phases, as a function of the lattice parameter. A change of a few per cent in the atomic radius brings...... the calculated ground state properties into agreement with experiment. The magnetisation is studied as function of volume in several models, and it is shown that a Stoner picture provides an extremely accurate description of the full calculation provided the sp-d hybridisation is taken into account. It is found...

  2. Effects of UV light and chromium ions on wood flavonoids

    International Nuclear Information System (INIS)

    The individual and simultaneous effect of UV light and chromium ions was investigated by spectrophotometric methods on inert surfaces impregnated with quercetin or robinetin. The UV-VIS spectra of the silica gel plates impregnated with these flavonoids were modified characteristically after irradiating ultraviolet light. Even a half an hour of irradiation has caused irreversible changes in the molecule structure. A certain chemical - presumably complexation - was concluded from the change of spectral bands assigned to flavonoids when impregnated with chromic ions. Hexavalent chromium caused more complex changes in the absorption spectra. The differences in the spectra could indicate either the oxidation and decomposition of flavonoids, or some kind of coordination process and the reduction of hexavalent chromium. The simultaneous application of UV light and chromium ions caused more pronounced effects. The complexation process between chromium(III) and flavonoid was completed

  3. CHROMIUM BIOACCUMULATION FROM COMPOSTS AND VERMICOMPOSTS BASED ON TANNERY SLUDGES

    Directory of Open Access Journals (Sweden)

    Krzysztof GONDEK

    2008-07-01

    Full Text Available Storage of waste substances is not indifferent to ecological equilibrium in the environment therefore should not be the ultimate way to limit waste arduousness. Therefore, the conducted investigations aimed to determine the effect of tannery composts and vermicomposts loaded with chromium on this element bioaccumulation in earthworm bodies and biomass of selected plants. Chromium in composts and vermicomposts based on tannery sludges occurred in small quantities and easily soluble compounds. Chromium concentrations in redworm biomass points to this metal accumulation in Eisenia fetida body tissues. This element content in redworm biomass was signifi cantly positively correlated with its content in composts. Chromium content in plants was diversifi ed and on treatments was generally smaller than on mineral treatment or farmyard manure. Chromium absorbed by plants was stored mainly in the root systems, and over the norm content of this element found in vermicomposts did not cause its excessive accumulation in plant biomass.

  4. Biosorption potency of Aspergillus niger for removal of chromium (VI).

    Science.gov (United States)

    Srivastava, Shaili; Thakur, Indu Shekhar

    2006-09-01

    Aspergillus niger isolated from soil and effluent of leather tanning mills had higher activity to remove chromium. The potency of Aspergillus niger was evaluated in shake flask culture by absorption of chromium at pH 6 and temperature 30 degrees C. The results of the study indicated removal of more than 75% chromium by Aspergillus niger determined by diphenylcarbazide colorimetric assay and atomic absorption spectrophotometry after 7 days. Study of microbial Cr(VI) reduction and identification of reduction intermediates has been hindered by the lack of analytical techniques that can identify the oxidation state with subcellular spatial resolution. Therefore, removal of chromium was further substantiated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX), which indicated an accumulation of chromium in the fungal mycelium. PMID:16874547

  5. Specific features of the electrocrystallization of chromium together with molybdenum

    International Nuclear Information System (INIS)

    A study was made on molybdenum effect on surface structure and some physicomechanical properties of electrolytic chromium during Cr-Mo electrodeposition from CrO3 solutions with additions of SO42- and SiFe62- anions. Cr-Mo deposition was conducted at 55 deg C and 0.5 A/cm2 current density which corresponds to conditions of hard chromizing. It is shown that the change hardness, hydridation and internal stresses of chromium coatings during their alloying with molybdenum is conditioned by structure change. Mo introduction into chromium is not manifested clearly in these characteristics. The change of chromium structure during deposition with molybdenum is probably related both with change of anion relation in cathode film (decrease of catalytic anion content in it) and peculiarities of chromium electrocrystallization. This requires special study with application of methods for investigation into fine and surface structure

  6. Selenium protection from cadmium and chromium poisoning

    International Nuclear Information System (INIS)

    The interaction of selenium with cadmium and chromium was studied in 168 chicken-broilers (DWCxWR) divided into four equal groups. Eight-week old control animals received an intravenous dose of /sup 115m/Cd Chloride 370 KBq/Kg (Group I), or 51Cr Chloride 370 KBq/Kg (Group II). The kinetics of these isotopes were studied by scintillation spectrometry (NaI/TI) carried out for whole blood, plasma, plasma proteins, urine, feces and homogenates of all organs at various time intervals. Animals in Groups III and IV received eight subcutaneous doses of sodium selenate (5ug) at 8-week intervals prior to /sup 115m/Cd or 51Cr. The kinetics of these elements were studied as in the previous two groups. It was found that selenium affected those kinetics in two ways: (a) by increasing the excretion of Cd by 11 +/- 3% (P < 0.001) and that of Cr by 7 +/- 1% (P < 0.001); and (b) by favoring redistribution of those elements, with significant (P < 0.001) reductions in liver, endocrine glands and kidney and increases (P < 0.01) in bone. The study suggests that selenium protects the animals' vital organs from environmental pollutants, such as cadmium and chromium

  7. The hydrogen anode in chromium electrowinning

    International Nuclear Information System (INIS)

    The use of a hydrogen anode for electrowinning of chromium from an ammonium chromium sulfate electrolyte (chrome alum process) was investigated in a laboratory-scale cell equipped with a diaphragm. The composition of the solution and the temperature followed industrial practice. Current density, pH, and anolyte flow rate through the diaphragm were varied and optimized for the cell. For a cathodic current density of 915 A/m2 at 50oC, the optimum initial pH was 2.37. The hydrogen anode was made of a platinized Toray carbon paper (0.35 mg Pt per cm2) supplied by E-TEK. The hydrogen pressure was maintained at 2 cm H20 above ambient atmosphere. The potential of the hydrogen anode was about 1 V lower than that of a Pb-Ag anode (1%Ag) in a similar cell. As expected, no Cr+6 was generated in the anolyte. The cathodic current efficiency was slightly lower with the hydrogen anode than with the Pb-Ag anode. (author)

  8. Biliary excretion of chromium in the rat

    International Nuclear Information System (INIS)

    The relative amount of chromium excreted in rat bile after injection of Cr-III is much less than after injection of Cr-VI, about 0.1% and from 6-8% during 5 hours respectively, for corresponding dose levels. The liver to bile ratio was 50-100 for Cr-III injection for Cr-VI the ratio was 2-3. With doses up to 18 μmol Cr/kg, only Cr-III was found in bile even after injection of CR-VI.Glutathione depletion of the liver with cyclohexene oxide decreased chromium excretion in bile. Such treatment also decresed the reduction of Cr-VI to Cr-III in the liver cell as only Cr-VI was found in bile. A different distribution of Cr-III in the liver dependent on whether derived from Cr-VI or taken up by the liver as such must be assumed. Taking into account the usual low penetration of biological membranes by Cr-III, a possible active transport mechanism or a specific diffusable Cr-III compound must be postulated. (author)

  9. Theoretical investigation of superconductivity in ternary silicide NaAlSi with layered diamond-like structure

    Science.gov (United States)

    Tütüncü, H. M.; Karaca, Ertuǧrul; Srivastava, G. P.

    2016-04-01

    We have investigated the electronic structure, phonon modes and electron-phonon coupling to understand superconductivity in the ternary silicide NaAlSi with a layered diamond-like structure. Our electronic results, using the density functional theory within a generalized gradient approximation, indicate that the density of states at the Fermi level is mainly governed by Si p states. The largest contributions to the electron-phonon coupling parameter involve Si-related vibrations both in the x-y plane as well as along the z-axis in the x-z plane. Our results indicate that this material is an s-p electron superconductor with a medium level electron-phonon coupling parameter of 0.68. Using the Allen-Dynes modification of the McMillan formula we obtain the superconducting critical temperature of 6.98 K, in excellent agreement with experimentally determined value of 7 K.

  10. Analysis of optical and magnetooptical spectra of Fe5Si3 and Fe3Si magnetic silicides using spectral magnetoellipsometry

    International Nuclear Information System (INIS)

    The optical, magnetooptical, and magnetic properties of polycrystalline (Fe5Si3/SiO2/Si(100)) and epitaxial Fe3Si/Si(111) films are investigated by spectral magnetoellipsometry. The dispersion of the complex refractive index of Fe5Si3 is measured using multiangle spectral ellipsometry in the range of 250–1000 nm. The dispersion of complex Voigt magnetooptical parameters Q is determined for Fe5Si3 and Fe3Si in the range of 1.6–4.9 eV. The spectral dependence of magnetic circular dichroism for both silicides has revealed a series of resonance peaks. The energies of the detected peaks correspond to interband electron transitions for spin-polarized densities of electron states (DOS) calculated from first principles for bulk Fe5Si3 and Fe3Si crystals

  11. Workshop on effects of chromium coating on Nb3Sn superconductor strand: Proceedings

    International Nuclear Information System (INIS)

    This report discusses the following topics: Chromium coating on superconductor strand -- an overview; technology of chromium plating; comparison of wires plated by different platers; search for chromium in copper; strand manufactures' presentations; chromium plating at the Lawrence Livermore National Laboratory; a first look at a chromium plating process development project tailored for T.P.X. and I.T.E.R. strand; and influence of chromium diffusion and related phenomena on the reference ratios of bare and chromium plated Nb3Sn strand

  12. Stabilization of chromium salt in ordinary portland cement

    Indian Academy of Sciences (India)

    Damir Barbir; Pero Dabić; Petar Krolo

    2012-12-01

    Ordinary Portland cement (OPC) samples containing the chromium salt have been investigated using differential microcalorimetry, conductometry and Fourier transform infrared spectroscopic analysis. The effect of chromium on OPC hydration was evaluated by continuous observing of early hydration. The microcalorimetrical results show that with increasing the share of chromium salt, heat maximums assume lower values and the occurrence of the maximum registered in the earlier hydration times. Conductometrical measurements show that with increasing addition of chromium salt, curve did not show any specific shape, immediate drop in specific conductivity is noticed and the maximum is reached earlier. This coincides with microcalorimetrical results. It can be concluded that the addition of chromium does not affect the mechanism of the hydration process, but it does affect the kinetic parameters and dynamics of the cement hydration process. It was found that chromium salt addition to the cement–water system is acceptable up to 2 wt.%. According to standard EN 196-3 for OPC, the beginning of binding time should occur after 60 minutes. Increased amount of chromium over 2 wt.% significantly accelerate the beginning of binding time and for the system it is not acceptable.

  13. Chromium speciation in rainwater: temporal variability and atmospheric deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kieber, R.J.; Willey, J.D.; Zvalaren, S.D. [University of North Carolina at Wilmington, Wilmington, NC (United States). Dept. of Chemistry

    2002-12-15

    Chromium is released into the atmosphere by a variety of anthropogenic activities which include steel manufacturing, leather tanning, wood presentation and fossil fuel combustion. The concentrations of the various chromium species were determined in 89 rainwater samples collected in Wilmington, NC from October 1, 1999 to December 31, 2001. Volume weighted annual average concentrations of Cr{sub total}, particulate Cr, Cr(III)(aq), and Cr(VI)(aq) were 4.6, 2.2, 0.8 and 1.2 nM, respectively. There was distinct seasonal and diurnal variability in the concentrations of the various chromium species. Chromium emissions to the global atmosphere by both natural and anthropogenic sources are estimated to be 2.2 x 10{sup 9} mol/yr. Using rainwater concentration data along with other published rainwater Cr concentrations and an estimate for total global annual rain, the total global flux of chromium removed from the atmosphere via wet deposition is 2.1 x 10{sup 9} mol/yr. This represents complete removal of Cr and indicates that essentially all chromium released into the global atmosphere is removed via rain. About half this chromium is dissolved with roughly equal concentrations of toxic Cr(VI) and relatively harmless Cr(III) species. 48 refs., 4 figs., 3 tabs.

  14. Bioavailability of a potato chromium complex to the laboratory rat

    International Nuclear Information System (INIS)

    Research objectives were to study the effect of food source, preparation method and chemical form on bioavailability of chromium. Chromium concentration in potatoes was determined and tubers labeled either intrinsically or extrinsically with radioactive chromate. A labeled chromium complexes was isolated from preparations of raw, baked or fried potatoes and chromatographed on gel permeation media. Availability of the potato chromium complex to the rat was examined in three feeding studies. Animals were dosed with radioactive extrinsically or intrinsically labeled potato extract or with chromate. A labeled chromium complex was isolated from gastrointestinal contents of rats and chromatographed. Potato pulp and peel contained 1.63 and 2.70 μg Cr/g tissue respectively. True and apparent absorption from extrinsically labeled feedings were 33.4 +/- 4.7 and 29.8 +/- 11.2% respectively, and no differences existed between absorption from raw and cooked potatoes. Absorption from the extrinsic labeled potatoes differed significantly from absorption of inorganic chromatium. Apparent absorption of raw (11.1 +/- 7.9%) and cooked (-0.7 +/- 2.8%) intrinsically labeled feedings differed significantly. Absorption of inorganic chromium was 17.8% (true) and 11.5% (apparent). Examination of the chromium complex isolated from gastrointestinal tract contents showed enlargement of the complex in the stomach after consumption

  15. Chromium-induced membrane damage: protective role of ascorbic acid

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Importance of chromium as environmental toxicant is largely due to impact on the body to produce cellular toxicity. The impact of chromium and their supplementation with ascorbic acid was studied on plasma membrane of liver and kidney in male Wistar rats (80 - 100gbody weight). It has been observed that the intoxication with chromium ( i. p. ) at the dose of 0.8 mg/100g body weight per day for a period of 28 days causes significant increase in the level of cholesterol and decrease in the level of phospbolipid of both liver and kidney. The alkaline pbosphatase, total ATPase and Na + -K + -ATPase activities were significantly decreased in both liver and kidney after chromium treatment,except total ATPase activity of kidney. It is suggested that chromium exposure at the present dose and duration induce for the alterations of structure and function of both liver and kidney plasma membrane. Ascorbic acid ( i.p. at the dose of 0.5 mg,/100g body weight per day for period of 28 days) supplementation can reduce these structural changes in the plasma membrane of liver and kidney. But the functional changes can not be completely replenished by the ascorbic acid supplementation in response to chromium exposure. So it is also suggested that ascorbic acid (nutritional antioxidant) is useful free radical scavenger to restrain the chromium-induced membrane damage.

  16. Fertilizers and Mixed Crop Cultivation of Chromium Tolerant and Sensitive Plants under Chromium Toxicity

    OpenAIRE

    B. Dheeba; Sampathkumar, P; Kannan, K.

    2015-01-01

    Zea mays (maize) and Vigna radiata (green gram) are found to be the chromium (Cr) tolerant and sensitive plants, respectively. In the present paper, we investigate the reduction of the toxicity of Cr in the sensitive plants by the mixed crop cultivation in the field using various amendments. Further, the potassium dichromate was used as the source of hexavalent Cr. The results indicated that Cr adversely affects both the growth and yield of plants. The soil properties vary with Cr and differe...

  17. Microbial Diversity of Chromium-Contaminated Soils and Characterization of Six Chromium-Removing Bacteria

    Science.gov (United States)

    He, Zhiguo; Hu, Yuting; Yin, Zhen; Hu, Yuehua; Zhong, Hui

    2016-06-01

    Three soil samples obtained from different sites adjacent to a chromium slag heap in a steel alloy factory were taken to examine the effect of chromium contamination on soil bacterial diversity as determined by construction of 16S rDNA clone libraries and sequencing of selected clones based on restriction fragment length polymorphism (RFLP) analysis. Results revealed that Betaproteobacteria, Gammaproteobacteria, Firmicutes, and Alphaproteobacteria occurred in all three soil samples, although the three samples differed in their total diversity. Sample 1 had the highest microbial diversity covering 12 different classes, while Sample 3 had the lowest microbial diversity. Strains of six different species were successfully isolated, one of which was identified as Zobellella denitrificans. To our knowledge, this is the first report of a strain belonging to the genus Zobellella able to resist and reduce chromium. Among all isolates studied, Bacillus odysseyi YH2 exhibited the highest Cr(VI)-reducing capability, with a total removal of 23.5 % of an initial Cr(VI) concentration of 350 mg L-1.

  18. Chromium removal from tannery wastewater by using of flying ash

    International Nuclear Information System (INIS)

    A simple and economic method to chromium removal from tannery wastewater by means of flying ash is presented. The chromium removal operation is a discontinuous process that involve the mass of flying ash, time of contact and temperature or ph as variables, their which are optimized through Box-Wilson type experimental design. The results were successful: From an initial fluid whit chromium concentration of 1850m ppm, final concentrations of 0.008 ppm and 0.5 ppm of Cr+3 and Cr+6 respectively were achieved. These post-treatment concentrations are into the approved range definite by Government's Laws to this waste type

  19. A REVIEW OF BIOSORPTION OF CHROMIUM IONS BY MICROORGANISMS

    Directory of Open Access Journals (Sweden)

    Inga Zinicovscaia

    2012-12-01

    Full Text Available Due to its widespread industrial use, chromium has become a serious pollutant in diverse environmental settings. The main source of chromium pollution including the Republic o Moldova is industry. It is a great need to develop new eco-friendly methods of chromium removal. Biosorption of heavy metals is a most promising technology involved in the removal of toxic metals from industrial waste streams and natural waters. This article is an extended abstract of a communication presented at the Conference Ecological Chemistry 2012

  20. Thermal incorporation behavior during the reduction and stabilization of chromium wastes

    OpenAIRE

    Yang, Jun; 楊駿

    2015-01-01

    The possibility of employing periclase to stabilize chromium in chromium wastes into spinel-based ceramics through thermal method was investigated by heating mixture of simulated chromium waste and magnesium oxide. Different types of magnesium oxide precursors were introduced to incorporate chromium oxide into magnesiochromite (MgCr2O4) ranging from 550 ºC to 1350 ºC. Magnesium oxide precursors of both types can effectively incorporate chromium oxide but via different mechanisms. Three main f...

  1. Effects of Supplemental Dietary Chromium on Yield and Nutrient Digestibility of Laying Hens Under Low Temperature

    OpenAIRE

    ŞAHİN, Kazım; ERTAŞ, O. Nihat; GÜLER, Talat; ÇİFTÇİ, Mehmet

    2001-01-01

    This study was conducted to determine the effects of chromium picolinate (CrPi) added into diet containing 710.3 ppb chromium on yield and nutrient digestibility of laying hens at low temperature. Forty-six-week-old laying hens were randomly assigned to four groups of 30 hens per group. Treatment groups were fed different supplemental dietary chromium levels. Thus, hens were fed diets with no supplemental chromium (Control Group), 100 ppb of supplemental chromium (100 Group), 200 ppb of s...

  2. Evaluation of the comprehensiveness and reliability of the chromium composition of foods in the literature ☆

    OpenAIRE

    Thor, Mayly Y.; Harnack, Lisa; King, Denise; Jasthi, Bhaskarani; Pettit, Janet

    2011-01-01

    In the early 1960s, trivalent chromium Cr3+ became recognized as an essential trace element due to its potential metabolic and cardiovascular benefits. No comprehensive chromium database currently exists; thus a thorough review of the literature was conducted to examine the availability and reliability of chromium data for foods. A number of key issues were identified that challenge the feasibility of adding chromium to a food and nutrient database. Foremost, dietary chromium data reported in...

  3. Chromium(III) complexation to natural organic matter : Mechanisms and modeling

    OpenAIRE

    Gustafsson, Jon Petter; Persson, I.; Oromieh, A. G.; Van Schaik, J. W. J.; Sjöstedt, Carin; Kleja, D. B.

    2014-01-01

    Chromium is a common soil contaminant, and it often exists as chromium(III). However, limited information exists on the coordination chemistry and stability of chromium(III) complexes with natural organic matter (NOM). Here, the complexation of chromium(III) to mor layer material and to Suwannee River Fulvic Acid (SRFA) was investigated using EXAFS spectroscopy and batch experiments. The EXAFS results showed a predominance of monomeric chromium(III)-NOM complexes at low pH (<5), in which o...

  4. Abatement of Chromium Emissions from Steelmaking Slags - Cr Stabilization by Phase Separation

    OpenAIRE

    Albertsson, Galina

    2013-01-01

    Chromium is an important alloying element in stainless steel but also environmentally harmful element. A number of mineralogical phases present in the slag matrix can contain chromium and lead to chromium leaching. Chromium in slag if not stabilized, could oxidize to the cancerogenic hexavalent state, and leach out if exposed to acidic and oxygen rich environment. Other environmental concerns are slag dusting and chromium escape to the atmosphere. Despite the fact that there is a certain risk...

  5. The oxidation and reduction of chromium of stainless steels in an eletric arc furnace

    OpenAIRE

    Arh, B.; F. Tehovnik

    2011-01-01

    The oxidation of chromium during the elaboration of stainless steels occurs with oxygen in solution blown inthe melt and with oxides in the slag. A higher content of silicon in the furnace charge decreases the extent of oxidation of chromium, however, the efficient reduction of chromium from the slag is of essential importance for a minimal loss of chromium. In this survey, the theory of the oxidation of chromium, its reduction from the slag and the conditions for the formation of foaming sla...

  6. Chromium accumulation, microorganism population and enzyme activities in soils around chromium-containing slag heap of steel alloy factory

    Institute of Scientific and Technical Information of China (English)

    HUANG Shun-hong; PENG Bing; YANG Zhi-hui; CHAI Li-yuan; ZHOU Li-cheng

    2009-01-01

    The environmental risk of chromium pollution is pronounced in soils adjacent to chromate industry. It is important to investigate the functioning of soil microorganisms in ecosystems exposed to long-term contamination by chromium. 45 soil samples obtained from different places of the slag heap in a steel alloy factory were analyzed for chromium contamination level and its effect on soil microorganisms and enzyme activities. The results show that the average concentrations of total Cr in the soil under the slag heap, adjacent to the slag heap and outside the factory exceed the threshold of Secondary Environmental Quality Standard for Soil in China by 354%, 540% and 184%, respectively, and are 15, 21 and 9 times higher than the local background value, respectively. Elevated chromium loadings result in changes in the activity of the soil microbe, as indicated by the negative correlations between soil microbial population and chromium contents. Dehydrogenase activity is greatly depressed by chromium in the soil. The results imply that dehydrogenase activity can be used as an indicator for the chromium pollution level in the area of the steel alloy factory.

  7. Evaluation of chromium in red blood cells as an indicator of exposure to hexavalent chromium: An in vitro study.

    Science.gov (United States)

    Devoy, Jérôme; Géhin, Antoine; Müller, Samuel; Melczer, Mathieu; Remy, Aurélie; Antoine, Guillaume; Sponne, Isabelle

    2016-07-25

    Chromium(VI) compounds are classified as carcinogenic to humans. Whereas chromium measurements in urine and whole blood (i.e., including plasma) are indicative of recent exposure, chromium in red blood cells (RBC) is attributable specifically to Cr(VI) exposure. Before recommending Cr in RBC as a biological indicator of Cr(VI) exposure, in-vitro studies must be undertaken to assess its reliability. The present study examines the relationship between the chromium added to a blood sample and that subsequently found in the RBC. After incubation of total blood with chromium, RBC were isolated, counted and their viability assessed. Direct analysis of chromium in RBC was conducted using Atomic Absorption Spectrometry. Hexavalent, but not trivalent Cr, was seen to accumulate in the RBC and we found a strong correlation between the Cr(VI) concentration added to a blood sample and the amount of Cr in RBC. This relationship appears to be independent of the chemical properties of the human blood samples (e.g., different blood donors or different reducing capacities). Even though in-vivo studies are still needed to integrate our understanding of Cr(VI) toxicokinetics, our findings reinforce the idea that a single determination of the chromium concentration in RBC would enable biomonitoring of critical cases of Cr(VI) exposure. PMID:27178267

  8. The fate of chromium during tropical weathering

    DEFF Research Database (Denmark)

    Berger, Alfons; Frei, Robert

    2014-01-01

    We performed a mineral, geochemical and Cr–Sr–Pb isotope study on a laterite profile developed on ca. 540 Ma old tonalitic bedrock in Madagascar with special emphasis on the behavior of chromium during tropical weathering. The observed strong depletions of Ca, Si, and P, and enrichment of Fe and Al...... weathering profile. The negatively fractionated δ53Cr values measured in the weathering profile relative to the unaltered tonalitic bedrock characterized by a high temperature magmatic inventory Cr isotope signature are consistent with loss of a positively fractionated Cr(VI) pool formed during weathering...... highly oxidative conditions, which in well drained sulfide-bearing parent bedrocks potentially lead to both, acid dissolution of sulfide-hosted Cr and redox-promoted mobilization of Cr(VI) from silicates during later stages of weathering under basic pH conditions....

  9. Neutron capture by the chromium isotopes

    International Nuclear Information System (INIS)

    Capture cross sections of the chromium isotopes have been measured at neutron energies up to 350 keV using the capture cross section facility at the 40 m station of the Oak Ridge Electron Linear Accelerator. Parameters have been derived for 180 resonances. A moderate correlation [rho(gamma-n-0,gamma-gamma) approximately 0.45] is observed between reduced neutron widths and radiative widths for s-wave resonances. Calculations of valence widths show that valence capture can only account for the correlated component of the observed radiative widths. An additional mechanism such as a 2p-1h doorway state must therefore be occurring to explain the uncorrelated component. (author)

  10. 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.

  11. Mechanical properties of C40-based ternary Mo(Si,Al)2 and quaternary (Mo,Zr)(Si,Al)2 silicides

    International Nuclear Information System (INIS)

    Refractory silicides with transition metals are of interest as structural materials operating at very high temperatures to improve energy efficiency. MoSi2 is particularly attractive because of its high melting point (2,030 C), relatively low density (6.24 g/cm3), superior oxidation resistance and high thermal conductivity. Nevertheless, MoSi2 still has several problems which must be overcome before structural application. In this paper an attempt to improve the ductility, toughness and high-temperature strength of C40-based MoSi2 silicides was made by controlling additional Al and Zr contents in order to change the ductility, species of the constituent phase and the volume fraction of each phase

  12. 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)

    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)

  13. Chromium and Polyphenols from Cinnamon and Insulin Sensitivity

    Science.gov (United States)

    Factors that improve insulin sensitivity usually lead to improvements in risk factors associated with the metabolic syndrome, diabetes, and cardiovascular diseases. Naturally occurring bioactive compounds that have been shown to improve insulin sensitivity include chromium and polyphenols found in ...

  14. Contingency plans for chromium utilization. Publication NMAB-335

    International Nuclear Information System (INIS)

    The United States depends entirely on foreign sources for the critical material, chromium, making it very vulnerable to supply disruptions. This vulnerability results because chromium is essential for the fabrication of corrosion-resisting steels and high-temperature, oxidation-resisting alloys in applications that are vital to the nation's technological well-being; because no substitutes are known for these materials in those applications; and because the known, substantial deposits of chromite ore are only in a few geographical locations that could become inaccessible to the United States as a result of political actions. The effectiveness of programs such as stockpiling, conservation, and research and development for substitutes to reduce the impact of disruption of imports of chromite and ferrochromium are discussed. Alternatives for decreasing chromium consumption also are identified for chromium-containing materials in the areas of design, processing, and substitution

  15. Synthesis and characterization of novel chromium pillared clays

    International Nuclear Information System (INIS)

    New chromium pillared clays of basal spacing 2.45 nm were synthesized and characterized. The chromium oligomers used for intercalation were prepared by quick addition of base and acid to Cr(III) monomeric solutions followed by reflux. The synthesized clays exhibit increased BET surface area and higher micropore volume compared to clays with lower galleries, pillared either by smaller Cr(III) oligomers or by Cr(III) monomers. Important parameters affecting the d001 basal spacing were studied, e.g. the pH of the pillaring solution, the intercalation time, the chromium concentration and the counter-anion present in the chromium solutions. Scanning electron micrographs were acquired to demonstrate changes of the clay texture before and after pillaring. The thermal behavior of the synthesized clays was also examined

  16. Adsorption Properties of Chromium (VI by Chitosan Coated Montmorillonite

    Directory of Open Access Journals (Sweden)

    Dahe Fan

    2006-01-01

    Full Text Available The adsorption of chromium (VI by Chitosan Coated Montmorillonite (CCM from aqueous solution was studied. To evaluate the adsorption capacity, the effects of pH, initial concentration and temperature on the adsorption were investigated. The isothermal data was applied to Langmuir linear and the Freundlich linear isotherm equation and the thermodynamic parameters (ΔH, ΔG, ΔS were calculated according to the values of binding Langmuir constant, KL. Results indicated that the adsorption between CCM and chromium (VI was significantly physical, the negative ΔH constant at lower temperature confirmed that the more chromium (VI was adsorbed by chitosan coated montmorillonite at lower temperature. The kinetics of the sorption process of chromium (VI on chitosan coated montmorillonite were investigated using the pseudo-first order and pseudo-second order kinetics, results showed that the pseudo-second order equation model provided the best correlation with the experimental results.

  17. IRIS Toxicological Review of Hexavalent Chromium (Peer Review Plan)

    Science.gov (United States)

    EPA is conducting a peer review of the scientific basis supporting the human health hazard and dose-response assessment of hexavalent chromium that will appear on the Integrated Risk Information System (IRIS) database.

  18. Fabrication of high rate chromium getter sources for fusion applications

    International Nuclear Information System (INIS)

    Design and fabrication techniques are described for the manufacture of large-capacity chromium getter sources, analogous to the commercially available titanium getter source known as Ti-Ball, manufactured by Varian Associates

  19. Detecting Grain-Boundary Chromium Depletion in Inconel 600

    Science.gov (United States)

    Airey, G. P.; Vaia, A. R.; Pessall, N.; Aspden, R. G.

    1981-11-01

    Techniques to evaluate grain-boundary chromium depletion in Inconel Alloy 600 were investigated. Procedures studied were a modified Huey test, reactivation polarization, magnetic permeability measurements, and eddy current measurements. Results from these tests were correlated with susceptibility to stress-assisted intergranular cracking in polythionic acid. Thermally treated Inconel Alloy 600 steam generator tubing was the principal source of material evaluated, but experimental heats of Ni-Cr-Fe alloys with 8-18 wt.% Cr were prepared to determine the critical chromium level below which stress-assisted intergranular cracking occurs; this critical chromium content was found to be between 9.8 and 11.7 wt.%. All four techniques were considered suitable to evaluate grain-boundary chromium depletion; the modified Huey test and reactivation polarization technique showed a greater sensitivity than the magnetic permeability and eddy current measurements.

  20. The diffusion of chromium in a duplex alloy steel

    International Nuclear Information System (INIS)

    Diffusion of chromium in a duplex stainless steel containing approximately 8% ferrite has been investigated in the temperature range 600 to 10000C using the standard serial sectioning technique. The resulting concentration profiles exhibited up to four distinct regions. The two main regions are attributed to volume diffusion in the austenite and ferrite phases, the other zones being due to short circuiting paths. Volume diffusion in the austenite phase is in good agreement with chromium diffusion in Type 316 steel. The chromium diffusion coefficient in the ferrite phase of approximate composition 25 wt % Cr, 5 wt % Ni is given by: Dsub(α) = (6.0(+11,-3)) x 10-6 exp - ((212+-5)/RT) m2s-1 the activation energy being expressed in kJ.mol-1. Little evidence was found for enhanced chromium diffusion along austenite/ferrite interface boundaries. (author)

  1. Chromium plating pollution source reduction by plasma source ion implantation

    International Nuclear Information System (INIS)

    There is growing concern over the environmental toxicity and workers' health issues due to the chemical baths and rinse water used in the hard chromium plating process. In this regard the significant hardening response of chromium to nitrogen ion implantation can be environmentally beneficial from the standpoint of decreasing the thickness and the frequency of application of chromium plating. In this paper the results of a study of nitrogen ion implantation of chrome plated test flats using the non-line-of-sight Plasma Source Ion Implantation (PSII) process, are discussed. Surface characterization was performed using Scanning Electron Microscopy (SEM), Auger Electron Spectroscopy (AES), and Electron Spectroscopy for Chemical Analysis (ESCA). The surface properties were evaluated using a microhardness tester, a pin-on-disk wear tester, and a corrosion measurement system. Industrial field testing of nitrogen PSII treated chromium plated parts showed an improvement by a factor of two compared to the unimplanted case

  2. New Chromium Carbonyl Catalysts for [6+2] Cycloaddition Reactions

    OpenAIRE

    Kundig, Ernst Peter; Robvieux, Fabrice; Kondratenko, Mikhail

    2002-01-01

    The complexes, (benzene)chromiumdicarbonyl(methyl acrylate) and chromiumdicarbonylbis(cyclohexadiene), are precursors for the highly coordinatively unsaturated chromium dicarbonyl fragment 3, a catalyst for the cycloaddition of activated olefins to cycloheptatriene.

  3. The Laser Ablation as a perspective technique for the deposition of metal-silicide nanoparticles in situ embedded in PECVD of Si:H thin films

    Czech Academy of Sciences Publication Activity Database

    Stuchlíková, The-Ha; Fajgar, Radek; Koštejn, Martin; Dřínek, Vladislav; Remeš, Zdeněk; Stuchlík, Jiří

    Tokyo: The Japan Society of Applied Physics, 2015 - (Asano, T.), "011302-1"-"011302-5" ISBN 978-4-86348-491-7. [International Conference and Summer School on Advanced Silicide Technology 2014. Tokyo (JP), 19.07.2014-21.07.2014] R&D Projects: GA MŠk LH12236 Institutional support: RVO:68378271 ; RVO:67985858 Keywords : PECVD * amorphous silicon * reactive laser ablation Subject RIV: BM - Solid Matter Physics ; Magnetism

  4. Silicene versus two-dimensional ordered silicide: atomic and electronic structure of Si-(√19×√19)R23.4◦/Pt(111)

    Czech Academy of Sciences Publication Activity Database

    Švec, Martin; Hapala, Prokop; Ondráček, Martin; Merino, P.; Blanco-Rey, M.; Mutombo, Pingo; Vondráček, Martin; Polyak, Yaroslav; Cháb, Vladimír; Martín Gago, J.A.; Jelínek, Pavel

    2014-01-01

    Roč. 89, č. 20 (2014), "201412-1"-"201412-5". ISSN 1098-0121 R&D Projects: GA MŠk(CZ) LM2011029; GA ČR(CZ) GA14-02079S Grant ostatní: SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : silicene * silicide * surface alloy * STM * photoemission spectroscopy * ARUPS * DFT Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  5. 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)

  6. Biosorption of Chromium (VI) from Aqueous Solutions onto Fungal Biomass

    OpenAIRE

    Ismael Acosta R.; Xöchitl Rodríguez; Conrado Gutiérrez; Ma. de Guadalupe Moctezuma

    2004-01-01

    The biosorption of chromium (VI) on eighteen different natural biosorbents: Natural sediment, chitosan, chitin, Aspergillus flavus I-V, Aspergillus fumigatus I-ll, Helmintosporium sp, Cladosporium sp, Mucor rouxii mutant, M. rouxii IM-80, Mucor sp-I and 2, Candida albicans and Cryptococcus neoformans was studied in this work. It was found that the biomass of C. neoformans, natural sediment, Helmintosporium sp and chitosan was more efficient to remove chromium (VI) (determined spectrophotometr...

  7. Stainless Steel Leaches Nickel and Chromium into Foods During Cooking

    OpenAIRE

    Kamerud, Kristin L.; Hobbie, Kevin A.; Anderson, Kim A.

    2013-01-01

    Toxicological studies show that oral doses of nickel and chromium can cause cutaneous adverse reactions such as dermatitis. Additional dietary sources, such as leaching from stainless steel cookware during food preparation, are not well characterized. This study examined stainless steel grades, cooking time, repetitive cooking cycles, and multiple types of tomato sauces for their effects on nickel and chromium leaching. Trials included three types of stainless steels and a stainless steel sau...

  8. Genetic Predisposition for Dermal Problems in Hexavalent Chromium Exposed Population

    OpenAIRE

    Priti Sharma; Vipin Bihari; Agarwal, Sudhir K.; Goel, Sudhir K.

    2012-01-01

    We studied the effect of genetic susceptibility on hexavalent chromium induced dermal adversities. The health status of population was examined from the areas of Kanpur (India) having the elevated hexavalent chromium levels in groundwater. Blood samples were collected for DNA isolation to conduct polymorphic determination of genes, namely: NQO1 (C609T), hOGG1 (C1245G), GSTT1, and GSTM1 (deletion). Symptomatic exposed subjects (n = 38) were compared with asymptomatic exposed subjects (n = 108)...

  9. Chromium (V) compounds as cathode material in electrochemical power sources

    Science.gov (United States)

    Delnick, F.M.; Guidotti, R.A.; McCarthy, D.K.

    A cathode for use in a thermal battery, comprising a chromium (V) compound. The preferred materials for this use are Ca/sub 5/(CrO/sub 4/)/sub 3/Cl, Ca/sub 5/(CrO/sub 4/)OH, and Cr/sub 2/O/sub 5/. The chromium (V) compound can be employed as a cathode material in ambient temperature batteries when blended with a suitably conductive filler, preferably carbon black.

  10. SCIENCE AND TECHNOLOGY ACTIVITIES FOR CHROMIUM IN THE 100 AREAS

    Energy Technology Data Exchange (ETDEWEB)

    PETERSEN SW

    2009-07-02

    {sm_bullet} Primary Objective: Protect the Columbia River - Focus is control and treatment of contamination at or near the shoreline, which is influenced by bank storage {sm_bullet} Secondary Objective: Reduce hexavalent chromium to <48 parts per billion (ppb) in aquifer (drinking water standard) - Large plumes with isolated areas of high chromium concentrations (> 40,000 ppb), - Unknown source location(s); probably originating in reactor operation areas

  11. DANGER OF HEXAVALENT CHROMIUM AND STRATEGY FOR THE REMEDITATION

    OpenAIRE

    Aniruddha Roy; Ayan Das; Nirmal Paul

    2013-01-01

    Some metals as micronutrients have a major role in the life and growth process of plants and animals. However, certain forms of some metals may also act as toxic material even in relatively small quantities. Chromium is such a metal, whose concentration above a certain limit may cause a serious problem to the health of living organisms. Chromium (Cr) may occur in several chemical forms in organic and inorganic systems. In biological systems only Cr (III) and Cr (VI) are signifi...

  12. Stereology of carbide phase in modified hypereutectic chromium cast iron

    Directory of Open Access Journals (Sweden)

    J. Suchoń

    2010-04-01

    Full Text Available In paper are presented results of studies of carbide phase stereology modified hypereutectic wear resistance chromium cast iron which contains carbon about 3,5% and chromium about 25%. Three substances were applied to the modification: boron carbide (B4C, ferroniobium (FeNb and mixture of ferroniobium and rare-earth (RE. The measurements of geometrical features of carbides were conducted on microsection taken from castings wich were cooled with various velocities.

  13. Stereology of carbide phase in modified hypereutectic chromium cast iron

    OpenAIRE

    J. Suchoń; A. Studnicki; M. Przybył

    2010-01-01

    In paper are presented results of studies of carbide phase stereology modified hypereutectic wear resistance chromium cast iron which contains carbon about 3,5% and chromium about 25%. Three substances were applied to the modification: boron carbide (B4C), ferroniobium (FeNb) and mixture of ferroniobium and rare-earth (RE). The measurements of geometrical features of carbides were conducted on microsection taken from castings wich were cooled with various velocities.

  14. Chromium reduction from slag on electromelting of stainless steel

    International Nuclear Information System (INIS)

    Specific features of chromium reduction from the slag on electromelting of stainless steel type Kh18N10T according to one- or two-slag procedure were studied. It was shown that one-slag melting technology allows double decrease of chromium losses in the form of incompletely reduced oxides. This occurs due to additional chemical reactions between metal and slag on their combined pouring into the ladle. 1 ref.; 3 figs

  15. 40 CFR Appendix Xii to Part 266 - Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery...

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 26 2010-07-01 2010-07-01 false Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery Furnaces XII Appendix XII to Part 266... FACILITIES Pt. 266, App. XII Appendix XII to Part 266—Nickel or Chromium-Bearing Materials that may...

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

    Science.gov (United States)

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

    2015-12-01

    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-FeSi2 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.

  17. Interaction transfer of silicon atoms forming Co silicide for Co/√(3)×√(3)R30°-Ag/Si(111) and related magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Cheng-Hsun-Tony; Fu, Tsu-Yi; Tsay, Jyh-Shen, E-mail: jstsay@phy.ntnu.edu.tw [Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan (China)

    2015-05-07

    Combined scanning tunneling microscopy, Auger electron spectroscopy, and surface magneto-optic Kerr effect studies were employed to study the microscopic structures and magnetic properties for ultrathin Co/√(3)×√(3)R30°-Ag/Si(111). As the annealing temperature increases, the upward diffusion of Si atoms and formation of Co silicides occurs at temperature above 400 K. Below 600 K, the √(3)×√(3)R30°-Ag/Si(111) surface structure persists. We propose an interaction transferring mechanism of Si atoms across the √(3)×√(3)R30°-Ag layer. The upward transferred Si atoms react with Co atoms to form Co silicide. The step height across the edge of the island, a separation of 0.75 nm from the analysis of the 2 × 2 structure, and the calculations of the normalized Auger signal serve as strong evidences for the formation of CoSi{sub 2} at the interface. The interaction transferring mechanism for Si atoms enhances the possibility of interactions between Co and Si atoms. The smoothness of the surface is advantage for that the easy axis of magnetization for Co/√(3)×√(3)R30°-Ag/Si(111) is in the surface plane. This provides a possible way of growing flat magnetic layers on silicon substrate with controllable silicide formation and shows potential applications in spintronics devices.

  18. Evaluating trivalent chromium toxicity on wild terrestrial and wetland plants.

    Science.gov (United States)

    Lukina, A O; Boutin, C; Rowland, O; Carpenter, D J

    2016-11-01

    Elevated chromium levels in soil from mining can impact the environment, including plants. Mining of chromium is concentrated in South Africa, several Asian countries, and potentially in Northern Ontario, Canada, raising concerns since chromium toxicity to wild plants is poorly understood. In the first experiment, concentration-response tests were conducted to evaluate effects of chromium on terrestrial and wetland plants. Following established guidelines using artificial soil, seeds of 32 species were exposed to chromium (Cr(3+)) at concentrations simulating contamination (0-1000 mg kg(-1)). This study found that low levels of chromium (250 mg kg(-1)) adversely affected the germination of 22% of species (33% of all families), while higher levels (500 and 1000 mg kg(-1)) affected 69% and 94% of species, respectively, from 89% of the families. Secondly, effects on seedbanks were studied using soil collected in Northern Ontario and exposed to Cr(3+) at equivalent concentrations (0-1000 mg kg(-1)). Effects were less severe in the seedbank study with significant differences only observed at 1000 mg kg(-1). Seeds exposed to Cr(3+) during stratification were greatly affected. Seed size was a contributing factor as was possibly the seed coat barrier. This study represents an initial step in understanding Cr(3+) toxicity on wild plants and could form the basis for future risk assessments. PMID:27543852

  19. Wear resistance of chromium cast iron – research and application

    Directory of Open Access Journals (Sweden)

    A. Studnicki

    2006-04-01

    Full Text Available Purpose: A short characteristic of wear resistance chromium cast iron has been presented as well as possibilities of this material researches realization in Foundry Department have been discussed.Design/methodology/approach: Main attention was given on research process of crystallization and analysis of chromium cast iron microstructure and its resistance on erosion wears. Separate part of paper was devoted to discuss the bimetallic castings with chromium cast iron layer as well as typical applications of chromium cast iron castings in minig, proccesing, metallurgical and power industry.Findings: The new method of crystallization process research with three testers (DTA-K3 was found in the work. The method makes possible to characterize sensitivity of chromium cast iron on cooling kinetic.Research limitations/implications: DTA-K3 method can be used for research of crystallization proccess of cast materials particularly for abrasion-resisting alloy.Practical implications: Wide scope researches of chromium cast iron in Foundry Department enable extending applications its material in many industries.Originality/value: Value of the paper is the presentation of researches possibilities which undertaken in Foundry Department within the range of wear resistant materials.

  20. Experimental skin deposition of chromium on the hands following handling of samples of leather and metal

    DEFF Research Database (Denmark)

    Bregnbak, David; Thyssen, Jacob P.; Jellesen, Morten Stendahl;

    2016-01-01

    Background: Chromium is an important skin sensitizer. Exposure to it has been regulated in cement, and recently in leather. Studies on the deposition of chromium ions on the skin as a result of handling different chromium-containing materials are sparse, but could improve the risk assessment of...... contact sensitization and allergic contact dermatitis caused by chromium. Objectives: To determine whether the handling of chromium-containing samples of leather and metal results in the deposition of chromium onto the skin. Methods: Five healthy volunteers participated. For 30 min, they handled samples...... of leather and metal known to contain and release chromium. Skin deposition of chromium was assessed with the acid wipe sampling technique. Results: Acid wipe sampling of the participants' fingers showed chromium deposition on the skin in all participants who had been exposed to leather (range 0...

  1. Effect of recasting on the thickness of metal-ceramic interface of nickel-chromium and cobalt-chromium alloys

    OpenAIRE

    Mirković Nemanja; Draganjac Miroslav; Stamenković Dragoslav; Ristić Ljubiša

    2008-01-01

    Introduction/Aim. This research was done to establish recasting effects of nickel-chromium and cobalt-chromium alloys on the thickness of their metal-ceramic interface in making fixed partial dentures. Metal-ceramic interface determines their functional integrity and prevents damages on ceramics during mastication. Investigation of metal-ceramic samples is supposed to show if base metal alloys for metalceramics are successfully recycled without any risk of reduction of metal-ceramic interface...

  2. USE OF TWO DIGESTION METHODS IN THE EVALUATION OF CHROMIUM CONTENT IN CATTLE'S MEAT SUPPLEMENTED WITH CHROMIUM CHELATES

    OpenAIRE

    R. L. T. Andrade; P.S.A. Moreira; R. Arruda; F. J. Lourenço; C. Palhari, F. F. Faria, V. B. Arevalo; Faria, F. F.; V. B. Arevalo

    2015-01-01

    The present study aimed to analyze the chromium content in beef using two digestion methods. There were used samples from 24 18-month-old male cattle, and twelve of them were supplemented and twelve were not supplemented with chromium chelate. These samples were evaluated by atomic absorption spectroscopy, previously submitted to digestion method using nitric acid (65%) with hydrogen peroxide (35%) and to digestion method, using solution of nitric perchloric acid in the proportion 3:1. Immedi...

  3. Activation of bentonite to remove the chromium from waste water produced by panning industry, and studying the chromium recovery efficiency

    International Nuclear Information System (INIS)

    The fast development of tanning industry led to an increase in environmental problems resulting from discharging its wastes to the surrounding environment. Thus solving this problem became one of the most important aims that the researchers work on. The chromium content of the industrial water wastes of the tanning industry considered as the main pollutant for the environment. The Aleppo Bentonite is used in early research to remove the chromium from the industrial waste water.The current research aims to find a method to activate the Aleppo Bentonite in order to increase the effective removal of chromium from the industrial waste water which is produced by tanning industry, as well as to specify the optimal conditions for chromium recovery.This study used the Aleppo Bentonite, whose origin is Tal Ajar-Aleppo to study the activation aspects using Sulfuric Acid, Hydrochloric Acid and Nitric Acid, in addition to study the recovery aspects using the same acids and hydrogen peroxide and to specify the optimal conditions for chromium recovery through applying some experiments based on three main factors: concentration, settling time and temperature.It was observed from the applied experiments that it is possible to recover chromium from Bentonite efficiently up to (80% - 90%) by treating the Bentonite with hydrogen peroxide(33% concentration) at room temperature, or by treating it with hydrogen peroxide(8.25% concentration) at 75oC, while the settling time factor proved that full recovery of chromium is obtained during the first hour, and increasing the time factor does not affect the efficiency of chromium recovery. (author)

  4. Atomically precise self-organization of perfectly ordered gadolinium–silicide nanomeshes controlled by anisotropic electromigration-induced growth on Si(1 1 0)-16 × 2 surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Ie-Hong, E-mail: ihhong@mail.ncyu.edu.tw [Department of Electrophysics, National Chiayi University, Chiayi 60004, Taiwan (China); Institute of Optoelectronics and Solid State Electronics, National Chiayi University, Chiayi 60004, Taiwan (China); Chen, Tsung-Ming; Tsai, Yung-Feng [Institute of Optoelectronics and Solid State Electronics, National Chiayi University, Chiayi 60004, Taiwan (China)

    2015-09-15

    Highlights: • This work provides a clear understanding of the template-directed self-organization mechanism of a perfectly ordered Gd-silicide nanomesh on a double-domain Si(1 1 0)-16 × 2 and identifies that the anisotropic electromigration is the driving force governing the two-dimensional self-ordering of the atomically precise silicide nanomesh. • The ability to self-organize a variety of the perfectly ordered silicide nanomeshes on Si(1 1 0) with atomic precision represents a promising route for the optimal bottom-up fabrication of well-defined crossbar nanocircuits, which opens the possibility for their utilizations in crossbar nanoarchitectures and Si-based magnetoelectronic nanodevices. - Abstract: Detailed scanning tunneling microscopy and spectroscopy (STM and STS) studies for the effects of thermal migration and electromigration on the growth of gadolinium–silicide nanomeshes on double-domain Si(1 1 0)-16 × 2 surfaces are presented to identify the driving force for the self-organization of a perfectly ordered silicide nanomesh on Si(1 1 0). STM results clearly show that the anisotropic electromigration effect is crucial for the control of the spatial uniformity of a self-ordered silicide nanomesh on Si(1 1 0). This two-dimensional self-ordering driven by the anisotropic-electromigration-induced growth allows the sizes and positions of crossed nanowires to be precisely controlled within a variation of ±0.2 nm over a mesoscopic area, and it can be straightforwardly applied to other metals (e.g., Au and Ce) to grow a variety of highly regular silicide nanomeshes for the applications as nanoscale interconnects. Moreover, the STS results show that the anisotropic electromigration-induced growth causes the metallic horizontal nanowires to cross over the semiconducting oblique nanowires, which opens the possibility for the atomically precise bottom-up fabrication of well-defined crossbar nanoarchitectures.

  5. Atomically precise self-organization of perfectly ordered gadolinium–silicide nanomeshes controlled by anisotropic electromigration-induced growth on Si(1 1 0)-16 × 2 surfaces

    International Nuclear Information System (INIS)

    Highlights: • This work provides a clear understanding of the template-directed self-organization mechanism of a perfectly ordered Gd-silicide nanomesh on a double-domain Si(1 1 0)-16 × 2 and identifies that the anisotropic electromigration is the driving force governing the two-dimensional self-ordering of the atomically precise silicide nanomesh. • The ability to self-organize a variety of the perfectly ordered silicide nanomeshes on Si(1 1 0) with atomic precision represents a promising route for the optimal bottom-up fabrication of well-defined crossbar nanocircuits, which opens the possibility for their utilizations in crossbar nanoarchitectures and Si-based magnetoelectronic nanodevices. - Abstract: Detailed scanning tunneling microscopy and spectroscopy (STM and STS) studies for the effects of thermal migration and electromigration on the growth of gadolinium–silicide nanomeshes on double-domain Si(1 1 0)-16 × 2 surfaces are presented to identify the driving force for the self-organization of a perfectly ordered silicide nanomesh on Si(1 1 0). STM results clearly show that the anisotropic electromigration effect is crucial for the control of the spatial uniformity of a self-ordered silicide nanomesh on Si(1 1 0). This two-dimensional self-ordering driven by the anisotropic-electromigration-induced growth allows the sizes and positions of crossed nanowires to be precisely controlled within a variation of ±0.2 nm over a mesoscopic area, and it can be straightforwardly applied to other metals (e.g., Au and Ce) to grow a variety of highly regular silicide nanomeshes for the applications as nanoscale interconnects. Moreover, the STS results show that the anisotropic electromigration-induced growth causes the metallic horizontal nanowires to cross over the semiconducting oblique nanowires, which opens the possibility for the atomically precise bottom-up fabrication of well-defined crossbar nanoarchitectures

  6. Scientific Opinion on chromium(III) lactate tri-hydrate as a source of chromium added for nutritional purposes to foodstuff

    OpenAIRE

    EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS)

    2012-01-01

    The Panel on Food Additives and Nutrient Sources added to Food provides a scientific opinion on the safety and bioavailability of chromium(III) lactate tri-hydrate as a source of chromium(III) added for nutritional purposes to foodstuffs. The safety of chromium itself, in terms of the amounts that may be consumed, is outside the remit of this Panel. No new data have been provided as regards the safety and bioavailability of chromium from chromium(III) lactate tri-hydrate. The Panel c...

  7. Creep deformation of TD--nickel chromium

    International Nuclear Information System (INIS)

    The creep behavior of thoria dispersed nickel-chromium (TD-NiCr) was examined at 10930C. Major emphasis was placed on 1) the effects of the material and the test related variables (grain size, temperature, stress, strain and strain rate) on the deformation characteristics, and 2) the evaluation of single crystal TD-NiCr material produced by a directional recrystallization technique. Creep activation enthalpies were found to increase with increasing grain size reaching maximum values for the single crystal TD-NiCr. Stress exponent of the steady state creep rate was also significantly higher for the single crystal material as compared with that determined for the polycrystalline TD-NiCr. The elevated temperature deformation of TD-NiCr was analyzed in terms of two parallel-concurrent processes: 1) diffusion controlled grain boundary sliding and 2) dislocation motion. The characteristics of the dislocation motion deformation mode (as observed in the single crystal TD-NiCr) suggest that strong particle-dislocation interactions are present. The relative contributions of dislocation motion and grain boundary sliding in TD-NiCr were estimated. In creep, grain boundary sliding was found to predominate for the small, equiaxed grain structures, whereas the dislocation deformation mode became significant for only the large grain TD-NiCr and the single crystal material

  8. Low energy spin excitations in chromium metal

    Energy Technology Data Exchange (ETDEWEB)

    Pynn, R. [Los Alamos National Lab., NM (United States); Azuah, R.T. [Hahn-Meitner-Inst., Berlin (Germany); Stirling, W.G. [Univ. of Liverpool (United Kingdom). Dept. of Physics; Kulda, J. [Inst. Laue Langevin, Grenoble (France)

    1997-12-31

    Neutron scattering experiments with full polarization analysis have been performed with a single crystal of chromium to study the low-energy spin fluctuations in the transverse spin density wave (TSDW) state. A number of remarkable results have been found. Inelastic scattering observed close to the TSDW satellite positions at (1 {+-} {delta},0,0) does not behave as expected for magnon scattering. In particular, the scattering corresponds to almost equally strong magnetization fluctuations both parallel and perpendicular to the ordered moments of the TSDW phase. As the Neel temperature is approached from below, scattering at the commensurate wavevector (1,0,0) increases in intensity as a result of critical scattering at silent satellites (1,0, {+-} {delta}) being included within the spectrometer resolution function. This effect, first observed by Sternlieb et al, does not account for all of the inelastic scattering around the (1,0,0) position, however, Rather, there are further collective excitations, apparently emanating from the TSDW satellites, which correspond to magnetic fluctuations parallel to the ordered TSDW moments. These branches have a group velocity that is close to that of (1,0,0) longitudinal acoustic (LA) phonons, but assigning their origin to magneto-elastic scattering raises other unanswered questions.

  9. A Rare Terminal Dinitrogen Complex of Chromium

    Energy Technology Data Exchange (ETDEWEB)

    Mock, Michael T.; Chen, Shentan; Rousseau, Roger J.; O' Hagan, Molly J.; Dougherty, William G.; Kassel, W. S.; DuBois, Daniel L.; Bullock, R. Morris

    2011-10-12

    The reduction of dinitrogen to ammonia from N2 and H2 is currently carried out by the Haber-Bosch process, an energy intensive process that requires high pressures and high temperatures and accounts for the production of millions of tons of ammonia per year. The development of a catalytic, energy-efficient process for N2 reduction is of great interest and remains a formidable challenge. In this communication, we are reporting the preparation, characterization and computational electronic structure analysis of a rare 'Chatt-type' ((P-P)2M(N2)2, P-P = diphosphine ligand) complex of chromium, cis-[Cr(N2)2(PPh2NBn2)2] and its reactivity with CO. This complex is supported by the diphosphine ligand PPh2NBn2, containing non-coordinating pendant amine bases, to serve as proton relays. Future studies for this complex are aimed at answering fundamental questions regarding the role of proton relays in the second coordination sphere in their ability to facilitate proton movement from an external acid to metal-bound dinitrogen ligands in the challenging multi-proton/electron reduction of N2 to ammonia.

  10. A Rare Terminal Dinitrogen Complex of Chromium

    International Nuclear Information System (INIS)

    The reduction of dinitrogen to ammonia from N2 and H2 is currently carried out by the Haber-Bosch process, an energy intensive process that requires high pressures and high temperatures and accounts for the production of millions of tons of ammonia per year. The development of a catalytic, energy-efficient process for N2 reduction is of great interest and remains a formidable challenge. In this communication, we are reporting the preparation, characterization and computational electronic structure analysis of a rare 'Chatt-type' ((P-P)2M(N2)2, P-P = diphosphine ligand) complex of chromium, cis-(Cr(N2)2(PPh2NBn2)2) and its reactivity with CO. This complex is supported by the diphosphine ligand PPh2NBn2, containing non-coordinating pendant amine bases, to serve as proton relays. Future studies for this complex are aimed at answering fundamental questions regarding the role of proton relays in the second coordination sphere in their ability to facilitate proton movement from an external acid to metal-bound dinitrogen ligands in the challenging multi-proton/electron reduction of N2 to ammonia.

  11. Hexavalent Chromium Reduction and Its Distribution in the Cell and Medium by Chromium Resistant Fusarium solani

    Directory of Open Access Journals (Sweden)

    Mousumi Sen

    2013-01-01

    Full Text Available In the present work, batch biosorption of Cr(VI was studied using the fungal strain isolated from soil. The fungal strain was characterized as Fusarium solani. The total Cr distribution in the biomass (fungus and in the media obtained from the experiment conducted at 500 mg l -1 initial Cr(VI concentration and pH 5.0. The results indicated both intracellular and extracellular accumulation and enzymatic reduction of Cr(VI and this was supported by the Transmission Electron Microscopic (TEM observation at the same Cr(VI concentration and pH value. Chromium elution from Fusarium solani containing Cr was then tried out using a number of chromium eluting reagents and a maximum Cr could be eluted using 0.5N sodium hydroxide solution without destructing the biomass structure. The total Cr was recovered by pH adjustment from both biomass and media was found to be 44% of the initial Cr(VI concentration (500 mg l-1.

  12. Program for qualifying CNEA (National Atomic Energy Commission) as a manufacturer of low enriched uranium silicide fuels

    International Nuclear Information System (INIS)

    Full text: This report presents the program for the production and irradiation of a low enriched uranium (LEU) fuel element containing a dispersion of U3Si2 particles in an Al matrix, with a total uranium content of 4.8 g/cm3. The project is being carried out by the Nuclear Fuels Department of the National Atomic Energy Commission (CNEA) of Argentina and aims at qualifying our organization as manufacturer of LEU fuel elements for research reactors. The program involves the design, fissile material production, components fabrication and inspection, assembly, irradiation and postirradiation tests of two prototypes. The meat will be a dispersion of U3Si2 in an Al matrix with a total uranium content of 4.8 g/cm3. The irradiations will be performed at the RA-3. The first prototype is conceived in such a way to facilitate the posterior disassembly and PIE examinations. The second one will have the design of the future normal fuel elements of the RA-3. This project relies on the experience in CNEA in the production of standard fuel elements for the RA-3 and of uranium silicide mini plates successfully tested at the Oak Ridge Research Reactor within the RERTR program (Reduced Enrichment for Research and Test Reactors). Important investments have already been made in the installations for fuel elements production and PIE

  13. Electron microscopy studies of lutetium doped erbium silicide (Er0.9Lu0.1)5Si4

    International Nuclear Information System (INIS)

    Examination of bulk microstructures of lutetium doped erbium silicide (Er0.9Lu0.1)5Si4 (space group: Pnma) using scanning and transmission electron microscopy (SEM, TEM) reveals the existence of thin plates of a hexagonal phase (space group: P63/mcm) where the stoichiometric ratio in moles between the rare earths and Si is 5 to 3, i. e the 5:3 phase. The orientation relationship between the matrix and the plates was determined as [010]m ∼ -parallel [-1010]p. This observation adds credence to the assumption that all linear features noted in alloys of the rare-earth intermetallic family R5(SixGe1-x)4 are of the stoichiometric ratio 5:3 and possess a common orientation relationship with the parent 5:4 alloys. - Highlights: → The linear features observed in the (Er0.9Lu0.1)5Si4 sample are hexagonal 5:3 plates. → Thickness of 5:3 plates in 5:4 alloys made by tri-arc pulling is greater than made by arc-melting. → The orientation relationship between 5:3 plates and the matrix is [010]m ∼ ||[-1010]p.

  14. A comparison of the metallurgical behaviour of dispersion fuels with uranium silicides and U6Fe as dispersants

    International Nuclear Information System (INIS)

    In the past few years metallurgical studies have been carried out to develop fuel dispersions with U-densities up to 7.0 Mg U m-3. Uranium silicides have been considered to be the prime candidates as dispersants; U6Fe being a potential alternative on account of its higher U-density. The objective of this paper is to compare the metallurgical behaviour of these two material combinations with regard to the following aspects: (1) preparation of the compounds U3Si, U3Si2 and U6Fe; (2) powder metallurgical processing to miniature fuel element plates; (3) reaction behaviour under equilibrium conditions in the relevant portions of the ternary U-Si-Al and U-Fe-Al systems; (4) dimensional stability of the fuel plates after prolonged thermal treatment; (5) thermochemical behaviour of fuel plates at temperatures near the melting point of the cladding. Based on this data, the possible advantages of each fuel combination are discussed. (author)

  15. Electron transfer. 75. Reduction of carboxylato-bound chromium(V) with vanadium(IV). Intervention of chromium(IV)

    International Nuclear Information System (INIS)

    The chelated (carboxylato)chromium(V) anion bis(2-hydroxy-2-ethylbutyrato)oxochromate(V) (I), [(Lig)2Cr(O)]-, reacts with oxovanadium(IV) to form a strongly absorbing species (lambda/sub max/ = 515 nm; epsilon = 1.7 x 103 M-1) in the presence of 2-hydroxy-2-ethylbutyric acid buffers (pH 2-4). EPR data support 1:1 stoichiometry with VO2+ in deficiency, indicating the formation of a chromium(IV) species by reduction. With excess VO2+ a chromium(III) product was obtained. Spectral and ion-exchange properties of this product correspond to those observed for the titanium(III) and iron(II) reductions of chromium(V) and are consistent with the formulation of the product as a bis(hydroxycarboxylate) chelate of (H2O)2Cr/sup III/. With excess vanadium(IV), the reaction exhibits triphasic kinetics. The remaining step of the reaction is the reduction of the chromium(IV) intermediate with VO2+. Rates for all steps increase with decreasing [H+] and level off at low [H+]. The limiting rate constants for the formation of the chromium(IV) intermediate by the (Lig)3Cr(O)2- and (Lig)2Cr(O)- pathways are 2.8 x 103 and 2.2 x 102 M-1s-1. The bimolecular limiting rate constant for the reduction of chromium(IV) is computed to be 7.7 x 102 M-1 s-1. 33 references, 7 tables

  16. Chromium propionate enhances adipogenic differentiation of bovine intramuscular adipocytes

    Directory of Open Access Journals (Sweden)

    Rebecca eTokach

    2015-09-01

    Full Text Available In vitro experiments were performed to determine the effects of increasing concentrations of chromium propionate on mRNA and protein abundance of different enzymes and receptors. Intramuscular and subcutaneous preadipocytes and bovine satellite cells were isolated from the longissimus muscle to determine the effect of treatment on glucose transporter type 4 (GLUT4 and peroxisome proliferator-activated receptor γ mRNA and GLUT4 protein abundance. Preadipocyte cultures were treated with differentiation media plus either sodium propionate or different concentrations of chromium propionate (CrPro for 96, 120, and 144 h before harvest. This study indicated adipogenesis of the bovine intramuscular adipocytes were more sensitive to the treatment of chromium propionate as compared to subcutaneous adipocytes. Enhancement of adenosine monophosphate-activated protein kinase and GLUT4 mRNA by CrPro treatment may enhance glucose uptake in intramuscular adipocytes. Chromium propionate decreased GLUT4 protein levels in muscle cell cultures suggesting those cells have increased efficiency of glucose uptake due to exposure to increased levels of CrPro. In contrast, each of the two adipogenic lines had opposing responses to the CrPro. It appeared that CrPro had the most stimulative effect of GLUT4 response in the intramuscular adipocytes as compared to subcutaneous adipocytes. These findings indicated opportunities to potentially augment marbling in beef cattle fed chromium propionate during the finishing phase.

  17. Anthropogenic chromium emissions in china from 1990 to 2009.

    Science.gov (United States)

    Cheng, Hongguang; Zhou, Tan; Li, Qian; Lu, Lu; Lin, Chunye

    2014-01-01

    An inventory of chromium emission into the atmosphere and water from anthropogenic activities in China was compiled for 1990 through to 2009. We estimate that the total emission of chromium to the atmosphere is about 1.92×10⁵ t. Coal and oil combustion were the two leading sources of chromium emission to the atmosphere in China, while the contribution of them showed opposite annual growth trend. In total, nearly 1.34×10⁴ t of chromium was discharged to water, mainly from six industrial categories in 20 years. Among them, the metal fabrication industry and the leather tanning sector were the dominant sources of chromium emissions, accounting for approximately 68.0% and 20.0% of the total emissions and representing increases of 15.6% and 10.3% annually, respectively. The spatial trends of Cr emissions show significant variation based on emissions from 2005 to 2009. The emission to the atmosphere was heaviest in Hebei, Shandong, Guangdong, Zhejiang and Shanxi, whose annual emissions reached more than 1000t for the high level of coal and oil consumption. In terms of emission to water, the largest contributors were Guangdong, Jiangsu, Shandong and Zhejiang, where most of the leather production and metal manufacturing occur and these four regions accounted for nearly 47.4% of the total emission to water. PMID:24505309

  18. Anthropogenic chromium emissions in china from 1990 to 2009.

    Directory of Open Access Journals (Sweden)

    Hongguang Cheng

    Full Text Available An inventory of chromium emission into the atmosphere and water from anthropogenic activities in China was compiled for 1990 through to 2009. We estimate that the total emission of chromium to the atmosphere is about 1.92×10⁵ t. Coal and oil combustion were the two leading sources of chromium emission to the atmosphere in China, while the contribution of them showed opposite annual growth trend. In total, nearly 1.34×10⁴ t of chromium was discharged to water, mainly from six industrial categories in 20 years. Among them, the metal fabrication industry and the leather tanning sector were the dominant sources of chromium emissions, accounting for approximately 68.0% and 20.0% of the total emissions and representing increases of 15.6% and 10.3% annually, respectively. The spatial trends of Cr emissions show significant variation based on emissions from 2005 to 2009. The emission to the atmosphere was heaviest in Hebei, Shandong, Guangdong, Zhejiang and Shanxi, whose annual emissions reached more than 1000t for the high level of coal and oil consumption. In terms of emission to water, the largest contributors were Guangdong, Jiangsu, Shandong and Zhejiang, where most of the leather production and metal manufacturing occur and these four regions accounted for nearly 47.4% of the total emission to water.

  19. Enhancement of chromium uptake in tanning using oxazolidine.

    Science.gov (United States)

    Sundarapandiyan, S; Brutto, Patrick E; Siddhartha, G; Ramesh, R; Ramanaiah, B; Saravanan, P; Mandal, A B

    2011-06-15

    Monocyclic and bicyclic oxazolidines were offered at three different junctures of chrome tanning process viz. prior to BCS offer, along with BCS and after basification. It was found that oxazolidine when offered after basification brought about better chromium uptake and reduction of chromium load in the wastewater. Offer of oxazolidine was also varied. Increase in offer of oxazolidine from 0.25% to 1% was found to enhance the chromium uptake and decrease the chromium load in wastewater. But the increase in uptake was not proportionate to the increase in oxazolidine offer more than 0.75%. Offer of 1% Zoldine ZA 78 (monocyclic oxazolidine) and Zoldine ZE (bicyclic oxazolidine) after basification brought about 63.4% and 73.1% enhancement in chrome content in leather compared to control where oxazolidine was not offered. The tone of the wetblue was found to be altered moderately. However this did not call for any process adjustments in wet-finishing. The oxazolidine treated leathers were found to be immensely fuller and tighter. It was found experimentally that offer of 1% of oxazolidine facilitated reduction in the offer of syntans administered for filling and grain tightening by around 46%. Oxazolidine could bring about significant reduction in cost of chemicals apart from resulting environmental benefits due to enhancement of chromium uptake during tanning. PMID:21536383

  20. Low-chromium reduced-activation ferritic steels for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Alexander, D.J.; Kenik, E.A. [Oak Ridge National Laboratory, TN (United States)

    1996-04-01

    Development of reduced-activation ferritic steels has concentrated on high-chromium (8-10 wt% Cr) steels. However, there are advantages for a low-chromium steel, and initial ORNL studies on reduced-activation steels were on compositions with 2.25 to 12% Cr. Those studies showed an Fe-2.25Cr-2W-0.25V-0.1C (2 1/4Cr-2WV) steel to have the highest strenglth of the steels studied. Although this steel had the best strength, Charpy impact properties were inferior to those of an Fe-9Cr-2W-0.25V-0.07Ta-0.1C (9Cr-2WVTa) and an Fe-2.25Cr-2W-0.1C (2 1/4Cr-2W) steel. Therefore, further development of the low-chromium Cr-W steels was required. These results indicate that it is possible to develop low-chromium reduced-activation ferritic steels that have tensile and impact properties as good or better than those of high-chromium (7-9% Cr) steels. Further improvement of properties should be possible by optimizing the composition.

  1. FORMATION AND DESTRUCTION OF HEXAVALENT CHROMIUM IN A LABORATORY SWIRL FLAME INCINERATOR

    Science.gov (United States)

    The partitioning of chromium (Cr) in combustion systems was investigated theoretically and experimentally. Theoretical predictions were based on chemical equilibrium and suggested that hexavalent chromium [Cr(VI)] was favored by the presence of chlorine (Cl) and diminished by the...

  2. Chromium solubility in anhydrous Phase B

    Science.gov (United States)

    Bindi, Luca; Sirotkina, Ekaterina A.; Bobrov, Andrey V.; Nestola, Fabrizio; Irifune, Tetsuo

    2016-02-01

    The crystal structure and chemical composition of a crystal of (Mg14- x Cr x )(Si5- x Cr x )O24 ( x ≈ 0.30) anhydrous Phase B (Anh-B) synthesized in the model system MgCr2O4-Mg2SiO4 at 12 GPa and 1600 °C have been investigated. The compound was found to be orthorhombic, space group Pmcb, with lattice parameters a = 5.900(1), b = 14.218(2), c = 10.029(2) Å, V = 841.3(2) Å3 and Z = 2. The structure was refined to R 1 = 0.065 using 1492 independent reflections. Chromium was found to substitute for both Mg at the M3 site (with a mean bond distance of 2.145 Å) and Si at the octahedral Si1 site (mean bond distance: 1.856 Å), according to the reaction Mg2+ + Si4+ = 2Cr3+. Such substitutions cause a reduction in the volume of the M3 site and an increase in the volume of the Si-dominant octahedron with respect to the values typically observed for pure Anh-B and Fe2+-bearing Anh-B. Taking into account that Cr3+ is not expected to be Jahn-Teller active, it appears that both the Cr3+-for-Mg and Cr3+-for-Si substitutions in the Anh-B structure decrease the distortion of the octahedra. Electron microprobe analysis gave the Mg13.66(8)Si4.70(6)Cr0.62(4)O24 stoichiometry for the studied phase. The successful synthesis of this phase provides new information for the possible mineral assemblages occurring in the Earth's deep upper mantle and shed new light on the so-called X discontinuity that has been observed at 275-345 km depth in several subcontinental and subduction zone environments.

  3. Scientific Opinion on chromium(III lactate tri-hydrate as a source of chromium added for nutritional purposes to foodstuff

    Directory of Open Access Journals (Sweden)

    EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS

    2012-10-01

    Full Text Available

    The Panel on Food Additives and Nutrient Sources added to Food provides a scientific opinion on the safety and bioavailability of chromium(III lactate tri-hydrate as a source of chromium(III added for nutritional purposes to foodstuffs. The safety of chromium itself, in terms of the amounts that may be consumed, is outside the remit of this Panel. No new data have been provided as regards the safety and bioavailability of chromium from chromium(III lactate tri-hydrate. The Panel concurs with its earlier views stating that no evidence was provided supporting the bioavailability of chromium from chromium(III lactate tri-hydrate. Chromium(III lactate tri-hydrate is claimed to be freely soluble in water, however, chromium(III lactate tri-hydrate exists as a weak complex that may influence the bioavailability of chromium(III in the gastrointestinal tract. The Panel re-iterates that because of the complex chemistry of chromium(III lactate tri-hydrate in aqueous solutions and its limited solubility at pH >5, the bioavailability of chromium(III from chromium(III lactate tri-hydrate is low. Based on a conservative exposure estimate, the Panel calculated the combined intake of chromium(III from supplements and from foods fortified with chromium(III lactate tri-hydrate, for both adults and children, to be approximately 240 μg chromium(III/day, which is below the value of 250 µg/day established by the WHO for supplemental intake of chromium that should not be exceeded. The Panel noted that the use of chromium(III lactate tri-hydrate in the form of a premix with lactose, added to foods, would result in an exposure at the mean for adults of approximately 7-37 mg lactose/day (0.12-0.62 μg lactose/kg bw/day and to 36-192 μg lactate/day (0.60-3.20 μg/kg bw/day. Given that subjects with lactose maldigestion will tolerate up to 12 g of lactose with no or minor symptoms, these levels are not of safety concern.

  4. Biosorption of hexavalent chromium in a tannery industry wastewater using fungi species

    OpenAIRE

    Sivakumar, D.

    2016-01-01

    The isolated fungi species of different kinds from chromium contaminated soil sites located in Nagalkeni, Chennai were used for reducing chromium(VI) in a tannery industry wastewater of Nagalkeni, Chennai.  The experiments were conducted to know biosorption potential of isolated fungi species for removing chromium(VI) in a tannery industry wastewater against the different pH, fungi biomass and chromium(VI) concentration (dilution ratio).  The results of this study indicated that the order of ...

  5. Investigation of hexavalent chromium removal from Synthetic wastewater by using Peaganum

    OpenAIRE

    Ali Akbar Taghizadeh; Maryam khodadadi; Taher Shahriary; Hadighe Dorri; mahla zaferanieh; rasoul khosravi

    2012-01-01

    Background and Aim: Discharge of industrial wastewater containing hexavalent chromium into the environment can have harmful effects to the types of organisms. So, chromium should remove before discharging to the environment with an effective method. The purpose of this study of is hexavalent chromium removed with Peganum harmala granular seeds(PGS).   Materials and Methods: In this experimental study, The removal of hexavalent chromium with using PGS, with changes in time, pH, adsorbent dose,...

  6. Chromium Exposure and Hygienic Behaviors in Printing Workers in Southern Thailand

    OpenAIRE

    Somsiri Decharat

    2015-01-01

    Objectives. The main objective of this study was to assess the chromium exposure levels in printing workers. The study evaluated the airborne, serum, and urinary chromium levels and determines any correlation between level of chromium in specimen and airborne chromium levels. Material and Methods. A cross-sectional study was conducted with 75 exposed and 75 matched nonexposed subjects. Air breathing zone was measured by furnace atomic absorption spectrophotometer. Serum and urine samples were...

  7. Structure and morphology studies of chromium film at elevated temperature in hypersonic environment

    OpenAIRE

    Hegde, GM; Kulkarni, V; Nagaboopathy, M; Reddy, KPJ

    2012-01-01

    This paper presents the after shock heated structural and morphological studies of chromium film coated on hypersonic test model as a passive drag reduction element. The structural changes and the composition of phases of chromium due to shock heating (2850 K) are characterized using X-ray diffraction studies. Surface morphology changes of chromium coating have been studied using scanning electron microscopy (SEM) before and after shock heating. Significant amount of chromium ablation and sub...

  8. Cutaneous absorption of trivalent chromium: tissue levels and treatment by exchange transfusion

    OpenAIRE

    Kelly, W F; Ackrill, P; Day, J P; O'Hara, Maureen; Tye, C T; Burton, I.; Orton, C.; Harris, M.

    1982-01-01

    ABSTRACT A man was accidentally immersed in hot acidic trivalent chromium sulphate solution but none was swallowed. The clinical course was dominated by burns, intravascular haemolysis, and acute renal failure. Blood concentrations of chromium were measured during treatment and tissue concentrations were measured at death. Exchange transfusion reduced blood chromium concentrations by two-thirds. The total quantities of chromium absorbed and removed by various routes were calculated. In-vitro ...

  9. The risk to groundwater from wastewater irrigation using high chromium tannery effluent

    OpenAIRE

    Stuart, M E; Milne, C. J.

    2001-01-01

    Wastewater from Leon containing high concentrations of chromium from the tanning industry is used to irrigate agricultural land overlying an aquifer used for to supply potable water. Chromium from irrigation water is accumulating in agricultural soils, and in the lagoon and canal sediments, but groundwater appears to be unaffected and chromium concentrations remain low. A limited area of very high chromium concnetrations in groundwater was confirmed to be derived from a factory supplying the ...

  10. Liver Toxicity Resulted From Ingestion of Chromium Picolinate

    Directory of Open Access Journals (Sweden)

    Baltacı D et al.

    2010-03-01

    Full Text Available Herein, liver toxicity resulted from chronic ingestion of chromium picolinate, recommended daily allowance of over-the-counter (OTC have been presented. A woman of 32 years-old presented with pruritis since three days. On physical examination, she had no skin rashes, discoloration and urticarial lesions. With detailed inquiry of the patient, it has been determined that she had been using over-the-counter medicine containing chromium picolinate to enhance weight loss and increase lean body mass. On blood test examination follows: ALT: 484 U/I, AST: 182, Total/direct Bilirubin: 0,43/0,88 mg/dl. Complete Blood Count (CBC was normal. Chromium supplements may cause serious liver function impairment although when ingested within normal doses. Medication histories should include attention to the use of OTC nutritional supplements.

  11. Influence of chromium, oxygen, carbon and nitrogen on iron viscosity

    International Nuclear Information System (INIS)

    Kinetic viscosity of 70 beforehand melted iron samples with additions of chromium (up to 2%) and carbon (up to 1%) has been investigated. Different conditions of melting brought about differences in oxygen and nitrogen contents. Viscosity of most samples has been determined in the 1550-1650 deg C temperature range. It is stated that small additions to pure iron of each of the investigated elements (O, Cr, C, N) decrease its viscosity. Combined effect of these additions on viscosity is inadditive. Simultaneous introduction of oxygen and carbon may result in increase of melt viscosity. The same fact is observed at combined introduction of chromium and nitrogen. Simultaneous introduction of other impurities-chromium with oxygen or carbon, nitrogen with oxygen causes amplification of their individual effect. Reasons for the observed regularities result from changes in energies of interparticle interactions in the melt and therefore rebuilding of structure of its short-range order

  12. A study of the process of desorption of hexavalent chromium

    Directory of Open Access Journals (Sweden)

    W.B. Amorim

    2003-09-01

    Full Text Available In this work the process of desorption of hexavalent chromium, a toxic metal ion, from the marine algae Sargassum sp, following biosorption experiments 2³ factorial design was studied. A technique was applied to three eluents: HCl, H2SO4 and EDTA. Three factors of importance were evaluated: concentration of eluent, the ratio between mass of biosorbent and volume of eluent (S/L and process time. A statistical analysis of the experimental results showed that the three variables evaluated are significant for all three eluents. The models for chromium desorption were validated, as the results agreed well with the observed values. Through use of the response surface methodology, a factorial design based optimization technique; it was possible to identify the most suitable eluent and the interval of values for the process variables that resulted in the most significant desorption of chromium, which is relevant information for work aiming at process optimization.

  13. Structural and magnetic properties of chromium doped zinc ferrite

    International Nuclear Information System (INIS)

    Zinc chromium ferrites with chemical formula ZnCrxFe2−xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared by Sol - Gel technique. The structural as well as magnetic properties of the synthesized samples have been studied and reported here. The structural characterizations of the samples were analyzed by using X – Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The single phase spinel cubic structure of all the prepared samples was tested by XRD and FTIR. The particle size was observed to decrease from 18.636 nm to 6.125 nm by chromium doping and induced a tensile strain in all the zinc chromium mixed ferrites. The magnetic properties of few samples (x = 0.0, 0.4, 1.0) were investigated using Vibrating Sample Magnetometer (VSM)

  14. Chromium Resistant Bacteria: Impact on Plant Growth in Soil Microcosm

    Directory of Open Access Journals (Sweden)

    Sayel Hanane

    2014-07-01

    Full Text Available Three chromium resistant bacterial strains, Pseudomonas fluorescens PF28, Enterobacter amnigenus EA31 and Enterococcus gallinarum S34 isolated from tannery waste contaminated soil were used in this study. All strains could resist a high concentration of K2Cr2O7 that is up to 300 mg/L. The effect of these strains on clover plants (Trifolium campestre in the presence of two chromium salts CrCl3 and K2Cr2O7 was studied in soil microcosm. Application of chromium salts adversely affected seed germination, root and shoot length. Bacterial inoculation improved the growth parameters under chromate stress when compared with non inoculated respective controls. There was observed more than 50% reduction of Cr(VI in inoculated soil microcosms, as compared to the uninoculated soil under the same conditions. The results obtained in this study are significant for the bioremediation of chromate pollution.

  15. Studies of removal of chromium by model constructed wetland

    Directory of Open Access Journals (Sweden)

    C. Mant

    2005-09-01

    Full Text Available Chromium is a pollutant present in tannery wastewater, its removal is necessary for protection of the environment. Penisetum purpureum, Brancharia decumbens and Phragmites australis were grown hydroponically in experimental gravel beds to determine their potential for the phytoremediation of solutions containing 10 and 20 mg Cr dm-3. These concentrations, similar to tannery wastewater after initial physico-chemical treatment were used with the aim of developing an economic secondary treatment to protect the environment. All the systems achieved removal efficiencies of 97 - 99.6% within 24 hours. P. purpureum and B. decumbens removed 78.1% and 68.5% respectively within the first hour. Both P. purpureum and B. decumbens were tolerant of the concentrations of chromium applied, but P. purpureum showed the greatest potential because its faster growth and larger biomass achieved a much greater chromium removal over the whole length of time of the experiment.

  16. On the rational alloying of structural chromium-nickel steels

    International Nuclear Information System (INIS)

    A study was made on the influence of chromium nickel, phosphorus on the critical brittleness temperature of Cr-Ni-Mo-V structural steels. It is shown that the critical brittleness temperature of these steels increases at chromium content more over than 2% and nickel content more than 2% in the result of carbide transformations during tempering. Increase of nickel content in Cr-Ni-Mo-V-steels strengthens the tendency to embrittlement during slow cooling, from tempering temperature owing to development of process of phosphorus grain-boundary segregation. Two mentioned mechanisms of embrittlement determine principles of rational steel alloying. The extreme dependence of the critical brittleness temperature on chromium and nickel content, which enables to choose the optimum composition of Cr-Ni-Mo-V-steels, was established

  17. Chromium accumulation by the hyperaccumulator plant Leersia hexandra Swartz.

    Science.gov (United States)

    Zhang, Xue-Hong; Liu, Jie; Huang, Hai-Tao; Chen, Jun; Zhu, Yi-Nian; Wang, Dun-Qiu

    2007-04-01

    Leersia hexandra Swartz (Gramineae), which occurs in Southern China, has been found to be a new chromium hyperaccumulator by means of field survey and pot-culture experiment. The field survey showed that this species had an extraordinary accumulation capacity for chromium. The maximum Cr concentration in the dry leaf matter was 2978 mg kg(-1) on the side of a pond near an electroplating factory. The average concentration of chromium in the leaves was 18.86 times as that in the pond sediment, and 297.41 times as that in the pond water. Under conditions of the nutrient solution culture, it was found that L. hexandra had a high tolerance and accumulation capacity to Cr(III) and Cr(VI). Under 60 mg l(-1) Cr(III) and 10 mg l(-1) Cr(VI) treatment, there was no significant decrease of biomass in the leaves of L. hexandra (p>0.05). The highest bioaccumulation coefficients of the leaves for Cr(III) and Cr(VI) were 486.8 and 72.1, respectively. However, L. hexandra had a higher accumulation capacity for Cr(III) than for Cr(VI). At the Cr(III) concentration of 10 mg l(-1) in the culture solution, the concentration of chromium in leaves was 4868 mg kg(-1), while at the same Cr(VI) concentration, the concentration of chromium in leaves was only 597 mg kg(-1). These results confirmed that L. hexandra is a chromium hyperaccumulator which grows rapidly with a great tolerance to Cr and broad ecological amplitude. This species could provide a new plant resource that explores the mechanism of Cr hyperaccumulation, and has potential for usage in the phytoremediation of Cr-contaminated soil and water. PMID:17207838

  18. Heat resistance of carbon steel with chromium-based gas-thermal sprayed coatings

    International Nuclear Information System (INIS)

    Heat resistance of steel with chromium-base plasma sprayed coating is studied in comparison with chromium coating and base material. The specimens were oxidized at the air under 1250 K during 48 h. Investigations into steel-chromium coating interface were carried out and the structure of cinder was studied. Refs. 7, figs. 2

  19. Evaluation of flexural bond strength of porcelain to used nickel-chromium alloy in various percentages

    Directory of Open Access Journals (Sweden)

    VNV Madhav

    2012-01-01

    Fresh nickel-chromium alloy shows the greatest porcelain adherence.There is no significant change in bond strength of ceramic to alloy with up to 75% of used nickel-chromium alloy.At least 25%- of new alloy should be added when recycled nickel-chromium alloy is being used for metal ceramic restorations.

  20. 75 FR 60454 - Draft Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the...

    Science.gov (United States)

    2010-09-30

    ... AGENCY Draft Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the..., ``Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the Integrated Risk..., 2010. The listening session on the draft assessment for hexavalent chromium will be held on November...

  1. 76 FR 20349 - Draft Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the...

    Science.gov (United States)

    2011-04-12

    ... AGENCY Draft Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the..., ``Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the Integrated Risk... workshop on the draft assessment for Hexavalent Chromium will be held on May 12, 2011, beginning at 8:30...

  2. 77 FR 61431 - Hexavalent Chromium Standards; Extension of the Office of Management and Budget's (OMB) Approval...

    Science.gov (United States)

    2012-10-09

    ... Occupational Safety and Health Administration Hexavalent Chromium Standards; Extension of the Office of...) approval of the information collection requirements specified in the Hexavalent Chromium Standards for... requirements specified in the Hexavalent Chromium (Cr(VI)) Standards for General Industry (29 CFR...

  3. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium-cobalt-aluminum oxide. 73.3110a Section... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3110a Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide (Pigment Blue 36) (CAS Reg....

  4. Speciation dependent radiotracer studies on chromium preconcentration using iron doped calcium alginate biopolymer

    International Nuclear Information System (INIS)

    The work aims to study the differential attitude of Ca-alginate (CA) and Fe-doped calcium alginate (Fe-CA) and towards Cr(III) and Cr (IV) so that, depending on the oxidation state of chromium effluent, environmentally sustainable methodologies can be prescribed for removal of chromium. Throughout the experiment 51Cr has been used as the precursor of stable chromium

  5. 40 CFR 749.68 - Hexavalent chromium-based water treatment chemicals in cooling systems.

    Science.gov (United States)

    2010-07-01

    ... Cooling Systems § 749.68 Hexavalent chromium-based water treatment chemicals in cooling systems. (a... distribution in commerce of hexavalent chromium-based water treatment chemicals for use in cooling systems. (d... holds hexavalent chromium-based water treatment chemicals for use in cooling systems. (6) Cooling...

  6. Chromium supplementation alters both glucose and lipid metabolism in feedlot cattle during the receiving period

    Science.gov (United States)

    Crossbred steers (n = 20; 235 +/- 4 kg) were fed 53 days during a receiving period to determine if supplementing chromium (Cr; KemTRACE®brandChromium Propionate 0.04%, Kemin Industries) would alter the glucose or lipid metabolism of newly received cattle. Chromium premixes were supplemented to add 0...

  7. Enhancement of the acute phase response to lipopolysaccharide (LPS) challenge in steers supplemented with chromium

    Science.gov (United States)

    The study examined the effect of chromium supplementation on the response of steers to an LPS challenge. Twenty steers received a premix that added 0 (control) or 0.2 mg/kg of chromium (KemTRACE®brandChromiumProprionate 0.04%, Kemin Industries) to the total diet on a dry matter basis for 55 d. Steer...

  8. Chromium supplementation alters the glucose and lipid metabolism of feedlot cattle during the receiving period

    Science.gov (United States)

    Crossbreed steers (n = 20; 235 ± 4 kg) were fed 53 d during a receiving period to determine if supplementing chromium (Cr; KemTRACE®brand Chromium Propionate 0.04%, Kemin Industries) would alter the glucose or lipid metabolism of newly received cattle. Chromium premixes were supplemented to add 0 (C...

  9. Soil dehydrogenase activity in the presence of chromium (III) and (VI)

    OpenAIRE

    Wolińska A.; Stępniewska Z.

    2005-01-01

    The paper presents the influence of chromium forms (III) and (VI) on the soil dehydrogenase activity. Enzyme activities can be considered effective indicators of soil quality changes resulting from environmental stress or management practices. It was found that chromium compounds have detrimental effects on soil dehydrogenase activity. After the addition of chromium, a rapid and significant decrease in enzymatic activities was observed.

  10. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Science.gov (United States)

    2010-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject...

  11. 40 CFR 721.2097 - Azo chromium complex dyestuff preparation (generic name).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Azo chromium complex dyestuff... New Uses for Specific Chemical Substances § 721.2097 Azo chromium complex dyestuff preparation... substance identified generically as an azo chromium complex dyestuff preparation (PMN P-95-240) is...

  12. Hot corrosion resistance of nickel-chromium-aluminum alloys

    Science.gov (United States)

    Santoro, G. J.; Barret, C. A.

    1977-01-01

    The hot corrosion resistance of nickel-chromium-aluminum alloys was examined by cyclically oxidizing sodium sulfate-coated specimens in still air at 900, 1000, and 1100 C. The compositions tested were within the ternary region: Ni, Ni-50 at.% Cr, and Ni-50 at.% Al. At each temperature the corrosion data were statistically fitted to a third order regression equation as a function of chromium and aluminum contents. From these equations corrosion isopleths were prepared. Compositional regions with the best hot corrosion resistance were identified.

  13. Primary and secondary crystallization of modified hypoeutectic chromium cast iron

    Directory of Open Access Journals (Sweden)

    A. Studnicki

    2010-04-01

    Full Text Available The paper presents investigations of crystallization of modified hypoeutectic wear resistant chromium cast iron which contains carbon about 2% and chromium on three levels (12%, 18% and 25%. Three substances were applied to the modification ( boron carbide (B4C, ferroniobium (FeNb and mixture of ferroniobium and mischmetal (RE. The investigations of crystallization were conducted the DTA method in DTA-C and DTA-Is testers. The influence on the course of the process of primary and secondary crystallization was observed.

  14. Electrodeposited tungsten-nickel-boron: A replacement for hexavalent chromium

    International Nuclear Information System (INIS)

    Chromium, deposited from acidic solutions of its hexavalent ion, has been the rule for wear resistant, corrosion resistant coatings for many years. Although chromium coatings are durable, the plating process generates air emissions, effluent rinse waters, and process solutions that are toxic, suspected carcinogens, and a risk to human health and the environment. Tungsten-nickel-boron (W-Ni-B) alloy deposition is a potential substitute for hexavalent chrome. It has excellent wear, corrosion, and mechanical properties and also may be less of an environmental risk. This study examines the electroplating process and deposit properties of W-Ni-B and compares them with those of hexavalent chrome

  15. Beryllium Silicide Clusters, BenSin, Be2nSin (n = 1 - 4) and possible MgB2-like Superconductivity in some of them

    OpenAIRE

    Isikaku-Ironkwe, O. P.

    2012-01-01

    The symmetry of the Periodic Table makes it possible to predict certain properties of similar elements and compounds using one of them as a template. Magnesium diboride, MgB2, presents a useful template in the search for similar materials. Starting from electronegativity, valence electron and atomic number equivalency, we identify many potential similar materials. One of them is the beryllium silicide, Be2nSin cluster system. We establish that though not yet produced in bulk, Be2Si exists. We...

  16. Modification by H-termination in growth process of titanium silicide on Si(0 0 1)-2 x 1 observed with scanning tunneling microscopy

    International Nuclear Information System (INIS)

    Formation processes of titanium silicide on hydrogen-terminated H/Si(0 0 1)-2 x 1 surface are studied at the atomic scale with a scanning tunneling microscopy (STM). Square-shaped nanoislands were observed on the Ti/H/Si(0 0 1) surface after annealed at 873-1073 K. These are the epitaxial nanoislands moderately grown due to the local orientation relationship between C49-TiSi2 and Si(0 0 1), because passivation by surface hydrogen on Si(0 0 1) suppresses active and complex bond formation of Ti-Si.

  17. The effect of silicide ceramic coatings on the high-temperature strength and plasticity of niobium alloys of the Nb-W-Mo-Zr system

    International Nuclear Information System (INIS)

    A study is made into short-term rupture strength and plasticity of 5VMTs alloy of Nb-W-Mo-Zr system and a 5VMTs-silicide ceramic coating composite material in vacuum, inert environment and in the air within a temperature range of 290-2070 K. The kinetics of defect generation and development both in the protective coating and the matrix is studied. The values of limiting plastic strains are determined at which the composite materials preserves its carrying capacity in high temperature aggressive and oxidizing gaseous media

  18. M5Si3(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications

    Energy Technology Data Exchange (ETDEWEB)

    Zhihong Tang

    2007-12-01

    Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600 C. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti{sub 5}Si{sub 3}-based alloys was investigated. Oxidation behavior of Ti{sub 5}Si{sub 3}-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters the oxidation behavior of Ti{sub 5}Si{sub 3} by nucleation and growth of nitride subscale. Ti{sub 5}Si{sub 3.2} and Ti{sub 5}Si{sub 3}C{sub 0.5} alloys exhibited an excellent oxidation resistance in nitrogen bearing atmosphere due to limited dissolution of nitrogen and increased Si/Ti activity ratio. MoSi{sub 2} coating developed by pack cementation to protect Mo-based Mo-Si-B composites was found to be effective up to 1500 C. Shifting coating composition to T1+T2+Mo{sub 3}Si region showed the possibility to extend the coating lifetime above 1500 C by more than ten times via formation of slow growing Mo{sub 3}Si or T2 interlayer without sacrificing the oxidation resistance of the coating. The phase equilibria in the Nb-rich portion of Nb-B system has been evaluated experimentally using metallographic analysis and differential thermal analyzer (DTA). It was shown that Nb{sub ss} (solid solution) and NbB are the only two primary phases in the 0-40 at.% B composition range, and the eutectic reaction L {leftrightarrow} Nb{sub SS} + NbB was determined to occur at 2104 {+-} 5 C by DTA.

  19. Electrical properties of amorphous and epitaxial Si-rich silicide films composed of W-atom-encapsulated Si clusters

    International Nuclear Information System (INIS)

    We investigated the electrical properties and derived the energy band structures of amorphous Si-rich W silicide (a-WSin) films and approximately 1-nm-thick crystalline WSin epitaxial films (e-WSin) on Si (100) substrates with composition n = 8–10, both composed of Sin clusters each of which encapsulates a W atom (WSin clusters). The effect of annealing in the temperature range of 300–500 °C was also investigated. The Hall measurements at room temperature revealed that a-WSin is a nearly intrinsic semiconductor, whereas e-WSin is an n-type semiconductor with electron mobility of ∼8 cm2/V s and high sheet electron density of ∼7 × 1012 cm−2. According to the temperature dependence of the electrical properties, a-WSin has a mobility gap of ∼0.1 eV and mid gap states in the region of 1019 cm−3 eV−1 in an optical gap of ∼0.6 eV with considerable band tail states; e-WSin has a donor level of ∼0.1 eV with sheet density in the region of 1012 cm−2 in a band gap of ∼0.3 eV. These semiconducting band structures are primarily attributed to the open band-gap properties of the constituting WSin cluster. In a-WSin, the random network of the clusters generates the band tail states, and the formation of Si dangling bonds results in the generation of mid gap states; in e-WSin, the original cluster structure is highly distorted to accommodate the Si lattice, resulting in the formation of intrinsic defects responsible for the donor level

  20. The oxidation and reduction of chromium of stainless steels in an eletric arc furnace

    Directory of Open Access Journals (Sweden)

    B. Arh

    2011-07-01

    Full Text Available The oxidation of chromium during the elaboration of stainless steels occurs with oxygen in solution blown inthe melt and with oxides in the slag. A higher content of silicon in the furnace charge decreases the extent of oxidation of chromium, however, the efficient reduction of chromium from the slag is of essential importance for a minimal loss of chromium. In this survey, the theory of the oxidation of chromium, its reduction from the slag and the conditions for the formation of foaming slag are discussed.