Energy response study of modified CR-39 neutron personnel dosimeter

International Nuclear Information System (INIS)

Sathian, Deepa; Bakshi, A.K.; Datta, D.; Nair, Sreejith S.; Sathian, V.; Mishra, Jitendra; Sen, Meghnath

2018-01-01

Personnel neutron dosimetry is an integral part of radiation protection. No single dosimeter provides the satisfactory energy response, sensitivity, angular dependence characteristics and accuracy necessary to meet the requirement of an ideal personnel neutron dosimeter. The response of a personnel neutron dosimeter is critically dependent upon the energy distribution of the neutron field. CR-39 personnel neutron dosimeters were typically calibrated in the standard neutron field of 252 Cf and 241 Am-Be in our laboratory, although actual neutron fields may vary from the calibration neutron spectrum. Recently the badge cassette of the personnel neutron dosimeter was changed due to frequent damage of the PVC badge used earlier. This paper discusses energy response of CR-39 solid state nuclear track detector loaded in this modified badge cassette as per latest ISO recommendation

Energy transfer from Cr to Nd in substitutional crystal Y{sub 3}Ga{sub x}Al{sub 5−x}O{sub 12} codoped with Nd and Cr

Energy Technology Data Exchange (ETDEWEB)

Takagi, Kazuki [Department of Mathematical and Design Engineering, Gifu University, Gifu 501-1193 (Japan); Yamaga, Mitsuo, E-mail: yamaga@gifu-u.ac.jp [Department of Mathematical and Design Engineering, Gifu University, Gifu 501-1193 (Japan); Villora, Encarnacion G.; Shimamura, Kiyoshi [National Institute for Materials Science, Tsukuba 305-0044 (Japan); Hasegawa, Kazuo; Ito, Hiroshi; Mizuno, Shintaro; Takeda, Yasuhiko [Toyota Central R& D Laboratories, Nagakute 480-1192 (Japan); Han, Thomas P.J. [Department of Physics, University of Strathclyde, Glasgow G4 0NG, Scotland (United Kingdom)

2016-01-15

Garnet crystals codoped with Nd{sup 3+} and Cr{sup 3+} ions are a candidate for solar-pumped laser materials. Substitutional disordered crystals Y{sub 3}Ga{sub x}Al{sub 5−x}O{sub 12} were prepared to improve the pumping efficiency of Nd{sup 3+} luminescence and energy transfer from Cr{sup 3+} to Nd{sup 3+} ions. The substitutional disordered crystal host produced inhomogeneous broadening of the Nd{sup 3+} and Cr{sup 3+} optical spectra. Enhancement of overlapping between the Cr{sup 3+} absorption bands and the solar spectrum, and between the Cr{sup 3+} luminescence bands and the Nd{sup 3+} absorption lines led to the increases of the pumping efficiency and the energy transfer rates, respectively. The excitation spectrum of the Nd{sup 3+} luminescence, the nonexponential decay curves of the Cr{sup 3+} luminescence, and the quantum yields of the Cr{sup 3+} and Nd{sup 3+} luminescence have given evidence on the energy transfer from Cr{sup 3+} to Nd{sup 3+} ions. - Highlights: • Substitutional disordered garnet crystals as solar-pumped laser materials. • Inhomogeneous broadening of Nd{sup 3+} and Cr{sup 3+} optical spectra. • Enhancement of energy transfer from Cr{sup 3+} to Nd{sup 3+} due to inhomogeneous broadening.

Development of an Interferometric Phased Array Trigger for Balloon-Borne Detection of the Highest Energy Cosmic Particles

Science.gov (United States)

Vieregg, Abigail

Through high energy neutrino astrophysics, we explore the structure and evolution of the universe in a unique way and learn about the physics inside of astrophysical sources that drives the acceleration of the highest energy particles. Neutrinos travel virtually unimpeded through the universe, making them unique messenger particles for cosmic sources and carrying information about very distant sources that would otherwise be unavailable. The highest energy neutrinos (E>10^{18} eV), created as a by-product of the interaction of the highest energy cosmic rays with the cosmic microwave background, are an important tool for determining the origin of the highest energy cosmic rays and still await discovery. Balloon-borne and ground-based experiments are poised to discover these ultra-high energy (UHE) cosmogenic neutrinos by looking for radio emission from two different types of neutrino interactions: particle cascades induced by neutrinos in glacial ice, and extensive air showers in the atmosphere induced by the charged-particle by-product of tau neutrinos interacting in the earth. These impulsive radio detectors are also sensitive to radio emission from extensive air showers induced directly by UHE cosmic rays. Balloon-borne experiments are especially well-suited for discovering the highest energy neutrinos, and are the only way to probe the high energy cutoff of the sources themselves to reveal the astrophysics that drives the central engines inside the most energetic accelerators in the universe. Balloon platforms offer the chance to monitor extremely large volumes of ice and atmosphere, but with a higher energy threshold compared to ground-based observatories, since the neutrino interaction happens farther from the detector. This tradeoff means that the sensitivity of balloon-borne experiments, such as the Antarctic Impulsive Transient Antenna (ANITA) or the ExaVolt Antenna, is optimized for discovery of the highest energy neutrinos. We are developing an

Microstructure and mechanical properties of Ti-Zr-Cr biomedical alloys.

Science.gov (United States)

Wang, Pan; Feng, Yan; Liu, Fengchao; Wu, Lihong; Guan, Shaokang

2015-06-01

The Ti-15Zr-xCr (0≤x≤10, wt.%) alloys were investigated to develop new biomedical materials. It was found that the phase constitutions and mechanical properties strongly depended on the Cr content. The Ti-15Zr alloy was comprised of α' phase and a small fraction of β phase was detected with adding 1wt.% Cr. With addition of 5wt.% or more, the β phase was completely retained. In addition, the ω phase was detected in the Ti-15Zr-5Cr alloy and Ti-15Zr-7Cr alloy which exhibited the highest compressive Young's modulus and the lowest ductility. On the other hand, all the Ti-15Zr-xCr alloys without ω phase exhibited high microhardness, high yield strength and superior ductility. Furthermore, the elastic energy of Ti-15Zr-10Cr alloy (5.89MJ/m(3)) with only β phase and that of Ti-15Zr-3Cr alloy (4.04MJ/m(3)) with α' phase and small fraction of β phase was higher than the elastic energy of c.p. Ti (1.25MJ/m(3)). This study demonstrated that Ti-15Zr-3Cr alloy and Ti-15Zr-10Cr alloy with superior mechanical properties are potential materials for biomedical applications. Copyright © 2015. Published by Elsevier B.V.

Energy transfer efficiency from Cr(3+) to Nd(3+) in solar-pumped laser using transparent Nd/Cr:Y(3)Al(5)O(12) ceramics.

Science.gov (United States)

Hasegawa, Kazuo; Ichikawa, Tadashi; Mizuno, Shintaro; Takeda, Yasuhiko; Ito, Hiroshi; Ikesue, Akio; Motohiro, Tomoyoshi; Yamaga, Mitsuo

2015-06-01

We report energy transfer efficiency from Cr3+ to Nd3+ in Nd (1.0 at.%)/Cr (0.4 at.%) co-doped Y3Al5O12 (YAG) transparent ceramics in the laser oscillation states. The laser oscillation has performed using two pumping lasers operating at 808 nm and 561 nm; the former pumps Nd3+ directly to create the 1064 nm laser oscillation, whereas the latter assists the performance via Cr3+ absorption and sequential energy transfer to Nd3+. From the laser output power properties and laser mode analysis, the energy transfer efficiency was determined to be around 65%, which is close to that obtained from the spontaneous Nd3+ emission.

Effect of Cr3C2 content on the microstructure and properties of Mo2NiB2-based cermets

International Nuclear Information System (INIS)

Xie, Lang; Li, XiaoBo; Zhang, Dan; Yang, ChengMing; Yin, FuCheng; Xiangtan Univ., Hunan; Xiangtan Univ., Hunan; Xiao, YiFeng

2015-01-01

Four series of Mo 2 NiB 2 -based cermets with Cr 3 C 2 addition of between 0 and 7.5 wt.% in 2.5 wt.% increments were studied by means of scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffractometry. The transverse rupture strength and hardness were also measured. It was found that Cr 3 C 2 completely dissolved in Mo 2 NiB 2 -based cermets. Cr 3 C 2 addition improved the wettability of the Ni binder phase on the Mo 2 NiB 2 hard phase, which resulted in a decrease in the porosity and an increase in the phase uniformity. The cermets with 2.5 wt.% Cr 3 C 2 content showed relatively fine grains and almost full density. A high Cr 3 C 2 content resulted in the formation of M 6 C (M = Mo, Cr, Ni) phase. In addition, energy dispersive X-ray spectroscopy results showed that the content of Mo in the binder decreased with increasing Cr 3 C 2 content. The cermets with 2.5 wt.% Cr 3 C 2 addition exhibited the highest transverse rupture strength of 2210 MPa, whereas the cermets without Cr 3 C 2 addition exhibited the highest hardness.

Immediate remediation of heavy metal (Cr(VI)) contaminated soil by high energy electron beam irradiation

International Nuclear Information System (INIS)

Zhang, Jing; Zhang, Guilong; Cai, Dongqing; Wu, Zhengyan

2015-01-01

Highlights: • An immediate remediation method for Cr(VI) contaminated soil (CCS) was developed. • High energy electron beam (HEEB) irradiation could reduce Cr(VI) in CCS to Cr(III). • This effect was attributed to electrons, hydrated electrons, and reductive radicals. • This remediation method was effective, environmentally friendly, and low-cost. - Abstract: This work developed an immediate and high-performance remediation method for Cr(VI) contaminated soil (CCS) using high energy electron beam (HEEB) irradiation. The result indicated that, compared with γ-ray irradiation, HEEB irradiation displayed a significant reduction efficiency on Cr(VI) in CCS to Cr(III) with substantially lower toxicity, which was mainly attributed to the reduction effects of electrons, hydrated electrons, and reductive radicals generated in the irradiation process of HEEB. This work could provide a one-step and effective method for the remediation of heavy metal contaminated soil (HMCS)

Immediate remediation of heavy metal (Cr(VI)) contaminated soil by high energy electron beam irradiation

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jing; Zhang, Guilong [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei 230031 (China); Bioenergy Forest Research Center of State Forestry Administration, Hefei 230031 (China); Cai, Dongqing, E-mail: dqcai@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei 230031 (China); Bioenergy Forest Research Center of State Forestry Administration, Hefei 230031 (China); Wu, Zhengyan, E-mail: zywu@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei 230031 (China); Bioenergy Forest Research Center of State Forestry Administration, Hefei 230031 (China)

2015-03-21

Highlights: • An immediate remediation method for Cr(VI) contaminated soil (CCS) was developed. • High energy electron beam (HEEB) irradiation could reduce Cr(VI) in CCS to Cr(III). • This effect was attributed to electrons, hydrated electrons, and reductive radicals. • This remediation method was effective, environmentally friendly, and low-cost. - Abstract: This work developed an immediate and high-performance remediation method for Cr(VI) contaminated soil (CCS) using high energy electron beam (HEEB) irradiation. The result indicated that, compared with γ-ray irradiation, HEEB irradiation displayed a significant reduction efficiency on Cr(VI) in CCS to Cr(III) with substantially lower toxicity, which was mainly attributed to the reduction effects of electrons, hydrated electrons, and reductive radicals generated in the irradiation process of HEEB. This work could provide a one-step and effective method for the remediation of heavy metal contaminated soil (HMCS)

Electrodynamics at the highest energies

International Nuclear Information System (INIS)

Klein, Spencer R.

2002-01-01

At very high energies, the bremsstrahlung and pair production cross sections exhibit complex behavior due to the material in which the interactions occur. The cross sections in dense media can be dramatically different than for isolated atoms. This writeup discusses these in-medium effects, emphasizing how the cross section has different energy and target density dependencies in different regimes. Data from SLAC experiment E-146 will be presented to confirm the energy and density scaling. Finally, QCD analogs of the electrodynamics effects will be discussed

Electronic structure of the Ga1-xCr xN studied by high-energy photoemission spectroscopy

International Nuclear Information System (INIS)

Kim, J.J.; Makino, H.; Yao, T.; Takata, Y.; Kobayashi, K.; Yamamoto, T.; Hanada, T.; Cho, M.W.; Ikenaga, E.; Yabashi, M.; Miwa, D.; Nishino, Y.; Tamasaku, K.; Ishikawa, T.; Shin, S.

2005-01-01

Valence band spectra of Ga 1-x Cr x N have been investigated by high-energy photoemission spectroscopy at the photon energy of 5.95 keV. Cr doping does introduce a novel electronic structure in the bandgap and causes some change in valence band structure. Based on the first-principle calculation, Cr-associated electronic levels in the bandgap are assigned to nonbonding and antibonding d states while the change of the valence band suggests that the Ga 4s originated states are significantly modified through hybridization with the Cr 3d orbital. The present result evidences that the Ga valence electrons are considerably modified through the interaction with the second nearest-neighbour Cr atoms

Response of CR-39 SSNTD to high energy neutrons using zirconium convertors - a Monte Carlo and experimental study

International Nuclear Information System (INIS)

Pal, Rupali; Sapra, B.K.; Bakshi, A.K.; Datta, D.; Biju, K.; Suryanarayana, S.V.; Nayak, B.K.

2016-01-01

Neutron dosimetry in ion accelerators is a challenging field as the neutron spectrum varies from thermal, to fast and high-energy neutrons usually extending beyond 20 MeV. Solid-state Nuclear Track Detectors (SSNTDs) have been increasingly used in numerous fields related to nuclear physics. Extensive work has also been carried out on determining the response characteristics of such detectors as nuclear spectrometers. In nuclear reaction studies, identification of reaction products according to their type and energy is frequently required. For normally incident particles, energy-dispersive track-diameter methods have become useful scientific tools using CR-39 SSNTD. CR-39 along with 1 mm polyethylene convertor can cover a neutron energy range from 100 keV to 10 MeV. The neutron interacts with the hydrogen in CR-39 producing recoil protons from elastic collisions. This detectable neutron energy range can be increased by modification in the radiator/convertor used along with CR-39. CR39 detectors placed in conjunction with judiciously chosen thicknesses of a polyethylene radiator and a lead absorber (or degrader) are used to increase energy range upto 19 MeV. A portable neutron counter has been proposed for high-energy neutron measurement with 1 cm thick Zirconium (Zr) as the converter outside a spherical HDPE shell of 7 inch diameter. Zr metal has been found to show (n,2n) cross section for energies above 10 MeV starting from 0.01 barns for 8 MeV upto 1 barns for 22 MeV. Above these energies, the experimental data is scarce. In this paper, Zr was used in conjunction with CR-39 which showed an enhancement of track density on the CR-39. This paper demonstrates the enhancement of neutron response using Zr on CR-39 with both theoretical and experimental studies

Migration of Cr-vacancy clusters and interstitial Cr in α-Fe using the dimer method

International Nuclear Information System (INIS)

Chen, D.; Gao, F.; Hu, S. Y.; Sun, X.; Heinisch, H. L.; Henager, C. H.; Khaleel, M. A.; Hu, W. Y.; Terentyev, D.

2010-01-01

The migration mechanisms and the corresponding activation energies of Cr-vacancy (Cr-V) clusters and Cr interstitials in α-Fe have been investigated using the dimer and the nudged elastic-band methods. Dimer searches are employed to find the possible transition states of these defects and the lowest-energy paths are used to determine the energy barriers for migration. A substitutional Cr atom can migrate to a nearest-neighbor vacancy through an energy barrier of 0.56 eV but this simple mechanism alone is unlikely to lead to the long-distance migration of Cr unless there is a supersaturated concentration of vacancies in the system. The Cr-vacancy clusters can lead to long-distance migration of a Cr atom that is accomplished by Fe and Cr atoms successively jumping to nearest-neighbor vacancy positions, defined as a self-vacancy-assisted migration mechanism, with the migration energies ranging from 0.64 to 0.89 eV. In addition, a mixed Cr-Fe dumbbell interstitial can easily migrate through Fe lattices, with the migration energy barrier of 0.17, which is lower than that of the Fe-Fe interstitial. The on-site rotation of the Cr-Fe interstitial and Cr atom hopping from one site to another are believed to comprise the dominant migration mechanism. The calculated binding energies of Cr-V clusters are strongly dependent on the size of clusters and the concentration of Cr atoms in clusters.

First-Principles Calculations for Chemical Reaction between Sodium Diethyldithiocarbamate and Transition-Metal (Cr) atom to Produce Cr(DDC)3 and Cr(DDC)2ODDC

Science.gov (United States)

Setiyanto, Henry; Muhida, Rifki; Kishi, Tomoya; Rempillo, Ofelia; Rahman, Mahmudur; Dipojono, Hermawan Kresno; Di\\ {n}o, Wilson Agerico; Matsumoto, Shigeno; Kasai, Hideaki

2006-10-01

We investigate the chemical reaction between a Cr transition-metal atom and sodium diethyldithiocarbamate (NaDDC), a complexing agent used to detect and extract Cr in human blood samples. Using density-functional-theory-based calculations, we determine their stable structures of Cr(DDC)2ODDC and Cr(DDC)3 complexes and obtain their dissociation energies. We found dissociation energies of -10.66 and -3.24 eV for Cr(DDC)2ODDC and Cr(DDC)3 complexes, respectively. Hence, on the basis of dissociation energies, we have verified that the reaction of NaDDC with Cr produces Cr(DDC)2ODDC as a major product.

Inverse Resistance Change Cr2Ge2Te6-Based PCRAM Enabling Ultralow-Energy Amorphization.

Science.gov (United States)

Hatayama, Shogo; Sutou, Yuji; Shindo, Satoshi; Saito, Yuta; Song, Yun-Heub; Ando, Daisuke; Koike, Junichi

2018-01-24

Phase-change random access memory (PCRAM) has attracted much attention for next-generation nonvolatile memory that can replace flash memory and can be used for storage-class memory. Generally, PCRAM relies on the change in the electrical resistance of a phase-change material between high-resistance amorphous (reset) and low-resistance crystalline (set) states. Herein, we present an inverse resistance change PCRAM with Cr 2 Ge 2 Te 6 (CrGT) that shows a high-resistance crystalline reset state and a low-resistance amorphous set state. The inverse resistance change was found to be due to a drastic decrease in the carrier density upon crystallization, which causes a large increase in contact resistivity between CrGT and the electrode. The CrGT memory cell was demonstrated to show fast reversible resistance switching with a much lower operating energy for amorphization than a Ge 2 Sb 2 Te 5 memory cell. This low operating energy in CrGT should be due to a small programmed amorphous volume, which can be realized by a high-resistance crystalline matrix and a dominant contact resistance. Simultaneously, CrGT can break the trade-off relationship between the crystallization temperature and operating speed.

An energy and direction independent fast neutron dosemeter based on electrochemically etched CR-39 nuclear track detectors

International Nuclear Information System (INIS)

James, K.; Matiullah; Durrani, S.A.

1987-01-01

A computer-based model is presented, which simulates the dose equivalent response of electrochemically etched CR-39 to fast neutrons of various energies and angles of incidence. Most previous calculations of the response of CR-39 have neglected the production of recoiling oxygen and carbon nuclei as well as α particles in the CR-39. We calculate that these 'heavy recoils' and α particles are the major source of electrochemically etchable tracks in bare CR-39 at neutron energies above approx. 2 MeV under typical etching conditions. Our calculations have been extended to predict the response of CR-39 used in conjunction with various combinations of polymeric front radiators and we have determined the radiator stack configuration with produces the most energy independent response. Again, the heavy recoils and α particles cannot be neglected and, for energies above approx. 2 MeV, these produce typically about 20% of the total response of our optimum stack. This type of fast neutron dosemeter is, however, strongly direction dependent. We have integrated the response over all appropriate angles to predict the dose equivalent response for two representative neutron fields, and we suggest a method for minimising the angular dependence. (author)

Strain control of Urbach energy in Cr-doped PrFeO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Kumar, Anil; Warshi, M.K.; Mishra, Vikash; Saxena, Shailendra K.; Kumar, Rajesh; Sagdeo, Pankaj R. [Indian Institute of Technology Indore, Material Research Laboratory, Discipline of Physics and MEMS, Indore (India)

2017-09-15

Polycrystalline samples of PrFe{sub 1-x}Cr{sub x}O{sub 3} having average particle size of ∝90 nm have been prepared by wet chemical route. The structural phase purity of the prepared samples is confirmed by powder X-ray diffraction followed by Rietveld refinements. It is observed that with Cr doping, the Urbach energy (E{sub u}) increases. The E{sub u} is measure of the various disorders present in the sample, such as chemical and structural. To understand the contribution to the E{sub u} due to chemical and structural disorders, we have probed the chemical and structural disorders in the samples by elemental mappings and through X-ray diffraction experiments, respectively. Elemental mapping confirms chemical homogeneity of prepared samples. It is observed that with Cr doping the crystallographic strain increases and Urbach energy shows the similar scaling. (orig.)

Nanostructured Fe-Cr Alloys for Advanced Nuclear Energy Applications

Energy Technology Data Exchange (ETDEWEB)

Scattergood, Ronald O. [North Carolina State Univ., Raleigh, NC (United States)

2016-04-26

We have completed research on the grain-size stabilization of model nanostructured Fe14Cr base alloys at high temperatures by the addition of non-equilibrium solutes. Fe14Cr base alloys are representative for nuclear reactor applications. The neutron flux in a nuclear reactor will generate He atoms that coalesce to form He bubbles. These can lead to premature failure of the reactor components, limiting their lifetime and increasing the cost and capacity for power generation. In order to mitigate such failures, Fe14Cr base alloys have been processed to contain very small nano-size oxide particles (less than 10 nm in size) that trap He atoms and reduce bubble formation. Theoretical and experimental results indicate that the grain boundaries can also be very effective traps for He atoms and bubble formation. An optimum grain size will be less than 100 nm, ie., nanocrystalline alloys must be used. Powder metallurgy methods based on high-energy ball milling can produce Fe-Cr base nanocrystalline alloys that are suitable for nuclear energy applications. The problem with nanocrystalline alloys is that excess grain-boundary energy will cause grains to grow at higher temperatures and their propensity for He trapping will be lost. The nano-size oxide particles in current generation nuclear alloys provide some grain size stabilization by reducing grain-boundary mobility (Zener pinning – a kinetic effect). However the current mitigation strategy minimizing bubble formation is based primarily on He trapping by nano-size oxide particles. An alternate approach to nanoscale grain size stabilization has been proposed. This is based on the addition of small amounts of atoms that are large compared to the base alloy. At higher temperatures these will diffuse to the grain boundaries and will produce an equilibrium state for the grain size at higher temperatures (thermodynamic stabilization – an equilibrium effect). This would be preferred compared to a kinetic effect, which is not

Consequence of doping mediated strain and the activation energy on the structural and optical properties of ZnO:Cr nanoparticles

International Nuclear Information System (INIS)

Bhargava, Richa; Sharma, Prashant K.; Kumar, Sanjeev; Pandey, Avinash C.; Kumar, Naresh

2010-01-01

We report on the sol-gel synthesis of Zn 1-x Cr x O (x=0.0, 0.05, 0.10, 0.15 and 0.20) nanoparticles. These nanoparticles were characterized by using thermogravimetry/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman and Photoluminescence (PL). Electronegativity of Cr ions (Cr 3+ ) reduces the final decomposition temperature by 40 o C and activation energy of the reaction when Cr is doped into ZnO. Doping of higher Cr concentration (x≥0.10) into ZnO shows formation of secondary spinel (ZnCr 2 O 4 ) phase along with the hexagonal (ZnO) and is revealed by XRD. Formation of secondary phase changes the activation energy of the reaction and thus the strain in ZnO lattice. In Raman spectra, additional Raman modes have been observed for Zn 1-x Cr x O nanoparticles, which can be assigned to the modes generated due to Cr doping. The Cr doping into ZnO is also supported by PL, in which vacancies are formed with Cr ion incorporation and emission band shifts towards higher wavelength. - Graphical abstract: Cr-doped ZnO nanostructures were synthesized by sol-gel. XRD (a) revealed secondary phase of ZnCr 2 O 4 with increase in Cr concentration. The Cr concentration also changes activation energy of the reaction (b).

Distribution of chromium species in a Cr-polluted soil: presence of Cr(III) in glomalin related protein fraction.

Science.gov (United States)

Gil-Cardeza, María L; Ferri, Alejandro; Cornejo, Pablo; Gomez, Elena

2014-09-15

The accumulation of Cr in soil could be highly toxic to human health; therefore Cr soil distribution was studied in rhizosphere soils from Ricinus communis and Conium maculatum and bare soil (BS) from an industrial and urban area in Argentina. Total Cr, Cr(VI) and Cr(III) concentrations were determined in 3 soil fractions: total, extractable and associated to total-glomalin-related protein (T-GRSP). BS had the highest total Cr and total Cr(VI) concentrations. Total Cr(VI) concentration from both rhizosphere soils did not differ from the allowed value for residential area in Argentina (8 μg Cr(VI) g(-1) soil), while total Cr(VI) in BS was 1.8 times higher. Total Cr concentration in all the soils was higher than the allowed value (250 μg Cr g(-1) soil). Extractable and associated to T-GRSP Cr(VI) concentrations were below the detection limit. Cr(III) bound to T-GRSP was the highest in the BS. These findings are in agreement with a long term effect of glomalin in sequestrating Cr. In both plant species, total Cr was higher in root than in shoot and both species presented arbuscular mycorrhizal fungi (AMF). As far as we know, this is the first study that reports the presence of Cr in T-GRSP fraction of soil organic matter. These findings suggest that Cr mycorrhizostabilization could be a predominant mechanism used by R. communis and C. maculatum to diminish Cr soil concentration. Nevertheless, further research is needed to clarify the contribution of native AMF isolated from R. communis and C. maculatum rhizosphere to the Cr phytoremediation process. Copyright © 2014 Elsevier B.V. All rights reserved.

Ground-state energies and highest occupied eigenvalues of atoms in exchange-only density-functional theory

Science.gov (United States)

Li, Yan; Harbola, Manoj K.; Krieger, J. B.; Sahni, Viraht

1989-11-01

The exchange-correlation potential of the Kohn-Sham density-functional theory has recently been interpreted as the work required to move an electron against the electric field of its Fermi-Coulomb hole charge distribution. In this paper we present self-consistent results for ground-state total energies and highest occupied eigenvalues of closed subshell atoms as obtained by this formalism in the exchange-only approximation. The total energies, which are an upper bound, lie within 50 ppm of Hartree-Fock theory for atoms heavier than Be. The highest occupied eigenvalues, as a consequence of this interpretation, approximate well the experimental ionization potentials. In addition, the self-consistently calculated exchange potentials are very close to those of Talman and co-workers [J. D. Talman and W. F. Shadwick, Phys. Rev. A 14, 36 (1976); K. Aashamar, T. M. Luke, and J. D. Talman, At. Data Nucl. Data Tables 22, 443 (1978)].

Correlation of the highest-energy cosmic rays with the positions of nearby active galactic nuclei

NARCIS (Netherlands)

Abraham, J.; Abreu, P.; Aglietta, M.; Aguirre, C.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Alvarez-Muniz, J.; Ambrosio, M.; Anchordoqui, L.; Andringa, S.; Anzalone, A.; Aramo, C.; Argiro, S.; Arisaka, K.; Armengaud, E.; Arneodo, F.; Arqueros, F.; Asch, T.; Asorey, H.; Assis, P.; Atulugama, B. S.; Aublin, J.; Ave, M.; Avila, G.; Baecker, T.; Badagnani, D.; Barbosa, A. F.; Barnhill, D.; Barroso, S. L. C.; Bauleo, P.; Beatty, J. J.; Beau, T.; Becker, B. R.; Becker, K. H.; Bellido, J. A.; BenZvi, S.; Berat, C.; Bergmann, T.; Bernardini, P.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanch-Bigas, O.; Blanco, F.; Blasi, P.; Bleve, C.; Bluemer, H.; Bohacova, M.; Bonifazi, C.; Bonino, R.; Brack, J.; Brogueira, P.; Brown, W. C.; Buchholz, P.; Bueno, A.; Burton, R. E.; Busca, N. G.; Caballero-Mora, K. S.; Cai, B.; Camin, D. V.; Caramete, L.; Caruso, R.; Carvalho, W.; Castellina, A.; Catalano, O.; Cataldi, G.; Cazon, L.; Cester, R.; Chauvin, J.; Chiavassa, A.; Chinellato, J. A.; Chou, A.; Chye, J.; Clay, R. W.; Colombo, E.; Conceicao, R.; Connolly, B.; Contreras, F.; Coppens, J.; Cordier, A.; Cotti, U.; Coutu, S.; Covault, C. E.; Creusot, A.; Criss, A.; Cronin, J.; Curutiu, A.; Dagoret-Campagne, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Donato, C.; Bg, S. J. de Jong; De La Vega, G.; de Mello, W. J. M.; de Mello Neto, J. R. T.; De Mitri, I.; de Souza, V.; del Peral, L.; Deligny, O.; Della Selva, A.; Delle Fratte, C.; Dembinski, H.; Di Giulio, C.; Diaz, J. C.; Diep, P. N.; Dobrigkeit, C.; D'Olivo, J. C.; Dong, P. N.; Dornic, D.; Dorofeev, A.; dos Anjos, J. C.; Dova, M. T.; D'Urso, D.; Dutan, I.; DuVernois, M. A.; Engel, R.; Epele, L.; Escobar, C. O.; Etchegoyen, A.; Luis, P. Facal San; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferrer, F.; Ferry, S.; Fick, B.; Filevich, A.; Filipcic, A.; Fleck, I.; Fracchiolla, C. E.; Fulgione, W.; Garcia, B.; Gaimez, D. Garcia; Garcia-Pinto, D.; Garrido, X.; Geenen, H.; Gelmini, G.; Gemmeke, H.; Ghia, P. L.; Giller, M.; Glass, H.; Gold, M. S.; Golup, G.; Albarracin, F. Gomez; Berisso, M. Gomez; Herrero, R. Gomez; Goncalves, P.; do Amaral, M. Goncalves; Gonzalez, D.; Gonzalezc, J. G.; Gonzalez, M.; Gora, D.; Gorgi, A.; Gouffon, P.; Grassi, V.; Grillo, A. F.; Grunfeld, C.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Gutierrez, J.; Hague, J. D.; Hamilton, J. C.; Hansen, P.; Harari, D.; Harmsma, S.; Harton, J. L.; Haungs, A.; Hauschildt, T.; Healy, M. D.; Hebbeker, T.; Hebrero, G.; Heck, D.; Hojvat, C.; Holmes, V. C.; Homola, P.; Hoerandel, J.; Horneffer, A.; Horvat, M.; Hrabovsky, M.; Huege, T.; Hussain, M.; Larlori, M.; Insolia, A.; Ionita, F.; Italiano, A.; Kaducak, M.; Kampert, K. H.; Karova, T.; Kegl, B.; Keilhauer, B.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Knapik, R.; Knapp, J.; Koanga, V. -H.; Krieger, A.; Kroemer, O.; Kuempel, D.; Kunka, N.; Kusenko, A.; La Rosa, G.; Lachaud, C.; Lago, B. L.; Lebrun, D.; LeBrun, P.; Lee, J.; de Oliveira, M. A. Leigui; Lopez, R.; Letessier-Selvon, A.; Leuthold, M.; Lhenry-Yvon, I.; Aguera, A. Lopez; Bahilo, J. Lozano; Garcia, R. Luna; Maccarone, M. C.; Macolino, C.; Maldera, S.; Mancarella, G.; Mancenido, M. E.; Mandatat, D.; Mantsch, P.; Mariazzi, A. G.; Maris, I. C.; Falcon, H. R. Marquez; Martello, D.; Martinez, J.; Bravo, O. Martinez; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurizio, D.; Mazur, P. O.; McCauley, T.; McEwen, M.; McNeil, R. R.; Medina, M. C.; Medina-Tanco, G.; Meli, A.; Melo, D.; Menichetti, E.; Menschikov, A.; Meurer, Chr.; Meyhandan, R.; Micheletti, M. I.; Miele, G.; Miller, W.; Mollerach, S.; Monasor, M.; Ragaigne, D. Monnier; Montanet, F.; Morales, B.; Morello, C.; Moreno, J. C.; Morris, C.; Mostafa, M.; Muller, M. A.; Mussa, R.; Navarra, G.; Navarro, J. L.; Navas, S.; Necesal, P.; Nellen, L.; Newman-Holmes, C.; Newton, D.; Nhung, P. T.; Nierstenhoefer, N.; Nitz, D.; Nosek, D.; Nozka, L.; Oehlschlaeger, J.; Ohnuki, T.; Olinto, A.; Olmos-Gilbaja, V. M.; Ortiz, M.; Ortolani, F.; Ostapchenko, S.; Otero, L.; Pacheco, N.; Selmi-Dei, D. Pakk; Palatka, M.; Pallotta, J.; Parente, G.; Parizot, E.; Parlati, S.; Pastor, S.; Patel, M.; Paul, T.; Pavlidou, V.; Payet, K.; Pech, M.; Pekala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Petrera, S.; Petrinca, P.; Petrov, Y.; Pichel, A.; Piegaia, R.; Pierog, T.; Pimenta, M.; Pinto, T.; Pirronello, V.; Pisanti, O.; Platino, M.; Pochon, J.; Privitera, P.; Prouza, M.; Quel, E. J.; Rautenberg, J.; Redondo, A.; Reucroft, S.; Revenu, B.; Rezende, F. A. S.; Ridky, J.; Riggi, S.; Risse, M.; Riviere, C.; Rizi, V.; Roberts, M.; Robledo, C.; Rodriguez, G.; Martino, J. Rodriguez; Rojo, J. Rodriguez; Rodriguez-Cabo, I.; Rodriguez-Frias, M. D.; Ros, G.; Rosado, J.; Roth, M.; Rouille-d'Orfeuil, B.; Roulet, E.; Roverok, A. C.; Salamida, F.; Salazar, H.; Salina, G.; Sanchez, F.; Santander, M.; Santo, C. E.; Santos, E. M.; Sarazin, F.; Sarkar, S.; Sato, R.; Scherini, V.; Schieler, H.; Schmidt, A.; Schmidt, F.; Schmidt, T.; Scholten, O.; Schovanek, P.; Schuessler, F.; Sciutto, S. J.; Scuderi, M.; Segreto, A.; Semikoz, D.; Settimo, M.; Shellard, R. C.; Sidelnik, I.; Siffert, B. B.; Sigl, G.; De Grande, N. Smetniansky; Smialkowski, A.; Smida, R.; Smith, A. G. K.; Smith, B. E.; Snow, G. R.; Sokolsky, P.; Sommers, P.; Sorokin, J.; Spinka, H.; Squartini, R.; Strazzeri, E.; Stutz, A.; Suarez, F.; Suomijarvi, T.; Supanitsky, A. D.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Takahashi, J.; Tamashiro, A.; Tamburro, A.; Tascau, O.; Tcaciuc, R.; Thao, N. T.; Thomas, D.; Ticona, R.; Tiffenberg, J.; Timmermans, C.; Tkaczyk, W.; Peixoto, C. J. Todero; Tome, B.; Tonachini, A.; Torres, I.; Travnicek, P.; Tripathi, A.; Tristram, G.; Tscherniakhovski, D.; Tueros, M.; Ulrich, R.; Unger, M.; Urban, M.; Galicia, J. F. Valdes; Valino, I.; Valore, L.; van den Berg, A. M.; van Elewyck, V.; Vazquez, R. A.; Veberic, D.; Veiga, A.; Velarde, A.; Venters, T.; Verzi, V.; Videla, M.; Villasenor, L.; Vorobiov, S.; Voyvodic, L.; Wahlberg, H.; Wainberg, O.; Warner, D.; Watson, A. A.; Westerhoff, S.; Wieczorek, G.; Wiencke, L.; Wilczynska, B.; Wilczynski, H.; Wileman, C.; Winnick, M. G.; Wu, H.; Wundheiler, B.; Yamamoto, T.; Younk, P.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zech, A.; Zepeda, A.; Ziolkowski, M.

Data collected by the Pierre Auger Observatory provide evidence for anisotropy in the arrival directions of the cosmic rays with the highest-energies, which are correlated with the positions of relatively nearby active galactic nuclei (AGN) [Pierre Auger Collaboration, Science 318 (2007) 938]. The

Synthesis and energy transfer studies of LaMgAl{sub 11}O{sub 19}:Cr{sup 3+}, Nd{sup 3+} phosphors

Energy Technology Data Exchange (ETDEWEB)

Zhu, Jicheng; Xia, Zhiguo; Liu, Quanlin, E-mail: qlliu@ustb.edu.cn

2016-02-15

Highlights: • Cr{sup 3+}/Nd{sup 3+} co-doped LaMgAl{sub 11}O{sub 19} phosphors were synthesized. • The energy transfer mechanism is ascribed to the dipole–quadrupole interaction. • The materials can convert the UV–vis light into near-infrared emission. - Abstract: Cr{sup 3+}/Nd{sup 3+} co-activated LaMgAl{sub 11}O{sub 19} phosphors have been synthesized by high temperature solid-state method. In the LaMgAl{sub 11}O{sub 19}:Cr{sup 3+}/Nd{sup 3+} system, Cr{sup 3+} can absorb the UV–vis photons (350–650 nm), and then energy transfer takes place between Cr{sup 3+} and Nd{sup 3+}, and finally the samples give near infrared emission originated from Nd{sup 3+}. Energy transfer from Cr{sup 3+} to Nd{sup 3+} is discussed via the variations of the lifetime values of Cr{sup 3+}, and the mechanism has been ascribed to the dipole–quadrupole interaction. The absorption of Cr{sup 3+} in the visible region and the following energy transfer from Cr{sup 3+} to Nd{sup 3+} indicated that the material can potentially serve as spectral convertors to improve the photovoltaic conversion efficiency of silicon-based solar cell.

Local Energies and Energy Fluctuations — Applied to the High Entropy Alloy CrFeCoNi

Science.gov (United States)

Fukushima, Tetsuya; Katayama-Yoshida, Hiroshi; Sato, Kazunori; Ogura, Masako; Zeller, Rudolf; Dederichs, Peter H.

2017-11-01

High entropy alloys show a variety of fascinating properties like high hardness, wear resistance, corrosion resistance, etc. They are random solid solutions of many components with rather high concentrations. We perform ab-initio calculations for the high entropy alloy CrFeCoNi, which equal concentration of 25% for each element. By the KKRnano program package, which is based on an order-N screened Korringa-Kohn-Rostoker Green's function method, we consider a face-centered cubic (FCC) supercell with 1372 randomly distributed elements, and in addition also smaller supercells with 500 and 256 atoms. It is found from our calculations that the local moments of the Cr atoms show a large environmental variation, ranging from -1.70 μB to +1.01 μB with an average of about -0.51 μB. We present a new method to calculate "local energies" of all atoms. This is based on the partitioning of the whole space into Voronoi cells and allows to calculate the energetic contribution of each atomic cell to the total energy of the supercell. The supercell calculations show very large variations of the local energies, analogous to the variations of the local moments. This shows that the random solid solution is not stable and has a tendency to form an L12-structure with the Cr-atoms ordered at the corner of the cube and the elements Fe, Co, and Ni randomly distributed on the three other FCC sublattices. For this structure the variation of the local moments are much smaller.

Academic Training - Tevatron: studying pp collisions at the highest energy

CERN Multimedia

2006-01-01

ACADEMIC TRAINING LECTURE SERIES 15, 16, 17, 18 May Main Auditorium, bldg. 500 on 15, 16, 17 May - Council Chamber on 18 May Physics at the Tevatron B. HEINEMANN, Univ. of Liverpool, FERMILAB Physics Results from the Tevatron The Tevatron proton-antiproton collider at Fermilab in the US is currently the world's highest energy collider. At the experiments CDF and D0 a broad physics programme is being pursued, ranging from flavour physics via electroweak precision measurements to searches for the Higgs boson and new particles beyond the Standard Model. In my lecture I will describe some of the highlight measurements in the flavour, electroweak and searches sectors, and the experimental techniques that are used. ENSEIGNEMENT ACADEMIQUE ACADEMIC TRAINING Françoise Benz 73127 academic.training@cern.ch If you wish to participate in one of the following courses, please tell to your supervisor and apply electronically from the course description pages that can be found on the Web at: http://www.cern.ch/...

Structural, electrical, and dielectric properties of Cr doped ZnO thin films: Role of Cr concentration

Energy Technology Data Exchange (ETDEWEB)

Gürbüz, Osman, E-mail: osgurbuz@yildiz.edu.tr; Okutan, Mustafa

2016-11-30

Highlights: • Magnetic material of Cr and semiconductor material of ZnO were grown by the magnetron sputtering co-sputter technique. • Perfect single crystalline structures were grown. • DC and AC conductivity with dielectric properties as a function of frequency (f = 5Hz–13 MHz) at room temperature were measured and compared. • Cr doped ZnO can be used in microwave, sensor and optoelectronic devices as the electrical conductivity increases while dielectric constant decreases with the Cr content. - Abstract: An undoped zinc oxide (ZnO) and different concentrations of chromium (Cr) doped ZnO Cr{sub x}ZnO{sub 1−x} (x = 3.74, 5.67, 8.10, 11.88, and 15.96) thin films were prepared using a magnetron sputtering technique at room temperature. These films were characterized by X-ray diffraction (XRD), High resolution scanning electron microscope (HR-SEM), and Energy dispersive X-ray spectrometry (EDS). XRD patterns of all the films showed that the films possess crystalline structure with preferred orientation along the (100) crystal plane. The average crystallite size obtained was found to be between 95 and 83 nm which was beneficial in high intensity recording peak. Both crystal quality and crystallite sizes decrease with increasing Cr concentration. The crystal and grain sizes of the all film were investigated using SEM analysis. The surface morphology that is grain size changes with increase Cr concentration and small grains coalesce together to form larger grains for the Cr{sub 11.88}ZnO and Cr{sub 15.96}ZnO samples. Impedance spectroscopy studies were carried out in the frequencies ranging from 5 Hz to 13 MHz at room temperature. The undoped ZnO film had the highest dielectric value, while dielectric values of other films decreased as doping concentrations increased. Besides, the dielectric constants decreased whereas the loss tangents increased with increasing Cr content. This was considered to be related to the reduction of grain size as Cr content in Zn

Some characteristics of the CR-39 solid state nuclear-track detector for protons and low energy alpha particles

International Nuclear Information System (INIS)

Fonseca, E.S. da.

1983-01-01

Experimental results related to certain registration properties of the CR-39 solid state nuclear-track detector for charged particles are presented and discussed. The determination of the CR-39 chemical etching in NaOH and KOH solutions, comprising concentration (2-10N) and temperature effects (50-90 0 C), showed the existence of an inverse proportion between the induction time and the temperature as well as the normal concentration of the solutions. The critical energy and the critical energy-loss rate of CR-39 track detectors for registration of protons were experimentally determined. A number of samples was exposed to 24MeV proton beams in the IEN-CNEN Cyclotron (CV-28), using a scattering chamber with a tantalum thin target and aluminium absorbers in contact with the samples in order to provide the required fluctuation in the scattered beam energy. From the mean track-diameter plotted against incident proton energy for 16h and 24h chemical etching (6.25 NaOH, 70 0 C), and considering 1.5 μm as the minimum observable track-diameter, the values (21.0 + - 1.5) MeV and (22.5 + - 1.5) MeV were deduced, respectively, for the critical energy. From the calculated energy-loss rate versus energy curve, the critical energy-loss rate was evaluated as 24 + - 2 MeV.cm 2 /g. Finally, the CR-39 response for low energy alpha particles (E [pt

Beam profile measurement with CR-39 track detector for low-energy ions

CERN Document Server

Sato, F; Tanaka, T; Iida, T; Yamauchi, T; Oda, K

1999-01-01

A CR-39 track detector was successfully used to measure the outline of thin low-energy ion beams. After the etching, the surface of the detector was examined with an observation system composed of a Normarski microscope, a CCD camera and a digital image processing computer. Beam images obtained with the system were in good agreement on the outline of the beam formed with a beam aperture. Also, the resolving power in the beam outline measurement was roughly explained from the consideration of the ion range and the etch-pit growth in the chemical etching for the CR-39 detector.

Challenges for highest energy circular colliders

CERN Document Server

Benedikt, M; Wenninger, J; Zimmermann, F

2014-01-01

A new tunnel of 80–100 km circumference could host a 100 TeV centre-of-mass energy-frontier proton collider (FCC-hh/VHE-LHC), with a circular lepton collider (FCCee/TLEP) as potential intermediate step, and a leptonhadron collider (FCC-he) as additional option. FCC-ee, operating at four different energies for precision physics of the Z, W, and Higgs boson and the top quark, represents a significant push in terms of technology and design parameters. Pertinent R&D efforts include the RF system, topup injection scheme, optics design for arcs and final focus, effects of beamstrahlung, beam polarization, energy calibration, and power consumption. FCC-hh faces other challenges, such as high-field magnet design, machine protection and effective handling of large synchrotron radiation power in a superconducting machine. All these issues are being addressed by a global FCC collaboration. A parallel design study in China prepares for a similar, but smaller collider, called CepC/SppC.

Structural, thermal, and photoacoustic study of nanocrystalline Cr{sub 3}Ge produced by mechanical alloying

Energy Technology Data Exchange (ETDEWEB)

Prates, P. B.; Maliska, A. M.; Ferreira, A. S. [Departamento de Engenharia Mecânica, Universidade Federal de Santa Catarina, Campus Universitário Trindade, S/N, C.P. 476, 88040-900 Florianópolis, Santa Catarina (Brazil); Poffo, C. M. [Universidade Federal de Santa Catarina, Campus de Araranguá, 88900-000 Araranguá, Santa Catarina (Brazil); Borges, Z. V. [Departamento de Física, Universidade Federal do Amazonas, 3000 Japiim, 69077-000 Manaus, Amazonas (Brazil); Lima, J. C. de, E-mail: fsc1jcd@fisica.ufsc.br [Departamento de Física, Universidade Federal de Santa Catarina, Campus Universitário Trindade, S/N, C.P. 476, 88040-900 Florianópolis, Santa Catarina (Brazil); Biasi, R. S. de [Seção de Engenharia Mecânica e de Materiais, Instituto Militar de Engenharia, 22290-270 Rio de Janeiro (Brazil)

2015-10-21

A thermodynamic analysis of the Cr-Ge system suggested that it was possible to produce a nanostructured Cr{sub 3}Ge phase by mechanical alloying. The same analysis showed that, due to low activation energies, Cr-poor crystalline and/or amorphous alloy could also be formed. In fact, when the experiment was performed, Cr{sub 11}Ge{sub 19} and amorphous phases were present for small milling times. For milling times larger than 15 h these additional phases decomposed and only the nanostructured Cr{sub 3}Ge phase remained up to the highest milling time used (32 h). From the differential scanning calorimetry measurements, the Avrami exponent n was obtained, indicating that the nucleation and growth of the nanostructured Cr{sub 3}Ge phase may be restricted to one or two dimensions, where the Cr and Ge atoms diffuse along the surface and grain boundaries. In addition, contributions from three-dimensional diffusion with a constant nucleation rate may be present. The thermal diffusivity of the nanostructured Cr{sub 3}Ge phase was determined by photoacoustic absorption spectroscopy measurements.

Study of the V{sup 51} (p,n)Cr{sup 51} reaction and the energy levels in Cr{sup 51}; Etude de la reaction {sup 51}V (p,n){sup 51}Cr et contribution a la spectroscopie de {sup 51}Cr

Energy Technology Data Exchange (ETDEWEB)

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

1966-07-01

Neutrons and gamma rays from the reaction {sup 51}V(p,n){sup 51}Cr have been studied between 2.3 and 5.1 MeV Energy levels of {sup 51}Cr at 0.75, 1.15, 1.35, 1.47 and 1.56 MeV and unresolved levels at 1.94, 2.4, 2.75 and 2.9 MeV are observed. The gamma ray cascades of the low-lying states of {sup 51}Cr up to 2.5 MeV excitation energy have been completely determined through coincidence measurements. From the cascade ratios and gamma ray yields, excitation functions for the {sup 51}V(p,n){sup 51}Cr reactions, leading to the five lowest levels of {sup 51}Cr have been obtained from reaction threshold to 4.6 MeV. The analysis of cross section fluctuations with good resolution shows they are due to the excitation of unresolved compound nucleus isolated resonances. From the decay scheme and an Hauser-Feshbach calculation of the {sup 51}V(p,n) excitation functions, spin assignments of 3/2{sup -}, or 5/2{sup -} (0.75 MeV), 7/2{sup -} (1.15 MeV), 3/2{sup -} (1.35 MeV), 5/2{sup -} (1.47 MeV) are proposed. (author) [French] La reaction {sup 51}V(p,n){sup 51}Cr a ete etudiee entre 2,3 et 5,1 MeV en detectant les neutrons et le rayonnement gamma de desexcitation des niveaux de {sup 51}Cr a 0,75, 1,15, 1,35, 1,47 et 1,56 MeV et de groupes non resolus de niveaux a 1,94, 2,4, 2,75 et 2,9 MeV. Des mesures de coincidence ont permis de determiner completement les desexcitations en cascade dans {sup 51}Cr jusqu'a 2,5 MeV et d'etablir, a partir des mesures de rayonnement gamma, les fonctions d'excitation des reactions {sup 51}V(p,n){sup 51}Cr formant les cinq premiers niveaux de {sup 51}Cr depuis le seuil jusqu'a 4,6 MeV. L'analyse en bonne resolution des fluctuations observees sur les sections efficaces montrent qu'elles sont dues a des resonances isolees du noyau compose non resolubles dans cette experience. Le schema de desexcitation de {sup 51}Cr et un calcul Hauser-Feshbach des fonctions d'excitation conduisent a proposer les spins suivants: 3/2{sup -} ou 5/2{sup -} pour le niveau

Liquidus projection of the Nb-Cr-Al system near the Al3(Nb,Cr) + Cr(Al,Nb) eutectic region

International Nuclear Information System (INIS)

Souza, S.A.; Ferrandini, P.L.; Nunes, C.A.; Coelho, A.A.; Caram, R.

2006-01-01

The system Nb-Cr-Al was investigated in the region near the Al 3 (Nb,Cr) + Cr(Al,Nb) eutectic and the liquidus projection of that region was determined based on the microstructural characterization of arc melted alloys. The characterization utilized scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential thermal analysis (DTA) and X-ray diffraction (XRD). The results allowed one to determine three primary solidification liquidus surfaces ((Cr,Al) 2 Nb, Cr(Al,Nb) and Al 3 (Nb,Cr)), that are originated from the binary systems Cr-Nb, Cr-Al and Al-Nb. It is proposed the occurrence of the invariant reaction L + (Cr,Al) 2 Nb ↔ Al 3 (Nb,Cr) + Cr(Al,Nb) and of a point of minimum, which involves a three phase reaction, L ↔ Al 3 (Nb,Cr) + Cr(Al,Nb). All alloys studied showed formation of the Al 3 (Nb,Cr) + Cr(Al,Nb) eutectic as the last solidification step with Al(Nb)Cr 2 precipitating from Cr(Al,Nb)

In silico CrNF, a half-metallic ferromagnetic nitride–fluoride mimicking CrO2

International Nuclear Information System (INIS)

Matar, Samir F.

2014-01-01

Isoelectronic with CrO 2 , CrNF is proposed in silico based on rutile derived structures with DFT computations. The ground state structure defined from cohesive energies is of MgUO 4 -type, characterized by short covalent Cr–N and long ionic Cr–F distances. Like CrO 2 it is a half-metallic ferromagnet with M=2 μ B /FU integer magnetization with reduced band gap at minority spins. Major difference of magnetic response to pressure characterizes CrNF as a soft ferromagnet versus hard magnetic CrO 2 . The chemical bonding properties point to prevailing covalent Cr–N versus ionic Cr–F bonding. Different synthesis routes are examined. - Highlights: • DFT identification of CrNF is based on isoelectronicity and rutile derivatives. • Similarly to CrO 2 , CrNF is a half-metallic ferromagnet with reduced band gap. • Strong pressure dependence of magnetization of CrNF oppositely to CrO 2 . • Covalent Cr–N bonding prevails in spite of the presence of ionic Cr–F. • Cohesive energies favor the synthesis for which protocols are proposed

Gibbs free energy difference between the undercooled liquid and the beta phase of a Ti-Cr alloy

Science.gov (United States)

Ohsaka, K.; Trinh, E. H.; Holzer, J. C.; Johnson, W. L.

1992-01-01

The heat of fusion and the specific heats of the solid and liquid have been experimentally determined for a Ti60Cr40 alloy. The data are used to evaluate the Gibbs free energy difference, delta-G, between the liquid and the beta phase as a function of temperature to verify a reported spontaneous vitrification (SV) of the beta phase in Ti-Cr alloys. The results show that SV of an undistorted beta phase in the Ti60Cr40 alloy at 873 K is not feasible because delta-G is positive at the temperature. However, delta-G may become negative with additional excess free energy to the beta phase in the form of defects.

Some characteristics of the CR-39 solid state nuclear - Track Detector for register of protons and low energy alpha particles

International Nuclear Information System (INIS)

Fonseca, E.S. da.

1983-01-01

Experimental results related to registration properties of the CR-39 Solid State Nuclear Track Detector for charged particles are presented and discussed. The existence of an inverse proportion between the induction time and the temperature as well as normal concentration of solutions, is showed by the study of CR-39 chemical etching characteristics in NaOH and KOH solutions, comprising varied concentration and temperature. The bulk-etch rate and activation energy of the process were obtained. The critical energy and critical energy-loss rate of CR-39 track-detectors for registration of protons were experimentally determined. Samples were exposed to 24 Mev proton beams in the IEN/CNEN Cyclotron (CV-28), using scattering chamber with a tantalum thin target and aluminium absorbers in contact with the samples, in order to provide the required fluctuation in the scattered beam energy. From the mean track-diameter plotted against incident proton energy the critical energy was obtained. From the calculated energy-loss rate vs. energy curve, the critical energy loss rate were evaluated. The CR-39 response for low energy alpha particles (E = 7h) under the conditions of 6.25 N NaOH at 70 0 C. It is shown that successive chemical etchings do not produce the same track geometry as obtained by means of a continous revelation with the same total etching time. (Author) [pt

Electronic structure of metastable bcc Cu–Cr alloy thin films: Comparison of electron energy-loss spectroscopy and first-principles calculations

Energy Technology Data Exchange (ETDEWEB)

Liebscher, C.H.; Freysoldt, C. [Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf (Germany); Dennenwaldt, T. [Institute of Condensed Matter Physics and Interdisciplinary Center for Electron Microscopy, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne (Switzerland); Harzer, T.P.; Dehm, G. [Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf (Germany)

2017-07-15

Metastable Cu–Cr alloy thin films with nominal thickness of 300 nm and composition of Cu{sub 67}Cr{sub 33} (at%) are obtained by co-evaporation using molecular beam epitaxy. The microstructure, chemical phase separation and electronic structure are investigated by transmission electron microscopy (TEM). The thin film adopts the body-centered cubic crystal structure and consists of columnar grains with ~50 nm diameter. Aberration-corrected scanning TEM in combination with energy dispersive X-ray spectroscopy confirms compositional fluctuations within the grains. Cu- and Cr-rich domains with composition of Cu{sub 85}Cr{sub 15} (at%) and Cu{sub 42}Cr{sub 58} (at%) and domain size of 1–5 nm are observed. The alignment of the interface between the Cu- and Cr-rich domains shows a preference for {110}-type habit plane. The electronic structure of the Cu–Cr thin films is investigated by electron energy loss spectroscopy (EELS) and is contrasted to an fcc-Cu reference sample. The experimental EEL spectra are compared to spectra computed by density functional theory. The main differences between bcc-and fcc-Cu are related to differences in van Hove singularities in the electron density of states. In Cu–Cr solid solutions with bcc crystal structure a single peak after the L{sub 3}-edge, corresponding to a van Hove singularity at the N-point of the first Brillouin zone is observed. Spectra computed for pure bcc-Cu and random Cu–Cr solid solutions with 10 at% Cr confirm the experimental observations. The calculated spectrum for a perfect Cu{sub 50}Cr{sub 50} (at%) random structure shows a shift in the van Hove singularity towards higher energy by developing a Cu–Cr d-band that lies between the delocalized d-bands of Cu and Cr. - Highlights: • Compositional fluctuations on the order of 1–5 nm in Cu- and Cr-rich domains are observed. • EELS determines a single van Hove singularity for bcc Cu–Cr solid solutions. • The electronic structure is dominated by d

Pr{sup 3+1}S{sub 0}->Cr{sup 3+} energy transfer and ESR investigation in Pr{sup 3+} and Cr{sup 3+} activated SrAl{sub 12}O{sub 19} quantum cutting phosphor

Energy Technology Data Exchange (ETDEWEB)

Nie Zhaogang [BK21 Physics Program and Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Lim, Ki-Soo, E-mail: kslim@chungbuk.ac.k [BK21 Physics Program and Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Zhang Jiahua [Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Wang Xiaojun [Department of Physics, Georgia Southern University, Statesboro, GA 30460 (United States)

2009-08-15

With the help of the Dexter's theory, the energy transfer mechanism from Pr{sup 3+1}S{sub 0} to Cr{sup 3+} is investigated theoretically in SrAl{sub 12}O{sub 19}:Pr{sup 3+}, Cr{sup 3+} quantum cutting phosphors. The electron spin resonance (ESR) spectra of Pr{sup 3+} and Cr{sup 3+}-doped SrAl{sub 12}O{sub 19} with magnetoplumbite structure have been studied. The Cr{sup 3+} ion is found to enter the Al4(4f) site, which is very close to the Sr(2d) site replaced by the Pr{sup 3+} ions in the host. The theoretical results indicate that the efficient Pr{sup 3+1}S{sub 0}->Cr{sup 3+} energy transfer can only take place in the intermediate mirror planes, in which for the nearest and next-nearest Pr{sup 3+}-Cr{sup 3+} pairs, both dipole-dipole and dipole-quadrupole interactions can play their parts in the transfer. Finally, an overview is given about the research on the energy transfer from Pr{sup 3+1}S{sub 0} to codopants in their co-doped materials.

Activation energy of etching for CR-39 as a function of linear energy transfer of the incident particles

CERN Document Server

Awad, E M

1999-01-01

In this work, we have studied the effect of the radiation damage caused by the incident particles on the activation energy of etching for CR-39 samples. The damage produced by the incident particle is expressed in terms of the linear energy transfer (LET). CR-39 samples from American Acrylic were irradiated to three different LET particles. These are N (LET sub 2 sub 0 sub 0 = 20 KeV/mu m) as a light particle, Fe (LET sub 2 sub 0 sub 0 = 110 KeV/mu m) as a medium particle and fission fragments (ff) from a sup 2 sup 5 sup 2 Cf source as heavy particles. In general the bulk etch rate was calculated using the weight difference method and the track etch rate was determined using the track geometry at various temperatures (50-90 deg. C) and concentrations (4-9 N) of the NaOH etchant. The average activation energy E sub b related to the bulk etch rate v sub b was calculated from 1n v sub b vs. 1/T. The average activation energy E sub t related to the track etch rate v sub t was estimated from 1n v sub t vs. 1/T. It...

Thermodynamic analysis of Cr(VI) extraction using TOPO impregnated membranes

Energy Technology Data Exchange (ETDEWEB)

Praveen, Prashant; Loh, Kai-Chee, E-mail: chelohkc@nus.edu.sg

2016-08-15

Highlights: • Cr(VI) extraction by extractant impregnated membranes (EIM) was investigated. • EIM exhibited high extraction efficiency, mass transfer rate and stability. • Mass transfer mechanism was proposed based on kinetics and equilibrium data. • Uptake of Cr(VI) by EIMs was endothermic and spontaneous. • Cr(VI) extraction by EIMs was dominated by physical interactions. - Abstract: Solid/liquid extraction of Cr(VI) was accomplished using trioctylphosphine oxide impregnated polypropylene hollow fiber membranes. Extraction of 100–500 mg/L Cr(VI) by the extractant impregnated membranes (EIM) was characterized by high uptake rate and capacity, and equilibrium was attained within 45 min of contact. Extraction equilibrium was pH-dependent (at an optimal pH 2), whereas stripping using 0.2 M sodium hydroxide yielded the highest recovery of 98% within 60 min. The distribution coefficient was independent of initial Cr(VI) concentration, and the linear distribution equilibrium isotherm could be modeled using Freundlich isotherm. The mass transfer kinetics of Cr(VI) was examined using pseudo-second-order and intraparticle diffusion models and a mass transfer mechanism was deduced. The distribution coefficient increased with temperature, which indicated endothermic nature of the reaction. Enthalpy and entropy change during Cr(VI) extraction were positive and varied in the range of 37–49 kJ/mol and 114–155 J/mol, respectively. The free energy change was negative, confirming the feasibility and spontaneity of the mass transfer process. Results obtained suggest that EIMs are efficient and sustainable for extraction of Cr(VI) from wastewater.

Cr and Yb markers determination in animal feces by energy dispersive X-ray fluorescence

International Nuclear Information System (INIS)

Almeida, Eduardo de; Senicato, Luis A; Nascimento Filho, Virgilio F.; Gomide, Catarina A.

2007-01-01

Chromium and Ytterbium elements are utilized in animal nutritional studies as markers. This paper describes an analytical method for Cr and Yb determination in solid buffalo feces sample using standard addition method and energy dispersive X-ray spectrometry (EDXRF) technique. One gram dried sample was pressed manually in an XRF sample cup with Mylar film (6.3 μm thickness) in the bottom. The experimental conditions were: Mo target X-ray tube with Zr filter, operated at 25 kV/10 mA, and 500 s of acquisition time. The limits of detection for Cr and Yb were 16.6 and 11.4 mg/kg, respectively. This methodology has showed appropriated for simultaneous Cr and Yb determination as marker in animal feces. (author)

Cr and Yb markers determination in animal feces by energy dispersive X-ray fluorescence

Energy Technology Data Exchange (ETDEWEB)

Almeida, Eduardo de; Senicato, Luis A; Nascimento Filho, Virgilio F. [Centro de Energia Nuclear na Agricultura (CENA), Piracicaba, SP (Brazil). Lab. de Instrumentacao Nuclear (LIN)]. E-mail: edualm@usp.br; Gomide, Catarina A. [Universidade de Sao Paulo (USP), Pirassununga, SP (Brazil). Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Dept. de Zootecnia]. E-mail: cbgomide@usp.br

2007-07-01

Chromium and Ytterbium elements are utilized in animal nutritional studies as markers. This paper describes an analytical method for Cr and Yb determination in solid buffalo feces sample using standard addition method and energy dispersive X-ray spectrometry (EDXRF) technique. One gram dried sample was pressed manually in an XRF sample cup with Mylar film (6.3 {mu}m thickness) in the bottom. The experimental conditions were: Mo target X-ray tube with Zr filter, operated at 25 kV/10 mA, and 500 s of acquisition time. The limits of detection for Cr and Yb were 16.6 and 11.4 mg/kg, respectively. This methodology has showed appropriated for simultaneous Cr and Yb determination as marker in animal feces. (author)

Microstructure and morphology of powder particles TiC-NiCr, synthesized in plasma jet, at high-energy actions on components of initial composition Ti-C-NiCr

Science.gov (United States)

Solonenko, Oleg P.; Smirnov, Andrey V.; Chesnokov, Anton E.

2017-10-01

The results of experiments on in-situ synthesis of the microspherical, in particular hollow, cermet powder TiC- 30vol.%NiCr at processing of the Ti-C-NiCr agglomerates in argon-helium plasma jet flowing out into controlled atmosphere are presented. Preparation of the agglomerates consisted of the following stages: (i) high-energy treatment of the initial powders Ti and NiCr in planetary mill with their subsequent uniform mixing with glass black powder, (ii) preparation of dough from mechanically mixed powders and binder, and their granulation using the extrusion method, (iii) drying and classification of granules by the sizes.

Partial decay energy of 51Cr from inner bremsstrahlung spectrum

International Nuclear Information System (INIS)

Sanjeeviah, H.; Sanjeevaiah, B.

1980-01-01

The inner bremsstrahlung spectrum accompanying orbital electron capture decay of 51 Cr to the first excited state in 51 V was measured in coincidence with 320 keV gamma rays. From the Jauch plot of the spectrum the partial decay energy was deduced to be 433 +- 18 keV in good agreement with the previously measured value and the accepted mass difference. The overall shape factor of the inner bremsstrahlung spectrum was found to be a constant X(1.1 +- 0.1). (author)

On the possibility of highest energy cosmic rays bursts and their correlation with gamma rays bursts e.g. March 5th, 1979 event

International Nuclear Information System (INIS)

Drukier, K.

1982-01-01

The avalanche production of magnetic monopoles is possible in neutron stars. Big part of the magnetic field energy can be used to accelerate a pulse of 10 30 monopoles to the energy E > approximately 10 17 eV. Thus the neutron stars may be ''point'' sources of bursts of highest energy Cosmic Rays. The emission of brehmsstrahlung photons by these highly relativistic monopoles would be seen as X and gamma bursts. This ''exotic'' model for March 5th, 1979 event, predicts that it has been followed by burst of highest energy Cosmic Rays coming from the direction of LMC supernovae remanent N49

Correlation between bulk- and surface chemistry of Cr-tanned leather and the release of Cr(III) and Cr(VI).

Science.gov (United States)

Hedberg, Yolanda S; Lidén, Carola; Odnevall Wallinder, Inger

2014-09-15

About 1-3% of the adult general population in Europe is allergic to chromium (Cr). The assessment of the potential release of Cr(III) and Cr(VI) from leather is hence important from a human health and environmental risk perspective. The Cr(VI) content in leather was recently restricted in the European Union. The aim of this study was to assess possible correlations between the bulk and surface chemistry of leather, released Cr(III) and Cr(VI), and capacities of co-released leather specific species to reduce and complex released Cr. Four differently tanned leathers were characterized by scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and the diphenylcarbazide colorimetric method. Their characteristics were compared with results on Cr(III) and Cr(VI) release into artificial sweat (ASW, pHleather-specific species were shown to reduce Cr(VI), both in ASW and in PB. Their reduction capacities correlated with findings of the surface content of Cr and of released Cr. Leather samples without this capacity, and with less aromatic surface groups visible by ATR-FTIR, revealed Cr(VI) both at the surface and in solution (PB). Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Temperature dependence of optical properties in Nd/Cr:YAG materials

International Nuclear Information System (INIS)

Honda, Yoshiyuki; Motokoshi, Shinji; Jitsuno, Takahisa; Miyanaga, Noriaki; Fujioka, Kana; Nakatsuka, Masahiro; Yoshida, Minoru

2014-01-01

The energy transfer from Cr 3+ to Nd 3+ for Nd/Cr:YAG (Nd: 1.0%, Cr: 2.0%) materials was investigated by measuring the temperature dependences of fluorescence characteristics. The fluorescence intensity of Nd 3+ increased with temperature owing to enhancement of the absorption coefficient of Cr 3+ . The energy transfer efficiency was constant from 77 to 450 K. The energy transfer time decreased with increasing temperature. -- Highlights: • We investigate the energy transfer from Cr 3+ to Nd 3+ in Nd/Cr:YAG materials by measuring the temperature dependence of fluorescence characteristics. • The fluorescence intensity of Nd 3+ increased with temperature owing to enhancement of the absorption coefficient of Cr 3+ . • The energy transfer efficiency was constant from 77 to 450 K. • The energy transfer time decreased with increasing temperature. • Nd/Cr:YAG ceramics pumped by a flash lamp would not only provide high conversion efficiency, but can also be expected to function as an effective laser operating at high temperature

Electron energy loss spectroscopy of CH3N2CH3 adsorbed on Ni(100), Ni(111), Cr(100), Cr(111)

International Nuclear Information System (INIS)

Schulz, M.A.

1985-07-01

A study of the adsorption of CH 3 N 2 CH 3 on Ni(100), Ni(111), Cr(100), and Cr(111) using high resolution electron energy loss spectroscopy (EELS) is presented. Under approximately the same conditions of coverage, the vibrational spectra of CH 3 N 2 CH 3 on these four surfaces are quite distinct from one another, implying that the CH 3 N 2 CH 3 -substrate interaction is very sensitive to the physical and electronic structure of each surface. In addition to the room temperature studies, the evolution of surface species on the Ni(100) surface in the temperature range 300 to 425 K was studied. Analysis of the Ni(100) spectra indicates that molecular adsorption, probably through the N lone pair, occurs at room temperature. Spectra taken after annealing the CH 3 N 2 CH 3 -Ni(100) surfaces indicate that CH and CN bond scission occurred at the elevated temperatures. Decomposition of CH 3 N 2 CH 3 takes place on the Ni(111), Cr(100), and Cr(111) surfaces at room temperature, as evidenced by the intensity of the carbon-metal stretch in the corresponding spectra. Possible identities of coadsorbed dissociation products are considered. The stable coverage of surface species on all four surfaces at 300 K is less than one monolayer. A general description of an electron energy loss (EEL) spectrometer is given. Followed by a more specific discussion of some recent modifications to the EEL monochromator assembly used in this laboratory. Both the previous configuration of our monochromator and the new version are briefly described, as an aid to understanding the motivation for the changes as well as the differences in operation of the two versions. For clarity, the new monochromator design is referred to as variable pass, while the previous design is referred to as double pass. A modified tuning procedure for the new monochromator is also presented. 58 refs., 11 figs

Enhancement of the Corrosion Resistance of 304 Stainless Steel by Cr–N and Cr(N,O Coatings

Directory of Open Access Journals (Sweden)

Mihaela Dinu

2018-04-01

Full Text Available Chromium nitride and oxynitride coatings were deposited as monolayers ((Cr–N, Cr(N,O and bilayers (Cr–N/Cr(N,O, Cr(N,O/Cr–N on 304 steel substrates by reactive cathodic arc method. The coatings were characterised by X-ray diffraction (XRD, scanning electron microscopy (SEM, energy dispersive X-ray spectrometry (EDS, surface profilometry, and scratch tester. The anticorrosive properties of the coatings were assessed by electrochemical tests in 0.10 M NaCl + 1.96 M H2O2, carried out at 24 °C. Cr2N, CrN, and Cr(N,O phases were identified in the coatings by grazing incidence X-ray diffraction (GI-XRD measurements. The measured adhesion values ranged from 19 N to 35 N, the highest value being obtained for the bilayer with Cr(N,O on top. Electrochemical tests showed that Cr(N,O presence in both mono- and bilayered coatings determined the lowest damage in corrosive solution, as compared to the Cr–N coatings. This improvement was ascribed to the more compact structure, lower coatings porosity, and smoother surface.

Golden mean energy equals highest atomic electron orbital energy

Energy Technology Data Exchange (ETDEWEB)

Malinowski, Leonard J. [Interdisciplinary Research Club, P.O. Box 371, Monroeville, PA 15146 (United States)], E-mail: LJMalinowski@gmail.com

2009-12-15

The golden mean numerical value {phi} = 0.5({radical}5 - 1) has been given a physical manifestation through E infinity theory. This short paper relates the golden mean energy 0.618034 MeV to atomic electron orbitals.

Golden mean energy equals highest atomic electron orbital energy

International Nuclear Information System (INIS)

Malinowski, Leonard J.

2009-01-01

The golden mean numerical value φ = 0.5(√5 - 1) has been given a physical manifestation through E infinity theory. This short paper relates the golden mean energy 0.618034 MeV to atomic electron orbitals.

Analysis of the highest transverse energy events seen in the UAl detector at the Spp-barS collider

International Nuclear Information System (INIS)

1987-06-01

The first full solid angle analysis is presented of large transverse energy events in pp-bar collisions at the CERN collider. Events with transverse energies in excess of 200 GeV at √s = 630 GeV are studied for any non-standard physics and quantitatively compared with expectations from perturbative QCD Monte Carlo models. A corrected differential cross section is presented. A detailed examination is made of jet profiles, event jet multiplicities and the fraction of the transverse energy carried by the two jets with the highest transverse jet energies. There is good agreement with standard theory for events with transverse energies up to the largest observed values (approx. √s/2) and the analysis shows no evidence for any non-QCD mechanism to account for the event characteristics. (author)

Correlation between bulk- and surface chemistry of Cr-tanned leather and the release of Cr(III) and Cr(VI)

Energy Technology Data Exchange (ETDEWEB)

Hedberg, Yolanda S., E-mail: yolanda@kth.se [KTH Royal Institute of Technology, School of Chemical Science and Engineering, Department of Chemistry, Division of Surface and Corrosion Science, SE-10044 Stockholm (Sweden); Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-17177 Stockholm (Sweden); Lidén, Carola, E-mail: carola.liden@ki.se [Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-17177 Stockholm (Sweden); Odnevall Wallinder, Inger, E-mail: ingero@kth.se [KTH Royal Institute of Technology, School of Chemical Science and Engineering, Department of Chemistry, Division of Surface and Corrosion Science, SE-10044 Stockholm (Sweden)

2014-09-15

Graphical abstract: - Highlights: • Released reducing/complexing leather-specific species can reduce released Cr(VI). • No co-released species enable the formation of Cr(VI) in solution. • The major Cr species released from leather in phosphate buffer was Cr(III) (>82%). • No Cr(VI) was released into artificial sweat. - Abstract: About 1–3% of the adult general population in Europe is allergic to chromium (Cr). The assessment of the potential release of Cr(III) and Cr(VI) from leather is hence important from a human health and environmental risk perspective. The Cr(VI) content in leather was recently restricted in the European Union. The aim of this study was to assess possible correlations between the bulk and surface chemistry of leather, released Cr(III) and Cr(VI), and capacities of co-released leather specific species to reduce and complex released Cr. Four differently tanned leathers were characterized by scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and the diphenylcarbazide colorimetric method. Their characteristics were compared with results on Cr(III) and Cr(VI) release into artificial sweat (ASW, pH < 6.5) and phosphate buffer (PB, pH 7.5–8.0), measured by means of spectrophotometry and atomic absorption spectroscopy. Co-released leather-specific species were shown to reduce Cr(VI), both in ASW and in PB. Their reduction capacities correlated with findings of the surface content of Cr and of released Cr. Leather samples without this capacity, and with less aromatic surface groups visible by ATR-FTIR, revealed Cr(VI) both at the surface and in solution (PB)

Modeling on Fe-Cr microstructure: evolution with Cr content

International Nuclear Information System (INIS)

Diaz Arroyo, D.; Perlado, J.M.; Hernandez-Mayoral, M.; Caturla, M.J.; Victoria, M.

2007-01-01

Full text of publication follows: The minimum energy configuration of interstitials in the Fe-Cr system, which is the base for the low activation steels being developed in the European fusion reactor materials community, is determined by magnetism. Magnetism plays also a role in the atomic configurations found with increasing Cr content. Results will be presented from a program in which the microstructure evolution produced after heavy ion irradiation in the range from room temperature to 80 K is studied as a function of the Cr content in alloys produced under well controlled conditions, i.e. from high purity elements and with adequate heat treatment. It is expected that these measurements will serve as matrix for model validation. The first step in such modeling sequence is being performed by modeling the evolution of displacement cascades in Fe using the Dudarev -Derlet and Mendeleev potentials for Fe and the Caro potential for Fe-Cr. It is of particular interest to study the evolution of high-energy cascades, where an attempt will be made to clarify the role of the evolution of sub-cascades. Kinetic Monte Carlo (kMC) techniques will be used then to simulate the defect evolution. A new parallel kMC code is being implemented for this purpose. (authors)

Measurement of excitation yields of low energy prompt γ-ray from proton bombardment of Cr-foils with energies ranging between 1.0 and 3.0 MeV

International Nuclear Information System (INIS)

Goncharov, A.

2014-01-01

The goal of this work is measurement of differential cross sections for the production of 378 keV γ-rays from the reactions 52 Cr(p,γ1) 53 Mn and 53 Cr(p,nγ1) 53 Mn for proton energies ranging between 1.0 and 3.0 MeV at the laboratory angle of 90° using foils with thickness ∼1.9×10 18 at/cm 2 (∼ 0.23 μm) of nat Cr.

Structure, magnetism, and electron-transport properties of Mn2CrGa-based nanomaterials

Directory of Open Access Journals (Sweden)

Wenyong Zhang

2016-05-01

Full Text Available Mn2CrGa in the disordered cubic structure has been synthesized using rapid quenching and subsequent annealing. The cubic phase transforms to a stable tetragonal phase when a fraction of Cr or Ga is replaced by Pt or Al, respectively. All samples are ferrimagnetic with high Curie temperatures (Tc; Mn2CrGa exhibits the highest Tc of about 813 K. The tetragonal samples have appreciable values of magnetocrystalline anisotropy energy, which leads to an increase in coercivity (Hc that approaches about 10 kOe in the Pt-doped sample. The Hc linearly increases with a decrease of temperature, concomitant with the anisotropy change with temperature. All samples are metallic and show negative magnetoresistance with room-temperature resistivities on the order of 1 mΩcm. The magnetic properties including high Tc and low magnetic moment suggest that these tetragonal materials have potential for spin-transfer-torque-based devices.

Electrochemical Reduction of Oxygen and Nitric oxide at low Temperature on La1-xSrxCr0.97V0.03O3-δ Cathodes

DEFF Research Database (Denmark)

Kammer Hansen, Kent

2013-01-01

Five La1-xSrxCr0.97V0.03O3-δ (x = 0, 0.05, 0.15, 0.25, 0.35) perovskites were synthesized and characterized by powder XRD and cyclic voltammetry on cone-shaped electrodes in 10% oxygen in argon or 1% nitric oxide in argon at 200, 300 and 400°C. It was shown that the activation energy for the redu......Five La1-xSrxCr0.97V0.03O3-δ (x = 0, 0.05, 0.15, 0.25, 0.35) perovskites were synthesized and characterized by powder XRD and cyclic voltammetry on cone-shaped electrodes in 10% oxygen in argon or 1% nitric oxide in argon at 200, 300 and 400°C. It was shown that the activation energy...... for the reduction of oxygen is higher than the activation energy for the reduction nitric oxide. The activity for the reduction of both oxygen and nitric oxide was shown to be highest for the end member La0.65Sr0.35Cr0.97V0.03O3-δ. The highest ratio between the current densities in the nitric oxide and oxygen...... containing atmospheres was found for the end member LaCr0.97V0.03O3-δ. The chromites also showed activity as anodes for either oxygen evolution or oxidation of nitric oxide to nitrogen dioxide....

Cr/alpha-Cr2O3 monodispersed spherical core-shell particles based solar absorbers

CSIR Research Space (South Africa)

Khamlich, S

2011-07-01

Full Text Available as reported. The coated Cr/alpha-Cr2O3 spherical particles on rough copper substrates by a simple self-assembly-like method were characterized by scanning electron microscopy, energy dispersive spectrometry, Raman spectroscopy, and diffuse reflectance UV...

Thermodynamic Assessment of the La-Cr-O System

DEFF Research Database (Denmark)

Povoden, E.; Chen, Ming; Grundy, A.N.

2009-01-01

of oxygen partial pressure. In the La-Cr system reported solubility of lanthanum in bcc chromium is considered in the modeling. In the La-Cr-O system the Gibbs energy functions of La2CrO6, La-2(CrO4)(3), and perovskite-structured LaCrO3 are presented, and oxygen solubilities in bcc and fcc metals......The La-Cr and the La-Cr-O systems are assessed using the Calphad approach. The calculated La-Cr phase diagram as well as LaO1.5-CrO1.5 phase diagrams in pure oxygen, air, and under reducing conditions are presented. Phase equilibria of the La-Cr-O system are calculated at 1273 K as a function...... are modeled. Emphasis is placed on a detailed description of the perovskite phase: the orthorhombic to rhombohedral transformation and the contribution to the Gibbs energy due to a magnetic order-disorder transition are considered in the model. The following standard data of stoichiometric perovskite...

Alpha particle spectroscopy for CR-39 detector utilizing matrix of energy equations

Energy Technology Data Exchange (ETDEWEB)

Awad, E.M. [Department of General Sciences, Yanbu Industrial College, PO Box 30436, Madinat Yanbu Al-Sinaiya (Saudi Arabia); Physics Department, Faculty of Science, Menofia University, Shebin El-Koom (Egypt)], E-mail: ayawad@yahoo.com; Soliman, A.A. [Department of Mathematics, Faculty of Education (AL-Arish), Suez Canal University, AL-Arish 45111 (Egypt); Department of Mathematics, Teacher' s College (Bisha), King Khalid University, Bisha, PO Box 551 (Saudi Arabia)], E-mail: asoliman_99@yahoo.com; Rammah, Y.S. [Physics Department, Faculty of Science, Menofia University, Shebin El-Koom (Egypt)

2007-10-01

A method for determining alpha-particle energy using CR-39 detector by utilizing matrix of energy equation was described. The matrix was composed from two axes; the track minor axis (m) and diameter of etched out track end (d) axis of some selected elliptical tracks. The energy E in (m,d) coordinate was approximated by matrix of energy equations given by: E{sub k}={sigma}{sub i,j=0}{sup 2}a{sub ij}d{sub k}{sup i}m{sub k}{sup j}, which was identified using two different approaches. First, i and j were treated as power exponents for d and m. The adjusting parameters values a{sub ij} were obtained and the energy of a given track was deduced directly from it. Second, i and j were treated as indices of some chosen tracks that were fitted to obtain iso-energy curves that were superimposed on m-d scatter plot as calibration curves. The energy between any two successive iso-energy curves in this case was assumed varied linearly with d for a given m. The energy matrix in both cases was solved numerically. Results of the two approaches were compared.

Structural, optical and ferromagnetic properties of Cr doped TiO2 nanoparticles

International Nuclear Information System (INIS)

Choudhury, Biswajit; Choudhury, Amarjyoti

2013-01-01

Graphical abstract: Doping of Cr 3+ distorts the lattice of TiO 2 , generate oxygen vacancies and create d-band states in the mid band gap of TiO 2 . Incorporation of Cr 3+ also imparts magnetism in non-magnetic TiO 2 by undergoing coupling with the neighboring oxygen vacancies. -- Highlights: • Incorporation of Cr 3+ increases the concentration of oxygen vacancies in TiO 2 nanoparticles. • Doped TiO 2 nanoparticles contain absorption peaks corresponding to d–d transition of Cr 3+ into TiO 2 . • Pure and doped TiO 2 nanoparticles contain emission peaks related to oxygen vacancies. • Pure TiO 2 shows diamagnetism while Cr doped TiO 2 shows ferromagnetism. • The ferromagnetism is due to the interaction of Cr 3+ ions via oxygen vacancies. -- Abstract: Cr doped TiO 2 nanoparticles are prepared with three different concentrations of chromium, 1.5%, 3.0% and 4.5 mol% respectively. Doping decreases the crystallinity and increases the width of the X-ray diffraction peak. The Raman active E g peak of TiO 2 nanoparticles become asymmetric and shifted to higher energy on doping of 4.5% chromium. Electron paramagnetic resonance spectra reveal the presence of Cr 3+ in the host TiO 2 matrix. The absorption spectra of Cr doped TiO 2 nanoparticles contain absorption peaks corresponding to d–d transition of Cr 3+ in octahedral coordination. Most of the visible emission peaks are due to the electrons trapped in the oxygen vacancy centers. Undoped TiO 2 nanoparticles show diamagnetism at room temperature while all chromium doped samples show ferromagnetism. The magnetization of the doped samples increases at 1.5% and 3.0% and decreases at 4.5%. The ferromagnetism arises owing to the interaction of the neighboring Cr 3+ ions via oxygen vacancies. The decrease of magnetization at the highest doping is possibly due to the antiferromagnetic interactions of Cr 3+ pairs or due to Cr 3+ -O 2− -Cr 3+ superexchange interaction in the lattice

Effect of d electrons on defect properties in equiatomic NiCoCr and NiCoFeCr concentrated solid solution alloys

Science.gov (United States)

Zhao, Shijun; Egami, Takeshi; Stocks, G. Malcolm; Zhang, Yanwen

2018-01-01

The role of d electrons in determining distributions of formation and migration energies for point defects in equiatomic NiCoCr and NiCoFeCr concentrated solid solution alloys (CSAs) are studied regarding electron density deformation flexibility based on first-principles calculations. The disordered state is taken into account by constructing special quasirandom structures. The migration barriers are determined by directly optimizing the saddle point. It is found that the formation energies of interstitials in CSAs are lower than those in pure Ni, whereas the formation energies of vacancies are higher. In both NiCoCr and NiCoFeCr, Co-related dumbbell interstitials exhibit lower formation energies. Notably, the distributions of migration energies for Cr interstitials and vacancies exhibit a remarkable overlap region. A detailed analysis of electronic properties reveals that the electronic charge deformation flexibility regarding eg to t2g transition has a dominant effect on defect energetics for different elements in CSAs. Thus the electron deformation ability is suggested as a key factor in understanding the peculiar defect behavior in CSAs.

BISON Fuel Performance Analysis of FeCrAl cladding with updated properties

Energy Technology Data Exchange (ETDEWEB)

Sweet, Ryan [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); George, Nathan M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Terrani, Kurt A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wirth, Brian [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2016-08-30

In order to improve the accident tolerance of light water reactor (LWR) fuel, alternative cladding materials have been proposed to replace zirconium (Zr)-based alloys. Of these materials, there is a particular focus on iron-chromium-aluminum (FeCrAl) alloys due to much slower oxidation kinetics in high-temperature steam than Zr-alloys. This should decrease the energy release due to oxidation and allow the cladding to remain integral longer in the presence of high temperature steam, making accident mitigation more likely. As a continuation of the development for these alloys, suitability for normal operation must also be demonstrated. This research is focused on modeling the integral thermo-mechanical performance of FeCrAl-cladded fuel during normal reactor operation. Preliminary analysis has been performed to assess FeCrAl alloys (namely Alkrothal 720 and APMT) as a suitable fuel cladding replacement for Zr-alloys, using the MOOSE-based, finite-element fuel performance code BISON and the best available thermal-mechanical and irradiation-induced constitutive properties. These simulations identify the effects of the mechanical-stress and irradiation response of FeCrAl, and provide a comparison with Zr-alloys. In comparing these clad materials, fuel rods have been simulated for normal reactor operation and simple steady-state operation. Normal reactor operating conditions target the cladding performance over the rod lifetime (~4 cycles) for the highest-power rod in the highest-power fuel assembly under reactor power maneuvering. The power histories and axial temperature profiles input into BISON were generated from a neutronics study on full-core reactivity equivalence for FeCrAl using the 3D full core simulator NESTLE. Evolution of the FeCrAl cladding behavior over time is evaluated by using steady-state operating conditions such as a simple axial power profile, a constant cladding surface temperature, and a constant fuel power history. The fuel rod designs and

Analysis of the highest transverse energy events seen in the UA1 detector at the Spanti pS collider

International Nuclear Information System (INIS)

Albajar, C.; Bezaguet, A.; Cennini, P.

1987-01-01

This is the first full solid angle analysis of large transverse energy events in panti p collisions at the CERN collider. Events with transverse energies in excess of 200 GeV at √s=630 GeV are studied for any non-standard physics and quantitatively compared with expectations from perturbative QCD Monte Carlo models. A corrected differential cross section is presented. A detailed examination is made of jet profiles, event jet multiplicities and the fraction of the transverse energy carried by the two jets with the highest transverse jet energies. There is good agreement with standard theory for events with transverse energies up to the largest observed values (≅ √s/2) and the analysis shows no evidence for any non-QCD mechanism to account for the event characteristics. (orig.)

Structure and magnetic properties of NdFeB thin films with Cr, Mo, Nb, Ta, Ti, and V buffer layers

International Nuclear Information System (INIS)

Jiang, H.; O'Shea, M.J.

2000-01-01

Layers of NdFeB of the form A(20 nm)/NdFeB(d nm)/A(20 nm) where A represents Cr, Mo, Nb, Ta, Ti, V were prepared on a silicon substrate by magnetron sputtering. The purpose is to determine how (i) the chosen buffer layer and (ii) NdFeB layer thickness d (especially d 2 Fe 14 B with no preferred crystalline orientation. Our highest coercivities occur for buffer layer elements from row five of the periodic table, 20 kOe (1600 kA/m) in a Nb buffered sample with d of 180 nm and 17 kOe (1350 kA/m) in a Mo buffered sample with d of 180 nm. Buffer layers from row four (Ti, V, and Cr) and row six (Ta) all give lower coercivities. Our largest energy product, 10.3 MG-Oe (82 kJ/m 3 ), is obtained for the Mo buffered sample. Average Nd 2 Fe 14 B crystallite size for this sample is 27 nm. Only the Cr and Ti buffered films show a large coercivity (≥2 kOe) for d of 54 nm with the Cr films showing the highest coercivity, 2.7 kOe (215 kA/m). In films subjected to a rapid thermal anneal (anneal time 30 s) we find that both the coercivity and energy product are larger than in samples subjected to a 20 min anneal. In our Nb buffered systems we obtain coercivities as high as 26.3 kOe (2090 kA/m) after a rapid thermal anneal

Corrosion and Mechanical Properties of Al-5 At. Pct Cr Produced by Cryomilling and Subsequent Consolidation at Various Temperatures

Science.gov (United States)

Esquivel, J.; Darling, K. A.; Murdoch, H. A.; Gupta, R. K.

2018-04-01

An Al-5 at. pct Cr alloy was produced by high-energy ball milling at liquid nitrogen temperature followed by consolidation using equal-channel axial extrusion at 200 °C, 300 °C and 450 °C. The microstructure and corrosion response were compared with a cast alloy of the same composition. Rather than the intermetallics expected by the phase diagram and seen in the cast alloy, consolidated HEBM alloys exhibited extended solid solubility of Cr in the aluminum matrix in addition to a finely dispersed Cr-rich phase. This led to improvement in the corrosion behavior as investigated via potentiodynamic polarization and constant immersion tests in NaCl solution. Hardness and tensile tests were performed to evaluate the mechanical properties. The highest consolidation temperature (450 °C) contributed to significant grain growth and Cr diffusion, lessening the beneficial effects of processing with HEBM.

Black Cr/α-Cr2O3 nanoparticles based solar absorbers

International Nuclear Information System (INIS)

Khamlich, S.; Nemraoui, O.; Mongwaketsi, N.; McCrindle, R.; Cingo, N.; Maaza, M.

2012-01-01

Monodisperse spherical core–shell particles of Cr/α-Cr 2 O 3 with high adhesion were successfully coated on rough copper substrates by a simple self-assembly-like method for the use in solar thermal absorbers. The structure and morphology of the core-shell particles of Cr/α-Cr 2 O 3 were effectively controlled by deposition temperature and the pH of the initial precursor solution. Their characterizations were carried out with X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry and attenuated total reflection, as well as UV–vis diffuse reflectance spectroscopy. The samples aged for more than 40 h at 75 °C exhibit the targeted high absorbing optical characteristic “Black chrome” while those aged for ≤40 h show a significant high UV–vis diffuse reflectance “green color”.

Up to the highest peak!

CERN Multimedia

CERN Bulletin

2010-01-01

In the early hours of this morning, the beam energy was ramped up to 3.5 TeV, a new world record and the highest energy for this year’s run. Now operators will prepare the machine to make high-energy collisions later this month. CERN Operations Group leader Mike Lamont (foreground) and LHC engineer in charge Alick Macpherson in the CERN Control Centre early this morning. At 5:23 this morning, Friday 19 March, the energy of both beams in the LHC was ramped up to 3.5 TeV, a new world record. During the night, operators had tested the performance of the whole machine with two so-called ‘dry runs’, that is, without beams. Given the good overall response, beams were injected at around 3:00 a.m. and stabilized soon after. The ramp started at around 4:10 and lasted about one hour. Over the last couple of weeks, operation of the LHC at 450 GeV has become routinely reproducible. The operators were able to test and optimize the beam orbit, the beam collimation, the injection and ext...

Cr 3d surface and bulk states in Sn1-xCrxTe/Cr crystals

International Nuclear Information System (INIS)

Guziewicz, E.; Szamota-Sadowska, K.; Kowalski, B.J.; Grodzicka, E.; Story, T.; Orlowski, B.A.; Johnson, R.L.

1997-01-01

We report a new approach to investigate metal-semiconductor interface formation. Photoemission spectroscopy was applied in order to investigate the clean surface of a Sn 0.97 Cr 0.03 Te crystal and to observe its changes under sequential deposition of small amounts of Cr atoms. In order to analyse the Cr 3d contribution to the valence band, the Fano-type resonance tuned to the Cr 3p-3d transmission was used. The experiment was designed to follow the Sn 0.97 Cr 0.03 Te/Cr interface formation process. At the clean Sn 0.97 Cr 0.03 Te surface, the Cr 3d states contribution to the valence band was found to be positioned 0.8 eV below Fermi level. After the Cr deposition processes the contribution shifted to a higher binding energy and another contribution 5.8 eV below the Fermi level also observed. (author)

Characterization of Cr-rich Cr-Sb multilayer films: Syntheses of a new metastable phase using modulated elemental reactants

International Nuclear Information System (INIS)

Regus, Matthias; Mankovsky, Sergiy; Polesya, Svitlana; Kuhn, Gerhard; Ditto, Jeffrey; Schürmann, Ulrich; Jacquot, Alexandre; Bartholomé, Kilian; Näther, Christian; Winkler, Markus; König, Jan D.; Böttner, Harald; Kienle, Lorenz; Johnson, David C.; Ebert, Hubert; Bensch, Wolfgang

2015-01-01

The new metastable compound Cr 1+x Sb with x up to 0.6 has been prepared via a thin film approach using modulated elemental reactants and investigated by in-situ X-ray reflectivity, X-ray diffraction, differential scanning calorimetry, energy dispersive X-ray analysis as well as transmission electron microscopy and atomic force microscopy. The new Cr-rich antimonide crystallizes in a structure related to the Ni 2 In-type structure, where the crystallographic position (1/3, 2/3, 3/4) is partially occupied by excess Cr. The elemental layers of the pristine material interdiffused significantly before Cr 1+x Sb crystallized. A change in the activation energy was observed for the diffusion process when crystal growth starts. First-principles electronic structure calculations provide insight into the structural stability, magnetic properties and resistivity of Cr 1+x Sb. - Graphical abstract: 1 amorphous multilayered film 2 interdiffused amorphous film 3 metastable crystalline phase 4 thermodynamic stable phase (and by-product). - Highlights: • Interdiffusion of amorphous Cr and Sb occurs before crystallization. • Crystallization of a new metastable phase Cr 1.6 Sb in Ni 2 In-type structure. • The new Cr-rich phase shows half-metallic behavior

Spatial distribution of the X- and γ- rays induced energy deposition on semi-insulating GaAs:Cr based pixel radiation detector

International Nuclear Information System (INIS)

Meneses Gonzalez, Annie; Leyva Fabelo, Antonio; Pinnera Hernandez, Ibrahin; Cruz Inclan, Carlos M.; Abreu Alfonso, Yamiel; Chelkov, Georgy; Zhemchugov, Alexey

2015-01-01

Radiation detectors based on Cr compensated GaAs are characterized by high resistivity and good electron transport properties. These characteristics, its high atomic number and good radiation hardness, make GaAs:Cr a promising semiconductor detector within a wide photon energy range. The excellent imaging performance of these detectors for medical and other several applications are already reported in the literature. In this study, the spatial distributions of photon radiation energy deposition on a GaAs:Cr pixel detector with the real device dimensions (900 μm thick, pixels of 45x45 μm 2 and pitch of 55 μm) are presented. The charge carrier distribution profiles generated by the incident photons was additionally determined and discussed. Using the calculated weighting potential for the detector was possible to estimate the percent of charge carriers that shall contribute to the signal generated in the device electrodes. All the calculations were made for the typical photon energies of 241 Am and the energy corresponding to the K α1 characteristic lines of Mo. The MCNPX code system and ARCHIMEDES program were used for mathematical modeling of radiation transport in matter and for semiconductor device simulations respectively. (Author)

Design and development of wide energy neutron REM equivalent spectrometer-dosimeters based on polycarbonates and Cr-39

International Nuclear Information System (INIS)

Faermann, S.

1985-03-01

This work describes a system composed of a Rem response personnel neutron dosemeter, based on boron radiators and a polycarbonate track detector, for monitoring dose equivalents in the energy range 1 eV to 14 MeV, an electrochemical etching system for revealing damage sites in solid state track etch detectors, a reader for magnifying the etched pits and a microprocessor for evaluating the dose equivalents and their uncertainties. The performance and directional dependence of the dosemeter when exposed to monoenergetic and polyenergetic neutron fields in the epithermal and fast energy regions are discussed. Saturation effects in polycarbonate foils are presented and a comparison is made between the response of polycarbonate and CR-39 foils, used as passive detectors in the dosemeter. A new passive miniature fast neutron spectrometer-dosimeter is also described. The device is based on the detection of proton tracks by electrochemical etching of CR-39 foils covered with thin polyethylene layers of different thicknesses. By means of this device it is possible to assess the fast neutron energy spectrum in 10 energy intervals in the energy range 0.5-15 MeV. Dose equivalents can be determined in the dose equivalent range 20 mRem to 8 Rem, approximately (author)

Characterization of ion-irradiated ODS Fe–Cr alloys by doppler broadening spectroscopy using a positron beam

Energy Technology Data Exchange (ETDEWEB)

Parente, P.; Leguey, T. [Departamento de Física and IAAB, Universidad Carlos III de Madrid, 28911 Leganés (Spain); Castro, V. de, E-mail: vanessa.decastro@uc3m.es [Departamento de Física and IAAB, Universidad Carlos III de Madrid, 28911 Leganés (Spain); Gigl, T.; Reiner, M.; Hugenschmidt, C. [FRM II and Physics Department, Technische Universität München, 85747 Garching (Germany); Pareja, R. [Departamento de Física and IAAB, Universidad Carlos III de Madrid, 28911 Leganés (Spain)

2015-09-15

The damage profile of oxide dispersion strengthened steels after single-, or simultaneous triple-ion irradiation at different conditions has been characterized using a low energy positron beam in order to provide information on microstructural changes induced by irradiation. Doppler broadening and coincident Doppler broadening measurements of the positron annihilation line have been performed on different Fe–Cr–(W,Ti) alloys reinforced with Y{sub 2}O{sub 3}, to identify the nature and stability of irradiation-induced open-volume defects and their possible association with the oxide nanoparticles. It was found that irradiation induced vacancy clusters are associated with Cr atoms. The results are of highest interest for modeling the damage induced by 14 MeV neutrons in reduced activation Fe–Cr alloys relevant for fusion devices.

Characterization of ion-irradiated ODS Fe–Cr alloys by doppler broadening spectroscopy using a positron beam

International Nuclear Information System (INIS)

Parente, P.; Leguey, T.; Castro, V. de; Gigl, T.; Reiner, M.; Hugenschmidt, C.; Pareja, R.

2015-01-01

The damage profile of oxide dispersion strengthened steels after single-, or simultaneous triple-ion irradiation at different conditions has been characterized using a low energy positron beam in order to provide information on microstructural changes induced by irradiation. Doppler broadening and coincident Doppler broadening measurements of the positron annihilation line have been performed on different Fe–Cr–(W,Ti) alloys reinforced with Y 2 O 3 , to identify the nature and stability of irradiation-induced open-volume defects and their possible association with the oxide nanoparticles. It was found that irradiation induced vacancy clusters are associated with Cr atoms. The results are of highest interest for modeling the damage induced by 14 MeV neutrons in reduced activation Fe–Cr alloys relevant for fusion devices

Influence of temperature on Yb:YAG/Cr:YAG microchip laser operation

Science.gov (United States)

Šulc, Jan; Eisenschreiber, Jan; Jelínková, Helena; Nejezchleb, Karel; Å koda, Václav

2017-02-01

The goal of this work was an investigation of the temperature influence (in range from 80 up to 320 K) on the laser properties of Yb:YAG/Cr:YAG Q-switched diode-pumped microchip laser. This laser was based on monolith crystal (diameter 3mm) which combines in one piece an active laser part (Yb:YAG crystal, 10 at.% Yb/Y, 3mm long) and saturable absorber (Cr:YAG crystal, 1.36mm long, initial transmission 90% @ 1031 nm). The laser resonator pump mirror (HT for pump radiation, HR for generated radiation) was directly deposited on the Yb:YAG monolith part. The output coupler with reflection 55% for the generated wavelength was placed on the Cr:YAG part. The microchip laser was placed in the temperature controlled cupreous holder inside vacuum chamber of the liquid nitrogen cryostat. For Yb:YAG part longitudinal pulsed pumping (pumping pulse length 2.5 ms, rep-rate 20 Hz, power amplitude 21W) a fibre coupled (core diameter 400 μm, NA= 0:22) laser diode, operating at wavelength 933 nm, was used. The microchip laser mean output power, pulse duration, repetition rate, emission wavelength, and laser beam profile were measured in dependence on temperature. The generated pulse length was in range from 2.2 ns to 1.1 ns (FWHM) with the minimum at 230 K. The single pulse energy was peaking (0.4 mJ) at 180 K. The highest peak power (325 kW) was obtained at 220 K. The highest pulse repetition rate (38 kHz) and output mean power (370mW) was reached for temperature 80 K.

Energy-dependent etching-related impacts on CR-39 alpha detection efficiency for the Rn-222 and Rn-220 decay chains

Science.gov (United States)

Tan, Y.; Yuan, H.; Kearfott, K. J.

2018-04-01

CR-39 detectors are widely used to measure environmental levels of Rn-222, Rn-220 and their progeny. Prior research reported the CR-39 detection efficiency for alpha particles from Rn-222, Rn-220 and their progeny under a variety of etching conditions. This paper provides an explanation for interesting observations included in that work, namely that the critical incidence angle decreases with the increasing particle energy and the detection efficiency for 8.78 MeV alpha particles is zero. This paper explains these phenomena from a consideration of the interaction of alpha particles with the CR-39 detectors and the physics of etching dynamics. The proposed theory provides a rationale for an approach to optimizing the etching conditions of CR-39 detector for measuring Rn-222, Rn-220 and their progenies.

Modeling of chromium precipitation in Fe-Cr alloys

International Nuclear Information System (INIS)

Wallenius, J.; Olsson, P.; Lagerstedt, C.; Sandberg, N.; Chakarova, R.; Pontikis, V.

2004-01-01

We have implemented a set of Embedded Atom Method (EAM) potentials for simulation of Fe-Cr alloys. The functions for the pure elements were fitted to the respective elastic constants, vacancy formation energy, and thermal expansion coefficients. For Cr, properties of the paramagnetic state were applied, providing a positive Cauchy pressure and hence applicability of the EAM. By relaxing the requirement of reproducing the pressure-volume relation at short interaction distances, stability of the self-interstitial could be obtained. Our Fe-potential gives E lang110rang f -E lang111rang f =-0.23 eV. Mixed Fe-Cr pair potentials were fitted to the calculated mixing enthalpy of ferromagnetic Fe-Cr, which is negative for Cr concentrations below 6%. Simulation of thermal aging in Fe-Cr alloys using a potential fitted to the mixing enthalpy of Fe-20Cr exhibited pronounced Cr-precipitation for temperatures below 900 K, in agreement with the phase diagram. No such ordering was observed at any temperature using a potential fitted to the mixing enthalpy of Fe-5Cr. Applied to recoil cascade simulations the new potentials predict a smaller number of surviving defects than potentials found in the literature. We obtain a cascade efficiency of 0.135 NRT for damage energies in between 10 and 20 keV. An enhanced probability for Cr atoms to end up in defect structures is observed

Study of α-energy discrimination in CR-39 track etch detectors for use as a radon/thoron dosemeter

International Nuclear Information System (INIS)

Kandaiya, S.; Al-Najjar, S.A.R.; Piesch, E.

1988-01-01

The properties of CR 39 nuclear track detectors were evaluated for their α-energy discrimination up to 8.77 MeV using a combination of chemical-electrochemical track revealing techniques. Using three field strengths, α-energy discrimination by ECE track diameter and track density as a function of chemical pre-etching time were studied. α-energy spectra using different irradiation geometries were then evaluated using the optimum conditions and then compared with those obtained form other techniques. (author)

Microcosm investigation on phytoremediation of Cr using Azolla pinnata.

Science.gov (United States)

Rai, Prabhat Kumar

2010-01-01

The extent of Chromium (Cr) pollution in Singrauli industrial region, India was assessed and phytoremediation capacity of a small water fern, Azolla pinnata R.BR (Azollaceae) was observed to purify waters polluted by Cr under microcosm condition. Azolla pinnata endemic to India is a potential hyper-accumulator of heavy metals. During 13 days of the experiment the fern was grown in the aqueous medium containing Cr3+ and CrO4(2-) ions, each in a concentration 0.5, 1.0, and 3.0 mg L(-1). The presence of these ions caused a + 3.1 to -37.5% inhibition of Azolla pinnata growth in comparison to the control. After 13 days of the experiment, metal contents in the solution was decreased up to 70% (CrO4(2-) 3.0 mg L(-1) treatment) to 88% (CrO4(2-) 0.5 mg L(-1) treatment). In the Azolla pinnata tissues, the concentration of couple of the ionic forms of Cr under investigation ranged from 415 to 1095 mg kg(-1) dry mass (dm); the highest level being found for Cr (III) containing solution.

Structure and grindability of dental Ti-Cr alloys

International Nuclear Information System (INIS)

Hsu, H.-C.; Wu, S.-C.; Chiang, T.-Y.; Ho, W.-F.

2009-01-01

The purpose of this study was to investigate the structure and microhardness of a series of binary Ti-Cr alloys with Cr contents up to 30 wt%. In addition, the grindability was also evaluated using an electric dental handpiece with SiC wheels, with the goal of developing a titanium alloy with better mechanical properties and machinability than commercially pure titanium (c.p. Ti), a metal generally considered to be difficult to machine. This study evaluated the phase and structure of Ti-Cr alloys, using an X-ray diffraction (XRD) for phase analysis and optical microscope for microstructure of the etched alloys. Grindability was evaluated by measuring the amount of metal volume removed after grinding for 1 min. Results indicated that the structure of Ti-Cr alloys is sensitive to the Cr content. The cast c.p. Ti has a hexagonal α phase. With 5 wt% Cr, metastable β phase starts to be retained. With Cr contents higher than 10 wt%, the equi-axed β phase is almost entirely retained. In addition, athermal ω phase was found in the Ti-5Cr and Ti-10Cr alloys. The largest quantity of ω phase and highest microhardness were found in Ti-10Cr alloy. The grinding rate of the Ti-Cr alloys showed a similar tendency to the microhardness. The Ti-10Cr alloy exhibited the best grindability, especially at 1000 m/min, which presumably due to the brittle nature of the alloy containing the ω phase in the β matrix.

Investigations of CR39 dosimeters for neutron routine dosimetry

International Nuclear Information System (INIS)

Weinstein, M.; Abraham, A.; Tshuva, A.; German, U.

2004-01-01

CR-39 is a polymeric nuclear track detector which is widely used for neutron dosimetry. CR-39 detector development was conducted at a number of laboratories throughout the world(1,2) , and was accepted also for routine dosimetry. However, there are shortcomings which must be taken into consideration the lack of a dosimetry grade material which causes batch variations, significant angular dependence and a moderate sensitivity. CR-39 also under-responds for certain classes of neutron spectra (lower energy neutrons from reactors or high energy accelerator-produced neutrons).In order to introduce CR-39 as a routine dosimeter at NRCN, a series of checks were performed. The present work describes the results of some of our checks, to characterize the main properties of CR-39 dosimeters

Observations of copper clustering in a 25Cr-7Ni super duplex stainless steel during low-temperature aging under load

Science.gov (United States)

Thuvander, M.; Zhou, J.; Odqvist, J.; Hertzman, S.; Hedström, P.

2012-07-01

Atom-probe tomography was used to investigate phase separation and copper (Cu) clustering in the ferrite phase of a 25Cr-7Ni super duplex stainless steel. The steel was subjected to a tensile load during aging at 325°C for 5800 h. The degree of phase separation into α (Fe-rich) and α‧ (Cr-rich) was small, but still, it was the highest in the steel subjected to the highest load. Cu was found to cluster, and the number density of clusters increased with increasing load. In the material subjected to the highest load, Cu was enriched in regions that were neither Fe-rich nor Cr-rich. These regions also had the highest number density of Cu clusters.

Epitaxial Bi2 FeCrO6 Multiferroic Thin Film as a New Visible Light Absorbing Photocathode Material.

Science.gov (United States)

Li, Shun; AlOtaibi, Bandar; Huang, Wei; Mi, Zetian; Serpone, Nick; Nechache, Riad; Rosei, Federico

2015-08-26

Ferroelectric materials have been studied increasingly for solar energy conversion technologies due to the efficient charge separation driven by the polarization induced internal electric field. However, their insufficient conversion efficiency is still a major challenge. Here, a photocathode material of epitaxial double perovskite Bi(2) FeCrO(6) multiferroic thin film is reported with a suitable conduction band position and small bandgap (1.9-2.1 eV), for visible-light-driven reduction of water to hydrogen. Photoelectrochemical measurements show that the highest photocurrent density up to -1.02 mA cm(-2) at a potential of -0.97 V versus reversible hydrogen electrode is obtained in p-type Bi(2) FeCrO(6) thin film photocathode grown on SrTiO(3) substrate under AM 1.5G simulated sunlight. In addition, a twofold enhancement of photocurrent density is obtained after negatively poling the Bi(2) FeCrO(6) thin film, as a result of modulation of the band structure by suitable control of the internal electric field gradient originating from the ferroelectric polarization in the Bi(2) FeCrO(6) films. The findings validate the use of multiferroic Bi(2) FeCrO(6) thin films as photocathode materials, and also prove that the manipulation of internal fields through polarization in ferroelectric materials is a promising strategy for the design of improved photoelectrodes and smart devices for solar energy conversion. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The roles of polycarboxylates in Cr(VI)/sulfite reaction system: Involvement of reactive oxygen species and intramolecular electron transfer

Energy Technology Data Exchange (ETDEWEB)

Jiang, Bo, E-mail: bjiang86upc@163.com [State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao 266580, Shandong (China); School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao 266033 (China); Wang, Xianli; Liu, Yukun [State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao 266580, Shandong (China); Wang, Zhaohui [College of Environmental Science and Engineering, Donghua University, Shanghai 201620 (China); Southern Cross GeoScience, Southern Cross University, Lismore, NSW 2480 (Australia); Zheng, Jingtang, E-mail: jtzheng03@163.com [State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao 266580, Shandong (China); Wu, Mingbo, E-mail: wumb@upc.edu.cn [State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao 266580, Shandong (China)

2016-03-05

Highlights: • The formations of SO{sub 4}·{sup −} and OH·, involve in Cr(VI) reduction induced by S(IV). • Affinity of polycarboxylate to Cr(VI) accelerates Cr(VI) reduction rate. • Polycarboxylates can act as electron donors for Cr(VI) reduction retrenching S(IV). • Only oxalate can enhance the formations of SO{sub 4}·{sup −} and OH· in Cr(VI)/S(IV) system. - Abstract: In this study, the effects of polycarboxylates on both Cr(VI) reduction and S(IV) consumption in Cr(VI)/S(IV) system was investigated in acidic solution. Under aerobic condition, the productions of reactive oxygen species (ROS), i.e., SO{sub 4}·{sup −} and OH·, have been confirmed in S(IV) reducing Cr(VI) process by using electron spin resonance and fluorescence spectrum techniques, leading to the excess consumption of S(IV). However, when polycarboxylates (oxalic, citric, malic and tartaric acid) were present in Cr(VI)/S(IV) system, the affinity of polycarboxylates to CrSO{sub 6}{sup 2−} can greatly promote the reduction of Cr(VI) via expanding the coordination of Cr(VI) species from tetrahedron to hexahedron. Besides, as alternatives to S(IV), these polycarboxylates can also act as electron donors for Cr(VI) reduction via intramolecular electron transfer reaction, which is dependent on the energies of the highest occupied molecular orbital of these polycarboxylates. Notably, the variant electron donating capacity of these polycarboxylates resulted in different yield of ROS and therefore the oxidation efficiencies of other pollutants, e.g., rhodamine B and As(III). Generally, this study does not only shed light on the mechanism of S(IV) reducing Cr(VI) process mediated by polycarboxylates, but also provides an escalated, cost-effective and green strategy for the remediation of Cr(VI) using sulfite as a reductant.

CrN/AlN superlattice coatings synthesized by pulsed closed field unbalanced magnetron sputtering with different CrN layer thicknesses

International Nuclear Information System (INIS)

Lin Jianliang; Moore, John J.; Mishra, Brajendra; Pinkas, Malki; Zhang Xuhai; Sproul, William D.

2009-01-01

CrN/AlN superlattice coatings with different CrN layer thicknesses were prepared using a pulsed closed field unbalanced magnetron sputtering system. A decrease in the bilayer period from 12.4 to 3.0 nm and simultaneously an increase in the Al/(Cr + Al) ratio from 19.1 to 68.7 at.% were obtained in the CrN/AlN coatings when the Cr target power was decreased from 1200 to 200 W. The bilayer period and the structure of the coatings were characterized by means of low angle and high angle X-ray diffraction and transmission electron microscopy. The mechanical and tribological properties of the coatings were studied using the nanoindentation and ball-on-disc wear tests. It was found that CrN/AlN superlattice coatings synthesized in the current study exhibited a single phase face-centered cubic structure with well defined interfaces between CrN and AlN nanolayers. Decreases in the residual stress and the lattice parameter were identified with a decrease in the CrN layer thickness. The hardness of the coatings increased with a decrease in the bilayer period and the CrN layer thickness, and reached the highest value of 42 GPa at a bilayer period of 4.1 nm (CrN layer thickness of 1.5 nm, AlN layer thickness of 2.5 nm) and an Al/(Cr + Al) ratio of 59.3 at.% in the coatings. A low coefficient of friction of 0.35 and correspondingly low wear rate of 7 x 10 -7 mm 3 N -1 m -1 were also identified in this optimized CrN/AlN coating when sliding against a WC-6%Co ball.

CR-39 track detector for multi-MeV ion spectroscopy.

Science.gov (United States)

Jeong, T W; Singh, P K; Scullion, C; Ahmed, H; Hadjisolomou, P; Jeon, C; Yun, H; Kakolee, K F; Borghesi, M; Ter-Avetisyan, S

2017-05-19

We present the characteristics of track formation on the front and rear surfaces of CR-39 produced by laser-driven protons and carbon ions. A methodological approach, based on bulk etch length, is proposed to uniquely characterize the particle tracks in CR-39, enabling comparative description of the track characteristics in different experiments. The response of CR-39 to ions is studied based on the energy dependent growth rate of the track diameter to understand the intrinsic particle stopping process within the material. A large non-uniformity in the track diameter is observed for CR-39 with thickness matching with the stopping range of particles. Simulation and experimental results show the imprint of longitudinal range straggling for energetic protons. Moreover, by exploiting the energy dependence of the track diameter, the energy resolution (δE/E) of CR-39 for few MeV protons and Carbon ion is found to be about 3%.

Development of Cr3C2-25(Ni20Cr) nanostructured coatings

International Nuclear Information System (INIS)

Cunha, Cecilio Alvares da

2012-01-01

This study is divided in two parts. The first part is about the preparation of nanostructured Cr 3 C 2 -25(Ni20Cr) powders by high energy milling followed by characterization of the milled and the as received powder. Analyses of some of the data obtained were done using a theoretical approach. The second part of this study is about the preparation and characterization of coatings prepared with the nanostructured as well as the as received Cr 3 C 2 -25(Ni20Cr) powders. The high temperature erosion-oxidation (E-O) behavior of the coatings prepared with the two types of powders has been compared based on a technological approach. The average crystallite size of the Cr 3 C 2 -25(Ni20Cr) powder decreased rapidly from 145 nm to 50 nm in the initial stages of milling and thereafter decreased slowly to a steady state value of around 10 nm with further increase in milling time. This steady state corresponds to the beginning of a dynamic recovery process. The maximum lattice strain (ε = 1,17%) was observed in powders milled for 16 hours, and this powders critical crystallite size was 28 nm. In contrast, the lattice parameter attained a minimum for powders milled for 16 hours. Upon reaching the critical crystallite size, the dislocation density attained a steady state regime and all plastic deformation introduced in the material there after was in the form of events occurring at the grain boundaries, due mainly to grain boundary sliding. The deformation energy stored in the crystal lattice of the Cr 3 C 2 -25(Ni20Cr) powders milled for different times was determined from enthalpy variation measurements. These results indicated that the maximum enthalpy variation (δH = 722 mcal) also occurred for powders milled for 16 hours. In a similar manner, the maximum specific heat variation (δC p = 0,278 cal/gK) occurred for powders milled for 16 hours. The following mechanical properties of Cr 3 C 2 -25(Ni20Cr) coatings prepared using the HVOF thermal spray process were determined

Compositional and structural properties of pulsed laser-deposited ZnS:Cr films

Science.gov (United States)

Nematollahi, Mohammadreza; Yang, Xiaodong; Seim, Eivind; Vullum, Per Erik; Holmestad, Randi; Gibson, Ursula J.; Reenaas, Turid W.

2016-02-01

We present the properties of Cr-doped zinc sulfide (ZnS:Cr) films deposited on Si(100) by pulsed laser deposition. The films are studied for solar cell applications, and to obtain a high absorption, a high Cr content (2.0-5.0 at.%) is used. It is determined by energy-dispersive X-ray spectroscopy that Cr is relatively uniformly distributed, and that local Cr increases correspond to Zn decreases. The results indicate that most Cr atoms substitute Zn sites. Consistently, electron energy loss and X-ray photoelectron spectroscopy showed that the films contain mainly Cr2+ ions. Structural analysis showed that the films are polycrystalline and textured. The films with ~4 % Cr are mainly grown along the hexagonal [001] direction in wurtzite phase. The average lateral grain size decreases with increasing Cr content, and at a given Cr content, increases with increasing growth temperature.

Defect properties of CuCrO2: A density functional theory calculation

International Nuclear Information System (INIS)

Fang Zhi-Jie; Zhu Ji-Zhen; Zhou Jiang; Mo Man

2012-01-01

Using the first-principles methods, we study the formation energetics properties of intrinsic defects, and the charge doping properties of extrinsic defects in transparent conducting oxides CuCrO 2 . Intrinsic defects, some typical acceptor-type, and donor-type extrinsic defects in their relevant charge state are considered. By systematically calculating the formation energies and transition energy, the results of calculation show that, V Cu , O i , and O Cu are the relevant intrinsic defects in CuCrO 2 ; among these intrinsic defects, V Cu is the most efficient acceptor in CuCrO 2 . It is found that all the donor-type extrinsic defects have difficulty in inducing n-conductivity in CuCrO 2 because of their deep transition energy level. For all the acceptor-type extrinsic defects, substituting Mg for Cr is the most prominent doping acceptor with relative shallow transition energy levels in CuCrO 2 . Our calculation results are expected to be a guide for preparing promising n-type and p-type materials in CuCrO 2 . (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17%Cr and Cu-17%Cr-5%Al. Part 1; Oxidation Kinetics

Science.gov (United States)

Raj. Sai V.

2008-01-01

The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu- 17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9 9.5 kJ mol-1. In contrast, the oxidation kinetics for the Cu-17%Cr- 5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR- 5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

CR-39 nuclear track detector application for the diagnostics of low energy high power ion beams

Energy Technology Data Exchange (ETDEWEB)

Opekounov, M S; Pechenkin, S A; Remnev, G E [Nuclear Physics Institute, Tomsk (Russian Federation); Ivonin, I V [Siberian Physical-Technical Institute, Tomsk (Russian Federation)

1997-12-31

The results of investigation of the spectral composition of ion beams generated by the magneto-insulated ion diode of the MUK-M and TEMP accelerators. The energy and mass characteristics of the accelerated ion beam were determined by a Thomson spectrometer with a CR-39 plate detector (MOM - Atomki Nuclear Track Detector, Type MA-ND/p). The accelerated ion energy was from 40 to 240 keV. The ion current density range was from 1 to 10 A/cm{sup 2}. The mass composition contained hydrogen, nitrogen, carbon and aluminum ions. The individual track analysis showed the track form, depth and diameter in dependence on the ion mass and energy. (author). 2 figs., 5 refs.

Is CR39 worth the effort?

International Nuclear Information System (INIS)

Griffith, R.V.

1987-01-01

CR39 proton sensitive track detectors were greeted by the radiation protection community at the end of the last decade as a major breakthrough for personnel neutron dosimetry. A number of laboratories eagerly began research on application of CR39 to their dosimetry needs. However, in the last two or three years the enthusiasm has subsided, and many health physicists have stopped working with the material. The number of participants using CR39 in the Oak Ridge National Laboratory Personnel Intercomparison Studies dropped from six in 1985 to three in 1986. On a national level, the Federal Republic of Germany with researchers active in CR39 research recently adopted an albedo system as their national standard. In contrast, the United States Department of Energy (DOE) is supporting development of a CR39 based combination dosimeter to meet Department wide dosimetry needs. The English National Radiological Protection Board (NRPB) now features the use of CR39 in the NRPB PADC(CR39). There has obviously been a range of experiences with CR39 in the dosimetry community. Why has this been the case, and what is the proper role for CR39 in personnel neutron dosimetry. 12 refs., 2 figs., 1 tab

On creep of directionally solidified eutectic Co-Cr-C-base superalloys

International Nuclear Information System (INIS)

Hildebrandt, U.W.

1981-01-01

It is shown in the present paper that the stress exponent and the activation energy of an Al-modified 73 C-alloy agree with the following mechanisms: diffusion controlled climbing of dislocation takes place and, the activation energy is in accordance with the self-diffusion energy of chromium, particularly that of Cr in Cr 7 C 3 . (orig.) [de

A study on alpha particles range in Cr-39

International Nuclear Information System (INIS)

Ibrahim, Z.A.; Talaat, T.M.; Abdel-Aziz, Kh.M.A.; El-Asser, M.R.

2000-01-01

Cr-39 plastic nuclear track detector has been used in range determination of alpha particles. A set of experiments was carried out for studying alpha energy and track diameter relationships. This work was done under the optimum conditions of Cr-39 etching in 6.25 N NaOH at 70 degree C for various etching times. Determination of alpha range in Cr-39 recorders was studied at different energy values using the over etched track profile technique. Data are discussed within the framework of track formation theory in plastic foils, comparison between experimental and theoretical values of alpha range is included

Stacking fault energy measurements in solid solution strengthened Ni-Cr-Fe alloys using synchrotron radiation

Energy Technology Data Exchange (ETDEWEB)

Unfried-Silgado, Jimy [Metals Characterization and Processing Laboratory, Brazilian Nanothecnology National Laboratory - CNPEM/ABTLuS, Caixa Postal 6192, CEP 13083-970, Campinas, Sao Paulo (Brazil); Universidade Estadual de Campinas UNICAMP, Faculdade de Engenharia Mecanica FEM, Campinas (Brazil); Universidad Autonoma del Caribe, Grupo IMTEF, Ingenieria Mecanica, Barranquilla (Colombia); Wu, Leonardo [Metals Characterization and Processing Laboratory, Brazilian Nanothecnology National Laboratory - CNPEM/ABTLuS, Caixa Postal 6192, CEP 13083-970, Campinas, Sao Paulo (Brazil); Furlan Ferreira, Fabio [Universidade Federal do ABC, Centro de Ciencias Naturais e Humanas (CCNH), Sao Paulo (Brazil); Mario Garzon, Carlos [Universidad Nacional de Colombia, Departamento de Fisica, Bogota (Colombia); Ramirez, Antonio J, E-mail: antonio.ramirez@lnnano.org.br [Metals Characterization and Processing Laboratory, Brazilian Nanothecnology National Laboratory - CNPEM/ABTLuS, Caixa Postal 6192, CEP 13083-970, Campinas, Sao Paulo (Brazil)

2012-12-15

The stacking fault energy (SFE) in a set of experimental Ni-Cr-Fe alloys was determined using line profile analysis on synchrotron X-ray diffraction measurements. The methodology used here is supported by the Warren-Averbach calculations and the relationships among the stacking fault probability ({alpha}) and the mean-square microstrain (<{epsilon}{sup 2}{sub L}>). These parameters were obtained experimentally from cold-worked and annealed specimens extracted from the set of studied Ni-alloys. The obtained results show that the SFE in these alloys is strongly influenced by the kind and quantity of addition elements. Different effects due to the action of carbide-forming elements and the solid solution hardening elements on the SFE are discussed here. The simultaneous addition of Nb, Hf, and, Mo, in the studied Ni-Cr-Fe alloys have generated the stronger decreasing of the SFE. The relationships between SFE and the contributions on electronic structure from each element of additions were established.

Development of Cr{sub 3}C{sub 2}-25(Ni20Cr) nanostructured coatings; Desenvolvimento de revestimentos nanostruturados de Cr{sub 3}C{sub 2}-25(Ni20Cr)

Energy Technology Data Exchange (ETDEWEB)

Cunha, Cecilio Alvares da

2012-07-01

This study is divided in two parts. The first part is about the preparation of nanostructured Cr{sub 3}C{sub 2}-25(Ni20Cr) powders by high energy milling followed by characterization of the milled and the as received powder. Analyses of some of the data obtained were done using a theoretical approach. The second part of this study is about the preparation and characterization of coatings prepared with the nanostructured as well as the as received Cr{sub 3}C{sub 2}-25(Ni20Cr) powders. The high temperature erosion-oxidation (E-O) behavior of the coatings prepared with the two types of powders has been compared based on a technological approach. The average crystallite size of the Cr{sub 3}C{sub 2}-25(Ni20Cr) powder decreased rapidly from 145 nm to 50 nm in the initial stages of milling and thereafter decreased slowly to a steady state value of around 10 nm with further increase in milling time. This steady state corresponds to the beginning of a dynamic recovery process. The maximum lattice strain ({epsilon} = 1,17%) was observed in powders milled for 16 hours, and this powders critical crystallite size was 28 nm. In contrast, the lattice parameter attained a minimum for powders milled for 16 hours. Upon reaching the critical crystallite size, the dislocation density attained a steady state regime and all plastic deformation introduced in the material there after was in the form of events occurring at the grain boundaries, due mainly to grain boundary sliding. The deformation energy stored in the crystal lattice of the Cr{sub 3}C{sub 2}-25(Ni20Cr) powders milled for different times was determined from enthalpy variation measurements. These results indicated that the maximum enthalpy variation ({delta}H = 722 mcal) also occurred for powders milled for 16 hours. In a similar manner, the maximum specific heat variation ({delta}C{sub p} = 0,278 cal/gK) occurred for powders milled for 16 hours. The following mechanical properties of Cr{sub 3}C{sub 2}-25(Ni20Cr) coatings

Energy spectrum of iron nuclei measured inside the MIR space craft using CR-39 track detectors

International Nuclear Information System (INIS)

Guenther, W.; Leugner, D.; Becker, E.; Flesch, F.; Heinrich, W.; Huentrup, G.; Reitz, G.; Roecher, H.; Streibel, T.

1999-01-01

We have exposed stacks of CR-39 plastic nuclear track detectors inside the MIR space craft during the EUROMIR95 space mission for almost 6 months. Over this long period a large number of tracks of high LET events was accumulated in the detector foils. The etching and measuring conditions for this experiment were optimized to detect tracks of stopping iron nuclei. We found 185 stopping iron nuclei inside the stack and identified their trajectories through the material of the experiment. Based on the energy-range relation the energy at the surface of the stack was determined. These particles allow the determination of the low energy part of the spectrum of iron nuclei behind shielding material inside the MIR station

Porous CrN thin films by selectively etching CrCuN for symmetric supercapacitors

KAUST Repository

Wei, Binbin

2018-03-18

Transition metal nitrides are regarded as a new class of excellent electrode materials for high-performance supercapacitors due to their superior chemical stability and excellent electrical conductivity. We synthesize successfully the porous CrN thin films for binder-free supercapacitor electrodes by reactive magnetron co-sputtering and selective chemical etching. The porous CrN thin film electrodes exhibit high-capacitance performance (31.3 mF cm−2 at 1.0 mA cm−2) and reasonable cycling stability (94% retention after 20000 cycles). Moreover, the specific capacitance is more than two-fold higher than that of the CrN thin film electrodes in previous work. In addition, a symmetric supercapacitor device with a maximum energy density of 14.4 mWh cm−3 and a maximum power density of 6.6 W cm−3 is achieved. These findings demonstrate that the porous CrN thin films will have potential applications in supercapacitors.

Porous CrN thin films by selectively etching CrCuN for symmetric supercapacitors

Science.gov (United States)

Wei, Binbin; Mei, Gui; Liang, Hanfeng; Qi, Zhengbing; Zhang, Dongfang; Shen, Hao; Wang, Zhoucheng

2018-05-01

Transition metal nitrides are regarded as a new class of excellent electrode materials for high-performance supercapacitors due to their superior chemical stability and excellent electrical conductivity. We synthesize successfully the porous CrN thin films for binder-free supercapacitor electrodes by reactive magnetron co-sputtering and selective chemical etching. The porous CrN thin film electrodes exhibit high-capacitance performance (31.3 mF cm-2 at 1.0 mA cm-2) and reasonable cycling stability (94% retention after 20000 cycles). Moreover, the specific capacitance is more than two-fold higher than that of the CrN thin film electrodes in previous work. In addition, a symmetric supercapacitor device with a maximum energy density of 14.4 mWh cm-3 and a maximum power density of 6.6 W cm-3 is achieved. These findings demonstrate that the porous CrN thin films will have potential applications in supercapacitors.

Electronic and magnetic properties of SmCrSb3 and GdCrSb3: A first principles study

International Nuclear Information System (INIS)

Sandeep; Ghimire, M.P.; Thapa, R.K.

2011-01-01

The density of states (DOS) and the magnetic moments of SmCrSb 3 and GdCrSb 3 have been studied by first principles full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). For the exchange-correlation potential, the local-spin density approximations with correlation energy (LSDA+U) method have been used. Total and partial DOS have been computed using the WIEN2k code. DOS result shows the exchange-splittings of Cr-3d and rare-earth (R) 4f states electrons, which are responsible for the ground state ferromagnetic (FM) behavior of the systems. The FM behavior of these systems is strongly influenced by the average number of Cr-3d and Sm (Gd) 4f-electrons. The effective moment of SmCrSb 3 is found to be 7.07 μ B while for GdCrSb 3 it is 8.27 μ B . The Cr atom plays a significant role on the magnetic properties due to the hybridization between Cr-3d and Sb-5p states. - Highlights: → DOS and the magnetic moments of SmCrSb 3 and GdCrSb 3 are studied by full-FP-LAPW method. → Exchange splitting of eg and t2g of Cr-3d states and the rare-earth 4f state electrons are responsible for ground state ferromagnetism. → Rare-earth magnetic moments are greater than Cr moment indicating presence of 4f states.

Identification of new fluorescence processes in the UV spectra of cool stars from new energy levels of Fe II and Cr II

Science.gov (United States)

Johansson, Sveneric; Carpenter, Kenneth G.

1988-01-01

Two fluorescence processes operating in atmospheres of cool stars, symbiotic stars, and the Sun are presented. Two emission lines, at 1347.03 and 1360.17 A, are identified as fluorescence lines of Cr II and Fe II. The lines are due to transitions from highly excited levels, which are populated radiatively by the hydrogen Lyman alpha line due to accidental wavelength coincidences. Three energy levels, one in Cr II and two in Fe II, are reported.

Effect of Si on DC arc plasma generation from Al-Cr and Al-Cr-Si cathodes used in oxygen

Science.gov (United States)

Zhirkov, I.; Landälv, L.; Göthelid, E.; Ahlgren, M.; Eklund, P.; Rosen, J.

2017-02-01

Al2O3 alloyed with Cr is an important material for the tooling industry. It can be synthesized from an arc discharge using Al-Cr cathodes in an oxygen atmosphere. Due to formation of Al-rich oxide islands on the cathode surface, the arc process stability is highly sensitive to oxygen pressure. For improved stability, the use of Al0.70Cr0.25Si0.05 cathodes has previously been suggested, where Si may reduce island formation. Here, we have investigated the effect of Si by comparing plasma generation and thin film deposition from Al0.7Cr0.3 and Al0.7Cr0.25Si0.05 cathodes. Plasma ion composition, ion energies, ion charge states, neutral species, droplet formation, and film composition have been characterized at different O2 flow rates for arc currents of 60 and 90 A. Si and related compounds are detected in plasma ions and in plasma neutrals. Scanning electron microscopy and energy dispersive X-ray analysis show that the cathode composition and the film composition are the same, with Si present in droplets as well. The effect of Si on the process stability, ion energies, and ion charge states is found to be negligible compared to that of the arc current. The latter is identified as the most relevant parameter for tuning the properties of the reactive discharge. The present work increases the fundamental understanding of plasma generation in a reactive atmosphere, and provides input for the choice of cathode composition and process parameters in reactive DC arc synthesis.

Change of Cr atoms distribution in Fe85Cr15 alloy caused by 250 keV He+ ion irradiation to different doses

International Nuclear Information System (INIS)

Dubiel, S.M.; Żukrowski, J.

2015-01-01

Highlights: • Effect of He-ion irradiation dose on Fe 85 Cr 15 alloy. • Irradiation-induced clustering of Cr atoms. • Irradiation-caused reorientation of the surface magnetization vector. • Irradiation-caused increase of Fe-site spin-density. - Abstract: Redistribution of Cr atoms in a Fe 85 Cr 15 alloy caused by its irradiation with 250 keV He + ions to different doses, D = 8 ⋅ 10 16 , 16 ⋅ 10 16 and 48 ⋅ 10 16 ions/cm 2 was investigated by means of conversion electrons Mössbauer spectroscopy. The redistribution was expressed in terms of the Warren–Cowley short-range order parameters α 1 , α 2 and α 12 pertaining to the first (1NN), second (2NN) and both i.e. 1NN + 2NN shells, respectively. Clear evidence was found, both for non-irradiated and irradiated samples that the actual distribution of Cr atoms is characteristic of the shell, and for a given shell it depends on the irradiation dose. In particular, α 1 is positive, hence indicates an under population of Cr atoms in 1NN with respect to the random case, α 2 is negative, giving evidence thereby that 2NN is overpopulated by Cr atoms, and α 12 is weakly positive. Under the applied irradiation the number of Cr atoms in both neighbor shells decreased signifying thereby a clustering of Cr atoms. The underlying decrease of Cr concentration within the 1NN–2NN volume around the probe Fe atoms was estimated at 1.5 at.% ranging between 2.1 for the lowest and 0.8 at.% for the highest dose

Estimativa das necessidades energéticas em pacientes com doença renal crônica Estimating the energy requirement of chronic kidney disease patients

Directory of Open Access Journals (Sweden)

Juliana Cordeiro Dias Rodrigues

2013-02-01

Full Text Available Estabelecer as necessidades energéticas de pacientes com doença renal crônica é importante para que se possam tratar os distúrbios nutricionais encontrados nessa população. Segundo os guias de condutas voltados ao cuidado nutricional de pacientes com essa doença, a recomendação energética pode variar entre 30 e 40kcal/kg/dia. Contudo, trabalhos que avaliaram os componentes do gasto energético nos pacientes com doença renal crônica sugerem que as necessidades energéticas dessa população podem diferir do valor recomendado acima, a depender da condição clínica (presença de comorbidades, da modalidade de tratamento empregado e do nível de atividade física. Dessa forma, o presente trabalho tem como objetivo fazer uma revisão dos estudos sobre o gasto energético de pacientes com doença renal crônica, com o intuito de abordar as seguintes questões: (1 as atuais recomendações de energia para pacientes com doença renal crônica estão adequadas? (2 qual equação de predição poderia ser empregada para estimar as necessidades energéticas desse grupo de pacientes? Assim, esta revisão busca auxiliar o nutricionista ao estimar as necessidades energéticas de pacientes com doença renal crônica.Estimating the energy requirement of patients with chronic kidney disease is highly important for treating the nutritional disorders often seen in this population. According to the specific guidelines for patients with chronic kidney disease, the currently recommended daily energy intake varies from 30 to 40kcal/kg/day. However, studies that investigated energy expenditure components of patients with chronic kidney disease suggested that the energy requirement may differ from the one proposed earlier, depending on overall clinical condition (i.e. presence of comorbidities, treatment modality and level of physical activity. With this perspective in mind, the present study aims to review the studies assessing energy expenditure

Robust Strategy for Crafting Li5Cr7Ti6O25@CeO2 Composites as High-Performance Anode Material for Lithium-Ion Battery.

Science.gov (United States)

Mei, Jie; Yi, Ting-Feng; Li, Xin-Yuan; Zhu, Yan-Rong; Xie, Ying; Zhang, Chao-Feng

2017-07-19

A facile strategy was developed to prepare Li 5 Cr 7 Ti 6 O 25 @CeO 2 composites as a high-performance anode material. X-ray diffraction (XRD) and Rietveld refinement results show that the CeO 2 coating does not alter the structure of Li 5 Cr 7 Ti 6 O 25 but increases the lattice parameter. Scanning electron microscopy (SEM) indicates that all samples have similar morphologies with a homogeneous particle distribution in the range of 100-500 nm. Energy-dispersive spectroscopy (EDS) mapping and high-resolution transmission electron microscopy (HRTEM) prove that CeO 2 layer successfully formed a coating layer on a surface of Li 5 Cr 7 Ti 6 O 25 particles and supplied a good conductive connection between the Li 5 Cr 7 Ti 6 O 25 particles. The electrochemical characterization reveals that Li 5 Cr 7 Ti 6 O 25 @CeO 2 (3 wt %) electrode shows the highest reversibility of the insertion and deinsertion behavior of Li ion, the smallest electrochemical polarization, the best lithium-ion mobility among all electrodes, and a better electrochemical activity than the pristine one. Therefore, Li 5 Cr 7 Ti 6 O 25 @CeO 2 (3 wt %) electrode indicates the highest delithiation and lithiation capacities at each rate. At 5 C charge-discharge rate, the pristine Li 5 Cr 7 Ti 6 O 25 only delivers an initial delithiation capacity of ∼94.7 mAh g -1 , and the delithiation capacity merely achieves 87.4 mAh g -1 even after 100 cycles. However, Li 5 Cr 7 Ti 6 O 25 @CeO 2 (3 wt %) delivers an initial delithiation capacity of 107.5 mAh·g -1 , and the delithiation capacity also reaches 100.5 mAh g -1 even after 100 cycles. The cerium dioxide modification is a direct and efficient approach to improve the delithiation and lithiation capacities and cycle property of Li 5 Cr 7 Ti 6 O 25 at large current densities.

On the crystal structure of Z-phase Cr(V,Nb)N

DEFF Research Database (Denmark)

Danielsen, Hilmar Kjartansson; Hald, John; Grumsen, Flemming Bjerg

2006-01-01

The Z-phase Cr(YNb)N particles in various 9 to 12 pct Cr creep-resistant steels were investigated with electron diffraction, energy dispersive spectroscopy (EDS), and electron energy loss spectroscopy(EELS). In addition to the well-known tetragonal crystal structure for Z phase, a cubic crystal s...

Ab-initio study of the structural, magnetic and electric properties of NixCr1-x x={0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875}

Directory of Open Access Journals (Sweden)

R. Golsorkhtabar

2007-03-01

Full Text Available  We investigated the structural, magnetic and electronic properties of NixCr1-x alloy in the range 0.125≤ x ≤0.875 by using FP-LAPW method to solve Kohn-Sham equations. In structural study, we calculated the formation energy, lattice parameter and bulk modulus for bcc and fcc structures within ferromagnetic, ferromagnetic and paramagnetic phases. Our results indicate that the system preference for alloy formation is higher in the range of x=0.625 – 0.75 compared to other studied concentrations. Moreover, by investigation of the values obtained for the lattice parameter and bulk modulus we found out that Cr-Ni bond is weaker than Ni-Ni and Cr-Cr bonds. Additionally, our magnetic results indicate that the magnetic interactions among atoms in bcc structures have probably RKKY behavior. Finally, our results show that the Ni0.75Cr0.25 alloy with fcc structure ans spin polarization of 90% has the highest magnetic and structural stability.

Proton an alpha detections by track recording technique in CR-39

International Nuclear Information System (INIS)

Oliveira, W.A. de; Franco, M.A.R.; Herdade, S.B.; Khouri, M.C.F.; Goncalez, O.L.

1986-07-01

The plastic CR-39 is utilized as proton track detector in the study of the reaction 27 A (e, p) and 59 Co (e, p), near threshold. Preliminary results are presented for the energy calibration (mean track diameter as a function of proton energy) of CR-39 with mono-energetic protons of a Van de Graaff accelerator, in the energy range 1-3 MeV. (author) [pt

Precipitation Kinetics of Cr2N in High Nitrogen Austenitic Stainless Steel

Institute of Scientific and Technical Information of China (English)

SHI Feng; WANG Li-jun; CUI Wen-fang; LIU Chun-ming

2008-01-01

The precipitation behavior of Cr2N during isothermal aging in the temperature range from 700℃to 950℃ in Fe-18Cr-12Mn-0.48N(in mass percent)high nitrogen austenitic stainless steel,including morphology and content of precipitate,was investigated using optical microscopy,scanning electron microscopy,and transmission electron microscopy.The isothermal precipitation kinetics curve of Cr2N and the corresponding precipitation activation energy were obtained.The results show that Cr2N phase precipitates in a cellular way and its morphology is transformed from initial granular precipitates to lamellar ones in the cell with increasing aging time.The nose temperature of Cr2N precipitation is about 800℃,with a corresponding incubation period of 30 min,and the ceiling temperature of Cr2N precipitation is 950℃.The diffusion activation energy of Cr2N precipitation is 296 kJ/mol.

Influence of N2/Ar Flow Ratio on Microstructure and Properties of the AlCrSiN Coatings Deposited by High-Power Impulse Magnetron Sputtering

Directory of Open Access Journals (Sweden)

Bai-Song Li

2017-12-01

Full Text Available The cutting properties of tools can be greatly improved by AlCrSiN coatings. The AlCrSiN coatings with nitrogen content in the range of 28.2–56.3 at.% were prepared by varying the N2/Ar flow ratio from 1/4 to 1/1. The influence of N2/Ar flow ratio on composition, microstructure, and mechanical properties, as well as the tribological properties, of the coatings was investigated. With increasing N content, the coating microstructure gradually evolved from single fcc-(Cr,AlN (200 phase to the mixture of fcc-(Cr,AlN and hcp-(Cr,AlN phase, which corresponds to an increased crystallinity within the coatings. The coating presents the highest hardness and best wear resistance for an N2/Ar flow ratio of 1/1, but the film adhesive strength and inner stress decreased obviously with increasing N2/Ar flow ratio, which was attributed to the rapid reduction of particle kinetic energy induced by the obstruction of neutral nitride particles between target and substrates. The highest H3/E*2 value exhibited the lowest wear rate, at 0.81 × 10−14 m3/(N·m, indicating that it had the best resistance to plastic deformation. The main wear mechanisms of the as-deposited coatings were abrasive wear and adhesive wear. The increasing crystallinity of the interior coatings resulted in higher hardness and better tribological behavior with an increase in N2/Ar flow ratio.

Magnetic properties of point defect interaction with impurity atoms in Fe-Cr alloys

Science.gov (United States)

Nguyen-Manh, D.; Lavrentiev, M. Yu.; Dudarev, S. L.

2009-04-01

An integrated ab initio and statistical Monte Carlo investigation has been recently carried out to model the thermodynamic and kinetic properties of Fe-Cr alloys. We found that the conventional Fe-Cr phase diagram is not adequate at low temperature region where the magnetic contribution to the free energy plays an important role in the prediction of an ordered Fe 15Cr phase and its negative enthalpy of formation. The origin of the anomalous thermodynamic and magnetic properties of Fe-Cr alloys can be understood using a tight-binding Stoner model combined with the charge neutrality condition. We investigate the environmental dependence of magnetic moment distributions for various self-interstitial atom dumbbells configurations using spin density maps found using density functional theory calculations. The mixed dumbbell Fe-Cr and Fe-Mn binding energies are found to be positive due to magnetic interactions. Finally, we discuss the relationship between the migration energy of vacancy in Fe-Cr alloys and magnetism at the saddle point configuration.

Energy Harvesting Characteristics from Water Flow by Piezoelectric Energy Harvester Device Using Cr/Nb Doped Pb(Zr,Ti)O3 Bimorph Cantilever

Science.gov (United States)

Kim, Kyoung-Bum; Kim, Chang Il; Jeong, Young Hun; Cho, Jeong-Ho; Paik, Jong-Hoo; Nahm, Sahn; Lim, Jong Bong; Seong, Tae-Hyeon

2013-10-01

A water flow energy harvester, which can convert water flow energy to electric energy, was fabricated for its application to rivers. This harvester can generate power from the bending and releasing motion of piezoelectric bimorph cantilevers. A Pb(Zr0.54Ti0.46)O3 + 0.2 wt % Cr2O3 + 1.0 wt % Nb2O5 (PZT-CN) thick film and a 250-µm-thick stainless steel were used as a bimorph cantilever. The electrical impedance matching was achieved across a resistive load of 1 kΩ. Four bimorph cantilevers can generate power from 5 to 105 rpm. The output powers were steadily increased by increasing the rpm. The maximum output power was 68 mW by 105 rpm. It was found that the water flow energy harvester can generate 58 mW by a flow velocity of (2 m/s) from the stream with the four bimorph cantilevers.

Interdiffusion processes at irradiated Cr/Si interfaces

Energy Technology Data Exchange (ETDEWEB)

Luneville, L., E-mail: laurence.luneville@cea.fr [DEN/DANS/DM2S/SERMA/LLPR/LRC-CARMEN, CEA Saclay, 91191 Gif-sur-Yvette (France); Largeau, L. [LPN-UPR20/CNRS, Route de Nozay, 91460 Marcoussis (France); Deranlot, C. [Unite Mixte de Physique CNRS/Thales, 1 Avenue Augustin Fresnel, 91767 Palaiseau (France); Ribis, J. [DEN/DANS/DMN/SRMA/LA2M/LRC-CARMEN, CEA Saclay, 91191 Gif-sur-Yvette (France); Ott, F. [DSM/IRAMIS/LLB/CEA/CNRS, CEA Saclay, 91191 Gif-sur-Yvette (France); Moncoffre, N. [IPNL/CNRS, Domaine scientifique de la Doua, 69622 Villeurbanne (France); Baldinozzi, G. [CNRS-SPMS/UMR 8580/LRC CARMEN Ecole Centrale Paris, 92295 Chatenay-Malabry (France); Simeone, D. [DEN/DANS/DMN/SRMA/LA2M/LRC-CARMEN, CEA Saclay, 91191 Gif-sur-Yvette (France)

2015-03-25

Highlights: • Interdiffusion at Cr/Si interfaces induced by ion beam mixing at room temperature. • Creation of Cr/Si alloy metastable phases. • Reconstruction of Cr/Si interdiffusion profile by X-ray reflectometry. • Quantitative correlation between Cr and Si profiles extracted from XRR and measured by EDX–TEM. - Abstract: Chromium silicon CrSi alloys are foreseen as possible materials for spintronic devices. Ion beam mixing could be an efficient technique to produce thin films of such alloys at room temperature while avoiding thermal diffusion. In order to assess this point, we have irradiated 20 nm Cr layer on a (1 0 0) Si wafer with 70 keV Kr ions. The X-ray reflectometry technique combined with Transmission Electron Microscopy and Energy Dispersive X-ray analysis was applied to analyze, at the nanometric scale, the formation of Cr/Si blurred interfaces induced by ion beam mixing. From the analysis of reflectivity curves, it appears that nanometric Cr{sub 5}Si{sub 3} and CrSi{sub 2} phases are produced at the early stage of the process. The existence of these two paramagnetic phases gives some clues to explain the reason why the experimentally observed ferrimagnetism was weaker than predicted.

Low-energy elastic-scattering of alpha particles from [sup 34]S, [sup 50]Cr and [sup 62]Ni

Energy Technology Data Exchange (ETDEWEB)

Bredbacka, AA. (Department of Physics, AAbo Akademi, 20500 AAbo (Finland)); Brenner, M. (Department of Physics, AAbo Akademi, 20500 AAbo (Finland)); Kaellman, K.-M. (Department of Physics, AAbo Akademi, 20500 AAbo (Finland)); Manngaard, P. (Department of Physics, AAbo Akademi, 20500 AAbo (Finland)); Mate, Z. (Institute of Nuclear Research of the Hungarian Academy of Sciences, H-4001 Debrecen Pf. 51 (Hungary)); Szilagyi, S. (Institute of Nuclear Research of the Hungarian Academy of Sciences, H-4001 Debrecen Pf. 51 (Hungary)); Zolnai, L. (Institute of Nuclear Research of the Hungarian Academy of Sciences, H-4001 Debrecen Pf. 51 (Hungary))

1994-07-11

Angular distributions of elastically scattered alpha particles were measured for the [sup 34]S, [sup 50]Cr and [sup 62]Ni target nuclei in the energy range 12.8-20.0 MeV. The experimental data were analysed using the phenomenological optical model with the Saxon-Woods form factor; in the case of [sup 34]S the squared Saxon-Woods form factor was also applied. Phenomena such as the anomalous energy dependence of the potential near the Coulomb barrier, the discrete ambiguity problem, the low-mass and low-energy limit of applicability of the optical model are discussed using the real volume integral values obtained. ((orig.))

Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al. Part 1; Oxidation Kinetics

Science.gov (United States)

Raj, S. V.

2008-01-01

The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu-17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9+/-9.5 kJ/mol. In contrast, the oxidation kinetics for the Cu-17%Cr-5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR-5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

Effects of V and Cr on Laser Cladded Fe-Based Coatings

Directory of Open Access Journals (Sweden)

Haiyang Wang

2018-03-01

Full Text Available Fe-based coatings with high V and Cr content were obtained by laser cladding using Fe-based powder with different Cr3C2 and FeV50 content. The results showed that Fe-based coatings were uniform and dense. The constituent phases were mainly composed of α-Fe solid solution with the increase of Cr3C2 and FeV50, γ-Fe and V8C7 phases were achieved. The microstructure of the coatings exhibited a typical dendrite structure. The concentration of C, V and Cr were saturated in dendritic areas, and the other alloying elements were mainly dissolved in the interdendritic areas. The hardness and wear resistance of Fe-based coatings were enhanced with the Cr3C2 and FeV50 addition. The specimen with 15% Cr3C2 and 16% FeV50 had the highest hardness of 66.1 ± 0.6 HRC, which was 1.05 times higher than the sample with 4.5% Cr3C2 and 5% FeV50, and the wear resistance of the former was three times greater than the latter.

Communication: The highest frequency hydrogen bond vibration and an experimental value for the dissociation energy of formic acid dimer

DEFF Research Database (Denmark)

Kollipost, F.; Larsen, René Wugt; Domanskaya, A.V.

2012-01-01

The highest frequency hydrogen bond fundamental of formic acid dimer, ν24 (Bu), is experimentally located at 264 cm−1. FTIR spectra of this in-plane bending mode of (HCOOH)2 and band centers of its symmetric D isotopologues (isotopomers) recorded in a supersonic slit jet expansion are presented...... thermodynamics treatment of the dimerization process up to room temperature. We obtain D0 = 59.5(5) kJ/mol as the best experimental estimate for the dimer dissociation energy at 0 K. Further improvements have to wait for a more consistent determination of the room temperature equilibrium constant....

FeCrAl and Zr alloys joined using hot isostatic pressing for fusion energy applications

International Nuclear Information System (INIS)

Park, Dong Jun; Kim, Hyun Gil; Park, Jeong Yong; Jung, Yang Il; Park, Jung Hwan; Koo, Yang Hyun

2016-01-01

Highlights: • FeCrAl and Zr alloys were successfully joined by hot isostatic pressing (HIP). • The thickness of diffusion layer increased with an increase in HIP temperature. • Significant inter-diffusion was observed for HIP at 1150 °C. • Maximum joint strength was achieved at HIP temperature of 700 °C. - Abstract: FeCrAl and Zr alloys were joined by a hot isostatic pressing (HIP) method for fusion energy applications. The optimum conditions for the joining process were studied. The HIP temperatures were varied from 700 to 1050 °C. The mechanical properties of the HIPed samples were evaluated by four-point bending and tensile tests. The FeCrAl and Zr alloys HIPed at 700 °C showed higher joint strength than the other samples. The joint strength decreased with an increase in the HIP temperature from 700 to 950 °C and significantly dropped at 1050 °C. Transmission electron microscopy, scanning electron microscopy, and optical microscopy were used to characterize the joints and interface region of the HIPed samples. The joints appeared to be tightly bonded and no intermetallic compounds or gaps were observed at the interface for HIP temperatures up to 950 °C. A diffusion layer formed at the interface and its thickness increased with the HIP temperature. HIP at 1050 °C, on the other hand, resulted in significant inter-diffusion and formation of brittle inter-metallic compounds at the interface.

Vacancy migration energy dependence on local chemical environment in Fe–Cr alloys: A Density Functional Theory study

Energy Technology Data Exchange (ETDEWEB)

Costa, D., E-mail: davide.costa.ge@gmail.com [Unité Matériaux et Transformations, CNRS UMR8207, Université de Lille 1, F-59655 Villeneuve d’Ascq Cédex (France); EDF-R and D Département MMC, Les Renardières, F-77818 Moret sur Loing Cédex (France); Laboratoire commun (EDF–CNRS): Etude et Modélisation des Microstructures pour le Vieillissement des Matériaux (EM2VM) (France); Adjanor, G. [EDF-R and D Département MMC, Les Renardières, F-77818 Moret sur Loing Cédex (France); Laboratoire commun (EDF–CNRS): Etude et Modélisation des Microstructures pour le Vieillissement des Matériaux (EM2VM) (France); Becquart, C.S. [Unité Matériaux et Transformations, CNRS UMR8207, Université de Lille 1, F-59655 Villeneuve d’Ascq Cédex (France); Laboratoire commun (EDF–CNRS): Etude et Modélisation des Microstructures pour le Vieillissement des Matériaux (EM2VM) (France); Olsson, P. [Laboratoire commun (EDF–CNRS): Etude et Modélisation des Microstructures pour le Vieillissement des Matériaux (EM2VM) (France); KTH Royal Institute of Technology, Reactor Physics, Roslagstullsbacken 21, 106 91 Stockholm (Sweden); and others

2014-09-15

The first step towards the understanding and the modelling of the Fe–Cr alloy kinetic properties consists in estimating the migration energies related to the processes that drive the microstructure evolution. The vacancy’s migration barrier is expected to depend on the vacancy–migrating atom pair atomic environment as pointed out by Nguyen-Manh et al. or Bonny et al. In this paper, we address the issue of the dependence on the vacancy’s local atomic environment of both the vacancy migration energy and the configurational energy change ΔE that occurs when the vacancy jumps towards one of its nearest neighbour sites. A DFT approach is used to determine the ground state energy associated to a given configuration of the system. The results are interpreted in the light of the chromium–chromium and chromium–vacancy binding energies as well as the substitutional chromium atoms magnetic properties.

Interface bonding of NiCrAlY coating on laser modified H13 tool steel surface

Science.gov (United States)

Reza, M. S.; Aqida, S. N.; Ismail, I.

2016-06-01

Bonding strength of thermal spray coatings depends on the interfacial adhesion between bond coat and substrate material. In this paper, NiCrAlY (Ni-164/211 Ni22 %Cr10 %Al1.0 %Y) coatings were developed on laser modified H13 tool steel surface using atmospheric plasma spray (APS). Different laser peak power, P p, and duty cycle, DC, were investigated in order to improve the mechanical properties of H13 tool steel surface. The APS spraying parameters setting for coatings were set constant. The coating microstructure near the interface was analyzed using IM7000 inverted optical microscope. Interface bonding of NiCrAlY was investigated by interfacial indentation test (IIT) method using MMT-X7 Matsuzawa Hardness Tester Machine with Vickers indenter. Diffusion of atoms along NiCrAlY coating, laser modified and substrate layers was investigated by energy-dispersive X-ray spectroscopy (EDXS) using Hitachi Tabletop Microscope TM3030 Plus. Based on IIT method results, average interfacial toughness, K avg, for reference sample was 2.15 MPa m1/2 compared to sample L1 range of K avg from 6.02 to 6.96 MPa m1/2 and sample L2 range of K avg from 2.47 to 3.46 MPa m1/2. Hence, according to K avg, sample L1 has the highest interface bonding and is being laser modified at lower laser peak power, P p, and higher duty cycle, DC, prior to coating. The EDXS analysis indicated the presence of Fe in the NiCrAlY coating layer and increased Ni and Cr composition in the laser modified layer. Atomic diffusion occurred in both coating and laser modified layers involved in Fe, Ni and Cr elements. These findings introduce enhancement of coating system by substrate surface modification to allow atomic diffusion.

Colour due to Cr3+ ions in oxides: a study of the model system MgO:Cr3+

International Nuclear Information System (INIS)

Aramburu, J A; García-Fernández, P; Moreno, M; García-Lastra, J M; Barriuso, M T

2013-01-01

Seeking to understand why the cubic centre in MgO:Cr 3+ has the same 10Dq value as emerald, ab initio cluster and periodic supercell calculations have been performed. It is found that the equilibrium Cr 3+ –O 2− distance, R, in MgO:Cr 3+ is equal to 2.03 Å and thus 0.06 Å higher than that measured for the emerald. Calculations carried out on the isolated CrO 6 9- complex at R = 2.03 Å give 10Dq = 14 510 cm −1 , which is 10% smaller than the experimental figure for MgO:Cr 3+ . Nevertheless, when the internal electric field, E R (r), due to the rest of the lattice ions is also taken into account, the calculated 10Dq = 16 210 cm −1 coincides with the experimental value. Accordingly, the colour shift for different oxides doped with Cr 3+ can be well understood on the basis of this extrinsic contribution to 10Dq usually ignored in a ligand field description. The calculated electrostatic potential, V R (r), related to E R (r), is found to be attractive when the electronic density is lying along 〈110〉 directions and |r| > 1 Å driven by the first shell of twelve Mg 2+ ions. The action of V R (r) upon the CrO 6 9- complex slightly decreases the energy of t 2g (xy,xz,yz) orbitals with respect to that for e g (3z 2 − r 2 ,x 2 − y 2 ) orbitals, thus enhancing the 10Dq value by 0.2 eV. However, the addition of V R (r) induces very small changes in the electronic density, a relevant fact that is related to the 2 E( 2g 3 ) → 4 A 2 (t 2g 3 ) emission energy being nearly independent of the host lattice along the series of Cr 3+ -doped oxides. (paper)

Surface half-metallicity of half-Heusler compound FeCrSe and interface half-metallicity of FeCrSe/GaP

Energy Technology Data Exchange (ETDEWEB)

Khalaf Al-zyadi, Jabbar M., E-mail: jabbar_alzyadi@yahoo.com [Department of Physics, College of Education for Pure Sciences, University of Basrah (Iraq); Jolan, Mudhahir H. [Department of Physics, College of Education for Pure Sciences, University of Basrah (Iraq); Yao, Kai-Lun, E-mail: klyao@mail.hust.edu.cn [School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China); International Center of Materials Physics, Chinese Academy of Sciences, Shenyang 110015 (China)

2016-04-01

Recent studies showed that half-Heusler FeCrSe exhibits half-metallic ferromagnetism (Huang et al. [20]). In this paper, we investigate extensively the electronic, magnetic, and half-metallic properties of the half-Heusler alloy FeCrSe (111) and (001) surfaces and the interface with GaP (111) substrate by using the first-principles calculations within the density functional theory. The atomic density of states demonstrates that the half-me tallicity verified in the bulk FeCrSe is maintained at the CrSe-terminated (001) and Se-terminated (111) surfaces, but lost at both Cr- and Fe-terminated (111) surfaces and the Fe-terminated (001) surface. Alternatively, for the interface of FeCrSe/GaP (111), the bulk half-metallicity is destroyed at Se–P configuration while Se–Ga interface and subinterface show nearly 100% spin polarization. Moreover, the calculated interfacial adhesion energies exhibit that Se–Ga shape is more stable than the Se–P one. The calculated magnetic moments of Se, Ga at the Se–Ga (111) interface and P at the Se–P (111) interface increase with respect to the corresponding bulk values while the atomic magnetic moment of Se atom at the Se–P (111) interface decreases. We also notice that the magnetic moments of subinterface Fe at both Se–Ga and Se–P (111) interfaces decrease compared to the bulk values. - Highlights: • The half-metallicity verified in the bulk FeCrSe is kept at the CrSe-terminated (001) and Se-terminated (111) surfaces. • The calculated interfacial adhesion energies exhibit that Se–Ga shape is more stable than Se–P. • The magnetic moments of Se, Ga and P atoms at the interface increase. • The Se–Ga interface shows nearly 100% spin polarization.

Solving The Longstanding Problem Of Low-Energy Nuclear Reactions At the Highest Microscopic Level - Final Report

Energy Technology Data Exchange (ETDEWEB)

Quaglioni, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2016-09-22

A 2011 DOE-NP Early Career Award (ECA) under Field Work Proposal (FWP) SCW1158 supported the project “Solving the Long-Standing Problem of Low-Energy Nuclear Reactions at the Highest Microscopic Level” in the five-year period from June 15, 2011 to June 14, 2016. This project, led by PI S. Quaglioni, aimed at developing a comprehensive and computationally efficient framework to arrive at a unified description of structural properties and reactions of light nuclei in terms of constituent protons and neutrons interacting through nucleon-nucleon (NN) and three-nucleon (3N) forces. Specifically, the project had three main goals: 1) arriving at the accurate predictions for fusion reactions that power stars and Earth-based fusion facilities; 2) realizing a comprehensive description of clustering and continuum effects in exotic nuclei, including light Borromean systems; and 3) achieving fundamental understanding of the role of the 3N force in nuclear reactions and nuclei at the drip line.

α-cluster states in {sup 46,54}Cr from double-folding potentials

Energy Technology Data Exchange (ETDEWEB)

Mohr, Peter [Diakonie-Klinikum, Schwaebisch Hall (Germany); Institute for Nuclear Research (Atomki), Debrecen (Hungary)

2017-10-15

α-cluster states in {sup 46}Cr and {sup 54}Cr are investigated in the double-folding model. This study complements a recent similar work by Souza and Miyake, Eur. Phys. J. A 53, 146 (2017), which was based on a specially shaped potential. Excitation energies, reduced widths, intercluster separations, and intra-band transition strengths are calculated and compared to experimental values for the ground state bands in {sup 46}Cr and {sup 54}Cr. The α-cluster potential is also applied to elastic scattering at low and intermediate energies. Here, as a byproduct, a larger radial extent of the neutron density in {sup 50}Ti is found. (orig.)

Point defect properties of ternary fcc Fe-Cr-Ni alloys

Energy Technology Data Exchange (ETDEWEB)

Wróbel, J.S., E-mail: jan.wrobel@inmat.pw.edu.pl [Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland); Nguyen-Manh, D.; Dudarev, S.L. [CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Kurzydłowski, K.J. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland)

2017-02-15

Highlights: • Properties of point defects depend on the local atomic environment. • As the degree of chemical order increases, the formation energies increase, too. • Relaxation volumes are larger for the more ordered structures. - Abstract: The properties of point defects in Fe-Cr-Ni alloys are investigated, using density functional theory (DFT), for two alloy compositions, Fe{sub 50}Cr{sub 25}Ni{sub 25} and Fe{sub 55}Cr{sub 15}Ni{sub 30}, assuming various degrees of short-range order. DFT-based Monte Carlo simulations are applied to explore short-range order parameters and generate representative structures of alloys. Chemical potentials for the relevant structures are estimated from the minimum of the substitutional energy at representative atoms sites. Vacancies and 〈1 0 0〉 dumbbells are introduced in the Fe{sub 2}CrNi intermetallic phase as well as in two Fe{sub 55}Cr{sub 15}Ni{sub 30} alloy structures: the disordered and short range-ordered structures, generated using Monte Carlo simulations at 2000 K and 300 K, respectively. Formation energies and relaxation volumes of defects as well as changes of magnetic moments caused by the presence of defects are investigated as functions of the local environment of a defect.

Partially filled intermediate band of Cr-doped GaN films

International Nuclear Information System (INIS)

Sonoda, S.

2012-01-01

We investigated the band structure of sputtered Cr-doped GaN (GaCrN) films using optical absorption, photoelectron yield spectroscopy, and charge transport measurements. It was found that an additional energy band is formed in the intrinsic band gap of GaN upon Cr doping, and that charge carriers in the material move in the inserted band. Prototype solar cells showed enhanced short circuit current and open circuit voltage in the n-GaN/GaCrN/p-GaN structure compared to the GaCrN/p-GaN structure, which validates the proposed concept of an intermediate-band solar cell.

Distribution of /sup 51/Cr labelled endotoxin on tissue and intracellular organella in mice

Energy Technology Data Exchange (ETDEWEB)

Saito, K; Suzuki, M; Okuaki, A; Saito, M [Fukushima Medical Coll. (Japan)

1976-10-01

The distribution of /sup 51/Cr labelled endotoxin was investigated in mice. The degree of toxicity between non-labelled endotoxin and /sup 51/Cr labelled endotoxin did not change. /sup 51/Cr-endotoxin was distributed in the highest levels in the liver, and to a lesser degree in the intestine, lungs, spleen and kidneys. The affinity of the tissue to /sup 51/Cr-endotoxin was strongest in the liver followed by the spleen, lungs, kidneys and intestine. /sup 51/Cr-endotoxin was distributed mainly in the mitochondrial fraction and the nuclear fraction in the intracellular species. /sup 51/Cr-endotoxin was distributed only in the liver and the intestine when a small dose was administered. It was also distributed in the lungs, spleen and kidneys when a large dose was given, but the uptake in the liver was somewhat limited. /sup 51/Cr-endotoxin was distributed mainly in the liver and the spleen in the mice that survived one week.

Effect of CrO3 Sealing Time on Anodized A12024-T3

Science.gov (United States)

Korda, Akhmad A.; Hidayat, R. Z.

2016-08-01

The effect of CrO3 sealing time on anodized aluminum alloy has been investigated. A1 2024-T3 were used as substrate. Anodizing was carried out using chromic acid. CrO3 sealing was conducted in CrO3 solution for 30, 60, 90, 120 and 150 minutes. As comparison, other specimens were also prepared as anodized and boiled water sealing. Thickness of the coating was observed by optical microscope. Anodized and sealing layer was analyzed by X- ray diffraction. The hardness of as anodized, boiled water sealing and CrO3 sealing were compared. The highest hardness is achieved by CrO3 sealed specimen and followed by boiled water sealing and as anodized specimens. The longer the processes of CrO3 sealing the higher layer thickness and therefore the higher hardness of the oxide layer. The best resistance to electrolyte penetration is achieved by the CrO3 sealed specimen followed by boiled water sealed and as anodized specimens. The higher thickness of oxide layer, the higher the resistance against electrolyte penetration.

Effect of CrO_3 Sealing Time on Anodized A12024-T3

International Nuclear Information System (INIS)

Korda, Akhmad A; Hidayat, R Z

2016-01-01

The effect of CrO_3 sealing time on anodized aluminum alloy has been investigated. A1 2024-T3 were used as substrate. Anodizing was carried out using chromic acid. CrO_3 sealing was conducted in CrO_3 solution for 30, 60, 90, 120 and 150 minutes. As comparison, other specimens were also prepared as anodized and boiled water sealing. Thickness of the coating was observed by optical microscope. Anodized and sealing layer was analyzed by X- ray diffraction. The hardness of as anodized, boiled water sealing and CrO_3 sealing were compared. The highest hardness is achieved by CrO_3 sealed specimen and followed by boiled water sealing and as anodized specimens. The longer the processes of CrO3 sealing the higher layer thickness and therefore the higher hardness of the oxide layer. The best resistance to electrolyte penetration is achieved by the CrO_3 sealed specimen followed by boiled water sealed and as anodized specimens. The higher thickness of oxide layer, the higher the resistance against electrolyte penetration. (paper)

The 52Cr(p, γ)53Mn reaction

NARCIS (Netherlands)

Vuister, P.H.

The 52Cr(p, γ)53Mn reaction was investigated in the energy region Ep = 1.36–2.26 MeV. The resonance energies, the corresponding 53Mn excitation energies and the resonance strengths of 199 resonances, assigned to this reaction, are reported. The excitation energies and gamma-ray branchings of 13

Alpha-particle response characteristics of CR-39

International Nuclear Information System (INIS)

Abou El-Khier, A.A.; Gaber, M.; El-Khatib, A.M.; Fawzy, M.A.

1987-01-01

The form of the response curve of the polycarbonate CR-39 for α-particles at relatively low energies has been established. The investigation included measurements of both bulk- and track-etch rates. The latter was measured as a function of α-particle energies. (author)

High Temperature Behavior of Cr3C2-NiCr Coatings in the Actual Coal-Fired Boiler Environment

Science.gov (United States)

Bhatia, Rakesh; Sidhu, Hazoor Singh; Sidhu, Buta Singh

2015-03-01

Erosion-corrosion is a serious problem observed in steam-powered electricity generation plants, and industrial waste incinerators. In the present study, four compositions of Cr3C2-(Ni-20Cr) alloy coating powder were deposited by high-velocity oxy-fuel spray technique on T-91 boiler tube steel. The cyclic studies were performed in a coal-fired boiler at 1123 K ± 10 K (850 °C ± 10 °C). X-ray diffraction, scanning electron microscopy/energy dispersive X-ray analysis and elemental mapping analysis techniques were used to analyze the corrosion products. All the coatings deposited on T-91 boiler tube steel imparted hot corrosion resistance. The 65 pctCr3C2 -35 pct (Ni-20Cr)-coated T-91 steel sample performed better than all other coated samples in the given environment.

Doping of Czochralski-grown bulk β-Ga2O3 single crystals with Cr, Ce and Al

Science.gov (United States)

Galazka, Zbigniew; Ganschow, Steffen; Fiedler, Andreas; Bertram, Rainer; Klimm, Detlef; Irmscher, Klaus; Schewski, Robert; Pietsch, Mike; Albrecht, Martin; Bickermann, Matthias

2018-03-01

We experimentally evaluated segregation of Cr, Ce and Al in bulk β-Ga2O3 single crystals grown by the Czochralski method, as well as the impact of these dopants on optical properties. The segregation of Cr and Ce and their incorporation into the β-Ga2O3 crystal structure strongly depends on O2 concentration in the growth atmosphere which has a noticeable impact on decomposition of Ga2O3 and Cr2O3, as well as on the charge state of Cr and Ce. Effective segregation coefficients for Cr are in the range of 3.1-1.5 at 7-24 vol% O2, while for Ce they are roughly below 0.01 at 1.5-34 vol% O2. The effective segregation coefficient for Al is 1.1 at 1.5-21 vol% O2. Both dopants Ce and Al have a thermodynamically stabilizing effect on β-Ga2O3 crystal growth by supressing decomposition. While Ce has no impact on the optical transmittance in the ultraviolet and visible regions, in Cr doped crystals we observe three absorption bands due to Cr3+ on octahedral Ga sites, one in the ultraviolet merging with the band edge absorption of β-Ga2O3 and two in the visible spectrum, for which we estimate the absorption cross sections. Al doping also does not induce dopant related absorption bands but clearly shifts the absorption edge as one expects for a solid-solution crystal Ga2(1-x)Al2xO3 still in the monoclinic phase. For the highest doping concentration (Ga1.9Al0.1O3) we estimate an increase of the energy gap by 0.11 eV.

Oxidation behavior of arc evaporated Al-Cr-Si-N thin films

Energy Technology Data Exchange (ETDEWEB)

Tritremmel, Christian; Daniel, Rostislav; Mitterer, Christian; Mayrhofer, Paul H.; Lechthaler, Markus; Polcik, Peter [Christian Doppler Laboratory for Advanced Hard Coatings, Department of Physical Metallurgy and Materials Testing, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, A-8700 Leoben (Austria); Christian Doppler Laboratory for Application Oriented Coating Development, Department of Physical Metallurgy and Materials Testing, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, A-8700 Leoben (Austria); OC Oerlikon Balzers AG, Iramali 18, LI-9496 Balzers (Liechtenstein); PLANSEE Composite Materials GmbH, Siebenbuergerstrasse 23, D-86983 Lechbruck am See (Germany)

2012-11-15

The impact of Al and Si on the oxidation behavior of Al-Cr-(Si)-N thin films synthesized by arc evaporation of powder metallurgically prepared Al{sub x}Cr{sub 1-x} targets with x = Al/(Al + Cr) of 0.5, 0.6, and 0.7 and (Al{sub 0.5}Cr{sub 0.5}){sub 1-z}Si{sub z} targets with Si contents of z = 0.05, 0.1, and 0.2 in N{sub 2} atmosphere was studied in detail by means of differential scanning calorimetry, thermogravimetric analysis (TGA), x-ray diffraction, and Raman spectroscopy. Dynamical measurements in synthetic air (up to 1440 Degree-Sign C) revealed the highest onset temperature of pronounced oxidation for nitride coatings prepared from the Al{sub 0.4}Cr{sub 0.4}Si{sub 0.2} target. Isothermal TGA at 1100, 1200, 1250, and 1300 Degree-Sign C highlight the pronounced improvement of the oxidation resistance of Al{sub x}Cr{sub 1-x}N coatings by the addition of Si. The results show that Si promotes the formation of a dense coating morphology as well as a dense oxide scale when exposed to air.

X-ray attenuation coefficient measurements for photon energies 4.508-13.375 keV in Cu, Cr and their compounds and the validity of the mixture rule

International Nuclear Information System (INIS)

Turgut, Ue.; Simsek, Oe.; Bueyuekkasap, E.; Ertugrul, M.

2004-01-01

To investigate the validity of the mixture rule which is used to compute the mass attenuation coefficients in compounds, the total mass attenuation coefficients for Cu, Cr elements and Cu 2 O, CuC 2 O 4 , CuCl 2 ·2H 2 O, Cu(C 2 H 3 O 2 ) 2 ·H 2 O, Cr 2 O 3 , Cr(NO 3 ) 3 , Cr 2 (SO 4 ) 3 ·H 2 O, Cr 3 (CH 3 CO 7 )(OH) 2 compounds were measured at photon energies between 4.508 and 13.375 keV by using the secondary excitation method. Ti, Mn, Fe, Ni, Zn, Ge, As, Rb elements were used as secondary exciters. 59.5 keV gamma rays emitted from an 241 Am annular source were used to excite the secondary exciters and Kα (K-L 3 , L 2 ) rays emitted from the secondary exciter were counted by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. Our measurements indicate that the mixture rule is not a suitable method for the computation of mass attenuation coefficients of compounds especially at an energy that is near the absorption edge. Obtained values were compared with theoretical values

Millimeter-wave spectroscopy of CrC (X(3)Σ(-)) and CrCCH (X̃ (6)Σ(+)): Examining the chromium-carbon bond.

Science.gov (United States)

Min, J; Ziurys, L M

2016-05-14

Pure rotational spectroscopy of the CrC (X(3)Σ(-)) and CrCCH (X̃ (6)Σ(+)) radicals has been conducted using millimeter/sub-millimeter direct absorption methods in the frequency range 225-585 GHz. These species were created in an AC discharge of Cr(CO)6 and either methane or acetylene, diluted in argon. Spectra of the CrCCD were also recorded for the first time using deuterated acetylene as the carbon precursor. Seven rotational transitions of CrC were measured, each consisting of three widely spaced, fine structure components, arising from spin-spin and spin-rotation interactions. Eleven rotational transitions were recorded for CrCCH and five for CrCCD; each transition in these cases was composed of a distinct fine structure sextet. These measurements confirm the respective (3)Σ(-) and (6)Σ(+) ground electronic states of these radicals, as indicated from optical studies. The data were analyzed using a Hund's case (b) Hamiltonian, and rotational, spin-spin, and spin-rotation constants have been accurately determined for all three species. The spectroscopic parameters for CrC were significantly revised from previous optical work, while those for CrCCH are in excellent agreement; completely new constants were established for CrCCD. The chromium-carbon bond length for CrC was calculated to be 1.631 Å, while that in CrCCH was found to be rCr-C = 1.993 Å - significantly longer. This result suggests that a single Cr-C bond is present in CrCCH, preserving the acetylenic structure of the ligand, while a triple bond exists in CrC. Analysis of the spin constants suggests that CrC has a nearby excited (1)Σ(+) state lying ∼16 900 cm(-1) higher in energy, and CrCCH has a (6)Π excited state with E ∼ 4800 cm(-1).

CR-39 plastic nuclear track detector and its application in nuclear science

International Nuclear Information System (INIS)

Zhai Pengji; Tang Xiaowei; Wang Long; Liang Tianjiao

2000-01-01

The transparent and stable plastic material CR-39 can be used as a nuclear track detector which is highly sensitive to charged particles. It can record tracks induced by protons , alphas, fission fragments and other charged particles. Among various available solid state nuclear track detectors CR-39 has the lowest deposited energy density detection-threshold. The response of CR-39 to charged particles and the response curve of υ T of different charged particles to REL are given. The CR-39 detector is widely used in studies of nuclear reactions, angular distributions and reaction cross-sections caused by neutrons and charged particles. Neutron spectra, over a wide energy range, can be measured by the combination of CR-39 and a transformation screen. The successful applications of CR-39 in alpha particle dosimetry, environmental science (especially in the measurement of radon) and in biomedicine, such as the analysis of alpha radioactivity in sections of organic tissues, are described

Mineral Composition and Nutritive Value of Isotonic and Energy Drinks.

Science.gov (United States)

Leśniewicz, Anna; Grzesiak, Magdalena; Żyrnicki, Wiesław; Borkowska-Burnecka, Jolanta

2016-04-01

Several very popular brands of isotonic and energy drinks consumed for fluid and electrolyte supplementation and stimulation of mental or physical alertness were chosen for investigation. Liquid beverages available in polyethylene bottles and aluminum cans as well as products in the form of tablets and powder in sachets were studied. The total concentrations of 21 elements (Ag, Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Na, Ni, P, Pb, Sr, Ti, V, and Zn), both essential and toxic, were simultaneously determined in preconcentrated drink samples by inductively coupled plasma-optical emission spectrometry (ICP-OES) equipped with pneumatic and ultrasonic nebulizers. Differences between the mineral compositions of isotonic and energy drinks were evaluated and discussed. The highest content of Na was found in both isotonic and energy drinks, whereas quite high concentrations of Mg were found in isotonic drinks, and the highest amount of calcium was quantified in energy drinks. The concentrations of B, Co, Cu, Ni, and P were higher in isotonic drinks, but energy drinks contained greater quantities of Ag, Cr, Zn, Mn, and Mo and toxic elements, as Cd and Pb. A comparison of element contents with micronutrient intake and tolerable levels was performed to evaluate contribution of the investigated beverages to the daily diet. The consumption of 250 cm(3) of an isotonic drink provides from 0.32% (for Mn) up to 14.8% (for Na) of the recommended daily intake. For the energy drinks, the maximum recommended daily intake fulfillment ranged from 0.02% (for V) to 19.4 or 19.8% (for Mg and Na).

Micro calcification evaluation using CR plates in computerized mammography

International Nuclear Information System (INIS)

Bustos F, M.; Prata M, A.

2017-10-01

Cancer is one of the leading causes of mortality in the world. In 2012, about 14 million new cases were registered, of which 1.6 million are breast cancer, according to the World Health Organization. The National Cancer Institute of Brazil estimated 57 thousand new cases of breast cancer by 2016. Mammography is the imaging technique most used worldwide for the early diagnosis of breast cancer. Computed radiography (CR) plates are used for digital radiography, and are widely used to obtain digital mammograms. This work aims to evaluate te response of CR plates to the variation of exposure in mammography equipment. Three CR plates for mammography of different models were used for the study. X-ray beams were selected to perform successive exposures of CR plates by varying the exposure time. These exposures were performed to obtain raw images that were subsequently analyzed using ImageJ software, from which the value of intensity recorded in the central region of each image was obtained, correlating it with the exposure time. From these data the necessary correlations were made to determine the exposure time for which the CR plate begins to saturate, observing that the saturation occurs first for the highest value of the applied voltage. Finally, successive exposures of the CR plate were made using the compressed breast simulator made of acrylic plates and containing microcalcifications of different sizes to determine the qualitative resolution of CR plates, observing that only microcalcifications above 177 μm are visible in the image. The knowledge of saturation characteristics and resolution of the CR plate allows the selection of more adequate parameters to work without approaching the saturation region. (Author)

Phase stability and elastic properties of Cr-V alloys

Science.gov (United States)

Gao, M. C.; Suzuki, Y.; Schweiger, H.; Doǧan, Ö. N.; Hawk, J.; Widom, M.

2013-02-01

V is the only element in the periodic table that forms a complete solid solution with Cr and thus is particularly important in alloying strategy to ductilize Cr. This study combines first-principles density functional theory calculations and experiments to investigate the phase stability and elastic properties of Cr-V binary alloys. The cluster expansion study reveals the formation of various ordered compounds at low temperatures that were not previously known. These compounds become unstable due to the configurational entropy of bcc solid solution as the temperature is increased. The elastic constants of ordered and disordered compounds are calculated at both T = 0 K and finite temperatures. The overall trends in elastic properties are in agreement with measurements using the resonant ultrasound spectroscopy method. The calculations predict that addition of V to Cr decreases both the bulk modulus and the shear modulus, and enhances the Poisson’s ratio, in agreement with experiments. Decrease in the bulk modulus is correlated to decrease in the valence electron density and increase in the lattice constant. An enhanced Poisson’s ratio for bcc Cr-V alloys (compared to pure Cr) is associated with an increased density of states at the Fermi level. Furthermore, the difference charge density in the bonding region in the (110) slip plane is highest for pure Cr and decreases gradually as V is added. The present calculation also predicts a negative Cauchy pressure for pure Cr, and it becomes positive upon alloying with V. The intrinsic ductilizing effect from V may contribute, at least partially, to the experimentally observed ductilizing phenomenon in the literature.

Micro calcification evaluation using CR plates in computerized mammography

Energy Technology Data Exchange (ETDEWEB)

Bustos F, M.; Prata M, A., E-mail: mabelita.bfm@gmail.com [Federal University of Minas Gerais, School of Engineering, Department of Nuclear Engineering, Av. Antonio Carlos CEP 131270-901 Belo Horizonte, Minas Gerais (Brazil)

2017-10-15

Cancer is one of the leading causes of mortality in the world. In 2012, about 14 million new cases were registered, of which 1.6 million are breast cancer, according to the World Health Organization. The National Cancer Institute of Brazil estimated 57 thousand new cases of breast cancer by 2016. Mammography is the imaging technique most used worldwide for the early diagnosis of breast cancer. Computed radiography (CR) plates are used for digital radiography, and are widely used to obtain digital mammograms. This work aims to evaluate te response of CR plates to the variation of exposure in mammography equipment. Three CR plates for mammography of different models were used for the study. X-ray beams were selected to perform successive exposures of CR plates by varying the exposure time. These exposures were performed to obtain raw images that were subsequently analyzed using ImageJ software, from which the value of intensity recorded in the central region of each image was obtained, correlating it with the exposure time. From these data the necessary correlations were made to determine the exposure time for which the CR plate begins to saturate, observing that the saturation occurs first for the highest value of the applied voltage. Finally, successive exposures of the CR plate were made using the compressed breast simulator made of acrylic plates and containing microcalcifications of different sizes to determine the qualitative resolution of CR plates, observing that only microcalcifications above 177 μm are visible in the image. The knowledge of saturation characteristics and resolution of the CR plate allows the selection of more adequate parameters to work without approaching the saturation region. (Author)

Structure and grindability of cast Ti-5Cr-xFe alloys

International Nuclear Information System (INIS)

Hsu, H.-C.; Pan, C.-H.; Wu, S.-C.; Ho, W.-F.

2009-01-01

The purpose of this study was to investigate the structure, microhardness and grindability of Ti-5Cr and a series of ternary Ti-5Cr-xFe alloys with 0.1, 0.5, 1, 3 and 5 wt.% Fe, respectively. This study evaluated the phase and structure of Ti-5Cr and Ti-5Cr-xFe alloys, using an X-ray diffraction (XRD) for phase analysis and optical microscope for microstructure of the etched alloys. In addition, grindability was evaluated by measuring the amount of metal volume removed after grinding for 1 min at each of the four rotational speeds of the wheel (500, 750, 1000 or 1200 m/min), with the goal of developing a titanium alloy with better machinability than commercially pure titanium (c.p. Ti). The results showed that the structure of Ti-5Cr-xFe alloys is sensitive to the Fe content. With Fe contents higher than 0.5 wt.%, the equi-axed β phase is entirely retained, while ω phase was found in the Ti-5Cr, Ti-5Cr-0.1Fe, Ti-5Cr-0.5Fe and Ti-5Cr-1Fe alloys. The largest quantity of ω phase and highest microhardness were found in Ti-5Cr-0.5Fe and Ti-5Cr-1Fe alloys. The grinding rates of the Ti-5Cr and Ti-5Cr-xFe alloys showed a similar tendency to the microhardness. The Ti-5Cr, Ti-5Cr-0.1Fe, Ti-5Cr-0.5Fe and Ti-5Cr-1Fe alloys exhibited the best grindability, especially at 500, 750 and 1000 m/min. Furthermore, the grindability of the tested metals increased in proportion to grinding speed up to 1000 m/min, with a decrease after 1200 m/min. This study concluded that Fe may be used to harden titanium and improve the grindability

The LLNL CR-39 personnel neutron dosimeter

International Nuclear Information System (INIS)

Hankins, D.E.; Homann, S.; Westermark, J.

1987-01-01

We developed a personnel neutron dosimetry system based on the electrochemical etching of CR-39 plastic at elevated temperatures. The doses obtained using this dosimeter system are more accurate than those obtained using other dosimetry systems, especially when varied neutron spectra are encountered. This CR-39 dosimetry system does not have the severe energy dependence that exists with albedo neutron dosimeters or the fading and reading problems encountered with NTA film. 3 refs., 4 figs

Study of the oxidation of Fe-Cr alloys at high temperatures; Estudo da oxidacao de ligas Fe-Cr a altas temperaturas

Energy Technology Data Exchange (ETDEWEB)

Carneiro, J.F.; Sabioni, A.C.S. [Universidade Federal de Ouro Preto (LDM/DF/UFOP), MG (Brazil). Dept. de Fisica. Lab. de Difusao em Materiais; Trindade, V.B. [Universidade Federal de Ouro Preto (DEMM/UFOP), MG (Brazil). Dept. de Engenharia Metalurgica e de Materiais; Ji, V. [Laboratoire d' Etude des Materiaux Hors-Equilibre (LEMHE), Orsay (France)

2010-07-01

The high temperature oxidation behavior of Fe-1.5%Cr, Fe-5.0%Cr, Fe-10%Cr and Fe- 15%Cr model alloys were investigated from 700 to 850 deg C, in air atmosphere. The oxidation treatments were performed in a thermobalance with a sensitivity of 1{mu}g. The oxide films grown by oxidation of the alloys were characterized by scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The oxide films are Fe-Cr spinels with variable composition depending on the alloy composition. For all conditions studied, the oxidation kinetics of these alloys follow a parabolic law. The comparison of the oxidation rates of the four alloys, at 700 deg C, shows that the parabolic oxidation constants decrease from 1.96x10{sup -9}g{sup 2}.cm{sup -4}.s{sup -1}, for the alloy Fe-1.5% Cr, to 1.18 x 10-14g{sup 2}.cm{sup -4}.s{sup -1} for the alloy Fe-15% Cr. Comparative analysis of the oxidation behavior of the Fe-10%Cr and Fe-15%Cr alloys, between 700 and 850 deg C, shows that the oxidation rates of these alloys are comparable to 800 deg C, above this temperature the Fe-10%Cr alloy shows lower resistance to oxidation. (author)

Effect of interfacial defects on the electronic and magnetic properties of epitaxial CrAs/InAs and CrAs/CdSe half-metallic multilayers

International Nuclear Information System (INIS)

Galanakis, I.; Lekkas, I.

2010-01-01

We present an extended study of single impurity atoms at the interface between the half-metallic ferromagnetic zinc-blende CrAs compound and the zinc-blende binary InAs and CdSe semiconductors in the form of very thin multilayers. Contrary to the case of impurities in the perfect bulk CrAs studied in Galanakis and Pouliasis [J. Magn. Magn. Mater. 321 (2009) 1084] defects at the interfaces do not alter in general the half-metallic character of the perfect systems. The only exception are Void impurities at Cr or In(Cd) sites which lead, due to the lower-dimensionality of the interfaces with respect to the bulk CrAs, to a shift of the p bands of the nearest neighboring As(Se) atom to higher energies and thus to the loss of the half-metallicity. But Void impurities are Schottky-type and should exhibit high formation energies and thus we expect the interfaces in the case of thin multilayers to exhibit a robust half-metallic character.

The study of Cr3+/Cr2+ redox system by polarographic method

Directory of Open Access Journals (Sweden)

S. A. Pokhmyolkina

2014-08-01

of redox Cr+3/ Cr+2. The specific reaction rate found by extrapolating the straight line constructed in the lgK = f (E coordinates to the equilibrium potential Ep. Equilibrium potential found by the Eyring method as half-wave potential for the reversible waves.We have constructed the initial currents of irreversible waves, considering that the beginning of irreversible and reversible waves practically coincide. Specific reaction rate (K is associated with activation energy given by: lgK= lg(ВТ/h∙ δ – ΔF/2,3RT, where: B is the Boltzmann constant, T is temperature Kelvin , h - Planck constant , δ - the distance between ions 2 ∙ 10-8 cm , R - universal gas constant , ΔF- changing activation energy. Substituting the values of the constants in the equation, we obtain an expression for calculating the activation energy: ΔF = 6,86∙103 – 1,35∙103lgК. An important characteristic of irreversible processes is the change in entropy, as the derivative of the entropy increment in time (diS / dt = ΔS. This quantity can be expressed in terms of current strength (J and overvoltage (η: ΔS = (diS / dt = 1 / T ∙ J η. In polarographic it indicates that the electrochemical process is complicated as compared with delivery of reactant to the electrode. With increasing temperature, we saw insignificant changes in the kinetic characteristics of both anodic and cathodic reduction of chromium salts. Obviously, accelerate the process of discharging ions prevents complication. Conclusion. This indicates a different state of ions of bivalent and trivalent chromium in solution and various ways of the electrode processes.

Removal of Cr(VI) ions by sewage sludge compost biomass from aqueous solutions: Reduction to Cr(III) and biosorption

Science.gov (United States)

Chen, Huixia; Dou, Junfeng; Xu, Hongbin

2017-12-01

Sewage sludge compost biomass was used as a novel biosorbent to remove hexavalent chromium from water. Surface area analysis, scanning electron microscopy, fourier-transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and point zero charge was applied to study the microstructure, compositions and chemical bonding states of the biomass adsorbent. Effects of contact time, biomass dosage, agitation speed, pH, the initial concentration of Cr(VI) and Cr(Ⅲ) on its adsorption removal were also performed in the batch experiments. A model describing adsorption, desorption and reduction phenomena during the sorption process has been referenced to model Cr(VI) sorption onto sewage sludge compost biomass. The result of characterization test shows that adsorption of Cr(VI) onto sewage sludge compost biomass followed by the partial reduction to Cr(Ⅲ) by biomass groups such as hydroxyl, carboxyl, and amino groups. The absorption kinetics model in the description of adsorption-coupled reduction of Cr(VI) fits successfully the kinetic data obtained at different temperatures and describes the kinetics profile of total, hexavalent and trivalent chromium. The study shows that sewage sludge compost biomass could be used as a potential biosorbent for removal of hexavalent chromium from wastewaters.

LET calibration for CR-39 detectors in different oxygen environments

International Nuclear Information System (INIS)

Zhou, D.; Semones, E.; Weyland, M.; Benton, E.R.

2007-01-01

High LET (linear energy transfer) radiation is the main contributor to the radiation field in low Earth orbit (LEO) in terms of dose equivalent. CR-39 plastic nuclear track detectors (PNTDs) can measure the LET spectrum and charge spectrum for the complicated radiation field in space. Previous research indicated that the sensitivity of CR-39 is different for CR-39 PNTDs working in different oxygen environments. LET calibration for CR-39 detectors in different oxygen environments is needed. Almost all the previous LET calibration work was carried out for CR-39 detectors in good-oxygen condition, LET calibration work for CR-39 in poor-oxygen condition has not been conducted until our work. Systematic LET calibrations were carried out by JSC-SRAG (Space Radiation Analysis Group) for CR-39 detectors working in different oxygen environments and abundant results of LET calibrations were obtained. This paper introduces the method for CR-39 LET calibration, presents and discusses the calibration results and some applications

Nuclear Energy Advanced Modeling and Simulation (NEAMS) Accident Tolerant Fuels High Impact Problem: Coordinate Multiscale FeCrAl Modeling

Energy Technology Data Exchange (ETDEWEB)

Gamble, K. A. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hales, J. D. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Zhang, Y. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Andersson, D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Capolungo, L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wirth, B. D. [Univ. of Tennessee, Knoxville, TN (United States)

2017-07-26

Since the events at the Fukushima-Daiichi nuclear power plant in March 2011 significant research has unfolded at national laboratories, universities and other institutions into alternative materials that have potential enhanced ac- cident tolerance when compared to traditional UO2 fuel zircaloy clad fuel rods. One of the potential replacement claddings are iron-chromium-alunimum (FeCrAl) alloys due to their increased oxidation resistance [1–4] and higher strength [1, 2]. While the oxidation characteristics of FeCrAl are a benefit for accident tolerance, the thermal neu- tron absorption cross section of FeCrAl is about ten times that of Zircaloy. This neutronic penalty necessitates thinner cladding. This allows for slightly larger pellets to give the same cold gap width in the rod. However, the slight increase in pellet diameter is not sufficient to compensate for the neutronic penalty and enriching the fuel beyond the current 5% limit appears to be necessary [5]. Current estimates indicate that this neutronic penalty will impose an increase in fuel cost of 15-35% [1, 2]. In addition to the neutronic disadvantage, it is anticipated that tritium release to the coolant will be larger because the permeability of hydrogen in FeCrAl is about 100 times higher than in Zircaloy [6]. Also, radiation-induced hardening and embrittlement of FeCrAl need to be fully characterized experimentally [7]. Due to the aggressive development schedule for inserting some of the potential materials into lead test assemblies or rods by 2022 [8] multiscale multiphysics modeling approaches have been used to provide insight into these the use of FeCrAl as a cladding material. The purpose of this letter report is to highlight the multiscale modeling effort for iron-chromium-alunimum (FeCrAl) cladding alloys as part of the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program through its Accident Tolerant Fuel (ATF) High Impact Problem (HIP). The approach taken throughout the HIP is to

Enhancement of mechanical and tribological properties in AISI D3 steel substrates by using a non-isostructural CrN/AlN multilayer coating

Energy Technology Data Exchange (ETDEWEB)

Cabrera, G. [Thin Film Group, Universidad del Valle in Cali (Colombia); Caicedo, J.C., E-mail: jcaicedoangulo@gmail.com [Thin Film Group, Universidad del Valle in Cali (Colombia); Amaya, C. [Thin Film Group, Universidad del Valle in Cali (Colombia); Laboratory of Hard Coatings, CDT-ASTIN SENA in Cali (Colombia); Yate, L. [Department de Fisica Aplicada i Optica, Universitat de Barcelona, Catalunya (Spain); Munoz Saldana, J. [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Queretaro (Mexico); Prieto, P. [Thin Film Group, Universidad del Valle in Cali (Colombia); Center of Excellence for Novel Materials - CENM, Calle 13 100-00 320-026, Cali (Colombia)

2011-02-15

Enhancement of mechanical and tribological properties on AISI D3 steel surfaces coated with CrN/AlN multilayer systems deposited in various bilayer periods ({Lambda}) via magnetron sputtering has been studied in this work exhaustively. The coatings were characterized in terms of structural, chemical, morphological, mechanical and tribological properties by X-ray diffraction (XRD), electron dispersive spectrograph, atomic force microscopy, scanning and transmission electron microscopy, nanoindentation, pin-on-disc and scratch tests. The failure mode mechanisms were observed via optical microscopy. Results from X-ray diffraction analysis revealed that the crystal structure of CrN/AlN multilayer coatings has a NaCl-type lattice structure and hexagonal structure (wurtzite-type) for CrN and AlN, respectively, i.e., made was non-isostructural multilayers. An enhancement of both hardness and elastic modulus up to 28 GPa and 280 GPa, respectively, was observed as the bilayer periods ({Lambda}) in the coatings were decreased. The sample with a bilayer period ({Lambda}) of 60 nm and bilayer number n = 50 showed the lowest friction coefficient ({approx}0.18) and the highest critical load (43 N), corresponding to 2.2 and 1.6 times better than those values for the coating deposited with n = 1, respectively. The best behavior was obtained when the bilayer period ({Lambda}) is 60 nm (n = 50), giving the highest hardness 28 GPa and elastic modulus of 280 GPa, the lowest friction coefficient ({approx}0.18) and the highest critical load of 43 N. These results indicate an enhancement of mechanical, tribological and adhesion properties, comparing to the CrN/AlN multilayer systems with 1 bilayer at 28%, 21%, 40%, and 30%, respectively. This enhancement in hardness and toughness for multilayer coatings could be attributed to the different mechanisms for layer formation with nanometric thickness such as the Hall-Petch effect and the number of interfaces that act as obstacles for the

CrN thin films prepared by reactive DC magnetron sputtering for symmetric supercapacitors

KAUST Repository

Wei, Binbin

2016-12-29

Supercapacitors have been becoming indispensable energy storage devices in micro-electromechanical systems and have been widely studied over the past few decades. Transition metal nitrides with excellent electrical conductivity and superior cycling stability are promising candidates as supercapacitor electrode materials. In this work, we report the fabrication of CrN thin films using reactive DC magnetron sputtering and further their applications for symmetric supercapacitors for the first time. The CrN thin film electrodes fabricated under the deposition pressure of 3.5 Pa show an areal specific capacitance of 12.8 mF cm at 1.0 mA cm and high cycling stability with 92.1% capacitance retention after 20 000 cycles in a 0.5 M HSO electrolyte. Furthermore, our developed CrN//CrN symmetric supercapacitor can deliver a high energy density of 8.2 mW h cm at the power density of 0.7 W cm along with outstanding cycling stability. Thus, the CrN thin films have great potential for application in supercapacitors and other energy storage systems.

Influence of Mo addition on the tempered properties of 13Cr martensitic stainless steel

International Nuclear Information System (INIS)

Jung, Byong Ho; Ahn, Yong Sik

1998-01-01

In order to investigate the effect of Mo addition on the mechanical properties of 13Cr-0.2C martensitic stainless steel, tensile test and Charpy V-notch test were performed after tempering at the temperature range of 200∼700 .deg. C following austenitizing at 1100 .deg. C. The yield strength and hardness of the steel were increased with the increase of Mo content at all tempering conditions, because Mo causes retardation of precipitation and coarsening of carbides and solid solution strengthening of matrix. Except 500 .deg. C of tempering temperature, the Charpy impact energy was significantly increased with Mo content and showed the highest value at 1.5 wt% addition. The increase of impact energy of the steel containing Mo is thought to be caused by δ-ferrite formed in the tempered martensitic matrix. At 500 .deg. C tempering, Charpy impact energy was decreased drastically due to temper embrittlement and it was not possible to prevent it even though Mo was added up to 1.5 wt%

N–Mg dual-acceptor co-doping in CuCrO{sub 2} studied by first-principles calculations

Energy Technology Data Exchange (ETDEWEB)

Xu, Ying, E-mail: 1080071@hnust.edu.cn [School of Physics, Hunan University of Science and Technology, Xiangtan 411201 (China); Nie, Guo-Zheng [School of Physics, Hunan University of Science and Technology, Xiangtan 411201 (China); Zou, Daifeng [School of Physics, Hunan University of Science and Technology, Xiangtan 411201 (China); Shenzhen Key Laboratory of Nanobiomechanics, Shenzhen Institutes of Advanced Technology, Chinese Academy of Science, Shenzhen 518055 (China); Tang, Jing-Wu [School of Physics, Hunan University of Science and Technology, Xiangtan 411201 (China); Ao, Zhimin, E-mail: Zhimin.Ao@gdut.edu.cn [Institute of Environmental Health and Pollution Control, School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006 (China)

2016-11-25

In this paper, N–Mg dual-acceptor co-doping in CuCrO{sub 2} is investigated by first-principles calculations. The electronic structure and formation energies of Mg substituting Cr-site, N substituting O-site, and co-doping of both Mg on Cr-site and N on O-site in CuCrO{sub 2} are calculated. It is found that the structure with N and Mg codoped at the nearest sites has the lowest energy due to a modest attractive interaction between the two dopants. Compared with single N or Mg doped CuCrO{sub 2}, the N–Mg codoped CuCrO{sub 2} has a lower formation energy and shallower transition level. In addition, the total density of states (DOS) analysis shows that more hole states appear above the Fermi level and higher DOS for N–Mg co-doping is obtained in the N–Mg codoped CuCrO{sub 2}, which is good to enhance the p-type conductivity in CuCrO{sub 2}. - Highlights: • N–Mg dual-acceptor co-doping in CuCrO{sub 2} is investigated. • N–Mg complex has a lower formation energy and shallower transition level. • More hole states appear above the Fermi level for N–Mg co-doping. • N–Mg co-doping in CuCrO{sub 2} can be expected to have more stable p-type conductivity.

Microbial Precipitation of Cr(III)-Hydroxide and Se(0) Nanoparticles During Anoxic Bioreduction of Cr(VI)- and Se(VI)-Contaminated Water.

Science.gov (United States)

Kim, Yumi; Oh, Jong-Min; Roh, Yul

2017-04-01

This study examined the microbial precipitations of Cr(III)-hydroxide and Se(0) nanoparticles during anoxic bioreductions of Cr(VI) and Se(VI) using metal-reducing bacteria enriched from groundwater. Metal-reducing bacteria enriched from groundwater at the Korea Atomic Energy Research Institute (KAERI) Underground Research Tunnel (KURT), Daejeon, S. Korea were used. Metal reduction and precipitation experiments with the metal-reducing bacteria were conducted using Cr(VI)- and Se(VI)-contaminated water and glucose as a carbon source under an anaerobic environment at room temperature. XRD, SEM-EDX, and TEM-EDX analyses were used to characterize the mineralogy, crystal structure, chemistry, shape, and size distribution of the precipitates. The metal-reducing bacteria reduced Cr(VI) of potassium chromate (K₂CrO₄) to Cr(III) of chromium hydroxide [Cr(OH)3], and Se(VI) of sodium selenate (Na₂SeO₄) to selenium Se(0), with changes of color and turbidity. XRD, SEM-EDX, and TEM-EDX analyses revealed that the chromium hydroxide [Cr(OH)₃] was formed extracellularly with nanoparticles of 20–30 nm in size, and elemental selenium Se(0) nanoparticles had a sphere shape of 50–250 nm in size. These results show that metal-reducing bacteria in groundwater can aid or accelerate precipitation of heavy metals such as Cr(VI) and Se(VI) via bioreduction processes under anoxic environments. These results may also be useful for the recovery of Cr and Se nanoparticles in natural environments.

Comparison of the microstructure and phase stability of as-cast, CAD/CAM and powder metallurgy manufactured Co-Cr dental alloys.

Science.gov (United States)

Li, Kai Chun; Prior, David J; Waddell, J Neil; Swain, Michael V

2015-12-01

The objective of this study was to identify the different microstructures produced by CC, PM and as-cast techniques for Co-Cr alloys and their phase stability following porcelain firings. Three bi-layer porcelain veneered Co-Cr specimens and one monolithic Co-Cr specimen of each alloy group [cast, powder metallurgy (PM), CAD/CAM (CC)] were manufactured and analyzed using electron backscatter diffraction (EBSD), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). Specimens were treated to incremental numbers of porcelain firings (control 0, 5, 15) with crystallographic data, grain size and chemical composition subsequently obtained and analyzed. EBSD datasets of the cast alloy indicated large grains >200 μm whereas PM and CC alloy consisted of mean arithmetic grain sizes of 29.6 μm and 19.2 μm respectively. XRD and EBSD results both indicated the highest increase in hcp content (>13vol%) for cast Co-Cr alloy after treatment with porcelain firing while PM and CC indicated .05) was observed in CC. EDS line scans indicated an increase in Cr content at the alloy surface after porcelain firing treatment for all three alloys. PM and CC produced alloy had superior fcc phase stability after porcelain firings compared to a traditional cast alloy. It is recommended that PM and CC alloys be used for porcelain-fused-to-metal restorations. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Crystal structure, Raman scattering and magnetic properties of CuCr2-xZrxSe4 and CuCr2-xSnxSe4 selenospinels

Science.gov (United States)

Pinto, C.; Galdámez, A.; Barahona, P.; Moris, S.; Peña, O.

2018-06-01

Selenospinels, CuCr2-xMxSe4 (M = Zr and Sn), were synthesized via conventional solid-state reactions. The crystal structure of CuCr1.5Sn0.5Se4, CuCr1.7Sn0.3Se4, CuCr1.5Zr0.5Se4, and CuCr1.8Zr0.2Se4 were determined using single-crystal X-ray diffraction. All the phases crystallized in a cubic spinel-type structure. The chemical compositions of the single-crystals were examined using energy-dispersive X-ray analysis (EDS). Powder X-ray diffraction patterns of CuCr1.3Sn0.7Se4 and CuCr1.7Sn0.3Se4 were consistent with phases belonging to the Fd 3 bar m Space group. An analysis of the vibrational properties on the single-crystals was performed using Raman scattering measurements. The magnetic properties showed a spin glass behavior with increasing Sn content and ferromagnetic order for CuCr1.7Sn0.3Se4.

Broadband downshifting luminescence in Cr³⁺₋Yb³⁺ codoped garnet for efficient photovoltaic generation.

Science.gov (United States)

Ye, Song; Zhou, Jiajia; Wang, Shiting; Hu, Rongxuan; Wang, Deping; Qiu, Jianrong

2013-02-25

The Cr³⁺₋Yb³⁺ codoped YAG crystals were synthesized by the solid state reaction method, in which the intense near-infrared emission around 1000 nm originated from Yb³⁺ ²F₅/₂ →²F₇/₂ transition was obtained due to the efficient energy transfer from Cr³⁺ to Yb³⁺. The stable and transient spectral measurements revealed that the phonon assistant energy transfer process is responsible for the energy transfer from Cr³⁺ to Yb³⁺ upon both the excitations of Cr³⁺: ⁴T₁ and ⁴T₂> energy levels. Due to the effective absorption of Cr³⁺ in the visible region in YAG and the efficient energy transfer to Yb³⁺, this material can be developed as spectral convertors to improve silicon solar cell photovoltaic conversion efficiency.

Lowest cost due to highest productivity and highest quality

Science.gov (United States)

Wenk, Daniel

2003-03-01

Since global purchasing in the automotive industry has been taken up all around the world there is one main key factor that makes a TB-supplier today successful: Producing highest quality at lowest cost. The fact that Tailored Blanks, which today may reach up to 1/3 of a car body weight, are purchased on the free market but from different steel suppliers, especially in Europe and NAFTA, the philosophy on OEM side has been changing gradually towards tough evaluation criteria. "No risk at the stamping side" calls for top quality Tailored- or Tubular Blank products. Outsourcing Tailored Blanks has been starting in Japan but up to now without any quality request from the OEM side like ISO 13919-1B (welding quality standard in Europe and USA). Increased competition will automatically push the quality level and the ongoing approach to combine high strength steel with Tailored- and Tubular Blanks will ask for even more reliable system concepts which enables to weld narrow seams at highest speed. Beside producing quality, which is the key to reduce one of the most important cost driver "material scrap," in-line quality systems with true and reliable evaluation is going to be a "must" on all weld systems. Traceability of all process related data submitted to interfaces according to customer request in combination with ghost-shift-operation of TB systems are tomorrow's state-of-the-art solutions of Tailored Blank-facilities.

Prediction of half-metallic properties in TlCrS{sub 2} and TlCrSe{sub 2} based on density functional theory

Energy Technology Data Exchange (ETDEWEB)

Hashimzade, F.M.; Huseinova, D.A. [Institute of Physics, National Academy of Sciences of Azerbaijan, AZ 1143 Baku (Azerbaijan); Jahangirli, Z.A. [Institute of Physics, National Academy of Sciences of Azerbaijan, AZ 1143 Baku (Azerbaijan); Institute of Radiation Problems, National Academy of Sciences of Azerbaijan, AZ 1143 Baku (Azerbaijan); Mehdiyev, B.H., E-mail: bachschi@yahoo.de [Institute of Physics, National Academy of Sciences of Azerbaijan, AZ 1143 Baku (Azerbaijan)

2017-08-01

Highlights: • Half-metallic properties of TlCrS2, TlCrSe2 and hypothetical TlCrSSe have been investigated by first-principles all-electron full-potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method based on density functional theory (DFT). • Total magnetic moment keeps its integer value on a relatively wide range of changes in volume (−10% ÷ 10%) for TlCrS2 and TlCrSSe, while total magnetic moment TlCrSe2 decreases with increasing volume, approaching to integer value 3 μB. • The states at the Fermi level in the case of spin-up channel consist of a hybridization of p-states of the atom S(Se) with d-states of Cr. - Abstract: Half-metallic properties of TlCrS{sub 2}, TlCrSe{sub 2} and hypothetical TlCrSSe have been investigated by first-principles all-electron full-potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method based on density functional theory (DFT). The results of calculations show that TlCrS{sub 2} and TlCrSSe are half-metals with energy gap (E{sub g}) ∼0.12 eV for spin-down channel. Strong hybridization of p-state of chalchogen and d-state of Cr leads to bonding and antibonding states and subsequently to the appearance of a gap in spin-down channel of TlCrS{sub 2} and TlCrSSe. In the case of TlCrSe{sub 2}, there is a partial hybridization and p-state is partially present in the DOS at Fermi level making this compound nearly half-metallic. The present calculations revealed that total magnetic moment keeps its integer value on a relatively wide range of changes in volume (−10% ÷ 10%) for TlCrS{sub 2} and TlCrSSe, while total magnetic moment of TlCrSe{sub 2} decreases with increasing volume approaching to integer value 3 μB.

Reactive synthesis of Ti-W-Cr-B mixing powder by spark plasma sintering; Hoden plasma shoketsu ni yoru Ti-W-Cr-B kongo funmatsu no hanno gosei

Energy Technology Data Exchange (ETDEWEB)

Kaga, H. [Hokkaido Industrial Technology Center, Sapporo (Japan); Carrillo-Heian, E.M.; Munir, Z.A. [University of California, CA, (United States)

2000-08-15

The reactive sintered compacts of Ti-W-Cr-B mixed powders were manufactured by a pulse electric current technique. Identification and characterization of the resulting boride phase were done using EPMA, XRD and other methods. The density of the sintered compacts rose rapidly with sintering temperature up to 1,773 K, at which temperature the relative density was 94%. Above this temperature, the density rose only slightly with increasing sintering temperature. The borides of Ti and W were synthesized from mixed metal powders by this method. The type of boride formed and its composition depended on sintering temperature. Compacts sintered at lower temperatures consisted of WB{sub 2} and TiB{sub 2} phases, but at the highest sintering temperature, 2,173K, the main phase was (Ti, W, Cr)B{sub 2} solid solution, in which W and Cr were dissolved in TiB{sub 2}. There was also a very small amount of {beta}-(W, Ti, Cr)B phase. By annealing compact sintered at high temperature, the (Ti, W, Cr)B{sub 2} solid solution phase decomposed and the amount decreased. (author)

Kinetic stable Cr isotopic fractionation between aqueous Cr(III)-Cl-H2O complexes at 25 °C: Implications for Cr(III) mobility and isotopic variations in modern and ancient natural systems

Science.gov (United States)

Babechuk, Michael G.; Kleinhanns, Ilka C.; Reitter, Elmar; Schoenberg, Ronny

2018-02-01

The stable Cr isotope fractionation preserved in natural substances has been attributed predominantly to Cr(III)-Cr(VI) redox transformations. However, non-redox reaction pathways (e.g., ligand-promoted dissolution, ligand exchange, adsorption of Cr(III)) are liable to contribute to isotopic fractionation in natural systems given that soluble Cr(III)-ligands have been directly documented or modeled in several marine, continental, and hydrothermal environments. This study isolates the stable Cr isotope fractionation accompanying Cl-H2O ligand exchange during the transformation of three aqueous species in the Cr(III)-Cl-H2O system, [CrCl2(H2O)4]+aq (abr. CrCl2+ or S1), [CrCl(H2O)5]2+aq (abr. CrCl2+ or S2), and [Cr(H2O)6]3+aq (abr. Cr3+ or S3), at low pH (≤2). In dilute HCl (0.01 to 1 M), Cr3+ is the kinetically favoured species and transformation of CrCl2+ to CrCl2+ to Cr3+ via 2 steps of dechlorination/hydrolyzation begins immediately upon dissolution of a Cr(III)-Cl solid. Individual species are separated with cation exchange chromatography at different stages of transformation and inter- and intra-species (across an elution peak of one species) isotopic fractionation of up to 1 and 2‰ (δ53/52Cr), respectively, is documented. Comparison of peak elution characteristics with Cr-Cl-H-O isotopologue mass abundances suggests mass-dependent sorting of isotopologues alone cannot explain intra-species fractionation, supporting a previously published proposal that preferential adsorption of light Cr isotopes on the resin is driven by vibrational energy effects. The transformation of CrCl2+ to CrCl2+ is faster than CrCl2+ to Cr3+ and the rates of both transformations increase with solution pH. Preferential reaction of light Cr(III) isotopes into product species occurs during each transformation, consistent with closed-system, kinetic fractionation during Cl-H2O ligand exchange. Inter-species fractionation is assessed using time-series experiments beginning from the

The relationships between heavy metal (Cd, Cr, Cu, Fe, Pb, Zn) levels and the size of six Mediterranean fish species

International Nuclear Information System (INIS)

Canli, Mustafa; Atli, Gueluezar

2003-01-01

Significant relationships between metal concentrations and fish size were negative. - Heavy metal (Cd, Cr, Cu, Fe, Pb, Zn) concentrations in the muscle, gill and liver of six fish species (Sparus auratus, Atherina hepsetus, Mugil cephalus, Trigla cuculus, Sardina pilchardus and Scomberesox saurus) from the northeast Mediterranean Sea were measured and the relationships between fish size (length and weight) and metal concentrations in the tissues were investigated by linear regression analysis. Metal concentrations (as μg/g d.w.) were highest in the liver, except for iron in the gill of Scomberesox saurus and lowest in the muscle of all the fish species. Highest concentrations of Cd (4.50), Cr (17.1) and Pb (41.2) were measured in liver tissues of T. cuculus, Sardina pilchardus and A. hepsetus, respectively. The liver of M. cephalus showed strikingly high Cu concentrations (202.8). The gill of Scomberesox saurus was the only tissue that showed highest (885.5) iron concentrations. Results of linear regression analysis showed that, except in a few cases, significant relationships between metal concentrations and fish size were negative. Highly significant (P<0.001) negative relationships were found between fish length and Cr concentrations in the liver of A. hepsetus and M. cephalus, and Cr concentrations in the gill of T. cuculus. Cr and Pb concentrations in the liver and Cu concentrations in all the tissues of Scomberesox saurus also showed very significant (P<0.001) negative relationships. Negative relationships found here were discussed

Microstructure and damage behavior of W-Cr alloy under He irradiation

Science.gov (United States)

Huang, Ke; Luo, Lai-Ma; Zan, Xiang; Xu, Qiu; Liu, Dong-Guang; Zhu, Xiao-Yong; Cheng, Ji-Gui; Wu, Yu-Cheng

2018-04-01

In this study, a large-power inductively coupled plasma source was designed to perform the continuous helium ion irradiations of W-Cr binary alloy (W-20 wt%Cr) under relevant conditions of the International Thermonuclear Experimental Reactor. Surface damages and microstructures of irradiated W-20Cr were observed by using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. The addition of Cr dramatically enhanced the micro-hardness of the obtained bulk materials, and the interface between the W matrix and the second phase Cr-O is a semi-coherent interface. After irradiation, the doping of Cr element effectively reduces the damage of the W matrix during the irradiation process. The semi-coherent interface between the second phase and the W matrix improves the anti-irradiation performance of the W-20Cr alloy.

Preparation and Oxidation Performance of Y and Ce-Modified Cr Coating on open-cell Ni-Cr-Fe Alloy Foam by the Pack Cementation

Science.gov (United States)

Pang, Q.; Hu, Z. L.; Wu, G. H.

2016-12-01

Metallic foams with a high fraction of porosity, low density and high-energy absorption capacity are a rapidly emerging class of novel ultralight weight materials for various engineering applications. In this study, Y-Cr and Ce-Cr-coated Ni-Cr-Fe alloy foams were prepared via the pack cementation method, and the effects of Y and Ce addition on the coating microstructure and oxidation performance were analyzed in order to improve the oxidation resistance of open-cell nickel-based alloy foams. The results show that the Ce-Cr coating is relatively more uniform and has a denser distribution on the surface of the nickel-based alloy foam. The surface grains of the Ce-Cr-coated alloy foam are finer compared to those of the Y-Cr-coated alloy foam. An obvious Ce peak appears on the interface between the coating and the alloy foam strut, which gives rise to a "site-blocking" effect for the short-circuit transport of the cation in the substrate. X-ray diffraction analysis shows that the Y-Cr-coated alloy foam mainly consists of Cr, (Fe, Ni) and (Ni, Cr) phases in the surface layer. The Ce-Cr-coated alloy foam is mainly composed of Cr and (Ni, Cr) phases. Furthermore, the addition of Y and Ce clearly lead to an improvement in the oxidation resistance of the coated alloy foams in the temperature range of 900-1000 °C. The addition of Ce is especially effective in enhancing the diffusion of chromium to the oxidation front, thus, accelerating the formation of a Cr2O3 layer.

Distribution of Cr atoms in the surface zone of Fe-rich Fe–Cr alloys quenched into various media: Mössbauer spectroscopic study

International Nuclear Information System (INIS)

Dubiel, Stanisław M.; Cieślak, Jakub; Żukrowski, Jan

2015-01-01

Graphical abstract: Chromium depletion, Δx = x_k − x, in Fe_1_0_0_−_xCr_x (x = 2.2, 3.9, 6.4, 8.5, 10.25, 10.75, 14.9, 15.15) alloys quenched into LN (left panel) and those quenched onto brass (right panel) as found from CEMS (pre surface zone) and TRANS (bulk) Mössbauer spectra (x_k – Cr content in the pre surface or bulk as estimated from the average hyperfine field found for the quenched samples). - Highlights: • Effect of quenching media on Cr atom distribution in Fe–Cr alloys was determined. • Significant differences between bulk and pre surface zone were revealed. • Quenching into water and LH resulted in surface oxidation of samples. • Samples quenched onto a block of brass were not oxidized. - Abstract: Effect of a quenching medium (water, liquid nitrogen and block of brass) on a distribution of Cr atoms in the surface zone of Fe_1_0_0_−_xCr_x (x ≤ 19) alloys was studied with the Mössbauer spectroscopy. The distribution of Cr atoms was expressed in terms of the Cowley–Warren short-range order (SRO) parameters: 〈α_1〉 for the first neighbor-shell, 〈α_2〉 for the second neighbor-shell and 〈α_1_2〉 for both neighbor-shells. It was revealed that none of the quenching media resulted in a random distribution of atoms, yet the degree of randomness was the highest for the samples quenched onto the block of brass. The quenching into water and liquid nitrogen caused a partial oxidation of samples’ surface accompanied by a chromium depletion of the bulk. Quantitative analysis of various phases in the studied samples both in their bulk as well as in pre surface zones was carried out.

Cr(III) reactivity and foot dermatitis in Cr(VI) positive patients

DEFF Research Database (Denmark)

Hansen, Malene Barré; Menné, Torkil; Johansen, Jeanne Duus

2006-01-01

Chromium allergy has become synonymous with Cr(VI) allergy. However, real exposure to chromium from leather products may include both Cr(III) and Cr(VI). In this study, we investigate the reactivity to both Cr(VI) and Cr(III) in consecutive patients to analyse the relation between foot eczema/leather...... to Cr(III). The increased risk was not due to a higher degree of sensitivity to Cr(VI). Leather was reported most frequently as the suspected cause of chromium dermatitis (54%). However, Cr(VI) allergics having foot eczema and positive or doubtful Cr(III) reactions often had positive reactions to other...

Application of double-spike isotope dilution for the accurate determination of Cr(III), Cr(VI) and total Cr in yeast.

Science.gov (United States)

Yang, Lu; Ciceri, Elena; Mester, Zoltán; Sturgeon, Ralph E

2006-11-01

A method is presented for the simultaneous determination of Cr(III) and Cr(VI) in yeast using species-specific double-spike isotope dilution (SSDSID) with anion-exchange liquid chromatography (LC) separation and sector field inductively coupled plasma mass spectrometric (SF-ICP-MS) detection. Total Cr is quantitated using ID SF-ICP-MS. Samples were digested on a hot plate at 95+/-2 degrees C for 6 h in an alkaline solution of 0.5 M NaOH and 0.28 M Na2CO3 for the determination of Cr(III) and Cr(VI), whereas microwave-assisted decomposition with HNO3 and H2O2 was used for the determination of total Cr. Concentrations of 2,014+/-16, 1,952+/-103 and 76+/-48 mg kg-1 (one standard deviation, n=4, 3, 3), respectively were obtained for total Cr, Cr(III) and Cr(VI) in the yeast sample. Significant oxidation of Cr(III) to Cr(VI) (24.2+/-7.6% Cr(III) oxidized, n=3) and reduction of Cr(VI) to Cr(III) (37.6+/-6.5% Cr(VI) reduced, n=3) occurred during alkaline extraction and subsequent chromatographic separation at pH 7. Despite this significant bidirectional redox transformation, quantitative recoveries for both Cr(III) and Cr(VI) were achieved using the SSDSID method. In addition, mass balance between total Cr and the sum of Cr(III) and Cr(VI) concentrations was achieved. Method detection limits of 0.3, 2 and 30 mg kg-1 were obtained for total Cr, Cr(VI) and Cr(III), respectively, based on a 0.2-g sub-sample.

The helium effect at grain boundaries in Fe-Cr alloys: A first-principles study

Energy Technology Data Exchange (ETDEWEB)

Zemła, M.R., E-mail: marcin.zemla@wimpw.edu.pl [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland); Wróbel, J.S.; Wejrzanowski, T. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland); Nguyen-Manh, D. [CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Kurzydłowski, K.J. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland)

2017-02-15

Helium is produced in the structural materials in nuclear power plants by nuclear transmutation following neutron irradiation. Since the solubility of helium in all metals is extremely low, helium tends to be trapped at defects such as vacancies, dislocations and grain boundaries, which cause material embrittlement. Density functional theory (DFT) calculations were performed in order to investigate the helium effect at grain boundaries (GBs) in iron-chromium alloys. Both cohesive energy and magnetic properties at symmetric Σ3(1 1 1) and Σ5(2 1 0) tilt Fe GBs are studied in the presence of Cr and He atoms. It is found that the presence of Cr atoms increases cohesive energy, at different He concentrations, and strongly influences magnetic properties at the GBs. The effect of the segregation energy of helium atom as a function of the different positions of Cr atoms located inside/outside a GB has been considered. Results of the present first-principles study enable one to clarify the role of Cr in understanding the helium effect in Fe-Cr-based alloys.

Analysis of precipitation in a Cu-Cr-Zr alloy

Institute of Scientific and Technical Information of China (English)

Zhao Mei; Lin Guobiao; Wang Zidong; Zhang Maokui

2008-01-01

Precipites in Cu-0.42%Cr-0.21%Zr alloy were analyzed by using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDXS) and transmission electron microscope (TEM). After the solid solution was performed at 980℃ for 2 h, water-quenched and aged at 450℃ for 20 h, the precipite had a bimodal distribution of precipitate size. The coarse precipitates are pure Cr and Cu5Zr, the dispersed fine precipitate is CrCu2(Zr, Mg) and pure Cr ranging from 1 to 50 nm. The coarse phases formed during solidification and were left undissolved during solid solution. The fine precipitates are the hardening precipitates that form due to decomposition of the supersaturated solid solution during aging.

Density functional theory study of bulk and single-layer magnetic semiconductor CrPS4

Science.gov (United States)

Zhuang, Houlong L.; Zhou, Jia

2016-11-01

Searching for two-dimensional (2D) materials with multifunctionality is one of the main goals of current research in 2D materials. Magnetism and semiconducting are certainly two desirable functional properties for a single 2D material. In line with this goal, here we report a density functional theory (DFT) study of bulk and single-layer magnetic semiconductor CrPS4. We find that the ground-state magnetic structure of bulk CrPS4 exhibits the A-type antiferromagnetic ordering, which transforms to ferromagnetic (FM) ordering in single-layer CrPS4. The calculated formation energy and phonon spectrum confirm the stability of single-layer CrPS4. The band gaps of FM single-layer CrPS4 calculated with a hybrid density functional are within the visible-light range. We also study the effects of FM ordering on the optical absorption spectra and band alignments for water splitting, indicating that single-layer CrPS4 could be a potential photocatalyst. Our work opens up ample opportunities of energy-related applications of single-layer CrPS4.

Direct observation of low energy nuclear spin excitations in HoCrO3 by high resolution neutron spectroscopy.

Science.gov (United States)

Chatterji, T; Jalarvo, N; Kumar, C M N; Xiao, Y; Brückel, Th

2013-07-17

We have investigated low energy nuclear spin excitations in the strongly correlated electron compound HoCrO3. We observe clear inelastic peaks at E = 22.18 ± 0.04 μeV in both energy loss and gain sides. The energy of the inelastic peaks remains constant in the temperature range 1.5-40 K at which they are observed. The intensity of the inelastic peak increases at first with increasing temperature and then decreases at higher temperatures. The temperature dependence of the energy and intensity of the inelastic peaks is very unusual compared to that observed in other Nd, Co, V and also simple Ho compounds. Huge quasielastic scattering appears at higher temperatures presumably due to the fluctuating electronic moments of the Ho ions that get increasingly disordered at higher temperatures. The strong quasielastic scattering may also originate in the first Ho crystal-field excitations at about 1.5 meV.

Atomic investigation of alloying Cr, Ti, Y additions in a grain boundary of vanadium

Energy Technology Data Exchange (ETDEWEB)

Zhang, Pengbo, E-mail: zhangpb@dlmu.edu.cn [Department of Physics, Dalian Maritime University, Dalian 116026 (China); Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Ministry of Education, Dalian 116024 (China); Li, Xiaojie; Zhao, Jijun [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Ministry of Education, Dalian 116024 (China); Zheng, Pengfei; Chen, Jiming [Southwestern Institute of Physics, Chengdu 610041 (China)

2016-01-15

The effect of alloying additions (Cr, Ti and Y) in a vanadium (V) ∑3 (111) grain boundary (GB) is investigated by first-principles calculations. To determine site preference and segregation properties of Cr, Ti and Y in the GB and bulk, we calculate the formation energies and segregation energies for different interstitial and substitutional sites. Cr/Ti/Y atom prefers to segregate to the substitutional sites of the GB from bulk environment, whereas Cr segregation to GB is very weak. Based on the Rice and Wang's model, Cr acts as the GB cohesion, while Ti and Y are strong embrittlers. The analysis of atomic and electronic structures provides a reasonable expansion for the embrittlement behavior. Moreover, the effect of Cr, Ti and Y in the GB on solution of interstitial impurities C, N, O, H, and He are determined. The results show that Cr restrains solution of these impurities in the GB, while Ti tends to form Ti–N complex by absorbing N impurities and Y can absorbs O and He impurities. The present calculations are helpful for understanding the behavior of alloying Cr, Ti, Y additions at the grain boundary of vanadium.

XRD and TEM analysis of microstructure in the welding zone of 9Cr ...

Indian Academy of Sciences (India)

Unknown

XRD and TEM analysis of microstructure in the welding zone of. 9Cr–1Mo–V–Nb ... steel, which has highest Cr content in the heat-resisting. Cr–Mo ... This research provides essential ... film samples were observed under TEM and select elec-.

Track detection on the cells exposed to high Linear Energy Transfer heavy-ions by Cr-39 plastic and terminal deoxynucleotidyl transferase(Td T)

International Nuclear Information System (INIS)

Mehnati, P.; Keshtkar, A.; Mesbahi, A.; Sasaki, H.

2006-01-01

The fatal effect of ionizing radiation on cells depends on Linear Energy Transfer level. The distribution of ionizing radiation is sparse and homogeneous for low Linear Energy Transfer radiations such as X or y, but it is dense and concentrated for high Linear Energy Transfer radiation such as heavy-ions radiation. Materials and Methods: Chinese hamster ovary cells (CHO-K1) were exposed to 4 Gy Fe-ion 2000 keV/μm. The Cr-39 is a special and sensitive plastic used to verify exact position of heavy-ions traversal. Terminal deoxynucleotidyl transferase is an enzyme labeled with [3 H ] d ATP for detection of cellular DNA damage by autoradiography assay. Results: The track of heavy ions traversals presented by pit size was almost similar for all different doses of radiation. No pits to show the track of traversal were found in 20% of the cell nuclei of the irradiation. Apparently these fractions of cells wave not hit by heavy ions. Conclusion: This study indicated the possible usefulness of both the Cr-39 plastics and DNA labeling with Terminal deoxynucleotidyl transferase method for evaluating the biological effect of heavy-ions in comparison with low Linear Energy Transfer ionizing radiation

NMR of Cu satellites in the Kondo alloy CuCr

International Nuclear Information System (INIS)

Azevedo, L.J.; Follstaedt, D.; Narath, A.

1978-01-01

Using pulsed NMR techniques, resonances of Cu nuclei which are near neighbors to Cr impurities (c = 100 and 200 ppM) in CuCr (theta/sub k/ approx. 3K) have been studied in the temperature range 1 to 4K and applied fields H 0 = 20 to 125 kOe. At the highest fields and lowest temperatures the satellite shifts approach saturation. Above approx. 40 kOe the spin-lattice relaxation rate T 1 -1 is proportional to T/H 0 2 , indicating that the dominant relaxation mechanism arises from transverse fluctuations of a polarized local moment. The measured rates yield a local-moment/conduction-electron exchange interaction vertical bar J 0 vertical bar/g = 0.30, where g is the Cr g-value. Below approx. 40 kOe T 1 -1 appears to be slightly enhanced in comparison with the high-field behavior, but becomes field independent below approx. 30 kOe. Both effects are attributed to Kondo anomalies

Study on Cr(VI) Leaching from Cement and Cement Composites

Science.gov (United States)

Palascakova, Lenka; Kanuchova, Maria

2018-01-01

This paper reports an experimental study on hexavalent chromium leaching from cement samples and cement composites containing silica fume and zeolite additions that were subjected to various leaching agents. The water-soluble Cr(VI) concentrations in cements ranged from 0.2 to 3.2 mg/kg and represented only 1.8% of the total chromium content. The presence of chromium compounds with both chromium oxidation states of III and VI was detected in the cement samples by X-ray photoelectron spectroscopy (XPS). Leaching tests were performed in a Britton-Robinson buffer to simulate natural conditions and showed increased dissolution of Cr(VI) up to 6 mg/kg. The highest amount of leached hexavalent chromium was detected after leaching in HCl. The findings revealed that the leaching of chromium from cements was higher by 55–80% than that from the cement composites. A minimum concentration was observed for all cement samples when studying the relationship between the soluble Cr(VI) and the cement storage time. PMID:29690550

Optical properties of single doped Cr3+ and co-doped Cr3+-Nd3+ aluminum tantalum tellurite glasses

International Nuclear Information System (INIS)

Rodriguez-Mendoza, U.R.; Speghini, A.; Jaque, D.; Zambelli, M.; Bettinelli, M.

2004-01-01

The optical properties for single doped Cr 3+ and co-doped Cr 3+ -Nd 3+ aluminum tantalum tellurite glasses have been studied as a function of temperature. For the single doped glass, the existence of two bands in the emission spectra at low temperature indicates the presence of two different sites for the Cr 3+ ions, labelled as usual as low- and high-field sites. The broad band centred in the Near Infrared region, corresponds to low-field sites transition 4 T 2 → 4 A 2 , and the narrow band centred at approximately 715 nm to the high-field sites transition 2 E→ 4 A 2 . The emission intensity for both high- and low-field sites shows a strong decrease with increasing temperature, with the emission for the former sites vanishing at RT. In both cases the quenching observed with the increase of temperature can be ascribed to the presence of non-radiative relaxation mechanisms. Experimental observations for the co-doped glass show that both radiative and non-radiative energy transfer processes from Cr 3+ to Nd 3+ are present

Thermodynamic properties of CdCr2S4

International Nuclear Information System (INIS)

Kesler, Ya.A.; Shchelkotunov, V.A.; Tret'yakov, Yu.D.; Kamyshova, V.K.; Gordeev, I.V.; Alferov, V.A.

1977-01-01

The true thermal capacity of ferromagnetic chromium spinel CdCr 2 S 4 has been measured in the temperature range of 172-673 K. Coefficient of linear expansion has been measured in the temperature range of 173-677 K. A change in heat content of the compound has been found by the mixing method (298-750 K). The lattice contribution into thermal capacity, the contribution of thermal expansion, the values of isothermal compressibility factor, and the Crueneisen constants have been calculated from true and mean heat capacity of CdCr 2 S 4 in a wide temperature range. The lattice energy V has been calculated for CdCr 2 S 4 ; it amounts -4226 kcal/mol

The Use Of Optical Properties Of Cr-39 In Alpha Particle Equivalent Dose Measurements

International Nuclear Information System (INIS)

Shnishin, K.A.

2007-01-01

In this work, optical properties of alpha irradiated Cr-39 were measured as a function of optical photon wavelength from 200-1100 nm. Optical energy gap and optical absorption at finite wavelength was also calculated and correlated to alpha fluence and dose equivalent. Alpha doses were calculated from the corresponding irradiation fluence and specific energy loss using TRIM computer program. It was found that, the optical absorption of unattached Cr-39 was varied with alpha fluence and corresponding equivalent doses. Also the optical energy gab was varied with fluence and dose equivalent of alpha particles. This work introduces a reasonably simple method for the Rn dose equivalent calculation by Cr-39 track

Charge resolution of a Hungarian brand CR-39(MA-ND) detector exposed to a 84Kr beam of energy 0.45A GeV

International Nuclear Information System (INIS)

Bhattacharyya, D.P.; Basu, B.; Pal, P.; Mukherjee, S.C.; Ganguly, A.K.; Hunyady, I.

1990-01-01

The Hungarian brand CR-39(MA-ND) plastic has been irradiated with a 84 Kr ion beam of energy 0.45A GeV and etched for four different etching times, viz. 4, 6, 8 and 12 h. The estimated charge resolution of a CR-39(MA-ND) detector for registering the nuclei 32 ≤ Z ≤ 36 was found to be 0.18e which is close to our previous observation of the response with a CR-39(DOP) Pershore made plate exposed to a 1.88A GeV 56 Fe beam at the Lawrence Berkeley Laboratory's Bevalac. It was found that the estimated etch rate ratio V T /V G is independent of etching time. The cone length and minor axis of the etch pits has been found to increase with etching time. (orig.)

CORRELATION OF THE FERMI ENERGY OF Ni, Cr, Mn WITH THE ELECTROCATALYTIC ACTIVITY OF THE TRIPLE ALLOYS ON THE BASE OF THESE METALS

Directory of Open Access Journals (Sweden)

A. D. Andreyanov

2016-04-01

Full Text Available It was established the dependence of the electrocatalytic activity of alloys Ni-Cr-Mn at the variable contents of copper with values of Fermy energy of their components. Electrocatalytic activity of alloys was estimated by density of the current, determined by the method of suspended half-element. For Fermi energy calculation of various metals Sommerfeld model, in which distribution of electrons by speed is described by Fermi-Dirac statistic was used.

Approach of the estimation for the highest energy of the gamma rays

International Nuclear Information System (INIS)

Dumitrescu, Gheorghe

2004-01-01

In the last decade there was under debate the issue concerning the composition of the ultra high energy cosmic rays and some authors suggested that the light composition seems to be a relating issue. There was another debate concerning the limit of the energy of gamma rays. The bottom-up approaches suggest a limit at 10 15 eV. Some top-down approaches rise this limit at about 10 20 eV or above. The present paper provides an approach to estimate the limit of the energy of gamma rays using the recent paper of Claus W. Turtur. (author)

Angle and temperature dependence of the magnetocrystalline anisotropy energy and the microscopic magnetic moments of the ferromagnetic semi-metal CrO{sub 2}; Winkel- und Temperaturabhaengigkeit der magnetokristallinen Anisotropieenergie und der mikroskopischen magnetischen Momente des ferromagnetischen Halbmetalls CrO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Gold, S.

2005-07-01

The aim of this work was to examine, by use of XMCD-effect and additional measurements with SQUID-magnetometer, spin moments and hysteresis loops, but also to clarify the intrinsic properties like magnetocrystalline anisotropy, magnetic dipole term, and the nearly quenched orbital moment. The XMCD-measurements were done at the Cr L{sub 2,3}- and the O K-edge. The results for CrO{sub 2} show a strong dependence of the orbital, the sum of spin moment and magnetic dipole term, and the magnetocrystalline anisotropy energy from the angle between rutile a- and c-axis. Even more than the complete orbital moment, two separable and different spectral features show strong alterations of the different orbital moments. In a second part of this work the temperature dependence was investigated. The aim was to clarify the origin of the orbital moment, dipole term, and MAE in dependence of the spin moment and compare the results to different theoretical models. The extracted orbital moments and the magnetic dipole term show the same temperature dependence as the spin moment. In the following a dependence of the squared measured spin moment could be found for the MAE. For the first time the magnetic dipole term could be identified as the reason of the magnetocrystalline anisotropy energy. A strong Cr-O hybridisation was found, which shows in a similar structure and temperature dependence of the orbital moments for Cr L{sub 2,3} and the XMCD effect at O-K edge. (orig.)

Nuclear structure of light Ca and heavy Cr isotopes

International Nuclear Information System (INIS)

Buerger, A.

2007-01-01

In the present thesis, the shell structure in exotic nuclei has been investigated. The focus of the work was on finding new experimental data in neutron-rich Cr and proton-rich Ca isotopes. The investigation of light Ca isotopes concentrated on the nucleus 36 Ca which was produced in a knockout reaction from a radioactive 37 Ca beam. For 36 Ca, the excitation energy of the first 2 + state has been measured for the first time. Furthermore, momentum distributions were analyzed using a Monte-Carlo simulation of the knockout reaction. This analysis yielded the contributions of neutrons from individual orbitals to the total knockout cross section. In principle, these may be used to calculate spectroscopic factors, but such a calculation is hampered by difficulties of present knockout-reaction models in predicting precise single-particle cross sections. The measured branching ratio to the ground and excited states, on the other hand, is close to the predicted value. A remaining difference might be due to emission of protons which cannot be detected with the present experimental setup. Both the branching ratio and the large excitation energy are compatible with a large N=16 gap in 36 Ca that leads to relatively pure configurations both in the ground state and the excited 2 + state. As a by-product of the experiment, two excitation energies in the T=2 nuclei 32 Ar and 28 S have been confirmed, and two γ-ray transitions have been observed for the first time in 37 Ca. While the mirror energy differences in the T=2 pairs 36 Ca- 36 S, 32 Ar- 32 Si, and 28 S- 28 Mg can be reproduced in shell model calculations using a modified USD interaction, these modifications are not sufficient to explain the mirror energy differences for the pair 37 Ca- 37 Cl. In the heavy Cr isotopes, new experimental evidence for a sub-shell closure at N=32 was found in a measurement of B(E2) values using high-energy Coulomb excitation of radioactive beams. Prior to this experiment, the assumption of a

Analysis of spectra of the Cr3+ impurities in a number of crystals with an account of Trees correction

International Nuclear Information System (INIS)

Grechushnikov, B.N.; Veremejchik, T.F.; Kalinkina, I.N.

1977-01-01

A diagram showing the Cr 3+ ion levels in the crystals of MgO, spinel (MgAl 2 O 4 ), garnet (Y 3 Al 5 O 12 ), emerald (BeAl 2 ) and corundum (SiO 3 ) 6 was calculated to elucidate the nature of the interaction described by the Trees correction αL (L+1) and the effect of the term on the accuracy of the calculations of the energy levels of admixed α 3 ions with d 3- -configurations. The calculation was performed in a semiempirical version of the crystalline field. The optimum parameters were found using a computer with account for the accuracy in estimating the said levels by the absorption spectra of the basis and excited states. The inclusion of the Trees correction, αL (L+1), in the calculation was shown to considerably improve the agreement between the calculated and experimentally obtained energy levels of Cr 3+ ions in the given crystals. The highest effect was observed in the range constituting the states 2 E, 2 T 1 and 2 T 2 (lines R, R' and B). Basing on an analysis of α value for these crystals, the conclusion was made that the term αL (L+1) chiefly described the interaction of the configurations

Chromium 51 em K2CrO4: reactions of dopant atoms in solid state

International Nuclear Information System (INIS)

Valim, J.B.; Nascimento, R.L.G. do; Collins, C.H.; Collins, K.E.

1986-01-01

The study of the chemistry of 'dopant' 51 Cr(III) atoms in crystalline Cr(VI) compounds began as a sub-field of Hot Atom Chemistry. We shall review the attempts to use 'dopant' chromium-51 atoms as surrogate chromium recoil atoms with the special property of having a low-energy, recoil-dam-age-free history. These dopant atoms have shown behaviors very similar to those of high energy recoil 51 Gr atoms, thus offering little hope of learning about special damage site structures and reactions by behavioral differences. Recent work has shown that at least some of the 'dopant' 51 Cr(III) is present as a second, non-chromate solid phase in 'doped crystal' experiments. Monodisperse 51 Cr(OH) 3 particles mixed with pure K 2 CrO 4 are very reactive. (Author) [pt

HELIOS-CR - A 1-D radiation-magnetohydrodynamics code with inline atomic kinetics modeling

International Nuclear Information System (INIS)

MacFarlane, J.J.; Golovkin, I.E.; Woodruff, P.R.

2006-01-01

HELIOS-CR is a user-oriented 1D radiation-magnetohydrodynamics code to simulate the dynamic evolution of laser-produced plasmas and z-pinch plasmas. It includes an in-line collisional-radiative (CR) model for computing non-LTE atomic level populations at each time step of the hydrodynamics simulation. HELIOS-CR has been designed for ease of use, and is well-suited for experimentalists, as well as graduate and undergraduate student researchers. The energy equations employed include models for laser energy deposition, radiation from external sources, and high-current discharges. Radiative transport can be calculated using either a multi-frequency flux-limited diffusion model, or a multi-frequency, multi-angle short characteristics model. HELIOS-CR supports the use of SESAME equation of state (EOS) tables, PROPACEOS EOS/multi-group opacity data tables, and non-LTE plasma properties computed using the inline CR modeling. Time-, space-, and frequency-dependent results from HELIOS-CR calculations are readily displayed with the HydroPLOT graphics tool. In addition, the results of HELIOS simulations can be post-processed using the SPECT3D Imaging and Spectral Analysis Suite to generate images and spectra that can be directly compared with experimental measurements. The HELIOS-CR package runs on Windows, Linux, and Mac OSX platforms, and includes online documentation. We will discuss the major features of HELIOS-CR, and present example results from simulations

Phase stability and elastic properties of Cr-V alloys

Energy Technology Data Exchange (ETDEWEB)

Gao, M C; Suzuki, Y; Schweiger, H; Doğan, Ö N; Hawk, J; Widom, M

2013-01-23

V is the only element in the periodic table that forms a complete solid solution with Cr and thus is particularly important in alloying strategy to ductilize Cr. This study combines first-principles density functional theory calculations and experiments to investigate the phase stability and elastic properties of Cr–V binary alloys. The cluster expansion study reveals the formation of various ordered compounds at low temperatures that were not previously known. These compounds become unstable due to the configurational entropy of bcc solid solution as the temperature is increased. The elastic constants of ordered and disordered compounds are calculated at both T = 0 K and finite temperatures. The overall trends in elastic properties are in agreement with measurements using the resonant ultrasound spectroscopy method. The calculations predict that addition of V to Cr decreases both the bulk modulus and the shear modulus, and enhances the Poisson’s ratio, in agreement with experiments. Decrease in the bulk modulus is correlated to decrease in the valence electron density and increase in the lattice constant. An enhanced Poisson’s ratio for bcc Cr–V alloys (compared to pure Cr) is associated with an increased density of states at the Fermi level. Furthermore, the difference charge density in the bonding region in the (110) slip plane is highest for pure Cr and decreases gradually as V is added. The present calculation also predicts a negative Cauchy pressure for pure Cr, and it becomes positive upon alloying with V. The intrinsic ductilizing effect from V may contribute, at least partially, to the experimentally observed ductilizing phenomenon in the literature.

Remediation of Cr(VI) contaminated soil using long-duration sodium thiosulfate supported by micro–nano networks

International Nuclear Information System (INIS)

He, Lulu; Wang, Min; Zhang, Guilong; Qiu, Guannan; Cai, Dongqing; Wu, Zhengyan; Zhang, Xin

2015-01-01

Highlights: • This work aims to develop a long-duration remediation agent (LRA). • LRA was obtained using Na 2 S 2 O 3 supported by attapulgite (ATP) micro–nano networks. • ATP micro–nano networks was induced by high-energy electron beam irradiation. • LRA can effectively control the migration of Cr(VI) and reducing Cr(VI) to Cr(III). • LRA displayed high performance on the remediation of heavy metal contaminated soil. - Abstract: In this work, a long-duration remediation agent (LRA) on hexavalent chromium (Cr(VI)) was developed using sodium thiosulfate (ST) supported by attapulgite (ATP) micro–nano networks induced through high-energy electron beam (HEEB) irradiation. The ATP networks could effectively reduce the leaching amount of Cr(VI) in soil. More importantly, the ATP networks could significantly control the leaching behavior of ST, and then prolong the duration and increase the reduction efficiency of ST on Cr(VI). As a result, LRA displayed high performance on controlling the migration of Cr(VI) and reducing Cr(VI) to Cr(III). Additionally, pot experiment indicated that LRA could effectively decrease the absorbed amount of Cr(VI) in corn, and reduce the inhibition effect of Cr(VI) on the growth of corn. Therefore, this work could provide a facile approach to remediate the Cr(VI)-contaminated soil and lower the harmful effect of Cr(VI) on crop

Remediation of Cr(VI) contaminated soil using long-duration sodium thiosulfate supported by micro–nano networks

Energy Technology Data Exchange (ETDEWEB)

He, Lulu [School of Life Sciences, Anhui Agricultural University, Hefei 230036 (China); Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Wang, Min; Zhang, Guilong [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Bioenergy Forest Research Center of State Forestry Administration, Hefei 230031 (China); Qiu, Guannan [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Cai, Dongqing, E-mail: dqcai@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Bioenergy Forest Research Center of State Forestry Administration, Hefei 230031 (China); Wu, Zhengyan, E-mail: zywu@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Bioenergy Forest Research Center of State Forestry Administration, Hefei 230031 (China); Zhang, Xin, E-mail: xinzhang@ahau.edu.cn [School of Life Sciences, Anhui Agricultural University, Hefei 230036 (China)

2015-08-30

Highlights: • This work aims to develop a long-duration remediation agent (LRA). • LRA was obtained using Na{sub 2}S{sub 2}O{sub 3} supported by attapulgite (ATP) micro–nano networks. • ATP micro–nano networks was induced by high-energy electron beam irradiation. • LRA can effectively control the migration of Cr(VI) and reducing Cr(VI) to Cr(III). • LRA displayed high performance on the remediation of heavy metal contaminated soil. - Abstract: In this work, a long-duration remediation agent (LRA) on hexavalent chromium (Cr(VI)) was developed using sodium thiosulfate (ST) supported by attapulgite (ATP) micro–nano networks induced through high-energy electron beam (HEEB) irradiation. The ATP networks could effectively reduce the leaching amount of Cr(VI) in soil. More importantly, the ATP networks could significantly control the leaching behavior of ST, and then prolong the duration and increase the reduction efficiency of ST on Cr(VI). As a result, LRA displayed high performance on controlling the migration of Cr(VI) and reducing Cr(VI) to Cr(III). Additionally, pot experiment indicated that LRA could effectively decrease the absorbed amount of Cr(VI) in corn, and reduce the inhibition effect of Cr(VI) on the growth of corn. Therefore, this work could provide a facile approach to remediate the Cr(VI)-contaminated soil and lower the harmful effect of Cr(VI) on crop.

Spin magnetic moments from single atoms to small Cr clusters

Energy Technology Data Exchange (ETDEWEB)

Boeglin, C.; Decker, R.; Bulou, H.; Scheurer, F.; Chado, I. [IPCMS-GSI - UMR 7504, 67037 Strasbourg Cedex (France); Ohresser, P. [LURE, 91405 Orsay (France); Dhesi, S.S. [ESRF, BP 220, 38043 Grenoble Cedex (France); Present permanent address: Diamond Light Source, Chilton, Didcot OX11 0QX (United Kingdom); Gaudry, E. [LMCP, 4, place Jussieu, 75252 Paris (France); Lazarovits, B. [CCMS, T.U. Vienna, Gumpendorfstr. 1a, 1060 Wien (Austria)

2005-07-01

Morphology studies at the first stages of the growth of Cr/Au(111) are reported and compared to the magnetic properties of the nanostructures. We analyze by Scanning Tunneling Microscopy and Low Energy Electron Diffraction the Cr clusters growth between 200 K and 300 K. In the early stages of the growth the morphology of the clusters shows monoatomic high islands located at the kinks of the herringbone reconstructed Au(111) surface. By X-ray Magnetic Circular Dichroism performed on the Cr L{sub 2,3} edges it is shown that the temperature dependent morphology strongly influences the magnetic properties of the Cr clusters. We show that in the sub-monolayer regime Cr clusters are antiferromagnetic and paramagnetic when the size reaches the atomic limit. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Personnel neutron dosimetry using electrochemically etched CR-39 foils

International Nuclear Information System (INIS)

Hankins, D.E.; Homann, S.; Westermark, J.

1986-01-01

A personnel neutron dosimetry system has been developed based on the electrochemical etching of CR-39 plastic at elevated temperatures. The doses obtained using this dosimeter system are more accurate than those obtained using other dosimetry systems, especially when varied neutron spectra are encountered. This Cr-39 dosimetry system does not have the severe energy dependence that exists with albedo neutron dosimeters or the fading and reading problems encountered with NTA film. The dosimetry system employs an electrochemical etch procedure that be used to process large numbers of Cr-39 dosimeters. The etch procedure is suitable for operations where the number of personnel requires that many CR-39 dosimeters be processed. Experience shows that one full-time technician can etch and evaluate 2000 foils per month. The energy response to neutrons is fairly flat from about 80 keV to 3.5 MeV, but drops by about a factor of three in the 13 to 16 MeV range. The sensitivity of the dosimetry system is about 7 tracks/cm 2 /mrem, with a background equivalent to about 8 mrem for new CR-39 foils. The limit of sensitivity is approximately 10 mrem. The dosimeter has a significant variation in directional dependence, dropping to about 20% at 90 0 . This dosimeter has been used for personnel neutron dosimetry at the Lawrence Livermore National Laboratory for more tha 18 months. 6 refs., 23 figs., 2 tabs

Microstructural characterization of second phases in X10CrMoVNb9-1 and 12CrMoWCuVNb steels after long steam exposure time at 550 C

International Nuclear Information System (INIS)

Rodak, Kinga; Hernas, Adam; Vodarek, Vlastimil

2015-01-01

Microstructural changes in high alloy (9-12% Cr) creep resistant martensitic X10CrMoVNb9-1 and 12CrMoW . CuVNb steels after 100 000 h of steam exposure at 550 C have been studied using scanning transmission electron microscopy. Precipitates were identified using electron diffraction patterns and energy dispersive X-ray spectroscopy analysis. After long time exposure, a significant coarsening of M 23 C 6 carbides, and intensive precipitation of the coarse Laves phase were observed. Moreover, in the 12CrMoW . CuVNb steel, a low amount of the modified Z-phase particles was detected. The microstructures of the X10Cr . MoVNb9-1 and 12CrMoWCuVNb steels after 100 000 h of exposure differ in several aspects.

Microstructural characterization of second phases in X10CrMoVNb9-1 and 12CrMoWCuVNb steels after long steam exposure time at 550 C

Energy Technology Data Exchange (ETDEWEB)

Rodak, Kinga; Hernas, Adam [Silesian Univ. of Technology, Inst. of Materials Science, Katowice (Poland); Vodarek, Vlastimil [VSB-Technical Univ. of Ostrava (Czech Republic)

2015-07-15

Microstructural changes in high alloy (9-12% Cr) creep resistant martensitic X10CrMoVNb9-1 and 12CrMoW . CuVNb steels after 100 000 h of steam exposure at 550 C have been studied using scanning transmission electron microscopy. Precipitates were identified using electron diffraction patterns and energy dispersive X-ray spectroscopy analysis. After long time exposure, a significant coarsening of M{sub 23}C{sub 6} carbides, and intensive precipitation of the coarse Laves phase were observed. Moreover, in the 12CrMoW . CuVNb steel, a low amount of the modified Z-phase particles was detected. The microstructures of the X10Cr . MoVNb9-1 and 12CrMoWCuVNb steels after 100 000 h of exposure differ in several aspects.

Effect of Cr content on the SHS reaction of Cr-Ti-C system

International Nuclear Information System (INIS)

Zhang, W.N.; Wang, H.Y.; Wang, P.J.; Zhang, J.; He, L.; Jiang, Q.C.

2008-01-01

The effect of Cr content on the self-propagating high temperature synthesis (SHS) reaction of Cr-Ti-C system has been investigated in this research. The thermodynamics calculation indicates that the TiC possesses higher thermodynamic stability than the Cr 23 C 6 , Cr 7 C 3 and Cr 3 C 2 phases, and the formation of TiC is the most exothermic. Additionally, the adiabatic combustion temperature (T ad ) decreases with the increase of Cr content except for the phase transition regions. The XRD result shows that the type of products synthesized by SHS changes that a higher Cr content corresponds to higher chromium carbide. When Cr content is 10 wt.%, only solid solution (Ti,Cr)C ss is formed in the products. When Cr content increases to 20 wt.%, besides (Ti,Cr)C ss , the Cr 7 C 3 phase is also detected. With the Cr content further increasing to 30 and 40 wt.%, the products consist of (Ti,Cr)C ss , Cr 23 C 6 , Cr 7 C 3 and Cr, and therefore, much higher chromium carbide is synthesized. When Cr content reaches 50 wt.%, however, the Cr 7 C 3 disappears and the final products become (Ti,Cr)C ss , Cr 23 C 6 and Cr. Moreover, when Cr content increases from 10 to 20 wt.%, the lattice parameter of (Ti,Cr)C ss decreases, while it increases when the Cr content ranges from 20 to 50 wt.%. Furthermore, the microstructure shows that the TiC particulate size decreases from ∼8 to ∼2 μm with the increase of Cr content from 10 to 50 wt.%, and the morphology shape of TiC particulate becomes more and more spherical

Preliminary Microstructural and Microscratch Results of Ni-Cr-Fe and Cr3C2-NiCr Coatings on Magnesium Substrate

Science.gov (United States)

Istrate, B.; Munteanu, C.; Lupescu, S.; Benchea, M.; Vizureanu, P.

2017-06-01

Thermal coatings have a large scale application in aerospace and automotive field, as barriers improving wear mechanical characteristics and corrosion resistance. In present research, there have been used two types of coatings, Ni-Cr-Fe, respectively Cr3C2-NiCr which were deposited on magnesium based alloys (pure magnesium and Mg-30Y master alloy). There have been investigated the microstructural aspects through scanning electronic microscopy and XRD analysis and also a series of mechanical characteristics through microscratch and indentation determinations. The results revealed the formation of some adherent layers resistant to the penetration of the metallic indenter, the coatings did not suffer major damages. Microstructural analysis highlighted the formation of Cr3C2, Cr7C3, Cr3Ni2, Cr7Ni3, FeNi3, Cr-Ni phases. Also, the apparent coefficient of friction for Ni-Cr-Fe coatings presents superior values than Cr3C2-NiCr coatings.

Influence of trimethylsilane flow on the microstructure, mechanical and tribological properties of CrSiCN coatings in water lubrication

International Nuclear Information System (INIS)

Wu, Zhiwei; Zhou, Fei; Wang, Qianzhi; Zhou, Zhifeng; Yan, Jiwang; Li, Lawrence Kwok-Yan

2015-01-01

Highlights: • CrSiCN coatings with different Si and C contents were deposited. • CrSiCN coatings consisted of Cr(C,N) nanocrystallites and amorphous phases such as a-Si_3N_4(SiC, SiCN) and a-C(a-CN_x). • CrSiCN coatings exhibited the highest hardness of 21.3 GPa at the TMS flow of 10 sccm. • CrSiCN coatings deposited at the TMS flow of 10 sccm possessed the excellent tribological properties in water. • The wear mechanism changed from tribochemical wear to mechanical wear when the TMS flow increased. - Abstract: CrSiCN coatings with different silicon and carbon contents were deposited on silicon wafers and 316L stainless steels using unbalanced magnetron sputtering via adjusting trimethylsilane (TMS) flow, and their microstructure and mechanical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy(SEM), X-ray photoelectrons spectroscopy(XPS) and nano-indenter, respectively. The tribological properties of CrSiCN coatings sliding against SiC balls in water were investigated using ball-on-disk tribometer. The results showed that the CrSiCN coatings had fine composite microstructure consisting of nanocrystallites of Cr(C, N) crystal and amorphous phases such as a-Si_3N_4 and a-C(a-CN_x). The typical columnar structures changed from fine cluster to coarse ones when the Si content was beyond 3.4 at.%. With an increase in the TMS flow, the hardness and Young's modulus of Corsican coatings all first increased, and then rapidly decreased, but the compressive stress in the coatings varied in the range of 2.8–4.8 GPa. When the TMS flow was 10 sccm, the CrSiCN coatings exhibited the highest hardness of 21.3 GPa and the lowest friction coefficient (0.11) and wear rate (8.4 × 10"−"8 mm"3/N m). But when the TMS flow was beyond 15 sccm, the tribological properties of CrSiCN coatings in water became poor.

Electrodialytic extraction of Cr from water-washed MSWI fly ash by changing pH and redox conditions

DEFF Research Database (Denmark)

Chen, Wan; Kirkelund, Gunvor Marie; Jensen, Pernille Erland

2018-01-01

Electrodialytic process offers a range of possibilities to waste management by electrodialytic separation (EDS) of heavy metals, depending on how the process is designed. Using three EDS cell setups (two two-compartment and one three-compartment) and their combinations, the extraction of Cr from...... rate of 27.5%, is an improvement on the single-step that extracted maximum 3.1%. The highest extraction was obtained due to the combined extraction of Cr(III) under low pH (accompanied with high redox) conditions and Cr(VI) under high pH (low redox) conditions subsequently. The Cr leaching from...... the treated ashes with acidic pH was lower than from those with alkaline pH; after the three-step treatment, Cr leaching was much lower from the coarse fraction (> 50 µm), as compared to the fine (≤ 50 µm) or the unsieved ash. As for the coarse fraction, two/three-step treatment reduced the leaching of Cr...

The electronic structure of the metastable layer compound 1T-CrSe2

NARCIS (Netherlands)

Fang, C.M.; Groot, R.A. de; Wiegers, G.A.; Haas, C.; vanBruggen, C.F.; deGroot, R.A.

1997-01-01

The electronic structure of the metastable compound 1T-CrSe2 (a = 3.399 Å, c = 5.911 Å, space group P_3m1) was calculated with and without spin polarization using the LSW method. The energy is 0.29 eV/mol CrSe2 lower for the spin-polarized calculation. The total magnetic moment of +2.44 μB on Cr

Ostwald ripening of decomposed phases in Cu-Ni-Cr alloys

International Nuclear Information System (INIS)

Hernandez-Santiago, Felipe; Lopez-Hirata, Victor; Dorantes-Rosales, Hector J.; Saucedo-Munoz, Maribel L.; Gonzalez-Velazquez, Jorge L.; Paniagua-Mercado, Ana Ma.

2008-01-01

A study of the coarsening process of the decomposed phases was carried out in the Cu-34 wt.% Ni-4 wt.% Cr and Cu-45 wt.% Ni-10 wt.% Cr alloys using transmission electron microscopy. As aging progressed, the morphology of the coherent decomposed Ni-rich phase changed from cuboids to platelets aligned in the Cu-rich matrix directions. Prolonged aging caused the loss of coherency between the decomposed phases and the morphology of the Ni-rich phase changed to ellipsoidal. The variation of mean radius of the coherent decomposed phases with aging time followed the modified LSW theory for thermally activated growth in ternary alloy systems. The linear variation of the density number of precipitates and matrix supersaturation with aging time, also confirmed that the coarsening process followed the modified LSW theory in both alloys. The coarsening rate was faster in the symmetrical Cu-45 wt.% Ni-10 wt.% Cr alloy due to its higher volume fraction of precipitates. The activation energy for thermally activated growth was determined to be about 182 and 102 kJ mol -1 in the Cu-34 wt.% Ni-4 wt.% Cr and Cu-45 wt.% Ni-10 wt.% Cr alloys, respectively. The lower energy for the former alloy seems to be related to an increase in the atomic diffusion process as the chromium content increases. The size distributions of precipitates in the Cu-Ni-Cr alloys were broader and more symmetric than that predicted by the modified LSW theory for ternary alloys

Annealing effect on the structural and optical properties of Cr/α-Cr2O3 monodispersed particles based solar absorbers

International Nuclear Information System (INIS)

Khamlich, S.; McCrindle, R.; Nuru, Z.Y.; Cingo, N.; Maaza, M.

2013-01-01

Graphical abstract: A cost-effective and environmentally friendly green chemical method, the so-called aqueous chemical growth (ACG) method, was used to deposit chromium/alpha-chromium(III) oxide, Cr/α-Cr 2 O 3 , monodispersed particles, for solar absorbers applications. Highlights: ► Cr/α-Cr 2 O 3 have been deposited by the aqueous chemical growth (ACG) method. ► High temperature annealing affects the optical selectivity of the deposited particles. ► Oxygen diffusion to the interface at high temperature results in the oxidization of the substrate. - Abstract: A cost-effective and environmentally friendly green chemical method, the so-called aqueous chemical growth (ACG) method, was used to deposit chromium/alpha-chromium(III) oxide, Cr/α-Cr 2 O 3 , monodispersed particles, for solar absorbers applications. The deposited particles were annealed at various temperatures in a hydrogen atmosphere for 2 h to study the annealing temperature dependence of the structural, chemical and optical properties of the particles grown on tantalum substrates. The deposited Cr/α-Cr 2 O 3 was characterized by X-ray diffraction (XRD), attenuated total reflection (ATR), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and diffuse reflectance UV–vis–NIR spectroscopy. The XRD and ATR analysis indicated that by increasing annealing temperature, the particles crystallinity was improved and Ta 2 O 5 was formed around 600 °C, due to the fast oxygen diffusion from the deposited α-Cr 2 O 3 toward the tantalum substrate. The optical measurements show that samples annealed at 400 and 500 °C exhibit the targeted high absorbing optical characteristics of “Black chrome”, while those annealed below 400 °C and above 500 °C show a significant low absorptivity and high emissivity.

Study of the oxidation of Fe-Cr alloys at high temperatures

International Nuclear Information System (INIS)

Carneiro, J.F.; Sabioni, A.C.S.

2010-01-01

The high temperature oxidation behavior of Fe-1.5%Cr, Fe-5.0%Cr, Fe-10%Cr and Fe- 15%Cr model alloys were investigated from 700 to 850 deg C, in air atmosphere. The oxidation treatments were performed in a thermobalance with a sensitivity of 1μg. The oxide films grown by oxidation of the alloys were characterized by scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The oxide films are Fe-Cr spinels with variable composition depending on the alloy composition. For all conditions studied, the oxidation kinetics of these alloys follow a parabolic law. The comparison of the oxidation rates of the four alloys, at 700 deg C, shows that the parabolic oxidation constants decrease from 1.96x10 -9 g 2 .cm -4 .s -1 , for the alloy Fe-1.5% Cr, to 1.18 x 10-14g 2 .cm -4 .s -1 for the alloy Fe-15% Cr. Comparative analysis of the oxidation behavior of the Fe-10%Cr and Fe-15%Cr alloys, between 700 and 850 deg C, shows that the oxidation rates of these alloys are comparable to 800 deg C, above this temperature the Fe-10%Cr alloy shows lower resistance to oxidation. (author)

RIGScan CR: RIGScan CR49.

Science.gov (United States)

2004-01-01

RIGScan CR49, a 125I-labelled CR monoclonal antibody directed against the tumour-associated antigen TAG-72, is undergoing development with Neoprobe for the intraoperative detection of metastatic colorectal cancer. The Neoprobe's proprietary RIGS (radioimmunoguided surgery) technology combines an injectable radiolabelled cancer-targeting agent and hand-held radiation detection probe that emits an audible tone when located tissue has accumulated a significant amount of the radioactive agent. Neoprobe's RIGS technology also includes a patented surgical method providing surgeons with real-time information to locate tumour deposits that can not be detected by other conventional methods. The RIGS technology has been evaluated in late clinical studies for the detection of adenocarcinomas including primary colorectal, gastrointestinal, breast, ovarian, pancreatic, prostate and neuroendocrine/endocrine. Neoprobe signed an option agreement for its first-generation RIGScan compound, RIGScan CR, with OncoSurg Inc. (formerly NuRigs Ltd). The second-generation humanised RIGScan CR agent was also optionally licensed to OncoSurg Inc. In 1997, Neoprobe filed for approval with the US FDA and the EMEA for RIGScan CR for the intraoperative detection of metastatic colorectal cancer. Both regulatory agencies have requested additional clinical data. On 19 April 2004, Neoprobe announced that it had met with the US FDA to discuss its position on submitting additional clinical information in response to the FDA's questions regarding the Biologic Licence Application (BLA) for RIGScan CR49. The company provided the FDA with new information related to a survival differential for patients whose colorectal cancer was evaluated with RIGScan CR49. The information was not available at the time of the BLA's submission in 1997. The agency indicated that it would consider accepting survival data from one of the two phase III trials, NEO2-14, but not from another trial NEO2-13, as supportive data for a

Nuclear structure of light Ca and heavy Cr isotopes

Energy Technology Data Exchange (ETDEWEB)

Buerger, A.

2007-07-01

In the present thesis, the shell structure in exotic nuclei has been investigated. The focus of the work was on finding new experimental data in neutron-rich Cr and proton-rich Ca isotopes. The investigation of light Ca isotopes concentrated on the nucleus {sup 36}Ca which was produced in a knockout reaction from a radioactive {sup 37}Ca beam. For {sup 36}Ca, the excitation energy of the first 2{sup +} state has been measured for the first time. Furthermore, momentum distributions were analyzed using a Monte-Carlo simulation of the knockout reaction. This analysis yielded the contributions of neutrons from individual orbitals to the total knockout cross section. In principle, these may be used to calculate spectroscopic factors, but such a calculation is hampered by difficulties of present knockout-reaction models in predicting precise single-particle cross sections. The measured branching ratio to the ground and excited states, on the other hand, is close to the predicted value. A remaining difference might be due to emission of protons which cannot be detected with the present experimental setup. Both the branching ratio and the large excitation energy are compatible with a large N=16 gap in {sup 36}Ca that leads to relatively pure configurations both in the ground state and the excited 2{sup +} state. As a by-product of the experiment, two excitation energies in the T=2 nuclei {sup 32}Ar and {sup 28}S have been confirmed, and two {gamma}-ray transitions have been observed for the first time in {sup 37}Ca. While the mirror energy differences in the T=2 pairs {sup 36}Ca-{sup 36}S, {sup 32}Ar-{sup 32}Si, and {sup 28}S-{sup 28}Mg can be reproduced in shell model calculations using a modified USD interaction, these modifications are not sufficient to explain the mirror energy differences for the pair {sup 37}Ca-{sup 37}Cl. In the heavy Cr isotopes, new experimental evidence for a sub-shell closure at N=32 was found in a measurement of B(E2) values using high-energy

Crystallization kinetics and magnetic properties of FeSiCr amorphous alloy powder cores

Energy Technology Data Exchange (ETDEWEB)

Xu, Hu-ping [School of Logistics Engineering, Wuhan University of Technology, Wuhan 430063 (China); Wang, Ru-wu, E-mail: ruwuwang@hotmail.com [National Engineering Research Center For Silicon Steel, Wuhan 430080 (China); College of Materials Science and Metallurgical Engineering, Wuhan University of Science and Technology, Wuhan 430081 (China); Wei, Ding [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Zeng, Chun [National Engineering Research Center For Silicon Steel, Wuhan 430080 (China)

2015-07-01

The crystallization kinetics of FeSiCr amorphous alloy, characterized by the crystallization activation energy, Avrami exponent and frequency factor, was studied by non-isothermal differential scanning calorimetric (DSC) measurements. The crystallization activation energy and frequency factor of amorphous alloy calculated from Augis–Bennett model were 476 kJ/mol and 5.5×10{sup 18} s{sup −1}, respectively. The Avrami exponent n was calculated to be 2.2 from the Johnson–Mehl–Avrami (JMA) equation. Toroid-shaped Fe-base amorphous powder cores were prepared from the commercial FeSiCr amorphous alloy powder and subsequent cold pressing using binder and insulation. The characteristics of FeSiCr amorphous alloy powder and the effects of compaction pressure and insulation content on the magnetic properties, i.e., effective permeability μ{sub e}, quality factor Q and DC-bias properties of FeSiCr amorphous alloy powder cores, were investigated. The FeSiCr amorphous alloy powder cores exhibit a high value of quality factor and a stable permeability in the frequency range up to 1 MHz, showing superior DC-bias properties with a “percent permeability” of more than 82% at H=100 Oe. - Highlights: • The crystallization kinetics of FeSiCr amorphous alloy was investigated. • The FeSiCr powder cores exhibit a high value of Q and a stable permeability. • The FeSiCr powder cores exhibit superior DC-bias properties.

Cr3+ and Cr4+ luminescence in glass ceramic silica

International Nuclear Information System (INIS)

Martines, Marco A.U.; Davolos, Marian R.; Jafelicci, Miguel Junior; Souza, Dione F. de; Nunes, Luiz A.O.

2008-01-01

This paper reports on the effect of glass ceramic silica matrix on [CrO 4 ] 4- and Cr 2 O 3 NIR and visible luminescence. Chromium-containing silica was obtained by precipitation from water-glass and chromium nitrate acid solution with thermal treatment at 1000 deg. C. From XRD results silica and silica-chromium samples are crystalline. The chromium emission spectrum presents two main broad bands: one in the NIR region (1.1-1.7μm) and other in the visible region (0.6-0.7μm) assigned to Cr 4+ and to Cr 3+ , respectively. This thermal treated glass ceramic silica-chromium sample stabilizes the [CrO 4 ] 4- where Cr 4+ substitutes for Si 4+ and also hexacoordinated Cr 3+ group probably as segregated phase in the system. It can be pointed out that luminescence spectroscopy is a powerful tool for detecting the two chromium optical centers in the glass ceramic silica

Development of neutron dosimeter using CR-39 for measurement of ambient dose equivalent

International Nuclear Information System (INIS)

Maki, Daisuke; Shinozaki, Wakako; Ohguchi, Hiroyuki; Yamamoto, Takayoshi; Nakamura, Takayoshi

2010-01-01

A CR-39 has good advantages such as cumulative type dosimeter, small fading effect and gamma-ray insensitive. Therefore, we developed the wide energy-range environmental neutron dosimeter using eight CR-39s for area monitoring in this study. This dosimeter is made of octagonal columnar polyethylene block which height is 60 mm and bottom side is 25 mm. The dosimeter contains two types of CR-39s for fast neutron detection and slow neutron detection. Four CR-39s for fast neutron detection are used for detection of recoil protons produced by H (n, p) reactions. Four CR-39s for slow neutron detection are used with boron nitride converter to detect alpha-rays produced by 10 B (n, α) 7 Li reactions. Ambient dose equivalent is obtained by adding the number of etch-pits observed in four CR-39s for fast neutron detection to the number of etch-pits observed in four CR-39s for slow neutron detection with appropriate constants respectively. Dosimeters were irradiated with some energetic neutrons and evaluated results of ambient dose equivalent were compared with results from neutron transport calculations. Energy response of dosimeter shows good agreement with neutron fluence to ambient dose equivalent conversion coefficients. Directional dependence of dosimeter is at the same level as the rem-counter. (author)

Investigation of the near-surface electronic structure of Cr(001)

International Nuclear Information System (INIS)

Klebanoff, L.E.; Robey, S.W.; Liu, G.; Shirley, D.A.

1985-01-01

An angle-resolved photoelectron spectroscopy (ARPES) study of Cr(001) near-surface electronic structure is presented. Measurements are reported for energy-band dispersions along the [010] direction parallel to the crystal surface. The periodicity of these band dispersions indicates that the valence electrons experience and self-consistently establish antiferromagnetism in the near-surface layers of Cr(001). We also present highly-surface-sensitive ARPES measurements of the energy-band dispersions along the [001] direction normal to the surface. The results suggest that the surface magnetic moments, which couple ferromagnetically to each other within the surface layer, couple antiferromagnetically to the moments of the atoms in the second layer. Temperature-dependent studies are presented that reveal the persistence of near-surface antiferromagnetic order for temperatures up to 2.5 times the bulk Neel temperature. The temperature dependence of this antiferromagnetic order suggests that its thermal stability derives in part from the stability of the Cr(001) ferromagnetic surface phase

Capture cross sections for Cr, Fe and Ni

International Nuclear Information System (INIS)

Corvi, F.

1990-01-01

Since stainless steel represents about 25% of the volume of a fast power reactor, its constituent elements strongly influence its two main neutronic parameters: critical enrichment and breeding gain. Also, capture in the narrow p and d-wave resonances of Cr, Fe and Ni contributes as much as 10 to 15% of the Doppler coefficient of reactivity. Following sensitivity calculations, typical accuracy requirements in the energy range 0.1-100 keV are 5-10% for capture in Fe and 10-20% for capture in Ni and Cr. 11 refs, 2 tabs

Effects of Cr-N-ZrO 2 seed layer formed on glass substrates for longitudinal recording media

Science.gov (United States)

Suzuki, Hiroyuki; Djayaprawira, David D.; Takahashi, Yoshio; Ishikawa, Akira; Ono, Toshinori; Yahisa, Yotsuo

1999-03-01

Effects of Cr-N-ZrO 2 seed layer deposited on glass substrates before the deposition of C/Co-Cr-Pt/Cr-Ti layers for longitudinal recording media have been investigated. The product of v and Is, the activation volume and the saturation magnetization per unit volume, media noise Nd and S0/ Nd, which is the half value of peak-to-peak output voltage of an isolated pulse over Nd at 11.8 kFC/mm, are evaluated. We find that vIs is decreased by adding N and ZrO 2 to Cr seed layer. Nd is reduced as vIs decreases by adding nitrogen to the Cr seed layer. This is mainly due to the decreased grain sizes of both Cr-Ti underlayer and Co-Cr-Pt magnetic layer. The Nd is further reduced by the addition of ZrO 2 to the Cr-N seed layer. Highest S0/ Nd is achieved for the media with Cr-N-ZrO 2 seed layer. On the other hand, the media with Cr-ZrO 2 seed layer deposited without nitrogen show the higher Nd. Therefore the decrease of the grain size by addition of nitrogen into Ar is essential to reduce Nd, and the ZrO 2 addition to the Cr-N seed layer seems to enhance the effect of grain size reduction by nitrogen addition.

X-ray fluorescence analysis of Cr6+ component in mixtures of Cr2O3 and K2CrO4

International Nuclear Information System (INIS)

Tochio, Tatsunori; Sakakura, Shusuke; Oohashi, Hirofumi

2010-01-01

X-ray fluorescence analysis using Cr K α spectra was applied to the determination of the mixing ratio of Cr 6+ to (Cr 6+ + Cr 3+ ) in several mixtures of K 2 CrO 4 and Cr 2 O 3 . Because the powder of K 2 CrO 4 contained large particles that were more than 50 μm in diameter, it was ground between a pestle and a mortar for about 8 h. The coarse particles still remaining were removed by using a sieve with 325-mesh (44 μm) in order to reduce the difference in absorption effects between emissions from Cr 6+ and those from Cr 3+ . The mixing ratio, K 2 CrO 4 /(K 2 CrO 4 + Cr 2 O 3 ), of the five mixtures investigated is 0.50, 0.40, 0.20, 0.10, and 0.05 in weight, respectively. Each spectrum obtained was analyzed by decomposing it into two reference spectra, those of the two pure materials, K 2 CrO 4 and Cr 2 O 3 , with a constant background. The results for the mixtures containing K 2 CrO 4 of more than 20 wt% are that the relative deviation from the true value is less than ∼5%. On the other hand, when the content of K 2 CrO 4 decreases to less than 10 wt%, the relative deviation gets so large as 20 - 25%. The error coming from a peak separation of spectrum involved in our results were estimated by applying our method to five sets of data for each mixture computationally generated, taking into account the uncertainty in total counts of real measurements. (author)

X-ray fluorescence analysis of Cr(6+) component in mixtures of Cr(2)O(3) and K(2)CrO(4).

Science.gov (United States)

Tochio, Tatsunori; Sakakura, Shusuke; Oohashi, Hirofumi; Mizota, Hirohisa; Zou, Yanhui; Ito, Yoshiaki; Fukushima, Sei; Tanuma, Shigeo; Shoji, Takashi; Fujimura, Hajime; Yamashita, Michiru

2010-01-01

X-ray fluorescence analysis using Cr K(alpha) spectra was applied to the determination of the mixing ratio of Cr(6+) to (Cr(6+) + Cr(3+)) in several mixtures of K(2)CrO(4) and Cr(2)O(3). Because the powder of K(2)CrO(4) contained large particles that were more than 50 microm in diameter, it was ground between a pestle and a mortar for about 8 h. The coarse particles still remaining were removed by using a sieve with 325-mesh (44 microm) in order to reduce the difference in absorption effects between emissions from Cr(6+) and those from Cr(3+). The mixing ratio, K(2)CrO(4)/(K(2)CrO(4) + Cr(2)O(3)), of the five mixtures investigated is 0.50, 0.40, 0.20, 0.10, and 0.05 in weight, respectively. Each spectrum obtained was analyzed by decomposing it into two reference spectra, those of the two pure materials, K(2)CrO(4) and Cr(2)O(3), with a constant background. The results for the mixtures containing K(2)CrO(4) of more than 20 wt% are that the relative deviation from the true value is less than approximately 5%. On the other hand, when the content of K(2)CrO(4) decreases to less than 10 wt%, the relative deviation gets so large as 20 - 25%. The error coming from a peak separation of spectrum involved in our results were estimated by applying our method to five sets of data for each mixture computationally generated, taking into account the uncertainty in total counts of real measurements.

Fracture toughness of MgCr2O4-ZrO2 composities

International Nuclear Information System (INIS)

Singh, J.P.

1985-01-01

The effect of unstabilized ZrO 2 inclusions on the fracture surface energy of MgCr 2 O 4 was studied as a function of ZrO 2 content. It was observed that fracture surface energy increases with increasing ZrO 2 content, and reaches the maximum value of 24.5 j/m 2 at 16.5 vol% ZrO 2 . This represents an approx. = fourhold increase in the fracture surface energy of Mg 2 O 4 as a result of ZrO 2 inclusions. It is proposed that this improvement results from the energy absorbed by the microcracks formed in the MgCr 2 O 4 matrix as a result of the tetragonal → monoclinic phase transormation of ZrO 2 and the associated volume expansion

Bonding and bio-properties of hybrid laser/magnetron Cr-enriched DLC layers

Energy Technology Data Exchange (ETDEWEB)

Jelinek, Miroslav, E-mail: jelinek@fzu.cz [Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i, Na Slovance 2, 18221 Prague (Czech Republic); Czech Technical University in Prague, Faculty of Biomedical Engineering, nam. Sitna 3105, 27201 Kladno (Czech Republic); Zemek, Josef [Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i, Na Slovance 2, 18221 Prague (Czech Republic); Vandrovcová, Marta; Bačáková, Lucie [Institute of Physiology of the Czech Academy of Sciences of the Czech Republic, v.v.i., Videnska 1083, 14220 Prague 4 (Czech Republic); Kocourek, Tomáš; Remsa, Jan; Písařík, Petr [Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i, Na Slovance 2, 18221 Prague (Czech Republic); Czech Technical University in Prague, Faculty of Biomedical Engineering, nam. Sitna 3105, 27201 Kladno (Czech Republic)

2016-01-01

Chromium-enriched diamond-like carbon (DLC) layers were prepared by a hybrid technology using a combination of pulsed laser deposition (PLD) and magnetron sputtering. XRD revealed no chromium peaks, indicating that the layers are mostly amorphous. Carbon (sp{sup 2} and sp{sup 3} bonds) and chromium bonds were determined by XPS from C 1s, O 1s, and Cr 2p photoelectron peaks. Depending on the deposition conditions, the concentration of Cr in DLC layers moved from zero to 10 at.% for as-received sample surfaces, and to about 31 at.% after mild sputter-cleaning by argon ion cluster beam. It should be noted that the most stable Cr{sup 3+} bonding state is in Cr{sub 2}O{sub 3} and Cr(OH){sub 3}, and that there is the toxic Cr{sup 6+} state in CrO{sub 3}. The surface content of hexavalent chromium in the Cr 2p3/2 spectra is rather low, but discernible. The population density of Saos-2 cells was the highest in samples containing higher concentrations of chromium 7.7 and 10 at.%. This means that higher concentrations of chromium supported the cell adhesion and proliferation. In addition, as revealed by a LIVE/DEAD viability/cytotoxicity kit, the cells on all Cr-containing samples maintained high viability (96 to 99%) on days 1 and 3 after seeding. However, this seemingly positive cell behavior could be associated with the risk of dedifferentiation and oncogenic transformation of cells. - Highlights: • DLC and chromium-enriched DLC layers were prepared by hybrid laser–magnetron deposition. • The content of chromium in DLC varied up to 10 at.% (31 at.% after ion beam sputtering). • The surface content of toxic hexavalent chromium in the Cr 2p3/2 spectra is rather low but discernible. • Higher concentrations of chromium supported the cell adhesion and proliferation. • Cells on all Cr-containing samples maintained high viability (96 to 99%).

Simulation of radiation damage in Fe and Fe-Cr

International Nuclear Information System (INIS)

Lagerstedt, Christina

2005-11-01

Steel is an important structural material in nuclear reactors used for example in pressure vessels and fast reactor cladding. In reactor environments it has been observed that ferritic steels are more resistant to swelling than the austenitic steels typically used. Much effort has been put into developing basic models of FeCr alloys which can serve as model alloys for describing ferritic steels. As a result, a number of interatomic potentials for Fe and FeCr alloys exist today. For the work in this thesis, basic material properties coming from experiments or ab initio calculations were used to fit interatomic potentials for Fe, Cr and FeCr implementing both the embedded atom method and the Finnis-Sinclair formalisms. The potentials were then validated by molecular dynamic calculations of material properties such as defect formation energies, migration energies and thermal expansion. Further studies of potential performance were carried out in simulations of radiation damage cascades and thermal aging. The influence of the interatomic potential on the primary defect state in materials under irradiation was analyzed in a study comparing results obtained using four different potentials. The objective of the study was to find correlations between potential properties and the primary damage state produced in simulations of displacement cascades. The defect evolution and clustering during different cascade stages were also investigated to try to gain a better understanding of these processes

Sulfidation behavior of Fe20Cr alloys

International Nuclear Information System (INIS)

Pillis, Marina Fuser

2001-01-01

Alloys for use in high temperature environments rely on the formation of an oxide layer for their protection. Normally, these protective oxides are Cr 2 O 3 , Al 2 O 3 and, some times, SiO 2 . Many industrial gaseous environments contain sulfur. Sulfides, formed in the presence of sulfur are thermodynamically less stable, have lower melting points and deviate much more stoichiometrically, compared to the corresponding oxides. The mechanism of sulfidation of various metals is as yet not clear, in spite of the concerted efforts during the last decade. To help address this situation, the sulfidation behavior of Fe20Cr has been studied as a function of compositional modifications and surface state of the alloy. The alloys Fe20Cr, Fe20Cr0.7Y, Fe20Cr5Al and Fe20Cr5Al0.6Y were prepared and three sets of sulfidation tests were carried out. In the first set, the alloys were sulfidized at 700 deg C and 800 deg C for 10h. In the second set, the alloys were pre-oxidized at 1000 deg C and then sulfidized at 800 deg C for up to 45h. In the third set of tests, the initial stages of sulfidation of the alloys was studied. All the tests were carried out in a thermobalance, in flowing H 2 /2%H 2 S, and the sulfidation behavior determined as mass change per unit area. Scanning electron microscopy coupled to energy dispersive spectroscopy and X-ray diffraction analysis were used to characterize the reaction products. The addition of Y and Al increased sulfidation resistance of Fe20Cr. The addition of Y altered the species that diffused predominantly during sulfide growth. It changed from predominant cationic diffusion to predominant anionic diffusion. The addition of Al caused an even greater increase in sulfidation resistance of Fe20Cr, with the parabolic rate constant decreasing by three orders of magnitude. Y addition to the FeCrAl alloy did not cause any appreciable alteration in sulfidation resistance. Pre-oxidation of the FeCrAl and FeCrAlY alloys resulted in an extended

Bulk and surface properties of liquid Al-Cr and Cr-Ni alloys

International Nuclear Information System (INIS)

Novakovic, R

2011-01-01

The energetics of mixing and structural arrangement in liquid Al-Cr and Cr-Ni alloys has been analysed through the study of surface properties (surface tension and surface segregation), dynamic properties (chemical diffusion) and microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) in the framework of statistical mechanical theory in conjunction with quasi-lattice theory. The Al-Cr phase diagram exhibits the existence of different intermetallic compounds in the solid state, while that of Cr-Ni is a simple eutectic-type phase diagram at high temperatures and includes the low-temperature peritectoid reaction in the range near a CrNi 2 composition. Accordingly, the mixing behaviour in Al-Cr and Cr-Ni alloy melts was studied using the complex formation model in the weak interaction approximation and by postulating Al 8 Cr 5 and CrNi 2 chemical complexes, respectively, as energetically favoured.

Bulk and surface properties of liquid Al-Cr and Cr-Ni alloys.

Science.gov (United States)

Novakovic, R

2011-06-15

The energetics of mixing and structural arrangement in liquid Al-Cr and Cr-Ni alloys has been analysed through the study of surface properties (surface tension and surface segregation), dynamic properties (chemical diffusion) and microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) in the framework of statistical mechanical theory in conjunction with quasi-lattice theory. The Al-Cr phase diagram exhibits the existence of different intermetallic compounds in the solid state, while that of Cr-Ni is a simple eutectic-type phase diagram at high temperatures and includes the low-temperature peritectoid reaction in the range near a CrNi(2) composition. Accordingly, the mixing behaviour in Al-Cr and Cr-Ni alloy melts was studied using the complex formation model in the weak interaction approximation and by postulating Al(8)Cr(5) and CrNi(2) chemical complexes, respectively, as energetically favoured.

Mechanical alloying of Cu-xCr (x = 3, 5 and 8 wt.%) alloys

International Nuclear Information System (INIS)

Aguilar, C.; Ordonez, S.; Guzman, D.; Rojas, P.A.

2010-01-01

This work studies the structural evolution of Cu-xCr (x = 3, 5 and 8 wt.%) alloys processed by mechanical alloying using X-ray diffraction profiles, scanning microscopy and microhardness analysis. X-ray diffraction analysis using the modified Williamson-Hall and Warren-Averbach methods were used to determine structural properties, such as crystallite size, stacking fault probability and energy, dislocation density, lattice parameters and crystallite size distribution of metallic powder as a function of Cr amount and milling time. Lattice defects increase the Gibbs free energy and the Gibbs free energy curves shift upward, therefore the solubility limit change.

Study of the Effects of High Temperatures on the Engineering Properties of Steel 42CrMo4

Science.gov (United States)

Brnic, Josip; Turkalj, Goran; Canadija, Marko; Lanc, Domagoj; Brcic, Marino

2015-02-01

The paper presents and analyzes the experimental results of the effect of elevated temperatures on the engineering properties of steel 42CrMo4. Experimental data relating to the mechanical properties of the material, the creep resistance as well as Charpy impact energy. Temperature dependence of the mentioned properties is also shown. Some of creep curves were simulated using rheological models and an analytical equation. Finally, an assessment of fracture toughness was made that was based on experimentally determined Charpy impact energy. Based on the obtained results it is visible that the tensile strength (617 MPa) and yield strength (415 MPa) have the highest value at the room temperature while at the temperature of 700 °C (973 K) these values significantly decrease. This steel can be considered resistant to creep at 400 °C (673 K), but at higher temperatures this steel can be subjected to low levels of stress in a shorter time.

Plastic deformation behavior of Fe–Co–B–Si–Nb–Cr bulk metallic glasses under nanoindentation

Energy Technology Data Exchange (ETDEWEB)

Kim, J.T.; Hong, S.H.; Lee, C.H. [HMC, Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Park, J.M., E-mail: jinman_park@hotmail.com [Materials Research Center, Samsung Advanced Institute of Technology (SAIT), San 14-1, Nongseo-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-712 (Korea, Republic of); Kim, T.W.; Lee, W.H. [HMC, Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Yim, H.I. [Department of Physics, Sookmyung Women’s University, Hyochangwongil 52, Yongsan-ku, Seoul 140-742 (Korea, Republic of); Kim, K.B., E-mail: kbkim@sejong.ac.kr [HMC, Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of)

2014-02-25

Highlights: • Additional Cr modulation of atomic structure of Fe-Co-B-Si-Nb BMGs. • An amount of free volume characterized by a combination of nanoindentation and AFM. • Free volume determined by height measurement of AFM after nanoindentation. -- Abstract: In this work, we investigate the effect of Cr addition on thermal properties and indentation behavior of Fe{sub 52}Co{sub 20−x}B{sub 20}Si{sub 4}Nb{sub 4}Cr{sub x} alloys with x = 0, 1, 3 and 5 at.%, respectively. Among all studied alloys, the Fe{sub 52}Co{sub 17}B{sub 20}Si{sub 4}Nb{sub 4}Cr{sub 3} bulk metallic glass (BMG) exhibits the highest thermal stability with large supercooled liquid region of 40 K and the pronounced plastic deformation features which is serrated flow (pop-in event) and significant pile-up of materials around indents. This demonstrates that the appropriate addition of Cr in Fe-based BMG can induce the internal atomic structure modulation and promote the mechanical softening, which are discussed in terms of free volume concept.

Plastic deformation behavior of Fe–Co–B–Si–Nb–Cr bulk metallic glasses under nanoindentation

International Nuclear Information System (INIS)

Kim, J.T.; Hong, S.H.; Lee, C.H.; Park, J.M.; Kim, T.W.; Lee, W.H.; Yim, H.I.; Kim, K.B.

2014-01-01

Highlights: • Additional Cr modulation of atomic structure of Fe-Co-B-Si-Nb BMGs. • An amount of free volume characterized by a combination of nanoindentation and AFM. • Free volume determined by height measurement of AFM after nanoindentation. -- Abstract: In this work, we investigate the effect of Cr addition on thermal properties and indentation behavior of Fe 52 Co 20−x B 20 Si 4 Nb 4 Cr x alloys with x = 0, 1, 3 and 5 at.%, respectively. Among all studied alloys, the Fe 52 Co 17 B 20 Si 4 Nb 4 Cr 3 bulk metallic glass (BMG) exhibits the highest thermal stability with large supercooled liquid region of 40 K and the pronounced plastic deformation features which is serrated flow (pop-in event) and significant pile-up of materials around indents. This demonstrates that the appropriate addition of Cr in Fe-based BMG can induce the internal atomic structure modulation and promote the mechanical softening, which are discussed in terms of free volume concept

Biliary excretion and distribution of 51Cr(III) and 51Cr(VI) in rats

International Nuclear Information System (INIS)

Cikrt, M.; Bencko, V.

1979-01-01

The biliary excretion and distribution of 51 Cr after intravenous administration of 51 Cr(III) ( 51 CrCl 3 ) or 51 Cr(VI) (Na 2 51 CrO 4 .4H 2 O) were studied in rats. The cumulative biliary excretion of 51 Cr 24 hrs after the injection was significantly higher after administration of 51 Cr(VI) than of 51 Cr(III) (3.51+-0.7% and 0.51+-0.05% of administered dose, respectively). This difference was especially due to a higher rate of biliary excretion of 51 Cr in the first hours after 51 Cr(VI) administration. The excretion of 51 Cr via feces was also higher after administration of 51 Cr(VI) (7.35+-0.45%) of administered dose, as against 4.23+-0.23% after 51 Cr(III). On the other hand, no significant difference in urinary excretion of 51 Cr was found. Statistically significant differences were also observed in the distribution of 51 Cr in the organism after administration of both valence states of the metal. (author)

Microstructure and mechanical properties of nanostructure multilayer CrN/Cr coatings on titanium alloy

International Nuclear Information System (INIS)

Wiecinski, Piotr; Smolik, Jerzy; Garbacz, Halina; Kurzydlowski, Krzysztof J.

2011-01-01

Five different nanostructured, multilayer coatings (CrN/Cr)x8 with different thickness ratio of Cr and CrN layers were deposited by PAPVD (Plasma Assisted Physical Vapour Deposition) vacuum arc method on Ti6Al4V titanium alloy. The microstructure, chemical and phase composition of the CrN and Cr sub-layers were characterized by SEM with EDX and Cs-corrected dedicated STEM on cross-sections prepared by focus ion beam. Besides, hardness and Young's modulus of the (Cr/CrN)x8 coatings has been measured. The adhesion has been tested by scratch test method. The obtained (CrN/Cr) multilayer coatings, 5-6 μm in thickness, have homogeneous and nanocrystalline structure, free of pores and cracks. The microstructures of Cr and CrN layers consist of columnar grains below 100 nm in diameter. The hardness and Young's modulus of these coatings depend linearly on thickness ratio of Cr and CrN layers. The decrease of the thickness ratio Cr/CrN 0.81 to 0.15 results in the increase of hardness from 1275 HV to 1710 HV and Young's modulus from 260 GPa to 271 GPa.

Isolation and characterization of a chromium-resistant bacterium Serratia sp. Cr-10 from a chromate-contaminated site.

Science.gov (United States)

Zhang, Kundi; Li, Fuli

2011-05-01

A novel bacterium, Cr-10, was isolated from a chromium-contaminated site and capable of removing toxic chromium species from solution by reducing hexavalent chromium to an insoluble precipitate. Sequence analysis of 16S rRNA gene of strain Cr-10 showed that it was most closely related to Serratia rubidaea JCM 1240(T) (97.68%). Physiological and chemotaxonomic data also supported that strain Cr-10 was identified as Serratia sp., a genus which was never specially reported chromate-resistant before. Serratia sp., Cr-10 was tolerant to a concentration of 1,500 mg Cr(VI) L(-1), which was the highest level reported until now. The optimum pH and temperature for reduction of Cr(VI) by Serratia sp. Cr-10 were found to be 7.0 and 37 °C, respectively. The Cr(VI) reduction was significantly influenced by additional carbon sources, and among them fructose and lactose offered maximum reduction, with a rate of 0.28 and 0.25 mg Cr(VI) L(-1) h(-1), respectively. The cell-free extracts and filtrate of the culture were able to reduce Cr(VI) while concentration of total chromium remained stable in the process, indicating that the enzyme-catalyzed mechanism was applied in Cr(VI) reduction by the isolate. Additionally, it was found that there was hardly any chromium on the cell surface of the strain, further supporting that reduction, rather than bioadsorption, plays a major role in the Cr(VI) removal.

Isolation and characterization of a chromium-resistant bacterium Serratia sp. Cr-10 from a chromate-contaminated site

Energy Technology Data Exchange (ETDEWEB)

Zhang, Kundi; Li, Fuli [Chinese Academy of Sciences, Qingdao (China). Qingdao Inst. of Bioenergy and Bioprocess Technology

2011-05-15

A novel bacterium, Cr-10, was isolated from a chromium-contaminated site and capable of removing toxic chromium species from solution by reducing hexavalent chromium to an insoluble precipitate. Sequence analysis of 16S rRNA gene of strain Cr-10 showed that it was most closely related to Serratia rubidaea JCM 1240{sup T} (97.68%). Physiological and chemotaxonomic data also supported that strain Cr-10 was identified as Serratia sp., a genus which was never specially reported chromate-resistant before. Serratia sp., Cr-10 was tolerant to a concentration of 1,500 mg Cr(VI) L{sup -1}, which was the highest level reported until now. The optimum pH and temperature for reduction of Cr(VI) by Serratia sp. Cr-10 were found to be 7.0 and 37 C, respectively. The Cr(VI) reduction was significantly influenced by additional carbon sources, and among them fructose and lactose offered maximum reduction, with a rate of 0.28 and 0.25 mg Cr(VI) L{sup -1} h{sup -1}, respectively. The cell-free extracts and filtrate of the culture were able to reduce Cr(VI) while concentration of total chromium remained stable in the process, indicating that the enzyme-catalyzed mechanism was applied in Cr(VI) reduction by the isolate. Additionally, it was found that there was hardly any chromium on the cell surface of the strain, further supporting that reduction, rather than bioadsorption, plays a major role in the Cr(VI) removal. (orig.)

Correlation of the highest-energy cosmic rays with nearby extragalactic objects

NARCIS (Netherlands)

Pierre Auger Collaboration, [No Value; Abraham, J.; Abreu, P.; Aglietta, M.; Aguirre, C.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Alvarez, C.; Alvarez-Muñiz, J.; Ambrosio, M.; Anchordoqui, L.; Andringa, S.; Anzalone, A.; Aramo, C.; Argirò, S.; Arisaka, K.; Armengaud, E.; Arneodo, F.; Arqueros, F.; Asch, T.; Asorey, H.; Assis, P.; Atulugama, B. S.; Aublin, J.; Ave, M.; Avila, G.; Bäcker, T.; Badagnani, D.; Barbosa, A. F.; Barnhill, D.; Barroso, S. L. C.; Bauleo, P.; Beatty, J.; Beau, T.; Becker, B. R.; Becker, K. H.; Bellido, J. A.; BenZvi, S.; Berat, C.; Bergmann, T.; Bernardini, P.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanch-Bigas, O.; Blanco, F.; Blasi, P.; Bleve, C.; Blümer, H.; Bohácová, M.; Bonifazi, C.; Bonino, R.; Boratav, M.; Brack, J.; Brogueira, P.; Brown, W. C.; Buchholz, P.; Bueno, A.; Busca, N. G.; Caballero-Mora, K. S.; Cai, B.; Camin, D. V.; Caruso, R.; Carvalho, W.; Castellina, A.; Catalano, O.; Cataldi, G.; Cazón-Boado, L.; Cester, R.; Chauvin, J.; Chiavassa, A.; Chinellato, J. A.; Chou, A.; Chye, J.; Clark, P. D. J.; Clay, R. W.; Colombo, E.; Conceição, R.; Connolly, B.; Contreras, F.; Coppens, J.; Cordier, A.; Cotti, U.; Coutu, S.; Covault, C. E.; Creusot, A.; Cronin, J.; Dagoret-Campagne, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Donato, C.; de Jong, S. J.; De La Vega, G.; de Mello Junior, W. J. M.; de Mello Neto, J. R. T.; De Mitri, I.; de Souza, V.; del Peral, L.; Deligny, O.; Della Selva, A.; Delle Fratte, C.; Dembinski, H.; Di Giulio, C.; Diaz, J. C.; Dobrigkeit, C.; D'Olivo, J. C.; Dornic, D.; Dorofeev, A.; dos Anjos, J. C.; Dova, M. T.; D'Urso, D.; DuVernois, M. A.; Engel, R.; Epele, L.; Erdmann, M.; Escobar, C. O.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Fernández, A.; Ferrer, F.; Ferry, S.; Fick, B.; Filevich, A.; Filipcic, A.; Fleck, I.; Fonte, R.; Fracchiolla, C. E.; Fulgione, W.; García, B.; García Gámez, D.; Garcia-Pinto, D.; Garrido, X.; Geenen, H.; Gelmini, G.; Gemmeke, H.; Ghia, P. L.; Giller, M.; Glass, H.; Gold, M. S.; Golup, G.; Gomez Albarracin, F.; Gómez Berisso, M.; Gómez Herrero, R.; Gonçalves, P.; Gonçalves do Amaral, M.; Gonzalez, D.; Gonzalez, J. G.; González, M.; Góra, D.; Gorgi, A.; Gouffon, P.; Grassi, V.; Grillo, A.; Grunfeld, C.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Gutiérrez, J.; Hague, J. D.; Hamilton, J. C.; Hansen, P.; Harari, D.; Harmsma, S.; Harton, J. L.; Haungs, A.; Hauschildt, T.; Healy, M. D.; Hebbeker, T.; Heck, D.; Hojvat, C.; Holmes, V. C.; Homola, P.; Hörandel, J.; Horneffer, A.; Horvat, M.; Hrabovsky, M.; Huege, T.; Iarlori, M.; Insolia, A.; Ionita, F.; Italiano, A.; Kaducak, M.; Kampert, K. H.; Keilhauer, B.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Knapik, R.; Knapp, J.; Koang, D.-H.; Kopmann, A.; Krieger, A.; Krömer, O.; Kümpel, D.; Kunka, N.; Kusenko, A.; La Rosa, G.; Lachaud, C.; Lago, B. L.; Lebrun, D.; Le Brun, P.; Lee, J.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Leuthold, M.; Lhenry-Yvon, I.; López, R.; Lopez Agüera, A.; Lozano Bahilo, J.; Maccarone, M. C.; Macolino, C.; Maldera, S.; Malek, M.; Mancarella, G.; Manceñido, M. E.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Maris, I. C.; Martello, D.; Martínez, J.; Martínez Bravo, O.; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurizio, D.; Mazur, P. O.; McCauley, T.; McEwen, M.; McNeil, R. R.; Medina, M. C.; Medina-Tanco, G.; Meli, A.; Melo, D.; Menichetti, E.; Menschikov, A.; Meurer, Chr.; Meyhandan, R.; Micheletti, M. I.; Miele, G.; Miller, W.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morales, B.; Morello, C.; Moreno, E.; Moreno, J. C.; Morris, C.; Mostafá, M.; Muller, M. A.; Mussa, R.; Navarra, G.; Navarro, J. L.; Navas, S.; Nellen, L.; Newman-Holmes, C.; Newton, D.; Nguyen Thi, T.; Nierstenhöfer, N.; Nitz, D.; Nosek, D.; Nozka, L.; Oehlschläger, J.; Ohnuki, T.; Olinto, A.; Olmos-Gilbaja, V. M.; Ortiz, M.; Ostapchenko, S.; Otero, L.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Parente, G.; Parizot, E.; Parlati, S.; Pastor, S.; Patel, M.; Paul, T.; Pavlidou, V.; Payet, K.; Pech, M.; Pçkala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Petrera, S.; Petrinca, P.; Petrov, Y.; Ngoc, DiepPham; Ngoc, DongPham; Pham Thi, T. N.; Pichel, A.; Piegaia, R.; Pierog, T.; Pimenta, M.; Pinto, T.; Pirronello, V.; Pisanti, O.; Platino, M.; Pochon, J.; Porter, T. A.; Privitera, P.; Prouza, M.; Quel, E. J.; Rautenberg, J.; Reucroft, S.; Revenu, B.; Rezende, F. A. S.; Rídky, J.; Riggi, S.; Risse, M.; Rivière, C.; Rizi, V.; Roberts, M.; Robledo, C.; Rodriguez, G.; Rodríguez Frías, D.; Rodriguez Martino, J.; Rodriguez Rojo, J.; Rodriguez-Cabo, I.; Ros, G.; Rosado, J.; Roth, M.; Rouillé-d'Orfeuil, B.; Roulet, E.; Rovero, A. C.; Salamida, F.; Salazar, H.; Salina, G.; Sánchez, F.; Santander, M.; Santo, C. E.; Santos, E. M.; Sarazin, F.; Sarkar, S.; Sato, R.; Scherini, V.; Schieler, H.; Schmidt, F.; Schmidt, T.; Scholten, O.; Schovánek, P.; Schüssler, F.; Sciutto, S. J.; Scuderi, M.; Segreto, A.; Semikoz, D.; Settimo, M.; Shellard, R. C.; Sidelnik, I.; Siffert, B. B.; Sigl, G.; Smetniansky De Grande, N.; Smialkowski, A.; Smída, R.; Smith, A. G. K.; Smith, B. E.; Snow, G. R.; Sokolsky, P.; Sommers, P.; Sorokin, J.; Spinka, H.; Squartini, R.; Strazzeri, E.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Takahashi, J.; Tamashiro, A.; Tamburro, A.; Tascau, O.; Tcaciuc, R.; Thomas, D.; Ticona, R.; Tiffenberg, J.; Timmermans, C.; Tkaczyk, W.; Todero Peixoto, C. J.; Tomé, B.; Tonachini, A.; Torresi, D.; Travnicek, P.; Tripathi, A.; Tristram, G.; Tscherniakhovski, D.; Tueros, M.; Tunnicliffe, V.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van den Berg, A. M.; van Elewyck, V.; Vázquez, R. A.; Veberic, D.; Veiga, A.; Velarde, A.; Venters, T.; Verzi, V.; Videla, M.; Villaseñor, L.; Vorobiov, S.; Voyvodic, L.; Wahlberg, H.; Wainberg, O.; Waldenmaier, T.; Walker, P.; Warner, D.; Watson, A. A.; Westerhoff, S.; Wieczorek, G.; Wiencke, L.; Wilczynska, B.; Wilczynski, H.; Wileman, C.; Winnick, M. G.; Wu, H.; Wundheiler, B.; Xu, J.; Yamamoto, T.; Younk, P.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zech, A.; Zepeda, A.; Ziolkowski, M.

2007-01-01

Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrated a correlation between the arrival directions of cosmic rays with energy above 6 × 1019 electron volts and the positions of active galactic nuclei (AGN) lying within ~75 megaparsecs. We rejected the

Precipitation kinetics in austenitic 18Cr-30Ni-Nb cast steel

Directory of Open Access Journals (Sweden)

M. Garbiak

2008-08-01

Full Text Available The study presents the results of investigations on the precipitation kinetics in austenitic 18%Cr-30%Ni cast steel stabilised with an addition of 1.84 wt% niobium. Phase analysis of isolates extracted from the alloy subjected to annealing within the temperature range of 600–1000oC during 10–1000 h was made. The phase constitution of the isolates mainly comprised niobium carbides of the NbC type and complex chromium carbides of the Cr23C6 type. In specimens annealed within the temperature range of 700–900oC, a high-silicon G phase was additionally identified. The highest kinetics of the precipitation process was recorded after annealing at the temperatures of 800 and 900oC.

Cr-Ni ALLOY ELECTRODEPOSITION AND COMPARISON WITH CONVENTIONAL PURE Cr COATING TECHNIQUE

Directory of Open Access Journals (Sweden)

M. Moniruzzaman

2012-12-01

Full Text Available Cr coating is widely used as the outer surface of precision parts due to its attractive appearance and superior corrosion resistance properties. It is obtained by electrodeposition via a conventional bath with hexavalent Cr ions. This manufacturing technique has many drawbacks, such as very low efficiency and high operating temperature and it is hazardous to health. In this work, we studied a Cr-Ni alloy deposition technique and compared the alloy coating properties to those with conventional Cr coating. Sequential two-step alloy electrodeposition was also compared. We took varying concentrations of Cr, Ni and complexing agents for the electrodeposition of Cr-Ni alloy and sequential Cr-Ni alloy coating on mild steel. Operating parameters, i.e. current density and temperature, were varied to examine their effects on the coating properties. The coatings thus obtained were characterized by visual observation, corrosion test, microhardness measurement, morphology and chemical analysis. The Cr-Ni alloy coating was found to be more corrosion resistant in 5% NaCl solution and harder than the pure Cr coating obtained by conventional electrodeposition. Toxic gas was produced in a much lower extent in the alloy coating than the conventional Cr coating technique. Again, the two-step Cr-Ni alloy coating was found better in terms of corrosion resistance as well as hardness compared to the Cr-Ni alloy coating. The process was also found to be much more environmentally friendly.

Electronic structure and magnetic ordering of the semiconducting chromium trihalides CrCl3, CrBr3, and CrI3

KAUST Repository

Wang, Hao

2011-03-01

We present results from an electronic structure investigation of the chromium halides CrCl3, CrBr3, and CrI3, as obtained by the linearized augmented plane wave method of density functional theory. Our interest focuses on the chloride. While all three halides display strong ferromagnetic coupling within the halide-Cr-halide triple layers, our emphasis is on differences in the interlayer magnetic coupling. In agreement with experimental results, our calculations indicate ferromagnetic ordering for CrBr3 as well as CrI3. The antiferromagnetic state of CrCl3 can be reproduced by introducing an on-site electron-electron repulsion. However, we observe that the ground state depends critically on the specific approach used. Our results show that a low temperature structural phase transition from monoclinic to trigonal is energetically favourable for CrCl3. © 2011 IOP Publishing Ltd.

Cr(Vi) reduction capacity of activated sludge as affected by nitrogen and carbon sources, microbial acclimation and cell multiplication

International Nuclear Information System (INIS)

Ferro Orozco, A.M.; Contreras, E.M.; Zaritzky, N.E.

2010-01-01

The objectives of the present work were: (i) to analyze the capacity of activated sludge to reduce hexavalent chromium using different carbon sources as electron donors in batch reactors, (ii) to determine the relationship between biomass growth and the amount of Cr(VI) reduced considering the effect of the nitrogen to carbon source ratio, and (iii) to determine the effect of the Cr(VI) acclimation stage on the performance of the biological chromium reduction assessing the stability of the Cr(VI) reduction capacity of the activated sludge. The highest specific Cr(VI) removal rate (q Cr ) was attained with cheese whey or lactose as electron donors decreasing in the following order: cheese whey ∼ lactose > glucose > citrate > acetate. Batch assays with different nitrogen to carbon source ratio demonstrated that biological Cr(VI) reduction is associated to the cell multiplication phase; as a result, maximum Cr(VI) removal rates occur when there is no substrate limitation. The biomass can be acclimated to the presence of Cr(VI) and generate new cells that maintain the ability to reduce chromate. Therefore, the activated sludge process could be applied to a continuous Cr(VI) removal process.

Detection of light charged particles from plasma focus by CR-39

Energy Technology Data Exchange (ETDEWEB)

Antanasijevic, R.; Vukovic, J.; Popovic, S.; Popovic, M. (Belgrade Univ. (Yugoslavia). Inst. za Fiziku); Puric, J.; Cuk, M. (Faculty of Physical Science, Belgrade (Yugoslavia))

1991-01-01

An analysis of a deuteron (D{sup +}) beam, emitted from a plasma focus has been carried out, using a CR-39 plastic nuclear track detector. The CR-39 was pretreated using different processes to destroy the existing background before exposing it to the particles produced in the plasma focus. From measurements of the diameters of the tracks, the estimated energy of the D{sup +} ions is about 0.5 MeV. The total number of emitted D{sup +} ions was 10 particles/pulse. Some preliminary results on imaging etched CR-39 with an Atomic Force Microscope (NanoScope AFM) are also presented. (author).

Detection of light charged particles from plasma focus by CR-39

International Nuclear Information System (INIS)

Antanasijevic, R.; Vukovic, J.; Popovic, S.; Popovic, M.

1991-01-01

An analysis of a deuteron (D + ) beam, emitted from a plasma focus has been carried out, using a CR-39 plastic nuclear track detector. The CR-39 was pretreated using different processes to destroy the existing background before exposing it to the particles produced in the plasma focus. From measurements of the diameters of the tracks, the estimated energy of the D + ions is about 0.5 MeV. The total number of emitted D + ions was 10 particles/pulse. Some preliminary results on imaging etched CR-39 with an Atomic Force Microscope (NanoScope AFM) are also presented. (author)

Effect of casting atmosphere on the marginal deficiency and misfit of Ni-Cr alloys with and without beryllium.

Science.gov (United States)

da Silva, Leandro J; Leal, Monica B; Valente, Mariana L C; de Castro, Denise T; Pagnano, Valéria O; Dos Reis, Andréa C; Bezzon, Osvaldo L

2017-07-01

The marginal adaptation of prosthetic crowns is still a significant clinical problem. The purpose of this in vitro study was to evaluate the marginal deficiency and misfit of Ni-Cr alloys with and without beryllium under different casting conditions. Four casting conditions were selected: flame-torch, induction/argon, induction/vacuum, and induction/air; and 2 alloys were used, Ni-Cr-Be and Ni-Cr. For each group, 10 metal specimens were prepared. Silicone indirect impressions and analysis of the degree of rounding were used to evaluate the marginal deficiencies of metal copings, and a standardized device for the setting pressure associated with optical microscopy was used to analyze the marginal misfit. Results were evaluated with 2-way ANOVA (α=.05), followed by the Tukey honest significant difference post hoc test, and the Pearson correlation test (α=.05). Alloy (Pcasting technique (Pcast using the torch technique showed the highest marginal deficiency, and the Ni-Cr-Be cast in a controlled argon atmosphere showed the lowest (Pcasting techniques (P=.206) did not affect the marginal misfit, but significant differences were found in the interaction (P=.001); the lowest misfit was achieved using the Ni-Cr-Be, and the highest misfit occurred with the molten Ni-Cr, using the cast torch technique. No correlation was found between deficiency and marginal misfit (r=.04, P=.69). The interactions demonstrated that the alloy containing beryllium that was cast in an argon atmosphere led to reduced marginal deficiency. Improved marginal adaptation can be achieved for the same alloy by using the torch technique. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Treatment of Cr(VI)-containing wastewaters with exopolysaccharide-producing cyanobacteria in pilot flow through and batch systems

Energy Technology Data Exchange (ETDEWEB)

Colica, Giovanni; Mecarozzi, Pier Cesare; De Philippis, Roberto [Florence Univ., Firenze (Italy). Dept. of Agricultural Biotechnology

2010-08-15

Seven exopolysaccharide-producing cyanobacteria were tested with regard to their capability to remove Cr(VI) from the wastewater of a plating industry. The cyanobacterium which showed, under lab conditions, the most promising features with regard to both Cr(VI) removal (about 12 mg of Cr(VI) removed per gram of dry biomass) and growth characteristics (highest growth rate and simplest culture medium) was Nostoc PCC7936. Furthermore, in lab experiments, it was also found that a HCl pretreatment is essential to abate the concentration of Cr(VI) in solution and that the viability of the biomass is not necessary. Subsequently, three pilot devices were tested, one batch (a dialysis cell) and two flow-through systems (a filter press and a column filled with quartz grain). The best performances were obtained with the filter press, where it was observed a sharp decrease in the concentration of Cr(VI), partly due to the adsorption of the metal by the biomass (about 50%) and partly due to its reduction to Cr(III). The results are discussed in terms of the role played by the different components (biomass and polysaccharide) of the cyanobacterial cultures in the removal of Cr(VI). (orig.)

MD simulation of atomic displacement cascades in Fe-10 at.%Cr binary alloy

International Nuclear Information System (INIS)

Tikhonchev, M.; Svetukhin, V.; Kadochkin, A.; Gaganidze, E.

2009-01-01

Molecular dynamics simulation of atomic displacement cascades up to 20 keV has been performed in Fe-10 at.%Cr binary alloy at a temperature of 600 K. The N-body interatomic potentials of Finnis-Sinclair type were used. According to the obtained results the dependence of 'surviving' defects amount is well approximated by power function that coincides with other researchers' results. Obtained cascade efficiency for damage energy in the range from 10 to 20 keV is ∼0.2 NRT that is slightly higher than for pure α-Fe. In post-cascade area Cr fraction in interstitials is in range 2-5% that is essentially lower than Cr content in the base alloy. The results on size and amount of vacancy and interstitial clusters generated in displacement cascades are obtained. For energies of 2 keV and higher the defect cluster average size increases and it is well approximated by a linear dependence on cascade energy both for interstitials and vacancies.

MD simulation of atomic displacement cascades in Fe-10 at.%Cr binary alloy

Energy Technology Data Exchange (ETDEWEB)

Tikhonchev, M., E-mail: tikhonchev@sv.ulsu.r [Ulyanovsk State University, Leo Tolstoy Str., 42, Ulyanovsk 432970 (Russian Federation); Joint Stock Company, ' State Scientific Center Research Institute of Atomic Reactors' , 433510 Dimitrovgrad-10 (Russian Federation); Svetukhin, V.; Kadochkin, A. [Ulyanovsk State University, Leo Tolstoy Str., 42, Ulyanovsk 432970 (Russian Federation); Gaganidze, E. [Forschungszentrum Karlsruhe, IMF II, 3640, D-76021 Karlsruhe (Germany)

2009-12-15

Molecular dynamics simulation of atomic displacement cascades up to 20 keV has been performed in Fe-10 at.%Cr binary alloy at a temperature of 600 K. The N-body interatomic potentials of Finnis-Sinclair type were used. According to the obtained results the dependence of 'surviving' defects amount is well approximated by power function that coincides with other researchers' results. Obtained cascade efficiency for damage energy in the range from 10 to 20 keV is approx0.2 NRT that is slightly higher than for pure alpha-Fe. In post-cascade area Cr fraction in interstitials is in range 2-5% that is essentially lower than Cr content in the base alloy. The results on size and amount of vacancy and interstitial clusters generated in displacement cascades are obtained. For energies of 2 keV and higher the defect cluster average size increases and it is well approximated by a linear dependence on cascade energy both for interstitials and vacancies.

Observations of defect structure evolution in proton and Ni ion irradiated Ni-Cr binary alloys

Energy Technology Data Exchange (ETDEWEB)

Briggs, Samuel A., E-mail: sabriggs2@wisc.edu [University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Barr, Christopher M. [Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Pakarinen, Janne [University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); SKC-CEN Belgian Nuclear Research Centre, Boeretang 200, B-2400 Mol (Belgium); Mamivand, Mahmood [University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Hattar, Khalid [Sandia National Laboratories, PO Box 5800, Albuquerque, NM 87185 (United States); Morgan, Dane D. [University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Taheri, Mitra [Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Sridharan, Kumar [University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States)

2016-10-15

Two binary Ni-Cr model alloys with 5 wt% Cr and 18 wt% Cr were irradiated using 2 MeV protons at 400 and 500 °C and 20 MeV Ni{sup 4+} ions at 500 °C to investigate microstructural evolution as a function of composition, irradiation temperature, and irradiating ion species. Transmission electron microscopy (TEM) was applied to study irradiation-induced void and faulted Frank loops microstructures. Irradiations at 500 °C were shown to generate decreased densities of larger defects, likely due to increased barriers to defect nucleation as compared to 400 °C irradiations. Heavy ion irradiation resulted in a larger density of smaller voids when compared to proton irradiations, indicating in-cascade clustering of point defects. Cluster dynamics simulations were in good agreement with the experimental findings, suggesting that increases in Cr content lead to an increase in interstitial binding energy, leading to higher densities of smaller dislocation loops in the Ni-18Cr alloy as compared to the Ni-5Cr alloy. - Highlights: • Binary Ni-Cr alloys were irradiated with protons or Ni ions at 400 and 500 °C. • Higher irradiation temperatures yield increased size, decreased density of defects. • Hypothesize that varying Cr content affects interstitial binding energy. • Fitting CD models for loop nucleation to data supports this hypothesis.

First-principles study on half-metallic zinc-blende CrS and its (001) surface

Energy Technology Data Exchange (ETDEWEB)

Xu, Bin, E-mail: hnsqxb@163.com [Department of Mathematics and Information Sciences, North China university of Water Resources and Electric Power, Zhengzhou 450011 (China); Chen, Leiming [Zhengzhou Institute of Aeronautical Industry Management, Zhengzhou, 450015 (China)

2016-11-01

Half-metallic magnets with complete (100%) spin polarization have attracted growing interest due to the potential in spintronic applications. In this paper, we use the first-principles calculations to explain the seeming contradiction between the recent experimental ferromagnetism (Demper et al., 2012 [22]) and the previous theoretical antiferromagnetic ground state for half-metallic zinc-blende CrS, and the experimental ferromagnetism of zinc-blende CrS arises from the substrate effect. We also show that both Cr- and S-terminated (001) surfaces of CrS preserve the bulk half-metallicity. The calculated surface energy indicates that the S-terminated (001) surface is more stable than the Cr-terminated (001) surface within the whole effective Cr chemical potentials, and thus the S-terminated (001) surface is more likely than the Cr-terminated (001) surface when the CrS thin films are grown on ZnSe substrate.

Hardening of Fe-Cr-Mn steels cold plastic working

International Nuclear Information System (INIS)

Malinov, L.S.; Konop-Lyashko, V.I.; Nikoporets, N.M.

1983-01-01

The dependence is established between the level of proper-- ties obtained after cold plastic working and development of martensite transformations when loading in Fe-Cr-Mn steels containing 0.1-0.5% C, 13% Cr, 8-12% Mn, as well as in a number of complex alloyed steels. It is shown that the highest level of mechanical properties can be obtained after cold plastic working only in steels with definite austenite stability. Cold plastic working can both activize and stabilize austenite relatively to martensite formation during loading. The first thing is found when under the effect of preliminary cold working dislocation splitting takes place, as well as the formation of a small amount of E-phase and martensite. The second thing manifests itself when under the effect of cold working performed above Md (Md<20 deg C) cell dislocation structure is formed and dislocation pinning takes place

Measurement of (n,α) cross-sections for Cr, Fe and Ni at 14 MeV neutron energy

International Nuclear Information System (INIS)

Wattecamps, E.; Liskien, H.; Arnotte, F.

1983-01-01

Helium production cross-sections for the main constituents of stainless steel (Cr, Fe, Ni) have recently been published for neutron energies between 5 and 10 MeV. The α-particles were detected with a multi-angle telescope and cross-section data relative to the well known n-p scattering cross-section were deduced. Those measurements have been performed now also at 14 MeV. At this energy the background condition had to be improved by changing the neutron collimation, by reducing the sensitive volume of the ΔE-proportional counters, and by replacing remaining low-Z material inside the chamber by tantalum. Listing mode data acquisition is used and α-particle identification is performed by transforming the observed (ΔE,E) signal into a (MZ 2 ,E) signal. The measurements yield the angle-differential cross sections for five fixed angles. Angle-integrated cross-sections are compared with the few results available in literature. (Auth.)

Photofunctional Co-Cr Alloy Generating Reactive Oxygen Species for Photodynamic Applications

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Kang-Kyun Wang

2013-01-01

Full Text Available We report the fabrication of photofunctional Co-Cr alloy plate that is prepared by a simple modification process for photodynamic application. Photoinduced functionality is provided by the photosensitizer of hematoporphyrin (Hp that initially generates reactive oxygen species (ROS such as superoxide anion radical and singlet oxygen. The photosensitizer with carboxyl group was chemically bonded to the surface of the Co-Cr alloy plate by esterification reaction. Microstructure and elemental composition of the Co-Cr alloy plate were checked with scanning electron microscopy (SEM and energy dispersive X-ray spectrometer (EDS. Fabrication of the photofunctionality of the Co-Cr alloy plate was confirmed with X-ray photoelectron spectroscopy (XPS, reflectance UV-Vis absorption, and emission spectroscopy. Reactive oxygen generation from the photofunctional Co-Cr alloy plate was confirmed by using the decomposition reaction of 1,3-diphenylisobenzofuran (DPBF. The results suggest that the immobilized photosensitizer molecules on the surface of Co-Cr alloy plate still possess their optical and functional properties including reactive oxygen generation. To open the possibility for its application as a photodynamic material to biological system, the fabricated photofunctional Co-Cr alloy is applied to the decomposition of smooth muscle cells.

Oxidation resistance of TiN, CrN, TiAlN and CrAlN coatings deposited by lateral rotating cathode arc

International Nuclear Information System (INIS)

Chim, Y.C.; Ding, X.Z.; Zeng, X.T.; Zhang, S.

2009-01-01

In this paper, four kinds of hard coatings, TiN, CrN, TiAlN and CrAlN (with Al/Ti or Al/Cr atomic ratio around 1:1), were deposited on stainless steel substrates by a lateral rotating cathode arc technique. The as-deposited coatings were annealed in ambient atmosphere at different temperatures (500-1000 o C) for 1 h. The evolution of chemical composition, microstructure, and microhardness of these coatings after annealing at different temperatures was systematically analyzed by energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and nanoindentation experiments. The oxidation behaviour and its influence on overall hardness of these four coatings were compared. It was found that the ternary TiAlN and CrAlN coatings have better oxidation resistance than their binary counterparts, TiN and CrN coatings. The Cr-based coatings (CrN and CrAlN) exhibited evidently better oxidation resistance than the Ti-based coatings (TiN and TiAlN). TiN coating started to oxidize at 500 o C. After annealing at 700 o C no N could be detected by EDX, indicating that the coating was almost fully oxidized. After annealed at 800 o C, the coating completely delaminated from the substrate. TiAlN started to oxidize at 600 o C. It was nearly fully oxidized (with little residual nitrogen detected in the coating by EDX) and partially delaminated at 1000 o C. Both CrN and CrAlN started to oxidize at 700 o C. CrN was almost fully oxidized (with little residual nitrogen detected in the coating by EDX) and partially delaminated at 900 o C. The oxidation rate of the CrAlN coating is quite slow. After annealing at 1000 o C, only about 19 at.% oxygen was detected and the coating showed no delamination. The Ti-based (TiN and TiAlN) coatings were not able to retain their hardness at higher temperatures (≥ 700 o C). On the other hand, the hardness of CrAlN was stable at a high level between 33 and 35 GPa up to an annealing temperature of 800 o C and still kept at a comparative high value of

The influence of Chromium supplied by tanning and wet finishing processes on the formation of cr(vi in leather

Directory of Open Access Journals (Sweden)

W. F. Fuck

2011-06-01

Full Text Available Chromium used in leather manufacturing can be oxidized from the trivalent to the hexavalent state, causing environmental concerns. In this study, the influence of Cr(III from tanning, deacidification pH, fatliquors, chrome retanning and vegetable retanning on the formation of Cr(VI in leather was analyzed by comparing natural and aged samples. In wet-blue leather, even after aging and in fatliquored leathers that did not suffer the aging process, the presence of Cr(VI was always below the detection limit of 3 mg/kg. Considering the presence of Cr(VI, the supply of chromium during the retanning step had a more significant effect than during the tanning. In the fatliquoring process with sulfites, fish and synthetic fatliquor leather samples contained Cr(VI when aged, and the highest concentration detected was 26.7 mg/kg. The evaluation of Cr(VI formation led to recommendations for regulation in the leather industry.

Level crossing in a molecular Cr8 ring

International Nuclear Information System (INIS)

Affronte, M.; Guidi, T.; Caciuffo, R.; Carretta, S.; Amoretti, G.; Hinderer, J.; Sheikin, I.; Smith, A.A.; Winpenny, R.E.P.; Slageren, J. van; Gatteschi, D.

2004-01-01

The heat capacity of a molecular Cr 8 ring was measured as a function of temperature and magnetic field in order to follow the evolution of the Schottky anomaly through the first (S=0 to |1,-1>) level crossing occurring at B c1 =6.9 T. The results are interpreted within the framework of a spin Hamiltonian approach and they nicely fit the pattern of the energy levels derived by inelastic neutron spectroscopy. At B c1 , the Schottky anomaly almost vanishes suggesting that a true crossing occurs in Cr 8 in contrast to what was observed for ferric wheels

Theoretical investigation of spin-filtering in CrAs/GaAs heterostructures

International Nuclear Information System (INIS)

Stickler, B. A.; Ertler, C.; Pötz, W.; Chioncel, L.

2013-01-01

The electronic structure of bulk zinc-blende GaAs, zinc-blende and tetragonal CrAs, and CrAs/GaAs supercells, computed within linear muffin-tin orbital (LMTO) local spin-density functional theory, is used to extract the band alignment for the [1,0,0] GaAs/CrAs interface in dependence of the spin orientation. With the lateral lattice constant fixed to the experimental bulk GaAs value, a local energy minimum is found for a tetragonal CrAs unit cell with a longitudinal ([1,0,0]) lattice constant reduced by ≈2%. Due to the identified spin-dependent band alignment, half-metallicity of CrAs no longer is a key requirement for spin-filtering. Based on these findings, we study the spin-dependent tunneling current in [1,0,0] GaAs/CrAs/GaAs heterostructures within the non-equilibrium Green's function approach for an effective tight-binding Hamiltonian derived from the LMTO electronic structure. Results indicate that these heterostructures are promising candidates for efficient room-temperature all-semiconductor spin-filtering devices

Electron microscopy characterization of Ni-Cr-B-Si-C laser deposited coatings.

Science.gov (United States)

Hemmati, I; Rao, J C; Ocelík, V; De Hosson, J Th M

2013-02-01

During laser deposition of Ni-Cr-B-Si-C alloys with high amounts of Cr and B, various microstructures and phases can be generated from the same chemical composition that results in heterogeneous properties in the clad layer. In this study, the microstructure and phase constitution of a high-alloy Ni-Cr-B-Si-C coating deposited by laser cladding were analyzed by a combination of several microscopy characterization techniques including scanning electron microscopy in secondary and backscatter imaging modes, energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The combination of EDS and EBSD allowed unequivocal identification of micron-sized precipitates as polycrystalline orthorhombic CrB, single crystal tetragonal Cr5B3, and single crystal hexagonal Cr7C3. In addition, TEM characterization showed various equilibrium and metastable Ni-B, Ni-Si, and Ni-Si-B eutectic products in the alloy matrix. The findings of this study can be used to explain the phase formation reactions and to tune the microstructure of Ni-Cr-B-Si-C coatings to obtain the desired properties.

Applications of CR-39 solid state nuclear track detector to ion beam diagnosis

International Nuclear Information System (INIS)

Kanasaki, Masato; Hattori, Atsuto; Oda, Keiji; Yamauchi, Tomoya; Fukuda, Yuji; Sakaki, Hironao; Nishiuchi, Mamiko; Kondo, Kiminori; Kurashima, Satoshi; Kamiya, Tomihiro

2012-01-01

CR-39 solid state nuclear track detector, which was developed for optical lens, has been applied for various field such as radon surveys, measurement of galactic cosmic ray, cell irradiation experiment and so on. The CR-39 detectors have the great advantages of being insensitive to high energy photons and electrons and capable of detecting only ions in the mixed fields such as laser driven relativistic plasmas. Though there are some analytical methods of CR-39 to diagnose ion beam, unfortunately, only few researchers in the field of plasma know the methods. This article looks at how to use CR-39 detectors and introduce the accomplishment of the joint study JAEA and Kobe Univ. for application of CR-39 detectors to ion beam diagnosis. (author)

Reduction of Cr(VI) in aqueous solution with DC diaphragm glow discharge

International Nuclear Information System (INIS)

Wang, Xiaoyan; Jin, Xinglong; Zhou, Minghua; Chen, Zhenhai; Deng, Kai

2013-01-01

This paper investigated the reduction of Cr(VI) in aqueous solution with direct current diaphragm glow discharge (DGD). The glow discharge sustained around the hole on a quartz tube which divided the electrolyte cell into two parts. The reduction efficiencies of Cr(VI) under different applied voltages, initial conductivities, hole diameters, hole numbers, initial pH values and initial concentrations were systematically studied. The results showed that the reduction efficiency of Cr(VI) increased with the increase of applied voltage, initial conductivity, hole diameter and hole number. The different initial pH values showed less effects on the reduction of Cr(VI). The reduction efficiency decreased with the increasing initial concentration. In addition, the simultaneous reduction of Cr(VI) and decolorization of acid orange (AO) with DGD were also fulfilled. Furthermore, the energy efficiency for Cr(VI) reduction with DGD was calculated and compared with those in photocatalysis and other glow discharge reactor

Structure and magnetic properties of Cr nanoparticles and Cr2O3 nanoparticles

International Nuclear Information System (INIS)

Zhang, W.S.; Brueck, E.; Zhang, Z.D.; Tegus, O.; Li, W.F.; Si, P.Z.; Geng, D.Y.; Buschow, K.H.J.

2005-01-01

We have synthesized Cr nanoparticles by arc-discharge and Cr 2 O 3 nanoparticles by subsequent annealing the as-prepared Cr nanoparticles. The structure of these nanoparticles is studied by means of X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscope. Most of the particles show a good crystal habit of well-defined cubic or orthorhombic shape, while some small particles show spherical shape. The as-prepared Cr nanoparticles have a BCC Cr core coated with a thin Cr 2 O 3 layer. Cr in the core of the particles heated at 873 K for 4 h is changed to Cr 2 O 3 . The results of magnetic measurements show that the Cr nanoparticles exhibit mainly antiferromagnetic properties, in addition to a weak-ferromagnetic component at lower fields. The weak-ferromagnetic component may be ascribed to uncompensated surface spins. For the field-cooled Cr 2 O 3 nanoparticles, an exchange bias is observed in the hysteresis loops, which can be interpreted as the exchange coupling between the uncompensated spins at the surface and the spins in the core of the Cr 2 O 3 nanoparticles

Magnetism of CrO overlayers on Fe(001)bcc surface: first principles calculations

Science.gov (United States)

Félix-Medina, Raúl Enrique; Leyva-Lucero, Manuel Andrés; Meza-Aguilar, Salvador; Demangeat, Claude

2018-04-01

Riva et al. [Surf. Sci. 621, 55 (2014)] as well as Calloni et al. [J. Phys.: Condens. Matter 26, 445001 (2014)] have studied the oxydation of Cr films deposited on Fe(001)bcc through low-energy electron diffraction, Auger electron spectroscopy and scanning tunneling microscopy. In the present work we perform a density functional approach within Quantum Expresso code in order to study structural and magnetic properties of CrO overlayers on Fe(001)bcc. The calculations are performed using DFT+U. The investigated systems include O/Cr/Fe(001)bcc, Cr/O/Fe(001)bcc, Cr0.25O0.75/Fe(001)bcc, as well as the O coverage Ox/Cr/Fe(001)bcc (x = 0.25; 0.50). We have found that the ordered CrO overlayer presents an antiferromagnetic coupling between Cr and Fe atoms. The O atoms are located closer to the Fe atoms of the surface than the Cr atoms. The ground state of the systems O/Cr/Fe(001)bcc and Cr/O/Fe(001)bcc corresponds to the O/Cr/Fe(001)bcc system with a magnetic coupling c(2 × 2). The effect of the O monolayer on Cr/Fe(001)bcc changes the ground state from p(1 × 1) ↓ to c(2 × 2) and produces an enhancement of the magnetic moments. The Ox overlayer on Cr/Fe(001)bcc produces an enhancement of the Cr magnetic moments.

Fatigue failure analysis of V-4Ti-4Cr alloy

International Nuclear Information System (INIS)

Aglan, H.; Gan, Y.X.; Grossbeck, M.

1999-01-01

In the present work, the fatigue fracture and failure behavior of a V-4Ti-4Cr has been studied. Static tests were conducted to study the overloading behavior and to select the magnitude of the stress level for the fatigue studies. Fatigue tests were performed using single edge notched (SEN) specimens under tension-tension load control conditions. Fatigue crack propagation (FCP) data such as the crack length, number of cycles, and hysteresis loops were recorded to calculate the crack speed, the energy release rate, and the change in work expended on damage formation and dissipative processes within the material. Parameters characterizing the fatigue fracture resistance of V-4Ti-4Cr alloy, namely the specific energy of damage (γ'), and the dissipative coefficient (β'), were determined from the fatigue data using the modified crack layer (MCL) theory. Fracture surface examination using scanning electron microscopy (SEM) revealed ductile failure mechanisms under tensile overloading conditions. The fatigue fracture surface of the V-4Ti-4Cr consists of three distinct regions, corresponding to the threshold, stable and unstable crack propagation stages. (orig.)

Adsorption studies on fruits of Gular (Ficus glomerata): Removal of Cr(VI) from synthetic wastewater

International Nuclear Information System (INIS)

Rao, Rifaqat A.K.; Rehman, Fouzia

2010-01-01

The adsorption of Cr(VI) was studied in batch system using fruits of Ficus glomerata as adsorbent. The effect of temperature, pH, initial Cr(VI) concentration and time was investigated. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) was used to investigate surface morphology and active functional groups present on the adsorbent surface. Thermodynamic parameters like free energy change (ΔG 0 ), enthalpy (ΔH 0 ) and entropy (ΔS 0 ) indicate the spontaneous, endothermic and increased randomness nature of Cr(VI) adsorption. Equilibrium data were fitted well with Langmuir isotherm at 50 deg. C. The magnitude of mean free energy indicates chemical nature of adsorption. The breakthrough and exhaustive capacities were found to be 5 and 23.1 mg g -1 respectively. The applicability of the adsorbent has been demonstrated by removing Cr(VI) from electroplating wastewater.

INVESTIGATION OF NONAXISYMMETRIC STRESS STATE FOR QUASI-STATIC THERMAL POWER LOADING UNDER CONDITIONS OF HIGHEST-ENERGY PARTICLE IRRADIATION

Directory of Open Access Journals (Sweden)

A. V. Chigarev

2013-01-01

Full Text Available The paper contains a virtual modeling 2D(r, θ for deformation of singly-connected cylindrical solid under conditions of thermo-irradiation impact. Influence of a circumferential distortion on nonaxisymmetric strain-stress state for various values of temperature amplitudes has been investigated in the paper. A solid cylinder  with internal heat sources has been considered as a model body. Properties of the model body correspond to cermet fuel (40 % UO2 + 60 % Cr. 

Characterization of Cr/Bentonite and HZSM-5 Zeolite as Catalysts for Ethanol Conversion to Biogasoline

Directory of Open Access Journals (Sweden)

Robert Ronal Widjaya

2012-04-01

Full Text Available In this research it has been done characterization on Cr/Bentonit and Zeolit HZSM-5 catalysts for ethanol catalytic process to biogasoline (equal to gasoline. Cr/Bentonit has high acidity and resistant to a lot of moisture, so in addition to being able to processing feed which a lot of moisture (>15% from ethanol-water mixture, also it is not easy deactivated. Cr/Bentonit which is then used as the catalyst material on the process of ethanol conversion to be biogasoline and the result was compared with catalyst HZSM-5 zeolite. Several characterization methods: X-ray diffraction, Brunauer Emmett Teller (BET, thermogravimetry analysis (TGA, and catalyst activity tests using catalytic Muffler instrument and gas chromatography-mass spectrometry (GC-MS for product analysis were performed on both catalysts. From acidity measurement, it is known that acidity level of Cr/Bentonit is the highest and also from XRD result, it is known there is shift for 2theta in Cr/Bentonit, which indicates that Cr-pillar in the Bentonite can have interaction. It is also supported by BET data that shows the addition of specific surface are in Cr/Bentonite compared with natural Bentonite before pillarization. Futhermore catalyst activity test produced the results, analyzed by GC-MS, identified as butanol and also possibly formed hexanol, decane, dodecane, undecane, which are all included in gasoline range (C4 until C12.

Wear behavior of Cu-Ag-Cr alloy wire under electrical sliding

International Nuclear Information System (INIS)

Jia, S.G.; Liu, P.; Ren, F.Z.; Tian, B.H.; Zheng, M.S.; Zhou, G.S.

2005-01-01

The wear behavior of a Cu-Ag-Cr alloy contact wire against a copper-base sintered alloy strip was investigated. Wear tests were conducted under laboratory conditions with a special sliding wear apparatus that simulated train motion under electrical current conditions. The initial microstructure of the Cu-Ag-Cr alloy contact wire was analyzed by transmission electron microscopy. Worn surfaces of the Cu-Ag-Cr alloy wire were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). The results indicate that the wear rate of the Cu-Ag-Cr wire increased with increasing electrical current and sliding. Within the studied range of electrical current, the wear rate increases with increasing electrical current and sliding speed. Compared with the Cu-Ag contact wire under the same testing conditions, the Cu-Ag-Cr alloy wire has much better wear resistance. Adhesive, abrasive, and electrical erosion wear are the dominant mechanisms during the electrical sliding processes

Al{sub 2}O{sub 3}:Cr{sup 3+} microfibers by hydrothermal route: Luminescence properties

Energy Technology Data Exchange (ETDEWEB)

Liu, Dianguang [School of Materials Science and Engineering, Shaanxi University of Science and Technology, Xi’an 710021 (China); Zhu, Zhenfeng, E-mail: zhuzf@sust.edu.cn [School of Materials Science and Engineering, Shaanxi University of Science and Technology, Xi’an 710021 (China); Liu, Hui; Zhang, Zhengyang; Zhang, Yanbin; Li, Gege [School of Materials Science and Engineering, Shaanxi University of Science and Technology, Xi’an 710021 (China)

2012-09-15

Highlights: ► Uniform Al{sub 2}O{sub 3}:Cr{sup 3+} microfibers were synthesized via a hydrothermal route and thermal decomposition. ► The length and diameter of Al{sub 2}O{sub 3}:Cr{sup 3+} microfibers were about 3–9 μm and 300 nm, respectively. ► Al{sub 2}O{sub 3}:Cr{sup 3+} microfibers presented a broad R band at 696 nm when excited at 400 nm. ► It is shown that the 0.07 mol% of doping concentration of Cr{sup 3+} ions in α-Al{sub 2}O{sub 3}:Cr{sup 3+} is optimum. ► Critical distance between Cr{sup 3+} ions for energy transfer was determined to be 38 Å. -- Abstract: Uniform Al{sub 2}O{sub 3}:Cr{sup 3+} microfibers were synthesized by using a hydrothermal route and thermal decomposition of a precursor of Cr{sup 3+} doped ammonium aluminum hydroxide carbonate (denoted as AAHC), and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) spectra and decay curves. XRD indicated that Cr{sup 3+} doped samples calcined at 1473 K were the most of α-Al{sub 2}O{sub 3} phase. SEM showed that the length and diameter of these Cr{sup 3+} doped alumina microfibers were about 3–9 μm and 300 nm, respectively. PL spectra showed that the Al{sub 2}O{sub 3}:Cr{sup 3+} microfibers presented a broad R band at 696 nm. It is shown that the 0.07 mol% of doping concentration of Cr{sup 3+} ions in α-Al{sub 2}O{sub 3}:Cr{sup 3+} was optimum. According to Dexter's theory, the critical distance between Cr{sup 3+} ions for energy transfer was determined to be 38 Å. It is found that the curve followed the single-exponential decay.

Interatomic Potential to Simulate Radiation Damage in Fe-Cr Alloys

International Nuclear Information System (INIS)

Bonny, G.; Pasianot, R.; Terentyev, D.; Malerba, L.

2011-01-01

The report presents an Fe-Cr interatomic potential to model high-Cr ferritic alloys. The potential is fitted to thermodynamic and point-defect properties obtained from density functional theory (DFT) calculations and experiments. The developed potential is also benchmarked against other potentials available in literature. It shows particularly good agreement with the DFT obtained mixing enthalpy of the random alloy, the formation energy of intermetallics and experimental excess vibrational entropy and phase diagram. In addition, DFT calculated point-defect properties, both interstitial and substitutional, are well reproduced, as is the screw dislocation core structure. As a first validation of the potential, we study the precipitation hardening of Fe-Cr alloys via static simulations of the interaction between Cr precipitates and screw dislocations. It is concluded that the description of the dislocation core modification near a precipitate might have a significant influence on the interaction mechanisms observed in dynamic simulations.

Interatomic Potential to Simulate Radiation Damage in Fe-Cr Alloys

Energy Technology Data Exchange (ETDEWEB)

Bonny, G.; Pasianot, R.; Terentyev, D.; Malerba, L.

2011-03-15

The report presents an Fe-Cr interatomic potential to model high-Cr ferritic alloys. The potential is fitted to thermodynamic and point-defect properties obtained from density functional theory (DFT) calculations and experiments. The developed potential is also benchmarked against other potentials available in literature. It shows particularly good agreement with the DFT obtained mixing enthalpy of the random alloy, the formation energy of intermetallics and experimental excess vibrational entropy and phase diagram. In addition, DFT calculated point-defect properties, both interstitial and substitutional, are well reproduced, as is the screw dislocation core structure. As a first validation of the potential, we study the precipitation hardening of Fe-Cr alloys via static simulations of the interaction between Cr precipitates and screw dislocations. It is concluded that the description of the dislocation core modification near a precipitate might have a significant influence on the interaction mechanisms observed in dynamic simulations.

A Comparative Physics Study of Commercial PWR Cores using Metallic Micro-cell UO{sub 2}-Cr (or Mo) Pellets with Cr-based Cladding Coating

Energy Technology Data Exchange (ETDEWEB)

Hwang, Dae Hee; Hong, Ser Gi [Kyung Hee University, Yongin (Korea, Republic of); In, Wang Kee [KAERI, Daejeon (Korea, Republic of)

2016-05-15

In this work, a comparative neutronic analysis of the cores using ATFs which include metallic micro-cell UO{sub 2}-Cr, UO{sub 2}-Mo pellets and Cr-based alloy coating on cladding was performed to show the effects of the ATF fuels on the core performance. In this study, the cores having different ATFs use the same initial uranium enrichments. The ATF concepts studied in this work are the metallic microcell UO{sub 2} pellets containing Cr or Mo with cladding outer coating composed of Cr-based alloy which have been suggested as the ATF concepts in KAERI (Korea Atomic Energy Research Institute). The metallic micro-cell pellets and Cr-based alloy coating can enhance thermal conductivity of fuel and reduce the production of hydrogen from the reaction of cladding with coolant, respectively. The objective of this work is to compare neutronic characteristics of commercial PWR equilibrium cores utilizing the different variations of metallic micro-cell UO{sub 2} pellets with cladding coating composed of Cr-based alloy. The results showed that the cores using UO{sub 2}-Cr and UO{sub 2}-Mo pellets with Cr-based alloy coating on cladding have reduced cycle lengths by 60 and 106 EFPDs, respectively, in comparison with the reference UO{sub 2} fueled core due to the reduced heavy metal inventories and large thermal absorption cross section but they do not have any significant differences in the core performances parameters. However, it is notable that the core fueled the micro-cell UO{sub 2}-Mo pellet and Cr-based alloy coating has considerably more negative MTC and slightly more negative FTC than the other cases. These characteristics of the core using micro-cell UO{sub 2}-Mo pellet and Cr-based alloy coating is due to the hard neutron spectrum and large capture resonance cross section of Mo isotopes.

Homogeneous and Heterogeneous (Fex, Cr1-x)(OH)3 Precipitation: Implications for Cr Sequestration.

Science.gov (United States)

Dai, Chong; Zuo, Xiaobing; Cao, Bo; Hu, Yandi

2016-02-16

The formation of (Fe, Cr)(OH)3 nanoparticles determines the fate of aqueous Cr in many aquatic environments. Using small-angle X-ray scattering, precipitation rates of (Fe, Cr)(OH)3 nanoparticles in solution and on quartz were quantified from 0.1 mM Fe(III) solutions containing 0-0.25 mM Cr(III) at pH = 3.7 ± 0.2. Concentration ratio of aqueous Cr(III)/Fe(III) controlled the chemical composition (x) of (Fex, Cr1-x)(OH)3 precipitates, solutions' supersaturation with respect to precipitates, and the surface charge of quartz. Therefore, the aqueous Cr(III)/Fe(III) ratio affected homogeneous (in solution) and heterogeneous (on quartz) precipitation rates of (Fex, Cr1-x)(OH)3 through different mechanisms. The sequestration mechanisms of Cr(III) in precipitates were also investigated. In solutions with high aqueous Cr(III)/Fe(III) ratios, surface enrichment of Cr(III) on the precipitates occurred, resulting in slower particle growth in solutions. From solutions with 0-0.1 mM Cr(III), the particles on quartz grew from 2 to 4 nm within 1 h. Interestingly, from solution with 0.25 mM Cr(III), particles of two distinct sizes (2 and 6 nm) formed on quartz, and their sizes remained unchanged throughout the reaction. Our study provided new insights on homogeneous and heterogeneous precipitation of (Fex, Cr1-x)(OH)3 nanoparticles, which can help determine the fate of Cr in aquatic environments.

The response of CR-39 nuclear track detector to 1-9 MeV protons

International Nuclear Information System (INIS)

Sinenian, N.; Rosenberg, M. J.; Manuel, M.; McDuffee, S. C.; Casey, D. T.; Zylstra, A. B.; Rinderknecht, H. G.; Gatu Johnson, M.; Seguin, F. H.; Frenje, J. A.; Li, C. K.; Petrasso, R. D.

2011-01-01

The response of CR-39 nuclear track detector (TasTrak) to protons in the energy range of 0.92-9.28 MeV has been studied. Previous studies of the CR-39 response to protons have been extended by examining the piece-to-piece variability in addition to the effects of etch time and etchant temperature; it is shown that the shape of the CR-39 response curve to protons can vary from piece-to-piece. Effects due to the age of CR-39 have also been studied using 5.5 MeV alpha particles over a 5-year period. Track diameters were found to degrade with the age of the CR-39 itself rather than the age of the tracks, consistent with previous studies utilizing different CR-39 over shorter time periods.

A CR-39 track dosemeter for routine individual neutron monitoring

International Nuclear Information System (INIS)

Luszik-Bhadra, M.; Alberts, W.G.; Dietz, E.; Guldbakke, S.; Matzke, M.; d'Errico, F.

1994-01-01

A personal neutron dosemeter for routine individual monitoring is proposed. It is based on a CR-39 track detector covered on three separate areas by converters with different boron contents and inserted into a commercial TLD albedo dosemeter capsule. The dose readings from three areas of the electrochemically etched CR-39 detector are combined to yield a dose equivalent response which is almost independent of the incident neutron energy in the range from thermal neutrons up to 20 MeV. In addition, the dose contributions of thermal, intermediate and fast neutrons can be determined separately. Unlike the TLD albedo dosemeter, which in general requires prior in-field calibration and whose use is then restricted to that field, this dosemeter can be used in neutron fields without any knowledge of the spectral distribution with the same calibration factor. The angular dependence of the dosemeter's response has been measured and compared with that of the directional dose equivalent H'(10). The lower limit of detection is 0.15 mSv. It is possible to obtain an independent, second dose reading from the same Cr-39 detector for neutron energies above 100 keV. The dosemeter has also been successfully tested for use in accident dosimetry applying chemical etching and an optical density reading of the CR-39 detector. (author)

The use of CR1aa for ovine in vitro embryo production

Directory of Open Access Journals (Sweden)

Yulnawati

2006-06-01

Full Text Available The aim of this study was to investigate the capacity of CR1aa as a simple medium for maturation, fertilization and culture of ovine embryo in vitro. Oocytes were collected by slicing method in Phosphate Buffer Saline (PBS supplemented with 5% Fetal Bovine Serum (FBS and 100 IU/ml penicillin streptomycin. Oocytes were matured in Tissue Culture Medium (TCM-199 as control or CR1aa as treatment medium. Both maturation medium were supplemented with 10% Fetal Bovine Serum (FBS, 10 IU/ml Follicle Stimulating Hormone (FSH, 10 IU/ml Luteinizing Hormone (LH, 1 μg/ml Estradiol and 100 IU/ml penicillin-streptomycin. Oocytes were incubated in 5% CO2 incubator, 38˚C for 24 h. Matured oocytes were fertilized in BO or CR1aa medium, supplemented with 2.5 mM caffeine benzoate and 20 mg /ml heparin. After 18 h in vitro fertilization, oocytes were cultured in TCM-199 or CR1aa medium, both supplemented with 5% FBS, 5 mg/ml insulin and 100 IU/ml penicillin streptomycin. Results showed that the highest maturation rate was found in TCM-199 medium (73.27% and significantly different (P0.05 between cleavage rate of ovine embryos in TCM-199 and CR1aa medium (39.45% vs 50.94%. In conclusion, optimum result on ovine in vitro embryo production can be achieved from a combination of TCM-199 as maturation medium and CR1aa as fertilization and culture medium.

Hot corrosion of Co-Cr, Co-Cr-Al, and Ni-Cr alloys in the temperature range of 700-750 deg C

Science.gov (United States)

Chiang, K. T.; Meier, G. H.

1980-01-01

The effect of SO3 pressure in the gas phase on the Na2SO4 induced hot corrosion of Co-Cr, Ni-Cr, and Co-Cr-Al alloys was studied in the temperature range 700 to 750 C. The degradation of the Co-Cr and Ni-Cr alloys was found to be associated with the formation of liquid mixed sulfates (CoSO4-Na2SO4 or NiSO4-Na2SO4) which provided a selective dissolution of the Co or Ni and a subsequent sulfidation oxidation mode of attack which prevented the maintenance of a protective Cr2O3 film. A clear mechanism was not developed for the degradation of Co-Cr-Al alloys. A pitting corrosion morphology was induced by a number of different mechanisms.

Effect of cold deformation on latent energy value and high-temperature mechanical properties of 12Cr18Ni10Ti steel

International Nuclear Information System (INIS)

Maksimkin, O.P.; Shiganakov, Sh.B.; Gusev, M.N.

1997-01-01

Energetic and magnetic characteristics and also the high-temperature mechanical properties depending on the preliminary cold deformation of 12Cr18Ni10Ti steel are presented. It is shown that the value of storage energy in the steel has being grown with increase of the deformation. The rate of its growth has been increased after beginning of martensitic γ→α'- transformation when value of comparative storage energy at first decreased and then has been stay practically constant. Level of mechanical properties of the steel at 1073 K has been determined not only by value of cold deformation but and structural reconstruction corresponding to deformations 35-45% and accompanying with α'-phase martensite formation and change of energy accumulating rate. Preliminary cold deformation (40-60 %) does not improve high- temperature plasticity of steel samples implanted by helium. refs. 7, figs. 2

Kyle Cranmer receives the highest recognition from the US government

CERN Multimedia

Allen Mincer

Kyle Cranmer with Clay Sell, Deputy Secretary of EnergyKyle Cranmer, who has worked on ATLAS as a graduate student at the University of Wisconsin-Madison, a Goldhaber Fellow at Brookhaven National Laboratory, and, most recently, an Assistant Professor at New York University, has been awarded a Presidential Early Career Award for Scientists and Engineers (PECASE). As described at the United States Department of Energy web page: "The PECASE Awards are intended to recognize some of the finest scientists and engineers who, while early in their research careers, show exceptional potential for leadership at the frontiers of scientific knowledge during the twenty-first century...The PECASE Award is the highest honor bestowed by the U.S. government on outstanding scientists and engineers beginning their independent careers." Kyle's work on ATLAS focuses on tools and strategies for data analysis, triggering, and searches for the Higgs.At the awards ceremony, which took place on Thursday Nov. 1st in Washington, D.C.,...

An electrochemical study of U(VI) and Cr(VI) in molten borates

International Nuclear Information System (INIS)

Brigaudeau, M.; Gregori de Pinochet, I. de

1977-01-01

The electrochemical reduction of U(VI) and Cr(VI), in molten Na 2 B 4 O 7 at 800 deg C was studied by means of linear sweep voltammetry, and chronopotentiometry. The reduction of U(VI) to U(V) proceeded reversibly at a platinum electrode. The diffusion coefficient for the U(VI) species at 800 deg C was 4.10 -7 cm 2 .s -1 . The activation energy of diffusion was (34,8 +- 0,8) kcal. mole -1 . Electrochemical studies of Cr(VI) at 800 0 C reveal a two-step reduction process at a platinum electrode. Only the voltammogram for the first step charge transfer process was studied. Analysis indicated that Cr(VI) is reversibly reduced to Cr(III) at a platinum electrode. The diffusion coefficient for Cr(VI) at 800 0 C is 1,9.10 -7 cm 2 .s -1 [fr

Experimental Monitoring of Cr(VI) Bio-reduction Using Electrochemical Geophysics

International Nuclear Information System (INIS)

Birsen Canan; Gary R. Olhoeft; William A. Smith

2007-01-01

Many Department of Energy (DOE) sites are contaminated with highly carcinogenic hexavalent chromium (Cr(VI)). In this research, we explore the feasibility of applying complex resistivity to the detection and monitoring of microbially-induced reduction of hexavalent chromium (Cr(VI)) to a less toxic form (Cr(III)). We hope to measure the change in ionic concentration that occurs during this reduction reaction. This form of reduction promises to be an attractive alternative to more expensive remedial treatment methods. The specific goal of this research is to define the minimum and maximum concentration of the chemical and biological compounds in contaminated samples for which the Cr(VI) - Cr(III) reduction processes could be detected via complex resistivity. There are three sets of experiments, each comprised of three sample columns. The first experiment compares three concentrations of Cr(VI) at the same bacterial cell concentration. The second experiment establishes background samples with, and without, Cr(VI) and bacterial cells. The third experiment examines the influence of three different bacterial cell counts on the same concentration of Cr(VI). A polarization relaxation mechanism was observed between 10 and 50 Hz. The polarization mechanism, unfortunately, was not unique to bio-chemically active samples. Spectral analysis of complex resistivity data, however, showed that the frequency where the phase minimum occurred was not constant for bio-chemically active samples throughout the experiment. A significant shifts in phase minima occurred between 10 to 20 Hz from the initiation to completion of Cr(VI) reduction. This phenomena was quantified using the Cole-Cole model and the Marquardt-Levenberg nonlinear least square minimization method. The data suggests that the relaxation time and the time constant of this relaxation are the Cole-Cole parameters most sensitive to changes in biologically-induced reduction of Cr(VI)

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

Science.gov (United States)

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

2018-01-01

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

A ternary nanocatalyst of Ni/Cr/Co oxides with high activity and stability for alkaline glucose electrooxidation

International Nuclear Information System (INIS)

Gu, Yingying; Yang, Haihong; Li, Benqiang; An, Yarui

2016-01-01

Highlights: • Ni-Cr-Co nanomaterial was synthesized by thermal decomposition method. • Ni 4 -Cr 1 -Co 1.5 has the highest GOR activity among the prepared catalysts. • A catalytic current density of 23.8 mA × cm −2 is attained for alkaline GOR. - Abstract: A novel ternary nanocatalyst of Ni-Cr-Co oxides is synthesized as anode electro-catalysts for glucose oxidation. The nanostructure is characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), which indicates that the catalyst particles are well dispersed with average size of 30 nm when the calcination temperature is 500 °C. The electrochemical performance is evaluated via cyclic voltammetry (CV). Compared with the bimetallic Ni-Cr and Ni-Co nanocatalysts, Ni-Cr-Co electrocatalysts exhibites more negative onset potential (0.4 V) and high oxidation peak current density (23.8 mA cm −2 ) in alkaline media towards glucose oxidation. Meanwhile, the results also show that the Ni-Cr-Co nanomaterial possesses good performance of anti-poisoning capability, reproducibility and long-time stability, which make it an excellent candidate for fuel cell electrocatalyst.

Dose-equivalent response CR-39 track detector for personnel neutron dosimetry

International Nuclear Information System (INIS)

Oda, K.; Ito, M.; Yoneda, H.; Miyake, H.; Yamamoto, J.; Tsuruta, T.

1991-01-01

A dose-equivalent response detector based on CR-39 has been designed to be applied for personnel neutron dosimetry. The intrinsic detection efficiency of bare CR-39 was first evaluated from irradiation experiments with monoenergetic neutrons and theoretical calculations. In the second step, the radiator effect was investigated for the purpose of sensitization to fast neutrons. A two-layer radiator consisting of deuterized dotriacontane (C 32 D 66 ) and polyethylene (CH 2 ) was designed. Finally, we made the CR-39 detector sensitive to thermal neutrons by doping with orthocarbone (B 10 H 12 C 2 ), and also estimated the contribution of albedo neutrons. It was found that the new detector - boron-doped CR-39 with the two-layer radiator - would have a flat response with an error of about 70% in a wide energy region, ranging from thermal to 15 MeV. (orig.)

Chromium sorption and Cr(VI) reduction to Cr(III) by grape stalks and yohimbe bark.

Science.gov (United States)

Fiol, Núria; Escudero, Carlos; Villaescusa, Isabel

2008-07-01

In this work, two low cost sorbents, grape stalks and yohimbe bark wastes were used to remove Cr(VI) and Cr(III) from aqueous solutions. Batch experiments were designed to obtain Cr(VI) and Cr(III) sorption data. The mechanism of Cr(III) and Cr(VI) removal and Cr(VI) reduction to Cr(III) by the two vegetable wastes, has been investigated. Fourier transform infrared rays (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis on solid phase were performed to determine the main functional groups that might be involved in metal uptake and to confirm the presence of Cr(III) on the sorbent, respectively. Results put into evidence that both sorbents are able to reduce Cr(VI) to its trivalent form.

Microstructure and Mechanical Properties of n-irradiated Fe-Cr Model Alloys

International Nuclear Information System (INIS)

Matijasevic, Milena; Al Mazouzi, Abderrahim

2008-01-01

High chromium ( 9-12 wt %) ferritic/martensitic steels are candidate structural materials for future fusion reactors and other advanced systems such as accelerator driven systems (ADS). Their use for these applications requires a careful assessment of their mechanical stability under high energy neutron irradiation and in aggressive environments. In particular, the Cr concentration has been shown to be a key parameter to be optimized in order to guarantee the best corrosion and swelling resistance, together with the least embrittlement. In this work, the characterization of the neutron irradiated Fe-Cr model alloys with different Cr % with respect to microstructure and mechanical tests will be presented. The behavior of Fe-Cr alloys have been studied using tensile tests at different temperature range ( from -160 deg. C to 300 deg. C). Irradiation-induced microstructure changes have been studied by TEM for two different irradiation doses at 300 deg. C. The density and the size distribution of the defects induced have been determined. The tensile test results indicate that Cr content affects the hardening behavior of Fe-Cr binary alloys. Hardening mechanisms are discussed in terms of Orowan type of approach by correlating TEM data to the measured irradiation hardening. (authors)

2nd Gen FeCrAl ODS Alloy Development For Accident-Tolerant Fuel Cladding

Energy Technology Data Exchange (ETDEWEB)

Dryepondt, Sebastien N. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Massey, Caleb P. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Edmondson, Philip D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2016-08-01

Extensive research at ORNL aims at developing advanced low-Cr high strength FeCrAl alloys for accident tolerant fuel cladding. One task focuses on the fabrication of new low Cr oxide dispersion strengthened (ODS) FeCrAl alloys. The first Fe-12Cr-5Al+Y₂O₃ (+ ZrO₂ or TiO₂) ODS alloys exhibited excellent tensile strength up to 800 C and good oxidation resistance in steam up to 1400 C, but very limited plastic deformation at temperature ranging from room to 800 C. To improve alloy ductility, several fabrication parameters were considered. New Fe-10-12Cr-6Al gas-atomized powders containing 0.15 to 0.5wt% Zr were procured and ball milled for 10h, 20h or 40h with Y2O3. The resulting powder was then extruded at temperature ranging from 900 to 1050 C. Decreasing the ball milling time or increasing the extrusion temperature changed the alloy grain size leading to lower strength but enhanced ductility. Small variations of the Cr, Zr, O and N content did not seem to significantly impact the alloy tensile properties, and, overall, the 2nd gen ODS FeCrAl alloys showed significantly better ductility than the 1st gen alloys. Tube fabrication needed for fuel cladding will require cold or warm working associated with softening heat treatments, work was therefore initiated to assess the effect of these fabrications steps on the alloy microstructure and properties. This report has been submitted as fulfillment of milestone M3FT 16OR020202091 titled, Report on 2nd Gen FeCrAl ODS Alloy Development for the Department of Energy Office of Nuclear Energy, Advanced Fuel Campaign of the Fuel Cycle R&D program.

Ab initio study of Cr interactions with point defects in bcc Fe

International Nuclear Information System (INIS)

Olsson, P.; Domain, Ch.; Wallenius, J.

2008-01-01

Full text of publication follows. Ferritic martensitic steels are candidate structural materials for fast neutron reactors, and in particular high-Cr reduced-activation steels. In Fe-Cr alloys, Cr plays a major role in the radiation-induced evolution of the mechanical properties. Using ab initio calculations based on density functional theory, the properties of Cr in α-Fe have been investigated. The intrinsic point defect formation energies were found to be larger in model bcc Cr as compared to those in ferromagnetic bcc Fe. The interactions of Cr with point defects (vacancy and self interstitials) have been characterised. Single Cr atoms interact weakly with vacancies but significantly with self-interstitial atoms. Mixed interstitials of any interstitial symmetry are bound. Configurations where two Cr atoms are in nearest neighbour position are generally unfavourable in bcc Fe except when they are a part of a interstitial complex. Mixed interstitials do not have as strong directional stability as pure Fe interstitials have. The effects on the results using the atom description scheme of either the ultrasoft pseudo-potential (USPP) or the projector augmented wave (PAW) formalisms are connected to the differences in local magnetic moments that the two methods predict. As expected for the Fe-Cr system, the results obtained using the PAW method are more reliable than the ones obtained with USPP. (authors)

Advances in the development of Cr-39 based neutron dosimeters

International Nuclear Information System (INIS)

Hadlock, D.E.; Parkhurst, M.A.

1987-12-01

A combination thermoluminescent dosimeter (TLD) and track etch dosimeter (TED), which can be used for detecting neutrons over a wide energy range, has been developed through recent research in passive neutron dosimetery. This dosimeter uses Li-600 TLDs to detect thermal and low energy neutrons reflected from the body, and the TED polymer of CR-39, to detect fast neutrons from proton recoil interactions with the polyethylene radiator or with CR-39 itself. Some form of the combination dosimeter is currently in use at several US Department of Energy (DOE) facilities, and its use is expected to expand over the next year to include all DOE facilities where significant neutron exposures may occur. The extensive research conducted on the TED component over the past six years has continually focused on material improvements, reduction in processing time and dosimeter handling, and ease of sample readout with the goal of automating the process as much as possible. 1 fig

Bio-reduction of Cr(VI) by exopolysaccharides (EPS) from indigenous bacterial species of Sukinda chromite mine, India.

Science.gov (United States)

Harish, R; Samuel, Jastin; Mishra, R; Chandrasekaran, N; Mukherjee, A

2012-07-01

Chrome mining activity has contributed intensively towards pollution of hexavalent chromium around Sukinda Valley, Orissa, India. In an attempt to study the specific contribution of exopolysaccharides (EPS) extracted from indigenous isolates towards Cr(VI) reduction, three chromium (VI) tolerant strains were isolated from the effluent mining sludge. Based on the tolerance towards Cr(VI) and EPS production capacity, one of them was selected for further work. The taxonomic identity of the selected strain was confirmed to be Enterobacter cloacae (showing 98% similarity in BLAST search to E. cloacae) through 16S rRNA analysis. The EPS production was observed to increase with increasing Cr(VI) concentration in the growth medium, highest being 0.078 at 100 mg/l Cr(VI). The extracted EPS from Enterobacter cloacae SUKCr1D was able to reduce 31.7% of Cr(VI) at 10 mg/l concentration, which was relevant to the prevailing natural concentrations at Sukinda mine effluent sludge. The FT-IR spectral studies confirmed the surface chemical interactions of hexavalent chromium with EPS.

Suitability of CR-39 dosimeters for personal dosimetry around CANDU reactors

International Nuclear Information System (INIS)

Cross, W.G.

1992-08-01

The capabilities and limitations of CR-39 damage track detectors have been evaluated for their use as personal neutron dosimeters around CANDU reactors. Since the energy response is a critical characteristic, the neutron energy spectra expected within CANDU containments were studied. In the boiler rooms, around the moderator cooling systems, and in most of the fueling machine vaults, the spectra vary considerably, but the majority of the dose is expected to be delivered by neutrons above 80 keV, the approximate threshold for electrochemically-etched CR-39 detectors. In the Pickering A fueling machine vault, and in areas in other stations to which neutrons from reactors have been multiply scattered, lower energy neutrons may be important. In nearly all areas where people work, it appears that working times will be limited by gamma rays rather than by neutrons. The characteristics of other neutron dosimeters - bubble and superheated drop detectors, albedo detectors, and Si real-time detectors - were also reviewed. For workers who typically receive neutron doses that are small compared with regulatory limits, CR-39 is the most suitable available dosimeter for demonstrating compliance. All single dosimeters have poor angular response over the range 0 to 180 degrees because of the shielding of the body. Albedo and Si detectors have particularly poor energy responses over the energy range of importance. Bubble and superheated drop detectors have the advantages of immediate readout and high sensitivity, but the disadvantages of inability to integrate doses over a long period, temperature dependence, very limited range and higher cost. (Author) (110 refs., 45 figs.)

Research of mercury removal from sintering flue gas of iron and steel by the open metal site of Mil-101(Cr).

Science.gov (United States)

Zhao, Songjian; Mei, Jian; Xu, Haomiao; Liu, Wei; Qu, Zan; Cui, Yong; Yan, Naiqiang

2018-06-05

Metal-organic frameworks (MOFs) adsorbent Mil-101(Cr) was introduced for the removal of elemental mercury from sintering flue gas. Physical and chemical characterization of the adsorbents showed that MIL-101(Cr) had the largest BET surface area, high thermal stability and oxidation capacity. Hg 0 removal performance analysis indicated that the Hg 0 removal efficiency of MIL-101(Cr) increased with the increasing temperature and oxygen content. Besides, MIL-101(Cr) had the highest Hg 0 removal performance compared with Cu-BTC, UiO-66 and activated carbon, which can reach about 88% at 250 °C. The XPS and Hg-TPD methods were used to analyze the Hg 0 removal mechanism; the results show that Hg 0 was first adsorbed on the surface of Mil-101(Cr), and then oxidized by the open metal site Cr 3+ . The generated Hg 2+ was then combined surface adsorbed oxygen of adsorbent to form HgO, and the open metal site Cr 2+ was oxidized to Cr 3+ by surface active oxygen again. Furthermore, MIL-101(Cr) had good chemical and thermal stability. Copyright © 2017 Elsevier B.V. All rights reserved.

Correlation of microstructure and fracture toughness of advanced 9Cr/CrMoV dissimilarly welded joint

Energy Technology Data Exchange (ETDEWEB)

Guo, Qian [Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Lu, Fenggui, E-mail: Lfg119@sjtu.edu.cn [Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Liu, Xia [Shanghai Turbine Plant of Shanghai Electric Power Generation Equipment Co. Ltd., Shanghai 200240 (China); Yang, Renjie [Shanghai Turbine Works Company, Shanghai 200240 (China); Cui, Haichao [Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Gao, Yulai, E-mail: ylgao@shu.edu.cn [State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai 200072 (China)

2015-06-25

In this paper, the fracture toughness and the related microstructure characteristics of dissimilarly welded joint manufactured by advanced 9Cr and CrMoV steels were systematically investigated. The dissimilarly welded joint was fabricated by narrow gap submerged arc welding (NG-SAW) applying multi-layer and multi-pass technique. Fracture toughness, as one of the most important property to assess the reliability of welded joint, was studied for different regions including CrMoV base metal (CrMoV-BM), heat affected zone (HAZ) of CrMoV side (CrMoV-HAZ), weld metal (WM), heat affected zone of 9Cr side (9Cr-HAZ) and 9Cr base metal (9Cr-BM). It was found that the fracture toughness of CrMoV-BM, CrMoV-HAZ and WM was better than that of 9Cr-HAZ and 9Cr-BM. In order to illustrate these results, the microstructure of the whole welded joint was observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM) detailedly. It was found that the fine high-temperature tempered martensite and bainite in WM, CrMoV-BM and CrMoV-HAZ contribute to the higher fracture toughness, while lower fracture toughness for 9Cr-BM and HAZ was caused by coarse tempered lath-martensite. Furthermore, the fracture morphology showed that ductile fracture occurred in WM and CrMoV side, while brittle fracture appeared in BM and HAZ of 9Cr side.

Irradiation of Wrought FeCrAl Tubes in the High Flux Isotope Reactor

Energy Technology Data Exchange (ETDEWEB)

Linton, Kory D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Field, Kevin G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Petrie, Christian M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-09-01

The Advanced Fuels Campaign within the Nuclear Technology Research and Development program of the Department of Energy Office of Nuclear Energy is seeking to improve the accident tolerance of light water reactors. Alumina-forming ferritic alloys (e.g., FeCrAl) are one of the leading candidate materials for fuel cladding to replace traditional zirconium alloys because of the superior oxidation resistance of FeCrAl. However, there are still some unresolved questions regarding irradiation effects on the microstructure and mechanical properties of FeCrAl at end-of-life dose levels. In particular, there are concerns related to irradiation-induced embrittlement of FeCrAl alloys due to secondary phase formation. To address this issue, Oak Ridge National Laboratory has developed a new experimental design to irradiate shortened cladding tube specimens with representative 17×17 array pressurized water reactor diameter and thickness in the High Flux Isotope Reactor (HFIR) under relevant temperatures (300–350°C). Post-irradiation examination will include studies of dimensional change, microstructural changes, and mechanical performance. This report briefly summarizes the capsule design concept and the irradiation test matrix for six rabbit capsules. Each rabbit contains two FeCrAl alloy tube specimens. The specimens include Generation I and Generation II FeCrAl alloys with varying processing conditions, Cr concentrations, and minor alloying elements. The rabbits were successfully assembled, welded, evaluated, and delivered to the HFIR along with a complete quality assurance fabrication package. Pictures of the rabbit assembly process and detailed dimensional inspection of select specimens are included in this report. The rabbits were inserted into HFIR starting in cycle 472 (May 2017).

Low-field spin dynamics of Cr7Ni and Cr7Ni-Cu -Cr 7Ni molecular rings as detected by μ SR

Science.gov (United States)

Sanna, S.; Arosio, P.; Bordonali, L.; Adelnia, F.; Mariani, M.; Garlatti, E.; Baines, C.; Amato, A.; Sabareesh, K. P. V.; Timco, G.; Winpenny, R. E. P.; Blundell, S. J.; Lascialfari, A.

2017-11-01

Muon spin rotation measurements were used to investigate the spin dynamics of heterometallic Cr7Ni and Cr7Ni -Cu-Cr7Ni molecular clusters. In Cr7Ni the magnetic ions are arranged in a quasiplanar ring and interact via an antiferromagnetic exchange coupling constant J , while Cr7Ni -Cu-Cr7Ni is composed of two Cr7Ni linked by a bridging moiety containing one Cu ion, that induces an inter-ring ferromagnetic interaction J'≪J . The longitudinal muon relaxation rate λ collected at low magnetic fields μ0H BPP)-like heuristic fitting model that takes into account of a distribution of electronic spin characteristic times for T >5 K, while the shoulder presented by Cr7Ni can be reproduced by a BPP function that incorporates a single electronic characteristic time theoretically predicted to dominate for T <5 K. The flattening of λ (T ) in Cr7Ni -Cu-Cr7Ni occurring at very low temperature can be tentatively attributed to field-dependent quantum effects and/or to an inelastic term in the spectral density of the electronic spin fluctuations.

Adsorption and diffusion of fluorine on Cr-doped Ni(111) surface: Fluorine-induced initial corrosion of non-passivated Ni-based alloy

Energy Technology Data Exchange (ETDEWEB)

Ren, Cui-Lan, E-mail: rencuilan@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai 201800 (China); Han, Han [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Gong, Wen-Bin [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Shanghai 215123 (China); Wang, Cheng-Bin; Zhang, Wei [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai 201800 (China); Cheng, Cheng [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Huai, Ping, E-mail: huaiping@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Zhu, Zhi-Yuan [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai 201800 (China)

2016-09-15

Adsorption and diffusion behaviors of fluorine on Cr-doped Ni(111) surface are investigated by using first-principles simulation. It shows that the Cr in the Cr-doped Ni(111) surface serve a trap site for fluorine with adsorption energy 3.52 eV, which is 1.04 eV higher than that on Ni(111) surface. Moreover, the Cr atom is pulled out the surface for 0.41 Å after the fluorine adsorption, much higher than that on Ni(111) surface. Further diffusion behaviors analysis confirms the conclusion because the fluorine diffusion from neighbored sites onto the Cr top site is an energy barrierless process. Detailed electronic structure analysis shows that a deeper hybrid state of F 2 p-Cr 3 d indicates a strong F−Cr interaction. The Ni−Cr bond is elongated and weakened due to the new formed F−Cr bonding. Our results help to understanding the basic fluorine-induced initial corrosion mechanism for Ni-based alloy in molten salt environment.

/sup 51/Cr-bleomycin, a new oncophilic radiopharmaceutical. Pt. 1

Energy Technology Data Exchange (ETDEWEB)

Rembelska, M J; Liniecki, J

1982-04-01

A method was developed for labelling bleomycin with /sup 51/Cr. The complex was administered to mice (Swiss and C57-B1/6) bearing 5 transplantable tumours: Ehrlich ascites tumour, NK/Ly lymphoma, Lewis lung carcinoma, melanoma B-16, and Sarcoma 180. Activity concentration in neoplasms, blood and numerous organs was determined 12, 24 and 48 hrs after injection. An identical procedure was applied using /sup 58/Co-bleomycin as a reference oncophilic substance. Tumour/non-tumor ratios exceeding substantially unity were found for blood, muscle and bone indicating preferential accumulation of both /sup 58/Co and /sup 51/Cr in all the neoplasms tested. The ratios were lower (by a factor 2-3) for /sup 51/Cr than for /sup 58/Co; however, it is postulated that the gamma-quantum energy of /sup 51/Cr which is higher than that of the commonly used /sup 57/Co, should offset to some degree this difference when scintigraphic tumour detection in a patient is to be attempted. In conclusion, clinical trials with /sup 51/Cr-bleomycin, which is cheaper than its /sup 57/Co-counterpart, appear warranted.

The complementary relationship (CR) approach aids evapotranspiration estimation in the data scarce region of Tibetan Plateau: symmetric and asymmetric perspectives

Science.gov (United States)

Ma, N.; Zhang, Y.; Szilagyi, J.; Xu, C. Y.

2015-12-01

While the land surface latent and sensible heat release in the Tibetan Plateau (TP) could greatly influence the Asian monsoon circulation, the actual evapotranspiration (ETa) information in the TP has been largely hindered by its extremely sparse ground observation network. Thus the complementary relationship (CR) theory lends great potential in estimating the ETa since it relies on solely routine meteorological observations. With the in-situ energy/water flux observation over the highest semiarid alpine steppe in the TP, the modifications of specific components within the CR were first implemented. We found that the symmetry of the CR could be achieved for dry regions of TP when (i) the Priestley-Taylor coefficient, (ii) the slope of the saturation vapor pressure curve and (iii) the wind function were locally calibrated by using the ETa observations in wet days, an estimate of the wet surface temperature and the Monin-Obukhov Similarity (MOS) theory, respectively. In this way, the error of the simulated ETa by the symmetric AA model could be decreased to a large extent. Besides, the asymmetric CR was confirmed in TP when the D20 above-ground and/or E601B sunken pan evaporation (Epan) were used as a proxy of the ETp. Thus daily ETa could also be estimated by coupling D20 above-ground and/or E601B sunken pans through CR. Additionally, to overcome the modification of the specific components in the CR, we also evaluated the Nonlinear-CR model and the Morton's CRAE model. The former does not need the pre-determination of the asymmetry of CR, while the latter does not require the wind speed data as input. We found that both models are also able to simulate the daily ETa well provided their parameter values have been locally calibrated. The sensitivity analysis shows that, if the measured ETa data are absence to calibrate the models' parameter values, the Nonlinear-CR model may be a particularly good way for estimating ETabecause of its mild sensitivity to the parameter

Cr(III) and Cr(VI) in leather and elicitation of eczema

DEFF Research Database (Denmark)

Hansen, Malene Barré; Menne, Torkil; Johansen, Jeanne Duus

2006-01-01

The aim of the present study was to investigate the relation between the content of Cr(VI) and soluble Cr(III) in leather and the ability of the leather to elicit eczema in chromium allergic patients. An array of chromium-tanned leather samples was analysed for the content of total Cr(VI) and sol...

Short-period oscillations in photoemission from thin films of Cr(100)

Science.gov (United States)

Vyalikh, Denis V.; Zahn, Peter; Richter, Manuel; Dedkov, Yu. S.; Molodtsov, S. L.

2005-07-01

Angle-resolved photoemission (PE) study of thin films of Cr grown on Fe(100) reveals thickness-dependent short-period oscillations of the PE intensity close to the Fermi energy at k‖˜0 . The oscillations are assigned to quantum-well states (QWS) caused by the nesting between the Fermi-surface sheets around the Γ and the X points in the Brillouin zone of antiferromagnetic Cr. The experimental data are confirmed by density-functional calculations applying a screened Korringa-Kohn-Rostoker Green’s function method. The period of the experimentally observed QWS oscillations amounts to about 2.6 monolayers and is larger than the fundamental 2-monolayer period of antiferromagnetic coupling in Cr.

Effect of Ti/Cr additive on helium diffusion and segregation in dilute vanadium alloys

Energy Technology Data Exchange (ETDEWEB)

Zou, Tingting [Information Science and Technology College, Dalian Maritime University, Dalian 116026 (China); Zhang, Pengbo, E-mail: zhangpb@dlmu.edu.cn [Department of Physics, Dalian Maritime University, Dalian 116026 (China); Zhao, Jijun [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024 (China); Zheng, Pengfei; Chen, Jiming [Southwestern Institute of Physics, Chengdu 610041 (China)

2017-02-15

Highlights: • He prefers to segregate to Ti region rather than Cr region in the vanadium alloys. • He diffusion barrier decreases towards Ti while it increases towards Cr. • The He{sub n}Ti complexes are more stable than the He{sub n}Cr complexes energetically. - Abstract: The effect of Ti/Cr additive on He diffusion and segregation properties in dilute vanadium alloys is investigated using first-principles calculations. First we determined the He preference site and investigated the He-Cr/He-Ti interactions. Energetically, He prefers to segregate to Ti regions rather than Cr regions. The most stable site for interstitial He is a tetrahedral site near Ti. He-Ti interactions have a weak attraction while He-Cr interactions have a weak repulsion. Kinetically, He diffusion to Ti has a lower energy barrier; contrarily the He barrier increases towards Cr. Furthermore, we discuss the stability of He{sub n}-Cr/Ti complexes and He{sub n}-vacancy-Cr and Ti complexes with n = 1–8. It is found that the He{sub n}Ti complexes are more stable than the He{sub n}Cr complexes while the He{sub n}-vacancy-Ti complexes are less favorable than He{sub n}-vacancy-Cr. The findings give a reference for understanding the mechanism of He embrittlement under irradiation.

Microstructures Evolution and Micromechanics Features of Ni-Cr-Si Coatings Deposited on Copper by Laser Cladding

Directory of Open Access Journals (Sweden)

Peilei Zhang

2018-05-01

Full Text Available Three Ni-Cr-Si coatings were synthesized on the surface of copper by laser cladding. The microstructures of the coatings were characterized by optical microscopy (OM, X-ray diffraction (XRD, and scanning electron microscopy (SEM with an energy dispersive spectrometer (EDS. According to the analysis results of phase compositions, Gibbs free energy change and microstructures, the phases of three coatings appeared were Cr3Si+γ-Ni+Cuss (Coating 1, Ni-26Cr-29Si, Cr6Ni16Si7+Ni2Si+Cuss (Coating 2, Ni-10Cr-30Si and Cr3Ni5Si2+Cr2Ni3+Cuss (Coating 3, Ni-29Cr-16Si. The crystal growth in the solidification process was analyzed with a modified model, which is a combination of Kurz-Giovanola-Trivedi (KGT and Lipton-Kurz-Trivedi (LKT models. The dendrite tip undercooling in Coating 2 was higher than those of Coating 1 and Coating 3. Well-developed dendrites were found in Coating 2. A modification of Hunt’s model was adopted to describe the morphological differences in the three coatings. The results show that Coating 1 was in the equiaxed dendrite region, while Coatings 2 and 3 were in the columnar dendrite region. The average friction coefficients of the three coatings were 0.45, 0.5 and 0.4, respectively. Obvious plastic deformation could be found in the subsurface zone of Coatings 2 and 3.

Cr-substitution effect on structural, optical and electrical properties of Cr{sub x}Ce{sub 1−x}PO{sub 4} (x = 0.00, 0.08, 0.10 and 0.20) nanorods

Energy Technology Data Exchange (ETDEWEB)

Fadhalaoui, Amor [Laboratoire de Chimie des Matériaux, Faculté des Sciences de Bizerte, Zarzouna, Bizerte 7021 (Tunisia); Dhaouadi, Hassouna, E-mail: dhaouadihassouna@yahoo.fr [Laboratoire Matériaux Traitement et Analyse, INRAP, Technopôle Sidi-Thabet, Tunis 2020 (Tunisia); Marouani, Houda [Laboratoire de Chimie des Matériaux, Faculté des Sciences de Bizerte, Zarzouna, Bizerte 7021 (Tunisia); Kouki, Abdessalem [L3M, FSB, Zarzouna, Bizerte 7021 (Tunisia); Madani, Adel [Department of Physics, Applied Science College, Umm Al Qura University, Makkah (Saudi Arabia); Rzaigui, Mohamed [Laboratoire de Chimie des Matériaux, Faculté des Sciences de Bizerte, Zarzouna, Bizerte 7021 (Tunisia)

2016-01-15

Graphical abstract: The Cr{sub x}Ce{sub 1−x}PO{sub 4} (x = 0.00, 0.08, 0.10 and 0.20) nanorods synthesized under hydrothermal conditions. - Highlights: • Cr{sub x}Ce{sub 1−x}PO{sub 4} (x = 0.00–0.20) nanorods were synthesized by hydrothermal method. • Mean crystallite size of the products decreases with Cr-content. • Obvious improvements of the electrical conductivity comparatively to CePO4. - Abstract: Cr{sub x}Ce{sub 1−x}PO{sub 4} (x = 0.00–0.20) nanorods were synthesized using the hydrothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), infrared absorption spectroscopy (IR) and transmission electron microscopy (TEM). The XRD results revealed the formation of a pure CePO{sub 4} hexagonal phase. TEM images confirmed the nano-size character of the as-prepared samples. Impedance spectroscopy analysis was used to analyze the electrical behavior of samples as a function of frequency at different temperatures. The increase of Cr-amount led to an increase in the total conductivities and decreased the activation energies (E{sub a} (x = 0.00) = 1.08 eV to E{sub a} (x = 0.20) = 0.80 eV). The optical properties of Cr{sub x}Ce{sub 1−x}PO{sub 4} nanomaterials were investigated using UV–vis spectroscopy. The band-gap energy values decreased with increasing Cr-content showing a red-shift trend. The improvement of the electrical conductivity and optical properties makes the Cr{sub x}Ce{sub 1−x}PO{sub 4} nanomaterials possible candidates to be used as electrolytes in solid oxide fuel cells, in photocatalytic and photovoltaic applications.

Heavy doping of CdTe single crystals by Cr ion implantation

Science.gov (United States)

Popovych, Volodymyr D.; Böttger, Roman; Heller, Rene; Zhou, Shengqiang; Bester, Mariusz; Cieniek, Bogumil; Mroczka, Robert; Lopucki, Rafal; Sagan, Piotr; Kuzma, Marian

2018-03-01

Implantation of bulk CdTe single crystals with high fluences of 500 keV Cr+ ions was performed to achieve Cr concentration above the equilibrium solubility limit of this element in CdTe lattice. The structure and composition of the implanted samples were studied using secondary ion mass spectrometry (SIMS), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS) to characterize the incorporation of chromium into the host lattice and to investigate irradiation-induced damage build-up. It was found that out-diffusion of Cr atoms and sputtering of the targets alter the depth distribution and limit concentration of the projectile ions in the as-implanted samples. Appearance of crystallographically oriented, metallic α-Cr nanoparticles inside CdTe matrix was found after implantation, as well as a strong disorder at the depth far beyond the projected range of the implanted ions.

Electronic structure and magnetic ordering of the semiconducting chromium trihalides CrCl3, CrBr3, and CrI3

KAUST Repository

Wang, Hao; Eyert, Volker; Schwingenschlö gl, Udo

2011-01-01

for CrBr3 as well as CrI3. The antiferromagnetic state of CrCl3 can be reproduced by introducing an on-site electron-electron repulsion. However, we observe that the ground state depends critically on the specific approach used. Our results show that a

Mathematical models applied to the Cr(III) and Cr(VI) breakthrough curves.

Science.gov (United States)

Ramirez C, Margarita; Pereira da Silva, Mônica; Ferreira L, Selma G; Vasco E, Oscar

2007-07-19

Trivalent and hexavalent chromium continuous biosorption was studied using residual brewer Saccharomyces cerevisiae immobilized in volcanic rock. The columns used in the process had a diameter of 4.5 cm and a length of 140 cm, working at an inlet flow rate of 15 mL/min. Breakthrough curves were used to study the yeast biosorption behavior in the process. The saturation time (ts) was 21 and 45 h for Cr(III) and Cr(VI), respectively, and a breakthrough time (tb) of 4 h for Cr(III) and 5 h for Cr(VI). The uptake capacity of the biosorbent for Cr(III) and Cr(VI) were 48 and 60 mg/g, respectively. Two non-diffusional mathematical models with parameters t0 and sigma were used to adjust the experimental data obtained. Microsoft Excel tools were used for the mathematical solution of the two parameters used.

The lattice distortion effect for zinc-blende CrAs and CrSb

International Nuclear Information System (INIS)

Yamana, Keita; Geshi, Masaaki; Tsukamoto, Hidekazu; Uchida, Ichiro; Shirai, Masafumi; Kusakabe, Koichi; Suzuki, Naoshi

2004-01-01

We investigated the stability of the ferromagnetism of CrAs and CrSb in the zinc-blende structure against the lattice distortion, systematically. A calculation within the generalized gradient approximation using a full potential linearized augmented plane wave method was performed. We compared the ferromagnetic state and the antiferromagnetic state assuming tetragonal distortion with the lattice constants a and c changing independently and determined the spin polarization ratio in the ferromagnetic phase. The result shows that complete spin polarization (half-metallic ferromagnetism) remains stable even in the presence of large tetragonal distortion. On the other hand, our calculation shows that two monolayers of CrAs is enough to produce a half-metallic state in the CrAs/GaAs multilayer. Thus, the present result suggests that the half-metallic nature persists in various atomic-scale superlattices made of distorted CrAs or CrSb

Selective Oxidation of Glycerol with 3% H2O2 Catalyzed by LDH-Hosted Cr(III Complex

Directory of Open Access Journals (Sweden)

Gongde Wu

2015-11-01

Full Text Available A series of layered double hydroxides (LDHs –hosted sulphonato-salen Cr(III complexes were prepared and characterized by various physico-chemical measurements, such as Fourier transform infrared spectroscopy (FTIR, ultraviolet-visible spectroscopy (UV-Vis, powder X-ray diffraction (XRD, transmission electron microscope (TEM, scanning electron microscope (SEM and elemental analysis. Additionally, their catalytic performances were investigated in the selective oxidation of glycerol (GLY using 3% H2O2 as an oxidant. It was found that all the LDH-hosted Cr(III complexes exhibited significantly enhanced catalytic performance compared to the homogeneous Cr(III complex. Additionally, it was worth mentioning that the metal composition of LDH plates played an important role in the catalytic performances of LDH-hosted Cr(III complex catalysts. Under the optimal reaction conditions, the highest GLY conversion reached 85.5% with 59.3% of the selectivity to 1,3-dihydroxyacetone (DHA. In addition, the catalytic activity remained after being recycled five times.

Use of CR-39 foils for personnel neutron dosimetry: improved electrochemical etching chambers and procedures

International Nuclear Information System (INIS)

Hankins, D.E.; Homann, S.G.; Westermark, J.

1986-01-01

The electrochemical etching procedures for the new dosimetry system that uses foils of CR-39 plastic has been improved. During 1985, the etching chambers were modified to correct several problems and the changes to the etching procedures were studied, which gave a more uniform track density and size. The currently recommended etch parameters are given. A new generation of CR-39 material from the manufacturer proved to have a considerably lower background track density and a higher sensitivity; the new foils are also more uniform in thickness, which eliminates the need to numerically compensate for thickness variations. The energy dependence of the CR-39 using monoenergetic neutrons from accelerators at Battelle Northwest Laboratories and at Los Alamos National Laboratory was determined. Some variation was found in the energy dependence, but it is believed this was caused by changes in the etching procedures and by uncertainties in the fluences of the neutrons from the accelerators. A means by which the counting of CR-39 tracks may be automated is suggested; this would be very useful in adapting the CR-39 dosimetry system to large-scale use

Calculations of the electronic levels, spin-Hamiltonian parameters and vibrational spectra for the CrCl{sub 3} layered crystals

Energy Technology Data Exchange (ETDEWEB)

Avram, C.N. [Faculty of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania); Gruia, A.S., E-mail: adigruia@yahoo.com [Faculty of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania); Brik, M.G. [College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); Institute of Physics, University of Tartu, Ravila 14C, Tartu 50411 (Estonia); Institute of Physics, Jan Dlugosz University, Armii Krajowej 13/15, PL-42200 Czestochowa (Poland); Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Barb, A.M. [Faculty of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania)

2015-12-01

Calculations of the Cr{sup 3+} energy levels, spin-Hamiltonian parameters and vibrational spectra for the layered CrCl{sub 3} crystals are reported for the first time. The crystal field parameters and the energy level scheme were calculated in the framework of the Exchange Charge Model of crystal field. The spin-Hamiltonian parameters (zero-field splitting parameter D and g-factors) for Cr{sup 3+} ion in CrCl{sub 3} crystals were obtained using two independent techniques: i) semi-empirical crystal field theory and ii) density functional theory (DFT)-based model. In the first approach, the spin-Hamiltonian parameters were calculated from the perturbation theory method and the complete diagonalization (of energy matrix) method. The infrared (IR) and Raman frequencies were calculated for both experimental and fully optimized geometry of the crystal structure, using CRYSTAL09 software. The obtained results are discussed and compared with the experimental available data.

Response of CR-39 based personnel neutron dosemeter in terms of directional dose equivalent, in free air and on phantom

International Nuclear Information System (INIS)

Pal, Rupali R.; Sathian, Deepa; Jayalakshmi, V.; Chougaonkar, M.P.

2011-01-01

CR-39 is the most sensitive of nuclear track detectors for protons and is recommended as an effective neutron dosimeter because of it's low threshold energy of 100 keV neutrons. The fraction of protons that gives detectable tracks in CR-39 depends on the energy of the proton angle of incidence and etching conditions. As a consequence the registration efficiency of neutrons in the CR-39 plastics used for neutron personnel monitoring is strongly influenced by the direction of radiation incidence. This paper presents the relative response of CR-39 at varying neutron incident angles, for 241 Am-Be neutron source spectra in free air and on ISO phantom, in terms of operational quantities. It is observed that the angular dependence of CR-39 for irradiations in air and on phantom is essentially the same indicating that the phantom does not affect the directional response of CR-39. (author)

Modeling of Cr contamination in the agricultural lands of three villages near the leather industry in Kasur, Pakistan, using statistical and GIS techniques.

Science.gov (United States)

Shafiq, Muhammad; Shaukat, Tahira; Nazir, Aisha; Bareen, Firdaus-E-

2017-08-01

Kasur is one of the hubs of leather industry in the Punjab, Pakistan, where chrome tanning method of leather processing is extensively being used. Chromium (Cr) accumulation levels in the irrigation water, soil, and seasonal vegetables were studied in three villages located in the vicinity of wastewater treatment plant and solid waste dumping site operated by the Kasur Tanneries Waste Management Agency (KTWMA). The data was interpreted using analysis of variance (ANOVA), clustering analysis (CA), and principal component analysis (PCA). Interpolated surface maps for Cr were generated using the actual data obtained for the 30 sampling sites in each of the three villages for irrigation water, soil, and seasonal vegetables. The level of contamination in the three villages was directly proportional to their distance from KTWMA wastewater treatment plant and the direction of water runoff. The highest level of Cr contamination in soil (mg kg -1 ) was observed at Faqeeria Wala (37.67), intermediate at Dollay Wala (30.33), and the least in Maan (25.16). A gradational variation in Cr accumulation was observed in the three villages from contaminated wastewater having the least contamination level (2.02-4.40 mg L -1 ), to soil (25.16-37.67 mg kg -1 ), and ultimately in the seasonal vegetable crops (156.67-248.33 mg kg -1 ) cultivated in the region, having the highest level of Cr contamination above the permissible limit. The model used not only predicted the current situation of Cr contamination in the three villages but also indicated the trend of magnification of Cr contamination from irrigation water to soil and to the base of the food chain. Among the multiple causes of Cr contamination of vegetables, soil irrigation with contaminated groundwater was observed to be the dominant one.

Search for ultra-high energy photons with AMIGA muon counters

Energy Technology Data Exchange (ETDEWEB)

Gonzalez, Nicolas Martin [Instituto de Tecnologias en Deteccion y Astroparticulas, Buenos Aires (Argentina); Institut fuer Kernphysik, Karlsruher Institut fuer Technologie. (Germany); Collaboration: Pierre-Auger-Collaboration

2016-07-01

The study of the composition of ultra-high energy (UHE) cosmic rays (CR) is one of the topical problems of astroparticle physics. The discovery of UHE photons, i.e. photons with energies around 1 EeV, in primary cosmic rays could be of particular interest for the field of astroparticle physics, and also for fundamental physics, since they are tracers of the highest-energy processes in the Universe. For the search for UHE photons at the Pierre Auger Observatory (PAO), several parameters have been proposed to distinguish between primary hadrons and photons. One of the most promising approaches to search for primary gamma rays is the study of the muon component in extensive air showers (EAS) produced in the interaction between the CR and the nuclei in the atmosphere. The number of muons in showers induced by gamma primaries is an order of magnitude lower than the hadronic primaries counterpart. The AMIGA extension of the PAO, consisting of an array of buried scintillators counters, allows the study of the muons produced during the EAS development. In this talk, the sensitivity of the muon counters to photon-initiated EAS and the possible discrimination procedures are discussed using dedicated EAS simulations with software package CORSIKA, including the detector response using the Offline package developed by the Pierre Auger Collaboration.

Proton Radiography with CR-39 by Using the Protons from High Power Femto-second Laser System

International Nuclear Information System (INIS)

Choi, Chang Il; Lee, Dong Hoon; Kang, Byoung Hwi; Kim, Yong Kyun; Choi, Il Woo; Ko, Do Kyeong; Lee, Jong Min

2008-01-01

Proton radiography techniques are useful to obtain a high quality image of a thin object, because protons travel straight in matter. Generation of the high energy proton using conventional accelerator costs high and requires large accelerating facility. But proton radiography using high power femto-second(10-15 second) laser has been interested, because it can generate high energy protons at lower price than the conventional accelerator like a cyclotron. For this study, we used the CR-39 SSNTD (Solid State Nuclear Track Detector) as the proton radiography screen. Commonly, CR-39 is used to detect the tracks of energetic charged particles. Incident energetic charged particles left latent tracks in the CR-39, in the form of broken molecular chains and free radicals. These latent tracks show high chemical reactivity. After chemical etching with the caustic alkali solution such as NaOH or KOH, tracks are appeared to forms of hole. If protons with various energies enter the two targets with another thickness, number of protons passed through the target per unit area is different each other. Using this feature of protons, we can a proton radiographic image with CR-39. We studied proton radiography with CR-39 by using energetic protons from high power femto-second laser and evaluated potentiality of femto-second laser as new energetic proton generator for radiography

Migration mechanisms of self-interstitial atoms and their clusters in Fe-Cr alloys

International Nuclear Information System (INIS)

Terentyev, D.; Malerba, L.

2006-06-01

The mobility of self-interstitial atoms (SIAs) and their clusters in pure iron and iron-chromium alloys was studied by atomic scale modelling techniques. Molecular dynamics (MD) was used to simulate thermally activated motion, i.e. diffusion, and its mechanisms whereas molecular statics was used to estimate energies of interactions of SIA and SIA clusters with Cr-impurities. It is shown that the presence of Cr atoms reduces the diffusivity of SIAs and their clusters in a non monotonic way with increasing Cr concentration. The main reason for this reduction is the presence of a long-range attractive interaction between self-interstitials in the crowdion configuration and Cr atoms. The migration mechanisms behind this effect are discussed relying on the results obtained from the MD simulations. (author)

Comparison of Model Systems (M+n·[CrX63−] and M3CrX6 + 18MX Based on Quantum-Chemical Calculations (X: F, Cl

Directory of Open Access Journals (Sweden)

Vyacheslav Kremenetsky

2016-01-01

Full Text Available On the basis of quantum-chemical calculations the most stable particle compositions are estimated in such model systems as (M+n·[CrCl6] and M3CrCl6 + 18MCl (M = Na, K, and Cs. In all systems these particles are positively charged. For systems (M+n·[CrCl6], (M+n·[CrF6], M3CrF6 + 18MCl, M3CrF6 + 18MF, and M3CrCl6 + 18MCl (M = Na, K, and Cs a number of energy parameters characterizing the state of the system before and after electron transfer are calculated. The results indicate the possibility of electron transfer from the cathode to the melt system, which is in the initial state. However, this possibility cannot be realized in systems where LUMOs (lowest unoccupied molecular orbitals have purely ligand character. In this case, the preliminary deformation of a cationic shell of electroactive species is required; it transforms the initial system to the transition state. However, in all considered systems the search of the transition state should be carried close to the initial state Pi. This greatly simplifies a problem and transforms it from a purely theoretical sphere to the field of practical tasks that do not require exceptional cost of computer time.

Bioaccumulation and subcellular partitioning of Cr(III) and Cr(VI) in the freshwater green alga Chlamydomonas reinhardtii

Energy Technology Data Exchange (ETDEWEB)

Aharchaou, Imad [Laboratoire Interdisciplinaire des Environnements Continentaux, UMR 7360, Université de Lorraine and CNRS, 8 rue du Général Delestraint, 57070 Metz (France); Rosabal, Maikel; Liu, Fengjie [Institut National de la Recherche Scientifique, Centre Eau Terre Environnement (INRS-ETE), 490 rue de la Couronne, Québec (Québec) G1K 9A9 (Canada); Battaglia, Eric; Vignati, Davide A.L. [Laboratoire Interdisciplinaire des Environnements Continentaux, UMR 7360, Université de Lorraine and CNRS, 8 rue du Général Delestraint, 57070 Metz (France); Fortin, Claude, E-mail: claude.fortin@ete.inrs.ca [Institut National de la Recherche Scientifique, Centre Eau Terre Environnement (INRS-ETE), 490 rue de la Couronne, Québec (Québec) G1K 9A9 (Canada)

2017-01-15

Highlights: • C. reinhardtii accumulated similar levels of Cr(III) and Cr(VI). • The subcellular partitioning of Cr(III) and Cr(VI) was similar. • Cr(III) and Cr(VI) associated mainly with organelles and heat-stable proteins. • Metallomic analysis showed two main Cr-binding biomolecules after 72 h of exposure. - Abstract: Chromium occurs in aquatic environments under two main redox forms, namely Cr(III) and Cr(VI), with different geochemical and biochemical properties. Cr(VI) readily crosses biological membranes of living organisms and once inside the cells it undergoes a rapid reduction to Cr(III). The route of entry for the latter form is, however, poorly known. Using the radioactive tracer {sup 51}Cr we compared the accumulation (absorption and adsorption) of the two Cr forms by the green unicellular alga Chlamydomonas reinhardii after 1 h and 72 h of exposure to 100 nM of either Cr(III) or Cr(VI) at pH 7. Both Cr forms had similar accumulation, with a major part in the extracellular (adsorbed) fraction after 1 h and a major part of total accumulated Cr in the intracellular (absorbed) fraction after 72 h. We also investigated the intracellular partitioning of Cr using an operational fractionation scheme and found that both Cr forms had similar distributions among fractions: Cr was mostly associated with organelles (23 ± 12% after 1 h and 37 ± 7% after 72 h) and cytosolic heat-stable proteins and peptides (39 ± 18% after 1 h and 35 ± 3% after 72 h) fractions. Further investigations using a metallomic approach (SEC-ICP-MS) were performed with the heat-stable proteins and peptides fraction to compare the distribution of the two Cr forms among various biomolecules of this fraction. One Cr-binding biomolecule (∼28 kDa) appeared after 1 h of exposure for both Cr species. After 72 h another biomolecule of lower molecular weight (∼0.7 kDa) was involved in binding Cr and higher signal intensities were observed for Cr(VI) than for Cr(III). We show, for the

Bioaccumulation and subcellular partitioning of Cr(III) and Cr(VI) in the freshwater green alga Chlamydomonas reinhardtii

International Nuclear Information System (INIS)

Aharchaou, Imad; Rosabal, Maikel; Liu, Fengjie; Battaglia, Eric; Vignati, Davide A.L.; Fortin, Claude

2017-01-01

Highlights: • C. reinhardtii accumulated similar levels of Cr(III) and Cr(VI). • The subcellular partitioning of Cr(III) and Cr(VI) was similar. • Cr(III) and Cr(VI) associated mainly with organelles and heat-stable proteins. • Metallomic analysis showed two main Cr-binding biomolecules after 72 h of exposure. - Abstract: Chromium occurs in aquatic environments under two main redox forms, namely Cr(III) and Cr(VI), with different geochemical and biochemical properties. Cr(VI) readily crosses biological membranes of living organisms and once inside the cells it undergoes a rapid reduction to Cr(III). The route of entry for the latter form is, however, poorly known. Using the radioactive tracer "5"1Cr we compared the accumulation (absorption and adsorption) of the two Cr forms by the green unicellular alga Chlamydomonas reinhardii after 1 h and 72 h of exposure to 100 nM of either Cr(III) or Cr(VI) at pH 7. Both Cr forms had similar accumulation, with a major part in the extracellular (adsorbed) fraction after 1 h and a major part of total accumulated Cr in the intracellular (absorbed) fraction after 72 h. We also investigated the intracellular partitioning of Cr using an operational fractionation scheme and found that both Cr forms had similar distributions among fractions: Cr was mostly associated with organelles (23 ± 12% after 1 h and 37 ± 7% after 72 h) and cytosolic heat-stable proteins and peptides (39 ± 18% after 1 h and 35 ± 3% after 72 h) fractions. Further investigations using a metallomic approach (SEC-ICP-MS) were performed with the heat-stable proteins and peptides fraction to compare the distribution of the two Cr forms among various biomolecules of this fraction. One Cr-binding biomolecule (∼28 kDa) appeared after 1 h of exposure for both Cr species. After 72 h another biomolecule of lower molecular weight (∼0.7 kDa) was involved in binding Cr and higher signal intensities were observed for Cr(VI) than for Cr(III). We show, for the

The stored energy in processed Cu-0.4 wt.%Cr-0.12 wt.%Zr-0.02 wt.%Si-0.05 wt.%Mg

International Nuclear Information System (INIS)

Li, X.F.; Dong, A.P.; Wang, L.T.; Yu, Z.; Meng, L.

2011-01-01

Research highlights: → The crystal orientation in processed Cu-0.4 wt.%Cr-0.12 wt.%Zr-0.02 wt.%Si-0.05 wt.%Mg is deviating from the as-cast specimens and microstrain of the alloy is gradually increasing as the draw ratio rising before η ≤ 6.7. → The dynamic recovery has taken place as 6.7 texture is formed with the draw ratio rising. Meanwhile, the stored energy also increases with the draw ratio rising and a peak is reached with draw ratio of 6.7. The release of stored energy is primarily due to the decrease of dislocation density. The flow stress estimated from the stored energy has a similar variation trend with the measured data with a stress difference ∼20 to 120 MPa. The main strengthening effect is attributed to dislocation mechanism.

Chromium Fractions Changes Compared With Total-Cr As Determined by Neutron Activation Analysis Technique

International Nuclear Information System (INIS)

Abdel-Sabour, M.F.; Abdou, F.M.; Elwan, I.M.; Al-Salama, Y.J.

2003-01-01

Fifteen soil samples were chosen from different locations (five different locations at north greater Cairo, Egypt to represent different soils (alluvial and sandy) as well as different source of contaminated wastewater (sewage and industrial effluent). Using sequential extraction technique (extracting the soil with different solutions, which is designed to separate metal fractions), Cr was separated into six operationally defined fractions water soluble, exchangeable, carbonate bound, Fe-Mn oxides bound, organic bound and residual fractions. Result of soil total-Cr indicated the serious accumulation of Cr in soils subjected to prolonged irrigation with contaminated wastewater. As it could seen, total-Cr in the tested contaminated soils exceeds the permissible levels (75-100)ppm Cr by several order of magnitude particularly at the surface and subsurface layers. The highest accumulation of total Cr down to depth 60 cm was observed in case of soil E. Data showed that values of total Cr determined by NAA method were always higher than the relevant values determined either by AAS or those calculated after the sequential extraction method. T-test analysis showed the significant difference between NAA and either AAS or sequential extraction methods. Although T-test analysis showed that were significant differences between total content in soils as determined by destructive (AAS or SUM) and non-destructive (NAA) analytical techniques however, strong liner relation between NAA and other tested methods was obtained. Chromium distribution between different extractants shows that the greatest amounts are found in the residual and Occluded in Fe and Mn-Oxides fractions followed by carbonate or organic fractions. In most cases the proportion of all tested Cr-forms has increased in contaminated soil layers with higher enrichment in organically bound Cr, occluded in Fe and Mn oxides, carbonate exchangeable and soluble fractions. Results indicate that soil properties have a

A mechanical and tribological study of Cr/CrN multilayer coatings

Energy Technology Data Exchange (ETDEWEB)

Arias, D.F., E-mail: diegomas@gmail.com [Grupo GEMA, Universidad Católica de Pereira, Pereira (Colombia); Gómez, A. [Laboratório de Fenômenos de Superficie, Escola Politécnica, Universidade de Sao Paulo, Sao Paulo (Brazil); Pontificia Universidad Javeriana Cali (Colombia); Vélez, J.M. [Escuela de Ingeniería de Materiales, Universidad Nacional de Colombia Sede Medellín (Colombia); Souza, R.M. [Laboratório de Fenômenos de Superficie, Escola Politécnica, Universidade de Sao Paulo, Sao Paulo (Brazil); Olaya, J.J. [Departamento de Ingeniería Mecánica y Mecatrónica, Universidad Nacional de Colombia, Bogotá (Colombia)

2015-06-15

Multilayer Cr/CrN coatings with different periodicities were grown on silicon substrates by means of a magnetron sputtering technique. Thin films with only Cr or CrN were also grown, in order to use them as reference samples. Structural, morphological, mechanical and tribological characterization were carried out by using X-ray diffraction (XRD), atomic force microscopy (AFM), nanohardness and nanoscratch techniques, respectively. The characterization results were analyzed as a function of the bilayer thickness (period). In general, the multilayer hardness value increased with the decrease in period. In addition, the validity of the Hall-Petch relationship was confirmed for grain sizes and period values greater than 146 nm and 333 nm, respectively. The coefficient of friction (COF) increased with increasing load, which indicates the contribution of the adhesion to the COF. - Highlights: • Multilayer Cr/CrN coatings with layer thickness between 200 and 1000 nm were grown. • Neither bias voltage not temperature were applied during deposition. • The hardness improves with the increase of the number of bilayers. • The wear rate decreases with the increase of the number of bilayers.

A fast neutron spectrometer based on an electrochemically etched CR-39 detector with degrader and front radiator

International Nuclear Information System (INIS)

Matiullah; Durrani, S.A.

1987-01-01

In addition to having promising applications for the development of a fast-neutron dosemeter, electrochemically etched (ECE) CR-39 detectors also offer the possibility of energy-selective fast-neutron detection. This property stems basically from the fact that, to produce 'sparkable' trails in the polymeric detector subjected to ECE, the charged particle resulting from a neutron interaction must fall within a definite 'energy window'. The lower and upper limits of proton energies that can yield ECE spots in CR-39 have been experimentally determined to be ∼ 50 keV and ∼ 2.2 MeV under our processing conditions. To accomplish our objective, we have developed a technique based on ECE spot-density measurements in CR-39 detectors placed in conjuction with judiciously chosen thicknesses of a polyethylene radiator and a lead degrader. The optimum thicknesses of the radiator and the degrader, for a given neutron energy, are determined by computer calculations. (author)

TSEE from Fe-Cr alloy system and its application to the estimation of gasoline deterioration

International Nuclear Information System (INIS)

Shimada, H.; Nakajima, K.

1983-01-01

The exoelectron glow curves for oxide surface on Fe-Cr alloy were measured as a function of Cr content. It was seen that with increasing Cr content the total counts of thermally stimulated exoelectron emission (TSEE), threshold temperature for measuring the glow curve (starting temperature of the glow curve) and the activation energy clearly indicate a good coincidence with the oxidation process of the surface. The interaction of Fe-Cr alloy with gasoline was examined by applying the test for the oxidation induced period (ASTM D525). The induction period became minimum at about 4%Cr, and the deposit of gasoline gum was maximum at its composition. The results were compared with that of TSEE, and it was found that the catalytic effect of Fe-Cr alloy on the deterioration of gasoline is explained from the starting temperature of the glow curves. (author)

Tissue distribution, subcellular localization and endocrine disruption patterns induced by Cr and Mn in the crab Ucides cordatus

International Nuclear Information System (INIS)

Correa, Jose Dias; Ramos da Silva, Miguel; Bastos da Silva, Antonio Carlos; Araujo de Lima, Silene Maria; Malm, Olaf; Allodi, Silvana

2005-01-01

The essential trace elements Cr and Mn are toxic at high concentrations and information about low concentration is insufficient in the literature. In polluted mangroves, the crab Ucides cordatus can represent a useful tool to assess information on the potential impact of trace elements like Cr and Mn on the environment, since this species is comestible and thus, commercially negotiated. Therefore, U. cordatus crabs were exposed in vivo to different concentrations of Cr and Mn solved in seawater and had their tissue distribution and subcellular deposits evaluated. The gill, hepatopancreas and muscle concentrations were determined by atomic absorption spectroscopy and the results showed that Cr and Mn presented the highest values in the gills rather than in the hepatopancreas and muscular tissue. Electron microscopy and analytical X-ray microanalysis revealed Cr precipitates on the gill surface, co-localized with epiphyte bacteria. In addition, since Cr and Mn did not equally accumulate in most of the tissues studied, glycemic rate of animals, which received injections of extracts of eyestalks of the contaminated crabs, were measured in order to evaluate whether the studied concentrations of Cr and Mn could produce any metabolic alteration. The results indicated that extracts of the eyestalks of crabs submitted to Cr and Mn salts and injected into normal crabs markedly influenced crustacean hyperglycemic hormone synthesis and/or release. The results are discussed with respect to sensitivity of the employed methods and the possible significance of the concentrations of Cr and Mn in the organisms

Species dependent radiotracer study of Cr(VI) and Cr(III) using an aqueous biphasic system

Energy Technology Data Exchange (ETDEWEB)

Roy, K.; Lahiri, S. [Chemical Sciences Div., Saha Inst. of Nuclear Physics, Kolkata (India)

2008-07-01

The speciation study of Cr(III) and Cr(VI) was carried out using a polyethylene glycol (PEG) based aqueous biphasic extraction system (ABS). Neutron activated Cr(III) and Cr(VI) salts were assayed in a HPGe detector before and after employing aqueous biphasic extraction. Different salts of various salting out abilities were taken as the salt rich phase. The best condition for extraction of Cr(VI) and the maximum differential attitude of ABS to Cr(VI) and Cr(III) was observed when 2 M Na{sub 2}SO{sub 4} and PEG 4000 (50% w/w) solutions were used. Cr(III) can also be extracted by the PEG with prior complexation with diphenylthiocarbazone (dithizone). The chromium dithizonate complex is quantitatively extracted by the PEG rich phase. (orig.)

Gamma irradiation effects on the thermal, optical and structural properties of Cr-39 nuclear track detector

International Nuclear Information System (INIS)

Nouh, S.A.; Said, A.F.; Atta, M.R.; EL-Mellegy, W.M.; EL-Meniawi, S.

2006-01-01

A study of the effect of gamma irradiation on the thermal, optical and structural properties of CR-39 diglycol carbonate solid state nuclear track detector (SSNTD) has been carried out. Samples from CR-39 polymer were irradiated with gamma doses at levels between 20 and 300 KGy. Non-isothermal studies were carried out using thermo-gravimetry (TG), differential thermo-gravimetry (DTG) and differential thermal analysis (DTA) to obtain the activation energy of decomposition and the transition temperatures for the non-irradiated and irradiated CR-39 samples. In addition, optical and structural property studies were performed on non-irradiated and irradiated CR-39 samples using refractive index and X-ray diffraction measurements. The variation of onset temperature of decomposition (To) thermal activation energy of decomposition (Ea) melting temperature (Tm) refractive index (n) and the mass fraction of the amorphous phase with the gamma dose were studied. It was found that many changes in the thermal, optical and structural properties of the CR-39 polymer could be produced by gamma irradiation via the degradation and cross linking mechanisms. Also, the gamma dose gave an advantage for increasing the correlation between the thermal stability of CR-39 polymer and the bond formation created by the ionizing effect of gamma radiation

P-type Al-doped Cr-deficient CrN thin films for thermoelectrics

Science.gov (United States)

le Febvrier, Arnaud; Van Nong, Ngo; Abadias, Gregory; Eklund, Per

2018-05-01

Thermoelectric properties of chromium nitride (CrN)-based films grown on c-plane sapphire by dc reactive magnetron sputtering were investigated. In this work, aluminum doping was introduced in CrN (degenerate n-type semiconductor) by co-deposition. Under the present deposition conditions, over-stoichiometry in nitrogen (CrN1+δ) rock-salt structure is obtained. A p-type conduction is observed with nitrogen-rich CrN combined with aluminum doping. The Cr0.96Al0.04N1.17 film exhibited a high Seebeck coefficient and a sufficient power factor at 300 °C. These results are a starting point for designing p-type/n-type thermoelectric materials based on chromium nitride films, which are cheap and routinely grown on the industrial scale.

Effects of La2O3 on microstructure and wear properties of laser clad γ/Cr7C3/TiC composite coatings on TiAl intermatallic alloy

International Nuclear Information System (INIS)

Liu Xiubo; Yu Rongli

2007-01-01

The effects of La 2 O 3 addition on the microstructure and wear properties of laser clad γ/Cr 7 C 3 /TiC composite coatings on γ-TiAl intermetallic alloy substrates with NiCr-Cr 3 C 2 precursor mixed powders have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive spectrometer (EDS) and block-on-ring wear tests. The responding wear mechanisms are discussed in detail. The results are compared with that for composite coating without La 2 O 3 . The comparison indicates that no evident new crystallographic phases are formed except a rapidly solidified microstructure consisting of the primary hard Cr 7 C 3 and TiC carbides and the γ/Cr 7 C 3 eutectics distributed in the tough γ nickel solid solution matrix. Good finishing coatings can be achieved under a proper amount of La 2 O 3 -addition and a suitable laser processing parameters. The additions of rare-earth oxide La 2 O 3 can refine and purify the microstructure of coatings, relatively decrease the volume fraction of primary blocky Cr 7 C 3 to Cr 7 C 3 /γ eutectics, reduce the dilution of clad material from base alloy and increase the microhardness of the coatings. When the addition of La 2 O 3 is approximately 4 wt.%, the laser clad composite coating possesses the highest hardness and toughness. The composite coating with 4 wt.%La 2 O 3 addition can result the best enhancement of wear resistance of about 30%. However, too less or excessive addition amount of La 2 O 3 have no better influence on wear resistance of the composite coating

Benchmarking FeCr empirical potentials against density functional theory data

International Nuclear Information System (INIS)

Klaver, T P C; Bonny, G; Terentyev, D; Olsson, P

2010-01-01

Three semi-empirical force field FeCr potentials, two within the formalism of the two-band model and one within the formalism of the concentration dependent model, have been benchmarked against a wide variety of density functional theory (DFT) structures. The benchmarking allows an assessment of how reliable empirical potential results are in different areas relevant to radiation damage modelling. The DFT data consist of defect-free structures, structures with single interstitials and structures with small di- and tri-interstitial clusters. All three potentials reproduce the general trend of the heat of formation (h.o.f.) quite well. The most important shortcomings of the original two-band model potential are the low or even negative h.o.f. for Cr-rich structures and the lack of a strong repulsion when moving two solute Cr atoms from being second-nearest neighbours to nearest neighbours. The newer two-band model potential partly solves the first problem. The most important shortcoming in the concentration dependent model potential is the magnitude of the Cr–Cr repulsion, being too strong at short distances and mostly absent at longer distances. Both two-band model potentials do reproduce long-range Cr–Cr repulsion. For interstitials the two-band model potentials reproduce a number of Cr–interstitial binding energies surprisingly well, in contrast to the concentration dependent model potential. For Cr interacting with clusters, the result can sometimes be directly extrapolated from Cr interacting with single interstitials, both according to DFT and the three empirical potentials

Metabolic Effects of CX3CR1 Deficiency in Diet-Induced Obese Mice.

Directory of Open Access Journals (Sweden)

Rachana Shah

Full Text Available The fractalkine (CX3CL1-CX3CR1 chemokine system is associated with obesity-related inflammation and type 2 diabetes, but data on effects of Cx3cr1 deficiency on metabolic pathways is contradictory. We examined male C57BL/6 Cx3cr1-/- mice on chow and high-fat diet to determine the metabolic effects of Cx3cr1 deficiency. We found no difference in body weight and fat content or feeding and energy expenditure between Cx3cr1-/- and WT mice. Cx3cr1-/- mice had reduced glucose intolerance assessed by intraperitoneal glucose tolerance tests at chow and high-fat fed states, though there was no difference in glucose-stimulated insulin values. Cx3cr1-/- mice also had improved insulin sensitivity at hyperinsulinemic-euglycemic clamp, with higher glucose infusion rate, rate of disposal, and hepatic glucose production suppression compared to WT mice. Enhanced insulin signaling in response to acute intravenous insulin injection was demonstrated in Cx3cr1-/- by increased liver protein levels of phosphorylated AKT and GSK3β proteins. There were no differences in adipose tissue macrophage populations, circulating inflammatory monocytes, adipokines, lipids, or inflammatory markers. In conclusion, we demonstrate a moderate and reproducible protective effect of Cx3cr1 deficiency on glucose intolerance and insulin resistance.

Manufacturing of Porous Al-Cr Preforms for Composite Reinforcing Using Microwave Activated Combustion Synthesis

Directory of Open Access Journals (Sweden)

Naplocha K.

2014-10-01

Full Text Available The combustion synthesis of porous skeletons (preforms of intermetallic Al–Cr compounds intended for metal matrix composite MMC reinforcing was developed. Mixture of Al and Cr powders with granularity of −10, −44, −74mm were cold isostatic pressed and next ignited and synthetized in a microwave reactor under argon atmosphere (microwave-activated combustion synthesis MACS. In order to ignite the synthesis, microwave energy was focused by a tuner on the specimen. The analysis of reaction temperature diagrams revealed that the synthesis proceeded through the following peritectic transformations: L(liquidus+Al7Cr→L+Al11Cr2→L+Al4Cr. Moreover, EDS and XRD examinations showed that the reaction proceeded between a solid Cr and a liquid Al to create a distinct envelope of Al9Cr4 on Cr particle which next extended and spreaded over the entire structure. The produced preforms with uniform structure and interconnected porosity were infiltrated with liquid Cu and Al alloy. The obtained composite materials exhibited high hardness, wear and distinct temperature oxidation resistance.

Characterization of Ni–Cr alloys using different casting techniques and molds

International Nuclear Information System (INIS)

Chen, Wen-Cheng; Teng, Fu-Yuan; Hung, Chun-Cheng

2014-01-01

This study differentiated the mechanical properties of nickel–chromium (Ni–Cr) alloys under various casting techniques (different casting molds and casting atmospheres). These techniques were sampled by a sand mold using a centrifugal machine in ambient air (group I) and electromagnetic induction in an automatic argon castimatic casting machine (group II). The specimen casting used a graphite mold by a castimatic casting machine (group III). The characteristics of the Ni–Cr alloys, yield and ultimate tensile strength, bending modulus, microhardness, diffraction phase, grindability, ability to spring back, as well as ground microstructure and pattern under different casting conditions were evaluated. The group III specimens exhibited the highest values in terms of strength, modulus, hardness, and grindability at a grind rate of 500 rpm. Moreover, group III alloys exhibited smaller grain sizes, higher ability to spring back, and greater ductility than those casted by sand investment (groups I and II). The main factor, “casting mold,” significantly influenced all mechanical properties. The graphite mold casting of the Ni–Cr dental alloys in a controlled atmosphere argon casting system provided an excellent combination of high mechanical properties and good ability to spring back, and preserved the ductile properties for application in Ni–Cr porcelain-fused system. The results can offer recommendations to assist a prosthetic technician in selecting the appropriate casting techniques to obtain the desired alloy properties. - Highlights: • Properties of Ni–Cr alloys using various casting techniques are characterized. • Alloys cast by graphite mold exhibited higher recovery angle and more ductility. • Alloys cast by graphite mold exhibited higher strength and grinding rate. • Alloys in this study increase operative room to adjust the precision for prosthesis

Characterization of Ni–Cr alloys using different casting techniques and molds

Energy Technology Data Exchange (ETDEWEB)

Chen, Wen-Cheng, E-mail: wencchen@fcu.edu.tw [Advanced Medical Devices and Composites Laboratory, Department of Fiber and Composite Materials, College of Engineering, Feng Chia University, Taichung 40724, Taiwan (China); Teng, Fu-Yuan [Department of Dentistry, Kaohsiung Armed Forces General Hospital, Kaohsiung 802, Taiwan (China); School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Hung, Chun-Cheng [School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Department of Dentistry, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China)

2014-02-01

This study differentiated the mechanical properties of nickel–chromium (Ni–Cr) alloys under various casting techniques (different casting molds and casting atmospheres). These techniques were sampled by a sand mold using a centrifugal machine in ambient air (group I) and electromagnetic induction in an automatic argon castimatic casting machine (group II). The specimen casting used a graphite mold by a castimatic casting machine (group III). The characteristics of the Ni–Cr alloys, yield and ultimate tensile strength, bending modulus, microhardness, diffraction phase, grindability, ability to spring back, as well as ground microstructure and pattern under different casting conditions were evaluated. The group III specimens exhibited the highest values in terms of strength, modulus, hardness, and grindability at a grind rate of 500 rpm. Moreover, group III alloys exhibited smaller grain sizes, higher ability to spring back, and greater ductility than those casted by sand investment (groups I and II). The main factor, “casting mold,” significantly influenced all mechanical properties. The graphite mold casting of the Ni–Cr dental alloys in a controlled atmosphere argon casting system provided an excellent combination of high mechanical properties and good ability to spring back, and preserved the ductile properties for application in Ni–Cr porcelain-fused system. The results can offer recommendations to assist a prosthetic technician in selecting the appropriate casting techniques to obtain the desired alloy properties. - Highlights: • Properties of Ni–Cr alloys using various casting techniques are characterized. • Alloys cast by graphite mold exhibited higher recovery angle and more ductility. • Alloys cast by graphite mold exhibited higher strength and grinding rate. • Alloys in this study increase operative room to adjust the precision for prosthesis.

Influence of a niobium coating on sulfidation resistance of FeCr and FeCrY alloys; Influencia de um revestimento de niobio sobre a resistencia a sulfetacao das ligas FeCr e FeCrY

Energy Technology Data Exchange (ETDEWEB)

Geribola, Gulherme Altomari

2014-07-01

Niobium and niobium based alloys are currently used in many industrial applications because they offer excellent resistance to degradation in various corrosive environments. These media include gaseous atmospheres at high temperatures such as those found in existing coal gasifying plants in power plants for energy generation. These atmospheres are complex gas mixtures that contain sulfur and oxygen, among other compounds. Sulphides are thermodynamically less stable, have lower melting points and often have larger deviations from stoichiometry compared to the corresponding oxides. Although there are studies regarding the use of refractory metals in high temperature sulphidizing atmospheres, the use of niobium compounds has not been adequately evaluated and there is very little studies available in the literature about its use as a protective coating. The aim of this study was to evaluate the effect of a niobium film, deposited by magnetron sputtering on the isothermal sulphidation behavior of Fe-20Cr and Fe-20Cr-1Y alloys. The sulphidation tests were carried out at 500, 600 and 700 deg C for 2h in H{sub 2}/2% H2S atmosphere. The sulphidation resistance was determined by mass gain per unit area. The sulphidation behavior of the coated and uncoated alloys was similar at 500 deg C, and none of the alloys scaled. At 700 deg C FeCr alloy scaled in the form of a fine powder, while the reaction product formed on the alloy FeCrY scaled in the form of plates. The effect of niobium became pronounced at 700 deg C. The reaction product layer formed on the coated alloy was thinner and more plastic than that formed on the uncoated alloy. The mass gain per unit area of the coated alloys decreased significantly and they did not scaled. (author)

gamma-induced modification on optical band gap of CR-39 SSNTD

International Nuclear Information System (INIS)

Zaki, M.F.

2010-01-01

effect of gamma irradiation on optical absorption of nuclear track detectors like CR-39 was studied at different absorbed doses using ultraviolet-visible (UV-VIS)spectroscopy. the existence of the peaks, their shifting and broadening as a result of gamma irradiation has been discussed. the width of the tail of localized states in the band gap (E u )was evaluated using the Urbach edge method. finally the indirect and direct band gap in pristine and gamma irradiated CR-39 have been determined. the values of indirect band gap have been found to be lower than the corresponding values of direct band gap. a decrease in the optical energy gap with increasing the gamma absorbed dose can be discussed on the basis of gamma-irradiation-induced defects in the CR-39. the correlation between optical band gap and the number of carbon atoms in a cluster with modified Tauc's equation has been discussed in case of CR-39.

Level crossing in a molecular Cr{sub 8} ring

Energy Technology Data Exchange (ETDEWEB)

Affronte, M. E-mail: affronte@unimore.it; Guidi, T.; Caciuffo, R.; Carretta, S.; Amoretti, G.; Hinderer, J.; Sheikin, I.; Smith, A.A.; Winpenny, R.E.P.; Slageren, J. van; Gatteschi, D

2004-05-01

The heat capacity of a molecular Cr{sub 8} ring was measured as a function of temperature and magnetic field in order to follow the evolution of the Schottky anomaly through the first (S=0 to |1,-1>) level crossing occurring at B{sub c1}=6.9 T. The results are interpreted within the framework of a spin Hamiltonian approach and they nicely fit the pattern of the energy levels derived by inelastic neutron spectroscopy. At B{sub c1}, the Schottky anomaly almost vanishes suggesting that a true crossing occurs in Cr{sub 8} in contrast to what was observed for ferric wheels.

Phase separation and exchange bias effect in Ca doped EuCrO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Deng, Dongmei, E-mail: dmdeng@shu.edu.cn [Department of Physics and Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Wang, Xingyu; Zheng, Jiashun; Qian, Xiaolong [Department of Physics and Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Yu, Dehong; Sun, Dehui [Bragg Institute, Australian Nuclear Science and Technology Organization, Kirrawee DC, NSW 2232 (Australia); Jing, Chao [Department of Physics and Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Lu, Bo [Analysis and Measurement Center and Laboratory for Microstructures of Shanghai University, Shanghai 200444 (China); Kang, Baojuan; Cao, Shixun; Zhang, Jincang [Department of Physics and Materials Genome Institute, Shanghai University, Shanghai 200444 (China)

2015-12-01

The rare-earth chromites have attracted increasing interests in recent years, as a member of a few single-phase multiferroic materials. We studied the structure and magnetic property of a series of Ca-doped EuCrO{sub 3} samples by using X-ray powder diffraction and Physical Property Measurement System. Phase separation, rotation of magnetization in M(T) curve and exchange bias effect have been identified. The Eu{sub 0.7}Ca{sub 0.3}CrO{sub 3} polycrystalline sample may be intrinsically phase-separated, with Cr{sup 3+}-rich, Cr{sup 4+}-rich canted antiferromagnetic regions surrounded by spin glass-like frustrated phase, resulting in several magnetic features including: (1) a broad and slow increase of M(T) curve with the decrease of temperature; (2) rotation of magnetization with increasing cooling field; (3) exchange bias and glassy magnetism. The rotation of magnetization is ascribed to the rotation of the moment of Cr{sup 4+}-rich regions, arising from the competition between exchange coupling energy and magnetostatic energy. The exchange bias effect suggests the formation of weak ferromagnetic unidirectional anisotropy during field cooling, due to the exchange coupling among weak ferromagnetic domains and surrounding spin glass-like regions. This result helps understanding the interaction among different magnetic domains and phases in a complex system. - Highlights: • Exchange bias effect and glassy magnetism were observed in Eu{sub 0.7}Ca{sub 0.3}CrO{sub 3}. • Rotation of the moments of Cr{sup 4+}-rich regions result in the rotation of magnetization in M(T) curve. • Spin glass-like regions contribute to the observed exchange bias effect.

THE HIGHEST-ENERGY COSMIC RAYS CANNOT BE DOMINANTLY PROTONS FROM STEADY SOURCES

Energy Technology Data Exchange (ETDEWEB)

Fang, Ke [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Kotera, Kumiko [Sorbonne Universités, UPMC Univ. Paris 6 et CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, F-75014 Paris (France)

2016-11-20

The bulk of observed ultrahigh-energy cosmic rays could be light or heavier elements and originate from an either steady or transient population of sources. This leaves us with four general categories of sources. Energetic requirements set a lower limit on single-source luminosities, while the distribution of particle arrival directions in the sky sets a lower limit on the source number density. The latter constraint depends on the angular smearing in the skymap due to the magnetic deflections of the charged particles during their propagation from the source to the Earth. We contrast these limits with the luminosity functions from surveys of existing luminous steady objects in the nearby universe and strongly constrain one of the four categories of source models, namely, steady proton sources. The possibility that cosmic rays with energy >8 × 10{sup 19} eV are dominantly pure protons coming from steady sources is excluded at 95% confidence level, under the safe assumption that protons experience less than 30° magnetic deflection on flight.

Effects of the Cr2O3 Content on the Viscosity of CaO-SiO2-10 Pct Al2O3-Cr2O3 Quaternary Slag

Science.gov (United States)

Wu, Tuo; Zhang, Yanling; Yuan, Fang; An, Zhuoqing

2018-04-01

The present study experimentally investigates the effect of Cr2O3 on the viscosity of molten slags. The viscosities of CaO-SiO2-10 pct Al2O3-Cr2O3 quaternary slags with two different binary basicities (R, basic slag with R = 1.2 and acidic slag with R = 0.8) were measured by the rotating cylindrical method from 1813 K to 1953 K (1540 °C to 1680 °C). The results showed that the viscosity of both types of slag decreased as the Cr2O3 content increased, but the viscosity of acidic slags exhibited a greater decrease. The slags showed good Newtonian behavior at such high temperatures. Cr2O3 could act as a network modifier to simplify the Si-O-Si tetrahedral structure, as verified by the Raman spectral analysis, which was consistent with the decreasing trend of viscosity. The activation energy of viscous flow decreased slightly with increasing Cr2O3, but increasing the basicity seemed to be more effective in decreasing the viscosity than adding Cr2O3.

Characterization of Ni-Cr alloys using different casting techniques and molds.

Science.gov (United States)

Chen, Wen-Cheng; Teng, Fu-Yuan; Hung, Chun-Cheng

2014-02-01

This study differentiated the mechanical properties of nickel-chromium (Ni-Cr) alloys under various casting techniques (different casting molds and casting atmospheres). These techniques were sampled by a sand mold using a centrifugal machine in ambient air (group I) and electromagnetic induction in an automatic argon castimatic casting machine (group II). The specimen casting used a graphite mold by a castimatic casting machine (group III). The characteristics of the Ni-Cr alloys, yield and ultimate tensile strength, bending modulus, microhardness, diffraction phase, grindability, ability to spring back, as well as ground microstructure and pattern under different casting conditions were evaluated. The group III specimens exhibited the highest values in terms of strength, modulus, hardness, and grindability at a grind rate of 500 rpm. Moreover, group III alloys exhibited smaller grain sizes, higher ability to spring back, and greater ductility than those casted by sand investment (groups I and II). The main factor, "casting mold," significantly influenced all mechanical properties. The graphite mold casting of the Ni-Cr dental alloys in a controlled atmosphere argon casting system provided an excellent combination of high mechanical properties and good ability to spring back, and preserved the ductile properties for application in Ni-Cr porcelain-fused system. The results can offer recommendations to assist a prosthetic technician in selecting the appropriate casting techniques to obtain the desired alloy properties. Copyright © 2013 Elsevier B.V. All rights reserved.

Role of defects on the electronic and magnetic properties of CrAs, CrSe and CrSb zinc-blende compounds

International Nuclear Information System (INIS)

Galanakis, I.; Pouliasis, S.G.

2009-01-01

We present an extended study of single impurity atoms and atomic swaps in half-metallic CrAs, CrSb and CrSe zinc-blende compounds. Although the perfect alloys present a rather large gap in the minority-spin band, all defects under study, with the exception of void impurities at Cr and sp sites and Cr impurities at sp sites (as long as no swap occurs), induce new states within the gap. The Fermi level can be pinned within these new minority states depending on the lattice constant used for the calculations and the electronegativity of the sp atoms. Although these impurity states are localized in space around the impurity atoms and very fast we regain the bulk behavior, their interaction can lead to wide bands within the gap and thus loss of the half-metallic character

Fracture toughness and sliding properties of magnetron sputtered CrBC and CrBCN coatings

Science.gov (United States)

Wang, Qianzhi; Zhou, Fei; Ma, Qiang; Callisti, Mauro; Polcar, Tomas; Yan, Jiwang

2018-06-01

CrBC and CrBCN coatings with low and high B contents were deposited on 316L steel and Si wafers using an unbalanced magnetron sputtering system. Mechanical properties including hardness (H), elastic modulus (E) and fracture toughness (KIc) as well as residual stresses (σ) were quantified. A clear correlation between structural, mechanical and tribological properties of coatings was found. In particular, structural analyses indicated that N incorporation in CrBC coatings with high B content caused a significant structural evolution of the nanocomposite structure (crystalline grains embedded into an amorphous matrix) from nc-CrB2/(a-CrBx, a-BCx) to nc-CrN/(a-BCx, a-BN). As a result, the hardness of CrBC coating with high B content decreased from 23.4 to 16.3 GPa but the fracture toughness was enhanced. Consequently, less cracks initiated on CrBCN coatings during tribological tests, which combined with the shielding effect of a-BN on wear debris, led to a low friction coefficient and wear rate.

Characterization of CR 39 nuclear track detector for use as a radon/thoron dosemeter

International Nuclear Information System (INIS)

Kandaiya, S.

1988-02-01

For the estimation of radon, thoron and their short-lived daughter products in air radon diffusion chambers with passive α-track etch detectors have been used. The report describes the properties of CR 39 track etch detectors in particular with respect to the spectrometric detection of α-particles in the energy range up to 8.77 MeV using chemical and a combination of chemical-electrochemical etching technique. In order to optimize the etching conditions for an α-energy discrimination in the energy range up to 8.77 MeV, the ECE track size diameter and the track density have been investigated as a function of the chemical pre-etching time using three electrical field strengths. In a mixed α-spectrum the contributions of various α-particles with energies between 4.6 to 8.77 MeV have been determined experimentally in CR 39 and compared with the spectral measurement using a surface barrier detector and the same irradiation geometry. Beside CR 39 detectors etched chemically and electrochemically, in addition surface barrier detectors and a Monte Carlo calculation have been used to evaluate the α-energy spectrum for thoron and its daughter products emitted by α-decays in the air volume and the plate-out of daughters at the inner surface on the diffusion chamber. (orig./HP) [de

Structural relaxation and colour in the spinel-magnesiochromite (MgAl2O4-MgCr2O4) and gahnite-zincochromite (ZnAl2O4-ZnCr2O4) solid solution series

Science.gov (United States)

Hålenius, U.; Andreozzi, G. B.; Skogby, H.

2009-04-01

Recent studies on binary mineral solid solution series utilising synchrotron based x-ray absorption spectroscopies have indicated strong structural relaxation. For instance, it has been suggested that the real Cr-O bond distances remain nearly constant (relaxation parameter (ɛ) of 0.85, where ɛ=1 equals full relaxation) over the entire compositional range of the MgAl2O4-MgCr2O4 series (Juhin et al. 2007). In the present study we have measured room temperature optical absorption spectra of synthetic single crystals of the ZnAl2-2xCr2xO4 (0.03?x?1) and MgAl2-2xCr2xO4(0.02?x?1) series with the aim to explore the real architecture of the structure and in particular the Cr-O distance as function of composition. Our crystals were synthesized by means of flux-growth methods under atmospheric pressure and temperature profiles resulting in an estimated cation ordering temperature of ca 850 °C. Crystals close to the spinel (sensu stricto) and gahnite end-member compositions were faintly red in colour. With increasing Cr-content the crystals become more intensely red-coloured and at the higher Cr-contents there is a distinct shift towards a dark greenish colouration. These colour changes are reflected in the measured optical spectra by the position and intensity of the two spin-allowed electronic d-d transitions in octahedrally coordinated Cr3+ at ca 18000 (4A2g -4T2g (4F) transition) and 25000 cm-1(4A2g -4T1g (4F) transition). The energy of the first transition (?1-band) is ca 1200 cm-1 lower in magnesiochromite than in weakly Cr-doped spinel (x=0.02) and ca 1400 cm-1 lower in zincochromite than in gahnite with the lowest Cr-content (x=0.03). Concomitantly the energy of the second transition (?2-band) decreases with increasing Cr-content in both series by ca. 1800 cm-1. From the position of the ?1-band, a decrease in crystal field splitting, 10Dq, for six-coordinated Cr3+ with increasing Cr-content in the MgAl2-2xCr2xO4 and ZnAl2-2xCr2xO4 series of 6.5 and 7

SU-F-T-299: An Experimental 2D Computed Radiography (CR) Dosimeter for IMRT. Are In-Field Measurements Affected by the Low Energy Photon Overresponse?

Energy Technology Data Exchange (ETDEWEB)

Crijns, W [University Hospital Leuven, Leuven (Belgium); Vandenbroucke, D; Leblans, P [Agfa Healthcare N.V., Mortsel (Belgium); Depuydt, T

2016-06-15

Purpose: Computed Radiography (CR) dosimetry could offer film dosimetry resolution and flexibility but with reusability and instantaneous processing. For an experimental CR-plate, designed for radiotherapy (Zeff=18), CR’s typical out-of-field over-response to low energy photons was previously reduced to 8%. The present work assesses the impact of the residual over-response when open-fields are combined or when intensity modulated fields are used. Methods: Agfa Healthcare’s experimental CRplate was scanned and erased 4min after each irradiation using a flying-spot CR-15-X-engine based reader, which was adapted for radiotherapy dosimetry. A CR-plate specific calibration and uniformity correction was used.For open-fields two abutting half beams (5×10cm{sup 2}) captured out-offield and in-field doses in a single image. Additionally, both half beams were measured individually as well as a 3×18Gy open-field SBRT-lung treatment. For intensity modulated fields standard test patterns (Chair and Pyramid) and a clinical 5×5Gy rectal VMAT plan were captured. All measurements were compared to the corresponding dose calculations. Results: For open-fields the out-of-field overdose was clearly larger than the in-field overdose (10% vs. 4%). The sum of the individual measurements corresponded well with the combined measurement (dose difference, ΔD<−2.2%). The SBRT case had no overdose in the high dose region; ΔD=−5.6%±3.3%, the deviation was attributed to CR-fading effects (−0.3%/min) which were not corrected for.Compared to open-fields, intensity modulated deliveries had a further increased over-response out-offield (ΔD=+58% to +125% [Chair] +43% [Pyramid]), due to the increased amount of low energy photons for IMRT. However, this effect was not measured in-field where even decreased dose signals were observed (ΔD=−0.3% to +2.25% [Chair], −4.5% to −0.1% [Pyramid]). The rectal VMAT treatment had a dose difference +2.4%±6.0%. The in-field deviations were

Tailoring optical properties of TiO2-Cr co-sputtered films using swift heavy ions

Science.gov (United States)

Gupta, Ratnesh; Sen, Sagar; Phase, D. M.; Avasthi, D. K.; Gupta, Ajay

2018-05-01

Effect of 100 MeV Au7+ ion irradiation on structure and optical properties of Cr-doped TiO2 films has been studied using X-ray photoelectron spectroscopy, soft X-ray absorption spectroscopy, UV-Visible spectroscopy, X-ray reflectivity, and atomic force microscopy. X-ray reflectivity measurement implied that film thickness reduces as a function of ion fluence while surface roughness increases. The variation in surface roughness is well correlated with AFM results. Ion irradiation decreases the band gap energy of the film. Swift heavy ion irradiation enhances the oxygen vacancies in the film, and the extra electrons in the vacancies act as donor-like states. In valence band spectrum, there is a shift in the Ti3d peak towards lower energies and the shift is equivalent to the band gap energy obtained from UV spectrum. Evidence for band bending is also provided by the corresponding Ti XPS peak which exhibits a shift towards lower energy due to the downward band bending. X-ray absorption studies on O Kand Cr L3,2 edges clearly indicate that swift heavy ion irradiation induces formation of Cr-clusters in TiO2 matrix.

The Reduction of Cr(VI) to Cr(III) by Natural Fe-Bearing Minerals: A Synchrotron XAS Study

Science.gov (United States)

Xu, H.; Guo, X.; Ding, M.; Migdissov, A. A.; Boukhalfa, H.; Sun, C.; Roback, R. C.; Reimus, P. W.; Katzman, D.

2017-12-01

Cr(VI) in the form of CrO42- is a pollutant species in groundwater and soils that can pose health and environmental problems. Cr(VI) associated with use as a corrosion inhibitor at a power plant from 1956-1972 is present in a deep groundwater aquifer at Los Alamos National Laboratory. A potential remediation strategy for the Cr contamination is reduction of Cr(VI) to Cr(III) via the acceptance of electrons from naturally occurring or induced Fe(II) occurring in Fe-bearing minerals. In this work, using synchrotron-based X-ray techniques, we investigated the Cr reduction behavior by Fe-bearing minerals from outcrop and core samples representative of the contaminated portion of the aquifer. Samples were exposed to solutions with a range of known Cr (VI) concentrations. XANES and EXAFS spectra showed that all the Cr(VI) had been reduced to Cr(III), and micro XRF mapping revealed close correlation of Cr and Fe distribution, implying that Fe(II) in minerals reduced Cr(VI) in the solution. Similar behavior was observed from in-situ XANES measurements on Cr reduction and adsorption by mineral separates from the rock samples in Cr(VI)-bearing solutions. In addition, to obtain reference parameters for interpreting the data of natural samples, we collected Cr and Fe EXAFS spectra of Cr(III)-Fe(III) hydroxide solid solutions, which show progressive changes in the local structure around Cr and Fe over the whole series.

Distinct effects of Cr bulk doping and surface deposition on the chemical environment and electronic structure of the topological insulator Bi{sub 2}Se{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Yilmaz, Turgut, E-mail: yilmaz@phys.uconn.edu [Department of Physics, University of Connecticut, Storrs, CT 06269 (United States); Hines, William [Department of Physics, University of Connecticut, Storrs, CT 06269 (United States); Sun, Fu-Chang [Department of Materials Science and Engineering, University of Connecticut, Storrs, CT 06269 (United States); Pletikosić, Ivo [Department of Physics, Princeton University, Princeton, NJ 08544 (United States); Budnick, Joseph [Department of Physics, University of Connecticut, Storrs, CT 06269 (United States); Valla, Tonica [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973 (United States); Sinkovic, Boris [Department of Physics, University of Connecticut, Storrs, CT 06269 (United States)

2017-06-15

Highlights: • Cr doping into the bulk of Bi{sub 2}Se{sub 3} opens an energy gap at the Dirac point which is observable in the non-magnetic state. • Cr surface deposition does not lead to open an energy gap at the Dirac point of Bi{sub 2}Se{sub 3}. • Formation of two distinct Bi and Cr core level peaks was observed upon the deposition of Cr on the surface of Bi{sub 2}Se{sub 3}. - Abstract: In this report, it is shown that Cr doped into the bulk and Cr deposited on the surface of Bi{sub 2}Se{sub 3} films produced by molecular beam epitaxy (MBE) have strikingly different effects on both the electronic structure and chemical environment. Angle resolved photoemission spectroscopy (ARPES) shows that Cr doped into the bulk opens a surface state energy gap which can be seen at room temperature; much higher than the measured ferromagnetic transition temperature of ≈10 K. On the other hand, similar ARPES measurements show that the surface states remain gapless down to 15 K for films with Cr surface deposition. In addition, core-level photoemission spectroscopy of the Bi 5d, Se 3d, and Cr 3p core levels show distinct differences in the chemical environment for the two methods of Cr introduction. Surface deposition of Cr results in the formation of shoulders on the lower binding energy side for the Bi 5d peaks and two distinct Cr 3p peaks indicative of two Cr sites. These striking differences suggests an interesting possibility that better control of doping at only near surface region may offer a path to quantum anomalous Hall states at higher temperatures than reported in the literature.

LaCrO{sub 3}-dispersed Cr for metallic interconnect of planar SOFC

Energy Technology Data Exchange (ETDEWEB)

Song, Rak-Hyun; Shin, Dong Ryul [Korea Institute of Energy Research, Taejon (Korea, Republic of); Dokiya, Masayuki [National Institute of Materials and Chemical Research, Ibaraki (Japan)

1996-12-31

In the planar SOFC, the interconnect materials plays two roles as an electrical connection and as a gas separation plate in a cell stack. The interconnect materials must be chemically stable in reducing and oxidizing environments, and have high electronic conductivity, high thermal conductivity, matching thermal expansion with an electrolyte, high mechanical strength, good fabricability, and gas tightness. Lanthanum chromite so far has been mainly used as interconnect materials in planar SOFC. However, the ceramic materials are very weak in mechanical strength and have poor machining property as compared with metal. Also the metallic materials have high electronic conductivity and high thermal conductivity. Recently some researchers have studied metallic interconnects such as Al{sub 2}O{sub 3}/Inconel 600 cermet, Ni-20Cr coated with (LaSr)CoO{sub 3}, and Y{sub 2}O{sub 3-} or La{sub 2}O{sub 3}-dispersed Cr alloy. These alloys have still some problems because Ni-based alloys have high thermal expansion, the added Al{sub 2}O{sub 3}, Y{sub 2}O{sub 3} and La{sub 2}O{sub 3} to metals have no electronic conductivity, and the oxide formed on the surface of Cr alloy has high volatility. To solve these problems, in this study, LaCrO{sub 3}-dispersed Cr for metallic interconnect of planar SOFC was investigated. The LaCrO{sub 3}-dispersed Cr can be one candidate of metallic interconnect because LaCrO{sub 3} possesses electronic conductivity and Cr metal has relatively low thermal expansion. The content of 25 vol.% LaCrO{sub 3} Was selected on the basis of a theoretically calculated thermal expansion. The thermal expansion, electrical and oxidation properties were examined and the results were discussed as related to SOFC requirements.

Characterisation of the Microstructure of Fe–Al/Cr3C2 Composite Coatings

Science.gov (United States)

Liu, Xiaoming; JunhuiDong; Yang, Yuehong; Sun, Changming; Tuo, Ya; Li, Yanwei

2018-03-01

An Fe-Al/Cr3C2 composite coating is investigated to assess its suitability for treating high-temperature components in a power plant. The coating exhibits excellent high- temperature properties including good corrosion, erosion and friction-wear resistance at high temperatures. To deduce the formation of the Fe-Al/Cr3C2 composite coating and to provide an adequate theoretical basis for its extensive application, its structures and microstructures are investigated. Scanning electronic microscopy (SEM)is used along with energy-dispersive X-ray analysis (EDAX) to analyse the surface of the coating. Energy-dispersive spectroscopy (EDS) is used to analyse the cross-section of the coating. Further, X-ray diffraction (XRD) and transmission electron microscopy (TEM) are used to analyse the phases and micro structural features within the coating. The results reveal that the basic phases are two orderly inter metallic compounds (Fe3Al and FeAl) and that the reinforcement includes two oxides (Al2O3 and Cr2O3) as well as substantial quantities of Cr3C2. Al2O3is formed using two mechanisms: oxidation of aluminium in the coating and separation of Al2O3crystals from Fe3Al and FeAl. The grain size of Al2O3 and Cr2O3 in the coatings is nanometric. These two oxides may increase the corrosion-erosion and wear resistances of the coating when they are used as reinforcements.

Theoretical calculation of zero field splitting parameters of Cr{sup 3+} doped ammonium oxalate monohydrate

Energy Technology Data Exchange (ETDEWEB)

Kripal, Ram, E-mail: ram_kripal2001@rediffmail.com; Yadav, Awadhesh Kumar, E-mail: aky.physics@gmail.com

2015-06-15

Zero field splitting parameters (ZFSPs) D and E of Cr{sup 3+} ion doped ammonium oxalate monohydrate (AOM) are calculated with formula using the superposition model. The theoretically calculated ZFSPs for Cr{sup 3+} in AOM crystal are compared with the experimental value obtained by electron paramagnetic resonance (EPR). Theoretical ZFSPs are in good agreement with the experimental ones. The energy band positions of optical absorption spectra of Cr{sup 3+} in AOM crystal calculated with CFA package are in good match with the experimental values.

Sensitivity determination of CR-39 from Normal and inclined incidence

International Nuclear Information System (INIS)

Abou, A.A.; El-Kheir, A.A.; Daas, A.F.; Awwad, Z.; Reda, A.M.

2000-01-01

An experimental study have been carried out on alpha- particle track opening (Major and minor axes) using alpha-particles of different energies incident with different angels in addition to the normal incidence. The sensitivity of CR-39 in present work is determined for each of normal and inclined incidence. The results indicated a difference in the sensitivity according to angle of incidence. The variation of alpha- particle tracks (major and minor axes) are calculated and compared with our measured values. Also, it is found that the sensitivity of CR-39 detector is change due to the storage time at room temperature

PROFIL LOGAM BERAT Cd, Cr (VI DAN Pb PADA LOKASI BERBEDA DI PROVINSI LAMPUNG SERTA BIOAKUMULASINYA PADA TANAMAN PANGAN

Directory of Open Access Journals (Sweden)

Hening Widowati

2015-11-01

Full Text Available The heavy metal profile analysis of Cd, Cr(VI and Pb in the different location in Lampung Province and their bioaccumulation to crops has been conducted. The aims were finding out the difference of metal accumulation in the different pollutant area and determining how it happened to the vegetables surrounding, which were kangkoong and spinach. The research methods were purposive sampling in the different location in Lampung Province, namely 1 highlands, 2 paddy fields, 3 road sides and 4industrial areas. Based on the results, it is found that the highest metal concentration of Cd, Cr(VI and Pb are in the industrial area. Commonly, the value of BCFo-w (0,12-2,00 is higher than BCF¬o-s (0,01-0,18 which shows that there is low metal accumulation of Cd, Cr(VI and Pb in kangkoong and spinach. Furthermore, the BCF value of Cd and Cr(VI are higher compared to Pb.  Keywords: Logam berat, Cd, Cr(VI, Pb,bioakumulasi.

Microstructures and mechanical properties of welded joints of novel 3Cr pipeline steel using an inhouse and two commercial welding wires

International Nuclear Information System (INIS)

Zhu, Jinyang; Xu, Lining; Chang, Wei; Hu, Lihua; Lu, Minxu

2014-01-01

Highlights: • Weldability of novel 3Cr pipeline steel was investigated using two commercial and an inhouse welding wires. • Mechanical properties were measured and microstructure characteristics were observed. • Fracture positions of tensile test just corresponded to the minimum hardness region of the joints. • The inhouse wire R01 can provide the highest cost-performance ratio. - Abstract: The welded joints of the novel 3Cr pipeline steel were fabricated via the gas tungsten arc welding (GTAW) technique using an inhouse welding wire labeled as R01 and two kinds of commercial wires (H08Cr3MoMnA and TGS-2CML). Microhardness, impact toughness and tensile properties of the joints were measured, and microstructure characteristics were observed by scanning electron microscopy (SEM). The results show that under selected welding procedure, the joints of R01 can achieve quite good mechanical properties without preheating and post weld heat treatment (PWHT). After thermal refining, elongation (15.2%) doubled and met the DNV-OS-F101 standard. For low carbon or super low carbon pipeline steels such as 3Cr steel, the revised formula with the carbon applicable coefficient (A(c)) was quite good for predicting the maximum hardness in heat affected zone (HAZ). Compared with these two selected commercial wires, the inhouse welding wire R01 can provide the highest cost-performance ratio

Thermochemistry of α-D-xylose(cr)

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Ribeiro da Silva, Maria D.M.C.; Lobo Ferreira, Ana I.M.C.; Shi, Quan; Woodfield, Brian F.; Goldberg, Robert N.

2013-01-01

Highlights: ► Well-characterized material. ► Oxygen bomb calorimetry. ► Heat capacities obtained by using a Physical Property Measurement System. ► Thermochemical Network Calculations. ► Accurate thermodynamic property values of a key biochemical substance. -- Abstract: The thermochemistry of α-D-xylose(cr) was studied by means of oxygen bomb calorimetry and a Physical Property Measurement System (PPMS) in zero magnetic field. The sample of α-D-xylose(cr) used in this study was one well-characterized by HPLC, Karl Fischer analysis, NMR, and by carbon dioxide analysis. The standard molar enthalpy of combustion was found to be Δ c H m o = −(2342.2 ± 0.8) kJ·mol −1 at T = 298.15 K and at the standard pressure p° = 0.1 MPa. The standard molar heat capacity for α-D-xylose(cr) was measured with the PPMS over the temperature range 1.9001 ⩽ T/K ⩽ 303.66. At T = 298.15 K, C p,m o = (178.1 ± 1.8) J·K −1 ·mol −1 . The values of C p,m o were fit as a function of T by using theoretical and empirical models for appropriate temperature ranges. The results of these fits were used to calculate values of C p,m o , the entropy increment Δ 0 T S m o , Δ 0 T H m o , and Φ m o =(Δ 0 T S m o -Δ 0 T H m o /T) from T = 0.5 K to T = 300 K. Derived quantities for α-D-xylose(cr) are the standard molar enthalpy of formation Δ f H m o = −(1054.5 ± 1.1) kJ·mol −1 , the third law standard molar entropy S m o = (175.3 ± 1.9) J·K −1 ·mol −1 , and the standard molar Gibbs energy of formation Δ f G m o = −(750.5 ± 1.0) kJ·mol −1 . A comparison of values of Δ c H m o and S m o for the five-carbon aldoses demonstrated a striking similarity in the values of these respective properties for α-D-xylose(cr), D-ribose(cr), and D-arabinose(cr). Thermochemical network calculations were performed that led to values of the standard formation properties at T = 298.15 K for a variety of biochemical substances: D-xylose(aq), D-xylose − (aq), D-xylose 2�

Effective Adsorption/Reduction of Cr(VI) Oxyanion by Halloysite@Polyaniline Hybrid Nanotubes.

Science.gov (United States)

Zhou, Tianzhu; Li, Cuiping; Jin, Huiling; Lian, Yangyang; Han, Wenmei

2017-02-22

Halloysite@polyaniline (HA@PANI) hybrid nanotubes are synthesized by the in situ chemical polymerization of aniline on halloysite clay nanotubes. By facilely tuning the dopant acid, pH, and apparent weight proportion for aniline (ANI) and halloysite (HA) nanotubes in the synthesis process, PANI with tuned oxidation state, doping extent, and content are in situ growing on halloysite nanotubes. The reaction system's acidity is tuned by dopant acid, such as HCl, H 2 SO 4 , HNO 3 , and H 3 PO 4 . The adsorption result shows the fabricated HA@PANI hybrid nanotubes can effectively adsorb Cr(VI) oxyanion and the adsorption ability changes according to the dopant acid, pH, and apparent weight proportion for ANI and HA in the synthesis process. Among them, the HA@PANI fabricated with HCl as dopant acid tuning the pH at 0.5 and 204% apparent weight proportion for ANI and HA (HP/0.5/204%-HCl) shows the highest adsorption capacity. The adsorption capacity is in accordance well with the doping extent of PANI in HA@PANI. Furthermore, when HP/0.5/204%-HCl is redoped with HNO 3 , H 2 SO 4 , and H 3 PO 4 , the adsorption capacity declines, implying the dopant acid in the process of redoping exhibits a marked effect on Cr(VI) oxyanion adsorption for the HA@PANI hybrid nanotubes. HP/0.5/204%-HCl and HP/0.5/204%-H 3 PO 4 have demonstrated good regenerability with an above 80% removal ratio after four cycles. Moreover, the HA@PANI adsorbent has better sedimentation ability than that of pure PANI. The adsorption behavior is in good agreement with Langmuir and pseudo second-order equations, indicating the adsorption of HA@PANI for Cr(VI) oxyanion is chemical adsorption. FT-IR and XPS of HA@PANI after Cr(VI) oxyanion adsorption indicate that the doped amine/imine groups (-NH + /═N + - groups) are the main adsorption sites for the removal of Cr(VI) oxyanion by electrostatic adsorption and reduction of the adsorbed Cr (VI) oxyanion to Cr(III) simultaneously.

Plantago lanceolata growth and Cr uptake after mycorrhizal inoculation in a Cr amended substrate

Directory of Open Access Journals (Sweden)

Amaia Nogales

2012-03-01

Full Text Available Arbuscular mycorrhizal fungi from two chromium contaminated sites, one with 275 mg kg-1 of Cr (zone A and the other with 550 mg kg-1 Cr (zone B, were multiplied and tentatively identified. The effect of both fungal consortia on Plantago lanceolata plant growth in a substrate amended with 200 mg kg-1 of Cr and with 400 mg kg-1 Cr was assessed and compared with the growth of plants inoculated with Glomus intraradices BEG72. Only the plants inoculated with G. intraradices BEG72 and with the fungal consortia obtained from the area with a high Cr contamination (zone B grew in the soil with 400 mg kg-1 of Cr. The consortia of fungi from zone B, decreased the plant’s uptake/translocation of the heavy metal compared with G. intraradices BEG72. These results underscore the differential effect of AM fungi in conferring bioprotection in Cr contaminated soils.

Effect of Cr4+ impurities in Nd:Cr:GSGG and Nd:Cr:YAG laser materials on parameters of lasers at solar pumping

International Nuclear Information System (INIS)

Payziyev, Sh.D.; Bakhramov, S.A.; Shayimov, F.F.; Fayziev, A.Sh.

2015-01-01

The analysis of an effect of Cr 4+ impurity ions, existent in Nd 3+ :Cr 3+ :GSGG and Nd 3+ :Cr 3+ :YAG laser materials on output parameters of solar pumped lasers is carried out by modeling of lasing process at solar pumping. (authors)

Assessment of Cr, Ni and Pb Pollution in Rural Agricultural Soils of Tonalite-Trondjhemite Series in Central India.

Science.gov (United States)

Shukla, Kriti; Kumar, Bijendra; Agrawal, Rahul; Priyanka, Kumari; Venkatesh, Madavi; Anshumali

2017-06-01

Chromium (Cr), nickel (Ni) and lead (Pb) contamination was investigated in wheat cultivated rain-fed and irrigated rural agricultural soils (n = 31) of Tonalite-Trondjhemite Series in Central India. The soil sampling was carried out by using stratified random sampling method. The mean concentrations of Cr, Ni and Pb were 54.8, 38.1 and 68.9 mg/kg, respectively. The average values of enrichment factor (EF), geoaccumulation index (I geo ) and contamination factor (CF) followed the order as: Pb > Ni > Cr. Distribution patterns of soil parent material and weathering processes govern mineral enrichments, irrespective of rainfed or irrigated agricultural practices. Principal component analysis (PCA) showed strong loading of Cr and Ni (PC1) and Pb and clay (PC3). The strong loading on Cr and Ni indicates soils are originating from basic and volcanic rocks in the study area. The strong loading of Pb and clay indicates Pb is strongly adsorbed on clay minerals and Fe-oxides. The cancer risk (CR) index showed negligible carcinogenic risk to the residing population. However, hazard index (HI) values for children exceed the safe limit (HI > 1) for Cr and Pb. Spatial distribution of pollution load index suggest highest pollution in the northeastern part of the district. The study revealed that geogenically enriched soils of the area are suitable for agricultural activities under present conditions.

Calculating CR-39 Response to Radon in Water Using Monte Carlo Simulation

International Nuclear Information System (INIS)

Razaie Rayeni Nejad, M. R.

2012-01-01

CR-39 detectors are widely used for Radon and progeny measurement in the air. In this paper, using the Monte Carlo simulation, the possibility of using the CR-39 for direct measurement of Radon and progeny in water is investigated. Assuming the random position and angle of alpha particle emitted by Radon and progeny, alpha energy and angular spectrum that arrive at CR-39, the calibration factor, and the suitable depth of chemical etching of CR-39 in air and water was calculated. In this simulation, a range of data were obtained from SRIM2008 software. Calibration factor of CR-39 in water is calculated as 6.6 (kBq.d/m 3 )/(track/cm 2 ) that is corresponding with EPA standard level of Radon concentration in water (10-11 kBq/m 3 ). With replacing the skin instead of CR-39, the volume affected by Radon and progeny was determined to be 2.51 mm 3 for one m 2 of skin area. The annual dose conversion factor for Radon and progeny was calculated to be between 8.8-58.8 nSv/(Bq.h/m 3 ). Using the CR-39 for Radon measurement in water can be beneficial. The annual dose conversion factor for Radon and progeny was calculated to be between 8.8-58.8 nSv/ (Bq.h/m 3 ).

Effect of Pb and Cr Substitutions on Phase Formation and Excess Conductivity of Bi-2212 Superconductor

International Nuclear Information System (INIS)

Khir, F. L. M.; Mohamed, Z.; Yusuf, A. A.; Yusof, M. I. M.; Yahya, A. K.

2010-01-01

The influence of Pb and Cr substitutions on the superconducting properties of Bi 2 Sr 2 CaCu 2 O 8 (Bi-2212) superconductors is reported. The samples were prepared from Bi 2-x Pb x Sr 2 Ca 2-y Cr y Cu 3 O 10-δ (x = 0-0.3, y = 0-0.3) starting composition by the solid-state-reaction method. XRD analysis showed formation of pure Bi-2212 for (x = 0, y = 0), (x = 0.3, y = 0.2,) and (x = 0.3, y = 0.2,) starting compositions. Excess conductivity analysis based on Asmalazov-Larkin theory on single-phased Bi2212 samples showed 2D to 3D transition in superconducting fluctuation behavior (SFB) for all the samples. Highest 2D-3D transition temperature, T 2D-3D was observed at Pb and Cr substitutions of x = 0.3, and x = 0.2, respectively.

The Effect of Radiator on CR-39 Registration of Fast Neutrons

International Nuclear Information System (INIS)

El-Badrya, B.A.; Hegazya, T.M.; Morsya, A.A.; Zaki, M.F.

2008-01-01

Three different configurations of a personal neutron dosimeter using CR-39 plastic detector were placed in Plastiplast pouch composed from inside to outside of Aluminum ( 27 Al, 40 Ξ m), polyethylene (PE, 20 Ξ m), Cellulose Nitrate (CN, 40 Ξ m). One dosimeter was composed of a CR-39 detector and a PE radiator (1 mm thick), another of two CR-39 detectors with one serving as radiator, and the other of CR-39 alone (without radiator). These dosimeters have been irradiated with fast neutrons of average energy 4.5 MeV with neutron fluence ranging from 5.5 x 10 6 to 0.5 x 10 8 cm - 2 emitted from 241 Am-Be neutron source. The polymeric materials have been chosen on the basis of their hydrogen contents, which are as followed: CR-39, 48%, Polyethylene, 66.7% and CN, 32% by atomic ratio to produce protons via (n, p) elastic scattering with hydrogen and increasing the detection efficiency of CR-39. After irradiation, the dose equivalent response of the detectors has been studied by using conventional etching for two periods, 6h and 8h for these configurations. The thicknesses and compositions of the radiators are chosen so as to suppress the CR-39 response below 4 MeV by preventing the recoils of hydrogen nuclei, out of the hydrogen-rich radiators (PE, CR-39), from reaching the post-etch surface of the detector. Track counting was performed using an automated system. It was found that the dosemeter responses were linear as a function of a neutron equivalent dose and that the CR-39 detector has the same response with radiator or without radiator and thus appears as a promising fast neutron dosimeter. The results are discussed and compared with the literature

Sintering behaviour and mechanical properties of Cr3C2–NiCr ...

Indian Academy of Sciences (India)

fracture toughness. Keywords. Cermet; Cr3C2–NiCr; sintering; mechanical properties. ... et al investigated the mechanical properties of VC, Cr3C2 and NbC doped ..... Huang S G, Li L, Van der Biest O and Vleugels J 2008 J. Alloys. Compds.

Precise Wavelengths and Energy Levels for the Spectra of Cr I, Mn I, and Mn III, and Branching Fractions for the Spectra of Fe II and Cr II

Science.gov (United States)

Nave, Gillian

I propose to measure wavelengths and energy levels for the spectra of Cr I, Mn I, and Mn III covering the wavelength range 80 nm to 5500 nm, and oscillator strengths for Fe II and Cr II in the region 120 nm to 2500 nm. I shall also produce intensity calibrated atlases and linelists of the iron-neon and chromium-neon hollow cathode lamps that can be compared with astrophysical spectra. The spectra will be obtained from archival data from spectrometers at NIST and Kitt Peak National Observatory and additional experimental observations as necessary from Fourier transform (FT) and grating spectrometers at NIST. The wavelength uncertainty of the strong lines will be better than 1 part in 10^7. The radiometric calibration of the spectra will be improved in order to reduce the uncertainty of measured oscillator strengths in the near UV region and extend the wavelength range of these measurements down to 120 nm. These will complement and support the measurements of lifetimes and branching fractions by J. E. Lawler in the near UV region. An intensive effort by NIST and Imperial College London that was partly funded by previous NASA awards has resulted in comprehensive analyses of the spectra of Fe II, Cr II and Cu II, with similar analyses of Mn II, Ni II, and Sc II underway. The species included in this proposal will complete the analysis of the first two ionization stages of the elements titanium through nickel using the same techniques, and add the spectrum of Mn III - one of the most important doubly-ionized elements. The elements Cr I and Mn I give large numbers of spectral lines in spectra of cool stars and important absorption lines in the interstellar medium. The spectrum of Mn III is important in chemically peculiar stars and can often only be studied in the UV region. Analyses of many stellar spectra depend on comprehensive analyses of iron-group elements and are hampered by incomplete spectroscopic data. As a result of many decades of work by the group at the

Influence of a niobium coating on sulfidation resistance of FeCr and FeCrY alloys

International Nuclear Information System (INIS)

Geribola, Gulherme Altomari

2014-01-01

Niobium and niobium based alloys are currently used in many industrial applications because they offer excellent resistance to degradation in various corrosive environments. These media include gaseous atmospheres at high temperatures such as those found in existing coal gasifying plants in power plants for energy generation. These atmospheres are complex gas mixtures that contain sulfur and oxygen, among other compounds. Sulphides are thermodynamically less stable, have lower melting points and often have larger deviations from stoichiometry compared to the corresponding oxides. Although there are studies regarding the use of refractory metals in high temperature sulphidizing atmospheres, the use of niobium compounds has not been adequately evaluated and there is very little studies available in the literature about its use as a protective coating. The aim of this study was to evaluate the effect of a niobium film, deposited by magnetron sputtering on the isothermal sulphidation behavior of Fe-20Cr and Fe-20Cr-1Y alloys. The sulphidation tests were carried out at 500, 600 and 700 deg C for 2h in H 2 /2% H2S atmosphere. The sulphidation resistance was determined by mass gain per unit area. The sulphidation behavior of the coated and uncoated alloys was similar at 500 deg C, and none of the alloys scaled. At 700 deg C FeCr alloy scaled in the form of a fine powder, while the reaction product formed on the alloy FeCrY scaled in the form of plates. The effect of niobium became pronounced at 700 deg C. The reaction product layer formed on the coated alloy was thinner and more plastic than that formed on the uncoated alloy. The mass gain per unit area of the coated alloys decreased significantly and they did not scaled. (author)

The effects of the impurity distribution on the electrical and optical properties of Cr2+:ZnSe nanowires: First-principles study

Directory of Open Access Journals (Sweden)

Shenyu Dai

2018-03-01

Full Text Available The structural, electrical and mid-infrared optical properties of wurtzite structured ZnSe nanowires with different Chromium impurity distribution are investigated using first-principles calculation based on density-functional theory (DFT. The formation energies have been calculated to study the relative stabilities of different Cr doping positions. It is shown that when the Cr doping position shifted from the center to the edge, the splitting energy between 5T2 and 5E levels of Cr d-orbitals is decreased and a redshift is observed in the calculated infrared absorption spectra. A probable reason for these effects of the impurity distribution is discussed. Keywords: First-principles, Nanowires, Impurity distribution, Cr-doped ZnSe

[Structure and luminescence properties of Ga2O3 : Cr3+ by Al doping].

Science.gov (United States)

Wang, Xian-Sheng; Wan, Min-Hua; Wang, Yin-Hai; Zhao, Hui; Hu, Zheng-Fa; Li, Hai-Ling

2013-11-01

The Al doping gallate phosphor (Ga(1-x)Al(x))2O3 : Cr3+ (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) was synthesized by a high temperature solid-state reaction method. The X-ray diffractions show that the phase of the phosphors remains to be Ga2 O3 structure with increase in the contents of Al3+ ion. Beside, the fact that the X-ray diffraction peak shifts towards big angles with increasing Al3+ ions content shows that Al3+ ions entered the Ga2 O3 lattice. The peaks of the excitation spectra located at 258, 300, 410 and 550 nm are attributed to the band to band transition of the matrix, charge transfer band transition, and 4A2 --> 4T1 and 4A2 --> 4T2 transition of Cr3+ ions, respectively. Those excitation spectrum peak positions show different degrees of blue shift with the increase in the Al3+ ions content. The blue shift of the first two peaks are due to the band gap energy of substrate and the electronegativity between Cr3+ ions and ligands increasing, respectively. The blue shift of the energy level transition of Cr3+ ion is attributed to crystal field strength increasing. The Cr3+ ion luminescence changes from a broadband emission to a narrow-band emission with Al3+ doping, because the emission of Cr3+ ion changed from 4 T2 --> 4A2 to 2E --> 4A2 transition with the crystal field change after Al3+ ions doping. The Al3+ ions doping improved the long afterglow luminescence properties of samples, and the sample showed a longer visible near infrared when Al3+ ions content reaches 0.5. The thermoluminescence curve shows the sample with suitable trap energy level, and this is also the cause of the long afterglow luminescence materials.

High Cr ODS steels R and D for high burnup fuel cladding

International Nuclear Information System (INIS)

Kimura, A.; Kasada, R.; Kishimoto, H.; Iwata, N.; Cho, H.-S.; Toda, N.; Yutani, K.; Ukai, S.; Fujiwara, M.

2007-01-01

High-performance cladding materials is essential to realize highly efficient and high-burnup operation over 150 GWd/t of so called Generation IV nuclear energy systems, such as supercritical-water-cooled reactor (SCWR) and lead-cooled fast reactor (LFR). Oxide dispersion strengthening (ODS) ferritic/ martensitic steels, which contain 9-12%Cr, show rather high resistance to neutron irradiation embrittlement and high strength at elevated temperatures. However, their corrosion resistance is not good enough in SCW and in lead at high temperatures. High-Cr ODS steels have been developed to improve corrosion resistance. An increase in Cr content an addition resulted in a drastic improvement of corrosion resistance in SCW and in lead. On the contrary, high-Cr steels often show an enhancement of aging embrittlement as well as irradiation embrittlement. Anisotropy in tensile properties is another issue. In order to overwhelm these issues, surveillance tests of the material performance have been performed for high Cr-ODS steels produced by new processing technologies. It is demonstrated that the dispersion of nono-sized oxide particles in high density is effective to attain high-performance and high-Cr ODS steels have a high potential as fuel cladding materials for SCWR and LFR with high efficiency and high burnup. (authors)

Characteristics of latent damage trails due to high energy 208Pb and 238U ions in CR-39 and muscovite mica

International Nuclear Information System (INIS)

Chohan, A.S.; Akhtar, S.M.

1988-01-01

Experiments have been performed to study the characteristics of latent damage trails produced by (a) 17.14 MeV/nucleon- 208 Pb ions in mica and CR-39 track detectors and (b) 13.7 MeV/nucleon- 238 U in CR-39 track detectors. The parameters studied include (a) V t , average etching velocity along the track, (b) thermal stability of the latent damage trails, (c) the total etchable ranges, and (d) V g the general etching velocity of CR-39 track detectors previously annealed at different temperatures. It has been observed that the latent damage trails in CR-39 are greatly affected at temperatures around 200 0 C in CR-39 track detectors. The general etching velocity of a CR-39 detector has been found to increase with increasing annealing temperatures. (author)

LHC project. Exploring the smallest world with the highest energy beam

International Nuclear Information System (INIS)

Kondo, Takahiko; Kobayashi, Tomio

2007-01-01

The LHC accelerator at CERN will be completed soon and the experiments are about to start, making it possible to explore the TeV energy region for the first time in human history. There exists a clear reason why the TeV region is especially important for experimental exploration. The Higgs particle, the last elusive element of the Standard Model, will be discovered with very high probability. In addition there are high chances to discover signs of new physics beyond the Standard Model such as SUSY particles. Dark matter may be discovered. As an introduction of the mini-special issue for LHC, its goals and history is briefly reviewed, followed by a description on LHC accelerator, four LHC experiments as well as the contributions by Japan. (author)

Isotope Effects in the Bonds of beta-CrOOH and beta-CrOOD

DEFF Research Database (Denmark)

Nørlund Christensen, A.; Hansen, P.; Lehmann, M. S.

1976-01-01

Samples of orthorhombic chromium oxide hydroxide, beta -CrOOH, and the deuterated compound, beta -CrOOD, were prepared hydrothermally. The crystal structures were determined by powder profile refinement technique using neutron diffraction data. Unit cells are: beta -CrOOH: a equals 4. 862(2) A, b...... equals 4. 298(a) A, c equals 2. 995(1) A; beta -CrOOD: a equals 4. 873(5) A, b equals 4. 332(7) A, c equals 2. 963(2) A, with Z equals 2. The space group is P2//1nm or Pnnm....

Fe, Cr, Ni, Cu, Mg, Al, Ti, and S contents in plants and soil of heaps of nickel smelting works

Energy Technology Data Exchange (ETDEWEB)

Banasova, V; Hajduk, J

1977-01-01

The writers established the Fe, Ce, Cr, Ni, Ca, Mg, Al, Ti and S contents in the neopedon of heaps piling up from processing of nickel ore as well as in the plants: Cardaria draba, Salsola cali, Agropyrum repens, Bromus erectus, Calamagrostis epigeios, Cynodon dactylon and Matricaria inodora, growing on such heaps. Ca, Mg and S contents were found to be higher in dicotyledons and Fe, Al, Ti, Ni and Cr contents higher in monocotyledons. The analyzed dicotyledons appeared to be concentrators of Ca and S. Highest Fe, Al, Ti, Ni and Cr contents were found in individuals of the species Agropyrum repens. The neopedon as well as the plants had extraordinarily high Cr concentrations. The species Salsola cali has been found to possess an unusually higher affinity to the dump substrate after processing of nickel ore and to be a concentrator of Mg. 16 references, 1 table.

Density of Liquid Ni-Cr Alloy

Institute of Scientific and Technical Information of China (English)

无

2003-01-01

The density of liquid Ni-Cr alloy was measured by a modified sessile drop method. The density of liquid Ni-Cr alloywas found to decrease with increasing temperature and Cr concentration in the alloy. The molar volume of liquidNi-Cr alloy increases with increasing the Cr concentration in the alloy. The molar volume of Ni-Cr alloy determinedin the present work shows a positive deviation from the linear molar volume.

Removal of Cr(VI and Toxic Ions from Aqueous Solutions and Tannery Wastewater Using Polymer-Clay Composites

Directory of Open Access Journals (Sweden)

Abd El-Azeem Sallam

2017-10-01

Full Text Available Polymer-clay composites were prepared by natural zeolite (clinoptilolite or naturally local clay deposits in an N,N-methylene-bis-acrylamide as cross-linked. The resultant composites were used for the removal of Cr(VI from an aqueous solution. Additionally, their effects on soluble ions of tannery wastewater were investigated. The produced composites were characterized using X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FT-IR, and scanning electron microscopy (SEM. The results showed that Cr(VI removal is dependent upon initial concentrations and pH. The adsorption quantity of Cr(VI onto the polymerized clay deposit followed by polymerized zeolite exhibited higher values than their original samples. The polymer-clay composite of clay deposit showed the highest removal of 76.3–100% overall initial concentrations of 10–50 mg L−1 and at initial pH of 2. Kinetics of Cr(VI removal by various sorbents was predicted using a pseudo–second order model. Our findings showed that the levels of salinity and various soluble ions (Cr2+, Na+, Cl− and SO42− in tannery wastewater are very high, and their levels were reduced after treatment, especially by polymerized sorbents. It could be concluded that the polymer-clay composites may be employed as a highly efficient sorbent for the removal of Cr(VI and toxic ions from the wastewater.

Analysis of PTA hardfacing with CoCrWC and CoCrMoSi alloys

Directory of Open Access Journals (Sweden)

Adriano Scheid

2013-12-01

Full Text Available CoCrWC alloys are widely used to protect components that operate under wear and high temperature environments. Enhanced performance has been achieved with the CoCrMoSi alloys but processing this alloy system is still a challenge due to the presence of the brittle Laves phase, particularly when welding is involved. This work evaluated Plasma Transferred Arc coatings processed with the Co-based alloy CoMoCrSi - Tribaloy T400, reinforced with Laves phase, comparing its weldability to the CoCrWC - Stellite 6, reinforced with carbides. Coatings were also analyzed regarding the response to temperature exposure at 600°C for 7 days and subsequent effect on microstructure and sliding abrasive wear. Coatings characterization was carried out by light and scanning electron microscopy, X-ray diffraction and Vickers hardness. CoCrWC coatings exhibited a Cobalt solid solution dendritic microstructure and a thin interdendritic region with eutectic carbides, while CoCrMoSi deposits exhibit a large lamellar eutectic region of Laves phase and Cobalt solid solution and a small fraction of primary Laves phase. Although phase stability was observed by X-ray diffraction, coarsening of the microstructure occurred for both alloys. CoCrMoSi showed thicker lamellar Laves phase and CoCrWC coarser eutectic carbides. Coatings stability assessed by wear tests revealed that although the wear rate of the as-deposited CoCrMoSi alloy was lower than that of CoCrWC alloy its increase after temperature exposure was more significant, 22% against 15%. Results were discussed regarding the protection of industrial components in particular, bearings in 55AlZn hot dip galvanizing components.

Quasi-static tensile properties of the Cranial Cruciate Ligament (CrCL) in adult cattle: towards the design of a prosthetic CrCL.

Science.gov (United States)

Diotalevi, Lucien; Petit, Yvan; Brailovski, Vladimir; Nichols, Sylvain; Marchionatti, Emma; Wagnac, Éric

2018-03-01

Mechanical properties of the Cranial Cruciate Ligament (CrCL) in adult cattle are not well documented and protocols used in the literature focus on testing a full femur-CrCL-tibia complex rather than an isolated CrCL. The aim of this study was to assess a wider range of tensile properties of the CrCL along its anatomic axis with experimental measurements of the global elongation, displacement and strain fields, in order to provide guidelines for the design of CrCL prosthetic surrogates. Fourteen bovine CrCL were harvested from seven mature cows (5.1 ± 1.3 years) weighing 631 ± 90kg. The mean CrCL length was 41.4 ± 1.5mm and its mean cross-section was 103.9 ± 23.8mm 2 . Pre-conditioning was achieved with 30 cycles of loading from 30 to 200N at a strain rate of 0.02s -1 . Specimens were then loaded to failure at the same strain rate. The following results were obtained: the mean ultimate tensile load (UTL) 4372 ± 1485N and the median [quartiles] maximal global elongation 19.3 [17.8; 21.4] %. At first physical signs of tearing, the mean load was 3315 ± 1336N and mean elongation 13.5 ± 4.9%. The mean absorbed energy at failure was 5.23 ± 2.08 MJ.mm -3 and the mean stiffness at various levels of elongation was: 220 ± 195N.% -1 (5%), 285 ± 162N.% -1 (10%), 239 ± 200N.% -1 (15%), 146 ± 59N.% -1 (20%), 153 ± 136N.% -1 (25%). None of these properties were related to the bovine weight, age and side of the body (p > 0.05). An ideal prosthetic surrogate should then follow these sets of properties and the experimental data suggest that the in-vivo maximal elongation is below 13.5%. Copyright © 2018 Elsevier Ltd. All rights reserved.

Directional Track Selection Technique in CR39 SSNTD for lowyield reaction experiments

Science.gov (United States)

Ingenito, Francesco; Andreoli, Pierluigi; Batani, Dimitri; Bonasera, Aldo; Boutoux, Guillaume; Burgy, Frederic; Cipriani, Mattia; Consoli, Fabrizio; Cristofari, Giuseppe; De Angelis, Riccardo; Di Giorgio, Giorgio; Ducret, Jean Eric; Giulietti, Danilo; Jakubowska, Katarzyna

2018-01-01

There is a great interest in the study of p-11B aneutronic nuclear fusion reactions, both for energy production and for determination of fusion cross-sections at low energies. In this context we performed experiments at CELIA in which energetic protons, accelerated by the laser ECLIPSE, were directed toward a solid Boron target. Because of the small cross-sections at these energies the number of expected reactions is low. CR39 Solid-State Nuclear Track Detectors (SSNTD) were used to detect the alpha particles produced. Because of the low expected yield, it is difficult to discriminate the tracks due to true fusion products from those due to natural background in the CR39. To this purpose we developed a methodology of particle recognition according to their direction with respect to the detector normal, able to determine the position of their source. We applied this to the specific experiment geometry, so to select from all the tracks those due to particles coming from the region of interaction between accelerated protons and solid boron target. This technique can be of great help on the analysis of SSNTD in experiments with low yield reactions, but can be also generally applied to any experiment where particles reach the track detector with known directions, and for example to improve the detection limit of particle spectrometers using CR39.

Comparison of mechanical behavior of TiN, TiNC, CrN/TiNC, TiN/TiNC films on 9Cr18 steel by PVD

Science.gov (United States)

Feng, Xingguo; Zhang, Yanshuai; Hu, Hanjun; Zheng, Yugang; Zhang, Kaifeng; Zhou, Hui

2017-11-01

TiN, TiNC, CrN/TiNC and TiN/TiNC films were deposited on 9Cr18 steel using magnetron sputtering technique. The morphology, composition, chemical state and crystalline structure of the films were observed and analyzed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Hardness and adhesion force were tested by nanoindentation and scratch tester, respectively. The friction and wear behavior of TiN, TiNC, CrN/TiNC and TiN/TiNC films sliding against GCr15 balls were investigated and compared synthetically using ball-on-disk tribometer. It was found that Tisbnd N, Tisbnd C, Tisbnd Nsbnd C and Csbnd C bonds were formed. The TiN/TiNC film was composed of TiN, TiC and TiNC phases. Hardness and adhesion force results indicated that although the TiN film possessed the highest hardness, its adhesion force was lowest among all the films. Tribological test results showed that the friction coefficient of TiN/TiNC was much lower than that of TiN and the wear rate decreases remarkably from 2.3 × 10-15 m3/Nm to 7.1 × 10-16 m3/Nm, which indicated the TiN/TiNC film has better wear resistance.

Energy and crisis

International Nuclear Information System (INIS)

Rosa, L.P.

1984-01-01

Several aspects of the Brazilian energy policy are dealt with, regarding petroleum, electric energy and the nuclear question. Regional and international aspects relating to the energy crisis are discussed, and some alternatives for this crisis are suggested. (I. de C.R.) [pt

Microstructure and Mechanical Characterization of a Dissimilar Friction-Stir-Welded CuCrZr/CuNiCrSi Butt Joint

Directory of Open Access Journals (Sweden)

Youqing Sun

2018-05-01

Full Text Available Dissimilar CuNiCrSi and CuCrZr butt joints were successfully frictionstirwelded at constant welding speed of 150 mm/min and rotational speed of 1400 rpm with the CuCrZr alloy or the CuNiCrSi alloy located on the advancing side (AS. The microstructure and mechanical properties of joints were investigated. When the CuCrZr alloy was located on the AS, the area of retreating material in the nugget zone was a little bigger. The Cr solute-rich particles were found in the nugget zone on CuCrZr side (CuCrZr-NZ while a larger density of solute-rich particles identified as the concentration of Cr and Si element was found in the nugget zone on CuNiCrSi side (CuNiCrSi-NZ. The Cr precipitates and δ-Ni2Si precipitates were found in the base metal on CuNiCrSi side (CuNiCrSi-BM but only Cr precipitates can be observed in the base metal on CuCrZr side (CuCrZr-BM. Precipitates were totally dissolved into Cu matrix in both CuCrZr-NZ and CuNiCrSi-NZ, which led to a sharp decrease in both micro-hardness and tensile strength from BM to NZ. When the CuNiCrSi was located on the AS, the tensile testing results showed the fracture occurred at the CuCrZr-NZ, while the fracture was found at the mixed zone of CuNiCrSi-NZ and CuCrZr-NZ for the other case.

53Cr NMR study of CuCrO2 multiferroic

Science.gov (United States)

Smol'nikov, A. G.; Ogloblichev, V. V.; Verkhovskii, S. V.; Mikhalev, K. N.; Yakubovskii, A. Yu.; Kumagai, K.; Furukawa, Y.; Sadykov, A. F.; Piskunov, Yu. V.; Gerashchenko, A. P.; Barilo, S. N.; Shiryaev, S. V.

2015-11-01

The magnetically ordered phase of the CuCrO2 single crystal has been studied by the nuclear magnetic resonance (NMR) method on 53Cr nuclei in the absence of an external magnetic field. The 53Cr NMR spectrum is observed in the frequency range νres = 61-66 MHz. The shape of the spectrum depends on the delay tdel between pulses in the pulse sequence τπ/2- t del-τπ- t del-echo. The spin-spin and spin-lattice relaxation times have been measured. Components of the electric field gradient, hyperfine fields, and the magnetic moment on chromium atoms have been estimated.

Heterogeneity of Cr in Mytilus edulis: Implications for the Cr isotope system as a paleo-redox proxy

Science.gov (United States)

Bruggmann, Sylvie; Klaebe, Robert; Frei, Robert

2017-04-01